Damage and microstructure evolution for rolling contact fatigue of a CSS-42L gear steel under mixed lubrication

Abstract

In this study, a plasto-elastohydrodynamic lubrication model is employed to analyze the contact stress distribution in rolling contact fatigue (RCF) of a CSS-42L steel, which takes into account the effects of surface roughness and plastic deformation. Numerical simulation reveals that the maximum von Mises stress occurs at subsurface and it is not significantly affected by the presence of lubricating oil due to the relatively low surface roughness of the sample. The experiments are conducted under a mixed lubrication state, i.e., the hydrodynamic lubricant film and rough surface asperity contact coexists. Numerical analysis further indicates that the hydrodynamic lubricant film dominates the contact zone. It is supported by experimental observations that subsurface spalling pits are the main cause for the RCF failure in CSS-42L steel. In contrast, the oxidative wear damage from solid-solid asperity contact primarily leads to micro-pitting on the sample surface. Microstructure characterization indicates that the high-density carbide effectively impedes the RCF crack growth by influencing the path of crack propagation. The refinement of microstructure is also observed during the RCF, which is attributed to the cyclic plastic deformation caused by repetitive high contact stress.