Oxidation and electrical behavior of CuFe2O4 spinel coated Crofer 22 APU stainless steel for SOFC interconnect application

• CuFe2O4 was prepared by glycine nitrate process to prepare alloy coating.
• The coating was developed by screen-printing combined with a powder reduction.
• The coating was crack-free and well-bonded to the substrate.
• The coating significantly improved the oxidation resistance of the alloy.
• The coating acted as a barrier to Cr outward diffusion and greatly reduced the ASR values.

In an attempt, CuFe2O4 spinel coating was investigated with the purpose of increasing the performance of Crofer 22 APU ferritic stainless steel as a potential SOFC interconnect material. The samples are characterized by X-ray diffraction (XRD), scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS) and 4-probe area specific resistance (ASR) tests. CuFe2O4 spinel layers were deposited via screen-printing method on the bare and pre-oxidized samples. Good bonding between the coating and the substrate was achieved by the reactive sintering process of the reduced coating. Long term oxidation experiments and ASR measurements are investigated. The results indicated that the spinel protection layers not only significantly decreased the ASR, but also inhibited the subscale growth by acting as a barrier to the inward diffusion of oxygen. An ASR of 13.8 and 26.7 mΩ ⋅ cm2at 800 °C after 400 h oxidation were achieved for the bare and pre-oxidized CuFe2O4 spinel coated samples, respectively, which were much lower than that of the bare substrate (48 mΩ ⋅ cm2) at the same temperature. The ASR of 14.3 mΩ ⋅ cm2was reached after 600 h of exposure at 800 for the coated sample. The high electrical conductivity of CuFe2O4 spinel and its doping by Mn, inhibition of the resistive Cr2O3 oxide scale growth, and good adherent between the coating and substrate are supposed to be responsible for the substantial electrical conductivity improvement.