Discussion of Nonconventional Effects in Solid‐State Sintering of Cemented Carbides

Abstract

WC–Co materials are usually produced through a powder metallurgy route, including a liquid‐phase sintering step in the 1350°–1450°C temperature range. However, it is well established that a large part of sintering already occurs in the solid‐state for micrometer or submicrometer WC particles. Solid‐state spreading of the Co‐rich binder phase and local rearrangement of WC particles are responsible for the compact densification. But important issues still remain unexplained. First, densification by pure rearrangement should stop at a critical packing fraction of the WC refractory phase. Second, a strong influence of the C/W ratio on the spreading and sintering kinetics is observed experimentally. Both these effects are discussed in this paper, based on experimental dilatometric results, microstructural investigations by SEM and transmission electron microscopy, and considerations about interfacial energies in the system.

Effects of WC particle size on sintering behavior and mechanical properties of coarse grained WC–8Co cemented carbides fabricated by unmilled composite powders

“…2 (a) that all compacts expanded slightly in the beginning and dilatometric shrinkage took place until about 1100 o C on heating. There was a sharp increase in shrinkage rate after about 1300 o C on each curve, then getting a peak which was associated with the liquid phase formation temperature of WC-8Co cemented carbides [20].…”

Influences of the preparation methods of WC–Co powders on the sintering and microstructure of coarse grained WC–8Co hardmetals

“…The Curie temperature of pure Co, which is 1131°C, is lowered by dissolving WC [17]. In the case of WC-Co, the Curie temperature of Co corresponds to the starting shrinkage temperature.…”

“…The sharp peak on the right of the plots in Fig. 4(b) corresponds to the liquid phase formation temperature [17]. The characteristic temperatures and shrinkages of WC-8Co compacts derived from Fig.…”

A Phenomenological Analysis of Sintering Mechanisms of W-Cu from the Effect of Copper Content on Densification Kinetics

“…A critical packing fraction for the end of particle rearrangement was also deduced from sintering experiments of WC-Co cemented carbides. [26] The value was higher (66 to 69 pct), which was explained by a significant contribution of shape accommodation due to the higher solubility of particles in the liquid in this system. The effect of copper on the solid-state sintering of the W skeleton is more difficult to analyze from the raw dilatometric data, since the samples do not have the same density at corresponding temperatures.…”