The Synthesis of Nanostructured WC‐Based Hardmetals Using Mechanical Alloying and Their Direct Consolidation

Abstract

Tungsten carbide- (WC-) based hardmetals or cemented carbides represent an important class of materials used in a wide range of industrial applications which primarily include cutting/drilling tools and wear resistant components. The introduction and processing of nanostructured WC-based cemented carbides and their subsequent consolidation to produce dense components have been the subject of several investigations. One of the attractive means of producing this class of materials is by mechanical alloying technique. However, one of the challenging issues in obtaining the right end-product is the possible loss of the nanocrystallite sizes due to the undesirable grain growth during powder sintering step. Many research groups have engaged in multiple projects aiming at exploring the right path of consolidating the nanostructured WC-based powders without substantially loosing the attained nanostructure. The present paper highlights some key issues related to powder synthesis and sintering of WC-based nanostructured materials using mechanical alloying. The path of directly consolidating the powders using nonconventional consolidation techniques will be addressed and some light will be shed on the advantageous use of such techniques. Cobalt-bonded hardmetals will be principally covered in this work along with an additional exposure of the use of other binders in the WC-based hardmetals.

Influence of consolidation process and sintering temperature on microstructure and mechanical properties of near nano- and nano-structured WC-Co cemented carbides

“…In contrast to conventional cemented carbides that toughness decreases with increasing hardness values, the increase of hardness in nanostructured cemented carbides does not decrease their fracture toughness [2]. For samples of near nano-and nanostructured cemented carbides analysed in this paper the relationship between Palmqvist toughness and Vickers hardness is not linear and does not change with the change of hardness.…”

“…While in conventional cemented carbides fracture toughness decreases with increasing hardness values, the increase of hardness in nanostructured cemented carbides does not decrease their bulk fracture toughness [3]. According to published literature, there is no reduction in fracture toughness versus hardness level when the grain size reaches nanoscale [2] which is the result of a very homogeneous microstructure without grain growth and homogeneous distribution of cobalt between carbide grains.…”

“…Nanostructured cemented carbides are characterised by a unique combination of a very fine grained homogenous microstructure and good mechanical properties, which makes them the best choice for many areas of application. Mechanical properties are directly dependent on the developed microstructure in the sintered parts, which is governed by several factors such as WC crystallite size, mean free path of the binding phase, and the contiguity of WC grains [2]. Improvement of hardness and toughness of cemented carbides can be achieved with a decrease in WC grain size to nanoscale, which has industrial importance and a significant influence on the duration and robustness of tools manufactured from cemented carbides [3,4].…”

Defect Analysis in Microgroove Machining of Nickel-Phosphide Plating by Small Cross-Angle Microgrooving

“…The mold material should have sufficiently high hardness at molding temperature and favourable micromachinability at room temperature. Silicon carbide (SiC) and tungsten carbide (WC) are too hard to be machined, while the copper and aluminium are too soft to maintain the microshape under high pressure [10,11].…”

Influence of Grain Growth Inhibitors and Powder Size on the Properties of Ultrafine and Nanostructured Cemented Carbides Sintered in Hydrogen

“…One of the biggest challenges of sintering ultrafine and nanoscaled powders is the retention of a small WC grain size in the sintered product [1,2]. Numerous attempts to achieve nanostructured cemented carbides have failed due to high sintering activity of WC nanopowders [2,3]. For that reason, the nano-and near nanopowders with very low sintering activity with respect to the re-crystallization during liquid phase sintering were developed [2,4].…”