UDC 620.178.015:559.3
It is dedicated to the memory of an outstanding specialist in the field of powder metallurgy and hard alloys, Professor Silvana Lux (Johannesburg, South Africa), whose scientific talent and organizational abilities made it possible to conduct joint research between scientists of Ukraine and South Africa.
Yu. IN. Mylman (Kyiv)
milman@ipms.kiev.ua
The influence of the structural state and temperature on the mechanical properties and deformation mechanisms of the hard alloy WC–Co (p. 3–23)
The results of publications in which a systematic study of the influence of the structural state of WC–Co hard alloys (cobalt bond content, WC grain size, contiguity) and temperature on mechanical properties and deformation mechanisms were summarized. The ductile-brittle transition, strain hardening, features of deformation in different temperature ranges, specifics of the mechanical properties of WC–Co alloys with submicron WC grains are discussed.
Key words: hard alloy WC–Co, hardness, yield strength and strength, strain hardening, temperature of the viscous-brittle transition, mechanism of plastic deformation.
UDC 544.47+544.146.5
THERE ARE. IN. Ishchenko, S. IN. Gaidai*, A. G. Dyachenko, E. IN. Prylutsky, A. AND. Beda, T. M. Zakharova (Kyiv)
*gaidaisv@mail.ru
Oxide Cu–Co–Fe system applied to carbon nanotubes synthesized on Fe2O3 (p. 24–32)
The catalytic activity of oxygen-containing Cu–Co–Fe catalysts deposited on carbon nanotubes in the CO oxidation reaction was investigated. Carbon nanotubes were synthesized on the Fe2O3 catalyst. It is shown that the activity of oxide Cu–Co–Fe catalysts depends on the processing of the initial metal-carbon material, the content and the technology of application of the active component. According to the data of X-ray phase analysis, thermodesorption mass spectrometry and transmission electron microscopy, the active component is a mixture of Cu2(OH)3NO3 and CuО phases, the ratio and distribution of which depends on the optimal conditions of catalyst synthesis, due to which the structural formation of active centers in the CO oxidation reaction occurs. The presence in the surface layer of a massive oxide Cu–Co–Fe component, obtained by a single application of the active component on carbon nanotubes, leads to a higher activity of catalysts in the oxidation of CO compared to catalysts obtained during its stepwise application.
Keywords: CO oxidation, applied oxide catalysts, carbon nanotubes.
UDC 669.762
V. T. Golovchan (Kyiv)
tverdosplav@ism.kiev.ua
On the mathematical theory of microstructure evolution during the final stage of liquid phase sintering (p. 33–40)
A new mathematical theory of the microstructure evolution during the final isothermal stage of liquid phase sintering has been developed. The basis of this theory has been formed by materials science and continuum mechanics. The microstructure evolution has been described by the system of non-linear differential equations, which contain more than ten parameters. Finite difference analysis has been performed for a heavy alloy cylindrical specimen. The results of the calculations have been compared with experimental data.
Keywords: mathematical theory, microstructure evolution, liquid-phase sintering, finite difference method, heavy alloys.
UDC 536.2:669.782
AT. N. Kaidash*, I.P.Fesenko (Kyiv)
I.AND.Kryl (Ivano-Frankivsk)
*ivv@ism.kiev.ua
Thermal conductivity, physical and mechanical properties and their relationship with the structure of free-sintered composites obtained from the nanodisperse system Si3N4–Al2O3–Y2O3(–ZrO2) (pp. 41–52)
The microstructure and properties of high-density materials obtained by free sintering of nanodispersed powders of the composite composition Si3N4–Al2O3–Y2O3(–ZrO2) were studied.It is shown that these self-reinforced materials with a low glass phase content have a bending strength Rbm = 720–850 MPa, Vickers hardness – 15.3–15.7 GPa, crack resistance – 6.0–6.1 MPa×m1/2, thermal conductivity – 15–25 W/(m·K). Factors affecting the level of physical and mechanical properties and thermal conductivity of silicon nitride materials are discussed.
Key words: silicon nitride, Si3N4, nanodisperse powder, free sintering, bending strength, Vickers hardness, crack resistance, thermal conductivity.
UDC 622.24.051:536.2:004.942
IN. AND. Dutka (Kyiv)
vadutka@yandex.ru
Numerical modeling of liquid phase permeation during sintering of ceramic composites (pp. 53–67)
A numerical model of permeation of porous samples of ceramic materials during sintering is presented. The mathematical model of the permeation process is based on the Richards equation and the Van Genuchten relations, which describe the permeability properties of the porous structure and the permeating liquid. The finite element method and a stable implicit time-difference scheme were used to discretize the Richards equation. Based on the results of solving test problems, comparing the obtained numerical results with the results of other authors and with the results of The adequacy of the numerical model was established by the experimental results. The results of computer simulation of liquid silicon impregnation of porous silicon carbide samples of various geometric shapes and sizes are presented.
Keywords: numerical simulation, impregnation, sintering, ceramic composites.
UDC 621.923
V. K. Starkov* (Moscow, Russia)
P. Blau, J. Gentzen (Chemnitz, Germany)
*v.starkov@stankin.ru
Study of the grinding process of steel cams with a cubic boron nitride tool without cooling (pp. 68–77)
Experimental studies simulating the grinding of cams from hardened alloyed steel have established that their processing with minimal heating of the treated surface with cooling by oil mist or without cooling is possible with a highly porous cubic boron nitride wheel. It was found that in order to minimize the thermodynamic stress of dry grinding, it is expedient to assign a processing mode with the maximum possible depth of cut of the circle and the minimum speed of rotation of the part.
Key words: dry grinding, high porosity grinding wheel, cubic boron nitride, oil mist cooling, grinding mode parameters.
UDC 621.9.029:620.19
AND. WITH. Manokhin, S. AND. Klymenko*, M. Yu. Kopeykina, S. An. Klymenko (Kyiv)
IN. IN. Roschupkin, M. M. Lyakhovytskyi (Moscow)
*atmu@ism.kiev.ua
Tribology of the cutting process with a tool equipped with PSTM based on KNB (pp. 78–92)
Mechanisms of contact interaction in the cutting zone of a tool equipped with PSTM based on KNB are considered, and their relationship with the conditions of thermobaric loading on the tool – cutting temperature and contact stresses – is shown.
Key words: tool, cubic boron nitride, cutting, cutting temperature, contact stresses, wear.
UDC 621.921.34–492.544.023.5:539.215
IN. G. Poltoratskyi, G. AND. Petasiuk* (Kyiv)
M. N. Safonova** (Yakutsk, Republic of Sakha, Russia)
AND. AND. Bochecka***, V. N. Tkach, V. WITH. Shamraeva (Kyiv)
*petasyuk@ukr.net
**marisafon_2006@mail.ru
***abochechka@mail.ru
New composite abrasive material from unclaimed natural diamond powders (p. 93–104)
The results of the study of physical properties and dimensional characteristics of unclaimed natural diamond powders are given. The procedure for compacting such powders by the method of physical and chemical synthesis at pressures lower than atmospheric is described. Sanding powders of a wide range of grain sizes were produced by the compact dispersion method and their morphometric and operational characteristics were studied. It is shown that such powders are suitable for use in diamond-abrasive tools and in the production of pastes.
Key words: unclaimed natural diamond powders, physical and chemical synthesis, compacts, grinding powders, morphometric and operational characteristics.