Effect of HfC Content on the Elevated-Temperature Ablation Behavior of W-HfC Composites

The effects of HfC content on the ablation resistance of W-HfC composites were systematically studied. The oxy-acetylene flame ablation test was conducted at 2800 °C. Post-ablation samples were characterized via XRD, section morphology, and EDS. W-10HfC showed the best ablation resistance, with a linear ablation rate of just 0.0175 mm/s. This enhanced performance is attributed to the formation of a dense HfW2O8 oxide layer with negative thermal expansion properties, reinforced by uniformly dispersed blocky HfO2 particles. However, excessive HfC content induces a stratified oxide structure. The thermal expansion coefficient mismatch between HfW2O8 and HfO2 causes microcrack formation, ultimately degrading ablation resistance. These findings establish critical guidelines for HfC content optimization in W-HfC composite design.