Carbide is the most widely used class of high speed machining (HSM) tool materials, which are produced by powder metallurgy processes, consisting of hard carbides (usually WC) particles and softer metal binders composition. At present, there are hundreds of different components of the WC-based carbide, most of them are using cobalt (Co) as a binder, nickel (Ni) and chromium (Cr) is also commonly used binder elements, in addition to other Some alloying elements. Today, we mainly introduce the cementing process of carbide cutting tools.

The tungsten carbide powder is obtained by carburizing a tungsten (W) powder. The characteristics of the tungsten carbide powder (especially its particle size) depend largely on the particle size of the raw tungsten powder and the temperature and time of the carburization. Chemical control is also critical, and the carbon content must be kept constant (close to the theoretical ratio of 6.13% by weight). In order to control the particle size by subsequent processes, a small amount of vanadium and / or chromium may be added before the carburizing treatment. Different downstream process conditions and different final processing applications require a combination of specific tungsten carbide particle size, carbon content, vanadium content and chromium content, and a variety of tungsten carbide powders can be produced by these combinations. Carbide Tool For example, ATI Alldyne, a manufacturer of tungsten carbide powder, manufactures 23 standard grades of tungsten carbide powder, and the tungsten carbide powder based on user requirements can reach more than five times the standard grade tungsten carbide powder.

When the tungsten carbide powder is mixed with a metal binder to produce a grade of cemented carbide powder, a variety of combinations can be used. The most commonly used cobalt content of 3% -25% (weight ratio), and the need to enhance the corrosion of the tool in the case of the need to add nickel and chromium. In addition, it is also possible to further improve the metal binder by adding other alloy components. For example, the addition of ruthenium to the WC-Co cemented carbide significantly improves its toughness without reducing its hardness. Increasing the amount of binder can also improve the toughness of the cemented carbide, but it reduces its hardness.

Reducing the size of the tungsten carbide particles can increase the hardness of the material, but in the sintering process, the particle size of tungsten carbide must remain constant. At the time of sintering, the tungsten carbide particles are combined and grown by dissolving the re-precipitation process. In the actual sintering process, in order to form a completely dense material, the metal binder to become liquid (known as liquid phase sintering). The growth rate of tungsten carbide particles can be controlled by adding other transition metal carbides, including vanadium carbide (VC), chromium carbide (Cr3C2), titanium carbide (TiC), tantalum carbide (TaC) and niobium carbide (NbC). These metal carbides are usually added when the tungsten carbide powder is mixed with a metal binder, although vanadium carbide and chromium carbide can also be formed when carburizing the tungsten carbide powder.

The use of recycled waste carbide materials can also produce grades of tungsten carbide powder. Recycling and reusing of used cemented carbide has a long history in the cemented carbide industry and is an important part of the industry's entire economy chain. It helps to reduce material costs, conserve natural resources and avoid unnecessary waste Harm disposal. Waste cemented carbide can generally be recycled through APT (Ammonium paratungstate) process, zinc recovery process or by pulverization. These "regenerated" tungsten carbide powders generally have better, predictable densities because their surface area is smaller than the tungsten carbide powder produced directly by the tungsten carburizing process.

 The processing conditions for the mixing of the tungsten carbide powder and the metal binder are also critical process parameters. Two of the most commonly used milling techniques are ball milling and ultrafine grinding. Both of these processes allow the milled powder to be mixed evenly and reduce the particle size. In order for the workpiece to be pressed later to have sufficient strength, the workpiece shape can be maintained and the operator or the robot can be picked up for the operation of the workpiece, and an organic binder is usually added during milling. Carbide Tool The chemical composition of this binder can affect the density and strength of the workpiece. In order to facilitate operation, it is preferable to add a high-strength binder, but this will result in a lower compression density and may cause lumps, resulting in defects in the final product.

After the milling is completed, the powder is usually spray dried to produce a free-flowing mass agglomerated together by an organic binder. By adjusting the composition of the organic binder, the flowability and charge density of these agglomerates can be tailored as needed. By screening out coarse or finer particles, the particle size distribution of the agglomerates can be further tailored to ensure that it has good fluidity when loaded into the mold cavity.