THE PROPERTIES OF CARBON LAYERS DEPOSITED ONTO TITANIUM SUBSTRATES

Thin, hard, amorphous carbon layers, deposited using a dense r.f. meth ane plasma onto titanium substrate, were investigated. This includes a n examination of the interface between the carbon layer and the substr ate and the optimization of the process and its application. The subst rates coated with carbon layers were analysed by Auger electron spectr oscopy (AES) and scanning electron microscopy (SEM). Results of AES st udies show that the surface layer, several thousand angstroms thick, c onsists 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 ad hesion to Ti substrates. These coatings also protect metal implants ag ainst corrosion, and protect man from a serious illness, metallosis. P reliminary,investigations in vivo and in vitro confirm the biocompatib ility of the C/TiC/Ti system and its biointegration. In addition, inve stigations 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 app ly 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.