Additive manufacturing processes for producing structures

Abstract

The present invention relates to a method for manufacturing a structure by means of an additive manufacturing technique implementing chemical vapor deposition assisted by focused energy radiation, the method comprising forming a reinforcement comprising a plurality of interconnected ceramic or carbon reinforcement elements which together define an interstitial volume having a tortuous shape along said deposition axis.

Description

Technical Field

[0001] The present invention relates to the manufacture of reinforcements, in particular for components manufactured from ceramic matrix composite materials (CMC materials) by additive manufacturing techniques, and more particularly by chemical vapor deposition assisted by focused energy radiation. Background Art

[0002] Components made of CMC materials are known to have good mechanical properties that allow them to be used in structural elements, as well as the ability to maintain these properties at high temperatures. CMC components include fiber reinforcements made of refractory fibers (usually carbon or ceramic), which are densified by a ceramic matrix made, for example, of silicon carbide (SiC). Currently, ceramic matrix composite technology is essentially based on the use of woven fiber reinforcements. In addition to the high cost of refractory fibers, the weaving operation is also expensive and there may be limitations in the geometry of the components, particularly for components with small dimensions and complex geometries, due to the insufficient pitch of the woven fabric.

[0003] Additive manufacturing techniques are also known, which allow the manufacture of components of metal or polymer materials, but these techniques currently do not give completely satisfactory results for the deposition of refractory materials such as ceramics.

[0004] It would therefore be desirable to have a method that allows for the fabrication of structures having complex geometries and that is suitable for the deposition of a variety of refractory materials. Summary of the Invention

[0005] The present invention relates to a method for manufacturing a structure by additive manufacturing, the method comprising at least:

[0006] - A reinforcement is formed by chemical vapor deposition assisted by focused energy radiation, the reinforcement being deposited along a deposition axis and comprising a plurality of interconnected reinforcing elements made of ceramic or carbon defining a gap volume between them, the gap volume having a tortuous shape along the deposition axis.

[0007] The present invention proposes a method for additive manufacturing in which a structure is gradually built up and comprises at least one reinforcement and possible matrix and interface, which are formed as the reinforcement is formed, as described in detail below. The reinforcement and the matrix and interface (when present) are each formed by chemical vapor deposition assisted by focused energy radiation. The proposed additive manufacturing technology implements chemical vapor deposition on the one hand, wherein, under the action of local and point heating generated by focused energy radiation, there is a conversion of one or more precursors, which allows the deposition of a variety of materials according to the selection of precursors. On the other hand, local heating of this (these) precursors is carried out by horizontal focused energy radiation only in the area where the material is desired to be deposited, which allows access to the complex geometry of the reinforcement and, in particular, the gap volume between the reinforcing elements. Thus, a reinforcement with a complex shape is obtained, which has a gap volume, which has a tortuous shape at least along the deposition axis, that is, a serpentine and non-linear shape when moving along this axis. The complex shape of the reinforcement allows the replacement of woven fabrics and leads to optimized reinforcement properties. The method according to the invention offers a great diversity of accessible forms without carrying out a fiber braiding operation to manufacture the reinforcement and by overcoming the limitations associated with this technology.

[0008] In one exemplary embodiment, the reinforcement is a 4D reinforcement. However, the present invention is not limited with respect to the geometry of the reinforcement.

[0009] According to a variant, it is possible to provide the reinforcement with another shape, such as a honeycomb shape, for example, the shape of the reinforcement being adapted to the desired application.

[0010] In one exemplary embodiment, the method comprises alternating between deposition of layers of the reinforcement and deposition of a matrix, the matrix being present in the interstitial volumes of the obtained reinforcement, by chemical vapor deposition assisted by focused energy radiation.

[0011] In this case, the matrix is ​​deposited when the reinforcement is formed. Thus, a component made of composite material is directly obtained, which has a matrix that densifies the interstitial volumes between the reinforcing elements.

[0012] In one exemplary embodiment, the method includes at least:

[0013] - depositing the first layer of reinforcement,

[0014] - depositing the matrix in the interstitial volumes of the first layer of reinforcement to obtain a dense first layer of reinforcement, and

[0015] - Depositing a second layer of reinforcement on the first layer of dense reinforcement.

[0016] In this case, the matrix is ​​deposited in the interstitial volume of the previously deposited layers of reinforcement. However, it would not depart from the scope of the invention to the contrary in which the matrix is ​​deposited first and the reinforcement layers are deposited around the previously deposited matrix.

[0017] In particular, the method may further comprise forming an interface on the reinforcing elements of the first layer of the reinforcement before depositing the matrix, the interface being able to be formed by chemical vapor deposition assisted by focused energy radiation.

[0018] In this case, when the reinforcement and the matrix are formed, the formation of the interface is also performed.

[0019] In one exemplary embodiment, there is a focusing of the energy radiation on the solid portion situated in the vicinity of the zone where deposition has to be performed.

[0020] In this case, the focus of the energy radiation is not in the gas phase, but on a solid part, which can correspond to the substrate on which the structure is to be formed or to a part of the structure itself on which the deposition is intended to take place, that is, to a part of a previously deposited structure. In this case, heating of the solid part transfers energy locally to the gaseous precursor in order to convert it and obtain deposition. Compared to direct heating of the gas phase, this feature allows for improved control over the deposition location. This feature further allows operation in a cold-wall reactor, which allows greater flexibility in gas pressure and deposition temperature while avoiding any risk of nucleation in a homogeneous phase. This makes it easier to adjust the deposition dynamics.

[0021] It should be noted that during the formation of the structure, a combination of focusing of the energy radiation on the solid part and in the gas phase can be used. As a variant, the energy radiation can be focused only on the solid part or only in the gas phase.

[0022] In one exemplary embodiment, the focused energy radiation is a focused laser beam.

[0023] In particular, the wavelength of the focused laser beam may be comprised between 1,058 nm and 1,068 nm, for example substantially equal to 1,063 nm.

[0024] These wavelength values ​​in the near infrared allow maximum energy absorption by the solid part when the laser beam is focused thereon. For example, in the case of a laser beam focused in the gas phase, the wavelength can be lower in the UV or visible region.

[0025] However, the invention is not limited to the use of lasers as energy radiation. As a variant, it is therefore possible to use a focused electron beam.

[0026] Thus, it is possible to use the same gaseous precursor to form the entire reinforcement, or to change the gaseous precursor as the reinforcement is deposited. The gaseous precursor can further be varied between deposition of the reinforcement and deposition of the matrix and possible interfaces. The matrix and possible interfaces can be made of materials different from the reinforcement. For example, it is possible to deposit silicon carbide reinforcement, a high-temperature carbon or boron nitride interface, and a silicon carbide matrix in the interstitial volume.

[0027] By way of example, the structure may comprise at least one of the following materials: a carbide ceramic (e.g. silicon carbide), a nitride ceramic, a carbonitride ceramic, an oxide ceramic (e.g. aluminum oxide), or a ceramic of eutectic composition. In particular, the reinforcement, the matrix, and any interfaces may independently comprise materials selected from the aforementioned list.

[0028] In an exemplary embodiment, the reinforcement is a reinforcement of a turbine component. In particular, the reinforcement may constitute a reinforcement of a turbine blade, nozzle, or turbine ring segment. The reinforcement may constitute a reinforcement of an aircraft turbine component. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The deposition of a first layer of reinforcement within the framework of an embodiment of the method according to the invention is schematically and partially represented.

[0030] Figure 2 Schematic and partial representation of the matrix in Figure 1 Deposition of a first layer of reinforcement in the interstitial volume.

[0031] Figure 3 Schematically and partially represented by Figure 2 Deposition of a second layer of reinforcement on a dense first layer of matrix.

[0032] Figure 4 Schematic and partial representation of the matrix in Figure 3 Deposition of a second layer of reinforcement in the interstitial volume.

[0033] Figure 5 represents a 4D reinforcement obtained by implementing an embodiment of the method according to the invention.

[0034] Figure 6 Shown is a turbine component obtained by implementing an embodiment of the method according to the invention. DETAILED DESCRIPTION

[0035] about Figures 1 to 4, a possible embodiment of the deposition of a structure layer by layer by chemical vapor deposition assisted by focused energy radiation will be described. For reasons of readability, the dimensions of the layers have been exaggerated in the figures. In the illustrated embodiment, the structure manufactured comprises a reinforcement and a matrix which densifies the reinforcement formed during its deposition. According to this embodiment, the structure is formed by alternating between the deposition of layers of reinforcement and the deposition of the matrix. According to a variant that is not shown, and according to the same principle, an interface can also be formed on the reinforcing element after the deposition of the layers of reinforcement and before the deposition of the matrix. The structure is formed layer by layer by additive manufacturing, the layers of the structure corresponding to its sections along the deposition axis and comprising, in the embodiment considered, the reinforcement, the matrix and any interfaces.

[0036] Figure 1 The formation of a first layer 10 of reinforcement is shown by chemical vapor deposition assisted by focused energy radiation from a gaseous precursor G1 1. The first layer 10 is deposited on a support S present in a sealed reaction chamber C, for example in contact with the same.

[0037] Before starting deposition, trace amounts of water and dioxygen are removed from the reaction chamber C. To this end, multiple cycles of pumping and expansion of a gas (such as argon) can be performed. Through the gas introduction channel 15, a gaseous precursor G11 is introduced into the reaction chamber C. Those skilled in the art know how to select a gaseous precursor from gaseous precursors known in conventional chemical vapor deposition according to the desired material to be deposited. The technology for monitoring the injection and pumping of gaseous precursors is also part of common sense and does not need to be described in detail here. For example, methyltrichlorosilane (CH3SiCl3 or MTS) or monomethylsilane (MMS) can be used to deposit silicon carbide. Propane and / or methane can be used to deposit carbon. In a manner similar to that practicable in conventional chemical vapor deposition techniques, the gaseous precursor can be diluted in a complementary neutral or reactive gas. Therefore, it is possible to add hydrogen and / or nitrogen to the precursor.

[0038] The gaseous precursor G11 is subjected to local heating by means of focused energy radiation E11 so as to deposit a first layer 10 of reinforcement having the desired geometry. The deposited first layer 10 comprises a plurality of interconnected reinforcing elements 22 defining between them a gap volume V having a predetermined and monitored shape, which will be described below with reference to the embodiment of the invention. Figure 5, detailing an embodiment of the reinforcement geometry. To achieve the desired geometry, the energy radiation E11 is continuously focused in the area where deposition is desired, in order to locally provide heat and locally convert the gaseous precursor G11. As described above, the focus of the energy radiation E11 can be located at the level of a solid part, such as the level of the support S or the level of a previously deposited part, in order to cause it to heat up and to convert the nearby precursor G11, thereby depositing the material. According to a less preferred variant, the focus of the energy radiation E11 can be located directly in the gaseous precursor G11.

[0039] In the embodiment shown, the energy radiation E11 comes from a laser. The system shown according to this embodiment includes a radiation device D, which includes a laser source 30, a collimator 33, an optical scanner 35 that allows the laser beam to be oriented during the method, and a focusing device 34 (such as a lens) that makes it possible to focus the laser beam in the area where deposition must occur. The laser source can be an infrared source with a wavelength between 1,058 nm and 1,068 nm, for example, a source of the Yb type that can be fiberized photodiodes. As an alternative, the wavelength of the laser can be in the ultraviolet or visible range, especially in the case of direct heating of the gas phase. The laser source 30 can preferably be operated in continuous mode, or in discontinuous mode if it is desired to avoid providing too much surface power. However, if an energy source other than a laser is used, such as an electron beam, it does not depart from the scope of the present invention. In the various envisaged cases, focusing of the heat source is performed by using optical or electromagnetic focusing devices in a manner known to those skilled in the art. Regardless of the nature of the energy radiation used, the power of the focused energy radiation can be between 1 mW and 100 W, preferably between 20 mW and 5 W.

[0040] The focused energy radiation E11 can be moved so as to deposit the first reinforcement layer 10 having the desired geometry by modifying the position and / or inclination of the optical scanner 35. A device for monitoring the radiation (not shown) allows the movement of the energy radiation E11 to be monitored. This thus allows the focused energy radiation E11 to be scanned in predetermined areas where the constituent material of the first layer 10 must be deposited. The device for moving the focused energy radiation is similar to that used in selective laser structuring (SLM) technology. It will be noted that, in addition to or instead of moving the focused energy radiation E11, the support S can be moved and / or tilted during deposition. A support monitoring device (not shown) allows such movement or tilting to be achieved. Thus, the support S can be moved in at least one direction in space, for example and preferably in the vertical direction Z, or even in three directions in space. As a variant or combination, the support S can be tilted about at least one direction in space, or even about all directions. However, it does not depart from the scope of the present invention if the support S remains fixed and the deposition of the first layer 10 is achieved solely by moving the focused energy radiation E11 in a plurality of predetermined areas.

[0041] As an indication, the pressure in the reaction chamber C during the formation of the structure can be comprised between 5 mbar and 3 bar, for example between 5 mbar and 15 mbar, or between 1 bar and 3 bar. The reaction chamber C may comprise a pressure sensor (not shown) and a pumping device P to measure and regulate the pressure in the reaction chamber C respectively during the deposition of the structure. The reaction chamber C comprises a gas outlet channel 17 through which the residual gaseous precursor GR11 and the reaction by-products are pumped out of the reaction chamber. If desired, it is possible to use a separator device (such as a chromatography system) to separate the precursors and reinject them into the chamber C and remove the by-products. A person skilled in the art will determine the pressure in the reaction chamber C and the surface power of the energy radiation applied according to the properties of the precursors used in order to adapt the deposition dynamics. The reaction chamber C may further comprise a thermal sensor (not shown), such as a thermal camera, to measure the local temperature at the focus of the energy radiation, and a regulating device that allows the power of the focused energy radiation to be modified according to the measurements from the thermal sensor so as to apply the desired predetermined power to convert the precursor and perform the deposition.

[0042] Just about Figure 1 The deposition of the first layer 10 of reinforcement has been described. In the embodiment considered, the deposition of reinforcement is temporarily interrupted in order to form the matrix M in the interstitial volume of the previously formed first layer 10, as will now be described with reference to Figure 2 Descriptive.

[0043] Once the first layer 10 of the reinforcement has been deposited, the irradiation by the focused energy radiation E11 is interrupted and the reaction chamber C is purged. A gaseous precursor G12 is then introduced into the reaction chamber C, which is intended to form the matrix M in the interstitial volume of the first layer 10 by chemical vapor deposition assisted by the focused energy radiation. The precursor G12 can be different from the precursor G11 and lead to the deposition of the matrix M formed by a material different from that of the first layer 10 of the reinforcement. In order to carry out the deposition of the matrix M in the desired areas, the energy radiation E12 and / or the support S are driven in a manner similar to that just described above for the first layer 10. The surface power of the energy radiation E12 can be different from the surface power of the energy radiation E11 by being adapted to the precursor G12. The monitoring of the pressure in the reaction chamber and the treatment of the mixture of residual matrix precursor GR12 and by-products can be carried out as in the case of the deposition of the first layer 10 described above.

[0044] The matrix M may include or consist essentially of a mass of a carbide, nitride or oxide ceramic. For example, the matrix may include or consist essentially of a mass of silicon carbide.

[0045] In a variant not shown, the embrittlement-relieving interface is similarly deposited on the reinforcing elements of the first layer of the reinforcement, prior to forming the matrix, by chemical vapor deposition assisted by focused energy radiation. The interface can be single-layer or multi-layer. The interface may comprise, for example, silicon carbide, boron nitride, or boron nitride (BN(Si)) doped with silicon or high-temperature carbon (PyC). The interface has the function of embrittlement-relieving the composite material, promoting the deflection of any cracks that have already propagated in the matrix and reach the interface, thereby preventing or delaying fracture of the reinforcement.

[0046] After the matrix M has been deposited in the interstitial volume of the first layer 10 of reinforcement, the deposition of the reinforcement is continued by depositing a second layer 20 of ceramic or carbon reinforcement on the first layer 10 densified by the matrix M, as shown in FIG. Figure 3 shown.

[0047] The irradiation by the focused energy radiation E12 is interrupted and the reaction chamber C is cleaned. Then, a gaseous precursor G21 is introduced into the reaction chamber C, which is intended to form the second layer 20 of the reinforcement by chemical vapor deposition assisted by the focused energy radiation. The focused energy radiation E21 is applied so as to deposit the second layer 20 of the reinforcement in the desired geometry on the first layer 10, similar to what is described above. The characteristics described above for depositing the first layer 10 remain applicable to depositing the second layer 20. It should be noted that the precursor G21 can be the same as or different from the precursor G11. The material of the second layer 20 of the reinforcement can be the same as or different from the material of the first layer 10 of the reinforcement. Preferably, the material of the second layer 20 of the reinforcement is the same as the material of the first layer 10 of the reinforcement. The surface power of the energy radiation E21 can be the same as or different from the surface power of the energy radiation E11. The pressure in the reaction chamber can be monitored and the mixture of residual precursor GR21 and by-products can be processed as described above for the case of deposition of the first layer 10.

[0048] During the deposition of the second layer 20, the energy radiation E21 can scan a set of areas that define a different pattern relative to the pattern defined by the set of areas scanned by the energy radiation E11 during the deposition of the first layer 10. Here, the second layer 20 is superposed on the first layer 10 along a deposition axis defined by the perpendicular direction Z. The second layer 20 can be deposited in contact with the first layer 10. The second layer 20 can cover substantially the entire first layer 10, or only a portion thereof. The second layer 20 comprises a plurality of interconnected reinforcing elements made of ceramic or carbon, which define interstitial volumes between them having a shape that differs from the shape of the interstitial volumes between the reinforcing elements of the first layer 10, so as to provide the interstitial volume of the reinforcement 1 with a tortuous shape along the deposition axis Z. The shape of the interstitial volume of the second layer 20 can differ substantially from that of the interstitial volume of the first layer 10, so as to correspond to the desired orientation of the reinforcement.

[0049] Once the second layer 20 of reinforcement has been deposited, the irradiation by the focused energy radiation E21 is interrupted and the reaction chamber C is purged. Then, a gaseous precursor G22 is introduced into the reaction chamber C, which is intended to form a matrix M ( Figure 4 ). The method then continues as described above to deposit the matrix M in the interstitial volume of the second layer 20 by driving the focused energy radiation E22 and / or the support S, thereby depositing the matrix M in the desired area. The mixture of residual precursor GR22 and by-products can be processed as described above. As described above, the interface can be deposited on the reinforcing elements of the second layer 20 before the matrix M is deposited.

[0050] A composite structure 100 is then obtained, comprising a reinforcement 1 and a matrix M of dense reinforcements. The reinforcement volume ratio in this structure may be comprised between 15% and 55%, for example between 25% and 35%. The reinforcement is controlled and oriented in space according to the load direction of the component to be obtained.

[0051] The illustrated embodiment shows the manufacture of a structure 100 in which two layers of reinforcement 10 and 20 are deposited. Of course, the method can continue by depositing a third layer of reinforcement in a similar manner on the second layer 20. The interstitial volume of each deposited layer can have a different shape so that the interstitial volume of the reinforcement has a tortuous shape.

[0052] An embodiment has just been described in which a structure forming a matrix is ​​formed when the reinforcement is formed. However, the formation of this matrix is ​​optional, and the reinforcement can simply be formed layer by layer without concurrently forming the matrix, or simply by forming the interface when the reinforcement is formed. According to variations, the matrix and / or interface can be formed after the reinforcement is formed using known techniques.

[0053] Now about Figure 5 Examples of geometric shapes of reinforcements 1 that can be obtained by implementing the invention are described. Figure 5 The reinforcement 1 shown corresponds to a 4D reinforcement. The reinforcement 1 includes a plurality of reinforcing elements 22 oriented along the four directions given by the diagonals of a cube and defining a gap volume V therebetween, the gap volume V having a zigzag shape along the vertical direction Z of deposition. The reinforcing elements 22 can have various shapes, such as parallelepipeds, beams with, for example, circular, elliptical, square, or rectangular cross-sections, spheres, ellipsoids, etc. The reinforcing elements 22 can be solid or hollow. The diameter of the reinforcing elements 22 can be less than or equal to 100 μm. The reinforcing elements 22 can be further arranged in a network to form a reinforcement. Regardless of the embodiment considered, the reinforcement 1 has a connected gap volume, that is, there is a path that allows movement from one space between the reinforcing elements 22 to another space without passing through the material of the reinforcing elements. The gap volume is defined by the inner surface of the ceramic or carbon material. When the gap volume is connected, this inner surface of the ceramic or carbon material is continuous in the structure. Those skilled in the art will have no difficulty recognizing that structures other than 4D reinforcement structures are possible.

[0054] Figure 6 Examples of components that can be obtained by implementing the method according to the invention are illustrated. The invention can allow the formation of turbine components, such as aircraft turbine components. Figure 6 As shown, it is possible to form a turbine blade 40. Other embodiments are possible, such as, for example, a turbine ring segment or a turbine nozzle segment.

[0055] The expression "included and between" must be understood as including the limits.

Claims

1. A method for manufacturing a structure by additive manufacturing, the method comprising at least: - Forming a reinforcement from at least one gaseous precursor by chemical vapor deposition assisted by focused energy radiation, said reinforcement being deposited along a deposition axis and comprising a plurality of interconnected reinforcing elements made of ceramic or carbon, said reinforcing elements defining between them a gap volume having a tortuous shape along said deposition axis and, when moving along this axis, said gap volume having a sinuous and non-rectilinear shape; said method comprising alternating between deposition of layers of said reinforcement and deposition of a matrix, said matrix being present in the gap volume of the obtained reinforcement, by chemical vapor deposition assisted by focused energy radiation.

2. The method according to claim 1, wherein The reinforcement is a 4D reinforcement.

3. The method according to claim 1, wherein the method comprises at least: - depositing the first layer of reinforcement, - depositing a matrix in the interstitial volumes of the first layer of reinforcement to obtain a dense first layer of reinforcement, and - Depositing a second layer of reinforcement on the first layer of dense reinforcement.

4. The method according to claim 3, wherein: The method further includes forming an interface on the reinforcement elements of the first layer of the reinforcement before depositing the matrix, the interface being formed by chemical vapor deposition assisted by focused energy radiation.

5. The method according to claim 1, wherein On the solid parts situated in the vicinity of the area where deposition has to be carried out, there is energy radiation.

6. The method according to claim 1, wherein The focused energy radiation is a focused laser beam.

7. The method according to claim 6, wherein: The wavelength of the focused laser beam is comprised between 1,058 nm and 1,068 nm.

8. The method of claim 1, wherein the reinforcement comprises at least one of the following materials: a carbide ceramic, a nitride ceramic, a carbonitride ceramic, an oxide ceramic, or a ceramic of a eutectic composition.

9. The method according to any one of claims 1 to 8, wherein The reinforcement is a reinforcement of a turbine component.

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