Fe含量对Fe_(x)Si_(y)改性C/C-ZrC-SiC复合材料的显微结构和烧蚀性能的影响

Effect of Fe content on microstructure and ablation properties of Fe_(x)Si_(y) modified C/C-ZrC-SiC composites

为了改善C/C-ZrC-SiC复合材料的烧蚀性能,采用反应熔渗法(RMI)在1850℃制得一种新型耗散防热Fe_(x)Si_(y)改性C/C-ZrC-SiC复合材料,并研究熔渗母料中Fe含量的变化对该复合材料显微结构和烧蚀性能的影响。结果表明:随着熔渗母料中Fe含量的升高,复合材料的密度呈现先降低后增加的趋势。当Fe含量超过6%(摩尔分数)时,沿垂直无纬布方向,复合材料中出现独立于SiC和ZrC之间的Fe_(x)Si_(y)C固溶相,其相含量随Fe含量的升高而增多;沿平行无纬布方向,复合材料中发现众多以灰色Fe_(x)Si_(y)C相间隔的“团粒型”排布的ZrC相,其粒径约为10μm。通过对不同Fe含量的Fe_(x)Si_(y)改性C/C-ZrC-SiC复合材料烧蚀性能进行表征,结果表明,当Fe含量为8.5%(摩尔分数)时,Fe_(x)Si_(y)改性C/C-ZrC-SiC复合材料的烧蚀性能最佳,质量烧蚀率和线烧蚀率分别为2.3×10^(−3) g/s和0.7×10^(−3) mm/s,相比纯C/C-ZrC-SiC复合材料分别降低3.6×10^(−3) g/s和3.61×10^(−3) mm/s。其优异的抗烧蚀性能主要得益于低熔Fe_(x)Si_(y)相的耗氧耗热和SiO2熔体补偿,促使样品表面形成一层致密、低氧透过率的富SiO2层,避免基体的进一步烧蚀。

To improve the ablation performance of C/C-ZrC-SiC composites,a new type of dissipative heat-proof Fe_(x)Si_(y) 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 Fe_(x)Si_(y)C 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 Fe_(x)Si_(y)C are found in the composites,and the particle size is about 10μm.The ablative properties of Fe_(x)Si_(y) modified C/C-ZrC-SiC composites with different Fe content were characterized.The results show that the ablative properties of Fe_(x)Si_(y) 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 Fe_(x)Si_(y) 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.