Oxidation behavior of Fe-Cr- And Ni-Cr-based alloy interconnects in CH ₄-H₂O for solid oxide fuel cells

Oxide scale formations in CH₄-H₂O atmospheres were compared for different alloys as interconnects in solid oxide fuel cells (Fe-Cr and Ni-Cr alloys). Oxidation with anode gases (CH₄, H₂O, CO, and CO₂) caused a relatively thick oxide scale formation on the alloy surfaces even in the low oxygen partial pressures at 1073 K. The distribution of elements in the oxide scale and the growttf-rates of oxide scales were precisely analyzed among the examined alloys by glow discharge optical emission spectrometry. Mn spinels formed on the top surface of oxide scales for both Fe-Cr and Ni-Cr alloys. Oxide scale thickness grew with annealing time by a parabolic relationship, and the growth rates were in the orders of 10^-6-10^-5 μm² s^-1 at 1073 K. Ni-Cr alloy shows relatively low growth rate compared with the Fe-Cr alloy. The electrical conductivity after forming oxide scales was different depending on the oxide scale phases and thickness, which was on the order of 10-100 S cm^-1 at 1073 K.