Method for manufacturing a turbine engine blade and turbine engine blade

Abstract

A method for manufacturing a blade (10) comprising a first portion and a second portion is disclosed, the method comprising: a step (E1) of forming the first portion, the step comprising forming a first portion mold from a removable material, then forming a first shell mold from the first portion mold, and then forming a single crystal or columnar first portion from a first metal alloy in the first shell mold from a single crystal seed; a step (E2) of forming the second portion, wherein the second portion is formed on the first portion, and wherein the first portion and the second portion are made of different materials, the second portion being polycrystalline and formed of the second metal alloy. Also disclosed is a blade comprising a single crystal or columnar first portion made of the first metal alloy and a polycrystalline second portion made of a second metal alloy different from the first metal alloy.

Description

Technical Field

[0001] The present disclosure relates to the manufacture of blades for compressors or turbine engines, and in particular to the manufacture of high-pressure turbine blades. Background Art

[0002] Methods for producing single-crystal high-pressure turbine blades by lost wax casting are known.

[0003] These methods involve forming a blade model in wax or resin, then forming a ceramic shell mold around the blade model through sequential soaking and drying. The wax or resin is then removed during a dewaxing step, followed by sintering the shell mold, ultimately leaving a hollow shell mold. A single crystal seed is placed in the shell mold, and liquid metal is poured into it. The shell mold is gradually lowered out of the hot chamber in which it resides, causing the liquid metal to directionally solidify from the single crystal seed. This results in a single crystal blade.

[0004] Material selection is a crucial criterion for ensuring good performance. More specifically, single-crystal blades must respond to specific creep stresses while remaining as lightweight as possible. Creep stresses, including mechanical and thermal stresses, are imposed on blades in turbine engines during operation, and the material must withstand these stresses. Cost optimization also influences material selection.

[0005] More specifically, single-crystal blades obtained using earlier methods can only be manufactured from a single piece and a single material. Typically, a blade comprises an airfoil and a root. Consequently, the material's properties are affected by the most severe conditions to which the complete blade, when deployed in a turbine engine, will be subjected during operation. For example, the airfoil of a turbine engine blade is subjected to greater stresses during operation than the root of the blade. The material comprising the airfoil, and therefore the blade, must meet the constraints required to respond to these stresses, which typically makes it more expensive and / or heavier than a material that needs to respond to less significant stresses.

[0006] Therefore, a balance should be found between material performance and blade cost. The purpose of developing alloys is to optimize the specifications of single crystal blades, but there is still room for improvement.

[0007] More specifically, there is a need for improved methods for manufacturing blades.

[0008] Furthermore, it should be noted that the present disclosure relates to both stationary and movable blades. Summary of the Invention

[0009] The present disclosure relates to a method for manufacturing a blade comprising a first portion and a second portion, the method comprising: a step of forming the first portion, the step comprising forming a first portion model from a removable material, then forming a first shell mold from the first portion model, and then forming a single crystal or columnar first portion from a first metal alloy in the first shell mold by a grain selection member; a step of forming the second portion, wherein the second portion is formed on the first portion, and wherein the first portion and the second portion are made of different materials, the second portion being polycrystalline and formed from the second metal alloy.

[0010] It should be understood that a polycrystalline portion is not a directionally grown portion (single crystal or columnar). Thus, a polycrystalline portion may include a plurality of grains randomly oriented in all directions.

[0011] In the present disclosure, non-limiting examples may include removable wax or resin materials.

[0012] In certain embodiments, the first portion is an airfoil and the second portion is a root.

[0013] In an operating turbine engine, the root and airfoil of a blade are subject to different stresses. By choosing the airfoil as the first part and the root as the second part, it is possible to provide separate specifications for the materials constituting these two parts, each of which is specifically adapted to the environment to which the airfoil or root is subjected, respectively.

[0014] Such a method makes it possible to design turbine engine blades with a root and airfoil made of different optimized materials. Thus, it is possible to form the root using materials meeting less stringent specifications, particularly regarding the creep properties of the material used to form the airfoil. More specifically, compared to single-crystal blades or blades with a columnar structure known in the art, partially polycrystalline blades can be obtained more quickly and cheaply.

[0015] Thus, using this method, it is possible to simultaneously optimize the creep performance and cost of a single-crystal / cylindrical blade without compromising its performance or even reducing its weight. More specifically, it is possible to independently optimize the material constituting the blade airfoil and the material constituting the blade root, knowing that these two elements will be subject to different stresses once the blade is installed in an operating turbine engine.

[0016] Furthermore, this method makes it possible to manufacture blades including the envisaged parts in different materials, without the need for welding, gluing or more general assembly steps. This method is simpler, faster and, above all, more efficient, in particular in terms of the strength of the connection between the two materials, thanks to the diffusion phenomenon.

[0017] Furthermore, in known methods, the blade must be completely single-crystal / cylindrical due to its ultimate strength. Specifically, in single-crystal / cylindrical blades, the presence of polycrystalline grains, such as equiaxed grains, in the blade's airfoil can weaken the blade by forming boundaries known as grain boundaries, where cracks can easily propagate, leading to the risk of blade failure. However, this risk primarily affects the airfoil, which is subject to the greatest stress. The present method overcomes this risk by splitting the blade into two parts.

[0018] In certain embodiments, the first portion and the second portion are formed from two different nickel-based alloys.

[0019] In the present disclosure, a nickel-based alloy is an alloy in which nickel is the largest element by mass, preferably greater than 40%.

[0020] In this configuration, it is possible to provide two materials with different properties, one constituting the airfoil and the other constituting the root, each material being optimized according to the environment and stresses to which it is subjected in an operating turbine engine. Furthermore, the use of alloys having the same nickel base for the first and second parts makes it possible to ensure a good metallic bond (perfect epitaxy) between the two parts.

[0021] In certain embodiments, the method includes at least one processing step after the step of forming the second portion.

[0022] This processing step makes it possible to optimize the mechanical properties of the material that makes up the turbine engine blades.

[0023] In certain non-limiting examples, the polycrystalline alloy forming the second portion has a solution temperature T corresponding to the solution temperature of the precipitate γ′ in the alloy. γ’ The treatment step may then comprise two heat treatment steps, the first at the solution temperature T γ’ The second step is carried out at a temperature between 95% and 105% of the solution temperature T γ’ The temperature is between 65% and 75%.

[0024] In the configuration of the aforementioned example, during the first heat treatment step, the single crystal first portion undergoes an aging treatment, while the second polycrystalline portion undergoes a solution treatment. Thus, both treatments are performed in a single first heat treatment step, which represents a saving of time and resources.

[0025] Furthermore, during the second processing step, the first single crystal portion undergoes a second aging treatment, while the second polycrystalline portion undergoes an aging treatment. As with the first thermal treatment step, both treatments are performed in a single second thermal treatment step. This therefore represents a savings in time and resources.

[0026] In certain embodiments, forming the second portion includes forming the second portion from the second metal alloy on the first portion by powder bed fusion.

[0027] In this configuration, it is possible to provide the blade root using a method independent of the method used to form the airfoil, while simultaneously adding it directly to the airfoil. This operation is cheaper and faster than a casting step. As a powder bed fusion method, for example, the method known as SLM (short for Selective Laser Melting) can be cited.

[0028] This method is a method for producing three-dimensional parts layer by layer, during which one or more layers of powder are at least partially melted by a laser. The laser scans the powder layer at the locations where the powder is desired to be melted. After the laser scans through a layer, a new layer of powder is deposited on top of the previously scanned layer and scanned by the laser. The part is thus built up layer by layer.

[0029] This method saves costs and manufacturing time while ensuring mechanical properties close to those obtained by traditional methods such as forging or casting.

[0030] In fact, powder bed fusion manufacturing can overcome the need to make molds and / or weld and / or assemble various components to form the desired part. Therefore, it is easier to go from the design step to the production step of the part.

[0031] In certain embodiments, the method includes a step of machining the joint after the step of forming the second portion.

[0032] It is thus possible to adjust the blade root and even the blade profile and correct possible defects arising from the powder bed fusion method.

[0033] In some embodiments, the step of forming the second part includes forming a second part model made of a removable material, then forming a second shell mold based on the second part model, and then forming the second part from a second metal alloy in the second shell mold.

[0034] This configuration provides an alternative to forming the root and airfoil of the blade independently.

[0035] In certain embodiments, the step of forming the second portion includes an equiaxed cooling step.

[0036] The cooling step is therefore fast and results in the formation of a polycrystalline root. This step therefore represents a time saving compared to the directional cooling step required in known solutions for forming single crystal / cylindrical blades.

[0037] In certain embodiments, the joined portion of the first portion is remelted during the step of forming the second portion.

[0038] In this configuration, the metallurgical bond between the first portion and the second portion is improved.

[0039] Furthermore, the present disclosure relates to a blade comprising a single-crystal or columnar first portion made of a first metal alloy and a polycrystalline second portion made of a second metal alloy different from the first metal alloy.

[0040] Such a blade has the advantages described above.

[0041] In certain embodiments, the blade is obtained by one of the aforementioned methods.

[0042] In certain embodiments, the first portion and the second portion of the blade are formed from two different nickel-based alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The invention and its advantages will be better understood by reading the following detailed description of various embodiments of the invention presented by way of non-limiting examples. This description makes reference to the accompanying drawings, in which:

[0044] [ Figure 1 ] Figure 1 A single crystal or cylindrical blade obtained by a method according to an embodiment is shown.

[0045] [ Figure 2 ] Figure 2 A single crystal or cylindrical blade obtained by a method according to an embodiment is shown placed on a second shell mold.

[0046] [ Figure 3 ] Figure 3 A second shell mould formed around a blade according to a second embodiment of the method is shown.

[0047] [ Figure 4 ] Figure 4 Method steps according to various embodiments are schematically shown. DETAILED DESCRIPTION

[0048] Figure 1 A blade 10 is shown that includes an airfoil 12 and a root 14. The airfoil 12 and the root 14 are formed from different metal alloys. By way of non-limiting example, the airfoil 12 and the root 14 are formed from a nickel-based alloy. Specifically, the root 14 may be polycrystalline and made from a less expensive and / or lighter alloy than the alloy of the airfoil 12. In the case where the root is polycrystalline, its solution temperature T γ’ This corresponds to the solution temperature of the precipitate γ′ in the alloy constituting the root 14 .

[0049] In the embodiment described, the first portion corresponds to the airfoil 12, while the second portion corresponds to the root 14. However, it is possible to subdivide the blade in another way, wherein the first and second portions do not necessarily correspond to the airfoil 12 and the root 14. In particular, the level of thermomechanical loads of the airfoil to be formed and the associated manufacturing method determine the location of the joint.

[0050] Furthermore, the blade 10 may include a platform corresponding to a planar portion extending at the contact height between the root 14 and the airfoil 12. Thus, it is possible to include the platform in the first portion or in the second portion, as desired. It is also possible to provide a portion of the platform on the first portion of the blade 10 and a second portion of the platform on the second portion of the blade 10.

[0051] The blade 10 is formed by Figure 4 The method schematically shown in the figure is obtained, comprising an airfoil forming step (or step of forming a first portion) E1, wherein a single-crystal airfoil 12 is formed after a step of forming a second portion E2, in which the root 14 is formed.

[0052] The airfoil forming step E1 comprises a step E11 of forming an airfoil pattern from a removable material, followed by a step E12 of forming a first shell mold, wherein the airfoil pattern formed during step E11 is used to form the first shell mold by successive soaking and drying, and then the first shell mold is dewaxed and sintered. The airfoil forming step E1 then comprises a casting step E13, in which a grain selection is provided in the first shell mold, and liquid metal intended to form a first metal alloy is poured into the first shell mold, which is then placed in a hot chamber. Finally, the airfoil forming step E14 comprises a directional solidification step E14 performed in the hot chamber, in which the first shell mold is slowly removed from the hot chamber to form a single-crystal airfoil 12 starting from the grain selection.

[0053] In certain configurations, the airfoil 12 is formed in a columnar manner. In this configuration, the airfoil 12 is composed of grains that are oriented and crystallized along preferential directions based on the preferential directions of the grains selected by the grain selector.

[0054] In a known manner, the airfoil 12 may be subjected to a heat treatment to homogenize the dendrites and the interdendritic chemical species. This also enables the distribution of the precipitates in the airfoil 12 to be controlled. For example, the airfoil 12 may be subjected to a heat treatment at a solution temperature T γ’ The heat treatment is carried out at a temperature between 110% and 115% of the above range. In this example, this range corresponds to a range of 1260°C to 1330°C.

[0055] This airfoil forming method E1 making it possible to form the airfoil 12 is conventional and precedes the following two embodiments of the step E2 of forming the second portion. Furthermore, in the following embodiments, by way of non-limiting example, the material used to form the airfoil 12 is a nickel-based alloy

[0056] Root formation by powder bed additive manufacturing

[0057] In a first embodiment, the root 14 is formed by adding to the airfoil 12. Figure 4 On the left side, during step E2 of forming the second part, the root 14 is formed starting with a root forming step E31. The root 14 is formed on the single-crystal airfoil 12 using a selective laser melting (SLM) method. During this step, the root 14 is formed layer by layer from a bed of metal powder, into which the airfoil 12 is inserted. A laser selectively melts the powder particles by scanning the bed along the contour of the root 14, forming the root 14 as the particles melt and then solidify. The root 14 formed in this way is polycrystalline.

[0058] The shaped root 14 then undergoes a hot isostatic pressing step E32 . This step increases the density of the already shaped root 14 . In this example, the hot isostatic pressing is performed between 1130° C. and 1190° C., followed by slow cooling to 1050° C. and 1100° C.

[0059] The blade 10 can then be machined during a machining step E33. During this step, the configuration and condition of the surface of the root E31 are adjusted. The blade 10 is then brought into conformity with the desired profile. In particular, the root and / or the joint can be machined.

[0060] In this embodiment, by way of non-limiting example, the material used to form the root portion 14 is a nickel-based alloy. 77.

[0061] In this embodiment, the airfoil 12 may comprise a portion of the platform of the blade 10, while the root may comprise another portion of the platform of the blade 10. Furthermore, it is possible to separate the first and second portions above and below the platform. Thus, the junction between the first and second portions may be located in the airfoil or the root.

[0062] To achieve the desired surface finish, a casting step can be provided after step E2 of forming the second part. This step involves partially remelting the root 14 in a mold. This additional step has the advantage of improving the surface finish of the root 14 by homogenizing potential surface irregularities caused by successive laser passes (particularly the so-called underskin areas, i.e., areas without solid material support during their formation). It also makes it possible to produce the additively manufactured areas using less fine and focused laser light, thus reducing production time.

[0063] Root formation by lost wax casting

[0064] In the second embodiment, the root portion 14 is formed by a lost wax casting method. Figure 4 On the right side, step E2 of forming the second part includes step E21 of forming a blade model made of removable material, wherein a root model is formed on the airfoil 12 formed during step E1 of forming the airfoil. Thus, the root model made of removable material and the airfoil 12 form a blade model. Blade model forming step E21 is followed by step E22 of forming a second shell mold, wherein the blade model is used to form a second shell mold 30 by continuous soaking and drying, and then second shell mold 30 is dewaxed and sintered.

[0065] In the present embodiment, the airfoil 12 is held in place in the second shell mold 30 during these steps. The root forming step E2 then comprises a blade casting step E23, in particular of the blade root 14, during which liquid metal of the second metal alloy intended to form the blade is poured into the second shell mold 30, which is then placed in a hot chamber. Finally, the airfoil forming step E2 comprises an equiaxed solidification step E24 of the root 14, carried out in the hot chamber, from which the second shell mold 30 is quickly removed, so as to form the blade 10 starting from the single-crystal airfoil 12 and the polycrystalline root 14.

[0066] Figure 2 FIG. 4 shows a blade model obtained after the blade model forming step E21 according to the embodiment. Figure 2 As shown, the airfoil 12 formed during the forming step E1 comprises an attachment portion 122 and a tapered end portion 124. The tapered end portion 124 is provided at the end of the airfoil 12 that is in contact with the root 14 to be formed.

[0067] The tapered end portion 124 is the portion of the airfoil 12 that is remelted during the blade casting step E23. This ensures an almost perfect extension between the airfoil 12 and the root 14. In fact, during the blade casting step E23, only the upper portion of the second shell mold 30 is placed in the hot chamber, in other words, the portion corresponding to the root 14.

[0068] The attachment portion 122 is configured so that the root model formed during the blade model forming step E21 can be positioned accurately around the airfoil 12 and so as to ensure good attachment between the root model and the airfoil 12 .

[0069] Figure 3 The blade 10 obtained after the equiaxed solidification step E24 of the root 14 on the airfoil 12 is shown. In the second shell mold 30, the blade 10 thus has two parts: the single-crystal airfoil 12 and the polycrystalline root 14. The tapered end portion 124 of the airfoil 12 has been re-fused with the root 14.

[0070] In this embodiment, by way of non-limiting example, the material used to form the root portion 14 is a nickel-based alloy. 792.

[0071] In this embodiment, the root 14 may include the entire platform of the blade 10 .

[0072] Optionally, the final blade 10 obtained by one of the preceding embodiments may undergo a treatment step E25 . This treatment may include a heat treatment and / or the deposition of additional layers. This may be added to the heat treatment in order to homogenize the airfoil 12 .

[0073] In both the first and second embodiments, the processing step E25 may first comprise a step of depositing an anti-oxidation layer. In this case, by way of non-limiting example, this layer is a NiCoCrAlYTa layer deposited at least on the airfoil 12 of the blade 10 .

[0074] Then, in a first heat treatment step, the blade 10 is subjected to a heat treatment in which the blade 10 is heated to a temperature between 1080°C and 1100°C for 4 hours and then cooled with air. This treatment allows the anti-oxidation layer to diffuse into the material constituting the blade 10. In the case of 792, this treatment may also allow for solution treatment.

[0075] More generally, in this first heat treatment step, the blade 10 is heated to a temperature between the solution temperature T γ’ The temperature of the single-crystal airfoil 12 is between 95% and 105% of the initial temperature. In this example, this range corresponds to the range between 1080°C and 1180°C. During this step, the single-crystal airfoil 12 undergoes an aging treatment, while the polycrystalline root 14 undergoes a solution treatment. Thus, both treatments are performed in a single first heat treatment step, which represents a saving in time and resources.

[0076] Then, in a second heat treatment step, the blade 10 may be subjected to a treatment between 840° C. and 870° C. for 20 to 24 hours, followed by cooling with air. This step allows the material constituting the blade 10 to age.

[0077] More generally, during the second heat treatment step, the blade 10 is heated to the solution temperature T γ’ The temperature is between 65% and 75% of the initial heat treatment temperature. In this example, this range corresponds to between 750°C and 880°C. During this step, the airfoil 12 undergoes a second aging treatment, while the polycrystalline root 14 undergoes an aging treatment. As with the first heat treatment step, both treatments are performed in a single second heat treatment step. This therefore represents a savings in time and resources.

[0078] Furthermore, process step E25 may comprise depositing an abrasive coating at the blade head, distal end of the airfoil 12. Distal end refers to the end of the airfoil 12 not in contact with the root 14. In this example, the abrasive coating is a zirconium oxide deposit.

[0079] Although the present invention has been described with reference to specific exemplary embodiments, it will be apparent that modifications and variations can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, the various features of the various embodiments shown / mentioned may be combined in additional embodiments, and the materials and their processing may be modified. In general, polycrystalline parts may be produced by powder metering or any other manufacturing method. The description and drawings are therefore to be regarded as illustrative rather than restrictive.

[0080] It is also self-evident that all features described with reference to the method can be transferred, alone or in combination, to the device, and conversely, all features described with reference to the device can be transferred, alone or in combination, to the method.

Claims

1. A method for manufacturing a blade comprising a first portion and a second portion, the method comprising: a step of forming the first portion, said step comprising forming a first portion pattern from a removable material, then forming a first shell mold from the first portion pattern, and then forming a single crystal or columnar first portion from a first metal alloy in the first shell mold from a selection of grains, the step of forming the second portion, wherein the second portion is formed on the first portion, and wherein the first portion and the second portion are made of different materials, the second portion is polycrystalline and formed of a second metal alloy, The method comprises at least one processing step after the step of forming the second portion, The processing steps include: a first heat treatment step in which the blade is heated to a temperature between 95% and 105% of the solution temperature of the second portion; and a second heat treatment step wherein the blade is heated to a temperature between 65% and 75% of the solution temperature.

2. The method according to claim 1, characterized in that The first portion is an airfoil and the second portion is a root.

3. The method according to claim 1 or 2, characterized in that The first portion and the second portion are formed of two different nickel-based alloys.

4. The method according to claim 1 or 2, characterized in that The step of forming the second portion includes forming the second portion from a second metal alloy on the first portion by a powder bed fusion method.

5. The method according to claim 4, characterized in that The method comprises a step of machining the joint after the step of forming the second portion.

6. The method according to claim 1 or 2, characterized in that The step of forming the second part includes forming a second part model made of a removable material, then forming a second shell mold based on the second part model, and then forming the second part from a second metal alloy in the second shell mold.

7. The method according to claim 6, characterized in that The step of forming the second portion includes an equiaxed cooling step.

8. The method according to claim 6, characterized in that During the step of forming the second portion, the joined portion of the first portion is remelted.

9. Blade comprising a monocrystalline or columnar first portion made of a first metal alloy and a polycrystalline second portion made of a second metal alloy different from the first metal alloy, said blade being obtained by the method according to any one of claims 1 to 8.

10. The blade according to claim 9, characterized in that The first portion and the second portion are formed of two different nickel-based alloys.

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