Showing papers on "Powder metallurgy published in 1976"

Processing materials with lasers

Abstract: How can we make an alloy to fit a specific materials requirement? The oldest method of alloy fabrication, casting, has two inherent limitations: Phases with high melting points are difficult to melt; and the cooling of the alloys from the melt is slow, so that alloy segregation and phase separation have time to occur. The other traditional method, powder metallurgy, has helped with the second of these problems: Allowing the homogeneous melt to be cooled in tiny droplets makes it possible at least to limit segregation to the scale of the resulting powder particles.

Method of injection molding powder metal parts

Abstract: Parts are formed from metal powder by mixing the powder with a plastic medium comprising an organic binder dissolved in a solvent in which it is soluble at room temperature but in which it is substantially less soluble at a higher temperature such that the plastic binder becomes viscous at that temperature. Binder modifiers may be incorporated to promote mold release and promote healing of interfaces within the molded part and prevent the formation of drying cracks. The plastic mixture is injected under pressure into a closed die preheated to the above mentioned higher temperature, whereby the rejection of solvent and increase in viscosity of the plastic medium produces a compact sufficiently self-supporting to hold its molded shape and be ejected from the die. The compact is then dried to evaporate the remaining solvent, thus leaving interconnecting pores in the compact for the escape of gases resulting from subsequent burning out of the binder during the sintering operation.

Method for the controlled mechanical working of sintered porous powder metal shapes to effect surface and subsurface densification

Abstract: METHOD FOR THE CONTROLLED MECHANICAL WORKING OF SINTERED POROUS POWDER METAL SHAPES TO EFFECT SURFACE AND SUBSURFACE DENSIFICATION Abstract of Disclosure A method is provided for partially densifying a selected surface portion of a sintered porous powder metal element while applying restraining pressure to other selec-ted portions of said element in order to inhibit growth and cracking of said element during the partial cold deforma-tion thereof. The method is particularly applicable to the production of annular bearing rings.

Method and apparatus for pressurizing hot-isostatic pressure vessels

Abstract: A method and apparatus for the rapid, high-capacity pressurization of hot-isostatic pressing vessels, specifically of the type adapted for the hot-isostatic pressing of alloy shapes from powder metallurgy alloy charges. This is achieved by pressurizing with argon gas which is obtained by pumping cryogenic liquid argon at relatively low pressure to a relatively higher pressure and vaporizing said pumped liquid argon to produce said gas, which gas after use in the vessel for compacting is reclaimed and reliquefied for reuse.

Reconstituted metal oxide varistor

Abstract: Reconstituted metal oxide varistors are formed by hot pressing powdered metal oxide varistor ceramic with plastic resin. Metal electrodes may be pressed directly into the ceramic-plastic composite to provide improved contact characteristics.

The Liquid–Phase Sintering of Titanium Carbide

Abstract: (1976). The Liquid–Phase Sintering of Titanium Carbide. Powder Metallurgy: Vol. 19, No. 3, pp. 162-170.

Method of producing high carbon hard alloys

Abstract: A method for forming high carbon hard alloys using powdered metal techniques wherein the carbon content of the atomized powdered metal particles is minimized and the carbon content to achieve the desired composition is provided by blending carbon or carbon containing powder with the powdered metal particles prior to compaction and sintering. The compact may be sintered just above the solidus temperature of the alloy.

Method for consolidating precision shapes

Abstract: A method for consolidating powder metal preforms and for thereby producing high performance metal shapes from powder particles. The powder particles are consolidated into a shaped porous preform, and a coating is then applied to the resulting preform. The coating is initially porous whereby the coated preform can 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 coating is densified to the extent that it becomes non-porous. The coated preform is then subjected to a hot isostatic pressing operation whereby formation of a high integrity, fully dense metal shape results.

Colloidal graphite forging lubricant and method

Abstract: An improved colloidal graphite hot forming lubricant and hot forming process for high density ferrous powdered metal articles using this lubricant. Extremely fine powdered copper is included in an otherwise conventional colloidal graphite hot forming lubricant. High quality, including high density, ferrous metal articles are produced by coating a ferrous powdered metal preform with this lubricant, presintering the coated preform at a higher temperature of 2100° - 2500° F. for a short time by induction heating, allowing the presintered preform to cool to a desired hot forming temperature below 2000° F., and then hot forming the preform in the usual manner. Lubricant-preform interaction at the higher temperature is precluded, making long presintering times and special presintering equipment necessary.

Cobalt-base sintered alloy

Abstract: A cobalt-base sintered alloy which comprises: being manufactured from a reduced powder by the conventional powder metallurgy process with said reduced powder as a material powder, said reduced powder being prepared by simultaneously reducing a mixed powder consisting of powders of oxides of elements constituting said sintered alloy with a carbon powder added and mixed therein, and said reduced powder consisting of powders of said constituent elements and powders of carbides thereof; and consisting essentially of, in weight percentage: Chromium from 15.0 to 35.0% Tungsten from 3.0 to 19.0% Nickel from 0.2 to 12.0% Molybdenum from 0.1 to 15.0% Iron from 0.05 to 5.00% Titanium from 0.05 to 2.00% Silicon from 0.05 to 1.50% Manganese from 0.05 to 1.00% Carbon from 0.2 to 3.5% And The balance cobalt and incidental impurities. The above-mentioned cobalt-base sintered alloy, also containing, in weight percentage, from 0.05 to 1.00% boron. These cobalt-base sintered alloys provide a relatively wide range of sintering temperatures applicable in the manufacture thereof, and have furthermore a high sintered density of at least 95% of the theoretical value and are excellent in machinability, heat resistance, wear resistance and corrosion resistance.

Metal coating by a powder metallurgy technique

Abstract: A method for coating a metal wire with a thin layer of a second powdered metal. A metal flake powder having a residual surface lubricant from a prior milling operation is placed in the lubricant holding box of a conventional draw bench. The wire to be coated is passed through the metal flake powder and drawn through a conventional drawing die to provide a green-coat wire having a mechanically adherent metal flake powder coating. The green-coat wire is subsequently sintered to metallurgically bond the coating to the wire surface.

Niobium-tin superconducting wire by the infiltration process

Abstract: Superconducting wires containing filaments of the A15 compound, Nb3Sn, were made by powder metallurgy techniques. This article describes the various approaches employed for achieving a desired level of porosity in rods of sintered niobium that were later infiltrated with liquid tin. The influence of various mechanical deformation processes on filament morphology is reported. The critical current density of finished wires was measured under pulsed fields. The results indicate a pronounced Ic dependence on the type of deformation process used. Encouragingly high values of current-carrying capacity were observed.

Metal powder compositions

Abstract: In a mixture of metal powders from which ferrous alloy articles may be made by the process of powder metallurgy, the mixture consisting of the following in percentages by weight; nickel, 0.5 to 4%, manganese, 0.5 to 6%, carbon (graphite), 0.05 to 1.5%, copper, if present, up to 5%, boron, if present, up to 0.4%, iron and usual impurities, balance to 100%, the improvement consisting in that the nickel and manganese are in the form of a powdered binary alloy having a nickel to manganese ratio by weight in the range 15 : 85 to 65 : 35 and all of said powdered alloy passes through a 400 mesh B.S.S. sieve.

Hot-Forged Copper Powder Compacts

Abstract: The effects of powder size, preform density, sintering treatment, preheat temperature, ..forging rate, and forging load on the properties and structure of hotforged copper compacts have been investigated. The most important effect is produced by the die temperature, irrespective of the preheat temperature, because of the chilling of the Cu preform before hot forging. Sintering time and powder size have smaller effects. Major variations which arise in the occurrence and extent of recrystallization during hot· forging are accompanied by changes in the rate of densification. The variation in mechanical properties is discussed in terms of the structural observations.

Physical properties of a nickel-base alloy prepared by isostatic pressing and sintering of the powdered metal.

Abstract: Summary The physical and mechanical properties of samples of a nickel-base alloy fabricated by powder metallurgy were determined. The particle sizes of the powders used to make the samples varied from –80/+ 200 mesh to –325 mesh. The compaction pressure varied from 138 to 414 MN/m2 and the sintering temperature varied from 1150 to 1250°C. The shrinkage during processing, the porosity, tensile strength, yield strength, elongation, and elastic modulus were used to characterize the samples. The strength of the samples generally increased with decreasing particle size of the powder and increasing compaction pressure and sintering temperatures. The porosity and strength, therefore, could be varied over a wide range by controlling the various parameters. The properties of the samples prepared by powder metallurgy were compared with those of the cast alloy and compact bone. Conditions can be selected that will yield equivalent or better properties by powder metallurgy than by casting.

Base metal plate for directly heated oxide cathode

Abstract: A base metal plate for directly heated oxide cathode comprising a plate of Ni-W-Zr alloy containing 20 to 30% by weight of W and 0.3 to 5.0% by weight of Zr, which can further contain a small amount of other reducing element such as Mg, Al, or Si, and having a thickness of not more than 50μ. The base metal plate is prepared by powder metallurgy, and has a good life time of electron emission and a good strength in the operating temperature range of cathode.

Method for producing alloy particles

Abstract: A method for producing metal and alloy particles from an article thereof wherein the article is first diffused with a source of gas, such as hydrogen, and then subjected to localized heating to melting temperature. Upon localized melting the diffused gas within the article is liberated to produce an atomizing effect upon the melted material. This atomized material is then cooled sufficiently rapidly to form discrete particles which are then collected for further use, such as in powder metallurgy applications.

Method of making bulk porous anodes for electrolytic capacitors

Abstract: A method of making bulk porous anodes for electrolytic capacitors consists of preparing a suspension of a valve metal powder, selected from the group consisting of tantalum, niobium and titanium in an amount of 30-250 parts by weight, a binding material, which is also a charger of powder metal particles, constituting a 0.2-1.5% aqueous solution of a salt selected from the group consisting of sodium and ammonium salts of carboxymethyl cellulose of celluloseglycolic acid in an amount of 10-35 parts by volume, and a dispersion medium being alcohol or acetone an amount of 15-30 parts by volume. Said suspension is subjected to the effect of an electric field established by a voltage applied to the electrodes and causing deposition of metal powder of the latter with a bulk porous body being thus formed, which is then sintered at a temperature of 1600-2000° C to produce a bulk porous anode. Said method is intended for the production of electrolytic capacitors of various shapes and sizes.

Stabilised ferritic chromium stainless steel - with high resilience, mfd. by powder metallurgy

Abstract: A process for mfg. a stabilised ferritic Cr stainless steel with high resilience in the welded state is described. The steel in the liq. state is atomised in Ar and the powder is compacted and sintered and hot or cold formed as desired pref. into strip. The steels can be used in welded constructions, Nitrides, carbides and carbonitrides of Ti in the steel only agglomerate slowly and grain growth is inhibited. The corrosion resistance and mechanical properties of these weldments are comparable to those of steels of similar compsn. but mfrd. conventionally. The compsn. of the liq. metal is pref. is not >0.03% C, is not >0.03% N, 10-30% Cr, is not >5% Ni, is not >3.0% Cu, is not >1.0% Si, is not >2.0% Mn, 0.5-4.0% Mo, C and N stabilising elements in quantities at least stoichiometrically necessary for carbide and nitride formation, and bal. Fe.

Finely divided tungsten carbide prepn. - by reacting tungsten oxide and carbon monoxide below sintering or agglomerating temps (NL150676)

Abstract: Finely-divided WC is prepd. by reacting WO3, with CO. The CO is pref. passed over WO3 particles. Reaction mixt. is heated to a temp. at which CO and WO3 react and WC is formed, but which is below temp. causing caking or sintering together of W-contg. matls. WC is used as an abrasive, in powder metallurgy, and can be re-converted to WO3 of smaller particle size and higher active surface than starting matl. by heating in air at a low temp. WC obtd. has small particle size, pref. 100 angstroms and active surface is approx. =20 m2/g.

Characterization of porosity of isostatically pressed and sintered nickel-base powdered metal.

Abstract: Characterization of the pore structure of compacted and sintered parts made from a nickel-base powder was accomplished using the mercury porosimetry method. The theoretical density values for the sintered specimens varied from 56.3 to 96.7% which corresponds to a porosity of 43.7 to 3.3%. A maximum interconnecting median pore diameter of 21 mum resulted from a -80/+200 mesh powder compacted at 138 MN/m2 and sintered for 2 h at 1250 degrees C. Photomicrographs of the same sample showed that it had a maximum pore diameter of 200 mum. The interconnected pore volume decreased with decreasing particle size of the powder, increasing compaction pressure, and increasing sintering temperature. Mechanical properties of tensile strength, yield strength, elastic modulus and percentage elongation were correlated with the pore structure. Proper selection of particle size, compaction pressure, sintering times and sintering temperatures should permit parts with controlled porosity characteristics to be produced that possess adequate mechanical properties for application as implants.

Heat-and wear resistant aluminium alloy - produced by powder metallurgy

Abstract: The alloy, which is produced by compacting and sintering a powder mixt. of the constituents, has improved heat and wear resistance, and is suitable for piston in internal combustion engines. The Al alloy has the compn. total 5%, pref. 4% of one or several of the metals Fe, Ni and/or Cr, 0.3-5% Cu, 0.3-3% pref. 2% Mg, 0.5-5% pref. 2% Si carbide, balance Al. It contains in addn. pref. total of up to 3% of one or several of the metals Mn, Ti and/or Si.

Hot Re-pressing of Powder Made from Mild Steel Machining Swarf

Abstract: Since economic studies indicate that powder produced from mild steel machining swarf in a cryogenic hammer mill is significantly cheaper than that made by any other method, it was decided to investigate whether powder-metallurgy products of acceptable properties could be obtained from such powder by a number of alternative methods. The powder was first isostatically compacted, either with or without prior heat-treatment, at room temperature at pressures of up to 1·38 GN/m2 (200000 Ibf/in2). The cylindrical preforms were then used to produce specimens by the alternative routes of sintering, or hot forging, or sintering followed by hot forging at small strains. The density and tensile properties of the .swarf powder metal were determined as a function of the process variables. By using certain processing routes the density closely approached that of the parent metal while elongation and ultimate tensile strength remained relatively lower, partly because the limited capacity of the forging machine restricted the plastic strain and hence bonding of the particles, partly owing to contamination of the swarfpowder. The presence of non-metallic inclusions caused considerable scatter in the results.

The Production of Mild Steel Rings by a Combined Powder Metallurgy and Cold Forging Process

Abstract: (1976). The Production of Mild Steel Rings by a Combined Powder Metallurgy and Cold Forging Process. Powder Metallurgy: Vol. 19, No. 3, pp. 141-152.