The properties of carbon layers deposited onto titanium substrates

Thin, hard, amorphous carbon layers, deposited using a dense r.f. methane plasma onto titanium substrate, were investigated. This includes an examination of the interface between the carbon layer and the substrate and the optimization of the process and its application. The substrates coated with carbon layers were analysed by Auger electron spectroscopy (AES) and scanning electron microscopy (SEM). Results of AES studies show that the surface layer, several thousand angstroms thick, consists of carbon. The carbon film passes smoothly into a thick layer (about 1 mu m) consisting of titanium carbide. The composition varies across the transitional layer between carbon and carbide regions. This coating structure ensures a high mechanical strength and very good adhesion to Ti substrates. These coatings also protect metal implants against corrosion, and protect man from a serious illness, metallosis. Preliminary,investigations in vivo and in vitro confirm the biocompatibility of the C/TiC/Ti system and its biointegration. In addition, investigations of the mechanical, anticorrosive and structural properties of the coatings, deposited using a dense methane plasma excited in an r.f. electric field, show that this can be a very good material to apply in cardiovascular surgery. The r.f. decomposition of methane seems to be a very convenient method for the production of superhard carbon coatings on Ti substrates for medical applications.