Mechanical Characteristics of High Pressure Sintered ZrB₂-TiB₂ and ZrB₂-SiC Composite Materials

The ZrB₂ and HfB₂ materials are promising for application in hypersonic aerospace, cutting tools, metallurgy, microelectronics and refractory industries. The structure and properties of sintered under high pressure (4 GPa) - high temperature (1800 ^oC) or HP-HT conditions ZrB₂, HfB_2,ZrB₂+30%TiB₂and ZrB₂-20% SiC refractory materials are under consideration. HP-HT sintered HfB₂ (a=0.3141, c=0.3473 nm γ=10.42 g/cm³) demonstrated hardness H_V(9.8 N)=21.27±0.84 GPa, H_V(49 N)=19.29±1.34 GPa, and H_V(98 N)=19.17±0.5 GPa and fracture toughness K_1C(9.8 N)=6.47 MN×m^0.5. High pressure sintered ZrB₂(a=0.3167 , c=0.3528 nm, γ=6.1 g/cm³) demonstrated H_V(9.8N)= 17.66±0.60 GPa, H_V(49 N)= 15.25±1.22 GPa, and H_V(98 N)= 15.32±0.36 GPa and K_1C(9.8 N)=3.64 MN×m^0.5. Addition of 30 wt.% of TiB₂ to ZrB₂ did not allow to increase hardness of the material essentially (H_V(9.8 N)=17.75±2.36 GPa, γ=5.29 g/cm³ ). Addition of 20 wt.% of SiC to ZrB₂and sintering under high pressure allowed essential increase of hardness to H_V(9.8 N)=24.18±0.7 GPa, H_V(49 N)=16.68±0.5 GPa, and H_V(98 N)=17.59±0.4 GPa and fracture toughness (K_1C(9.8 N)=6.49 ± 0.25 MN×m^0.5, K_1C(49 N)=7.06± 1.55 MN×m^0.5, K_1C(98 N)=6.18± 1.24 MN×m^0.5) of composite ZrB₂- SiC material (γ=5.03 g/cm³). The work is supported by Projects NATO SPS G5773; 03-03-20, ISM-29/20, III-3-20 (0779), of NASU.