UDC 544.31:621.921.34:661.878
V. Ya. Zabuga, G. G. Tsapyuk, T. O. Shpadkivska, O. O. Bochechka* (Kyiv)
*tetiana.sh@ukr.net
**bochechka@ism.kiev.ua
Thermodynamic aspect of the mechanism of diamond oxidation in the presence of tungsten (pp. 3–11)
The thermodynamics of reactions possible in the carbon–tungsten–oxygen system under the conditions of kinetic experiments on the oxidation of diamond by oxygen in the presence of tungsten is analyzed. A kinetic scheme of the process is proposed, consisting of reactions in which the Gibbs energy changes are the largest in magnitude and negative in sign. The scheme satisfactorily explains the fact of a decrease in the rate of diamond oxidation by the modification of its active centers by tungsten. At low tungsten content, the reaction slows down by the mechanism of “inhibition”, at high – by the mechanism of “negative catalysis”.
Keywords: thermodynamic calculations, oxidation kinetics, diamond, tungsten, tungsten trioxide, nanopowder.
UDC 536.421.1:620.187:661.057.5
I. A. Petrusha*, A. S. Osipov, M. V. Nikishina, T. I. Smirnova, Yu. A. Melnychuk (Kyiv)
P. Klimczyk (Krakow, Poland)
*dialab@ism.kiev.ua
Preventive action of silicon nitride during high-temperature sintering of cubic boron nitride under high pressure conditions (pp. 12–27)
The peculiarities of cBN sintering at a pressure of ~7.7 GPa and a temperature of ~2300°С in the presence of Si3N4 additive (~3% (by mass)), which allows blocking the process of penetrating melt percolation from the external environment, leading to intergranular destruction, were studied. The resulting material with extremely high (3.46±0.02 g/cm3) density is intended for wide use in cutting tools, including for processing hard alloys of the VK group. The mechanism of preventive protective action of Si3N4 is discussed.
Keywords: high pressure, high temperature, cubic boron nitride, silicon nitride, percolation, high density, cutting tool.
UDC 514.72.02
IN. M. Overturned, O. B. Loginova*, S. AND. Lysovenko (Kyiv)
*pol@ism.kiev.ua
On criteria of surface activity and classification of surface tension isotherms based on data on melt structure (pp. 28–38)
The existence of a relationship between the structure of metal melts of eutectic systems and systems with a negative heat of mixing with the participation of p-elements and their physical and chemical properties is considered. It is shown that the appearance of extrema on the experimental isotherms of density and surface tension is associated with a change in the nature of atomic ordering in the melt. The structural elements formed in the melt can show surface activity if the energy of the bond between the atoms forming this structural element is higher than the energy of their bond with the main metal-solvent. At the same time, the criterion of surface activity in systems with any type of interaction may be the appearance of a covalent component in the structure of a chemical bond between atoms of the same type of melt, as well as the presence of decompression areas.
Key words: melt structure, nature of atomic ordering, density, surface tension, classification of surface tension isotherms.
UDC 621.922.079
R. WITH. Shmegera, Ya. AT. Podoba, V. AND.Kush*, A. WITH.Belyaev (Kyiv)
*vkushch@bigmir.net
The influence of the contact thermal conductivity of the diamond-metal bond interface on the thermal conductivity of diamond-containing composites (pp. 39–52)
The influence of the contact thermal conductivity of the diamond-metal bond interface on the thermal conductivity of diamond-containing composites with two- and three-component metal bonds based on nickel has been studied. A setup and method for measuring the dependence of the thermal conductivity coefficient of bonds and composites based on them on the composition (in particular, the presence of carbide-forming additives) and structure have been developed, and such a dependence has been studied. A theoretical model of the thermal conductivity of the composite has been proposed, which ensures that the real shape of the diamond crystal and the contact thermal conductivity of its faces are taken into account. The estimate of the contact thermal conductivity of the interphase boundary obtained by solving the inverse problem is in satisfactory agreement with the data of direct physical studies known in the literature and similar estimates for composites on aluminum and copper bonds. The modeling results indicate a significant influence of the contact resistance on the temperature regime of the diamond tool.
Keywords: diamond, metal bond, composite diamond-containing material, interphase boundary, thermal resistance, model, effective thermal conductivity.
UDC 621.793.74:620.22-419:621.89
A. P. Umansky, E. N. Polyarus, M. S. Ukrainets, I. S. Martsenyuk, V. I. Subbotyn (Kyiv)
*kermet@voliacable.com
**elena_polyarus@ukr.net
***maximukrainets22@gmail.com
Research of the structure, physical and chemical properties and tribotechnical characteristics of composite materials of the NiAl–Zrb2 system (pp. 53–62)
The wetting and features of the contact interaction in the NiAl–ZrB2 system were studied. The phase and chemical compositions of the interaction products in the system under study are analyzed. Studied structure and properties of composite materials of the NiAl–ZrB2 system and coated from them, intended for the protection of parts of gas turbine engines operating under conditions of high temperatures and loads. The friction surfaces of the developed plasma-coated NiAl and NiAl–15ZrB2 are studied. It is shown that the oxides formed on the friction surface act as a solid lubricant. It was established that the nature and intensity of wear is significantly influenced by the temperature of the tested material, as well as the presence of a reinforcing boride phase.
Key words: intermetallic NiAl, zirconium diboride ZrB2, wetting, composite materials, plasma coatings, high-temperature tribotests, wear resistance.
UDC 621.923
IN. I. Lavrynenko, A. AND. Devitsky*, O. AT. Pasichny, S. AND. Kuharenko (Kyiv)
*ceramic@ism.kiev.ua
**devitsky@mail.ua
Thermoelectric phenomena in processing processes and the study of their functioning during grinding with STM wheels (pp. 63–75)
Thermoelectric phenomena in the processes of grinding wheels made of superhard materials are investigated.It was established that a negative value of tribo-thermoEMF is characteristic when machining hard alloys with diamond wheels, and a positive value when machining high-speed steels with cubic boron nitride (CBN) wheels. With the growth of tribo-thermo EMF when grinding with KNB wheels, the wear of the wheels decreases, and when grinding with diamond wheels, it increases, with the same processing performance. It is shown that by introducing modifying metal additives into the glass coating of the grains of superhard materials, it is possible to change the value of tribo-thermo-EMF: when grinding with wheels from KNB, to reduce the tribo-thermo-EMF, metallization of the glass coating of the grains with copper should be used, and to increase it – with titanium or nickel.
Key words: thermoelectric power, triboelectric power, grinding, glass coatings, modifying metallic impurities, superhard materials, grinding wheels.
UDC 621.924.93
AND. F. Salenko, V. T. Shchetinin, A. N. Fedotyev, V. AND. Dudyuk (Kremenchug) WITH. AND. Klymenko*, A. I. Borymskyi, T. AND. Sorochenko (Kyiv)
*salenko2006@ukr.net
**atmu@ism.kiev.ua
Cutting workpieces from hard alloy and polycrystalline superhard material based on cubic boron nitride (pp. 76–90)
The results of the hydroabrasive, laser with gas purging of the cutting zone, laser with liquid cooling, and laser-jet cutting of workpieces made of hard alloy and polycrystalline superhard material based on cubic boron nitride are presented. It is shown that hydroabrasive cutting practically does not lead to the appearance of a layer of thermal destruction on the treated surface, while laser cutting forms a defective layer up to 0.8 mm thick, which can be reduced to 0.10–0.55 mm when performing laser cutting with water cooling, with a simultaneous increase in the depth of cut by 50–70%. Laser-jet cutting ensures the minimum width of the cut and the size of the zone of thermal destruction of no more than 0.06 mm with surface roughness up to Ra = 3.2–6.3 μm.
Key words: hard alloys, superhard materials, hydroabrasive, laser, laser jet cutting.
UDC 621.919
WITH. F. Student* (Kyiv)
P. M. Yeromin**, O. IN. Chernyavsky (Kirovograd)
*ism20zam@ukr.net, ism20@ism.kiev.ua
**24124@mail.ru
The influence of deformation conditions during processing with hard alloy combined broaches on the structure and strengthening of the surface layer of cast irons (pp. 91–99)
Using testing and metallographic equipment, as well as a modern scanning electron microscope, the state of the metal base and graphite inclusions during cold plastic deformation of the surface layer of graphite-containing cast iron samples with a hard alloy tool was investigated.
Keywords: hard alloy, deformation-cutting broaches, graphite-containing cast iron, cold plastic deformation, surface structure.
UDC 661.657.5:537.31
V. A. Mukhanov, V. L. Solozhenko* (Paris)
*vladimir.solozhenko@univ-paris13.fr
On the electrical conductivity of boron melts and its compounds under pressure (pp. 100–102)
The electrical conductivity of melts of boron and boron carbide B4C, BN nitride, and BP phosphide was studied at pressures up to 7.7 GPa and temperatures up to 3500 K, and it was shown that these melts are good conductors, comparable in terms of specific electrical conductivity to iron melt at atmospheric pressure.
Key words: boron, boron compounds, high pressure, high temperature, melt, electrical conductivity.