Evaluation of Binary Fe–Ni Alloys as Intermediate-Temperature SOFC Interconnect

Abstract

Binary Fe–Ni alloys with 45–60Ni (wt %) were evaluated as an interconnect material for intermediate-temperature solid oxide fuel cells (SOFCs). The oxidation resistance of the Fe–Ni alloys in air improved with increasing Ni content. The thermally grown oxide scale on these alloys generally consisted of a top layer and a spinel inner layer, with the thickness of the layer decreasing as the Ni content increased. No measurable weight change was observed after isothermal oxidation in at and a metallic surface was maintained. The coefficient of thermal expansion (CTE) increased with the Ni content in these alloys and the CTE values were similar to those of other cell components. The spinel with a composition similar to that thermally grown on the Fe–50Ni alloy exhibited a CTE value close to the alloy substrate, which aids scale spallation resistance for this alloy. The scale area specific resistance of the Fe–Ni alloys was found to be comparable to that of the current interconnect alloys, as a result of high electrical conductivity of the spinel. The promise and issue with these Fe–Ni alloys as interconnect materials are highlighted and potential approaches to address the issue are outlined.