Evaluation of Fretting Protection Property of Lubricating Grease Applied to Thrust Ball Bearing

Abstract

Fretting wear is often the case when ball-and-roller bearings oscillate under grease lubrication. Against the backdrop of fretting wear on the wheel bearing of automobiles caused by rail transportation, the ASTM D4170 fretting test method was developed to evaluate fretting protection property of lubricating grease. The ASTM test is conducted under a fixed load, but its condition of industrial machines usually fluctuate. Currently, there is no global specification to evaluate the fretting wear under fluctuating load. In this study, using thrust ball bearing the authors examined 14 kinds of commercially produced greases and three kinds of originally prepared greases on fretting protection evaluation under bom the ASTM test and the impact fretting test. Consequently, the authors found the inversion of the order of fretting protection superiority between the ASTM test and the impact fretting test. As for the kinematic viscosity of base oil of grease, the amount of wear of ASTM test increases with increasing the kinematic viscosity, on the other hand the wear of impact fretting test decreases with increasing the kinematic viscosity.