Surface integrity and fatigue performance of Ti6Al4V alloy peened by sinking bead abrasive jet

Abstract

Exploring a green, low-cost peening process to improve the surface integrity of titanium alloys, increasing fatigue life, and breaking through the limitations in large-scale applications is an urgent need at present. The study presents a novel peening method using sinking beads as the shot, combined with the low dust pollution and water film cushioning advantages of waterjet peening. The impact of the process on the surface integrity of titanium alloys is meticulously discussed to elucidate the microstructural evolution. Constant stress fatigue tests are performed to evaluate the effectiveness of the proposed method. It was found that the jet pressure and feed rate determined the energy density and the number of peening for sinking bead abrasives, which were the key factors affecting the surface material properties of the peening specimen. By optimizing the process parameters, the maximum surface residual compressive stress can reach 875.5 MPa, the microhardness can attain 481.7 HV, and the surface roughness can be reduced to 1.594 μm. The surface of the peened specimen is covered with impact craters, exhibiting a plastic deformation layer with evident grain refinement and lattice distortion. The ductility of the peened specimen decreased, with axial deformation reducing from 0.278 mm to 0.260 mm under constant cyclic stress. Due to the increase in microhardness and the introduction of residual compressive stresses, the fatigue cycles of the specimen were increased from 20692 to 33615, improving the fatigue life by 62.45%.