抄録
In order to investigate the influence of radical nitriding on the fatigue strength of high strength steels, rotating bending fatigue tests were carried out for a high chromium bearing steel SUJ2 and a low alloy steel SNCM439 which were radical nitrided to the quenched and tempered specimens. By nitriding, fatigue strengths were decreased in SUJ2 and increased in SNCM439,though surface hardening, compressive residual stress and softening of matrix were yield in the same degree in both steels. The difference in the influence of nitriding on the fatigue strength was mainly caused by the difference in the ductility of material. By removing the compound layer from the specimen surface, the fracture origin was changed from the specimen subsurface to the surface, meaning the suppression of initiation of a surface crack by the compound layer.
