Adhesion properties of diamond-like coated orthopaedic biomaterials

This study details an experimental analysis to investigate the most suitabl e orthopaedic alloy for diamond-like carbon deposition using a saddle field neutral beam deposition process. The paper specifically identifies the adh esion strength properties of diamond-like coatings and its dependence on pr ocess parameters for application to orthopaedic steels and polymer substrat es. Sub-micron thickness films were deposited directly on stainless steel, cobalt chrome alloy, titanium alloy and ultra high mel. wt. polyethylene su bstrates. It was found from Rockwell and pull-off adhesion tests that super ior adhesion is acquired for stainless steel substrates followed by cobalt chrome and titanium alloys. Adhesion strength was also shown to be inversel y related to increases in deposition pressure and to increase with time up to a threshold. The maximum adhesion strength of coatings deposited on the polymer substrates was 60% of the value for stainless steel. Surface roughn ess was also inversely related to adhesion strength for the substrates exam ined. It is demonstrated that stainless steel offers a superior substrate m aterial for the application of diamond-like thin-films where wear mechanism s and mechanical constraints are operational such as in orthopaedic articul ating joint replacements. (C) 2001 Elsevier Science B.V. All rights reserve d.