High-temperature characteristics and electrical properties of CrN-coated and Mn/Cu/CrN-coated 430 stainless steel for solid oxide fuel cell metal interconnects

To limit the growth of oxides with low electrical conductivity and to suppress the inter-diffusion of elements between coating and substrate, an additional CrN sublayer is pre-deposited by arc ion plating. The Mn/Cu layers are electrodeposited in an aqueous solution. The results show that the CrN layer is about 2 µm and decomposes rapidly at 750 °C, and only CrN and CrO are detected after 1 h. The inner layer of CrN is not entirely decomposed after 100 h, and little Fe from the substrate diffuses into the CrN layer. When Mn/Cu-coated 430 stainless steel (SS) oxidized for 10 h, a mass of Fe-rich oxides are found in the oxide layer. For Mn/Cu/CrN-coated 430 SS, CrO and CrN bilayer structure and an internal oxidation zone containing some gaseous nitrogen are found near the interface. After oxidation for 10 h, area-specific resistance (ASR) of Mn/Cu-coated 430 SS is the smallest among the three oxide coatings. The ASR of the CrN layer and Mn/Cu/CrN layer oxidized for 10 h is very high. After 100 h, a part of CrN is oxidized into the CrO layer, and the ASR of the CrN layer decreases.