Isothermal Oxidation Resistance of As-cast NiAl and NiAl-(Cr, Mo) Eutectic Alloys at 1000°C

Abstract

The isothermal oxidation resistance of as-cast NiAl, NiAl-34Cr, and NiAl-28Cr-6Mo was investigated at 1000°C for 100 h. The corresponding oxidation mechanism is discussed. The parabolic rate constants of as-cast NiAl, NiAl-34Cr, and NiAl-28Cr-6Mo were 6.045 × 10⁻¹⁵, 1.397 × 10⁻¹⁴, and 1.052 × 10⁻¹⁴ g²/cm⁴·s, respectively. The generated oxide scales on NiAl, NiAl-34Cr, and NiAl-28Cr-6Mo are dominated by metastable θ-Al₂O₃ with a certain amount of stable α-Al₂O₃. The addition of Cr in NiAl can accelerate the θ-α transformation and such an effect is further enhanced when replacing 6 at.% Cr with Mo. Thus, NiAl-28Cr-6Mo outperforms NiAl and NiAl-34Cr concerning isothermal oxidation resistance at 1000°C.