Cemented carbides cover a wide range of applications in many relevant industries, i.e. as cutting tools (turning, milling, drilling) for machining of metal components in the automotive and/or aerospace industry, as components of drill bits or road headers in the rock tools and mining area or as wear parts in wire drawing dies or punch tools. In this review selected cemented carbide and cermet microstructures are presented. The focus is on microstructures, both those that are already established in the cemented carbide industry and those which have drawn scientific attention due to new potential applications. Cemented carbides are here divided in four groups based on microstructure and chemistry: WC morphology and chemistry, cubic carbide containing cemented carbide and cermets, functionally graded cemented carbides, and binder design of cemented carbides. Furthermore, this review covers some historical background that motivated the microstructure design as well as the status of each class of materials nowadays. The paper aims at categorising cemented carbides in a structured way and to serve as an introduction to cemented carbide microstructures for engineers, researchers and scientists.

Cemented carbide microstructures: a review

Cemented carbides are, from a technical point of view, one of the most successful composite materials. The physical and chemical aspects of the components (transition-metal carbides and iron-group metals) and of their interaction in hardmetals are reviewed with emphasis on the materials science point of view focusing on those compositions which have gained technical interest. Crystal structures and phase relationships are discussed in detail. The interaction of components (wetting, residual stresses) and some microstructural aspects (size, contiguity, and shape) are treated also. These fundamentals are the basis of understanding the production processes and the properties of cemented carbides.

Physical and chemical nature of cemented carbides

The effect of WC, Mo2C, TaC content on the microstructure and properties of ultra-fine TiC0.7N0.3 cermet

Six Ti(C,N)-TiN-WC-Co cermet materials originating from the same powder mixture but sintered to different stages of the sintering cycle have been studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDX), electron energy-loss spectroscopy (EELS), and energy-filtered transmission electron microscopy (EFTEM). At 1350 °C, the binder phase exists both as solid and as liquid phase. The cobalt is nanocrystalline before melting, probably due to deformation during milling. A tungsten-rich inner rim starts to form and is very inhomogeneously distributed on the Ti(C,N) cores, indicating that it is difficult to nucleate the inner rim. The outer rim mainly forms at the sintering temperature and accounts for grain growth during the holding time. There are no major variations in metal content of the carbonitride phases in the materials sintered to 1350 °C or higher, although the N/(C+N) atomic ratio changes somewhat. Close to the core-rim boundary of the materials sintered at 1430 °C, there is often an enrichment of nitrogen in the core that is believed to be the result of nitrogen diffusion from the tungsten-rich rim to the titanium-rich core during cooling.

Development of cermet microstructures during sintering

An extremely fine and homogeneous (Ti, Mo)C–Ni nanocomposite powder was synthesized by high-energy ball milling of a mixture of Ti, Mo, Ni, and C powders. The nanocomposite powder was sintered to full density and a homogeneous grain structure has been obtained instead of the usual core-rim microstructure.

Mechanochemical synthesis of nanocomposite powder for ultrafine (Ti, Mo)C-Ni cermet without core-rim structure

The relationship between the mechanical properties and the structure of the sintered carbide WC–TiC–Co has been studied. Specimens containing 7 and 15% cobalt were sintered at temperatures between ...

K. G. Stjernberg

Papers

SOME RELATIONS BETWEEN THE STRUCTURE AND MECHANICAL PROPERTIES OF WC–TiC–Co ALLOYS*