Investigation of Oxide-Nucleation on Ferritic FeCr Interconnect Alloys for Solid Oxide Fuel Cells Exposed to Anode and Cathode Gases at 850°C

Abstract

In recent years solid-oxide fuel cell (SOFC) interconnect components have proven to be a key-component accountable for the functionality of high temperature fuel cells. Amongst adequate thermal expansion and high temperature strength, highest oxidation resistance in anode and cathode gases under thermal cycling conditions is required in order to reach long term durability, particularly when using thin film light-weight components with particular focus on automotive applications. In order to match the challenging parameter profile Plansee developed the mechanically alloyed ITM, a ferritic P/M Fe26Cr alloy strengthened with additions of Y2O3 dispersoids, since it has been observed that apart from their HT strengthening effect, which is of specific interest for thin sheets components, finest ODS particles reduce the growth and enhance the adhesion of the forming oxide layers. The latter effect is of particular interest in applications where alloys are exposed to HT cyclic conditions. In this work the nucleation phase of the oxide scale formation on P/M ODS Fe26Cr ITM is compared to that on a reference ingot steel Fe22Cr in typical anode gases containing significant amounts of H2, CO and approximately 3% H2O as well as in laboratory air at 850°C. Thermal cycling oxidation tests following the COTEST standard up to 168h are carried out in both environments. Moreover cyclic oxidation tests are performed in dry anode gas. Detailed studies of oxide scale formation and evolution by means of electron microscopy of cross sections as well as oxide surfaces are undertaken.