New-generation hard alloys

The first research area focuses on the use of submicron- and micron-sized tungsten carbide powders obtained by the SHS technology. The sintering kinetics of VK5 and VK6 hard alloys made of micron- and submicron-sized tungsten SHS powders was studied. The sintering of SHS WC powders with cobalt was shown to obey the conventional regularities of sintering of hard alloys. The hardness, bending strength, and crack-growth resistance values for VK5 quasi-nanocrystalline alloy were 19.4 GPa, 2130 MPa, and 9.5 MPa•m0.5, respectively. The hardness, bending strength, and crack-growth resistance values for VK6 microcrystalline alloy intended for manufacturing inserts for perforation drilling were 14.5 GPa, 2480 MPa, and 13.1 MPa•m0.5, respectively. The hardness, bending strength, and crack-growth resistance values for VK6 microcrystalline alloy intended for manufacturing of road boring tools were 11.3 GPa, 2290 MPa, and 15.2 MPa•m0.5, respectively. The second research area focuses on the replacement of cobalt binder with an intermetallide one. The mathematic model of the interaction between tungsten carbide and Ni3Al intermetallide under different conditions was developed. The factors determining the nature of interaction between tungsten carbide and Ni3Al are ascertained. The technological modes of mixing, compaction, and sintering of alloys of different composition were optimized. The physical, mechanical, and chemical properties of these alloys were determined. A pilot batch of cutting tools and dies made of alloys with the optimal composition and properties (conditionally designated as VA6 and VA8) was manufactured. The tools were tested at OOO Technical Ceramics Plant (Moscow) and OAO Metallokeram (Kyiv, Ukraine). The third research area is associated with the production of nano-sized silicon nitride coatings on hard alloys for manufacturing tools. The kinetic regularities of gas-phase deposition of silicon nitride on hard solution were studied: 1) the activation energy of the process was determined; 2) the kinetic regularities of this process for producing a nanodispersed coating were determined and the dependence of the deposition rate of the coating on conditions of the process was studied; 3) the technology (modes) of coating deposition from Si3N4 on a hard-alloy substrate was fine-tuned; 4) the coating structure, nucleation mechanism, and growth process were investigated. The main approaches to the elaboration of a mathematical model of interaction between silicon nitride with a hard alloy (which was used to determine the existence regions of a condensed Si3N4 precipitate) have been developed. 1) The elaborated technology was used to manufacture various samples with Si3N4 nanodispersed coating, which will be used to produce tools; 2) the oxidation resistance of the samples and their diffusion interaction with cast iron and steel were studied; 3) the strength of cohesion between the coating and a hard-alloy substrate was determined; 4) the wear resistance tests of the cutting tools with the coating applied were carried out.