Effect of co-doping of two reactive elements on alumina scale growth of β-NiAl at 1200°C

The microstructure and cyclic oxidation behaviour of β-NiAl alloys doped with two reactive elements (REs) were investigated. Hf and Zr as well as Y and La co-precipitated into one phase during alloy preparation, while Dy and Hf as well as Hf and La precipitated alone into different phases. All the co-doped alloys exhibited reduced oxidation rate as compared to the RE-free alloy. The Hf and Zr, Y and La co-doping even led to lower oxidation rate than the corresponding single-doping. The synergistic effect associated with co-segregation of RE ions on alumina scale growth rate was discussed.