Pressureless sintering of titanium carbide doped with boron or boron carbide

Abstract Titanium carbide ceramics with different contents of boron or B 4 C were pressureless sintered at temperatures from 2100 °C to 2300 °C. Due to the removal of oxide impurities, the onset temperature for TiC grain growth was lowered to 2100 °C and near fully dense (>98%) TiC ceramics were obtained at 2200 °C. TiB 2 platelets and graphite flakes were formed during sintering process. They retard TiC grains from fast growth and reduced the entrapped pores in TiC grains. Therefore, TiC doped with boron or B 4 C could achieve higher relative density (>99.5%) than pure TiC (96.67%) at 2300 °C. Mechanical properties including Vickers’ hardness, fracture toughness and flexural strength were investigated. Highest fracture toughness (4.79 ± 0.50 MPa m 1/2 ) and flexural strength (552.6 ± 23.1 MPa) have been obtained when TiC mixed with B 4 C by the mass ratio of 100:5.11. The main toughening mechanisms include crack deflection and pull-out of TiB 2 platelets.