Abstract
The effects of dispersion and superficial application of various rare earth oxides (Y2O3, La2O3, CeO2, Eu2O3, Gd2O3) on the isothermal oxidation of Fe-20Cr sintered alloy have been studied at 1373 K in air. The dispersion of these rare earth oxides reduced the oxidation rate but the effect on the oxidation rate was dependent on the kind of the dispersoid. That is, the dispersion of La2O3, Y2O3 and Gd2O3 greatly reduced the oxidation rate, while the effect of Eu2O3 dispersion was far less than that of the other rare earth oxides. The dispersion of rare earth oxides except for CeO2 suppressed the spalling of the scale. The superficial application of rare earth oxides except for Gd2O3 also markedly reduced the oxidation rate. The superficial application of Gd2O3 as well as Al2O3 had a negligible effect on the oxidation rate.
In the case of alloys which showed lower oxidation rate single layered Cr2O3 scale was maintained stably and the formation of Fe2O3 scale outside the Cr2O3 scale was suppressed; whereas thick Fe2O3 scale grew outside the Cr2O3 scale on the alloys which showed larger mass gain. The results suggested that the rare earth oxides which induced into the Cr2O3 scale suppressed outward migration of Fe ions through the Cr2O3 scale.
