Oxidation behavior of monolithic HfSi2 and SiC fiber-reinforced composites fabricated by melt infiltration using Si–8.5 at%Hf alloy at 800–1200°C in dry air

摘要

The low-temperature melt-infiltration method using eutectic Si alloys is a novel process of fabricating SiC fiber-reinforced SiC-based matrix composites (SiC_f/SiCs) for high-temperature structural applications. SiC_f/SiCs were fabricated by the melt-infiltration method using a eutectic Si–8.5 at%Hf alloy to evaluate their dry oxidation behavior at 800–1200°C for times ranging from 10–100 h. The oxidation behavior of monolithic HfSi₂ (Monolith) fabricated by spark plasma sintering was also evaluated in dry air. The oxidation behavior of the composite matrix and Monolith obeyed the parabolic law in dry conditions. The steps to form the oxidation layer were expected to produce HfO₂ and Si, followed by SiO₂, and, finally, HfSiO₄. The oxidation rate of the matrix was similar to that of Monolith and 102–104 times larger than that of Si. The oxidation activation energy employed in oxidation of HfSi₂ was calculated as 258 kJ/mol in dry air.