Composite material part

Abstract

Composite material part The present invention relates to a part (1) made of composite material comprising a fibrous reinforcement of ceramic or carbon wires (3), a ceramic matrix (5) and an interphase (7) covering the wires and located between the latter and the matrix, the part being characterized in that the interphase comprises a first layer (71) of amorphous boron nitride in contact with the wires and a second layer (72) of crystalline boron nitride covering the first layer. Figure for abstract: Fig. 1.

Description

Title of the invention: Composite material part Technical field

[0001] The present disclosure relates to a part made of a ceramic matrix composite material ("Ceramic Matrix Composite"; "CMC"), for example with a silicon carbide matrix, having improved damage tolerance, as well as associated manufacturing methods. Prior art

[0002] Ceramic matrix composite materials withstand temperatures ranging from 600°C to 1400°C. Due to their better resistance to high temperatures, CMCs require less cooling. This cooling traditionally comes from a sample in 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 manufactured by forming a silicon carbide pre-densification matrix in the porosity of a fiber preform, followed by introduction of silicon carbide particles and siliciding. This method makes it possible to obtain a fully dense Si-SiC matrix of high modulus and a composite with a high linearity limit. In the range mentioned, the wires are initially covered with an amorphous boron nitride interphase which acts as a mechanical fuse, mainly by means of a fiber / BN debonding allowing the consumption of cracking energy and the deflection of the matrix cracks to prevent them from reaching the fiber reinforcement.

[0004] However, the breaking behavior (elongation at break) of the parts obtained by this range can be variable, thus reducing the damage tolerance zone of the material. Statement of the invention

[0005] The present invention relates to a part made of composite material comprising a fibrous reinforcement of ceramic or carbon threads, a ceramic matrix and an interphase covering the threads and located between the latter and the matrix, the part being characterized in that the interphase comprises a first layer of amorphous boron nitride (BN) in contact with the threads and a second layer of crystalline boron nitride covering the first layer.

[0006] The inventors found that the observed variability in mechanical behavior was linked to the functioning of the interphase between the fibers and the matrix. The presence of an amorphous layer of BN in contact with the fibers makes it possible to obtain a strong bond on this interface, contributing to obtaining the desired mechanical properties for the part, thereby preventing debonding from starting too early and lowering the breaking stress level of the composite. The presence of the second layer makes it possible to reduce the risk of brittle fracture by reducing the strength of the fiber / matrix bond compared to the use of a completely amorphous BN interphase as in the prior art.The invention is thus remarkable in that it comprises a layer of crystalline BN which forms weaker bond interfaces and makes it possible to increase the potential for crack deflection before they reach the fiber reinforcement, thereby reducing the variability of the observed fracture behavior. BN also has the advantage of oxidizing to form a liquid oxide B2O3 which acts as a diffusion barrier to oxygen, preventing the surrounding atmosphere from affecting the fiber reinforcement.

[0007] In an example of the embodiment, the second layer of crystalline boron nitride has a local thickness of between 20 nm and 50 nm.

[0008] Such a characteristic advantageously makes it possible to further promote the deviation of cracks without overly complicating the manufacturing range since the layer of crystallized BN maintains a reduced thickness, associated with a limited deposition time.

[0009] In an exemplary embodiment, the second layer of crystalline boron nitride is located at a distance from the wires not exceeding 100 nm.

[0010] Such a characteristic is advantageous because the second layer of crystalline BN is not too far from the wires so that it allows the latter to be covered in a relatively unitary manner, and thus further increases the protection of the reinforcement against cracks.

[0011] In an exemplary embodiment, the first layer of amorphous boron nitride has a local thickness greater than or equal to 50 nm.

[0012] Such a feature makes it possible to further improve the protection of the fibers in the event of a crack at the second layer by ensuring the presence of a relatively thick layer of amorphous BN between the fibers and the second layer.

[0013] In an exemplary embodiment, the interphase further comprises a third layer of amorphous boron nitride covering the second layer and in contact with the matrix.

[0014] In this case, the crystalline BN layer is intercalated between the amorphous BN layers. This avoids any risk of debonding occurring at the interface. interphase / matrix and ensure that it occurs systematically in the crystalline BN layer.

[0015] In an exemplary embodiment, the fibrous reinforcement has a three-dimensional weave.

[0016] Such a characteristic makes it possible to further improve the mechanical properties of the part by using a non-delaminating reinforcement.

[0017] In an exemplary embodiment, the wires are made of silicon carbide and at least a portion of the matrix in contact with the interphase is made of silicon carbide.

[0018] The invention also relates to a method of manufacturing a part as described above, comprising: - coating the wires with the first, second and possibly third layers of the interphase by chemical vapor deposition, - the production of a fibrous preform forming the fibrous reinforcement of the part to be obtained from the yarns thus coated, comprising the formation of a fibrous blank by carrying out one or more textile operations, and the shaping of this blank, and - the formation of the matrix in the porosity of the fiber preform.

[0019] This case corresponds to a deposition of the interphase on the threads before formation of the fiber preform.

[0020] In particular, the coating of the wires by the interphase can be carried out while the latter are transported through a treatment chamber.

[0021] Alternatively, the invention relates to a method of manufacturing a part as described above, comprising: - the production of a fibrous preform forming the fibrous reinforcement of the part to be obtained, comprising the formation of a fibrous blank by implementing one or more textile operations, and the shaping of this blank, - the coating of the threads in the fiber preform thus produced by the first, second and possibly third layers of the interphase by chemical vapor infiltration, and - the formation of the matrix in the porosity of the fiber preform comprising the yarns thus coated.

[0022] This case corresponds to a deposition of the interphase in the porosity of the already formed fiber preform. Brief description of the drawings [Fig.l] [Fig.l] represents, schematically and partially, an example of a part made of composite material according to the invention. [Fig.2] [Fig.2] represents a succession of steps of a first example of the manufacturing process of the part of [Fig.l]. [Fig.3] [Fig.3] schematically and partially represents an example of a device for forming the interphase which can be used in the context of the method of [Fig.2], [Fig.4] [Fig.4] represents a succession of steps of a second example of the manufacturing process of the part of [Fig. 1]. Description of the embodiments

[0023] The invention is now described by means of figures, present for descriptive purposes to illustrate certain embodiments of the invention and which should not be interpreted as limiting the latter.

[0024] The part 1 illustrated in [Fig.l] comprises a fibrous reinforcement in ceramic or carbon threads 3, a ceramic matrix 5 which densifies the reinforcement and an interphase 7 interposed between the threads 3 and the matrix 5. An internal surface S71 of the interphase 7 is in contact with the threads 3, and an external surface S73, opposite the internal surface S71, is in contact with the matrix 5.

[0025] The wires 3 may be made of silicon carbide. Examples of usable silicon carbide wires may be wires marketed under the reference “Nicalon”, “Hi-Nicalon”, “Hi-Nicalon-S” or Tyranno SA3 from the company UBE Industries. The ceramic wires may have an oxygen content of less than or equal to 1% in atomic percentage. The “Hi-Nicalon-S” wires, for example, have such a characteristic.

[0026] Different textile operations can be implemented to form the reinforcement, as will be described below.

[0027] The interphase 7 has a weakening function and acts as a mechanical fuse by allowing cracks propagating in the direction of the wires 3 to be deflected and thus improves the lifetime of the material. The interphase 7 has, in the invention, a multilayer structure and comprises a first layer 71 of amorphous boron nitride in contact with the wires 3 (defining the internal surface S71) and a second layer 72 of crystalline boron nitride covering the first layer 71 here in contact with the latter. The illustrated example further comprises a third layer 73 of amorphous boron nitride covering the second layer 72 here in contact with the latter and in contact with the matrix 5 (defining the external surface S73 here). The second layer 72 is here interposed between the first 71 and third 73 layers. The second layer 72 introduces a microstructure heterogeneity (crystalline BN) compared to the rest of the interphase which is amorphous.This singular zone constitutes the mechanical fuse. Generally speaking, the amorphous or crystalline character of boron nitride can be demonstrated, in the composite, by scanning electron microscopy (SEM) or transmission electron microscopy (TEM) using . techniques known to those skilled in the art. X-ray diffraction can also be used to assess whether a layer of BN deposited in isolation (not part of a composite material) is amorphous or crystalline. The amorphous or crystalline nature of boron nitride is, for example, determined based on the coherence length. A coherence length of 3 nm or less indicates an amorphous boron nitride, while a coherence length of more than 3 nm indicates a crystalline boron nitride.

[0028] The local thickness e71 of the first layer 71 may be greater than or equal to 25 nm, for example between 25 nm and 500 nm, preferably between 50 nm and 150 nm. The local thickness e72 of the second layer 72 may be greater than or equal to 20 nm or less than or equal to 50 nm and for example between 20 nm and 50 nm. The second layer 72 may be located at a distance d from the wires 3 less than or equal to 100 nm, for example between 50 nm and 100 nm. The local thickness e73 of the third layer 73 may be greater than or equal to 25 nm, for example between 25 nm and 500 nm, preferably between 50 nm and 150 nm. Generally speaking, the local thickness of the interphase layers or the distances between the constituents of the part can be measured by scanning electron microscopy (SEM) or transmission electron microscopy (TEM) using techniques known to those skilled in the art.Vapor deposition techniques (chemical vapor deposition or chemical vapor infiltration) allow a layer of uniform thickness to be obtained over a cross-section of a wire. Unless otherwise stated, the cross-section of a wire is taken perpendicular to its length. The local thickness values ​​described above can be verified on at least one cross-section of all or part of the wires.

[0029] According to a possible example, the matrix 5 may comprise a first part made of silicon carbide in contact with the interphase, here in contact with the third layer 73, and a second part covering this third part in Si-SiC resulting from siliciding.

[0030] An example of a possible structure for a part 1 according to the invention has just been described. The following provides details relating to the manufacture thereof. Figures 2 and 3 which will now be described concern the case where the preform is obtained after formation of the interphase 7 on the wires 3.

[0031] In the example of [Fig.2], we can successively carry out: - the coating of the wires 3 by the first 71, second 72 and third 73 layers of the interphase 7 by chemical vapor deposition (“CVD”), this coating being carried out while the wires 3 are continuously transported through a treatment chamber (step E10), - the production of a fibrous preform forming the fibrous reinforcement of the part to be obtained from the yarns thus coated, comprising the formation of a fibrous blank by implementing one or more textile operations, and the shaping of this blank (step E20), and - the formation of the matrix in the porosity of the fiber preform (step E30).

[0032] [Fig. 3] illustrates the formation of the interphase layers on the wires continuously transported in a treatment chamber (step E10). This embodiment can be implemented using techniques known per se and reference can for example be made to document FR 3 044 022. A brief description of an example of a device 100 suitable for forming the interphase 7 on the wires 3 is presented below with reference to [Fig. 3].

[0033] The device 100 comprises a treatment chamber 4 in which a plurality of wires 3 are transported by being driven by a conveying system, here comprising pulleys 6. The chamber 4 forms three treatment zones 41, 42 and 43 in which the wires 3 pass successively to form each of the layers 71, 72 and 73. A precursor mixture IP of BN is introduced into each of the zones 41-43, and is evacuated as materialized by the arrows EP. Conditions for forming amorphous BN or crystalline BN are known per se. A mixture of BC13 and NH3 can be introduced into each of the zones 41-43. However, the temperature imposed in the zones 41 and 43 can be different from that in the zone 42 in order to obtain in the latter a layer of crystalline BN. Thus, a temperature between 700°C and 900°C and a pressure between 0.1 kPa and 0.9 kPa can be imposed in zones 41 and 43 in order to form the amorphous BN layers.A temperature greater than or equal to 1150°C, for example between 1150°C and 1450°C, and a pressure between 0.1 kPa and 0.9 kPa may be imposed in zone 42 in order to form the layer of crystalline BN.

[0034] Once the yarns 3 are coated with the interphase 7, a fiber blank can be obtained by three-dimensional weaving, that is to say a weaving method by which at least some of the warp yarns bind weft yarns over several weft layers. The three-dimensional weaving can for example be an “interlock” weave, that is to say a weave in which each layer of warp yarns binds a plurality of layers of weft yarns, with all the yarns of the same warp column having the same movement in the plane of the weave. The roles of the warps and wefts can be reversed, and this inversion must also be considered to be covered by the claims. The use of other types of 3D weaving does not, of course, depart from the scope of the invention. Various suitable weaving techniques are described in WO 2006 / 136755.It is also possible to start from fibrous textures such as two-dimensional fabrics or unidirectional sheets, and obtain the . reinforcement by draping such fibrous textures over a shape. These textures can optionally be linked together, for example by sewing or implantation of threads to form the reinforcement.

[0035] The blank is then shaped in a shaping tool in a manner known per se, so as to obtain the fiber preform which has substantially the shape and dimensions of the part to be obtained.

[0036] A ceramic matrix is ​​then formed in the porosity of the fiber preform thus obtained (step E30). The formation of the matrix uses techniques known per se.

[0037] The preform may first be consolidated in the shaping tool by depositing a consolidation matrix phase on the interphase 7. This deposition may be carried out by chemical vapor infiltration. The consolidation phase may be made of silicon carbide. The consolidation phase here corresponds to the part of the matrix 5 illustrated in [Fig.l]. The thickness of the consolidation phase is sufficient to consolidate the fiber preform, i.e. to bind the wires together sufficiently to allow the preform to be handled while retaining its shape without the assistance of holding tooling.

[0038] The consolidated preform can then be removed from its shaping tool and a silicon carbide pre-densification matrix can be deposited on the consolidation phase, for example by chemical vapor infiltration.

[0039] After formation of the pre-densification matrix, a slip can be introduced into the residual porosity of the preform which comprises silicon carbide particles, possibly with added carbon particles, and then infiltration can be carried out with silicon or a silicon alloy in the molten state in order to obtain a Si-SiC matrix phase. The Si-SiC matrix phase forms a densification matrix which covers, here in contact with, the pre-densification matrix.

[0040] An example of a possible range for manufacturing the matrix has just been described, but the person skilled in the art will recognize that variations are possible without departing from the scope of the invention. For example, the matrix may be formed in whole or in part by a polymer infiltration and pyrolysis technique (“Polymer Infiltration and Pyrolysis”; “PIP”), or entirely by chemical vapor infiltration.

[0041] [Fig.4] illustrates a variant of manufacturing the composite material part of [Fig.l] in which the fiber preform is first formed in a similar manner to that described above (step E200), then in which the interphase 7 is formed in the porosity of the already produced fiber preform using the same deposition conditions as that described above except that the preform is not in motion during deposition (step E100). A ceramic matrix is ​​then formed on the interphase as described above (step E300).

[0042] Generally, the part 1 may be an aircraft engine turbine part. For example, the part 1 may be a turbine ring or a turbine ring sector, a moving blade, a fixed blade, a combustion chamber wall, a distributor or a part of a distributor.

[0043] The above description describes an interphase 7 with three layers 71-73 but it is not outside the scope of the invention if the interphase comprises more layers, for example with several layers of crystalline BN alternating with layers of amorphous BN. According to a variant not illustrated, the interphase is two-layer and comprises only the first layer of amorphous boron nitride in contact with the wires and the second layer of crystalline boron nitride covering the first layer. In this case, the second layer is in contact with the first layer and may be in contact with the matrix.

[0044] The expression “between ... and ...” must be understood as including the limits.

Claims

Claims

1. Part (1) made of composite material comprising a fibrous reinforcement of ceramic or carbon wires (3), a ceramic matrix (5) and an interphase (7) covering the wires and located between the latter and the matrix, the part being characterized in that the interphase comprises a first layer (71) of amorphous boron nitride in contact with the wires and a second layer (72) of crystalline boron nitride covering the first layer, in which the interphase further comprises a third layer (73) of amorphous boron nitride having a coherence length less than or equal to 3 nm covering the second layer and in contact with the matrix.

2. Part (1) according to claim 1, in which the second layer (72) of crystalline boron nitride has a local thickness (e72) of between 20 nm and 50 nm.

3. Part (1) according to claim 1 or 2, wherein the second layer (72) of crystalline boron nitride is located at a distance (d) from the wires (3) not exceeding 100 nm.

4. Part (1) according to any one of claims 1 to 3, in which the first layer (71) of amorphous boron nitride has a local thickness (e71) greater than or equal to 50 nm.

5. Part (1) according to any one of claims 1 to 4, in which the fibrous reinforcement has a three-dimensional weave.

6. Part (1) according to any one of claims 1 to 5, in which the wires (3) are made of silicon carbide and at least a part of the matrix (5) in contact with the interphase is made of silicon carbide.

7. A method of manufacturing a part (1) according to any one of claims 1 to 6, comprising: - the coating (E10) of the threads (3) with the first (71), second (72) and possibly third (73) layers of the interphase (7) by chemical vapor deposition, - the production of a fiber preform (E20) forming the fiber reinforcement of the part to be obtained from the threads thus coated comprising the formation of a fiber blank by carrying out one or more textile operations, and the shaping of this blank, and

8.

9. - the formation of the matrix (E30) in the porosity of the fiber preform. Method according to claim 7, in which the coating of the wires (3) by the interphase (7) is carried out while the latter are transported through a treatment chamber (4). Method of manufacturing a part (1) according to any one of claims 1 to 6, comprising: - the production of a fibrous preform (E200) forming the fibrous reinforcement of the part to be obtained, comprising the formation of a fibrous blank by implementing one or more textile operations, and the shaping of this blank, - the coating (E100) of the threads (3) in the fibrous preform thus produced by the first (71), second (72) and possibly third (73) layers of the interphase (7) by chemical vapor infiltration, and - the formation of the matrix (5) in the porosity of the fibrous preform comprising the yarns thus coated.

Images