AbstractUsing Mn/Al/B/diamond powder as raw material, a Mn2AlB2-based multi-element composite coating was formed on the diamond surface through thermal explosion synthesis technology. The effect of different Al contents on the phase composition and microscopic morphology of the binders and coatings was studied. X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy were used to analyze the phase composition and morphology of the thermal explosion samples. Results showed that the Mn/Al/B/diamond compacts were transformed to porous loose blocks after thermal explosion reaction. The binders obtained after separation was mainly composed of Mn2AlB2. Other byproducts, such as Al, MnB, MnB2, Al78Mn23, Al8Mn5, and Mn2AlC, were also obtained. The coating fully wrapped the surface of the diamond, and the coating structure was composed of many nanometer and micrometer grains.

AbstractThe effect of composition and activating impurities on the structure of a Al2O3–C composite was studied. Porosity and structural morphology features were investigated. Such physicomechanical properties of synthesized samples as bending strength and hardness were also measured. Optimal values of these parameters with respect to composition and technological regimes of synthesis were established.

Abstract—Some results of studying the acoustic emission signal in the drilling of a carbon fiber reinforced polymer (CFRP) were given for different cutting regimes and geometry of a drill manufactured of diamond hard-alloy plates. The regularities of change in the acoustic emission signal in the process of drilling at the stages of drill penetration into a workpiece and exit and the effect of cutting regimes on the quality of a formed hole were established. The relation between the level of an acoustic emission signal at the stage when the transversal edge comes out of the workpiece and the defectiveness of drilled holes was established. The effect of the transversal edge width on the magnitude of an acoustic emission signal was investigated.

AbstractThe modern generation of instrumental composite materials with a fundamentally new mechanism of contact interaction with processed materials was created through the use of binder polymers with embedded metallocene fragments. The structure of hybrid oligomers obtained by the interaction of oligophenylene and complex compounds of vanadium, iron, and copper was determined; it is a combination of organic and inorganic fragments. Inorganic fragments are represented by metal ions and clusters, bonded by covalent and coordination bonds with organic fragments. Organic fragments have a metallocene structure connected by methylene sites with weakly conjugated benzene rings. Clusters and metal ions can be located both between the planes of metallocenes and weakly conjugated rings and between oligomer chains as their continuation.

AbstractUsing CBN, Si3N4, Al2O3, AlN and Y2O3 as raw materials, PCBN tool materials were prepared by high temperature and high pressure. The effects of sintering temperature (1400–1700°C) on the microstructure, mechanical properties and cutting performance of tool materials were studied. The results show that PCBN tool materials with higher density and better comprehensive properties can be obtained by using high temperature and high pressure technology. At 1500°C, it was observed that the α-Si3N4 in the binder had a tendency to transform to β-Si3N4, and the grains were well developed. With the increase of sintering temperature, the density, flexural strength, and hardness of the samples increased continuously. At 1700°C, the flexural strength and hardness reached 879.6 MPa and 38.8 GPa, respectively. At the same time, the cutting performance of the samples sintered at 1700°C is also the best. When cutting ductile cast iron with a cutting distance of 7 km, the tool wear is the smallest, which is 0.26 mm.

AbstractThe structure and mechanical properties (hardness Н, elasticity modulus Е, estimative parameters for determining the resistance to elastic H/E and plastic Н3/Е2 deformations, ultimate bending Rbm and compression Rcm strength) of diamond-containing Сdiamond–WC–Co–CrB2 composite materials (DCM) formed by spark plasma sintering and the ability of their hard-alloy matrix to retain diamond grains from falling out have been studied as a function of the chromium diboride content (within a range from 0 to 10 wt %). It has been established that the addition of CrB2 at a concentration of 4 wt % to 25Cdiamond–70.5WC–4.5C leads to an increase in the ultimate bending Rbm (from 2040 ± 20 to 2375 ± 50 MPa) and compression Rcm (from 5100 ± 30 to 5650 ± 70 MPa) strengths and in the estimative parameters for determining the resistance to elastic H/E (from 0.043 to 0.051) and plastic Н3/E2 (from 0.062 ± 0.0040 to 0.080 ± 0.0070 GPa) deformations. A further increase in the CrB2 concentration (to 10 wt %) in a specimen leads to a gradual decrease in the ultimate bending Rbm (to 1840 ± 80 MPa) and compression Rcm (to 5100 ± 100 MPa) strengths with a growth in Н/E (to 0.054) and Н3/Е2 (to 0.088 GPa). As a criterion for estimating the hard-alloy matrix ability to retain diamond grains from falling out, it is proposed to use the state of the surface relief of fracture in a DCM specimen. Under such a condition, the relief surface of diamond is indicative of strong adhesion between diamond grains and a hard-alloy matrix. The destruction of a DCM specimen along the diamond–matrix interface indicates that the adhesion between diamond grains and a hard-alloy matrix is weak to worsens the performance characteristics of such DCMs. It has been shown that the mentioned mechanical and performance characteristics of DCM specimens can be attained by adding 4 wt % of CrB2 into DCMs to decrease the growth rate of WC grains and, as a consequence, to form a homogeneous fine-grained microstructure in their hard-alloy matrix.

AbstractThe structure, mechanical properties (hardness H and elastic modulus E), evaluation parameters for determining the resistance of the material to elastic (H/E) and plastic (H3/E2) deformations, resistance 1/(E2/H) to abrasive wear, and the ability of the hard alloy matrix to hold diamond grains from their precipitation in the 25 wt % Cdiamond‒70.5 wt % WC‒4.5 wt % Co composite diamond-containing materials (CDMs) with different contents of ZrO2 (in the range from 0 to 10 wt %), which are formed by the spark plasma sintering (SPS) method in the temperature range of 20‒1350°C under a pressure of 30 MPa for 3 min. The initial CDMs have a coarse grained structure with weak adhesion of diamond grains to the hard alloy matrix and are characterized by low values of H/E, H3/E2, and 1/(E2H), which is the reason for the premature loss of diamond grains. The presence of ZrO2 in the composition of CDMs interferes with the processes of Oswald ripening and acts as a growth inhibitor that ensures the reduction of WC grains, the formation of strong adhesion of diamond grains to the matrix, and a substantial increase in the H/E, H3/E2, and 1/(E2H) parameters. As a result, the ability of the matrix to reliably hold diamond grains from premature loss during the CDMs operation increases. It is shown that the addition of zirconium dioxide in the amount of 10 wt % to the composition of the 25 wt % Cdiamond‒70.5 wt % WC‒4.5 wt % Co composite leads to increases in the H/E parameter from 0.043 to 0.057, in the H3/E2 parameter from 0.05 to 0.075 GPa, and in the 1/(E2H) parameter from 0.75 × 10–7 to 2.75 × 10–7 GPa–3. Moreover, signs of strong adhesion between the diamond grains and the carbide matrix in the CDMs samples are revealed.

AbstractWe studied the plastic mode of processing brittle materials, the effect of the change in the working surface of the diamond wheel during processing, and ways to achieve such a mode. To assess adequately the energy intensity of processing with diamond wheels, we proposed to calculate the specific energy density of grinding, considering the volume of material spent during the processing of the wheel working layer. We derived an equation for calculating the specific energy density during the diamond grinding of ceramics. The plastic regime occurs precisely when the specific energy density of grinding becomes close to the specific heat of melting of ceramic materials.

AbstractWe prepared dense high-entropy ceramic material (TiZrHfNbTa)C by hot pressing; the optimum hot-pressing temperature is 2000°C. At lower temperatures, zirconium oxides, hafnium oxides, and undissolved carbides were observed in the ceramic composition. The strength of the resulting ceramics at room temperature was 394 ± 72 MPa, at a temperature of 1600°С, it was 119 ± 31 MPa. For pure carbides, a significant drop in hardness was observed at an increased load on the indenter, while for (TiZrHfNbTa)C, hardness is retained under any load. To achieve the maximum hardness and strength of high-entropy ceramics (TiZrHfNbTa)C, the amount of ZrO2 and HfO2 in the composition of ceramics should be decreased with a simultaneous decrease in grain size by using submicrometer-scale powders and selecting proper technological modes of production.

AbstractVickers hardness of boron subarsenide B12As2 has been predicted using three modern theoretical models and experimentally studied by microindentation. The polycrystalline material exhibits hardness of about 31 GPa, and hence B12As2 belongs to a family of (super)hard phases.

AbstractAs a reinforcement phase to form metal matrix composites, graphene has attracted more and more attention due to its excellent properties i.e. optical, electrical and mechanical properties. However, the dispersion of graphene has always been an important factor that significantly effects its development. This paper mainly summarizes the physical methods to improve the dispersion of graphene and analyzes its internal mechanism, moreover the advantages and disadvantages of these methods are depicted and compared. Finally, the improvement of the dispersion of graphene and its future applications are prospected.

AbstractThe phase composition, element distribution, and mechanical properties of the TiSiN/NbN(TiN) multilayer coatings obtained by vacuum arc deposition are anlyzed. The effect of the bias potential on the mechanical and tribological characteristics of the coatings is studied, and the adhesion strengths of the coatings to the substrate are measured. The results of X-ray diffraction studies of the coatings show that a two-fold increase in the bias potential leads to increases in all phase and structural parameters—in particular, lattice parameters, crystallite sizes, and microdeformation levels of the components of the coatings. The intensities of δ diffraction peaks of TiN and NbN indicate the presence of a strong (200) texture. Tribotechnical studies of the coatings have shown that they are erased during scratching, but their detachment from the substrate has not been recorded. This means that the coatings are worn by the cohesive mechanism associated with plastic deformation and the formation of fatigue cracks in the coating volume. Different modes of coating formation correspond to different values of acoustic emission that occurs, depending on the conditions, in the loading zone.

AbstractIt is known that the theory of contact interaction of rough surfaces is based on roughness parameters and, first of all, on the reference profile curve (on which this study is focused) and how it is related to other roughness parameters. It is shown that the greater index tp of the relative length of the reference profile, the greater the bearing capacity of such a surface. That is, the higher the reference curve rises, the greater the tp parameter. For example, at the level of 20 or 50% Rmax, the greater the degree of filling of the rough surface, the greater its bearing capacity. The surface area located below the reference curve characterizes the degree of filling of the rough surface with the finishing material. It is shown that the plasma effect of medium power generally has a positive effect on the treated surface when the surface has not yet melted, which leads to a certain degree of ordering and substantial improvement of the supporting surface. Plasma exposure with melting worsens both the microroughness height and the bearing capacity of the surface. It is proved that the simultaneous use of compacts and diamond grains in wheels allows one to achieve a decrease in the roughness of the treated surface and to obtain the specific microroughness profile, in which a surface with the increased degree of microprofile filling and the increased bearing capacity is obtained, when so-called “lubricant pockets” are formed.

AbstractThe effect of the conditions of synthesis on the formation of micro- and nanoparticles of zirconium dioxide from a fluoride solution has been studied. It is shown that the finest particles are formed by precipitation from dilute solutions with a zirconium concentration of 0.02–0.04 mol/L and impurities of polyvinyl alcohol at a mass ratio of mZr : mPVC 1 : 0.1. To sinter ZrO2 nanoparticles, it is proposed to use the electroconsolidation method in a vacuum to obtain ceramics with high values of the hardness and elastic modulus.

AbstractThe estimate of energy expenditures in the diamond abrasive treatment by wheels from superhard materials has been analyzed to determine the consistent data on these parameters. It has been shown that they almost coincide with the literature data reduced to the same dimension (kJ/cm3). At the same time, such data on the relative specific energy intensity of grinding are much higher than the specific melting heat capacity of the treated material. To resolve the existing contradiction, it is proposed for treatment by wheels of superhard materials to calculate the specific energy intensity of grinding with consideration for the abrasive wheel layer spent in the process of grinding, and the formula for calculating the specific energy intensity is proposed. It is shown that calculation by this formula provides an adequate energy intensity estimate, which corresponds to the data on the specific melting heat capacity of such treated tool materials as high-speed steels and oxicarbide ceramics for both the processes of diamond treatment and the treatment with cubic boron nitride wheels.

AbstractAs a result of studying the mechanism of polishing the polymer optical materials with disperse systems composed of micro- and nanoparticles of polishing powders, it has established that the energy of sludge and wear particles during the resonant transfer of energy from the disperse phase particles of a polishing disperse system to a treated surface and backward is inversely proportional to the spectral separation between them. It has been shown that the energies of sludge and wear particles are decreased during the polishing of polymer materials with a disperse system of nanopowders by 5 time with an increase in the spectral separation from 27 to 78 cm–1 and from 17 to 24 cm–1, respectively. When polishing is performed with the disperse system of micropowders, their energies are decreased by 2–5 times with an increase in the spectral separation from 8 to 95 cm–1 and from 16 to 57 cm–1. When the spectral separation between a treated material and a polishing powder is decreased, the volumes of sludge and wear particles and, correspondingly, the polishing efficiency and grows alongside with the intensity of wear on the disperse phase particles of the disperse system. It has been found that the polishing efficiency strongly depends on the efficiency of the Forster resonant energy transfer and grows with a decrease in the product of the ratios between the vibration frequencies of molecular moieties on the surface of polishing powder particles and the treated surface and an increase in the ratio between the lifetimes of treated surface clusters and clusters of polishing powder particles in an excited state. It has been shown that the results of theoretical calculations on the performance efficiency of polishing the optical materials coincides with experimental results with a deviation of 1–8%.

AbstractThe study of the interaction mechanism of an optical surface with a polishing disperse system during polishing showed that the energy transfer between them occurs according to the Förster mechanism. With resonance energy transfer from the particles of the dispersed phase of the polishing system to the surface to be treated and from the material being processed to the particles of the polishing powder, with a decrease in the spectral separation between them, the energy of the sludge particles and wear particles decreases, and the energy transfer efficiency increases. The spectral separation was characterized by energy mismatch, 2.8–4.0 meV for sludge particles and 2.8–12.2 meV for wear particles. The spatial separation between the treated surface and polishing powder particles was estimated as the arithmetic mean deviation of the polished surface profile, 5.6–8.0 nm. A decrease in the spatial and spectral separation between the material being processed and polishing powder particles increases the size of sludge particles and wear particles, causing a deterioration in the roughness of optical surfaces. The results of a theoretical calculation of the productivity of polishing optical materials coincide with the experimental results with a deviation of 2–7%.

AbstractWe present the results of the study of the microstructure of a ceramic composite based on aluminum nitride with different concentrations of yttrium oxide, synthesized by pressureless sintering. The thermal conductivity of the obtained materials was investigated, and the optimal amount of yttrium oxide in the composition for sintering large-sized parts used in electrotechnical devices was determined.

AbstractPublished reports on the comparative study of morphometric characteristics, technological, and physical properties of powders of synthetic and natural technical diamonds are reviewed. Applied and methodological aspects of using grain projections of diamond powders as the most acceptable and accessible expression of their 3D shapes for estimating the quality of such powders are analyzed. Based on the results of the literature review, it is emphasized that the shape similarity indices of grain projections of such powders and the methods used to identify the grain projection shapes are of great practical significance for abrasive treatment. A comparative analysis of the shape similarity of grain projections of synthetic and natural technical diamond grinding powders and their uniformity with respect to this characteristic as an important quality feature is performed. The results of determining the shape similarity indices are given, and the trends in their change are established.

AbstractResidual stresses in vacuum-arc coatings of the TiAlSiYN system deposited on a PcBN base were studied by X-ray diffractometry. The substructure characteristics of the TiN phase suggest that all the studied coatings have compressive stress from –1.51 to –5.85 GPa and significant (up to ε = 1.13 × 10–2) microstrain at the microlevel. The equivalent stress Seqv in the near-contact layer of the tool material is determined in samples with residual compressive stress in the coating. We evaluated the effect of residual stress in protective coatings on the equivalent stress in the tool under the action of contact loads typical for the machining process. Compressive stress in the coatings of –1.0 GPa helps to decrease the equivalent stress at critical points at the front surface of the tool in the initial period of cutting. To lower the equivalent stress from the back surface of the tool with significant (~0.3 mm) wear, coatings with a residual compressive stress of –3 GPa are optimal. The most significant decrease (from 1.9 to 0.5 GPa) in equivalent stress at critical points at the front surface of the tool was observed upon impact loads.