Insights in the interaction between roughness reduction and fatigue crack growth in rolling contacts

Rolling contact fatigue (RCF) failure is a primary life-limiting mechanism in tribological contacts, often driven by microscale phenomena that lead to plastic deformation under cyclic loading. Surface topography and hardness play critical roles in controlling the extent of plastic deformation at and beneath the surface. This study investigates fatigue crack initiation and propagation as influenced by surface machining processes and different hardness levels of the CrMoV steel rolling elements obtained from industrial steel rolls. The obtained results, from a set of RCF tests under identical loading and testing conditions, indicated that fatigue wear is a dominant degradation mechanism and is driven by asperity-level features. Surface topography significantly affects the orientation and location of crack initiation, while the hardness and the evolution of surface features during testing influence the rate of crack propagation. A comparison of the propagation rates across different hardness levels revealed an optimal hardness ratio at which fatigue damage is minimized. The outcomes indicated that crack length dispersion increases as the hardness deviates from the optimal level.