Growth Rates and Electrical Conductivity of Oxide Scales on Ferritic Steels Proposed as Interconnect Materials for SOFCs

摘要

The oxidation behaviour of two ferritic steel variants was studied at 800℃ in air. The scale formation mechanisms were investigated during oxidation times ranging from a few minutes up to 6000 hours. For scale characterization a number of conventional analysis techniques such as optical metallography, scanning electron microscopy and x-ray diffraction was used in combination with two-stage oxidation studies using ~(18)O-tracer. It was found that the oxidation rates were not only governed by the main scale forming alloying elements Cr and Mn, but to a substantial extent by the minor additions of Si and Al. At the studied temperature of 800℃ these elements affect the growth rates of the scales although they are not directly incorporated in the surface scales. However, independent of the detailed alloy composition, the conductivity of the scales on the ferritic steels are generally higher than that of pure chromia.