High pressure infiltration sintering behavior of WC-Co alloys

In this paper, two average tungsten carbide particle sizes of 2, 0.5m are placed respectively, in contact with a WC-16Co substrate, pressed at the pressure of 4.5-5.5GPa, and heated to temperatures ranging from 1350 degrees C to 1500 degrees C in a large-volume cubic press. During the process Co was forced out of the WC-16Co substrate into the compressed powder. The resulting infiltrated samples were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), Vickers hardness and cutting performance tests. The results of XRD confirmed that the sintered bulks have WC and Co phases. The scanning electron microscopy (SEM) analysis reveals that the WC grains in well-sintered alloys are round in shape and cobalt with lower content is uniformly dispersed in the WC grain boundaries. The sintered sub-micron WC-Co alloy with a cobalt content of 3.8wt% exhibits a prominent combination of high hardness value of 23.1GPa and a large fracture toughness value of 8.6MPam(1/2). The high-speed cutting tests indicating its cutting performance is significantly superior to the commercial YG6X (WC-6wt%Co with WC grain size of 0.5m).