Improvement of 'Pest' Resistance of MoSi2 Intermetallic Compound at 500 degrees C and 600 degrees C via Addition of B Fabricated by Spark Plasma Sintering

摘要

Mo-Si-B alloys were obtained by spark plasma sintering (SPS) using fine Mo-Si-B alloy powders with a particle size of 2.5 mu m. The SPS Mo-Si-B alloys consisted of fine MoSi2/Mo2Bi5(Mo5Si3)/MoB/SiO2 phases. Under isothermal conditions, the weight-gain kinetics of the Mo-Si-B alloys obtained by SPS exhibited parabolic time dependence and these Mo-Si-B alloys showed better oxidation resistance at moderate temperatures of 500 degrees C and 600 degrees C with no "pest" failure. The oxide scale on the sample surface consisted of MoO3, amorphous borosilicate and crystalloid SiO2 phases. An increase in the oxidation temperature from 500 to 600 degrees C caused a significantly higher fluidity and a shorter incubation stage for the formation of a continuously protective borosilicate layer, so that the mass gain was smaller than 1 mg/cm(2) for oxidation at 600 degrees C for 100 h, which corresponds to the excellent oxidation resistance.