Laser shock processing improving the high temperature oxidation resistance of the aluminized coating on GH202 by pack cementation

The effects of laser shock processing (LSP) on the microstructures and high-temperature-oxidation resistance of the specimens with the aluminized coatings were investigated. Electron backscattered diffraction, transmission electron microscopy, and scanning electron microscopy were used to characterize the microstructures of the specimens before and after LSP. The results show that the aluminized coating is mainly composed of nanoscale NiAl, Ni₂Al₃, and a small concentration of Al₈₆Cr₁₄. The shock waves induced by LSP produced only a few crystal defects in the coating, while a large number of dislocation lines, dislocation tangles and dislocation arrays generated by LSP refine the coarse grains of the substrate. The regulating effects of the LSP on the coating surface help form a continuous and dense oxidation film very quickly, delaying the phase transition (θ-Al₂O₃ to α-Al₂O₃). Thus, the high-temperature-oxidation resistance is significantly improved by LSP.