The influence of the nstridsng temperature on the fatigue limit of 42CrMo4 and En40B steel

摘要

The positive effects of surface treatments like nitriding, carburizing, induction hardening and shot-peening on the fatigue properties of construc-tion materials have been known for several decades [1-5]. It has been shown that the improvement in fatigue properties is due to a combination of compressive macrostresses in the outer layer and an improvement of the intrinsic fatigue strength of the material in the layer [6, 7]. The macrostresses are due to a volume expansion of the surface layer caused by the thermomechanical surface treatment. The improvement of the fatigue strength of the surface layer is due to precipitates (nitriding and carburizing) or to a refinement of the microstructure (induction hardening and shot-peening). Usually the influence of macro- and microstresses cannot be separated easily as both effects are the result of the same treatment.