SiCw toughened HfTaC2 composites prepared by a one-step spark plasma sintering method: An effective strategy for synchronous enhanced mechanical and ablation resistance

Abstract

Ultra-high-temperature HfTaC₂ solid solution ceramics are promised as coating materials for thermal protection systems of space vehicles due to their ultrahigh melting point and high modulus. However, the inherent brittleness of HfTaC₂ ceramic significantly limits its applications in the aerospace field. To solve this problem, a silicon carbide whisker toughened HfTaC₂ composite was fabricated by a one-step spark plasma sintering method. The mechanical properties and ablation resistance of the SiC_w-HfTaC₂ composites were investigated, respectively. The results shows that the introduction of 30 vol% SiC_w increased its fracture toughness from 2.67 MPa m^1/2 to 5.33 MPa m^1/2 due to the hindering effect of whiskers on crack propagation. The ablation resistance of SiC_w-HfTaC₂ composites is superior to that of HfTaC₂ ceramic under the heat flux density of 2.38 MW/m². Since SiO₂ glass generated by the oxidation of SiC_w could fill the micropores in the Hf-Ta-O ablation layer, thereby a dense Hf-Ta-Si-O oxygen diffusion barrier layer was induced to be formed on the surface of SiC_w-HfTaC₂ composites during ablation. Compared to HfTaC₂ ceramic, the mass ablation rate (0.44 mg s⁻¹) and linear ablation rate (−2.17 μm s⁻¹) of the 30 vol% SiC_w-HfTaC₂ composite were decreased by 35.3 % and 57.2 %, which also were lowest than that of 10, 20, 40 vol% SiC_w-HfTaC₂ composites, respectively.