Powder Metallurgy and Metal Ceramics (v.56, #9-10)

Highly Dispersed Powders in Boride–Silicide Systems by G. N. Makarenko; L. A. Krushinska; I. I. Timofeeva; M. A. Vasylkivska; V. E. Matsera; D. P. Zyatkevich; V. K. Medukh; R. M. Medukh; V. F. Labunets; I. V. Uvarova (487-495).
Nanosized composite powders with a composition of titanium diboride–silicides of group IV–VI transition metals are obtained in boride–silicide systems by mechanochemical synthesis for 5–30 min. The initiation effect of TiB2 on the formation of silicide phases during joint mechanochemical synthesis is shown. It is established that the powder particles are 40–70 nm in size. The powders tend to agglomerating. The properties of hot-pressed compacted TiB2–20 wt.% MoSi2 samples are studied: ultimate bending strength 421 ± 29 MPa; microhardness 25 ± 0.8 GPa. Electrolytic Ni–TiB2–MoSi2 coating possesses high wear-resistance in sliding friction and can be recommended for hardening and recovering the surfaces of machinery and mechanical parts.
Keywords: composite powders; titanium diboride; silicides of transition metals; mechanochemical synthesis; electrolytic coating

The influence of rolling temperature on the microstructure and mechanical properties of AA5083–1% Al2O3 composites has been analyzed in this study. The alloy was deformed with the method of warm accumulative roll bonding in various temperature conditions, i.e., at ambient temperature, 200°C, and 300°C up to 5 cycles (
Keywords: aluminum; metallic matrix composites; heat treatment; rolling

Features of Physical and Chemical Adsorption During Interaction of Polycrystalline and Nanocrystalline Materials with Gases by V. A. Lavrenko; I. A. Podchernyaeva; D. V. Shchur; An. D. Zolotarenko; Al. D. Zolotarenko (504-511).
Diborides of group IV transition metals are considered in the context of the features of two types of adsorption (physical and chemical) during interaction of polycrystalline and nanocrystal materials (carbon nanotubes, highly dispersed iron powder etc.) with gases (CO2, H2O-vapor). Due to Raman scattering spectroscopy, it is established that, in the case of adsorption, only gas chemical adsorption with typical minimal distance between absorbed gas molecule and adsorbing agent surface occurs on the surfaces of all synthesized nanoparticles. It is confirmed that the reference Raman spectrum of the correspondent nanoparticles (according to the Hirsch reference book) remains in all cases. The adsorption of oxygen and nitrogen during oxidation of diborides of group IV transition metals is investigated.
Keywords: physical adsorption; chemical adsorption; carbon nanotubes; iron nanopowders; Raman scattering spectroscopy; nanomaterials; borides of transition metals; distortion of electron shell of surface atoms

Features of Chromium Carbide Synthesis Using Different Forms of Carbon by N. A. Pinchuk; M. P. Gadzyra; I. D. Hnylytsia (512-515).
The interaction of chromium oxide with different forms of carbon in a wide temperature range is investigated. The phase composition and morphology of the resulting powder product are examined. It is established that Cr3C2 and Cr7C3 single-phase chromium carbide is formed at 1400 and 1500°C, respectively. It is shown that the smallest particle size (0.85 μm) is due to the mixed structural state of Cr7C3 and Cr3C2 carbides.
Keywords: chromium carbide; carbon nanotubes; exfoliated graphite; natural graphite; chromium oxide; synthesis; induction furnace

New Copper-Based Composites for Heavy-Loaded Friction Units by T. A. Roik; O. A. Gavrysh; Iu. Iu. Vitsiuk; O. I. Khmiliarchuk (516-522).
Constraints in the use of bushings produced of the new copper-based bearing composite material alloyed with nickel and molybdenum and containing the additives of CaF2 (DN5M3KF9) solid lubricant are analyzed. The structure and tribotechnical properties are examined during reverse friction under heavy load (temperature 400–600°C and load up to 6.0 MPa in air). The study focuses on the distribution of CaF2 in a composite with Cu–Ni–Mo matrix, the role of calcium fluoride in the self-lubrication of the material, and the distribution of chemical elements of friction pair and CaF2 in the friction zone under extreme operating conditions. It is shown that the solid lubricant is evenly distributed along the contact surfaces as it envelops the entire friction zone during reverse friction under heavy load. It is established that tribofilms formed in the presence of CaF2 solid lubricant provide high wear resistance. Also, the new material possesses high thermal conductivity. These properties extend the application of new cooper-based composite bearing bushings in a chassis.
Keywords: bearing bushing; copper; composite material; solid lubricant; technology; friction films; wear resistance; chassis

Study of Processing and Microstructure of Copper Composite Reinforced with Graphene Nanosheet by Powder Metallurgy Technique by N. Vijay Ponraj; A. Azhagurajan; S. C. Vettivel; X. Sahaya Shajan; P. Y. Nabhiraj (523-534).
Copper (Cu) composite reinforced with graphene nanosheet (GNS) is obtained by powder metallurgy technique. The microstructure and mechanical properties were investigated based on the Cu composite reinforced with various GNS content (0, 1, and 2 wt.%). The characterization is carried out through Raman spectra (RS), Fourier transform infrared (FTIR), X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), and transmission electron microscopy (TEM). The results show that GNS is uniformly dispersed in the Cu particle. Raman spectra and FTIR demonstrate the reduction of GNS from Graphene oxide (GO) oxide in GNS after heat treatment at 550 and 650°C. The TEM analysis confirms GNS to be 3–5 nm in size. During compression tests, the Cu–2 wt.% GNS composite demonstrates 9% higher compressive stress compared to pure Cu.
Keywords: copper; GNS; FTIR; HRSEM; sintering; powder metallurgy

Diffusion Chromizing of Molybdenum-Based Plasma Coatings by R. M. Medyukh; V. K. Medyukh; I. V. Uvarova (535-540).
Thermochemical treatment (chromizing) of compacted steel parts on molybdenum-based plasma coatings was studied. The effect of heat treatment parameters on the structure and size of parts was examined. The sintering and diffusion hardening are recommended to be combined into one stage to simplify the production process and improve the performances of parts.
Keywords: diffusion hardening; chromizing; porosity; molybdenum plasma coatings; corrosion characteristics

Composition and Microstructure of Zinc-Substituted Tricalcium Phosphate and Plasma Biocoating Based Hereon by A. V. Lyasnikova; O. A. Dudareva; V. N. Lyasnikov; O. A. Markelova; I. P. Grichina (541-545).
The structure of zinc-substituted tricalcium phosphate is investigated by IR-spectroscopy and X-ray diffraction analysis. Size and shape of the grains are examined using transmission electron microscopy and scanning electron microscopy. Scanning electron microscopy of plasma coatings based on zinc-substituted tricalcium phosphate is conducted; the chemical composition is analyzed. Data on the adhesion and hydrophilic properties of the coatings are obtained.
Keywords: substituted tricalcium phosphate; plasma spraying

The thermodynamic assessment of the Co–Cu–Fe system has been updated. The critical review of the literature data on the ordered B2 phase formation has been provided. For the Co–Fe and Co–Cu–Fe systems, the parameters of the bcc solution and ordered phase have been adjusted to describe the thermodynamic properties and to predict the phase equilibria at low temperatures. For the ordered B2 phase, the two-sublattice model has been adopted. The high-temperature phase equilibria have been verified using the newly available literature information on liquidus and solidus. The available data on the ordered B2 phase have been analyzed using the developed thermodynamic assessment. The results of the calculations are in satisfactory agreement with the experimental data.
Keywords: thermodynamic modeling; thermodynamic functions; phase diagram; B2 phase; Co–Cu–Fe system

Thermochemical Properties of Binary Ba–In Alloys by M. A. Shevchenko; V. G. Kudin; M. I. Ivanov; V. V. Berezutskii; V. S. Sudavtsova (556-566).
The thermochemical properties of binary Ba–In melts were studied using calorimetry at 1070–1320 K over a wide composition range. It is shown that these melts are characterized by significant exothermic heat effects of mixing. The ideal associated solution model was used to calculate the activities of components, Gibbs energies, and mixing entropies of the alloys and to construct the liquidus curve in the phase diagram. These parameters agree with the literature data.
Keywords: thermodynamic activity; melt; barium; indium; calorimetry method; ideal associated solution model

Electrochemical Properties of ZrMnCrNiV Alloy in Long-Term Cycling After Air Oxidation by Yu. M. Solonin; O. Z. Galiy; E. A. Graivoronska; V. A. Lavrenko (567-572).
A zirconium-containing alloy was subjected to air oxidation to examine its influence on the lattice parameters and cyclic resistance. The samples made of freshly prepared alloy powder and of powder oxidized in air for 7, 15, and 30 days were studied. Cyclic voltammetry was used to analyze in detail the current–voltage characteristics and X-ray diffraction was employed to determine the lattice parameters. The freshly prepared alloy was found to be very unstable and significantly lose its activity in the hydrogenation–dehydrogenation process. This results from oxidation of the alloy, which induces interfacial stresses and causes mechanical damage of the electrodes. Air oxidation of the alloy powder followed by compaction of the electrodes stabilizes its electrochemical properties and, as a result, increases the cyclic resistance. According to X-ray diffraction, the phase ratio after air oxidation remains practically unchanged, and the lattice expansion (within 1%) can be attributed to measurement errors.
Keywords: zirconium-containing alloy; hydrogenation; air oxidation

Behavior of Ultrahigh-Temperature ZrB2-Based Ceramics in Oxidation by O. N. Grigoriev; I. P. Neshpor; T. V. Mosina; V. B. Vinokurov; A. V. Koroteev; O. V. Buriachek; D. V. Vedel; A. N. Stepanchuk; L. Silvestroni (573-580).
Ultrahigh-temperature ZrB2-based ceramics with different sintering additions was developed for extreme conditions. Its strength characteristics, phase composition, and structure were examined. The ceramics was oxidized in air at 1250 and 1550°C. In addition, the most stable composites were subjected to temperature cycling in a flow of aviation fuel combustion products in a temperature range of 1400–1500°C. All materials show high oxidation resistance. The method used to produce samples influences their oxidation behavior: materials produced by vacuum hot pressing show higher oxidation resistance than those produced by hot pressing in a CO–CO2 atmosphere, probably because of their higher final density. The best results were obtained when ZrB2 sintering was combined with introduction of MoSi2 and CrB2.
Keywords: oxidation; ultrahigh-temperature ceramics; zirconium diboride; temperature cycling test

Interaction of Ground SmCo4.8Zr0.2 Alloy with Hydrogen by I. I. Bulyk; I. V. Borukh (581-588).
The hydrogen pressure and reaction time were studied during disproportionation of the ground SmCo4.8Zr0.2 alloy. The alloy ground at ν = 100 rpm for τ = 24 h disproportionates at 0.5 MPa hydrogen pressure within 15–30 min, the alloy ground at ν = 200 rpm for τ = 6 and 12 h disproportionates at 0.5 MPa hydrogen pressure, and the alloy ground at ν = 300 rpm for τ = 6 h disproportionates into SmHx and ht-Co below 0.1 MPa hydrogen pressure. Residues of the CaCu5–type ferromagnetic phase were found among the disproportionation products.
Keywords: disproportionation; mechanochemical grinding; hydrogen; phase transformation; magnetic material; samarium–cobalt alloys; X-ray diffraction

Base Alloy Concept in the Development of High-Entropy Materials by M. O. Krapivka; O. M. Myslyvchenko; M. V. Karpets (589-598).
The requirements to be met by a high-entropy alloy to be used as a base one for the development of new high-entropy materials have been formulated. Four alloys that comply with these requirements were selected. The use of CrMnFeCoNi alloy with an fcc lattice as a base one was analyzed, considering that this alloy has been the most extensively studied and has adequate ductility. The influence of 12 elements (Al, Ti, Zr, Hf, V, Nb, Ta, Mo, W, Re, Cu, Y) on the phase composition of the base alloy at the equiatomic content of each additive was studied. The maximum solubility of each element in the base alloy was determined. It is found that doping of the base alloy allows the bcc, B2, σ, μ, χ, and C14 and C15 Laves phases to be obtained. The feasibility of using the base alloy to develop new high-entropy materials with the approaches applied to develop conventional alloys is shown.
Keywords: high-entropy alloys; phase formation; solid-solution strengthening

Post-Processing of NiTi Alloys: Issues and Challenges by N. Sharma; K. Kumar; V. Kumar (599-609).
Nitinol (NiTi) exists in an equiatomic phase of Ni and Ti. Nitinol has growing applications in aerospace and medical industries due to its unique properties of pseudoelasticity, corrosion resistance, shape memory effect, and biocompatibility. NiTi can be produced by conventional and nonconventional manufacturing routes and its behavior can be modified by altering the composition, changing the porosity, and shape setting under varying thermal and mechanical treatment. After the fabrication, several post-processing operations are required on NiTi for desired application. This paper presents a brief on post-processing like machining, surface coating, and mechanical and thermal treatment for shape setting of NiTi alloys, and their issues and challenges.
Keywords: nitinol (NiTi); shape memory alloy (SMA); post-processing; machining; surface coating; heat treatment; shape setting