High-temperature stress-rupture properties of a ferritic steel for solid oxide fuel cell interconnect

The high-temperature stress-rupture properties of a ferritic steel (Crofer 22 H) for use as an interconnect material in planar solid oxide fuel cells are investigated. Constant-load creep tests are carried out at 650 to 800°C For a given applied stress, the creep rupture time is decreased with an increase in temperature. The creep rupture time is well correlated with the applied stress by a simple power law for each testing temperature. The fitted power-law curves of 650-750 ^°C look somewhat parallel to each other while the curve of 800°C is steeper than the others. A greater reduction of creep strength in the long-life region is present at 800°C Larson-Miller relationship also does well in correlating the creep rupture time with applied stress and temperature. Fractographic and microstructural observations indicate such a significant reduction of creep strength in the long-life region at 800 ^°C can be partially attributed to a precipitate coarsening effect.