Ultrafine WC-10Co cemented carbides fabricated by electric-discharge compaction

Abstract

This research investigates the microstructure and mechanical properties of ultrafine WC-10Co cemented carbides fabricated by an electric-discharge compaction (EDC) process, from powder synthesized by a spray-conversion process (SCP). Due to a short holding time during EDC, a grain size as small as 120 nm can be achieved. We also found that dispersion of pores in WC-Co cemented carbides may contribute to fracture toughness, besides the bridging ligament mechanism.

Microstructure of WC in WC–Co cemented carbides consolidated by electric discharge

“…54 GPa accompanied with a instantaneous rise of temperature, which is also calculated in previous analysis. 7 This maximum thermal stress is comparable with the local residual stress estimated from lattice distortion.…”

“…It is raised to 95% and the height of compacts almost reduces by 50% during only one electric discharge. 7 The volumetric strain rate, which describes how fast the materials are deformed, is used in this work to present the strain rate in powder compacts. It can be expressed as : where : e is the volumetric strain rate, de V is the change of volume strain, and t is time.…”

“…3 In electric discharge compaction (EDC) processing of WC-Co nanocrystalline powders, although liquid phase was formed by the processing, stacking faults in WC were found owing to the densification processing. 7 Therefore, investigation into the microstructure of WC in WC-Co cemented carbides is important in revealing the essence of EDC processing. On the other hand, although a wide range of materials such as metals, ceramics, polymers and composites from coarse grained to nanograined have been fabricated by field assisted sintering such as spark plasma sintering (SPS) and EDC, the mechanism is still not clear.…”

Plasma Synthesis of Tungsten Carbide Nanopowder from Ammonium Paratungstate

“…Many investigations also have shown that the reduction of tungsten carbide grain size gives a significant improvement in the mechanical properties of the consolidated compacts. Thus, the production of nanosized tungsten carbide powder is critical 6–10 …”

High rate electrical discharge compaction of powders under controlled oxidation

“…The components with high mechanical characteristics and high density are produced in a short time (Alp et al, 1987). The EDC is applicable to: hard facing materials (Darvizeh et al, 1982), polymer-metal composites (Darvizeh et al, 1982;Alp et al, 1988), nano-crystalline powders (Rock et al, 1998), metal-ceramics (Alitavoli and Darvizeh, in press), and ultra fine WC-10Co cemented carbides (Wu et al, 2004). The process has been used for fabricating porous implants to overcome the adverse effects in the conventional sintering process due to grain growth and inclusion of oxide film.…”