Alloy for manufacturing tools intended for manufacturing aeronautical parts made of composite material

Abstract

The invention relates to an alloy for manufacturing a tool intended for manufacturing aeronautical parts made of composite material, the alloy comprising, by weight : 32.6% ≤ Ni ≤ 38.0%, 0.80% ≤ Co ≤ 4.20%, with: Co ≥ -1.00 x Ni% + 36.80%, where Ni% denotes the Ni content in weight percent in the alloy; and Co ≤ -1.63 x Ni% + 62.72%, where Ni% denotes the Ni content in weight percent in the alloy, 1.0% ≤ Ti ≤ 2.0%, 0.0010% ≤ rare earths ≤ 0.0500%, 0.10% ≤ Si ≤ 0.35%, 0.15% ≤ Mn ≤ 0.60% and 0.005% ≤ C ≤ 0.04%, the remainder being iron and impurities resulting from the production process.

Description

[0001] Alloy for the manufacture of tools intended for the manufacture of aeronautical parts made of composite material

[0002] The present invention relates to an alloy for the manufacture of tools, in particular molds or mold parts, intended for the manufacture of aeronautical parts made of composite material.

[0003] The search for a compromise between weight and mechanical properties in the aeronautics industry leads to the production of an increasing number of aeronautical parts, in particular structural parts or functional components, such as wings or fuselages, in composite materials. These composite materials generally comprise a polymer matrix, in which reinforcing fibers are embedded. The polymer matrix is, for example, formed by a thermosetting resin, in particular by an epoxy, polyester, vinylester, polyamide or phenol resin. Furthermore, the reinforcing fibers are, for example, chosen from glass, carbon, Kevlar, aluminum or titanium fibers. In some cases, the fibers are woven in order to further improve the mechanical properties of the part.

[0004] For the manufacture of these parts, a Prepreg is usually used as the starting material, i.e. a composite in the form of a strip comprising the reinforcing fibers embedded in the polymer matrix. The part is then manufactured from this starting material by one of the following two processes:

[0005] (a) Lamination and crosslinking under autoclave, comprising the following successive steps: a. Deposition of the starting material, in successive layers, on a metal mold of convex or concave shape to obtain a lamination on the metal mold, b. Vacuum encapsulation of the lamination to eliminate air bubbles and to apply the lamination to the more or less complex shapes of the mold, c. Crosslinking of the polymer matrix of the composite by heat treatment of the assembly comprising the mold with the lamination in an autoclave, under pressure, at temperatures between 120°C and 180°C, for several hundred minutes;

[0006] (b) Die casting, this process being analogous to process (a), but comprising, instead of the autoclave crosslinking step, a step of crosslinking the composite under pressure, by hot pressing the lamination between a first mold on which the lamination is applied and a second mold having a cavity complementary to that of the first mold. The hot pressing is carried out at temperatures and for durations analogous to those mentioned with regard to process (a).

[0007] The tools used to produce aeronautical parts from composite material using the processes mentioned above must therefore ideally have the following properties:

[0008] - good mechanical resistance to the crosslinking temperatures of polymer matrices and to the numerous thermal cycles resulting from the reuse of tools,

[0009] - a coefficient of thermal expansion adapted to that of the composite material in use, dimensional stability,

[0010] - vacuum sealing.

[0011] Furthermore, these tools must allow for lower-cost production, particularly in terms of manufacturing cost, final weight, lead times, etc.

[0012] For the manufacture of composite material parts comprising carbon fibers embedded in an epoxy resin matrix, the thermal expansion coefficient of the tooling is considered to be adapted to that of the composite in use if the metal alloy from which the tooling is made has a thermal expansion coefficient between 20°C and 200°C of between 2.2.10 -6o C -1 and 2.9.10 -6o C -1 .

[0013] Invar M93 has a suitable coefficient of thermal expansion for the manufacture of such tools. Furthermore, it also has advantageous properties for such an application, in particular in terms of impact and scratch resistance, increased tool life compared to non-metallic molds, the possibility of producing a mechanically welded tool or mold structure and the possibility of machining the tool from a mechanically welded structure.

[0014] In order to reduce production costs and improve productivity associated with the production of tools for the applications mentioned above, we are seeking to produce these tools using additive manufacturing processes. Indeed, additive manufacturing allows these tools to be manufactured flexibly and quickly. It also allows the manufacture of tools that can withstand more thermal cycles with limited maintenance.

[0015] In order to further improve productivity, relatively high deposition rates are sought in the additive manufacturing process, for example deposition rates greater than or equal to approximately 450 cm 3 / h.

[0016] One way to increase the deposition rate in the additive manufacturing process is to reduce the time between two successive material deposition passes, hereinafter referred to as the inter-pass time. However, the inventors of the present invention found, when manufacturing test walls by arc-wire additive manufacturing using a wire made of Invar M93, that reducing the inter-pass time resulted in the walls collapsing due to the increase in inter-pass temperatures. In particular, the inventors noted that the wall began to show drips from an inter-pass temperature of 600°C. Such a process therefore does not allow parts of satisfactory quality to be manufactured with the targeted productivity.

[0017] One aim of the invention is to propose an alloy enabling the additive manufacturing of tools intended for the manufacture of aeronautical parts in composite material with improved productivity.

[0018] To this end, the invention relates to an alloy for the manufacture of tools intended for the manufacture of aeronautical parts made of composite material, the alloy comprising, by weight:

[0019] 32.6% < Ni < 38.0%

[0020] 0.80% < Co < 4.20% with:

[0021] Co > -1.00 x Ni% + 36.80%, where Ni% denotes the Ni content in percent by weight in the alloy; and

[0022] Co < -1.63 x Ni% + 62.72%, where Ni% denotes the Ni content in percent by weight in the alloy

[0023] 1.0% < Ti < 2.0%

[0024] 0.0010% < rare earths < 0.0500%

[0025] 0.10% < If < 0.35%

[0026] 0.15% < Mn < 0.60%

[0027] 0.005% < C < 0.04% the remainder being iron and impurities resulting from the production.

[0028] Preferably, the impurities resulting from the preparation comprise, by weight: Ca < 0.0015% Mg < 0.0035% Al < 0.0085% O < 0.0025% S < 0.0035% P < 0.0100% B < 0.0005% Mo < 0.1% Cr < 0.1% Cu < 0.1%

[0029] Number < 0.01%

[0030] V < 0.01%.

[0031] Preferably, the rare earths comprise yttrium, cerium, lanthanum, neodymium, praseodymium or mixtures thereof.

[0032] The invention also relates to a filler wire made from the alloy as defined above.

[0033] The invention also relates to a method of manufacturing a filler wire as defined above, the method comprising the following steps:

[0034] - supply of a semi-finished product made from an alloy as defined above;

[0035] - hot transformation of this semi-finished product to form an intermediate wire; and

[0036] - transformation of the intermediate wire into filler wire, of diameter smaller than that of the intermediate wire, said transformation comprising a wire drawing step.

[0037] The invention also relates to a use of the alloy as defined above, for manufacturing at least part of a tool intended for the manufacture of an aeronautical part made of composite material.

[0038] The invention also relates to a part or part of a part made from an alloy as defined above.

[0039] According to specific characteristics of the part or part of the part:

[0040] - said part or part of part being obtained by metallic additive manufacturing.

[0041] - the part is a tool, in particular a mold, intended for the manufacture of an aeronautical part made of composite material.

[0042] The invention also relates to a method for manufacturing a part or part of a part, comprising a step of manufacturing said part or part of a part by a metal additive manufacturing method using, as filler material, a filler wire made from the alloy as defined above and / or a powder made from the alloy as defined above.

[0043] According to specific characteristics of the manufacturing process:

[0044] - the additive manufacturing process is chosen from an arc-wire, laser-wire, electron beam-wire process and a hybrid additive manufacturing process combining arc-wire and laser-powder or arc-wire and laser-wire technologies.

[0045] The invention also relates to a use of the filler wire as defined above as filler wire in the context of a metal additive manufacturing process.

[0046] The invention also relates to a metal powder made from an alloy as defined above. The invention also relates to a method for manufacturing a metal powder as defined above, said method comprising a step of providing a filler wire as defined above, as well as a step of plasma atomization of this filler wire to obtain the metal powder.

[0047] The invention will be better understood on reading the following description, given solely by way of example, and made with reference to the appended drawings, in which:

[0048] - Figure 1 is a graph illustrating the range of permitted contents for cobalt in the alloy according to the invention as a function of the nickel content of the alloy, the contents being expressed as a percentage by weight; and

[0049] - Figure 2 is a schematic perspective view of a part obtained by additive manufacturing according to the invention.

[0050] The alloy according to the invention comprises, by weight:

[0051] 32.6% < Ni < 38.0%

[0052] 0.80% < Co < 4.20% with:

[0053] Co > -1.00 x Ni% + 36.80%, where Ni% denotes the Ni content in percent by weight in the alloy; and

[0054] Co < -1.63 x Ni% + 62.72%, where Ni% denotes the Ni content in percent by weight in the alloy

[0055] 1.0% < Ti < 2.0%

[0056] 0.0010% < rare earths < 0.0500%

[0057] 0.10% < If < 0.35%

[0058] 0.15% < Mn < 0.60%

[0059] 0.005% < C < 0.04% the remainder being iron and impurities resulting from the production.

[0060] Processing impurities are elements that are present in the raw materials used to produce the alloy or that originate from the equipment used for its production, for example, from the refractories in the furnaces. These residual elements have no metallurgical effect on the alloy.

[0061] The impurities resulting from the production include in particular, by weight:

[0062] Ca < 0.0015%

[0063] Mg < 0.0035%

[0064] Al < 0.0085%

[0065] O < 0.0025%

[0066] S < 0.0035%

[0067] P < 0.0100% B < 0.0005%

[0068] Mo < 0.1%

[0069] Cr < 0.1%

[0070] Cu < 0.1%

[0071] Number < 0.01%

[0072] V < 0.01%.

[0073] More particularly, the contents of sulfur, phosphorus, oxygen, boron, magnesium, aluminum and calcium are preferably limited to the upper limits mentioned above so as not to degrade the weldability of the alloy. In particular, limiting the contents of magnesium, aluminum, calcium and oxygen to the contents specified above makes it possible to avoid degrading the stability of the electric arc in arcing mode, in particular in the context of additive manufacturing. Limiting the contents of sulfur, phosphorus and boron to the contents mentioned above makes it possible to avoid degrading the resistance to hot cracking of the parts made from this alloy.

[0074] Finally, the molybdenum, chromium, copper, niobium and vanadium contents are preferably limited to the contents mentioned above in order to avoid degrading the thermal expansion coefficient of the alloy.

[0075] The alloy described above is an Invar type alloy.

[0076] The alloy according to the invention is an austenitic alloy at a temperature equal to room temperature (approximately 20°C).

[0077] The average coefficient of thermal expansion o2o=c 2oo=c between 20°C and 200°C of the alloy according to the invention is between 2.2.10 -6 °C -1 and 2.9.10 -6o It 1. An average coefficient of thermal expansion between 20°C and 200°C included in this range is advantageous, in particular in the case where the alloy according to the invention is used to produce tools intended for the manufacture of aeronautical parts made of composite material, and in particular comprising an epoxy resin matrix in which carbon reinforcing fibers are embedded, according to the methods mentioned above. Indeed, such a coefficient makes it possible to ensure compatibility, in terms of thermal expansion, between the tooling made from the alloy described above and the composite material from which the aeronautical part to be manufactured is made.However, a lack of compatibility of the average coefficients of thermal expansion of the tooling and the part risks causing the part during manufacture to undergo distortions or deformations due to the relative expansion of the part in relation to the tooling or to create stresses in the part during cooling after the crosslinking treatment. In addition, detachments between the composite material and the tooling, during curing, can generate drips leaving exposed fibers, and making the part defective. Thus, the alloy according to the invention makes it possible to obtain parts made of composite material for aeronautical applications, in particular made of composite material comprising an epoxy resin matrix in which carbon reinforcing fibers are embedded respecting the theoretical dimensions, having fibers totally protected by the resin, and devoid of residual stresses.

[0078] Furthermore, an average coefficient of thermal expansion a2o=c 2oo=c between 20°C and 200°C between 2.2.10 -6 °C -1 and 2.9.10 -6o It 1 ensures good dimensional stability.

[0079] Furthermore, the alloy according to the invention makes it possible to obtain parts, such as tools or parts of tools for producing aeronautical parts, having:

[0080] - good mechanical resistance to the crosslinking temperatures of polymer matrices and to the numerous thermal cycles resulting from the reuse of tools; and

[0081] - vacuum sealing.

[0082] In the alloy according to the invention, the nickel content is between 32.6% by weight and 38.0% by weight. If the nickel content is less than 32.6% by weight, martensitic transformation may occur at temperatures close to room temperature, and the alloy may no longer be austenitic at room temperature, which impairs its dimensional stability. If the nickel content is greater than 38.0% by weight, the coefficient of thermal expansion of the alloy becomes too high, and the dimensional stability of the alloy is compromised.

[0083] According to the invention, the cobalt content is between 0.80% by weight and 4.20% by weight, and further complies with the following conditions: Co > -1.00 x Ni% + 36.80% and Co < -1.63 x Ni% + 62.72%. In these inequalities, Ni% denotes the nickel content as a percentage by weight in the alloy and Co denotes the cobalt content as a percentage by weight in the alloy.

[0084] The range of permitted contents for cobalt, expressed as a percentage by weight, as a function of the nickel content, expressed as a percentage by weight, is illustrated in Figure 1. In this figure:

[0085] - the line C_sup has the equation: Co = 4.20%

[0086] - the line CJnf has the equation: Co = 0.80%

[0087] - the line C1 has the equation: Co = -1.00 x Ni% + 36.80%

[0088] - the line C2 has the equation: Co = -1.63 x Ni% + 62.72%.

[0089] In this figure, the domain according to the invention corresponds to the domain delimited by the rights C1, C2, CJnf and C_sup. A cobalt content included in this domain makes it possible to obtain an average coefficient of thermal expansion between 20°C and 200°C of between 2.2.10 -6 °C -1 and 2.9.10' 6o It 1 .

[0090] When the cobalt content is greater than 4.20% by weight, corresponding to cobalt contents located above the line C_sup in Figure 1, the average coefficient of thermal expansion between 20°C and 200°C is likely to be lower than the lower limit of 2.2.10' 6 o It 1 desired for the application mentioned above, namely the manufacture of tools intended for the manufacture of aeronautical parts. Furthermore, in this case, there is an increased risk of martensitic transformation by work hardening, and in particular by plastic deformation, for example during wire drawing, which increases the cost of wire drawing manufacturing processes, by requiring the implementation of intermediate austenitization annealing, at intermediate wire diameters, for example of the order of 2 mm.

[0091] When the cobalt content is less than 0.80% by weight, corresponding to cobalt contents located below the line CJnf in Figure 1, the average coefficient of thermal expansion between 20°C and 200°C is likely to be greater than the upper limit of 2.9.10' 6o It 1 desired for the above-mentioned application.

[0092] When the cobalt content is below the C1 line, i.e. when Co < -1.00 x Ni% + 36.80%, the average coefficient of thermal expansion between 20°C and 200°C may be higher than the upper limit of 2.9.10' 6o It 1 desired for the above-mentioned application.

[0093] When the cobalt content is above the C2 line, i.e. when Co > -1.63 x Ni% + 62.72%, the average coefficient of thermal expansion between 20°C and 200°C is likely to be higher than the upper limit of 2.9.10' 6o It 1desired for the above-mentioned application.

[0094] In the alloy according to the invention, the titanium content of between 1.0% by weight and 2.0% by weight makes it possible to obtain good resistance to collapse of the liquid bath during the additive manufacturing of parts made in the alloy according to the invention by arc-wire additive manufacturing and therefore makes it possible in particular to avoid the formation of drips in the part.

[0095] When the titanium content is less than 1.0% by weight, the collapse resistance of the liquid bath during the additive manufacturing of parts made from the alloy according to the invention, in particular by arc-wire additive manufacturing, is insufficient and high manufacturing productivity, in particular a deposition rate greater than or equal to 450 cm 3 / h during additive manufacturing, generates unwanted drips. When the titanium content is higher than 2.0% by weight, the average coefficient of thermal expansion between 20°C and 200°C may be higher than the upper limit of 2.9.10 -6o It 1 desired for the above-mentioned application.

[0096] In the alloy according to the invention, the rare earth content is between 0.0010% and 0.0500%. The addition of rare earths at the mentioned contents makes it possible to reinforce the role of titanium, and thus to improve the resistance to collapse of the liquid bath during the additive manufacturing of parts made from the alloy according to the invention, in particular by arc-wire additive manufacturing.

[0097] Rare earths are particularly chosen from yttrium, cerium, lanthanum, neodymium and praseodymium or their mixtures.

[0098] For example, rare earths consist of yttrium.

[0099] Alternatively, rare earths comprise a mixture of cerium and lanthanum, and originate, for example, from MischmétaL. In particular, rare earths consist of a mixture of cerium and lanthanum.

[0100] In the alloy according to the invention, silicon, manganese and carbon are added for desulfurization and deoxidation of the alloy. Their contents, by weight, are chosen from the following ranges:

[0101] 0.10% < If < 0.35%

[0102] 0.15% < Mn < 0.60%

[0103] 0.005% < C < 0.04%

[0104] When the silicon and / or manganese contents are higher than the limits described above, the coefficient of thermal expansion may be higher than the upper limit of 2.9.10 -6o It 1 desired for the above-mentioned application.

[0105] A carbon content above 0.04% may lead to hot cracking problems during solidification, due to the precipitation of titanium carbides, and thus to poor solidification behavior during welding.

[0106] The alloy according to the invention is advantageous. Indeed, it allows the manufacture, by additive manufacturing, of tools or parts of tools intended for the manufacture of aeronautical parts in composite material, comprising in particular a matrix made of epoxy resin in which carbon fibers are embedded as reinforcing fibers, of good quality, in a simple and flexible manner and with high productivity. Indeed, it has the desired properties for such alloys mentioned above, and in particular an average coefficient of thermal expansion between 20°C and 100°C of between 2.2.10 -6 °C -1 and 2.9.10 -6o C -1, resulting in satisfactory compatibility between the tooling and the part to be manufactured, and good resistance to the collapse of the liquid bath during the additive manufacturing of parts, which allows the manufacturing of good quality parts with high manufacturing productivity, in particular with a deposition rate greater than or equal to 450 cm 3 / h during additive manufacturing.

[0107] The alloy according to the invention can be produced by any suitable method known to those skilled in the art.

[0108] For example, in the first step, starting materials are placed in an electric arc furnace. These starting materials are then melted in the electric arc furnace, followed by refining in a new ladle (VOD) using standard methods, in order to obtain:

[0109] - decarburization by blowing oxygen and vacuum pumping (of the order of a few mbar);

[0110] - deoxidation and desulfurization under lime-based slag; and

[0111] - adjustment of the silicon content.

[0112] The invention also relates to a filler wire made from an alloy having a composition as described above.

[0113] Such a filler wire is particularly suitable for use as a filler wire in a metal additive manufacturing process.

[0114] The additive manufacturing process is, for example, an additive manufacturing process using an electric arc, a laser beam and / or an electron beam as an energy source to achieve the melting of the filler wire.

[0115] The additive manufacturing process is in particular a Directed Energy Deposition additive manufacturing process. During this process, the filler material is deposited, in particular by a nozzle, and immediately fused by concentrated thermal energy, in particular a laser beam, an electron beam and / or an electric arc.

[0116] For example, the additive manufacturing process is an arc-wire process ("WAAM" or "Wire arc additive manufacturing" in English), Laser-wire, electron beam-wire ("Electron Beam Free Form Fabrication" or "Electron beam additive manufacturing" in English) or a hybrid additive manufacturing process combining arc-wire and Laser-powder or arc-wire and Laser-wire technologies.

[0117] In the case of a hybrid arc-wire and laser-powder process, the powder used has the same composition as the wire.

[0118] Such a powder, whose particle size after sieving is between 20 pm and 150 pm, is for example obtained from the filler wire according to the invention, by means of a plasma atomization technology. Preferably, the filler wire used to manufacture the powder has a diameter of approximately 3 mm. The particle size of the powders is in particular determined by the following measuring method. The batches of powders are separated into several powder size distributions by means of ultrasonic vibrating stainless steel sieves. The analysis of the powder size distribution resulting from the sieving is carried out according to the ASTM B214-07 standard. The sieving makes it possible to obtain 5 size classes: < 20 pm - 20 pm to 45 pm - 45 pm to 75 pm - 75 pm to 105 pm - >105 pm.

[0119] The plasma atomization technology for making powder from wire is known per se, and therefore is not described in further detail.

[0120] The invention also relates to a method of manufacturing a filler wire made from the alloy as described above.

[0121] This process comprises, in a first step, the supply of a semi-finished product made from this alloy. For this purpose, the alloy is either cast into ingots or cast directly in the form of billets, in particular by means of continuous casting, in particular rotary casting. The semi-finished products obtained at the end of this step are therefore advantageously ingots or billets, and have, for example, a diameter of between 130 and 230 mm, and more particularly equal to approximately 150 mm.

[0122] Then the semi-finished products are transformed by hot processing to form an intermediate wire.

[0123] In particular, during this hot transformation stage, the semi-finished products, i.e. in particular the ingots or billets, are reheated, in particular in a gas furnace, to a temperature between 1180°C and 1220°C.

[0124] They are then subjected to hot roughing in order to reduce their section, giving them, for example, a square section, of approximately 100 mm to 200 mm on each side. This produces a semi-finished product with a reduced section. The length of this semi-finished product with a reduced section is notably between 10 m and 20 m.

[0125] The semi-finished products of reduced cross-section are then hot-processed again, at a temperature between 950°C and 1150°C, to obtain the intermediate wire. The intermediate wire may in particular be a wire rod. It has, for example, a diameter between 5 mm and 21 mm, and in particular approximately equal to 5.5 mm. Advantageously, during this step, the intermediate wire is produced by hot rolling on a wire mill.

[0126] Optionally, the intermediate wire is then subjected to hyperquenching in a pool, after heat treatment in a gas furnace at a temperature between 1150°C and 1220°C for a duration of between 60 minutes and 120 minutes.

[0127] The intermediate wire is then stripped and wound into a coil. Optionally, the intermediate wire thus obtained is drawn using a known type of wire drawing installation to obtain the filler wire. This filler wire has a diameter smaller than that of the starting wire. Its diameter is notably between 0.5 mm and 3.5 mm. It is advantageously between 0.8 mm and 2.4 mm.

[0128] The wire drawing step includes, depending on the final diameter to be achieved, one or more drawing passes, preferably with annealing between two successive drawing passes. This annealing is, for example, carried out on the run in a reducing atmosphere at a temperature of around 1150°C.

[0129] The drawing step is preferably followed by cleaning the surface of the drawn wire, then winding the wire onto a reel.

[0130] The drawing passes are carried out cold.

[0131] Any other methods of producing the alloy according to the invention and of manufacturing finished products made from this alloy known to those skilled in the art may be used for this purpose.

[0132] The invention also relates to a method of manufacturing a part or part of a part 1 as shown schematically in Figure 2, made from an alloy as described above, comprising:

[0133] - the supply of a filler wire made from this alloy; and

[0134] - the manufacture of part 1 or part of part by a metal additive manufacturing process using, as filler material, a filler wire made from the alloy as described above and / or a powder made from the alloy as described above.

[0135] The part 1 or part of a part is preferably a tool or a part of a tool intended to be used for the manufacture of aeronautical parts made of composite materials, the composite material comprising, in particular, an epoxy resin matrix in which reinforcing fibers in the form of carbon fibers are embedded. In particular, the part 1 is a mold or a part of a mold intended to be used for the manufacture of aeronautical parts made of composite materials, the composite material comprising, in particular, an epoxy resin matrix in which reinforcing fibers in the form of carbon fibers are embedded. By way of example, the part 1 defines a molding surface of a tool intended to be used for the manufacture of aeronautical parts made of composite materials and further comprises, optionally, a structure for supporting said molding surface.The additive manufacturing process is, for example, an additive manufacturing process using an electric arc, a laser beam and / or an electron beam as an energy source to achieve the melting of the filler material.

[0136] The additive manufacturing process is in particular a Directed Energy Deposition additive manufacturing process. During this process, the filler material is deposited, in particular by a nozzle, and immediately fused by concentrated thermal energy, in particular a laser beam, an electron beam and / or an electric arc.

[0137] For example, the additive manufacturing process is an arc-wire, laser-wire, electron beam-wire process ("Electron Beam Free Form Fabrication" or "Electron beam additive manufacturing" in English) or a hybrid additive manufacturing process combining arc-wire and laser-powder or arc-wire and laser-wire technologies.

[0138] In the case where a hybrid additive manufacturing process combining arc-wire and laser-powder or arc-wire and laser-wire technologies is used, the powder and the filler wire are made in the alloy as described above.

[0139] The additive manufacturing processes mentioned above are known per se, and are therefore not described in detail.

[0140] However, according to the invention, the additive manufacturing method comprises several passes, each pass corresponding to the formation of a layer of the part 1 or part of the part to be manufactured, the duration between two successive passes being defined by the minimum time necessary for the tool, and in particular the tool for melting the filler material, for example the laser beam, the electron beam and / or the electric arc, to return to the start of the deposition zone.

[0141] Given the advantageous properties of the alloy according to the invention described above, this manufacturing process makes it possible to flexibly manufacture high-quality parts 1 or parts of parts with high productivity, and in particular with a deposition rate greater than or equal to 450 cm 3 / h.

[0142] In the case where the filler material comprises a powder, in particular in the context of the hybrid arc-wire and laser-powder process, the process also comprises, prior to the manufacture of the part 1 or part of the part, a step of providing a powder made from the alloy as described above. This powder, the particle size of which after sieving is between 20 μm and 150 μm, is for example manufactured by plasma atomization from a wire made from an alloy as described above, the wire having in particular a diameter of approximately 3 mm.

[0143] The plasma atomization method is known per se, and is therefore not described in detail. The invention also relates to a part 1 or a part of a part made from an alloy as described above obtained by metal additive manufacturing.

[0144] The part 1 or part of a part is preferably a tool or a part of a tool intended to be used for the manufacture of aeronautical parts made of composite materials, the composite material comprising, in particular, an epoxy resin matrix in which reinforcing fibers in the form of carbon fibers are embedded. In particular, the part 1 is a mold or a part of a mold intended to be used for the manufacture of aeronautical parts made of composite materials, the composite material comprising, in particular, an epoxy resin matrix in which reinforcing fibers in the form of carbon fibers are embedded. By way of example, the part 1 defines a molding surface of a tool intended to be used for the manufacture of aeronautical parts made of composite materials and further comprises, optionally, a structure for supporting said molding surface.

[0145] The metal additive manufacturing process uses in particular, as filler material, a filler wire made from the alloy as described above and / or a powder made from the alloy as described above.

[0146] The additive manufacturing process is, for example, an additive manufacturing process using an electric arc, a laser beam and / or an electron beam as an energy source to achieve the melting of the filler material.

[0147] The additive manufacturing process is in particular a Directed Energy Deposition additive manufacturing process. During this process, the filler material is deposited, in particular by a nozzle, and immediately fused by concentrated thermal energy, in particular a laser beam, an electron beam and / or an electric arc.

[0148] For example, the additive manufacturing process is an arc-wire, laser-wire, electron beam-wire process ("Electron Beam Free Form Fabrication" or "Electron beam additive manufacturing" in English) or a hybrid additive manufacturing process combining arc-wire and laser-powder or arc-wire and laser-wire technologies.

[0149] In the case where a hybrid additive manufacturing process combining arc-wire and laser-powder or arc-wire and laser-wire technologies is used, the powder and the filler wire are made in the alloy as described above.

[0150] A part 1 or part of a part obtained by a metal additive manufacturing process is as-solidified. It therefore has a solidification microstructure typical of the nickel alloy considered, such a microstructure typically comprising columnar dendrites which grow epitaxially on top of each other and whose orientation depends on the width and height of the manufactured metal wall. Furthermore, a part 1 obtained by an additive manufacturing process has, due to its additive manufacturing process, a succession of superimposed solidification layers. Each layer, obtained by solidification of deposited drops of molten metal, remelts the skin of the previous layer in order to generate metallurgical continuity, and consequently heats the rest of the lower layers. The reheating temperature is lower the further the layer in question is from the zone undergoing melting and solidification.This particular microstructure can be observed by metallographic observation on metallographic sections of the parts 1.

[0151] A part 1 or part of a part obtained by a metal additive manufacturing process can thus be distinguished from parts obtained by other processes, and in particular from a part obtained by conventional metallurgy which produces a recrystallized structure with homogeneous grains.

[0152] Tests

[0153] The inventors vacuum-formed in the laboratory alloys having compositions as defined above, as well as comparative alloys, having compositions different from the composition described above, then cast these alloys in the laboratory to obtain truncated ingots, having a diameter equal to 120 mm at the base of the cone and 60 mm at the top of the cone. The ingots thus obtained were hot forged to obtain bars 100 mm in diameter and 500 mm long, which were then surface-machined to remove the scale and forged using a rotary forge marketed by the company GFM to produce bars 30 mm in diameter and 3 m long. These bars were then cold-drawn to produce a wire having a diameter of 5.5 mm and a length of 15 meters.The cold drawing step comprises a plurality of successive drawings with recrystallization heat treatments at a temperature of 1000°C for one hour interspersed between two successive drawings. At the end of the cold drawing, the wire was annealed at a temperature of 1150°C for one hour in a gas furnace, then pickled and finally drawn on an industrial wire drawing machine to produce a laboratory filler wire of 1.2 mm in diameter, wound into 15 kg coils.

[0154] This manufacturing process is conventionally used to manufacture filler wire in the laboratory and produces a filler wire having the same composition, surface cleanliness and suitability for use as a filler wire as the process previously described for manufacturing filler wire.

[0155] The alloy compositions of each of the filler wires thus obtained are shown in Table 1 below.

[0156] Table 1: Composition of filler wires

[0157] In Table 1 above, alloys with compositions that are not according to the invention are underlined. In this table, “-” means that the element in question is present at most in trace quantities.

[0158] In all alloys, the remainder is iron, plus impurities resulting from the elaboration.

[0159] Finally, the inventors manufactured walls from these wires using an arc-wire additive manufacturing process using a Fronius TPS500i welding station and a Yaskawa MH24 robot, with the following manufacturing conditions:

[0160] Gas: Argon + 2.5% CO2; Flow rate 18L / min

[0161] Fronius CMT process

[0162] Synergy: INVAR WAAM Wire speed: 8.6 m / min

[0163] Welding speed: 30 cm / min

[0164] Arc correction: -1.6

[0165] Dynamic correction: 6.2

[0166] Single scan: amplitude 6 mm; frequency 2 Hz, stops at points 1 and 3 of 0.4 s

[0167] Pause time between passes: 240 s

[0168] Pass increment: 2.5 mm

[0169] Deposition rate: 580 cm 3 / h.

[0170] The walls thus produced have a length of 150 mm, a width of 150 mm and a height of 70 mm.

[0171] For each alloy, the inventors determined the number of drips occurring during the manufacture of the wall, as well as the average coefficient of thermal expansion of the alloy between 20°C and 200°C.

[0172] The number of drips is visually observed on the walls during manufacture.

[0173] The average coefficient of thermal expansion between 20°C and 200°C was measured as follows. The expansion of AL alloys was measured when heated between 20°C and 200°C, then the average coefficient of thermal expansion a[20°C_200°C] between 20°C and AI

[0174] 200°C was calculated using the expression: a[20°C_200°C] = — x — , where AT = 200°C-20°CL o AT and Lo is the initial length of the specimen (50 mm).

[0175] Table 2 summarizes the results of the tests carried out using wires made from alloys Nos. 1 to 22, as well as Invar M93 from Table 1.

[0176] Table 2: Results of wall fabrication tests using the alloys in Table 1

[0177] In Table 2 above, tests which are not according to the invention are underlined.

[0178] The tests carried out by the inventors revealed that the walls made from the Invar M93 filler wire showed numerous drips. This material is therefore not satisfactory for manufacturing tools or parts of tools intended for the manufacture of aeronautical parts in composite material with improved productivity, i.e. with a relatively short inter-pass time as used in the tests.

[0179] Alloys Nos. 1 to 4 of Table 1 above have titanium and / or rare earth contents lower than the lower limits of the corresponding ranges of the alloy according to the invention. The inventors have found that the walls made from wires made from these alloys also have a non-zero number of drips, respectively equal to 7, 5, 3 and 1. These alloys are therefore also not satisfactory for manufacturing tools or parts of tools intended for the manufacture of aeronautical parts in composite material with improved productivity.

[0180] Furthermore, it is observed that alloy No. 1 also has an average coefficient of thermal expansion between 20°C and 200°C lower than the lower limit desired for this application. The inventors believe that this too low value of the average coefficient of thermal expansion comes from the fact that the titanium content is lower than its lower limit in the alloy according to the invention.

[0181] Alloy No. 9 has a titanium content higher than the upper limit of the corresponding range of the alloy according to the invention. This wall does not show any drips. On the other hand, its average coefficient of thermal expansion between 20°C and 200°C is 3.3.10 -6o It 1 and is too high for the application considered.

[0182] Alloys Nos. 10, 11, 14 and 18 have cobalt contents of less than - 1.00 x Ni% + 36.80% and / or less than 0.80% by weight. Walls made from wires made from these alloys do not show any drips. However, the average coefficients of thermal expansion between 20°C and 200°C of these alloys are too high for the application considered.

[0183] Alloys No. 16 and 21 have cobalt contents greater than -1.63 x Ni% + 62.72%. Walls made from wires made from these alloys do not show any drips. However, the average coefficients of thermal expansion between 20°C and 200°C of these alloys are respectively 3.1.10 -6o C -1 and 3.5.10 -6o C -1 and are too high for the application considered.

[0184] Alloy No. 22 has a cobalt content greater than 4.20% by weight. Walls made from wires made from this alloy do not show any drips. However, the average coefficient of thermal expansion between 20°C and 200°C of this alloy is 2.0.10 -6o It 1 and is too weak for the application considered.

[0185] On the contrary, the walls made from the alloy according to the invention, corresponding to compositions No. 5, 6, 7, 8, 12, 13, 15, 17, 19 and 20 do not show any drips. In addition, these alloys have average coefficients of thermal expansion between 20°C and 200°C of between 2.2.10 -6 °C -1 and 2.9.10 -6o C -1, and therefore allow the manufacture of tools or parts of tools intended for the manufacture of aeronautical parts in composite material with improved productivity, that is to say with a relatively short interpass time as used in the context of tests.

Claims

DEMANDS 1. Alloy for the manufacture of tooling intended for the manufacture of aeronautical parts made of composite material, the alloy comprising, by weight: 32.6% < Ni < 38.0% 0.80% < Co < 4.20% with: Co > -1.00 x Ni% + 36.80%, where Ni% denotes the Ni content as a percentage by weight in the alloy; and Co < -1.63 x Ni% + 62.72%, where Ni% denotes the Ni content as a percentage by weight in the alloy 1.0% < Ti < 2.0% 0.0010% < rare earths < 0.0500% 0.10% < If < 0.35% 0.15% < Mn < 0.60% 0.005% < C < 0.04% the remainder being iron and impurities resulting from the processing.

2. Alloy according to claim 1, wherein the impurities resulting from the manufacturing process comprise, by weight: Ca < 0.0015% Mg < 0.0035% Al < 0.0085% O < 0.0025% S < 0.0035% P < 0.0100% B < 0.0005% Mo < 0.1% Cr < 0.1% Cu < 0.1% Number < 0.01% V < 0.01%.

3. Alloy according to claim 1 or 2, wherein the rare earths comprise yttrium, cerium, lanthanum, neodymium, praseodymium or mixtures thereof.

4. Filler wire made from an alloy according to any one of claims 1 to 3.

5. A method for manufacturing a filler wire according to claim 4, the method comprising the following steps: - supply of a semi-finished product made from an alloy according to any one of claims 1 to 3; - hot processing of this semi-finished product to form an intermediate wire; and - transformation of the intermediate wire into a filler wire, of a diameter smaller than that of the intermediate wire, said transformation including a wire drawing step.

6. Use of the alloy according to any one of claims 1 to 3, to manufacture at least part of a tooling intended for the manufacture of an aeronautical part made of composite material.

7. Part (1) or part of a part made of an alloy according to any one of claims 1 to 3.

8. Part (1) or part of part according to claim 7, said part or part of part being obtained by metal additive manufacturing.

9. Part (1) or part of a part according to any one of claims 7 or 8, the part being a tool, in particular a mold, intended for the manufacture of an aeronautical part made of composite material.

10. A method for manufacturing a part or part of a part, comprising a step of manufacturing said part or part of a part by a metal additive manufacturing process using, as a filler material, a filler wire made in the alloy according to any one of claims 1 to 3 and / or a powder made in the alloy according to any one of claims 1 to 3. 11.- Manufacturing process according to claim 10, wherein the additive manufacturing process is selected from an arc-wire, laser-wire, electron beam-wire process and a hybrid additive manufacturing process combining arc-wire and laser-powder or arc-wire and laser-wire technologies.

12. Use of the filler wire according to claim 4 as a filler wire in the context of a metal additive manufacturing process.

13. Metal powder made in an alloy according to any one of claims 1 to 3.

14. Method for manufacturing a metal powder according to claim 13, said method comprising a step of supplying a filler wire according to claim 4, and a step of plasma atomizing this filler wire to obtain the metal powder.

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