Effect of shot peening intensity and surface coverage on room-temperature fatigue property of TC4 titanium alloy

TC4 titanium alloy was shot-peened by multiple kinds of intensity and surface coverage. Surface roughness and topography, residual stress profile were compared. Moreover room-temperature rotating-bending fatigue property was tested. The results show when the intensity is raised, the surface roughness, the depth of residual compressive stress depth and the location of the maximum residual stress are increased and the surface residual stress is decreased. The enfoldment appears on the surface with the increase of surface coverage. Rotating-bending fatigue property is enhanced by shot-peening. Compared with median fatigue life estimated value of 5.06×104 cycles at grinding state, the fatigue cycles ranges are raised to 5.12×106-5.28×106 cycles after shot-peened at the intensity 0.12 mmA and 3.28×106-4.23×106 cycles at 0.25 mmA, indicating that the fatigue property is decreased with the increase of the intensity. By comparison, when the intensity is low (0.12 mmA), the coverage has no impact on the fatigue property. However, fatigue cycles decline from 4.23×106 cycles to 3.28×106 cycles when the coverage is inclined from 125% to 600% and the intensity is relatively high (0.25 mmA). Furthermore, on the premise of considering the surface stress concentration of the external load and the residual stress of shot peening, the position of the dangerous section with large actual stress after shot peening is calculated and verified by the fracture analysis