Method of 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) made of composite material, - assembling a metal leading edge (24) on the composite material 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 metal 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 of manufacturing a turbomachine blade and a turbomachine blade manufactured by such a method. Prior art

[0002] The manufacture of turbomachine blades, in particular 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 phenomena. When an aircraft flies in a harsh environment, for example through an expanse of sand or a volcanic eruption cloud, the engine 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 above-mentioned problem. Statement of the invention

[0005] This disclosure is the result of technological research aimed at improving the erosion resistance of the leading edge of the blades with a view to increasing their service life.

[0006] A first aspect of the present disclosure relates to a method of manufacturing a turbomachine blade, comprising the following steps: -manufacture of a blade in composite material, -assembly of a metal leading edge on the composite material blade thus manufactured, characterized in that the method comprises a surface treatment step by applying a mechanical surface prestress to at least part of the metal leading edge.

[0007] The introduction, in a controlled manner, of residual compressive stresses on the surface of said at least one part of the metal leading edge makes it possible to modify the surface mechanical properties in this area. This treatment makes it possible to mechanically strengthen said at least one part of the metal leading edge and therefore to enable it to combat erosion and withstand micro-shocks without undergoing 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; - ball impact peening involves balls (for example made of glass or ceramic) having a diameter of between 0.18 and 2 mm which are projected onto said at least one part of the metal leading edge at a speed VI greater than or equal to 100 m / s, for a duration of between two and five minutes; - ultrasonic pre-stressing shot peening involves balls (for example made of glass or ceramic) having a diameter of between 0.6 and 2 mm which are projected onto said at least one part of the metal leading edge at a speed V2 < 20 m / s, for a duration of less than 2 minutes, the temperature of said at least one part of the metal leading edge being between 25 and 200°C; - laser shock 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 20 ns, for a duration of less than 20s; -the surface treatment step is applied to the metal leading edge after the assembly of the metal leading edge on the composite material blade; -the surface treatment step is applied to the metal leading edge before assembling the metal leading edge onto the composite material blade; - the assembly of the metal leading edge on the composite material blade is carried out by gluing; - the composite material blade is made from a fiber preform obtained by three-dimensional weaving; -the fiber preform comprises 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 one part of the metallic leading edge comprises the part of the leading edge which is most exposed to the phenomenon of (random) erosion, namely the generator of the leading edge.

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

[0010] The metal leading edge of the blade may have, on at least one part, a residual surface mechanical prestress of 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 μm. Brief description of the drawings

[0012] The invention will be better understood and its advantages will appear better, on reading the detailed description which follows, of embodiments represented by way of non-limiting examples. The description refers to the appended drawings which are schematic and aim above all to illustrate the principles of the disclosure.

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

[0014] [Fig-1] [Fig.l] schematically illustrates a turbomachine blade aircraft according to one embodiment of the invention.

[0015] [Fig.2] [Fig.2] illustrates a first possible example of carrying out the method according to the invention.

[0016] [Fig.3] [Fig.3] illustrates a second possible example of carrying out the method according to the invention. Description of the embodiments

[0017] In order to make the disclosure more concrete, embodiments are described in detail below, with reference to the accompanying drawings. It is recalled, however, that the invention is not limited to these embodiments.

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

[0019] [Fig.l] schematically represents a fan blade 10.

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

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

[0022] It will be noted that the metal leading edge can be manufactured in different ways. For example, the metal leading edge can be manufactured via the following steps: providing a metal bar, forging the bar by extrusion to obtain a U-shaped or V-shaped intermediate part (e.g., bending), shaping in a tool of appropriate shape and finishing step (polishing, etc.). More information is available in document WO2011161385.

[0023] Alternatively, the metal leading edge may be manufactured by the following steps: providing two metal sheets, hot forming each of the sheets, diffusion welding the two sheets for assembly and compacting and finishing-polishing.

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

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

[0026] The injection of a resin into the fiber preform is carried out after the shaping of the fiber preform, forming of this preform. The injection of resin is for example carried out by means of a tool comprising a mold, a counter-mold and resin injection means. The preform impregnated with resin is thus put under pressure and heated in the tool. More information is available in patent application FR3068640.

[0027] The method then comprises a step of assembling the metal leading edge 24 on the composite material blade 10 thus manufactured and a step of surface treatment by applying a mechanical surface prestress to at least part of the metal leading edge.

[0028] However, the order of the 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 may, in a firstly, be assembled, for example by gluing, on the leading edge of composite material 20 of [Fig.l]. It will be noted that other types of assembly may also be suitable such as, for example, welding or mechanical assembly.

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

[0031] It will be noted that the reverse order is also possible, that is to say that the leading edge first undergoes the surface treatment step mentioned above and is then assembled with the blade as described above. The treatment of the metal leading edge before assembly on the blade makes it possible to avoid the risks of damage to the fiber preform, for example by the impact of balls or others depending on the method used.

[0032] Figures 2 and 3 respectively illustrate the main steps (S1, S2, S3 or S1, S3, S2) of a treatment method according to the invention following the two possible orders of intervention of the steps mentioned above.

[0033] More particularly, the surface treatment is chosen from the following surface treatments: ball impact peening, ultrasonic impact peening, laser impact peening. It will be noted that a tonnage tribofinishing step can be carried out after the peening in order to achieve the desired roughness.

[0034] The surface treatment is applied to at least a portion of the leading edge and, in particular, to the area thereof which is most exposed to the erosion phenomenon, namely area 24a in [Fig.l] and which corresponds to the generatrix of the leading edge. The surface treatment does not depend on the portion of the leading edge to which it is applied and can of course be applied over the entire height of the leading edge, in particular over the entire length of the generatrix of the leading edge. The treatment is generally applied to a strip which extends in width or transversely (perpendicular to the generatrix of the leading edge) on the two extrados and intrados facets of the leading edge, in particular over a strip of a few millimeters.In other words, the treatment is established here on a limited band which extends on either side of the generator of the leading edge, without necessarily going to the edge of the extrados and intrados facets of the leading edge.

[0035] In a first embodiment, the leading edge undergoes prestressing shot peening by ball impact which involves balls having a diameter of between 0.18 and 2 mm. These are, for example, balls made of a material such as 100C6 which are projected onto said at least one part of the metal leading edge at a speed 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 rate, which is defined as the ratio of the surface subjected to plastic deformation by shot peening effect to the total surface to be treated, is greater than 125%. The temperature of the leading edge during this prestressing shot peening is generally less than 200°C, and is, for example, between room temperature and 150°C.

[0036] It will be noted that such a method 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 external surface of the leading edge and along the projection direction of the balls, i.e. perpendicular to the surface of the leading edge) of approximately 200 μm.

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

[0038] It will be noted that such a method 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 external surface of the leading edge and following the direction of projection of the balls, i.e. perpendicular to the surface of the leading edge) of approximately 250 μm.

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

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

[0041] It will be noted that such a method 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 following the direction of projection of the balls, i.e. perpendicular to the surface of the leading edge) of approximately 220 pm.

[0042] The effectiveness of this type of controlled shot peening (surface work hardening) comes from both the hardening effect and the introduction of residual surface compressive stresses on the different zones of the leading edge. These two effects play a vital 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 (whatever the embodiment envisaged) impacts the surface of the leading edge by creating plastic deformation in this surface over a small depth. The leading edge thus treated offers better resistance to erosion and fatigue, which makes it possible to increase 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 means that the engine performance is not penalized.

[0043] Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that various modifications and changes may 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 discussed may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims

Claims

1. Method for manufacturing a turbomachine blade, comprising the following steps: - manufacturing a blade (10) made of composite material, - assembling a metal leading edge (24) on the composite material blade thus manufactured, characterized in that the method comprises a surface treatment step by applying a mechanical surface prestress to at least part of the metal leading edge (24).

2. Method according to claim 1, according to which the surface treatment is chosen from the following surface treatments: shot peening by ball impact, shot peening by ultrasound, shot peening by laser impact.

3. Method according to claim 2, according to which the ball impact prestressing peening involves balls having a diameter of between 0.18 and 2 mm which are projected onto said at least one part of the metal leading edge at a speed VI greater than or equal to 100 m / s, for a duration of between two and five minutes.

4. Method according to claim 2, according to which the ultrasonic pre-stressing shot peening involves balls having a diameter of between 0.6 and 2 mm which are projected onto said at least one part of the metal leading edge at a speed V2 < 20 m / s, for a duration of less than 2 min, the temperature of said at least one part of the metal leading edge being between 25 and 200°C.

5. Method according to claim 2, according to which the laser shock peening involves a laser generating a laser beam whose power is between 5 and 15 GW / cm2 with a wavelength between 0.135 and 0.308 pm and having a pulse duration between 5 and 20ns, for a duration of less than 20s.

6. Method according to one of the preceding claims, according to which the surface treatment step is applied to the metal leading edge (24) after assembly of the metal leading edge on the composite material blade (10).

7. A method according to one of claims 1 to 5, wherein the surface treatment step is applied to the metal leading edge (24) before assembling the metal leading edge to the blade made of material composite (10).

8. Method according to claim 6 or 7, according to which the assembly of the metal leading edge (24) on the blade made of composite material is carried out by gluing.

9. Method according to one of the preceding claims, according to which the composite material blade (10) is manufactured from a fibrous preform obtained by three-dimensional weaving.

10. Method according to the preceding claim, according to which the fibrous preform comprises fibers which are chosen from carbon fibers and glass fibers.

11. Method according to one of the preceding claims, according to which the metal of the metallic leading edge is chosen from titanium alloys and steels.

12. A method according to any preceding claim, wherein said at least one portion of the metal leading edge comprises the portion of the leading edge (24a) which is most exposed to the erosion phenomenon.

13. Turbomachine blade manufactured by the manufacturing method according to one of the preceding claims.

14. Turbomachine blade according to the preceding claim, in which the metal leading edge (24) has on at least one part a residual surface mechanical prestress less than or equal to 1100 MPa.

15. Turbomachine blade according to the preceding claim, in which 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.

Images