An examination of microstructure and dry wear properties of Nano-Y2O3 incorporated in fine-grained W-Ni-Cu alloy prepared by conventional and spark plasma sintering

Abstract

Due to the importance of wear behavior in tungsten base alloys, this issue has rarely been considered. The present study deal with the effect of Y2O3, its amount and sintering on the microstructural and wear behavior of W-Ni-Cu-Y2O3 alloys. After 25 h of mechanical milling, alloys containing 0–0.6 wt% of yttrium oxide nanoparticles were prepared by conventional (1400 °C, 30 min) and spark plasma sintering (1100 °C, 4 min). The composition, structure and morphology of the milled powders were investigated by SEM and XRD. Then, the microstructure, density, micro-hardness and wear behavior of the composite alloys were evaluated. The result of milling in the presence of yttria nanoparticles is a homogeneous distributed fine-grained powder whose crystallite size has been reduced from 34 to 24 nm. The addition of yttrium oxide nanoparticles caused microstructural modification including grain refinement, (Ni,Cu) binder phase distribution and reduced contiguity of the tungsten grains. Spark plasma specimens, although sintered at lower temperature, exhibited enhanced properties due to the finer grains (less than 4 μm) compared to conventional sintering. The spark plasma sintered alloys with 0.6 wt% of Y2O3 and an average grain size of 2.56 μm were found to have maximum relative density (96.9 g.cm−3), highest microhardness (504 HV) and minimum wear volume (9.5 × 10−5 cm3) and rate (0.064 × 10−7 cm3.N−1.m−1). Also, the coefficient of friction was lower and decreased with increasing of yttria for these specimens. Delamination, cracking, and brittle wear behavior in conventional sintered have turned into plastic deformation in spark plasma specimens.