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New methods for compacting graphite fiber powder composites developed by the authors are described. These methods help to remove considerable amounts of gases and liquid vapors from powder loaded into the punch-and-die set and from the compact prior to the main compacting operation.

The feasibility study of elaboration of metal composite coatings by detonation spray using the blends of iron, nickel, copper, cobalt, and aluminum powders was performed using different spray modes. The numerical simulation of particle parameters showed that the particles formed the coating in solid, semi-molten, or molten state depending on the spraying modes, particle material, and particle size. It was shown that successful formation of the coating containing all powder mixture components could be achieved in case of proper optimization of spraying parameters. Obtained Fe-Co-Ni, Fe-Co-Ni-Cu, and Fe-Co-Ni-Cu-Al coatings had the uniform lamellae structure. However, the composition of the coatings differed from the initial powder mixture composition due to different deposition efficiencies of the powders. It was also found the mutual influence of blend components on bonding. In particular, the deposition efficiency of iron particles was probably affected by copper.

The novel idea of alloying, which is based on the utilization of multiple principal elements in high concentrations, has created a novel class of promising materials called high entropy alloys (HEAs). So far, several HEAs with outstanding properties beyond those of conventional alloys have been discovered, and new superior high-entropy alloys are still expected to be developed in the future. However, the fabrication process of HEAs through conventional manufacturing techniques suffers from significant limitations due to the intrinsic requirements of HEAs. Additive manufacturing (AM), on the other hand, has provided new opportunities for fabricating geometrically complex HEAs with the possibility of in situ tailoring of their microstructure features. Considering the growing interest in AM of HEAs during most recent years, this review article aims at providing the state of the art in AM of HEAs. It describes the feedstock requirements for laser based AM techniques. Thereafter, a comprehensive picture of the current state of nearly all HEAs processed by laser metal deposition (LMD), selective laser melting (SLM) and selective electron beam melting (SEBM) is presented. Special attention is paid to the features of AM derived microstructures along with their outstanding properties and underlying mechanisms for various material processing combinations. The AM of interstitial solute hardening HEAs, HEA matrix composites as well as non-beam based AM of HEAs will also be addressed. The post-AM treatments and the strategies to fabricate defect-free HEAs are summarized. Finally, a conclusion of current state and future prospects of additive manufacturing of HEAs will be presented.

The article describes the technology and equipment used at the enterprises of the Russian Federation in 70-90 years in the XX century for the production of bimetallic rods, the basis of the new technology is described, and the designs of mills with multi-roller calibers are presented. New mill designs, patented in the U.S., Japan, Europe and other countries, have a fairly simple design, with the use of multi-roller mills it is possible to use drives from conventional two-roller mills, the presence of radial and axial adjustment of the rolls extends the technological capabilities of the mill, the calibers of different sizes can be obtained on a single set of rolls. On such mills it is possible to obtain sections from low plastic, difficult to deform materials, as well as bimetallic compositions. These products are in high demand in aviation, space, engineering and many other industries, which are strategic directions of the state development.

We propose a technology of hardening of the working surfaces of the rollers of dies intended for the treatment of titanium alloys. The detonation deposition of the WC–10Co–4Cr alloy with a thickness of 600 μm and subsequent fusion of this layer with the help of a laser make it possible to increase the hardness of the working layer up to 1057 HV (> 67 HRC). In this case, the wear resistance becomes more than seven times higher as compared with the case of traditional thermal treatment applied for Kh12MFsteel.

Cold spray is the solid-state process for elaboration of metal coatings and free-standing parts. The absence of material melting during build-up of deposit allows to apply this technology for producing metal composites with innovative properties. The cold spray metal composites could be produced by deposition of composite powders or by simultaneous spraying of powder mixtures. The second approach is considered as the most robust and the simplest one that is important for industrial application. In the present paper, the comprehensive review of the actual knowledge about the formation of metal composite by simultaneous cold spraying of several powders is performed. The main advantages of this approach as well as the issues and the limits are analyzed. The eventual applications of the cold spray composite deposits are also discussed.

Currently restoration and strengthening of a component working surface for structural purposes (objects of stamping equipment, highly loaded assemblies of cars and units, and components operating in corrosive media) is conducted mainly by means of welding operations that do not provide a functional coating and as a result do not provide the life required for a restored or strengthened object. This work concerns a study of laser cladding for restoration of working surface for stamping equipment. Work on laser cladding is conducted on the basis of DMD (Direct Metal Deposition) technology performed in a FL-Clad–R-4 robotic unit that includes a KUKA KR-120 robot. Cobalt-based material is used to create a coating and the substrate (stamp) material is AISI L6 steel. This provides solution for the production problem with selection of regimes for a coating with the required physical and mechanical properties for stamp surface hardening, as well as specific compositions of powder materials used to develop technology for object mass production. Attention is drawn to the fact that alloy used for powder production must have the required physical and mechanical properties and during cladding (after cooling) a coating must not experience thermal stresses and also has the required adhesion.

Mathematical modeling of plastic deformations in rolling consists in a consequent combination of the general energetic relationship in plasticity and the variation inequality expressed the principle of minimum of entire deformation energy. A real deformation state in a plastic zone beneath rolls and corresponding kinematic and dynamics conditions on the contact surface are considered as a limited one for the consequent approximate deformation states and are found out by the method of approximated approach. Any realization of this method on personal computers requires a rational construction of a kinematic-possible velocity field in the spatial domain on plastic flow. Using the ordinary propositions and a new assumptions the authors have constructed a simple kinematic-possible velocity field in the plastic zone beneath rolls. On the base of the consequent approach in which the general energetic relationship and the variation inequality are interrelated the authors have been able to find out the geometric, kinematic and dynamics characteristics of plastic deformation’s states in metal rolling.

This article discusses advanced developments in the field of manufacture of electrical machine brushes. A new method for manufacturing by mixing coke pitch and graphitoplast compositions for making brushes, a new mixer design, and a new graphitoplast composition are presented.

The article is devoted to processes and equipment for the production of non-reinforced brushes and reinforced with a contact wire. The shortcomings of the block molding technology of brushes are shown: high labor intensity of the process, low productivity, long duration of operations in the manufacture of brushes, high demand for various devices and equipment for machining, including diamond equipment, and a laborious and inefficient operation for providing brushes with current leads. Finished products receive insufficient density and reduced physical and mechanical properties. As a solution to these problems, the improved patented methods for the manufacture of brushes for electric machines, the device for their pressing, developed by the scientists of SUSU are given, and the phenomena that occur in the implementation of these methods are described.

The possibility of stabilizing different amounts of medium-entropy intermetallic compounds (MEIMCs) within a multicomponent matrix using laser cladding is demonstrated. The results indicated that MEIMC with a B2 structure could be successfully formed within a multicomponent BCC matrix during laser cladding of a proper ratio of Al, Fe, Co, Cu, Mn, and Ni powders. Two coatings with different contents of MEIMC were fabricated by changing the feeding rate of the powder mixture. Based on the X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) analyses, the Al-rich intermetallic particles were qualitatively identified as (Fe0.55Co0.18Cu0.22Ni0.03Mn0.02)Al MEIMC. It was also found that the feeding rate affects the content of MEIMC, and consequently, the grain structure and microhardness values. Finally, we propose MEIMC-reinforced alloys as a more effective alternative system to be used for fabricating high-performance coatings using laser cladding.

The known designs of the contact heads of the current collectors of trolleybuses with graphite-plastic inserts are analyzed. Designs of new contact heads developed at South Ural State University are presented. Keywords trolleybus, current collector, contact head, carbon composition, insert, electrical resistance, density

One of the methods of local improvement of the wear resistance of aluminum alloy parts is the deposition of hard tungsten carbide-based coatings on the surfaces subjected to intense external influence. This paper is devoted to the characterization of the WC–10Co–4Cr (wt.%) coating deposited on an Al–4Cu–1Mg (wt.%) alloy by the detonation spray method. In comparison with the common thermal spray techniques like High Velocity Oxygen Fuel (HVOF) or Atmospheric Plasma Spraying (APS), the heat input delivered to the substrate during detonation spray is significantly lower, that is especially important in case of coating deposition on aluminum alloys. The paper presents the results of morphology investigation, microstructure, phase composition, microhardness, and cohesive strength of deposited carbide-based detonation spray coating. Results showed that the coating has a porosity less than 0.5% and the carbide grain refinement down to the submicron size during coating deposition was detected. According to the investigation, the variation of spraying distance from 270 to 230 mm does not influence on the coating microstructure and composition.

Electrochemical degradation procedure for the removal of organic dye Reactive Blue 52 using nano-magnetite-doped carbonaceous electrodes was proposed. The electrode was prepared by calcination of graphite grains mixed with phenol–formaldehyde binder modified with iron nitrate. The morphology and phase composition of the electrodes were investigated using scanning electron microscopy and powder X-ray diffraction. Electrochemical degradation was done in Nafion membrane-divided cell where anodic part was filled with color solution and cathodic with supporting electrolyte. Parameters affecting on decolorization rate were investigated. A high increase in the removal efficiency, under optimized parameters, was noticed using carbon electrodes containing 1 mass% of magnetite in the presence of 3 mM hydrogen peroxide and 7 mass% of magnetite in the presence of 10 mM hydrogen peroxide. Almost 100% decolorization was achieved during 30 min with 62–77% of the mineralization. Based on these results, it can be concluded that this approach offered green, cheap and efficient degradation of reactive dyes and could be used as promising candidate for wastewater processing in the textile industry.

The influence of laser power on the microstructural, strength, and tribological characteristics of aluminum bronze coatings applied to steel by laser cladding was studied. It was found that with an increase in laser power, the morphology of the coating surface becomes more uniform without extreme height differences. This study revealed that the coating microstructure corresponds to that of a composite material and consists of a bronze matrix and iron dendrites of different sizes (depending on the laser power). Such a microstructure affects the microhardness indices, which have a scatter of values over the coating thickness. There is a diffusion zone at the steel&ndash, bronze interface, which promotes adhesion of the matrix and coating materials. According to the results of tribological tests, the dry friction coefficient for the studied samples is in the range of 0.389&ndash, 0.574.

The C-N samples were synthesized at 500 °C from melamine and four kinds of pitch. At 50–100 mass % of pitch all samples were single phase nitrogen solid solutions in graphitic carbon. Maximal detected concentration of 22.4 mass % N correspond to solid solution with formula C100H26.8N26.3O3.1. According to infrared spectroscopy the N atoms chaotically substitute carbon. The electric resistivity of samples with 22.4 mass % N was 1.3–67 Ω ∗ m, which is 100–1000 times lower than resistivity of corresponding graphitic carbon without doping (430–6700 Ω ∗ m). The resistivity of graphitic C3N4 is about 1011 Ω∗m.

The paper is devoted to the design of new devices for the production of long-length bars of consumable electrodes for vacuum-arc melting.

Самодурова Марина Николаевна, канд. техн. наук, доцент, доцент кафедры процессов и машин обработки металлов давлением, Южно-Уральский государственный университет, г. Челябинск; mar-samodur@yandex.ru, samodurovamn@susu.ru. Огарков Николай Николаевич, д-р техн. наук, профессор, заведующий кафедрой технологии машиностроения, Магнитогорский государственный технический университет им. Г.И. Носова, г. Магнитогорск; ogarkovnikolai@mail.ru. Платов Сергей Иосифович, д-р техн. наук, профессор, заведующий кафедрой машин и технологий обработки давлением, Магнитогорский государственный технический университет им. Г.И. Носова», г. Магнитогорск; psipsi@mail.ru. M.N. Samodurova1, mar-samodur@yandex.ru, samodurovamn@susu.ru, N.N. Ogarkov2, ogarkovnikolai@mail.ru, S.I. Platov2, psipsi@mail.ru 1 South Ural State University, Chelyabinsk, Russian Federation, 2 Nosov Magnitogorsk State Technical University, Magnitogorsk, Russian Federation

The first devices for preparing workpieces (bars) of refractory metal powders (tungsten and molybdenum) in the form of dismountable steel dies installed in a hydraulic press of special construction with vertical and horizontal cylinders were developed by the American firm General Electric in 1909. This article considers known and new die and device constructions for molding bars from refractory metal powders developed by scientists of Ural scientific schools.

The article presents new methods of obtaining products of electrical engineering from carbon compositions such as current collector inserts for trolleybus transport. In the process of manufacturing inserts, several problems are solved related to the imperfection of technology and methods of pressing carbon products: an unreliable current collector, increased contact wire wear, etc. Such methods of making inserts improve the quality of the finished product by increasing its density, and also increase the productivity of the process as a whole.

The results of studying the surfaces roughness of rolls, dies, and workpiece are presented and analyzed. Recommendations are formulated on selecting rational surface finishing methods for rolls and dies and methods for preparation of blanks for drawing. The oil absorption capacity of surfaces depending on their roughness caused by the machining method used is determined. The results can be used for choosing surface finishing methods, tools, and materials, depending on the intended metal-forming process.

Analysis is provided for known and new technology and construction of dies for molding gas-saturated powders of tungsten and carbon powder composites made on the basis of YuUrGU scientist inventions. Gas saturation of tungsten powder is connected with the unusually low bulk density equal to 0.06–0.12 of the density of pore-free tungsten, and small powder particle size within the limits of 1–3 μm. High gas saturation of powder composites based on carbon is determined by the high capacity of carbon for adsorption of gas and liquid vapor molecules at particle surfaces.

This paper reports on a computer simulation of plastic deformation of refractory material porous billets when rolling in four-roll-pass mills. This model allows calculating the geometrical, kinematic, and energy parameters of the rolling process accounting for the preset law of porous billet compacting in the deformation zone. The theoretical study of porous billet rolling process using the mathematical model has proved the decrease of billet elongation compared with that of non-porous ones. The computer analysis has shown that in the process of rolling falling of creep value, the rolling force and rolling moment take place. The experimental test of the computer simulation results has shown a good correspondence of main rolling process parameters.

The results are provided for research and also development of mill technology and construction with fourroll passes for rolling small section nickel-base superalloys. The design of roll passes, mechanical property test results for rolled bars of nickel-base superalloys at 20°C and working temperatures of 850–950°C, and indicators of stress-rupture strength are provided.

Titanium alloy product manufacturing is traditionally considered to be a rather difficult task. Additive manufacturing technologies, which have recently become quite widespread, can ensure the manufacture of titanium alloys products of an arbitrary geometrical shape. During this study, we have developed a methodology for manufacturing titanium alloys products using additive technologies on FL-Clad-R-4 complex of laser melting of metals by combined Selective Laser Melting (SLM) and Direct Metal Deposition (DMD) methods. Ti&ndash, 6Al&ndash, 4V and Ti&ndash, 4Mo&ndash, 1V alloys were used for the manufacture of samples. We studied the microstructure of the obtained details and measured the microhardness of the samples. We discovered a gradient of the structure throughout the height of the details walls, which is connected with the peculiarities of thermal cycles of the technology used. This affected the microhardness values: in the upper part of the details, the microhardness is 10&ndash, 25% higher (about 500 HV) than in the lower part (about 400 HV). Products made according to the developed technique do not have visible defects and pores. The obtained results indicate the competitiveness of the proposed methodology.

Drop and rotary forgings of molybdenum or tungsten rods and wire rods requires a great number of operations accompanied by significant losses in expensive metals and low quality of half-finished products. Therefore, it is of great importance to develop new effective methods as well as the appropriate equipment for high-quality treatment of molybdenum, tungsten, and their alloys. The paper presents one of the methods—multi-pass rolling with multi-sided reduction of powder sintered blocks. Intensive three- or four-sided reduction of the block leads to a favorable strain-deformation conditions at the point of the applied deformation allowing to obtain the appropriate scheme of that state of the material. As a result, the plasticity of the rolled material increases and its cross-flowing slows down. High plasticity of the material allows to increase the degree of multi-sided reduction of rods or stocks and, therefore, to reduce the total number of treatment operations, to reduce the losses of metals, and to improve the quality of rolled products and their mechanical characteristics. Slowing down the cross-flowing of the metal during multi-sided reduction of its blocks in the process of rolling allows for a more effective deformation, low energy consumption, and cut number of block passes. Thus, four-sided reduction gives the most favorable scheme of the strain-deformation state of the material under the condition of multi-sided, nonuniform reduction of the blocks in the process of rolling.

The possibility of obtaining alloy/composite coatings by detonation spraying of Fe + Co + Ni and Fe + Co + Ni + Cu powders mixtures was evaluated for the first time. The conditions of spraying were selected such that the particles of all three (four) metals were flying out of the gun barrel in the fully molten state, as confirmed by the calculated particle temperatures. The deposited layers had a dense composite structure consisting of metallic lamellae. A common feature of the deposited layers was a diminished concentration of iron relative to the feedstock mixtures. The results of the present work show that, upon a proper adjustment of the composition of the feedstock mixture, detonation spaying can be used to form dense precursors of high-entropy alloy coatings.

High entropy alloys (HEAs) have provided a unique opportunity to design novel structure-function integrated materials through modulating chemical composition and tailoring microstructural features. In this study, a novel self-lubricating CoCrCu1-xFeNix (x = 0, 0.1, 0.3 and 0.5) HEA coating was in-situ prepared by laser cladding. The adequate amount of nearly pure copper segregated into the interdendritic regions could effectively smear the surface of the alloy and provide a Cu-rich protective oxide layer during dry sliding condition at an intermediate temperature of 400 °C. These findings serve as a proof of concept for the application of laser cladding as a high throughput process to rapidly fabricate self-lubricating HEA coatings through combining the intrinsic features of HEAs and additive manufacturing.

For experimental evaluation of the efficiency of two-, three-, and four-directional rolling, round, square, and triangular bars made of AK6 aluminum alloy were used. It is established that the most efficient process is the four-directional rolling of square bars, which allow obtaining higher reduction without lateral flow of metal and with minimum roll force and minimum energy consumption.

The contact interaction of a heterogeneous powder medium with the surface of a steel or hard-alloy tool is subjected to mathematical simulation. Under known compacting conditions, the developed mathematical model can be used to find the character of particle motion in the medium to be compacted and the density distribution over the volume of the semiproduct or the end product.

This work is devoted to the study of the microstructure and the properties of the Cu-W composite coatings deposited using cold spray technology. This process allows fabrication of high-quality coatings on large surfaces of different types of materials. The technology is widely used and investigated due to technological simplicity, wide range of sprayed materials and operating temperatures. However, there are some technological problems which appear when materials with low melting temperatures are sprayed. During softening, the particles adhere to the nozzle walls and block spraying. By the way, it is possible to solve the problem adding some ceramics particles to the spraying mixture of powders. As a result, the formed coating will have better mechanical properties and the technological problem will be solved. The analysis of the general results of the microstructure studies and experiments, and comparison with other coating methods are given. Moreover, the experimental procedure of samples preparation and used equipment are given. It is shown the microstructure before and after heat treatment of the samples sprayed, microhardness measurements, thermal conductivity measurements.

This paper presents the study results of the drawing machine intermediate block surface hardening treatment by the methods of additive technologies. Laser surfacing of powder material Fe-4,5Cr-4,5Mo-5,5 W-4V on the intermediate block working surface a wear-resistant layer with a hardness of 52-54 HRC with a thickness of more than 1.5 mm. The laser complex LaserClad 4 C R120 based on the industrial robotic manipulator KUKA KR-120 together with the positioner is able to melt powder material only on the working surface of the intermediate block, thereby significantly reducing its cost and labor intensity during its manufacture. The applying of detonation spraying with subsequent penetration for this type of product proved to be ineffective. The detonation coating itself with a powder material based on tungsten carbide turned out to be uniform and had a hardness in the range of 61 -65 HRC. But rather large pores and cracks appeared in it after penetration, which is associated with a significant difference in the coefficients of thermal linear expansion of steel 41Cr4 (14-10-6 1/K) and an alloy based on tungsten carbide (3,9-10-6 1/K).

The Russian and foreign technology used since the beginning of the last century to industrially produce collector profiles made of copper-cadmium bronze is characterized by low productivity, large losses of metal, and semifinished and finished products of inferior quality. The technology includes casting and pressing ingots obtain semifinished products of trapezoidal, square, or rectangular cross section, which are then rolled or drawn to obtain billets for subsequent final drawing. The pressing and rolling or drawing of the trapezoidal semifinished products is accompanied by bending of the ribs and twisting of the product, and the quality of the finished profiles is compromised by their curvature. The authors have developed new methods and equipment for rolling collector profiles in tapered rolls to avoid the formation of such defects. Results are reported from tests of the methods, which involve rolling in tapered rolls with intersecting axes.

An analysis is made of existing and promising new designs and methods of obtaining carbon materials for such electrotechnical products as the inserts of the sliding contacts used on trolley buses. Original designs of sliding contacts are described along with fundamentally new methods invented by the authors to make them.

An analysis is made of existing and new designs of carbon brushes and collectors for the pantographs of trams and electric trains. Descriptions are given of a new method of making carbon brushes and a new design of pantograph collector. The new method and the new design are based on inventions of the authors of the article.

The compressibility of bars and hydraulically forged workpieces made of tungsten and molybdenum is studied during rotary swaging and rolling in mills with two-, three-, and four-roll passes. The compressibility of molybdenum MCh bars and hydraulically forged molybdenum M-MP workpieces is investigated during rotary swaging and rolling in three- and four-roll passes. The compressibility of tungsten VA and VL bars and hydraulically forged tungsten V-MP workpieces is investigated during rotary swaging and rolling in three- and four-roll passes. The compressibility of the hydraulically forged tungsten V-MP workpieces is analyzed under two- and four-roll pass rolling conditions.

Development of high-speed workpiece stamping technology for objects of domestic designation from iron-based powders is analyzed. Results of experiments performed by the authors are discussed for cold high-speed stamping of objects such as bushes with a conical section made from iron powder grades PZhV3 and PZhV4 followed by sintering, and also by high-speed stamping of these objects. A die construction and methods for preparing workpieces of the bush type with a conical end section proposed by the authors are protected by patents.

A mathematical model is developed to calculate the geometric, kinematic, force, and energy parameters and to determine the change of density during the rolling of initially porous square bars and octagon semiproducts. The model is based on a basic energy equation and a variational equation derived from the principle of the minimum total deformation energy. The model is used to analyze the effect of the percent reduction, the friction coefficient, the roll radius, and the temperature on the geometry, the kinematics, and the energy-force parameters of the process.

The industrial technology which has been used since the beginning of the last century to make products from tungsten powders is still complicated and involves multiple operations. The technology is time-consuming because engineering studies that determine the parameters of the operations of compacting, sintering, welding, and shaping the tungsten compacts need to be performed before the first large batch of commercial products can be made. A factorial experiment showed that these operations can be made less labor-intensive by constructing regression relations for the density of the powder, sample weight, and the forces in the compaction process. New designs of molds have been developed together with a new method of compacting tungsten powder.

Data are provided for particle shape, component and grain size composition, for information about the connection of compact density with compaction pressure for powder materials with special properties based on tungsten and carbon.

Well-established and new processes for the high-energy shaping of materials are analyzed along with the equipment they use. Most of the attention is given to the latest methods of high-energy compaction of metallic and nonmetallic powders on equipment made by the Swedish company Hydropulsor. Results are presented from studies performed on metal powders by scientists at the Swedish companies Hoganas and Sinterheat and Dalarna University, on powder ceramics (Al2O3) by French scientists, on copper and iron powders by Chinese scientists, and on carbon powders by the authors of the article.

An analysis is made of the results of theoretical studies, experimental studies, and commercial trials of methods and equipment for the static forming of semifinished and finished products made of carbon-based powders and powder compositions with special properties. Both literature data and new results obtained at the South Ural State University are discussed. The article also examines experimental studies made of processes for the high-energy forming of specimens of preforms from pure graphite powder, graphite with a binder, graphite with a binder and copper powder, graphite with a binder and powdered coke, and graphite with coke and zinc stearate. High-energy forming was performed with speeds of 1.10-3.58 m/sec and energies of 212-2247 J at the Technical Center of the National University in Saint-Etienne, France. © 2012 Springer Science+Business Media, Inc.