Oxidation behavior of a Mo(Si,Al)_2 composite at 900-1600 C in dry air

摘要

The oxidation of a Mo(Si,Al)_2-based composite is investigated in the temperature range 900-1600 C in dry air. Exposure time was 72 h. Comparisons are made with the oxidation behavior of a conventional MoSi _2-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 α-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 MoO_3 volatilization could be found for the Mo(Si,Al)_2 material.