IMPROVED WEAR-RESISTANCE OF CERAMICS THROUGH THE USE OF COATINGS

Ceramic materials operating in a mild wear regime display extremely low wear rates. However, a transition to a severe wear regime results in the formation of wear debris, the presence of which may contribute to the formation of protective surface films. Aluminas represent ceramics with very high wear rates in the severe regime which generally result in failure of the system. Thus there is a potential for extending the mild wear regimes of aluminas by applying a surface coating. Tribological properties of uncoated and WC/C-coated alumina in plane, closed contact sliding in air and water were characterized before and after testing utilizing advanced electron microscopy techniques. It is concluded that the WC/C-coated Al2O3 can have a wear resistance several orders of magnitude higher than uncoated Al2O3 couples when tested in both air and water. The explanation for this is believed to be that the WC/C coating protects the alumina surface by reducing the magnitude of the local contact stresses and thus the tendency for wear by brittle fracture.