Effect of pressure on the electrical resistance flash sintering of tungsten carbide

The application of external pressure during the Electrical Resistance Flash Sintering of tungsten carbide (WC), a “metallic ceramic” with positive temperature coefficient (PTC) for resistivity, results in a limited densification of the powder. In the present work, the effect of pressure on the ultrafast sintering of WC is analysed in detail. In particular, the application of pressure at different stages of flash sintering is studied by varying independently the processing parameters i.e., voltage, time and pressure. Microstructural characterization performed by FE-SEM and XRD identifies biphasic structures of WC and W2C, which compositions result almost unchanged for different sintering parameters. Increasing the external load from 4 up to 100 MPa leads to microporous materials, limiting the attainable final density. Pressure is demonstrated to control the flash phenomenon directly by affecting the flash duration and intensity, thus controlling the electrical energy dissipated during the power surge with respect to the overall process.