BE738054A - Production of metallic powders - Google Patents

Abstract

Particles of a non-porous compound have a coherent internal structure and are consolidated. One constituent at least comprises at least 15% in volume of particles of a compression deformable metal. This produces a consolidated product with an almost uniform microstructure containing no more than 10% by high volume of segregation regions. Their minimum size is more than 25 microns. Metallic powders made according to this process have the advantage of a high degree of isotropic and are free of linear inclusions.

Description

  

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   "Metal powders and their 'production"
The present invention relates to metallic products and to their manufacture by powder metallurgy.



   When metal products are obtained by fusing, many problems are encountered. These include the appearance of dendrites and other forms of segregation in

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 castings of complex alloys, which lead to difficulties in machining as well as a non-uniform response to heat treatment. Brittle segregations interfere with the ductility of the cast material.

   If the segregations have a very low melting point composition, they can lead to the phenomenon known as "hot brittleness", which severely limits the allowable hot work range and even when machining work is possible. , the segregating regions persist in an elongated form which results in anisotropic properties and other disadvantages.



   These problems can to some extent be overcome by the techniques of powder metallurgy, which are also the easiest way to produce dispersion-strengthened metals and alloys as well as other products consisting of finely-mixed immiscible constituents. - targeted. However, powder metallurgy presents other problems of its own.



   Since the possibility of homogenization is limited to that which can be provided by sintering, solid state thermal diffusion and localized melting, there is a need for a starting material which contains the constituents in a finely divided form. aimed and distributed evenly. Thus, to make an alloy from a mixture of elementary powders, the latter must be very fine, that is to say with a dimension of 25.10 or even 3 microns or less, so that the The alloy can be made homogeneous by diffusion in a reasonably short time and these powders tend to be pyrophoric and collect impurities, for example oxygen from the atmosphere, which contaminate and disruptively affect the products made from them.



  -; Powders of different densities mechanically mixed also tend to provide segregation during storage and handling of the mixture, which leads to defects in uniformity

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 in the products obtained from the mixture.



   To avoid the need for mechanical mixing, one can use pre-alloyed powders, for example those obtained by atomization from a molten bath of the alloy, but these powders are expensive, difficult to obtain with a dimension particle size controlled and may even contain significant dendritic segregation.



   Similar difficulties arise in the preparation of dispersion reinforced metals and alloys by consolidating mechanical mixtures of the components. In this case, particularly fine metal powders are desirable, with an associated risk of contamination and there are also the additional problems that the refractory dispersed particles tend to flocculate due to static electric charges and that constituents of different densities tend to flocculate. separate during storage and handling of the mixture. Flocculation and segregation lead to non-uniformity of the final shaped product, due to the formation of linear inclusions of dispersoid particles and adjacent dispersoid depleted areas.



   Such linear inclusions and associated defects are a cause of disturbance in structural members subjected to stress, particularly at high temperatures. Depleted regions do not contribute appreciably to product strength and a body in which depleted areas constitute more than 10% by volume will be significantly weaker than a body without these defects. In addition, high concentrations of refractive particles. Tears in linear inclusions themselves are places of stress concentration and can be an important factor in the appearance of a defect at high temperatures, especially due to fatigue.

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   Non-mechanical processes for the production of mixtures of metallic and non-metallic particles for consolidation include the internal oxidation process, in which a powder, for example of nickel or copper containing a soluble reactive element such as aluminum; silicon, titanium, zirconium or thorium, is selectively oxidized to form fine particles of refractory oxide dispersed throughout the crystalline mass of the metal. This process also requires fine metal particles, is generally limited to simple binary alloy systems, and furthermore difficult to apply to nickel base alloys containing chromium as well as stainless steels. without oxidation of chromium.

   Thus, this process is generally only applicable to simple systems such as Ni-Al, Cu-Al,
Ni-Th or Cu-Si, where the free energy of matrix metal oxide formation reaches up to 80,000 calories / gram of oxygen.



   However, if all of the alloy powder is first oxidized and then selectively reduced to leave the oxide refractory, it is difficult to completely reduce the metal oxide forming the matrix, especially if it includes particles. oxides of metals such as chromium, aluminum and titanium.



   Various wet techniques have also been proposed for the production of dispersion hardened metals and alloys.



   The surface ignition coating process involves coating the metal or alloy powders with a decomposable salt of the contemplated refractory oxide dispersoid, mixing the particles with a solution of the salt and evaporating the liquid. Thus, nickel powder can be mixed with a solution of thorium nitrate in alcohol. The coated powder is then heated in an inert or reducing atmosphere to convert the salt to the corresponding oxide, as particles which coat the surface of the metal particles.

   Here again, the need for fine metal powders to achieve tight particle spacing.

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 dispersolde introduces the risk of contamination; Care must be taken to avoid pyrophytic combustion of the powder when it is treated to decompose salt. and segregation may occur, since the last part of the liquid to be evaporated tends to be very high in salt. Microstructures of fabricated metal products produced by this process tend to reveal linear inclusions of dispersed oxide.



   In the selective oxide reduction process, an intimate mixture of metal oxides, one of which is reducible while the other provides the dispersed oxide phase, is prepared for example by coprecipitation of the hydrates of the metals, converting these hydrates to oxides and selectively reducing the metal matrix oxide to the metal. The resulting powders can be extremely fine and pyrophoric and therefore highly susceptible to contamination. This process and other wet processes raise delicate material handling problems, tend to be dirty, and are usually expensive.



   It has been proposed in an earlier patent to use, as starting materials for powder metallurgy processes, powders comprising composite particles consisting of a hard refractory material with a high melting point, and a ductile metal. , the particles of one of the constituents being coated by the other. Methods of preparing these particles include chemical or vapor deposition of the metal on the refractory particles and providing on the ductile metal particles a surface layer of a refractory oxide-forming metal which is then oxidized.

   Similar particles result from the routine processing in the ball mill of mixtures of a ductile metal and a refractory oxide, for example mixtures of nickel and thorium oxide, for prolonged periods at the usual ball / powder ratios. , that is to say ratios which can reach up to 3/1. All compound powders of this type have the disadvantage that the particle size of the metal core is.

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 essentially that of the initial powder used and that this relatively coarse structure is transferred into the processed products obtained from the powder, resulting in linear inclusions of dispersoid and associated areas free of dispersoid.



   When preparing powder metallurgical products starting from metals normally immiscible in the liquid and / or the solid, for example iron and copper, a sintered skeleton of the powder of a metal may be subjected to infil - Tration by the other molten metal, or it is possible to sinter a mixture of the two metal powders. Whatever the process used, the distribution of copper is limited either by the size of the pores of the skeleton, or by the relative size of the initial powders.



   The presence of a liquid phase during infiltration or -filtering also tends to cause micro-segregation.



   The present invention overcomes these various difficulties and provides consolidated metal products which possess a very high degree of microstructural uniformity and isotropy and which are substantially free from segregation and linear inclusions.



   Other details and features of the invasion will emerge from the description below, given by way of non-limiting example and with reference to the accompanying drawings, in which:
Figure 1 is a schematic representation of a ball mill type friction wear apparatus capable of providing agitation grinding for producing compound powders for use in accordance with the invention.



   Figure 2 is a reproduction of a photomicrograph obtained at a magnification of 100 diameters and illustrating in longitudinal section a microstructure of a superalloy reinforced by dispersion, obtained according to the invention after annealing at 2,250 F for 4 hours in the argon.

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   Figure 3 is a reproduction of an electron photomicrograph obtained with a magnification of 10,000 diameters of a surface reproduction of a dispersion reinforced superalloy as shown in Figure 2.



   Fig. 4 is an electron transmission photomicrograph obtained with a magnification of 100,000 diameters, illustrating the structure of another dispersion reinforced superalloy obtained in accordance with the invention.



   Broadly speaking, the invention contemplates the production of consolidated metal products characterized by a high degree of microstructural uniformity and practically free of segregation and linear inclusions by consolidation, for example by hot extrusion, hot pressing, forenge etc, bound particles containing at least 15% by volume of a deformable metal while the remainder consists of a metal or a non-metal, these particles providing a mechanically alloyed and interdispersed internal structure.



   A reinforced product without dispersion should be considered practically free from linear inclusions or segregation if it contains less than 10% by volume of linear inclusions or regions exceeding 25 microns in minimum dimension in which there is an appreciable variation in composition. from the average, i.e. a compositional deviation exceeding 10% of the average content of the separated alloying element. The boundaries of a separate region are considered to be where the deviation of the composition from the mean is half the maximum deviation in that region. Composition deviation regions less than 25 microns in minimum dimension are not considered separate regions.

   Preferably, the minimum dimension of the linear inclusion or region offering variations in composition is not more than 10 microns. Preferably equal-

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   ..tent, the proportion of linear inclusions or separated regions is less than 5% by volume. variations in composition on the scale defined above can, for example, be detected and measured by examination using an electron microprobe. the products are advantageously obtained according to the invention through the consolidation of special compound powders.



   These powders and their production processes have been described in Belgian Patent No. 729,149 of February 28, 1969.



   The powders used consist of worked compound particles having a coherent non-porous internal structure composed of two or more constituents intimately united and interdispersed, at least one of the constituents, totaling at least 15% by volume of the particles, being a metal deformable by compression and the compound particles individually having substantially the composition of the powder. The internal structure of the compound particles can be regarded as a mechanical alloy.



   The constituents of the compound particles, other than the deformable metal, can be other metals or non-metals, especially refractory oxides and other hard phases of interest for dispersion-reinforced alloys. The term "metal" used in this patent is to be understood as encompassing alloys.



   The average spacing between the sub-particles of the interdisperse components in the compound particles should be as small as possible to facilitate thermal diffusion of the components which are susceptible to interdiffusion when heated to promote alloying. spacing does not exceed 10 microns and preferably, particularly in the case of dispersion-reinforced products, it does not exceed
3 microns or even 1 micron and it can be much less than a micron, while the compound particles have utilemeht a

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 average size from 20 to 200 microns.

   although larger particles can be used when it is possible to form them with a sufficiently fine internal structure and smaller particles can be used when the systems used are sufficiently noble to avoid pyrophoricity
It will be appreciated that the advantage of using such engineered compound particles to form consolidated powder metallurgy products arises from the fact that the particles act as building blocks for the final structure, the high degree. uniformity of each of the composite particles being carried over and maintained in the final work product.

   Conversely, the use of homogeneous compound particles containing dispersals for the production of consolidated products will not lead to homogeneous products. The spacing between the constituents of the product will obviously depend on the extent of the reduction occurring during consolidation and this spacing will generally be less than that in the particles of the powder.



   Spaces of less than 3 microns or even one micron, preferably even much smaller, are particularly advantageous in the case of powders containing refractory dispersants.



   The powder particles are advantageously in a highly strain-hardened state since this accelerates the alloying of the constituents by thermal diffusion during heating and facilitates hot deformation, such as for example hot extrusion for example. consolidation of an enclosed mass of powder particles. This is considered to be due to the very fine grain structure resulting from coalescence of the work hardened structure upon heating for hot deformation.



   The powder can be obtained, according to the main patent, by subjecting a mixture consisting of at least 15% by volume

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 several other powders of metals or non-metals to high energy impact crushing, usefully in a stirred ball mill, sufficiently energetic and sufficiently prolonged to reduce the particles of the deformable metal to less than half and preferably this to less than a fifth or even a tenth of their original thickness and to pulverize and bond together the constituents of the mixture to form non-porous compound wrought particles exhibiting a coherent interdisperse internal structure.

   In order to produce the desired structure, grinding may be continued, under conditions where strain hardening occurs, at least until the hardness of the compound particles has been increased by half of the difference between the base hardness and. the constant saturation hardness obtained during prolonged grinding. During vigorous dry grinding, the compound particles are constantly broken up and reformed by cold working, with a gradual increase in the uniformity of the composition of the particles and the refining of their internal structure. Advantageously, the powder is ground to saturation hardness and preferably grinding is continued beyond this point, until the structure has been refined to the desired extent.

   Grinding beyond the saturation point of hardness is particularly desirable in the case of complex alloys, since these reach saturation hardness while their structure is less uniform than in the case of unalloyed metals. due to the hardening effect of other hard constituents, for example fragments of parent alloys.



   The compound particles thus comprise ground fragments of the original metal particles welded or metallurgically bonded together, the minimum size of the fragments usually being less than one-fifth and preferably less than one-tenth of the average size of the product. initial whose fragment

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 was derived. Refractory particles incorporated in the initial powder are distributed throughout the individual composite particles in a state of fine dispersion approximately equal to the minimum size of the fragments.

   Thus, the average distance between the refractory particles in the compound particles; is much smaller than the particle size of the original metal and is preferably less than one micron and even down to 0.5 micron or less. In such particles, there are virtually no islands or zones in the compound particles devoid of dispersoid.



   High energy dry impact milling can usefully be carried out in an agitating ball mill comprising a stationary vertical axis cylinder containing a charge of balls or balls and having a rotating agitator shaft located coaxially with respect to it. to the mill, with spaced agitator arms extending substantially horizontally from this shaft and serving to maintain the mass of the load of balls in continuous relative motion.

   Such a crusher has been described in the work of
Perry "Chemical Engineer's Handbook" Fourth Edition, 1963, pages 8 to 26 and is illustrated schematically in Figure 1 of the accompanying drawings, which shows in partial section a vertical cylinder 13 surrounded by a cooling jacket 14 having orifices of. The inlet and outlet 15 and 16 are respectively intended for circulating water or other cooling medium. A shaft 17 is supported coaxially in the cylinder by means not shown and has horizontal arms 18, 19 and 20 in one piece with this shaft. The crusher is filled with balls or balls 21 to a sufficient depth to flood at least part of the arms.



   The grinding time t required to produce a satisfactory dispersior, the speed W of the agitator (in revolutions per minute), the radius er of the cylinder (in centimeters and the ratio R between the volume of the balls and that of the powder are associated by the ex-

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 next press:
1 / t = K w3 r2 R in which K is a constant depending on the system used.



  Thus, once a satisfactory set of conditions has been established in a mill of this type, other sets of satisfactory conditions for this mill and other like mills can be established using the expression which precedes.



   Unless otherwise indicated, the impact milling mentioned in each of the examples of this patent was carried out in a mill of this type cooled by water. The grinding speed indicated in rpm is the speed of rotation of the agitator. Unless otherwise specified, the crusher has been sealed in order to prevent the access of air during grinding except that
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   Regardless of the type of mill used the balls or other frictional wear elements should be hard and tough enough to compress the deformable metal and they are preferably made of metal or cement, for example steel, stainless steel, nickel or tungsten carbide, with a small diameter relative to the mill and with a practically uniform dimension.



  For further details of the production of the powders, reference is made to the main patent.



   Composite powders can offer an extraordinarily wide range of compositions and they can be used to produce an equally wide variety of composite products.



  The compositions include a very wide range of metal systems corresponding to both simple binary alloys and more complex alloys, as long as they include a metal deformed by compression.

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   Simple alloys include those based on lead, zinc, aluminum and magnesium, copper, nickel, cobalt, iron and refractory metals. More complex alloys include well-known heat-resistant alloys, for example those based on nickel-chromium, cobalt-chromium and iron-chromium systems containing one or more additions.
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 alloys such as tungsten molybdenum, niobium, tantalum, aluminum, titanium, silicon, zirconium. etc. with or without non-metals such as carbon and boron.



   Dispersion hardened wrought alloys, both simple and complex, can be produced from compound powders having uniform dispersions of a hard refractory phase. Refractory compounds include oxides, carbides, nitrides, borides of refractory metals such as thorium, yttrium, zirconium, hafnium, titanium and even certain refractory oxides such as those of silicon, aluminum, cerium, uranium, magnesium, calcium, beryllium and the mixture of rare earth oxides, didyma oxide.

   Refractory oxides generally useful as dispersed phases are those whose free energy does not
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 The formation gative-per gram-atom oxygen / about 25 ° C is at least about 90,000 calories and has a melting point at least that of the matrix. The proportion of hard phases. may be sufficient to produce cermet compositions as long as sufficient ductile metal is present to provide a receiving matrix for the hard phase or dispersal.

   When only dispersion strengthening of crafted compositions is desired, such as in high temperature alloys, the amount of dispersal may range from 0.05% to 25% by volume and more preferably from 0.05% to 5%. % or 10% by volume.

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   The process according to the invention is also particularly useful for obtaining manufactured products from metal systems the components of which have limited solubility or even practically no mutual solubility in the liquid state and / or the solid state, for example. lead or iron with copper, tungsten with copper or silicon and chromium with copper.

   It should be particularly noted that since the constitution of the compound powders is that of a mechanical alloy with an extremely fine structure, their compositions and therefore those of the products obtained from these powders are not limited by normal practical considerations when the use of melting techniques or conventional powder metallurgy techniques and that the practical absence of segregation in the products leads in many cases to a remarkable improvement in the workability by comparison with cast alloys of the same composition. Many new and advantageous alloy compositions are thus becoming available in manufactured forms.



   The many advantages of using the wrought compound particles for the production of consolidated metal products obtained by powder metallurgy include the protection of reactive components such as chromium, aluminum and titanium against oxidation thanks to their. incorporation and isolation in the matrix of the deformable metal. The compound particles also combine the advantages of a coarse powder, including storage with minimal contamination, ease of degassing for sheath extrusion, non-pyrophoric properties, good flow characteristics and high flowability. high bulk density, with an extremely intimate and fine dispersion of the constituents in each particle.

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   The consolidation of the compound powder into metallic products can be carried out by any suitable mechanical machining process, including extrusion in a closed sheath, crushing, rolling and hot pressing. The work will obviously depend on the nature of the composition enviosegée During the heating of the particles to the temperature used for the machining any homogenization and any annealing such particles which may occur will generally take place, but any other heat treatment can be carried out subsequently if desired .

   it is generally desirable to degas the powder as much as is practicable to do so before performing the machining or working.



  Some of the various types of manufactured products according to the invention
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Superaliages
Complex high-temperature alloys based on nickel, cobalt or iron (usually referred to as superalloys) which contain chromium and which are made susceptible to age hardening thanks to alloying elements such as niobium, titanium and l Aluminum and / or are hardened to a solid solution by molybdenum or tungsten, tend to suffer from segregation in casting, particularly with high contents of the alloying element.

   This leads to a non-uniform response to age hardening and difficulties in hot machining. If one uses powder metallurgy techniques or an elemental powder mixture. or partially pre-alloyed, it is found that chromium tends to be oxidized and that aluminum and titanium tend to be lost through oxidation, so that they are no longer available for aging hardening and other disadvantages such as segregation also occurs as already mentioned.

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   Difficulties are encountered in seeking to deplicate dispersion reinforcement to superalloys, because of the easy termination of linear dispersoid inclusions with fear of resalting large amounts of the alloy which are devoid of dispersoid The fabrication of superalloys by Consolidation of powders composed of openings according to the invention facilitates the elimination of segregation in normal superalloy compositions. It allows the content of alloying elements to be increased for age hardening or solid solution hardening and it allows the easy production of dispersion reinforced superalloys.

   The resulting wrought products have a microstructure which is substantially uniform throughout, are substantially free of segregation, primary gamma prime phase and linear inclusions, and have a uniform distribution of precipitation hardening phases as indicated by electronically transmitted photomicrographs.



   They can be enhanced by dispersion with any of a wide variety of refractory oxides) carbides, nitrides and borides as defined above in more detail.



   It has been remarkably noticed that bodies produced by hot working or hot machining of mechanically consolidated alloy powders can be worked to a much greater extent than bodies conventionally produced with the same composition as the body. matrix alloy. This is shown by the reduced temperatures required for comparable values of hot strain, reduced working pressures and higher allowable values of working stress.



   Generally, alloys have a melting point of at least 1.093 C and they contain 4 to 65% by weight of chromium, at least 1% in total of one or more of the components - niobium , aluminum and titanium, preferably 0.2 to 15% aluminum (for example 0.5 to 6.5%), and 0.2 to 25% titanium (for example

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   0.5 to 6.5%, 0 to 40% molybdenum, o to 40% tungsten, 0 to
20% niobium, 0 to 30% tantalum, 0 to 2% vanadium, up to 15% manganese, up to 2% carbon, up to 1% silicon, up to 1% boron , up to 2% zirconium and up to 0,

  5% magnesium, the remainder (at least 25%) consisting essentially of iron, nickel or cobalt with or without dispersion strengthening constituents, such as yttrium oxide, oxide lanthanum, alumina, thorium oxide, etc., in amounts of 0.05% to 10% and preferably 0.05 to 10% by volume of the total composition.



   The superalloys to which the invention relates more particularly include those falling in the gamma of 5 to 35% chromium, 0.05 to 8% aluminum, 0.5 to 10% titanium, up to 12% molybdenum up to 20% tungsten, up to 8% niobium, up to 10% tantalum, up to 2% vanadium, up to 2% manganese, up to 1% carbon, up to 1.5% silicon, up to 0.1% boron, up to 1% zirconium, up to 2% hafnium, up to 0.3% magnesium, up to '45% iron, up to 10% by volume of dispersolde which is advantageously thorium oxide, yttrium oxide, lantan oxide,

   cerium oxide or mixtures of rare earth oxides such as didyme oxide can usefully be present in amounts of at least 0.2% and preferably 0.5 to 5% by volume, the remaining (at least 40%) being constituted by nickel and / or cobalt.

   Some specific examples of superalloy compositions which can be produced with or without a dispersoid are given in Table 1 below.

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The stable refractory compound particles can be kept as fine as possible. , for example with a dimension less than 0.5 micron. A range of particle sizes determined to be particularly useful for the production of dispersion enhancement systems and: from 10 to 1,000 Angstroms (0.000 to 0.1 microns).



   Particularly advantageous is the extensive cold work imparted to the compound metal particles produced by grinding the high melting point metals to produce the superalloy compositions. It increases the effective diffusion coefficients in the produced powder and this factor together with the intimate mixing in the produced powder of metal fragments from the primitive components in order to establish small interdiffusion distances, promotes rapid homogenization and alloying the produced powder upon heating to homogenizing temperatures and improves hot workability as explained above.

   The foregoing factors are of particular value in the production of powder metallurgical articles having fairly complex alloy matrices.



   We will now give some examples: EXAMPLE 1
A pulverulent mixture consisting by weight of 14.9%., / Of a parent Ni-Ti-Al alloy in powder form containing 72.93% of Ni, 16, 72% of Ti, 7.75% of Al, 1.55% Fe, 0.62% Cu, 0.033% C, 0.05% Al2O3 0.036% TiO2 62.25% nickel carbonyl powder with a particle size of 5-7 microns, 19 , 8% chromium powder with a particle size of 74 microns and 3.5% thorium oxide with a particle size of 0,

  04 micron was premixed and 1300 grams of this mixture was dry impact crushed under argon atmosphere for 48 hours in

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 an attrition mill with a ball / powder ratio of 17/1, rotating at 176 rpm. The product consisted of particles of compound powder offering an excellent interdispersion of the ingredients in the individual particles and having a striated structure under a magnification of 750. Analysis of the powder gave 73.86% Ni, 19.3 % Cr 2.16% Ti, 1.19% Al, 0.017%
C, less than 0.05% Cu, 2.93% ThO2 0.015% Al2O3 0.013% TiO2 The amount of other impurities was negligible.



   After removing a few coarse particles larger than 350 microns, the powder having a particle size range of 45 to 350 microns was extruded into a bar in a stainless steel pot after vacuum degassing (2 x 10-5 mm Hg) at 350 C using an extrusion ratio of 16/1 and a temperature of 1175 C. The extruded rod contained a fine and uniform dispersion of thorium oxide particles with an average size of 0.04 microns and a particle spacing less than 1 micron, without linear inclusion and with a hardness of 275 Vickers.

   Heating in solution for 16 hours at 1200 C reduced the hardness at 235 Vickers, while subsequent aging for 16 hours at 705 C caused precipitation hardness increasing to 356 Vickers.



   By comparison, wrought alloys having substantially the same matrix composition and produced by conventional smelting techniques had a hardness of 200-250 Vickers after annealing, which was increased to 290-320 Vickers by one. similar aging treatment.



   EXAMPLE 11
A mixture consisting by weight of 39.5% of a powdered master alloy with a particle size of less than 43 microns and containing 67.69% Ni, 8.95% Mo, 5.70% Nb, 15.44% Al, 1.77% Ti, 0.053% C, 0.06% Zr and 0.01% B, 45.74%

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 carbonyl nickel powder with a particle size of 5 microns, 11.64% chromium powder with a particle size less than 74 microns and 3.12% thorium oxide with a particle size of 0 , 04 micron,

   was dry milled for 48 hours in air in a mill / attritor with a ball / powder ratio of 29/1 by volume and a speed of 176 rpm. Microscopic examination of the powder revealed that the constituents had united intimately to form compound metal powder particles which provided excellent interdispersion of the ingredients,
Part of the pulverulent product, after removal of coarse particles greater than 350 microns, was extruded into a bar in a stainless steel pot (after degassing under vacuum at 425 C), using an extrusion ratio of 16 / 1 and a temperature of 1200 C. The resulting bar had the following composition analyzed:

   0.07% C, 10.40% Cr. 3.005 of Mo 1.60% of Nb, 5.20% of Al. 0.65% of Ti, 0.007% of B, 0.03% of Zr, 3.20%
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 of Th0, 1.38% of A12o3 d 0.018 of TiO2. 0.016% cr203, the remainder being Ni. The Al2O3 was present as an intimate dispersion and the proportion of foreign oxides, TiO2 and Cr2O3 was thus very low.



   Parts of the extruded bar were heated at 1240 C for 4 hours under argon to dissolve the alloy, increase its grain size and complete the homogenization of the structure then oven cooled to allow precipitation hardening to occur. . The grain structure of the alloy after this treatment is shown at 100 magnification in Figure 2 of the drawings. Note that the grain structure is elongated in the direction of extrusion.

   Thanks to an examination under an electron microscope after this treatment, it was observed that

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 the alloy contained both a gamma prime precipitation hardening phase and an intimate dispersion of thorium oxide particles with an average size of 0.05 micron, with particle spacing less than 1 micron. The fine structure observed with an electron microscope under 10,000 times magnification is shown in Figure 3 of the drawings.



   The high temperature properties of the alloy after heat treatment are given in Table II.



     TABLE II
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 <tb> 760 <SEP> 69.6 <SEP> 79.0 <SEP> 7, <SEP> 5 <SEP> 10.0
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 <tb>
 <tb>
 <tb> 982 <SEP> 19.3 <SEP> 24.9 <SEP> He, 0 <SEP>: <SEP> $ * Ci
 <tb>
 
 EMI22.4
 1,093 7.5:

   ¯¯¯ $ t2 ¯ 9 * ¯ ^ ZT ¯
The improvement provided by the dispersion of thorium oxide in the alloy is revealed by comparing the stress failure properties of the heat treated alloy with those of a cast and precipitation hardened high temperature alloy. (alloy 713) not containing thorium oxide and having a composition similar to that of the matrix of the alloy containing thorium oxide, namely 74.84% Ni, 12.0% Cr, 4.5% Mo, 2.0% Nb, 0.06% Ti, 5.9% Al, 0.05% C, 0.1% Zr, and 0.01% B.

   These properties are compared in Table III as a function of the stress under which the alloys offer lives of 100 and 1000 hours at 1093 c
TABLE III
 EMI22.5
 
 <tb> Life, hours <SEP>: <SEP> Effort <SEP> for <SEP> the <SEP> life <SEP> specified <SEP> kg / mm2 <SEP> alloy
 <tb>
 <tb> ¯¯¯¯¯¯¯¯¯: <SEP> alloy <SEP> with <SEP> ThO2 <SEP> 713
 <tb>
 <tb>
 <tb> 100 <SEP> 6.0 <SEP>: <SEP> 4.5
 <tb>
 <tb>
 <tb>
 <tb> 1000 <SEP> 5.4 <SEP>:

    <SEP> 2.9
 <tb>
 

  <Desc / Clms Page number 23>

 
EXAMPLE III An 8.5 kg powder charge of 1550 parts of a
 EMI23.1
 master nickel alloy containing 7% aiunsiaiua, 14% titanium and 9% dīdyme; (a mixture of rare earth metals containing 50% lanthanum with neodymium and praseodymium and other rare earth metals) crushed so as to pass a 74 micron sieve, 1800 parts of chroma powder smaller than 74 microns , 20.4 parts of Ni Zr master alloy 3.87 parts of Ni-B master alloy and 5,241 parts of nickel carbon powder # vle, was crushed under dry impact in a 38 attrition mill. liters containing 189 kilos of 6.3mm nickel grains for 40 hours at a stirrer speed of 132 rpm.

   The product was sifted through a 350 micron sieve and enclosed in an 8.9 cm steel pot
 EMI23.2
 in diameter--, -which-was- obtained.1r-é -s.mls-wacuati.on, ¯¯aüsd-1.C3 $ - * C- - and extruded into a round bar of 1 , 9 cm in diameter. The powder was consolidated by upsetting into the container prior to extrusion and good hot workability was evident from the fact that extrusion was possible at the relatively low temperature of 1.038 ° C. The extruded bar was was subjected to a heat treatment comprising heating for 2 hours at 1275 C, followed by heating for 7 hours at 1.080 C and then for 16 hours at 705 C. A coarse-grained structure elongated in the direction of extrusion was present .

   The extruded bar was characterized by a finely divided and well distributed dispersion of the rare earth metal oxides, mainly lanthanum, resulting from internal oxidation by reaction of the extremely finely divided rare earth metal and the oxygen present. in the ground powder.



   The stress failure properties of the heat treated bar were very good as illustrated by the data offered in Table 4 below, indicating a very uniform dispersion of fine particles of refractory oxide.

  <Desc / Clms Page number 24>

 



    TABLE IV
 EMI24.1
 t'e: 'p., Stni: Effort: Time until Elongation: Striction (Ci (k <; / :: nr.; 2): the break (6) ¯¯¯¯¯¯¯¯¯s¯¯¯¯¯¯¯¯¯¯¯¯¯ & âjJ¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
 EMI24.2
 
 <tb> lose <SEP> 12.7 <SEP> 1.5 <SEP> 8.0 <SEP> 11.6
 <tb>
 <tb>
 <tb> 1088 <SEP> 11.2 <SEP> 472.7 <SEP> 4.0 <SEP> 6.0
 <tb>
 <tb> 1038 <SEP> 9.8 <SEP> 389.7 <SEP> 2.7 <SEP> 3.9
 <tb>
 <tb>
 <tb> 760 <SEP> 35.2 <SEP> 16.3 <SEP> 2.7 <SEP> 3.9
 <tb>
 <tb>
 <tb> 760 <SEP> 28.1 <SEP> 193.1 <SEP> 4.4 <SEP> 7.0
 <tb>
 
This example illustrates a particular characteristic of the invention,

     according to which dispersion reinforced metals can be produced by taking as starting material a powder in which is distributed on a microscopic scale a metal the oxide of which has a heat of formation high at 23 ° C exceeding 90,000 calories per gram atom oxygen.



   This metal is oxidized in place by the oxygen available in limited quantity in the powder, due to the very small diffusion distances involved, with the result that the resulting oxide is very fine and very well distributed in the resulting consolidated form in which the oxide is an effective dispersion strengthening element.



   EXAMPLE IV
A new 8.5 kilogram powder charge containing approximately 1490 parts of a master aluminum alloy with 17% Ni and 8.5% Ti, ground to minus / 75 microns, 2000 parts chromium with a dimension less than 75 microns, 1330 parts of fine nickel carbonyl powders premixed with 10% by weight of fine yttrium oxide (400 A), in a Waring mixer, 24.8 parts of an alloy- mother Ni-Zr with a dimension less than 75 microns;

   3.9 parts of a Ni - B parent alloy with a dimension of less than 75 microns and 5.290 parts of carbonyl nickel powder, was ground * for 40 hours in a 38 liter attrition mill

  <Desc / Clms Page number 25>

 containing 180 kilos of 6.3 mm nickel grains, at 132 t / m. The produced powder was sieved through a 350 micron sieve and enclosed in a steel pot with a diameter of 8.9 centimeters.



   The pot was evacuated to a mercury pressure of less than 10-4 mm. at 425 c and sealed by welding. The vacuum sealed jar was heated to 1093 c and extruded into a bar with a diameter of 15.5 mm. The extruded bar was heated in argon for 2 hours at 1275 C, then at 1080 C for 7 hours and cooled in air. It was then heated for 16 hours at 700 C and again cooled in air. A desirable coarse-grained structure elongated in the direction of extrusion was obtained.

   The bar contained 0.061% C, 0.92% soluble Al, 2.46% soluble Ti, 20.4%
Cr, 0.029% soluble Zr, 0.005% B, l, 22% Y203 and 0.37%
Al2O3
Samples of the heat treated extruded bar were subjected to stress failure testing with the excellent results defined in Table V below.



   TABLE V
 EMI25.1
 
 <tb> Temp .: <SEP> Effort <SEP> life <SEP> until <SEP> the <SEP> break <SEP> Elongation: <SEP> Striction
 <tb>
 
 EMI25.2
 (C k m¯n2 rs) (%) 96
 EMI25.3
 
 <tb> 1038 <SEP>: <SEP> 12.7 <SEP> 5.8 <SEP> 3.2 <SEP> 9.0
 <tb>
 <tb>
 <tb> 1038: <SEP> 11.5 <SEP> 70.9 <SEP> 4.0 <SEP> 9.4
 <tb>
 <tb>
 <tb> 1038: <SEP> 11.2 <SEP> 393.6 <SEP> 2.7 <SEP> 1.6
 <tb>
 <tb>
 <tb> 927 <SEP>: <SEP> 17.6 <SEP> 7.1 <SEP> 6, <SEP> 2 <SEP> 10.5
 <tb>
 
 EMI25.4
 927 15.8 117.4 5.3 11.6 760: le, 20, 7fi: 35.2 E, O 7.2 20, 5
 EMI25.5
 
 <tb> 760 <SEP> 28.1 <SEP> 131.3 <SEP> 6.4 <SEP> 21.5
 <tb> 760 <SEP>:

    <SEP> 28.1 <SEP> 53.3 <SEP> 10.0 <SEP> 19.1
 <tb>
 
In addition, the yttrium oxide-containing material was found to be significantly more resistant to sulphurization corrosion resulting from exposure to 927 ° C to a molten salt bath containing 90% sulphate by weight. sodium and 10%

  <Desc / Clms Page number 26>

 of sodium chloride, than the base alloy not reinforced by dispersion. Likewise, the yttrium oxide-containing material was significantly stronger than the non-dispersed base alloy in a cyclic oxidation test at 1093 C in circulating air, where specimens were cycled at room temperature every 24 hours.

   In particular, the yttrium oxide-containing material was much more resistant to below-surface penetration than normal material during these tests.



   Fig. 4 is a transmission electron photomicrograph obtained at 100,000 times magnification from the material of the present example containing yttrium oxide. The fine and practically uniform distribution of the finely divided dispersol (yttrium oxide and alumina) as indicated by the reference G and a practically uniform distribution of the gamma prime phase as indicated by the reference H is clearly apparent from the description. Figure 4. Slightly larger MC metal carbides indicated by the reference J are also evident in Figure 4.



   This figure 4 demonstrates the absence of segregation which characterizes the materials according to the present invention.



   EXAMPLE V
Alloy powders composed with the composition of a classic nickel - based superalloy, containing 10% Cr,
3% Mo, 15% Co, 5.5% Al, 4.7% Ti, 1% V, 0.18% C, 0.06% Zr, 0.014% B, the remainder being Ni, were produced by mechanical training; of alloy.

   A mixture / 441 grams of Cr powder (less than 150 microns), 134 grams of Mo powder less than 44 microns), 663 grams of Co powder (less than 44 microns), 1005 grams of carbonyl nickel powder , 7.6 grams of graphite powder, 1050 grams of powder with a dimension less than 75 microns of a nickel master alloy with 15.96% Al and 3.68% Ti, 932 grams of a smaller dimension powder

  <Desc / Clms Page number 27>

 at 75 microns of a mother nickel alloy containing 9.08% Al and 17.5%
Ti, 71 grams of a powder of size less than 150 microns of a nickel master alloy with 65% V,

   12 grams of a powder of size less than 75 microns of a master nickel alloy with 28% Zr and 14.5% Al and 3.3 grams of a powder of a size less than 75 microns of a niclcel master alloy with 18% B, was placed in a high energy horizontal ball mill with a capacity of 15 liters having a stationary tank and a driven horizontal shaft equipped with multiple agitator arms s' extending perpendicular to this shaft, to be processed at a speed of 220 rpm with 90 kilos of 9.5 mm steel balls.



   A nitrogen atmosphere was maintained in the mill. Two loads were treated for 16 hours, one for 8 hours and one for 4 hours.



   The internal powder structure of batches treated for 16 hours was observed to be substantially homogeneous with the majority of ingredient fragments in particles composed of a size less than 1 micron. In contrast, the structures of loads treated for 8 and 4 hours were progressively less homogeneous, although all exhibited the same general size distribution of the compound particles.



   3.066 grams of one of the charges treated for 16 hours sieved through a 350 micron sieve were enclosed in a mild steel pot 8.9 centimeters in diameter -4 and evacuated to a pressure of mercury less than 10 mm at 425 c via a stainless steel tube provided for this purpose. The pot was sealed by fusion welding of the tube and consolidated by hot extrusion into a bar with a diameter of
2.5 centimeters, at 1177 c the extraction was carried out without difficulty. by requiring less than 2/3 of the press capacity and unwinding with a piston speed of 33 to 61 centimeters per second.

  <Desc / Clms Page number 28>

 



  This despite the fact that the composition as normally produced is not readily susceptible to hot work and must be precisely cast to the final shape.



   The results of the hardness tests carried out on samples of this extrusion in the as-extruded state and after two annealing treatments are given in Table VI.



   TABLE VI
 EMI28.1
 
 <tb> State <SEP>: <SEP> Hardness
 <tb> Rc
 <tb>
 <tb>
 <tb>
 <tb> Tel <SEP> than extruded <SEP>: <SEP> 48
 <tb>
 <tb>
 <tb>
 <tb> 2 <SEP> hours <SEP> to <SEP> 1243 c <SEP> 42.5
 <tb>
 <tb>
 <tb>
 <tb> 2 <SEP> hours <SEP> 1266 c <SEP> 40.5
 <tb>
 Dispersion reinforced fabricated electric heating elements
 EMI28.2
 -The alloys '"resistBmt # to the * chaiGur" poi.! r "of the' electric heating elements, comprising iron and / or nickel alloyed with chromium and / or aluminum, suffer from segregation when They are obtained by casting Equalization to homogenize the structure only leads to little improvement and may result in coarser grain, accompanied by disruptive effects on the forging ability, extrusion and rolling.



  In particular, certain well-known alloys which contain both aluminum and chromium, together with nickel or iron or both, are brittle at room temperature although flexible at high temperatures. One of these alloys contains 67% iron, 25% chromium, 5% aluminum and 3% cobalt and another 55% iron; 37.5% chromium and 7.5% aluminum. Both of these alloys provide excellent resistance to oxidation and corrosion at elevated operating temperatures of about 1200 to 1300 ° C but tend to flow and lose their shape during use as electrical resistance elements.



   These disadvantages are overcome with the dispersion hardened fabricated electric heating alloys offered following

  <Desc / Clms Page number 29>

 the invention, which is characterized through and through by uniformity of composition (i.e. absence of segregation) and by ---- a high degree of uniformity of dispersion and absence of 'inclusions - linear with the associated dispersal-free regions.



   In general, the alloys envisaged are those containing at least 10% in total of chromium and / or aluminum, the chromium content not exceeding 40% and the aluminum content not exceeding 34%, and from 0 to 5% silicon, the remainder of the alloy (except for impurities) consisting of at least 50% in total of iron (5 to 75%), cobalt (up to 15%) and / or nickel (5 to 80%) while comprising from 0.05 to 25% by volume (based on the total composition) of a refractory compound dispersoid.
 EMI29.1
 



  ---- 'one-way-general the alloys¯8nt an electrical resistance of at least 100 microhms / cm3.



   Advantageously, the chromium content is 15 to 40%, the cobalt content does not exceed 10%, the aluminum content does not exceed 32% the sum of the iron, cobalt and nickel contents reaching 50 to 80% and the dispersal content of 0.05 to 10% by volume of the total composition.



   A particularly desirable composition range for electrically heated alloys contains 15 to 40% chromium, 3 to 20% aluminum, the remainder being iron, with 0.05 to 5% by volume dispersold.



   Particularly useful dispersants are yttrium oxide, lanthanum oxide, triumium oxide and the mixture of rare earths called didyma, with dimensions less than 1 micron and preferably less than 0.1 micron. Oxides of zirconium, titanium and beryllium as well as carbides, nitrites and borides of all the metals defined above can also be used. Generally speaking, suitable refractory oxides are those of metals whose negative free energy of formation

  <Desc / Clms Page number 30>

 of the oxide per gram atom of oxygen at 25 C is at least 90,000 calories and has a melting point of at least 1300 C.



   Specific examples of alloys which can be reinforced by dispersion according to the invention are given in Table VII below:
TABLE VII
 EMI30.1
 
 <tb> Alloy: Resistance <SEP> 3: <SEP> Composition Nominal <SEP>
 <tb>
 
 EMI30.2
 N: Microhms / cm: 9 Cr: 9 A1: Fe. Neither. other
 EMI30.3
 
 <tb>: to <SEP> 20 C.
 <tb>
 <tb>
 <tb>



  17 <SEP> 1387 <SEP> 23 <SEP>: <SEP> 5 <SEP>: <SEP> 72 <SEP> -
 <tb>
 <tb>
 <tb> 18 <SEP> 1662 <SEP> 37.5 <SEP> 7.5 <SEP> 55 <SEP>: <SEP> -
 <tb>
 <tb>
 <tb> 19 <SEP> 1379 <SEP> 20 <SEP>. <SEP> 5 <SEP>: <SEP> 73.5 <SEP> 1.5 <SEP> If
 <tb>
 <tb>
 <tb> 20 <SEP> 1163 <SEP>: <SEP> 20 <SEP>: <SEP> - <SEP>: <SEP> 8.5 <SEP>: <SEP> 68 <SEP> 2 <SEP> If
 <tb>
 <tb>
 <tb> 21 <SEP> 1122 <SEP> 16 <SEP>. <SEP> - <SEP>. <SEP> 22.5 <SEP> 60 <SEP> 1.5 <SEP> If
 <tb>
 
 EMI30.4
 . ^ 2 2 S 5 67: - :: 3 Co
 EMI30.5
 
 <tb> 23 <SEP>. <SEP> 15 <SEP>: <SEP> 5 <SEP>. <SEP> - <SEP> 80-
 <tb>
 <tb> 24 <SEP> 20 <SEP>. <SEP> 4 <SEP>. <SEP> 76 <SEP> -
 <tb>
 <tb> 25 <SEP>: <SEP> 15 <SEP>: <SEP> 5 <SEP>. <SEP> 5 <SEP> 75-
 <tb>
 <tb> 26 <SEP> 15 <SEP>: remaining <SEP>: <SEP> -
 <tb>
 <tb> 27 <SEP> 1013 <SEP> 20 <SEP>: <SEP> - <SEP>:

    <SEP> 43.5 <SEP> 35 <SEP> 1.5 <SEP> If <SEP>
 <tb>
 <tb> 28 <SEP> 31.5: <SEP> 68.5 <SEP>: <SEP> -
 <tb>
 <tb> 29 <SEP> 20 <SEP>. <SEP> - <SEP>. <SEP> 80-
 <tb>
 
Some examples will now be given:
EXAMPLE VI
An alloy of iron and aluminum dispersion reinforced with Al2O3 is prepared from a compound powder produced by dry impact grinding of a sponge iron filler of
65 microns and an Fe-Al master alloy ground to a powder of size less than 74 microns in appropriate proportions with 3% by volume of 0.03 micron gamma alumina, using a ball / powder ratio of 20 / 1 and 6mm nickel balls or balls and an agitator speed of 175 rpm.

   Grinding during 45 hours produced a strongly cold worked powder,
 EMI30.6
 z ...... 'h, ..- 0 .., f ..... 1 ... "1" "

  <Desc / Clms Page number 31>

 the particles of which were constituted by a practically homogeneous interdispersion of all the ingredients. The powder was vacuum sealed in a mild steel pot which was sealed by welding, heated to 1093 C and extruded at a 16/1 ratio.



   After removing the material from the pot, the extruded bar was hot and cold worked into tape and wire for use as electric heaters.



   EXAMPLE VII
In the production of a dispersion-reinforced wrought electric heating alloy containing by weight 20% Cr, 5% Al. 1.5% Si and 73.5% iron with 4% by volume of Y2O3 2.300 grams of a brittle parent alloy containing by weight 63.25% Fe, 21.7% Al, 6.5% Si and 8.55% yttrium
 EMI31.1
 ¯¯¯¯¯ ¯¯ ¯ ¯tal3ic, ground an¯¯partirulc-sinfrie-usâ? 5¯ microns ¯.¯¯ have¯t¯¯ ¯ mixed with 4,870 grams of high purity iron sponge of
150 microns and 2.830 grams of 75 micron ferrochrome powder. The mixture was dry impact crushed in an attrition mill with stirring with a capacity of 38 liters, at 180 t / m and using balls 6 mm hardened steel and a 15/1 ball / powder ratio.

   Grinding for 24 hours provided a fully hardened compound powder after sifting off particles larger than 0.35mm, the powder was vacuum packed and sealed in a mild steel pot, and the assembly was heated to 1.093 C. During this heating the oxygen accidentally present in the powders combined with the metallic yttrium to give a fine uniform dispersion of Y2O3 with an average particle size of less than 0.1 microns. The pot was then extruded at 1.93 ° C with an extrusion ratio of 16/1 into a bar suitable for stretching to sizes suitable for electric heaters.

  <Desc / Clms Page number 32>

 



   ¯ EXAMPLE VIII
To produce an electrically heated alloy reinforced by dispersion of ThO2 containing 15% Cr, 5% Al, 5%
Fe and 75% NI a brittle mother alloy containing 67% Al, the remainder being iron, was ground to particles smaller than 150 microns. 89.5 grams of the ground powder was mixed with 68.3 'fat of a commercial powder of 70% Cr and 30% Fe with a particle size of less than 150 microns, 132.2 grams of Cr powder with a particle size of less than 75 microns.

   900 grams of Fisher size nickel carbonyl powder of 5-7 microns and a sufficient amount of ThO 2 of 0.02 micron size to provide 3% by volume of ThO2 in the product. The mixture was dry impact crushed for 50 hours at 185 rpm. , in a stirred attrition mill with a capacity of 3.8 liters, using 6 mm nickel balls with a bead / powder ratio of 18/1. The compound powder was sieved through a 0.35mm mesh sieve and vacuum packed and sealed by welding in a mild steel pot, then heated to 1093c and extruded at a 15: 1 ratio into a rectangular section bar.



   The bar contained ThO2 particles less than 0.02 micron in size uniformly dispersed throughout it, which gave stiffness and sag resistance when used at elevated temperatures.



   Other dispersion reinforced products which can be advantageously prepared include, with dispersion reinforcement, nickel, copper, low alloy steels, maraging steels, zinc base alloys, chromium refractory metals, niobium, tantalum, molybdenum and tungsten and their alloys, for example with up to 50% of another metal, platinum metal base alloys and metal base alloys

  <Desc / Clms Page number 33>

 
Nickel reinforced by dispersion EXAMPLE IX
A filler consisting of 1173 grams of nickel carbonyl powder having an average particle size of 3 to 5 microns and 27 grams of thorium oxide with a particle size of 0,

  05 micron was premixed in a high speed food mixer and then dry impact crushed in air at room temperature for 24 hours. The mill contained 3.8 liters of nickel carbonyl balls with an average diameter of 6.2 mm the ratio between the balls and the powder being 18/1 by volume and the mill was operated with a stirrer speed of 176 rpm, which served to keep the beads practically tested in a highly active state of mutual collision in which the ratio of powders to dynamic pore volume was about 1/18 by volume.



   The ground product consisted of particles composed of nickel with particles of thorium oxide very finely and uniformly dispersed over them and having a saturation hardness of 640 to 650 Vickers. After removing the few coarse particles, the powder was placed in a mild steel extrusion pot, vacuum degassed at 400 C and then sealed in the pot and extruded into a bar at 980 C, with a 16/1 extrusion ratio.

   The extruded product consisted of a nickel matrix with a grain size of less than 5 microns, exhibiting a fine, stable and substantially uniform dispersion of thorium oxide particles of less than 0.2 microns and, for the most part, d. about 0.02 microns.



   The properties of the material, in the state as extruded and after various cold section reduction, are given in the following table:

  <Desc / Clms Page number 34>

 TABLE VIII
 EMI34.1
 
 <tb> Tenpessai: <SEP> Resistance <SEP> to <SEP> the <SEP> break <SEP> by <SEP> traction <SEP> to <SEP> hot <SEP> kg / mm2
 <tb>
 
 EMI34.2
 "C¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯% necking
 EMI34.3
 
 <tb>: <SEP> State <SEP> extruded: <SEP> 40% <SEP>: <SEP> 61% <SEP>: <SEP> 75%
 <tb>
 <tb>
 <tb> 760 <SEP> 13.1- <SEP>: <SEP> - <SEP>: <SEP> 26.2
 <tb>
 <tb>
 <tb> 982 <SEP> 7.4 <SEP>: <SEP> 11.5 <SEP>: <SEP> 15.4 <SEP> 18.5
 <tb>
 <tb> 1093 <SEP>: <SEP> 5.3 <SEP>: <SEP> - <SEP>:

    <SEP> 14.7
 <tb>
 
It will be observed that this very satisfactory structure of the extruded material and the associated high level of properties have been obtained starting from the powder composed of the invention, with an extrusion ratio of only 16/1.



   EXAMPLE x
Powder charges composed of nickel and thorium oxide were prepared by dry impact grinding charges of 777.4 grams of nickel carbonyl powder and 22.6 grams of thorium oxide, with a particle size 100-500 Angstroms, premixed in a high speed mixer, for 24 hours in air at room temperature in the attrition mill of Example 9, using nickel carbonyl balls or balls. 'an average diameter of 4.5 mm and with a ball / powder ratio of 26/1. The speed of the agitator was 176 rpm.

   After combining several charges of the powder produced and removing particles too large to pass through a 0.35mm mesh sieve, 2,500 grams of the compound powder was enclosed in a mild steel pot 8.9 centimeters in diameter. and extruded into a bar with a diameter of 2.200 centimeters at 982 C. Breaking stress tests at 1093 C on samples of the bar which had previously undergone a 75% reduction in section area gave the following results:
TABLE IX
 EMI34.4
 
 <tb> Effort <SEP> life <SEP> ( <SEP> hours <SEP>) <SEP> Elongation
 <tb>
 
 EMI34.5
 
 <tb> 9.14 <SEP> 4.3
 <tb>
 
 EMI34.6
 8.44 3 12.5:

   2, g -

  <Desc / Clms Page number 35>

 
EXAMPLE XI
The strength of an alloy of 90% tantalum and 10% tungsten is increased by the incorporation of thorium oxide A mixture of 2,160 grams of tantalum and 240 grams of tungsten, with a particle size of 3 to 40 microns , with 28 grams of 0.02 micron ThO2 (about 2% by volume) was pre-started and then dry impact crushed in a nitrogen atmosphere for 40-50 hours at 176 t / m, using the hardened steel shot of one centimeter in diameter with a ball / powder ratio of 20/1 in an attrition mill as described in the example
IX. After 48 hours, the powder produced had reached saturation hardness.

   After separation by sieving of particles larger than 0.35 mm, the compound powder was placed in a molybdenum pot with a diameter of 8.9 cm, which was evacuated, sealed and extruded to a diameter of 8.9 cm. 2 centimeters at 1300 C. The dispersion of thorim oxide in the resulting work bar was very uniform both longitudinally and transversely.



   EXAMPLE XII
When producing dispersion-enhanced niobium,
1100 grams of 10-50 micron Nb powder was mixed with 26 grams of 0.4 micron thorim oxide powder and ground in a dry attrition mill in a nitrogen atmosphere at 176 rpm for 48 hours, using 6mm tool steel balls with 18/1 ball to powder ratio. After sieving through a 0.35 mm sieve, the compound powder was loaded into an 8.9 cm diameter molybdenum pot which was evacuated, sealed, heated to 1482 C in hydrogen and extruded into a bar of 2.5 centimeters at 1482 C.



   EXAMPLE XII
Dispersion or aging hardened tungsten was produced by grinding a 2,500 gram charge of W powder with 27 grams of ThO2 (2% by volume) as in the example.

  <Desc / Clms Page number 36>

 previous, in order to obtain a compound powder which has been sieved and. extruded in a Mo pot 8.9 centimeters in diameter placed under vacuum, after heating at 1925 c in hydrogen, into a bar 2.5 centimeters in diameter.

  <Desc / Clms Page number 37>

 



  Low alloy steels reinforced by dispersion
The dispersion reinforcement of low alloy steels, in particular those containing molybdenum or vanadium, with or without chromium, which have for example the composition defined in the following table, makes it possible to produce low alloy steels having improved resistance to heat. high temperature traction and creep.



   Low alloy steels which can be produced according to the invention include steels containing up to 0.8% carbon, at least 0.25% Cr (up to 5% and / or Mo (up to
5% from 0 to 2% of V, from 0 to 2% of W, from 0 to 5% of Ni, from 0 to 2% of
Si and from 0 to 2% of Mn.

   The examples of such steels are given in Table X below,
PAINTINGS
 EMI37.1
 
 <tb> Alloy <SEP> ¯¯¯¯Composition Nominal <SEP> <SEP> in <SEP> weight
 <tb>
 
 EMI37.2
 steel n "cl Cr. 5>. ' z Fe, 0, -c 'Others,% ¯
 EMI37.3
 
 <tb> 1 <SEP> 0.08 <SEP> 5 <SEP> 0.5 <SEP> remaining <SEP> 0.5 <SEP> Ti
 <tb>
 <tb>
 <tb>
 <tb> 2 <SEP> 0.12 <SEP> 5 <SEP> 0.5 <SEP> 1,2 <SEP> If
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 3 <SEP> 0.15 <SEP> 0.5
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 4 <SEP> 0.17 <SEP> 0.5 <SEP> 0.5
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 5 <SEP> 0.12 <SEP> 1 <SEP> 0.5
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 6 <SEP> 0.13 <SEP> 0.6 <SEP> 0.01 <SEP> 0.65 <SEP> Mn
 <tb>
 <tb> 0.018 <SEP> P
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 7 <SEP> 0.08 <SEP> 1, <SEP> 25 <SEP> 0.5 <SEP> 0.06 <SEP> Zr
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 8 <SEP> 0.13 <SEP> 2 <SEP> 1,

  0
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 9 <SEP> 0.12 <SEP> 2.25 <SEP> 0.5
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 10 <SEP> 0.4 <SEP> 2 <SEP> 0.35 <SEP> -
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 11 <SEP> 0.4 <SEP> 1 <SEP> 0.25 <SEP> v
 <tb>
   EXAMPLE 14
When producing a dispersion-reinforced low alloy steel containing 2% Cr, 1% Mo and 0.4% C, a brittle alloy containing 30% Cr, 15% Mo, 5% C, the remainder being iron, was ground to pass a ..... - sieve.

  <Desc / Clms Page number 38>

 



   74 microns and 80 g were premixed with 1120 g of 65 micron iron sponge. This mixture was dry ground with 30 g of 0.02 micron ThO2, as in the previous example. After sieving through a 0.35 mm sieve, the compound powder was placed in an 8.9 cm mild steel jar, which was heated to 80 cm, under vacuum, cooled rapidly under vacuum, sealed with. sealed and extruded at 982 c into a bar 2 cm in diameter.



   Dispersion reinforced maraginq steel
 EMI38.1
 The recently designed maraging steels, that is to say steels which can be hardened by aging in the martensitic state and have compositions falling broadly in the range 10 to 30% Ni, 0.2 to 9 % Ti and up to 5% Al, such that (Ti + Al) does not exceed 9%, up to 25% of '
 EMI38.2
 .¯Go, s qul0 stēMo .estant- tazltn m ± x mo.nprl would benefit from dispersion reinforcement. The rather strenuous diffusion capacity of molybdenum and other materials in powder mixtures can be compensated for by use. vant 'powders composed sui the present invention.

   The incorporation of a dispersoid in the powder allows obtaining a product reinforced by dispersion by hot extrusion, with improved strength properties in the range of 480 to 650 ° C.



   Dispersion Reinforced Zinc Metals
Zinc and wrought zinc alloys containing, for example, 50% or more zinc, can be dispersed according to the invention, thereby increasing their creep resistance.



   Examples of such alloys include: 0.15-0.35% Pb 0.15-30% Cd, the remainder being Zn; 0.005-0.1% Pb, 0.5-1.5% Cu, 0.12-1.5% Ti, the remainder being Zn; up to 0.025% Mg,
0.25-0.6% of Al, the remainder being Zn; up to 3.5% Cu 0.02
0.1% Mg, 3.5-4.5% Al the remainder being Zn.



   EXAMPLE 15
When producing dispersion-enhanced zinc,
 EMI38.3
 1500 gr. of Zn powder. crossing a ,. 150 micron tam.s have

  <Desc / Clms Page number 39>

 was premixed with 25 grams of 0.02 micron gamma alumina and dry impact crushed for 50 hours at 180 rpm using hardened steel balls in a ball to powder ratio.
20/1.

   After sieving to remove coarse particles larger than 0.35mm, the compound powder was cold pressed into a 6.3cm diameter cylinder, which was sintered for 3 hours at 315 ° C in hydrogen. very anhydrous the sintered billet was softened by machining and consolidated by extrusion at 177 c into a bar 1.6 cm in diameter which had a very uniform dispersion of Al2O3 particles both lengthwise and transversely and which is practically free from linear inclusions.



   Dispersion-reinforced platinum group metals and alloys
Reinforcement by dispersion of metals based on pla-.
 EMI39.1
 



  --- .. t.ine..is¯p.qrticulièr ..? JI! .e.nt desirable .J29..ur improve resistance ------ to high temperatures and alloys which may be Advantageously reinforced include platinum with up to 50% Pd, platinum with 3.5-40% Rh, platinum with up to 35% Ir, platinum with up to 8% W. Examples Dispersion reinforced platinum-based metals which can be produced as fabricated forms according to the invention are: platinum with
2% by volume of 0.02 micron ThO2, 75% platinum and 25% Rh with 3% by volume 0.04 micron yttrium oxide, 92% Pt and 8% W with 5% by volume of 1 micron Ti carbide, 90% Pt, 10% Pd with 2% by volume of 0.1 micron ZrO2.



  Dispersion Reinforced Gold Metals
Gold is very soft and has low creep resistance.



  It can be hardened by the addition of alloying elements and this hardening process can be replaced or supplemented by dispersion or aging hardening according to the invention. Gold-based metals which can be so advantageously hardened include gold alloys, e.g. 54-60% Au, 14-18% Au.
 EMI39.2
 Pt, 1-8% Pd,,; ll11% Ag, 7-13%. C, U. Maximum 19 of Ni, '; :: "1;:,.,.,' 1" ". -. ' ...,

  <Desc / Clms Page number 40>

 
At least 1% Zn; 62-64% of Au, 7-13% of Pd, 6% maximum of Pd 9- les da Ag 7-14% of Cu, 2% maximum of Zn and 70% of Au -30% of Pt.



     Additions by volume of up to 10% or more of dispersiodes such as therium oxide, yttrium oxide, alumina, and refractory carbars can readily be produced in wrought gold weatherstripping metals. . curvre re-pierced by dispersion
An example of copper dispersion reinforcement to improve its resistance to creep at high temperatures while maintaining high electrical and thermal conductivity is the following.



   EXAMPLE 16
A load of 1173 gr of Cu powder of dimension
Fisher (sub-sieve) of 7-10 microns and 27 gr of 0.03 micron alumina was dry milled for 30 hours at 176 rpm in the attrition mill with agitation of Figure 1, using a - reading hardened steel balls of 6.5 mm the ball / powder ratio being 18/1 The compound powder (after sieving) was placed and sintered in hydrogen at 850 C for more than one hour, then vacuum welded in a Cu pot and hot extruded at a ratio of 18/1 at 800 C to give a worked Cu product substantially free from linear inclusions.

   The product after reduction to wire exhibited high electrical and thermal conductivities together with significantly higher strength at both ambient and high temperatures than pure copper.



  , Sintered refractory metal compositions
Sintered refractory metal materials. Such as refractory sintered carbides, also known as cemented carbides, which are widely used for cutting or abrasion resistant tools, oil drilling drills and dies, consist of 24 % or more by volume of finely divided particles of the pure refractory compound and

  <Desc / Clms Page number 41>

 ductile metal to form a body of great hardness and high compressive strength.

   Conventionally, the sintered body is formed by packing a mixture of the refractory compound, eg tungsten carbide, and the bonding metal forming the matrix, in the form of finely divided powders, and heating. the tablet in vacuo or in anhydrous hydrogen to cause liquid phase sintering.



   The preferred binder metal is cobalt, as this only dissolves about 1% tungsten carbide at ambient temperatures and therefore provides a tough matrix. Iron and nickel dissolve more tungsten carbide and thus form less ductile dies.



   The mixture of tungsten carbide, cobalt and an organic wax binder is obtained by grinding the powder for
60 hours or more in a protective fluid, such as hexane, containing stainless steel balls. During grinding, part of the cobalt powder is spread over the surface of the carbide particles as a very thin coating.



   The microstructure of the compounds, in particular the size of the matrix carbide particles, their distribution and porosity as well as the quality of the bond between the binder metal and the carbide particles, are factors which affect the hardness and strength of the material. sintered product. The average particle size of the refractory carbides in the sintered product is limited by that of the starting materials, which is generally 2 to 10 microns.



   This difficulty is overcome and an extremely finely dispersed structure of very fine particles of carbide or other refractory compound is obtained when the carbide is incorporated into the compound particles interdispersed with the binder metal by impact or dry impact grinding following the main patent. These particles must be distinguished from those resulting

  <Desc / Clms Page number 42>

 of a conventional mixing operation, in which the binder metal is spread over the hard particles as a coating.

   According to the invention, sintered refractory compound materials are obtained by compressing and sintering compound particles containing finely divided and interdispersed components in which the distance between the component sub-particles is preferably less than 10 microns and preferably less than 2 microns or even 1 micron. This can be done in a number of ways. A powder body can be consolidated by hot pressing at a temperature high enough to cause sintering; it may first be hot or cold pressed and sintered under non-oxidizing conditions, or the mixture may be extruded into a pot, for example of steel, and the whole may be extruded at a temperature high enough that sintering occurs during extrusion.

   The wrought products obtained by any of these methods have a high degree of hard phase dispersion uniformity in the matrix.



   The refractory compound, which constitutes 30% or more by volume of the composition, can be a carbide, a boride or a nitride of titanium, zirconium, hafnium, chromium, tungsten, molybdenum, vanadium, of columbium or tantalum, a silicon carbide or an oxide of aluminum, of beryllium, a rare earth metal, for example cerium, lanthanum or yttrium, magnesium, zirconium, titanium and thorium. Intermetallic compounds such as aluminides, silicides or silicides can be used under conditions in which they retain their identity.



   The bonding metal forming the matrix may comprise at least one metal from the following groups (a) metals from the group of iron, iron, nickel, cobalt; alloys of these metals with one another and alloys of at least one metal from the iron group with at least one of the metals chromium, molybdenum, tungsten,

  <Desc / Clms Page number 43>

 niobium, tantalum, vanadium, titanium, zirconium and hafnium.



   (b) a metal or alloy of the silver group, copper and a ductile metal of the platinum group (eg, platinum, palladium, rhodium or ruthenium).



   (c) aluminum, zinc, lead or their alloys.



   The binder metals forming the matrix of group (b) are particularly useful for the production of wear resistant electrical contact elements.



   The binder alloys of group (a) include well known superalloy compositions capable of being aged hardened at temperatures of about 600 to 1000 C. These compositions are resistant to softening under conditions where The Dupe tool is used with relatively high cutting speeds which tend to overheat the cutting edge of the tool.

   Examples of superalloy compositions which can be age hardened are those falling in the following proportions by weight 4 to 65% chromium, at least 1% in total of an age-hardening element selected from the group consisting of: up to 15% aluminum and up to 25% titanium, up to 40% molybdenum, up to 20% niobium, up to 40% tungsten, up to 30% tan- tale, up to 2% vanadium, up to 15% manganese, up to 2% carbon, up to 1% silicon, up to 1% boron, up to 2% zirconium, up to 4% hafnium and up to 0.5% magnesium, the remainder consisting essentially of at least one element from the group consisting of iron, nickel and cobalt,

   the total of these being present in an amount of at least about 25%.



   Examples of compositions are as follows: 15-25% Co with up to 3% by weight (TaC + TiC), the remainder being WC; 25-45% Co with up to 2% by weight (TaC + TiC), the remainder being WC; 15-25% Co with 10-22% by weight TiC, the remainder being WC: 15-25% Co with 18-30% TaC, the remainder being WC:

  <Desc / Clms Page number 44>

 a 15-50% Ni-Mo alloy, with 85-50% TiC.



  The Ni-Mo matrix alloy of the latter composition may contain 25 to 70% and preferably 35 to 60% molybdenum, the remainder being nickel.



   The compositions also include the heat resistant metal carbide compositions recently designed for high temperature applications, known as cermets, for example 85 to 24% by volume and preferably at least 60% titanium carbides and of chromium with the remainder consisting of nickel or a nickel-based alloy as the binder metal. The carbide phase generally consists predominantly of TiC with up to 25% Cr carbide.



   Some examples will now be given.
 EMI44.1
 



  ----- ---- ------ ¯ ¯¯-¯ ¯¯ --- - EXAMPLE 17;
A powder mixture of 25% Co of 5-7 microns and 75% WC of 3-5 microns, by weight (63% WC by volume) is dry impact crushed in an attrition mill with agitation of the type shown in Figure 1, at 185 rpm, using hardened hardened balls with a 25/1 ball / powder ratio for 50 hours to form a worked compound powder consisting of particles with inter-dispersed WC particles homogeneously in a Co matrix. WC particles were reduced in size to less than one micron.

   The powder was consolidated by hot pressing in a graphite matrix at
1350 c for 3 minutes, using a pressure of 35 kg per cm2
EXAMPLE 18
In order to produce a heat and oxidation resistant cermet composition of TiC / Ni 80-Cr 20 alloy, a mixture of 1240 gr of 5-7 micron TiC particles, 448 gr of 4- nickel carbonyl 8 microns and 112 gr of a Cr powder less than 75 microns was dry impact crushed in an agitation grinder of the type shown in Figure 1, at 180 turns /

  <Desc / Clms Page number 45>

 minute for 50 hours, using 6 mm ¯ hardened steel balls with a 20/1 ball to powder ratio to produce a worked compound powder in which the particles consisted of Ni,

   uniformly interspersed Cr and TiC
EXAMPLE 19
This is an example of the production of a sintered electrical contact material containing 50% Ag and 50% WC, by weight (40% WC by volume).



   A compound powder was prepared by dry grinding 1000 gr of Ag with a particle size less than 75 microns - and
1000 gr of 5-7 micron WC powder, using an attrition mill containing hardened steel balls with a bead / powder ratio of 18/1 and spinning at 185 rpm for 45 hours. The WC particles were reduced by grinding to a size smaller than the micron.

   The powder is then sieved to remove particles larger than 100 microns and then it is hot pressed into shapes for electrical contacts in a graphite matrix, exerting a pressure of 35 kg / cm2 for 3 minutes at a temperature slightly above melting point of silver, for example at 980 c
An example of another composition which may be obtained is by analogous techniques a composition of titanium carbide.
79% by volume 65% by weight of TiC containing 35% by weight of a 50-50 alloy of nickel and molybdenum as a binder.



  Metallic systems with limited solubility
Metal systems comprising two or more metal constituents with limited mutual solubility in the liquid and / or solid state, i.e. which are not immiscible or only partially miscible, tend to exhibit segregation. or separation during solidification if it is desired to obtain them by melting.

   An infiltration of a molten metal in a solid skeleton of the other, for example copper in

  <Desc / Clms Page number 46>

 iron, or the compression of mixtures of the respective powders followed by sintering in the liquid phase, also lead to non-uniform microstructures exhibiting segregation, which are subject to the limits imposed by the particle sizes of the powders. used. -----
The consolidated metal products of these systems are readily obtainable from the suitable compound powders according to the invention with a highly refined internal structure substantially free from segregation, segregating masses or the formation of dentritic nuclei.



   Examples of limited solubility binary systems include lead-copper, copper-iron, copper-tungsten, silver-tungsten, copper-chromium, silver-chromium, copper-molybdenum, silver-molybdenum, silver-manganese, silver-nickel, platinum -gold, beryllium- 'molybdenum, and silver-platinum. The invention can also be applied to metal systems with limited solubility containing 3 or more than 3 elements, such as for example copper-nickel-chromium.



   Examples of the ranges of compositions which can be produced are as follows: with 1695% Pb; Fe with 1-95% Cu; W with 5-95% Cu; W with 2-98% Ag; and Cu with 5-95% Cr.



   EXAMPLE 20
This is an example of the production of a powder composed of iron and copper containing 80% Fe and 20% Cu.



   Hydrogen-reduced copper with a particle size of less than 45 microns and sponge iron with a particle size of less than 150 microns were impact crushed. dry in air in a high speed 50cc capacity agitator mill operating at 1200 cycles per minute, which produced compound metal particles in a very short period of time compared to the high speed agitator mill. 'attrition of Figure 1. The mill was loaded with 10 gr of powder and 45 gr

  <Desc / Clms Page number 47>

 6.2 mm nickel balls or balls so as to obtain a ball / powder ratio of 4.5 / 1 and a ratio between the dynamic interstitial volume and the powder volume of 41/1.



   Grinding for 30 minutes produced particles composed of 353 Vickers hardness and an average size of 135 microns, with a fine, uniformly ridged structure, the average spacing between the ridges being about 1 micron.



   Consolidation by compression in a steel tube which has been vacuum sealed, followed by hot froging at
982 c at full density gave a very uniform workmanship.



   EXAMPLE 21
This is an example of producing a 50% copper and 50% lead product with lifted solubility.



    Equal volumes of hydrogen-reduced lead and copper filings, with a particle size of less than 45 microns, were ground in the agitator mill of the previous example with a ball / powder ratio of 4/1 After
10 minutes, the product particles had a hardness of 34.6
Vickers and a particle size of 100-200 microns and, after 30 minutes, a hardness of 69.5 Vickers and a particle size of 100-150 microns.

   In each case, the individual composite particles contained the two interdispersed elements substantially uniformly, the particle spacing being about 5 microns after 10 minutes and about 1 micron after 30 minutes. The structure did not show any streaks.



   This is believed to be due to the fact that lead, which pos-. A melting point of about 600 k undergoes natural annealing when worked at ambient temperatures.



   Because of the large amount of lead present, the compound powder can be cold deformed, for example by cold extrusion or cold pressing into a die, to any shape desired, for example for an element. anti-friction bearing.

  <Desc / Clms Page number 48>

 



     Thanks to a similar technique, very uniform worked products with as constituents 50% Ag-50% W for electrical contact materials; 25% -50% Cu / 75% -50% W; 80% Au / 20% Pb; 50% -95% pt / 50-5% Ag and 50-95% Pb / 50-5% Au can be obtained. Analogously, compositions in the immiscibility range of 6-63% Cu in the Cu-Cr system, eg 70% Cu-30% Cr; the range of immiscibility of the Cu-Mo system, for example from 2 to 98% Cu with the remainder of the
Mo can be produced.

   Silver and nickel compositions suitable for electrical contact applications, comprising 60% Ag-40% Ni, can be produced, as can compositions of beryllium and molybdenum comprising 50% Be and 50%. % Mo. Beryllium powder can receive a thin oxide coating due to its propensity for surface oxidation. This oxide can be used to provide dispersion reinforcement in the final product.



   Dispersion-reinforced stainless steel
Stainless steel alloys are particularly prone to segregation when they are cast into ingots, which makes it difficult to forge such ingots. Thus, the rather slow solidification of large ingots leads to the formation of large dendrites, large grains not uniformly distributed and composition segregations along the length and width of the ingots.



  Prolonged equalization at high temperatures to seek to homogenize the metallurgical structure of the ingots generally provides little improvement and may even cause the formation of coarser grains, with other disruptive effects on the hot forging capacity. extrusion or rolling.

   This tendency to segregate also leads to a non-uniform precipitation hardening response in steels containing hardening constituents of the stainless steel product.

  <Desc / Clms Page number 49>

 the disadvantages already defined above, in particular that of the oxidation of the most active alloying elements, for example chromium and hardeners by precipitation such as aluminum and titanium during the treatment and, in the case of compositions hardened by dispersion or aging, forming linear inclusions.



   A preferred class of products according to the present invention is that comprising dispersion-reinforced wrought stainless steels which are characterized by a high degree of uniformity of composition and, in the case of precipitation-hardening compositions, a high degree of uniformity of composition. response to curing together with an absence of segregation and linear inclusions.



   This is easily achieved by using particles composed with the corresponding composition produced by high energy impact grinding to saturation hardness and beyond, as previously described, according to Belgian Patent No. 729,149, since these particles compounds are practically uniform both statistically and internally.



  Stainless steels / may be / produced according to the invention may have compositions ranging, by weight, from 4 to 30% chromium, 0 to 35% nickel, up to 10% manganese and up to 1.0% carbon, together with 0.05 to 25%, for example 0.05 to 10% by volume of a dispersal of a refractory compound, the remainder, excluding impurities and incidental ingredients, being iron in an amount of at least 45%. It should be understood that in the present case, as everywhere in the present description, the percentages of the constituents other than the dispersoid refer to the composition of the alloy matrix.



   Even more preferably, steels contain 8 to 30% chromium, up to 20% nickel, up to 5% manganese and up to 0.25% even better up to 0.15 % carbon, conjoin-
 EMI49.1
 - - --- j .., ..... ", -......... 1 Hm", of a dispersal of a compound 1

  <Desc / Clms Page number 50>

 
As will be appreciated, the stainless steel compositions can contain other alloy additions, for example up to 5% silicon, up to 5% molybdenum, up to 8% tungsten, up to 2% aluminum, up to 2% titanium, up to 2% niobium / tantalum, up to 7% copper.



   Stainless steels susceptible to precipitation hardening include those containing at least 0.2% by weight of one or more of the following additives aluminum up to 2%, titanium up to 2%, niobium up to 2% and copper up to 2%. 'at 7%.



  These steels may contain up to 0.4% phosphorus and up to 0.3% nitrogen. Preferred amounts of dispersoid range from about 0.05 to 5% by volume with dimensions of less than 1 micron.



   Impurities and incidental ingredients which may be present include some sulfur and / or selenium for easy machining, etc.



   Examples of the types of stainless steel which can be produced according to the invention are given in the following Table XI.

  <Desc / Clms Page number 51>

 



  TABLE XI
 EMI51.1
 
 <tb> Type Nominal <SEP>
 <tb>
 
 EMI51.2
 AISI% C% hin -% Si / Cr% Ni Other Austenitic steels 201 .0.15 max -5.50-7.50 .1.0 max '16 -18 3.5-5.5 0.25N max
 EMI51.3
 
 <tb> 202 <SEP> 0.15 <SEP> max <SEP> 7.5 <SEP> - <SEP> 10 <SEP> 1.0 <SEP> max <SEP> 17-19 <SEP> 4 <SEP> - <SEP> 6 <SEP> 0.25N <SEP> max
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 301 <SEP> 0.15 <SEP> max <SEP> 2.0 <SEP> max <SEP> 1.0 <SEP> max <SEP> 16-18 <SEP> 6 <SEP> - <SEP> 8 <SEP> ------
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 302 <SEP> 0.15 <SEP> max <SEP> 2.0 <SEP> max <SEP> 1.0 <SEP> max <SEP> 17-19 <SEP> 8 <SEP> - <SEP> 10 <SEP> --------
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 303 <SEP> 0.15 <SEP> max <SEP> 2.0 <SEP> max <SEP> 1.0 <SEP> max <SEP> 17-19 <SEP> 8-10 <SEP> 0.15 <SEP> min <SEP> S
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 308 <SEP> 0.08 <SEP> max <SEP> 2,

  0 <SEP> max <SEP> 1.0 <SEP> max <SEP> 19-21 <SEP> 10 <SEP> - <SEP> 12 <SEP> -------
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 309 <SEP> 0.20 <SEP> max <SEP> 2.0 <SEP> max <SEP> 1.0 <SEP> max <SEP> 22-24 <SEP> 12 <SEP> - <SEP> 15 <SEP> -------
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 314 <SEP> 0.25 <SEP> max <SEP> 2.0 <SEP> max <SEP> 2.0-3.0 <SEP> 23-26 <SEP> 19 <SEP> - <SEP> 22 <SEP> --------
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 316 <SEP> 0.08 <SEP> max <SEP> 2.0 <SEP> max <SEP> 1.0 <SEP> max <SEP> 16-18 <SEP> 10 <SEP> - <SEP> 14 <SEP> 2.0-3.0 <SEP> MB
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 321 <SEP> 0.08 <SEP> max <SEP> 2.0 <SEP> max <SEP> 1.0 <SEP> max <SEP> 17-19 <SEP> 9 <SEP> - <SEP> 12 <SEP> 5xteneur <SEP> min.
 <tb>
 <tb>
 <tb>



  Ti
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb>
 <tb> 347 <SEP> 0.08 <SEP> max <SEP> 2.0 <SEP> max <SEP> 1.0 <SEP> max <SEP> 17-19 <SEP> 9 <SEP> - <SEP> 13 <SEP> the <SEP> x <SEP> content
 <tb>
 
 EMI51.4
 min. Nb / Ta Martensitiaue steel
 EMI51.5
 
 <tb> 403 <SEP> 0.15 <SEP> max <SEP> 1.0 <SEP> max <SEP> 0.5 <SEP> max <SEP> 11.5-13 <SEP> -------
 <tb> 414 <SEP> 0.15 <SEP> max <SEP> 1.0 <SEP> max <SEP> 1.0 <SEP> max <SEP> 11.5-13, <SEP> 1.25-2.5
 <tb> 431 <SEP> 0.20 <SEP> max <SEP> 1.0 <SEP> max <SEP> 1.0 <SEP> max <SEP> 15-17 <SEP> 1.25-2.5 <SEP> --------
 <tb> 440B <SEP> 0.75-0.95 <SEP> 1.0 <SEP> max <SEP> 1.0 <SEP> max <SEP> 16-18 <SEP> ----- <SEP> 0.75 <SEP> MB <SEP> max
 <tb> 440C <SEP> 0.95-1.2 <SEP> 1.0 <SEP> max <SEP> 1.0 <SEP> max <SEP> 1.6-18 <SEP> ------ <SEP> 0.75 <SEP> MB <SEP> Max
 <tb> 501 <SEP> 0.1 <SEP> max <SEP> 1.0 <SEP> max <SEP> 1,

  0 <SEP> max <SEP> 4-6 <SEP> ----- <SEP> 0.04-0.65 <SEP> MB
 <tb>
 <tb> ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ Composition Nominal <SEP> <SEP> ¯¯¯¯¯¯¯ <SEP> ¯¯¯¯¯¯¯¯¯¯.
 <tb>



  405 <SEP> 0.08 <SEP> aax <SEP> 1.0 <SEP> max <SEP> 1.0 <SEP> max <SEP> 11.5-14.5 <SEP> ---- <SEP> 0.1-0.3 <SEP> Al
 <tb> 430 <SEP> 0.12 <SEP> max <SEP> 1.0 <SEP> max <SEP> 1.0 <SEP> max <SEP> 14-18 <SEP> --- <SEP> ---
 <tb> 430F <SEP> 0.12 <SEP> max <SEP> 1.25 <SEP> max <SEP> 1.0 <SEP> max <SEP> 14-18 <SEP> ---- <SEP> 0.15 <SEP> S <SEP> min
 <tb>
 
 EMI51.6
 446 0.2 max, .5 max, 0 max 23-27 ----- 0.25 DT max

  <Desc / Clms Page number 52>

 TABLE XI (continued)
 EMI52.1
 
 <tb> Typē¯¯¯¯¯¯¯¯¯¯¯¯Qualities <SEP> no <SEP> standardized
 <tb> AISI <SEP>: <SEP>% <SEP> c <SEP>% <SEP> MN <SEP>% <SEP> If <SEP>: <SEP>% <SEP> Cr <SEP>% <SEP> Neither <SEP> Others
 <tb>
 <tb> 316 <SEP> F <SEP> 0.6 <SEP> 1.5 <SEP> 0.5 <SEP> 18 <SEP> 13 <SEP> - <SEP> 2.25 <SEP> MB
 <tb> 0, <SEP> 13P <SEP> 0.155
 <tb> 418 <SEP> 0.17 <SEP> 0.4 <SEP> 0.3 <SEP> 12.75 <SEP>:

    <SEP> 2.0 <SEP> 3.0 <SEP> w
 <tb>
 <tb> Inoxyda-
 <tb>
 
 EMI52.2
 ble W O, 07 O, 5 O, 5 16.75 6, 5 O, 8 Ti: 0, AI 17-4PH: 0, 4 tri, 4 O, S 16.50: 4, 25: z ?, 25 Nb
 EMI52.3
 
 <tb> 3.6 <SEP> Cu
 <tb>
 
 EMI52.4
 17-7PH O, 07 0.7 z I7, O 7, O 1.15 Al: t: z Pli 15-7 0, 7 O, 7 O, 4 15, O 7, i3 1, 5 Al Mo: 2 , 2 5MB 17-IOP: 0, 12:

   O, i5 - O, 5 17, O: la, 5: tu, 2 $ P
To obtain the dispersion reinforced worked stainless steel product, a filler of the dense compound metal particles worked, mechanically alloyed, with the appropriate composition and preferably having an average size such as the area per unit volume. particles is not greater
 EMI52.5
 at 6,000 cm 2 / cm3 of the particles, i.e. essentially free of particles smaller than 5 microns, is hot formed into a metalwork form. This can usefully be achieved by hot extrusion of the powder enclosed in a metal pot, for example of mild steel.



   Annealing of the heavily cold-machined powder takes place during heating in the pot to extrusion temperature.



   Two examples of stainless steel production will now be given:
EXAMPLE XXII
A mixture comprising, by weight, 27.2% low carbon powdered ferrochrome, with a particle size of 44 to 74 microns containing 70% Cr, 1.01% Si, 1.35% of SiO 0.54% of Cr2O3 the remainder being iron, as well as 62.8% of powder

  <Desc / Clms Page number 53>

 high purity iron sponge, with a particle size less than 150 microns and 10% carbonyl nickel powder with an average particle size of 3 to 5 microns, was ground in a grinder. attiition with agitation of the type illustrated in figure 1, rotating at 176 rpm with a ball / powder ratio of 24/1 in two batches,

   the first for 16 hours and the second for 48 hours. Each product consisted of particles composed of an average size of 125 to 135 microns, the particles crushed for 48 hours having a much finer and more homogeneous microstructure. The hardness of the powders as produced and after various heat treatments is given in Table XII, which reveals that the hardness of the powder treated for 48 hours was retained to a greater extent upon heating.



   TABLE XII
 EMI53.1
 
 <tb> Processing Thermal <SEP> <SEP>: <SEP> Grinding <SEP> 16 <SEP> hours <SEP> Grinding <SEP> 48 <SEP> hours
 <tb> Hardness <SEP> Vickers
 <tb>
 <tb> Tel <SEP> that <SEP> crushed <SEP> 785 <SEP> 794
 <tb>
 <tb> 30 <SEP> min / 982 C <SEP> 381 <SEP> 523
 <tb>
 <tb> 30 <SEP> min / 1066 c <SEP> 324 <SEP> 409
 <tb>
 <tb> 1 <SEP> time <SEP> 1204 c <SEP>:

    <SEP> 220-220
 <tb>
 
After heating for 30 minutes at 1,066 degrees C the internal structure of the particles treated for 48 hours was homogeneous and compression to 56.2 kg / mm2 gave a tablet with a density of 74% of actual density and resistance to water. untreated condition of 76.2 kg / cm2. The initial hardness of the particles was remarkably high compared to the 233 Vickers hardness of a commercial atomized stainless steel powder.

  <Desc / Clms Page number 54>

 



   EXAMPLE XXIII
Another stainless steel composition was produced by dry grinding a mixture containing 84 grams of nickel carbonyl powder with an average particle size. 3 to 5 microns, 341 grams of a high purity ferrochrome powder (0.1% SiO2 70% Cr, the remainder being iron), with an average particle size of 120 microns and 760 grams - high purity iron sponge powder (0.032% carbon, 0.115% silica), with a particle size smaller than:
150 microns / for 40 hours in air in an allocation mill rotating at 176 t / m, with a bead / powder ratio of 18/1 by volume.

   The resulting compound particles had an average particle size of 85 microns. Extrusion of the product, vacuum sealed in a mild steel pot, into a bar with an extrusion ratio of 12.5 / 1 at 1.038 C, gave a product exhibiting 9% Ni, 20% on analysis. soluble Cr, 0.09%
Si, 2.15% Cr 2 O 3, the remainder being iron, which contained a finely divided greyish dispersal which was evenly distributed therein. The dispersal is considered to be formed by chromium oxide.

   At room temperature, the material offered a tensile strength of 137.5 kg / mm2, elastic limitation
2 (0.2% strain) of 121.0 kg / mm an elongation of 7.5% a necking of 29% and a modulus of elasticity of 18.8 x 103 kg / mm2.



  The material had a Vickers hardness of 421 and was very slightly ferromagnetic.



   After heating for 90 hours at 1093 c this material was non-magnetic and had a Vickers hardness of 390, and at 650 c it had a stress rupture time of 44.9 hours with an elongation of 2.5% under tension of 24.6 2- 2 kg / mm. At 816 ° C. and under a load of 7 kg / mm2 the sample was still not broken after 70 hours.



   The properties clearly demonstrated that this material was enhanced by dispersion:

  <Desc / Clms Page number 55>

 
EXAMPLE XXIV
In the preparation of a product of worked stainless steel, reinforced by dispersion and susceptible to hardening by precipitation, of the type 17-7-pH containing, by weight, 0.07% C, 0.7 % Mn, 0.4% Si, -17% Cr, 7% Ni; 1.15% Al and 2.5% zirconium oxide, the remainder except impurities being iron, the following starting materials were used: (au: low carbon ferrochrome containing en- about 70% chromium and some silicon with a particle size of 44 to 75 microns;

   (b) a high purity iron sponge with a particle size of less than 150 microns; (c) carbonyl nickel powder with an average size of about 3 to 5 microns; (d) ferroaluminum containing about 65% aluminum
 EMI55.1
 "munlunTe't dil'okyde" dà -z i rcbn i ur, 5ae c-un-dimen siorr -moyec .--- d'-en ---- about 400 Angstroms. A batch of 900 grams calculated to give the above composition was placed in the attrition mill as described above and dry impact crushed in a nitrogen atmosphere for 40 hours at 176t / m, using a volume of 3.8 liters of nickel grains of a size giving a ball / powder ratio of 24/1.

   After milling for 48 hours, the compound particles had optimum uniformity and exhibited an average particle size of about 100 microns.



   After removal from the mill and passing through a 177 micron sieve, the powder was sealed under vacuum by welding in a mild steel pot. The potted powder was then heated for 1.5 hours at 1.038 C and extruded into a bar with an extrusion ratio of 16/1, the extruded material having approximately the nominal composition of 17-7 PH stainless steel, at except for the presence of a very uniform dispersion of finely divided zirconium oxide (with a dimension

  <Desc / Clms Page number 56>

 average about 400 Angstroms Extruded bar was annealed
 EMI56.1
 3 dissolve at 120J c, warmed to about? 6O O for one and a half hours, cooled in air and again warmed to 565 C for one and a half hours and cooled.

   Thus, the steel is strengthened using the dual effect of dispersion strengthening and hardening. by precipitation.



   A particular group of two-phase stainless steels are known at the present time which are adjusted in composition so as to provide a microstructure containing ferrite and either martensite or austenite. These steels contain
2% and preferably 4.5-8% or 12% nickel, 18% preferably 23-28% or even 35% chromium, up to 1.5% titanium, up to 1% chromium. vanadium, the remainder being essential = ent iron.



   It has been found that powdery mixtures of powders calculated to give such steels, crushed to saturation hardness and beyond in a high energy impact mill, for example an attrition mill, provides of--; exceptionally fine two-phase structures after hot consolidation by extrusion or hot forcing of powders in pots, at temperatures in the range, for example, from 1700 to 2000 F. Such consolidated fine-structure or microduplex-structured materials provide superplasticity at high temperatures.



   High carbon tool steels
High carbon tool steels are particularly prone to segregation during ingot solidification when obtained by casting processes, with the formation of large dendrites and carbide segregations or aggregates. Carbides are brittle and disturbingly affect ingot ductility, but segregations or aggregates can with difficulty be dispersed to a limited extent by mechanical working of the ingot. So leads the

  <Desc / Clms Page number 57>

 Carbide tends to be distributed throughout the forged or hot worked product in the form of linear inclusions elongated in the direction of the work, with the intermediate areas depleted of carbides.



   It is also difficult to achieve good homogeneity of the composition with solid state diffusion at elevated temperatures when using powder metallurgy processes, since alloying ingredients such as that chromium, tungsten and molybdenum diffuse only painfully in the powder state.



   The use of a compound powder produced by high energy dry grinding of starting powder mixtures calculated to give a high carbon tool steel composition as a starting material for production by metallurgy powders of rapid tool steels permit the production of worked high carbon tool steel characterized by a substantially uniform dispersion of finely divided carbides and a practical absence of carbide segregations and aggregates. The degree of structural uniformity depends on the uniformity, both statistical and internal, of the compound particles.

   The increased diffusion and alloying rate resulting from the high degree of cold working in the composite particles is particularly advantageous in overcoming the slow diffusion tendencies of the alloying elements.



   In general, the following tool steels
 EMI57.1
 the invention contain q7 to 4% ..par. E '' 'tP'mf'1 n n n. 7%, for example from 0.9 to 3.5% of carbon and at least 0.1%, advantageously at least 1% of at least one of the following alloying elements: chromium, vanadium, tungsten and molybdenum, up to 'with 2% silicon, up to 2% manganese, up to 5% nickel and up to 15% cobalt, the. remaining (at least 40%), excluding impurities, being iron

  <Desc / Clms Page number 58>

 
The alloying elements can advantageously be present in the ranges from 3 to 15% chromium, up to 10 or 20% vanadium, up to 25% tungsten and up to 12% molybdenum.



  A particularly useful Cr - VW tool steel composition is that containing 3 to 9% Cr, 0.3 to 10% V, 1 to 25% W, 0 to 10% Mo, iron constituting the remainder. A particular advantage of the invention is that carbide formers such as tantalum, niobium, hafnium, zirconium and titanium can be added in amounts up to 15% and well distributed in the form of carbides in the mixture. resulting tool steel composition. Examples of particular alloys which can be obtained are given in the following Table XIII, the remainder in each composition being iron.

  <Desc / Clms Page number 59>

 



    T A B L E A XII Composition nomi le% weight Thpo of steel Mn Si Cr
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  <Desc / Clms Page number 61>

 
In addition to the dispersion reinforcement of tool steels which results from the presence of the extremely finely dispersed carbides, other dispersoids can be incorporated into the compound powder used to form the steels, and therefore into the steels themselves, in an amount. from 0.05 to 25%, preferably not more than 10%
In preparing steels, a powder composed with the desired composition can be hot consolidated into a metalwork form, for example by vacuum enclosing a charge of the particles in a mild steel pot which is then heated to. 425 C under vacuum, suddenly cooled under vacuum,

     welding operation followed by hot extrusion usually at a temperature of about 815 C or higher; for example from 1.038 to 1260 c The homogenization and annealing can be carried out while heating the powders in pots, beforehand; extrusion.



   Some examples of the production of wrought tool steels according to the invention are as follows: EXAMPLE XXV - To produce a complex high carbon tool steel containing 20% tungsten, 12% cobalt,
4% chromium, 2% vanadium, 0.8% carbon, the remainder being iron, a mixture of 28.6 grams is produced. ^ Ses of a master alloy of 70% V dt 30% de Fe with a particle size of less than 150 microns, 57.2 grams of a master alloy of 70% Cr and 30% Fe with a particle size of less than 150 microns, 200 grams of a powder of W of 10 microns,
120 grams of a cobalt powder with a particle size less than 44 microns,

   8.0 grams of flake graphite with a particle size of less than 150 ocrons and 586.2 grams of 65 micron iron sponge powder. This mixture is

  <Desc / Clms Page number 62>

 dry impact crushed in an attrition mill of the type shown in Figure 1, for 40-50 hours at 180 rpm using 6.2mm hardened steel balls, with a ball / powder ratio of 20/1. The compound powder thus produced had a microstructure comprising an interdispersion of substantially all of the components. After being vacuum sealed in a mild steel pot, the powder was extruded at 1175c-16: 1 into a worked bar free from dendrites, segregations and carbide aggregates.



     The complex high speed steel product is quenched by heating at a temperature of 1290 ° C for 5-10 minutes, followed by quenching in oil at room temperature, the cooled steel being-then-subjected to a double -came by heating to a temperature of 565 C for about 2 hours, cooling in air and reheating at 565 C for a further 2 hours.



   EXAMPLE XXVI
A high carbon fabricated steel containing 0.85% C, 0.2% Cr, O, 7% Mn 0.3% Si, the remainder being iron, was produced as follows. - Brittle high carbon mother containing 4.25% C. 1% Cr, 3.5% Mn, 1.5% Si, the remainder being iron, was shelled and ground in particles smaller than 75 microns.

   The resulting powder (400 grams) was mixed evenly with 1600 grams of 65 micron high purity iron sponge powder and the mixture was dry impact crushed as in Example XXV, using beads. 6.2 mm hardened steel with a bead / powder ratio of 18/1 and a stirrer speed of 175 rpm for 45 hours to obtain a highly cold-worked compound metal powder with practically interdispersion homogeneous of all alloy constituents.The compound powder was vacuum sealed in a mild steel pot

  <Desc / Clms Page number 63>

 which was sealed by welding, heated to 1.095 C and then hot extruded into a round bar with an extrusion ratio of 16/1.

   This steel, which was free from carbide segregations and aggregates, was quenched by quenching in oil from an austenitizing temperature of 788 C, followed by tempering at a temperature of
177 C.



   EXAMPLE XXVII
To prepare a semi-rapid steel composition worked with the following constituents: 1.2% of 0.4% Cr, 3% V,
4% Mo, 0.3% Mn, 0.3% Si, le. the remainder being iron a brittle high carbon mother alloy containing 4.85 C, 16% Cr,
12% V, 125 MO 1.2% Mn 1.2% Si, the remainder being iron was cast into shells and then ground to particles smaller than
75 microns.

     400 grams of this powder was mixed with 1200 grams of high purity 65 micron iron sponge powder and the mixture was dry impact crushed as in Example XXv for 48 hours at 175 rpm. , using 6.3 mm hardened steel balls, with a ball / powder ratio of 18/1 by volume. The resulting heavily cold-worked compound metal powder had a microstructure comprising a substantially homogeneous dispersion of all alloy constituents and was used to prepare tool steel shapes by hot extrusion at 1.095 c in. a mild steel pot which was evacuated and sealed by. welding, A square bar was produced with an extrusion ratio of 15/1.

   A tool made from the bar can be heat treated by abruptly cooling from 1232 C in oil and then tempering (secondary hardening) by heating to 538 C and holding for one hour. , with a good answer.

  <Desc / Clms Page number 64>

 
 EMI64.1
 



  :: '>;:;'. F'g. :: r- l:} f ï p,:; '. R pr), t .it' <! -.:n 3 ..: '1 <!! r r3piJ-c to hutt * ::; ar an -7 'T. \ r)' ;. tt!. '! 1.:1nt d n s' from C, 4. ,,):' ;; by Cr. b i <3 Mo, .1, 1t,. ': ... ", h" V, \;> .: Jt! if, the rtst .. \: 1t being iron .1. '. :: 'v5: .i r ..' 11.l: 1t.i un .aL: 3â: ßt, 'of 112. t, 1raJ1 \ èS of graphite:. "f' :: 3I>,>, - i; ',: ii3ai.T-ai,., ¯'¯: 9:'.. "7i..2r.ÎY 'Ût3llï4 E: 31" tr-' de 70 .'- * '.'. ¯ ' 1 .3 '.' * Pc, 1:! 0, r arn..e3 of a powder of Cr, all these
 EMI64.2
 ';;: "): 1!.:. L ::.;.). :) t3 ajanr a dim * nsion less than 150 microns, 11' 5r.:"".;.>sl* powder of? * 3 and 225 fat of powder of Co, aric unj d1.:sion i1ppare: te less than 45 microns, 270 grams of a powder of and 'of 10 microns and 3,191 grams of laying iron sponge of 65 microns.

   This mixture was dry impact crushed for 15 hours in a horizontal stirred ball mill containing 91 kilograms of hardened steel balls with a rotor speed of 245 rpm in a nitrogen atmosphere, to give a powder. A highly cold worked composite metal having a microstructure comprising a substantially homogeneous interdispersion of all alloying elements.

  <Desc / Clms Page number 65>

 



   The powder was vacuum sealed in a mild steel pot which was sealed by welding and extruded a bar at 1093 c with an extrusion ratio of 16/1. The extruded bar had a remarkably high hardness of 62.5 Rc. A tool obtained from this bar was quenched by heating it slowly to 870 C, then heating it to 1205 C temperature at which it was held for 5 minutes and then quenched in oil. After double tempering by heating it twice for two hours at 538 C and cooling by ai.r, the hardness reached up to 67 Rc.



   The structure of this complex high carbon steel was exceptionally fine and uniform, containing less than about 5% by volume of segregation regions exceeding 10 microns in size. The microstructure of this very high carbon tool steel was remarkably thinner and with much less segregation than that of conventional tool steels with much lower carbon and other alloy contents.



   When making products containing dispersed oxyaea, the compound particles used in the process need not necessarily contain the desired oxide ultimately. On the contrary, one can use compound particles containing components which react upon subsequent heating to form refractory oxides or other refractory phases which are not originally present.

   Thus, one can prepare compound particles in which are intimately distributed metals which form stable refractory oxides, for example yttrium, thane, cerium, thorium, chromium, silicon, aluminum, beryllium or mixtures of rare earth metals such as didyma, together with a less stable oxide of another metal, such as for example nickel oxide and others

  <Desc / Clms Page number 66>

 alloy constituents. Alternatively, oxygen can be added as absorbed oxygen or gaseous oxygen to the grinding atmosphere, this oxygen being absorbed and mechanically alloyed with the solid constituents of the powder mixture.

   Such powders can then be consolidated and heated to allow oxidation of the metal providing the stable oxide by diffusion of oxygen from the less stable oxide or mechanically alloyed metastable oxygen. By controlling the effective interdiffusion distance over which oxygen should flow to less than one micron and even less than 0.5 micron, the refractory oxide particles can be produced in a very fine state of dispersion by heating for only a short time. The process can advantageously be used to prepare nickel or nickel-containing alloys reinforced by dispersion with lanthanum oxide, yttrium oxide, thorium oxide, etc., from compound particles. containing the corresponding metal and mechanically alloyed oxygen.

   If more than one oxidizable metal is present, the process can be controlled by limiting the oxygen supply to the amount needed to oxidize only the metal with the more stable oxide.



   The following example illustrates the use of this.Process for the preparation of a nickel alloy reinforced by dispersion with alumina.



   EXAMPLE XXIX
A mixture of 781 g. of carbonyl nickel powder with a particle size of 3-5 microns, 44 g. of nickel oxide (NiO) with a particle size less than 44 microns and 75 gr. of an 80% Ni and 20% Al master alloy powder, with a particle size of less than 44 microns, is dry ground in a nitrogen atmosphere for 48 hours in the mill

  <Desc / Clms Page number 67>

 of Example I with a ball / powder ratio of 22/1, the speed of rotation being 176 revolutions per minute. The formed composite particles, after removing a small coarse fraction, are vacuum sealed in a mild steel pot.

   The sealed pot is then heated to 982 C for 2 hours to allow the constituents in the compound metal particles to diffuse into each other and to allow the oxygen in the nickel oxide to agitate with the aluminum. to convert a stoichiometric proportion thereof to Al2O3 which is formed as a fine dispersion throughout the alloy. The heated pot is then extruded with an extrusion ratio of 16/1.



   Two incompatible constituents can also be combined in the same alloy by separating them by a third mutually compatible constituent, the two incompatible constituents being introduced during successive grinding operations. Remembering that harder or less ductile components will tend to be dispersed in softer or more ductile components, many combinations of components can be used in a hierarchy. Such a hierarchical compound can be combined with one or more other hierarchical compounds in a common matrix. In this way, new structures can be produced which could not be prepared in any other way.



   A hierarchical process of this type is illustrated by the following example.



    EXAMPLE XXX.



   A filler consisting of 50% by volume of 5 micron tungsten powder and 50% by volume of zirconium oxide powder with a particle size of 0.03 microns was

  <Desc / Clms Page number 68>

 dry crushed in a high speed laboratory stirrer mill for approximately 3 hours. A compound powder comprising zirconium oxide distributed through a tungsten matrix was produced. 40% by volume of powder was then mixed with 60% of carbonyl nickel powder having an average particle size of 3 to 5 microns and the mixture was again dry milled in the high speed agitator mill, for a total of two o'clock.

   Hard tungsten-zirconium oxide powder particles were pulverized and distributed in the produced powder as a finely dispersed phase. The resulting relatively coarse product powder contained 20% zirconium, 20% tungsten and 60% nickel by volume, in a hierarchical relationship with minimal contact between zirconium oxide and nickel.



   It should be expected that in the preceding examples, when a dispersion reinforced product, for example a superalloy or dispersion reinforced stainless steel, was produced, this product contained less than 10% by volume of segregation exceeding a size of 3 microns, and, more commonly, such regions did not exceed a size of 1 micron or even 0.5 microns;
Other fabricated metal systems which are advantageously produced according to the invention include the following:
1 Compositions which are difficult to make because of the low boiling point of one of the constituents, for example alloys with lithium, such as an alloy of nickel with 1% lithium, for uses requiring high strength corrosion;

   systems comprising boron, such as for example nickel compositions

  <Desc / Clms Page number 69>

 and boron and steels containing boron, such as Cr-Ni 18-8 steels or AISI 347 type steels with boron.



  Compositions in which one component is highly reactive, for example, rare earth metal compositions such as RCOS for permanent magnets, in which R is a rare earth metal such as cerium or samarium. Rare earth metals readily react with refractory linings of crucibles used for smelting, such that levitation or arc smelting consumable in a metal mold
 EMI69.1
 - - - - cooled is normally used, which results in an - # grain size of undesirable size.



   Iron-silicon alloys for transformer sheets, for example iron with 5 to 7% Si, nickel free; or with up to 10% nickel to improve magnetic properties.



   The invention applies most particularly to deformable metals having an absolute melting point greater than 600 K and preferably greater than 1000 K, given that such metals are capable of being worked hard with the grinding process.

   For metals with lower melting points,; which tend to natural anneal under vigorous working conditions at substantially room temperature, they can be treated with other metals at room temperatures to produce a usable, worked compound metal powder. On the other hand, when it becomes necessary, such metals can be processed at a temperature below their recrystallization temperature by working at temperatures significantly below the temperature.

  <Desc / Clms Page number 70>

 ambient temperature in order to achieve a practically stable state of equilibrium between the welding and grinding factors.



   It should be understood that the present invention is in no way limited to the above embodiments and that many modifications can be made thereto without departing from the scope of the present patent.



   CLAIMS.



   1. Process for the manufacture of a metallic product, characterized in that it consists in consolidating the worked compound particles having a coherent non-porous internal structure formed by at least two constituents united intimately and inter-
 EMI70.1
 dispersed at least one- component- comprising at least 5% by volume of the particles, being a metal deformable by compression, so as to provide a consolidated product with a substantially uniform microstructure containing not more than 10% by volume of regions of segregations with a minimum dimension greater than 25 microns.

 

Claims (1)

2. Method according to claim 1, characterized in that the consolidated product does not contain more than 10% by volume of segregation regions of minimum dimension greater than 10 microns. 3. Method according to claim 1, characterized in that the consolidated product does not contain more than 10% by volume of segregation regions of minimum dimension greater than 3 microns. 4. Method according to claim 1, characterized in that the constituents of the compound particles comprise a stable refractory compound with a high melting point and the consolidated product does not contain more than 10% by volume of segregation regions of minimum dimension greater than 1. micron. <Desc / Clms Page number 71> 5. A method according to claim 1 characterized in that the constituents of the compound particles comprise, dispersed therein, a metal which forms a stable refractory oxide having a heat of formation of at least 90,000 calories per gram atom. oxygen. A method according to claim 5, characterized in that the composition of the compound particles comprises oxygen available to react with said metal upon heating to produce in said consolidated product a dispersion of the oxide of said metal. 7. Method according to claim 1, characterized in that the composite particles are consolidated by hot% extrusion. 8. A method according to claim 1. characterized in that the compound particles are consolidated by pressing and sintering. 9. The method of claim 1. characterized in: that the compound particles are consolidated by hot pressing. 10. The method of claim 1, characterized in that the compound particles comprise at least one constituent capable of alloying with said deformable metal during a heat treatment by diffusion. 11. The method of claim 1 characterized in that the composition of the compound particles comprises at least two metals having limited mutual solubility. 12. The method of claim 1, characterized in that it is applied to the production of a metal reinforced by dispersion. 13. The method of claim 12, characterized in that a metal reinforced by dispersion is capable of hardening ment by aging and resistant to heat and stress. <Desc / Clms Page number 72> 14 The method of claim 12, characterized in that the alloy reinforced by dispersion is a stainless steel reinforced by dispersion. 1 The method of claim 12, characterized in re that the alloy reinforced by dispersion is an alloy of electrical resistance. 16. The method of claim 12, characterized in that the dispersion reinforced alloy is a high carbon tool steel. 17. Consolidated metallic product obtained by powder metallurgy, characterized in that its microstructure exhibits practical uniformity and an absence of linear inclusions with less than the% by volume of regions of segregation of dimension greater than 25 microns. A metallic product according to claim 17, characterized in that said regions of segregation have a size of not more than 10 microns. 19. A metallic product according to claim 17, characterized in that said regions of segregation have a size of not more than 5 microns. 20. A metal product according to claim 17, characterized in that the metal has a melting point of at least about. 1000k, and said segregation regions, are not larger than / about 1 micron. ; 21. Metal product according to claim 17, reinforced, ced by dispersion, characterized in that the metal is chosen from the group consisting of super ¯, alloys, stainless steels, alloys for electrical resistance, nickel, copper , low alloy steels, so-called maraging steels, chromium and <Desc / Clms Page number 73> chromium alloys, niobium and niobium alloys, tantalum and tantalum alloys, molybdenum and molybdenum alloys, tungsten and tungsten alloys, metallic platinum-based alloys and gold-based alloys. 22. Superalloy obtained by powder metallurgy and reinforced by dispersion, according to claim 17, characterized in that it contains, by weight, about 4 to about 65% chromium, at least about 1% in total of. a metal from the group consisting of niobium, aluminum and titanium, up to 40% molybdenum, up to 40% tungsten, up to 30% tantalum, up to 2% vanadium, up to up to 15% manganese, up to 2% carbon, up to 1% boron, up to 2% / zirconium, up to 0.5% magnesium, the remainder being at least 25 % of a metal of the with ./ group consisting of iron, nickel and cobalt, up to about 10% by volume of a high melting point refractory dispersoid finely distributed throughout the alloy. 23. Alloy for electrical resistance obtained by powder metallurgy and reinforced by dispersion, according to claim 17, characterized in that it contains at least 10% by weight of a metal selected from the group consisting of chromium and aluminum, the chromium content not exceeding about 40% and that of aluminum about 34%, from 0 to 5% silicon, the remainder of the alloy being constituted essentially by a metal chosen from the group consisting of 5 to 75% iron, 0 to 15% cobalt and 5 to 80% nickel, with up to 25% by volume of a refractory compound dispersoid finely dispersed therein. 24. Consolidated refractory composition obtained by powder metallurgy, according to claim 17, characterized in that it consists essentially of at least 24% of <Desc / Clms Page number 74> volume of a hard refractory compound dispersed in a ductile metal matrix. 25. refractory cutting or abrasion resistant tool, obtained by powder metallurgy according to claim 24, characterized in that the refractory compound has a dimension not exceeding 1 micron and / selected from the group consisting of oxides of aluminum, beryllium, a rare earth metal, yttrium, magnesium, zirconium, titanium and thorium and the carbides, borides and nitrides of titanium, zirconium, hafnium, chromium, tungsten, molybdenum, vanadium, colombium and tantalum and silicon carbide, while the ductile metal is chosen from the group consisting of iron, cobalt and nickel and the alloys of these metals between them and with chromium, molybdenum, tungsten, niobium, tantalum, vanadium, titanium, zirconium and hafnium, silver, copper and ductile metals of the platinum group as well as alloys of these metals, aluminum, zinc, lead and their alloys. 26. Consolidated metal product obtained by powder metallurgy according to claim 17, characterized in that the metals have limited solubility in one another. 27. Metal product according to claim 26, characterized in that the metals are chosen from the group consisting of copper with 1 to 95% lead, iron with 1 to 95% copper, tungsten with 5 to 95%. % copper, tungsten with 2 to 98% silver, copper with 5 to 95% chromium, copper and molybdenum, silver and molybdenum, silver and nickel, platinum and gold, beryllium and molybdenum, and silver and platinum. 28..Consolidated high carbon tool steel, <Desc / Clms Page number 75> obtained by powder metallurgy according to claim 17, characterized in that it contains approximately 0.7 to 4% carbon, at least 0.1% of a metal selected from the group consisting of chromium, vanadium, tungsten and molybdenum, up to 2% silicon, up to 5% nickel, up to 15% cobalt, the remainder being mostly iron. 29. Tool steel according to claim 28, characterized in that at least one metal from the group consisting of 3 to 15% of chromium, 0 to 20% of vanadium, 0 to 25% of tungsten and 0 to 12% of molybdenum is present. 30. Consolidated stainless steel obtained by powder metallurgy according to claim 17, characterized in that it contains from 4 to 35% of chromium, from 0 to 35% of nickel, from 0 to 10% of manganese, up to 1% carbon, up to 2% aluminum, up to 2% titanium, up to 2% niobium, up to 7% copper, up to 0.4% phosphorus, up to at 0.3% nitrogen, up to 25% by volume of a refractory compound dispersoid, the remainder being essentially iron. 31. Stainless steel according to claim 30, characterized in that it contains from about 0.05% to about 10% by volume of a dispersoid selected from the group consisting of alumina, titanium oxide, l. zirconium oxide, yttrium oxide, a rare earth metal oxide, chromium oxide and thorium oxide. 32. Process for preparing a metallic product and a consolidated metallic product obtained by powder metallurgy, as described above or in accordance with the accompanying drawings.