what is tungston carbide

Hardfacing Material: A Compound of Tungsten and Carbon

This exceptionally hard composite is a chemical compound containing tungsten and carbon atoms. It exists as a gray powder, but it can be pressed and formed into various shapes for industrial machinery, cutting tools, abrasives, and other applications. It exhibits exceptional hardness, wear resistance, and high melting point.

Composition and Production

The stoichiometric formula is typically written as WC. While deviations may occur, the compound ideally contains approximately 6% carbon by weight. Production generally involves combining tungsten powder with carbon black at high temperatures in a reducing atmosphere. The process often involves sintering, where the compacted powder is heated to a temperature below its melting point, causing the particles to bond together.

Properties

  • Hardness: Exceptionally hard, often measured on the Rockwell A scale.
  • Melting Point: High melting point, typically around 2870 °C (5200 °F).
  • Density: Significantly dense, typically around 15.63 g/cm³.
  • Chemical Inertness: Relatively inert, providing resistance to many forms of chemical attack.
  • Electrical Conductivity: Exhibits electrical conductivity, although not as high as many metals.
  • Thermal Conductivity: Good thermal conductivity.

Grades and Alloys

Pure WC is often too brittle for many applications. It is typically alloyed with other metals, most commonly cobalt (Co), to create cemented types, also known as hardmetals. These materials consist of WC grains embedded in a cobalt matrix. The proportion of cobalt influences the hardness and toughness of the resulting alloy; higher cobalt content generally increases toughness but reduces hardness. Other metals, such as titanium, tantalum, and niobium, can also be added to modify specific properties.

Applications

  • Cutting Tools: Widely used in the manufacturing of cutting tools for machining metals, wood, and other materials.
  • Drilling and Mining Equipment: Employed in drill bits, mining tools, and other equipment subject to high wear and impact.
  • Wear Parts: Used in wear-resistant parts for pumps, nozzles, bearings, and other machinery.
  • Abrasives: Utilized in abrasive materials for grinding, polishing, and lapping.
  • Armor-Piercing Ammunition: Due to its high density and hardness, it has been used in armor-piercing projectiles.
  • Jewelry: Increasingly used in jewelry, such as rings, due to its durability and scratch resistance.

Health and Safety Considerations

Inhalation of dust may pose a health hazard. Appropriate ventilation and respiratory protection should be used when handling the powder. Cobalt, a common binder, is a known sensitizer and potential carcinogen, so precautions should be taken to minimize exposure during manufacturing and processing of cemented carbides.