Heat Treatment and Oxidation Characteristics of Nb-20Mo-15Si-5B-20(Cr,Ti) Alloys from 700 to 1400°C
Nb-20Mo-15Si-5B-20(Cr,Ti) alloys have been subjected to annealing treatment for 2 hours in a range of temperatures from 700 to 1400oC and quenched in water to perform the microstructural characterization for these two new alloys. As cast structure consists of a solid solution phase, , and silicides (Nb5Si3) in both alloys but Cr alloy also contains NbCr2 and Nb3Si phases. Heating to higher temperature introduces Ti silicides in the microstructure for Ti alloy. The oxidation in air has been conducted on these alloys in the same temperature range for 24 hours. Weight gain per unit area as a function of temperature provides the oxidation curves while characterization techniques using SEM, EDS on SEM, x-ray mapping, and XRD has yielded the analyses of the oxide scale. The scale consists of various oxides of Nb, Mo, Cr, Si, and Ti. Cr alloy appears to offer higher oxidation resistance in the selected range of oxidation temperatures.
T. Chandra, N. Wanderka, W. Reimers , M. Ionescu
S. Natividad et al., "Heat Treatment and Oxidation Characteristics of Nb-20Mo-15Si-5B-20(Cr,Ti) Alloys from 700 to 1400°C", Materials Science Forum, Vols. 638-642, pp. 2351-2356, 2010