Properties of WC–8Co hardmetals with plate-like WC grains prepared by plasma-assisted milling

Abstract

WC–8Co hardmetals with different proportions of prismatic WC grains and plate-like WC grains were directly produced through sintering the W–C–8Co elemental powder mixture which was fabricated by dielectric barrier discharge plasma (DBDP)-assisted milling. The morphology of prepared WC–8Co hardmetals, geometry and the preferential orientation of plate-like WC were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. The results demonstrate that the microstructure and mechanical properties of the sintered hardmetals are related to the morphology of W grain which is dependent on DBDP-milling time. The DBDP for 1 h (DBDP-1 h)-milled W–C–Co powder contains granular W particles that tend to form prismatic WC grains, while the DBDP for 3 h (DBDP-3 h)-milled powder contains lamellar W particles that generate plate-like WC grains. By adjusting the weight ratio of DBDP-1 h powder and DBDP-3 h powder in W–C–8Co mixture, the proportion of plate-like WC in the hardmetals can be controlled, and relatively high transverse rupture strength (TRS) is obtained as the proportion of plate-like WC grain in the hardmetals is about 35 % in present experimental condition. The DBDP-1 h-milled W–C–8Co powder (Sample A) contains granular W particles that tend to form prismatic WC grains, while the DBDP-3 h-milled powder (Sample B) contains lamellar W particles that generate plate-like WC grains. When the weight ratio of Samples A to B powder is 1:1, Sample A1B1 has relatively high transverse rupture strength (TRS) along both Sections V and P, with proportion of plate-like WC grain of ~35 %.