Powder Metallurgy and Metal Ceramics (v.57, #5-6)

The Structure and Properties of High-Carbon Ferrochromium Powder Produced from FKh800 Ferroalloy by V. A. Maslyuk; E. S. Karaimchuk; V. D. Kurochkin; A. A. Mamonova; O. I. Khomenko (251-256).
The structure, chemical and phase compositions, and process properties of the high-carbon ferrochromium powder produced by grinding the lump pig FKh800 ferroalloy have been examined. The pycnometric and bulk densities of the powder and its compressibility at 600–800 MPa have been determined. It is shown that the content of harmful impurities, S and P, in the FKh800 powder complies with the requirements of GOST 4757–91. The resultant powder consists of complex (Cr, Fe)7C3 carbide and a solid solution of carbon in chromium ferrite.
Keywords: powder materials; composite; complex iron–chromium carbide; iron; FKh800; sintering; hardness

The influence of deformation modes on the mechanical properties of metal matrix composites produced from the aluminum powder strengthened with SiC nanoparticles has been studied. Symmetric and asymmetric rolling processes were employed at room temperature. Rolling as an additional deformation processing step improves the composite structure by refining the SiC agglomerates, asymmetric rolling being a more effective deformation processing technique. This complex hardening mechanism allows the strength to be increased twofold without decrease in the elastic and ductile parameters.
Keywords: powder composite; nanoparticles; hardening; strength; ductility; elastic modulus

In this study, aluminum and graphene nanoplatelet (GNP) powders were mixed in different ratios and sintered by the conventional method. The powder mixtures were stirred for 2 h at a speed of 35 rpm in a V-type mixer to obtain a homogeneous dispersion. The nanocomposite powder mixtures were pressed by the CIP (Cold Isostatic Pressing) method at a pressure of 400 MPa. Sintering was carried out at 620°C for 1 h under argon gas. The density, surface roughness, weight loss, and Vickers hardness of the nanocomposites were evaluated. SEM, EDX, and XRD analyses were performed and the obtained results were examined. The effect of the graphene addition to aluminum was evaluated, and the optimum contribution of 0.8 wt.% GNP has been determined.
Keywords: powder metallurgy; aluminum; graphene; sintering; CIP

The Production and Properties of High-Temperature Electrical-Insulation and Heat-Resistant Aluminum Nitride Materials by T. V. Dubovik; A. I. Itsenko; T. P. Hrebenok; A. A. Rogozinsky; N. S. Zyatkevich; R. V. Litvin; M. S. Kovalchenko (272-276).
The effect of activating additives on the formation of aluminum nitride composites in the sintering process has been studied. The production and properties of the sintered composites have been optimized. The properties of the aluminum nitride composites with an optimum ratio of components allow them to be used as electrical insulators in radioisotope and electrical equipment, as thermal shields in vacuum furnaces, and as corrosion-resistant refractories operating in contact with steel, aluminum, zinc, copper, and cast iron melts.
Keywords: aluminum nitride AlN; pressing; activating additives; sintering; phase formation; composite material

Surface Modification of ZrB2–SiC Ceramics for Improving Their Corrosion Resistance by I. P. Neshpor; T. V. Mosina; O. M. Grigoriev; D. V. Vedel; A. V. Vasin; A. B. Rusavsky; O. M. Nazarov (277-284).
To improve the corrosion resistance of the ZrB2–15 vol.% SiC composite, SiC, SiOC, and SiO2–Er2O3 coatings were deposited on its surface by magnetron sputtering. The surface modification of the ZrB2–15 vol.% SiC ceramics improves their corrosion resistance through the development of a dense layer consisting of high-temperature phases formed in the oxidation process. In addition, the mechanical properties become twice as high (bending strength of the coated samples is 803–875 MPa). X-ray diffraction and scanning electron microscopy were used to examine the phase composition of the oxidation products and the structure of the resultant oxide film.
Keywords: erbium; corrosion resistance; magnetron sputtering; oxide film

The Structure and Electrical Properties of Graphene-Containing Thick Films by A. V. Paustovsky; V. E. Sheludko; E. Ya. Telnikov; A. K. Marchuk; V. V. Kremenitsky; O. P. Tarasyuk; S. P. Rogalsky (285-292).
The use of graphene for ‘conducting phase + glass’ thick films that are screen-printed onto an alumina ceramic substrate and then heat-treated in a vacuum furnace has been studied. Quantitative microanalysis of carbon and glass elements has been carried out and the microstructure and electrical properties of the films have been examined. The film surface layer shows an increased carbon content, the current–voltage curve is linear, indicating that Ohm’s law is obeyed, and resistivity decreases with increasing temperature. The temperature resistance coefficient is negative. It has been concluded that graphene can be used as a conducting phase in thick films.
Keywords: graphene; thick film; screen printing; microstructure; electrical properties

The Properties of Cr–Co–Cu–Fe–Ni Alloy Films Deposited by Magnetron Sputtering by L. R. Shaginyan; V. F. Britun; N. A. Krapivka; S. A. Firstov; A. V. Kotko; V. F. Gorban (293-300).
In spite of great efforts undertaken to produce and examine the properties of new high-entropy alloys (bulk or film alloys), the available information is still insufficient for creating scientific ideas that would connect the properties and process parameters of these alloys. We studied the dependence of the composition and structure of Co–Cr–Cu–Fe–Ni films deposited by magnetron sputtering on the physical parameter such as energy flux delivered to the growing film surface. This parameter is directly related to process parameters such as magnetron discharge current (I d) and substrate bias voltage (U b). The films have a nanocrystalline microstructure and crystallize as a two-phase fcc and bcc solid solution with the following lattice parameters: a = 0.363 nm for the fcc phase and a = 0.294 nm for the bcc phase. Ion bombardment of the growing film induced by bias voltage U b varying from 0 to –300 V in the substrate influences the film structure and composition. Thus, the films deposited at ~300 eV are noticeably depleted of copper, while the composition of the films deposited without ion bombardment is the same as that of the target. Greater energy flux delivered to the growth surface (higher I d and/or U b in the substrate) increases the growth surface temperature, leading to grain coarsening and film texturing. The bcc phase also substantially decreases in volume, vanishing in the films deposited at U b = –300 V. The films formed by the bombardment of ions with ≈100 eV energy showed the maximum (~19 GPa) microhardness.
Keywords: high-entropy alloys; films; sputtering; composition; structure; mechanical properties

The Gd2Zr2O7-Based Materials for Thermal Barrier Coatings by E. V. Dudnik; S. N. Lakiza; N. I. Hrechanyuk; A. K. Ruban; V. P. Red’ko; M. S. Hlabay; A. B. Myloserdov (301-315).
Zirconates of rare earth elements with a pyrochlore-type structure, as a class of ceramics with low thermal conductivity, are among the most promising materials for a ceramic layer in thermal barrier coatings (TBCs) for gas turbine engines with operating temperatures above 1200°C. The paper presents an overview of studies focusing on the development of the upper Gd2Zr2O7 TBC layer. The microstructural design of these materials is based on the ZrO2–Gd2O3–Al2O3 phase diagram. Methods for increasing the fracture toughness of Gd2Zr2O7 materials and preventing the interaction of Gd2Zr2O7 and Al2O3 formed in TBC operation are presented. The features of multilayer and functional gradient coatings are addressed. Complex improvement of the composition, architecture, and deposition of the coatings ensures the properties required for long-term operation of Gd2Zr2O7 TBCs.
Keywords: thermal barrier coatings; zirconia; pyrochlore; Gd2Zr2O7 ; ZrO2 solid solution; complex doping; multilayer coatings; functional gradient coatings

Properties of Electro-Spark Deposited Coatings Modified Via Laser Beam by N. Radek; M. Scendo; I. Pliszka; O. Paraska (316-324).
The main purpose of this work was to determine the influence of laser treatment on microstructure, X-ray diffraction, microhardness, surface geometric structure, corrosion resistance, adhesion tests and tribological properties of coatings deposited on C45 carbon steel by the electro-spark deposition (ESD) process. The studies were conducted using WC–Cu electrodes produced by the powder metallurgy method. The tests show that the laser-treated electro-spark deposited WC–Cu coatings are characterized by higher corrosion resistance, adhesion, surface geometric structure and seizure resistance which result from lower microhardness. The laser treatment process causes the homogenization of the chemical composition, structure refinement and healing of microcracks and pores of the electro-spark deposited coatings. Laser treated ESD coatings can be applied in sliding friction pairs and as protective coatings.
Keywords: electro-spark deposition; laser treatment; coating; powder metallurgy; properties

Galvanomagnetic Properties of Thin-Film (Fe, Co, Ni)/Rare Earth Metal Oxide Structures by A. M. Kasumov; V. M. Karavaeva; A. A. Mikitchenko; K. O. Shapoval; M. A. Perepelitsa; G. V. Lashkarev (325-328).
The magnetic interaction between contacting films of 3d and 4f metals has long been known to promote the formation of complex magnetic structures promising for spintronic applications. The replacement of 4f metals by their oxides, mainly possessing paramagnetic and dielectric properties, opens up an opportunity to create systems with both magnetic and electric complex structures. This further extends the applications of such multilayer films. However, the study of the (Fe, Co, Ni)/rare earth metal (REM) oxide systems is still in the initial stage. The dependence of galvanomagnetic properties (magnetoresistance and magnetization) on the chemical composition of layers in the (Fe, Co, Ni)/REM oxide system and magnetic field strength suggests that there is magnetic interaction between the 3d and 4f electronic shells at interface. The maximum increase in these parameters is observed in the Fe/Dy2O3 system when the magnetic field vector is parallel to the current through the metal film.
Keywords: films; Fe; Co; Ni; REM oxides; properties; interaction

Friction and Adhesive Wear Study of HVOF Sprayed Ni–WC–Co-Based Powder Coating by Sushil Kumar; Shashi Prakash Dwivedi; Satpal Sharma (329-335).
Ni-based alloys are being widely used to improve the wear resistance of various industrial components in normal and severe environments and addition of rare earth elements to these alloys further improves the various mechanical and tribological properties of the coatings. In the present work, commercially available MEC 86 (NiCrBSi/WC–Co = 65/35) powder was modified with the optimum addition of 0.4 wt.% La2O3. The coatings were deposited by high velocity oxy-fuel (HVOF) spraying process. Rare earth addition refines the microstructure and increases the microhardness of the coatings. The increase in microhardness with the addition of La2O3 is approximately 22%. Sliding wear resistance of the coating modified with La2O3 is higher than of that without La2O3. The average wear resistance increases by approximately 14%. Further, the addition of La2O3 to the coating reduces the friction coefficient as compared to the one without the rare earth element. The coefficient of friction was found lower with the addition of La2O3, which is approximately 18%.
Keywords: Ni-based alloy; high-velocity oxy-fuel (HVOF); pin-on-disk test; microstructure; hardness; adhesive wear

Low-Temperature Thermodynamic Functions of Gadolinium Hafnate (Gd2Hf2O7) by A. R. Kopan; N. P. Gorbachuk; S. M. Lakiza; Ya. S. Tischenko; D. S. Korablov (336-343).
The isobar heat capacity of Gd2Hf2O7 is studied for the first time by adiabatic calorimetry in the range 80–298.15 K. It is shown that Cp of gadolinium hafnate changes monotonically and no anomalies are observed. The temperature dependences of the principal thermodynamic functions of Gd2Hf2O7 in the range 10–300 K are established. The heat capacity, entropy, reduced Gibbs energy, and enthalpy are determined for standard conditions: Cp∘ $$ {C}_p^{circ } $$ (298.15 K) = 224.2 ± 0.9 J × × mol–1·K–1, S°(298.15 K) = 237.1 ± 2 J · mol–1 · K–1, Φ′ (298.15 K) = 109.4 ± 1.6 J · mol–1 · K–1, and H°(298.15 K) – H°(0 K) = 38084 ± 190 J · mol–1. The temperature dependence of the Gd2Hf2O7 heat capacity is evaluated using the Neumann–Kopp rule of additivity. The difference between the experimental and evaluated heat capacities of Gd2Hf2O7 in the range 80–298.15 K is no more than 3.4%, while the difference in Cp∘ $$ {C}_p^{circ } $$ (298.15 K) is 0.4%.
Keywords: thermodynamics; heat capacity; enthalpy; entropy; reduced Gibbs energy; gadolinium hafnate

Mixing Enthalpies of Liquid Cu–Hf–Ti Alloys Studied by High-Temperature Calorimetry by P. G. Agraval; M. A. Turchanin; A. A. Vodopyanova; L. A. Dreval (344-348).
The partial enthalpies of mixing of titanium and hafnium in liquid Cu–Hf–Ti alloys were investigated at 1873 K along the xCu/xHf = 3 (at xTi = 0–0.25) and xCu/xTi = 3 (at xHf = 0–0.5) sections by a hightemperature isoperibolic calorimeter. The limiting partial enthalpy of mixing of supercooled liquid titanium in liquid Cu–Hf alloy is 2.0 ± 1.5 kJ/mol. The limiting partial enthalpy of mixing of supercooled liquid hafnium in liquid Cu–Ti alloy is –43.0 ± 4.5 kJ/mol. The integral mixing enthalpies of components along the investigated sections are calculated by integrating the Gibbs–Duhem equation. The integral mixing enthalpy is negative in the investigated composition range. The comparison of our experimental results with the calculations according to Miedema’s model shows that this model’s prediction for the ΔmixH function should be treated with caution.
Keywords: calorimetry; glass-forming metallic liquids; mixing enthalpy; thermodynamics; copper; titanium and hafnium alloys

Physicochemical Stability of Hydroxyapatite–Low-Molecular Polyethylene Glycol 400 Composite Systems in Biological Media by N. V. Boshytska; L. S. Protsenko; O. N. Budilina; N. V. Kaplunenko; A. V. Minitskiy; I. V. Uvarova (349-352).
The physicochemical stability of the composite system consisting of hydroxyapatite (HAP) including 10, 25, and 50% polyethylene glycol (PEG) with a molecular weight of 400 in different physiological solutions has been studied. In the interaction of HAP + PEG 400 composite systems with physiological solutions, the amount of Ca in the filtrate changes versus the PEG content of the composite and the salt composition of the reaction media. The rate of calcium release in Ringer and Ringer–Lokk solutions, whose chemical composition is close to that of the tissue fluid of living organisms, is almost twice as high as in a 0.9% NaCl solution. Chemical analysis has shown that the HAP +10% PEG 400 composite system interacts with physiological solutions and is likely to promote calcium interchange between the experimental material and tissue fluid. Infrared spectroscopy has demonstrated that polyethylene glycol is present in the HAP + 10% PEG system over 120 h of interaction with biological media of living organisms, which will promote the restoration of nervous impulses in the treatment of bone defects. The HAP + 10% PEG 400 composite system can be recommended for further study in the development of novel composite materials for rehabilitation orthopedics.
Keywords: hydroxyapatite; polyethylene glycol; interaction; calcium; physiological solution; infrared spectroscopy

The fractal analysis of fractographic surfaces employing digital processing of scanning electron microscope (SEM) images is considered. Mathematical tools for digital photogrammetry, particularly in stereological or stereometric options, are proposed. The mathematical formalism for processing SEM images is employed. The fractal analysis of SEM images is analyzed for correctness.
Keywords: scanning electron microscopy (SEM); SEM images; fractal dimensions; digital photogrammetry

Microstructure and Phase Transformation in Ni50Mn40Sn10 Shape Memory Alloy by D. Saini; S. Singh; M. K. Banerjee; K. Sachdev (361-366).
In the present work, a ternary Heusler alloy of composition Ni50Mn40Sn10 with a high martensitic transformation temperature has been prepared by arc-melting technique. The crystal structure of the obtained alloy is investigated by X-ray diffraction. The microstructure of the specimen sintered at 950°C for 72 h followed by ice-water quenching shows needle-like martensitic structure. Energy dispersive spectroscopy is utilized for compositional study. The differential scanning calorimetry result shows that the alloy undergoes a martensitic transformation at 190°C upon cooling. The M–H curve suggests paramagnetic nature of the martensite phase at room temperature. The present alloy system has a great potential to be used for high-temperature shape memory applications. Experimental data of this study may be useful for developing Ga-free high-temperature shape memory alloys.
Keywords: Heusler alloy; martensitic transformation; arc melting; shape memory alloys

A high-modulus composite material consisting of AS 400 diamonds and a VK6 hardmetal matrix has been developed. This material has been used to produce diamond dressers for straightening abrasive grinding wheels. Tests of the diamond dressers for straightening diamond wheels have shown that the performance of the new dressers is 5.1 times better than that of standard diamond dressers.
Keywords: abrasive tools; diamond wheels; diamond dressers; metal binder; straightening

Correction to: Electrode Materials Based on LaMgNi4–x Co x (0 ≤ x ≤ 1) Alloys by Yu. V. Verbovytskyy; V. V. Shtender; P. Ya. Lyutyy; I. Yu. Zavaliy (372-372).
The third author’s name should be P. Ya. Lyutyy