Tungsten carbide, often simply called “carbide” in industrial settings, is an engineered composite material renowned for its extreme hardness and durability. It is a man-made compound created through a process called powder metallurgy, which combines tungsten and carbon. The resulting material is one of the hardest compounds available, second only to diamond on certain scales. This exceptional material is used in demanding applications where resistance to wear and deformation is necessary.
Quantifying Tungsten Carbide’s Hardness
The hardness of tungsten carbide is quantified using standard material science tests, providing objective data that places it far above conventional metals. On the Mohs scale of mineral hardness, which measures resistance to scratching, tungsten carbide typically scores between 9 and 9.5. This measurement is just below the maximum score of 10, which belongs to diamond, the hardest naturally occurring substance. A more precise measurement of its indentation resistance is provided by the Vickers hardness test. Depending on the exact composition, tungsten carbide typically registers between 1,500 and 2,500 Vickers Hardness (HV). Common hardened steel used in tools generally measures around 800 to 1,200 HV. This difference means tungsten carbide is significantly more resistant to permanent deformation and wear under load than high-grade steel.
The Atomic Structure Responsible for Strength
The extraordinary hardness of tungsten carbide is a direct result of its atomic arrangement and chemical bonding. The material is formed from tungsten atoms bonded with carbon atoms, which creates tungsten carbide grains with a rigid hexagonal crystal structure. The strength comes primarily from the strong, short-range covalent bonds that form between the tungsten and carbon atoms. These bonds require a vast amount of energy to break or deform, which gives the material its characteristic stiffness and resistance to scratching.
Industrial tungsten carbide is technically a metal-matrix composite, or cermet, not a pure compound. These microscopic tungsten carbide grains are held together by a metallic binder, most commonly cobalt. The cobalt matrix acts as a ductile “glue” that surrounds the hard carbide particles, allowing the overall material to absorb some stress. This structure blends the high hardness of the ceramic-like tungsten carbide with the relative toughness provided by the metallic binder. The precise ratio of cobalt to tungsten carbide is carefully controlled to balance maximum hardness with necessary mechanical stability.
High Hardness and Real-World Use
The high hardness profile of tungsten carbide dictates its primary applications across various industries, from manufacturing to consumer goods. Its ability to resist abrasion makes it ideal for use in high-performance cutting tools, such as drill bits, end mills, and inserts for machining hardened materials. It is also used extensively in wear-resistant components like mining drill tips and nozzles that must withstand the constant friction of abrasive slurries.
However, the material illustrates a trade-off between hardness and toughness. Hardness is the resistance to plastic deformation, while toughness is the ability to absorb energy before fracturing. Because of its rigid atomic structure and strong bonds, tungsten carbide is inherently brittle. This means it can be susceptible to chipping or fracturing under sudden, sharp impact, unlike more ductile materials such as steel. Manufacturers must carefully design parts to minimize impact stress, ensuring the material’s high hardness can be fully utilized.