Powder Metallurgy and Metal Ceramics (v.52, #7-8)

Effect of High-Voltage Electrical Discharge Treatment of Diamond Powders on Their Mechanical Characteristics by O. N. Sizonenko; N. A. Oleinik; G. A. Petasyuk; G. D. Il’nitskaya; G. A. Bazalii; V. S. Shamraeva; É. I. Taftai; A. S. Torpakov; A. D. Zaichenko; E. V. Lipyan (365-369).
The effect of pulsed high-voltage electrical discharge (HVED) treatment on the morphometrical, structural adsorption, and mechanical properties of diamond micropowders and abrasive powders is examined. These properties largely determine the performance and wear resistance of abrasive tools for machining process. It is shown that pulsed HVED treatment is efficient in the production of diamond micropowders and abrasive powders with low impurity content and high abrasive ability.
Keywords: synthetic diamond powders; hydrodynamic waves; pulsed high-voltage electrical discharge treatment

Effect of Grinding in Hydrogen and Vacuum Treatment on the Phase Composition of SmCo5 Alloy by I. I. Bulyk; A. M. Trostyanchyn; P. Ya. Lyutyy (370-379).
It is shown that the phase composition of commercial ferromagnetic KS37 alloy depends on the conditions of its grinding in hydrogen and subsequent heat treatment in vacuum. Treatment parameters (hydrogen saturation pressure and grinding of the alloy, mill rotation frequency, grinding time, vacuum treatment temperature) that allow a wide variation in the phase composition of the alloy and in the quantitative ratio of the phases have been established. Depending on the above-mentioned conditions, several phase compositions involving SmCo5, Sm2Co17, Sm2Co7, and Sm5Co19 can be obtained.
Keywords: mechanochemical alloying; hydrogen; phase transformation; magnetic material; samarium–cobalt alloy; X-ray diffraction

Effect of Hydrogen on the Absolute Thermoelectric Power of Powders by T. V. Kopan’; I. A. Selezneva; N. V. Khutoryanskaya; V. S. Kopan (380-385).
The effect of hydrogen adsorption by Pt, Ni, Fe, Ag, and Cu powders and carbon nanotubes on their absolute thermoelectric power (adsorption thermoelectric effect) and other properties is studied. The absolute thermoelectric power E p of the powder is lower than E s of the solid material (wire, foil) resulting from the tunneling of charges (electrons, holes) through the gaps between powder particles. The adsorption thermoelectric effect increases E p in the following series: carbon nanotubes, Cu, Ag, Fe, Ni, Pt. The higher the E p of iron powder, the higher the rupture stress of the associated solid material. The adsorption thermoelectric effect is recommended for quick quality check of powders prior to compaction.
Keywords: adsorption thermoelectric effect; metal powder; rupture stress

Powder Forging: Today and Tomorrow by V. Yu. Dorofeev; Yu. G. Dorofeev (386-392).
The current status and prospects of powder forging for producing structural engineering parts are discussed. The causes of the reduced scope of research in the field of powder forging in 1990–2010, as well as the advantages and disadvantages of the process, are analyzed. The method makes it possible to produce high-dense materials for high-stress applications. The complexity of parts’ shape is limited by the performances of hot-forging equipment in use. The need for substantial capital expenditures for basic and auxiliary equipment is the critical area of the process, so powder forging would not be appropriate for mass production of parts. Promising areas for the development of powder forging are identified.
Keywords: powder forging; porous preforms; mechanical properties; density; strength; shape; structural parts

Simulation of Powder-Cored Wire Drawing by E. G. Kirkova; L. N. Tkachenko; A. V. Kuz’mov; M. B. Shtern; A. P. Maidanyuk (393-400).
The powder-cored wire drawing process is simulated using the finite-element method. To describe the behavior of the powder core, a plasticity model of porous and granular media with planar defects is proposed. The model takes into account bimodulus behavior and susceptibility to dilatancy. The densification of the powder core after one and six wire-drawing passes is studied. Substantial transverse nonuniformity in the density distribution of the powder core is found. The dependence of the densification behavior of the powder core on the initial porosity and fraction of planar effects is established.
Keywords: powder-cored wire drawing; bimodulus behavior; plastic deformation; porous materials with planar defects; associated flow rule

Wear-Resistant Heterophase Fe–Si–B–C Powder Materials by G. A. Baglyuk; S. G. Napara-Volgina; V. K. Kud; L. N. Orlova; A. D. Kostenko (401-408).
The microstructure, mechanical characteristics, and tribological properties of Fe–Si–B–C powder composites are analyzed to determine scientific and engineering principles for their production by single pressing and sintering followed by heat treatment. The composites have heterophase structure and can be recommended for wear-resistant parts for dry friction applications.
Keywords: composites; boron carbide; silicon carbide; ferrosilicon; wear resistance

Powder Metallurgy Production of Ti–5.4 wt.% Si Alloy. I. Simulating the Formation of Powder Particles by Centrifugal Atomization by D. N. Brodnikovskii; N. I. Lugovoi; N. P. Brodnikovskii; V. N. Slyunyaev; L. D. Kulak; A. D. Vasil’ev; S. A. Firstov (409-416).
The powder-metallurgy production of porous Ti–5.4 wt.% Si material used in solid oxide fuel cells is examined. The cooling rate of powder particles, as the main factor influencing their structure in the centrifugal atomization process, is estimated by simulation. It is shown that the cooling rate is mainly dependent on the particle size rather than on the speed of the electrode.
Keywords: Ti–Si alloys; quenching; centrifugal atomization; eutectic composition; phase transformation

Improvement of the Performance Parameters of Precision Friction Couples in the Magnetic Field by M. N. Svirid; E. Wajs; L. B. Primak; V. N. Borodii; A. E. Yakobchuk (417-423).
The paper considers the possibility to control the restoration and wear processes during friction depending on the location of magnetic poles using electromagnetic techniques. It is shown that both the steel piston and copper cylinder can be restored in the magnetic field separately (without disassembling the mechanism). A method is developed for restoring the friction surfaces in oil modified with different magnetic powders in a pulsed magnetic field. The influence of a pulsed magnetic field on the tribological characteristics of the friction couple in oil with different magnetic nanopowders is analyzed to reveal that the surfaces are the most functional in S/N pulsed magnetic field.
Keywords: friction; oil; magnetic field; powder; sample; counterface; wear; restoration

The paper is devoted to analysis of friction and wear of real porous sliding bearings modified with solid lubricant layers at high temperature. For this purpose, a special homemade friction tester was applied. The technology of sleeve nitriding is described. The results of the friction tests reveal about the achievement of quasi-hydrodynamic lubrication regime of powder bearings. The lowest friction coefficient is found to be f = 0.04 at 300°C. The great effect of wear rate diminishing is obtained at 300°C as interaction of microasperities is preserved at the sliding interface in quasi-hydrodynamic lubrication regime.
Keywords: sliding friction; wear; sliding bearing; powder materials; quasi-hydrodynamic lubrication regime

The paper considers vacuum activated diffusion saturation of carbon–carbon composites, including that in liquid environments and self-propagating high-temperature synthesis. The coatings are formed under a synergetic impact of energy and mass flows. Thermodynamic analysis of forming complex C–B–Si coatings based on refractory metals, such as tungsten, molybdenum, zirconium, and hafnium, is carried out. Oxidation and heat resistance of the carbon coatings is tested in the range 1500–1900°C.
Keywords: carbon material; coating; diffusion; activation; heat resistance; temperature

Previous data on the constitution of the solidus surface in the Al–Cr–Pt system at 0–100 at.% Pt and results from study of the associated cast alloys are used for metallurgical, X-ray diffraction, electron microprobe, and differential thermal analyses to construct the liquidus surface on the composition triangle and analyze the alloy solidification processes. This has allowed the construction of the Al–Cr–Pt melting diagram in the composition range 50–100 at.% Pt for the first time. It is determined that the liquidus surface consists of six primary solidification fields of the platinum solid solution and phases based on binary and one ternary compounds. Four invariant four-phase equilibria involving the liquid phase (two eutectic and two transition equilibria) and three invariant threephase eutectic equilibria are found in the system.
Keywords: liquidus surface; primary solidification; invariant equilibrium; melting diagram

Constitution of Rh–Sc–Ti Alloys in the 50% (At.) Rh Section and Adjacent Composition Range by O. L. Semenova; Yu. V. Kudryavtsev; V. M. Petyukh; O. S. Fomichov (444-455).
Physicochemical analysis methods (metallography, X-ray diffraction, differential thermal analysis, and resistometry) are used to examine phase equilibria in the Rh–Sc–Ti system in the ScRh–TiRh section and in the adjacent composition range. It is shown that the ScRh–TiRh section is quasibinary. Intermetallic ScRh and TiRh phases with the same crystalline structure form an infinite series of solid solutions with cubic CsCl structure at subsolidus temperature. Replacement of titanium by scandium stabilizes the high-temperature phase at room temperature. The martensitic transformation in TiRh alloys proceeds in two stages as follows: cubic (CsCl) → tetragonal (AuCu) → monoclinic (TiNi).
Keywords: titanium; rhodium; scandium; phase equilibrium; quasibinary section; martensitic transformation

Thermodynamic Properties of Liquid Fe–Sc Alloys by V. S. Sudavtsova; M. O. Shevchenko; V. V. Berezutskii; M. I. Ivanov (456-464).
The partial and integral mixing enthalpies of Fe–Sc melts are determined by calorimetry at 1873 K over the entire composition range. It is established that the minimum enthalpy of mixing is −12.4 ± 0.6 at x Sc = 0.46 and the first partial enthalpies of mixing are $ Delta overline{H}_{mathrm{Sc}}^{infty }=-43.8pm 4.4 $ and $ Delta overline{H}_{mathrm{Fe}}^{infty }=-38.1pm 3.8 $ (kJ/mol). Thermodynamic properties of the Fe–Sc melts are calculated with the model of ideal associated solutions. It is found that the activities of components have negative deviations from parameters of ideal solutions.
Keywords: calorimetry; Fe–Sc alloys; thermodynamic properties

Size Effects in Corrosion of Thin Steel Films in Alkaline (NaOH) Environments in the Magnetic Field by A. F. Andreeva; A. M. Kasumov; N. A. Vlasenko; V. M. Karavaeva (465-468).
Thin films of iron and iron-containing materials are promising for applications in spin electronics and nanotechnologies. The lifetime of items made of these films depends on their corrosion resistance under the magnetic fields induced by flowing currents. The corrosion of thin low-carbon steel films in acid (HCl) and salt (NaCl) water solutions, seawater, and maritime air was studied previously. This paper considers the corrosion characteristics of thin films (electrode potential, corrosion current and rate, controlling factor) in an alkaline NaOH solution. It is shown that all these parameters depend on film thickness both with and without a constant magnetic field. The influence of the magnetic field is due to variation in properties of the films and NaOH solution.
Keywords: films; iron; corrosion; magnetic field; NaOH solution

The paper discusses the production and properties of wear-resistant eutectic coatings in the Fe–Mn–CB–Si–Ni–Cr system. The coatings are produced by gas metal arc (GMA) welding in a protective argon atmosphere with use of powder wires (2.4 mm in diameter). After wear-resistance tests, the phase composition, microstructure, distribution of elements, and nanohardness of eutectic coatings are examined. The powder wires are used for strengthening and recovery of knives used in equipment for shredding of motor tires.
Keywords: eutectic alloy; powder wire; welding; coating

The paper overviews the origin and development of metallurgical technologies, including the production of metals and alloys, methods of their treatment, and applications of metallic materials in the Bronze Age.
Keywords: history; metals; alloys; gold; copper; silver; tin; lead; bronze; casting; deformation processing; use of metallic materials; Bronze Age