Tungsten Carbide..the hardest known alloy

Tungsten carbide (WC) is an inorganic chemical compound containing equal parts of tungsten and carbon atoms. Colloquially, tungsten carbide is often simply called carbide. In its most basic form, it is a fine gray powder, but it can be pressed and formed into shapes for use in industrial machinery, tools, abrasives, as well as jewelry. Tungsten carbide is approximately three times stiffer than steel, with a Young's modulus of approximately 550 GPa,^[2] and is much denser than steel or titanium. It is comparable with corundum (α-Al₂O₃ or sapphire) in hardness and can only be polished and finished with abrasives of superior hardness such as silicon carbide, cubic boron nitride and diamond amongst others, in the form of powder, wheels and compounds.

DomesticTungsten carbide is sometimes used to make the rotating ball in the tips of ballpoint pens that disperse ink during writing.

A tungsten carbide ringTungsten carbide can now be found in the inventory of some jewelers, most notably as a primary material in men's wedding rings. When used in this application the bands appear with a lustrous dark hue often buffed to a mirror finish. The color is more similar to that of hematite than to that of platinum. The finish is highly resistant to scratches and scuffs, holding its mirror-like shine for years. Although it is possible to inlay precious metals, woods, and other materials, these are less scratch-resistant than tungsten carbide.

A common misconception concerning tungsten carbide rings is that they cannot be removed in the course of emergency medical treatment, requiring the finger to be removed instead. Emergency rooms and many full-service jewelry repair shops are equipped with jewelers' saws that can cut through tungsten carbide rings without injuring the hand or finger. An easier way to remove tungsten carbide rings is to use a tool such as a vise, which can be used to shatter the ring.

Many manufacturers of this emerging jewelry material state that the use of a cobalt binder may cause unwanted reactions between the cobalt and the natural oils on human skin. Skin oils cause the cobalt to leach from the material. This is said to cause possible irritation of the skin and permanent staining of the jewelry itself. Many manufacturers now advertise that their jewelry is "cobalt free". This is achieved by replacing the cobalt with nickel as a binder.