Effect of milling type on the microstructural and mechanical properties of W-Ni-ZrC-Y2O3 composites

Abstract

This study reports the effect of milling type on the microstructural, physical and mechanical properties of the W-Ni-ZrC-Y2O3 composites. Powder blends having the composition of W-1 wt% Ni-2 wt% ZrC-1 wt% Y2O3 were milled at room temperature for 12 h using a Spex(TM) 8000D Mixer/Mill or cryomilled in the presence of externally circulated liquid nitrogen for 10 min using a Spex(TM) 6870 Freezer/Mill or sequentially milled at room temperature and cryogenic condition. Then, powders were compacted in a hydraulic press under a uniaxial pressure of 400 MPa and green bodies were sintered at 1400 degrees C for 1 h under Ar/H-2 atmosphere. Phase and microstructural characterization of the milled powders and sintered samples were performed using X-ray diffractometer (XRD), TOPAS software, scanning electron microscope/energy dispersive spectrometer (SEM/EDS), X-ray fluorescence (XRF) spectrometer and particle size analyzer (PSA). Archimedes density and Vickers microhardness measurements, and sliding wear tests were also conducted on the sintered samples. The results showed that sequential milling enables the lowest average particle size (214.90 nm) and it is effective in inhibiting W grain coarsening during sintering. The cryomilled and sintered composite yielded a lower hardness value (5.80 +/- 0.23 GPa) and higher wear volume loss value (149.42 mu m(3)) than that of the sintered sample after room temperature milling (6.66 +/- 0.39 GPa; 102.50 mu m(3)). However, the sequentially milled and sintered sample had the highest relative density and microhardness values of 95.09% and 7.16 +/- 0.59 GPa and the lowest wear volume loss value of 66.0 mu m(3).