Powder Metallurgy and Metal Ceramics (v.55, #5-6)

Crystallographic Features of Nanosized Titanium Carbide Produced from Titanium and Carbon in a Planetary-Ball Mill by M. P. Saviak; O. B. Mel’nik; I. V. Uvarova; A. V. Kotko; O. O. Udovik (251-258).
Structural changes that occur in titanium during grinding of a powder mixture of titanium and carbon in an AIR-015M planetary-ball mill are studied. Grinding of the powder mixture results in the formation of titanium carbide single crystals with particles 7–50 nm in size over the entire reaction zone. At the initial stage of grinding, texturing of titanium occurs and the titanium lattice cell increases in volume, thus inducing internal stresses. Based on these data, it is suggested that the introduction of carbon into the strained titanium particles leads to stacking faults in the titanium hcp lattice, acting as nuclei of fcc titanium carbide in the titanium sites fragmented. Single-crystal TiC 10–20 nm nanoparticles are formed in these sites. The length of titanium–carbon contacts naturally increases with grinding time, giving rise to more nuclei of the new fcc phase. This promotes a mechanically induced self-propagating reaction. The heat generated in the reaction contributes to the sintering of titanium carbide nanoparticles. This results in the formation of particle aggregates 0.1–0.5 μm in size.
Keywords: mechanical synthesis ; titanium carbide ; crystal lattice ; stacking faults

Features of Brittle Material Powder Compaction During Pressing by M. S. Kovalchenko; T. P. Hrebenok; N. P. Brodnikovskii; A. A. Rogozinskaya (259-269).
The compaction of (i) titanium, vanadium, and molybdenum carbide powders, (ii) mixtures of these powders with the addition of nickel, chromium, and niobium carbide powders, and (iii) coarse titanium and tungsten carbides as well as diamond powders clad with cobalt under compressive loading with a constant rate on the powder in a die at room temperature is studied. Based on the variation of the relative density of the compacts with current pressure, the variation of stresses in the matrix (forming a porous body) with its strain is determined. This enables to reveal the features of compaction, strain hardening, and fracture of brittle powder particles during pressing. It is established that for the molybdenum carbide powder, consisting of powder particles with pronounced irregular shape, the initial elastic deformation of the matrix abruptly transits into the stage of plastic deformation with almost linear strain hardening. At the final stage of the powder compaction, the particles are fractured. At the initial stage of pressing, an increase in the packing density of the powder particles and in their strain hardening occurs for titanium and vanadium carbide powders, whose particle shape is close to the rounded. With the increase in the density of the porous body, it is observed an almost linear strain hardening of the matrix, which changes into decay with decreasing shear stress, when the powder body approaches its non-porous state. As a result of pressing, the size of the coherent X-ray scattering areas decreased to 62 nm and the dislocation density in the titanium carbide particles grew to 8.3 · 1010 cm–2. With an increasing content of plastic metallic particles in the matrix with the particles of brittle materials, it is the metallic particles that predominantly undergo the plastic strain with strain hardening. This causes a sharp increase in the total strain hardening, reducing the density of the porous body during pressing. It is established an effective compacting of coarse titanium and tungsten carbide powders with cobalt-clad particles 200–600 μm in size. In this case the variation of the stress in the matrix with the strain of the matrix has a sharp yield point associated with high elastic limit, significantly exceeding the yield stress, and the time delay in the transition from a purely elastic deformation of the body to its plastic flow.
Keywords: carbides powders; particles; mixture; pressing; compaction; strain hardening

This series of papers are devoted to the development of process approaches for producing complex composite inoculants to manufacture agricultural machines from spheroidal graphite cast iron. Complex composite inoculants as strips and their fragments can be produced by rolling of powder mixtures. The first paper justifies the choice of inoculants and characterizes the starting powders they consist of. Weight and volume correlations between the brittle and ductile components for different compositions of inoculants are calculated. It is established that all powder compositions belong to critical systems that have approximately 50 vol.% of both brittle and ductile components. Such systems require special process approaches to make high-quality products. Process characteristics of the powders that influence the quality of the rolling strips are determined. These are apparent density of the starting powders and their mixtures, friction index (Hausner ratio), and shear angle and its tangent.
Keywords: powders; cast iron; inoculant mixtures; rolling; strip

The Effect of Vanadium and Titanium on Mechanical Properties of Microalloyed PM Steel by S. Gunduz; M. A. Erden; H. Karabulut; M. Turkmen (277-287).
The effect of Ti and V additives on the microstructure and mechanical properties of microalloyed powder metallurgy (PM) steels is investigated. The microstructure of microalloyed PM steels is characterised with the help of optic microscope, SEM and EDS. The results showed that the addition of Ti and V elements has a beneficial effect on the improved mechanical properties. Ti–V microalloyed PM steels can be used to take advantage of improved grain refining propensity of titanium, whilst allowing vanadium to be used as dispersion strengtheners and to enhance the hardenability and transformation characteristics.
Keywords: powder metallurgy; microallyed steels; microstructure

The effect of intermetallic Ni3Al addition and heating mode on the electrochemical behavior of sintered austenitic (316L) and ferritic (434L) stainless steels is studied. The green compacts were sintered by conventional and microwave methods in solid state at 1350°C in H2 for a period of 60 min. The sintered samples were then subjected to several characterization techniques for evaluating their density and hardness, and finally their electrochemical response was evaluated through potentiodynamic polarization scan (1 mV/sec) in 0.1 N H2SO4. Upon addition of nickel aluminide, there was an increase in the densification of the composites, which was found more pronounced in case of 434L stainless steel with nickel-aluminide dispersoid composites. A positive response was also observed on the corrosion resistance of the composites as compared with the bare stainless steel compacts.
Keywords: stainless steel; sintering; intermetallic; density; hardness

Effect of Process Conditions on the Structure and Properties of the Hot-Forged Fe3Al Intermetallic Alloy by G. A. Baglyuk; A. I. Tolochin; A. V. Tolochina; R. V. Yakovenko; A. N. Gripachevckii; M. E. Golovkova (297-305).
Two kinds of powder mixtures are used for producing Fe3Al intermetallic alloys. The mixtures are prepared by mixing elemental powders in a drum mixer or grinding in a planetary mill. Compacted and sintered from this mixtures, the billets are subjected to the hot forging and annealing at 1100 and 1300°C. The effect of process conditions on the structure and properties of the materials produced is investigated. It is established that, after hot forging, the strength and fracture toughness of the intermetallic alloy produced from a ground charge are higher than those of the intermetallic alloy produced from non-ground charge. The annealing of the samples at 1100°C causes the decrease in the strength and fracture toughness of both alloys, while increasing the annealing temperature to 1300°C leads to some increase in these characteristics. The hardness of the intermetallic alloy prepared from non-ground powders is higher in comparison with that prepared from pre-ground charge and the annealing and its temperature increase lead to a noticeable decrease in the material hardness.
Keywords: Fe 3 Al intermetallic alloy ; powder ; charge ; hot forging ; microstructure ; mechanical properties ; grinding ; annealing

Basalt Scale-Reinforced Hydroxyapatite by N. V. Kaplunenko; N. V. Ulyanchych; V. D. Klipov; V. F. Gorban’ (306-311).
Production and physical and mechanical properties of basalt scale-reinforced hydroxyapatite (HAP) are described. The HAP samples reinforced with 5 and 10% of basalt scale are investigated after sintering at 700, 800, 900, 950, 1000, 1070, and 1250°C. X-ray analysis revealed the formation of the β-TCP (tribasic calcium phosphate) phase (typical for HAP produced by low-temperature synthesis) at 1250°C. The formation of this phase and a possibility to control the HAP–β-TCP ratio is very promising for producing materials with desired properties.
Keywords: hydroxyapatite ; basalt ; sintering ; pressing ; automatic indentation ; X-ray analysis

Small Energy Multi-Impact and Static Fatigue Properties of Cemented Carbides by Wei Liu; Zhen-hua Chen; Hui-ping Wang; Zhong-jian Zhang; Liang Yao; Ding Chen (312-318).
The small energy multi-impact (SEMI) and static fatigue properties of cemented carbides with different Co content (11, 15, and 18%) are studied. It is established that the cemented carbide with higher cobalt content ensures longer SEMI and static fatigue life, when the impact energy is lower than the impact fracture energy at one time and the static stress is lower than the bending strength (σbb). However, with the same value of λ (the ratio of the impact energy to the impact fracture energy at one time) and θ (the ratio of the static stress to the bending strength), the SEMI and static fatigue life of three alloys decrease with increasing the Co content. It is determined that the cemented carbide with a Co content of 18% has a higher dynamic fatigue and static fatigue sensitivity and corresponding weak fatigue crack propagation resistance, which means that high cobalt alloys need a higher safety factor under operating conditions. The static fatigue life of notched samples is lower than that of smooth samples. When θ equals to 0.8, the fatigue life ratio of three smooth samples and three notched samples (with Co content of 18, 15, and 11%) is approximately 1 : 2 : 7 and 1 : 1 : 2, respectively, indicating that pre-notched samples cover the defects of cemented carbides. The fracture of the hardmetals bearing low energy (SEMI and static fatigue) results from the growth and connection of holes (or coarse WC) and micro-cracks.
Keywords: cemented carbides ; small energy multi-impact ; static fatigue ; cobalt content

Structure and Properties of Permeable Highly Porous Glass-Ceramics for Orthopedics and Traumatic Surgery by E. E. Sych; A. P. Yatsenko; T. V. Tomila; A. B. Tovstonog; Ya. I. Yevych (319-327).
Highly porous glass-ceramics based on biogenic hydroxyapatite (50, 60, 66.7, and 70 wt.%) and glass of the SiO2–Na2O–CaO system are prepared using a replication method of the polymer template structure at 900°C. It is established that during sintering of the samples, the biogenic hydroxyapatite decomposes and reacts with the glass phase, which results in the formation of multicomponent glass-ceramics containing buchwaldite NaCaPO4, calcium phosphate silicate Ca5(PO4)2SiO4, calcium pyrophosphate Ca2P2O7, pectolite NaCa2Si3O8(OH), and hydroxyapatite Ca5(PO4)3(OH). The phase ratio in the prepared materials depends on the starting BHA : glass ratio. It is shown that all materials possess permeable open-pore structure with a total open porosity of 78–85%, which increases with content of biogenic hydroxyapatite in the starting composition. The prepared glass ceramics are adsorptive, satisfy structural and mechanical requirements for highly porous implant materials, and can be promising for the replacement of bone tissue defects in orthopedics and traumatic surgery.
Keywords: hydroxyapatite ; glass ; glass ceramics ; highly porous material ; replication of polymeric template structure ; implant

Comprehensive Characterization of Plasma-Sprayed Coatings Based Silver- and Copper-Substituted Hydroxyapatite by A. V. Lyasnikova; O. A. Markelova; O. A. Dudareva; V. N. Lyasnikov; A. P. Barabash; S. P. Shpinyak (328-333).
The physicochemical and biomedical properties of plasma-sprayed biocomposite coatings based silver- and copper-substituted hydroxyapatite powders on a titanium substrate are comprehensively studied and compared. Infrared spectroscopy shows that powder samples of all types correspond mainly to synthetic hydroxyapatite. Scanning electron microscopy confirmed the presence of metal-substituted hydroxyapatite nanoparticles in all coatings. The coatings are characterized by marked hydrophilic properties, the greatest ones being shown by silver-substituted hydroxyapatite coatings. The coatings produced from copper-substituted hydroxyapatites exhibit greater biological activity and the highest adhesion properties, but pronounced antimicrobial properties are possessed only by silver-substituted hydroxyapatite coatings.
Keywords: metal-substituted hydroxyapatite; plasma spraying; biocompatibility

The experimental data obtained for the Hf–Ru–Rh alloys at 0−50 at.% Hf in as-cast state and after annealing at subsolidus temperatures are used to construct vertical sections of the Ru–HfRu–HfRh–Rh partial system for the first time at 10, 25, 33.00 ± 0.33, and 37.5 ± 0.5 at.% Hf, as well as at 5 at.% Ru, by physicochemical analysis techniques. These sections demonstrate peculiarities of the phase diagram, in particular, temperature ranges of alloy crystallization and nature of phase transformations.
Keywords: phase diagram; alloy; annealing; vertical section; isopleth; temperature range of crystallization; phase transformation

Structural Phase Transformations in Zr50Co25Ni25 Alloy by O. L. Semenova; J.-C. Tedenac; O. S. Fomichev (339-346).
High-temperature X-ray diffraction is applied to study for the first time the structural phase transformations in the Zr50Co25Ni25 alloy at 30–800°C. It is shown that this alloy contains one phase at room temperature, with an orthorhombic crystal structure of CrB type. When temperature increases to 400°C, this phase transforms into a tetragonal phase of AuCu type. A phase with a cubic crystal structure of CsCl type and a monoclinic one of TiNi type show up at 800°C. The TiNitype phase remains up to room temperature when the sample is cooled down.
Keywords: crystal structure; phase; high-temperature martensitic transformations

Synthesis of Barium Cuprate by Secondary Induction Heating and its Electrical Properties by S. A. Nedil’ko; I. V. Fesych; O. G. Dzyazko; A. S. Bulachok; S. O. Solopan; T. O. Plutenko (347-354).
Barium cuprate has been synthesized using secondary induction heating. It is found that the single-phase product is formed when the equimolar mixture of Ba(NO3)2 and CuO is kept in the induction furnace for 40 min at 1173 K. Reflections in the diffraction patterns are indexed in cubic syngony (space group Im3m). Parameters of the unit cell are refined applying the Rietveld method: a = = 1.82996(7) nm and V = 6.1281(7) nm3 (R Bragg = 4.42% and R f = 3.61%). Iodometric titration data show that a half of the copper atoms are in oxidized state in BaCuO2.25. Partial oxidation of copper (Cu2.5+) influences the electrical properties of the synthesized cuprate, examined using impedance spectroscopy within the range 453 K ≤T ≤ 593 K. The electrical conductivity of BaCuO2.25, which is nonstoichiometric toward oxygen, exhibits semiconducting nature with activation energy E dc = 0.29 eV.
Keywords: barium cuprate; secondary induction heating; oxygen nonstoichiometry; impedance spectroscopy; electrical conductivity

Interaction of ZrB2–MoSi2 Ceramics with Basalt Melt by T. V. Mosina; I. P. Neshpor; O. M. Grigoriev; V. V. Pasichnyi; V. P. Konoval; G. F. Gorbachev; O. O. Zubarev (355-360).
The interaction mechanism in the (ZrB2–MoSi2) composite–molten basalt system is studied at different temperatures to examine the use of boride ceramics to replace platinum alloy for the manufacture of bushings. The wetting in the (ZrB2–MoSi2)–basalt system and the formation of a stable interaction area of limited thickness testify that the material is suitable for the manufacture of bushings to produce basalt fibers.
Keywords: ceramic material; basalt; bushing; wetting

High-Temperature Phase Transformations in Multicomponent Fecocrnival Alloy by M. V. Karpets; O. S. Makarenko; V. F. Gorban’; M. O. Krapivka; O. A. Rokitska; S. Yu. Makarenko (361-368).
The phase transformations proceeding in as-cast high-entropy FeCoCrNiVAl alloy are studied using high-temperature in situ X-ray diffraction in a helium atmosphere at 293–1273 K. In starting state, this alloy is a single-phase bcc solid solution ordered according to B2 type. It is found for the first time that a tetragonal σ phase of CrFe type forms at 1073 K on the alloy. The surface layer of the σ phase is ~22 μm thick. The influence of annealing on variation in phase composition of the highentropy alloy is analyzed. Optical and scanning electron microscopy is employed to examine the alloy microstructure. The microhardness and reduced Young’s modulus of the high-entropy alloy are determined at room temperature.
Keywords: high-entropy alloy; high-temperature in situ X-ray diffraction; solid solution; σ phase; microhardness; microstructure

Effect of the Coating Type on Retaining SiC Particles in the Composite During Grinding by V. P. Bondarenko; O. V. Evdokimova; A. A. Matveichuk; T. M. Duda (369-373).
The problem of retaining coarse (150 μm) SiC particles in the composite during grinding with a cup diamond wheel with fine grains (20/14 μm) is considered. SiC particles are coated with Co, Ni, Cu, and WC and are referred to as SiC(Co), SiC(Ni), SiC(Cu), and SiC(WC), respectively. The prepared powders are pressed in a steel die with a diameter of 8.15 mm. The compacts are 5–8.5 mm in height. The compacts are sintered in hydrogen at 980–1470°C with holding for 1–2 h. In addition, the samples containing SiC(WC) particles are impregnated with WC + Ni eutectic melt (VN65). Metallographic analysis shows that in the samples containing SiC(Co), SiC(Ni), and SiC(Cu), SiC particles cannot be retained during grinding because of the formation of brittle silicides, when sintering. In case of WC-coated SiC particles, most of the SiC particles do not leave the composite during grinding. When SiC(WC) samples are impregnated with TN65 eutectic mixture, most of the SiC particles do not leave during grinding.
Keywords: coating; grinding; retention; particles; composite

The wear-resistance of powder cobalt alloys with titanium carbide is studied in fretting corrosion conditions at 20, 300, 650, 800, and 1050°C under varying loads and durations. The alloys of different porosity are obtained by hot pressing of the powders of cobalt, chromium, aluminum, iron, and titanium carbide. The wear of alloys with 30, 50, and 70 vol.% carbide is determined. The dependence of the average linear wear of powder alloys on the sample porosity and loads during the tests is established. The wear-resistance of alloys is mainly affected by the temperature: the average linear wear rate increases with increasing temperature, regardless of the carbide content. The results are the basis for choosing the optimal alloy composition for the field tests during developing friction materials for aviation applications.
Keywords: wear resistance; powder cobalt alloys; titanium carbide; loads