Ta–Al multilayer coatings were fabricated through cyclical gradient concentration deposition by direct current magnetron co-sputtering. The as-deposited coatings presented a multilayer structure in the growth direction. The oxidation behavior of the Ta–Al multilayer coatings was explored. The results specified that Ta-rich Ta–Al multilayer coatings demonstrated a restricted oxidation depth after annealing at 600 °C in 1% O2–99% Ar for up to 100 h. This was attributed to the preferential oxidation of Al, the formation of amorphous Al-oxide sublayers, and the maintenance of a multilayer structure. By contrast, Ta2O5 formed after exhausting Al in the oxidation process in an ambient atmosphere at 600 °C which exhibited a crystalline Ta2O5-amorphous Al-oxide multilayer structure.
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