Semi-empirical model for predicting LAB and HAB formation in bearing steels

The formation of white etching bands (WEBs), including both low- (LAB) and high- (HAB) angle bands, in the subsurface of steel bearings due to rolling contact fatigue (RCF) has been investigated over decades to understand their characteristics and predict their formation during operation. A few studies recently have modelled the development of LABs theoretically based on thickening of lenticular carbides adjacent to the band controlled by dislocation-assisted carbon migration. To date, no study has been reported to predict the formation of HABs. Based on the percentage of white etched region formed in the subsurface of the bearings, this study presents a semi-empirical model that predicts the formation of both LABs and HABs in steel bearings for different contact pressures. The LAB semi-empirical model is compared with a theoretical model from literature and experimental data. According to this, the new model more realistically predicts the initiation of LABs than the carbide thickening model. This is achieved by involving the formation of ferrite (cellular and elongated) shown as white areas under optical images. Literature data have been used to evaluate the LAB and HAB models. The growth pattern obtained in this study provides strong evidence of a diffusion-based mechanism leading to WEB formation

Re-investigation of dark etching regions and white etching bands in SAE 52100 bearing steel due to rolling contact fatigue

Microstructural alterations such as dark etching regions (DERs) and white etching bands (WEBs) have been known to manifest in the subsurface of steel bearings due to rolling contact fatigue (RCF) under medium-high stress cycles. Even though such manifestations have been reported substantially in literature for decades, their formation and their evolution mechanisms are not fully understood. As part of the re-investigation of DERs and WEBs, this paper presents the results from characterization of DER and WEBs, including both low angle bands (LABs) and high angle bands (HABs), formed in SAE 52100 bearings at different stages of bearing life. Angular contact ball bearings (ACBBs), subjected to RCF testing under different contact pressure, stress cycles and steel cleanliness, have been examined to reveal new information related to the microstructural alteration processes, e.g. the 3-D structure of the WEBs and their growth pattern. Contrary to some of the literature results, the experimental results have shown that the mean depths and density of WEBs (LABs and HABs), as opposed to DER, are correlated with the position and distribution of the principle shear stress. The results also show that HABs form as a consequence of LABs especially in densed LAB areas in the ACBBs studied here

Further understanding of rolling contact fatigue in rolling element bearings - a review

Rolling bearings are one of the most widely used components in industrial machinery. If suitably mounted, loaded, lubricated and isolated from contamination, rolling contact fatigue (RCF) is believed to be the most probable mode of failure resulting in subsurface originated failures. Over the past several decades many researchers have studied the failure and microstructural alterations in bearings such as dark etching regions and white etching bands and how operating conditions such as pressure, temperature and running time impact them during RCF. This paper aims to provide an overview of such alterations, their properties, formation mechanisms and impact on bearing failure