FR3070693A1 - METHOD AND APPARATUS FOR COATING DEPOSITION FOR MULTI-PERFORATED AIRCRAFT ENGINE COMPONENTS WITH EVENT BLOWING - Google Patents

Abstract

The invention relates to a method for treating a mechanical part of an aircraft engine by applying a coating, the part comprising, within its internal volume, internal cooling channels in which a gas can circulate, each cooling channel opening onto a surface of the workpiece at a vent, the gas being blown through the action of a dispensing tool through each channel of a plurality of internal cooling channels of the workpiece, and expelled through vents, during a thermal spraying step of a coating layer on the surface of the workpiece.

Description

Coating deposition method and device for multi-perforated aircraft engine components with air blowing

TECHNICAL FIELD OF THE INVENTION AND STATE OF THE ART

The present invention is in the technical field of surface treatment of parts brought to undergo significant thermomechanical and / or environmental stresses, such as turbomachine components.

Increasing the operating temperature of high-pressure turbines (TuHP) in stationary terrestrial systems, or systems for aeronautical propulsion, is one solution chosen to improve efficiency. Such a technical choice imposes very significant temperature constraints on the components of the turbines. A component with high thermal stress is conventionally provided with an internal cooling circuit using "cold" air traversing the internal volume of the component, and opening on its surface through vents. Such components can be called "multi-perforated" and when in operation, cold air flows through the internal cooling channels, largely ensuring their cooling. However, depending on the materials used for these components - for example metallic superalloys, or ceramic matrix composite materials (CMC) - additional protection may be necessary to maintain a sufficiently low surface temperature guaranteeing the functional integrity of the materials. components and limiting their oxidation / corrosion by the surrounding atmosphere.

As such, it is known to apply protections of the “thermal barrier” (BT) or “environmental barrier” (EBC) type to the surface of the parts, which can take the form of complex multilayer stacks . These protections can simultaneously provide a function of protection against oxidation and / or corrosion, and a function of limiting the temperature of the components when they are in operation, or even chemical protection against external contaminants such as aluminosilicates. calcium and magnesium also called CMAS. For a substrate of which a basic material is a metal alloy, or a composite material, generally several layers are applied superimposed on the substrate, before putting the component in place within the engine. A thermal barrier system can in particular be composed of a refractory ceramic (often yttria zirconia). The dual thermal and environmental protection makes it possible to extend the operating temperature range of the TuHPs, without degrading the performance of the superalloy.

However, during the application of successive layers of protective coating, the cooling circuit traversing the internal volume of the parts may be partially obstructed or fouled by particles of the chemical compound constituting the coating. For conventional thermal spray deposition, the cooling channels can be largely blocked. In addition to the obstruction of the ventilation vents on their opening part, part of the coating particles can be deposited on the internal walls of the vent without reducing the apparent external section, but producing a fouling of a part. internal of the cooling channel associated with the vent. By way of illustration, FIG. 1 represents this phenomenon for a coating deposition by APS (plasma spraying of powders at atmospheric pressure - "Atmospheric Plasma Spraying"). In this figure, a tool 6 ensures the projection of coating particles deposited on the surface of a part 1, for example made of metal superalloy, provided with an internal cooling channel 10 leading to a vent 11. The process not only causes the formation of a coating layer 4 on the surface of the part by stacking, but also the projection of particles within the channel 10, causing in FIG. 1 the obstruction of the vent 11.

An alternative to work around this problem is to use an EB-PVD coating technique (Electron Beam Physical Vapor Deposition), which is not a thermal spray deposition technique. In addition to increased thermomechanical properties, these EB-PVD coatings have the advantage of retaining the integrity of the air vents. However, some of the vapors can still settle within a cooling channel of the coated part and slightly foul the channel, to a level generally considered acceptable.

In addition, if they make it possible to obtain coatings having increased thermomechanical properties, the techniques of coating deposition by EB-PVD are not the most effective with a view to providing a coating having the lowest possible thermal conductivity. Indeed, the general tendency is to increase as far as possible the operating temperatures of TuHPs, and thermal spray deposits alternative to EB-PVD deposition provide coatings with high porosity, making it easier to reach conductivities. thermal systems meeting current performance requirements in turbines.

Coating deposition techniques identified for their propensity to provide a coating of low thermal conductivity are liquid input plasma spraying techniques. Examples are SPS (suspension of fine particles

- "Suspension Plasma Spraying"), SPPS (projection of precursors in solution

- "Solution Precursor Plasma Spraying"), and variants exist consisting of injecting liquid into a flame at high speed, such as S-HVOF ("Suspension High Velocity Oxygen Fuel", also called HVSFS "High Velocity Suspension Flame Spray ”), In addition to the advantage of a low thermal conductivity obtained for the coating layer, these thermal spray deposition techniques are advantageous in that they allow the production of continuous composition gradients at the level of the coating layer. , and obtaining microstructure coatings, all at a moderate cost. However, all of these techniques are likely to cause, as seen above, partial fouling of the vent and the cooling channel.

Furthermore, it is known to “mask” the internal volume of the internal cooling channels of the multi-perforated component, that is to say to plug these channels with a chemical compound different from the coating before applying the coating to the surface of the room. The mask is then removed after formation of the coating layer. This technique can preserve the integrity of the channels and prevent their fouling during coating deposition, but requires two additional steps (masking the vents, and removing the mask), these long and costly steps lengthening the manufacturing cycle and risk of scrap parts.

There is therefore a need not covered by the prior art for a coating process by thermal spraying on the surface of a multi-perforated component which allows both to form a coating with the lowest thermal conductivity possible, and not to obstruct or foul the cooling channels of the multi-perforated component, so that steps of masking the vents before application of the coating, or of drilling the vents after application, are not necessary - such steps induce additional manufacturing costs, and can have harmful consequences on the mechanical strength of the parts by locally weakening the components.

GENERAL PRESENTATION OF THE INVENTION

To this end, the present invention relates to a coating deposition process by thermal spraying on the surface of multi-perforated components, gas being blown through the cooling channels previously practiced in the internal volume of the parts. The invention thus takes advantage of the already existing internal cooling circuit 15, using the latter to circulate gas at high pressure. This has the effect of repelling the coating particles during the thermal spray deposition step so as not to allow them to solidify and deposit at the vents and inside the cooling channels.

According to a first aspect, the invention therefore relates to a method of treating a mechanical part of an aircraft engine by applying a coating, the part comprising, within its internal volume, internal cooling channels in which a gas, each cooling channel emerging at the surface of the room at a vent, the gas being blown by the action of a distribution tool through each channel of a plurality of internal cooling channels of the room , and expelled through the vents, during a step of deposition by thermal spraying of the coating layer on the surface of the part.

Optional and non-limiting characteristics of a process according to the invention are as follows:

• Deposition by thermal spraying can be carried out according to a protocol taken from High Velocity Oxi-Fuel, plasma spraying of powders at atmospheric pressure 35 (APS), Plasma Spraying Suspension, Precursor Plasma Spraying Solution,

High Velocity Suspension Flame Spray, plasma projection under inert gas "Inert Plasma Spraying" (IPS).

• The gas is expelled through vents against the current in the direction of deposit of 5 coating particles on the surface of the part;

• The gas expelled through the vents is compressed air;

• The gas expelled through the vents is argon;

• The process includes a preliminary step of chemical cleaning and / or texturing of the surface of the part to improve the adhesion of the coating layer at the end of the process;

15 · The process includes, before the thermal spray deposition step, a step of preheating the part to be coated;

• The coating deposited by thermal spraying is a layer of ceramic material forming a thermal barrier;

• The deposited thermal barrier comprises yttria zirconia, or any other composition having a thermal insulation property recognized by those skilled in the art;

25 · The coating layer deposited by thermal spraying forms an environmental barrier, comprising a material taken from M0S12, BSAS (BaOi-xSrOx-AI ₂ O3-2SiO ₂ ), Mullite (3 AI2O3-2 SiO ₂ ), mono- and di-silicates of rare earths, fully or partially stabilized, or even doped zirconia, or any other composition having an environmental barrier property recognized by a person skilled in the art;

• The method comprises, immediately before the step of depositing a thermal barrier coating, a step of depositing an aluminoforming bonding layer;

35 · In the case immediately above, the bonding layer is then produced according to a protocol chosen from physical evaporation deposition (PVD), low pressure plasma spraying (LPPS), plasma spraying under an inert atmosphere (IPS) , chemical evaporation deposition (CVD), flash sintering (Spark Plasma Sintering), electrolytic deposition, plasma spraying of powders at atmospheric pressure (APS), High Velocity Oxi-Fuel, Snecma vapor phase aluminization (APVS );

• In the same case, the bonding layer is formed of a material taken from alloys of the MCrAlY type (M = Ni, Co, Ni and Co), nickel aluminides type β-ΝϊΑΙ (modified or not by Pt , Hf, Zr, Y, Si or combinations of these), aluminides of γ-Νϊ-γ'-ΝϊβΑΙ alloys (modified or not by Pt, Cr, Hf, Zr, Y, Si or combinations of these elements), the MAX phases (M _n + iAX _n (n = 1,2,3) where M = Sc, Y, La, Mn, Re, W, Hf, Zr, Ti; A = groups II IA, IVA , VA, VIA; X = C, N).

• The thickness of all of the superposed deposited layers is between 10 pm and 1000 pm, preferably between 20 pm and 500 pm.

According to a second aspect, the invention relates to a mechanical part of a multi-perforated aircraft engine, coated by thermal spraying according to a coating treatment method in accordance with the above, the mechanical part being traversed in its internal volume by a plurality of internal cooling channels 20, said channels opening on the surface of the part onto vents.

Thanks to the blowing of gas into the cooling channels during the deposition of the coating layer by thermal spraying, the internal cooling channels and the vents of the room are neither obstructed nor clogged at the end of the process. coating application.

Such a mechanical part of an aircraft engine may have the following additional characteristics:

• The part is a high pressure turbine blade, a high pressure turbine distributor, a turbine ring, or a combustion chamber element;

• A part material is a ceramic matrix composite material (CMC);

The part is formed of a Ni or Co-based superalloy, for example an AM 1, MC-NG, CMSX4, René superalloy;

After deposit of the coating layer (s), the thermal barrier layers and / or environmental barriers and / or environmental thermal barriers and / or functional layers have a homogeneous microstructure, or homogeneous and porous, or vertically microcracked, or microcracked vertically and porous, or columnar, or columnar and porous, or dense, or micro-fissured and dense.

GENERAL PRESENTATION OF THE FIGURES

Other characteristics, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and not limiting. This description should be read with reference to FIG. 1 already presented above, as well as to the following other appended drawings, among which:

FIG. 2 schematically represents a step of depositing a coating by thermal spraying of the APS (Atmospheric Plasma Spraying) type with blowing of the vents, in contrast to FIG. 1.

FIG. 3 schematically represents a step of depositing a coating by thermal spraying of the SPS (Suspension Plasma Spraying) type of the state of the art.

FIG. 4 schematically represents a step of depositing a coating by thermal spraying of the SPS type with blowing of the vents, in contrast to FIG. 3.

FIG. 5 is a block diagram illustrating a particular embodiment of a coating method by thermal spraying on the surface of a multi-perforated component.

FIG. 6 schematically represents an assembly suitable for implementing a coating deposition on a blade of a turbomachine turbine, with blowing of compressed air through the vents of the blade.

FIG. 7 schematically represents an assembly suitable for implementing a coating deposition on the surface of a multi-perforated combustion chamber of a turbomachine, with blowing of compressed air through the vents of the chamber.

FIG. 8 represents several examples of possible configurations of cooling channels leading to vents, on the surface of the same multi-perforated component.

FIG. 9 illustrates the result of the coating deposition process represented in FIG. 5, taken according to a first variant.

FIG. 10 illustrates the result of the coating deposition process represented in FIG. 5, taken according to a second variant.

Figure 11 illustrates the result of the coating deposition process shown in Figure 5, taken according to a third variant.

FIG. 12 illustrates the result of the coating deposition process represented in FIG. 5, taken according to a fourth variant.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

The description which follows relates to the surface treatment of mechanical parts. In general, the treatment method described below comprises the deposition, by a thermal spray coating technique, of a coating layer on the surface of the parts. In what follows, the parts treated are mechanical parts of an aircraft engine intended to be subjected to extreme thermal stresses, and the application of a coating of the thermal and / or environmental barrier type may aim to preserve the part from variations. excessively high temperatures - which makes it possible to increase the engine operating temperatures without compromising the performance of the part - and / or to protect the part against external attack, for example against corrosion. In the following, we can speak of a multi-perforated part or multi-perforated component, it being understood that the method would be applicable identically for a part having only one cooling channel and one vent.

FIG. 1 has already been described above, and illustrates the disadvantages of a coating process by plasma spraying of powders at atmospheric pressure (APS - "Atmospheric Plasma Spraying") of the state of the art. In comparison, FIG. 2 illustrates the advantages of a coating process by thermal spraying with gas blowing through the internal cooling channels 10 of the part 1 and through the vents 11. In all the description which follows and in the appended figures, elements or analogous process steps bear the same reference numeral.

In all the description below, the gas expelled through the vents 11 of the part 1 is compressed air. Alternatively, provision could be made for high-pressure blowing via the vents of another gas. In particular, in the case where the coating deposition by thermal spraying is carried out according to the technique of plasma spraying under an inert atmosphere ("Inert Plasma Spraying", or IPS), the gas blown through the vents can advantageously be argon .

By a tool not visible in Figure 2, compressed air is expelled through the vent 11, simultaneously with the coating deposition by APS. Coating particles are melted and accelerated towards the surface of the part, at the level of the vent 11 and in a direction substantially opposite to the direction of blowing of the compressed air out of the cooling channel 10. Because of this blowing, the coating particles are:

- either pushed directly from the internal surface of the channel 10 and the vicinity of the vent 11 if their kinetic energy is low, then evacuated to the extraction system used elsewhere for depositing coating,

- either partially solidified, which prevents their adhesion to the substrate on the surface of the part 1, then subsequently evacuated to the extraction system.

The coating particles are typically accelerated toward the surface of the part. The direction of projection of the coating particles on the surface may be substantially perpendicular locally to said surface. It is also possible to provide a projection direction which is not perpendicular to the surface of the part, as a function of the kinematics of the coating deposit. The flow of compressed air passing through the internal cooling channels and expelled through the vents is typically directed opposite the projected coating particles, counter-current to the direction of projection of the coating particles.

Blowing the vents helps prevent fouling of the cooling channels and vents by unfounded fine particles, or the formation of a partial coating layer within the channels. A subsequent drilling of the cooling channels after application of the coating, in order to guarantee the integrity and functionality of the cooling channels, is no longer necessary.

FIG. 3 and FIG. 4 illustrate comparatively a method of coating deposition respectively without blowing and with blowing of compressed air out of a cooling channel, in the case of deposition by SPS - "Suspension Plasma Spraying". These two figures correspond respectively to FIG. 1 and to FIG. 2 for filing by APS. The coating layer 4 thus deposited on the surface of the part 1 forms a columnar deposit.

FIG. 5 illustrates the successive stages of a complete cycle of coating deposition by thermal spraying according to a particular embodiment, this embodiment serving as a reference throughout the rest of this description.

A first preliminary stage 100, optional, of preparation of the part 1 to be coated, can comprise a chemical cleaning 101 of the surface of the part in order to remove organic residues adsorbed on the surface. The preparation step 100 may also include, in addition to or independently of the chemical cleaning step 101 (before or after this last step) a texturing step 102 on the surface of the part, for example by sanding, to promote the formation and adhesion of the layer or layers of coating deposited (es) at later stages.

Then, in a step 200, a compressed air distribution tool is connected manually or automatically to the surface of the part to be treated. This tool includes compressed air distribution channels (which can also be in the form of channels), each of which can be aligned with an internal cooling channel formed in the internal volume of the room. As seen above in relation to FIGS. 1 to 4, the internal cooling channels each open out through an air hole, also called a vent, on the surface of the multi-perforated component to be coated. The concrete implementation of step 200 depends on the relative configuration of the surface on which the coating is deposited in the subsequent steps, and on the compressed air distribution tool. Concrete examples will be exposed in relation to the following figures.

In addition, if subsequent steps, and in particular the step of depositing by thermal spraying of coating, provide for the rotation of the treated part simultaneously with the blowing of compressed air by the vents, a rotary passage can be arranged between the source of compressed air and the compressed air distribution tool, in order to allow said tool to be rotated integrally with the part to be coated.

In a subsequent step 300, the distribution of a compressed air flow and the expulsion of compressed air are activated through the internal cooling circuit of the room and through the vents. The compressed air expulsion pressure is less than 10 Bar, typically between 1 and 10 Bar. The system preferably guarantees an identical pressure at the level of each of the vents which blow compressed air. In the case where the same compressed air distribution tool is connected to several multi-perforated components to be coated, it is preferable to guarantee an identical compressed air expulsion pressure for each of the multi-perforated parts treated.

At this stage of the process, a subsidiary step 310 of preheating the part (temperature between 100 ° C and 1100 ° C, preferably between 150 ° C and 500 ° C), in order to ensure the quality of the coating deposit , can be implemented, for example by moving the part connected to the compressed air distribution tool in a higher temperature space, or by scanning a torch (plasma, flame) on the surface of the part. This preheating step is implemented here simultaneously with the blowing of compressed air through the vents 11.

Then, the multi-perforated part can be coated with as many coating layers deposited by thermal spraying as necessary. The part can also undergo, before or after the coating of the coating by thermal spraying, other surface treatments.

The method according to the embodiment described here comprises an optional step 320 of depositing a bonding layer, then a step 400 of deposition by thermal spraying of coating forming a thermal barrier, environmental barrier, or thermo-environmental barrier, then a step optional 410 for depositing a functional layer. These three layers are superimposed in this order.

The bonding layer formed on the surface of the part in step 320 can be deposited by thermal spraying or by another technique. This bonding layer can help protect the part against oxidation and / or corrosion, and also allows better mechanical bond between the substrate underlying the bonding layer and the overlying coating. Preferably, it is an aluminoforming bonding layer. This bonding layer is for example produced according to a protocol taken from physical evaporation deposition (PVD), low pressure plasma spraying (LPPS), plasma spraying under inert atmosphere (IPS), chemical evaporation deposition (CVD) , flash sintering (Spark Plasma Sintering), electrolytic deposition, plasma spraying of powders at atmospheric pressure (APS), High Velocity Oxi-Fuel, Snecma vapor phase aluminization (APVS). Some of these methods are therefore not thermal spray deposition techniques.

A material of the bonding layer, which is preferably an aluminoforming layer, can be taken from alloys of the MCrAlY type (M = Ni, Co, Ni and Co), nickel aluminides type β-NiAI (modified or not by Pt, Hf, Zr, Y, Si or combinations of these elements), aluminides of γ-γ-γ'-iagesβΑΙ alloys (modified or not by Pt, Cr, Hf, Zr, Y, Si or combinations of these elements), MAX phases (M _{n +} iAX _n (n = 1,2,3) where M = Sc, Y, La, Mn, Re, W, Hf, Zr, Ti; A = groups 11IA, IVA , VA, VIA; X = C, N). The bonding layer can be formed from any mixture of the above-mentioned compounds.

In the embodiment described in relation to FIG. 5, the step 320 of depositing the bonding layer is immediately followed by the step 400 of depositing the coating by thermal spraying.

The coating layer produced at the end of step 400 corresponds to the generic description of a thermal, environmental or thermoenvironmental barrier. The deposition by thermal spraying of said thermal barrier layers, environmental barriers, environmental thermal barriers, can be ensured, but not exclusively, by APS, HVOF, SPS, SPPS, S-HVOF (also called HVSFS), IPS, and any other suitable process. . Figures 1 and 2 illustrate a layer of lamellar coating, while Figures 3 and 4 illustrate a columnar coating layer.

In the case where the coating deposited in step 400 is a thermal barrier, this barrier may advantageously comprise yttria-containing zirconia (for example with a mass percentage of Y2O3 amounting to between 7 and 8%). Another type of refractory ceramic coating can be envisaged. If it is an environmental barrier system (EBC), or environmental thermal barrier (TEBC) - in particular with a view to protecting parts made of CMC ceramic matrix compound, this barrier may, but not exclusively, include one of the materials following or a mixture of these materials: M0S12, BSAS (BaOi-x-SrOx-ALOs ^ SiCh), Mullite (3 AI2O3-2 S1O2), mono- and di-silicates of rare earths (rare earth = Y , La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), fully or partially stabilized or even doped zirconia, and any other suitable composition.

An optional step 410 of depositing a functional layer overlying the thermal, environmental or thermo-environmental barrier can then be envisaged. Such a layer can, for example, constitute a protection of a thermal barrier against external aggressions such as calcium and magnesium aluminosilicates, otherwise called CMAS - oxides of calcium, magnesium, aluminum and silicon, capable of infiltrating the melt and dissolve the thermal barrier. The step 410 for depositing the functional layer can be carried out by the same techniques noted above with regard to step 400 for depositing the coating. The application of a single functional layer or of several functional layers can be envisaged. Each of these layers can comprise, but not exclusively, a material or a mixture of materials taken from the rare earth zirconates RE2Zr20ï (RE = Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Yb , Dy, Ho, Er, Tm, Tb, Lu), fully stabilized zirconia, delta phases A4B3O12 (A = Y -> Lu and B = Zr, Hf), composites Y2O3 with ZrC> 2, mono (RE2S1O5 ) or di- (RE2S12O7) rare earth silicates (RE = Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu).

Once all of the desired layers on the surface to be treated have been produced, the method of FIG. 5 comprises an optional step 420 of cooling the part.

To end the process of surface treatment of the room, it is advisable to interrupt the distribution of compressed air by the compressed air distribution channels, and to stop the blowing by the vents of the room, during a step 500, then disconnecting the dispensing tool from the part during a step 600. An optional step 700 for cleaning the external part of the coated part can then be implemented, it being well considered that the blowing of the vents made it possible to eliminate a large part of any fine unfounded particles of coating which could have been projected onto the surface of the part - these superfluous particles resulting from thermal spraying being known to a person skilled in the art under the name “overspray ".

It should be noted that the surface treatment method of the multiperforated component can also comprise a step of depositing a thermal barrier by a technique other than thermal spraying. EB-PVD electron beam evaporation has a number of advantages presented in the introduction above. A solution-gelling process (sol-gel) could also be implemented. In general, the treatment process may include a step of depositing a coating layer by any technique which makes it possible to preserve the integrity of the internal cooling channels and the vents.

At the end of the process of FIG. 5, the total thickness deposited on the surface of the coated part is preferably between 10 and 1000 micrometers, advantageously between 20 and 500 micrometers depending, for example, on the dimensions of the part treated.

FIG. 6 represents the state, during step 300 during which compressed air is expelled through the cooling circuit, of a system comprising a tool 2 for distributing compressed air, connected to a turbine blade 1 forming a multi-perforated component.

The blade 1 includes a plurality of internal cooling channels 10, three in the figure. These channels are usually used to cool the blade during operation, in the face of the extreme thermal stresses imposed on the high pressure turbine (TuHP) of which the blade is a part. The cooling channels pass through the internal volume of the blade; they are initiated at the foot of dawn, and lead to the surface of the dawn head each on a vent 11.

The compressed air distribution tool 2 comprises a compressed air network 22 (comprising in particular a pressure source) and a pressure adapter 21 adjusting the pressure to less than 10 Bar, for example between 1 and 10 Bar. The tool of FIG. 6 comprises, downstream of this adapter 21, a single compressed air distribution path dividing, in the vicinity of an external interface of the tool 2, into three air distribution paths 20 tablet overlooking the outside interface. The blade root can be arranged on this interface, so as to align the channels 10 for which it is desired that there is blowing of compressed air out of the vents with the outputs of the channels 20 of compressed air distribution. Here, tool 2 has the advantage of keeping the blade 1 in place during deposit steps 320 to 410. The distribution tool 2 may also include a rotary passage, in order to maintain the passage of the compressed air during a rotation of the vane 1 or the distribution paths 20.

The system of FIG. 7 is slightly different to adapt to the case of a part to be coated in a non-flat shape. Here, the multi-perforated part 1 is in fact a combustion chamber element, for example of empty cylindrical shape. The operation of the compressed air distribution tool is similar to that of the tool in FIG. 6. Here, the tool comprises a straight part 23, and a peripheral part 24 adapted to grip the part to be coated. All or part of the length of the part can be encompassed by the part 24. The vents 10 of the part can thus expel compressed air simultaneously, while a tool can be inserted at the longitudinal axis of the part, to carry out the deposition by thermal spraying in a direction opposite to that of the blowing, on all or part of the internal surface of the combustion chamber part. Furthermore, the distribution tool can, also here, include a rotary passage to keep the passage of compressed air in rotation.

In FIG. 8, several possible vent configurations 11 of an internal cooling channel 10 are envisaged. The vents 11 have a diameter between 0.1 and 1 millimeter, preferably between 0.25 and 0.6 millimeters. Furthermore, the angle defined by a vent with the surface of the part is preferably between 50 ° and 130 °, preferably between 70 ° and 110 °. The angle thus defined (described by the longitudinal axis of the cooling channel with respect to the surface of the part) can thus be acute, straight or obtuse.

Several possible configurations obtained at the end of the application of a process as illustrated in FIG. 5, on the surface of a multi-perforated part, are shown in FIGS. 9 to 12.

In FIG. 9, the part 1 is made of superalloy, for example based on nickel or cobalt, like a superalloy AM 1, MC-NG, CMSX4 and derivatives, or René and derivatives. On the surface of this part, comprising before venting a vent 11, a coating layer 4 forming a thermal barrier has been deposited while the vent 11 has been blown. This allowed the integrity of the cooling channel 10 to be preserved, despite the application of layer 4: the cooling channel follows the path drawn by the flow of compressed air expelled during the deposition of the coating, and extends to the beyond the orifice 11 previously forming the vent, towards an orifice 11 ′ on the surface of the layer 4, forming a new vent in the channel 10. Here, there was no application of a bonding layer or functional layer in addition to the coating 4, the coating 4 forming a complete multifunctional thermal barrier system implemented entirely by thermal spraying.

In the embodiment illustrated in FIG. 10, the part 1 is also made of metal superalloy, and is coated with a bonding layer 3 before the deposition by thermal spraying of a layer 4 of thermal barrier ceramic. On the shape of the cooling channel 10 at the end of the process for treating the surface of the part 1, the result is similar, namely that a vent 11 ’is obtained in the extension of the previous vent 11.

On the system illustrated in FIG. 11, an additional functional layer 5 has been implemented in addition to the bonding layer 3 and the coating layer 4, the part 1 always being made of metallic superalloy. Again, a channel 10 leading to a vent 11 ’in the extension of the previous vent 11 is obtained.

The part 1 illustrated in FIG. 12 mainly consists of CMC - ceramic matrix compound. This part is coated with a coating layer 4 forming a complete environmental barrier system, capable of protecting the material constituting the part 1. Here again, the surface treatment process described above in relation to FIG. 5 makes it possible to preserve the shape of the channel 10 after depositing the coating by thermal spraying, a vent 11 ′ being obtained in the extension of the previous vent 11.

In addition to the guarantee, as indicated above, that the integrity and functionality of the internal cooling channels and the vents of the coated multi-perforated part are preserved, the cleaning step 700 of the process illustrated in FIG. 5 allows the elimination of unfounded fine particles generated by thermal spraying. In addition, the coated multi-perforated part is cooled, during projection, by the compressed air flow circulating in the cooling channels.

Expensive subsequent steps of drilling parts at the vents, or masking the vents during the application of the coating, are no longer necessary, which simplifies the production line of multi-perforated components.

Claims (12)

1. Method for treating a part (1) of an aircraft engine by applying a coating, the part comprising, within its internal volume, internal cooling channels (10) in which a gas can flow, each channel cooling system leading to a surface of the part at a vent (11), the method being characterized in that during a step (400) of deposition by thermal spraying of at least one coating layer (4) on the surface of the part, the gas is blown by the action of a tool (2) for distribution through each channel of a plurality of internal cooling channels (10) of the part, the gas being expelled through vents (11). 2. The coating treatment method according to claim 1, in which during the step (400) of deposition by thermal spraying, the gas is expelled through the vents against the current of the direction of deposition of coating particles on the surface. of the room. 3. A coating treatment method according to one of the preceding claims, in which the gas expelled through the vents is compressed air, or argon. 4. Coating treatment method according to one of the preceding claims, in which the step (400) of coating deposition (4) by thermal spraying is carried out according to a protocol taken from High Velocity Oxi-Fuel, plasma spraying of APS atmospheric pressure powders, the Plasma Suspension Spraying, the Precursor Plasma Spraying Solution, the High Velocity Suspension Flame Spray, plasma spraying under an inert IPS atmosphere. 5. A coating treatment method according to claim 1, comprising a preliminary step of chemical cleaning (101) and / or texturing (102) of the surface of the part to improve the grip of the coating layer. at the end of the process. 6. A coating treatment method according to one of the preceding claims, in which the coating layer (4) forms a thermal barrier, and comprises yttria zirconia or any other composition recognized for its thermal barrier properties. 7. Coating treatment method according to one of the preceding claims, in which the deposited coating layer (4) forms an environmental barrier, comprising a material taken from MoSÎ2, te BSAS (BaOi-x-SrO _x -Al2O3- 2SiO2), Mutlite (3 AI2O3-2 S1O2), mono- and di-silicates of rare earths, zirconia totally or partially stabilized, even doped, or any other composition recognized for its environmental barrier properties. 8. A method of treatment by coating according to one of the preceding claims, in which the thickness of all of the superposed deposited layers is between 10 μm and 1000 μm, preferably between 20 μm and 500 μm. 9. A coating treatment method according to claim 1, further comprising a step of depositing a thermal barrier layer by a technique not related to thermal spraying, for example evaporation under an electron beam. EB-PVD or a solution-gelling process, without blocking the vents. 10. Mechanical part (1) of a multi-perforated aircraft engine coated by thermal spraying according to a coating treatment method of one of the preceding claims, the mechanical part being traversed in its internal volume by a plurality of channels of internal cooling (10), said channels opening onto the surface of the part on vents (11). 11. Mechanical part of an aircraft engine according to claim 10, the material of the part being a ceramic matrix composite material (CMC), or being a superalloy based on Ni or Co, for example a superalloy AMI, MC- NG, CMSX4, René. 12. Mechanical part of an aircraft engine according to one of claims 10 or 11, taken from a high pressure turbine blade, a high pressure turbine distributor, a turbine ring, a combustion chamber element.