EP2245206B1 - Process for manufacturing a metal part reinforced with ceramic fibres - Google Patents

Abstract

A process for manufacturing a metal part reinforced with ceramic fibers, in which: a housing is formed for an insert in a main metal body having an upper face; an insert formed from a bundle of fibers with a metal matrix is placed in the housing; a metal cover is placed on the main body so as to cover the insert; the cover is welded onto the metal body; a hot isostatic pressing operation is carried out; and the part obtained is machined to the desired shape. The housing has the shape of a notch of L-shaped cross section with a face perpendicular to the upper face and a face parallel to the upper face, the cover having an internal notch of L-shaped cross section, this having a shape complementary to that of the metal body with said insert, the cover being shaped on the outside so that the pressure forces are exerted perpendicular to said faces of the notch.

Description

The present invention relates to the manufacture of metal parts comprising internal reinforcements formed of ceramic fibers, and comprising the incorporation of a composite material insert of the type consisting of ceramic fibers in a metal matrix.

In order to reduce the mass of the metal parts while providing greater strength especially in tension or compression, it is known to incorporate ceramic fibers in the mass. These are for example silicon carbide fibers, SiC, which have a tensile strength and compression much higher than that of a metal such as titanium.

The manufacture of these parts requires the prior formation of inserts from metal matrix ceramic son which comprise a ceramic fiber coated with metal. They are also called CMM fibers or coated wires. The metal gives the elasticity and the flexibility necessary for their handling.

A known method of manufacturing such parts with reinforcement comprises producing a coil of wire coated around a mandrel. The coil is then introduced into a container or metal main body in which a groove forming a housing has been previously machined. The depth of the groove is greater than the height of the winding. A lid is placed on the container and welded to its periphery after evacuation. The cover has a post complementary shape to that of the groove, and its height is adapted to that of the coil placed in the groove so as to fill the groove. A hot isostatic pressing step is then carried out during which the lid is deformed and the winding is compressed by the tenon.

The technique of hot isostatic compression consists of placing the part in an enclosure where it is subjected to a high pressure, of the order of 1000 bar and a temperature also high, of the order of 1000 ° C for a few hours.

The metallic sheaths of the coated wires weld together and with the walls of the groove by diffusion to form a dense compound of metal alloy within which the ceramic fibers extend. The resulting part is then machined to the desired shape.

The method allows the manufacture of axisymmetric aeronautical parts such as rotor disks, bladed disks, shafts, cylinder bodies, housings, etc. Oblong parts are also produced to form connecting rods for example.

The machining of the groove in the main body is difficult to achieve especially because of the small rays in the bottom of the groove. This small radius is necessary to allow the housing of the insert which has a rectangular section. Machining the corresponding post in the cover is not easy either because of the non-emerging angles. When in particular the parts to be produced are not axisymmetric but are long, with an oval shape or with rectilinear portions, precise adjustment over long lengths is difficult to obtain. This is even more difficult for inserts formed of very rigid coated son because of the ceramic fibers that require the realization of housing in which they fit perfectly.

Instead of making the insert separately and then transferring it into the groove of the main body, the patent FR 2886290 In the name of Snecma proposes to realize, according to a variant, the winding directly on the main body. Instead of a groove there are two shoulders in it. The first has a bearing surface for the direct winding of a coated wire. This surface is parallel to the winding direction. When the winding is complete, the groove is reconstructed by placing a piece on the main body which is of complementary shape to that of a second shoulder forming a step relative to the first shoulder. Then we have the cover with the pin on the insert that has just wound and compacts the whole. This solution only partially solves the manufacturing problem because the assembly remains complex.

The applicant has set itself the objective of improving the manufacturing process of such parts in the sense of simplifying the steps of the range and reducing costs.

According to the invention the method of manufacturing a metal piece reinforced with ceramic fibers, according to which
forming a housing for an insert in a metal body having an upper face,
there is at least one insert formed from metal matrix fibers in the housing,
a metal cover is placed on the body so as to cover the insert,
the lid is welded to the metal body after it has been evacuated,
the assembly is subjected to a hot isostatic pressing treatment and
the treated unit is machined to the desired shape,
is characterized in that the housing has the shape of an L-section notch with two faces perpendicular to each other, the lid having an internal section L-shaped section and complementary shape to that of the notch of the metal body with said insert, the cover being shaped externally so that the pressure forces are exerted perpendicularly to said faces of the notch.

Preferably, the notch of the metal body comprises a face perpendicular to said upper face and a face parallel to said upper face.

By thus modifying the geometry of the parts to be assembled with respect to the prior art, better access is available for the machining tool of the housing of the insert both for the main body and for the lid, which makes these operations less difficult to perform and therefore less expensive. The number of parts is reduced to two which simplifies the assembly compared to the previous solution. Moreover this geometry allows an application of pressure forces in two non-parallel directions contributing to a more efficient compaction. It should be noted that in the case of an annular insert, the deformation of the insert is parallel to its axis.

This solution allows different implementations. According to a first embodiment, the insert is first formed by winding a coated wire and is placed in place in the notch. According to another embodiment, the insert is formed by winding a wire coated directly in the notch, the latter forming a winding mandrel.

This solution also allows the realization of different parts. The insert may have an annular shape. It can thus, depending on the geometry of the part to be reinforced, form an axisymmetric ring or even for pieces of elongated shape presenting at least one rectilinear portion. The insert can also for parts of elongate shape not be annular and be formed of one or more rectilinear elements.

More precisely, the cross section of the winding is rectangular, a first face of the winding bearing against one face of the notch and a second face of the winding bearing against the other face of the notch.

Advantageously, the cover has a centering surface portion cooperating with a face of the notch, in particular the face of the notch of the main body perpendicular to the upper face thereof, for centering and guiding the deformation of the lid on the body. main.

• La figure 1 représente un schéma de réalisation d'une pièce avec insert selon l'art antérieur.
• La figure 2 montre la solution de l'art antérieur tel que présenté dans le brevet FR 2886290 avec deux épaulements.
• La figure 3 montre la solution de l'invention avec une encoche à la fois sur le corps principal et sur le couvercle.
• Les figures 4 et 5 sont une simulation de la déformation du couvercle et de l'insert pendant l'opération de compression isostatique à chaud.
• La figure 6 montre l'application de l'invention à la réalisation d'une pièce axisymétrique.
• La figure 7 montre l'application de l'invention à la réalisation d'une pièce de forme allongée.
• La figure 8 montre un exemple de pièce finie réalisée conformément à l'invention, après usinage.

The invention will now be described in more detail with reference to the accompanying drawings in which

• The figure 1 represents a diagram of embodiment of a piece with insert according to the prior art.
• The figure 2 shows the solution of the prior art as presented in the patent FR 2886290 with two shoulders.
• The figure 3 shows the solution of the invention with a notch on both the main body and the lid.
• The Figures 4 and 5 are a simulation of the deformation of the lid and the insert during the hot isostatic pressing operation.
• The figure 6 shows the application of the invention to the realization of an axisymmetric part.
• The figure 7 shows the application of the invention to the production of an elongate piece.
• The figure 8 shows an example of finished part made according to the invention, after machining.

The scheme of the figure 1 illustrates a procedure of the prior art. The main body P, metal, comprises a rectangular groove R. In this groove is disposed the insert I consisting of a bundle of coated son temporarily held and bonded to each other. A second cover member C is placed on the main body P; it has a post T of shape adapted to the groove R and which is based on the insert I. The edges of the groove R or the tenon T are chamfered so as to provide clearance with the part of the lid adjacent to the pin. During the hot isostatic compression operation. The pressure is exerted in the direction perpendicular to the surface of the lid. The pressure and the heat allow the metal of the matrix to occupy the voids between the coated wires constituting the insert. The volume of the insert decreases by 23%. The tenon is thus moved down and the game on both sides of the tenon is absorbed. At the end of the process the metal has merged; the piece is thus reinforced by the wires imprisoned in the mass. A similar technique is described in the patent EP 831 154 .

As we see on the figure 2 , resumption of the patent FR 2886290 a main body 139 of revolution about the axis 140, of titanium alloy for example, comprises a central inner portion relative to the height axis H 'equal to the height of the container. Its periphery 142 is chamfered to a first shoulder 143 of height h and width d. At the periphery of this shoulder is a second shoulder 144 whose radial dimension completes the width of the container. Its surface 145 extends at an altitude lower than that of the surface of the first annular shoulder. An annular insert 147 formed of a bundle of coated wires temporarily bonded together was placed. An outer ring 146 has been reported on the second shoulder height corresponding to that of the central portion of the main body. The outer ring 147 is welded to reconstruct a groove with the first shoulder. The cover 148 has an annular projection 149 and bears on the bundle of coated son. We find from this phase the previous method.

The following figures show a non-limiting embodiment of the solution of the invention.

The figure 3 shows, in cross section with perspective, a part of a workpiece incorporating an insert. The main body 2 of the metal part, of titanium alloy for example, has an upper face 21 is a peripheral edge 22; a notch 23 with an L-shaped section is machined behind the edge 22. This notch has a face 23 P, perpendicular to the upper face 21, and a face 23S parallel to the latter. The height H of 23P and the width L of 23S are determined according to the dimensions of the insert to be placed. Between the notch 23 and the edge 22, the main body 2 has an edge surface portion 24 at one end. lower altitude than the 23S surface; a shoulder 25 forms the transition between the two parts 23 and 22.

An insert 3 formed from a bundle of coated son and rectangular cross section is housed in the notch. Its height Hi is slightly lower than that of the face 23P and its width Li is also lower than that of the face 23S.

The insert may advantageously be produced, in a nonlimiting manner, according to one of the methods taught by the patent. FR 2,886,290 . This includes the structure of the coated yarns, their manufacture, the manufacture of a bonded ply of coated yarns, the joining of this ply either to the metal support on which it is wound or to the lower ply, the welding of yarns by laser or by contact between two electrodes.

When the insert is rectilinear, it is advantageously already compacted and manufactured according to the technique described in the patent application filed by the applicant under the number FR 0705454 July 26, 2007 .

There is placed on the main body 2 a cover 4 shaped to fit the different parts of the main body with the insert. More specifically, it comprises a bottom wall 41 which bears on the upper face 21, an edge wall 44 which bears on the edge surface portion 24 and a side wall 42 perpendicular to the two walls 41 and 44. This side wall has an internal notch 43. The notch 43 has an L-shaped cross-section with a face 43P perpendicular to the bottom wall 41. This face extends on the side of the shoulder 25 that it overlaps. The notch has a face 43S parallel to the face 23S of the notch 23 of the main body 2 and bears against the upper face of the insert 3. The width of the face 43S is the same as that of the face 23S. As the height Hi of the insert is slightly less than the height H of the face 23P, the wall 42 is in contact with the latter by its surface portion 42P.

The lid does not marry the main body 2 in three places. A chamfer is machined between the upper face 21 of the main body and the notch 23 forming a clearance with the bottom wall 41. This clearance can also be obtained by digging the bottom wall. Similarly a clearance is provided between the edge wall 44 and the edge surface 24. It is also noted that the width Li of the insert being slightly smaller than that of the face 23S of the notch 23, a space is created between the face 43P of the notch 43 of the lid and the insert.

When the cover and the main body are thus arranged, welded and under vacuum, the assembly is subjected to a hot isostatic pressing treatment. The pressure is exerted on the assembly producing forces in two directions P1 and P2. The pressure force in the direction P1 is exerted on the outer face of the cover of the bottom wall 41 and the edge wall 44 which are parallel. The pressure is also exerted in the direction P2 perpendicular to P1 on the outer face of the side wall 42 which is perpendicular to the first two outer faces.

The forces on the cover in the direction P1 lead to a deformation thereof in parallel with the faces 23P and 43P with compaction of the insert in this direction and absorption of clearance between the bottom walls 41 and edge 44 of the cover 4 and the upper faces 21 and edge 24 of the main body 2.

The clearance between the face 43P of the notch of the lid and the insert is also absorbed by the deformation of the lid resulting from the pressure forces in the direction P2.

Insofar as the insert is of annular shape it does not undergo deformation in the plane perpendicular to the axis of the ring.

We have shown on Figures 4 and 5 a simulation of the deformations undergone by the lid and the insert. The insert is of axisymmetric shape, the deformations are oriented in the direction of the axis of the insert.

Because of the simple shapes involved, the method of the invention has the advantage of being able to make the notch on the main body using a conventional milling tool. It is the same for the notch on the lid.

The notch can be of revolution for the realization of an axisymmetrical part. The figure 6 perspective watch with part torn off the assembly of a main body 102 with a lid 104.

The main body 102 has a notch of revolution 123 about the axis thereof, for the housing of an insert 103 which is shaped annular. The assembly is covered with a lid 104 with a notch 143. We find the same elements as in the figure 3 with an increased reference of 100. The insert is retained between the notch 123 of the body 102 and the notch 143 of the lid 104. the object of the isostatic compression is the compression of the insert 103 in the direction P1. The faces 142P and 143P of the notch 143 slide along the faces 123P and 125 of the body 102 by compressing the insert 103. The secondary compression is provided by the efforts in the direction P2 which deform the wall 142.

The insert can be made by winding separately and then attached to the notch. However the shape allows a direct winding on the notch.

The invention allows the realization of parts which are not axisymmetric as that represented on the figure 7 . The references point to the same parts as to the figure 3 and are increased by 200. The main body 202 has an elongated shape which is divided into two half-circle portions connected by two straight portions. The notch 223 is of elongate shape with two parts in a semi-circle and two straight parts. This notch receives an insert of corresponding shape. The part comprises two faces with two notches 223 which are covered by two lids. 204 which each comprise a notch 243.

There is shown in 210 the assembled part ready for hot isostatic compression treatment.

On the figure 8 we see an example of a piece that can be made with the process. The insert 3 is embedded in the mass of the body 2, it is visible in the figure by transparency. The piece has been machined to give it the desired shape. By this technique it is thus possible to produce elongated parts such as connecting rods in an aircraft landing gear working in both traction and compression.

More generally, it is easy to arrange in a main body a notch which is not necessarily annular. It may be for example rectilinear portions. The machining of corresponding notches is also easy.

Claims (10)

1. A process for manufacturing a metal part reinforced with ceramic fibers, in which: a housing for an insert is formed in a main metal body (2) having an upper face (21); an insert (3) formed from fibers with a metal matrix is positioned in the housing; a metal cover (4) is placed on the main body (2) so as to cover the insert (3); the cover is welded to the metal body under vacuum; the assembly is subjected to a hot isostatic pressing treatment; and the treated assembly is machined to the desired shape, said process being characterized in that the housing has the shape of a notch (23) of L-shaped cross section with two mutually perpendicular faces (23P and 23S), the cover (4) having an internal notch (43) of L-shaped cross section and of shape complementary to that of the notch (23) in the metal body with said insert (3), the cover (4) being shaped on the outside so that the compressive forces are exerted perpendicular to said faces (23P and 23S) of the notch (23).
2. The process as claimed in claim 1, in which the notch (23) in the metal body comprises a face (23P) perpendicular to the upper face (21) of the main metal body (2) and a face (23S) parallel to the upper face (21) of said body (2).
3. The process as claimed in claim 1 or 2, in which the insert (3) is formed beforehand by winding a coated filament and it is placed in the notch (23) of the main metal body (2).
4. The process as claimed in claim 1 or 2, in which the insert is formed by winding a coated filament directly in the notch (23) of the main metal body, said notch forming a winding mandrel.
5. The process as claimed in either of claims 3 and 4, in which the insert has an annular shape.
6. The process as claimed in the preceding claim, in which the insert forms an axisymmetric ring.
7. The process as claimed in claim 5, in which the ring formed by the insert has at least one straight portion.
8. The process as claimed in one of claims 3 to 7, the cross section of the winding of which is rectangular, a first face of the winding bearing against one face of the notch (23) of the main metal body (2) and a second face of the winding bearing against the other face of the notch (23).
9. The process as claimed in one of the preceding claims, the cover of which has a centering surface portion that cooperates with one face of the notch (23) of the main metal body in order to center and guide the deformation of the cover on the main body.
10. The process as claimed in the preceding claim, the face (23P) being perpendicular to the upper face (21) of the main metal body, the centering surface portion of which cooperates with said face (23P) of the notch perpendicular to the upper face (21) of said notch.

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