TiN–NCD composite coating produced on the Ti6Al4V alloy for medical applications

Titanium alloys, materials that show the best mechanical biocompatibility with human bones, should be modified in order to improve their chemical biocompatilbility and friction properties. In this work we have produced a perfectly bioinert composite build of d.c. ion nitrided Ti6Al4V alloy coated with NCD (nanocrystalline diamond) film. Examinations of friction coefficient (μ) and wear (Δm) of the alloy unmodified, nitrided and coated with the composite layer in contact with polyethylene (HDPE and UHMWPE) were performed under conditions simulating the operation of the total joint implant within a human body (dry, contact pressure 4 MPa). The results indicate that, although the modification of surface worsened its roughness and μ value, the coating reduced wear (Δ m) up to 103 times. The composite produced at 850 °C provided the best protection and the NCD film diminished friction in a specific way via a “third body” lubricant.