FR3054799A1 - PROCESS FOR REPAIRING BY RECHARGING A PLURALITY OF TURBOMACHINE PARTS - Google Patents

Abstract

A method of repair by reloading a plurality of parts (40) of a turbomachine, characterized in that it comprises the steps of a) wedging each of said parts to be repaired in a holding member (42), which comprises a surface of end (50) contained in a plane P passing substantially through an end surface (46a) to be reloaded from the part, b) engaging the holding member of each piece in a recess (54) of a block (52). ), said block having a support surface contained in the plane P, and c) perform the reloading of each piece, at its end surface, by means of an additive manufacturing machine, layer by layer, by fusion selective powder bed deposited on said support surface of the block.

Description

(57) Method for repairing by recharging a plurality of parts (40) of a turbomachine, characterized in that it comprises the steps consisting in a) wedging each of said parts to be repaired in a holding member (42), which comprises an end surface (50) contained in a plane P passing substantially through an end surface (46a) to be reloaded from the part, b) engaging the retaining member of each part in a recess (54) of a block (52), said block comprising a support surface contained in the plane P, and c) reloading each part, at its end surface, by means of an additive manufacturing machine, layer by layer , by selective melting on a powder bed deposited on said block support surface.

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Method for repairing by recharging a plurality of parts of a turbomachine

TECHNICAL AREA

The present invention relates to a method for repairing by recharging a plurality of parts of a turbomachine.

STATE OF THE ART

It is known to repair by reloading parts of a turbomachine. Parts, generally worn, are repaired by adding material to the worn area or to be recharged. Different recharging techniques exist.

It has already been proposed to use reloading by additive manufacturing. The technique used is generally that of depositing material by LMD technology (acronym for English Laser Metallic

Deposition). However, this operation is generally unitary, which means that the parts to be reloaded can only be recharged one after the other, which is long and expensive.

There is therefore a need for a repair technology by reloading of parts, which allows serial repair on a large scale.

The present invention provides a simple, effective and economical solution to this problem.

STATEMENT OF THE INVENTION

To this end, the invention provides a method of repairing by recharging a plurality of parts of a turbomachine, characterized in that it comprises the steps consisting in:

a) wedge each of said parts to be repaired in a holding member, which has an end surface contained in a plane P passing substantially through an end surface to be recharged from the part,

b) engaging the retaining member of each part in a recess of a block, said block comprising a support surface contained in the plane P, and

c) reloading each part, at its end surface, using an additive manufacturing machine, layer by layer, by selective melting on a powder bed deposited on said block support surface.

The method according to the invention thus uses SLM technology (acronym for Selective Laser Melting) of additive manufacturing, consisting in fusing powder by means of a high energy beam such as a laser beam. In practice, a powder bed is deposited on a support plate and is scanned by the laser beam to make a part layer by layer, a third layer of fused powder being placed above a second layer which is itself disposed above the above a first layer. In this case, the support plate is formed by the block and the melting of the powder can be located only on the end surfaces of the parts so as to reload them in these areas, which limits the consumption of material and therefore the overall cost of reloading.

The method according to the invention may include one or more of the following characteristics or steps, taken in isolation from one another or in combination with each other:

- the block includes several adjacent recesses configured to each receive a member for holding a part,

- the or each recess has a general parallelepiped shape,

- the block is made of steel or aluminum,

- each member is formed by the assembly of two half-shells defining between them an imprint of a shape complementary to the part. Method according to one of the preceding claims, in which the member is rigidly fixed to the block during step c),

the method comprises an additional step of grinding by machining the recharged portion, by mounting said block on a grinding machine, and

- the parts are turbomachine blades, which are each recharged at a free end of the blade.

DESCRIPTION OF THE FIGURES

The invention will be better understood and other details, characteristics and advantages of the invention will appear more clearly on reading the following description given by way of non-limiting example and with reference to the accompanying drawings in which:

FIG. 1 is a very schematic view of an additive manufacturing machine on a powder bed, and

- Figures 2a to 2d illustrate steps of the method according to the invention.

DETAILED DESCRIPTION

There are two types of additive manufacturing of a part: either the part is produced by successive deposits of molten material, or the part is produced by selective melting on a powder bed as illustrated in Figure 1.

The machine 6 of FIG. 1 makes it possible to manufacture or recharge a part 8, for example aeronautical, by selective melting of layers of powder by high energy beam.

The machine 6 comprises a supply bin 10 containing powder of an electrically conductive material, a roller 12 for transferring this powder from this bin 10 and spreading a first layer 14 of this powder on a tray 16 of construction support (it can be a solid support, part of another room or a support grid used to facilitate the construction of certain rooms).

The machine 6 also includes a recycling tank 18 for recovering a tiny part of the used powder (in particular not melted or unsintered) and the major part of the excess powder, after spreading the powder layer on the support plate 16 Thus, most of the powder in the recycling bin 18 is made up of new powder.

Also, this recycling bin 18 is commonly called by the profession overflow bin or ashtray.

The machine 6 also includes a laser beam generator 20 22, and a control system 24 capable of directing this beam 22 onto any region of the support plate 16 so as to sweep any region of a powder layer . The shaping of the laser beam and the variation of its diameter on the focal plane are done respectively by means of a beam dilator 26 and a focusing system 28, the assembly constituting an optical system.

This device for applying the process comparable to a direct metal deposition process or DMD (acronym for English Direct Métal Déposition) on a powder can use any high energy beam in place of the laser beam 22, as long as this the beam is sufficiently energetic to in the first case melt or in the other case to form necks or bridges between the powder particles and part of the material on which the particles rest.

The roller 12 can be replaced by another suitable depositing system, such as a reel (or hopper) associated with a scraper blade, a knife or a brush, capable of transferring and spreading the powder in a layer.

The control system 24 comprises for example at least one orientable mirror 30 on which the laser beam 22 is reflected before reaching a layer of powder, each point of the surface of which is always located at the same height relative to the lens of focusing, contained in the focusing system 28, the angular position of this mirror 30 being controlled by a galvanometric head so that the laser beam scans at least one region of the first layer of powder, and thus follows a pre-established part profile .

The machine 6 operates as follows. A first layer 14 of powder of a material is deposited using the roller 12 on the support plate 16, this powder being transferred from a feed tank 10 during a forward movement of the roller 12 and then it is scraped off, and possibly slightly compacted, during one (or more) return movement (s) of the roller 12. The excess powder is recovered in the recycling tank 18. A region of this first layer 14 of powder is carried, by scanning with the laser beam 22, at a temperature higher than the melting temperature of this powder (liquidus temperature). The galvanometric head is ordered according to the information contained in the database of the computer tool used for the computer-aided design and manufacture of the part to be manufactured. Thus, the powder particles 32 of this region of the first layer 14 are melted and form a first bead 34 in one piece, integral with the support plate 16. At this stage, it is also possible to scan several regions with the laser beam. independent of this first layer to form, after melting and solidification of the material, several first cords 34 disjoint from each other. The support plate 16 is lowered by a height corresponding to the already defined thickness of the first layer (between 20 and 100 μm and in general from 30 to 50 μm). The thickness of the powder layer to be merged or consolidated remains a variable value from one layer to another because it is highly dependent on the porosity of the powder bed and its flatness while the pre-programmed movement of the tray support 16 is an invariable value to the nearest game. A second layer 36 of powder is then deposited on the first layer 14 and on this first bead 34, then a region of the second layer 36 which is partially or completely above this first bead is heated by exposure to the laser beam 22 34, so that the powder particles of this region of the second layer 36 are melted, with at least part of the first bead 34, and form a second bead 38 in one piece or consolidated, all of these two cords 34 and 38 thus forming a block. To this end, the second cord 38 is advantageously already fully linked as soon as a part of this second cord 38 binds to the first cord34. It can be understood that, depending on the profile of the part to be constructed, and in particular in the case of an undercut surface, it is possible that the aforementioned region of the first layer 14 is not, even partially, below the aforementioned region. of the second layer 36, so that in this case the first codon 34 and the second cord 38 do not then form a single block. This process of building the part is then continued layer by layer by adding additional layers of powder to the assembly already formed. The scanning with the beam 22 makes it possible to construct each layer by giving it a shape in accordance with the geometry of the part to be produced. The lower layers of the room cool more or less quickly as the upper layers of the room are built.

In order to reduce contamination of the part, for example dissolved oxygen, oxide (s) or another pollutant during its layer-by-layer manufacture as described above, this manufacture must be carried out in an enclosure at degree d '' hygrometry controlled and adapted to the process / material couple, filled with a neutral gas (non-reactive) with respect to the material considered such as nitrogen (N2), argon (Ar) or helium (He ) with or without the addition of a small amount of hydrogen (H2) known for its reducing power. A mixture of at least two of these gases can also be considered. To prevent contamination, in particular by oxygen from the surrounding environment, it is customary to put this enclosure under overpressure.

Thus, according to the current state of the art, selective melting or selective sintering by laser makes it possible to build with good dimensional accuracy of lightly polluted parts whose geometry in three dimensions can be complex.

Selective melting or selective sintering by laser also preferably uses powders of spherical morphology, clean (that is to say not contaminated with residual elements from the synthesis), very fine (the size of each particle is between 1 and 100 pm and preferably between 45 and 90 pm), which makes it possible to obtain an excellent surface condition of the finished part.

Selective melting or selective sintering by laser also allows a reduction in manufacturing times, costs and fixed costs, compared to a part molded, injected or machined in the mass.

Figures 2a to 2d illustrate an embodiment of the method according to the invention.

A first step shown in FIGS. 2a and 2b consists in wedging each part 40 to be recharged in a holding member 42. In the example shown, the part to be recharged is a blade 40 of a turbomachine and for example of a turbomachine compressor. The blade 40 comprises a blade 43 connected at its lower longitudinal end to a foot 44, the radially outer end 46 being free and representing a zone of wear and therefore of recharging the blade. Indeed, the upper end of the blade can in operation cooperate by friction with an abradable coating of a casing of the turbomachine, which can cause wear of the blade.

The retaining member 42 here comprises two half-shells 42a defining between them an imprint 48 of shape complementary to the blade 40. In the example shown, the blade 40 is entirely enclosed between the two half-shells 42a.

The member 42 comprises at its upper end a planar end surface 50, which extends in a plane P passing substantially through the surface 46a of the free end of the blade (FIG. 2b).

The member 42 further comprises means for fixing or clamping to a block of material 52 shown in Figure 2c, for their attachment.

The block 52 comprises several recesses 54 intended to receive respectively several members 42 for holding several blades 40. In the example shown, the block 52 comprises twelve recesses and can therefore be used to simultaneously recharge twelve blades 40, which are all disposed of the same way. The block is for example made of steel or aluminum.

As seen in Figure 2c, each member 42 is, in the assembled position, configured to be inserted by translation in a recess 54 of the block. Each member can be configured to be fully housed in the corresponding recess. In other words, the recess has a shape complementary to that of the member which, as mentioned in the foregoing, includes means for fixing to the block. In the example shown, these means comprise a lug 56 carried by each half-shell and pierced with an orifice for the passage of a screw or the like.

After insertion of the members 42 in the recesses 54 and fixing of the members 42 to the block 52, the assembly is obtained as shown in FIG. 2d in which both the end surfaces 46a, 50 of the blades 40 and the members 42 as well as the upper surface 52a of the block 52, are coplanar and therefore contained in the same plane P.

This plane serves as a reference surface for reloading surfaces 46a by additive manufacturing by selective melting on a powder bed. An additive manufacturing machine, such as that described with reference to FIG. 1, is thus applied to reload the blades 40 at their surfaces 46a. This therefore makes it possible to reload a large quantity of coins simultaneously, namely twelve in the example shown.

Reloading here benefits from the advantages of additive manufacturing, namely that it can be produced precisely by adding fine and / or complex structures, for example honeycomb.

The block 52 having been used for recharging the blades can then be used for resumption by machining of the recharged portions. The block is then mounted on a recovery machine and can be wedged against this machine so that the block serves as a reference in space for positioning the blades to be machined.

Likewise, the block 52 can, before the reloading operation, be used for surfacing or for rectifying the end surfaces 46a of the blades 40, so as to guarantee that all these surfaces are, for example, flat and coplanar. This surfacing can be carried out manually or by means of an appropriate machine.

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Claims (9)

1. Method for repairing by recharging a plurality of parts (40) of a turbomachine, characterized in that it comprises the steps consisting in: a) wedging each of said parts to be repaired in a holding member (42), which has an end surface (50) contained in a plane P passing substantially through an end surface (46a) to be recharged from the part, b) engaging the retaining member of each part in a recess (54) of a block (52), said block comprising a support surface contained in the plane P, and c) reloading each part, at its end surface, using an additive manufacturing machine, layer by layer, by selective melting on a powder bed deposited on said block support surface. 2. Method according to claim 1, wherein the block (52) comprises several adjacent recesses (54) configured to each receive a member (42) for holding a part (40). 3. Method according to claim 1 or 2, wherein the or each recess (54) has a generally parallelepiped shape. 4. Method according to one of the preceding claims, wherein the block (52) is made of steel or aluminum. 5. Method according to one of the preceding claims, in which each member (42) is formed by the assembly of two half-shells (42a) defining between them an imprint (48) of shape complementary to the part (40). 6. Method according to one of the preceding claims, in which the member (42) is rigidly fixed to the block (52) during step c). 7. Method according to one of the preceding claims, in which it comprises an additional step of grinding by machining the recharged portion, by mounting said block (52) on a grinding machine. 8. Method according to one of the preceding claims, in which it comprises a preliminary step of surfacing the end surface. 5 (42a) of the part (40). 9. Method according to one of the preceding claims, wherein the parts are blades (40) of a turbomachine, which are each recharged at a free end (46) of the blade (43). 1/2