The objective of this revised Phase I SBIR proposal is to develop a technology for the deposition of nanocrystalline Co-Cr coatings onto Co-Cr prostheses for enhanced wear and scratch resistance. It is hypothesized that a hard coating deposited directly on a Co-Cr articulating surface will help maintain the original surface finish of the metal substrate and consequently reduce wear in the mating UHMWPE. It is further hypothesized that chemical compatibility between nanocrystalline Co-Cr coatings and microcrystalline Co-Cr substrates will lead to improved coating adhesion compared to ceramic coatings. Target hardness values of at least 10 GPa are hypothesized to result from microstructural control and average grain sizes of 3-20 nm. It is assumed that these hardness levels will provide the necessary scratch resistance to inhibit surface roughening in the presence of third body wear debris. The primary experimental goals of this proposal are to demonstrate, in-vitro, that nanocrystalline Co-Cr coatings reduce UHMWPE wear in the presence of abrasive third body particles. Preliminary to this goal, 1) appropriate processing parameters will be identified, 2) it will be demonstrated that nanocrystalline coatings are harder than the substrate, 3) reduced in-vitro wear/scratch resistance of coated Co-Cr components will be demonstrated.
Superhard, ultrasmooth, ductile, nanocrystalline Co-Cr coatings with good adhesion to Co-Cr prostheses would significantly extend the lifetime of prosthetic components. The U.S. hip and knee implant market exceeded $1.7 billion in 1995, up 7.3% from 1994, which corresponds to over 500,000 procedures. The European market was $1.48 billion in 1994 and is expected to reach $1.89 billion by 2001. The present market perception, based on the link between PE wear debris and osteolysis, is shifting to consider alternative materials combinations as well as improvements in traditional systems. These areas alone represent enormous commercial opportunities.
