Micro-pitting and wear characterization for different rolling bearing steels: Effect of hardness and heat treatments

Abstract

The current trend of increased power density and reduction of oil viscosity in machine components is forcing engineers and scientists to engineer surfaces to endure higher contact pressures and stresses induced from rolling/sliding motion. Typically, surface-initiated rolling contact fatigue represents the main failure mode and has been gaining more and more attention lately. In this paper, the extent and morphology of the surface damage of different bearing steels in disc-on-disc contact under reduced lubrication conditions are studied. For this, rough-on-smooth contact was selected to promote surface fatigue damage on the smoother surface. Special attention was given to study both the effect of the hardness difference of the discs and the influence of different heat treatments, i.e. surface induction hardening (SIH) or through hardening (TH), on micro-pitting and wear performance. It was demonstrated through tribo-testing that the faster, rough surface undergoes only mild wear and plastic deformation of asperities. However, three different damage modes were observed and assessed on the slower, smoother surface, where the damage mode showed a strong dependence on a surface hardness difference between the smooth and the rough surface. Furthermore, it was observed that a plain medium carbon steel (DIN C56E2) showed better surface fatigue resistance than a low alloy high carbon steel (DIN 100Cr6) at similar surface hardness levels if SIH is applied on the former.