Tungsten Carbide

Chemical formula: WC

Melting point: 2830 Cº

Density: 15.6

Popularly known in Spain and other European countries as "Widia", a term derived from the German wie Diamant ("like diamond"), tungsten carbide began industrial production in the first half of the 20th century, and by the 1950s, it had already found numerous applications. Unlike other carbides used only as additives in high-speed steels, WC is used both in its nearly pure sintered state and combined with metallic matrices, primarily cobalt or nickel, to form cermet-type composite materials. 

In its primary state, tungsten carbide is a grayish, chemically inert, and brittle powder, obtained through the reaction of metallic tungsten or its trioxide (WO₃) with high-purity carbon under an inert atmosphere. It is practically immune to conventional reagents and can only be slowly attacked by an acidic mixture of hydrofluoric and nitric acid in a 1:1 ratio.

WC sintered with cobalt generates what is known as "hard metal" or cemented carbide, a cermet that combines extreme hardness with the necessary toughness for cutting and abrasive tools. The proportion of cobalt is critical, as an excess reduces hardness and a deficiency increases brittleness. When sintered with nickel, the resulting material is used as shielding against nuclear radiation, blocking fast neutrons, gamma rays, and alpha and beta particles, replacing lead due to its superior mechanical properties and lack of toxicity.

This carbide possesses a Young's modulus approximately three times greater than that of common steel and a compressive strength that no other publicly accessible material can surpass. Its structure is practically impossible to plastically deform and maintains stability even at high temperatures.

Tungsten carbide is the benchmark for cutting, drilling, extrusion, and abrasive tools, commonly found in drill bits, milling cutters, blades, and components subjected to extreme wear. In the armaments industry, it is used in high-penetration projectiles capable of piercing armor where lead proves ineffective. In jewelry, its smooth surface, metallic gray tone, and scratch resistance have made it a material of growing popularity for high-end rings and accessories.

WC is also a key element in the manufacturing of high-speed steels (HSS) alloyed with tungsten, although this use has diminished in favor of steels reinforced with vanadium, chromium, or molybdenum for cost reasons. In tools made entirely of sintered WC, durability and oxidation resistance are excellent, though they require protection against abrupt impacts due to their relative brittleness.

It is important to distinguish between high-speed steels with variable tungsten content (from 1% to 20%) and tools made with true sintered tungsten carbide. Furthermore, this compound should not be confused with more brittle alternative carbides, such as titanium carbide (TiC), nor with titanium nitride (TiN) surface coatings, which only provide a golden finish without achieving the hardness and durability of WC.

Tungsten carbide continues to be considered a "supermaterial." Neither metallic nitrides nor borides, nor more exotic carbides like those of tantalum, niobium, or hafnium, have comprehensively surpassed the combination of hardness, thermal stability, chemical resistance, and technological versatility offered by this compound. Its reputation remains intact both in industry and in advanced and specialized consumer applications.