Evolution processes of electrical discharge in EHD contact lubricated with conductive grease

Conductive grease is generally considered to mitigate electrically induced bearing damage (EIBD), but the underlying mechanisms remain unclear. The grease analysis and electrical discharge tests were conducted using a ball-on-disc rig to characterize the lubrication and electrical properties of conductive greases with ionic liquid, while recording the evolution of electrical discharge processes in EHD contacts lubricated with conductive grease. Firstly, the grease analysis demonstrates that the addition of ionic liquids alters the electrical properties of the lubricant, resulting in higher dielectric strength and conductivity of the grease. Secondly, electrical discharge test results indicate that the discharge behavior is significantly influenced by the EHL characteristics and lubricant properties. Meanwhile, electrical discharge induces film recession and fluctuation, primarily caused by Joule heating and localized pressure variations. Test results show that higher conductivity and viscosity lubricant can effectively reduce the recession of lubrication caused by electrical discharge. A correction factor was established for predicting lubrication under the electric field, and the calculated film thickness aligns well with the measured film thickness in full film lubrication. The comparison between corrected and measured film thickness further validates the discharge characteristics and mechanism of conductive grease.