Fabrication of WC-Al2O3 Composite by Reactive Spark Plasma Sintering of WO3, C, and Al

This study reports the successful fabrication of Al2O3-WC composites by mechanical milling and reactive spark plasma sintering of WO3, C, and Al. In the first step of milling, WO3 and Al powders were milled at a stoichiometric ratio of (WO3/Al = 1/2) for 3 h for the reduction of WO3 by Al via mechanically induced selfsustaining reactions. The resulting Wand Al2O3 powder was mixed with carbon (W/Al2O3/C) and milled at different milling times of 0, 0.5, 3, and 6 h. Results showed no formation of the WC phase after the milling process. The mixed powders were then sintered at 1350 degrees C. Sintering of these samples at 1350 degrees C led to the complete formation of the Al2O3-WC composite. X-ray diffraction pattern and field emission scanning electron microscopy were used to investigate the microstructures, available phases, and morphology of the synthesized components. The mechanical properties were evaluated by hardness, flexural strength, and fracture toughness measurements. Prolonging the milling time declined the grain size and porosity. Regarding the significant impact of the grain size and porosity on the mechanical properties, the sample obtained from 6 h milled precursors had optimum properties. A high relative density of 98.8 +/- 0.5% was obtained for this sample. Flexural strength, hardness, and fracture toughness of this sample were 1242 +/- 20 MPa, 24.12 +/- 0.23 GPa, and 11.1 +/- 0.3 MPa m(1/2), respectively.