PNNL

Abstract

Over the past several years, advances in the design and fabrication of planar SOFCs have led to a steady reduction in the temperatures necessary for their operation. Consequently, it appears more realistic now to use low cost heat resistant alloys for interconnect sub-components in the SOFC stack. However, no specific criteria or inclusive study are available as a reference to help select and evaluate suitable candidates from the hundreds of available heat resistant alloy compositions, which overall demonstrate oxidation resistance at high temperatures. In this work, composition criteria have been proposed for pre-selection of heat resistant compositions, such as Ni-, Fe-, and Co-base superalloys, Cr-base alloys and stainless steels. The proposed criteria have been employed to establish a database of heat resistant alloys at PNNL, where a systematic approach has been initiated to evaluate and modify/develop metallic alloys for SOFC interconnect applications. The pre-selected compositions are further evaluated by referring our screening studies and published data. It appears that it would be very difficult for traditional alloys to fully satisfy the materials requirements for long-term operation at the intermediate temperature range of 700~850 degrees C. The applicability however can be improved through surface/bulk-modification and implementation of novel stack designs.