Preliminary investigation on development of functionally graded cemented tungsten carbide with solid lubricant via ball milling and spark plasma sintering

Abstract

Functionally graded cemented tungsten carbide belongs to a hybrid Functionally Graded Materials family. However synthesis of functionally graded cemented tungsten carbide is a great challenge due to possibility of “Co migration” and CaF2 vaporization during liquid phase sintering. Hence the present work deals with the development of nanocrystalline materials using ball milling and consolidation of milled material by Spark Plasma Sintering (SPS) for the preparation of functionally graded cemented tungsten carbide. The effects of ball milling and contents of Co, CaF2 and WC on WC/Co/CaF2 powder mixture were analyzed. Grain morphology, particle size, micro-strain, crystallite size, etc. of milled samples were investigated using scanning electron microscopy and X-Ray diffraction techniques. In addition to that, density, microstructure, hardness, fracture toughness and residual stress of consolidated sample are also reported. These tests confirm the formation of nanocrystalline particles and sub-sequent consolidation of functionally graded cemented tungsten carbide with solid lubricant. Hence ball milling with SPS is a prominent and viable process combination for the preparation of functionally graded cemented tungsten carbide.