Research on Thermal Oxidation/Vacuum Diffusion Treatment on Surface of Ti6Al4V Alloy and Its Effect on Wear Resistance

Ti6Al4V alloy was processed with thermal oxidation at 800℃ for 1 h or at 900℃ for 15 min, then processed with vacuum diffusion at 850℃ for 20 h.At 25℃ and 400℃,dry sliding wear tests were performed for the alloy that underwent thermal oxidation at 900℃ for 15 min and vacuum diffusion at 850℃ for 20 h.A comparative study on microhardness distributions of the samples after vacuum diffusion and weight losses of the samples with or without processing was carried out.Microstructures and morphologies of the samples after oxidation or oxidation/diffusion and wear tests were analyzed by XRD, SEM,and EDS etc.The results show that titanium oxide forms on the surface after thermal oxidation, then TiO₂decomposes after vacuum diffusion.Between the surface oxide layer and the substrate,an oxygen diffusion layer generates and enhances their binding force,exhibiting a hardening effect.At the same time,some Al₃Ti appears.Under different load or temperature,the weight losses of the samples after oxidation/vacuum diffusion are much smaller than those of the samples without processing.Therefore,it can be concluded that the wear resistance of Ti6Al4V alloy after thermal oxidation at 900℃ for 15 min and vacuum diffusion at 850℃ for 20 h is significantly improved.