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

Abstract

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.