Oxidation and Scale Adhesion of a Type 430 Stainless Steel in Ar–CO2 Gas Mixtures at 800 °C

Abstract

Biogas is an alternative source of fuel potentially used to run solid oxide fuel cells (SOFCs). It mainly consists of CH4 and CO2 which can degrade the SOFC interconnect, which is typically made of stainless steel. To investigate the effect of each gas constituent, we focussed here on the effect of CO2 on high-temperature oxidation behavior of and scale adhesion on the stainless steel interconnect, Type 430 stainless steel. The samples studied were oxidised in CO2 at contents of 5–100% at 800 °C. The oxidation kinetics were found to be parabolic with the rate constant increasing when the CO2 content increased. The scale adhesion was assessed using a tensile-test method. The scale formed in the atmosphere containing higher CO2 content exhibited poorer scale adhesion, as indicated by a lower strain initiating the first spallation and a larger spallation percentage after the first spallation took place. The worsened scale adhesion relates to pores formed at the scale/steel interface. The adhesion energies were further quantified giving the values of about 40–100 J m–2. Oxidation mechanisms were suggested based on the dependence of the parabolic rate constant on the oxygen partial pressure and the inward diffusion of carbon-bearing species.