Comparison of oxidation behavior and electrical properties of doped NiO- and Cr₂O₃-forming alloys for solid-oxide, fuel-cell metallic interconnects

The goal of this paper was to determine if NiO-forming alloys are a viable alternative to Cr₂O₃-forming alloys for solid-oxide fuel-cell (SOFC) metallic interconnects. The oxide-scale growth kinetics and electrical properties of a series of Li- and Y₂O₃-alloyed, NiO-forming Ni-base alloys and La-, Mn-, and Ti-alloyed Fe-18Cr-9W and Fe-25Cr base ferritic Cr₂O₃-forming alloys were evaluated. The addition of Y₂O₃ and Li reduced the NiO scale growth rate and increased its electrical conductivity. The area-specific-resistance (ASR) values were comparable to those of the best (lowest ASR) ferritic alloys examined. Oxidation of the ferritic alloys at 800°C in air and air+10% H₂O (water vapor) indicated that Mn additions resulted in faster oxidation kinetics/thicker oxide scales, but also lower oxide scale ASRs. Relative in-cell performance in model SOFC stacks operated at 850°C indicated a 60-80% reduction in ASR by Ni+Y₂O₃, Ni+Y ₂O₃, Li, and Fe-25Cr+La,Mn,Ti interconnects over those made from a baseline, commercial Cr₂O₃-forming alloy. Collectively, these results indicate that NiO-forming alloys show potential for use as metallic interconnects.