Oxidation Kinetics and Composite Scale Formation in the System Mo(Al,Si)2

The oxidation kinetics of hot‐pressed Mo(Al0.01Si0.99)2 and Mo(Al0.1Si0.9)2 were measured at 480°C, and between 1200° and 1600°C. The qualitative oxidation of arc‐melted Mo(Al0.1Si0.9)2, Mo(Al0.3Si0.7)2, Mo(Al0.5Si0.5)2, and Mo3Al8 was examined after 600°C for 1000 h in air. At all temperatures, the compositional difference between the materials yielded very different oxidation rates and scale microstructures. At 1400° and 1500°C, microstructural evolution of the oxide scales resulted in improved oxidation resistance at long times (>400 h). At these temperatures, a significant reduction in the long‐time oxidation kinetics was correlated with the in situ formation of an inner mullite scale. At 480° and 600°C, oxidation resistance improved significantly with increasing aluminum concentration. Contrary to the behavior of MoSi2, samples of Mo(Al0.01Si0.99)2 did not demonstrate catastrophic oxidation, and samples of Mo(Al0.1Si0.9)2 were very oxidation resistant.