Characteristics of Fatigue Strength for Various Surface Treated Tool Steel, SKD61

In order to investigate the effect of surface treatment on fatigue strength of a hard steel, cantilever-type rotating-bending fatigue test in air was conducted using the smooth specimens of alloy tool steel, SKD61,with four kinds of surface treatment; that is, TiN coating by PVD method, plasma assisted ion-nitriding, duplex treatment with the ion-nitriding followed by the TiN coating and gas-nitriding. Fatigue fracture of nitriding specimens was occurred at non-metallic inclusion inside of the specimen with fish-eye. No difference in S-N curve among the surface treated specimens was observed in the region of long fatigue lives, in spite of the difference in distribution of residual stress and hardness