Hrebenok T. Formation of the structure and properties of hard alloys based on titanium carbide with additives of other carbides.

The thesis is devoted to the study of the carbides additions influence of V and VI groups transition metals and titanium-carbide-based hardmetals composition with nickel-chromium binder on their structure and properties formation. It was found that alloying titanium carbide with niobium, vanadium, molybdenum carbides reduces the solubility of the refractory base in the hardmetal and retards the growth of titanium carbide grains during recrystallization through the liquid phase. The chemical composition and technological modes of vacuum sintering and pressure sintering have been optimized. It was found that the introduction of solid solutions into the alloys composition activates the sintering process under pressure, reduces porosity and leads to the formation of a fine-grained alloy structure. Based on the dependences of the billets relative density upon the pressure, the dependences of the rootmean-square stress in the matrix forming the porous body on its root-mean-square deformation were determined, which made it possible to reveal the features of densification, strain hardening and destruction of brittle powder particles, determined by the size and shape of powder particles, during cold pressing. The effect of molybdenum, vanadium and niobium carbides, nickel-chromium binder, and the method of obtaining alloys on the structural state of titanium-carbidebased hardmetals with a nickel-chromium binder has been investigated. The synthesis of solid solutions was studied by sintering and hot pressing at various temperatures and holding times. The basic laws of the pressure-free sintering process and hot pressing as well as the physical-mechanical and test properties of titanium-carbide-based hardmetals have been investigated. On the basis of the results obtained, the optimization of the hardmetals composition based on titanium carbide and the methods of its manufacture were carried out in order to obtain a high level of physical, mechanical and performance properties of products made from it. It has been established that an increase in the strength and hardness of alloys based on complex carbide (Ti, Nb, V, Mo) C is achieved due to a decrease in porosity and a decrease in the size of carbide grains. The wear rate of the plates made of the material obtained by the standard technology is approximately three times higher than that of the alloy obtained by the technology with obtaining solid solution on titanium carbide basis, and when the wear of the plates along the flank surface is 0.2 mm, the duration of the plates was 16 minutes respectively and 38 minutes. Keywords: titanium carbide, solid solution, cold pressing, densification, pressure sintering, wear.