Research on surface integrity of Ti-6Al-4V alloy with compound treatment of laser shock peening and shot peening

Ti-6A1-4V alloys are widely used in aero-engine and their surface integrity directly affects engine's reliability. In present paper, compound surface treatment of Laser shock peening (LSP) and Shot peening (SP) was carried out to achieve the strengthening of Ti-6A1-4V alloys and its effect on surface integrity was obtained. The results showed that the compound treatment had better strengthening effect on distribution of microhardness and residual stress as compared with single LSP or SP treatment. The surface hardness increased by 19.9% at maximum and the thickness of hardening layer was about 200 μm. The surface compressive residual stress had reached to −804.6 MPa with an affected depth of about 1300 μm. The roughness of compound treatment was 0.86 ± 0.1 μm, which was between LSP (0.47 ± 0.05 μm) and SP (1.12 ± 0.2 μm). Nanocrystalline and high dense dislocations were observed on the surface layer, which indicated grain refinement on the surface.