Abstract

The synthesis and characteristics of W-Ni-Fe nanocomposite powder by hydrogen reduction of ball milled W-Ni-Fe oxide mixture were investigated. The ball milled oxide mixture was prepared by high energy attrition milling of W blue powder, NiO and Fe_2O_3 for 1 h. The structure of the oxide mixture was characteristic of nano porous agglomerate composite powder consisting of nanoscale particles and pores which act as effective removal path of water vapor during hydrogen reduction process. The reduction experiment showed that the reduction reaction starts from NiO, followed by Fe_2O_3 and finally W oxide. It was also found that during the reduction process rapid alloying of Ni-Fe yielded the formation of gamma-Ni-Fe. After reduction at 800°C for 1 h, the nano-composite powder of W-4.57Ni-2.34Fe comprising W and gamma-Ni-Fe phases was produced, of which grain size was35nm for W and 87 nm for gamma-Ni-Fe, respectively. Sinterability of the W heavy alloy nanopowder showing full density and sound microstructure under the condition of 1470°C/20 min is thought to be suitable for raw material for powder injection molding of tungsten heavy alloy.