UDC 539.89:621.762.5:621.921.34-492.2
A. A. Bochechka (Kyiv)
Features of the structure of nanodispersed diamond powders and their consolidation under the influence of high pressures and temperatures (review)
A review of works devoted to the production of polycrystalline materials under the influence of high pressures and temperatures on nanodispersed diamond powders is carried out. In connection with this problem, works on the production, study of the structure, composition and properties of these powders are also considered. The reasons for the deterioration of the sintering process of diamond nanoparticles are analyzed. Promising methods for the formation of nanostructure in polycrystalline diamond-based materials are discussed.
UDC 548.33:539.2
V. F. Britun, A. V. Kurdyumov, I. A. Petrusha (Kyiv)
Structural Features of the Nucleation of Dense Phases during Compression of Hexagonal Graphite
The structural features of the transformation of hexagonal graphite under high pressures of static compression are studied. The initial samples were plates of highly textured pyrographite. Structural studies were carried out using transmission electron microscopy. Based on the obtained data on changes in the real structure of graphite, on the shape of crystals of the resulting dense phases and their orientation with respect to the matrix phase, a dislocation model of the nucleation of dense phases is proposed. According to the model, the formation of a particular dense phase is determined by the mutual orientation of the Burgers vectors of neighboring transformation dislocations. It is shown that the formation of hexagonal or cubic diamonds is determined by the field of elastic stresses in the matrix near the growing crystal.
UDC 539.216.2:546.26-162
A. V. Romanyuk, Yu. I. Gorlov (Vyshgorod) V. M. Perevertaylo, L. Yu. Ostrovskaya (Kyiv)
Features of Thermal Destruction of the Functional Coating of the Surface of Diamond and Diamond-Like Films
Using the quantum-chemical method MO LCAO in the AM1 approximation, the schemes of elementary processes of thermal destruction of surface compounds on diamond-like films, as well as similar structures on the surface of diamond, are considered. The thermal effects of these processes are estimated. The results of the analysis are in good agreement with the experimental data on thermal destruction of the functional coating of the studied films in contact with aggressive environments.
UDC 62-987:661.657.5
I. A. Borimsky, A. A. Leshchuk (Kyiv)
Study of temperature fields in high-pressure apparatuses of the “anvil with recesses” type during the synthesis of cubic boron nitride
Based on the results of computer modeling of the crystallization regions of cubic boron nitride with a change in the heating current power, an analysis of the efficiency of the high-pressure apparatus of the “anvil with recesses” type with various schemes of equipment of the reaction cell was carried out.
UDC 620.186:620.22-419
S. V. Tkach, E. F. Kuzmenko, V. N. Tkach, A. G. Gontar, A. A. Shulzhenko (Kyiv)
Possibilities of high-resolution digital scanning microscopy in studying the structure of a two-layer composite
A device for matching a scanning electron microscope with a computer PCI bus is described, allowing one to obtain 24-bit high-resolution images measuring 4096×4096 pixels. The structure of a cutting two-layer plate consisting of a carbide substrate and a composite based on cubic boron nitride: (WC—Co)-(cBN, TiN, Al) was studied using this device. The grain size of the composite was determined. It is shown that a thin (5 μm) layer containing 16 ‰ cobalt and 11 ‰ aluminum is formed at the substrate-composite interface during sintering. The composite has a wide (up to 60 μm) intermediate zone with a cobalt content of 8 ‰. The presence of an intermediate zone enriched with cobalt and the absence of cobalt in the composite at a distance of more than 60 μm ensure high performance properties of the cutting two-layer plate.
UDC 62-987: 620. 178.4/.6
P. A. Balabanov, A. I. Borimsky, S. B. Polotnyak, L. I. Aleksandrova (Kyiv)
Durability and typical types of failure of steel matrices of high-pressure apparatuses during the synthesis of superhard materials
The cyclic durability of steel matrices of high-pressure apparatuses during the synthesis of superhard materials was estimated numerically using the finite element method and the typical types of their failure during repeated alternating elastic-plastic deformation were investigated. A comparative analysis of the influence of mechanical characteristics of the matrix material on the number of cycles before its failure from low-cycle fatigue was performed. It was found that the cyclic durability of the matrix is determined, first of all, by the ultimate strength of its material, as well as the yield strength in the region in which the matrix is deformed plastically.
UDC 621.923
V. I. Kushch, A. E. Shilo, V. T. Chaly (Kyiv)
Mathematical model of heat transfer in the diamond grain-coating-polymer bond system
A theoretical method for assessing the thermal regime of a coated diamond grain when it operates as part of a grinding wheel on a polymer bond is proposed, providing a detailed description of the temperature field in the diamond-coating-bond system. By means of numerical modeling, It has been established that the application of both glass and metal coatings significantly reduces the peak temperature during the grain operating cycle, but the mechanisms for such a reduction are different. As calculations show, the glass coating is a barrier for short thermal pulses, while the role of the metal coating is mainly to increase the effective thermal conductivity of the working surface of the wheel and, consequently, to reduce the temperature at the diamond-part contact. The results of a study of the effect of coating thickness and contact time on the thermal regime of the bond are presented, analytical formulas are proposed that allow thermophysical calculations of glass coatings to be carried out with sufficient accuracy for engineering calculations. The developed model can be used in combination with laboratory studies to optimize both the design of the grinding wheel and the technological parameters of its operation. UDC 621.913 : 621.833
A. V. Krivosheya (Kiev) V. E. Melnik, A. V. Korinets (Zhitomir)
Mathematical models of shaping links of flat gear systems
Using the theory of multiparameter mappings of affine space, a generalizing unified and compact mathematical model of shaping links of flat gear systems without deriving cumbersome analytical dependencies has been developed. In the universal integrated system for automation of mathematical and scientific-technical calculations Mathcad, a software package has been developed for the assignment, mathematical description, shaping and visualization of links of flat gear systems.
UDC 621.941
S. A. Klimenko, M. Yu. Kopeikina, Yu. A. Melniychuk, O. G. Kulik, I. A. Petrusha, Yu. A. Mukovoz (Kyiv)
Improving the efficiency of a cutting tool equipped with a CBN-based PSTM
The possibility of increasing the efficiency of a cutting tool made of polycrystalline superhard materials based on cubic boron nitride by controlling the chemical interaction of the tool and workpiece materials in the cutting zone is shown. The results of testing a tool equipped with a new cubic boron nitride-silicon nitride composite when turning hard-to-machine steels and alloys are presented.
UDC 666.792.34:539.89
A. A. Shulzhenko, D. A. Stratiychuk, V. G. Gargin, N. N. Belyavina (Kyiv)
Production and physical and mechanical properties of cermet based on B—C—Si