Study of the effect of coatings on mechanical properties of TC4 titanium alloy during laser shock processing

During the process of laser shock processing (LSP), we use high power Nd:Glass laser systems which result in significantly improve fatigue properties and stress corrosion cracking in titanium components. An ablative coating such as black painting and aluminum foil are used to protect the titanium component from surface melting by laser pulse, which adversely affects sample fatigue life. Three different shock-processing configurations are considered: non-ablative exposure, aluminum foil and confined ablation with black painting. We analyzed effect of the coatings on the shock wave propagation into the titanium specimen and the resulting change in mechanical properties versus depth. Near the surface, yield strength and hardness are found to be increased by laser shock, the titanium surface for all coatings increased in yield strength by 16% to 37%. The result have demonstrated that surface hardness can be improved by 31 percent over a machine worked surface with black paintings and be improved by 25 percent with aluminum foil. The experiment aim is to report the effect of the ablative, sacrificial coatings on the laser pulse generation of shock waves and their propagation into the titanium alloys and the resulting change in mechanical properties below the surface versus depth.