UDC 621.762.5
A. A. Shulzhenko, N. P. Bezhenar, S. V. Tkach, V. N. Tkach, S. A. Bozhko (Kiev)
Formation of the structure and hardness of cubic boron nitride composites during reaction sintering on a hard-alloy substrate
The article presents the results of a study of the elemental composition, structure and hardness of two-layer composites with a hard-alloy substrate and a working layer based on cubic boron nitride. It is shown that the composition and structure of the transition zone of two-layer plates are formed as a result of impregnation processes and reaction interaction in the cBN—Al—Co system, and a strong bond between the substrate and the working layer is ensured by limiting the reaction interaction in the Al—Co system.
UDC 661.657:539.89
V. L. Solozhenko, A. A. Kurakevich (Paris) V. Z. Turkevich, D. V. Turkevich (Kyiv)
Synthesis of boron suboxide B6O at pressures up to 1 GPa
Boron suboxide B6O was synthesized in a high-pressure multi-punch apparatus from the initial β-rhombohedral boron and boron oxide (III) at a pressure of 1 GPa and temperatures up to 2500 K by crystallization from the melt of the B—B2O3 system. The obtained samples were studied by X-ray diffractometry, scanning electron microscopy and X-ray microanalysis. It was found that at temperatures above 2000 K, B6O is formed with a stoichiometry close to the theoretical one, regardless of the composition of the initial reaction mixture in the concentration range from 78 to 98 ‰ (mol.) of boron. The interaction of boron and B2O3 at temperatures below 2000 K occurs with low intensity and is not accompanied by the formation of B6O.
UDC 544.72
V. M. Perevertaylo, S. V. Shmegera, L. Yu. Ostrovskaya (Kyiv)
Estimation of the surface energy of carbon materials based on measuring wetting angles
The effective free surface energy γ of carbon materials (diamond, diamond and diamond-like films) was estimated based on measuring the wetting angles, taking into account the pressure of adsorbed vapors. The obtained values of γ are in quantitative agreement with the available literature data taking into account the surface reconstruction, and refine them, showing that the degree of wettability and the value of γ are also determined by the type of chemisorbed adsorbates.
UDC 661.65:661.55
S. N. Dub, N. V. Novikov, Yu. V. Milman (Kiev)
Method for Determining Young’s Modulus under Elastic Local Deformation of a Sample Surface
A new method for determining the elastic modulus of solids under nanoindentation is proposed, which is more local and more accurate than the generally accepted Oliver and Farr method. To find the elastic modulus, the elastic section of the loading curve of a flat sample surface with a spherical blunting at the top of the Berkovich indenter is used. The problem of elastic contact of a sphere with a half-space has an exact solution (the Hertz problem), which allows finding the elastic modulus based on the dependence of the elastic displacement of the Berkovich indenter tip on the load at ultra-shallow depths. Tests of materials with a known elastic modulus on the Nano Indenter II device showed that the blunting at the tip of the Berkovich indenter has a shape close to spherical, and allowed us to determine its radius. The elastic modulus values for a number of single crystals were obtained, which coincide well with the reference values.
UDC 539.434:669.5:546.261
V. O. Kochubey, V. A. Lavrenko (Kiev) D. Naumenko, E. Vessel, L. Singaiser, V. D. Quadekkers (Jülich, Germany)
The influence of impurity carbon and chromium carbides formed at the scale-metal interface on the features of high-temperature oxidation of heat-resistant alloys of the Fe-Cr-Al-Y system
The features of oxidation in air at 1200 °C of Fe-Cr-Al-Y alloys with a carbon content of 92 and 530 ppm were studied. In both cases, the formation of chromium carbides Cr7C3 and Cr3C2 was detected at the grain boundaries of the alloys after their long-term (up to 20,000 h) exposure to air at 1200 °C, and in the case of an alloy with a high carbon content, their formation was also detected at the alloy-scale (Al2O3) interface. It was shown that in the case of oxidation of an alloy with a high carbon content, this effect reduces the adhesion of the scale to the metal substrate and, in combination with more intense formation of chromium carbides at the grain boundaries, leads to scale peeling off approximately 2000 h after the start of oxidation.
UDC 548
A. V. Lysenko (Kyiv)
Force constants of elastic deformation of chemical σ-bonds in diamond and superhard single crystals with sphalerite lattice
A relationship between the parameters of external and internal deformation of polyhexacyclic stereomers was established using a complex method of continuum and molecular mechanics. An algorithm for direct and inverse calculation of elastic constants of the studied single crystals from the value of elastic deformation constants of chemical σ-bonds and reversible deformation of valence angles was determined. The algorithm found was used to model the elastic constants of the least studied covalent single crystals with sphalerite lattice.
UDC 620.178.3.16:621.9.048
V. Yu. Danilchenko, O. M. Semirga (m. Kiev)
Patterns of molding carbide electro-spark coatings on a steel base
To The regularities of the cobalt stage of forming a carbide electrospark coating on a lining of U8 steel have been observed. It has been shown that the increase in coating is due to the development of rare-float and solid-phase mass transfer in a type with the mechanism of erosion of the adjacent phase warehouses of the light-duty electrode for the T15K6 alloy.
UDC 621.9
V. I. Sidorko, Yu. D. Filatov, A. Yu. Filatov, L. V. Poperenko (Kyiv)
Study of the state of the surfaces of the workpiece and tool during polishing of non-metallic materials
As a result of studying the optical constants of the workpiece in situ during polishing, it was shown that the absorption and reflection coefficients of light increase with a decrease in the phase difference of oscillations of mutually perpendicular components of the electric vector of the beam, which passed twice through the thickness of the sample, reflecting from the workpiece surface. The dependences of the optical constants of the workpiece on the polishing time were obtained experimentally and approximated by periodic functions. It was found that periodic changes in the optical constants of the workpiece and the state of the surface of the working layer of the tool are associated with the formation of plaque.
UDC 621.928.4; 621.921.1:621.922.34
N. V. Novikov, G. P. Bogatyreva, G. A. Petasyuk (Kyiv)
On the issue of increasing the information content of morphological characteristics of powders from superhard materials determined on video-computer diagnostic complexes
An analysis of the information content of the characteristics of powders from superhard materials obtained by averaging by finding the arithmetic mean was carried out. To increase the information content of the main characteristics, it is proposed to use additional indicators. A new parameter called the stability index of the main characteristic indicator is proposed. The advantage of the introduced additional indicator in comparison with other parameters that can be used as additional indicators is scientifically substantiated and confirmed by practical examples. Recommendations are given on the practical application of the methodology of additional indicators for comparing the quality of powders from superhard materials with similar main characteristics.
UDC 548.58
V. A. Mukhanov, V. S. Kovalenko (Aleksandrov, Vladimir Region, Russia)
Isolation of diamond from sapphire sludge.