Papers by Edwin Gevorkyan
Solid State Phenomena, 2013
The change of matrix and usage of the aluminum alloys designed for the metal forming in making th... more The change of matrix and usage of the aluminum alloys designed for the metal forming in making the composite suspension allows to extend the processing possibility of this type of materials. The possibility of the metal forming of the composites obtained by mechanical mixing will extend the range of composite materials usage. Applying of the metal forming e.g. matrix forging, embossing, pressing or rolling, will allow to remove the incoherence of the structure created while casting and removing casting failures. In order to avoid the appearance of the casting failures the homogenization conditions need to be changed. Inserting the particles into the matrix influences on the shortening of the composite solidification. The type of the applied particles influenced the sedimentation process and reinforcement agglomeration in the structure of the composite. Opposite to the composites reinforced with one-phase particles applying the fasess mixture (glassy carbon and silicon carbide) trigg...
Ceramics International, Jan 31, 2024
Eastern-European Journal of Enterprise Technologies, Feb 10, 2021
Human Physiology, 2004
Effects of examination stress on psychological characteristics and indices of the autonomic nervo... more Effects of examination stress on psychological characteristics and indices of the autonomic nervous system were studied in pupils of the eighth and tenth grades of high schools providing differential (test group, “Neuron” gymnasium) and general education (control group). General health state and levels of activity and mood (feeling, activity, mood; FAM) and neuroticism (according to Eysenck) were determined in both groups. Main hemodynamic indices (heart rate and blood pressure) were measured, and mathematical analysis of the heart rate by was performed according to Baevskii. Comparative analysis of psychophysiological tests and heart rate changes in the control and test groups points to a high tension in the cardiac rhythm regulation mechanisms and strong anxiety in schoolchildren in the differential education school. The character and depth of preexamination stress depended on the type of autonomic control of cardiac activity. Schoolchildren with sympathicotonic cardiac rhythm reg...
13th International Ceramics Congress - Part E, 2014
Application of modern ways of ceramic materials’ consolidation and association of synthesis metho... more Application of modern ways of ceramic materials’ consolidation and association of synthesis methods of organic and inorganic chemistry, sol-gel method and mechanochemistry, allowing to control processes of synthesis of the defined phases at molecular level, gives the chance to create highly effective composite materials. It is known that properties of composites on the basis of refractory compounds become dimensionally dependent at reduction of the particles’ size to several interatomic distances in one, two or three dimensions . Obtaining of durable nanostructural ceramics on the basis of ZrO2 with substantial increase of mechanical properties can be realized by creation of material with fine homogeneous structure, on the basis of powders of nonoxygen compounds when strength properties and crack resistance increase at creation of –intra and –inter nanostructures. In work results of creation of the consolidated nanomaterials and composite ceramics with usage of the peculiarities set...
Journal of Superhard Materials
Eastern-European Journal of Enterprise Technologies, Dec 22, 2021
The availability of a variety of machined metals necessitates designing a wide range of cutting m... more The availability of a variety of machined metals necessitates designing a wide range of cutting materials, each of which would have its specific application area [4, 5]. Potential fields of the practical application of various cutting materials depending on the cutting speed and feed rate are shown in Fig. 1 [6].
Materials, Sep 1, 2022
Peculiarities of the Phase Formation during Electroconsolidation of Al 2 O 3-SiO 2-ZrO 2 Powders ... more Peculiarities of the Phase Formation during Electroconsolidation of Al 2 O 3-SiO 2-ZrO 2 Powders Mixtures.
Eastern-European Journal of Enterprise Technologies, Oct 31, 2021
6 2. Literature review and problem statement Much attention is paid to the problems of obtaining ... more 6 2. Literature review and problem statement Much attention is paid to the problems of obtaining composite materials based on zirconium dioxide and deter
Zbìrnik naukovih pracʹ, Jun 10, 2022
Анотація. Досліджено метод формування композиційних матеріалів на основі нанопорошків частково ст... more Анотація. Досліджено метод формування композиційних матеріалів на основі нанопорошків частково стабілізованого оксидом церію діоксиду цирконію, отриманих із розчинів фторидних солей. Підібрано найбільш оптимальний метод отримання нанопорошків з метою виготовлення з них щільних наноструктурних композитів біоінженерного використання. Отримання композитів на основі частково стабілізованого діоксидом церію діоксиду цирконію при гарячому пресуванні у вакуумі методом електроспікання дає змогу отримати високощільні композити з високою тріщиностійкістю, твердістю і модулем пружності вже при температурі 1400 °С, тиску 30 МПа та часу витримки 3 хвилини. Виявлено, що метод електроконсолідації у вакуумі забезпечує спікання зразків з високими значеннями модуля пружності і тріщиностійкості. Проведені дослідження дають змогу припустити, що з метою подальшого підвищення властивостей композитів на основі оксиду цирконію, частково стабілізованого діоксидом церію, необхідно поліпшити однорідність вихідних сумішей, а також додавати інші оксиди, зокрема оксид алюмінію, нітрид алюмінію, оксиди кремнію та магнію. Ключові слова: біоінженерія, діоксид цирконію, електроконсолідація, кераміка, оксид церію.
Zbìrnik naukovih pracʹ, May 12, 2022
The article represents the results of research of various methods of obtaining antifriction mater... more The article represents the results of research of various methods of obtaining antifriction material "copper-lead-graphite" by methods of powder metallurgy. With the help of hot vacuum electroconsolidation of powders, which is effective for refractory materials, the conditions for separate cold pressing are determined, namely, product formation at 500 MPa and sintering at 900 °C, which is more productive for metal powders. The initial formation of the samples was carried out in a collapsible steel mold on a hydraulic press with a force of up to 200 tons from a mixture of powders of copper, lead and graphite, which had dimensions of 60-200 μm. Sintering was performed in a vacuum oven at temperatures of 700-900 °C for 20-30 minutes. To obtain a density of more than 5.6 g / cm 3 , it is necessary to significantly increase the pressure during the formation of powders. During the formation of the dry mixture, compression transverse cracks appear. Liquefied kerosene was selected from the list of studied organic liquids, which allowed to obtain high-quality products without cracks with a density of 5.6-5.9 g/cm 3 at a load force of about Збірник наукових праць Українського державного університету залізничного транспорту Збірник наукових праць УкрДУЗТ, 2021, вип. 198 8 500 MPa. Sintering was performed in an inert nitrogen environment, which reduced lead losses to 2-5 % at temperatures above 700 °С. Nitrogen was first supplied to the vacuum chamber to a pressure of 1 atmosphere, and after increasing the temperature in the chamber, the nitrogen pressure rose to 1.2 atm. The hardness of the obtained samples was 42-46 HB according to Brinell (135-150 MPa). Machining of samples with different cutting tools was performed at different speeds and showed good machinability. Processed parts during storage have not changed their size. With the help of the developed technology it is possible to produce composite materials with a density of 4.4-6.2 g/cm 3 and a Brinell hardness of 30-48 HB (99.9-159 MPa).
Materials, Aug 29, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
22nd International Scientific Conference Engineering for Rural Development Proceedings
The research was performed in the context of feasibility examinations of chromia application as c... more The research was performed in the context of feasibility examinations of chromia application as cutting tool materials. In the paper, a study on the Cr2O3 –based ceramic cutting tools is presented from the perspective of structural features and durability under various machining parameters. Comparative analysis was performed using alumina-based ceramic cutting inserts. Microstructure was examined using scanning and transmission electron microscopy (SEM and TEM), LEO1455 VP (ZEISS) and MIRA3 TESCAN, respectively. It was found that Cr2O3 –based ceramic with AlN additions after electroconsolidation exhibited more fine structure with evenly distributed AlN inclusions and small amount of spherical pores, below 2%. The cutting durability tests were performed with both hardened NC11LV and non-hardened C45 (1.0503) steels, using multiedge cutting inserts of dimensions 14.75 mm × 14.75 mm × 4.75 mm, made of respective ceramics. The machine tool Mazak QTE was used for the tests, and the wear ...
Acta Physica Polonica A, 2021
The paper presents a study of interdiffusion processes in a binary Fe-Ni system (obtained by elec... more The paper presents a study of interdiffusion processes in a binary Fe-Ni system (obtained by electroconsolidation of nickel and iron powders) by X-ray energy dispersive spectroscopy. Well-separated regions of almost pure iron and nickel have been discovered. The content of nickel, estimated from the concentration dependence of the interdiffusion coefficient, which determines the kinetics of the homogenization process of the electroconsolidated Fe-Ni composite sample, was ≈ 70 at.%. The value of the interdiffusion coefficient of the electroconsolidated Fe-Ni composite is significantly higher than that of the alloy of similar composition which probably results from the effect of spark plasma sintering technology (pressure and current along the same direction during consolidation) but also from a significant contribution of diffusion with mass transfer along the particle boundaries in the composite. topics: Fe-Ni binary system, electron microscopy, interdiffusion processes, spark plasma sintering technology and mass transfer effect
Modern Physics Letters B, 2021
The structure and processes of mass, charge and heat transfer are investigated in an equiatomic F... more The structure and processes of mass, charge and heat transfer are investigated in an equiatomic Fe–Ni composite fabricated by electroconsolidation using the spark plasma sintering (SPS) technology. The system contains regions of almost pure Fe and Ni, separated by areas with variable concentration of components, formed in consequence of the interdiffusion in the electroconsolidation process. The interdiffusion coefficient of the Fe–Ni system has been revealed to be significantly higher than that of an alloy of a similar composition at the same temperature, which is likely the result of the employed SPS technology and the enhanced diffusion along the grain boundaries. The concentration dependence of the interdiffusion coefficient passes through a maximum at a Ni concentration of [Formula: see text]70 at.%. The electrical and thermal conductivity of the studied system is significantly higher than that of an alloy of the same composition. The temperature dependence of the resistivity o...
Low Temperature Physics, 2019
A comparative study of the thermal conductivity of composite ceramic material samples prepared us... more A comparative study of the thermal conductivity of composite ceramic material samples prepared using electroconsolidation with direct current transmission, was performed in the temperature range of 15–300 K. The experimental data on the temperature dependence of thermal conductivity are approximated within the framework of the Debye phonon spectrum model, taking into account various scattering mechanisms. The optimal consolidation temperature, which ensures the maximum thermal conductivity of the composite, is determined.
Remanufacturing and Advanced Machining Processes for New Materials and Components, 2022
Collection of Scientific Works of the Ukrainian State University of Railway Transport
For the sintering of ceramic products, high-temperature electric furnaces are used, which work bo... more For the sintering of ceramic products, high-temperature electric furnaces are used, which work both in a protective environment and in air. In some technological processes, for example, for the production of ceramic carriers for afterburning car exhaust gases based on SiC and Al2O3, only air furnaces are used. Silicon carbide (SiC – silicate) heaters and molybdenum disilicide (MoSi2) are used as resistive heaters in such furnaces. Due to the relatively small resource of their work, it is energetically beneficial to use the residual heat when cooling the furnace. At the same time, there is a significant saving of electricity for heating. The residual heat is largely determined by the thermal insulation of the lining and the correct distribution of the heat balance of the furnace. The speed of temperature rise affects the thermal balance of the furnace in general, and even the speed of cooling of the furnace, which creates additional energy saving opportunities, which reduces the cost...
Machines
The paper is dedicated to the enhancement of Polycrystalline Diamond Bits (PDC) designed for oil ... more The paper is dedicated to the enhancement of Polycrystalline Diamond Bits (PDC) designed for oil and gas industry. A novel diamond-reinforced composite was applied for cutting inserts, with the addition of 4 wt% chromium diboride to the WC-Co matrix. The addition of CrB2 ensured improvement of bending strength and fracture toughness by nearly 30% and 40%, respectively, and enhanced the diamond retention force. The efficiency of PDC bits was further improved by incorporating constructional features in both bottomhole and reaming parts. An analytical relationship between the feeding speed and geometrical parameters was found, including the wings and calibrating inserts numbers, as well as the rotational speed of the cutter. Under the conditions of rock fracture by reaming inserts, the approximate value of the required power was calculated.
Advances in Science and Technology Research Journal
The paper presents research results on the enhancement of diamond composites designed for tools a... more The paper presents research results on the enhancement of diamond composites designed for tools application for mining industry, hard rocks cutting, able to withstand harsh conditions under heavy dynamical loads. In the present study, both CrB 2 micropowder and VN nanopowder additives were used in proportions up to 5 wt.% and 6 wt.%, respectively, together with the basic matrix composition of 51 wt.% Fe, 32 wt.% Cu, 9 wt.% Ni, and 8 wt.% Sn. Addition of both components, CrB 2 and VN, appeared to be advantageous in proportion of 2 wt.% and 4 wt.%, respectively. This composition exhibited the highest relative density of 0.9968, better than that without additives. Similarly, the highest values of compressive strength R cm and flexural strength R bm were reached for the composite with the same percentage of CrB 2 and VN. Compared to the composite with no addition of CrB 2 and VN, R cm improved by almost 70%, while R bm by 81%. Additionally, the abovementioned additives enhanced the ability of the matrix to prevent the diamond reinforcement from being torn out of the composite, which is very important under harsh working conditions of the cutting tools. The presence of CrB 2 micropowder and VN nanopowder promoted densification of the matrix and adhesion between the diamond grits and the Fe-Cu-Ni-Sn matrix.
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Papers by Edwin Gevorkyan