Obtaining ceramics from boron carbide with chromium-based additives (Cr3C2, CrB2)

This study presents the results of spark plasma sintering of powders within the boron–carbon–chromium system, focusing on boron carbide (B 4 C), chromium carbide (Cr 3 C 2 ), and chromium diboride (CrB 2 ). The powders were synthesized using the original vacuum-free direct current arc reactor, where the starting powder mixture was exposed to an arc discharge for 60 s under a direct current of 200 A. Bulk samples based on B 4 C and CrB 2 were sintered under identical conditions, with a temperature of 1800 °C and a pressure of 60 MPa, while the sintering of Cr 3 C 2 -based ceramics was conducted at 1300 °C and 30 MPa. In some cases, sintering additives – 25 wt. % Cr 3 C 2 and 20 wt. % CrB 2 – were introduced during the sintering of B 4 C-based bulk samples. The phase composition of the sintered samples was analyzed using X -ray diffraction (XRD), while the microstructure and elemental composition were examined via scanning electron microscopy (SEM). The hardness of the sintered ceramics was measured using a Vickers indenter under a load of 1 kg, revealing hardness values of 22.7 ± 1.8 GPa for B 4 C, 12.6 ± 0.3 GPa for CrB 2 , and 11.4 ± 0.1 GPa for Cr 3 C 2 . The introduction of 25 wt. % Cr 3 C 2 as a sintering additive in B 4 C-based ceramics reduced the hardness to 17.7 ± 5.6 GPa; however, it significantly improved the fracture toughness, increasing it from 2.5 ± 0.2 to 3.3 ± 0.3 MPa·m 1/2 . Conversely, the addition of 20 wt. % CrB 2 during B 4 C sintering led to an increase in the bulk sample’s hardness from 22.7 ± 1.8 GPa to 26.8 ± 1.3 GPa.