Surface medication of Ti-15Mo alloy by thermal oxidation: Evaluation of surface characteristics and corrosion resistance in Ringer's solution

Ti-15Mo alloy has received considerable attention for biomedical applications (currently listed by ASTM) due to its non-toxic nature, good mechanical properties and better corrosion resistance. Thermal oxidation is an effective method to form a thicker oxide layer on Ti and its alloys. In the present study, thermal oxidation of Ti-15Mo alloy is explored for the first time. The objective of the study is to ascertain the surface, structural and morphological characteristics of Ti-15Mo alloy subjected to thermal oxidation at different temperatures (500, 650 and 800 °C), for various periods of time (8, 16, 24 and 48 h). It is also aimed at to evaluate their corrosion behavior in Ringer's solution in order to assess their suitability for biomedical applications. Thermal oxidation increased the average surface roughness (R _a ) and microhardness, while decreasing the water contact angle of the Ti-15Mo alloy. The phase contents of the oxide layer show a strong dependence on treatment conditions with a predominance of the rutile phase over the anatase phase at temperatures >650 °C and for time periods >16 h. A more positive E _corr and a lower i _pass are observed for the thermally oxidized Ti-15Mo alloys when compared with the untreated alloy. For the experimental conditions employed in the present study, it is clear that Ti-15Mo alloy subjected to thermal oxidation at 650 °C for 8-48 h offers a better corrosion resistance than those treated at 800 °C for 8 h.