FR3069554A1 - DEVICE FOR PROTECTING A WAVE FOOT DURING AN ALUMINIZATION PROCESS - Google Patents

Abstract

The invention relates to a protective device adapted to the protection of a blade root during a process for depositing a vapor phase coating, comprising: a first and a second half-shells (100a, 100b) designed to be assembled according to a reference plane (P) so as to form a protective shell (100) adapted to encompass the blade root, and - a frame (200) able to hold the two half against each other -shells (100a, 100b) assembled according to the reference plane, in which each of the half-shells (100a, 100b) has an inner main wall (110a) extending substantially parallel to the reference plane and having a recessed area ( 112) and a projecting zone (111), the recessed area (112) forming a housing of shapes and dimensions adapted to receive the blade root, the projecting zone (111) forming, in contact with the projecting zone the other half-shell, a waterproof protection against the coating.

Description

DEVICE FOR PROTECTING A DAWN DURING AN ALUMINIZATION PROCESS

TECHNICAL AREA

The present invention relates to a device for protecting a foot of dawn during a deposition process of a coating in the vapor phase and, in particular, the deposition of an aluminum layer. The invention also relates to the use of this protective device. The invention finds applications in the field of aircraft construction and, in particular, in the field of the manufacture of turbine engine blades.

STATE OF THE ART

It is known, in the aeronautical field, that a turbomachine is subjected to very high thermal stresses. The materials used for the manufacture of these turbomachines are therefore selected to withstand these operating conditions and the walls of the parts swept by the hot gases, such as for example the moving blades of the turbine, are generally provided with cooling means. In addition, because of their metallic constitution in nickel or cobalt-based superalloys, it is also necessary to protect these parts from oxidation and corrosion caused by hot engine gases.

One known means for ensuring the protection of these parts is to deposit a metal coating, preferably based on aluminum, on surfaces liable to be damaged by gases. This coating - a few tens of microns thick - attaches to the substrate by metallic inter-diffusion and forms a protective oxide layer on the surface of the part.

To produce such a protective layer, it is known to deposit aluminum in the vapor phase, called the aluminization process. An example of such an aluminization process is described by the applicant in document FR 2 992 977. According to this process, the parts to be treated are placed in a metallization enclosure, in which the atmosphere consists of a mixture an inert or reducing gas, for example argon or hydrogen, and an active gas comprising an aluminum halide. At the reaction temperature - between approximately 900 ° C and 1150 ° C - the halide decomposes on the surface of the part into gaseous halogen and aluminum which diffuses into the metal.

However, when the parts to be treated are turbine blades, the process must be carried out only on specific areas of said blades. The metal coating must not be deposited over the entire blade as this may cause the blade to be non-conforming. In particular, the metal coating should not be placed on the dawn.

To protect the blade roots during the aluminization process, protective devices are generally placed around the base of each blade. An example of a protection device is described by the applicant in document FR 2 995 616. This protection device, an example of which is shown in FIG. 1, comprises two half-shells 3a, 3b intended to wrap the blade root 4 so as to form a protective shell 2 around said foot. A bead 5, formed on the internal periphery of each half-shell 3a, 3b, is intended to be inserted into a groove in the blade root in order to form a tight barrier to the metallic coating (based on aluminum) in the vapor phase .

However, this bead being in contact with the blade root over its entire length, it causes a tearing of the metal deposit at the junction zone of the blade root and the blade body, at the time of removing the half -Shells. In fact, during the vapor phase, a metallic deposit generally forms along the joint between the bead of each half-shell and the groove of the blade root. The removal of the half-shells causes the metal deposit to be torn off in the vicinity of the joint so that the metal coating of the specific areas of the blade is damaged.

SUMMARY OF THE INVENTION

To respond to the problem mentioned above of metal deposit tearing, the applicant proposes a device for protecting the blade roots in which the zone of each half-shell which surrounds the blade root is in mechanical contact with the zone of the other half-shell surrounding the blade root.

According to a first aspect, the invention relates to a protection device suitable for the protection of a blade root during a process for depositing a coating in the vapor phase, comprising:

- a first and a second half-shell designed to be assembled according to a reference plane so as to form a protective shell capable of encompassing the blade root, and

- A frame capable of holding one against the other the two half-shells assembled according to the reference plane.

This device is characterized by the fact that each of the half-shells comprises an internal main wall extending substantially parallel to the reference plane and comprising a recessed area and a projecting area, the recessed area forming a housing of shape and dimensions adapted to receive the blade root, the projecting area forming, by contact with the projecting area of the other half-shell, a tight protection against the coating.

This protective device makes it possible to protect, from any metallic coating, the foot of a blade during the aluminization phase of said blade without risk of the coating being torn off in the areas adjacent to the blade root.

In the following description, the walls and other components of the half-shells are defined in transverse, lateral and / or longitudinal directions. In particular, the transverse walls are defined along the XZ plane of an orthonormal reference frame XYZ (also called transverse plane T), the main walls are defined according to the XY plane (called the reference plane P) and the lateral walls are defined according to the YZ plan.

Advantageously, the recessed area and the projecting area of the protection device are connected by a recess of a thickness substantially equal to half a dimension of the blade root in a transverse plane, perpendicular to the reference plane. . In this way, when the two half-shells are assembled, the protruding areas of the half-shells form a tight barrier to the metal deposit.

Advantageously, each half-shell has a transverse wall extending perpendicular to the reference plane and covering one end of the blade root, the projecting area of the internal main wall extending longitudinally from the transverse wall to beyond. a bead intended to be inserted into a groove in the blade root.

According to certain embodiments, the projecting zone of each half-shell comprises, in at least a portion remote from the transverse wall, an oblique transverse stop forming a draft.

According to certain embodiments, each half-shell of the protection device comprises two side walls, parallel to each other and extending perpendicular to the reference plane and to the transverse wall, the lateral and transverse walls of the first half-shell comprising a joint zone of shapes and dimensions complementary to the joint zone of the second half-shell

According to certain embodiments, each half-shell has a non-planar external main wall. This non-planar wall facilitates the assembly of the half-shells inside the frame.

According to one example, the main external wall is at least partially bevelled longitudinally. According to this example, the frame may include a closed border delimiting an orifice capable of surrounding the protective shell, the closed border having an internal wall which is bevelled negatively with respect to the main external walls of the half-shells.

According to certain embodiments, the external main wall of each half-shell comprises a spike system facilitating the insertion of the half-shells into the frame.

According to one or more embodiments, each half-shell of the protection device comprises two side walls, parallel to each other and extending perpendicular to the reference plane and to the transverse wall, the lateral and transverse walls of the first half-shell comprising a joint zone of shapes and dimensions complementary to the joint zone of the second half-shell.

According to a second aspect, the invention relates to a method of aluminizing a turbine blade disposed in a metallization enclosure. This method includes a dawn-foot protection operation by a protection device as defined above.

BRIEF DESCRIPTION OF THE FIGURES

Other advantages and characteristics of the invention will appear on reading the description, illustrated by the figures in which:

- Figure 1, already described, shows an open perspective view of a protection device according to the prior art;

- Figure 2 shows an exploded view of an exemplary device according to the invention;

- Figures 3A, 3B show perspective views, respectively, from the front and from above, of a half-shell of the device according to the invention;

- Figures 4A, 4B show perspective views of the assembly of two half-shells of the device of Figure 2; and

- Figure 5 shows a side view of the external face of a half-shell of Figure 2.

DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT

An exemplary embodiment of a protection device, in which the seal against metallization is obtained by contacting the projecting areas of the two half-shells, is described in detail below, with reference to the accompanying drawings. This example illustrates the characteristics and advantages of the invention. It is however recalled that the invention is not limited to this example.

In the figures, identical elements are identified by identical references. For reasons of readability of the figures, the size scales between the elements represented are not respected.

FIG. 2 represents, in an exploded view, an example of the two half-shells 100a, 100b and of the frame 200 of the protection device according to the invention. The two half-shells 100a, 100b are adapted to be opposite one another, on either side of a reference plane P intersecting said frame 200 transversely in its middle. The frame 200 fits in a transverse plane T, perpendicular to the reference plane P. The two half-shells 100a, 100b are mainly symmetrical in their shapes and dimensions, with respect to the reference plane P, only the periphery of the joint 121a, 121b of the half-shells differing from one another.

Each half-shell 100a, 100b comprises, as shown in FIGS. 3A, 3B:

- a main wall 110 designed to extend parallel to the reference plane P when the two half-shells are assembled;

- a transverse wall 130 designed to extend perpendicular to the reference plane P and parallel to the transverse plane T; and

- two side walls 120, facing one another, and perpendicular to the main 110 and transverse 130 walls.

When the two half-shells are assembled, the side walls 120 and main 110 of the two half-shells form an enclosure around the blade root and the transverse walls 130 cover a free end of said blade root. In other words, the transverse walls 130 form the ceiling of the enclosure surrounding the foot of dawn. When the two half-shells 100a, 100b are assembled, they form a hull 100 around said blade root. Thus, the two half-shells wrap the blade root so as to trap it and leave only the blade body outside the shell 100.

The main wall 110 of each half-shell has, on its internal face 110c, a recessed area 112 and a protruding area 111. The recessed area 112 and the protruding area 111 are connected to each other by an offset zone 113 of a thickness substantially equal to half the lateral dimension of the blade root. The recessed area 112 and the projecting area 111 are substantially planar areas, generally parallel to the reference plane P when the half-shells are assembled. The recessed area 112 has a shape and dimensions adapted to the shape and dimensions of the dawn foot so as to form a housing for the dawn foot.

The recess area 113, simply called recess 113, is substantially perpendicular to the projecting area and to the recessed area and constitutes the contour of the housing for the dawn. This housing has shapes and dimensions adjusted to the shapes and dimensions of the dawn foot, to the nearest play value. This play, of a predefined value, can be for example 0.2mm. When the half-shells are assembled around the blade root, the drop zone 113 is, over the majority of its length, opposite the blade root except in its parts located in the vicinity of each of the side walls 120, called free ends 114. The detachment zone 113 of a half-shell can be, for example, 2.8 mm thick. This recess area 113 allows, when in contact with the recess area of the other half-shell, to ensure the sealing of the blade root against metallization.

The protruding areas 111 of the two half-shells form a lining in the enclosure formed by the walls 110,120,130, this lining filling at least partially the space between the walls and the blade root. The protruding area 111 of each half-shell may comprise several portions such as, for example, a first and a second lateral portion 111a, 111c extending from each of the lateral faces 120 to the housing intended to receive the blade root. . It may further include a transverse portion 111b extending along the transverse wall 130, between the first and second lateral portions 111a, 111c.

This arrangement of recessed areas and protruding areas of the half-shells 100a, 100b, when the two half-shells are assembled, forms a tight barrier around the blade root, this tight barrier ensuring protection of the blade root against metallization.

In one or more embodiments, the internal face 110a of the main wall 110 comprises a bead 140 projecting from said internal face. This bead 140 is designed to be inserted into a groove in the dawn foot in order to avoid any risk of metallization in the groove in the dawn foot. The bead 140 extends between the two lateral portions 111a, 111c of the projecting area 111, in the thickness of the recess 113. In other words, the bead 140, which extends downstream of the waterproof barrier, has a thickness less than the thickness of the step 113, which avoids any risk of tearing off the metallization.

In certain embodiments, the projecting zone 111 - in particular the lateral portions 111a, 111c- extends longitudinally from the transverse wall 130 at least to the groove of the blade root intended to potentially receive the bead 140. In the embodiments with bead, the projecting zone 111 extends as far as the bead 140. The two lateral portions 111a, 111c of the projecting zone 111 can extend over different lengths. For example, as shown in FIGS. 3A, 3B, the second lateral portion 111c can extend from the transverse wall 130 to a short distance beyond the bead 140 while the first lateral portion 111a extends over a greater longitudinal distance than the second lateral portion.

In certain embodiments, the free ends 114a, 114c of the offset zone 113 are rounded according to a predetermined radius of curvature. The radius of curvature R can vary from one loose end 14a to the other 114c, generating a different rounding for each of the two free ends of the same half-shell 100a, 100b. The rounding of the recesses 113 makes it possible to improve the sealing function of said recesses.

In certain embodiments, such as that shown in FIGS. 3A, 3B, the lateral portions 111a, 111c of the projecting zone each have, in their free end respectively 114a, 114c, an oblique transverse stop, respectively 115a, 115c . The oblique transverse stop 115a / 115c extends from the rounding of the free end 114a / 114c to the side wall 120, forming a draft 116a / 116c to absorb the foundry residues generated during the manufacture of the half-shells 100a, 100b. The bodies 116a, 116c are located, opposite one another, at the intersection of the internal face 110a and one of the side walls 120. These bodies 116a, 116c make it possible to house the residues which may appear during the manufacture of the protection device so that they do not interfere in any way with the assembly of the half-shells 100a, 100b and have no impact on the protection of the blade root.

As described above, the two half-shells 100a, 100b are partially symmetrical with respect to the reference plane P so that the projecting zones 111 and the recessed zones 112 of a half-shell, for example the half-shell 100a, are mirroring the projecting areas 111 and the recessed areas 112 of the other half-shell 100b. However, each half-shell 100a, 100b comprises at least one joint zone 121 which is not symmetrical with the joint zone of the other half-shell, respectively 100b, 100a. In fact, as shown in FIG. 2, the half-shell 100a has a joining area 121a and the half-shell 100b has a joining area 121 b, the joining area 121 a and the joining area 121 b being shaped and dimensions complementary to each other. For example, the joint area 121 a of the half-shell 100a may be a protruding contour of the side walls 120 and transverse 130 which extends towards the half-shell 100b and the joint area 121b of the half-shell 100b may be an excavated contour of the side walls 120 and transverse 130 which extends towards the half-shell 100a. The excavation joint zone 121b is adapted to receive, over its entire length, the protruding zone 121a so that the two joint zones 121a, 121b fit into each other as shown in FIGS. 4A- 4B, when the two half-shells are assembled.

Those skilled in the art will understand that, although the differentiation of the joining zones 121a, 121b is represented over all of the joining zones, this differentiation could be only partial, that is to say carried out only on the walls lateral 120 or on the transverse walls 130 or on a portion of said lateral and transverse walls.

FIGS. 4A-4B show an example of two half-shells 100a, 100b, respectively, during assembly and assembled by means of a frame 200. The two half-shells 100a, 100b are assembled by interlocking their zones respective joins. The assembly is maintained by the frame 200 adapted to surround the two half-shells. Whether the differentiation of the joining zones is partial or total, as described above, the interlocking of said joining zones 121 a, 121 b and their retention by the frame 200 allows a tight assembly of the two half-shells 100a, 100b.

The frame 200 has a closed border 210 defining an orifice 240 designed to receive the two half-shells 100a, 100b. The closed edge 210 has an outer wall 220 and an inner wall 230. The inner wall 230, which forms the outline of the orifice 240, has a shape and dimensions adjusted to the shape and dimensions of the two assembled half-shells.

In certain embodiments, such as that shown in FIGS. 2 and 5, the external face 110b of the main wall 110 of each half-shell is non-planar and, in particular, at least partially bevelled. For example, a portion of the external face 110b close to the transverse wall 130 may be planar, while a portion further away from the transverse wall may be bevelled, that is to say at an angle to the planar portion . In these embodiments, the internal wall 230 of the frame 200 is bevelled, with a negative bevel relative to the bevel of the main wall 110b. Indeed, the bevel of the inner wall of the frame 200 is preferably complementary to the bevel of the outer face 110b of the half-shells so that the frame 200 and the shell 100 are of complementary shapes. These bevelled walls and faces facilitate the positioning of the half-shells in the frame and ensure the clamping, that is to say the tightest possible holding, of the half-shells during the metallization phase.

In one or more embodiments, the main wall 110 has a border remote from the transverse wall 130, called distal border 117. As shown in FIGS. 2 and 5, the distal border 117 can be equipped with a pin system 150 designed to facilitate the positioning of the protection device in the metallization enclosure (not shown in the figures). This pin system 150 may include two pins 151, 152 formed in the continuity of the internal face 110a of the main wall. These two pins 151, 152, with a maximum width of 2 mm, can be formed separately on the distal edge 117 or else formed on a strip 118 projecting in the extension of the external face 110b of the main wall 110. By increasing the contact surface between the shell 100 and the metallization enclosure, this system of pins improves the positioning of the protection device within the enclosure without however having any effect on the metallized surface.

The protection device which has just been described can be used to protect a blade root during the process of depositing the metal coating on the blade body and, in particular, during the process of aluminization by vapor deposition . This protective device makes it possible to protect the foot of the blade from any metallic coating during the aluminization phase of the blade, while avoiding the tearing of the metallic coating in the area where the blade root meets the body of the blade. 'dawn.

Although described through a certain number of examples, variants and embodiments, the protection device according to the invention includes various variants, modifications and improvements which will be obvious to those skilled in the art, it being understood that these variants , modifications and improvements are part of the scope of the invention.

Claims (10)

1. Protective device suitable for protecting a blade root during a process of depositing a coating in the vapor phase, comprising: - a first and a second half-shell (100a, 100b) designed to be assembled according to a reference plane (P) so as to form a protective shell (100) capable of encompassing the blade root, and - A frame (200) able to hold the two half-shells (100a, 100b) assembled against the other, assembled according to the reference plane, characterized in that each of the half-shells (100a, 100b) has a wall main internal (110a) extending substantially parallel to the reference plane and comprising a recessed area (112) and a projecting area (111), the recessed area (112) forming a housing of shapes and dimensions adapted to receive the blade root, the projecting area (111) forming, by contact with the projecting area of the other half-shell, a tight protection against the coating. 2. Protection device according to claim 1, characterized in that the recessed area (112) and the projecting area (111) are connected by a recess area (113) of a thickness substantially equal to half of a dimension of the blade root in a transverse plane (T) perpendicular to the reference plane (P). 3. Protective device according to claim 1 or 2, characterized in that each half-shell (100a, 100b) has a transverse wall (130) extending perpendicular to the reference plane (P) and covering one end of the foot d 'dawn, the projecting area (111) of the inner main wall extending longitudinally from the transverse wall (130) to beyond a bead (140) intended to be inserted in a groove of the blade root . 4. Protective device according to claim 3, characterized in that the projecting zone (111) of each half-shell comprises, in at least a portion remote from the transverse wall (130), an oblique transverse stop (115) forming a body (116). 5. Protection device according to claim 3 or 4, characterized in that each half-shell of the protection device has two side walls (120), parallel to each other and extending perpendicular to the reference plane ( P) and to the transverse wall (130), the lateral and transverse walls of the first half-shell comprising a joining zone (121) of shapes and dimensions complementary to the joining zone of the second half-shell. 6. Protection device according to any one of claims 1 to 5, characterized in that each half-shell has an outer main wall (110b) not planar. 7. Protective device according to claim 6, characterized in that the main external wall (110b) is at least partially bevelled longitudinally. 8. Protective device according to any one of claims 6 and 7, characterized in that the frame (200) has a closed border (210) delimiting an orifice (240) capable of surrounding the protective shell (100), the closed border having an internal wall (230) beveled negatively with respect to the main external walls (110b) of the half-shells. 9. Protective device according to any one of claims 6 to 8, characterized in that the main external wall (110b) of each half-shell comprises a stud system (150) facilitating the insertion of the half-shells into the frame (200). 10. A method of aluminizing a turbine blade disposed in a metallization enclosure, characterized in that it comprises an operation for protecting the blade root by a protection device according to any one of claims 1 to 9 .