Investigation of Microstructural Features and Mechanical Characteristics of the Pressureless Sintered B(4)C/C(Graphite) Composites and the B(4)C-SiC-Si Composites Fabricated by the Silicon Infiltration Process

The B(4)C/C(graphite) composites were fabricated by employing a pressureless sintering process. The pressureless sintered B(4)C/C(graphite) composites exhibited extremely low mechanical characteristics. The liquid silicon infiltration technique was employed for enhancing the mechanical property of B(4)C/C(graphite) composites. Since the porosity of the B(4)C/C(graphite) composites was about 25–38%, the liquid silicon was able to infiltrate into the interior composites, thereby reacting with B(4)C and graphite to generate silicon carbide. Thus, boron carbide, silicon carbide, and residual silicon were sintered together forming B(4)C-SiC-Si composites. The pressureless sintered B(4)C/C(graphite) composites were transformed into the B(4)C-SiC-Si composites following the silicon infiltration process. This work comprises an investigation of the microstructure, phase composition, and mechanical characteristics of the pressureless sintered B(4)C/C(graphite) composites and B(4)C-SiC-Si composites. The XRD data demonstrated that the pressureless sintered bulks were composed of the B(4)C phase and graphite phase. The pressureless sintered B(4)C/C(graphite) composites exhibited a porous microstructure, an extremely low mechanical property, and low wear resistance. The XRD data of the B(4)C-SiC-Si specimens showed that silicon infiltrated specimens comprised a B(4)C phase, SiC phase, and residual Si. The B(4)C-SiC-Si composites manifested a compact and homogenous microstructure. The mechanical property of the B(4)C-SiC-Si composites was substantially enhanced in comparison to the pressureless sintered B(4)C/C(graphite) composites. The density, relative density, fracture strength, fracture toughness, elastic modulus, and Vickers hardness of the B(4)C-SiC-Si composites were notably enhanced as compared to the pressureless sintered B(4)C/C(graphite) composites. The B(4)C-SiC-Si composites also manifested outstanding resistance to wear as a consequence of silicon infiltration. The B(4)C-SiC-Si composites demonstrated excellent wear resistance and superior mechanical characteristics.