Experimental Investigation and Computer Simulation of Gradient Zone Formation in WC-Ti(C,N)-TaC-NbC-Co Cemented Carbides

The thermodynamic and diffusion databases for multi-component W-C-Co-Ti-Ta-Nb-N cemented carbides have been developed through a combination of experimental, theoretical and assessment work. Using the CALPHAD approach, the thermodynamic database has been established based on the literature information and experimental investigations. The diffusion database contains the atomic mobility parameters for different diffusing elements in liquid, which were calculated by a modified Sutherland equation. According to the present thermodynamic and diffusion databases, a gradiently sintered WC-Ti(C,N)-(Ta,Nb)C-Co cemented carbides has been designed and prepared. Scanning electron microscopy was employed to investigate the microstructure of the gradient zone, and electron probe microanalysis was used to determine the concentration profiles and distributions of the elements. The gradient zone formation of the cemented carbides was then simulated by DICTRA, and the simulation results show a good agreement with the experimental results.