UDC 621.762.5:661.657.5
M. P. Bezhenar, S. M. Konoval, S. A. Bozhko, M. G. Loshak, L. I. Aleksandrova, M. I. Zaika, P. A. Nagorny, N. M. Bilyavina (Kyiv)
Physical and mechanical properties of cBN composites obtained by high-pressure reaction sintering of cubic boron nitride powders with aluminum
The studied physical and mechanical properties (crack resistance, hardness and its dependence on temperature) of experimental samples of cBN—Al composites obtained at a pressure of 4.2 GPa and a temperature of 1750 K with varying the aluminum content in the charge and the duration of sintering are presented. The influence of the phase composition and real crystal structure on the properties of the composite is shown.
Key words: cubic boron nitride, composite, high pressure, reactive sintering, crack resistance, hardness.
UDC 666.233: 621.7.044.2
IN. Yu. Dolmatov (St. Petersburg, Russia)
Detonation nanodiamonds in oils and lubricants
The main results of studies on the possibility of using detonation nanodiamonds and their diamond-containing charge (a semi-product of the synthesis of nanodiamonds) as highly effective antifriction and antiwear additives in oil compositions are presented. The effectiveness of the use of the specified products is shown: the resource of tools and parts increases by 1.5-4.0 times and the growth of ultimate loads on the friction pair – by 4 times.
Key words: detonation nanodiamonds, diamond-containing charge, antifriction and antiwear additives, oil compositions.
UDC 661.88
AND. AND. Sivkov, A. I. Park (Tomsk, Russia)
On the possibility of dynamic synthesis of ultradispersed crystalline phases of the B—C—N system in a hypervelocity plasma jet
The results of research studies on the dynamic synthesis of cubic boron nitride cBN and cubic carbon nitride cС3N4 in a hypervelocity pulse jet of boron-carbon electric discharge plasma flowing into space with a nitrogen medium are presented. The plasma source is a high-current pulse coaxial magneto-plasma accelerator with a graphite accelerator channel. The obtained data show the possibility of synthesis of ultradispersed cubic boron nitride and covalent carbon nitride.
Key words: hypervelocity jet, boron-carbon plasma, dynamic synthesis, ultradispersed cubic boron nitride, ultradispersed crystalline covalent carbon nitride.
UDC 544.3:621.762
AND. F. Lysovsky (Kyiv)
On the thermodynamic interpretation of Laplace pressure
The results obtained using the thermodynamic method of J. are presented. IN. Gibbs’s expression of Laplace pressure and justified areas of its correct application. It is shown that the expression can be used only when applied to macro-objects to describe surfaces with a constant value of curvature, namely: spherical, cylindrical, and flat, but not to describe nanodispersed systems, as well as surfaces with variable values of curvature.
Key words: Laplace pressure, thermodynamics, consolidation.
UDC 666.3:539.5
AND. P. Fesenko, T. B. Serbeniuk, V. AND. Chasnyk, V. WITH. Bilovol, V. M. Kolodnitskyi, M. G. Loshak, A. AND. Marchenko, Yu. M. Tuz, Yu. AT. Strunin, S. IN. Tkach, E. AND. Fesenko, I. P. Shashurin (Kyiv)
Physical and technical properties of ceramics and composites with a ceramic matrix based on wurtzite AlN
Ceramic materials developed on the basis of wurtzite aluminum nitride, obtained by free sintering and hot pressing methods, are presented. The materials have a high level of mechanical and thermophysical properties: structural ceramics with hardness HV = 16.8 GPa, crack resistance KIc = 4.7—4.9 MPa×m1/2, bending strength s = 370—430 MPa; functional ceramics for heat sinks – with thermal conductivity up to 140 W/(m·K), for microwave absorption – with dielectric permittivity ε = 23, dielectric loss tangent tgδ = 0.025, electromagnetic energy attenuation coefficient L up to 36.3 dB/cm (frequency 3 GHz). The developed materials were compared with materials from world manufacturers.
Keywords: AlN, composites, microstructure, thermal conductivity, hardness, dielectric properties.
UDC 621.822.71: 666.22.037
K.G. Shchetnikovych (Minsk)
Study of the kinematics of balls made of brittle non-metallic materials during fine grinding with a coaxial ring tool made of superhard materials
A description of the design of the tool for grinding balls made of brittle non-metallic materials between the coaxially installed lower drive disc and clamping rings is given. The kinematics of balls sliding on one and two surfaces in contact with the tool is considered. The forces of adhesion and friction of the ball with the tool at increased load on the fixed ring are determined. The obtained dependence between the loads on the ring and the angle of inclination of the instantaneous axis of rotation of the ball.
Key words: tools for fine grinding of balls, brittle non-metallic materials, adhesion and friction forces, kinematic characteristics.
UDC 621.923
R. M. Strelchuk, M. D. Uzunyan (Kharkov)
Analysis of energy consumption of diamond-spark grinding of nanostructured hard alloy VolKar
Rassmot recent issues of processability of the new nanostructured hard alloy VolKar based on the analysis of the specific energy intensity of the diamond-spark grinding process. It is shown that, despite the slightly higher energy consumption of grinding the VolKar alloy compared to the VK6 alloy, the total technological cost of its use is significantly lower, since the tools sharpened by it have a higher wear resistance.
Key words: nanostructured hard alloy VolKar, specific energy intensity, total technological cost, diamond-spark grinding.
UDC 004.942:621.785:621.9.025.7
IN. AND. Dutka (Kyiv)
Computer modeling of the creation of a difference in mechanical properties on the surface of a carbide cutter holder as a result of quenching after induction brazing
It is proposed to use a scheme for intensive cooling of a part of a steel carbide cutter holder during the quenching process after induction brazing. According to this scheme, cooling of different parts of the holder surface is carried out in such a way as to obtain different martensite contents in them to create a difference in mechanical properties. The scheme is illustrated by examples of computer prediction of the difference in mechanical properties of a 35KhGSA steel carbide cutter holder during quenching in aqueous solutions of Na-CMC polymer and in I-20 lubricant. It is shown that by choosing a quenching medium and a cooling scheme, it is possible to ensure a high level of hardness of the most worn part of the holder surface during the operation of the cutter and its high impact strength in the area of attachment of the cutter in the tool.
Keywords: computer modeling, induction brazing, hardening, difference in mechanical properties.