Microstructure and Morphology of Hardmetals

Mechanical properties of cemented carbides and cermets depend on the choice of their constituents and on their microstructure, especially the composition and distribution of the different phases. Such parameters as grain size, grain morphology, grain boundary/interface composition and structure, mean free path in the binder phase, and contiguity of the WC particle skeleton are addressed. The main part of this chapter is devoted to WC-Co alloys, especially to the influence of the composition on the microstructure of these alloys. The phase distribution is to a large extent monitored by the relative energy of the grain boundaries and interfaces. Available experimental and calculated data of the literature obtained from wetting experiments or atomistic simulations are presented. Then the microstructure of WC-TiC-Co, TiC-Mo2C-Ni cemented carbides and Ti(C,N)-based cermets is briefly described. This chapter aims to give keys to understand the origin of the microstructural features observed in the cemented carbides and cermets and to be a guide for the optimization of the alloys accordingly to their applications.