An EBSD Investigation on the Evolution of the Surface Microstructure of D2 Wheel Steel During Rolling Contact Fatigue

In this work, the relationship between rolling contact fatigue (RCF) failure and the microstructure of D2 wheel steel was studied using a GPM-30 fatigue tester under oil lubrication conditions. The microstructural evolution during the RCF process can be divided into three stages: In the first stage, the misorientation of the proeutectoid ferrite is 2°–10°, the ferrite phase in pearlite is less than 2°, and the dislocation density is low. In the second stage, with the increase in cycles, the misorientation of the proeutectoid ferrite increases to more than 10°, and the ferrite phase in pearlite increases to 2°–10°. In the third stage, the misorientation of the ferrite phase in pearlite increases to more than 10°, the ferrite phase is divided into fine grains, and the dislocation density is high. RCF cracks are formed in the third stage. Crack initiation is ascribed to the refinement of the surface ferrite phase and proeutectoid ferrite and the increase in dislocation density. RCF cracks are initiated and propagate primarily at the interface of pearlite/proeutectoid ferrite and in proeutectoid ferrite.