A review of liquid phase migration and methods for fabrication of functionally graded cemented tungsten carbide

Since functionally graded WC-Co (FG WC-Co) offers superior combinations of wear resistance, fracture toughness, and strength, and provides superior engineering performance over conventional homogeneous WC-Co, many processes have been developed to produce FG WC-Co, a few of which are commercialized today. However, with respect to the underlying principles on how the graded structures form in WC-Co, there are considerable gaps in understandings. Based on the most recent studies, the present authors examined the processes for making FG WC-Co and found that in most cases the formation of graded structure in WC-Co is achieved through liquid phase migration which can be induced by different techniques. Several representative FG WC-Co processes are reviewed and explained using the theory of liquid phase migration. A new process that induces liquid migration by carburizing fully sintered WC-Co is described. (c) 2012 Elsevier Ltd. All rights reserved.