(1.School of Mechanical and Electrical Engineering, Shaanxi University of Science & Technology, Xi’an 710021, China) (2. National Joint Engineering Research Center for Abrasion Control and Molding of Metal Materials, Henan University of Science and Technology, Luoyang 471000, China)
To improve the mechanical properties of B4C based ceramics, B4C-20wt%SiC composite ceramics were prepared by hot-pressing sintering under different pressures (30, 35 and 40 MPa), and the physical-mechanical properties of composite ceramics were studied. The Archimedes method, indentation method, three-point bending method and single edge notched beam (SENB) method were used to test the density, porosity, Vickers hardness, bending strength and fracture toughness of the composites. SEM and XRD methods were used to analyze the microstructure, phase composition and fractured morphologies of the B4CSiC composite ceramics. The results showed that the B4C-SiC composite ceramics were mainly composed of B4C phases and SiC phases, and their microstructure became denser with the increase of sintering pressure. When the sintering pressure increased from 30 to 40 MPa, the density of B4C-SiC composite ceramics increased from 2.22 to 2.64 g·cm-3, the porosity decreased from 1.47% to 1.02%, the Vickers hardness increased from 17.0 to 32.6 GPa, the bending strength increased from 312.7 to 447.6 MPa, and the fracture toughness increased from 4.79 to 7.21 MPa·m1/2. When the sintering pressure was 40 MPa, the crack deflection phenomenon was significantly observed on the fracture morphology of the composite, and the reason for this phenomenon may be related to the dense microstructure and the thermal expansion coefficient mismatch between B4C and SiC phases.