EP2443265B1 - Process for the manufacture of a metallic workpiece incorporating an annular fibrous reinforcement - Google Patents

Description

The invention relates to a metal part having an annular portion including a coaxial annular fiber reinforcement, in the form of a coil of composite material enclosed in a metal matrix. The invention relates more particularly to the manufacture of such a piece with improved strength. It also relates to a metal part enclosing such a coaxial annular reinforcement, see for example DE-A-10 2004 001 262 .

It is known to reduce the mass of an annular metal part while providing a very high resistance in tangential tension or compression, by incorporating fibers of composite material such as ceramic in the metal mass. The ceramic is, for example, silicon carbide wire which has a tensile or compressive strength greater than that of a metal, such as titanium for example.

To obtain such a part, it is possible to produce a winding of metal-coated ceramic wire inside a blank of the part. For example, the document FR 2,886,290 proposes to carry out the winding directly on a part of the blank forming the winding mandrel. It is therefore an "external" winding of the most classic. More precisely, this part has two shoulders. The radially innermost shoulder forms a lateral bearing surface for the winding. The adjacent cylindrical portion forms the base surface on which the winding is made. It has a rectangular shape in right cross section. After winding, complete the blank by complementary metal parts, including an outer ring and a side cover having a pin coming into contact with the winding. This assembly is then subjected to a hot isostatic pressing step during which the cover, in particular, is deformed so that the winding is compressed by the tenon. The hot isostatic pressing operation is known per se; it consists in placing the aforementioned assembly in a box and subjecting this assembly, for several hours, to a high pressure of the order of 1000 bar and at a temperature of the order of 1000 ° C. After this operation, the piece, from a single block, is machined to the desired shape and dimensions. Generally, the different parts of the blank and the sheathing of the ceramic wire are of the same metal so that the finished part is provided with a wound composite insert, embedded in a homogeneous metal matrix.

The zone reinforced by the winding has a generally rectangular cross section. To lighten the part and increase the tensile strength / compression in the tangential direction, it is desirable that this reinforced area, surrounded by exclusively metal parts, occupies as large a volume as possible.

This rectangular cross-section insert arrangement may not be completely satisfactory in the direction of the forces applied to the workpiece. While the fiber strength is excellent tangential to both tensile and compressive, it is lower than that of pure metal when the forces are applied in a direction transverse to the fibers. As examples, this is particularly the case when the annular piece thus manufactured is a rotating part provided with blades, such as a turbine disk, in particular for an aircraft turbojet engine. Another piece subjected to transverse forces is the "rotating sleeve" connected to jacks in a landing gear mechanism.

With a part provided with a winding with rectangular straight cross-section, breaks are possible in the outside part of the reinforced zone.

The basic idea of the invention consists in establishing a "zone of progressivity" in pure metal in this outer radial region, laterally between the periphery and the zone where the turns are located. This leads, according to the invention, to conform the winding so that it has a right cross section of axial length decreasing radially outwardly at least in an outer radial zone of the axisymmetric part.

For example, a coiled portion having a trapezoidal or triangle-shaped cross section at least in its radially outermost portion is capable of responding to the problem data. A half-wave shape may also be considered provided that the proportion of pure metal increases radially outward of the room, all other things being equal.

Another difficulty is then to make the part because the "external" winding as described above is difficult to envisage. The invention also proposes a new approach to winding, called "internal winding".

• élaborer une ébauche métallique annulaire de ladite pièce,
• pratiquer ou achever une cavité ouvrant sur une face intérieure coaxiale de ladite ébauche et présentant une section transversale droite de longueur axiale décroissant radialement vers l'extérieur sur au moins une partie de sa hauteur,
• enrouler un fil de renfort dans ladite cavité de façon à remplir sensiblement tout l'espace de celle-ci par une bobine,
• fermer ladite cavité enmettant en place un élément de paroi métallique en regard de l'ouverture de ladite cavité, puis,
• soumettre l'ensemble à un processus de compression isostatique à chaud, et
• usiner ladite ébauche pour obtenir la géométrie finale de ladite pièce.

More specifically, the invention relates to a method for manufacturing an annular axisymmetric metal piece reinforced by inclusion therein of a coaxial annular reinforcement in the form of a composite material coil, characterized in that it comprises the steps of :

• developing an annular metal blank of said part,
• practicing or completing a cavity opening on a coaxial inner face of said blank and having a right cross section of axial length decreasing radially outwardly over at least a portion of its height,
• winding a reinforcing wire into said cavity so as to fill substantially all the space thereof with a coil,
• closing said cavity by putting in place a metal wall element facing the opening of said cavity, then,
• subject the assembly to a process of hot isostatic compression, and
• machining said blank to obtain the final geometry of said part.

The term "right cross section", a section in a plane containing the axis of the axisymmetrical part considered, more precisely the axis of the blank in the above definition.

According to an advantageous characteristic, the reinforcing wire is composed of a ceramic core, sheathed with metal.

The shape of the coil thus obtained, that is to say, in fine, the shape of the zone provided with ceramic fibers makes it possible to reserve radially outwards of said zone and on either side thereof larger masses of pure metal (titanium for example) allowing a substantially radial force to transfer "progressively" in the fibers along directions turning it into effort more and more oriented tangentially.

The coil can be stabilized during its formation by welds joining certain turns together by their metal sheath.

To proceed with the so-called "internal" winding, the winding of the reinforcing wire is initiated by fixing an end thereof to the bottom of the cavity and the winding is continued by rotating the blank about its axis while feeding the wire at a controlled speed relative to the speed of rotation of the blank.

Advantageously, the feeding speed of the wire is such that it urges said blank in the direction of rotation thereof.

• les figures 1, 2, 3A et 4 à 6 illustrent par des vues en coupe transversale droite les différentes étapes du procédé de fabrication d'une pièce métallique annulaire axisymétrique renforcée par bobinage d'un fil de renfort ;
• la figure 3B est une vue partielle en perspective illustrant la phase de la figure 3A ; et
• la figure 7 représente la pièce ainsi obtenue.

The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description illustrating a method of manufacturing an axisymmetric annular metal part reinforced by a coaxial winding, given only as a examples and with reference to the accompanying drawings, in which:

• the Figures 1, 2, 3A and 4 to 6 illustrate by cross-sectional views right the different steps of the method of manufacturing an axisymmetric annular metal part reinforced by winding a reinforcing wire;
• the figure 3B is a partial perspective view illustrating the phase of the figure 3A ; and
• the figure 7 represents the piece thus obtained.

Referring to the drawings, there will be described a method for producing an annular piece such as a rotor disc, from a metal blank 11, for example titanium, itself annular and axisymmetric, here cross section rectangular right, as shown on the figure 1 . The axis of revolution of the blank is referenced X.

Of course, this section may have a different shape depending on the geometry of the final part that is desired.

The blank has a coaxial inner face 12, here cylindrical.

This is both to lighten said final piece while giving it increased mechanical strength.

After the development of such a draft, the next step ( figure 2 ) is to practice, in the mass of the blank, for example by machining, a cavity 14 opening (opening) on said coaxial inner face 12. It is possible for example to rotate the blank about the axis X and introduce a cutting tool by the central portion, accessible, of said blank. Material is removed until an annular cavity opens on said coaxial inner face of the blank. Note it can be from an already hollow blank, the machining operation simply to complete the cavity to give it the desired shape and dimensions.

According to an important characteristic, the cavity 14 has a right cross section of axial length decreasing radially outwardly over at least a portion of its height. In the example, the cavity has (in a right cross-section and in a radial direction from the inside to the outside) a rectangular shape 15 extended by a trapezoidal shape 16. This second part of the cavity could have a triangular shape or any other shape whose axial length (along the X axis) decreases from the inside to the outside.

This results in a reserve of pure metal in the lateral zones 17, 18 indicated in dotted lines, compared to what would be obtained if the cavity had a rectangular cross section.

The following operation is to wind in situ a reinforcing wire 21, here ceramic (silicon carbide) coated with metal. The metal is here titanium, that is to say the same metal as that which constitutes the blank. This operation, illustrated in figure 3A , is carried out by introducing the wire through the opening of the cavity and depositing it from the cylindrical bottom 23 of the cavity by adjacent turns and then by successive layers of turns until the entire space of the cavity is completely filled, by a coil of contiguous turns 25.

For winding, this can be done. The wire is fed via a rigid tubular guide 27 movable in a controlled manner parallel to the X axis (to form a layer) and radially recessed (to develop the following successive layers). The guide 27 is oriented as shown on the Figures 3A and 3B that is, its end 27A is at a small angle to the circumferential winding direction of the turns.

The winding of the wire 21 is started by fixing (by welding) one end thereof to the cylindrical bottom wall 23 of the cavity, near one end thereof, and the blank 11 is rotated around its end. X axis, and feeding the wire at a controlled speed relative to the speed of rotation of the blank. For example, it is possible to continuously adjust the speed at which the wire 21 is brought so that this speed is always substantially equal to the winding speed. taking into account the speed of rotation of the blank and the diameter of the layer of turns during winding.

It will also be possible to ensure that the feed speed of the wire is such that it solicits the roughing in the direction of rotation of the latter. For example, the wire 21 may be pushed inside the guide 27 by a drive rotary roller drive system (not shown) with possibility of longitudinal sliding so that said wire is in slight compression between its output of the guide 27 and the point where it takes its place in the winding. It can even be envisaged that the blank 11 is mounted in free rotation and that it is the stress exerted on the wire itself which drives it in rotation during the winding.

To avoid expansion, the turns are stabilized at given winding intervals, by welding points or lines joining the metal sheaths of certain turns.

In a manner known per se, the weld can be an electrical or induction weld, under vacuum or in a neutral atmosphere of argon. A welding process as described in FR 2,886,290 can be implemented.

The following operation, figure 4 consists, for example, in closing a cavity 14 filled with the coil 25. For example, a cylindrical metal annular wall 30, here made of titanium, is placed in register with the opening of the cavity. This wall here has the same length as the axial length of the opening so that during hot isostatic compression, it can deform radially outwardly penetrate the cavity, compacting the winding itself. The cylindrical annular wall 30 can be dimensioned so that its diameter is slightly greater than that of the central opening of the blank but while carrying this annular wall at a low temperature (by dipping it in liquid nitrogen, for example ) before putting it in place. Thus, even before the start of the hot isostatic pressing operation, the annular wall 30 engages the cavity by starting to compact the coil.

Advantageously, the closure of said cavity comprises its evacuation with hermetic closure by a welded metal sheet 32. This metal sheet is welded on both sides of the opening of the cavity, before the hot isostatic pressing operation.

The hot isostatic pressing operation proper, consisting of, for example, placing the blank, modified as shown, is then carried out. figure 4 , in a box for several hours, bringing the pressure to 1000 bar and the temperature to 1000 ° C, approximately.

The result is represented figure 5 . It can be seen that the annular wall 30 is engaged in the cavity, driving the metal foil 32. The assembly forms only a single block with a large part of the volume occupied by a coil of high-strength ceramic wire, embedded in a metal matrix resulting from the melting of the metal sheath of the wire used during winding.

We then proceed to a series of machining operations ( figure 6 ) intended, from the blank transformed by the hot isostatic pressing operation, to define the contour of the desired part (shown in dashed line on the figure 6 ). The final piece 36 of the figure 7 comprises purely metallic external lateral zones (17a, 18a), making it possible to increase the transverse mechanical strength of the part and locally to limit the breaks of stiffness favoring breaks. These so-called "progressivity" zones have the effect of bringing the efforts gradually, by shearing, into the fibrous reinforcement (the winding) in order to convert the tensile forces / circumferential compression for which the resistance of the wound zone is optimal.

Claims (6)

1. A method of fabricating an axisymmetric annular metal part reinforced by including coaxial annular reinforcement therein in the form of a winding of composite material, the method comprising the steps consisting in:

   preparing an annular metal blank (11) for said part;

   making or finishing off a cavity (14) that opens out into a coaxial inside face of said blank and that possesses a right cross-section of axial extent that decreases going radially outwards over at least a portion of its height; and

   • winding a reinforcing yarn (21) in said cavity so as to fill substantially all of the space therein with a winding,

   the method being characterized in that it further comprises the steps consisting in:

   • closing said cavity by putting into place a metal cylindrical wall (30) in register with the opening of said cavity; then

   • subjecting the assembly to a hot isostatic compression process; and

   • machining said blank to obtain the final shape of said part.
2. A method according to claim 1, characterized in that said reinforcing yarn (21) is made up of a core of composite material such as ceramic, sheathed in metal, and in that the winding that is being formed is stabilized by welds bonding together certain turns via their metal sheaths.
3. A method according to claim 1 or 2, characterized in that the winding of the reinforcing yarn is started by fixing one end thereof to the bottom (23) of the cavity, and in that winding is continued by causing said blank to turn about its axis (X) while feeding the yarn at a speed that is controlled relative to the speed of rotation of the blank.
4. A method according to claim 3, characterized in that the yarn (21) is fed at a speed that is such that it applies a force on said blank in its direction of rotation.
5. A method according to any one of the preceding claims, characterized in that said open cavity is shaped in such a manner as to give it a cross-section that is triangular or trapezoidal (16) at least in part, at least in the radially outermost portion thereof.
6. A method according to any one of the preceding claims, characterized in that closing said cavity includes evacuating it and hermetically closing it with a metal foil (32) that is welded on either side of the opening in said cavity, prior to performing the hot isostatic compression operation, said metal foil covering radially inwards said metal cylindrical wall (30) and being taken with it during the hot isostatic compression process.

Images