Application of PVD TiN coating to Co-Cr-Mo based surgical implants

The requirements for successful joint arthroplasty are particularly exacting; a balanced combination of mechanical properties together with good biocompatibility are essential. Co-Cr based alloys have been used for many years on account of their relative inertness, good load bearing properties and excellent wear resistance. There is, however, concern that a slow accumulation of metal ions such as cobalt and chromium can lead to adverse clinical reactions; modern cementless fixation techniques may exacerbate this problem. In an attempt to reduce the release of potentially harmful metal ions from Co-Cr-Mo based surgical implants, a thin coating of TiN has been applied via Physical Vapour Deposition (PVD). In vitro corrosion performance has been investigated using electrochemical techniques, and also by atomic absorption analysis. The release of cobalt and chromium ions is shown to be reduced by the presence of the TiN coating, and these results are discussed in terms of the electrochemistry and microstructure of the coating and substrate.