Turbomachine blade and method for manufacturing by metal injection moulding

Abstract

A first aspect of the invention relates to a turbomachine turbine blade (10) comprising an airfoil (100) extending in a longitudinal direction defining a length of the airfoil and comprising an outer surface having: - a suction face and a pressure face opposite one another in a transverse direction, - a leading edge (116) and a trailing edge (118) connecting the suction face to the pressure face and separated from one another by a width of the airfoil, wherein: - the turbine blade is made of a material comprising a metal material (140) coating at least one fibre (150) arranged in the turbine blade and at a distance from the outer surface thereof, - at least one of the fibres is a reinforcing fibre (152) extending longitudinally in the airfoil and along the entire length thereof.

Description

TITLE: TURBOMACHINE BLADE AND MANUFACTURING METHOD BY METAL INJECTION MOLDING TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of turbomachine turbine blades and particularly to turbine blades manufactured by a metal injection molding process.

[0002] The present invention also relates to a method for manufacturing a turbine blade for a turbomachine. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Turbine blades, and particularly moving blades, are typically made from intermetallic materials. Some moving blades are made of titanium aluminide (TiAl). Titanium aluminide is a material perfectly suited for turbine blades because it offers good mechanical strength without deterioration due to heat exposure, low thermal expansion, and a density of 3.9 g / cm³. 3 This is mechanically advantageous. Indeed, thanks to the low density of titanium aluminide, it is possible to design moving blades with a significantly larger size, which improves the performance of the turbomachine.

[0004] However, titanium aluminide has a ductility of between 0.2% and 0.5% at room temperature, making it a very brittle material, especially when cold. During turbomachine operation, objects from other turbomachine components, such as hooks, sheet metal, abradables, and scrapers, can impact the blades. This can generate cracks or fissures opposite the point of impact, and these cracks or fissures can potentially propagate and cause the component to break. Due to its low ductility, titanium aluminide blades have low impact resistance, which reduces their lifespan.

[0005] Titanium aluminide turbine blades can be manufactured using a metal injection molding (MiM) process. This process involves injecting a mixture of metal powder and a polymer binder into a mold to create the turbine blade.

[0006] To ensure the robustness of turbine blades made of titanium aluminide and prevent breakage, impact resistance criteria were implemented during the design phase. These criteria help prevent the propagation of cracks or fissures caused by impacts, but they also limit the optimization of several characteristics, including turbine blade mass, blade repairability, the acceptability of production non-conformities, and turbomachine performance. Therefore, there is a need for a turbine blade that meets these various performance criteria while offering optimized mass and repairability, and increasing the acceptability of non-conformities during production. SUMMARY OF THE INVENTION

[0007] The invention offers a solution to the problems mentioned above, by proposing a turbomachine turbine blade comprising fibers.

[0008] A first aspect of the invention relates to a turbomachine turbine blade comprising a turbomachine turbine blade including a blade extending along a longitudinal direction L defining a blade length and comprising an external surface comprising: - an extrados face and an intrados face opposite each other along a transverse direction T perpendicular to the longitudinal direction L, and - a leading edge and a trailing edge connecting the extrados face to the intrados face and separated from each other by a width of the blade.

[0009] The turbine blade is made of a material comprising a metallic material encapsulating at least one fiber arranged within the turbine blade and at a distance from the external surface of the turbine blade. At least one of the fibers is a reinforcing fiber extending longitudinally within the blade and along its entire length.

[0010] The turbine blade according to the first aspect of the invention, thanks to the presence of fibers distributed within the metallic material of the turbine blade, improves resistance to the propagation of cracks or fissures generated in a turbomachine turbine blade following an impact. Indeed, the use of fibers exhibiting good tensile strength makes it possible to limit or even stop the propagation of cracks or fissures in the metallic material of the turbine blade.

[0011] Advantageously, at least one of the fibers is a retaining fiber that crosses at least one reinforcing fiber and is attached to the reinforcing fiber by a knot. This feature ensures that the reinforcing fibers remain in position within a mold during the metal injection molding process of the turbine blade.

[0012] Preferably, the turbine blade comprises at least one platform attached to one end of the blade and extending across the entire width of the blade, and one of the retaining fibers is arranged within the platform. This feature allows the platform to be used for positioning the retaining fibers, thus preventing the risk of deformation of the turbine blade.

[0013] Advantageously, at least one of the retaining fibers is arranged in a central portion of the turbine blade. This feature optimizes the retention of the reinforcing fibers in position within the mold during the metal injection molding process of the turbine blade.

[0014] Preferably, each fiber is a carbon fiber. The use of carbon fibers facilitates their integration into a metal part, particularly one made of titanium aluminide. Furthermore, carbon fibers withstand very high temperatures, up to 3000°C, which is well beyond the operating temperature of turbomachinery parts and the temperatures reached during the manufacturing process.

[0015] Advantageously, each fiber exhibits a tensile strength between 4 and 7 gigapascals. The use of high-strength fibers optimizes the tensile strength of the turbine blade material.

[0016] Preferably, each fiber has a Young's modulus of elasticity of approximately 250 gigapascals. Using fibers with such a Young's modulus improves the ductility of the turbine blade material.

[0017] Advantageously, the metallic material of the turbine blade material is an aluminum and titanium alloy, preferably titanium aluminide.

[0018] Preferably, several reinforcing fibers are arranged, spaced apart along the transverse direction T and substantially parallel to each other. This characteristic allows the reinforcing fibers to be distributed uniformly throughout the blade across its entire width.

[0019] Advantageously, the reinforcing fiber is non-woven for at least 90% of its length. The reinforcing fiber does not cross with a support fiber for at least 90% of its length. When the reinforcing fiber crosses a support fiber, it is secured to it by a knot. Since the blades of the turbine blades are primarily subjected to tensile stress, reinforcement is required in this direction, and the support fibers can therefore be minimized.

[0020] Preferably, the blade comprises at least two parallel reinforcing fibers, each of which includes a straight, non-woven portion representing at least 90% of the reinforcing fiber's length. Reinforcing fibers alone are more flexible and therefore easier to position in the mold than woven fibers.

[0021] Advantageously, the turbine blade comprises only the metallic material sandwiched between two straight, non-woven sections of two adjacent reinforcing fibers. This results in a greater quantity of metal in the blade for a given volume.

[0022] A second aspect of the invention relates to a turbomachine turbine comprising a turbine blade according to the first aspect of the invention.

[0023] A third aspect of the invention relates to a method for manufacturing a turbine blade according to the first aspect of the invention by metal injection molding, the manufacturing method comprising the following steps: - formation of the raw material by mixing a metallic powder with a binder, - injection of raw material into a cavity of a mold forming an injected part, - debinding of the injected part by dissolving the binder, forming a part with a metallic structure, and sintering of the metal structure part by heat treatment of the metal structure part in a furnace forming the turbine blade with its external surface.

[0024] The manufacturing process includes, before the raw material injection stage, a step of inserting each fiber into the mold cavity.

[0025] The manufacturing process according to the third aspect of the invention allows fibers to be integrated directly into the turbine blade mold, and then during the injection stage of the raw material into the mold, the raw material will become lodged between the fibers and thus form a turbine blade reinforced by fibers.

[0026] Advantageously, the mold comprises a first and a second distinct part in contact with each other at a contact plane, and at least some fibers extend into this contact plane. This feature allows the fibers to be held in position by pinching between the first and second parts of the mold during the raw material injection step.

[0027] Preferably, during the insertion step, at least one of the inserted fibers includes at least one extended portion that protrudes outside the mold cavity and is pinched between the first and second mold halves. After the sintering step, each extended portion of the fiber protrudes outside the turbine blade, passing through the outer surface of the blade. The manufacturing process includes a final step of cutting each extended portion of the fiber. This feature allows the reinforcing fibers to be held in position by the retaining fibers via the nodes connecting the reinforcing fibers to the retaining fibers during the raw material injection step.

[0028] Advantageously, during the insertion step, at least two fibers are reinforcing fibers and are positioned at a distance from each other along the longitudinal direction L; and each inserted retaining fiber is attached to the reinforcing fibers to hold them in position in the mold cavity.

[0029] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0030] Other advantages and features of the invention will become apparent from the following description, illustrated by the figures in which: - Figure 1 is a schematic view of a turbine blade according to one embodiment of the invention; - Figure 2 is a schematic cross-sectional view AA of the turbine blade of Figure 1; - Figure 3 is a schematic longitudinal cross-sectional view BB of the turbine blade of Figure 1, according to a first example of the first embodiment of the turbine blade; - Figure 4 is a schematic longitudinal section view BB of the turbine blade of Figure 1, according to a second example of the first embodiment of the turbine blade; - Figure 5 is a schematic cross-sectional view of the manufacturing process of a turbine blade by metal injection molding; - Figure 6 is a schematic longitudinal cross-sectional view of the turbine blade of Figure 3 in a mold, during the manufacturing process, according to a first variant of the manufacturing process; - Figure 7 is a schematic cross-sectional view of the turbine blade and mold of Figure 6, during the manufacturing process, according to the first variant of the manufacturing process; - Figure 8 is a schematic longitudinal cross-sectional view of the turbine blade of Figure 3 in a mold, during the manufacturing process, according to a second variant of the manufacturing process; - Figure 9 is a schematic view of a section along the cutting plane D-D of the turbine blade and the mold of Figure 8 during the manufacturing process, according to the second variant of the manufacturing process; - Figure 10 is a schematic longitudinal cross-sectional view of the turbine blade of Figure 3, according to a third variant of the manufacturing process; DETAILED DESCRIPTION

[0031] Several examples of the embodiment of a turbine blade according to the invention are described in detail below, with reference to the accompanying drawings. These examples illustrate the features and advantages of the invention.

[0032] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0033] For the purposes of understanding the invention, an orthogonal coordinate system LVT, as shown in the figures, will be adopted, in which the longitudinal axis L and transverse axis T lie in a horizontal plane, following the orientation shown in the figures. A leading edge to a trailing edge of a turbomachine turbine blade is oriented along the transverse axis T.

[0034] Figures 1, 2, 3 and 4 illustrate examples of a turbine blade 10 of a turbomachine according to a first embodiment comprising: - a blade 100 extending along a longitudinal direction L between a first and a second end 120 defining a length L1 of the blade 100, the blade 100 comprising an external surface 110 having: o an extrados face 112 and an intrados face 114 opposed to each other along a transverse direction T perpendicular to the longitudinal direction L (see figure 2), and o a leading edge 116 and a trailing edge 118 connecting the extrados face 112 to the intrados face 114 and separated from each other by a width L2 of the blade 100, - a first and a second platform 160 each fixed respectively to the first and second ends 120 of the blade 100 and extending along the entire width L2 of the blade 100.

[0035] The turbine blade 10 is made of a material comprising a metallic material 140. Advantageously, the metallic material 140 of the material of the turbine blade 10 is an aluminum and titanium alloy, preferably titanium aluminide (TiAl).

[0036] The turbine blade 10 includes at least one fiber 150 arranged inside the turbine blade 10 at a distance from the external surface 110 of the turbine blade 10, each fiber 150 being coated by the metallic material 140 of the turbine blade material 10.

[0037] Preferably, each 150 fiber is a carbon fiber. More specifically, each 150 fiber has a tensile strength between 4 and 7 Gigapascals and a modulus of elasticity of approximately 250 Gigapascals. The use of carbon fibers with a very low density therefore has no influence on the mass of the turbine blade 10.

[0038] More specifically, according to the first embodiment as illustrated in Figures 2 and 3, the turbine blade 10 comprises a plurality of fibers 150, including at least one reinforcing fiber 152 and at least one retaining fiber 154. Each reinforcing fiber 152 extends longitudinally within the blade 100 and along the entire length L1 of the blade 100, that is, from the first to the second end 120 of the blade 100. The reinforcing fibers 152 are spaced apart along the transverse direction T and substantially parallel to each other. Each retaining fiber 154 extends in a median plane curved along the cross-sectional plane BB (see Figure 2). Each retaining fiber 154 extends along a longitudinal direction and crosses the reinforcing fibers 152. The reinforcing fibers 152 and the retaining fibers 154 are fixed to each other by a knot 156, at each crossing.

[0039] According to another embodiment not shown, the turbine blade 10 comprises a single reinforcing fiber 152 and may comprise one or more retaining fibers 154.

[0040] According to a first example of the first embodiment of the turbine blade 10, as shown in Figure 3, the turbine blade 10 comprises: - two retaining fibers 154, of which a first and a second retaining fiber 154 are arranged, respectively, in the first and second platform 160, in this case each of the two retaining fibers 154 extends along at least the entire width L2 of the blade 100, - several reinforcing fibers 152, in this case five in number, each connecting the first and second support fibers 154 together, and - several nodes 156 including, in this case here, five first nodes 156 linking the five reinforcing fibers 152 to the first retaining fiber 154 and five second nodes 156 linking the five reinforcing fibers 152 to the second retaining fiber 154.

[0041] In this example, the blade comprises at least two parallel reinforcing fibers 152 (in this case five), each reinforcing fiber comprising a straight non-woven portion representing at least 90% of the length of the reinforcing fiber.

[0042] According to a second example of the first embodiment which is a variant of the first example of the turbine blade 10, as shown in Figure 4, the turbine blade 10 is identical to the first example except that it further comprises four retaining fibers 154 arranged in a central portion 130 of the blade 100 and each connecting the five reinforcing fibers 152 to each other by nodes 156 (five nodes per retaining fiber 154), each retaining fiber 154 extending in the transverse direction T between a first and a fifth reinforcing fiber 152, the retaining fibers 154 being spaced apart from each other in the longitudinal direction L and substantially parallel to each other.

[0043] In this example, the blade comprises at least two parallel reinforcing fibers 152 (in this case five), each reinforcing fiber comprising several straight non-woven portions, the sum of whose lengths represent at least 90% of the length of the reinforcing fiber.

[0044]

[0045] The turbine blade 10 is manufactured using a metal injection molding (MiM) process. This process, as shown in Figure 5, requires the use of an injection device 20 comprising a machine 200 and a mold 210, and a raw material 220 in the form of a metal powder with a binder.

[0046] Machine 200 is equipped with: - a funnel 202 intended to receive the raw material 220, - a worm screw 204 configured to guide the raw material 220 towards the mold 210, and - a resistance 206 allowing the raw material 220 to be heated.

[0047] The mold 210 includes a cavity 216 into which the raw material 220 is injected.

[0048] Another aspect of the invention relates to a method for manufacturing a turbine blade, for example according to the first embodiment. The method comprises the following steps: formation of the raw material 220 by mixing a metal powder with a binder, and insertion of fibers 150 into cavity 216 of mold 210, - injection of raw material 200 into cavity 216 of mold 210 forming an injected part, - debinding of the injected part by dissolving the binder, forming a part with a metallic structure, and - sintering of the metal structure part by heat treatment of the metal structure part in a furnace forming the turbine blade 10 with its external surface 110.

[0049] The fiber insertion step 150 corresponds to the placement of the reinforcing fibers 152 and the holding fibers 154 linked together by the nodes 156 and includes a substep of locking the fibers 150 relative to the mold 210 according to which at least one fiber 150 is fixed to the mold 210.

[0050] Figures 6 to 10 illustrate different variations of the fiber blocking substep 150 with respect to the mold 210 of the blade manufacturing process according to the first example of the first embodiment. A first variation is shown in Figures 6 and 7, a second variation is shown in Figures 8 and 9, and a third variation is shown in Figure 10.

[0051] As illustrated in Figures 7 and 9, the mold 210 is divided into a first part 212 and a second part 214 along a vertical direction V perpendicular to the longitudinal direction L and transverse direction T. The first and second parts 212, 214 of the mold 210 are in contact with each other with respect to a contact surface P. The fibers 150, that is to say the set of reinforcing fibers 152 and holding fibers 154 include a part which extends into the contact surface P.

[0052] According to the first variant of the blocking substep as shown in Figures 6 and 7, each of the inserted retaining fibers 154 comprises a first and second extended portion 154E extending transversely outside the cavity 216 of the mold 210 and outside the mold 210. Each extended portion 154E of the retaining fiber 154 is pinched between the first and second parts 212, 214 of the mold 210 to hold it in position relative to the mold 210 during the injection step.

[0053] According to the second variant of the blocking substep as shown in Figures 8 and 9, each of the inserted reinforcing fibers 152 comprises a first and second extended portion 152E extending longitudinally outside the cavity 216 of the mold 210 and outside the mold 210. Each extended portion 152E is pinched between the first and second parts 212, 214 of the mold 210 to hold it in position relative to the mold 210 during the injection step.

[0054] According to the third variant of the blocking substep as shown in Figure 10, the set of reinforcement fibers 152 and retaining fibers 154 inserted each include a first and second extended portions 152E, 154E pinched between the first and second parts 212, 214 of the mold 210 to optimize the retention in position of the fibers 150 relative to the mold 210 during the injection step.

[0055] Therefore, after the sintering stage of the manufacturing process: - each extended portion 152E of the reinforcing fibers 152 extends outside the turbine blade 10, longitudinally traversing the external surface 110 of the blade 100 and the first and second platforms 160, and / or - each extended portion 154E of the retaining fibers 154 extends outside the turbine blade 10, passing transversely through the external surface 110 of the blade 100, from the leading edge 212 to the trailing edge 214.

[0056] The manufacturing process further includes a final cutting step of each extended portion 152E, 154E of the 150 fibers.

[0057] In the various examples shown, each reinforcing fiber 152 is non-woven over at least 90% of its length; in particular, it is non-woven (does not cross or is not knotted) between two knots adjacent to the two support fibers 154.

[0058] The blade comprises only the material including metallic material 140 between two straight non-woven portions of two adjacent reinforcing fibers 152.

[0059] The addition of 150 fibers distributed inside the turbine blade 10, and more specifically in the blade 100 along its entire length L1, significantly improves the damage resistance of the turbine blade 10. Furthermore, This allows for less stringent criteria, making it possible to optimize several characteristics, such as reducing the thickness of the leading edge 212 of the outer surface 210 of the turbine blade 200 10, and thus decreasing the mass of the part. Obtaining a part with optimized mechanical properties also reduces the scrap rate of turbine blades 10 in production and after-sales service.

Claims

DEMANDS

1. Turbine blade (10) of a turbomachine comprising a blade (100) extending in a longitudinal direction L defining a length (L1) of the blade (100) and comprising an external surface (110) having: - an extrados face (112) and an intrados face (114) opposite each other along a transverse direction T perpendicular to the longitudinal direction L, and - a leading edge (116) and a trailing edge (118) connecting the upper surface (112) to the lower surface (114) and separated from each other by a width (L2) of the blade (100), and - according to which: o the turbine blade (10) is made of a material comprising a metallic material (140) enclosing at least one fiber (150) arranged in the turbine blade (10) and at a distance from the external surface (110) of the turbine blade (10), and o at least one of the fibers (150) is a reinforcing fiber (152) extending longitudinally in the blade (100) and along the entire length (L1) of the blade (100).

2. Turbine blade (10) according to claim 1, wherein at least one of the fibers (150) is a retaining fiber (154) crossing at least one reinforcing fiber (152) and fixed to the reinforcing fiber (152) by a knot (156). [Claims] Turbine blade (10) according to claim 2, wherein: - the turbine blade (10) comprises at least one platform (160) fixed to one end (120) of the blade (100) and extending along the entire width (L2) of the blade (100), and - one of the support fibers (152) is arranged in the platform (160).

4. Turbine blade (10) according to claim 2 or 3, wherein at least one of the retaining fibers (154) is arranged in a central portion (130) of the blade (100) of the turbine blade (10). [Claims] Turbine blade (10) according to any one of the preceding claims, wherein each fiber (150) is a carbon fiber. [Claims] Turbine blade (10) according to any one of the preceding claims, wherein each fiber (150) has a breaking strength between 4 Gigapascals and 7 Gigapascals.

7. Turbine blade (10) according to any one of the preceding claims, wherein each fiber (150) has a modulus of elasticity of about 250 Gigapascals. [Claims] Turbine blade (10) according to any one of the preceding claims wherein the metallic material (140) of the turbine blade material (10) is an aluminum and titanium alloy, preferably titanium aluminide. [Claims] Turbine blade (10) according to any one of the preceding claims, wherein several reinforcing fibers (152) are arranged, spaced apart from each other along the transverse direction T and substantially parallel to each other.

10. Turbine blade (10) according to any one of claims 2 to 9, wherein the reinforcing fiber (152) is non-woven over at least 90% of its length.

11. Turbine blade (10) according to any one of the preceding claims, wherein it comprises at least two parallel reinforcing fibers (152) each reinforcing fiber comprising a straight non-woven portion representing at least 90% of the length of the reinforcing fiber.

12. Turbine blade (10) according to any one of claims 10 or 11, wherein it comprises only the material comprising metallic material (140) between two straight non-woven portions of two adjacent reinforcing fibers (152).

13. Turbomachine turbine comprising a turbine blade (10) according to any one of the preceding claims.

14. A method for manufacturing a turbine blade (10) of a turbomachine according to any one of the preceding claims 1 to 9 by metal injection molding, the manufacturing method comprising the following steps: - formation of the raw material (220) by mixing a metallic powder with a binder, - injection of the raw material (200) into a cavity (216) of a mold (210) forming an injected part, - debinding of the injected part by dissolving the binder, forming a part with a metallic structure, and - sintering of the metal structure part by heat treatment of the metal structure part in a furnace forming the turbine blade (10) with its external surface (110), - according to which it includes, before the raw material injection step (220), a step of inserting each fiber (150) into the cavity (216) of the mold (210).

15. A manufacturing method according to claim 11, wherein: - the mold (210) comprises a first and a second part (212, 214) that are distinct and in contact with each other at the level of a contact plane (P), and - at least some fibers (150) extend into the contact plane (P).

16. A manufacturing method according to claim 12, wherein: - during the insertion step, at least one of the inserted fibers (150) includes at least an extended portion (152E, 154E) extending outside the cavity (216) of the mold (210) and is pinched between the first and second parts (212, 214) of the mold (210), - after the sintering step each extended portion (152E, 154E) of the fiber (150) extends outside the turbine blade (10), passing through the external surface (110) of the blade (100), and - the manufacturing process includes a final cutting step of each extended portion (152E, 154E) of the fiber (150).

17. A manufacturing method according to any one of claims 11 to 13, wherein during the insertion step: - at least two fibers are reinforcing fibers (152) and are positioned at a distance from each other along the longitudinal direction L; and - each inserted retaining fiber (154) is fixed to the reinforcing fibers (152) to hold them in position in the cavity (216) of the mold (210).

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