The compound process of laser shock peening and vibratory finishing and its effect on fatigue strength of Ti-3.5Mo-6.5Al-1.5Zr-0.25Si titanium alloy

Vibratory finishing is an existing processing technology in the manufacturing process of aircraft engine blades. Laser shock peening (LSP) is to be applied in the blades manufacturing, and it is inevitable to combine with vibratory finishing. Firstly, the compound process sequence was determined by residual stress and surface roughness test on the Ti-3.5Mo-6.5Al-1.5Zr-0.25Si titanium alloy in this work, and the best-performing sequence of the compound process was ascertained to be LSP + vibratory finishing. Secondly, the surface microstructure was characterized after different surface treatments. It can be found that nanoscale grains were formed in the surface layer after LSP treatment, and more homogeneous nanostructure and lower surface roughness were achieved after LSP + vibratory finishing. Lastly, the vibration fatigue was chosen to verify the feasibility of the compound process. The results showed that the fatigue strength improved from 438 MPa to 544 MPa after the compound process treatment compared with the specimens treated by vibratory finishing only.