Powder Metallurgy and Metal Ceramics (v.48, #1-2)

The solubility of tungsten in Fe–Cu and Fe–Sn melts and the growth kinetics of W6Fe7 layer at the tungsten–melt interface at 1200°C are examined. The solubility of tungsten in these melts is well described by the following equations: lgXW = –4.3864 + 8.529XFe (Fe–Cu melt) and lgXW = = –4.544 + 14.293 XFe – 23.583 X Fe 2 (Fe–Sn melt). The melt composition in the three-phase equilibrium W–W6Co7 melt is established: XFe = 4.1 ∙ 10–3, XW = 4.5 ∙ 10–5, the rest is copper (Fe–Cu melt), XFe = 0.111, XW =5.6 ∙ 10–4, and the rest is tin (Fe–Sn melt). The substantial difference in kFe–Sn > kFe–Cu at the same iron activity aFe is attributed to the impact of admixtures (Cu and Sn) on the growth of the W6Fe7 layer.
Keywords: tungsten; iron; melts; solubility; kinetics; layer growth; three-phase equilibrium

Bulk changes and structurization in solid-phase sintering of titanium–silicon powder mixtures by E. N. Korosteleva; G. A. Pribytkov; A. V. Gurskikh (8-12).
Titanium–silicon powder materials produced by vacuum sintering of elementary powder mixtures containing up to 25 at.% Si are examined. The structurization of sintered materials with different compositions is studied. The bulk changes of samples in sintering depending on the content of the second component and sintering temperature are analyzed. The process conditions to produce materials of minimum porosity are determined.
Keywords: titanium; silicides; powder alloys; vacuum sintering; structurization

The impregnation of porous substrates with viscous media is examined. A mathematical model that most adequately describes the behavior of viscous media in porous substrates is proposed. A method to determine the optimal process parameters is outlined. The causes of failure are revealed and recommendations to eliminate them are formulated. The optimal process parameters for the impregnation with viscous media with substantial density and viscosity (μ ≥ 100 Pa ∙ sec) are determined as an example. The optimal range of the limiting pressure in isostatic treatment (up to 500 MPa) is justified and indicated.
Keywords: impregnation; ceramics; mathematical model; viscous media; isostat; fracture

Effect of metal-layer structure on the mechanical properties of multilayer metal–ceramic composites. I. fracture energy by V. V. Skorokhod; V. V. Panichkina; P. Ya. Radchenko; S. M. Solonin; V. P. Katashinskii (21-26).
The effect of the metal-layer geometry and of the interface structure on the fracture toughness of multilayer metal–ceramic composites is examined. The samples are produced by free sintering of layups consisting of alternating metal and ceramic layers. The ceramic layers are prepared by rolling fine pyrophyllite powders into strips. The metal layers are prepared from stainless steel fabric. Before sintering, the layups are pressed across and along the layers. The samples show 24–25% residual porosity after the free sintering of layups containing 15 vol.% metal phase at 1000°C. The fracture energy of the samples is determined. Their microstructure is examined. It is shown that the use of metal fabric substantially increases the fracture energy of composites. This is due to the developed skeleton structure of multilayer ceramic–metal fabric composites, which weakens the adverse effect of the residual porosity and sometimes poor adhesive contact between the metal and ceramic components on fracture toughness.
Keywords: multilayer metal–ceramic composites; sintering; microstructure; fracture energy

Wear of ceramic and ceramic–metal composites in high-speed dry sliding over steel by S. N. Kul’kov; N. L. Savchenko; S. F. Gnyusov (27-33).
The wear of zirconia-based ceramics and WC-based ceramic–metal composites in high-speed dry sliding over steel is examined. The pin-on-disk technique is used up to a sliding speed of 47 m/sec. It is shown that tribolayers with complex composition form over ceramic and metal–ceramic materials and cause nonmonotonic changes in wear and friction. At the first stage, wear changes from normal to extreme high-intensity one with increasing sliding speed. At the second stage, steady-state wear is observed for the metal–ceramic composite and the wear rate of the ceramic material decreases virtually to its initial level typical of low sliding speeds (0.1 m/sec). Practically wearless friction of ceramics is observed over this range of speeds.
Keywords: wear; dry friction; sliding; tribological behavior; ceramic–metal composites; zirconia; tribolayers

Structural features of hot-forged carbide steel (high-speed steel–titanium carbide) by G. A. Baglyuk; I. D. Martyukhin; T. M. Pavligo; G. G. Serdyuk; V. M. Tkach (34-37).
The structure of hot-forged R6M5K5–20% TiC carbide steel is examined. In comparison with sintered carbide steels, it has no transition ring zone at the interface between the carbide grain and the base metal. The matrix alloy has a fine structure and the texture of grains is perpendicular to the forging force.
Keywords: carbide steel; hot forging; structure

Internal nitration in iron−chromium (manganese) nitride powder systems by V. A. Maslyuk; L. A. Sosnovskii; G. G. L’vova; É. V. Prilutskii; V. Ya. Kurovskii; A. A. Mamonova (38-41).
The effect of the internal nitration of powder iron is examined by the introduction of nitrogen in the form of alloying additives such as chromium and manganese nitrides. It is established that the phase composition of these materials includes residual manganese and chromium nitrides and a solid solution of nitrogen in iron. To obtain a porousless or low-porosity hot-pressed material with evenly distributed fine inclusions of secondary nitrides and to maintain the composition, hot-pressed materials must be annealed in conditions that prevent nitrogen loss.
Keywords: internal nitration; chromium nitride; manganese nitride; hot-pressed material; fine powders

The current status of research on high-temperature composite oxide ceramics in the Al2O3–ZrO2–Ln2O3 systems (Ln are lanthanides, Y) is reviewed. It is emphasized that their use as structural materials at high temperatures (up to 1650°C) is promising. Conditions for growing binary and ternary eutectic composites and their properties are described. Weak and strong aspects of these materials are pointed out. The role of phase diagrams in developing high-temperature in situ composites is shown.
Keywords: directional solidification; in situ composites; ceramics; zirconia; alumina; lanthanide oxides; phase diagrams

Production, properties, and erosion characteristics of B4C−Al composite materials by Yu. G. Tkachenko; M. S. Koval’chenko; V. F. Britun; G. A. Bovkun; D. Z. Yurchenko; A. V. Laptev; and L. P. Isaeva (60-65).
The paper examines the phase composition, structure, and erosion properties of B4C–Al composite materials produced by hot pulse pressing. It is shown that powder components actively interact to form new phases during pressing, TiB2 and AlB12 being the main phases. The erosion properties of the composites are greatly dependent on the composition of powder mixtures and compaction temperature. The structural features of the composites, namely the nanosized secondary phases at B4C grain boundaries, intensify the anode mass transfer to the titanium substrate and the formation of a protective coating up to 50 μm thick. The microhardness of this coating is about 40 GPa and its wear resistance is threefold higher than that of the substrate material.
Keywords: boron carbide; composite material; hot pulse pressing; electric spark alloying; protective coatings

Characteristics of thin plasmachemical silicon carbon nitride films deposited using hexamethyldisilane by V. I. Ivashchenko; O. K. Porada; L. A. Ivashchenko; I. I. Timofeeva; O. K. Sinel’nichenko; O. O. Butenko; M. V. Ushakov; L. A. Ushakova (66-72).
Silicon carbon nitride (SiCN) coatings are produced by plasma-enhanced chemical vapor deposition using hexamethyldisilane, N2, and H2 as precursors at various nitrogen flow rates (F N). X-ray diffraction data, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, adhesion, friction coefficient, abrasive wear resistance, and microprofiling of the film surface are used to characterize the coatings deposited on silicon substrates. The x-ray diffraction analysis shows that all the films have an amorphous structure. The chemical bonding in the films results from the main Si―C, Si―N, and C―N interatomic interactions. With higher $ {F_{{{ ext{N}}_2}}} $ , the wear resistance of the films increases and their friction coefficient decreases since Si―C bonds are strengthened. The SiCN films deposited using hexamethyldisilane as the main source material exhibit tribological properties that are comparable with those of amorphous SiCN films deposited using other precursors.
Keywords: amorphous coatings; silicon carbon nitride; PECVD; hexamethyldisilane; chemical bonding; tribological properties

Microlayered bioimplants based on ZrO2−Y2O3−CeO2−Al2O3 by E. V. Dudnik; A. V. Shevchenko; A. K. Ruban; V. V. Kurenkova; L. M. Lopato (73-76).
Sequential slip casting is used to create laminates in the ZrO2–Y2O3–Ce2O3–Al2O3 system. It is shown that the microhardness of the layers varies from 8100 to 12700 MPa. The bending strength of the composite is 900 MPa. Various bioinert implants may be produced by controlling the properties of the laminates in the ZrO2–Y2O3–Ce2O3–Al2O3 system.
Keywords: laminate; slip casting; nanocrystalline powder; ZrO2–Y2O3–Ce2O3–Al2O3 system; bioinert implant

Calorimetry is used to study the enthalpy of the bounding compositions Pr3Se and Pr2Se3 of the Pr3–x Se4 phase (0 ≤ x ≤ 1/3) at 450–2300 K. The temperature–concentration dependences of the thermodynamic properties of Pr3–x Se4 selenides in the homogeneity range are determined at 298 ≤ T ≤ 2156 K. The Pr3–x Se4 enthalpy function has the following form: H(T, x) − H(298 K, x) = (2817 ⋅ 103 T −1 − 75912 + 234.6 ⋅ T − 4.718 ⋅ 10−2 T 2+ 2.624 ⋅ 10−5 T3) ⋅ e−0.2086x J/mole. An analysis of the partial enthalpies of Pr and Se shows that the chemical bonds between these elements change in simple substances and Pr3–x Se4.
Keywords: thermodynamic properties; heat capacity; enthalpy; entropy; Gibbs energy; praseodymium selenides; Pr2Se3 ; Pr3Se4 ; homogeneity range; partial enthalpy

Thermodynamic properties of melts in Al–TI(Zr, Hf) binary systems by V. S. Sudavtsova; N. V. Podoprigora (83-87).
Isoperibolic calorimetry is used to specify the partial and integral mixing enthalpies of liquid Al–Ti(Zr, Hf) alloys at 1770 ± 5 K and 1790 ± 5 K. The concentration dependences of the mixing enthalpies of Al–Hf alloys are determined for the first time for 0 < x Hf < 0.2 at 1790 ± 5 K and relevant quantities are modeled for the entire concentration range. The data show that the mixing enthalpies of Al–Ti melts depend on temperature. The values of ΔS and ΔG are calculated for Al–IVb metal melts.
Keywords: liquid alloys; binary system; aluminum; titanium; zirconium; hafnium; thermodynamic properties; calorimetry; entropy

Interaction in the MoSi2–W system at 1500 to 1800°C by P. I. Glushko; V. I. Zmii; N. A. Semenov; A. A. Sushchaya; V. I. Sheremet; B. M. Shirokov (88-92).
The paper studies the kinetics of the diffusion redistribution of phases in the MoSi2–W system when tungsten samples with molybdenum silicide coatings are heated in air at 1500–1800°C. It is established that the (Mo x ,W y )5Si3 phase, which represents a molecular solid solution of lower molybdenum and tungsten silicides, forms in an exchange reaction between molybdenum and tungsten at the MoSi2–W5Si3 interface. The MoSi2–W system is much more stable than the WSi2–W and MoSi2–Mo systems.
Keywords: stability; coatings; diffusion; tungsten; molybdenum; silicides; high-temperature oxidation resistance

Structural evolution in annealing of layered C–Cu composite films by A. A. Onoprienko; N. I. Danilenko (93-99).
Thin carbon–copper layered films are sputtered using a dc magnetron unit. Transmission electron microscopy and electron diffraction are used to examine the structural evolution of the films in annealing at 600°C in vacuum. Two types of films are examined: two-layer carbon–copper and three-layer carbon–copper–carbon films. In annealing, the copper layers disintegrate, ensembles of copper particles form, and diffusion coalescence of particles in the two-layer film is observed. Hence, the density of copper particles decreases and their ensemble-average size increases. The coalescence in the two-layer film is slower than that predicted by theory because of the actual microstructure of quasiamorphous carbon substrate film. In the three-layer film, no coalescence is observed because of the specific morphologic and structural features of copper particles and carbon layers.
Keywords: amorphous carbon; film; structure; diffusion coalescence; transmission electron microscopy; electron diffraction

Complex modifiers produced by rolling of powder mixtures for iron–carbon steels by S. M. Voloshchenko; K. A. Gogaev; A. K. Radchenko (100-104).
The paper examines the rolling of powder modifying mixtures to produce complex composite modifiers (CCMs). The mixtures contain hard-to-mold components constituting the major fraction (up to 70 wt.%) of complex modifiers. It is of primary importance to produce sufficiently strong and moldable billets in the form of modifier strips. The rolling parameters and the ratio of hard-to-mold and plastic materials in CCMs are examined to maximally increase the content of the main modifying components and thus to decrease the amount of CCM introduced into liquid metal to modify cast iron. Production tests show that rolled CCMs show good recovery, have a stable effect, and permit the production of high-strength cast iron without chill.
Keywords: complex composite modifier; powder; cast iron; rolling; strength

An engineering method for thermal analysis of centrifugal induction sintering is developed. The method allows for the geometrical, thermal, and electrophysical parameters of parts and powder layer and the joint effect of convective and radiant heat transfer on the outer surface of parts. Formulas are derived to determine the temperature distribution over a part from the temperature on the outer surface needed for powder layer sintering. A system to monitor and control temperature in centrifugal induction sintering is developed.
Keywords: thermal modes; calculation; centrifugal induction sintering; heating; monitoring and control system; powder material; coating

Effect of different production methods on the properties of permanent magnet powders by V. V. Nepomnyashchii; T. V. Mosina; A. K. Radchenko; V. A. Nazarenko (112-114).
The paper examines how the properties of permanent powder magnets depend on their chemical and phase composition and production methods. It is shown that magnetic materials produced by powder metallurgy methods can compete with YUNDK-15.18 industrial cast alloys.
Keywords: permanent powder magnets; polymer binder; coercive force; specific magnetic energy; pressing

Use of aqueous suspensions in plasma spraying of alumina coatings by V. E. Oliker; A. E. Terent’ev; L. K. Shvedova; I. S. Martsenyuk (115-120).
The paper examines and compares the properties of Al2O3 coatings sprayed using two methods: arc plasma spraying (APS) of micron powders (average particle size is 45 μm) and suspension plasma spraying (SPS) (average particle size is 2.9 μm). A system for feeding suspension into plasma spray is developed and fabricated. It is established that SPS coatings contain finer structural components than APS. This improves their mechanical characteristics such as microhardness and indentation fracture toughness.
Keywords: plasma spraying; alumina; powders; suspension; structure; properties

Tribotechnical characteristics of fluoroplastic materials containing an inorganic filler by I. I. Beloborodov; S. V. Sukhostavets; V. T. Varchenko (121-123).
The paper examines the tribotechnical characteristics of materials with a fluoroplastic matrix containing an inorganic filler. It is established that the tribotechnical properties of the test materials depend on the particle size of the filler, its content in the matrix, and friction pressure. With smaller particles, the friction coefficient and wear rate of the composite decrease. Comparing the dependence of the friction coefficient and wear rate on the amount of the filler, its particle size, and friction coefficient shows that composite containing 25% inorganic filler with particles smaller than 10 μm is optimal for actual use.
Keywords: powder material; fluoroplastic matrix; inorganic filler; friction coefficient; wear rate