Tungsten (W) and tungsten carbide (WC) are often grouped due to their shared element, yet they are fundamentally different materials valued for exceptional performance in high-stress engineering applications. Both are renowned for their strength, heat resistance, and density. The primary distinction lies in a single atomic addition—carbon—which transforms the base metal into a ceramic composite with a new set of properties. This chemical difference dictates why each material excels in specific roles, from aerospace components to industrial cutting tools.
Fundamental Composition and Chemical Structure
Tungsten is a pure chemical element, a refractory transition metal with the atomic symbol W and atomic number 74. In its purest form, it is a dense, grayish-white metal with a body-centered cubic crystal structure.
Tungsten carbide is an inorganic chemical compound with the formula WC, containing equal parts of tungsten and carbon atoms. The carbon atoms occupy interstitial spaces within the tungsten lattice, creating a highly rigid structure classified as a ceramic compound. For industrial use, WC is typically processed as a “cemented carbide.” This involves mixing fine WC powder with a binder metal, usually cobalt, and then sintering it. The binder acts as a metallic glue, holding the hard carbide grains together to form a tough composite material.
Comparative Physical and Mechanical Properties
The addition of carbon fundamentally changes mechanical performance, making tungsten carbide vastly harder than pure tungsten. Pure tungsten scores between 7.5 and 8 on the Mohs hardness scale. Tungsten carbide consistently measures between 9 and 9.5, placing it second only to diamond in hardness. This extreme hardness results from the strong, covalent-like bonds formed between the tungsten and carbon atoms within the crystal lattice.
The density of the two materials differs significantly, though both are exceptionally heavy compared to steel. Pure tungsten is one of the densest elements, clocking in at approximately 19.3 grams per cubic centimeter. Tungsten carbide, despite its high tungsten content, is slightly less dense, typically ranging from 15.6 to 15.8 grams per cubic centimeter, due to the inclusion of the lighter carbon atoms and the binding agent. Elemental tungsten is preferred where maximum mass in a small volume is required.
A trade-off exists between the materials regarding impact resistance and stiffness. Pure tungsten is relatively ductile, meaning it can deform under stress before fracturing, and exhibits better impact resistance. Tungsten carbide is extremely rigid and stiff, possessing a significantly higher Young’s Modulus than tungsten, but it is also more brittle. The cobalt binder in cemented carbide mitigates this inherent brittleness, enhancing the material’s toughness to prevent chipping or shattering under load.
Pure tungsten possesses the highest melting point of all known metals, at 3,422 degrees Celsius. Tungsten carbide’s melting point is lower but still high, around 2,870 degrees Celsius. The ceramic structure of tungsten carbide provides superior resistance to abrasion and wear, even at elevated temperatures, making it effective in high-friction environments.
Distinct Applications and Use Cases
The unique properties of each material dictate its distinct industrial applications. Pure tungsten is utilized primarily for its ultra-high melting point, high density, and electrical conductivity. Its most famous application is as the filament in incandescent light bulbs, where it withstands extreme temperatures without melting. Tungsten is also used in electrical contacts, TIG welding electrodes, and heating elements for high-temperature vacuum furnaces. Its high density makes it ideal for radiation shielding, specialized counterweights in aerospace, and kinetic energy penetrators for military purposes.
Tungsten carbide is the material of choice when extreme hardness and wear resistance are required. Its ability to maintain a sharp edge under intense abrasion makes it the standard for cutting tools, drill bits, and milling inserts used in machining virtually all other metals. The material’s durability is leveraged in the mining and construction industries for rock drilling tools, wear parts, and nozzles. Beyond heavy industry, the scratch resistance of tungsten carbide has made it popular for high-durability items like jewelry and the balls on the tips of ballpoint pens.