Key Engineering Materials Vol. 909

Abstract: For the first time, the time dependences of the temperature of aluminum, zinc and zinc-aluminum alloys alloyed with II A group elements under spontaneous cooling mode were obtained; an anomalous course and two characteristic times of the cooling process were found, and their mechanism was explained; the temperature dependence of the thermophysical properties of the investigated metals and alloys was established; the temperature dependence of the coefficients of convective heat transfer and radiation of Al, Zn and Zn55Al and Zn5Al alloys was experimentally determined; the influence of the concentration of II A group elements and temperature on the heat capacity and thermodynamic functions of Zn55Al and Zn5Al alloys was revealed.

Abstract: The object of these studies is the machine parts manufacturing process consisting of the following operations: pre-machining (rough and semi-finishing turning), surface hardening (high-energy heating by high-frequency currents) and finishing machining (finishing turning and diamond smoothing). We present the solution to the problem of quality forecasting in the conceptual design of hybrid process equipment. The developed methodology for substantiating the technical characteristics of machine tools based on mathematical simulation of its operating conditions provides the possibility of using automatic design systems at the initial stage of creating a general concept. We tested the developed design methodology and proposed a scheme for the implementation of hybrid metalworking process equipment based on the lathes. It is experimentally established that under the conditions of the developed hybrid processing it becomes possible to increase the surface microhardness of parts by 12-17 % and to increase the level of compressive residual stresses in the surface layer by 10-21 %.

Abstract: The paper presents the results of studies of the plasma spraying modes effect on the level of residual stresses in coatings. The analysis of experimental data has shown that the sign of residual stresses is not changed in the spraying process. The magnitude of the tensile stresses mainly depends on the temperature of samples heating, the biggest influence being that of plasma torch current arc. An increase in the current leads to an increase in the substrate temperature, which is explained by the increase in the thermal power of the plasma jet. An increase in the flow rate of the plasma-forming gas leads to a decrease in the temperature of the samples, since the heat content of the plasma decreases. An increase in the spraying distance has a similar effect, and its increase leads to a decrease in the substrate temperature. We obtained the functional dependence of the residual stress level on the plasma spraying modes.

Abstract: The paper presents approaches to solving the problem of protecting equipment against corrosion, aging and damage due to biological reasons, which is one of the most urgent practical problems. The practical significance of this problem is relevant when using machinery both for its intended purpose and during storage. As one of the research areas, the urgency of the problem determines the testing of new technologies and conservation materials developed on a fluorine-containing surfactant. Due to the fact that the preservation of equipment during long-term storage implies its being in a mothballed state for long periods of time - up to 12-15 years, it is rather inefficient to carry out full field tests due to a significant amount of time spent on the introduction of new technologies and their significant obsolescence during tests. Therefore, accelerated laboratory and climatic tests in accordance with standards and GOSTs were selected as the main test methods.

Abstract: The process of electrolyte plasma nitriding is presented consisting in surface saturation of steels in low-temperature hydrostatic glow-discharged plasma generated in nitrogen containing liquid electrolyte. The method can be applied for strengthening of small machine parts made of carbon steels or of low-alloyed steels for increase wear and corrosion resistant of components working in corrosive and wear conditions (moisture, humidity, sand, etc.). Processes of steels surface strengthening by nitriding in low-temperature electrolyte plasma are combined with their surface alloying by a metal element (chromium, aluminum, vanadium, titanium, tungsten, molybdenum, and niobium) and also by combination of metals. Microstructure and phase composition of diffusion layers are examined; results of wear and corrosion tests are discussed.

Abstract: The paper presents a method of producing a ceramic metal composite target by detonation gas-thermal spraying allowing spraying almost any powder compositions with high deposition efficiency of up to 90% and the possibility of spraying large areas at a relatively low cost, differentiation by coating thickness and size. The efficiency of detonation technology and related devices for the production of original composite cathodes for magnetron sputtering using the example of the powder composition Ni + Cr + B₄C is justified. These materials make it possible to obtain composite coatings with a unique composition and characteristics using a magnetron. Magnetron sputtering is one of the most suitable methods for the industry. The influence of the process mode of metal ceramic powder application on copper substrate is considered. The structure of a metal-ceramic composite target was studied by scanning electron microscopy. It was shown that the target surface is dense without visible pores. The elemental composition of the powder is uniformly distributed over the target surface.

Abstract: Based on the flow equation of the ferromagnetic liquid lubricant for the “thin layer”, the continuity equation and the Darcy equation describing the flow of a lubricant in a porous body, the paper presents an accurate self-similar solution of the V-shaped sliding support with a porous coating of the base ring surface taking into account the rheological properties of the lubricant with ferromagnetic properties when the working gap is partially filled at the laminar flow mode. Analytical dependencies were obtained for the field of velocities and pressures in lubricating and porous layers. Besides, the main working characteristics of the studied friction pair are determined: bearing capacity and friction force. The paper provides the assessment of the influence of parameters characterizing ferromagnetic rheological properties, length of the loaded region of the Hartmann number and parameter characterizing the presence of electromagnetic field on the bearing capacity and friction force.

Abstract: Two sets of cylinder specimens with a height to diameter ratio of 1.5 made of annealed technical copper and AK12pch silumin were tested for uniaxial compression to different degrees of plastic deformation. At the first stage of the experiments, the ends of the specimen were ground on skins of different grain sizes and polished. Then the micro-hardness of the ends of each sample was measured. Micro-hardness measurements were carried out by the Vickers method at three loads on the indenter: 0.196, 0.490, and 0.980 N. At the second stage, the samples were cut along the meridional section, each sample was poured with a compound based on epoxy resin into an individual mold so that the meridional section of the cut sample came out onto the surface of the mold. After the process of grinding and polishing the meridional section, the micro-hardness of the center of the section was measured under the same loads that were used for measurements at the ends. At the third stage, the dependences of the micro-hardness on the intensity of plastic deformation were made. A comparative analysis of the indicated dependences, made from the results of measurements at the ends of the specimen and the surface of their meridional sections, showed that friction at the ends of the specimen during compression has a significant effect on the position of the dependence “micro-hardness - plastic deformation”. The evaluation of hardening based on the micro-hardness of the ends leads to significant errors.

Abstract: The paper studies the tribological behavior of a Ni-B/Cr₇C₃ nanocomposite coating applied by magnetron sputtering on a Ni-Cr-B₄C composite target. The composite target was obtained by detonation gas-thermal spraying of Ni-Cr-B₄C powder composition. The study determined the hardness of the coating amounting to 7.8 GPa. The distribution of chemical elements in the contact zone of ball-coating friction by energy dispersive spectroscopy (EDS) was studied. The wear track width was 324 μm. Tribological wear tests and determination of adhesion/cohesion strength showed that Ni-B/Cr₇C₃ coatings have good wear resistance, and abrasive and adhesion wear mechanisms act simultaneously during wear. The resulting coatings can be used to protect critical parts and mechanisms susceptible to abrasive and adhesive wear.

Abstract: By the method of thermal oxidation of n-type CuInSe2 crystals, n - n+ structures with a maximum absolute current photosensitivity of up to 10 mA / W were obtained at low rectification and no-load photovoltage. The used modes of thermal oxidation led to the formation of n-type layers on the surface of the n-CuInSe2 plates, the resistivity of which is 2-2.5 times higher concerning the initial substance. Measurements of the stationary current-voltage characteristics have shown that the structures obtained have a slight rectification K. All the structures obtained exhibit photosensitivity, which dominates when illuminated from the side of the layer in the spectral region of about 1 eV. The optimization of the process can reveal the technological possibilities of a significant improvement in the rectifying properties of isotypic structures based on CuInSe2.