During atmospheric plasma spraying,a cooling process usually plays an important role in the coating quality,especially for the oxidation containment of metallic coatings.CuNiIn and Mo coatings were prepared using atmo...During atmospheric plasma spraying,a cooling process usually plays an important role in the coating quality,especially for the oxidation containment of metallic coatings.CuNiIn and Mo coatings were prepared using atmospheric plasma spraying with different cooling processes.The obtained coatings were characterized in terms of microstructure,microhardness and tensile strengths.The relation between the coating microstructure and their fretting fatigue behavior was emphasized.The results show that the sensitivity of Mo coatings to the cooling process is lower than CuNiIn coatings.The resistance to fretting fatigue is determined by the coating microhardness,correlated with the contents of oxides and pores.The fretting wear mechanisms of both the coatings are galling,third body abrasive wear and material transfer.展开更多
The halide-activated pack cementation process was used to form molybdenum diffusion coating on titanium substrate. The morphology, structure, elements diffusion distribution and microhardness of the coatings formed at...The halide-activated pack cementation process was used to form molybdenum diffusion coating on titanium substrate. The morphology, structure, elements diffusion distribution and microhardness of the coatings formed at different diffusion temperatures were studied. The results indicate that the coating is made up of deposition layer and diffusion layer, and the surface roughness of specimens is increased after diffusion. In the diffusion layer, the major phases are Mo and β-Ti phase with addition of α′-Ti phase and α″-Ti phase. And the phase composition of Mo→β→α″→α′ is formed for different Mo contents in the diffusion layer from outside to inside. The diffusion of Ti element is very obvious as well as Mo element. With increasing the diffusion temperature, the thickness of diffusion layer is increased rapidly, and the microhardness is changed more smoothly with diffusion depth, which shows the same distribution rules as the Mo content.展开更多
A novel Fe–Cr–Mo amorphous coating,a high-temperature corrosion-resistant material for water wall protection of power plant ultra-supercritical boilers,has been prepared via arc spraying.A systematic study was condu...A novel Fe–Cr–Mo amorphous coating,a high-temperature corrosion-resistant material for water wall protection of power plant ultra-supercritical boilers,has been prepared via arc spraying.A systematic study was conducted to evaluate the high-temperature corrosion behavior of this coating,and its resistance to corrosion at high temperatures was scientifically assessed.The results indicate that the thickness of Fe–Cr–Mo amorphous coating is approximately 350μm,exhibiting typical amorphous characteristics as confirmed by X-ray diffraction and transmission electron microscope characterization.During each stage of the 750℃corrosion test,the oxygen content of the amorphous coating was significantly lower than that of the contrast coating(PS45 alloy coating),indicating a superior corrosion protection effect at high temperature.After 100 h of continuous testing,the corrosion mass gain of the amorphous coating was only 28.62%that of PS45 coating and 3.89%that of T12 steel substrate,indicating significantly depressed high-temperature corrosion kinetics.The excellent high-temperature corrosion resistance of Fe–Cr–Mo amorphous coating is primarily attributed to the stable Fe/Cr oxide film generated by the metastable state of the amorphous state,which serves as an excellent barrier.Furthermore,under the influence of heat in a high-temperature environment,the amorphous structure gradually transforms into a nanocrystalline structure.In contrast,the oxide film of the amorphous/nanocrystalline coating has low thermal stress,leading to better adhesion with the coating and resistance to cracking and peeling,thus providing excellent sustained protection.展开更多
The forming process of silicide coatings on pure Mo and Mo-base alloys, obtained by the gas- phase deposition method. has been studied by examining the microstructure of coatings and the relationship between coating t...The forming process of silicide coatings on pure Mo and Mo-base alloys, obtained by the gas- phase deposition method. has been studied by examining the microstructure of coatings and the relationship between coating thickness and process parameters. It was shown that the growth of coatings was diffusion-controlled, the diffusion of silicon to be coated into Mo or Mo-base alloys was mainly responsible for the formation of silicide. The relationship between initial silicide thickness and oxidation resistance was also investigated, and the equation of service life of the coatings at high temperature in air is presented.展开更多
C/Mo duplex coating interfacially modified SiC fiber-reinforced γ-TiAl matrix composite （SiCf/C/Mo/γ-TiA1） was prepared by foil-fiber-foil method to investigate its interfacial modification effect. SiCf/C/TiAl com...C/Mo duplex coating interfacially modified SiC fiber-reinforced γ-TiAl matrix composite （SiCf/C/Mo/γ-TiA1） was prepared by foil-fiber-foil method to investigate its interfacial modification effect. SiCf/C/TiAl composites were also prepared under the same processing condition for comparision. Both kinds of the composites were thermally exposed in vacuum at 800 and 900℃ for different durations in order to study thermal stability of the interfacial zone. With the aids of scanning electron microscope （SEM） and energy dispersive spectrometer （EDS）, the interracial microstructures of the composites were investigated. The results reveal that, although adding the Mo coating, the interfacial reaction product of the SiCf/C/Mo/TiAl composite is the same with that of the SiCf/C/TiA1 composite, which is TiC/Ti2AlC between the coating and the matrix. However, C/Mo duplex coating is more efficient in hindering interfacial reaction than C single coating at 900 ℃ and below. In addition, a new layer of interfacial reaction product was found between Ti2AlC and the matrix after 900 ℃, 200 h thermal exposure, which is rich in V and close to the chemical composition of B2 phase.展开更多
The Cr-coated Zr alloys demonstrate excellent resistance to high-temperature steam oxidation.However,the rapid diffusion pathways for oxygen formed by the inter-diffusion between the coating and alloy at high temperat...The Cr-coated Zr alloys demonstrate excellent resistance to high-temperature steam oxidation.However,the rapid diffusion pathways for oxygen formed by the inter-diffusion between the coating and alloy at high temperatures significantly affect the steam oxidation resistance of the coated alloys.To address this issue,we developed a Mo/Cr bilayer coating on Zr alloy by a combination of dc-MS and HiPIMS surface treatments.The coating exhibits outstanding steam oxidation resistance at high temperatures,resulting in a mass gain approximately 86.6%and 44.1%lower than that of the bare Zr alloy and Cr coating,respectively,after 30 min of steam oxidation at 1200℃.This is mainly because,during the oxidation process,the Mo interface layer undergoes a transformation into a thin and high-quality double diffusion layer structure,effectively avoiding high-temperature inter-diffusion between the Cr coating and Zr alloy,thereby inhibiting the formation of oxygen diffusion pathways.展开更多
基金the National Natural Science Foundation of China[grant numbers 51875424,51501137 and 51702244]the Fundamental Research Funds for the Central Universities[WUT:2019III033].
文摘During atmospheric plasma spraying,a cooling process usually plays an important role in the coating quality,especially for the oxidation containment of metallic coatings.CuNiIn and Mo coatings were prepared using atmospheric plasma spraying with different cooling processes.The obtained coatings were characterized in terms of microstructure,microhardness and tensile strengths.The relation between the coating microstructure and their fretting fatigue behavior was emphasized.The results show that the sensitivity of Mo coatings to the cooling process is lower than CuNiIn coatings.The resistance to fretting fatigue is determined by the coating microhardness,correlated with the contents of oxides and pores.The fretting wear mechanisms of both the coatings are galling,third body abrasive wear and material transfer.
文摘The halide-activated pack cementation process was used to form molybdenum diffusion coating on titanium substrate. The morphology, structure, elements diffusion distribution and microhardness of the coatings formed at different diffusion temperatures were studied. The results indicate that the coating is made up of deposition layer and diffusion layer, and the surface roughness of specimens is increased after diffusion. In the diffusion layer, the major phases are Mo and β-Ti phase with addition of α′-Ti phase and α″-Ti phase. And the phase composition of Mo→β→α″→α′ is formed for different Mo contents in the diffusion layer from outside to inside. The diffusion of Ti element is very obvious as well as Mo element. With increasing the diffusion temperature, the thickness of diffusion layer is increased rapidly, and the microhardness is changed more smoothly with diffusion depth, which shows the same distribution rules as the Mo content.
基金The authors would like to acknowledge the financial support from China Power International Holding Ltd.(ZGDL-KJ-2022-024)Postgraduate Research&Practice Innovation Program of Jiangsu Province(SJCX23_0179).
文摘A novel Fe–Cr–Mo amorphous coating,a high-temperature corrosion-resistant material for water wall protection of power plant ultra-supercritical boilers,has been prepared via arc spraying.A systematic study was conducted to evaluate the high-temperature corrosion behavior of this coating,and its resistance to corrosion at high temperatures was scientifically assessed.The results indicate that the thickness of Fe–Cr–Mo amorphous coating is approximately 350μm,exhibiting typical amorphous characteristics as confirmed by X-ray diffraction and transmission electron microscope characterization.During each stage of the 750℃corrosion test,the oxygen content of the amorphous coating was significantly lower than that of the contrast coating(PS45 alloy coating),indicating a superior corrosion protection effect at high temperature.After 100 h of continuous testing,the corrosion mass gain of the amorphous coating was only 28.62%that of PS45 coating and 3.89%that of T12 steel substrate,indicating significantly depressed high-temperature corrosion kinetics.The excellent high-temperature corrosion resistance of Fe–Cr–Mo amorphous coating is primarily attributed to the stable Fe/Cr oxide film generated by the metastable state of the amorphous state,which serves as an excellent barrier.Furthermore,under the influence of heat in a high-temperature environment,the amorphous structure gradually transforms into a nanocrystalline structure.In contrast,the oxide film of the amorphous/nanocrystalline coating has low thermal stress,leading to better adhesion with the coating and resistance to cracking and peeling,thus providing excellent sustained protection.
文摘The forming process of silicide coatings on pure Mo and Mo-base alloys, obtained by the gas- phase deposition method. has been studied by examining the microstructure of coatings and the relationship between coating thickness and process parameters. It was shown that the growth of coatings was diffusion-controlled, the diffusion of silicon to be coated into Mo or Mo-base alloys was mainly responsible for the formation of silicide. The relationship between initial silicide thickness and oxidation resistance was also investigated, and the equation of service life of the coatings at high temperature in air is presented.
基金Projects(51201134,51271147)supported by the National Natural Science Foundation of ChinaProject(2015JM5181)supported by the Natural Science Foundation of Shaanxi Province,China+1 种基金Project(115-QP-2014)supported by the Research Fund of the State Key Laboratory of Solidification Processing(NWPU),ChinaProject(3102014JCQ01023)supported by the Fundamental Research Funds for the Central Universities,China
文摘C/Mo duplex coating interfacially modified SiC fiber-reinforced γ-TiAl matrix composite （SiCf/C/Mo/γ-TiA1） was prepared by foil-fiber-foil method to investigate its interfacial modification effect. SiCf/C/TiAl composites were also prepared under the same processing condition for comparision. Both kinds of the composites were thermally exposed in vacuum at 800 and 900℃ for different durations in order to study thermal stability of the interfacial zone. With the aids of scanning electron microscope （SEM） and energy dispersive spectrometer （EDS）, the interracial microstructures of the composites were investigated. The results reveal that, although adding the Mo coating, the interfacial reaction product of the SiCf/C/Mo/TiAl composite is the same with that of the SiCf/C/TiA1 composite, which is TiC/Ti2AlC between the coating and the matrix. However, C/Mo duplex coating is more efficient in hindering interfacial reaction than C single coating at 900 ℃ and below. In addition, a new layer of interfacial reaction product was found between Ti2AlC and the matrix after 900 ℃, 200 h thermal exposure, which is rich in V and close to the chemical composition of B2 phase.
基金financially supported by the National Natural Science Foundation of China(U22A20111)the Key Research and Development Program of Ningbo(20232ZDYF020062)
文摘The Cr-coated Zr alloys demonstrate excellent resistance to high-temperature steam oxidation.However,the rapid diffusion pathways for oxygen formed by the inter-diffusion between the coating and alloy at high temperatures significantly affect the steam oxidation resistance of the coated alloys.To address this issue,we developed a Mo/Cr bilayer coating on Zr alloy by a combination of dc-MS and HiPIMS surface treatments.The coating exhibits outstanding steam oxidation resistance at high temperatures,resulting in a mass gain approximately 86.6%and 44.1%lower than that of the bare Zr alloy and Cr coating,respectively,after 30 min of steam oxidation at 1200℃.This is mainly because,during the oxidation process,the Mo interface layer undergoes a transformation into a thin and high-quality double diffusion layer structure,effectively avoiding high-temperature inter-diffusion between the Cr coating and Zr alloy,thereby inhibiting the formation of oxygen diffusion pathways.
