Preparation and performances of Ni-Fe/CrNx dual layer coatings for ferritic stainless steel interconnects

Abstract

Dual layer coatings CrNx and Ni-Fe alloy have been developed for metallic interconnects application by a combined approach. The CrNx layer was deposited on ferritic stainless steel using multi-arc ion plating, and the Ni-Fe alloy coating was electroplated on the CrNx coated steel subsequently. After oxidation at 800 °C in air for 5 h, a multi-layer scale composed of NiFe2O4, Cr2O3, Ni-Fe-Cr alloy and CrNx from outside to inside was formed on the CrNx/substrate with a 1.6 μm thick Ni-32 at%Fe alloy coating. Further oxidation led to the decomposition of the CrNx layer, but no pores could be observed near the scale/substrate interface even after an oxidation of 1000 h. The CrNx layer acted as an effective barrier against the mutual diffusion of elements between the coating and the substrate either before or after decomposition. The employment of the Ni-Fe/CrNx dual layer coating decreased the growth rate of the Cr2O3 scale and thus a lower scale area specific resistance (ASR). The oxidation behavior of the Ni-Fe/CrNx coated substrate and the influence mechanism of the CrNx barrier layer were discussed. Keywords: Solid oxide fuel cell, Interconnect, NiFe2O4, CrNx, Oxidation resistance, Area specific resistance