Nanostructured Diamond Coated CoCrMo Alloys for Use in Biomedical Implants
A wide variety of materials are currently under consideration for use in biomedical implants. Within the scope of certain implants is the need to withstand extensive wear created by repeated use and pressure on high stress joints. Substantial research is directed toward metal-onmetal technology and cobalt chrome molybdenum (CoCrMo) is a prime candidate given its longevity . Wear-resistant surface coatings for the standard CoCrMo biomedical alloy may be a simple and effective way to extend implant lifetime. In this study, we show that an initial plasma nitriding step for CoCrMo alloy is beneficial for attaining adhesion of a nanostructured diamond coating subsequently grown by microwave plasma chemical vapor deposition (CVD). The initial plasma nitriding step is quickly and easily performed in the CVD reactor and results in the formation of chromium nitride phases (CrN, Cr2N) as well as a phase transformation of cobalt from hexagonal to face centered cubic. We suggest that the success in terms of achieving adhesion of the diamond coating to the CoCrMo alloy involves chromium nitride phases acting as a diffusion barrier to carbon, thus preventing direct reaction of carbon with cobalt and the extensive graphitization that would follow.
Panjian Li, Kai Zhang and Clifford W. Colwell, Jr.
T.R. Lawson et al., "Nanostructured Diamond Coated CoCrMo Alloys for Use in Biomedical Implants", Key Engineering Materials, Vols. 284-286, pp. 1015-1018, 2005