Preparation and high temperature performances of DyCrO3-based coatings on a ferritic stainless steel interconnect material

Abstract

The major concerns with the ferritic stainless steel interconnects of solid oxide fuel cells operated at intermediate temperatures are the growth of non-protective oxide scales and the Cr evaporation into the cathode, which can increase significantly the cell resistance and polarization resistance. An additional coating is needed to solve these problems. Perovskite DyCrO3-based coatings for a type 430 stainless steel (430SS) interconnect are prepared by a high-energy micro-arc alloying (HEMAA) process using a rod of DyCrO3-20 wt.%Ni as the deposition electrode. Area specific resistance and oxidation behavior of the uncovered and covered steel at 850 °C in both air and wet air are examined. The as-deposited DyCrO3-based coatings are mainly composed of DyCrO3 with some Ni and (Ni,Fe)Cr2O4, with a metallurgical bonding to the substrate. The coated steel in both air and wet air has a relatively fast mass gain in the initial stage, followed by a very low mass gain, forming a three-layered scale with a NiFe2O4 outer layer, a thick DyCrO3 sublayer and a thin Cr2O3-rich inner layer. The DyCrO3-based coatings can inhibit significantly the oxidation of 430SS, especially the breakaway oxidation in wet air, and have a low area specific electrical resistance.