Research Project
6071213
Functionally graded nanocrystalline metalloceramic coatings will be developed to reduce wear of ultra-high molecular weight polyethylene (UHMWPE) in orthopedic prostheses. UHMWPE wear is a primary cause of prosthesis failure, and roughness of the mating Co-Cr surface has been identified as a major contributing factor to UHMWPE wear. Third body wear particles, such as bone cement constituents, scratch the Co-Cr surface, roughening it and accelerating UHMWPE wear. Previous attempts by other investigators and commercial firms to apply hard ceramic coatings to the Co-Cr surface have not been successful due to difficulties in achieving adequate adhesion between the metallic substrate and the ceramic thin film. This program seeks to develop a multi-layer film structure (deposited in a single, continuous process), which has metallic initial layers and a hard, ceramic outer coating (Cr/CrTi/CrTiN). The transition between the metallic and ceramic layers will be gradual, significantly enhancing the bond strength between layers. Additionally, the thin film will be composed of ultra-fine grains (nanocrystallites of TiN and Cr), which significantly increase film hardness and ductility. This has been clearly shown in previous investigations at Spire, where extremely hard nitride ceramic films consisting of nanometer-scale grains have been deposited in a continuous deposition process using ion beam assisted deposition. Phase I will demonstrate increased adhesion, hardness, and scratch-resistance of the graded films, and ultimately demonstrate reduced UHMWPE wear in laboratory experiments. PROPOSED COMMERCIAL APPLICATIONS: There are over 500,000 hip and knee replacement surgeries performed each year in the United States. UHMWPE wear is a primary cause of device failure. Therefore, a means of reducing UHMWPE wear, and consequently joint failure, has significant commercial potential.
