Abstract
B(4)C-HfB(2)-SiC (BCHS) ceramic composites were fabricated by in situ reaction with B(4)C and HfSi(2) mixed powders through spark plasma sintering in this work. Effects of sintering temperature and sintering additive (HfSi(2)) content on the density, microstructure, and mechanical properties of the BCHS specimens were studied. The BCHS composite containing 15-30 vol.% HfSi(2) reached over 98% theoretical density in the temperature range of 1600-1750 °C under the pressure of 50 MPa. The Vickers hardness, fracture toughness, and room temperature flexural strength of BCHS sintered at 1650 °C with 25 vol.% HfSi(2) reached a maximum value of 31.3 GPa, 5.6 MPa·m(1/2), and 573.9 MPa, respectively. The flexural strength was not decreased at elevated temperatures, and the flexural strength at temperatures of 400 °C, 600 °C, and 800 °C was evaluated to be 540.7 MPa, 518.8 MPa, and 586.9 MPa, respectively. Dense B(4)C-HfB(2)-SiC composites were fabricated by the spark plasma sintering process. The introduction of HfSi(2) can significantly enhance the density and mechanical properties of B(4)C ceramic.