bluuebunny/crossref_metadata_2025 huggingface dataset:
Production of filler rods for repair welding of ML12 (ZK51) magnesium alloy castings
Authors: Koltygin A. V. , Bazhenov V. E. , Tavolzhanskii S. A. , Matveev S. V. , Plisetskaya I. V. , Belov M. V. , Samokhin A. V. , Belov V. D.
Published: January 2023

In magnesium alloys castings, the casting defects such as shrinkage porosity are often occur. Such defects can be suppressed by repair welding or surfacing using a special filler rod. Unfortunately, in Russia, the low amount of filler rod is consumed. Therefore, native enterprises do not manufacture it, limiting themselves to imports or homemade low-quality substitutes. Nevertheless, there is a need for filler rod, and recently it has become unprofitable to replace them with imported materials due to a significantly increased price. Therefore, there is a need to study the technology of its production to replace imported filler rod with native material. Magnesium alloys based on the Mg–Zn–Zr (La, Nd) system: SV1, SV122, and ML12 (ZK51) that used as a filler rod for repair welding of ZK51 alloy castings were studied in this work. The samples were obtained by permanent mold casting into aluminum molds followed by hot extrusion into a filler rod with a diameter of 4 mm. It was shown that all the investigated alloys could be obtained in the form of a rod with a diameter of 4 mm. Therefore, the investigated rod samples from the SV122 alloy were used as filler material for repair welding of ZK51 magnesium alloy castings. The weld seam in the T1 condition has an ultimate tensile strength (UTS) about 80 % of the UTS of the casting material.
Review of separation and concentration techniques for impurities in rare earth-based materials for further spectral and mass spectral analysis
Authors: Petrova K. V. , Es’kina V. V. , Baranovskaya V. B. , Doronina M. S. , Korotkova N. A. , Arkhipenko A. A.
Published: January 2023

The effectiveness of using materials based on rare earth elements (REE) largely depends on their impurity composition, which affects their structure and properties. Before the analytical quality control of REE-based materials and initial substances for their production, it is necessary to determine both macrocomponents and impurity elements with high sensitivity and accuracy. A complex of atomic emission and mass spectral analytical methods is often used for the determination of impurities in REE-based materials in the range from 10–5 to 5.0 wt.%. However, the analysis of such materials, even using these modern high-sensitivity methods is a difficult task due to spectral and matrix interferences. Therefore, different preliminary separation/concentration procedures are needed to determine both rare earth and other impurities. This article reviews publications is devoted to preconcentration methods for spectral and mass spectral analysis of REEbased materials and, in part, a number of other analytical techniques. It was shown that the most common approaches are liquid extraction and chromatography. Sorption, cloud-point extraction and coprecipitation are also used. There is no universal method. Each of the methods discussed in this article has its own advantages and limitations. The analytical completion of the method confirms the effectiveness of the selected separation/concentration method in each specific case.
Effect of reduction ratio during cold rolling and final annealing temperature on the properties and microstructure of Al–Mg–Sc alloy sheets
Authors: Grechnikov F. V. , Erisov Ya. A. , Surudin S. V. , Razzhivin V. A.
Published: January 2023

The study covers the effect of the reduction ratio during cold rolling (εh) and the final annealing temperature of sheets rolled with different reduction ratios on the microstructure and the complex of mechanical and processing properties of cold-rolled sheets made of the V-1579 aluminum alloy of the Al–Mg–Sc system. It was established that as εh increases, the nature of plastic anisotropy changes slightly, and an increase in tensile strength and yield strength with a decrease in relative elongation is observed. In this case, the ultimate strength and yield strength anisotropy is practically absent. As the reduction ratio increases to 30–40 %, the relative elongation anisotropy increases, and its value in the rolling direction decreases more rapidly. However, after rolling with εh > 50 %, the relative elongation anisotropy practically disappears. Regardless of the annealing temperature, samples rolled with a higher reduction ratio have better strength properties. It was found that as the annealing temperature increases, the ultimate strength and yield strength decrease, and the relative elongation increases. In this case, softening with an increase in the annealing temperature occurs more intensively for samples rolled with a lower reduction. After annealing, the distribution nature of anisotropy indices in the sheet plane does not decrease and corresponds to the deformation type of textures for all analyzed modes. Moreover, the value of the in-plane anisotropy coefficient decreases in comparison with a cold-rolled sample. At the same time, processing properties of samples rolled with a higher degree of deformation after annealing are higher than those of samples rolled with a lower reduction, regardless of the annealing temperature.
Features of the presence of precious metals in the zinc production clinker
Authors: Lobanov V. G. , Kolmachikhina O. B. , Polygalov S. E. , Khabibulina R. E. , Sokolov L. V.
Published: January 2023

The paper considers the features of gold deportments in technogenic raw materials – aged clinker of zinc production at the Belovsky zinc plant (Belovo, Kemerovo Region). The Belovsky plant operated from 1930 to 2003 using zinc concentrates from the Salairsky ore mining and processing plant. After the plant shutdown, clinker dumps were stored at the plant’s mill site and were repeatedly washed with acidic solutions to isolate copper. This form of storage and leaching led to the transformation of precious metal deportments in clinker, which currently makes it difficult to extract gold. The gold content in clinker is at the level of 2–3 g/t, which makes gold recovery profitable. The presence of carbon in clinker complicates the use of known methods of both analytical detection of gold and its recovery. A method is proposed for determining the deportment and content of gold taking into account the fact that gold may be present in the form of free fine gold, as well as gold finely disseminated in iron and its oxides, in sulfide phases, in the quartz-silicate part of clinker and in the carbonaceous phase. It was shown that gold deportments in clinker change depending on the storage conditions and preceding acid treatment, and this affects the choice of the material processing flow chart. The share of gold available for leaching is at least 40 %. The increased associativity of gold with the coal (flotation-active) phase and the sorption activity of coal significantly interfere with the study into the properties of gold deportments in clinker, which requires preliminary carbon removal.
Rationale for efficiency of flotation in the conditions of wetting film heating
Authors: Evdokimov S. I. , Gerasimenko T. E.
Published: January 2023

When studying the aggregative stability of dispersed systems by sediment volumetry, nanobubbles are formed due to water structure imperfections in the contact area, and the coalescence of nanobubbles results in a hydrophobic attraction force. Changes in the aggregative stability of aqueous dispersions of particles can be explained as follows: water molecules with a high potential of interaction with medium molecules are difficult to flow into the interfacial gap between particle surfaces, and the outflow of water molecules with a high intensity of interaction with a solid surface is impaired. Excessive osmotic pressure between hydrophilic surfaces causes their hydrophilic repulsion, and excessive osmotic pressure of the surrounding water (reduced osmotic pressure between surfaces) causes hydrophobic attraction of the surfaces. To change the result of flotation, it is sufficient to bring the heat flow to a thin liquid layer of nanoscale thickness with the action of forces of structural origin localized inside, which determine the stability of wetting films. To increase the temperature in the interfacial gap between theparticle and the bubble due to the heat of water vapor condensation, it is proposed to use a mixture of air with hot water vapor as a gas during flotation. The developed flotation method was tested in the flotation of gold-bearing ores. The rational vapor consumption determined based on the factorial experiment results is 10.7·10–3kg/(s·m2) at a xanthate consumption of 1.74 g/t. The rougher flotation operation used a jet method of flotation circuit design, which provides for the combination of the initial feed and the rough concentrate. In comparison with ore flotation according to the factory scheme, the yield of concentrate sent for hydrometallurgical processing is 23.4 rel.% less while maintaining the gold recovery level achieved.
New process solutions in the manufacture of thermochemically resistant ceramic molds for casting titanium alloys
Authors: Dubrovin V. K. , Kulakov B. A. , Karpinskii A. V. , Zaslavskaia O. M.
Published: January 2023

The paper provides the results of studies on interaction between titanium melts and silica-containing investment molds. Pure silicon, compounds of titanium oxides and silicides were detected by X-ray diffraction analysis in the contact zone. The problem of the negative impact exerted by the mold on the casting is solved by using thermally stable and chemically resistant monocorundum molds based on an alumina sol binder. A refractory suspension was developed for investment casting containing special additives to improve wax mold wetting with the suspension, and to increase the mold shell strength. The article studies sedimentation properties of suspension. A method was developed for accelerated curing of sequentially applied refractory suspension layers by vacuum drying and subsequent chemical curing with a gaseous reagent. The formation time is reduced from 3–5 h to 20–30 min per layer. Comparative studies of kinetics of alumina sol binder convective drying and vacuum dehydration were conducted. The process of moisture removal per unit surface of the applied refractory layer in a vacuum of 5–10 kPa increases by 2–6 times. X-ray phase analysis was used to study the alumina sol conversion during high-temperature heating. The solid gel of the α-Al2O3stable phase is obtained in the alumina sol mold shell when the calcination temperature rises to 1300–1350 °C with a sufficient strength of 9–12 MPa provided by sintering additives added to the suspension. Recommendations are given for additional protection of refractory ceramic layers after vacuuming and drying: treatment of the last layer with gaseous curing agents and application of a polyvinylacetal solution with a density of 1100–1200 kg/m3. The process solutions proposed will make it possible to increase both the efficiency of titanium alloy forming and casting processes and the quality of castings.
Self-propagating high-temperature synthesis of heterophase materials in the Zr–Mo–Si–B system. Kinetics and mechanisms of combustion and structure formation
Authors: Pogozhev Yu. S. , Potanin A. Yu. , Bashkirov E. A. , Levashov E. A. , Kovalev D. Yu. , Kochetov N. A.
Published: January 2023

The paper focuses on the study of the combustion kinetics and mechanisms of elemental mixtures in the Zr–Mo–Si–B system, as well as the analysis of phase and structural transformation stages in the combustion wave. A thermodynamic analysis of potential chemical reactions occurring in the combustion wave was carried out. The reaction of ZrB2 formation is preferred in the range of 298–2500 K. Above 2200 K, the formation of MoB becomes more thermodynamically advantageous as compared to MoSi2. Phase stability estimates of combustion products showed that ZrB2, MoSi2 and MoB phases are in equilibrium. Experimental dependences Тc(Т0) and Uc(Т0) are linear, which implies an unchanged combustion mechanism at T0 = 298÷800 K. Preheating leads to an increase in Uc. Similarly, an increase in the proportion of Zr and B in the mixture has a similar effect, i.e. an increase in heat emission and Tc. With a minimum content of Zr and B, the interaction between Mo and Si with the formation of MoSi2 by the reaction diffusion mechanism is decisive. As the proportion of Zr and B increases, the rise of T0 to 750 K does not affect the Tc. Eeff values (50–196 kJ/mol) confirm the significant influence of liquid-phase processes on the combustion kinetics. The mechanism of structure formation was studied. A Si–Zr–Mo melt is formed in the combustion front. The primary grains of ZrB2 and MoB crystallize from this melt as it is saturated with boron. At the same time, the melt spreads over the surface of Zr and Mo particles. This leads to the formation of ZrSix, MoSix films. Core-shell structures are formed behind the combustion front, which disappear as they move towards the post-combustion zone. The phase composition of products is formed in the combustion front in less than 0.25 s.
Thermodynamics of the effect of alloying on phase formation during crystallization of aluminum matrix composites with exogenous reinforcement
Authors: Prusov E. S. , Kechin V. A. , Deev V. B. , Shurkin P. K.
Published: January 2023

A thermodynamic assessment of the effect of alloying elements (Si, Mg, Cu, Ti) on phase formation processes during the production and liquid-phase processing of cast aluminum matrix composite materials with exogenous reinforcement (Al–SiC, Al–B4C) was carried out. It was shown that without suppressing Al–Si–C and Al4C3 carbide formation in the range of carbon concentrations from 0 to 4.5 wt.%, the equilibrium phase composition of Al–SiC composites in the solid state at 423 to 575 °C lies in the (Al) + Si + Al4SiC4 three-phase region, and the Al4SiC4 ternary carbide is replaced by the Al8SiC7 compound at a temperature below 423 °C. SiC and B4C phases in Al–SiC–Cu and Al–B4C–Cu systems are stable in the entire crystallization range and do not interact with aluminum or copper. In the Al–SiC–Mg system, the crystallization of composites containing more than 0.58 wt.% magnesium ends in the (Al) + Al3Mg2 + SiC + Mg2Si four-phase region. In the Al–SiC–Ti system, the end of crystallization is observed in the (Al) + Al3Ti + SiC three-phase region. In the Al–B4C system, once Al4C3 phase formation is suppressed, aluminum borides are formed with a deviation from the concentrations of elements providing 10 vol.% B4C towards boron increase and free carbon is formed with a deviation towards boron decrease. Under equilibrium conditions, Al–B4C–Si system crystallization ends in the (Al) + B4C + AlB12 + Al8SiC7 four-phase region (at a silicon content of up to 0.67 wt.%, and in the (Al) + Si + AlB12 + Al8SiC7 region at a higher silicon content. In the Al–B4C–Ti system, crystallization ends in the (Al) + TiB2 + B4C three-phase region at a titanium content of less than 0.42 wt.%.
Hereditary influence of deformed waste on the efficiency of Al–Si–Mg and Al–Mg alloy modification
Authors: Nikitin K. V. , Nikitin V. I. , Timoshkin I. Yu. , Biktimirov R. M. , Novikov A. P.
Published: January 2023

The paper provides the results of studies into the effect of the charge composition on the structure and mechanical properties of Al–Si–Mg (AK9ch) and Al–Mg (AMg6l) cast aluminum alloys. It was shown that deformed waste included in the charge composition (electrical waste of aluminum and waste of beverage cans based on the 3104 alloy – for AK9ch; AMg6 alloy plates – for AMg6l) contributes to the formation of dispersed micro- and macrostructure of working alloys in the solid state. The effect of modification (AlSr20 master alloy – for AK9ch; AlTi5 master alloy – for AMg6l) on the structure and mechanical properties of alloys obtained with various charge options was studied. Experiments on the effect of the charge composition on the AK9ch and AMg6l modifiability showed that the deformed waste structure is partially inherited by working alloys through the liquid state. With similar chemical compositions, alloys obtained with an increased proportion of deformed waste in the charge composition feature by smaller micro- and macrostructure sizes and improved mechanical properties (tensile strength and tensile elongation). It was found that when a certain amount of the modifier element (0.06 % Sr for the AK9ch alloy; 0.04 % Ti for the AMg6l alloy) is exceeded in these alloys, the over-modification effect appears. This is expressed in enlarged micro- and macrostructure parameters, as well as lowered tensile strength. The results obtained show that the optimal amount of the deformed waste proportion in the charge composition will make it possible to reduce the consumption of expensive modifying master alloys with a guaranteed effect of modification in practice.
Study of the structure and properties of cermets based on the NiAl–Al2O3 system
Authors: Agureev L. E. , Kostikov V. I. , Eremeeva Zh. V. , Ivanov B. S. , Savushkina S. V. , Laptev I. N. , Ashmarin A. A. , Ivanov A. V. , Sivtsova G. V.
Published: January 2023

The powder metallurgy method including mechanical activation of powders in a planetary mill and spark plasma sintering at 1470 °C in an inert atmosphere was used to obtain NiAl–45vol.%Al2O3 cermet samples with the addition of nanoparticles of magnesium aluminum spinel in an amount of 0.05 vol.%. The features of their microstructure were investigated. Spinel nanoparticles are located at the boundaries between the grains of composite components. The results of X-ray phase analysis at t = 25 and 800 °C were obtained. The main components of the material at t = 20 °C are α-Al2O3 and NiAl. The dependence of internal friction on temperature in the range of 20–900 °C was studied, and the influence of magnesium aluminum spinel nanoparticles on the nature of its change was established. The internal friction curve shows that vibration damping occurs up to 600 °C. Dependences of the ultimate bending strength of cermets at t = 20÷750 °C were determined. The positive effect of introducing a small amount of magnesium aluminum spinel on the elastic properties of composites was established. The best mechanical properties were demonstrated for NiAl–42vol.%Al2O3–0.05vol.%MgAl2O4 samples. On average, the ultimate bending strength of this material was 8–15 % higher compared to samples without nanoparticles. The materials obtained in this research had an ultimate bending strength under normal conditions of 460–490 MPa. A summarizing analysis of NiAl–Al2O3 cermet researches was carried out to determine the nature of the ultimate bending strength dependence on the ratio of components. It was found that it has an extreme nature: the maximum is observed when using the ratio of aluminum oxide to aluminum nickel equal to 0.5.
Possibilities of matrix lead alloy doping at non-gasostatic carbon-graphite impregnation
Authors: Gulevsky V. A.
Published: January 2023

The study covers the process of carbon-graphite – lead composite formation by impregnating a porous AG-1500 scaffold with a lead melt containing 2.0 at.% Cu. The paper describes the kinetics of filling the carbon-graphite open porosity with molten metal with the continuously heated furnace and impregnating device. A feature of this method is the volumetric expansion of the lead alloy impregnating porous carbon-graphite. It is placed in a sealed steel container filled with lead by 2/3 of its volume with further vacuuming, melt adding and sealing. Then the device is placed in the furnace so that the lead-copper alloy, already having a temperature below the liquidus temperature by 20–30 °C when heated in the furnace to 900 °C, impregnates the carbon-graphite scaffold with further expansion at constant heating. Porous scaffold capillaries are filled as the melt temperature continuously increases. Once graphite-carbon impregnated with lead alloy is taken out, it was investigated using X-ray spectral and energy-dispersive analysis. It was found that the elements of the impregnating alloy were redistributed at the carbon-graphite scaffold/Pb alloy interface depending on its initial composition. During the carbon-graphite scaffold impregnation with the Pb–2%Сu alloy under a pressure of up to 5 MPa, copper redistribution occurs on its inner pore surface and the boundary with the alloy, which leads to the formation of an interphase layer containing 70 % Cu. The conducted research made it possible to obtain a composite with a copper content of 1.85 at.% in the impregnating Pb alloy at the interface with carbon graphite.
Production of α-Fe 2O 3 powder material with multilevel gradient porosity
Authors: Demirov A. P. , Blinkov I. V. , Kuznetsov D. V. , Kuskov K. V. , Kolesnikov E. A. , Sedegov A. S.
Published: January 2023

The paper studies methods for obtaining a multilevel gradient porous material by the layer-by-layer sintering of distributed α-Fe2O3 nanopowders and submicron powders. Nanopowders with an average particle size of 12 nm were obtained by the coprecipitation method, and submicron powders, which are hollow spheres, were obtained using the spray pyrolysis method. Powders were consolidated by sintering in a muffle furnace, hot pressing, and spark plasma sintering (SPS) at various temperatures, loads, and holding times. It was shown that muffle furnace sintering and hot pressing methods cannot provide a compact of enough strength due to the different activity of nanopowders and submicron powders. Powder materials were obtained by spark plasma sintering when holding at 700, 750, 800, and 900 °С for 3 min. It was found that a series of samples obtained by SPS at 750 °С has sufficient strength and open porosity of 20 % with a total porosity of 37 %. Rising temperature in this method leads to an increase in the particle size in the nanopowder volume to a micron size and partial destruction of hollow submicron spheres. It was found during the study that the phase composition of samples obtained is identical to the phase composition of initial powders. However, for a series of samples obtained by hot pressing and SPS in the nanopowder volume, there is a directed growth of crystals towards the highest electrical and thermal conductivity [001] along the punch axis. This is due to the temperature gradient between the powder volume and punches and the lowest value of the plane surface energy (110), which includes direction [001].
Formation of structure and properties of hot-deformed powder steels microalloyed with sodium and calcium during thermal and thermomechanical treatment
Authors: Dorofeyev V. Yu. , Sviridova A. N. , Samoilov V. A.
Published: January 2023

One of the main problems limiting further growth in the production of parts by the hot forging of porous performs (HFPP) is that the obtained materials are prone to brittle fracture due to the poor quality of interparticle jointing formed during hot deformation, as well as the presence of impurities in the composition of initial powders. The paper studies the possibility of increasing the mechanical properties and endurance performance of hot-deformed powder steels by doping them with sodium or calcium microadditives and using thermomechanical treatment. Sodium bicarbonate and calcium carbonate were used for microalloying. Carbon was added as pencil graphite powder. The temperature of heating porous preforms before hot forging and the carbon content in steels were varied; the content of microalloying additives was, wt.%: 0.2 for sodium, and 0.3 for calcium. Mechanical properties as well as contact and low-cycle fatigue life were tested on 5 × 10 × 55 mm and 10 × 10 × 55 mm prismatic specimens, as well as ∅ 26 × 6 mm cylindrical specimens. In comparison with carburizing and thermal treatment, thermomechanical treatment improves the impact strength and endurance performance of hot-deformed powder steels with Na or Ca microadditives under the contact and low-cycle fatigue loading, and the hot repressing temperature of porous preforms is reduced without compromising the mechanical properties of powder steels obtained. It may be associated with the formation of a more fine-grained structure and higher microstresses of the crystal lattice. The cooling down of preform surface layers during hot forging process operations creates conditions for ausforming in them.
Influence of molybdenum and rhenium alloying additives on NiAl–Cr–Co cast alloy structure and properties
Authors: Sanin V. V. , Aheiev M. I. , Kaplanskii Yu. Yu. , Petrzhik M. I.
Published: January 2023

A centrifugal SHS casting technology was used to obtain NiAl–Cr–Co–(X) alloys where X = 2.5÷15.0 wt.% Mo and up to 1.5 wt% Re. The study covers the effect of modifying additives on the combustion process as well as the phase composition, structure, and properties of cast alloys. Alloying up to 15 % Mo and 1.5 % Re provided the highest improvement of properties in relation to the base alloy in terms of overall performance. Molybdenum formed a plastic matrix and improved strength properties to the following values: uniaxial compressive strength σucs = 1730±30 MPa, yield strength σys = 1560±30 MPa, plastic component of deformation εpd = 0.95 %, and annealing at t = 1250 °С improved them to: σucs = 1910±80 MPa, σys = 1650±80 MPa, εpd = 2.01 %. Rhenium modified the alloy structure and improved its properties to: σucs = 1800±30 MPa, σys = 1610±30 MPa, εpd = 1.10 %, and annealing further improved them to: σucs = 2260±30 MPa, σys = 1730±30 MPa, εpd = 6.15 %. The mechanical properties of the NiAl, (Ni,Cr,Co)3Mo3C, Ni3Al, (Cr, Mo) and MoRe2 phases, as well as the hypothetical Al(Re,Ni)3 phase, were determined by the nanoindentation method. According to the Guinier–Preston structural transformation, local softening upon annealing at t > 850 °С increases the proportion of plastic deformation during compression tests due to the lost coherence of the boundaries of nanosized plate-shaped Cr-based precipitates with a supersaturated solid solution. A hierarchical three-level structure of the NiAl–Cr– Co–15%Mo alloy was established: the first level is formed by β-NiAl dendritic grains with interlayers of molybdenum-containing phases (Ni,Co,Cr)3Mo3C and (Mo0.8Cr0.2)xBy with a cell size of up to 50 μm; the second one consists of strengthening submicron Cr(Mo) particles distributed along grain boundaries; the third one is coherent nanoprecipitates of Cr(Mo) (10–40 nm) in the body of β-NiAl dendrites. The cast alloy mechanical grinding techniques were used to obtain a precursor powder with an average particle size of Dav = 33.9 μm for subsequent spheroidization.
Using the developed cavitation test to evaluate erosion resistance of cermet thermal sprayed coatings
Authors: Alwan H. L. , Makarov A. V. , Soboleva N. N. , Korobov Yu. S. , Shumyakov V. I. , Lezhnin N. V. , Zavalishin V. A.
Published: January 2023

Many machinery parts working in contact with a fast-flowing fluid flow (e.g. turbine blades of hydroelectric power plants, valves, pump impeller blades, ship propellers, cooling systems for various units, etc.) are subjected to such type of wear as cavitation erosion. An important objective is to eliminate or reduce cavitation erosion so as to achieve a considerable economic effect. This research uses a patented technique developed to evaluate the cavitation erosion resistance of cermet thermal spray coatings (WC–10Co4Cr and WC–20CrC–7Ni). These coatings were prepared using high velocity air fuel thermal spraying (HVAF). The aim of this study is to test a new technique for evaluating coating cavitation resistance, which differs from the standard one by specimen positioning relative to the testing liquid. In addition, scanning electron microscopy (SEM) was used to analyze the initial structure of the coatings prepared and study their behavior after cavitation exposure. The material volume loss criterion during the cavitation test was used to evaluate the coating resistance. The results of cavitation tests showed that the WC–20CrC–7Ni coating has a somewhat higher cavitation resistance than that of WC–10Co4Cr despite its slightly lower average hardness (850±90 HV0.5 versus 950±60 HV0.5). The study of coating surfaces and cross-sections showed that they feature by different erosion mechanisms. It can be concluded that the presence of defects (pores) in the coating structure is the main reason for reducing their cavitation erosion resistance. Therefore, the developed technique proved effective in obtaining experimental data to analyze cermet thermal spray coatings for cavitation wear.
Anisotropy of the bending strength of LaB6–W2B5 reactive hot-pressed ceramics
Authors: Nesmelov D. D. , Novoselov E. S. , Ordan’yan S. S.
Published: January 2023

Refractory composite ceramic material in the LaB6–W2B5 system with a component ratio of 50 : 50 vol.% was obtained  by reactive hot pressing in a graphite mold. A heterophase powder containing lanthanum hexaboride, metallic tungsten, and  amorphous boron preliminarily ball-milled for 20 h with tungsten balls was used as the initial reaction mixture. The average particle size of the milled mixture was 2.9 μm. A relative density of 92 % was achieved at a temperature of 1800 °C with isothermal holding  for 15 min at 30 MPa in an argon atmosphere. The structure and composition of the LaB6–W2B5 material were studied by X-ray  diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The composition of the ceramics contained  two phases – cubic LaB6 lanthanum hexaboride and hexagonal W2B5 tungsten pentaboride. The ceramic structure featured by  ordered lamellar W2B5 particles in a LaB6 polycrystalline matrix. During the reactive hot pressing of the LaB6–W–B mixture, the  predominant growth of W2B5 crystals along (101) atomic planes was observed. Resulting lamellar W2B5 particles were oriented in  the LaB6 matrix perpendicular to the pressing load. Images obtained with electron microscopy were used for the three-dimensional  visualization of the LaB6–W2B5 structure. Three-point bending tests were conducted on 3×3×30 mm samples. The dependence  of bending strength on the direction of applied breaking load was established. When a breaking load was applied perpendicular to  the surface of the lamellar W2B5 particles, the ultimate strength was 420 MPa, while when loaded along the plane of the particles,  bending strength increases to 540 MPa. The anisotropy coefficient of ultimate strength was 0.78.
Structural and morphological study of the Al–Si–Mg–SiC composite material produced by mechanical alloying
Authors: Shavnev A. A. , Nerush S. V. , Kurbatkina E. I. , Kosolapov D. V. , Medvedev P. N.
Published: January 2023

The research focuses on aluminum composite granules obtained by the mechanical alloying of VAS1 aluminum alloy and silicon carbide initial powders. It was found that the morphology and average size of composite granules change as the time of mechanical alloying increases. There are the processes of aluminum matrix plastic deformation and the introduction of silicon carbide particles into the matrix, «cold welding» of agglomerates to each other and the growth of an average granule size up to 550 μm that occur for 40 hours of processing. After longer mechanical alloying (60 h), the structure of composite granules becomes uniform, and the average particle size reaches ~150 μm remaining virtually unchanged as the process time increases. X-ray analysis showed that there is a change not only in the morphology of composite granules, but also in their internal structure: coherent scattering regions decrease, the lattice constant of the aluminum matrix alloy changes, microdeformations and stacking faults increase. Transmission electron microscopy studies were conducted in order to study the material microstructure more deeply. Their results proved that the material has a uniform ultra-fine grain structure. The solid solution of aluminum has a maximum grain size of 160 nm. Dislocation density in the composite is rather high. The structure features nanosized plate-like Si particles and silicon carbide existing in the material as distributed splintery coarse particles. No diffusion zone between SiC particles and the base material was found.
MoSi2–MoS2 composite antifriction material
Authors: Smorchkov G. Yu. , Rachkovskij A. I. , Baranov G. V. , Kondrokhin D. N. , Kurganov S. S.
Published: January 2023

A new high-temperature antifriction composite material 90 % MoSi2 + 10 % MoS2 was developed with a static friction coefficient of less than 0.3. The material is functional at temperatures up 1500 °C under neutron irradiation in an inert gas environment. Modes of initial MoSi2 and MoS2 powder mixture preparation and hot pressing of the resulting charge in a vacuum induction unit in graphite molds were worked out at a temperature of 1600–1650 °C, specific hot pressing pressure of 25 MPa, and holding for 1 h at these values of temperature and pressure. Tribotechnical properties of the material depending on the compression force in the friction pair and on the counterbody material hardness were investigated. It was shown that the higher the compression force and the harder the counterbody material in the friction pair, the lower the coefficient of friction. The effect of temperature on the physical, mechanical and heat-transfer properties of the material was established. As the temperature increases from 20 to 1000 °C, the material compressive strength decreases from 1388 to 739 MPa. An increase in the temperature from 25 to 400 °C leads to an increase in the specific heat capacity from 427 to 596 J/(kg·K) and the coefficient of heat conductivity from 2.35 to 3.41 W/(m·K). Plain bearings made of this material successfully passed durability and reactor tests.
Effect of chromium addition on the copper binder structure, properties and adhesion to diamond
Authors: Loginov P. A. , Markov G. M. , Rupasov S. I.
Published: January 2023

The study covers the effect of chromium on the structure, mechanical properties, and adhesion of alloys used as a binder for metal-diamond composites. Cu–Cr powder mixtures were obtained by high-energy ball milling in a planetary centrifugal mill. This process was used to obtain two-phase Cu–Cr powders with uniformly distributed submicron Cr particles. Cu–Х%Cr compact samples (where Х = 10, 30 and 50 %) were obtained by hot pressing. It was found that Cu–30%Cr compact samples showed the best mechanical properties (9 times higher as compared to pure copper). These alloys feature a hardening mechanism based on the Hall–Petch law. The resulting alloys have a homogenous ultrafine structure, which results in high ultimate bending strength (2330 MPa). Chromium addition to the copper binder considerably increases its adhesion to diamond in metal-diamond composites due to chemical interaction between chromium included into the binder and diamond carbon with Cr3C2 carbide formation.
Effect of iron addition on the structure and properties of copper-based friction powder material used under friction conditions with lubrication
Authors: Ilyushchanka A. Ph. , Liashok A. V. , Dyachkova L. N. , Biryukov V. P.
Published: January 2023

Machines and mechanisms contain units responsible for their movement and stopping, and such units use friction materials. These units include oil-cooled brakes, hydromechanical transmissions, and clutches. They use mainly copper-based friction materials providing the high coefficient of friction and wear resistance. These materials feature by effective heat dissipation since a large amount of heat is released in these areas for a short period of time. The paper presents the results of studies into the effect of iron addition into a frictional powder material based on BrO6 and BrO12 bronze on its structure, mechanical and tribotechnical properties. It was shown that the introduction of iron contributes to an increase in the coefficient of friction from 0.034 to 0.055 for the BrO6-based friction material and from 0.042 to 0.073 for the BrO12-based friction material. It was determined that the ultimate compression strength of the BrO12-based friction material is 340 MPa without iron addition, 310 MPa at 10 vol.% of iron, and 180 MPa at 50 vol.% of iron. This is due to the fact that the iron content of more than 30 vol.% results in the change of the frame structure of the material to the matrix one having a sintering temperature higher than the temperature used in the paper for friction material sintering. It was found that for the BrO6-based friction material there are both rounded and elongated inclusions in the copper phase up to 2.5 μm in size with the iron content of 30–50 %. In the BrO12-based material there are more iron inclusions in the copper phase and their size are much larger, the length of inclusions reaches 20 μm, and the iron content in them is 49–73 %.
Activation energy of phase transformations at high-temperature synthesis of tungsten carbide by electrothermal explosion under pressure
Authors: Telepa V. T. , Alymov M. I. , Shcherbakov А. V.
Published: January 2023

The effect of activation energy on phase transformations (transitions) in the W–C system during the synthesis induced by an external heat source was investigated by electrothermal explosion (ETE) under pressure. The ETE technology combines self-propagating high-temperature synthesis (SHS) with additional sample heating by Joule heat – electric current passing through the synthesized mixture, and it makes it possible to determine the chemical reaction rate that is highly susceptible to external impacts such as pressure, concentration, sample shape, any film present on combustion products, etc. The chemical reaction rate, i.e. external source current, may be controlled by changing the activation energy. The study was conducted in the following conditions: temperature Т = 293÷3700 K; carbon concentration of 49.8–50.2 at.%; quasi-static compression at P = 96 MPa; external source voltage and current density V = 10 V, I = 20 МА/m2, respectively; samples 8 mm in diameter weighing 6 g. The Т–τ thermogram of the W–C system was used to determine the following parameters: four stages of the synthesis process, temperatures of special points of phase transformations, temperature boundaries of phases and process activation energy. Thermograms of intermediate states are presented as isothermal plateaus of phase transformations. The analysis of experimental results and the physical representation of the process make it possible to assert that temperature plateau parameters are the effective value of activation energy for synthesis mode maintenance. Each of the 4 W–C mixture synthesis stages is described. Pre-explosion stage I – sample heating in the temperature range of Т = 293÷563К, endothermic reaction, effective activation energy for synthesis mode maintenance Q = 2.96 kJ, and taking into account 1-mole mass Еа = 111.6 kJ/mol. Low-temperature (563–1190 К) stage II – ignition, Q = 5.46 kJ, Еа = 109.2 kJ/mol. High-temperature stage (III) in the range of Т = 1190÷2695К, order–disorder transformation, Q = 14.25 kJ, Еа = 424 kJ/mol. Finally, Stage IV occurs in the range of Т = 2695÷3695К, Q = 14.31 kJ, Еа = 143.2 kJ/mol. It was shown that the limiting stage with the highest activation energy is the melting process.
Structure and properties of Mo–Hf–Si–B coatings obtained by magnetron sputtering using MoSiB/Hf mosaic target
Authors: Sytchenko A. D. , Levashov E. A. , Kiryukhantsev-Korneev Ph. V.
Published: January 2023

Mo–Si–B and Mo–Hf–Si–B coatings were produced by magnetron sputtering of a MoSiB ceramic target equipped with 2 or 4 Hf segments. Their structure and composition were studied by scanning electron microscopy, energy dispersive spectro scopy, X-ray diffraction analysis, and Raman spectroscopy. Mechanical properties were determined by nanoindentation at a load of 4 N. The crack resistance of coatings was studied on a microhardness tester at loads of 0.25–1.0 N. The oxidation kinetics was studied at 1000 °C in air with a total exposure of 300 min. The heat resistance of coatings was determined as a result of short-term annealing at 1500 °C. Electrochemical tests were carried out by voltammetry in the 1N H2SO4 solution. The results showed that the Mo–Si–B coating and Mo–Hf–Si–B coating obtained using 2 Hf segments feature by a columnar structure. The use of 4Hf segments in coating deposition led to an increase in density and suppression of the undesirable columnar structure formation. It was shown that hafnium introduction into the coating composition increases the growth rate by 20% and reduces the grain size of the main component of the h-MoSi2 phase by an order of magnitude, while simultaneously promoting HfB2 formation. Maximum hardness (27 GPa), Young’s modulus (370 GPa) and elastic recovery (62 %) were achieved for the Mo-Si-B coating. The hardness of coatings obtained using 2 and 4 Hf segments decreases by 1.9 and 1.6 times, respectively. During the Mo–Si–B and Mo–Hf–Si–B (2Hf) coating microindentation, radial cracking was observed. The sample obtained with the maximum concentration of hafnium featured by the best crack resistance. Electrochemical tests showed that the corrosion resistance of coatings increases in the Mo–Hf–Si–B (2Hf) → Mo–Si–B → Mo–Hf–Si–B (4Hf) series. All coatings showed good oxidation resistance at 1000 and 1500 °C. However, coating delamination areas were observed on the surface of Mo–Si–B and Mo–Hf–Si–B (2Hf) samples. The Mo–Hf–Si–B (4Hf) coating showed a lower oxide layer thickness and better oxidation resistance due to the dense SiO2 + HfOх protective layer formation.
Using explosion loading to obtain coatings of chromium carbide and titanium mixtures in deposition mode
Authors: Krokhalev A. V. , Kharlamov V. O. , Chernikov D. R. , Kuz’min S. V. , Lysak V. I.
Published: January 2023

The paper presents the results of studies into the microstructure, chemical and phase composition of coatings deposited on a steel substrate using the sliding explosive loading of Cr3C2 chromium carbide and titanium powder mixtures. The equilibrium phase composition of coatings was calculated by computational thermodynamic modeling using the Thermo-Calc software package. The structure and elemental composition were studied using a FEI Versa 3D scanning electron microscope with an integrated EDAX Apollo X system for energy dispersive X-ray microprobe analysis. A Bruker D8 Advance diffractometer was used for X-ray phase analysis. It was shown that when the powder layer is loaded by a sliding detonation wave, it can be shifted along the substrate surface due to the horizontal mass velocity component of compacted material particles. This shift causes the inner layer of the compacted powder and the surface layer of the substrate to melt as a result of friction. The presence of a liquid phase prevents the compacted powder layer deceleration so that the major part of it is removed from the substrate surface. The liquid phase remaining on the surface undergoes rapid quenching due to heat removal into the substrate and forms a deposited coating containing both the components of the initial powder mixture and the components of the substrate to be coated. It was established that the deposited layer structure features by extremely high dispersion (grain size does not exceed 250 nm), and its phase composition turns out to be close to a thermodynamically equilibrium one. When using powder mixtures of chromium carbide with 40% titanium, a coating is formed consisting of titanium carbide with a metal binder based on solid solutions of iron and titanium in chromium.
About the experience of using hardmetals in the production of roller cone bits at Volgaburmash JSC
Authors: Zhadyaev A. A. , Zakharov D. A.
Published: January 2023

Since 2017, Volgaburmash JSC (Samara, Russia) tested purchased 90%WC–10%Co carbide powder mixtures and finished carbide drill bits from various manufacturers. The work was carried out in order to check the possibility of using purchased products as raw materials at the plant to reduce the production cycle for the manufacture of carbide inserts for roller cone bits. This intercommodity substitution (outsourcing) is carried out with the aim of potential cone bit cost reduction and production process acceleration so that the plant can operate in the heavily competitive environment of foreign and domestic markets. The article focuses on the analysis and detailed comparison of the micro- and macrostructure, physical, mechanical, chemical and processing properties of purchased hard-alloy mixtures and sintered inserts of various manufacturers including Volgaburmash JSC. All properties of materials under study were determined in accordance with the VBM JSC company standard STP 582-17. Much attention is paid to comparing crack resistance or Palmqvist fracture toughness values of the alloy and analysis of microstructure images and fracture propagation pattern after using scanning electron microscopy tests. In addition, consideration is given to such important hard alloy properties as hardness and transverse bending strength. Based on the results of the conducted research, conclusions are presented on the expediency of using purchased hard-alloy materials at the Volgaburmash JSC metallurgical shop in comparison with internally manufactured materials.
MAX phase Ti2AlN synthesis by reactive sintering in vacuum
Authors: Linde A. V. , Kondakov A. A. , Studenikin I. A. , Kondakova N. A. , Grachev V. V.
Published: January 2023

The synthesis of MAX phase Ti2AlN from several mixtures of Ti, Al, TiN, and AlN powders by vacuum sintering of greensamples in the form of dense compacts, bulk powder in silica tubes, and plain layer in a closed rectangular molybdenum boat was studied upon variation in charge composition and sintering temperature Ts. The sintering of 2 : 1 Ti–AlN mixture was carried out at 1100, 1200, 1300, 1400, and 1500 °С with exposure time of 60 min. The largest MAX phase content (94 wt.%) was reached at Ts = 1400 °С. The sintering of 1 : 1 TiAl : TiN composition at the same temperature gave 93 wt.% Ti2AlN. The best result (singlephase Ti2AlN in a 100-% yield) was achieved upon the sintering of 1 : 1 : 1 Ti–Al–TiN composition at Ts = 1400 °С. The scalability of our process was checked by the fabrication of a large (0.5 kg) and uniform cake of single-phase Ti2AlN. In experiments we used green samples with shielded lateral surface (bulk powder in silica tubes, plain layer in a closed molybdenum boat) and without shield (dense compacts). It has been shown that shielding of Ti–Al–TiN samples restricts the escape of Al vapor from a sintered mixture, thus providing more favorable conditions for the synthesis of single-phase Ti2AlN. Our process can be readily recommended for practical implementation.