Densification and microstructure development in spark plasma sintered WC-6 wt% ZrO₂ nanocomposites

Abstract

In this paper, we report the results of a transmission electron microscopy investigation on WC-6 wt% Zr0₂ nanocomposite, spark plasma sintered at 1300 ° C, for varying times of up to 20 min. The primary aim of this work was to understand the evolution of microstructure during such a sintering process. The investigation revealed the presence of nanocrystalline Zr0₂ particles (30-50 nm) entrapped within submicron WC grains. In addition, relatively coarser Zr0₂ (60-100 nm) particles were observed to be either attached to WC grain boundaries or located at WC triple grain junctions. The evidence of the presence of a small amount of W₂C, supposed to have been formed due to sintering reaction between WC and Zr0₂, is presented here. Detailed structural investigation indicated that Zr0₂ in the spark plasma sintered nanocomposite adopted an orthorhombic crystal structure, and the possible reasons for o- Zr0₂ formation are explained. The increase in kinetics of densification due to the addition of is believed to be caused by the enhanced diffusion kinetics in the presence of nonstoichiometric nanocrystalline Zr0₂.