Effects of shot peening intensity and coverage on the fatigue life and fracture characteristics of DZ125 alloy at room and high temperatures

Nickel-based superalloys are widely used in aerospace and other fields, with their fatigue life being one of the crucial factors affecting their reliability and performance. To extend the fatigue life of the DZ125 alloy, the high-temperature (760 °C) and room-temperature (25 °C) fatigue properties under different shot peening (SP) parameters were studied. For circumferential V-notch (kt = 2.5) samples of the DZ125 alloy, SP was conducted using S110 shots with Almen intensities of 0.21mmA and 0.17mmA and coverage rates of 100 %, 200 %, and 300 %. The fatigue life is evaluated using an SP simulation method based on finite element and discrete element method (FEM-DEM) coupling, combined with surface residual stress and roughness testing. The results showed that when the sample coverage rate increased from 200 % to 300 %, the surface residual compressive stress has little difference, and the roughness increased from 2.1 μm to 2.63 μm, consistent with simulation results. SP can improve the fatigue life of DZ125 alloy. When the Almen intensity and coverage of 0.17mmA and 200 % respectively, the fatigue performance is the best. At high temperatures, the fatigue life of specimens with 300 % coverage is 1/6 that of those with 200 % coverage, while in a normal temperature environment, the fatigue life of specimens with 300 % coverage is not significantly lower than those with 200 % coverage. This indicates that when SP coverage is excessive, there surface defects causing surface stress relaxation. Under the influence of high temperatures, there is an oxidation damage process at the crack tip that promotes crack initiation and propagation, reducing fatigue life. The research results provide improved methods and experimental basis for enhancing the fatigue life of the DZ125 alloy.