Structure and Conductivity of Thermally Grown Scales on Ferritic Fe-Cr-Mn Steel for SOFC Interconnect Applications

With the development of solid oxide fuel cells (SOFCs) that operate in the intermediate temperature range of 650-800°C, ferritic stainless steels have become promising candidate materials for interconnects in SOFC stacks. The SOFC interconnect requires that the alloy possess not only excellent surface stability, but also high electrical conductivity through the oxide scale that forms at elevated temperatures and contributes to the alloy's surface stability. It appears that ferritic Fe-Cr-Mn alloys may be potential candidates due to the formation of an electrically conductive scale containing spinel. To improve the understanding of scale growth on manganese-containing ferritic stainless steels and evaluate their suitability for use in SOFC interconnects, the oxidation behavior ( i.e. , growth kinetics, composition, and structure of the oxide scale) and the scale electrical conductivity of a commercially available Fe-Cr-Mn steel developed specifically for SOFC applications were investigated. The results are reported and compared with those of conventional ferritic stainless steel compositions.