Hard and tough ultrafine-grained B4C-cBN composites prepared by high-pressure sintering

Tough and hard ultrafine-grained B4C-cBN composites were firstly fabricated by high-pressure sintering mixed B4C and cBN nanopowders at 6 GPa and 1700 degrees C. The phase transition from cBN to hBN is avoided by high pressure during the sintering process. The effects of the cBN content on the densification and mechanical properties of B4C-cBN composites were evaluated. The results indicated that the hardness of the as-fabricated composites increased gradually with the increase of cBN content. The composite composed of 50 wt.% cBN exhibited excellent comprehensive mechanical properties with relative density of 98.6 %, density of 2.9 g/cm3, Vickers hardness of 36.2 GPa and fracture toughness of 6.7 MPa center dot m1/2. The introduction of superhard cBN maintained the lightweight and high hardness while enhancing the fracture toughness of the B4C. The main toughening mechanisms were crack bridging, crack deflection and pull-out of homogeneously dispersed cBN grains.

Automated summary

Tough and hard ultrafine-grained B4C-cBN composites were fabricated by high-pressure sintering, with the introduction of cBN enhancing the hardness and fracture toughness of the material. The composite with 50% cBN content exhibited excellent mechanical properties.