Si3N4/MoSi2 Composite with superior long-term oxidation Resistance at 1500°C

The long-term high-temperature cyclic oxidation (100 cycles, 10 000 h, 1500°C) of a Si3N4 material and a Si3N4-MoSi2 composite, both fabricated with Y2O3 as a sintering additive, was studied. Both materials exhibited similar oxidation rates due to surface silica formation described by a nearly parabolic law and a total weight gain of 3 to 4 mg/cm² after 10 000 h. As the consequence of the oxidation processes in the bulk microstructural damage was found in the Si3N4 material. These effects were not observed in the composite material. The remarkable microstructural stability observed offer the high potential of Si3N4-MoSi2 composite materials for structural long term applications at elevated temperatures up to 1500°C.