Paper VI (ii) Particle Detachment Processes in the Dry and Lubricated Wear of Ceramics

This Paper considers the possible relationships between crack growth and wear for four ceramics - alumina, silicon carbide, sialon and partially-stabilized zirconia (PSZ). Particular attention is given to defining the role of water in both crack growth and wear. Crack growth rates have been estimated from flexural tests in air, water, and a diester lubricant (di-2-ethylhexylsebacate) both dried and containing dissolved water. Wear measurements have been made in the same environments during sliding against diamond-containing surfaces. Only occasionally is it possible to find a one-to-one relationship between wear and crack growth rates: in most instances, the wear process is complicated by tribochemical reactions with water which inhibit particle detachment by microfracture. Ceramic wear rates can also become greater in lubricated conditions than in dry sliding because fluids prevent the formation of a third-body layer of aggregated debris.