WO2020212168A1 - Cvi densification apparatus - Google Patents

Cvi densification apparatus Download PDF

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Publication number
WO2020212168A1
WO2020212168A1 PCT/EP2020/059495 EP2020059495W WO2020212168A1 WO 2020212168 A1 WO2020212168 A1 WO 2020212168A1 EP 2020059495 W EP2020059495 W EP 2020059495W WO 2020212168 A1 WO2020212168 A1 WO 2020212168A1
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WO
WIPO (PCT)
Prior art keywords
heating means
loading
loading area
substrates
heating
Prior art date
Application number
PCT/EP2020/059495
Other languages
French (fr)
Inventor
Jean-François POTIN
Stéphane Goujard
Original Assignee
Safran Ceramics
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Publication date
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Publication of WO2020212168A1 publication Critical patent/WO2020212168A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/04—Coating on selected surface areas, e.g. using masks
    • C23C16/045—Coating cavities or hollow spaces, e.g. interior of tubes; Infiltration of porous substrates
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
    • C23C16/458—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for supporting substrates in the reaction chamber
    • C23C16/4582—Rigid and flat substrates, e.g. plates or discs
    • C23C16/4583—Rigid and flat substrates, e.g. plates or discs the substrate being supported substantially horizontally
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
    • C23C16/46—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for heating the substrate
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
    • C23C16/48—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating by irradiation, e.g. photolysis, radiolysis, particle radiation
    • C23C16/481—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating by irradiation, e.g. photolysis, radiolysis, particle radiation by radiant heating of the substrate
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
    • C23C16/52—Controlling or regulating the coating process
    • 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
    • C04B2235/614—Gas infiltration of green bodies or pre-forms

Definitions

  • the invention relates to installations or furnaces used to carry out heat treatments. Such installations are used in particular for carrying out the densification of porous substrates by chemical infiltration in the gas phase.
  • thermostructural composite material that is to say in composite material having both mechanical properties which make it suitable for constituting structural parts and the capacity to retain these properties at high temperatures.
  • thermostructural composite materials are carbon / carbon (C / C) composites having a reinforcement texture of carbon fibers densified by a pyrolytic carbon matrix or else ceramic matrix composites (CMC) having a reinforcement texture in refractory fibers
  • a well-known process of densifying porous substrates to make C / C composite or CMC parts is chemical gas infiltration (CVI).
  • CVI chemical gas infiltration
  • the substrates to be densified are placed in a loading area of an installation where they are heated.
  • a reactive gas containing one or more gaseous precursors of the material constituting the matrix is introduced into the furnace.
  • the temperature and the pressure in the installation are adjusted to allow the reactive gas to diffuse within the porosity of the substrates and to form there a deposit of the material constituting the matrix by decomposition of one or more constituents of the reactive gas or by reaction between several constituents, these constituents forming the precursor of the matrix.
  • the process is carried out under reduced pressure, in order to promote the diffusion of the reactive gases in the substrates.
  • the transformation temperature of the precursor (s) to form the material of the matrix is in most cases between 900 ° C and 1100 ° C, this temperature however being able to reach 2000 ° C in the case of of a massive deposition of pyrolytic carbon by chemical gas deposition (CVD).
  • CVD chemical gas deposition
  • thermochemical treatment in order to achieve a densification of the substrates which is homogeneous throughout the loading zone in terms of increase in density and in terms of microstructure of the matrix material formed, it is necessary that the temperature conditions are homogeneous within the loading area for the duration of the thermochemical treatment.
  • thermochemical treatment installations which makes it possible to enlarge their size compared with the installations currently in use, while maintaining operating conditions allowing homogeneous parts to be obtained within a batch.
  • the object of the invention is to propose a design of a thermochemical treatment installation making it possible, for example, to carry out the densification by chemical vapor infiltration of a large number of preforms, while ensuring that all of the composite material parts obtained after a densification treatment is homogeneous in terms of increase in density and in terms of microstructure of the matrix material formed.
  • the present invention provides a treatment installation
  • thermochemical comprising a loading zone comprising one or more supports suitable for receiving substrates to be treated, said loading zone comprising a first heating means comprising a cylindrical side wall delimiting the loading zone, a first opening allowing the injection of a gaseous phase into the loading zone, a second opening allowing the gas phase to exit from the loading area,
  • said loading zone further comprises a second heating means disposed in the center of the loading zone and in which the first heating means is an inductive heating means.
  • An installation according to the invention further comprises a temperature regulation system, comprising thermocouples for determining the
  • the temperature regulation system also includes a data acquisition unit, allowing the measurements taken by the various thermocouples of the regulation system to be centralized.
  • the regulation system further comprises a digital device capable, from the measurements made by the thermocouples, of adjusting the power delivered to each of the two heating means so as to control the temperature of the latter.
  • Such a temperature control system allows the temperature uniformity to be controlled and adjusted in the loading area in real time. In the absence of such a regulation system, an excessively large gradient can be observed between the edge of the loading zone and its center, and the densification is not homogeneous between all the preforms.
  • the installation may be an installation for treating a substrate by a chemical vapor infiltration (CVI) process.
  • CVI chemical vapor infiltration
  • the installation described comprises one or more supports, capable of receiving substrates to be treated.
  • These supports can for example be discs allowing the loading of a plurality of substrates in the form of stacks. These supports can make it possible to obtain an orderly distribution of the substrates in the loading zone, and thus to promote a homogeneous distribution of the substrates in the loading zone.
  • the heating is carried out by the joint action of the first and the second heating means, which makes it possible to obtain a uniform temperature profile throughout the loading zone.
  • the first heating means which comprises a cylindrical wall delimiting the loading zone imposes a heating having a radial gradient directed from the inside of the chamber towards the outside, while the second heating means disposed at the center of the loading zone ensures heating with an opposite gradient.
  • the joint use of the two heating means thus allows homogeneous heating throughout the loading area.
  • the first heating means can be composed of an armature, an insulating element and an inductor.
  • the armature may be the cylindrical side wall delimiting the loading zone, and be arranged to cooperate with the inductor, an insulating element being placed between the armature and the inductor. Energizing the inductor, for example by means of a generator, causes the armature to heat up, which heats the loading area by radiation.
  • the second heating means may be a resistive element, the heating of which is provided by the Joule effect. Such heating can be achieved by connecting the second heating element to a generator.
  • the second heating means has a homogeneous temperature throughout its height, which improves thermal homogeneity in the loading zone.
  • the second heating means has a height comparable to the first heating means in the vertical dimension of the installation.
  • the height of the two heating means does not differ by more than 10%, better still by more than 5%, or even by 1%. Having a comparable height between the first and the second heating element avoids the presence of a vertically directed thermal gradient in the loading area.
  • the installation further comprises a gas preheating chamber arranged between the first opening and the loading area.
  • a gas preheating chamber makes it possible to heat the gas flow before its introduction into the loading zone.
  • the preheating chamber is delimited by a portion of the first heating means and comprises at its center a portion of the second heating means.
  • the presence of the two heating means makes it possible to minimize the temperature gradient between the center and the periphery of the preheating chamber and thus to ensure a more homogeneous temperature of the gas prior to its admission into the loading zone.
  • the second heating means may be covered with a protective layer.
  • a protective layer can be chemically inert with respect to the reactive gas phase during operation of the installation, and thus prevent the formation of a deposit on the surface of the second heating means during a treatment.
  • thermochemical Such a layer makes it possible to guarantee the homogeneity of the heating of the second heating means throughout the duration of the thermochemical treatment.
  • Such a protective layer must have satisfactory characteristics in terms of thermal conductivity and heat resistance.
  • its thermal conductivity must be isotropic so that the temperature at the surface of a heating means coated with such a layer is homogeneous.
  • the thermal conductivity must be sufficient, so that the protective layer does not adversely affect the heating qualities of the second heating means. It must also be well determined, so that a person skilled in the art can take into account the presence of the layer when determining the temperature to be given to the second heating means.
  • the heat resistance of such a layer must be sufficient to allow a homogeneous and lasting hold of the layer on the second heating element throughout the life of the installation. An installation as described above can have a larger loading area than installations of the prior art, while maintaining more homogeneous temperature conditions during the heat treatment.
  • the invention relates to a method for densifying a plurality of substrates comprising a step of loading a plurality of substrates arranged in stacks in a loading zone of a thermochemical treatment installation as described.
  • said plurality of substrates arranged in stacks forming concentric circles around the center of the loading area, characterized in that it comprises after the loading step, a heating step carried out by means of the first and the second means of heating the loading area.
  • such a process may correspond to the chemical gas-phase infiltration of a fiber preform for the production of a ceramic material, carried out in an installation as described above.
  • the substrate is a porous preform of a composite material, such as a fibrous preform, for example of carbon fiber or of refractory fibers.
  • the thermal gradient in the loading zone may be less than 5%, or even less than 3%.
  • thermal gradient in the loading zone is defined as the ratio between the temperature of the coldest point and that of the hottest point in the loading zone. It can, for example, be determined by means of
  • thermocouples arranged in the loading area.
  • Figure 1 describes an installation of the invention shown in section along the radial direction of the loading area.
  • FIG. 2 describes an assembly of substrates arranged in a stack.
  • the invention relates very particularly to an installation used for carrying out thermochemical treatments such as the cementation of parts or the densification of porous substrates by chemical infiltration in the gas phase.
  • FIG. 1 schematically shows a densification installation by chemical gas infiltration 100, the loading zone 140 of which is delimited by a cylindrical side wall 101, a bottom wall 102 and an upper wall 103.
  • Substrates to be densified 130 may be disposed in the loading area 140 in a plurality of annular vertical stacks 131 which rest on a loading tray 120. This comprises a plurality of passages 121 aligned with the internal volumes 130a of the stacks and each. battery is closed at its upper part by a cover 132.
  • the stacks 131 of substrates 130 rest on the load bed 120 and can be divided into several superimposed sections separated by one or more intermediate trays 122 having central passages 122a aligned with those of the substrates 130.
  • Each substrate 130 is separated from it. an adjacent substrate or, where appropriate, a tray 120, 122 or the cover 132 by spacers 133 which define gaps.
  • the shims 133, or at least part of them, are arranged to provide passages for the gas between the volumes 130a and 141. These passages can be made so as to substantially balance the pressure between the volumes 130a and 141, such as described in U.S. Patent 5,904,957.
  • the loading plate 120, and where appropriate the intermediate plates 122 have a central opening openings 161 allowing their arrangement around the second heating means 160.
  • a gas stream 150 containing one or more gaseous precursors of the material constituting the matrix, is admitted into the oven through the inlet 104 delimited by a pipe 106.
  • the gas passes through a preheating chamber 170.
  • This preheating chamber 170 is delimited by the cylindrical wall 101 of the first heating element 110 and comprises a portion of the second heating means 160 arranged in the center.
  • Such a preheating chamber makes it possible to bring the gas flow to a
  • such a preheating chamber may include several perforated trays 1 1 1, 112, 1 13, 1 14 through which the gas flow passes before reaching the loading zone which heat the gas flow. during its passage through the preheating chamber 170.
  • the heating of the preheating chamber 170 by means of the first and second heating means 110, 160 allows a homogeneous heating of the gas flow 150 during its stay in the preheating chamber 170.
  • the gaseous phase is then conveyed through the passages 121 of the loading plate 120 into the internal volumes 130a of the cells 131.
  • the gas phase then passes into the volume 141 external to the cells inside the loading zone 140.
  • the effluent gas is extracted by a passage 105 formed in the upper wall 103, the passage 105 being connected by a pipe 107 to suction means, such as a vacuum pump (not shown).
  • the first heating means 110 of the installation is an induction heating element. More precisely, the cylindrical side wall 101 delimiting the loading zone 140 constitutes an armature, or susceptor, for example made of graphite, which is coupled with an inductor 108 located outside the furnace and formed of at least one induction coil. An insulator 109 is interposed between the inductor 108 and the wall 101.
  • the heating of the furnace is provided by heating the armature 101 when the inductor 108 is supplied with an alternating voltage.
  • the coil or coils of the inductor are connected to an alternating voltage generator (not shown).
  • inductor 108 induces in wall 101 (susceptor) an electric current which by Joule effect causes the latter to heat up, the elements present inside wall 101 being heated by radiation.
  • the first heating means 110 of the installation 100 can be provided by other means such as electric heating means consisting for example of heating resistors embedded in the wall 101.
  • the loading zone further comprises a second heating means 160 arranged in the center of the loading zone.
  • Such a heating means 160 is, in this embodiment, a resistor, connected to a voltage generator (not shown) allowing it to be heated by the Joule effect and the heating of the loading zone by radiation.
  • thermocouples 180 distributed evenly or not in the loading area.
  • thermocouples can for example be N or K type thermocouples.
  • a thermocouple is also introduced into contact with each of the heating elements, so as to know the precise temperature of the heating elements.
  • thermocouples 180 can be placed at the end of a metal or ceramic rod extending through the top wall 103.
  • the thermocouples 180 are connected, for example by wires to 181, to a regulation system.
  • the regulation system comprises an acquisition unit 182, for example a DCS acquisition unit, making it possible to collect the temperatures measured by each of the thermocouples 180.
  • the regulation system is also connected to the first and second heating means 1 10,160 in order to adjust the temperature of each of the heating means, and thus obtain a temperature in the loading zone that is as homogeneous as possible.
  • the regulation system can allow the comparison of the temperature values determined by the thermocouples 180 with each other and / or with a set value, and consequently increase or decrease the power delivered to the first 1 10 or to the second 160 heating means. , in order to increase or decrease the temperature specifically in certain areas of the oven.
  • the control system can be a digital system called
  • proportional / integral / derivative to regulate the setpoint temperature applied to the first 1 10 or to the second heating means 160 as a function of the difference between the measured temperature and the desired temperature.
  • each of the heating means 110 and 160 can be divided in the direction of the height, into independent sub-parts.
  • the first 1 10 and the second 160 heating means can be separated into three independent parts of the same size.
  • thermocouples 180 can be placed at different heights of the loading area, and the control system can independently control the power delivered to each of the sub-parts of the first 1 10 and second 160 heating means for check the temperature uniformity in the loading area in the vertical direction in addition to the radial direction.
  • the substrates 130 can be arranged in the form of stacks 131 forming several concentric circles Ci, C 2 , C 3 .
  • This arrangement in concentric circles around the second heating means makes it possible to ensure the homogeneity of the heating of the substrates during the
  • These batteries 131 can be previously placed on a support 120, before introduction into the loading zone 140.
  • the supports have a central opening 161 capable of allowing the second heating means 160 to pass during the introduction of the support 120 into the loading zone 140.
  • the substrates form three concentric circles Ci, C 2 and C 3 .
  • the substrates form three concentric circles Ci, C 2 and C 3 .
  • the use of the two heating means ensures good thermal homogeneity in the loading zone throughout the thermochemical treatment, which guarantees the homogeneity of the products obtained.
  • Example 1 (outside the invention): heating installation without central heating.
  • preforms are densified in a conventional densification oven, without central heating means.
  • the installation is provided with a single heating means, on the periphery of the loading area, in all respects similar to a first heating means of the invention.
  • the temperature of the preforms is measured at the periphery of the loading zone as well as in the center thereof throughout the duration of the preform densification.
  • the setpoint temperature applied to the heater is 1000 ° C. After a short period of heating, the temperature of the peripheral zone is close to 1000 ° C, while the central zone is at a temperature close to 900 ° C.
  • the temperature at the center of the loading zone is around 950 ° C while that of the peripheral zone is still
  • Example 2 heating installation according to the invention, provided with a central heating means.
  • preforms are densified in a densification oven provided with a central heating means.
  • the temperature of the preforms is measured at the periphery of the loading zone as well as at the center thereof throughout the duration of the densification of the preforms.
  • the set temperature applied to the heating means is 1000 ° C, however, the set temperature is given to the control system, which automatically controls the temperature of the first and second heating means.
  • the temperature measured is between 980 ° C and 1000 ° C at the periphery and in the center of the loading area during the entire densification cycle.

Abstract

The present invention relates to a thermochemical treatment apparatus (100) comprising a loading area (140) which comprises one or several supports (120, 122) capable of receiving substrates to be treated (130), the loading area comprising a first heating means (110) which comprises a cylindrical side wall (101) defining the loading area, a first opening (104) allowing a gas phase to be injected into the loading area, a second opening (105) allowing the gas phase to be released from the loading area, characterised in that the loading area further comprises a second heating means (160) arranged at the centre of the loading area.

Description

Description Description
Titre de l'invention : Installation de densification CVI Title of the invention: CVI densification plant
Domaine Technique Technical area
L’invention concerne les installations ou fours utilisés pour réaliser des traitements thermiques. De telles installations sont notamment utilisées pour réaliser la densification de substrats poreux par infiltration chimique en phase gazeuse. The invention relates to installations or furnaces used to carry out heat treatments. Such installations are used in particular for carrying out the densification of porous substrates by chemical infiltration in the gas phase.
Technique antérieure Prior art
Un domaine d’application de l’invention est celui de la réalisation de pièces en matériau composite thermostructural, c’est-à-dire en matériau composite ayant à la fois des propriétés mécaniques qui le rendent apte à constituer des pièces structurelles et la capacité de conserver ces propriétés à des températures élevées. One field of application of the invention is that of producing parts in thermostructural composite material, that is to say in composite material having both mechanical properties which make it suitable for constituting structural parts and the capacity to retain these properties at high temperatures.
Des exemples typiques de matériaux composites thermostructuraux sont les composites carbone/carbone (C/C) ayant une texture de renfort en fibres de carbone densifiée par une matrice de carbone pyrolytique ou encore les composites à matrice céramique (CMC) ayant une texture de renfort en fibres réfractaires Typical examples of thermostructural composite materials are carbon / carbon (C / C) composites having a reinforcement texture of carbon fibers densified by a pyrolytic carbon matrix or else ceramic matrix composites (CMC) having a reinforcement texture in refractory fibers
(carbone ou céramique) densifiée par une matrice céramique. (carbon or ceramic) densified by a ceramic matrix.
Un processus bien connu de densification de substrats poreux pour réaliser des pièces en composite C/C ou en CMC est l'infiltration chimique en phase gazeuse (CVI). Les substrats à densifier sont placés dans une zone de chargement d'une installation où ils sont chauffés. Un gaz réactif contenant un ou plusieurs précurseurs gazeux du matériau constitutif de la matrice est introduit dans le four. La température et la pression dans l’installation sont réglées pour permettre au gaz réactif de diffuser au sein de la porosité des substrats et y former un dépôt du matériau constitutif de la matrice par décomposition d'un ou plusieurs constituants du gaz réactif ou par réaction entre plusieurs constituants, ces constituants formant le précurseur de la matrice. Le processus est réalisé sous pression réduite, afin de favoriser la diffusion des gaz réactifs dans les substrats. La température de transformation du ou des précurseurs pour former le matériau de la matrice, tel que carbone pyrolytique ou céramique, est dans la plupart des cas comprise entre 900°C et 1100°C, cette température pouvant toutefois atteindre 2000°C dans le cas d’un dépôt massif de carbone pyrolytique par dépôt chimique en phase gazeuse (CVD). Par exemple, un tel processus est décrit dans le brevet US 9845534. A well-known process of densifying porous substrates to make C / C composite or CMC parts is chemical gas infiltration (CVI). The substrates to be densified are placed in a loading area of an installation where they are heated. A reactive gas containing one or more gaseous precursors of the material constituting the matrix is introduced into the furnace. The temperature and the pressure in the installation are adjusted to allow the reactive gas to diffuse within the porosity of the substrates and to form there a deposit of the material constituting the matrix by decomposition of one or more constituents of the reactive gas or by reaction between several constituents, these constituents forming the precursor of the matrix. The process is carried out under reduced pressure, in order to promote the diffusion of the reactive gases in the substrates. The transformation temperature of the precursor (s) to form the material of the matrix, such as pyrolytic carbon or ceramic, is in most cases between 900 ° C and 1100 ° C, this temperature however being able to reach 2000 ° C in the case of of a massive deposition of pyrolytic carbon by chemical gas deposition (CVD). For example, such a process is described in US patent 9845534.
Les traitements d’infiltration chimiques en phase vapeur à l’échelle industrielle sont très longs à réaliser et nécessitent des installations coûteuses. Il est donc hautement souhaitable d’augmenter la taille de telles installations afin d’en augmenter la productivité. Industrial scale chemical vapor infiltration treatments take a long time to perform and require expensive installations. It is therefore highly desirable to increase the size of such facilities in order to increase their productivity.
Néanmoins, afin de réaliser une densification des substrats qui soit homogène dans toute la zone de chargement en termes d’accroissement de densité et en termes de microstructure du matériau de matrice formé, il est nécessaire que les conditions de température soient homogènes au sein de la zone de chargement pendant toute la durée du traitement thermochimique. Nevertheless, in order to achieve a densification of the substrates which is homogeneous throughout the loading zone in terms of increase in density and in terms of microstructure of the matrix material formed, it is necessary that the temperature conditions are homogeneous within the loading area for the duration of the thermochemical treatment.
Or, les installations industrielles sont habituellement chauffées au moyen d’un élément de chauffage placé à la périphérie de la zone de chargement. Une telle disposition induit la présence d’un gradient de température entre la périphérie et le centre de la zone de chargement du fait de la distance inégale avec l’élément de chauffage. Le gradient existant doit rester suffisamment faible pour ne pas introduire d’inhomogénéité entre les différentes pièces d’un lot de fabrication, ce qui limite la taille des installations. However, industrial installations are usually heated by means of a heating element placed at the periphery of the loading area. Such an arrangement induces the presence of a temperature gradient between the periphery and the center of the loading area due to the unequal distance from the heating element. The existing gradient must remain sufficiently low so as not to introduce inhomogeneity between the different parts of a production batch, which limits the size of the installations.
Il demeure un besoin de proposer une nouvelle architecture des installations de traitement thermochimique qui permette d’en agrandir la taille par rapport aux installations actuellement utilisées, tout en maintenant des conditions opératoires permettant l’obtention de pièces homogènes au sein d’un lot. There remains a need to propose a new architecture for thermochemical treatment installations which makes it possible to enlarge their size compared with the installations currently in use, while maintaining operating conditions allowing homogeneous parts to be obtained within a batch.
Exposé de l’invention Disclosure of the invention
L’invention a pour but de proposer une conception d’installation de traitement thermochimique permettant par exemple de réaliser la densification par infiltration chimique en phase vapeur d’un grand nombre de préformes, tout en assurant que l’ensemble des pièces en matériau composite obtenues après un traitement de densification soit homogène en termes de d’accroissement de densité et en termes de microstructure du matériau de matrice formé. The object of the invention is to propose a design of a thermochemical treatment installation making it possible, for example, to carry out the densification by chemical vapor infiltration of a large number of preforms, while ensuring that all of the composite material parts obtained after a densification treatment is homogeneous in terms of increase in density and in terms of microstructure of the matrix material formed.
A cet effet, la présente invention propose une installation de traitement To this end, the present invention provides a treatment installation
thermochimique comprenant une zone de chargement comprenant un ou plusieurs supports aptes à recevoir des substrats à traiter, ladite zone de chargement comprenant un premier moyen de chauffage comprenant une paroi latérale cylindrique délimitant la zone de chargement, une première ouverture permettant l’injection d’une phase gazeuse dans la zone de chargement, une seconde ouverture permettant la sortie de la phase gazeuse hors de la zone de chargement, thermochemical comprising a loading zone comprising one or more supports suitable for receiving substrates to be treated, said loading zone comprising a first heating means comprising a cylindrical side wall delimiting the loading zone, a first opening allowing the injection of a gaseous phase into the loading zone, a second opening allowing the gas phase to exit from the loading area,
caractérisée en ce que ladite zone de chargement comprend en outre un deuxième moyen de chauffage disposé au centre de la zone de chargement et dans lequel le premier moyen de chauffage est un moyen de chauffage inductif. characterized in that said loading zone further comprises a second heating means disposed in the center of the loading zone and in which the first heating means is an inductive heating means.
Une installation selon l’invention comprend en outre un système de régulation de la température, comprenant des thermocouples permettant de déterminer la An installation according to the invention further comprises a temperature regulation system, comprising thermocouples for determining the
température à plusieurs endroits de la zone de chargement et en particulier, au moins à proximité de chacun des deux moyens de chauffage et à mi-chemin entre le premier et le deuxième moyen de chauffage. temperature at several places in the loading area and in particular, at least near each of the two heating means and halfway between the first and the second heating means.
Le système de régulation de la température comprend également une centrale d’acquisition, permettant de centraliser les mesures réalisées par les différents thermocouples du système de régulation. Le système de régulation comprend en outre un organe numérique, capable, à partir des mesurées réalisées par les thermocouples, d’ajuster la puissance délivrée à chacun des deux moyens de chauffage de sorte à contrôler la température de ces derniers. The temperature regulation system also includes a data acquisition unit, allowing the measurements taken by the various thermocouples of the regulation system to be centralized. The regulation system further comprises a digital device capable, from the measurements made by the thermocouples, of adjusting the power delivered to each of the two heating means so as to control the temperature of the latter.
Un tel système de régulation de la température permet de contrôler et d’ajuster en temps réel dans la zone de chargement l’uniformité de la température. En l’absence d’un tel système de régulation, il peut être observé un gradient trop important entre le bord de la zone de chargement et son centre, et la densification n’est pas homogène entre toutes les préformes. Such a temperature control system allows the temperature uniformity to be controlled and adjusted in the loading area in real time. In the absence of such a regulation system, an excessively large gradient can be observed between the edge of the loading zone and its center, and the densification is not homogeneous between all the preforms.
Dans un mode de réalisation, l’installation peut être une installation de traitement d’un substrat par un procédé d’infiltration chimique en phase vapeur (CVI). In one embodiment, the installation may be an installation for treating a substrate by a chemical vapor infiltration (CVI) process.
L’installation décrite comprend un ou plusieurs supports, aptes à recevoir des substrats à traiter. Ces supports peuvent par exemple être des disques permettant le chargement d’une pluralité de substrats sous la forme de piles. Ces supports peuvent permettre d’obtenir une répartition ordonnée des substrats dans la zone de chargement, et ainsi de favoriser une distribution homogène des substrats dans la zone de chargement. Dans une installation telle que décrite ci-dessus, le chauffage est réalisé par l’action conjointe du premier et du second moyen de chauffage ce qui permet d’obtenir un profil de température homogène dans toute la zone de chargement. The installation described comprises one or more supports, capable of receiving substrates to be treated. These supports can for example be discs allowing the loading of a plurality of substrates in the form of stacks. These supports can make it possible to obtain an orderly distribution of the substrates in the loading zone, and thus to promote a homogeneous distribution of the substrates in the loading zone. In an installation as described above, the heating is carried out by the joint action of the first and the second heating means, which makes it possible to obtain a uniform temperature profile throughout the loading zone.
Plus précisément, le premier moyen de chauffage qui comporte une paroi cylindrique délimitant la zone de chargement impose un chauffage ayant un gradient radial dirigé de l’intérieur de la chambre vers l’extérieur, tandis que le deuxième moyen de chauffage disposé au centre de la zone de chargement permet d’assurer un chauffage avec un gradient opposé. L’utilisation conjointe des deux moyens de chauffage permet ainsi un chauffage homogène dans toute la zone de chargement. More precisely, the first heating means which comprises a cylindrical wall delimiting the loading zone imposes a heating having a radial gradient directed from the inside of the chamber towards the outside, while the second heating means disposed at the center of the loading zone ensures heating with an opposite gradient. The joint use of the two heating means thus allows homogeneous heating throughout the loading area.
Une telle caractéristique est particulièrement satisfaisante dans le cas de la densification de préformes poreuses pour former des pièces en matériau composite par un traitement CVI, puisque l’homogénéité thermique dans la zone de Such a characteristic is particularly satisfactory in the case of the densification of porous preforms to form parts of composite material by a CVI treatment, since the thermal homogeneity in the zone of
chargement assure une densification homogène de chacun des substrats et par conséquent des caractéristiques thermomécaniques identiques entre toutes les pièces obtenues après traitement. loading ensures homogeneous densification of each of the substrates and consequently identical thermomechanical characteristics between all the parts obtained after treatment.
En particulier, le premier moyen de chauffage peut être composé d’un induit, d’un élément isolant et d’un inducteur. Dans un tel cas, l’induit peut être la paroi latérale cylindrique délimitant la zone de chargement, et être agencé pour coopérer avec l’inducteur, un élément isolant étant placé entre l’induit et l’inducteur. La mise sous tension de l’inducteur, au moyen par exemple d’un générateur, provoque le chauffage de l’induit qui chauffe la zone de chargement par rayonnement. In particular, the first heating means can be composed of an armature, an insulating element and an inductor. In such a case, the armature may be the cylindrical side wall delimiting the loading zone, and be arranged to cooperate with the inductor, an insulating element being placed between the armature and the inductor. Energizing the inductor, for example by means of a generator, causes the armature to heat up, which heats the loading area by radiation.
Dans un mode de réalisation, le deuxième moyen de chauffage peut être un élément résistif dont le chauffage est assuré par effet Joule. Un tel chauffage peut être obtenu en connectant le deuxième élément de chauffage à un générateur. Dans un mode de réalisation, le deuxième moyen de chauffage présente une température homogène dans toute sa hauteur ce qui améliore l’homogénéité thermique dans la zone de chargement. In one embodiment, the second heating means may be a resistive element, the heating of which is provided by the Joule effect. Such heating can be achieved by connecting the second heating element to a generator. In one embodiment, the second heating means has a homogeneous temperature throughout its height, which improves thermal homogeneity in the loading zone.
Dans un mode de réalisation, le deuxième moyen de chauffage présente une hauteur comparable au premier moyen de chauffage dans la dimension verticale de l’installation. Par exemple, la hauteur des deux moyens de chauffage ne diffère pas de plus de 10 %, mieux de plus de 5 %, voire de 1 %. Avoir une hauteur comparable entre le premier et le deuxième élément de chauffage permet d’éviter la présence d’un gradient thermique dirigé verticalement dans la zone de chargement. In one embodiment, the second heating means has a height comparable to the first heating means in the vertical dimension of the installation. For example, the height of the two heating means does not differ by more than 10%, better still by more than 5%, or even by 1%. Having a comparable height between the first and the second heating element avoids the presence of a vertically directed thermal gradient in the loading area.
Dans un mode de réalisation, l’installation comporte en outre une chambre de préchauffage du gaz disposée entre la première ouverture et la zone de chargement. Une telle chambre de préchauffage permet de chauffer le flux gazeux avant son introduction dans la zone de chargement. In one embodiment, the installation further comprises a gas preheating chamber arranged between the first opening and the loading area. Such a preheating chamber makes it possible to heat the gas flow before its introduction into the loading zone.
Dans un mode de réalisation, la chambre de préchauffage est délimitée par une portion du premier moyen de chauffage et comprend en son centre une portion du deuxième moyen de chauffage. La présence des deux moyens de chauffage permet de minimiser le gradient de température entre le centre et la périphérie de la chambre de préchauffage et ainsi d’assurer une température plus homogène du gaz préalablement à son admission dans la zone de chargement. In one embodiment, the preheating chamber is delimited by a portion of the first heating means and comprises at its center a portion of the second heating means. The presence of the two heating means makes it possible to minimize the temperature gradient between the center and the periphery of the preheating chamber and thus to ensure a more homogeneous temperature of the gas prior to its admission into the loading zone.
Dans un mode de réalisation, le deuxième moyen de chauffage peut être recouvert d’une couche protectrice. Une telle couche protectrice peut être inerte chimiquement vis-à-vis de la phase gazeuse réactive lors du fonctionnement de l’installation, et ainsi, éviter la formation d’un dépôt à la surface du deuxième moyen de chauffage au cours d’un traitement thermochimique. Une telle couche permet de garantir l’homogénéité du chauffage du deuxième moyen de chauffage pendant toute la durée du traitement thermochimique. In one embodiment, the second heating means may be covered with a protective layer. Such a protective layer can be chemically inert with respect to the reactive gas phase during operation of the installation, and thus prevent the formation of a deposit on the surface of the second heating means during a treatment. thermochemical. Such a layer makes it possible to guarantee the homogeneity of the heating of the second heating means throughout the duration of the thermochemical treatment.
Une telle couche protectrice doit présenter des caractéristiques satisfaisantes en termes de conductivité thermique et de résistance à la chaleur. En particulier, sa conductivité thermique doit être isotrope de sorte que la température à la surface d’un moyen de chauffage revêtu d’une telle couche soit homogène. Bien entendu, la conductivité thermique doit être suffisante, de sorte que la couche protectrice ne nuise pas aux qualités de chauffe du deuxième moyen de chauffage. Elle doit de plus être bien déterminée, pour que l’homme du métier puisse tenir compte de la présence de la couche quand il détermine la température à donner au deuxième moyen de chauffage. Par ailleurs, la résistance à la chaleur d’une telle couche doit être suffisante pour permettre une tenue homogène et durable de la couche sur le deuxième élément de chauffage pendant toute la durée de vie de l’installation. Une installation telle que décrite ci-dessus peut avoir une zone de chargement plus grande que des installations de l’art antérieur, tout en maintenant pendant le traitement thermique des conditions de température plus homogènes. Such a protective layer must have satisfactory characteristics in terms of thermal conductivity and heat resistance. In particular, its thermal conductivity must be isotropic so that the temperature at the surface of a heating means coated with such a layer is homogeneous. Of course, the thermal conductivity must be sufficient, so that the protective layer does not adversely affect the heating qualities of the second heating means. It must also be well determined, so that a person skilled in the art can take into account the presence of the layer when determining the temperature to be given to the second heating means. Furthermore, the heat resistance of such a layer must be sufficient to allow a homogeneous and lasting hold of the layer on the second heating element throughout the life of the installation. An installation as described above can have a larger loading area than installations of the prior art, while maintaining more homogeneous temperature conditions during the heat treatment.
De plus, la présence de deux moyens de chauffage disposés comme explicité ci- dessus permet également d’atteindre plus rapidement une température élevée et homogène dans une installation une fois le chargement effectué. Diminuer le temps de montée en température d’une installation représente une diminution du temps de traitement, et par conséquent un gain de productivité élevé. In addition, the presence of two heating means arranged as explained above also makes it possible to reach a high and uniform temperature more quickly in an installation once the loading has been carried out. Reducing the temperature rise time of an installation represents a reduction in processing time, and therefore a high gain in productivity.
Selon un autre de ses aspects, l’invention concerne un procédé de densification d’une pluralité de substrats comprenant une étape de chargement d’une pluralité de substrats disposés en piles dans une zone de chargement d’une installation de traitement thermochimique telle que décrite ci-dessus, ladite pluralité de substrats disposés en piles formant des cercles concentriques autour du centre de la zone de chargement, caractérisé en ce qu’il comprend après l’étape de chargement, une étape de chauffage réalisée au moyen du premier et du deuxième moyen de chauffage de la zone de chargement. According to another of its aspects, the invention relates to a method for densifying a plurality of substrates comprising a step of loading a plurality of substrates arranged in stacks in a loading zone of a thermochemical treatment installation as described. above, said plurality of substrates arranged in stacks forming concentric circles around the center of the loading area, characterized in that it comprises after the loading step, a heating step carried out by means of the first and the second means of heating the loading area.
Par exemple, un tel procédé peut correspondre à l’infiltration chimique en phase gazeuse d’une préforme fibreuse pour la réalisation d’un matériau céramique, réalisée dans une installation telle que décrite ci-dessus. For example, such a process may correspond to the chemical gas-phase infiltration of a fiber preform for the production of a ceramic material, carried out in an installation as described above.
Un tel procédé permet, lors du fonctionnement des deux moyens de chauffage, d’assurer une homogénéité thermique dans la zone de chargement améliorée, comparativement aux procédés de l’art antérieur. Such a method makes it possible, during the operation of the two heating means, to ensure thermal homogeneity in the improved loading zone, compared to the methods of the prior art.
Dans un mode de réalisation, le substrat est une préforme poreuse d’un matériau composite, comme une préforme fibreuse, par exemple en fibre de carbone ou en fibres réfractaires. In one embodiment, the substrate is a porous preform of a composite material, such as a fibrous preform, for example of carbon fiber or of refractory fibers.
En particulier, au cours d’un procédé selon l’invention le gradient thermique dans la zone de chargement peut être inférieur à 5%, voire inférieur à 3%. In particular, during a process according to the invention, the thermal gradient in the loading zone may be less than 5%, or even less than 3%.
L’expression « gradient thermique dans la zone de chargement » est définie comme le rapport entre la température du point le plus froid et celle du point le plus chaud de la zone de chargement. Il peut, par exemple, être déterminé au moyen de The term "thermal gradient in the loading zone" is defined as the ratio between the temperature of the coldest point and that of the hottest point in the loading zone. It can, for example, be determined by means of
thermocouples disposés dans la zone de chargement. Brève description des dessins thermocouples arranged in the loading area. Brief description of the drawings
[Fig. 1 ] La figure 1 décrit une installation de l’invention représentée en coupe selon la direction radiale de la zone de chargement. [Fig. 1] Figure 1 describes an installation of the invention shown in section along the radial direction of the loading area.
[Fig. 2] La figure 2 décrit un assemblage de substrats disposés en pile. [Fig. 2] FIG. 2 describes an assembly of substrates arranged in a stack.
Description des modes de réalisation Description of embodiments
L’invention concerne tout particulièrement une installation utilisée pour réaliser des traitements thermochimiques comme la cémentation de pièces ou la densification de substrats poreux par infiltration chimique en phase gazeuse. The invention relates very particularly to an installation used for carrying out thermochemical treatments such as the cementation of parts or the densification of porous substrates by chemical infiltration in the gas phase.
Un mode de réalisation d’une installation pour le traitement par CVI de préformes poreuses est décrit en relation avec la figure 1. One embodiment of an installation for CVI treatment of porous preforms is described in relation to Figure 1.
La figure 1 montre schématiquement une installation de densification par infiltration chimique en phase gazeuse 100, dont la zone de chargement 140 est délimitée par une paroi latérale cylindrique 101 , une paroi de fond 102 et une paroi supérieure 103. FIG. 1 schematically shows a densification installation by chemical gas infiltration 100, the loading zone 140 of which is delimited by a cylindrical side wall 101, a bottom wall 102 and an upper wall 103.
Des substrats à densifier 130 peuvent être disposés dans la zone de chargement 140 en une pluralité de piles verticales annulaires 131 qui reposent sur un plateau de chargement 120. Celui-ci comprend une pluralité de passages 121 alignés avec les volumes internes 130a des piles et chaque pile est obturée à sa partie supérieure par un couvercle 132. Substrates to be densified 130 may be disposed in the loading area 140 in a plurality of annular vertical stacks 131 which rest on a loading tray 120. This comprises a plurality of passages 121 aligned with the internal volumes 130a of the stacks and each. battery is closed at its upper part by a cover 132.
De préférence, les piles 131 de substrats 130 reposent sur le plateau de chargement 120 et peuvent être divisées en plusieurs sections superposées séparées par un ou plusieurs plateaux intermédiaires 122 ayant des passages centraux 122a alignés avec ceux des substrats 130. Chaque substrat 130 est séparé d'un substrat adjacent ou, le cas échéant, d'un plateau 120, 122 ou du couvercle 132 par des cales d'espacement 133 qui définissent des intervalles. Les cales 133, ou au moins une partie d'entre elles, sont aménagées pour ménager des passages pour le gaz entre les volumes 130a et 141. Ces passages peuvent être réalisés de manière à équilibrer sensiblement la pression entre les volumes 130a et 141 , comme décrit dans le brevet US 5 904 957. Le plateau de chargement 120, et le cas échéant les plateaux intermédiaires 122 présentent une ouverture centrale ouvertures 161 permettant leur disposition autour du deuxième moyen de chauffage 160. Preferably, the stacks 131 of substrates 130 rest on the load bed 120 and can be divided into several superimposed sections separated by one or more intermediate trays 122 having central passages 122a aligned with those of the substrates 130. Each substrate 130 is separated from it. an adjacent substrate or, where appropriate, a tray 120, 122 or the cover 132 by spacers 133 which define gaps. The shims 133, or at least part of them, are arranged to provide passages for the gas between the volumes 130a and 141. These passages can be made so as to substantially balance the pressure between the volumes 130a and 141, such as described in U.S. Patent 5,904,957. The loading plate 120, and where appropriate the intermediate plates 122 have a central opening openings 161 allowing their arrangement around the second heating means 160.
Un flux gazeux 150, contenant un ou plusieurs précurseurs gazeux du matériau constitutif de la matrice, est admis dans le four à travers l'entrée 104 délimitée par une conduite 106. A gas stream 150, containing one or more gaseous precursors of the material constituting the matrix, is admitted into the oven through the inlet 104 delimited by a pipe 106.
Dans ce mode de réalisation, entre l’ouverture permettant l’injection de la phase gazeuse 104 et la zone de chargement 140, le gaz passe par une chambre de préchauffage 170. In this embodiment, between the opening allowing the injection of the gas phase 104 and the loading zone 140, the gas passes through a preheating chamber 170.
Cette chambre de préchauffage 170 est délimitée par la paroi cylindrique 101 du premier élément de chauffage 1 10 et comprend une portion du deuxième moyen de chauffage 160 disposée au centre. This preheating chamber 170 is delimited by the cylindrical wall 101 of the first heating element 110 and comprises a portion of the second heating means 160 arranged in the center.
Une telle chambre de préchauffage permet de porter le flux gazeux à une Such a preheating chamber makes it possible to bring the gas flow to a
température favorable à sa décomposition dans la zone de chargement 140 avant son introduction dans la zone de chargement. Par exemple, comme représenté en figure 1 , une telle chambre de préchauffage peut comprendre plusieurs plateaux perforés 1 1 1 , 112, 1 13, 1 14 traversés par le flux gazeux avant d’atteindre la zone de chargement qui assurent un chauffage du flux gazeux lors de son passage dans la chambre de préchauffage 170. temperature favorable to its decomposition in the loading zone 140 before its introduction into the loading zone. For example, as shown in Figure 1, such a preheating chamber may include several perforated trays 1 1 1, 112, 1 13, 1 14 through which the gas flow passes before reaching the loading zone which heat the gas flow. during its passage through the preheating chamber 170.
Dans ce mode de réalisation, le chauffage de la chambre de préchauffage 170 au moyen des premier et deuxième moyens de chauffage 1 10, 160 permet un chauffage homogène du flux gazeux 150 lors de son séjour dans la chambre de préchauffage 170. In this embodiment, the heating of the preheating chamber 170 by means of the first and second heating means 110, 160 allows a homogeneous heating of the gas flow 150 during its stay in the preheating chamber 170.
La phase gazeuse est ensuite acheminée par les passages 121 du plateau de chargement 120 dans les volumes internes 130a des piles 131. La phase gazeuse passe ensuite dans le volume 141 externe aux piles à l'intérieur de la zone de chargement 140. Le gaz effluent est extrait par un passage 105 formé dans la paroi supérieure 103, le passage 105 étant relié par une conduite 107 à des moyens d'aspiration, tels qu'une pompe à vide (non représentée). The gaseous phase is then conveyed through the passages 121 of the loading plate 120 into the internal volumes 130a of the cells 131. The gas phase then passes into the volume 141 external to the cells inside the loading zone 140. The effluent gas is extracted by a passage 105 formed in the upper wall 103, the passage 105 being connected by a pipe 107 to suction means, such as a vacuum pump (not shown).
Dans l’exemple décrit ici, le premier moyen de chauffage 1 10 de l’installation est un élément de chauffage à induction. Plus précisément, la paroi latérale cylindrique 101 délimitant la zone de chargement 140 constitue un induit, ou suscepteur, par exemple en graphite, qui est couplé avec un inducteur 108 situé à l'extérieur du four et formé d'au moins une bobine d'induction. Un isolant 109 est interposé entre l'inducteur 108 et la paroi 101. De façon bien connue, le chauffage du four est assuré par réchauffement de l'induit 101 lorsque l'inducteur 108 est alimenté avec une tension alternative. A cet effet, la ou les bobines de l'inducteur sont reliées à un générateur de tension alternative (non représenté). In the example described here, the first heating means 110 of the installation is an induction heating element. More precisely, the cylindrical side wall 101 delimiting the loading zone 140 constitutes an armature, or susceptor, for example made of graphite, which is coupled with an inductor 108 located outside the furnace and formed of at least one induction coil. An insulator 109 is interposed between the inductor 108 and the wall 101. In a well-known manner, the heating of the furnace is provided by heating the armature 101 when the inductor 108 is supplied with an alternating voltage. For this purpose, the coil or coils of the inductor are connected to an alternating voltage generator (not shown).
Le champ magnétique créé par l'inducteur 108 induit dans la paroi 101 (suscepteur) un courant électrique qui provoque par effet Joule réchauffement de cette dernière, les éléments présents à l’intérieur de la paroi 101 étant chauffés par rayonnement. The magnetic field created by inductor 108 induces in wall 101 (susceptor) an electric current which by Joule effect causes the latter to heat up, the elements present inside wall 101 being heated by radiation.
Le premier moyen de chauffage 1 10 de l’installation 100 peut être assuré par d’autres moyens tels que des moyens de chauffage électriques constitués par exemple de résistances chauffantes noyées dans la paroi 101. The first heating means 110 of the installation 100 can be provided by other means such as electric heating means consisting for example of heating resistors embedded in the wall 101.
Dans l’exemple décrit, la zone de chargement comprend en outre un deuxième moyen de chauffage 160 disposé au centre de la zone de chargement. In the example described, the loading zone further comprises a second heating means 160 arranged in the center of the loading zone.
Un tel moyen de chauffage 160 est, dans ce mode de réalisation, une résistance, reliée à un générateur de tension (non représenté) permettant son échauffement par effet Joule et le chauffage de la zone de chargement par rayonnement. Such a heating means 160 is, in this embodiment, a resistor, connected to a voltage generator (not shown) allowing it to be heated by the Joule effect and the heating of the loading zone by radiation.
De plus, l’installation de chauffage 100 comprend également des thermocouples 180 répartis de manière régulière ou non dans la zone de chargement. Ces In addition, the heating installation 100 also includes thermocouples 180 distributed evenly or not in the loading area. These
thermocouples peuvent par exemple être des thermocouples de type N ou K. De manière préférée, un thermocouple est également introduit au contact de chacun des éléments chauffant, de sorte à connaître la température précise des éléments chauffants. thermocouples can for example be N or K type thermocouples. Preferably, a thermocouple is also introduced into contact with each of the heating elements, so as to know the precise temperature of the heating elements.
Comme figuré sur la figure 1 , les thermocouples 180 peuvent être placés au bout une canne métallique ou céramique s’étendant à travers la paroi supérieure 103.As shown in Figure 1, the thermocouples 180 can be placed at the end of a metal or ceramic rod extending through the top wall 103.
Les thermocouples 180 sont reliés, par exemple par des fils à 181 , à un système de régulation. Le système de régulation comprend une centrale d’acquisition 182, par exemple une centrale d’acquisition DCS, permettant de collecter les températures mesurées par chacun des thermocouples 180. Le système de régulation, est également relié aux premier et deuxième moyens de chauffage 1 10,160 de sorte à ajuster la température de chacun des moyens de chauffage, et ainsi obtenir une température dans la zone de chargement la plus homogène possible. Par exemple, le système de régulation peut permettre la comparaison des valeurs de température déterminées par les thermocouples 180 entre elles et/ou avec une valeur consigne, et augmenter ou diminuer en conséquence la puissance délivrée au premier 1 10 ou au second 160 moyen de chauffage, afin d’augmenter ou de diminuer la température spécifiquement à certains endroits du four. The thermocouples 180 are connected, for example by wires to 181, to a regulation system. The regulation system comprises an acquisition unit 182, for example a DCS acquisition unit, making it possible to collect the temperatures measured by each of the thermocouples 180. The regulation system is also connected to the first and second heating means 1 10,160 in order to adjust the temperature of each of the heating means, and thus obtain a temperature in the loading zone that is as homogeneous as possible. For example, the regulation system can allow the comparison of the temperature values determined by the thermocouples 180 with each other and / or with a set value, and consequently increase or decrease the power delivered to the first 1 10 or to the second 160 heating means. , in order to increase or decrease the temperature specifically in certain areas of the oven.
Le système de régulation peut être un système numérique dit The control system can be a digital system called
proportionnel/intégral/dérivée, pour réguler la température de consigne appliquée au premier 1 10 ou au deuxième moyen de chauffage 160 en fonction de la différence entre la température mesurée et la température souhaitée. proportional / integral / derivative, to regulate the setpoint temperature applied to the first 1 10 or to the second heating means 160 as a function of the difference between the measured temperature and the desired temperature.
Dans un mode de réalisation non représenté, chacun des moyens de chauffage 1 10 et 160 peut être divisé dans le sens de la hauteur, en sous-parties indépendantes. Par exemple, le premier 1 10 et le deuxième 160 moyen de chauffage, peuvent être séparés en trois parties indépendantes de même taille. In an embodiment not shown, each of the heating means 110 and 160 can be divided in the direction of the height, into independent sub-parts. For example, the first 1 10 and the second 160 heating means, can be separated into three independent parts of the same size.
Dans un tel mode de réalisation, des thermocouples 180 peuvent être placés à différentes hauteurs de la zone de chargement, et le système de régulation peut contrôler indépendamment la puissance délivrée à chacune des sous-parties du premier 1 10 et deuxième 160 moyen de chauffage pour contrôler l’homogénéité de la température dans la zone de chargement dans la direction verticale en plus de la direction radiale. In such an embodiment, thermocouples 180 can be placed at different heights of the loading area, and the control system can independently control the power delivered to each of the sub-parts of the first 1 10 and second 160 heating means for check the temperature uniformity in the loading area in the vertical direction in addition to the radial direction.
Obtenir un profil de température le plus homogène possible permet d’assurer l’homogénéité de la densification des préformes, où que ces dernières soient placées dans la zone de chargement. Obtaining the most homogeneous temperature profile possible ensures the homogeneity of the densification of the preforms, wherever they are placed in the loading area.
Comme représenté en figure 2, les substrats 130 peuvent être disposés sous la forme de piles 131 formant plusieurs cercles concentriques C-i, C2, C3. Cette disposition en cercles concentriques autour du deuxième moyen de chauffage permet d’assurer l’homogénéité du chauffage des substrats au cours du As shown in FIG. 2, the substrates 130 can be arranged in the form of stacks 131 forming several concentric circles Ci, C 2 , C 3 . This arrangement in concentric circles around the second heating means makes it possible to ensure the homogeneity of the heating of the substrates during the
fonctionnement de l’installation, en maintenant la symétrie circulaire de la zone de chargement et des deux moyens de chauffage. operation of the installation, maintaining the circular symmetry of the loading area and the two heating means.
Ces piles 131 peuvent être préalablement placées sur un support 120, avant l’introduction dans la zone de chargement 140. Dans le mode de réalisation représenté, les supports présentent une ouverture centrale 161 apte à laisser passer le deuxième moyen de chauffage 160 lors de l’introduction du support 120 dans la zone de chargement 140. These batteries 131 can be previously placed on a support 120, before introduction into the loading zone 140. In the embodiment shown, the supports have a central opening 161 capable of allowing the second heating means 160 to pass during the introduction of the support 120 into the loading zone 140.
Du fait de la disposition circulaire des piles de substrat 131 dans la zone de chargement, un agrandissement de la zone de chargement dans sa direction radiale mène à une augmentation importante du nombre de substrats pouvant être traité, chaque cercle de piles étant plus grand que celui autour duquel il est disposé. Due to the circular arrangement of the substrate stacks 131 in the loading area, an enlargement of the loading area in its radial direction leads to a large increase in the number of substrates that can be processed, each circle of cells being larger than that. around which it is arranged.
Dans le mode de réalisation représenté en figure 2, les substrats forment trois cercles concentriques C-i, C2 et C3. Malgré la grande taille de la zone de In the embodiment shown in FIG. 2, the substrates form three concentric circles Ci, C 2 and C 3 . Despite the large size of the
chargement, l’utilisation des deux moyens de chauffage permet d’assurer une bonne homogénéité thermique dans la zone de chargement tout au long du traitement thermochimique ce qui garantit l’homogénéité des produits obtenus. loading, the use of the two heating means ensures good thermal homogeneity in the loading zone throughout the thermochemical treatment, which guarantees the homogeneity of the products obtained.
Exemple. Example.
L’invention est à présent décrite au moyen d’un premier exemple hors invention et d’un deuxième exemple selon l’invention, qui représente seulement un mode de réalisation particulier et ne doit pas être interprété de manière limitative. The invention is now described by means of a first example outside the invention and of a second example according to the invention, which represents only a particular embodiment and should not be interpreted in a limiting manner.
Exemple 1 (hors invention) : installation de chauffage sans chauffage central. Example 1 (outside the invention): heating installation without central heating.
Dans cet exemple, des préformes sont densifiées dans un four de densification classique, dénué d’un moyen de chauffage central. L’installation est dotée d’un seul moyen de chauffage, en périphérie de la zone de chargement, en tout point similaire à un premier moyen de chauffage de l’invention. La température des préformes est mesurée en périphérie de la zone de chargement ainsi qu’au centre de celle-ci pendant toute la durée de la densification des préformes. In this example, preforms are densified in a conventional densification oven, without central heating means. The installation is provided with a single heating means, on the periphery of the loading area, in all respects similar to a first heating means of the invention. The temperature of the preforms is measured at the periphery of the loading zone as well as in the center thereof throughout the duration of the preform densification.
La température de consigne appliquée au moyen de chauffage est de 1000°C. Après un court moment de chauffage, la température de la zone périphérique est voisine de 1000°C, tandis que la zone centrale est à une température proche de 900°C. The setpoint temperature applied to the heater is 1000 ° C. After a short period of heating, the temperature of the peripheral zone is close to 1000 ° C, while the central zone is at a temperature close to 900 ° C.
A la fin du cycle de densification, la température au centre de la zone de chargement est voisine de 950°C tandis que celle de la zone périphérique est toujours de At the end of the densification cycle, the temperature at the center of the loading zone is around 950 ° C while that of the peripheral zone is still
1000°C. 1000 ° C.
Exemple 2 : installation de chauffage selon l’invention, dotée d’un moyen de chauffage central. Dans cet exemple, des préformes sont densifiées dans un four de densification doté d’un moyen de chauffage central. La température des préformes est mesurée en périphérie de la zone de chargement ainsi qu’au centre de celle-ci pendant toute la durée de la densification des préformes. Example 2: heating installation according to the invention, provided with a central heating means. In this example, preforms are densified in a densification oven provided with a central heating means. The temperature of the preforms is measured at the periphery of the loading zone as well as at the center thereof throughout the duration of the densification of the preforms.
La température de consigne appliquée au moyen de chauffage est de 1000°C, toutefois, la température de consigne est donnée au système de régulation, qui contrôle de manière automatique la température des premier et deuxième moyens de chauffage. The set temperature applied to the heating means is 1000 ° C, however, the set temperature is given to the control system, which automatically controls the temperature of the first and second heating means.
En début du cycle de densification, 85 % de la puissance électrique est injectée dans le premier moyen de chauffage, et 15 % dans le deuxième. At the start of the densification cycle, 85% of the electrical power is injected into the first heating means, and 15% into the second.
En fin de cycle, 92 % de la puissance électrique est injectée dans le premier moyen de chauffage et 8% dans le deuxième moyen de chauffage. At the end of the cycle, 92% of the electrical power is injected into the first heating means and 8% into the second heating means.
La température mesurée est comprise entre 980°C et 1000°C en périphérie et au centre de la zone de chargement pendant tout le cycle de densification. The temperature measured is between 980 ° C and 1000 ° C at the periphery and in the center of the loading area during the entire densification cycle.
Les deux exemples ci-dessus montrent qu’une enceinte de densification selon l’invention permet d’uniformiser la température tout au long d’un cycle de densification. The two examples above show that a densification enclosure according to the invention makes it possible to standardize the temperature throughout a densification cycle.

Claims

Revendications Claims
[Revendication 1] Installation de traitement thermochimique (100) [Claim 1] Thermochemical treatment plant (100)
comprenant une zone de chargement (140) comprenant un ou plusieurs supports (120, 122) aptes à recevoir des substrats à traiter (130), ladite zone de chargement comprenant un premier moyen de chauffage (110) comprising a loading zone (140) comprising one or more supports (120, 122) capable of receiving substrates to be treated (130), said loading zone comprising a first heating means (110)
comprenant une paroi latérale cylindrique (101) délimitant la zone de chargement, une première ouverture (104) permettant l'injection d'une phase gazeuse dans la zone de chargement, une seconde ouverture (105) permettant la sortie de la phase gazeuse hors de la zone de chargement, caractérisée en ce que la zone de chargement comprend en outre un deuxième moyen de chauffage (160) disposé au centre de ladite zone de chargement et dans laquelle le premier moyen de chauffage (110) est un moyen de chauffage inductif, l'installation comprenant en outre un système de régulation de la température, comprenant des thermocouples (180) reliés à une centrale d'acquisition et un organe numérique (182), capable d'ajuster la puissance délivrée par chacun des deux moyens de chauffage. comprising a cylindrical side wall (101) delimiting the loading zone, a first opening (104) allowing the injection of a gas phase into the loading zone, a second opening (105) allowing the exit of the gas phase out of the loading area, characterized in that the loading area further comprises a second heating means (160) arranged in the center of said loading area and in which the first heating means (110) is an inductive heating means, the installation further comprising a temperature regulation system, comprising thermocouples (180) connected to an acquisition unit and a digital device (182) capable of adjusting the power delivered by each of the two heating means.
[Revendication 2] Installation selon la revendication 1, dans laquelle le deuxième moyen de chauffage (160) est un élément résistif. [Claim 2] Installation according to claim 1, in which the second heating means (160) is a resistive element.
[Revendication 3] Installation selon l'une quelconque des revendications 1 à 2, dans laquelle le deuxième moyen de chauffage (160) est recouvert d'une couche protectrice. [Claim 3] Installation according to any one of claims 1 to 2, in which the second heating means (160) is covered with a protective layer.
[Revendication 4] Procédé de densification d'une pluralité de substrats (130) comprenant une étape de chargement d'une pluralité de substrats disposés en piles (131) dans une zone de chargement (140) d'une installation de traitement thermochimique (100) selon l'une quelconque des [Claim 4] A method of densifying a plurality of substrates (130) comprising a step of loading a plurality of substrates arranged in stacks (131) in a loading area (140) of a thermochemical treatment plant (100). ) according to any of the
revendications 1 à 3, ladite pluralité de substrats disposés en piles formant des cercles concentriques autour du centre de la zone de chargement, caractérisé en ce qu'il comprend après l'étape de chargement, une étape de chauffage réalisée au moyen du premier (110) et du deuxième moyen de chauffage (160) de la zone de chargement. claims 1 to 3, said plurality of substrates arranged in stacks forming concentric circles around the center of the loading zone, characterized in that it comprises after the loading step, a heating step carried out by means of the first (110 ) and the second heating means (160) of the loading area.
[Revendication 5] Procédé de densification selon la revendication 4, dans lequel les substrats (130) sont des préformes poreuses de matériaux composites. [Claim 5] A densification method according to claim 4, wherein the substrates (130) are porous preforms of composite materials.
[Revendication 6] Procédé de densification selon l'une quelconque des revendications 4 ou 5, dans lequel le gradient thermique dans la zone de chargement (140) est inférieur à 5 %. [Claim 6] A densification method according to any one of claims 4 or 5, wherein the thermal gradient in the loading zone (140) is less than 5%.
PCT/EP2020/059495 2019-04-19 2020-04-03 Cvi densification apparatus WO2020212168A1 (en)

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