Influence of Surface Modification Using a Rare Earth Element on Properties of Ferritic Stainless Steel Metallic Interconnects

Abstract

Iron and chromium based ferritic stainless steels have been considered to be a promising material for the metallic interconnect of solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs). However they have a drawback of chromium evaporation led by a scale growth at the steel surface when exposed at a high temperature oxidation atmosphere, which results in chromium poisoning of the air electrode and subsequent performance degradation of SOFCs and SOECs. Application of a surface modification or protective coating onto the metallic interconnects has been introduced to prevent the degradation by mitigating the chromium evaporation. In this study, ferritic stainless steels modified with a rare earth element of neodymium was investigated on the properties of high temperature oxidation and electrical conductivity. Detailed analyses on phase formation, microstructure evolution, and area specific resistance were carried out to figure out effects of the surface modification on the steels. Accordingly, the surface modified steels revealed decrease in the area specific resistance which was led by the reduction of scale growth since the rare earth element altered the chromium oxidation behavior.