Unlubricated tribological performance of advanced ceramics and composites at fretting contacts with alumina

Engineering ceramics and cermets are widely used for demanding tribological applications. In this perspective, the objective of this paper was to understand the friction and wear behavior of some of the potential tribomaterials, e.g., ZrO2-30 vol% TiB2 composite, sialon-40 vol% TiB2 composite, TiB2-based cermet with 16 vol% Ni-3(AI,Ti) binder, and monolithic TiB2 in fretting contacts. Wear tests on the TiB2-containing materials under dry unlubricated conditions (23-25 degreesC, 50-55% relative humidity) were performed against corundum on a ball-on-flat tribometer. The obtained friction and wear data were critically analyzed to investigate how the binder phase in TiB2 matrix influences the tribological performance. Furthermore, morphological investigations of the transfer layers on the worn surfaces were performed and the wear mechanisms discussed. X-ray photoelectron spectroscopy analysis of the worn surfaces in the monolithic TiB2/alumina revealed the pronounced transfer of mixed oxides containing TiO2 and B2O3 to the alumina counterbody and also indicated the transfer of alumina to TiB2 flat. Tribochemical reactions and abrasion along with the material transfer between the counterbodies were observed to play a major role in the wear of the fretting couples.