The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
Håkan Brodin - One of the best experts on this subject based on the ideXlab platform.
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tbc Bond coat top coat interface roughness influence on fatigue life and modelling aspects
Surface & Coatings Technology, 2013Co-Authors: Robert Eriksson, Lars Ostergren, Soren Sjostrom, Sten Johansson, Håkan Brodin, Xin-hai LiAbstract:Abstract Thermal barrier coatings (TBCs), when used in gas turbines, may fail through thermal fatigue, causing the ceramic top coat to spall off the Metallic Bond coat. The life prediction of TBCs often involves finite element modelling of the stress field close to the Bond coat/top coat interface and thus relies on accurate modelling of the interface. The present research studies the influence of Bond coat/top coat interface roughness on the thermal fatigue life of plasma sprayed TBCs. By using different spraying parameters, specimens with varying interface roughnesses were obtained. During thermal cycling it was found that higher interface roughness promoted longer thermal fatigue life. The interfaces were characterised by roughness parameters, such as Ra , Rq and R ∆ q , as well as by autocorrelation, material ratio curves and slope distribution. The variation of spray parameters was found to affect amplitude parameters, such as Ra , but not spacing parameters, such as RSm . Three different interface geometries were tried for finite element crack growth simulation: cosine, ellipse and triangular shapes. The cosine model was found to be an appropriate interface model and a procedure for obtaining the necessary parameters, amplitude and wavelength, was suggested. The positive effect of high roughness on life was suggested to be due to a shift from predominantly interface failure, for low roughness, to predominantly top coat failure, for high roughness.
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TBC Bond coat–top coat interface roughness: Influence on fatigue life and modelling aspects
Surface and Coatings Technology, 2013Co-Authors: Robert Eriksson, Sten Johansson, Soren Sjostrom, Håkan Brodin, Lars OstergrenAbstract:Thermal barrier coatings (TBCs), when used in gas turbines, may fail through thermal fatigue, causing the ceramic top coat to spall off the Metallic Bond coat. The life prediction of TBCs often inv ...
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Advanced Ceramic Coatings and Interfaces IV - Fracture Mechanical Modelling of a Plasma Sprayed TBC System
Advanced Ceramic Coatings and Interfaces IV, 2010Co-Authors: Håkan Brodin, Sten Johansson, Robert Eriksson, Sören SjöstrmAbstract:A thermal barrier coating (TBC) system subjected to thermal cycling will develop a microcrack partem near the interface between the Metallic Bond coat and the ceramic top coat. These small cracks l ...
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Bond Coat Influence on TBC Life
2009Co-Authors: Håkan Brodin, Xin-hai LiAbstract:Thermal barrier coatings (TBC) are applied on hot components in airborne and land-based gas turbines when higher turbine inlet temperature, meaning better thermal efficiency, is desired. The TBC is mainly applied to protect underlying material from high temperatures, but also serves as a protection from the aggressive corrosive environment.Plasma sprayed coatings are often duplex TBC's with an outer ceramic top coat (TC) made from partially stabilised zirconia - ZrO2 + 6-8% Y2O3. Below the top coat there is a Metallic Bond coat (BC). The BC is normally a MCrAlX coating (M=Ni, Co, Fe ... and X=Y, Hf, Si ... ). In gas turbine components exposed to elevated temperatures nickel-based superalloys are commonly adopted as load carrying components. In the investigations performed here a commercial wrought Ni-base alloy Haynes 230 has been used as substrate for the TBC. As BC a NiCoCrAlY serves as a reference material and in all cases 7% yttria PS zirconia has been used. Phase development and failure mechanisms in APS TBC during service-like conditions have been evaluated in the present study. This is done by combinations of thermal cycling and low cycle fatigue tests. The aim is to achieve better knowledge regarding how, when and why thermal ban'ier coatings fail. As a fmal outcome of the project a model capable of predicting fatigue life of a given component will help engineers and designers of land based gas turbines for power generation to better optimise TBC's.In the investigations it is seen that TBC life is strongly influenced by oxidation of the BC and interdiffusion between BC and the substrate. The Bond coat is known to oxidise with time at high temperature. The initial oxide found during testing is alumina. With increased time at high temperature Al is depleted from the Bond coat due to interdiffusion and oxidation. Oxides others than alumina start to form when the Al content is reduced below a critical limit. It is here believed that spinel appears when the Al content is lowered below 2w/o in the Bond coat. Here it was shown that a faster growing oxide, rich in Ni, Cr and Co forms at the interface. Al depletion is also linked to BC phases. Initially the Bond coat is a γ/s-material possibly with very fine dispersed γ'. Simultaneously with Al-depletion the s-phase is found to disappear. This occurs simultaneously with the formation of spinel. However, oxidation is not only a disadvantage. Low cycle fatigue tests reveal that oxide streaks within the Bond coat will slow down crack growth due to crack deflection and crack branching. Therefore benefit of or damage from oxide growth on crack initiation and propagation is dependent on crack mode, spalling of the ceramic TC or growth of "classic" cracks perpendicular to the surface.From the observations conclusions are drawn regarding fatigue behaviour ofTBC systems. The basic idea is that all cracks leading to failure initiate in the thermally grown oxide (TGO). Following the initiation, they can, however, grow to form either delamination cracks leading to top coat spallation or cracks transverse to the surface leading to component failure.
Robert Eriksson - One of the best experts on this subject based on the ideXlab platform.
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tbc Bond coat top coat interface roughness influence on fatigue life and modelling aspects
Surface & Coatings Technology, 2013Co-Authors: Robert Eriksson, Lars Ostergren, Soren Sjostrom, Sten Johansson, Håkan Brodin, Xin-hai LiAbstract:Abstract Thermal barrier coatings (TBCs), when used in gas turbines, may fail through thermal fatigue, causing the ceramic top coat to spall off the Metallic Bond coat. The life prediction of TBCs often involves finite element modelling of the stress field close to the Bond coat/top coat interface and thus relies on accurate modelling of the interface. The present research studies the influence of Bond coat/top coat interface roughness on the thermal fatigue life of plasma sprayed TBCs. By using different spraying parameters, specimens with varying interface roughnesses were obtained. During thermal cycling it was found that higher interface roughness promoted longer thermal fatigue life. The interfaces were characterised by roughness parameters, such as Ra , Rq and R ∆ q , as well as by autocorrelation, material ratio curves and slope distribution. The variation of spray parameters was found to affect amplitude parameters, such as Ra , but not spacing parameters, such as RSm . Three different interface geometries were tried for finite element crack growth simulation: cosine, ellipse and triangular shapes. The cosine model was found to be an appropriate interface model and a procedure for obtaining the necessary parameters, amplitude and wavelength, was suggested. The positive effect of high roughness on life was suggested to be due to a shift from predominantly interface failure, for low roughness, to predominantly top coat failure, for high roughness.
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Thermal Barrier Coatings : Durability Assessment and Life Prediction
2013Co-Authors: Robert ErikssonAbstract:Thermal barrier coating (TBC) systems are coating systems containing a Metallic Bond coat and a ceramic top coat. TBCs are used in gas turbines for thermal insulation and oxidation resistance. Life ...
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TBC Bond coat–top coat interface roughness: Influence on fatigue life and modelling aspects
Surface and Coatings Technology, 2013Co-Authors: Robert Eriksson, Sten Johansson, Soren Sjostrom, Håkan Brodin, Lars OstergrenAbstract:Thermal barrier coatings (TBCs), when used in gas turbines, may fail through thermal fatigue, causing the ceramic top coat to spall off the Metallic Bond coat. The life prediction of TBCs often inv ...
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Advanced Ceramic Coatings and Interfaces IV - Fracture Mechanical Modelling of a Plasma Sprayed TBC System
Advanced Ceramic Coatings and Interfaces IV, 2010Co-Authors: Håkan Brodin, Sten Johansson, Robert Eriksson, Sören SjöstrmAbstract:A thermal barrier coating (TBC) system subjected to thermal cycling will develop a microcrack partem near the interface between the Metallic Bond coat and the ceramic top coat. These small cracks l ...
Jing Liu - One of the best experts on this subject based on the ideXlab platform.
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interfacial wetting behaviors of liquid ga alloys fega3 based on Metallic Bond interaction
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2019Co-Authors: Yuntao Cui, Fei Liang, Yujie Ding, Zheshuai Lin, Jing LiuAbstract:Abstract This work presents a peculiar Metallic Bond interaction which strongly improves wetting performance and adsorption energy at the liquid Ga/FeGa3 interfaces and gets stronger with the increasing content of gallium. To quantitatively evaluate the interfacial wetting phenomenon, an interfacial wetting model based on the Metallic Bond interaction is built and investigated. The underlying mechanism attributes to the interMetallic FeGa3 formed and covering on the Fe substrate surface, which forms the strong Metallic Bond interaction with Ga atoms to bring about an excellent wetting performance. Based on the first principles calculations and simulations, comparable electrostatic potentials of Ga atom on FeGa3(010) disclose the valence electrons can exchange easily between liquid Ga atom and the Fe-Ga interlayers of FeGa3, thus leading to valence electron hybridization. The calculation results for the density of states (DOS) exhibit that the peaks of valence electron hybridization emerged between Ga and FeGa3(010), which results in the Metallic Bond interaction. Moreover, the experimental findings and the predicted data show that the Metallic Bond interaction has been confirmed to be accordant with the interfacial wetting behavior and adsorption energy of liquid Ga alloys (LGAs) on the FeGa3 slab.
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Interfacial wetting behaviors of liquid Ga alloys/FeGa3 based on Metallic Bond interaction
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2019Co-Authors: Yuntao Cui, Fei Liang, Yujie Ding, Zheshuai Lin, Jing LiuAbstract:Abstract This work presents a peculiar Metallic Bond interaction which strongly improves wetting performance and adsorption energy at the liquid Ga/FeGa3 interfaces and gets stronger with the increasing content of gallium. To quantitatively evaluate the interfacial wetting phenomenon, an interfacial wetting model based on the Metallic Bond interaction is built and investigated. The underlying mechanism attributes to the interMetallic FeGa3 formed and covering on the Fe substrate surface, which forms the strong Metallic Bond interaction with Ga atoms to bring about an excellent wetting performance. Based on the first principles calculations and simulations, comparable electrostatic potentials of Ga atom on FeGa3(010) disclose the valence electrons can exchange easily between liquid Ga atom and the Fe-Ga interlayers of FeGa3, thus leading to valence electron hybridization. The calculation results for the density of states (DOS) exhibit that the peaks of valence electron hybridization emerged between Ga and FeGa3(010), which results in the Metallic Bond interaction. Moreover, the experimental findings and the predicted data show that the Metallic Bond interaction has been confirmed to be accordant with the interfacial wetting behavior and adsorption energy of liquid Ga alloys (LGAs) on the FeGa3 slab.
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Metallic Bond-Enabled Wetting Behavior at the Liquid Ga/CuGa2 Interfaces
ACS applied materials & interfaces, 2018Co-Authors: Yuntao Cui, Fei Liang, Yujie Ding, Zheshuai Lin, Zhenze Yang, Xi Zhao, Jing LiuAbstract:Interface interaction can strongly modify contact angle, adsorption energy, interfacial tension, and composition of the contact area. In particular, the interfaces between gallium-based liquid metal (LM) and its interMetallic layer present many mysterious and peculiar wetting phenomena, which have not been fully realized up to now. Here in this study, we found that a gallium-based liquid metal droplet can quickly transform into a puddle on the CuGa2 surface through a spreading–wetting procedure. The mechanism lying behind this phenomenon can be ascribed to the formation of an interMetallic CuGa2 on Cu plate surface, which provides a stable Metallic Bond to induce the wetting behavior. For a quantitative evaluation of the interface force, a Metallic Bond-enabled wetting model is established on the basis of the density functional theory. The first-principles density functional calculations are then performed to examine the work function, density of states, and adsorption energy. The predicted results show t...
Lars Ostergren - One of the best experts on this subject based on the ideXlab platform.
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tbc Bond coat top coat interface roughness influence on fatigue life and modelling aspects
Surface & Coatings Technology, 2013Co-Authors: Robert Eriksson, Lars Ostergren, Soren Sjostrom, Sten Johansson, Håkan Brodin, Xin-hai LiAbstract:Abstract Thermal barrier coatings (TBCs), when used in gas turbines, may fail through thermal fatigue, causing the ceramic top coat to spall off the Metallic Bond coat. The life prediction of TBCs often involves finite element modelling of the stress field close to the Bond coat/top coat interface and thus relies on accurate modelling of the interface. The present research studies the influence of Bond coat/top coat interface roughness on the thermal fatigue life of plasma sprayed TBCs. By using different spraying parameters, specimens with varying interface roughnesses were obtained. During thermal cycling it was found that higher interface roughness promoted longer thermal fatigue life. The interfaces were characterised by roughness parameters, such as Ra , Rq and R ∆ q , as well as by autocorrelation, material ratio curves and slope distribution. The variation of spray parameters was found to affect amplitude parameters, such as Ra , but not spacing parameters, such as RSm . Three different interface geometries were tried for finite element crack growth simulation: cosine, ellipse and triangular shapes. The cosine model was found to be an appropriate interface model and a procedure for obtaining the necessary parameters, amplitude and wavelength, was suggested. The positive effect of high roughness on life was suggested to be due to a shift from predominantly interface failure, for low roughness, to predominantly top coat failure, for high roughness.
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TBC Bond coat–top coat interface roughness: Influence on fatigue life and modelling aspects
Surface and Coatings Technology, 2013Co-Authors: Robert Eriksson, Sten Johansson, Soren Sjostrom, Håkan Brodin, Lars OstergrenAbstract:Thermal barrier coatings (TBCs), when used in gas turbines, may fail through thermal fatigue, causing the ceramic top coat to spall off the Metallic Bond coat. The life prediction of TBCs often inv ...
Xin-hai Li - One of the best experts on this subject based on the ideXlab platform.
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tbc Bond coat top coat interface roughness influence on fatigue life and modelling aspects
Surface & Coatings Technology, 2013Co-Authors: Robert Eriksson, Lars Ostergren, Soren Sjostrom, Sten Johansson, Håkan Brodin, Xin-hai LiAbstract:Abstract Thermal barrier coatings (TBCs), when used in gas turbines, may fail through thermal fatigue, causing the ceramic top coat to spall off the Metallic Bond coat. The life prediction of TBCs often involves finite element modelling of the stress field close to the Bond coat/top coat interface and thus relies on accurate modelling of the interface. The present research studies the influence of Bond coat/top coat interface roughness on the thermal fatigue life of plasma sprayed TBCs. By using different spraying parameters, specimens with varying interface roughnesses were obtained. During thermal cycling it was found that higher interface roughness promoted longer thermal fatigue life. The interfaces were characterised by roughness parameters, such as Ra , Rq and R ∆ q , as well as by autocorrelation, material ratio curves and slope distribution. The variation of spray parameters was found to affect amplitude parameters, such as Ra , but not spacing parameters, such as RSm . Three different interface geometries were tried for finite element crack growth simulation: cosine, ellipse and triangular shapes. The cosine model was found to be an appropriate interface model and a procedure for obtaining the necessary parameters, amplitude and wavelength, was suggested. The positive effect of high roughness on life was suggested to be due to a shift from predominantly interface failure, for low roughness, to predominantly top coat failure, for high roughness.
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Bond Coat Influence on TBC Life
2009Co-Authors: Håkan Brodin, Xin-hai LiAbstract:Thermal barrier coatings (TBC) are applied on hot components in airborne and land-based gas turbines when higher turbine inlet temperature, meaning better thermal efficiency, is desired. The TBC is mainly applied to protect underlying material from high temperatures, but also serves as a protection from the aggressive corrosive environment.Plasma sprayed coatings are often duplex TBC's with an outer ceramic top coat (TC) made from partially stabilised zirconia - ZrO2 + 6-8% Y2O3. Below the top coat there is a Metallic Bond coat (BC). The BC is normally a MCrAlX coating (M=Ni, Co, Fe ... and X=Y, Hf, Si ... ). In gas turbine components exposed to elevated temperatures nickel-based superalloys are commonly adopted as load carrying components. In the investigations performed here a commercial wrought Ni-base alloy Haynes 230 has been used as substrate for the TBC. As BC a NiCoCrAlY serves as a reference material and in all cases 7% yttria PS zirconia has been used. Phase development and failure mechanisms in APS TBC during service-like conditions have been evaluated in the present study. This is done by combinations of thermal cycling and low cycle fatigue tests. The aim is to achieve better knowledge regarding how, when and why thermal ban'ier coatings fail. As a fmal outcome of the project a model capable of predicting fatigue life of a given component will help engineers and designers of land based gas turbines for power generation to better optimise TBC's.In the investigations it is seen that TBC life is strongly influenced by oxidation of the BC and interdiffusion between BC and the substrate. The Bond coat is known to oxidise with time at high temperature. The initial oxide found during testing is alumina. With increased time at high temperature Al is depleted from the Bond coat due to interdiffusion and oxidation. Oxides others than alumina start to form when the Al content is reduced below a critical limit. It is here believed that spinel appears when the Al content is lowered below 2w/o in the Bond coat. Here it was shown that a faster growing oxide, rich in Ni, Cr and Co forms at the interface. Al depletion is also linked to BC phases. Initially the Bond coat is a γ/s-material possibly with very fine dispersed γ'. Simultaneously with Al-depletion the s-phase is found to disappear. This occurs simultaneously with the formation of spinel. However, oxidation is not only a disadvantage. Low cycle fatigue tests reveal that oxide streaks within the Bond coat will slow down crack growth due to crack deflection and crack branching. Therefore benefit of or damage from oxide growth on crack initiation and propagation is dependent on crack mode, spalling of the ceramic TC or growth of "classic" cracks perpendicular to the surface.From the observations conclusions are drawn regarding fatigue behaviour ofTBC systems. The basic idea is that all cracks leading to failure initiate in the thermally grown oxide (TGO). Following the initiation, they can, however, grow to form either delamination cracks leading to top coat spallation or cracks transverse to the surface leading to component failure.