Microstructure and mechanical properties of super-hard B4C ceramic fabricated by spark plasma sintering with (Ti3SiC2+Si) as sintering aid

B 4 C ceramics were fabricated by spark plasma sintering with 5% (Ti 3 SiC 2 +Si) as sintering aid. The effects of sintering temperatures and sintering aid on microstructures and properties of B 4 C ceramics were investigated. The results indicated that the addition of a small amount of (Ti 3 SiC 2 +Si) could effectively improve the sintering characteristic of B 4 C ceramics and reduce the sintering temperature. The as-sintered ceramics fabricated at 1700 °C exhibited excellent mechanical properties , including a super-high Vickers hardness of 38.4 GPa, a high flexural strength of 457.6 MPa and a good fracture toughness of 5.61 MPa m 0.5 . Following reasons may be responsible for the improvement of the hardness of B 4 C ceramics: high relative density due to the combination use of (Ti 3 SiC 2 +Si) sintering aids and SPS technology, fine-grained structure of the B 4 C ceramics benefited from the low sintering temperature, formation of the second phases TiB 2 and SiC by chemical reaction and existence of the nano-sized unit of (TiB 2 +SiC) in B 4 C grains.