Investigation of the long-term Oxidation behaviour of Mo(Si,Al)2 composite at 1300°C and 1400°C

This study investigates the long-term oxidation behaviour of Mo(Si,Al)2-based composites with varying Alumina (Al2O3) additions. Samples are synthesised using laboratory and industrial methods and subjected to oxidation at 1300 and 1400 °C for up to 1000 h. Isothermal oxidation is conducted under passive conditions and electrical heating (furnace tests). Under both test environments, a dense external Al2O3 scale and an intermediate Mo5Si3 layer form, while the Mo(Si,Al)2 matrix remains stable. Increasing Al2O3 addition to the Mo(Si,Al)2-based composites coarsens surface grains and reduces the thickness of the intermediate layer without significantly affecting oxide scale growth. Aluminium (Al) depletion is observed in the Mo5Si3 layer. An Al gradient is built up between the bulk and regions close to the Mo5Si3 layer. Long-term oxidation during furnace tests results in a moderate increase in electrical resistivity. Overall, moderate Al2O3 reinforcements (5–10~wt%) within industrial synthesized Mo(Si,Al)2-based composites appear to offer the best compromise between oxidation resistance, phase stability, and microstructural homogeneity at both 1300 and 1400 °C.