Classifications

• • 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
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/22—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip
• • 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
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/20—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces by extruding
• • 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
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/22—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip
  • B22F3/227—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip by organic binder assisted extrusion
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28B1/00—Producing shaped prefabricated articles from the material
  • B28B1/30—Producing shaped prefabricated articles from the material by applying the material on to a core or other moulding surface to form a layer thereon
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28B5/00—Producing shaped articles from the material in moulds or on moulding surfaces, carried or formed by, in or on conveyors irrespective of the manner of shaping
  • B28B5/02—Producing shaped articles from the material in moulds or on moulding surfaces, carried or formed by, in or on conveyors irrespective of the manner of shaping on conveyors of the endless-belt or chain type
  • B28B5/026—Producing shaped articles from the material in moulds or on moulding surfaces, carried or formed by, in or on conveyors irrespective of the manner of shaping on conveyors of the endless-belt or chain type the shaped articles being of indefinite length
  • B28B5/027—Producing shaped articles from the material in moulds or on moulding surfaces, carried or formed by, in or on conveyors irrespective of the manner of shaping on conveyors of the endless-belt or chain type the shaped articles being of indefinite length the moulding surfaces being of the indefinite length type, e.g. belts, and being continuously fed
• • 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
  • C22C1/045—Alloys based on refractory metals
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C26/00—Alloys containing diamond or cubic or wurtzitic boron nitride, fullerenes or carbon nanotubes
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C47/00—Making alloys containing metallic or non-metallic fibres or filaments
  • C22C47/14—Making alloys containing metallic or non-metallic fibres or filaments by powder metallurgy, i.e. by processing mixtures of metal powder and fibres or filaments
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C49/00—Alloys containing metallic or non-metallic fibres or filaments
  • C22C49/02—Alloys containing metallic or non-metallic fibres or filaments characterised by the matrix material
  • C22C49/10—Refractory metals
• • 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
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/10—Sintering only
  • B22F3/105—Sintering only by using electric current other than for infrared radiant energy, laser radiation or plasma ; by ultrasonic bonding
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C26/00—Alloys containing diamond or cubic or wurtzitic boron nitride, fullerenes or carbon nanotubes
  • C22C2026/002—Carbon nanotubes

Definitions

• the invention relates to a method for producing a refractory metal component, the method comprising the following steps: providing a starting material comprising a refractory metal powder of at least one refractory metal and / or a compound thereof and at least one binder ; and prototyping the starting material to at least one green body.
• the invention also relates to a refractory metal component produced by the method.
• the invention is particularly applicable to X-ray tubes or fusion reactors, in particular for a surface of an X-ray anode, accelerator targets or the wall and structural component of a fusion reactor.
• refractory metals in particular tungsten, are used.
• the film casting process for refractory metals is known from WO 2007/147792 A1.
• WO 2007/147792 A1 discloses a process for the production of planar, shaped articles from a tungsten or molybdenum heavy metal alloy, from which a slurry for film casting is produced, from which slurry a film is poured and the film is debinded after drying and sintered to to obtain the molded article.
• tungsten or molybdenum heavy metal alloy is to be understood as meaning materials selected from the group consisting of tungsten heavy metal alloys, tungsten, tungsten alloys, molybdenum and molybdenum alloys.
• Tungsten heavy metal alloys consist of about 90% to about 97% by weight. made of tungsten or tungsten alloys.
• the remainder is binder metal.
• metallic binder the elements Fe, Ni and / or Cu in proportions greater than 1% by mass are preferred.
• the metallic binders provide simplified manufacturing processes through lower sintering temperatures, improved mechanical properties, in particular ductility, and improved machinability, such as better machinability. These materials are intended for use in radiation shielding applications, with a high density of alloys in the foreground.
• GB 928 626 A discloses a method for producing a dense, substantially crack-free and distortion-free refractory metal component by means of cold rolling and sintering.
• pure tungsten powder can be mixed with organic binder and water and subsequently extruded under heat to provide a starting material for cold rolling.
• the cold rolled stock was subsequently air dried and then sintered.
• a method for producing a component comprising (at least) the following steps: providing a starting material (molding compound) which is a refractory metal powder of at least one refractory metal and or a compound thereof ("refractory metal powder") and at least one binder; and prototyping the starting material to at least one green body.
• the starting material additionally has short fibers.
• such a method has the advantage that the admixture of the short fibers makes the starting material also formable by methods which are virtually closed to starting material with long fibers. Nevertheless, the short fibers may still cause pseudoplasticity in the refractory metal composite component if they are significantly longer than the microstructural sizes (eg, grain size, pore size, etc.) of the refractory metal matrix in the final product. In this case, the pseudoplasticity may come into play. The more one approximates the fiber geometry to a spherical geometry of the reinforcement phase (eg, through coated tungsten fibers or particles), the sooner the conventional heterogeneous properties of composites come into play.
• the effect is that they also affect the microstructure. They can bring about a change in the grain boundary stability, in particular with regard to a recrystallization behavior and / or a grain boundary sliding.
• a stress distribution and the crack profile in the refractory metal composite component and a stability of the microstructure can be set in a targeted manner, whereby in the use of the polymer, for example. critical load conditions can be reduced or excluded.
• Body or workpiece to be understood which has been produced by means of the method.
• Short fibers are understood as a solid which is suitable for carrying out the cold forming (eg film casting, extrusion, etc.), optionally also with heat support.
• the starting material may in particular be a refractory metal powder / short fiber / liquid mixture of defined viscosity, in particular with an anhydrous liquid.
• One or more powders of one or more pure refractory metals eg tungsten and / or molybdenum
• alloys thereof eg tungsten-rhenium, WRe
• WRe tungsten-rhenium
• the refractory metal powder may include, for example, tungsten, molybdenum, rhenium and / or tantalum and / or alloys thereof and / or compounds thereof.
• archetypes can be understood in particular a manufacture of a first shape of powder-containing molding composition to molding material (in particular semi-finished).
• a solid body can be made in particular from a formless material.
• Archetypes are used, for example, to produce a first form of a geometrically determined, solid body and / or to create the substance together.
• thermal processing of the at least one refractory metal powder takes place in the absence of oxygen, e.g. under a protective gas atmosphere, reducing atmosphere or under vacuum. This prevents oxidation of the refractory metal powder.
• the binder can in principle have any organic and / or non-organic binder or binder.
• the binder binds the refractory metal powder functionally similar to an adhesive. Preference is given to organic binders, for example Polvvenylbutyral. It is a development that the starting material has additional additives such as dispersants, plasticizers, solvents, etc. In particular, a viscosity of the starting material and the properties of the original shaped green body (eg its strength and / or deformation capacity) influence.
• a dispersing agent ensures that the wetting behavior of the particles of the refractory metal powder and possibly of the (in particular coated) short fibers is improved and agglomeration is prevented.
• the solvent e.g. Ethanol and / or toluene, dissolves organic components, in particular the binder.
• a plasticizer about an admixture of a plasticizer, the flexibility and strength of the green body and thus its handling can be adjusted.
• Various mixing and grinding processes produce a virtually homogeneous starting material. It may be necessary to degas the feedstock prior to primary forming to avoid blistering in the feedstock.
• a mixture of the individual powders and optionally the short fibers in a tumble mixer, in ball mills, etc. take place. Care must be taken that the grinding and mixing process does not destroy the fiber or particle geometry
• a length of the short fibers is at least ten times the microstructural sizes of the refractory metal or the refractory metal matrix, e.g. at least ten times the mean grain size of the refractory metal or the refractory metal matrix. This can cause a pseudoplasticity and at the same time even with large grain sizes of e.g. 200 to 500 microns, a short enough length for use with the master mold.
• a grain size may, in particular, be understood as meaning a median diameter or equivalent diameter, D50, which is exceeded or undershot by 50 percent of the grains.
• a length of the short fibers at least five microns, in particular at least 20 Micrometer, is.
• a pseudoplasticity even at very small grain sizes of the refractory metal powder, for example, of 500 nm, caused and processing is particularly simplified.
• a length of the short fibers does not exceed five millimeters. This provides the advantage that the length does not hinder the prototyping and this length in particular also maximum typical layer thicknesses, e.g. of green films, does not exceed. In turn, an embedding and relatively free orientation of the short fibers can be achieved even for thin components, which in turn suppresses a directional dependence of the orientation of the short fibers and thus a direction-dependent shrinkage.
• a length of the short fibers does not exceed three millimeters, in particular two millimeters.
• nanofibers can bring about a change in the grain boundary stability, in particular with regard to a recrystallization behavior and / or a grain boundary sliding.
• the short fibers have the material of at least one of the refractory metal powders.
• a deterioration of the properties of the finished refractory metal composite component with regard to its temperature resistance can be excluded. Even so unwanted chemical reactions can be excluded.
• a thermo-mechanical mismatch due to expansion coefficients, etc. can be suppressed, but this may also be desirable in composite materials.
• the fiber or a fiber coating is a ceramic (eg oxide or carbide) fiber or fiber coating, which in particular affects the crack profile in the interface with the matrix.
• both the refractory metal powder and the short fibers may be made of high purity tungsten.
• the starting material may include both high purity tungsten powder and tungsten rhenium powder, and the short fibers may be e.g. consist of pure tungsten and / or tungsten rhodium.
• the fiber has a coating to achieve or enhance pseudoplasticity.
• the short fibers are or have carbon nanotubes.
• the carbon nanotubes may be single tubes or form a fibrous tissue.
• the short fibers are coated in order to adjust their shear strength against the Refrak- tärmetall- particles, in turn, to influence the mechanical properties, in particular the crack profile, the refractory metal composite component.
• the starting material comprises ceramic powder.
• This provides the advantage that a recrystallization behavior and / or a strength of the subsequently produced refractory metal composite component can be influenced.
• the presence of ceramics stabilizes the grain boundaries of the refractory metal, in particular in the context of dispersion hardening, and in particular can suppress grain boundary growth. This in turn gives the refractory metal composite component increased resistance to thermal shock (eg triggered by a punctual thermal cycling).
• thermal shock eg triggered by a punctual thermal cycling.
• the ceramic particles La 2 0 3 , Y 2 0 3 , Tic and / or HfC have or consist of.
• a ceramic powder may, in particular, be present as nanopowder or micropowder.
• a powder having a mean grain size (for example, expressed by an equivalent diameter) in the micrometer range, that is, a powder under a nanopowder may be used. of a millimeter or less, but more than a micron, be understood.
• Powders can be made along with other components of the feedstock or can be achieved by an optional prefixed mixing and milling process (e.g., in a ball mill, tumbler or attritor, etc.). Among other things, a particle size distribution can be adjusted.
• the starting material has no metal binder, ie no low-melting metallic binder.
• the absence of the metal as a binder can be realized in particular by a lack of metal, mixtures or alloys thereof as an independent powder in the starting material.
• Such a configuration has the advantage that the material properties of the finished refractory metal composite component, in particular its high melting point and its breaking strength under thermal cycling, are not degraded by the metal or metals in the binder (which would otherwise be the case).
• a refractory metal composite component produced in this way can withstand higher temperatures without destruction and / or have a longer service life.
• the process is not or not essential to perform more complicated than in the presence of a metallic binder.
• the starting material is extrusion compound (often also called “feedstock") and the primary molding comprises extrusion of the extrusion composition.
• An extrusion composition may generally be understood to mean a solids-containing, viscous suspension comprising the refractory metal powder and the short fibers as a solid, which is suitable for carrying out the extrusion. This is made possible only by the short length of the short fibers.
• the technique of extrusion is generally well known and need not be further explained here. In principle, all suitable extrusion processes are applicable.
• extrusion comprises extruding a (composite) green sheet.
• a (composite) green sheet As a result, large-area semi-finished products or components can be produced without further aftertreatment (for example rolling).
• an extruder die may be appropriately shaped and e.g. have a slot or gap-like discharge opening.
• the starting material is slip
• the primary forms a casting, in particular film pouring or Schlickergie H
• the slip comprises and the green body is formed as a slip layer.
• Slip can generally be understood to mean a solids-containing, viscous suspension with the refractory metal powder and the short fibers as a solid, which is suitable for carrying out the casting.
• the casting comprises a foil casting or a foil casting process.
• the technique of film casting is basically well known and need not be further explained here. In principle, all suitable film casting methods are applicable.
• the result is a (composite) slip layer, which is also referred to as "green film".
• the green foil can be an independent workpiece.
• the casting comprises a slip casting or a slip casting process. In this case, a carrier is pulled once or several times through the slurry or sprayed with it. The deposited as a green body, deposited slurry layer can then be thermally treated together with the carrier.
• the result is a refractory metal composite component with the carrier as the main body and at least one refractory metal layer.
• the slip layer may in particular be in the form of a thin layer of the slip, ie in particular still contain the binder.
• the slip layer, in particular green film, may be dimensionally stable, in particular for further processing.
• a thickness of the (individual) slip layer is about fifty micrometers to about five millimeters, preferably about three millimeters. Thereby, a sufficiently high layer thickness for accommodating a plurality of grains of the refractory metal powder can be provided. In addition, a sufficient homogeneity of the individual Schuicker joser can be ensured across the thickness. It is a further development that a layer thickness corresponds to at least approximately five times to ten times the largest particle of the at least one refractory metal powder and / or ceramic powder (if present). This avoids that a film is built on its thickness or height only by a few grains.
• the slurry is applied by means of a film casting (as a green sheet) on a carrier film.
• a film casting as a green sheet
• the carrier film can then be removed again, for example stripped off, for example before a heat treatment of the green film.
• several (two or more) slurry layers, in particular green sheets are stacked on top of one another (eg laminated, isostatically pressed, cast or extruded).
• a high (basically unlimited) thickness of the refractory metal composite component can be achieved with a constant material density.
• a refractory metal composite component may therefore alternatively be produced by stacking (possibly fiber-free) green sheets, in particular green sheet, and (optionally oriented) fiber layers.
• a layer of oriented fibers may be laminated to a green sheet.
• a layer of oriented fibers may be pressed between two green sheets.
• thermo-mechanical properties and the fracture behavior of the layer stack can be adapted constructively.
• such a layer stack enables the production of connection zones which allow attachment of refractory metal to external components, such as an anode support or a carrier of plasma chamber components in the fusion reactor.
• stresses can be influenced by different thermal expansion coefficients of the components or the reaction behavior at the interfaces.
• a content of refractory metal, a type and / or composition of the refractory metal or a compound thereof eg a content of W; Ta; Re; Mo, etc.
• a presence, a type (material, countries ge etc.) and / or a content of short fibers eg a microscopic structure (eg a particle size distribution), and / or a macroscopic structure (eg a size of the powder particles, a porosity, etc.).
• the layer stack can be constructed by layering W layers with W / Re layers, or dense tungsten layers alternate with porous tungsten layers.
• the porosity can be adjusted, for example, via the sintering activity of the refractory metal powders.
• the slurry layers of the layer stack have a gradient structure.
• a gradient structure is a crack-optimized and practically safe trained component produced.
• the gradient material may in particular by a gradual (in particular stepwise) change at least one property of
• Slip layers may be applied to the support, e.g. as gradient layers.
• greensheets produced by extrusion can be designed and combined in an analogous manner, e.g. to a gradient layer stack.
• the films or components can be applied to components in the "green state” and passed together through the heat treatment.
• a median grain size of the particles of the refractory metal powder, D50 is less than two microns. These small grain sizes suppress grain growth at high sintering temperatures because the use of such fine powder fractions enables high sintering reactivity and therefore lower final sintering temperatures. It is also an embodiment that the refractory metal powder is a powder of pure tungsten, tungsten-rhenium, WRe, or tungsten-tantalum, WTa. It is also an embodiment that the proportion of the refractory metal or the compound thereof to the starting material is 50% by weight to 99% by weight.
• the step of the original form is followed by a step of shaping the (composite) green body.
• the green body e.g. a green sheet, for example, can be cut to a desired geometry by means of a knife, bent, rolled, etc.
• the green body can also be brought into various geometries (for example in the form of a tube).
• the method therefore not only permits the production of planar green bodies, but also the production of complex three-dimensionally shaped green bodies or refractory metal composite components.
• a step of heat treatment of the at least one (composite) green body to the step of the primary forming and optionally shaping.
• the heat treatment may include a step of debinding the at least one green body.
• the at least one green body can be heated so much that the binder is removed (thermal debinding).
• debinding may be carried out by chemical debinding, in which the organic constituents of the binder are generally dissolved by solvents from the green body.
• the heat treatment may also include a step of sintering the at least one green body. Thereby, a compacted refractory metal composite member containing the short fibers is obtained.
• Sintering can be applied in particular to Binder follow.
• the sintering may in particular be a pressureless sintering.
• Debinding and sintering can be carried out in one work step, for example by guiding the at least one green body through the same furnace or the same installation. This avoids relocating and shortens a process time.
• a continuous process in a reducing and carbon-free atmosphere is preferred in order to keep the carbon and oxygen content low.
• the process may be carried out under vacuum or hydrogen atmosphere.
• the step of heat treatment can thus be a step of hot pressing, in particular hot isostatic pressing, of the at least one (pre) sintered refractory metal composite workpiece.
• the step of heat treatment may alternatively or additionally comprise a step of so-called "spark plasma" sintering.
• spark plasma a step of so-called "spark plasma" sintering.
• the step of heat treatment may alternatively or additionally comprise a step of microwave sintering.
• the debinded and pre-sintered at comparatively low temperatures refractory metal workpiece is irradiated with microwaves to bring it to the final density at low temperatures.
• the step of heat treatment has a step of sintering below a maximum sintering temperature to a density below the maximum density and, following, a heat treatment step of further compacting.
• At least one green body is at least closed-pored by the heat treatment.
• at least closed-pored a closed-pored or dense (in particular, maximum, dense) state can be understood. This suppresses formation or propagation of surface cracks, e.g. by thermally induced stresses, thus improving longevity.
• the refractory metal composite components (plates or structures, eg tubes) with short fibers produced by the above process may already be the final product or as Semi-finished over conventional joining techniques, such as soldering, are applied to surfaces.
• green bodies in particular green sheets or green sheets, can be applied to components before oven processes. In this case, these components must undergo the temperature treatment of the green body in a manner similar to the slip casting process.
• the object is also achieved by a component (refractory metal composite component) or body, which has been produced by means of the method as described above.
• the component may in particular be designed analogously to the method and have the same advantages.
• the refractory metal composite component has short fibers as described above.
• the refractory metal composite component consists of several (two or more) layers, which may differ in particular in their properties.
• the layers may have a gradient structure.
• the refractory metal composite component is a three-dimensional component.
• the refractory metal composite component is a closed-pored component or a dense component.
• Fig. 2 shows an apparatus for film casting for carrying out the method
• Fig.l shows a sequence of a method for producing a refractory metal composite component by primary forming in several variants.
• a first preparation step S1 for producing a starting material M comprises providing a powder mixture of refractory metal powder in the form of two tungsten powders.
• the two tungsten powders differ in their mean grain size, D50, namely once at 0.7 micrometers and once at 1.7 micrometers.
• a second preparation step S2 comprises providing short fibers, e.g. of pure tungsten to achieve pseudoplasticity and / or as carbon nanotubes for altering grain boundary stability.
• a third preparation step S3 comprises providing additives such as a dispersing agent (hypermer KD1), solvents in the form of ethanol and toluene, and a binder in the form of polvvenyl butyral (Pioloform BR 18) and a plasticizer in the form of dibutyl phthalate.
• a dispersing agent hypermer KD1
• solvents in the form of ethanol and toluene solvents in the form of ethanol and toluene
• a binder in the form of polvvenyl butyral Pioloform BR 18
• plasticizer in the form of dibutyl phthalate.
• the dispersant ensures that the wetting behavior of the refractory metallic powder particles and the short fibers is improved and agglomeration is prevented.
• the solvents ethanol and toluene dissolve the organic components of the binder, in particular the binder Pioloform BR18.
• a plasticizer About the admixture of a plasticizer, the flexibility and strength of urformed green body 4, 17 (see also Figures 2 and 3) and thus its handling can be adjusted.
• Various homogeneous mixing and milling processes produce a homogeneous starting material M. In some cases, it may be necessary to degas the starting material M or molding compound prior to primary molding to avoid blistering in the reformed green body 4, 17.
• the aim is a weight fraction or volume fraction of 70% to 99% of refractory metallic powder in the starting material.
• the prototype S5 comprises the step S6 of a film casting.
• the starting material M is used as a slip to produce green bodies in the form of the short fibers having green sheet (s).
• the starting material M is filled into a storage chamber 2 of a film casting installation 1, as shown in FIG.
• the starting material M flows out of the storage chamber 2 and is by means of a Main doctor blade ("Doctor Blade") 3 as a green sheet 4 on a carrier sheet 5 stripped off.
• the carrier foil 5 lies on a flat base 6.
• a pre-doctor blade 7 upstream of the main doctor blade 3 can be used to set a hydrostatic pressure in front of the main doctor blade 3, which thus influences the thickness of the cast green foil 4.
• the viscosity of the starting material M or slip and the pulling speed (relative speed between carrier film 5 and main blade 3 in the direction of movement indicated by the arrow) likewise influence the thickness of the cast green film 4.
• the prototyping S5 comprises the step S7 of an extrusion.
• the starting material M is now used as an extruder mass or feedstock to produce rod-like green bodies.
• the starting material M is introduced into a filling funnel 12 of an extrusion plant 11, as shown in FIG. 3 as a single-screw
• Plasticizing extruder is shown filled.
• the starting material M passes from the hopper 12 into a cylinder 13, in which an extruder screw 14 is driven by a motor 15 rotates.
• the extruder screw 14 conveys the starting material M to a tip of the cylinder 13, on which an optionally heatable extrusion die 16 is located.
• the rod-like green body 17 is pushed out as an extrudate. Due to the short length of the short fibers promotion in the extruder screw 14 is not hindered.
• the green body 4, 17 can be formed.
• the green sheet 4 may be cut and / or shaped, in particular three-dimensionally shaped.
• the extrusion green body 17 may be cut off, cold rolled, etc., for example.
• step S9 the cut / shaped green body 4, 17 is heat-treated to produce the finished refractory metal composite component.
• the cut / shaped green body 4, 17 is heat-treated to produce the finished refractory metal composite component.
• Base body 4 17 entbindert, in particular by a heat treatment.
• the debindered and possibly shaped main body 4, 17 is sintered, in a coherent, in particular pressureless, sintering process at a correspondingly high sintering temperature until a dense or practically nonporous refractory metal composite component is present.
• step Sil the debinded and possibly shaped green body 4, 17 is first sintered ("pre-sintered") at a comparatively lower sintering temperature in step S 12, wherein it does not yet reach its dense state, but remains porous (closed-pored).
• step S13 the presintered refractory metal work piece is compacted by hot isostatic pressing to form the refractory metal composite component, in particular compressed without pores, in particular at least approximately to its maximum possible density.
• This has the advantage that the temperatures required for hot isostatic pressing are lower than the sintering temperature required in step S12 and thus a grain growth (which increases with increasing temperature) is inhibited.
• a spark plasma sintering step S14 and / or a microwave sintering step S15 may be performed.

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• 2012
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