Preparation and hydrothermal corrosion behavior of Cf/SiCN and Cf/SiHfBCN ceramic matrix composites

Cf/SiCN and Cf/SiHfBCN-based ceramic matrix composites (CMC) were fabricated using the precursor infiltration and pyrolysis technique (PIP). Their behavior in subcritical hydrothermal conditions was investigated at 150–250 °C using exposition times of 48, 96 and 240 h and shown to rely on active corrosion. The data of the mass loss as a function of the corrosion time and temperature at S/V of 0.075 were used to rationalize the corrosion kinetics of the CMCs. Both materials have been shown to exhibit excellent stability in subcritical hydrothermal conditions. The corrosion rates of Cf/SiHfBCN were lower than those determined for Cf/SiCN; furthermore, SEM investigation indicates that spallation occurred in the Cf/SiCN samples; whereas the ceramic matrix was still attached on the individual carbon fibers in Cf/SiHfBCN. The results indicate that the incorporation of Hf and B into SiCN matrix leads to a significant improvement of its hydrothermal corrosion performance.