Promising trends in the development of methods of fabricating structural powder materials (survey)

In the new millennium a trend focused on making improvements in existing technologies of powder metallurgy and on the development of new and promising trends in the creation of powder structural materials is observed. The development of the technology of powder metallurgy is intended to improve methods of warm and injection molding, laser and mechanical alloying, and nitration of high-and lowalloy steels. Considerable attention has been paid to the production of structural materials made of intermetallic compounds, materials, the properties of which exhibit functional gradients. There has also been emphasis on creating nanomaterials fabricated by the sol-gel method, mechanical alloying, and powder spraying. __________ Translated from Poroshkovaya Metallurgiya, Nos. 5–6(449), pp. 92–100, May–June, 2006.     

Plastic deformation of metal particles in gas-dynamic spraying

The main stage of the gas-dynamic spraying process is the deformation and heating of particles upon impact with the substrate. A solution of the impact deformation problem by use of the finite element method is given. The model developed enables determination of the extent of particle deformation and the time and temperature of impact as functions of the material and particle properties and the initial velocity and temperature of particles. Ukraine State Metallurgical Academy, Dnepropetrovsk. Translated from Poroshkovaya Metallurgiya, Nos. 7–8(402), pp. 10–15, July–August, 1998.     

Layerwise analysis of vacuum copper-chromium condensates by glow-discharge mass spectrometry

Features are examined of using high-sensitivity mass-spectral layerwise analysis in a glow discharge to examine Cu-Cr composite material made by electron-beam evaporation. A mathematical model is used to calculate the concentrations of molecular ions in the glow-discharge plasma in order to select isotopes free from molecular ions. The argon-ion etching allows one to examine the distributions of the main and impurity elements with a sensitivity of 10⁻⁵–10⁻⁶% with micrometer-scale spatial resolution. The distributions of Ti, Cr, Mn, Fe, Ni, Cu, and Ag in the layers have been examined to determine the effects of the trace impurities on the condensation of the atomic vapor. __________ Translated from Poroshkovaya Metallurgiya, Nos. 7–8(450), pp. 106–115, July–August, 2006.     

Changes in Structure and Physicochemical Properties of Spark Coatings Based on TiN and TiB2 after Treatment with Concentrated Solar Radiation

Studies have been made on the structure and properties of spark coatings made of TiN and TiB₂ on steel U8 after treatment with concentrated solar radiation. It is found that the absorption capacity of the steel raised by a factor 2–3. The concentrated radiation reduces the coefficient of friction of the spark coatings made of TiN and TiB₂ by a factor 1.4, while the wear rate is reduced by a factor 1.6–2 by comparison with the untreated material. __________ Translated from Poroshkovaya Metallurgiya, Nos. 7–8(444), pp. 64–69, July–August, 2005.     

Use of plasma technology in creating catalysts on carriers

The use of plasma spraying technology is suggested for creating catalysts on carriers (crust catalysts) of spherical or similar shape (diameter 3–30 mm). The number of production operations is significantly reduced (to one to two) compared with impregnation technology. Examples are provided for testing and application of crust catalysts (silver, nickel, and nickel-chromium) in different chemical reactions. The activity and selectivity of these catalysts is higher than for catalysts prepared by impregnation technology. Translated from Poroshkovaya Metallurgiya, Nos. 3/4(412), pp. 116–119, March–April, 2000.     

Self-propagating high-temperature synthesis for the deposition of thermal-sprayed coatings

The paper reviews the relevant literature and results of the author’s research into self-propagating high-temperature synthesis (SHS) used to deposit protective thermal-sprayed coatings. The compositions of different SHS-produced powders, which are used to deposit thermal-sprayed coatings, are indicated. The combination of spraying and synthesis of the material to form coatings by the interaction of composite powder particles is considered. __________ Translated from Poroshkovaya Metallurgiya, Vol. 47, No. 1–2 (459), pp. 105–125, 2008.     

Behavior of multilayer steel-bronze composites on frictional loading

Tribological aspects are examined for layered composites made by consolidation. Dry friction tests at sliding speeds of 1.6–4.3 m/sec show that this multilayer antifriction material is better by 1–2 orders of magnitude in wear resistance than the initial material. The multilayer composite can withstand a load increased by an order of magnitude without losing its viability under the conditions of surface-structure adaptation. Deceased. Translated from Poroshkovaya Metallurgiya, Nos, 1–2(411), pp. 38–44, January–February, 2000.     

High-chromium cast iron sintered of sprayed powders

The paper examines basic technological characteristics of high-chromium cast iron powders resulting from gas or water melt spraying. Sintering of billets made of these powders is investigated. It is shown that Fe-Cr-Mo-Cr powder alloys can combine high hardness and thermal stability. Therefore, they are candidate materials for operation in intensive wear and at high temperatures. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 3–4 (454), pp. 111–115, 2007.     

Side milling cutters with working elements made of high-speed steel powder. II. Properties of cutting materials

Investigations were carried out into the materials for blanks of side milling cutters produced from high-speed steel powder by hot upsetting ring-shaped porous blanks with the centripetal flow of the material. A method of evaluating the quality of material on the basis of the density and specific work of failure of specimens, cut from the discs in different areas and in different directions, was developed and applied for this purpose. The use in the blank of a central insert produced from rolled structural steel results in higher properties (“the head” effect). The results of testing the durability of cutters with working elements produced from high-speed steel powder show that their durability decreases less rapidly with increasing cutting speed than that of the cutters made of rolled material. Novocherkassk State Technical University. Novocherkassk Electric Locomotive Plant Scientific and Production Association. Translated from Poroshkovaya metallurgiya, Nos. 3–4(406), pp. 118–122, March–April, 1999.     

Preparation of finely-crystalline powders for tools steels

The possibility is examined of preparing finely-crystalline powders of tool steel R6M5F3 by the electric hydropulse method for treating molten metal before spraying. It is established that there is a reduction in gases and nonmetallic inclusions. As a result of this there is a reduction in the kinematic viscosity of the molten steel, and an increase in surface tension and the degree of undercooling. These factors promote the preparation of finely-crystalline powder with improved physical and production properties. Institute for Materials Science Problems, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 3–4, pp. 38–40. March–April, 1997.     

Nonuniformity of the deformation of microstructural components of multiphase steels in evaluating the limiting formability of flat-rolled products

An integrated method has been found to construct diagrams that depict the limiting stable deformation of sheets during cold-working. The method is based on estimates of the local flow of the sheet material. Stereological methods in quantitative metallography are used to analyze limiting strain state that precedes the onset of instability by examining the structural factors which are involved. It is shown that a texture analysis can be performed to help evaluate the stability of the material’s flow in thin-walled products made of multiphase steels. __________ Translated from Metallurg, No. 5, pp. 29–32, May, 2006.     

等离子喷涂及梯度功能材料研究进展

等离子喷涂技术在耐磨、耐蚀涂层应用已较为广泛，从50年代至今，其应用领域由航空、航天扩展到了汽车制造、石油化工、纺织机械、船舶等领域。近年来，等离子喷涂在梯度功能材料等方面的应用研究也获得较大进展，显示了良好应用前景。     

Principles of the design of highly porous layered composites working in the bending mode

A comparative analysis is made of the spesific mechanical characteristics of a sandwich-type laminated porous composite under bending. The external layers of the composite are compact while the internal layer consists of a highly porous material made by using a pore-forming agent. The specific stiffness, strength, and yield load as a function of the volume fraction of pores Θ and the porous/compact-layer thickness ratio λ are considered. The stiffness, strength, and yield load are shown to be affected by variations of Θ and λ when the weight of the composite is constant. Translated from Poroshkovaya Metallurgiya, Nos. 3/4(412), pp. 70–78, March–April, 2000.     

Plasma coatings of (TiCrC)-(FeCr) composite powder alloys: Structure and properties

The coatings of the (TiCrC)-(FeCr) composite are deposited on steel and titanium alloy by plasma method. The composition, structure, and tribotechnical properties of these coatings are studied in comparison with traditional materials based on the Ni-Cr alloy. The effect of preliminary surface treatment methods, i.e., sandblasting treatment and electrospark alloying, on coating properties is examined. The fretting corrosion of coatings is investigated. It is established that coatings based on double titanium-chromium carbide have considerably greater wear resistance than that of Ni-Cr alloys at almost equal friction coefficients. It is established that electrospark alloying is competitive with traditional sandblasting treatment in environmental effect and coating-to-based adhesion. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 3–4 (454), pp. 37–45, 2007.     

Effects of sintering activators on aluminum nitride compaction

Measurements have been made on the effects of sintering activators on the compaction of aluminum nitride. The relative density of the AIN-based material is substantially dependent on the form, amounts and ratios of the components. High densities occur in sintered materials that contain additives having cations large compared with Al ³⁺. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5–6(407), pp. 20–24, May–June, 1999.     

Consolidation of a porous material in hot pressing in a closed mold fitted with a compensator

A method has been developed for calculating the compaction of a porous material in hot pressing in a closed mold fitted with a compensation slot. Simulation is reported for various initial porosities and compensating slot heights. The results from pressing in a closed mold with compensator and in an open mold are compared. Materials Science Institute, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5–6, pp. 14–18, May–June, 1998.     

Thermal stability of finely dispersed ferromagnetic powders

The oxidation mechanism and kinetics have been examined for finely dispersed powders of iron and compounds containing it and noble and platinum metals; these powders were made by a thermochemical method and examined at 20–400°C. The powders do not change in composition and magnetic characteristics up to 110°C because the surfaces of the particles are protected by iron oxides and carbide. This allows the powders to be used to make materials for medical purposes, since they can be sterilized at that temperature. Translated from Poroshkovaya Metallurgiya, Nos. 5–6(413), pp. 1–4, May–June, 2000.     

Structure and phase formation of nanostructural ion-plasma Ti-Cr-Al-N coatings on a hard-alloy cutting tool

A The possibility to of fabricate fabricating nanostructural Ti-Al-Cr-N coatings on a cutting hard-alloy tool with crystallites 20–60 nm in size by the method of ion-plasma arc deposition with the use of a tree-cathode system for sputtering materials and the separation of plasma flows from a drop phase is shown. The dependences of that structure and phase formation in the coating material have on the accelerating bias potential (U = −100 to −160 V) supplied to a the substrate and determining the energy of sputtered particles and condensation temperature, as well as on a the current (I _Cr = 90–130 A) of a the sputtering arc at a the chromium cathode and the chromium concentration that depending depends on the the current within the vapor phase and the formed coating, are determined.     

Increasing the wear resistance of piston rings by plasma spraying

Conclusions A simple and economical method of coating piston rings with wear-resistant alloys has been proposed, in which plasma spraying is employed instead of electrodeposition. An optimum technique has been developed for the plasma spraying of sintered piston rings. It is proposed that Kh12M steel be used as the wear-resistant coating material. The sprayed layer exhibits a wear resistance which is 4 times higher than that of chromium-plated cast iron and causes less wear of mating materials.Translated from Poroshkovaya Metallurgiya, No. 5 (53), pp. 46–51, May, 1967.     

A model for wear-resistant coating on aluminum alloy formed by spark mass transfer of a composite ceramic

Measurements have been made on the mass-transfer kinetics, structure, and properties of the surface layer in spark mass transfer of composite ceramics in the systems AlN-Ti(Zr)B₂ and LaB₆-ZrB₂. A model is proposed for the formation of the wear-resistant coating on aluminum alloys, which is based on the screening action of the vapors and particles of the nonconducting phases in the electrode gap and involves the differing wettability of the alloying components by the substrate material. __________ Translated from Poroshkovaya Metallurgiya, Nos. 1–2(447), pp. 51–58, January–February, 2006.