EP4301531A1 - Method for manufacturing a near net shape (nns) component of complex shape using pressure-assisted sintering - Google Patents

Method for manufacturing a near net shape (nns) component of complex shape using pressure-assisted sintering

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Publication number
EP4301531A1
EP4301531A1 EP22711275.2A EP22711275A EP4301531A1 EP 4301531 A1 EP4301531 A1 EP 4301531A1 EP 22711275 A EP22711275 A EP 22711275A EP 4301531 A1 EP4301531 A1 EP 4301531A1
Authority
EP
European Patent Office
Prior art keywords
preform
powder
manufacturing
sintering
particle size
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.)
Pending
Application number
EP22711275.2A
Other languages
German (de)
French (fr)
Inventor
Foad NAIMI
Arnaud DELEHOUZE
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.)
Sintermat SAS
Original Assignee
Sintermat SAS
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 Sintermat SAS filed Critical Sintermat SAS
Publication of EP4301531A1 publication Critical patent/EP4301531A1/en
Pending legal-status Critical Current

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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
    • B22F3/12—Both compacting and sintering
    • B22F3/14—Both compacting and sintering simultaneously
    • B22F3/15—Hot isostatic pressing
    • B22F3/156—Hot isostatic pressing by a pressure medium in liquid or powder form
    • 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
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B22F1/052—Metallic powder characterised by the size or surface area of the particles characterised by a mixture of particles of different sizes or by the particle size distribution
    • 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
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/10—Formation of a green body
    • 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
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/60—Treatment of workpieces or articles after build-up
    • B22F10/64—Treatment of workpieces or articles after build-up by thermal means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
    • B33Y40/20—Post-treatment, e.g. curing, coating or polishing
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
    • C04B35/63—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B using additives specially adapted for forming the products, e.g.. binder binders
    • C04B35/638—Removal thereof
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/64—Burning or sintering processes
    • C04B35/645—Pressure sintering
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/653—Processes involving a melting step
    • 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
    • B22F3/02—Compacting only
    • B22F3/03—Press-moulding apparatus therefor
    • B22F2003/033—Press-moulding apparatus therefor with multiple punches working in the same direction
    • 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
    • B22F2003/1051—Sintering only by using electric current other than for infrared radiant energy, laser radiation or plasma ; by ultrasonic bonding by electric discharge
    • 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
    • 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
    • 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
    • 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
    • B22F3/02—Compacting only
    • B22F3/03—Press-moulding apparatus therefor
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/50—Constituents or additives of the starting mixture chosen for their shape or used because of their shape or their physical appearance
    • C04B2235/54—Particle size related information
    • C04B2235/5418—Particle size related information expressed by the size of the particles or aggregates thereof
    • C04B2235/5436—Particle size related information expressed by the size of the particles or aggregates thereof micrometer sized, i.e. from 1 to 100 micron
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/50—Constituents or additives of the starting mixture chosen for their shape or used because of their shape or their physical appearance
    • C04B2235/54—Particle size related information
    • C04B2235/5463—Particle size distributions
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/60—Aspects relating to the preparation, properties or mechanical treatment of green bodies or pre-forms
    • C04B2235/602—Making the green bodies or pre-forms by moulding
    • C04B2235/6026—Computer aided shaping, e.g. rapid prototyping
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/65—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes
    • C04B2235/66—Specific sintering techniques, e.g. centrifugal sintering
    • C04B2235/666—Applying a current during sintering, e.g. plasma sintering [SPS], electrical resistance heating or pulse electric current sintering [PECS]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Definitions

  • the invention relates to a process for manufacturing a part close to the dimensions (Near Net Shape or NNS) of complex shape by sintering under load from a preform produced according to a first method of manufacture, for example by an additive or molding technique.
  • NNS Near Net Shape
  • Sintering corresponds to the thermal consolidation of a pulverulent material of its constituents. It is one of the most delicate and often the most expensive operations during the preparation of ceramics.
  • the microstructure is put in place, by transport of matter between grains, in order to minimize excess interface energies, which is generally accompanied by a reduction in porosity.
  • the latter is manifested macroscopically by a shrinkage in relation to the “raw” part.
  • the raw material of a sintered component is generally a metal or ceramic powder. The characteristics of the part to be obtained determine the chemical composition of the powder.
  • hot isostatic pressing is a method of producing a high quality metal component such that it can be used in many applications, for example aerospace.
  • HIP is a heat treatment method that uses high temperatures and pressures to sinter particles of material, resulting in a component with improved structural properties on forged or cast objects.
  • the HIP process subjects a material, either in solid or powder form, to both elevated temperature and isostatic gas pressure in a high pressure containment vessel.
  • the material can for example be a metal powder.
  • HIP can be used to densify existing metal components with internal voids, or to join two components together.
  • Metal powders can be either pure metal powders (iron, copper) or alloy powders (bronze, brass, steel, etc.). The different nature of the powders (sponge, irregular, spherical, laminar), gives different properties to the component.
  • CIC FH I P hot isostatic compaction
  • the Chinese patent application CN102189261 a process for densifying a type of porous product consisting of placing a porous product in a sheath, the sheath and endpiece junction being implemented by welding and sealing before applying isostatic pressing.
  • This solution involves the use of a silica-type powder which considerably limits the type of materials that can be used, and leads to a porous part to be densified without in-situ extraction of the binder contained in the part produced.
  • Patent application WO2011030815 relates to a process for producing an electrically conductive molded object, which involves a step of sintering a premolded object, which is an object produced by molding a first electrically conductive powder, by a process flash sintering to form the electrically conductive molded object.
  • the precast object is sintered by applying a DC pulse current to the precast object while applying pressure to the precast object by a second electrically conductive powder.
  • Patent application DE2219410 relates to a process for the manufacture of molded parts pressed from powder, in particular from a high-strength refractory material down to an almost theoretical density by preforming a part pressed from a material powder having voids, by enclosing the molded part in a loose mass of pressure transmitting powder which, in a mold, by applying unidirectional pressure to the pressure transferring powder in the mold to further compress the molded part and , while simultaneously heating the body to at least the compaction temperature of the body, preferably in a controlled atmosphere, in which the temperature and/or pressure is increased to the densification temperature of the refractory material, thereby virtually eliminating all voids in the compressed form.
  • the present invention relates, in its most general sense, to a process for manufacturing a part by sintering under load, characterized in that it comprises:
  • a second step of heat treatment under pressure of said solid and non-porous preform consisting of: • Prepare a thermal sintering tool with the following steps: o Installation of a lower piston in a graphite matrix, o Insertion into said lower piston of a quantity of a first reusable compaction powder, with a particle size greater than the particle size of said bonded particles of the preform and having a melting temperature higher than the sintering temperature of said particles of said preform o Positioning of said solid and non-porous preform directly above said bed of compacting powder o Insertion of a second quantity a second reusable compacting powder, with a particle size greater than the particle size of said bonded particles of the preform and reusable, directly on said preform o Positioning of the upper piston in the graphite matrix,
  • the binder is not removed before the SPS step, and therefore the part has a non-porous homogeneous state, the interstice between the grains being filled by the bonding matrix , which is then extracted during the sintering step, and not before the heat treatment step under pressure jointly ensures the effect of grain surface welding and densification.
  • said preform is manufactured by additive manufacturing of a pulverulent material having a particle size D50 of between 1 and 10 miti.
  • said sintering powder has a D50 particle size of between 15 and 30 miti.
  • said first and second compacting powders are identical.
  • said compacting powder or powders are non-metallic powders.
  • the said compacting powder or powders are carbon graphite powders or an oxide ceramic.
  • Figure 1 shows a schematic view of a tool for the implementation of the invention
  • Figure 2 shows a partial schematic view of the tooling during the densification phase
  • Figure 3 shows a schematic view of the decapsulation of the sintered part.
  • the process that is the subject of the invention is broken down into two phases: the preparation of a massive, non-porous preform from metal or ceramic particles held together by a binder the positioning of the preform in a volume of compaction powder placed between two pistons
  • a post-treatment intended to increase the rate of densification and simultaneously the removal of the binder by the application of pressure on the pistons and heating to the sintering temperature to cause the debinding, the binder diffusing into the compacting powder as well as the simultaneous sintering of the metallic or ceramic particles of the preform.
  • the process is similar to a Hot Isostatic Pressing (HIP) process which makes it possible not to use special tools to apply the pressure although the load is not applied in a perfectly isotropic manner, more than to an SPS process which provides a perfectly uniaxial action.
  • HIP Hot Isostatic Pressing
  • the preform is placed in an enclosure into which an inert gas is injected (argon, nitrogen) under an applied pressure of approximately 100 MPa, homogeneously in all directions including at incoming angles.
  • an inert gas argon, nitrogen
  • it is not an inert gas which transmits the pressure, but a volume of powder which transmits the pressure and the heat to the preform.
  • the first step of the invention consists in manufacturing a preform made up of metallic or ceramic particles or more generally of a sinterable material. These particles must have a D50 particle size of less than 15 miti, which means that half of the grains are less than 15 miti in section, and half more than 15 miti. Preferably, the particle size dispersion is low and less than 1% of the particles have a section different from ⁇ 10% of the median section.
  • the preparation of a preform can be carried out in different ways.
  • One way is to manufacture a part by a “Bound Metal Deposition” type process developed for metal using the polymer melt deposition process (FDM or FFF) or by laser sintering, from a wire, bars or pellets that will be extruded. These are composed of metallic powder and of a binder.
  • the “binder jetting” type process is less appropriate because the parts produced by “binder jetting” at the raw stage are relatively dense.
  • the metal powder is, for example, 316L steel, the sintering temperature of which is greater than 600° C. with a mass percentage of binder of the order of 15%, in the form of metal wire with a binder envelope.
  • the part obtained is a solid, non-porous part, formed by a combination of ceramic or metal and plastic.
  • the manufacture of the preform can also be carried out by a laser process by bonding grains in a fusible phase (two-phase material) using a powder coated with the fusible binder. During the laser transfer, the binder occupies the interstice between the metallurgical grains to form a massive part without porosity.
  • the fusible binder is generally made up of polymers.
  • the major drawback of these methods is that the object produced is not of relevant quality and that the functional tests cannot be carried out under real conditions of use.
  • the preform has a geometry taking into account the deformation resulting from the sintering step, by mathematical modeling or by empirical adjustments.
  • the densification step consists of introducing the preform into a bed of powder with a particle size greater than that of the powders used for the manufacture of the preform.
  • This powder completely surrounds the preform; it is subjected to pressure under the effect of two opposing heated pistons.
  • the powder transmits heat to the preform, causing the binder to carbonize and the preform powder to sinter. Any gaseous effluent produced by the heating of the binder is evacuated through the grains of the powder bed surrounding the preform.
  • the preparation of the sintering tool comprises the following steps:
  • Insertion of a quantity of compacting powder of a first type The chemical nature, the particle size and the quantity of the powder are chosen by following the chemical nature of the powders the preform, its particle size, its geometric complexity, ...
  • the properties of this powder can be identical in all respects to the first powder bed, but can also differ (in particular the quantity and the granulometry);
  • the part is positioned on the compacting powder bed in such a way as to optimize densification while reducing shrinkage in certain directions.
  • a deformation study and a main axis of pressing is identified by modeling or an empirical approach. Optimization of positioning is carried out either by numerical study, but most often empirically.
  • the quantity of powder is chosen so as to absorb by capillarity the gaseous/liquid phases of binder forming during this sintering step.
  • the compaction powder allows the load transfer of the compression pistons while accommodating the shape of the part.
  • the characteristics of the compaction powder are such that the sintering temperature is significantly higher than that of the printed powder constituting the part to be densified or else chemically compatible and allowing the use of shake-out processes after densification.
  • the compaction/sintering powder ensures that the pressure stresses apply quasi-isotropically.
  • the part is sized (local extra thickness) in order to be in-fine “near net shape” (close to the final shape), which limits the machining finishing steps as much as possible to obtain the shape in a “net shape” state. ".
  • the part can be hollow and the inside is also filled with sintering powder.
  • the tool consists of an upper piston (10) and a lower piston (20) actuated in opposite directions along a longitudinal axis (1) by cylinders (11, 21) exerting an opposing thrust on the pistons (10, 20) .
  • the pistons (10, 20) are made of an electrically conductive material and are connected to a pulsed current generator (30).
  • the piston (10) is extended by a connecting block (12) called “spacer” also electrically conductive and having an upper die (13) defining with a lower die (23) a treatment enclosure (15).
  • the lower die (23) forms the end of a connecting block (22) called a “spacer”, which is also electrically conductive and extends the piston (20).
  • the part (16) obtained by additive manufacturing is placed in this enclosure (15), on a layer (17) of compacting powder then covered with a second layer (18) of compacting powder.
  • the compacting powder will for example be graphite carbon or an oxide ceramic.
  • the experimental results lead to a preferential use of a graphite compaction powder and on green parts produced exclusively by additive manufacturing of the fused wire deposition type (in English FDM Fused deposition modeling).
  • the nature of the materials is advantageously chosen from the following: inco 625, 315L, 17-4-ph, H13, TiAl, alumina, zirconia and SiC.
  • the invention is particularly advantageous through the reuse of the graphite forming the compaction powder.
  • the production process provides for a thermal cycle presenting, after the compaction stage, an in-situ debinding step allowing the binder not to flash off, thus protecting the part.
  • Differential compaction of the graphite powder is carried out in order to promote good sintering of the part, which makes it possible to have a forced deformation in a single direction in space, facilitating the retro-dimensioning of green parts.

Abstract

The invention relates to a method for manufacturing a near net shape (NNS) component of complex shape using pressure-assisted sintering from a preform produced according to a first method of manufacture. This method of manufacturing a component using pressure-assisted sintering is characterized in that it comprises a first step of producing a preform by agglomerating particles of particle size D50 less than 15 µm in a binding die, the preform forming a non-porous and non-debound solid monolithic component, and a second step of heat-treating said solid and non-porous preform under pressure.

Description

PROCEDE DE FABRICATION D'UNE PIECE PRES-DES-COTES (Near Net Shape ou NNS) DE FORME COMPLEXE PAR FRITTAGE SOUS CHARGE PROCESS FOR MANUFACTURING A NEAR-THE-SIDE PART (Near Net Shape or NNS) WITH A COMPLEX SHAPE BY SINTERING UNDER LOAD
Domaine de l'invention Field of invention
L'invention se rapporte à un procédé de fabrication d'une pièce près-des-cotes (Near Net Shape ou NNS) de forme complexe par frittage sous charge à partir d'une préforme réalisée selon un premier mode de fabrication, par exemple par une technique additive ou par moulage. The invention relates to a process for manufacturing a part close to the dimensions (Near Net Shape or NNS) of complex shape by sintering under load from a preform produced according to a first method of manufacture, for example by an additive or molding technique.
Pour fabriquer une pièce de forme complexe présentant des qualités mécaniques de dureté et de ténacité élevée, la solution la plus évidente consiste à usiner une pièce massive. Cette solution permet de bénéficier des qualités intrinsèques du matériau. To manufacture a complex-shaped part with mechanical qualities of high hardness and toughness, the most obvious solution is to machine a massive part. This solution makes it possible to benefit from the intrinsic qualities of the material.
On peut aussi réaliser une telle pièce par fonderie ou moulage. Toutefois, ces techniques limitent les géométries réalisables, sauf à utiliser des moules complexes à plusieurs tiroirs. Par ailleurs, il est difficile de préserver des caractéristiques isotropes. It is also possible to produce such a part by foundry or molding. However, these techniques limit the achievable geometries, except to use complex molds with several drawers. Furthermore, it is difficult to preserve isotropic characteristics.
Une autre solution consiste à réaliser une pièce par frittage sous charge. Le frittage correspond à la consolidation thermique d'un matériau pulvérulent de ses constituants. C'est l'une des opérations les plus délicates et souvent la plus coûteuse lors de la préparation des céramiques. Au cours du cycle thermique, la microstructure se met en place, par transport de matière entre grains, afin de minimiser les excès d'énergies d'interface, ce qui s'accompagne généralement d'une diminution de la porosité. Cette dernière se manifeste de façon macroscopique par un retrait par rapport à la pièce « crue ». La matière première d'un composant fritté est généralement une poudre métallique ou céramique. Les caractéristiques de la pièce à obtenir déterminent la composition chimique de la poudre. Another solution consists in producing a part by sintering under load. Sintering corresponds to the thermal consolidation of a pulverulent material of its constituents. It is one of the most delicate and often the most expensive operations during the preparation of ceramics. During the thermal cycle, the microstructure is put in place, by transport of matter between grains, in order to minimize excess interface energies, which is generally accompanied by a reduction in porosity. The latter is manifested macroscopically by a shrinkage in relation to the “raw” part. The raw material of a sintered component is generally a metal or ceramic powder. The characteristics of the part to be obtained determine the chemical composition of the powder.
En particulier, le pressage isostatique à chaud (HIP) est un procédé de production d'un composant métallique de haute qualité tel qu'il peut être utilisé dans de nombreuses applications, par exemple l'aérospatiale. In particular, hot isostatic pressing (HIP) is a method of producing a high quality metal component such that it can be used in many applications, for example aerospace.
HIP est une méthode de traitement thermique qui utilise des températures et des pressions élevées pour fritter des particules de matériau, ce qui donne un composant avec des propriétés structurelles améliorées sur des objets forgés ou moulés. HIP is a heat treatment method that uses high temperatures and pressures to sinter particles of material, resulting in a component with improved structural properties on forged or cast objects.
Le procédé HIP soumet un matériau, soit sous forme solide soit sous forme de poudre, à la fois à une température élevée et à une pression isostatique de gaz dans un récipient de confinement à haute pression. The HIP process subjects a material, either in solid or powder form, to both elevated temperature and isostatic gas pressure in a high pressure containment vessel.
Le matériau peut par exemple être une poudre métallique. The material can for example be a metal powder.
Par exemple, HIP peut être utilisé pour densifier des composants métalliques existants avec des vides internes, ou pour joindre deux composants ensemble. For example, HIP can be used to densify existing metal components with internal voids, or to join two components together.
Les poudres métalliques peuvent être soit des poudres de métal pur (fer, cuivre), soit des poudres alliées (bronze, laiton, acier, etc). La nature différente des poudres (éponge, irrégulière, sphérique, laminaire), confère des propriétés différentes au composant. Metal powders can be either pure metal powders (iron, copper) or alloy powders (bronze, brass, steel, etc.). The different nature of the powders (sponge, irregular, spherical, laminar), gives different properties to the component.
Enfin, on connaît les techniques d'impression additive, qui permettent de créer des pièces de formes complexes (creux, courbes, entrelacement) en intégrant même des fonctionnalités à l'intérieur d'une même pièce. Finally, we know the techniques of additive printing, which make it possible to create parts of complex shapes (hollows, curves, interlacing) by even integrating functionalities inside the same part.
On compte une variété de familles de fabrication par addition de couche : la fusion de fil au travers d'une buse chauffante (procédé FDM ou FFF), la projection de liant sur un substrat de type poudre (3DP), la projection de gouttes de matériaux (Polyjet), l'assemblage de couches à partir de feuilles ou plaques découpéesThere are a variety of manufacturing families by layer addition: melting wire through a heating nozzle (FDM or FFF process), spraying binder onto a powder type substrate (3DP), spraying drops of material (Polyjet), assembling layers from cut sheets or plates
(Stratoconception), la polymérisation d'une résine sous l'effet d'un laser ou d'une source UV (Stéréolithographie), la solidification d'un lit de poudre sous l'action d'une source d'énergie moyenne à forte puissance (laser) (SLS) et la projection d'un flux de poudre dans un flux d'énergie laser (CLAD). (Stratodesign), the polymerization of a resin under the effect of a laser or a UV source (Stereolithography), the solidification of a bed of powder under the action of a medium to high energy source power (laser) (SLS) and the projection of a stream of powder in a stream of laser energy (CLAD).
Les qualités mécaniques des pièces ainsi obtenues sont généralement assez médiocres et elles sont dégradées par la présence de liant. The mechanical qualities of the parts thus obtained are generally quite mediocre and they are degraded by the presence of binder.
On a proposé d'améliorer les qualités des pièces obtenues par fabrication additive par une étape additionnelle de compaction isostatique à chaud (CIC FH I P). La CIC / HIP sert à éliminer les pores et les cavités, afin d'augmenter les caractéristiques des matériaux. Sous des pressions typiques entre 400 et 2070 bar et des températures allant jusqu'à 2000 °C, les matériaux peuvent atteindre 100 % de sa densité théorique maximum. La CIC/HIP permet d'augmenter la ductilité et la résistance à la fatigue des pièces obtenues par fabrication additive. It has been proposed to improve the qualities of the parts obtained by additive manufacturing by an additional step of hot isostatic compaction (CIC FH I P). CIC/HIP is used to eliminate pores and cavities, in order to increase the characteristics of materials. Under typical pressures between 400 and 2070 bar and temperatures up to 2000°C, materials can reach 100% of its maximum theoretical density. CIC/HIP makes it possible to increase the ductility and fatigue resistance of parts obtained by additive manufacturing.
État de la technique State of the art
La demande de brevet chinois CN110773735A (D1) décrit un procédé de formage d'une pièce métallique par pressage isostatique à chaud, le procédé comprenant les étapes consistant à : Chinese patent application CN110773735A (D1) describes a process for forming a metal part by hot isostatic pressing, the process comprising the steps of:
• Former une ébauche initiale à former selon le modèle tridimensionnel dans un mode d'impression par pulvérisation tridimensionnelle, de sorte que le liant est pulvérisé sur le contour extérieur de la pièce à former, et l'ébauche initiale obtenue comprend une coque avec le contour extérieur et le métal poudre remplie dans la coque ; • Forming an initial blank to be formed according to the three-dimensional pattern in a three-dimensional spray printing mode, so that the binder is sprayed on the outer contour of the part to be formed, and the initial blank obtained comprises a shell with the outer contour and the metal powder filled in the shell;
• placer l'ébauche primaire dans une gaine pour un pressage isostatique à chaud, remplir un espace entre la gaine et l'ébauche primaire avec de la poudre de métal ou de céramique, puis effectuer un pressage isostatique à chaud sur la gaine, dans lequel, dans le processus, des particules de poudre métallique discrètes générer une déformation de fluage de dislocation,• placing the primary blank in a sheath for hot isostatic pressing, filling a space between the sheath and the primary blank with metal or ceramic powder, then performing hot isostatic pressing on the sheath, in which , in the process, discrete metal powder particles generate dislocation creep deformation,
• enlever la gaine, la poudre métallique ou céramique destinée à remplir l'espace entre la gaine et l'ébauche, et la coque dans ladite ébauche, de manière à obtenir la pièce de forme souhaitée. • removing the sheath, the metal or ceramic powder intended to fill the space between the sheath and the blank, and the shell in said blank, so as to obtain the part of the desired shape.
Le recours à la technique HIP implique une enveloppe métallique qui n'est pas compatible avec tous les matériaux. The use of the HIP technique involves a metal casing which is not compatible with all materials.
La demande de brevet chinois CN102189261 un procédé de densification d'un type de produit poreux consistant à placer un produit poreux dans une gaine, la jonction gaine et embout étant mise en œuvre par soudure et scellement avant d'appliquer un pressage isostatique. The Chinese patent application CN102189261 a process for densifying a type of porous product consisting of placing a porous product in a sheath, the sheath and endpiece junction being implemented by welding and sealing before applying isostatic pressing.
Cette solution implique le recours à une poudre type silice qui limite considérablement le type de matériaux utilisables, et conduit à une pièce à densifier poreuse sans extraction in-situ du liant contenu dans la pièce réalisée. This solution involves the use of a silica-type powder which considerably limits the type of materials that can be used, and leads to a porous part to be densified without in-situ extraction of the binder contained in the part produced.
La demande de brevet WO2011030815 se rapporte à un processus de production d'un objet moulé électriquement conducteur, qui implique une étape consistant à fritter un objet prémoulé, qui est un objet produit par le moulage d'une première poudre électriquement conductrice, par un procédé de frittage flash pour former l'objet moulé électriquement conducteur. Lors de l'étape, l'objet prémoulé est fritté par l'application d'un courant d'impulsion CC à l'objet prémoulé tout en appliquant une pression à l'objet prémoulé par une seconde poudre électriquement conductrice. La demande de brevet DE2219410 concerne un procédé de fabrication de pièces moulées pressées à partir de poudre, notamment à partir d'un matériau réfractaire à haute résistance jusqu'à une densité quasi théorique par préformage d'une pièce pressée à partir d'un matériau pulvérulent présentant des vides, en enfermant la pièce moulée dans une masse libre d'un poudre de transmission de pression qui , dans un moule, en appliquant une pression unidirectionnelle à la poudre de transfert de pression dans le moule pour comprimer davantage la pièce moulée et, tout en chauffant simultanément le corps à au moins la température de compactage du corps, de préférence dans une atmosphère contrôlée, dans lequel la température et / ou la pression est augmentée jusqu'à la température de densification du matériau réfractaire, ce qui élimine pratiquement tous les vides dans la forme comprimée. Patent application WO2011030815 relates to a process for producing an electrically conductive molded object, which involves a step of sintering a premolded object, which is an object produced by molding a first electrically conductive powder, by a process flash sintering to form the electrically conductive molded object. In the step, the precast object is sintered by applying a DC pulse current to the precast object while applying pressure to the precast object by a second electrically conductive powder. Patent application DE2219410 relates to a process for the manufacture of molded parts pressed from powder, in particular from a high-strength refractory material down to an almost theoretical density by preforming a part pressed from a material powder having voids, by enclosing the molded part in a loose mass of pressure transmitting powder which, in a mold, by applying unidirectional pressure to the pressure transferring powder in the mold to further compress the molded part and , while simultaneously heating the body to at least the compaction temperature of the body, preferably in a controlled atmosphere, in which the temperature and/or pressure is increased to the densification temperature of the refractory material, thereby virtually eliminating all voids in the compressed form.
Inconvénient de l'art antérieur Disadvantage of the prior art
La solution décrite dans le brevet CN1 10773735A conduit à une déformation de la préforme ce qui conduit à la perte de la géométrie visée. Le liant constitue un enrobage de la matière pulvérulente de la préforme. The solution described in patent CN1 10773735A leads to a deformation of the preform which leads to the loss of the target geometry. The binder constitutes a coating of the pulverulent material of the preform.
Solution apportée par l'invention Solution provided by the invention
Afin de remédier aux inconvénients de l'art antérieur, la présente invention concerne selon son acception la plus générale un procédé de fabrication d'une pièce par frittage sous charge caractérisé en ce qu'il comporte : In order to remedy the drawbacks of the prior art, the present invention relates, in its most general sense, to a process for manufacturing a part by sintering under load, characterized in that it comprises:
- une première étape de réalisation d'une préforme par agglomération de particules de granulométrie D50 inférieure à 15 miti dans une matrice de liaison, ladite préforme formant une pièce homogène et monolithique solide non poreuse et non déliantée, - a first step of producing a preform by agglomeration of particles with a D50 particle size of less than 15 miti in a bonding matrix, said preform forming a homogeneous and monolithic solid non-porous and non-debinded part,
- une deuxième étape de de traitement thermique sous pression de ladite préforme solide et non poreuse consistant à : • Préparer un outillage de frittage thermique avec les étapes suivantes : o Mise en place d'un piston inférieur dans une matrice graphite, o Insertion dans ledit piston inférieur d'une quantité d'une première poudre de compaction réutilisable, de granulométrie supérieure à la granulométrie desdites particules liées de la préforme et présentant une température de fusion supérieure à la température de frittage desdites particules de ladite préforme o Positionnement de ladite préforme solide et non poreuse directement au-dessus dudit lit de poudre de compactage o Insertion d'une seconde quantité d'une deuxième poudre de compactage réutilisable, de granulométrie supérieure à la granulométrie desdites particules liées de la préforme et réutilisable, directement sur ladite préforme o Mise en place du piston supérieur dans la matrice graphite,- a second step of heat treatment under pressure of said solid and non-porous preform consisting of: • Prepare a thermal sintering tool with the following steps: o Installation of a lower piston in a graphite matrix, o Insertion into said lower piston of a quantity of a first reusable compaction powder, with a particle size greater than the particle size of said bonded particles of the preform and having a melting temperature higher than the sintering temperature of said particles of said preform o Positioning of said solid and non-porous preform directly above said bed of compacting powder o Insertion of a second quantity a second reusable compacting powder, with a particle size greater than the particle size of said bonded particles of the preform and reusable, directly on said preform o Positioning of the upper piston in the graphite matrix,
• Exercice d'une pression axiale sur lesdits pistons et d'un chauffage à une température de frittage desdites particules de ladite préforme. • Exercise of an axial pressure on said pistons and heating to a sintering temperature of said particles of said preform.
Selon l'invention, contrairement à l'art antérieur, on ne retire pas le liant avant l'étape SPS, et de ce fait la pièce présente un état homogène non poreux, l'interstice entre les grains étant comblé par la matrice de liaison, qui est ensuite extraite pendant l'étape de frittage, et non pas avant l'étape de traitement thermique sous pression assure conjointement à l'effet de soudure de surface des grains et de densification. According to the invention, unlike the prior art, the binder is not removed before the SPS step, and therefore the part has a non-porous homogeneous state, the interstice between the grains being filled by the bonding matrix , which is then extracted during the sintering step, and not before the heat treatment step under pressure jointly ensures the effect of grain surface welding and densification.
De préférence, ladite préforme est fabriquée par fabrication additive d'un matériau pulvérulent présentant une granulométrie D50 comprise entre 1 et 10 miti. Avantageusement, ladite poudre de frittage présente une granulométrie D50 comprise entre 15 et 30 miti. Preferably, said preform is manufactured by additive manufacturing of a pulverulent material having a particle size D50 of between 1 and 10 miti. Advantageously, said sintering powder has a D50 particle size of between 15 and 30 miti.
Selon un mode de réalisation particulier, les dites premières et deuxièmes poudres de compactage sont identiques. De préférence, la ou lesdites poudres de compactage sont des poudres non métalliques. According to a particular embodiment, said first and second compacting powders are identical. Preferably, said compacting powder or powders are non-metallic powders.
Avantageusement, la ou lesdites poudres de compactage sont des poudres carbone graphite ou une céramique oxyde. Advantageously, the said compacting powder or powders are carbon graphite powders or an oxide ceramic.
Description détaillée d'un exemple non limitatif de réalisation Detailed description of a non-limiting embodiment
La présente invention sera mieux comprise à la lecture de la description qui suit, concernant un exemple non limitatif de réalisation illustré par les dessins annexés où: The present invention will be better understood on reading the following description, concerning a non-limiting example of embodiment illustrated by the appended drawings where:
• la figure 1 représente une vue schématique d'un outillage pour la mise en œuvre de l'invention • Figure 1 shows a schematic view of a tool for the implementation of the invention
• la figure 2 représente une vue schématique partielle de l'outillage pendant la phase de densification • Figure 2 shows a partial schematic view of the tooling during the densification phase
• la figure 3 représente une vue schématique du désencapsulage de la pièce frittée. • Figure 3 shows a schematic view of the decapsulation of the sintered part.
Principe général General principle
Le procédé objet de l'invention se décompose en deux phases : la préparation d'une préforme massive et non poreuse à partir de particules métalliques ou céramiques maintenues par un liant le positionnement de la préforme dans un volume de poudre de compaction disposée entre deux pistons The process that is the subject of the invention is broken down into two phases: the preparation of a massive, non-porous preform from metal or ceramic particles held together by a binder the positioning of the preform in a volume of compaction powder placed between two pistons
Un post-traitement destiné à augmenter le taux de densification et simultanément l'élimination du liant par l'application d'une pression sur les pistons et d'un chauffage à la température de frittage pour provoquer le déliantage, le liant diffusant dans la poudre de compactage ainsi que le frittage simultané des particules métalliques ou céramiques de la préforme.A post-treatment intended to increase the rate of densification and simultaneously the removal of the binder by the application of pressure on the pistons and heating to the sintering temperature to cause the debinding, the binder diffusing into the compacting powder as well as the simultaneous sintering of the metallic or ceramic particles of the preform.
Le procédé s'apparente à un procédé Hot Isostatic Pressing (HIP) qui permet de ne pas utiliser d'outillage particulier pour appliquer la pression bien que la charge ne soit pas appliquée de manière parfaitement isotrope, plus qu'à un procédé SPS qui prévoit une action parfaitement uniaxiale. The process is similar to a Hot Isostatic Pressing (HIP) process which makes it possible not to use special tools to apply the pressure although the load is not applied in a perfectly isotropic manner, more than to an SPS process which provides a perfectly uniaxial action.
Selon le procédé HIP connu dans l'art antérieur la préforme est placée dans d'une enceinte dans laquelle un gaz neutre est injecté (argon, azote) sous une pression appliquée d'environ 100 MPa, de manière homogène dans toutes les directions y compris dans les angles entrants. According to the HIP process known in the prior art, the preform is placed in an enclosure into which an inert gas is injected (argon, nitrogen) under an applied pressure of approximately 100 MPa, homogeneously in all directions including at incoming angles.
Selon l'invention, ce n'est pas un gaz neutre qui transmet la pression, mais un volume de poudre qui transmet sur la préforme la pression et la chaleur. According to the invention, it is not an inert gas which transmits the pressure, but a volume of powder which transmits the pressure and the heat to the preform.
Description détaillée de l'invention Detailed description of the invention
La première étape de l'invention consiste à fabriquer une préforme constituée de particules métalliques ou céramique ou plus généralement d'un matériau frittable. Ces particules doivent présenter une granulométrie D50 inférieure à 15 miti, ce qui signifie que la moitié des grains font moins de 15 miti de section, et la moitié plus de 15 miti. De préférence la dispersion de granulométrie est faible et moins de 1% des particules présentent une section différente de ±10% de la section médiane. The first step of the invention consists in manufacturing a preform made up of metallic or ceramic particles or more generally of a sinterable material. These particles must have a D50 particle size of less than 15 miti, which means that half of the grains are less than 15 miti in section, and half more than 15 miti. Preferably, the particle size dispersion is low and less than 1% of the particles have a section different from ±10% of the median section.
Préparation de la préforme Preparation of the preform
La préparation d'une préforme peut-être réalisée de différentes façons. The preparation of a preform can be carried out in different ways.
Une façon consiste à fabriquer une pièce par un procédé de type « Bound Métal Déposition » développée pour le métal à partir du procédé polymère de dépôt de matière fondue (FDM ou FFF) ou par frittage laser, à partir d'un fil, de barreaux ou de granulés qui seront extrudés. Ceux-ci sont composés de poudre métallique et d'un liant. Le procédé de type « binder jetting » est moins approprié car les pièces produites par « binder jetting » au stade cru, sont relativement denses. One way is to manufacture a part by a “Bound Metal Deposition” type process developed for metal using the polymer melt deposition process (FDM or FFF) or by laser sintering, from a wire, bars or pellets that will be extruded. These are composed of metallic powder and of a binder. The “binder jetting” type process is less appropriate because the parts produced by “binder jetting” at the raw stage are relatively dense.
La poudre métallique est par exemple de l'acier 316L dont la température de frittage est supérieure à 600°C avec un pourcentage massique de liant de l'ordre de 15 %, sous forme de fil métallique avec une enveloppe liant. The metal powder is, for example, 316L steel, the sintering temperature of which is greater than 600° C. with a mass percentage of binder of the order of 15%, in the form of metal wire with a binder envelope.
La pièce obtenue est une pièce massive, non poreuse, formée par une combinaison de céramique ou de métal et de plastique. The part obtained is a solid, non-porous part, formed by a combination of ceramic or metal and plastic.
La fabrication de la préforme peut aussi être réalisée par un procédé laser par collage de grains dans une phase fusible (matériau biphasé) utilisant une poudre enrobée par le liant fusible. Lors du transfert laser, le liant occupe l'interstice entre les grains métallurgique pour former une pièce massive sans porosité. The manufacture of the preform can also be carried out by a laser process by bonding grains in a fusible phase (two-phase material) using a powder coated with the fusible binder. During the laser transfer, the binder occupies the interstice between the metallurgical grains to form a massive part without porosity.
Le liant fusible est, généralement, constitué par des polymères. L'inconvénient majeur de ces procédés est que l'objet réalisé n'est pas de qualité pertinente et que les tests fonctionnels ne peuvent pas être effectués dans des conditions d'usage réelles. The fusible binder is generally made up of polymers. The major drawback of these methods is that the object produced is not of relevant quality and that the functional tests cannot be carried out under real conditions of use.
La préforme présente une géométrie prenant en compte la déformation résultant de l'étape de frittage, par modélisation mathématique ou par des ajustements empiriques. The preform has a geometry taking into account the deformation resulting from the sintering step, by mathematical modeling or by empirical adjustments.
Étape de densification de la préforme Preform densification step
L'étape de densification consiste à introduire la préforme dans un lit de poudre de granulométrie supérieure à celle des poudres utilisées pour la fabrication de la préforme. Cette poudre entoure complètement la préforme ; elle est soumise à une pression sous l'effet de deux pistons chauffés antagonistes. La poudre transmet la chaleur à la préforme, ce qui provoque la carbonisation du liant et le frittage de la poudre de la préforme. Les éventuels effluant gazeux produit par le chauffage du liant sont évacués à travers les grains du lit de poudre entourant la préforme. La préparation de l'outillage de frittage comporte les étapes suivantes : The densification step consists of introducing the preform into a bed of powder with a particle size greater than that of the powders used for the manufacture of the preform. This powder completely surrounds the preform; it is subjected to pressure under the effect of two opposing heated pistons. The powder transmits heat to the preform, causing the binder to carbonize and the preform powder to sinter. Any gaseous effluent produced by the heating of the binder is evacuated through the grains of the powder bed surrounding the preform. The preparation of the sintering tool comprises the following steps:
Mise en place du piston inférieur dans la matrice graphite, Installation of the lower piston in the graphite matrix,
Mise en place d'un système de libération de la pièce inférieur (papier graphite ou spray graphite, ou tout autre système connu de l'homme du métier), Installation of a release system for the lower part (graphite paper or graphite spray, or any other system known to those skilled in the art),
Insertion d'une quantité de poudre de compactage d'un premier type : La nature chimique, la granulométrie et la quantité de la poudre sont choisis en suivant la nature chimique des poudres la préforme, sa granulométrie, sa complexité géométrique, ... Insertion of a quantity of compacting powder of a first type: The chemical nature, the particle size and the quantity of the powder are chosen by following the chemical nature of the powders the preform, its particle size, its geometric complexity, ...
Positionnement de la pièce par-dessus le précédent lit de poudre Insertion d'une seconde quantité de poudre de compactage, afin de recouvrir la préforme précédemment introduite : les propriétés de cette poudre peuvent être identiques en tout point au premier lit de poudre, mais peuvent aussi différer (notamment la quantité et la granulométrie) ; Positioning of the part over the previous powder bed Insertion of a second quantity of compacting powder, in order to cover the previously introduced preform: the properties of this powder can be identical in all respects to the first powder bed, but can also differ (in particular the quantity and the granulometry);
Mise en place d'un système de libération de la pièce supérieur (papier graphite ou spray graphite, ou BN, ou tout autre système connu de l'homme du métier), Installation of an upper part release system (graphite paper or graphite spray, or BN, or any other system known to those skilled in the art),
Mise en place du piston supérieur dans la matrice graphite, Installation of the upper piston in the graphite matrix,
Compaction préliminaire de l'ensemble avant insertion dans la presse. Preliminary compaction of the assembly before insertion into the press.
La pièce est positionnée sur le lit de poudre de compactage de telle manière à optimiser la densification tout en réduisant les retraits dans certaines directions. Au préalable une étude de déformation et d'un axe principal de pressage est identifié par modélisation ou approche empirique. L'optimisation du positionnement est réalisée soit par étude numérique, mais le plus souvent de manière empirique. The part is positioned on the compacting powder bed in such a way as to optimize densification while reducing shrinkage in certain directions. Beforehand, a deformation study and a main axis of pressing is identified by modeling or an empirical approach. Optimization of positioning is carried out either by numerical study, but most often empirically.
La quantité de poudre est choisie de manière à absorber par capillarité les phases gazeuses/liquides de liant se formant durant cette étape frittage. The quantity of powder is chosen so as to absorb by capillarity the gaseous/liquid phases of binder forming during this sintering step.
De manière générale, la poudre de compaction permet le transfert de charge des pistons de compression tout en accommodant la forme de la pièce. Les caractéristiques de la poudre de compaction sont telles que la température de frittage est nettement supérieure à celle de la poudre imprimée constituant la pièce à densifier ou alors compatible chimiquement et permettant l'utilisation de procédés de décochage après densification. La poudre de compaction/frittage assure que les contraintes de pression s'appliquent de manière quasi-isotrope. In general, the compaction powder allows the load transfer of the compression pistons while accommodating the shape of the part. The characteristics of the compaction powder are such that the sintering temperature is significantly higher than that of the printed powder constituting the part to be densified or else chemically compatible and allowing the use of shake-out processes after densification. The compaction/sintering powder ensures that the pressure stresses apply quasi-isotropically.
La pièce est dimensionnée (surépaisseur locale) afin d'être in-fine « near net shape » (proche de la forme finale), ce qui limite au maximum les étapes de parachèvements d'usinage pour obtenir la forme dans un état « net shape ». La pièce peut être creuse et l'intérieur est également rempli de poudre de frittage. The part is sized (local extra thickness) in order to be in-fine “near net shape” (close to the final shape), which limits the machining finishing steps as much as possible to obtain the shape in a “net shape” state. ". The part can be hollow and the inside is also filled with sintering powder.
Description de l'outillage Description of the tool
L'outillage est constitué par un piston supérieur (10) et un piston inférieur (20) actionnés en direction opposées selon un axe longitudinal (1) par des vérins (11 , 21) exerçant une poussée antagoniste sur les pistons (10, 20). Les pistons (10, 20) sont réalisés en une matière conductrice électriquement et sont reliés à un générateur de courant pulsé (30). The tool consists of an upper piston (10) and a lower piston (20) actuated in opposite directions along a longitudinal axis (1) by cylinders (11, 21) exerting an opposing thrust on the pistons (10, 20) . The pistons (10, 20) are made of an electrically conductive material and are connected to a pulsed current generator (30).
La piston (10) est prolongé par un bloc de liaison (12) dit « spacer » également conducteur électriquement et présentant une matrice supérieure (13) définissant avec une matrice inférieure (23) une enceinte de traitement (15). La matrice inférieure (23) constitue l'extrémité d'un bloc de liaison (22) dit « spacer » également conducteur électriquement prolongeant le piston (20). The piston (10) is extended by a connecting block (12) called "spacer" also electrically conductive and having an upper die (13) defining with a lower die (23) a treatment enclosure (15). The lower die (23) forms the end of a connecting block (22) called a “spacer”, which is also electrically conductive and extends the piston (20).
La pièce (16) obtenue par fabrication additive est disposée dans cette enceinte (15), sur une couche (17) de poudre de compactage puis recouverte avec une seconde couche (18) de poudre de compactage. La poudre de compactage sera par exemple du carbone graphite ou une céramique oxyde. The part (16) obtained by additive manufacturing is placed in this enclosure (15), on a layer (17) of compacting powder then covered with a second layer (18) of compacting powder. The compacting powder will for example be graphite carbon or an oxide ceramic.
On applique ensuite une pression grâce aux deux pistons (10, 20), conjointement au passage d'un courant électrique qui va traverser l'enceinte (15) et assurer la montée en température pour provoquer le frittage des particules de la préforme (16). La pièce (16) densifiée et frittée est ensuite retirée de l'enceinte (16) et les matériaux pulvérulents (17, 18) peuvent être récupérés pour une nouvelle réalisation. Pressure is then applied using the two pistons (10, 20), together with the passage of an electric current which will pass through the enclosure (15) and ensure the temperature rise to cause the particles of the preform (16) to sinter. . The densified and sintered part (16) is then removed from the enclosure (16) and the pulverulent materials (17, 18) can be recovered for a new production.
Mode de mise en œuyre préférentiel Preferred implementation mode
Les résultats expérimentaux conduisent à une utilisation préférentielle d'une poudre de compaction en graphite et sur des pièces vertes produites exclusivement en fabrication additive de type dépôt de fil fondu (en anglais FDM Fused déposition modeling). La nature des matériaux est avantageusement choisie parmi les suivants : inco 625, 315L, 17-4-ph, H13, TiAl, alumine, zircone et SiC. The experimental results lead to a preferential use of a graphite compaction powder and on green parts produced exclusively by additive manufacturing of the fused wire deposition type (in English FDM Fused deposition modeling). The nature of the materials is advantageously chosen from the following: inco 625, 315L, 17-4-ph, H13, TiAl, alumina, zirconia and SiC.
L'invention est particulièrement avantageuse par la réutilisation du graphite formant la poudre de compaction. The invention is particularly advantageous through the reuse of the graphite forming the compaction powder.
Le processus de production prévoit un cycle thermique présentant après l'étape de compaction un pallier de déliantage in-situ permettant de ne pas faire partir le liant de manière flash, protégeant ainsi la pièce. The production process provides for a thermal cycle presenting, after the compaction stage, an in-situ debinding step allowing the binder not to flash off, thus protecting the part.
On réalise une compaction différentielle de la poudre graphite afin de favoriser le bon frittage de la pièce qui permet d'avoir une déformation forcée dans une seule direction de l'espace, facilitant le rétro-dimensionnement de pièces vertes. Differential compaction of the graphite powder is carried out in order to promote good sintering of the part, which makes it possible to have a forced deformation in a single direction in space, facilitating the retro-dimensioning of green parts.

Claims

Revendications Claims
1 - Procédé de fabrication d'une pièce par frittage sous charge caractérisé en ce qu'il comporte : une première étape de réalisation d'une préforme par agglomération de particules de granulométrie D50 inférieure à 15 miti dans une matrice de liaison, ladite préforme formant une pièce monolithique solide non poreuse et non déliantée une deuxième étape de traitement thermique sous pression de ladite préforme solide et non poreuse consistant à : 1 - Process for manufacturing a part by sintering under load characterized in that it comprises: a first step of producing a preform by agglomeration of particles of particle size D50 less than 15 miti in a bonding matrix, said preform forming a non-porous, non-debinded solid monolithic part a second step of heat treatment under pressure of said solid, non-porous preform consisting of:
Préparer un outillage de frittage thermique avec les étapes suivantes : o Mise en place d'un piston inférieur dans une matrice graphite, o Insertion dans ledit piston inférieur d'une quantité d'une première poudre de compaction réutilisable, de granulométrie supérieure à la granulométrie desdites particules liées de la préforme et présentant une température de fusion supérieure à la température de frittage desdites particules de ladite préforme o Positionnement de ladite préforme solide et non poreuse directement au-dessus dudit lit de poudre de compactage o Insertion d'une seconde quantité d'une deuxième poudre de compactage réutilisable, de granulométrie supérieure à la granulométrie desdites particules liées de la préforme et réutilisable, directement sur ladite préforme o Mise en place du piston supérieur dans la matrice graphite, Exercer une pression sur lesdits pistons et d'un chauffage à une température de frittage desdites particules de ladite préforme. 2 - Procédé de fabrication d'une pièce par frittage selon la revendication 1 caractérisé en ce que la préforme est fabriquée par fabrication additive d'un matériau pulvérulent présentant une granulométrie D50 comprise entre 1 et 10 miti. Prepare a thermal sintering tool with the following steps: o Installation of a lower piston in a graphite matrix, o Insertion into said lower piston of a quantity of a first reusable compaction powder, with a particle size greater than the particle size of said bonded particles of the preform and having a melting temperature higher than the sintering temperature of said particles of said preform o Positioning of said solid and non-porous preform directly above said bed of compacting powder o Insertion of a second quantity of a second reusable compacting powder, with a particle size greater than the particle size of said bound particles of the preform and reusable, directly on said preform o Placing the upper piston in the graphite matrix, Exerting pressure on said pistons and heating at a sintering temperature of said particles of said preform. 2 - A method of manufacturing a part by sintering according to claim 1 characterized in that the preform is manufactured by additive manufacturing of a powder material having a D50 particle size between 1 and 10 miti.
3 - Procédé de fabrication d'une pièce par frittage selon la revendication 1 caractérisé en ce que ladite poudre de compaction présente une granulométrie D50 comprise entre 15 et 30 miti. 3 - A method of manufacturing a part by sintering according to claim 1 characterized in that said compaction powder has a D50 particle size between 15 and 30 miti.
4 - Procédé de fabrication d'une pièce par frittage selon la revendication 1 caractérisé en ce que les dites premières et deuxièmes poudres de compactage sont identiques. 5 - Procédé de fabrication d'une pièce par frittage selon la revendication 1 caractérisé en ce qu'il comporte une étape mise en place d'un système de libération de la pièce supérieur déposée entre la poudre de compaction et le piston. 4 - A method of manufacturing a part by sintering according to claim 1 characterized in that said first and second compacting powders are identical. 5 - A method of manufacturing a part by sintering according to claim 1 characterized in that it comprises a step of setting up a system for releasing the upper part deposited between the compaction powder and the piston.
6 - Procédé de fabrication d'une pièce par frittage selon la revendication 1 caractérisé en ce que la ou lesdites poudres de compactage sont des poudres non métalliques. 6 - A method of manufacturing a part by sintering according to claim 1 characterized in that said compacting powder or powders are non-metallic powders.
7 - Procédé de fabrication d'une pièce par frittage selon la revendication 1 caractérisé en ce que la ou lesdites poudres de compactage sont des poudres carbone graphite ou une céramique oxyde. 7 - A method of manufacturing a part by sintering according to claim 1 characterized in that said compacting powder or powders are carbon graphite powders or an oxide ceramic.
EP22711275.2A 2021-03-02 2022-03-02 Method for manufacturing a near net shape (nns) component of complex shape using pressure-assisted sintering Pending EP4301531A1 (en)

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PCT/FR2022/050370 WO2022185009A1 (en) 2021-03-02 2022-03-02 Method for manufacturing a near net shape (nns) component of complex shape using pressure-assisted sintering

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CA954262A (en) * 1971-04-20 1974-09-10 Frederick F. Lange Method of compacting shaped powdered objects
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CN102189261A (en) * 2011-05-30 2011-09-21 华中科技大学 Densification method of porous workpiece
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