Synthesis of nanophase tungsten carbide by electrical discharge machining

Tungsten carbide nanopowders were synthesized successfully by electric discharge machining followed by annealing under a nitrogen atmosphere. The tungsten workpieces were initially melted and evaporated on the working surface during the electric discharge machining process, and then the tungsten powders were reacted with the carbon electrode and the working medium of kerosene to form the nanocrystalline WC1-x, powders. The powders produced were characterized by XRD, SEM, and TEM. When annealing the powders under an N-2 atmosphere, the cubicphases of WC1-x gradually changed to hexagonal W2C and then were transformed fully to nanocrystalline hexagonal WC at 1200 degrees C, with the nanocrystalline tungsten carbide encapsulated in a carbon shell. On the other hand, under an H-2 atmosphere, the WC1-x phase changed via a WC1-x phase to reduced powders of pure tungsten at 1000 degrees C or were reduced directly from WC1-x, to elemental W. (c) 2005 Elsevier Ltd and Techna Group S.r.l. All rights reserved.