Cyclic Oxidation of (La,Sr)(Cr,V)O3 Coated Crofer 22 APU Alloy for SOFC Interconnects

摘要

La_(0.8)Sr_(0.2)Cr_(0.7)V_(0.3)O3 (LSCV) was synthesized by co-precipitation method and used for coating of Crofer 22 APU commercial alloy, as a candidate material for intermediate- temperature solid oxide fuell cell (SOFC) interconnect. LSCV thick films were deposited on Crofer specimens by screen-printing method. The films were 20-60 μm in thickness. (La,Sr)(Cr,V)O3 coated Crofer 22 APU was isothermally and cyclically oxidized at 800 and 900 °C in air. Cyclic oxidation kinetics of the prepared (La,Sr)(Cr,V)O3/Crofer 22 APU material and of uncoated alloy, used for comparison, were investigated in laboratory air for up to 380 hrs, after which the materials were cooled down to a room temperature. In the case of both tested materials, oxidation kinetics followed approximately the parabolic rate law. The oxidation rate was considerably reduced by the (La,Sr)(Cr,V)O3 protection coating, as expected taking into account the oxide scale characterization. The oxidation process of the coated steel, taking place in variable temperature cycles, showed good compactness of the protective layer, as well as good adhesion to the metal substrate, resulting from the structural modification of the coating/steel interface due to the formation of an intermediate, chromia-rich layer between the coating and metal substrate. The microstructure and chemistry of the interphase products were characterized by SEM- EDS and XRD. Our investigations showed that, due to oxidation corrosion resistance (La,Sr)(Cr,V)O3/Crofer 22 APU composite material is a potential material for the future construction of metallic interconnects for planar-type SOFCs.