Cemented carbide is a particularly hard metal that is noted for being able to handle tough materials, fast machine speeds, and high temperatures. The material is also known as harmetal, Widia™, or tungsten-carbide cobalt. It is often used in the production of items such as stainless steel or carbon steel.
Modern cemented carbide is usually a combination of particles of tungsten carbide and metallic cobalt or tantalum carbide and metallic nickel with cobalt. These materials are bonded together in a process known as sintering, or less commonly, hot isostatic pressing (HIP), where melted cobalt is mixed with solid grains of tungsten carbide. The strength and durability of the final product can vary widely, depending on the amount of each ingredient in the mix.
Two of the most distinct weaknesses of cemented carbide are its inherent brittleness and the high expense of producing the material. Though the cobalt does provide additional durability, tools made of this material are still prone to breakage or chipping. Often a sturdier metal, such as carbon tool steel, will be used as a shank into which a tip of carbide can be inserted. This can cut costs by both reducing the total cost of making the tool and the replacement cost of the carbide piece.
Cemented carbide inserts can also be reinforced with special coatings, such as titanium carbide-nitride, titanium aluminum nitride, or diamond-like carbon. These coatings can help to increase the lubrication of the tool. Coating can also lengthen an insert’s lifespan by reducing temperature during cutting, and thus cutting back on wear and tear.
The first cemented carbide was developed in the late 1800s by Henri Moissan, a French chemist. Moissan had set out to create diamonds, but his experiments led to the development of a porous, brittle version of modern tungsten-carbide. The Germans Karl Schroeter and Heinrich Baumhauef discovered that the material could be made stronger and more appropriate for industrial uses, such as cutting, with the addition of cobalt.
Commercial use of cemented carbide began in Germany in the late 1920s. The pioneering brand was Widia™, which is a version of wie diament, a German phrase that means “like diamond.” This brand name has endured as a sort of generic term for cemented carbide.
In the 1930s the replacement of tungsten carbide with a bonded mixture of tantalum carbide and metallic nickel helped to create a more durable form of cemented carbide. Now the material is made with several different variations of the traditional and modern mixtures. The one constant has been that the mixture typically consists of one part melted material bonded with the grains of another element.
By K.C. Bruning