ZrO2 (3Y) toughened WC composites prepared by spark plasma sintering

• Adding ZrO2 into WC can facilitate sintering, but will not cause rapid WC-grain-growth.
• The Palmqvist cracks are observed in the high ZrO2-content grade composites.
• The fracture toughness of the WC materials increases from ∼6 to ∼10.6 MPa m1/2.

WC–ZrO2 (3Y) composites were densified by spark plasma sintering. The influence of ZrO2 content on the densification behavior, microstructure and mechanical properties of the composites were investigated. Adding ZrO2 into WC can facilitate sintering, but will not cause rapid WC-grain-growth. After sintering, most of the tetragonal ZrO2 remain until at room temperature, and partially transform to monoclinic structure during fracture, which exerts toughening effect. The Palmqvist cracks, rather than half-penny cracks, are observed in the high ZrO2-content grade composites (⩾6 wt.%). As the ZrO2 content increases from 0 to 6 wt.%, the fracture toughness of the WC materials increases from ∼6 MPa m1/2 to ∼10.6 MPa m1/2 with an elevation of ∼77%; while the ZrO2 content continues to increase to 10 wt.%, the fracture toughness of the WC–ZrO2 composites is near constant.