Properties improvement of laser cladded TC4 Titanium alloy by laser shock processing

The laser cladded samples of TC4 titanium alloy was shocked by pulse laser to compare the hardness, surface residual stress, microstructure and the fatigue life of samples before and after laser shock processing (LSP). The surface residual tensile stress in heat affect zone (AFZ) of laser cladded sample is 225 MPa. LSP reliefs the tensile stress and generates 449 MPa compressive stress, and the surface residual compressive stress after LSP in metal matrix reaches 672 MPa. The hardness in AFZ after laser cladding is 333 HV, while that is 381 HV after LSP. A nanocrystalline surface layer is found by TEM after three impacts. The high cycle fatigue tests of laser cladded samples were carried out before and after LSP. The results show that LSP treatment can improve the high cycle fatigue endurance limit of laser cladding titanium alloy by 15.8%. The nanocrystalline grained surface layer with residual compressive stress makes great contribution to the fatigue properties improvement of titanium alloy.