Spark plasma sintering of hard wear-resistant graphene nanoplatelet-reinforced TiB2 + SiC composites from TiC-B4C-SiC

Graphene nanoplatelet (GNP)-reinforced TiB2 + SiC composites were fabricated by reactive spark plasma sintering (SPS) from a TiC-B4C-SiC powder mixture with equal-volume percentages, optimizing their SPS temperature and evaluating their unlubricated sliding wear against diamond. First, it is shown that during the heating ramp of the SPS cycle, TiC and B4C react according to the chemical reaction 2TiC + B4C -> 2TiB(2) + 3C, and that the thus-formed C is graphenized as GNPs, leading to composites with microstructures consisting of a ceramic matrix of fine TiB2 and SiC grains with abundant randomly oriented GNPs at grain boundaries. It is also shown that this reactive SPS is optimal at 2000 degrees C (under 75 MPa pressure and 5 min soaking), resulting in a very hard (similar to 28.5-29.9 GPa) and very tough (similar to 6.7(3) MPa m(1/2)) composite. And second, it is shown that these two properties and its proneness to develop an oxide tribolayer make this composite very resistant to unlubricated sliding wear against diamond (similar to 2.8(1)<middle dot>10(8) (N m)/mm(3)), undergoing only very mild two-body abrasion. Finally, opportunities for the fabrication of toughened and very hard ceramic composites for contact-mechanical and tribological applications are discussed.