Effect of high-temperature preoxidation treatment on the low-temperature oxidation behavior of a MoSi2-based composite at 500 °C

In order to investigate the effect of protective scale formed by high-temperature preoxidation process on the low-temperature oxidation behavior of a MoSi2-based composite, the oxidation experiment at 500 °C in air was performed by employing X-ray diffraction, scanning electron microscopy and thermo-gravimetric analysis. The results show that the preferred low-temperature oxidation/pest sites are the externally cylindrical face of the sample without high-temperature preoxidation treatment. With the prolonging of oxidation, the pest advances radially in cylinder sample. When the oxidation time reaches 288 h, the mass gain is arrived at 0.466 mg cm−2. A glass protective scale is formed on the surface of material by high-temperature preoxidation treatment. The scale can play a role of barrier layer of oxygen. This results in a reduced rate of low-temperature oxidation, and the pest is restrained. When the oxidation has been for 288 h, the mass gain of high-temperature preoxidation sample is only −0.007 mg cm−2, and the surface microstructure is still smooth, without undergoing the pest oxidation. High-temperature preoxidation treatment can effectively restrain the low-temperature oxidation behavior, and avoid the pest phenomenon of MoSi2-based composite.