Influence of powder preparation technique on microstructure, densification, mechanical and tribological properties of composites based on Al₂O₃ with addition of WC-Co hard metal

In the present work, the influence of the powder preparation technique on the sintering behavior of 80 wt.% Al ₂ O ₃ -18 wt.% WC-2 wt.% Co composites was investigated. The powders were mixed with a mechanical stirrer for 10 min (MM) and by high-energy milling (HEM) for 50 h. They were then compacted at 200 MPa and sintered in a resistive dilatometric furnace for 1 h under argon atmosphere at a heating rate of 10°C/min for two sintering temperatures (1300°C and 1550°C). The powders prepared by MM and HEM were further characterized by XRD, SEM and dynamic light scattering (DLS), while the sintering kinetics was evaluated by dilatometry. The powders processed by HEM presented better dispersion and homogenization than those obtained by mechanical mixing (MM). The HEM approach enhances the sintering of immiscible systems that present low sinterability, as well as improves dispersion, phase refining and produces composite particles with greater interaction of the milled elements. In addition, HEM decreases the particle/crystallite size and increases the microstrain. The results showed that composites prepared by HEM and sintered at 1550 ºC presented better densification, Vickers microhardness and tribological behavior.