Influences of Inclusion Size and Position on Fatigue Life of 51CrV4 Spring Steel

The fatigue fracture was analyzed with EDS and SEM. Influences of inclusion size and position on the fatigue life of 51CrV4 spring steel were studied.The results show that the fatigue strength of the steel was 702.5 MPa. Fatigue cracks originated from ellipsoidal and low plasticity alumina inclusions without scratches and pittings on the surface. The larger the inclusion size and the closer the inclusion position from the surface, the shorter the fatigue life. The critical size of surface inclusions was estimated to be 5.47 μm when σ-1was 710 MPa.