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.