Composition for an abradable seal for a turbomachine

Abstract

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

Description

COMPOSITION FOR ABRADABLE TURBOMACHINE SEAL

[0001] The invention relates to the field of sealing turbomachines using a two-phase abradable seal. The invention also proposes a method for producing an abradable seal and a turbomachine equipped with this seal. Prior art

[0002] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various carbon emission restrictions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new aircraft types and those already in operation, requiring the implementation of technological solutions to ensure their compliance with current regulations. Civil aviation has been mobilizing for several years now to contribute to the fight against climate change.

[0003] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical 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] Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes and minimizing greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0005] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, particularly through the materials used and lighter on-board equipment, the development of the use of electrical technologies to ensure propulsion, and, as an essential complement to technological progress, aeronautical biofuels.

[0006] In this context, the invention relates more particularly to the aspects related to the sealing of the air stream. Indeed, within the primary stream, the clearance between the radial ends of the rotating blades and the casing can be the location of leaks or vortices, leading to a reduction in the efficiency of the turbomachine, and consequently higher consumption for equal power delivered.

[0007] To reduce these leaks, it is imperative to bring the blades closer to the casing while maintaining a safety margin. Indeed, in the event of contact, both the blades and the casing can be damaged, and jeopardize the operational safety of the turbomachine. These cases remain commonplace due to vibrations, ingestion, centrifugal force, expansion, and rotor misalignments in particular. Therefore, adding a layer of abradable material to the interface between the casing and the blades makes it possible to control damage in the event of contact since the degradation is concentrated in the material of the seal which is intended to crumble.

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

[0009] The inventors have highlighted the fact that corrosion is not completely eliminated with these compositions, particularly when the substrate on which these seals are deposited is made of a material sensitive to corrosion. Also, the inventors have observed wear due to erosion due to the air flow rubbing against the abradable seal. This erosion appears especially under the high pressure and temperature conditions allowed by the new generations of turbomachines, which are more compact, more powerful and more frugal.

[0010] The invention aims to propose a composition for an abradable seal which overcomes the drawbacks mentioned above and in particular which allows better resistance to corrosion (independently of the substrate on which the seal is deposited) and to erosion, and in particular at high temperature.

[0011] The invention relates to a composition for an abradable turbomachine compressor seal, the composition comprising a metallic phase and a non-metallic phase, the latter constituting 5 to 50% of the total mass of the composition, the metallic 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.

[0012] By "abradable" or "abradable seal" we mean a material capable of crumbling on contact with a turbomachine rotor element.

[0013] The presence, in combination, of cobalt or chromium in a rate between 5 and 20% on the one hand, and traces of copper, magnesium, manganese or zirconium on the other hand, has been demonstrated by the inventors as beneficial in improving resistance to erosion and in particular to high temperatures (above 150°C).

[0014] The composition can be in the form of a powder, with the metallic phase and the non-metallic phase each forming separate grains. Depending on the composition of the phase, the addition of a binding agent between the two phases is used. The two phases are then thoroughly mixed to be uniformly dispersed.

[0015] According to an advantageous embodiment of the invention, the metallic phase comprises 5 to 17% cobalt.

[0016] According to an advantageous embodiment of the invention, the metallic phase comprises 15% cobalt and 4% zirconium.

[0017] According to an advantageous embodiment of the invention, the mass of cobalt or chromium, combined with the mass of copper, magnesium, manganese or zirconium, is between 10% and 22% of the mass of the metallic phase.

[0018] According to an advantageous embodiment of the invention, the non-metallic phase comprises, by mass, between 30% and 35% of one or more of the following elements: polyester, methyl methacrylate, hexagonal boron nitride, calcium fluoride, graphite, bentonite, talc, or molybdenum disulfide.

[0019] 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.

[0020] The invention also relates to a method for producing an abradable axial turbomachine seal, the method comprising the deposition of a composition according to one of the above embodiments by plasma spraying on an internal surface of a shell or a compressor casing element.

[0021] The invention also relates to a turbomachine comprising a low-pressure compressor with a row of rotor blades and an abradable seal surrounding the row of rotor blades, remarkable in that the seal is formed by the method set out above.

[0022] Indeed, the mass proportions of the different elements are not altered by the deposition process and a joint obtained by the process of the invention is therefore quite distinct from a joint obtained by a process using another composition.

[0023] illustrates a sectional view of a turbomachine compressor. Detailed description

[0024] In the following description, the terms "internal" and "external" refer to a positioning relative to the axis of rotation of an axial turbomachine. The axial direction corresponds to the direction along the axis of rotation of the turbomachine. The radial direction is perpendicular to the axis of rotation. Upstream and downstream refer to the main flow direction of the flow in the turbomachine.

[0025] Lane dimensions are not to scale and in particular thicknesses or radial dimensions are exaggerated to facilitate reading of the figures.

[0026] It represents a sectional view of a compressor 4 of an axial turbomachine.

[0027] Preferably, the compressor 4 corresponds to a low-pressure compressor. The turbomachine further comprises other components not shown in the, such as a high-pressure compressor, a combustion chamber and one or more levels of turbines. The turbine(s) drive a rotating rotor 12. The rotor supports several rows of rotor blades 24 associated with rows of stator blades 26. The rotation of the rotor 12 about its axis of rotation 14 thus makes it possible to compress an air flow progressively up to the inlet of the combustion chamber.

[0028] A blower 16 (partially shown) is coupled to the rotor 12 and generates an airflow that splits into a primary flow 18 and a secondary flow 20. The primary 18 and secondary 20 flows are separated by a separation nozzle 22.

[0029] The rotor blades 24 may extend radially from a rotor support which may be a dovetail platform, a single-piece bladed drum inner ring, or any other type of support of a composite rotor.

[0030] The stator vanes 26 extend essentially radially from an outer casing 28, 30. They can be fixed and immobilized there using fixing pins 32 and platforms 34. They pass radially through the primary flow 18 to an inner shell 40.

[0031] The turbomachine may be a multi-flow turbomachine. We will focus on one of these flows, delimited by an air stream. Thus, the air stream concerned by the invention may be a primary air stream, compressing the air intended to enter the combustion chamber; a secondary air stream, propelled by a ducted fan; or a tertiary stream originating from the primary stream and joining a secondary flow of an unducted turbojet (CROR “Counter-Rotating Open Rotor” or USF “Unducted Single Fan”).

[0032] A layer of abradable material or abradable seal 38 is deposited opposite the radial end of the rotor blades 24.

[0033] The wall 30 thus serves as a fixing support for the fixing platforms 34 of the stator blades 26 and as a support for the abradable seals 38 ensuring dynamic seals around the rotor blades 24. A dynamic seal is understood as a limitation of the flow between the abradable and a rotor blade rotating during operation of the turbomachine. The radially internal surface of the abradable seal 38 is flush with the radially internal surface of the platforms 34. The abradable seals 38 form homogeneous annular layers, such as circular ribbons whose thicknesses can be greater than 2.00 mm.

[0034] If the invention favors the positioning of an abradable seal in the compressor, the teaching of the invention can also be adapted to any rotating element, for example sealing baffles or labyrinths. Thus, the internal surface of the shells 40 can also contain an abradable material of composition similar, or not, to the abradable 38. The composition of the invention can also be implemented at the turbine level, given its heat resistance.

[0035] The casing 28, and in particular its wall 30, may be made of an organic matrix composite material. The composite material may comprise an epoxy resin and a preform with a stack of three-dimensionally woven carbon fiber plies. Alternatively, the casing may be made of metal, such as a titanium or aluminum alloy.

[0036] The composition of the material forming the abradable layer 38 may comprise two mixed phases, namely a metallic phase and a non-metallic phase. The non-metallic phase may be mineral and / or organic. The abradable may be composite; and / or granular; and / or may contain spaces filled by some of its constituents. The composition may be in the form of a powder, the metallic phase and the non-metallic phase each forming distinct grains. Alternatively, the non-metallic phase may form inclusions (nodules) in grains predominantly formed of the metallic phase. The non-metallic phase may form a lubricant.

[0037] The non-metallic phase may represent 5 to 50%, preferably 15% to 25%, and more preferably 20%, of the total mass of the composition. The metallic phase may form the remaining weight, namely 50 to 95% of the total weight, preferably 75 to 85%, and more preferably 80%, of the total mass of the composition.

[0038] The metallic phase can represent the majority of the volume of the abradable layer, thus, the metallic phase can form a matrix receiving the second phase.

[0039] Optionally, the abradable layer can be formed from grains of metal powders whose inter-grain spaces are filled by the second phase.

[0040] The metallic phase consists mainly of aluminum. That is, among the metals in the abradable, the one with the highest mass is aluminum. The preponderance of aluminum promotes a good compromise between joint mass, corrosion resistance, and mechanical strength.

[0041] The metallic phase of the abradable coating 38 also comprises nickel, in a lower mass proportion than that of aluminum. The mass proportions of nickel and aluminum in the metallic phase are: 10% to 45%, preferably 25 to 30% of nickel; and 45% to 80%, preferably 70 to 75% of aluminum.

[0042] In addition, the metallic phase comprises between 5% and 20% chromium, or between 5% and 20% cobalt, or between 5% and 20% of the combined mass of chromium and cobalt. This range may preferably be restricted to 10 to 17%.

[0043] Additionally, the metallic phase comprises between 1 and 5% copper, magnesium, manganese and / or zirconium. When two of these elements are present, their combined mass falls within this range. Alternatively, the level of these elements may be present in trace amounts.

[0044] Preferably, chromium and / or cobalt, on the one hand, and copper, magnesium, manganese and / or zirconium, on the other hand, together constitute between 10 and 22% of the metallic phase, preferably between 16 and 18%.

[0045] The non-metallic phase may comprise one or more organic materials, and / or one or more mineral materials.

[0046] For example, the non-metallic phase may contain, by mass, 15% to 35%, and preferably 30% to 35% of one or more of the following elements: polyester, methyl methacrylate, hexagonal boron nitride, calcium fluoride, graphite, bentonite, talc, or molybdenum disulfide.

[0047] The non-metallic phase may also contain a resin (ketone or phenol).

[0048] The non-metallic phase may also include a binding agent to bind the metallic phase to the non-metallic phase.

[0049] The composition described above can be applied to the casing by plasma spraying. Such a thermal technique is known in particular in 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 possible: the composition can be applied to the support by sintering, possibly with prolonged heating.

[0050] When the abradable layer is deposited, some grains may melt and then solidify. Since the initial mass ratios remain the same in the final layer, it is possible to distinguish it from a layer obtained from a different composition.

Claims

Composition for an abradable seal (38) of a turbomachine compressor (4), the composition comprising a metallic phase and a non-metallic phase, the latter 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% of aluminum; - 10% to 45% of nickel; - 5% to 20% of cobalt or chromium; and - 1 to 5% of copper, magnesium, manganese or zirconium. Composition according to claim 1, characterized in that the metallic phase comprises 5 to 17% cobalt. Composition according to claim 1 or 2, characterized in that the metallic phase comprises 15% cobalt and 4% zirconium. Composition according to one of claims 1 to 3, characterized in that the mass of cobalt or chromium, combined with the mass of copper, magnesium, manganese or zirconium, is between 10% and 22% of the mass of the metallic phase. Composition according to one of claims 1 to 4, characterized in that the non-metallic phase comprises, by mass, between 30% and 35% of one or more of the following elements: polyester, methyl methacrylate, hexagonal boron nitride, calcium fluoride, graphite, bentonite, talc, or molybdenum disulfide. Composition according to one of claims 1 to 5, characterized in that the nickel and cobalt, or the nickel and chromium, together do not exceed 45% of the mass of the metallic phase. Method for producing an abradable seal (38) for a turbomachine compressor (4), the method comprising the deposition of a composition according to one of the preceding claims by plasma projection on an internal surface of a shell (30) or of a casing element (28) of the compressor (4). A turbomachine comprising a low-pressure compressor (4) with a row of rotor blades (24) and an abradable seal (38) surrounding the row of rotor blades (24), characterized in that the seal is formed by the method of claim 7.

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