Comparison of the Effect of 2 at. % Additions of Nb and Ta on the 1100 °C Oxidation Behavior of Ni-6Al-(4,6,8) Cr Model Alloys
To continue improving alloy performance in harsh service environments, the development of alumina-forming nickel-based superalloys is essential. Current generations of these alloys heavily rely on the addition of refractory elements to enhance their mechanical properties at high temperatures; however, a systematic understanding of how such additions affect the overall oxidation behavior is still not well established, particularly from the standpoint of predicting the transition from internal to external alumina formation. The present work seeks to better understand the intrinsic effects that common minor additions of Ta and Nb have on the oxidation behavior of alumina-scale-forming γ-Ni model alloys. By combining a novel simulation approach with high-temperature oxidation experiments and advanced characterization techniques, the present study provides insightful details on the differing effects that 2 at. % addition of Ta and Nb have on the alumina scale formation of Ni-based alloys during 1100 °C oxidation.