Hot corrosion mechanism of laser metal deposited Ni-based single crystal superalloy under fuel gas atmosphere

In this research, the hot corrosion behavior of laser repaired Ni-based single crystal superalloy in fuel gas environment is analyzed and compared with that of the substrate, and the corrosion mechanism is determined. The deposited single crystal layer is comprised of the γ(Ni) matrix and abundant spherical γ′(Ni3Al) nanoparticle phases. The corrosion products exhibited layered structure including the outer layer dominated by NiO, NaTaO3 and (Ni,Co)Cr2O4, the inner layer mainly comprising Al2O3 and Cr2O3, and the internal γ′ depleted layer. The hot corrosion resistance of the deposited part is superior than that of the substrate, owing to the synergistic effects of much finer γ′ phase, higher volume fraction of γ′ phase, and more compact corrosion product of the deposited component. Our work provides a practical strategy for enhancing the hot corrosion resistance of laser repaired superalloy by manipulating the size and morphology of γ′ phase.