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

Abstract: 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 μm. 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 °C and 600 °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 °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/cm² for oxidation at 600 °C for 100 h, which corresponds to the excellent oxidation resistance. Graphic Abstract: [Figure not available: see fulltext.].