Study on the sintered characteristics and properties of nanostructured WC-15Â wt% (Fe-Ni-Co) and WC-15Â wt% Co hard metal alloys

The following figure shows the fracture morphology of the WC-(Fe-Ni-Co) and WC-Co specimens by means of high-magnification SEM after the KIC tests. Fig. a shows that numerous binder phases (Fe-Ni-Co) existed in the crack areas, which resisted the penetration and extension of the cracks. Due to the bridging effect of the binder phase, the stress concentration of the crack tip will be resolved through plastic deformation; thus, the cracks did not continue to extend. Once the deformation reaches a critical value, the crack propagation occurs. Meanwhile, the binder phase can link together the two crack faces through the bridging process. Although parts of the cracked areas also showed the bridging effect in the WC-Co specimens, as shown by the arrows (Fig. b), the crack propagation path was not obviously affected. This result corresponds to the tortuosity phenomenon. Consequently, the bridging process suppressed the crack propagation and resulted in the increase in tortuosity. SEM observations of the bridging role of the (a) 1300 °C sintered WC-(Fe-Ni-Co), and (b) 1350 °C sintered WC-Co hard metal alloys after KIC tests.