Effects of Patterned Peening on 304L Stainless Steel Fatigue Life

Position and Energy Controlled Surface Mechanical Attrition Treatment (PECSMAT) has increased the High Cycle Fatigue (HCF) life of 304L stainless steel (SS). Previous studies have increased the fatigue life of 304L SS via Shot Peening (SP) and Surface Mechanical Attrition Treatment (SMAT). A novel technique called PECSMAT was recently been used to increase the yield strength of 304 SS and can potentially increase fatigue life. This study includes the preparation of 304L round stock into fatigue samples which were then annealed to produce a consistent grain structure and remove any history effects. Some samples were treated by the PECSMAT process and compared with untreated samples. All samples were tested under various stresses in a stress-controlled fatigue test frame in fully reversed tension compression (R = -1). The results were summarized and compared with literature. PECSMAT effectively increased the endurance limit by 50 MPa. The fracture surfaces of two samples with similar cycle counts were compared, and crack initiation was found at the surface of both PECSMAT and untreated samples.