Interface Reactions between Conductive Ceramic Layers and Fe-Cr Steel Substrates in SOFC Operating Conditions

To improve contact resistance and protect the cathode from chromium poisoning, perovskite (La,Sr)CrO3, (La,Sr)CoO3 and spinel MnCo2O4 coatings were applied onto the surfaces of Fe-25Cr (DIN 50049) steel by means of the screen-printing method. The oxidation process of the coated steels under cyclic-oxidation conditions showed high compactness of the protective layer, good adhesion to the metal substrate, as well as acceptable area specific resistance level for SOFC metallic interconnect materials, which was the result of the structural modification of the coating/steel interface reaction, i.e. the formation of an intermediate, chromia-rich multilayer between the conductive coating and the metal substrate. The cross-sectional morphology and nanostructure of interface products formed during long-term thermal oxidation in air and the H-2/H2O gas mixture at 1073 K were characterized using SEM-EDS and conventional TEM-SAD. Cr-vaporization tests showed that the perovskite and spine] coatings may play the role of barriers that effectively decrease the volatilization rate of chromia species. [doi:10.2320/matertrans.MB201013]