EP1242642B1 - method for production of powder mixture or composite powder - Google Patents
method for production of powder mixture or composite powder Download PDFInfo
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- EP1242642B1 EP1242642B1 EP00991157A EP00991157A EP1242642B1 EP 1242642 B1 EP1242642 B1 EP 1242642B1 EP 00991157 A EP00991157 A EP 00991157A EP 00991157 A EP00991157 A EP 00991157A EP 1242642 B1 EP1242642 B1 EP 1242642B1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/16—Making metallic powder or suspensions thereof using chemical processes
- B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/04—Making non-ferrous alloys by powder metallurgy
- C22C1/05—Mixtures of metal powder with non-metallic powder
- C22C1/051—Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/16—Making metallic powder or suspensions thereof using chemical processes
- B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
- B22F9/20—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds
- B22F9/22—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds using gaseous reductors
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/16—Making metallic powder or suspensions thereof using chemical processes
- B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
- B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
- B22F2998/10—Processes characterised by the sequence of their steps
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
Definitions
- the present invention relates to a process for the preparation of powder mixtures or composite powders which consist of at least two types of powder or solid phases in disperse form and which are used as precursors for particle composites or as wettable powders for surface coatings.
- these composite powders contain high-melting metals (such as W and Mo) or hard materials (such as WC, TiC, TiN, Ti (C, N) TaC, NbC and Mo 2 C) or ceramic powders (such as TiB 2 and B 4 C) on the one hand and binding metals (such as Fe, Ni, Co, Cu and Sn) or mixed crystals and alloys of these binding metals on the other hand.
- particle composites hard metals, cermets, heavy metals and Functional materials with special electrical (contact and switching materials) and thermal properties (heat sinks).
- the effective properties of these particle composites e.g. Hardness, modulus of elasticity, Fracture toughness, strength and wear resistance, but also electrical and thermal conductivity are in addition to the properties and proportions of the phases especially by the degree of dispersion, the homogeneity and the topology of these Phases as determined by structural defects (pores, impurities).
- This Structural characteristics of the particle composites are in turn due to the powdery Raw materials and their powder metallurgical processing (pressing, sintering) determined to compact materials.
- Hard metals are particle composites from at least two phases, the WC hard material phase (97 - 70 m%) and the eutectic Co-WC binder metal phase (3 - 30 m%), which are formed by dissolving W and C in Co during liquid phase sintering and which WC particles bind.
- the hard metals can include other hard material phases such as the cubic (W, Ti) and (W, Ta / Nb) mixed carbides with proportions from 1 to 15 m% included. If the hard metals are particularly corrosive, the Co-based binder is completely or partially replaced by Ni, Cr (Fe) alloys. VC and Cr 3 C 2 ⁇ 1 m%) to control grain growth and microstructure.
- the hard material particles are carriers of hardness, wear resistance and high temperature properties, while the binder metals primarily determine fracture toughness, thermal shock resistance and flexural strength.
- Hard metals are characterized in particular by very favorable combinations of hardness and toughness as well as high temperature stability and wear / corrosion resistance. This is achieved in that either the hard material particles are fully dispersed in the binder metal or, with decreasing binder metal content, two mutually penetrating phase regions of hard material and binder are formed. During sintering, this structure runs parallel to the compaction of the compact.
- the densification during the sintering process takes place to 70-85% of the increase in density in the solid-phase sintering stage, ie the WC grains move into energetically preferred positions under the effect of the viscous flowing and wetting binder.
- the eutectic composition is finally achieved and the binding metal melts through the simultaneous diffusion of W and C into the co-particles.
- the state of the art of hard metal production can be found, for example, in SCHEDLER, Tungsten carbide for the practitioner, Düsseldorf 1988.
- the carbide composition are the separately produced hard material and binder metal powders first weighed, mixed and ground.
- the toilet powder is always carbide grade with their grain sizes in the range of 0.5 ... 50 ⁇ m mostly slightly agglomerated and must have sufficient chemical purity.
- By varying the toilet grain sizes and the binder metal content between 3 and 30 m% can important properties such as hardness, toughness and Wear resistance varies greatly and is adapted to the specific application become.
- US-A-5 248 328 describes a method comprising a component (SE metal) via a precipitation in a suspension
- SE metal component
- Hard material or a binder metal is mixed in relatively small amounts.
- hard material and binding metal are mixed and grind.
- the different types of wet grinding are used today Powder components transferred into a finely divided mixture.
- a grinding fluid serve organic liquids such as B. hexane, heptane, gasoline, tetralin, alcohol or acetone. Grinding liquid and medium (carbide balls) allow a highly disperse distribution of the powder particles, with increasing fineness and dispersity
- organic grinding fluid it increases moisture and Gas absorption and oxidation of the powder.
- After grinding it will Powder mixture by sieving from the grinding balls and by evaporation from the Grinding liquid separated, dried and granulated if necessary.
- the grinding takes place mainly in attritors and ball mills, sometimes also in vibrating mills.
- the currently dominant one that has been used on an industrial scale for around 20 years The form of drying is spray drying under inert gas, with simultaneous Granulation of the composite powder.
- the dried and optionally granulated Mixtures are pressed, extruded or injection molded (MIM) into molded parts processed and then sintered.
- the actual compression process are dewaxing, d. H. driving out pressing aids and presintering upstream for deoxidation and pre-compression. Sintering takes place either under vacuum or inert gas pressures up to 100 bar at temperatures between 1350 and 1500 ° C.
- the hard material particles be electrolytically mixed to coat a coating of the binder metal in order to remove the complex grinding with all to overcome their disadvantages.
- this procedure is cumbersome Handling is not suitable for the industrial scale and also has the disadvantage that only one metal, but not several mixed homogeneously on the Hard material particles can be applied since different metals in general have different electrochemical deposition potentials.
- WO 95/26843 (EP-A 752 922, US-A 5 529 804) describes a process hard particles in polyols with reducing properties, e.g.
- this method must be economically justifiable to achieve Yields of binder metals between 5 - 40 moles of reducing agent per mole Metal components are used and the resulting during the reduction volatile compounds (alkanals, alkanones, alkanoic acids) must be distilled off become. About the disposal of these unwanted by-products and the Remain the large amount of excess reducing agent, which is also by-products contains no information. The long reduction time required limits the throughput capacity of the process. These conditions inevitably lead to high procedural costs.
- WO 97/11805 the process of reduction with polyols is described in WO 95/26843 modified to reduce the enormous excess of reducing agents and improve profitability.
- the reduction reaction in liquid After consumption of a stoichiometric amount of polyol, based on the phase Metal insert, canceled to suppress the formation of unwanted by-products and to be able to recirculate the excess polyol.
- the hard metal intermediate is filtered and then dry under hydrogen at 550 ° C and a very long reduction time of approx. 24 h to the finished composite powder reduced.
- Ni-containing solution of the hard material suspended and by adding ammonia or a hydroxide is a metal compound on the surface of the hard material particles dejected.
- this intermediate product reduced at elevated temperature under hydrogen.
- the reduced amount used on polyols as solvents and reducing agents and the suppression of Side reactions must be carried out by means of a significantly longer reduction of the intermediate product can be compensated under hydrogen and at elevated temperature.
- alcohols are also used to dissolve metal compounds therein to reduce metal or alloy powder or on an im Precipitate solvent-dispersed substrate as a metal film.
- substrates include glass powder, Teflon, graphite, aluminum powder and fibers used.
- US-A 5 352 269 describes the Spray Conversion Process (NANODYNE Inc.).
- aqueous solutions e.g. B. W and Co contained in suitable concentrations and proportions and are prepared for example from ammonium metatungstate and cobalt chloride, spray dried.
- the metals W and Co are mixed at the atomic level in the amorphous precursor powders formed in the process.
- finely crystalline WC particles with coma dimensions of 20-50 nm are formed, which, however, are strongly agglomerated and interspersed with cobalt areas or are bound and have a diameter of approx.
- composite powder with very good homogeneity, dispersity and possibly also special topology of the components / phases produced thereby can be that the desired binder metal powder (phases) in submitted Suspensions that already like the other components of the composite powder contain high-melting metal or hard material or ceramic powder, as Oxalate can be felled.
- the present invention relates to a method according to claim 1.
- Metals with melting points above 2000 ° C. such as molybdenum, tungsten, tantalum, niobium and / or rhenium, are used as the high-melting metals.
- molybdenum and tungsten have gained technical importance.
- tungsten carbide, titanium carbide, titanium nitride, titanium carbonitride, tantalum carbide, niobium carbide, molybdenum carbide and / or their mixed metal carbides and / or mixed metal carbonitrides are suitable as hard materials, optionally with the addition of vanadium carbide and chromium carbide.
- TiB 2 or B 4 C are suitable as ceramic powders. Powders and mixtures of high-melting metals, hard materials and / or ceramic powders can also be used.
- the first type of powder can in particular be in the form of finely divided powders with medium Particle diameters down to more than 10 ⁇ m can be used.
- Cobalt, nickel, iron, copper and tin are used as binding metals and their alloys used
- the binder metals are used as precursor compounds in the form of their water-soluble salts and their mixtures used in aqueous solution.
- Suitable salts are chlorides, sulfates, nitrates or complex salts. by virtue of Chlorides and sulfates are generally preferred for ease of availability.
- Oxalic acid or water-soluble oxalates such as are suitable for the precipitation as oxalate Ammonium oxalate or sodium oxalate.
- the oxalic acid component can be aqueous Solution or suspension can be used.
- the first type of powder can be in the aqueous solution of the precursor compound the second type of powder and an aqueous solution or Suspension of the oxalic acid component are added. It is also possible to Oxalic acid component in powder form in the suspension, which is the first type of powder contains to stir.
- the first type of powder can also be in the aqueous solution or Suspension of the oxalic acid component and the aqueous solution of the precursor compound for the second type of powder.
- the two suspensions or the suspension are mixed with the Solution with vigorous stirring.
- the precipitation can be carried out continuously by simultaneous, continuous introduction into a flow reactor with continuous withdrawal of the precipitate. It can also be carried out discontinuously by presenting those containing the first powder type Suspension and initiation of the second precipitation partner take place. It can it to ensure a uniform precipitation over the precipitation reactor volume be expedient, the oxalate component in the form of a solid powder in the suspension from the first type of powder and solution of the precursor compound for the second type of powder stir in so that the oxalate component can be evenly distributed, before the precipitation occurs through its dissolution. You can also use the depot effect the use of a solid oxalate component the particle size for the precipitate Taxes.
- the oxalic acid component is preferably 1.02 to 1.2 times stoichiometric Amount based on the precursor compound used for the second type of powder.
- the concentration of the oxalic acid component in the precipitation suspension can be 0.05 to 1.05 mol / l, particularly preferably more than 0.6, particularly preferably be more than 0.8 mol / l.
- the solid mixture consists of precipitate and the first type of powder separated from the mother liquor. This can be done by filtration, centrifugation or Decanting is done.
- the solid mixture of the first type of powder and precipitate is treated under a reducing gas atmosphere at temperatures of preferably 350 to 650 ° C.
- Hydrogen or a hydrogen / inert gas mixture is preferably used as the reducing gas, more preferably a nitrogen-hydrogen mixture.
- the oxalate is completely broken down into gaseous components, some of which promote the reduction (H 2 O, CO 2 ; CO), and the second type of powder is produced by reduction to metal.
- the oxalate decomposition and reduction can be in the moving or static bed, for example in tube furnaces or rotary tube furnaces or push-through furnaces continuously or be carried out discontinuously and under flowing, reducing gases. Any are also suitable for carrying out solid gas reactions suitable reactors, such as fluidized bed furnaces.
- powder mixtures or composite powders obtainable according to the invention some of the powders of the first and second types as separate (“powder mixture”), partly as adhering (“composite powder”) components in extremely uniform Distribution essentially without formation of agglomerates. she can be processed without any further treatment.
- the powders are suitable for the production of hard metals, cermets, heavy metals, metal-bonded diamond tools or electrotechnical functional materials by sintem, optionally using organic binders for the production sinterable green body. They are also suitable for surface coating parts and tools, for example by thermal or plasma spraying or for processing by extrusion or metal injection molding (MIM).
- MIM metal injection molding
- a hard metal test was carried out with this powder without any other treatment according to the following procedure: producing a green body with a pressure of 150 MPa, heating the green body in vacuo at a rate of 20 K / min to 1100 ° C., holding for 60 minutes at this temperature, further heating at a rate of 20 K / min to 1400 ° C, holding for 45 minutes at this temperature, cooling to 1100 ° C, holding for 60 minutes at this temperature and then cooling to room temperature.
- tungsten carbide of the DS 80 type (supplier HCStarck) and 1 g of carbon black were homogeneously dispersed over a period of 60 minutes in a suspension of 465.4 g of oxalic acid dihydrate in 1.6 l of deionized water. Then 2 l of Co solution with 893.4 g of CoCl 2 * 6H 2 O were added quickly and the mixture was stirred for a further 10 min to complete the precipitation. After filtration and washing of the precipitate with deionized water (until chloride was no longer detectable in the outlet), the mixture was spray-dried and then in a tubular oven for 90 min at 420 ° C.
- the resulting composite powder contained 8.24% Co, 5.63% total carbon, 0.06% carbon free (according to DIN ISO 3908), 0.395% oxygen and 0.0175% nitrogen.
- the SEM images show a well deagglomerated mixture (FIG. 3) in SEI mode and a very uniform distribution of the cobalt in the composite powder (FIG. 4) in the case of emergence-dispersive evaluation.
- a hard metal test was carried out with this powder under conditions similar to those in Example 1 and the following properties were measured on the resulting sintered body: density 14.71 g / cm 3 , coercive force 19.1 kA / m or 240 Oe, hardness HV30 1626 kg / mm 2 or HRA 92.0 , magnetic saturation 157.8 G cm 3 / g or 15.8 ⁇ Tm 3 / kg, low porosity A00 B02 C00 and a homogeneous, microdisperse structure.
- the resulting composite powder contained 3.60% Co, 2.50% Ni, 2.56% Fe, 5.53% total carbon, 0.07% carbon free, 0.596% oxygen and 0.0176% nitrogen.
- the SEM analysis shows a well deagglomerated composite powder (Fig. 5) with an even distribution of Fe, Co and Ni (Fig. 6-8).
- the resulting composite powder had the following chemical composition: 4.46% Ni, 4.26% Fe, 5.52% total carbon, 0.08% carbon-free, 0.653% oxygen, 0.0196% nitrogen, the rest tungsten.
- the SEM analysis shows a well deagglomerated powder (FIG. 9) with a uniform Fe and Ni distribution (FIGS. 10 and 11).
- tungsten metal powder grade HC 100, supplier HCStarck
- tungsten metal powder grade HC 100, supplier HCStarck
- a solution of 1.592 kg of CuS0 4 * 5H 2 O in 6 l of deionized water was added and the precipitated suspension formed was stirred for a further 30 minutes to complete the precipitation and homogenize the suspension.
- the precipitate was subsequently filtered, washed free of anions with deionized water, then spray-dried and reduced in a tubular oven at 500 ° C. for 120 minutes under hydrogen.
- the resulting composite powder contained 80.78% W and 18.86% Cu in addition to a residual oxygen content of 0.37%.
- the SEM analysis shows a very fine-grained powder (FIG. 12) and, in the case of energy-dispersive evaluation, a uniform distribution of the copper in the tungsten powder matrix (FIG. 13).
Abstract
Description
Die vorliegende Erfindung betrifft ein Verfahren zur Herstellung Pulvermischungen bzw. Verbundpulver, die aus mindestens zwei Pulverarten bzw. Feststoffphasen in disperser Form bestehen und die als Vorstoffe für Teilchenverbundwerkstoffe oder als Spritzpulver für Oberflächenbeschichtungen eingesetzt werden. Hinsichtlich der Zusammensetzung enthalten diese Verbundpulver hochschmelzende Metalle (wie z. B. W und Mo) oder Hartstoffe (wie z.B. WC, TiC, TiN, Ti(C,N) TaC, NbC und Mo2C) oder keramische Pulver (wie z.B. TiB2 und B4C) einerseits und Bindemetalle (wie z. B. Fe, Ni, Co, Cu und Sn) oder Mischkristalle und Legierungen dieser Bindemetalle andererseits.The present invention relates to a process for the preparation of powder mixtures or composite powders which consist of at least two types of powder or solid phases in disperse form and which are used as precursors for particle composites or as wettable powders for surface coatings. In terms of composition, these composite powders contain high-melting metals (such as W and Mo) or hard materials (such as WC, TiC, TiN, Ti (C, N) TaC, NbC and Mo 2 C) or ceramic powders (such as TiB 2 and B 4 C) on the one hand and binding metals (such as Fe, Ni, Co, Cu and Sn) or mixed crystals and alloys of these binding metals on the other hand.
Die wichtigsten Anwendungen als Teilchenverbunde sind Hartmetalle, Cermets, Schwermetalle und Funktionswerkstoffe mit speziellen elektrischen (Kontakt- und Schaltwerkstoffe) und thermischen Eigenschaften (Heat sinks).The most important Applications as particle composites are hard metals, cermets, heavy metals and Functional materials with special electrical (contact and switching materials) and thermal properties (heat sinks).
Die effektiven Eigenschaften dieser Teilchenverbunde wie z.B. Härte, Elastizitätsmodul, Bruchzähigkeit, Festigkeit und Verschleißwiderstand, aber auch elektrische und thermische Leitfähigkeit werden neben den Eigenschaften und Anteilen der Phasen vor allem durch den Dispersionsgrad, die Homogenität und die Topologie dieser Phasen so wie durch Strukturdefekte (Poren, Verunreinigungen) bestimmt. Diese strukturellen Charakteristika der Teilchenverbunde werden ihrerseits durch die pulverförmigen Vorstoffe und deren pulvermetallurgische Verarbeitung (Pressen, Sintern) zu kompakten Werkstoffen bestimmt.The effective properties of these particle composites, e.g. Hardness, modulus of elasticity, Fracture toughness, strength and wear resistance, but also electrical and thermal conductivity are in addition to the properties and proportions of the phases especially by the degree of dispersion, the homogeneity and the topology of these Phases as determined by structural defects (pores, impurities). This Structural characteristics of the particle composites are in turn due to the powdery Raw materials and their powder metallurgical processing (pressing, sintering) determined to compact materials.
Gemäß dem Stand der Technik gibt es verschiedene Technologien, um derartige Vorstoffe, d. h. Gemische aus mindestens zwei Pulvertypen herzustellen. Ohne Einschränkung der Allgemeinheit werden der Stand der Technik, die mit ihm verbundenen Nachteile und das Wesen dieser Erfindung am Beispiel der Hartmetalle und der W-Cu- und Mo-Cu-Verbunde dargestellt.According to the prior art, there are various technologies for such Precursors, d. H. To produce mixtures of at least two types of powder. Without restriction the general state of the art, the associated with it Disadvantages and the essence of this invention using the example of hard metals and the W-Cu and Mo-Cu composites are shown.
Hartmetalle sind Teilchenverbunde aus mindestens zwei Phasen, der WC- Hartstoffphase (97 - 70 m%) und der eutektischen Co-W-C-Bindemetallphase (3 - 30 m%), die sich durch Lösung von W und C in Co beim Flüssigphasensintern ausbildet und die WC-Teilchen bindet. Je nach Anwendung (Schneidwerkzeuge für Stähle, Stahlund Grauguss, Nichteisenmetalle, Beton, Stein und Holz oder Verschleiß- und Konstruktionsteile) können die Hartmetalle weitere Hartstoffphasen wie die kubischen (W, Ti)- und (W, Ta/Nb)-Mischcarbide mit Anteilen von 1 bis 15 m % enthalten. Bei besonders starker korrosiver Beanspruchung der Hartmetalle wird der Co-basierte Binder ganz oder teilweise durch Ni,Cr(Fe)-Legierungen ersetzt und bei Feinstkornhartmetallen dienen Dopezusätze wie z. B. VC und Cr3C2 ≤ 1 m %) zur Steuerung von Komwachstum und Gefügeausbildung.Hard metals are particle composites from at least two phases, the WC hard material phase (97 - 70 m%) and the eutectic Co-WC binder metal phase (3 - 30 m%), which are formed by dissolving W and C in Co during liquid phase sintering and which WC particles bind. Depending on the application (cutting tools for steel, cast steel and cast iron, non-ferrous metals, concrete, stone and wood or wear and construction parts), the hard metals can include other hard material phases such as the cubic (W, Ti) and (W, Ta / Nb) mixed carbides with proportions from 1 to 15 m% included. If the hard metals are particularly corrosive, the Co-based binder is completely or partially replaced by Ni, Cr (Fe) alloys. VC and Cr 3 C 2 ≤ 1 m%) to control grain growth and microstructure.
Die Hartstoffteilchen (WC und Mischcarbide) sind Träger der Härte, Verschleißfestigkeit und der Hochtemperatureigenschaften, während die Bindemetalle vorrangig die Bruchzähigkeit, die Thermoschockfestigkeit und die Biegebruchfestigkeit bestimmen. Hartmetalle zeichnen sich insbesondere durch sehr günstige Kombinationen von Härte und Zähigkeit sowie Hochtemperaturstabilität und Verschleiß-/Korrosionsfestigkeit aus. Dies wird dadurch erreicht, dass entweder die Hartstoffteilchen vollständig dispergiert im Bindemetall eingebunden vorliegen oder bei abnehmendem Bindemetallgehalt sich zwei einander durchdringende Phasenbereiche von Hartstoff und Binder herausbilden. Diese Strukturausbildung verläuft beim Sintern parallel zur Verdichtung des Presslings. Die Verdichtung während des Sinterprozesses erfolgt zu 70 - 85 % des Dichtezuwachses im Stadium der Festphasensinterung, d. h. die WC-Körner bewegen sich unter Wirkung des viskos fließenden und benetzenden Bindemetalls in energetisch bevorzugte Lagen, siehe z. B. GILLE, SZESNY, LEITNER; Proc. 14th Int. Plansee Seminar, Vol. 2, Reutte 1997. Über die gleichzeitig ablaufende Diffusion von W und C in die Co-Teilchen wird schließlich die eutektische Zusammensetzung erreicht und das Bindemetall schmilzt. The hard material particles (WC and mixed carbides) are carriers of hardness, wear resistance and high temperature properties, while the binder metals primarily determine fracture toughness, thermal shock resistance and flexural strength. Hard metals are characterized in particular by very favorable combinations of hardness and toughness as well as high temperature stability and wear / corrosion resistance. This is achieved in that either the hard material particles are fully dispersed in the binder metal or, with decreasing binder metal content, two mutually penetrating phase regions of hard material and binder are formed. During sintering, this structure runs parallel to the compaction of the compact. The densification during the sintering process takes place to 70-85% of the increase in density in the solid-phase sintering stage, ie the WC grains move into energetically preferred positions under the effect of the viscous flowing and wetting binder. B. GILLE, SZESNY, LEITNER; Proc. 14 th Int. Plansee Seminar, Vol. 2, Reutte 1997. The eutectic composition is finally achieved and the binding metal melts through the simultaneous diffusion of W and C into the co-particles.
Danach laufen die restlichen 15 - 30 % der Verdichtung über weitere Teilchenumlagerungen und Porenauffüllung mit flüssigem Binder ab. Die Endphase der Verdichtung und Strukturausbildung erfolgt durch OSTWALD-Reifung, d.h. kleine Hartstoffteilchen gehen wegen des höheren Lösungsdruckes im flüssigen Binder in Lösung und scheiden sich an größeren, benachbarten Hartstoffleilchen wieder aus. Diese Umlösung führt zu einer Komvergröberung und bestimmt die endgültige Hartstoff-Binder-Topologie. Im Hinblick auf die hier vorliegende Erfindung ist insbesondere der Tatbestand wichtig, dass bis zu 85 % der Verdichtung und Strukturbildung im Stadium der Festphasensinterung erfolgen und dieses wiederum stark durch die Eigenschaften und die Qualität der Vorstoffe, d. h. der Verbundpulver geprägt wird.After that, the remaining 15 - 30% of the compression runs through further particle rearrangements and filling the pores with liquid binder. The final stage of compression and structure formation takes place through OSTWALD maturation, i.e. small Hard material particles go in because of the higher solution pressure in the liquid binder Solution and excrete on larger, adjacent hard material particles. This redeployment leads to a coarsening of the grain and determines the final hard material-binder topology. With regard to the present invention is particular the fact that up to 85% of the compaction and structure formation is important at the stage of solid phase sintering and this in turn is strongly influenced by the Properties and quality of raw materials, d. H. the composite powder is embossed.
Der Stand der Technik der Hartmetallherstellung ist beispielsweise in SCHEDLER, Hartmetall für den Praktiker, Düsseldorf 1988 dargestellt. Gemäß der Hartmetallzusammensetzung werden die separat hergestellten Hartstoff- und Bindemetallpulver zunächst eingewogen, gemischt und vermahlen. Die WC-Ausgangspulver liegen je nach Hartmetallsorte mit ihren Korngrößen im Bereich von 0,5 ... 50 µm, sind meistens leicht agglomeriert und müssen ausreichende chemische Reinheit besitzen. Durch die Variation der WC-Komgrößen und der Bindemetallgehalte zwischen 3 und 30 m % können wichtige Eigenschaften wie Härte, Zähigkeit und Verschleißwiderstand in starkem Maße variiert und dem speziellen Einsatz angepasst werden.The state of the art of hard metal production can be found, for example, in SCHEDLER, Tungsten carbide for the practitioner, Düsseldorf 1988. According to the carbide composition are the separately produced hard material and binder metal powders first weighed, mixed and ground. The toilet powder is always carbide grade with their grain sizes in the range of 0.5 ... 50 µm mostly slightly agglomerated and must have sufficient chemical purity. By varying the toilet grain sizes and the binder metal content between 3 and 30 m% can important properties such as hardness, toughness and Wear resistance varies greatly and is adapted to the specific application become.
US-A-5 248 328 beschreibt ein Verfahren wobei eine Komponente (SE- Metall) über eine Fällung in einer Suspension einem Hartstoff oder einem Bindemetall in relativ kleinen Mengen zugemischt wird. Um ein Hartmetall herzustellen werden Hartstoff und Bindemetall gemischt und vermahlen.US-A-5 248 328 describes a method comprising a component (SE metal) via a precipitation in a suspension Hard material or a binder metal is mixed in relatively small amounts. In order to produce a hard metal, hard material and binding metal are mixed and grind.
Bei der heute durchgängig angewandten Nassmahlung werden die verschiedenen Pulverbestandteile in ein feinstdisperses Gemenge überführt. Als Mahlflüssigkeit dienen organische Flüssigkeiten wie z. B. Hexan, Heptan, Benzin, Tetralin, Alkohol oder Aceton. Mahlflüssigkeit und -medium (Hartmetallkugeln) ermöglichen zwar eine hochdisperse Verteilung der Pulverteilchen, mit steigender Feinheit und Dispersität setzt jedoch trotz der organischen Mahlflüssigkeit verstärkt eine Feuchtigkeitsund Gasaufnahme sowie eine Oxidation der Pulver ein. Nach der Mahlung wird das Pulvergemisch über Absieben von den Mahlkugeln und über Verdampfen von der Mahlflüssigkeit getrennt, getrocknet und gegebenenfalls granuliert. Die Mahlung erfolgt vorwiegend in Attritoren und Kugelmühlen, manchmal auch in Schwingmühlen. Die gegenwärtig dominierende und großtechnisch seit ca. 20 Jahren angewandte Form der Trocknung ist die Sprühtrocknung unter Inertgas, mit gleichzeitiger Granulierung der Verbundpulver. Die getrockneten und gegebenenfalls granulierten Mischungen werden gepresst, stranggepresst oder über Spritzguss (MIM) zu Formteilen verarbeitet und anschließend gesintert. Dem eigentlichen Verdichtungsprozess sind das Entwachsen, d. h. das Austreiben von Presshilfsmitteln sowie das Vorsintern zur Desoxidation und Vorverdichtung vorgeschaltet. Die Sinterung erfolgt entweder unter Vakuum oder Inertgasdrücken bis zu 100 bar bei Temperaturen zwischen 1350 und 1500 °C.The different types of wet grinding are used today Powder components transferred into a finely divided mixture. As a grinding fluid serve organic liquids such as B. hexane, heptane, gasoline, tetralin, alcohol or acetone. Grinding liquid and medium (carbide balls) allow a highly disperse distribution of the powder particles, with increasing fineness and dispersity However, despite the organic grinding fluid, it increases moisture and Gas absorption and oxidation of the powder. After grinding, it will Powder mixture by sieving from the grinding balls and by evaporation from the Grinding liquid separated, dried and granulated if necessary. The grinding takes place mainly in attritors and ball mills, sometimes also in vibrating mills. The currently dominant one that has been used on an industrial scale for around 20 years The form of drying is spray drying under inert gas, with simultaneous Granulation of the composite powder. The dried and optionally granulated Mixtures are pressed, extruded or injection molded (MIM) into molded parts processed and then sintered. The actual compression process are dewaxing, d. H. driving out pressing aids and presintering upstream for deoxidation and pre-compression. Sintering takes place either under vacuum or inert gas pressures up to 100 bar at temperatures between 1350 and 1500 ° C.
Dieser oben skizzierte, großtechnisch dominierende Standardprozess der Hartmetallherstellung hat hinsichtlich der Mischungsfertigung (Verbundpulverherstellung) durch Nassmahlung folgende Nachteile:
- Der Prozess ist zeit-, energie- und kostenintensiv. Typischerweise liegen die Mahldauem in Attritoren bei 8 - 15 h, in Kugelmühlen bei 50 - 120 h und wegen der organischen Mahlflüssigkeiten ist exgeschützte Anlagentechnik notwendig. Die Anlagentechnik ist außerdem sehr platzaufwendig, da in einem Mahlgefäß nur ca. 20 % des Volumens durch die Pulvermischung, der Rest durch Leerraum, Mahlkugeln und -flüssigkeit beansprucht werden.
- Der Verschleiß der teuren Mahlkugeln (Hartmetall) und der Mahlgefäße (V2A-Stahl) verursacht hohe Kosten und Verunreinigungen der Mischung.
- Die Feuchtigkeits- und Gasaufnahme führt zur Oxidation der Pulver, behindert das Sinterverhalten und kann zur Porosität und damit zur Verschlechterung von Eigenschaften, insbesondere der Festigkeit, führen. Dem muss durch entsprechend aufwendige Maßnahmen beim Vorsintem und Sintern entgegengewirkt werden, z. B. durch Desoxidation mit H2 und ausreichende Entgasung vor dem Dichtsintern.
- Die Duktilität der Bindemetalle kann beim Mahlen dazu führen, dass die Pulver nicht nur deagglomeriert oder feiner dispergiert werden, sondern im Gegenteil zu flachen Scheiben (flakes) oder anderweitig ungünstigen Formen plastisch verformt und ausgeschmiedet werden. Dies tritt insbesondere bei den plastisch gut verformbaren Bindemetallen mit kfz-Struktur auf und kann im gesinterten Hartmetall zur inhomogenen Bindenrerteilung und zu festigkeitsmindemden Poren führen.
- Die Nassmahlung kann bestenfalls eine vollständige Deagglomeration, ein teilweises Aufbrechen von Primärteilchen und eine homogene, feinstdisperse Verteilung der Pulverkomponenten bewirken. Es ist jedoch nicht möglich, eine spezielle, für die weitere Verarbeitung vorteilhafte Phasentopologie wie beispielsweise die Beschichtung der Hartstoffteilchen mit Bindemetall (composite sphere) zu erreichen.
- The process is time, energy and cost intensive. Typically, grinding times in attritors are 8 - 15 h, in ball mills 50 - 120 h and because of the organic grinding fluids, ex-protected plant technology is necessary. The system technology is also very space-consuming, since only about 20% of the volume in a grinding vessel is used by the powder mixture, the rest by empty space, grinding balls and liquid.
- The wear of the expensive grinding balls (hard metal) and the grinding vessels (V2A steel) causes high costs and contamination of the mixture.
- Moisture and gas absorption leads to oxidation of the powder, hinders sintering behavior and can lead to porosity and thus to deterioration in properties, in particular strength. This must be counteracted by correspondingly complex measures during pre-sintering and sintering, e.g. B. by deoxidation with H 2 and sufficient degassing before the dense sintering.
- The ductility of the binding metals during grinding can result in the powders not only being deagglomerated or dispersed more finely, but, on the contrary, being plastically deformed and forged into flat disks (flakes) or other unfavorable shapes. This occurs particularly in the case of the plastically easily deformable binder metals with a motor vehicle structure and can lead to inhomogeneous binder distribution and to pores that reduce strength in the sintered hard metal.
- At best, wet grinding can result in complete deagglomeration, a partial breakdown of primary particles and a homogeneous, finely dispersed distribution of the powder components. However, it is not possible to achieve a special phase topology which is advantageous for further processing, such as coating the hard material particles with a binding metal (composite sphere).
Entsprechend diesen Nachteilen der Nassmahlung unter organischen Mahlflüssigkeiten, die gegenwärtig nahezu hundertprozentig angewandt wird, wurden verschiedene Vorschläge unterbreitet und Technologien entwickelt, um diese Nachteile zu beseitigen.Corresponding to these disadvantages of wet grinding under organic grinding liquids, which are currently used almost 100 percent, have been different Proposals and technologies developed to address these drawbacks remove.
So wird in der GB-A 346 473 vorgeschlagen, die Hartstoffpartike) elektrolytisch mit einem Überzug des Bindemetalls zu beschichten, um die aufwendige Mahlung mit all ihren Nachteilen zu umgehen. Dieses Verfahren ist jedoch wegen des umständlichen Handlings nicht für den industriellen Maßstab geeignet und besitzt darüber hinaus den Nachteil, dass nur ein Metall, aber nicht mehrerere homogen gemischt auf die Hartstoffpartikel aufgebracht werden können, da unterschiedliche Metalle im allgemeinen unterschiedliche elektrochemische Abscheidungspotentiale besitzen.In GB-A 346 473 it is proposed that the hard material particles) be electrolytically mixed to coat a coating of the binder metal in order to remove the complex grinding with all to overcome their disadvantages. However, this procedure is cumbersome Handling is not suitable for the industrial scale and also has the disadvantage that only one metal, but not several mixed homogeneously on the Hard material particles can be applied since different metals in general have different electrochemical deposition potentials.
In der WO 95/26843 (EP-A 752 922, US-A 5 529 804) wird ein Verfahren beschrieben, bei dem Hartstoffpartikel in Polyolen mit reduzierenden Eigenschaften, wie z.B. WO 95/26843 (EP-A 752 922, US-A 5 529 804) describes a process hard particles in polyols with reducing properties, e.g.
Ethylenglykol, unter Zusatz von löslichen Cobalt- oder Nickelsalzen dispergiert werden. Bei Siedehitze des Lösungsmittels und 5stündiger Reduktionszeit wird Cobalt oder Nickel auf den Hartstoffpartikeln abgeschieden. Das resultierende Verbundpulver ergibt tatsächlich ohne kostenintensive Mahlung nach Abtrennung des Feststoffes, Waschen, Trocknen, Pressen und Sintern dichte Gefügestrukturen in der Hartmetallegierung. Die beigefügten REM-Fotos lassen aber erkennen, dass relativ grobe Hartstoffpartikel mit Durchmessern um 3 - 5 µm zur Beschichtung mit jeweils einem Bindemetall eingesetzt wurden.Ethylene glycol, with the addition of soluble cobalt or nickel salts. At the boiling point of the solvent and 5 hours reduction time, cobalt or nickel deposited on the hard material particles. The resulting composite powder results in fact without costly grinding after separation of the solid, Washing, drying, pressing and sintering dense structures in the Hard metal alloy. However, the attached REM photos show that relative coarse hard material particles with diameters around 3 - 5 µm for coating with each a binding metal were used.
Weiterhin müssen bei diesem Verfahren zur Erzielung wirtschaftlich vertretbarer Ausbeuten an Bindemetallen zwischen 5 - 40 Mole Reduktionsmittel pro Mol Metallkomponente aufgewendet werden und die während der Reduktion entstehenden flüchtigen Verbindungen (Alkanale, Alkanone, Alkansäuren) müssen abdestilliert werden. Über die Entsorgung dieser unerwünschten Nebenprodukte und den Verbleib der großen Menge überschüssigen Reduktionsmittels, das auch Nebenprodukte enthält, werden keine Angaben gemacht. Die erforderliche lange Reduktionszeit schränkt die Durchsatzkapazität des Verfahrens ein. Diese Bedingungen führen zwangsläufig zu hohen Verfahrenskosten.Furthermore, this method must be economically justifiable to achieve Yields of binder metals between 5 - 40 moles of reducing agent per mole Metal components are used and the resulting during the reduction volatile compounds (alkanals, alkanones, alkanoic acids) must be distilled off become. About the disposal of these unwanted by-products and the Remain the large amount of excess reducing agent, which is also by-products contains no information. The long reduction time required limits the throughput capacity of the process. These conditions inevitably lead to high procedural costs.
Nach WO 97/11805 wird das Verfahren der Reduktion mit Polyolen nach WO 95/26843 modifiziert, um den enormen Überschuss an Reduktionsmitteln zu verringern und die Wirtschaftlichkeit zu verbessern. Die Reduktionsreaktion in flüssiger Phase wird nach Verbrauch einer stöchiometrischen Menge Polyol, bezogen auf den Metalleinsatz, abgebrochen, um die Bildung unerwünschter Nebenprodukte zu unterdrücken und das überschüssige Polyol rezirkulieren zu können. Das Hartstoff-Metall-Zwischenprodukt wird filtriert und nachfolgend auf trockenem Weg unter Wasserstoff bei 550 °C und sehr langer Reduktionszeit von ca. 24 h zum fertigen Verbundpulver reduziert. In einer alternativen Ausführungsform wird in einer wässrigen Cooder Ni-haltigen Lösung der Hartstoff suspendiert und durch Zufügen von Ammoniak oder einem Hydroxid eine Metallverbindung auf der Oberfläche der Hartstoffpartikel niedergeschlagen. Nach Abtrennung der Lösung wird dieses Zwischenprodukt bei erhöhter Temperatur unter Wasserstoff reduziert. Die verringerte Einsatzmenge an Polyolen als Lösungs- und Reduktionsmittel und das Unterdrücken von Nebenreaktionen muss durch eine deutliche längere Nachreduktion des Zwischenproduktes unter Wasserstoff und bei erhöhter Temperatur kompensiert werden.According to WO 97/11805, the process of reduction with polyols is described in WO 95/26843 modified to reduce the enormous excess of reducing agents and improve profitability. The reduction reaction in liquid After consumption of a stoichiometric amount of polyol, based on the phase Metal insert, canceled to suppress the formation of unwanted by-products and to be able to recirculate the excess polyol. The hard metal intermediate is filtered and then dry under hydrogen at 550 ° C and a very long reduction time of approx. 24 h to the finished composite powder reduced. In an alternative embodiment, in an aqueous cooder Ni-containing solution of the hard material suspended and by adding ammonia or a hydroxide is a metal compound on the surface of the hard material particles dejected. After separation of the solution, this intermediate product reduced at elevated temperature under hydrogen. The reduced amount used on polyols as solvents and reducing agents and the suppression of Side reactions must be carried out by means of a significantly longer reduction of the intermediate product can be compensated under hydrogen and at elevated temperature.
Gemäß US-A 5 759 230 werden ebenfalls Alkohole benutzt, um darin gelöste Metallverbindungen zum Metall- oder Legierungspulver zu reduzieren oder auf einem im Lösungsmittel dispergiertem Substrat als Metallfilm niederzuschlagen. Als Substrate werden unter anderem Glaspulver, Teflon, Graphit, Aluminiumpulver und Fasern eingesetzt.According to US-A 5 759 230 alcohols are also used to dissolve metal compounds therein to reduce metal or alloy powder or on an im Precipitate solvent-dispersed substrate as a metal film. As substrates include glass powder, Teflon, graphite, aluminum powder and fibers used.
Ein weiteres Verfahren beschreibt WO 95/26245 (US-A 5 505 902). Metallsalze der Eisengruppe, z.B. Co-acetat, werden in einem polaren Lösungsmittel, z.B. Methanol, gelöst und ein Komplexbildner, wie z.B. Triethanolamin, zugesetzt. Wahlweise kann ein Kohlenstoff-Träger, wie z.B. Zucker, zugesetzt werden. In dieser Lösung wird der gut deagglomerierte Hartstoff dispergiert und durch nachfolgendes Verdampfen des Lösungsmittels mit einer metallhaltigen organischen Schicht umhüllt. In der folgenden thermischen Verfahrensstufe wird zwischen 400-1100°C unter Stickstoff und/oder Wasserstoff die organische Hülle der Hartstoffpartikel ausgebrannt und danach in einem letzten Schritt bei ca. 700°C, vorzugsweise unter Wasserstoff, und mit Glühzeiten von 120-180 min. zum Verbundpulver reduziert. Statt Wasserstoff können auch andere reduzierende Gase oder Gasgemische eingesetzt werden. Nach Angabe können mit dem auf diese Weise entstandenen Verbundpulver unter üblichen Bedingungen Sinterkörper mit porenfreier Gefügestruktur erhalten werden. Die Nachteile dieses Verfahrens sind vergleichsweise hohe Lösungsmittelverluste, entsprechende sicherheitstechnische Vorkehrungen und zweifache thermische Behandlung, verfahrenstechnische Probleme durch das Handling mit hochviskosen Mischungen beim Verdampfen des Lösungsmittels und aufwendige Reinigung/Entsorgung der Zersetzungsprodukte beim Ausbrennen der organischen Hülle im ersten thermischen Verfahrensschritt. Another method is described in WO 95/26245 (US-A 5 505 902). Metal salts of Iron group, e.g. Co-acetate are in a polar solvent, e.g. methanol, dissolved and a complexing agent, e.g. Triethanolamine added. Optionally can a carbon carrier, e.g. Sugar. In this solution the well deagglomerated hard material dispersed and by subsequent evaporation of the solvent is coated with a metal-containing organic layer. In the following thermal process stage is between 400-1100 ° C under nitrogen and / or hydrogen burned out the organic shell of the hard material particles and then in a last step at approx. 700 ° C, preferably under hydrogen, and with glow times of 120-180 min. reduced to composite powder. Instead of hydrogen other reducing gases or gas mixtures can also be used. To Specification can be made with the composite powder created in this way under usual Conditions sintered body can be obtained with a pore-free structure. The Disadvantages of this process are comparatively high solvent losses, corresponding safety precautions and double thermal treatment, procedural problems due to handling with highly viscous Mixtures on evaporation of the solvent and expensive Cleaning / disposal of the decomposition products when the organic burns out Shell in the first thermal process step.
Die US-A 5 352 269 beschreibt den Spray Conversion Process (NANODYNE Inc.). Gemäß diesem Prozess werden zunächst wässrige Lösungen, die z. B. W und Co in geeigneten Konzentrationen und Anteilen enthalten und beispielsweise aus Ammoniummetawolframat und Kobaltchlorid hergestellt werden, sprühgetrocknet. In den dabei gebildeten, amorphen Precursorpulvern sind die Metalle W und Co auf atomarer Ebene gemischt. Bei einer nachfolgenden carbothermischen Reduktion und Carburierung unter H2/CH4-, H2/CO- und CO/CO2-Gasatmosphären entstehen feinstkristalline WC-Teilchen mit Komabmessungen von 20 - 50 nm, die jedoch stark agglomeriert und mit Kobaltbereichen durchsetzt bzw. gebunden sind und als hohlkugelförmige Aggregate Durchmesser von ca. 70 µm aufweisen. Obwohl die WC- und Co-Teilchen bei diesem Spray Conversion Prozess nicht mehr separat hergestellt werden und am Ende dieses Prozesses bereits als Mischung vorliegen, ist dennoch eine Mahlung notwendig, um die Homogenität der Phasenverteilung und vor allem das Press- und Schrumpfungsverhalten zu verbessern. Der entscheidende Nachteil dieser Verbundpulver liegt jedoch darin, dass die prozesstechnisch bedingte, niedrige Carburierungstemperatur (≤ 1000 °C) zu stark gestörten WC-Kristallgittern und dies wiederum zu starkem Komwachstum beim Sintern führt. Eine Anhebung der Carburierungstemperatur zur Ausbildung eines perfekteren Kristallgitters ist wegen der Anwesenheit des Bindemetalls nicht möglich, da sonst bereits ein Sinterprozess zwischen dem WC und Co einsetzen würde.US-A 5 352 269 describes the Spray Conversion Process (NANODYNE Inc.). According to this process, aqueous solutions, e.g. B. W and Co contained in suitable concentrations and proportions and are prepared for example from ammonium metatungstate and cobalt chloride, spray dried. The metals W and Co are mixed at the atomic level in the amorphous precursor powders formed in the process. In a subsequent carbothermal reduction and carburization under H 2 / CH 4 , H 2 / CO and CO / CO 2 gas atmospheres, finely crystalline WC particles with coma dimensions of 20-50 nm are formed, which, however, are strongly agglomerated and interspersed with cobalt areas or are bound and have a diameter of approx. 70 µm as hollow spherical aggregates. Although the WC and Co particles are no longer produced separately in this spray conversion process and are already available as a mixture at the end of this process, grinding is still necessary in order to improve the homogeneity of the phase distribution and above all the compression and shrinkage behavior. The decisive disadvantage of these composite powders, however, is that the process-related, low carburization temperature (≤ 1000 ° C) leads to severely disturbed WC crystal grids and this in turn leads to strong grain growth during sintering. An increase in the carburization temperature to form a more perfect crystal lattice is not possible due to the presence of the binding metal, since otherwise a sintering process between the toilet and the like would start.
Ein analoges Vorgehen wie bei den zuletzt beschriebenen Patenten für Hartmetallverbundpulver wird in den US-A 5 439 638, 5 468 457 und 5 470 549 für W-Cu-Verbundpulver und den daraus hergestellten Verbundwerkstoffen dargestellt. Diese W-Cu-Verbunde mit 5 - 30 m % Cu finden Einsatz bei elektrischen Kontakten und Schaltern sowie bei Heat sinks und werden bislang vorwiegend über das Tränken von porösen W-Sinterskelettkörpem mit flüssigem Cu hergestellt. Die zitierten Patente sollen die Schwierigkeiten, die derzeit noch mit dem rein pulvermetallurgischen Verfahren verbunden sind, abbauen und dieser Technologie zum Durchbruch verhelfen, indem verbesserte W-Cu-Verbundpulver eingesetzt werden. A procedure analogous to that of the recently described patents for composite carbide powder U.S. Patent Nos. 5,439,638, 5,468,457 and 5,470,549 to W-Cu composite powder and the composite materials produced from it. This W-Cu composites with 5 - 30 m% Cu are used for electrical contacts and Switches as well as heat sinks and are so far mainly about the impregnation of porous W-sintered skeleton body made with liquid Cu. The cited patents The difficulties that are currently encountered with the purely powder metallurgical process are said to be connected, dismantle and help this technology break through, by using improved W-Cu composite powders.
In der US-A 5 439 638 werden wegen des besseren Misch- und Mahlverhaltens zunächst W- und Cu-Oxidpulver miteinander vermahlen und anschließend mit H2 zu Metallgemischen reduziert. Um eine noch bessere Vermischung der Metallkomponenten W und Cu zu erreichen, werden gemäß den US-A 5 468 457 und 5 470 549 zunächst Komplexoxide wie z. B. das Kupferwolframat (Cu WO4) durch Glühen erzeugt. Bei der nachfolgenden Reduktion mit H2 wird die im Oxid auf atomarer Ebene vorliegende Mischung von W und Cu genutzt, um hochdisperse W- und Cu-Bereiche bzw. -teilchen im Metallgemisch zu erreichen (W und Cu sind ineinander faktisch nicht löslich). Obwohl die Feinheit und Dispersität der Pulver und der daraus hergestellten W-Cu-Verbunde nach diesem Verfahren deutlich besser als bei dem Tränkverfahren sind, wird dies mit einem relativ aufwendigen und teuren Verfahren, d.h. mit Wolframatsynthese, Reduktion und pulvermetallurgischer Weiterverarbeitung, erreicht. Außerdem müssen teure Ausgangsstoffe wie z.B. das Ammoniummetawolframat eingesetzt werden.In US Pat. No. 5,439,638, because of the better mixing and grinding behavior, W and Cu oxide powders are first ground together and then reduced to metal mixtures with H 2 . In order to achieve an even better mixing of the metal components W and Cu, according to US Pat. Nos. 5,468,457 and 5,470,549, complex oxides such as, for. B. the copper tungstate (Cu WO 4 ) generated by annealing. In the subsequent reduction with H 2 , the mixture of W and Cu present in the oxide at the atomic level is used to achieve highly disperse W and Cu areas or particles in the metal mixture (W and Cu are in fact not soluble in one another). Although the fineness and dispersity of the powders and the W-Cu composites produced from them are significantly better using this process than in the impregnation process, this is achieved with a relatively complex and expensive process, ie with tungstate synthesis, reduction and further powder metallurgical processing. In addition, expensive starting materials such as ammonium metatungstate have to be used.
All diese alternativen Verfahren vermeiden zwar die aufwendige Nassmahlung, sie haben aber immer noch die Nachteile, dass sie im technischen Maßstab entweder nicht realisierbar sind und/oder einen unverhältnismäßig großen Einsatz an Reduktionsmitteln erfordern, eine große Zahl und Menge unerwünschter Nebenprodukte erzeugen und lange Verfahrenszeiten benötigen. Die Nebenprodukte führen zu Entsorgungsproblemen und -kosten. Die langen Verfahrenszeiten verteuern das Produkt. Spezielle Topologien wie die Beschichtung der Hartstoffteilchen mit Bindemetallen lassen sich zwar gemäß GB-A 346 473 erreichen, eine großtechnische Umsetzung ist jedoch aus Verfahrens- und Kostengründen nie erfolgt.All of these alternative methods avoid the elaborate wet grinding, they but still have the disadvantages that they are on an industrial scale either are not feasible and / or a disproportionate use of reducing agents require a large number and quantity of undesirable by-products generate and require long process times. The by-products lead to disposal problems and costs. The long process times make the product more expensive. Special topologies such as the coating of hard particles with binding metals can be achieved in accordance with GB-A 346 473, is a large-scale implementation however, for procedural and cost reasons, never occurred.
Es wurde nun gefunden, dass Verbundpulver mit sehr guter Homogenität, Dispersität und gegebenenfalls auch spezieller Topologie der Komponenten/Phasen dadurch hergestellt werden können, dass die erwünschten Bindemetallpulver (-phasen) in vorgelegte Suspensionen, die bereits die anderen Komponenten des Verbundpulvers wie hochschmelzende Metall- oder Hartstoff- oder keramische Pulver enthalten, als Oxalat gefällt werden. It has now been found that composite powder with very good homogeneity, dispersity and possibly also special topology of the components / phases produced thereby can be that the desired binder metal powder (phases) in submitted Suspensions that already like the other components of the composite powder contain high-melting metal or hard material or ceramic powder, as Oxalate can be felled.
Nach der Mischfällung liegt eine Mehrkomponentensuspension mit mindestens zwei unterschiedlichen Feststoffphasen, z.B. den vorab suspendierten WC-Teilchen und den gefällten Co-, Fe-, Ni-, Cu-, Sn-Bindemetallen, vor. Dieses Reaktionsprodukt wird gewaschen und getrocknet, thermisch unter reduzierender Atmosphäre behandelt und kann dann, gegebenenfalls nach Agglomerierung, ohne weitere aufwendige Mahlung gepresst und gesintert werden. Die so hergestellten Sinterprodukte sind hinsichtlich Porosität, Gefügeausbildung und den mechanisch-physikalischen Eigenschaften den konventionell hergestellten Produkten mindestens gleichwertig oder überlegen.After the mixed precipitation there is a multi-component suspension with at least two different solid phases, e.g. the previously suspended toilet particles and the precipitated Co, Fe, Ni, Cu, Sn binder metals. This reaction product is washed and dried, thermally treated under a reducing atmosphere and can then, if necessary after agglomeration, without further complex Grinding pressed and sintered. The sintered products thus produced are with regard to porosity, microstructure and the mechanical-physical properties at least equivalent to the conventionally manufactured products or think.
Gegenstand der vorliegenden Erfindung ist ein Verfahren nach Anspruch 1.The present invention relates to a method according to claim 1.
Als hochschmelzende Metalle werden Metalle mit Schmelzpunkten oberhalb von 2000°C wie Molybdän, Wolfram, Tantal, Niob und/oder Rhenium verwendet. Technische Bedeutung haben insbesondere Molybdän und Wolfram erlangt. Als Hartstoffe sind insbesondere Wolframcarbid, Titancarbid, Titannitrid, Titancarbonitrid, Tantalcarbid, Niobcarbid, Molybdäncarbid und/oder deren Mischmetallcarbide und/oder Mischmetallcarbonitride geeignet, gegebenenfalls unter Zusatz von Vanadiumcarbid und Chromcarbid. Als keramische Pulver kommen insbesondere TiB2 oder B4C in Frage. Ferner können Pulver und Mischungen aus hochschmelzenden Metallen, Hartstoffen und/ oder keramischen Pulvern eingesetzt werden. Metals with melting points above 2000 ° C., such as molybdenum, tungsten, tantalum, niobium and / or rhenium, are used as the high-melting metals. In particular, molybdenum and tungsten have gained technical importance. In particular, tungsten carbide, titanium carbide, titanium nitride, titanium carbonitride, tantalum carbide, niobium carbide, molybdenum carbide and / or their mixed metal carbides and / or mixed metal carbonitrides are suitable as hard materials, optionally with the addition of vanadium carbide and chromium carbide. In particular, TiB 2 or B 4 C are suitable as ceramic powders. Powders and mixtures of high-melting metals, hard materials and / or ceramic powders can also be used.
Die erste Pulverart kann insbesondere in Form von feinteiligen Pulvern mit mittleren Teilchendurchmessern im Nanometerbereich bis zu mehr als 10 µm eingesetzt werden. Als Bindemetalle werden Cobalt, Nickel, Eisen, Kupfer und Zinn sowie deren Legierungen eingesetztThe first type of powder can in particular be in the form of finely divided powders with medium Particle diameters down to more than 10 µm can be used. Cobalt, nickel, iron, copper and tin are used as binding metals and their alloys used
Erfindungsgemäß werden die Bindemetalle als Vorläuferverbindungen in Form ihrer wasserlöslichen Salze und deren Mischungen in wässriger Lösung eingesetzt. Geeignete Salze sind Chloride, Sulfate, Nitrate oder auch Komplexsalze. Aufgrund der leichten Verfügbarkeit sind im allgemeinen Chloride und Sulfate bevorzugt.According to the invention, the binder metals are used as precursor compounds in the form of their water-soluble salts and their mixtures used in aqueous solution. Suitable salts are chlorides, sulfates, nitrates or complex salts. by virtue of Chlorides and sulfates are generally preferred for ease of availability.
Für die Fällung als Oxalat geeignet sind Oxalsäure oder wasserlösliche Oxalate wie Ammoniumoxalat oder Natriumoxalat. Die Oxalsäurekomponente kann als wässrige Lösung oder Suspension eingesetzt werden.Oxalic acid or water-soluble oxalates such as are suitable for the precipitation as oxalate Ammonium oxalate or sodium oxalate. The oxalic acid component can be aqueous Solution or suspension can be used.
Erfindungsgemäß kann die erste Pulverart in der wässrigen Lösung der Vörläuferverbindung der zweiten Pulverart suspendiert werden und eine wässrige Lösung oder Suspension der Oxalsäurekomponente zugegeben werden. Ferner ist es möglich, die Oxalsäurekomponente in Pulverform in die Suspension, die die erste Pulverart enthält, einzurühren.According to the invention, the first type of powder can be in the aqueous solution of the precursor compound the second type of powder and an aqueous solution or Suspension of the oxalic acid component are added. It is also possible to Oxalic acid component in powder form in the suspension, which is the first type of powder contains to stir.
Erfindungsgemäß kann aber auch die erste Pulverart in der wässrigen Lösung oder Suspension der Oxalsäurekomponente suspendiert werden und die wässrige Lösung der Vorläuferverbindung für die zweite Pulverart zugegeben werden. Vorzugsweise erfolgt die Vermischung der beiden Suspensionen bzw. der Suspension mit der Lösung unter kräftigem Rühren.According to the invention, however, the first type of powder can also be in the aqueous solution or Suspension of the oxalic acid component and the aqueous solution of the precursor compound for the second type of powder. Preferably the two suspensions or the suspension are mixed with the Solution with vigorous stirring.
Die Fällung kann kontinuierlich durch gleichzeitige, kontinuierliche Einleitung in einen Durchflußreaktor unter kontinuierlichem Abzug des Fällungsproduktes erfolgen. Sie kann ferner diskontinuierlich durch Vorlage der die erste Pulverart enthaltenden Suspension und Einleiten des zweiten Fällungspartners erfolgen. Dabei kann es zur Gewährleistung einer über das Fällungsreaktorvolumen gleichmäßigen Fällung zweckmäßig sein, die Oxalatkomponente in Form eines festen Pulvers in die Suspension aus erster Pulverart und Lösung der Vorläuferverbindung für die zweite Pulverart einzurühren, so dass die Oxalatkomponente gleichmäßig verteilt werden kann, bevor die Fällung durch deren Auflösung erfolgt. Femer lässt sich über die Depotwirkung des Einsatzes einer festen Oxalatkomponente die Teilchengröße für das Fällungsprodukt steuern.The precipitation can be carried out continuously by simultaneous, continuous introduction into a flow reactor with continuous withdrawal of the precipitate. It can also be carried out discontinuously by presenting those containing the first powder type Suspension and initiation of the second precipitation partner take place. It can it to ensure a uniform precipitation over the precipitation reactor volume be expedient, the oxalate component in the form of a solid powder in the suspension from the first type of powder and solution of the precursor compound for the second type of powder stir in so that the oxalate component can be evenly distributed, before the precipitation occurs through its dissolution. You can also use the depot effect the use of a solid oxalate component the particle size for the precipitate Taxes.
Bevorzugt wird die Oxalsäurekomponente in 1,02 bis 1,2-facher stöchiometrischer Menge, bezogen auf die Vorläuferverbindung für die zweite Pulverart eingesetzt.The oxalic acid component is preferably 1.02 to 1.2 times stoichiometric Amount based on the precursor compound used for the second type of powder.
Die Konzentration der Oxalsäurekomponente in der Fällungssuspension, bezogen auf den Beginn der Fällung, kann 0,05 bis 1,05 mol/l, besonders bevorzugt mehr als 0,6, insbesondere bevorzugt mehr als 0,8 mol/l betragen.The concentration of the oxalic acid component in the precipitation suspension, based on the beginning of the precipitation can be 0.05 to 1.05 mol / l, particularly preferably more than 0.6, particularly preferably be more than 0.8 mol / l.
Nach beendeter Fällung wird die Feststoffmischung aus Präzipitat und erster Pulverart von der Mutterlauge abgetrennt. Dies kann durch Filtration, Zentrifugieren oder Dekantieren erfolgen.After the precipitation has ended, the solid mixture consists of precipitate and the first type of powder separated from the mother liquor. This can be done by filtration, centrifugation or Decanting is done.
Vorzugsweise erfolgt anschließend eine Waschung mit entionisiertem Wasser zur Entfernung anhaftender Mutterlauge, insbesondere der Anionen der Vorläuferverbindung.This is preferably followed by washing with deionized water Removal of adhering mother liquor, especially the anions of the precursor compound.
Nach einem gegebenenfalls getrennten Trocknungsschritt wird die Feststoffmischung aus erster Pulverart und Präzipitat unter einer reduzierenden Gasatmosphäre bei Temperaturen von vorzugsweise 350 bis 650°C, behandelt. Bevorzugt wird als reduzierendes Gas Wasserstoff oder ein Wasserstoff /Inertgas-Gemisch, weiter bevorzugt ein Stickstoff-Wasserstoffgemisch eingesetzt. Dabei wird das Oxalat vollständig in gasförmige, zum Teil die Reduktion fördernde Komponenten (H2O, CO2; CO) zerlegt und die zweite Pulverart durch Reduktion zum Metall erzeugt. After an optionally separate drying step, the solid mixture of the first type of powder and precipitate is treated under a reducing gas atmosphere at temperatures of preferably 350 to 650 ° C. Hydrogen or a hydrogen / inert gas mixture is preferably used as the reducing gas, more preferably a nitrogen-hydrogen mixture. The oxalate is completely broken down into gaseous components, some of which promote the reduction (H 2 O, CO 2 ; CO), and the second type of powder is produced by reduction to metal.
Die Oxalatzersetzung und Reduktion kann im bewegten oder statischen Bett, beispielsweise in Rohröfen oder Drehrohröfen oder Durchschuböfen kontinuierlich oder diskontinuierlich und unter strsömenden, reduzierenden Gasen durchgeführt werden. Geeignet sind ferner beliebige für die Durchführung von Feststoff-Gasreaktionen geeignete Reaktoren, wie beispielsweise Wirbelschichtöfen.The oxalate decomposition and reduction can be in the moving or static bed, for example in tube furnaces or rotary tube furnaces or push-through furnaces continuously or be carried out discontinuously and under flowing, reducing gases. Any are also suitable for carrying out solid gas reactions suitable reactors, such as fluidized bed furnaces.
In den erfindungsgemäß erhältlichen Pulvermischungen bzw. Verbundpulvem liegen die Pulver der ersten und zweiten Art teilweise als getrennte ("Pulvermischung"), teilweise als aneinander haftende ("Verbundpulver") Komponenten in äußerst gleichmäßiger Verteilung im wesentlichen ohne Ausbildung von Agglomeraten vor. Sie können ohne jede weitere Behandlung weiterverarbeitet werden. Insbesondere sind die Pulver geeignet für die Herstellung von Hartmetallen, Cermets, Schwermetallen, metallgebundenen Diamantwerkzeugen oder elektrotechnischen Funktionswerkstoffen durch Sintem, gegebenenfalls unter Einsatz organischer Bindemittel zur Herstellung sinterfähiger Grünkörper. Sie sind weiter geeignet zur Oberflächenbeschichtung von Teilen und Werkzeugen beispielsweise durch thermisches oder Plasma-Spritzen oder zur Verarbeitung durch Strangpressen oder Metal Injection Molding (MIM).In the powder mixtures or composite powders obtainable according to the invention some of the powders of the first and second types as separate ("powder mixture"), partly as adhering ("composite powder") components in extremely uniform Distribution essentially without formation of agglomerates. she can be processed without any further treatment. In particular are the powders are suitable for the production of hard metals, cermets, heavy metals, metal-bonded diamond tools or electrotechnical functional materials by sintem, optionally using organic binders for the production sinterable green body. They are also suitable for surface coating parts and tools, for example by thermal or plasma spraying or for processing by extrusion or metal injection molding (MIM).
Die Erfindung wird ohne Beschränkung der Allgemeinheit durch die nachfolgenden Beispiele erläutert: The invention is without limitation of generality by the following Examples explained:
5,02 kg Wolframcarbid (Sorte WC DS 80, Lieferant H.C.Starck) wurden in 5 l Lösung dispergiert, die durch Auflösen von 2,167kg CoCl2*6H2O in entionisiertem Wasser hergestellt wurde. Unter ständigem Rühren wurde bei Raumtemperatur über eine Zeit von 20 min eine Lösung von 1,361 kg Oxalsäuredihydrat in 13 l entionisiertem Wasser zugegeben und weitere 60 min zur Vervollständigung der Fällung nachgerührt. Das Präzipitat wurde über eine Nutsche filtriert, mit entionisiertem Wasser gewaschen, bis im ablaufenden Filtrat kein Chlorid mehr nachweisbar war, und nachfolgend sprühgetrocknet. Das sprühgetrocknete Pulver wurde anschließend im Rohrofen bei 500°C unter Wasserstoff 90 min reduziert und an diesem Verbundpulver die chemische Zusammensetzung und die physikalischen Eigenschaften gemessen: Co 9,51 %; C total 5,52 %; C frei 0,04 % (nach DIN ISO 3908); O 0,263 %; FSSS 0,76 µm (ASTM B 330); Komverteilung mit Laserbeugungsmethode d10=1,01µm, d50=1,83µm, d90=3,08µm (ASTM B 822). Eine REM-Analyse (Fig. 1) mit energiedispersiver Auswertung (Fig. 2) zeigt eine gleichmäßige Verteilung des Cobalts zwischen den Wolframcarbidkömem.5.02 kg of tungsten carbide (grade WC DS 80, supplier HCStarck) were dispersed in 5 l of solution, which was prepared by dissolving 2.167 kg of CoCl 2 * 6H 2 O in deionized water. With constant stirring, a solution of 1.361 kg of oxalic acid dihydrate in 13 l of deionized water was added at room temperature over a period of 20 minutes and the mixture was stirred for a further 60 minutes to complete the precipitation. The precipitate was filtered through a suction filter, washed with deionized water until chloride was no longer detectable in the filtrate flowing off, and then spray-dried. The spray-dried powder was then reduced in a tube furnace at 500 ° C. under hydrogen for 90 minutes and the chemical composition and the physical properties were measured on this composite powder: Co 9.51%; C total 5.52%; C free 0.04% (according to DIN ISO 3908); O 0.263%; FSSS 0.76 µm (ASTM B 330); Grain distribution with laser diffraction method d10 = 1.01µm, d50 = 1.83µm, d90 = 3.08µm (ASTM B 822). A SEM analysis (Fig. 1) with energy-dispersive evaluation (Fig. 2) shows a uniform distribution of the cobalt between the tungsten carbide grains.
Mit diesem Pulver wurde ohne jede sonstige Behandlung ein Hartmetalltest nach fogender Verfahrensweise ausgeführt: Herstellen eines Grünkörpers mit einem Pressdruck von 150 MPa, Aufheizen des Grünkörpers im Vakuum mit einer Rate von 20 K/min auf 1100°C, 60 min Halten bei dieser Temperatur, weiteres Aufheizen mit einer Rate von 20 K/min auf 1400°C, 45 min Halten bei dieser Temperatur, Abkühlung auf 1100°C, 60 min Halten bei dieser Temperatur und dann Abkühlung auf Raumtemperatur. Am Sinterkörper wurden folgende Eigenschaften gemessen: Dichte 14,58 g/cm3; Koerzitivkraft 19,9 kA/m bzw. 250 Oe; Härte HV30 1580 kg/mm2 bzw. HRA 91,7; magnetische Sättigung 169,2 Gcm3/g bzw. 16,9 µTm3/kg; Porosität AOO B00 C00 nach ASTM B 276 (unter dem Lichtmikroskop bei 200facher Vergrößerung keine sichtbare Porosität) bei einwandfreier, mikrodisperser Gefügestruktur. Die lineare Schrumpfung des Sinterkörpers wurde mit 19,06 % gemessen.A hard metal test was carried out with this powder without any other treatment according to the following procedure: producing a green body with a pressure of 150 MPa, heating the green body in vacuo at a rate of 20 K / min to 1100 ° C., holding for 60 minutes at this temperature, further heating at a rate of 20 K / min to 1400 ° C, holding for 45 minutes at this temperature, cooling to 1100 ° C, holding for 60 minutes at this temperature and then cooling to room temperature. The following properties were measured on the sintered body: density 14.58 g / cm 3 ; Coercive force 19.9 kA / m or 250 Oe; Hardness HV 30 1580 kg / mm 2 or HRA 91.7; magnetic saturation 169.2 Gcm 3 / g or 16.9 µTm 3 / kg; Porosity AOO B00 C00 according to ASTM B 276 (under the light microscope at 200x magnification no visible porosity) with a perfect, micro-dispersed structure. The linear shrinkage of the sintered body was measured at 19.06%.
In einer Suspension von 465,4g Oxalsäuredihydrat in 1,6 l entionisiertem Wasser wurden in einer alternativen Ausführungsform 2000 g Wolframcarbid der Sorte DS 80 (Lieferant H.C.Starck) und 1 g Ruß über 60 min homogen dispergiert. Dann wurden 2 1 Co-Lösung mit 893,4 g CoCl2*6H2O schnell hinzugefügt und weitere 10 min zur Vervollständigung der Fällung gerührt. Nach Filtration und Waschung des Präzipitates mit entionisiertem Wasser (bis im Ablauf kein Chlorid mehr nachweisbar war) wurde die Mischung sprühgetrocknet und nachfolgend im Rohrofen 90 min bei 420°C in einer Atmosphäre aus 4 Vol.-% Wasserstoff und 96 Vol.-% Stickstoff reduziert. Das resultierende Verbundpulver enthielt 8,24 % Co, 5,63 % Kohlenstoff gesamt, 0,06 % Kohlenstoff frei (nach DIN ISO 3908), 0,395 % Sauerstoff und 0,0175 % Stickstoff. Die physikalischen Eigenschaften wurden mit FSSS 0,7 µm, Komgrößenverteilung mit Laserbeugungsmethode d10=0,87 µm, d50=1,77 µm und d90=3,32µm gemessen. Die REM-Aufnahmen zeigen in SEI-Mode ein gut deagglomeriertes Gemisch (Fig. 3) und bei emergiedispersiver Auswertung eine sehr gleichmäßige Verteilung des Cobalts im Verbundpulver (Fig. 4). Mit diesem Pulver wurde unter analogen Bedingungen wie im Beispiel 1 ein Hartmetalltest ausgeführt und am resultierenden Sinterkörper folgende Eigenschaften gemessen: Dichte 14,71 g/cm3, Koerzitivkraft 19,1 kA/m bzw. 240 Oe, Härte HV30 1626 kg/mm2 bzw. HRA 92,0, magnetische Sättigung 157,8 G cm3/g bzw. 15,8 µTm3/kg, eine geringe Porosität A00 B02 C00 und eine homogene, mikrodisperse Gefügestruktur.In an alternative embodiment, 2000 g of tungsten carbide of the DS 80 type (supplier HCStarck) and 1 g of carbon black were homogeneously dispersed over a period of 60 minutes in a suspension of 465.4 g of oxalic acid dihydrate in 1.6 l of deionized water. Then 2 l of Co solution with 893.4 g of CoCl 2 * 6H 2 O were added quickly and the mixture was stirred for a further 10 min to complete the precipitation. After filtration and washing of the precipitate with deionized water (until chloride was no longer detectable in the outlet), the mixture was spray-dried and then in a tubular oven for 90 min at 420 ° C. in an atmosphere of 4% by volume hydrogen and 96% by volume nitrogen reduced. The resulting composite powder contained 8.24% Co, 5.63% total carbon, 0.06% carbon free (according to DIN ISO 3908), 0.395% oxygen and 0.0175% nitrogen. The physical properties were measured with FSSS 0.7 µm, grain size distribution with laser diffraction method d10 = 0.87 µm, d50 = 1.77 µm and d90 = 3.32 µm. The SEM images show a well deagglomerated mixture (FIG. 3) in SEI mode and a very uniform distribution of the cobalt in the composite powder (FIG. 4) in the case of emergence-dispersive evaluation. A hard metal test was carried out with this powder under conditions similar to those in Example 1 and the following properties were measured on the resulting sintered body: density 14.71 g / cm 3 , coercive force 19.1 kA / m or 240 Oe, hardness HV30 1626 kg / mm 2 or HRA 92.0 , magnetic saturation 157.8 G cm 3 / g or 15.8 µTm 3 / kg, low porosity A00 B02 C00 and a homogeneous, microdisperse structure.
357,7 g CoCl2*6H2O, 266,04 g NiSO4*6H2O und 180,3 FeCl2*2H2O wurden mit entionisiertem Wasser zu 2 l Mischsalzlösung aufgelöst und darin 2 kg Wolframcarbid der Sorte DS 80 (Lieferant H.C.Starck) und 1 g Ruß über 60 min dispergiert. Als Fällungsmittel wurden 5 l Oxalsäurelösung mit 480,2 g (COOH)2*2H2O zugesetzt und nachfolgend weitere 10 min zur Vervollständigung der Fällung gerührt. Dann wurde filtxiert, der Niederschlag mit entionisiertem Wasser frei von Anionen gewaschen und nachfolgend im Rohrofen 90 min bei 500°C in einer Atmosphäre aus 96 Vol.-% Stickstoff und 4 Vol.-% Wasserstoff reduziert. Das entstandene Verbundpulver enthielt neben der Hauptkomponente Wolframcarbid 3,60 % Co, 2,50 % Ni, 2,56 % Fe, 5,53 % Kohlenstoff gesamt, 0,07 % Kohlenstoff frei, 0,596 % Sauerstoff und 0,0176 % Stickstoff. Die Korngröße wurde mit FSSS 0,7 µm gemessen und die Komgrößenverteilung mit dem Laserbeugungsverfahren mit d10=1,69 µm, d50=3,22 µm und d90=5,59 µm. Die REM-Analyse zeigt ein gut deagglomeriertes Verbundpulver (Fig. 5) mit gleichmäßiger Verteilung des Fe, Co und Ni (Fig. 6-8).357.7 g CoCl 2 * 6H 2 O, 266.04 g NiSO 4 * 6H 2 O and 180.3 FeCl 2 * 2H 2 O were dissolved with deionized water to 2 l mixed salt solution and 2 kg tungsten carbide of the type DS 80 ( Supplier HCStarck) and 1 g of carbon black dispersed over 60 min. 5 l of oxalic acid solution with 480.2 g (COOH) 2 * 2H 2 O were added as precipitant and the mixture was subsequently stirred for a further 10 min to complete the precipitation. The mixture was then filtered, the precipitate washed free of anions with deionized water and subsequently reduced in a tubular furnace for 90 min at 500 ° C. in an atmosphere of 96% by volume nitrogen and 4% by volume hydrogen. In addition to the main component tungsten carbide, the resulting composite powder contained 3.60% Co, 2.50% Ni, 2.56% Fe, 5.53% total carbon, 0.07% carbon free, 0.596% oxygen and 0.0176% nitrogen. The grain size was measured with FSSS 0.7 µm and the grain size distribution with the laser diffraction method with d10 = 1.69 µm, d50 = 3.22 µm and d90 = 5.59 µm. The SEM analysis shows a well deagglomerated composite powder (Fig. 5) with an even distribution of Fe, Co and Ni (Fig. 6-8).
In 2 l Lösung mit 300,4 g FeCl2*2H2O und 443,4 g NiSO4*6H2O wurden 2 kg Wolframcarbid der Sorte DS 80 und 1 g Ruß unter kräftigem Rühren über 60 min dispergiert. Zur Fällung des Fe und Ni wurden 489,3 g (COOH)2*2H2O, in 1,7 l entionisiertem Wasser aufgelöst, zugegeben und weitere 10 min zur Komplettierung der Fällung gerührt. Das Präzipitat wurde filtriert, mit entionisiertem Wasser frei von Anionen gewaschen und sprühgetrocknet. Dieses Vorläuferpulver wurde nachfolgend im Rohrofen 90 min bei 500°C in einem Gemisch aus 96 Vol.-% Stickstoff und 4 Vol.-% Wasserstoff reduziert. Das resultierende Verbundpulver zeigte folgende chemische Zusammensetzung: 4,46 % Ni, 4,26 % Fe, 5,52 % Kohlenstoff gesamt, 0,08 % Kohlenstofffrei, 0,653 % Sauerstoff, 0,0196 % Stickstoff, Rest Wolfram. Die Korngröße wurde mit FSSS 0,74 µm und die Komgrüßenverteilung mit Laserbeugungsverfahren mit d10= 1,92 µm, d50=3,55 µm und d90=6,10 µm bestimmt. Die REM-Analyse zeigt ein gut deagglomeriertes Pulver (Fig. 9) mit gleichmäßiger Feund Ni-Verteilung (Fig. 10 und 11). 2 kg of tungsten carbide of the DS 80 type and 1 g of carbon black were dispersed in 2 l of solution with 300.4 g of FeCl 2 * 2H 2 O and 443.4 g of NiSO 4 * 6H 2 O with vigorous stirring for 60 min. To precipitate the Fe and Ni, 489.3 g (COOH) 2 * 2H 2 O, dissolved in 1.7 l of deionized water, were added and the mixture was stirred for a further 10 min to complete the precipitation. The precipitate was filtered, washed with deionized water free of anions and spray dried. This precursor powder was subsequently reduced in a tube furnace for 90 minutes at 500 ° C. in a mixture of 96% by volume nitrogen and 4% by volume hydrogen. The resulting composite powder had the following chemical composition: 4.46% Ni, 4.26% Fe, 5.52% total carbon, 0.08% carbon-free, 0.653% oxygen, 0.0196% nitrogen, the rest tungsten. The grain size was determined with FSSS 0.74 µm and the grain size distribution with laser diffraction methods with d10 = 1.92 µm, d50 = 3.55 µm and d90 = 6.10 µm. The SEM analysis shows a well deagglomerated powder (FIG. 9) with a uniform Fe and Ni distribution (FIGS. 10 and 11).
In eine Suspension von 872 g Oxalsäuredihydrat in 3,05 l entionisiertem Wasser wurden 1,6 kg Wolframmetallpulver (Sorte HC 100, Lieferant H.C.Starck) eingetragen und über 15 min Rührdauer homogen dispergiert. Dazu wurde eine Lösung von 1,592 kg CuS04 *5H2O in 6 l entionisiertem Wasser gegeben und die entstehende Fällsuspension weitere 30 min zur Komplettierung der Fällung und Homogenisierung der Suspension gerührt. Das Präzipitat wurde nachfolgend filtriert, mit entionisiertem Wasser frei von Anionen gewaschen, dann sprühgetrocknet und im Rohrofen bei 500°C 120 min unter Wasserstoff reduziert. Das resultierende Verbundpulver enthielt 80,78 % W und 18,86 % Cu neben einem Restsauerstoffgehalt von 0,37 %. Die Korngröße, gemessen mit dem FSSS-Verfahren, wurde mit 1,12 µm bestimmt und die Korngrößenverteilung unter Anwendung des Laserbeugungsverfahrens mit d10=1,64 µm, d50=5,31 µm, d90=12,68 µm. Die REM-Analyse zeigt ein sehr feinkörniges Pulver (Fig. 12) und bei energiedispersiver Auswertung eine gleichmäßige Verteilung des Kupfers in der Wolframpulver-Matrix (Fig. 13).1.6 kg of tungsten metal powder (grade HC 100, supplier HCStarck) were introduced into a suspension of 872 g of oxalic acid dihydrate in 3.05 l of deionized water and homogeneously dispersed over a stirring period of 15 minutes. For this purpose, a solution of 1.592 kg of CuS0 4 * 5H 2 O in 6 l of deionized water was added and the precipitated suspension formed was stirred for a further 30 minutes to complete the precipitation and homogenize the suspension. The precipitate was subsequently filtered, washed free of anions with deionized water, then spray-dried and reduced in a tubular oven at 500 ° C. for 120 minutes under hydrogen. The resulting composite powder contained 80.78% W and 18.86% Cu in addition to a residual oxygen content of 0.37%. The grain size, measured with the FSSS method, was determined to be 1.12 µm and the grain size distribution using the laser diffraction method was determined to be d10 = 1.64 µm, d50 = 5.31 µm, d90 = 12.68 µm. The SEM analysis shows a very fine-grained powder (FIG. 12) and, in the case of energy-dispersive evaluation, a uniform distribution of the copper in the tungsten powder matrix (FIG. 13).
Claims (8)
- A process for the preparation of powder mixtures or composite powders comprising at least one first type of powder from the group consisting of metals having a melting point above 2000°C, hard materials and ceramic powders and at least one second type of powder from the group consisting of binder metals, binder-metal mixed crystals and binder-metal alloys, wherein the second type of powder is formed from precursor compounds in the form of water-soluble salts in an aqueous suspension of the first type of powder by precipitation as oxalate, removal of the mother liquor and reduction to the metal, wherein the precursor compounds employed are water-soluble compounds of Co, Ni, Fe, Cu and/or Sn.
- A process as claimed in claim 1, characterized in that the first type of powder employed is a metal having a melting point above 2000°C, such as Mo and/or W, and/or a carbidic or nitridic hard material, such as WC, TiC, TiN, Ti (C,N), TaC, NbC and Mo2C, and/or mixed metal carbides thereof and/or ceramic powders, such as TiB2 or B4C.
- A process as claimed in claim 1 or 2, characterized in that the first type of powder is initially introduced in aqueous suspension containing the precursor(s) of the second type of powder in the form of dissolved salts, and oxalate and/or oxalic acid solution is added to the suspension.
- A process as claimed in claim 1 or 2, characterized in that the first type of powder is suspended in oxalate and/or oxalic acid solution, and the precursor(s) of the second type of powder is (are) added to the suspension in the form of a solution of its water-soluble salts.
- A process as claimed in one of claims 1 to 4, characterized in that the oxalic acid component is employed in a 1- to 2-fold, preferably a 1.02- to 1.2-fold, stoichiometric amount, based on the precursor compounds for the second type of powder.
- A process as claimed in one of claims 1 to 5, characterized in that the precipitation suspension has a concentration of from 0.05 to 1.05 mol/1 of oxalic acid component.
- A process as claimed in one of claims 1 to 6, characterized in that the precipitation is carried out with vigorous stirring.
- A process as claimed in one of claims 1 to 6, characterized in that the mixture or composite of the first type of powder and the precipitate is agglomerated before the reduction.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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DE19962015 | 1999-12-22 | ||
DE19962015A DE19962015A1 (en) | 1999-12-22 | 1999-12-22 | Compound powder mixtures used, e.g., for particle blasting, are produced using one powder type of a metal with a high melting point, hard material or ceramic together with a bonding metal |
PCT/EP2000/012484 WO2001046484A1 (en) | 1999-12-22 | 2000-12-11 | Powder mixture or composite powder, a method for production thereof and the use thereof in composite materials |
Publications (2)
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EP1242642A1 EP1242642A1 (en) | 2002-09-25 |
EP1242642B1 true EP1242642B1 (en) | 2003-10-01 |
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EP00991157A Expired - Lifetime EP1242642B1 (en) | 1999-12-22 | 2000-12-11 | method for production of powder mixture or composite powder |
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US (1) | US6887296B2 (en) |
EP (1) | EP1242642B1 (en) |
JP (1) | JP4969008B2 (en) |
KR (1) | KR100747805B1 (en) |
CN (1) | CN1159464C (en) |
AT (1) | ATE251228T1 (en) |
AU (1) | AU3156401A (en) |
CA (1) | CA2394844A1 (en) |
CZ (1) | CZ20022198A3 (en) |
DE (2) | DE19962015A1 (en) |
ES (1) | ES2208465T3 (en) |
IL (1) | IL149808A (en) |
PL (1) | PL356370A1 (en) |
PT (1) | PT1242642E (en) |
TW (1) | TWI232211B (en) |
WO (1) | WO2001046484A1 (en) |
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CN114535588A (en) * | 2022-01-07 | 2022-05-27 | 中交隧道工程局有限公司 | Co/Ni Co-coated WC powder and preparation method thereof |
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-
1999
- 1999-12-22 DE DE19962015A patent/DE19962015A1/en not_active Withdrawn
-
2000
- 2000-12-08 TW TW089126135A patent/TWI232211B/en not_active IP Right Cessation
- 2000-12-11 KR KR1020027008010A patent/KR100747805B1/en not_active IP Right Cessation
- 2000-12-11 CN CNB008176434A patent/CN1159464C/en not_active Expired - Lifetime
- 2000-12-11 IL IL14980800A patent/IL149808A/en not_active IP Right Cessation
- 2000-12-11 JP JP2001546978A patent/JP4969008B2/en not_active Expired - Fee Related
- 2000-12-11 EP EP00991157A patent/EP1242642B1/en not_active Expired - Lifetime
- 2000-12-11 WO PCT/EP2000/012484 patent/WO2001046484A1/en active IP Right Grant
- 2000-12-11 US US10/168,272 patent/US6887296B2/en not_active Expired - Fee Related
- 2000-12-11 CA CA002394844A patent/CA2394844A1/en not_active Abandoned
- 2000-12-11 DE DE50003952T patent/DE50003952D1/en not_active Expired - Lifetime
- 2000-12-11 ES ES00991157T patent/ES2208465T3/en not_active Expired - Lifetime
- 2000-12-11 CZ CZ20022198A patent/CZ20022198A3/en unknown
- 2000-12-11 AT AT00991157T patent/ATE251228T1/en active
- 2000-12-11 PL PL00356370A patent/PL356370A1/en unknown
- 2000-12-11 PT PT00991157T patent/PT1242642E/en unknown
- 2000-12-11 AU AU31564/01A patent/AU3156401A/en not_active Abandoned
Also Published As
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DE19962015A1 (en) | 2001-06-28 |
AU3156401A (en) | 2001-07-03 |
KR100747805B1 (en) | 2007-08-08 |
TWI232211B (en) | 2005-05-11 |
US20030000340A1 (en) | 2003-01-02 |
IL149808A0 (en) | 2002-11-10 |
KR20020064950A (en) | 2002-08-10 |
IL149808A (en) | 2005-09-25 |
PT1242642E (en) | 2004-02-27 |
ES2208465T3 (en) | 2004-06-16 |
CZ20022198A3 (en) | 2003-03-12 |
DE50003952D1 (en) | 2003-11-06 |
EP1242642A1 (en) | 2002-09-25 |
ATE251228T1 (en) | 2003-10-15 |
CA2394844A1 (en) | 2001-06-28 |
CN1413268A (en) | 2003-04-23 |
JP2003518195A (en) | 2003-06-03 |
JP4969008B2 (en) | 2012-07-04 |
US6887296B2 (en) | 2005-05-03 |
WO2001046484A1 (en) | 2001-06-28 |
CN1159464C (en) | 2004-07-28 |
PL356370A1 (en) | 2004-06-28 |
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