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Abstract <p>The effect of the content of SiC additives to HfB<sub>2</sub> and their physicochemical properties (grain morphology and size of SiC powders, content and composition of their impurities, 6H or β crystal structure) on the level of compaction in hot-pressed ultra-high-temperature HfB<sub>2</sub>–SiC composites, their mechanical properties (hardness, fracture toughness, Young modulus), and heat resistance (resistance to ablation) under heating in air to high temperature with a gas burner was studied. The Vickers microhardness <i>H</i><sub>V</sub> and fracture toughness <i>K</i><sub>Ic</sub> of the best from the developed composites were, respectively, <i>H</i><sub>V</sub> = 38.6 ± 2.5 GPa and <i>K</i><sub>Ic</sub> = 7.7 ± 0.9 MPa m<sup>0.5</sup> (after the indentor load of 9.8&#xa0;N), and the Young modulus is 510 GPa. This composite was synthesized from a HfB<sub>2</sub>–30 wt % SiC (5–10 µm) mixture under hot pressing (at a pressure of 30 MPa, 1950°C, 30 min) and had a density of 6.54 g/cm<sup>3</sup>. The studies of resistance to ablation in air for hot-pressed HfB<sub>2</sub> and HfB<sub>2</sub>–SiC specimens heated with a gas burner show that HfB<sub>2</sub> ceramic with addition of 30 wt % SiC and an average grain size of 30–50 µm (clastic grains with sharp edges and an approximate stoichiometry SiC<sub>1.6</sub>O<sub>0.1</sub>, 6_H SiC) and 5–10 µm (single-crystal grains with a hypercubic nearly spherical shape almost free from impurities with an approximate stoichiometry SiC<sub>1,5</sub>, β-SiC) are highly refractory: they are resistant to the temperatures of 2766 and 2780°C, respectively, at a mass loss of 0.25 mg/s as compared to the HfB<sub>2</sub> ceramic free from additives, the specimens from which were cracked as soon as at a temperature of 1870°C, and also more resistant than the HfB<sub>2</sub>–30 wt % SiC ceramic synthesized with addition of SiC with sharp clastic grains with a size of 1 µm (with a shape lamellar or strongly elongated in one direction and an approximate stoichiometry SiC<sub>4.6</sub>O<sub>0.75</sub>, 6H-SiC) or 3–10 µm (with an approximate stoichiometry SiC<sub>2.3</sub>O<sub>0.25</sub>, 6H-SiC), which was cracked as soon as at a temperature of 1787 and 1455°C, respectively. A better heat resistance (resistance to ablation) exhibited by the HfB<sub>2</sub>–SiC ceramic with addition of certain SiC types can be explained by high hardness and Young modulus values, the formation of solid solutions on the basis of HfB<sub>2</sub> and SiC phases with a small quantity of impurity oxygen, and the distribution of the present phases over the volume of the composite.</p>

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Effect of the SiC Content and Physicochemical Properties on the Heat Resistance and Mechanical Characteristics of Ultra-High-Temperature HfB2–SiC Composites Synthesized by Hot Pressing

  • 期刊论文

  • 发表日期：

    2026年2月1日

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  • P. P. Barvitskyi,
  • T. O. Prikhna,
  • H. Ünsal,
  • V. E. Moshchil,
  • M. Hičák,
  • P. Tatarko,
  • M. V. Karpets,
  • A. S. Lokatkina,
  • V. M. Kolodnitskyi,
  • V. V. Bilorusets,
  • S. S. Ponomaryov,
  • L. M. Devin,
  • S. V. Rychev,
  • O. V. Prysiazhna,
  • A. A. Marchenko

摘要

Abstract

The effect of the content of SiC additives to HfB2 and their physicochemical properties (grain morphology and size of SiC powders, content and composition of their impurities, 6H or β crystal structure) on the level of compaction in hot-pressed ultra-high-temperature HfB2–SiC composites, their mechanical properties (hardness, fracture toughness, Young modulus), and heat resistance (resistance to ablation) under heating in air to high temperature with a gas burner was studied. The Vickers microhardness HV and fracture toughness KIc of the best from the developed composites were, respectively, HV = 38.6 ± 2.5 GPa and KIc = 7.7 ± 0.9 MPa m0.5 (after the indentor load of 9.8 N), and the Young modulus is 510 GPa. This composite was synthesized from a HfB2–30 wt % SiC (5–10 µm) mixture under hot pressing (at a pressure of 30 MPa, 1950°C, 30 min) and had a density of 6.54 g/cm3. The studies of resistance to ablation in air for hot-pressed HfB2 and HfB2–SiC specimens heated with a gas burner show that HfB2 ceramic with addition of 30 wt % SiC and an average grain size of 30–50 µm (clastic grains with sharp edges and an approximate stoichiometry SiC1.6O0.1, 6_H SiC) and 5–10 µm (single-crystal grains with a hypercubic nearly spherical shape almost free from impurities with an approximate stoichiometry SiC1,5, β-SiC) are highly refractory: they are resistant to the temperatures of 2766 and 2780°C, respectively, at a mass loss of 0.25 mg/s as compared to the HfB2 ceramic free from additives, the specimens from which were cracked as soon as at a temperature of 1870°C, and also more resistant than the HfB2–30 wt % SiC ceramic synthesized with addition of SiC with sharp clastic grains with a size of 1 µm (with a shape lamellar or strongly elongated in one direction and an approximate stoichiometry SiC4.6O0.75, 6H-SiC) or 3–10 µm (with an approximate stoichiometry SiC2.3O0.25, 6H-SiC), which was cracked as soon as at a temperature of 1787 and 1455°C, respectively. A better heat resistance (resistance to ablation) exhibited by the HfB2–SiC ceramic with addition of certain SiC types can be explained by high hardness and Young modulus values, the formation of solid solutions on the basis of HfB2 and SiC phases with a small quantity of impurity oxygen, and the distribution of the present phases over the volume of the composite.