Effect of aluminium addition on the oxidation and carburization behaviour of austenitic stainless in high-temperature SCO2 environments

Abstract

The AFA stainless steels with 2.5 and 5 wt% Al were developed, and Al addition had a great influence on intermetallic compounds in AFA alloys, especially resulting in increasing of B2-NiAl phase. After 3000 h exposure in SCO2, the thickness of oxide scales for two AFA alloys was 5–7 times thinner than that of ASS without Al, and the structure of formed oxide scale significant changed, i.e., from single Cr2O3 to double-layer with Fe/Cr oxide and Al oxide. As for AFA-2.5%, the formed Al-riched oxide inner layer was amorphous and unstable, resulting in the severe internal oxidation and carburization occurrence.