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

The dry-sliding wear mechanisms of Si3N4, partially stabilized zirconia (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 careful examination of wear morphologies. The three pairings behave differently, even if some wear mechanisms were common to the three systems. The PSZ-steel pair showed the least wear in mild load-velocity conditions, followed by the Si3N4-steel pair in harder sliding conditions. It is suggested that the wear of ceramics is mainly related to transgranular or intergranular fracture. Steel discs presented much more intricate wear patterns, including abrasion, oxidation and delamination. Also, the wear rate (mm3 s-1) of each component is shown to be related to the ''frictional power'' provided to the tribological system. This important result led us to propose an alternative approach of the classical wear rate concept.