Oxygen Diffusion Layer on Ti–6Al–4V Alloy: Scratch and Dry Wear Resistance

Ti–6Al–4V has prominent physical and mechanical properties, which nominate it for various engineering applications. A drawback of the alloy, however, is low scratch and wear resistance, which can be improved by a diffusion treatment. Oxygen diffusion layer (ODL) was produced on Ti–6Al–4V by thermal oxidation at a temperature of 850 °C for 3 and 6 h. Hardness of the samples was measured using a nano-indentation tester. Micro-scratch tests were performed under progressive and constant normal loads of 0–50 N. Dry wear behavior of the samples was studied using a ball-on-disk tribometer. The wear tests were carried out under various normal loads of 7.5, 15 and 30 N for sliding distances of 50, 100, 200 and 300 m using alumina balls as the counterface. The wear and scratch tracks were examined by scanning electron microscope and surface profilometer. The ODL samples showed higher hardness and lower plastic deformation as compared with Ti–6Al–4V. The brittle behavior of the ODL samples caused the formation of cracks and the development of large acoustic signals during scratching under normal loads of 40 and 50 N. The results also showed a higher scratch and wear resistance of the ODL samples compared with Ti–6Al–4V. However, the oxygen diffusion layer formed after 3 h of oxidation showed a sharp increase in the wear rate of the alloy under a normal load of 30 N and a sliding distance of 100 m.