Acceleration of mechanical size reduction of chromium carbide powders and mixtures based on chromium carbide

We have investigated how mechanical activation by rolling on smooth rollers affects the dispersion kinetics of chromium carbide powders and mixtures of chromium carbide powder with nickel in a ball mill. We have shown that preliminary double rolling of chromium carbide powder on a rolling mill accelerates particle size reduction in the ball mill down to a size of 1.4–1.5 μm by a factor of 4.6 compared with unrolled powder. In this case, the size reduction increases from 36 to 91 in relative units. The mean particle diameter for the powders and mixtures decreases exponentially as the grinding time increases from 12 h to 84 h. Translated from Poroshkovaya Metallurgiya, Nos. 1–2(411), pp. 1–8, January–February, 2000.     

超细球形镍粉的制备

在不使用分散剂和表面活性剂的条件下,以水溶液为反应体系,水合肼为还原剂,采用液相还原法制备超细镍粉.通过扫描电子显微镜、X射线衍射仪、激光粒度分析仪、能谱分析仪等测试仪器对粉体进行表征,研究了反应温度和[N2H4]/[Ni2+]浓度比对镍粉平均粒径、形貌、分散性、还原率以及纯度的影响,探讨了镍粉从刺球形向球形转变过程中...     

Hot rolling of blanks from copper and nickel powders

Summary The authors investigated the hot rolling of preformed blanks from electrolytic copper and carbonyl nickel powders. The blanks were prepared by cold pressing, cold rolling, wedge pressing, and sintering loosely poured powder. The hot rolling was carried out in a special mill, in a hydrogen atmosphere. The investigation showed that at high rates of deformation, a rolling temperature of 0.8–0.9 T_melt, and a reduction of 50% the hot rolling of preformed copper and nickel blanks in one pass can yield strip with a relative density of 100%, a fine-grained structure, and mechanical properties which are not inferior to those of materials obtained by sintering powder compacts or cold-rolled strip.Translated from Poroshkovaya Metallurgiya, No. 6 (66), pp. 25–28, June, 1968.     

Electroless deposition of metals on alumina powders

Conclusions A study was made of the processes of electroless plating of alumina powders with nickel and copper. Electroless nickel and copper plating with full pretreatment was performed at room temperature. In nickel plating by the process investigated the number of pretreatment operations can be reduced by raising the solution temperature to 50–55°C, although nickel plating with full pretreatment is to be preferred from a practical point of view. The concentrated solutions investigated are suitable for the application of nickel and copper layers of considerable thickness to alumina powder particles.Translated from Poroshkovaya Metallurgiya, No. 5(209), pp. 14–16, May, 1980.     

Study of specific pressure during the rolling of metal powders

Conclusions The nature of the distribution of specific pressure on the contact arc of roller-metal is shown experimentally.A dependence is established for the ptessibility of powders of iron, 1Kh18N9T stainless steel and copper during vertical and horizontal rolling.An equation is proposed, describing the dependence of densification of the powder on the maximum specific pressure on the metal-roller contact arc.The dependence between the critical angle, the contact angle and the maximum specific pressure during vertical and horizontal rolling of iron powder is investigated, an increase in these angles being noted with an increase in pressure on the roller.It was established that the pressibility of powders during rolling is higher than during pressing by 10–15%.     

Use of low-temperature plasma for the production of ultrafine copper powders

Conclusions In an investigation of the hydrogen reduction of copper chloride in a stream of arc-discharge argon plasma ultrafine (d<0.1 m) copper powders of spherical particle shape were obtained characterized by comparatively narrow particle size distribution functions. Their oxygen content was 0.1 wt. %. It was found by experiment that the mean particle size of such a copper powder and its particle size distribution vary as functions of the rate of supply of copper chloride, but are independent of the rate of feed of the plasma-forming gas, which is in accord with the proposed model of frontal reaction of copper chloride with hydrogen on the scale of turbulent globules. Ultrafine copper powders produced by the method described can be pressed at room temperature to a residual porosity of not more than 5%.Translated from Poroshkovaya Metallurgiya, No. 11(263), pp. 23–28, November, 1984.     

Producing thin sheet materials of copper-tin powders

Conclusions A study was carried out on rolling powders of copper with 6.5% tin, sintering, compression rolling, and thermal stabilization of the strip. The thin strip of tin bronze is used as tools for cutting diamond crystals.Translated from Poroshkovaya Metallurgiya, No. 6 (66),pp. 95–97, June, 1968.     

Properties of fine metal powders produced by the formate pyrolysis method

Conclusions Optimum parameters have been determined for the processes of preparation of fine copper, nickel, and cobalt powders by the pyrolysis of formates in a protective argon atmosphere. Use of fine copper, nickel, and cobalt powders prepared by this method as interlayers in the vacuum diffusion welding of copper and steel parts enables the temperature of the process to be substantially lowered. Copper coatings can be applied to metallic and nonmetallic materials in the course of the pyrolysis of copper formate.Translated from Poroshkovaya Metallurgiya, No. 3(207), pp. 1–6, March, 1980.     

用粘结剂处理的预合金Mo钢基预混粉取代扩散粘结粉

现已采用成本较低的粘结剂处理预混粉FLOMET 44A和44B取代扩散粘结粉。为避免镍与铜的偏析和改善预混粉的流动性。将以0．85％Mo预合金ATOMET 4401作基体粉，并添加镍、铜与石墨制取的预混粉进行粘结剂处理。其性能类似于扩散粘结粉。FLOMET 44A和44B已用于制造汽车、电动工具与农机零件。研究了它们的压缩性、重量稳定性、力学性能与显微组织，并分别与含1．75％Ni和4．0％Ni的扩散粘结粉做对比。低成本的粘结剂处理预混粉其尺寸变化、稳定性和力学性能与扩散粘结混合粉相同。     

NiAl powder alloys: I. Production of NiAl powders

The influence of five methods of production of Ni₅₀Al₅₀ powder alloys on the processes occurring during reactive alloy formation of nickel monoaluminide during heating is considered. It is shown that, when powder mixtures obtained by agitation in ball mills and cladded composite powders with a low level of internal stresses are used, it is possible to produce a material with a nearly equilibrium phase composition in the course of reactive sintering due to an exothermic effect with the participation of a liquid phase (aluminum melt) in the reaction. The sintered material is porous and has an island structure. Mechanical alloying in a high-energy ball mill (attritor) results in the formation of layered Ni/Al granules with a developed interface and a high level of internal stresses and defects, which makes it possible to decrease the temperatures of initiation of reactive interaction by ∼300°C. This interaction develops in the solid phase according to a slow diffusive mechanism leading to the formation of intermediate nickel aluminides and hindering the achievement of equilibrium phase composition. The microingot granules (∼80 wt % particles 100–400 μm in size) produced by melt spraying by gases (N, Ar) has the composition of the melt, but grain boundaries are depleted of aluminum in comparison with the volume. The NiAl powders (∼90 wt % particles <40 μm in size) produced by combined hydride-calcium reduction are characterized by a highly homogeneous nickel and aluminum distribution, and their composition is close to equilibrium. These two types of powders are selected as the initial material for investigating the compacting and production of NiAl-based alloys.     

Double mixtures of ultrafine metal powders: Production, rolling, and sintering. I. Thermal decomposition of double metal formate mixtures

The paper considers the production of double mixtures of ultrafine powder materials. An attempt is made to determine the role of the second component and its effect on thermal decomposition, rolling, and sintering.     

The angle parameters of the metal-powder rolling process

Summary The investigation established the regularity of variation of the angle _P as a function of the maximum specific pressure during the rolling of aluminum, iron, copper, and nickel powders, as well as the regularity of the relationship between the angle _P and strip thickness as a function of conditions of powder feed into the deformation zone. The character of variation and the value of the neutral angle during the rolling of iron, copper, and nickel powders were determined.     

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).     

Development of a Technology for the Production of Tubes from Ni ― Mo Alloy Powder

Technology for the production of tubes from mixtures of nickel and molybdenum powders by hot pressing and cold rolling was developed. The operational parameters for hot pressing were determined and the engineering and mechanical properties of the tubes studied. The effect of annealing temperature on the mechanical properties of the hot-pressed metal was investigated. Regimes for cold rolling the hot-pressed tubes in rolling mills were determined. The rolled tubes were tested in accordance with the accepted specifications for alloy ÉP982. All tubes passed the engineering tests; the mechanical properties of the tube metal are superior to those of alloy ÉP982. The proposed technology is quite economical, the yield of satisfactory product is 80-85%.     

Industrial production of powders of copper alloys by impact atomization of a jet of melt

A plant for use in impact atomization of a jet of a metallic melt by fast turning impact blades is described. Using as an example industrial production of powders of copper alloys at a rate of 2–2.5 t/h, several positive elements of the method of impact atomization are demonstrated including high yield of satisfactory fractions (90–92%) with comparatively low electricity consumption (4–8 W per kilogram of melt), as well as small overall dimensions, simplicity, and low cost of the impact atomization plant. The characteristics of deposited bronze powders are presented. It is demonstrated that application of impact atomization for large-scale production of powders of copper, iron, and nickel alloys as well as special nickel-and copper-based powders in an inert medium is highly promising. __________ Translated from Poroshkovaya Metallurgiya, Nos. 1–2(447), pp. 112–117, January–February, 2006.     

Formation of an ultrafine nickel powder

The phase compositions and structures of ultrafine nickel powders fabricated by chemical dispersion are studied by X-ray diffraction. The kinetic characteristics of metallization during the formation of a nickel powder with nanoparticles are determined.     

Character of electrical resistivity variation in the sintering of ultrafine powders

Conclusions As a result of oxidation of compacts from nickel and copper UFPs, their electrical resistivities may vary within a wide range. During the vacuum sintering of nickel and copper UFPs changes in electrical resistivity are recorded before densification. During heating the electrical resistivity of compacts may fall at a rate of up to half an order a minute. Measurements of and L/L during repeated heating-and-cooling cycles reveal increases in the electrical resistivity and elongation of specimens, which may be linked with elastic after-effect phenomena. A small rise in electrical resistivity during heating to 100C may also be brought about by elastic stress relaxation. An increase in electrical resistivity accompanied by shrinkage during a rise in temperature after isothermal sintering is indicative of rupture of contacts during densification; the extent of this process, which may be linked with sliding of whole particles relative to one another, diminishes with rise in temperature.Translated from Poroshkovaya Metallurgiya, No. 2(266), pp. 24–28, February, 1985.     

The rolling coefficients of metal powders

Summary The investigation established that, in contrast to compaction in a closed die, the compressibility coefficient for the rolling of metal powders is not equal to the densification coefficient. The ratio of the compressibility coefficient to the densification coefficient for the rolling of metal powders gives the extension coefficient of the powder volume, the value of which is constant for each material being rolled and is always greater than unity.With a gravity feed of powder, the values of the compressibility and densification coefficients are uniquely determined by the maximum specific pressure and, consequently, by the strip density. When the rolling width, strip thickness, and angle of rolling are varied by changing the conditions of powder feed into the deformation zone at a given strip density, the rolling coefficients are not affected.     

废旧锂离子电池正负极混合物氨浸液电沉积研究

利用电沉积法处理废旧锂离子电池正负极混合物氨浸液,考察了电流对电沉积过程中金属钴、锂、镍、铜的回收率,阴极金属粉末中金属分布率、物相与形貌的影响。结果表明,随着电流的升高,金属钴、镍和铜的回收率总体呈升高趋势,而锂的回收率总体较低,当电流为1.0 A时,钴、镍、铜和锂的回收率分别为98.15%、99.11%、99.91%和15.36%。阴极金属粉末中钴的占比最大,最高占比可达80.71%。电流大小对阴极金属粉末的XRD物相影响不大。从阴极金属粉末微观形貌来看,提高电流有利于减小阴极粉末的粒径。     

Solid-phase sintering of ultrafine W(Mo)-Cu composite powders

Conclusions The solid-phase sintering of W-Cu composites can be markedly intensified by using ultrafine starting powder charges, the degree of intensification being a maximum with charges produced by reduction of oxide mixtures subjected to prior annealing in air. In this way it is possible to obtain virtually nonporous W-Cu composites with copper contents of 10–35%. The composition dependence of shrinkage in the solid-phase sintering of ultrafine W(Mo)-Cu powder composites is nonmonotonic in character. An anomaly is observed which would appear to be linked with the phenomenon of zonal isolation.Translated from Poroshkovaya Metallurgiya, No. 1(253), pp. 19–25, January, 1984.