Adhesion of oxide scales grown on ferritic stainless steels in solid oxide fuel cells temperature and atmosphere conditions

Adhesion of thermal oxide scales grown at 800 °C on ferritic stainless steels F18TNb (AISI 441) and F18MT (AISI 444) proposed as interconnectors in solid oxide fuel cells (SOFCs) was investigated. The effect of oxidising atmosphere – synthetic air or 2% H2O in H2 as the representative cathode and anode atmosphere respectively – was considered. Using a room temperature tensile test sitting in the SEM chamber, thermally grown oxide scales were forced to spall and their adhesion energy was derived. Adhesion energy, considered as the elastic energy per unit area stored in oxide was determined at the strain of first spallation or at the strain where the derivative of spallation versus strain was maximum. Adhesion energies were shown to lie in the range 10–100 J cm−2. Adhesion values exhibited decreasing values with increasing oxide thickness, with higher values for oxidation in 2% H2O/H2 compared to oxidation in synthetic air. The adhesion energy of scales on F18MT was lower than that on F18TNb due to the presence of Mo-containing intermetallic compounds at the metal/scale interface.