The beginning of failure of a (ZrO2-7%Y2O3)/(Ni-22%Co-17%Cr-12.5%Al-0.6%Y) duplex andgraded coating systems on lnconel 617 and IN738LC in burner rig tests has been characterized.The test conditions are 40 s heating up...The beginning of failure of a (ZrO2-7%Y2O3)/(Ni-22%Co-17%Cr-12.5%Al-0.6%Y) duplex andgraded coating systems on lnconel 617 and IN738LC in burner rig tests has been characterized.The test conditions are 40 s heating up to 75O℃ substrate temperature followed by 80 s aircooling. Failure is considered at the appearance of the first bright spot during heating period.Stresses due to thermal expansion mismatch strains on cooling are the probable cause of life-limiting in this conditions of testing.展开更多
Ru-doped NiAlHf coatings were deposited on Ni-based single crystal substrate by arc ion plating technology.The failure mechanism and interfacial diffusion behavior were comparatively investigated with NiAlHf coating u...Ru-doped NiAlHf coatings were deposited on Ni-based single crystal substrate by arc ion plating technology.The failure mechanism and interfacial diffusion behavior were comparatively investigated with NiAlHf coating using scanning electron microscopy,electron probe micro-analyzer,and transmission electron microscopy.The results indicated that microstructure evolution of oxide scale induced by element diffusion process significantly affected oxidation resistance of NiAlHf/Ru coatings,resulting in formation of cracks and voids,thereby accelerating failure process.The precipitates in interdiffusion zone and secondary reaction zone of the substrate initiated by interfacial element diffusion were P phase andσphase,respectively.And the discrepancy in content was elucidated from the perspective of thermodynamics and kinetics.Besides,microstructural evolution between NiAlHf/Ru coatings and substrate was also deliberated.The research could not only provide profound understanding of NiAlHf/Ru coatings failure mechanism,but also had significant guidance for suppressing precipitation of topological close-packed phases and facilitating development of single crystal Ni-based superalloys.展开更多
Mg and its alloys evince strong candidature for biodegradable bone implants,cardiovascular stents,and wound closing devices.However,their rapid degradation rate causes premature implant failure,constraining clinical a...Mg and its alloys evince strong candidature for biodegradable bone implants,cardiovascular stents,and wound closing devices.However,their rapid degradation rate causes premature implant failure,constraining clinical applications.Bio-functional surface coatings have emerged as the most competent strategy to fulfill the diverse clinical requirements,besides yielding effective corrosion resistance.This article reviews the progress of biodegradable and advanced surface coatings on Mg alloys investigated in recent years,aiming to build up a comprehensive knowledge framework of coating techniques,processing parameters,performance measures in terms of corrosion resistance,adhesion strength,and biocompatibility.Recently developed conversion and deposition type surface coatings are thoroughly discussed by reporting their essential therapeutic responses like osteogenesis,angiogenesis,cytocompatibility,hemocompatibility,anti-bacterial,and controlled drug release towards in-vitro and in-vivo study models.The challenges associated with metallic,ceramic and polymeric coatings along with merits and demerits of various coatings have been illustrated.The use of multilayered hybrid coating comprising a unique combination of organic and inorganic components has been emphasized with future perspectives to obtain diverse bio-functionalities in a facile single coating system for orthopedic implant applications.展开更多
文摘The beginning of failure of a (ZrO2-7%Y2O3)/(Ni-22%Co-17%Cr-12.5%Al-0.6%Y) duplex andgraded coating systems on lnconel 617 and IN738LC in burner rig tests has been characterized.The test conditions are 40 s heating up to 75O℃ substrate temperature followed by 80 s aircooling. Failure is considered at the appearance of the first bright spot during heating period.Stresses due to thermal expansion mismatch strains on cooling are the probable cause of life-limiting in this conditions of testing.
基金This work was supported by Guangdong Special Support Program(No.2019BT02C629)GDAS0 Project of Science Technology Development(No.2020GDASYL-20200402005)+1 种基金The Scientific Research Fund of Guangdong Province,China(No.2016A030312015)Doctoral Research Initiation Program(No.84KZ-KZ08072).
文摘Ru-doped NiAlHf coatings were deposited on Ni-based single crystal substrate by arc ion plating technology.The failure mechanism and interfacial diffusion behavior were comparatively investigated with NiAlHf coating using scanning electron microscopy,electron probe micro-analyzer,and transmission electron microscopy.The results indicated that microstructure evolution of oxide scale induced by element diffusion process significantly affected oxidation resistance of NiAlHf/Ru coatings,resulting in formation of cracks and voids,thereby accelerating failure process.The precipitates in interdiffusion zone and secondary reaction zone of the substrate initiated by interfacial element diffusion were P phase andσphase,respectively.And the discrepancy in content was elucidated from the perspective of thermodynamics and kinetics.Besides,microstructural evolution between NiAlHf/Ru coatings and substrate was also deliberated.The research could not only provide profound understanding of NiAlHf/Ru coatings failure mechanism,but also had significant guidance for suppressing precipitation of topological close-packed phases and facilitating development of single crystal Ni-based superalloys.
文摘Mg and its alloys evince strong candidature for biodegradable bone implants,cardiovascular stents,and wound closing devices.However,their rapid degradation rate causes premature implant failure,constraining clinical applications.Bio-functional surface coatings have emerged as the most competent strategy to fulfill the diverse clinical requirements,besides yielding effective corrosion resistance.This article reviews the progress of biodegradable and advanced surface coatings on Mg alloys investigated in recent years,aiming to build up a comprehensive knowledge framework of coating techniques,processing parameters,performance measures in terms of corrosion resistance,adhesion strength,and biocompatibility.Recently developed conversion and deposition type surface coatings are thoroughly discussed by reporting their essential therapeutic responses like osteogenesis,angiogenesis,cytocompatibility,hemocompatibility,anti-bacterial,and controlled drug release towards in-vitro and in-vivo study models.The challenges associated with metallic,ceramic and polymeric coatings along with merits and demerits of various coatings have been illustrated.The use of multilayered hybrid coating comprising a unique combination of organic and inorganic components has been emphasized with future perspectives to obtain diverse bio-functionalities in a facile single coating system for orthopedic implant applications.
