The role of a reactant film on water-lubricated Si_3N_4/hBN surfaces

摘要

Sliding characteristics of the sintered hBN and Si_3N_4 were investigated in water. The friction coefficient of the sintered hBN/hBN was 0.23 - 0.25 in dry air, but decreased to 0.06 - 0.12 in a distilled water. EPMA analysis on the sliding surface of Si_3N_4 and hBN revealed that the observed low friction coefficient was attributed to the oxide film or its hydrate. Ammonia was also formed during sliding in the water and determined quantitatively by chemical analysis. As the results, high chemical wear rate which was defined as NH_3/total worn nitrogen was observed in regions of low ware rate, and a low friction force was observed at high chemical wear rate region of Si_3N_4 sliding. Furthermore, the results indicated a combination of pin of Si_3N_4 on hBN plate sliding in water shows a very stable sliding with rather low friction coefficient as 0.04.