Powder Metallurgy and Metal Ceramics (v.54, #1-2)

The interaction of powder components in the titanium hydride–ferromanganese silicon system is investigated. It is demonstrated that titanium actively reacts with ferromanganese silicon during heating, which is accompanied by the dissociation of the latter and the formation of a complex multiphase system where the main phases are titanium silicide Ti5Si3 and titanium carbide TiC. It is noted, that additional carbon in the charge results in a fine alloy structure.
Keywords: metal matrix alloy ; titanium hydride ; ferromanganese silicon ; thermal synthesis ; master alloy ; phase formation

Production of Products of Various Shapes From Si3N4-Based Refractory Compounds by Spark Plasma Sintering by M. V. Zamula; A. V. Derevyanko; V. G. Kolesnichenko; O. B. Zgalat-Lozinskii; A. V. Ragulya (8-15).
The possibility of manufacturing ball-, cylinder-, and hollow cylinder-shaped products based on Si3N4 and TiN nanocomposites by spark plasma sintering (SPS) is demonstrated. The features of the product properties associated with different conductivity of composites. The mechanical properties of ball- and hollow cylinder-shaped materials measured: HV ~ 11.5 GPa, KIc ~ 4.1 MPa · m1/2 (for Si3N4); and HV ~ 12.7 GPa, KIc ~ 4.8 MPa · m1/2 (for Si3N4–TiN).
Keywords: titanium nitride; silicon nitride; spark plasma sintering; nanocomposites

Interaction Between Components of the Copper-Based Self-Lubricating Antifriction Composite at 900 and 950°C by A. G. Kostornov; O. I. Fushchich; T. M. Chevychelova; M. V. Karpets; A. Yu. Koval’ (16-22).
It is shown that a self-lubricating antifriction composite with microheterogeneous structure is synthesized during sintering of the Cu–Ni–P–MoS2 powder in hydrogen at 900 and 950°C. The structure of the self-lubricating antifriction composite formed at 900°C represents an α-solid solution of nickel in copper hardened by complex phosphide MoNiP, in which sulfide Cu2Mo3S4 is distributed. Molybdenum disulfide interacts with hydrogen at 950°C to form Cu2S and MoP. The structure of the self-lubricating antifriction composite formed at 950°C differs from the previous one in the amount of α-solid solution of nickel in copper, type (MoP) and content of hardening phase in it, and type (Cu2Mo3S4 and Cu2S) and amount of antifriction structural component.
Keywords: self-lubricating antifriction composite; sintering; temperature; interaction; structure; structural component; phase composition

Granular composite films based on BaB 6 –LaB 6 , Sn 0.9 Sb 0.1 O 2 , and alumina borosilicate glass produced by screen-printing followed by heat treatment are studied. To find the thicknesses of nanosized dielectric layers between the conducting particles, predetermining the conductivity mechanism and film properties, a novel calculation method is used. To evaluate the reliability of the results, film structures are studied by atomic force microscopy. The calculated data are in good agreement with the experiment. The method may be applied in examining the structure and properties of new conductor–dielectric composites.
Keywords: film ; dielectric layer ; conducting phase ; calculation ; atomic force microscopy

The effect of Sm content Li0.5Sm x Fe2.5–x O4 (x = 0, 0.05, 0.1, and 0.2) and sintering temperature on the phase evolution, microstructure, and bulk magnetic properties of lithium ferrite prepared by mechanical alloying is investigated. XRD results of pure samples confirmed that the single ferrite phase is formed after sintering at 800°C; however, increasing of samarium content led to the formation of secondary phase (SmFeO3) and enhanced intensity. The bulk magnetic properties decreased with increase Sm content and increased with sintering temperatures. Single-phase ferrites Li0.5Sm x Fe2.5–x O4 were produced by sintering of sample at 800°C, which is lower than the temperature associated with the conventional ceramic procedure.
Keywords: ferrites; high energy ball milling; magnetic properties; nanostructured material; sintering

The elastic properties and adhesion strength of double-layer coatings, produced by plasma-spray deposition of yttrium-stabilized zirconia onto a CoNiCrAlY alloy bond coat are studied. A model for determining the normal and shear stresses in a double-layer coating is developed. The fracture mechanisms in a plasma-sprayed ceramic top coat on a plasma-sprayed metallic bond coat are established. It is shown that the tensile load creates numerous cracks in the ceramic top coat that penetrate the metallic bond coat, resulting in further separation of the ceramic top coat. An increase in the thickness of the top coat alters the fracture mechanism.
Keywords: double-layer coating; plasma spray; adhesion strength; tensile test; modulus of elasticity; normal and shear stresses; powders

Properties of Ceramic Oxide Coatings on Magnesium and Titanium Alloys Synthesized in Electrolytic Plasma by N. Yu. Imbirovich; M. D. Klapkiv; V. M. Posuvailo; O. Yu. Povstyanoi (47-52).
The properties of ceramic oxide coatings on magnesium and titanium alloys are examined with electrolytic plasma oxidation. The oxide ceramics protect the alloys against corrosive environments. It is found that the ceramic oxide coatings increase the wear resistance of the alloys by 10–15 times and their corrosion resistance by one or two orders of magnitude compared to the starting metal.
Keywords: electrolytic plasma oxidation; ceramic oxide coating; magnesium alloys; titanium alloys; wear resistance; corrosion resistance

Structure and Tribotechnical Characteristics of NiAl–CrB2 Composite Materials and Coatings by A. P. Umanskii; E. N. Polyarus; M. S. Ukrainets; L. M. Kapitanchuk (53-59).
The influence of chromium diboride additions on the tribotechnical characteristics of NiAl–CrB2 composite coatings in friction against a counterface made of NiAl plasma-sprayed coating is studied. The friction surfaces of the plasma-sprayed composite NiAl coatings with different chromium diboride contents (5, 15, and 30 wt.%) are examined. It is established that wear substantially depends on the amount of refractory component.
Keywords: NiAl intermetallic; chromium diboride; composite coatings; high-temperature tribological tests; wear resistance

The consolidation of nanocomposite powders of refractory nitrides (TiN, Si3N4, AlN) in the microwave field (2.45 GHz) is studied. The structurization of sintered samples with aspect ratio l/h >>5 is examined. The structure and properties of the composites consolidated by microwave and conventional (resistance) heating are compared. The use of microwaves for sintering of bulk parts from Si3N4–Y2O3–Al2O3 and TiN–AlN nanocomposites with a great l/h ratio revealed a number of issues in producing homogenous nanoceramics.
Keywords: microwave sintering; TiN; Si3N4 ; AlN; structure

Synthesis and Properties of Si-Modified Biogenic Hydroxyapatite Ceramics by E. E. Sych; N. D. Pinchuk; V. P. Klimenko; I. V. Uvarova; A. B. Tovstonog; T. V. Tomila; Ya. I. Evich (67-73).
The paper examines the production of Si-modified biogenic hydroxyapatite ceramics. The introduction of methylsilicic acid hydrogel in amounts converted to 2 and 5 wt.% Si and subsequent sintering at 600°C increase the specific surface area by 10 times, from 6.1 to 59.8 m2/g. The porosity of ceramics increases from 43.0 to 62.3% when the modifying addition reaches up to 5 wt.%, the compressive strength being equal to 27–33 MPa. The modifying addition also influences the structure and reduces the minimum grain size of the material from 0.65 to 0.1μm
Keywords: hydroxyapatite; silica; biomaterial; specific surface area; structure

Tribotechnical Characteristics of Superhard Boron Nitride-Based Materials During Dry Friction of Like Pairs by A. A. Adamovskii; A. V. Bochko; A. D. Kostenko; V. T. Varchenko (74-79).
Friction units are made of superhard cubic boron nitride-based materials by vacuum brazing and subjected to end-to-end dry friction testing. It is established that the friction factor decreases as the modulus of elasticity of superhard material is decreased and the loading and friction speed are increased.
Keywords: friction factor; dry friction; wearing; superhard material; loading

Thermodynamic Properties of Binary Al–Ce and Ce–Fe Alloys by M. I. Ivanov; V. V. Berezutskii; M. A. Shevchenko; V. G. Kudin; V. S. Sudavtsova (80-92).
The mixing enthalpies of liquid alloys in the binary systems Al–Ce (at 1540 K in the composition range 0.7 < x Ce < 1) and Ce–Fe (at 1830 K in the entire composition range) are determined by calorimetry. The thermodynamic properties of liquid alloys are calculated in the entire composition range using the model of ideal associated solutions. The thermodynamic activities of components show large negative deviations from the ideal solution for the Al–Ce melts and small ones for the Ce–Fe melts. The mixing enthalpies correspond to exothermic effects. The minimum values of the mixing enthalpies of liquid alloys are −45.8 ± 2.2 kJ/mol at x Ce = 0.37 for the Al–Ce system (1870 K) and −1.0 kJ/mol at x Ce = 0.36 for the Ce–Fe system (1830 K).
Keywords: calorimetry ; melts ; thermodynamic properties ; enthalpies ; activities ; aluminum ; cerium ; iron

Interaction of Molybdenum with Cobalt–TiN and Cobalt–Copper Melts by V. V. Skorokhod; V. P. Titov; M. E. Golovkova; N. I. Filippov (93-100).
The solubility of molybdenum in Co–Cu and Co–Sn melts and the growth of Mo 6 Co 7 layer at the molybdenum–melt interface at 1200°C are examined. The solubility of molybdenum in these melts is well described by the equations: lgC Mo = −3.642 + 24.589 ⋅ C Co – 134.787 ⋅ C Co 2 (Co–Cu melt) and lgC Mo = −3.363 + 6.552 ⋅ C Co – 6.284 ⋅ C Co 2 (Co–Sn melt). The melt composition (in atomic fractions) in the three-phase Mo–Mo 6 Co 7 –melt equilibrium is established: C Co = 5.34 ⋅ 10 −3 , C Mo = = 3.05 ⋅ 10 −4 , the rest being Cu (Co–Cu melt); C Co = 0.176, C Mo = 5.7 ⋅ 10 −3 , the rest being Sn (Co–Sn melt). The substantial difference in growth rate constants in the melts (k Co–Sn >> k Co–Cu ) with the same cobalt activity α Co is attributed to the impact of admixtures (Cu and Sn) on the growth of the Mo 6 Co 7 layer. Data on the solubility of molybdenum in Co–Cu and Co–Sn melts and the growth kinetics of Mo 6 Co 7 are obtained for the first time.
Keywords: solubility ; three-phase equilibrium ; intermetallics ; layer growth ; molybdenum ; cobalt ; copper ; tin

Four different types of electrolyte (aluminate, silicate, borate, and phosphate) solutions were optimized to be used for the surface treatment of aluminum alloy 7075 by plasma electrolytic oxidation. Microstructure, phase composition, and corrosion resistance of ceramic coatings on the surface were analyzed by SEM, X-ray diffraction, and electrochemical work station. It was demonstrated that ceramic coatings prepared in aluminate solution had excellent continuity and a compact structure with micro hardness of HV 0.1 = 1100 MPa. The majority of all coatings consisted of γ-Al 2 O 3 and bits of α-Al 2 O 3 . The corrosion potential was increased to a small extent, while the corrosion current density was significantly reduced.
Keywords: electrolyte parameters ; ceramic coatings ; plasma electrolytic oxidation ; aluminum alloy

Processing of rice husk into SiC is the most efficient recycling method since it allows both of its constituents to be used: carbon and amorphous silica. Silicon carbide powder is synthesized from hydrothermally carbonized rice husk by nonisothermal heating at a rate of 3–10 °C/min to 1600°C in argon gas.
Keywords: rice husk; silicon carbide; hydrothermal treatment; nonisothermal heating

Interfacial Reaction in Cu–Se Diffusion Couples at Low Temperatures by Bin Yang; Hongqing Jiang; Jingen Zhang; Bai Xiong Liu; Hang Wang (115-118).
Interfacial reactions between Cu and Se using Cu–Se diffusion couples are studied. The investigation is carried out at temperatures of 150°C and 200°C. Heat treated diffusion couples are examined by energy dispersive spectroscopy coupled with scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Different intermetallic compounds are found to form at the interface: CuSe 2 at 150°C, Cu 2 Se and CuSe 2 at 200°C. The growth kinetics of the intermetallic compounds is followed the parabolic law. The incubation time for the intermetallic compounds is calculated. The formation of intermetallic compounds and its implication for designing novel layered composite brass materials are briefly discussed.
Keywords: interfacial reactions ; diffusion couple ; copper ; selenium ; compound layers

The paper examines the effect of operating parameters of new high-speed nickel-based composite bearing materials alloyed by molybdenum and tungsten and with additions of a solid lubricant, calcium fluoride CaF2, on the formation of dissipative secondary structures (friction films). It is shown that friction parameters substantially influence the nature of secondary structures responsible for antifriction properties. The wear mechanism of the materials is studied in different conditions of friction. Antiscoring films with smoothed microgeometry of contact surfaces are formed at 800–1000 rpm under a load of 6 MPa in air. In these friction conditions, the films ensure high wear resistance of the nickel-based bearing materials for rotary offset printing machines.
Keywords: high-speed bearings ; solid lubricant ; nickel ; operating parameters ; bifurcation mechanism ; attractor ; dissipative secondary structures ; antifriction properties ; rotary printing machines