1. Properties of boron carbide
Boron carbide (B4C) is gray-black and is a very hard artificial material. Its Mohs hardness is 9.3 and its microhardness is 5500~6700kg/mm2, second only to diamond and cubic boron nitride. The crystal structure of boron carbide is hexagonal crystal. Density is 2.52g/cm3. The melting point is 2450°C. When the temperature is higher than 2800°C, it decomposes and volatilizes rapidly. Its linear expansion coefficient is 4.5×10-6/℃ (20~1000℃), its thermal conductivity is 121.42 (100℃) W (m·K), 62.80 (700℃) W/(m·K), and its resistivity It is 0.44 (20℃)Ω·cm and 0.02 (500℃)Ω·cm.
Boron carbide is resistant to acid and alkali corrosion and does not wet with most molten metals, and has very high chemical stability. Boron carbide can resist the oxidation of air at 1000°C, but it is easily oxidized above 900°C in an oxidizing atmosphere. Boron carbide powder has a very high grinding ability, which is 50% higher than that of silicon carbide and 1 to 2 times higher than that of corundum. It is an excellent abrasive material and wear-resistant material.
2. Uses of boron carbide
The biggest use of boron carbide is as an abrasive and a raw material for making abrasive tools. It is suitable for grinding, polishing, drilling and other processing of various carbide tools, molds, parts, components and gemstones. Using an appropriate amount of engine oil or water as lubricant, boron carbide can be made into abrasive and polishing pastes.
Boron carbide can also be used as a raw material for manufacturing metal borides, boron alloys, boron steel, etc. Except for special needs, it can be used to manufacture boron carbide hot-pressed products for wear-resistant and high-temperature-resistant parts, such as nozzles, sealing rings, gyroscopes, petrochemical parts, and lightweight and high-strength parts in military engineering. Control rods of an atomic reactor.
