Steel alloy interconnects

For these reasons, most SOFC developers favor ferritic stainless steels for interconnect materials. FSS steels also appear as the alloys of choice for MS-SOFC supports and will thus be discussed in detail in this chapter. For optimizing performance and stability of FSS candidates, two additional parameters should be considered, namely the particle size and the oxidation rate constant of the alloys, as discussed below. 

To reduce the fabrication costs, the possibility of using ferritic steels for SOFC interconnects operated at T = 700-800 °C has recently been considered. The formation of an oxide scale is inevitable for alloy interconnects at both the air and the fuel sides during SOFC operation. Even in the reducing atmosphere at fuel side, the surface of alloy is oxidized due to the presence of water vapor. Hence, the durability of these alloy intercoimects depends on the electrical conductivity of the oxide scales formed during the operation time. 

Other categories of chromia forming alloys—including Ni(-Fe)-Cr base and Fe(-Ni)-Cr base alloys (e.g., austenitic stainless steels)—have a face-centered cubic (FCC) substrate structure. In comparison to the FSS, the FCC base alloys, in particular the Ni(-Fe)-Cr base alloys, are generally much stronger and potentially more oxidation resistant in the SOFC interconnect operating environment [6, 123-129], However, the FCC Ni(-Fe)-Cr base alloys with sufficient Cr for an appropriate... 

Metallic materials for be used as interconnects in SOFCs should fulfil a number of specific requirements [1, 2], Crucial properties of the materials are high oxidation resistance in both air and anode environment, low electrical resistance of the oxide scales formed on the alloy surface as well as good compatibility with the contact materials. Additionally, the value of the coefficient of thermal expansion (CTE) should match with those of the other cell components [3], These requirements can potentially be achieved with high chromium ferritic steels [4], however, previous studies [5] have shown that none of the commercially available ferritic steels seems to possess the suitable combination of properties required for long term reliable cell performance. 

Interconnect Stainless steels, doped LaCr03 Other high-temperature alloys and doped oxides... 

Shaigan N, Qu W, Ivey DG, Chen W (2010) A review of recent progress in coatings, surface modificatirais and alloy developments for solid oxide fuel cell ferritic stainless steel interconnects. J Power Sources 195 1529-1542... 

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