Unravelling the oxidation behaviors of porous stainless steel 430L substrate for metal-supported solid oxide fuel cells

Abstract

Metal-supported solid oxide fuel cell (MS-SOFC) has been attracting increasing attention due to relatively low materials cost and robust mechanic strength particularly for mobile applications. However, long term stability has been an issue for its application. It is challenging to isolate the degradation behavior and predict maximum lifetime of the metal substrate when assembled as full cell since many parameters may affect cell performance and life expectancy. We systematically investigated and reported the long-term oxidation behavior of porous stainless steel 430 L for up to 1500 h at 800°C under dry and 3 vol% H2O humidified H2/Ar mixture (10 vol% H2) atmosphere to simulate its applications in MS-SOFC. Our results show that the surface oxide scale of the porous 430Lsubstrate in both atmospheres are dominated by Cr2O3 and small amounts of MnCr2O4 or FeCr2O4 spinel oxides depending on the gas conditions, where the oxidation process could be divided into three stages with distinct characteristics. Stepwise surface color change, morphology and thickness of the formed oxide scale, elemental migration and distribution along the bulk alloy/oxide scale interface, and oxidation kinetics as a function of exposure time are systematically and thoroughly studied at high resolution. Based on the measured weight gains and thicknesses, oxidation kinetic parameters are extracted. These kinetic parameters are not only valuable for understanding the oxidation rate of porous 430 L in high temperature applications such as in MS-SOFC, but also can be used to predict the life expectancy of 430 L supported SOFC device which is critical for real and long-term applications.