抄録
Rotating bending fatigue tests were carried out for radical nitrided SNCM439 steels in order to investigate the influence of nitriding time on the fatigue strength. The hardend layer was increased with increase in nitriding time. However, there was not or little influence of nitriding time on the fatigue strength, though the fatigue strength was increased by nitriding. Fracture at low stress levels occurred from internal inclusions near the boundary between hardened and non-hardened layers. By removing the compound layer, the origin of fracture was changed from subsurface to surface and fatigue strength was decreased.
