Impact wear mechanism of 2Cr13 steel under small stress multi-impact conditions

The current study investigates the impact wear mechanism of 2Cr13 steel under small stress multi-impact (SSMI) conditions. Self-made cyclic impact equipment, with a flat-on-flat impact mode, is utilized to achieve SSMI behavior. The results reveal that the impact wear process can be divided into three stages: the pitting damage stage, lump spalling damage stage, and lamellar spalling damage stage. Transmission electron microscopy images of the near-surface wear indicate that the distribution of dislocations changed from linear dislocations to entangled dislocations to sub-grain boundaries with an increase in impact cycles, resulting in cumulative plastic deformation, grain refinement and strain hardening of the impact surface layer. Several pits appear on the impact surface without any significant damage during the pitting damage stage. Therefore, the failure mechanism during the pitting damage stage can be ascribed to the local Hertzian stress. Moreover, both lump and lamellar spalling damage stages experience crack initiation and propagation processes under SSMI conditions, corresponding to the impact fatigue spalling. The failure mechanism of lump and lamellar spalling damage stages can be mainly attributed to the cumulative plastic deformation and hardening of the impact surface during the SSMI process.