Preparation of low binder WC-Co-Ni cemented carbides with fine WC grains and homogeneous distribution of Co/Ni

Abstract

Fine grained WC-Co-Ni cemented carbides with a low binder content have been successful manufactured via the powder metallurgy method. The WC-Co-Ni composite powder with homogeneous distributions of Co and Ni was synthesized by chemical co-precipitation with the raw materials of WC powder, oxalic acid and chlorides of Co and Ni. In this study, the effects of cobalt and nickel contents on the properties of cemented carbides were investigated systematically. The experimental results demonstrated that the alloy prepared by vacuum sintering had uniform grain size distribution and no abnormal growth of WC grains. When the cobalt content was 4 wt% and 5 wt%, the obtained composites almost completely consolidated with excellent hardness and fracture toughness. Among them, for the sample WC-4 wt%Co, the relative density could reach 99.37%, and the Vickers hardness and fracture toughness were 2010 HV30 and 8.55 MPa·m1/2, respectively. When Ni was added to replace part of Co, the relative density of WC-Co-Ni decreased and the fracture toughness was improved without basically sacrificing the hardness. For the sample WC-2 wt%Co-2 wt%Ni, the hardness decreased to 1921 HV30, while the fracture toughness increased to 8.97 MPa·m1/2.