Sliding wear studies of selected nitride coatings and their potential for long-term use in orthopaedic applications.

In the area of orthopaedic implants, particularly total hip joint replacements, a metal-plastic combination is still the most popular choice consisting of a femoral head fabricated from 316L stainless steel, Ti alloy or Co-Cr alloy in contact with an ultra-high molecular weight polyethylene (UHMWPD) acetabular cup. It is recently considered that wear of the UHMWPE cup is of major concern. Generation of the wear debris can have adverse effects on the body, both localized and systemic. It is envisaged that wear of the prosthetic components, particularly those fabricated from UHMWPE can be reduced through the use of surface coatings. The aim of this investigation was to deposit a selection of refractory element nitride-based coatings (TiN, TiA1N, ZrN) onto 316L stainless steel substrates, using physical vapour deposition (PVD) technology and to study their sliding wear behaviour in contact with both UHMWPE and 316L stainless steel pins, using a pin-on-plate testing rig. Tests were conducted in Ringers solution and Ringers solution plus bone cement particles. The volume of material removed from the pins served as an indication of their wear behaviour. Wear mechanisms were identified using scanning electron microscopy. The results of these findings and the potential for these coatings to be used in orthopaedic applications are discussed.