Enabling Inexpensive Metallic Alloys as SOFC Interconnects: An Investigation into Hybrid Coating Technologies to Deposit Nanocomposite Functional Coatings on Ferritic Stainless Steel

• Published in: International journal of hydrogen energy Vol. 32; no. 16
• Main Authors: Gannon, Paul, Gorokhovsky, Vladimir I., Deibert, Max, Smith, Richard J., Kayani, Asghar N., White, P T., Sofie, Stephen W., Yang, Z Gary, Mccready, David E., Visco, S., Jacobson, C., Kurokawa, H.
• Format: Journal Article
• Language: English
• Published: United States 01.11.2007
• Subjects: 30 DIRECT ENERGY CONVERSION; ALLOYS; COATINGS; DEPOSITION; DIFFUSION BARRIERS; ELECTRIC CONDUCTIVITY; ELECTRON BEAMS; EVAPORATION; FERRITIC STEELS; FUNCTIONALS; hybrid coating technology; MATERIALS SCIENCE; metallic alloys; nanocomposite functional coatings; OXIDATION; PHYSICAL VAPOR DEPOSITION; PROTECTIVE COATINGS; RUTHERFORD BACKSCATTERING SPECTROSCOPY; SOFCs; SOLID OXIDE FUEL CELLS; STABILITY; STAINLESS STEELS; TRANSPIRATION; X-RAY DIFFRACTION
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2006.08.012

Reduced operating temperatures (600-800°C) of Solid Oxide Fuel Cells (SOFCs) may enable the use of inexpensive ferritic steels as interconnects. Due to the demanding SOFC interconnect operating environment, protective coatings are required to increase long-term stability. In this study, large area filtered arc deposition (LAFAD) and hybrid filtered arc-assisted electron beam physical vapor deposition (FA-EBPVD) technologies were used to deposit two-segment coatings with Cr-Al-Y-O nanocomposite bottom segments and Mn-Co-O spinel-based top segments. Coatings were deposited on ferritic steels and subsequently annealed in air for various times. Surface oxidation was investigated using SEM/EDS, XRD and RBS analyses. Cr-volatilization was evaluated by transpiration and ICP-MS analysis of the resultant condensate. Time dependent Area Specific Resistance (ASR) was studied using the four-point technique. The oxidation behavior, Cr volatilization rate, and ASR of coated and uncoated samples are reported. Significant long-term (>1,000 hours) surface stability, low ASR, and dramatically reduced Cr-volatility were observed with the coated specimens. Improvement mechanisms, including the coating diffusion barrier properties and electrical conductivity are discussed.