Powder producing processes and properties
Kontsevoi Yu.V., Pastukhov E.A., Ignatiev I.E., Bulanov V.Ya., Ignatieva E.V.
Vibroaeratic mixing of powders in gas medium
Report 2. Calculation of kinematics of valve movement and powder flow, determination of optimal dimensions of mixer elements
The principles of determination of functional parameters and optimal dimensions of a mixing chamber and its working elements have been developed. By the example of mixer operation at vibration frequency f = 15 Hz and amplitude А = 0,006 m, the correction factors in the equations of dispersoid motions with open and closed valves have been obtained. Powder flow diagrams in the mixing chamber were plotted and analyzed, and, on this basis, the optimal dimensions of the valve were found to provide the specified time mode of its opening. The objective data of mixer operation are given in terms of charge material photography at 200X magnification and diffractograms of mixture compositions of four samples.
Key words: powder mass, finely dispersed powder, conglomerates, dispersoids, vibratory processing, vibroaeratic mixing, air stream, mixer.
Theory and processes of powder material formation and sintering
Matrenin S.V., Il’in A.P., Slosman A.I., Tolbanova L.O.
Iron powder sintering process activation by introduction of nanosized additions
The results of studying the effect of additions of nanosized iron powder (Fe-NP) produced by electric explosion technique on the industrial PZhV grade iron powder formation and sintering processes are given. The effect of Fe-NP added to the charge material on compactability and moldability of compacts; properties, microstructure, and phase composition of sintered material is analyzed. The electrically explosive Fe-NP is shown to be low-technologic. Containing as many as 20 % Fe-NP, charge materials based on PZhV grade coarse-grained powder have good compactability and moldability. Introduction of Fe-NP into charge material causes the activation of sintering process and facilitates producing sintered samples with fine-crystalline structure and improved physical-mechanical characteristics. The effect of Fe-NP additions on the effective sintering activation energy is evaluated.
Key words: activated sintering, nanopowder, compaction, microstructure.
Saifullin R.N.
Production of sintered powder bands with mesh wire by pulsed electric resistance rolling
A technique to produce sintered bands used for buildup-welding purposes is described by electric resistance rolling. Description of the device for band production is given. The conditions necessary for calculation of the modes of electric resistance rolling are given.
Key words: sintered band, electric resistance rolling, part rebuilding, coatings.
Litvinova T.A., Yegorov S.N.
Powder steel formation at the conditions of electric resistance compaction
Iron-graphite burden homogenization has been studied at the conditions of electric resistance compaction and the optimal technological conditions to form powder steel having bainite structure have been found. The effect of pressure applying and current passing durations, current density and compaction pressure on the degree of homogenization of powder steel to be formed is shown. The process conditions dependence of amount of free and fixed carbon has been determined. The microstructures of powder steel are given.
Key words: homogenization, electric resistance compaction, iron-graphite burden, structure formation, porosity, microstructure, microhardness.
Basov V.V., Panov V.S.
Some aspects of studying fuel compaction during repeated thermal treatment
The questions of interrelation of fuel reactor compaction under irradiation and its behavior during repeated thermal treatment (resintering) are considered. It is shown that fuel testing by its resintering allows us to control its quality, estimate the stability of the production process, and forecast its in-pile behavior by determination of the amount of unstable small pores in it. The main propositions of selecting the parameters of repeated thermal treatment of fuel are stated. Formulas are given to calculate its capacity to resinter.
Key words: in-pile behavior of fuel, reactor compaction, thermally activated compaction, irradiation compaction simulation, repeated thermal treatment, resintering, resintering procedure, temperature and time of tests, composition and moisture content of gaseous atmosphere, resintering capacity, resintering assessment.
Rusin N.M.
The effect of temperature and equal-channel angular pressing on powder shape and structure being formed in compacts
The results of studies to vary form and fragmentation of PA-2 grade aluminum powders of 300–500 μm in grain size, the briquettes of which have been subject to equal-channel angular pressing (ECAP) at the room temperature and 350 °C. ECAP was carried out in a number of routes up to five passes. The structure of samples was analyzed metallographically in longitudinal and cross sections. When carrying up ECAP at the room temperature including five-fold pressing (ε > 5,5), deformation fragmentation of initial powders does not occur. In case of hot ECAP after the fourth pass, the sample density is close to theoretical one. The structure of material produced by ВС and А routes consists of fine grains, and after ECAP by C route it has the duplex nature and includes both small and coarse grains.
Key words: aluminum powders, equal-channel angular pressing, structure.
Self-propagating high-temperature synthesis
Levashov E.A., Kudryashov A.E., Zamulaeva E.I., Pogozhev Yu.S., Sanin V.N., Andreev D.Е., Yukhvid V.I.
Particular qualities of formation, structure, composition and properties of electrospark coatings on ZhS6U nickel alloy in using KhTN-61 SHS-Ts
Particular qualities of mass transfer of KhTN SHS-Ts electrode material onto ZhS6U nickel alloy substrate in varying frequency (1000–1400 Hz) and duration (25–70 μsec) of pulsed discharges have been studied. A complex of studies of structure, composition, and properties of formed coatings has been carried out. The optimal frequency-energetic treatment mode (Е = 0,30 J, f = 1000 Hz, τ = 50 μsec) being characterized by high rate of coating growth with satisfactory degree of roughness of the surface layer is found. As a result of electrospark alloying (ESA) at the optimal energetic parameters, coatings of 40 μm thick, uniformity of 95 %, and microhardness of 5,2 GPa are formed on the surface of nickel alloy. The ESA processing of ZhS6U nickel alloy by KhTN SHS-Ts electrode material allows improvement of its wear resistance (more than 10 times), hardness (2,0 times), heat resistance and decrease in friction coefficient (5 times).
Key words: electrospark alloying, self-propagating high-temperature synthesis (SHS), electrode materials, coatings, substrate, pulsed discharge energy.
Refractory, ceramic, and composite materials
Grabovetskaya G.P., Mishin I.P., Kolobov Yu.R.
The effect of precipitating hardening on regularities and mechanisms of submicron-grain copper creep
Regularities and mechanisms of submicron-grain copper and Cu–1,1 vol.% Al2O3 dispersion-hardened composite within a temperature range of (0,2–0,35)Тm Cu have been investigated. The role of grain boundary condition and precipitating hardening of the cited material by nanosized (10–40 nm) Al2O3 particles in development of plastic deformation during creep has been analyzed.
Key words: submicron-crystalline structure, dispersion-hardened composite, creep, grain boundaries, grain-boundary slide, localization of deformation.
Porous materials and biomaterials
Lopatin V.Yu., Levchenko V.S., Yermilov A.G., Bogatyryova E.V., Mailyants I.А.
Production of porous materials from organometallic mixtures
Report 2
Surface and fracture morphology of high-porous materials produced by thermal destruction of organometallic mixtures has been investigated. The size and shape of pore channels in finished product is shown to be determined by particle size range and shape in organometallic mixtures. The effect of porosity on permeability and strength of sintered materials is analyzed. It is shown that permeability depends not only on the size but on the shape of pore channels. Overlapping of the powder metallurgy with chemical-metallurgical processes allows production of materials with 70–80 % in porosity and strength no lower than 5–25 MPa. Pore size being 10–100 μm, the material permeability was (in 10–12 m2): 1?3 for Mo; 0.5?6 for Mo–Ni; 2?6 for Ti–Mo.
Key words: porosity, pore channels, permeability, strength, surface and fracture morphology, molybdenum binder, diffusion interaction.
Bashkirtsev G.V.
Development of foundry alloy preparation method for production of high-porous permeable cellular chromal
The purpose of the work is an experimental study, simulation, and optimization of foundry alloy crushing methods. The kinetics of Fe–Cr–Al foundry alloy powder crushing carried out in drum and vibration mills was investigated. Particle sizes were measured by two techniques: light microscopy and specific surface area of powder. Necessary dispersability of foundry alloy (average particle size dp = 0,73 μm) in drum mill is obtained for 75 h in the alcohol environment. Crushing in the argon environment for 18 h (dp = 1,4 μm) is the optimal mode in vibration mill. As compared with drum mill, vibration mill cut time of foundry alloy preparation 1,5–2 times providing decrease in product cost.
Key words: high-porous permeable cellular materials, chromal, scale resistance, granulation.
Surface modifying, using charge-particle beams, photon and plasma fluxes
Yares’ko S.I.
The effect of cobalt phase composition in hard alloys on tool wear after laser hardening
Investigations of the effect of laser pulsed processing (LP) on the composition of cobalt phase of solid W–Co alloys and the operational characteristics of cut tool made on their basis have been carried out. The defining role of binding cobalt in the formation of alloy hardening mechanism has been found. The LP at the optimal modes results in additional dissolution of WC in Co binder and enrichment of the alloy surface layer in the zone of laser attack by cobalt. The indicated effects provide the improvement of tool durability at the conditions of adhesive-fatigue wear. The joint effect of LP and cutting modes on hardened tool durability are analyzed, and the conditions are determined when durability increasing is maximum one.
Key words: laser processing, hard alloy, Co-phase, tool durability, adhesive-fatigue wear.
Chronicle
Yevgeny Aleksandrovich Levashov is 50 years old
Viktor Vladimirovich Polyakov is 60 years old
