An electron backscatter diffraction investigation on microstructural evolution of pearlite wheel steel near rolling contact fatigue crack tip

Abstract

AbstractAfter rolling contact fatigue (RCF) failure, ultrafine grains are formed in the proeutectoid ferrite (PF) and ferrite grains near the RCF crack tip. During the RCF process, the plastic strain of the samples increases as the cycle increases. When the RCF crack is initiated, a stress field is formed at the RCF crack tip. The accumulation of plastic strain before initiation of the RCF crack is the main reason to result in grain refinement near the RCF crack tip. The stress field also contributes to the grain refinement near the RCF crack tip. The accumulation of plastic strain and the stress field at the RCF crack tip lead to the generation of a large number of dislocations in the PF and ferrite grains in the zone in front of the RCF crack tip. Then, the dislocations are gradually transformed into subboundaries. Finally, the subboundaries evolve into high‐angle grain boundaries, leading to grain refinement. The RCF cracks are mainly propagated at the interface between the grain refinement zone and the unrefined zone at the RCF crack tip. The local grain refinement zone at the RCF crack tip can accelerate the propagation of the RCF cracks.