Fatigue life improvement by shot peening for pre‐fatigue tested carburized steel

Abstract The effect of shot peening (SP) on pre‐fatigue tested carburized steel was investigated. Plane‐bending fatigue tests were conducted on carburized CrMo steel that was pre‐fatigue tested and treated with SP. Fatigue cracks were induced by pre‐fatigue tests with a stress amplitude of σ a = 1000 MPa, and the number of the pre‐fatigue test cycles was 2.0 × 10 4 ( L 5 test) and 4.0 × 10 4 ( L 15 test). We compared the fatigue lives of the fatigue‐damaged and smooth specimens without fatigue damage treated with the same SP. The fatigue life of the L 5 tested specimens with SP was longer than that of the non‐fatigue damaged smooth specimens after SP. Therefore, the fatigue cracks introduced by the L 5 test can be rendered harmless by SP. Furthermore, near‐surface material properties were evaluated and the mechanisms of rendering surface cracks harmless were investigated.