Tungsten and tungsten alloy cutting and turning are the main processes in tungsten and tungsten alloy machining operation. The cutting and turning processes have some articular concerns according to the method of producing the tungsten and tungsten alloys.
The sintered unalloyed tungsten with a minimum relative density of 0.93 belongs to the high-density tungsten. The cutting velocity for high-density tungsten needs to reach to the point where the sheared zone can be heated enough to generate the continuously formed chips. Otherwise, the life of the turning tool will not be optimized.
It’s easier to process a turning operation when working with unalloyed tungsten materials, such as porous tungsten which has a relative density lower than 0.93, even when using lower density cutting tools. The tool life is also longer due to the decreased density.
Various Tungsten Alloys
Among the various tungsten alloys that are more machinable than unalloyed tungsten materials, tungsten-rare earth oxide basis alloys (W-REO) and tungsten heavy alloys are the most commonly applied.
Tungsten heavy alloys are tungsten-based alloys with Ni, Cu, Fe binders. Due to the dopants of other alloyed elements and liquid-phase sintering technology, tungsten heavy alloys can boast both the high-density characteristic and good machinability for turning at the same time. The density of tungsten heavy alloys ranges from 16.5g/cc to 19.5 g/cc.
Solid solution strengthened tungsten alloys, dispersion strengthened tungsten alloys and tungsten carbide all have extremely high strength and hardness. Besides, these tungsten alloys process a high DBTT so as to be very brittle under low temperature. Therefore, the turning process is difficult to operate to solid solution strengthened tungsten alloys, dispersion strengthened tungsten alloys and tungsten carbide. Solid solution strengthened tungsten alloys include Tungsten-rhenium Alloy (WRe), Tungsten-molybdenum alloy (WMo), Tungsten-niobium alloy (WNb) and Tungsten-tantalum alloy (WTa).
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