UDC 548.39:539.2
N. A. Bondarenko, N. V. Novikov, V. A. Mechnik, G. S. Oleynik, V. M. Vereshchaka (Kyiv)
Structural features of superhard composites of the diamond-hard alloy VK6 system, characterized by wear resistance
The results of the study of the structural state and mechanisms of destruction of two types of superhard composites are presented – diamond-hard alloy VK6 and diamond-hard alloy VK6 with additives CrB2 and W2B5, obtained by hot pressing. It is concluded that the strength of the diamond-matrix contact, which determines diamond retention in the composite, and the characteristics of its abrasive wear are determined by a combination of a number of factors – the degree of continuity of the diamond-matrix interface, the nature of the interaction during contact at the diamond-matrix interface, the homogeneity of the grain microstructure and phase composition of the matrix, the nature of the stress-strain state on the diamond-matrix contact surface.
UDC 661.65:661.55
S. N. Dub, N. V. Novikov (Kiev)
Nanohardness Testing of Solids
A method of mechanical testing of solids for nanohardness is considered. The Oliver and Farah method for finding nanohardness by the depth of an indentation at maximum load on the indenter and the method for finding the average contact pressure for all data points of the Berkovich indenter loading diagram are presented. The possibilities of the nanoindentation method for testing thin films, studying the mechanisms of plastic deformation of materials, the effect of high pressure on matter and the mechanical behavior of nanovolumes of materials are shown.
UDC 542.943:621.921.34
S. K. Gordeev, S. B. Korchagina (St. Petersburg)
Are nanodiamonds “small”?
The results of oxidation of nanodiamonds with atmospheric oxygen are presented. Oxidation with oxygen is presented as a simple way to reduce the size of a nanodiamond particle. It is established that nanodiamond samples from different manufacturers have different reactivity. Analysis of the sizes of the RCS and the values of the specific surface of nanodiamonds with oxidation states up to 80-90 ‰ allows us to discuss the possibility of obtaining diamond particles with sizes less than 4 nm.
UDC 620.186:620.22-419
S. V. Tkach, E. F. Kuzmenko, V. N. Tkach, A. G. Gontar, A. A. Shulzhenko (Kyiv)
Determination of microhardness in local areas of a two-layer cutting plate created on the basis of cBN
The effect of the structure in local areas of a two-layer cutting plate of the composition VK6—(cBN, TiN, AlN) on microhardness was studied. It was found that the average value of microhardness of the composite (cBN, TiN, AlN) corresponds to 29 GPa. The dispersion of microhardness does not exceed 10 ‰, which indicates sufficient homogeneity of the mechanical characteristics of the composite. The presence of cobalt (≈ 8 ‰) at a distance of up to 60 μm from the boundary with the VK substrate causes a decrease in the microhardness of the zone to 23 GPa, promotes a smooth change in the mechanical characteristics across the thickness of the two-layer plate and allows obtaining stable characteristics of the tool made of this material.
UDC 539.266
V. P. Kazimirov, A. S. Roik, V. M. Perevertaylo, O. B. Loginova (Kiev)
Structure of nickel-carbon melt of Ni92C8 composition
The results of X-ray study of liquid nickel and Ni92C8 melt are presented. The analysis of the local structure of atoms was carried out using models reconstructed from experimental curves of the structure factor using the inverse Monte Carlo method. It is shown that carbon atoms in the melt form predominantly curved chains of different lengths, the distance between the atoms in which is 1.40 Å, as well as closed formations in the form of triangles and tetrahedra, the proportion of which is very small. Nickel atoms form clusters of nanometer size (20-25 Å), the structural element of which is a decahedron – a seven-vertex polyhedron formed by five weakly deformed tetrahedra connected to each other by faces.
The relationship between the nature of the ordering of atoms in the melt and the capillary properties of the graphite-melt nickel-carbon contact system is discussed.
UDC 544.3:669.018.45
V. P. Bondarenko, I. V. Epik (Kyiv)
Thermodynamic Analysis of Reduction Processes in the Manufacture of Hard Alloys
Thermodynamic studies of heterogeneous reactions in the reduction processes of tungsten and cobalt and nickel binder metals from single oxides and binary oxide systems (WO3—H2, Со3О4—Н2, NiO—H2, WO3—Со3О4—H2 and WO3—NiO—H2) were carried out. The features of reduction processes in binary oxide systems were studied. The effect of the relative content of oxides in binary oxide systems on the amount of hydrogen required for their reduction was shown. The amount of hydrogen required to complete individual stages of heterogeneous chemical reactions and for the complete reduction of metals from oxides, as well as the value of the equilibrium dew point of hydrogen over W, Co and Ni oxides at a temperature of 1000 °C, was calculated.
UDC 539.213
S. P. Starik, O. G. Gontar, V. Yu. Gorokhov, B. A. Gorshteyn (Kyiv)
Optical characteristics of carbon coatings on backings silicon
The optical parameters of carbon coatings on silicon substrates were studied. The existence of a transition region between silicon and diamond-like melt was revealed. A software program has been created to unravel the wrapped task of ellipsometry.
UDC 621.315.592
A. N. Katrusha, S. A. Ivakhnenko, O. A. Zanevsky (Kyiv)
Features of Changes in the Defect-Impurity Composition of Natural Diamond Single Crystals under High Pressure and Temperature
The effect of thermobaric treatment at a temperature of 1800-2000 °C and a pressure of 5.5-6.5 GPa on the change in the defect-impurity composition of natural brown diamond single crystals, the concentration of impurity nitrogen in which exceeds 1020 cm3, was studied. The effect of the dominant aggregate form of nitrogen on the nature of color change during treatment was studied. Scientifically substantiated criteria for selecting diamond single crystals for targeted action on the defect-impurity composition in order to decolorize and obtain an orange color were developed.
UDC 621.623
V. V. Skryabin, Yu. D. Filatov, V. I. Sidorko (Kyiv)
Regularities of polishing products made of aluminosilicate materials with a tool with a bonded polishing powder
For modeling the structure of aluminosilicate materials, a fragment of MeAlSi3O was proposed, which, taking into account the interaction of the tool materials and the workpiece in the multi-frequency mode, made it possible to extend the cluster model of wear of silica-containing materials to the class of aluminosilicate materials. As a result of the conducted studies, it was shown that the values of the height parameter of roughness Ra of the polished surface and the polishing productivity depend on the difference in the frequencies of the natural oscillations of the fragments on the surfaces of the tool and the workpiece.
UDC 620.178.3: 621.9.025.72
A. G. Sulima (Kyiv)
Setup for dynamic testing of strength and crack resistance
A technique for calibrating a vertical impact testing machine for dynamic testing of metal and alloy samples is described. A method for increasing the reliability of starting a measuring system using a piezoceramic sensor is described.