ADDED MANUFACTURING PROCESS FOR A METAL WORKPIECE

Description

Technical field of the invention

[0001] The present invention relates to a method for additively manufacturing a metal part. The present invention relates in particular to a method for manufacturing thin parts made of metal alloy, and particularly parts that can form part of an aircraft turbomachine. State of the prior art

[0002] In this text, "additive manufacturing process" means both an initial manufacture of the part and a repair of a part already manufactured (by any technique whatsoever) and of which an area is refilled by "additive manufacturing", that is to say by an addition of material which can be an LMD process as below.

[0003] Thus, we know additive manufacturing processes by depositing material on a part forming a substrate, with a localized energy input which allows the material to be locally brought to the melting temperature.

[0004] If a laser is used to deliver the energy, these processes are called "LMD" for Laser Metal Deposition.

[0005] When a significant height boss is to be formed using such an additive manufacturing process, one of the additive manufacturing processes involves adding material using a metal wire (a technique called LMD wire). This allows several beads of material to be formed, preferably adjacent to each other, obtained by melting a wire serving as a filler metal. The heat source is, for example, a laser beam. By stacking several layers of molten wire, a boss several millimeters high relative to the substrate can be formed.

[0006] However, for thin substrate parts made of metal alloy, typically parts less than 2 mm thick, the LMD technique with wire deposition requires a significant energy input, and this energy input tends to impact and deform the part forming the substrate on which the deposition is carried out.

[0007] If we take for example a structural part like a casing shell, it is typically a part generally extending over a large surface with a local thickness of less than 2 mm and this part must have a plurality of local shapes to fix auxiliary equipment to it.

[0008] Furthermore, there is a constraint on manufacturing times which encourages the planning of rapid processes to obtain the desired parts.

[0009] A need therefore arose to propose a solution for more quickly creating a boss using an additive manufacturing process on a part less than 2 mm thick, without substantially deforming the said part.

[0010] In the configuration of a refill of an existing part, it may be desired that the deformation induced by the addition of material does not exceed a predetermined value, for example 0.5 mm or for example 1 mm, because otherwise there may in certain cases be buckling of the part or a negative impact on the microstructure, this must however be assessed with regard to a very low deposition rate, involving a manufacturing time and a manufacturing cost that is too high. CN 108 161 229 A and US 2012 / 132627 A1 relate to additive manufacturing processes by deposition of material on a part forming a substrate with surface energy control. Summary of the invention

[0011] It is in this context that an additive manufacturing process is proposed by depositing material on a part forming a substrate, said part forming a substrate being made of a metal alloy, the process comprising: / a / - at least one low energy input deposition step, corresponding to a surface energy of less than 400 J / mm 2< , on a predefined surface to be deposited, to form a base layer, / b / - at least one high energy input deposition step, corresponding to a surface energy of greater than 500 J / mm 2< , by depositing a wire (meaning at least one wire) on the already formed base layer, to thus form one or more additional layers, the base layer providing a shielding effect which attenuates the thermal impact of the high energy input step on the substrate part, in which during the low energy input deposition step / a / metal is added in powder form.

[0012] Thanks to these provisions, the heat-affected zone ('HAZ' in acronym) is relatively limited, because the base layer is produced by a low-energy deposition step and regarding the high-energy deposition step(s), the base layer naturally provides a shielding effect which mitigates the thermal impact of the high energy input on the substrate part. However, the productive high-energy deposition steps are used to produce the desired shape in a limited and minimum possible process time given the absence of the need for further machining or forming on the part.

[0013] To obtain the desired surface energy, the following 3 parameters are determined: beam power, surface area of ​​the impact zone and feed rate.

[0014] In various embodiments of the invention, one and / or the other of the following arrangements may optionally be used, taken alone or in combination.

[0015] According to one aspect, the substrate-forming part has a thickness (e3) of less than 2 mm at the target location of the deposition. In this case, the deformation induced by the proposed method will preferably be aimed at of less than 0.3 mm, preferably less than 0.2 mm. The proposed method thus makes it possible to process thin parts, such as certain casings or shells, various trim parts that can be found in the aircraft and in particular in the turbomachine. In this case, for initial manufacturing, the casting step can be simplified and then any desired shape(s) can be added using the proposed method.

[0016] According to another aspect, a maximum deformation stress is further established, said substrate-forming part (3) having to undergo a deformation of less than 1 mm. Advantageously, the method can be applied regardless of the thickness of the substrate-forming part, the parameter forming the limiting stress being the deformation undergone by the part during the recharging process, or even during its initial manufacture if it is very thin.

[0017] According to another aspect, the low energy input deposition step is carried out with a surface energy of between 50 J / mm 2< and 200 J / mm 2< , whereby a low thermal impact on the substrate is advantageously observed. According to one aspect, one pass makes it possible to deposit material to a height of the order of 0.5 mm.

[0018] According to another aspect, the high energy deposition step is carried out with a surface energy of between 800 J / mm 2 and 1200 J / mm 2. According to one aspect, a pass makes it possible to deposit material over a height of between 1 mm and 1.5 mm. This provides rapid execution of the wire passes.

[0019] According to the invention, during the low energy deposition step ( / a / ) metal is supplied in powder form, which is sprayed onto the substrate via the energy source. This gives flexibility and controllability to the process. This technique can be summarized in the same way as the wire LMD technique was presented above, except that the powder then replaces the wire.

[0020] According to another aspect, the energy source is a laser. A first laser source can be used for the deposition step with low power energy input around 500W (to within 10%); a technique called powder LMD. A second laser source can be used for the deposition step with high power energy input around 1000W (to within 10%) or more; a technique called wire LMD.

[0021] It should be noted, however, that for the high-energy deposition step(s), sources other than a laser may be used. Thus, instead of a wire LMD deposition technique, it is possible to use, for example, well-known processes: a TIG process (arc welding process with a non-consumable electrode, in the presence of a filler metal if necessary. TIG is an acronym for Tungsten Inert Gas, where Tungsten refers to the electrode and Inert Gas refers to the type of plasma gas used, or CMT process ((Cold Metal Transfer) which is a welding process which, in comparison with the more conventional MIG / MAG welding, is relatively cold, via a permanent passage from hot to cold.

[0022] The advantage of the laser, however, is that it can perfectly control the impact zone of the energy beam and maintain the energy delivered well.

[0023] In another aspect, the substrate part is formed from a steel-based metal alloy loaded with nickel or titanium. These are high-performance materials for aircraft turbomachine parts.

[0024] In another aspect, the substrate part is formed from INCONEL 718.

[0025] In another aspect, the substrate part is formed from TA6V titanium.

[0026] According to another aspect, a waiting time may be provided between step / a / and step / b / . Whereby it is possible to wait for the temperature of the deposited material to drop before depositing more material on top, this making it possible to limit the thermal impact in the underlying substrate part.

[0027] According to another aspect, several successive low-energy deposition steps may be provided. Optionally, waiting times may be provided between the different low-energy deposition passes. This makes it possible to limit the temperature rise and in particular the local peak temperature in the part forming the substrate under the deposition; this limits the extent of the heat-affected zone.

[0028] According to another aspect, the height of the layer(s) deposited by low energy input has a dimension equivalent to the transverse excursion (R1) of the heat-affected zone. Here, transverse excursion of the heat-affected zone is understood to mean an area around the area having received the deposit and which is thermally affected. For example, for a discoid-shaped deposit, we observe a corolla-shaped area around the discoid shape.

[0029] According to another aspect, several successive high-energy deposition steps can be provided. It is thus possible to form a projection of any desired height, even a fairly large one, by using several high-energy deposition passes.

[0030] In another aspect, the material supplied in powder and / or wire is identical to the substrate material. This results in consistent fusion and optimal crystalline adhesion.

[0031] According to another aspect, the finished shape formed by the base layer (which is the first layer deposited on the substrate) and the additional layer(s) (subsequently deposited on the base layer), forms a boss of height (H5 below) greater than the thickness (e3 below) of the substrate at the location of the deposition of the layers. There is then no longer any real limit to the height of the shape to be produced.

[0032] According to another aspect, provision is made for the use of a thermal martyr piece which is arranged adjacent to the substrate piece opposite the deposition zone. This martyr piece may for example be made of copper and acts as a thermal bridge to evacuate calories.

[0033] A workpiece is defined as a workpiece that is placed opposite the worked face of the workpiece and to which a force is applied to hold it against the workpiece. It preferably has at least locally the same shape as the workpiece.

[0034] It allows, through mechanical support, to reduce the deformations of the part and the sagging that could exist when adding bosses on the reloading area. In addition, such martyr parts are made of copper and thus allow better evacuation of the heat accumulated in the part during work. This makes it possible to limit the deformations of the part during work.

[0035] The present disclosure also relates to an intermediate casing shell of an aircraft turbomachine comprising one or more bosses obtained by the method described above, considered with all or part of its characteristics. This aspect is not covered by the claims. Brief description of the figures

[0036] Other aspects, aims and advantages of the invention will appear on reading the following description of an embodiment of the invention, given by way of non-limiting example. The invention will also be better understood with reference to the attached drawings in which: [ Fig. 1 ] illustrates a low energy deposition step on a metal substrate part according to one embodiment of the invention, [ Fig. 2 ] illustrates a high energy deposition step on the metal substrate part, following the low energy deposition step, [ Fig. 3 ] illustrates a finished form, obtained according to the proposed method, [ Fig. 4 ] illustrates an example of a succession of steps, [ Fig. 5 ] illustrates a part of the shell of a turbomachine casing, [ Fig. 6 ] illustrates an example of an intermediate casing shell of an aircraft turbomachine. In the aeronautical field, turbomachines are complex machines that consist of an assembly of a multitude of technical parts. To manufacture such technical parts, manufacturing processes such as: casting / foundry, forging, stamping, machining, electro-erosion, surface treatment, heat treatment are traditionally used. In addition, additive manufacturing techniques are experiencing significant development, and this is the subject of the following presentation.

[0037] In the various figures, the same references designate identical or similar elements. Detailed description of the invention

[0038] There figure 6 illustrates a shell of an intermediate casing of an aircraft turbomachine, generally referenced 9. It is desired to produce various shapes in projection relative to the main body of the casing 90, that is to say in external projection in the direction of the thickness or the height, the two terms being synonymous; these shapes are generically identified by the reference 5.

[0039] The thickness is the dimension of the part which is at least 10 times smaller than one of its other dimensions, length and width respectively if a flat part is assumed. In the case of the intermediate casing shell 9, the thickness or height are along the Z axis, in the orthonormal X,Y,Z reference frame, the axis of the (annular) shell being (shell mounted in the turbomachine) the X axis, which is the longitudinal axis of the turbomachine, or axis of rotation of the rotor part (turbine / compressor) relative to the stator part (casing for example).

[0040] The proposed method provides for a deposition of metal on a substrate part marked 3. The substrate part has a thickness e3 less than 2 mm at the target location of the deposition. Any thickness e3 between 1 mm and 2 mm is considered for the application of the proposed method.

[0041] The substrate part is made of a metal alloy. The part material may be a nickel alloy of type N18. The part material may be an alloy of type Astroloy ™< . The part material may be an alloy of type INCONEL 718. The part material may be a titanium alloy of type TA6V.

[0042] The proposed method provides for making a first deposit of material with a low thermal impact on the part forming the substrate and then carrying out a second, more productive deposit of material allowing a substantial quantity of material to be deposited quickly above the first deposit.

[0043] More precisely, we expect a first step noted / a / .

[0044] This is a low energy input deposition step / a / . This low energy input is quantified by a surface energy of less than 400 J / mm 2< . Preferably, the deposition can be carried out with a surface energy of between 50 J / mm 2< and 200 J / mm 2< . The material is provided in the form of powder 11. It is a metallic material, similar or identical to the metallic material of the substrate part.

[0045] For the low energy deposition step, a first laser source 4 with a power of around 500W can be used.

[0046] In another aspect, for the low energy input deposition step, the laser power may be between 200 W and 700 W. The scanning speed of the laser may be between 1200 mm / s and 2000 mm / s. The diameter of the surface illuminated by the laser may be between 100 µm and 1 mm. The combination of the laser power, its impact surface and its scanning speed makes it possible to obtain a desired surface energy for a low surface energy input as mentioned above.

[0047] One or more deposition passes can be performed with this low energy input. Advantageously, each pass allows material to be deposited to a height of 0.5 mm (within 20%).

[0048] This forms a base layer, marked 1 for the first pass and respectively 1a, 1b, for the following passes. The passes can be considered as sub-steps (marked a2, a3, in figure 4 ) of the first step / a / .

[0049] After the first step, a second step is planned, noted / b / .

[0050] This is a high energy deposition step / b / . This high energy input is quantified by a surface energy greater than 500 J / mm 2< . Preferably, the deposition can be carried out with a surface energy of between 800 J / mm 2< and 1200 J / mm 2< .

[0051] The material is supplied in the form of wire 21. For the wire in question, it is a metallic material, similar or identical to the metallic material of the substrate part. The wire in question can come from an extrusion process and be stored in a reel or a reel. According to one configuration, the section of this wire is round. However, it is not excluded to have a different section, for example hexagonal, octagonal, decagonal, etc.

[0052] The molten wire is deposited on the already formed base layer. For the high-energy deposition step, a second laser source 4' with a power of around 1000W or more can be used. The source is emitted by a laser head 63, for example a CO2, YAG or other laser type.

[0053] In another aspect, for the high energy input deposition step, the laser power may be between 800 W and 1000 W. The laser scanning speed may be between 100 mm / s and 1500 mm / s. The diameter of the illuminated surface may be between 100 µm and 1 mm. The combination of the laser power, its impact surface and its scanning speed makes it possible to obtain a desired surface energy for a high surface energy input as mentioned above.

[0054] At step / b / , an additional layer is formed, marked 2 for the first pass and respectively 2a, 2b, 2c, 2d for the following passes. The passes can be considered as sub-steps (marked b2, b3) of the second step / b / .

[0055] It is noted that a waiting time can be provided between step / a / and step / b / . By waiting for the temperature of the deposited material to drop before depositing more material on top, this makes it possible to limit the thermal impact in the underlying substrate part; this limits the extent of the thermally affected zone ZAT, both in depth and in transverse excursion.

[0056] The material supplied in powder and / or wire form is preferably identical to the material of the substrate. However, the material supplied, either in powder or wire form, may be of a different shade compared to the material of the substrate 3.

[0057] Generally, more details on how to perform step / b / can be found in document FR3046739 from the applicant.

[0058] On the figure 1 , a metal powder deposition head 61 is shown, with the laser beam 4 centered on the axis A, an annular nozzle for dispensing the powder 11, an annular nozzle for dispensing the argon flow 16. This type of metal powder deposition head associated with a laser beam is known per se and therefore not detailed further in this document.

[0059] In the example illustrated, the head moves towards the right and at the location of the impact of the laser beam 14 the powder melts then solidifies in the form of a bead of deposited material 13.

[0060] On the figure 2 , a head 62 for depositing metal wire 21 is shown, with the laser source 63 emitting a laser beam 4' centered on the axis A, the deposition head 62 extends arranged in front of the axis during the movement of the head.

[0061] In the illustrated example, the head advances to the right and at the location of the impact of the laser beam 24 the wire melts then solidifies in the form of a bead of deposited material 23. The method can provide for back and forth movements to form several beads of melted wire from each other. Optionally, the use of a thermal martyr part, denoted 8, is provided, which is arranged adjacent to the inner surface 30 of the substrate.

[0062] This martyred part 8 can for example be made of copper and acts as a thermal bridge to evacuate calories, and avoid temperature peak zones inside the part forming substrate 3.

[0063] Thanks to the presence of this martyred piece 8, the depth of the heat-affected zone noted 'e' can be limited and remain relatively moderate, especially if we compare it to a deposit with high energy input as a first stage.

[0064] There figure 4 illustrates various time delays. A time delay Tempo2 is provided between the first step / a / and the second step / b / . A time delay Tempo1 is provided between the first two sub-steps of the first step. A time delay Tempo11 is provided between two other sub-steps of the first step.

[0065] On the figure 3 , we note that the height H1 of the layer(s) deposited by low energy input has a dimension equivalent to the transverse excursion R1 of the heat-affected zone ZAT. The transverse excursion of the heat-affected zone can have different forms; it extends around the zone having received the deposit and which is thermally affected. For example, for a discoid-shaped deposit, we observe a corolla-shaped zone around the discoid shape.

[0066] We will typically see H1 and R1 in the order of 2 to 5 mm.

[0067] Generally, the overall deposition rate obtained by the proposed process can reach 800 cm 3 < per hour. For example, for low energy input, the deposition rate can be of the order of 100 cm 3 < / h; for high energy input steps, the deposition rate can be of the order of 1000 cm 3 < / h.

[0068] Depending on the surface area / height ratio, the larger the surface area and the lower the height, the more the low energy input process will be used compared to the high energy input.

[0069] On the figure 5 , we see that several boss shapes can be obtained by the method previously described. For example, a first cylindrical boss 5 with a slightly wider base, another pure cylindrical boss 5', and a boss with a rounded top 5".

[0070] According to another configuration not illustrated in the figures, the thickness of the part forming the substrate is not limited (e3 > 2mm) but the process requires a maximum deformation stress.

[0071] For example, said part forming substrate 3 must undergo a deformation of less than 0.5 mm or less than 1 mm. Starting with one or more low-energy input steps and then continuing with one or more high-energy input steps also makes it possible in this case to limit the thermal impact on the part and to circumscribe the heat-affected zone HAZ to the smallest possible size.

[0072] Note that instead of moving the heads, we could alternatively move part 3 for the deposition(s) while keeping the laser head fixed.

Claims

1. A method for additive manufacturing by depositing material on a part forming a substrate (3), said part forming a substrate being made of a metal alloy, and the method comprising: / a / - at least one step of low-energy deposition, corresponding to a surface energy of less than 400 J / mm2, on a predefined surface to be deposited, to form a base layer (1;1a), / b / - at least one step of high-energy deposition, corresponding to a surface energy greater than 500 J / mm2, by depositing a wire on the base layer already formed, to form one or more additional layers (2;2a;2b), the base layer providing a screening effect that lowers the thermal impact of the high-energy deposition on the substrate part, wherein during the low-energy deposition step, metal in powder form (11) is provided.

2. A method according to claim 1, wherein the said part forming a substrate (3) has a thickness (e3) of less than 2 mm at the target location of the deposition.

3. A method according to claim 1 or 2, wherein a maximum deformation stress is further established, the said part forming a substrate (3) having to undergo a deformation of less than 1 mm.

4. A method according to any of claims 1 to 3, wherein the energy source is a laser (4;4').

5. A method according to any of claims 1 to 4, wherein the part forming a substrate is formed from a metal alloy based on steel loaded with nickel or titanium.

6. A method according to any of claims 1 to 5, wherein provision is made for a waiting time Tempo1 between step / a / and step / b / .

7. A method according to any of claims 1 to 6, wherein provision is made for several successive steps of low-energy depositions.

8. A method according to any of claims 1 to 7, wherein provision is made for several successive steps of high-energy depositions.

9. A method according to any of claims 1 to 6, wherein the material supplied in powder and / or wire form is identical to the material of the part forming a substrate.

10. A method according to any of claims 1 to 8, wherein the finished form (5) formed by the base layer (1; 1a; 1b) and the additional layer(s) (2; 2a; 2b) deposited thereon, forms a boss of height (H5) greater than the thickness (e3) of the part forming a substrate at the location of the deposition.