Oxidation behavior and electrical property of ferritic stainless steel interconnects with a Cr–La alloying layer by high-energy micro-arc alloying process

Chromium volatility, poisoning of the cathode material and rapidly decreasing electrical conductivity are the major problems associated with the application of ferritic stainless steel interconnects of solid oxide fuel cells operated at intermediate temperatures. Recently, a novel and simple high-energy micro-arc alloying (HEMAA) process is proposed to prepare LaCrO3-based coatings for the type 430 stainless steel interconnects using a LaCrO3–Ni rod as deposition electrode. In this work, a Cr–La alloying layer is firstly obtained on the alloy surface by HEMAA using Cr and La as deposition electrode, respectively, followed by oxidation treatment at 850 °C in air to form a thermally grown LaCrO3 coating. With the formation of a protective scale composed of a thick LaCrO3 outer layer incorporated with small amounts of Cr-rich oxides and a thin Cr2O3-rich sub-layer, the oxidation rate of the coated steel is reduced remarkably. A low and stable electrical contact resistance is achieved with the application of LaCrO3-based coatings, with a value less than 40 mΩ cm2 during exposure at 850 °C in air for up to 500 h.