Vol 55, No 2 (2019)

In this study, Fe–Al₂O₃ composite cladding is fabricated on the carbon steel AISI 1040 (CK40) substrates by the cost-effective process of gas tungsten arc welding. For this purpose, after milling, Fe–Al₂O₃ composite powders were placed on the steel surface through the sodium silicate binder. After the surface was dried, under a constant voltage and current in a range of 110 to 180 A, the melting and the fabrication of the surface composite were carried out. For non-destructive investigations, samples were analyzed by radiographic testing which showed that there are no cracks in the surface layer created and Al₂O₃ particles are distributed uniformly in the surface layer. Microstructural examinations by optical microscopy, scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction proved the presence of a pure Fe–Al₂O₃ phase in the surface layer. Microscopic images showed coaxial fine grains in the weld metal, which can be caused by a thermal gradient between the weld metal and substrates and rapid solidification. Increasing the current due to enhanced input heat leads to a reduction of the grain size and an increase of dramatic micro hardness that leads to agglomeration of Al₂O₃ particles and reduction of the quality of the cladding layer. The purpose of this research is to achieve optimal parameters of claddings to attain specific objectives of engineering by using steel via an inexpensive supplementary method.

The results of observations of the photosensitivity of CdS films during their electrochemical deposition are described. An equivalent electrical circuit characterizing the electrode processes is proposed. A mathematical model to describe these processes is constructed.

A new method is presented for two similar plane surfaces of high-performance dimensional treatment with an electric arc (DTEA) where the components are hard-to-cut materials in a bipolar mode without the traditional application of an electrode tool. In comparison to DTEA with the use of an electrode tool, this new method provides an increase in the efficiency of treatment by 230%. It is shown that for passing from unipolar DTEA of VK-15 hard alloy with a graphite electrode-tool to bipolar DTEA of two samples of the same alloy, a considerable increase in heat energy of the cathode area is found due to the energy of the arc column, which can overrun the heat energy of the anode area and lead to inversion, that is, a change in the direction of the prevailing electric erosion. This increase in the heat energy of the arc cathode area explains the growth in the productivity of the bipolar DTEA of two samples of the hard alloy VK-15 over the unipolar one.

The focus of this investigation is on the modification of Fe-rich intermetallics morphology and wear and friction properties of eutectic Al–Si alloys. Eutectic Al–Si specimens were fabricated by tilt casting after addition of different amounts of iron and manganese to the molten alloy. Dry sliding tribological behavior of the samples was investigated using a reciprocating wear tester at room temperature in atmospheric environment. It is found that the addition of iron up to 1.5 wt % to the alloy decreases the wear resistance of the alloy owing to the formation of brittle plate-like interme-tallic compounds of β-Al₅FeSi. As Manganese is added to the β-containing alloy up to the half of the iron content (corresponding to a Mn/Fe ratio of 0.5), the platelet phases are completely replaced by the star-like intermetallic α-Al₁₅(Fe, Mn)₃Si₂ resulting in improved wear resistance of the alloy. Introducing 0.8 wt.pct Mn to the alloy containing 1.6 wt % Fe did not convert the plate-like beta intermetallics to the modified alpha compounds completely and had no impressive impact on the wear rate of the alloy.

The purpose of this work was to study the basic construction, energy, and technological features of the electrochemical reactors used in the manufacture of whey, a dairy by-product and a biologically very valuable liquid. The choice of optimal regimes for processing various types of whey was specified aimed at increasing the efficiency of the recovery of whey protein fractions in the protein-mineral concentrates through reduction of the energy consumption. It is demonstrated that features of the electric reactors must be reasonably selected, including the distances between the electrodes and between the electrodes and the membrane, as well as their geometric shape, to avoid occurrence of dead areas and to ensure a high efficiency of the process. It was also important to find the most appropriate options for electric parameters and processing regimes (periodic or continuous). In addition, the ratio of the whey volume and the main electrode area, the type of the regimes membrane, the initial content of the dry matter in each type of the whey (in particular, its protein composition), and the compositions and concentration of the anodic (secondary) liquid, were taken into account. The results of the study are significant for the development of a wasteless technology of processing the dairy by-products.

To substantiate the quantitative values of the process of destruction of weeds by means of electric impulse and to elucidate the mechanism of damage and the sequence of disturbances that occur in the internal structure of the processed plants, it is necessary to know not only the design of the electrical circuit of the plant tissue substitution but also to have information on the nature of the change in the parameters of the elements of this scheme during electric damage. The presented technique allows (with the help of inexpensive and accessible technical means) to control the damage to the tissues of a weed plant and to calculate quantitative values using developed mathematical apparatus. The analysis shows that the damage to weed plant tissues can be characterized, first of all, by the loss of cell membranes in their semipermeable functions and an increase in the active conductivity of the processed areas of plants. Such changes in the internal structure of plant tissue lead to loss of cell viability in the areas subjected to the electric impulse treatment. The presented analysis fits the current thinking of biophysicists on the electrical damage to the internal structure of biological objects. The technological studies of the process of the electric impulse irreversible damage to plant tissues conducted, based on the analysis presented in the article, allow us to limit the supplied electric energy that makes it possible to make electric impulse weeding an energy-saving means of combating weeds.

This work analyzes the manufacturing process of an electron-beam additive form by heating as a result of remelting the supplied filler wire as a control object. Control actions and output values are designated that can be used in constructing a control systems with feedback. A mathematical modeling technique is used to study heat transfer in a nonstationary formulation, taking into account the influence of the latent heat of fusion. The transient processes of temperature changes were studied at points, whose values can be used to estimate the extension of the weld pool and the degree of metal overheating. An analysis of the results of computational experiments is carried out, and the range of variations of control actions are shown. The possibility of an independent temperature control in the range of the beam and the extension of the liquid bath is also justified. Recommendations are given for the technical implementation of the system and the option of implementing local regulators, types of sensors, and their installation.