Microstructure and environmental resistance of low Cr ODS FeCrAl

Abstract

Three oxide dispersion strengthened (ODS) Fe–12 wt-%Cr–5 wt-%Al (12 at-%Cr–9·7 at-%Al) alloys were mechanically alloyed with different oxide additions: (1) Y2O3, (2) Y2O3+HfO2 and (3) Y2O3+ZrO2. The as extruded microstructure was characterised including the oxide particle composition and size distribution. The 700°C Pb–Li compatibility was evaluated for a fusion energy application and the steam oxidation resistance at 1200°C and higher temperatures was evaluated for a nuclear accident tolerant fuel cladding application. The alloy prepared with only a Y2O3 addition contained some low Al regions and did not perform well, but provided a baseline for comparison. The other alloys contained sufficient Cr and Al to form a protective LiAlO2 surface oxide, which inhibits dissolution in isothermal Pb–Li. Also, a protective α-Al2O3 scale formed in steam oxidation at 1200°C, similar to the scale formed in dry air at 1200°C. For the alloy with HfO2, the scale remained protective to 1475°C in steam.