HfB2-SiC ceramics fabricated by reactive melt infiltration and its long-term oxidation behavior at 1650°C

High-density HfB 2 -SiC ceramics were prepared by reactive melt infiltration (RMI) at a relatively low temperature (1500°C). The ceramics had the open porosity of 0.5 % and the uniform distribution of constituent phases. The long-term oxidation behavior of HfB 2 -SiC ceramics in air was investigated at 1650°C. After oxidation for 100 h, the weight gain rates of ceramics varied within the range of 1.30–2.26 %. The oxidation products included SiO 2 , HfO 2 , and HfSiO 4 phases, among which the HfSiO 4 compound possessed the higher stability resulting from the reaction between the HfO 2 and SiO 2 phases. The samples all exhibited the typical feature of layered scale structure after HfB 2 -SiC oxidation, which was composed of the outermost SiO 2 glass layer with the uneven thickness, followed by a relatively porous oxide layer containing white HfO 2 and slight HfSiO 4 , below it was the unoxidized HfB 2 -SiC. The presence of this multiphase glass layer endowed the samples with excellent oxidation resistance.