Method for manufacturing a metal alloy part

Abstract

The invention relates to a method for manufacturing a metal alloy part, comprising the following steps: - supplying (E11, E12) at least one metal alloy by recycling parts, - atomizing (E2) the parts in order to obtain a powder (P), - manufacturing (E5) the part by additive manufacturing, by means of laser powder bed fusion.

Description

Method for manufacturing a part made of a metal alloy

[0001] The invention relates to a method for manufacturing a part made of metal alloy. This method uses additive manufacturing of the 3D printing type.

[0002] It is known that machining is used to manufacture a part from a metal alloy. This involves starting with a blank larger than the final part and removing excess material by chipping. This technology, called subtractive machining, results in a significant loss of material in the form of chips, depending on the volume of excess material removed.

[0003] It is still common practice to manufacture a part from a metal alloy by casting or forging. These technologies, which come in many variations, require the creation of a mold (casting) or tooling (forging). This costly step is only economically viable for a large number of identical parts produced.

[0004] It has recently become known that 3D printing is a method for manufacturing metal alloy parts. This type of 3D printing involves building the part layer by layer through the successive addition of material. This technology is called additive manufacturing. Its advantage lies in its ability to create complex shapes that are inaccessible to machining, forging, or casting due to the inherent constraints of these techniques, such as the need for draft angles to allow for demolding or removal of the forging tool. Crucially, this technology is advantageous because it wastes little to no material. This is particularly beneficial for alloys, some components of which are seeing their prices rise daily. Furthermore, this technology is especially well-suited for producing parts in small batches.

[0005] One 3D printing technique for metal alloy parts is laser powder bed fusion or LPBF (from the English "Laser Powder Bed Fusion").

[0006] The material in question is a metallic alloy. The current problem that the invention aims to address is the difficulty in sourcing certain alloys or alloying elements. This difficulty may stem from: a tight global market, delicate geopolitical situations making access to deposits difficult, the scarcity of certain components due to overconsumption, or strong competitive demand. This results in supply difficulties and / or a drastic increase in material costs. Conversely, stocks of parts that are out of service, non-compliant for their intended use, or destined for scrap remain unused.

[0007] This supply issue is compounded by a technical manufacturing challenge: ensuring just-in-time production of finished parts. This just-in-time approach means identifying a technical solution that optimizes the use of alloy resources available to industrial players. Producing new parts from recycled materials presents a challenge because the recycled materials may be slightly different alloys, with variations in alloying element content within the limits specified below. The difficulty lies in achieving sufficiently good physical and mechanical characteristics in the new parts, meaning they meet the manufacturer's technical specifications. Specifically, the just-in-time solution aims to provide an economical solution tailored to industrial needs.

[0008] Therefore, a manufacturing process is needed that can utilize existing stocks of parts of varying compositions within the same alloy family (recycling), is economical in material use, and is preferably suitable for small-batch production. This manufacturing process can, in particular, be used to support the concept of "just-in-time" production by enabling the achievement of different quality levels depending on the parameters used.

[0009] The invention aims to provide a manufacturing process that meets these criteria.

[0010] For this purpose, the invention relates to a method for manufacturing a new part in metal alloy, comprising the following steps: - supplying at least one metal alloy by recycling parts, - atomizing the recycled parts, so as to obtain a powder, - manufacturing the new part by additive manufacturing, by laser powder bed fusion, using the powder previously obtained.

[0011] Specific characteristics or embodiments, usable alone or in combination, include: - the procurement stage includes identification of parts to be recycled by chemical analysis of the material,

[0012] According to the present invention, the term "material" means any metallic alloy.

[0013] According to a preferred embodiment of the invention, the material according to the invention is an alloy of copper, aluminum, iron and nickel, preferably with a copper content of between 65 and 96%, an aluminum content of between 4 and 15%, an iron content of between 0 and 10%, and a nickel content of between 0 and 10%,

[0014] The proportion of each metal in the metallic alloy is expressed in % (m / m) m / m meaning mass of element over mass of alloy.

[0015] - The supply stage includes identification of parts to be recycled by recognizing their shape; - The material supply stage also includes a dry sandblasting stage to remove a superficial layer of material; - The material atomization stage is carried out by gas atomization; - The material atomization stage is carried out by ultrasonic atomization; - The material atomization stage is carried out by grinding and spheroidization; - The atomization stage is followed by a powder sieving stage, comprising a mechanical sieving stage by passing through a vibrating sieve with at least one stage and a pneumatic classification or elutriage stage; - The resulting powder has a particle size distribution between 15 and 45 µm, with a Gaussian distribution; - The resulting powder has a particle size distribution between 10 and 63 µm, with a Gaussian distribution.- The 3D printing parameters are as follows: laser power is between 250 W and 400 W, preferably 250 W; laser scanning speed is between 800 mm / s and 1400 mm / s, preferably 1100 mm / s; the distance between two scanned lines is between 0.08 mm and 0.12 mm, preferably 0.1 mm; the laser beam diameter is between 0.05 mm and 0.1 mm, preferably 0.08 mm; and the layer thickness is between 0.02 mm and 0.1 mm, preferably 0.03 mm. - The process also includes, between the atomization and manufacturing stages, a chemical and rheological powder control stage. - The material is an alloy of copper, aluminum, iron, and nickel, with a copper content between 65 and 96%, an aluminum content between 4 and 15%, an iron content between 0 and 10%, and a nickel content between 0 and 10%,

[0016] In a further preferred embodiment, the material according to the invention is a metallic alloy consisting of a copper content of 88%, an aluminum content of 10% and an iron content of 2% and a nickel content of 0% or alternatively a copper content of 80%, an aluminum content of 10% and an iron content of 5% and a nickel content of 5%.- the powder P obtained is derived from a mixture of several recycled parts whose exact composition differs from one part to another while remaining alloys of copper, aluminum, iron and nickel, with a copper content between 65 and 96%, an aluminum content between 4 and 15%, an iron content between 0 and 10%, and a nickel content between 0 and 10%.

[0017] According to one embodiment, the powder P obtained according to the invention is derived from a mixture of several parts to be recycled, the composition of which consists of a metallic alloy comprising a copper content of 88%, an aluminum content of 10% and an iron content of 2% and a nickel content of A% or a copper content of 80%, an aluminum content of 10% and an iron content of 5% and a nickel content of 5%.

[0018] The invention will be better understood upon reading the following description, given solely by way of example, and with reference to the figures in the appendix in which:

[0019] shows, a flowchart of the process,

[0020] demonstrates the principle of 3D printing by laser powder bed fusion,

[0021] shows, in perspective view, a gas atomization tower,

[0022] shown in a cutaway perspective view, the atomizer boiler from the previous figure,

[0023] The diagram shows, in cross-section, the outlet of the atomizer crucible from the two preceding figures and the principle of gaseous atomization.

[0024] shows a diagram illustrating a powder distribution.

[0025] shows, in schematic view, the ultrasonic atomization process with plasma fusion or TIG.

[0026] shows, in schematic view, the ultrasonic atomization process with induction crucible melting.

[0027] With reference to the [reference to the relevant document], the invention relates to a method for manufacturing a part made of a metal alloy. This manufacturing method comprises the following steps.

[0028] In a first step E11, E12, at least one metal alloy is supplied. According to an important feature of the invention, this supply of metal alloy is achieved by recycling parts. These parts may be old or scrap parts, or machining chips. This advantageously allows for obtaining at least one inexpensive metal alloy, since parts are reused. These parts may be old parts, typically parts that have been replaced at the end of their functional life due to wear. They may also be scrap parts, typically parts with a manufacturing defect that have been discarded. Finally, they may be machining chips or waste. These metal alloys are economically inexpensive because they come from available and amortized stock or from lost material.These metal alloys are especially inexpensive from an environmental standpoint, since they do not require new extractive resources.

[0029] The selected parts belong to the same alloy family, copper-aluminum, also known as aluminum bronze. The terms alloy family or alloy range refer to the compositions of copper-aluminum. Copper-aluminum is an alloy of copper, aluminum, iron, and nickel, with a copper content between 65% and 96%, an aluminum content between 4% and 15%, an iron content between 0% and 10%, and a nickel content between 0% and 10%. The parts to be recycled may be of exactly the same composition and processed to be as pure as possible. These parts may also undergo less extensive and therefore less expensive processing. Finally, these parts may be of slightly different alloys, within the limits mentioned above.

[0030] In another step E2, the supplied material is atomized to obtain a powder P. This powder is necessary for the manufacturing step E5.

[0031] In a final step E5, the part is manufactured. This manufacturing is carried out using additive technology, preferably laser powder bed fusion or LPBF (from the English "Laser Powder Bed Fusion").

[0032] With reference to the [reference to the previous text], powder bed fusion works as follows. A vat contains a powder P consisting of calibrated microbeads of the material from which the part is to be made. The surface of the powder P is aligned with a 3D printing current plane. This printing current plane evolves during the E5 manufacturing step from the bottom to the top, as indicated by the upward arrow. This defines the Z direction, with the powder plane P defining an XY plane. In the printing current plane, the laser L fuses the powder P at a point x, y. The succession of fusion points x, y, in the printing current plane, creates a section of the part belonging to that printing current plane. In each successive XY printing plane, from bottom to top, the fusion thus allows the creation of a layer of the part.Plan by plan, the piece is built from the bottom up, each new layer merging with the previous layer below.

[0033] It has been observed that the metal alloy(s) are sourced from stocks of old parts, scrap, or shavings. Before recycling a part to recover its material and produce a powder P suitable for printing using LPBF technology, it is necessary to verify that the recycled part is indeed made of the correct material, i.e., one of the candidate metal alloys.

[0034] If several parts are processed simultaneously, the invention provides for the possibility of producing a powder P from parts that do not necessarily have the same composition. The composition of this powder P is therefore variable. The composition of powder P corresponds to an average composition relative to that of the recycled parts, meaning that the content of each element is the average of that of the parts introduced into the process. In all cases, this composition remains within the limits mentioned previously.

[0035] According to a first embodiment, the procurement step includes identifying candidate parts, that is, parts made of one of the candidate metal alloys that can be recycled. This identification is carried out by chemical analysis of the metal alloy of the part. This chemical analysis can be performed by any technique capable of determining or verifying the composition of a given metal alloy. For example, it can be performed by ICP (Inductively Coupled Plasma), an analytical technique using inductively coupled plasma to measure the content of an inorganic element present in a sample, or by EDX in a scanning electron microscope (Energy Dispersion X-ray Spectroscopy), which, by exciting the atoms of a sample with an electron beam, causes them to emit characteristic X-rays that are analyzed to identify and quantify the elements present.

[0036] Alternatively, in another embodiment, it is taken into account that the stock of old or scrap parts or shavings is not arbitrary. Indeed, this stock contains a limited number of part numbers. Moreover, advantageously, a given part is always made from a known range of alloys. Therefore, advantageously, the identification of candidate parts—that is, parts made from candidate metal alloys that can be recycled—is carried out by shape recognition. This shape recognition can be performed, for example, by an operator who observes and compares the parts to a drawing or a known part, or alternatively by taking a photograph and using a computer program trained for recognition by machine learning. Shape recognition, especially in a stock with a limited number of part numbers, is relatively simple to implement and is much simpler than chemical analysis.This pattern recognition indirectly allows us to determine the range of metal alloys, since in this case there is an injective function between the shapes of the parts and their material. Pattern recognition can be performed using any method.

[0037] Given that these are old parts and may have been stored for a long time without specific preservation measures, their surface condition, particularly due to oxidation, is likely no longer pristine. Therefore, according to another characteristic, in order to remove a degraded surface layer of material, the material supply step E11, E12 includes a further dry blasting step E12. This step aims to remove a thin layer of surface material. This thickness is advantageously between 50 and 500 µm, in order to expose sound material.

[0038] LPBF technology requires that the input material be introduced as a powder P composed of regular and calibrated microbeads. Therefore, starting with large pieces to be recycled, the process includes an atomization step E2 to obtain such a powder P.

[0039] Parts to be recycled of at least one composition are mixed for the atomization stage in a way that advantageously limits sorting and fine identification operations.

[0040] The parts to be recycled into the various candidate metal alloys are supplied together to the atomization process to be transformed back into a powder P. The advantage of the process is that it allows mixing at this stage, different alloys of the same family thus limiting sorting and identification operations.

[0041] Any technique that allows for obtaining such a P powder could be a candidate. We will mention three techniques here as examples.

[0042] According to another characteristic, the E2 atomization step of the material is carried out by gas atomization. Gas atomization can be of the EIGA type or the VIGA type. The EIGA process (from the English "Electrode Induction Melting Gas Atomization") consists of gas atomization by electrode induction. The VIGA process (from the English "Vacuum Induction Melting Gas Atomization") consists of gas atomization by induction under vacuum. Such VIGA gas atomization is carried out using an atomizer of the type illustrated in Figures 3-5.

[0043] As illustrated in Figure 1, an atomizer 1 comprises a boiler 2 in which the material is heated until it becomes liquid. Following this boiler 2 is an atomization chamber 3. At the heart of the atomizer 1 is the atomization zone 7. A gas flow circulates between an inlet 5 and an outlet 6. In the atomization zone 7, the gas flow encounters the liquid material to effectively perform atomization. The particles or microbeads thus produced cool and solidify as they fall through the atomization chamber 3. They are collected in a container 4.

[0044] Referring to the diagram, a close-up shows the boiler 2 and its interior. The boiler 2 contains a crucible 8. This crucible 8 holds the material to be atomized. The crucible 8 is heated by an inductor 9. The heated crucible 8 melts the material. The crucible 8 extends at its base into a nozzle 11. A stopper rod 10 allows the outlet from the crucible 8 to the nozzle 11 to be selectively opened or closed.

[0045] With reference to the, zooming in again on the atomization zone 7. We are here at the end of the nozzle 11. The molten metal 12 flows through the nozzle 11. Here it meets a flow of gas 13 which circulates around the metal 12 within a constriction 14 so as to pulverize the metal 12 into a powder P.

[0046] This powder P cools during its fall along the atomization chamber 3 until it is collected in the pot 4 provided for this purpose.

[0047] According to an alternative feature, the E2 atomization step of the material is carried out by ultrasonic atomization. This embodiment is preferred for the process because it is better suited to the small quantities of material to be atomized, linked to the criterion of small batches.

[0048] In the ultrasonic atomization process, illustrated with reference to the diagram, the material is melted by induction ( ), TIG, or plasma ( ). It is supplied in the form of a metal rod or wire 16 in the case of TIG or plasma, or in any form placed in a crucible 22 in the case of induction. The molten metal 20 comes into contact with a sonotrode 19 with a frequency between 20 kHz and 60 kHz. The ultrasonic vibration breaks the molten metal 20 into small droplets 21 whose diameter depends on the frequency, viscosity, and density of the liquid metal 20. The droplets 21 are ejected, in an atmosphere of neutral gas 17, as spheres due to surface tension and solidify rapidly into a metallic powder upon cooling.

[0049] According to another, alternative characteristic, the E2 atomization step of the material can be carried out by a grinding and spheroidization process.

[0050] The composition of the P powder may vary slightly from one batch of recycled parts to another. "Slightly" means that the composition necessarily remains within the limits mentioned previously.

[0051] Regardless of the atomization process E2 chosen, it may produce a powder P containing unsuitable microbeads due to their shape, for example, non-spherical, or due to their diameter, which may be too small or too large. Therefore, the atomization step E2 is advantageously followed by a sieving step E31, E32 of the powder P from the atomizer 1. This sieving step E31, E32 is advantageously carried out in two stages E31, E32, which can be performed in any order. According to another characteristic, the sieving step E31, E32 includes a mechanical sieving step E31 by passing the powder through a vibrating sieve with at least one stage. This step 31 is typically carried out using a sieve shaker. This sieve shaker passes the powder P through a sieve, the mesh size of which defines the maximum size of the separated microbeads. The sifter is typically equipped with an ultrasonic system that makes the sieve cloth vibrate.The ultrasonic system ensures better particle passage through the mesh and limits sieve clogging. Mechanical sieving of the P powder is performed with a mesh size corresponding to the maximum diameter of the microbeads, in this case 45 µm. This sieving process removes, by retaining them, particles that are too large, as well as non-spherical particles, such as flakes (particles crushed against the atomizer walls that have not had time to solidify) and large impurities.

[0052] The main purpose of this step is to remove particles that are too large and could cause a problem during fusion.

[0053] According to another characteristic, the E31, E32 sieving step still includes a pneumatic sieving or classification or lutriage step E32.

[0054] To efficiently separate particles with diameters less than 15 µm, pneumatic classification equipment is used. Pneumatic classification allows for separation within fine particle size ranges (from 5 to 40 µm). The principle of pneumatic separators is based on separating particles dispersed in a gaseous medium according to their settling velocity within a carrier gas. Within this gas stream, the trajectory of the particles is determined by their dimensions. It is therefore possible to sort these particles according to their size. Pneumatic classification is used to separate and eliminate particles with a diameter less than 15 µm.

[0055] The main purpose of this step is to remove particles that are too small. These particles are likely to clump together and obstruct the flow of the P powder when feeding the 3D printer.

[0056] Powder P contains approximately spherical microbeads with a diameter that is neither too large to be melted sufficiently quickly by the laser, nor too small to agglomerate. Therefore, a powder P with a particle size distribution between 5 and 100 µm is advantageously selected. Preferably, the distribution is between 15 and 45 µm. The distribution within this powder P is Gaussian. Alternatively, the distribution is between 16 and 63 µm. The distribution within this powder P is Gaussian.

[0057] This illustrates such a distribution. Curve C1 shows the volume fraction of particles as a function of diameter and curve C2 shows the same volume fraction cumulatively.

[0058] According to another characteristic, the process also includes, between the atomization step E2 and the manufacturing step E5, a chemical and rheological control step E4 of the powder P.

[0059] Rheological control consists of verifying the properties of the powder P, and primarily its flowability. This measurement is performed by a standard Hall cone flowability test of the powder P.

[0060] Chemical testing involves verifying the chemical composition of the powder P to check the quality of the material. It is typically performed by scanning electron microscopy (EDX, from "Energy Dispersive X-ray") or preferably ICP (Inductively Coupled Plasma).

[0061] Next, the P powder is transferred to the manufacturing stage by 3D printing.

[0062] A wide range of alloys can be obtained after atomization, enabling the LPBF process. This is where one of the process's challenges lies. A range of acceptable metallic alloy variability for obtaining an acceptable P powder has been studied. This range, described later, allows for porosity levels between 0 and 1%. The porosity level is measured by image analysis on a polished section of a 3D-printed sample. The selected range of variability results in a porosity of approximately 0.05% for a test batch.

[0063] According to another characteristic, the 3D printing parameters that emerged from the tests, and which give satisfactory results, mentioned previously, are as follows: the laser power L is between 250 W and 400 W, preferably equal to 250 W, the laser scanning speed is between 800 mm / s and 1400 mm / s, preferably equal to 1100 mm / s, the distance between two scanned lines is between 0.08 mm and 0.12 mm, preferably equal to 0.1 mm, the diameter D of the laser beam is between 0.05 and 0.1 mm, preferably equal to 0.08 mm and the thickness e of a layer is between 0.02 mm and 0.1 mm, preferably equal to 0.03 mm.

[0064] The material of a part produced in this way exhibits a homogeneity of material and mechanical characteristics that are more than satisfactory, in terms of value and homogeneity, compared, for example, to a material from a foundry.

[0065] According to another characteristic, the process is more particularly applicable to parts to be recycled made of copper, aluminum, iron and nickel alloy, with a copper content between 65 and 96%, an aluminum content between 4 and 15%, an iron content between 0 and 10%, and a nickel content between 0 and 10%.

[0066] Examples of metal alloy part material that can be recycled for the process, corresponding to the above conditions, include: CuAl10Fe2, CuAl10Ni3Fe2, CuAl10Fe5Ni5, and CuAl11Fe6Ni6.

[0067] The invention has been illustrated and described in detail in the drawings and the preceding description. This description is to be considered illustrative and given by way of example, and not as limiting the invention to this single description. Numerous embodiments are possible.

[0068] 1: atomizer, 2: boiler, 3: atomization chamber, 4: powder collection pot, 5: gas inlet, 6: gas outlet, 7: atomizer core, 8: crucible, 9: inductor, 10: plug, 11: nozzle, 12: molten material, 13: gas flow, 14: choke, 15: tungsten electrode, 16: metal rod, 17: inert gas flow, 18: plasma arc, 19: sonotrode, 20: molten metal, 21: metal particles, C1: density, C2: cumulative density, D: beam diameter, e: layer thickness, E11: material supply, E12: sandblasting, E2: atomization, E31: mechanical sieving, E32: pneumatic sieving, E4: control, E5: LPBF printing, L: laser, P: powder.

Claims

A method for manufacturing a new part made of a metal alloy, characterized in that it comprises the following steps: - supplying (E11, E12) at least one metal alloy by recycling parts, - atomizing (E2) the recycled parts, so as to obtain a powder (P), - manufacturing (E5) the new part by additive manufacturing, by laser powder bed fusion, using the powder (P) previously obtained. A method according to claim 1, wherein the supply step includes identifying parts to be recycled by chemical analysis. A method according to claim 1, wherein the supply step includes identifying parts to be recycled by recognizing the shape of the parts. A method according to any one of claims 1 to 3, wherein the material supply step (E11) further comprises a dry sandblasting step (E12) to remove a superficial layer of material. A method according to any one of claims 1 to 4, wherein the atomization step (E2) of the material is carried out by gas atomization. A method according to any one of claims 1 to 4, wherein the atomization step (E2) of the material is carried out by ultrasonic atomization. A method according to any one of claims 1 to 4, wherein the atomization step (E2) of the material is carried out by grinding and spheroidization. A method according to any one of claims 1 to 7, wherein the atomization step (E2) is followed by a sieving step (E31, E32) of the powder (P) comprising a mechanical sieving step (E31) by passing through a vibrating sieve with at least one stage and a pneumatic classification or elutring step (E32). A process according to claim 8, wherein the powder (P) obtained has a particle size distribution between 15 and 45 µm, with a Gaussian distribution. A process according to claim 8, wherein the powder (P) obtained has a particle size distribution between 10 and 63 µm, with a Gaussian distribution. A method according to any one of claims 1 to 10 wherein the 3D printing parameters are as follows: the laser power is between 250 W and 400 W, preferably equal to 250 W, the laser scanning speed is between 800 mm / s and 1400 mm / s, preferably equal to 1100 mm / s, the distance between two scanned lines is between 0.08 mm and 0.12 mm, preferably equal to 0.1 mm, the diameter of the laser beam is between 0.05 mm and 0.1 mm, preferably equal to 0.08 mm and the thickness of a layer is between 0.02 mm and 0.1 mm, preferably equal to 0.03 mm. A process according to any one of claims 1 to 11, further comprising, between the atomization step (E2) and the manufacturing step (E5), a chemical and rheological control step (E4) of the powder (P). A method according to any one of claims 1 to 12, wherein the material is an alloy of copper, aluminum, iron and nickel, with a copper content of between 65 and 96%, an aluminum content of between 4 and 15%, an iron content of between 0 and 10%, and a nickel content of between 0 and 10%. A process according to any one of claims 1 to 13 wherein the powder P obtained is derived from a mixture of several parts to be recycled, the exact composition of which differs from one part to another, remaining alloys of copper, aluminum, iron and nickel, with a copper content between 65 and 96%, an aluminum content between 4 and 15%, an iron content between 0 and 10%, and a nickel content between 0 and 10%. A process according to any one of claims 1 to 14, or the powder P obtained is derived from a mixture of several parts to be recycled, the composition of which is 88% copper, 10% aluminum, 2% iron, and 0% nickel, or 80% copper, 10% aluminum, 5% iron, and 5% nickel.

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