Research on the internal and external synergistic strengthening mechanism of fatigue performance of austenitic stainless steel

In this study, the effects of the synergy between pre-tensioning and surface mechanical rolling on the microstructure and fatigue performance of 304 stainless steel were discussed. The 304 stainless steel was subjected to pre-tensioning treatment, and a transformation in the microstructure was observed, with refinement of the grain size accompanied by the occurrence of martensitic transformation, and a quantitative analysis of the martensitic phase change was conducted. The yield strength of 304 stainless steel rises with pre-tensioning, equalizing with tensile strength after 50 % pre-tensioning. The hardness of the specimen was increased after pre-tensioning. After surface mechanical rolling, the hardness values exhibited a gradation decreasing progressively from the surface to the subsurface and then to the center. Based on the rotating bending fatigue test, under the combined effects of 50 % pre-tensioning and surface mechanical rolling, the fatigue limit of the specimen was increased from 365 MPa to 940 MPa, representing an improvement of 157.53 %. Based on the analysis of the properties and microstructure of processed 304 stainless steel, the effects of the pre-tensioning process and surface mechanical rolling on the material are discussed. The mechanism of the process enhancing fatigue properties through the combined effect of pre-tensioning and surface mechanical rolling is discussed.