Effect of Fe content on microstructure and ablation properties of FexSiy modified C/C-ZrC-SiC composites

To improve the ablation performance of C/C-ZrC-SiC composites, a new type of dissipative heat-proof FexSiy modified C/C-ZrC-SiC composites was prepared by the reactive infiltration method (RMI) at 1850 ℃, and the effect of Fe content in the infiltration masterbatch on the microstructure and ablation properties was studied. The results indicate that, with the increase of Fe content, the density of the composites first decreases and then increases. When the Fe content exceeds 6% (mole fraction), the FexSiyC solid solution phase independent of SiC and ZrC appears in the vertical weft free direction, and the phase content increases with the increase of Fe content along the parallel weft free direction, many "granular" ZrC phases separated by gray FexSiyC are found in the composites, and the particle size is about 10 μm. The ablative properties of FexSiy modified C/C-ZrC-SiC composites with different Fe content were characterized. The results show that the ablative properties of FexSiy modified C/C-ZrC-SiC composites are the best when the Fe content is 8.5% (mole fraction), and the mass ablative rate and linear ablative rate are 2.3×10-3 g/s and 0.7×10-3 mm/s, respectively. Compared with the pure C/C-ZrC-SiC composites, the ablation rate was reduced by 3.6×10-3 g/s and 3.61×10-3 mm/s, respectively. Its excellent ablation resistance is mainly due to the oxygen and heat consumption of low melting FexSiy phase and the compensation of SiO2 melt, which promotes the formation of a dense SiO2 rich layer with low oxygen permeability on the surface of the sample to avoid further ablation of the matrix. © 2021, Science Press. All right reserved.