EP3331657A1

EP3331657A1 - Method for producing a part consisting of a composite material

Info

Publication number: EP3331657A1
Application number: EP16757320.3A
Authority: EP
Inventors: Guillaume Fribourg
Original assignee: Safran Aircraft Engines SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 2015-08-06
Filing date: 2016-08-02
Publication date: 2018-06-13
Anticipated expiration: 2036-08-02
Also published as: US11097345B2; EP3331657B1; FR3039839B1; CN107921539B; US20180221957A1; CN107921539A; FR3039839A1; WO2017021652A1

Abstract

The invention relates to a method for producing a part (15) consisting of a composite material comprising a fibrous reinforcement densified by a metal matrix (14).

Description

Process for manufacturing a composite material part

Background of the invention

The invention relates to a method for manufacturing a composite metal matrix part.

Reinforcement of metal parts by long fibers based on a ceramic material such as silicon carbide has been envisaged in order to improve the mechanical properties (elastic limit, modulus dYoung) of these parts. However, the integration of long fibers in a metal matrix by conventional shaping processes (foundry, forging, machining) is complex. In addition, the cohesion between the fibers and the metal matrix is generally low, due to either a weak diffusion between these two elements or a reaction between the fibers and the matrix.

One solution for improving the cohesion of the fibers with the metal matrix consists in using fibers consisting of a core of ceramic material and a metal sheath surrounding this core. The sheath may for example have been deposited by high speed coating. A heat diffusion welding treatment can then be performed to secure the fibers to a pre-shaped part, for example forged and / or machined. Such a solution is for example described in document FR 2 886 180. This solution works but it requires a large succession of operations: shaping of the initial part, machining of grooves to introduce the fibers, welding of a cover for close the workpiece, and heat diffusion welding treatment. In addition, in this type of solution, the distribution of the fibers requires each time specific operations, making their distribution in multiple positions relatively long to achieve. Document US 2011/0027119 discloses a method for manufacturing parts with an insert of metal matrix composite material. EP 2 418 297 discloses a method for manufacturing an article made of a metal matrix composite material. There is therefore a need for more simple methods for producing metal matrix composite parts reinforced with ceramic fibers while retaining satisfactory mechanical properties for the parts obtained.

Object and summary of the invention

For this purpose, the invention proposes, in a first aspect, a method of manufacturing a composite material part comprising a fibrous reinforcement densified by a metal matrix, the method comprising at least the following steps:

a) positioning a plurality of fibers comprising a core of ceramic material coated with a metal sheath on a first preform of a first part of the part to be manufactured, said first preform comprising at least one metal powder of a first alloy and a first binder,

b) positioning a second preform of a second part of the part to be manufactured on the first preform to obtain a stacked structure, the fibers being present between the first preform and the second preform in said stacked structure, said second preform comprising at least one metal powder of a second alloy and a second binder, the melting temperature Ti of the first alloy, the melting temperature T ₂ of the second alloy and the melting temperature T ₃ of the metal sheath of the fibers satisfying the two following conditions: | T ₃ - Τι \ ΠΊ≤ 25% and | T ₃ - T ₂ | / T ₂ <25%,

c) elimination of the first and second binders present in the stacked structure obtained after implementation of step b) in order to obtain a stacked structure unbound,

d) heat treatment of the unbonded stacked structure in order to obtain the piece of composite material during which the metal sheath of the fibers is assembled with the powders of the first and second alloys by diffusion bonding and during which the powders of the first and second alloys are sintered to form the metal matrix.

Unless otherwise stated, the melting temperatures ΤΊ, T ₂ and T ₃ are expressed in ° C (degrees Celsius). Unless otherwise stated, the size noted | A | denotes the absolute value of magnitude A. The fact that the temperatures Ti, T ₂ and T ₃ satisfy the above two inequalities makes it possible to guarantee good compatibility between the metallic sheath of the fibers and the first and second powders in order to achieve efficient diffusion welding and to obtain an interface of good quality between the fibers and the metal matrix thus making it possible to have a part having the desired mechanical properties.

The fact of using first and second preforms based on powders advantageously makes it possible to significantly simplify the manufacture of the composite material part, in particular because of the possibility of using the same heat treatment step both to densify the first and second preforms and forming the metal matrix as well as to make the sheath of the fibers integral with the metal matrix. Obtaining parts with satisfactory mechanical properties by such a simplified process is made possible by the use of materials having particular melting temperatures to ensure efficient diffusion welding as mentioned above.

The first binder and the second binder may be the same or different. The metal powder of the first alloy may be present in the first preform in a volume content of between 50% and 80% and the first binder may be present in the first preform in a volume content of between 20% and 50%. Similarly, the metal powder of the second alloy may be present in the second preform in a volume content of between 50% and 80% and the second binder may be present in the second preform in a volume content of between 20% and 50%.

Preferably, the following two conditions can be verified: | T ₃ - 15% and | T ₃ - T ₂ | / T ₂ <15%.

The fact of verifying these two inequalities advantageously makes it possible to further improve the quality of the diffusion welding carried out allowing the assembly of the metal sheath of the fibers with the metal matrix and thus to further improve the mechanical properties of the parts obtained.

In an exemplary embodiment, the first and second preforms may each be formed by implementing a metal injection molding process. The implementation of a metal injection molding process ("Metal Injection Molding") to form the first and second preforms advantageously makes it possible to further simplify the process insofar as it is thus possible to obtain directly the first and second preforms to the desired ribs or practically to the desired ribs and therefore reduce the duration of the subsequent machining, or even to emancipate.

The core of the fibers may, for example, be silicon carbide, zirconia or alumina.

Preferably, the metal sheath of the fibers, the first alloy and the second alloy may each consist mainly of a mass of the same metal element. In other words, it is necessary in this case to understand that the metal sheath of the fibers consists of at least 50% by weight of a chemical element X and that each of the first and second alloys consist of at least 50% by weight of this same element X.

Such an embodiment advantageously makes it possible to further improve the compatibility between the metal sheath of the fibers and the metal matrix of the part obtained.

In particular, the material forming the metal sheath of the fibers may be identical to the first alloy and / or the second alloy.

In an exemplary embodiment, the fibers may, in the stacked structure, be housed in grooves formed on the surface of the first preform and / or on the surface of the second preform.

Such an exemplary embodiment advantageously makes it possible to use relatively thick fibers for the fibrous reinforcement of the part, the grooves compensating all or part of the thickness of these fibers.

In an exemplary embodiment, the metal sheath of all or part of the fibers may be in the form of a continuous layer of a metallic material.

In an exemplary embodiment, the metal sheath of all or part of the fibers may be in the form of a plurality of metal strands surrounding the core, for example helically wound around the core. In an exemplary embodiment, the fibers may include a first set of fibers extending along a first direction and a second set of fibers extending along a second direction not parallel to the first direction.

Advantageously, the following two conditions can be verified: | T ₂ - ΤΊΙ / ΤΊ <25%, preferably | T ₂ - Ti | / Ti <15%. Such an embodiment advantageously makes it possible to further improve the quality of the metal matrix obtained.

In particular, the first alloy may be identical to the second alloy. Alternatively, the first alloy may be different from the second alloy.

In an exemplary embodiment, the first alloy and the second alloy may be chosen from: titanium-based alloys, nickel-based alloys, cobalt-based alloys, aluminum-based alloys or steels.

Brief description of the drawings

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

FIGS. 1A to 1G represent different steps of an exemplary method according to the invention,

FIGS. 2A and 2B show the structure of the fibers used in the exemplary method illustrated in FIGS. 1A to 1G,

FIGS. 3A and 3B show an alternative fiber structure that can be implemented in the context of a method according to the invention,

FIG. 4A represents an example of possible positioning of the fibers on the first preform,

FIG. 4B represents another example of possible positioning of the fibers on the first preform,

FIGS. 5A to 5D represent different steps of an alternative method according to the invention,

FIGS. 6A to 6K represent different steps of an alternative method according to the invention, and - Figure 7 illustrates a detail of an alternative embodiment of the invention.

Detailed description of embodiments

FIGS. 1A to 1G show the implementation of the various steps of a first exemplary method according to the invention. FIG. 1A shows a molding cavity 3 which is defined between a mold 1 and a counter-mold 2 and in which a metal injection molding process is intended to be implemented in order to obtain the first or the second preform . The metal injection molding process is a technique known per se. The molding cavity 3 has the shape of the preform to be manufactured. An injection composition 5 is first injected under pressure into the molding cavity 3. The injection composition 5 comprises a powder of a metal alloy and a binder and is intended to form one of the first and second preforms. The metal alloy used in the injection composition 5 may, for example, be a titanium-based alloy, a nickel-based alloy, a cobalt-based alloy, an aluminum-based alloy, or an aluminum alloy. steel. Unless stated otherwise, a material said to be "based on a chemical element X" has the element X in a mass content greater than or equal to 50%.

The binder can be chosen from: paraffins, thermoplastic resins, agar gel, cellulose, polyethylene, polyethylene glycol, polypropylene, stearic acid, polyoxy methylene and mixtures thereof. The volume content of the metal alloy powder in the injection composition may for example be between 50% and 80%. The volume content of the binder in the injection composition may for example be between 20% and 50%. The injection composition 5 may first be mixed at a temperature between 150 ° C and 200 ° C in a neutral atmosphere for example, and may then be injected into the molding cavity 3 at such a temperature.

In the illustrated example, the injection composition 5 is injected into the molding cavity 3 through a single injection point 4. Of course, it is not beyond the scope of the present invention when the composition of injection is injected into the mold cavity through a plurality of injection points allowing simultaneous injection or not of the injection composition in several parts of the molding cavity. During the injection, the mold 1 and the counter-mold 2 can be regulated in temperature. The mold 1 and the counter mold 2 can, for example, be maintained at a temperature between 30 ° C and 70 ° C to promote cooling of the blank. The blank thus produced is said in a "green state" or plastic. It is advantageous to perform the injection of the injection composition 5 in a molding cavity 3 in which the vacuum has been made, in order to facilitate the injection and to ensure the homogeneity of the blank that will be formed.

In the example illustrated with reference to FIGS. 1A to 1G, each of the first and second preforms is obtained during two separate injections. These two injections can for example be performed one after the other in the same molding cavity or, alternatively, can be performed in two different molding cavities simultaneously or not.

Once the injection is made, the blanks 6a and 6b of the first and second preforms are demolded as shown in Figure 1C. Once extracted from the molding cavity 3, the blanks 6a and 6b can be machined in the green state to remove burrs or cores or injection points. The machining performed may, in addition, be carried out in order to modify the surfaces of the blanks 6a and 6b intended to be placed next to each other in the following process and / or to provide grooves on the surface. surface of the first and / or second preforms as will be detailed below. After completion of this machining operation, a first preform 7a of a first part of the part to be manufactured is obtained, this first preform 7a comprising at least one metal powder of a first alloy and a first binder and a second preform 7b of a second part of the workpiece comprising at least one metal powder of a second alloy and a second binder. The powder of the first alloy and / or the powder of the second alloy may, for example, have a grain size D90 of less than or equal to 150 μm (ie in this case at least 90% of the grains of the powder have a size less than or equal to at 150 μιτι).

The present invention is not limited to the implementation of a metal injection molding process in order to obtain the first and second preforms. Indeed, one can alternatively use a tape casting process ("tape casting") or a powder compaction process. Implementing a metal injection molding process to form the first and second preforms, however, is advantageous in order to quickly obtain a blank of said preforms having dimensions close to desired ribs, thereby simplifying the step of machining of these blanks. The implementation of a metal injection molding process also advantageously makes it possible to quickly obtain preforms having relatively complex shapes. The part intended to be formed in the context of the process of the invention may for example be a turbomachine part, for example a turbomachine blade. As a variant, said part may have an axisymmetric shape and for example constitute a turbine ring, segmented or not.

A step a) is then carried out during which a plurality of fibers 10 are positioned on the surface of the first preform 7a as illustrated in FIG. 1E. The positioning of the fibers 10 on the first preform 7a may or may not be automated. FIGS. 2A and 2B show the structure of the fibers 10 used. Fig. 2A is a view of a fiber 10 in cross-section and Fig. 2B is a view of this fiber 10 in longitudinal section. The fibers 10 each comprise a core of ceramic material 10a coated with a metal sheath 10b. The metallic material forming the sheath 10b may be a metal or a metal alloy. In the illustrated example, the metal sheath 10b is in the form of a continuous layer of a metallic material, for example obtained by a high-speed coating process (EGV). The core of ceramic material 10a may for example be alumina, zirconia or silicon carbide. The core 10a may for example have a diameter (greater transverse dimension) greater than or equal to 1 μm, for example between 1 μm and 140 μm. The thickness of the metal sheath 10b may, for its part, be greater than or equal to 1 μm, for example between 1 μm and 140 μm. As will be detailed below, the metal sheath is intended to form the interface between the core 10a of the fibers 10 and the metal matrix of the piece of composite material obtained. FIGS. 3A and 3B show a variant of fiber 10 'that can be used in the context of the method according to the invention. In this variant, the metal sheath 10'b is in the form of a plurality of metal strands 10'c surrounding the core 10'a. The metal strands 10'c can each be wound around the core 10'a. The diameter of the core 10'a and the thickness of the metal sheath 10'b may be as described above in connection with Figures 2A and 2B. In the configuration illustrated in Figures 3A and 3B, at least six metal strands 10'c can surround the core 10'a fibers 10 '.

As illustrated, the fibers 10 may, once positioned on the first preform 7a, extend over the majority (more than 50%) of the length of the first preform 7a and for example extend, as illustrated, on the the entire length of the first preform 7a. The fibers 10 may, once positioned on the first preform 7a extend from a first end 17a of the first preform 7a to a second end 18a of the first preform 7a located on the side opposite the first end 17a. The fibers 10 may, once positioned on the first preform 7a, have over-extension zones 11 and 12 extending beyond the first preform 7a. In the example illustrated in FIG. 1E, the over-length zones 11 and 12 extend from opposite ends 17a and 18a of the first preform 7a. In general, the fibers 10 are positioned during step a) along the axes of mechanical stress of the part to be obtained. The density of fibers 10 positioned on the first preform 7a may be greater than or equal to 5 fibers per centimeter width of the first preform 7a. This fiber density may be less than or equal to 10 fibers per centimeter width of the first preform 7a and for example be between 5 and 10 fibers per centimeter width of the first preform 7a.

FIG. 4A shows an example of possible positioning for the fibers 10 on the first preform 7a. Figure 4A is a top view of the fibers 10 and the first preform 7a. As illustrated in FIG. 4A, the fibers 10 may, once positioned on the first preform 7a, be spaced from one another. The spacing e between the fibers 10 may, for example, be constant as illustrated in FIG. 4A. The fibers 10 are, in the example of Figure 4A, parallel to each other once positioned on the first preform 7a. As illustrated in FIG. 4A, the fibers 10 can, once positioned on the first preform 7a, extend substantially rectilinear (in a straight line). In a variant not shown, the spacing between the fibers positioned on the first preform may vary. In a variant not shown, the fibers may, once positioned on the first preform, be in contact with each other.

FIG. 4B shows a possible positioning variant for the fibers 10 on the first preform 7a. In this variant, the fibers 10 comprise a first set of fibers 10 extending along a first direction X and a second set of fibers 10 extending along a second direction Y not parallel to the first direction X The first direction X may, for example, as illustrated in FIG. 4B be perpendicular to the second direction Y. FIGS. 4A and 4B illustrate possible positioning examples for the fibers 10 on the first preform 7a, any arrangement of fibers on the first preform being conceivable within the scope of the invention.

Once the fibers 10 have been positioned on the first preform 7a, the process continues with a step b) during which the second preform 7b is approaching the first preform 7a covered by the fibers 10 and is positioned on the first preform 7a as illustrated in FIG. Figure 1F. Once step b), the fibers 10 are interposed between the first preform 7a and the second preform 7b. The fibers 10 are in contact with the first 7a and the second preform 7b. The second preform 7b covers the first preform 7a and the fibers 10. The positioning of the fibers made during step a) is not modified during the positioning of the second preform 7b. The details described above relative to the positioning of the fibers 10 remain valid after implementation of step b). The first 7a and second 7b preforms are, before positioning the fibers 10, without any fibrous reinforcing element. The fibers 10 are indeed intended to constitute the fibrous reinforcement of the composite part to be obtained and are present at the interface between the first 7a and second 7b preforms.

After step b), the fibers 10 may extend over the majority (more than 50%) of the length of the overlap area of the first preform 7a by the second preform 7b and for example extend, as illustrated, over the entire length of this area. The overlap area of the first preform 7a by the second preform 7b corresponds to the area on which the first and second preforms 7a and 7b are superimposed. The fibers 10 may, once step b) performed, extend from a first end 17b of the second preform 7b to a second end 18b of the second preform 7b located on the opposite side to the first end 17b. The oversize zones 11 and 12 of the fibers 10 may extend beyond the overlap area of the first preform 7a by the second preform 7b as illustrated.

As mentioned above, the first alloy, the second alloy and the material constituting the fiber sheath are not chosen arbitrarily. Indeed, the melting temperature Ti of the first alloy, the melting temperature T ₂ of the second alloy and the melting temperature T ₃ of the metal cladding of the fibers satisfy the following two conditions: | T ₃ - Ti | / Ti≤ 25 % and | T ₃ - T ₂ | T ₂ ≤ 25%. Verification of these two inequalities concerning the relative difference between T ₃ and Ti on the one hand and the relative difference between T ₃ and T ₂ on the other hand advantageously makes it possible to ensure a good diffusion bonding of the metallic sheath of fibers with the metal matrix formed from the powders of the first and second alloys and, consequently, to optimize the mechanical properties of the part obtained.

Advantageously, the following combinations can be implemented:

first and second nickel-based alloys and metallic sheath of the nickel-based fibers,

first and second iron-based alloys and metallic sheath of the iron-based fibers,

first and second titanium-based alloys and metallic sheath of the titanium-based fibers,

first and second cobalt-based alloys and metallic sheath of cobalt-based fibers,

first and second iron-based alloys and metallic sheath of the nickel-based fibers,

first and second nickel-based alloys and metallic sheath of the iron-based fibers, first and second cobalt-based alloys and metallic sheath of the nickel-based fibers,

first and second nickel-based alloys and metallic sheath of the cobalt-based fibers.

Preferably, the first and second alloys and the metal sheath of the fibers may each be based on the same metal element. In particular, the first and second alloys may be identical and the material constituting the metal sheath of the fibers may be identical to the material constituting the first and second alloys.

Some examples of possible combinations that can be implemented in the context of the invention are given below:

metallic sheath of TiAl 48-2-2 fibers with first and second TiAl 48-2-2 alloys,

metallic sheath of Ta6V fibers with first and second TiAl 48-2-2 alloys,

metallic sheath of T40 titanium fibers with first and second TiAl 48-2-2 alloys,

- metal sheath of Inconel® 718 fibers with first and second Inconel® 718 alloys,

- metallic sheath of Inconel® 625 fibers with first and second alloys in Inconel® 718,

- metallic sheath of nickel fibers with first and second alloys in Inconel® 718,

- metallic sheath of nickel fibers with first and second 304L stainless steel alloys,

- metallic sheath of 304L stainless steel fibers with first and second 304L stainless steel alloys,

- metallic sheath of 316L stainless steel fibers with first and second 304L stainless steel alloys.

Once the second preform has been positioned on the first preform, step b) may optionally include carrying out a heating step to assemble the first preform, the second preform and the fibers via the first and second preforms. second binders. This assembly step makes it possible to obtain a consolidated stacked structure comprising the first and second preforms as well as that the fibers interposed between said preforms. After carrying out this heating step, a machining step of the consolidated stacked structure can be performed in order to adjust its dimensions to the desired dimensions for the final part.

The stacked structure obtained after implementation of step b) is then unbound (step c)). During debinding, there is selective removal of the first and second binders present in the stacked structure. It is possible to perform during step c) a chemical debinding of the stacked structure during which the stacked structure is brought into contact with one or more solvents for solubilizing all or part of the first and second binders. Alternatively or in combination, it is possible to perform during step c) thermal debinding. In this case, thermal debinding can be performed in a sintering chamber so as not to have to move the stacked structure between step c) and step d). Thermal debinding can be performed after implementation of chemical debinding. The conditions for debinding used in the context of the present invention are known per se.

Next, a step d) of heat treatment of the unbonded stacked structure is performed in order to obtain the piece 15 made of metal matrix composite material 14 (see FIG. 1G). During step d), the metal sheath of the fibers is assembled with the powders of the first and second alloys by diffusion welding and these powders are sintered to form the metal matrix. It is possible, for example, during step d) to impose on the unbound stacked structure a treatment temperature greater than or equal to 1200 ° C., for example between 1250 ° C. and 1350 ° C. The duration during which this treatment temperature is imposed may for example be greater than or equal to 120 minutes, for example between 120 minutes and 180 minutes. Step d) makes it possible to densify the powders of the first and second alloys and to create bonds between the first and second preforms and the metal sheaths of the fibers. As explained above, the fact of introducing sheathed fibers with a material compatible with the metal matrix makes it possible to improve the cohesion of the fibers with the metal matrix, thus optimizing the mechanical behavior of the part obtained. On the other hand, the over-length areas 11 and 12 of the fibers 10 have been eliminated. This elimination of the over-length zones 11 and 12 can be carried out after step d) or before step d), or even before step c). Once the part 15 has been obtained, it is possible to carry out an additional machining step thereof in order to adjust the dimensions of the part 15 to the desired ribs. The resulting piece can then undergo hot isostatic compaction treatment or any finishing treatment.

In a non-illustrated variant of the invention, it is possible after placing the second preform on the fibers and the first preform, to position again on the second preform on the opposite side to the first preform of the sheathed ceramic core fibers as described above. top then position a third preform comprising a metal powder of an alloy and a binder. The assembly can then undergo debinding followed by a heat treatment according to step d) in order to obtain the piece of composite material. Thus, the part obtained in the context of the process according to the invention may comprise one or more layers of fibers.

FIGS. 5A to 5D show an alternative method according to the invention in which the first and second preforms are formed during the same injection step. More specifically, the injection composition 25 is injected into the molding cavity 23 defined between the mold 21 and the counter-mold 22 through the injection point 24. This injection method makes it possible to form a parent blank 26 which can then undergo a machining step. A step is then made to cut the possibly machined mother blank to form the first 27a and second 27b preforms (see Figure 5D). The process is then continued in a manner similar to that described above once the first 27a and second 27b preforms obtained.

FIGS. 6A to 6K show steps of an alternative embodiment of a method according to the invention. FIG. 6A (seen from above) and FIG. 6B (longitudinal sectional view) show a first preform 37a which is present on a support 30. The first preform 37a is present between two side walls 31 and 32 of the support 30 and fibers 10 are present on the first preform 37a and on the side walls 31 and 32. As illustrated, each of the side walls 31 and 32 has openings 31a, 31b, 32a and 32b. FIGS. 6C (seen from above), 6D (longitudinal sectional view) and 6E (cross-sectional view), show the structure obtained after positioning on each of the lateral walls 31 and 32 of a positioning element 35 or 36 As illustrated, the positioning members 35 and 36 each have a plurality of teeth 39 between which the fibers 10 are accommodated and thus allowing the fibers 10 to be held in the desired orientation. In addition, the positioning elements 35 and 36 each have openings 35a, 35b, 36a and 36b which are positioned facing the openings 31a, 31b, 32a and 32b of the side walls 31 and 32 of the support 30. As illustrated in FIGS. 6F and 6G, the positioning members 35 and 36 are then attached to the support 30 by fasteners 40a, 40b, 41a and 41b as screw-nut systems in the illustrated example. The second preform 37b is then positioned on the fibers 10 (see FIGS. 6H and 61) and the first preform 37a. The preforms 37a, 37b and the fibers 10 are then assembled by heat treatment through the binder (s) present in the preforms 37a and 37b as explained above. The consolidated stacked structure constituted by the first and second preforms 37a and 37b and the fibers 10 is then removed from the support 30 (see FIGS. 6J and 6K) in order to undergo debinding and heat treatment according to step d) as explained above. .

FIG. 7 illustrates an alternative embodiment in which the fibers 10 are, in the stacked structure, housed in grooves 42a and 42b formed on the surface of the first preform 37a and / or on the surface of the second preform 37b. All or part of the thickness of the fibers 10 can be accommodated in these grooves 42a and 42b. It is not beyond the scope of the invention when only one of the first and second preforms has such grooves on its surface.

Example

Firstly, a mixture of a metal powder and a binder is produced. This mixture is composed of 60% by volume of a metal powder of TA6V alloy and 40% by volume of a mixture of polyethylene glycol, polyethylene and polypropylene constituting the binder. The D90 size of the TA6V metal powder used was less than 35 μm and this powder was obtained by atomization under argon.

From this mixture of TA6V powder and binder, first and second preforms were obtained. For this, the mixture was injected into two injection molds. The injection temperature of the mixture was of the order of 190 ° C and the molds were cooled to about 50 ° C. First and second blanks of part of the part to be obtained were obtained after injection and molding of the mixture in the molds. The two blanks were deburred and the injection cores were removed in order to obtain a first and a second preform each constituting the preform of a half of the part to be obtained.

Fibers were then positioned on the surface of one of the two preforms. The fibers used consisted of a central core of silicon carbide 80 microns in diameter and a pure titanium sheath (99% titanium content in the sheath greater than 99%) of a thickness of 10 microns. The titanium sheath was deposited on the ceramic cores by high speed coating. The fibers were deposited in a number to cover 10% of the surface of the preform by depositing 10 fibers per 10 millimeters of preform width. Tooling has been used to facilitate the positioning of the fibers and their maintenance, the use of this tooling being optional.

Once the fibers are positioned on the first preform, the second preform has been positioned on the first preform as well as on said fibers. The assembly constituted by the stacking of the two preforms with the fibers interposed between these two preforms and by the holding tooling was then placed in an oven maintained at 70 ° C. for one hour. This steaming made it possible to bind the two preforms together by means of the binder present in these preforms and to obtain the consolidated stacked structure. The consolidated stacked structure was then separated from the holding tool. This structure then underwent a first chemical debinding step by immersion in a demineralized water bath while stirring the bath. The bath temperature was 60 ° C. and this debinding step was carried out for 24 hours.

Once this debinding with demineralised water carried out, the partially debonded structure was placed on a zirconia plate and introduced into an oven in order to undergo a heat treatment to thermally finalize debinding. The heat treatment was then continued in order to sinter the metal powders to form the matrix of the part as well as to secure the metal sheath of the fibers to said matrix. An argon atmosphere at 20 mbar pressure was imposed during this heat treatment. The heat treatment performed had the following characteristics:

- passage from 20 ° C to 200 ° C with a ramp at 5 ° C / minute,

- passage from 200 ° C to 350 ° C with a ramp at 2 ° C / minute and 1 hour of maintenance at 350 ° C,

- passage from 350 ° C to 470 ° C with a ramp at 2 ° C / minute and 1 hour of maintenance at 470 ° C,

- passage from 470 ° C to 1250 ° C with a ramp at 5 ° C / minute and 3 hours of maintenance at 1250 ° C,

- passage from 1250 ° C to 80 ° C with a cooling ramp to

10 ° C / minute.

Once this heat treatment performed, the piece obtained was removed from the oven, the portions of the fibers protruding from the room were cut. The part can then possibly be machined to adjust its shape and dimensions to the desired application.

The expression "understood between ... and ..." or "from ... to ..." must be understood as including the boundaries.

Claims

A method of manufacturing a composite material part (15) comprising a fibrous reinforcement densified by a metal matrix (14), the method comprising at least the following steps:

a) positioning a plurality of fibers (10; 100 comprising a core of ceramic material (10a; 10'a)) coated with a metal sheath (10b; 10'b) on a first preform (7a; 27a; 37a); a first part of the part to be manufactured, said first preform (7a; 27a; 37a) comprising at least a metal powder of a first alloy and a first binder,

b) positioning a second preform (7b; 27b; 37b) of a second portion of the workpiece to be made on the first preform (7a; 27a; 37a) to obtain a stacked structure; the fibers (10; being present between the first preform (7a; 27a; 37a) and the second preform (7b; 27b; 37b) in said stacked structure, said second preform (7b; 27b; 37b) comprising at least one metal powder of a second alloy and a second binder, the melting temperature Ti of the first alloy, the melting temperature T ₂ of the second alloy and the melting temperature T ₃ of the metal cladding (10b; 10'b) of the fibers (10; 100 satisfying the two following conditions: | T ₃ - ΤιΙ Ί <25% and | T ₃ - T ₂ | / T ₂ ≤ 25%, the melting temperatures Ti, T ₂ and T ₃ being expressed in ° C,

d) heat treatment of the unbonded stacked structure to obtain the composite material part (15) during which the metal sheath (10b; 10'b) of the fibers (10; 100) is assembled with the powders of the first and second alloys by diffusion welding and during which the powders of the first and second alloys are sintered to form the metal matrix (14).

2. Method according to claim 1, wherein the two following conditions are verified: T ₃ - Ti | / Ti <15% and | T ₃ - T2I / T2 <15%.

3. Method according to any one of claims 1 or 2, wherein the first (7a, 27a, 37a) and second (7b; 27b; 37b) preforms are each formed by implementation of an injection molding process of metal.

4. Method according to any one of claims 1 to 3, wherein the metal sheath (10b; 10'b) of the fibers (10; 100, the first alloy and the second alloy each consist predominantly in bulk of the same metal element.

The method according to any one of claims 1 to 4, wherein the material forming the metal sheath (10b; 10'b) of the fibers (10; 100) ^is identical to the first alloy and / or the second alloy.

6. A method according to any one of claims 1 to 5, wherein the fibers (10) are, in the stacked structure, housed in grooves (42a; 42b) formed on the surface of the first preform (37a) and / or on the surface of the second (37b) preform.

7. A method according to any one of claims 1 to 6, wherein the metal sheath (10b) of all or part of the fibers (10) is in the form of a continuous layer of a metallic material.

8. A method according to any one of claims 1 to 7, wherein the metal sheath (10'b) of all or part of the fibers (100 is in the form of a plurality of metal strands (10'c) surrounding the soul (10'a).

The method of any one of claims 1 to 8, wherein the fibers comprise a first set of fibers extending along a first direction (X) and a second a set of fibers extending along a second direction (Y) not parallel to the first direction (X).

The method of any one of claims 1 to 9, wherein the first alloy is the same as the second alloy.

11. A method according to any one of claims 1 to 10, wherein the first alloy and the second alloy are selected from: titanium-based alloys, nickel-based alloys, cobalt-based alloys, alloys aluminum-based or steels.