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 composite is investigated in the temperature range 900-1600 degrees C in dry air. Exposure time was 72 h. Comparisons are made with the oxidation behavior of a conventional MoSi2-based material. Cross-sections are examined with scanning electron microscopy and transmission electron microscopy; the phase composition is analyzed by X-ray diffraction and convergent beam electron diffraction. The material forms a continuous external a-alumina scale throughout the temperature range. Below the scale, there is a continuous Mo-5(Si,Al)(3) layer that overlies Mo(Si,Al)(2) in the bulk. The Mo(Si,Al)(2) phase immediately beneath the Mo-5(Si,Al)(3) layer is depleted in Al. No indications of MoO3 volatilization could be found for the Mo(Si,Al)(2) material.