Diffusion Behaviour of the Grain-Growth Inhibitor VC in Hardmetals

Diffusion couples of the type WC-Co/VC-Co were employed to observe the diffusion behaviour of the grain-growth inhibitor (GOD VC within nano- and ultrafine-grained WC-10wt.% Co samples. Since diffusion of the GGI during heating occurs already in the solid-state regime, interrupted sintering experiments were performed up to the liquid phase formation temperatures. By the use of light-optical and scanning electron microscopy the impact of GGI concentration on the microstructure as a function of depth from the interface was investigated. Electron Probe Microanalysis (EPMA) was used in order to quantify the amount of vanadium diffused into WC-Co as a function of distance. In first approximation, an activation energy of 3.45 eV (332,6 kJ/mol) for vanadium transport was determined.