Influence of Electric Erosion on the Early Lubrication State of Rolling Bearings

This paper investigated the influence of electrical erosion on the early lubrication state of rolling bearings. Using a bearing test rig, the friction torque and outer ring temperature of 6204 deep groove ball bearings were measured under an electric field environment. Post-test analysis of the bearing surface was conducted using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Additionally, the lubricant film thickness and friction coefficient under the electric field environment were measured using an optical elastohydrodynamic lubrication (EHL) film test rig. The results indicated that in the initial stages of electrical erosion, a direct current (DC) electric field leaded to a reduction in film thickness and friction coefficient. Discharges within the lubricant film created electrical erosion pits on the bearing surface, inducing material transfer and oxide formation in the contact pairs. The higher speed, the greater the extent of damage to the bearing surface caused by discharges. The primary reasons for the rise in bearing temperature were the localized high temperatures caused by discharges and Joule heating generated when current passed through the contact area. The localized thermal effect caused by Joule heating leaded to the formation of microbubbles, which was the main reason for the reduction in oil film thickness. When the voltage in the contact area was sufficiently high, destructive discharges could occur near the contact area, and the occurrence of such discharge phenomena was related to the presence of microbubbles.