Cemented carbide is a tool material that has all properties necessary for heavy-duty tools, including hardness and strength. Cemented carbide is made by powdered tungsten carbide (WC), mixing cobalt (Co) powder in it as a binder, and sintering the mixture. It can be likened to concrete. Small stones (tungsten carbide) are surrounded by cement (cobalt). Cemented carbide, when sintered, will have nearly twice as high gravity, and about half as much volume as before the sintering process. Sintered cemented carbide is ground by a diamond grinding tool and can then be used as a cutting tool.
Cemented carbide manufacturing processes
The compaction process is performed under very high pressure in a mechanical press as shown in Figure 1-1 or in an isostatic chamber to form a part with the consistency of blackboard chalk. A small amount of wax (paraffin) is added to increase the green strength and help in handling the compacted shape. In this “green” state, it can be formed or shaped by conventional methods such as turning, milling, grinding, and drilling ( Figure 1-2). The formed and shaped carbide is then sintered (placed in a vacuum furnace at a high temperature). During the sintering process, the carbide may shrink as much as 20% linearly or nearly 48% by volume.
For an “as-sintered” part, it is considered an industry standard to be able to hold a tolerance of ± 0.8% of the dimension or ± 0.005”, whichever is greater. Tighter tolerances can be held on smaller pressed parts. After sintering, cemented carbide has achieved its full density and hardness. It can then be fabricated by diamond wheel grinding or electrical discharge machining (EDM) techniques.