Vol 25, No 4 (2023)

Introduction. The paper presents a comprehensive overview of the manufacturing methods, materials, properties, and challenges associated with cellular metallic foams, primarily focusing on aluminum and titanium-based foams. Cellular metallic foams are gaining interest due to its unique combination of low density, high stiffness, and enhanced energy absorption capabilities. Cellular metallic foam is renowned for its special combinations of physical and mechanical characteristics, containing their increased stiffness, specific strength at high temperatures, light weight, and good energy absorption at relatively low plateau stress. It has extensive uses in the automotive, shipbuilding and space industries. It has high porosity, low relative density and high strength, which increases performance of the product. The aerospace and automotive industries require a material with a high strength-to-weight ratio. Methods. To meet this need, many metal foam production methods have been developed, such as melt route method, deposition method and powder metallurgy method. Melt route method is widely used to manufacture metallic foam as compared to other methods. Results and Discussion. In the production of aluminum foams, the melt route method is usually used. Titanium hydride (TiH2) has been a popular foaming agent, but its high decomposition rate and cost limitations have led to the development of alternative foaming agents, such as CaCO3 (calcium carbonate). Titanium foam is often manufactured using the space holder method. This method involves mixing titanium powder with a space holder material, forming a preform, and then sintering to remove the space holder and produce a porous structure as the space holder method allows for precise control over the properties of the foam, including pore size, porosity, and relative density. Results also indicate that porosity in cellular metallic foams can range from 50 % to 95 %, as reported in various journals. Pore structures can include mixed types, open cells, and closed cells, each offering different mechanical and thermal properties. It is also observed from various literature sources that relative density, which is the ratio of the foam's density to the bulk material's density, varies from 0.02 to 0.44 based on the production method used.

Introduction. The metallurgical industry in the territory of the Russian Federation has accumulated a significant amount of slags obtained during the smelting of steels and cast iron. The presence of slag dumps adversely affects the ecology of regions with metallurgical enterprises. When reducing iron from slags, the by-product becomes an oxide agglomerate, which can be considered as a flux composition for arc welding/surfacing under a layer of flux, fillers of powder wires, coatings of welding stick electrodes. The purpose of the work is to establish the possibility of arc welding using the flux obtained by the authors and to determine the optimal welding modes with the condition of achieving the geometric parameters of the seam according to GOST 8713-79 and the quality of the welded joint (absence of internal defects). In this paper, butt welded joints of sheet steel VSt3sp with a thickness of 5 mm obtained by automatic welding under a layer of flux at direct current with forced formation of a root roller on ceramic linings using flux from recycled metallurgical slag of an electric steelmaking enterprise are investigated. Automatic welding of flat specimens was carried out on a tractor-type ADF-1250 machine with a wire with a diameter of 3 mm, at a constant welding speed of 54 cm/min with varying current and arc voltage within 400–600 A and 27–37 V. The methods of investigation: Visual measuring and radiographic control, determination of deformation of specimens by laser scanning and computer processing of 3D models were used to evaluate the quality of welded joints. Statistical modeling in the form of a two-factor experiment was also used in the work, with obtaining adequate regression equations of the influence of welding modes on the geometric parameters of the seam: the height of reinforcement and the width of the seam on the front and back of the joint. Results and discussion. The possibility of obtaining welding fluxes from metallurgical slags of an electric steelmaking enterprise and its use for creating welded joints is shown. Optimal modes of arc welding of thin-walled sheet parts made of low-carbon steel with forced formation of a root roller on ceramic linings is established, ensuring the absence of internal defects in the form of pores, cracks and lacks of penetration, a minimum of residual deformations and compliance of the weld size with the requirements of the existing standard. The nominal values of the geometric parameters of the seam according to GOST 8713-79-C4 correspond to welding mode: welding speed 54 cm/min, welding current 550 A, arc voltage 30 V. The results of the work can be applied in metallurgical electric steelmaking enterprises producing low-carbon steel in the development of technologies for the use of welding materials from slag.

Introduction. Deformation of low-plastic materials requires a high degree of compressive stress. This requirement is implemented, for example, in the process of equal channel angular pressing (ECAP). However, the products obtained by the ECAP method have a cross-section identical to the initial blank, which is one of the disadvantages of this method. The method of nonequal channel angular pressing (NECAP), in contrast to ECAP, makes it possible to change the shape of the initial blank towards closer to the shape of the finished product. However, the well-known NECAP device allows obtaining products only in the form of a thin strip of rectangular cross-section. Well-known devices for multichannel pressing of non-angular type also have a disadvantage — it is implemented only on horizontal type presses, where it is possible to receive long products on the workshop areas. The aim of the work is the evaluation of the bars’; multichannel angular pressing scheme, combining a change in the shape of the initial workpiece in cross-section, as well as the accumulation of a high level of strain during deformation. Research methods: finite element modeling using the DEFORM software module. Results and discussion. The paper considers the scheme of the angular pressing process with the use of a device that allows, for example, to obtain magnesium bars with a diameter of d = 4.1 mm with the number of matrix channels n = 3 from a blank of round cross-section. The container of this device in its lower part has a rectangular groove where the matrix is inserted. Modeling of the process under study using a matrix with the axes of its channels located in the plane of the orthogonal axis of the container and, in the first variant, along the axis of a rectangular groove, and in the second variant, along the radius of the container, allowed us to estimate the distribution of the average stress. It is established that the metal of the blank in both variants of the deformation process is affected by compression stresses at a high level (-1,600 MPa). The assessment of the degree of deformation of the pressed bars allowed us to find out that at the initial stage of both process variants, the maximum strain degree can reach 2.6, and at the steady stage it reaches 5.0. It is established that in the case of the first variant of the matrix, the strain level along the length of the bars is lower than when using the second variant of the matrix. The difference reaches 20 %. By evaluating the distribution of the strain degree in the cross section of the pressed bars near the deformation site, it was found that in the case of the first variant of the matrix, the pressed bars of the first and third channels have an uneven dimensions, and the greater value of the strain degree is on the peripheral part of the rods from the side bordering the central bar. This difference in the strain degree reaches 20 %. When placing the second version of the matrix, this unevenness decreases to 12 %. Thus, in the case of using a matrix with the arrangement of the channel axes along the radius of the container, the strain degree is distributed more evenly compared to the strain degree when using a matrix with the arrangement of the channel axes along the axis of a rectangular groove.

Introduction. High-speed machining of stainless steel has long been a focus of research. Due to characteristics such as low thermal conductivity and work hardening, AISI 304 is considered to be a difficult material to cut. Machinability indicators provide important information about the efficiency and effectiveness of the machining process, enabling manufacturers to optimize their operations for increased productivity and precision. The purpose of the work. Coated carbide tools are most often used for machining AISI 304 stainless steel. Few studies, meanwhile, have examined the effects of pre-and post-treated coated carbide tools when turning these alloys at high speeds. In addition, only a small number of studies have simultaneously optimized the cutting parameters while employing pre-and post-treated tools. The methods of investigation. The present work comparatively evaluates the performance of coated and coated-microblasted tools during the turning of AISI 304 stainless steel. The tools were PVD-AlTiN coated, PVD-AlTiN coated with microblasting as a post-treatment (coated-microblasted), and MTCVD-TiCN/Al2O3 coated (MTCVD). The experimental-based mathematical models were developed to predict and optimize the turning performance. Results and Discussion. In this study, it is found that PVD-AlTiN coated tools have the lowest cutting forces and surface roughness, followed by PVD-AlTiN coated-microblasted and MTCVD-TiCN/Al2O3 coated tools. However, there is no significant difference observed in these responses for coated and coated-microblasted tools. It is found that the cutting forces increased with feed and depth of cut while decreasing with cutting speed. However, this effect is significant for MTCVD-coated tools. On the other hand, higher tool life is observed with MTCVD-TiCN/Al2O3 coated tools, followed by PVD AlTiN coated-microblasted and PVD-AlTiN coated tools. Tool life was largely affected by cutting speed. However, PVD-AlTiN coated tools exhibited this effect more noticeably. The models, with correlation coefficients found above 0.9, can be utilized to predict responses in turning AISI 304 stainless steel. The optimization study revealed that turning AISI 304 stainless steel with MTCVD-TiCN/Al2O3 coated tools incurs lower cutting forces of 18–27 N, produces a minimum surface roughness of 0.3–0.44 μm, and has a better tool life of 36–51 min compared to PVD-AlTiN coated (C) and PVD-AlTiN coated-microblasted (CMB) tools.

Introduction. Drilling holes with standard tolerance varying from IT8 to IT12 is widely used in industrial production. However, at present time, there are neither comprehensive studies, nor scientifically justified recommendations for the rational choice of the geometry of the cutting part of drills with a toroidal flank surface. Therefore, the computer-aided design (CAD) of new drill designs with a toroidal flank surface and finite element modeling (FEM) of the stressed state of its cutting part are important tasks. The purpose of the work is reducing both the range of change in the rake angle and the wedge angle of the cutting wedge along the cutting edge from the periphery to the center and the equivalent stresses in the cutting wedge. In this paper we investigate changes in the rake and wedge angles of the cutting wedge depending on the radius of the generatrix line of the toroidal flank surface as well as changes in equivalent stresses in the cutting wedge, which depend on changes in the radius of the generatrix line of the toroidal flank surface. The research methods include the fundamentals of the theory of cutting, CAD methods, and the FEM, which was applied in this work to new drill designs. Results and discussion. It is found that the range of changes in the rake angle and the wedge angle of the cutting wedge of the drill decreases compared to the standard design with decreasing radius of the generatrix line of the flank surface. A CAD system for drills with a toroidal flank surface is developed. As a result, the range of changes in the rake angle along the cutting edge decreased by 86 % for a drill with a minimum radius of the generatrix line of the toroidal surface compared to that with the conical flank surface, the range of the wedge angle of the cutting wedge decreased by 56 %, and the maximum equivalent stresses decreased by 2.13 times. It is also important to note that in this case, the wedge angle is close to constant for half of the drill tooth. These indicators exceed those for existing designs of the twist drills that indicate the key achievement of this paper.

Introduction. The development and application of additive manufacturing depends on many factors, including the printing process performance and buy-to-fly ratio. Wire-feed electron-beam additive manufacturing (EBAM) is attracting more and more attention from research teams. Moreover, the use of electron beams is the most effective and competitive for additive manufacturing of parts from alloys possessing high oxidation characteristics, e.g., titanium, stainless steels, since selective laser melting occurs in vacuum. Welding titanium wire VT6sv is the most preferable choice due to its availability and a wide range of thickness. This alloy, however, has fewer alloying elements than VT6 (Ti–6Al–4V) alloys. The high performance of wire-feed 3D printing and the VT6sv alloy composition affect the structure, phase composition, and properties of the fabricated alloy. As is known, the elastic modulus and hardness of alloys are important parameters, which can be measured rapidly also using non-destructive testing. The purpose of this work is to study the application of different approaches to measuring the elastic modulus and hardness of products obtained by wire-feed EBAM using the equipment of the Institute of Strength Physics and Materials Science SB RAS. Research methods. The structure of VT6sv titanium alloys fabricated by 3D printing and VT1-0 (Grade 2), VT6 (Ti–6Al–4V) alloys, was investigated by different methods such as metallography, ultrasonic gauging, instrumented indentation technique, macro- and micro-indentation, indentation hardness testing. Results and Discussion. Titanium alloy fabricated from VT6sv titanium wire under different thermal conditions has a typical columnar structure throughout the forging height. The structure formation determines the elastic modulus and hardness at various points of the forging. It is found that the elastic modulus is higher than that of as-delivered Ti–6Al–4V alloys, while the hardness is lower. Micro-indentation shows lower values of the elastic modulus than macro-indentation, which approach to values obtained by ultrasonic gauging and in other works. Different values of the elastic modulus at different points of the 3D printed forging indicate its sensitivity to the structure and phase composition of the material and demonstrate capabilities of measuring techniques used in this work.

Introduction. Plasma cutting of various metals and alloys is one of the most productive processes for obtaining workpieces, especially when using reverse polarity plasmatrons. The use of plasma cutting in the production of workpieces of large thicknesses potentially allows to increase the productivity of the process. In the domestic industry plasma cutting equipment of foreign production is widely used, which poses the problem of import substitution of manufactured products and equipment with the corresponding parts of Russian companies. For this reason, at present the Institute of Strength Physics and Materials Science together with the company "ITS Siberia" develops plasma cutting equipment on reverse polarity currents. At the same time, in order to determine the peculiarities of influence of parameters and modes of plasma cutting process on the structure of metal in the cutting zone, it is necessary to conduct comparative studies on different metals and alloys. Aim of the work: is to identify the characteristics of the influence of high energy impact on the structure and properties of surface layers of aluminum and titanium alloys during plasma cutting using a plasma torch operating with reverse polarity currents. The research methods are optical metallography, microhardness measurement and laser scanning microscopy of the surface after plasma cutting. Results and discussions. The conducted researches show a wide range of possibilities to adjust the process parameters of plasma cutting of aluminum alloys AA5056 and AA2124, and titanium alloy Grade2. For the alloys used in this work there are optimal values of process parameters, deviations from which lead to various violations of cut quality. Aluminum alloys show a tendency to significant de-strengthening in the cutting zone, which is associated with the formation of a large crystalline structure and large incoherent secondary phases with simultaneous depletion of the solid solution with alloying elements. Titanium alloys are characterized by quenching effects in the cutting zone with increasing microhardness values. Oxides are also formed in the surface layers despite the use of nitrogen shielding gas. In the alloy Ti-4Al-1Mn, in the previously conducted works, the formation of oxide films with high hardness is not noted, while in the Grade2 alloy at cutting in the surface layers oxides are formed sharply increasing the values of microhardness of the material up to values of about 15 GPa. This situation can complicate mechanical processing of titanium alloys after plasma cutting. The obtained results indicate a rather low value of the allowance for further machining after plasma cutting of aluminum and titanium alloys.

Introduction. To obtain metallic glass coatings it is necessary to achieve high cooling rates of melt. FeWCrMoBC composition has high melt viscosity and sufficient glass-forming ability to fix of the amorphous state at cooling rates implemented by electric discharge alloying with the use of a crystalline electrode. The purpose of the work is one-stage deposition of amorphous coating by electric discharge alloying, using crystalline anode FeWCrMoBC, prepared by casting and studying the properties of modified surface of carbon steel: wettability, high-temperature resistance, tribological properties. Methods and Results. The structure of anode and coatings was investigated by X-ray diffraction analysis in CuKα radiation on a DRON-7 diffractometer. In contrast to the X-ray patterns of the anode material, sharp Bregg reflexes were not observed on the X-ray patterns of the coatings, but a wide halo was present in the range of angles 2? = 40–50°, which indicates its amorphous structure. The cyclic high-temperature resistance test was carried out at 700 °C for 100 hours. The wear rate and coefficient of friction of the specimens were studied under dry sliding friction at a speed of 0.47 m/s at a load of 25 N with the use of a counterbody made of high-speed steel M45. The influence of the discharge pulse duty cycle on the character of mass transfer (anode erosion, cathode weight gain, mass transfer coefficient) during coating formation was investigated. With a decrease in the duty cycle of the discharge pulses up to 9 times, the erosion of the anode increased up to 5 times, and the cathode mass gain increased up to 2.2 times. The maximum mass-transfer coefficient was achieved at the highest duty cycle. An increase in a number of surface properties of carbon steel after coating was observed: the hardness of the surface of the specimens increased by 2.3–2.6 times; the average thickness of the coatings was in the range of 56–80.6 µm; the wetting angle was in the range of 108.4–121.3°; the coefficient of friction decreased by 1.2–1.4 times; the wear resistance increased by 2–3.3 times; oxidizability in air decreased by 14–18 times. Scope and Conclusions. The achieved higher properties (hardness, wear resistance, high-temperature resistance, and hydrophobicity) of the executive surfaces of parts made of carbon steel after deposition of the proposed coatings can be used in various branches of engineering production. The results of the work confirmed the possibility of deposition of metallic glass coatings by electric discharge alloying with the use of cast anode material FeWCrMoBC on carbon steel.

Introduction. Predicting solid particle erosion (SPE) in gaseous flow and managing its intensity is still a relevant problem in mechanical engineering. It requires the development of a general modeling methodology, which also depends upon many special cases studying various physical processes. Such studies should also include verification analysis, process parameters and model sensitivity studies. Mainly computational fluid dynamics and finite element analysis (and mesh-free methods such as smooth particle hydrodynamics or similar) are used to simulate the erosion process. Papers focused on CFD simulation of solid particle erosion of metal alloys are widely presented, but most of it is associated with relatively low or medium particle velocities (< 100–150 m/s) and is close to uniform diameter distribution. This paper presents a CFD study of Ti6Al4V titanium alloy SPE at relatively high particle velocities and sufficiently non-uniform unimodal particle diameter distribution. The paper also studies the turbulence model influence and particle shape effect which appears as a “shape factor” coefficient in the particle drag model. Methods. The heterogenous flow simulation was based on the Reynolds-averaged Navier-Stokes formulation, where the particles, according to Euler-Lagrange formulation, were simulated as mathematical points with corresponding properties. The influence of turbulence models, such as k-epsilon standard, RNG k-epsilon, and a relatively new Generalized equation k-omega (GEKO) model and its coefficients were also studied. Oka and DNV erosion models were also compared based on the general sample mass loss and more specific erosion intensity profile criterions. The simulation results were compared to the lab-scale experimental results. Results and discussion. It is shown that neither erosion intensity profile or sample mass loss do not depend upon the turbulence model choice or GEKO parameters variation. As expected, erosion is dependent on the erosion model and its coefficients. A notable influence of the shape factor is shown. As the drag coefficient increased due to the particle shape, the erosion intensity decreased and the erosive profile on the surface also changed due to the changing velocity and diameter distribution of the heterogenous flow. It is expected that such results would be useful not only for erosion prediction in all areas of mechanical engineering, but also for wear management in mechanical assemblies and shot peening / shot peen forming management and simulation.