Tribological behaviour of Ti6Al4V modified by surface treatments

Abstract

At present, there are no good materials that can substitute ultra-high molecular weight polyethylene (UHMWPE), therefore the only way forward is to find a material for femoral heads with high wettability and hardness able to minimize the wear phenomena between metal and UHMWPE. In this work, the effects of surface treatments to improve the tribological behaviour of titanium alloy (Ti6Al4V) were studied. Ion implantation, CVD and PVD were the surface treatments investigated. Ti6Al4V modified and not modified samples were tested against γ-ray sterilized UHMWPE pins using a pin-on-flat wear test machine. The results have been compared with the wear behaviour of stainless steel (AISI 316L). Tests were carried out in accordance with ASTM F 732-82 practice, a specific wear test for materials used in total joint prostheses. Metal samples were characterized by SEM micrographs, roughness and hardness measurements, wettability and friction coefficient. UHMWPE wear rates were assessed by weighing the pins at intervals of 250 000 cycles and were expressed by linear regression analysis applied to the weight losses. Ion implantation of the titanium alloy results in lower wear of UHMWPE pins, in particular, chromium implantation is the most efficient among all surface treatments. A tentative explanation of the results is given.