Conventional two-layered thermal barrier coatings （TBCs） are prepared by electron beam physical vapor deposition （EB-PVD） with ZrO2-8 wt% Y2O3 （8YSZ） as top coat and CoCrAlY as bond coat on disk-shaped Ni based ...Conventional two-layered thermal barrier coatings （TBCs） are prepared by electron beam physical vapor deposition （EB-PVD） with ZrO2-8 wt% Y2O3 （8YSZ） as top coat and CoCrAlY as bond coat on disk-shaped Ni based super-alloy. In this paper, three kinds of shot peening process with different lengths of operating time were adopted for bond coating. As a result, changes took place in its surface roughness and the surface micro-hardness. A thermal cycling test at 1 273 Kx55 rain and another at room temperature for 5 min were performed to study the effects of shot peening process on the thermal cycling lifetime of TBCs. It is found that a moderate shot peening process will be able to prolong the life time. The oxidation dynamic of the as-processed TBCs basically accords with the parabolic rule, and the oxidation test also attests to the spallation between YSZ and thermal growth oxide （TGO） responsible mainly for the failure of TBCs.展开更多
Conventional two-layered structure thermal barrier coatings (TBCs) were prepared onto γ'-Ni3Al based alloy IC-6 by electron beam physical vapor deposition (EB-PVD). Isothermal oxidation and thermal cycling tests ...Conventional two-layered structure thermal barrier coatings (TBCs) were prepared onto γ'-Ni3Al based alloy IC-6 by electron beam physical vapor deposition (EB-PVD). Isothermal oxidation and thermal cycling tests were carried out to investigate the effect of Mo content at the interface between bond coat and ceramic top coat caused by diffusion. It has been found that the alloy coated with TBCs presented the lowest oxidation weight gain value for the reason that the ceramic top coat in TBC system can effectively stop Mo oxides evaporating. The life time of TBCs has close relation with Mo content at the interface between the bond coat and top coat. Spaliation of ceramic top coat occurred during thermal cyclic testing when Mo atoms accumulated at the interface up to certain amount to decline the combination between the bond coat and top coat.展开更多
ZrO_(2)-7 wt% Y_(2)O_(3)(7YSZ)thermal barrier coatings(TBCs)with three different structures were prepared by atmospheric plasma spraying(APS),electron beam physical vapor deposition(EB-PVD)and plasma spray-physical va...ZrO_(2)-7 wt% Y_(2)O_(3)(7YSZ)thermal barrier coatings(TBCs)with three different structures were prepared by atmospheric plasma spraying(APS),electron beam physical vapor deposition(EB-PVD)and plasma spray-physical vapor deposition(PS-PVD).Al films were deposited onto the top 7YSZ TBCs by magnetron sputtering,and the Al-deposited 7YSZ TBCs were subjected to vacuum heat treatment.The effects of Al modification on the thermal insulation properties of 7YSZ TBCs were investigated.The results showed that Al modification could significantly improve the thermal insulation of 7YSZ TBCs at 1000℃.Moreover,the maximum improvement of thermal insulation for PS-PVD 7YSZ TBCs was approximately 100℃,but the improvement decreased with increasing temperature.This is mainly because with increasing temperature,the rate of radiation heat transfer increases,and the effects of convection heat transfer and thermal conductivity on thermal insulation are weakened.At the same temperature,Al modification of PS-PVD7YSZ TBCs provides better temperature insulation than those of APS 7YSZ TBCs and EB-PVD 7YSZ TBCs because of its wider and deeper inter-columnar gaps.When the temperature was 12000C,Al modification still caused a good insulation effect in PS-PVD 7YSZ TBCs;the improvement was approximately 50℃,but in APS and EB-PVD 7YSZ TBCs,the insulation effect disappeared.展开更多
The TBC system is examined with regards to its response to thermal exposure at high temperature. It has been established before that the thermally grown oxide (TGO) layer that forms upon bond coat oxidation is the key...The TBC system is examined with regards to its response to thermal exposure at high temperature. It has been established before that the thermally grown oxide (TGO) layer that forms upon bond coat oxidation is the key factor determining the performance of the TBC system and/or its failure. However, characteristics of TGO growth, bond coat rumpling, principles governing failure of TBC systems and the various failure mechanisms have been studied extensively in case of just super alloy with bond coat or with thick top coating. In this study super alloy/bond coat system with single splats of YSZ instead of thick topcoat is analyzed in order to scrutinize the effect on the first layer of splats during thermal exposure. The splats with microcracks are the building blocks of the top coat. The most important aspect of this layer is the inherent inter-splat and intra-splat porosity which undergoes sintering during thermal exposure. The interactions between the YSZ splats and the evolving TGO is directly linked to the presence or absence of bond coat oxidation. Therefore the high temperature behavior of this system is analyzed with variations in heat treatment involving, temperature, duration and environment of thermal exposure.展开更多
The TBC system’s response to thermal exposure at high temperature is discussed here. The relevance of the microstructural aspects of each component of the TBC system is emphasized. The top coat is a YSZ ceramic coati...The TBC system’s response to thermal exposure at high temperature is discussed here. The relevance of the microstructural aspects of each component of the TBC system is emphasized. The top coat is a YSZ ceramic coating consisting of a collection of splats on top of one another. The most important aspect of this layer is the inherent inter-splat and intra-splat porosity which undergoes sintering during thermal exposure. This study investigates the effect of thermal exposure on the microstructure and sintering behavior in single splats produced using different starting powders since this has been shown to influence the basic microstructure of YSZ topcoat. The bond coat is an MCrAlY metallic coating which serves as an Al reservoir and allows the formation of a protective alumina, Thermally Grown Oxide (TGO) layer between the bond coat (BC) and the top coat (TC) layers. This oxide scale formed upon thermal exposure prevents further oxidation of the underlying component (substrate) and thus provides protection. As such, the content of free Al in the bond coat layer is of significance and makes it crucial to understand the influence of bond coat microstructure evolution and oxidation involved during its formation. The interaction between the bond coat, the TGO and the top coat layers is examined in this study to understand the high temperature behavior of the TBC system with regards to variations in the top coat and bond coat material systems used.展开更多
Improving and optimizing the target properties of ceramics via the high entropy strategy has attracted significant attention.Rare earth niobate is a potential thermal barrier coating(TBCs)material,but its poor high-te...Improving and optimizing the target properties of ceramics via the high entropy strategy has attracted significant attention.Rare earth niobate is a potential thermal barrier coating(TBCs)material,but its poor high-temperature phase stability limits its further application.In this work,four sets of TBCs high-entropy ceramics,(Sm_(1/5)Dy_(1/5)Ho_(1/5)Er_(1/5)Yb_(1/5))(Nb_(1/2)Ta_(1/2))O_(4)(5NbTa),(Sm_(1/6)Dy_(1/6)Ho_(1/6)Er_(1/6)Yb_(1/6)Lu_(1/6))(Nb_(1/2)Ta_(1/2))O_(4)(6NbTa),(Sm_(1/7)Gd_(1/7)Dy_(1/7)Ho_(1/7)Er_(1/7)Yb_(1/7)Lu_(1/7))(Nb_(1/2)Ta_(1/2))O_(4)(7NbTa),(Sm_(1/8)Gd_(1/8)Dy_(1/8)Ho_(1/8)Er_(1/8)Tm_(1/8)Yb_(1/8)Lu_(1/8))(Nb_(1/2)Ta_(1/2))O_(4)(8NbTa)are synthesized using a solid-state reaction method at 1650℃for 6 h.Firstly,the X-ray diffractometer(XRD)patterns display that the samples are all single-phase solid solution structures(space group C 2/c).Differential scanning calorimetry(DSC)and the high-temperature XRD of 8NbTa cross-check that the addition of Ta element in 8HERN increases the phase transition temperature above 1400℃,which can be attributed to that the Ta/Nb co-doping at B site introduces the fluctuation of the bond strength of Ta-O and Nb-O.Secondly,compared to high-entropy rare-earth niobates,the introduction of Ta atoms at B site substantially reduce thermal conductivity(re-duced by 44%,800℃)with the seven components high entropy ceramic as an example.The low thermal conductivity means strong phonon scattering,which may originate from the softening acoustic mode and flattened phonon dispersion in 5–8 principal element high entropy rare earth niobium tantalates(5–8NbTa)revealed by the first-principles calculations.Thirdly,the Ta/Nb co-doping in 5–8NbTa systems can further optimize the insulation performance of oxygen ions.The oxygen-ion conductivity of 8NbTa(3.31×10^(−6)S cm^(−1),900℃)is about 5 times lower than that of 8HERN(15.8×10^(−6)S cm^(−1),900℃)because of the sluggish diffusion effect,providing better oxygen barrier capacity in 5–8NbTa systems to inhibit the overgrowth of the thermal growth oxide(TGO)of TBCs.In addition,influenced by lattice dis-tortion and solid solution strengthening,the samples possess higher hardness(7.51–8.15 GPa)and TECs(9.78×10^(−6)K−1^(-1)0.78×10^(−6)K^(−1),1500℃)than the single rare-earth niobates and tantalates.Based on their excellent overall properties,it is considered that 5–8NbTa can be used as auspicious TBCs.展开更多
Thermal barrier coatings(TBCs)are extensively utilized in aero-engines and heavy-duty gas turbines due to their outstanding properties,including low thermal conductivity,corrosion,high-temperature oxidation,and wear r...Thermal barrier coatings(TBCs)are extensively utilized in aero-engines and heavy-duty gas turbines due to their outstanding properties,including low thermal conductivity,corrosion,high-temperature oxidation,and wear resistance.The rising thrust-to-weight ratio and service temperature in engine hot sections have presented a significant challenge in TBC's materials,structure,and preparation process;it is one of the current research hotspots in the aviation field.This paper reviews the recent advancement in turbine blade TBCs.It focuses on the TBC's structure,deposition mechanism and the key performance evaluation indexes for TBCs applied to turbine blades.Finally,the future research field of TBCs for turbine blades is also be prospected.展开更多
Ti_(2)AlC has been demonstrated as the promising protective layer material for thermal barrier coatings(TBCs)against calcium-magnesium-alumina-silicate(CMAS)attack.In this study,the reliability of Ti_(2)AlC coatings a...Ti_(2)AlC has been demonstrated as the promising protective layer material for thermal barrier coatings(TBCs)against calcium-magnesium-alumina-silicate(CMAS)attack.In this study,the reliability of Ti_(2)AlC coatings against the CMAS corrosion was explored,and new Ti_(2)AlC/YSZ TBCs more efficiently resistant to CMAS were designed.The fabricated Ti_(2)AlC coatings inevitably contain some impurity phases(TiC and Al2Ti3),the contents of which were minimized by optimizing the spraying distance.Corrosion tests revealed that Ti_(2)AlC/YSZ TBCs yielded higher resistance to the CMAS attack than YSZ TBCs,but with long-term exposure to CMAS,the Ti_(2)AlC protective coating exhibited microstructure degradation due to the presence of the impurity phases,which caused the formation of a layer mixed with Al_(2)O_(3)and TiO_(2)rather than a continuous compact Al_(2)O_(3)layer on the surface.Pre-oxidation schemes were designed in air or with a controlled oxygen partial pressure,which revealed that the pre-oxidation at an oxygen partial pressure of~630 Pa could promote a continuous Al_(2)O_(3)layer formed on the Ti_(2)AlC protective coating surface.Furthermore,a vacuum heat treatment at 867℃for 10 h before pre-oxidation was beneficial for the formation of the compact Al_(2)O_(3)layer.Through the above scheme design,new Ti_(2)AlC/YSZ TBCs were obtained,which had reduced impurity phase contents and a pre-oxide layer with an ideal structure on the surface.New TBCs exhibit higher microstructure stability exposed to CMAS and more efficient CMAS resistance.展开更多
Plasma spray-physical vapor deposition(PS-PVD)as a novel process was used to prepare feather-like columnar thermal barrier coatings(TBCs).This special microstructure shows good strain tolerance and non-line-of-sight(N...Plasma spray-physical vapor deposition(PS-PVD)as a novel process was used to prepare feather-like columnar thermal barrier coatings(TBCs).This special microstructure shows good strain tolerance and non-line-of-sight(NLOS)deposition,giving great potential application in aero-engine.However,due to serious service environment of aero-engine,particle erosion performance is a weakness for PS-PVD 7YSZ TBCs.As a solution,an Al-modification approach was proposed in this investigation.Through in-situ reaction of Al and ZrO2,anα-Al2O3 overlay can be formed on the surface of 7YSZ columnar coating.The results demonstrate that this approach can improve particle erosion resistance since hardness improvement of Al-modified TBCs.Meanwhile,as another important performance of thermal cycle,it has a better optimization with 350-cycle water-quenching,compared with the as-sprayed TBCs.展开更多
基金National Natural Science Foundation of China (50571005 50420130032)
文摘Conventional two-layered thermal barrier coatings （TBCs） are prepared by electron beam physical vapor deposition （EB-PVD） with ZrO2-8 wt% Y2O3 （8YSZ） as top coat and CoCrAlY as bond coat on disk-shaped Ni based super-alloy. In this paper, three kinds of shot peening process with different lengths of operating time were adopted for bond coating. As a result, changes took place in its surface roughness and the surface micro-hardness. A thermal cycling test at 1 273 Kx55 rain and another at room temperature for 5 min were performed to study the effects of shot peening process on the thermal cycling lifetime of TBCs. It is found that a moderate shot peening process will be able to prolong the life time. The oxidation dynamic of the as-processed TBCs basically accords with the parabolic rule, and the oxidation test also attests to the spallation between YSZ and thermal growth oxide （TGO） responsible mainly for the failure of TBCs.
基金This work is sponsored by the National Natural Science Foundation of China (NFSC) and Specialized Research Fund for the Doctoral Program of Higher Education of China (SRFDP).
文摘Conventional two-layered structure thermal barrier coatings (TBCs) were prepared onto γ'-Ni3Al based alloy IC-6 by electron beam physical vapor deposition (EB-PVD). Isothermal oxidation and thermal cycling tests were carried out to investigate the effect of Mo content at the interface between bond coat and ceramic top coat caused by diffusion. It has been found that the alloy coated with TBCs presented the lowest oxidation weight gain value for the reason that the ceramic top coat in TBC system can effectively stop Mo oxides evaporating. The life time of TBCs has close relation with Mo content at the interface between the bond coat and top coat. Spaliation of ceramic top coat occurred during thermal cyclic testing when Mo atoms accumulated at the interface up to certain amount to decline the combination between the bond coat and top coat.
基金financially supported by the National Natural Science Foundation of China(Nos.51801034 and 52172067)Guangdong Province Outstanding Youth Foundation(No.2021B1515020038)+2 种基金Guangdong Special Support Program(No.2019BT02C629)Key R&D project in ShanXi Province(No.2019ZDLGY01-07)Guangdong Academy of Sciences Program(No.2020GDASYL-20200104030)。
文摘ZrO_(2)-7 wt% Y_(2)O_(3)(7YSZ)thermal barrier coatings(TBCs)with three different structures were prepared by atmospheric plasma spraying(APS),electron beam physical vapor deposition(EB-PVD)and plasma spray-physical vapor deposition(PS-PVD).Al films were deposited onto the top 7YSZ TBCs by magnetron sputtering,and the Al-deposited 7YSZ TBCs were subjected to vacuum heat treatment.The effects of Al modification on the thermal insulation properties of 7YSZ TBCs were investigated.The results showed that Al modification could significantly improve the thermal insulation of 7YSZ TBCs at 1000℃.Moreover,the maximum improvement of thermal insulation for PS-PVD 7YSZ TBCs was approximately 100℃,but the improvement decreased with increasing temperature.This is mainly because with increasing temperature,the rate of radiation heat transfer increases,and the effects of convection heat transfer and thermal conductivity on thermal insulation are weakened.At the same temperature,Al modification of PS-PVD7YSZ TBCs provides better temperature insulation than those of APS 7YSZ TBCs and EB-PVD 7YSZ TBCs because of its wider and deeper inter-columnar gaps.When the temperature was 12000C,Al modification still caused a good insulation effect in PS-PVD 7YSZ TBCs;the improvement was approximately 50℃,but in APS and EB-PVD 7YSZ TBCs,the insulation effect disappeared.
文摘The TBC system is examined with regards to its response to thermal exposure at high temperature. It has been established before that the thermally grown oxide (TGO) layer that forms upon bond coat oxidation is the key factor determining the performance of the TBC system and/or its failure. However, characteristics of TGO growth, bond coat rumpling, principles governing failure of TBC systems and the various failure mechanisms have been studied extensively in case of just super alloy with bond coat or with thick top coating. In this study super alloy/bond coat system with single splats of YSZ instead of thick topcoat is analyzed in order to scrutinize the effect on the first layer of splats during thermal exposure. The splats with microcracks are the building blocks of the top coat. The most important aspect of this layer is the inherent inter-splat and intra-splat porosity which undergoes sintering during thermal exposure. The interactions between the YSZ splats and the evolving TGO is directly linked to the presence or absence of bond coat oxidation. Therefore the high temperature behavior of this system is analyzed with variations in heat treatment involving, temperature, duration and environment of thermal exposure.
文摘The TBC system’s response to thermal exposure at high temperature is discussed here. The relevance of the microstructural aspects of each component of the TBC system is emphasized. The top coat is a YSZ ceramic coating consisting of a collection of splats on top of one another. The most important aspect of this layer is the inherent inter-splat and intra-splat porosity which undergoes sintering during thermal exposure. This study investigates the effect of thermal exposure on the microstructure and sintering behavior in single splats produced using different starting powders since this has been shown to influence the basic microstructure of YSZ topcoat. The bond coat is an MCrAlY metallic coating which serves as an Al reservoir and allows the formation of a protective alumina, Thermally Grown Oxide (TGO) layer between the bond coat (BC) and the top coat (TC) layers. This oxide scale formed upon thermal exposure prevents further oxidation of the underlying component (substrate) and thus provides protection. As such, the content of free Al in the bond coat layer is of significance and makes it crucial to understand the influence of bond coat microstructure evolution and oxidation involved during its formation. The interaction between the bond coat, the TGO and the top coat layers is examined in this study to understand the high temperature behavior of the TBC system with regards to variations in the top coat and bond coat material systems used.
基金support from Yunnan Major Scientific and Technological Projects(No.202302AG050010)Yunnan Fundamental Research Projects(Nos.202101AW070011 and202101BE070001–015)+1 种基金National Natural Science Foundation of China(No.52303295)Project Funds of“Xingdian Talent Support Program”.
文摘Improving and optimizing the target properties of ceramics via the high entropy strategy has attracted significant attention.Rare earth niobate is a potential thermal barrier coating(TBCs)material,but its poor high-temperature phase stability limits its further application.In this work,four sets of TBCs high-entropy ceramics,(Sm_(1/5)Dy_(1/5)Ho_(1/5)Er_(1/5)Yb_(1/5))(Nb_(1/2)Ta_(1/2))O_(4)(5NbTa),(Sm_(1/6)Dy_(1/6)Ho_(1/6)Er_(1/6)Yb_(1/6)Lu_(1/6))(Nb_(1/2)Ta_(1/2))O_(4)(6NbTa),(Sm_(1/7)Gd_(1/7)Dy_(1/7)Ho_(1/7)Er_(1/7)Yb_(1/7)Lu_(1/7))(Nb_(1/2)Ta_(1/2))O_(4)(7NbTa),(Sm_(1/8)Gd_(1/8)Dy_(1/8)Ho_(1/8)Er_(1/8)Tm_(1/8)Yb_(1/8)Lu_(1/8))(Nb_(1/2)Ta_(1/2))O_(4)(8NbTa)are synthesized using a solid-state reaction method at 1650℃for 6 h.Firstly,the X-ray diffractometer(XRD)patterns display that the samples are all single-phase solid solution structures(space group C 2/c).Differential scanning calorimetry(DSC)and the high-temperature XRD of 8NbTa cross-check that the addition of Ta element in 8HERN increases the phase transition temperature above 1400℃,which can be attributed to that the Ta/Nb co-doping at B site introduces the fluctuation of the bond strength of Ta-O and Nb-O.Secondly,compared to high-entropy rare-earth niobates,the introduction of Ta atoms at B site substantially reduce thermal conductivity(re-duced by 44%,800℃)with the seven components high entropy ceramic as an example.The low thermal conductivity means strong phonon scattering,which may originate from the softening acoustic mode and flattened phonon dispersion in 5–8 principal element high entropy rare earth niobium tantalates(5–8NbTa)revealed by the first-principles calculations.Thirdly,the Ta/Nb co-doping in 5–8NbTa systems can further optimize the insulation performance of oxygen ions.The oxygen-ion conductivity of 8NbTa(3.31×10^(−6)S cm^(−1),900℃)is about 5 times lower than that of 8HERN(15.8×10^(−6)S cm^(−1),900℃)because of the sluggish diffusion effect,providing better oxygen barrier capacity in 5–8NbTa systems to inhibit the overgrowth of the thermal growth oxide(TGO)of TBCs.In addition,influenced by lattice dis-tortion and solid solution strengthening,the samples possess higher hardness(7.51–8.15 GPa)and TECs(9.78×10^(−6)K−1^(-1)0.78×10^(−6)K^(−1),1500℃)than the single rare-earth niobates and tantalates.Based on their excellent overall properties,it is considered that 5–8NbTa can be used as auspicious TBCs.
基金supported by the National Natural Science Foundation of China(Grant No.52271087).
文摘Thermal barrier coatings(TBCs)are extensively utilized in aero-engines and heavy-duty gas turbines due to their outstanding properties,including low thermal conductivity,corrosion,high-temperature oxidation,and wear resistance.The rising thrust-to-weight ratio and service temperature in engine hot sections have presented a significant challenge in TBC's materials,structure,and preparation process;it is one of the current research hotspots in the aviation field.This paper reviews the recent advancement in turbine blade TBCs.It focuses on the TBC's structure,deposition mechanism and the key performance evaluation indexes for TBCs applied to turbine blades.Finally,the future research field of TBCs for turbine blades is also be prospected.
基金sponsored by the National Natural Science Foundation of China(Grant No.51971156).
文摘Ti_(2)AlC has been demonstrated as the promising protective layer material for thermal barrier coatings(TBCs)against calcium-magnesium-alumina-silicate(CMAS)attack.In this study,the reliability of Ti_(2)AlC coatings against the CMAS corrosion was explored,and new Ti_(2)AlC/YSZ TBCs more efficiently resistant to CMAS were designed.The fabricated Ti_(2)AlC coatings inevitably contain some impurity phases(TiC and Al2Ti3),the contents of which were minimized by optimizing the spraying distance.Corrosion tests revealed that Ti_(2)AlC/YSZ TBCs yielded higher resistance to the CMAS attack than YSZ TBCs,but with long-term exposure to CMAS,the Ti_(2)AlC protective coating exhibited microstructure degradation due to the presence of the impurity phases,which caused the formation of a layer mixed with Al_(2)O_(3)and TiO_(2)rather than a continuous compact Al_(2)O_(3)layer on the surface.Pre-oxidation schemes were designed in air or with a controlled oxygen partial pressure,which revealed that the pre-oxidation at an oxygen partial pressure of~630 Pa could promote a continuous Al_(2)O_(3)layer formed on the Ti_(2)AlC protective coating surface.Furthermore,a vacuum heat treatment at 867℃for 10 h before pre-oxidation was beneficial for the formation of the compact Al_(2)O_(3)layer.Through the above scheme design,new Ti_(2)AlC/YSZ TBCs were obtained,which had reduced impurity phase contents and a pre-oxide layer with an ideal structure on the surface.New TBCs exhibit higher microstructure stability exposed to CMAS and more efficient CMAS resistance.
基金We would like to acknowledge the financial support from the National Natural Science Foundation of China(52172067)Guangdong Province Outstanding Youth Foundation(2021B1515020038)+1 种基金Guangdong Special Support Program(2019BT02C629)Guangdong Academy of Sciences Program(2020GDASYL-20200104030).
文摘Plasma spray-physical vapor deposition(PS-PVD)as a novel process was used to prepare feather-like columnar thermal barrier coatings(TBCs).This special microstructure shows good strain tolerance and non-line-of-sight(NLOS)deposition,giving great potential application in aero-engine.However,due to serious service environment of aero-engine,particle erosion performance is a weakness for PS-PVD 7YSZ TBCs.As a solution,an Al-modification approach was proposed in this investigation.Through in-situ reaction of Al and ZrO2,anα-Al2O3 overlay can be formed on the surface of 7YSZ columnar coating.The results demonstrate that this approach can improve particle erosion resistance since hardness improvement of Al-modified TBCs.Meanwhile,as another important performance of thermal cycle,it has a better optimization with 350-cycle water-quenching,compared with the as-sprayed TBCs.
