Showing papers on "Powder metallurgy published in 1970"

Alumina as a ceramic material

Abstract: INTRODUCTION. NOMENCLATURE. PREPARATION OF ALUMINA PHASES. Bauxite. Preparation of Bayer Alumina. Wet Alkaline Processes. Wet Acid Processes. Furnace Processes. Carbothermic Processes. Electrolytic Processes. Amorphous and Gel Aluminas. Preparation of the Alumina Trihydroxides. Gibbsite. Bayerite. Nordstrandite, Bayerite II, Randomite. Preparation of the Alumina Monohydroxides. Boehmite. Disapore. Transition Aluminas. Dehydration Mechanism. Sequence of Transition. Phases Formed on Aluminum. Rehydration. Alpha Alumina. Preparation. Factors Affecting Alumina Transitions. Special Ceramic Aluminas. Beta and Zeta Aluminas. Suboxides and Gaseous Phases. STRUCTURE AND MINERALOGICAL PROPERTIES. Structure of the Alumina Phases. Pseudomorphosis. Surface Area of Alumina. Porosity. Sorptive Capacity. MECHANICAL PROPERTIES OF ALUMINA. General Considerations. Bending, Compressive, Tensile, and Torsional Strength. Impact Strength. Moduli of Elasticity (E), and Rigidity (G). Poisson's Ration (i). Creep Characteristics. Thermal Shock. Internal Friction. Fatigue. Hardness and Abrasiveness of Alumina THERMAL PROPERTIES. Thermophysical and Thermochemical Constants. Specific Heat. Thermal Expansion. Thermal Conductivity. Thermal Diffusivity SONIC EFFECTS IN ALUMINA. Velocity of Sound in Alumina. Ultrasonic Absorption. ELECTRICAL PROPERTIES OF ALUMINA. Introduction. Electrical Conductivity of Alumina. Dielectric Constant and Loss Factor of Alumina. Dielectric Strength MAGNETIC PROPERTIES OF ALUMINA. Magnet Susceptibility. Magnetic Resonance of Alumina. OPTICAL PROPERTIES OF ALUMINA. Refractive Index of Alumina. Transmission, Emissivity, and Absorption of Alumina. Phosphorescence, Fluorescence, and Thermoluminescence. Optical Spectra of Alumina. Color in Alumina. Chromia-Alumina System, Laser Applications RADIATION AND ALUMINA. CHEMICAL PROPERTIES OF ALUMINA. Wet Chemical Reactions of Sintered Alumina. Reaction of the Chemical Elements with Alumina. Slagging Effects. Ash Slags. Slags Containing Sulfates. Steel Furnace Slags. Glass Furnace Reactions. Calcium Aluminate Slags. Aluminum Slag Reactions. Miscellaneous Reactions COLLOIDAL PROPERTIES OF ALUMINA. Plasticity. Surface Charge and Zeta Potential of Alumina. Flocculation and Deflocculation Effects. Additives GRINDING CERAMIC ALUMINA. FORMING ALUMINA CERAMICS. Cold Forming of Alumina. Hot-Pressing. Miscellaneous Forming Methods SINTERING. Introduction. Sintering Atmospheres. Sintering Additives ALUMINA IN REFRACTORIES. General. High-Alumina Refractories. Fused Cast Alumina Refractories. Clay-Bonded Alumina Refractories, Mullite Refractories. Spinel, Cordierite, Alumina-Chromite. Refractory Equipment. Refractories for Aluminum and Other Nonferrous Uses. Lightweight Alumina Refractories. Binders for Alumina Refractories ALUMINA AS AN ABRASIVE MATERIAL. Introduction. Loose Grain Abrasive. Grinding Wheels. Ceramic Tools ELECTRICAL APPLICATIONS. Spark Plug Insulators. Electron Tube Elements, High-Frequency Insulation. Alumina Porcelain Insulation. Resistors and Semiconductors CEMENT. Calcium Aluminate Cement. Barium Aluminates ALUMINA IN GLASS. Introduction. Bottle Glass. Devitrified Glasses Containing Alumina. Boron Glasses. Lithium Glasses, Phosphate Glasses. Optical Glasses ALUMINA IN COATINGS. Introduction. Anodic Coatings on Aluminum. Glazes and Enamels. Flame-Sprayed Coatings. Painted, Cast, or Troweled Coatings. Electrolytic Coatings. Evaporated Coatings. Dip Coatings, Cementation Coatings. Coatings on Alumina and Other Ceramic Bases. Alumina Coatings for Electrical Insulation. Alumina Coatings by Sputtering ALUMINA IN CERMETS AND POWDER METALLURGY. Introduction. Chromium-Alumina Cermets. (Iron, Nickel, Cobalt)-Alumina Cermets. Aluminum-Alumina Alloys. Miscellaneous Cermets ALUMINA IN AIRBORNE CERAMICS. Introduction. Gas-Turbine Accessories. Radomes and Rocket Equipment. SEALS, METALLIZING, WELDING. FIBERS, WHISKERS, FILAMENTS. Introduction. Alumina Fibers. Glass Fibers MISCELLANEOUS CERAMIC APPLICATIONS OF ALUMINA. References.

Liquid-phase sintering.

Abstract: Industrial advances frequently depend on the development of new, special-purpose ma- terials possessing specific magnetic, electrical, optical, strength, friction, antifriction, and other properties. Metal alloys produced by the conventional technique of metallurgical reduc- tion often do not meet these new requirements. Powder metallurgy, therefore, is of consider- able importance in solving many problems of present-day materials science. Its production techniques-solid-phase and liquid-phase sintering, impregnation, hot pressing - make it pos,...sible to obtain materials from metallic components which are immiscible in the liquid state and also materials in which metals are combined with nonmetallic components such as refract- ory compounds- oxides, carbides, nitrides, borides, sUicides, sulfides, etc. The properties of sintered parts depend essentially on the processes occurring during their formation. One of the most promising methods of producing sintered materials of high density with the best combination of various properties is liquid-phase sintering. In recent years, many publications have appeared concerning processes of sintering specific combinations of com- ponents, the theoretical basis of liquid-phase sintering, and the laws governing this process. The present work examines liquid-phase sintering processes and the action of capillary forces in models of dispersed solid-liquid systems, and also gives data from theoretical and experi- mental studies of liquid-phase sintering in various metal and metal-ceramic systems. Some theoretical generalizations on the principles of sintering processes are presented, and the driv- ing forces of sintering and the effect of different conditions on liquid-phase sintering processes are considered.

Solid-State Sintering

Abstract: The theory of solid-state sintering is reviewed, with particular emphasis on the effects of several concurrent mechanisms on sintering behavior. Computer synthesis of both non-isothermal and isothermal sintering data has been used to predict initial sintering behavior under a wide variety of conditions. This approach has been successful in describing the sintering of compacts of spherical particles of Fe, Cu, Fe2 O3, Ag, and LiF. The relative importance of surface, grain boundary, and volume diffusion and vapor transport are discussed. Experimentally observed sintering behavior is discussed in terms of the theoretical model.

Intergranular brittleness studies in tungsten using auger spectroscopy.

Abstract: The present investigation was aimed at understanding the problem of brittleness in powder metallurgy tungsten by utilizing Auger Electron Emission Spectroscopy as a tool for direct chemical analysis of fracture surfaces Substantial segregation of phosphorus to the grain boundaries was observed in tungsten and the concentration of phosphorus can be related to the ductile-brittle transition temperatures The amount of segregation was dependent upon the grain size—the larger the grain size, the greater the concentration of phosphorus at the grain boundary and the associated embrittlement

Powder metallurgy process

Abstract: A METHOD OF PRODUCING AN IMPROVED TOOL STEEL HAVING A SUPERIOR ALLOY HOMOGENEITY WHICH COMPRISES THE STEPS OF PROVIDING A CHARGE OF IRREGUALRLY-SHAPED, FRACTURED, PREALLOYED TOOL STEEL POWDER OF A HOMOGENEOUS COMPOSITION, EXPOSING THE POWDERED PARTICLES TO A HYDROGEN REDUCING ATMOSPHERE TO REDUCE THE ODIXE CONTENT AND SLOWLY COOLING THE REDUCED POWDER PARTICLES TO AVOID IMPARTING AN OBJECTIONABLE DEGREE OF HARDNESS WHICH WOULD INTERFERE WITH SUBSEQUENT COLD PRESSING OF REDUCED POWDER PARTICLES, COLD PRESSING THE REDUCED POWDER PARTICLES TO A BILLET FORM HAVING A GREEN STRENGTH ADEQUATE TO MAINTAIN STRUCTURAL INTEGRITY UPON FURTHER HANDLING OF THE BILLET, AND SINTERING THE COLD PRESSED BILLET TO IMPART A THEORETICAL DENSITY OF AT LEAST 85% TO THE TOOL STEEL WITH THE SINTERING BEING CARRIED ON UNDER CONDITIONS TO MINIMIZE GRAIN GROWTH AND PHASE SEPARATION OF A DEGREE INSENSITIVE TO SUBSEQUENT PROCESSING.

Method for producing a metal die or mold

Abstract: A method for producing a metal die or mold including the steps of placing a layer of sintering powder, such as iron, copper, tungsten carbide or titanium carbide, in a frame or box, placing in contact with the sintering powder a pattern made of an infiltrant metal, such as copper, lead, cobalt, nickel, iron or alloys thereof, having a lower melting point than that of the sintering powder, the pattern corresponding in configuration to that of the cavity surface of the desired die, heating the powder together with the pattern in the frame to sintering temperature, whereby to sinter the powder and infiltrate the infiltrant metal forming the pattern into the powder, and cooling so as to obtain a hardened sintered mold having a surface whose configuration complements that of the pattern surface.

Fabrication of uranium mononitride compacts

Abstract: used for the sintering studies. The effects of sintering temperature and time on the density, grain size, and oxygen and carbon content of the sintered compacts were studied. Coarse (70 to 150 pm) UN powder was compacted by hot isostatic pressing. The effects of pressing pressure, temperature, and canning materials were studied.

Powder metallurgy sintered corrosion and heat-resistant, age hardenable nickel-chromium refractory carbide alloy

Abstract: An age hardenable, corrosion and heat resistant nickel-chromium, refractory carbide alloy is provided by powder metallurgy for use at elevated temperatures as high as 2000 DEG F (1090 DEG C) comprising primary grains of at least one refractory carbide selected from the group consisting of TiC, CbC, VC and TaC dispersed through a matrix of an age hardenable, corrosion and heat resistant nickel-chromium alloy consisting essentially by weight of about 5 to 30 percent chromium, up to about 15 percent iron, about 0.5 to 5 percent titanium, about 0.2 to 5 percent aluminum, up to about 25 percent cobalt, up to about 0.25 percent carbon and the balance essentially nickel.

Apparatus for the manufacture of powder metal helical gears

Abstract: Apparatus for pressing powder metal helical gears and similar articles of manufacture wherein the powder is pressed with a twisting motion of the punches. A cam arrangement is described for a pressing apparatus which rotates the punches during pressing.

Powder metal magnetic pole piece

Abstract: A powder metallurgy produced wear resistant magnetic pole piece for use as a pickup head with magnetic playback tapes is provided made of a magnetically soft ferrous alloy containing effective amounts of silicon and aluminum. A powder of the alloy is oxidized to provide a thin oxide on the particles thereof. The powder is then hot pressed in vacuum at an elevated temperature into a dense sintered body. The presence of oxide in the grain boundaries confers wear resistant properties to the alloy. An oxygen content of about 3,400 to 4,400 ppm is preferred.

Method and furnace for sintering

Abstract: A method and furnace are disclosed for continuous sintering powdered metal products. The furnace includes a high temperature heating zone through which the powdered metal products pass for sintering. The high temperature heating zone includes a thermally stable medium preferably alumina sand, in which the sintered product is carried through the furnace. The invention provides a sintering furnace which is capable of achieving and maintaining higher temperatures in continuous operation than previously possible for commercially operated furnaces.

Refractory metal alloy bonded carbides for cutting tool applications

Abstract: THIS PATENT DESCRIBES A REFRACTORY METAL BONDED CARBIDE ALLOY FOR USE IN CUTTING TOOLS AND IN OTHER APPLICATIONS WHERE HIGH HARDNESS AND ABRASION RESISTANCE ARE REQUIRED. THE DESIRED FINE-GRAINED COMPOSITE STRUCTURE IS OBTAINED PREFERABLY BY METAL PHASE PRECIPITATION OF METAL ALLOYS WITHIN THE CARBIDE GRAINS, OF PREVIOUSLY PREPARED CERTAIN TERNARY OR HIGHER ALLOYS OF REFRACTORY TRANSITION METALS WITH CARBON. CONSOLIDATION OF THE COMPOSITES CAN BE AC- COMPLISHED BY MELTING AND CASTING OR POWDER METALLURGY TECHNIQUES.

Apparatus for making powder metal

Abstract: An apparatus for making metal powder of ultra high purity which comprises a vessel defining a main collection chamber filled with an inert gas which serves as a heat transfer medium for effecting a cooling and solidification of molten metal particles injected therein. The apparatus further includes heat transfer conduits for cooling and recirculating the heat transfer gas through the main collection chamber and a refrigerated secondary collection chamber in which further cooling of the spherical powder particles is attained. Suitable controls are provided to assure appropriate pressure levels within the apparatus, whereby metal powders of optimum properties are produced.

Techniques for the Study of Homogenization in Compacts of Blended Powders

Abstract: The production of alloys by powder metallurgy may be accomplished by conventional powder processing of prealloyed powders or by the processing of compacted blends of powders. The latter method necessarily requires the insertion of a homogenization step in the processing sequence. In general, the homogenization is achieved through solid-state inter-diffusion of the components in the compacted blend.

Method of making large sintered powdered metal parts without dies

Abstract: A CONTAINER OF INFILTRATABLE METAL, SUCH AS BRASS OF COPPER, AND OF THE APPROXIMATE SHAPE DESIRED FOR THE FINISHED PART, IS STAMPED OR OTHERWISE FORMED, FILLED WITH THE METAL POWDER OF WHICH THE PART IS TO BE MADE, PLACED IN A SINTERING OVEN AND SINTERED. DURING SINTERING, THE CONTAINER HOLDS THE PARTICLES OF THE POWDER TOGETHER UNTIL THEY COALESCE, WHEREUPON THE CONTINUED APPLICATION OF HEAT CAUSED THE CONTAINER TO MELT AND THE METAL OF WHICH IT IS COMPOSED TO FLOW INTO THE INTERSTICES BETWEEN THE POWDERED METAL PARTICLES, THEREBY INFILTRATING THE PART. THE PART CAN THEN BE FURTHER DENSIFIED, IF DESIRED, BY FORGING, AND TEETH FORMED.

Metal Matrix Composites by Decomposition Sintering of Titanium Hydride.

Abstract: : Titanium hydride powders were pressure sintered in vacuum, and spontaneously decomposed, giving compacts of titanium metal. Under these conditions lower temperatures were required for sintering than are normally needed for titanium metal powders. The method, therefore, was investigated for its applicability to titanium matrix composites in order to minimize chemical reactivity problems generally encountered in processing materials of this kind. Models containing tungsten and stainless steel wire reinforcement were synthesized this way, and some tensile properties were determined. To this extent, process feasibility is indicated. An important aspect is matrix ductility, maintained by impurity control, as needed for titanium. The present models are seen to be ductile fiber-ductile matrix systems. (Author)

High Purity Fine Particulate Stabilized Zirconia (Zyttrite).

Abstract: : Sintering and hot pressing process studies were conducted on 100 A particle diameter 6 1/2 mole percent Y2O3 stabilized ZrO2 powder produced by an organometallic route. Powder characteristics to include particle size, agglomerate size, agglomerate bonding and chemistry were correlated with processing behavior and used as a guide in achieving 99 percent dense fabricated shapes with grain sizes between 5 and 20 microns for sintered bodies and 0.4 and 7 microns for hot pressed shapes. Sintering temperature was 600C lower than that required for commercial 2 micrometer single phase stabilized zirconia powder because of the good solid solution dispersion and high powder activity. Low pressure (5 Kpsi) hot pressing was performed 140C lower than sintering. Intermediate pressure ( 100 Kpsi < 200 Kpsi) hot pressing processes were investigated. Purity was maintained in sintering; however, from 40 to 600 ppm carbon was introduced during hot pressing which was reduced to between 10 and 300 ppm during annealing. Several samples possessed second phase inclusions such as monoclinic ZrO2 or ZrSiO4 but, in general, single phase structures were produced. The powder surface chemistry, inter-agglomerate bonding and agglomerate size were extremely important variables in governing the production of uniform sintered microstructures. Best results were achieved with alcohol washed powder. (Author)

The Forging Of Powder Metallurgy Preforms

Abstract: The forging of powder metallurgy preforms in closed dies is a relatively new technology, especially for ferrous materials. The best features of two established technologies are melded into a manufacturing process that offers increased design freedom and improved properties at reduced costs for a variety of engineering components.

Powder metallurgy sintered corrosion and wear resistant high chromium refractory carbide alloy

Abstract: A corrosion and wear resistant high chromium refractory carbide alloy is provided by powder metallurgy suitable for use as a seaming tool in the food canning industry comprising primary carbide grains of at least one refractory carbide selected from the group consisting of TiC, CbC, VC and TaC dispersed through a high chromium alloy matrix consisting essentially by weight of about 14 to 24 percent chromium, about 0.4 to 1.2 percent carbon, up to about 3 percent nickel, up to about 5 percent molybdenum, and the balance essentially iron.

Compacted and sintered powder mass having a discrete cavity in the mass and method of forming

Abstract: A STRUCTURE AND METHOD OF FORMING THE STRUCTURE OF A COMPACTED AND SINTERED POWDER MASS HAVING ONE OR MORE DISCRETE CAVITIES IN THE MASS. EACH CAVITY WITHIN THE MASS IS FORMED BY THE VAPORIZATON THROUGH SINTERING OF A CORE MATERIAL COMPACTED WITHIN THE POWDER MASS PRIOR TO SINTERING.

Porous structure and method

Abstract: AN OPEN-PORE POLYURETHANE STRUCTURE CONTAINING POWDERED METAL COMPRISING COHERENT SPHERICAL PARTICLES SEPARATED BY INTERCONNECTED INTERSTICES AND A METHOD OF PRODUCING THIS STRUCTURE COMPRISING MIXING METAL POWDER WITH THE COMPONENTS TO MAKE A POLYURETHANE STRUCTURE IN A CONTAINER, POLYMERIZING THE MIXTURE IN PLACE WITHOUT STIRRING AFTER ONSET OF GELLATION. THE POLYURETHANE CAN BE REMOVED PREFERABLY BY HEATING IN AIR AT A TEMPERATURE BELOW THE SINTERING TEMPERATURE FOR THE METAL, AND THE REMAINING METAL CAN THEN BE SINTERED FORMING A SINTERED POROUS METAL OR METAL OXIDE STRUCTURE DEPENDING ON THE METAL USED AND SINTERING CONDITIONS. A NUMBER OF POROUS NICKEL PRODUCTS WERE MADE BY THE PROCESS OF THE INVENTION AND AFTER THE REMOVAL OF THE POLYURETHANE DEPENDING ON THE PARTICLE SIZE OF THE NICKEL AND THE AMOUNT AND CONDITIONS OF SINTERING DENSITIES OF THE PRODUCTS RANGED FROM 1 TO 5 G./CC., COMPRESSIVE STRENGTHS FROM 100 TO 20,000 AND POROSITY FROM 20 TO 80%. THE POROUS METALS OR SINTERED POROUS METALS CAN BE USED IN MECHANICAL SUPPORT, AIR AND LIQUID FILTERS, POROUS BEARING, POROUS ELECTRODES, ACOUSTIC FILTERS, IMPACT ABSORBERS, CAPILLARY WICKS, VOID FILLERS, INTEGRAL CONDUCTOR-INSULATOR RODS, AND THREE-DIMENSIONAL HIGH-MODULUS REINFORCEMENTS.

Shaping of metal powders - A survey

Abstract: 1. The principles of a discrete contact theory of pressing have been formulated. 2. Extensive experimental data have been accumulated on standard pressing techniques (pressing in closed die sets, hydrostatic and hot pressing). 3. Special equipment has been built to meet the requirements of powder metallurgy; experience with its use has demonstrated, however, that the designs of the existing presses require modification. 4. Investigations of new shaping techniques (vibratory, impact, hydrodynamic, explosive) have laid foundations for their wide application in industry. 5. Too little attention is being paid to such shaping techniques as pressing with simultaneous spark sintering, ultrasonic pressing, hot casting, shaping in a magnetic field, etc. Work conducted with the aim of studying and employing such techniques will promote further technical progress in our country.

Preparation and Properties of Ferromagnetic Bronze‐Iron Composite Materials

Abstract: A combination of powder metallurgy and wire drawing techniques was used to prepare composite materials consisting of fine iron fibers in a 5% Sn bronze matrix. In addition to being ferromagnetic, the materials have excellent mechanical properties and corrosion resistance. Property data are reported on alloys containing 2.0, 5.6, 9.9, and 14.3 vol % Fe. The 9.9 vol % Fe alloy, after 99.9+% reduction in area, has a coercive force of 320 Oe, a remanent induction of 1800 G, and a hysteresis loop squareness, Ir/Is=0.85. The tensile strength of the same alloy is 156 000 psi (1077 MN/m2) and its corrosion rate in a solution of 5% NaCl in H2O is not measurably different from the bronze matrix material. The magnetic and mechanical properties are easily controlled by varying the amount of cold working. The magnetic properties attained are within the range of applicability for magnetic recording, and with modest improvements in properties, the alloys could be used in other applications for hard magnetic materials.

Sintered titanium-molybdenum alloys

Abstract: 1. A study was made of the conditions of preparation and physicochemical and physicomechanical properties of sintered titanium-molybdenum alloys containing up to 50 wt% Mo. 2. An investigation of the corrosion resistance of such alloys in 20% HCl and 40% H2SO4 solutions demonstrated that Ti33Mo powder metallurgy alloys sintered in argon at a temperature of 1200°C exhibit the highest resistance to corrosion attack. 3. Sintered Ti33Mo alloys may be recommended for the manufacture of porous permeable materials from titanium and molybdenum powders.