Method for manufacturing a part made of composite material

Abstract

The invention relates to a method for manufacturing a part (PA) made of a ceramic matrix composite material, the method comprising: - obtaining a fibre preform of the part to be obtained, the preform comprising ceramic or carbon yarns (3) coated with an interphase comprising at least one layer (71) made of boron nitride; - heat treating the at least one layer of boron nitride, after obtaining the preform, by applying a treatment temperature of between 1050°C and 1250°C for a treatment period of between 0.25 hours and 5 hours; and - densifying the preform, after the heat treatment, with the ceramic matrix (5). Drawing_references_to_be_translated

Description

Description Title of the invention: Method for manufacturing a part made of composite material Technical Field

[0001] The present disclosure relates to a method of manufacturing a part made of a ceramic matrix composite material ("Ceramic Matrix Composite"; "CMC"), for example a silicon carbide matrix, having improved damage tolerance. 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. Since this cooling traditionally comes from a tap in the compressor, which impacts the efficiency of the turbomachine, CMC materials therefore improve engine efficiency, which reduces fuel consumption. Furthermore, their use contributes to optimizing the performance of turbomachines, particularly 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 the 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 (BN) 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 matrix cracks to prevent them from reaching the fiber reinforcement. In particular, FR 2 995 892 is known which discloses the performance of a heat treatment of i stabilization of the boron nitride of the interphase at a temperature above 1300°C and at least equal to the maximum temperature encountered thereafter until densification is complete. This treatment freezes the structure of the boron nitride and limits its reactivity with ambient air. This treatment is also likely to strengthen the bond with the fiber and densify the coating.

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

[0005] The present invention relates, according to a first embodiment, to a method for manufacturing a part made of ceramic matrix composite material, comprising: - obtaining a fibrous preform of the part to be obtained comprising ceramic or carbon wires coated with an interphase comprising at least one layer of boron nitride, - a heat treatment of said at least one layer of boron nitride, after obtaining the preform, by applying a treatment temperature of between 1050°C and 1250°C for a treatment time of between 0.25 hours and 5 hours, and - densification of the preform, after heat treatment, by the ceramic matrix.

[0006] This case corresponds to a heat treatment carried out on the already formed fiber preform and whose wires are coated with the boron nitride interphase.

[0007] The present invention relates, according to a second embodiment, to a method for manufacturing a part made of ceramic matrix composite material, comprising: - obtaining ceramic or carbon wires coated with an interphase comprising at least one layer of boron nitride, - a heat treatment of said at least one layer of boron nitride on the wires by applying a treatment temperature of between 1050°C and 1250°C for a treatment time of between 0.25 hours and 5 hours, - the production of a fibrous preform of the part to be obtained from the yarns thus coated, after the heat treatment, comprising the formation of a fibrous blank by carrying out one or more textile operations, and the shaping of this blank, and - the densification of the preform thus produced by the ceramic matrix.

[0008] This case corresponds to a heat treatment carried out at the wire stage, before formation of the fiber preform.

[0009] The inventors found that the observed variability in mechanical behavior was linked to the functioning of the interphase between the fibers and the matrix. In the first and second embodiments described above, the heat treatment implemented makes it possible to promote intra-BN cracking and no longer at the fiber / BN interface as usual. The invention is remarkable for the use of this heat treatment which makes it possible to reduce the fiber / matrix interfacial bond strength and makes it possible to increase the potential for crack deflection before they reach the fiber reinforcement, which makes it possible to reduce the observed variability in fracture behavior.This heat treatment, carried out under controlled conditions of time and temperature, allows fine control of the strength of the fiber / matrix bond while maintaining a sufficiently strong bond that contributes to obtaining the desired mechanical properties for the part, thus preventing debonding from starting too early and lowering the level of breaking stress of the composite, while being sufficiently low to reduce the risk of brittle fracture. The moderate heat treatment makes it possible to accommodate the chemical bond energy between the BN layer and the matrix layer that then covers it; these benefits are retained even if a higher temperature is used in the rest of the densification process.It may nevertheless be preferable to apply a temperature not exceeding the treatment temperature at least during the formation of the portion of the ceramic matrix located on the side, for example in contact, of said at least one layer of boron nitride.

[0010] 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.

[0011] In an exemplary embodiment, the treatment temperature is between 1150°C and 1250°C.

[0012] Such a treatment temperature makes it possible to further improve the fracture behavior of the part.

[0013] In an exemplary embodiment, the processing time is between 1 hour and 2 hours.

[0014] Such a feature helps to further improve the breaking behavior of the part while controlling the duration of the manufacturing cycle.

[0015] In an exemplary embodiment, the interphase comprises a first and a second boron nitride layer, the second layer covering the first layer, and wherein: - heat treatment is carried out after the formation of the first and second layers, and - a preliminary stabilization heat treatment is carried out after the formation of the first layer and before the formation of the second layer by imposing a temperature greater than 1300°C and at least equal to the maximum temperature encountered subsequently until completion of the densification of the preform by the matrix for a period of between 0.25 hours and 5 hours.

[0016] Such a characteristic corresponds to a multi-layer interphase architecture in which the first layer, located between the fibers and the second layer, has undergone a stabilization heat treatment in accordance with FR 2 995 892, and the second layer has undergone the fiber / matrix bond modulation heat treatment described above. In this case, the cracks are located in the second BN layer, with preservation of the first BN layer around the fiber so as to further improve the protection of the fibers.

[0017] In one exemplary embodiment, the densification comprises at least the formation, by chemical vapor infiltration, of a silicon carbide matrix phase covering said at least one boron nitride layer.

[0018] Such a characteristic advantageously makes it possible to protect the boron nitride from oxidation in air by the silicon carbide of the matrix.

[0019] In particular, densification may further include: - the introduction of silicon carbide particles, possibly with added carbon particles, into the residual porosity of the preform densified by the silicon carbide matrix phase, and - the formation of a second Si-SiC matrix phase covering the silicon carbide matrix phase by infiltration of silicon or a silicon alloy after introduction of the particles.

[0020] Such a characteristic advantageously makes it possible to obtain a totally dense Si-SiC matrix of high modulus and a composite with a high linearity limit.

[0021] In an exemplary embodiment, the fiber preform has a three-dimensional weave.

[0022] Such a feature allows to further improve the mechanical properties of the part by using a non-delaminating reinforcement.

[0023] In one exemplary embodiment, the wires are made of silicon carbide and at least a portion of the matrix is ​​made of silicon carbide. Brief description of the drawings [Fig. 1] Figure 1 represents a succession of steps of a method for manufacturing a part made of ceramic matrix composite material according to the first embodiment of the invention. [Fig. 2] Figure 2 represents, schematically and partially, a comparison of the propagation of cracks between an architecture obtained by implementing the invention and an architecture obtained by implementing a technique outside the invention. [Fig. 3] Figure 3 represents, schematically and partially, an architectural variant that can be obtained by implementing the invention. [Fig. 4] Figure 4 represents a succession of steps of a method of manufacturing a part in ceramic matrix composite material according to the second embodiment of the invention. [Fig. 5] Figure 5 is a test result comparing the performance of parts obtained within the framework of the invention with those of parts obtained by techniques outside the invention. Description of the embodiments

[0024] 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.

[0025] Figure 1 corresponds to a succession of possible steps in the context of the first embodiment where the heat treatment is carried out after production of the fiber preform.

[0026] A fiber preform comprising ceramic or carbon wires coated with an interphase comprising at least one layer of boron nitride can be obtained in different ways, in accordance with the alternative steps E10 and E11 which will be described. The fiber preform is intended to form the reinforcement of the part to be obtained.

[0027] In step E10 the fiber preform is first formed and then the interphase is formed in the porosity thereof.

[0028] The preform is produced by techniques known per se by forming a fiber blank by carrying out one or more textile operations, followed by shaping this blank. According to one example, the fiber blank can be obtained by three-dimensional weaving, that is to say a weaving method by which at least some of the warp threads bind weft threads on several weft layers. The three-dimensional weaving can for example be with an “interlock” weave, that is to say a weave in which each layer of warp threads binds a plurality of layers of weft threads, with all the threads 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 fiber textures such as two-dimensional fabrics or unidirectional webs, and to obtain the blank by draping such fiber textures on. a shape. These textures can possibly be linked together, for example by sewing or implantation of threads to form the rough outline.

[0029] The wires 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 UBE Industries. Ceramic wires may have an oxygen content of less than or equal to 1% in atomic percentage. "Hi-Nicalon-S" wires, for example, have such a characteristic.

[0030] The blank is then shaped in a shaping tool in a manner known per se, so as to obtain the fiber preform which substantially has the shape and dimensions of the part to be obtained.

[0031] After formation of the preform, the wires of the latter may be coated with an interphase comprising at least one layer of boron nitride, using techniques known per se. Generally, the layer or layers of boron nitride of the interphase may be formed by chemical vapor infiltration from a mixture of BCh and NH3, by imposing a temperature less than or equal to 800°C, for example between 650°C and 800°C, and a pressure less than or equal to 5 kPa, for example between 0.2 kPa and 5 kPa.

[0032] In step E11, the interphase is first formed on the wires and then the fiber preform is obtained in the same way as described above. In this case, the coating of the wires with the interphase can be carried out by chemical vapor deposition (“CVD”), for example with continuous transport of the wires through a treatment chamber. This can be carried out using techniques known per se and reference can be made, for example, to document FR 3 044 022. The conditions in terms of precursor, pressure and temperature for depositing the boron nitride remain as described above.

[0033] After carrying out step E10 or E11, a heat treatment of said at least one boron nitride layer is carried out by applying a treatment temperature of between 1050°C and 1250°C for a treatment time of between 0.25 hours and 5 hours (step E20). The treatment temperature may be between 1100°C and 1250°C, for example between 1150°C and 1250°C, for example between 1175°C and 1225°C, or even between 1190°C and 1210°C or between 1100°C and 1200°C. The treatment time may be between 1 hour and 5 hours, for example between 1 hour and 2 hours, or between 0.25 hours and 2 hours. The heat treatment may be carried out in a neutral atmosphere, for example under argon or nitrogen. Alternatively or in combination, the heat treatment may be carried out in a vacuum, for example at a pressure less than or equal to 400 mbar. The heat treatment is initiated once the deposition of the interphase is complete. It is distinct from the heat treatment imposed during the formation of the interphase.

[0034] Figure 2 schematically illustrates the effect of the invention compared to a solution implementing a heat treatment at a higher temperature outside the invention.

[0035] The PA part obtained by implementing a method according to the invention and illustrated in figure 2 comprises a fibrous reinforcement in ceramic or carbon wires 3, a ceramic matrix 5 which densifies the reinforcement and an interphase, here in the form of a single layer 71 of boron nitride, interposed between the wires 3 and the matrix 5. An internal surface SI of the layer 71 is in contact with the wires 3, and an external surface SE, opposite the internal surface SI, is in contact with the matrix 5.

[0036] The interphase has a weakening function and acts as a mechanical fuse by allowing the cracks F propagating in the direction of the wires 3 to be deflected, as illustrated in Figure 2. This thus improves the lifetime of the material. The layer 71 has the particularity of having undergone a heat treatment, noted THT A, according to step E20 which was described above. In this way, intra-BN cracking is favored, as illustrated, which makes it possible to protect the wires 3. By way of illustration, the thickness e71 of the layer 71 may be greater than or equal to 50 nm, for example between 50 nm and 1000 nm, for example between 200 nm and 600 nm. Generally speaking, vapor deposition techniques (chemical vapor deposition or chemical vapor infiltration) make it possible to obtain layers of uniform thickness on the fibers. The matrix 5 is then formed directly after the THT A heat treatment.

[0037] The associated PB part manufactured by a process outside the invention implementing a THT B heat treatment at a higher temperature, for example of 1400°C, leads to the stabilization of the boron nitride layer 7, which can limit the fracture behavior as illustrated by allowing more propagation of cracks F up to wires 3.

[0038] Figure 3 represents a PC part having an alternative interphase obtained by implementing a method variant according to the invention. According to this example, the interphase comprises several layers, here a first layer 7 of stabilized BN having undergone the THT B heat treatment which is located on the side of the wires 3, for example in contact with them, and a second layer 71 of BN having undergone the THT A treatment so as to promote intra-BN deflection. The second layer 71 covers the first layer 7. The second layer 71 may be in contact with the first layer 7. The second layer 71 may be in contact with the matrix 5. The thickness e7 of the first layer 7 may be greater than or equal to 50 nm.The first layer 7 may have undergone a preliminary stabilization heat treatment by imposing a temperature greater than 1300°C and at least equal to the maximum temperature encountered subsequently until completion of the densification of the preform by the matrix for a period of between 0.25 hours and 5 hours, for example between 1 hour and 2 hours. The temperature of the preliminary heat treatment may be greater than or equal to 1400°C. The layer 71 is formed directly after the preliminary heat treatment, then the THT A heat treatment described above is carried out. The matrix 5 is then formed directly after the THT A heat treatment.

[0039] The following section deals with the formation of the ceramic matrix (step E30), after heat treatment. The formation of the matrix uses techniques known per se. The formation of the matrix is ​​initiated after the heat treatment is completed. There is no introduction of the matrix material during the heat treatment.

[0040] A consolidation matrix phase can first be formed on the interphase, in contact with it. This deposition can be carried out by chemical vapor infiltration. A temperature imposed during the formation of the consolidation matrix phase can be less than or equal to 1050°C and, more generally, not exceed the treatment temperature. The consolidation phase can be made of silicon carbide. The thickness of the consolidation phase consolidation is sufficient to consolidate the fiber preform, that is, to bind the yarns together sufficiently to allow the preform to be handled while retaining its shape without the assistance of holding tooling.

[0041] 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.

[0042] 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 an 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 being in contact with, the pre-densification matrix.

[0043] 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.

[0044] The variant of Figure 4 relates to the second embodiment in which the heat treatment is carried out before production of the fiber preform. In this case, the interphase is first formed on the wires (step E12) as described in the context of step E11 mentioned above, then the heat treatment is carried out (step E200) on the wires with conditions similar to those described above for step E20. The fiber preform is then formed in the same way as described above in the case of Figure 1 (step E14), then this preform is densified (step E300) by implementing conditions similar to those of step E30.

[0045] Figure 5 presents a summary of experimental results obtained by the inventors by subjecting the boron nitride interphase to different heat treatments (case of curves A-1100, A-1200 and B-1400) or by omitting the heat treatment (case of curve C). For each of these experiments, composite material specimens were produced as follows: - three-dimensional weaving of a preform from silicon carbide threads, - formation of a BN interphase layer by CVI in the porosity of the preform, - carrying out a heat treatment of the BN interphase at 1100°C (test A-1100 according to the invention), 1200°C (test A-1200 according to the invention) or 1400°C (test B-1400 outside the invention), the duration of each of the heat treatments was 2 hours, or omission of this heat treatment (test C outside the invention), - formation of a first part of the silicon carbide matrix by CVI on the interphase after heat treatment, and - formation of a second part of the Si-SiC matrix by siliciding after introduction of a SiC slip, after formation of the first part of the matrix.

[0046] Figure 5 shows that the specimens obtained by implementing the invention (curves A-1100 and A-1200) exhibit a significantly improved fracture behavior compared to carrying out a heat treatment at a temperature of 1400°C (curve B-1400), or to the absence of heat treatment (curve C). In particular, the stress and strain at fracture are increased by implementing the invention. The heat treatment at 1200°C provides even better results than that at 1100°C. In addition, the invention makes it possible to maintain an elastic range close to that obtained with the heat treatment at 1400°C. The results presented in Figure 5 correspond to an average carried out on several specimens taken from the same plate.

[0047] 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 nozzle or a portion of a nozzle.

[0048] The expression "between ... and ..." must be understood as including the limits.

Claims

Claims

1. Method for manufacturing a part (PA; PC) made of ceramic matrix composite material, comprising: - obtaining (E10; Eli) a fibrous preform of the part to be obtained comprising ceramic or carbon wires (3) coated with an interphase comprising at least one layer (71) of boron nitride formed by chemical vapor infiltration, - a heat treatment (E20) of said at least one layer of boron nitride, after obtaining the preform, by applying a treatment temperature of between 1175°C and 1225°C for a treatment duration of between 0.25 hours and 5 hours, and - densification (E30) of the preform, after heat treatment, by the ceramic matrix (5).

2. Method for manufacturing a part (PA; PC) made of ceramic matrix composite material, comprising: - obtaining (E12) ceramic or carbon wires (3) coated with an interphase comprising at least one layer (71) of boron nitride, the coating of the wires with the interphase being carried out by chemical vapor deposition, - a heat treatment (E200) of said at least one layer of boron nitride on the wires by applying a treatment temperature of between 1175°C and 1225°C for a treatment duration of between 0.25 hours and 5 hours, - the production of a fibrous preform (E14) of the part to be obtained from the yarns thus coated, after the heat treatment, comprising the formation of a fibrous blank by carrying out one or more textile operations, and the shaping of this blank, and - the densification (E300) of the preform thus produced by the ceramic matrix (5).

3. Method according to claim 1 or 2, in which the treatment time is between 1 hour and 2 hours.

4. A method according to any one of claims 1 to 3, wherein the interphase comprises a first (7) and a second (71) boron nitride layer, the second layer covering the first layer, and wherein: - the heat treatment (E20; E200) is carried out after the formation of the first and second layers, and - a preliminary stabilization heat treatment is carried out after the formation of the first layer and before the formation of the second layer by imposing a temperature greater than 1300°C and at least equal to the maximum temperature encountered subsequently until completion of the densification of the preform by the matrix (5) for a period of between 0.25 hours and 5 hours.

5. Method according to any one of claims 1 to 4, in which the densification (E30; E300) comprises at least the formation, by chemical vapor infiltration, of a matrix phase (5) of silicon carbide covering said at least one layer (71) of boron nitride.

6. The method of claim 5, wherein the densification (E30; E300) further comprises: - the introduction of silicon carbide particles, possibly with added carbon particles, into the residual porosity of the preform densified by the silicon carbide matrix phase, and - the formation of a second Si-SiC matrix phase covering the silicon carbide matrix phase by infiltration of silicon or a silicon alloy after introduction of the particles.

7. A method according to any one of claims 1 to 6, wherein the fibrous preform has a three-dimensional weave.

8. A method according to any one of claims 1 to 7, wherein the wires (3) are made of silicon carbide and at least part of the matrix (5) is made of silicon carbide.

Images