Effect of humidity on fatigue strength of shot peened maraging steel

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.

Influence of reverted austenite on fatigue life of 18 % nickel maraging steel

“…Fatigue, for example, has been cited as a key cause of landing gear failures [1]. Maraging steels have considerable inherent strength and toughness, but they have relatively poor fatigue strength [2][3][4][5].…”

“…Surface treatments such as shot peening, laser peening or nitriding of maraging steels lead to a complex shape of the SÀ N curve which shows two drops [2,3,[24][25][26]. Shot peening increases the high cycle fatigue life and helps to reduce the sensitivity to humid environments [2,18,24,27]. Laser shock peening helps in delaying both crack initiation and propagation [8,9].…”