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• 151.
Chalmers University of Technology.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Chalmers University of Technology.
Oxygen influenced intergranular crack propagation: analysing microstructure and chemistry in the crack tip region2011In: Materials at High Temperature, ISSN 0960-3409, E-ISSN 1878-6413, Vol. 28, no 4, p. 336-341Article in journal (Refereed)

Ni-base superalloys have for decades been studied with regard to environmentally influenced intergranular crack propagation. For high temperature fatigue frequencies andlt;0.1 Hz, it has been shown that an oxygen-rich environment promotes time-dependent crack growth while at andgt;0.1 Hz and/or in inert environments (e.g. vacuum) crack growth is cycle dependent. Oxygen interaction at, or ahead of, the crack tip has been pointed out as the reason for the degraded mechanical properties. While many aspects of this type of crack growth have been previously investigated there is still no consensus about the detailed mechanisms, mainly due to the lack of in-detail investigations of the crack-tip region. less thanbrgreater than less thanbrgreater thanHere, crack tip regions in the Ni-base superalloy Alloy 718 were studied. Specimens were subjected to 90 s hold-times at 550 degrees C and 650 degrees C. Crack growth was arrested before final fracture, allowing cross-sectional analyses of the crack-tip region using scanning electron microscopy (SEM). Detailed studies of the crack-tip region were performed using transmission electron microscopy (TEM) and atom probe tomography (APT). For both APT and TEM samples, site-specific focussed ion beam (FIB) sample preparation was performed in a combined FIB-SEM system. The methodology of accessing and analysing the crack tip region is shown. Initial results on oxidation, oxygen penetration and plastic deformation are shown and discussed.

• 152.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
Thermomechanical Fatigue Behavior of Aged Heat Resistant Austenitic Alloys2017Conference paper (Refereed)
• 153.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Sandvik Materials Technology, Sandviken, Sweden. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
Thermomechanical Fatigue Behaviour of Aged Heat Resistant Austenitic Alloys2019In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, no 127, p. 509-521Article in journal (Refereed)

The increasing demands for efficiency and flexibility result in more severe operating conditions for the materials used in critical components of biomass power plants. These operating conditions involve higher temperature ranges, more pronounced environmental effects and cyclic operations. Austenitic stainless steels have shown to possess promising high temperature properties which makes them suitable as candidates for critical components in biomass power plant. However, their behaviour under such conditions is not yet fully understood. This work investigates three commercial austenitic alloys: Esshete 1250, Sanicro 25 and Sanicro 31HT. The alloys were subjected to in-phase (IP) thermomechanical fatigue (TMF) testing under strain-control in the temperature range of 100–800 °C. Both virgin and pre-aged TMF specimens were tested in order to simulate service degradation resulting from long-term usage. The results show that the pre-aged specimens suffered shorter TMF-life compared to the virgin specimens. The scanning electron microscopy methods electron backscatter diffraction (EBSD) and energy dispersive spectroscopy (EDS) were used to analyse and discuss active failure and deformation mechanisms. The difference in TMF-life produced by the two testing conditions was attributed to an embrittling effect by precipitation, reduced creep properties and oxidation assisted cracking.

The full text will be freely available from 2021-06-18 08:00
• 154.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
Influence of Ageing on Thermomechaical Fatigue of Austenitic Stainless Steels2019In: Structural Integrity Procedia / [ed] Elsevier, Elsevier, 2019Conference paper (Refereed)
• 155.
School of Materials Science and Engineeering, Beihang Univeristy, Beijing, China.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. School of Materials Science and Engineeering, Beihang Univeristy, Beijing, China. School of Materials Science and Engineeering, Beihang Univeristy, Beijing, China. School of Materials Science and Engineeering, Beihang Univeristy, Beijing, China. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
Al2O2 Nanoparticle Reinforced Fe-based Alloys Synthesized by Thermite Reaction2012In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 47, no 8, p. 3585-3591Article in journal (Refereed)

It is very difficult to manufacture oxide nanoparticle strengthened alloys through the conventional casting in the gravity field or even in the space microgravity environment. A thermite reaction process was used to produce molten metal that was then solidified in a graphite mold in super gravity field caused by centrifugal force; we were able to obtain Al2O3 nanoparticle reinforced Fe-based alloys. The formation of Al2O3 nanoparticles was related to the addition of TiO2 xerogel to the thermite mixture, and their uniform distribution in the alloy can be explained by their assembly in (Ni, Fe)Al intermetallics during solidification owing to the low interfacial energy between them.

• 156.
Université de Lyon, Ecole Nationale d'Ingénieurs de Saint-Etienne (ENISE), Saint-Etienne, France.
Dept of Mechanical ang Materials Engineering, Karlstad University. Université de Lyon, Ecole Nationale d'Ingénieurs de Saint-Etienne (ENISE), Saint-Etienne, France. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Université de Lyon, Ecole Nationale d'Ingénieurs de Saint-Etienne (ENISE), Saint-Etienne, France.
Energy Input Effect on Morphology and Microstructure of Selective Laser Melting Single Track from Metallic Powder2013In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 213, no 4, p. 606-613Article in journal (Refereed)

Process parameters of selective laser melting affect the response of a powder–substrate system and, therefore, the geometry and microstructure of the manufactured parts. The experiments were carried out at fixed values of laser power (50 W), spot diameter (70 μm) and powder layer thickness (80 μm). In this research, influence of the energy input parameters (80–900 °C preheating temperature and 0.08–0.28 m/s laser scanning speed) on microstructure and geometry of single tracks fabricated of stainless steel grade 316L powder was analysed. Both factors were found statistically significant with regard to their influence on the remelted depth and the primary cell spacing in the colonies observed in the tracks cross-sections. More specifically, the contact angle and track height were controlled by the preheating temperature, and track width and contact zone characteristics were governed by the laser scanning speed. Because of the threshold behaviour of these two factors, values starting with 700 °C and 0.24 m/s were found not optimal and causing instability and balling effect. Conclusions regarding the selection of process parameters for the formation of tracks with the desired geometry and microstructure were formulated based on statistical analysis of the experimental data.

• 157.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery AB, Finspång. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, China.
Interdiffusion and Microstructure Simulation in Ni and Co Based Overlay Coatings on a Ni-Based Superalloy at High Temperatures2013Conference paper (Refereed)
• 158.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery AB, Finspång, Sweden. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. University of Science and Technology, Beijing, China.
MCrAIY Coating Design Based on Oxidation-Diffusion Modelling. Part I: Microstructural Evolution2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 254, p. 79-96Article in journal (Refereed)

To improve the efficiency of modern gas turbines, it is highly desired to develop durable MCrAlY alloys, to be used as protective coatings against oxidation and corrosion for superalloys which are the base materials for some hot components like turbine blades and vanes. In this paper, an oxidation-diffusion model was used to simulate the diffusion of alloying elements and the corresponding microstructural changes in different superalloy-coating systems at high temperature. Two important processes are considered in this model: oxidation of the coating and interdiffusion between the superalloy and the coating. The model showed an accurate predictability of the diffusion and microstructural evolution in real superalloy-coating diffusion couples studied at high-temperature exposure. The model was further applied to investigate the elemental effects of Ni, Co, Cr and Al on the microstructural evolution, considering the development of two important phases in superalloys and coatings, i.e. FCC-γ′ and BCC-β, at different temperatures. The results in this paper deepen the knowledge of the MCrAlY coating design for superalloy-coating systems in high-temperature applications.

• 159.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery AB, Finspång. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, China.
Modeling of the microstructural evolution and lifetime prediction of MCrAlX coatings on Nickel based superalloys in high temperature oxidation2013In: Surface and Coatings Technology, Vol. 232, no 15, p. 204-215Article in journal (Refereed)

At high temperature, MCrAlX coatings are deposited onto the surface of superalloy to provide oxidation and corrosion protection by forming a thermalgrowing oxide scale. In this project, the oxidation behavior of an HVOF CoNiCrAlYSi coating on IN792 was studied in both isothermal oxidation (900, 1000 and 1100 °C) and thermal cycling (1100-100 °C). The microstructural evolution in the MCrAlX coatings after oxidation was investigated. It was found that Al-rich β phase is gradually consumed due to two effects: surface oxidation and coating-substrate interdiffusion. Some voids and oxides along the coating-substrate interface, or inside the coating, were considered to play a role in blocking the diffusion of alloying elements. Based on the microstructural observation, an oxidation-diffusion model was developed by using Matlab and DICTRA software to predict the lifetime of MCrAlX coatings. Several effects influencing the microstructural evolution were included: surface oxidation, coating-substrate interdiffusion and diffusion blocking. The results showed good agreement between the experimental composition profiles and modeling ones. Furthermore, by choosing suitable diffusion blocking factors, the accuracy of coating life prediction could be improved.

• 160.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery AB, Finspång, Sweden. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. University of Science and Technology, Beijing, China.
Hot corrosion behavior of HVOF-sprayed CoNiCrAlYSi coatings in a sulphate environment2015In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 122, no Part A, p. 47-53Article in journal (Refereed)

HVOF-sprayed CoNiCrAlYSi coatings were tested at 900 °C in a hot corrosion environment containing sodium–potassium sulphates. The HVOF spraying caused the typical splat-on-splat structure. The results after the hot corrosion testing showed that the corrosion preferentially occurred at the coating surface and the splat boundaries. The oxidation along the splat boundaries can isolate the splat from the underlying coating matrix. In those isolated splats or coating parts, internal oxidation and nitridation of Al took place, following that the Al-depleted coating fragments were then oxidized to spinels. For those coatings which had a worse splat boundary quality (i.e. with higher porosity and intersplat oxides) or had a worse coating surface quality (i.e. with more small coating fragments therefore more interfaces), heavier corrosion attack was observed on those coatings due to the corrosion of the splats or the coating fragments. The results indicated that the as-sprayed coating quality including porosity and surface morphology was important for the hot-corrosion resistance of the coatings.

• 161.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery AB, Finspång, Sweden. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. University of Science and Technology, Beijing, China.
Some aspects of elemental behaviour in HVOF MCrAlY coatings in high-temperature oxidation2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 261, p. 86-101Article in journal (Refereed)

MCrAlY coatings are widely used to protect superalloys against oxidation and corrosion at high temperature in gas turbine engines. To design a durable MCrAlY coating, the elemental behaviour in coating-superalloy couples needs to be better understood. After oxidation tests in temperature range between 900 °C to 1100 °C, the microstructural development in the samples were analysed. The investigation was mainly focused on the microstructures at the coating surface or in areas near the coating-superalloy interface. Some interdiffusion simulations were also done to model the diffusion behaviour of alloying elements in different coatingsuperalloy couples. The results showed that both oxidation at the coatings’ surfaces and the elements’ diffusion inside of the materials were temperature- and chemical-composition dependent. The behaviour of some minor elements like Y, Hf, Ru and Ir in the oxidation processes was particularly studied by tracking their position and composition in the materials.

• 162.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery AB, Finspång, Sweden. Swerea KIMAB, Kista, Sweden. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. University of Science and Technology, Beijing, China.
Hot corrosion of MCrAlY coatings in sulphate and SO2 environment at 900 °C: is SO2 necessarily bad?2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 261, p. 41-53Article in journal (Refereed)

MCrAlY coatings can be corroded due to the basic fluxing (Type-I corrosion) of suppose-to-be protective alumina scale in a molten sulphate environment. In this study, two MCrAlY coatings, coating A (10 wt.% Al, 20 wt.% Cr) and coating B (7 wt.% Al, 28 wt.% Cr), were tested in a sodium-potassium sulphate environment with and without SO2 (500 ppm) in air with 100-900 °C thermal cycling up to about 500 hours. The aim was to test the effect of SO2 at the typical Type-I-corrosion temperature – 900 °C. The results showed that the corrosion behavior of the MCrAlY coatings depended not only on the coating composition but also on the corrosion environment. It was found that in coating A alumina scale was more resistant in the sulphate plus SO2 condition than that in the sulphate only condition. Such phenomenon indicated a beneficial effect of SO2. On Coating B, however, a mixed oxide layer, consisting of alumina and other oxides and sulphides, after a certain cycles in the sulphate environments with and without SO2 gas. In this coating, the addition of SO2 in the sulphate environment changed the corrosion mode from the basic fluxing of alumina to the sulfidation of Cr.

• 163.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery AB Finspång, Sweden. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. University of of Science and TechnologyBeijing, China.
Influence of Ru, Mo and IR on the behavior of Ni-based MCrAlY coatings in high temperature oxidation2014In: Proceedings of the ASME Turbo Expo, American Society of Mechanical Engineers (ASME) , 2014, Vol. 6Conference paper (Refereed)

To improve the oxidation/corrosion resistance of MCrAlY coatings (M for Ni and/or Co), elements like Y, Si and Ta have been added into the coatings in past decades. In this study the oxidation performance of a Ni-based MCrAlY coating with small proportion of Ru, Mo and/or Ir were investigated after high-temperature exposure. The oxidation tests were carried out at 900C 1000C or 1100C The microstructure study showed that the addition of Ru, Mo and/or Ir had significant influence on the oxidation behavior at the coating surface and the microstructural evolution in the material. The microstructural evolution was quantitatively evaluated by measuring the phase degradation of β-NiAl in the coating and γ′-Ni3Al in the substrate of superalloy. Since no oxides of Ru, Mo and Ir were found on the coating surface, it was believed that the effects by those elements were mainly due to their dissolution in the metallic phases in the coatings.

• 164.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery AB, Finspång. Siemens Industrial Turbomachinery AB, Finspång. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, China.
Analysis on Microstructural Evolution of PtAl Diffusion Coating on Ni-based Superalloy Influenced by Creep Process2012Conference paper (Other academic)

The microstructural evolution of PtAl diffusion coating on a nickel-base superalloy IN792 was studied to assess the influence of high temperature (850 °C and 950 °C) and static creep loading conditions. The chemical composition analysis by EDS reveals that local enrichment of Cr, W and Mo is responsible for the formation of σ, Cr-α and μ/R particles in the different characteristic zones in the PtAl coating. Being taken as an approach to describe the coating’s microstructure evolution, a so-called Effective Coating Thickness (ECT) is defined and was measured for different creep conditions. It is found that the value of ECT is controlled by the inward diffusion of Al and Pt, being demonstrated by the existence of a linear correlation between ECT and $\sqrt{D^A^l x {t}}{(D^A^l:}$ diffusion coefficient of Al in substrate; t: diffusion time). Simulated ECT development of the PtAl diffusion coating agrees well with the experimental results at 850 °C and 950 °C.

• 165.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery AB, Finspång. Siemens Industrial Turbomachinery AB, Finspång. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, China.
Creep Fracture Mechanism of Polycrystalline Ni-based Superalloy with Diffusion Coatings2013Conference paper (Other academic)

Diffusion coatings are widely used to increase oxidation and corrosion resistance of hot superalloy components for gas turbines. The aim of this study is to investigate the effect of coatings (NiAl and PtAl) on the creep fracture mechanism of samples with a substrate of IN792. The samples have been creep tested at two temperatures (850 °C and 950 °C) and different applied tensile stresses, until failure between 205 and 21000 hrs. The observation of cross-sections by SEM shows that the microstructural evolution in the coating is dependent on the diffusion of alloying elements in the sample. Furthermore the time and temperature induced growth of the coating is found to be controlled only by inward diffusion of Al. Grain-boundary cracking is the basic fracture mode in the substrate in all samples irrespective if the crack is initiated from coating or substrate. The analysis of microstructure shows that the diffusion coatings display two types of mechanical behavior - being easily plasticized or cracked - dependent on temperature and type of coating, and therefore can be considered as non-load carrying regions. After recalculating the creep stress to exclude the final effective coating thickness from the total sample thickness, the coated samples showed similar creep rupture behavior as the uncoated samples in the Larson-Miller diagram.

• 166.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery AB, Finspång. Siemens Industrial Turbomachinery AB, Finspång. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, China.
Creep Fracture Mechanism of Polycrystalline Ni-based Superalloy with Diffusion Coatings2013Conference paper (Refereed)
• 167.
Linköping University, Department of Management and Engineering.
Linköping University, Department of Management and Engineering. Finspang, Sweden. Linköping University, Department of Management and Engineering.
Hot Corrosion Behavior of HVOF-sprayed CoNiCrAlYSi Coatings in a Sulphate Environment2015In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 122, no part A, p. 47-53Article in journal (Refereed)

HVOF-sprayed CoNiCrAlYSi coatings were tested at 900 °C in a hot corrosion environment containing sodium–potassium sulphates. The HVOF spraying caused the typical splat-on-splat structure. The results after the hot corrosion testing showed that the corrosion preferentially occurred at the coating surface and the splat boundaries. The oxidation along the splat boundaries can isolate the splat from the underlying coating matrix. In those isolated splats or coating parts, internal oxidation and nitridation of Al took place, following that the Al-depleted coating fragments were then oxidized to spinels. For those coatings which had a worse splat boundary quality (i.e. with higher porosity and intersplat oxides) or had a worse coating surface quality (i.e. with more small coating fragments therefore more interfaces), heavier corrosion attack was observed on those coatings due to the corrosion of the splats or the coating fragments. The results indicated that the as-sprayed coating quality including porosity and surface morphology was important for the hot-corrosion resistance of the coatings.

• 168.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery AB, Finspång. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
Influence of Precracked Diffusion Coating of Pt-Modified Aluminide on HCF Fracture Mechanism of IN 792 Nickel-Based Superalloy2012In: Applied Mechanics and Materials, ISSN 1660-9336, E-ISSN 1662-7482, Vol. 148-149, p. 24-29Article in journal (Refereed)

High-cycle-fatigue (HCF) fracture mechanism of nickel-based superalloy IN 792 coated with Pt-modified aluminide outward-diffusion coating is studied with focus on the influence of coating cracks. It is found that cracking of the diffusion coating prior to HCF tests has little influence on the fatigue limit of specimens with thin coating (50 μm) but lowers the fatigue limit of specimens with thick coating (70 μm). By fractographic analysis, three types of fractural modes are established according to their crack initiations: internal, external and mixed. While external fractural mode is related to the propagation of existing cracks in the coating, internal facture initiates often at Ti-Ta-W-rich carbides and/or topological-close-packed (TCP) phases and grainboundaries in the superalloy. Increasing the thickness of diffusion coating or the amplitude stress promotes the fractural mode transition from internal/mixed to external. The influence of precracking of coatings on the HCF fracture mechanism can be qualitatively explained by its influence on the stress intensity factor.

• 169.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery AB, Finspång, Sweden. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. University of Science and Technology, Beijing, China.
Simulation of oxidation-nitridation-induced microstructural degradation in a cracked Ni-based superalloy at high temperature2014In: MATEC Web of Conferences Vol. 14 (2014), EUROSUPERALLOYS 2014 – 2nd European Symposium on Superalloys and their Applications Giens, France, May 12–16, 2014, Les Ulis, France: E D P Sciences , 2014, Vol. 14, no 16004, p. 16004-Conference paper (Refereed)

In turbine engines, high temperature components made of superalloys may crack in a creep process during service. With the inward flux of the gases, e.g. oxygen and nitrogen, along those cracks, the microstructure of the superalloy substrate nearby the cracks may degrade by internal oxidation and nitridation. The aim of this study is to investigate and simulate the oxidation-nitridation-induced microstructural degradation in superalloys by taking a variant of Ni-based superalloy IN-792 as a sample. After the creep testing of the superalloy in air, the microstructures on the cross section of the superalloy were analysed in a scanning electron microscope, equipped with energy/wavelength dispersive systems. Internal oxidation and nitridation, presenting by Al/Ti oxides and nitrides, were observed under a porous and even cracked Cr-oxide scale which was formed on the superalloy surface or along the creep cracks connecting the superalloy surface. Meanwhile, the reinforcing γ′ precipitates were depleted. Such oxidation-nitridation-induced microstructural degradation was simulated by using an oxidation-diffusion model, focusing the diffusion of the alloying elements in metallic phases of the superalloy.

• 170.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
Hot Corrosion Behavior of HVOF CoNiCrAlY(Hf) Coating on Ni-based Superalloys2017Conference paper (Refereed)
• 171.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
Investigation of Element Effect on High-Temperature Oxidation of HVOF NiCoCrAlX Coatings2018In: Coatings, ISSN 2079-6412, Vol. 8, no 4, p. 129-145Article in journal (Refereed)

MCrAlX (M: Ni or Co or both, X: minor elements) coatings have been used widely to protect hot components in gas turbines against oxidation and heat corrosion at high temperatures. Understanding the influence of the X-elements on oxidation behavior is important in the design of durable MCrAlX coatings. In this study, NiCoCrAlX coatings doped with Y + Ru and Ce, respectively, were deposited on an Inconel-792 substrate using high velocity oxygen fuel (HVOF). The samples were subjected to isothermal oxidation tests in laboratory air at 900, 1000, and 1100 °C and a cyclic oxidation test between 100 and 1100 °C with a 1-h dwell time at 1100 °C. It was observed that the coating with Ce showed a much higher oxidation rate than the coating with Y + Ru under both isothermal and cyclic oxidation tests. In addition, the Y + Ru-doped coating showed significantly lower β phase depletion due to interdiffusion between the coating and the substrate, resulting from the addition of Ru. Simulation results using a moving phase boundary model and an established oxidation-diffusion model showed that Ru stabilized β grains, which reduced β-depletion of the coating due to substrate interdiffusion. This paper, combining experiment and simulation results, presents a comprehensive study of the influence of Ce and Ru on oxidation behavior, including an investigation of the microstructure evolution in the coating surface and the coating-substrate interface influenced by oxidation time.

• 172.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Department of Management and Engineering, Linköping University, Linköping, Sweden.
Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT). Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Siemens Industrial Turbomachinery AB, Finspång, Sweden. Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT). Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT). Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
Isothermal oxidation behavior of HVAF-sprayed NiCoCrAlY coatings: Effect of surface treatment2017In: Proceedings of International Thermal Sprayed Conference (ITSC), May 7-9,Germany, 456-461 (2017), 2017, p. 456-461Conference paper (Other academic)

NiCoCrAlY coatings are widely used as bond coats for ceramic thermal barrier coatings (TBCs) andoxidation and corrosion protective overlay coatings in industrial gas turbines. High temperature oxidation behaviour of NiCoCrAlYs has a great influence on the coating performance and lifetime of TBCs. A promising route to decrease the oxidation rate of such coatings is post-coating surface modification which can facilitate formation of a uniform alumina scale with a considerably slower growth rate compared to the as-sprayed coatings. In this work, the effect of surface treatment by means of shot peening and laser surface melting (LSM) on the oxidation resistance of high velocity air-fuel (HVAF) sprayed NiCoCrAlY coatings was studied. Isothermal oxidation was carried out at 1000⁰C for 1000h. Results showed that the rough surface of as-sprayed HVAF sprayed coatings was significantly changed after shot peening and LSM treatment, with a compact and smooth appearance. After the exposure, the oxide scales formed on surface-treated NiCoCrAlY coatings showed different morphology and growth rate compared to those formed on as-sprayed coating surface. The oxidation behaviour of surface treated HVAF-sprayed NiCoCrAlY coatings were revealed and discussed.

• 173.
Division of Production and Materials Engineering, Lund university.
Division of Production and Materials Engineering, Lund university. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery, Finspång. Division of Production and Materials Engineering, Lund university.
Effect of Tool Wear on Subsurface Deformation of Nickel-based Superalloy2011In: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 19, p. 407-413Article in journal (Refereed)

Increased demand of energy efficiency for the components used in aerospace and energy industries requires high efficiency and low cost in the production of component made of nickel-based superalloy, such as aged Inconel 718. With use of whisker reinforced ceramic cutting tool in finishing machining process, higher cutting speed and higher production efficiency can be reached accordingly. However, surface integrity of the part produced by this process still needs to be studied due to the high demand of surface quality. The paper analyses the effects of tool wear on subsurface deformation of nickel-based super-alloy in finishing turning. The objective is to understand the nature of subsurface deformation under the influence of tool wear for prediction of the surface integrity in machined components based upon the machining conditions and material behaviours that give rise to them. Machined samples were studied under a Backscattered electron microscope to distinguish the subsurface features produced by the machining. The electron back scatter diffraction (EBSD) was also used to quantify the depth of deformation zones in the subsurface after the machining.

• 174.
Division of Production and Materials Engineering, Lund university.
Division of Production and Materials Engineering, Lund university. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery, Finspång. Division of Production and Materials Engineering, Lund university.
On Process Induced Subsurface Deformation of Aged Inconel 718 in Relation to Different Cutting Conditions2011Conference paper (Refereed)
• 175.
Division of Production and Materials Engineering, Lund university.
Division of Production and Materials Engineering, Lund university. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Division of Production and Materials Engineering, Lund university.
Analysis of Subsurface Microstructure and Residual Stresses in Machined Inconel 718 with PCBN and Al2O3-SiCw Tools2014In: 2ND CIRP CONFERENCE ON SURFACE INTEGRITY (CSI), Elsevier, 2014, Vol. 13, p. 150-155Conference paper (Refereed)

Subsurface microstructural alterations and residual stresses caused by machining significantly affect component lifetime and performance by influencing fatigue, creep, and stress corrosion cracking resistance. Assessing the surface quality of a machined part by characterizing subsurface microstructural alterations and residual stresses is essential for ensuring part performance and lifetime in aero-engines and power generators. This comparative study characterizes and analyzes subsurface microstructural alterations and residual stresses in Inconel 718 subjected to high-speed machining with PCBN and whisker-reinforced ceramic cutting tools. Effects of cutting tool materials and microgeometry on subsurface deformation, microstructural alterations, and residual stresses were investigated. Surface and subsurface regions of machined specimens were investigated using X-ray diffraction, electron channeling contrast imaging, and electron back-scatter diffraction to characterize microstructural alterations and measure deformation intensity and depth.

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