A Comparison of the Friction and Wear Behavior of Nitrogen Ion Implanted Co-Cr-Mo Alloy, Co-Cr-Mo, and Zirconia under the Reciprocating, Plowing Conditions of the Prosthetic Knee

摘要

The friction and wear performance of untreated and nitrogen ion implanted Co-Cr has been compared with that of a zirconia ceramic in reciprocating, sliding-plowing type wear against ultra high molecular weight polyethylene (UHMWPE). The wear tests were conducted using a right cylinder-on-flat geometry under worst case stress conditions found in the non-conforming artificial knee. UHMWPE wear was significantly lower for articulation against zirconia. Additionally, the coefficient of friction (COF) was significantly less for the zirconia ceramic than both nitrogen ion implanted Co-Cr and unimplanted Co-Cr. These test results indicate that nitrogen ion implanted Co-Cr does not perform better than unimplanted Co-Cr in either COF behavior or UHMWPE wear, and may actually perform worse. These results are not surprising since both ion implanted and unimplanted metallic materials currently employed as bearing surfaces in total joint replacement (TJR) are susceptible to passive surface film damage via articulation against UHMWPE. Additionally, nitrogen ion implantation may decrease the corrosion resistance of F-75 Co-Cr due to a reduction in available chromium (via formation of chromium nitride precipitates) for passive film formation (Cr{sub}2O{sub}3 and Cr-oxy-hydroxide films). Zirconia is not susceptible to oxidative wear and microstructural degradation for the conditions found in TJR and is distinctly superior in tribological performance to both nitrogen ion implanted and untreated F-75 Co-Cr.