Enhancing stability of Co gradient in nano-structured WC–Co functionally graded composites using graphene additives

摘要

A new approach for stabilizing a predesigned Co gradient in the microstructure of nano WC–Co thinning structure via graphene additions is presented. For this purpose, laminated specimens of green WC–Co functionally graded material, having three layers structured, with and without graphene additions in the intermediate layer were sintered at solid and liquid sintering temperatures of 1290 and 1400°C, respectively, using the hot isostatic pressing technique (HIP). With graphene additions, the mean average grain size of WC matrix phase is reduced, a new inter-phase layer is created and the amplitude of predesigned Co gradient, which had lost during liquid phase sintering of graphene-free WC–Co composite, is maintained through the cross section of the predesigned structure. As a consequence, the liquid state sintered specimens containing graphene show better hardness to toughness relationships compared to the graphene-free specimens fabricated under the same processing conditions. Such improvements are attributed to the extraordinary thermo-mechanical properties of graphene, and its beneficial role in grain refinement and creation of inter-phase layer that enables the stabilization of the predesigned Co-gradient.