Improving the high temperature oxidation resistance of Ni-based superalloy GH202 induced by laser shock processing

Laser shock processing (LSP) is employed to improve the high temperature oxidation resistance of Ni-based superalloy GH202. Many crystal defects of the surface after treated were found by transmission electron microscope. The residual compressive stress (maximum −305 MPa) and the micro-hardness (maximum 579 HV) of specimens treated were improved significantly. The isothermal oxidation kinetics of GH202 before and after LSP showed that the weight gain of all the treated specimens slowed relatively, and it was more obviously at 900 °C. The oxidation film of the LSP-treated GH202 was mainly composed of Cr2O3, TiO2, NiCr2O4 and a little of Al2O3. High density dislocations provided many channels of Cr3+ diffusing to the surface of the LSP-treated GH202, which would facilitate formation of a denser protective oxidation film compared to untreated specimens. The results showed that the high temperature oxidation resistance of the LSP-treated GH202 was improved, especially more significantly at 900 °C.