Powder Metallurgy and Metal Ceramics (v.47, #5-6)

The paper considers the production of double mixtures of ultrafine powder materials. An attempt is made to determine the role of the second component and its effect on thermal decomposition, rolling, and sintering.
Keywords: formate; metals; ultrafine powder; thermal decomposition; phase composition

The paper presents the results from computer simulation and analysis of experimental data on the densification of copper and iron powder billets during hot shock compaction. It is established for the first time that the shear viscosity of the porous material matrix shows a stronger dependence on the initial impact velocity than the billet temperature does. The estimated activation energy of the viscous flow in the matrix is equal to 0.35 eV for copper, 0.3 eV for α-Fe, and 0.5 eV for γ-Fe.
Keywords: simulation; analysis; densification dynamics; porous body; copper; iron; hot shock compaction

Effect of cold isostatic pressing on the synthesis and particle size of lanthanum manganate by S. Yu. Prilipko; V. M. Timchenko; G. Ya. Akimov; V. I. Tkach (284-287).
X-ray diffraction and thermogravimetry are used to examine the influence of temperature and cold isostatic pressing on the synthesis and crystalline growth of lanthanum manganate. Coprecipitated {ie284-01} samples compacted under different pressures before synthesis are examined. It is shown that pressing promotes synthesis, decreases its temperature, and retards crystalline growth. The results demonstrate that cold isostatic pressing is promising for obtaining nanocrystalline manganates.
Keywords: lanthanum manganate; oxygen nonstoichiometry; synthesis; structure; cold isostatic pressing; nanotechnology; ceramics; high hydrostatic pressure

Densification kinetics of Mo-Ni-Sn composites in liquid-phase sintering by V. I. Nizhenko; V. Ya. Petrishchev; V. V. Skorokhod (288-294).
The paper examines the densification kinetics in liquid-phase sintering of Mo-Ni-Sn samples containing 90 wt.% of molybdenum and 10 wt.% of liquid phase in which the content of nickel varies from 5 to 67.5 wt.%. The samples continuously densify with increasing nickel content. It is examined how the amount of the 28 wt.% Ni-72 wt.% Sn liquid phase influences the densification kinetics of samples with varying content of molybdenum. The densification parameter increases with the amount of the liquid phase.
Keywords: densification kinetics; liquid-phase sintering; molybdenum; nickel; tin

High-porous materials made from alloy steel fibers: Production, structure, and mechanical properties by A. G. Kostornov; O. V. Kirichenko; N. P. Brodnikovskii; Yu. A. Guslienko; V. N. Klimenko (295-298).
New high-porous corrosion-resistant materials are produced from steel fibers and a base porous material made by pressing and sintering of St.10 steel fibers. The materials obtained by chromizing (4.8–7.1 wt.%) and nickelizing (2.1–2.4 wt.%) a 60–90%-porosity base material have yield strength higher by a factor of 2 to 6 than that of the base material. The materials obtained by electrochemical coating of a base fibrous material with eutectic composite Ni-Ni3B and subsequent liquid-phase sintering at 1120 °C contain 3.5–14.0 wt.% Ni. The yield strength of these materials at a porosity of 60–90% is higher by a factor of 2 to 3 than that of the base material.
Keywords: porous fibrous materials; carbon steel; alloying

Production and properties of copper-based powder antifriction material by L. A. Ryabicheva; Yu. N. Nikitin (299-303).
The paper examines how temperature and strain rate influence the deformation of a porous powder billet made of an antifriction material. Copper and nickel-based alloy powders produced from industrial waste are used as the initial material. The ultimate strain in compression is established and used to calculate the mold sizes in tool development. Ambiguous temperature dependence of the mechanical and antifriction properties is obtained. Temperature and strain rate that ensure satisfactory mechanical and antifriction properties are found. Processes for producing parts from the antifriction material are proposed.
Keywords: antifriction material; copper; nickel, ultimate strain; mechanical properties

The machinability of powder metallurgy materials is considered to be poor. The main factors that deteriorate the machining of PM parts are introduced in this work. They are those which participate in different ranges and modes in the formation of a sintered body with required mechanical and other characteristics. The effect of base iron powders, alloying systems, and alloying elements, as well as the effect of processing routes, especially solid-state sintering, are mentioned. The characteristic heterogeneous microstructures are presented. The effect of porosity in terms of interrupted and deformation cutting theories is discussed and demonstrated. The main measures to improve machinability of PM materials are described.
Keywords: powder metallurgy; sintered steels; microstructure; machinability; machining aids

Ultrafine high-cobalt hard alloys. II. Connection between mechanical properties and structure by A. I. Tolochin; A. V. Laptev; M. E. Golovkova; M. S. Koval’chenko (316-323).
The experimental dependences of strength, plastic properties, hardness, and fracture toughness on sintering or pressing temperature for ultrafine alloy WC-41 wt.% Co are presented. The alloy densifies in solid phase and temperature varies from 950 to 1250°C. The dependences of mechanical properties are extreme, excepting fracture toughness. The properties reach their maximum values at 1050 to 1150°C depending on the type of testing. Fracture toughness continuously increases with densification temperature. The highest values of some properties are reached after additional solid-phase annealing. The mechanical properties of ultrafine high-cobalt alloy samples are assessed with the use of structural parameters and empirical equations established for standard hard WC-Co alloys sintered in liquid phase. The calculated and experimental values of properties differ: transverse rupture strength, fracture toughness, and yield strength show higher values, while hardness and compressive strength have lower values as compared with calculated ones.
Keywords: tungsten carbide; cobalt; solid-phase densification; ultrafine structure; mechanical properties

Globular structure of electrospark-deposited coatings on VK8 alloy by I. A. Podchernyaeva; O. V. Stepanova; A. D. Panasyuk; I. V. Uvarova; D. I. Yurechko (324-329).
The paper examines the composition and structure of electrospark coatings based on AlN-TiB2 (TBSAN) and AlN-ZrB2 (TsBSAN) electrode materials deposited on VK8 alloy. Kinetic dependences of mass transfer are studied. In spite of the close structures and mechanical properties of TBSAN and TsBSAN electrode materials, the coatings substantially differ in structure and properties. The kinetic dependences of mass transfer, which differ for TsBSAN and TBSAN electrodes, generally confirm that the mass transfer in electrospark alloying of a hard-alloy substrate occurs in three stages and show distinctions in the electroerosion mechanism for these electrode materials.
Keywords: hard alloy; electrospark alloying; microstructure; composite ceramics

Laser processing of LaB6-based thick film resistors by A. V. Paustovskii; B. M. Rud’; V. E. Shelud’ko; E. Ya. Tel’nikov; V. V. Kremenitskii; P. S. Smertenko; I. V. Zakharchenko; A. A. Rogozinskaya (330-337).
The paper studies the effect of laser processing on the structure and electrophysical properties of LaB6-based thick film resistors (TFR). The phases and structure of the composition are investigated. The exposure to micro-and nanosecond pulses, unlike millisecond ones, is shown to insignificantly increase the electrical resistance of the film and to aid in forming more uniform and fine TFR structure. LaB6-based TFRs are more resistant to long-term exposure to nanosecond laser radiation than BaB6-and (BaB6-LaB6)-based ones.
Keywords: thick film resistor (TFR); laser processing; structure; electrophysical properties

Al2O3-ZrO2-Yb2O3 phase diagram. II. Liquidus surface by S. M. Lakiza; Z. O. Zaitseva; L. M. Lopato (338-343).
The liquidus surface for the Al2O3-ZrO2-Yb2O3 phase diagram is constructed for the first time. No ternary compounds are found in the system. The liquidus surface is completed by seven primary crystallization fields. Two four-phase invariant eutectic equilibria, two four-phase invariant transition equilibria, and one three-phase invariant eutectic equilibrium are found in the ternary system. Since ZrO2 interacts with other phases eutectically, composite materials can combine the unique properties of ZrO2-based T-and F-phases with the properties of other phases of the Al2O3-ZrO2-Yb2O3 system.
Keywords: zirconia; alumina; ytterbia; interaction; liquidus surface; phase diagram

Thermodynamic assessment of the Cu-Ti-Zr system. I. Cu-Ti system by M. A. Turchanin; P. G. Agraval; A. R. Abdulov (344-360).
The CALPHAD method is used for the thermodynamic assessment of the Cu-Ti system that bounds the ternary Cu-Ti-Zr system, which is capable of forming amorphous alloys. The self-consistent parameters of thermodynamic models of the phases are obtained from data on the phase equilibria and thermodynamic properties of liquid alloys and intermetallic compounds. The Gibbs energy of the liquid phase is described using the associated ideal solution model. To describe the thermodynamic properties of the Cu4Ti and CuTi intermetallic compounds with homogeneity range, sublattice models are used. The calculated phase diagram of the system and the thermodynamic properties of the phases are in good agreement with experimental data.
Keywords: phase diagram; thermodynamics; thermodynamic modeling; copper-titanium alloys

The paper presents a thermodynamic analysis of chemical equilibrium characteristics of Fe-Cr-Ni-Mo and Co-Cr-Ni-Mo alloys used to produce retention coatings on dentures by diffusion saturation from point sources under 0.1 MPa at 500–1500 K. It is shown that metals are transported through the gaseous phase with FeCl and FeCl2, CoCl and CoCl2, CrCl and CrCl3, NiCl and NiCl2, and MoCl3 and MoCl4 molecules. Chromium, nickel, and molybdenum in the iron-based system should be expected to be alloyed with iron and chromium transport should be expected in the cobalt-based system.
Keywords: thermodynamic analysis; equilibrium; temperature; alloys; composition; compound; gas; concentration; cyclic reaction

Mechanical resonance spectroscopy of interparticle boundaries in high-density iron powder compacts by A. V. Vdovichenko; Yu. N. Podrezov; V. V. Skorokhod (366-372).
Characteristics of mechanical resonance are measured on powder iron samples with a porosity of 0.06 produced by die compaction and sintering at 573 to 1373 K. Young’s modulus and parameter CN that describes how the resonant frequency varies with increasing amplitude of oscillation are calculated. It is established that CN decreases with increasing temperature of sintering. Comparing the resonance characteristics with results from fracture toughness tests and structural analysis shows that CN correlates with fracture toughness and failure mode of samples. The results indicate that CN is related to the evolution of the interparticle boundaries and may be used as a highly sensitive criterion to quantitatively assess the quality of sintered powder materials.
Keywords: powder iron; sintering; interparticle boundaries; mechanical resonance