Tungsten carbide is high melting, 2,870 °C (5,200 °F), extremely hard 8.5–9.0 Mohs scale[citation needed] at 22 GPa Vickers hardness with low electric

Tungsten carbide is high melting, 2,870 °C (5,200 °F), extremely hard 8.5–9.0 Mohs scale[citation needed] at 22 GPa Vickers hardness with low electrical resistivity (1.7–2.2x10-7 ohm-m), comparable with metals (e.g. vanadium 1.99x10-7 ohm-m).

WC is readily wetted by both molten nickel and cobalt. Investigation of the phase diagram of the W-C-Co system shows that WC and Co form a pseudo binary eutectic. The phase diagram also shows that there are so-called η-carbides with composition (W,Co)6C that can be formed and the fact that these phases are brittle is the reason why control of the carbon content in WC-Co hard metals is important.

Chemical properties

There are two well characterized compounds of tungsten and carbon, WC and W2C. Both compounds may be present in coatings and the proportions can depend on the coating method.

WC can be prepared by reaction of tungsten metal and carbon at 1400–2000 °C. Other methods include a patented fluid bed process that reacts either tungsten metal or blue WO3 with CO/CO2 mixture and H2 between 900 and 1200 °C. Chemical vapor deposition methods that have been investigated include:

tungsten hexachloride with hydrogen, as reducing agent and methane as the source of carbon at 670 °C (1,238 °F)
WCl6 + H2 + CH4 → WC + 6HCl
reacting tungsten hexafluoride with hydrogen as reducing agent and methanol as source of carbon at 350 °C (662 °F)
WF6 + H2 + CH3OH → WC + 6HF + H2O
At high temperatures WC decomposes to tungsten and carbon and this can occur during high temperature thermal spray, e.g. high velocity oxygen fuel (HVOF) and high energy plasma (HEP) methods.
Oxidation of WC starts at 500–600 °C. It is resistant to acids and is only attacked by hydrofluoric acid/nitric acid (HF/HNO3) mixtures above room temperature. It reacts with fluorine gas at room temperature and chlorine above 400 °C (752 °F) and is unreactive to dry H2 up to its melting point.
WC has been investigated for its potential use as a catalyst and it has been found to resemble platinum in its catalysis the production of water from hydrogen and oxygen at room temperature, the reduction of tungsten trioxide by hydrogen in the presence of water, and the isomerization of 2,2-dimethylpropane to 2-methylbutane.[5] It has been proposed as a replacement for the iridium catalyst in hydrazine powered satellite thrusters.

Tungsten carbide is used as the rotating ball in the tips of ballpoint pens to disperse ink during writing. Links Tools

Tungsten carbide is used as the rotating ball in the tips of ballpoint pens to disperse ink during writing.

Tungsten carbide steel is used in most razors.

Tungsten carbide can now be found in the inventory of some jewelers, most notably as the primary material in men's wedding bands. 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.

A common misconception held concerning tungsten carbide rings is 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 gold, silver, platinum, titanium, and tungsten carbide rings without injuring the patient when the ring cannot be slipped off easily. Tungsten carbide rings can also be removed in an emergency situation by cracking them into pieces with standard vice grip–style locking pliers.

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.


Markets Now
Shop Links
Easy Shopping
World Travel
Jobs and Friendship Dating
Online Shops