UDC 621.921.34-492.2:620.22-419
S.N. Nazarchuk, A. AND. Bochechka, V.S. Gavrilova, L.A. Romanko, N.N. Belyavina, L. I. Alexandrova, V. N. Tkach, E.F. Kuzmenko, S.D. Zabolotny (Kyiv)
Polycrystalline composite material diamond–tungsten carbide
The sintering at high pressure and temperature of a diamond composite made of diamond and tungsten powders in the submicro- and nanoranges is described. It is shown that as a result of interaction between diamond and tungsten during the sintering process, tungsten carbide particles chemically bonded to diamond particles are formed in the spaces between diamond particles. In the composite, a structure is observed throughout the volume, where the grains of tungsten carbide and diamond are placed regularly and are uniform in size. The introduction of a large diamond component into the composite increases its wear resistance. The optimal sintering parameters and composition of such a composite have been determined.
Key words: diamond composite, sintering, high pressure, diamond nanopowder, tungsten carbide.
UDC 548:533:951
AND. IN. Kurdyumov, V. F. Brytun, V. IN. Yarosh, Yu. M. Solonin, N. I. Borymchuk, V. B. Zelyavsky, A. I. Danylenko (Kyiv)
Shock-wave synthesis of diamond nanofibers and their structure
Diamond nanofibers obtained by high-temperature impact compression of graphite nanofibers in the presence of KCl salt at pressures of 25–35 GPa and temperatures of 3000–3500 K are described. Synthesized fibers consist of chaotically disoriented diamond nanograins with an admixture of an amorphous phase, the content of which decreases with increasing shock compression pressure.
Key words: shock compression, phase transformations, diamond nanofibers, amorphous carbon.
USD 661.657:539.31:519.6
Thabo E. Letsoalo, J. E. Lowther (Johannesburg, South Africa)
Computational investigation into elastic properties of bulk and defective ultrahard B6O
Elastic properties of bulk B6O – an important material with superhard properties have been studied. The influence of O vacancies and light substitutional defects such as C and N has been examined. It has been shown that vacancies in particular exert a pronounced effect on such properties of the material as elastic constants and melting temperature.
Keywords: ultrahard B6O, superhard properties, elastic properties, vacancies, substitutional defects, elastic constants, melting temperature.
UDC 621.921.34-666.233
V.M. Dmitriev, A.V. Terekhov (Kharkov) V.N. Uvarov A.D. Shevchenko (Kyiv) Ya. Tsvyk (Wroclaw) A.A. Shulzhenko A.N. Sokolov (Kyiv) D.S. Kondrashev (Kharkov)
Features of magnetoresistive effects in nanostructured diamond compacts
The results of the study of the behavior of specific electrical resistance in nanostructured diamond compacts obtained by barothermal treatment of various nanodiamond powders in a wide range of temperatures and external magnetic fields are presented. It was established that the conductivity of nanostructured diamond compacts is not related to the presence of impurity atoms in the samples and can be caused by the presence of dislocations playing the role of acceptor centers. The effects of positive and negative magnetoresistance, which can be associated with the growth of the contribution to ohmic losses at low temperatures of quantum corrections, are found.
Key words: diamond, nanostructure, compact, high pressure, conductivity, magnetic resistance
UDC 621.762; 546.261
V.V. Ivzhenko, O.N. Kaidash, G.F. Sarnavskaya, S.N. Dub, V.A. Popov, L.M. Bologova, S. AND. Lysovenko (Kyiv)
Peculiarities of structure formation and properties of materials from the B4C–TiH2 powder system during reaction sintering under pressure
The results of the research of reactive sintering under pressure in the В4С–TiН2 system are presented. It is shown that the structure of the materials consists of a B4C matrix phase and an intergranular titanium diboride (carboboride) phase with low mutual solubility of the components. The physical and mechanical properties of materials depending on their composition are studied. An increase in the content of titanium hydride to 9 ‰ (by volume) leads to a decrease in hardness by 16 ‰, slightly affects the bending strength (≈ 500 MPa), increases the crack resistance by 60 ‰ to 6.0 MPa·m1/2, and the coefficient of thermal expansion by 90 ‰ to 5.2·10–6/K.
Key words: boron carbide, titanium diboride, hot pressing, reaction sintering, hardness, bending strength, crack resistance, coefficient of thermal expansion.
UDC 621.623
AND. Yu. Filatov, L. IN. Poperenko, V. P. Yashchuk, V. I. Sydorko (Kyiv) U. Heisel, M. Storchak (Stuttgart, Germany)
Formation of plaque of wear products on the surface of the working layer of the polishing tool
On the basis of the quantum-mechanical theory of scattering, the interaction of particles of sludge of the processed material and particles of tool wear in the contact zone during the polishing process is described. It is shown that forward scattering of sludge particles occurs mainly on sludge particles, and the probability of their scattering on wear particles is insignificant. The distribution function of the total cross-section of the scattering of sludge particles along the radius of the circular zones of the working surface of the tool is determined ment and the coordinates of the plaque localization zone, the approximate number and sizes of plaque fragments are established. The results of experimental confirmation of theoretical calculations are given.
Keywords: polishing, sludge particles, particle scattering, scattering cross section, plaque.
UDC 621.9
V. I. Lavrinenko (Kyiv) V. Yu. Solod (Dneprodzerzhinsk) B. V. Sytnik, Yu. I. Nikitin (Kyiv)
Application of supporting elements in the structure of the working layer of wheels made of superhard materials to increase their operational indicators
A study is presented to identify ways of effective application of supporting elements in the working layer of wheels made of superhard materials in the form of layered compacts or crushed cyborite to increase the operational parameters of such wheels in grinding processes.
Keywords: support element, working layer, grinding wheel, compact, kyborite, wear resistance.
UDC 621.921
IN. I. Kush, N. AND. Bondarenko, D. L. Korostyshevsky, A. WITH. Osipov (Kyiv)
Influence of the geometry and properties of the diamond–hard alloy interface on the resistance to destruction of diamond–hard alloy plates
A developed theoretical approach to the assessment of the influence of the geometry and properties of the diamond–hard alloy interface surface on the final technological stresses and resistance to destruction of diamond–hard alloy plates is presented. Unlike those known in the literature, the proposed model assumes the ultimate strength of the connection of the working layer with the substrate and adequately describes the process of initiation and growth of an interfacial crack under the action of final stresses and external loads. Model parameters were identified by comparison with experimental data, and the influence of thermobaric parameters of the sintering process on the level and distribution of final stresses was investigated. In the mode of the computational experiment, the minimally necessary and real adhesive strength of the connection of the diamond layer with the substrate was determined. The model provides a solution to the problems of designing diamond-hard alloy plates with a minimum level of ultimate stress and rational selection of the profile of the interfacial surface to increase resistance to brittle fracture.
Keywords: final stresses, interfacial surface, adhesive strength, mathematical model, sintering pressure, shear test.
UDC 666.792.34:539.89
D. AND. Stratychuk, M. AND. Tonkoshkura, V. WITH. Turkevich (Kyiv)
Formation of superhard phases in Salm-AlB12 and Salm-AlB2 systems under conditions of high pressures and temperatures
The chemical interaction of diamond with aluminum borides with the formation of ternary compounds in the diamond–diamond intergranular space is reported.
Keywords: aluminum borides, high pressures, interphase boundaries, sintering of diamond micropowders.