Comparative Analysis of Methods for Determining the Critical Binder Volume Concentration in Hard Metal Pastes

We present a comparative study on determining the critical binder volume concentration (CBVC) of a hard metal paste using the following techniques: theoretical calculation, density method, oil titration, binder titration, and Reddy's model. The theoretical calculations involve density measurements to discern the carbide powder-free volume. The titration methods consist of a stepwise increase of the organic content while the mixer torque is recorded. In contrast, Reddy's model requires the preparation of several feedstocks at varying solid loadings, which are tested in a capillary rheometer to obtain the CBVC. The paste consists mainly of nano-sized tungsten carbide-cobalt (powder phase) and a macromolecular multiphase system (organic phase). The accuracy and expenditure of experimental work of the different methods are discussed.