DE102005001198A1 - Metallic powder mixtures - Google Patents

Abstract

The invention relates to mixtures of metal, alloy or composite powders having a mean particle diameter D50 of at most 25 μm, which are produced by a process in which initially a starting powder is formed into platelet-shaped particles and then comminuted in the presence of grinding aids, with further Additives and the use of these powder mixtures and molded articles made therefrom.

Description

The The invention relates to mixtures of metal, alloy or composite powders with a mean particle diameter D50 of at most 25 μm, the be prepared by a method in which initially a Starting powder to platelet-shaped particles transformed and then crushed in the presence of grinding aids with other additives and the use of these powder mixtures and Molded articles made therefrom.

From the not yet disclosed patent application PCT / EP / 2004/00736 powders are known which are prepared by a process for the production of metal, alloy and composite powders with a mean particle diameter D50 of at most 25 microns, determined by means of the particle measuring device Microtrac ^® X 100 according to ASTM C 1070-01, are obtainable from a starting powder having a larger average particle diameter, wherein the particles of the starting powder are processed in a deformation step into platelet-shaped particles whose ratio of particle diameter to particle thickness is between 10: 1 and 10000: 1 and these platelet-shaped particles be subjected in a further process step of a comminution grinding in the presence of a grinding aid. This process is advantageously followed by a deagglomeration step. This deagglomeration step, in which the powder agglomerates are broken down into their primary particles, can be carried out, for example, in a counterblown gas mill, an ultrasonic bath, a kneader or a rotor stator. Such powders are referred to in this document as PZD powder.

These PZD powder face usual Metal, alloy and / or composite powders suitable for powder metallurgy Applications are used on various advantages, such as one improved green strength, Compressibility, sintering behavior, widened temperature range for the Sintering and a lower sintering temperature, but also better Strength, oxidation and corrosion behavior of the produced Moldings and lower production costs. The disadvantages are at These powders, for example, poorer flow capabilities. Also the changed Shrinkage characteristics can can in conjunction with the lower packing density in powder metallurgy Processing in the application to problems as a result of stronger sintering shrinkage to lead. These properties of the powders are described in PCT / EP / 2004/00736, to which reference is made.

Also conventional Powders which are obtainable, for example, by atomization of molten metals Disadvantages. These are in particular for certain alloy compositions, so called high alloyed materials, lack of sintering activity, bad compressibility and high production costs. These disadvantages have in particular in metal powder injection molding (metal Injection Molding, short MIM), slip casting, wet powder spraying and thermal Spraying is less important. Due to the bad green strength the conventional one Metal powder (in the sense of metal, alloy and composite powder, short MLV) these materials are conventional powder metallurgical Pressing, powder rolling and cold isostatic pressing (Cold Isostatic Pressing, CIP for short) with subsequent green processing unsuitable because the greenlings not the one for that have sufficient strength.

task The present invention is the provision of metal powders for the Pulvermetallurgie, which the aforementioned disadvantages of usual Metal powder (MLV) and the PZD powder do not have, but their respective advantages, such as high sintering activity, good pressability, high Green strength, good pourability, preferably largely unite.

A Another object of the present invention is to provide of powders with functional additives, that of PZD powder formed molded articles can give characteristic properties, such as additives that the impact resistance or increase abrasion resistance, like superhard powders, or additives, the processing of greenlings facilitate, or additives, which act as a template for controlling the pore structure.

A Another object of the present invention is to provide of highly alloyed powders for the entire spectrum of powder metallurgical molding processes, so that even applications are possible in areas that are conventional Metal, alloy or composite powders are not accessible.

This object is achieved by metallic powder mixtures containing a component I, a Metal, alloy and composite powder microns with a mean particle diameter D50 of at most 25 as determined by the particle measuring instrument Microtrac ^® X100 in accordance with ASTM C 1070-01, obtainable by a process, wherein the particles to platy a starting powder having a larger average particle diameter in a deformation step Particles are particles whose particle diameter to particle thickness ratio between 10: 1 and 10000: 1 and these platelet-shaped particles are subjected to a crushing in the presence of a grinding aid in a further process step, a component II, which is a conventional metal powder (MLV) for powder metallurgy applications is, and / or a component III, which is a functional additive.

These Task will as well solved by metallic powder mixtures containing a component I, a metal, alloy and composite powder whose shrinkage, determined by means of dilatometer according to DIN 51045-1, until reaching the temperature of the first shrinkage maximum at least 1.05 times the shrinkage of one produced by atomization Metal, alloy or composite powder of the same chemical composition and the same average particle diameter D50, wherein the test powder before measuring the shrinkage on a Press density of 50% of the theoretical density is compressed, a Component II, which is a conventional Metal powder (MLV) for powder metallurgical applications and / or a component III, which is a functional addition.

The Use of component I also allows the production of metallic powder mixtures in which the contents of oxygen, Nitrogen, carbon, boron, silicon can be targeted. in the Trap of oxygen or nitrogen can pass through it the high energy input in the production of the component I too Formation of oxide and / or nitride phases come. Such phases may be for certain Applications desired be, as they can lead to a material reinforcement. This effect is called "oxide dispersion strengthening effect" (ODS for short) known. Often, however, the introduction of such phases with a Deterioration of processing properties (for example Compressibility, sintering activity) connected. Due to the usually inert properties the dispersoids opposite of the alloy component the latter therefore have a sintering inhibiting effect.

By the crushing milling are the phases in the produced Powder dispersed immediately. Therefore lie in the component I the formed phases (e.g., oxides, nitrides, carbides, borides) significantly finer and more homogeneous distributed than conventional powders. this leads to turn to an increased Sintering activity, compared with discreetly incorporated similar phases. hereby also becomes the sinterability the metallic powder mixture according to the invention improved. Such powders with finely dispersed deposits are in particular with targeted delivery of oxygen during accessible to the grinding process and lead for the formation of very finely divided oxides. In addition, you can target Mahlhilfungsmittel be used, which are suitable as ODS particles and while the grinding process, a mechanical homogenization and dispersion Experienced.

The metallic powder mixture according to the present invention Invention is for the application in all powder metallurgical molding processes suitable. Powder Metallurgical Forming Processes in the sense of Invention are pressing, sintering, slip casting, film casting, wet powder spraying, Pulse rolls (both cold hot or hot powder rolls), hot pressing and hot Isostatic pressing (Hot Isostatic Pressing, HIP for short), sintering HIP, Sintering powder beds, Cold isostatic pressing (CIP), especially with green processing, Thermal spraying and build-up welding.

The Use of metallic powder mixtures in powder metallurgy Forming process leads to significant differences in the processing, the physical and material properties and allows the production of shaped objects, which have improved properties, although the chemical composition with conventional Metal powders is comparable or identical. The presence of the Component III allows a targeted "tuning" of component properties such as high temperature strength, strength, toughness, wear resistance, oxidation resistance or porosity.

Pure Thermal spray powders can Furthermore as a repair solution for components be used. The use of pure agglomerated / sintered Powders according to the still unpublished patent application PCT / EP / 2004/00736 as thermal Spray powder allows the inherent coating of components with a surface layer, which shows a better Abbrasions- and corrosion behavior than the Base metal. These properties result from finely divided ceramic inclusions (oxides of the most oxygen-sensitive elements) in the alloy matrix due to mechanical stress in the preparation of the powders according to PCT / EP / 2004/00736.

Component I is a metal, alloy and composite powder which is obtainable by a two-stage process, in which first a starting powder is shaped into platelet-shaped particles and then these are comminuted in the presence of grinding aids. In particular, the component is I micron, a metal, alloy and composite powder having an average particle diameter D50 of at most 25 as determined by the particle measuring instrument Microtrac ^® X100 in accordance with ASTM C 1070-01, obtainable by a process in the middle of a raw powder having a larger particle diameter are available, wherein the particles of the starting powder are processed in a deformation step to platelet-shaped particles whose particle diameter to particle thickness ratio between 10: 1 and 10000: 1 and these platelet-shaped particles are subjected in a further process step of a crushing mill in the presence of a grinding aid.

The particle measuring instrument Microtrac ^® X100 is commercially available from Honeywell, USA.

to Determination of the ratio from particle diameter to particle thickness become the particle diameter and the particle thickness determined by means of optical microscopy. These are the platelet-shaped powder particles first with a viscous, transparent epoxy resin in the ratio 2 volume percent resin and 1 volume of platelets mixed. Thereafter, by evacuating this mixture while mixing expelled introduced air bubbles. The bubble-free mixture is poured on a flat surface and then with a roll rolled wide. In this way, the platelet-shaped particles are directed in the flow field between roller and pad preferably made. The preferred situation is expressed in that the surface normals the slide on average parallel to the surface normal align the flat surface, so the platelets on average flat the pad are arranged in layers. After curing, be from the epoxy resin plate on the base samples of suitable dimensions worked out. These samples become perpendicular and parallel to the Underlay examined microscopically. Using a microscope with a calibrated optics and taking into account the sufficient Particle orientation will measure at least 50 particles and an average value is formed from the measured values. This average represents the particle diameter of the platelet-shaped particles. To a vertical section through the pad and to be examined Sample is used to determine the particle thicknesses using the microscope with a calibrated optics, which is also used to determine the Particle diameter was used. It is important to ensure, that only possible be measured parallel to the substrate particles. There the particles are coated on all sides by the transparent resin it is not difficult to select suitably oriented particles and safely assign the boundaries of the particles to be evaluated. In turn, at least 50 particles are measured and taken from the measured values an average is formed. This mean value represents the particle thickness the platelet-shaped particles. The relationship from particle diameter to particle thickness results arithmetically from the previously determined sizes.

With In particular, fine, ductile metal, Alloy or Produce composite powder. Under ductile metal, alloy or Composite powders are understood to mean those powders which are mechanical Stress until reaching the yield point of a plastic Experience stretching or deformation before significant material damage (material embrittlement, material breakage) entry. Such plastic material changes are material-dependent and are at 0.1 percent up to several 100 percent, based on the initial length.

The Degree of ductility, i.e. the ability of materials themselves, under the action of a mechanical stress plastic, i. permanent to deform, one can by means of mechanical Tensile and / or pressure test determine or describe.

to Determination of the degree of ductility by means of mechanical tensile test from the material to be evaluated, a so-called tensile test ago. This may be e.g. to act a cylindrical sample, the in the middle region of the length a reduction of the diameter by about 30-50% over a length of about 30-50% of the total sample length having. The tensile test is in a tensioning device of an electro-mechanical or electro-hydraulic tensile testing machine clamped. In front the actual mechanical test be in the middle of the sample length measuring probe on a measuring length, which is about 10% of the total sample length is, Installed. These probes allow it while the application of a mechanical tension tension the enlargement of the Length in the chosen one measuring length to pursue. You raise the voltage until it comes to the break of the sample, and evaluates the plastic part of the change in length based on the strain-voltage recording. Materials that in such an arrangement, a plastic change in length of at least 0.1% reach, are referred to in the sense of this document as ductile.

In analogously, it is also possible a cylindrical material sample showing a ratio of diameter to Thickness of about 3: 1, a mechanical compressive stress in a commercial pressure testing machine to subjugate. It comes after the creation of a sufficient mechanical pressure-voltage also to a permanent deformation of the cylindrical sample. After the pressure relief and removal of the sample you put one Magnification of the ratio of the diameter to the thickness of the sample. Materials in one such attempt a plastic change of at least 0.1% are also referred to as ductile in the sense of this document.

Preferably Are produced by the method fine ductile alloy powder, the one degree of ductility of at least 5%.

The Crushability of alloy granules which can not be further comminuted or metal powders is by the use of mechanical, mechanochemical and / or chemically acting grinding aids added in a targeted manner or produced in the milling process, improved. An essential Aspect of this approach is the chemical "target composition" of the so produced Powder in total not to change or even to influence it so that the processing properties, such as. Sintering behavior or flowability can be improved.

The Method is suitable for the production of a variety of finer Metal, alloy or composite powder with an average particle diameter D50 of at most 25 μm.

The produced metal, alloy or composite powders are characterized by a small mean particle diameter D50. Preferably, the average particle diameter D50 is not more than 15 microns, as determined by ASTM C 1070-01 (measuring device: Microtrac ^® X 100). In the sense of improving product properties in which fine alloy powders are rather unfavorable (porous structures in which a certain material thickness can better resist oxidation / corrosion in the sintered state), it is also possible to obtain significantly higher D50 values (25 to 300 μm ) while maintaining the improved processing properties (pressing, sintering) set as mostly sought.

When Starting powder can For example, powders are used which already have the composition of the desired Have metal, alloy or composite powder. However, it is also possible, to use a mixture of several starting powders in the process, the first by suitable choice of the mixing ratio of the desired composition result. The composition of the manufactured metal, alloy or composite powder can about it also be influenced by the choice of grinding aid, if this remains in the product.

Preferably are used as starting powder powders with spherical or spiky shaped Particles and a mean particle diameter D50, determined according to ASTM C 1070-01 of greater than 25 microns, preferably from 30 to 2000 μm, particularly preferably used from 30 to 1000 microns.

The required Starting powder can for example, by atomization of molten metals and, if necessary, subsequent sighting or sieves are obtained.

The starting powder is first subjected to a deformation step. The deformation step can be carried out in known devices, for example in a rolling mill, a Hametag mill, a high-energy mill or an attritor or a stirred ball mill. By suitable choice of the procedural parameters, in particular by the effect of mechanical stresses sufficient to achieve a plastic deformation of the material or powder particles, the individual particles are reshaped so that they ultimately have platelet shape, the thickness of the platelets preferably 1 is up to 20 microns. This can, for example, by one-time charges in a roller or a hammer mill, by multiple stressing in "small" deformation steps, for example by impact milling in a Hametag mill or Simoloyer ^®, or by a combination of impact and frictional grinding, for example in an attritor The high material load during this forming leads to structural damage and / or material embrittlement, which can be used in the following steps for comminuting the material.

As well can known melt metallurgical Rasch solidification process for the production of ribbons or "flakes" are used. These are then like the mechanically generated platelets for the following Crushing grinding suitable.

The Device in which the deformation step is performed the milling media and the other grinding conditions are preferred chosen so that the impurities are due to attrition and / or reactions with oxygen or nitrogen if possible are low and below the for the application of the product critical size or within the for the material applicable specification.

This is for example by a suitable choice of Mahlbehälter- and Mahlmedienwerkstoffe, and / or the use of the oxidation and Nitriding obstructing gases and / or the addition of protective solvent while the deformation step possible.

In a particular embodiment of the process become the platelet-shaped particles in a rapid solidification step, e.g. by so-called "melt spinning" directly from the melt by cooling on or between one or more, preferably cooled rolls generated, so that directly platelets (Flakes) arise.

The in the deformation step obtained platelet-shaped particles become a Subjected to comminution grinding. On the one hand, the ratio of Particle diameter to particle thickness, which is usually primary particles with a relationship from particle diameter to particle thickness of 1: 1 to 10: 1 become. On the other hand, the desired average particle diameter of at most 25 microns set without again difficult to break up particle agglomerates occur.

The Crushing can, for example, in a mill, about an Excenterschwingmühle, but also be carried out in high-bed rolls, extruders or similar devices, the one material disruption due to different movement and strain rates effect in the platelet.

The Crushing is carried out in the presence of a grinding aid. When Grinding aids can for example liquid Mahlhilfsmittel, waxes and / or brittle powder are added. It can the grinding aids act mechanically, chemically or mechanochemically.

For example the grinding aid may be paraffin oil, paraffin wax, metal powder, Alloy powder, metal sulfides, metal salts, salts organic acids and / or hard powder.

Brittle powder or phases act as mechanical grinding aids and can, for example in the form of alloy, element, hard material, carbide, silicide, Oxide, boride, nitride or salt powder are used. For example Pre-shredded element and / or alloy powders are used, together with the used, difficult to crush starting powder the desired Composition of the product powder yield.

When brittle Powders are preferably used those made of binary, ternary and / or higher Compositions of occurring in the starting alloy used Elements A, B, C, and / or D exist, where A, B, C and D further have meanings given below.

It can also liquid and / or easily deformable grinding aids, for example waxes be used. For example, be hydrocarbons, such as Hexane, alcohols, amines or aqueous Called media. These are preferably compounds, the for the following steps of further processing are needed and / or which can be easily removed after comminution grinding.

It is possible, too, to use special organic compounds known from pigment production are there, and there find use to non-agglomerating single platelets in a liquid Stabilize environment.

In a particular embodiment grinding aids are used, which are a targeted chemical reaction with the starting powder to achieve the Mahl progress and / or to adjust a particular chemical composition of the Enter product. This can be, for example, decomposable chemical compounds, of which only one or more Ingredients needed to adjust a desired composition, wherein at least one component or a component by a thermal process can be largely removed.

Examples which may be reduced and / or decomposable compounds, such as hydrides, oxides, sulfides, salts, sugars, which in a subsequent processing step and / or the powder metallurgy Verar Processing of the product powder are at least partially removed from the millbase and supplement the powder composition in the desired manner chemically with the remainder.

It is possible, too, that the grinding aid is not added separately, but during the Crushing grinding is generated in situ. It can, for example be proceeded so that the production of the grinding aid by Addition of a reaction gas is carried out under the conditions of Crushing with the starting powder to form a brittle Phase reacts. The reaction gas used is preferably hydrogen.

The in the treatment with the reaction gas, for example by education of hydrides and / or oxides, resulting brittle phases can be in the Usually by appropriate process steps after crushing grinding or while the processing of the resulting fine metal, alloy or Remove compound powder again.

Become Mahlhilfsmittel used, not or only partially from the removed metal, alloy or composite powder, these are preferably chosen that the remaining constituents are a property of the material in the desired Influence how, for example, the improvement of mechanical Characteristics, reducing the susceptibility to corrosion, increasing the hardness and Improvement of the abrasion behavior or the friction and sliding properties. For example, here is the use of a hard material called, the increased in proportion in a subsequent step, that the hard material together with the alloy component to a Further processed carbide or a hard material-alloy composite can be.

After the deformation step and the comminution grinding the primary particles of the metal, alloy or composite powder have a mean particle diameter D50, determined according to ASTM C 1070-01 (Microtrac ^® X 100) of at most 25 microns.

by virtue of the known interactions between fines can it despite the use of grinding aids in addition to the desired Formation of fine primary particles for the formation of coarser ones secondary particles (Agglomerates) come whose particle diameter well above the desired mean particle diameter of at most 25 microns.

Therefore includes Preferably, the comminution grinding is a deagglomeration step if that product to be produced does not permit (coarse) agglomeration or requires - at the agglomerates are broken up and the primary particles are released. The deagglomeration can be achieved, for example, by applying shear forces in Form of mechanical and / or thermal stresses and / or by Removing separation layers previously introduced in the process between primary particles respectively. The special deagglomeration method to be used depends on the degree of agglomeration, the intended use and the susceptibility to oxidation the finest powder, and the permissible Impurities in the finished product.

The Deagglomeration can for example be done by mechanical methods, for example, by treatment in a gas counter jet mill, screening, sifting or treatment in an attritor, a kneader or a rotor-stator-disperser. Possible is also the use of a field of tension, as with an ultrasonic treatment is generated, a thermal treatment, such as dissolution or Conversion of a previously introduced separation layer between the primary particles by cryogenic or high temperature treatments, or a chemical Conversion of introduced or specifically generated phases.

Preferably is the deagglomeration in the presence of one or more liquids, Dispersing aids and / or binders performed. This way you can Slip, a paste, a plasticine, or a suspension with a solids content between 1 and 95 wt .-% can be obtained. In the case of solids contents between 30 and 95 wt .-%, these can by known powder technology methods, such as injection molding, Film casting, Coating, hot-casting directly be processed, then in appropriate steps of drying, Debinding and sintering to be converted to a final product.

to Deagglomeration of particularly oxygen-sensitive powder is preferred a gas counter-jet mill used under inert gases, such as argon or Nitrogen is operated.

The produced metal, alloy or composite powders are distinguished from conventional powders with the same average particle diameter and the same chemical composition, which For example, be prepared by atomization, by a number of special properties.

The For example, metal powders of component I exhibit excellent properties Sintering behavior. At lower sintering temperature, the achieve the same sintering densities as produced by atomization Powders. At the same sintering temperature, starting from Powder compacts of a defined compact density higher sintering densities to reach. This increased sintering activity shows, for example, that until reaching the Shrinkage maximum, the shrinkage during the sintering process is higher than at conventional produced powders and / or that the (normalized) temperature, in which the Schwindungsmaximum occurs, in the case of PZD powder lower is ..

at the metal powders of component I are metal powders, their shrinkage, determined by means of dilatometer according to DIN 51045-1, until reaching the temperature of the first shrinkage maximum at least 1.05 times the shrinkage of a product produced by atomization Metal, alloy or composite powder of the same chemical composition and the same average particle diameter D50, wherein the test powder before measuring the shrinkage on a Press density of 50% of the theoretical density is compressed.

The Metal powders of component I are characterized by a special Particle morphology with rough particle surface in addition by comparatively better pressing behavior and due to a comparatively broad Particle size distribution by high press density. This manifests itself in that compacts from dull Powder under otherwise identical conditions of production a smaller Flexural strength (so-called green strength) have as the compacts of PZD powders of the same chemical composition and the same mean particle size D50.

The Sintering behavior of powders of component I can also be targeted by influence the choice of grinding aid. So can as a grinding aid one or more alloys are used due to their low melting point compared to the starting alloy during the Heating up already liquid Form phases that affect the particle rearrangement, as well as the material diffusion and thus improve the sintering behavior or the shrinkage behavior and thus higher Sintered densities at the same sintering temperature or at lower Sintering temperature the same sintered density as the comparison powder achieve. It can also be used chemically decomposable compounds whose decomposition products with the base material liquid Phases or phases with elevated Generate diffusion coefficients that favor densification.

Conventional metal powders (MLV) for powder metallurgical applications are powders of a substantially spherical shape of the particles, such as in 1 PCT / EP / 2004/00736. These metal powders may be elemental powder or alloy powder. These powders are known to those skilled in the art and are commercially available. For their preparation, numerous metallurgical or chemical processes are known. If fine powders are to be produced, the known methods often begin with the melting of a metal or an alloy. The mechanical coarse and fine comminution of metals or alloys is also frequently used for the production of "conventional powders", but results in a non-spherical morphology of the powder particles, and, if functioning well, is a very simple and efficient method of powder production (W. Schatt, K.-P. Wieters in "Powder Metallurgy - Processing and Materials", EPMA European Powder Metallurgy Association, 1997, 5-10).

Provided the breakdown of the melt over an atomization takes place, the powder particles form directly from the produced melt droplets by solidification. Depending on the type of cooling (treatment with air, Inert gas, water), the process parameters used, about the nozzle geometry, Gas velocity, gas temperature or the nozzle material, as well as the material Parameters of the melt, such as melting and solidification point, solidification behavior, Viscosity, chemical composition and reactivity with the process media a variety of ways but also limitations of Method (W. Schatt, K.-P. Wieters in "Powder Metallurgy - Processing and Materials ", EPMA European Powder Metallurgy Association, 1997, 10-23).

Since powder production by means of atomization is of particular technical and economic importance, various atomization concepts have become established. Depending on the required powder properties, such as particle size, particle size distribution, particle morphology, impurities, and properties of the melts to be atomized, such as melting point or reactivity, as well as the tolerable costs, certain processes are selected. Nevertheless, there are often limits in economic and technical terms, a certain property profile of the powders (particle size distributions, impurity contents, Yield of "target grain", morphology, sintering activity, etc.) at reasonable cost (W. Schatt, K.-P. Wieters in "Powder Metallurgy - Processing and Materials", EPMA European Powder Metallurgy Association, 1997, 10-23).

The Production of conventional Metal powders for powder metallurgical applications by means of atomizing has the disadvantage that big Amounts of energy and atomizing gas have to be used which makes this procedure very expensive. In particular, the production fine powder of refractory alloys with a melting point> 1400 ° C is little economically, because on the one hand the high melting point a very high energy input for the production of the melt conditionally, and on the other hand the Gas consumption with decreasing desired Particle size strong increases. In addition, difficulties often arise, if at least an alloying element has a high oxygen affinity. Through the use of specially developed nozzles cost advantages in the Production of particularly fine alloy powder can be achieved.

Next the production of conventional Metal powders for Powder metallurgical applications by atomization are common too other single-stage fusion metallurgical processes used, such as so-called "melt spinning", i.e. the pouring of a Melt on a chilled Roller, creating a thin, usually easily comminuted tape or so-called "crucible-melt-extraction", i.e. immersion a chilled, profiled rapidly rotating roller into a molten metal, taking Particles or fibers are recovered.

A Another important variant of the production of conventional Metal powders for Powder metallurgical applications is the chemical route via reduction of metal oxides or metal salts. The extraction of alloy powders However, this is not possible in this way (W. Schatt, K.-P. Wieters in "Powder Metallurgy - Processing and Materials ", EPMA European Powder Metallurgy Association, 1997, 23-30).

Extreme fine particles, particle sizes below of a micrometer can also by the combination of evaporation and condensation processes of metals and alloys, as well as generated by gas-phase reactions (W. Schatt, K.-P. Wieters in "Powder Metallurgy - Processing and Materials ", EPMA European Powder Metallurgy Association, 1997, 39-41). These However, processes are technically very complicated.

He follows the cooling off the melt in a larger volume / block, become mechanical process steps of coarse, fine and Feinstzerkleinerung required to powder metallurgically processable metal or Produce alloy powder. An overview of mechanical powder production W. Schatt, K.-P. Wieters in "Powder Metallurgy - Processing and Materials ", EPMA European Powder Metallurgy Association, 1997, 5-47.

The mechanical comminution, especially in mills, as the oldest method the particle size adjustment, is very advantageous from a technical point of view because it is inexpensive and applicable to a variety of materials. She poses However, certain demands on the input material, for example in terms Size of pieces and brittleness of the material. In addition, leaves the crushing does not continue indefinitely. Rather forms a balance of malt, which also sets when you begins the grinding process with finer powders. The conventional Grinding processes are then modified when the physical limits the comminution for the respective regrind are reached, and certain phenomena, such as embrittlement at low temperatures or the effect of grinding aids that Improve grinding behavior or the shredding. After these The above-mentioned methods are the conventional metal powders for powder metallurgy Applications available.

The Components I and II can independently be chemically identical or different from each other and can elemental powder, Alloy powder or mixtures thereof.

The metal powders of components I and II can be a composition of the formula I hA-iB-jC-kD (I) own, where
A for one or more of the elements Fe, Co, Ni,
B for one or more of the elements V, Nb, Ta, Cr, Mo, W, Mn, Re, Ti, Si, Ge, Be, Au, Ag, Ru, Rh, Pd, Os, Ir, Pt,
C for one or more of the elements Mg, Al, Sn, Cu, Zn, and
D for one or more of the elements Zr, Hf, Mg, Ca rare earth metal (Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) stands,
and h, i, j, and k indicate the parts by weight, where
h, i, j and k are each independently 0 to 100% by weight,
with the proviso that the sum of h, i, j and k is 100% by weight.

In a further embodiment of the invention are in the formula I.
A for one or more of the elements Fe, Co, Ni,
B for one or more of the elements V, Cr, Mo, W, Ti,
C for one or more of the elements Mg, Al and
D for one or more of the elements Zr, Hf Y, La.

H stands for 50 to 80 wt .-%, or for 60 to 80 wt .-%. i means 15 to 40 wt .-%, or 18 to 40 wt .-%. j means 0 to 15 wt .-%, or 5 to 10 wt .-%. k is 0 to 5% by weight, or 0 to 2% by weight.

In Another embodiment of the invention is in the Components I or II to element powder or binary alloy powder, so that a molded article made from a metallic powder mixture according to the invention available is, has a corresponding more complex composition. For example can in this embodiment of the invention by using binary Alloys for the components I and II are obtained a molded article, the one from a quaternary Alloy exists.

In Another embodiment of the invention is in the Components I or II to higher Alloy powder like binary or quaternary Alloy powder, leaving a shaped object, which consists of a metallic powder mixture according to the invention available is, has a corresponding more complex composition. So can the Components I and II independent from each other also alloys containing two, three four or also five different metals exist, so that more complex alloys are possible. For example, in this embodiment of the invention by Using a binary Alloys for Component I and a quaternary alloy for the component II, a molded article obtained from a six Metals containing alloy.

In Another embodiment of the invention are the compositions the components I and II of the metallic powder mixture and a molded article obtained therefrom each different from each other.

In a further embodiment of the invention has a molded article, which is obtained by using a metallic powder mixture according to the invention subjected to a powder metallurgical molding process, a composition of formula I.

In a further embodiment of the invention consists of the molded Subject matter, component I and / or component II in essence selected from an alloy from the group consisting of Fe20Cr10A10.3Y, Fe22Cr7V0.3Y FeCrVY, Ni57Mo17Cr16FeWMn, Ni17Mo15Cr6Fe5W1Co, Ni20Cr16Co2.5Til, 5Al and Ni53Cr20Co18Ti2,5Al1,5Fe1,5.

In In a further embodiment of the invention, the component I and / or II itself a powder mixture of different element powders or alloy powders. For example, a molded article containing six metals as alloying ingredients in this case be obtained by that a component I, which is a binary alloy is, with a component IIa and a component IIb, respectively binary Alloys are mixed and a process of powder metallurgy Shaping is subjected.

The amount of the component II in the metallic powder mixture depends on the nature and extent of the intended effect to be achieved and the desired chemical composition of the molded article obtained by subjecting the metallic powder mixture to a powder metallurgy molding process. If components I and II are identical, the chemical composition of the molded article is already established. However, if components I and II have a different composition, the composition of the resulting shaped article will depend on the nature, composition and content of components I and II, and these must be adjusted accordingly. In this case, according to the invention, the production of molded articles highly alloyed metallic materials by processes that were previously not suitable for their production. The person skilled in the art is in principle familiar with the effects that occur, so that the optimum mixtures for the particular application can be set by a small number of experiments. In general, the conventional metal powder is used in ratios of component I: component II in the ratio of 1: 100 to 100: 1 or of 1:10 to 10: 1 or of 1: 2 to 2: 1 or of 1: 1.

The present invention can be used for the production of highly alloyed materials. Possible procedures are explained in more detail here. The preparation of complex alloy constituents for the metallic powder mixture can be described in general terms as follows, the sum of factors a, b and c being added to 100% by weight and the symbols aBMP-bLEM-cDOT-dMHM-eFUZ being used as follows: BMP (base metal powder): Fe, Ni, Co LEM (alloying elements): Cr, Al, Ti, Mo, W, Nb, Ta, V, ... DOT (dopings): SE (rare earth metals), Zr, Hf Mg, Ca MHM (grinding aid) Paraffin, hydrocarbons, brittle intermetallic phases, other brittle phases (Ceramics, hard materials) FUZ (functional addition) Ceramics, Hydrocarbons, Sulfides,

The Indices d and e indicate the amount of grinding aid or functional Additive, in addition may be included.

In one embodiment of the invention, the alloy composition is retained. The metallic powder mixture is composed as follows:

In this case, the alloy constituting the molded article obtained from the metallic powder mixture is composed as follows:
(a ₁ + a ₂ ) BMP - (b ₁ + b ₂ ) LEM - (c ₁ + c ₂ ) DOT (without grinding aid)

In this case, a ₁ = a ₂ and b ₁ = b ₂ and c ₁ = c ₂ , that is, it is a mixture of the same alloys, in which component I is a PZD powder.

The (organic) grinding aids (MHM) is not mentioned because it is completely removed in the course of processing and the Alloy not changed. The proportions of components I and II may vary depending on the requirement the processing or functional properties between 100% Comp. I and 0% comp. II and 1% comp. I and 99% comp. II, respectively, vary.

In a further embodiment of the invention, the alloy composition changes according to the proportions of components I and II. The metallic powder mixture is composed as follows:

In this case, the alloy constituting the molded article obtained from the metallic powder mixture is composed as follows:
(a ₁ + a ₂ ) BMP - (b ₁ ) LEM - (c ₂ ) DOT (without grinding aid)

In this case, a ₁ ≠ a ₂ and b ₁ ≠ b ₂ and c ₁ ≠ c ₂ , that is, they are two alloys. The component I consists only of base metal powder (BMP) and alloying elements (LEM), the component II contains the doping in concentrated form as a compound to be added, advantageously with special metallurgical (eg low melting point) and / or mechanical (eg brittle, easily comminuted) property companies. In this way one can use powder technology advantages (liquid phase sintering) to represent the desired final alloy. The doping is introduced here in the form of a masterbatch, which may be advantageous depending on the type and composition of the alloys. The (organic) grinding aid is not mentioned because it is completely removed during processing and does not alter the alloy. The proportions of components I and II are selected by the person skilled in the art according to the target composition.

In a further embodiment of the invention, the alloy composition changes according to the proportions of components I, IIa and IIb. The metallic powder mixture is composed as follows:

In this case, the alloy constituting the molded article obtained from the metallic powder mixture is composed as follows:
(a ₁ + a ₂ + a ₃ ) BMP - (b ₁ ) LEM - (c ₂ ) DOT (without grinding aid)

In this case, a ₁ ≠ a ₂ ≠ a ₃ and b ₁ ≠ b ₂ and c ₁ ≠ c ₂ , that is, the components are two alloys and a base metal powder. The component I consists only of base metal powder (BMP) and alloying elements, the component II contains as mixture the doping in "concentrated" form together with base metal and / or alloying elements in order to advantageously use special metallurgical and mechanical properties In this way, in addition to the powder technology advantages of the embodiment described immediately above, technical and economic advantages can be utilized the processing is completely removed and the alloy is not changed.

In a further embodiment of the invention, the alloy composition changes according to the proportions of components I and II. As a grinding aid, a brittle alloy is advantageously used. The metallic powder mixture is composed as follows:

In this case, the alloy constituting the molded article obtained from the metallic powder mixture is composed as follows:
(a ₁ + a ₂ + a ₃ ) BMP - (b ₁ ) LEM - (c ₂ ) DOT (without grinding aid)

In this case, a ₁ ≠ a ₂ ≠ a ₃ that is, it is an alloy and a base metal. Component I consists only of base metal powder (BMP) and alloying elements (LEM). The grinding aid used is a particularly brittle composition consisting of BMP and DOT. As component III powdered paraffin is mixed in. With component II, in this case a base metal powder, corrections of the composition can be made. In this way, one can use the powder technology advantages of the alloy (a ₂ BMP-c ₂ DOT). The grinding aid is not listed separately because it is absorbed in the alloy constituting the molded article.

In a further embodiment of the invention, the composition changes according to the proportions of components I and II. The grinding aid used is a brittle alloy a ₂ BMP-c ₂ DOT, and organic components and ceramic particles are used as the functional additive (FUZ). The metallic powder mixture is composed as follows:

In this case, the alloy constituting the molded article is composed of metallic powder mixture is obtained as follows:
(a ₁ + a ₂ + a ₃ ) BMP - (b ₁ ) LEM - (c ₂ ) DOT (without grinding aid)

In this case, a ₁ ≠ a ₂ ≠ a ₃ , that is, it is an alloy and a base metal powder. Component I consists of base metal powder and alloying elements. The grinding aid used is a brittle composition consisting of base metal and doping. With the base metal powder corrections of the composition can be made. Component III contains PVA (polyvinyl alcohol) and Kermamikpartikel, which are advantageous for further processing, for example by spray drying. This mixture can be processed, for example, to a thermal spray powder. In this way, one can use the powder technology advantages of the alloy (a ₂ BMP - c ₂ DOT) and the effect of functional additives (hardness, wear resistance), if the powder accordingly, for example by thermal spraying, processed as a wear protection layer.

When Component III, the metallic powder mixture functional additions contain. Functional additives can impart characteristic properties to molded articles made of PZD powder, such as additives that the impact resistance or increase abrasion resistance, like superhard powders, or additives, the processing of greenlings facilitate by the brittleness of the green compact and / or the green strength increase, or additives, as a template for controlling the pore structure or surface properties act.

Under functional additives are understood to be homogeneously introduced additives that either largely or completely remain in the finished product, a molded object or the largely or completely be removed from the product.

in the first case are functional additives that have the mechanical properties such as hardness, Strength, damping, or impact resistance, or the chemical properties such as oxidation / corrosion behavior or functional properties such as tribology, haptics, electrical and magnetic conductivity, Modulus of elasticity, electrical burning behavior, magnetostrictive behavior, electrostrictive Control behavior by their proportions and primary properties.

The complex mechanical, chemical and functional properties can be brought about by introducing various phases / constituents such as ceramic particles or hard materials, for example carbides, borides, nitrides, oxides, silicides, hydrides, diamonds, in particular carbides, borides and nitrides of the elements of groups 4, 5 and 6 of the Periodic Table, oxides of elements of Groups 4, 5 and 6 of the Periodic Table and oxides of aluminum and rare earth metals, silicides of aluminum, boron, cobalt, nickel, iron, molybdenum, tungsten, manganese, zirconium, tantalum hydrides, niobium , Titanium, magnesium and tungsten; Lubricants with lubricating properties such as graphite, sulfides, oxides, in particular molybdenum sulfide, zinc sulfide, tin sulfides (SnS, SnS ₂ ), copper sulfide or even intermetallic compounds with special magnetic or electrical properties based on rare earth cobalt or rare earth iron.

On that way with a metallic powder mixture also the coating of superhard powders with PZD powders. This will be beneficial achieved by fluidized bed granulation.

Coarse (50-100 μm) hard material particles of, for example, BN and TiB ₂ can be used as feedstock in fluidized-bed granulation and provided with a corrosion-resistant coating. This makes it possible to operate novel applications in the field of wear under high corrosive and mechanical loads. After coating, the agglomerates are debinded, sintered in an inert atmosphere and applied by thermal spraying.

In the second case, ie functional additives, which are largely or completely removed from the product, are additives, so-called placeholders, which are removed by suitable chemical or thermal methods and thus act as a template. These may be hydrocarbons or plastics. Suitable hydrocarbons are long-chain hydrocarbons such as low molecular weight, waxy polyolefins, such as low molecular weight polyethylene or polypropylene, but also saturated, fully or partially unsaturated hydrocarbons having 10 to 50 carbon atoms, or having 20 to 40 carbon atoms, waxes and paraffins. Suitable plastics are in particular those with a low ceiling temperature, in particular with a ceiling temperature of less than 400 ° C., or lower than 300 ° C. or lower than 200 ° C. Above the ceiling temperature, plastics are not thermodynamically stable and tend to break down into monomers (depolymerization). Suitable plastics are, for example, polyurethanes, polyacetal, polyacrylates, in particular polymethyl methacrylate, or polystyrene. In another Embodiment of the invention, the plastic in the form of preferably foamed particles is used, such as foamed polystyrene beads, such as are used as a precursor or intermediate in the production of packaging or thermal insulation materials used. Also, sublimation-prone inorganic compounds may function as wildcards, such as some oxides of refractory metals, particularly oxides of rhenium and molybdenum, as well as partially or fully decomposable compounds such as hydrides (Ti hydride, Mg hydride, Ta hydride), organic (Metal stearates) or inorganic salts

By Addition of these functional additives can be largely dense components (90 to 100% of the theoretical Density), slightly porous (70 to 90% of the theoretical density) and highly porous (5 to 70% of the theoretical density) components by making a metallic powder mixture according to the invention, the contains such a functional addition as a placeholder, a subjected to powder metallurgical molding process.

The Amount of functional additives depends on Type and extent of the intended effect to be achieved, with which the person skilled in the art is familiar in principle, so that by a small Number of attempts to set the optimal mixes can. When using these compounds, make sure that the links used as wildcard / template in one of their Suitable structure in the metallic powder mixture, so in the form of particles, as granules, powder, spherical particles or similar..

in the Generally, the functional additives are in proportions of Component I: Component III in the ratio of 1: 100 to 100: 1 or from 1:10 to 10: 1 or from 1: 2 to 2: 1 or from 1 : 1 inserted. Is it the functional additives to Hard materials, for example tungsten carbide, boron nitride or titanium nitride, so these are advantageous in amounts of 3: 1 to 1: 100 or from 1: 1 to 1:10, or from 1: 2 to 1: 7 or from 1: 3 to 1: 6.3 used.

In In another embodiment of the invention, the functional additions advantageously in amounts of from 3: 1 to 1: 100 or from 1: 1 to 1 : 10 or from 1: 2 to 1: 7 or from 1: 3 to 1: 6.3.

In Another embodiment of the invention is the metallic powder mixture a mixture of component I with component II and / or component III with the proviso that the ratio of component I to component III at 3: 1 to 1: 100, or of 1: 1 to 1:10, or from 1: 2 to 1: 7, or from 1: 3 to 1 : 6.3 is In a further embodiment of the invention is the metallic powder mixture a mixture of component I with component II and / or component III with the proviso that in the presence of a hard material in the component III, the ratio of component I to component III at 3: 1 to 1: 100, or from 1: 1 to 1:10, or from 1 : 2 to 1: 7, or from 1: 3 to 1: 6.3.

In Another embodiment of the invention is the metallic powder mixture a mixture of component I with component II and / or component III with the proviso in the presence of tungsten carbide in component III, the relationship of component I to component III at 3: 1 to 1: 100, or of 1: 1 to 1:10, or from 1: 2 to 1: 7, or from 1: 3 to 1 : 6.3 lies.

Further Additives should in particular the processing properties such as the pressing behavior, strength of the agglomerates or redispersibility improve. These can be waxes, such as polyethylene waxes or oxidized polyethylene waxes, ester waxes such as montan acid esters, oleic esters, Esters of linoleic acid or linolenic acid or mixtures thereof, paraffins, plastics, resins such as Rosin, salts of long-chain organic acids, such as metal salts of montanic acid, oleic acid, linoleic acid or linolenic acid, metal stearates and metal palmitates, for example zinc stearate, in particular the Alkali and alkaline earth metals, for example magnesium stearate, sodium palmitate, Calcium stearate, or lubricants. It is about to substances that are common in powder processing (pressing, MIM, foil casting, slip casting) and are known in the art. The compression of the to be examined Powder can be customary with the addition press supportive Agents such as paraffin wax or other waxes or Salts of organic acids, e.g. Zinc stearate, done. Suitable additives are further described in W. Schatt, K.-P. Wieters in "Powder Metallurgy - Processing and Materials ", EPMA European Powder Metallurgy Association, 1997, 49-51 "What Reference is made.

The The following examples serve the closer explanation of the invention, the examples facilitating the understanding of the invention should and not as a restriction are to be understood.

The given in the Examples mean particle diameter D50 were determined using a Microtrac ^® X 100 from Honeywell / US in accordance with ASTM C 1070-01.

example 1

As a starting powder atomised by means of argon alloy melt of the type Nimonic ^® 90 was used with the composition Ni20Cr16Co2,5Ti1,5Al. The resulting alloy powder was screened between 53 and 25 microns. The density was about 8.2 g / cm ³ . The starting powder had largely spherical particles.

The starting powder was subjected to deformation grinding in a vertical stirred ball mill (Netzsch Feinmahltechnik, type: PR 1S), so that the originally spherical particles assumed platelet shape. In detail, the following parameters were used: • Grinding container volume: 5 l • Rotation speed: 400 rpm • peripheral speed: 2.5 m / s • ball filling: 80% by volume (bulk volume of the balls) • grinding container material: 1000r6 (DIN 1.3505: approx. 1.5% by weight Cr, about 1 wt .-% C, about 0.3 wt .-% Si, about 0.4 wt% Mn, <0.3 wt% Ni, <0.3 Wt.% Cu, balance Fe) • Ball material: Carbide (WC-10Co) • Ball diameter: approx. 6 mm (total mass: 25 kg) • Powder scale: 500 g • treatment duration: 2 h

Subsequently, a crushing grinding was performed. In this case, a so-called eccentric vibration mill (Siebtechnik GmbH, ESM 324) was used with the following procedural parameters: • Grinding container volume: 5 l operated as a satellite (diameter 20 cm, Length about 15 cm) • ball filling: 80% by volume (bulk volume of the balls) • grinding container material: 1000r6 (DIN 1.3505: approx. 1.5% by weight Cr, approx. 1% by weight C, about 0.3% by weight Si, about 0.4% by weight Mn, <0.3 wt% Ni, <0.3 wt% Cu, balance Fe) • Ball material: 100 Cr6 • Ball diameter: 10 mm • Powder scale: 150 g • grinding aids: 2 g paraffin Oscillation amplitude: about 10 mm • grinding atmosphere: Argon (99.998%)

To a grinding time of 2 hours became very fine particle agglomerates receive. In a SEM image at 1000-fold magnification of the The product obtained is the cauliflower-like structure of the agglomerate (Offspring) recognizable, wherein the primary particles Have particle diameter of well below 25 microns.

A Sample of primary particles or Feinstteilchen agglomerates was in a 3rd step of a Deagglomeration by a 10-minute ultrasound treatment in isopropanol in an ultrasonic device TG 400 (Sonic Ultraschallanlagenbau GmbH) at 50% of the maximum power to separated primary particles to obtain.

The particle size distribution of the sample was deagglomerated ^® X100 (manufactured by Honeywell / US) by Microtrac determined according to ASTM C 1070-01. The D50 value of the starting powder was 40 μm and has been reduced by the treatment to about 15 μm.

The remaining amount of primary particles from the crushing milling were in an alternative 3rd step a deagglomeration by treatment in a counter gas jet mill and followed by Ultrasonic treatment in isopropanol in a TG 400 ultrasonic device (Sonic Ultraschallanlagenbau GmbH) at 50% of the maximum power subjected. Again a particle size determination by Microtrac was carried out X100. The D50 value was now only 8.4 microns.

The introduced grinding aid paraffin can during powder metallurgy Further processing of the alloy powder by thermal decomposition and / or evaporation can be removed, or can be used as a pressing aid serve.

A metallic powder mixture according to the invention was made from the PZD powder obtained as described above as follows produced.

(20 microns: 10 .mu.m and d90 d50) 5 kg Nimonic ^® 90 - - PZD powder (d50: 10 .mu.m and d90 20 microns) powder, prepared as described above, and 5 kg of spherical (gasverdüstes) Nimonic ^® 90 together with 233 g of a powdery pressing aid (Licowax C) placed in an Eirichmischer. During a period of 20 minutes, an intensive mixing of the 3 components takes place. This powder is called VSP-711.

Analogous to this, 10 kg of pure atomized (conventional) powder (Nimonic ^® 90 powder (d50: 10 .mu.m and d90: 20 microns)) are processed in a similar manner, but using 300 g of Licowax be added. This powder is called KON-711.

Both Powders were prepared by uniaxial pressing at a pressure of 500 MPa to cylinders of a height of 10 mm and a diameter of 30 mm. The compact density of KON-711 was 75% of the theoretical density, but the test piece had only a low green strength. The body obtained from VSP-711 Despite a lower theoretical density (70%), it showed a clear improved strength.

• nmb: nicht messbar, Proben zerfällt bereits bei der Handhabung

For the exact determination of the green strength cuboidal compacts are produced at a pressure of 500 MPa. 1 shows a basic relationship between the powder grades VSP_711 or KON_711 with different levels of pressing aids and the green strength. The green strength of the compacts produced from VSP_711 is up to 2.5 MPa under the conditions described and is therefore at least twice as high as that of the comparative sample KON_711. The determination of the compact strength of specimens with a rectangular cross-section under bending stress is based on DIN ISO 3995/1985. The results of these measurements are listed in Table 1. Table 1: Green strength

• nmb: not measurable, samples disintegrate during handling

Both powders (VSP-711 and KON-711) are tested on a metal powder press to form another test specimen, a PM tensile test rod in accordance with DIN ISO 3927 with an area of 6.35 cm ² (parallel to the pressing direction) and a length of approx mm pressed. The pressure is varied from 300 to 800 MPa. The density of the components increases with increasing pressing pressure. Table 2 describes this dependence of the influence of the pressing pressure on the green density of tensile test specimens directly pressed from powders (with A (area in pressing direction): 6.35 cm ² ; L (length of the specimen in pressing direction): 4-5 mm) It should be noted that the density values given refer to the mixture of metal powder and pressing aid (3% Licowax).

Table 2 press density

The PM tensile bars are debinded in the gas stream under hydrogen at a heating rate of 2 K / min from room temperature to 600 ° C and then sintered under high vacuum at about 10 ^-3 mbar at a temperature of 1290 ° C for 2 h. The sample of the powder type KON-711 shows after debinding and sintering damage (cracks, destructions), which were not visible in the pressing state. In contrast, VSP-711 tensile specimens show no damage and, moreover, have a more uniform sample surface with little roughness. The bodies are in 2 displayed. In addition, partial quantities of the two powder types are compressed after debindering at a heating rate of 2 K / min from room temperature to 600 ° C under hydrogen by hot pressing (1150 ° C / 2h / 35 MPa / nitrogen) in a graphite mold. After the hot pressing, the temperature is lowered at about 5 to 15 K / min until room temperature is reached. The resulting discs have a density of 8.18 g / cm3 (KON-711) and 8.14 g / cm3 (VSP-711). These discs (diameter: 100 mm, thickness: about 5 mm) are brought to a thickness of 3.5 mm by grinding on both sides. From them by means of water jet cutting flat tensile specimens as in 3 in a tensile test machine, the mechanical properties (Rm, the tensile stress at break, Pp0,2, mechanical stress at which elongation of the tensile test specimen is measured by 0.2%) are evaluated. In 4 the measured curves of the tensile tests are plotted and allow a comparison of the strengths at room temperature.

Press compacts were pressed at 500 MPa and sintered in an oven at 1300 and 1330 ° C for two hours in an argon-hydrogen atmosphere (6.5 vol .-% H ₂ ), after the organic Preßhilfmittelanteil was removed to 600 ° C under hydrogen , Table 2b shows the results.

Table 2b:

Another peculiarity is the pore structure of the samples prepared from KON-711 and VSP-711 which are available in 5 is shown.

Example 2

Making a good one compressible, flowable and good sinterable Granulates in the following way:

5 kg Nimonic ^® 90 - PZD powder (d50: 10 .mu.m and d90: 20 .mu.m), prepared as in Example 1, and 5 kg of spherical (gasverdüstes) Nimonic ^® 90 - powder (d50: microns 20: 10 .mu.m and d90) are added together with an organic binder (polyvinyl alcohol, PVA, 3 wt .-%) and a surface-active stabilizer in 2-3 liters of water. This mixture is dispersed until a stable suspension has formed. This suspension is processed by spray drying to form an agglomerate of largely spherical individual particles with a diameter of 1 to 150 μm. As the working gas for drying the suspension, heated nitrogen (gas temperature: 30 to 80 ° C) is used in countercurrent. The gas mixture produced during drying is released to the environment via a filter at the outlet of the spray dryer.

to Improvement of further processability and compliance health-related criteria, the "dusty" fines (<10 μm) and the proportion of coarse granules of> 150 microns separated by sieving. Such granules (-150 microns +10 microns possesses an excellent flow behavior. The granules thus obtained are referred to as VSP-712.

Parallel to the production of this granulate, an atomized (conventional) powder (10 kg) (Nimonic ^® 90 powder (d50: 10 μm and d90: 20 μm)) is processed analogously to a granulate (-150 μm +10 μm). This powder is called KON-712.

Both Powders (VSP-712 and KON-712) are prepared in an analogous manner as in Example 1 described - in terms the press properties, green strength, the sintering behavior and the surface quality (roughness) of the sintered Parts rated. This results in a match to those in the above illustrated example, data and properties.

Example 3

Making a tight bulk forming granulate

It each became a compact by cold isostatic pressing (CIP) by using the example given in FIG 1 produced powder blends VSP-711 and KON-711. To the granules are filled in a rubber mold, sealed gas-tight and subsequently compacted with a hydrostatic pressure of 2000 bar. At the compacts From KON-711 a compression of 70% TD is measured, VSP-711 achieved By contrast, a compact density of about 65% TD. Then be the CIP compacts successively by machining (clamping in a lathe and making rough "chips" by turning them off) divided. In the case of the VSP-711 succeeds, a large proportion (> 50% with a particle size of d50:> 100 microns) too coarse grains to process. For the compact KON-711 mainly produces a dusty product (particles> 100 μm (<5%)).

These Pre-granules are then further processed by means of a sieve granulating plate. The edges of the "powder chips" are rounded off and it creates a better flowable granules. After screening, a fraction -65μm +25 microns, so a fraction with a Particle size of smaller than 65 μm and bigger than 25 μm, obtained become. This granules can be prepared by powder metallurgy molding be further processed. The fractions are named VSP-721 and KON-721, respectively designated. The overall yields in the production of high-density and flowable granules will be 20 to 50% in the case of VSP-721 and <20% in the case of KON-721. The not within the desired Kornbandes lying granulate portion can each again in the Manufacturing process used for the CIP body become.

The Investigation of the processing properties of the metallic powder mixtures VSP-721 and KON-721 from example 2 (green strength, sintering properties) leads to comparable results. VSP-721 shows higher green strength and higher sintering density compared to KON-721 at given sintering temperature, when same initial densities are used.

Example 4

Production of a porous body VSP-721, KON-721 and Atomized Powder VER-6525 (fraction: -65 +25 μm) same composition

The previously produced granules VSP-721 and KON-721 and a powder produced by inert gas atomization same composition VER-6525 and the same particle size as the granules used (-65 / + 25 microns) are processed in the following manner to form porous bodies:
First, the respective filling of the 3 grains in each 3 equal sintered shells (base: 6 cm × 2 cm, Schütthöhe: 3 cm). These are brought to a temperature of 600 ° C. under hydrogen in a debindering oven at a heating rate of 2 K / min. Thereafter, the heating takes place at 1250 ° C with a heating rate of 10K / min. The temperature of 1250 ° C is maintained for 2 hours, after which the furnace with the sintered bodies is brought to room temperature at a rate of 10 K / min.

The formed (lost) moldings are removed and in Three-point bending test rated. It turns out that the moldings subsequent achieve very different bending fracture strengths: VSP-721: 40- about 20 MPa, KON-721: about 20-5 MPa and VER-6525: <5 MPa. The comparatively higher sintering activity the variant VSP-721 thus allows the production sufficiently solid shaped body, as for example the use in filter elements are desired. An optimization the sintering conditions allowed for VSP-721's strength over To increase 50 MPa.

Example 5

Porous pipe

manufacturing a porous one body in the form of a tube by sintering a powder bed of granules (VSP-721, KON-721) of high density and a powder prepared by atomization (VER-6525) of the same chemical composition and particle size as the Granules. For this purpose, in each case a correspondingly produced granules or the gross annoyance Powder is placed in a ceramic mold with a burn-out core. The core is called thin-walled Plastic tube formed, which is sufficiently stable, the Pressure of the powder on its circumference after filling to resist. charged If only a narrow granule or Powder fraction (-65 +25 μm), which was made by sieving.

In a next step, the organic components and the inserted tube are removed by thermal decomposition or expulsion in an oven and at the same time at a higher temperature (1000 ° C) initiated a pre-sintering. The pre-sintered body is then - also standing - placed in another furnace, which reaches a high temperature of gas purity (vacuum, pressure of 10 ^-2 mbar) a temperature of 1300 ° C. After sintering, a molded article is obtained from the VSP-721 granules, which obtains sufficient shrinkage and also adequate strength. In contrast, the molded body of KON-721 shows a lower strength. The molded body of coarse powder (VER_6525) achieves only a strength of about 5 MPa under the conditions used, which makes a technical use due to the insufficient strength impossible.

Example 6

Made of powder compact Granules of high strength

The granules VSP-721 and KON-721 described above are filled in the cavity of a powder press tool of a uniaxial press. Under uniaxial pressing pressure of 700 MPa, molded articles are produced which achieve the following densities: VSP-721: 5.3 g / cm 3 (65% of the theoretical density) or KON-721 approx. 6 g / cm 3 (73% of the theoretical density ). The green strengths are 10 to 15 MPa for VSP-721 molded articles and 2 to 5 MPa for KON-721 molded articles. After sintering according to the temperature-time program described in Example 4, the molded articles sintered from VSP-721 reach densities of 7.8 g / cm 3 (95% of the theoretical density), the molded articles sintered from KON-721 reach densities of 7, 7 g / cm3 (94% of the theoretical density). A typical structure is as 5 displayed.

Example 7

fluidized bed granulation for producing good flow and ready to use powder

The processing of PZD powder (NIMONIC ^® 90 according to Example 1) by fluidized bed granulation (using the machine ProCell Fa. Glatt) allows the production of agglomerates with particle diameters of 10 to about 300 microns. An aqueous suspension is produced, which is sprayed into a fluidized-bed chamber. By drying the injected material, the droplets first form tiny agglomerates that are composed of several primary particles. These serve as nuclei for fluidized bed granulation. Further deposition of droplets and their drying produces agglomerates of increasing diameter. This growth process is accompanied by shocks between the growing particles, resulting in superficial compaction. The binder contained in the suspension bonds the primary particles to the surface of the seeds and growing agglomerates. By suitably adjusting the flow conditions and air volumes, the particle size and the agglomerate properties can be influenced. Agglomerates produced in this way show a particularly good homogeneity of the constituents in the single agglomerate grain.

Example 8

Production of coarse Powder by agglomeration in a mill

By using pure Nimonic ^® 90 - PZD powder having a d50 of 10 microns and d90 of 20, prepared in analogy to Example 1, it is possible to pre-agglomeration, in which the primary properties of the fine powder (in particular, sintering and Press behavior) is largely retained.

in the For this purpose, 600 g of the PZD powder into a grinding container Given eccentric vibrating mill. There are steel balls with a diameter of 15 mm from the material 1000r6 (DIN 1.3505) used. After a grinding time of 1 h at a speed of 1500 rev / min in argon 4.8 as a medium, a Kugelfüllgrad of 80% and a grinding container volume from 51 you can visit the mill remove a clearly "coarsened" powder. The particle size d50 is about 40 microns.

Example 9

Metallic powder mixture with functional components by spray drying producing a easily flowable granules for use as a powder for the thermal spraying in the following way:

A spherical atomized Ni17Mo15Cr6Fe5W1Co alloy having an average particle diameter D50 of 40 microns, which is commercially available under the name Hastelloy ^® C, as described in Example 1 subjected to a deformation step.

The crushing of the resulting platelet-shaped particles was carried out in the presence of tungsten carbide as a grinding aid under the following conditions in an eccentric vibratory mill: • Grinding container volume: 5 l • ball filling: 80% by volume • grinding container material: 100 Cr6 (DIN 1.3505) • Ball material: WC-10Co cemented carbide material • Ball diameter: 6.3 mm • Powder scale: 150 g Oscillation amplitude: 12 mm • grinding atmosphere: Argon (99.998%) • grinding time: 90 minutes • grinding aids: 13.5 g WC (D50 = 1.8 μm)

in the As a result of comminution grinding, an alloy-hard material composite powder was produced, in which the alloying component is based on an average particle diameter D50 of approx. 5 μm and the hard material component to an average particle diameter D50 of approx. 1 μm was crushed. The hard material particles were largely homogeneous distributed in the volume of the alloy powder.

1.5 kg of the thus obtained Hastelloy C ^® -PZD powder with d50 of 5 microns and d90 of 10 and 9.5 kg of Tungsten carbide (d50: 1 μm, d90: 2 μm) are processed together by granulation by spray granulation as described in Example 2 in the preparation of VSP-712. The parameters were adjusted during the spray granulation so that a minimal fines content could arise. In order to remove the portions which are unsuitable for subsequent further processing (thermal spraying), the particles having a diameter greater than 65 μm were sieved off and the coarse fraction was returned to the ready-to-spray suspension (mixed in). The fraction with a diameter of less than 65 microns is placed in a Sinterschiffchen base 15 cm × 15 cm to a height of 3 cm and then debindered under hydrogen (heating at a rate of 2 k / min to 600 ° C) and a Temperature of 1150 ° C sintered. The sinter cake is removed after cooling and further processed by gentle crushing in a mortar. The resulting fine fraction is classified with a 50 μm sieve "top" and a 25 μm sieve "bottom". The resulting fraction with a particle size of less than 50 microns to 25 microns is applied by thermal spraying (high velocity flame spraying) as a wear and corrosion resistant layer on a little wear-resistant Hastelloy C material. In 6 It is observed that a homogenous matrix alloy is formed, which encloses the hard particles, thus providing the expected resistance to corrosion and wear, in contrast to the use of elementary starting powders (drawing "A "), which were granulated in an analogous manner to spray ready powders, to inhomogeneities in the layer produced. This can lead to increased corrosion under conditions of corrosive environment.

Example 10

Making a light redispersible spray granules (LRDG).

The Production is carried out in accordance with Example 2. However as a solvent a mixture of benzene (about 10% by volume) and ethyl alcohol (about 90%) Vol%) and used as plastic polymethyl methacrylate (PMMA). After spray drying considering the conditions for The handling of highly flammable solvents is a granulate before, in which a largely solid connection of the individual particles (Hastelloy C and tungsten carbide) is present. The parameters for spray granulation are adjusted so that coarse granules with a low fines content arises, which has a good flowability (d50: 100 microns, d90: 150 microns). It is by examining individual narrower fractions by X-ray fluorescence analysis quantitatively verifiable that in the different fractions the Same chemical composition and therefore the same ratio of used powder constituents is present. This can be on a homogeneous Distribution of the produced granules are closed, as well therefore, because no demixing in chemical terms expected is, even if a segregation of individual faction components should occur. Even after a long time Move - to Example when determining the head density according to DIN EN ISO 787-11 or ASTM B 527 - step only marginal changes the particle size distribution on, which suggests that in the granules a firm bond of the powder constituents used was achieved.

Example 11

Production of a powdery Feedstocks made of easily redispersible granules (LRDG) for further processing via metal powder injection molding

By stirring the granules produced in Example 10 in alcohol, it is possible to expose the individual particles (Hastelloy C and tungsten carbide). By adding waxes, polypropylene and stabilizers with the simultaneous action of high shear forces on a shear roller at a sufficiently high process temperature, a homogeneous distribution of the powdered functional substances in the organic environment is achieved. The bubble-free mass is processed via a granulation system to an easily eligible and homogeneously melting cold granules. This can then be introduced into the feed system of a metal powder injection molding machine, heated and "sprayed" with process parameters to be determined (temperature, pressure, pressure change, holding pressure, cooling time in the injection mold, etc.) Thereafter, the residual thermal debinding is carried out by slow heating of the specimens under hydrogen (heating rate of 1 K / min from room temperature to 600 ° C.) In the same furnace, the presintering of the parts takes place at to a temperature of 1000 ° C. These samples are then sintered in a vacuum oven at a pressure of about 10 ^-2 to 10 ^-3 mbar (heating at 5 K / min from room temperature to 1250 ° C, 2h hold at 1250 ° C and cooling with 10 K) / min to room temperature).

Example 12

Production of a component by cold powder rolling

The Granules VSP-712 and KON-712 produced in Example 2 are successively placed in the nip of a vertical powder rolling machine and pressed. As a result of this pressure arises in the case of VSP-712 a good manageable sheet with a green strength from 2 to 10 MPa. For the granulate KON-712 fails to remove specimens on which reliable the green strength could determine.

By a thermal aftertreatment, debinding and sintering as under Example 11, it is possible to produce a sheet of VSP-712, that - depending on the chosen one Sintering temperature - tight (93 up to 98% of the theoretical density) or porous (60 to approx. 90% the theoretical density). Despite the low density of the porous structure these sheets still have a strength of at least 50-100 MPa.

Example 13

Component through powder rolling - sheet metal production

The in Example 2 prepared granules VSP-712 and KON-712 as a loose powder bed debinded and pre-sintered for stabilization (solidification) of the granules. This is done under the conditions described in Example 5 for Debinding / presintering up to 1000 ° C. After defragmentation, including classification to -50 +25 μm as in Example 9 was described, the resulting granules each by Pulse rolls to a green ribbon processed. The strength of the green tape is sufficient in the case of granules VSP-712 for a further processing by sintering. The fragments out KON-712 are for the desired further processing to a sheet unsuitable. He follows the sintering of green tape VSP-712 at a temperature of 1300 ° C, as described in Example 5, can have a density of over 92% of the theoretical density can be achieved.

Example 14

Component through warm re-compaction by rolling

The Green ribbon described in Example 13 is not necessarily compacted by sintering. An easy way The compaction consists in the green tape before entering in a rolling gap inductively under an inert protective gas atmosphere (argon) at 1100 ° C to warm up and subject it to intense pressure at this temperature. From this way, a sheet-metal component is created in a very simple way in which by varying the nip a complete compaction (> 98% of the theoretical density) or a desired residual porosity (50 to 90% of the theoretical density) can be adjusted. Here too shows the variant KON-712 a lower green strength to a sintered Get component.

Example 15

Remove part by tape casting and sintering

outgoing and based on the route described in Example 10, an easy to produce redispersible powder mixture, a granulate is produced, that only from Hastelloy C powder consists. The tungsten carbide content is waived to only one To manufacture made of an alloy sheet metal.

Analogous and based on the processing described in Example 11 Intensive grinding produces a film-pourable, non-porous mass.

These Mass is by squeegee applied continuously on a smooth surface. After a Drying is a filled with metal powder foil with organic Ingredients as green in front, which is a rubber-like Texture. This green is now a debinder subjected by heating at a rate of 0.1 K / min from room temperature to 600 ° C heated becomes. Subsequently, will the part of a sintering under the conditions described in Example 5 subjected to an increase in strength. In this Step typically occurs a linear shrinkage. These can - ever to sintering temperature and duration -10 to 25%.

Example 16

Component with "normal" porosity

One green compact produced analogously to Example 15 is produced with a punching tool in the form of a dot matrix printer (punches as needles with a diameter formed from 0.1 to 0.5 mm) treated so that tubular disturbances - perpendicular to the surface normal - remain behind.

To debindering and sintering under those described in Example 5 Conditions arise a sheet, which consists of dense material areas and normal to the surface lying pore channels consists. By the number and the diameter of these channels can in a simple way, the flow resistance adjust without the particle size of the powder particles directly plays a role, what for the setting of any corrosion and oxidation properties may be significant if very fine powder particles are used come.

Example 17

Mixture of VSP and organic Placeholders for the production of fine-celled porous structures

From 3.7 kg of PZD powder (VSP-711), 148 g of powdered (<30 ... 50 μm) polymethyl methacrylate (PMMA) and a sufficient amount of a mixture of benzene (about 10% by volume) and ethyl alcohol (approx 90% by volume), in a kneader, a bubble-free feedstock having a "honey-like" viscosity is prepared, followed by 0.67 1 bead (∅ 1 to 1.5 mm) of foamed polystyrene mixed into this kneader in the kneader. Volume 0.9 ... 1.1 1) is placed in a flat ceramic mold (about 30 × 30 × 1.5 cm ³ ) and dried.The resulting green body is heated to about 400 ° C by slow heating (0.5 K / min) under hydrogen from the organic constituents (polystyrene placeholder, PMMA, residual solvent) .Then the molding is heated in the same furnace with 5 K / min from room temperature to 1000 ° C. The finish-sintering takes place in a Vacuum oven (10 ^-2 -10 ^-3 mbar) by the pre-sintered samples from room temperature at 10 k / min brought to 1300 ° C and d place to be kept for 2 h. Compared to the initial volume (about 1 1), the volume of the finished sintered body has decreased to about 0.4 1. This corresponds to a linear shrinkage of approx. 26%. The pores (due to the placeholders) have been reduced from originally 1 to 1.5 mm in the green state to 0.74 to 1.1 mm, in the metallic range a material density of about 7.4 g / cm ^{3 is} achieved.

Example 18

Mechanical properties a hot pressed Fe22Cr7V0,3Y alloy

The preparation of the PZD powder is carried out in analogy to Example 1, wherein deviating from Besipiel 1 as educt (instead of Nimonic ^® 90 powder) an atomized Fe22Cr7V0,3Y alloy was used.

Out the correspondingly prepared PZD powder and conventional (spherical) Powders (-25 microns, -53 microns / + 25 microns) were the processable powder mixtures summarized in Table 3 produced in an Eirich mixer.

Table 3: Fe22Cr7V0.3Y powder with different contents of PZD powders

In front processing by hot pressing Submissions from 18.2, 18.3 and 18.4 are accompanied by a childbirth a heating rate of 2 K / min from room temperature to 600 ° C under hydrogen subjected. The hot pressing takes place under the following conditions: 1150 ° C / 2h / 35 MPal Argon 4.8 in one Graphite tool. After the hot pressing The temperature is lowered at about 5 to 15 K / min, to room temperature is reached. The resulting discs have a diameter of about 100 mm. From you by water jet cutting tensile test samples prepared in analogy to Example 1 and to the same thickness (about 3.4 mm) ground. All samples show almost identical material densities between 7.55 and 7.50 g / cm3. The results of the mechanical tensile test at Room temperature are summarized in Table 4.

Of the Table 4 shows that the strength values Rp0,2 and Rm for all variants containing PZD powder are better (Rp0.2: + 5-70% / Rm: + 20-50 %). With regard to elongation (At-Fmax: elastic and plastic Proportion) has 18.1 the best values, the PZD-containing variants achieve At-Fmax values between 95 and 45%. Considered you about it addition, the fact that only the variants 18.2, 18.3 and 18.4 at all can be processed by pressing and sintering, arise the basic advantages the metallic powder mixtures according to the invention.

Table 4: Mechanical test results (Rp0,2, Rm and At-Fmax) for hot-pressed FeCrVY samples

Example 19

mechanical Properties of "free sintered Fe22Cr7V0.3Y powder compacts By mixing the powder mixtures 18.1, 18.2 18.3 and 18.4 mixed with Licowax as a pressing aid gives the Powder mixtures 19.1, 19.2 19.3 and 19.4. With these it is possible by uniaxial pressing molding in the form of tension rods (A (area in pressing direction): 6.35 cm 2, 1 (length in pressing direction): 4-5 mm, p: 700 MPa). The amount of Licowax is chosen in each case so that a total of 4 wt% of organic components are contained in the compact. This high salary is only for the PZD-free variant (18.1 or 19.1) necessary for it at all succeeds, from it compacts with sufficient green strength to obtain. For better comparability, the remaining powders provided with the same amount of pressing aids.

To The moldings were manufactured a debindering (2 K / min from room temperature to 600 ° C) under Subjected to hydrogen. In a cold wall oven with Mo heater (Fa. Thermal Technology) then sintered at 4 different Temperatures (1290, 1310, 1340 and 1350 ° C) under argon 4.8. The heating up takes place at 10 K / min, the maximum temperature was maintained for 2 h. After sintering, the samples became 10 at a cooling rate cooled to room temperature up to 15 K / min.

The Results are summarized in the following tables. In spite of greatest care succeeded in the case of 19.1 for 1310 and 1340 ° C not, testable To produce samples. This is not due to the sintering temperature, but on the errors that occurred after pressing, which are not easy are visible, but often already lead to destruction after debindering. Such problems occurred at 19.2 to 19.4 not on.

It It should be noted that (if determinable) all the properties of the Samples according to the invention (19.2, 19.3 and 19.4) were equal to or better than those of the conventional one Powder 19.1. At optimal temperatures became an improvement from Rm + 40-130% (Table 5.1), from Rp0.2 by 5-45% (Table 5.2), from At-Fmax + 0-270% (Table 5.3) and the density of 0-2% (Table 5.4). It is important to mention that so far no optimization of the sintering processes has taken place. After this is above all an improvement of the characteristics of 19.2 to 19.4, as these are due to their much lower Inclination to "pressing errors" distinct advantages to expect in the reproduction of the properties.

Table 5.1 "Influence of sintering temperature on the fracture stress of freely sintered Fe22Cr7V0.3Y samples"

Table 5.2 "Influence of sintering temperature on Rp0.2 of freely sintered Fe22Cr7V0.3Y samples"

Table 5.3 "Influence of sintering temperature on the elongation (At-Fmax) of free sintered Fe22Cr7V0.3Y samples"

Table 5.4 "Influence of sintering temperature on the density of freely sintered Fe22Cr7V0,3Y samples"

Example 20

Sintering behavior of Fe20C10A10.3Y alloys

The preparation of the PZD powder is carried out analogously to Example 1. Instead of Nimonic ^® 90 powder, an atomized Fe20Cr10A10.3Y alloy is used as starting material. The produced PZD powder is designated as 20.1 (PZD-720), the comparison powder as 20.2 (KON-720). Table 6 contains information on the processed powder blends. The pressing aid used was Licowax.

Table 6 "FeCrAlY Powder with 4% Pressing Aid"

The powders contained in Table 6 were processed into tensile bars (A: 6.35 cm 2, 1: 4 ... 5 mm, p: 700 MPa). By means of cut-offs (perpendicular to the pressing direction) test samples for dilatometer measurements were generated, which were then measured perpendicular to the pressing direction. In addition to a slow heating at a heating rate of 2 K / min from room temperature to 500 ° C. for debinding, the measurement included heating to 1320 ° C. at 10 K / min (holding time: 10 min) and heating at a cooling rate of 10 k / min from 1320 ° C to room temperature. The result is in 7 shown. The heating rate is represented by the lower unlabeled curve, the curve for 20.1 is solid, the curve for 20.2 is shown interrupted. Table 7 summarizes the results. From the course of the shrinkage, it can be seen that the Pulverpreßling undergoes an expansion from conventional powder 20.2 to about 1290 ° C as a result of the thermal expansion coefficient. A shrinkage maximum is not available up to a temperature of 1320 ° C. To achieve this, an increase in the sintering temperature would be required. By contrast, the sintering shrinkage of the PZD sample 20.1 already starts at about 1000 ° C. The first shrinkage maximum, not shown, is approximately 1300 ° C.

This corresponds to the behavior described in patent application PCT / EP / 2004/00736 of conventionally via atomization and the PZD powders produced there. It is also noteworthy that despite a lower starting density of 4.78 g / cm ³ (without organic constituents) of 20.1 after sintering, a density of about 7.5 g / cm ^{3 is} achieved. In contrast, the conventional sample 20.2 reaches only a density of about 5.7 g / cm ³ at an initial density of 5 g / cm ³ . This clarifies which advantages - apart from the manufacturability of powder compacts - are achieved in the sintering of PZD powders.

Table 7

Claims (18)

Metallic powder mixtures containing a component I, a metal, alloy and composite powder having a mean particle diameter D50 of at most 25 microns, determined by means of the particle measuring device Microtrac ^® X100 according to ASTM C 1070-01, obtainable by a method wherein the particles of a starting powder with larger average particle diameter are processed in a deformation step into platelet-shaped particles whose particle diameter to particle thickness ratio is between 10: 1 and 10000: 1 and these platelet-shaped particles are subjected to comminution grinding in the presence of a grinding aid in a further process step, a component II, which conventional metal powder (MLV) for powder metallurgical applications and / or a component III, which is a functional additive. Metallic powder mixtures containing a component I, a metal, alloy and composite powder whose shrinkage, determined by means of dilatometer according to DIN 51045-1, until reaching the temperature of the first shrinkage maximum at least 1.05 times the shrinkage of a product produced by atomization Metal, alloy or composite powder of the same chemical composition and the same average particle diameter D50, wherein the test powder before measuring the shrinkage on a Press density of 50% of the theoretical density is compressed, a Component II, which is a conventional Metal powder (MLV) for powder metallurgical applications is and / or a component III, which is a functional additive. Metallic powder mixture according to one of claims 1 or 2, characterized in that the components I or II are the same or different independently of one another and a composition of the formula I hA-iB-jC-kD (I) where A is one or more of Fe, Co, Ni, B for one or more of the elements V, Nb, Ta, Cr, Mo, W, Mn, Re, Ti, Si, Ge, Be, Au, Ag, Ru, Rh, Pd, Os, Ir, Pt, C for a or more of the elements Mg, Al, Sn, Cu, Zn, and D represent one or more of the elements Zr, Hf Mg, Ca, rare earth metal, and h, i, j, and k indicate the proportions by weight, where h, i, j and k are each independently 0 to 100% by weight, with the proviso that the sum of h, i, j and k is 100% by weight. Metallic powder mixture according to claim 3, characterized marked that A for one or more of the elements Fe, Co, Ni, B for one or more of the elements V, Cr, Mo, W, Ti, C for one or more of the elements Mg, Al and D for one or more of the elements Zr, Hf, Y, La stands. Metallic powder mixture according to claim 3 or 4, characterized in that h for 50 to 80% by weight, i for 15 up to 40% by weight, j for 0 to 15 wt .-%, and k for 0 to 5% by weight stands, with the proviso that the sum of h, i, j and k is 100% by weight. Metallic powder molding according to claim 1 or 2, where component I and / or II is an alloy selected from the group consisting of Fe20Cr10A10.3Y, Fe22Cr7V0.3Y, Ni17Mo15Cr6Fe5W1Co, FeCrVY, Ni20Cr16Co2.5Ti1.5Al, Ni53Cr20Co18Ti2.5Al1.5Fe1.5 and Ni57Mo17Cr16FeWMn Metallic powder mixture according to one or more the claims 1 to 6 containing conventional Processing aids or pressing aids Metallic powder mixture according to one or more the claims 1 to 7, which is a mixture of components I and II. Metallic powder mixture according to one or more the claims 1 to 8, which is a mixture of components I and III. Metallic powder mixture according to one or more the claims 1 to 9, which is a mixture of components I, II and III. Metallic powder mixture according to one or more the claims 1 to 10, wherein as component III a hard material, a lubricant or an intermetallic compound is contained. Metallic powder mixture according to one or more of claims 1 to 11, wherein as component III carbides, borides, nitrides, oxides, silicides, hydrides, diamonds; Carbides, borides and nitrides of the elements of Groups 4, 5 and 6 of the Periodic Table; Oxides of elements of Groups 4, 5 and 6 of the Periodic Table; Oxides of aluminum and rare earth metals; Silicides of aluminum, boron, cobalt, nickel, iron, manganese, molybdenum, tungsten, zirconium; Hydrides of tantalum, niobium, titanium, magnesium and tungsten; Graphite, sulfides, oxides, molybdenum sulfide, zinc sulfide, tin sulfide (SnS, SnS ₂ ), copper sulfide; Boron nitride, titanium boride or intermetallic compounds with special magnetic or electrical properties on rare earth cobalt or rare earth iron base are included. Metallic powder mixture according to one or more the claims 1 to 12, wherein as component III long-chain hydrocarbons, Waxes, paraffins, plastics, fully decomposable hydrides, refractory metal oxides, organic and / or inorganic salts are included. Metallic powder mixture according to one or more the claims 1 to 13, wherein as component III low molecular weight polyethylene or polypropylene, polyurethanes, polyacetal, polyacrylates, polystyrene, rhenium oxide, molybdenum oxide, Titanium hydride, magnesium hydride, tantalum hydride are included. Method for producing a molded article, wherein a metallic powder mixture according to one or more of claims 1 to 14 subjected to powder metallurgical molding process becomes. The method of claim 15, wherein the powder metallurgical Forming method selected is from the group consisting of pressing, sintering, slip casting, foil casting, wet powder spraying, Powder rollers (both cold and hot) Warm powder rolls), hot pressing and hot Isostatic pressing (Hot Isostatic Pressing, HIP for short), sintering HIP, Sintering powder beds, Cold isostatic pressing (CIP), especially with green processing, Thermal spraying and build-up welding. A shaped article obtainable by a process according to claim 15 or 16. A molded article containing a powder mixture according to one or more of claims 1 to 14.