Influence of thermal oxidation temperature on the microstructural and tribological behavior of Ti6Al4V alloy

Thermal oxidation process under water vapor environment was performed on biomedical titanium alloys for 4 h at different treatment temperature changing from 600 °C to 800 °C to improve the surface properties for the application of artificial joints. In order to ascertain the suitability of thermal oxidized sample as a bio-implant, the morphological features, structural characteristics, microhardness and tribological behavior in dry friction were evaluated. Alumina and rutile as the new phases appeared for the thermal oxidized samples with the hardness increasing. The mechanism of oxidation involved nucleation of a thin layer of oxide followed by its agglomeration and growth to completely cover the surface. The representative coating thickness values for samples oxidized at 600 °C, 700 °C and 800 °C were 1.2, 7.5 and 34.9 μm, respectively. The coefficient of friction for oxidized Ti6Al4V alloy was lower than the untreated with the maximum reduction of 62% when oxidized at 700 °C. The wear volume results indicated that thermal oxidization effectively improved the tribological behavior with a reduction of 80% at most. In this investigation, the results proved that thermal oxidation temperature could effectively influence the microstructural and tribological behavior of Ti6Al4V alloy and the optimal oxidation temperature was 700 °C.