Comparative study of the effects of surface mechanical attrition treatment and conventional shot peening on low cycle fatigue of a 316L stainless steel

In this work, the effects of surface mechanical attrition treatment (SMAT) and conventional shot peening (CSP) are comparatively studied on the surface characteristics and low cycle fatigue (LCF) properties of a 316L stainless steel. For this purpose, surface topography, residual stress and work hardening are evaluated on the treated samples. Both CSP and SMAT are performed with the same Almen intensity and the same coverage. Total strain controlled LCF tests are carried out in order to compare the effects of these two techniques on the fatigue properties of the studied steel. The results show that the samples treated by SMAT and CSP exhibit similar trends of cyclic stress amplitude evolution, and higher mechanical strength than the untreated samples. However, the samples treated by CSP manifest higher fatigue life under low strain amplitude (±0.5%), but lower fatigue life under high strain amplitude (±1.25%), compared to the SMATed samples. The fatigue life results are discussed based on the analysis of different characteristics including surface topography, microstructure, residual stress and its relaxation, as well as fracture surfaces. •LCF properties of 316L steel processed by SMAT and shot peening are studied.•Same Almen intensity and coverage are applied to compare the two techniques.•Fatigue life is governed by competition between residual stress/surface topography.•Role of compressive residual stress is dominant under low strain amplitude.•Surface cracks and roughness are controlling factors under high strain amplitude.