Isothermal and cyclic oxidation behaviours of MoSi2 with additions of B at 1250 degrees C prepared by spark plasma sintering

摘要

Mo-Si-B alloys were obtained by spark plasma sintering (SPS) using Mo-57Si-10B and Mo-52Si-15B alloy powders, and the effects of the B content and powder size on the isothermal and cyclic oxidation behaviours of the Mo-Si-B alloys at 1250 degrees C were investigated. A SiO2 phase was introduced during the SPS process and the Mo-Si-B alloys consisted of a fine MoSi2/Mo2B5/MoB/SiO2 microstructure. Under isothermal and cyclic oxidation conditions, the kinetic curves of the SPS Mo-Si-B alloys exhibited parabolic time dependence on the weight gain. The increase in the nominal B caused a decrease in the incubation stage of the formation of continuously protective borosilicate layer but increased the mass gain due to the higher fluidity of the borosilicate layer. The SiO2 phase was found to supply the borosilicate layer with a "Mechanical locking" mechanism through the spilling of the SiO2 phase in the SPS samples, especially under the cyclic oxidation condition.