Tungsten carbide (another name is tungsten monocarbide) is a chemical compound of tungsten, carbon and ceramics. This substance is one of the strongest of all known ceramics, in hardness comparable to diamond: HRC is about 90 units, on the mineralogical scale of Mohs is 9th. Another positive feature of tungsten carbide is its good wear resistance, high melting point and excellent oxidation resistance. This substance is currently actively used to create cutting tools and cores of armor-piercing shells.
Physical properties of tungsten carbide
1. Under normal conditions, granular tungsten carbide is a gray powder with a metallic sheen.
2. Soluble in water.
3. Rockwell hardness is from 87 to 92 units.
4. The melting point of tungsten carbide is 2870 degrees.
5. The density is 15.8 g / centimeter³.
6. The elastic modulus is 450 ÷ 650 GPa
7. The thermal effect is 8.4 +/- 0.2 kcal / mol
8. The standard entropy is 8.5 +/- 1.5 calories / (mol per hail).
9. The heat capacity at a temperature of 293 degrees is 8.53 calories / (mol per hail).
10. Thermal conductivity at an ambient temperature of 25 degrees is 0.07 cal / (centimeter / s / deg).
11. The thermal expansion coefficient is 3.84 (3.9) * 106 deg-1.
12. The electrical resistivity at a temperature of 200 degrees is 19.2 +/- 0.3 microohm / centimeter.
13. The electrical conductivity is 52200 Ohm-1 * centimeter-1.
Tungsten Carbide Structure
Currently, two WC forms are known - β-WC high-temperature cubic and α-WC hexagonal.
Tungsten Carbide Application
- in technology for the manufacture of tools that must have high hardness and good corrosion resistance;
- for wear-resistant surfacing of various parts that will be used in conditions of intensive wear with medium impact loads;
- widespread use in the manufacture of a variety of cutters, drills, abrasive disks, drill bits, milling cutters and other cutting tools;
- the cost of tungsten allows its alloys to be used in a variety of fields (it is in the composition of hard alloys known under the names "Pobedit" and "Relit", about 90%);
- used in surfacing and thermal spraying in the form of powder material for the manufacture of wear-resistant coatings;
- This is one of the materials that is used to replace the chrome plating by a gas-flame high-speed spraying method;
- Currently, tungsten carbide is dominant in the manufacture of shells and cores of armor-piercing bullets (however, there is a tendency to the gradual displacement of tungsten carbide by depleted uranium);
- in the production of heavy-duty balls 1 mm in size for ballpoint pens (polishing is carried out in a special apparatus for several days using a small amount of diamond paste);
- in the manufacture of bracelets for luxury Swiss watches, jewelry - rings, bracelets and pendants, which, thanks to the wear resistance of tungsten carbide, guarantee eternal shine;
- used as a substrate for a platinum catalyst;
- tungsten carbide is used to create mechanical shaft seals of some mechanisms in cases where the environment has high viscosity and / or abrasion.
Tungsten Carbide Toxicity
This substance is chemically inert. For this reason, under normal conditions, it does not pose any danger to humans. The lethal dose is not determined neither for humans nor for animals. Studies conducted at the University of Dresden and Leipzig University of Technology have shown that tungsten carbide dust can penetrate living organisms. At the same time, small particles are non-toxic, but when combined with some substances, they pose a danger to the well-being of cells. With prolonged exposure to cobalt dust and the substance we are considering, fibrosis can develop in the body.