Functional properties of CuMn1.9Fe0.1O4-based coatings deposited on Crofer 22 APU steel exposed to selected pre-oxidation conditions

Abstract

The study investigates how pre-oxidation conditions affect the properties of cobalt-free protective coatings for solid oxide fuel cell (SOFC) interconnects. Coatings were composed of commercial spinel CuMn 1.9 Fe 0.1 O 4 , applied to Crofer 22 APU via electrophoretic deposition (EPD). Steel samples underwent pre-oxidation at 600–850 °C in air. Pre-oxidation at 800 °C proves to be the most effective, forming a uniform oxide layer that reduced ASR by over 50 % compared to pristine steel. All coatings demonstrate consistent thickness (13–26 μm) and low porosity (11–13 %), with structural characteristics that effectively limit gas-phase transport. Following sintering, XRD studies revealed a dual-phase composition of the coatings comprising spinel (Cu,Mn) 3 O 4 and bixbyite (Mn,Fe) 2 O 3 , which is likely to enhance Cr trapping while remaining stable electrically and mechanically. Analysis using artificial neural networks (ANN) based on ASR results confirm that pre-oxidation at 800 °C ensures mid-term stability, with minimal chromium diffusion observed after 200 h of testing at 700 °C. • Effect of steel pre-oxidation on formation of the protective coating revealed. • Properties of the coatings based on cobalt-free CuMn 1.9 Fe 0.1 O 4 material studied. • XRD showed dual-phase composition: spinel (Cu,Mn,Fe) 3 O 4 and bixbyite (Mn,Fe) 2 O 3 . • Pre-oxidation at 800 °C was found as optimal for the mitigation of the Cr diffusion.