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- Bexell, Ulf, et al.
(författare)
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Chromium evaporation from plastically deformed pre-coated Sandvik Sanergy HT 22% Cr ferritic interconnect steel
- 2010
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Ingår i: 2010 Conference Memory Stick 9th European SOFC Forum. - Lucerne.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Ferritic stainless steel has attracted a great deal of attention for its use as an interconnector in solid oxide fuel cells (SOFCs). The ferritic Sandvik Sanergy HT chromium steel is specially developed for interconnectors in SOFC with a unique chemical composition, which gives the alloy a good high temperature corrosion resistance as well as good surface conductivity in the formed chromium oxide scale. However, chromium evaporation from metallic interconnectors in SOFC fuel cells tends to poison the cathode of the fuel cell. Furthermore, the evaporation of chromium species from the oxide surface tends to increase the oxidation rate resulting in increased contact resistance. It is nowadays well known that thin coatings of e.g. cobalt can substantially reduce the chromium evaporation from the interconnectors. In this study, a 22% Cr ferritic steel, Sandvik Sanergy HT has been coated with a thin metallic cobalt film. The coated material was plastically deformed and the effect of chromium evaporation was studied as a function of the degree of deformation. Coated samples are also compared to uncoated material. The results show that the metallic cobalt film cracks when the steel sheet is formed but the chromium evaporation is more or less unaffected.
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| 2. |
- Froitzheim, Jan, 1981, et al.
(författare)
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Investigation of Chromium Volatilization from FeCr Interconnects by a Denuder Technique
- 2010
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 1945-7111 .- 0013-4651. ; 157:9, s. B1295-B1300
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Tidskriftsartikel (refereegranskat)abstract
- A technique is presented for accurate and time-resolved quantification of chromium volatilization from alloys at high temperature. A denuder tube which is coated with Na2CO3 is placed downstream of the samples. CrO2(OH)(2) that evaporated from the samples is collected on the denuder and converted to the thermally stable Na2CrO4. The chromate is then dissolved in water and determined quantitatively. Three commercially available ferritic 22% Cr steels intended for use as solid oxide fuel cell interconnect materials (Sanergy HT, Crofer 22 APU, and ZMG 232) have been investigated with respect to chromium volatilization and oxidation rate. The effect on chromium volatilization of a submicrometer cobalt coating on the steel surface is reported. Comparisons are made with a conventional thick ceramic coating. The experiments are carried out at 850 degrees C in N-2 - 20% O-2 - 3% H2O atmosphere. The submicrometer Co coatings proved to be very efficient, reducing Cr volatilization by 1 order of magnitude. Microscopic studies show that both uncoated steel and steel coated with a submicrometer cobalt film develop two-layered oxide scales with the bottom part consisting of a Cr-rich corundum-type oxide. The uncoated samples develop a top layer consisting of (Cr, Mn)(3)O-4 oxide, whereas the Co-coated samples exhibit a top layer consisting of Co-rich spinel oxide. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3462987] All rights reserved.
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