Дослiджено структуру композитiв на основi системи NbC з мiдною зв'язкою, отриманих шляхом просочування металевим розплавом пористих NbC карбiдних каркасiв у вакуумi. З метою отримання пористого каркасу порошокNbC iз середнiми розмiром ~1 мкм замiшували на 5 %-ному розчинi каучуку в бензинi. Пiсля сушiння сумiш перетирали на ситi у гранули, якi пресували у брикети розмiрами 55×30×10 мм. Для забезпечення iнтенсифiкацiї процесу та змочуваностi просочування проводилось за температури 1400 °C. У результатi було отримано матерiал iз дрiбнозернистою двофазовою структурою. Дослiдження мiкроструктури проводили методом скануючої електронної мiкроскопiї (SEM), хiмiчного складу -методом енергодисперсiйного аналiзу (EDS). Твердiсть вимiрювали за Роквеллом (шкала С), трiщиностiйкiсть за непрямим методом Еванса-Чарльза. Структура композиту складається iз округлих зерен NbC, якi утворюють неперервний скелет та прошаркiв мiдної зв'язки. Середнiй розмiр зерен та мiжзернових прошаркiв зв'язки становить 1,8 мкм та 1,1 мкм, вiдповiдно. Аналiз зони взаємодiї мiж NbC та Cu методом EDS дозволив встановити присутнiсть дифузiйної зони товщиною 0,5 мкм, яка утворюється внаслiдок перерозподiлу Nb та Cu шляхом обмеженої розчинностi. Наявнiсть дифузiйної зони дозволяє забезпечити мiцний зв'язок мiж фазами та, вiдповiдно, високий рiвень механiчних властивостей. Твердiсть та трiщиностiйкiсть отриманого матерiалу становлять 40 HRC та 24 МПа×м 1/2 ,вiдповiдно. Враховуючи фазовий склад та властивостi розробленого композиту, його рекомендується застосовувати як альтернативний до композитiв системи WC-Cu у виглядi монолiтного матерiалу або покриттiв. Покриття наносили методом електроiскрового легування iз використанням ручної установки МП-ЭЛ2. Товщина покриття становить 30 мкм, мiкротвердiсть ~500 МПа, а коефiцiєнт тертя по сталi без змащування 0,04. Розробленi матерiали рекомендуються для застосування в парах тертя у виглядi монолiтного матерiалу або покриттiв антифрикцiйного призначення Ключовi слова: керамiко-металiчнi матерiали, матрично-армована структура, триботехнiчнi характеристики, електроiскрове легування, антифрикцiйнi покриття
An analysis of common reinforcement methods of machine parts and theoretical bases for the selection of their chemical composition were carried out. Prospects for using flux-cored arc welding (FCAW) to restore and increase the wear resistance of machine parts in industries such as metallurgy, agricultural, wood processing, and oil industry were presented. It is noted that conventional series electrodes made of tungsten carbide are expensive, which limits their widespread use in some industries. The scope of this work includes the development of the chemical composition of tungsten-free hardfacing alloys based on the Fe-Mo-B-C system and hardfacing technology and the investigation of the microstructure and the mechanical properties of the developed hardfacing alloys. The composition of the hardfacing alloys was developed by extending the Fe-Mo-B-C system with Ti and Mn. The determination of wear resistance under abrasion and impact-abrasion wear test conditions and the hardness measurement by means of indentation and SEM analysis of the microstructures was completed. The results obtained show that the use of pure metal powders as starting components for electrodes based on the Fe-Mo-B-C system leads to the formation of a wear-resistant phase Fe(Mo,B)2 during FCAW. The addition of Ti and Mn results in a significant increase in abrasion and impact-abrasion wear resistance by 1.2 and 1.3 times, respectively.
The great development witnessed by investments in renewable energy has made it the focus of researchers’ attention in order to increase its efficiency. This is due to the increase in demand for electrical energy due to rapid technological growth, increase in population numbers, and high fuel prices that are used in the production of traditional electrical energy, but it suffers from a problem that is greatly affected by two factors, namely, the change in the intensity of solar irradiation and temperature, which makes its electrical characteristics non-linear, which causes a decrease in its efficiency. To address the efficiency problem, the researchers developed several techniques for tracking the MPP point and extracting the maximum energy from the solar panels under various measurement conditions. Maximum power point tracking technology (MPPT) technology is the most widely used technology in solar energy systems. In this article, MPPT technology is simulated using MATLAB/Simulink for the purposes of extracting maximum power and managing the duty cycle of a DC-DC buck converter. The performance of the photovoltaic system under various irradiance fluctuations and settings of constant temperature could well be determined using simulation results. Under standard and varied test settings, allowing the inverter to convert over 99% of the electricity provided by the solar panels.
The rational materials selection for friction pairs is an important prerequisite in promoting of reliable operation of mechanical seals used in centrifugal pumps. The experience of mechanical seals exploitation shows that most preferable is combination of “hard” and “soft” materials. As “hard” materials ceramics based on SiC, Al2O3, Si3N4, are the most commonly employed and for “soft” materials metal alloys, composites and carbon materials are widely used. In this study chromium carbide based composite metal-ceramic material with copper-nickel-manganese binder was developed for using in mechanical seals rings friction couples with silicon carbide (SiC) ring. Metal-ceramic sealing rings were manufactured by infiltration of pre-sintered porous chromium carbide skeletons with Cu60-Ni20-Mn20 melt at 1150 °C in protective (argon) atmosphere. Results of experimental investigations and theoretical modelling of heat transfer during friction, show significant advantages of proposed materials combination over ceramic-ceramic pairs through its better tribological characteristics and resistance to thermal shock. Industrial testing allows us to conclude that using of mechanical seal rings of proposed materials combination almost completely prevents failures of sealing rings surfaces caused by thermal cracking.
The prospects of using biopolymer nano-containing films for wound healing were substantiated. The main components of biopolymer composites are gelatin, polyvinyl alcohol, glycerin, lactic acid, distilled water, and zinc oxide (ZnO) nanoparticles (NPs). Biopolymer composites were produced according to various technological parameters using a mould with a chrome coating. The therapeutic properties of biopolymer films were evaluated by measuring the diameter of the protective effect. Physico-mechanical properties were studied: elasticity, vapour permeability, degradation time, and swelling. To study the influence of technological parameters of the formation process of therapeutic biopolymer nanofilled films on their therapeutic and physico-mechanical properties, the planning of the experiment was used. According to the results of the experiments, mathematical models of the second-order were built. The optimal values of technological parameters of the process are determined, which provide biopolymer nanofilled films with maximum healing ability (diameter of protective action) and sufficiently high physical and mechanical properties: elasticity, vapour permeability, degradation time and swelling. The research results showed that the healing properties of biopolymer films mainly depend on the content of ZnO NPs. Degradation of these biopolymer films provides dosed drug delivery to the affected area. The products of destruction are carbon dioxide, water, and a small amount of ZnO in the bound state, which indicates the environmental safety of the developed biopolymer film.
The prospects of plasma electrolytic oxidation (PEO) technology applied for surface hardening of aluminum alloys are substantiated. The work aims to optimize the technological process of PEO for aluminum in flowing electrolyte. The design of the equipment and the technological process of the PEO for aluminum deformed alloy D16T in flowing silicate–alkaline electrolyte have been developed. Oxide coatings were formed according to various technological parameters of the PEO process. The properties of the oxide coatings were evaluated, respectively, by measurements of coating thickness, geometric dimensions of the samples, microhardness, wear tests, and optical and scanning electron microscopy. To study the influence of the technological parameters of the PEO process of forming oxide coatings on geometrical, physical, and mechanical properties, planning of the experiment was used. According to the results of the conducted experiments, a regression equation of the second order was obtained and the response surfaces were constructed. We determined the optimal values of the technological parameters of the PEO process: component concentration ratio (Na2SiO3/KOH), current density, flow rate, and electrolyte temperature, which provide the oxide coating with minimal wear and sufficiently high physical and mechanical properties and indicators of the accuracy of the shape of the parts. The research results showed that the properties of oxide coatings mainly depend on almost all constituent modes of the PEO process. Samples with Al2O3 oxide coating were tested during dry friction according to the “ring–ring” scheme. It was established that the temperature in the friction zone of aluminum samples with an oxide coating is lower compared to steel samples without a coating, and this indicates high frictional heat resistance of the oxide coating.
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