UDC 536.42:661.657.5
A. A. Shulzhenko, N. P. Bezhenar, S. A. Bozhko (Kiev), A. V. Romanyuk (Vyshgorod)
Sintering of cubic boron nitride polycrystals from powders obtained in different growth systems
The sintering of polycrystals from CBN powders obtained in different growth systems was studied — with excess nitrogen around the growing crystal (amber CBN) and with excess boron (black CBN). The effect of the composition of the growth system on the physical and mechanical properties of polycrystals was shown. When sintering polycrystals without process-activating additives, it is preferable to use black CBN powders to obtain higher hardness.
UDC 621.762
M. O. Kuzenkova, S. M. Dub, I. P. Fesenko, R. S. Shmegera (metro Kiev)
High-temperature melting of AlN-ceramics
Changes in the structure and mechanical power of aluminum nitride are described, which are observed at high temperatures at temperatures of 2, 20, 50 and 100 years. It was revealed that the average size of AlN grains changes with an hour of isothermal heating according to a parabolic law and grows from 4.0 to 12.0 µm. At 20-year sintering, stresses in the AlN crystal grain decrease, the elastic modulus increases and stabilizes. The thermal expansion coefficient of AlN is developed, the hardness and Young’s modulus of AlN grains are determined.
UDC 548
A. V. Lysenko (Kyiv)
Molecular relationship between plastic flow parameters, hardness and structure of the densest forms of carbon
A mechanochemical model of diamond plastic deformation is considered, taking into account the effect of rupture (and subsequent restoration) of chemical σ-C—C bonds in the cores of gliding dislocations on the mechanism of plastic flow. The influence of diamond plasticity parameters on the crystallographic anisotropy of its hardness is investigated. The inapplicability of classical metallophysical methods for increasing the mechanical characteristics of materials to diamond is shown. The possibility of synthesizing stressed forms of carbon with mechanical properties superior to diamond is considered.
UDC 62-987
A. I. Prikhna (Kyiv)
High-pressure apparatus with a compressible cylinder
A high-pressure apparatus for diamond synthesis is described, containing a hollow cylinder composed of springs or wedges. Its advantages over traditional apparatuses are shown.
UDC 669.018.25
V. I. Kushch, A. F. Lisovsky, S. I. Shestakov (Kyiv)
Modeling of mesostructure in sintered hard alloys
A rigorous approach to modeling nonlinear mechanical behavior of a hard alloy with a mesostructure is proposed, based on a finite element solution of spatial model boundary value problems. Based on the numerical analysis of elastic-plastic deformation of mesoalloys under uniaxial compression, their deformation diagrams are constructed, the dependences of Young’s modulus on the volume content of cobalt are established. Good agreement is obtained between the calculated and experimental data on the elasticity of traditional hard alloys. For mesoalloys based on VK6 and VK15, the specific work of deformation of the composite as a whole and for each of the phases is determined, the total work of deformation, its elastic and plastic components are calculated. It was found that for a given volume of cobalt, the deformation work for the VK15+Co mesoalloy is 1.8 times greater than for the VK6-based mesoalloy. Based on the proposed criterion for the transition of the considered mesoalloys to the ultimate state, a forecast was given for the value of their strength limits and ultimate elastic-plastic deformation under uniaxial compression.
UDC 544.722.1:620.22
V. M. Perevertaylo, O. B. Loginova, O. I. Aslanova (Kiev)
Wetting of solids of different physicochemical nature with aqueous solutions
The wettability of carbon modifications, boron nitride, stabilized tetragonal zirconium dioxide, aluminum oxide, silicon oxide with water, glycerol and aqueous solutions with different pH values was studied, a conclusion was made about the influence of the degree of ionicity of the solid phase and the nature of the functional groups located on the surface of solids on wetting.
UDC621.941
S. A. Klimenko, Yu. A. Melniychuk (Kyiv)
Fractal approach to studying the machinability of protective coatings by cutting
The results of the study of the machinability of a number of wear-resistant quasi-amorphous gas-thermal coatings by cutting are presented. Based on the provisions of fractal formalism, a single integral characteristic of machinability is proposed – the fractal dimension of the set of mechanical properties of the material, comprehensively characterizing the homogeneity of its structure and the spread of properties by value. The prospects of using the proposed method for assessing the nature of heat distribution in a material with a heterogeneous structure by a fractal indicator for determining the thermophysical characteristics of sprayed coatings are shown.
UDC 621.923.4:621.922.34+621.047.7
N. V. Novikov, R. A. Gurvich (Kyiv)
Change in effective power under the influence of electric potential during diamond electrolytic treatment of hard alloys with polycrystalline cathodes
Information on the features of the anomalous change in the effective power in diamond-electrolytic processing of hard alloys with polycrystalline cathodes with smooth working surfaces. The dependences of the change in power on the value of voltage on the electrodes and the “residual effect” of voltage on the processed hard alloy are shown. It is noted that the anomalous change in Neff is inadequate to the change in the density of the process current with an increase in voltage on the electrodes. The original experimental data on the relationship between power, process current and voltage on the electrodes for various combinations of processing options are presented in the form of oscillograms. Based on the analysis of the relationship between the parameters in the main areas of the volt-ampere characteristic, it is recommended to carry out the process of diamond electrolytic processing of hard alloys with polycrystalline cathodes at a voltage of 15 V.
UDC 621.923
P. G. Matyukha, V. V. Poltavets (Donetsk)
Calculation of the loading of sections of the working surface of the wheel in the axial section
The distribution of the load on the sections of the working surface of the wheel during flat grinding of R6M5F3 steel with a 1A1 250×76×15 3 AC6 100/80100M2-01 wheel was studied. It was found that the section that first comes into operation during the transverse feed of the wheel is loaded to the greatest extent (85‰ of the total tangential cutting force on the wheel). When grinding with electrical discharge control effects on the working surface of the wheel with a transverse feed of 0.8 of the wheel height, the deviation from the straightness of the wheel profile in the axial section is minimal.
UDC 621.928.4:621.921.1:621.922.34
N. V. Novikov, Yu. I. Nikitin, G. A. Petasyuk (Kyiv)
Computer diagnostic sieve for identifying the grain size and grain composition of microscopic samples of diamond grinding powders
The methodology and algorithmic foundations of indirect diagnostics of grinding powders from synthetic diamonds are presented in order to determine the grain composition indicators and establish the grain size without conducting a standard procedure for control sieve analysis. A method for solving problems of this class based on microscopic analysis data is proposed, which the authors call a computer diagnostic sieve. Examples of typical problems arising in the practice of using grinding powders from synthetic diamonds and the results of their solution by the developed method are given. An express method for establishing the grain size of grinding powders from synthetic diamonds by the average values of the grain width and the coefficient of their shape is proposed.