Effects of Thermal Cycling on the Formation of Oxide Scale of Fe-Cr Alloy Interconnects for Solid Oxide Fuel Cells

Abstract

Effects of thermal cycling on the formation of oxide scales were investigated in Fe–Cr alloy interconnects for solid oxide fuel cells. Thermal cycling between 293 and 1073 K with a heating rate of 250 K/h was examined. Relatively large oxide scale grains were formed on the surface. These grains mainly consisted of the spinel-based oxides formed by fast diffusion of Mn along the grain boundaries of the Fe–Cr alloy. Although the oxide scale/alloy interface showed strong contact without exfoliation, some cracks were found at the oxide scale surface. The elemental distribution in the oxide scale was similar to that of samples with the normal annealing (without thermal cycling). The growth of oxide scale was promoted by thermal cycling especially at the grain boundary of the Fe–Cr alloy, which eventually resulted in the formation of a thick oxide scale. An increase of oxide-scale growth rates with the thermal cycling was evaluated taking into account microstructures and elemental distributions.