Machinable B4C/BN ceramic composites were fabricated by a hot-pressing process at 1,850 oC for 1 h under a pressure of 30MPa. In this article, the mechanical property, thermal shock behavior and machinability of the B4C/BN ceramic composites were investigated. The fracture strength and fracture toughness of B4C/BN nanocomposites were significantly improved in comparison with B4C/BN microcomposites. The Vickers hardness of B4C/BN nanocomposites and B4C/BN microcomposites decreased gradually with an increase in the content of h-BN, while the machinability of B4C/BN nanocomposites and B4C/BN microcomposites were significantly improved. The B4C/BN ceramic composites with an h-BN content of more than 20 wt% exhibited excellent machinability. The thermal shock resistance of the B4C/BN ceramic composites was much better than that of the B4C monolith, and the thermal shock resistance of B4C/BN nanocomposites was much better than that of B4C/BN microcomposites. The thermal shock temperature difference (ΔTc) of the B4C monolith was about 300 oC, while the ΔTc of B4C/BN microcomposites was about 500 oC and the ΔTc of B4C/BN nanocomposites was about 600 oC.

Keywords: Boron carbide, Boron nitride, Mechanical property, Thermal shock resistance, Machinability.