Experimental studies and modeling for the transition from internal to external oxidation of three-phase Nb-Si-Cr alloys

Abstract A modified oxidation model, which assumes the cylindrical-like morphology of Cr 2 Nb phase, has been proposed to examine the conditions to form external scale of three-phase Nb-base alloys in this paper. The oxidation behavior of three-phase Nb-base alloys was tested at 1250 °C for 1 h and 7 h, and the experimental results were compared with the simulated results. The results show that the external CrNbO 4 scale can be achieved by length-radius ratio and volume fraction increasing for Cr 2 Nb phase. The simulated results are consistent with the experimental results.