Powder producing processes and properties

Kulmetieva V.B., Porozova S.E., Gnedina E.S.
Synthesis of nanocrystalline zirconium dioxide, stabilized by yttrium oxide, for low-temperature sintering
The process of synthesis of nanocrystalline zirconium dioxide powder stabilized by yttrium oxide by co-precipitation method has been developed, thus allowing to sinter ceramics on its base at temperatures lower than 1400 °С. Using X-ray diffraction, thermal desorption of nitrogen, and electron microscopy, the performances of zirconium dioxide powder depending on the synthesis conditions have been studied. The ultrasonic effect during elutriation of jelly-like deposits as well as powder degradation after drying and calcination allow improving the agglomerated state of the powder and diminishing the agglomerate size. Based on the data of thermomechanical analysis, decrease of heating rate down to the isothermal hold time temperature during sintering allows us to diminish predisposition of ceramics from nanocrystalline zirconium dioxide powder to zonal sintering.

Key words: zirconium dioxide, chemical synthesis, nanopowder, zirconium ceramics, presintering.

Onishchenko D.V., Popovich A.A., Wang Qingsheng
Synthesis of nanosized tungsten carbide powder for production of functional nanocomposite materials
Using mechanical synthesis and mechanical activation, promising nanometric tungsten carbide has been produced for creation of functional nanocomposite materials, being prospective for manufacture of cutting tools and anode electrodes. The structure formation of nanometric tungsten carbide has been investigated and the interaction regularities in the metal-nonmetal system are established.

Key words: tungsten carbide, nanocomposite materials, mechanical synthesis, mechanical activation, renewable plant raw materials.

Theory and processes of powder material formation and sintering

Pribytkov G.A., Korzhova V.V., Korosteleva E.N.
Solid-phase sintering of powder SHS-foundry alloys of the Al–Cr(Si,Ti) system
Volume changes, phase composition, and structure of materials sintered from two- and three-component Al-Cr(Si,Ti) powder alloys have been investigated during solid-phase sintering. Powders for sintering are produced by self-propagating high-temperature synthesis (SHS) in elemental powder mixtures of four target compositions followed by cake crushing and fines breeze screening. Sintering of all studied compacts resulted in volume shrinkage that expands steadily with growth of temperature and isothermal holding time. The results of structural investigations of sintered materials performed by X-ray crystallography, microX-ray spectrum analysis, optical and scanning electron microscopy are discussed in combination with the results of volume changes.

Key words: aluminum, chromium, powder alloys, solid state sintering, volume changes, phase composition, microstructure.

Ermilov A.G., Instrunina Yu.A., Levchenko V.S., Lopatin V.Yu.
Metalloorganic substances as a cold binder for pressing the powder
The possibility in principle is shown to use molybdenum-containing organometallic compound (Mo-OM) as a cold binder on the basis of the experiments concerned with introducing this compound in carbonyl iron powder. It was determined that introducing Mo-OM in carbonyl iron powder activates its sintering due to intensification of contact neck growth. The strength of samples obtained using Mo-OM is higher than those with synthetic rubber added. Higher adhesive capacity of Mo-OM as compared with synthetic rubber allows decreasing the volume fraction of cold binder approx. 1,5 times.

Key words: organometallic compound, cold binder, sintering activation, powder material microstructure

Self-propagating high-temperature synthesis (SHS)

Amosov A.P., Makarenko A.G. , Samboruk A.R., Seplyarsky B.S., Samboruk A.A., Gerasimov I.O., Orlov A.V., Yatsenko V.V.
Pelletization in powder technology of self-propagating high-temperature synthesis
Such a simple approach for artificial structure formation of the powder medium as green mixture pelletizing is popular in conventional powder technology but it has been used very seldom for realization of SHS processes. It is demonstrated by the examples of SHS processes of various types (with directional gas filtering, reducing stage, in aluminum melt, and combustion of thermit mixture) that batch pelletizing can significantly affect both the SHS process parameters and the SHS product properties.

Key words: SHS, powder, pelletizing, combustion, pressure, sintering, product, properties.

Sanin V.N., Andreev D.E., Yukhvid V.I.
SHS-metallurgy of pipes with wear-resistant protective coating with the use of technogenic waste of metallurgical productions
The possibility of recovering technogenic waste from metallurgical production and secondary raw material (aluminum) by self-propagating high-temperature synthesis (SHS) in the field of centrifugal forces and producing metal pipes with inner ceramic coating has been examined. The basic process operations of preliminary preparation of initial raw materials are completed and the functional components ensuring high abrasive durability are determined. The results of tests of prepared samples have shown that the durability of pipes with applied coating increases more than 20 times. The possibility of creating energy-effective SHS-process of recovering technogenic waste from the metallurgical production and manufacturing pipes with high abrasive resistance is shown.

Key words: self-propagating high-temperature synthesis (SHS), metal-ceramic pipes, abrasive resistance, ceramic coatings, secondary aluminum, technogenic waste, SHS in the field of centrifugal forces.

Refractory, ceramic, and composite materials

Artemiev A.A., Sokolov G.N., Dubtsov Yu.N., Lysak V.I.
Formation of composite structure of wear-resistant deposited weld metal with boride precipitation hardening
Development and formation of composite structure of wear-resistant alloy built-up by electroslag method by introduction of high-melting titanium diboride granules into welding pool have been investigated. The surfacing was executed with flux cored wires containing titanium diboride powder with granules of 5–30 μm in size the amount of which was varied in a range of 8–28 wt.%. Metallographic and durometric investigations as well as abrasion resistance tests of built-up specimens have been carried out. Ensuring increase in hardness and wear resistance of the coating, metal composite structure is shown to form in the process of surfacing. The ways of increase in wear resistance of built-up metal in the conditions of alloying by high-melting metal borides are specified.

Key words: composite structure, electroslag surfacing, titanium diboride, flux cored wire, abrasion resistance.

Babushkin A.V., Gordeeva A.V.
Experimental investigation of fatigue of powder structurally-nonhomogeneous material under biaxial (tension-twist) loading
The technique has been developed to study multiaxial fatigue of powdered material when using the equipment and the software of "Instron" (USA). The tests of powdered structurally-nonhomogeneous material on the basis of technically pure iron under the conditions of biaxial (tension-compression and twist) synchronous cyclic loading have been carried out. An analysis of their stress and strain state in the rupture zone is made. Using the obtained experimental results, fatigue curves are plotted. The experimental and design data are compared and the satisfactory coincidence of the results is obtained.

Key words: fatigue of powdered materials, service life, fatigue curve, strain cycling, stress and strain state.

Antonova N.M.
Adhesive strength of composite coatings with aluminum powder, which are dispersion-hardened with Zr particles
The effect of submicrometer zirconium particles on the adhesive strength of composition coatings (CC) with aluminum powder has been examined. Using electron microscopy, sedimentation of metal particles in CC has been investigated. It is found that the presence of small metal particles in CC and sodium chloride microcrystals is the factor improving the adhesive strength of coating with metal. A mechanism of NaCl microcrystal formation in CC is offered. A comparison of mechanical properties of coatings filled with aluminum powder with and without additives of zirconium.

Key words: composite coating, substrate, adhesive strength, filler, carboxymethyl cellulose, aluminum powder, zirconium powder, NaCl microcrystals.

Surface modifying, using charge-particle beams, photon and plasma fluxes

Rakoch A.G., Bardin I.V., Kovalyov V.L., Avanesyan T.G.
Microarc oxidation of light structural alloys. Part 1. The basic representation of microarc oxidation of light structural alloys
The method of microarc oxidation of materials is described; its advantages before traditional anodiс treatment for application of protective coatings onto the surface of light aluminum and structural alloys are shown as well as the basic provisions of the mechanism of this process are given how the authors of the present article understand them.

Key words: anodic treatment, microarc oxidation, light alloys, protective coatings.

Gadalov V.N., Ageev E.V., Romanenko D.N., Statinov V.V., Samoilov V.V., Grigoriev S.B.
On optimization of process of electrophysical machining of ball-bearing and tool steels62
The reasons and ways of improving wear resistance of the machining tool and machine components as well as the advantages and limitations of electrophysical methods have been considered. The processes of electrospark alloying and electro-acoustic application of coatings onto the tools and machine components are developed and optimized. The effect of electrospark alloying parameters on the surface layer roughness is investigated. The optimum conditions of VK and TK type alloy coating application are defined.Key words: cutting tool, wear resistance, rapid steel, hard alloy, electrophysical method of hardening.

Chronicle

Panov V.S., Vasina Zh.G.
In memoriam of Vladimir V. Basov
V.V. Basov’s works in the field of scientific grounds and processes of fuel pellets for a reactor of atomic power plants are annotated. His role in improvement of qualitative and operating performances of the fuel component used in the fuel element of atomic power station reactors is noticed. When the author participated in the works at OAO "Machine-Building Plant" (Electrostal city), the uranium-gadolinium pellet producing process was developed and successfully utilized, allowing to expand the reactor lifetime. It is shown that, thanks to the investigations executed under the guidance and with the participation of V.V. Basov, the qualitative and operating performances of fuel component are essentially raised, ways and techniques are developed for the further improvement of the fuel element properties for the purpose of burnup increase to more than 50 MW·day/kg of uranium.

Keywords: fuel, pellet, reactor, properties, density, porosity, grain size, pore shape, fuel element, microstructure, compaction, sintering, powder