Tungsten is a pure chemical element, not an alloy. The confusion is understandable because the metal is rarely used in its pure form in industrial applications. Tungsten serves as a foundational component in a wide variety of high-performance materials. Its unique properties, which include the highest melting point of any metal, make it necessary for materials designed to withstand extreme conditions. Commercial applications almost always involve combining the element with other substances to enhance its usability.
Understanding Elements and Alloys
A chemical element is a pure substance defined by the fact that all of its atoms contain the same number of protons in their nuclei. Elements cannot be broken down into simpler substances by ordinary chemical means and are organized on the Periodic Table, where Tungsten is designated by the symbol W and atomic number 74. An alloy is a metallic substance created by mixing two or more elements together. At least one of these components must be a metal. The resulting material typically exhibits improved properties, such as greater strength or corrosion resistance, compared to its individual constituents.
The Nature of Pure Tungsten
Tungsten (W) is a transition metal that possesses a unique set of physical characteristics that distinguish it from all other metals. It boasts the highest melting point of any known element, measuring 3,422 degrees Celsius (6,192 degrees Fahrenheit). This extreme thermal stability is a result of the exceptionally strong metallic bonds that form between the tungsten atoms. Tungsten is also one of the densest naturally occurring elements, comparable to gold and nearly twice as dense as lead. These properties, which also include a low coefficient of thermal expansion, make the element indispensable in high-temperature applications like light bulb filaments and X-ray targets.
Why Tungsten is Used in Mixtures
While the properties of pure tungsten are impressive, the material is inherently challenging to work with for most manufacturing processes. At room temperature, pure tungsten is quite brittle, meaning it can easily crack or fracture when subjected to stress. This brittleness, combined with its extreme hardness, makes conventional machining methods difficult and costly to perform. The material’s high hardness quickly wears down standard cutting tools. Consequently, tungsten is often combined with other elements to improve its ductility and machinability, making it a more versatile and economically feasible material for commercial use.
Practical Examples of Tungsten Materials
Tungsten Carbide (WC)
One of the most common materials utilizing tungsten is Tungsten Carbide (WC), a ceramic compound formed by a chemical reaction between tungsten and carbon. Tungsten carbide is known for its extreme hardness, rating just below diamond on the Mohs scale. This makes it the preferred material for cutting tools, drill bits, and industrial wear parts. The compound is typically processed by mixing WC grains with a binder metal, like cobalt or nickel, to create a composite material.
Tungsten Heavy Alloys
Another significant application is in Tungsten Heavy Alloys, which are true metal alloys composed of 90% to 97% tungsten, often mixed with nickel and iron, or nickel and copper. These alloys retain the high density of pure tungsten, typically ranging from 17.0 to 18.5 grams per cubic centimeter. The addition of these binder metals adds necessary ductility and significantly improves machinability. Tungsten Heavy Alloys are routinely used in applications requiring high mass in a small volume, such as counterweights in aircraft and radiation shielding in medical and industrial settings.