Protective edge for a blade and method of manufacturing said edge

Abstract

A method of manufacturing a protective edge for a blade, wherein a protective edge (30) made of an anodizable metal is provided, and that protective edge (30) undergoes a micro-arc oxidation electrolytic treatment. Protective edge (30) manufactured using said method.

Claims

1. A method of manufacturing a a blade, comprising: providing a protective edge made of an anodizable metal, the protective edge having an outer face and an internal face opposed to each other, the outer face being configured to define an aerodynamic surface of the blade, and the internal face being configured to be glued on a body of the blade to form a leading edge of the blade, performing a micro-arc oxidation electrolytic treatment on the protective edge, applying the treatment to both the inner face and the outer face of the protective edge, forming a coating over the inner face and the outer face, a surface layer of the coating having a surface porosity and a roughness, and gluing the inner face of the protective edge on the body of the blade body; retaining the surface porosity and the roughness of the surface layer of the coating over the inner face until the inner face is glued to the body of the blade.

2. The method according to claim 1, wherein the protective edge has an outer face defining in part the aerodynamic surface of the blade, and the method further comprises polishing the outer face after performing the micro-arc oxidation electrolytic treatment.

3. The method according to claim 1, wherein performing the micro-arc oxidation electrolytic treatment comprises the following steps: immersing the protective edge in an electrolytic bath, the protective edge forming a first electrode, immersing a second electrode in the electrolytic bath, and applying a voltage to the first and second electrodes.

4. The method according to claim 3, wherein when the voltage is applied, a current is imposed whose intensity has pulses.

5. The method according to claim 3, wherein the second electrode is arranged in the electrolytic bath facing the inner face of the protective edge.

6. The method according to claim 3, wherein when the voltage is applied, a current is imposed whose intensity has pulses.

7. The method according to claim 3, wherein the second electrode is arranged in the electrolytic bath facing the inner face of the protective edge.

8. The method according to claim 1, wherein the protective edge is made of titanium or titanium alloy.

9. A blade manufactured using the method according to claim 1.

10. The blade according to claim 9, wherein the body is made of an organic matrix composite material, the protective edge defining the leading edge or the trailing edge of the blade.

11. The blade according to claim 10, wherein the blade is a fan blade of an aeronautical turbomachine.

12. A turbomachine comprising a blade according to claim 10.

13. The method according to claim 1, wherein the blade body is made of an organic matrix composite material.

14. The method according to claim 1, wherein the protective edge is made of titanium or titanium alloy.

15. A method of manufacturing a blade, comprising: providing a protective edge made of an anodizable metal, the protective edge having an outer face and an internal face opposed to each other, the outer face being configured to define an aerodynamic surface of the blade, and the internal face being configured to be glued on a body of the blade to form a leading edge of the blade, performing a micro-arc oxidation electrolytic treatment on the protective edge, applying the treatment to both the inner face and the outer face of the protective edge, a coating over the inner face and the outer face, a surface layer of the coating having a surface porosity and a roughness; and after performing the micro-arc oxidation electrolytic treatment, polishing the outer face of the protective edge and gluing the inner face of the protective edge on the body of the blade; retaining the surface porosity and the roughness of the surface layer of the coating over the outer face until the outer face is polished, and retaining the surface porosity and the roughness of the surface layer of the coating over the inner face until the inner face is glued to the body of the blade.

16. The method according to claim 15, the micro-arc oxidation electrolytic treatment comprises the following steps: immersing the protective edge in an electrolytic bath, the protective edge forming a first electrode, immersing a second electrode in the electrolytic bath, and applying a voltage to the first and second electrodes.

17. A blade manufactured using the method according to claim 15.

18. A blade according to claim 17, wherein the blade body is made of an organic matrix composite material.

19. The blade according to claim 18, wherein the blade is a fan blade of an aeronautical turbomachine.

20. A turbomachine comprising a blade according to claim 18.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The appended drawings are schematic and are not to scale; their primary purpose is to illustrate the principles of the invention.

(2) In these drawings, from one figure (FIG) to another, similar elements (or parts of elements) are identified using the same reference signs.

(3) FIG. 1 is a side view of a blade comprising a protective edge.

(4) FIG. 2 is a partial view of the blade of FIG. 1, in sectional view along cross-sectional cutting plane A-A.

(5) FIG. 3 is a general view of a micro-arc oxidation electrolytic treatment installation.

(6) FIG. 4 is a schematic view showing the intensity pulses applied in one embodiment of the invention.

(7) FIG. 5 shows, schematically, in sectional view, the structure of an example coating created using the micro-arc oxidation electrolytic treatment on the substrate.

DETAILED DESCRIPTION OF THE INVENTION

(8) FIGS. 1 and 2 show a turbomachine engine blade 10. The blade may be a fan blade of an airplane turbojet engine. This blade 10 is intended to be situated in the stream of fluid flowing through the turbojet engine. Upstream and downstream are defined relative to the normal flow direction of this fluid.

(9) The aerodynamic surface 12 of the blade extends, from upstream to downstream, between a leading edge 16 and a trailing edge 18, and along a longitudinal direction 20 between a shank 22 and an apex 24. The blade 10 is secured by its shank 22 to a rotating support disc, which is shared by several blades.

(10) The suction 13 and pressure 11 faces are the side faces of the aerodynamic surface 12 of the blade that connect the leading edge 16 to the trailing edge 18.

(11) The blade 10 comprises a body 9 on which a protective edge 30 is secured by gluing. This protective edge 30 extends over the entire height of the aerodynamic surface 12 of the blade 10, along the longitudinal direction 20. The protective edge 30 has an outer face 31 and an inner face 32 which are opposed to each other. The outer face 31 of the protective edge 30 defines the leading edge 16 and part of the suction 13 and pressure 11 faces. The rest of the suction 13 and pressure 11 faces and the trailing edge 18 are defined by the body of the blade 9. The inner face 32 of the protective edge 30 is in contact with the body 9.

(12) The protective edge 30 has a substantially U-shaped section and is positioned straddling the edge of the body 9. This reinforcement has a base 39 that is the thickest zone of the reinforcement and that defines the leading edge 16. This base 39 is extended by two side flanks 35 and 37 respectively situated on the pressure surface side and the suction surface side of the blade 10. The flanks 35, 37 have, in cross-section (see FIG. 2), a profile that becomes thinner going toward the trailing edge 18.

(13) FIG. 3 schematically shows an example of a micro-arc oxidation electrolytic treatment installation 1. This installation comprises a tank 2 containing an electrolytic bath 3 or electrolyte. For example, this electrolytic bath is made up of an aqueous solution of a hydroxide of an alkali metal (e.g., potassium or sodium) and of an oxyacid salt of an alkali metal. A substrate 5 forming a first electrode, made of metal or a metal alloy and having semiconductor properties, on the one hand, and at least one second electrode 4, called counter electrode, on the other hand, are immersed into the electrolytic bath 3. The installation also comprises a current supply source 6, a voltage generator 7 and control means (for example, a microcomputer 8) controlling and monitoring the variable parameters depending on the treatment sequences. The control means 8 in particular allow to regulate the intensity I of the current flowing through the electrolytic bath. This installation allows to form a coating on the substrate 5 by transforming the metal constituting that substrate 5. The general operation and control of such an installation being known from the prior art, they will not be described in further detail here.

(14) In the proposed method, the substrate 5 is formed by the protective edge 30. For example, the protective edge 30 is made of titanium or titanium alloy. The usage ranges of the installation 1 for creating a coating on this protective edge 30 are, for example, the following: Current density: from 20 to 400 A/dm.sup.2; Voltage: from 200 to 1000 V, more particularly from 400 to 800 V; Intensity pulse frequency: from 1 to 500 Hz, and preferably from 10 to 500 Hz; Charge ratio q.sub.p/q.sub.n: from 0.4 to 1.8 (q.sub.p being the positive charge and q.sub.n the negative charge that are transmitted); Treatment duration: from 10 to 90 min; Temperature of the bath: from 5 to 40 C., and preferably from 10 to 40 C.; pH of the bath: from 6 to 14; Conductivity of the bath: from 100 to 1000 mS/m.

(15) The electrolyte bath 3 may comprise demineralized water and a mixture of potassium and/or sodium salts in various forms, such as hydroxides, silicates, aluminates, phosphates, thiosulfates, tungstates, thiocyanates or vanadate, with a composition comprised between 0.1 and 50 g/l.

(16) To facilitate the treatment of the inner face 32 of the protective edge 30, the second electrode or counter-electrode 4 may be positioned facing that inner face 32, and may in particular be positioned between the flanks 35, 37 of the protective edge 30 and/or have a geometry similar to the first electrode 5. In the example of FIG. 3, two counter-electrodes 4 are used and positioned on both sides of the protective edge 30, very close to the latter.

(17) The following measures are taken to increase the effectiveness of the micro-arc oxidation treatment:

(18) On the one hand, ultrasounds are diffused in the electrolytic bath 3 during the application of the treatment.

(19) On the other hand, the intensity applied between the substrate 5 and the electrodes 4 is not a direct intensity, but a variable alternating intensity, having periodic pulses applied at time intervals with a duration T. This duration T is chosen to be greater than 20 ms, for example 30 ms, so that the frequency of the pulses remains below 50 Hz.

(20) The variations as a function of time t of the intensity I are shown in FIG. 4.

(21) Each pulse is bipolar and includes: an intensity climb ramp, with duration T1, increasing the intensity from 0 to a positive plateau intensity I+; a plateau with duration T2 during which the intensity remains equal to I+; an intensity descent ramp, with duration T3, decreasing the intensity from I+ to 0; a plateau with duration T4 during which the intensity remains equal to 0; an intensity descent ramp, with duration T5, decreasing the intensity from 0 to a negative plateau intensity I; a plateau with duration T6 during which the intensity remains equal to I; an intensity climb ramp, with duration T7, increasing the intensity from I to 0. As soon as one pulse is complete, a new pulse is applied.

(22) The intensities I+ and I of the positive and negative intensity plateaus are not necessarily equal.

(23) The positive and negative plateaus are separated by a short length of time with duration T4 during which the applied intensity is zero.

(24) FIG. 5 shows schematically, in sectional view, the structure of an example coating 50 created using the micro-arc oxidation electrolytic treatment on the substrate 5. In this example, the coating 50 has a porous surface structure 52 and a denser layer 51 situated between the porous layer 52 and the substrate 5. The dense layer 51 is denser and harder than the porous layer 52. As shown, the porous layer 52 has a relatively high porosity and a rough outer surface 53.

(25) After the micro-arc of electrolytic treatment, the outer face 31 of the protective edge 30 may be polished, in particular by tribofinishing or by means of traditional abrasive silicon carbide discs having a particle size decreasing from 80 to 4000 grains per cm.sup.2 or equivalent. For example, the desired roughness level for the outer face 31 may be approximately 0.6 microns, which corresponds to a certain level of aerodynamic requirements. This polishing step, in the case of the coating 50 of FIG. 4, amounts to eliminating the porous layer 52, as diagrammed by the dotted line D. The dense layer 51 is thus on the surface and exposed.

(26) The inner face 32 of the protective edge, on the other hand, may remain raw, i.e., not be polished. In the case of the coating 50 of FIG. 4, this amounts to preserving the illustrated multi-layer structure.

(27) Thus, when the protective edge 30 has a coating 50 of the type shown in FIG. 4, the outer face 31 of the protective edge 30 is defined by the outer face of the dense layer 51, defined by the dotted line D, while the inner face 32 of the protective edge 30 is defined by the outer face 53 of the porous layer 52.

(28) The protective layer 30 thus has a hard and smooth outer face 31, improving the protection of the blade 10 and compatible with a certain level of aerodynamic requirements, and a porous and rough inner face 32 promoting the adhesion of the protective edge 30 on the body 9 of the blade 10.

(29) The examples or embodiments described herein are provided purely as an illustration and in a non-limiting manner, a person skilled in the art being easily able, in light of this description, to modify these embodiments or examples, or to consider others, while remaining within the scope of the invention.

(30) Furthermore, the different features of these examples or embodiments can be used alone or combined with one another. When they are combined, these features may be combined as described above or differently, the invention not being limited to the specific combinations described in this description. In particular, unless otherwise specified, a feature described in relation with one embodiment or example may be applied in an analogous manner to another embodiment or example.