High Temperature Oxidation of TiAl and TiAl8Nb Alloys in Air

Isothermal oxidation of two g-TiAl-based intermetallic alloys: Ti48Al and Ti46Al8Nb alloys was studied in synthetic air at 1073-1223 K for up to 240 hrs. Mass change per unit area for the oxidized samples followed approximately the parabolic rate law. The kp values for the studied temperature interval were in the range from 7.2×10-13 to 1.8×10-11 g2cm-4s-1. The activation energy for oxidation of Ti48Al alloy in air at 1073-1223 K was Ea = 165±12 kJ/mol. Niobium addition to Ti48Al alloy in the amount of 8% increased its oxidation resistance. Structure and chemical composition of the oxidation products, and morphology of the oxidized samples were investigated using XRD, SEM-EDS, and TEM. The …