Oxidation behavior and thermal stability of Cr-doped Nb(Si,Al)2 and Nb3Si5Al2 matrix compacts prepared by spark plasma sintering

Powder compacts with a few different compositions of the Nb–Si–Al–Cr system and Nb3Si5Al2 matrix compacts with a composition of Nb–47Si–20Al (at.%) were prepared by spark plasma sintering, and their oxidation behavior and thermal stability were examined. Cr-doped Nb(Si,Al)2 matrix compacts with a composition of Nb–56Si–11Al–3Cr (at.%) showed extremely good oxidation resistance in the temperature range of 773–1673K. When they were exposed to air above 1273 K, protective Al2O3 scale was formed. Oxidation mechanisms of the Cr-doped Nb(Si,Al)2 matrix compacts followed parabolic rate law above 1273 K. According to XRD analyses, it was clarified that Nb3Si5Al2 does not decompose at 1418K and that Nb3Si5Al2 is stable below this temperature.