Microstructure and properties of hot pressed TiB2 and SiC reinforced B4C–based composites

Abstract

B4C ceramics were strengthened by introducing the hard second–phase particles TiB2 and SiC, and the effects of TiB2 and SiC contents on the microstructure and properties of the composites were investigated. B4C–TiB2 binary composites with TiB2 contents of 10, 20, 30, and 40 vol% were prepared by hot pressing. The microstructure, mechanical properties, and electrical properties of the composites with different TiB2 contents were investigated and compared. The results showed that the B4C–30 vol%TiB2 composite obtained the best comprehensive properties, with a relative density, hardness, bending strength, fracture toughness, and conductivity of 97.9 %, 29.5 GPa, 590 MPa, 6.41 MPa m1/2, and 7.6 × 104 S/m. The compressive stress generated on B4C, crack deflection induced by TiB2, and conductive network formed by TiB2 are of great significance in the context of the properties of the B4C–TiB2 composites. In addition, B4C–TiB2–SiC ternary composites with SiC contents of 0, 10, and 20 vol% were also fabricated by hot pressing. The effect of SiC content on the microstructure and mechanical properties, and the effect of SiC on the antioxidant properties of the composites were investigated. The results showed that the B4C–30 vol%TiB2–10 vol%SiC composite had the best comprehensive properties, with a relative density, hardness, flexural strength, fracture toughness, and residual flexural strength (1600 ℃) of 98.8 %, 29.5 GPa, 621 MPa, 6.80 MPa m1/2, and 465 MPa. The inhibition of the growth of SiC to other grains, removal of oxide impurities, and repair of damage by SiC oxidation products play an important role in the performance of the B4C–TiB2–SiC composites.