Effect of columnar nano-grain structure on the oxidation behavior of low-Cr Fe–Co–Ni base alloy in air at 800 °C

The nanocrystalline coating of a low-Cr Fe–Co–Ni base alloy with 0.36 wt.% Si was deposited on the as-cast low-Cr alloy with identical compositions by means of magnetron sputtering. The effect of sputtered columnar nano-grain structure on the oxidation behavior of the low-Cr alloy was investigated in air at 800 °C. It was found that the columnar nano-grain structure significantly lowered the oxidation rate and changed the surface oxide structure of this alloy. The formation of a continuous Cr2O3 inner layer beneath the CoFe2O4 spinel outer layer on the sputtered nanocrystalline coating resulted in a remarkable improvement in oxidation resistance compared to the cast low-Cr alloy.

► Sputtered nanocrystalline coating of a low-Cr alloy was deposited.
► Columnar nano-grain structure enhanced the oxidation resistance of this alloy.
► Columnar nano-grain structure promoted the formation of an inner Cr2O3 layer.
► A double-layer scale of CoFe2O4 atop Cr2O3 was developed on the coating.