OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 1 2022 Mechanically activated tungsten occurs in the material in the form of separate particles sized 25 nm and more and sintered agglomerates having the cross dimension of up to 0.4 mm. In Figure 4 b, one can see nanoparticles of tungsten located within the sintered agglomerate of cobalt and at the interface of cobalt and the Cu3Sn intermetallic phase; its cross dimension is around 100 nm. Thus, in spite of its higher reactivity and lower melting temperature, tungsten nanoparticles did not get dissolved either in cobalt or in the liquid phase during sintering. Figure 5 demonstrates that mechanical activation of tungsten contributes to its more uniform distribution in the sintered material. Apparently, the uniform distribution of fi nely dispersed particles of the carbideforming tungsten must have a positive effect on adhesion of the binder to the surface of diamond and contribute to stronger retention of diamond grains in the binder [23]. In Figure 3, the effect of mechanical activation of tungsten on the size of cobalt particles can be seen. As a rule, during liquid phase sintering of systems with limited solubility of components, what occurs in it a b Fig. 3. Structure of the sintered Sn-Cu-Co-W material: a – without mechanical activation of tungsten; b – with mechanically activated tungsten a b Fig. 4. Particles of mechanically activated tungsten in the sintered material structure: a – submicron, b – nanosized
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