Repair of parts made of ceramic matrix composite material

Abstract

Repair of parts made of ceramic matrix composite material. A method for repairing a part (11) made of ceramic matrix composite material (100) comprising a fibrous reinforcement of refractory fibers densified by a matrix comprising at least one ceramic material. The method comprises removing the composite material (100) from a damaged area of ​​the part so as to form a hollowed portion. It further comprises: - the deposition of one or more repair strips (40) in the hollowed portion, each repair strip comprising at least one silicon powder, one powder of a ceramic material identical to said at least one ceramic material of the matrix, and a binder; and - heating the deposited repair strip(s) (40) to a temperature above the melting point of silicon. Figure for the abstract: Fig. 5.

Description

Title of the invention: Repair of parts made of ceramic matrix composite material Technical field

[0001] The invention relates to the repair of parts made of ceramic matrix composite (CMC) material, i.e. comprising a fibrous reinforcement densified by a matrix at least partially made of ceramic. Prior art

[0002] Ceramic matrix materials (CMC) have good mechanical properties making them suitable for forming structural elements and advantageously retain these properties at high temperatures. Due to their better resistance to high temperatures, CMCs require less cooling. In the field of aeronautical engines, cooling is traditionally provided by a sample from the compressor which impacts the efficiency of the turbomachine. CMC materials therefore make it possible to improve engine efficiency, which reduces fuel consumption. Furthermore, their use contributes to optimizing the performance of turbomachines, in particular by reducing the overall mass of the turbomachine, which further contributes to a reduction in fuel consumption and therefore to a significant reduction in pollutant emissions.

[0003] CMC parts can be damaged following shock or impact. This is the case, for example, of turbine or rectifier blades of aeronautical engines which are subjected in service to impacts with foreign objects such as birds or any debris.

[0004] The damaged area must be repaired before the part can be returned to service.

[0005] Document US 2013 / 022471 discloses a method of repairing a blade of CMC turbine which involves filling a cavity in the blade with a ceramic paste comprising a ceramic powder and a binder, heating the paste to remove the binder and form a porous ceramic material, and then infiltrating the porous ceramic material with a molten ceramic material. However, this process is relatively complex to implement because it requires a first step of filling the cavity with a ceramic paste and a second step of infiltration with a molten ceramic material. These two steps also involve heating the blade to be repaired twice: once to remove the binder and again during infiltration with the molten ceramic material. Statement of the invention

[0006] The invention aims to propose a solution for the repair of parts in ceramic matrix composite material that is both reliable and easy to implement.

[0007] This aim is achieved by means of a method for repairing a part made of ceramic matrix composite material comprising a fibrous reinforcement made of refractory fibers densified by a matrix comprising at least one ceramic material, the method comprising the removal of the composite material at a damaged area on the part so as to form a hollowed-out portion, the method being characterized in that it further comprises:

[0008] - depositing one or more repair strips in the hollowed-out portion, each repair tape comprising at least one silicon powder, a powder of a ceramic material identical to said at least one ceramic material of the matrix and a binder, and

[0009] - heating the deposited repair strip(s) to a temperature su above the melting temperature of silicon.

[0010] The use of silicon powder in the repair strip(s) makes it possible to increase the mechanical strength of the repair. In fact, the melting of the silicon powder makes it possible to braze the ceramic particles to the composite material of the part to be repaired. This ensures good cohesion between the repair material and the composite material of the part.

[0011] Furthermore, a single heating step is sufficient to remove the binder and melt the silicon. The thermal exposure of the part to be repaired is therefore limited.

[0012] According to a particular characteristic of the repair method of the invention, the deposited repair strip(s) are heated by means of a laser beam. This produces local heating of the repair strip(s) without subjecting the entire part to high temperatures.

[0013] According to another particular characteristic of the repair method of the invention, the repair strip(s) are bonded by thermocompression. This ensures that each repair strip is held in position in the hollowed-out portion.

[0014] According to another particular characteristic of the repair method of the invention, each repair strip contains between 10% and 25% by volume of silicon powder.

[0015] According to another particular characteristic of the repair method of the invention, each repair strip contains between 10% and 25% by volume of ceramic material powder.

[0016] According to a particular characteristic of the repair method of the invention, the total powder content is between 20% and 50% by volume of powder and preferably between 25% and 40%.

[0017] According to another particular characteristic of the repair method of the invention, each repair strip further comprises short refractory fibers continuous materials such as silicon carbide or SiC or alumina. This increases the structural character of the repair material.

[0018] According to another particular characteristic of the repair method of the invention, each repair strip further comprises a plasticizer. A plasticizer facilitates the formation of the repair strip and gives it properties which are particularly useful for its implementation (flexibility for handling).

[0019] According to another particular characteristic of the repair method of the invention, each repair strip further comprises a carbon powder. The carbon reacts with the silicon powder to form SiC and increase the SiC content in the repaired area.

[0020] According to another particular characteristic of the repair method of the invention, the ceramic material of the powder is made of silicon carbide or SiC. When each repair strip comprises a carbon powder, the increase in the SiC content in the repaired area to the detriment of the free silicon therefore makes it possible to bring the composition of the repaired area closer to that of the ceramic matrix of the part.

[0021] According to another particular characteristic of the repair method of the invention, each repair strip further comprises a boron powder. The addition of boron makes it possible to limit the reactivity of the silicon present in the repair strip with the repaired ceramic matrix composite material. Brief description of the drawings

[0022] Other characteristics and advantages of the invention will emerge from the following description of particular embodiments of the invention, given as non-limiting examples, with reference to the appended drawings, in which:

[0023] [Fig-1] [Fig.l] is a schematic perspective view of a turbine blade presenting a damaged area,

[0024] [Fig.2] [Fig.2] is a partial sectional view of the blade of [Fig.l] along section plane II,

[0025] [Fig.3] [Fig.3] shows the blade portion of [Fig.2] after preparation of the damaged area,

[0026] [Fig.4] [Fig.4] shows the blade portion of [Fig.3] after deposition of several repair strips,

[0027] [Fig.5] [Fig.5] shows the heating of the repair strips deposited in the blade portion of [Fig.3],

[0028] [Fig.6] [Fig.6] shows the blade portion of [Fig.5] after melting of the silicon powder present in the repair strips. Description of the embodiments

[0029] The invention applies generally to any part made of composite material with ceramic matrix (CMC), i.e. comprising a fibrous reinforcement made for example with refractory fibers, such as carbon or ceramic fibers and densified by a matrix comprising at least one ceramic material which may in particular be silicon carbide or SiC, silicon nitride or Si3N4, or alumina or A12O3.

[0030] The invention will be described below in the context of its application to the repair of a turbine blade of an aeronautical gas turbine engine made of SiC / SiC composite material.

[0031] [Fig. 1] shows a turbine blade 11 which is here made of SiC / SiC composite material. In a well-known manner, parts made of SiC / SiC material are formed by a fibrous reinforcement of silicon carbide (SiC) fibers which is densified by a matrix at least partially made of SiC.

[0032] The blade is manufactured from a fibrous structure intended to form the fibrous reinforcement of the blade which is here produced with high-performance SiC fibers such as the fibers supplied by the Japanese company Nippon Carbon under the reference “Hi-Nicalon®” or, preferably, under the reference “Hi-Nicalon Type-S®” having a high elastic elongation limit.

[0033] The fibrous structure is preferably obtained by three-dimensional weaving or by multi-layer weaving.

[0034] By "three-dimensional weaving" or "3D weaving" is meant here a weaving method by which at least some of the warp threads bind weft threads over several weft layers, such as for example an "interlock weave". By "interlock weave" is meant here a 3D weave weave in which each warp layer binds several weft layers with all the threads of the same warp column having the same movement in the plane of the weave.

[0035] By "multi-layer weave" is meant here a 3D weave with several weft layers whose basic weave of each layer is equivalent to a conventional 2D fabric weave, such as a plain, satin or twill weave, but with certain points of the weave which bind the weft layers together.

[0036] The production of the fibrous structure by 3D or multi-layer weaving makes it possible to obtain a connection between the layers, and therefore to have good mechanical strength of the fibrous structure and of the composite material part obtained, in a single textile operation. A detailed example of production of a fibrous preform intended to form the fibrous reinforcement of a blade for an aeronautical engine from a 3D woven fibrous blank is notably described in detail in documents US 7,101,154, US 7,241,112 and WO 2010 / 061140.

[0037] The fibrous structure can also be produced by stacking two-dimensional layers or folds of SiC fibers.

[0038] The fibrous structure is shaped and maintained in its shape by means of a shaping tool, to obtain a fibrous preform having a shape close to that of the part to be manufactured. Examples of shaping fibrous preforms from a fibrous structure can be found in particular in patent application US 2011 / 0293828.

[0039] The preform being held in its shaping tool, for example in graphite, a weakening interphase is formed in a known manner by chemical vapor infiltration or CVI on the fibers of the preform, this interphase being in particular based on boron nitride (BN). The thickness of the interphase is preferably between 10 nm and 1000 nm.

[0040] A predensification of the fiber preform is then carried out comprising the formation of a first matrix phase by chemical gas infiltration (CVI) with a first SiC precursor.

[0041] A slip loaded with a powder of solid SiC fillers is then injected into the fiber preform to fractionate its internal porosity (“Slurry Cast”),

[0042] The densification of the preform is completed by infiltration of the latter with molten silicon or an alloy thereof so as to form a ceramic matrix, a densification process known under the designation MI process ("Melt Infiltration").

[0043] The turbine blade 11 comprises a blade 110 extending in the longitudinal direction and a root 111 formed by a part of greater thickness, for example with a bulb-shaped section connected by a stilt 112 to the blade 110. The blade 11 is mounted on a turbine rotor (not shown in [Fig. 1]) by engagement of the root 111 in a housing of corresponding shape arranged on the periphery of the rotor.

[0044] In Figures 1 and 2, the blade 11 has a damaged area 20 resulting for example from an impact with an object ingested by the engine or from debris coming from a part of the engine.

[0045] In [Fig. 2] and in the example described here, the blade 11 comprises a SiC / SiC material 100 defining the general shape of the blade and in particular its volume. The composite material here comprises a coating 101 such as for example an environmental barrier type protective coating (also called “EBC” from the English “Environmental Barrier Coating”) to protect the SiC / SiC material 100 from corrosion at high temperature.

[0046] The repair of the blade 11 begins by machining, for example by abrasion, the blade at the damaged area 20 in order to remove the affected composite material. The removal of the composite material is carried out over a determined surface and depth of the blade in the area identified as damaged.

[0047] We thus obtain, as illustrated in [Fig.3], a hollowed-out portion 30 which opens out on the outer surface of the blade 11.

[0048] According to the invention, one or more repair strips 40 are deposited in the hollowed-out portion 30. In the example described here in [Fig. 4], several repair strips 40 are deposited in order to fill the hollowed-out portion 30.

[0049] Each repair strip 40 comprises at least one silicon powder, one powder of a ceramic material identical to that of the ceramic material present in the matrix of the material of the part, here silicon carbide and a binder.

[0050] Each repair strip can be prepared by a tape casting technique, notably known as "tape casting" in English. Such a principle is relatively simple and consists of a slip being deposited on a support by passing a shoe.

[0051] An adjustment of a thickness of the deposit is ensured by a system consisting of two blades. To produce a repair strip according to the invention, a slip comprising at least one silicon powder, a powder of a ceramic material identical to that of the ceramic material present in the matrix of the material of the part, a binder and an organic solvent is used.

[0052] A sheet of slip is thus deposited and then dried in order to remove the solvent, thus making it possible to obtain a repair strip.

[0053] Each repair strip has a thickness of between 0.1 mm and 1 mm and preferably between 0.2 mm and 0.6 mm.

[0054] Each strip contains between 10% and 25% by volume of silicon powder and between 10% and 25% by volume of powder of ceramic material identical to that of the ceramic material present in the matrix of the material of the part, in the example described here SiC, the remainder of the strip being composed of the binder and, where appropriate, a plasticizer when the strip does not comprise other elements. In the presence of the plasticizer, the binder / plasticizer mass ratio is preferably between 0.4 and 0.6.

[0055] The silicon powder is micronic with an average particle size of between 1 pm and 10 pm and preferably between 1 pm and 5 pm.

[0056] The powder of ceramic material identical to that of the ceramic material present in the matrix of the material of the part, in the example described here the SiC powder, is micronic with an average particle size of between 1 pm and 10 pm and preferably between 1 pm and 5 pm.

[0057] The binder can be chosen from one of the following organic binders: PVA, Degalon 920 (acrylic polymer), Polyvinylbutyral (PVB), glycerol, Polyvinylpyrolidone (PVP).

[0058] The plasticizer may in particular be polyethylene glycol or PEG, produced from phthalates such as Dibutylphthalate for example).

[0059] In the example described here, the repair strips 40 are made up of:

[0060] - 20% by volume of SiC powder,

[0061] - 15% by volume of Si powder,

[0062] - 65% by volume of binder and plasticizer with a binder / plasticizer mass ratio of 0.5.

[0063] The repair strip(s) according to the invention may further comprise one or more of the following elements or compounds:

[0064] - refractory fibers, for example of SiC or alumina, short discontinuous having a size between 100 pm and 1000 pm and made of a material preferably identical to the material of the fibers of the part to be repaired, these short fibers making it possible to increase the structural character of the repair, these fibers preferably being of the same nature as that of the fibers of the fibrous reinforcement of the part to be repaired,

[0065] - a carbon powder,

[0066] - a boron powder.

[0067] The repair strip(s) may be deposited in the recessed area by thermocompression, for example via a heating press or an autoclave. This makes it possible to bond and, consequently, to hold in position the strip deposited on the surface of the recessed portion or on an underlying repair strip.

[0068] Once the repair strip(s) 40 have been deposited in the hollowed-out portion 30, a heat treatment of the strip(s) is carried out at a temperature higher than the melting temperature of silicon, namely at a temperature higher than 1400°C. The heating of the repair strip(s) is preferably local heating. For this purpose, the repair strip(s) may be heated by means of a laser beam 61 emitted by a laser 60 as illustrated in [Fig. 5].

[0069] Heating the repair strip(s) to a temperature above the melting temperature of silicon allows the removal of the binder and plasticizer present in each repair strip and the melting of the silicon particles present in each repair strip to be carried out in a single step. Thanks to the melting of the silicon particles, good cohesion is ensured between the deposited repair material and the composite material of the part to be repaired. The integrity of the repaired part can thus be preserved.

[0070] The part to be repaired provided with the repair strip(s) can also be heated in a furnace to a temperature above the melting temperature of silicon (1410°C).

[0071] After the heating step and as shown in [Fig.6], a repair portion 50 is obtained comprising at least one ceramic material identical to that of the matrix of the part, in the example described here SiC, and silicon.

[0072] In the case where the repair strip(s) further comprise discontinuous short refractory fibers, the repair portion further comprises a reinforcement fibrous material made up of these fibers which improves the structural character of the repair.

[0073] In the example described here, the composite material 100 of the blade 11 to be repaired comprises a coating 101 which has been removed from the area to be repaired. In this case, after obtaining the repair portion 50, a new coating deposit is made above the repair portion to restore the continuity of the coating 101 on the surface of the blade ([Fig.6]).

[0074] In a non-limiting manner, the invention advantageously applies to the repair of turbine moving blades, outlet guide vanes (OGV) and turbine ring sectors of gas turbine engines.

Claims

Claims

1. A method of repairing a part (11) made of ceramic matrix composite material (100) comprising a fibrous reinforcement of refractory fibers densified by a matrix comprising at least one ceramic material, the method comprising removing the composite material (100) at a damaged area (20) on the part so as to form a hollowed-out portion (30), the method being characterized in that it further comprises: - depositing one or more repair strips (40) in the hollowed-out portion (30), each repair strip comprising at least one silicon powder, a powder of a ceramic material identical to said at least one ceramic material of the matrix and a binder, and - heating the deposited repair strip(s) (40) to a temperature above the melting temperature of silicon.

2. A method according to claim 1, wherein, in the heating step, the deposited repair strip(s) (40) are heated by means of a laser beam (61).

3. Method according to claim 1 or 2, in which, during the deposition step, the repair strip(s) (40) are bonded by thermocompression.

4. A method according to any one of claims 1 to 3, wherein each repair strip (40) contains between 10% and 25% by volume of silicon powder.

5. A method according to any one of claims 1 to 4, wherein each repair strip (40) contains between 10% and 25% by volume of ceramic material powder.

6. A method according to any one of claims 1 to 5, wherein each repair strip (40) further comprises short discontinuous refractory fibers.

7. A method according to any one of claims 1 to 6, wherein each repair strip (40) further comprises a plasticizer.

8. A method according to any one of claims 1 to 7, wherein each repair strip (40) further comprises a carbon powder.

9. A method according to any one of claims 1 to 8, wherein the ceramic material of the powder is silicon carbide.

10. A method according to any one of claims 1 to 9, wherein each repair strip (40) further comprises a boron powder.

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