Microstructure and mechanical properties of WC-TiC0.4 composites doped with ZrO2 or 3Y-ZrO2

The ZrO2 or 3Y-ZrO2 incorporated WC-TiC0.4 composites were consolidated employing spark plasma sintering (SPS) technology at different temperatures. The impacts of ZrO2 and 3Y-ZrO2 as toughening agents on the densification, phase composition, microstructure and mechanical properties of the WC-based composites were assessed. The results revealed that the WC-5 wt% TiC0.4–9 wt% ZrO2 (W5Ti9Zr) composite required a lower sintering temperature of 1700 °C for nearly full densification than WC-5 wt% TiC0.4–9 wt% 3Y-ZrO2 (W5Ti9Zr-3Y) composite. The diffraction peaks of monoclinic ZrO2 (m-ZrO2) existed only in the W5Ti9Zr composite. The evenly dispersed ZrO2 and 3Y-ZrO2 achieved the relatively homogeneous and fine microstructure in W5Ti9Zr and W5Ti9Zr-3Y composites. Moreover, the semi-coherent interfaces of (W1-x, Tix)Cn layer with WC, (W1-x, Tix)Cn layer with m-ZrO2, and (W1-x, Tix)Cn with m-ZrO2 brought about a rise in the fracture toughness of W5Ti9Zr composite. The W5Ti9Zr composite yielded the better comprehensive mechanical properties with a combination of hardness (20.8 GPa) and fracture toughness (9.9 MPa·m1/2) as compared to those of W5Ti9Zr-3Y composite. Furthermore, the main toughening mechanisms of W5Ti9Zr and W5Ti9Zr-3Y composites included grain refinement of WC matrix, a mixed transgranular and intergranular fracture, stress-induced transformation of t-ZrO2 to m-ZrO2, and crack deflection. •The m-ZrO2 diffraction peaks were detected only in the W5Ti9Zr composite.•The interfaces of (W1-x, Tix)Cn layer/WC and (W1-x, Tix)Cn layer/m-ZrO2 had a semi-coherent relationship.•The W5Ti9Zr composite exhibited more comprehensive mechanical properties than W5Ti9Zr-3Y composite.•The stress-induced transformation of t-ZrO2 to m-ZrO2 occurred in the W5Ti9Zr and W5Ti9Zr-3Y composites.