Technical tungsten powder qualities are prepared by hydrogen reduction and are available in average particle sizes from 0.1 (100nm) to 100µm. The reduction process is, in some respects, unique. It offers the possibility to produce tungsten powder of any desired average particle size within the above limits only by changes in reduction conditions.
The whole palette of particle sizes finds applications in cemented carbide production. The main portion of tungsten powder is directed to that manufacture. Starting tungsten powder for ductile tungsten and powdermetallurgically produced tungsten alloys covers particle sizes between 2 and 6µm. Extremely coarse powder gained by screening to separate any finer particles has excellent flow characteristics and is used in plasma spraying.
The purity of the tungsten powder is of particular importance in all applications and is mainly influenced by the purity of the original APT. Typical upper limits of foreign element concentrations in µg/g are:
The crucial physical properties are average particle size, particle size distribution, apparent, tap and compact or green density, specific surface area, degree of agglomeration and morphology. They are to a certain extent related to each other and can be influenced between limits by the oxide properties and the reduction conditions.
Tungsten powder customers have in most cases very rigid specifications.
Tungsten metal powder is packaged in sealed polyethylene-lined steel drums.