Development of ferritic steels for application as interconnect materials for intermediate temperature solid oxide fuel cells (SOFCs)

Abstract

Fuel cells are considered as new energy production systems. High temperature fuel cells has experimented a large interest due to its high efficiencies much higher than that encountered for low temperature fuel cells. However, the materials requirements for high operation temperature makes that some kinds of materials are under development. One ofthese critical components are the interconnect materials. These are subjected at two different atmospheres, i.e. air and $H^{2}$-$H^{2}$0 mixtures. The present work examines the possibility of using commercial alloys and the suitability of different model alloys developed exclusive as construction materials for SOFC interconnect. It was confirmed that none of the available commercial steels seem to be suitable for such application. Therefore, large efforts were put on the development of a new interconnect material. From this work, two suitable alloy compositions are given, which derived into two commercial (Crofer 22APU) and semi-commercial (JS3) batches that are currently under real SOFC tests. The obtained results confirm that high Cr contents are needed to overcome the high operation temperatures, ca. 800°C. At the same time, suitable additions of minor alloying elements are needed reducing the formation of volatile chromium species (Mn), strengthening the nearsurface zone of the alloy (Ti) and improving the scale adhesion (La). Additionally, other minor alloying elements, such as Al and Si may affect strongly the oxidation behaviour for these FeCrNIn(Ti/La) type alloys, thus they should be strongly controlled