Oxidation behavior of multiphase Mo5SiB2 （T2）-based alloys at high temperatures

• Published in: Transactions of Nonferrous Metals Society of China 2007, Vol.17 (6), p.1242-1247
• Main Author: 王方 单爱党 董显平 吴建生
• Format: Article
• Language: English
• Subjects: MosSiB2合金; 微观结构; 氧化作用; 金属间化合
• ISSN: 1003-6326

Two MosSiB2 （T2）-based alloys with nominal compositions of Mo-12.5Si-25B and Mo-14Si-28B （molar fraction, %） were prepared in an arc-melting furnace, and their oxidation kinetics from 1 000 to 1 300 ℃ were studied. The microstructures of the alloys were characterized by X-ray diffractometry（XRD） and scanning electron microscopy（SEM） with energy dispersive spectroscopy （EDS）. The oxide scales of both alloys oxidized at 1 200 ℃ for l0 min, 2 h and 100 h were investigated by surface XRD and cross-sectional SEM-EDS. The results show that the matrix of both alloys consists of T2. The dispersions of Mo-12.5Si-25B alloy are Mo and Mo3Si, and the dispersions of Mo-14Si-28B alloy are MosSi3 （T1） and MoB. The cyclic oxidation kinetics data exhibit initial rapid mass loss followed by slow mass loss. The mass loss of Mo-12.5Si-25B alloy is much faster than that of Mo-14Si-28B alloy at 1 200 and 1 300 ~C. For l0 min exposure, both alloys form irregular and porous thin scale. For 2 h exposure, Mo-12.5Si-25B alloy forms irregular thin scale and the scale contains large cracks, and Mo-14Si-28B alloy forms sound and continuous scale. For 100 h exposure, Mo-12.5Si-25B and Mo-14Si-28B alloys form sound and continuous scale about 50-75 μm and 40-45 μm in thickness, respectively. The better oxidation resistance of Mo-14Si-28B alloy is due to a sound and continuous B-SiO2 layer formation in the early stage of oxidation.