Effect of Oxidation on Creep Strength and Resistivity of Porous Fe-26Cr-1Mo

Abstract

To investigate its application as a material for solid oxide fuel cell interconnects, oxidation rates of replicated E-Brite (Fe-26Cr-1Mo, wt pct) foams with 43 and 51 pct open porosity were measured in static laboratory air for up to 200 hours. Results correlate well with previously reported values for dense material when normalized by surface area. Area-specific resistance measurements, taken in the range of 823 K to 1073 K (550 °C to 800 °C) after 24 hours of oxidation at 1123 K (850 °C), yield activation energies in the range 69 to 82 kJ mol−1 for porous E-Brite that closely match dense E-Brite. Compressive creep properties, measured at 1073 K (800 °C) for pristine and oxidized porous E-Brite, show that pre-oxidation (10 hours at 1073 K (800 °C)) led to a ~100-fold decrease in creep rate. This is due to strengthening of the alloy foam by the formation of a continuous network of oxide, which coats the internal pore surface and reduces porosity by as much as 10 pct after 200 hours of oxidation at 1073 K (800 °C). Choking of the fenestrations between the pores, however, leads to an increase in closed porosity. Strengthening and pore filling effects should be taken into account in the design of the SOFC stack when using E-Brite as a porous interconnect material.