Oxidation of reaction-bonded silicon carbide-boron carbide in air

Abstract The oxidation behaviour of reaction-bonded silicon carbide-boron carbide (RBSBC) in air for durations of 5–96 was investigated in the temperature range of 1250–1350 °C. Scanning electron microscopy observations showed that the oxide layer became uniform after 48 h, with a thickness of 3–5 μm. Transmission electron microscopy, Raman spectroscopy, and secondary ion mass spectroscopy analyses showed that the addition of 7 wt% B4C and a (SiC + Si)/B4C ratio of ∼13 resulted in an amorphous silica-rich borosilicate layer with no phase segregation and random mixing of the borates in the silica network. The oxidation kinetics profile was parabolic, where the transport of ionic oxygen is the rate-controlling step for oxide growth. The oxidation kinetics and activation energy of 353 kJ mol‒1 are close to those reported for CVD-SiC and siliconised-SiC, suggesting that the oxide behaves like pure silica. RBSBC with 7% B4C can provide a more economical alternative to SiC materials for oxidation-resistant applications, with a lower density.