Formation of White Etching Cracks under electrical current flow - Influence of load, slip and polarity

Abstract

White Etching Cracks (WEC) are currently discussed as a common cause for premature failure of roller bearings in various applications. The formation mechanism of WEC is still under debate in the literature. However, it is emphasized that varying additional loads like electrical current or hydrogen, have an amplifying effect on the formation of WEC. In this work, the formation of WEC under the influence of electrical current was investigated. The testing was conducted on a three-ring on roller test rig using rollers made from the steel AISI/SAE 52100. These rollers were tested utilising different electrical polarities, current intensities, Hertzian pressures and slide-roll-ratios. As a result of the testing, possible WEC formation values for the tested electrical intensities and Hertzian pressures were found. Furthermore, no additional slip has to be present for the WEC formation under the influence of electrical current. Detailed microstructure analysis using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) have been conducted to investigate the effect of electrical current, polarisation and slide-roll- ratio on the microstructural alterations. The analyses showed that in the investigated regions different reaction layers are formed depending on the electrical polarity. Furthermore, the formation of the nanocrystalline structure can be attributed to high local plastic deformation.