Effect of Mo, Ta, and Re on high-temperature oxidation behavior of minor Hf doped β-NiAl alloy

• Effects of Mo, Ta, and Re on oxidation behavior of β-NiAlHf alloys are investigated.
• Ta and Hf (so do Re and Hf) co-precipitate into one phase during alloy preparation.
• Mo, Ta, and Re reduce the oxidation resistance in different ways.
• The effectiveness of Mo, Ta, and Re depends on their concentration in the alloys.
• The interaction mechanism between Ta and Hf as well as Re and Hf is discussed.

The microstructure and cyclic oxidation behavior of minor Hf-doped NiAl alloys with addition of different alloying elements including Mo, Ta, and Re were investigated. Co-precipitation of Ta and Hf as well as Re and Hf occurred during alloy preparation, whereas Mo and Hf precipitated individually into different phases. Over 0.5 at.% addition of Mo, Ta and Re had negative influence on the oxidation behavior of β-NiAlHf alloy, while the effect could be ignorable once the concentration reduced to less than 0.05 at.%. The interaction mechanism between Ta and Hf as well as Re and Hf was discussed.