FR3141700A1 - Double treatment gas phase chemical infiltration plant - Google Patents

Abstract

Double treatment gas phase chemical infiltration installation A CVI or CVD installation (100) comprises an enclosure (110) enclosing a first reaction chamber (120) connected to a first gas supply source (155), the installation further comprising a first heating system (1112) configured to heat the first reaction chamber.The enclosure (110) further contains a second reaction chamber (130) connected to a second gas supply source (185 ), the installation further comprising a second heating system (1114) configured to heat the second reaction chamber (130). The first and second gas supply sources (155, 185) each deliver a gas phase comprising at least one different precursor gas. The first and second heating systems (1112, 1114) are independent of each other. Figure for abstract: Fig. 1.

Description

Double treatment gas phase chemical infiltration plant

The invention relates to installations or ovens used to carry out thermochemical treatments such as the densification of porous substrates by infiltration or chemical deposition in the gas phase.

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 maintain these properties up to high temperatures. Typical examples of thermostructural composite materials are carbon/carbon (C/C) composites having a carbon fiber reinforcement texture densified by a pyrolytic carbon matrix and ceramic matrix composites (CMC) having a fiber reinforcement texture refractories (carbon or ceramic) densified by a ceramic matrix.

A well-known process for densifying porous substrates to produce CMC composite parts is chemical gas infiltration (CVI). The substrates to be densified are placed in a loading zone of a facility where they are heated. A reactive gas containing one or more gaseous precursors of the material constituting the matrix is introduced into the oven. The temperature and pressure in the installation are adjusted to allow the reactive gas to diffuse within the porosity of the substrates and form a deposit of the material constituting the matrix by decomposition of one or more constituents of the reactive gas or 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 reactive gases in the substrates. The transformation temperature of the precursor(s) to form the matrix material is in most cases between 900°C and 1100°C.

Document US 5,904,957 discloses a gas phase chemical infiltration installation comprising a reaction chamber in which several substrates to be densified are stacked. If this type of installation allows, thanks to its loading capacity, to densify a large number of substrates at the same time by CVI, it nevertheless has the disadvantage of being able to carry out only one type of CVI (i.e. the deposition of a only type of matrix) at the same time for all the substrates. This lack of flexibility can prevent optimization of the loading of the installation and/or disrupt production rates. Indeed, in the case of batches of substrates having to be subjected to different treatments, each batch must be treated in the installation one after the other, which leads to a lack of optimization of the loading of the installation when the number of substrates per batch to be processed is less than the maximum loading capacity of the installation. If we wish to wait until we have an optimal number of substrates in relation to the loading capacity of the installation, the installation then becomes a factor in slowing down production, which is also not desirable.

For this purpose, the present invention proposes an installation for chemical infiltration in the gas phase or for chemical deposition in the gas phase comprising an enclosure enclosing a first reaction chamber comprising a first gas inlet, a first preheating chamber, a first loading and a first gas outlet, the first gas inlet being connected to a first gas supply source, the first gas outlet being connected to at least one gas evacuation pipe, the installation further comprising a first heating system configured to heat the first reaction chamber,
characterized in that the enclosure further contains a second reaction chamber comprising a second gas inlet, a second preheating chamber, a second loading zone and a second gas outlet, the second gas inlet being connected to a second gas supply source, the second gas outlet being connected to said at least one gas evacuation pipe, the installation further comprising a second heating system configured to heat the second reaction chamber, in that the first and second gas supply sources each deliver a gas phase comprising at least one different precursor gas and in that the first and second heating systems are independent of each other.

The installation according to the invention makes it possible to carry out two different types of treatment simultaneously because the two reaction chambers are independent of each other chemically and thermally. In fact, each chamber can be supplied with a different gas phase and the chambers are associated with independent heating systems allowing each chamber to be heated to a different temperature. The installation therefore has much better adaptability to different types of part production, which makes it possible to optimize manufacturing rates as well as the amortization of the installation which represents a significant part in the production cost of the parts. pieces.

According to one embodiment of the invention, the first and second reaction chambers are superimposed inside the enclosure while the first gas outlet of the first reaction chamber is adjacent to the second reaction chamber. The first gas outlet from the first chamber advantageously forms a buffer zone or non-useful zone between the loading zones of the two reaction chambers in which the temperature must be precisely controlled. Thus, when the two loading zones are heated to different temperatures, there is no risk of thermal disturbance between these zones, which allows precise control of the temperature in the loading zone of each reaction chamber.

According to a particular aspect, the first and second reaction chambers are thermally isolated from each other by a thermal insulator present between the first gas outlet and the second reaction chamber. This increases the thermal decoupling between the two reaction chambers.

According to another particular aspect, the installation further comprises an internal gas supply circuit bypassing the first reaction chamber, said internal gas supply circuit being connected to the second gas inlet of the second reaction chamber.

According to another particular aspect, the second gas inlet of the second reaction chamber comprises a flow rectifier module.

According to another embodiment of the invention, the first and second reaction chambers are superimposed inside the enclosure while the first and second gas evacuation outlets of the first and second reaction chambers are opposite each other. -opposite each other, the first and second gas inlets of the first and second reaction chambers are at opposite locations in the enclosure.

The first and second gas outlets advantageously form a buffer zone or non-useful zone between the loading zones of the two reaction chambers in which the temperature must be precisely controlled. Thus, when the two loading zones are heated to different temperatures, there is no risk of thermal disturbance between these zones, which allows precise control of the temperature in the loading zone of each reaction chamber.

According to a particular aspect, the first and second reaction chambers are thermally isolated from each other by a thermal insulator present between the first and second gas evacuation outlets of the first and second reaction chambers. This increases the thermal decoupling between the two reaction chambers.

The invention also relates to a gas-phase chemical infiltration or gas-phase chemical deposition process comprising:

- loading substrates or fibrous preforms into first and second loading zones respectively of a first reaction chamber and a second reaction chamber of a gas phase chemical infiltration or phase chemical deposition installation gaseous according to the invention,

- controlling the first heating system of the installation to heat the first reaction chamber to a first temperature,

- controlling the second heating system of the installation to heat the second reaction chamber to a second temperature,

- the introduction of a first gas phase into the first reaction chamber,

- the introduction of a second gas phase into the second reaction chamber,

- the first and second gas phases each comprise at least one different precursor.

According to a particular aspect, the first and second gas phases are introduced respectively into the first and second reaction chambers at different flow rates.

According to another particular aspect, the first and second heating temperatures are different.

There is a schematic sectional view of a gas phase chemical infiltration or gas phase chemical deposition installation according to one embodiment of the invention,

There is a top view of part of the installation of the according to a cutting plane II-II,

There is a top view of part of the installation of the according to a III-III section plan,

There is a top view of part of the installation of the according to a section plan IV-IV,

There is a top view of part of the installation of the according to a VV cutting plan,

There is a schematic sectional view of a gas-phase chemical infiltration or gas-phase chemical deposition installation according to another embodiment of the invention.

The invention applies to any type of installations or ovens used to carry out thermal treatments and, in particular, those used to carry out thermochemical treatments for densification of porous substrates by infiltration or chemical deposition in the gas phase.

There illustrates a gas phase chemical infiltration (CVI) or gas phase chemical deposition (CVD) installation 100 intended for the densification of fibrous preforms in accordance with one embodiment of the invention. The installation 100 is delimited by an enclosure 110 comprising here a cylindrical side wall 111, a bottom wall 112 and an upper wall 113.

The installation 100 comprises, inside the enclosure 110, a first reaction chamber 120 delimited by a wall 121 and comprising a first gas inlet 122 present at a first end of the reaction chamber 120, a first preheating chamber 123, a first loading zone 124 and a first gas outlet 125. The first preheating chamber 123 comprises several multi-perforated plates 1230, 1231 and 1232 and is present between the first gas inlet 122 and a first end 1241 of the first loading zone 124. The first gas evacuation outlet 125 is present at a second end 1242 of the loading zone opposite the first end 1241.

In the example described here, the gas evacuation outlet 125 comprises a gas phase depletion module 1250 comprising vents 1251 connected to a gas evacuation pipe (not shown in the figure). ) connected to the enclosure 110 of the installation (figures 1 and 4).

In accordance with the invention, the installation 100 further comprises, inside the enclosure 110, a second reaction chamber 130, the first and second reaction chambers 120 and 130 being superimposed. The second reaction chamber 130 is delimited by a wall 131 and comprises a second gas inlet 132 present at a first end of the reaction chamber 120, a second preheating chamber 133, a second loading zone 134 and a second gas outlet. gas 135. The second preheating chamber 133 comprises several multi-perforated plates 1330, 1331 and 1332 and is present between the second gas inlet 132 and a first end 1341 of the second loading zone 134. The second gas evacuation outlet gas 135 is present at a second end 1342 of the loading zone opposite the first end 1341.

In the example described here, the gas evacuation outlet 135 comprises a gas phase depletion module 1350 comprising vents 1351 connected to a gas evacuation pipe (not shown in the figure). ) connected to the enclosure 110 of the installation.

In accordance with the invention, the first and second reaction chambers 120 and 130 are independent of each other both chemically and thermally. More precisely, the first and second reaction chambers are each supplied with a different gas phase. By “gas phase” is meant here a gas or a gas mixture comprising at least one precursor capable of depositing a solid deposit by chemical reaction. The gas phases introduced respectively into the first and second reaction chambers differ from each other in that they each comprise at least one different precursor.

For this purpose, the first gas inlet 122 of the first reaction chamber 120 comprises a first injection port 140 connected to a first reactive gas pipe 150. The gas inlet 122 is connected to a first power source in gas 155 via the first gas pipe 150 ( ). The first gas supply source 155 delivers a first gas phase 10 having a composition determined with regard to the nature of the gas or gases used as well as the proportion of each of the gases in the composition of the gas phase. The first gas supply source 155 is also configured to control the flow rate of the gas phase introduced into the first reaction chamber 120.

The second reaction chamber 130 is supplied with reactive gas via an internal gas supply circuit 160 bypassing the first reaction chamber 120 ( ). The internal supply circuit 160 is connected, on the one hand, to a second injection port 170 connected itself to a second reactive gas line 180 and, on the other hand, to the second gas inlet 132 of the second reaction chamber 120. The second injection port 170 comprises an injection ring 171 connected to the second reactive gas pipe 180 ( ). The second gas inlet 132 is connected to a second gas supply source 185 via the second reactive gas line 180 ( ). The second gas supply source 185 delivers a second gas phase 20 having a composition determined with regard to the nature of the gas or gases used as well as the proportion of each of the gases in the composition of the gas phase. The second gas supply source 185 is also configured to control the flow rate of the gas phase introduced into the second reaction chamber 130. The second gas supply source delivers a gas phase containing at least one precursor different from a precursor present in the gas phase delivered by the first power source.

In the example described here, the internal supply circuit 160 comprises four circulation channels 161, 162, 163 and 164 each running along the wall 121 of the first reaction chamber 120, the upper ends 1610, 1620, 1630 and 1640 of the circulation channels 161, 162, 163 and 164 cooperating with injection orifices 1710 of the injection ring 171 while the lower ends 1611, 1621, 1631 and 1641 of the circulation channels 161, 162, 163 and 164 open out at the gas inlet 132 of the second reaction chamber 130. The internal supply circuit can of course include a different number of circulation channels. In particular, it may include only one circulation channel or include two circulation channels.

According to a particular aspect, the gas inlet 132 of the second reaction chamber 130 comprises a flow rectifier module 1320 comprising a plurality of perforations 1321 making it possible to straighten the gas flow delivered at the lower ends 1611, 1621, 1631 and 1641 circulation channels 161, 162, 163 and 164 when entering the second reaction chamber 130.

According to another particular aspect, the circulation channels of the internal gas supply circuit may include baffles (not shown in Figures 1 to 5) in order to improve the heating of the gas.

According to the invention, the first and second reaction chambers 120 and 130 are each provided with an independent heating system, that is to say that one of the first and second reaction chambers can be heated to a temperature different from that of the other reaction chamber. The installation 100 thus comprises a first heating system 1112 configured to heat the first reaction chamber 120 to a first determined temperature and a second heating system 1114 configured to heat the second reaction chamber 130 to a second determined temperature.

In the example described here, the first and second heating systems are produced by induction. More precisely, the cylindrical side wall 111 of the enclosure 110 comprises an armature, or susceptor 1110, for example made of graphite. The first heating system 1112 is formed by a first portion of the susceptor 1110 which surrounds the first reaction chamber 120 and which is coupled with an inductor located outside the enclosure 110 and formed of at least one first coil of induction 1113. An insulator 1111 is interposed between the first coil(s) 1113 and the susceptor 1110. In a well-known manner, the heating of the first reaction chamber 120 is ensured by the heating of the susceptor 1110 when the coil(s) 1113 are powered with an alternating voltage. For this purpose, the coil(s) of the inductor are connected to a first alternating voltage generator (not shown). The magnetic field created by the coil(s) 1113 induces an electric current in the susceptor 1110 which causes the latter to heat up by the Joule effect, the elements present inside the enclosure 110 being heated by radiation. The intensity of the current circulating in the coil(s) 1113 determine the heating temperature of the first reaction chamber.

The second heating system 1114 is formed by a second portion of the susceptor 1110 which surrounds the second reaction chamber 130 and which is coupled with an inductor located outside the enclosure 110 and formed of at least a second coil of induction 1115. An insulator 1111 is interposed between the second coil(s) 1115 and the susceptor 1110. In a well-known manner, the heating of the second reaction chamber 130 is ensured by the heating of the susceptor 1110 when the coil(s) 1115 are powered with an alternating voltage. For this purpose, the coil(s) of the inductor are connected to a second alternating voltage generator (not shown). The magnetic field created by the coil(s) 1115 induces an electric current in the susceptor 1110 which causes the latter to heat up by the Joule effect, the elements present inside the enclosure 110 being heated by radiation. The intensity of the current circulating in the coil(s) 1115 determine the heating temperature of the first reaction chamber.

The independent heating of the first and second chambers 120 and 130 can be ensured by other means such as electric heating means consisting for example of heating resistors embedded in the side wall of the enclosure or placed outside the wall lateral like the coils 1113 and 1115 shown on the . In the latter case, these are resistor cages.

We thus obtain, as illustrated in , an installation 100 which comprises first and second useful zones corresponding respectively to the first and second loading zones 124 and 134 of the first and second reaction chambers 120 and 130. It is in these first and second useful zones that the temperature must be controlled in order to precisely control the solid deposit from the first and second gas phases 10 and 20 introduced respectively into the first and second reaction chambers 120 and 130.

An intermediate zone or non-useful zone is present between the first and second useful zones. In the example described here, the non-useful zone extends between the second end 1242 of the first loading zone 124 adjacent to the first gas outlet 125 of the first reaction chamber 120 and the second gas inlet 132 of the second reaction chamber 130. The non-useful zone allows thermal decoupling between the useful zones of the reaction chambers, which facilitates control of the temperature in each useful zone.

Because the first and second useful zones can be independently heated to different temperatures, the temperature in the non-useful zone cannot be controlled and is different from the processing temperatures present in the first and second useful zones. This does not cause any disadvantages in the operation of the installation 100 because in the non-useful zone no part is treated. In the example described here, the non-useful zone mainly corresponds to the first gas outlet 125 equipped with the gas phase depletion module 1250. The function of this zone is to trap and evacuate the reaction by-products. Consequently, in such a zone, the temperature tolerance is much higher than in the useful zones because it is not necessary to control the quality of the deposit in this zone.

Optionally, the first and second reaction chambers 120 and 130 can be thermally isolated from each other by a thermal insulator 101, for example a graphite felt present between the first gas outlet 125 and the second reaction chamber. reaction 130. The thermal insulator 101 makes it possible to increase the thermal decoupling between the first and second useful zones.

Each reaction chamber can be heated by a single-zone or multi-zone (2 or 3 zones) heating system. Multi-zone heating has the advantage, at the scale of each reaction chamber, of implementing thermal homogeneity over a greater height. We now describe the operation of the thermochemical treatment installation 100 in application with a process for manufacturing parts made of composite material.

Substrates or fibrous preforms 50 to be densified are placed in the first reaction chamber 120. The preforms 50 are distributed over the height of the first loading zone 124 of the first reaction chamber 120.

Substrates or fibrous preforms 60 to be densified are placed in the second reaction chamber 130. The preforms 60 are distributed over the height of the second loading zone 134 of the second reaction chamber 130.

A first gas phase 10 delivered by the first gas supply source 155 and containing at least one first gaseous matrix precursor, is admitted into the first reaction chamber 120 through the first reactive gas line 150 and the first port of injection 140. Likewise, a second gas phase 20 delivered by the second gas supply source 185 and containing at least a second matrix precursor is admitted into the second reaction chamber 130 through the second reactive gas line 180 and the first injection port 170.

The gas phases 10 and 20 are preheated during their circulation respectively in the first and second preheating chambers 123 and 133 before their introduction into the loading zones 124 and 134.

The temperature in the first and second reaction chambers 120 and 130 are adjusted independently to allow the gas to diffuse within the porosity of the fibrous preforms and form a deposit of the material(s) constituting a matrix by decomposition of one or several constituents of the gas, these constituents forming the precursor of the matrix. The process is carried out under reduced pressure, in order to promote the diffusion of reactive gases in the substrates. The transformation temperature of the precursor(s) to form the matrix material, such as a ceramic, is in most cases between 900°C and 1100°C.

The gas flow in one of the reaction chambers can be 1.5 times, or even 2 times higher than in the other reaction chamber while the average temperature difference in the useful zones, between the two chambers reaction can be higher than 50°C, or even higher than 150°C, or even 200°C, depending on the types of deposits desired in each of the chambers.

The gas phase 10 circulates through the preforms 50 present in the first loading zone 124 from the preheating chamber 123 to the first gas outlet 125. A first matrix is deposited in the preforms 50 by decomposition of the gas phase 10 The second gas phase 20 is conveyed to the inlet 122 of the second reaction chamber 130 by the circulation channels 161, 162, 163 and 164 of the internal supply circuit 160 in order to circulate through the preforms 60 present in the. second loading zone 134 from the preheating chamber 133 to the second gas outlet 135. A second matrix is deposited in the preforms 60 by decomposition of the gas phase 20.

The by-products 11 resulting from the decomposition of the first gas phase 10 are evacuated through the first gas outlet 125. In this way, no by-product potentially responsible for inhibition of the growth of the deposit by CVI is transmitted to the second reaction chamber 130. This greatly reduces the risk of the appearance of a gradient in the deposition of matrix by CVI in the fibrous preforms 50 and in particular those present in the loading zone 134 of the second chamber reaction chamber 130 present below the first reaction chamber 120.

There represents another embodiment of a gas phase chemical infiltration (CVI) or gas phase chemical deposition (CVD) installation 200 which differs from the installation 100 described above in that two reaction chambers 220 and 230 are superimposed in the enclosure of the installation by placing their gas evacuation outlet opposite each other and their gas inlet at each of the vertical ends of the enclosure. The reactive gas(es) are injected both at the upper end and the lower end of the enclosure.

More precisely, the installation 200 is delimited by an enclosure 210 comprising here a cylindrical side wall 211, a bottom wall 212 and an upper wall 213.

The installation 100 comprises, inside the enclosure 210, a first reaction chamber 220 delimited by a wall 221 and comprising a first gas inlet 222 present at a first end of the reaction chamber 220, a first preheating chamber 223, a first loading zone 224 and a first gas outlet 225. The first preheating chamber 223 comprises several multi-perforated plates 2230, 2231 and 2232 and is present between the first gas inlet 222 and a first end 2241 of the first loading zone 224. The first gas evacuation outlet 225 is present at a second end 2242 of the loading zone opposite the first end 2241. The gas inlet 222 comprises a first injection port 240 connected to a first reactive gas pipe 250 present at the upper wall 213 of the enclosure 210.

In the example described here, the gas evacuation outlet 225 comprises a gas phase depletion zone 2250 comprising vents 2251 connected to a gas evacuation pipe 290 connected at the bottom wall 212 of the enclosure 210.

In accordance with the invention, the installation 200 further comprises, inside the enclosure 210, a second reaction chamber 230, the first and second reaction chambers 220 and 230 being superimposed. The second reaction chamber 230 is delimited by a wall 231 and comprises a second gas inlet 232 present at a first end of the reaction chamber 220, a second preheating chamber 233, a second loading zone 234 and a second gas outlet. gas 235. The second preheating chamber 233 comprises several multi-perforated plates 2330, 2331 and 2332 and is present between the second gas inlet 232 and a first end 2341 of the second loading zone 234. The second gas evacuation outlet gas 235 is present at a second end 2342 of the loading zone opposite the first end 2341. The second gas outlet 235 is here opposite the first gas outlet 225 of the first reaction chamber 220 The gas inlet 232 comprises a second injection port 270 connected to a second reactive gas pipe 280 present at the bottom wall 212 of the enclosure 210.

In the example described here, the gas evacuation outlet 235 comprises a gas phase depletion module 2350 comprising vents 2351 connected to the gas evacuation pipe 290 connected at the bottom wall 212 of the enclosure 210.

The first and second reaction chambers 220 and 230 are independent of each other both chemically and thermally. More precisely, the first and second reaction chambers are each supplied with a different gas phase. The gas phases introduced respectively into the first and second reaction chambers differ from each other in that they each comprise at least one different precursor.

For this purpose, the first gas inlet 222 of the first reaction chamber 220 comprises a first injection port 240 connected to a first reactive gas pipe 250. The gas inlet 222 is connected to a first power source in gas 255 via the first gas pipe 250 ( ). The first gas supply source 255 delivers a first gas phase 30 having a composition determined with regard to the nature of the gas or gases used as well as the proportion of each of the gases in the composition of the gas phase. The first gas supply source 255 is also configured to control the flow rate of the gas phase introduced into the first reaction chamber 220.

The second gas inlet 232 of the second reaction chamber 220 comprises a second injection port 270 connected to a second reactive gas line 280. The gas inlet 232 is connected to a second gas supply source 285 via the second gas line 280 ( ). The second gas supply source 285 delivers a second gas phase 40 having a composition determined with regard to the nature of the gas or gases used as well as the proportion of each of the gases in the composition of the gas phase. The second gas supply source 285 is also configured to control the flow rate of the gas phase introduced into the second reaction chamber 230. The second gas supply source delivers a gas phase containing at least one precursor different from a precursor present in the gas phase delivered by the first power source.

According to the invention, the first and second reaction chambers 220 and 230 are each provided with an independent heating system, that is to say that one of the first and second reaction chambers can be heated to a temperature different from that of the other reaction chamber. The installation 200 thus comprises a first heating system 2112 configured to heat the first reaction chamber 220 to a first determined temperature and a second heating system 2114 configured to heat the second reaction chamber 230 to a second determined temperature.

In the example described here, the first and second heating systems are produced by induction. More precisely, the cylindrical side wall 211 of the enclosure 210 comprises an armature, or susceptor 2110, for example made of graphite. The first heating system 2112 is formed by a first portion of the susceptor 2110 which surrounds the first reaction chamber 220 and which is coupled with an inductor located outside the enclosure 210 and formed of at least one first coil of induction 2113. An insulator 2111 is interposed between the first coil(s) 2113 and the susceptor 2110. In a well-known manner, the heating of the first reaction chamber 220 is ensured by the heating of the susceptor 2110 when the coil(s) 2113 are powered with an alternating voltage. For this purpose, the coil(s) of the inductor are connected to a first alternating voltage generator (not shown). The magnetic field created by the coil(s) 2113 induces an electric current in the susceptor 2110 which causes the latter to heat up by the Joule effect, the elements present inside the enclosure 210 being heated by radiation. The intensity of the current circulating in the coil(s) 2113 determine the heating temperature of the first reaction chamber.

The second heating system 2114 is formed by a second portion of the susceptor 2110 which surrounds the second reaction chamber 230 and which is coupled with an inductor located outside the enclosure 210 and formed of at least one second coil. induction 2115. An insulator 2111 is interposed between the second coil(s) 2115 and the susceptor 2110. In a well-known manner, the heating of the second reaction chamber 230 is ensured by the heating of the susceptor 2110 when the coil(s) 2115 are powered with an alternating voltage. For this purpose, the coil(s) of the inductor are connected to a second alternating voltage generator (not shown). The magnetic field created by the coil(s) 2115 induces an electric current in the susceptor 2110 which causes the latter to heat up by the Joule effect, the elements present inside the enclosure 210 being heated by radiation. The intensity of the current circulating in the coil(s) 2115 determine the heating temperature of the first reaction chamber.

The independent heating of the first and second chambers 220 and 230 can be ensured by other means such as electric heating means consisting for example of heating resistors embedded in the side wall of the enclosure.

We thus obtain, as illustrated in , an installation 200 which comprises first and second useful zones corresponding respectively to the first and second loading zones 224 and 234 of the first and second reaction chambers 220 and 230. It is in these first and second useful zones that the temperature must be controlled in order to precisely control the solid deposit from the first and second gas phases 30 and 40 introduced respectively into the first and second reaction chambers 220 and 230.

An intermediate zone or non-useful zone is present between the first and second useful zones. In the example described here, the non-useful zone extends over the depletion zones 2250 and 2350 respectively of the first and second gas outlets 225 and 235 of the first and second reaction chambers 120 and 130. Like the first and second useful zones can be heated independently to different temperatures, the temperature in the non-useful zone cannot be controlled and is different from the processing temperatures present in the first and second useful zones. This does not cause any disadvantages in the operation of the installation 200 because in the non-useful zone no part is treated. In the example described here, the useful zone corresponds to the gas phase depletion zones. The function of these zones is to trap and evacuate reaction by-products. Consequently, in such zones, the temperature tolerance is much higher than in the useful zones because it is not necessary to control the quality of the deposit in this zone.

Optionally, the first and second reaction chambers 220 and 230 can be thermally isolated from each other by a thermal insulator 201, for example a graphite felt present between the two depletion zones 2250 and 2350. The thermal insulator 201 makes it possible to increase the thermal decoupling between the first and second useful zones.

We now describe the operation of the thermochemical treatment installation 200 in application with a process for manufacturing parts made of composite material.

Substrates or fibrous preforms 70 to be densified are placed in the first reaction chamber 220. The preforms 70 are distributed over the height of the first loading zone 224 of the first reaction chamber 220.

Substrates or fibrous preforms 80 to be densified are placed in the second reaction chamber 230. The preforms 80 are distributed over the height of the second loading zone 234 of the second reaction chamber 230.

A first gas phase 30 delivered by the first gas supply source 255 and containing at least one first gaseous matrix precursor, is admitted into the first reaction chamber 220 through the first reactive gas line 250 and the first port of injection 240. Likewise, a second gas phase 40 delivered by the second gas supply source 285 and containing at least a second matrix precursor is admitted into the second reaction chamber 230 through the second reactive gas line 280 and the first injection port 270.

The gas phases 30 and 40 are preheated during their circulation respectively in the first and second preheating chambers 223 and 233 before their introduction into the loading zones 224 and 234.

The temperature in the first and second reaction chambers 220 and 230 are adjusted independently to allow the gas to diffuse within the porosity of the fibrous preforms and form a deposit of the material(s) constituting the matrix by decomposition of one or more constituents of the gas, these constituents forming the precursor of the matrix. The process is carried out under reduced pressure, in order to promote the diffusion of reactive gases in the substrates. The transformation temperature of the precursor(s) to form the matrix material, such as a ceramic, is in most cases between 900°C and 1100°C.

The gas flow in one of the reaction chambers can be 1.5 times, or even 2 times higher than in the other reaction chamber while the average temperature difference in the useful zones, between the two chambers reaction can be higher than 50°C, or even higher than 150°C, or even 200°C, depending on the types of deposits desired in each of the chambers.

The first gas phase 30 circulates through the preforms 70 present in the first loading zone 224 from the preheating chamber 223 to the first gas outlet 225. A first matrix is deposited in the preforms 70 by decomposition of the gas phase 30. The second gas phase 40 circulates through the preforms 80 present in the second loading zone 234 from the preheating chamber 233 to the second gas outlet 235. A second matrix is deposited in the preforms 80 by decomposition of the gas phase 40.

We now describe two examples of combined treatments which can be carried out in one of the CVI/CVD installations 100 and 200 described previously.

Example 1:

In this example, a first matrix of silicon carbide (SiC) is deposited in preforms present in the first reaction chamber while a second matrix of carbon (C) is deposited in preforms present in the second reaction chamber. The gas phase introduced into the first reaction chamber comprises methyltrichlorosilane (CH₃SiCl₃) as a precursor of SiC and hydrogen while the gas phase introduced into the second reaction chamber comprises methane (CH₄) as a carbon precursor.

The operating conditions for the two CVI/CVD treatments carried out simultaneously are as follows: Processing parameters First reaction chamber Second reaction chamber Gas phase CH ₃ SiCl ₃ /H ₂ CH ₄ Flow (Nl/min) 5/60 100 Useful zone temperature (°C) 975 1020 Useful zone pressure (mbar) 16.5 16.5

Example 2:

In this example, a first matrix of silicon carbide (SiC) is deposited in preforms present in the first reaction chamber while a second matrix of Si-B-C is deposited in preforms present in the second reaction chamber. The gas phase introduced into the first reaction chamber comprises methyltrichlorosilane (CH₃SiCl₃) as a precursor of SiC and hydrogen while the gas phase introduced into the second reaction chamber comprises methyltrichlorosilane (CH₃SiCl₃) as the first precursor, boron trichloride (BCl₃) as a second precursor and hydrogen.

The operating conditions for the two CVI/CVD treatments carried out simultaneously are as follows: Processing parameters First reaction chamber Second reaction chamber Gas phase CH ₃ SiCl ₃ /H ₂ CH ₃ SiCl ₃ /BCl ₃ /H ₂ Flow rate (Nl/min) 5/50 1.5/7/45 Useful zone temperature (°C) 1050 900 Useful zone pressure (mbar) 50 50

Claims (10)

Gas phase chemical infiltration or gas phase chemical deposition installation (100) comprising an enclosure (110) enclosing a first reaction chamber (120) comprising a first gas inlet (122), a first preheating chamber (123 ), a first loading zone (124) and a first gas outlet (125), the first gas inlet being connected to a first gas supply source (155), the first gas outlet being connected to at least a gas evacuation pipe, the installation further comprising a first heating system (1112) configured to heat the first reaction chamber,
characterized in that the enclosure (110) further contains a second reaction chamber (130) comprising a second gas inlet (132), a second preheating chamber (133), a second loading zone (134) and a second gas outlet (135), the second gas inlet being connected to a second gas supply source (185), the second gas outlet being connected to said at least one gas evacuation pipe, the installation further comprising a second heating system (1114) configured to heat the second reaction chamber, in that the first and second gas supply sources (155, 185) each deliver a gas phase comprising at least one different precursor gas and in that the first and second heating systems (1112, 1114) are independent of each other. Installation according to claim 1, in which the first and second reaction chambers (120, 130) are superimposed inside the enclosure and in which the first gas outlet (125) of the first reaction chamber (120) is adjacent to the second reaction chamber (130). Installation according to claim 2, in which the first and second reaction chambers (120, 130) are thermally isolated from each other by a thermal insulator (101) present between the first gas outlet (125) and the second reaction chamber (130). Installation according to claim 2 or 3, further comprising an internal gas supply circuit (160) bypassing the first reaction chamber (120), said internal gas supply circuit being connected to the second gas inlet (132). ) of the second reaction chamber (130). Installation according to claim 4, in which the second gas inlet (132) of the second reaction chamber (130) comprises a flow rectifier module (1320). Installation according to claim 1, in which the first and second reaction chambers (220, 230) are superimposed inside the enclosure and in which the first and second gas evacuation outlets (225, 235) of the first and second reaction chambers (220, 230) face each other while the first and second gas inlets (222, 232) of the first and second reaction chambers are at opposite locations in the enclosure (210). Installation according to claim 6, in which the first and second reaction chambers are thermally isolated from each other by a thermal insulator (201) present between the first and second gas evacuation outlets (225, 235) of the first and second reaction chambers (220, 230). Gas phase chemical infiltration or gas phase chemical deposition process comprising:
- loading substrates or fibrous preforms into first and second loading zones (124, 134) respectively of a first reaction chamber and a second reaction chamber of a gas phase chemical infiltration installation or gas phase chemical deposition (100) according to any one of claims 1 to 7,
- controlling the first heating system (1112) of the installation to heat the first reaction chamber (120) to a first temperature,
- controlling the second heating system (1114) of the installation to heat the second reaction chamber (130) to a second temperature,
- the introduction of a first gas phase (10) into the first reaction chamber (120),
- the introduction of a second gas phase (20) into the second reaction chamber (130),
- the first and second gas phases each comprise at least one different precursor. A method according to claim 8, wherein the first and second gas phases are introduced respectively into the first and second reaction chambers (120, 130) at different flow rates. A method according to claim 8 or 9, wherein the first and second heating temperatures are different.