A comparison of the microstructures of WC-VC-TiC-Co and WC-VC-Co cemented carbides

In this study, large additions of VC or VC and TiC were made to WC-Co cemented carbide to create a harder and more wear-resistant material. The effectiveness of Ti as a grain growth inhibitor was investigated. Backscattered electron SEM imaging of the microstructure of WC-VC-Co revealed a core-rim structure in the (W, V)C grains. SEM-EDS revealed a composition gradient in these (W, V)C grains. These results were confirmed by bright-field TEM investigations, which showed the presence of a core-rim Structure and dislocations in the core-rim interface. Backscattered electron SEM imaging did not show a core-rim structure in (W,Ti,V)C grains, and this result was confirmed by SEW and TEM-EDS analyses, which did not reveal any evidence of a composition gradient in these grains. The lattice parameters of (W,V)C and (W,Ti,V)C were determined, using XRD, and found to be 0.420 nm and 0.429 nm, respectively. The Co binder composition of both materials was found to be similar. The average grain size of the cubic carbides decreased from 2.0 to 1.7 mu m and the grain size distribution became more narrow with the addition of TiC, and the HV30 hardness increased from 1519 to 1549. A model for the hardness of WC-Co with large cubic carbide additions is proposed. (C) 2006 Elsevier Ltd. All rights reserved.