Comparative insights into C/C–ZrC–SiC composites with different substrate carbon on microstructures, mechanical properties, and ablation behaviors

Abstract

The microstructures, mechanical properties, and ablation behaviors of carbon-fiber reinforced carbon and ZrC–SiC ceramic matrix composites (C/C–ZrC–SiC) fabricated through reactive melt infiltration were systematically researched, of which preforms were densified using different substrate carbon: (i) resin carbon (RdC) and (ii) pyrolitic carbon (PyC) for comparison. The results showed that the densification process with pores that differ in location and size dominated the distribution of ceramic phases within pristine carbon-fiber reinforced carbon (C/C). In addition, the C/C–ZrC–SiC samples with different carbon substrates possessed different mechanical properties. The flexural strength of the C/PyC-ZrC-SiC composites was significantly higher, exhibiting a ductile fracture behavior, which is different from that of the brittle fracture model in C/RdC-ZrC-SiC composites. However, after being exposed to an oxyacetylene ablation torch at 2500 °C for 30–240 s, the C/RdC-ZrC-SiC composites exhibited better ablation resistances because there were more carbon matrix and carbide blocks per unit volume in the composites, and the structure of C/RdC-ZrC-SiC possessed a shorter healing time for pores during ablation. In other words, an integrated oxide scale on the ablated surface can be formed in a relatively shorter time. Therefore, the superior ablation behavior can largely be ascribed to the formation of dense oxides containing molten-like SiO 2 , which could effectively resist scouring and seal the pores promptly during ablation.