Fatigue characteristics of bearing steel in very high cycle fatigue

Very high cycle fatigue (VHCF) tests were carried Out to find the fatigue characteristics of a super-long life range by using a cantilever type rotational bending fatigue test machine on three kinds of specimens in bearing steel which were quenched and tempered in air (A: non-shot peened and B: shot peened after heat treatment) and under vacuum environment(C: non-shot peened) in this Study. S-N curves obtained from the VHCF tests of the B and C specimens tend to come down again in the super-long life (10(9) cycles) range due to fish-eye type cracking, while most of the A and B specimens were fractured by surface detects Such Lis scratches and slip lines. This duplex S-N behavior of bearing steel has to be reviewed by the change of the fracture modes.