Effect of MoS{sub}2 additive on electrical pitting mechanism of lubricated surface for Babbitt alloy/bearing steel pair under ac electric field

摘要

In this study, a static electrical pitting tester, SEM, and EDS are employed to investigate the effects of supply voltage, supply current, MoS{sub}2 concentration, and oil film thickness on the mechanism of electrical pitting for the lubricated surface of Babbitt alloy/bearing steel pair under ac electric field. The pitting regimes, consisting of pitting and no-pitting regimes, have been established in terms of the supply voltage, the oil film thickness, and MoS{sub}2 concentration at different supply currents. The area of pitting regime increases with increasing MoS{sub}2 concentration and supply current. It is seen from the pitted surfaces of the Babbitt alloy block that there exists an obvious concave crater with a few plateaus. According to the force measurement, the formation process of the metal column is proposed. The cross-sectional area of the plateau significantly increases with increasing oil film thickness and MoS{sub}2 concentration. Moreover, the ratio of pitting area to interface power (A{sub}P/P) increases with increasing MoS{sub}2 concentration and oil film thickness at the oil film thickness less than 6 μm. When the oil film thickness increases from 6 to 10 μm, the value of A{sub}p/P quickly increases to about 10 times, because MoS{sub}2 powders can sufficiently suspend on the oil across the gap.