Influence of the electrolysis temperature on the formation, composition, structure, and magnetic properties of highly dispersed iron and iron-nickel alloy powders

The influence of the electrolysis temperature on the formation, chemical and phase composition, structure, and magnetic properties of highly dispersed iron and iron-nickel (50∶50) powders is investigated. The optimal thermal conditions are determined for the production of powders with micron-sized particles in a two-layer electrolytic bath from concentrated solutions of electrolytes. Institute of Colloid Chemistry and Water Chemistry, UkranianAcademy of Sciences Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5/6(395), pp. 37–42, May–June, 1997.     

Production and properties of brass-base P/M constructional materials. A review

Conclusions The best processing properties are exhibited by brass powders manufactured by the diffusional impregnation technique, using a zinc powder, brass swarf, or a copper-zinc master alloy as a point source. However, as this is a very labor-intensive process, normally preference should be given to melt atomization as a method of manufacture of brass powders. Brass P/M parts produced by the conventional method consisting of pressing a powder and sintering the resultant compacts have porosities of not less than 7–10%, and consequently this method is not widely used for the production of constructional brass parts. The sintering of compacts from copper and copper-zinc master alloy powders gives more stable zinc contents compared with the sintering of compacts from copper and zinc powders; the greatest stability of chemical composition is exhibited by sintered compacts from a homogenized brass powder. The formation of diffusional porosity accompanying the evaporation of zinc may be prevented by performing sintering in the presence of a liquid phase (which appears in the presence of a phosphorus or lead addition), saturating the sintering atmosphere with zinc vapor, and adding carbonates or halides of alkali and rare-earth metals to starting powders. The mechanical properties of materials can be markedly improved by eliminating their porosity. This may be achieved by subjecting porous preforms to hot forging, which enables brass P/M parts to be obtained whose mechanical properties are comparable to those of cast parts.Translated from Eoroshkovaya Metallurgiya, No. 3(255), pp. 56–64, March, 1984.     

Plasma-arc spray-coating of powders of self-fluxing iron-base alloys. II. Structure and properties of the coatings

The structure and some properties of coatings of a self-fluxing iron-base alloy powder, sprayed on by means of the plasma of propane—butane combustion products have been studied. The phase and chemical compositions of the coatings were determined and an analysis was made to learn how the porosity and the base-coating adhesive strength depend on the particle-size composition of the powder. Boron may be lost because of oxidation when powder of the 50–63 µm fraction is sprayed. The chemical composition of coatings of powders with a larger particle size differs only slightly from that of the initial material. The coating porosity ranges from 3 to 8% and the adhesive strength, from 25 to 40 MPa.Kiev Polytechnic Institute. Translated from Poroshkovaya Metallurgiya. Nos. 3/4, pp. 38–43, March–April, 1995.     

High-temperature synthesis of powder titanium alloys

A method is developed for cladding powders of titanium and alloys VT-5 and 2M2A with aluminum. It consists of the following: in a molten mixture of the relative metal chlorides a set of chemical processes takes place simultaneously involving deoxidation of the titanium powder surface, diffusion coating with aluminum, transformation of the alloy components into chemically active form, transport of components, and coating titanium and its alloys with aluminum in order to provide controlled synthesis of the relative compounds. The alloy powders may be used to produce articles for various applications.Institute of General and Inorganic Chemistry, Ukrainian National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5/6, pp. 1–5, May–June, 1995.     

Structure and mechanical and corrosion properties of Kh13 stainless steel powders

Conclusions Production of Kh13 steel by the HVP method without the presintering of porous blanks and final high-temperature diffusional annealing of dense compacts is possible only when an alloyed powder of the required composition is used. Use of a mixture of chromium and iron powders for the manufacture of Kh13 steel by the HVP process without additional operations — sintering of blanks and diffusional annealing of compacts does not give satisfactory results because diffusion processes cannot be completed during the short period of heating of blanks for HVP. With steel produced from an alloyed powder, the presintering of blanks and diffusional annealing of dense compacts after HVP are not essential because, while improving the mechanical characteristics of the steel, they decrease its corrosion resistance. The highest level of properties in dense P/M Kh13 steel, comparable to that characterizing cast steel of the same composition, is attainable only when a prealloyed powder is used in its manufacture. When such a powder is not available, a mixture of metallic iron and chromium powders can be employed, but the level of mechanical properties and corrosion resistance of the resultant steel will be much lower.A 13% Cr grade — Translator.Translated from Poroshkovaya Metallurgiya, No. 6(234), pp. 43–48, June, 1982.     

Effect of electrolysis conditions on the formation,structure, and magnetic properties of a finely divided iron-cobalt alloy

Conclusions An investigation was carried out into the effect of electrolyte concentration and current density on current efficiency in the electrodeposition of Fe, Co, and Fe-Co alloy powders. It was established that raising the electrolyte concentration from 6.65 to 26.62 g/liter of Fe²⁺ + Co²⁺ increases current efficiency, whose maximum value is about 90%. The highest current efficiency is attained at i_c of 20–30 A/dm². Changing the electrolyte concentration and current density does not significantly affect the composition of alloy deposits. At an iron-to-cobalt ion content ratio in the electrolyte of 11 the rate of discharge of Fe²⁺ during alloy formation in the twolayer bath is greater than that of Co²⁺. X-ray structural analysis revealed that the greatest changes in the internal structure of a very finely divided iron-cobalt alloy take place at low electrolyte concentrations. That raising the electrolyte concentration facilitates alloy formation is confirmed by a decrease in the degree of defectiveness of the particles and a stabilization of the crystal lattice parameter of the alloy; i_c does not have such an effect on the structure of the alloy. Magnetometric measurements demonstrated that the coercive force of alloy powders is greater at higher densities of dislocations in their particles.Translated from Poroshkovaya Metallurgiya, No. 8(224), pp. 5–11, August, 1981.     

Sintering of very fine molybdenum and tungsten powders

Conclusions Vacuum annealing at a temperature above 900°K enables the specific surfaces of very fine loose tungsten and molybdenum powders to be varied in a wide range. The vacuum sintering of compacts pressed from very fine (particle size less than 0.05m tungsten and molybdenum powders is accompanied by severe cracking. In the hot pressing of very fine Mo and W powders produced by the pyrolysis of carbonyls in a stream of high-temperature plasma, a specimen density close to theoretical is reached at 1600°K i.e., at a temperature not less than 400°K lower than the sintering temperatures of powders of particle size more than 1 m. Sintering lowers the amounts of carbon and oxygen in Mo and W by more than half compared with the starting condition.Translated from Poroshkovaya Metallurgiya, No. 1(229), pp. 47–51, January, 1982.     

Properties of titanium alloy VT6 fibers obtained by rapid solidification of the melt

We have studied the chemical, physicochemical, and technological properties of titanium alloy VT6 fibers in the initial state and after vacuum annealing for one hour at 500–1300°C. We have carried out fractographic, microstructural, and qualitative x-ray spectral microanalysis of the fibers. We have established that in the initial state, the fibers possess high values of the physicomechanical characteristics; the decrease in the properties of the fibers with a rise in temperature was determined by observing changes in the microscopic and macroscopic structure and the chemical composition. Vacuum annealing of VT6 fibers allows us to improve their compressibility with different combinations of hardness, strength, and conductivity characteristics.Institute of Problems in Materials Science, National Academy of Sciences of Ukraine, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 3–4, pp. 85–90, March–April, 1994.     

Feasibility of producing cadmium-zinc alloy powders

Conclusions Electrolytic deposition of cadmium-zinc alloy powders from sulfate solutions is possible provided that the reduction of cadmium ions is performed under limiting diffusion current conditions. Simultaneous discharge of cadmium and zinc ions is not accompanied by super- and depolarization phenomena, which enables the alloy composition to be predicted using polarization curves of reduction of the two kinds of ion in individual solutions. Because of growth of the alloy deposit surface during galvanostatic deposition, the composition of the powder is a function of buildup time, and can be changed only by varying the solution composition. Consequently, it is best to produce such powders either under potentiostatic conditions or under galvanostatic conditions but with continual removal of deposited powder from the basis.Translated from Poroshkovaya Metallurgiya, No. 8 (272), pp. 6–10, August, 1985.     

Production of VT20 AND VT9 titanium alloy powders

Conclusions The hydrogenation-dehydrogenation method offers an effective means of producing industrial titanium alloys in powder form. It has been established that hydride-grade titanium alloy powders meet, without charge enrichment, the chemical composition requirements laid down by technical standards for VT20 and VT9 industrial alloys. The H-D process brings about changes in the phase composition and structure of alloys: The amount of the -phase diminishes, and the alloy structure becomes more fine-grained. Consequently, by varying H-D process parameters it is possible to exercise control over the properties of powders.Translated from Poroshkovaya Metallurgiya, No. 11(227), pp. 1–6, November, 1981.     

Effect of B on the microstructure and mechanical properties of mechanically milled TiAl alloys

The present study is concerned with γ-(Ti₅₂Al₄₈)_100−x B _x (x=0, 0.5, 2, 5) alloys produced by mechanical milling/vacuum hot pressing (VHPing) using melt-extracted powders. Microstructure of the as-vacuum hot pressed (VHPed) alloys exhibits a duplex equiaxed microstructure of α₂ and γ with a mean grain size of 200 nm. Besides α₂ and γ phases, binary and 0.5 pct B alloys contain Ti₂AlN and Al₂O₃ phases located along the grain boundaries and show appreciable coarsening in grain and dispersoid sizes during annealing treatment at 1300 °C for 5 hours. On the other hand, 2 pct B and 5 pct B alloys contain fine boride particles within the γ grains and show minimal coarsening during annealing. Room-temperature compressing tests of the as-VHPed alloys show low ductility, but very high yield strength >2100 MPa. After annealing treatment, mechanically milled alloys show much higher yield strength than conventional powder metallurgy and ingot metallurgy processed alloys, with equivalent ductility to ingot metallurgy processed alloys. The 5 pct B alloy with the smallest grain size shows higher yield strength than binary alloy up to the test temperature of 700 °C. At 850 °C, 5 pct B alloy shows much lower strength than the binary alloy, indicating that the deformation of fine 5 pct B alloy is dominated by the grain boundary sliding mechanism. This article is based on a presentation made in the symposium “Mechanical Behavior of Bulk Nanocrystalline Solids,” presented at the 1997 Fall TMS Meeting and Materials Week, September 14–18, 1997, in Indianapolis, Indiana, under the auspices of the Mechanical Metallurgy (SMD), Powder Materials (MDMD), and Chemistry and Physics of Materials (EMPMD/SMD) Committees.     

Some properties of components from iron powder alloyed with 6% chromium

Summary The process developed at the Institute for thermal diffusion impregnation from point sources is simple and reliable, and permits production of iron-chromium alloy powders of any desired composition. Compared with parts of pure iron, constructional components obtained from these powders exhibit higher strength, ductility, and oxidation resistance.Translated from Poroshkovaya Metallurgiya, No. 8(56), pp. 28–33, August, 1967.     

Permanent magnets from fine iron and iron-cobalt alloy powders

Conclusions It has been established that, to obtain the optimum, magnetic properties in isotropic materials from fine iron and iron-cobalt alloy powders, the powders should be heat-treated for 4 h at a temperature of 280°C and compacted under a pressure of 15–16 kbar. Heat treatment tends to destroy dendritic axes of the second and third orders on the powder particles, heal structural defects, and increase the flowability of particles during pressing, thereby ultimately improving the magnetic properties of the resultant components. The maximum magnetic energy is 4.6 kJ/m³ for isotropic magnets from iron powders and 8.6 kJ/m³ for magnets from iron-cobalt alloy powders.Translated from Poroshkovaya Metallurgiya, No. 10 (142), pp. 61–63, October, 1974.     

Effect of alloying method on sintering and physico-mechanical properties of Al-A.4% Cu-0.5% Mg powder alloy

Conclusions The method of alloying with copper and magnesium has a strong effect on compacting in sintering and on the physicomechanical characteristics of Al-4.4% Cu-0.5% Mg alloy.The alloy based on Al-0.5% Mg master alloy is characterized by the highest density but its sintering requires higher temperatures (615–635°C) and long holding times. This alloy produced in the optimum conditions is characterized by high physicomechanical properties in the sintered state but by low efficiency of heat treatment. The optimum physicomechanical properties were recorded for the alloy containing the elementary powders of copper and magnesium which was sintered at 595°C for 45 min.Translated from Poroshkovaya Metallurgiya, No. 10(310), pp. 37–41, October, 1988.     

Porous permeable materials from a nickel-molybdenum alloy

Conclusions A study was carried out of the preparation of porous permeable materials from a Ni-30% Mo alloy by the techniques of sintering fine powders with the use of fillers and of sintering granulated powders. A technology has been developed for producing two-layer filters from the Ni-30% Mo alloy.Translated from Poroshkovaya Metallurgiya, No. 12 (72), pp. 35–41, December, 1968.     

Protective properties of detonation-deposited coatings from powders alloyed with aluminum and boron

Conclusions The corrosion resistance of detonation-deposited coatings from aluminum- and boron-containing PKh20N80 alloy, nickel, and stainless steel powders markedly surpasses that of constructional steel. The electrochemical properties of such detonation-deposited coatings are determined by their composition and thickness. The basis material is effectively protected against corrosion by 600-Mm-thick coatings. Under conditions of corrosive and mechanical wear detonation-deposited coatings from aluminum- and boron-containing 20% Cr-80% Ni alloy, nickel, and stainless steel powders operate satisfactorily under loads of not more than 5 MPa. The results of service tests have demonstrated the usefulness of detonation-deposited coatings from alloyed powders. Coating with powder of composition III was found to increase the useful life of certain parts of spraying equipment two to two and a half times.Translated from Poroshkovaya Metallurgiya, No. 8 (272), pp. 52–55, August, 1985.     

Chemical reaction of aluminum alloy powders with water

Conclusions As a result of an investigation into the reaction of powders of several aluminum alloys with water it was established that the most active with respect to water are aluminum alloys containing magnesium, lithium, zinc, and other active elements. The rates of the reactions of these alloy powders with water are determined by the following factors: alloy composition, water and powder temperatures, and suspension concentration (s1). The highest rate of reaction with water (of the three industrial powders investigated — AMLD, PV-90, and SAS-1) is exhibited by the AMLD alloy powder, which contains lithium. The reaction of such alloy powders with water can be retarded or even completely prevented by the introduction of inhibitors — a measure permitting safe handling (e.g., hydrostatic pressing) of all aluminum alloy powders.Translated from Poroshkovaya Metallurgiya, No. 8(308), pp. 15–19, August, 1988.     

Effect of palladium on the process of diffusional alloy formation and microstructure during the sintering of tungsten-rhenium powders with well-developed surfaces

Conclusions Low-temperature coreduction of tungsten trioxide and ammonium perrhenate can be employed as a means of preparing active tungsten-rhenium powders having well-developed surfaces and good sinterability. The action of an alloy formation activator manifests itself most strongly with active powders produced by the method of low-temperature coreduction of tungsten trioxide and ammonium perrhenate. Diffusional reaction between the tungsten and rhenium in such a case begins already during the reduction process. At temperatures of intense alloy formation phase interlayers of activator solid solutions form at grain boundaries in tungsten-rhenium alloys. As a result, the diffusional permeability of the boundaries to rhenium atoms grows, which activates the process of diffusional alloy formation.Translated from Poroshkovaya Metallurgiya, No. 1(205), pp. 36–40, January, 1980.     

Composition,Structure, and Properties of Sintered Silicon-Containing Titanium Alloys

The main factors limiting the application of high-temperature creep-rupture resistant titanium alloys synthesized from powder components by pressing and subsequent vacuum sintering for the manufacture of parts for gas turbine engines are analyzed. The method for synthesizing the VT1-0 alloy and an alloy whose chemical composition corresponds to the high-temperature creep-rupture resistant VT8 alloy is described. Their chemical and phase composition, strength, hardness, and distribution of doping elements are examined. Upon analysis of the composition, structure, and properties of the samples produced from the test alloys synthesized from PT5 titanium powders with different particle sizes by powder metallurgy methods, it was concluded that semi-finished products could be produced from the VT1-0 and VT8 titanium alloys. The effect of the particle size of the titanium matrix on the chemical composition of the synthesized alloys is studied. The chemical composition of the test alloy complies with the industry standard for semi-finished products of hightemperature creep-rupture resistant titanium alloys. The influence of the particle-size distribution of titanium powder on the strength, hardness, and residual porosity of the synthesized alloys is established. Regardless of the particle size of the powder mixture matrix (ranging from 40 to 400 μm), the strength, ductility, and hardness of the test VT8 alloy do not comply with the requirements of standards OST 90002–70 and OST 90006–70, which govern these properties for bars and blanks of gas turbine engine blades. It is concluded that a series of measures are required to eliminate the residual porosity and impart the blade structure to the material to improve the strength properties.     

Theory, manufacturing technology, and properties of powders and fibers

The properties of ferromagnetic powders after reduction annealing are examined. It is shown that magnetite and a destructured composite organic coating ensure the resistance of such powders to external effects. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 7–8 (456), pp. 3–7, 2007.