A rough draft of a turbomachine blade obtained by casting metal and a manufacturing process for such a rough draft.

Abstract

This disclosure relates to a cast metal turbomachine blade blank comprising a first direction (Z) along which a blade (13), a platform (12), and a foot (11) are successively formed, the platform (12) extending along a second direction (X) substantially perpendicular to the first direction (Z), the blade (13) comprising an intrados face (14) and an extrados face (15) connected to each other by a trailing edge (16) and a leading edge (17), the foot comprising retaining surfaces (23, 24) along the first direction (Z) of the rotating blade intended to cooperate with corresponding surfaces of a turbomachine disk, the blade blank (100) being notable in that it comprises at least one web (200) extending along a third direction (Y) substantially perpendicular to the first and second directions (Z, X), this web connecting a retaining surface (25) according to the first direction to the platform.Figure 2.

Description

Title of the invention: A blank of a turbomachine blade obtained by casting metal and a method for manufacturing such a blank. technical field

[0001] The present disclosure falls within the field of turbomachine blades, in particular that of blade blanks obtained by casting a molten alloy in a mold according to the casting technique in disposable material, such as for example lost wax, so as to obtain final blades. Previous technique

[0002] Traditionally, the lost-wax casting technique begins by creating a model in wax, or any other easily removable material, of the part to be produced. This model is equivalent to the blade to be molded and may include an internal ceramic core representing the cavities desired to appear inside the blade. The wax model is then dipped several times in slips made from a suspension of ceramic particles to create, through processes known as stenciling and drying, a shell mold. The shell mold thus encloses the wax model.

[0003] The next step involves dewaxing the shell mold, an operation by which the wax or material constituting the original model is removed from the shell. After this removal, a ceramic mold is obtained whose cavity reproduces all the shapes of the blade and which still contains, where applicable, the ceramic core intended to generate its internal cavities. The mold then undergoes a high-temperature heat treatment or "firing" which gives it the necessary mechanical properties.

[0004] The shell mold is then ready for the manufacture of the metal part by casting. After checking the internal and external integrity of the shell mold, the next step consists of pouring molten metal, which fills the voids of the shell mold, and then solidifying it. This produces a blade blank, that is to say, a semi-finished part, corresponding substantially to the final blade but requiring one or more additional steps, for example, surface treatment or finishing, in order to obtain a final blade meeting the imposed geometric criteria. In the field of lost-wax casting, several solidification techniques and several casting techniques are currently distinguished, depending on the nature of the alloy and the expected properties of the resulting casting.Examples include directional solidification with a columnar structure (DS), directional solidification with a single-crystal structure (SX), or equiaxed solidification (EX).

[0005] After the alloy is poured, the shell is broken by a shakeout operation. Then, in a subsequent step, if necessary, the ceramic core that remains trapped in the resulting blade blank is chemically removed. The resulting metal blade blank then undergoes finishing operations to obtain the finished part.

[0006] Examples of the production of turbine blades by the lost-wax casting technique are given in the applicant's patent applications FR2875425 and FR2874186.

[0007] Figure 1 illustrates a turbine blade 10 known from prior art. Arrow F on Figure 1 indicates the direction of gas flow through a turbomachine, the terms "upstream" and "downstream" being subsequently defined with respect to this arrow F.

[0008] In a first direction, also described as the longitudinal direction Z in the following, such a blade 10 mainly comprises a foot 11, a platform 12 and a blade 13. The blade 13 and the foot 11 extend mainly in the longitudinal direction Z while the platform 12 extends mainly in a second direction, also described as the axial direction X in the following, this axial direction X being substantially perpendicular to the longitudinal direction Z. The blade 10 further comprises a strut 18 connecting the foot 11 to the platform 12. The blade 13 comprises an intrados face 14 (visible in [Fig. 4]) and an extrados face 15 connected to each other by a trailing edge 16 downstream and a leading edge 17 upstream.

[0009] Conventionally, each blade 10 is mounted on a turbine disk, for example a high-pressure one, the root 11 of the blade 10 being mounted in a groove in the rim of the disk, and the blade 13 extending radially outwards from the root 11 of the blade 10. The root 11 of each blade 10 is at least partially received longitudinally and retained radially in one of the grooves in the rim of the disk. The root 11 of each blade 10 here has a lobed cross-section (in a third direction, referred to as the transverse direction Y in the following description), the root 11 possibly comprising longitudinally a first lobe 21 and a second lobe 22. Each lobe 21, 22 comprises respectively a first retaining surface 23 and a second retaining surface 24, also commonly called bulbs or bearing surfaces, intended to cooperate with a corresponding surface of a turbomachine disk.The first retaining surface 23 is positioned between the platform 12 and the second retaining surface 24. The first and second retaining surfaces 23, 24 radially hold the rotating blade foot 11 in the groove of the disc.

[0010] Furthermore, as illustrated in [Fig. 1], an upstream reinforcement portion 25, also commonly called the upstream spoiler, extends in the transverse direction Y, this direction Y being substantially perpendicular to the longitudinal direction Z and axial direction X, that is to say in a plane formed by the longitudinal direction Z and transverse direction Y, from the platform 12 towards the foot 11. In [Fig. 1], the upstream reinforcement portion 25 is arranged near the upstream face 26 of the foot 11, and in particular in the longitudinal extension of the upstream face 26. The upstream reinforcement portion 25 thus comprises an upstream face common to the upstream face 26 of the foot 11, a downstream face 29 of the upstream reinforcement portion opposite the upstream face 26, and a longitudinal face of the upstream reinforcement portion 30 joining the upstream and downstream faces of the upstream reinforcement portion 25. A downstream reinforcement portion 28 can furthermore be arranged near the downstream face 27 of the foot 11, in particular in the longitudinal extension of the downstream face 27.

[0011] In a conventional process for melting an alloy in a shell mold obtained using the lost-wax casting technique, several blades are poured simultaneously into a casting cluster. The alloy is introduced into the upper part of the cluster and thus fills the shell mold by gravity. The lower part of the mold is therefore filled before the upper part. It is understood, therefore, that the solidification front of the alloy moves from the lower part to the upper part of the shell mold. According to common practice, the shell mold is arranged in the cluster so that the blade 13 is positioned at the bottom, and the foot 11 is positioned at the top. Consequently, the solidification front moves from the blade 13 to the foot 11, and therefore the blade 13 is poured before the foot 11.

[0012] The manufacture of blades from new metallic alloys, including, for example, rhenium (Re) and / or ruthenium (Ru), allows for increased stress on these parts during operation compared to commonly used alloys, such as AMI. However, it has been observed that these new alloys lead to the appearance of casting defects during metal solidification, which weakens the part and renders it non-conforming. The observed defects may, for example, be of the shrinkage type, that is, a defect in the form of a cavity forming in the solid part of a cast metal component and due to the contraction of the metal during its solidification. In particular, such a shrinkage-type defect may be observed on one of the upstream reinforcement portions 25 or downstream portion 26 of the blade 10.

[0013] The present disclosure is therefore intended in particular to address these solidification defects which may appear on blade blanks obtained by casting a metallic alloy. Summary

[0014] To this end, the present disclosure proposes a prototype turbomachine blade obtained by metal casting, comprising a first direction along which a blade, a foot and a platform extending according to are successively formed a second direction substantially perpendicular to the first direction, the blade comprising an intrados face and an extrados face connected to each other by a trailing edge and a leading edge, the base comprising retaining surfaces along the first direction of the rotating blade intended to cooperate with corresponding surfaces of a turbomachine disk, wherein the blade blank comprises at least one web extending along a third direction substantially perpendicular to the first and second directions, this web connecting a retaining surface along the first direction to the platform.

[0015] The veil may also have the following characteristics, taken alone or in combination: - the veil is formed at the upstream end of the foot of the awl; - the veil can be formed on the same side as the extrados surface and / or intrados of the blade; - the veil has a first concave curved face oriented upstream; - the veil has a second curved convex face oriented towards the downstream side.

[0016] The foot may further include, on the same side as the side of the extrados and / or intrados face of the blade, according to the first direction, a first retaining surface and a second retaining surface, the first retaining surface being positioned according to the first direction between the platform and the second retaining surface, the web connecting the first retaining surface to the platform.

[0017] The platform may further include a portion of reinforcement for the connection to the wall, said portion of reinforcement extending along the third direction and having a longitudinal face, the thickness of the wall being between 0.2 and 0.8 times the thickness of the longitudinal face of the upstream portion of reinforcement.

[0018] This disclosure also proposes a method for manufacturing a turbomachine blade from a model made of disposable material with geometry and dimensions corresponding to those of the blade blank defined above, the method comprising:

[0019] - form a shell mold around the model, the shell mold defining a imprint suitable for obtaining said rough awl,

[0020] - eliminate the model from the shell mold,

[0021] - orient the shell mold so that, for the blade blank, the first the direction should be oriented vertically, with the head in a low position and the foot in a high position, and

[0022] - pouring metal into the shell mold, in the upper part of said mold.

[0023] During the process, a plurality of shell molds can be distributed circumferentially around an axis parallel to the first direction for the blade blank of each of the molds.

[0024] Subsequently, the veil of the dawn outline is removed to obtain the dawn. Brief description of the drawings

[0025] Other features, details and advantages will become apparent from reading the detailed description below and from analyzing the accompanying drawings, in which: Fig. 1

[0026] [Fig.1] shows a partial perspective view of an earlier art dawn, from its downstream face. Fig. 2

[0027] [Fig.2] shows a partial perspective view of a rough blade design according to the present disclosure, from its upstream face. Fig. 3

[0028] [Fig.3] shows a partial longitudinal view of the blade blank of [Fig.2], illustrating a sail according to the present disclosure. Fig. 4

[0029] [Fig.4] shows a view from the upstream face of the blade blank of the [Fig.2]. Fig. 5

[0030] [Fig.5] is a longitudinal view of the blade blank of [Fig.2]. Fig. 6A

[0031] [Fig.6A] illustrates a casting of an alloy for obtaining a prior art blade. Fig. 6B

[0032] [Fig.6B] illustrates a casting of an alloy to obtain a blade blank according to the present disclosure. Description of the implementation methods

[0033] Figures 2 to 5 illustrate an example of a blade blank 100 according to the present disclosure, the blade blank 100 being shown only partially. The blade blank 100 is similar to the blade 10 shown in [Fig. 1], except that it also includes a web 200. The web 200 is arranged between the upstream reinforcement portion 25 and the first retaining surface 23, so as to form a material extension between the upstream reinforcement portion 25 and the first retaining surface 23 that delimit it. The sail 200 illustrated in figures 2-5 is formed at the upstream end 26 of the foot 11 of the blade 10. According to another example, the sail can be formed at the downstream end 27 of the foot 11. According to yet another example, each upstream and downstream end 26, 27 can each have a sail.

[0034] In the example illustrated in the figures, the sail 200 is formed on the same side as the side of the upper surface 15 of the blade 13. Alternatively, the sail 200 can be formed from the same side of the intrados face of blade 13. Two sails can also be provided, each arranged on one side of the faces of blade 13.

[0035] According to the example illustrated and more clearly visible in [Fig. 5], the web 200 may have a first curved face 201, which is concave upstream. The web 200 may also have a second curved face 202, which is convex downstream. The first and second curved faces 201, 202 make it easier to remove the blade blank from the mold compared to a blank that does not include the web 200.

[0036] The thickness L200 of the web 200 can be measured between the first and second curved faces 201, 202, in the axial direction X. This thickness L200 can be less than the thickness L30 of the longitudinal face of the upstream reinforcement portion 25. By way of example, the thickness L200 can be between 0.2 and 0.8 times the thickness L30 of the longitudinal face of the upstream reinforcement portion 30. As a result, the web 200 and the upstream reinforcement portion 25 are connected together by a connection radius of the upstream reinforcement portion R25 and by a connection radius of the web R200, the ratio of which is less than or equal to 0.5 (R30 / R200 < 0.5), and preferably between 0.3 and 0.4, and for example equal to 0.37. These dimensions guarantee a web thickness that does not extend onto the connecting radii of the upstream reinforcement portion, making machining of the area after web removal as simple as possible.

[0037] Advantageously, the 200 wall eliminates the observed solidification defects and in particular the shrinkage cavity phenomenon detailed above, on the upstream reinforcement portion 25, or alternatively on the downstream end 27 if the 200 wall is arranged there.

[0038] According to the example in which the web is arranged between the upstream reinforcement portion 25 and the first retaining surface 23, as illustrated in Figures 2 to 5, the web 200 provides a continuous supply of hot alloy to the upstream reinforcement portion, thereby improving the solidification of said portion. By way of comparison, [Fig. 6A] illustrates the solidification of the alloy during its casting to form a conventional blade without a web, and [Fig. 6B] also illustrates the solidification of the same alloy to form a blade blank including a web 200. In [Fig. 6A], in the circled area, the solidification front is interrupted on the upstream reinforcement portion 25, creating an isolated zone 35 at the end of the upstream reinforcement portion 30. Solidification has thus already occurred around this isolated zone 35, which is therefore no longer supplied with molten alloy.During solidification, the alloy undergoes shrinkage, resulting in a decrease in its occupied volume. The isolated zone 35, due to its rupture during the molten alloy feed, therefore experiences a shrinkage phenomenon without compensation by a supply of molten alloy, leading to a shrinkage cavity in this isolated zone 35. In [Fig. 6B], the solidification front moves. progressively from platform 12 to the first retaining surface 23, i.e., without interruption of the solidification front. The web 200 thus provides a molten alloy supply zone so as not to interrupt the supply in the upstream reinforcement section 25. Thanks to the web 200, the solidification front remains continuous in the upstream reinforcement section 25.

[0039] Furthermore, the presence of the 200 blade is incompatible with the final blade. Therefore, the 200 blade is present only on the blade blank 100, and not on the final blade. Indeed, the presence of this 200 blade prevents the longitudinal insertion of the blade's base into the groove of the disc rim.

[0040] Furthermore, the veil 200 can be defined by its volume. Preferably, the volume of the veil is between 16.5 cm3 and 18.3 cm3, which corresponds to a volume 3.5 to 5 times greater than the volume of the area where the shrinkage phenomenon observed on a prior art blade can occur.

[0041] To manufacture the blade blank 100 described above, the manufacturing process can be described as below.

[0042] The process includes a preliminary step of preparing a shell mold with a shape complementary to that of the blade blank to be obtained. A shell mold is thus formed around a model made of a disposable material with geometry and dimensions corresponding to those of said blade blank 100, the shell mold defining an impression suitable for obtaining said blade blank.

[0043] Several molds can be joined together in a casting cluster so as to cast several parts simultaneously. Each mold is oriented so that the part obtained is oriented with the blade pointing downwards, and the foot pointing upwards.

[0044] The alloy is then poured into the shell mold from the upper part of said mold.

[0045] After the alloy cast in the mold has solidified, a blade blank 100, including the web 200, is obtained. Following the manufacture of said blade blank 100, it must undergo one or more machining steps to obtain the final blade, and in particular a step in which the web 200 is removed from the blade blank 100, this web representing a non-functional volume of material. The longitudinal face of the upstream reinforcement portion 30 is then finished.

Claims

Demands

1. A turbomachine blade blank obtained by metal casting, comprising a first direction (Z) along which a blade (13), a platform (12), and a base (11) are successively formed, the platform (12) extending along a second direction (X) substantially perpendicular to the first direction (Z), the blade (13) comprising an intrados face (14) and an extrados face (15) connected to each other by a trailing edge (16) and a leading edge (17), the base comprising retaining surfaces (23, 24) along the first direction (Z) of the rotating blade intended to cooperate with corresponding surfaces of a turbomachine disk, characterized in that the blade blank (100) comprises at least one web (200) extending along a third direction (Y) substantially perpendicular to the first and second directions (Z, X), this web connecting a retaining surface (23) according to the first direction to the platform (12),in which the veil (200) has a first concave curved face (201) oriented upstream along the second direction (X) and a second convex curved face (202) oriented downstream along the second direction (X).

2. Blade blank according to claim 1, wherein the web (200) is formed at the upstream end (26) of the foot (11).

3. Blade blank according to claim 1 or 2, wherein the web (200) is formed on the same side as the side of the extrados face (15) or intrados face (14) of the blade (13).

4. Blade blank according to any one of the preceding claims, wherein the foot (11) comprises, on the same side as the side of the upper surface (15) or lower surface (14) of the blade (13), along the first direction (Z), a first retaining surface (23) and a second retaining surface (24), the first retaining surface (23) being positioned along the first direction (Z) between the platform (12) and the second retaining surface (24), the web (200) connecting the first retaining surface (23) to the platform (12).

5. Blade blank according to any one of the preceding claims, wherein the platform (12) comprises a reinforcing portion (25, 28) for connection to the web (200), said reinforcing portion (25, 28) extending along the third direction (Y) and having a longitudinal face (30), the thickness (L200) of the web (200) being between 0.2 and 0.8 times the thickness (L30) of the longitudinal face of the upstream reinforcement portion (30).

6. A method for manufacturing a turbomachine blade from a model made of a discardable material having geometry and dimensions corresponding to those of the blade blank (100) defined according to any one of the preceding claims, the method comprising: - forming a shell mold around the model, the shell mold defining an impression suitable for obtaining said blade blank (100), - removing the model from the shell mold, - orienting the shell mold so that, for the blade blank, the first direction is oriented vertically and so that the head is in a low position and the foot in a high position, - pouring metal into the shell mold, in the upper part of said mold.

7. A method according to claim 6, wherein a plurality of shell molds are distributed circumferentially around an axis parallel to the first direction for the blade blank of each of the molds.

8. Method according to claim 6 or 7, wherein the web (200) of the blade blank (100) is removed to obtain the blade.

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