The effect of hard shot-peening on high cycle fatigue properties of SUS 316 L steel (evaluation of surface roughness effects using the annealing method)

Hard shot-peening (HSP) treatment was very successful for the improvement of the high cycle fatigue strength of SUS 316 L steel. However, the surface roughness by the HSP treatment was one of the dropping factors on the fatigue strength. In order to separate surface roughness effects from effects of compressive residual stress and strain hardening by the HSP treatment, the HSP-treated SUS 316 L was annealed in the vacuum to remove residual stress and recrystallization in hardened layer. The rotating bending fatigue tests for the annealed specimen were carried out under water cooling condition. The fatigue limit of annealed SUS 316 L was about 60 MPa lower than that of non-peened specimen which was about 200 MPa. To simulate the actual surface roughness, fatigue tests for the single notch specimens and small drilled holes specimens were carried out. As a result, the surface roughness effects by the HSP treatment were not consistent with the √area parameter model. The effects were explained by considering the stress concentration factor.