New insights into wear of Ti6Al4V by ultra-high molecular weight polyethylene under water lubricated conditions

Laboratory studies indicate that sliding Ti6Al4V against soft ultra-high molecular weight polyethylene (UHMWPE) pins produces severe damage to the titanium and the lubricant (water) changes colour suggesting chemical change. Blackening of periprosthetic tissues associated with titanium wear debris was also observed in clinical investigations. To increase scientific understanding of the mechanism involved, systematic characterisation work has been conducted employing grow discharge spectrometry (composition), scanning electron microscopy (wear morphology) and cross-sectional transmission electron microscopy (phase identification). Experimental results show that hydrogen may play an important role in promoting the formation of abrasive particles in the Ti6Al4V/UHMWPE tribosystem under water lubricated conditions. The observed abnormal wear of Ti6Al4V by soft UHMWPE can be to a large extent attributed to hydrogen evolution and formation of titanium hydride. Based on experimental results and discussion, a hydrogen-assisted wear mechanism is proposed.