Powder Metallurgy and Metal Ceramics (v.55, #9-10)

The formation of inoculants by pressing and rolling is studied. To obtain process-strong inoculant billets (moldings), optimal routes for the formation of mixtures containing brittle materials that the complex inoculants consist of (up to 60 wt.%) are worked out. It is established that the decrease in the apparent relative density of the powders of ductile components allows decreasing the total content of the latter. The application of large diameter rolls allows obtaining thicker strips, whose strength and density greatly exceeds the required processing strength of the moldings. The increase in the final strip thickness allows increasing the weight of the billet and, therefore, increasing the process efficiency. The powder rolling ensures the production of 5–6 tons of inoculants per month using a 500 mm roller mill.
Keywords: powders; inoculant mixtures; cast iron; rolling; strip

Copper Hardening with Fine Iron Particles by P. Ya. Radchenko; O. I. Get’man; V. V. Panichkina; V. V. Skorokhod; N. I. Danilenko (511-517).
The production of sintered bulk Cu–(5–25% Fe) pseudoalloys retaining the α-iron phase is studied. The pseudoalloys with a relative density of 97.5–98.1% are prepared by sintering a powder mixture of the metals reduced from their nanosized oxides. The microstructure of the composites represents a copper matrix with α-iron phase inclusions of about 20–200 nm in size, formed by 6.5–16 nm nanocrystallites. When iron content is 5 and 10%, the composites show matrix microstructure in relation to copper, providing 47–52% electrical conductivity and promoting higher hardness (to 1380 MPa) through precipitation hardening of the copper matrix by iron nanoparticles. The composites acquire matrix-statistical microstructure with increasing iron content.
Keywords: pseudoalloys; copper; iron; nanostructure

Shock-Wave Sintering of the 70 vol.% Kh13M2–30 vol.% Cr3C2 Carbonized Steel in a Wide Temperature Range by A. I. Tolochin; A. V. Laptev; R. V. Yakovenko; V. A. Maslyuk (518-529).
The compaction of the 70 vol.% Kh13M2–30 vol.% Cr3C2 carbonized steel is carried out by the shock-wave sintering under 1200 MPa in the 950–1200°C temperature range and the free sintering is performed at 1250°C in vacuum (0.13 Pa). The effect of the compacting temperature and annealing at 1150°C on the structure and physical and mechanical properties of the composite is studied. It is shown that an active interaction between carbide phase and steel matrix occurs in the structure of the material during heating. As a result, the amount of carbide component in the composite increases by 10 vol.% and by 30 vol.% during annealing, compared to the starting carbonized steel. High strength and plasticity properties of the composite are obtained at a shockwave sintering temperature of ≥1100°C. The carbonized steel possesses the following properties: bending strength 1165 MPa, compression strength 2665 MPa, compressive plastic strain 8.2%, fracture toughness 20.4 MPa · m1/2, and the Rockwell hardness 78 HRA.
Keywords: carbonized steel; shock-wave sintering; structure; properties; chromium carbide

Synthesis and Preparation of Mono-Layer h-BN Nanopowders by Using a Combination of CVD Method with Isopropanol-Assisted Exfoliation Process by Rasoul Moradi; Javad Karimi-Sabet; Mojtaba Shariaty-Niassar; Seyed Mahdi Hedayat (530-540).
An experimental study is performed to introduce a new procedure for producing single-layer hexagonal-boron nitride (h-BN) nanopowders. In our modified procedure, synthesis and exfoliation processes are employed to achieve a two-dimensional (2D) h-BN. In the first stage, h-BN nanosheets are successfully synthesized through reacting of boric anhydride (B2O3) with guanidine hydrochloride (CH5N3 ∙ HCl) in nitrogen/hydrogen (N2/H2 = 90/10, v/v) atmosphere in the chemical vapor deposition (CVD) furnace. This process results in efficient synthesis of multi-layer h-BN. In fact, the product is significantly cost-effective and applicable for various purposes, such as subsequent exfoliation to obtain single-layer h-BN. In the next step, the prepared h-BN is characterized by using various methods: X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR), and micro-Raman spectroscopy. Finally, the formed multi-layer h-BN nanosheets are converted into single-layer 2D h-BN through a series of solvent-assisted exfoliation experiments. According to our experimental results, the distance between h-BN layers expands through intercalating isopropanol (IP) molecules among them under ultrasonic treatment. As a result of this process, the platelets are completely separated and single-layer h-BN nanosheets are produced. Therefore, this process is recommended for the straight forward production of 2D h-BN.
Keywords: hexagonal-boron nitride; chemical vapor deposition; two-dimensional materials; exfoliation

The paper proposes principles for controlling the microstructural parameters of cold-pressed heterogeneous Cu–W materials to reach the process strength and high energy reserve of the products. It is found that decrease in the matrix–inclusion particle size ratio increases the density of heterogeneous compacts. It is shown that the theory for controlling the microstructure of porous bodies can be applied to assess the structure-sensitive properties of the test materials using calculation of the composite matricity parameter. The effectiveness of this approach to predict the process strength of compacts is demonstrated. The principles for reaching the process strength of green heterogeneous powder compacts by considering the particle size ratio of the mixture components, volume fraction of the particles, and size of inclusions are addressed.
Keywords: heterogeneous powder material; compacts; process strength; matricity

Conductive Composite Materials Based on Thermally Stable Fluorine-Containing Polyamide and Binary Filler by A. V. Paustovskii; B. M. Rud’; V. E. Shelud’ko; E. Ya. Tel’nikov; N. I. Siman; P. S. Smertenko; V. V. Kremenitskii; Yu. I. Bogomolov (552-558).
The feasibility of producing “binary filler + polymer matrix” conductive composite film is demonstrated. The mixture of nickel boride and carbon nanofiber at various ratios is chosen as the filler. The film microstructure is studied by SEM. The electrical–physical properties of the films (volt-amps diagrams and the R(T) dependence are determined). It is established that the thermal resistivity constant reverses sign, when the carbon nanofiber is introduced.
Keywords: conductive composite film; nickel boride; carbon nanofiber; microstructure; electrical-physical properties

Electrode Materials Based on LaMgNi4–x Co x (0 ≤ x ≤ 1) Alloys by Yu. V. Verbovytskyy; V. V. Shtender; P. Ya. Lyutyi; I. Yu. Zavaliy (559-566).
The LaMgNi4–xCox (x = 0, 0.33, 0.67, 1) alloys are prepared by sintering and prolonged heat treatment at 500°C, with the main cubic phase of MgCu4Sn type. The alloy samples ball-milled in an argon atmosphere show the glass-forming ability. Electrochemical experiments of the LaMgNi4–xCox electrodes are performed at charge and discharge current densities of 100 mAh. The maximum discharge capacity is exhibited by the powdered alloys (218–302 mAh/g) compared to the ball-milled ones (92–134 mAh/g). The cobalt content of the LaMgNi4–xCox alloys influences the electrode characteristics. The highest discharge capacity is shown by the powdered alloy with x = 0.33. The ball-milled alloys have slightly higher cyclic stability.
Keywords: rare earth alloys; magnesium-based alloys; hydrides; electrochemical properties; electrode materials

Friction and Wear of the TiB2–30 vol.% B4C Composite Consolidated in Spark Plasma Sintering by M. V. Zamula; V. T. Varchenko; S. A. Umerova; O. B. Zgalat-Lozinskii; A. V. Ragulya (567-573).
The tribotechnical properties of the TiB2–30 wt.% B4C composite material in pair with VK6 hard metal are investigated. The material demonstrates high wear resistance under dry friction conditions: the intensity of linear wear of the friction pair does not exceed 1.83 μm/km, the friction coefficient of the friction pair is 0.5. The analysis of 3D profiles of the sample surface shows the effect of smoothing of the surface of the ceramic composite by transfer of hard metal submicron particles on its surface and formation of tribofilm.
Keywords: composites; tribotechnical properties; spark plasma sintering

Stability of the Phase Composition of Hydroxyapatite Powder Systems Reinforced with Basalt Scale, when Interacting with Biological Environments by N. V. Boshytska; Yu. O. Fedorenko; A. O. Perekos; N. V. Kaplunenko; I. V. Uvarova; K. Yu. Boshytskii (574-579).
The changes in the phase composition of basalt scale-reinforced hydroxyapatite composite systems with different component ratio, depending on the annealing temperature of the powder mixture and after the interaction of the latter with biological environments simulating life environments, are investigated. It is established that after the interaction of HA + BS composite system annealed at 1200°C with corresponding biological environments the X-ray diffraction pattern discovers the lines of additional phases. Furthermore, the oxidation of Fe3O4 into Fe2O3 is observed. It is established that the HA + 10% BS composite system annealed at 900°C is the most promising material for the intraosseous reconstructive surgery (anaplastic surgery) from the point of view of physicochemical stability in biological environments and the strength properties similar to those of the natural bone.
Keywords: hydroxyapatite; basalt scale; biological environment; X-ray diffraction analysis

Comparative Estimation of the Structure and Electrical Properties of Functional Layers Based on PbO–ZnO–B2O3 Glass–Ceramic Sealant by Z. Duriagina; T. Kovbasyuk; M. Zagula-Yavorska; S. Bespalov; M. Drajewicz; K. Dychton; M. Kindrachuk (580-584).
The formation of dielectric layers based on the glass–ceramic sealant in the PbO–ZnO–B2O3 system on the 40Kh13 steel substrates for flat heating elements is enhanced. The chemical composition of the glass–ceramic sealant and the heat treatment modes of the coatings are optimized. The effect of the microstructure and microtopography of the surface on the electrical–physical properties of the coatings in the 20–500°C temperature range is determined.
Keywords: sealant; dielectric coatings; glass–ceramic; microstructure; electrical–physical properties

Electrode Materials for Composite and Multilayer Electrospark-Deposited Coatings from Ni–Cr and WC–Co Alloys and Metals by V. B. Tarelnyk; A. V. Paustovskii; Yu. G. Tkachenko; E. V. Konoplianchenko; V. S. Martsynkovskyi; B. Antoszewski (585-595).
The layer-by-layer electrospark deposition of Cu, In, Pb, Cd, and Sn group metals and Ti, V, and W metals, as well as their carbides and hardmetals of WC type, onto metallic surfaces is studied. This technique improves the quality and wear resistance of the surface layer compared to coatings without a sublayer. The sintered electrode materials containing 10–30 wt.% of the (Ni–Cr–Si–B)–WC6 alloy allow electrospark coatings with thickness up to 100 μm and microhardness 12.3–14.2 GPa to be formed. The wear resistance and service life of these coatings are substantially higher than of those made of standard hardmetal WC6. Among the Ni–Cr–Al alloys, the best effectiveness in worn-part recovery is shown by the alloy from the ternary eutectic region (50.3 wt.% Ni, 40.2 wt.% Cr, 9.5 wt.% Al), which may provide coating thickness up to 1.0 mm. The novel coating technique and proposed electrode materials increase the resistance of cutting tools and life of equipment parts.
Keywords: electrospark deposition; electrode materials; erosion properties; coating properties; wear resistance; multilayer coatings

Properties of Cr–C–Al2O3 Deposits Prepared on a Cu Substrate Using Cr3+-Based Plating Baths by Ching An Huang; Jhih You Chen; Chin Huo Chuang; Joachim Mayer (596-602).
Cr–C–Al2O3 deposits with different Al2O3 concentrations were successfully prepared on a Cu substrate from Cr3+-based electroplating baths. The microstructures of the Cr–C–Al2O3 deposits were examined using optical, scanning, and transmission electron microscopes. The hardness values, the corrosion and wear resistance of the Cr–C and Cr–C–Al2O3 deposited specimens were evaluated. Based on the experimental results, Al2O3 nanoparticles were uniformly distributed within the Cr–C deposits after electroplating in a Cr3+-based plating bath. The hardness values of the Cr–C–Al2O3 deposits increased with the Al2O3 concentration in the electroplating bath. The corrosion resistance of the Cr–C-deposited specimens could be noticeably improved by adding Al2O3 nanoparticles to the deposit. This is attributed to decrease in the number of cracks in the Cr–C specimens codeposited with Al2O3 nanoparticles. According to the transmission electron microscopy study, the crack-reduction mechanism in the Cr–C–Al2O3 deposits was proposed. The Cr–C–Al2O3 deposited specimen, which was prepared in an electroplating bath with an Al2O3 concentration of 50 g/L, had a relatively high corrosion resistance compared to the other specimens.
Keywords: Cr–C–Al 2 O 3 deposits ; electroplating ; Cu substrate ; Cr 3+ -based plating bath ; Al 2 O 3 nanoparticles ; corrosion resistance

Thermodynamic Properties of Al–La–Ni Melts by V. G. Kudin; M. O. Shevchenko; M. I. Ivanov; V. V. Berezutskii; P. M. Subotenko; V. S. Sudavtsova (603-611).
The mixing enthalpies of liquid ternary Al–La–Ni alloys are determined by isoperibol calorimetry for sections (Al0.42La0.58)1–xNix (0 < x < 0.27) at 1430 K and (La0.25Ni0.75)1–xAlx at 1770 K (0 < < xAl < 0.3) or 1800 K (0.3 < xAl < 0.39). The experimental mixing enthalpies and those calculated with the Redlich–Kister model are characterized by exothermic effects. The minimum mixing enthalpy of the melts is –54 kJ/mol for composition Al0.4La0.2Ni0.4.
Keywords: thermodynamic properties; melt; aluminum; lanthanum; nickel

The Role of Stoichiometry in Contact Interaction of Zirconia with Metal Melts by A. V. Durov; M. V. Karpets; T. V. Sydorenko; B. D. Kostyuk; Yu. V. Naidich (612-616).
As a transition metal compound, zirconia can lose oxygen with the formation of nonstoichiometric phases. The stoichiometry affects the properties of material, therefore, the wetting of nonstoichiometric zirconia with inert metals (Cu, Ni, Sn, Ge, Ag, Pt) and alloys (Cu–Ga, Cu–Ge, Cu–Ni) is studied under conditions when the high oxygen deficit in zirconia is caused by the contact interaction with metal melts (such as Cu–Ti, Ni–Ti, Ti). It is established that the melts of inert metals can wet nonstoichiometric zirconia. This effect is explained as follows: the oxygen deficit may be considered as the zirconium surplus; this surplus of zirconium dissolves in the metal melt and, when the melt composition changes, then, the surface properties of the melt change too. Since zirconium is an active metal, the adhesion of the melt to the oxide substrate increases. In case of nickel, the microstructural study reveals nickel–zirconium intermetallide on the metal–oxide interface indicating the interaction of the nickel melt with zirconium from the substrate. Thermodynamic calculations show that such process is quite possible. Thin films are also considered. It is found out that Pt, Pd, and Ni films on stoichiometric zirconia are congregated in the islands at the temperatures significantly lower than the melting temperatures of corresponding metals, while they remain continuous on nonstoichiometric zirconia. Also, it can be explained by the chemical interaction of the metal film with the substrate.
Keywords: inert metals ; zirconia ; stoichiometry ; wetting ; contact interaction

The structurization of Fe–Mo alloys at 5–30 wt.% Mo is studied and contact interaction of these alloys with titanium diboride is examined. The Fe–5 wt.% Mo and Fe–9 wt.% Mo alloys consist of an α-Fe metallic structure with inclusions of Fe2Mo intermetallics. The Fe–13% Mo alloy based on the α-Fe solid solution contains individual inclusions of Fe3Mo2 intermetallics. When Mo content of the alloys increases to 17–30 wt.%, Fe2Mo and Fe3Mo2 intermetallics form intensively and make the alloy brittle. Zero contact angles are observed for the (Fe–13 wt.% Mo) and (Fe–17 wt.% Mo) alloys. The TiB2–(Fe–13 wt.% Mo) system is characterized by chemical interaction leading to additional molybdenum, iron, and titanium boride phases. The TiB2–(Fe–13 wt.% Mo) system shows no brittle intermetallic phases. The contact interaction in the TiB2–(Fe–17 wt.% Mo) system leads to the intensive formation of complex molybdenum–iron–titanium borides; there is also a great number of Fe3Mo2 intermetallics. The TiB2–(Fe–13 wt.% Mo) system is promising for the development of new composite materials and coatings with high wear resistance.
Keywords: alloy ; structure ; iron ; molybdenum ; titanium diboride ; contact interaction

Qualification of the Method for Determining the Content of Multiwall Carbon Nanotubes by V. V. Garbuz; L. S. Suvorova; V. A. Petrova; L. N. Kuzmenko (625-631).
The oxidation temperature for multiwall carbon nanotubes purified chemically and evaluated morphologically is qualified by scanning electron microscopy. The samples obtained by different methods have oxidation temperature 1033 ± 10 K. The results are based on the oxidative extraction of carbon, as CO2, in an oxygen flow and on coulometry at 773–1173 K. That carbon does not oxidize at lower and higher temperatures indicates that the carbon component is pure. For the standardization system of carbon nanomaterials developed by ISO, this chemical method for measuring the amount for multiwall nanotubes is suitable.
Keywords: qualification; composition determination method; carbon nanomaterials; multiwall nanotubes