The shot-peening effect on the HCF behavior of high-strength martensitic steels

High-cycle rotating–bending fatigue tests were conducted on high-strength martensitic steel using smooth and notched specimens. The effect of shot peening on the HCF behavior of this steel within a hardness range 370–475 HB was also investigated. Furthermore, after shot peening, the specimens were stress relieved at 400°C for 1 h and finally tested under the same conditions in the HCF regime. The results indicate that the fatigue endurance limit of the shot-peened specimens is higher than the corresponding limit of the virgin specimens by about 20%. The subsequent stress-relief treatment of the shot-peened specimens reduces that amount by only 3%, making the total increase about 17% on average for all material conditions. Therefore, the shot-peening strengthening effect on the HCF behavior of this steel cannot be attributed solely to induced residual compressive stresses. Following recent theories on short fatigue crack behavior, most of that strengthening can be rather attributed to the texture introduced by the rotation of surface crystals.