Fabrication and characterization of B4C-based ceramic composites with different mass fractions of hexagonal boron nitride

In this paper, hexagonal boron nitride (hBN) was introduced into boron carbide (B4C) and B4C-based ceramic composites with different mass fractions of hBN were fabricated via hot pressing. The phase composition, microstructures, mechanical properties, and machinability of the B4C-based ceramic composites were investigated. The tribological properties of the B4C-based ceramic composites against AISI 321 austenitic stainless steel under dry sliding conditions were also studied. It was found that, with increasing the content of hBN, the bulk density, relative density, bending strength, fracture toughness and Vickers hardness of the B4C-based ceramic composites decreased, while the porosity increased. When the content of hBN came up to 20 wt%, the B4C-based ceramic composites could be machined easily by using cemented carbide drills. The addition of hBN into the B4C matrix improved the tribological properties of the B4C-based ceramic composites due to the formation of a tribofilm consisting of boron and metal oxides.