ASSESSMENT OF TRIBOLOGICAL PROPERTIES OF CAST AND FORGED Ti-6Al-7Nb AND Ti-6Al-4V ALLOYS FOR DENTAL APPLICATIONS

摘要

Thermal oxidation treatment is an easy and environment friendly technique that can be used to harden the surface of titanium alloys, and hence improve the poor tribological properties of these materials. The aim of the present research was to evaluate the tribological behavior of cast and forged Ti6Al7Nb and Ti6Al4V implants after different thermal oxidation treatments. A significant increase in surface hardness of the two alloys was achieved due to the formation of a hard oxide layer and oxygen diffusion zone beneath it. The oxygen diffusion zone, which was generated at 900°C, showed the best wear resistance in case of Ti6Al4V alloy. On the other side, no remarkable enhancement was observed in the Ti6Al7Nb alloy even at 1100°C, regardless of the improved surface hardness. In addition, the development of alpha case in the cast samples was different from the forged ones. The widmanstaetten microstructure of the cast samples showed thinner alpha case compared to the equiaxed structure of the forged samples in both alloys.