Theory and processes of powder material forming and sintering
Kostikov V.I., Yeremeeva Zh.V., Dorofeev V.Yu., Zherditskaya N.N.
Structure formation and properties during heat treatment of powder steels with various carbon-containing components
The effect by heat treatment on the formation of the structure of hot-stamped powder carbon steels, which contain various carbon-bearing components, has been determined. Such processes of heat treatment as quenching, tempering, and annealing have been investigated. The initial structure inheriting was observed in all stages of heat treatment.
Key words: powder carbon steels, carbon-containing components, quenching, tempering, annealing.
Romanov G.N.
Liquid-phase sintering of the Al–Si system powder bodies
Liquid-phase sintering of the Al-Si system powder bodies is carried out in two stages: increase in volume (growth) of powder bodies (the first stage) and shrinkage (the second stage). Volumetric changes are caused by diffusion by nature of interaction of two metals, one of which is in the liquid state. The mechanisms of polyhedral structure formation are dissolution of aluminum particles and melt crystallization on undissolved particles when cooling and the process of dissolution-precipitation in the conditions of holding at constant temperature.
Key words: liquid-phase sintering, powder body, dilatometry, growth, shrinkage, diffusion, polyhedral structure, melt.
Basov V.V., Petrov I.V., Panov V.S.
Investigation of the effect of parameters of fuel pellets on their endurance under thermal shocks
The parameters of tests and the main results of investigations related to the behavior of VVER and RBMK type domestic fuel pellets in affecting thermal shocks on them are described. Pellets with fine grain structure and high level of closed porosity are shown to be more resistant to damages that can arise in the pellets in the starting sequence, reactor power maneuvering as well as in case of cladding failure. Pellet strength decreases when the grain size increases to ≥ 25 μm. Simultaneously, the residual strength of pellets to failure thus resulting in loss of their integrity is reduced as well.
Key words: fuel pellets, power maneuvering, linear power increase rate, thermal shocks, gas-vapor mixture, pellet microstructure, grain size, porosity, critical temperature drop, crack size, initial and critical residual strength, failure morphology.
Self-propagating high-temperature synthesis
Shiganova L.A., Bichurov G.V., Amosov A.P., Titova Yu.V., Ermoshkin A.A., Bichurova P.G.
Self-propagating high-temperature synthesis of nanostructured titanium nitride powder with the use of sodium azide and titanium-containing halide
The use of the "(NH4)2TiF6 ammonium hexafluorotitanate – NaN3 sodium azide" system in the SHS process has allowed us to obtain nanosrtuctured titanium nitride powder. Using similar "halide of element to be nitrided – sodium azide" systems, nanopowders of silicon, boron, and aluminum nitrides were produced by the SHS. It is confirmed that the use of element compounds in the starting powder mixture for the SHS instead of pure elements allows us to reduce essentially the dimension of combustion product structure and obtain them in the form of nanostructured particles, nanofibers, and nanopowders.
Key words: titanium nitride, sodium azide, ammonium hexafluorotitanate, nanostructured powder.
Refractory, ceramic and composite materials
Kachenyuk M.N.
Production and wear resistance study of titanium carbosilicide based composite material
Titanium carbosilicide based composite material (CM) with the content of 50 % titanium carbide having microcrystalline structure has been produced by mechanosynthesis in a planetary mill followed by hot compaction. High-nonequilibrium structure of powder material obtained at the cost of high-energy processing allowed us to produce the material with relative density of 96 % at the hot compaction temperature of 1400 °С and pressure of 20 MPa. Comparative wear tests of produced CM and silicon carbide show lesser wear of a counterbody and lesser friction coefficient, however wear of the composite material itself is observed in case of using the abrasive medium.
Key words: mechanosynthesis, titanium carbosilicide, composite material, hot compaction, wear resistance, microstructure.
Porous materials and biomaterials
Litvinova T.A., Yegorov S.N.
The effect of technical regimes of electrocontact compaction on powder steel porosity
The effect of duration of applied pressure and passage of current, current density and compacting pressure on the powder steel porosity is shown. The regime process dependence of quantity of combined carbon in the iron-graphite composition has been found. A comparison of iron powder and iron-graphite composition porosity has been carried out at different regimes of electrocontact compaction.
Key words: electro-deformation impact, electrocontact compaction, iron-graphite composition, intensification, localization, porosity.
Surface modifying, including by charged beams, photon and plasma fluxes
Potyomkin G.V.
Implanter with compounded ion beam for modification of construction material surface properties
An accelerator for energy of single-charged ions as high as 70 keV and total current as high as 100 mA has been designed for modification of construction material properties. The two-stage universal ion source at low-pressure discharge with target sputtering by plasma allows us to produce gas and drip-free compounded beams of charged particles with controlled Ме+/Г+ ion ratio in the accelerator operating as a bipolar diode.
Key words: modification, ion source, sputtering, gas-vapor plasma, compounded ion beam.
Blinkov I.V., Anikin V.N., Kratokhvil R.V., Ivanov A.N. , Petrzhik M.I., Mikhalsky Yu., Nakonechny A.
Production and properties of wear-resistant combined PVD/CVD-coatings on cemented carbide tool
Investigations of structure and phase formation processes in producing combined PVD/CVD-coatings on cemented carbide tool have been carried out. Creation of PVD-barrier layer from Cr is shown to impede the formation of η-phase during the subsequent application of TiC–Ti(C,N)–TiN CVD-coating. Processing of CVD-coating by ion-plasma flux and application of finishing TiN PVD-layer result in formation of {111} texture and its subgrain refining as small as 30 nm in the coating. Strength of coated carbide blades and their hardness increases in passing from CVD-coating parts to combined PVD–CVD–PVD-coating parts. This can be explained by the effect of corresponding phase and structural transformations, which take place in the coating and along the boundaries of the phase interface in the process of their formation, on these factors. The results of certification tests of tools and cutters in operations of continuous and intermittent cutting can evidence on the efficiency of the designed coatings both for turning work and particularly for mill operation when high toughness is the determining characteristic along with hardness.
Key words: physical deposition, chemical deposition, combined coatings, strength, hardness, degree of wear resistance, nanostructure, texture.
Nikitenkov N.N., Khashkhash A.M., Shulepov I.A., Khoruzhy V.D., Tyurin Yu.I., Chernov I.P., Kudryavtseva E.N.
Plant for investigation of radiation and thermal evolution of gas from nonorganic materials
A high-vacuum plant has been designed and manufactured for qualitative and quantitative investigation of the content of monoatomic and molecular gases (hydrogen, oxygen, nitrogen, water vapors, gas hydrocarbons, CO2, CO, etc.) on the surface and near-surface layers of compacted and porous materials. The techniques of radiation and thermostimulated desorption as well as processing of solid material degassing by electron irradiation are realized in the plant. The results of studying the content of hydrogen in the course of its saturation and its engress from polycrystalline (average grain diameter d > 1 µm) and submicrocrystalline (d > 0,1 µm) titanium under radiation and thermal effect are given as an example of application of the above techniques.
Key words: plant, thermal desorption, radiationstimulated engress, gases, hydrogen, submicrocrystalline alloy.
Nano-structured materials and functional coatings
Antsiferova I.V.
Nanomaterials and potential ecological risks
Being arisen in the production process and nanoproduct consumption, the potential risks have been analyzed for the environment and human health. The approaches to the management of such risks are considered. Development of the systems to observe, control, forecast, and prevent the development of unfavorable emergency situations as a result of nanotechnology affecting is one of the primary objectives in this field.
Key words: natural environment, nanotechnologies, environmental pollution, management of risks concerned with nanomaterials.
Application of powder materials and functional coatings
Levinsky Yu.V., Patrikeev Yu.B., Filyand Yu.M.
Hydrogen absorption kinetics with yttrium dehydride powder
It is investigated kinetics absorption of hydrogen by a powder yttrium dihydride. The sample with a known specific surface and the structure close to the bottom border of area of homogeneity dihydride, sated with hydrogen in installation of Sivertsa at temperatures 300–450 °C and pressure of hydrogen 5–45 кПа. Factors of diffusion of hydrogen (DH) counted on kinetic curves of absorption of gas with use developed before a technique based on possibility of neglect by curvature of a surface at degrees of saturation, aspiring to zero. Dependence DH (m2/c) from temperature in a range 300–450 °C looks like lg DH = –12,7 – 1770/T.
Key words: hydrides, hydrogen power, a powder yttrium dihydride.
