Enhanced Densification of Liquid-Phase-Sintered WC-Co by Use of Coarse WC Powder: Experimental Support for the Pore-Filling Theory

Densification during liquid‐phase sintering of WC–Co with various WC powder sizes has been measured in order to identify the densification mechanism. During heating of powder compacts in the solid state, densification was enhanced with a reduction of WC powder size. However, the behavior was reversed when the densification occurred in the presence of a liquid: enhanced densification with increasing WC powder size. This result is in contradiction to a prediction of the conventional theory of liquid‐phase sintering, the contact flattening theory, but in good agreement with a prediction of the pore‐filling theory. Microstructural analysis further confirmed that the densification at the liquid‐phase sintering temperature occurred by pore filling. The calculated densification kinetics based on the pore‐filling theory also fitted well with the measured data. The observed densification behavior thus demonstrates experimentally the prediction of the pore‐filling theory that the densification is enhanced with increasing average grain size for the same pore size distribution.