A TRANSMISSION ELECTRON-MICROSCOPY STUDY OF WC-10CO CEMENTED CARBIDES WITH MODIFIED HARD AND BINDER PHASES

The alloy design of WC-10Co cemented carbide, modified with addition of a hard carbide phase, TiC, and with Ni and Mo in the binder phase, has been highlighted by the authors in a number of publications. The present article deals with the fine microstructural features of various phases in such cemented carbides. WC grains in all the investigated cemented carbide compositions appear to develop straight facets during sintering because of their anisotropic nature. In contrast, the TiC phase is characterized by its rounded shape. Dislocations are present in both WC and TiC grains, being of lesser density in the latter. The binder phase is always associated with stacking faults. The nature of the hard phase/binder interfaces has been found to be dependent on the binder phase chemistry. The observed changes in microstructures and mechanical properties have been correlated with the wettability and solubility of the hard phases in the binder melt, and with the different strengthening mechanisms in the binder phase.