Oxidation behaviour of Nb-rich Ni-Cr-Fe alloys: Role and effect of carbides precipitates

Present work aims to find the influence of carbide precipitates on the oxidation behaviour of Nb-rich Ni-Cr-Fe alloys at 1000 °C in air. Three Ni-Cr-Fe alloys, NC-15Fe-1Nb, NC-15Fe-1Nb-0.8C, NC-15Fe-1Nb-0.8C-0.5Ti were designed by alloying with Ti, Nb and C. Results show that the formation of NbC is crucial for the preferential oxidation of Cr. Moreover, either preventing NbC formation or favouring (Ti,Nb)C formation is found detrimental on such a beneficial effect, where the latter has a more intense influence. Roles of the precipitates in oxidation mechanism give new insights into the alloy optimization.