Evaluation of Protective La0.67Sr0.33MnO3-δ Coatings on Various Stainless Steels Used for Solid Oxide Fuel Cell Interconnects

Four metallic alloys, namely 2205 duplex stainless steel (2205DSS), ZMG232, and stainless steels SS430 and SS304 are investigated for use as interconnects in solid oxide fuel cells (SOFCs). A La0.67Sr0.33MnO3-delta (LSMO) film is deposited on these metallicalloy substrates using a pulsed-DC magnetron sputtering system in the reactive mode, leading to the formation of a cubic perovskite structure. The coated alloys are then subjected to oxidizing heat treatments in air at 600 degrees C, 700 degrees C, 800 degrees C, and 900 degrees C, and their microstructures as well as electrical resistances are evaluated. The electrical resistance measurements are performed at 800 degrees C, and the area-specific resistance (ASR) of the film-coated 2205DSS alloy is found to be less than that of the uncoated alloy. This is because a thick layer of Cr2O3 and a (Mn, Fe)Cr2O4 spinel phase layer are formed, and some divalent metallic ions migrate into the Cr2O3 layer. It is found that alloys coated with a thin film of LSMO are more suitable for use as metallic interconnects in SOFCs with intermediate-temperature operating ranges.