Tungsten and tungsten alloys are heavy refractory metals or alloys with a very high melting point and high density.
Tungsten is a steel-gray metal that with impurities is brittle and not very workable but in pure form is very ductile and easy to work with. Of all metals in pure form, tungsten has the highest melting point, lowest thermal expansion coefficient, and highest tensile strength. Alloying tungsten with materials such as steel can greatly increase its strength.
Tungsten Alloys and Materials
There are three common types of tungsten-based alloys which are formed for different applications.
- Tungsten nickel iron alloys are the most common alloys in the heavy metals industry. They are favored where (in addition to the density) maximum ductility and strength are required for the application.
- Tungsten nickel copper alloys are particularly useful when magnetic permeability may be an issue. Although the introduction of copper results in lower tensile strength and ductility, the lack of magnetic properties make them an excellent choice for oncology systems, shielding electrical sensors in applications such as well logging, or rotating inertia members used near guidance systems.
- Tungsten carbide is formed from a chemical reaction between tungsten metal powder and pure carbon powder. It behaves similarly to unalloyed tungsten and is resistant to chemical attack, although it reacts strongly with chlorine to form tungsten hexachloride. Because of its hardness, it is the main constituent in cemented carbide. As the most important tungsten compound, tungsten carbide is used to make all types of wear-resistant cutting and abrasive machine tools and blades for different industries, and accounts for about 60% of current tungsten consumption.
Selecting metal alloys requires an analysis of the desired dimensions and specifications. Dimensions to consider include outer diameter (OD), inner diameter (ID), overall length, and overall thickness. Other specifications of importance (based on application) include product shape, tensile strength, yield strength, melting point, conductivity, corrosion resistance, ductility, and malleability. These properties differ based on the forming method and alloy composition.
High density tungsten alloys are used for radiation shielding, weights and counterbalances, boring bars and grinding quills, crankshaft balancing, rotating inertia members, ordnance components, and high-temperature tooling applications.