INFLUENCE OF CARBIDE SIZE, HARDNESS AND TEMPERATURE ON SLIDING FRICTION AND WEAR OF A BOUNDARY LUBRICATED HIGH-SPEED STEEL AND SI3N4 CERAMICS

In this study,, the authors investigated the friction and wear perform ance of a high-speed steel (AISI T1 grade) and an Si3N4 ceramic under boundary lubricated sliding conditions. Moreover, the effects of hardn ess, carbide size, and temperature on friction and wear were investiga ted. Tribological tests were performed with pairs of T1 steel and Si3N 4 ceramic at temperatures ranging from 22 degrees to 150 degrees C. Th e steel samples contained hard carbide particles ranging in size from 2 to 8 mu m and exhibited hardness values ranging from 730 to 934 kg/m m(2). The specific wear rates of pills were deduced from height displa cement and from wear scar diameter, while the wear of disks was calcul ated from profilometry traces across the wear grooves. The results of wear tests showed that the combination of a Si3N4 ball on a T1 steel d isc resulted in the lowest pin wear rate of 10(-15) mm(3)/ N.mm. The v ariation of hardness and carbide size in T1 steel had negligible effec ts on wear. The increase test temperature caused an increase In wear. Finally, under conditions of boundary lubrication, the tribological ch aracteristics of Si3N4 and T1 high-speed steel were remarkably similar to one another.