UDC 621.315.592
N. V. Novikov, A. N. Katrusha, S. A. Ivakhnenko, O. A. Zanevsky (Kyiv)
The Effect of High-Temperature Treatment on the Defect-Impurity Structure and Color of Diamond Single Crystals (Review)
The article discusses the development directions of a new method for treating natural and synthetic diamond single crystals using high temperatures and pressures, proposed by General Electric. It describes the application of this method to change the defect-impurity composition of diamond single crystals in order to obtain a unique color of crystals — rich yellow, orange, pink, light blue, green, and others.
UDC 541.1:546.273.171
V. Z. Turkevich, V. L. Solozhenko, O. G. Kulik, P. P. Itsenko, A. N. Sokolov, A. N. Lutsenko, A. N. Vashchenko (Kiev)
Phase diagram of the Mg—B—N system at high pressures
The experimental study of phase equilibria in the ternary Mg—B—N system at a pressure of 4.5 GPa was performed using synchrotron radiation diffraction, metallographic, X-ray and micro-X-ray spectral analyses of samples quenched from high pressures. The obtained results were used to find the interaction parameters in phenomenological models of the phases of the studied system. Thermodynamic calculation of phase equilibria with the participation of boron nitride at a pressure of 4.5 GPa was performed. The Mg—B—N system is characterized by the presence of seven invariant four-phase equilibria, six of which are peritectic and one is eutectic. The minimum crystallization temperature of cBN from a solution in a melt at 4.5 GPa is 1600 K and corresponds to the temperature of stable equilibrium of cubic boron nitride with a liquid phase of the composition 46 ‰ (mol.) Mg, 21 ‰ (mol.) B, 33 ‰ (mol.) N in the plane of peritectic equilibrium L + BN = Mg3B2N4 + MgB2.
UDC 666.233:62-987
N. V. Novikov, A. A. Leshchuk, L. I. Aleksandrova, A. I. Borimsky, A. N. Vashchenko (Kiev)
Experimental study of diamond crystallization zones in a high-pressure apparatus of the “anvil with cavities” type
Experiments were conducted on the synthesis of diamonds in a high-pressure apparatus of the “anvil with cavities” type with uniform placement of powder reaction components (a mixture of graphite powder and Ni-Mn alloy particles) in the reaction cell. An electron microscopic study of diamond crystallization zones on fractures of sinters obtained at different values of the heating current power during the synthesis was performed. The obtained experimental data confirm the results of previously performed computer modeling of crystallization zones of diamonds of different habits.
UDC 539.374:539.893
S. B. Polotnyak (Kyiv)
Effect of high pressure and shear strain on structural changes in materials during deformation on diamond anvils
The effect of anvil rotation and, accordingly, additional plastic shear strain on phase transition processes occurring in materials under compression and shear on diamond anvils is studied. Analytical dependences of pressure distribution over the surface of a deformed sample during a phase transition; dependences of the sample thickness and the radius of the transformation region on the volume concentration of the new phase; equations for the relationship between the volume concentration of the new phase in the transition region and the angle of rotation of the anvil are obtained. It is shown that anvil rotation leads to a decrease in the sample thickness and stimulation of the phase transformation process due to a decrease in the transition pressure. Improvement of the phase transition conditions during anvil rotation is associated with an additional displacement that compensates for the decrease in volume during the transition.
UDC 621.762
I. A. Podchernyaeva, A. D. Panasyuk, S. S. Zatulovsky, D. V. Yurechko, V. V. Varyukhno, A. M. Bloschanevich (Kyiv)
Structure formation and mass transfer of wear-resistant coatings during electric spark alloying of Al—Si alloys with composite ceramics of the LaB6—ZrB2 system
The kinetics of mass transfer, composition, structure and tribological properties of coatings formed on the surface of aluminum alloys AL9 and AL25 during their electric spark alloying with electrode materials of the LaB6—ZrB2 system were studied. It was shown that the presence of a dielectric component in the electrode electrical erosion products suppresses the electrical erosion of the aluminum cathode. A positive effect of solid solutions of oxides with La2O3, formed both during the coating formation and tribooxidation under friction conditions without lubrication, on the wear rate of coatings at low (≤0.2 m/s) sliding speeds was established.
UDC 621.922
A. A. Adamovsky, A. B. Lyashchenko, Yu. B. Paderno (Kiev)
Zirconium dodecaboride — an effective abrasive material
The feasibility of using zirconium dodecaboride ZrB12 as an abrasive in diamond tools for processing titanium and its alloys and an additional abrasive in diamond wheels for processing glass is considered. The prospects for its use in grinding wheels, honing stones, and abrasive belts are shown.
UDC 621.9
A. V. Usov, G. A. Oborsky (Odessa)
The influence of thermomechanical phenomena on the stability of the cutting process and wear of cutting tools
The dynamics of the cutting process is considered taking into account the contact temperature in the processing zone. It is established that the process is best stabilized in the contact temperature zone of 0.4-0.6 of the melting temperature of the material being processed. The minimum wear of the tool occurs in the zone of its contact with the material being processed.
UDC 621.923
A. A. Shepelev (Kiev)
Kinematics of the vibration-precession grinding process
The kinematic diagram of the vibration-precession grinding process is considered, which is based on a combination of directional vibration and precession effects and ensures the formation of cutting surfaces with a quasi-regular microrelief. This allows the implementation of this process without the additional use of external vibration sources, achieving a significant increase in processing productivity and a decrease in its effective power.
UDC 621.922.029
M. A. Grigoryan (Yerevan)
Technological Possibility of Increasing Wear Resistance of Corner Diamond Dressing Rollers
To improve wear resistance of the dressing roller top, a diamond corner roller with a special top containing large diamond grains on a cylindrical belt is proposed, and the results of its use in the process of profiling worm wheels are studied. It is shown that the service life of such a roller is almost twice as long as that of conventional ones. Theoretical and experimental studies of brittle fracture of diamond grain in dynamic mode are carried out.
UDC 681.7.023.7
V. V. Rogov, A. G. Vetrov (Kyiv) A. A. Boyarintsev (Kharkov)
Development of diamond micromilling technology for parts made of non-metallic materials