Fine-grained γ-Ni3Al coatings were developed by a two-step process： co-electrodeposition of Ni with A1 particles and subsequent annealing in vacuum at 600℃ or 800℃. After oxidation at 1000℃ in air for 20 h, the scales formed on both coatings exhibited better adhesion than that on a coarse-grained Ni3Al alloy, because the fine-grained coating structure suppressed the formation of voids at the scale/metal interface. Moreover, the scale formed on the coating by annealing at 800℃ consisted of NiO, NiAl2O4 and Al2O3, while the scale on the coating by annealing at 600℃ consisted of NiAl2O4 and Al2O3. The reason for this result is related to that the latter coating had a finer-grained structure, which promoted rapid formation of a continuum layer of Al2O3.
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