WEAR MECHANISMS OF SILICON-NITRIDE, PARTIALLY-STABILIZED ZIRCONIA ANDALUMINA IN UNLUBRICATED SLIDING AGAINST STEEL

The dry-sliding wear mechanisms of Si3N4, partially stabilized zirconi a (PSZ) and Al2O3 were studied using a ball-on-disc wear apparatus. A wide range of sliding velocities and normal loads was tested in order to draw experimental load-velocity friction and wear maps through care ful examination of wear morphologies. The three pairings behave differ ently, even if some wear mechanisms were common to the three systems. The PSZ-steel pair showed the least wear in mild load-velocity conditi ons, followed by the Si3N4-steel pair in harder sliding conditions. It is suggested that the wear of ceramics is mainly related to transgran ular or intergranular fracture. Steel discs presented much more intric ate wear patterns, including abrasion, oxidation and delamination. Als o, the wear rate (mm3 s-1) of each component is shown to be related to the ''frictional power'' provided to the tribological system. This im portant result led us to propose an alternative approach of the classi cal wear rate concept.