Behavior of Interconnect Steels in Carbon Containing Simulated Anode Gas of Solid Oxide Fuel Cells

• Published in: Journal of the Electrochemical Society 2012-01, Vol.159 (11), p.F725-F732
• Main Authors: Niewolak, L., Wessel, E., Hüttel, T., Asensio-Jimenez, C., Singheiser, L., Quadakkers, W. J.
• Format: Article
• Language: English
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/2.033211jes

The corrosion behavior of three commercially available high chromium ferritic steels and one austenitic steel was tested in CO-containing simulated anode gas of a Solid Oxide Fuel Cell. Aim of the study was to evaluate the suitability of selected steels for interconnects in SOFC's with an operating temperature around 600°C. Main emphasis was put on the effect of a nickel contact layer on the materials behavior in the high simulated anode gas. In spite of the high carbon activity in the gas (aC>1) the steels in the as ground condition were found to form protective, chromium rich surface oxide scales and did not show indications for metal dusting or internal carburization, up to the maximum test times of 300 h. Presence of a metallic nickel layer resulted in carbon uptake of the steels, whereby the relative amounts increased with decreasing steel chromium content. Interdiffusion between ferritic steel and nickel layer lead to austenite formation, with or without σ-phase formation. Diffusion of chromium into the nickel layer resulted in formation of a thin chromia based surface scale on the initial nickel coating. This effect impedes the transfer of carbon from the gas into the nickel coated steel.