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.     

NiAl powder alloys: II. Compacting of NiAl powders produced by various methods

The technological properties of granulated NiAl powders produced by gas spraying of melts and NiAl powders produced by calcium hydride reduction (CHR) of mixtures of nickel and aluminum oxides are compared. The possibilities of production of compact workpieces from these powders using hydrostatic pressing, hot pressing, hot isostatic pressing, and hot extrusion are estimated. To improve compressibility, preliminary milling and/or mechanical activation of the powders are proposed. The strength properties of NiAl rods with a diameter of 20 mm extruded from a temperature of 1100°C and made from the granulated powders are slightly higher than those made from the CHR powders. At temperatures higher than 800°C the properties becomes similar. Transition point t _d.b from the ductile to brittle state of samples made from powders sprayed in nitrogen and argon is 100?C150°C higher than those made from the CHR powders. The difference in the mechanical properties is caused by the structural and chemical microheterogeneity of granules (microingots), which is inherited in the rods after hot deformation and annealing at 1200?C1400°C and is (0.67?C0.88)T _m NiAl (T _m is the melting point, K).     

Properties of an atomized iron powder of branched particle shape

Conclusions The experimental atomized iron powders described combine good compactibility with high compressibility. The level of mechanical properties of parts from the experimental powders is much higher than that of parts from the control powders investigated. The optimum sintering temperature, ensuring the best combination of strength and ductility properties in parts from the experimental powders, is 1100°C. Metallographic investigations of the particle shapes of powders and of the structures of parts sintered from them have shown that, because of the well-developed particle surface of the corallike powders, the resultant materials have a fine porous structure and good mechanical properties.The authors are most grateful to S. M. Solonin for assistance with experiments and helpful discussion of results.Translated from Poroshkovaya Metallurgiya, No. 10(262), pp. 1–7, October, 1984.     

Magnetic properties and magnetization mechanism of anisotropic NdFeB/SmFeN hybrid bonded magnets prepared with different coercivity NdFeB powders

Anisotropic NdFeB/SmFeN hybrid bonded magnets were prepared by warm compaction process under an orientation magnetic field of 22 kOe,mixing with anisotropic SmFeN powders in different addition and HDDR-NdFeB powders in different coercivity.With the addition of 20 wt% SmFeN,the density and remanence of hybrid magnets increase from 5.58 g/cm³,8.4 kGs to 6.02 g/cm³,9.0 kGs,respectively.And as the addition amount of SmFeN powders varies from 20 wt% to 40 wt%,the maximum energy ...     

Hot Pressing Technology to Produce Wear-Resistant P/M Structural Materials with Dispersed Solid Inclusions

We have examined the possibility of milling iron, nickel, chromium, high-speed steel, and titanium carbide powders in an attritor (attrition mill) for use in producing carbide steel. The powders were milled to a particle size of 1–3 μm for TiC and 10 μm for metal components. As a rule, such powders and mixture of powders do not flow or form, which makes it impossible to produce blanks for hot pressing by the traditional die pressing method. Shells pressed from iron powders are proposed for forming a blank. We tested techniques for hot pressing dispersed powders into such envelopes. __________ Translated from Poroshkovaya Metallurgiya, Nos. 7–8(444), pp. 43–50, July–August, 2005.     

Synthesis of Invar 36 type alloys from elemental and prealloyed powders by mechanical alloying

Invar 36 (Fe₆₄Ni₃₆) nanocrystalline powders were successfully obtained by the mechanical alloying process. The mechanically alloyed Invar 36 powders were obtained from both, Fe–Ni elemental and Fe–Ni₃Fe prealloyed powders. XRD, DSC and magnetic measurements were used to characterise the Invar 36 powders. The lattice parameter evolution versus temperature of Invar 36 powders was investigated by in-situ high-temperature X-ray diffraction (HT-XRD). For both, Invar 36 (Fe, Ni) and Invar 36 (Fe, Ni₃Fe) powders, the lattice parameter values are constant up to about 350°C. The magnetic measurement also indicated that the Invar 36-type alloys are formed after 16?h of milling.     

SPHEROIDIZATION OF IRREGULARLY SHAPED METAL POWDERS

Abstract

Irregularly shaped powders of aluminium, 90:10 bronze, 302B stainless steel, electrolytic copper, titanium, molybdenum, and tungsten carbide were converted into spherically shaped powders by dropping the powders through vertical furnaces. Several types of furnaces were built and used. The operating temperatures extended from 1650 to 3000°C, depending on the material being spheroidized, and the protective atmosphere was argon, helium, or hydrogen. The finished powders had excellent sphericity and density.     

Clssified refractory compound powders

Conclusions Technical quality requirements for refractory compound abrasive powders and optimum conditions for the comminution and classification of some refractory compound powders have been determined. A study was made of some physicomechanical properties (strength, abrasive ability, specific surface, and apparent density) of TiB₂, TiC, and TiN powders. The existence of a method for the manufacture of refractory compound abrasive powders and data yielded by a study of their physicomechanical characteristics will enable these powders to be used in the near future on a wider scale in tool production.Translated from Poroshkoyaya Metallurgfya, No. 6(234), pp. 92–98, June, 1982.     

Manufacture of magnetic cores from various iron powders

Conclusions Coercive force measurements were made on grades PZh4M3, PZhCh3SV, PZhCh3MV, NC 100.24, PZhR(0) and PZhÉ iron powders and magnetic cores heat treated in the temperature range 750–1200°C. Iron powders of large specific surface are characterized by greater coercive forces compared with powders of small specific surface. Grades PZhCh3SV, PZhCh3MV, NC 100.24, and PZhR(0) iron powders are suitable for the manufacture of magnetic cores after they have been alloyed with elements decreasing internal stresses in alloys. Sintered magnetic cores from PZhÉ electrolytic iron powder meet all the requirements of TU 16-538.225-74 without alloying. The properties of grades EMP300M, PM282N, KiP 270.MS, and SC 100.26 iron powders were assessed. KiP 270.MS and SC 100.26 powders possess the same properties as PZhCh3SV, PZhCh3MV, and NC 100.24 powders, but in grade SC 100.26 powder high oxygen contents are not permissible. Consequently, magnetic cores made from this powder will exhibit high coercivity. Grades EMP300M and PZhR(0) iron powders are similar in all their properties, and the magnetic characteristics of cores made from them will therefore also be comparable. Grade PM282N iron powder is produced by the electrolysis of solutions and characterized by a dendritic particle shape. Owing to the large specific surface of the particles of this powder, its coercive force will be 25–30 A/m greater than that of PZhÉ. In the manufacture of magnetic cores from this powder recourse must therefore be had to alloying with silicon in order to decrease their coercivity.Translated from Poroshkovaya Metallurgiya, No. 6(234), pp. 73–78, June, 1982.     

粉末冶金用PEG80F蜡粉对压坯成形性的影响

本文研究了PEG80F蜡粉作为模压成形剂其本身的成形性及其对WC粉、铁粉和不锈钢合金316L+2%Cu+2%Sn混合粉成形性的影响。结果表明:PEG80F蜡粉具有良好的成形性;加入PEG80F蜡粉的WC粉、铁粉和不锈钢合金混合粉也均具有良好的成形性,其中,加入1.5%和0.75%PEG80F蜡粉的不锈钢合金混合粉在817 MPa下压制后的压坯具有较高的生坯强度,边缘保形性较好。     

Highly dispersed composite iron—Copper powders obtained from oxalates by a thermochemical method

The preparation of highly dispersed composite iron—copper powders with various concentrations of copper from mixed iron and copper oxalates was studied. The physico-chemical properties of the powders were determined. The powders were corrosion resistant, hydrophilic, practically monodispersed, bacteriocidal and tolerated the sterilization at elevated temperatures. Their magnetic properties could be regulated in the process of forming the initial components. Such powders can be useful in medicine, biology and technology. Institute of Colloid and Water Chemistry, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 7–8(402), pp. 1–4, July–August, 1998.     

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.     

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.     

Cryomilling for the fabrication of a particulate B4C reinforced Al nanocomposite: Part II. Mechanisms for microstructural evolution

Cryomilling was successfully employed to fabricate particulate B₄C-reinforced Al matrix nanocomposite powders. In order to investigate the microstructural evolution during cryomilling, composite powders were milled for different times. These powders were collected from the milling chamber and the microstructures were characterized to reveal the formation mechanism for this nanocomposite. The microstructural evolution, including the morphology and size of the milled composite powders, the size and distribution of the B₄C, and the dimension of the Al grains, is discussed on the basis of the experimental results.     

Effect of thermal conditions of preparation of dispersion-strengthened nickel powders on the character of distribution of the strengthening phase

Conclusions The thermal conditions of treatment of oxide powders produced by chemical coprecipitation exert a pronounced influence on the mechanical properties of semifinished products of dispersion-strengthened nickel made from these powders. Raising the calcining temperature of such oxide powders activates particle redistribution processes and has an adverse effect on the uniformity of distribution of the strengthening phase, which leads to the formation of large particles in the subsequent stages of plastic working and heat treatment of the powders and a steady deterioration in the mechanical properties of semifinished products.Translated from Poroshkovaya Metallurgiya, No. 8(236), pp. 43–46, August, 1982.     

Volume changes accompanying the sintering of compacts from mixtures of titanium and iron powders

Conclusions The sintering of compacts from mixtures of titanium and iron powders at temperatures below the eutectic point is accompanied by their shrinkage, the sintering process being mainly determined by the particle size of the starting powders. During the sintering of compacts from mixtures of titanium and iron powders at temperatures exceeding the eutectic point the compacts grow in size, the extent of the growth depending on the particle size of the powders. This phenomenon may be attributed to the effect of heterodiffusion on sintering processes and to the crystallization pressure generated during the formation of intermetallic compounds.Translated from Poroshkovaya Metallurgiya, No. 5(233), pp. 17–21, May, 1982.     

Electrodeposition of Co-Ni-MoxOy Powders: Part I. The Influence of Deposition Conditions on Powder Composition and Morphology

The Co-Ni-Mo_xO_y powders were obtained electrochemically at a constant current density from ammonia electrolyte. Ni and Co were anomalously deposited, inducing Mo deposition, which cannot be deposited separately from aqueous solutions. The obtained Co-Ni-Mo_xO_y powders were investigated by energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and scanning electon microscope (SEM) methods. Based on the obtained experimental results, it was concluded that the particle size of deposited powders is influenced by the chemical composition of the electrolyte and current density imposed. XRD results suggested that obtained powders were of amorphous structure, although a Co₃Mo compound can be formed if certain experimental conditions are applied.     

THE PROPERTIES OF POROUS NICKEL PRODUCED BY PRESSING AND SINTERING

Abstract

The effects of compacting pressure and of sintering temperature and time on the properties of porous sintered nickel compacts have been studied, using three carbonyl and two reduced nickel powders. For all five powders, the density of the green compacts and the porosity of the sintered compacts were linearly related to the log compacting pressure. Similar relationships with pressure were observed for strength and electrical conductivity.

Photomicrographs of sections through the sintered compacts made from the reduced nickel powders show that there are pores in two different size ranges, originating from the porosity between the original powder particles and the pores within the particles. It is concluded that sintered compacts from all five powders containing 40–50% porosity have adequate strength and conductivity for use in fuel-cell electrodes.     

On selection of milling atmosphere for production of Al–10%Ti powders

Abstract

A mixture of aluminium and 10 wt-% titanium powders was attrition milled for 10 h under air, nitrogen and vacuum atmospheres; pure aluminium powders were also prepared in a like manner. Particle size distribution, morphology and microstructure of the powders were studied by laser diffraction, scanning electron microscopy (SEM) and X-ray diffraction (XRD); special attention was paid to the influence of the milling atmosphere. There were differences in powder particle size obtained from pure Al powders that were not observed for Ti containing powders, however the same homogeneous morphology and microstructure was attained for the different milling atmospheres. The effect of milled powder annealing on microstructure was studied by differential scanning calorimetry (DSC) and XRD. New phases and their crystallite size were characterised as a function of annealing temperature, milling atmosphere, and powder microhardness. In short, the studied milling atmospheres for the production of Al–10%Ti powders do not affect the properties of the obtained powders, and in general, low cost atmospheres could be used.     

High-dispersion iron powders produced by the thermochemical method

The problem of producing high-dispersion iron powders is very complicated because of the fact that these powders are highly pyrophoric and, consequently, the number of methods of production of these powders is limited. Another difficulty is that the majority of these methods do not make it possible to vary the properties of microcrystals in the required range and this greatly restricts the application of powders. Institute of Colloidal Chemistry of Water, National Academy of Sciences of the Ukraine. Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5–6, pp. 1–4, May–June, 1998.