Sandvik Materials Technology develops nanocoatings for SOFC stainless steel interconnects. The properties of cerium cobalt coated AISI441 (EN 1.4509) have previously been studied extensively (1-4). However, the trend in SOFC have been to decrease working temperatures from above 800°C and today commercial systems are sold that operate below 650°C. The lower operating temperature opens up new possibilities in selection of component materials. In this study we have examined precoated AISI 441 used in solid oxide fuel cell interconnects at 650°C and compared to previous studies at 800°C. The coating characteristics after different oxidation times were studied by SEM. Also, the variation of cobalt coating thickness and the development of the surface oxides were examined by SEM.

By using the double trench approach (3) samples with and without priming at 900°C for 5 hours followed by heat treatment at 650°C, were compared. These samples were also compared to the results from (3) with a sample prepared at 800°C for a total of 504 hours.

Figure 1. Mass gain of pre-coated cerium cobalt AISI441 (EN 1.4509) from cyclic oxidation at 650°C and 800°C in ambient air. The mass gains are not corrected for Cr evaporation, which shows for the 650°C as it displays flat or negative mass gains.

References

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2. J.G. Grolig, J. Froitzheim, J.E. Svensson, J. of Power Sources, 248 1007 (2014)
3. R. Berger, M. W. Lundberg, J. Westlinder, H. Holmberg, ECS Trans. 68 1649 (2015)
4. H. Falk-Windisch, J. Claquesin, M. Sattari, J.-E. Svensson, J. Froitzheim, J. of Power Sources, 343 1 (2017)