Microstructure and ablation resistance of HfCN-modified C/C composites prepared via slurry impregnation-assisted reactive melt infiltration

To improve the tolerance capacity of thermal protection system in ultra-high temperature environment, slurry impregnation-assisted reactive melt infiltration (SIRMI) process was adopted to simultaneously realize the ceramic modification of C/C composites and preparation of HfC_0.54N_0.46 coating. Compared with the in-situ HfC coating, the formed HfC_0.54N_0.46 coating exhibits higher hardness (23.2 GPa) and elastic modulus (240.8 GPa), along with improved toughness reflected by higher H/E and H³/E² values. The HCN sample exhibits lower linear ablation rate of −4.09 μm/s, representing a 14.4% reduction than HC sample (−4.78 μm/s). The enhanced toughness of HCN suppresses the formation of through-thickness cracks during ablation, making the formed oxide sacle consisting of intact outer layer and dense inner layer. This oxide structure endows HCN an advantage in ablation resistance over HC.