Oxidation behavior of metallic interconnects for SOFC in coal syngas

Crofer 22 and Haynes 230 alloys, which are candidates for solid oxide fuel cell (SOFC) interconnects, were exposed at 800 °C to a simulated coal syngas (29.1CO + 28.5H2 +11.8CO2 + 27.6H2O + 2.1N2 + 0.01CH4) and air. The samples were characterized by SEM/EDS, XRD and ASR. Results indicated that the compositions of the oxide scales in syngas and in air were similar. For Crofer 22, scales formed in both air and coal syngas were composed of (Cr,Fe)2O3, Mn–Cr compounds and Fe3O4. For Haynes 230 the main composition was Cr2O3. However, it was found that the morphologies of the scales formed in coal syngas were different from those formed in air. Besides, the cross section element distributions of oxide scales formed on Crofer 22 were disparate. In addition, the ASR values of the oxide scales formed in coal syngas and in air were similar at 800 °C but the activation energies for electronic conduction of the oxide scales formed in coal syngas were higher.