Comparison of electroplating and sputtering Ni for Ni/NiFe2 dual layer coating on ferritic stainless steel interconnect

Abstract

Ni/NiFe2 dual layer coating is fabricated to improve the performance of SUS 430 steel as solid oxide fuel cells (SOFCs) interconnects by a combined approach. Ni layer is deposited by electroplating or magnetron sputtering, and subsequently the NiFe2 layer is sputtered on it. The coated steels are evaluated at 800 °C in air corresponding to SOFC cathode environment. It is found that the coating with electroplated Ni and sputtered NiFe2 results in breakaway oxidation after 5 weeks. Preoxidation treatment in 900 °C air for electroplated Ni steel prior to depositing NiFe2 layer improves oxidation resistance. The sputtered Ni and NiFe2 sample exhibits superior oxidation resistance and inhibition against Cr outward migration while maintaining a low area-specific resistance (ASR) of surface scale. Comparative analyses of the coating preparation and resultant oxidation behavior with possible mechanisms and implications are discussed.