Additive manufacturing of a metal part

Abstract

Additive manufacturing of a metal part. A layer-by-layer additive manufacturing process for a metal part comprising the movement of an arc welding torch (3) over a substrate (40), wherein, during the movement of the torch (3): - an electric arc (43) is formed, in particular between the torch (3) and the substrate (40), creating a weld pool (45) on the substrate (40), - a metal deposit is made on the substrate (40) using two filler wires (11, 14), the first filler wire (11) being wound towards the welding arc (43), the second filler wire (14) being wound so as to plunge into the weld pool (45), - vibrations are transmitted to the weld pool (45) with the second wire (14). Figure for the abbreviation: Fig. 1

Description

Title of the invention: Additive manufacturing of a metal part technical field

[0001] The present invention relates to the field of metal part manufacturing. The invention relates in particular to a method for the additive manufacturing of a metal part and to an installation for implementing this method. Prior art

[0002] To manufacture metal parts, there are various known processes, the principle of which is to carry out a successive addition of material.

[0003] Successive deposition can, for example, be achieved by powder deposition as in the SLM (selective laser melting) process. This process makes it possible to obtain a part with an equiaxed microstructure by adjusting the deposition parameters.

[0004] It is also possible to use a wire-arc additive manufacturing process or WAAM (in English, "Wire-Arc Additive Manufacturing"). However, this process leads to a microstructure made up of large columnar grains, thus producing parts with relatively weak and anisotropic mechanical properties.

[0005] In order to improve the microstructure of parts produced by WAAM processes, it has been proposed to vibrate the melt pool during deposition by transmitting ultrasound through the substrate, as described, for example, in the article by CJ Todaro, "Grain structure control during metal 3D printing by high-intensity ultrasound." However, with this method, it is complex to control the amplitude of the vibrations in the melt pool because it depends strongly on the geometry of the part, which changes during manufacturing, as well as on the positioning of the vibrating actuator.

[0006] CN113102862 proposes vibrating the molten pool using a non-fusible vibrating needle. Similarly, T. Yuan's article "Grain refining by ultrasonic stirring of the molten pool" proposes vibrating a tungsten metal tip in the liquid metal of the molten pool.

[0007] CN110484843 and the article by Ding Yuan "Grain refining of Ti-6A1-4V alloy fabricated by laser and wire additive manufacturing assisted by ultrasonic vibration" propose to carry out ultrasonic hammering during deposition.

[0008] Takehiko Watanabe's article, "Improvement of mechanical properties of ferritic stainless steel weld metal by ultrasonic vibration," proposes a deposition process using a vibrating filler wire. In this process, the wire must still be sufficiently rigid upon contact with the weld pool to ensure good vibration transmission. To achieve this, the wire must pass under the electric arc as quickly as possible, which can lead to process instability. It is also possible to melting the wire solely by the heat of the melting bath leads to limited deposition rates.

[0009] Kun Zhang's article "Effect of latter feeding wire on double-wire GTA-AM stainless Steel" describes an additive manufacturing process with a TIG torch using two filler wires, one fed towards the welding arc and the other towards the weld pool.

[0010] CN108067715 describes a plasma torch process using two filler wires.

[0011] CN111215898 describes a WAAM method using a vibrating pressure roller on the layer of metal after its deposition.

[0012] CN108356387 proposes to improve the stability of the deposit by using two torches of welding producing two arcs.

[0013] It has also been proposed to produce pulses in the protective gas flow of the torch. However, this method is complex to implement.

[0014] There is a need for a stable additive manufacturing process for a part made of metallic material, with good productivity and enabling the production of a good microstructure. Description of the invention

[0015] The present invention meets this need by means of, according to one of its aspects, a layer-by-layer additive manufacturing process for a metal part comprising the movement of an arc welding torch, in particular with an electrode (fusible or non-fusible), above a substrate, in which, during the movement of the torch:

[0016] - an electric arc is formed, in particular between the torch and the substrate, by example between the electrode and the substrate, a melt pool on the substrate,

[0017] - a metal deposit is made with two filler wires, a first filler wire being unwound towards the welding arc, a second filler wire is unwound so as to plunge into the weld pool,

[0018] - vibrations are transmitted to the melting bath with the second wire.

[0019] The second wire transmits vibrations to the molten pool while simultaneously depositing additional material to complement the material deposited by the first wire. Thanks to the vibrations within the molten pool, the process improves the microstructure of the deposited metal, thereby enhancing the mechanical properties of the manufactured part. It also increases productivity through the double material deposit. The process thus ensures suitable geometry and deposition speed, as well as good mechanical characteristics for the resulting part, including isotropic mechanical properties.

[0020] The process makes it possible, in particular, to obtain a finer microstructure with smaller grains and a lower aspect ratio. In addition, the maximum MUD structure density is reduced, leading to more isotropic properties of the part.

[0021] Furthermore, the use of a second filler wire can take place without adding too much complexity to existing single-wire arc manufacturing processes and without requiring a significant amount of additional energy.

[0022] Unlike some prior art, the transmission of vibrations to the melting bath is not influenced by the bulk, size, material, and geometry of the manufactured part. The process is therefore suitable for manufacturing all types of parts.

[0023] Moreover, since the transmission of vibrations is done by a filler wire, there is little contamination of the deposited metal, unlike some prior art with a non-fusible vibrating needle.

[0024] The use of two filler wires makes it possible in particular to increase the deposition rate compared to a single-wire process, for example, up to about 40%.

[0025] Additive manufacturing is carried out layer by layer. The steps of the process can be carried out successively during the deposition of each of the different layers.

[0026] The welding torch can be moved relative to the substrate at a speed generally between 10 and 100 cm / min, for example 40 cm / min. Bringing wires

[0027] Preferably, the second filler wire is kept away from the welding arc.

[0028] The second wire that dips into the molten bath can also constitute a point Cold temperatures in the molten pool lead to a change in its thermal gradient. In particular, when the second wire vibrates, it can produce a thermal pumping of heat from the molten pool, allowing, for example, control of its cooling.

[0029] The second wire can plunge into a pasty part of the melting bath.

[0030] By "pasty part of the weld pool" is meant the part of the weld pool that is solidifying. This part is located at the rear of the weld pool relative to the direction of movement of the welding torch.

[0031] In this case, the vibrations will be transmitted to the pasty part of the melting bath and will interact with the metal during solidification and cause significant grain germination and decrease their size and aspect ratio.

[0032] The second wire can plunge into the molten bath on its downstream side relative to a direction of advancement of the torch.

[0033] The portion of the second wire immersed in the molten bath is at least partially in a solid state between a point of penetration into the molten bath of the second wire and a total melting point of the second wire, the distance between the penetration point and the total melting point along the second wire being non-zero. This ensures good vibration transmission.

[0034] The diameter of the first wire can be identical to that of the second wire. In this case, the ratio between the winding speed of the first wire and that of the second wire can be between 1.1 and 10, preferably between 2 and 6, better between 3 and 4, for example equal to approximately 3.6.

[0035] The ratio of the quantity of metal deposited on the substrate between the first wire and the second wire can be between 1.1 and 10, preferably between 2 and 6, better between 3 and 4, for example equal to about 3.6.

[0036] The quantity of material deposited therefore comes mainly from the first filler wire. Thus, the first filler wire primarily ensures a good deposition rate, and the second wire primarily ensures the quality of the microstructure and secondarily increases the deposition rate.

[0037] The filler wires may have a diameter between 0.5 mm and 10 mm, in particular between 0.8 mm and 3.2 mm.

[0038] The feed wires can have unwinding speeds between 50 cm / min and 1000 cm / min, in particular between 50 cm / min and 400 cm / min.

[0039] The wires may comprise steel, in particular stainless steel, aluminum alloy, nickel-based alloy, titanium alloy or any other weldable metal or alloy usable in WAAM arc-wire additive manufacturing, for example a Ti64 alloy.

[0040] The material of the first wire can be identical to that of the second wire.

[0041] Alternatively, the material of the first wire may be different from that of the second wire.

[0042] The substrate and the wires can be made of the same material, in particular a titanium alloy. Substrate

[0043] The substrate may have, before implementation of the process, a flat or curved shape, preferably flat.

[0044] The process may include a preliminary step of preparing a substrate surface onto which the deposit will be made. This step may include surface treatment, such as sanding, or cleaning, for example with ethanol.

[0045] The substrate is preferably metallic. The substrate may comprise steel, in particular stainless steel, an aluminum alloy, a nickel-based alloy, a titanium alloy or any other weldable metal or alloy usable in WAAM arc-wire additive manufacturing, for example a Ti64 alloy. Welding torch

[0046] The welding torch can be a standard torch, for example a conventional commercial model.

[0047] The welding torch can, in a known way, produce a flow of protective gas. • Non-fusible electrode#

[0048] The welding torch may include a non-consumable electrode, in particular made of tungsten. In particular, the torch is a TIG (Tungsten Inert Gas) welding torch. • Fuse electrode#

[0049] The first wire can form an electrode wire.

[0050] The welding torch is in particular a MIG torch (in English "Metal Inert Gas"), a MAG torch (in English "Metal Active Gas"), a submerged arc torch or a plasma torch. Vibes

[0051] The transmission of vibrations to the melting bath is achieved by vibrating the second wire, the vibration of the second wire being carried out in particular in a direction substantially perpendicular to the winding axis of the second wire.

[0052] Vibrations advantageously provide energy to induce cavitation in the liquid bath. The amount of energy required to induce cavitation depends on the frequency and amplitude of the vibration, as well as other factors such as the nature of the liquid material in the melting bath.

[0053] The vibration of the second wire can also be carried out in other directions, for example along the longitudinal axis of the wire.

[0054] The maximum vibration amplitude of the second wire can be between 5 pm and 200 pm, in particular around 50 pm.

[0055] The vibration of the second wire can have a frequency between 5kHz and 50kHz, preferably between 20kHz and 30kHz.

[0056] The vibration frequency of the second wire can be constant during the process, for example predetermined according to the deposition parameters.

[0057] The vibration frequency of the second wire can be variable during the process, for example to achieve thermal pumping of the heat from the melting bath with dynamic adjustment, particularly when the wire vibrates along its unwinding direction.

[0058] The vibration pattern of the second wire is in particular sinusoidal, square, triangular, preferably sinusoidal. Device for additive manufacturing

[0059] The invention also relates, according to another of its aspects, independently or in combination with the foregoing, to a device for the additive manufacturing of a a metal part, in particular for implementing the process according to the invention as defined above, comprising:

[0060] - means for connecting to an arc welding torch, in particular a torch with an electrode,

[0061] - a first reel for a first feed wire,

[0062] - a second reel for a second feed wire,

[0063] - a vibratory device for making the second feed wire vibrate. Vibrating device

[0064] The invention also relates, according to another of its aspects, independently or in combination with the above, to a vibratory device for the additive manufacturing of a metal part, in particular for the implementation of the process according to the invention, as defined above.

[0065] The vibrating device includes a means for connecting to an arc welding torch, in particular a torch with an electrode.

[0066] The vibratory device can be adapted to vibrate a second filler wire with a diameter between 0.5 mm and 10 mm, in particular between 0.8 mm and 3.2 mm, for example equal to 1.2 mm.

[0067] The vibrating device can be adapted to vibrate a second feed wire at a frequency between 5kHz and 50kHz, preferably between 20kHz and 30kHz.

[0068] The vibrating device can be adapted to vibrate a second feed wire with a maximum spatial amplitude between 5 pm and 200 pm, in particular around 50 pm.

[0069] The vibrating device can cause the second feed wire to vibrate by transmitting mechanical vibrations. The vibrating device may thus include a vibrating element configured to be brought into contact with the second feed wire, in particular with a portion of the wire exiting a spool.

[0070] The vibrating element can be excited by at least one piezoelectric cell.

[0071] The vibrating element may be a blade, in particular a metallic one, comprising a An opening, including a cavity or notch, configured to be traversed by the second filler wire. The notch may be crescent-shaped, polygonal, square, or triangular.

[0072] The vibrating element can also be a vibrating roller.

[0073] The vibrating element can also be located in a second feed wire reel.

[0074] The contact surface between the vibrating element and the second feed wire is preferably sufficiently small so as not to unduly constrain the unwinding direction. of the second feed wire but large enough to have good transmission of vibrations from the element to the second feed wire.

[0075] The vibrating device may include an articulated arm, in particular along at least two axes. This makes it easy to position the vibrating device relative to the second feed wire.

[0076] The connection means may include a clamp for attaching to the welding torch or to a stand supporting the welding torch, or a screw-on plate. Additive manufacturing facility

[0077] The invention also relates, according to another aspect, independently or in combination with the foregoing, to an installation for the additive manufacturing of a metal part, in particular for implementing the process according to the invention, as defined above, this installation comprising:

[0078] - an arc welding torch, in particular with an electrode,

[0079] - a first reel for a first feed wire,

[0080] - a device, in particular as described above, comprising:

[0081] o a second reel for a second feed wire,

[0082] o a vibratory device for vibrating the second feed wire, including a vibrating device as described previously.

[0083] The torch may include a non-fusible electrode, in particular made of tungsten, and preferably the torch is a TIG (Tungsten Inert Gas) welding torch.

[0084] The first wire can form an electrode wire, the welding torch then preferably being a MIG torch (in English "Metal Inert Gas"), a MAG torch (in English "Metal Active Gas"), a submerged arc torch or a plasma torch.

[0085] The installation may include a movable arm allowing the torch to be moved, the first wire after being unwound from the first reel and the second wire after being unwound from the second reel. Brief description of the drawings

[0086] The invention will be better understood upon reading the detailed description that follows, the non-limiting examples of its implementation, and upon examination of the accompanying drawing, in which

[0087] [Fig-1] illustrates, in perspective, an example of an installation according to the invention,

[0088] [Fig.2] illustrates, in isolation, a part of the vibrating device of the installation of the [Fig.l],

[0089] [Fig.3] illustrates, in isolation, in perspective, the ends of vibrating devices according to the invention,

[0090] [Fig.4] illustrates, schematically, in side view, an example of a process according to the invention,

[0091] [Fig. 5] illustrates, schematically, in side view, another example of a process according to the invention,

[0092] [Fig.6] represents a series of grain maps from three cord cross-sections obtained through additive manufacturing processes, and

[0093] [Fig.7] is a graph representing the grain size and aspect ratio of the grains of the maps of [Fig.6]. Detailed description

[0094] In the following description, identical elements or elements with identical functions bear the same reference numeral. For the sake of brevity, they are not described opposite each figure; only the differences between the embodiments are described.

[0095] In the figures, the actual proportions have not been respected, for the sake of clarity.

[0096] Figure 1 illustrates an installation 1 for the additive manufacturing of a metal part according to the invention.

[0097] The installation 1 comprises a movable arm 2 that can be moved in three directions orthogonal to each other by means of different actuators controlled by a control unit. In [Fig. 1], only the end of the arm 2 is shown for clarity of the drawing.

[0098] The end of the arm 2 may include, as illustrated, an L-shaped piece.

[0099] The installation 1 also includes a welding torch 3, in this example a torch 3 with a non-consumable tungsten electrode 4 of the TIG type.

[0100] The torch 3 is carried by the arm 2 by means of a support 5 positioned on the upper surface of the lower part of the L of the arm 2. This lower part has an opening, not visible, allowing the torch 3 to pass through the part L.

[0101] The torch 3 is connected via a power supply cable 6 to a standard TIG welding station, not shown. As illustrated, the cable 6 can be surrounded by a protective sheath.

[0102] The installation 1 also includes a first feeder 10 of a first filler wire 11, the pen feeder 12 of which is visible on [Fig.1], and a second feeder 13 of a second filler wire 14, the pen feeder 15 of which is visible on [Fig.1].

[0103] The reels 11 and 13 each include, in a known manner, a control panel for the unwinding parameters and a reel, not shown in the drawings for the sake of clarity.

[0104] For example, the pens 12 and 15 are fixed on the arm 2 using supports 16 having a gripping head 17 whose orientation is adjustable.

[0105] The installation 1 also includes a vibrating device 20 comprising a vibrating blade 21 in contact with the second wire 14.

[0106] The blade 21 is partially embedded in a housing 22 and can be set into vibration by means of at least one piezoelectric cell present in the housing 22.

[0107] For example, the housing 22 extends along the elongation axis of the blade 21.

[0108] The housing 22 is connected to an arm 23 which is itself fixed to the arm 2 of the installation 1 by a plate 24 screwed onto arm 2.

[0109] The arm 23 of the vibrating device allows the housing 22 and therefore the blade 21 to be moved in order to bring it into contact with the second wire 14.

[0110] For example, the arm 23 has two linear axes 25 and 26 allowing the housing 22 and the blade to be moved in translation along two directions A and B which are not parallel to each other, in particular orthogonal.

[0111] For example, the arm 23 also includes pivots, in particular three pivots 30, 31 and 32, allowing the housing 22 and the blade 21 to be rotated respectively along the axes A, C and B, the axis C being orthogonal to the axes A and B.

[0112] An enlargement of blade 21 is given in [Fig.2].

[0113] As illustrated, the blade 21 has a substantially constant width L along the elongation axis M. The blade 21 can have a constant thickness E over a major part of its length and a reduction in its thickness E at the outlet 33 of the housing 22.

[0114] For example, the width L is approximately twice the diameter of the second wire 2

[0115] The free end 35 of the blade 21 has, for example, a configured notch 36 to allow the passage of the second wire 14. This notch 36 makes it possible in particular to ensure a stable contact between the blade 21 and the second wire 14.

[0116] For example, as illustrated in Figure 3a, the notch 36 may have a triangular shape with an opening angle of less than 45°. The contact area between the triangular notch 36 and the second wire 14 is small enough not to unduly constrain the winding direction of the second wire 14 but large enough to allow good transmission of vibrations from the blade 21 to the second wire 14.

[0117] For example, as illustrated in Figure 3b, the notch 36 may have a keyhole shape. The opening 100 of the notch 36 has a width less than the diameter of the second wire 14, allowing the latter to be inserted by snapping into the notch 36 through the deformation of arms 101 of the blade 21 that surround the notch 36. Once positioned in the notch 36, the second wire 14 is thus held in place. In addition, the edge of the notch 36 is circular with a diameter slightly larger than the diameter of the second wire 14, allowing the latter to translate within the notch 36 along its unwinding axis. This allows to limit as much as possible the loss of contact between the blade 21 and the second wire 14, the notch 36 forming with the second wire 14 a pivot joint with axis allowing the translation of the second wire 14 along its unwinding axis and the rotation of the second wire 14 around its unwinding axis, the other movements being substantially blocked.

[0118] During the installation of the installation 1, one can begin by positioning the second wire 14 so as to orient its unwinding axis in a predetermined direction and then, once in position, the vibrating device 20, in particular the notch 36, is positioned on the second wire 14.

[0119] Examples of additive manufacturing processes for a metal part are illustrated in Figures 4 and 5.

[0120] In the first example in [Fig.4], installation 1 of figures 1 to 3 is used. It is represented schematically in [Fig.4] for the sake of clarity.

[0121] First, the installation 1 is placed on top of a metallic substrate 40, in this example made of Ti64 alloy. The substrate 40 is in this example of planar shape.

[0122] The surface 41 of the substrate 40 on which the deposit will be made may undergo a preliminary surface treatment, for example cleaning.

[0123] The torch 3, the first wire 11, the second wire 14 and the vibrating device 20 are then set in motion above the substrate 40 in a direction of advancement D to form a first layer 42, at a speed for example between 30 cm / min and 60 cm / min.

[0124] During movement, the torch 3 forms an arc 43 between the substrate 40 and the electrode 4, thus generating a molten pool 44 on the substrate 40. The arc 43 is protected by a laminar flow of protective gas coming from the torch 3.

[0125] In parallel, the first wire 11 and the second wire 14 are unwound so as to make a deposit 45 of metal on the substrate 40.

[0126] For example, wires 11 and 14 have a diameter of 1.2 mm and are made of a Ti64 alloy.

[0127] The ratio between the winding speed of the first wire 11 and that of the second wire 14 is here between 3 and 4. The diameters being for example identical for the wires 11 and 14, the ratio of quantity of material deposited between the wires 11 and 14 is also between 3 and 4.

[0128] The first wire 11 is unwound towards the welding arc 43 so as to melt the end 50 of the first wire 11 with the energy of the arc 43.

[0129] The second wire 14 is unwound so as to plunge into the melting bath 44 downstream of it relative to the advance direction D, in this example in its pasty part 51.

[0130] The second wire 14 is moved away from the arc 43, allowing its end 52 to be immersed in the molten pool 45 in a solid state. The solid part of the end 52 melts as it is immersed in the molten pool 45, allowing a second supply of material.

[0131] In particular, the second wire 14 is in a solid state between its point of penetration 521 in the melting bath 45 and a total melting point 522 of the second wire 14, the distance separating the point of penetration 521 and the total melting point 522 along the second wire 14 being non-zero, in particular at least 1 mm.

[0132] The second wire 14 thus functions as a "cold wire", that is to say that it melts without substantial input of additional energy, in comparison with the first wire 11, which is a "hot wire", that is to say that its melting is caused by an input of heat much greater than the heat supplied to the second wire 14.

[0133] The second wire 14 vibrates under the action of the blade 21 of the vibrating device 20.

[0134] The vibration is for example carried out along an axis perpendicular to the direction of advancement D and the unwinding axis L2 of the second wire 14.

[0135] The second wire 14 vibrates according to a sinusoidal periodic pattern with a frequency between 20kHz and 30 kHz and a spatial amplitude between 5 pm and 200 pm.

[0136] The vibrations of the second wire 14 propagate to the melt pool 45 via the end 52.

[0137] Next, the melt bath 45 cools until solidification so as to form, continuously, the layer 42.

[0138] Fig. 5 represents a variant of the process of Fig. 4.

[0139] In this variant, the installation 1 includes a torch 3 with a fusible electrode 4, for example a MIG welding torch 3.

[0140] The electrode 4 is here formed by the first wire 11, thus forming a wire-electrode.

[0141] Moreover, the second wire material 14 comprises, for example, a different material of that of the first thread 11.

[0142] On [Fig.5], a first layer 42 has been made on a substrate 40 and a second layer 55 is being made on the first layer 42. Examples

[0143] Figures 6 and 7 illustrate the microstructure of three metal parts produced by three different additive manufacturing processes with a non-fusible TIG electrode.

[0144] The first is a single-wire filler process, the second a process with two filler wires, a first filler wire being unwound towards the welding arc, a second filler wire being unwound so as to plunge into the weld pool, the second wire not transmitting vibrations to the weld pool, and the third a process according to the invention, namely with two filler wires, one of which is vibrating.

[0145] In the three tests, the electrode 3 is positioned 4 mm above the substrate 40, and moved at a speed of 40 cm / min, the electrical current in the TIG electrode is 185 A, the substrate 40 and the filler wires are made of Ti64 and the filler wires have a diameter of 1.2 mm.

[0146] In the single-wire process, the filler wire is unwound at a speed of 420 cm / min.

[0147] In the other two processes, the first filler wire is unwound at a speed of 360 cm / min and the second wire at a speed of 100 cm / min.

[0148] Figure 6 illustrates EBSD mapping (Electron Backscattered Diffraction") of weld bead cross-sections produced using the three processes. This mapping allows visualization of the G grains of the bead microstructure.

[0149] Cord a) corresponds to the single-wire process, cord b) to the process with two wires without vibration and cord to the process according to the invention.

[0150] These EBSD maps allow visualization of the size of the grains G as well as their shape, in particular their aspect ratio between their largest dimension and their smallest dimension.

[0151] The average grain size T and the average aspect ratio Ra of the maps in [Fig.6] are illustrated in the graph in [Fig.7].

[0152] In the graph, columns a) represent the single-wire process, columns b) the two-wire process without vibration and columns c) the process according to the invention.

[0153] As clearly visible, the average grain size T and the average aspect ratio Ra of the third process are smaller than those of the other two tests. The grains of the bead obtained by the process of the invention are therefore finer and more equiaxed, which improves the mechanical properties and makes them more isotropic compared to the other two processes.

[0154] Furthermore, the maximum MUD texture density is 9.21 for the single-wire process, 10.60 for the two-wire process without vibration, and 6.66 for the process according to the invention. The invention therefore makes it possible to obtain a reduced solidification texture and thus more isotropic properties.

[0155] The invention is not limited to the examples just described.

[0156] In particular, the substrate may have a different composition or shape, for example be curved.

[0157] The vibration of the second wire can be different, for example take place along the wire unwinding axis.

[0158] The vibrating element may be different, for example in the form of a vibrating roller or a vibrating reel.

Claims

Demands

1. A layer-by-layer additive manufacturing process for a metal part comprising the movement of an arc welding torch (3) over a substrate (40), wherein, during the movement of the torch (3): - an electric arc (43) is formed, in particular between the torch (3) and the substrate (40), a weld pool (45) on the substrate (40), - a metal deposit is made on the substrate (40) with two filler wires (11, 14), a first filler wire (11) being wound towards the welding arc (43), a second filler wire (14) being wound so as to plunge into the weld pool (45), - vibrations are transmitted with the second wire (14) to the weld pool (45).

2. A method according to claim 1, wherein the ratio of the amount of metal deposited on the substrate between the first wire (11) and the second wire (14) is between 1.1 and 10, preferably between 2 and 6, better between 3 and 4, for example equal to about 3.

6.

3. A method according to any one of claims 1 and 2, wherein the material of the first wire (11) is identical to that of the second wire (14).

4. A method according to any one of the preceding claims, wherein the second wire (14) dips into the molten pool (45) on the downstream side thereof, relative to a forward direction (D) of the torch (3).

5. A method according to any one of the preceding claims, wherein the portion of the second wire (14) immersed in the molten bath (45) is at least partially in a solid state between a penetration point (521) in the molten bath (45) of the second wire (14) and a total melting point (522) of the second wire (14), the distance separating the penetration point (521) and the total melting point (522) along the second wire (14) being non-zero.

6. A method according to any one of the preceding claims, wherein the diameter of the first wire (11) is identical to that of the second wire (14), the ratio between the winding speed of the first wire (11) and that of the second wire (14) being between 1.1 and 10, preferably between 2 and 6, better between 3 and 4, for example equal to approximately 3.

6.

7. A method according to any one of the preceding claims, wherein the welding torch (3) comprises a non-consumable electrode (4), in particular made of tungsten, in particular the torch (3) is a TIG (Tungsten Inert Gas) welding torch.

8. A method according to any one of claims 1 to 6, wherein the first wire (11) forms a wire electrode, the welding torch (3) being in particular a MIG (Metal Inert Gas) torch, a MAG (Metal Active Gas) torch, a submerged arc torch or a plasma torch.

9. A method according to any one of the preceding claims, wherein the vibration of the second wire (1) is carried out in a direction substantially perpendicular to the winding axis of the second wire (14).

10. A method according to any one of the preceding claims, wherein the maximum vibration amplitude of the second wire (14) is between 5 pm and 200 pm

11. A method according to any one of the preceding claims, wherein the vibration of the second wire (14) has a frequency between 5kHz and 50kHz, preferably between 20kHz and 30 kHz, the vibration pattern of the second wire (14) being in particular sinusoidal, square, triangular, preferably sinusoidal.

12. A method according to any one of the preceding claims, wherein the substrate (40) and the wires (11, 14) are made of a titanium alloy.

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