Water vapor effect on high-temperature oxidation behavior of Fe₃Al intermetallics

Abstract

Fe₃Al intermetallics (Fe₃Al, Fe₃Al-Zr, Fe₃Al-Zr,Mo and Fe₃Al-Zr, Mo, Nb) were oxidized at 950 °C in dry and humid (11 vol% water) synthetic air. Thermogravimetric measurements showed that the oxidation rates of the tested intermetallics were lower in humid air than in dry air (especially for Fe₃Al-Zr, Mo and Fe₃Al-Zr, Mo, Nb). The addition of small amounts of Zr, Mo or Nb improved the kinetics compared with that of the undoped Fe₃Al. Fe₃Al showed massive spallation, whereas Fe₃Al-Zr, Fe₃Al-Zr, Mo and Fe₃Al-Zr, Mo, Nb produced a flat, adherent oxide layer. The rapid transformation of transient alumina into alpha alumina may explain the decrease in the oxidation rate in humid air.