EP3036057B1 - Composite reinforcement insert and manufacturing method - Google Patents

Description

TECHNICAL AREA

The present invention relates to a reinforcing insert, preferably for a turbomachine part, as well as to a method of manufacturing such a reinforcing insert.

STATE OF THE PRIOR ART

In the field of aeronautics in particular, a constant objective is the optimization of the resistance of parts for a minimum mass and size. Thus some parts may now include a reinforcement insert made of composite material with a metal matrix. Such a composite material generally comprises a metal alloy matrix, for example of titanium alloy Ti, nickel Ni or aluminum Al, in which fibers extend, for example ceramic fibers of SiC silicon carbide. Such fibers have a tensile strength much greater than that of titanium (typically 4000 MPa against 1000 MPa) and a rigidity typically three times higher. It is therefore the fibers that take up the forces, the metal alloy matrix ensuring the transfer of charges between the fibers, a binder function with the rest of the part, as well as a function of protection and separation of the fibers, which must not come into contact with each other. In addition, the ceramic fibers are strong, but fragile and must necessarily be protected by metal.

These composite materials can be used in the manufacture of disks, shafts, cylinder bodies, housings, spacers, as reinforcements of monolithic parts such as blades, etc. They may also find application in other fields where a field of voluminal forces applies to a part, for example a pressure envelope such as a gun or a pressure fluid reservoir.

In order to obtain such a reinforcing insert made of composite material, it is previously formed so-called "coated son", comprising a frame formed of a ceramic fiber, coated with a metal sheath. The metal coating gives the wire a greater stiffness but a better toughness, useful for its handling.

In the prior art, the coating of silicon carbide (SiC) fibers is most often carried out by a physical gas phase deposition method EBPVC (Electron Beam Physical Vapor Deposition). However, this process is not very profitable in terms of yield. In addition, the coating process is long, since the deposition rate is of the order of one meter per minute.

The prior art also proposes to perform the coating of SiC fibers by a direct coating process of the SiC fiber in a molten metal bath levitation. Such a coating process is for example described in the document EP0931846 . This document proposes to keep the liquid metal levitated in a suitable crucible, so as to at least partially remove the contact with the walls of the latter, at an appropriate temperature. Levitation is achieved by electromagnetic means surrounding the crucible. The ceramic fiber, held taut by means of pre-emption, is drawn through the metal bath. The rate of passage of the fiber into the metal bath is set according to the desired metal thickness on the fiber. This process is faster than the previous one, but it produces an off-center fiber. In addition, it does not allow to easily adjust the ratio between the percentage of SiC fiber and the percentage of metal matrix. In addition, destabilizations may appear in the inserts manufactured according to this method.

SUMMARY OF THE INVENTION

The invention aims to overcome the drawbacks of the state of the art by providing a reinforcing insert according to claim 1 which has a reinforced strength and whose composition can be chosen.

• un toron formé par une fibre centrale en matériau céramique entourée par des brins en alliage métallique enroulés en hélice autour de la fibre centrale,
• une couche de renfort métallique recouvrant le toron.

To do this, is proposed according to a first aspect of the invention, a composite reinforcing insert, preferably for a turbomachine, comprising:

• a strand formed by a central fiber made of ceramic material surrounded by metal alloy strands wound helically around the central fiber,
• a metal reinforcing layer covering the strand.

A "strand" is an assembly whose strands or fibers are arranged in concentric layers around a strand or central fiber.

Thus, unlike the reinforcing inserts of the prior art in which the reinforcing layer is deposited directly on the central fiber, the invention proposes to previously wind the metal alloy fibers around the central fiber, and then to coat the assembly obtained with a metal reinforcement layer. The reinforcement insert thus obtained has improved strength. It also has the advantage of having a central fiber centered relative to the metal part surrounding it. In addition, such a reinforcing insert is particularly advantageous because it is possible to choose the ratio between the percentage of ceramic material and the percentage of metal alloy easily.

The reinforcing insert according to the invention may also have one or more of the following features taken individually or in any technically possible combination.

According to various embodiments, the strand may comprise N strands of metal alloy with N greater than or equal to 6. N is preferably equal to 7, 19 or 37. The diameter of the metal strands and their number N are determined so that the insert has a chosen number Vf. The number Vf corresponds to the surface ratio between the ceramic fiber and the surrounding metal alloy strands. When the strand has 6 strands of metal alloy, these strands are preferably arranged to form a single layer around the central fiber. Vf is then equal to 1/7 or 14.3%. When constructions with Vf of less than 14% are selected, the strand has number of strands beyond 18 or 19 around the core fiber and these strands are preferably arranged to form a plurality of concentric layers around the core fiber.

The central fiber is preferably made of silicon carbide, which has good mechanical properties.

Advantageously, the strands are made of a metal alloy based on titanium, nickel or aluminum so that the reinforcing insert has a good ratio strength / weight.

The metal reinforcing layer is preferably made of the same metallic base material as the metal alloy forming the strands.

• (a) Toronnage de brins en alliage métallique autour de la fibre centrale de façon à former un toron;
• (c) Enduction du toron d'une couche protectrice métallique.

A second aspect of the invention also relates to a method for producing a reinforcing insert according to claim 7, preferably for a turbomachine, from a ceramic core fiber, the method comprising the following steps:

• (a) Stranding of metal alloy strands around the core fiber to form a strand;
• (c) Coating the strand with a protective metal layer.

Such a method is simple and fast, and it allows to obtain reinforcement inserts whose composition can be chosen. In addition, the ceramic fiber of the insert thus produced is centered.

The method may also comprise a step (b) of fixing the strands by welding points. This step can be performed by laser or electron beam. However, this fixing step is not essential if the strand has a mechanical strength without expansion of the strands.

The coating step preferably comprises a step of passage of the strand in a liquid molten metal bath levitation.

The levitated liquid molten metal preferably comprises a filler of the same material as the base material of the strands.

The method may also comprise, between steps (b) and (c), a step of coating of the strand by a protective layer against oxidation. This protective layer is particularly useful when the metal alloy of the strands is sensitive to oxidation. This is for example the case when the strands are made of an aluminum alloy. The strand can then be covered with a protective layer, which is preferably a copper nanolayer. This protective layer disappears during the passage of the strand in the liquid metal bath.

Another aspect of the invention also relates to a metal part for a turbomachine comprising an insert according to the first aspect of the invention or made according to a method according to the second aspect of the invention.

• Mise en place par trancanage d'un insert de renfort selon le premier aspect de l'invention ou obtenu par un procédé selon le deuxième aspect de l'invention autour de la pièce de turbomachine ;
• Compaction de la pièce de turbomachine par compression isostatique à chaud.

The invention also relates to a method for producing a metal part for a turbomachine comprising the following steps:

• Placement by trancanage of a reinforcing insert according to the first aspect of the invention or obtained by a method according to the second aspect of the invention around the turbomachine part;
• Compaction of the turbomachine part by hot isostatic compression.

BRIEF DESCRIPTION OF THE FIGURES

• La figure 1, une vue en coupe d'une fibre en céramique ;
• La figure 2, une vue en coupe d'une fibre en céramique entourée par des brins en alliage métallique ;
• La figure 3, une vue en perspective de trois torons ;
• La figure 4, un toron recouvert d'une couche de renfort ;
• La figure 5 donne l'évolution du rapport le rayon des brins métalliques et celui de la fibre, ainsi que le Vf obtenu en fonction du nombre de brins pour des constructions monocouche.

Other characteristics and advantages of the invention will emerge on reading the detailed description which follows, with reference to the appended figures, which illustrate:

• The figure 1 a sectional view of a ceramic fiber;
• The figure 2 a sectional view of a ceramic fiber surrounded by metal alloy strands;
• The figure 3 , a perspective view of three strands;
• The figure 4 a strand covered with a reinforcing layer;
• The figure 5 gives the evolution of the ratio of the radius of the metal strands and that of the fiber, as well as the Vf obtained as a function of the number of strands for monolayer constructions.

For the sake of clarity, identical or similar elements are identified by signs of identical references on all the figures.

DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT

A method of producing a reinforcing insert according to one embodiment of the invention is described with reference to Figures 1 to 4 . The reinforcing insert is made from a central fiber 1 ceramic. This central fiber 1 is made of silicon carbide.

The method comprises a first step (a) of making a strand by winding strands 2 of metal alloy around the central fiber 1. The strands are preferably made of a metal alloy based on titanium, nickel or aluminum. aluminum. The strands are helically wrapped around the core fiber to form a helix around the core fiber. Depending on the ratio Vf, the strand may comprise more or fewer strands 2. The number Vf is defined as the surface ratio between the central fiber and the metal strands. For example, a central fiber 1 of 140 μm in diameter has a section of 15400 μm ² . A strand of 10 strands of 70 microns diameter has 10 sections of 3850 microns ² is 38500 microns ² . That is a total area of 38500 + 15400 = 53900 μm ² . The surface ratio Vf is therefore equal to 15400 × 53900 × 100 = 29%.

Avec :

• R1 rayon de la fibre céramique, R2 rayon du brin métallique
• N nombre de brins métalliques

The strand generally comprises N strands with N greater than or equal to 6. The strands 2 are arranged in concentric layer (s) around the central fiber 1. It is also possible to vary the diameter of the central fiber 1 and the diameter strands 2 depending on the ratio Vf wanted between the percentage of silicon carbide fiber relative to the percentage of material of the strand. The sizing relationships are: $$\begin{array}{cc}\sin \left(\mathrm{180}\mathrm{°}/\mathrm{NOT}\right)=\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="imgf0001.png"\; state="\{\{state\}\}">R</figure-callout>}\mathrm{2}/\left(\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="imgf0001.png"\; state="\{\{state\}\}">R</figure-callout>}\mathrm{1}+\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="imgf0001.png"\; state="\{\{state\}\}">R</figure-callout>}\mathrm{2}\right)& \mathrm{vf}={\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="imgf0001.png"\; state="\{\{state\}\}">R</figure-callout>}\mathrm{1}}^{\wedge \mathrm{2}}\end{array}/\left({\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="imgf0001.png"\; state="\{\{state\}\}">R</figure-callout>}\mathrm{1}}^{\wedge \mathrm{2}}+\mathrm{NOT}*{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="imgf0001.png"\; state="\{\{state\}\}">R</figure-callout>}\mathrm{2}}^{\wedge \mathrm{2}}\right)$$

With:

• R1 radius of the ceramic fiber, R2 radius of the wire strand
• N number of metal strands

The evolution of the number Vf as a function of the number of strands in the case of a single layer stranding is represented on the figure 5 , as well as the evolution of the ratio R2 / R1 in depending on the number of strands at the periphery.

For example, a silicon carbide fiber of 140 μm in diameter surrounded by 7 strands of 107 μm in diameter and coated with a protective layer of 3 μm, gives a percentage of silicon carbide fiber SiC of 20%.

During the stranding operation of the metal alloy strands around the central fiber 1, it is imperative to circulate the central fiber without generating radii of curvature less than 20 mm in order not to damage the central fiber. For this, the pulleys used to wind the central fiber during the stranding operation must be large enough not to generate bending radii in the core fiber less than 20 mm.

If the strand exhibits expansion phenomena around the central fiber, it is possible to perform small spot welding of the strands in line with the stranding machine. A technique by laser welding or electron beams can be used

Moreover, when the strands 2 are made of metal alloys sensitive to oxidation, the method may comprise a step (c) of coating the strand with a protective layer. For example, when the metal alloy used for the strands 2 is aluminum-based, the protective layer may be a copper nanolayer. This protective layer disappears in the next step.

Indeed, the method then comprises a step (c) of coating the strand by a metal reinforcement layer 3. For this, the strand is passed through a molten liquid metal bath levitation of a charge of the same material as the strands placed helically around the central fiber 1. Thus, when the strands 2 are made of an alloy Based on titanium, the charge of the liquid metal bath preferably comprises titanium. Similarly, when the strands 2 are made of an aluminum-based metal alloy, the load preferably comprises aluminum. Methods of coating the strand with a liquid metal bath are known from the prior art. Such methods are for example described in the documents EP 0 931 846 or EP 1,995,342 . During the coating step, the strands 2 are not completely remelted. At the end of this step (c) of coating, the strand is coated with a metal reinforcement layer 3. This reinforcing layer 3 is continuous.

The method then comprises a step of solidification of the reinforcing insert, during which the reinforcing insert becomes rigid.

• Un toron comportant :
  • ∘ Une fibre centrale 1 en céramique ;
  • ∘ Des brins 2 en alliage métallique entourant la fibre centrale 1 de façon à former une hélice autour de la fibre centrale ;
• Une couche de renfort 3 en alliage métallique recouvrant le toron.

A reinforcement insert is thus obtained according to an embodiment of the invention comprising:

• A strand comprising:
  • ∘ A central fiber 1 made of ceramic;
  • Metal alloy strands 2 surrounding the central fiber 1 so as to form a helix around the central fiber;
• A reinforcing layer 3 of metal alloy covering the strand.

The reinforcement insert thus obtained is easy to manufacture, very resistant. In addition, its composition can easily be modified.

The reinforcement insert thus obtained can then be used to reinforce parts, particularly in the field of aeronautics. For this purpose, the reinforcing insert can then be shaped by tran-canning around a turbomachine part, and especially around a casing or a turbomachine disc. The reinforcement insert is placed in the part to be reinforced. The resulting assembly can then be compacted by hot isostatic pressing. In order to obtain a totally compact composite part.

Claims (10)

1. A composite reinforcement insert including:

   - a strand formed by a centre fibre (1) of ceramic material surrounded by filaments (2) of metal alloy helically wound around the centre fibre (1),

   - a metal reinforcement layer (3) covering the strand.
2. The reinforcement insert according to the preceding claim, wherein the strand includes N filaments (2) with N higher than or equal to 6, N being preferably equal to 7, 19 or 37 filaments (2).
3. The reinforcement insert according to one of the preceding claims, wherein the centre fibre (1) is made of silicon carbide.
4. The reinforcement insert according to one of the preceding claims, wherein the filaments (2) are made of a titanium, nickel or aluminium-based alloy.
5. The reinforcement insert according to one of the preceding claims, wherein the reinforcement layer (3) is made of the same material as the base material of the filaments (2).
6. A turbomachine piece reinforced by a reinforcement insert according to one of the preceding claims.
7. A method for manufacturing a composite reinforcement insert from a centre fibre (1) of ceramics, the method including the following steps of:

   - (a) stranding filaments (2) of metal alloy around the centre fibre so as to form a strand;

   - (c) coating the strand with a metal reinforcement layer (3)
8. The method according to the preceding ciaim, wherein the coating step includes a step of passing the strand through a levitation molten liquid metal bath, the levitation molten liquid metal including a load of the same material as the base material of the filaments.
9. The method according to one of claims 7 and 8, further including a step (b) of attaching the strands by welding points.
10. The method according to one of claims 7 to 9, further including, between steps (a) and (c), a step of coating the strand with an oxidation protective layer.

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