材料期刊网

Reciprocating ball-on-flat dry sliding friction and wear experiments have been conducted on single-phase gamma-Y(2)SO(7) ceramic flats in contact with AISI 52100 bearing steel and Si(3)N(4) ceramic balls at 5-15 N normal loads in an ambient environment. The kinetic friction coefficients of gamma-Y(2)Si(2)O(7) varied in the range over 0.53-0.63 against AISI 52100 steel and between 0.51-0.56 against Si(3)N(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 gamma-Y(2)Si(2)O(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 gamma-Y(2)Si(2)O(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 gamma-Y(2)Si(2)O(7)/Si(3)N(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. (C) 2009 Elsevier B.V. All rights reserved.