Composition for abradable seal of turbomachine

Abstract

The present invention proposes a composition for an abradable seal (38) of a compressor (4), the composition comprising a metallic phase and a non-metallic phase, the non-metallic phase constituting 5% to 50% of the total mass of the composition, the metallic phase comprising, by mass: 45% to 80% aluminum; from 10% to 45% of nickel; from 5% to 20% cobalt or chromium; and 1% to 5% of copper, magnesium, manganese or zirconium. The invention also relates to a method for producing the seal and a turbomachine comprising the seal.

Description

Technical Field

[0001] The invention relates to the field of sealed turbomachines using two-phase abradable seals. The invention also proposes a method for producing an abradable seal and a turbomachine equipped with such a seal. Background Art

[0002] Climate change is a major concern for many legislative and regulatory bodies around the world. In fact, states have, are or will adopt various carbon emission restrictions. In particular, a strict standard applies to new aircraft and aircraft already in service, requiring the implementation of technical solutions to ensure their compliance with current regulations. For many years, civil aviation has been actively taking action to contribute to the fight against climate change.

[0003] Technical research work has led to very significant improvements in the environmental performance of aircraft. The applicant has taken into account the influencing factors at all stages of design and development in order to obtain less energy-intensive and more environmentally friendly aviation components and products, whose integration and use in civil aviation have moderate environmental consequences, with the aim of improving the energy efficiency of aircraft.

[0004] Therefore, Applicants have been working to reduce the negative impact of greenhouse gases on the climate by using methods, operating benign development and manufacturing processes, and minimizing greenhouse gas emissions to reduce the environmental footprint of greenhouse gas activities.

[0005] This ongoing research and development work focuses on new generation aircraft engines, aircraft weight reduction (particularly through the materials used and lighter onboard equipment), the development of the use of electrical technologies to ensure propulsion, and aviation biofuels as an important complement to technological progress.

[0006] In this context, the invention more particularly relates to aspects related to the sealing of the air flow path. In fact, in the main flow path, the gap between the radial ends of the rotating blades and the casing may be a location where leakage or vortices may occur, resulting in a reduction in the efficiency of the turbine and thus an increase in the consumption required to output the same power.

[0007] To reduce these leakages, it is necessary to bring the blades closer to the casing while maintaining a safety margin. In fact, if contact occurs, both the blades and the casing will be damaged and the operational safety of the turbine will be compromised. These situations are still common due to vibrations, ingestion, centrifugal forces, expansion and especially rotor misalignment. Therefore, adding a layer of abradable material to the interface between casing and blades makes it possible to control the damage in case of contact, since the degradation is concentrated in the material of the seal, which is designed to break.

[0008] Documents EP 3 023 511 A1 and EP 3 444 443 A1 disclose compositions for abradable turbine seals. These compositions are intended to maximize the durability of abradable seals.

[0009] The inventors have stressed the fact that corrosion cannot be completely eliminated with these compositions, especially when the substrates on which these seals are deposited are made of corrosion-sensitive materials. In addition, the inventors have observed wear due to erosion caused by friction between the air flow and the abradable seals. This erosion occurs in particular under the high pressures and temperatures allowed by the new generation of turbines, which are more compact, more powerful and less expensive. Summary of the invention

[0010] Technical issues

[0011] The object of the present invention is to propose a composition for abradable seals which overcomes the above-mentioned disadvantages by providing, in particular, better corrosion resistance (regardless of the substrate on which the seal is deposited) and erosion resistance, in particular at high temperatures.

[0012] Technical Solution

[0013] The present invention relates to a composition for an abradable seal of a compressor of a turbine, the composition comprising a metal phase and a non-metal phase, the non-metal phase constituting 5% to 50% of the total mass of the composition, the metal phase comprising by mass: 45% to 80% of aluminum; 10% to 45% of nickel; 5% to 20% of cobalt or chromium; and 1% to 5% of copper, magnesium, manganese or zirconium.

[0014] "Abradable" or "abradable seal" refers to a material that is capable of breaking when in contact with a rotor element of a turbomachine.

[0015] The inventors have demonstrated that the presence of a combination of 5% to 20% cobalt or chromium on the one hand and trace amounts of copper, magnesium, manganese or zirconium on the other hand is beneficial for improving corrosion resistance, especially at high temperatures (above 150° C.).

[0016] The composition may be in the form of a powder, with the metal phase and the non-metal phase each forming different particles. Depending on the composition of the phases, a binder is added between the two phases. The two phases are then fully mixed to uniformly disperse the two phases.

[0017] According to an advantageous embodiment of the invention, the metallic phase contains 5% to 17% cobalt.

[0018] According to an advantageous embodiment of the invention, the metallic phase contains 15% of cobalt and 4% of zirconium.

[0019] According to an advantageous embodiment of the invention, the sum of the mass of cobalt or chromium and the mass of copper, magnesium, manganese or zirconium is between 10% and 22% of the mass of the metallic phase.

[0020] According to an advantageous embodiment of the invention, the non-metallic phase contains 30 to 35% by mass of one or more of the following elements: polyester, methyl methacrylate, hexagonal boron nitride, calcium fluoride, graphite, bentonite, talc or molybdenum disulfide.

[0021] According to an advantageous embodiment of the invention, nickel and cobalt, or nickel and chromium together, do not exceed 45% of the mass of the metallic phase. This prevents premature wear of the abradable material.

[0022] The invention also relates to a method for producing an abradable seal for an axial turbomachine, which method comprises depositing a composition according to one of the above-described embodiments on the inner surface of a ferrule or a compressor housing element by plasma spraying.

[0023] The invention also relates to a turbomachine comprising a low-pressure compressor having a row of rotor blades and an abradable seal surrounding the row of rotor blades, characterized in that the seal is formed by the above-described method.

[0024] In fact, the mass ratios of the different elements do not vary as a result of the deposition process, so that the seal obtained by the method of the invention is different from a seal obtained by implementing a process of another composition. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] [ Figure 1 ] shows a cross-sectional view of a compressor of a turbine. DETAILED DESCRIPTION

[0026] In the following description, the terms "inner" and "outer" refer to the positioning relative to the axis of rotation of the axial turbine. The axial direction corresponds to the direction along the axis of rotation of the turbine. The radial direction is perpendicular to the axis of rotation. Upstream and downstream refer to the main flow direction of the flow in the turbine.

[0027] Figure 1 The dimensions are not drawn to scale and, in particular, the thickness or radial dimensions are exaggerated for ease of reading.

[0028] Figure 1 A cross-sectional view of a compressor 4 of an axial turbomachine is shown.

[0029] Preferably, the compressor 4 corresponds to a low-pressure compressor. The turbomachine also comprises Figure 1Other components not shown in the drawing, such as a high-pressure compressor, a combustion chamber and one or more turbine stages. The one or more turbines drive the rotor 12 to rotate. The rotor supports a plurality of rows of rotor blades 24 associated with a plurality of rows of stator blades 26. Thus, the rotation of the rotor 12 about its axis of rotation 14 makes it possible to gradually compress the air flow to the inlet of the combustion chamber.

[0030] A fan 16 (partially shown) is coupled to the rotor 12 and generates an air flow that is split into a primary flow 18 and a secondary flow 20. The primary flow 18 and the secondary flow 20 are separated by a splitter nose 22.

[0031] The rotor blades 24 may extend radially from a rotor support, which may be a dovetail platform, an inner crown of a bladed drum, or any other type of composite rotor support.

[0032] The stator blades 26 extend substantially radially from the outer casings 28, 30. The stator blades 26 may be mounted and secured to the outer casings 28, 30 using a retaining shaft 32 and a platform 34. The stator blades 26 extend radially through the main flow 18 to an inner ferrule 40.

[0033] The turbine may be a multi-flow turbine. We will focus on one of these flows defined by the air flow path. Thus, the air flow path to which the invention relates may be a primary air flow path that compresses the air intended to enter the combustion chamber; a secondary air flow path driven by a ducted fan; or a tertiary air flow path originating from the primary flow path and rejoicing with the secondary flow of an unducted turbofan (CROR "Counter-Rotating Open Rotor" or USF "Unducted Single Fan").

[0034] A layer of abradable material or abradable seal 38 is deposited facing the radial end of rotor blade 24 .

[0035] Thus, the wall 30 serves as a support for the fixed platform 34 of the stator blades 26 and as a support for the abradable seal 38 to ensure a dynamic seal around the rotor blades 24. Dynamic sealing is understood as a restriction of the flow between the abradable seal and the rotating rotor blades during operation of the turbine. The radially inner surface of the abradable seal 38 is flush with the radially inner surface of the platform 34. The abradable seal 38 forms a uniform annular layer, such as a circular band, the thickness of which may be greater than 2.00 mm.

[0036] Although the present invention is advantageous for positioning an abradable seal in a compressor, the teachings of the present invention may also be applied to any rotating element, such as a baffle or a labyrinth seal. Thus, the inner surface of the ferrule 40 may also include an abradable material similar to or different in composition from the abradable seal 38. Given the heat resistance of the composition of the present invention, the composition of the present invention may also be implemented on a turbine.

[0037] The shell 28, in particular the wall 30 of the shell 28, can be made of a composite material with an organic matrix. The composite material can include a preform of epoxy resin and a stack of three-dimensionally woven carbon fiber plies. Alternatively, the shell can be made of metal, such as titanium or aluminum alloy.

[0038] The composition of the material forming the abradable seal 38 may include two mixed phases, namely a metallic phase and a non-metallic phase. The non-metallic phase may be a mineral phase and / or an organic phase. The abradable seal may be composite; and / or, the abradable seal may be composed of particles; and / or, the abradable seal may contain spaces filled with some components of the abradable seal. The composition may be in the form of a powder, with the metallic phase and the non-metallic phase each forming different particles. Alternatively, the non-metallic phase may form inclusions (nodules) in particles formed primarily of the metallic phase. The non-metallic phase may form a lubricant.

[0039] The non-metallic phase may account for 5% to 50% of the total weight of the composition, preferably 15% to 25%, more preferably 20%. The metallic phase may form the remaining weight, i.e., the metallic phase may account for 50 to 95%, preferably 75 to 85%, more preferably 80% of the total weight of the composition.

[0040] The metallic phase may comprise a majority of the volume of the abradable sealing layer and, thus, the metallic phase may form a matrix that receives the secondary phase.

[0041] Alternatively, the abradable sealing layer may be formed from metal powder particles whose inter-particle spaces are filled with a second phase.

[0042] The metal phase mainly contains aluminum. That is, among the metals that can wear the seal, the metal with the largest mass is aluminum. The dominance of aluminum is conducive to a good compromise between seal quality, corrosion resistance and mechanical strength.

[0043] The metal phase of the abradable coating 38 also contains nickel in a lower mass proportion than aluminum. The mass proportions of nickel and aluminum in the metal phase are: 10% to 45%, preferably 25% to 30% nickel; and 45% to 80%, preferably 70% to 75% aluminum.

[0044] Furthermore, the metallic phase contains 5% to 20% chromium, or 5% to 20% cobalt, or a sum of 5% to 20% by mass of chromium and cobalt. The range may preferably be limited to 10% to 17%.

[0045] Furthermore, the metallic phase contains between 1% and 5% of copper, magnesium, manganese and / or zirconium. When two of these elements are present, the sum of the masses of these two elements falls within this interval. In a variant, the proportions of these elements may be present in trace amounts.

[0046] Preferably, chromium and / or cobalt on the one hand and copper, magnesium, manganese and / or zirconium on the other hand together make up 10% to 22%, preferably 16% to 18%, of the metallic phase.

[0047] The non-metallic phase may comprise one or more organic materials and / or one or more mineral materials.

[0048] For example, the non-metallic phase may contain 15 to 35%, preferably 30 to 35%, by mass, of one or more of the following elements: polyester, methyl methacrylate, hexagonal boron nitride, calcium fluoride, graphite, bentonite, talc or molybdenum disulfide.

[0049] The non-metallic phase may also contain a resin (ketone or phenol).

[0050] The non-metal phase may also contain a binder to bond the metal phase to the non-metal.

[0051] The composition can be applied to the housing by plasma spraying. This thermal technique is known in particular from document EP 1 010 861 A2. The powder constituting the non-metallic phase can be introduced into the plasma jet downstream of the powder constituting the metallic phase. Other techniques are also conceivable: the composition can be applied to the support by sintering (which may require prolonged heating).

[0052] During deposition of the abradable layer, some particles may melt and then solidify. The initial mass ratio of the final layer remains unchanged, making it possible to distinguish the final layer from layers obtained with a different composition.

Claims

1. A composition for an abradable seal (38) for a compressor (4) of a turbomachine, the composition comprising a metallic phase and a non-metallic phase, the non-metallic phase constituting 5% to 50% of the total mass of the composition, the composition being characterized in that the metallic phase comprises, by mass: -45% to 80% aluminum; -10% to 45% nickel; -5% to 20% cobalt or chromium; and -1% to 5% copper, magnesium, manganese or zirconium.

2. The composition according to claim 1, It is characterized in that The metallic phase contains 5% to 17% cobalt.

3. The composition according to claim 1 or 2, It is characterized in that The metallic phase contains 15% cobalt and 4% zirconium.

4. A composition according to any one of claims 1 to 3, It is characterized in that The sum of the mass of cobalt or chromium and the mass of copper, magnesium, manganese or zirconium is 10% to 22% of the mass of the metal phase.

5. The composition according to any one of claims 1 to 4, It is characterized in that The non-metallic phase contains 30% to 35% by mass of one or more of the following elements: polyester, methyl methacrylate, hexagonal boron nitride, calcium fluoride, graphite, bentonite, talc or molybdenum disulfide.

6. The composition according to any one of claims 1 to 5, It is characterized in that Nickel and cobalt, or nickel and chromium together, do not exceed 45% by mass of the metallic phase.

7. A method for producing an abradable seal (38) for a compressor (4) of a turbomachine, said method comprising depositing a composition according to any one of the preceding claims on the inner surface of a ferrule (30) or a casing element (28) of the compressor (4) by plasma spraying.

8. A turbomachine comprising a low-pressure compressor (4) having a row of rotor blades (24) and an abradable seal (38) surrounding the row of rotor blades (24), It is characterized in that The seal is formed by the method of claim 7.

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