Fabrication and characterization of NiCoCrAlY coating deposited on nickel-based superalloy substrates

NiCoCrAlY coatings were prepared on GH3128 nickel-based superalloy substrates using radio-frequency magnetron sputter deposition. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy measurements showed different particle growth in the thin films after annealing the as-deposited coatings at various heat treatment conditions. In addition, X-ray diffraction data revealed that the annealed coatings showed in common only one main peak, which was assigned to theγ′-Ni3Al phase. Cross-sectional SEM analysis showed that NiCoCrAlY coating after heat treatment at 1100 °C in air for 3 h had five layers, including the oxide layer, outer layer, middle layer, substrate, and interdiffusion layer. Elemental line scanning confirmed that the oxide layer contained Al and O. The electrical resistance of the insulating films at high temperature was measured over the range of 400 °C-800 °C. Our results revealed that the use of non-oxidizing gas during pre-heat treatment contributed to improving the electrical insulation behavior of the films.