Experimental investigation and simulation of the effect of Ti and N contents on the formation of fcc-free surface layers in WC–Ti(C,N)–Co cemented carbides

Abstract

The effect of Ti and N contents on the formation of fcc-free surface layers in WC–Ti(C,N)–Co cemented carbides is systematically studied by experimental investigations and DICTRA simulations. The cemented carbides with different Ti and N contents have been sintered in a nitrogen free atmosphere. The microstructure, concentration distributions and concentration profiles have been analyzed via SEM, EPMA and EDX, respectively. The thermodynamic database for multi-component cemented carbides has been developed through a combination of experimental, theoretical and assessment work. Ti and N activity profiles between the surface and bulk are thermodynamically calculated to show the influence to the gradient zone. The modified Sutherland equation is employed to construct the diffusion database. Based on the databases, the gradient zone formation of the cemented carbides is simulated by DICTRA software. The simulation results are compared with the experimental results to demonstrate the application of the established databases. Besides, the growth rate of the fcc-free surface layers and the maximum value of cobalt peak in cemented carbides as a function of nitrogen or titanium content are predicted.