U.S. patent application number 10/765416 was filed with the patent office on 2004-10-07 for active cooling panel of thermostructural composite material and method for its manufacture.
This patent application is currently assigned to Snecma Propulsion Solide. Invention is credited to Bouquet, Clement, Larrieu, Jean-Michel, Thebault, Jacques, Uhrig, Gilles.
Application Number | 20040194941 10/765416 |
Document ID | / |
Family ID | 31726076 |
Filed Date | 2004-10-07 |
United States Patent
Application |
20040194941 |
Kind Code |
A1 |
Larrieu, Jean-Michel ; et
al. |
October 7, 2004 |
Active cooling panel of thermostructural composite material and
method for its manufacture
Abstract
The active cooling panel comprises a first part and a second
part of thermostructural composite material, each having an inside
face and an opposite outside face, the parts being assembled
together by bonding their inside faces together, and channels being
formed by indentations formed in the inside face of at least one of
the first and second parts. The panel further includes a sealing
layer bonded to at least one of the first and second parts and
situated at a distance from the assembled-together inside faces
thereof. The invention is applicable to making heat exchanger walls
such as the walls for the combustion chambers of aircraft engines,
or the diverging portions of rocket engines, or plasma confinement
chambers in nuclear fusion reactors.
Inventors: |
Larrieu, Jean-Michel;
(Macau, FR) ; Uhrig, Gilles; (Pyla Sur Mer,
FR) ; Thebault, Jacques; (Bordeaux, FR) ;
Bouquet, Clement; (Bordeaux, FR) |
Correspondence
Address: |
WEINGARTEN, SCHURGIN, GAGNEBIN & LEBOVICI LLP
TEN POST OFFICE SQUARE
BOSTON
MA
02109
US
|
Assignee: |
Snecma Propulsion Solide
|
Family ID: |
31726076 |
Appl. No.: |
10/765416 |
Filed: |
January 27, 2004 |
Current U.S.
Class: |
165/170 |
Current CPC
Class: |
F28F 21/081 20130101;
F02K 9/974 20130101; F02K 9/64 20130101; F23R 3/007 20130101; Y02E
30/10 20130101; F23R 3/005 20130101; F28F 3/12 20130101; F02K 9/972
20130101; F28D 2021/0078 20130101 |
Class at
Publication: |
165/170 |
International
Class: |
F28F 003/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 30, 2003 |
FR |
0301041 |
Claims
What is claimed is:
1. An active cooling panel comprising first and second parts of
thermostructural composite material each having an inside face and
an opposite outside face, the parts being assembled together by
bonding their inside faces together, and channels being formed by
indentations formed in the inside face of at least one of the first
and second parts, the panel further comprising a sealing layer
bonded to at least one of the first and second parts and situated
at a distance from the assembled-together inside faces thereof.
2. A panel according to claim 1, wherein a sealing layer is
situated within at least one of the first and second parts,
separating the part into two portions between its inside face and
its outside face, the two portions being bonded together by the
sealing layer.
3. A panel according to claim 1, wherein a sealing layer covers at
least one of the outside faces of the first and second parts.
4. A panel according to claim 1, wherein the sealing layer is a
thin metal layer.
5. A panel according to claim 4, wherein the sealing layer is made
of a metal selected from niobium, nickel, tantalum, molybdenum,
tungsten, and rhenium.
6. A panel according to claim 2, wherein the sealing layer and the
portions situated on the outside of the part provided with the
sealing layer projects from the periphery of the panel.
7. A panel according to claim 1, wherein the channels are formed in
the inside face of the part whose outside face constitutes the face
of the panel that is to be exposed to high temperatures while the
panel is in use.
8. A panel according to claim 1, wherein stiffening ribs project
from the outside face of the part situated on its side opposite
from its side that is to be exposed to high temperatures while the
panel is in use.
9. A panel according to claim 1, wherein the inside faces of the
first and second parts are bonded together by brazing.
10. A panel according to claim 1, wherein the inside faces of the
first and second parts are provided with metal coatings that are
bonded directly together.
11. A method of manufacturing an active cooling panel, the method
comprising the steps consisting in providing first and second parts
of thermostructural composite material, each having an inside face
and an outside face opposite to the inside face, the inside face of
at least one of the parts presenting indentations forming channels,
and in assembling the first and second parts together by bonding
their inside faces together in such a manner as to obtain a cooling
panel made of thermostructural composite material having
circulation channels integrated therein, wherein at least one of
the first and second parts is provided with a sealing layer
situated at a distance from the inside face of the part.
12. A method according to claim 11, wherein a sealing layer is
integrated within at least one of the first and second parts
between its inside face and its outside face.
13. A method according to claim 12, wherein at least one of the
first and second parts is made up of two distinct portions, and the
portions are assembled together with the sealing layer interposed
between them.
14. A method according to claim 11, wherein the outside face of at
least one of the first and second parts is provided with a sealing
layer.
15. A method according to claim 12, wherein a metal foil is used
for the sealing layer.
16. A method according to claim 15, wherein a foil is used that is
made of a metal selected from niobium, nickel, tantalum,
molybdenum, tungsten, and rhenium.
17. A method according to claim 15, wherein the metal foil is
assembled to the composite material of the first or second part by
hot compression.
18. A method according to claim 17, wherein the metal foil is
assembled to the composite material of the first or second part by
hot isostatic pressing.
19. A method according to claim 11, wherein the inside faces of the
first and second parts are assembled together by brazing.
20. A method according to claim 11, wherein at least one metal
coating layer is formed on the inside faces of the first and second
parts and said inside faces are assembled together by hot
compression.
21. A method according to claim 20, wherein said inside faces are
assembled together by hot isostatic pressing.
22. A method according to claim 11, wherein, prior to assembling
together the inside faces of the first and second parts, treatment
is performed to reduce the surface porosity of the thermostructural
composite material in at least one of said inside faces of the
parts.
23. A method according to claim 22, wherein the treatment for
reducing porosity comprises: applying a suspension to the surface
of at least one of said inside faces of the parts, the suspension
comprising a ceramic powder and a ceramic material precursor in
solution, and then transforming the precursor into ceramic
material.
24. A method according to claim 23, wherein the precursor is a
polymer which is cross-linked and transformed into ceramic by heat
treatment.
25. A method according to claim 23, wherein, once the precursor has
been transformed into ceramic material, a ceramic deposit is
provided by chemical vapor infiltration or deposition.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an active cooling panel of
thermostructural composite material.
[0002] The term "active cooling panel" is used herein to mean a
panel having a cooling fluid passing therethrough for the purpose
of taking away the heat received by the panel being exposed to high
temperature or high heat flux.
[0003] The term "thermostructural composite material" is used
herein to mean a composite material having mechanical properties
which make it suitable for constituting structural elements and
having the ability to conserve these mechanical properties at high
temperature. Thermostructural composite materials are typically
carbon-carbon (C/C) type composite material comprising a
reinforcing structure made of carbon fibers densified by a matrix
of carbon, and ceramic matrix composite (CMC) materials comprising
a reinforcing structure of refractory fibers (in particular carbon
fibers or ceramic fibers) densified by a ceramic matrix.
[0004] Applications of the invention lie in particular in
constituting the walls of a combustion chamber in an aircraft
engine, which walls convey a cooling fluid which may be constituted
by the fuel that is injected into the chamber, or walls for the
diverging portions of rocket engines which are likewise cooled by
fluid, which fluid may be a propellant component injected into the
combustion chamber of the rocket engine, or indeed the walls of a
plasma confinement chamber in a nuclear fusion reactor. In such
applications, the panel acts as a heat exchanger between its face
that is exposed to high temperature or high heat flux and the fluid
it conveys.
[0005] In such heat exchanger walls, the use of active cooling
panels made of thermostructural composite material enables the
operation of systems including such heat exchangers to be extended
to higher temperatures and/or enables the lifetime of such systems
to be extended. Increasing operating temperature can enable
performance to be increased, in particular the efficiency of
combustion chambers or nozzles in aviation or space engines, and
can also reduce the amount of pollution emitted by aircraft
engines.
[0006] Making a part out of thermostructural composite material
generally requires a porous fiber preform to be prepared of a shape
that is close to the shape of the part that is to be made, with the
preform then being densified.
[0007] Densification can be performed by a liquid technique or by a
gas technique. Liquid densification consists in impregnating the
preform with a liquid that is a precursor of the matrix material,
which precursor is generally a resin, and in transforming the
precursor, usually by heat treatment. The gas technique or chemical
vapor infiltration (CVI) consists in placing the preform in an
enclosure and in admitting a reaction gas into the enclosure, which
gas diffuses under determined conditions of pressure and
temperature into the pores of the preform and forms a solid deposit
therein by one or more of the components of the gas decomposing or
reacting together. Both techniques, using a liquid or CVI are well
known and they can be combined, for example by performing
predensification or consolidation of the preform using a liquid
followed by CVI.
[0008] Whatever the densification method used, thermostructural
composite materials present residual porosity so they are
unsuitable for use on their own in forming cooling panels having
internal fluid-conveying passages, since the walls of such passages
are not leakproof.
[0009] Several solutions have been proposed to overcome this
difficulty and to enable active cooling by means of a flowing fluid
to be combined with the use of porous refractory materials.
[0010] A first solution consists in making a panel having a front
plate made of graphite on its side that is exposed to high
temperatures, and a rear plate made of metal, in particular steel,
with the channels for conveying the cooling fluid being made
therein. The two plates are assembled together by brazing, with
layers of metal being interposed to match the different
coefficients of thermal expansion of steel and of graphite. The
presence of solid metal is penalizing in terms of the mass of the
cooling panel. In addition, the length of the path along which heat
travels through the graphite plate and the metal plate puts a limit
on capacity to cool the exposed surface.
[0011] Another solution consists in forming passages in a block of
thermostructural composite material and in making the walls of the
passages leakproof by brazing a metal lining, e.g. made of
copper.
[0012] Yet another solution consists in making two plates out of
thermostructural composite material, one of which plates presents
channels machined in its face that is to be assembled with a facing
face of the other plate, with assembly being performed by
brazing.
[0013] The second and third solutions are satisfactory in terms of
mass and of shortening heat flow path length, but leakage problems
can arise due to the metal lining or the brazing cracking following
repeated exposure to very high temperatures and excess stresses
induced by the shape of the channels.
OBJECT AND SUMMARY OF THE INVENTION
[0014] In one of its aspects, the invention seeks to provide an
active cooling panel of thermostructural composite material that
presents leaktightness which is effective and durable relative to a
fluid flowing in internal passages of the panel.
[0015] This object is achieved by a panel of the type comprising
first and second parts of thermostructural composite material each
having an inside face and an opposite outside face, the parts being
assembled together by bonding their inside faces together, and
channels being formed by indentations formed in the inside face of
at least one of the first and second parts, which panel, according
to the invention, further comprises a sealing layer bonded to at
least one of the first and second parts and situated at a distance
from the assembled-together inside faces thereof.
[0016] Such a panel is remarkable in that sealing is achieved not
at the interface between the parts, i.e. at the walls of the flow
channels, but at a different level of the panel, remote from said
interface.
[0017] Thus, the integrity of the sealing layer and its bond with
the thermostructural composite material are not affected by excess
stresses of the kind that are encountered if the sealing layer is
to follow or be subjected to the indentations of the channels at
the interface between the parts. In addition, it is then possible
to displace the sealing layer further away from the face of the
panel that is exposed in operation to high temperatures, thereby
reducing the thermomechanical stresses to which the sealing layer
is exposed.
[0018] In an embodiment of the panel, a sealing layer is situated
within at least one of the first and second parts, separating the
part into two portions between its inside face and its outside
face, the two portions being bonded together by the sealing
layer.
[0019] In another embodiment, a sealing layer covers at least one
of the outside faces of the first and second parts.
[0020] Advantageously, the sealing layer is a thin metal layer, for
example a metal selected from niobium, nickel, tantalum,
molybdenum, tungsten, and rhenium.
[0021] When the sealing layer is formed within a part, it is
possible to provide for the sealing layer and the portion situated
on the outside of the part provided with the sealing layer to
project around the periphery of the panel, in particular to
facilitate installing a sealing gasket around the periphery of the
panel.
[0022] Preferably, the channels are formed in the inside face of
the part whose outside face constitutes the face of the panel that
is to be exposed to high temperatures while the panel is in
use.
[0023] The panel may be provided with stiffening ribs which project
from the outside face of the part situated on the side opposite
from the side that is to be exposed to high temperatures while the
panel is in use.
[0024] The inside faces of the first and second parts may be bonded
together by brazing.
[0025] In a variant, the inside faces may be provided with metal
coatings that are bonded directly to each other.
[0026] In another aspect, the invention seeks to provide a method
of manufacturing an active cooling panel as defined above.
[0027] This object is achieved by a method of the type comprising
the steps consisting in providing first and second parts of
thermostructural composite material, each having an inside face and
an outside face opposite to the inside face, the inside face of at
least one of the parts presenting indentations forming channels,
and in assembling the first and second parts together by bonding
their inside faces together in such a manner as to obtain a cooling
panel made of thermostructural composite material having
circulation channels integrated therein, in which method, according
to the invention, at least one of the first and second parts is
provided with a sealing layer situated at a distance from the
inside face of the part.
[0028] In a particular implementation of the method, a sealing
layer is integrated within at least one of the first and second
parts between its inside face and its outside face.
[0029] For this purpose, advantageously, at least one of the first
and second parts is made up of two distinct portions, and the
portions are assembled together with the sealing layer interposed
between them.
[0030] In another implementation of the method, the outside face of
at least one of the first and second parts is provided with a
sealing layer.
[0031] In either case, the sealing layer may be implemented as a
metal foil, e.g. made of a metal selected from niobium, nickel,
tantalum, molybdenum, tungsten, and rhenium.
[0032] The metal foil may be assembled to the composite material of
the first or second part by hot compression, in particular by hot
isostatic pressing.
[0033] The inside faces of the first and second parts may be
assembled together by brazing.
[0034] In a variant, it is possible to form at least one metal
coating layer on the inside faces of the first and second parts and
to assemble said inside faces together by hot compression, in
particular by hot isostatic pressing.
[0035] Advantageously, prior to assembling together the inside
faces of the first and second parts, treatment is performed to
reduce the surface porosity of the thermostructural composite
material in at least one of said inside faces of the parts.
[0036] The treatment for reducing porosity may comprise applying a
suspension to the surface of at least one of said inside faces of
the part, the suspension comprising a ceramic powder and a ceramic
material precursor in solution, the treatment further comprising
transforming the precursor into a ceramic material.
[0037] The precursor is typically a polymer which is cross-linked
and transformed into ceramic by heat treatment.
[0038] Optionally, after the precursor has been transformed into
ceramic material, chemical vapor deposition or chemical vapor
infiltration is performed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] The invention will be better understood on reading the
following description given by way of non-limiting indication and
made with reference to the accompanying drawings, in which:
[0040] FIG. 1 is a cross-section view of an embodiment of an active
cooling panel in accordance with the invention;
[0041] FIG. 2 is a fragmentary section view on plane II-II of FIG.
1;
[0042] FIG. 3 is a section view on plane III-III of FIG. 2;
[0043] FIGS. 4 to 8 show successive steps in implementing a method
in accordance with the invention for manufacturing a panel of the
type shown in FIG. 1; and
[0044] FIGS. 9 to 13 are cross-section views of other embodiments
of an active cooling panel in accordance with the invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0045] A first embodiment of an active cooling panel 10 is shown in
FIGS. 1 to 3.
[0046] The panel 10 comprises two parts 20 and 30 that are
generally in the form of rectangular parallelepipeds and that are
assembled to each other via their inside faces 21 and 31. In this
example, assembly is performed by brazing 12. The part 20 whose
outside face 22 opposite from its face 21 defines the front face of
the panel that is to be exposed to high temperatures or to intense
heat flow is made of a thermostructural composite material.
Channels 24 for circulating a cooling fluid are formed by
indentations formed in the inside face 21. A plurality of channels
24 parallel to two opposite sides of the panel 10 extend between
two manifolds 40, 42 that are internal to the panel 10 and that are
situated close to two other opposite sides thereof.
[0047] The part 30 comprises two portions 34 and 36 in the form of
plates made of thermostructural composite material. The portions 34
and 36 are assembled via facing faces 35, 37 with a sealing layer
38 being interposed between them. The faces of the portions 34 and
36 that are opposite from their faces 35 and 37 define respectively
the inside face 31 and the opposite outside face 32 of the part 30.
The face 32 constitutes the rear face of the panel 10.
[0048] The manifolds 40, 42 are formed by elongate openings or
slots formed in the portion 34. The manifolds 40, 42 communicate
with the outside of the panel via holes 41, 43 formed through the
sealing layer 38 and the portion 36, and provided with metal
inserts 44, 46 enabling the panel to be connected with a circuit
for circulating fluid and/or with an adjacent panel by means of a
connecting coupling.
[0049] In a variant, the channels 24 may each have at least one end
opening out into a side end of the part 20. After the cooling panel
has been made, the open ends of the channels can then be connected
by means of couplings either to a manifold external to the panel,
or else to similar channels in an adjacent panel.
[0050] The part 20 and the part 30 (portions 34 and 36) are made of
a C/C or a CMC thermostructural composite material. For
applications at very high temperature, in particular in an
oxidizing medium, it is preferred to use CMC, typically comprising
composite materials reinforced by silicon carbide (SiC) fibers or
carbon fibers with a matrix of SiC or a matrix that has at least an
outer phase of SiC. The channels and the manifolds may be made by
machining.
[0051] Whatever the thermostructural composite material used, it
presents residual porosity. The sealing layer 38 makes it possible
to prevent any fluid flowing along the channels 24 from leaking to
the rear face 32 of the panel 10.
[0052] In the example shown in FIGS. 1 to 3, the part 20 is not
provided with a sealing layer. This is acceptable when there is no
requirement for a high degree of leaktightness between the channels
24 and the front face 22 of the panel 10. This can apply for an
active cooling panel for a combustion chamber wall when the cooling
fluid used is a fuel and when a certain amount of leakage into the
combustion chamber can be tolerated.
[0053] The sealing layer 38 is a metal layer bonded to the faces
35, 37 of the portions 34, 36 of the part 30, e.g. a layer of
niobium, nickel, tantalum, molybdenum, tungsten, or rhenium.
[0054] A method of manufacturing a cooling panel of the kind shown
in FIGS. 1 to 3 is described below with reference to FIGS. 4 to
8.
[0055] The part 20 and the portions or plates 34, 36 of the part 30
are made separately out of thermostructural composite material, in
particular C/C or CMC material. The recesses needed for forming the
channels 24 and the manifolds are formed by machining the inside
face 21 of the part 20 and the portion 34 of the part 30. It should
be observed that the part 20 and the portions 34, 36 may be cut out
from a single block of thermostructural material prior to machining
the locations for the channels and the manifolds.
[0056] The detailed views of FIG. 4 show in highly diagrammatic
manner the surface porosity of the thermostructural composite
material.
[0057] Advantageously, treatment is applied to reduce the porosity
of the inside face 21 of the part 20 in which the channels 24 are
formed, and the face 31 of the portion 34, i.e. those faces that
are to be assembled together.
[0058] Porosity can be reduced by applying a suspension onto the
faces 21 and 31, the suspension containing a solid filler in the
form of a ceramic powder and a ceramic precursor in solution, and
then transforming the precursor into ceramic material. The
precursor may be a polymer which is cross-linked and then
transformed into ceramic by heat treatment. By way of example, for
the precursor it is possible to use a polycarbosilane (PCS) or a
polytitanocarbosilane (PTCS) as a precursor for SiC, which
precursor is put into solution in a solvent, e.g. xylene. The
ceramic powder contributes to filling in surface pores effectively.
It is possible to use an SiC powder, for example.
[0059] The liquid composition may be applied using a brush or a
spray gun, with the quantity of solvent being selected to make
application easy and to encourage penetration of the liquid
composition into the surface pores.
[0060] After the liquid composition has been applied and has been
dried by eliminating the solvent, the precursor polymer is
cross-linked and then transformed into ceramic. When using PCS, for
example, cross-linking can be performed by raising the temperature
to about 350.degree. C., and ceramization by raising the
temperature to about 900.degree. C.
[0061] After ceramization, it is optionally possible to shave the
surface of the part in order to restore it to its initial
shape.
[0062] Two detail views in FIG. 5 show in highly diagrammatic
manner how pores are filled in by the material 51 comprising the
ceramization residue and the ceramic powder.
[0063] It is also advantageous for pores to be filled in further by
forming a deposit of ceramic, e.g. SiC, by chemical vapor
infiltration or deposition, thus making it possible to obtain a
uniform and continuous coating 52 anchored to the thermostructural
composite material.
[0064] The ceramic coating 52 obtained by chemical vapor
infiltration or deposition (shown in the detailed views of FIG. 5)
may be formed not only on the inside faces 21 and 31, but also on
the other faces on the outside of the part 20, and in particular
its outside face 22 and on other surfaces on the outside of the
portion 34.
[0065] It should be observed that the method of filling in pores by
depositing a suspension containing a ceramic powder and a ceramic
precursor polymer, and then transforming the precursor into
ceramic, followed by shaving and then forming a ceramic coating by
chemical vapor infiltration is described in the patent application
in the name of the present Applicant and entitled "A method of
surface-treating a thermostructural composite material part and its
application to brazing thermostructural composite material
parts".
[0066] The following step of the method consists in interposing a
sealing layer between the portions 34 and 36, possibly after
machining the faces 35 and 37 of the portions 34 and 36 in order to
lay bare the composite material. The sealing layer is
advantageously formed by a metal foil 38 (FIG. 6), e.g. made of a
metal selected from niobium, nickel, tantalum, molybdenum,
tungsten, and rhenium. The thickness of the foil 38 typically lies
in the range 0.05 millimeters (mm) to 0.3 mm.
[0067] The portions 34 and 36 are bonded together and to the foil
38 by hot compression.
[0068] This can be done using known methods such as the hot
isostatic pressing (HIP) assembly method or the method of hot
pressing in a press.
[0069] Bonding by hot isostatic pressing is performed by placing
the elements for assembly against each other in an enclosure while
encapsulating the part in a leakproof cover 45 (FIG. 7).
Temperature and pressure are then raised in substantially uniform
manner in the enclosure. Bonding is achieved by metal from the foil
38 diffusing into the surface pores of the faces 35, 37. The
leakproof cover 45 encapsulating the parts is constituted, for
example, by a metal film such as a film of niobium, or indeed of
nickel, of iron, or of an alloy thereof. Tooling elements such as
plates of graphite 46, 47 may be interposed between the metal film
and the outside surfaces of the portions 34, 36 in order to prevent
the metal of the film 45 becoming embedded in said surfaces due to
the hot isostatic pressing when the presence of said metal on said
surfaces is undesirable. This may apply in particular to the face
31, depending in particular on the method used subsequently for
bonding it to the face 21 of the part 20.
[0070] Bonding by pressing in a press consists in raising the
temperature of the elements to be assembled together and in
pressing them against one another by exerting pressure on the faces
31 and 32 in a press.
[0071] The pressure used for hot compression bonding lies, for
example, in the range 80 megapascals (MPa) to 120 MPa. The
temperature is a function of the nature of the metal sealing layer
used for bonding the parts together. It is substantially lower than
the melting temperature of the metal of said metal layer, generally
lying in the range 60% to 80% of said melting temperature.
[0072] When the metal sealing layer is made of niobium, the
temperature is selected more particularly to lie in the range
900.degree. C. to 1200.degree. C. both for bonding by hot isostatic
pressing and for bonding by pressing in a press.
[0073] Once the part 30 has been made, it is assembled to the part
20, e.g. by brazing. For this purpose, a layer of brazing 48 is
interposed between the reduced-porosity faces 21 and 31 (FIG.
8).
[0074] Brazing together parts made of thermostructural composite
material is, in itself, known. For example, it is possible to use a
brazing material based on silicon of the type described in the
French patent applications published under the Nos. 2 748 471 and 2
749 787. Other brazing compositions can be used, in particular
compositions based on silicon or on titanium such as those sold
under the name TiCuSil.RTM. by Wesgo Metals, a division of the US
supplier Morgan Advanced Ceramics.
[0075] In a variant, the parts 20 and 30 can be bonded together by
hot compression.
[0076] For this purpose, the surfaces 21 and 31 are initially
provided with metal coatings which, in addition to providing
bonding by hot compression, can also perform a sealing
function.
[0077] By way of example, each face 21, 31 is provided with a first
layer of a metal that advantageously performs a barrier function
against chemical reaction with the underlying material and/or a
matching function, and a second metal layer having the ability to
bond by hot compression.
[0078] The second layer may be a metal selected from nickel,
copper, iron, or an alloy of at least one of them. Nickel (Ni) or a
nickel alloy present the advantages of good thermal conductivity,
good ability to bond by hot compression, and a high melting
temperature avoiding passage into the liquid state during bonding
by hot compression.
[0079] The first layer may be made of a metal selected from
rhenium, molybdenum, tungsten, and tantalum. When the
thermostructural composite material has an SiC matrix and fiber
reinforcement of carbon or of SiC, and/or when a coating of SiC has
previously been formed thereon, rhenium presents the advantage of
not reacting with SiC. It also presents good conductivity and it
has a high melting temperature ensuring that it does not pass to
the liquid state during subsequent bonding under hot compression.
Furthermore, rhenium has a coefficient of expansion that is
intermediate between those of SiC and Ni and therefore also
constitutes a mechanical matching layer when the second metal layer
is constituted at least in part by Ni.
[0080] The first and second metal layers are deposited in
succession. It is possible to use conventional deposition methods
of the physical vapor deposition type or the plasma sputtering
type.
[0081] Prior to bonding the parts together by hot compression, a
metal foil may be interposed between the facing inside faces of the
parts, which metal foil is preferably made of the same material as
the second metal layer of the metal coating formed on the inside
surfaces 21, 31.
[0082] The parts 20 and 30 are bonded together by hot compression,
possibly after inserting a metal foil.
[0083] It is possible to use the hot isostatic pressing assembly
method or the method of pressing in a press as described above.
[0084] When the parts 20 and 30 are bonded together by hot
compression, it is possible to make said bond simultaneously with
the bond between the portions 34, 36 and the sealing layer 38,
after forming the metal coatings on the inside faces 21 and 31.
[0085] FIGS. 9 to 13 illustrate various other embodiments of an
active cooling panel in accordance with the invention.
[0086] Thus, the panel of FIG. 9 differs from that of FIGS. 1 to 3
in that the portion 36 of the part 30 and the sealing layer 38
project around the periphery of the panel.
[0087] The panel can then be housed in a frame 54 comprising a base
55 from which there projects a rim 56. A sealing gasket 58 is
disposed in the space defined by the base 55, the periphery of the
panel 30 in the vicinity of the part 20 and the portion 34, the
projecting portion 36 and layer 38, and the rim 56. The gasket 58
serves to contain cooling fluid leaks around the periphery of the
panel.
[0088] The panel of FIG. 10 differs from that of FIGS. 1 to 3 in
that the part 30 is provided with stiffeners 60. These are in the
form of stiffening ribs projecting from the outside face 32 of the
portion 36 of the part 30.
[0089] The ribs 60 may be made integrally with the portion 36.
[0090] The ribs 60 give the panel greater ability to withstand the
forces to which it is subjected, preventing deformation which might
damage the bonds between the portions 34, 36 of the part 30 and
between the parts 20 and 30.
[0091] The panel of FIG. 11 differs from that of FIGS. 1 to 3 in
that not only the part 30, but also the part 20 is provided with a
sealing layer 62 integrated within the part 20 and at a distance
from the interface between the parts 20 and 30.
[0092] The layer 62 may be of the same kind and may be put into
place in the same manner as the sealing layer 38, in which case the
part 30 is likewise made by assembling together two distinct
portions with the layer 62 being interposed between them.
[0093] The panel of FIG. 12 differs from that of FIGS. 1 to 3 in
that the part 30 is a single piece of thermostructural composite
material and the sealing layer 64 is disposed on the outside face
32 of the part 30 instead of being disposed within it.
[0094] The layer 64 may be of the same kind as the sealing layer 38
and it may likewise be assembled to the part 30 by hot
compression.
[0095] As shown in FIG. 13, the part 20 of a panel of the kind
shown in FIG. 12 may also be provided with a sealing layer 66
assembled to its outside face 22.
[0096] The panels of FIGS. 12 and 13 are easier to make than those
of the other panels. However integrating the sealing layer within a
part, between two portions of thermostructural composite material,
enables said sealing layer to be protected against oxidation by the
presence of the composite material. In addition, placing the
sealing layer on the outside face of a part can make it necessary
for the sealing layer to be shaped so as to take account of the
possible presence of stiffeners or interfaces with the outside of
the panel.
[0097] Naturally, a single panel may be provided with a sealing
layer based on an outside face of one of the two parts of the
panel, and with a sealing layer disposed within the other part.
[0098] It is also possible to place the panels of the embodiments
shown in FIGS. 10 and 11 in a frame, as shown for the embodiment of
FIG. 9.
EXAMPLE
[0099] A part 20 and portions 34, 36 of the kind shown for the
embodiment of FIGS. 1 to 3 have been made out of C/SiC
thermostructural composite material, with the channels and the
manifolds being formed by machining.
[0100] The porosity of the inside surfaces 21, 31 was reduced by
brushing thereon a composition containing an SiC powder of mean
grain size equal to about 9 microns (.mu.m) in a solution of PCS in
xylene. After drying in air, the PCS was cross-linked at about
350.degree. C. and then transformed into SiC by raising the
temperature to about 900.degree. C. A thin coating of SiC having
thickness equal to about 100 .mu.m was then deposited by chemical
vapor infiltration, said coating then being formed over the entire
outside surface of the part 20 and the portion 34, and not only on
the inside faces 21 and 31. In combination with the residue of
ceramizing the PCS in association with the SiC powder, the SiC
coating contributes to effective reduction of porosity.
[0101] The faces 35, 37 of the portions 34, 36 were then machined
in order to lay bare the composite material so as to present open
pores, encouraging mechanical bonding with the foil subsequently
put into place between these faces. A 0.1 mm thick niobium foil was
interposed between the faces 35 and 37, and assembly was then
performed by hot isostatic pressing. For this purpose, the elements
34, 38, and 37 were encapsulated in a 0.5 mm thick niobium foil
with plates of graphite being interposed between the outside
surfaces of the elements to be assembled together and the niobium
foil.
[0102] Hot isostatic pressing was performed at a pressure of about
90 MPa and at a temperature of about 1000.degree. C.
[0103] The part 30 as obtained in this way was assembled to the
part 20 by brazing using a silicon-based brazing composition.
* * * * *