Technical tungsten powder qualities are prepare d by hydrogen reduction and are available in average particle sizes from 0.1 to 100µm. The reduction process is in some respect, unique. It offers the possibility to produce tungsten powder of any desired average grain size within the above limits only by changes in reduction conditions.
The whole palette of grain sizes finds their 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 grain sizes between 2 and 6µm. Extremely coarse powder gained by screening to separate any finer particles has excellent flow character is used in plasma spraying.
The purity of the tungsten powder is of particular importance in all application and is mainly influenced by the purity of the origin al APT. Typical upper limits of foreign element concentrations in pg/g are: Co, Cu, Mg, Mn, Pb≤2 Al, Fe, Ni, Si, Ca, Cr, Sn≤<10 Mo≤20.
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 an d the reduction conditions.
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