Two surface treatments, molybdenizing and depositing NiCrAIY coating, were applied to improve the microhardness and the oxidation resistance of titanium and Ti-6Al-4V. Coupons were analyzed using optical microscopy ...Two surface treatments, molybdenizing and depositing NiCrAIY coating, were applied to improve the microhardness and the oxidation resistance of titanium and Ti-6Al-4V. Coupons were analyzed using optical microscopy （OM）, scanning electron microscopy （SEM） with X-ray energy dispersive spectrometer （EDS）, and X-ray diffraction （XRD）. Vickers hardness and isothermal oxidation tests were carried out to evaluate the effects of these two surface treatments on the microhardness and oxidation resistance of the substrates. The post vacuum heat treatment of the NiCrAlY coating and the molybdenizing parameters were also discussed. It is found that molybdenizing can obviously increase the surface hardness of titanium due to the formation of β, α＂, and α″ phases in the diffusion layer. As γ＇ phase is formed after vacuum heat treatment, the NiCrAlY coating is effective in improving the surface hardness of Ti-6Al-4V. The NiCrAlY coating can obviously decrease the oxidation rate of Ti-6Al-4V at 700-900℃, which can be attributed to the formation of Al2O3 and Cr2O3 mixed scale during the oxidation.展开更多
Ti2AlNb orthorhombic alloy is an attractive high temperature structural material for aero-industries due to its high specific strength and fracture toughness as well as excellent creep resistance. However, insufficien...Ti2AlNb orthorhombic alloy is an attractive high temperature structural material for aero-industries due to its high specific strength and fracture toughness as well as excellent creep resistance. However, insufficient wear-resistance is the main drawback which restricts the actual uses of this alloy in many circumstances. A double glow plasma surface molybdenizing on Ti2AlNb alloy is carried out as an attempt to resolve this problem. This paper deals with the effects of key process parameters on the diffusion behavior of Mo. The composition distribution and microstructare of the alloying layer are analyzed by SEM, XRD and GDS. Micro-hardness distribution profile is measured along the distance from surface to center. The results indicate that both the temperature and the processing time have significant effects on the diffusion process. Finally, the dif- fusion coefficient at optimized temperature of 980℃ is calculated through regression analysis.展开更多
基金supported by the National Key Program of the 10th Five Year Plan of China (No. 05-MKP-089)
文摘Two surface treatments, molybdenizing and depositing NiCrAIY coating, were applied to improve the microhardness and the oxidation resistance of titanium and Ti-6Al-4V. Coupons were analyzed using optical microscopy （OM）, scanning electron microscopy （SEM） with X-ray energy dispersive spectrometer （EDS）, and X-ray diffraction （XRD）. Vickers hardness and isothermal oxidation tests were carried out to evaluate the effects of these two surface treatments on the microhardness and oxidation resistance of the substrates. The post vacuum heat treatment of the NiCrAlY coating and the molybdenizing parameters were also discussed. It is found that molybdenizing can obviously increase the surface hardness of titanium due to the formation of β, α＂, and α″ phases in the diffusion layer. As γ＇ phase is formed after vacuum heat treatment, the NiCrAlY coating is effective in improving the surface hardness of Ti-6Al-4V. The NiCrAlY coating can obviously decrease the oxidation rate of Ti-6Al-4V at 700-900℃, which can be attributed to the formation of Al2O3 and Cr2O3 mixed scale during the oxidation.
基金The Commission of Science Technology and Industry for National Defense China
文摘Ti2AlNb orthorhombic alloy is an attractive high temperature structural material for aero-industries due to its high specific strength and fracture toughness as well as excellent creep resistance. However, insufficient wear-resistance is the main drawback which restricts the actual uses of this alloy in many circumstances. A double glow plasma surface molybdenizing on Ti2AlNb alloy is carried out as an attempt to resolve this problem. This paper deals with the effects of key process parameters on the diffusion behavior of Mo. The composition distribution and microstructare of the alloying layer are analyzed by SEM, XRD and GDS. Micro-hardness distribution profile is measured along the distance from surface to center. The results indicate that both the temperature and the processing time have significant effects on the diffusion process. Finally, the dif- fusion coefficient at optimized temperature of 980℃ is calculated through regression analysis.
