Key Engineering Materials Vol. 910

Abstract: This paper was devoted to the technological process of manufacturing a biocomposites tube made of low-density polyethylene and barley straw fibers. 50% of HDPE, 42% barley straw, 5% of shungite (mineral filler), 2% Maleid F (N, N-metaphenylenediamine) as coupling agent, and 1% Hexol CLA as lubricant were pre-mixed before compounding. The compounding of the raw materials was carried out on a co-rotating twin-screw extruder. The resulting granules were fed into the single screw extruder to obtain thermoplastic composite tubes. The temperature regime for the HDPE/barley straw composite processing was in the range of 145-160 °C and the screw rotation speed was 50 rpm. The tensile strength and modulus were found to be 27.7 MPa and 1687 MPa, respectively. The water absorption (24-h) and density of the specimens were 1.43% and 1.158 g/cm³, respectively. Based on the findings obtained from the present study, it can be said that the barley straw can be efficiently used in the production of tube formed HDPE composites.

Abstract: One of the ways to develop existing methods of hardening is creation of hybrid technologies that combine the principles of chemical heat treatment and surface plastic deformation. This paper proposes a nitriding technology followed by ultrasonic treatment. As a result of such sequence, a surface layer is formed that has an increased hardness and depth of hardening, in comparison with combined methods used separately.

Abstract: The article proposes an approach to control the uniformity of wear of friction surfaces under conditions of non-uniform wear on the surface. The core of the approach is the regulation of the composition of the sprayed coating material with the addition of a strengthening additive, depending on the intensity of the wear effects. To improve the quality of the coating, a combined process of spraying the coating with its subsequent plasma reflow, as well as processing to remove residual stresses in the coating and final plasma strengthening is proposed.

Abstract: The features of the formation of the structure of welded joints for various welding modes and energy parameters of welding capsules for hot isostatic pressing are given. Mechanical properties are investigated for each of the modes.

Abstract: The work is devoted to the basics of surface modification of structural materials for the effective protection of machine parts and mechanisms operated in extreme conditions from the mechanical impact of aggressive media, by the method of plasma-chemical exposure to concentrated streams of matter and energy by means of plasma generators, which allow for surface renovation and engineering.

Abstract: Increasing of the hardness and wear resistance of the working surfaces of parts made of aluminum and its alloys is achieved by modifying them by the method of micro-arc oxidation in alkalescent electrolytes. This technology consists in the formation of a highly hard and wear-resistant ceramic layer by means of the spark discharges and implies an enormous investment of energy and time. The finished product surface roughness in numerous cases fails to meet the requirements, and demands additional machining. High hardness of the hardened layer, at the same time causes an increased wear of the processing tool. A method in which the technological process is carried out in two stages allows improving energy efficiency of this technology. At the beginning, when using an electrolyte with a high content of liquid glass, a primary oxide layer, consisting predominantly of silicon oxide, is formed. At the next stage of micro arc oxidation, the content of the liquid glass in the electrolyte decreases, which allows the formation of predominantly high rigid aluminum oxide in ceramic layer. This technology can significantly reduce the time of formation of a coating and reduces energy consumption. To reduce the processing tool wear it is proposed to keep the surface of the modified by oxidation workpiece in hydrofluoric acid for 5 - 30 minutes. This operation allows to reduce the hardness of the upper layer, consisting mainly of silicates, without affecting the lower layer, formed mainly of aluminum oxide. As a result, it is possible to receive the required surface micro geometry with less tools wear, less time and energy. There was achieved a reduction of time for getting the finished product by 1.6 - 2.3 times, electricity by 2 - 2.7 times, tool wear by 8.7 - 12 times.

Abstract: The influence of electrolysis conditions and the composition of electrolyte for iron plating in the flow of electrolyte on the adhesion strength, microhardness and wear resistance of coatings were studied. The optimal composition of electrolyte for iron plating and the structure of coatings that provide the highest abrasive wear resistance were determined. Advisability of using iron plating in the flow of electrolyte for restoration of spools for hydraulic control valves was demonstrated.

Abstract: In the work, a variant of mathematical modeling of the solution of the heat transfer problem was developed, analytical analysis of the dependencies of the parameters of technological parameters was carried out to determine the parameters of current pulses that ensure a uniform distribution of current density over the treated surface. A diagram of the stages of constructing a complete mathematical model of the ECDP process (electrochemical dimensional processing) of titanium, aluminum, and their alloys is given. The above equations reflect the theory of mass transfer processes, include the temperature parameter. The limitations of the possibility of carrying out the treatment process are modeled, the peculiarities of formation and development of the gas-liquid layer, changes in its physical properties, and violation of the treatment stability are taken into account. It has been found that to eliminate the processing instability associated with the appearance of turbulence in the electrode reaction zone due to the large gas filling of the interelectrode gap, a series of relationships must be considered DT = f (i, Q, t_imp) to determine optimal parameters of pulse current.

Abstract: The technology of friction-electric modification of the surfaces of machine parts with W₂C and WC tungsten carbides is considered. A method of modifying the surface layer by implantation of materials based on tungsten carbides is investigated in order to increase the wear resistance of parts forming tribo-conjugations in heavily loaded units of multi-purpose tracked and wheeled vehicles.

Abstract: In this study, the process of high-velocity impact welding of commercially pure Al and Ti plates was simulated using smoothed particle hydrodynamics (SPH) method. The paper aimed to determine by numerical simulation the range of collision parameters suitable for Al and Ti welding, and to compare the results obtained with the known semi-empirical models used to construct the "weldability window". For this, a set of simulations with different collision point velocity and collision angle was carried out. From the data obtained, it follows that SPH simulation reproduces well the shape of the interface, typical for high-velocity impact welding, and provides better understanding of material flow and related phenomena. This method allows one to select the collision parameters that are optimal for a high-quality joint.