Obtaining of a finely dispersed powder of gadolinium hydroxide

Finely dispersed powders of gadolinium hydroxide are obtained by chemical deposition (dispersing). The influence of various factors on the powder characteristics such as dispersity, morphology, and chemical composition is investigated. The dependence that the mentioned characteristics have on the character of the anion of the gadolinium salt, the concentration and acidity of its solution, and the concentration of the precipitant and pH of precipitation, is established. The optimal results are observed with the use of diluted chloride solutions of gadolinium and a 5–10 wt % precipitant in the form of the NH₃ solution.     

Laws governing vibrating feeding of finely dispersed powder into a laser sintering zone

A vibrating powder feeder that makes it possible to deposit powder in a laser sintering zone in a continuous flow or in discrete portions has been developed. The dependence of the rate of flow of the powder on the rate of the vibrations, the parameters of the construction of the feeder, and the properties of the powder is investigated. The possibility of regulating the process of deposition of the powder is considered.     

Laws governing vibrating feeding of finely dispersed powder into a laser sintering zone

A vibrating powder feeder that makes it possible to deposit powder in a laser sintering zone in a continuous flow or in discrete portions has been developed. The dependence of the rate of flow of the powder on the rate of the vibrations, the parameters of the construction of the feeder, and the properties of the powder is investigated. The possibility of regulating the process of deposition of the powder is considered.     

Investigation of the magnetic properties of strip made from iron powder

Conclusions Strip with a porosity of 25%, when sintered at a temperature of 1200°C in hydrogen with a dewpoint of –30°C, is refined with respect to carbon and oxygen. At the lower sintering temperatures of 1000 and 1100°C, the carbon content is reduced to 0.03–0.02%; the quantity of not easily reducible oxides remains unaltered.With regard to the kinetics of grain growth, nonporous strip made from iron powder may be classed with steels which are coarse-grained by their prehistory.Porosity substantially affects the value of coercivity. Each 2% of pores increases the coercivity approximately by 0.1 oersted.If temperatures of 1200°C and above, with holding times of 2–3 hr are used for presintering, and temperatures of 900–1000°C for the final heat treatment of the nonporous strip, the magnetic properties of the strip can satisfy the requirements of GOST 3836-47 for low-carbon, electrical engineering thin sheet steel.     

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 properties of highly dispersed boron nitride powder

Translated from Poroshkovaya Metallurgiya, No. 6(306), pp. 52–56, June, 1988.     

粉末冶金工艺对纯铁磁粉芯力学性能的影响

在铁粉中添加耐热型树脂粘结剂,通过球磨使铁粉颗粒表面包覆一层均匀的绝缘膜,再利用模压和热处理制备纯铁磁粉芯,研究球磨工艺对铁粉形貌和粒径的影响,分析压制压力、热处理工艺以及粘结剂含量对纯铁磁粉芯力学性能的影响。结果表明,在转速400 r/min、球料质量比15:1、球磨时间10 h的条件下可将粉末研磨成适合于制备铁磁粉芯的鳞片状铁粉,平均粒径为100μm;在粘结剂总含量2.65%、压制压力1 200 MPa、压坯在N2保护气氛下500℃保温1 h条件下,获得的磁粉芯力学性能最佳,抗压强度达到502.98 MPa。     

Some properties of reduced iron powder manufactured from Mill-scale

Conclusions Some key data are presented on the properties of iron powder reduced with a solid reducing agent from low-carbon steel mill-scale and on the mechanical characteristics of specimens pressed from this powder and sintered in hydrogen and dissociated ammonia atmospheres. The properties of iron powder manufactured by the process described meet the requirements of powder metallurgy.Translated from Poroshkovaya Metallurgiya, No. 3 (135), pp. 102–106, March, 1974.     

Mechanical properties of fully densified injection-molded carbonyl iron powder

The mechanical properties of carbonyl iron powder shaped by injection molding techniques are affected by the grain size, sintered density, and carbon content. Control of the carbon level depends on several factors, including the binder composition, debinding approach, and sintering conditions (atmosphere, temperature, time, and furnace design). Sintered compacts were densified by containerless hot isostatic pressing, giving smaller grain sizes and superior properties than were possible by pressureless sintering at a high temperature. A quick hot isostatic pressing route (gas forging) with a peak pressure higher than 500 MPa for 1 minute helps retain carbon and results in excellent properties due to a high final density and small grain size. This approach resulted in a final strength of 732 MPa with extensive ductility (23 pct reduction of area) for injection-molded carbonyl iron.     

Increasing the anticorrosion properties of diffusion chromized porous powder metallurgy iron

Translated from Poroshkovaya Metallurgiya, No. 4, pp. 28–31, April, 1992.     

Relationship between the electromagnetic and physicochemical properties of carbonyl iron powder

Summary The relationship is examined between the electromagnetic properties of carbonyl iron powder and some factors involved in the manufacture of this powder. The electromagnetic properties depend on the onion skin structure of the powder particles and the chemical composition and particle size of the powder.Translated from Poroshkovaya Metallurgiya, No. 7 (43), pp. 38–44, July, 1966.     

Influence of dispersed microadditives on the structure and properties of powder carbon and high-chromium steels

The influence of dispersed different nature microadditives on structure formation and volume changes during sintering, and strength of powder carbon and high-chromium steel is investigated. Mechanisms of the effect of additives on the formation of their structure are described. It is shown that the introduction of sodium bicarbonate provides the largest strengthening of carbon steel, while the introduction of boron nitride provides that of high-chromium steel. The level of increasing the strength depends on the sintering temperature and amount of additive.