Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C24/00—Coating starting from inorganic powder
  • C23C24/08—Coating starting from inorganic powder by application of heat or pressure and heat
  • C23C24/082—Coating starting from inorganic powder by application of heat or pressure and heat without intermediate formation of a liquid in the layer
  • C23C24/085—Coating with metallic material, i.e. metals or metal alloys, optionally comprising hard particles, e.g. oxides, carbides or nitrides
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C24/00—Coating starting from inorganic powder
  • C23C24/08—Coating starting from inorganic powder by application of heat or pressure and heat
  • C23C24/082—Coating starting from inorganic powder by application of heat or pressure and heat without intermediate formation of a liquid in the layer
  • C23C24/085—Coating with metallic material, i.e. metals or metal alloys, optionally comprising hard particles, e.g. oxides, carbides or nitrides
  • C23C24/087—Coating with metal alloys or metal elements only

Definitions

• the invention relates to a method for producing a thin metal layer with open porosity from a sinterable metal powder.
• porous bodies are required for the most varied of applications, through which a flowing medium flows, whereby either reactive processes are to be supported or solid particles contained in the flowable medium are retained, i. H. should be filtered out.
• Filter bodies made of ceramic material have to be made relatively thick due to the risk of breakage.
• filter bodies made of pressed and sintered metal powders are relatively thick for manufacturing reasons. Because of the thickness that cannot be reduced, correspondingly large flow resistances occur, particularly in the case of fine-pored material.
• the use of plastics as filter material is limited by the lower strength and the low temperature resistance.
• the use of metallic materials as a porous layer is known in the form of woven or non-woven fabrics made from metal fibers.
• a method for producing porous, metallic sintered workpieces in which a metal powder is first suspended in a carrier liquid which consists of a binder dissolved in a solvent and which is adjusted so that the Suspension is pourable. This suspension is poured into a mold. The solvent is then evaporated, so that the metal powder is solidified by the remaining binder in the geometry given by the shape and forms a manageable green body. After separation from the mold, the green body is sintered in the usual way.
• This previously known method is preferably provided for the production of relatively thick-walled sintered parts which, due to their geometry, can be produced better by a casting process than in the conventional method by pressing a metal powder into a mold. Thin-layered, open, porous parts cannot be produced with this process.
• the invention is based on the object of improving the known method in such a way that thin, porous and, if necessary, self-supporting metal layers can also be produced.
• the individual powder particles although firmly connect in 'sintering, however, remain between the powder particles clearances arising an open porosity with respect to the thickness of the metal layer so that the metal layer for flowing media is permeable.
• the size of the porosity can be influenced via the particle size of the metal powder used, so that very thin porous metal layers with a predeterminable pore size can be produced. Since inhomogeneities and cavities can occur during production, the layer thickness must correspond to at least 3 times the diameter D of the powder particles.
• the above-mentioned ratio between the layer thickness s and the particle diameter D ensures that there are always several “layers” of powder particles one above the other and continuous “holes” that are larger than the desired porosity are avoided. It is particularly expedient here if the layer thickness ⁇ is 5 to 15 times, preferably 10 to 15 times the diameter D of the powder particles. In this way, "continuous deletion" can be avoided.
• Diameter D is to be understood as the mean particle diameter of the metal powder used.
• Metal powders in the sense of the invention are to be understood not only as powders made from pure metals, but also powders made from metal alloys and / or powder mixtures made from different metals and metal alloys. These include, in particular, steels, preferably chromium-nickel steels, bronzes, nickel-based alloys such as Hastalloy, Inconel or the like, where powder mixtures can also contain high-melting components, such as platinum or the like.
• the metal powder to be used and its particle size depend on the particular application.
• the consistency of the suspension to be set via the carrier liquid essentially depends on how the suspension is applied to the carrier body. In the case of a casting, possibly with subsequent wiping of an over Shot from the cast suspension layer, the suspension can be adjusted in a slightly thick consistency. In the case of so-called film casting or spraying, a low-viscosity consistency must be specified.
• the carrier liquid is formed by a binder liquefied with an evaporable solvent. This ensures that the green layer also has sufficient strength due to the adhesion of the individual powder particles to one another via the binder.
• the suspension is applied to the carrier body in succession in several thin partial layers.
• the individual sub-layers can each be built up from an identical suspension. In a further embodiment of the invention, however, it is also possible for the individual
• Sub-layers to use suspensions with different size distributions for the metal powder used and / or different metal powders This makes it possible, for example, to use metal powder on the one hand that gives the finished sintered metal layer a particularly good porosity, and on the other hand it is also possible to produce at least one metal layer that has particularly favorable properties in its metal composition for the intended use, for example catalytic properties.
• the partial layer applied in each case is at least dried before the next partial layer is applied. This ensures that the partial layer initially applied is sufficiently solidified so that it is not deformed by the application method, for example by spraying on the next partial layer. On the other hand, the remaining solvent content in the previously applied, dried partial layer ensures makes sure that the next sub-layer is connected reliably and with the same packing density and that the finished green layer has the desired strength.
• Another embodiment of the invention provides that the respective partial layer is sintered before the next partial layer is applied.
• This method is particularly advantageous when different metal powders are used in a multi-layer structure that require highly divergent sintering temperatures.
• This makes it possible for the partial layer which contains the metal powder with the highest sintering temperature to be applied first, and after the sintering of the first metal layer in a corresponding sequence to apply and sinter the next partial layers with the respectively lower sintering temperatures.
• This has the advantage that the desired porosity of the individual partial layers is retained by the individual sintering steps, which would be lost if the suspension were applied in one layer with such a heterogeneous powder mixture and sintered in one step.
• the remaining, low-sintering powder portions would become densely internal, so that the porosity would be largely lost.
• the suspension is applied as a layer to a flat, flexible carrier body and, after drying, is separated from the carrier body as a green layer and sintered separately to form a membrane-like, porous finished part.
• the advantage of this process is that a comparatively large-area green sheet can first be produced, from which, after drying by punching or cutting, sections of film and green sheet can be produced in the desired shape. In these sections, the green layer is removed from the carrier body and then sintered as an independent part. Plastic or metal foils can be used as carriers.
• the carrier body is expediently coated with a release agent before the suspension is applied.
• the suspension is applied as a layer to a high-temperature-resistant, preferably flat carrier body, dried thereon, sintered and then removed from the carrier body as a membrane-like, porous, metallic finished part.
• a material is used as the carrier body that does not form a connection with the green layer on the carrier body during sintering, as is the case, for example, with ceramic materials, this method offers the possibility of producing a small proportion of membrane-like metallic porous finished parts industrially to manufacture by hand with extensive automation.
• the particular advantage here is that the dry, still sensitive green layer for carrying out the sintering process does not have to be lifted from the support body and handled here, but that it is only removed after sintering.
• the suspension can be applied to the carrier body by pouring or spraying.
• a contour mask is placed on the carrier body before the suspension is applied. This makes it possible to apply the suspension to the carrier already in the intended final contour, so that a subsequent cutting process is not necessary.
• Another advantage of using a contour mask is that the brought suspension also has the predetermined layer thickness in the edge area delimited by the contour mask.
• the sintered membrane is ductile, mechanically stable and within certain limits is also elastic, with the particular advantage that a membrane of this type can be produced with a porosity and low flow resistance defined with narrow tolerances, the porosity being essentially determined by the particle size and the flow resistance by the thickness and Particle size of the sintered metal layer is determined.
• the method also provides that the sintered porous membrane is calibrated by rolling. This measure allows a defined thickness to be set and the surface to be smooth. Furthermore, the pore size in the metal layer can be reduced in a defined manner since the small one
• Thickness is not only the surface areas, but the metal layer as a whole is "completely reforested". But this also gives you the option of initially using a membrane 8th
• the carrier body is also a component of the finished part and accordingly the metal layer is to be firmly connected to it
• the suspension is applied to at least one surface of a metallic carrier body, dried and the green layer is then firmly attached to the carrier body is sintered on.
• the carrier body can in turn be a sintered molded part, also a porous sintered molded part with a coarser pore structure.
• the suspension can in turn be applied to the surface of the carrier body by thin-layer casting, spraying or dipping.
• the metal layer can be applied to the outer wall and / or the inner wall.
• the metallic carrier body is formed by a tubular carrier body, then in an embodiment of the method according to the invention it is provided that when applying the
• Suspension and at least during part of the drying time of the carrier body is rotated about the tube axis. This ensures that the layer thickness is retained as a green layer on the carrier body until the suspension solidifies.
• Porous membranes produced as a finished part or porous metal layers applied to a porous carrier body are particularly suitable for use as a filter and, with a corresponding adjustment of the porosity of the metal layer, also as a microfilter.
• a component can also be used as catalysts with a suitable composition with regard to the metal powder used and with a corresponding porosity.
• Fig. 3 shows a process flow in which the part is formed by an injection molding process and sintered with the aid of a carrier body.
• a suspension formed from a sinterable metal powder and a carrier liquid is applied to a carrier body 2 in the form of a larger film section made of a plastic film or metal film as a thin layer 3 with the aid of a spray or pouring head 1.
• the carrier body 2 coated with a thin suspension layer 3 is then passed through a larger film section into a drying device 4, in which the carrier liquid, for example ethanol or isopropanol, is evaporated under the action of heat.
• the carrier liquid for example ethanol or isopropanol
• the film section thus dried and now provided with a solid green layer 3.1 is subsequently fed to a punching device 5, in which a part 7 is punched out in the desired outer contour together with the film part adhering as carrier body 2 with the aid of a punch knife 6.
• the part 2.1 of the carrier film which is also punched out is removed from the green layer 3.1, which is then introduced as green compact 3.2 into a sintering furnace 9 and sintered there under the conditions to be specified for the respective powder composition.
• the finished part 3.3 in the form of a solid, thin metal layer with open porosity can then be removed from the sintering furnace 9.
• a mask 10 is placed on a flexible but otherwise dimensionally stable support body 2.2, for example made of a silicone rubber, which is provided with a cutout 11 which corresponds to the desired final contour of the porous metal layer part to be produced. Then - as described with reference to FIG. 1 - the carrier body 2.2 provided with a corresponding mask is sprayed with the metal suspension with the aid of a spray or pouring head 1, so that the area delimited by the cutout 11 of the mask 10 has a corresponding area on the carrier body 2.2 , thin suspension layer 3 is applied.
• the mask 10 can be provided with a corresponding plurality of cutouts 11 with a corresponding area size of the carrier body 2.2.
• the mask 10 is removed so that the carrier body 2.2 with the thin suspension layer 3 remaining thereon can be introduced into the drying oven 4, in which the carrier liquid is evaporated.
• the green layer 3 is removed from the carrier body 2.2, which is indicated schematically here by bending the carrier body 2.2 at the edge of a cutting edge 12, so that the isolated green body is then sintered again in the sintering furnace 9.
• the finished part 3.3 can then be obtained from the sintering furnace 9 in the form of a solid, thin one LO LO t to l- 1 P 1 ⁇ i O L ⁇ o L ⁇ o L ⁇

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Powder Metallurgy (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Filtering Materials (AREA)

Applications Claiming Priority (1)

Publications (2)

Family

ID=8166941

Family Applications (1)

Country Status (8)

Families Citing this family (35)

Family Cites Families (20)

• 1998
  • 1998-04-17 JP JP2000544849A patent/JP2002512308A/ja active Pending
  • 1998-04-17 ES ES98922732T patent/ES2171025T3/es not_active Expired - Lifetime
  • 1998-04-17 KR KR1020007009077A patent/KR20010041043A/ko not_active Application Discontinuation
  • 1998-04-17 DE DE59802992T patent/DE59802992D1/de not_active Expired - Lifetime
  • 1998-04-17 WO PCT/EP1998/002254 patent/WO1999054524A1/fr not_active Application Discontinuation
  • 1998-04-17 AT AT98922732T patent/ATE212681T1/de not_active IP Right Cessation
  • 1998-04-17 US US09/647,790 patent/US6652804B1/en not_active Expired - Fee Related
  • 1998-04-17 EP EP98922732A patent/EP1073778B1/fr not_active Expired - Lifetime

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events