Theory and processes of powder material forming and sintering
Maltsev I.M. The effect of electromagnetic field, skin- and pinch-effects in sintering metal powder under rolling by application of high-density electric pulses
The article describes the effect of electromagnetic field, skin- and pinch-effects in sintering iron and copper powder under rolling by application of high-density electric pulses (108 109 A/m2) on the properties of rolled products and the process parameters proceeding in the deformation zone. The macrostructure and properties of powder rolled products are shown to vary after sintering under rolling.
Key words: electromagnetic field, skin-effect, pinch-effect, sintering under rolling.
Kostikov V.I., Eremeeva Zh.V., Dorofeev V.Yu. The effect of parameters of thermal cyclic treatment on mechanical properties of hot-formed powder steel
For the purpose of improving the properties of powder carbon steels and grain refining, their thermal-cycle treatment has been carried out using both induction and furnace heating. Extra-fine-grain structure and increased strength, ductility, and impact strength have been obtained as a result. Optimum number of cycles is 3-10.
Key words: hot forming, cold compaction, thermal-cycle treatment, powder steel, structure, optimum conditions.
Self-propagating high-temperature synthesis (SHS)
Levashov E.A., Pogozhev Yu.S., Shtansky D.V., Petrzhik M.I. Self-propagating high-temperature synthesis of ceramic materials based on Mn+1AXn-phases in the Ti-Cr-Al-C system
Compact ceramic materials based on Mn+1AXn-phases in the Ti-Cr-Al-C system have been produced by SHS compaction. The mechanisms of structure and phase formation in synthesis products as well as the SHS-mixture burning macrokinetics have been studied. Complex investigations of structure, phase composition, physical and mechanical properties of new Ti2 -хCrхAlC ceramic materials synthesized under different parameters of burdening (х = 0, 0,5, 1, 1,5, 2) have been implemented. It was found that the most part (96-98 %) Mn+1AXn phase content in the composition of the synthesis products can be produced in the samples where just one of the main elements: titanium (x = 0) or chromium (x = 2) is present. The produced materials have high temperature strength, and increase in chromium concentration conduces to marked growth of resistance to high-temperature oxidation.
Key words: self-propagating high-temperature synthesis, ceramic materials, Mn+1AXn phases.
High-melting, ceramic and composite metallic materials
Ivanov D.A., Sitnikov A.I., Shlyapin S.D. Special features of technology and physical-mechanical properties of laminated Al2O3-Al cermet
A technological approach that permits to produce laminated cermets of Al2O3-Al composition is surveyed. Industrial PAP-2 grade powder of laminated particle form served as starting crude. Powder compacts were produced by compaction under pressure (Р) from 100 to 1000 MPa. Their heat treatment was carried out in the air by heating in furnace up to 600 °C. It was found that solid phase or reaction sintering of compacts can be realized in the filtration burning mode depending on P value. In the composite produced, the oxide phase content is varied from 5 to 40 vol.%, and density and bending strength is changed within the ranges of 2,53-2,0 g/cm3 and 330-98 MPa respectively. The laminated structure of the material is kept after thermal aging in the air at t = 600 °С for no more than 1000 h.
Key words: cermet, composite material, laminated structure, aluminum - aluminum oxide, compaction, reaction sintering, filtration burning, solid-state sintering, powder technology, shrink-off, strength, density, porosity, thermal aging.
Polushin N.I., Pozdnyakov A.A., Andreev L.A., Novikova E.A., Yakovtseva S.M. Gas release out of ZrO2-Y2O3 ceramics used for seeded growth of diamond monocrystals
Gas release out of ZrO2-Y2O3 ceramics used for seeded growth of diamond monocrystals within the range from 100 to 700 °С and pressure of 10-4 Pa has been investigated. It has been found experimentally that the air content in pores of the ceramic container elements is 0,086 norm.cm3/g. Gas release and diffusion coefficients have been determined. The coefficients allow determining the degassing time during which the gas portion in the sample from the starting amount will reach a definite value. It was found that vacuum annealing at temperature no less than 700 °С and Р = 10-4 Pa allows decreasing the content of adsorbed gas by an order of magnitude on the elements of a reaction cell.
Key words: synthetic monocrystals, ZrO2-Y2O3 ceramics, gas release.
Nano-structured materials and functional coatings
Kudryashov A.E., Levashov E.A., Vetrov N.V., Shalkevich A.B., Ivanov E.V., Solntseva I.S. A new class of electrospark coatings for titanium alloy products for extreme operation conditions
Creation, structure, composition, and properties of electrospark coatings on titanium alloys (VT 6, VT 20) are considered in using hard-alloy electrode materials (EM) based on titanium carbide and boride, nanosized tungsten carbide. The peculiar properties of EM mass transfer onto VT 20 grade titanium alloy in varying the parameters (current, frequency, duration) of pulsed current discharges have been studied. The optimum power level of electrospark Ti-alloy deposition by new EM (I = 175 A, f = 800 Hz, = 62 µs) has been determined. A complex of investigations of structure, phase composition, and properties (such as uniformity; thickness; microhardness; friction coefficient; wear, fire, and fretting resistance) for formed electrospark coatings has been carried out. Their phase composition after high-temperature action (600 С, 100 h) and topography has been studied. The electrospark processing by new hard-alloy EM is shown to ensure the increased properties of electrospark coatings on VT 20 titanium alloy as compared with the same ones produced in using widely distributed VK8, T15K6, and relit (cast tungsten carbide) electrodes.
Key words: electrospark deposition (ESD), self-propagating high-temperature synthesis (SHS), electrode materials, coatings, nanosized powders, nanostructured materials, energy of pulsed discharge.
Nemirovsky Yu.V., Yankovsky A.P. Determination of optimum parameters of thin rigid coatings on plates
Based on the general representations of the linear theory of elasticity, a problem of calculation of ring plates with strengthening coatings is formulated. A numerical method of integration of the set problem is developed and concrete calculations are implemented. On the basis of the analysis of the computed stress fields in the basic plate material and coatings it was possible to explain such effects as plate strengthening in applying hyperfine high-modulus coatings of 0,1-0,8 mm thick on their front surfaces and plate annealing in case of thicker coatings.
Key words: plates, thin coatings, strengthening, boundary layer, theory of elasticity.
Application of powder materials and functional coatings
Kostikov V.I., Eremeeva Zh.V., Slyuta D.A., Yaitsky D.L., Sharipzyanova G.Kh. Friction properties of carbon-carbon composite materials
Carbon-carbon fibers based composite material friction against counter-couple made of SG-T grade siliconized graphite have been studied. The friction conditions arising within the period under certain loads are analyzed. The structure of wear products has been investigated using electron microscopy.
Key words: carbon-carbon fibers based composite material, friction and antifriction materials, friction load, friction couple, wear products, friction conditions.
Chronicle
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