EP3924122A1

EP3924122A1 - Method of additive manufacturing with separation via a frangible zone

Info

Publication number: EP3924122A1
Application number: EP20706800.8A
Authority: EP
Inventors: Sébastien Yohann POUZET; Guillaume Valentin Giamondo MARION
Original assignee: Safran Aircraft Engines SAS; Safran SA
Current assignee: Safran Aircraft Engines SAS; Safran SA
Priority date: 2019-02-14
Filing date: 2020-02-07
Publication date: 2021-12-22
Also published as: WO2020165530A1; CN113438997A; US20220111441A1

Abstract

The invention relates to the field of additive manufacturing and more particularly to a method of additive manufacturing through the addition of a metallic material, the melting of runs of the metallic material through the application of energy, and solidification of the runs. In this method, the intensity, per unit length of run, of the energy supplied for melting one or more initial runs 1a, 1b of the metallic material applied to a first part 2 of a component is appreciably lower than that of the energy supplied for melting one or more subsequent runs 1c, 1d of the metallic material added to the initial runs 1a, 1b. This then yields a frangible region 11, formed by the initial runs 1a, 1b, via which region a second part 3 of the component formed by this method can easily be separated from the first part 2 so as to avoid the spread of cracks between the first and second parts 2, 3 of the component.

Description

Title of the invention: ADDITIVE MANUFACTURING PROCESS WITH SEPARATION

BY SECABLE ZONE

Technical area

[0001] The present invention relates to the field of additive manufacturing and in particular that of additive manufacturing by direct metal deposition (DMD, from the English "Direct Metal Deposition").

By additive manufacturing process by direct metal deposition is meant an additive manufacturing process in which a metallic material, for example in the form of powder or wire, is supplied to a substrate and melted by an energy beam, for example a laser or electron beam, to form a bead of molten metal on the substrate. After solidification of this bead, other cords can be successively superimposed on it in the same way, to form a three-dimensional metal part.

In the publications of patent applications US 2018/243828 A1, US

2015/306667 A1, and WO 2015/019070 A1, it has also been proposed to modulate the power of the energy beam in additive manufacturing processes by direct metal deposition, so as to create partially consolidated zones, which can subsequently be cut or eliminated .

[0004] In the mechanical field, it is sometimes desirable to create frangible zones intended to be sacrificed in order to protect other more critical elements.

Disclosure of the invention [0005] The present disclosure aims to remedy these drawbacks, by proposing an additive manufacturing process of a part which makes it possible to insert a frangible zone between a first and a second part of the part to stop the part. propagation of cracks between said first and second parts of the part.

[0006] According to a first aspect, this object can be achieved thanks to the fact that in this method, which comprises steps of supplying metallic material on a substrate, fusion of one or more initial beads of the metallic material brought to the first part of the part, solidification of the initial beads, addition of metallic material to the initial beads, fusion of one or more subsequent beads of the metallic material brought to the initial cords, and solidification of the subsequent cords, the fusion of the subsequent cords is carried out by an energy input of a second intensity per unit of cord length, which is appreciably greater than a first intensity per unit of cord length which is that of the energy contribution by which the fusion of the initial cords takes place.

[0007] Thanks to these arrangements, the wetting surface of the initial cords on the first part of the part, and therefore their strength of adhesion to this first part, can be less than that between the superimposed cords, thus creating a frangible zone to stop the propagation of cracks between the first part of the part and a second part formed at least partially by the subsequent beads.

[0008] According to a second aspect, the metallic material can be supplied in powder form, and in particular be supplied by spraying from a spray nozzle. However, alternatives, such as for example the provision of a wire of the metallic material, may possibly be considered.

[0009] According to a third aspect, the initial cords can comprise at

minus two superimposed cords. Thus, the second, higher intensity of the energy input per unit length of bead can only be used from a third layer of material, thus avoiding the boundary layer between the substrate and the initial beads. can be remelted by the energy input for the fusion of the subsequent beads, which could consolidate the substrate to the initial beads.

[0010] According to a fourth aspect, the energy input during the melting steps can be carried out by scanning an energy beam, in particular a laser beam, and more precisely a laser beam emitted in continuous mode. In order to obtain different intensities of the energy input per unit length of the cord, a transmission power of the energy beam during the fusion of the initial cords can be appreciably less than a transmission power. of the energy beam during the fusion of the subsequent cords, and in particular to be between one half and three quarters, and more specifically about two thirds, of the emission power of the energy beam during the fusion of the subsequent cords. In this case, a scanning speed and / or a laser point diameter may be substantially equal during the fusion of the initial beads and during the fusion of the subsequent beads, so as to ensure the continuity of the beads. Alternative means to the laser beam can nevertheless be envisaged for ensuring the energy supply during the fusion steps, for example an electron beam.

[0011] According to a fifth aspect, the material may be an alloy based on

titanium, and in particular TÎ6AI4V. However, nickel-based alloys are also possible.

[0012] According to a sixth aspect, the method can include a preliminary step of additive manufacturing of the first part of the part, before the step of adding metallic material to the first part of the part

Brief description of the drawings

The invention will be well understood and its advantages will appear better on reading the following detailed description of an embodiment shown by way of non-limiting example. The description refers to the accompanying drawings in which:

[0014] [Fig. 1 A-1 D] Figures 1 A to 1 D schematically illustrate steps

successive of an additive manufacturing process according to this embodiment,

[0015] [Fig. 2A-2B] Figures 2A and 2B illustrate cross sections of

beads of metallic material deposited on a substrate, and melted with different energy inputs per unit length of the bead, and

[0016] [Fig. 3] Figure 3 illustrates the operation of separating the substrate from a part produced by additive manufacturing according to the process illustrated in Figures 1 A to 1 D

Description of embodiments

[0017] An additive manufacturing process by direct metal deposition, more

specifically by laser metal deposition (LMD, standing for "Laser Metal Deposition ") is illustrated in Figures 1A to 1 D. As can be seen in these figures, in this process beads 1a to 1d of metallic material can be successively formed on a substrate, which can be formed by a first part 2 of a three-dimensional part to be manufactured, superimposed to create a wall forming a second part 3 of the three-dimensional part.

To form each bead 1 a to 1 d, the metallic material can be projected in the form of powder, comprising particles of diameters for example between 45 and 75 μm, from a projection nozzle 4, and melted by a beam

energy 5, while the first part 2, carried for example by a movable table 7 movable in three dimensions XYZ by linear actuators 8 connected to a control unit 9, is moved, relative to the projection nozzle 4, with a scanning speed v of, for example, 200 to 400 mm / min, in an XY plane parallel to the surface of the first part 2. The particles can be impelled by an inert gas such as argon, and form a beam of particles 6 converging, which can be, as illustrated, coaxial with the energy beam 5, for example by using an annular projection nozzle 4. The metallic material of the particles can in particular be a titanium-based alloy, such as for example TÎ6AI4V, and the particle beam 6 have a mass flow rate dm / dt of, for example, 2 to 3 g / min.

In order to prevent the rise of impurities, the first part 2 can be in the same metallic material or in a material with a sufficiently similar composition. The energy beam 5 can be a laser beam, and in particular a continuous laser beam, emitted for example by a YAG disk laser or by a fiber laser. The wavelength l of this laser beam can be, for example,

1030 µm for a YAG disc laser, or 600 µm for a fiber laser. The process can be carried out under an inert atmosphere, in particular under argon.

As illustrated in Figure 1A, a first bead 1a can thus be formed directly on the first part 2. The focal points of convergence f _p and fi of the particle beam 6 and of the energy beam 5, respectively, can be located above the surface of the first part 2 so that these beams have respective diameters d _p and di of, for example, 1, 5 to 2 mm and 2 to 3 mm, at the level of the surface of the first part 2. Thus, the metallic material is simultaneously deposited on the first part 2 and melted by the energy input of the energy beam 5, so as to create a liquid bath 10 solidifying downstream with respect to the direction of scanning of the beams of particles 6 and energy 5 on the first part 2, to form this first bead 1 a . The energy input of the energy beam 5 can be regulated so as to minimize the wetting surface of the liquid bath 10 on a first part 2, and therefore the contact surface A _c of the bead 1 a with the first part 2, as illustrated on FIG. 2A, illustrating a cross section of the bead 1 A on the first part 2. This regulation can in particular take place through the transmission power P-, of the energy bundle 5 for this first bead 1 a. This first emission power P- can thus be, for example, between 350 and 430 W. It is thus possible to obtain a liquid bath 10 with a first depth r _1; which may be for example 1.1 mm, and a first length h, which may be for example 2.6 mm. By way of comparison, if the transmission power, and therefore the energy contribution of the energy beam, were higher, the cross section of the bead 1 a would be that illustrated in FIG. 2B, with a contact surface A _c appreciably more wide, which would increase the cohesion with the first part 2.

[0020] In order to create a three-dimensional part, additional cords,

subsequently formed in a manner analogous to the first bead 1 a, can be superimposed, in the Z axis perpendicular to the surface of the first part 2, to this first bead 1 a. For this, after having formed the first bead 1 a, the distance in the Z axis between the first part 2 and the projection nozzle 4 can be increased by an increment Ad _z , before starting to form, on the first bead 1 a, a second bead 1 b analogously, as illustrated in FIG. 1 B. This increment Ad _z can be, for example, between 0.7 and 0.9 mm. The various parameters of the particle 6 and energy 5 beams, such as their angles of convergence, the mass flow rate dm / dt as well as the emission power R _1; used to form the first bead 1 a, can be maintained for this second bead 1 b, just like the scanning speed v, so as to maintain an energy supply per unit length of the bead which is substantially identical and therefore substantially the same length h and depth p-, of the liquid bath 10, and avoid remelting the first bead 1 a in the first part 2. However, after having formed this second bead 1 b on the first bead 1 a, the energy input per unit of length of bead can be increased substantially to form subsequent cords 1 c, 1 d superimposed on the first and second cords 1 a, 1 b, in order to increase the cohesion between the superimposed cords. Thus, for the subsequent beads, a second transmission power P ₂ substantially greater than the first transmission power P ₁ can be used, while maintaining the angles of convergence of the beams 5 and 6, the mass flow dm / dt and the scanning speed v. The second transmission power P ₂ can in particular be greater by a third up to twice the first transmission power Pi. Thus, if the first transmission power P ₁ is between 350 and 430 W, the second transmission power P ₂ can be approximately 600 W. It is thus possible to obtain a liquid bath 10 ′ with a second depth p ₂ and a second length l ₂ substantially greater, respectively, than the first depth p-, and the first length li, which were those of the liquid bath 10 obtained with the first transmission power Pi. Thus, for example, the second depth p ₂ can increase to 1, 7 mm, and the second length l ₂ to 3.5 mm.

[0022] For each subsequent bead 1 c, 1 d, the distance in the Z axis between the

first part 2 and the projection nozzle 4 can be further increased by an additional Ad _z increment, as illustrated in FIGS. 1 C and 1 D. The superimposed beads 1 a to 1 d can thus form a second part 3, for example in the form of a wall, with a frangible zone 1 1 of reduced thickness compared to the second part 3, directly interposed between the first and second parts 2, 3 of the part, thus facilitating their subsequent separation, as illustrated in FIG. 3 , in particular to prevent the propagation of cracks between the first and second parts 2, 3 of the part.

Although the present invention has been described with reference to a specific embodiment, with projection of the metallic material in powder form and energy supply by laser beam, it is obvious that various modifications and changes can be made on these examples without departing from the general scope of the invention as defined by the claims. For example, the number of initial stacked cords for which the energy input per unit cord length is significantly less than that of Subsequent cords can be one, rather than two, or greater than two. Furthermore, the energy input per unit length of cord can be regulated not only through the transmission power of the energy beam, but also, alternatively or in addition to this power regulation, through the scanning speed v and / or the mass flow dm / dt of the metallic material supplied. The metallic material may be supplied in the form of a wire and / or the energy supply may be effected by an electron beam. The first part of the part may itself have been manufactured at least partially by additive manufacturing in a step prior to the addition of metallic material intended to form the frangible zone. Therefore, the description and the drawings should be taken in an illustrative rather than a restrictive sense.

Claims

[Claim 1] A method of additive manufacturing of a part with a frangible zone (11) interposed between a first and a second part (2,3) of the part to stop the propagation of cracks between said first and second parts (2, 3) of the part, comprising at least the following steps:

- addition of metallic material on the first part (2) of the part,

- fusion of one or more initial cords (la, lb) of the metallic material brought to the first part (2) of the part, by an energy supply of a first intensity per unit of cord length,

- solidification of the initial cords (la, lb),

- addition of metallic material on the initial cords (la, lb),

- fusion of one or more subsequent beads (lc, ld) of the material

metallic provided on the initial cords (la, lb), by an energy input of a second intensity per unit of cord length, greater than the first intensity per unit of cord length, and

- solidification of subsequent cords (lc, ld).

[Claim 2] Additive manufacturing method according to the first

claim, wherein the metallic material is supplied in powder form.

[Claim 3] An additive manufacturing method according to claim 2, wherein the metallic material is sprayed from a spray nozzle (4).

[Claim 4] An additive manufacturing method according to any one of claims 1 to 3, wherein the initial cords (la, lb)

include at least two superimposed cords.

[Claim 5] An additive manufacturing method according to any one of claims 1 to 4, in which the melting of each bead (la-ld) is simultaneous with the supply of corresponding metallic material.

[Claim 6] An additive manufacturing method according to any one of claims 1 to 5, in which the energy input during the melting steps is effected by scanning an energy beam (5).

[Claim 7] An additive manufacturing method according to claim 6, wherein the energy beam (5) is a laser beam.

[Claim 8] An additive manufacturing method according to claim 7, wherein the laser beam is emitted in continuous mode.

[Claim 9] The additive manufacturing method according to any one of claims 6 to 8, wherein a transmit power of the energy beam (5) upon melting of the initial strands is less than a transmit power of the energy beam. (5) during the fusion of the subsequent beads.

[Claim 10] The additive manufacturing method according to claim 9, wherein the transmit power of the energy beam (5) upon melting of the initial strands (la, lb) is between one half and three quarters of the power of emission of the energy beam during the fusion of the subsequent cords (lc, ld).

[Claim 11] An additive manufacturing method according to any one of claims 9 or 10, wherein a scanning speed and / or a laser spot diameter are substantially equal during the fusion of the initial strands (la, lb) and during the fusion. of the fusion of subsequent cords (lc, ld).

[Claim 12] An additive manufacturing method according to any one of claims 1 to 11, wherein the material is a titanium-based alloy.

[Claim 13] An additive manufacturing method according to any one of claims 1 to 12, comprising a preliminary step of additive manufacturing of the first part (2) of the part, before the step of adding metallic material to the first. part (2) of the part. j