Tungsten carbide coating

Tungsten carbide is a compound composed of tungsten and carbon, with a molecular formula of WC and a molecular weight of 195.85. It is a black hexagonal crystal with a metallic luster and hardness similar to diamond. It is a good conductor of electricity and heat. Tungsten carbide is insoluble in water, hydrochloric acid, and sulfuric acid, but soluble in a mixed acid of nitric acid and hydrofluoric acid. Pure tungsten carbide is fragile. If a small amount of metals such as titanium and cobalt are added, brittleness can be reduced. Tungsten carbide used as a steel cutting tool is often added with titanium carbide, tantalum carbide, or their mixtures to enhance its blast resistance. Tungsten carbide has stable chemical properties. Application of tungsten carbide powder in the production of hard alloy materials.

Since 1893, German scientists have been producing tungsten carbide by heating tungsten trioxide and carbon together to high temperatures in an electric furnace, and attempting to use its high melting point, high hardness, and other characteristics to manufacture wire drawing molds, thereby replacing diamond materials. However, tungsten carbide has not been applied in industry due to its high brittleness, easy cracking, and low toughness. In the 1920s, German scientist Karl Schroter discovered that pure tungsten carbide could not adapt to the changes in strong stress during the drawing process. Only by adding low melting point metals to WC can the billet have a certain degree of toughness without reducing its hardness. In 1923, Schroter proposed the method of powder metallurgy, which involves mixing tungsten carbide with a small amount of iron group metals (iron, nickel, cobalt), and then pressing and sintering them in hydrogen gas at temperatures above 1300 to produce hardness alloys.