Effect of water vapor on the phase transformation of alumina grown on NiAl at 950 °C

This particular study includes the analysis of the effect of H2O on promoting the phase transformation in thermally grown aluminum oxides formed on NiAl at 950 °C. Oxidation of NiAl is carried out at 950 °C in O2 and O2 + 15 vol.% H2O. It is observed that transient alumina initially formed on NiAl transforms to stable α-alumina in the presence of water vapor which promotes the subject transformation and eventually results in a compact scale, offering superior oxidation resistance. Present study includes the analysis of θ to α-alumina transformation under the effect of temperature and environment.

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► The oxidation dynamics of NiAl in both humid and dry air are investigated.
► Al2O3 grown on NiAl at 950 °C are characterized.
► θ-Al2O3 grown on NiAl in dry O2 is more stable than that in O2 + H2O.
► Effect of water vapor on the transformation of θ to α-alumina is discussed.