The effect of Mn on the oxidation behavior and electrical conductivity of Fe–17Cr alloys in solid oxide fuel cell cathode atmosphere

Four Fe–17Cr alloys with various Mn contents between 0.0 and 3.0 wt.% are prepared for investigation of the effect of Mn content on the oxidation behavior and electrical conductivity of the Fe–Cr alloys for the application of metallic interconnects in solid oxide fuel cells (SOFCs). During the initial oxidation stage (within 1 min) at 750 °C in air, Cr is preferentially oxidized to form a layer of Cr2O3 type oxide in all the alloys, regardless the Mn content, with similar oxidation rate and oxide morphology. The subsequent oxidation of the Mn containing alloys is accelerated caused by the fast outward diffusion of Mn ions across the Cr2O3 type oxide layer to form Mn-rich (Mn, Cr)3O4 and Mn2O3 oxides on the top. After 700 h oxidation a multi-layered oxide scale is observed in the Mn containing alloys, which corresponds to a multi-stage oxidation kinetics in the alloys containing 0.5 and 1.0 wt.% of Mn. The oxidation rate and ASR of the oxide scale increase with the Mn content in the alloy changes from 0.0 to 3.0 wt.%. For the application of metallic interconnects in SOFCs, Mn-free Fe–17Cr alloy with conducting Cr free spinel coatings is preferred.

► Fe–17Cr alloys with various Mn contents between 0.0 and 3.0 wt.% are prepared as candidate materials for interconnects of solid oxide fuel cells. ► Cr2O3 is preferentially formed within 1 min of oxidation at 750 °C in air in all alloys; multi-layered oxide scale is observed. ► Oxidation rate increases with Mn content, resulting higher ASR. ► Mn-free Fe–17Cr alloy is preferred in terms of oxidation and conductivity.