Development of nano-oxide particles dispersed alumina scale formed on Zr-added FeCrAl ODS ferritic alloys

In order to develop a robust alumina scale dispersed with nano-oxide particles for FeCrAl oxide dispersion strengthened (ODS) ferritic alloys, the oxidation behavior of FeCrAl ODS ferritic alloys with zirconium and excessive oxygen (Ex. O) additions was investigated at 900 degrees C in air. Zirconia incorporation into alumina scale was not observed in the Ex. O-added FeCrAl ODS alloys at 900 degrees C, instead of this, a distribution with dense Y-Zr oxide particles inside the alumina scale was found, which is expected to enhance the stability of the alumina scale during service at elevated temperatures in nuclear applications. Preexisting large Zr-enriched precipitates formed during the alloy fabrication process are incorporated into the alumina scales during oxidation, which would increase the oxidation rate via providing a short-circuit paths for oxygen inward diffusion by themselves and associated porosity. In addition to a traditional spherical shape, a unique tadpole-like shape of the fine Y-Zr oxide particles in alumina was also observed, which is considered to be related to those incorporated coarse Zr-Y oxide inclusions in alumina scale.