Ablation behavior and mechanism of C/C-HfC-SiC composites

•C/C composites modified by hafnium carbide and silicon carbide were fabricated.•Precursor infiltration and pyrolysis process was used for preparing the composites.•The composites were ablated under oxyacetylene flame.•The micro-structure evolution of the composites during ablation was discussed.•The effect of ablation products on the ablation properties was analyzed.

In order to investigate the ablation behavior and mechanism of carbon/carbon (C/C) composites modified by hafnium carbide (HfC) and silicon carbide (SiC), the composites were ablated by oxyacetylene flame for different time from 30 s to 120 s. Results show that linear ablation rate and mass ablation rate increased with ablation time prolonging. Two ablation regions were discussed: the center-most ablation region which was the most severely ablated and brim ablation region which was only slightly ablated. By analysis of the morphologies evolution of the two regions, it can be demonstrated that ablation products, hafnium oxide (HfO2) and silicon oxide (SiO2), acting as a protection layer for the composites, were produced. While the ablation products lost their protection gradually with ablation time going on. Moreover, mechanical denudation and thermal chemical ablation damaged more severely with ablation time prolonging.