抄録
The influence of internal oxides on the fatigue strength of carburized steel is strongly affected by the amount of retained austenite (γR) and the nonmartensitic microstructure near the surface. Rotating bending fatigue tests were carried out on three types of carburized specimens that have the same depth of internal oxides but contain 20% and 46% γR (peak value), and 20% γR with nonmartensitic microstructure. Internal oxides reduced the fatigue strength about 30% on the specimen with 20% γR, whereas the specimen with 46% γR has a comparable fatigue strength as the one without internal oxides which was prepared by electropolishing the surface. It is also shown that the specimen with nonmartensitic microstructure has higher fatigue strength than that with only internal oxides. These three types of specimens exhibited almost the same fatigue strength when the internal oxides were removed from the surface.
