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

Abstract

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.