Influence of milling time on the microstructure evolution and oxidation behavior of NiCrAlY coatings by laser induction hybrid cladding

The influence of milling time on the microstructure evolution and oxidation behavior of NiCrAlY coatings generated by laser induction hybrid cladding was investigated. Mechanical milling induced γ'-Ni3Al formation in the NiCrAlY powder. With longer milling times, the NiCrAlY coatings experienced an equiaxed-to-columnar transition, and their compositions became homogenized. Furthermore, the relative intensities of the diffraction peaks of α-Al2O3, Cr2O3 and NiCr2O4 decreased and the oxidation resistance of the NiCrAlY coatings improved. Therefore, milling time is another critical parameter for the control of the columnar growth in NiCrAlY coatings, whose oxidation kinetics depend on both the grain boundaries and lattice diffusion.