Effect of ZrC nano-powder addition on the microstructure and mechanical properties of binderless tungsten carbide fabricated by spark plasma sintering

Binderless tungsten carbide with varied amounts of ZrC nano-powder (0-9 wt.%) were prepared by spark plasma sintering at 1600 °C under an applied pressure of 50 MPa. The effect of ZrC nano-powder addition on the densification behavior, phase composition, microstructure and mechanical properties of the composites were investigated. With appropriate amount of ZrC nano-powder, the coarsening and abnormal growth of WC grains were suppressed, resulting in more homogeneous microstructure of the materials. The Vickers hardness, flexural strength and fracture toughness of the as-prepared composites first increased and then decreased with increasing addition fraction of ZrC nano-powder. When the added fraction of ZrC nano-powder was 1 wt.%, the hardness and fracture toughness reached their maximum values of about 2800 HV10 and 8.1 MPa·m1/2, respectively. When the added fraction of ZrC nano-powder was 3 wt.%, the flexural strength presented its maximum value of about 1100 MPa.