Fatigue Fracture Behavior of Bearing Steel GCr15 in Very High Cycle Regime

Abstract:

In order to investigate the fatigue behaviors in very high cycle fatigue regime of bearing steel GCr15 (Chinese standard), cantilever-type rotary bending fatigue test was carried out, by using an hourglass-shaped specimen. As a result, the S-N data were classified into surface grinding flaw or inclusion induced fracture mode, subsurface inclusion without ‘granular-bright-facet’ (GBF) area induced fracture mode and subsurface inclusion with GBF area induced fracture mode. Formation of a GBF area was clearly observed in the vicinity of subsurface inclusion on the fracture surface ruptured at high- cycle fatigue regime. The cause of the S-N curves of GCr15 obtained by this experiment continuously decreased, which is different from the common ‘duplex S-N’ curve. Experiments on fracture surface was carried out based on the ‘dispersive decohesion of spherical carbide’ model aimed to clarify the mechanism of the formation of GBF area.