Effect of shot peening on fatigue strength of 18%Ni maraging steel

Rotating bending fatigue tests were carried out on an 18%Ni maraging steel to investigate the effect of shot peening on fatigue strength. Fatigue stre ngth was increased markedly by shot peening. The increase in fatigue streng th due to shot peening depended on shot size and stress level. Fracture mod e changed from surface fracture in the short-life region to interior fractu re, i.e., fish-eye fracture, in the long-life region. Tn the middle-life re gion, however, cracks initiated from both the surface and the inside of the material individually coalesced and led to the final fracture. These resul ts were discussed on the basis of the effects of shot size on surface rough ness, the depth and magnitude of compressive residual stress and work harde ning.