Investigation of the fatigue life of AISI304 stainless steel round rod with small hole subjected to laser shot peening

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The fatigue properties of AISI304 stainless steel round rod with small hole subjected to laser shot peening (LSP) were investigated. Laser shot peening was performed for rods with and without sacrificial layer, respectively. After laser treatment, the surface morphologies of peened and unpeened regions were observed, and residual stress was measured by the X-ray diffraction method. Fatigue test was employed to conduct fatigue tension test on laser-treated and untreated rods. The fracture micro-topography was detected using a scanning electron microscope. The results show that micro-dents appear on the surface of the peened rod coated with sacrificial layer. The surface of the rod irradiated directly by laser is ablated, and tensile residual stresses are generated on the irradiated region. The fatigue lives of the laser-treated specimens with and without sacrificial layer are 1.2 and 1.1 times, respectively, compared with that of the laser-untreated specimen. The location of fatigue crack initiation is transformed from the hole edge to the wall of rod after LSP, and the average fatigue striation spacing of the processed rod with sacrificial overlay is narrowest, and that of the unprocessed rod is widest. Furthermore, the size and depth of the dimples on the fatigue fracture region of the laser-peened rod with sacrificial overlay are largest and deepest, which is closely related to the severe plastic deformation in the samples with LSP.