FR3064519A1 - PROCESS FOR MANUFACTURING A METAL PIECE BY ADDITIVE MANUFACTURE - Google Patents

Abstract

The invention relates to a method for manufacturing a metal part (1) comprising at least the following steps: forming (step E1) a blank (10) of the part on a support (20), the blank being formed layer by layer from a metal powder by a process of the additive manufacturing type, the blank comprising a useful part (1) corresponding to the part to be manufactured and a sacrificial portion (14, 16; 14 ', 16') extending between the support (20) and the useful part, and the separation (step E2) of the useful part (1) of the blank (10) thus formed of the support (20). The step of separating the useful part of the blank from the support comprises cutting with water jet of the sacrificial portion of the blank.

Description

(57) The invention relates to a method of manufacturing a metal part (1) comprising at least the following steps: the formation (step E1) of a blank (10) of the part on a support (20), the raw part being formed layer by layer from a metallic powder by a process of the additive manufacturing type, the raw part comprising a useful part (1) corresponding to the part to be produced and a sacrificial portion (14, 16; 14 ', 16 ') extending between the support (20) and the useful part, and the separation (step E2) of the useful part (1) from the blank (10) thus formed from the support (20). The step of separating the useful part of the blank from the support comprises cutting with the water jet the sacrificial portion of the blank.

Invention background

The present invention relates to the general field of manufacturing metal parts by additive manufacturing. The invention relates more particularly, but not exclusively, to the manufacture of distributor or rectifier sectors of a gas turbine, for example of aeronautical turbomachines.

The distributor or rectifier sectors of gas turbines generally comprise at least one part of internal shell, part of external shell, and blades which extend between these two ferrules. It is now advantageous to manufacture these parts by additive manufacturing, for example by laser fusion on a powder bed (known in English under the term "Selective Laser Melting" or SLM), in particular to gain simplicity and speed in the process. Manufacturing. In such a process, the sector is produced layer by layer on a manufacturing support from a powder. During manufacture, the part is attached to the support because of the fusion of the first metallic layer with the support in a so-called dilution zone. Thus, once the production of the raw part of the part on the support is complete, it is necessary to separate the part from the support.

Conventionally, this separation is carried out by wire cutting EDM (process also known in English under the term "Wire Electro Discharge Machining" or WEDM). In known manner, the part immersed in a dielectric medium is connected to a current generator and a wire-electrode tool is also used which is also connected to the generator in order to separate the part from the support by the formation of electric arcs at the separation zone. This process, although effective, is long, generates a heat affected zone and is expensive to implement.

Subject and summary of the invention

The main object of the present invention therefore is to overcome such drawbacks by proposing a method for manufacturing a finished metal part comprising at least the following steps:

- The formation of a blank on a support, the blank being formed layer by layer from a metal powder by a process of the additive manufacturing type, the blank comprising a useful part corresponding to the finished part and a portion sacrificial extending between the support and the useful part, and

- Separation of the useful part of the raw part thus formed from the support, the method being characterized in that the step of separation of the useful part of the raw part from the support comprises the water jet cutting of the sacrificial portion of the gross part.

Thus, the method according to the invention makes it possible to achieve in a simple, repeatable, and precise manner, the separation of the formed part (from the useful part of the raw part) by additive manufacturing on the support. The number of steps compared to a separation carried out by EDM is also reduced. Cutting with a water jet is made possible here in particular by the presence of a sacrificial portion between the support and the raw part formed. The invention applies equally to metal parts or metal alloy, obtained by an additive manufacturing process in which the part is linked to its manufacturing support. For example, the blank can be formed by laser fusion on a powder bed (SLM) or laser sintering on a powder bed (SLS).

The blank may include several sacrificial portions. The sacrificial portion may extend between the support and a support portion of the useful part of the blank, that is to say a portion through which the blank is in contact with the support and through which it is fixed on the support.

In an exemplary embodiment, the sacrificial portion may comprise at least one alveolar portion, for example be hollow and have a structure comprising cells or cavities. This arrangement facilitates the step of separating the useful part of the raw part from the support, the water jet having more facility for cutting the sacrificial portion. In addition, a sacrificial portion having an alveolar portion is faster to manufacture than a massive, that is to say full, portion.

In an exemplary embodiment, the method can also comprise a step of pickling with a pressurized water jet from a surface of the useful part of the blank so as to clean said surface. This step of pickling with a water jet makes it possible to treat a surface of the useful part of the raw part in order to remove, for example, particles of non or partially molten powders, or weakly adherent particles, following the formation of the raw part. by additive manufacturing. This step can be important when the part to be manufactured must meet dimensional or aerodynamic requirements related to its use, for example in a turbomachine. This step can be automated. By using a water jet, the speed and repeatability of this step is further optimized, which was conventionally carried out by a manual sanding step.

In an exemplary embodiment, the blank can also comprise at least one low cell wall manufacturing extending between the support and the useful part, the method further comprising a step of removing the low cell wall from the useful part of the gross part. Honeycomb manufacturing walls are known in the field of additive manufacturing to be able to support during manufacturing parts of the workpiece that are cantilevered. It will be noted that, in the invention, a distinction is made between the sacrificial portion which is cut out in order to separate the useful part of the blank part from the support, from the honeycomb manufacturing walls. When present, the manufacturing walls are generally distinct from the sacrificial portion of the blank.

In an exemplary embodiment, the step of removing the cellular wall can be carried out at least in part by a pressurized water jet. In this case, the pressurized water jet used during the step of removing the cellular wall may include abrasive particles. Such particles can be made of one of the following materials: corundum, alumina, boron nitride, boron carbide, diamond, glass beads, plastic beads, organic media.

In an exemplary embodiment, it is possible to manufacture a first and a second angular sector of an annular part and the method can successively comprise the following steps:

- the formation of the first and second sector blanks on the support, and

the separation of the useful part of the blank from the first sector of the support by cutting the sacrificial portion of the blank from the first sector, the cutting being carried out by at least one water jet formed by a nozzle moving angularly at the periphery of the support, a protective element being interposed between the blank of the first sector and the blank of the second sector so as to avoid damage to the blank of the second sector by the water jet during cutting of the sacrificial portion of the raw part of the first sector.

With such an arrangement, it is possible to manufacture several sectors of an annular part at the same time on the support, in particular at least two, three or four of these sectors on the same support, and then to separate them from the support without the jet of water will damage them. Indeed, without the presence of the protective element, it would not be possible to form several blanks on the plate and cut them with a water jet: the water jet cutting a blank could damage neighboring blanks. This makes it possible to easily manufacture a plurality of parts on the same support, then to automate the separation by a method according to the invention. The protective element may include an abrasion resistant material such as polyoxymethylene (POM).

In an exemplary embodiment, it is possible to manufacture at least one angular sector of a gas turbine distributor or rectifier, said angular sector comprising an internal ferrule sector, an external ferrule sector and a plurality of blades extending between the internal ferrule sector and external ferrule sector. In this case, the sacrificial portion can extend between the support and each sector of internal ferrule and external ferrule. In this case, a honeycomb manufacturing wall may be present between the support and the vanes of the angular sector of the distributor or rectifier, in order to support the vanes during the manufacturing of the sector.

In an exemplary embodiment, the sacrificial portion may have a thickness greater than or equal to 2 mm. For example, the sacrificial part may have a thickness of between 2 mm and 4 mm. In particular, it will be possible to ensure that the thickness is sufficient for the sacrificial portion to be cut by a jet of pressurized water, and sufficiently small so as not to lengthen the duration of the manufacturing process too much. In particular, the dimensions of the sacrificial portion can be adapted according to the characteristics of the pressurized water jet (pressure, diameter of the jet, presence of abrasive particles, etc.). The dimensions of the sacrificial portion can be adapted so as to limit the deformations of the part during water jet cutting due to the release of the residual stresses generated in the part by the stages upstream of the cutting stage.

Brief description of the drawings

Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate an embodiment thereof devoid of any limiting character. In the figures:

FIG. 1 is a flowchart showing the steps of a manufacturing process according to an embodiment of the invention,

FIG. 2 is a perspective view showing a support on which a gas turbine rectifier ring sector has been manufactured by a method according to an embodiment of the invention,

FIG. 3 is a perspective view mounting a support on which a gas turbine rectifier ring sector has been manufactured by a variant method according to the invention,

FIG. 4 shows the arrangement of three rectifier sectors on a support in a method of the prior art,

FIG. 5A shows the arrangement of three rectifier sectors on a support in a method according to an embodiment of the invention,

FIG. 5B is a sectional view of the assembly of FIG. 5A at the level of the plane VB,

FIG. 6 shows a sectional view of a machine for separating the rectifier sectors from the support by cutting with a water jet, and

FIG. 7 is a view in direction VII of the machine in FIG. 6.

Detailed description of the invention

An example of a method according to the invention will be described in connection with the flow diagram of FIG. 1 which illustrates different stages thereof. The example process will be described in the context of the manufacture of one or more angular sectors 1 of a gas turbine distributor or rectifier, for example of a land or aeronautical gas turbine. A distributor or rectifier constitutes, in a known manner, an annular part around an axis. As illustrated in FIGS. 1 and 2 in particular, a sector 1 of distributor or rectifier comprises a plurality of blades 2 which extend radially (relative to the axis of the distributor or rectifier, not shown) between an internal ferrule 4 and an outer shell 6. Of course, here we see sectors of the inner shell and the outer shell.

In step E1, a blank 10 of sector 1 is formed on a support 20 by a process of the additive manufacturing type. In known manner, in a method of the additive manufacturing type, the blank 10 is manufactured layer by layer from a powder, for example a metallic powder. The metal powder can for example comprise a titanium-based alloy such as TA6V, nickel-based such as INCONEL® 718, cobalt-based such as CoCrMo, iron-based such as 40CDV12. In particular, in a process such as selective melting on a powder bed or selective sintering on a powder bed, a layer of powder is deposited on the support 20, and part of the layer deposited on the surface is selectively fused or sintered. using a heating means (for example a laser or an electron beam) to form a first layer of the blank to be manufactured. This is done successively until the blank 10 is obtained. Still in known manner, the blank 10 is produced on a support 20 made of a refractory material suitable for supporting the piece and on which the blank 10 is fixed by means of the first layer of the blank 10 which can also merge with the support 20. This adhesion of the blank 10 on the support 20 ensures the stability of the blank 10 during its manufacture.

In the particular case of the manufacture of a part which has one or more cantilevered or suspended portions, that is to say which are not directly supported when the part is laid, walls must be provided Manufacturing. In the example illustrated in FIG. 1, the cantilever portions of sector 1 correspond to the vanes 2, and it can be seen that the blank 10 here has manufacturing walls 12 to support the vanes 2 during the formation of the raw piece 10. The manufacturing walls 12 are honeycomb walls whose characteristics are determined to effectively support the blades 2 while allowing easy removal of the walls 12 from the blank 10 once formed.

Ί

According to the invention, the blank part comprises a useful part, corresponding here to sector 1, and a sacrificial portion which extends between the support and the useful part. In the example illustrated, the blank 10 thus comprises two sacrificial portions 14 and 16 present respectively between the support 20 and the internal ferrule 4 and between the support 20 and the external ferrule 6. The sacrificial portions 14 and 16 are formed during of step E1. In the example illustrated, the sacrificial portions 14 and 16 have a thickness e of between 2 mm and 4 mm. The size of the sacrificial portions 14 and 16 will be adapted according to the parameters of the water jet which will be used for cutting. Unlike the honeycomb manufacturing walls 12, already known, whose function is to support the blades 2 during the formation of the blank 10, the sacrificial portions 14 and 16 are present to allow easy separation of the sector 1 from the support 20 by cutting with a water jet, as will be explained in more detail later. The sacrificial portions 14 and 16 are here present between the support 20 and the bearing surfaces 8 and 9 of the sector 1, that is to say the surfaces by which the sector 1 is fixed on the support 20. With such a arrangement, it is understood that the dimensions of the manufacturing walls 12, in particular their height, must be increased so as to accommodate the presence of the sacrificial portions 14 and 16. In the example illustrated in FIG. 2, the sacrificial portions 14 and 16 are solid or massive, that is to say that they are not alveolar or hollow.

A variant blank 10 that can be formed in a method according to the invention during step E1 is represented in FIG. 3. In this variant, the sacrificial portions 14 ′ and 16 ′ are alveolar, so that they are produced faster (because less material is needed to make them) and to allow easier cutting of the latter by a pressurized water jet.

In order to increase the number of parts produced on the same support, for example three sectors 1, it is known in the prior art to form as many corresponding blanks 10i, 10 ₂ , 10 ₃ , one behind the other to occupy the surface of the support 20 and to orient them for example in the same way on the support 20, as illustrated in FIG. 4. However, when the sectors 1 are then separated from the support by cutting with a water jet, as required by the invention, the neighboring parts can be damaged by the water jet when cutting the sacrificial portion of a sector.

In accordance with an advantageous arrangement of the invention illustrated in FIGS. 5A and 5B, the above-mentioned problem is overcome by providing a protective element 30, preferably designed from an abrasion-resistant material such as polyoxymethylene, formed here by a block configured so that, when a pressurized water jet formed by a nozzle 40 (its path is shown in dashes in FIG. 5A) moving angularly at the periphery of the support 20 cuts the sacrificial portion (not shown ) of the first blank 10i, the second blank IO2 located opposite on the support, and the third blank 10 ₃ located next to it on the support, is not damaged by said water jet. In particular, the protective element 30 is disposed between the first 10i blank and the second IO2 blank. In the example illustrated, the blanks 10i, 10 ₂ and 10 ₃ are arranged around the protective element 30, the internal ferrule of each being directed towards the protective element.

In the following step E2, in accordance with the invention, the useful part of the blank is separated from the support by cutting with a water jet from the sacrificial portion of the blank. To do this, a water jet cutting machine 100 is used as illustrated in FIGS. 6 and 7. This machine uses the advantageous arrangement of the blanks 10 on the support 20 as illustrated in FIGS. 5A and 5B . The machine 100 comprises a vertical frame 110 present in a tank 120 filled with water. A rotary plate 130 around a horizontal axis A is mounted on a vertical face of the frame 110. The rotation of the plate 130 is effected by conventional means not shown. The support 20 on which the blanks 10 of the sectors 1 have been formed is fixed on the rotary plate 130 by fixing means such as flanges 131. The protective element 30 is fixed on the one hand to the rotary plate 130 and d on the other hand to the support 20. Holding flanges 140 are fixed respectively on the one hand to the protective element 30 and on the other hand to each blank 10. These flanges 140 make it possible to maintain the sectors 1 so as not to only they fall once separated from the support 20 by cutting with a water jet. In the example illustrated, the protective element 30 has a height greater than the height of the blanks 10 formed on the support 20, and in particular greater than the thickness e of the sacrificial portions 14, 16 of the blanks 10.

The sacrificial cutting of the sacrificial portions of each blank 10 is carried out by a water jet formed by the nozzle 40. The nozzle 40 is here located above the tank 120. The nozzle 40 can be mounted on a automated polar or Cartesian robot with numerical control (not shown), in a manner known per se, so as to keep a constant distance between the nozzle and the edge of the sector to be separated. During cutting, the water jet can make, with the normal to the face of the blank 10 being cut, an angle between 0 ° and 30 °. It is possible to use a nozzle of the mono-jet type. The nozzle can be located between 0.5 mm and 25 mm from the blank. The jet can move on the blank to be cut with a speed between 0.05 mm / s and 1 mm / s. The diameter of the nozzle can be between 0.1 mm and 0.5 mm. The water jet pressure can be between 4000 bars and 8000 bars. The water jet flow can be between 2 L / min and 30 L / min. The water jet can comprise abrasive particles, for example of corundum, alumina, boron nitride, boron carbide or diamond, or of an organic material. The flow of abrasive particles in the water jet can be between 200 g / min and 1000 g / min.

We can cut the blank 10i, then rotate the plate 130 to then cut the blank IO2, and finally continue with the blank IO3. With the illustrated arrangement, the protective element 30 protects the blank part located opposite that which is being cut from the water jet. Once all the blanks have been cut, the flanges 140 can be removed from the machine 100 and the sectors 1 can be recovered (useful parts of the blanks).

In a following step E3, the surfaces of each sector 1 can be scoured using a pressurized water jet in order to clean them. This step makes it possible to remove the particles of unmelted or partially molten metal powder which have remained on sector 1, and thus to clean its surfaces. During this step, it is possible to use a machine different from the machine 100. In particular, it is possible to use a horizontal machine (not shown) comprising a tank and channels or channels on which the sectors 1 are placed, the nozzle being able to move at - above the sectors. It is possible to use a nozzle of the single-jet type, or else a multi-jet so as to cover a larger surface. The nozzle can be located between 5 mm and 100 mm from the blank. The jet can move on the blank with a speed between 1 mm / s and 20 mm / s. The diameter of the nozzle can be between 0.5 mm and 5 mm. The pressure of the water jet can be between 500 bars and 6000 bars. Care should be taken that the pressure is not too high to avoid damaging the part and not to generate surface defects. The water jet flow can be between 2 L / min and 30 L / min. During this stage, the water jet is preferably free of abrasive particles.

In a step E4, which can be carried out before or after step E3, the alveolar manufacturing walls are removed from the blank 10 so as to obtain the sector 1. Part of this step can consist simply in breaking the honeycomb manufacturing walls 12 of the blank 10 separated from the support 20. Once the walls 12 are broken, residue from the walls is generally present on sector 1, which is undesirable, especially when they are present on parts having an aerodynamic function as is the case of the vanes 2 of sector 1. During this stage, a machine identical to that used for stage E3 can be used.

This completes the step of removing the manufacturing walls using a pressurized water jet, in order to remove the residues from the manufacturing walls. In other words, the step of removing the honeycomb manufacturing walls here includes a step of deburring with a water jet. For this, a single-jet nozzle is preferably used. The nozzle can be located between 5 mm and 100 mm from the blank. The jet can move on the blank with a speed between 1 mm / s and 20 mm / s. The water jet can be rotatable. The diameter of the nozzle can be between 0.5 and 5 mm. The pressure of the water jet can be between 500 bars and 6000 bars. The water jet flow can be between 2 L / min and 30 L / min. The water jet can comprise abrasive particles, for example of corundum, alumina, boron nitride, boron carbide, diamond, or an organic material, glass or ceramic beads. The abrasive particles may have a size (D50) of less than or equal to 1 mm, preferably less than or equal to 200 μm, more preferably less than or equal to 50 μm, to reduce the risk of marking the part and of encrusting particles in the room. The flow of abrasive particles in the water jet can be between 200 g / min and 1000 g / min. The use of a water jet during the step of removing the cellular production walls allows, unlike the manual polishing steps used in the prior art, to remove surface irregularities in a reproducible manner and optimize the quantity of material removed from the parts.

Thanks to the invention and its advantageous arrangements implementing water jet cutting or water jet stripping, it is thus possible to reduce the time, the number of steps, and thus the cost, of the manufacturing process. '' a metal part by additive manufacturing.

Claims (9)

1. Method for manufacturing a finished metal part (1) comprising at least the following steps: - The formation (step E1) of a raw part (10) of the part on a support (20), the raw part being formed layer by layer from a metal powder by a process of the additive manufacturing type, the part rough comprising a useful part (1) corresponding to the part to be manufactured and a sacrificial portion (14, 16; 14 ', 163 extending between the support (20) and the useful part, and - Separation (step E2) of the useful part (1) from the raw part (10) thus formed from the support (20), characterized in that the step of separating the useful part from the raw part from the support comprises the water jet cutting of the sacrificial portion of the blank. 2. Method according to claim 1, in which the sacrificial portion (14 ′, 163 comprises at least one alveolar portion. 3. Method according to any one of claims 1 and 2, further comprising a step of etching with a pressurized water jet (step E3) of a surface of the useful part of the blank so as to clean said surface. 4. Method according to any one of claims 1 to 3, wherein the blank (10) further comprises at least one low cell wall (12) extending between the support (20) and the useful part (1 ), the method further comprising a step of removing the alveolar manufacturing wall from the useful part of the blank (step E4). 5. Method according to claim 4, wherein the step (E4) of removal of the cellular wall (12) is carried out at least in part by a pressurized water jet. 6. The method of claim 5, wherein the pressurized water jet used during step (E4) of removal of the cellular wall comprises abrasive particles. 7. Method according to any one of claims 1 to 6, in which a first and a second angular sector of an annular part are manufactured, the method successively comprising the following steps: the formation of the blanks (10ι, IO2) of the first and of the second sector on the support (20), and - The separation of the useful part (1) of the blank (10i) of the first sector of the support by cutting the sacrificial portion (14, 16) of the blank of the first sector (10i), the cutting being carried out by less a water jet formed by a nozzle (40) moving angularly around the periphery of the support, a protective element (30) being interposed between the raw part of the first sector (10i) and the raw part of the second sector (IO2 ) so as to avoid damaging the raw part of the second sector (IO2) by the water jet when cutting the sacrificial portion (14, 16) of the raw part of the first sector (10i). 8. Method according to any one of claims 1 to 7, in which at least one angular sector (1) of a gas turbine distributor or rectifier is manufactured, said angular sector comprising an internal ferrule sector (4), a outer ferrule sector (6) and a plurality of vanes (2) extending between the inner ferrule sector and the outer ferrule sector. 9. Method according to any one of claims 1 to 8, wherein the sacrificial portion (14, 16) has a thickness (e) greater than or equal to 2 mm. 1/7