Showing papers on "Powder metallurgy published in 1972"

Microstructural development during the liquid-phase sintering of VC-Co alloys

Abstract: A study was made of the microstructural changes that occur during the liquid-phase sintering of VC-Co alloys. It was found that considerable growth of the carbide grains takes place and that this growth can be described by the equation: $$\bar d^3 - \bar d_o^3 = Kt$$

Method for producing metal dies or molds containing cooling channels by sintering powdered metals

Abstract: A sintered metal die or mold having formed therein an internal channel for conducting a heat transfer medium therethrough, and a method for producing same. The method includes the steps of disposing sintering powder, such as iron, copper, tungsten carbide or titanium carbide, in a frame or box, about 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 channel for the heat transfer medium and being positioned within the sintering powder in the position desired for the channel, heating the powder together with the pattern 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 sintered metal die or mold having an internal channel whose configuration complements that of the pattern surface.

Iron-chromium-aluminum alloys with improved high temperature properties

Abstract: A powder metallurgy product comprising iron and chromium, and/or aluminum and characterized by elongated grains that are stable at elevated temperatures. A method of producing such a product, including mechanically alloying a suitable powder charge, consolidating the mechanically alloyed powder, working the consolidated product so as to achieve therein a reduction of at least about 10%; and, then, heating the worked product to produce coarse elongated grains therein. The product produced according to the present invention exhibits good oxidation resistance and good room temperature and elevated temperature strength and ductility.

Cu-Zr and Cu-Zr-Cr alloys produced from rapidly quenched powders

Abstract: The production of alloys by means of ingot technology leads to micro-and macrosegregation, separation of phases and impurities, often into large, brittle particles, and coarse grain size. Alloy development is frequently restricted because of the coarseness of the structure and the resultant imposed limitations on hot and cold plasticity. One ready means of avoiding these problems is to produce the alloy in powder or pellet form; this permits attainment of high cooling rates in the liquid and solid, minimizes segregation, alters phase separation and distribution advantageously, and results in significantly finer structures. The powders utilized to produce wrought shapes may be much coarser than press-and-sinter powders, leading to important processing economies without sacrifice of structure refinement. The alloy systems Cu-Zr and Cu-Zr-Cr were selected for the present study; these are high conductivity, high strength alloys of commercial interest. Cooling rates for these specific powders using nitrogen atomization varied from about 103 to 104°CJsec. Powders were cleaned, canned, and hot extruded to produce bar stock; mechanical testing was performed on both as-extruded and thermomechanically-worked samples, with highly beneficial improvements in strength, ductility, and high-temperature structural stability.

Powdered metal process

Abstract: MALLEABLE METAL POWDERS HAVING LOW GREEN STRENGTH CAN BE CONVERTED TO HIGH GREEN STRENGTH, IRREGULARLY SHAPED PARTICLES ACCORDING TO A PROCESS COMPRISING MECHANICALLY WORKING, AS BY BALL MILLING, THE LOW GREEN STRENGTH POWDERS TO FLAKE FORM, ANNEALING THE FLAKES ABOVE THE RECRYSTALLIZATION TEMPERATURE THEREOF IN A NON-OXIDIZING ATMOSPHERE TO AGGLOMERATE THE FLAKE PARTICLES INTO A SINTER CAKE SUSCEPTIBLE OF SUBSEQUENT BREAK-UP AND MECHANICALLY DISINTEGRATING THE SINTER CAKE INTO THE IRREGULARLY SHAPED PARTICLES. ACCORDING TO THIS PROCESS, BLENDS OF LOW GREEN STRENGTH SPHERICAL ELEMENTAL POWDERS MAY BE CONVERTED TO HIGH GREEN STRENGTH, HIGH TRANSVERSE STRENGTH, HIGH HARDNESS ALLOY PARTICLES.

Method for making an electric contact by powder metallurgy and the resulting contact

Abstract: A layer of refractory metal or metal compound powder which is mixed with a low melting temperature metal or metal alloy powder, and a layer of low temperature melting metal or metal alloy powder, are arranged together in the cavity of a compacting die and consolidated together to form an integrated two-layer compact which is thereafter heated above said low temperature but below the refractory powder's sintering temperature to cause the pores of the compact's refractory portion to be impregnated with the low temperature melting component while leaving an excess thereof forming a thin layer in the refractory portion. Because the two layers of the compact are consolidated together so that the compact may be moved safely without the layers separating during the heating, the use of a continuous furnace for the heating is commercially practical; and because the refractory portion is not sintered, the finished product's dimensions can be accurately predetermined by the compacting die cavity dimensions. By heating the compact with its low temperature melting end down and resting on a refractory carrier surface having a plurality of depressions beneath this end, said layer is formed with a smooth exposed surface suitable for soldering or welding to a supporting metal part. Thus, a finished electric contact, for example, may be produced by the two steps of compacting and heating only, having a thick contact layer resistant to arc burning and contact welding trouble and a thin support layer that is solderable or weldable to a metal support or operating element. If the low temperature melting metal powder mixed with refractory powder in the refractory portion of the compact, and the low temperature melting powder in the other portion of the compact, are different metals, the heating of the compact can cause alloying or intersolution of the different metals so that in the final product the low temperature melting component of the product has the same composition throughout.

Activated Sintering of ThO2 and ThO2-Y2O3 with NiO

Abstract: Scanning electron microscopy and isothermal shrinkage measurements were used to study the effects of additives on the sintering of Thoria-Yttria compacts and loose powders. Small amounts of the oxides of Ni, Zn, Co, and Cu were found to reduce the sintering temperature (which is normally above 2000 C). In particular, NiO, at a concentration of 0.8 wt %, was found to yield high-density bodies at temperatures below 1500 C. Densification occurs very rapidly, and is followed by a much slower sintering process typical of volume diffusion.

Process of working a sintered powder metal compact

Abstract: A process of manufacturing articles by means of powder metallurgy, including the conventional steps of forming a blank out of metal powder compressing the blank and sintering it. Pursuant to the disclosure, an additional step is provided, wherein the sintered blank is subjected in a die to one or more further press operations in which the material of the blank is allowed to flow freely in the direction transverse to the direction in which pressure is applied. In this manner the density of the product is increased. Preferably the article is sintered again or annealed after the further press operation or operations to provide it with the required strength characteristics. The additional step is advantageously carried out at room temperature.

Powder metal mix containing carbonaceous binder and green compacts made therefrom

Abstract: Iron and/or copper powder metal mixes to which about 0.5 percent to about 12 percent coal tar pitch is added can be cold-pressed into green compacts having improved green strength. The green compacts can be sintered and repressed into iron and/or copper powder metal compacts which can contain residual carbon. Iron and/or copper powder metal compacts which contain uncombined carbon and/or combined carbon can be used as wear members and friction lining material in braking devices. The amount of residual carbon in the iron and/or copper powder metal compacts can be increased by substituting graphite or carbon black for a portion of the coal tar pitch added to the iron and/or copper powder metal mixes.

Process for heating and sintering ferrous powder metal compacts

Abstract: An induction field is utilized for rapidly raising the temperature of a ferrous powder metal compact to a sintering temperature where the compact is deoxidized and its particles coalesced into a homogenous mass. In order to overcome a characteristic incubation period which delays initial increase in temperature of such a compact in an induction field, the outer surfaces of the compact are preheated for a relatively short time by known heating means to raise its surface temperature to about 400 DEG F prior to subjecting the compact to a magnetic induction field. After the preheating step, heating in the induction field is used to raise the temperature of the entire compact to a level above 1,800 DEG F, and this temperature is maintained for a sufficient period of time to deoxidize and sinter the compact. After the heating and sintering treatments, the compact is cooled to a temperature of about 1,500 DEG -1,900 DEG F for a final forming operation which establishes a useful, full, dense, finished shape.

Tungsten filament having uniform concentration gradient of thoria particles

Abstract: An improved tungsten filament is disclosed containing approximately 1-2 percent by weight thoria particles distributed in the tungsten matrix as a dispersed phase. The thoria particles are distributed in the tungsten matrix to provide a slight but uniform compositional gradient which diminishes continuously with increasing distance from the exterior surface of the filament to the longitudinal central axis. Upon recrystallization of the filament or wire product there is also formed a tungsten grain structure having a more uniform size and shape of the individual tungsten grains than can be obtained by conventional powder metallurgy preparation.

Method of making valve seat rings from a mixture of c,pb and a pre-alloy of fe-co-ni-mo by powder metallurgy

Abstract: A POWDER METALLURGICAL METHOD OF MAKING VALVE SEAT RINGS HAVING A HIGH HEAT RESISTANCE, WHILE EMPLOYING A METAL POWDER WHICH IN ADDITION TO IRON CONTAINS FROM 0.5 TO 1% OF CARBON, FROM 0.7 TO 1.5% OF LEAD, FROM 1 TO 2% OF NICKEL, FROM 1.0 TO 2.0% OF MULYBDENUM, AND COBALT. AS STARTING MIXTURE IS EMPOLYED A PULVERIZED PRE-ALLOY WHICH CONTAINS FROM 1 TO 2% OF NICKEL, 1.0 TO 2% OF MOLYBDENUM, FROM 6.0 TO 7.0% OF COBALT, AND THE REMAINDER IRON. TO THE TUUS PRE-ALLOYED STEEL POWDER THERE IS ADDED CARBON IN QUANTITIES OF FROM 0.5 TO 1.0%, AND LEAD AT A QUANTITY OF FROM 0.7 TO 1.5%.SUBEEQUENTLY, THE MIXTURE IS BRIQUETTED, SINTERED COLD OR HOT POST-COMPRESSED, AND IF DESIRED, IS ANNEALED.

Method of forming articles of manufacture from superalloy powders

Abstract: A highly alloyed superalloy material is obtained using prealloyed powders. The material is easily shaped at high temperatures when it becomes superplastic because of its particular microstructure.

Pre-alloyed nickel-free silicon-free minimal oxide low alloy iron powder

Abstract: A pre-alloyed nickel-free silicon-free low-alloy iron powder with minimal oxide content yet possessing good hardenability and good mechanical and metallurgical properties for the production of sintered powdered metal articles is prepared by alloying iron with approximately one-half of one per cent molybdenum and approximately one-half of one per cent of manganese. Any desired carbon content is obtained either by combining carbon with the molten alloy prior to atomization or by adding graphite thereafter to the pre-alloyed powder by blending prior to compacting. The detrimental oxides normally created during the production of these compactible metal powders by the high temperature atomization of the molten metal from which they are formed are reduced to negligible amounts having harmless effects by passing the pre-alloyed powder through a sintering furnace containing a reducing atmosphere, such as a hydrogen or dissociated ammonia gas atmosphere. The sintered powdered alloy cake thus produced is then pulverized to form the alloy powder of the present invention. Comparative tests described, and their results set forth herein, show that the present invention alloy powder, although omitting the nickel content previously thought necessary, nevertheless retains the functions of, and compares favorably in performance with the prior nickel-content iron alloy powders.

Powder metallurgy method for making an electric contact and the resulting contact

Abstract: A layer of refractory metal or metal compound powder and a layer of low temperature melting metal or metal alloy powder are arranged together in the cavity of a compacting die and consolidated together to form an integrated two-layer compact which is thereafter heated above said low temperature but below the refractory powder''s sintering temperature to cause the pores of the compact''s refractory portion to be impregnated with the low temperature melting component while leaving an excess thereof forming a thin layer on the refractory portion. Because the two layers of the compact are consolidated together so that the compact may be moved safely without the layers separating during the heating, the use of a continuous furnace for the heating is commercially practical, and because the refractory portion is not sintered, the finished product''s dimensions can be accurately predetermined by the compacting die cavity dimensions. By heating the compact with its low temperature melting end down and resting as a refractory carrier surface having a plurality of depressions beneath this end, said layer is formed with a smooth exposed surface suitable for soldering or welding to a supporting metal part. Thus, a finished electric contact, for example, may be produced by the two steps of compacting and heating only, having a thick contact layer resistant to arc burning and contact welding trouble and a thin support layer that is solderable or weldable to a metal support or operating element.

Study of a columnar grain structure produced in a superalloy by gradient-annealing prealloyed powder extrusions

Abstract: Annealing in a temperature gradient was used to produce a structure of continuous columnar grains in alloy 713 C made by extrusion of prealloyed powder. The columnar-grained specimens had tensile strengths within plus or minus 5 percent of those of the as-cast alloy at 760 C and 980 C but were significantly stronger at room temperature. Stress-rupture tests at 760 C and 980 C showed lives scattered from 17 to 376 percent of those of as-cast 713 C tested under the same conditions. X-ray diffraction studies showed the large grains formed upon annealing to have a well-defined texture, although the as-extruded material had none.

Vibration resistant lamp

Abstract: An incandescent lamp having a filament made of tungsten wire containing between 1-2 percent by weight thoria has greatly improved resistance to fracture caused by shock and vibration thereby increasing the service life of the lamp. The thoriated tungsten filament has a recrystallized grain structure which is characterized by approximately equiaxed crystals of tungsten of a smaller and more uniform size and thoria particles which are more uniformly distributed throughout the tungsten matrix than can be obtained by conventional powder metallurgy.

Sintering of Cobalt-Rare Earth Permanent Magnets

Abstract: The process sequence used to fabricate high performance cobalt‐rare earth Permanent magnets is a powder metallurgy type of process with sintering as a key step. Precise control of the composition of the sintered magnet is essential if high magnetic performance is to be achieved. In this study we compare results from two approaches: 1) direct control of composition at the melting stage, and 2) control of composition by blending together powders of different compositions at a stage prior to alignment and densification.

SINTERED FE{13 CR{13 C{13 {8 MO{13 V{13 Ni{9 {11 ALLOYS IMPREGNATED WITH Pb OR Rb-BASE ALLOYS

Abstract: A lead-filled sintered ferrous alloy containing carbon and chrome and preferably also molybdenum and vanadium is prepared in a powder metallurgy method and impregnated in its voids with lead. The alloy is characterized for its increased wear and heat resistant abilities and is accordingly advantageous when used as a material of a valve seat of an internal combustion engine using leadless fuel.

Effect of processing variables on powder-metallurgy Rene' 95

Abstract: A Rene' 95 powder-metallurgy processing study was conducted to determine a cost effective method for producing Rene' 95 disks and also gain an understanding of the effects of powder-processing variables on properties and producibility. Variables studied included powder manufacturing method (argon atomiza-tion, rotating electrode, and H2/ vacuum atomization), particle-size distribution, consolidation techniques (extrusion vs. HIP), forging reductions and temperatures, and heat-treatment schedules. Forging multiples ranged from four pounds for the laboratory portion of the investigation to over four hundred pounds for the engine disks. For the parameters studied, decreases in powder particle size resulted in increases in 1200F stress-rupture lives of both extruded and HIP consolidated powders. Tensile properties of extruded compacts were superior to HIP properties and were unaffected by prior particle size while HIP compact tensile properties were inversely proportional to powder size. Subsequent forging of the compacts greatly minimized differences caused by the original powder size distribution and resulted in comparable tensile strengths for both consolidation methods. Stress-rupture lives and ductilities, however p were superior for the HIP forgings. Forging at lower temperature (1975F VS. 2O75iF) and at higher forging reductions improved tensile properties. Forgeability of the consolidated powders was good for virtually all conditions. In summary, the best powder metallurgy forging properties were achieved using powders having a fine particle size distribution that were consolidated at 2OqOF (below y8 solvus) and forged at 1975F. Introduction Jet-engine compressor and turbine rotor disks are the most critical and highly stressed major components in today's advanced engines. They are produced from complex highly alloyed precipitation strengthened superalloys that, because of their alloy content, are difficult to produce and consequently are very expensive. The powder metallurgy process as a method for producing these parts offers significant advantages over conventional cast plus wrought methods used until now. These advantages may be categorized as: 1) Lower Costs because of improved metal utilization, decreased forging operations and better forgeability and 2) Improved Properties attributed to the inherent homogeneity of powders. The powder metallurgy processes that may be used to produce these components cover a wide spectrum, but two of these have found the most favor. One is extrusion of powders followed by forging and the other is hot-isostatic pressing (HIP) plus forging. The work reported here is centered about these two generalized processes. Powder metallurgy variables utilizing these processes were investigated to determine their effect upon properties and producibility of a superalloy disk material, Rene' 95, with the intention of establishing a cost effective method for producing such disks.

A maraging steel produced by the powder metallurgy method

Abstract: 1. In a study into the effect of sintering temperature and duration on the density, microhardness, and martensite lattice constant of a powder metallurgical maraging steel and also on the character of formation of its micro structure, the following mechanical properties were attained after sintering and aging: σB=101 kg/mm2, σ0.2=98 kg/mm2, δ=4%, ψ=12%, aH=7.9 kg-m/cm2, and HRC=25–27. 2. The influence exerted by plastic deformation on all the mechanical properties was established. The best combination of strength and ductility, comparable with that exhibited by the cast high-strength maraging steel, was found to be ensured by a complex treatment (sintering + aging + plastic deformation + aging).

Forged Metal Powder Products.

Abstract: : Minimum deformation forging of prealloyed steel powders was used to produce complex-shaped components having a quality level equivalent to conventional forgings. Various 4600 and 4300 prealloyed steel powders, mixed with graphite to give 0.40% carbon, were investigated. Sintered compacts were forged with conventional and minimum-deformation type tooling. Minimum deformation forging produced high-quality flash-free forgings with no draft angles. Results of the study on the 4640 composition have shown that P/M forgings are competitive with conventionally wrought materials. Forgings with near theoretical density (99% plus) were capable of providing notched impact strength and ductility comparable to bar stock forgings. (Author)