Abstract
The isothermal oxidation behavior of sintered Fe-20Cr alloys with a simultaneous addition of Y2O3-A1, Y2O3-Si and La2O3-Si was investigated in the temperature range from 1273 to 1523 K.
Simultaneous addition of Al and Si with rare earth oxides significantly reduced the oxidation rate of the alloy and suppressed the break-away oxidation. In the case of the simultaneous addition of rare earth oxides with Si, La2O3 was more effective than Y2O3, especially at higher temperatures. The spalling of the scale was also excellently suppressed by the simultaneous addition of Al and Si with rare earth oxides, although the singular addition of Al and Si accelerated the spalling of the scale.
Dense internal oxide layer of Al2O3 and SiO2 formed beneath the Cr2O3 scale in the alloys containing Al and Si. However, it seemed unlikely that the simultaneous addition of Al and Si with rare earth oxides enhanced the internal oxidation of Al and Si and changed the shape of the internal oxide layer. From the result obtained in this study, it seemed reasonable that the excellent improvement in the scale adhesion induced by the simultaneous addition of Al and Si with rare earth oxides was not explained only by "keying" and "vacancy sink" models.
