Effects of oxygen and water vapour on adhesion of scale grown on ferritic stainless steels in solid oxide fuel cells

Abstract

The adhesion of thermal oxide scale grown at 800°C on ferritic stainless steel AISI 441 proposed as SOFCs interconnectors was investigated. The influence of oxidising atmosphere was considered by 20% O2-N2 or 20% H2O-N2 as the representative cathode and anode atmospheres, respectively. A tensile test in an SEM chamber was used to assess the adhesion behaviour. The spallation of oxide scale on AISI 441 has to important as the candidate of interconnectors in SOFCs. The adhesion energy was considered as strain energy stored in the oxide, which was calculated at the first spallation of scale. The adhesion energy of scale on steel substrate was shown in the range of 173-214 J m-2. The adhesion energy of scale on steel oxidised in water vapour was higher than that in oxygen. This might be due to the presence of a silica layer at the scale-steel interface of steel oxidised in water vapour. The qualitative assessment of scale adhesion in terms of strain initiating the first spallation suggested the good adhesion behaviour of scale grown in the anode atmosphere.