Open Access

ARTICLE

Effects of Reverted Austenite and Hardness on Fatigue Properties of Shot Peened Maraging Steel in Long Life Region

T. Nagano¹, M. Moriyama^2,3, N. Kawagoishi⁴, Y. Kobayashi⁴

1 Miyakonojo Nat. Coll. of Tech., Miyakonojo, Miyazaki, Japan; E-mail: takanori@cc.miyakonojonct.ac.jp
2 Dai-ichi University, Kagoshima, Kirishima, Japan.
3 Kagoshima University, Kagoshima, Japan.
4 Shinto Kogyo Ltd., Toyokawa,Aichi, Japan; E-mail: y-kobayashi@sinto.co.jp

Structural Longevity 2010, 3(3), 201-211. https://doi.org/10.3970/sl.2010.003.201

Abstract

In the present study, rotating bending fatigue tests up to 108 cycles were carried out to investigate the effects of hardness of base steel and shot and reverted austenite, γ, on the fatigue strength and the fracture mechanism in wide range of fatigue life of shot peened 3.5GPa-grade maraging steel. By shot peening, hardening and compressive residual stress were yielded in the surface layer of specimen, causing increase in fatigue strength in the wide region of fatigue life. The S — N curves showed duplex S — N properties because of the transition of fracture origin from the specimen surface in the short life region to the subsurface in the long life one. The effect of hardness of base steel on fatigue strength was very small in both regions of the surface and subsurface fractures. On the other hand, fatigue strength in surface fracture region was increased by using hard shot. By formation of γ, fatigue strength was increased in the subsurface fracture region, but the effect was not recognized in the surface fracture region. A clear fish-eye was formed around the origin of subsurface fracture in the steel withγ, though it was not observed in the steel without γ.

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Keywords

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