Electric current-induced tribological and microstructural degradation in bearing steel

The complex electrical environments inherent in electric vehicles often lead to premature failures of bearings. A comprehensive understanding of material behavior under current-carrying conditions is therefore essential. In this study, a current-carrying pin-on-disk tribometer was used to investigate the tribological response and microstructural degradation of bearing steel subjected to electric current. The results show that electric current significantly intensifies adhesive, oxidative, and abrasive wear, leading to increased coefficient of friction (COF) and wear volume. After 120 min of sliding, the average COF increases from 0.058 at 0 A to 0.066 at 1.5 A and 0.072 at 6 A, while the corresponding wear volumes at 1.5 A and 6 A are approximately 1.5 and 2 times that at 0 A, respectively. This deterioration is attributed to the combined effects of electro-thermal and athermal mechanisms. Specifically, arc discharge in conjunction with frictional heating rapidly raises the surface temperature, inducing subsurface tempering and dynamic recrystallization. These thermally activated processes lead to microstructural softening, which in turn facilitates severe plastic deformation. Meanwhile, athermal effects accelerate dislocation motion and rearrangement, further affecting the material's mechanical properties.