Superfine crystal tungsten carbide has many characteristics, such as high hardness, high bending strength, and so on, which is widely used in industrial field. It has been made into micro drill, dot matrix printer, syringe needle, holed hole cutting tool, woodworking tool, precision mould, drill press, hard machining material and cutter. The tool products made by ultrafine tungsten carbide have excellent performance.

 

With the development of research on ultrafine tungsten carbide and nano tungsten carbide, many kinds of preparation technologies for ultrafine tungsten carbide powder have been developed, such as direct reduction carbonization, chemical precipitation, mechanical alloying, spray conversion or spray drying.

 

 

1, Direct Reduction Carbonization

Direct reduction carbonization is carried out with tungsten or tungsten compounds as raw materials, carbon black, CO or hydrocarbon gas as reducing agent and carbonization raw material, so that two processes of reduction and carbonization continue. This is a widely used method for the preparation of WC-Co composite powder.

 

2, Chemical Precipitation

Precursor of tungsten cobalt compound is prepared after the coprecipitation of tungsten salt and cobalt salt by carburizing.

 

3, Mechanical Alloying

During the process, the alloying element powder is proportioning and mechanically mixed. After the long time of high-speed operation through high energy ball milling powder in the tank under repeated collision and compression shear friction force multiple force after repeated cold extrusion welding and grinding into ultrafine particles dispersed, alloying in solid state.

 

4, Spray-Drying Process

Spray-drying or thermochemical synthesis is a method of combining the chemical and physical with the atomization of the solution by means of physical means. The spray conversion process is the main method for the industrial mass production of WC-Co nano composite powder at present.

 

5, In Situ Reduction of Violet Tungsten

Nanocrystalline violet tungsten has large specific surface area and sharp instability. It can be rapidly reduced to produce bead like ultrafine tungsten single crystals under the action of high temperature hydrogen. This method inhibits or weakens the migration of chemical vapor phase, thus restraining the grain growth of ultrafine tungsten powder.

 

Using a single phase ultrafine tungsten powder and carbon black as raw materials, the mixture is carbonized at high temperature. Then raw materials were simultaneously carbonized into ultrafine tungsten carbide powder by carbonization reaction.