What are the composition and powder production methods of tungsten carbide spray coating materials?

Superhard tungsten carbide coating usually refers to covalent bonding compounds (carbides, nitrides) and elements (diamond) composed mainly of III, IV, and V. There are various types of polycrystalline and amorphous materials, such as diamond, cubic boron nitride (C-BN), carbon nitride (C3N4 and CNX), boron carbon nitride (BCN), and diamond-like carbon (DLC). Its hardness is very high, close to the hardness of natural diamonds. Generally speaking, the hardness of superhard coatings is 800GPA. However, some scholars consider the above-mentioned covalent bond compound coatings as superhard coatings with 4000GPA. The hardness of diamond-like carbon coatings varies greatly, which is related to the content of SP3 bonds in the structure.

Composition of tungsten carbide coating material

Generally speaking, tetragonal hydrogen free amorphous carbon TA-C is also known as amorphous diamond coating and is considered a superhard coating, while other diamond-like coatings are considered ordinary hard coatings. Except for diamonds, all other materials are synthetic and have no natural counterparts. In addition, the hardness of nano multilayer structure coatings and nano crystalline composite coatings widely studied in recent years is also within the hardness range of superhard coatings, and their comprehensive performance is excellent, thus they are favored by people.

Superhard tungsten carbide coating materials can be divided into single component (elemental) compounds, binary compounds, ternary compounds, and multicomponent compounds. The main characteristics of superhard coating materials are:

(1) Covalent bonds are the main chemical bonds, while ionic bonds have fewer components;

(2) Nitrogen, carbides, and third group element substances, with the atomic radius of the IV constituent elements being very small.

Production method of tungsten carbide powder

1. Preparation of tungsten powder (average particle size 3-5m) by hydrogenation reduction of tungsten trioxide WO3. Using tungsten powder and carbon black as raw materials, the average particle size of the ball mill is 3-5m. The tungsten powder is dry mixed with an equal amount of carbon black, thoroughly mixed, pressed into shape, placed in a graphite plate, and then heated to 1400-1700 in a graphite resistance furnace or induction furnace, controlled at 1550-1650. W2C， Tungsten carbide is continuously produced through high-temperature reactions.

Alternatively, tungsten powder can be prepared by thermal decomposition of hexacarbonyl [tungsten (co) 6] in a CO atmosphere of 650-1000, and then reacted with carbon monoxide at 1150 to obtain tungsten carbide. W2C can be generated above this temperature.

2. Gas phase decomposition method. This is tungsten powder made by thermal decomposition of hexabasic tungsten (carbon monoxide) 6. Then prepare tungsten carbide by carbonizing with carbon monoxide gas. The characteristic of this method is that tungsten carbide can be easily prepared at low temperature (1150), rather than the high temperature of preparation method 1.

1. Particle size distribution specification table (using Fischer mean particle size detection method)

2. Coarse grained tungsten carbide particles

Coarse grained tungsten carbide powder has certain special properties, and its use is different from that of medium grained tungsten carbide powder. Especially, high-temperature tungsten carbide powder has a series of advantages such as fewer structural defects, microhardness, and microstrain. Therefore, coarse-grained tungsten carbide powder is receiving increasing attention from various industries.

Coarse grained tungsten carbide powder is widely used in fields such as geological tools, stamping molds, petroleum drilling, and hard surface materials. In recent years, coarse-grained tungsten carbide with high binding carbon, complete grain growth, large grain size, low impurity content, and few microscopic defects has become the goal pursued by many manufacturers.

in general. The research and development of tungsten powder and tungsten carbide powder worldwide not only has a long history, but is also thriving. The research hotspots are clearly polarized. One direction is to research and develop ultrafine (nanoscale) tungsten carbide powder, and the other direction is to research and develop large particle single crystal tungsten carbide. For coarse-grained tungsten carbide, research hotspots have shifted from studying trace elements, behavior, reduction processes, kinetics, powder shape, and particle size to developing new process methods and new application areas. For example, after years of research on coarse-grained tungsten carbide powder for manufacturing mining tools, it has now reached a higher level.