Advanced Microstructural Investigations of AISI 441 Early Stage Oxidation in Wet Atmosphere

• DOI: 10.4028/www.scientific.net/kem.728.3
• Publication Date: 2017-02-16T06:25:25Z
• Authors: Wichitra Wongpromrat; Valérie Parry; Walairat Chandra-...; Somrerk Chandra-A...; Alain Galerie; Yves Wouters
• Keywords: 01 natural sciences; 7. Clean energy; 0104 chemical sciences

AISI 441 ferritic stainless steel is a good candidate for metallic interconnects in solid oxide fuel cells (SOFCs). The minor elements Ti and Nb are used to stabilize the ferritic matrix and also to reduce creep by a combination of solid solution strengthening and precipitation of intermetallic Laves phase particles along the grain boundaries. However their influence on the oxidation behavior is not well understood. This study focuses on the early stages oxidation (from 4 to 24 h) at 800 °C of AISI 441 under 5% H2O in O2. A relatively smooth micro-crystallized oxide scale and Ti, Nb containing nodules are observed. The internal microstructure of these objects is studied by FIB tomography which allows computing cross sectional views in any direction of interest. FIB study reveals a complex microstructure and a development strongly linked to the presence of niobium and/or titanium in the substrate.