Effects of Si and Al concentrations in Fe–Cr alloy on the formation of oxide scales in H2–H2O

Effects of silicon and aluminum concentrations in Fe–Cr alloys on the formation of oxide scales were examined in H2–H2O atmosphere for interconnects of solid oxide fuel cells (SOFCs). The morphology and oxide scale growth rates were compared between conventional and modified Fe–Cr alloys (Si and Al concentration reduced). The formed oxide scales were characterized by surface and depth profile analyses. Oxide scales were composed of the following oxide phases from surface to inner oxide scale: Mn–Cr–(Fe) spinel, Cr2O3, Si-rich interface, and Al2O3 internal oxide. Although the scale formation mechanism is similar between conventional and modified alloys, the oxide scale growth rates were decreased in the modified Fe–Cr alloy. The electrical conductivity of oxidized Fe–Cr alloys was improved in the modified Fe–Cr alloy due to thinner oxide scale thickness and complete Cr2O3 film with less distribution of insulating Si and Al internal oxides.