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

Abstract

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 °C in air. Zirconia incorporation into alumina scale was not observed in the Ex. O-added FeCrAl ODS alloys at 900 °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.

Keywords

• FeCrAl ferrite
• ODS
• Oxidation
• Alumina