INFLUENCE OF MACHINING ON FRICTION AND WEAR OF LUBRICATED CERAMICS IN SLIP-ROLLING CONTACTS

The slip-rolling friction and wear tests were performed in a twin disc tribometer of the Amsler-type at a Hertzian pressure of 3 GPa over 2 million revolutions. Paraffinic oil with no additives was used as lubricant. The ceramics were machined with different processes, resulting in different surface roughness (i.e., rough and fine honed, rough and fine ground, rough and fine lapped, and rough and fine polished). Ceramic materials like HIP-Si₃N₄, S-SiC, HIP-ZrO₂, and GPS-Si₃N₄-TiN were investigated as self-mated couples. This paper summarizes the results. Si₃N₄, Si₃N₄-TiN, and ZrO₂ generally exhibit a small wear coefficient in the range of 10^-9 mm³/Nm in paraffinic oil and their wear coefficients correlate with the initial surface roughness and the material removal rate. The lowest wear coefficients were exhibited by ZrO₂- With a reduction of the Hertzian pressure to 1.5 GPa, S-SiC exhibits the same tribological behavior as the other ceramics.