Effect of tricresyl phosphate on wear of silicon nitride sliding against bearing steel

Abstract

Wear tests of a silicon nitride ball pressed against a bearing steel rod were carried out at room temperature under lubrication with a light mineral oil using a lathe. The wear of the Si 3N 4 ball was measured at various fixed sliding distances up to a maximum distance of 3000 m. A mineral oil of low viscosity (base oil), and a mineral oil containing different amounts of phosphorus (added as tricresyl phosphate) and 0.2 wt.% S were supplied to the contact region between the Si 3N 4 ball and the steel rod. An addition of 0.5 wt.% P to the base oil reduced the wear volume of the Si 3N 4 ball by about 90% of that with the base oil. The reduction in the wear is ascribed to surface film formation. When using the base oil alone, the wear of the Si 3N 4 ball decreased more at high sliding velocities than at low sliding velocities.