Method for manufacturing a turbomachine blade and turbomachine blade thus manufactured

Abstract

The invention relates to a method for manufacturing a turbomachine blade, comprising the following steps: - manufacturing a blade (10) from composite material, - assembling a metallic leading edge (24) onto the composite blade thus manufactured, characterized in that the method comprises a surface treatment step by applying a mechanical surface prestress to at least a portion of the metallic leading edge (24). Figure for the abstract: Fig. 1.

Description

Title of the invention: Method for manufacturing a turbomachine blade and turbomachine blade thus manufactured technical field

[0001] The present invention relates to a method for manufacturing a turbomachine blade and a turbomachine blade manufactured by such a method. Prior art

[0002] The manufacture of turbomachine blades, particularly fan blades, is well known. The fan blades of new-generation engines are generally made of composite material with a metal leading edge. The leading edge serves to protect the blade against impacts and erosion. When an aircraft flies in a harsh environment, for example through a sand field or a volcanic eruption cloud, the engine's fan blades are exposed to aggressive erosion from this environment, or even to impacts, and suffer damage.

[0003] This damage results in significant degradation of aerodynamic performance and therefore a significant reduction in engine efficiency. Vibrations are also observed in the mechanical structure, which may be accompanied by intense noise. Repairing this damage will cause significant engine downtime and high maintenance costs.

[0004] In view of the above, it would therefore be useful to provide a solution to the aforementioned problem. Description of the invention

[0005] The present presentation is the result of technological research aimed at improving the erosion resistance of the leading edge of the blades in order to increase their lifespan.

[0006] A first aspect of the present exposition relates to a method for manufacturing a turbomachine blade, comprising the following steps: - manufacturing a blade from composite material, - assembling a metallic leading edge onto the blade from composite material thus manufactured, characterized in that the method includes a surface treatment step by applying a mechanical surface prestress on at least a part of the metallic leading edge.

[0007] The controlled introduction of residual compressive stresses on the surface of said at least a portion of the metallic leading edge makes it possible to modifying the surface mechanical properties in this area. This treatment mechanically strengthens at least part of the metallic leading edge, thus enabling it to resist erosion and withstand micro-shocks without deformation.

[0008] According to other possible characteristics: - the surface treatment is chosen from the following surface treatments: shot peening by ball impact, shot peening by ultrasound, shot peening by laser impact; - Shot peening by impact of balls involves balls (for example made of glass or ceramic) having a diameter between 0.18 and 2 mm which are projected onto said at least a part of the metallic leading edge at a speed V1 greater than or equal to 100 m / s, for a duration of between two and five minutes; - Shot peening by ultrasound involves balls (for example made of glass or ceramic) having a diameter between 0.6 and 2 mm which are projected onto said at least a part of the metallic leading edge at a speed V2< 20m / s, for a duration of less than 2 minutes, the temperature of said at least a part of the metallic leading edge being between 25 and 200°C; - Laser shock shot peening involves a laser generating a laser beam with a power between 5 and 15 GW / cm2 with a wavelength between 0.135 and 0.308 |am and a pulse duration between 5 and 20 ns, for a duration of less than 20s; -The surface treatment step is applied to the metal leading edge after the metal leading edge has been assembled onto the composite material blade; -The surface treatment step is applied to the metal leading edge before the metal leading edge is assembled onto the composite material blade; - the assembly of the metallic leading edge onto the composite material blade is carried out by gluing; -the blade made of composite material is manufactured from a fibrous preform obtained by three-dimensional weaving; -the fibrous preform includes fibers which are chosen from carbon fibers and glass fibers; -the metal of the metallic leading edge is chosen from titanium alloys and steels; -said at least a part of the metallic leading edge includes the part of the leading edge which is most exposed to the phenomenon of (random) erosion, namely the leading edge generatrix.

[0009] The invention also relates to a turbomachine blade manufactured by the manufacturing process as briefly described above. The blade thus manufactured offers the advantages of mechanical reinforcement and increased service life already mentioned above.

[0010] The metallic leading edge of the blade may have on at least part a residual surface mechanical prestress less than or equal to 1100 MPa.

[0011] The residual surface mechanical prestress is, for example, present over a depth taken from the outer surface of the leading edge which is between 100 and 300 pm. Brief description of the drawings

[0012] The invention will be better understood and its advantages will become clearer upon reading the following detailed description of embodiments shown by way of non-limiting examples. The description refers to the accompanying drawings, which are schematic and intended primarily to illustrate the principles presented.

[0013] In these drawings, from one figure to another, identical or equivalent elements (or parts of elements) are identified by the same reference numerals. In these attached drawings:

[0014] [Fig-1] [Fig.1] Schematically illustrates a turbomachine blade aircraft according to an embodiment of the invention.

[0015] [Fig.2] Fig.2 illustrates a first possible example of implementation of the process according to the invention.

[0016] [Fig.3] Fig.3 illustrates a second possible example of implementing the process according to the invention. Description of the implementation methods

[0017] To make the explanation more concrete, embodiments are described in detail below, with reference to the accompanying drawings. It should be noted, however, that the invention is not limited to these embodiments.

[0018] The following description of an exemplary embodiment of the invention applies to a fan blade of a known type of aircraft turbomachine. However, other blades present in a turbomachine may also be relevant to the invention.

[0019] Fig. 1 represents schematically a blower blade 10.

[0020] In a known manner, the blade 10 is made of composite material, for example, carbon fibers. This blade comprises, in a known manner, a foot 12, a blade 14, an upper surface 16 located in the background of the figure, and an lower surface 18 visible in the foreground of the figure. The blade 10 also comprises a leading edge 22 and a trailing edge 24. The embodiment details are omitted in order to highlight the main aspects.

[0021] As shown in [Fig. 1], a metallic leading edge or reinforcement edge 24 is intended to be attached to the composite material leading edge 22 in order to strengthen the latter. The metal of the metallic leading edge is chosen from titanium alloys such as titanium Ta6V.

[0022] It should be noted that the metal leading edge can be manufactured in various ways. For example, the metal leading edge can be manufactured through the following steps: supplying a metal bar, forging the bar by extrusion to obtain an intermediate U or V-shaped piece (e.g., bending), shaping in a suitable forming tool, and a finishing step (polishing, etc.). Further information is available in document WO2011161385.

[0023] Alternatively, the metallic leading edge can be manufactured via the following steps: supply of two metal sheets, hot forming of each of the sheets, diffusion welding of the two sheets for their assembly and compaction and finishing-polishing.

[0024] Several different embodiments allowing the metal edge 24 to be mechanically reinforced (after the manufacturing steps of this edge as described above) in order to improve its resistance to erosion and fatigue (with the aim of increasing its lifespan) will now be described.

[0025] Generally, the process for manufacturing a composite material blade according to an embodiment of the invention begins with the manufacture of a blade such as blade 10 in [Fig. 1]. Such a composite material blade can be produced in a known manner from a fibrous preform where the reinforcing fibers are, for example, carbon fibers, obtained by three-dimensional weaving. It should be noted that other fibers can alternatively be used to produce such a fibrous preform, for example, glass fibers.

[0026] The injection of resin into the fibrous preform is carried out after the fibrous preform has been shaped. The resin injection is performed, for example, using tooling comprising a mold, a counter-mold, and resin injection means. The resin-impregnated preform is thus pressurized and heated within the tooling. Further information is available in patent application FR3068640.

[0027] The process then includes a step of assembling the metallic leading edge 24 onto the composite material blade 10 thus manufactured and a surface treatment step by applying a mechanical surface prestress on at least a part of the metallic leading edge.

[0028] However, the order of steps between the assembly step and the surface treatment step may differ depending on the operating conditions and the applications envisaged.

[0029] Thus, for example, the reinforcing metal leading edge 24 can initially be assembled, for example by bonding, onto the composite material leading edge 20 of [Fig. 1]. It should be noted that other types of assembly may also be suitable, such as, for example, welding or mechanical assembly.

[0030] Next, the leading edge thus assembled with the blade undergoes the surface treatment step mentioned above. When the treatment is carried out after assembly, measures are generally taken to protect the preform (masking, for example) during the treatment.

[0031] It should be noted that the reverse order is also possible, i.e., the leading edge first undergoes the surface treatment step mentioned above and is then assembled with the blade as described above. Treating the metallic leading edge before assembly onto the blade prevents the risk of damage to the fibrous preform, for example, from the impact of balls or other objects, depending on the process used.

[0032] Figures 2 and 3 respectively illustrate the main steps (SI, S2, S3 or SI, S3, S2) of a treatment process according to the invention following the two possible orders of intervention of the steps mentioned above.

[0033] More specifically, the surface treatment is selected from the following: shot peening, ultrasonic shot peening, and laser shot peening. It should be noted that a tonnage-based tribofinishing step can be carried out after shot peening to achieve the desired roughness.

[0034] The surface treatment is applied to at least part of the leading edge and, in particular, to the area most exposed to erosion, namely zone 24a in [Fig. 1], which corresponds to the leading edge generatrix. The surface treatment is independent of the specific part of the leading edge to which it is applied and can, of course, be applied along the entire height of the leading edge, including the entire length of the leading edge generatrix. The treatment is generally applied to a band extending widthwise or transversely (perpendicular to the leading edge generatrix) on both the upper and lower surfaces of the leading edge, specifically over a band a few millimeters wide.In other words, the treatment is established here on a limited band that extends on either side of the leading edge generatrix, without necessarily going as far as the edges of the extrados and intrados facets of the leading edge.

[0035] In a first embodiment, the leading edge undergoes shot peening by ball impact using balls with a diameter between 0.18 and 2 mm. These are, for example, balls made of a material such as the 100C6 shot is projected onto at least a portion of the metallic leading edge at a velocity VI greater than or equal to 100 m / s, for a duration of between two and five minutes. The projection direction is approximately 90°. The coverage ratio, which is defined as the ratio of the surface area subjected to plastic deformation by shot peening to the total surface area to be treated, is greater than 125%. The leading edge temperature during this shot peening is generally below 200°C, and is, for example, between ambient temperature and 150°C.

[0036] It will be noted that such a process makes it possible to induce in the leading edge thus treated maximum residual stresses of the order of 1000 to 1100 MPa over a depth (taken from the outer surface of the leading edge and along the direction of projection of the balls, i.e. perpendicular to the surface of the leading edge) of about 200 pm.

[0037] In a second embodiment, the leading edge undergoes ultrasonic shot peening using glass or ceramic beads with a diameter between 0.6 and 2 mm. The beads are projected onto at least a portion of the metallic leading edge at a velocity V2 < 20 m / s, for example, 15 m / s, for a duration of less than 2 minutes, for example, approximately 90 s. The beads are projected in a multidirectional manner. The coverage rate is, for example, greater than 125%. The temperature of at least a portion of the metallic leading edge during this shot peening is generally between 15 and 150°C.

[0038] It should be noted that such a process makes it possible to induce in the leading edge thus treated maximum residual stresses of the order of 700 to 800 MPa over a depth (taken from the outer surface of the leading edge and along the direction of projection of the balls, i.e. perpendicular to the surface of the leading edge) of about 250 pm.

[0039] In a third embodiment, the leading edge undergoes laser shot peening, which involves a laser generating a laser beam with a power between 5 and 15 GW / cm², for example, equal to IJ at 1064 nm. The laser beam is emitted with a wavelength between 0.135 and 0.308 pm, perpendicular to the surface of the leading edge to be treated, and with a pulse duration between 5 and 20 ns, for a duration of less than 20 s, for example, equal to 10 ns with a minimum duration of 5 s.

[0040] The coverage rate is greater than 125%. The leading edge temperature during this prestressing shot peening is generally between ambient temperature and 200°C, for example equal to 150°C.

[0041] It should be noted that such a process makes it possible to induce in the leading edge thus treated maximum residual stresses of the order of 800 to 900 MPa over a depth (taken from the outer surface of the leading edge and along the direction of projection of the balls, i.e. perpendicular to the surface of the leading edge) of about 220 pm.

[0042] The effectiveness of this type of controlled shot peening (surface work hardening) stems from both the hardening effect and the introduction of residual surface compressive stresses on the various areas of the leading edge. These two effects play a crucial role on the blades thus treated in order to combat erosion and withstand micro-shocks without inducing deformation. It should be noted that the work hardening depth does not exceed a few hundred microns. The process described above (regardless of the embodiment envisaged) impacts the surface of the leading edge, creating plastic deformation in this surface over a shallow depth. The leading edge thus treated offers improved resistance to erosion and fatigue, which increases its service life and therefore that of the blade.The aerodynamic performance of the blade, thus equipped with such a leading edge, is therefore not degraded as in the prior art, which prevents the engine's performance from being penalized.

[0043] Although the present invention has been described with reference to specific embodiments, it is evident that various modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. Furthermore, individual features of the various embodiments mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims

Demands

1. A method for manufacturing a turbomachine blade, comprising the following steps: - manufacturing a blade (10) from composite material, - assembling a metallic leading edge (24) onto the blade from composite material thus manufactured, characterized in that the method includes a surface treatment step by applying a mechanical surface prestress on a generatrix of the metallic leading edge (24) which is the part of the metallic leading edge (24) which is most exposed to the phenomenon of erosion.

2. A method according to claim 1, wherein the surface treatment is selected from the following surface treatments: shot peening by ball impact, shot peening by ultrasound, shot peening by laser impact.

3. A method according to claim 2, wherein shot peening by ball impact involves balls having a diameter between 0.18 and 2 mm which are projected onto said part of the metallic leading edge at a speed V1 greater than or equal to 100 m / s, for a duration of between two and five minutes.

4. A method according to claim 2, wherein the ultrasonic prestressing shot peening involves balls having a diameter between 0.6 and 2 mm which are projected onto said part of the metallic leading edge at a speed V2 < 20 m / s, for a duration of less than 2 minutes, the temperature of said at least a part of the metallic leading edge being between 25 and 200°C.

5. A method according to claim 2, wherein laser shock shot peening involves a laser generating a laser beam with a power of between 5 and 15 GW / cm2 with a wavelength of between 0.135 and 0.308 pm and a pulse duration of between 5 and 20ns, for a duration of less than 20s.

6. A method according to any one of the preceding claims, wherein the surface treatment step is applied to the metallic leading edge (24) after the assembly of the metallic leading edge onto the composite material blade (10).

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14. A method according to any one of claims 1 to 5, wherein the surface treatment step is applied to the metal leading edge (24) before the assembly of the metal leading edge onto the composite material blade (10). Method according to claim 6 or 7, wherein the assembly of the metallic leading edge (24) onto the blade made of composite material is carried out by bonding. A method according to any one of the preceding claims, wherein the blade made of composite material (10) is manufactured from a fibrous preform obtained by three-dimensional weaving. A method according to the preceding claim, wherein the fibrous preform comprises fibers that are selected from carbon fibers and glass fibers. A method according to any one of the preceding claims, wherein the metal of the metallic leading edge is selected from titanium alloys and steels. Turbomachine blade manufactured by the manufacturing process according to one of the preceding claims. Turbomachine blade according to the preceding claim, wherein the metallic leading edge (24) has on the part most exposed to the phenomenon of erosion a residual surface mechanical prestress less than or equal to 1100 MPa. Turbomachine blade according to the preceding claim, wherein the residual surface mechanical prestress is present over a depth taken from the outer surface of the leading edge which is between 100 and 300 pm.