Tungsten carbide (another name - Tungsten monocarbide) - a chemical compound of tungsten, carbon and ceramics.This substance is one of the strongest of all known ceramics, hardness comparable to diamond: HRC is about 90 units, mineralogical Mohs takes 9th place.Another positive feature of tungsten carbide is a good wear resistance, high melting point and excellent oxidation resistance.This material is now widely used for a cutting tool core and armor-piercing shells.
physical properties of tungsten carbide
1. Under normal conditions, a granular tungsten carbide is a gray powder with a metallic sheen.
2. Soluble in water.
3. Rockwell hardness of 87 to 92 units.
4. The melting point of tungsten carbide is 2870 degrees.
5. The density is 15.8 g / santimetr³.
6. The elastic modulus of 450 GPa ÷ 650
7. Effect of heat equal to 8.4 +/- 0.2 kkalory / mol
8. The entropy of a standard equal to 8.5 +/- 1.5 calories / (molin the hail).
9. The specific heat at a temperature equal to 293 degrees is 8.53 calories / (mol per degree).
10. Thermal conductivity at ambient temperature of 25 degrees is 0.07 cal / (cm / s / deg).
11. The coefficient of thermal expansion is equal to 3.84 (3.9) * 106 deg-1.
12. The resistivity resistivity at 200 degrees is 19.2 +/- 0.3 micro-ohm / cm.
13. Specific Conductivity is 52200 * 1 ohm-cm-1.
structure tungsten carbide
At present there are two forms of WC - β-WC high-cube and the hexagonal α-WC.
Application tungsten carbide
- in technology for the manufacture of tools that should have a high hardness and good corrosion resistance;
- for wear-resistant surfacing of different parts to be operated in heavy wear with medium impact loads;
- widely used in the manufacture of various cutting tools, drills, grinding wheels, drill bits for drilling, milling and other cutting tools;
- the price of tungsten alloys can be used in many different areas (it is composed of hard alloys, known under the name "Victory" and "Relit", about 90%);
- is used in welding and thermal spraying a powder material for the production of wear-resistant coatings;
- is one of the materials used to replace electroplated chromium plating of high-speed flame spraying;
- currently tungsten carbide is dominant in the manufacture of shells and cores of armor-piercing bullets (but there is a trend of gradual replacement of tungsten carbide depleted uranium);
- in the manufacture of heavy-duty balls 1 mm ballpoint pen (grinding is performed in a special unit for a few days with a small quantity of diamond paste);
- in the production of bracelets for luxury Swiss watches, jewelry - rings, bracelets and pendants, which due to the wear resistance of tungsten carbide is guaranteed eternal shine;
- is used as a substrate for the catalyst of platinum;
- tungsten carbide used to create the end seals shafts some arrangements where the environment has a high viscosity and / or abrasiveness.
toxicity of tungsten carbide
This material is chemically inert.For this reason, in normal conditions, it does not pose any hazard to humans.The lethal dose is not defined either for humans or for animals.Studies that have been carried out at the Dresden Technical University and Leipzig have shown that sprayed tungsten carbide can penetrate into living organisms.This fine particles are non-toxic, but when combined with certain substances, they pose a threat to the well-being of cells.When debt gets cobalt dust and we are considering the substance in the body can develop fibrosis.
