Study on electric erosion in grease lubrication using optical interference method

Abstract

Protecting bearings from electrical environments is crucial as modern industry evolves. With increasing exposure to electrical conditions, the risk of bearing failure due to electric erosion becomes a significant concern. To better understand how lubrication interacts with electric discharge in rolling bearings, an optical ball-on-disc tribometer was modified to measure film thickness under elastohydrodynamic lubrication (EHL) with electric discharge. The results of the study revealed that an electrical potential difference between the surfaces separated by the lubrication film leads to a reduction in film thickness, which can be attributed to the generation of Joule heating. As the electrical potential difference increases, the film thickness decreases even further, ultimately resulting in destructive electric discharge. Interestingly, sporadic discharge was observed in the region of minimum film thickness as the entrainment velocities increased prior to the occurrence of destructive discharge. In addition, the study also investigated the use of grease with a conductive additive, a double trifluoro-sulfonate ionic liquid. It was found that incorporating this ionic liquid into the grease can decrease the energy during discharge, thereby mitigating bearing electric erosion.