Mechanical and hydraulic characteristics of P/M titanium filters

Conclusions For the production, by hydrostatic pressing, of filters from PTÉK, PTÉS, and PTÉM electrolytic titanium powders and a screened 0.63–1.0 mm fraction of the powder forming during the crushing of TG-Tv titanium sponge, the recommended pressure range is 78.5–157 MPa. The mechanical strength of filters from screened TG-Tv powders is, other things being equal, 1.2–4 times higher than that of filters from electrolytic powders. The filtration indicators (coefficients of permeability and filtration) of filters from screened TG-Tv and electrolytic powders are generally virtually identical, but with coarse (0.63–1.0 mm) electrolytic powders they are two to seven times higher than with electrolytic powders.Translated from Poroskhovaya Metallurgiya, No. 7(235), pp. 34–39, July, 1982.     

Study of the Process of Phase Formation during Detonation Spraying of Composite Powders of the FeTi - SiC System

We have studied the dependences of the structure, phase composition, and properties of coatings obtained by detonation spraying of powders of the system 77 mass% FeTi - 23 mass% SiC on the method by which they are prepared. We have established substantial differences in morphology and composition for coatings sprayed from conglomerated and presintered powders. We have shown that the process of formation of new phases occurs more rapidly when spraying conglomerated powders.__________Translated from Poroshkovaya Metallurgiya, Nos. 1–2(441), pp. 67–73, January–February, 2005.     

Production of metal powders from melts by centrifugal atomization

Conclusions A study was made of centrifugal atomization of molten metals in argon at low argon consumption rates [(5.2–7.5) · 10^–3 NTP m³/kg]. Output with a single injector attained 30–40 kg/h. Increasing the molten metal head to 0.6–0.8 MPa and decreasing the nozzle diameter to 0.3 mm substantially increased the fineness of the powders. Raising the head still further influenced the effectiveness of atomization to a smaller extent, and decreasing the nozzle diameter to less than 0.3 mm coarsened the powders. Powders of magnesium, aluminum, and Br020 alloy. (20% Sn-Cu bronze) produced by centrifugal atomization of superheated (by about 30–50°K) melts in an inert atmosphere (argon) had spherical particle shapes, which imparted to them good flowability. The oxygen content of the powders was low (less than 0.08%).Translated from Poroshkovaya Metallurgiya, No. 12(276), pp. 5–10, December, 1985.     

Powder Metallurgy Overcomes Economic Difficulties

The state of the production of metallic and ceramic powders (including nano-dimensional powders) and of articles fabricated from these powders in North America is discussed. New technologies that produce an increase in the density and improvement in the mechanical properties of powder-based articles are considered. Technological developments and articles for which prizes were awarded by the North American Metal Powders Industry Federation in 2003 are adduced.__________Translated from Poroshkaya Metallurgiya, Nos. 1–2(441), pp. 117–125, January–February, 2005.     

Effects of raw material on the properties of partially alloyed powders and low-carbon materials based on them

Studies have been made on the effects of the raw material (cast iron and steel powders) on the properties of partially alloyed powders of grades D2, D2M, N2M, N2D2M, and N4D2M and also of materials based on them made by single pressing and sintering. When iron-bearing semifinished products are used, or the cast iron and steel powders, one can make partially alloyed powders with various compositions having good technological characteristics as well as materials based on them having good physical and technological properties.Institute of Problems of Materials Science, National Academy of Sciences of the Ukraine, Kiev. Translated from Poroshkovaya Metallurgiya, No. 7–8, pp. 67–72, July–August, 1994.     

Effect of surface-active agents on the properties of a copper powder produced by the autoclave method

Conclusions Carboxyl-containing water-soluble polymers have the strongest influence on the properties of copper powders and are the most effective in reducing their deposits on the inside reactor surface. The optimum SAA consumption rate is 0.003–0.007 g per 1 g of copper. Higher consumption rates intensify the flocculatton of powder particles and increase the carbon content of the powder, which is undesirable, since it makes the latter's subsequent processing more difficult. The carboxyl-containing substances currently produced by industry can be used as SAAs, but, because of their low carboxyl-group content (not more than 45–60%), powders produced in their presence become fairly severely contaminated with carbon owing to destruction of inert radicals. By suitable choice of type of carboxyl-containing SAA it is possible to vary the properties of powders in the following ranges: specific surface 0.02–0.18 m²/g, apparent density 0.9–2.9 g/cm³, mean particle size 20–42m, and flowability 0–2.6 g/sec.Translated from Poroshkovaya Metallurgiya, No. 7(283), pp. 5–8, July, 1986.     

Effect of the amount of electrolytic nickel in an iron charge on its distribution on the particle surfaces and on the powder particle size

Conclusions After the passage of 0.16 A · h of electricity per 1 g of the charge investigated, the amount of nickel in the powder was 13–14 wt.%. The surfaces of the powder particles, which had retained their original shape and dendritic structure, were covered with fairly even, 5- to 8-m-thick nickel layers. During nickel plating the powders coarsened as a result of coalescence of separate particles, which was especially pronounced with charges containing large nickel additions (up to 30–50%). Additional comminution of nickel-plated powders increased their fineness. The milling operation virtually restored the original fine particle size of powders containing 13–14% of nickel.Translated from Poroshkovaya Metallurgiya, No. 1(229), pp. 1–4, January, 1982.     

Laser synthesis of ultradisperse powders of aluminum oxide

We have studied laser synthesis and the structure and properties of ultradisperse aluminum oxide powders. We show that the laser radiation intensity affects the phase composition. We find that the following conditions are optimal for production of these powders: power 500 W, pressure 0.1 atm (1–10 kPa), helium as the synthesis atmosphere.Scientific-Research Institute of Problems in Powder Technology and Coatings, Republic Engineering and Technical Center of Powder Metallurgy, Perm. Translated from Poroshkovaya Metallurgiya, Nos. 1/2(377), pp. 1–4, January–February 1995.     

Interphase reactions in forming plasma coatings

Nickel-plated powders and coatings of titanium and chromium carbides and borides are studied. Components of the starting powders react between themselves and with oxygen from the atmosphere forming solid solutions, intermetallic compounds, and a shielding oxide film. During pulverization the surface of particles does not lose a plated layer and nickel metal is always available in the coating. In order to increase the life of coatings it is advisable to use powders with the minimum possible amount of oxygen which promotes decomposition of higher carbide. In order to reduce the amount of complex oxides and intermetallic compounds in the coating which make a brittle matrix it is recommended to use boride powders in a mechanical mixture with metal (alloy) powders.Institute of Problems of Materials Science, National Academy of Sciences of the Ukraine, Kiev. Translated from Poroshkovaya Metallurgiya, No. 5–6, pp. 54–60, May–June, 1994.     

Control over the particle size of stainless-steel powders

Conclusions Replacing some of the metallic iron by ferric oxide, Fe₂O₃, in the charge for the preparation of Kh18N15 and Kh23N28 stainless-steel powders by the calcium-hydride reduction process increases (two- to threefold) the yield of the fine fraction (-0.063 mm) without affecting the apparent density of the powders (1.4–1.85 g/cm³) or the sponge shape of their particles. At the present time, stainless-steel powders are being manufactured using a charge in which 20–30% of metallic iron has been replaced by the oxide Fe₂O₃.Translated from Poroshkovaya Metallurgiya, No. 2 (134), pp. 1–8, February, 1974.     

Equation of pressing of nickel powders

Conclusions It was shown experimentally that compaction of different nickel powders during pressing in the 29–490 MN/m² range cannot be described by any one of the investigated equations of pressing.In this pressure range pressing of carbonyl powder is described by Lipson's Eq. (4), whereas pressing of enlarged carbonyl and spherical electrolytic powders in the 98–490 MN/m² is described by a polytropic type Eq. (1). The constants involved in these equations were found.Translated from Poroshkovaya Metallurgiya, No. 2 (74), pp. 11–14, February, 1969.     

Structural studies of ceramics based on detonation-wave-treated graphite-like boron nitride

The formation of a structure during pressureless sintering of graphite-like boron nitride (BN) powders pretreated in detonation waves was studied. The treated powders contained 10–12% wurtzite BN phase and 2–3% sphalerite phase. During sintering at just 1200 °C a reverse transformation from dense BN phases to graphite-like phases and primary recrystallization of highly fragmented BN_g occur as a result of the pretreatment. Accretive recrystallization of BN_g begins at 1500 °C and at T=1700–1950 °C platy grains with a size of 1–3 µm are formed in the developed surface. At 1700 °C the density of the specimens reach 0.95 of the theoretical value. The specimens produced at 1950 °C have a higher compressive strength and radiation resistance than do those made without pretreatment.Deceased.Institute of Materials Science, Ukrainian Academy of Science, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5/6, pp. 75–80, May–June, 1995.     

Powder Metallurgy Use of Waste from Bearing Production

A technology has been developed for improving the properties of ShKhl7 steel powder, obtained from bearing production waste sludge by familiar technological processes. On the basis of theoretical and experimental studies, we have ascertained the optimal conditions for ball milling, grinding, and heat treatment of the powders so as to improve their fluidity and bulk density. The technological and strength characteristics of the powders studied make them suitable for the production of serviceable parts by powder metallurgy methods.__________Translated from Poroshkovaya Metallurgiya, Nos. 1–2(441), pp. 106–112, January–February, 2005.     

Purification of metal powders from oxide films in a jet mill

Conclusions During the jet comminution of metal powders covered with oxide films the latter shear off, and their particles detach themselves from the main volume of material. The amount of oxygen decreases during purification by a factor of 2–17 depending on the oxygen content of the starting material and the latter's hardness and particle size. The removal of oxide films is virtually completed in 5–30 min depending on the properties of the starting powder. For the purification of powders low-pressure (0.5-MPa) compressed air can be employed. During the comminution of powders covered with oxide films, in certain circumstances detached film particles may find their way into the comminuted material.Translated from Poroshkovaya. Metallurgiya, No. 2(230), pp. 1–4, February, 1982.E. A. Filler, of the Special Design and Technology Bureau of the Chemical Engineering Industry, also took part in this work.     

Thermodiffusion impregnation of iron and nickel powders with manganese

Summary A study was carried out on the thermodiffusion impregnation of iron and nickel powders with manganese from point sources at temperatures of 773–1373°K and holding durations of 2, 6, and 10 h, using charges containing 2–30% ammonium chloride. Manganese in the form of ferromanganese or metallic manganese was added to the charge in amounts ranging from 8 to 30%. It was demonstrated that the presence of excessive amounts of ammonium chloride in the charge leads to substantial manganese losses and is therefore undesirable. The optimum conditions have been established for the impregnation of iron and nickel powders with manganese.Translated from Poroshkovaya Metallurgiya, No. 6 (66), pp. 8–13, June, 1968.     

Changes in the surface structure of particles during the reduction of molybdic anhydride

Conclusions A study was made of the surface structures of molybdic anhydride and molybdenum powders produced by different methods. It is shown that particles of fine reduced molybdenum powders are agglomerates of small fragments of 0.1–0.2- size.Translated from Poroshkovaya Metallurgiya, No. 6 (150), pp. 5–8, June, 1975.     

Change in Iron Powder Properties with Treatment in Rolls

Conditioned iron powders are prepared by carbothermal reduction of “Blue Dust” (India) ore concentrate followed by compaction treatment in rolling mill and a decarburizing anneal. The properties of powder prepared by grinding in a vibration and rolling mill are determined. The method makes it possible to control the bulk density of the powder from 1.75 to 2.75 g/cm³. Determination of the production properties of the powders obtained and powder NC.100.24 by the same procedure established satisfactory conformity of the results. The technological desirability of preparing conditioned iron powder by treatment in a rolling mill is demonstrated.__________Translated from Poroshkovaya Metallurgiya, Nos. 3–4(442), pp. 12–16, March–April, 2005.     

Atmospheric oxidation of germanium,tin, and lead telluride powders

Conclusions In an air atmosphere with a relative humidity of 75–100%, germanium, tin, and lead telluride powders are subject to atmospheric corrosion at room temperature. For the tellurides investigated, intensity of attack decreases in the order GeTe > SnTe > PbTe. Increasing the specific surface of powders within the range investigated produces, to a first approximation, a proportional intensification of their atmospheric corrosion.Translated from Poroshkovaya Metallurgiya, No. 3 (123), pp. 51–56, March, 1973.     

Kinetics of pore size increase in the activated sintering of powdered tungsten

Conclusions An increase in the size of pores determined by the Barus-Bechgold method in porous specimens from fine tungsten and tungsten-nickel powders takes place during heating to the isothermal sintering temperature. The addition of nickel to tungsten activates the pore size growth process. The size of the increased pore channels in porous solids from W and W-0.46% Ni powders in the temperature range 1000–1300°C depends on the particle size and sintering temperature. A correlation has been found between the integral shrinkage during isothermal sintering and the capillary stresses acting on the attainment of the isothermal sintering temperature in compacts from W-0.46% Ni powders of various particle sizes. The rates of isothermal shrinkage are the same, being independent of the previous history of the powders.Translated from Poroshkovaya Metallurgiya, No. 9(249), pp. 18–23, September, 1983.