Hollow blade made of a metal alloy and having a monocrystalline structure for a turbine engine, and method for manufacturing same
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SAFRAN AIRCRAFT ENGINES SAS
- Filing Date
- 2026-01-23
- Publication Date
- 2026-08-06
Smart Images
Figure FR2026050065_06082026_PF_FP_ABST
Abstract
Description
[0001] Description
[0002] Title of the invention: HOLLOW BLADE MADE OF METALLIC ALLOY AND WITH A MONOCRYSTALLINE STRUCTURE FOR A TURBOMACHINE AND ITS MANUFACTURING METHOD
[0003] Technical field of the invention
[0004] The invention relates to the field of hollow blades for a turbomachine, in particular for aircraft, and a method for manufacturing such blades.
[0005] Technical background
[0006] The prior art includes in particular the documents US-A1-2007 / 201980, CN-A-103216273, US-A-6142734, WO-A1-2016 / 160030 and US-A1-2009 / 165988.
[0007] In a turbomachine, particularly an aircraft turbomachine, the hollow blades are generally located downstream of a turbomachine combustion chamber, and are thus subjected to very high combustion gas temperatures during engine operation. These hollow blades, whether moving or fixed, are part of, for example, a low-pressure or high-pressure turbine within the turbomachine.
[0008] Hollow blades are typically made of metallic or composite materials, particularly ceramic matrix composites (CMCs). These materials have the advantage of withstanding high temperatures. However, such blades can be subjected to temperatures exceeding those that metallic or composite materials can withstand.
[0009] Furthermore, increasing the gas temperature, particularly in the high-pressure turbine, improves the turbomachine's efficiency, and therefore the ratio between the turbomachine's thrust and the weight of an aircraft powered by that turbomachine. Consequently, efforts are underway to develop turbine blades that can withstand increasingly higher temperatures and to optimize their cooling.
[0010] In this context, it was proposed to equip the hollow blades with a cooling system. The cooling system comprises a cooling circuit arranged inside these blades, allowing air from the compressors (located upstream of the combustion chamber) to pass through them. The cooling circuit includes an internal cavity, delimited by an inner wall of the blade, which provides internal cooling. Furthermore, it was proposed to drill through the outer wall of the blades to create cooling passages (particularly in the form of slots) opening into the internal cavity, thus creating an air film around the blade and optimizing blade cooling.
[0011] Figures 1 to 4 illustrate an example of a hollow blade 2 comprising:
[0012] - an external wall 210 comprising a leading edge 21, a trailing edge 22, an intrados face 23 and an extrados face 24 which connect the leading edge 21 to the trailing edge 22 along a longitudinal axis A,
[0013] - an internal wall 212 delimiting an internal cavity 200, the internal cavity 200 comprising at least one cooling ramp 3 extending from a base 25 of the blade to its apex 26 along a plane perpendicular to the longitudinal axis A, and
[0014] - a series of cooling slots 220 located on the trailing edge 22, each cooling slot 220 being in fluidic communication with at least a part of the internal cavity 200.
[0015] A cooling airflow (FR) circulates within the internal cavity 200, entering through the base 25 and exiting through the series of slots 220, as indicated by arrows in the example figures. This FR flow is at a lower temperature than the combustion gases, which can reach approximately 1500°C. The FR flow originates upstream of the combustion chamber, for example, from a high-pressure compressor of the turbomachine. The cooler FR flow cools the walls 210, 212 of the blade 2, thus protecting it thermally and preserving its physical properties.
[0016] The series of slots 220 also allows the cooling of the blade 2 to be improved by expelling the flow F from the internal cavity 200, on the one hand, in order to be able to continuously supply the internal cavity 200 with flow FR, and on the other hand, to create the air film around the blade 2 and protect in particular by insulating the blade 2 from a primary flow F1 of hotter air (figure 2).
[0017] Although this architecture allows for the cooling of blade 2, it does present some difficulties, particularly in certain Z zones of the internal cavity 200, which may not be effectively cooled. Referring to Figures 3 and 4, the FR flux supplied by the base 25 circulates within a portion of the internal cavity 200 (specifically, the area near and at the level of the slot series 220) and exits directly through the slot series 220. Because the emission cross-section of the slots 220 is large, the ejection flow rate cannot be uniformly distributed throughout the entire cavity. In particular, a lower FR flux rate can be observed at the apex 26 of the internal cavity 200.
[0018] The absence or insufficiency of cooling of the internal cavity 200 at the apex 26 of the blade can generate degraded areas that may be premature. These degraded areas can be formed by erosion and / or thermal oxidation. These degraded areas can form cracks on the outer wall 210 of the blade. Some cracks can reach a size of approximately 4.5 mm. These degraded areas can thus reduce the blade's service life and generally affect the turbomachine's performance.
[0019] In this context, it is interesting to address at least some of the drawbacks of the prior art by proposing a reliable cooling solution with improved lifespan for hollow blades for a turbomachine, particularly for aircraft.
[0020] Summary of the invention
[0021] The present invention offers a simple, effective and economical solution to the aforementioned drawbacks of the prior art.
[0022] To this end, the invention relates to a hollow metal alloy blade with a single-crystal structure for a turbomachine, in particular for aircraft, the blade comprising: - an outer wall having a leading edge, a trailing edge, an intrados face and an extrados face which connect the leading edge to the trailing edge along a longitudinal axis A,
[0023] - an internal wall delimiting an internal cavity, the internal cavity comprising at least one cooling ramp extending from a base of the blade to its apex along a plane perpendicular to the longitudinal axis A, and - a series of cooling slots located on the trailing edge, each cooling slot being in fluidic communication with at least a part of the internal cavity.
[0024] According to the invention, the hollow blade further comprises micro-grooves on at least a portion of the inner wall of the internal cavity, these micro-grooves having a depth of between 0.01 mm and 0.1 mm. Thus, this solution makes it possible to achieve the aforementioned objective. Indeed, the invention makes it possible to efficiently cool the entire blade, particularly from the base to the tip of the blade. To this end, the hollow blade with a single-crystal structure includes micro-grooves that guide and circulate the cooling airflow throughout the entire internal cavity, notably by entering from the base of the blade to the tip. In particular, the depth of the micro-grooves maximizes the supply of cooling airflow to the entire inner wall of the blade, while creating turbulence in the internal cavity, particularly along a direction orthogonal to the micro-grooves.This turbulence disrupts the airflow circulation in the internal cavity (particularly on the side of the series of cooling slots) for better cooling of the internal cavity by air convection by allowing the airflow to reach the blade tip.
[0025] Furthermore, cooling the entire internal cavity of the blade helps to limit (or even eliminate) areas degraded by oxidation and / or thermal erosion. This improves the blade's service life and, consequently, the overall performance of the turbomachine.
[0026] The invention therefore has the advantage of being based on a simple design, offering very high reliability (in particular efficient and total cooling of the hollow blade), and little penalizing in terms of cost and size.
[0027] The hollow blade according to the invention may comprise one or more of the following features, considered independently of each other or in combination with each other:
[0028] - the micro-grooves extend over the entire inner wall of the base of the blade up to its apex;
[0029] - the internal cavity includes at least one transverse wall extending from the intrados face to the extrados face and delimiting with the internal wall at least two internal chambers each comprising a cooling ramp, in which one of the at least two internal chambers is in fluidic communication with the series of cooling slots;
[0030] - micro-grooves are formed by dendrites which are oriented in a radial direction relative to axis A;
[0031] - the blade is made of a single-crystal superalloy, for example nickel-based; - the internal cavity includes flow interferents with an elongated shape;
[0032] - the interfering elements are inclined and oriented at least 45° with respect to a plane perpendicular to the axis (A);
[0033] - The hollow blade is movable and / or fixed, for example, relative to the longitudinal axis; - The hollow blade is a low-pressure turbine blade and / or a high-pressure turbine blade.
[0034] - the hollow blade is a moving blade of a low pressure turbine, a moving blade of a high pressure turbine, a blade of a low pressure turbine distributor and / or a blade of a high pressure turbine distributor.
[0035] The present invention also relates to a turbomachine, in particular for aircraft, comprising at least one blade according to one of the features of the invention.
[0036] The turbomachine can be a turbojet, a turbomotor or a turboprop.
[0037] The present invention further relates to a method of manufacturing a blade according to one of the features of the invention, the method according to the invention comprising a step (a) of making the blade, and the method further comprising a step (b) of forming micro-grooves on at least a part of the internal wall of the internal cavity by chemical machining.
[0038] The process according to the invention makes it possible to form micro-grooves on at least a portion of the blade's inner wall to efficiently cool the entire blade. In particular, chemical machining makes it easier to generate micro-grooves on the inner wall from the blade's single-crystal structure. Indeed, chemical machining makes it easier to reveal the dendrites of the single-crystal structure as micro-grooves on the inner wall.
[0039] Furthermore, the micro-groove formation step can be automated (for example by a suitable machine).
[0040] The manufacturing process according to the invention may include one or more of the following features, considered independently of each other or in combination with each other: - chemical machining is carried out by injection and circulation of an acidic fluid in the internal cavity, entering through the base of the blade and exiting through the series of cooling slots;
[0041] - the acidic fluid is a mixture containing iron chloride and hydrochloric acid;
[0042] - chemical machining is carried out for a predetermined duration which is greater than 4 hours, preferably said predetermined duration is between 4 and 9 hours, even more preferably this predetermined duration is between 7 and 9 hours;
[0043] - chemical machining is carried out with a predetermined flow rate of approximately 5 liters / hour;
[0044] - after chemical machining, step (b) may include a substep (b') of rinsing and cleaning the internal cavity for example with a rinsing fluid (such as water and / or soda).
[0045] Step (a) of the manufacturing process according to the invention may include the following sub-steps:
[0046] (ai) fabrication of a core intended to form the internal cavity,
[0047] (32) creation of a model of the blade around the nucleus,
[0048] (as) creation of a mold of the awl's shell around the model,
[0049] (a₄) model withdrawal,
[0050] (a₅) Optionally, heat treat the shell mold,
[0051] (as) injection of a metallic alloy material into the shell mold so as to form the outer wall of the blade,
[0052] (a?) core removal to form the inner wall of the blade and its internal cavity, (a₈) machining of the series of cooling slots on the trailing edge,
[0053] (ag) optionally, machining of a blade foot at the blade base, (aw) optionally, application of at least one protective coating to the outer wall of the blade.
[0054] After injection of the metal alloy material, substep (as) can be followed by solidification of the metal alloy material and removal of the shell mold. Substep (aie) can be carried out after step (b). According to one embodiment of the method of the invention, step (b) can be carried out during step (a) by integrating airflow disruptors on the core, such as notches and / or fins, said disruptors extending radially along an external surface of the core.
[0055] Brief description of the figures
[0056] The invention will be better understood and other details, features and advantages of the invention will become more apparent upon reading the following description, given by way of non-limiting example and with reference to the accompanying drawings, in which: Figure 1 is a schematic perspective representation of a hollow blade according to the prior art for a turbomachine,
[0057] Figure 2 is a schematic perspective and top view representation of the dawn in Figure 1.
[0058] Figure 3 is another schematic perspective representation of the dawn shown in Figure 2.
[0059] Figure 4 is an enlarged view of a summit of the dawn in Figure 3.
[0060] Figure 5 is a schematic half-view in axial cross-section representing an aircraft turbomachine according to the invention,
[0061] Figure 6 is a schematic half-view in axial and enlarged cross-section of a turbine of the turbomachine shown in Figure 5.
[0062] Figure 7 is a schematic perspective representation of a hollow, single-crystal, metallic alloy blade according to the invention.
[0063] Figure 8 is a schematic perspective representation of several blades exhibiting equiaxed, columnar, and single-crystal structures.
[0064] Figure 9 is a schematic perspective representation of a first example of the blade of Figure 7, featuring micro-grooves on at least part of the inner wall of this blade.
[0065] Figure 10 is a schematic representation of the dendrites of the single-crystal structure at the level of the inner wall of the blade in Figure 9.
[0066] Figure 11 is a schematic axial cross-sectional representation of a second example of the blade of Figure 8, featuring micro-grooves on the inner wall of this blade; Figure 12 is a schematic axial cross-sectional representation of a third example of the blade of Figure 8, featuring micro-grooves on the inner wall of this blade.
[0067] Figure 13 is a block diagram of the steps in a manufacturing process for the hollow blade according to the invention,
[0068] Figure 14 is a schematic representation of a step in the injection of a metallic alloy material into a mold according to the process shown in Figure 13.
[0069] Figure 15 is a schematic representation of a step in the formation of micro-grooves according to the process of Figure 13.
[0070] Elements having the same functions in different implementations have the same references in the figures.
[0071] Detailed description of the invention
[0072] In general, in this application, the terms "longitudinal" and "axial" refer to the orientation of structural elements extending along a longitudinal axis (such as that of the turbomachine). The term "radial" refers to the orientation of structural elements extending in a direction perpendicular to the longitudinal axis. The terms "interior" and "exterior," and "internal" and "external," are used with reference to positioning relative to the longitudinal axis. Thus, a structural element extending along the longitudinal axis has an interior surface facing the longitudinal axis and an exterior surface opposite its interior surface.
[0073] Figures 1 to 4 have been described in the technical background of this application and illustrate a prior art hollow blade, in particular made of metallic alloy and with a single-crystal structure, for a turbomachine.
[0074] The invention applies in a non-limiting way to a turbomachine 1, in particular of an aircraft, such as a turbojet, a turbomotor or a turboprop.
[0075] Figure 5 illustrates an example of this turbomachine 1 of the double-flow type.
[0076] Turbomachine 1 can extend along a longitudinal X axis.
[0077] The turbomachine 1 may include, from upstream to downstream, a blower 1a, at least one compressor (such as a low pressure compressor 1b and a high pressure compressor 1c), a combustion chamber 1d, at least one turbine (such as a high pressure turbine 1e and a low pressure turbine 1f), and optionally a gas exhaust nozzle (not shown in Fig. 5).
[0078] The blower 1a (or in other words a propeller) allows the intake of an airflow F which divides into a primary flow F1 and a secondary flow F2. The primary flow F1 passes through the engine of the turbomachine 1 while the secondary flow F2 is directed towards a secondary duct.
[0079] The primary flow F1 is compressed within the low-pressure compressor 1b and then the high-pressure compressor 1c. The compressed air is then mixed with fuel and burned within the combustion chamber 1d. The gases formed by combustion pass through the high-pressure turbine 1e and the low-pressure turbine 1f. Finally, the gases escape through the nozzle, the cross-section of which allows the gases to be accelerated to generate propulsion.
[0080] In the example shown in Figure 5, the fan 1a is, for instance, shrouded. It is surrounded by an annular casing centered on the longitudinal axis X. The casing is, for example, surrounded by a nacelle (not shown in Figure 5) of the turbomachine 1. Alternatively, the turbomachine 1 may include an unshrouded fan 1a. With reference to Figures 6, 7, and 9, the turbomachine 1 (in particular the high-pressure turbine 1e and / or the low-pressure turbine 1f) may include at least one blade 2.
[0081] This blade 2 can be mobile (called rotor blade) or fixed (called stator blade).
[0082] Advantageously, the hollow blade 2 can be a moving blade of a high-pressure turbine 1e, a moving blade of a low-pressure turbine 1f, a distributor blade (or otherwise a fixed blade) of a high-pressure turbine 1e and / or a distributor blade of a low-pressure turbine 1f.
[0083] Each 2-bladed vane can extend as follows:
[0084] - a longitudinal axis A (approximately horizontal in figure 7) which is approximately parallel to the X axis of the turbomachine 1,
[0085] - a longitudinal axis B (approximately vertical in figure 7) which is approximately perpendicular to axis A, and
[0086] - a transverse axis C which is substantially perpendicular to axes A and B.
[0087] The blade 2 comprises: - an external wall 210 having a leading edge 21, a trailing edge 22, an intrados face 23 and an extrados face 24 which connect the leading edge 21 to the trailing edge 22 along the longitudinal axis A,
[0088] - an internal wall 212 delimiting an internal cavity 200, the internal cavity 200 comprising at least one cooling ramp 3 extending from a base 25 of the blade to its top 26 along a plane perpendicular to the axis A, and - a series of cooling slots 220 located on the trailing edge 22, each cooling slot 220 being in fluidic communication with at least a part of the internal cavity 200.
[0089] The internal wall 212 can be located inside the external wall 210. The internal wall 212 can extend along the axis B between the base 25 and the apex 26.
[0090] The slots 220 of the cooling slot series 220 allow the internal cavity 200 to be connected, in particular by fluidic means, to a primary flow of the turbomachine 1 in which the primary flow F1 circulates. These slots 220 improve the cooling of the blade 2 by expelling a cooling air flow FR from the internal cavity 200, firstly, to continuously supply the internal cavity 200 with FR flow, and secondly, to create the air film around the blade 2 and protect the blade 2 from the hotter primary air flow F1 by isolating it (figure 2).
[0091] The slots 220 can be inclined, particularly towards the trailing edge 22, to improve air film formation. Furthermore, a preform (not shown in the figures), particularly one with a trapezoidal shape, can be added to the slots 220 to ensure the air film is as close as possible to the outer wall 210.
[0092] The second blade according to the invention is hollow.
[0093] The blade 2 may include a blade 20. This blade 20 may include a portion of the outer wall 210 and the inner wall 212. In particular, the blade 20 may include the leading edge 21, the trailing edge 22, the lower surface 23, and the upper surface 24. The blade 20 may have an aerodynamic profile to form the aerodynamic part of the blade 2. For this purpose, the blade 20 may have a curved profile of variable thickness between the leading edge 21 and its trailing edge 22.
[0094] The blade 2 can extend along axis B between the base 25 (or blade root) and the tip 26 (or blade tip). The base 25 can be connected to the blade 20, for example, by a platform. The base 25 of each blade 2 is mounted in a movable or fixed disk of the turbomachine 1 (Figure 6). The base 25 can include one or more openings allowing the passage of a fluid (such as the FR cooling air flow from downstream of the combustion chamber 1d, and / or an acidic fluid FA) and the circulation of this fluid within the internal cavity 200. This opening can lead to the cooling manifold 3 of the internal cavity 200.
[0095] The internal cavity 200 may include at least one transverse wall 214 extending from the intrados face 23 to the extrados face 24. The transverse wall 214 may extend from the base 25 to the apex 26. The transverse wall 214 may, together with the internal wall 212, delimit at least two internal chambers 201, 202, each having a cooling ramp 3. The internal cavity 200 may include between one and ten transverse walls 214. This internal cavity 200 may include between two and eleven internal chambers.
[0096] In Figures 9 and 15, for example, the internal cavity 200 may have only one transverse wall 214 to delimit and form two internal chambers 201, 202. In other words, the internal cavity 200 can be divided into two internal chambers 201, 202, each with a cooling ramp 3. In Figure 11, for example, the internal cavity 200 may have approximately four transverse walls 214, forming approximately five internal chambers 200.
[0097] The internal cavity 200 of figure 12 may be devoid of a transverse wall 214, and thus comprise only one internal chamber 200.
[0098] In particular, the internal cavity 200 can include a downstream chamber 201 located on the trailing edge side 22 and an upstream chamber 202 located on the leading edge side 21. This configuration allows the leading edge 21 and the trailing edge 22 to be cooled by separate cooling ramps 3 which extend from the base 25 to the top 26. In the example of Figure 9, several intermediate chambers are located between the downstream chamber 201 and the upstream chamber 202.
[0099] One of the at least two internal chambers (specifically the downstream internal chamber 201) is in fluidic communication with the series of cooling slots 220. This allows the fluid entering through the base 25 and circulating in the downstream internal chamber 201 to cool a portion of the blade, to exit through these slots 220.
[0100] Referring to Figure 9, the internal cavity 200, preferably the downstream internal chamber 201, may include flow interferers 216 (or, in other words, flow perturbators). These interferers 216 may be elongated. The interferers 216 may be inclined and oriented at least 45° with respect to axis B. The interferers 216 may have a thickness greater than 2 mm. These interferers 216 increase the turbulence of the flow F R in the internal cavity 200 (figures 4 and 9), so as to maximize the cooling of the walls 210, 212 by air convection. The blade 2 is made of a metal alloy.
[0101] Referring to Figure 8, the blade 2 (notably produced by casting, i.e., by pouring a metallic or metallic alloy material and cooling it through directional solidification) can have various structural forms, such as an equiaxed SE structure, a columnar Sc structure, or a single-crystal SM structure. The equiaxed SE structure has grains Gr (or crystals) separated from each other by J-boundaries. However, these grain J-boundaries can initiate cracking during operation. The columnar Sc structure has grains Gr oriented parallel to a principal stress direction to reduce creep at the J-boundaries and minimize cracking. The single-crystal S structure M has a single grain Gr (or in other words a single crystal formed from a single seed) and therefore without J joints. This single-crystal structure thus presents better creep resistance.
[0102] In order to offer the best thermomechanical performance, the blade 2 according to the invention has a single-crystal structure.
[0103] As an example, blade 2 can be made from a single-crystal superalloy. This superalloy can be nickel-based, such as Inconel®, AM1, AM3, CMSX4, CMX4 SLS, CMX-4 Plus, DS200, etc.
[0104] One of the features of the invention is that the hollow blade 2 further comprises micro-grooves 230 on at least part of the inner wall 212 of the internal cavity 200, these micro-grooves 230 having a depth of between 0.01 mm and 0.1 mm. This allows the entire blade 2, and in particular the tip 26, to be cooled.
[0105] The depth of the micro-grooves 230 can be measured along a plane parallel to the Z axis.
[0106] The micro-grooves 230 can extend over the entire internal wall 212 from the base 25 of the blade to its apex 26.
[0107] The micro-grooves 230 can be formed by dendrites 232 oriented radially with respect to axis A. Indeed, the single-crystal structure of the blade 2 can include dendrites 232, which are notably branching, tree-like patterns (Figure 10). These dendrites 232 generally form during the solidification of the cast material. Referring to Figures 9 and 10, the micro-grooves 230 can correspond to the interfaces between the dendrites 232.
[0108] Figure 11 schematically and partially illustrates a first, non-limiting example of the blade 2 as described above with reference to Figures 7 to 10. This blade 2 thus includes the micro-grooves 230 on the inner wall 212 of the internal cavity 200 on the trailing edge side 22 (i.e., in the downstream internal chamber 201). This internal cavity 200 can have approximately five internal chambers. The micro-grooves 230 extend over the entire length of this internal wall 212.
[0109] Figure 12 schematically and partially illustrates a second, non-limiting example of blade 2. This blade 2 differs from that of the first example by the internal cavity 200, which forms a single internal chamber. In this example, the micro-grooves 230 can extend, on the one hand, from the leading edge 21 to the trailing edge 22, and on the other hand, from the base 25 to the tip 26. This allows for efficient cooling of the entire blade, particularly the entire tip 26, during operation.
[0110] With reference to Figures 13 to 15, the present application will now describe a manufacturing process for the hollow blade 2 as described above.
[0111] According to the invention, the manufacturing process for blade 2 comprises:
[0112] - a step (a) in the production of the second blade, and
[0113] - a step (b) of forming micro-grooves 230 on at least part of the internal wall 212 of the internal cavity 200.
[0114] Figure 13 summarizes the steps of the manufacturing process of the invention with the optional steps indicated in dotted lines.
[0115] Step (a) of the manufacturing process according to the invention may include the following sub-steps:
[0116] (ai) fabrication of a core 300 intended to form the internal cavity 200,
[0117] (32) realization of an M2 model of blade 2 around core 300,
[0118] (as) creation of a mold M for the blade shell 2 around the M2 model,
[0119] (a4) removal of the M2 model, (a5) optionally, heat treat the M shell mold,
[0120] (ae) injection of a metallic alloy material into the M shell mold so as to form the outer wall 210 of the blade 2,
[0121] (a7) removal of the core 300 so as to form the inner wall 212 of the blade 2 and its internal cavity 200,
[0122] (a8) machining of the series of cooling slots 220 on the trailing edge 22, (ag) optionally, machining of a blade foot at the blade base 25, (aw) optionally, deposition of at least one protective coating on the outer wall 210 of the blade 2.
[0123] Substep (a1) can be carried out by additive manufacturing or by molding. The 300 core can be made of ceramic material, refractory metal, or a mixture thereof.
[0124] Substep (a2) can be carried out by wax injection molding around core 300.
[0125] Substep (a3) can be carried out by successively dipping the model M2 into slips. The slips may include, for example, a ceramic material. The dipping process can be followed by a drying step of the M shell mold.
[0126] Substep (a4) can be carried out by pre-cooking the M carapace mold at a first temperature allowing dewaxing of the M carapace mold.
[0127] Substep (a5) can be carried out by firing the M shell mold at a second temperature higher than the first temperature. Such a substep increases the strength of the M shell mold.
[0128] Substep (a6) can be carried out under vacuum. The metal alloy material is molten during this substep. The metal alloy can be, for example, a nickel-based superalloy.
[0129] The substep (ae) can be followed by solidification of the metal alloy material and removal of the mold shell. Solidification is typically directional (e.g., the Bridgman process) using a grain selector or a seed crystal at the bottom of the mold to cool the cast material and form the single-crystal structure.
[0130] Figure 14 illustrates an example of an apparatus A, such as a furnace, comprising the shell mold M with the core 300 surrounded by the blade model M2, and a grain selector S G This grain selector enables directional solidification to form the single-crystal structure. Substep (a7) can be carried out by mechanical or chemical treatment. For example, blade 2 can be placed in a chemical bath to dissolve the core 300. At the end of substep (a?), blade 2 is obtained according to step (a) as illustrated in Figures 7 and 9 to 12.
[0131] At substep (a8), the slots 220 can be drilled by electro-erosion (EDM, English acronym for "Electrical Discharge Machining") or by laser.
[0132] Step (aw) can be performed after step (b).
[0133] Step (b) can be carried out by chemical machining.
[0134] Chemical machining can be performed by injecting and circulating the acidic fluid FA into the internal cavity 200, entering through the base 25 (specifically via the opening at the base 25) of the blade 2 and exiting through the series of cooling slots 220. The acidic fluid FA can be a mixture containing iron chloride (FeCh) and hydrochloric acid (HCl).
[0135] Figure 15 illustrates an example of an embodiment of step (b) in which the acid fluid FA can be injected into the internal cavity 200 through the base 25 and exit through the slots 220. The acid fluid FA exiting the slots 220 can be re-used for one or more further injection(s) into the internal cavity 200, or recycled for another use.
[0136] Chemical machining can be carried out for a predetermined duration, which may exceed 4 hours. Preferably, the predetermined duration may be between 4 and 9 hours. Even more preferably, this predetermined duration may be between 7 and 9 hours.
[0137] A first test was carried out by the inventors, in which blade 2 was exposed to the acidic fluid FA for a period of 3 hours. The inventors observed that the wall of this blade 2 is almost smooth.
[0138] A second test was carried out by the inventors, in which blade 2 was also exposed to the acidic fluid FA (identical to that of blade 2 in the first test) for a period of 9 consecutive hours. The inventors observed that the wall of this blade 2 had micro-grooves 230. Chemical machining with the acidic fluid FA for the predetermined duration thus reveals the dendrites 232 and forms the micro-grooves 230, particularly along the radial direction with respect to axis A. The chemical machining can be carried out with a predetermined flow rate. This predetermined flow rate allows, in particular, for the recirculation of the acidic fluid FA. A unsaturated in the internal cavity 200 without damaging the internal wall 212. The predetermined flow rate can be approximately 5 L / h (Liter per hour).
[0139] After chemical machining, step (b) may include a substep (b') of rinsing and cleaning the internal cavity 200, for example, with a rinsing fluid. This rinsing fluid may be water and / or sodium hydroxide (NaOH). The water in the rinsing fluid may be cold or hot. The hot water in the rinsing fluid may, for example, be at a temperature above 65°C, preferably around 80°C. c C. The cold water in the rinsing fluid can, for example, be at a temperature below 65°C.
[0140] According to one embodiment of the method of the invention, step (b) can be carried out during step (a) by incorporating airflow disruptors on the core, such as notches and / or fins, the disruptors extending radially along an external surface of the core. In this embodiment, the microgrooves 230 can be formed during substep (a7).
Claims
Demands 1. Hollow single-crystal structure metal alloy blade (2) for a turbomachine (1), in particular for aircraft, the blade (2) comprising: - an external wall (210) comprising a leading edge (21), a trailing edge (22), an intrados face (23) and an extrados face (24) which connect the leading edge (21) to the trailing edge (22) along a longitudinal axis (A), - an internal wall (212) delimiting an internal cavity (200), the internal cavity (200) comprising at least one cooling ramp (3) extending from a base (25) of the blade to its apex (26) along a plane perpendicular to the longitudinal axis (A), and - a series of cooling slots (220) located on the trailing edge (22), each cooling slot (220) being in fluidic communication with at least a part of the internal cavity (200), characterized in that the hollow blade (2) further comprises micro-grooves (230) on at least a portion of the internal wall (212) of the internal cavity (200), these micro-grooves (230) having a depth of between 0.01 mm and 0.1 mm, and in that the micro-grooves (230) are formed by dendrites (232) which are oriented in a radial direction with respect to the axis (A).
2. Blade according to claim 1, characterized in that the micro-grooves (230) extend over the entire internal wall (212) of the base (25) of the blade up to its top (26).
3. Blade according to claim 1 or 2, characterized in that the internal cavity (200) comprises at least one transverse wall (214) extending from the intrados face (23) to the extrados face (24) and delimiting with the internal wall (212) at least two internal chambers (201, 202, 203, 204, 206), each having a cooling ramp (3), in which one of the at least two internal chambers (201) is in fluidic communication with the series of cooling slots (220).
4. Blade according to any one of claims 1 to 3, characterized in that the blade (2) is made of a single-crystal superalloy, for example nickel-based.
5. Blade according to any one of claims 1 to 4, characterized in that the internal cavity (200) comprises flow interferants (216) having an elongated shape.
6. Blade according to claim 5, characterized in that the interferants (216) are inclined and oriented at least 45° with respect to a plane perpendicular to the longitudinal axis (A).
7. Blade according to any one of claims 1 to 6, characterized in that the hollow blade (2) is a low pressure turbine blade and / or a high pressure turbine blade.
8. Turbomachine (1), in particular for aircraft, comprising at least one hollow blade (2) according to any one of claims 1 to 7.
9. Method for manufacturing a hollow blade (2) according to any one of claims 1 to 7, the method comprising a step (a) of producing the blade (2), the method further comprising a step (b) of forming micro-grooves (230) on at least a part of the internal wall (212) of the internal cavity (200) by chemical machining.
10. Manufacturing method according to claim 9, characterized in that the chemical machining is carried out by injection and circulation of an acidic fluid (FA) in the internal cavity (200) entering through the base (25) of the blade (2) and exiting through the series of cooling slots (220).
11. Manufacturing process according to claim 10, characterized in that the acid fluid (AF) is a mixture comprising iron chloride and hydrochloric acid.
12. A manufacturing process according to any one of claims 9 to 11, characterized in that the chemical machining is carried out for a predetermined period which is greater than 4 hours, preferably said predetermined period is between 4 and 9 hours, even more preferably this predetermined period is between 7 and 9 hours.
13. Manufacturing process according to any one of claims 9 to 12, characterized in that the chemical machining is carried out with a predetermined flow rate of approximately 5 liters / hour.
14. Manufacturing method according to any one of claims 9 to 13, characterized in that after chemical machining, step (b) may include a substep (b') of rinsing and cleaning the internal cavity (200) for example with a rinsing fluid.