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

High-cycle rotating-bending fatigue tests were conducted on high-strength m artensitic steel using smooth and notched specimens. The effect of shot pee ning on the HCF behavior of this steel within a hardness range 370-475 HE w as also investigated. Furthermore, after shot peening, the specimens were s tress relieved at 400 degreesC for 1 h and finally tested under the same co nditions 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 treatmen t of the shot-peened specimens reduces that amount by only 3%, making the t otal increase about 17% on average for all material conditions. Therefore, the shot-peening strengthening effect on the HCF behavior of this steel can not be attributed solely to induced residual compressive stresses. Followin g recent theories on short fatigue crack behavior, most of that strengtheni ng can be rather attributed to the texture introduced by the rotation of su rface crystals. (C) 2001 Elsevier Science B.V. All rights reserved.