Oxidation behavior of a Mo(Si,Al)2 composite at 900–1600 C in dry air

The oxidation of a Mo(Si,Al)2-based compositeis investigated in the temperature range 900–1600 C indry air. Exposure time was 72 h. Comparisons are madewith the oxidation behavior of a conventional MoSi2-basedmaterial. Cross-sections are examined with scanning electronmicroscopy and transmission electron microscopy; thephase composition is analyzed by X-ray diffraction andconvergent beam electron diffraction. The material forms acontinuous external a-alumina scale throughout the temperature range. Below the scale, there is a continuousMo5(Si,Al)3 layer that overlies Mo(Si,Al)2 in the bulk. TheMo(Si,Al)2 phase immediately beneath the Mo5(Si,Al)3layer is depleted in Al. No indications of MoO3 volatilization could be found for the Mo(Si,Al)2 materia