Oxidation-resistant thin film coating on ferritic stainless steel by sputtering for solid oxide fuel cells

The electrical resistance of ferritic stainless steel 430 (SS430), which is used as an interconnect in solid oxide fuel cells for intermediate temperature operation, was improved by coating it with a protective thin layer. Inconel, La0.6Sr0.4CoO3, and La0.6Sr0.4CrO3 (LSCr) were used as the coating material. Each material was thinly coated on SS430 by using a radio frequency magnetron sputtering method. LSCr-coated SS430 showed the lowest electrical resistance, reducing the resistance to 1/3 of the uncoated SS430. Long-term durability test performed at 700 deg. C for 1000 h showed that the LSCr layer also reduced the oxidation rate because the LSCr perovskite was formed and maintained throughout the measurement. This was verified by X-ray diffraction analysis. On the other hand, the uncoated SS430 formed spinel structures, such as Mn3-xCrxO4, at the surface. Oxidative properties of the uncoated SS430 were inferior to the coated SS430 metals because the spinel structure has a relatively high oxidation rate and low electrical conductivity