High Stress Rolling Contact Fatigue Properties of 32Cr3MoVE Nitrided Bearing Steel

Surface nitriding treatment was conducted on 32Cr3MoVE bearing steel prepared by double vacuum melting process. The rolling contact fatigue performance was studied under the high stress of 4.5 GPa by rolling contact fatigue testing machine, and the failure mechanism of rolling contact fatigue was analyzed. The results show that the effective nitriding layer depth of the test steel was 350 μm; the residual compressive stress in the nitriding layer increased and then decreased with the increase of distance from the surface, and had the largest value of 610 MPa at 300 μm distance from surface. The white vein structure distributing along the grain boundaries appeared in the nitriding layer. The rolling contact fatigue characteristic lifetime, rated fatigue lifetime and median fatigue lifetime were 3.040×10⁸, 0.357×10⁸, 2.083×10⁸ cycles, respectively, calculated by two-parameter Weibull distribution. The rolling contact fatigue failure modes of the test steel included surface crack initiation and subsurface crack initiation, and the average diameter and depth of peeling pits in surface crack initiation sample were significantly larger than those of subsurface crack initiation sample. Surface crack initiation sample cracked along pits or scratches on the surface; the subsurface material properties of subsurface crack initiation sample degraded under the action of prolonged cyclic contact stress, resulting in crack initiation.