The stratified gradient thermal barrier coatings (TBCs) were obtained by laser cladding of ZrO 2 and NiCoCrAlY mixture powder. The coatings were four layer structure: cellular dendritic ZrO 2, dense ZrO 2, Ni based al...The stratified gradient thermal barrier coatings (TBCs) were obtained by laser cladding of ZrO 2 and NiCoCrAlY mixture powder. The coatings were four layer structure: cellular dendritic ZrO 2, dense ZrO 2, Ni based alloy bonding coating and substrate. The formation of the stratified TBCs was attributed to the insolubility of ZrO 2 in the Ni based alloy and the lower density of ZrO 2 than that of Ni based alloy when both of them were in melted condition. The formation of two layered ZrO 2 was related to the presence of Al in the Ni based alloy, i) Al could be preoxidized into Al 2O 3 that could be segregated in the grain boundaries of ZrO 2 during solidification process; ii) Al could be partially preoxidized into Al 2O 3, then Al and Al 2O 3 could be segregated simultaneously at the grain boundaries of ZrO 2 during solidification process. Two formation processes were presented.展开更多
Inspired by the coupling phenomena in biological systems, to improve the solid particle erosion resistance of Thermal Barrier Coatings （TBCs）, different kinds of bionic units were made on the coating surfaces using ...Inspired by the coupling phenomena in biological systems, to improve the solid particle erosion resistance of Thermal Barrier Coatings （TBCs）, different kinds of bionic units were made on the coating surfaces using Bionic Coupled Laser Remelting （BCLR） process. The NiCoCrAlYTa/ZrO2-7wt%Y2O3 double-layer structured TBCs were prepared by air plasma spraying. The microstructure, microhardness and phase composition of the as-sprayed and bionic specimens were examined. The solid particle erosion behaviors of bionic specimens as function of bionic unit shape were investigated. The results indicated that the bionic specimens had better erosion resistance than the as-sprayed specimen. The specimen with striation and grid bionic units had the better erosion resistance, while the dot showed the worse. The bionic units were characterized by the dense columnar crystal structure and the high hardness, which are the main reasons for improving the erosion resistance. Under the synergistic action of the shear stress and normal stress on the protrusive coating surface, the erosion failure of the as-sprayed TBCs was proved to be the fracture and spallation of the splats. By contrast, the spallation of segmented bionic unit occurred in the overlapping area between the adjacent laser irradiation, and the erosive unit surface presented the clear and deep furrows, which revealed that the erosion failure mechanism of bionic TBCs was dominated by brittle and some ductile erosion. These results showed more opportunities for bionic application in improving the solid particle erosion resistance of components in the windy and sandy environment.展开更多
Y2O3 stabilized ZrO2(YSZ)thermal barrier coatings(TBCs)are prone to hot corrosion by molten salts.In this study,the microstructure of atmospheric plasma spraying YSZ TBCs is modified by laser glazing in order to impro...Y2O3 stabilized ZrO2(YSZ)thermal barrier coatings(TBCs)are prone to hot corrosion by molten salts.In this study,the microstructure of atmospheric plasma spraying YSZ TBCs is modified by laser glazing in order to improve the corrosion resistance.By optimizing the laser parameters,a^18μm smooth glazed layer with some vertical cracks was produced on the coating surfaces.The as-sprayed and modified coatings were both exposed to hot corrosion tests at 700 and 1000℃for 4 h in V2O5 molten salt,and the results revealed that the modified one had improved corrosion resistance.After hot corrosion,the glazed layer kept structural integrity,with little evidence of dissolution.However,the vertical cracks in the glazed layer acted as the paths for molten salt penetration,accelerating the corrosion of the non-modified coating.Further optimization of the glazed layer is needed in the future work.展开更多
Thermal barrier coatings （TBCs） are mostly applied to hot components of advanced turbine engines to insulate the compo- nents from hot gas. The effect of sintering on thermal conductivity and thermal barrier effects...Thermal barrier coatings （TBCs） are mostly applied to hot components of advanced turbine engines to insulate the compo- nents from hot gas. The effect of sintering on thermal conductivity and thermal barrier effects of conventional plasma sprayed and nanostructured yttria stabilized zirconia （YSZ） thermal barrier coatings （TBCs） are investigated. Remarkable increase in thermal conductivity occurs to both typical coatings after heat treatment, The change of porosity is just the opposite. The grain size of the nanostructured zirconia coating increases more drastically with annealing time compared to that of the conventional plasma sprayed coating, which indicates that coating sintering makes more contributions to the thermal conductivity of the nanostructured coating than that of the conventional coating. Thermal barrier effect tests using temperature difference technique are performed on both coatings. The thermal barrier effects decrease with the increase of thermal conductivity after heat treat- ment and the decline seems more drastic in low thermal conductivity range. The decline in thermal barrier effects is about 80℃ for nanostructured coating after 100 h heat treatment, while the conventional coating reduces by less than 60 ℃ compared to the as-sprayed coating.展开更多
Inspired by the self-healing function of biological organisms,Bionic Laser Alloying(BLA)process was adopted to fabricate the bionic self-healing Thermal Barrier Coatings(TBCs).The BLA with different fractions of TiAl3...Inspired by the self-healing function of biological organisms,Bionic Laser Alloying(BLA)process was adopted to fabricate the bionic self-healing Thermal Barrier Coatings(TBCs).The BLA with different fractions of TiAl3 self-healing agent and Ceria and Yttria-Stabilized Zirconia(CYSZ)on the plasma-sprayed 7YSZ TBCs was carried out by a pulsed Nd:YAG laser.The effect of TiAl3 content on the microstructure,phase composition,and thermal shock behaviors of the bionic self-healing TBCs were investigated.Results indicated that the bionic self-healing TBCs had better thermal shock resistance than that of the as-sprayed TBCs.The thermal shock resistance increased first and then decreased with increasing TiAl3 fraction.The thermal shock resistance of the bionic self-healing TBCs with 15%TiAl3 is triple that of the as-sprayed TBCs.On one hand,the columnar crystals and vertical cracks could improve strain compatibility of TBCs during the thermal shock process;on the other hand,the TiAl3 as a self-healing agent reacted with oxygen in air at high temperature to seal the microcracks,thereby delaying the crack connection.展开更多
文摘The stratified gradient thermal barrier coatings (TBCs) were obtained by laser cladding of ZrO 2 and NiCoCrAlY mixture powder. The coatings were four layer structure: cellular dendritic ZrO 2, dense ZrO 2, Ni based alloy bonding coating and substrate. The formation of the stratified TBCs was attributed to the insolubility of ZrO 2 in the Ni based alloy and the lower density of ZrO 2 than that of Ni based alloy when both of them were in melted condition. The formation of two layered ZrO 2 was related to the presence of Al in the Ni based alloy, i) Al could be preoxidized into Al 2O 3 that could be segregated in the grain boundaries of ZrO 2 during solidification process; ii) Al could be partially preoxidized into Al 2O 3, then Al and Al 2O 3 could be segregated simultaneously at the grain boundaries of ZrO 2 during solidification process. Two formation processes were presented.
基金This work is supported by Science and Technology Project of Guangdong Province （2014B050502008）, Science and Technology plan projects of Guangdong Province （2017A070702016, 2017A070701027）, Guangzhou Science and Technology Program key projects （201510010095）, Natural Science Foundation of Guangdong Province （2016A030312015）, the National Natural Science Foundation for Youth （51501044）. and 111 Project of China （B16020）.
文摘Inspired by the coupling phenomena in biological systems, to improve the solid particle erosion resistance of Thermal Barrier Coatings （TBCs）, different kinds of bionic units were made on the coating surfaces using Bionic Coupled Laser Remelting （BCLR） process. The NiCoCrAlYTa/ZrO2-7wt%Y2O3 double-layer structured TBCs were prepared by air plasma spraying. The microstructure, microhardness and phase composition of the as-sprayed and bionic specimens were examined. The solid particle erosion behaviors of bionic specimens as function of bionic unit shape were investigated. The results indicated that the bionic specimens had better erosion resistance than the as-sprayed specimen. The specimen with striation and grid bionic units had the better erosion resistance, while the dot showed the worse. The bionic units were characterized by the dense columnar crystal structure and the high hardness, which are the main reasons for improving the erosion resistance. Under the synergistic action of the shear stress and normal stress on the protrusive coating surface, the erosion failure of the as-sprayed TBCs was proved to be the fracture and spallation of the splats. By contrast, the spallation of segmented bionic unit occurred in the overlapping area between the adjacent laser irradiation, and the erosive unit surface presented the clear and deep furrows, which revealed that the erosion failure mechanism of bionic TBCs was dominated by brittle and some ductile erosion. These results showed more opportunities for bionic application in improving the solid particle erosion resistance of components in the windy and sandy environment.
基金This research is sponsored by the National Natural Science Foundation of China(Grant No.51971156).
文摘Y2O3 stabilized ZrO2(YSZ)thermal barrier coatings(TBCs)are prone to hot corrosion by molten salts.In this study,the microstructure of atmospheric plasma spraying YSZ TBCs is modified by laser glazing in order to improve the corrosion resistance.By optimizing the laser parameters,a^18μm smooth glazed layer with some vertical cracks was produced on the coating surfaces.The as-sprayed and modified coatings were both exposed to hot corrosion tests at 700 and 1000℃for 4 h in V2O5 molten salt,and the results revealed that the modified one had improved corrosion resistance.After hot corrosion,the glazed layer kept structural integrity,with little evidence of dissolution.However,the vertical cracks in the glazed layer acted as the paths for molten salt penetration,accelerating the corrosion of the non-modified coating.Further optimization of the glazed layer is needed in the future work.
基金National Natural Science Foundation of China (50771009, 50731001, 51071013)
文摘Thermal barrier coatings （TBCs） are mostly applied to hot components of advanced turbine engines to insulate the compo- nents from hot gas. The effect of sintering on thermal conductivity and thermal barrier effects of conventional plasma sprayed and nanostructured yttria stabilized zirconia （YSZ） thermal barrier coatings （TBCs） are investigated. Remarkable increase in thermal conductivity occurs to both typical coatings after heat treatment, The change of porosity is just the opposite. The grain size of the nanostructured zirconia coating increases more drastically with annealing time compared to that of the conventional plasma sprayed coating, which indicates that coating sintering makes more contributions to the thermal conductivity of the nanostructured coating than that of the conventional coating. Thermal barrier effect tests using temperature difference technique are performed on both coatings. The thermal barrier effects decrease with the increase of thermal conductivity after heat treat- ment and the decline seems more drastic in low thermal conductivity range. The decline in thermal barrier effects is about 80℃ for nanostructured coating after 100 h heat treatment, while the conventional coating reduces by less than 60 ℃ compared to the as-sprayed coating.
基金supported by National Natural Science Foundation of China(Grant No.52105311)Natural Science Foundation of Zhejiang Province(Grant No.LQ21E010002)Fundamental Research Funds for the Provincial Universities of Zhejiang(Grant No.RF-A2020009).
文摘Inspired by the self-healing function of biological organisms,Bionic Laser Alloying(BLA)process was adopted to fabricate the bionic self-healing Thermal Barrier Coatings(TBCs).The BLA with different fractions of TiAl3 self-healing agent and Ceria and Yttria-Stabilized Zirconia(CYSZ)on the plasma-sprayed 7YSZ TBCs was carried out by a pulsed Nd:YAG laser.The effect of TiAl3 content on the microstructure,phase composition,and thermal shock behaviors of the bionic self-healing TBCs were investigated.Results indicated that the bionic self-healing TBCs had better thermal shock resistance than that of the as-sprayed TBCs.The thermal shock resistance increased first and then decreased with increasing TiAl3 fraction.The thermal shock resistance of the bionic self-healing TBCs with 15%TiAl3 is triple that of the as-sprayed TBCs.On one hand,the columnar crystals and vertical cracks could improve strain compatibility of TBCs during the thermal shock process;on the other hand,the TiAl3 as a self-healing agent reacted with oxygen in air at high temperature to seal the microcracks,thereby delaying the crack connection.
基金supported by Major Special Projects of Gansu Province,China(No.21ZD4WA017)University Industry Transformation Promotion Project of Gansu Province,China(No.2020C-11)+1 种基金the Program of“Science and Technology International Cooperation Demonstrative Base of Metal Surface Engineering along the Silk Road”,China(No.2017D01003)the National Natural Science Foundation of China(No.51901093)。
