The Structure and Properties of Plasma Sprayed Fe Doped Manganese Cobalt Oxide Spinel Coatings for SOFC Metallic Interconnectors

Manganese cobalt oxide spinel doped with Fe₂O₃ was studied as protective coatings on alloyed metallic interconnect plates for solid oxide fuel cell applications. Chromium alloying causes problems at high operation temperatures in oxidising conditions, on the cathode side of the fuel cell. The formed chromium oxide layer tends to form a thin layer of chromium trioxide or chromium hydroxide which evaporates at certain oxygen partial pressures more easily than chromium oxide and thus poisons the cathodes active area causing the degradation of the solid oxide fuel cell. Thermal spraying is regarded as a promising way to produce dense and protective layers on top of ferritic steels to lower the degradation processes and extend the lifetime of the SOFC device. In the present work, the ceramic Co-Mn-oxide spinel coatings were produced by using the atmospheric plasma spray process. The structures and compositions of the coatings were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) was used to study the phase structure in as-sprayed and heat treated coatings and mechanical properties were examined by using micro hardness tester. Coatings with low thickness and micro structurally dense structures were produced by using optimal deposition conditions.