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  • 1.
    Busse, Christian
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Gustafsson, D.
    Siemens Ind Turbomachinery AB, Sweden.
    Palmert, Frans
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Sjodin, B.
    Siemens Ind Turbomachinery AB, Sweden.
    Almroth, P.
    Siemens Ind Turbomachinery AB, Sweden.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Criteria evaluation for the transition of cracking modes in a single-crystal nickel-base superalloy2020Ingår i: Theoretical and applied fracture mechanics (Print), ISSN 0167-8442, E-ISSN 1872-7638, Vol. 106, artikel-id 102453Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Single-crystal nickel-base superalloys frequently experience two distinct fatigue crack growth modes. It has been observed that, under certain conditions, cracks transition from a path perpendicular to the loading direction to a crystallographic slip plane. As crystallographic cracking is associated with an increased fatigue crack growth rate, it is important to be able to predict when this transition occurs. In this work three different criteria for crystallographic cracking based on resolved anisotropic stress intensity factors are evaluated in a three-dimensional finite element context. The criteria were calibrated and evaluated using isothermal fatigue experiments on two different specimen geometries. It is suggested by the results, that a threshold value of a resolved shear stress intensity factor can act as a conservative criterion indicating cracking mode transition. Further, a trend hinting towards a loading frequency dependency could be observed.

  • 2.
    Stekovic, Svjetlana
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Jones, J P
    Engel, B
    Whittaker, M T
    Norman, Viktor
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Rouse, J P
    Pattison, S
    Hyde, C J
    Härnman, Patrik
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial.
    Lancaster, R J
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    DevTMF - Towards Code of Practice for Thermo-Mechanical Fatigue Crack Growth2020Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, nr 138, artikel-id 105675Artikel i tidskrift (Refereegranskat)
  • 3.
    Kanesund, Jan
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling. Linköpings universitet, Tekniska fakulteten.
    Brodin, Håkan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Siemens Ind Turbomachinery AB, Sweden.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    High temperature corrosion influence on deformation and damage mechanisms in turbine blades made of IN-792 during service2020Ingår i: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 110, artikel-id UNSP 104388Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A metallographic study is performed on a turbine blade from a land-based gas turbine in an industrial environment. The aim of the present work is to study the degradation of the turbine blade. The gas turbine has been running for about a month before shut down, which has established steady-state temperature gradients around the cooling holes, causing tensile stresses as a result of cold spots. The tensile stresses cause creep damage, which, in turn, plastically deformed the material, generating substructures and twins near the crack. Furthermore, by comparing substructures from the turbine blade formed during service with substructure from test bars subjected to thermal mechanical fatigue testing gives a strong indication that the damage of the turbine blade is not caused by thermal mechanical fatigue. The turbine blade is also exposed to chemical degradation by type I hot corrosion and internal corrosion/nitridation. Type I hot corrosion has formed Ti-sulfides in grain boundaries and nearby surroundings. Ti-sulfides are also found ahead of the crack tip region. The internal corrosion/nitridation has established TiN, AlN and simultaneously formed a depletion zone near the crack.

  • 4.
    Kahlin, Magnus
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Saab AB, Aeronaut, SE-58188 Linkoping, Sweden.
    Ansell, Hans
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten. Saab AB, Aeronaut, SE-58188 Linkoping, Sweden.
    Basu, D.
    Mfg Technol Ctr, England.
    Kerwin, A.
    Mfg Technol Ctr, England.
    Newton, L.
    Univ Nottingham, England.
    Smith, B.
    Mfg Technol Ctr, England.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Improved fatigue strength of additively manufactured Ti6Al4V by surface post processing2020Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 134, artikel-id 105497Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A major challenge for additively manufactured structural parts is the low fatigue strength connected to rough as-built surfaces. In this study, Ti6Al4V manufactured with laser powder bed fusion (L-PBF) and electron beam powder bed fusion (E-PBF) have been subjected to five surface processing methods, shot peening, laser shock peening, centrifugal finishing, laser polishing and linishing, in order to increase the fatigue strength. Shot peened and centrifugal finished L-PBF material achieved comparable fatigue strength to machined material. Moreover, the surface roughness alone was found to be an insufficient indicator on the fatigue strength since subsurface defects were hidden below smooth surfaces.

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  • 5.
    Kahlin, Magnus
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial.
    Ansell, Hans
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära.
    Basu, D
    Kerwin, A
    Newton, L
    Smith, B
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Improved Fatigue Strength of Additively Manufactured Ti6Al4V by Surface Post Processing2020Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, nr 134, artikel-id 105497Artikel i tidskrift (Refereegranskat)
  • 6.
    Cui, Luqing
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial.
    Liu, Jinlai
    Peng, Ru Lin
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Yu, Jinjiang
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Sun, Xiaofeng
    Low Cycle Fatigue Behavior and Microstructural Evolution of Nickel-based Superalloy M951G at Elevated Temperatures2020Ingår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, nr 163, artikel-id 110241Artikel i tidskrift (Refereegranskat)
  • 7.
    Azeez, Ahmed
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Low cycle fatigue life modelling using finite element strain range partitioning for a steam turbine rotor steel2020Ingår i: Theoretical and applied fracture mechanics (Print), ISSN 0167-8442, E-ISSN 1872-7638, Vol. 107, artikel-id 102510Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Materials made for modern steam power plants are required to withstand high temperatures and flexible operational schedule. Mainly to achieve high efficiency and longer components life. Nevertheless, materials under such conditions experience crack initiations and propagations. Thus, life prediction must be made using accurate fatigue models to allow flexible operation. In this study, fully reversed isothermal low cycle fatigue tests were performed on a turbine rotor steel called FB2. The tests were done under strain control with different total strain ranges and temperatures (20 °C to 625 °C). Some tests included dwell time to calibrate the short-time creep behaviour of the material. Different fatigue life models were evaluated based on total life approach. The stress-based fatigue life model was found unusable at 600 °C, while the strain-based models in terms of total strain or inelastic strain amplitudes displayed inconsistent behaviour at 500 °C. To construct better life prediction, the inelastic strain amplitudes were separated into plastic and creep components by modelling the deformation behaviour of the material, including creep. Based on strain range partitioning approach, the fatigue life depends on different damage mechanisms at different strain ranges at 500 °C. This allows for the formulation of life curves based on either plasticity-dominated damage or creep-dominated damage. At 600 °C, creep dominated while at 500 °C creep only dominates for higher strain ranges. The deformation mechanisms at different temperatures and total strain ranges were characterised by scanning electron microscopy and by quantifying the amount of low angle grain boundaries. The quantification of low angle grain boundaries was done by electron backscatter diffraction. Microscopy revealed that specimens subjected to 600 °C showed signs of creep damage in the form of voids close to the fracture surface. In addition, the amount of low angle grain boundaries seems to decrease with the increase in temperature even though the inelastic strain amplitude was increased. The study indicates that a significant amount of the inelastic strain comes from creep strain as opposed of being all plastic strain, which need to be taken into consideration when constructing a life prediction model.

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  • 8.
    Norman, Viktor
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Stekovic, Svjetlana
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Jones, J
    Swansea University, Swansea, UK.
    Whittaker, M
    Swansea University, Swansea, UK.
    Grant, B
    Rolls-Royce plc, Derby, UK.
    On the Mechanistic Difference Between In-phase and Out-of-phase Thermo-Mechanical Fatigue Crack Growth2020Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 135, s. 1-11, artikel-id 105528Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The crack driving mechanisms in a coarse grained nickel-base superalloy RR1000 when subjected to in- and out of phase thermo mechanical fatigue are investigated. It is found that the difference in fatigue crack growth rate between these two load conditions is accounted for by the different mechanical conditions at the crack tip region, rather than oxidation effects. This is based on digital image correlation and finite element analyses of the mechanical strain field at the crack tip, which demonstrate that in phase leads to larger crack tip deformation and crack opening. Notably, it is demonstrated that in- and out of phase crack growth rates coincide when correlated to the crack tip opening displacement.

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  • 9.
    Xu, Jinghao
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Gruber, Hans
    Boyd, Robert
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och ytbeläggningsfysik.
    Jiang, Shuang
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial.
    Peng, Ru Lin
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    On the Strengthening and Embrittlement Mechanisms of an Additively Manufactured Nickel-base Superalloy2020Ingår i: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, nr 10, artikel-id 100657Artikel i tidskrift (Refereegranskat)
  • 10. Beställ onlineKöp publikationen >>
    Pant, Prabhat
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Residual Stress Distributions in Additively Manufactured Parts: Effect of Build Orientation2020Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Additive manufacturing (AM) of parts using a layer by layer approach has seen a rapid increase in application for production of net shape or near-net shape complex parts, especially in the field of aerospace, automotive, etc. Due to the superiority of manufacturing complex shapes with ease in comparison to the conventional methods, interest in these kinds of processes has increased. Among various methods in AM, laser powder bed fusion (LPBF) is one of the most widely used techniques to produce metallic components.

    As in all manufacturing processes, residual stress (RS) generation during manufacturing is a relevant issue for the AM process. RS in AM are generated due to a high thermal gradient between subsequent layers. The impact of residual stresses can be significant for the mechanical integrity of the built parts and understanding the generation of RS and the effect of AM process parameters is therefore important for a broader implementation of AM techniques. The work presented in this licentiate thesis aims to investigate the influence of build orientation on the RS distribution in AM parts. For this purpose, L-shaped Inconel 718 parts were printed by LPBF in three different orientations, 0°, 45°, and 90°, respectively. Inconel 718 was selected because it is a superalloy widely used for making gas turbine components. In addition, IN718 has in general good weldability which renders it a good material for additive manufacturing.

    Residual stress distributions in the parts removed from the build plate were measured using neutron diffraction technique. A simple finite element model was developed to predict the residual stresses and the effect of RS relaxation due to the separation of the parts and build plate. The trend of residual stress distribution predicted was in good agreement with experimental results. In general, compressive RS at the part center and tensile RS near the surface were found. However, while the part printed in 0° orientation had the least amount of RS in all three principal directions of part, the part built in 90° orientation possessed the highest amount of RS in both compression and tension. The study has shown that residual stress distributions in the parts are strongly dependent on the building process. Further, it has shown that the relaxation of RS associated with the removal of the parts from the build plate after printing has a great impact on the final distribution of residual stress in the parts. These results can be used as guidelines for choosing the orientations of the part during printing.

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  • 11.
    Dong, Zhihua
    et al.
    KTH Royal Inst Technol, Sweden.
    Li, Wei
    KTH Royal Inst Technol, Sweden.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. AB Sandvik Mat Technol RandD Ctr, Sweden.
    Vitos, Levente
    KTH Royal Inst Technol, Sweden; Uppsala Univ, Sweden; Wigner Res Ctr Phys, Hungary.
    Strong temperature - Dependence of Ni -alloying influence on the stacking fault energy in austenitic stainless steel2020Ingår i: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 178, s. 438-441Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using ab initio alloy theory, we calculate the impact of Ni on the stacking fault energy in austenitic stainless steel as a function of temperature. We show that the influence of Ni strongly couples with temperature. While a positive effect on the stacking fault energy is obtained at ambient temperature, the opposite negative effect is disclosed at elevated temperatures. An important rationale behind is demonstrated to be the variation of magneto-volume coupling induced by Ni alloying. The alloy influence on the finite temperature evolution of Ni impact is evaluated for elements Cr, Mo and N. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  • 12.
    Jones, J.
    et al.
    Swansea Univ, Wales.
    Whittaker, M.
    Swansea Univ, Wales.
    Lancaster, R.
    Swansea Univ, Wales.
    Hyde, C.
    Univ Nottingham, England.
    Rouse, J.
    Univ Nottingham, England.
    Engel, B.
    Univ Nottingham, England.
    Pattison, S.
    Rolls Royce Plc, England.
    Stekovic, Svjetlana
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Jackson, C.
    Univ Birmingham, England.
    Li, H. Y.
    Univ Birmingham, England.
    The effect of phase angle on crack growth mechanisms under thermo-mechanical fatigue loading2020Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 135, artikel-id 105539Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The current paper describes TMF crack growth behaviour in an advanced nickel-based superalloy. Changes in behaviour are examined which occur as a function of the phase angle between applied stress and temperature. The fractography of the failed specimens reveals changes from transgranular to intergranular growth between high and low phase angle tests as a result of the onset of high temperature damage mechanisms. More targeted testing has also been undertaken to isolate the contributions of these mechanisms, with specific transitions in behaviour becoming clear in 90 degrees diamond cycles, where dynamic crack growth and oxidation strongly interact.

  • 13.
    Zhang, Pimin
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Peng, Ru Lin
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    The iron effect on hot corrosion behaviour of MCrAlX coating in the presence of NaCl at 900 °C2020Ingår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 815, artikel-id 152381Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cyclic hot corrosion tests of two MCrAlX coatings with different Fe contents were carried out in a molten salt (75 wt% Na2SO4 + 25 wt% NaCl) environment at 900 °C under type I hot corrosion. The positive effect of high Fe addition which reduces the advancing of corrosion front in the coating was discussed. The experimental results showed that the main corrosion reaction is the basic fluxing of Al, while Fe is relatively inert. Combined with thermodynamic modelling, it was demonstrated that a high Fe addition in MCrAlX coatings shifts the equilibrium Al content of the γ phase towards a low level and also reduces the loss of Cr from coating to the substrate. Both effects contributed to a higher “effective” Al supply of the coating to resist basic fluxing and thereby enhance the coating resistance to hot corrosion by reducing the rate of advancing of the corrosion front.

  • 14. Engel, B
    et al.
    Rouse, J P
    Hyde, C J
    Lavie, W
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Stekovic, Svjetlana
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Williams, S J
    Pattison, S
    Grant, B
    Whittaker, M T
    Jones, J P
    Lancaster, R J
    Li, H Y
    The Prediction of Crack Propagation in Coarse Grain RR1000 Using a Unified Modelling Approach2020Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, nr 137, artikel-id 105652Artikel i tidskrift (Refereegranskat)
  • 15.
    Eriksson, Robert
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chen, Zhe
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    A low cycle fatigue life model for a shot peened gas turbine disc alloy2019Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 124, s. 34-41Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Turbine disks in gas turbines are subjected to cyclic load at high temperature, making, especially the fir tree type blade attachments, susceptible to fatigue. Shot peening of the fir tree attachments may be used to increase the fatigue life by introducing compressive residual stresses. In the current study, both polished and shot peened notched specimens made from alloy 718 were subjected to low cycle fatigue at 450-550 degrees C. The shot peening generally increased the fatigue life, although the effect diminished for high loads. It was shown that the effect of shot peening could be handled as mean stress effects in a life model based on a Smith-Watson-Topper (SWT) type parameter, sigma(max)Delta epsilon/2. A material model which captured the mean stress was set up to get the SWT parameter at the notch root. It was shown that thermal relaxation of residual stresses and initial strain hardening from cold work could be excluded from the finite element analysis used to establish the mean stress; this since the plasticity in the first cycle dominated the plastic deformation of the specimen. Overall, the SWT-based life model worked satisfactorily. However, the prediction of correct mean stresses at 550 degrees C proved somewhat difficult as the degree of mean stress relaxation at this temperature varies widely in available literature data.

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  • 16.
    Balachandramurthi, Arun Ramanathan
    et al.
    Univ West, Sweden.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. 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 Properties2019Ingår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 1, artikel-id 68Artikel i tidskrift (Refereegranskat)
    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.

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  • 17.
    Yu, Cheng-Han
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Anisoptropic Mechanical Properties of Thin-walled Hastelloy X by Selective Laser Melting2019Ingår i: AAMS2019: Alloys for Additive Manufacturing Symposium, 2019, s. 94-94Konferensbidrag (Övrigt vetenskapligt)
  • 18.
    Yu, Cheng-Han
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Anisotropic Mechanical Properties of Thin-walled Hastelloy X by Selctive Laser Melting2019Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Introduction/Purpose

    The study of thin-walled structure improves the design freedom of additive manufacturing. Understanding the relation between anisotropic mechanical properties and microstructure gives better control on manufacturing process and challenges the limit of the practical application. As one of the key Ni-based superalloy in aerospace industries, thin-walled Hastelloy X will be beneficial to the light weight application and build a more sustainable environment.

    Methods

    Thin-walled structures with different thickness form 1mm to 4mm was built by Selective Laser Melting process from EOS M290 machine, and the used powder was EOS NickelAlloy HX. The microstructure and crystallographic orientation have been studied by SEM and EBSD. Tensile tests with directions parallel and perpendicular to building direction (BD) have been carried out at elevated temperature from 400˚C to 700˚C.

    Results

    The elongated grains have been observed partly parallel and partly 45˚ tilted to the BD from back scattered SEM images, and the contouring region shows smaller grain size . Along the BD, the major preferred orientation is <101> and the minor is <001>. The tensile test result indicates higher strength but lower elongation in the direction perpendicular to BD, and also a big elongation drop between 600˚C and 700˚C. EBSD result from highly deformed area shows different texture evolution mechanism between two different tensile directions.

    Conclusions

    The local thermal gradient created by the scanning strategy guides the grain growing direction, which is <001>, and <101> turns to be the preferred orientation along BD. The elongated grains are the main reason for the anisotropic mechanical properties. When the tensile direction is parallel to BD, the orientation evolution fits the theory and indicates lattice rotation.

  • 19.
    Yu, Cheng-Han
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial.
    Peng, Ru Lin
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Lundgren, Jan-Erik
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Anisotropic Mechanical Properties of Thin-walled Hastelloy X Manufactured by Laser Powder Bed Fusion2019Konferensbidrag (Refereegranskat)
  • 20.
    Azeez, Ahmed
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Filosofiska fakulteten. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Characterisation of Deformation and Damage in a Steam Turbine Steel Subjected to Low Cycle Fatigue2019Ingår i: Structural Integrity Procedia / [ed] Elsevier, 2019, Vol. 23, s. 155-160Konferensbidrag (Refereegranskat)
    Abstract [en]

    The increased use of renewable energy pushes steam turbines toward a more frequent operation schedule. Consequently, components must endure more severe fatigue loads which, in turn, requires an understanding of the deformation and damage mechanisms under high-temperature cyclic loading. Based on this, low cycle fatigue tests were performed on a creep resistant steel, FB2, used in ultra-supercritical steam turbines. The fatigue tests were performed in strain control with 0.8-1.2 % strain range and at temperatures of 400 °C and 600 °C. The tests at 600 °C were run with and without dwell time. The deformation mechanisms at different temperatures and strain ranges were characterised by scanning electron microscopy and by quantifying the amount of low angle grain boundaries. The quantification of low angle grain boundaries was done by electron backscatter diffraction. Microscopy revealed that specimens subjected to 600 °C showed signs of creep damage, in the form of voids close to fracture surface, regardless of whether the specimen had been exposed to dwell time or been purely cycled. In addition, the amount of low angle grain boundaries was lower at 600 °C than at 400 °C. The study indicates that a significant amount of the inelastic strain comes from creep strain as opposed to being all plastic strain.

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  • 21. Zhou, Jinming
    et al.
    Chen, Zhe
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Siemens Industrial Turbomachinery AB, Finspång.
    Persson, Henrik
    Div of Production and Materials Engineering, Lunds University.
    Peng, Ru Lin
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    M'Saoubi, Rachid
    Seco Tools AB, Fagersta.
    Gustafsson, David
    Siemens Industrial Turbomachinery AB, Finspång.
    Comparative Assessment of the Surface Integrity of AD730 and IN718 Superalloys in High-Speed Turning with a CBN Tool2019Ingår i: Journal of Manufacturing and Materials Processing, ISSN 2504-4494, Vol. 3, nr 3, artikel-id 73Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nickel-based superalloys are typical materials used in components of aeroengines and gas turbine machinery. The strength properties of these alloys at high temperatures are crucial not only to the performance (e.g., power generation efficiency, energy consumption, and greenhouse gas emissions) of aeroengines and industrial gas turbines, but also to machinability during component manufacturing. This study comparatively evaluated the surface integrity of two superalloys, AD730® and Inconel 718 (IN718), during high-speed finishing turning using cubic boron nitride (CBN) tools. IN718 is a conventional superalloy used for the hot section components of aeroengines and industrial gas turbines, while AD730® is a novel superalloy with enhanced high-temperature mechanical properties and good potential as a next-generation superalloy for these components. High-speed turning tests of two superalloys were conducted using a CBN cutting tool and jet stream cooling. The achieved surface integrity of the AD730® and IN718 superalloys was characterized and analyzed to assess the comparability of these alloys. 

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  • 22.
    Loukil, Mohamed
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. RISE SICOMP, Broderna Ugglas Gata,Hus 208B, S-58188 Linkoping, Sweden.
    Varna, Janis
    Lulea Univ Technol, Sweden.
    Crack face sliding displacement (CSD) as an input in exact GLOB-LOC expressions for in-plane elastic constants of symmetric damaged laminates2019Ingår i: International journal of damage mechanics, ISSN 1056-7895, E-ISSN 1530-7921, artikel-id UNSP 1056789519866000Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The crack opening and crack sliding displacements of both faces of an intralaminar crack are the main parameters defining the significance of each crack in laminate stiffness degradation, according to the previously published GLOB-LOC approach for symmetric laminates with an arbitrary number of cracks in all plies. In the exact stiffness expressions of this approach, the crack density is always multiplied by crack opening displacement and crack sliding displacement. The dependence of crack opening displacement on geometrical and elastic parameters of adjacent plies was studied previously and described by simple fitting functions. The crack sliding displacement has been analyzed for low-crack densities only and the proposed finite element method-based fitting expressions are oversimplified not including the out-of-plane ply stiffness effects. Based on finite element method analysis, more accurate expressions for so-called non-interactive cracks are suggested in the presented article. For the first time the shear stress perturbations are analyzed and interaction functions are presented with the feature that they always lead to slightly conservative predictions. The presented simple fitting functions, when used in the GLOB-LOC model, give predictions that are in a good agreement with finite element method results and with experimental data for laminates with damaged off-axis plies in cases when crack face sliding is of importance. The significance of including crack sliding displacement in stiffness predictions is demonstrated.

  • 23.
    Loukil, Mohamed Sahbi
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. RISE SICOMP, Linköping, Sweden.
    Varna, Janis
    Luleå University of Technology, Luleå, Sweden.
    Crack Face Sliding Displacement (CSD) as an Input in Exact GLOB-LOC Expressions for In-plane Elastic Constants of Symmetric Damaged Laminates2019Ingår i: International journal of damage mechanics, ISSN 1056-7895, E-ISSN 1530-7921, s. 1-23Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The crack opening and crack sliding displacements of both faces of an intralaminar crack are the main parameters defining the significance of each crack in laminate stiffness degradation, according to the previously published GLOB-LOC approach for symmetric laminates with an arbitrary number of cracks in all plies. In the exact stiffness expressions of this approach, the crack density is always multiplied by crack opening displacement and crack sliding displacement. The dependence of crack opening displacement on geometrical and elastic parameters of adjacent plies was studied previously and described by simple fitting functions. The crack sliding displacement has been analyzed for low-crack densities only and the proposed finite element method-based fitting expressions are oversimplified not including the out-of-plane ply stiffness effects. Based on finite element method analysis, more accurate expressions for so-called non-interactive cracks are suggested in the presented article. For the first time the shear stress perturbations are analyzed and interaction functions are presented with the feature that they always lead to slightly conservative predictions. The presented simple fitting functions, when used in the GLOB-LOC model, give predictions that are in a good agreement with finite element method results and with experimental data for laminates with damaged off-axis plies in cases when crack face sliding is of importance. The significance of including crack sliding displacement in stiffness predictions is demonstrated.

  • 24.
    Palmert, Frans
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Crack growth in single crystal nickel base superalloys under isothermal and thermomechanical fatigue2019Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This work concerns the fatigue crack growth behaviour of nickel base single crystal superalloys. The main industrial application of this class of materials is in gas turbine blades, where the ability to withstand severe mechanical loading in combination with high temperatures is required. In order to ensure the structural integrity of gas turbine blades, knowledge of the fatigue crack growth behaviour under service-like conditions is of utmost importance. The aim of the present work is both to improve the understanding of the crack growth behaviour of single crystal superalloys and also to improve the testing and evaluation methodology for crack propagation under thermomechanical fatigue loading conditions. Single crystal superalloys have anisotropic mechanical properties and are prone to localization of inelastic deformation along the close-packed planes of the crystal lattice. Under some conditions, crystallographic crack growth occurs along these planes and this is a complicating factor throughout the whole chain of crack propagation life simulation; from material data generation to component calculation. Fatigue crack growth testing has been performed, both using conventional isothermal testing methods and also using thermomechanical fatigue crack growth testing. Experimental observations regarding crystallographic crack growth have been made and its dependence on crystal orientation and testing temperature has been investigated. Quantitative crack growth data are however only presented for the case of Mode I crack growth under isothermal as well as thermomechanical fatigue conditions. Microstructural investigations have been undertaken to investigate the deformation mechanisms governing the crack growth behaviour. A compliance based method for the evaluation of crack opening force under thermomechanical fatigue conditions was developed, in order to enable a detailed analysis of the test data. The crack opening force evaluation proved to be of key importance in the understanding of the crack driving force under different testing conditions.

    Delarbeten
    1. Fatigue crack growth behaviour of an alternative single crystal nickel base superalloy
    Öppna denna publikation i ny flik eller fönster >>Fatigue crack growth behaviour of an alternative single crystal nickel base superalloy
    2018 (Engelska)Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 109, s. 166-181Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The fatigue crack growth behaviour of a single crystal nickel base superalloy was studied at three different temperatures (20 degrees C, 500 degrees C and 750 degrees C) and three different crystallographic orientations. At the highest testing temperature, the influence of hold time at maximum load was also evaluated. Under some of the testing conditions, crystallographic crack growth occurred along {1 1 1} planes, which were non-perpendicular to the loading direction. The propensity for crystallographic cracking was observed to be strongly temperature dependent with a maximum occurring at the intermediate testing temperature of 500 degrees C. During non-crystallographic, Mode I crack growth the crack tended to avoid the gamma particles and propagated preferentially through the gamma matrix.

    Ort, förlag, år, upplaga, sidor
    ELSEVIER SCI LTD, 2018
    Nyckelord
    Single crystal superalloy; Fatigue; Crack growth; Crystallographic crack growth; Temperature dependence; Orientation dependence; Hold time influence
    Nationell ämneskategori
    Teknisk mekanik
    Identifikatorer
    urn:nbn:se:liu:diva-145431 (URN)10.1016/j.ijfatigue.2017.12.003 (DOI)000425073100017 ()
    Anmärkning

    Funding Agencies|Siemens Industrial Turbomachinery AB in Finspang, Sweden; Swedish Energy Agency, via the Research Consortium of Materials Technology for Thermal Energy Processes [KME-702]

    Tillgänglig från: 2018-04-03 Skapad: 2018-04-03 Senast uppdaterad: 2019-09-23
    2. Thermomechanical fatigue crack growth in a single crystal nickel base superalloy
    Öppna denna publikation i ny flik eller fönster >>Thermomechanical fatigue crack growth in a single crystal nickel base superalloy
    2019 (Engelska)Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 122, s. 184-198Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Thermomechanical fatigue crack growth in a single crystal nickel base superalloy was studied. Tests were performed on single edge notched specimens, using in phase and out of phase thermomechanical fatigue cycling with temperature ranges of 100-750°C and 100-850°C and hold times at maximum temperature ranging from 10s to 6h. Isothermal testing at 100°C, 750°C and 850°C was also performed using the same test setup. A compliance-based method is proposed to experimentally evaluate the crack opening stress and thereby estimate the effective stress intensity factor range ΔKeff for both isothermal and nonisothermal conditions. For in phase thermomechanical fatigue, the crack growth rate is increased if a hold time is applied at the maximum temperature. By using the compliance-based crack opening evaluation, this increase in crack growth rate was explained by an increase in the effective stress intensity factor range which accelerated the cycle dependent crack growth. No significant difference in crack growth rate vs ΔKeff was observed between in phase thermomechanical fatigue tests and isothermal tests at the maximum temperature. For out of phase thermomechanical fatigue, the crack growth rate was insensitive to the maximum temperature and also to the length of hold time at maximum temperature. The crack growth rate vs ΔKeff during out of phase thermomechanical fatigue was significantly higher than during isothermal fatigue at the minimum temperature, even though the advancement of the crack presumably occurs at the same temperature. Dissolution of γ′ precipitates and recrystallization at the crack tip during out of phase thermomechanical fatigue is suggested as a likely explanation for this difference in crack growth rate.

    Ort, förlag, år, upplaga, sidor
    Elsevier, 2019
    Nyckelord
    single crystal superalloy, thermomechanical fatigue, crack growth, crack closure
    Nationell ämneskategori
    Materialteknik Teknisk mekanik Bearbetnings-, yt- och fogningsteknik Metallurgi och metalliska material Infrastrukturteknik
    Identifikatorer
    urn:nbn:se:liu:diva-154074 (URN)10.1016/j.ijfatigue.2019.01.014 (DOI)000462110100017 ()
    Anmärkning

    Funding agencies: Siemens Industrial Turbomachinery AB in Finspang, Sweden; Swedish Energy Agency, via the Research Consortium of Materials Technology for Thermal Energy Processes [KME-702]

    Tillgänglig från: 2019-01-28 Skapad: 2019-01-28 Senast uppdaterad: 2019-04-08
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    Crack growth in single crystal nickel base superalloys under isothermal and thermomechanical fatigue
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    presentationsbild
  • 25.
    Calmunger, Mattias
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Filosofiska fakulteten. Linköpings universitet, Tekniska fakulteten.
    Lindström, Thomas
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Effect of Additive Manufacturing on Fatigue Crack Propagation of a Gas Turbine Superalloy2019Ingår i: Structural Integrity Procedia, Elsevier, 2019Konferensbidrag (Refereegranskat)
  • 26.
    Chen, Zhe
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Peng, Ru Lin
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Zhou, Jinming
    Division of Production and Materials Engineering, Lund University, Lund, Sweden.
    M'Saoubi, Rachid
    Seco Tools AB, Fagersta, Sweden.
    Gustafsson, David
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Effect of Machining Parameters on Cutting Force and Surface Integrity when High-Speed Turning AD730™ with PCBN Tools2019Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 100, nr 9-12, s. 2601-2615Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The novel wrought nickel-based superalloy, AD 730™, is a good candidate material for turbine disc applications at high temperatures beyond 650 °C. The present study focuses on the machining performance of this newly developed alloy under high-speed turning conditions with advanced PCBN tools. Meanwhile, the machined surface integrity as influenced by cutting speed and feed rate was also investigated. The surface integrity was thoroughly characterized in terms of surface roughness and morphology, machining-induced plastic deformation, white layer formation, and residual stresses. It has been found that the cutting speed and feed rate had a strong effect on the cutting forces and resultant surface integrity. The cutting forces required when machining the alloy were gradually reduced with increasing cutting speed, while at 250 m/min and above, the flank tool wear became stronger which led to increased thrust force and feed force. A higher feed rate, on the other hand, always resulted in higher cutting forces. Increasing the cutting speed and feed rate in general deteriorated the surface integrity. High cutting speeds within the range of 200–250 m/min and a low feed rate of 0.1 mm/rev are preferable in order to implement more cost-effective machining without largely reducing the surface quality achieved. The formation of tensile residual stresses on the machined AD 730™, however, could be of a concern where good fatigue resistance is critical.

  • 27.
    Vaidyalingam Arumugam, Karthik
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial.
    Effect of Process Parameters on Contour Properties in Inconel 718 Structures Fabricated by Electron Beam Melting2019Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Additive Manufacturing (AM), commonly known as 3D printing is a production method that utilises repeated addition of layers in order to produce a final shape. AM utilises less raw material and does not have drawbacks such as tool wear and material wastage as seen in conventional machining. However, they do have drawbacks such as poor surface and internal defects.  A common practice in AM is the fabrication of contour and bulk region using separate parameters.

     The aim of this project was to study the effects of various process parameters on the contour properties. The process parameters considered were scanning speed, beam current and focus offset. The Nickel alloy Inconel 718 was utilised in Electron Beam Melting (EBM) to fabricate the test specimen. The samples used in this project were in an as-built condition which was priorly subjected to tensile testing for a different project. The tests performed in this project are hardness testing and microstructural investigation about grains, precipitates and the various defects.

     The test results helped to understand the effect of various process parameters on the hardness and microstructure of the samples. The samples with lower scanning speed had higher hardness and lesser lack of fusion than samples with higher speed. In the case of varying beam current, the samples with higher beam current had higher hardness values and fewer lack of fusions. Similarly, the effects of varying two or more process parameters were also studied and their findings recorded. The microstructure consisted of a large number of shrinkage porosities in the bulk and contour regions. The presence of Niobium rich precipitates at grain boundaries and the grain structure for various process parameters were identified and recorded.

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  • 28.
    Loukil, Mohamed Sahbi
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. RISE SICOMP, Sweden.
    Varna, Janis
    Lulea Univ Technol, Sweden.
    Effective shear modulus of a damaged ply in laminate stiffness analysis: Determination and validation2019Ingår i: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, artikel-id UNSP 0021998319874369Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The concept of the "effective stiffness" for plies in laminates containing intralaminar cracks is revisited presenting rather accurate fitting expressions for the effective stiffness dependence on crack density in the ply. In this article, the effective stiffness at certain crack density is back-calculated from the stiffness difference between the undamaged and damaged laminate. Earlier finite element method analysis of laminates with cracked 90-plies showed that the effective longitudinal modulus and Poissons ratio of the ply do not change during cracking, whereas the transverse modulus reduction can be described by a simple crack density dependent function. In this article, focus is on the remaining effective constant: in-plane shear modulus. Finite element method parametric analysis shows that the dependence on crack density is exponential and the fitting function is almost independent of geometrical and elastic parameters of the surrounding plies. The above independence justifies using the effective ply stiffness in expressions of the classical laminate theory to predict the intralaminar cracking caused stiffness reduction in laminates with off-axis plies. Results are in a very good agreement with (a) finite element method calculations; (b) experimental data, and (c) with the GLOB-LOC model, which gives a very accurate solution in cases where the crack face opening and sliding displacements are accurately described.

  • 29.
    Zhang, Pimin
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Sadeghimeresht, Esmaeil
    Dept of Engineering Science, University West, Trollhättan, Sweden.
    Chen, Shula
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Markocsan, Nicoclaie
    Dept of Engineering Science, University West, Trollhättan, Sweden.
    Joshi, Shrikant
    Dept of Engineering Science, University West, Trollhättan, Sweden.
    Chen, Weimin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Buyanova, Irina A
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Peng, Ru Lin
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Effects of Surface Finish on the Initial Oxidation of HVAF-sprayed NiCoCrAlY Coatings2019Ingår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Journal of Surface and Coatings Technology, ISSN 0257-8972, Vol. 364, s. 43-56Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Oxide scale formed on HVAF-sprayed NiCoCrAlY coatings and the effect of surface treatment were investigated by a multi-approach study combining photo-stimulated luminescence, microstructural observation and mass gain. The initial oxidationbehaviour of as-sprayed, polished and shot-peened coatings at 1000 °C is studied. Both polished and shot-peened coatings exhibited superior performance due to rapid formation of α-Al2O3 fully covering the coating and suppressing the growth of transient alumina, assisted by a high density of α-Al2O3 nuclei on surface treatment induced defects. Moreover, the fast development of a two-layer alumina scale consisting of an inward-grown inner α-Al2O3 layer and an outer layer transformed from outward-grown transient alumina resulted in a higher oxide growth rate of the as-sprayed coating.

  • 30.
    Busse, Christian
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Palmert, Frans
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Sjodin, B.
    Siemens Ind Turbomachinery AB, Sweden.
    Almroth, P.
    Siemens Ind Turbomachinery AB, Sweden.
    Gustafsson, D.
    Siemens Ind Turbomachinery AB, Sweden.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Evaluation of the crystallographic fatigue crack growth rate in a single-crystal nickel-base superalloy2019Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 127, s. 259-267Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cracks in single-crystal nickel-base superalloys have been observed to switch cracking mode from Mode I to crystallographic cracking. The crack propagation rate is usually higher on the crystallographic planes compared to Mode I, which is important to account for in crack growth life predictions. In this paper, a method to evaluate the crystallographic fatigue crack growth rate, based on a previously developed crystallographic crack driving force parameter, is presented. The crystallographic crack growth rate was determined by evaluating heat tints on the fracture surfaces of the test specimens from the experiments. Complicated crack geometries including multiple crystallographic crack fronts were modelled in a three dimensional finite element context, The data points of the crystallographic fatigue crack growth rate collapse on a narrow scatter band for the crystallographic cracks indicating a correlation with the previously developed crystallographic crack driving force.

    Publikationen är tillgänglig i fulltext från 2021-05-24 08:45
  • 31.
    Kihlberg, Ebba
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Norman, Viktor
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    König, Mathias
    Schmidt, Pål
    Evaluation of the ISO-standards for Graphite Image Analysis of Compacted Graphite Iron2019Konferensbidrag (Refereegranskat)
  • 32.
    Zhang, Pimin
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Peng, Ru Lin
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Failure Mechanism of MCrAlY Coating at the Coating-Substrate Interface under Type I Hot Corrosion2019Ingår i: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176, Vol. 70, nr 9, s. 1593-1600Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    MCrAlY coatings are widely used to provide protection of hot component in modern gas turbine engines against high‐temperature oxidation and hot corrosion. Coating‐substrate interface, where the substrate is only partially covered by the coatings, is vulnerable to the hot corrosion attack. The accelerated degradation at the coating‐substrate interface can cause fast spallation of the coating, leading to the early failure of the gas turbine components. In this paper, MCrAlY powder was deposited on IN792 disks by high‐velocity oxygen‐fuel spraying. The hot corrosion behavior of the coated sample was investigated using (0.8Na, 0.2K)2SO 4 salt deposition at 900°C in lab air. Results showed a minor attack in the coating center, however, an accelerated corrosion attack at the coating‐substrate interface. The fast growth of corrosion products from substrate caused large local volume expansions at the coating‐substrate interface, resulting in an early coating spallation.

  • 33.
    Jonnalagadda, Krishna Praveen
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Mahade, Satyapal
    Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Kramer, Stephanie
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling. Linköpings universitet, Tekniska fakulteten.
    Zhang, Pimin
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Curry, Nicholas
    Treibacher Industrie AG, Althofen, Austria.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB,Finspång,Sweden.
    Peng, Ru Lin
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Failure of Multilayer Suspension Plasma Sprayed Thermal Barrier Coatings in the Presence of Na2SO4 and NaCl at 900 °C2019Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 28, nr 1-2, s. 212-222Artikel i tidskrift (Refereegranskat)
    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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  • 34.
    Jonnalagadda, Krishna Praveen
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Mahade, Satyapal
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Kramer, Stephanie
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Zhang, Pimin
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Curry, Nicholas
    Treibacher Industrie AG, Althofen, Austria.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Peng, Ru
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Failure of Multilayer Suspension Plasma Sprayed Thermal Barrier Coatings in the Presence of Na2SO4 and NaCl at 900 degrees C2019Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 28, nr 1-2, s. 212-222Artikel i tidskrift (Refereegranskat)
    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.

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  • 35.
    Jonnalagadda, Krishna Praveen
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Filosofiska fakulteten.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, 61283, Finspång, Sweden.
    Peng, Ru Lin
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Fatigue life prediction of thermal barrier coatings using a simplified crack growth model2019Ingår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 39, nr 5, s. 1869-1876Artikel i tidskrift (Refereegranskat)
    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.

  • 36.
    Suo, Jiao
    et al.
    Wuhan Univ, Peoples R China.
    Peng, Zhifang
    Wuhan Univ, Peoples R China.
    Yang, Huachun
    Dongfang Boiler Grp Co Ltd, Peoples R China.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Sandvik Mat Technol, Sweden.
    Yu, Mingming
    Dongfang Boiler Grp Co Ltd, Peoples R China.
    Formation of Laves Phase in Sanicro 25 Austenitic Steel During Creep-Rupture Test at 700 degrees C2019Ingår i: METALLOGRAPHY MICROSTRUCTURE AND ANALYSIS, ISSN 2192-9262, Vol. 8, nr 2, s. 281-286Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The mechanisms for the formation of Laves phase located at grain boundaries and in grain interiors in Sanicro 25 steel after creep-rupture test at 700 degrees C and 150/180MPa for 9862/5665h were studied, respectively. Scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectrometer, and multi-phase separation technology analysis reveals that Laves phase particles nucleated adjacently either to Si-enriched spots present in the bulky M23C6 carbides or to the grain boundary areas rich in Si, which made the bulky M23C6 carbides gradually divide into small pieces and eventually resulted in the formation of a refined mixture of M23C6 and Laves phase at grain boundaries. Laves phase particles formed independently in austenitic matrix and also dependently at interfaces between austenitic matrix and Z phase in grain interiors. The size and morphology of Laves phase formed at grain boundaries (in M23C6 carbides) and in grain interiors (austenitic matrix) are different. It is hoped that the presented findings will be helpful to understand the Laves phase formation and the grain boundary precipitate refinement correlated with good mechanical properties of this class of austenitic steels/alloys.

  • 37.
    Calmunger, Mattias
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Wärner, Hugo
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    High Temperature Properties of Austenitic Stainless Steels for Future Power Plant Applications2019Konferensbidrag (Refereegranskat)
  • 38.
    Kanesund, Jan
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Brodin, Håkan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Siemens Ind Turbomachinery AB, Sweden.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Hot corrosion influence on deformation and damage mechanisms in turbine blades made of IN-792 during service2019Ingår i: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 96, s. 118-129Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The deformation and damage mechanisms of a gamma-prime hardened superalloy is investigated in the current paper. Two turbine blades made of precision cast polycrystalline superalloy IN-792 have been examined after service exposure under engine conditions typical for industrial gas turbines. This study is compared to a previous study with focus on deformation and damage mechanisms in IN-792 during thermal mechanical fatigue testing performed under laboratory conditions. The failure of the two turbine blades is explained as a combination of two damage mechanisms, mechanical and chemical damage. In the current investigation, type I hot corrosion and creep are the two dominant damage mechanisms. The type I hot corrosion is confirmed by the presence of Ti-sulfides and sulfur in free form at the grain boundaries, which has caused embrittlement and loss of resistance to crack growth. In turn, this has shortened the turbine blade life dramatically and intercrystalline failure is the dominant damage mechanism. Almost all cracks have propagated intercrystalline in the two turbine blades. In the previous study, mechanical damage mechanism is the dominant mechanism and for the highest temperature also oxidation give is contribution. In the previous study, almost all cracks propagated transcrystalline. When exposed to laboratory conditions, the areas around cracks are more plastically deformed compared to the area around the cracks in the turbine blades. In the two studies, dynamic recrystallization has occurred at the grain boundaries.

  • 39.
    Jonnalagadda, Krishna Praveen
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Zhang, Pimin
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Gupta, Mohit
    Department of Engineering Science, University West, Trollhättan.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång.
    Peng, Ru Lin
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Hot gas corrosion and its influence on the thermal cycling performance of suspension plasma spray TBCs2019Ingår i: Proceedings of ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition, New York, NY: American Society of Mechanical Engineers , 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    Thermal barrier coatings (TBCs) manufactured with suspension plasma spray (SPS) are promising candidates for use in gas turbines due to their high strain tolerance during thermal cyclic fatigue (TCF). However, corrosion often occurs alongside thermal fatigue and coating durability under these conditions is highly desirable. The current study focuses on understanding the corrosion behavior and its influence on the thermal cyclic fatigue life of SPS TBCs. Corrosion tests were conducted at 780 OC using a mixed-gas (1SO2-0.1CO-20CO2-N2(bal.) in vol. %) for 168h. They were later thermally cycled between 100-1100 ⁰C with a 1h hold time at 1100 ⁰C. Corrosion test results indicated that the damage predominantly started from the edges and a milder damage was observed at the center. Nickel sulfide was observed on top of the top coat and also in the columnar gaps of the top coat. Chromium oxides were observed inside the top coat columnar gaps but close to the bond coat/top coat interface. They were believed to reduce the strain tolerance of SPS TBCs to an extent and also amplify the thermal mismatch stresses during TCF tests. This, together with a fast growth of alumina during the TCF, resulted in a significant drop in the TCF life compared to the standard TCF tests.

  • 40.
    Wärner, Hugo
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Filosofiska fakulteten. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Influence of Ageing on Thermomechaical Fatigue of Austenitic Stainless Steels2019Ingår i: Structural Integrity Procedia / [ed] Elsevier, Elsevier, 2019Konferensbidrag (Refereegranskat)
  • 41.
    Mahade, Satyapal
    et al.
    Univ West, Sweden.
    Curry, Nicholas
    Treibacher Ind AG, Austria.
    Jonnalagadda, Krisha Praveen
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Peng, Ru
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Markocsan, Nicolaie
    Univ West, Sweden.
    Nylen, Per
    Univ West, Sweden.
    Influence of YSZ layer thickness on the durability of gadolinium zirconate/YSZ double-layered thermal barrier coatings produced by suspension plasma spray2019Ingår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 357, s. 456-465Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, three double layered thermal barrier coating (TBC) variations with different gadolinium zirconate (GZ) and YSZ thickness (400GZ/100YSZ, 250GZ/250YSZ and 100GZ/400YSZ respectively, where the prefixed numbers before GZ and YSZ represent the layer thickness in mu m), were produced by suspension plasma spray (SPS) process. The objective was to investigate the influence of YSZ thickness on the thermal conductivity and thermal shock lifetime of the GZ/YSZ double layered TBCs. The as sprayed TBCs were characterized using SEM, XRD and porosity measurements. Thermal diffusivity measurements were made using laser flash analysis and the thermal conductivity of the TBCs was calculated. The double layered TBC with the lowest YSZ (400GZ/100YSZ) thickness showed lower thermal diffusivity and thermal conductivity. The double layered TBCs were subjected to thermal shock test at a TBC surface temperature of 1350 degrees C. Results indicate that the TBC with a higher YSZ thickness (100GZ/400YSZ) showed inferior thermal shock lifetime whereas the TBCs with low YSZ thickness showed comparatively higher thermal shock lifetimes. Failure of the TBCs after thermal shock test was analyzed using SEM and XRD to gain further insights.

  • 42. Bergwall, Mats
    et al.
    Hederberg, Hampus
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Murtagh, Timothy
    Rinn, Florence
    Loukil, Mohamed Sahbi
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Innovative Out-of-Autoclave Composite Manufacturing Method for Saving Cost2019Konferensbidrag (Refereegranskat)
  • 43.
    Kihlberg, Ebba
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Norman, Viktor
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Skoglund, Peter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Schmidt, Pål
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Investigation of Microstructure Parameters and Thermo-Mechanical Fatigue Performance of Cast Iron2019Konferensbidrag (Refereegranskat)
  • 44.
    Azeez, Ahmed
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Filosofiska fakulteten. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Lindström, Stefan B
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Low Cycle Fatigue Modelling of Steam Turbine Rotor Steel2019Ingår i: Structural Integrity Procedia / [ed] Elsevier, Elsevier, 2019, Vol. 23, s. 149-154Konferensbidrag (Refereegranskat)
    Abstract [en]

    Materials in steam turbine rotors are subjected to cyclic loads at high temperature, causing cracks to initiate and grow. To allow for more flexible operation, accurate fatigue models for life prediction must not be overly conservative. In this study, fully reversed low cycle fatigue tests were performed on a turbine rotor steel called FB2. The tests were done isothermally, within temperature range of room temperature to 600 °C, under strain control with 0.8-1.2 % total strain range. Some tests included hold time to calibrate the short-time creep behaviour of the material. Different fatigue life models were constructed. The life curve in terms of stress amplitude was found unusable at 600 °C, while the life curve in terms of total strain or inelastic strain amplitudes displayed inconsistent behaviour at 500 °C. To construct better life model, the inelastic strain amplitudes were separated into plastic and creep components by modelling the deformation behaviour of the material, including creep. Based on strain range partitioning approach, the fatigue life depends on different damage mechanisms at different strain ranges. This allowed the formulation of life curves based on plasticity or creep domination, which showed creep domination at 600 °C, while at 500 °C, creep only dominates for higher strain range.

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  • 45.
    Wärner, Hugo
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Microscopic Evaluation of Creep-Fatigue Interaction in Heat Resistant Austenic Alloys2019Konferensbidrag (Refereegranskat)
  • 46.
    Jiang, Shuang
    et al.
    Northeastern Univ, Peoples R China.
    Peng, Ru
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Jia, Nan
    Northeastern Univ, Peoples R China.
    Zhao, Xiang
    Northeastern Univ, Peoples R China.
    Zuo, Liang
    Northeastern Univ, Peoples R China.
    Microstructural and textural evolutions in multilayered Ti/Cu composites processed by accumulative roll bonding2019Ingår i: Journal of Materials Science & Technology, ISSN 1005-0302, Vol. 35, nr 6, s. 1165-1174Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ti/Cu multilayered composites were fabricated via accumulative roll bonding (ARB). During co-deformation of the constituent metals, the hard Ti layers necked preferentially and then fragmented with the development of shear bands. Transmission electron microscopy showed that with increasing ARB cycles, grains in Ti were significantly refined even though dynamic recrystallization has occurred. For Cu the significant grain refinement was only found within the shear banded region when the composite was processed after five ARB cycles. Due to the diffusion of Cu atoms into Ti at the heterophase inter faces, amorphization with a width less than 10 nm was identified even in the composite processed by one cycle. At higher ARB cycles, the width of amorphous region increased and intermetallic compounds CuTi appeared from the region. The lattice defects introduced at the heterophase interfaces under roll bonding was responsible for the formation of the nano-scaled compounds. X-ray diffraction showed that an abnormal {11 (2) over bar0} fiber texture was developed in Ti layers, while significant brass-type textures were developed in Cu layers. Some orientations along the {11 (2) over bar0} fiber favored the prismatic amp;lt;aamp;gt; slip for Ti. Tensile tests revealed the elevated strength without a substantial sacrifice of ductility in the composites during ARB. The unique mechanical properties were attributed to the significantly refined grains in individual metals, the good bonding between the constituent metals, as well as the development of an abnormal {11 (2) over bar0} fiber texture in Ti layers. (C) 2019 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science amp; Technology.

  • 47.
    Balachandramurthi, Arun Ramanathan
    et al.
    Univ West, Sweden.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Univ West, Sweden.
    Dixit, Nikhil
    Univ West, Sweden.
    Deng, Dunyong
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Pederson, Robert
    Univ West, Sweden.
    Microstructural influence on fatigue crack propagation during high cycle fatigue testing of additively manufactured Alloy 7182019Ingår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 149, s. 82-94Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A study of the microstructure of additively manufactured Alloy 718 was performed in order to better understand the parameters that have an influence on the fatigue properties of the material. The specimens were manufactured using two powder bed fusion techniques - Electron Beam Melting (EBM) and Selective Laser Melting (SLM). Four point bending fatigue tests were performed at room temperature with a stress ratio of R = 0.1 and 20 Hz frequency, on material that was either in hot isostatically pressed (HIP) and solution treated and aged (STA) condition or in STA condition without a prior HIP treatment. The grains in the SLM material in the HIP + STA condition have grown considerably both in the hatch and the contour regions; EBM material, in contrast, shows grain growth only in the contour region. Fractographic analysis of the specimens in HIP + STA condition showed a faceted appearance while the specimens in STA condition showed a more planar crack appearance. The crack propagation occurred in a transgranular mode and it was found that precipitates such as NbC, TiN or 8-phase, when present, did not affect the crack path. The areas with larger grains corresponded to the faceted appearance of the fracture surface. This could be attributed to the plastic zone ahead of the crack tip being confined within one grain, in case of the larger grains, which promotes single shear crack growth mode.

  • 48.
    Kumara, Chamara
    et al.
    Univ West, Sweden.
    Segerstark, Andreas
    GKN Aerosp Engine Syst AB, Sweden.
    Hanning, Fabian
    Chalmers Univ Technol, Sweden.
    Dixit, Nikhil
    Univ West, Sweden.
    Joshi, Shrikant
    Univ West, Sweden.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Univ West, Sweden.
    Nylen, Per
    Univ West, Sweden.
    Microstructure modelling of laser metal powder directed energy deposition of alloy 7182019Ingår i: ADDITIVE MANUFACTURING, ISSN 2214-8604, Vol. 25, s. 357-364Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A multi-component and multi-phase-field modelling approach, combined with transformation kinetics modelling, was used to model microstructure evolution during laser metal powder directed energy deposition of Alloy 718 and subsequent heat treatments. Experimental temperature measurements were utilised to predict microstructural evolution during successive addition of layers. Segregation of alloying elements as well as formation of Laves and delta phase was specifically modelled. The predicted elemental concentrations were then used in transformation kinetics to estimate changes in Continuous Cooling Transformation (CCT) and Time Temperature Transformation (TTT) diagrams for Alloy 718. Modelling results showed good agreement with experimentally observed phase evolution within the microstructure. The results indicate that the approach can be a valuable tool, both for improving process understanding and for process development including subsequent heat treatment.

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  • 49.
    Deng, Dunyong
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Peng, Ru
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    On the dwell-fatigue crack propagation behavior of a high strength superalloy manufactured by electron beam melting2019Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 760, s. 448-457Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To demonstrate the reliability of additively manufactured superalloys for critical turbine engine components, dynamic tests simulating in-service condition are required. The present study aims to study the dwell-fatigue crack propagation behaviors of IN718 manufactured via electron beam melting (EBM). The textured and columnar-grained microstructure of EBM IN718 shows anisotropic dwell-fatigue cracking resistance when loading axis is aligned parallel and perpendicular to the columnar grains. High and low angle grain boundaries interact differently with the dwell-fatigue cracking path. The effect of different heat treatments on the cracking behavior is also discussed. The dwell-fatigue crack propagation rate of EBM IN718 is compared with forged IN718 under both dwell-fatigue test condition and pure fatigue test condition. The superiority of dwell-fatigue cracking resistance of EBM IN718 to forged IN718 is shown and discussed.

  • 50.
    Deng, Dunyong
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Peng, Ru
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    On the Dwell-Fatigue Crack Propagation Behavior of a High-Strength Ni-Base Superalloy Manufactured by Selective Laser Melting2019Ingår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study focuses on the dwell-fatigue crack propagation behavior of IN718 manufactured via selective laser melting (SLM). The dwell-fatigue test condition is 823 K (550 with a long 2160-s dwell-holding period. Effects of heat treatment and loading direction on dwell-fatigue crack propagation rates are studied. A grain boundary delta precipitate seems to be slightly beneficial to the dwell-fatigue cracking resistance of SLM IN718. A comparison has been made between SLM IN718 and forged counterparts at different temperatures, indicating that a creep damage mechanism is likely dominant for SLM IN718 under the present test condition. A general discussion of the inferior creep resistance of SLM IN718 is also included. The anisotropic dwell-fatigue cracking resistance has also been studied and rationalized with the effective stress intensity factor calculated from finite element modeling.

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