Author(s)

N. Kawagoishi, T. Nagano, M. Goto, Y. Maeda & M. Moriyama

Abstract

Rotating bending fatigue tests were carried out for maraging steels using shot peened and electro-polished specimens with various hardness of HV550~HV750 in atmosphere and controlled humidity to investigate the effects of hardness and humidity on the fatigue strength. Fracture occurred from specimen surface in short life region and from inclusion of specimen subsurface in long life one in shot peened specimen, while only surface fracture occurred in electro-polished specimen in wide life range. Hardness dependence of fatigue strength was different between surface fracture and internal one. That is, fatigue strength for internal fracture increased with increase in hardness within the tested hardness, while there was the peak of fatigue strength around HV600 and then fatigue strength decreased with increase in hardness in the relation between hardness and fatigue strength for surface fracture. These results were discussed from the sensitivities of fatigue strength for notch and humidity. Keywords: fatigue, maraging steel, shot-peening, hardness dependence, humidity, fracture mechanism.

Keywords

fatigue, maraging steel, shot-peening, hardness dependence, humidity, fracture mechanism