Iron-nickel Powders Research Articles

Mechanism and kinetics of reduction of complex oxides of the NiO-Fe2O3 system

For rational introduction of production of iron-nickel powder metallurgy alloys by the method of reduction of complex oxides [1-7] it is important to establish the mechanism and kinetic rules of reduction of the products of synthesis of NiO-Fe203 materials. For this purpose compositions with a molecular ratio of NiO and Fe20 ~ from 0.8154 to 36.1488, corresponding to iron-nickel alloys with 30-95% Ni, were synthesized under optimum conditions (temperature I~50~ time 3 h, air cool). The synthesis (ferritization) was done under conditions of activated annealing with the participation of the gaseous phase, the products of decomposition of NH4CI, added to the original charge in a quantity of 3%.

Bioassay of environmental nickel dusts in a particle feeding ciliate.

The ciliated protozoan Paramecium was used to quantitate cytotoxic and genotoxic effects of nickel particles. The biological response of these eukaryotic cells to pure nickel powder and iron-nickel powder was assayed and compared to the effect of the inorganic carcinogen nickel subsulfide. Cytotoxicity was determined by the percent survival of treated cells. Genotoxicity was indicated by significant increases in the fraction of nonviable offspring (presumed index of lethal mutations) found after self-fertilization (autogamy) in parents from the nickel-treated versus neutral control groups. The cells were exposed to the dusts and the biological effects determined. Only the nickel subsulfide consistently showed a significant increase in offspring lethality.

Deposition of iron-nickel powders from simple electrolytes in a two-layer electrolytic bath

Deposition of iron-nickel powders from simple electrolytes in a two-layer electrolytic bath

Manufacture and some properties of iron-chromium-nickel alloy powders

1. Techniques have been developed for the preparation of iron-chromium-nickel alloy powders representing a wide range of chemical compositions. In the preparation of such powders, use was made of the following processes: a) diffusion impregnation with chromium of iron-nickel alloy powders prepared by the coreduction of oxides of the metals involved; b) simultaneous interimpregnation of iron, nickel, and chromium powders; c) diffusion impregnation with chromium of an iron-nickel powder mixture prepared by the hydrogen reduction of nickel carbonate in the presence of iron powder. 2. A study of the properties of iron-chromium-nickel powders yielded by various processes has shown that homogeneous alloy powders in the range of compositions corresponding to Kh18N9, Kh18N15, and Kh23N18 austenitic steels can be prepared only by the method of diffusion impregnation of iron-nickel alloy powders with chromium. Such powders exhibit excellent compressibility, while sintered materials produced from them possess mechanical properties greatly superior to those of materials produced from powders prepared by other technological variants of the diffusion impregnation process.

Phase composition of carbonyl iron-nickel powders

1. A thermodynamic analysis is made of secondary reactions that may be responsible for contamination of carbonyl powders with carbon and oxygen. From a thermodynamic point of view, carbonyl iron-nickel powders may contain carbon in free form (carbon black) and in the form of cementite, Fe3C; the formation of nickel carbide, Ni3C, cannot be ruled out. Oxygen may be present in combined form as wustite, magnetite, and nickel oxide. 2. Carbonyl iron-nickel powders containing 20, 50, and 80% of nickel were analyzed for carbon and oxygen, and the phase condition of the contaminants was determined. 3. It was established by chemical phase analysis, and confirmed by x-ray diffraction and NGR methods, that much of the carbon in carbonyl iron-nickel powders is present in carbide form. 4. Oxygen in iron-nickel powders appears to be combined in the form of Fe3O4 (as revealed by x-ray structural analysis and an NGR study). 5. The relationship was established between the amount of carbon present in carbide form in iron-nickel powders and the latter's composition. It was found that, on passing from 20N to 80N powder, the amount of carbide-type carbon falls from 1.20 to 0.86%. 6. It is shown that the concentration of carbide-type carbon in an iron-nickel powder of a given composition is comparatively stable. When powder batches of the same composition exhibit total carbon content fluctuations attributable to the technological process of thermal decomposition, the fluctuations are due to variations in their carbon black content.

Manufacture of powders by the mechanical comminution of sulfur-containing iron-nickel alloys

1. Using 80N2M alloy as an example, it has been shown that mechanical comminution of sulfur-embrittled bulk alloys is a potentially useful method of preparation of iron-nickel alloy powders. 2. The optimum sulfur content of 80N2M alloy has been established ensuring that a fine grain is formed in the course of hot rolling and that the resultant hot-rolled alloy can be effectively comminuted in impact-type mechanical mills. 3. A comparative study was carried out of the physicotechnological properties of iron-nickel alloy powders produced by the techniques of coreduction of oxides, atomization or a molten metal stream, and mechanical communution of a sulfur-embrittled hot-rolled alloy. As a result of experiments on 80N2M alloy, the advantages have been demonstrated of mechanical comminution as a method of preparation of powders possessing high apparent and pyknometric densities. Such powders appear to be suitable for the formulation of high-permeability magnetic materials.

Concentration distribution in reduced iron-nickel powders

Concentration distribution in reduced iron-nickel powders

Some properties of carbonyl iron-nickel powders

1. Specimens from carbonyl iron-nickel powders prepared by the process developed at the Gipronikel' Institute are distinguished by their high chemical purity. The amount of carbon present in these powders drops in the course of sintering to thousandth parts of 1%, while their total gas content does not exceed 0.005–0.008% and the concentration of other impurities, 0.01%.

Process for the preparation of carbonyl iron-nickel powders

Process for the preparation of carbonyl iron-nickel powders

Electrolytic method of continuous production of multicomponent metal powders

1. A process has been developed for the continuous electrolytic preparation of iron-nickel powders of any desired component ratio. The process is based on the use for electrolysis of composite anodes and an auxiliary iron-gauze electrode with independent regulation of the currents passing through each electrode. 2. An investigation was conducted into the effects of electrolysis parameters (cathodic current density, solution composition, concentration and acidity, temperature, etc.) on the current yield, chemical composition, and particle size of the powder. By varying the cathodic current density, the Ni/Fe ratio of the solution, and, accordingly, the ratio of the anodic currents, it is possible to obtain iron-nickel powders of various particle sizes and any required composition. 3. The optimum electrolysis parameters for the preparation of iron-nickel powders of various compositions and particle sizes have been established. 4. The resulting powders were subjected to metallographic and x-ray diffraction examinations and sieve analysis, and their hydrogen and oxygen contents were determined. It was found that, structurally, the powders are solid solutions of one of the components in the other. 5. The new process for the electrolytic preparation of iron-nickel powders was tested and found to be effective at the Leningrad Coke and Gas Plant.

Electrodeposition of nickel ? Iron alloy powder

1. On the basis of an investigation into the properties of various solutions, the following optimum electrolyte composition (moles/liter) was chosen: 0.2 nickel and iron (jointly) in the form of sulfates, 0.38 (NH4)2SO4, 0.07 NaF, and 0.2 KCl; pH 5. 2. It is shown that the composition of the iron-nickel alloy powder is governed by the concentration of its components in the electrolyte, but is not affected by changes in current density or electrolyte temperature. These characteristics are attributed to the fact that the limiting discharge currents of nickel and iron are similar and change in an equivalent manner under the influence of electrolysis conditions. 3. A study was made of the phase composition of the alloy as a function of nickel and iron concentrations and current density. It was established that the alloys represent a continuous series of solid solutions. 4. The influence of electrolyte composition and electrolysis parameters on the current efficiency was investigated. It was concluded that the optimum electrolysis parameters are a current density of 3000 A/m2 and a temperature of 30°C. 5. The physical properties of the alloy powders were investigated as a function of electrolysis conditions. It was found that 54% of all particles in the powder produced under the optimum conditions are <42μ in size, and have an apparent density of 2.85–3.0 g/cm3 and a specific surface area of 1.84×10−2 m2/g. The current efficiency under such conditions is 72–74%.

Preparation and investigation of 50H carbonyl permalloy powder

1. A procedure has been worked out for the preparation of iron-nickel powders by dissociation of mixed carbonyls in a free heated space of a decomposer. 2. It has been shown that the carbonyl iron-nickel powders thus produced are contaminated with sooty carbon, which can be removed to within a few thousandths of a percent either from the powder or from pressings by treatment with dry or moist hydrogen, or in vacuo at higher temperatures (400–700°C). 3. It is suggested that the high activity of carbonyl powders results from the restricted growth in layers of iron and nickel crystals from the gas phase during decomposition of the carbonyl mixture. 4. Conditions are given for removal of carbon from pressings, and for formation of a uniform solid solution with excellent magnetic properties. 5. If a solution of polyvinyl alcohol is admixed to the powder, the compressibility becomes quite satisfactory, and the density of compressed samples increases. 6. The magnetic properties of the ultimate sintered samples of carbonyl 50H permalloy are much better than the values specified in GOST 10160-62.

The homogeneity of electrolytic iron-nickel powders

1. Like carbonyls, electrolytic iron-nickel powders are nonequilibrium alloys with a concentration heterogeneity (although it is considerably smaller than that of carbonyl powders). 2. With increasing annealing temperatures the concentration heterogeneity of electrolytic iron-nickel powders decreases. 3. The homogenization rate of electrolytic iron-nickel powders is considerably lower than that of carbonyl powders.

Investigation of homogeneity of carbonyl iron-nickel powders

1. Carbonyl iron-nickel powders, obtained by codecomposition of carbonyls, are nonequilibrium two-phased alloys with a considerable inhomogeneity of composition. 2. Annealing at low temperatures enables a considerable homogenization of the powders. 3. The “bulbous” structure of the particles of powder disappears after a low temperature anneal.

Gas Carburizing and Quenching of Sintered Iron-Nickel

Sintered iron-3%nickel specimens prepared from the mixture of reduced iron and carbonyl nickel powders were gas carburized and oil-quenched. The effects of nickel addition were examined. The results obtained are as follows :1) The increase in sintered density by nickel addition was found to be effective in reducing the penetration of carburizing gas to the interior of the sintered specimens. The carbon decrease in the carburized specimens is remarkable owing to the high density of the specimen obtained by the prolonged sintering.2) The surface carbon content of carburized specimens tends to decrease as compared with sintered and carburized iron specimens owing to the density increase and the change of the carbon activity in austenite by the nickel addition.3) The increase in quench-hardening ability by the nickel addition depends on the diffusion of nickel into iron during the sintering. The depth of the hardened case increases in the early stage, and then decreases, with increasing sintering time. This decrease of depth is due to the above mentioned carbon decrease during the prolonged sintering.

Prealloyed Iron-Nickel Powders by an Amalgamation Process

AbstractX-ray studies indicate that mixed iron and nickel “amalgams” are reactive even at room temperature. By distilling off the mercury from these amalgams at temperatures between 400 and 100°C, ultrafine iron-nickel alloy powders are readily obtained. X-ray studies show that these powders possess equilibrium structures corresponding to the temperature of preparation. Alloy powders belonging to many alloy systems and having controlled composition, purity, and particle size may be prepared by this process. One special use of the process is in the preparation of homogeneous alloy powders for studying solid state equilibria below 400°C, particularly in alloy systems with sluggish transformations, the process being invaluable in the temperature range between 200 and 100°C, Another is in the preparation of ultrafine metal and alloy powders with equally fine, if not finer, dispersions of other phases, suited for studying dispersion-strengthening. Both of these special uses are currently under investigation,