Effect of WO₃ Content on Microstructure and Properties of Ultracoarse Grained Cemented Carbide

Ultracoarse grained cemented carbide was prepared by in-situ fine grain dissolution-precipitation method with WC, WO3, Co and C as raw materials. The effects of different WO3 content on the microstructure and mechanical properties of the alloy were analyzed. The results show that the WO3 and C could undergo in-situ reduction-carbonization reaction to form fine WC with high activity. In the liquid phase sintering, fine WC dissolution-precipita(t)ion could promote the coarse WC grains growth, reducing the microdefects and growth steps, flattening the boundary of WC grains, which could make the morphology of coarse WC grains tend to a fully developed triangular prism. The ultracoarse WC grains with high flattening degree effectively increase the proportion of WC (0001) axial plane, improve the hardness, hinder the crack propagation, and strengthen the alloy. So, the alloy with 4.2wt% WO3 added have the maximum hardness (10633 MPa) and transverse rupture strength (2692 MPa).