Oxide scale formation and stability of Fe-Cr alloy interconnects under dual atmospheres and current flow conditions for SOFCs

Oxide scales formed on Fe-Cr alloys were characterized by electrochemical resistance measurements and microstructure observation. Fe-Cr alloy samples were exposed to air on one side and fuel gas (dilute CH4 - H2 O with N2) on the other side under current flow (0.3 Acm-2) (dual atmospheres and current flow). The alloys were connected with Pt-mesh cathode and Ni-mesh anode at 1073 K. The interface resistance changes at the Ni-meshFe-Cr alloy interfaces were monitored as a function of time, which increased with time in a parabolic relationship. The observed interface resistance after 800 h operation was less than 0.015 cm2 at 1073 K. The oxide scale phases formed were Cr-Mn-Fe spinel, Cr2 O3, and SiO2 layer from surface to inner alloy, which is almost the same with the oxide scales formed in a single atmosphere. No significant effects of dual atmosphere and current flow was observed in the formed oxide scale phases of both anode and cathode side on Fe-Cr alloys. Around the glass-sealing/alloy contact interfaces, a thick oxide scale was observed on the alloy. The reaction of glass components with alloy can affect the stability of oxide scales and alloys in the long-term operation.