EP0365460B1 - Méthode de préparation de revêtements sur pièces mécaniques par techniques P/M - Google Patents

Méthode de préparation de revêtements sur pièces mécaniques par techniques P/M Download PDF

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Publication number
EP0365460B1
EP0365460B1 EP89500102A EP89500102A EP0365460B1 EP 0365460 B1 EP0365460 B1 EP 0365460B1 EP 89500102 A EP89500102 A EP 89500102A EP 89500102 A EP89500102 A EP 89500102A EP 0365460 B1 EP0365460 B1 EP 0365460B1
Authority
EP
European Patent Office
Prior art keywords
paste
binder
additive
atmospheric pressure
metallic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP89500102A
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German (de)
English (en)
Other versions
EP0365460A1 (fr
Inventor
Antonio Romero Fernandes
Jesus Acedo Rosas
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sintermetal SA
Original Assignee
Sintermetal SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sintermetal SA filed Critical Sintermetal SA
Priority to AT89500102T priority Critical patent/ATE97701T1/de
Publication of EP0365460A1 publication Critical patent/EP0365460A1/fr
Application granted granted Critical
Publication of EP0365460B1 publication Critical patent/EP0365460B1/fr
Anticipated expiration legal-status Critical
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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
    • B22F7/00—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression
    • B22F7/02—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite layers
    • B22F7/04—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite layers with one or more layers not made from powder, e.g. made from solid metal
    • 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
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • 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
    • B22F3/1003—Use of special medium during sintering, e.g. sintering aid
    • 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
    • B22F3/1017—Multiple heating or additional steps
    • B22F3/1021—Removal of binder or filler
    • 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

Definitions

  • This invention applies to a method to obtain coatings on mechanical parts by P/M (Powder Metallurgy) techniques by means of a paste which is applied on the substrate part surface, the paste being formed by a binder and by metallic and/or ceramic powders, the operations being carried out by adding an additive to the paste at atmospheric pressure and temperature ranging between 10 and 50o C; homogeneizing the resulting paste mixture and additive by mechanical agitation at atmospheric pressure or applying vacuum for a period ranging 3 and 60 minutes and applying the product obtained this way on the substrate part to coat in any known way.
  • P/M Powder Metallurgy
  • Powder Metallurgy offers unique advantages, as for instance to obtain materials composed by a metallic matrix with non metallic inclusion or selflubricating materials with oil containing porosity. For this and other reasons, several P/M methods have been developed to obtain coatings on substrate parts.
  • the most common method to apply coatings on substrate parts is the single-axis pressing of two powder layers of different composition which form parts composed by two different materials after sintering.
  • the limit in this case is the impossibility of filling a die and densifying powders over non flat surfaces, for instance on spherical and conical surfaces.
  • Another application method is the injection moulding of a plastified mixture in a cavity where the substrate part is an insert or part of the mould. This method is especially suitable to large series.
  • a paste like product can be also applied by forming a sheet from which shapes are cut and stuck to the substrate part.
  • coatings can be obtained by any method for paste application, as for instance a brush, smoother, centrifugation etc.
  • the binder ratio varies according to the powder grain size or according to the specific powder surface.
  • the binder may be of wax basis, being formed, for instance, by wax and petrolatum or of polymeric basis, being formed, for instance by polymetylmetacrylate dissolved in toluene or of water based, formed, for instance, by a solution of cellulosic glue or by a combination of various.
  • the materials of the substrate part have only the limitation of being compatible with the temperature and atmosphere used when sintering the coating.
  • the pastes may be also used for manufacturing parts without substrate, i.e. totally formed by the coating material, by means of coating a substrate of the required shape and detachable after sintering, as for instance graphite.
  • Binder forming always comprises a thermal treatment stage for binder removal before sintering the powders. This stage is the most critical of the process, since faults easily appear, as for instance distortion of the part shape of cracks and craters on the surface. To avoid these defaults a very slow warmup and a very long process duration are necessary, resulting in a high cost, and consequently in a necessary limitation of the process to very specific applications.
  • binder composition influences the shaping properties of the paste and the coating behaviour during thermal treatment.
  • Pastes based on wax are very plastic at room temperature, consequently they are easily formable. However, as the temperature increases, its viscosity reduces and, therefore, they tend to flow and distort during the removal stage.
  • Pastes based on cellulose or water solved polysaccharides harden with temperature and retain well the shape during binder removal, but they have poor formability and its viscosity at room temperature is very affected by solvent losses during storage or handling.
  • Thermoplastic polymers with solvents also harden when heating and solvent evaporation, but they soften again when temperature further increases. They are easily conformable, but they are affected by distortion during removal and variable viscosity with solvent losses.
  • the minimum temperature to assure total removal of a organic type binder is 500o C and the most favorable atmosphere is oxidant.
  • the total process with usual heating speeds of 0,5o C per minute has a duration of 9 to 10 hours and results in very rusty parts.
  • This oxidation is used to furnish a cementing skeleton among the particles as the binder is disappearing.
  • it is negative for the sintering stage in major or minor degree, according to the alloy elements, since the oxide reduction requires high temperatures and longer exposure times to reducing atmospheres.
  • the dimensional change in sintering depends upon the oxidation degree and in the case of bronzes very much.
  • coatings of this type need a slow heating speed at the critical binder removal stage.
  • coatings of this type need a slow heating speed at the critical binder removal stage.
  • coatings are very thin (between 10 and 50 microns) or they are conceived for very concret applications, as for instance the coating described in the US Patent No. 4.596.692 from Morishita and others, or they use a specific and concret binder as mentioned in the US Patent No. 4.491.559 from Kennametal Inc. which contains metal particles of tungsten carbide.
  • parts can be entirely made from pastes suitable for coatings, as those manufactured according to the US Patent No. 4.626.406 from Inco Alloys International Inc. which discloses a process for the activated sintering of metallic powders.
  • a slurry is produced by mixing a metal powder, a binder (a hydroxyethyl cellulose polymer), water and an additive consisting of an aqueous solution of boric acid.
  • the slurry is introduced into a forming apparatus and formed into a desired shaped object.
  • the object is heated to remove the binder and then sintered.
  • the slurries of Dl are prepared by mixing the dry components and then adding the boric acid solution to form a clay like slurry.
  • the boric acid solution is prepared by dissolving boric acid in warm (49o C) distilled water.
  • the slurry is extruded into a rod and air dried for about 48 hours and subsequently the rod is heated to 482o C to remove the binder and then sintered at 1316o C.
  • these pastes present a serious obstacle consisting in the binder removal stage which must be carried out by a very slow temperature increase taking days and in some cases even weeks. Therefore, in such cases it is a question of very concret application processes.
  • the method subject to this invention allows coatings which admit a fast temperature increase from the moment of removing the water based vehicle or the polar solvent without outflow nor distortion after the binder removal has been finished.
  • the coating obtained according to the method subject of this invention shows an excellent homogeneity and after debinding a suitable strenght for hadling on trays, pallets and trucks without more care than usual in manufacturing plants.
  • Coating pastes obtained according to this invention allow fast heating from 120o C approximately and without shape distortions, cracks or craters and in a reducing, neutral or oxidant atmosphere and even in vacuum.
  • the coating accordingly the invention allows shorter debinding and is more flexible on alloy elements oxygen affinity than the methods known until now.
  • the method according to the invention is characterized in that said additive is formed by a solution, in a polar solvent, of free or complex metallic ions and in that after said coating of the substrate part the operations are carried out of performing a first binder removal stage by application of heat to a temperature of about 120oC, at a rate of temperature increase of about 0.5oC per minute, to remove the polar solvent and performing a second binder removal stage by heating at a higher rate of temperature increase than used in the first binder removal stage to remove the binder, the part then being ready to be submitted to the known sintering and finishing operations.
  • the mentioned additive is chosen among those which do not produce precipitates at atmospheric pressure below 80o C. They precipitate between 80 and 120o C and their precipitates are stable below 200o C.
  • the mentioned additive is chosen in such a way that its free metallic ions are compatible with the metallic and/or ceramic powders used to make the paste.
  • Spherical bronze 70 % Sn, particle size ranging between 250 and 125 microns was mixed with a binder formed by 80% petrolatum and 20% of Hoechst wax type C in a proportion of 93% powder and 7% binder.
  • This paste was applied on a cylindrical surface of P/M steel parts 2% copper, density 6.8 g/cc, forming a 1.2 mm thickness.
  • binder cycles were tested in an oven with air atmosphere with different heating speeds. In this way the cycle represented in figure 1, curve a, was determined as the shortest and still free of distortions and cracking.
  • An identical paste to the previous one was prepared but adding 2% of an additive formed by 17% of copper sulphate and 83% of water. Tests to determine the shortest cycle were performed and the cycle represented in figure 1, curve b, was obtained. It is noted that the presence of the additive according to this patent allows the reduction of binder removal practically to half the time.
  • a mixture of atomized iron powder with particle size below 100 microns and atomized nickel powder with particle size below 50 microns in a proportion of 96% iron and 4% nickel was prepared. This mixture was then mixed with a binder formed by 80% petrolatum and 20% Hoechst wax type V in a proportion of 90% to 10%.
  • the obtained paste was conformed as in the previous examples and submitted to removal cycles producing in all cases a coating overflow. To this paste was added 1% of an additive formed by 40% in weight of iron ammonic oxalate and 60% water.
  • Spherical bronze 90% Cu-10% Sn with a particle size ranging between 300 and 100 microns was mixed with a binder formed by 58,3% in petrolatum, 1,8% in weight of sodium alginate and 39,9% of water in a proportion of 85% powder and 15% binder.
  • This paste was applied on the cylindrical surface of test parts with 1.5 mm thickness.
  • the thermal cycle represented in figure 1, curve a was determined as the shortest to avoid cracks.
  • a paste identical to the previous one was prepared but by adding 1.5% of an additive formed by 17% in weight of copper sulphate and 83% of water.
  • the cycle represented in figure 1, curve b was obtained. Once again the presence of additive allows reducing the removal time.

Claims (3)

  1. Méthode pour l'obtention de couches par techniques de la métallurgie des poudres sur des pièces mécaniques par le moyen d'une pâte qui est appliquée sur la pièce substrat, la pâte étant composée d'un liant et de poudres métalliques ou céramiques, avec la réalisation des opérations d'ajouter un additif à la pâte à la pression atmosphérique et à température entre 10 et 50 degrés centigrades; d'homogénéiser le mélange de la pâte et de l'additif par agitation mécanique à la pression atmosphérique ou avec du vide, pendant un période entre 3 et 60 minutes et d'appliquer le produit obtenu de cette façon sur la pièce substrat à recouvrir par n'importe qu'elle procédure connue; caractérisé par ce que l'aditif cité est obtenu par solution dans un solvant polaire des ions métalliques libres ou complexes et par ce que après l'application de la couche sur la pièce substrat on fait les opérations d'une première étape d'elimination du liant par application de chaleur jusqu'a près 120 degrés centigrade et avec une vitesse de croissance de la température proche de 0,5 degrés centigrade par minute pour éliminer le solvant polaire et d'une deuxième étape avec une vitesse de croisance plus élevée que celle utilisée dans la première étape, avec le résultat de que la couche devienne prête pour les operations connues de frittage et finissage.
  2. Méthode pour l'obtention de couches suivant la revendication 1 caracterissée par ce que l'additif cité est choisi entre ceux qui ne produissent pas des précipités à la pression atmosphérique par dessous de 80 degrés centigrade, ils précipitent entre 80 et 120 degrés centigrade et ces précipités sont estables par dessous 200 degrés centigrades.
  3. Méthode pour l' obtention de couches suivant les revendications 1 et 2 caracterisée par ce que l'aditif cité est choisi de façon que les ions métalliques libres soient compatibles avec les poudres métalliques et/ou céramiques utilisés dans la preparation de la pâte.
EP89500102A 1988-10-17 1989-10-14 Méthode de préparation de revêtements sur pièces mécaniques par techniques P/M Expired - Lifetime EP0365460B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT89500102T ATE97701T1 (de) 1988-10-17 1989-10-14 Herstellungsverfahren von beschichtungen auf mechanischen teilen durch p/m-techniken.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ES8803147 1988-10-17
ES8803147A ES2009355A6 (es) 1988-10-17 1988-10-17 Procedimiento para preparar recubrimientos aplicables por tecnicas pulvimetalurgicas en piezas mecanicas.

Publications (2)

Publication Number Publication Date
EP0365460A1 EP0365460A1 (fr) 1990-04-25
EP0365460B1 true EP0365460B1 (fr) 1993-11-24

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EP89500102A Expired - Lifetime EP0365460B1 (fr) 1988-10-17 1989-10-14 Méthode de préparation de revêtements sur pièces mécaniques par techniques P/M

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EP (1) EP0365460B1 (fr)
AT (1) ATE97701T1 (fr)
DE (1) DE68910937T2 (fr)
ES (1) ES2009355A6 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4203773A1 (de) * 1992-02-10 1993-08-12 Huels Chemische Werke Ag Verfahren zur verguetung der oberflaeche eines koerpers
DE4237891C1 (fr) * 1992-11-10 1993-07-22 Degussa Ag, 6000 Frankfurt, De

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1185901B (de) * 1943-02-17 1965-01-21 Dr H C Hans Vogt Verfahren zum Herstellen von Sintermetallueberzuegen
US4371589A (en) * 1976-08-24 1983-02-01 Warner London Inc. Process for depositing protective coating and articles produced
US4626406A (en) * 1985-10-28 1986-12-02 Inco Alloys International, Inc. Activated sintering of metallic powders
DE3628363A1 (de) * 1986-08-21 1988-02-25 Mtu Muenchen Gmbh Verfahren zum herstellen von schutzschichten

Also Published As

Publication number Publication date
ES2009355A6 (es) 1989-09-16
EP0365460A1 (fr) 1990-04-25
ATE97701T1 (de) 1993-12-15
DE68910937D1 (de) 1994-01-05
DE68910937T2 (de) 1994-06-01

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