Tribological properties of γ-Y 2Si 2O 7 ceramic against AISI 52100 steel and Si 3N 4 ceramic counterparts

Abstract

Reciprocating ball-on-flat dry sliding friction and wear experiments have been conducted on single-phase γ-Y 2Si 2O 7 ceramic flats in contact with AISI 52100 bearing steel and Si 3N 4 ceramic balls at 5–15 N normal loads in an ambient environment. The kinetic friction coefficients of γ-Y 2Si 2O 7 varied in the range over 0.53–0.63 against AISI 52100 steel and between 0.51–0.56 against Si 3N 4 ceramic. We found that wear occurred predominantly during the running-in period and it almost ceased at the steady friction stage. The wear rates of γ-Y 2Si 2O 7 were in the order of 10 −4 mm 3/(N m). Besides, wear debris strongly influenced the friction and wear processes. The strong chemical affinity between γ-Y 2Si 2O 7 and AISI 52100 balls led to a thick transfer layer formed on both contact surfaces of the flat and counterpart ball, which changed the direct sliding between the ball and the flat into a shearing within the transfer layer. For the γ-Y 2Si 2O 7/Si 3N 4 pair, a thin silica hydrate lubricant tribofilm presented above the compressed debris entrapped in the worn track and contact ball surface. This transfer layer and the tribofilm separated the sliding couple from direct contact and contributed to the low friction coefficient and wear rate.