Multi-layer material for aeronautical parts

Abstract

The present invention relates to a multi-layer material (1) for aeronautical parts comprising a multi-perforated support layer (2), a barrier layer (3), and a porous layer (4) arranged between the support layer and the barrier layer; in which the barrier layer is formed of individual metal slabs (31) covering the porous layer in the manner of paving. Fig. 1

Description

Title of the invention: Multilayer material for aeronautical parts Technical field

[0001] The present invention relates to the technical field of materials for aeronautical parts. These materials allow at least one of thermal control and combustion of an energy system; for example for the manufacture of combustion chambers in aeronautical propulsion. State of the art

[0002] Currently, the walls of combustion chambers are made of metal alloy sheets. These metal alloy sheets are used at high temperature, welded, welded and then micro-perforated. The sheets act as both a mechanical element of pseudo-watertight structure to withstand the pressure difference on either side of them and to absorb the thermomechanical stresses and vibrations caused by the heat of the flame. The micro-orifices allow air to pass through these walls to both fuel combustion and cool the wall.

[0003] Despite this, the temperatures to which these walls are subjected remain very high and weaken them. In order to strengthen these walls, they are generally covered, on the flame side, with a ceramic coating forming a thermal barrier to limit the heating of the wall so that it retains its ability to withstand stresses. Indeed, the ceramic material has low conductivity and a low radiation absorption coefficient. This thermal barrier then protects the underlying sheet metal from the very high temperatures imposed by the flame. In this case too, the micro-orifices are made after the thermal barrier has been deposited so as not to be plugged by the latter. Unfortunately, this coating tends to peel off, leaving the sheet metal unprotected.

[0004] Improving combustion chambers also involves research into innovative and specific geometries depending on the areas of the chambers, in particular to obtain combustion chambers capable of withstanding stresses for longer, and to optimize combustion by improving the flow of air from the compressor stages.

[0005] Laser beam melting (LBM) processes offer greater freedom in the design of these geometries; the material and the holes in the wall can be manufactured simultaneously.

[0006] However, the use of these methods for the manufacture of single-layer metal walls of combustion chambers has a size limitation. Indeed, when the ceramic thermal barrier is removed, the orifices formed by LBM are covered by it, which makes these walls lose their interest.

[0007] Alternatively, these orifices may not be made during additive manufacturing but after the ceramic thermal barrier has been removed by laser drilling or electric discharge machining (known by the acronym EDM for "Electric Discharge Machining" in English). However, these solutions prove to be expensive, making them economically unviable.

[0008] Thus, there is a need for a solution that improves the situation. Summary of the invention

[0009] The solution identified by the present authors was not to find a new manufacturing process, but to modify the very geometry of the wall. The present invention therefore proposes a multilayer material for aeronautical parts comprising: - a multi-openwork support layer; - a barrier layer; and - a porous layer disposed between the support layer and the barrier layer; wherein the barrier layer is formed of individual metal slabs covering the porous layer in the manner of paving.

[0010] The support layer allows both the mechanical strength of the material and the distribution of air from one side to the other side. In this, the multi-perforated support layer plays the same role as the multi-perforated sheet of the state of the art.

[0011] The role of thermal barrier is played by the combination of the barrier layer and the porous layer. It is a geometric solution (combination of a porous layer and a layer of paving slabs) rather than a material one like the ceramic layer of the state of the art. The barrier layer is formed of slabs, that is to say of small thickness, which reduces its mass. This barrier layer is further fragmented by a plurality of slabs whose dimensions, spacing and pattern can be adapted locally. Given that this barrier layer does not support the structure of the multilayer material (the support layer playing this role), it can be made of metal; this material alone in conventional does not allow very severe thermal functions to be achieved because it weakens without melting at these temperatures whereas it must support the structure.

[0012] The porous layer is a semi-dense layer and is both permeable and relatively flexible. It serves to hold the slabs. Thus, this layer is not very thermally conductive and forms the link between the slabs on one side and the support layer on the other. the other side while limiting heat transfer to the support layer.

[0013] The multi-layer material can typically be produced by additive manufacturing and in particular by LBM. Additive manufacturing offers flexibility of execution making the formation of slabs possible whereas such a structure is not possible for conventional solutions. In addition, the manufacture of conventional solutions includes a perforation step, a step that is sometimes complicated to implement due to the sometimes very complex geometry of the sheet metal. The use of additive manufacturing makes it possible to design each hole more specifically and therefore to optimize and readjust the design more finely than before in order to obtain a multi-perforated support layer. Regarding complex parts, additive manufacturing also presents an advantage in terms of costs and lead time (reduction in development time and cost, reduction in production cost because only one transformation operation is necessary).

[0014] Thus, this multi-layer material presents an improved alternative to current combustion chamber walls made of metal alloy sheets.

[0015] Other optional features are as follows.

[0016] Each of the metal slabs may have a surface area of less than 100 mm2.

[0017] At least a portion of the slabs may have a regular polygonal shape. At least a portion of the slabs may have the shape of a triangle, a square, or a hexagon.

[0018] The porous layer may have a lattice-type structure.

[0019] The support layer may have holes of 0.2 to 3 mm in diameter.

[0020] The sum of the holes in the support layer can be from 1 to 30%.

[0021] The support layer may be made of a metal alloy or ceramic.

[0022] The multilayer material may comprise a ceramic coating layer on the barrier layer.

[0023] The multilayer material may have a convex face formed by the support layer, and a concave face formed by the barrier layer, or where appropriate the ceramic coating layer.

[0024] Another aspect of the invention is an aeronautical part made with the multilayer material described above. Figures

[0025] Other characteristics, effects and advantages will appear on reading the detailed description which follows with reference to the drawings given purely for illustrative purposes, among which:

[0026] [Fig.l] is a schematic sectional view of the multilayer material according to the invention;

[0027] [Fig.2] is a schematic sectional view of the multilayer material according to the invention having a convex face and a concave face;

[0028] [Fig.3] is a schematic view of an example of multilayer material observed from the support layer side;

[0029] [Fig.4] is a schematic view of an example of multilayer material observed from the barrier layer side, the latter having hexagonal slabs;

[0030] [Fig.5] is a schematic view of another example of a barrier layer with square slabs;

[0031] [Fig.6] is a schematic sectional view of the multilayer material according to the invention with a ceramic coating layer;

[0032] [Fig.7] is a schematic sectional view of the multilayer material according to the invention with a ceramic coating layer and having a convex face and a concave face;

[0033] [Fig.8] is a schematic view of a combustion chamber using the multi-layer material;

[0034] [Fig.9] shows examples of patterns for a lattice-like structure of the porous layer;

[0035] [Fig. 10] illustrates an example of a lattice-type structure obtained by repeating a pattern; and

[0036] [Fig. 11] shows an example of a porous layer comprising pores. Detailed description

[0037] A multilayer material for aeronautical parts according to the present invention is described below with reference to Figures 1 to 7.

[0038] This multilayer material 1 comprises a support layer 2, a barrier layer 3, and a porous layer 4 disposed between the support layer 2 and the barrier layer 3.

[0039] The support layer 2 is the layer giving the multilayer material its mechanical strength. The support layer 2 may be a layer of metal or ceramic alloy, for example based on nickel, cobalt, alumina, preferably Hastelloy X or Inconel718. The support layer 2 may have a thickness of 0.5 mm to 2 mm, preferably 0.8 mm to 1.5 mm.

[0040] The support layer 2 is multi-perforated and has a plurality of orifices 21. These orifices 21 may be regularly distributed over one or more parts of the support layer 2. These orifices 21 may also be regularly distributed over the entire support layer 2. A regular distribution means that the orifices 21 form a pattern, such as a triangular pattern (each orifice 21 has six nearest neighbors) or a square pattern (each orifice 21 has four nearest neighbors). The center-to-center distance between two nearest neighbor orifices 21 may be 0.5 to 15 mm, preferably 3 to 7 mm. The orifices 21 generally have a disc shape, but taking into account the use of additive manufacturing, any shape may be considered, such as such as square, octagonal, etc. The orifices 21 may have a diameter of 0.2 to 3 mm, preferably 0.5 to 1.0 mm. In the case of non-circular orifices 21, the diameter is understood to be the diameter of a circle having the same area as the shape considered. The occupancy rate of the orifices 21, defined as the ratio of the total surface area of the orifices 21 to the total surface area of the support layer 2, may be 1 to 30%, preferably 5 to 15%. The support layer 2 may have two zones, the distribution of the orifices 21 of the first zone being different from the distribution of the orifices 21 of the second zone in terms of at least one of the pattern, the center-to-center distance, the shape, the diameter and the occupancy rate.

[0041] The barrier layer 3 is a layer resistant to the high temperatures imposed by flames, in particular aeronautical combustion chambers. Thus, the barrier layer 3 resists flame temperatures of up to at least 2300°C.

[0042] The barrier layer 3 is formed of individual metal slabs 31 arranged in the manner of a paving, for example with an interstitial clearance 32 of 0.1 mm to 1 mm. The term paving comes from the mathematical expression “plane paving” designating a set of portions of a plane, for example polygons, the union of which is the entire plane without overlap. In the case of the present invention, the term paving refers to a set of portions of a plane, for example polygons, the union of which (with the interstitial clearances, if applicable) is the entire plane without overlap. Each of the slabs 31 forms a portion of the plane. When it is present, the interstitial clearance 32 is notably chosen so as not to be calibrating for the compressor air flow rate, that is to say that the sum of the area of the interstitial clearances 32 is greater than the sum of the area of the orifices 21 by at least one order of magnitude, or even at least two orders of magnitude.

[0043] The interstitial clearance 32 makes it possible to guarantee the absence of contact between a slab 31 and the adjacent slabs 31 at the end of manufacturing and especially during the service life of the multilayer material 1 facing the flame so as not to generate high thermomechanical stresses and not to transmit these stresses to the support layer 2.

[0044] Each of the slabs 31 may have a surface area of less than 100 mm2, for example less than 90 mm2, 80 mm2 or 70 mm2.

[0045] Thus, the slabs are not very massive, which allows them to cool quickly, in particular thanks to the arrival of air passing through (see example of paths 9) the material first through the support layer 2, then through the porous layer 4. The slabs 31 may have a thickness greater than 0.1 mm, preferably greater than 0.4 mm.

[0046] At least a portion of the slabs 31 may have a regular polygonal shape, for example the shape of a triangle, a square, a hexagon or an octagon. Preferred shapes are shapes that avoid the presence of spikes. Thus, of the four shapes exemplified here, the hexagonal shape will be preferred. The regular hexagonal shape has angles of 120° and therefore limits the spikes and furthermore allows the plane to be tiling using only hexagonal tiles. Consequently, this shape also limits the maximum temperature peaks while restricting the clearances between the tiles 31 in order to prevent the flame from licking and therefore overheating the support layer 2 in these areas.

[0047] The slabs 31 can be made of the same materials mentioned above for the support layer 2 and preferably are made of the same material as the support layer 2.

[0048] By porous layer 4 is meant herein a solid material with fine geometry, also called a matrix, containing small pores or cavities and capable of containing one or more fluids (liquid or gas). Thus, the porous layer 4 is a semi-dense layer that is both permeable and relatively flexible and serves to hold the slabs 31 in position. It is also not very electrically conductive and forms the mechanical link between the support layer 2 and the barrier layer 3. Its flexibility makes it possible not to induce too many mechanical stresses. Finally, its density limits the transfer of heat from the barrier layer 3 to the support layer 2.

[0049] Being porous, the porous layer 4 has a large cooling exchange surface. For example, when the material is used to manufacture a combustion chamber in aeronautical propulsion, this exchange surface is bathed in the air flow coming from the compressor, which allows the slabs 31 to be cooled by the air from the compressor indirectly through the porous layer 4.

[0050] The porous layer 4 may have a void rate of 80 to 95%, making it possible to maintain the slabs 31, avoid inducing too many mechanical constraints and ensure good heat transfer.

[0051] The porous layer 4 may have a porosity with pores of 0.2 to 1.0 mm.

[0052] The porous layer 4 may have a lattice-type structure (“lattice” or “ A lattice truss can be described as a structure composed of an assembly of bars forming polygons, including triangles and quadrilaterals as exemplified by [Fig.9]. These bars are oriented in the three spatial directions to form a three-dimensional structure. Advantageously, the lattice structure can be formed by the repetition of a unitary pattern (see example of repetition in [Fig. 10]).

[0053] Each of these bars acts as a cooling fin. Thus, the porous layer 4 can be seen as composed of a multitude of fins allowing the cooling of the slabs 31.

[0054] The length of these bars can be from 0.1 to 7 mm, preferably from 2 to 4 mm. The cross-section (area) of these bars can be from 0.1 mm2 to 1 mm2, preferably from 0.5 mm2 to 0.7 mm2.

[0055] Alternatively, the porous layer 4 may have a structure with pores, in particular open ones, more conventional as illustrated by [Fig. 11].

[0056] The lattice-like structure or pores can be obtained by additive manufacturing.

[0057] The thickness of the porous layer 4 may be 0.1 to 5 mm, preferably 2 to 3.5 mm.

[0058] The porous layer 4 can be made of the same materials mentioned above for the support layer 2 and preferably is made of the same material as the support layer 2.

[0059] The multilayer material 1 may further comprise a ceramic coating layer 5 on the barrier layer 3 (see [Fig.6] and [Fig.7]). Unlike the materials generally used for the manufacture of combustion chambers, there is no disadvantage in reinforcing the thermal barrier properties of the barrier layer 3 with a ceramic coating layer 5. Indeed, the barrier layer 3 protects the orifices 21 of the support layer 2 against being covered by the ceramic coating 5. Furthermore, although a partial blocking of the interstitial clearance between the slabs 31 is possible, it is not harmful, in particular if the total surface area occupied by the interstitial clearance between the slabs 31 is sized so as not to be calibrating for the compressor air flow rate.

[0060] The ceramic coating can be made of alumina or zirconia.

[0061] The ceramic coating 5 may have a thickness of 0.1 mm to 0.5 mm.

[0062] The multilayer material 1 may have a convex face 11 formed by the layer support 2, and a concave face 12 formed by the barrier layer 3, or where appropriate the ceramic coating layer 5 (see [Fig.2] and [Fig.7]). The convex face 11 is oriented towards the outside of the combustion chamber while the concave face 12 is oriented towards the inside thereof.

[0063] When it is indicated that the multilayer material 1 comprises the three layers, this does not necessarily mean that the three, or even four, layers 2, 3, 4, 5 are present over the entire surface of the multilayer material 1. Indeed, one or more zones may be produced only with the support layer 1, in particular if these zones are intended not to be exposed or only slightly exposed to a flame. Of course, the entire surface of the multilayer material 1 may comprise the three, or even four, layers 2, 3, 4, 5.

[0064] On this complex part, there is also an interest in costs and time (lower development time and cost, lower cost of obtaining because only one transformation operation is necessary). In addition, the porous layer 4 is not easy to manufacture other than by LBM and would prove expensive otherwise.

[0065] [Fig. 8] schematically represents an example of an aeronautical part 10 made with the multilayer material 1 described above. In this figure, only a portion of this aeronautical part 10 is shown. This part has an axis of revolution 10A and a casing 101 defining a combustion chamber 102. Seen from the combustion chamber 102, the casing 101 is concave. The casing 101 is made from the multilayer material 1 described above. Thus, the air from the compressor can pass through the casing 101 (example of path 9) to feed the flame F inside the combustion chamber 102.

[0066] However, the use of such a multilayer material as described here is not limited to the aeronautical part. Indeed, the multilayer material can be used for the manufacture of structural parts requiring in particular protection against hot flows.

Claims

Claims

1. Multilayer material (1) for aeronautical parts comprising: - a multi-perforated support layer (2); - a barrier layer (3); and - a porous layer (4) arranged between the support layer and the barrier layer; wherein the barrier layer is formed of individual metal slabs (31) covering the porous layer in the manner of paving with an interstitial clearance (32) of 0.1 mm to 1 mm.

2. A multi-layer material according to claim 1, wherein each of the metal slabs has a surface area of less than 100 mm2.

3. A multi-layer material according to claim 1 or claim 2, wherein at least a portion of the slabs has a regular polygonal shape.

4. A multi-layer material according to claim 3, wherein at least a portion of the slabs has the shape of a triangle, a square or a hexagon.

5. Multilayer material according to one of claims 1 to 4, wherein the porous layer has a lattice-type structure.

6. Multilayer material according to one of claims 1 to 5, in which the support layer has orifices (21) of 0.2 to 3 mm in diameter.

7. Multilayer material according to one of claims 1 to 6, in which the occupancy rate of the orifices, defined as the ratio of the total surface area of the orifices to the total surface area of the support layer, is 1 to 30%.

8. Multilayer material according to one of claims 1 to 7 in which the support layer is made of a metal or ceramic alloy.

9. Multilayer material according to one of claims 1 to 8, comprising a ceramic coating layer (5) on the barrier layer.

10. Multilayer material according to one of claims 1 to 9, having a convex face (11) formed by the support layer, and a concave face (12) formed by the barrier layer, or where appropriate the ceramic coating layer.

11. Aeronautical part made with the multilayer material according to one of claims 1 to 10.

Images