Showing papers on "Powder metallurgy published in 1978"

Particle Deformation and Sliding During Compaction of Spherical Powders: A Study by Quantitative Metallography

Abstract: (1978). Particle Deformation and Sliding During Compaction of Spherical Powders: A Study by Quantitative Metallography. Powder Metallurgy: Vol. 21, No. 4, pp. 179-187.

Method of forming and ultrasonic testing articles of near net shape from powder metal

Abstract: A method for sonic testing powder metal articles made by hot isostatic pressing in a thick-walled container including the steps of preparing the composite thick-walled container and article for sonic testing by machining sonic surfaces in the exterior surface of the thick-walled container and thereafter sonic testing the article through the walls of the container.

Preparation of Metal Powders

Abstract: Metal powders find extensive application in finely divided form or after consolidation into shaped products. Examples of the former include aluminum, copper, and bronze powders for use in paints and iron-base powder compositions for stick electrodes in welding. Powder consolida­ tion is reflected in a multitude of parts of varying size and geometry made by techniques involving pressing and sintering, the working of a powder preform, or the hot isostatic pressing of a loose powder compact. Con­ solidation of metal powders into a discrete rigid form constitutes the science and technology of powder metallurgy. With one or two exceptions, powder metallurgy is characterized by the absence of melting. Thus, the principles involved are similar to those utilized in the processing of ceramic materials. Whether intended for use in the finely divided form or for subsequent powder metallurgical processing, each application mandates a specific combination of powder properties and/or characteristics. Of primary importance are chemical composition, purity, structure, particle size (and size distribution), particle shape (and shape variations), surface area, and flow rate. In turn, powder "anatomy" is a direct function of mode of pre­ paration. Thus, the basis for characterization of a metal powder depends on a full knowledge and understanding of the method of preparation selected. The purpose of this review is to provide an up-to-date overview of powder production methods. Emphasis is placed on recent developments and expected trends. While reference is made to each of the major methods of powder production, the several established and emerging techniques of liquid metal atomization command most attention. These are of in­ creasing importance because they enable closer control of powder chemis­ try, purity, size, and shape. Indeed, the key to the healthy growth rate

Fracture Toughness of Powder Metallurgy and Conventionally Produced High-Speed Steels

Abstract: (1978). Fracture Toughness of Powder Metallurgy and Conventionally Produced High-Speed Steels. Powder Metallurgy: Vol. 21, No. 1, pp. 13-28.

Powder-metallurgy steel article with high vanadium-carbide content

Abstract: A powder metallurgy tool steel article for use in applications requiring high wear resistance having a carbide content of 10 to 18 volume percent of substantially all MC-type vanadium carbides, which carbides are substantially spherical and uniformly dispersed; the carbon content of the article is balanced relative to the carbide formers vanadium, chromium and molybdenum to provide an amount of carbon in the matrix of the article sufficient to permit the article to be heat treated to a hardness of at least 56 Rc.

Method for the production of precision shapes

Abstract: A method for producing precision shapes which includes the consolidation of powder metal preforms into a shaped porous preform. A first coating is applied to the preform, this first coating being porous while providing a diffusion barrier. A second coating which is also initially porous is then applied and the coated preform can then be degasified by subjecting the preform to a vacuum, particularly at elevated temperatures. The coated preform is then heated under vacuum to a temperature such that the second coating is densified to the extent that it becomes non-porous. Finally, the preform is subjected to a hot isostatic pressing operation whereby formation of high integrity, fully dense metal shape results.

Method for producing powder metallurgy articles

Abstract: This is a powder metallurgy method for producing fully dense compacted articles from powder charges of hydride-forming alloys, preferably titanium base alloys. The powder is hydrided, sealed in a collapsible container, heated to an elevated temperature and then hot compacted to produce a substantially fully dense article, which is then dehydrided, reheated and again compacted to remove any voids formed during dehydriding. The final article is characterized by relatively fine grain size and excellent formability.

Process for forming metal parts with less than 1 percent carbon content

Abstract: The disclosed process forms metal parts from a mixture containing a powdered metal, a plasticizer, and at least two binders. Some of these binder materials are selectively extractable from the mixture without sintering. After the mixture is shaped into the form of the desired part and prior to sintering, the plasticizer and the extractable binders are removed. This produces a part having both sufficient green strength and a relatively low binder content. On sintering, remaining binders decompose; and the resulting part has a carbon content of less than 1.0%.

Recrystallization in a powder metallurgy nickel-base superalloy

Abstract: In an extruded powder metallurgy superalloy, carbide particles are precipitated at the previous article boundaries. The role of these particles in the recrystallization behaviour has been studied by electron microscopy and hardness measurements. It was found that these carbide particles act as nucleation sites for recrystallization and inhibit growth of new grains.

Process for sintering powder metal parts

Abstract: PROCESS FOR SINTERING POWDER METAL PARTS ABSTRACT OF THE DISCLOSURE In a process for sintering powder metal parts comprising: (a) passing the parts through a furnace adapted therefor from its upstream end to its downstream end, said furnace having two successive zones, an upstream zone, which is maintained at a temperature in the range of about 800°F to about 2200°F and a cooling zone, said furnace further having an atmosphere therein comprising carbon monoxide, hydrogen, carbon monoxide, water and nitrogen distributed throughout the zones; (b) permitting the parts to reside in the upstream zone for a sufficient length of time to cause sintering; and (c) removing sintered parts from the furnace, the improvement comprising:introducing a mixture consisting essentially of methanol and nitrogen into the upstream zone at a point where a temperature of at least about 1500-F is maintained, the methanol and nitrogen being in a ratio sufficient to provide, when subjected to such temperature, an atmosphere comprising, in percent by volume, about 1 to about 20 percent carbon monoxide;and about 1 to about 40 percent hydrogen; and balance nitrogen. S P E C I F I C A T I O N

Method of making alloy and carbide powders of molybdenum and tungsten

Abstract: The present invention relates to a process for the production of an alloy powder (Mo, W) for powder metallurgy, which comprises chemically or mechanically mixing molybdenum and tungsten in the form of compounds and reducing the mixed powder with hydrogen, and a process for the production of a hard solid solution (Mo, W)C from the alloy powder (Mo, W), which comprises carburizing the alloy powder (Mo, W).

Method for preparing a composite metal sintered article

Abstract: A composite metal sintered article combining a metal shell which has been electroformed and/or electroless plated and/or vapor deposited, positioned inside or outside of a metal sintered compact. A method of making the composite metal sintered article using both a powder metallurgy process and a surface treating process. This composite metal sintered article has excellent surface properties and high dimensional accuracy and is favorably used for many kinds of forming molds, dies and structural members, especially for press molds in making glassware.

Method of sintering ceramics

Abstract: A compact is surrounded by a compatible, nonsinterable powder within a container with a layer of sinterable powder disposed on top of the nonsinterable powder and placed in a sintering oven. During sintering, the sinterable powder forms a cover that retards decomposition of the compact and serves to enhance densification of the compact.

Evaluation of Cyclic Behavior of Aircraft Turbine Disk Alloys

Abstract: An evaluation of the cyclic behavior of three aircraft engine turbine disk materials was conducted to compare their relative crack initiation and crack propagation resistance. The disk alloys investigated were Inconel 718, hot isostatically pressed and forged powder metallurgy Rene '95, and as-hot-isostatically pressed Rene '95. The objective was to compare the hot isostatically pressed powder metallurgy alloy forms with conventionally processed superalloys as represented by Inconel 718. Cyclic behavior was evaluated at 650 C both under continuously cycling and a fifteen minute tensile hold time cycle to simulate engine conditions. Analysis of the test data were made to evaluate the strain range partitioning and energy exhaustion concepts for predicting hold time effects on low cycle fatigue.

Relationships Between Density, Electrical Conductivity, Young's Modulus, and Toughness of Porous Iron Samples

Abstract: (1978). Relationships Between Density, Electrical Conductivity, Young's Modulus, and Toughness of Porous Iron Samples. Powder Metallurgy: Vol. 21, No. 1, pp. 1-6.

Application of Rapidly Solidified Alloys.

Abstract: : This program is being conducted for the purpose of applying the principle of rapid solidification of aluminum and iron alloy powders and subsequent development of stronger alloy compositions for fan blade application (Al alloys) and higher speed bearing material (Fe alloys). Centrifugal atomization and forced convective cooling are being used to produce the fast-cooled powder. During this report period, adaptation of the RSR (Rapid Solidification Rate) process to aluminum and iron systems was continued. Both Al and Fe alloys were produced and consolidated by direct extrusion. Hardness and mechanical testing were begun for initial evaluation of aluminum alloys. This program has demonstrated that controlled, rapid solidification can lead to a microcrystalline form, a condition which could possibly point the way to alloy homogeneity never before considered possible. It has also shown that a central rotary source can be used for liquid metal atomization into powder particles of sizes commensurate with average particle cooling rates of 100,000-1,000,000 K/sec. The specific objectives of this effort are the development of an improved aluminum alloy suitable for V/STOL-A fan blades and an improved iron alloy suitable for rolling element bearings for advanced aircraft powerplants. Originator supplied keywords include: Powder metallurgy.

Metallographic Aspects of Fatigue of Sintered Iron

Abstract: (1978). Metallographic Aspects of Fatigue of Sintered Iron. Powder Metallurgy: Vol. 21, No. 1, pp. 7-12.

Liquid phase sintering of rare earth–iron (Dy0.7Tb0.3Fe2) magnetostrictive materials

Abstract: A liquid phase powder metallurgy method has been evaluated for the production of dense, thermally stable Dy07Tb03Fe2 compacts The method involved the use of a rare earth rich alloy which forms the RFe2 phase and a RFe2‐R eutectic The latter is molten at the sintering temperature employed Dy07Tb03Fex alloys ranging in composition from x=165 to stoichiometric were ground, aligned, compacted and then sintered between 1130 and 1190 °C Densities as high as 98% were achieved for compositions between x=165 and 18 Densities were markedly lower for compositions beyond x=18 Although the magnetostriction of the compacts were lower than those found for cast polycrystalline Dy07Tb03Fe2, the magnetomechanical coupling coefficients (k33) of a number of the sintered compacts appeared to be as much as 50% higher than for the cast materials Suprisingly, the highest coupling was found for samples with 5 to 15% porosity When aged in air at 150 °C, the magnetoelastic properties of the liquid phase sintered m

Powder metallurgy process and product

Abstract: The invention consists of a process for the production of articles by powder metallurgy including the step of adding powdered mica to the metal powder before compacting and sintering. It also extends to a sintered metal product containing mica, in particular a valve seat insert and a shock absorber piston ring. The quantity of mica is preferably between 0.5% and 2% by weight of the metal.

Method for the production of sintered powder ferrous metal preform

Abstract: A method for the production of sintered powder metal preform employing a novel reduction step. As-water-atomized ferrous metal particles are coated by phenol resins by adding said phenol resins to said ferrous metal particles after heating the metal particles to about 130° C. to 150° C. Resin coated ferrous metal particles are then filled in a mold and compacted under high pressure to produce a compacted green preform sufficient to ensure adequate strength for handling after pressing. The green preform is then heated to a reduction temperature within the range of about 1100° C. to 1250° C. for a time sufficient to achieve reduction of said green preform.

Powder metallurgy production of spherical articles, such as bearing elements

Abstract: Low-cost articles characterized by a surface of revolution, such as truncated spherical balls, e.g., plain spherical bearing balls, are provided made by the powder metal compaction and sintering of blanks followed, in the case of ball elements, by densification of the outer spherical surface by mechanical working, such as by roll-forming, the balls so produced being characterized by improved sphericity and dimensional tolerance and improved wear resistance combined with optimum resistance to corrosion. The spherical surface of the ball is substantially free of pores, has a work hardened structure and has a density at and adjacent the surface of at least about 95% of the theoretical density of the metal, the density substantially below the surface being less and ranging to as low as at least about 70% of theoretical density.

Method for producing metal powder having rapid sintering characteristics

Abstract: A process for modifying or removing the prior powder particle boundaries and surface films from ferrous particulate metals and alloys, such as iron, low carbon steel and low alloy steel, for burnishing the clean, freshly revealed metal surfaces of the particles, and for inducing and storing energy of deformation into the surface layers of said particles. The sintering characteristics of metal powders are improved, and the most rapid sintering characteristics are produced. For example, in as-water-atomized ferrous metal particles, the surface film or skin is mostly oxides of iron and mixed oxides of the constituents of iron alloys. The skin is removed in a high velocity, turbulent whirling gas stream, which impacts the particles into each other, and the resulting burnished iron and steel cores are collected, together with the finely shattered oxide skins. The cores are then preferably magnetically separated from the non-ferrous material, and the finely shattered skin is separated from the coarser iron and steel cores. The bright metal cores may then be made into low oxide powder metallurgy objects as well as sheet and strip of low oxide steel. The bright metal highly energized and physically strained surfaces of the iron and steel cores promote very rapid sintering of the cores.

Method of and apparatus for hot pressing particulates

Abstract: Articles are formed by hot pressing metal or metallic particulates at temperatures between about the recrystallization temperature and about the solidus temperature for the metal or alloy after first preheating the particulates and the die. The particulates are hot pressed for a very short period of time, usually less than five seconds at about 12 tons per square inch or greater to compact and weld the particles together into a wrought metal article having substantially greater tensile strength and a better isotropic strength than a conventional cast or powder metallurgy article of the same metal or alloy. Additionally, the articles can be made with 99+ percent of theoretical density and with substantially no gas porosity. The article's surfaces may be smooth and held to relatively close tolerances with a good uniformity of surface hardness. Articles can be formed using conventional die presses to press articles repetitively without welding of the articles to die walls even when using aluminum particulates. The preferred particulates are substantially larger in size than the conventional powder materials used in powder metallurgy and appear to be strain hardened during the hot pressing thereof.

Process for manufacturing cobalt-base reduced powder

Abstract: A main raw material powder comprising cobalt oxide powder, chromium oxide powder and carbon powder is added with at least one metal oxide powder selected from the group consisting of manganese oxide powder, vanadium oxide powder, titanium oxide powder, tantalum oxide powder, niobium oxide powder, boron oxide powder, hafnium oxide powder, tungsten oxide powder, molybdenum oxide powder, iron oxide powder, nickel oxide powder and copper oxide powder; these powders are then mixed and pulverized to prepare a mixed powder; said mixed powder is then reduced by heating under vacuum or in a reducing atmosphere to obtain a reduced sponge-like mass; said sponge-like mass is finely pulverized, thereby manufacturing a cobalt-base reduced powder. A cobalt-base sintered alloy, produced by using said cobalt-base reduced powder thus manufactured as the material powder, has a relatively wide range of diffusion sintering temperatures applicable at the time of sintering thereof and has furthermore a high sintered density.

Powder metal pigment composition and its manufacture

Abstract: PURPOSE: To obtain a powder metal pigment composition having excellent chemical resistance and excellent weather resistance by the procedure in which an aqueous alkali silicate solution is reacted with a specific organic compound to form silica sol and the silica sol is deposited on the surfaces of metal pigment particles. CONSTITUTION: In an aqueous slurry of a powder metal pigment, an aqueous alkali silicate solution is reacted with an organic compound so as to form silica sol and then deposit it on the surfaces of the powder metal pigment particles in order to obtain a powder metal pigment composition. The powder metal pigment used includes pure silver, zinc, copper, and copper-zinc alloy in particular, and the pigment is dispersed into water alkalinized with ethanolamine, etc., to form a slurry. The preferred aqueous alkali silicate solution is the one of an SiO 2 /M 2 O (M is Na or K) raio of 2W4, and the organic compound used includes compounds containing active ions enough to convert alkali silicates into silicic acid and to polymerize its silanol groups to form siloxane bonds, e.g., carboxylic acid, etc. COPYRIGHT: (C)1980,JPO&Japio

Influence of Surface Oxide Layer on Sintering Process of Lead

Abstract: (1978). Influence of Surface Oxide Layer on Sintering Process of Lead. Powder Metallurgy: Vol. 21, No. 4, pp. 188-194.