The Influence of Electric Current on the Friction Behavior of Lubricant Molecules

Abstract

The electrical failure of bearings has become a critical issue that restricts the lifetime of all-electric motor-based power systems in electric vehicles (EVs). This study aims to explain the electrically induced frictional behavior of lubricants. The effect of external electric current applied between the friction pairs on tribological properties was examined using a disk-on-ring friction tester. The surface potential analysis demonstrated that applying a positive electric current by connecting the friction surface to the cathode decreased surface activity, whereas a negative electric current increased it. The direction of the electric current influenced the friction coefficient, with a rapid increase observed when a positive current was applied. The lower ring’s friction surface exhibited reduced lubricant adsorption. Consequently, fewer lubricant molecules were transferred to the friction interface, producing a high friction coefficient. Moreover, the wear surface experienced pitting after applying an external electric current, suggesting that pitting contributed to accelerated wear. These findings provide insights into the influence of electric current on the tribological properties of lubricants and have implications for the design of tribological systems in EVs.