UDC 621.921.34
G. S. Oleynik, V. I. Lyashenko (Kyiv)
Mechanism of BNр –> BNг transformation in nano- and microtubes
The authors present the first data on the transformation (at T = 1650 K) of the rhombohedral phase of boron nitride into a hexagonal one in faceted tubes. The transition occurs with the participation of basal shifts and the formation of intermediate structures in the form of multilayer polytypes. It is concluded that the development of transformations is due to the relaxation of stresses in the tubes arising in them due to the anisotropy of thermal expansion, which contribute to the development of plastic shifts along (0001) in BNр.
Keywords: boron nitride, modification, synthesis, transformation, multilayer polytypes, deformation, disordering.
UDC 620.17 : 621.921.34-492.2 : 546.26-162
A. A. Shulzhenko (Kiev), A. V. Nozhkina (Moscow, Russia), V. G. Gargin, R. K. Bogdanov, A. P. Zakora, G. P. Bogatyreva, G. A. Petasyuk, M. G. Loshak, L. I. Aleksandrova, N. A. Rusinova, V. L. Gvyazdovskaya, V. S. Shamraeva (Kiev)
Comparative physical and mechanical characteristics of micropowders of synthetic and natural diamond and polycrystalline composite materials based on them
The results of the study of the physical and mechanical characteristics of micropowders of synthetic (SD 40/28) and natural (ND 40/28) diamonds and polycrystalline composite materials based on them. It is shown that both powders meet the requirements of the DSTU 3292-95 standard. At the same time, the abrasive ability of natural diamond is slightly higher than the abrasive ability of synthetic diamond micropowder, and the density and specific surface area of the grains are lower than those of synthetic diamond. The elastic characteristics of sintered polycrystalline composite materials – Young’s modulus, shear modulus, modulus of uniform compression, Poisson’s ratio and wear resistance during mechanical processing of stone by friction are higher, and the durability during cyclic compression tests is slightly lower for a composite sintered on the basis of natural diamond micropowder than for a composite based on synthetic diamond.
Keywords: diamond, micropowders, composite, properties, pressure, temperature.
UDC 546.26-162
V. G. Sushchev, V. Yu. Dolmatov, V. A. Marchukov, M. V. Veretennikova (St. Petersburg, Russia)
Fundamentals of chemical cleaning of detonation diamond-containing charge with nitric acid
The main regularities of chemical cleaning of diamond-containing charge of detonation synthesis with diluted nitric acid under pressure are presented. It was found that the optimum temperature of the process is 230-240 °C, the excess of HNO3 is 200-300 ‰ from stoichiometry, the pressure is 7-8 MPa.
Keywords: detonation diamonds, chemical cleaning, nitric acid, pressure, autoclave, titanium
UDC 621.921.343
G. P. Bogatyreva, M. A. Marinich, V. Ya. Zabuga, G. G. Tsapyuk, A. N. Panova, G. A. Bazaliy (Kiev)
The influence of nanodiamond surface modification on their heat resistance
The influence of nanodiamond surface modification on heat resistance by changing its functional coating was studied. Nanodiamond modification by high-temperature surface activation followed by chemical treatment leads to a decrease in the concentration of metallic impurities and oxygen-containing surface groups, which desorb at temperatures below 773 K. As a result, the oxidation rate of modified diamonds in air decreases by 1.7 times upon reaching a temperature of 773 K. The oxidation onset temperature shifts by 100 degrees.
Keywords: nanodispersed diamonds, heat resistance, modification, surface.
UDC 661.88
A. A. Sivkov, E. P. Naiden, D. Yu. Gerasimov (Tomsk, Russia)
Direct dynamic synthesis of nanodispersed titanium nitride in a high-speed pulsed jet of electroerosive plasma
The possibility of obtaining nanodispersed TiN in a high-speed jet of electric discharge plasma generated by a coaxial magnetoplasma accelerator is shown. The process is implemented in a short-term (≈10–3 s) cycle of accelerator operation with titanium electrodes. The main consumable material is produced by electroerosive means from the surface of the accelerating channel. Depending on the specific supplied energy dissipated in the channel, the powder particles can have either a spherical or irregular shape and dimensions of 10–300 nm.
Key words: direct synthesis, nanodispersed TiN, magnetoplasma accelerator, hypervelocity jet.
UDC 661.657:548.73
M. P. Bezhenar, S. A. Bozhko, T. O. Garbuz, N. M. Bilyavina, V. Ya. Markiv (m. Kiev)
Titanium/aluminium diborides in composites removed by reaction adhesions under high pressure in the cBN–TiC–Al system
Using X-ray phase and X-ray diffraction analysis methods, it was shown that during the reaction splicing of cubic boron nitride composites the charge was cBN + 8 ‰ Al + 26 ‰ TiC in a high vise (4.2 GPa, 1750 K) in a warehouse of bonding ceramics, next to AlN, a solid structure Ti(x)Al(1-x)B(2y)N2(1-y) is created, in which titanium and aluminum atoms form a frame close to equimolar to the warehouse, and boron and nitrogen atoms statistics are divided into graphite-like networks.
Keywords: cubic boron nitride, sintering, high pressure, X-ray diffraction analysis, titanium diboride, aluminum diboride.
UDC 544.3:621.762:669.018.25
A. F. Lisovsky (Kyiv)
On filling a pore in a solid-liquid nanodisperse system
Thermodynamic functions describing the process of liquid migration from a pore into the volume of a sintered body are obtained, the existence of migration pressure in a nanocomposite body is proven, and the condition for liquid equilibrium in a pore is derived. The concept of a critical pore radius is introduced and an expression for calculating its value is proposed. All pores with a radius greater than the critical value are stable in the sintered body. Pores with a radius less than the critical value are filled with a liquid phase.
Keywords: thermodynamics, nanodispersed system, pore, sintered hard alloy.
UDC 621.9.01
Yu. G. Kravchenko, A. A. Semykin, A. Ya. Yaroshik (Dnepropetrovsk)
Optimization of the parameters of the turning process of high-hardness cast irons with PCBN plates
Empirical dependences of the turning process indicators on variable parameters, technical limitations of the indicators and the technological cost of processing are obtained. Calculations of cutting modes and blade geometry of polycrystalline cubic boron nitride plates are performed, an analysis of the influence of cast iron hardness and technical limitations on the estimated indicators is carried out.
Keywords: turning, cutting, high-hardness cast irons, polycrystalline cubic boron nitride, optimization parameters.
UDC 622.24.051:536.2:004.942
V. A. Dutka (m. Kiev)
Predicted value of the surface of a carbide cutter holder as a result of hardening after induction brazing
The results of numerical prediction of the possibility of damage to the working surface of a steel holder of a carbide cut as a result of hardening of salts and bases in water after induction brazing of the cut are presented. In this case, a previously developed computer model of the temperature field of a carbide cutter during the process of induction brazing, cooling on the surface when transferred from the inductor to the coolant medium, and when cooled in the cooler sumishi. Predictive estimates of the hardness of the hardened near-surface ball and the hardness of the working surface of the holder for different hardening modes are given.
Key words: computer modeling, hardening, phase transformation, hardness, hardening ball.
UDC 621.01:62-882
S. S. Eroshin (Lugansk)
Expansion of Technological Capabilities of Machines and Devices with Ring Working Elements
The possibility of creating technological machines and devices with a working element in the form of a wide flat ring, which has no mechanical supports and electrical contacts, is set in rotational motion, is held in space and perceives technological loads due to the magnetic field forces of the inductors, is shown. The criterion of stable rotation of a free ring rotor is theoretically obtained and experimentally confirmed. The technological and economic advantages of new designs are shown using a diamond cutting machine and a centrifugal pump as an example. The website http://www.elmache.com/ demonstrates diamond cutting with a free cutting wheel on a pass-through, rotation of the impeller of a centrifugal pump, which has neither a shaft nor bearings, and computer models of semiconductor single-crystal cutting machines.
Keywords: free rotor, motion stability, diamond cutting, centrifugal pump.
UDC 621.9.02
M. Yu. Kopeikina, S. A. Klimenko, Yu. A. Melniychuk, V. M. Beresnev (Kiev)
Performance of a cutting tool equipped with a CBN-based PSM with a vacuum-plasma coating
The article presents the results of a study on improving the performance of a cutting tool equipped with a CBN-based PSM and vacuum-plasma coatings. It is shown that a tool with a coating is characterized by increased reliability at the running-in stage and higher durability and allows the processing to be carried out with higher cutting modes.
Keywords: cutting tool, CBN-based PSM, vacuum-plasma coating, cutting modes, tool durability.