Reproduction of white etching cracks under rolling contact loading on thrust bearing and two-disc test rigs

Abstract

A common challenge in multiple fields of the mechanical driveline technology is the premature failure of rolling bearings due to white etching cracks (WEC). This failure mode is characterized by three-dimensional cracks, bordered by regions of altered material microstructure, which eventually lead to cracking or spalling of the raceway. Ultrasonic analysis of cylindrical roller thrust bearings have already shown that WEC are mainly located in the region under negative slip, which agrees with a cumulative frictional energy criteria. In this study, WEC were reproduced on a two-disc test rig using inner rings from radial cylinder roller bearings without pre-charging the samples with hydrogen. The investigations revealed an influence of the sliding direction and the lubrication regime on the WEC formation. The tests showed that a WEC failure induced by sliding occurs under boundary lubrication regime. Furthermore, it was determined that while single axial cracks and small WEC networks formed in the sample under positive slip; large WEC networks formed in the sample under negative slip.