Preparation of nickel and copper coated fine tungsten powder

Fine tungsten powders with an average particle size of 5 mu m were coated with nickel and copper via high pressure hydrogen reduction from nickel sulphate and ammonia solution at 130-140 degrees C, 4000 kPa pressure and via formaldehyde reduction of copper sulphate, ethylenediamine tetra acetic acid (EDTA) and sodium hydroxide solution at ambient temperature respectively. The nickel and copper contents coated on tungsten varied from 2 to 10 wt.% and 2 to 30 wt.% respectively. As-coated tungsten powders were characterised using X-ray diffraction and scanning electron microscopy. It was found that nickel and copper were homogeneously distributed around the tungsten particles in exceeding 4 to 5 wt.% of Ni/Cu content. No impurities, such as residual chemical agents and oxides were detected by chemical and XRD analysis. However, the aggregation of tungsten powder became serious for copper contents larger than 20 wt.%, which affects the fluidity of tungsten powders during the subsequent press operation. The penetration depth of a perforation device prepared from coated tungsten powders increased by 20 compared with that manufactured from conventionally blended elemental powders. (C) 1999 Elsevier Science S.A. All rights reserved.