Combined Application of Composite Powders WC-Co and Additives of Nanoparticles as an Effective Method of Improving the Properties of Hard Metals

Abstract

The results of experimental studies show that the use of composite powders (WC-Co) in combination with the modification by the additives of ceramic nanoparticles allows controlling the parameters of the microstructure and increasing the strength of the binder and the level of physical and mechanical properties of the hard metal in general. The coating of carbide particles with a layer of a binder is an effective starting method that allows to obtain a bulk compound that preserves the unique properties of the initial nanopowders and ensures a uniform distribution of the phases (WC, Co, Al2O3). Such multiphase fragmentary nanostructured composite is characterized by additional heterogeneity, determined by the differences in size and elastic properties of the phases. By combining the sizes and properties of the phase components in such heterogeneous composite, it is possible to increase the fracture energy (i.e. Palmqvist fracture toughness) up to 20 - 22 MPa∙m1/2 as a result of inhibition on inclusions of nanoparticles the stress relaxation and change in the trajectory of the intergranular crack. Based on the proposed stereological models and experimentally established relationships between composition and microstructure parameters, the required volume concentrations of nanoparticles’ additives and composite powders (WC-Co) were determined.