Powder Metallurgy and Metal Ceramics (v.54, #7-8)

Effect of Shock Compaction on the Synthesis of Silicon Carbide by A. V. Kurdyumov; V. F. Britun; V. V. Yarosh; A. I. Danilenko (381-389).
The process of SiC synthesis during shock compaction of silicon and carbon black powdered mixtures is investigated. Shock wave treatment of mixtures is carried out in cylindrical container and the shock wave is generated by projecting the outer shell. The variation in the fraction of Si reacted with C and SiC with the composition and density of the charge is investigated. Thermal effects of the shock compaction and exothermic reaction of silicon with carbon and the temperature of shock wave synthesis are determined taking into account the dependence of the melting parameters of Si and the formation enthalpy of SiC on pressure. It is established that, during shock compaction, the melting of silicon is accompanied by coalescence of Si particles that inhibits the interaction of Si with C and reduces the SiC yield at high concentrations of Si in the mixture. The optimal composition of the mixture providing the highest SiC yield is found.
Keywords: silicon ; carbon black ; silicon carbide ; shock compaction ; temperature ; pressure ; interaction degree

Three-Layer Al/Al–B4C Composite Material Prepared by Casting and Hot Rolling by Yingshui Yu; Jinchuan Jie; Shuang Zhang; Jinghan Tu; Tingju Li (390-396).
Casting and hot rolling are proposed to verify a semi-continuous casting and hot rolling process to produce a three-layer Al/Al–B 4 C metal-cermet composite. The outer layer is pure Al, the inner layer is Al matrix composite reinforced with B 4 C particles (the mass fraction of Al and B 4 C are 62.36 and 37.64%, respectively). The results show that the reinforced particles are distributed in the inner layer homogeneously, and both layers are sintered together with no pores or flaws. The clad ratios of the composites of 26, 5, 3, and 1 mm are 50.28, 54.67, 61.23, and 57.46%, respectively. The Vickers hardness varies from 46 HV for the outer pure aluminum layer to 158 HV for the inner composite layer in 3 mm specimen, indicating totally different properties in different layers.
Keywords: three-layer composite ; Al ; B 4 C ; hot rolling ; clad ratio

Improving Uv Radiation Absorption by Copper Oxide NPs/PMMA Nanocomposites for Electrical Switching Applications by V. Doddapaneni; Yichen Zhao; Fei Ye; R. Gati; H. Edin; M. S. Toprak (397-401).
Nanocomposites based on the radiation absorbing polymer (PNCs) are of interest for a variety of applications including circuit breakers, UV-shielding windows, contact lenses, and glasses among others. Such PNCs can be made by incorporating suitable radiation absorbing nanoparticles into a polymeric matrix by in situ polymerization. In this study, spherical nanoparticles (5–6 nm) of oleic acid (OA) surface modified cupric oxide (CuO) are synthesized and used to improve the ultra-violet (UV) radiation absorption property of a polymer matrix, i.e., polymethylmethacrylate (PMMA). The synthesis of spherical CuO nanoparticles, surface modification using OA, dispersion of CuO nanoparticles with different concentrations in PMMA, and UV radiation absorption property of the resultant PNC are investigated. Two different PNCs are produced using OA modified CuO nanoparticles with different concentrations. As synthesized CuO nanoparticles and OA modified CuO nanoparticles are examined by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR) techniques. The UV absorption edges are evaluated from the UV-Vis absorption spectra by using UV-Visible absorption spectroscopy. The results show that the UV radiation absorption of the PNC with higher concentration of CuO nanoparticles is improved compared with PMMA and the absorption edge moved towards longer wavelengths i.e., from 271 to 281 nm. These PNCs are successful in arc interruption process by absorbing a broad range of radiation emitted from high-energy copper arcs produced in the circuit breakers.
Keywords: polymer-based nanocomposites; cupric oxide; UV-absorption; nanoparticles; circuit breaker

Producing Nanodispersed Composite Nitride Powders by Nitriding of Precursors by L. A. Krushinskaya; G. N. Makarenko; I. V. Uvarova (402-409).
Highly dispersed and nanodispersed composite powders based on Si 3 N 4 –TiN, Si 3 N 4 –CrN, BN–AlN, and BN–Si 3 N 4 non-metallic nitrides are produced by nitriding of precursors. The main criteria for selecting precursors for the synthesis of these powders are determined. Features of the processare analyzed for powders of TiSi 2 , CrSi 2 , B 4 Si, and AlB 2 precursors in both mechanically activated and non-activated conditions. It is established that the mechanical activation of precursors substantially decreases the temperature of nitride formation and enables synthesizing nanodispersed composite nitride powders with a particle size of 30–70 nm. In comparison with the specimens produced from the powders synthesized by conventional techniques, the specimens produced by hot pressing and spark plasma sintering possess a highly dispersed microstructure with a uniform distribution of phases and advanced physical and mechanical properties.
Keywords: precursor ; mechanoactivation ; silicide ; nitride ; nitriding ; nanodisperse powders ; chemical bonds ; whiskers ; particles

A Simple Method to Synthesize Nanosized Li2TiO3 Powders Through High-Energy Ball-Milling by Jian-Li Ma; Zhi-Fen Fu; Juan Gao; Xiao-Sen Zhang (410-415).
Monoclinic Li 2 TiO 3 phase is prepared from Li 2 CO 3 and TiO 2 mixtures by using a high-energy ball milling method, combined with subsequent calcinations at low temperature. Pure phase Li 2 TiO 3 nanopowders with the average particle size of 36.8 nm are obtained from the precursor milled for 20 h and calcined at 500°C for 5 h, i.e., 300°C lower than required by a conventional solid state reaction process or chemical routes. It is suggested that high-energy ball-milling method is a simple and practical route to synthesize Li 2 TiO 3 nanopowders.
Keywords: nanopowders ; mechanical alloying ; X-ray diffraction ; microstructure

Structure and Properties of Kh20N80 Alloy Powders Produced by Impact Sintering at Different Temperatures by A. V. Laptev; A. I. Tolochin; D. G. Verbilo; I. Yu. Okun (416-427).
The compaction, structure, and mechanical properties of Kh20N80 powder samples are studied. Most of the powder particles were 25 μm in size. The powders were compacted by impact sintering in vacuum at 1100, 1150, 1200, 1250, and 1300°C at an impact energy of 1200 J/cm 3 . Isothermal holding at these temperatures lasted for 20 min, vacuum during heating and compaction was maintained at 0.013 Pa, and initial strain rate was 6.5 m/sec. The rectangular bars cut out of cylindrical disks were used to determine the density, electrical resistivity, tensile strength, fracture toughness or fracture work of a notched sample, Brinell hardness, compression strength, and plasticity of the samples in various test conditions. It is shown that the mechanical properties of Kh20N80 samples subjected to impact sintering at 1100–1300°C correspond to those of standard Kh20N80 alloy obtained by conventional melting and forging techniques. In particular, the average tensile strength varies from 630 to 740 MPa and compression strength from 800 to 830 MPa. The plasticity of the samples evaluated from necking changes from 30 to 54% with compaction temperature increasing from 1100 to 1300°C. The average plastic strain energy at break of a notched sample increases from 19.5 to 36.0 J/cm 2 .
Keywords: Kh20N80 nichrome alloy ; impact sintering ; structure ; properties

Effect of the Material and Sliding Rate of the Counterface on the Tribotechnical Properties of a CM(Ti–Mo–BN)–Steel Friction Pair by A. G. Kostornov; O. I. Fushchich; T. M. Chevychelova; V. T. Varchenko; O. D. Kostenko (428-435).
The effect of the material and sliding rate (1, 2, 4, 6, and 15 m/sec) of the counterface on the tribological characteristics of a (composite Ti–Mo–BN)–counterface (steels 45, 65G, ShKh15, 40Kh, and Kh18N9T, nitrided titanium, and BrO10 bronze) friction pairs in dry friction in air under a pressure of 0.8 MPa is investigated. It is established that, under these friction conditions, the composite in pair with BrO10 bronze is ineffective. During friction of the composite in pairs with steels 45, 65G, ShKh15, 40Kh, and Kh18N9T, an increase in the sliding rate from 1 to 6 m/sec results in an increase of the friction coefficient, linear wear of the friction pairs, mass loss of the composite and counterface, whereas the temperature of the friction surface increases. The highest temperature of the friction surface of the composite is reached in pair with steel 45. The temperature, sliding rate, and pressure applied lead to the synthesis of a secondary film (on the surface of the composite) of such a phase composition and structure that provide (in pair with steel 45) higher tribological characteristics of the composite than those in pairs with the other steels. At all sliding rates of the counterface, the tribological properties of the friction pairs depend not only on the properties of the composite material (chemical and phase composition, structure, and mechanical characteristics), but also on the same properties of the counterface material.
Keywords: composite material; friction pair; counterface; friction coefficient; linear wear of friction pair; mass loss of composite material; mass loss of counterface; steel; tribological properties; composition; structure

A complex nitride (Ti, Zr)N coating on chromium carbide steels Kh13M2–30 vol.% Cr 3 C 2 and Kh17N2–30 vol.% Cr 3 C 2 is obtained. The optimal deposition conditions are determined. The effect of deposition time on the hardness, structure, adhesion strength, and wear resistance of coatings during sliding friction (counterface—steel ShKh15) is investigated. It is established that annealing at 900–1200°C promotes an active interaction of the coating elements with the substrate accompanied by the formation of a transition zone. It is found that the (Ti, Zr)N coatings produced at nitrogen pressure P = 2 Pa, spray-off distance d = 230 mm, and deposition time 30–40 min possess the best mechanical and tribotechnical properties.
Keywords: carbide steel ; complex nitride ; coating ; durability ; deposition ; tribotechnical properties

Low-Temperature Synthesis of α-Al2O3 by E. V. Dudnik; Ya. S. Tishchenko; V. V. Tsukrenko; A. K. Ruban; V. P. Red’ko; V. M. Vereshchaka (444-449).
The paper examines the low-temperature γ-Al2O3 → α-Al2O3 phase transformation in γ-Al2O3 powder for chromatography with AlF3 mineralizer. Changes in the AlF3 amount (2–3 wt.%) and isothermal holding time at 850°C allow variation in the powder phase composition, specific surface area (from 85.5 to 0.2 m2/g), and morphology (from spheroids to lamellas). The experimental results serve as a basis for designing precipitation-strengthened composites consisting of a ZrO2 solidsolution matrix and a strengthening α-Al2O3 phase.
Keywords: ZrO2–Y2O3–CeO2–Al2O3–CoO system; AlF3 ; low-temperature phase transformation; γ- Al2O3 ; α-Al2O3

Synthesis, Characterization, and Sintering of Yttrium Aluminum Garnet Powder Through Double Hydrolysis Approach by Xianxue Li; Tareque Odoom-Wubah; Zhangxu Chen; Bingyun Zheng; Jiale Huang (450-454).
A double hydrolysis approach is first adopted to prepare yttrium aluminum garnet (YAG) powders using Y(NO3)3 · 6H2O and NaAlO2 as raw materials. A variety of techniques, such as thermogravimetry/differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are employed to characterize the as-synthesized samples. The results show that pure-phase YAG powders are accurately available at 900 °C and above. Among these, the YAG powders, produced at 1100°C, are elliptic in shape, with an average particle size of ~44 nm. Pellets of pressed YAG powders are sintered in vacuum at 1700°C for 8 h, resulting in a dense and nearly pore-free microstructure with an average grain size of ~7 μm.
Keywords: YAG ; double hydrolysis ; synthesis ; powder

Phase Equilibria in the Ti–Ti5Si3–Dy5Si3–Dy Region of the Ti–Dy–Si System by M. V. Bulanova; Yu. V. Fartushna; K. A. Meleshevich; A. V. Samelyuk (455-464).
Differential thermal analysis, X-ray diffraction, and metallography are employed to examine the phase equilibria in the Ti–Ti5Si3–Dy5Si3–Dy region of the Ti–Dy–Si system. Isothermal sections at 1100 and 900°C, vertical sections at 5Si, 65Ti, and 65Dy isopleths, and a reaction scheme are constructed. The ternary compound TiDySi (τ) exists at experimental temperatures and has no appreciable homogeneity range. The isothermal sections at 1100 and 900°C are similar and characterized by five three-phase regions (β + (α-Dy) + τ, β + (Ti3Si) + τ, (Ti3Si) + τ + (Ti5Si3), (α-Dy) + τ + (Dy5Si3), and (Ti5Si3) + τ + (Dy5Si3)) and respective two-phase fields. Three invariant four-phase equilibria are found in solid state: β + (Ti5Si3) ⇄ (Ti3Si) + τ (U3), β + τ + (Ti3Si) ⇄ α (P2), and β + τ + (α-Dy) ⇄ α (P3) at ~1150, 900, and 885°C, respectively. There is also a threephase equilibrium, β + τ ⇄ α, at 845°C (p4). The phase equilibria are summarized in the reaction scheme.
Keywords: Phase diagram ; Liquidus surface ; Solidus surface ; Melting diagram ; Isothermal sections ; Vertical sections ; reaction scheme

Thermodynamic Properties of Binary In–Ni Alloys by M. I. Ivanov; V. V. Berezutskii; M. O. Shevchenko; V. G. Kudin; V. S. Sudavtsova (465-470).
The mixing enthalpies of liquid binary In–Ni alloys (0.85 < x Ni < 1) at 1800 K were determined by isoperibol calorimetry. The thermodynamic properties of the In–Ni alloys were calculated for the entire composition range using the model of ideal associated solutions. The thermodynamic activities of melt components show negative deviations from the ideal behavior. The mixing enthalpies are characterized by moderate exothermic effects. The minimum mixing enthalpy of the melts is –12.0 ± 0.1 kJ/mol at x Ni = 0.59.
Keywords: mixing enthalpy; isoperibol calorimetry; In–Ni alloy; model of ideal associated solutions

Cocrystallization of Max-Phases in the Ti–Al–C System by S. V. Sleptsov; A. A. Bondar; V. T. Witusiewicz; U. Hecht; B. Hallstedt; V. M. Petyukh; O. I. Dovbenko; T. Ya. Velikanova (471-481).
The structure and phase transformations in the Ti–Al–C system were studied by X-ray diffraction, differential thermal analysis, and scanning electron microscopy, including energy-dispersive X-ray spectroscopy and electron backscatter diffraction on samples obtained by arc melting and annealing at high temperatures. The ternary system has a cocrystallization region for the two MAX-phases, N and H. The Ti41.5Al38.5C20 samples contain three phases at all experimental temperatures (from 650 to 1660°C): Ti3AlC2 (N-phase of Ti3SiC2 type), Ti2AlC (H, Cr2AlC type), and binary intermetallic TiAl3 (ε, its own crystal type). The morphology of the as-cast alloy and annealed samples (at temperatures above and below the solidus temperature, 1660 and 1250°C, respectively) shows that invariant solidification at 1405°C (solidus temperature) precedes the univariant simultaneous solidification of N- and H-phases, i.e. both MAX-phases separating from the melt.
Keywords: Al–Ti–C system ; MAX-phases ; Ti 3 AlC 2 ; Ti 2 AlC ; solidus

High-Temperatures Oxidation of AlN–TiCrB2 Composites. I. Kinetics and Mechanism of Air Oxidation Up to 1600°C by V. A. Lavrenko; V. P. Konoval; A. D. Panasyuk; A. P. Umanskii (482-489).
Thermal gravimetry and differential thermal analysis are employed to study the oxidation resistance of AlN–TiCrB2 materials in air up to 1600°C. The kinetic curves for the materials are parabolic, indicating that oxidation leads to the formation of dense oxide layers preventing oxygen diffusion deep into the samples. With increasing TiCrB2 content of the composite, its oxidation resistance decreases since B2O3 appears in and evaporates from the oxide film, resulting in its partial failure. The oxidation rate constants and activation energies are calculated for different temperature ranges with the Arrhenius equation based on collisions of oxygen molecules on the samples. The data obtained indicate that the oxidation mechanism is dependent on the material composition and temperature.
Keywords: aluminum nitride; titanium–chromium boride; high-temperature oxidation; kinetics and mechanism; activation energy

Structural and Phase Transformations in Fe–Al Intermetallic Powders During Mechanochemical Sintering by A. L. Borisova; I. I. Timofeeva; M. A. Vasil’kovskaya; A. N. Burlachenko; T. V. Tsymbalistaya (490-496).
The paper examines the structural and phase transformations in Fe–Al powders after mechanochemical sintering followed by heat treatment. The intermetallics are sintered through a series of successive stages, each resulting in a nanosized product. The amount of energy required for the formation of a single-phase intermetallic compound increases with aluminum content of the intermetallic phase (from Fe3Al to FeAl and then to Fe2Al5).
Keywords: mechanochemical sintering; intermetallic; phase; solid solution; X-ray diffraction

Phase Boundaries and Interfacial Energy in Quasibinary Boride and Metal Ceramic Eutectic Systems by D. A. Zakaryan; V. V. Kartuzov; A. V. Khachatryan (497-502).
The a priori pseudopotential method is employed to propose a model by which phase boundaries form in quasibinary eutectic systems. Interfacial energy for boride and cermet quasibinary eutectic composites, LaB 6 –TiB 2 and LaB 6 –ZrB 2 , is calculated for different temperatures.
Keywords: eutectic ; phase boundary ; interfacial energy ; a priori pseudopotential

Complex Oxidation-Resistant Coatings for Blades of Gas Turbine Engines by V. I. Zmii; S. G. Ruden’kii; E. V. Timofeeva; A. A. Korneev; V. V. Kunchenko; Yu. V. Kunchenko; T. P. Ryzhova; M. Yu. Bredikhin (503-507).
Multicomponent coatings on ZhS26 oxidation-resistant nickel alloys produced by liquid-phase activated diffusion process and self-propagating high-temperature synthesis are studied to protect turbine engine blades against high-temperature gas corrosion. Thermodynamic analysis of potential reactions in conditions of diffusion coating and chromium plating in a multicomponent mixture is carried out. Results of X-ray diffraction and high-temperature corrosion resistance of the coatings at 1200°C are presented. The coatings are corrosion-resistant and self-healing. Their oxidation resistance is much higher than that of the uncoated alloy.
Keywords: vacuum activated diffusion coating ; complex coating ; oxidation-resistant coating