Fabrication and characterization of Ni-W solid solution alloys via mechanical alloying and pressureless sintering

Ni-W solid solution alloy powders and sintered compacts were fabricated via mechanically alloying and pressureless sintering of powder batches with the compositions of Ni-xW (x=20, 30, 40wt.%). The crystallite size of the powders were between 11nm and 17nm, which decreased with increasing W contents, where a microhardness value of 6.88GPa for the Ni powders MM'd for 48h increased to 9.37GPa for the Ni40W powders MA'd for 48h. The MM'd/MA'd powders were sintered at 1300°C for 1h under Ar and H₂ gas flowing conditions. X-ray diffraction (XRD) patterns of the sintered Ni, Ni20W and Ni30W samples revealed the presence of only the solid solution phase, whereas the presence of elemental W and Ni₄W intermetallic phase were observed in the XRD patterns of the sintered Ni40W sample. Among all sintered samples, the sintered Ni sample had the highest relative density value of 96.36% and the lowest microhardness value of 1.59GPa. The relative densities of the sintered samples decreased with increasing W amounts, contrary to microhardness values which increased with W contents. Moreover, microstructural characterizations via scanning electron microscope and electron backscatter diffraction, room temperature compression tests and sliding wear experiments were conducted in order to reveal the effects of W contents on the properties of the sintered Ni-W alloys.