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

Chromium coatings were obtained from spent (waste) chromium electrolyte with the addition of nanosized aluminum oxide. The recovery of the waste chromium electrolyte is carried out by the activation of the chromium ions using the addition of Al2O3 nanoparticles. Electrochemically thin chromium films were deposited directly on S235 steel. The recovered chromium electrolyte has a concentration of nanoparticles of Al2O3 up to 10 g/l, which particles act as intensifiers of the electrochemical process. Analysis was performed with a “Polyvar Met” metallographic microscope and a Bruker D8 Advance powder X-ray diffractometer (XRD). The microstructure of the layer and the matrix were examined and the main phases were determined. SEM-EDS analysis of the chromium layer and the steel matrix was performed. The thickness of the obtained chrome coating with aluminum oxide nanoparticles was determined, which varies between 5 – 10μm.

In this paper, bars from carbon steel grade 45 deformed by a new technology are studied. This technology consists in drawing bars from medium carbon steel on a radial-shift rolling mill and subsequent drawing. As a result of deformation, bars with gradient microstructure were obtained. The surface zone of the bar is significantly crushed, the average ferrite size is 0.5 μm. In the neutral zone the deformation is not large enough, so the structure is not so strongly crushed, the ferrite grains are reduced to 2 microns. In the central zone, the microstructure consists of large grains with an average size of 7 μm. The quantitative ratio of large-angle boundaries in the surface zone is much higher than the central zone. To understand the relationship between strength and microstructure, the microhardness of the bar was determined. Thus for three deformation cycles the average value of microhardness in the central zone was 2085 MPa, in the neutral zone – 2505 MPa, and in the surface zone – 2915 MPa. As it can be seen, the hardness decreases as we move away from the surface zone to the central zone, this can be explained in terms of dislocation and boundary hardening.

This paper investigates the influence of aging parameters (temperature and time) on thermal, mechanical and structural properties of the EN AW-6060 aluminum alloy. Thermal diffusivity and hardness were measured after applied heat treatments followed by investigation on scanning electron and transmission electron microscopes. Heat treatments included: solutionizing at 550°C for 1 hour followed by quenching in ice water; after quenching samples were aged at two separate temperatures of 180°C and 200°C for 1-8 hours. The results show that hardness gradually increases with aging time achieving peak value of 95 HV10 after aging at 180°C for 5 hours. Thermal
diffusivity also increases with both aging time and temperature achieving peak values after aging at 200°C for 4 hours. SEM/EDS analysis show the existence of finely distributed precipitates containing Mg, Si and Fe. TEM investigation confirms the existence of rod-shaped precipitates several nanometers in length.

Here we present data on the preparation and adsorption properties of mixed zinc-calcium phosphates in aqueous dispersions. The phosphates were prepared by co-precipitation from aqueous solutions followed by autoclaving. The effects of various Ca/Zn initial molar ratios and the type of Ca- and Zn-precursor salts (chlorides and acetates) on the structure, morphology and adsorption properties of the obtained phosphates were investigated. Preliminary data on the adsorption of methylene blue indicated that the as obtained mixed zinccalcium phosphates are promising candidates for application as adsorbents.

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 paper presents the results of research aimed at determining the quality of renovation layers using laser technology. In order to repair and renovate shaped parts of molds for casting aluminum alloys under high pressure, samples of experimental welds were prepared on the base material quality 1.2343 (Dievar). The renovation layers were created using additional materials Dievar, UTP A 7002 and NIFIL NiCu7 res. NiCu7 with Dievar combination. The microstructures on the cross-sections of the deposits were checked using the light microscopy technique. The technique of scanning electron microscopy and semi-quantitative EDX microanalyses were analyzed distribution of alloys in deposits. The microhardness of the deposits was determined.

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.

This work discusses the properties of 3D titanium alloys with wear-resistant coatings of hard alloy electrodes based on WC-TiB2-B4C and solder mass of Co-Ni-Cr-B-Fe-Si-C, produced by reaction electrospark processing (RESP) at positive and negative polarity. Through profilometric, metallographic, XRD, SEM, EDS and tribological methods, the complex influence of polarity and pulse energy on the topography, composition, properties, and wear characteristics of the coated surfaces was investigated. The differences in the coatings obtained with the two polarities were identified. Coatings with similar roughness and thickness were obtained, which can be changed by changing the modes for RESP within the limits Ra =2.5÷5μm, δ= 8÷40μm, with microhardness 8 to 14 GPa and 2-4 times higher wear resistance than that of the substrate. At RESP with negative polarity and pulse energy up to 0.04 J, the coatings have comparable characteristics and properties to those at positive polarity, but lower roughness, finer structure and lower coefficient of friction. These coatings can be successfully used to reduce roughness and surface defects and improve the wear resistance of 3D titanium alloys. The pulse energy and polarity of RESР, producing coatings with minimum roughness and maximum wear resistance, have been determined.

The paper presents the results of microstructural studies of 16MnCrS5 steel hypereutectoid structure subjected to reforging under pulsating contact stress loading. It is revealed that the local evolution of the structure in the focus of contact loading has signs of selfimprovement with the transformation of the isotropic morphology of the carbide phase into an anisotropic one with signs of textural riveting. Instead of the initial structure with a uniform carbide phase distribution, signs of textural anisotropy with reinforcement elements of the modified layer high-carbon hypereutectoid zone with carbide inclusions are formed.

This article discusses the use of self-excited acoustical systems (SAS) for the non-invasive and quick study of aluminium castings used in the automotive industry. The SAS system is incorporated into the industry 4.0 standard production line and provides valuable insights into the quality and reliability of the aluminium castings. This approach is innovative and aims to enhance the efficiency of the production process.

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.

Electrochemical coatings of chromium modified with nanodiamond particles applied directly on niobium-aluminum alloy were obtained. Nanodiamond particles produced by detonation synthesis were used. Chromium coatings were deposited on a monolithic composite with a complex structure based on niobium and aluminum alloys, called later matrix for short. Standard chromium electrolyte and electrolyte with nanodiamond particles concentration of 10 g/l were used. Analyzes were performed by Scanning Electron Microscope system of Bruker Inc. and the Polyvar Met metallographic microscope. The microhardness was measured using a PolyvarMet 4000 microhardness tester. The obtained results of the microhardness were 788 kg/mm2 in the chromium layer and 168 kg/mm2 and 692 kg/mm2 in the matrix. The microstructural and SEM-EDS analysis showed the presence of two intermetallides Nb2Al and Nb3Al in the monolithic composite of niobium aluminum matrix. The average thickness of the chromium coatings modified with nanodiamond particles is 55 μm.