Tungsten, element 74 of the periodic table, has come a long way since its early use as a material for filaments in lightbulbs. This silvery-white lustrous metal is becoming more present in the industry thanks to the alloying process – that is, the ability to add metallic elements together to create new, improved materials known as alloys.
Tungsten is useful for glass-to-metal seals, as its thermal expansion coefficient is on par with borosilicate glass, and finds many uses in lamp filaments, television tubes, electrical contact points, x-ray targets, heating elements, and other high-temperature applications. It is most popular usages are in dry lubricant (tungsten disulfide) and alloys such as high-speed tool steels, hard metal, and of course tungsten carbide – but more on that in the next section.
Tungsten Carbide
Tungsten Carbide is an alloy of tungsten and carbon, made by heating tungsten powder with carbon and hydrogen at 1,400 - 1,600°C (2,550 - 2,900°F). The resulting alloy is 2-3 times as rigid as steel and has a compressive strength surpassing all known melted, cast, and forged metals. It is highly resistant to deformation and keeps its stability at both extreme cold and hot temperatures. When in its monocarbide form (chemical formula of WC), tungsten carbide rivals diamond for the hardest known material. Its impact resistance, toughness, and resistance to galling/abrasions/erosions are exceptional, lasting up to 100 times longer than steel in extreme conditions. Its properties place tungsten carbide in the metal-like substances since it is technically a ceramic cement of tungsten, carbon, and some binder (often cobalt), which is also why it cannot be heat-treated in any way. It has a density of 15.7 g/cm3 and is generally not the best electrical conductor. However, it conducts heat much faster than tool steel.
It is incredibly difficult to machine Tungsten Carbide Roller, as most machine bits and tools are made of tungsten carbide themselves. Tungsten carbide is generally only milled or lathed and is done so when in its soft, or “green” state, and can only be done with diamond-coated bits. It can also be cast and rapidly quenched to form an extremely hard crystal structure. Tungsten carbide is invaluable in making hard metal, which is a form of tungsten carbide, as well as making mill products, high-speed tools, military weapons, armor, and other rugged applications.
Comparing Tungsten & Tungsten Carbide
Most people will confuse tungsten and tungsten carbide, as tungsten carbide is the most widely understood form of tungsten available. However, there are some niche use cases for its pure form, and this section will contrast tungsten and Tungsten Carbide Coating Roller to illustrate how they differ.
Manufacture Process for Cemented Carbide Tools:
Cemented Carbide tools (which are very suitable for machining cast iron, non-ferrous metals and such non-metallic substances as plastics and marble) are formed by pressing a mixture of tungsten carbide and cobalt together in a hydraulic press and then heating the compact in a hydrogen atmosphere. Tungsten carbide is an extremely hard substance. Cobalt acts as a binder for the hard carbide grains.
Since tungsten carbide has the tendency to crater, it alone is not suitable for machining steel. The addition of titanium carbide helps to reduce this problem. Titanium carbide and molybdenum carbide bonded in nickel are also very suitable for machining steel. Most of the cemented carbides used today are made predominantly from the carbides of tungsten, titanium, and tantalum usually with cobalt as the binder metal.
The Cemented Carbide MWD can be applied to most chip-forming machining such as turning, boring, reaming, shaping, planing, milling, drilling, etc., as well as to many other applications such as wire-drawing and deep-drawing dies, cold heading and stamping.
Cemented carbide is extensively used as a cutting tool material because of the advantages it offers. Initially brazed cemented carbide tips were used which could be renewed by grinding when the cutting edge turned blunt. Brazing introduces stresses in the carbide matrix. Grinding of cutting edge also introduces grinding stresses in carbide.
Indexable tooling using indexable inserts, also known as the throw-away cutting edge concept does away with brazing and grinding of cutting edges. Cemented carbide tip in form of a triangle of the square is held mechanically in a holder.