“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.