Water-vapor-effect on the oxidation of Fe-21.5 wt.%Cr-5.6 wt.%Al at 1000°C

摘要: Fe-21.5 wt. %Cr-5.6 %Al oxidation, at 1000°C, in dry or wet oxygen shows that steam has an influence on the oxide-scale growth mechanism. Steam modifies kinetics of early-stage oxidation. In oxygen, initial fast linear regime is observed during one hour. Under conditions, weight-gain curves follow same parabolic over entire oxidation test. The scale structure strongly depends presence gaseous environment. With composed mainly ofα-Al2O3 after formation ofγ-Al2O3 identified by ESCA and RHEED. transient stage corresponds to necessary time for internal part initialγ-Al2O3 transform into a continuousα-Al2O3 diffusion barrier. oxides are as (Mg, Fe) (Cr, Al)2O4, MgAl2O4 (orthorhombic), Al2O3 (hexagonal), these (cubic), Cr3O4, Fe2O3,α-Al2O3, with time. When water vapor does not change drastically kinetics, induced iron chromium oxide could be responsible weakening protectiveness alumina scales.