Chemical vapor infiltration densification method using single-pile plates for a semi-forced flow

Abstract

A method for densifying porous annular substrates having a central passage by chemical vapor infiltration, the method including providing stacks of porous annular substrates, providing a plurality of individual modules including stacks disposed on a support plate having a perforated injection tube each mounted on a gas inlet opening, forming a stack of individual modules, aligning the individual modules of the stack in a sealed manner by means of an annular seal disposed between the injection tube of a second individual module and the gas inlet opening of a first individual module with which it cooperates, and injecting into the internal volume of each stack of porous annular substrates a gas phase including a gaseous precursor of a matrix material to be deposited within the porosities of the substrates.

Claims

1. A method for densification by pressure gradient chemical vapor infiltration of porous annular substrates having a central passage, the method comprising: providing a plurality of stacks of porous annular substrates, each stack comprising an internal volume formed by the central passages of the stacked substrates, providing a plurality of individual modules, each individual module comprising a support plate and a single stack of porous annular substrates disposed on the support plate, the support plate comprising a gas inlet opening and an injection tube mounted on the gas inlet opening and extending into the internal volume of the stack disposed on the support plate between a first tube end connected to the support plate and a second tube end which is free, the injection tube further comprising gas injection orifices opening into the internal volume, forming, in a chamber of a densification furnace, a stack of individual modules, each first individual module stacked on a second individual module having its gas inlet opening of the support plate communicating with the second end of the injection tube of the second individual module on which it is stacked so as to permit circulation of a gas between the individual modules, and injecting into the internal volume of each stack of porous annular substrates a gas phase comprising a gaseous precursor of a matrix material to be deposited within the porosities of the substrates, wherein, in each individual module, each first porous annular substrate is supported on a second porous annular substrate, or supported on the support plate, by means of a sealing ring providing radial sealing between the first porous annular substrate and the second porous annular substrate or between the first porous annular substrate and said support plate, and each sealing ring is coupled to an annular spacer having an inner diameter equal to an inner diameter of the porous annular substrates, each annular space being surrounded by the sealing ring with which it is associated in a plane perpendicular to the a direction in which the porous annular substrates are stacked, and having a thickness less than the thickness of the sealing ring with which it is coupled.

2. The method according to claim 1, wherein each stack comprises at least one cover disk supported on the porous annular substrate at the top of the stack by means of a sealing ring providing radial sealing between said cover disk and said porous annular substrate at the top of the stack.

3. The method according to claim 2, wherein each stack further comprises a deformable annular seal arranged to be compressed between the cover disk and the support plate of the upper individual module.

4. The method according to claim 1, wherein, in each individual module, the sealing rings are disposed at the radially outer periphery of the porous annular substrates.

5. The method according to claim 1, wherein, in each individual module, the sealing rings are alternately disposed, along the direction in which the porous annular substrates are stacked, at the radially outer periphery of the porous annular substrates and at the radially inner periphery of the porous annular substrates.

6. The method according to claim 1 wherein the sealing rings are made of inconel.

7. The method according to claim 1, wherein each sealing ring is welded to the annular spacer to which it is coupled.

8. The method according to claim 1, further comprising a seal alignment step of the individual modules of the stack comprising, for each first individual module stacked on a second individual module, insertion of the second end of the injection tube of the second individual module into the gas inlet opening of the first individual module stacked on said second individual module, an annular seal being disposed between the second end of the injection tube of the second individual module and the gas inlet opening of the first individual module stacked on said second individual module.

9. The method according to claim 8, wherein, for each individual module, the support plate comprises a first face supporting the stack of the individual module and a second face opposite the first face, the gas inlet opening comprises a frustoconical shape with a first diameter formed in the second face of the support and a second diameter smaller than the first diameter and formed in the first face or between the first face and second face of the support plate, and the second end of the injection tube comprises a complementary frustoconical shape cooperating with the frustoconical shape of the gas inlet opening.

10. The method according to claim 1, further comprising a step of disposing the stack of individual modules on a load-carrying shell disposed on a preheating zone of the densification furnace.

11. The method according to claim 1, wherein each individual module comprises an annular foot disposed between the support plate of the individual module and the stack of porous annular substrates of the individual module, the annular foot having radial grooves forming passages, along a direction orthogonal to the direction in which the porous annular substrates are stacked between a central cavity of the annular foot and the outside of the annular foot.

12. The method according to claim 1, wherein each porous annular substrate comprises carbon.

13. The method according to claim 1 , wherein each porous annular substrate constitutes a fibrous brake disc preform.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1, already described, very schematically shows an example of loading porous annular substrates according to the prior art.

(2) FIG. 2 diagrammatically illustrates a sectional view of an example of a stack of porous annular substrates according to the invention.

(3) FIG. 3 schematically shows a sectional view of a densification furnace according to the invention.

(4) FIG. 4 schematically shows a top view of an annular foot.

(5) FIG. 5 schematically shows a sectional view of an annular foot.

DESCRIPTION OF THE EMBODIMENTS

(6) A chemical vapor infiltration densification method according to the invention comprises firstly a step during which a plurality of stacks of porous annular substrates intended to be treated by chemical vapor infiltration are provided.

(7) FIG. 2 illustrates a sectional view of an example of a stack 20 of porous annular substrates 21. The porous annular substrates 21 have cylindrical symmetry and are stacked along a first direction Z. Each porous annular substrate 21 extends mainly in a plane perpendicular to the first direction Z. The sectional plane of the illustration in FIG. 2 comprises the first direction Z and a second direction X perpendicular to the first direction Z. The first direction Z coincides with the axis of symmetry of revolution of the porous annular substrates 21, and the second direction X corresponds to a radial direction.

(8) Each porous annular substrate 21 of the stack 20 thus has the shape of a ring with a central passage 21a. Each porous annular substrate 21 is disposed on an assembly comprising an annular spacer 22 and a sealing ring 23. The outer radial diameter of the annular spacer 22 is smaller than the outer radial diameter of the porous annular substrates 21, the diameters of the orifices of the annular spacers 22 and of the porous annular substrates 21 being equal.

(9) Each annular spacer 22 is surrounded by a sealing ring 23 in the plane perpendicular to the first direction Z. The thickness of the sealing ring 23 measured along the first direction Z is greater than that of the annular spacer 22, so that each porous annular substrate 21 rests on a sealing ring 23. The annular spacers 22 are used to center the sealing rings 23 in the first direction Z.

(10) The alternating stack of porous annular substrates 21 and sealing rings 23 forms, at the center of stack 20, an internal volume 24 of stack 20.

(11) In addition, the stack 20 is closed at its top by an annular cover disk 25. The cover disk 25 is placed on the stack via an annular spacer 22 and a sealing ring 23. The stack further comprises a deformable annular seal 26 made of compressed carbon fiber felt placed on the cover disk 25, and a disk 27 of expanded graphite disposed on the deformable annular seal 26 to prevent this deformable annular seal 26 from sticking to the support plate above.

(12) The stack 20 further comprises an annular secondary sealing ring 28 also made of compressed carbon fiber felt directly on the annular spacer 22 supporting the cover disk 25. The secondary sealing ring 28 covers the part of the annular spacer 22 not covered by the cover disk 25.

(13) The chemical vapor infiltration densification method according to the invention then comprises a step during which a plurality of individual modules 30 are supplied.

(14) FIG. 3 diagrammatically shows a sectional view of a densification furnace according to the invention.

(15) The densification furnace 40 according to the invention comprises a stack of a plurality of individual modules 30. Each individual module 30 comprises a support plate 31 on which is disposed a stack 20 of porous annular substrates via an annular foot 29, the annular foot 29 being disposed between the support plate 31 and the stack 20 of the same individual module 30.

(16) As shown in FIGS. 4 and 5, which show a top view and a sectional view of an annular foot 29, the annular foot 29 comprises radial grooves 295 forming passages along a radial direction, between a central cavity 290 of the annular foot 29 and the outside of the annular foot 29.

(17) As shown in FIG. 3, the support plate 31 of an individual module 30 comprises a gas inlet opening 32 and an injection tube 33 mounted on the gas inlet opening 32 and extending into the internal volume 24 of the stack 20 between a first tube end 33a connected to the support plate 31 and a second tube end 33b which is free.

(18) The injection tube 33 further comprises gas injection orifices 34 opening into the internal volume 24.

(19) The chemical vapor infiltration densification method according to the invention then comprises a step during which a stack of individual modules 30 is formed in the chamber of a densification furnace 40.

(20) FIG. 3 shows the support plate 31 of a first individual module 30a about to be stacked on a second individual module 30b.

(21) The step of forming the stack of individual modules 30 further comprises a step of sealed alignment of the individual modules 30 of the stack. As illustrated in FIG. 3, in order to achieve alignment, the second end 33b of the injection tube 33 of the second individual module 30b is inserted into the gas inlet opening 32 of the first individual module 30a.

(22) To seal the junction between the injection tube 33 of the second individual module 30b and the gas inlet opening 32 of the first individual module 30a, the second individual module 30a further comprises an annular seal 35 disposed between the second end 33b of the injection tube 33 of the second individual module 30b and the gas inlet opening 32 of the first individual module 30a.

(23) More particularly, each support plate 31 comprises a first face 31a on which the stack 20 is disposed and a second face 31b opposite the first face 31a. The gas inlet opening 32 has a frustoconical shape with a first diameter d1 formed in the second face 31b of the support plate 31 and a second diameter d2 smaller than the first diameter d1 and formed between the first face 31a and the second face 31b of the plate support 31.

(24) The second end 33b of each injection tube 33 comprises a frustoconical shape complementary to the frustoconical shape of a gas inlet opening 32 so that the two frustoconical shapes cooperate together. The complementary frustoconical shape of the second end 33b of the injection tube 33 comprises a third diameter larger than a fourth diameter, the fourth diameter being measured on a free distal end while the first diameter is measured on a proximal end coupled to the rest of the injection tube 33 and especially to a main portion 33c.

(25) As illustrated in FIG. 3, in order to improve the sealing of the stack of individual modules 30, the deformable annular seal 26 is dimensioned to fill the gap, along the first direction Z, between the cover disk 25 of the stack 20 of the second individual module 30b and the support plate 31 of the first individual module 30a.

(26) The chemical vapor infiltration densification method according to the invention then comprises a step of disposing the stack of individual modules 30 on a load-carrying shell 42 disposed on a preheating zone 44 of the densification furnace 40.

(27) The chemical vapor infiltration densification method according to the invention then comprises placing a solid cover 46 at the top of the stack of individual modules 30.

(28) The chemical vapor infiltration densification method according to the invention then comprises a step during which a gas phase comprising a gaseous precursor of a matrix material to be deposited within the porosities of substrates 21 is injected into the internal volume 24 of each stack 20 of porous annular substrates 21. The injection of the gas is represented in FIG. 3 by arrows G. The step of injecting a gas into the internal volume 24 of the stacks 20 preferably comprises regulating the pressure difference between the internal volume 24 of the stacks 20 and the outside of the stacks. The pressure difference is preferably maintained between 0 and 100 millibars. Such a range makes it possible to ensure a flow of the gas phase around the porous annular substrates 21 while avoiding the deposition of soot.