Oxidation of monolithic TiB2 and TiB2–20 wt.% MoSi2 composite at 850 °C

The isothermal oxidation behavior of monolithic TiB2 and TiB2–20 wt.% MoSi2 composite was evaluated at 850 °C in air. The monolithic TiB2 exhibited continuous weight gain with increasing time. The TiB2–MoSi2 composite showed continuous weight gain till 16 h and afterwards the weight gain decreased markedly. The weight loss observed in composite after 16 h has been related to the formation and subsequent vaporization of MoO3. The surfaces of the oxidized samples have been characterized by XRD and SEM. The XRD analysis indicated that the predominant phase present in the oxide was TiO2 (rutile). Cracking of the surface scales was observed for the composite and monolithic TiB2. Detailed SEM–EDS compositional analysis across oxide cross-section of the 64 h oxidized samples indicated enrichment of B2O3 on the surface of TiB2 and SiO2 in the case of the composite.