Powder Metallurgy and Metal Ceramics (v.46, #7-8)

Theory, manufacturing technology, and properties of powders and fibers by V. V. Nepomnyashchii; T. V. Mosina; A. K. Radchenko; G. Ya. Kalutskii (313-316).
The properties of ferromagnetic powders after reduction annealing are examined. It is shown that magnetite and a destructured composite organic coating ensure the resistance of such powders to external effects.
Keywords: electrolysis; reduction annealing; chemisorbed epoxy oligomers; polyconjugated multinuclear carbonic structure; specific magnetization; coercivity

The studies on the densification of WC-Co alloys in solid-phase sintering are analyzed. It is shown that solid-phase sintering of alloys with tungsten carbide particles smaller than 2.0 µm is characterized by high densification (shrinkage) and results in compact samples in some cases. Shrinkage is established to be nonmonotonic over a wide range of sintering temperatures. There are at least three different stages of densification over the range from room to solidus temperatures. Approximate temperature ranges for densification stages are 100 to 1050 °C, 1050 to 1200 °C, and 1200 °C to the eutectic melting temperature. The stages mainly differ in the extent and rate of shrinkage and in the activation energy. The compaction stages are separated by characteristic temperatures. The most important is 1200 °C, which separates the second and the third stages. The maximum rate of shrinkage is observed mostly at this temperature. The variation of initial WC particles from 5 to 2000 nm does not significantly affect the temperature at which the solid-phase shrinkage rate is maximum. In most cases, there are two maximum rates of shrinkage in WC-Co sintering: one at 1200 ± 30 °C and the other at the solidus temperature.
Keywords: hard alloy; solid-phase sintering; shrinkage; shrinkage rate; density

Electric-discharge sintering of TiN-AlN nanocomposites by M. V. Zamula; A. V. Derevyanko; V. G. Kolesnichenko; A. V. Samelyuk; O. B. Zgalat-Lozinskii; A. V. Ragulya (325-331).
The structurization and properties of TiN-AlN and TiN-AlN-Y2O3 nanocomposites consolidated by electric-discharge sintering are examined. TiN-AlN composites with a relative density of about 98 to 99% are produced. Their structure is not homogenous and consists of TiN and AlN grains of about 200 nm in size. There are also large spherical grains of titanium nitride of 2 to 10 µm. This effect is probably caused by microdischarges between particles of the conducting phase and subsequent meltback of the interacting surfaces. The effect of yttrium oxide additives on the material structure and properties is investigated. It is shown that TiN-AlN composites consolidated by electric-discharge sintering have high hardness (HV ∼ 25 GPa) and fracture toughness (K1c ∼ 6 MPa · m1/2).
Keywords: titanium nitride; aluminum nitride; structural anomalies; electric-discharge sintering

Sintered metals and alloys by A. S. Drachinskii; V. A. Maslyuk; Yu. I. Samsonov; G. F. Sarzhan; O. M. Shevchenko (332-337).
The paper examines the production of a composite material that is double hardened by adding titanium carbides and borides to the steel and by quenching the metal matrix and letting it to age. Samples containing 30 wt.% TiC or TiB2 are produced by liquid phase sintering, hot pressing, and hot forging. The effect of thermal treatment on the mechanical properties and structural state of the material is investigated. The material quenched and aged is established to be twice as durable and hard as the sintered one. Hence, it can be mechanically treated after sintering and then thermally treated. The highest possible strength of the material produced is 1400 to 1500 MPa and hardness 60 to 65 HRC. Strengthening worn reinforcing-wire knives with plates of the composite material prolonged their life by 50 to 100% compared with the standard knife.
Keywords: composite; aging; steel; hardening; titanium carbide; titanium boride

The paper focuses on the formation of phase composition, structure, and properties of high-strength aluminum materials that are mechanically alloyed with boron and have a large effective thermal-neutron capture cross-section. A technology based on reactive mechanical alloying is proposed. It is intended to produce dispersion-hardened nanostructured materials in the Al-B system. Structural high-temperature materials with a low density and a great effective thermal-neutron capture cross-section can be obtained by complex alloying of aluminum with elemental boron (up to 40%) and B2O3 (1.5%). When the boron content reaches its maximum (40%), the strength of the material is σt = 380 MPa and σ 100 500 = 101 MPa; when the boron content decreases to 10%, the strength increases to σt = 560 MPa and σ 100 500 = 150 MPa.
Keywords: boron; aluminum; mechanical alloying; dispersion hardening; effective thermal-neutron capture cross-section; strength

Refractory and ceramic materials by E. V. Dudnik; A. V. Shevchenko; A. K. Ruban; Z. A. Zaitseva; V. M. Vereshchaka; V. P. Red’ko; A. A. Chekhovskii (345-356).
The paper examines the consolidation of 95 mole% ZrO2-2 mole% CeO2-3 mole% Y2O3 nanocrystalline powder in cold uniaxial double-action pressing, cold isostatic pressing (60 and 120 MPa), and sintering. Five starting powders are produced by processing a suspension after hydrothermal decomposition in different conditions. It is established that a homogeneous microstructure forms only in a material from the powder subjected to two homogenizing grindings. After cold uniaxial pressing and cold isostatic pressing, the sintered samples reach a relative density of 0.96 to 0.94. The bending strength is 600 to 660 MPa. The efficient consolidation of ceramics requires comprehensive processing of starting nanocrystalline powders to modify their morphology.
Keywords: zirconia; nanocrystalline powder; uniaxial double-action pressing; cold isostatic pressing; consolidation

Physicochemical materials research by S. O. Katrych; V. M. Petyukh; A. A. Bondar; W. Steurer (357-364).
For alloys in the range Os-OsAl2-IrAl2.7-Ir, as-cast and annealed at 1400 °C (Os-OsAl-IrAl-Ir) and 1250°C (OsAl-OsAl2-IrAl2.7-IrAl), phase equilibria are studied by powder x-ray diffraction (PXRD), differential thermal analysis (DTA), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDX). Between isostructural aluminides OsAl and IrAl there exists a continuous solid solution (Os,Ir)Al. Other unary and binary phases form terminal solid solutions: (Os), (Ir), (OsAl2), and (IrAl2.7).
Keywords: intermetallics; x-ray diffraction; high-temperature alloys; differential thermal analysis

Phase diagram of the Al2O3-ZrO2-Er2O3 system. iv. vertical sections by S. M. Lakiza; V. P. Red’ko; L. M. Lopato (365-372).
For better presentation of the Al2O3-ZrO2-Er2O3 phase diagram over a wide temperature and concentration ranges, three vertical sections are plotted to show interactions in the ternary system. The Er2O3-(50 mole% Al2O3 · 50 mole% ZrO2) bisector shows the Er2O3-enriched region of the Al2O3-ZrO2-Er2O3 phase diagram and explains the mechanism of Er2O3 phase transformations X ⇆ H ⇆ A ⇆ B. The 15 mole% ZrO2 (15Z) isopleth shows the Al2O3-ZrO2-Er2O3 structure within the region adjacent to the Al2O3-Er2O3 binary bounding system. The ZrO2-ErAlO3 bisector depicts the ternary system in the ZrO2-enriched region. The vertical sections intersect each of the three triangulating sections of the ternary system and demonstrate the width variation in their two-phase regions.
Keywords: zirconia; alumina; erbia; phase diagram; vertical sections; eutectic materials

Thermodynamic properties of LuGe1.5 at 55 to 1790 K by N. P. Gorbachuk; S. N. Kirienko; V. R. Sidorko; I. M. Obushenko (373-377).
Adiabatic calorimetry and mixing are used to examine the LuGe1.5 heat capacity and enthalpy over a wide temperature range for the first time. Standard values and temperature dependences of the main thermodynamic functions are calculated and the enthalpy and entropy of polymorphic transformations and melting of LuGe1.5 are determined.
Keywords: thermodynamics; calorimetry; heat capacity; enthalpy; entropy; free Gibbs energy

Deformation behavior of skeletal composites under mechanical loading by V. V. Skorokhod; S. M. Solonin; V. P. Katashinskii; L. L. Kolomiets; V. A. Dubok; V. A. Zorin; A. A. Ivashin; N. P. Brodnikovskii; Yu. G. Bezymyannyi; V. G. Borovik (378-384).
The deformation behavior of ceramic-metal composites with a bulk-linked metal skeleton made of highly porous cellular nickel and a stainless wire mesh is examined. It is established that samples of skeletal ceramics remain intact after all types of destructive tests and show high plasticity and strain and fracture energies. A technique is developed for producing ceramics with a bulk-linked metal skeleton by filling a highly porous framework with a ceramic powder and subsequent pressing and sintering of the composite. The technique is tested for two types of skeletal ceramics: structural ceramics such as pyroceramics-highly porous cellular nickel and bioceramics such as hydroxyapatite-highly porous stainless wire skeleton. The hydroxyapatite-based composite has lower bending strength and shock bending energy but higher plasticity and nondestructability than the pyroceramics-based composite.
Keywords: bulk-linked skeleton; skeletal ceramics; fracture energy; macroplasticity; composites based on hydroxyapatite and pyroceramics

Effect of fine structure on mechanical properties of hot-forged powder steels by V. A. Maslyuk; A. A. Mamonova; A. I. Danilenko (385-391).
Comparative analysis of the substructural parameters and mechanical properties of hot-forged steels reveals regular changes in the mechanical characteristics depending on the degree of imperfection. It is shown that higher imperfection at lower forging temperatures of porous billets can increase the strain hardening of particles. The maximum strain hardening of carbon steels is revealed at the maximal structural imperfection and a density of 7.77 g/cm3 after forging a billet heated to 1100°C. The high strain hardening of chromium steel results from high dispersion of coherent scattering regions.
Keywords: temperature; forging; deformation; imperfection; mechanical properties

Powder metallurgy industry and managerial economics by P. A. Shpak; N. I. Grechanyuk; V. A. Osokin; E. L. Piyuk (392-397).
The phase composition and structure of two-layer thermal-barrier metal-ceramic coatings applied by electron-beam vapor deposition in one process cycle are investigated. It is shown that the outer ceramic layer has a two-phase (monoclinic-tetragonal) structure and is characterized by an axial growth texture of columnar crystallites with prevailing <001> orientation. High-temperature isothermal annealing in an oxidizing medium increases the amount of the tetragonal constituent in the outer ceramic layer of the thermal-barrier coating.
Keywords: thermal-barrier coating; outer ceramic layer; yttrium-stabilized zirconium oxide; electronbeam vapor deposition; annealing; microstructure; x-ray pattern; phase composition; texture

Exchange of experience by L. F. Kravchenko; V. D. Kurochkin; M. V. Kolomytsev; O. M. Romanenko; N. A. Derenovskaya (398-403).
Phosphorus and trace impurities in aluminum phosphate powders and coatings are identified with glow-discharge mass spectrometry (GDMS), atom emission spectrometry (AES), x-ray fluorescence (XRF), and chemical analysis. Alumina powders with particles 60 to 40 µm in size that are covered with Al(PO3)3 and AlPO4 with TiO2 additives are sprayed using a supersonic air plasmatron. The distribution of elements across the coating on a steel substrate is examined with GDMS. The effect of polyatomic clusters is taken into account in determining Mg, P, S, and Ti by mathematical simulation. Phosphorus is identified with AES in a dc air arc controlled to produce similar conditions for exciting PI lines in the evaporation of test and reference (Ca3(PO4)2) samples. Comparing the results obtained by different methods shows that x-ray fluorescence reveals the concentration from the surface of nucleus-shell particles. Measurements show that some part of phosphorus is lost in spraying because orthophosphates transform into metaphosphates.
Keywords: aluminum phosphates; thermal spraying; analysis; phosphorus; trace impurities; glow discharge mass spectrometry; atom emission spectrometry; x-ray fluorescence; chemical analysis

Antifriction composite materials for friction joints of centrifugal equipment by Yu. F. Shevchuk; T. A. Roik; V. T. Varchenko (404-407).
Mechanical and antifriction properties of promising copper-based powder materials are examined. The metallographic structure of the new materials is studied. It is shown that copper-based composite materials can be successfully used instead of babbits for friction joints operating at high sliding speeds.
Keywords: antifriction materials; high sliding speeds; friction joints

Powder metallurgy abroad by V. M. Kryachek; D. A. Levina; L. I. Chernyshev (408-413).
Asian companies are actively entering the market of powder metallurgy products. In 2005, the production of iron powder in Asia increased by 14% and of powder parts by more than 7%. The current manufacture of metal powders and their products in Japan, China, India, and South Korea is discussed. Applications of powder products in Asia are considered. Examples of developments that won awards of the Japan Powder Metallurgy Association (JPMA) in 2006 are shown.
Keywords: powders; products; powder metallurgy technology; market of powder products; applications