Surface Integrity Research of TC4 Titanium Alloy Treated by Laser Shock Peening and Shot Peening

In order to study the composite shot peening strengthening to improve the performance of aero-engine titanium alloy blades, the surface modification of TC4 titanium alloy was carried out by mechanical shot peening and laser shock peening. The effects of surface treatment sequence and process parameters on the surface integrity of titanium alloy were studied. The results show that the residual compressive stress field on the surface of composite shot peening strengthened titanium alloy has a coupled characteristic of separate mechanical shot peening and laser shock. The residual stress field feature near the surface is close to mechanical shot peening, and the residual stress field feature near the substrate is close to laser shock peening. The depth of the overall residual stress field is large and the surface stress value is high. The order of composite strengthening affects the distribution of stress values in the middle section of the residual stress layer. The residual stress after the first laser shock and then mechanical strengthening is relatively higher. When the mechanical shot peening strength is low, the process sequence has little effect on the surface roughness. When the mechanical shot peening intensity is high, the sequence has a great influence on the surface roughness. After the mechanical shot peening strengthening, the small angle grain boundaries and a little twinning formed in the near surface of the sample. Laser shock strengthening only resulted in small angle grain boundaries near the surface of sample, but no twinning was observed. The composite strengthening sample with the laser shock first produced more twinning.