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  • 1.
    Abrikosov, Igor
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Knutsson, Axel
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Tasnádi, Ferenc
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Lind, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Phase Stability and Elasticity of TiAlN2011In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 4, no 9, p. 1599-1618Article in journal (Refereed)
    Abstract [en]

    We review results of recent combined theoretical and experimental studies of Ti1−xAlxN, an archetypical alloy system material for hard-coating applications. Theoretical simulations of lattice parameters, mixing enthalpies, and elastic properties are presented. Calculated phase diagrams at ambient pressure, as well as at pressure of 10 GPa, show a wide miscibility gap and broad region of compositions and temperatures where the spinodal decomposition takes place. The strong dependence of the elastic properties and sound wave anisotropy on the Al-content offers detailed understanding of the spinodal decomposition and age hardening in Ti1−xAlxN alloy films and multilayers. TiAlN/TiN multilayers can further improve the hardness and thermal stability compared to TiAlN since they offer means to influence the kinetics of the favorable spinodal decomposition and suppress the detrimental transformation to w-AlN. Here, we show that a 100 degree improvement in terms of w-AlN suppression can be achieved, which is of importance when the coating is used as a protective coating on metal cutting inserts.

  • 2.
    Ahmad, Maqsood
    et al.
    Base Engine & Materials Technology, Volvo Group, Gothenburg.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    König, Mathias
    Materials Technology for Basic Engine, Scania CV, Södertälje.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Bending Fatigue Behavior of Blast Cleaned Grey Cast Iron2017In: Residual Stresses 2016: ICRS-10, Materials Research Proceedings 2 (2016), 2017, Vol. 2, p. 193-198Conference paper (Refereed)
    Abstract [en]

    This paper presents a detailed study on the effect of an industrial blast cleaning process on the fatigue behavior of a grey cast iron with regard to the residual stresses and microstructural changes induced by the process. A comparison was also made to the effect of a machining operation which removed the casting skin layer. The blast cleaning process was found to greatly improve the fatigue resistance in both the low and high cycle regimes with a 75% increase in the fatigue limit. Xray diffraction measurements and scanning electron microscopic analyses showed that the improvement was mainly attributed to compressive residual stresses in a surface layer up to 800 μm in thickness in the blast cleaned specimens. The machining also gave better fatigue performance with a 30% increase in the fatigue limit, which was ascribed to the removal of the weaker casting skin layer.

  • 3.
    Altgärde, Noomi
    Linköping University, Department of Physics, Chemistry and Biology.
    Local release of lithium from sol-gel coated orthopaedic screws: an in vitro and in vivo study2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

     

    In orthopaedic practice, fractures are usually stabilised with metal screws or rods. This is done in order to keep the fracture parts in place during the rather slow healing process. The healing time can potentially be reduced by local- or systemic treatment with different bone promoting drugs. In later years, lithium, otherwise used to treat bipolar disease, has shown promise to be such a drug.

     

    The aim of this master thesis was to find a way to coat metal bone screws with lithium and to characterise the coating. The coating was to be designed in such a way that it could release lithium to the surrounding bone tissue.

     

    Lithium chloride was incorporated into a titanate sol-gel and attached to silicon wafers and stainless steel screws by dip coating. Wafers were used for initial in vitro studies of how lithium changed coating characteristics. This was studied using ellipsometry, AFM and SEM. Lithium is most probably physisorbed and not incorporated into the network building up the sol-gel. Coating structure is changed as more lithium is incorporated. For large amounts of lithium, the nanoparticles normally formed when curing the sol-gel are inhibited. One effect of this is reduced bioactivity, seen as a reduced ability for calcium phosphate crystals to nucleate on the coating when immersed in simulated body fluid.

    Lithium release was investigated using AAS. Lithium is released from the coating, showing a burst effect. By changing the number of coating layers used, the release profile can be partly altered. The coating was also applied to screws, showing good attachment, and the lithium release profile was similar to the one seen from wafers.

    Finally, a screw model was used in rats to assess the effect of local lithium treatment from screws and systemic lithium treatment on fracture healing. In the model, a screw was inserted in tibia, mimicking a fracture. When the bone around the screw was healed, a pullout test was performed, giving information about the strength of the bone surrounding the screw. No significant difference could be found for either local- or systemic lithium treatment compared to control. However, when evaluating the strength of intact bone in a similar way, a positive effect of systemic lithium treatment could be seen. Therefore, it is still likely that lithium has a positive effect on bone and further studies are needed to fully evaluate its role in fracture healing.

     

  • 4.
    Andersson, Niklas
    Linköping University, Department of Management and Engineering.
    Gesällprovets tillverkningsprocess2008Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Examensarbetet är en beskrivande rapport om tillverkningsprocessen av ett gesällprov. Rapportens syfte är att beakta olika konstruktioner och hur de förvärvade kunskaperna används för att utföra en slutprodukt, i det här fallet ett gesällprov. Rapporten försöker svara på vilka faktorer som varit mest avgörande för ett lyckat resultat.

    Tyngdpunkten i arbetet ligger i att beskriva tillverkningsprocessen. Rapporten beskriver resonemanget kring valet av en möbel. Den presenterar olika träslag och hur de kan påverka möbelns uttryck. Vidare berättar rapporten om olika alternativ på skivmaterial att använda som blindträ. Uttag och hantering av faner och massivträ förklaras. Rapporten visar även olika konstruktioner och sammansättningar.

    I den avslutande delen presenteras resultatet av tillverkningen och granskarnas betygssättning. Ett resonemang förs angående vilka faktorer, så som erfarenheter, förvärvade kunskaper, noggrannhet etc. som påverkat resultatet. Slutligen beskrivs olika svårigheter och vad som skulle kunna göras annorlunda.

  • 5.
    Bakoglidis, Konstantinos
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Schmidt, Susann
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Improved adhesion of carbon nitride coatings on steel substrates using metal HiPIMS pretreatments2016In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 302, p. 454-462Article in journal (Refereed)
    Abstract [en]

    We investigate the effect of low-temperature metal pretreatments in order to improve the adhesion of CNx coatings on steel substrates, which is crucial for tribological applications. The substrate pretreatments were conducted using five different metal targets: Ti, Zr, Al, Cr, and W, operated in high power impulse magnetron sputtering mode, known to produce significant ionization of the sputtered material flux. The CNx adhesion, as assessed by Rockwell C tests, did not improve upon Ti and Zr pretreatments. This is primarily ascribed to the fact that no interlayer was formed owing to severe re-sputtering due to high fluxes of doubly-ionized metal species in the plasma. A slight improvement in adhesion was observed in the case an Al pretreatment was carried out, while the best results were obtained using Cr and W. Here, 30-s-long pretreatments were sufficient to clean the steel surface and form a metallic interlayer between substrate and coating. Transmission electron microscopy in combination with energy dispersive X-ray spectroscopy revealed that Al, Cr, and W created intermixing zones at the interlayer/substrate and the interlayer/CNx interfaces. The steel surfaces, pretreated using Cr or W, showed the highest work of adhesion with W-adh(Cr) = 1.77 J/m(2) and W-adh(W) = 1.66 J/m(2), respectively. (C) 2016 Elsevier B.V. All rights reserved.

  • 6.
    Balachandramurthi, Arun Ramanathan
    et al.
    Univ West, Sweden.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Univ West, Sweden.
    Mahade, Satyapal
    Univ West, Sweden.
    Pederson, Robert
    Univ West, Sweden.
    Additive Manufacturing of Alloy 718 via Electron Beam Melting: Effect of Post-Treatment on the Microstructure and the Mechanical Properties2019In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 1, article id 68Article in journal (Refereed)
    Abstract [en]

    Alloy 718 finds application in gas turbine engine components, such as turbine disks, compressor blades and so forth, due to its excellent mechanical and corrosion properties at elevated temperatures. Electron beam melting (EBM) is a recent addition to the list of additive manufacturing processes and has shown the capability to produce components with unique microstructural features. In this work, Alloy 718 specimens were manufactured using the EBM process with a single batch of virgin plasma atomized powder. One set of as-built specimens was subjected to solution treatment and ageing (STA); another set of as-built specimens was subjected to hot isostatic pressing (HIP), followed by STA (and referred to as HIP+STA). Microstructural analysis of as-built specimens, STA specimens and HIP+STA specimens was carried out using optical microscopy and scanning electron microscopy. Typical columnar microstructure, which is a characteristic of the EBM manufactured alloy, was observed. Hardness evaluation of the as-built, STA and HIP+STA specimens showed that the post-treatments led to an increase in hardness in the range of similar to 50 HV1. Tensile properties of the three material conditions (as-built, STA and HIP+STA) were evaluated. Post-treatments lead to an increase in the yield strength (YS) and the ultimate tensile strength (UTS). HIP+STA led to improved elongation compared to STA due to the closure of defects but YS and UTS were comparable for the two post-treatment conditions. Fractographic analysis of the tensile tested specimens showed that the closure of shrinkage porosity and the partial healing of lack of fusion (LoF) defects were responsible for improved properties. Fatigue properties were evaluated in both STA and HIP+STA conditions. In addition, three surface conditions were also investigated, namely the raw as-built surface, the machined surface with the contour region and the machined surface without the contour region. Machining off the contour region completely together with HIP+STA led to significant improvement in fatigue performance.

  • 7.
    Barazande, Saina
    Linköping University, Department of Management and Engineering, Carl Malmsten - furniture studies. Linköping University, The Institute of Technology.
    Om att berätta något: en undersökning av skapandeprocessen med berättelsen och jaget som utgångspunkt2014Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    This work is a search for a creative process that suits me. I gaze outwards to find new ways to do and provide more opportunities for me in my making and ultimately get closer to my own way of creating. Through interviews with active creative performers in various media, such as designers, a cartoonist, a musician and a poet I search for possible new methods and processes. Like the people I interview, I want to share stories, through my making, from my self and origin. I want to share stories to evoke thoughts, memories and reflection.

    My starting point is the methodology that Carl Malmsten Furniture Studies advocates. Through the interviews my process and methodology has evolved and I have explored new paths for my creativity. This has also resulted in two physical objects, a book of poetry and a storage. These two unitedly speaks my thoughts on the innermost room, which we all have within us.

  • 8.
    Bentzer, Justinius Erik
    Linköping University, Department of Management and Engineering, Carl Malmsten - furniture studies. Linköping University, The Institute of Technology.
    Textil, faner och jag: en möbelkollektion sprungen ur en undersökning av materialkombinationer faner och textil2014Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [sv]

    Jag har ett intresse för att utforska och undersöka olika material och hur vi upplever dessa material. I detta examensarbete skapar jag två möbler genom en gestaltningsprocess som grundar sig i ett undersökande av materialkombinationen faner och textil. Arbetet är uppdelat i två delar, en undersökande del där jag testar att kombinera olika faner, textilier och limmer, för att se hur jag upplever dessa och för att få en grund till min gestaltningsprocess. I den andra delen formger jag två möbler som har till syfte att väcka intresse för materialet hos betraktaren. Det blir ett klädskåp och en sittmöbel, som visar på olika sido !och mervärden med materialkombinationerna. Förhoppningsvis kan detta  arbete väcka intresset för nya materialkombinationer även hos er läsare.

  • 9.
    Berglund, Jonas
    Linköping University, Department of Management and Engineering, Malmstens Linköping University.
    Stark, starkare, starkast: en jämförelse av fasta tappar och centrumtappar med utgångspunkt i tappens dimensioner, inpassning, komprimering, antal och limning2018Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    I have in my thesis compared the strength of mortise and tenon joints and dowel joints in wooden furniture. I´ve made the comparison based on five parameters: the dimensions of the tenon or dowel, the fit of the tenon or dowel, the compression of the tenon or dowel, the number of tenons or dowels and the gluing of the tenon or dowel. The bigger question has been, “is the mortise and tenon joint or the dowel joint the strongest?” The goal has been to go through different theories regarding these two types of joinery and making a foundation to help cabinet makers and designers to make conscious decisions regarding their choices of these two types of joinery. Through studies of literature and visiting workshops I´ve gathered knowledge that lies as a foundation for a test of strength of different joinery made in the material testing facility of Linköping University. The test was based on a scenario of joining the back leg and side rim of a chair. The test shows, from the given definitions, that mortise and tenon joints are without exceptions stronger than dowel joints. It also shows that double tenons better will distribute the load and make for a stronger and tougher joint. Dowel joints will get tougher with an increased number of dowels but it will not necessarily make for a stronger joint. The fit and compression of the tenon or dowel will affect the joints strength.

  • 10.
    Bernard, Antoine
    Linköping University, Department of Management and Engineering.
    Offshore Oil and Gas Platform: Construction methods applied to Jackets erection2007Independent thesis Advanced level (degree of Magister), 20 points / 30 hpStudent thesis
    Abstract [en]

    My Master thesis was carried out from mid June 2006 until March 2007 within a major oil & gas subcontractor. My firm had been awarded a contract for the development of a new promising offshore oil field. Our role was limited to the fabrication of six Jackets designed to support the newly developed Topsides, each weighing more than fifteen thousands tonnes. Throughout the project, jacket after jacket, it has been felt that some room for improvement existed in the construction methods used for their erection. Safety always being the first motto of any oil & gas project, it is always of high interest to improve the erection methods used to carry out the most potentially dangerous operations. This is to be reached through a more detailed and careful approach of the heavy lifting operations design. More specifically, as part of the methods engineering department, my master thesis aimed at supporting the designing and setting up of all heavy lifting operations used for the erection and assembly of the external frames of the last Jacket to be fabricated. As an outcome of the work carried out by our department and all company’s teams, the Jacket was assembled and erected in due time with no remarkable incident.

  • 11.
    Brandtberg, Sebastian
    Linköping University, Department of Management and Engineering, Engineering Materials.
    Microstructural inhomogeneity and anisotropicproperties in IN-718 structures fabricated byElectron Beam Melting: Mikrostrukturell inhomogenitet och anisotropa egenskaper i strukturerav IN-718 tillverkade genom Electron Beam Melting2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Additive Manufacturing, or 3D printing, provides an opportunity to manufacture advanced 3D geometrieswith little material waste and reduced need for tooling compared to conventional methods. There are,however, challenges remaining regarding anisotropy in the mechanical properties of built components.

    The aim of this project is to investigate the anisotropy of additive manufactured material and the effect ofdifferent build directions. The material used is Inconel 718, which was manufactured by Electron BeamMelting as vertical and horizontal rods. The tests performed are microstructural investigations about thegrains, precipitates and porosities, but also include hardness testing and tensile testing. The material istested in its as-built state.

    The results show that the material consist of an anisotropic microstructure with elongated grains in thebuild direction. The build height has a bigger influence on the properties of the material than the builddirection for the specimens. The top pieces are consistently different from the others and are the leasthomogeneous. The microstructure consists of large quantities of delta-phase, and solidification pores arefound throughout the material. The hardness of the material differs from 324 HV to 408 HV depending onthe part of the build. The tensile testing shows that the vertically built specimens have a higher yieldstrength and ultimate tensile strength while the horizontally built specimens have a greater ductility.

  • 12.
    Broitman, Esteban
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Indentation Hardness Measurements at Macro-, Micro-, and Nanoscale: A Critical Overview2017In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 65, no 1Article, review/survey (Refereed)
    Abstract [en]

    The Brinell, Vickers, Meyer, Rockwell, Shore, IHRD, Knoop, Buchholz, and nanoindentation methods used to measure the indentation hardness of materials at different scales are compared, and main issues and misconceptions in the understanding of these methods are comprehensively reviewed and discussed. Basic equations and parameters employed to calculate hardness are clearly explained, and the different international standards for each method are summarized. The limits for each scale are explored, and the different forms to calculate hardness in each method are compared and established. The influence of elasticity and plasticity of the material in each measurement method is reviewed, and the impact of the surface deformation around the indenter on hardness values is examined. The difficulties for practical conversions of hardness values measured by different methods are explained. Finally, main issues in the hardness interpretation at different scales are carefully discussed, like the influence of grain size in polycrystalline materials, indentation size effects at micro-and nanoscale, and the effect of the substrate when calculating thin films hardness. The paper improves the understanding of what hardness means and what hardness measurements imply at different scales.

  • 13.
    Broitman, Esteban
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Advanced Carbon-Based Coatings2014In: Comprehensive Materials Processing, Elsevier, 2014, 4, p. 389-412Chapter in book (Refereed)
    Abstract [en]

    This chapter focuses on the development of alloyed diamondlike coatings, in particular a new class of fullerene-like (FL) materials. We describe unique resilient FL compounds by self-organization of nano-curved sp2-hybridized carbon features, with tuned mechanical and surface energy properties. These unique resilient materials consist of bent and intersecting hexagonal basal planes, fabricated by the incorporation of odd-member rings. Cross-linking enables the material to extend the strength of the covalently 2D hexagonal graphene network into 3D. The microstructural properties of three types of coatings, which have the possibility to be applied on a large scale, are described: carbon nitride, phosphorous carbide, and carbon fluoride.

  • 14.
    Broitman, Esteban
    et al.
    University of Buenos Aires, Argentina.
    Latorre, Daniel
    University of Buenos Aires, Argentina.
    Zimmerman, Rosa
    University of Buenos Aires, Argentina.
    Thin Film Temperature Sensors (Sensores de Temperatura de Película Delgada)1990In: Anales AFA, ISSN 1850-1158, Vol. 1, no 1, p. 336-338Article in journal (Refereed)
    Abstract [en]

    Ni thin films of 1800 Å thick were deposited by ion-plating and designed by photolithography to be used as temperature sensors. The resistive paths were finished with contact Cu welding terminals. After being coated with a protective layer of SiOx, they were subjected to heat stabilization treatments. Small, stable and accurate sensors were obtained.

  • 15.
    Brolin Nord, Elin
    Linköping University, Department of Management and Engineering, Malmstens Linköping University.
    En studie av skador hos stolar från renässansen 1560-tal till biedermeier 1850-tal.: Ett arbete om sambandet mellan konstruktion, material och skadebild.2018Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Through the selection of six representative typical Swedish chairs from each era, I present manufacturing techniques and how the craftsmanship has affected the style of the chairs over time. My main source material is the objects themselves. I chose to analyze the constructions and what can distinguish them apart in techniques, material choices, aesthetics and design. The main part of my work has been to find out what are the most occurring damages and its causes. Most damages from renaissance to biedermeier can be linked to the mortise joint. Through interviews with experienced conservators and with my own experiences as a cabinet maker and conservator, I discuss the concept of the ultimate chair design in terms of stability. I have come to the conclusion that the most solid chair is the eight to twelve framed chairs from the Renaissance, but the chair must be adapted to the intended use.

  • 16.
    Calamba, Katherine
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Univ Lorraine, France.
    Jöesaar Johansson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. SECO Tools AB, Sweden.
    Bruyere, S.
    Univ Lorraine, France.
    Pierson, J. F.
    Univ Lorraine, France.
    Boyd, Robert
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Andersson, J. M.
    SECO Tools AB, Sweden.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    The effect of nitrogen vacancies on initial wear in arc deposited (Ti-0.52,Ti- Al-0.48)N-y, (y < 1) coatings during machining2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 358, p. 452-460Article in journal (Refereed)
    Abstract [en]

    Nitrogen deficient c-(Ti0.52Al0.48)Ny, y = 0.92, y = 0.87, and y = 0.75 coatings were prepared in different N-2/Ar discharges on WC-Co inserts by reactive cathodic arc deposition. The microstructure of the y = 0.92 coating show that spinodal decomposition has occurred resulting in the formation of coherent c-TiN- and c-AIN rich domains during cutting. The y = 0.87 and y = 0.75 coatings have exhibited a delay in decomposition due to the presence of nitrogen vacancies that lowers the free energy of the system. In the decomposed structure, grain boundaries and misfit dislocations enhance the diffusion of elements from the workpiece and the substrate (e.g. Fe, Cr, and Co) into the coatings and it becomes more susceptible to crater wear. The y = 0.87 sample displays the highest crater wear resistance because of its dense grain boundaries that prevent chemical wear. The y = 0.92 sample has the best flank wear resistance because the decomposition results in age hardening. The y = 0.75 sample contains the MAX-phase Ti(2)AIN after cutting. The chemical alteration within the y = 0.75 sample and its high amount of macroparticles cause its low wear resistance. The different microstructure evolution caused by different amount of N-vacancies result in distinctive interactions between chip and coating, which also causes difference in the initial wear mechanism of the (Ti,Al)/N-y coatings.

  • 17.
    Chen, Zhe
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Surface Integrity and Fatigue Performance of Nickel-based Superalloys2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Due to global warming, the demand for more efficient gas turbines has increased. A way to achieve this, is by increasing the operating temperature of the gas turbine. Therefore, nickel-based superalloys have been developed to withstand these extreme temperatures and loads, especially in the hot sections. Today, the way of operating land-based gas turbines is changing. Instead of running for long periods of time, the operation is becoming more flexible, with ever-increasing cyclic loads and number of start and stop cycles. To handle the increased stress and cycles, component resistance to fatigue failures need to be improved.

    Surface integrity is critical to fatigue performance, since fatigue cracks normally initiate at a surface. Machining changes the surface integrity which can result in worse fatigue resistance. The work presented in this Ph.D. thesis was conducted in collaboration with Siemens Industrial Turbomachinery AB in Finspång, Sweden. Surface integrity changes which are induced during machining and their effects on fatigue performance have been studied on the alloy Inconel 718. Inconel 718 is a widely-used nickel-based superalloy for high temperature applications in modern gas turbines.

    Broaching, milling, and wire electrical discharge machining, related to component manufacturing in turbo machinery industries, were included in this study. Machining induced surface defects provide preferential sites for fatigue crack initiation which influence the fatigue performance of the alloy. If compressive residual stresses are induced during machining, they benefit the fatigue life by retarding fatigue crack initiation away from surface regions. Shot peening was performed on machined Inconel 718, by which high compressive residual stresses are deliberately induced. It results in enhanced fatigue performance.

    The high temperatures in gas turbines generally deteriorate the surface integrity. Recrystallization often occurs in the highly deformed surface layer. Microstructural degradation, in the form of α-Cr precipitates, have also been frequently observed in the deformed surface and sub-surface microstructure. Oxidation at elevated temperatures degrades the surface integrity and thereby also the fatigue performance. Fatigue cracks are preferably initiated at oxidized surface carbides, if thermal exposure has been made prior to the test. It is even worse when high temperatures relax the beneficial surface compression induced by shot-peening and thereby lowering the fatigue resistance.

    Machinability of a newly developed nickel-based superalloy, AD 730TM, and the surface integrity induced during turning have also been studied in this thesis project. AD 730TM is a candidate for turbine disc applications with an operating temperature above 650 °C. At such high temperatures, Inconel 718 is no longer stable and its mechanical properties start to degrade.

    To summarize, the results from this thesis work show the importance of understanding surface integrity effects for fatigue applications, especially in harsh environments. Moreover, the knowledge gained through this work could be used for surface enhancement of turbine components which are subjected to a high risk of fatigue failure. These will contribute to more efficient and flexible power generation by gas turbines.

    List of papers
    1. Surface Integrity and Structural Stability of Broached Inconel 718 at High Temperatures
    Open this publication in new window or tab >>Surface Integrity and Structural Stability of Broached Inconel 718 at High Temperatures
    Show others...
    2016 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 47A, no 7, p. 3664-3676Article in journal (Refereed) Published
    Abstract [en]

    The current study focused on the surface integrity issues associated with broaching of Inconel 718 and the structural stability of the broached specimen at high temperatures, mainly involving the microstructural changes and residual stress relaxation. The broaching operation was performed using similar cutting conditions as that used in turbo machinery industries for machining fir-tree root fixings on turbine disks. Thermal exposure was conducted at 723 K, 823 K, and 923 K (450 A degrees C, 550 A degrees C, and 650 A degrees C) for 30, 300, and 3000 hours, respectively. Surface cavities and debris dragging, sub-surface cracks, high intensity of plastic deformation, as well as the generation of tensile residual stresses were identified to be the main issues in surface integrity for the broached Inconel 718. When a subsequent heating was applied, surface recrystallization and alpha-Cr precipitation occurred beneath the broached surface depending on the applied temperature and exposure time. The plastic deformation induced by the broaching is responsible for these microstructural changes. The surface tension was completely relaxed in a short time at the temperature where surface recrystallization occurred. The tensile layer on the sub-surface, however, exhibited a much higher resistance to the stress relief annealing. Oxidation is inevitable at high temperatures. The study found that the surface recrystallization could promote the local Cr diffusion on the broached surface.

    Place, publisher, year, edition, pages
    Springer, 2016
    Keywords
    Structural integrity, Broaching, Inconel 718, Plastic deformation, Residual stresses, Thermal exposure, Superalloy
    National Category
    Materials Engineering Other Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-111056 (URN)10.1007/s11661-016-3515-6 (DOI)000377434700041 ()
    Funder
    Linköpings universitet, 2009-00971
    Note

    The original title of this article when published in manuscript form was Structural integrity of broached Inconel 718 subjected to thermal exposure.

    Available from: 2014-10-06 Created: 2014-10-06 Last updated: 2018-02-27Bibliographically approved
    2. On the Conjoint Influence of Broaching and Heat Treatment on Bending Fatigue Behavior of Inconel 718
    Open this publication in new window or tab >>On the Conjoint Influence of Broaching and Heat Treatment on Bending Fatigue Behavior of Inconel 718
    Show others...
    2016 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 671, p. 158-169Article in journal (Refereed) Published
    Abstract [en]

    In this study, the conjoint effect of a broaching operation, similar to that used for machining fir-tree slots on turbine discs, and subsequent heat treatments at 550 °C and 650 °C on the fatigue performance and corresponding crack initiation behavior of forged Inconel 718 has been investigated. Four-point bending fatigue tests were conducted under load control on specimens of two groups, i.e. a polished group and a broached group, with totally six different surface conditions. Compared to the as-polished specimens, a beneficial effect of the broaching operation was found on the fatigue life due to the high compressive residual stresses on the broached surface which transfer the fatigue crack initiation from surface to sub-surface regions. Introducing a heat treatment generally deteriorated the fatigue performance of the alloy because of the oxidation assisted crack initiation, while the reduction in fatigue life was found to be more remarkable for the broached specimens, in particular when heat treated at 650 °C, as the thermal impact also led to a great relaxation of the compressive residual stresses; the combined effect, together with the substantial anomalies created by broaching on the surface, such as cracked carbides and machining grooves, caused an increased propensity to surface cracking in fatigue and consequently a loss of the lifetime. Furthermore, it was found that the occurrence of surface recrystallization at elevated temperatures in machined Inconel 718 could lead to intergranular oxidation, creating micro-notches as preferable sites for the fatigue crack initiation.

    Keywords
    Broaching, Inconel 718, Surface integrity, thermal impact, Fatigue, Crack initiation
    National Category
    Other Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-129843 (URN)10.1016/j.msea.2016.06.030 (DOI)000381165400016 ()
    Note

    Funding agencies: Faculty grant SFO-MAT-LiU at Linkoping University [2009-00971]; Siemens Industrial Turbomachinery AB

    Available from: 2016-06-29 Created: 2016-06-29 Last updated: 2017-11-28
    3. Nano-scale characterization of white layer in broached Inconel 718
    Open this publication in new window or tab >>Nano-scale characterization of white layer in broached Inconel 718
    Show others...
    2017 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 684, p. 373-384Article in journal (Refereed) Published
    Abstract [sv]

    The formation mechanism of white layers during broaching and their mechanical properties are not well investigated and understood to date. In the present study, multiple advanced characterization techniques with nano-scale resolution, including transmission electron microscopy (TEM), transmission Kikuchi diffraction (TKD), atom probe tomography (APT) as well as nano-indentation, have been used to systematically examine the microstructural evolution and corresponding mechanical properties of a surface white layer formed when broaching the nickel-based superalloy Inconel 718.

    TEM observations showed that the broached white layer consists of nano-sized grains, mostly in the range of 20–50 nm. The crystallographic texture detected by TKD further revealed that the refined microstructure is primarily caused by strong shear deformation. Co-located Al-rich and Nb-rich fine clusters have been identified by APT, which are most likely to be γ′ and γ′′ clusters in a form of co-precipitates, where the clusters showed elongated and aligned appearance associated with the severe shearing history. The microstructural characteristics and crystallography of the broached white layer suggest that it was essentially formed by adiabatic shear localization in which the dominant metallurgical process is rotational dynamic recrystallization based on mechanically-driven subgrain rotations. The grain refinement within the white layer led to an increase of the surface nano-hardness by 14% and a reduction in elastic modulus by nearly 10% compared to that of the bulk material. This is primarily due to the greatly increased volume fraction of grain boundaries, when the grain size was reduced down to the nanoscale.

    Place, publisher, year, edition, pages
    Amsterdam: Elsevier, 2017
    Keywords
    Surface integrity; White layer; Broaching; Inconel 718; Adiabatic shear band; Mechanically-based subgrain rotation
    National Category
    Materials Chemistry Inorganic Chemistry Other Materials Engineering Paper, Pulp and Fiber Technology Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-134123 (URN)10.1016/j.msea.2016.12.045 (DOI)000393938300045 ()
    Note

    Funding agencies: AForsk Foundation [15-334];  [2009-00971]

    Available from: 2017-01-24 Created: 2017-01-24 Last updated: 2017-11-29Bibliographically approved
    4. Surface Integrity and Fatigue Performance of Inconel 718 in Wire Electrical Discharge Machining
    Open this publication in new window or tab >>Surface Integrity and Fatigue Performance of Inconel 718 in Wire Electrical Discharge Machining
    2016 (English)In: 3RD CIRP CONFERENCE ON SURFACE INTEGRITY, 2016, Vol. 45, p. 307-310Conference paper, Published paper (Refereed)
    Abstract [en]

    This paper presents a study to characterize the surface integrity in wire electrical discharge machining (EDM) of Inconel 718 and investigate its effect on the fatigue performance of the alloy in a four-point bending fatigue mode at room temperature. The EDM process generates a rough recast surface with multi-types of defects. Surface craters, micro-cracks and micro-voids within the recast layer have been found to be most detrimental from the point of view of fatigue as they could provide many preferential initiation sites for fatigue cracks. As a consequence, the specimens with an EDM cut surface show an approximately 30% decrease in fatigue life compared to those with a polished surface, and multiple crack origins were observed on the fracture surface. The high tensile residual stresses generated on the EDM cut surface, on the other hand, are also believed to be partly responsible for the loss in fatigue life of the alloy machined by EDM.

    Series
    Procedia CIRP, ISSN 2212-8271
    Keywords
    wire electrical discharge machining (wire EDM), surface integrity, fatigue, crack initiation, Inconel 718
    National Category
    Materials Engineering Other Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-130582 (URN)10.1016/j.procir.2016.02.053 (DOI)000417326500077 ()
    Conference
    3rd CIRP Conference on Surface Integrity (CIRP CSI)8-10 June, 2016, Charlotte, USA
    Note

    Funding agencies: Siemens Industrial Turbomachinery AB; Strategic Faculty Grant AFM at Linkoping University

    Available from: 2016-08-17 Created: 2016-08-17 Last updated: 2018-03-28
    5. Effect of Cooling and Shot Peening on Residual Stresses and Fatigue Performance of Milled Inconel 718
    Open this publication in new window or tab >>Effect of Cooling and Shot Peening on Residual Stresses and Fatigue Performance of Milled Inconel 718
    Show others...
    2017 (English)In: Residual Stresses 2016 ICRS 10 / [ed] T.M. Holden, O. Muránsky, and L. Edwards, 2017, Vol. 2, p. 13-18Conference paper, Published paper (Refereed)
    Abstract [en]

    The present study highlights the effect of cooling and post-machining surface treatment of shot peening on the residual stresses and corresponding fatigue life of milled superalloy Inconel 718. It was found that tensile residual stresses were created on the milled surface, regardless of the use of coolant, however, the wet milling operation led to a lower surface tension and a reduced thickness of the tensile layer. The shot peening performed on the dry-milled specimens completely annihilated the surface tensile residual tresses and introduced a high level of surface compression. A comparable fatigue life for the wet-milled specimens was obtained as compared with the specimens prepared by dry milling. This is very likely attributed to that the milling-induced surface damage with respect to cracked non-metallic inclusions is the predominant cause of the fatigue failure. The presence of the compressive layer induced by shot peening resulted in a significant increase of the fatigue life and strength, while the extent to which the lifetime was prolonged was decreased as the applied load was increased.

    Series
    Materials Research Proceedings, ISSN 2474-395X
    Keywords
    Residual stresses, surface integrity, milling, shot peening, superalloys, fatigue
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-132001 (URN)10.21741/9781945291173-3 (DOI)000401041500003 ()978-1-9452-9116-6 (ISBN)
    Conference
    10th International Conference on Residual Stresses ICRS-10, Sydney, Australia, 3-8 July 2016
    Note

    Funding agencies: Linkoping University [2009-00971]; Ytstruktur Arboga AB; Siemens Industrial Turbomachinery AB

    Available from: 2016-10-13 Created: 2016-10-13 Last updated: 2017-06-13Bibliographically approved
  • 18.
    Dalibon, Eugenia L.
    et al.
    University of Tecnol Nacl UTN FRCU, Argentina.
    Ghafoor, Naureen
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rogström, Lina
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Trava-Airoldi, Vladimir J.
    INPE, Brazil.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Bruhl, Sonia P.
    University of Tecnol Nacl UTN FRCU, Argentina.
    Carbon Based Coatings Deposited on Nitrided Stainless Steel: Study of Thermal Degradation2017In: PROCEEDINGS OF THE 3RD PAN AMERICAN MATERIALS CONGRESS, SPRINGER INTERNATIONAL PUBLISHING AG , 2017, p. 57-66Conference paper (Refereed)
    Abstract [en]

    Amorphous hydrogenated carbon (DLC) coatings have a high hardness depending on the relative amount of sp(3)/sp(2) bondings. They also exhibit an extremely low friction coefficient and are chemically inert. However, these coatings have some disadvantages which limit their applications. For instance, adhesion is poor when they are deposited on metallic substrates and they are also unstable at high temperatures, degrading into graphite and loosing hardness. In this work, DLC coatings were deposited on precipitation hardening stainless steel (PH Corrax) which was plasma nitrided before the coating deposition. The samples were submitted to annealing treatments for an hour at different temperatures from 200 to 600 degrees C, together with a control group, which was only coated but not nitrided. After each annealing cycle, Raman Spectroscopy, nanoindentation and microscopy were used to check film properties. It was demonstrated that the nitriding pre treatment improved not only adhesion but also the thermal stability of the DLC, slowing degradation and preventing delamination.

  • 19.
    Deng, Dunyong
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Additively Manufactured Inconel 718: Microstructures and Mechanical Properties2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Additive manufacturing (AM), also known as 3D printing, has gained significant interest in aerospace, energy, automotive and medical industries due to its capabilities of manufacturing components that are either prohibitively costly or impossible to manufacture by conventional processes. Among the various additive manufacturing processes for metallic components, electron beam melting (EBM) and selective laser melting (SLM) are two of the most widely used powder bed based processes, and have shown great potential for manufacturing high-end critical components, such as turbine blades and customized medical implants. The futures of the EBM and SLM are doubtlessly promising, but to fully realize their potentials there are still many challenges to overcome.

    Inconel 718 (IN718) is a nickel-base superalloy and has impressive combination of good mechanical properties and low cost. Though IN718 is being mostly used as a turbine disk material now, the initial introduction of IN718 was to overcome the poor weldability of superalloys in 1960s, since sluggish precipitation of strengthening phases λ’/λ’’ enables good resistance to strain-age cracking during welding or post weld heat treatment. Given the similarity between AM and welding processes, IN718 has been widely applied to the metallic AM field to facilitate the understandings of process-microstructure-property relationships.

    The work presented in this licentiate thesis aims to better understand microstructures and mechanical properties EBM and SLM IN718, which have not been systematically investigated. Microstructures of EBM and SLM IN718 have been characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and correlated with the process conditions. Monotonic mechanical properties (e.g., Vickers microhardness and tensile properties) have also been measured and rationalized with regards to the microstructure evolutions before and after heat treatments.

    For EBM IN718, the results show the microstructure is not homogeneous but dependant on the location in the components, and the anisotropic mechanical properties are probably attributed to alignment of porosities rather than texture. Post heat treatment can slightly increase the mechanical strength compared to the as-manufactured condition but does not alter the anisotropy. SLM IN718 shows significantly different microstructure and mechanical properties to EBM IN718. The as-manufactured SLM IN718 has very fine dendritic microstructure and Laves phases in the interdendrites, and is “work-hardened” by the residual strains and dislocations present in the material. Mechanical properties are different between horizontally and vertically built samples, and heat treatment can minimize this difference. Results from this licentiate thesis provide the basis for the further research on the cyclic mechanical properties of EBM and SLM IN718, which would be the focus of following phase of the Ph.D. research.

    List of papers
    1. Microstructure and Anisotropic Mechanical Properties of EBM Manufactued Inconel 718 and Effects of Post Heat Treatment
    Open this publication in new window or tab >>Microstructure and Anisotropic Mechanical Properties of EBM Manufactued Inconel 718 and Effects of Post Heat Treatment
    2017 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 693, p. 151-163Article in journal (Refereed) Published
    Abstract [en]

    Materials manufactured with electron beam melting (EBM) have different microstructures and properties to those manufactured using conventional manufacturing methods. A detailed study of the microstructures and mechanical properties of Inconel 718 manufactured with EBM was performed in both as-manufactured and heat-treated conditions. Different scanning strategies resulted in different microstructures: contour scanning led to heterogeneous grain morphologies and weak texture, while hatch scanning resulted in predominantly columnar grains and strong 〈001〉 building direction texture. Precipitates in the as-manufactured condition included γ′, γ″, δ  , TiN and NbC, among which considerable amounts of γ″ yielded relatively high hardness and strength. Strong texture, directionally aligned pores and columnar grains can lead to anisotropic mechanical properties when loaded in different directions. Heat treatments increased the strength and led to different δ precipitation behaviours depending on the solution temperatures, but did not remove the anisotropy. Ductility seemed to be not significantly affected by heat treatment, but instead by the NbC and defects inherited from manufacturing. The study thereby might provide the potential processing windows to tailor the microstructure and mechanical properties of EBM IN718.

    Place, publisher, year, edition, pages
    Elsevier, 2017
    Keywords
    Electron beam melting; Nickel based superalloy; Microstructure; Anisotropy; Mechanical properties; Heat treatments
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-137289 (URN)10.1016/j.msea.2017.03.085 (DOI)000401384400018 ()2-s2.0-85016252903 (Scopus ID)
    Note

    Funding agencies: Sandvik Machining Solutions AB in Sandviken, Sweden; Faculty Grant SFO-MAT-LiU at Linkoping University [2009-00971]; Chinese Scholarship Council; Agora Materiae

    Available from: 2017-05-10 Created: 2017-05-10 Last updated: 2018-01-24Bibliographically approved
  • 20.
    Deng, Dunyong
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Soderberg, Hans
    Sandvik Machining Solut AB, Sweden.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    On the formation of microstructural gradients in a nickel-base superalloy during electron beam melting2018In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 160, p. 251-261Article in journal (Refereed)
    Abstract [en]

    Electron beam melting (EBM) is one of the most widely used additive manufacturing (AM) methods for metallic components and has demonstrated great potential to fabricate high-end components in the aerospace and energy industries. The thermal condition within a melt pool and the complicated thermal cycles during the EBM process are of interest but not yet well-understood, and will significantly affect the microstructural homogeneity of as-manufactured nickel-base superalloy components. To establish the thermal profile evolution during electron beam melting of nickel-base superalloys, Inconel 718 (IN718) is manufactured and characterized in the as-manufactured condition, on account of its representative segregation and precipitation behaviours. The microstructure gradient within a build, specifically the Laves phase volume fraction evolution, is rationalized with the solidification condition and the following in-situ annealing. Precipitations of carbide/nitride/carbonitride, delta and gamma/gamma are also discussed. Hardness is measured and correlated to the Laves phase volume fraction evolution and the precipitation of gamma/gamma . The results of this study will (i) shed light on microstructure evolution during the EBM process with regard to thermal history; and (ii) deepen the current understandings of solidification metallurgy for additive manufacturing of Ni-base superalloys. (C) 2018 Elsevier Ltd. All rights reserved.

  • 21.
    Eklund, Edvin
    Linköping University, Department of Management and Engineering, Carl Malmsten - furniture studies. Linköping University, The Institute of Technology.
    Brännskuggat fanér - en metodanalys2013Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    This thesis is about a part of the marquetrytechnique, scorching. Scorching is made by heating up something, put a veneer into the heated substance and make a controlled burning. This technique is old but still used today and have according to me great potential for development. In my work I wanted to give the scorching greater room then I earlier have seen. I wanted the scorching to be the dominant ingredient for a decorative element in a piece of furniture or an interior. This, I believe, is one way of making the art of marquetry more modern.

     

    In my report I have written about the history of scorching, both in terms of how often the technique has been used throughout history, but also for its development during time. This part of the thesis is mainly based upon studies of literature and some interviews.

     

    The biggest part of the thesis tries to consolidate a method for how to achieve a successful scorching. The criterion for successful is an equal gradient, repeatability and controlled length for the scorching. I have mainly experimented with exposuretime, exposuretemperature and different substances to heat up. During this experiments I have tried to define the best way to work. Several different woodspieces have been used but I have mainly worked with veneer of birch. During my work I have also tested to achieve new esthetical looks still mainly using the same technique. Changing materials to heat up and changing the way of applying the veneer. These parts of the thesis is based on empirical studies and with the report there are some physical samples describing my results.

  • 22.
    Eriksen, Emmeli
    Linköping University, Department of Mechanical Engineering.
    Tre som materiale i smykker2006Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [nb]

    Sammendrag

    I mitt eksamensarbeid ved Malmstens CTD, Linköpings Universitet, har jeg forsøkt å beskrive en prosess fra ide til ferdig produkt. Tanken bak har vært å fremheve treverk i et produkt som historisk sett er preget av edle metaller. Ved å formgi et smykke i tre, er målet å få treverkets skjønnhet og eleganse frem i produktet og gi det et personlig preg. Arbeidsprosessen er inndelt i etapper, hver etappe er beskrevet og analysert i rapporten.

    Gjennom en inspirasjonsreise til Liv Blåvarp, en norsk smykkekunstner, har jeg fått innsikt i hva produksjon av smykker i tre kan innebære. Hennes arbeid har vært min viktigste inspirasjonskilde. Mitt formprosjekt ønsket jeg skulle resultere i et smykke som kan produseres i mindre nummererte serier, med størrelse tilpasset ”normalen” og uttrykksmessig kunne fremheve følelser fra våre fire årstider.

    Skisseetappen resulterte i tre armbånd. I rapporten er produksjonen av disse tre prototypene beskrevet med tekst og bilder.

    I smykkene har treverkets fremtoning fått mye plass. Jeg har valgt å beholde de naturlige trefargene og bruke dem bevisst. Kommentarer fra venner og kjente ble: Hvordan kan det bli så glatt og hvordan blir det slike mønster? Når interessen melder seg på denne måten har jeg oppnådd litt av mitt mål, de blir overrasket over tre som materiale på en positiv måte.

    Jeg har funderinger på utformingen av smykkene. De kan utvikles og bli bedre både i form og produksjonsvennlighet. Samtidig er jeg relativt fornøyd med resultatet, det er armbånd som fremhever treverket, de er lette og ledige på armen og gir bærer en følelse av egenhet og en viss verdighet. Treverk gir et varmt og vennlig uttrykk som hjelper den personlige karakteren frem. Armbåndene kan produseres med ulik indre diameter med enkle endringer, som gjør det mulig å tilpasse ”normalen”. Jeg har valgt ut hvilke årstider jeg synes fremhever formen på mine prototypener, men det var for optimistisk å regne med at folk flest funderte på sinnestemningen rundt årstid og utsmykning. Jeg kan håpe at det like vel ubevisst fører til å forsterke kroppspråk og utstråling.

  • 23.
    Eriksson, Robert
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Chen, Zhe
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Jonnalagadda, Krisha Praveen
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    BENDING FATIGUE OF THERMAL BARRIER COATINGS2017In: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2017, VOL 6, AMER SOC MECHANICAL ENGINEERS , 2017, article id V006T24A004Conference paper (Refereed)
    Abstract [en]

    Thermal barrier coatings (TBCs) are ceramic coatings used in gas turbines to lower the base metal temperature. During operation, the TBC may fail through, for example, fatigue. In the present study, a TBC system deposited on a Ni-base alloy was tested in tensile bending fatigue. The TBC system was tested as-sprayed and oxidized and two load levels were used. After interrupting the tests, at 10000-50000 cycles, the TBC tested at the lower load had extensive delamination damage whereas the TBC tested at the higher load was relatively undamaged. At the higher load, the TBC formed vertical cracks which relieved the stresses in the TBC and retarded delamination damage. A finite element analysis was used to establish a likely vertical crack configuration (spacing and depth) and it could be confirmed that the corresponding stress drop in the TBC should prohibit delamination damage at the higher load.

  • 24.
    Eriksson, Robert
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Jonnalagadda, Krisha Praveen
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    A STUDY ON CRACK CONFIGURATIONS IN THERMAL BARRIER COATINGS2017In: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2017, VOL 6, AMER SOC MECHANICAL ENGINEERS , 2017, article id V006T24A005Conference paper (Refereed)
    Abstract [en]

    Spallation of thermal barrier coatings subjected to thermal fatigue occurs through cracking in or close to the metal ceramic interface. To better match an experimentally observed damage progression curve with initially slow crack growth followed by rapid crack growth, a multitude of crack paths were modeled in a finite element analysis. Comparisons with experimental data enabled the most likely crack path to be identified. It was shown that the most likely failure type for the studied TBC system was crack initiation from pre-existing defects in the thermal barrier coating which propagated into the interface, leading to spallation. The results were used to fit a crack propagation model.

  • 25.
    Eriksson, Robert
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Arts and Sciences.
    Torstenfelt, Bo
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Klarbring, Anders
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    OPTIMIZING THERMAL BARRIER COATING DESIGN USING STRUCTURAL OPTIMIZATION METHODS2017In: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2017, VOL 6, AMER SOC MECHANICAL ENGINEERS , 2017, article id V006T24A003Conference paper (Refereed)
    Abstract [en]

    Thermal barrier coatings (TBCs) are used in gas turbines to reduce creep, thermo-mechanical fatigue, and oxidation, or to allow for reduced air cooling. TBCs may fail due to fatigue. Structural optimization methods were applied to optimize the. TBC thickness in such a way as to increase the life of the TBC. The TBC thickness was varied for three cases: 1) minimizing TBC volume, 2) minimizing TBC maximum effective stress, and 3) minimizing compliance (minimizing the strain energy). The results from the optimization were used to estimate the relative change in TBC life via a strain energy based failure criterion and a Coffin-Manson-like expression. Minimization of volume had limited use due to limitations in the current implementation. Minimization of effective stress did not give any significant increase in life. The minimization of compliance increased the estimated TBC life at highly stressed regions.

  • 26.
    Escalera, Edwin
    et al.
    Division of Materials Science, Luleå University of Technology.
    Antti, M.
    Division of Materials Science, Luleå University of Technology.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Thermal treatment and phase formation in kaolinite and illite based clays from tropical regions of Bolivia2012Conference paper (Refereed)
    Abstract [en]

    The aim of this study was to compare the thermal behaviour of clays containing illite and kaolinite in various proportions. The clays contained small amounts of K and Fe, which act as fluxing agents. In order to investigate the phase formations during heating, the samples were examined in a differential scanning calorimeter at temperatures up to 1300°C. The thermal expansion of the samples was determined by dilatometer measurements from room temperature up to 1150°C. Phases were identified using x-ray diffraction and scanning electron microscopy.

    In all samples, most of the kaolinite was transformed into metakaolinite during heating up to 650°C, while illite remained unchanged up to 950°C. There was no influence of K and Fe on dehydroxylation. Metakaolinite formed at temperatures above 950°C leading to a Si-Al spinel. Furthermore, mullite was formed in the temperature interval 1050-1150°C. In this temperature range, the mechanism of mullite formation depended on the amount of K and Fe in the samples, changing the temperature of formation of mullite. It was observed by x-ray diffraction that most of the illite was transformed into a Si-Al spinel phase at 1050°C, and during further heating transformed into mullite. An increased amount of illite in the clays slightly decreased the melting temperature. The dilatometer measurements showed expansion and shrinkage for the dehydroxylation and spinel-phase formation, respectively.

  • 27.
    Fager, Hanna
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Tengstrand, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Bolz, S.
    CemeCon AG, Germany.
    Mesic, B.
    CemeCon AG, Germany.
    Koelker, W.
    CemeCon AG, Germany.
    Schiffers, Ch.
    CemeCon AG, Germany.
    Lemmer, O.
    CemeCon AG, Germany.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Low-temperature growth of dense and hard Ti0.41Al0.51Ta0.08N films via hybrid HIPIMS/DC magnetron co-sputtering with synchronized metal-ion irradiation2017In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 121, no 17, article id 171902Article in journal (Refereed)
    Abstract [en]

    Hard Ti1-xAlxN thin films are of importance for metal-cutting applications. The hardness, thermal stability, and oxidation resistance of these coatings can be further enhanced by alloying with TaN. We use a hybrid high-power pulsed and dc magnetron co-sputtering (HIPIMS/DCMS) technique to grow dense and hard Ti0.41Al0.51Ta0.08N alloys without external heating (T-s amp;lt; 150 degrees C). Separate Ti and Al targets operating in the DCMS mode maintain a deposition rate of similar to 50 nm/min, while irradiation of the growing film by heavy Ta+/Ta2+ ions from the HIPIMS-powered Ta target, using dc bias synchronized to the metal-ion-rich part of each HIPIMS pulse, provides effective near-surface atomic mixing resulting in densification. The substrate is maintained at floating potential between the short bias pulses to minimize Ar+ bombardment, which typically leads to high compressive stress. Transmission and scanning electron microscopy analyses reveal dramatic differences in the microstructure of the co-sputtered HIPIMS/DCMS films (Ta-HIPIMS) compared to films with the same composition grown at floating potential with all targets in the DCMS mode (Ta-DCMS). The Ta-DCMS alloy films are only similar to 70% dense due to both inter-and intra-columnar porosity. In contrast, the Ta-HIPIMS layers exhibit no inter-columnar porosity and are essentially fully dense. The mechanical properties of Ta-HIPIMS films are significantly improved with hardness and elastic modulus values of 28.0 and 328 GPa compared to 15.3 and 289 GPa for reference Ta-DCMS films. Published by AIP Publishing.

  • 28.
    Filho, Luimar
    et al.
    Uppsala Univ, Sweden.
    Schmidt, Susann
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. IHI Ionbond AG, Switzerland.
    Leifer, Klaus
    Uppsala Univ, Sweden.
    Engqvist, Hakan
    Uppsala Univ, Sweden.
    Högberg, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Persson, Cecilia
    Uppsala Univ, Sweden.
    Towards Functional Silicon Nitride Coatings for Joint Replacements2019In: Coatings, ISSN 2079-6412, Vol. 9, no 2, article id 73Article in journal (Refereed)
    Abstract [en]

    Silicon nitride (SiNx) coatings are currently under investigation as bearing surfaces for joint implants, due to their low wear rate and the good biocompatibility of both coatings and their potential wear debris. The aim of this study was to move further towards functional SiNx coatings by evaluating coatings deposited onto CoCrMo surfaces with a CrN interlayer, using different bias voltages and substrate rotations. Reactive direct current magnetron sputtering was used to coat CoCrMo discs with a CrN interlayer, followed by a SiNx top layer, which was deposited by reactive high-power impulse magnetron sputtering. The interlayer was deposited using negative bias voltages ranging between 100 and 900 V, and 1-fold or 3-fold substrate rotation. Scanning electron microscopy showed a dependence of coating morphology on substrate rotation. The N/Si ratio ranged from 1.10 to 1.25, as evaluated by X-ray photoelectron spectroscopy. Vertical scanning interferometry revealed that the coated, unpolished samples had a low average surface roughness between 16 and 33 nm. Rockwell indentations showed improved coating adhesion when a low bias voltage of 100 V was used to deposit the CrN interlayer. Wear tests performed in a reciprocating manner against Si3N4 balls showed specific wear rates lower than, or similar to that of CoCrMo. The study suggests that low negative bias voltages may contribute to a better performance of SiNx coatings in terms of adhesion. The low wear rates found in the current study support further development of silicon nitride-based coatings towards clinical application.

  • 29.
    Gharavi, Mohammad Amin
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Nitride Thin Films for Thermoelectric Applications: Synthesis, Characterization and Theoretical Predictions2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Thermoelectrics is the reversible process which transforms a temperature gradient across a material into an external voltage through a phenomenon known as the Seebeck effect. This has resulted in niche applications such as solid-state cooling for electronic and optoelectronic devices which exclude the need for a coolant or any moving parts and long-lasting, maintenance-free radioisotope thermoelectric generators used for deep-space exploration. However, the high price and low efficiency of thermoelectric generators have prompted scientists to search for new materials and/or methods to improve the efficiency of the already existing ones. Thermoelectric efficiency is governed by the dimensionless figure of merit 𝑧𝑇, which depends on the electrical conductivity, thermal conductivity and Seebeck coefficient value of the material and has rarely surpassed unity.

    In order to address these issues, research conducted on early transition metal nitrides spearheaded by cubic scandium nitride (ScN) thin films showed promising results with high power factors close to 3000 μWm−1K−2 at 500 °C. In this thesis, rock-salt cubic chromium nitride (CrN) deposited in the form of thin films by reactive magnetron sputtering was chosen for its large Seebeck coefficient of approximately -200 μV/K and low thermal conductivity between 2 and 4 Wm−1K−1. The results show that CrN in single crystal form has a low electrical resistivity below 1 mΩcm, a Seebeck coefficient value of -230 μV/K and a power factor close to 5000 μWm−1K−2 at room temperature. These promising results could lead to CrN based thermoelectric modules which are cheaper and more stable compared to traditional thermoelectric material such as bismuth telluride (Bi2Te3) and lead telluride (PbTe).

    In addition, the project resulting this thesis was prompted to investigate prospective ternary nitrides equivalent to ScN with (hopefully) better thermoelectric properties. Scandium nitride has a relatively high thermal conductivity value (close to 10 Wm−1K−1), resulting in a low 𝑧𝑇. A hypothetical ternary equivalent to ScN may have a similar electronic band structure and large power factor, but with a lower thermal conductivity value leading to better thermoelectric properties. Thus the elements magnesium, titanium, zirconium and hafnium were chosen for this purpose. DFT calculations were used to simulate TiMgN2, ZrMgN2 and HfMgN2. The results show the MeMgN2 stoichiometry to be stable, with two rivaling crystal structures: trigonal NaCrS2 and monoclinic LiUN2.

  • 30.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Rhein Westfal TH Aachen, Germany.
    Mraz, S.
    Rhein Westfal TH Aachen, Germany.
    Hans, M.
    Rhein Westfal TH Aachen, Germany.
    Primetzhofer, D.
    Uppsala University, Sweden.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Schneider, J. M.
    Rhein Westfal TH Aachen, Germany.
    Unprecedented Al supersaturation in single-phase rock salt structure VAlN films by Al+ subplantation2017In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 121, no 17, article id 171907Article in journal (Refereed)
    Abstract [en]

    Modern applications of refractory ceramic thin films, predominantly as wear-protective coatings on cutting tools and on components utilized in automotive engines, require a combination of excellent mechanical properties, thermal stability, and oxidation resistance. Conventional design approaches for transition metal nitride coatings with improved thermal and chemical stability are based on alloying with Al. It is well known that the solubility of Al in NaCl-structure transition metal nitrides is limited. Hence, the great challenge is to increase the Al concentration substantially while avoiding precipitation of the thermodynamically favored wurtzite-AlN phase, which is detrimental to mechanical properties. Here, we use VAlN as a model system to illustrate a new concept for the synthesis of metastable single-phase NaCl-structure thin films with the Al content far beyond solubility limits obtained with conventional plasma processes. This supersaturation is achieved by separating the film-forming species in time and energy domains through synchronization of the 70-mu s-long pulsed substrate bias with intense periodic fluxes of energetic Al+ metal ions during reactive hybrid high power impulse magnetron sputtering of the Al target and direct current magnetron sputtering of the V target in the Ar/N-2 gas mixture. Hereby, Al is subplanted into the cubic VN grains formed by the continuous flux of low-energy V neutrals. We show that Al subplantation enables an unprecedented 42% increase in metastable Al solubility limit in V1-xAlxN, from x-0.52 obtained with the conventional method to 0.75. The elastic modulus is 325 +/- 5GPa, in excellent agreement with density functional theory calculations, and approximately 50% higher than for corresponding films grown by dc magnetron sputtering. The extension of the presented strategy to other Al-ion-assisted vapor deposition methods or materials systems is straightforward, which opens up the way for producing supersaturated single-phase functional ceramic alloy thin films combining excellent mechanical properties with high oxidation resistance. Published by AIP Publishing.

  • 31.
    Greek, Julia
    Linköping University, Department of Management and Engineering, Carl Malmsten - furniture studies.
    Komplexa parkettläggningar: Undersökning av metoder för repetitiva parkettläggningar2016Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    This bachelor’s thesis begins in the journeyman piece I made during my third and final year at Carl Malmsten Furniture Studies. I examine different methods that can be used to produce a complex parquet installation. And how do the methods compare when it comes to time consumption, cost, material consumption and aesthetic expression?

    Practically, I examine three methods: CNC milling, laser cutting and hand held milling.

    The goal of my thesis is to develop useful knowledge which provides guidance for the production of complex parquet installations.

    The result is in addition to experience and knowledge, swatches of the techniques I investigated, and products that show how you can use parquet installations in practice.

    Laser cutting provides the most consistent results, and is most rational to manufacture, despite a high investment cost.

  • 32. Grossmann, Birgit
    et al.
    Jamnig, Andreas
    Schalk, Nina
    Czettl, Christoph
    Pohler, Markus
    Mitterer, Christian
    Tailoring age hardening of Ti1-xAlxN by Ta alloying2017In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 35, no 060604Article in journal (Refereed)
    Abstract [en]

    The microstructure, mechanical properties, and thermal stability of arc evaporated Ti1-x-yAlxTayN hard coatings were systematically investigated by varying the Ta content in the range of 0<y<0.231. A combination of differential scanning calorimetry and vacuum annealing up to 1500°C with subsequent x-ray diffraction analysis and nanoindentation measurements provided comprehensive insight into the microstructural evolution of the coatings and the resulting impact on their mechanical properties. With the addition of Ta to the metastable Ti1-xAlxN solid solution, spinodal decomposition and wurtzite phase formation are shifted to higher temperatures. Consequently,the temperature range where Ta-alloyed coatings maintain their hardness is extended up to 1000°C.

  • 33.
    Gunnarsson Sarius, Niklas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Leisner, Peter
    SP Technical Research Institute of Sweden, Box 857, 501 15 Borås, Sweden/School of Engineering, Jönköping University, Sweden.
    Hald, J.
    ENKOTEC A/S, Denmark.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Electroplating of nickel in grooves under the influence of low and medium frequency ultrasound2011In: Journal for Electrochemistry and Plating Technology, ISSN 1866-7406, Vol. 1, no 3, p. 19-28Article in journal (Refereed)
    Abstract [en]

    The effect of ultrasonics on filling properties has been studied by Ni electroplating from a sulphamate electrolyte in high aspect ratio grooves. The experiments have been performed with two different modes of ultrasound: a) 25 kHz ultrasound with an effect of 225 W directed perpendicular to the substrate surface; b) ultrasonic standing waves of 100 kHz and 400 kHz parallel to the substrate surface. It was found that both methods improve the filling in grooves that are between 0.35 and 1 mm wide with aspect ratios between 0.6 and 3, compared to electroplating with conventional agitation. Under the investigated conditions the 400 kHz standing wave parallel to the surface was most efficient to improve filling of grooves.

  • 34.
    Gupta, Mohit
    et al.
    University of West, Sweden.
    Markocsan, Nicolaie
    University of West, Sweden.
    Li, Xin-Hai
    Siemens Ind Turbomachinery AB, Sweden.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Improving the lifetime of suspension plasma sprayed thermal barrier coatings2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 332, p. 550-559Article in journal (Refereed)
    Abstract [en]

    Development of thermal barrier coating systems (TBCs) for gas turbine applications allowing higher combustion temperatures is of high interest since it results in higher fuel efficiency and lower emissions. TBCs produced by suspension plasma spraying (SPS) have been shown to exhibit significantly lower thermal conductivity as compared to conventional systems due to their very fine porosity microstructure. However they have not been commercialised yet due to low reliability and life expectancy of the coatings. In addition to the initial topcoat microstructure and its sintering resistance, lifetime of a TBC system is highly dependent on bondcoat chemistry as it influences the growth rate of thermally grown oxide (TGO) layer. To enhance the lifetime of SPS TBCs, fundamental understanding of relationships between topcoat microstructure and its evolution with time, bondcoat chemistry, TGO growth rate, and lifetime is essential. The objective of this work was to study the effect of topcoat microstructure evolution and TGO growth rate on lifetime in SPS TBC systems. Experimental MCrAIY bondcoat powders with different aluminium activities were investigated and compared to a commercial bondcoat powder. High velocity air fuel spraying was used for bondcoat deposition while axial-SPS was used for yttria stabilized zirconia topcoat deposition. Lifetime was examined by thermal cyclic fatigue testing. Isothermal heat treatment was performed to study TGO evolution with time. The changes in microstructure of SPS coatings due to sintering under long term exposure at high temperatures were investigated. Different failure modes in SPS TBCs were also examined. The bondcoat with higher aluminium activity resulted in a significantly higher thermal cyclic lifetime of the corresponding TBC as it could have promoted protective alumina layer growth for a longer period of time. The results indicate that the significant changes in topcoat microstructure due to sintering as observed in this work could have a detrimental effect on TBC lifetime.

  • 35.
    Halim, Joseph
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Drexel University, PA 19104 USA; Drexel University, PA 19104 USA.
    Cook, Kevin M.
    Naval Air Syst Command, MD 20670 USA.
    Naguib, Michael
    Oak Ridge National Lab, TN 37831 USA.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Gogotsi, Yury
    Drexel University, PA 19104 USA; Drexel University, PA 19104 USA.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Barsoum, Michel
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Department of Materials Science & Engineering, Drexel University, Philadelphia, PA 19104, USA.
    X-ray photoelectron spectroscopy of select multi-layered transition metal carbides (MXenes)2016In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 362, p. 406-417Article in journal (Refereed)
    Abstract [en]

    In this work, a detailed high resolution X-ray photoelectron spectroscopy (XPS) analysis is presented for select MXenes a recently discovered family of two-dimensional (2D) carbides and carbonitrides. Given their 2D nature, understanding their surface chemistry is paramount. Herein we identify and quantify the surface groups present before, and after, sputter-cleaning as well as freshly prepared vs. aged multi layered cold pressed discs. The nominal compositions of the MXenes studied here are Ti-3 C2Tx,Ti3CNTx, Nb2CTx and Nb4C3Tx where T represents surface groups that this work attempts to quantify. In all the cases, the presence of three surface terminations, O, OH and F, in addition to OH-terminations relatively strongly bonded to H2O molecules, was confirmed. From XPS peak fits, it was possible to establish the average sum of the negative charges of the terminations for the aforementioned MXenes. Based on this work, it is now possible to quantify the nature of the surface terminations. This information can, in turn, be used to better design and tailor these novel 2D materials for various applications. Published by Elsevier B.V.

  • 36.
    Haraldsson, Joakim
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Johansson, Maria
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Barriers to and Drivers for Improved Energy Efficiency in the Swedish Aluminium Industry and Aluminium Casting Foundries2019In: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 11, no 7, p. 2043-Article in journal (Refereed)
    Abstract [en]

    Industrial energy efficiency is important for reducing CO2 emissions and could be a competitive advantage for companies because it can reduce costs. However, cost-effective energy efficiency measures are not always implemented because there are barriers inhibiting their implementation. Drivers for energy efficiency could provide means for overcoming these barriers. The aim of this article was to study the importance of different barriers to and drivers for improved energy efficiency in the Swedish aluminium industry and foundries that cast aluminium. Additionally, the perceived usefulness of different information sources on energy efficiency measures was studied. The data were collected through a questionnaire covering 39 barriers and 48 drivers, divided into different categories. Both the aluminium and foundry industries considered technological and economic barriers as the most important categories. The most important category of drivers for the aluminium industry was organisational drivers, while the foundries rated economic drivers as the most important. Colleagues within the company, the company group and sector, and the trade organisation were considered the most useful information sources. Important factors for driving work with improved energy efficiency included access to knowledge within the company, having a culture within the company promoting energy efficiency, and networking within the sector. The policy implications identified included energy labelling of production equipment, the law on energy audit in large companies and subsidy for energy audits in small- and medium-sized companies, voluntary agreements that included long-term energy strategies, increased taxes to improve the cost-effectiveness of energy efficiency measures, and EUs Emission Trading System.

  • 37.
    Haraldsson, Joakim
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Johansson, Maria
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Energy Efficiency in the Supply Chains of the Aluminium Industry: The Cases of Five Products Made in Sweden2019In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, no 2, p. 245-Article in journal (Refereed)
    Abstract [en]

    Improved energy efficiency in supply chains can reduce both environmental impact and lifecycle costs, and thus becomes a competitive advantage in the work towards a sustainable global economy. Viewing the supply chain as a system provides the holistic perspective needed to avoid sub-optimal energy use. This article studies measures relating to technology and management that can increase energy efficiency in the supply chains of five aluminium products made in Sweden. Additionally, energy efficiency potentials related to the flows of material, energy, and knowledge between the actors in the supply chains are studied. Empirical data was collected using focus group interviews and one focus group per product was completed. The results show that there are several areas for potential energy efficiency improvement; for example, product design, communication and collaboration, transportation, and reduced material waste. Demands from other actors that can have direct or indirect effects on energy use in the supply chains were identified. Despite the fact that companies can save money through improved energy efficiency, demands from customers and the authorities would provide the additional incentives needed for companies to work harder to improve energy efficiency.

  • 38.
    Haraldsson, Joakim
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Johansson, Maria
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Impact analysis of energy efficiency measures in the electrolysis process in primary aluminium production2019In: WEENTECH Proceedings in Energy, 2019, Vol. 4(2), p. 177-184Conference paper (Refereed)
    Abstract [en]

    The Paris Agreement includes the goals of ‘holding the increase in the global average temperature to well below 2°C above pre-industrial levels’ and ‘making finance flows consistent with a pathway towards low greenhouse gas emissions’. Industrial energy efficiency will play an important role in meeting those goals as well as becoming a competitive advantage due to reduced costs for companies. The aluminium industry is energy intensive and uses fossil fuels both for energy purposes and as reaction material. Additionally, the aluminium industry uses significant amounts of electricity. The electrolysis process in the primary production of aluminium is the most energy- and carbon-intensive process within the aluminium industry. The aim of this paper is to study the effects on primary energy use, greenhouse gas emissions and costs when three energy efficiency measures are implemented in the electrolysis process. The effects on the primary energy use, greenhouse gas emissions and costs are calculated by multiplying the savings in final energy use by a primary energy factor, emissions factor and price of electricity, respectively. The results showed significant savings in primary energy demand, greenhouse gas emissions and cost from the implementation of the three measures. These results only indicate the size of the potential savings and a site-specific investigation needs to be conducted for each plant. This paper is a part of a research project conducted in close cooperation with the Swedish aluminium industry.

  • 39.
    Haraldsson, Joakim
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Johansson, Maria
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Review of measures for improved energy efficiency in production-related processes in the aluminium industry: From electrolysis to recycling2018In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 93, p. 525-548Article, review/survey (Refereed)
    Abstract [en]

    The aluminium industry is facing a challenge in meeting the goal of halved greenhouse gas emissions by 2050, while the demand for aluminium is estimated to increase 2–3 times by the same year. Energy efficiency will play an important part in achieving the goal. The paper’s aim was to investigate possible production-related energy efficiency measures in the aluminium industry. Mining of bauxite and production of alumina from bauxite are not included in the study. In total, 52 measures were identified through a literature review. Electrolysis in primary aluminium production, recycling and general measures constituted the majority of the 52 measures. This can be explained by the high energy intensity of electrolysis, the relatively wide applicability of the general measures and the fact that all aluminium passes through either electrolysis or recycling. Electrolysis shows a higher number of emerging/novel measures compared to the other processes, which can also be explained by its high energy intensity. Processing aluminium with extrusion, rolling, casting (shape-casting and casting of ingots, slabs and billets), heat treatment and anodising will also benefit from energy efficiency. However, these processes showed relatively fewer measures, which might be explained by the fact that to some extent, these processes are not as energy demanding compared, for example, to electrolysis. In many cases, the presented measures can be combined, which implies that the best practice should be to combine the measures. There may also be a future prospect of achieving carbon-neutral and coal-independent electrolysis. Secondary aluminium production will be increasingly important for meeting the increasing demand for aluminium with respect to environmental and economic concerns and strengthened competitiveness. Focusing on increased production capacity, recovery yields and energy efficiency in secondary production will be pivotal. Further research and development will be required for those measures designated as novel or emerging.

  • 40.
    Hilfiker, James N.
    et al.
    JA Woollam Co Inc, NE 68508 USA.
    Hale, Jeffrey S.
    JA Woollam Co Inc, NE 68508 USA.
    Herzinger, Craig M.
    JA Woollam Co Inc, NE 68508 USA.
    Tiwald, Tom
    JA Woollam Co Inc, NE 68508 USA.
    Hong, Nina
    JA Woollam Co Inc, NE 68508 USA.
    Schoche, Stefan
    JA Woollam Co Inc, NE 68508 USA.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Estimating depolarization with the Jones matrix quality factor2017In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, p. 494-499Article in journal (Refereed)
    Abstract [en]

    Mueller matrix (MM) measurements offer the ability to quantify the depolarization capability of a sample. Depolarization can be estimated using terms such as the depolarization index or the average degree of polarization. However, these calculations require measurement of the complete MM. We propose an alternate depolarization metric, termed the Jones matrix quality factor, QJM, which does not require the complete MM. This metric provides a measure of how close, in a least-squares sense, a Jones matrix can be found to the measured Mueller matrix. We demonstrate and compare the use of QJM to other traditional calculations of depolarization for both isotropic and anisotropic depolarizing samples; including nonuniform coatings, anisotropic crystal substrates, and beetle cuticles that exhibit both depolarization and circular diattenuation. (C) 2016 Elsevier B.V. All rights reserved.

    The full text will be freely available from 2019-08-27 13:46
  • 41.
    Johansson, Maria
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Haraldsson, Joakim
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Karlsson, Magnus
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Energy efficient supply chain of an aluminium product in Sweden – What can be done in-house and between the companies?2018In: eceee 2018 Industrial Summer Study proceedings / [ed] Therese Laitinen Lindström, Ylva Blume & Nina Hampus, Stockholm, Sweden: European Council for an Energy Efficient Economy (ECEEE), 2018, p. 369-377Conference paper (Refereed)
    Abstract [en]

    According to the Energy Efficiency Directive executed by the European Union, each member state is obliged to set a national target on energy efficiency. This requirement constitutes the basis for governments to formulate policy measures directed towards industrial companies. Such policy measures, along with the demand for cost-effective production to remain competitive on the market, motivates industrial companies to improve their energy efficiency. The aluminium industry is energy intensive and consumes substantial amounts of electricity and fossil fuels, resulting in both direct and indirect greenhouse gas emissions. This paper presents a study of the production of an aluminium product in Sweden in terms of implemented energy efficiency measures in the supply chain and potential areas for further improvement. Most previous studies have focused on energy efficiency measures in individual companies (value chains). However, this paper presents and analyses energy efficiency measures not only in each individual company but also in the entire supply chain of the product. The supply chain studied starts with secondary aluminium production followed by the production of a part of an automobile motor and ends with installing the motor detail in a car. Empirical data were gathered through a questionnaire and a focus group. The study shows the great potential for further energy efficiency improvements in the value chains of each individual company and in the whole supply chain. The work shown here is a part of a larger research project performed in close cooperation with the Swedish aluminium industry.

  • 42.
    Johnson, Lars
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Thuvander, M.
    Chalmers University of Technology, Gothenburg, Sweden.
    Stiller, K.
    Chalmers University of Technology, Gothenburg, Sweden.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Blind deconvolution of time-of-flight mass spectra from atom probe tomography2013In: Ultramicroscopy, ISSN 0304-3991, E-ISSN 1879-2723, Vol. 132, p. 60-64Article in journal (Refereed)
    Abstract [en]

    A major source of uncertainty in compositional measurements in atom probe tomography stems from the uncertainties of assigning peaks or parts of peaks in the mass spectrum to their correct identities. In particular, peak overlap is a limiting factor, whereas an ideal mass spectrum would have peaks at their correct positions with zero broadening. Here, we report a method to deconvolute the experimental mass spectrum into such an ideal spectrum and a system function describing the peak broadening introduced by the held evaporation and detection of each ion. By making the assumption of a linear and time-invariant behavior, a system of equations is derived that describes the peak shape and peak intensities. The model is fitted to the observed spectrum by minimizing the squared residuals, regularized by the maximum entropy method. For synthetic data perfectly obeying the assumptions, the method recovered peak intensities to within +/- 0.33 at%. The application of this model to experimental APT data is exemplified with Fe-Cr data. Knowledge of the peak shape opens up several new possibilities, not just for better overall compositional determination, but, e.g., for the estimation of errors of ranging due to peak overlap or peak separation constrained by isotope abundances.

  • 43.
    Jonnalagadda, Krisha Praveen
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Failure mechanisms in APS and SPS thermal barrier coatings during cyclic oxidation and hot corrosion2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Thermal Barrier Coatings (TBCs) are advanced material systems that are being used in the hot sections of gas turbines such as combustor, turbine blades, and vanes. The top ceramic coating in TBCs provides insulation against the hot gases and the intermediate metallic bond coat provides oxidation and corrosion resistance to the underlying turbine components.

    Durability of thermal barrier coatings is very important for the overall performance of the gas turbine. TBCs can fail in several different ways and there is a combination of more than one failure mechanism in most situations. One of the most widely used TBC is atmospheric plasma sprayed (APS) yttria stabilized zirconia (YSZ). Both the deposition technique and the TBC material have certain limitations. The main aim of this research is to study new TBC materials and/or new deposition techniques and compare with the conventional YSZ and understand their failure mechanisms during cyclic oxidation and hot corrosion.

    Thermal cyclic oxidation of a newly developed high purity nano YSZ thermal barrier coating has been studied. Cross sectional analysis of exposed as well as completely failed samples showed a mixed-type failure caused by crack propagation parallel to the bond coat/top coat interface. The majority of the damage occurred towards the end of the coating life. A finite element model has been developed to study the probability of crack growth along different paths that leads to the final failure.

    Hot corrosion mechanism in suspension plasma sprayed two-layer gadolinium zirconate/YSZ, three-layer dense gadolinium zirconate/gadolinium zirconate/YSZ, and a single-layer YSZ has been studied in the presence of sodium sulfate and vanadium pentoxide. The test results showed that gadolinium zirconate coatings were more susceptible to corrosion compared to YSZ coatings despite gadolinium zirconate coatings having lower reactivity with the corrosive salts.

    Thermal cycling behavior of a high chromium bond coat has been studied. Cross-sectional analysis showed formation of sandwich type microstructure with chromium rich oxide and alumina as the top and the bottom layers.

    Inter-diffusion of minor elements between different MCrAlY coatings – substrate systems has been studied using, diffusion simulation software, DICTRA. The simulation results showed that the diffusion of minor elements in the coatings is dependent on the rate of β phase depletion in the beginning. After the depletion of β phase there was no clear dependence of the coating composition on the diffusion of minor elements.

    List of papers
    1. Hot Corrosion Mechanism in Multi-Layer Suspension Plasma Sprayed Gd2Zr2O7 /YSZ Thermal Barrier Coatings in the Presence of V2O5 + Na2SO4
    Open this publication in new window or tab >>Hot Corrosion Mechanism in Multi-Layer Suspension Plasma Sprayed Gd2Zr2O7 /YSZ Thermal Barrier Coatings in the Presence of V2O5 + Na2SO4
    Show others...
    2017 (English)In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, no 1, p. 140-149Article in journal (Refereed) Published
    Abstract [en]

    This study investigates the corrosion resistance of two-layer Gd2Zr2O7/YSZ, three-layer dense Gd2Zr2O7/ Gd2Zr2O7/YSZ, and a reference single-layer YSZ coating with a similar overall top coat thickness of 300-320 µm. All the coatings were manufactured by suspension plasma spraying resulting in a columnar structure except for the dense layer. Corrosion tests were conducted at 900 °C for 8 h using V2O5 and Na2SO4 as corrosive salts at a concentration of approximately 4 mg/cm2. SEM investigations after the corrosion tests show that Gd2Zr2O7-based coatings exhibited lower reactivity with the corrosive salts and the formation of gadolinium vanadate (GdVO4), accompanied by the phase transformation of zirconia was observed. It is believed that the GdVO4 formation between the columns reduced the strain tolerance of the coating and also due to the fact that Gd2Zr2O7 has a lower fracture toughness value made it more susceptible to corrosion-induced damage. Furthermore, the presence of a relatively dense layer of Gd2Zr2O7 on the top did not improve in reducing the corrosion-induced damage. For the reference YSZ coating, the observed corrosion-induced damage was lower probably due to combination of more limited salt penetration, the SPS microstructure and superior fracture toughness of YSZ.

    Place, publisher, year, edition, pages
    New York: Springer, 2017
    Keywords
    gadolinium zirconatehot corrosionmulti-layer thermal barrier coatingssuspension plasma sprayingvanadium pentoxide + sodium sulfate
    National Category
    Corrosion Engineering Manufacturing, Surface and Joining Technology Materials Chemistry
    Identifiers
    urn:nbn:se:liu:diva-134375 (URN)10.1007/s11666-016-0486-5 (DOI)000392060300014 ()
    Note

    Funding agencies: Vinnova in Sweden

    Available from: 2017-02-08 Created: 2017-02-08 Last updated: 2019-02-26Bibliographically approved
    2. Thermal fatigue failure of thermal barrier coatings with a high-Cr MCrAIY bond coat
    Open this publication in new window or tab >>Thermal fatigue failure of thermal barrier coatings with a high-Cr MCrAIY bond coat
    Show others...
    2016 (English)In: Proceedings of the International Thermal Spray Conference (ITSC), 2016, Vol. 324, p. 273-278Conference paper, Published paper (Refereed)
    Abstract [en]

    Thermal barrier coatings (TBCs) were air-plasma sprayed onto Hastelloy X substrates. The TBCs consisted of a high-Cr MCrAlY (M for Ni and Co) bond coat and a yttria-stabilized zirconia (YSZ) top coat. The TBC samples were thermally cycled between 100 ºC and 1100 ºC with 1 hour dwell time at 1100 ºC. The thermal fatigue failure of the TBCs was investigated via microstructure analyses. The final fatigue failure of the TBCs was caused by the formation of interface-parallel cracks in the YSZ top coat. The formation of the cracks was found to be strongly related to the oxidation behaviour of the MCrAlY bond coat. The development of the oxide layers was therefore studied in detail. A thermokinetic model was also used to deepen the understanding on the elemental diffusion behavior in the materials.

    National Category
    Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials Materials Chemistry Composite Science and Engineering
    Identifiers
    urn:nbn:se:liu:diva-134377 (URN)
    Conference
    International Thermal Spray Conference (ITSC), May 10-12, 2016, China
    Available from: 2017-02-08 Created: 2017-02-08 Last updated: 2017-02-16Bibliographically approved
  • 44.
    Jonnalagadda, Krisha Praveen
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Mahade, Satyapal
    Department of Engineering ScienceUniversity West, Trollhättan, Sweden.
    Curry, Nicholas
    Treibacher Industrie AG, Althofen, Austria.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Markocsan, Nicolaie
    Department of Engineering Science University West, Trollhättan, Sweden.
    Nylén, Per
    Department of Engineering Science University West, Trollhättan, Sweden.
    Björklund, Stefan
    Department of Engineering Science University West, Trollhättan, Sweden.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Hot Corrosion Mechanism in Multi-Layer Suspension Plasma Sprayed Gd2Zr2O7 /YSZ Thermal Barrier Coatings in the Presence of V2O5 + Na2SO42017In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, no 1, p. 140-149Article in journal (Refereed)
    Abstract [en]

    This study investigates the corrosion resistance of two-layer Gd2Zr2O7/YSZ, three-layer dense Gd2Zr2O7/ Gd2Zr2O7/YSZ, and a reference single-layer YSZ coating with a similar overall top coat thickness of 300-320 µm. All the coatings were manufactured by suspension plasma spraying resulting in a columnar structure except for the dense layer. Corrosion tests were conducted at 900 °C for 8 h using V2O5 and Na2SO4 as corrosive salts at a concentration of approximately 4 mg/cm2. SEM investigations after the corrosion tests show that Gd2Zr2O7-based coatings exhibited lower reactivity with the corrosive salts and the formation of gadolinium vanadate (GdVO4), accompanied by the phase transformation of zirconia was observed. It is believed that the GdVO4 formation between the columns reduced the strain tolerance of the coating and also due to the fact that Gd2Zr2O7 has a lower fracture toughness value made it more susceptible to corrosion-induced damage. Furthermore, the presence of a relatively dense layer of Gd2Zr2O7 on the top did not improve in reducing the corrosion-induced damage. For the reference YSZ coating, the observed corrosion-induced damage was lower probably due to combination of more limited salt penetration, the SPS microstructure and superior fracture toughness of YSZ.

  • 45.
    Jonnalagadda, Krisha Praveen
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Yuan, Kang
    Beijing Gen Research Institute Min and Met, Peoples R China.
    Li, Xin-Hai
    Siemens Ind Turbomachinery AB, Sweden.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Yu, Yueguang
    Beijing Gen Research Institute Min and Met, Peoples R China.
    Modeling the Diffusion of Minor Elements in Different MCrAlY-Superalloy Coating/Substrates at High Temperature2017In: ENERGY MATERIALS 2017, SPRINGER INT PUBLISHING AG , 2017, p. 251-263Conference paper (Refereed)
    Abstract [en]

    As demands of energy supply have been increased continuously and at the same time the uses of fossil fuel are limited and the greenhouse effect should be minimized, the gas turbine industries have been making efforts to increase gas turbine efficiency and to reduce emissions for power generations. One of the efforts is a continuous development of high temperature capacity of ceramic thermal barrier coatings (TBCs) and metallic MCrAlY overlays. The MCrAlY overlays are used as both protective coatings and bond coats to TBCs on underlying superalloy components in the gas turbines. During high temperature exposure, elemental diffusion occurs between the bond coat and the substrate which can affect the overall coating performance. The present study investigates the diffusion of minor elements like Re, Ta, Si, Mo and Ti in various MCrAlY overlays and superalloy substrates. An oxidation-diffusion model has been used to study the elemental diffusion. The diffusion process contains two stages: beta depletion stage and the b depleted stage. In the stage when MCrAlY overlays exhibit gamma + beta microstructure, the diffusion of minor elements in the coatings was observed to be related to the b depletion rate. After that the diffusion of the minor elements did not show any clear dependence on the coating composition. The development principle of the elemental diffusion is discussed in detail.

  • 46.
    Jonnalagadda, Krishna Praveen
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Thermal Barrier Coatings: Failure Mechanisms and Life Prediction2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Thermal barrier coatings (TBCs) use in the hot sections of gas turbine engine enables them to run at higher temperatures, and as a consequence, achieve higher thermal efficiency. For full operational exploitation of TBCs, understanding their failure and knowing the service life is essential. The broad objective of the current research is to study the failure mechanisms of new TBC materials and deposition techniques during corrosion and thermal cycling and to develop life models capable of predicting the final failure during thermal cycling.

    Yttria-stabilized zirconia (YSZ) has constraints such as limited operation temperature, despite being the current industry standard. Pyrochlores of A2B2O7 type have been suggested as a potential replacement for YSZ and were studied in this work. Additionally, improvements to the conventional YSZ in the form of nanostructured YSZ were also explored. The requirement for the new deposition process comes from the fact that the existing low-cost deposition processes, like atmospheric plasma spray (APS), generally exhibit lower strain tolerance. A relatively new technique, suspension plasma spray (SPS), known to be promising with better strain tolerance, has been studied in this work.

    At the gas turbine operating conditions, TBCs degrade and eventually fail. Common failure observed in gas turbines can be due to corrosion, thermal mismatch between the ceramic and the metallic layers, and bond coat oxidation during thermal cycling. SPS and APS TBCs were subjected to different test conditions to understand their corrosion behavior. A study on the multi-layered SPS TBCs in the presence of V2O5+Na2SO4 showed that YSZ based SPS coatings were less susceptible to corrosion damage compared to Gd2Zr2O7 SPS TBCs. A study on the influence of a sealing layer in multi-layered SPS TBCs in the presence of Na2SO4+NaCl showed that the sealing layer is ineffective if the material used for sealing is inert to the molten salts. A new study on the influence of corrosion, caused by a mixed-gas atmosphere, on the thermal cycling fatigue life of SPS TBCs was conducted. Results showed that corrosive products grew inside the top coat close to the bond coat/top coat interface along with accelerated growth of alumina. These, together, reduced the TCF life of corrosion exposed samples significantly. Finally, a study on the influence of salt concentration and temperature on a thin (dense) and a thick (porous) coating showed that thick and porous coatings have lower corrosion resistance than the thin and dense coatings. Additionally, a combination of low temperature and high salt concentration was observed to cause more damage.

    Thermal cycling studies were done with the objective of understanding the failure mechanisms and developing a life model. A life model based on fracture mechanics approach has been developed by taking into account different crack growth paths during thermal cycling, sintering of the top coat, oxidation of the bond coat and the thermal mismatch stresses. Validation of such a life model by comparing to the experimental results showed that the model could predict the TCF life reasonably well at temperatures of 1100 °C or below. At higher temperatures, the accuracy of the model became worse. As a further development, a simplified crack growth model was established. This simplified model was shown to be capable of predicting the TCF life as well as the effect of hold times with good accuracy.

    List of papers
    1. Hot Corrosion Mechanism in Multi-Layer Suspension Plasma Sprayed Gd2Zr2O7 /YSZ Thermal Barrier Coatings in the Presence of V2O5 + Na2SO4
    Open this publication in new window or tab >>Hot Corrosion Mechanism in Multi-Layer Suspension Plasma Sprayed Gd2Zr2O7 /YSZ Thermal Barrier Coatings in the Presence of V2O5 + Na2SO4
    Show others...
    2017 (English)In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, no 1, p. 140-149Article in journal (Refereed) Published
    Abstract [en]

    This study investigates the corrosion resistance of two-layer Gd2Zr2O7/YSZ, three-layer dense Gd2Zr2O7/ Gd2Zr2O7/YSZ, and a reference single-layer YSZ coating with a similar overall top coat thickness of 300-320 µm. All the coatings were manufactured by suspension plasma spraying resulting in a columnar structure except for the dense layer. Corrosion tests were conducted at 900 °C for 8 h using V2O5 and Na2SO4 as corrosive salts at a concentration of approximately 4 mg/cm2. SEM investigations after the corrosion tests show that Gd2Zr2O7-based coatings exhibited lower reactivity with the corrosive salts and the formation of gadolinium vanadate (GdVO4), accompanied by the phase transformation of zirconia was observed. It is believed that the GdVO4 formation between the columns reduced the strain tolerance of the coating and also due to the fact that Gd2Zr2O7 has a lower fracture toughness value made it more susceptible to corrosion-induced damage. Furthermore, the presence of a relatively dense layer of Gd2Zr2O7 on the top did not improve in reducing the corrosion-induced damage. For the reference YSZ coating, the observed corrosion-induced damage was lower probably due to combination of more limited salt penetration, the SPS microstructure and superior fracture toughness of YSZ.

    Place, publisher, year, edition, pages
    New York: Springer, 2017
    Keywords
    gadolinium zirconatehot corrosionmulti-layer thermal barrier coatingssuspension plasma sprayingvanadium pentoxide + sodium sulfate
    National Category
    Corrosion Engineering Manufacturing, Surface and Joining Technology Materials Chemistry
    Identifiers
    urn:nbn:se:liu:diva-134375 (URN)10.1007/s11666-016-0486-5 (DOI)000392060300014 ()
    Note

    Funding agencies: Vinnova in Sweden

    Available from: 2017-02-08 Created: 2017-02-08 Last updated: 2019-02-26Bibliographically approved
    2. Failure of Multilayer Suspension Plasma Sprayed Thermal Barrier Coatings in the Presence of Na2SO4 and NaCl at 900 °C
    Open this publication in new window or tab >>Failure of Multilayer Suspension Plasma Sprayed Thermal Barrier Coatings in the Presence of Na2SO4 and NaCl at 900 °C
    Show others...
    2019 (English)In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 28, no 1-2, p. 212-222Article in journal (Refereed) Published
    Abstract [en]

    The current investigation focuses on understanding the influence of a columnar microstructure and a sealing layer on the corrosion behavior of suspension plasma sprayed thermal barrier coatings (TBCs). Two different TBC systems were studied in this work. First is a double layer made of a composite of gadolinium zirconate + yttria stabilized zirconia (YSZ) deposited on top of YSZ. Second is a triple layer made of dense gadolinium zirconate deposited on top of gadolinium zirconate + YSZ over YSZ. Cyclic corrosion tests were conducted between 25 and 900 °C with an exposure time of 8 h at 900 °C. 75 wt.% Na2SO4 + 25 wt.% NaCl were used as the corrosive salts at a concentration of 6 mg/cm2. Scanning electron microscopy analysis of the samples’ cross sections showed that severe bond coat degradation had taken place for both the TBC systems, and the extent of bond coat degradation was relatively higher in the triple-layer system. It is believed that the sealing layer in the triple-layer system reduced the number of infiltration channels for the molten salts which resulted in overflowing of the salts to the sample edges and caused damage to develop relatively more from the edge.

    Keywords
    columnar microstructure, composite of gadolinium zirconate and YSZ, hot corrosion, suspension plasma spray
    National Category
    Manufacturing, Surface and Joining Technology
    Research subject
    ENGINEERING, Manufacturing and materials engineering; Production Technology
    Identifiers
    urn:nbn:se:liu:diva-154778 (URN)10.1007/s11666-018-0780-5 (DOI)000456599500019 ()2-s2.0-85055998259 (Scopus ID)
    Funder
    VINNOVA
    Note

    This article is an invited paper selected from presentations at the 2018 International Thermal Spray Conference, held May 7-10, 2018, in Orlando, Florida, USA, and has been expanded from the original presentation.

    Available from: 2018-11-06 Created: 2019-02-26 Last updated: 2019-02-26
    3. Factors Affecting the Performance of Thermal Barrier Coatings in the Presence of V2O5 and Na2SO4
    Open this publication in new window or tab >>Factors Affecting the Performance of Thermal Barrier Coatings in the Presence of V2O5 and Na2SO4
    Show others...
    2016 (English)In: JOURNAL OF CERAMIC SCIENCE AND TECHNOLOGY, ISSN 2190-9385, Vol. 7, no 4, p. 409-415Article in journal (Refereed) Published
    Abstract [en]

    This study investigates the influence of temperature, salt concentration and thickness on the corrosion resistance of seven YSZ thermal barrier coatings in the presence of V2O5 and Na2SO4. For this study, a thick, high-porosity APS coating (670 gm) using hollow spherical powder (HOSP) and a thin, low-porosity APS coating (300 pm) using agglomerated and sintered (Aamp;S) powder were fabricated. Corrosion tests were conducted at 750 degrees C and 900 degrees C with a mixture of Na2SO4 and V2O5 for four hours. At each temperature, salt concentrations of 4,10 and 20 mg/cm(2) were used. SEM and XRD investigations after the corrosion tests revealed that a combination of low temperature and high salt concentration resulted in higher corrosion-induced damage to the thin TBC coatings. With regard to the thick TBC coatings, all except one sample failed during the corrosion test. This suggests that thick TBC coatings with higher porosity may not be suitable in corrosive environments.

    Place, publisher, year, edition, pages
    GOLLER VERLAG GMBH, 2016
    Keywords
    HOSP; agglomerated and sintered YSZ; hot corrosion; TBC
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:liu:diva-134310 (URN)10.4416/JCST2016-00058 (DOI)000391246300013 ()
    Note

    Funding Agencies|Vinnova, Sweden

    Available from: 2017-02-06 Created: 2017-02-03 Last updated: 2019-02-26Bibliographically approved
    4. A study of damage evolution in high purity nano TBCs during thermal cycling: A fracture mechanics based modelling approach
    Open this publication in new window or tab >>A study of damage evolution in high purity nano TBCs during thermal cycling: A fracture mechanics based modelling approach
    Show others...
    2017 (English)In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 37, no 8, p. 2889-2899Article in journal (Refereed) Published
    Abstract [en]

    This work concerns the study of damage evolution in a newly developed high purity nano 8YSZ thermal barrier coating during thermal cyclic fatigue tests (TCF). TCF tests were conducted between 100 degrees C-1100 degrees C with a hold time of 1 hat 1100 degrees C, first till failure and later for interrupted tests. Cross section analysis along the diameter of the interrupted test samples revealed a mixed-type failure and that the most of the damage occurred towards the end of the coatings life. To understand the most likely crack growth mechanism leading to failure, different crack growth paths have been modelled using finite element analysis. Crack growing from an existing defect in the top coat towards the top coat/TGO interface has been identified as the most likely mechanism. Estimated damage by the model could predict the rapid increase in the damage towards the end of the coatings life. (C) 2017 Elsevier Ltd. All rights reserved.

    Place, publisher, year, edition, pages
    ELSEVIER SCI LTD, 2017
    Keywords
    Thermal cyclic fatigue; High purity nano YSZ; Crack growth modelling; Damage evolution
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:liu:diva-137827 (URN)10.1016/j.jeurceramsoc.2017.02.054 (DOI)000400531500015 ()
    Note

    Funding Agencies|Vinnova in Sweden

    Available from: 2017-06-02 Created: 2017-06-02 Last updated: 2019-02-26
    5. Comparison of Damage Evolution During Thermal Cycling in a High Purity Nano and Conventional Thermal Barrier Coating
    Open this publication in new window or tab >>Comparison of Damage Evolution During Thermal Cycling in a High Purity Nano and Conventional Thermal Barrier Coating
    Show others...
    2017 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 332, p. 47-56Article in journal (Refereed) Published
    Abstract [en]

    Thermal barrier coatings (TBCs), consisting of a ceramic top coat and a metallic bond coat, offer resistance against high temperature degradation of turbine components. Cyclic oxidation of the bond coat, thermal stresses due to their thermal mismatches during cyclic operations, and sintering of the top coat are considered to be the common ways by which thermal barrier coatings fail. To reduce sintering, a nano structured high purity yttria stabilized zirconia (YSZ) was developed. The focus of this work is to compare the damage development of such high purity nano YSZ TBC during thermal cycling with a conventional YSZ TBC. Thermal cyclic fatigue (TCF) tests were conducted on both the TBC systems between 100 °C and 1100 °C with a 1 h hold time at 1100 °C. TCF test results showed that conventional YSZ TBC exhibited much higher life compared to the high purity nano YSZ TBC. The difference in the lifetime is explained by the use of microstructural investigations, crack length measurements along the cross-section and the difference in the elastic modulus. Furthermore, stress intensity factors were calculated in order to understand the difference(s) in the damage development between the two TBC systems.

    Place, publisher, year, edition, pages
    Elsevier, 2017
    Keywords
    High purity nano, damage evolution, thermal cycling fatigue, crack length measurement, conventional TBC
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-142311 (URN)10.1016/j.surfcoat.2017.09.069 (DOI)000418968100007 ()2-s2.0-85030751243 (Scopus ID)
    Note

    Funding agencies: Vinnova in Sweden [2015-06870]

    Available from: 2017-10-25 Created: 2017-10-25 Last updated: 2019-02-26Bibliographically approved
    6. Thermal barrier coatings: Life model development and validation
    Open this publication in new window or tab >>Thermal barrier coatings: Life model development and validation
    2019 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 362, p. 293-301Article in journal (Refereed) Published
    Abstract [en]

    The failure of thermal barrier coatings (TBCs) during thermal cyclic fatigue (TCF) tests depends mainly on the thermal mismatch between the coating and the substrate, the thermally grown oxides (TGO) at the top coat-bond coat interface, and the sintering of the top coat. Understanding the interplay between these factors is essential for developing a life model. The present work focuses on further development of a previously established fracture mechanics based life model and its validation by comparing with the experimental results. The life model makes use of a Paris' law type equation to estimate the cycles to failure based on micro-crack growth. The fitting parameters for the Paris' law were obtained from the experimentally measured crack lengths after the interruption of TCF tests at different cycles. An alternative approach to obtain the fitting parameters through video monitoring was also discussed. It is shown that regardless of the approach to obtain the fitting parameters, the life model in its current form is able to predict the TCF life at different temperatures with reasonable accuracy. However, at very high temperatures (1150 °C) the predictive capabilities of the model appeared to be poor.

    Keywords
    Thermal barrier coatings, Thermal cyclic fatigue, Life modeling, Life prediction
    National Category
    Manufacturing, Surface and Joining Technology
    Identifiers
    urn:nbn:se:liu:diva-154779 (URN)10.1016/j.surfcoat.2019.01.117 (DOI)000461526400035 ()
    Note

    Funding agencies: VINNOVA in Sweden

    Available from: 2019-02-26 Created: 2019-02-26 Last updated: 2019-04-03
    7. Fatigue life prediction of thermal barrier coatings using a simplified crack growth model
    Open this publication in new window or tab >>Fatigue life prediction of thermal barrier coatings using a simplified crack growth model
    2019 (English)In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 39, no 5, p. 1869-1876Article in journal (Refereed) Published
    Abstract [en]

    Models that can predict the life of thermal barrier coatings (TBCs) during thermal cycling fatigue (TCF) tests are highly desirable. The present work focuses on developing and validating a simplified model based on the relation between the energy release rate and the TCF cycles to failure. The model accounts for stresses due to thermal mismatch, influence of sintering, and the growth of TGO (alumina and other non-protective oxides). The experimental investigation of TBCs included; 1) TCF tests at maximum temperatures of 1050 °C, 1100 °C, 1150 °C and a minimum temperature of 100 °C with 1 h and 5 h (1100 °C) hold times. 2) Isothermal oxidation tests at 900, 1000 and 1100 °C for times up to 8000 h. The model was calibrated and validated with the experimental results. It has been shown that the model is able to predict the TCF life and effect of hold time with good accuracy.

    Keywords
    Thermal barrier coatings, Thermal cycling fatigue, Life prediction model, Energy release rate
    National Category
    Manufacturing, Surface and Joining Technology
    Identifiers
    urn:nbn:se:liu:diva-154780 (URN)10.1016/j.jeurceramsoc.2018.12.046 (DOI)000459950700016 ()
    Note

    Funding agencies: Vinnova in Sweden

    Available from: 2019-02-26 Created: 2019-02-26 Last updated: 2019-03-20
  • 47.
    Jonnalagadda, Krishna Praveen
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Eriksson, Robert
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Arts and Sciences.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, 61283, Finspång, Sweden.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Fatigue life prediction of thermal barrier coatings using a simplified crack growth model2019In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 39, no 5, p. 1869-1876Article in journal (Refereed)
    Abstract [en]

    Models that can predict the life of thermal barrier coatings (TBCs) during thermal cycling fatigue (TCF) tests are highly desirable. The present work focuses on developing and validating a simplified model based on the relation between the energy release rate and the TCF cycles to failure. The model accounts for stresses due to thermal mismatch, influence of sintering, and the growth of TGO (alumina and other non-protective oxides). The experimental investigation of TBCs included; 1) TCF tests at maximum temperatures of 1050 °C, 1100 °C, 1150 °C and a minimum temperature of 100 °C with 1 h and 5 h (1100 °C) hold times. 2) Isothermal oxidation tests at 900, 1000 and 1100 °C for times up to 8000 h. The model was calibrated and validated with the experimental results. It has been shown that the model is able to predict the TCF life and effect of hold time with good accuracy.

  • 48.
    Jonnalagadda, Krishna Praveen
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Eriksson, Robert
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Arts and Sciences.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, 61283 Finspång, Sweden.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Thermal barrier coatings: Life model development and validation2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 362, p. 293-301Article in journal (Refereed)
    Abstract [en]

    The failure of thermal barrier coatings (TBCs) during thermal cyclic fatigue (TCF) tests depends mainly on the thermal mismatch between the coating and the substrate, the thermally grown oxides (TGO) at the top coat-bond coat interface, and the sintering of the top coat. Understanding the interplay between these factors is essential for developing a life model. The present work focuses on further development of a previously established fracture mechanics based life model and its validation by comparing with the experimental results. The life model makes use of a Paris' law type equation to estimate the cycles to failure based on micro-crack growth. The fitting parameters for the Paris' law were obtained from the experimentally measured crack lengths after the interruption of TCF tests at different cycles. An alternative approach to obtain the fitting parameters through video monitoring was also discussed. It is shown that regardless of the approach to obtain the fitting parameters, the life model in its current form is able to predict the TCF life at different temperatures with reasonable accuracy. However, at very high temperatures (1150 °C) the predictive capabilities of the model appeared to be poor.

  • 49.
    Jonnalagadda, Krishna Praveen
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Mahade, Satyapal
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Kramer, Stephanie
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Zhang, Pimin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Curry, Nicholas
    Treibacher Industrie AG, Althofen, Austria.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Failure of Multilayer Suspension Plasma Sprayed Thermal Barrier Coatings in the Presence of Na2SO4 and NaCl at 900 degrees C2019In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 28, no 1-2, p. 212-222Article in journal (Refereed)
    Abstract [en]

    The current investigation focuses on understanding the influence of a columnar microstructure and a sealing layer on the corrosion behavior of suspension plasma sprayed thermal barrier coatings (TBCs). Two different TBC systems were studied in this work. First is a double layer made of a composite of gadolinium zirconate+yttria stabilized zirconia (YSZ) deposited on top of YSZ. Second is a triple layer made of dense gadolinium zirconate deposited on top of gadolinium zirconate+YSZ over YSZ. Cyclic corrosion tests were conducted between 25 and 900 degrees C with an exposure time of 8h at 900 degrees C. 75wt.% Na2SO4+25wt.% NaCl were used as the corrosive salts at a concentration of 6mg/cm(2). Scanning electron microscopy analysis of the samples cross sections showed that severe bond coat degradation had taken place for both the TBC systems, and the extent of bond coat degradation was relatively higher in the triple-layer system. It is believed that the sealing layer in the triple-layer system reduced the number of infiltration channels for the molten salts which resulted in overflowing of the salts to the sample edges and caused damage to develop relatively more from the edge.

  • 50.
    Jonnalagadda, Krishna Praveen
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Mahade, Satyapal
    Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Kramer, Stephanie
    Linköping University, Department of Management and Engineering. Linköping University, Faculty of Science & Engineering.
    Zhang, Pimin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Curry, Nicholas
    Treibacher Industrie AG, Althofen, Austria.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB,Finspång,Sweden.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Failure of Multilayer Suspension Plasma Sprayed Thermal Barrier Coatings in the Presence of Na2SO4 and NaCl at 900 °C2019In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 28, no 1-2, p. 212-222Article in journal (Refereed)
    Abstract [en]

    The current investigation focuses on understanding the influence of a columnar microstructure and a sealing layer on the corrosion behavior of suspension plasma sprayed thermal barrier coatings (TBCs). Two different TBC systems were studied in this work. First is a double layer made of a composite of gadolinium zirconate + yttria stabilized zirconia (YSZ) deposited on top of YSZ. Second is a triple layer made of dense gadolinium zirconate deposited on top of gadolinium zirconate + YSZ over YSZ. Cyclic corrosion tests were conducted between 25 and 900 °C with an exposure time of 8 h at 900 °C. 75 wt.% Na2SO4 + 25 wt.% NaCl were used as the corrosive salts at a concentration of 6 mg/cm2. Scanning electron microscopy analysis of the samples’ cross sections showed that severe bond coat degradation had taken place for both the TBC systems, and the extent of bond coat degradation was relatively higher in the triple-layer system. It is believed that the sealing layer in the triple-layer system reduced the number of infiltration channels for the molten salts which resulted in overflowing of the salts to the sample edges and caused damage to develop relatively more from the edge.

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