International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

The physic-technological basis for fabrication of bulk rods and plates of amorphous, amorphous-nanocrystalline and 100% nanocrystalline alloys at melt cooling rates from 80 to 3200 K/s with crystal sizes from 10 to 50 nm has been developed. The multiphase structure formed in the initial bulk samples, as well as in the process of nanocrystallization of amorphous ribbons, is characterized by record microhardness values of 17-22 GPa. Amorphous powders (20-100 μm) of Fe55Ni8Co6Mo4Cr2V1Al2P9C6B5Si2 and Fe61.37Co6.84Cr3.78V0.85W0.82Mo1.06Nb0.85B19.87C1.99Si2.57 alloys are used to create a wear-resistant coating on structural stainless steels and low-carbon St3 by the gas-thermal “cold” method » sputtering and subsequent melting of the applied layer.The values of microhardness (Hμ) of nano-coatings significantly exceed the microhardness of all known tool steels. Examples of technology transfer and practical using of developed amorphous and nanocrystalline alloys are presented.

The process of obtaining bronze powders of grade BrSn5Zn5Pb5, obtained by the method of induction melting and spraying of the metal melt with an inert gas, has been studied. It is known that in the production of BrSn5Tsn5Pb5 powder, the main losses of zinc occur during the melting of the components. To study the possibility of reducing zinc losses in the melt, a zinc-containing composite alloying material has been developed. Its effect on the chemical composition of BrSn5Zn5Pb5 powders obtained by induction melting and spraying the melt with an inert gas has been studied.

Self-propagating high-temperature synthesis (SHS), refers to a technology for the production of useful materials (mainly composite powders) that uses combustion processes. The solid combustion process results in the release of more heat which is needed to rebond the elements of the system and it is this extra amount of heat that is used to self-sustain the combustion process and its development. This process is known as self-propagating high temperature synthesis.
This paper presents the study of the magnetic properties of the products obtained by this method in comparison with other methods which use nickel-zinc ferrites. The latter are widely used in radio devices, antennas and transformer cores, as well as in high-frequency filters where the current loss is significant.

The article presents the results of investigations of tribotechnical properties of powder composite materials based on the ironhigh-carbon (ФХ800) ferrochrome system during dry friction with ШХ15 steel at various loads of 30, 60, and 100 N. It was found that an increase of the load from 30 to 100 N leads to an increase in the coefficient of friction from 0,45 to 0,5 (for 25% ФХ800) and from 0,40 to 0,46 (for 40% ФХ800). At the same time, the mass wear of samples made of powder materials decreases with an increase in ФХ800 content from 25 to 40 (wt. %) and with growth of the load from 30 to 100 N, respectively, from 3,5 – 8,0 to 0,75 – 1,6 mg/km., which provides wear resistance improvement (km/mm) by 2,8 – 2,2 times. X-ray phase full profile analysis using the Rietveld method established that there are 2 phases: metallic α-Fe (79,68%) and carbide Me7C3 (20,32%) in the composite Fe – 25%ФХ800 and 3 phases: α-Fe (69,5%), γ-Fe (3,96%) and carbide Me7C3 (26,57%) in the Fe – 40% ФХ800 composite. Topographic studies of 2D profiles of worn surfaces of composites after friction under different loads were conducted. The results of optical profilometry show that the main mechanism of destruction of the powder composite surface during dry friction with ШХ15 steel is adhesive wear (seizing) of the contacting surfaces.

In the present work, the corrosion of Zn-Ni coated steel in the presence of acetic acid was studied. Corrosion tests were carried out in salt spray and the corrosion rate was determined by the weight loss method. The results showed that the Zn-Ni layer acted as sacrificial coatings on steel, the acetic acid, even if it is a weak acid. Also, in this paper, a simulation was carried out regarding the corrosion protection of steel attacked by acetic acid using a sacrificial anode (Zn alloy). The results obtained from the simulation agree with the experimental ones.

Porous materials are very efficient in absorbing mechanical energy, for instance, in combined armor, in order to improve the anti-ballistic protection characteristics. In the present study, porous titanium-based structures were manufactured via powder metallurgy methods using titanium hydride (TiH2) powder, which provided activated sintering, owing to dehydrogenation. The emission of hydrogen and shrinkage of powder particles on dehydrogenation also added a potential to control the sintering process and create desirable porosities. TiH2 powder was sintered with additions of ammonium as pore holding removable agents. The microstructures and porosities of sintered dehydrogenated titanium with different concentration ammonium were comparatively studied. Mechanical characteristics were evaluated using compression testing with strain rates varying from quasi-static to high levels. All testing methods were aimed at characterizing the energy-absorbing ability of the obtained porous structures. The desired strength, plasticity and energy-absorbing characteristics of porous titanium based structures were assessed, and the possibilities of their application were also discussed.

The relatively simple in implementation the pulsed electrical discharge method as an alternative to the gas atomization was performed for the production of powders of shape memory alloys such as Ti-Ni-based, Ni-Al, Cu-Al-Ni, Ni-Mn-Ga as well as the glass-forming alloy Zr-Ni-Cu-Ti-Al and pure Ti. Several methods have used to analyze the powder size distribution spanning from ordinary sieving and laser diffraction to SEM studying. The most effective SEM method gave the information both for powder sizes distribution and morphology of submicron and micron sized particles. The analysis of SEM images has shown that there are several peculiarities both in the powder size distributions and cumulative distributions. That features reflect the action of several mechanisms of the powder particles formation sized between several micrometers to hundred micrometers. In particularly the powders particles size is in average more in powders obtained in liquid nitrogen than in liquid argon independent on the materials of powder. As well that the number of hollows particles sized between 10 and 50 μm is much more in powders obtained in liquid nitrogen.

Composite materials based on regenerated thermoplastics of the polyolefin class with high parameters of stress-strain characteristics, which are highly resistant to open flame and combustion, have been developed. A synergistic effect was achieved by introducing a complex of modifiers into the matrix polymer, including regenerated particles of polytetrafluoroethylene, positioned as ultrafine particles (UPTFE), and residual products of the production of phosphate fertilizers – phosphogypsum (PG). The developed composite materials, processed by injection molding, make it possible to manufacture elements of metal-polymer rollers of belt conveyors used in the mining industry.

Mechanical tests of 5- and 6-component high-entropy alloys, which were obtained for the first time by the method of hot forging, were carried out. The test results showed a fairly high hardness and strength of the obtained alloys. The TiCrFeNiC alloy (without annealing) has the highest mechanical properties. Its high strength is due to solid-solution hardening, as well as the formation of carbides in situ. Fractographic studies showed mostly quasi-brittle destruction of alloy samples.

The influence of non-metallic inclusions on the formation of defects in deformed steels and their role in providing crack resistance are considered. It is shown that non-metallic inclusions as stress and strain concentrators are one of the most dangerous sources of defect initiation in steels during pressure treatment. It has been established that the nature of cracks and the features of their growth near nonmetallic inclusions are determined by the type of inclusions, as well as by the scheme of the local stress state, which depends on the loading conditions. An analysis was made of the features of the initiation and development of the cracks near non-metallic inclusions of various types during tensile strain, compressive and bending deformation. It is shown that the most severe way of deformation for the inclusion-matrix system is tensile strain, the softest is compression.

An observation of the current state of the beekeeping industry and the prevailing main problems was carried out. The prospects for increasing the efficiency and functional capabilities of the bee farms were analyzed. According to the long-term research activity, a technological regulation was contrived for producing innovative ceramic hives. The development is superior to the existing standard beehives made of other materials, in terms of complex operational indicators. The phase composition and technical characteristics of obtained samples of marl raw material (from Bulgarian deposits) were investigated, potentially applicable for the production of various
modifications of ceramic collapsible hives.

One of the effective ways to control the properties of copper is to refine its structure to a nano- or ultrafine-grained level, and primarily with the help of severe plastic deformation. At the same time, radial-shear rolling is one of the promising methods for obtaining long-length rods with a gradient ultra-fine-grained structure. It is known from a number of scientific works that one of the main factors influencing the possibility of obtaining an ultrafine-grained structure in various ferrous and non-ferrous metals and alloys is the deformation temperature of these metals and alloys. The aim of the work is to study the influence of the deformation temperature at the radial-shear rolling mill on the microstructure evolution of copper. The following deformation temperatures of copper rods were selected for the planned studies: 20°C, 100°C and 200°C. The conducted studies have shown that the implementation of radial-shear rolling at ambient temperature compared with rolling at temperatures of 100°C and 200°C made it possible to achieve more intensive refinement of the initial structure. And first of all, this is due to the fact that with radial-shear rolling of copper, realized at ambient temperature, there are no dynamic return processes.