Application of the ferritic steels for the stack fabrication

The application of ferritic steels as interconnect in solid oxide fuel cell is desirable because of the low material costs and inexpensive manufacturing. The commercially available steels 1.4742, 1.4845, Crofer 22 and ZMG232 as well as alloy IT-02 (Fa. Plansee) were tested as candidates for interconnector plates. The thermal expansion coefficients, oxidation behavior at 850 deg C, oxide layer resistance as function of time at 850 deg C and microstructure were investigated. The most suitable steels (IT-02, ZMG232, Crofer 22) have been tested as interconnector plates in one-cell stacks using electrolyte (5 mol% Y2O3- ZrO2) supported MEAs. Steels 1.4845, ZMG232, Crofer 22 and alloy IT02 have acceptable resistances of their oxide layers. Steel 1.4742 had too high resistance of the oxide layer and 1.4845 has a too high thermal expansion coefficient for use in the SOFC. The stacks made from IT-02, ZMG232 and Crofer22 showed similar performance and no degradation during 100 h of operation and after one thermal cycle.