ADHESION, RESIDUAL STRESSES AND TRIBOLOGY OF RF SPUTTER DEPOSITED TITANIUM CARBIDE COATINGS.

摘要

Mechanical properties of surface hard coatings depends strongly on both the adhesion of the coating to the substrate as well as the sign and magnitude of the residual stress in the coating. The residual stress in sputter deposited TiC films was found to be compressive and could be related to the trapped Ar concentration in the films. The Ar concentration, and hence the compressive stress, increased with decreasing Ar sputtering pressure, P(,Ar), due to the relationship between the substrate induced potential, V(,i), and P(,Ar). High compressive stress in the TiC films enable this brittle material to withstand high tensile strain. However, too high a compressive stress would induce a high Poisson tensile stress which result in the fracture of the interface and the bulging up of the film. Incorporation of moderate amount of oxygen in the TiC films during deposition will not cause compressive stress. However, high oxygen content in the film with O/Ti higher than 0.5 would lead to second phase segregation in the TiC(,x)O(,1-x) matrix and result in a high compressive stress.;Friction and wear properties of plastically loaded steel sliders against flat TiC coatings were found to be a function of apparent contact area. Reduction in the friction coefficient and in slider wear was achieved by the use of a photolithographically produced checkerboard structure with regularly spaced micro-reservoirs in the TiC films to reduce apparent contact area. The reduction in slider wear was also due to the trapping of wear debris inside the pockets of the checkerboard structure which decreased the abrasive slider wear caused by three-body-wear due to hard wear particles. Stick-slip motion of the slider was also reduced due to the intermitant breakage of asperity contact brought about by the regularly spaced micro-reservoirs structure.;Extremely good adhesion of sputter deposited TiC films to the 4140 steel substrates with an adhesive strength on the order of the shear strength of the steel was accomplished in this study. Improvement in the adhesion was achieved by reducing the oxygen content in the interface which produced a compositionally graded junction from TiC(,x)O(,1-x) in the interface to TiC in the bulk, both being the same structure.