Formation criterion and mechanism of electrical pitting on the lubricated surface under AC electric field

Abstract

The formation mechanism of electrical pitting on the lubricated surface of steel pair was investigated, and the threshold condition to avoid the occurrence of electrical pitting was also established by using a static electrical pitting tester with high precision under the influence of AC electric field. Experimental results show that when the electrical pitting occurs, the interface voltage, interface impedance, and interface power increases slowly with increasing film thickness at a certain supply current. However, the interface voltage and interface power increases with increasing supply current, and the interface impedance decreases with increasing supply current at a certain film thickness. Furthermore, the pitting area versus the interface power relationship is a cubic function, where the pitting area increases with increasing interface power. It is also found that the supply current is the parameter that influences the pitting area the most. Moreover, three electrical pitting regimes are found under the influences of shaft voltage and oil film thickness, namely, pitting, transition, and no-pitting regimes. The boundary between the transition and no-pitting regimes is called the first threshold voltage, and another boundary between the transition and pitting regimes is called the second threshold voltage. However, the supply current insignificantly influences these two threshold voltages. Correlation formula of threshold voltage and oil film thickness is also derived as the formation criterion of electrical pitting for a wide range of oil film thickness.