Introduction to Tungsten Carbide

Tungsten carbide is an alloy material composed of tungsten carbide (WC) and cobalt (Co), which has extremely high hardness, wear resistance and corrosion resistance. This alloy is widely used in the manufacture of cutting tools, molds and wear-resistant parts. The manufacturing process of tungsten carbide involves powder metallurgy, in which tungsten carbide acts as a "hard core" and cobalt acts as a binder to tightly connect the tungsten carbide particles together. In addition, other elements such as titanium carbide (TiC) or tantalum carbide (TaC) can be added as needed to enhance the performance of the alloy.

It has been exactly one hundred years since the invention of tungsten carbide.

In the early 1920s, Karl Schröter, an engineer at OSRAM, a German light bulb company, invented WC-Co cemented carbide in order to find an alternative material to the expensive diamond mold used to draw tungsten filaments. He applied for the first cemented carbide patent (German Patent No. 420,689) in 1923 and obtained authorization in 1925.

In 1926, KRUPP, a military giant that obtained the patent, produced the first batch of commercial cemented carbide, which was used as a machining cutting head to increase the processing efficiency exponentially, causing a sensation in the world and quickly became a strategic material with a high price. At that time, the price of one gram of cemented carbide was higher than one gram of gold.

Types of cemented carbide

01 Tungsten-cobalt cemented carbide

This type of cemented carbide contains only tungsten carbide and cobalt, or pure WC-Co cemented carbide with a very small amount (generally no more than 1%) of other additives. The international standard (ISO) calls it K-type cemented carbide, and the national standard of my country calls it tungsten-cobalt (YG)-type cemented carbide; for example, YG6 (WC-6Co), that is, a cemented carbide containing 6% cobalt (mass fraction) and the rest is tungsten carbide. This is the composition of the world's first commercial cemented carbide.

02 Tungsten-cobalt-titanium cemented carbide

Tungsten-cobalt-titanium cemented carbide, in addition to tungsten carbide and cobalt, also adds a certain amount (more than 1%) of titanium carbide (TiC) to tungsten-cobalt-titanium (WC-TiC-Co) cemented carbide, which is called P-type in the international standard and YT-type in the national standard. The amount of titanium carbide is usually less than that of tungsten carbide; if the amount of titanium carbide exceeds that of tungsten carbide, it becomes a "titanium carbide-based cemented carbide" or a more professional name is "titanium carbide-based cermet".

03 Tungsten-Cobalt-Titanium-Tantalum (Niobium) Cemented Carbide

The third category is WC-TiC-TaC(NbC)-Co cemented carbide with a certain amount of tantalum carbide (TaC) and/or niobium carbide (NbC) added to the second category. It is called M category in international standards and YW category in national standards.

There are also WC-Ni cemented carbides that use nickel (Ni) to replace cobalt, or steel-bonded cemented carbides that use iron alloy (steel) to replace cobalt. Engineers can design different compositions to obtain cemented carbides with different properties to meet the use requirements of different application fields by replacing WC and Co in WC-Co with metal carbides such as titanium carbide, tantalum carbide, niobium carbide, molybdenum carbide, chromium carbide, or metals such as nickel, iron, and chromium.

Performance of cemented carbide

(1) High hardness and good wear resistance. The hardness of cemented carbide is between 80 and 94 HRA, while the maximum hardness of tool steel after quenching and hardening is only 80 HRA or slightly higher. For a long time, cemented carbide was the material with the second-hardest hardness after diamond. In fact, the first generation of cemented carbide was named "Widia" (derived from the German word Wie Diamant, meaning "like diamond"), which was invented to replace diamond. Therefore, it can be said that cemented carbide was born for hardness.

(2) High strength and elastic modulus The bending strength of typical cemented carbide can reach 3000~5000 MPa (N/mm2), and it is not easy to deform.

(3) Heat resistance and corrosion resistance Generally, it can resist atmospheric, acid, alkali and other corrosion well, and is not easy to oxidize.

These characteristics make it the best material for wear-resistant structural parts used in high temperature and corrosive environments.

Uses of cemented carbide

Tool material

As a machining tool, cemented carbide is the most important use of cemented carbide, consuming more than half of cemented carbide production. Cemented carbide has been the best machining tool material since its birth.

Mold material

Cemented carbide is mainly used for cold drawing dies, cold punching dies, cold extrusion dies, cold heading dies and other cold working dies.

Measuring tools and wear-resistant parts

Carbide is used for easily worn surface inlays and parts of measuring tools, precision bearings of grinding machines, guide plates and guide rods of centerless grinders, lathe centers and other wear-resistant parts.

Special cemented carbide

With the advancement of science and technology, the production of high-end cemented carbide materials has also developed rapidly. With more product technical requirements in downstream industries, the market demand for cemented carbide materials has continued to increase. The production technology of cemented carbide materials has also been improved, and the corresponding special cemented carbide materials are currently widely used in military industry, aerospace, mechanical processing, metallurgy, oil drilling, mining tools, electronic communications, construction and other fields. In the fields of high-tech weapons and equipment manufacturing, the advancement of cutting-edge science and technology, and nuclear energy, cemented carbide products with high technology content and high quality stability are also used.