Study of the formation features of hard metal composites structure obtained from bimodal powder mixtures

Abstract

A new method of forming dispersion-hardening oxide inclusions in the process of thermoreactive synthesis from aluminum nanoparticles introduced into WC-Co powder mixture is proposed. Such multiphase and fragmentarily nanostructured composite is characterized by additional heterogeneity, which is determined by the difference in sizes and elastic properties of the phases. In the structure of WC-Al2O3-Co composites a “barrier” effect is provided, the length of the carbide grains contacts is reduced. Carbide grains are separated by a thin cobalt layer with increased strength. In accordance with the results of numerical estimates using finite element analysis (FEA) method, the maximum stress intensity in tungsten carbide is 9.1 GPa (occurring at an external tension of 3 GPa), which is 30% less than the maximum stress intensity in the basic material. The strength improvement predicted by the FEA method in fragmented nanostructured hardmetal composite correlates with experimental results of measurements of fracture toughness according to Palmqvist data. In case of the optimal amount of additives, the increase in crack resistance is equal to 50% compared with the basic material.