Preparation of complex-shaped Al2O3/SiCp/SiCw ceramic tool by two-step microwave sintering

Abstract A fine-grained Al2O3-based ceramic tool reinforced with SiC particles (SiCp) and SiC whiskers (SiCw) was prepared by two-step microwave sintering (TSMS, 1650 °C/5 min, 1100 °C/5 min). Effects of the content of binder polyvinyl alcohol (PVA) and molding pressure on relative density, mechanical properties and microstructure of the ceramic tool were studied. As the PVA content and molding pressure were 1.5 wt% and 150 MPa, respectively, the best properties were obtained. Compared to other researches on microwave sintering, the PVA content was reduced by 50%, which effectively extended the service life of the thermal insulation device and was beneficial to the densification of the ceramic tools. When the SiC particles and whiskers were 3 wt% and 1 wt%, the relative density, Vickers hardness, fracture toughness and grain size were 99.8 ± 0.1%, 18.8 ± 0.3 GPa, 4.8 ± 0.3 MPa m1/2 and 1.3 ± 0.2 μm, respectively. Compared with the single-step microwave sintering (SSMS) (1650 °C/5 min), the grain size was reduced by 35% while the Vickers hardness and fracture toughness were increased by 9.3% and 29.7%, respectively. The fine grains resulted from two-step sintering, and the pinning and pull-out effects of SiC whiskers contributed to the improvement of fracture toughness.