Electrical Current Effects on Rolling Contact Fatigue Damage in Bearing Steels: The Role of Inclusions

Bearings used in wind turbines and electric vehicles are increasingly exposed to stray electrical currents that accelerate rolling contact fatigue (RCF) and promote premature failure through white etching crack (WEC) formation. Although electrically assisted bearing failures have been extensively investigated, the influence of AISI 52100 steel composition on WEC formation remains poorly understood. This study compares the RCF performance of two commercially produced AISI 52100 bearing steels with similar hardness but different inclusion characteristics using an electrically loaded Micro Pitting Rig under five DC electrical loading conditions and lubricated with a WEC-forming gearbox oil. Bearing steel composition exerted a greater influence on fatigue performance than hardness. Steel 1 consistently exhibited longer RCF life and lower wear than Steel 2 despite its slightly lower hardness and higher overall inclusion content. Fatigue performance was governed primarily by the chemistry and local distribution of non-metallic inclusions, with MnS-containing inclusions identified as the predominant crack initiation sites. Electrical loading generally had a limited effect on fatigue life; however, low anodic current density increased RCF life by approximately fourfold through reduced friction, milder wear, and delayed crack initiation. Subsurface observations revealed two complementary WEC formation mechanisms: progressive near-surface tribomutation and inclusion-assisted crack initiation at the depth of maximum subsurface shear stress. These findings provide mechanistic insight into electrically assisted WEC formation and inform the design of more reliable bearing steels for electrified drivetrains.