A study of pest oxidation in polycrystalline MoSi_2
A study of pest oxidation in polycrystalline MoSi_2
复制标题
DOI：
10.1557/jmr.1992.2747
复制
发表时间：
1992-10
影响因子：
2.7
通讯作者：
C. G. Mckamey;P. Tortorelli;J. H. Devan;C. Carmichael
中科院分区：
文献类型：
--
作者：
C. G. Mckamey;P. Tortorelli;J. H. Devan;C. Carmichael
MoSi_2是一种很有前途的高温材料，具有低密度（6.3 g/cm^3）、高熔点（2020 °C）和在约1900 °C的温度下良好的抗氧化性。然而，在400 ° C和600 °C之间的中间温度范围内，它容易发生“有害”反应，这会通过氧化和断裂的组合引起灾难性的分解。在这项研究中，我们使用了多晶MoSi_2，由电弧铸造的纯元素和通过冷和热压的合金粉末，以表征害虫的反应，并确定成分，晶粒或相界，和物理缺陷的作用，在500 °C暴露于空气中的试样的氧化和断裂。结果表明，氧沿着沿着存在的裂纹和/或孔隙进入试样内部，并在那里反应生成MoO_3和SiO_2，从而发生分解。MoO_3在形成过程中产生的内应力使其分解成粉末。在化学计量比附近，对害虫崩解的敏感性随着钼含量的增加和密度的降低而增加。富硅合金即使在低至60%的密度下也能形成保护性的SiO_2，并且没有显示出崩解的迹象。
MoSi_2 is a promising high-temperature material with low density (6.3 g/cm^3), high melting point (2020 °C), and good oxidation resistance at temperatures to about 1900 °C. However, in the intermediate temperature range between 400 and 600 °C, it is susceptible to a “pest” reaction which causes catastrophic disintegration by a combination of oxidation and fracture. In this study, we have used polycrystalline MoSi_2, produced by arc-casting of the pure elements and by cold and hot pressing of alloy powders, to characterize the pest reaction and to determine the roles of composition, grain or phase boundaries, and physical defects on the oxidation and fracture of specimens exposed to air at 500 °C. It was found that pest disintegration occurs through transport of oxygen into the interior of the specimen along pre-existing cracks and/or pores, where it reacts to form MoO_3 and SiO_2. The internal stress produced during the formation of MoO_3 results in disintegration to powder. Near the stoichiometric ratio, the susceptibility to pest disintegration increases with increasing molybdenum content and with decreasing density. Silicon-rich alloys were able to form protective SiO_2 and showed no indication of disintegration, even at densities as low as 60%.