Spark plasma sintering of ultrafine WC-10Ni-ZrC hardmetals: Effects of adding ZrC nano-powder

Novel WC-Ni hardmetals with divergent adding amounts (0-9 wt%) of ZrC nano-powder were fabricated by spark plasma sintering the samples at 1350 degrees C under a pressure of 50 MPa. Through systematic characterizations by X-ray diffraction (XRD) and scanning electron microscopy (SEM) as well as physical properties measurements, the effects of adding ZrC nano-powder on the microstructure and mechanical properties of the samples were explored. In the sintered samples with ZrC nano-powder, ZrO2 instead of ZrC could be monitored by XRD in the detection limit. SEM observation revealed that the addition of ZrC nano-powder could suppress the grain growth of WC to a certain degree. As the adding amount of ZrC nano-powder increased, the relative density of the specimens initially rose and subsequently declined, attaining a maximum of 98.6% for the specimen with 3 wt% ZrC nano-powder. With the enhancement of the adding amount of ZrC nano-powder, the Vickers hardness of the acquired specimens initially increased and then decreased, reaching a maximum of about 1800 HV10 for the one with 3 wt% ZrC nano-powder. As the adding amount of ZrC nano-powder increased, the measured flexural strength gradually decreased from approximately 1500 to 1100 MPa.