EP3129516B1 - Thermal treatment of an aluminium-titanium based alloy - Google Patents

Thermal treatment of an aluminium-titanium based alloy Download PDF

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Publication number
EP3129516B1
EP3129516B1 EP15719501.7A EP15719501A EP3129516B1 EP 3129516 B1 EP3129516 B1 EP 3129516B1 EP 15719501 A EP15719501 A EP 15719501A EP 3129516 B1 EP3129516 B1 EP 3129516B1
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Prior art keywords
alloy
semi
finished product
casting
mould
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German (de)
French (fr)
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EP3129516A1 (en
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Guillaume Martin
Céline Jeanne MARCILLAUD
Marie MINEUR-PANIGEON
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Safran Aircraft Engines SAS
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Safran Aircraft Engines SAS
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
    • C22F1/18—High-melting or refractory metals or alloys based thereon
    • C22F1/183—High-melting or refractory metals or alloys based thereon of titanium or alloys based thereon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
    • B21K3/00—Making engine or like machine parts not covered by sub-groups of B21K1/00; Making propellers or the like
    • B21K3/04—Making engine or like machine parts not covered by sub-groups of B21K1/00; Making propellers or the like blades, e.g. for turbines; Upsetting of blade roots
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D13/00—Centrifugal casting; Casting by using centrifugal force
    • B22D13/02—Centrifugal casting; Casting by using centrifugal force of elongated solid or hollow bodies, e.g. pipes, in moulds rotating around their longitudinal axis
    • B22D13/026—Centrifugal casting; Casting by using centrifugal force of elongated solid or hollow bodies, e.g. pipes, in moulds rotating around their longitudinal axis the longitudinal axis being vertical
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D13/00—Centrifugal casting; Casting by using centrifugal force
    • B22D13/04—Centrifugal casting; Casting by using centrifugal force of shallow solid or hollow bodies, e.g. wheels or rings, in moulds rotating around their axis of symmetry
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D13/00—Centrifugal casting; Casting by using centrifugal force
    • B22D13/10—Accessories for centrifugal casting apparatus, e.g. moulds, linings therefor, means for feeding molten metal, cleansing moulds, removing castings
    • B22D13/107—Means for feeding molten metal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
    • B22D21/002—Castings of light metals
    • B22D21/005—Castings of light metals with high melting point, e.g. Be 1280 degrees C, Ti 1725 degrees C
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
    • B22D27/15—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using vacuum
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D7/00—Casting ingots, e.g. from ferrous metals
    • B22D7/005—Casting ingots, e.g. from ferrous metals from non-ferrous metals
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C14/00—Alloys based on titanium
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
    • F01D5/12—Blades
    • F01D5/14—Form or construction
    • F01D5/147—Construction, i.e. structural features, e.g. of weight-saving hollow blades
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
    • F01D5/12—Blades
    • F01D5/28—Selecting particular materials; Particular measures relating thereto; Measures against erosion or corrosion
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2220/00—Application
    • F05D2220/30—Application in turbines
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2230/00—Manufacture
    • F05D2230/20—Manufacture essentially without removing material
    • F05D2230/21—Manufacture essentially without removing material by casting
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2230/00—Manufacture
    • F05D2230/40—Heat treatment
    • F05D2230/42—Heat treatment by hot isostatic pressing

Definitions

  • the present invention relates to the heat treatments of metallurgical alloys and, more particularly, the heat treatments of an alloy based on titanium aluminide (titanium-aluminide alloy in English).
  • Titanium aluminides are a class of alloys whose compositions include at least titanium and aluminum, and typically some additional alloying elements.
  • Titanium aluminides and in particular those of the gamma type (gamma titanium-aluminide alloys in English), have the advantage of low density, good resistance to cyclic deformation at low and intermediate temperature, and good environmental resistance. They find application in aircraft engines, as low pressure turbine blades (stator or rotor), bearing supports, high pressure compressor housings, and sealing supports for low pressure turbine, in particular.
  • Titanium aluminides and in particular those of the gamma type, are typically prepared by melting, molding, then hot isostatic compression in order to reduce the porosity resulting from the casting, followed by at least one heat treatment to obtain a good compromise between mechanical properties in traction, fatigue and creep.
  • This treatment process is characterized by a heat treatment temperature which is between 1045 ° C and 1255 ° C for 10 to 40 hours.
  • This manufacturing process is characterized by a heat treatment at a temperature between 1045 ° C and 1255 ° C and for 10 to 40 hours.
  • this “pressure lower than that of hot isostatic compression” will therefore necessarily be less than 1700 ⁇ 10 5 Pa, and preferably less than 1000 ⁇ 10 5 Pa.
  • a preferred characteristic of the invention moreover provides that the step of obtaining the semi-finished product resulting from the molding by centrifugal casting comprises a casting in said permanent mold which the alloy will then fill in such a way that the size of the internal pores of this alloy is reduced after casting compared to what it was before.
  • the simple shape of the mold (without undercut) will be sought to allow it to be filled quickly with the alloy in such a way as to reduce the size of its internal pores compared to what this pore size would be without casting. in such a mold.
  • a hot spot is typically a zone where the temperature of the alloy cast in the mold is higher and / or the flow of this alloy is higher. less favorable, or the diffusion of heat from the metal to the mold also less favorable, such as at the location of an edge of the mold).
  • a characteristic of the proposed solution moreover provides that the semi-finished product raw molded can be heat treated and then machined directly, without intermediate dimensional control of a blank.
  • a simple geometry of the mold therefore of the blank which comes out of its cavity, (typically having at least one plane of symmetry and / or at most one inflection) will limit the risks of non-conformity (limitation of the rate of porosities by avoiding create hot spots).
  • the fact that the mold is a metal mold will eliminate the risk of obtaining ceramic inclusions from the ceramic shell in the case of the lost wax casting process
  • a simple geometry of the mold, therefore of roughing, will allow easy automation of machining.
  • the figure 1 therefore illustrates the main steps not only of treatment of the alloy concerned, but more generally, as a finished product, for example of a turbine blade made of a titanium aluminide-based alloy.
  • An alloy microstructure comprising gamma grains and / or lamellar grains (alpha2 / gamma).
  • step 13 machine in this form here of one or more turbine blades, the heat-treated semi-finished product (see figure 2 ).
  • a device 15 as illustrated may be used. figure 3 which will make it possible to mold a series of semi-finished blanks 7, each of which can have the shape of a bar as foundry where the finished part (s) will then be machined, here two blades 17 of turbomachine turbine.
  • the device 15 comprises a closed and sealed enclosure 19 in which a partial vacuum can be applied.
  • An ingot 21, here in an alloy based on titanium aluminide, and more precisely on titanium aluminide of the gamma type, is first melted in a crucible 23. When molten, the alloy is then poured into a mold. 25 permanent metal, via a funnel 26.
  • the mold 25 makes it possible to cast the alloy by centrifugation, in order to obtain the blanks 7. For this, it is rotated around an axis A.
  • the mold 25 comprises several cavities 27 which extend radially (axes B1 , B2 ...; figures 3, 4 ) around the axis A, preferably by means of a motor 29. These cavities are preferably regularly spaced angularly around the axis A which is here vertical.
  • the centrifugal forces generated by the rotation of the mold force the molten alloy to enter and fill these cavities.
  • the alloy to be cast brought towards the center of the mold, is distributed radially towards the peripheral cavities.
  • the mold 25 is opened and the molded blanks 7 are extracted.
  • the walls of the mold which surround the cavities 27 for collecting the metal are resistant to centrifugal forces, typically more than 10 g.
  • the particles are subjected to a centrifugal force, which can be increased with the angular speed. This increase is distributed over the entire mass of the liquid metal, uniformly over the entire length of each cavity 27.
  • the mold comprises several shells, such as 150a, 150b which open and close along a surface (here the parting line 152) which is generally transverse to the axis (A) around which the mold rotates.
  • a separable attachment 153 such as a lock, is established between the shells so, once the shells have been separated, to be able to exit the molded blank, through the released opening 154.
  • the lines 152 also materialize a parting line making it possible to close and open the mold in question.
  • the mold shown has first and second sides 33a, 33b opposite along the axis 35 and parallel to each other. These two sides are one the entry side of the casting; It is therefore radially internal and the axis 34 is parallel (or even coincident) with one of the axes B, such as B1.
  • this mold (and therefore the solid, polyhedral blank obtained) has here, between the aforementioned first and second sides, a third and a fourth sides (33c, 33d) which widen together from the first side 33a towards the second side, at a first angle and then, from a break in slope (or inflection) 35, at a second larger angle than the first.
  • this mold (its mold cavity) is defined by a first and a second truncated pyramids 37a, 37b, the second pyramid being the extension of the first pyramid by the large base of the first pyramid which is exactly superimposed on the small base of the second.
  • the mold and its molded blank have a plane of symmetry 39 perpendicular to the first and second sides 33a, 33b and which contains the axis 34.
  • the embodiment of the mold cavity of the figure 6 illustrates a blocky mold cavity having two opposite sides, each of generally trapezoidal shape 37a, 37b.
  • Access to the interior of the cavity can be effected radially by one of the two lateral sides, here the larger 41c.
  • the blank exhibits externally - on a determined side or face - at most one inflection by which the section of the semi-finished blank increases or decreases, with, depending on its axis of elongation, here 34 or 43, a maximum cross section S1 of the blank located at one end, along this axis.
  • the figure 7 shows another interesting mold solution where, individually, the open radially inner end 45a of the alloy casting cavity 27 has a shape tapering in section (zone 47a) towards the center of the cavity, along radial direction B.
  • a truncated cone could be suitable.
  • the shape here is in fact a double funnel (head-to-tail), therefore with a radially outer end part of the cavity, which is stepped, to present an enlarged end part 47b.
  • section S2, S3 of the mold / molded blank towards the (or at) ends there are thus maximums of section S2, S3 of the mold / molded blank towards the (or at) ends, it being specified that the sections S1, S2, S3 are each defined externally, transversely to the axis of elongation concerned, as shown.
  • the form 47a may correspond to the heel area of this blade and the end part 47b to the area of the enlarged foot, or vice versa.
  • VAR Vauum Arc Remelting - Recasting with the vacuum arc
  • PAM Pasma Arc Melting - Fusion by plasma arc
  • step 8 figure 1 After having unmolded these blanks 7, they can be cut (roughly) into semi-finished products (step 8 figure 1 ), according to said form "less complex" than that of the finished products which will finally be machined.
  • the unmolded blank can thus be cut into a shape which does not require dimensional control before the latter.
  • ci is machined according to the expected finished product; see final step 14 of dimensional control after machining, figure 1 .
  • each semi-finished product 7 will have been heat treated, without hot isostatic compression (CIC), in order to obtain an alloy microstructure comprising gamma grains and / or lamellar grains (alpha2 / gamma).
  • CIC hot isostatic compression
  • the figures 10.11 show TiAl 48-2-2 microstructures: 48% Al 2% Cr 2% Nb (at%) obtained respectively with and without hot isostatic compaction (CIC), for the same thermal history.
  • tests 1, in Rm, and 4, in A% show an almost exact agreement (superposition) of the results with hot isostatic compaction (solid diamonds) and without (hollow diamonds). The other results are close, two by two. And when they exist, dispersions are low.
  • test piece (a cylinder) made of TiAl 48-2-2.
  • the comparative case of figure 10 was obtained under the following conditions (see US 5609698 ): first treatment, called PLL treatment, comprising a pre-HIP treatment of 1145 ° C for 5 hours, HIP at 1255 ° C, and heat treatment at 1200 ° C, for 2 hours.
  • the alloy used may in particular be TiAl 48-2-2: 48% Al; 2% Cr; 2% Nb (at%), especially since this intermetallic material is useful for at least partially producing certain stages of a turbomachine turbine aircraft, the invention is more generally applicable in particular to the titanium aluminide alloys mentioned below having a composition capable of forming alpha2 and gamma phases, when the alloy is cooled from a melt.
  • gamma titanium aluminides are typically alloys of titanium, from about 40 to 50 atomic percent (at%) aluminum, with optionally small amounts of other alloying elements such as chromium, niobium, vanadium, tantalum, manganese and / or boron.
  • Preferred compositions are from about 45.0 to about 48.5 atomic percent of aluminum, and therefore are at the high end of the operating range.
  • Ti-48Al-2Cr-2Nb Ti-48Al-2Mn-2Nb, Ti-49Al-1V, Ti-47Al-1 Mn-2Nb-0.5W-0.5Mo- 0.2Si, and Ti-47Al- 5Nb-1W. If the manufacturing conditions (in particular the heat treatment) applied to these specific alloys correspond to the aforementioned case of TiAl 48-2-2, in conjunction with the figures 11-12 , the results provided figure 12 are applicable to them.

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  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • General Engineering & Computer Science (AREA)
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Description

La présente invention concerne les traitements thermiques des alliages métallurgiques et, plus particulièrement, les traitements thermiques d'un alliage à base d'aluminure de titane (titanium-aluminide alloy en anglais).The present invention relates to the heat treatments of metallurgical alloys and, more particularly, the heat treatments of an alloy based on titanium aluminide (titanium-aluminide alloy in English).

Les aluminures de titane sont une classe d'alliages dont les compositions comprennent au moins du titane et de l'aluminium, et typiquement quelques éléments d'alliage supplémentaires.Titanium aluminides are a class of alloys whose compositions include at least titanium and aluminum, and typically some additional alloying elements.

Les aluminures de titane, et en particulier ceux de type gamma (gamma titanium-aluminide alloys en anglais), ont l'avantage d'une faible densité, d'une bonne résistance à la déformation cyclique à température basse et intermédiaire, et une bonne résistance à l'environnement. Ils trouvent une application dans les moteurs d'avion, en tant qu'aubes (de stator ou rotor) de turbine basse pression, supports de palier, carters de compresseur haute pression, et supports d'étanchéité pour turbine basse pression, notamment.Titanium aluminides, and in particular those of the gamma type (gamma titanium-aluminide alloys in English), have the advantage of low density, good resistance to cyclic deformation at low and intermediate temperature, and good environmental resistance. They find application in aircraft engines, as low pressure turbine blades (stator or rotor), bearing supports, high pressure compressor housings, and sealing supports for low pressure turbine, in particular.

Les aluminures de titane, et en particulier ceux de type gamma, sont typiquement préparés par fusion, moulage, puis compression isostatique à chaud afin de réduire la porosité résultant de la coulée, suivi d'au moins un traitement thermique pour obtenir un bon compromis entre les propriétés mécaniques en traction, fatigue et fluage.Titanium aluminides, and in particular those of the gamma type, are typically prepared by melting, molding, then hot isostatic compression in order to reduce the porosity resulting from the casting, followed by at least one heat treatment to obtain a good compromise between mechanical properties in traction, fatigue and creep.

Pour obtenir une microstructure et un taux de porosité assurant de bonnes propriétés mécaniques, il a été proposé par le passé d'utiliser une combinaison d'une compression isostatique à chaud à température d'environ 1200°C, suivie d'un traitement thermique à plus haute température, soit environ 1300°C.To obtain a microstructure and a porosity rate ensuring good mechanical properties, it has been proposed in the past to use a combination of hot isostatic compression at a temperature of about 1200 ° C., followed by a heat treatment at highest temperature, around 1300 ° C.

Malheureusement, ceci nécessitait un four spécialisé coûtant cher et pouvant ne pas être logistiquement disponible dans tous les cas.Unfortunately, this required a specialized oven which was expensive and might not be logistically available in all cases.

Dans US 5609698 , il a ultérieurement été proposé, pour pallier ce problème, de procéder comme suit:

  • obtenir de coulée un alliage aluminure de titane de type gamma ayant d'environ 45,0 à environ 48,5 pour cent atomique d'aluminium (dans la présente demande, toutes les compositions d'alliages sont présentes en atomes pour cent -at %-, sauf indication contraire),
  • effectuer un prétraitement thermique (pre-HIP heat treatement) de cet alliage à une température comprise entre environ 1035°C (1900°F) et environ 1150°C (2100°F) pendant environ 5 à 50 heures,
  • effectuer ensuite une compression isostatique à chaud (HIP) de l'alliage prétraité, à une température d'environ 1175°C (2150°F) et à une pression d'environ 1000 à 1700x105Pa, pendant environ 3 à 5 heures,
  • puis effectuer un post-traitement thermique de l'alliage comprimé (post-HIP heat treatement) à une température entre environ 1010°C (1850°F) et environ 1200°C (2200°F), pendant environ 2 à 20 heures.
In US 5609698 , it was subsequently proposed, to overcome this problem, to proceed as follows:
  • obtain by casting a gamma-type titanium aluminide alloy having from about 45.0 to about 48.5 atomic percent aluminum (in the present application, all alloy compositions are present in atomic percent -at% -, unless otherwise stated),
  • perform a pre-HIP heat treatment of this alloy at a temperature between approximately 1035 ° C (1900 ° F) and approximately 1150 ° C (2100 ° F) for approximately 5 to 50 hours,
  • then perform hot isostatic compression (HIP) of the pretreated alloy, at a temperature of approximately 1175 ° C (2150 ° F) and at a pressure of approximately 1000 to 1700x10 5 Pa, for approximately 3 to 5 hours,
  • then perform post-HIP heat treatment of the compressed alloy at a temperature between about 1010 ° C (1850 ° F) and about 1200 ° C (2200 ° F), for about 2 to 20 hours.

Les valeurs maximales de ces gammes de températures de traitements thermiques sont certes notablement en dessous de la température d'environ 1300°C (2375°F) utilisée antérieurement.The maximum values of these heat treatment temperature ranges are certainly significantly below the temperature of about 1300 ° C (2375 ° F) previously used.

Mais, cette exigence de contrôle strict des trois paramètres que sont une pression élevée (pression HIP ou CIC en français), une température élevée et une durée assez longue demeure très contraignante.However, this requirement of strict control of the three parameters which are high pressure (HIP pressure or CIC in French), high temperature and a fairly long duration remains very restrictive.

Or, il est apparu contre toute attente aux inventeurs que, pour faciliter la mise en œuvre de traitements thermiques d'un alliage à base d'aluminure de titane, et notamment d'aluminure de titane de type gamma, y compris dans le cadre de la fabrication d'une aube de turbine en un tel alliage, ce n'est pas tant (ou essentiellement) la température qu'il faut réduire en liaison avec une compression isostatique à chaud que la compression isostatique à chaud en elle-même qu'il faut reconsidérer, contrairement à ce qu'enseigne au moins US 5609698 .However, it appeared against all expectations to the inventors that, in order to facilitate the implementation of heat treatments of an alloy based on titanium aluminide, and in particular on titanium aluminide of the gamma type, including in the context of the manufacture of a turbine blade in such an alloy, it is not so much (or essentially) the temperature which has to be reduced in connection with a hot isostatic compression as the hot isostatic compression itself as we must reconsider, contrary to what teaches at least US 5609698 .

Un autre document, Badami, Marco, and Francesco Marino. "Fatigue tests of un-HIP'ed γ-TïAl engine valves for motorcycles. " International journal of fatigue 28.7 (2006): 722-732 , est une contribution à un moulage centrifuge d'un alliage gamma-TiAl à une pression HIP exclusivement, sans détailler les conditions du traitement thermique auquel est soumis l'alliage.Another document, Badami, Marco, and Francesco Marino. "Fatigue tests of un-HIP'ed γ-TïAl engine valves for motorcycles." International journal of fatigue 28.7 (2006): 722-732 , is a contribution to centrifugal casting of a gamma-TiAl alloy at a HIP pressure exclusively, without detailing the conditions of the heat treatment to which the alloy is subjected.

De fait, la qualité des produits finis à obtenir (telles des aubes de turbine de turbomachine pour aéronefs), et les contraintes imposées notamment par les techniques antérieures (coûts, matériels, précisions), ont amené ces inventeurs à oser s'exonérer des préjugés techniques ci-avant évoqués.In fact, the quality of the finished products to be obtained (such as turbine engine turbine blades for aircraft), and the constraints imposed in particular by the prior techniques (costs, materials, details), led these inventors to dare to free themselves from prejudices. techniques mentioned above.

Ils ont ainsi pu percevoir qu'il semblait raisonnable de pouvoir se dispenser d'une étape de compactage isostatique à chaud, dans certaines conditions.They were thus able to perceive that it seemed reasonable to be able to dispense with a hot isostatic compaction step, under certain conditions.

Ils ont aussi pu définir un procédé de traitement d'un alliage à base d'aluminure de titane avec 40 à 50 pour cent atomique (at %) d'aluminium, comprenant les étapes suivantes :

  • réaliser un moulage d'un produit semi-fini par coulée centrifuge en moule permanent,
  • puis traiter thermiquement le produit semi-fini,
  • ceci à une pression sensiblement égale à la pression atmosphérique, jusqu'à obtenir une microstructure de l'alliage comprenant des grains gamma et/ou des grains lamellaires (alpha2/gamma).
They were also able to define a process for treating a titanium aluminide-based alloy with 40 to 50 atomic percent (at%) aluminum, comprising the following steps:
  • molding a semi-finished product by centrifugal casting in a permanent mold,
  • then heat treat the semi-finished product,
  • this at a pressure substantially equal to atmospheric pressure, until an alloy microstructure comprising gamma grains and / or lamellar grains (alpha2 / gamma) is obtained.

Ce procédé de traitement se caractérise par une température de traitement thermique qui est comprise entre 1045°C et 1255°C pendant 10 à 40 heures.This treatment process is characterized by a heat treatment temperature which is between 1045 ° C and 1255 ° C for 10 to 40 hours.

De manière comparable, ils ont défini un procédé de fabrication d'une pièce de turbomachine en alliage à base d'aluminure de titane, avec 40 à 50 pour cent atomique (at %) d'aluminium, comprenant les étapes suivantes :

  • réaliser un moulage par coulée centrifuge en moule permanent pour obtenir un produit semi-fini de forme moins complexe que celle du produit fini,
  • puis traiter thermiquement le produit semi-fini, sans compression isostatique à chaud,
  • ceci à une pression sensiblement égale à la pression atmosphérique, jusqu'à obtenir une microstructure comprenant des grains gamma et/ou des grains lamellaires (alpha2/gamma),
  • puis, usiner, suivant la forme de ladite pièce, le produit semi-fini thermiquement traité.
In a comparable manner, they defined a process for manufacturing a part of a turbomachine made of an alloy based on titanium aluminide, with 40 to 50 atomic percent (at%) of aluminum, comprising the following steps:
  • to carry out a casting by centrifugal casting in permanent mold to obtain a semi-finished product of less complex shape than that of the finished product,
  • then heat-treat the semi-finished product, without hot isostatic compression,
  • this at a pressure substantially equal to atmospheric pressure, until a microstructure comprising gamma grains and / or lamellar grains (alpha2 / gamma) is obtained,
  • then, machining, according to the shape of said part, the heat-treated semi-finished product.

Ce procédé de fabrication se caractérise par un traitement thermique à une température comprise entre 1045°C et 1255°C et pendant 10 à 40 heures.This manufacturing process is characterized by a heat treatment at a temperature between 1045 ° C and 1255 ° C and for 10 to 40 hours.

Sur la base des éléments précédemment fournis, on aura compris que cette « pression inférieure à celle d'une compression isostatique à chaud » sera donc nécessairement inférieure à 1700x105Pa, et de préférence inférieure à 1000x105Pa.On the basis of the elements provided above, it will be understood that this “pressure lower than that of hot isostatic compression” will therefore necessarily be less than 1700 × 10 5 Pa, and preferably less than 1000 × 10 5 Pa.

En outre, et de fait il a pu être vérifié :

  • que le moulage par coulée centrifuge en moule permanent permet de limiter notablement le nombre et la taille des porosités, si bien que les critères appliqués par exemple à une aube de turbine sont respectés à l'état brut de coulée,
  • et que les formes de moule les plus simples sont les plus efficaces pour réduire le taux de porosités.
In addition, and in fact it could be verified:
  • that casting by centrifugal casting in a permanent mold makes it possible to significantly limit the number and size of the porosities, so that the criteria applied for example to a turbine blade are respected in the as-cast state,
  • and that the simplest mold shapes are the most effective in reducing the rate of porosity.

Ceci a d'ailleurs été constaté par plusieurs analyses (observation au microscope optique, ressuage, radio RX) sur du TiAI 48-2-2 obtenu dans un moule cylindrique: les quelques porosités observées n'excédaient pas quelques centaines de micromètres de diamètre.This was moreover noted by several analyzes (observation under an optical microscope, penetrant testing, X-ray radio) on TiAI 48-2-2 obtained in a cylindrical mold: the few porosities observed did not exceed a few hundred micrometers in diameter.

Une caractéristique préférée de l'invention prévoit au demeurant que l'étape d'obtention du produit semi-fini issu du moulage par coulée centrifuge comprenne une coulée dans ledit moule permanent que l'alliage remplira alors de telle manière que la taille des pores internes de cet alliage soit réduite après coulée par rapport à ce qu'elle était avant.A preferred characteristic of the invention moreover provides that the step of obtaining the semi-finished product resulting from the molding by centrifugal casting comprises a casting in said permanent mold which the alloy will then fill in such a way that the size of the internal pores of this alloy is reduced after casting compared to what it was before.

On recherchera de fait que la forme simple du moule (sans contre-dépouille) permette qu'il soit rempli rapidement par l'alliage de telle manière à réduire la taille de ses pores internes par rapport à ce que cette taille de pores serait sans coulée dans un tel moule.In fact, the simple shape of the mold (without undercut) will be sought to allow it to be filled quickly with the alloy in such a way as to reduce the size of its internal pores compared to what this pore size would be without casting. in such a mold.

De façon pratique, on pourra favorablement, s'assurer à cette fin :

  • que le moule puisse être rempli à une vitesse (vitesse d'écoulement de l'alliage dans le moule) qui soit supérieure à la vitesse de solidification à cœur (c'est-à-dire dans le moule) de l'alliage, et/ou
  • que ladite forme simple du moule permette qu'il soit rempli en moins de une minute, de préférence 30 secondes, et de préférence encore 20 secondes, par l'alliage (tel TiAl 48-2-2, en particulier).
In practice, we can favorably ensure to this end:
  • that the mold can be filled at a speed (flow rate of the alloy in the mold) which is greater than the rate of solidification through the core (that is to say in the mold) of the alloy, and /or
  • that said simple shape of the mold allows it to be filled in less than one minute, preferably 30 seconds, and more preferably 20 seconds, with the alloy (such as TiAl 48-2-2, in particular).

On cherchera aussi, favorablement, qu'il ne génère pas de points chauds (Comme connu, un point chaud est typiquement une zone où la température de l'alliage coulé dans le moule est plus élevée et/ou l'écoulement de cet alliage est moins favorable, ou la diffusion de la chaleur du métal vers le moule également moins favorable, tel à l'endroit d'une arête du moule).We will also seek, favorably, that it does not generate hot spots (As known, a hot spot is typically a zone where the temperature of the alloy cast in the mold is higher and / or the flow of this alloy is higher. less favorable, or the diffusion of heat from the metal to the mold also less favorable, such as at the location of an edge of the mold).

En particulier si la vitesse de coulée/remplissage du moule est trop lente, il y a risque d'altération de la forme coulée.In particular if the casting / filling speed of the mold is too slow, there is a risk of alteration of the cast shape.

Quand on va traiter thermiquement le produit semi-fini, après donc le moulage ainsi réalisé sur une forme simple encore à usiner pour parvenir à la pièce finie, il est par ailleurs préféré que ceci soit réalisé à une pression :

  • inférieure à celle d'une compression isostatique à chaud,
  • et de préférence sensiblement égale à la pression atmosphérique.
When the semi-finished product is thermally treated, therefore after the molding thus produced on a simple form yet to be machined in order to reach the finished part, it is also preferred that this be carried out at a pressure:
  • lower than that of hot isostatic compression,
  • and preferably substantially equal to atmospheric pressure.

Il s'en suit alors que, si on le compare à ce qui est enseigné dans US 5609698 , où est donc mise en œuvre une solution complexe impliquant un contrôle simultané d'une haute température et d'une haute pression, le procédé ci-dessus consistera alors en quelque sorte à remplacer l'étape, jugée dans ce brevet antérieur indispensable, de compactage isostatique à chaud d'un produit de forme complexe (ayant la forme de la pièce finie) issu d'un moulage dans un moule temporaire, par une coulée centrifuge dans un moule permanent, en faisant suivre cette coulée par un traitement en température sans nécessairement la pression élevée de la compression isostatique à chaud.It follows then that, if we compare it to what is taught in US 5609698 , where a complex solution involving simultaneous control of a high temperature and a high pressure is therefore implemented, the above process will then consist in some way of replacing the step, considered in this prior patent essential, of hot isostatic compaction of a product of complex shape (having the shape of the finished part) resulting from molding in a temporary mold, by centrifugal casting in a permanent mold, following this casting by a temperature treatment without necessarily the high pressure of hot isostatic compression.

Toujours dans la même approche visant les effets précités, il est en outre conseillé que l'étape d'obtention du produit semi-fini issu de moulage comprenne :

  • à partir de la coulée d'alliage fondu, l'élaboration d'un premier lingot, dans ce matériau,
  • puis, après une refonte de ce lingot dans un creuset métallique refroidi, son versement dans un moule métallique permanent centrifugé, afin d'obtenir un lingot moulé,
  • ceci étant suivi d'un démoulage du lingot et si nécessaire de son découpage (grossier) en produit semi-fini.
Still in the same approach aimed at the aforementioned effects, it is further recommended that the step of obtaining the semi-finished product resulting from molding includes:
  • from the casting of molten alloy, the production of a first ingot, in this material,
  • then, after remelting this ingot in a cooled metal crucible, pouring it into a permanent centrifuged metal mold, in order to obtain a molded ingot,
  • this being followed by demolding of the ingot and, if necessary, its (coarse) cutting into a semi-finished product.

Concernant cet aspect moulage/découpe, on conseille d'ailleurs que l'étape précitée d'obtention du produit semi-fini issu de moulage comprenne ledit moulage dans un moule métallique, par coulée centrifuge de l'alliage, seul ou suivi d'une découpe (grossière) en parties dudit alliage moulé, suivant une ébauche de forme simple (correspondant à la forme simple du moule permanent utilisé):

  • présentant au moins un plan de symétrie, ou,
  • présentant extérieurement au plus une inflexion par laquelle la section de l'ébauche semi-finie augmente ou diminue, avec, suivant ledit axe:
    • -- des maximums d'épaisseur de l'ébauche situés à des extrémités (a priori opposées) de celle-ci, ou
    • -- un maximum d'épaisseur de l'ébauche situé à une seule extrémité.
Regarding this molding / cutting aspect, it is also recommended that the aforementioned step of obtaining the semi-finished product resulting from molding comprises said molding in a metal mold, by centrifugal casting of the alloy, alone or followed by a (rough) cutting into parts of said cast alloy, following a blank of simple shape (corresponding to the simple shape of the permanent mold used):
  • exhibiting at least one plane of symmetry, or,
  • exhibiting on the outside at most one inflection through which the section of the semi-finished blank increases or decreases, with, along said axis:
    • - maximum thicknesses of the blank located at ends (a priori opposite) thereof, or
    • - a maximum thickness of the blank located at one end.

La centrifugation dans un moule métallique permanent permettra :

  • d'optimiser le remplissage du moule, surtout si la forme est simple,
  • de minimiser la matière mise en œuvre ; en effet le centre du moule peut ne pas être totalement rempli contrairement à une solution de fonderie à moule temporaires/perdus (à cire perdue) où les amenées de coulées sont remplies de métal,
  • un démoulage et une découpe en un semi-produit de forme simple qui ne nécessitera pas de contrôle dimensionnel avant usinage.
Centrifugation in a permanent metal mold will allow:
  • to optimize the filling of the mold, especially if the shape is simple,
  • to minimize the material used; in fact, the center of the mold may not be completely filled, unlike a temporary / lost (lost wax) mold foundry solution where the casting feeds are filled with metal,
  • demoulding and cutting into a semi-finished product of simple shape which will not require dimensional control before machining.

Une caractéristique de la solution proposée prévoit d'ailleurs que le produit semi-fini brut de moulage puisse être traité thermiquement puis usiné directement, sans contrôle dimensionnel intermédiaire d'une ébauche.A characteristic of the proposed solution moreover provides that the semi-finished product raw molded can be heat treated and then machined directly, without intermediate dimensional control of a blank.

Une géométrie simple de moule, donc de l'ébauche qui sort de sa cavité, (typiquement possédant au moins un plan de symétrie et/ou au plus une inflexion) limitera les risques de non-conformité (limitation du taux de porosités en évitant de créer des points chauds). De plus, le fait que le moule soit un moule métallique supprimera le risque d'obtenir des inclusions de céramiques issues de la carapace en céramique dans le cas du procédé de fonderie à cire perdue Et une géométrie simple de moule, donc d'ébauche, permettra une automatisation aisée de l'usinage.A simple geometry of the mold, therefore of the blank which comes out of its cavity, (typically having at least one plane of symmetry and / or at most one inflection) will limit the risks of non-conformity (limitation of the rate of porosities by avoiding create hot spots). In addition, the fact that the mold is a metal mold will eliminate the risk of obtaining ceramic inclusions from the ceramic shell in the case of the lost wax casting process And a simple geometry of the mold, therefore of roughing, will allow easy automation of machining.

Il est précisé que les valeurs fournies dans la présente demande en liaison avec la solution proposée sont à considérer à 20% près.It is specified that the values provided in the present application in connection with the proposed solution are to be considered within 20%.

Plus précisément, il est conseillé que, pour traiter thermiquement le produit semi-fini, celui-ci soit porté successivement :

  • à une température comprise entre 1045°C et 1145°C. pendant 5 à 15 heures, à une sensiblement égale à la pression atmosphérique,
  • à une température comprise entre 1135°C et 1235°C, pendant 3 à 10 heures, à une pression sensiblement égale à la pression atmosphérique, puis
  • à une température comprise entre 1155°C et 1255°C, pendant 2 à 15 heures, à une pression sensiblement égale à la pression atmosphérique.
More precisely, it is recommended that, to heat treat the semi-finished product, it is carried successively:
  • at a temperature between 1045 ° C and 1145 ° C. for 5 to 15 hours, at approximately equal to atmospheric pressure,
  • at a temperature between 1135 ° C and 1235 ° C, for 3 to 10 hours, at a pressure substantially equal to atmospheric pressure, then
  • at a temperature between 1155 ° C and 1255 ° C, for 2 to 15 hours, at a pressure substantially equal to atmospheric pressure.

Plus loin dans la description, des résultats d'essais conduits dans ce cadre établissent la pertinence de telles valeurs.Further on in the description, the results of tests carried out in this context establish the relevance of such values.

On notera encore l'intérêt de la solution ici présenté si la pièce usinée est une aube de turbine pour aéronef, ou si l'alliage est destiné à une telle aube, lorsqu'on lit dans WO2014/057222 en pages 1-2 « qu'une compression isostatique à chaud CIC est [alors] nécessaire afin de refermer les éventuelles porosités ». Les développements ici présentés permettent de s'exonérer d'une compression CIC, sans que le taux de porosité en soit affecté.Note also the advantage of the solution presented here if the machined part is an aircraft turbine blade, or if the alloy is intended for such a blade, when read in WO2014 / 057222 on pages 1-2 "that CIC hot isostatic compression is [then] necessary in order to close any porosities". The developments presented here make it possible to be exempt from CIC compression, without the porosity rate being affected.

Avant cela, d'autres caractéristiques, détails et avantages de l'invention apparaîtront de ce qui suit relatif à des exemples de mise en œuvre et dont le contenu renvoie aux dessins d'accompagnement où:

  • la figure 1 est un diagramme fonctionnel possible pour le procédé de l'invention;
  • la figure 2 est un bloc issu de moulage correspondant à un produit semi-fini dans lequel ici des aubes vont pouvoir être usinées,
  • la figure 3 est une vue schématique d'un dispositif de moulage par coulée centrifuge en moule permanent, ici utilisable,
  • la figure 4 est une vue schématique de dessus du moule permanent de la figure 3 (flèche IV),
  • les figures 5,6 sont deux vues schématiques de moules permanents, ou cavités de moulage, de formes simples utilisables sur le dispositif précité, illustré figure 2;
  • les figures 8,9 schématisent un autre exemple de moule permanent, de forme simple (barreau cylindrique), en vue depuis l'arrière (flèche VIII de la figure 7), respectivement fermé et ouvert,
  • les figures 10,11 montrent des microstructures obtenues respectivement avec et sans compactage isostatique à chaud, pour la même histoire thermique,
  • et la figure 12 est un graphique obtenu à partir d'essais (numérotés 1 à 9 en abscisse) et illustre la différence entre le résultat concerné obtenu pour des pièce-éprouvettes (des cylindres) traité(e)s thermiquement avec compactage isostatique à chaud (losanges pleins) ou sans compactage isostatique à chaud (losanges creux).
Before that, other characteristics, details and advantages of the invention will emerge from what follows relating to examples of implementation and whose content refers to the accompanying drawings where:
  • the figure 1 is a possible functional diagram for the method of the invention;
  • the figure 2 is a block resulting from molding corresponding to a semi-finished product in which here blades will be able to be machined,
  • the figure 3 is a schematic view of a permanent mold centrifugal casting molding device, usable here,
  • the figure 4 is a schematic top view of the permanent mold of the figure 3 (arrow IV),
  • the figures 5.6 are two schematic views of permanent molds, or mold cavities, of simple shapes that can be used on the aforementioned device, illustrated figure 2 ;
  • the figures 8,9 schematize another example of a permanent mold, simple in shape (cylindrical bar), seen from the rear (arrow VIII of the figure 7 ), respectively closed and open,
  • the figures 10.11 show microstructures obtained respectively with and without hot isostatic compaction, for the same thermal history,
  • and the figure 12 is a graph obtained from tests (numbered 1 to 9 on the abscissa) and illustrates the difference between the relevant result obtained for specimen parts (cylinders) heat-treated with hot isostatic compaction (solid diamonds) or without hot isostatic compaction (hollow diamonds).

La figure 1 illustre donc les principales étapes non seulement de traitement de l'alliage concerné, mais plus généralement, en tant que produit fini, par exemple d'une aube de turbine en alliage à base d'aluminure de titane.The figure 1 therefore illustrates the main steps not only of treatment of the alloy concerned, but more generally, as a finished product, for example of a turbine blade made of a titanium aluminide-based alloy.

Il peut ainsi être confirmé qu'aucune compression isostatique à chaud n'a été réalisée dans ce cas.It can thus be confirmed that no hot isostatic compression was carried out in this case.

Concernant le traitement en tant que tel, il consiste donc successivement à:

  • réaliser, en 3, un moulage par coulée centrifuge, en versant pour cela l'alliage dans un moule permanent 5, ceci permettant d'obtenir un produit semi-fini 7 de forme simple, moins complexe que celle du produit fini 9, tel une aube de turbine de turbomachine,
  • traiter thermiquement le produit semi-fini, en 11, sans recourir nécessairement à une compression isostatique à chaud.
Regarding the processing as such, it therefore consists successively in:
  • perform, in 3, a molding by centrifugal casting, for this by pouring the alloy into a permanent mold 5, this making it possible to obtain a semi-finished product 7 of simple shape, less complex than that of the finished product 9, such as a turbomachine turbine blade,
  • heat treating the semi-finished product, at 11, without necessarily resorting to hot isostatic compression.

On obtient ainsi une microstructure d'alliage comprenant des grains gamma et/ou des grains lamellaires (alpha2/gamma).An alloy microstructure is thus obtained comprising gamma grains and / or lamellar grains (alpha2 / gamma).

Ensuite, pour la fabrication du produit fini 9, on va, à l'étape 13, usiner sous cette forme ici d'une ou plusieurs aubes de turbine, le produit semi-fini thermiquement traité (voir figure 2).Then, for the manufacture of the finished product 9, we will, in step 13, machine in this form here of one or more turbine blades, the heat-treated semi-finished product (see figure 2 ).

Pour le moulage par coulée centrifuge en moule permanent, on peut utiliser un dispositif 15 comme illustré figure 3 qui va permettre de mouler une série d'ébauches semi-finies 7, chacune pouvant avoir une forme de barreau brut de fonderie où seront ensuite usinée(s) la(les) pièce(s) finie(s), ici deux aubes 17 de turbine de turbomachine.For permanent mold centrifugal casting, a device 15 as illustrated may be used. figure 3 which will make it possible to mold a series of semi-finished blanks 7, each of which can have the shape of a bar as foundry where the finished part (s) will then be machined, here two blades 17 of turbomachine turbine.

Le dispositif 15 comprend une enceinte 19 fermée et étanche dans laquelle peut être appliqué un vide partiel. Un lingot 21, ici en un alliage à base d'aluminure de titane, et plus précisément d'aluminure de titane de type gamma, est d'abord fondu dans un creuset 23. En fusion, l'alliage est ensuite versé dans un moule 25 métallique permanent, via un entonnoir 26.The device 15 comprises a closed and sealed enclosure 19 in which a partial vacuum can be applied. An ingot 21, here in an alloy based on titanium aluminide, and more precisely on titanium aluminide of the gamma type, is first melted in a crucible 23. When molten, the alloy is then poured into a mold. 25 permanent metal, via a funnel 26.

Le moule 25 permet de couler l'alliage par centrifugation, afin d'obtenir les ébauches 7. Pour cela, il est mis en rotation autour d'un axe A. Le moule 25 comprend plusieurs cavités 27 qui s'étendent radialement (axes B1, B2...; figures 3, 4) autour de l'axe A, de préférence par l'intermédiaire d'un moteur 29. Ces cavités sont de préférence régulièrement espacées angulairement autour de l'axe A qui est ici vertical. Les forces centrifuges générées par la rotation du moule forcent l'alliage en fusion à pénétrer dans ces cavités et à les remplir. Ainsi, l'alliage à couler, apporté vers le centre du moule, se répartit radialement vers les cavités périphériques.The mold 25 makes it possible to cast the alloy by centrifugation, in order to obtain the blanks 7. For this, it is rotated around an axis A. The mold 25 comprises several cavities 27 which extend radially (axes B1 , B2 ...; figures 3, 4 ) around the axis A, preferably by means of a motor 29. These cavities are preferably regularly spaced angularly around the axis A which is here vertical. The centrifugal forces generated by the rotation of the mold force the molten alloy to enter and fill these cavities. Thus, the alloy to be cast, brought towards the center of the mold, is distributed radially towards the peripheral cavities.

Après refroidissement, le moule 25 est ouvert et les ébauches moulées 7 sont extraites. Les parois du moule qui entourent les cavités 27 de recueillement du métal résistent aux efforts centrifuges, typiquement plus de 10 g.After cooling, the mold 25 is opened and the molded blanks 7 are extracted. The walls of the mold which surround the cavities 27 for collecting the metal are resistant to centrifugal forces, typically more than 10 g.

Lors de la rotation autour de l'axe A, la coulée d'alliage va ainsi être plaquée contre les parois de ces cavités sous l'action de la force centrifuge. Pour ce faire, on préconise une vitesse de rotation de l'ordre de 150 à 400 tours/min.During the rotation around the axis A, the alloy casting will thus be pressed against the walls of these cavities under the action of centrifugal force. To do this, we recommend a speed of rotation of the order of 150 to 400 revolutions / min.

Comme connu, par la rotation du métal liquide coulé, les particules sont soumises à une force centrifuge, laquelle peut être augmentée avec la vitesse angulaire. Cette augmentation se répartit sur toute la masse du métal liquide, uniformément sur toute la longueur de chaque cavité 27.As known, by the rotation of the molten molten metal, the particles are subjected to a centrifugal force, which can be increased with the angular speed. This increase is distributed over the entire mass of the liquid metal, uniformly over the entire length of each cavity 27.

Sur la figure 4 comme sur les figures 5,6,8, outre les cavités (selon un mode de réalisation), on voit en pointillés le contour schématique de l'ébauche qui leur correspond.On the figure 4 as on figures 5.6 , 8 , in addition to the cavities (according to one embodiment), the schematic outline of the blank which corresponds to them can be seen in dotted lines.

A noter également que les figures 8,9 schématisent bien une caractéristique typique d'un moule permanent, utilisable plusieurs fois : le moule comprend plusieurs coquilles, telles 150a, 150b qui s'ouvrent et se ferment suivant une surface (ici le plan de joint 152) qui est globalement transversale à l'axe (A) autour duquel tourne le moule.Also note that the figures 8,9 schematize well a typical characteristic of a permanent mold, which can be used several times: the mold comprises several shells, such as 150a, 150b which open and close along a surface (here the parting line 152) which is generally transverse to the axis (A) around which the mold rotates.

Une fixation séparable 153, telle un verrou, est établie entre les coquilles pour, une fois les coquilles séparées, pouvoir sortir l'ébauche moulée, par l'ouverture 154 libérée.A separable attachment 153, such as a lock, is established between the shells so, once the shells have been separated, to be able to exit the molded blank, through the released opening 154.

Sur les figures 5,6, les traits 152 matérialisent aussi un plan de joint permettant de fermer et ouvrir le moule en cause.On the figures 5.6 , the lines 152 also materialize a parting line making it possible to close and open the mold in question.

Figure 5, le moule montré présente des premier et second côtés 33a,33b opposés le long de l'axe 35 et parallèles entre eux. Ces deux côtés sont l'un le côté d'entrée de la coulée ; Il est donc radialement interne et l'axe 34 est parallèle (voire confondu) à l'un des axes B, tel B1. Figure 5 , the mold shown has first and second sides 33a, 33b opposite along the axis 35 and parallel to each other. These two sides are one the entry side of the casting; It is therefore radially internal and the axis 34 is parallel (or even coincident) with one of the axes B, such as B1.

Pour optimiser l'atteinte d'une haute qualité de pièces finies et de consommation de matière aussi limitée que possible, ce moule (et donc l'ébauche pleine, polyédrique obtenue) présente ici, entre les premier et deuxième côtés précités, un troisième et un quatrième côtés (33c,33d) qui s'évasent entre eux depuis le premier côté 33a vers le deuxième côté, suivant un premier angle puis, à partir d'une rupture de pente (ou inflexion) 35, suivant un second angle plus important que le premier.To optimize the achievement of a high quality of finished parts and consumption of material as limited as possible, this mold (and therefore the solid, polyhedral blank obtained) has here, between the aforementioned first and second sides, a third and a fourth sides (33c, 33d) which widen together from the first side 33a towards the second side, at a first angle and then, from a break in slope (or inflection) 35, at a second larger angle than the first.

Globalement, ce moule (sa cavité de moulage) est défini(e) par une première et une deuxième pyramides tronquées 37a,37b, la deuxième pyramide étant le prolongement de la première pyramide par la grande base de la première pyramide qui se superpose exactement à la petite base de la deuxième.Overall, this mold (its mold cavity) is defined by a first and a second truncated pyramids 37a, 37b, the second pyramid being the extension of the first pyramid by the large base of the first pyramid which is exactly superimposed on the small base of the second.

Le moule et son ébauche moulée présentent un plan de symétrie 39 perpendiculaire aux premier et deuxième côtés 33a, 33b et qui contient l'axe 34.The mold and its molded blank have a plane of symmetry 39 perpendicular to the first and second sides 33a, 33b and which contains the axis 34.

On peut en outre prévoir, en liaison avec les angles marqués figure 5 :

  • que le premier angle α soit compris entre 0° et 15°,
  • que le second angle γ soit inférieur à 120°, et de préférence inférieur à 90°,
  • et que la rupture de pente 35 soit située à moins de 85%, et de préférence moins de 75%, de la plus courte distance entre les premier et deuxième côtés, en partant du premier côté 33a.
It is also possible to provide, in conjunction with the angles marked figure 5 :
  • that the first angle α is between 0 ° and 15 °,
  • that the second angle γ is less than 120 °, and preferably less than 90 °,
  • and that the slope break 35 is located within 85%, and preferably less than 75%, of the shortest distance between the first and second sides, starting from the first side 33a.

Le mode de réalisation de la cavité de moulage de la figure 6 illustre une cavité de moulage polyédrique présentant deux côtés opposés, chacun de forme générale trapézoïdale 37a, 37b.The embodiment of the mold cavity of the figure 6 illustrates a blocky mold cavity having two opposite sides, each of generally trapezoidal shape 37a, 37b.

Comme la cavité, l'ébauche moulée présente ici :

  • deux bases sensiblement trapézoïdale situées en face des deux côtés opposés de plus grandes surfaces 41a,41b, respectivement, le long de l'axe d'allongement 43, et,
  • une ouverture angulaire (α2) de chacune de ces deux bases trapézoïdales comprise entre 2° et 10°, de préférence entre 3° et 8°, x N, N étant le nombre de produits finis (prévus pour être) usinés intégralement dedans.
Like the cavity, the molded blank presents here:
  • two substantially trapezoidal bases located opposite the two opposite sides of larger surfaces 41a, 41b, respectively, along the axis of elongation 43, and,
  • an angular opening (α2) of each of these two trapezoidal bases of between 2 ° and 10 °, preferably between 3 ° and 8 °, x N, N being the number of finished products (intended to be) fully machined therein.

L'accès à l'intérieur de la cavité peut s'effectuer radialement par l'un des deux côtés latéraux, ici le plus grand 41c.Access to the interior of the cavity can be effected radially by one of the two lateral sides, here the larger 41c.

Ainsi, dans les deux cas ci-dessus, l'ébauche présente extérieurement -sur un côté ou une face déterminé(e)- au plus une inflexion par laquelle la section de l'ébauche semi-finie augmente ou diminue, avec, suivant son axe d'allongement, ici 34 ou 43, un maximum de section droite S1 de l'ébauche situé à une seule extrémité, le long de cet axe.Thus, in the two above cases, the blank exhibits externally - on a determined side or face - at most one inflection by which the section of the semi-finished blank increases or decreases, with, depending on its axis of elongation, here 34 or 43, a maximum cross section S1 of the blank located at one end, along this axis.

Toujours dans le cadre d'une maîtrise thermique, de préférence en combinaison avec celle des efforts, la figure 7 montre une autre solution intéressante de moule où, individuellement, l'extrémité radialement intérieure ouverte 45a de la cavité 27 de coulée de l'alliage présente une forme allant en rétrécissant de section (zone 47a) vers le centre de la cavité, le long de la direction radiale B. Un tronc de cône pourrait convenir. La forme est ici en fait en double entonnoir (tête-bêche), avec donc une partie extrême radialement extérieure de la cavité, qui est épaulée, pour présenter une partie terminale élargie 47b.Still within the framework of thermal control, preferably in combination with that of the forces, the figure 7 shows another interesting mold solution where, individually, the open radially inner end 45a of the alloy casting cavity 27 has a shape tapering in section (zone 47a) towards the center of the cavity, along radial direction B. A truncated cone could be suitable. The shape here is in fact a double funnel (head-to-tail), therefore with a radially outer end part of the cavity, which is stepped, to present an enlarged end part 47b.

On trouve ainsi des maximums de section S2,S3 de moule/d'ébauche moulée vers les (ou aux) extrémités, étant précisé que les sections S1,S2,S3 sont chacune définies extérieurement, transversalement à l'axe d'allongement concerné, comme illustré.There are thus maximums of section S2, S3 of the mold / molded blank towards the (or at) ends, it being specified that the sections S1, S2, S3 are each defined externally, transversely to the axis of elongation concerned, as shown.

Typiquement si au moins une pièce de turbomachine est ensuite usinée dans l'ébauche de forme correspondante coulée, la forme 47a pourra correspondre à la zone de talon de cette aube et la partie terminale 47b à la zone du pied élargi, ou inversement.Typically if at least one part of a turbomachine is then machined in the blank of corresponding cast shape, the form 47a may correspond to the heel area of this blade and the end part 47b to the area of the enlarged foot, or vice versa.

Comme déjà indiqué, de telles formes simples permettent de favoriser une partie au moins de ce qui suit:

  • optimiser le remplissage du moule,
  • faciliter les contrôles dimensionnels,
  • limiter les risques de non conformités (par diminution des défauts de fonderie),
  • automatiser facilement les usinages ultérieurs,
  • éviter de créer des points chauds et donc limiter le taux de porosités.
As already indicated, such simple shapes make it possible to promote at least part of the following:
  • optimize the filling of the mold,
  • facilitate dimensional checks,
  • limit the risks of non-conformities (by reducing foundry defects),
  • easily automate subsequent machining,
  • avoid creating hot spots and therefore limit the rate of porosity.

Un autre effet attendu/produit par ce moulage centrifuge en moule permanent à forme donc simple, est l'obtention, en fin de moulage, d'une ébauche 7 ayant, par rapport à la structure interne de l'alliage apporté dans chaque cavité 27, une (micro)structure interne dont les pores ont une taille (un volume) plus faible, voire ont disparu, pour tendre vers un matériau (plus) dense. La figure 11 montre ce résultat.Another expected effect / produced by this centrifugal molding in a permanent mold with a therefore simple shape, is the obtaining, at the end of molding, of a blank 7 having, with respect to the internal structure of the alloy introduced into each cavity 27 , an internal (micro) structure whose pores have a smaller size (volume), or even have disappeared, to tend towards a (more) dense material. The figure 11 shows this result.

Pour favoriser cela en combinant les effets de la gravité, il est recommandé, comme montré figure 1 :

  • qu'à partir d'une coulée initiale de l'alliage (non représentée), soit élaborée avec cet alliage fondu une première ébauche correspondant au lingot 21 qui sera alors brut de coulée,
  • puis, que cette première ébauche 21 soit donc refondue dans le creuset 23, l'alliage refondu étant versé dans le moule permanent centrifugé 25, pour obtenir une série de lingots moulés correspondant aux ébauches 7 (que l'on peut appeler secondes ébauches).
To promote this by combining the effects of gravity, it is recommended, as shown figure 1 :
  • that from an initial casting of the alloy (not shown), is produced with this molten alloy a first blank corresponding to the ingot 21 which will then be as-cast,
  • then, that this first blank 21 is therefore remelted in the crucible 23, the remelted alloy being poured into the centrifuged permanent mold 25, to obtain a series of molded ingots corresponding to the blanks 7 (which may be called second blanks).

Pour une bonne maîtrise technique, l'élaboration de la première ébauche s'opérera par VAR (Vacuum Arc Remelting -Refonte à l'arc sous vide) ou par PAM (Plasma Arc Melting - Fusion par arc sous plasma) puis la refonte de cette première ébauche s'opérera par VAR SM (Skull Melter - creuset froid de fusion).For a good technical mastery, the development of the first draft will be carried out by VAR (Vacuum Arc Remelting - Recasting with the vacuum arc) or by PAM (Plasma Arc Melting - Fusion by plasma arc) then the recasting of this first draft will be operated by VAR SM (Skull Melter - cold melting crucible).

Ensuite, et de préférence, après avoir démoulé ces ébauches 7, on pourra les découper (grossièrement) en produits semi-finis (étape 8 figure 1), suivant ladite forme « moins complexe » que celle des produits finis qui seront finalement usinés.Then, and preferably, after having unmolded these blanks 7, they can be cut (roughly) into semi-finished products (step 8 figure 1 ), according to said form "less complex" than that of the finished products which will finally be machined.

En particulier, si la forme de l'ébauche démoulée ou celle du produit fini le nécessite, par exemple pour obtenir un plan de symétrie favorable, l'ébauche démoulée pourra être ainsi découpée en une forme ne nécessitant pas de contrôle dimensionnel avant que celle-ci soit usinée suivant le produit fini attendu ; voir l'étape finale 14 de contrôle dimensionnel après l'usinage, figure 1.In particular, if the shape of the unmolded blank or that of the finished product so requires, for example to obtain a favorable plane of symmetry, the unmolded blank can thus be cut into a shape which does not require dimensional control before the latter. ci is machined according to the expected finished product; see final step 14 of dimensional control after machining, figure 1 .

Entretemps, chaque produit semi-fini 7 aura été traité thermiquement, sans compression isostatique à chaud (CIC), afin d'obtenir une microstructure d'alliage comprenant des grains gamma et/ou des grains lamellaires (alpha2/gamma).In the meantime, each semi-finished product 7 will have been heat treated, without hot isostatic compression (CIC), in order to obtain an alloy microstructure comprising gamma grains and / or lamellar grains (alpha2 / gamma).

Les figures 10,11 montrent des microstructures de TiAl 48-2-2: 48%Al 2%Cr 2%Nb (at%) obtenues respectivement avec et sans compactage isostatique à chaud (CIC), pour la même histoire thermique.The figures 10.11 show TiAl 48-2-2 microstructures: 48% Al 2% Cr 2% Nb (at%) obtained respectively with and without hot isostatic compaction (CIC), for the same thermal history.

Sur la figure 12, c'est, pour chaque essai (numéroté 1 à 9 en abscisse), la différence entre le résultat concerné obtenu pour une pièce-éprouvette (un cylindre) traitée thermiquement avec compactage isostatique à chaud (losanges pleins) puis une autre, identique, traitée sans compactage isostatique à chaud (losanges creux) qui est à chaque fois à considérer.On the figure 12 , it is, for each test (numbered 1 to 9 on the abscissa), the difference between the result concerned obtained for a test piece (a cylinder) heat treated with hot isostatic compaction (solid diamonds) then another, identical, treated without hot isostatic compaction (hollow diamonds) which is to be considered each time.

On trouve ainsi, de haut en bas sur le graphe :

  • (en ordonnées) entre 0.8 et 1, les résultats d'essais de traction (Contrainte maximale Rm),
  • entre 0.58 et 0.8, les résultats d'essais en limite d'élasticité à 0.2% de plasticité (Rp0.2),
  • entre 0.158 et 0.55, les résultats d'essais d'allongement à rupture (A%).
We thus find, from top to bottom on the graph:
  • (on the ordinate) between 0.8 and 1, the results of tensile tests (maximum stress Rm),
  • between 0.58 and 0.8, the results of tests in elasticity limit at 0.2% of plasticity (Rp0.2),
  • between 0.158 and 0.55, the results of elongation at break (A%) tests.

On aura constaté que les essais 1, en Rm, et 4, en A%, montrent une concordance (superposition) quasi exacte des résultats avec compactage isostatique à chaud (losanges pleins) et sans (losanges creux). Les autres résultats sont proches, deux à deux. Et quand elles existent, les dispersions sont faibles.It will have been noted that tests 1, in Rm, and 4, in A%, show an almost exact agreement (superposition) of the results with hot isostatic compaction (solid diamonds) and without (hollow diamonds). The other results are close, two by two. And when they exist, dispersions are low.

Tous ces essais ont été conduits à température ambiante, après traitements thermiques, à nouveau avec une pièce-éprouvette (un cylindre) en TiAl 48-2-2.All these tests were carried out at ambient temperature, after heat treatments, again with a test piece (a cylinder) made of TiAl 48-2-2.

Pour atteindre les résultats des figures 11,12, sans compactage isostatique à chaud, les essais ont montré que, lorsqu'on traitait thermiquement le produit semi-fini, ceci devait favorablement s'opérer pendant 10 à 40 heures, à une pression sensiblement égale à la pression atmosphérique ou, du moins, notablement inférieure à la pression CIC (800 - 1800x105 Pa).To achieve the results of figures 11.12 , without hot isostatic compaction, the tests have shown that, when the semi-finished product is heat treated, this should take place favorably for 10 to 40 hours, at a pressure substantially equal to atmospheric pressure or, at least, significantly lower than the CIC pressure (800 - 1800x10 5 Pa).

Une pression intermédiaire entre la pression atmosphérique et cette gamme de pressions CIC appliquée à l'alliage ne nuirait pas. Elle n'apparaît simplement pas indispensable. Les résultats d'essais fournis sont la conséquence de l'application de la pression atmosphérique.Pressure intermediate between atmospheric pressure and this CIC pressure range applied to the alloy would not be harmful. It simply does not appear to be essential. The test results provided are the consequence of the application of atmospheric pressure.

En termes de durées et températures, les résultats des figures 11, 12 sont les illustrations de ce qui a été obtenus indistinctement en testant les valeurs limites ci-après mentionnées.In terms of times and temperatures, the results of figures 11, 12 are illustrations of what was obtained without distinction by testing the limit values mentioned below.

Le cas comparatif de la figure 10 a été obtenu dans les conditions suivantes (voir US 5609698 ) : premier traitement, appelée traitement PLL, comprenant un traitement pré-HIP de 1145°C pendant 5 heures, HIP à 1255°C, et traitement thermique à 1200°C, pendant 2 heures.The comparative case of figure 10 was obtained under the following conditions (see US 5609698 ): first treatment, called PLL treatment, comprising a pre-HIP treatment of 1145 ° C for 5 hours, HIP at 1255 ° C, and heat treatment at 1200 ° C, for 2 hours.

De fait, les figures 11,12 montrent l'efficacité de la solution ici proposée de traitement du produit semi-fini encore à usiner, porté successivement :

  • à une température comprise entre 1045°C et 1145°C, pendant 5 à 15 heures, à une pression sensiblement égale à la pression atmosphérique,
  • à une température comprise entre 1135°C et 1235°C, pendant 3 à 10 heures, à une pression sensiblement égale à la pression atmosphérique, puis
  • à une température comprise entre 1155°C et 1255°C, pendant 2 à 15 heures, à une pression sensiblement égale à la pression atmosphérique à la pression atmosphérique.
In fact, the figures 11.12 show the effectiveness of the solution proposed here for treating the semi-finished product still to be machined, carried out successively:
  • at a temperature between 1045 ° C and 1145 ° C, for 5 to 15 hours, at a pressure substantially equal to atmospheric pressure,
  • at a temperature between 1135 ° C and 1235 ° C, for 3 to 10 hours, at a pressure substantially equal to atmospheric pressure, then
  • at a temperature between 1155 ° C and 1255 ° C, for 2 to 15 hours, at a pressure substantially equal to atmospheric pressure to atmospheric pressure.

L'alliage utilisé pourra en particulier être du TiAl 48-2-2 : 48%Al ; 2%Cr ; 2%Nb (at %), d'autant que ce matériau intermétallique s'avère utile pour réaliser au moins en partie certains étages d'une turbine de turbomachine d'aéronef, l'invention est plus généralement applicable en particulier aux alliages d'aluminure de titane ci-après cités ayant une composition capable de former des phases alpha2 et gamma, lorsque l'alliage est refroidi à partir d'une masse fondue. Il est à noter que ces alliages sont ici, comme généralement dans l'art antérieur, qualifiés de "gamma", même s'ils ne sont pas entièrement à l'intérieur du champ de phase gamma, étant précisé que les aluminures de titane gamma sont typiquement des alliages de titane, d'environ 40 à 50 pour cent atomique (at %) d'aluminium, avec éventuellement de faibles quantités d'autres éléments d'alliage tels que du chrome, du niobium, du vanadium, du tantale, du manganèse et/ou du bore.The alloy used may in particular be TiAl 48-2-2: 48% Al; 2% Cr; 2% Nb (at%), especially since this intermetallic material is useful for at least partially producing certain stages of a turbomachine turbine aircraft, the invention is more generally applicable in particular to the titanium aluminide alloys mentioned below having a composition capable of forming alpha2 and gamma phases, when the alloy is cooled from a melt. It should be noted that these alloys are here, as generally in the prior art, qualified as "gamma", even if they are not entirely inside the gamma phase field, it being specified that the gamma titanium aluminides are typically alloys of titanium, from about 40 to 50 atomic percent (at%) aluminum, with optionally small amounts of other alloying elements such as chromium, niobium, vanadium, tantalum, manganese and / or boron.

Les compositions préférées sont d'environ 45,0 à environ 48,5 pour cent atomique de l'aluminium, et sont donc à l'extrémité supérieure de la plage de fonctionnement.Preferred compositions are from about 45.0 to about 48.5 atomic percent of aluminum, and therefore are at the high end of the operating range.

Parmi les aluminures de titane gamma préférés et utilisables, on relèvera : Ti-48Al-2Cr-2Nb, Ti-48Al-2Mn-2Nb, Ti-49Al-1V, Ti-47Al-1 Mn-2Nb-0.5W-0.5Mo-0.2Si, et Ti-47Al- 5Nb-1W. Si les conditions de fabrication (en particulier le traitement thermique) appliquées à ces alliages spécifiques correspondent au cas précité du TiAl 48-2-2, en liaison avec les figures 11-12, les résultats fournis figure 12 leur sont applicables. On comprend donc l'importance d'un tel traitement thermique sans compression isostatique à chaud (CIC), à une pression sensiblement égale à la pression atmosphérique, et ce pendant 10 à 40 heures et entre 1045°C et 1255°C. Les conditions de vitesse d'écoulement de l'alliage dans le moule et de forme simple de ce moule ont aussi leur importance et sont celles qui ont été utilisées pour des essais dont les résultats sont comparables à ceux des figures 11-12.Among the preferred and usable gamma titanium aluminides, the following will be noted: Ti-48Al-2Cr-2Nb, Ti-48Al-2Mn-2Nb, Ti-49Al-1V, Ti-47Al-1 Mn-2Nb-0.5W-0.5Mo- 0.2Si, and Ti-47Al- 5Nb-1W. If the manufacturing conditions (in particular the heat treatment) applied to these specific alloys correspond to the aforementioned case of TiAl 48-2-2, in conjunction with the figures 11-12 , the results provided figure 12 are applicable to them. We therefore understand the importance of such a heat treatment without hot isostatic compression (CIC), at a pressure substantially equal to atmospheric pressure, for 10 to 40 hours and between 1045 ° C and 1255 ° C. The conditions of flow rate of the alloy in the mold and of the simple shape of this mold are also important and are those which were used for tests whose results are comparable to those of figures 11-12 .

Claims (14)

  1. A method for treating a titanium-aluminide alloy including 40 to 50 percent atomic (at%) aluminium, the method comprising the following steps:
    - carrying out a centrifugal casting in a permanent mould (25) in order to obtain a semi-finished product, then
    - heat treating the semi-finished product at a pressure substantially equal to atmospheric pressure, until a microstructure of the alloy comprising gamma grains and/or lamellar grains (alpha2/gamma) is obtained,
    characterised in that the heat treating is made between 1045°C and 1255°C and said treatment takes place during 10 to 40 hours.
  2. A method for fabricating, without a hot isostatic pressing, a turbine-engine part made from titanium-aluminide alloy, including 40 to 50 percent atomic (at%) aluminium, comprising the following steps:
    - carrying out a centrifugal casting in a permanent mould (25) in order to obtain a semi-finished product having a form less complex than that of a finished product (9, 17),
    - heat treating, at a temperature between 1045°C and 1255°C and during 10 to 40 hours, the semi-finished product without hot isostatic pressing, at a pressure substantially equal to atmospheric pressure, until an alloy microstructure comprising gamma grains and/or lamellar grains (alpha2/gamma) is obtained,
    - then machining the heat-treated semi-finished product (9, 17) to the form of said part.
  3. A method according to claim 1 or 2, wherein the step of obtaining the semi-finished product produced by the centrifugal casting comprises casting in said permanent mould (25) filled by the alloy, so that the size of the internal pores of this alloy is reduced after casting compared with what is was before, the mould being filled by the alloy:
    - with a speed of flow of the alloy in the mould greater than the rate of solidification of the alloy in the mould, and/or
    - in less than one minute, preferably 30 seconds, and more preferably 20 seconds.
  4. A method according to one of the preceding claims, where said alloy one of the following alloys: Ti-48AL-2Cr-2Nb, Ti-48AL-2Mn-2Nb, Ti-49Al-1V, Ti-47A1-1mn-2Nb-0.5W-0.5Mo-0.2Si, and Ti-47AI- 5nb-1W,
  5. A method according to one of the preceding claims, where said alloy is TiAl 48-2-2: 48% Al 2% Cr 2% Nb (at%).
  6. A method according to one of the preceding claims, where the step of obtaining a semi-finished product (7) produced by casting comprises:
    - said centrifugal casting of the alloy, in a metal mould, or
    - said centrifugal casting in a metal mould, following by cutting of said cast alloy into parts,
    in accordance with a blank (7) having at least one symmetry plane (39).
  7. A method according to one of the preceding claims, where said step of obtaining a semi-finished product produced by casting, which has an axis and, along this axis, a variable external cross section, comprises:
    - said centrifugal casting of the alloy, in a metal mould, or
    - said centrifugal casting in a metal mould, following by cutting of said cast alloy into parts,
    in accordance with a blank (7) having externally no more than one deflection by means of which the cross section of the semi-finished blank increases or decreases, with, along said axis:
    - cross-sectional maxima (S2, S3) of the blank situated at ends thereof, or
    - a cross-sectional maximum (S1) of the blank situated at only one end.
  8. A method according to claim 2 alone or in combination with any of claims 3 to 7, where the semi-finished product (7) as cast is heat treated and is then machined directly, without any intermediate dimensional check.
  9. A method according to claim 2 alone or in combination with any of claims 3 to 8, where the step of obtaining the semi-finished product (7) produced by casting comprises:
    - from a casting of said molten alloy, producing a first ingot in this material,
    - remelting the first ingot in a cooled metal crucible (23) and pouring the first remelted ingot into a centrifuged permanent metal mould (25) in order to obtain a cast remelted ingot,
    - removing the cast remelted ingot from the mould and cutting it into semi-finished product, in accordance with said less complex form.
  10. A method according to claim 9, wherein:
    - producing the first ingot is done by VAR (vacuum arc remelting) or by PAM (plasma arc melting), and
    - remelting the first ingot is done by VAR SM (skull melting - cold fusion crucible).
  11. A method according to one of the preceding claims, wherein the semi-finished product is heat treated by raising it successively:
    - to a temperature of between 1045°C and 1145°C, for 5 to 15 hours, at a pressure lower than that of hot isostatic pressing, which is preferably substantially equal to atmospheric pressure,
    - to a temperature of between 1135°C and 1235°C, for 3 to 10 hours, at a pressure lower than that of hot isostatic pressing, which is preferably substantially equal to atmospheric pressure, then
    - to a temperature of between 1155°C and 1255°C, for 2 to 15 hours, at a pressure lower than that of hot isostatic pressing, which is preferably substantially equal to atmospheric pressure.
  12. A method according to claim 1 or one of claims 3 to 11 when it is attached to claim 1, wherein the treatment of the alloy is done without hot isostatic pressing.
  13. A method according to claim 2 or one of claims 3 to 11 when it is attached to claim 2, wherein the machined part is a turbine blade for an aircraft.
  14. A method according to claim 1 or one of claims 3 to 11 when it is attached to claim 1, wherein the alloy is intended for a turbine blade for an aircraft.
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CN110195172B (en) * 2019-07-15 2021-03-23 哈尔滨工业大学 Ti2AlNb-based alloy material and preparation method thereof
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US5109603A (en) * 1989-08-09 1992-05-05 Texas Instruments Incorporated Method of waterproof sealing a lead from a pressure or temperature responsive switch
US5609698A (en) 1995-01-23 1997-03-11 General Electric Company Processing of gamma titanium-aluminide alloy using a heat treatment prior to deformation processing
AT5199U1 (en) * 2001-07-19 2002-04-25 Plansee Ag MOLDED PART FROM AN INTERMETALLIC GAMMA-TI-AL MATERIAL
US8858697B2 (en) * 2011-10-28 2014-10-14 General Electric Company Mold compositions
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