Effect of High-Energy Milling and Sintering Temperature on the Properties of Al2O3-WC-Co Composites

Abstract

Al2O3-WC-Co composites have specific properties, such as low density, high oxidation resistance and high melting point. In this work, Al2O3-WC-Co composites obtained by high-energy milling (HEM) were thermally and microstructurally assessed by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and dilatometry. Powder mixtures containing 80 wt.% Al2O3—18 wt.% WC—2 wt.% Co were processed by HEM using milling times in the range of 2 h to 50 h. The milled powders were compacted at 200 MPa and further sintered in a dilatometer (using argon atmosphere) at 1300 °C and 1550 °C. The raw materials were characterized by SEM, dynamic light scattering (DLS) and energy-dispersive X-ray spectroscopy (EDS). The XRD results showed a decrease in crystallite sizes, accompanied by an increase in the lattice micro-strain. The dilatometric curves showed that samples sintered at 1550 oC are denser than those prepared at 1300 oC. Moreover, higher grain growth was observed with increasing the sintering temperature. The green density values of the samples varied from 56 to 58%. The sintered samples obtained relative densities between 60 and 80%. The improved sample densification, achieving a relative density of 80% after sintering at 1550 °C is ascribed to a liquid-phase-assisted sintering mechanism.