Tungsten carbide (WC) is an industrial ceramic compound made from tungsten and carbon, known for its exceptional hardness and resistance to wear. It forms a class of materials called cemented carbides. The durability of tungsten carbide makes it a popular choice for high-stress applications like cutting tools and armor. Tungsten carbide is an exceptionally dense material, which is one of its defining physical characteristics and contributes significantly to its utility.
Defining the Weight of Tungsten Carbide
Density is defined as mass per unit volume and measures how heavy a material is for its size. The density of pure tungsten carbide is approximately 15.6 grams per cubic centimeter (g/cm³). Industrial materials are typically cemented carbides, which are composites of WC grains held together by a metallic binder like cobalt or nickel. The density of cemented carbide varies based on the binder proportion, typically ranging from 13.8 to 15.0 g/cm³. A higher percentage of the lighter binder metal results in a slightly lower overall density, making even small components feel surprisingly heavy compared to common steel.
The Atomic Structure Behind the Density
The remarkable density of tungsten carbide begins with its primary component, the element tungsten, which has a high atomic mass of nearly 184 atomic mass units. When combined with carbon, the resulting WC compound forms a highly compact crystal lattice structure. Tungsten carbide most commonly forms in a hexagonal structure where the atoms are arranged in a dense, tight-packing configuration. This structure minimizes empty space between the atoms, maximizing the mass contained within any given volume. The strong bonds between the tungsten and carbon atoms also contribute to its high hardness.
How Tungsten Carbide Compares to Other Metals
To put tungsten carbide’s density into perspective, it must be compared with more familiar materials. Light materials like aluminum (2.7 g/cm³) and titanium (4.5 g/cm³) are significantly less dense; WC is over five times denser than aluminum. Compared to common structural metals, the difference is also significant, as steel has a density of approximately 7.8 g/cm³, making WC nearly twice as dense. Even lead, known for its weight, has a density of about 11.3 g/cm³, making tungsten carbide substantially heavier. Tungsten carbide’s density is closest to that of pure gold (19.32 g/cm³) and pure tungsten (19.3 g/cm³), though it is slightly less dense than both.
Applications Requiring High Density
The exceptional density of tungsten carbide is utilized in applications where mass is the primary functional requirement, separate from its hardness. Its high mass-per-volume ratio makes it an ideal material for counterweights and balance weights in various mechanical systems. This includes counterbalances used in high-vibration dampening tools and for aircraft control surfaces in the aerospace industry. In the medical field, its radiographic density is useful in radiation shielding equipment and collimators used in radiation therapy. The material is also used in kinetic energy penetrators and armor-piercing ammunition, and it provides substantial “heft” to consumer items like high-end watch cases.