Microstructure and high-temperature resistance of Al₂O₃/CoNiCrAlY coatings by laser cladding

This work reports on systematic investigation of the microstructure and oxidation behavior of Al₂O₃/CoNiCrAlY coatings in-situ synthesized on a K438 nickel-based superalloy substrate via laser cladding. Scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction were used to evaluate the microstructure evolution, phase transition and high-temperature resistance. Results indicated that, as the Al₂O₃ fractions increased from 0 to 25 wt%, the average grain size of CoNiCrAlY-xAl₂O₃ coatings decreased from ∼100.23 μm to ∼42.56 μm, and the high-temperature resistance was effectively improved due to the formation of (Co,Ni)(Al,Cr)₂O₄. However, the other deleterious effect that shielding layers easily to be exfoliated with the excessive formation of (Co,Ni)(Al,Cr)₂O₄, caused a degradation in high-temperature resistance.