Evaluation of Laves-phase forming Fe–Cr alloy for SOFC interconnects in reducing atmosphere

A Laves-phase forming Fe–Cr alloy was evaluated as interconnects for solid oxide fuel cells (SOFCs) in reducing atmosphere (in H2-H2O). The oxide scale growth was compared between Laves-phase forming alloy and typical stainless steel (SUS430). The oxide scale growth rates were decreased in the Laves-phase forming alloy, and the area-specific resistance (ASR) of oxidized Laves-phase forming alloy showed the lower values than that of SUS430. The temperature dependence of 1/ASR for the oxidized alloy was different between Laves-phase forming alloy and SUS430. The oxygen diffusivity in the oxide scale was also evaluated by the stable isotope oxygen (18O2) diffusion in the scale. The chemical diffusion coefficients of isotope oxygen in the oxide scale showed the smaller value for the Laves-phase forming alloy (D = 7.0 × 10−13 cm2 s−1) than that for SUS430 (D = 4.6 × 10−12 cm2 s−1) at 1073 K. A relatively high diffusivity of oxygen was estimated in the Mn–Cr spinel oxide on the top surface of oxide scales. Inward diffusion of oxygen and outward diffusion of cation in the oxide scale were discussed to consider the oxide scale growth mechanism.