Friday, 1 April 2011
What sort of hardness can be achieved?
Tungsten Carbide has a high melting point, 2,870 °C (5,200 °F), is also extremely hard ( Vickers hardness number = 2242) and has a low electrical resistivity (~2×10−7 Ohm•m), compared to other metals (e.g. vanadium 2×10−7 Ohm•m).
The hardness of Tungsten Carbide grades is determined by using the Rockwell hardness tester. A pointed diamond indenter is forced into the carbide. The depth of the hole is a measure of the hardness. The Rockwell "A" scale is used for tungsten carbide. Rockwell "C" readings are only shown on the data sheet so that tooling people can compare values of carbide against tool steel. The "A" scale is used on tungsten carbide because the lower indenting force of 60 KGs is less likely to damage the diamond than the 150 KGs force used on the "C" scale.
Moh’s hardness scale
Tungsten Carbide falls between 8.5 and 9.0 on Moh's hardness scale, making it almost as hard as diamond.
In order to polish or finish tungsten carbide, a diamond covered tool must be used because any other metal or mineral would not be able to withstand its hardness. Only a diamond is hard enough to be able to scratch Tungsten Carbide.