FR3074813A1 - METHOD FOR DEPOSITING ANTI-WEAR MATERIAL ON A TANK ELEMENT FOR AN AIRCRAFT TURBOMACHINE - Google Patents

Abstract

Method of depositing an anti-wear material on a bladed element (10, 10 ') for an aircraft turbomachine, said bladed element being made of a material having a melting temperature Tf and comprising at least one blade extending between platforms, respectively internal (19) and external (20), at least one of these platforms having lateral edges (21, 22) configured to cooperate by circumferentially interlocking with complementary lateral edges (22, 21) of bladed elements. adjacent side edges, each of which has an anti-wear material (36) obtained by a step (E3) of depositing a drop of this molten material at a temperature T1 which is greater than Tf, characterized in that the step of removal is preceded by the steps of: - determination of a temperature threshold Ts which is a function of the temperature T1, and below which a risk of cracks may appear during the removal step, and - heating (E4) at least a part of the bladed element, up to a temperature T2, between Ts and k.Tf, k being between 0 and 1.

Description

Method of depositing an anti-wear material on a bladed element for an aircraft turbomachine

TECHNICAL FIELD The present invention relates to the general field of manufacturing bladed elements for an aircraft turbomachine, these bladed elements may be stator or rotor elements. It relates more particularly to a method of depositing an anti-wear material on such a bladed element.

STATE OF THE ART [0002] Conventionally, an axial turbine of a turbomachine consists of a succession of axial stages (according to the axis of circulation of the gas flows) arranged one behind the other. Each stage comprises a movable impeller with blades forming the rotor and a bladed distributor forming the stator. The movable wheel is rotated opposite the corresponding distributor.

In the present application, the upstream and downstream are defined with respect to the normal direction of flow of the air flows (from upstream to downstream) through the turbomachine. The axis of the turbomachine is the axis of rotation of the main rotor of the turbomachine. The axial direction corresponds to the direction of the axis of the turbomachine, and a radial direction is a direction perpendicular to the axis of the turbomachine and intersecting this axis. Likewise, an axial plane is a plane containing the axis of the turbomachine, and a radial plane is a plane perpendicular to this axis. The interior and exterior adjectives are used with reference to a radial direction so that the interior part of an element is, in a radial direction, closer to the axis of the turbomachine than the exterior part of the same element. The stacking axis of a blade is the axis perpendicular to the axis of the turbomachine, which passes through the center of gravity of the innermost section of the blade of the blade (ie, the most close to the axis of the turbomachine). Typically, a turbomachine blade comprises a blade extending along the stacking axis of the blade, between the proximal and distal (i.e., inner and outer) ends of the blade.

The movable wheel conventionally consists of an annular disc centered on the axis of rotation of the wheel, on which are fixed a plurality of vanes.

An example of a blade is shown in Figure 1. A blade of this type is described in patent document FR-B1-2 985 759. This blade 10 comprises a blade 16 extending along the axis d stack X of the blade, between the proximal 10A and distal 10B ends of the blade 10. At its proximal end 10A, the blade comprises a platform 19 and a foot 12 by which it is fixed to the disc (not shown) . At its distal end 10B, the blade 10 has a heel 14. When several blades 10 are fixed on the disc, their heels 14 are arranged edge to edge so as to form a circumferential crown delimiting a surface of revolution around the axis A wheel rotation. The function of this ring is in particular to delimit the external surface of the flow stream of the gas flows circulating between the blades 16 and to limit gas leaks at the level of the distal end 10B of the blades 10.

The heel 14 comprises a platform 20 externally delimiting the flow stream of the gas flowing between the blades 16, and having opposite lateral edges 21, 22. The platform 20 comprises an upstream part 24 called “upstream spoiler” and a downstream part 28 called “downstream spoiler”. The heel 14 also includes upstream 31 and downstream 32 sealing wipers extending radially outward from the outer face of the platform 20. Each of the lateral edges 21, 22 of the platform present, between the upstream wipers 31 and downstream 32, a profile substantially “U”. In the case of other blades, this profile can take the form of a “Z” or a “V”, for example.

In order to dampen the vibrations to which the blades 10 are subjected in operation and to give rigidity to the assembly, the blades 10 are mounted on their disc with a torsional stress around their stacking axis. X. The geometry of the heels 14 is such that each blade 10 is placed in torsional stress by pressing on the adjacent blades 10 at the side edges 21 and 22. These side edges 21, 22 therefore define inter-blade contact surfaces and are the place of significant friction during the operation of the turbomachine. To be protected against wear, these edges are provided with an anti-wear material resistant to friction. It may, for example, be a material sold under the brand name Stellite®. This anti-wear material 36 is visible in FIG. 2.

Conventionally, this anti-wear material 36 is deposited on lateral edges 21, 22 by welding, for example by drop welding, involving the creation of an electric arc for the melting of the material. This is often a manual operation, the Stellite® type alloy being in the form of a liquid drop during deposition.

[0009] The Stellite® alloy is a steel alloy with a high content of chromium (Cr) and cobalt (Co). It can also contain a small amount of tungsten (W) or molybdenum (Mo) and a small amount of carbon (C). The Stellite® alloy is not forgeable and must either be cast or fixed by welding on an object of which it forms a part or into which it is inserted.

The deposition operation is complex to carry out, and it has been observed that cracks appear after depositing the drop of Stellite® on blades, which induces the scrapping of these blades.

The present invention provides a simple, effective and economical solution to this problem.

PRESENTATION OF THE INVENTION The present invention provides a method of depositing an antiwear material on a bladed element for an aircraft turbomachine, this bladed element being produced in a material having a melting temperature Tf and comprising at least one blade extending between platforms, respectively internal and external, at least one of these platforms comprising lateral edges configured to cooperate by circumferential interlocking with lateral edges complementary to adjacent bladed elements, these lateral edges each comprising a anti-wear material obtained by a step of depositing a drop of this molten material at a temperature T1 which is higher than Tf, characterized in that the removal step is preceded by the steps of:

- determination of a temperature threshold Ts which is a function of the temperature T1, and below which a risk of cracks may appear during the removal step, and

- Heating of at least part of the bladed element, up to a temperature T2, between Ts and k.Tf, k being between 0 and 1.

The inventors have found that the cracks which appeared on the bladed elements were due to a too high thermal gradient between the temperature of the bladed element (too cold) and the temperature of the drop of material for example of Stellite® ( too hot). Heating the room reduces the gradient and prevents the appearance of cracks. For this, a maximum thermal gradient or difference that the part can withstand is determined and allows the threshold temperature Ts to be calculated beyond which the risk of the appearance of cracks is significantly reduced or canceled. The room is then heated to a temperature T2 higher than Ts to guarantee the deposition of a drop without the risk of cracks appearing. T2 is chosen according to the melting temperature of the part and is naturally lower than this temperature.

The method according to the invention may include one or more of the characteristics and / or steps below, taken in isolation from one another or in combination with each other:

- at least the or each platform intended to receive a drop of molten material is heated in step b),

- the entire bladed element is heated in step b),

- the bladed element is a turbine rotor blade or a turbine distributor sector; in the case of a rotor blade, the external platform is a heel of the blade and comprises at least one anti-wear material, for example of the Stellite® type; in the case of a turbine distributor, the internal and external platforms are connected by several blades and the internal platform comprises at least one anti-wear material, for example of the Stellite® type,

the heating is carried out in step b) by radiation, for example by means of a heating resistor; the radiant heating avoids any contact between the heating device and the part, which is advantageous because it simplifies the implementation of the heating and therefore of the manufacturing process; radiant heating also makes it possible to limit the risk of a temperature gradient occurring within the room itself;

the heating step comprises a sub-step for gradually increasing the temperature of the bladed element and then a sub-step for maintaining the bladed element at the temperature T2 for a predetermined duration,

- the process comprises, after the removal step, a step of gradual and controlled reduction of the temperature of the bladed element,

- The method comprises a preliminary step of mounting the bladed element in a tool, and a final step of dismantling the bladed element of this tool; the preliminary step precedes the heating step and the final step follows the step of removing or reducing the temperature of the bladed element,

- Ts is less than T1,

- k is for example 0.95 and preferably 0.90.

the temperature T1 is between 100 and 1600 ° C, and preferably between 1300 and 1500 ° C, Tf is between 1000 and 1500 ° C, and is for example around 1300 ° C, and the temperature Ts is between between 500 and 900 ° C, and preferably between 600 and 700 ° C, and

- the temperature T2 is between 800 and 1200 ° C., in particular for the range of values of Tf or the example of value of Tf indicated above.

BRIEF DESCRIPTION OF THE FIGURES The invention will be better understood and other details, characteristics and advantages of the invention will appear more clearly on reading the following description given by way of non-limiting example and with reference to the drawings annexed in which:

Figure 1 is a schematic perspective view of a turbine impeller wheel, Figure 2 is a schematic view on a larger scale of an upper part of the blade of Figure 1, Figure 3 is a view schematic of a turbine distributor sector, FIG. 4 is a block diagram illustrating steps of a process for manufacturing a bladed element, according to the prior art, FIG. 5 is a block diagram illustrating steps of a process for manufacturing a bladed element, according to the invention, and FIG. 6 is a schematic perspective view and in partial axial section of a heating device for the implementation of one of the steps of the process according to invention.

DETAILED DESCRIPTION OF AN EMBODIMENT The invention applies to a bladed element which can be a blade 10 of a moving wheel as described above with reference to Figures 1 and 2, or a turbine distributor such as shown in Figure 3.

In both cases, the bladed element comprises at least one blade 16 which extends between two platforms, respectively internal 19 and external 20. The internal platform 19 is connected to the radially internal end of each blade and comprises anti-wear coatings or materials 36 in the case of the turbine distributor sector of FIG. 3. The external platform 20 is connected to the radially external end of each blade and comprises hard anti-wear materials 36 in the case of the dawn of Figures 1 and 2.

FIG. 4 illustrates a method according to the prior art for manufacturing a bladed element. The method essentially comprises three steps, namely a first step E1 of preparing the bladed element, a second step E2 of depositing a drop of molten hard material intended to form the anti-wear material, and a third step E3 of finalization of the bladed element.

As mentioned in the above, in this process, the temperature of the bladed element is not controlled (hence the mention "#T >> in Figure 4) and a significant temperature difference may exist during step E2 between the temperature T1 of the molten material of the drop and of the bladed element.

It is important to note that the bladed element is made of a material, generally a metal alloy, which has a melting temperature Tf which is lower than the temperature T1.

The invention is illustrated by the following figure and proposes, before the removal step E2, to proceed:

- the determination of a temperature threshold Ts which is a function of the temperature T1, and below which a risk of cracks may appear during the removal step, and

- Heating (step E4) at least part of the bladed element, to a temperature T2, between Ts and k.Tf, k being between 0 and 1 and being for example equal to 0.95 and preferably equal to 0.90.

The invention thus provides a step E4 of heating the bladed element before depositing the drop in step E2, in order to reduce the aforementioned temperature gradient or difference and limit or even eliminate the risk of occurrence of coves.

All or part of the bladed element can be heated in step E4. The entire bladed element can be heated, preferably by radiation, using for example a heating resistor 40 as illustrated in FIG. 6. The heating resistor 40 advantageously forms a tubular torus inside which is housed l 'bladed element, here a blade 10 as illustrated in Figures 1 and 2. Alternatively, the part could be heated by placing it in an oven or by heat conduction systems (example: heating the jaw to transfer heat to the bladed element) or thermal convection in a space provided for this purpose (example: pressurized cabin and heated via a surrounding fluid incorporating the stellitage tooling).

Alternatively, only part of the bladed element is heated, namely the part intended to receive the drop of molten material. In the examples shown, this is the external platform or the heel of the blade in FIGS. 1 and 2, and the internal platform of the distributor in FIG. 3. In this case, the part to be heated can be by example by means of a warming slipper which covers this part or of a local thermal conduction device (passage of an electric current in the bladed element for example).

As schematically illustrated in Figure 5, step E4 advantageously but optionally comprises a sub-step E4a of gradual rise in temperature of the bladed element and then a sub-step E4b of maintaining the element blown at temperature T2, and therefore maintaining a temperature plateau.

Furthermore, the process advantageously but optionally, after the removal step E2, a next step E5 of gradual and controlled reduction of the temperature of the bladed element.

During step E1, called the preliminary step, the bladed element is preferably mounted in a dedicated tool for immobilizing the bladed element. Step E3, called the ultimate step, then includes the disassembly of the bladed element of this tool.

Advantageously, the temperature T1 is between 1200 and 1600 ° C, and preferably between 1300 and 1500 ° C, Tf is between 1000 and 1500 ° C, and is for example around 1300 ° C, Ts is between 500 and 900 ° C, and for example between 600 and 700 ° C, and T2 is between 800 and 1200 ° C.

Claims (10)

1. Method for depositing an anti-wear material on a bladed element (10, 10 ′) for an aircraft turbomachine, this bladed element being made of a material having a melting temperature Tf and comprising at least one blade s extending between platforms, respectively internal (19) and external (20), at least one of these platforms having lateral edges (21, 22) configured to cooperate by circumferential interlocking with lateral edges (22, 21) complementary to adjacent bladed elements, these lateral edges each comprising an anti-wear material (36) obtained by a step (E2) of depositing a drop of this molten material at a temperature T1 which is higher than Tf, characterized in that the removal step is preceded by the steps of: - determination of a temperature threshold Ts which is a function of the temperature T1, and below which a risk of cracks may appear during the removal step, and - Heating (E4) of at least part of the bladed element, up to a temperature T2, between Ts and k.Tf, k being between 0 and 1. 2. Method according to the preceding claim, characterized in that at least the or each platform (19, 20) intended to receive a drop of molten material is heated in step b). 3. Method according to any one of the preceding claims, characterized in that the entire bladed element (10, 10 ’) is heated in step b). 4. Method according to any one of the preceding claims, characterized in that the bladed element is a rotor blade (10) or a distributor sector (10 ’). 5. Method according to any one of the preceding claims, characterized in that the heating is carried out in step b) by radiation, for example by means of a heating resistor. 6. Method according to any one of the preceding claims, characterized in that the heating step (E4) comprises a sub-step (E4a) of progressive rise in temperature of the bladed element then a sub-step (E4b) maintaining the bladed element at the temperature T2 for a predetermined period. 7. Method according to one of the preceding claims, characterized in that it comprises, after the removal step (E2), a step (E5) of gradual and controlled reduction of the temperature of the bladed element. 8. Method according to any one of the preceding claims, characterized in that it comprises a preliminary step (E1) of mounting the bladed element in a tool, and a final step (E3) of dismantling the bladed element of this tool. 9. Method according to any one of the preceding claims, characterized in that the temperature T1 is between 100 and 1600 ° C, and preferably between 1300 and 1500 ° C, Tf is between 1000 and 1500 ° C, and is for example around 1300 ° C, and the temperature Ts is between 500 and 900 ° C, and preferably between 600 and 700 ° C. 10. Method according to the preceding claim, characterized in that the temperature T2 is between 800 and 1200 ° C. 1/2