Korrosions- und Kompatibilitätsstudien an Cr-Basislegierungen für den metallischen Interkonnektor der Hochtemperaturbrennstoffzelle (SOFC)
Korrosions- und Kompatibilitätsstudien an Cr-Basislegierungen für den metallischen Interkonnektor der Hochtemperaturbrennstoffzelle (SOFC)
In the present study the corrosion behaviour of different Cr5Fe-ODS alloys in typical SOFC atmospheres has been investigated in the temperature range between 950 and 1000 °C. The long term stability of these materials under SOFC conditions was estimated with special emphasis on the effect of the amo...
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Personal Name(s): | Hänsel, Michael (Corresponding author) |
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Quadakkers, Willem J. / Singheiser, Lorenz / Nickel, Hubertus | |
Contributing Institute: |
Publikationen vor 2000; PRE-2000; Retrocat |
Imprint: |
Jülich
Forschungszentrum Jülich, Zentralbibliothek, Verlag
1998
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Physical Description: |
II, 135 p. |
Document Type: |
Report Book |
Research Program: |
ohne Topic |
Series Title: |
Berichte des Forschungszentrums Jülich
3583 |
Link: |
OpenAccess OpenAccess |
Publikationsportal JuSER |
In the present study the corrosion behaviour of different Cr5Fe-ODS alloys in typical SOFC atmospheres has been investigated in the temperature range between 950 and 1000 °C. The long term stability of these materials under SOFC conditions was estimated with special emphasis on the effect of the amount and type of rare earth oxide dispersions, as well as manufacturing technique on the corrosion properties. For the reliable estimation of the behaviour, fundamental studies using thermogravimetry and SIMS for establishing the oxide scale growth mechanisms were combined wich results from long term exposures of the materials in SOFC relevant environments. All investigated Cr-ODS alloys show an excellent corrosion resistance in simulated SOFC atmospheres in comparison to conventional chromia forming alloys. In air and Ar-20%O$_{2}$ the oxidation rates of all the alloys are extremly small after an initial rapid oxidation. During very long term exposures the investigated materials show weight losses due to oxide spalling and evaporation. These mass losses are around 1mg/cm$^{2}$ after 3.000 hours. A conservative extrapolation to the expected service time of SOFC's of 40,000 hours reveals a very low mass loss of around 10mg/cm$^{2}$. The oxide growth rates are relatively independant of dispersion content (0,2-1,0%) and dispersion type (Y$_{2}$O$_{3}$ und La$_{2}$O$_{3}$). A clearly different behaviour has been found in simulated anode gases. Here the corrosion behaviour appeared to depend strongly on the manufacturing method of the materials. The oxidation rates of the materials produced by elementary mixing of starting powders were much higher than the oxidation rates of the mechanically alloyed materials. The reason for these diflerences in behaviour is the distribution of the rare earth oxide dispersion. All investigated materials showed an exellent scale adherence in the simulated anode gases. A prediction to service times of SOFC's of 40.000 hours and 1000°C reveals an oxide thickness of around 30$\mu$m for the mechanically alloyed materials and 160$\mu$m for the mixed materials. The exact amount of oxide dispersion (0.2-1.0%) had no significant effect on the oxidation rates in the simulated anode gases. Long term predictions of the oxidation data clearly show that, in spite of the excellent corrosion resistance of the Cr-based alloys, the formation of the surface oxide scales might lead to problems in respect to high contact resistances at the interfacces between interconnetctotr and contact materials to the electrodes. Therefore a number of surface modifications of the interconnector materials have been proposed which result in a decrease of the oxide growth rotes especially in the early stages of oxidation. Based on the present investigation, guidelines for SOFC materials selection and optimization have been derived. |