“Fe doped Ni–Co spinel protective coating on ferritic stainless steel for SOFC interconnect application”

•Ni–Co–Fe coatings were applied on ferritic stainless steel by sol-gel method.•Fe dopping into Ni–Co spinel reduced oxidation rate and ASR.•Formation of free NiO and Cr migration was inhibited by Fe dopping.•Fe dopping dramatically decreased the obtained spinel particle size.

In an attempt to reduce the oxidation and Cr evaporation rates, various protective coating layers with a nominal composition of NiCo2−xFexO4 (x = 0, 0.5, 1) were deposited on the SUS 430 ferritic stainless steel substrate, as interconnect for solid oxide fuel cell application, by sol-gel dip coating method. Then, the coated samples were soaked at 750 °C for 2.5 h in N2 and subsequently for 2.5 h in air. Phase composition and microstructure of the coatings were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Moreover, long-term isothermal oxidation experiment and area specific resistance (ASR) measurement were also carried out on the coated samples. Results showed that the addition of 1 mol of Fe into Ni–Co spinel (x = 1), led to a parabolic rate constant of 5.16 × 10−15(g2 cm−4 s−1) and an ASR of 17 mΩ cm2.