Characterization of Ni-W solid solution alloy powders and sintered compacts synthesized via mechanically activated hydrogen reduction of NiO-WO3 mixtures

Blended nickel oxide — tungsten oxide powders corresponding to the compositions of 70 wt% nickel — 30 wt% tungsten were mechanically alloyed (MA’d) for different durations such as 0 h, 6 h, 12 h and 24 h and reduced/alloyed at 550 °C for 1 h followed by 600 °C for 0.5 h under hydrogen (H 2 ) atmosphere. H 2 reduction of the MA’d fine oxide powders resulted in the fabrication of nanocrystalline Ni(W) solid solution alloy powders, whereas a mixture of Ni and WO 2 powders were obtained via hydrogen reduction of asblended oxide mixtures, which revealed the activation of the reduction process by MA. Obtained powders were sintered at 1300 °C for 1 h under H 2 and Ar gas flowing conditions. X-ray diffraction patterns taken from the sintered samples revealed the presence of the Ni(W) solid solution phase for all samples, whereas the presence of elemental W phase was observed in the sintered as-blended and reduced powders. The lowest relative density value of 92.04% and microhardness value of 1.27 GPa were measured for the sintered as-blended and reduced powders, which increased to between 97.62% and 98.72% and 2.19 GPa and 2.23 GPa, respectively, with the applied MA.