The Effects of Alloying Elements Cr, Al, and Si on Oxidation Behaviors of Ni-Based Superalloys

Oxidation behaviors of three Ni-based model alloys and pure Ni in the temperature range of 700-1200 °C are investigated to reveal effects of Cr, Al, and Si on the oxidation resistance of Ni-based superalloys. The formation and integrity of consecutive chromia or alumina layers are important for excellent oxidation resistance. The addition of 20 at.% Cr can effectively improve the oxidation resistance of Ni-based alloys by forming a thin chromia film below 1000 °C, while adding 15 at.% Al has a beneficial effect on the oxidation resistance of Ni-based alloys at temperatures above 900 °C. The addition of 2 at.% Si to Ni-Al alloy is insufficient to form a protective SiO2 layer but can accelerate the formation of alumina, which enables Ni-Al alloy to form a consecutive inner alumina layer at a relatively low temperature of 800 °C and further improve the oxidation resistance above 800 °C.