Tungsten Carbide is often referred to as a Hard Metal due to its very high hardness in relation to other metals. Typically a Tungsten Hard Metal can have a hardness value of 1600 HV, whereas mild steel would be in the region of 160 HV a factor of 10 lower. Although called a hard metal, Tungsten is actually a composite material with hard particles of Tungsten embedded in a softer matrix of metallic Cobalt .
What is Tungsten Carbide all about?
The chemical formula for Tungsten is WC. Tungsten was originally developed in Germany in the 1920’s as there was a requirement for die materials that were able to stand up to the high wear encountered in the drawing of tungsten filaments for light bulbs
How is Hard Metal or Tungsten Made?
Tungsten Hard Metals are primarily produced using a Powder Metallurgy process, whereby the powdered forms of Tungsten and cobalt are mixed using ball mills, a binder material is added to hold the powders together during the next stage of the process which is compaction or pressing.
During the compaction processes, hydraulic presses or isostatic presses are used to compact the powders into a shape which approximates the design of the finished product. Whilst in this condition, the powder compact can be easily machined using conventional metal working tools. This process is often referred to as “Green Machining”. Care has to be taken with the removal of the fine powder particles as they can pose a health hazard so effective extraction methods are required.
Following “Green Machining” the powder compact is then ready to be Sintered. Typically this is done in a vacuum furnace at temperatures between 1300 and 1600°C. The sintering process causes the Tungsten and cobalt matrix to fuse together to produce a dense “Hard Metal”. After sintering the material is so hard that it can only be machined by diamond grinding, a specialized form of micro machining that is relatively expensive as it is not possible to remove large amounts of materials by this process.
Applications of Tungsten and Hard Metals
Tungsten have a wide range of application in many industry sectors such as metal machining, wear parts for mining and oil industries, metal forming tools, cutting tips for saw blades and have now expanded to include consumer items such as wedding rings and watch cases, plus the ball that is in many ball point pens. Tungsten is prepared by reaction of tungsten metal and carbon at 1400–2000 °C. Other methods include a patented lower temperature fluid bed process that reacts either tungsten metal or blue. Tungsten carbide ammunition is now generally of the sabot type. SLAP, or sabered light armor penetrator where a plastic sabot discards at the barrel muzzle is one of the primary types of sabered small arms ammunition. Non-discarding jackets, regardless of the jacket material, are not perceived as sabots but bullets. Both of the designs are, however, common in designated light armor-piercing small arms ammunition.