WO2017060600A1

WO2017060600A1 - Method for additive manufacturing comprising a step of hot isostatic pressing

Info

Publication number: WO2017060600A1
Application number: PCT/FR2016/052534
Authority: WO
Inventors: Philippe JOVER; Daniel Cornu; Raphaël SALAPETE
Original assignee: Safran Aircraft Engines
Priority date: 2015-10-06
Filing date: 2016-10-04
Publication date: 2017-04-13
Also published as: FR3041889A1; FR3041889B1

Abstract

The invention relates to a method for producing a part (10) from powder, comprising a step of producing an envelope (12) of the part (10) by means of an additive manufacturing method, a step of filling the envelope (12), and a step of isostatically pressing the part (10).

Description

ADDITIVE MANUFACTURING METHOD COMPRISING A HOT ISOSTATIC PRESSING STEP

The present invention relates to an additive manufacturing process of complex parts.

Additive manufacturing makes it possible to obtain parts having relatively complex geometries while avoiding the constraints linked for example to the use of a mold.

However, these manufacturing processes are still limited by the required manufacturing time is long, high manufacturing costs and the reduced volume of parts that can be produced.

In addition, the additive manufacturing generally leads to a degree of anisotropy in the part produced which is unfavorable, especially for the mechanical properties of the part.

In addition, the manufacture of parts comprising several different materials remains relatively complex, both in additive manufacturing in traditional manufacturing.

Object and summary of the invention

The present invention aims to remedy at least in part these disadvantages.

For this purpose, the subject of the invention is a method for manufacturing a part, the method comprising the following steps:

- manufacture of an envelope of the part by an additive manufacturing process;

- filling the envelope;

- Isostatic pressing of the part.

The envelope having a reduced volume of material relative to the total volume of material included in the envelope, the time required to manufacture the envelope is reduced compared to the time required to manufacture the solid part by additive manufacturing. However, the possibility of producing a piece of complex geometry is retained. Depending on the piece that we want to obtain and / or the materials used, we can move by example to an additive manufacturing process on a powder bed or by projection.

The filling of the envelope with a powder or a mixture of powders, a liquid or a gas makes it possible to produce very varied parts, comprising for example empty volumes, zones having different densities, different materials. It is also conceivable to at least partially fill the envelope with electrical and / or electronic and / or mechanical and / or chemical systems. The envelope then protects its systems from the outside environment. Moreover, the use of several materials allows for example to obtain a part whose thermal expansion is zero and / or is controlled, or other physical properties such as conductivity. For example, tungsten wires may be provided in the envelope to provide a reheating function. It is also conceivable to insert piezoelectric compounds or materials. It is also conceivable to insert, in the envelope, vesicles comprising one or more chemicals, in the form of liquid and / or powder, for example to perform a chemical welding.

The hot isostatic pressing step, cold isostatic pressing or vacuum densification isostatic pressing makes it possible to obtain parts that do not exhibit particular anisotropy or unwanted porosity. Depending on the temperature conditions of the isostatic pressing, the part may be partially or fully densified. It is thus possible to apply to the same piece several isostatic pressing steps at given temperatures. Thus, for example, if the part comprises three materials, it is possible to carry out two isostatic pressings.

The manufacture of the envelope may comprise the manufacture of a structure internal to the envelope.

We can take advantage of the great versatility of forms that can be achieved by additive manufacturing to create in the envelope an internal structure that can allow to stiffen the room, to create material gradients or to create separate cavities within the envelope. This internal structure can also be used to control the deformations of the part during the hot isostatic pressing step. The internal structure may comprise a meshed internal structure.

It is thus possible to produce a part comprising two different materials each having a three-dimensional network, the two three-dimensional networks being intimately intertwined.

The envelope manufactured by the additive manufacturing process may comprise at least two regions each having a different internal structure.

It is thus possible to manufacture by additive manufacturing an envelope comprising for example a solid part and a part comprising an internal structure or a solid part and a hollow part or a combination of a solid part, a hollow part and of a part comprising an internal structure. The envelope may also include two different internal structures.

Prior to the isostatic pressing, it is possible to close the envelope at least partially.

Thus, one can choose to densify only the part of the part included in the closed part of the envelope.

The at least partial closure of the envelope can be achieved by additive manufacturing.

Prior to the filling of the envelope, it can empty the envelope of the unfused powder during additive manufacturing.

It is thus possible to create cavities within the envelope.

At least one cavity of the envelope may be filled with a powder different from the powder used for the envelope.

It is thus possible to form parts comprising several different materials.

It may also be envisaged to fill the cavity or cavities with a non or hardly fusible material, such as a metal alloy commonly designated by the trademark Astroloy ™, or a nickel-based metal alloy of the N18 type.

The method may comprise a step of machining the workpiece.

For example, the workpiece can be machined so as to remove a given thickness of material corresponding to a thickness of the envelope and / or to a thickness greater than the thickness of the envelope. The part may comprise a metal alloy and / or a ceramic material.

The piece may for example comprise a ceramic matrix reinforced with fibers. The fibers may be carbon fibers, mineral fibers and / or biological fibers.

The part that can be envisaged to produce by means of the manufacturing process defined above is for example a container combining different properties between the envelope and the inside, the envelope having for example a holding at corrosion greater than that of the interior of the room, or better welding properties. The interior may for example have a better structural strength and / or better thermal properties.

The envelope may be made of a material with or without a certain affinity with chemical species, for example, the envelope may be inert with respect to hydrogen. The envelope can also be made of a material protecting radiation, such as electromagnetic radiation.

The part may also be a multi-material part allowing the mechanical anchoring of another element or allowing the welding of another element or to control the thermal gradient within the room or allowing a control of the deformation (fibrous materials or elastic structure for example).

Depending on the type of material used for the filling of the envelope, it can produce a part that will be a gas / gas exchanger, gas / liquid, gas / solid, liquid / solid, solid / solid or liquid / liquid.

The part may also have a structural function and have a mesh or porous internal structure to ensure active cooling by transpiration or effusion.

It is also possible to manufacture parts that can serve as a heat sink, thermal barrier, molds having a complex mesh, such as a housing incorporating a heat exchanger.

Brief description of the drawings

Other features and advantages of the invention will become apparent from the following description of embodiments of the invention given to As non-limiting examples, with reference to the appended figures, in which:

- Figures 1 to 4 illustrate the steps of a first embodiment of the manufacturing method;

- Figures 5 to 14 illustrate the steps of a second embodiment of the manufacturing method; and

- Figure 15 is a perspective view of a part manufactured by the manufacturing method, showing a section of the part.

Detailed description of the invention

Figure 1 shows a sectional view of a part 10 after a first step of a manufacturing process. An envelope 12 of the part 10 has been manufactured by an additive manufacturing process. The additive manufacturing process can be a powder bed manufacturing method or an additive projection manufacturing process or any other additive manufacturing method.

This envelope 12 comprises a filling funnel 14 and an internal structure 16.

In the embodiment of FIG. 1, the internal structure 16 comprises a first region 18 in which the internal structure 16 is a solid internal structure 20 and a second region 22 in which the internal structure 16 is a mesh internal structure 24. The solid internal structure 20 and the internal mesh structure 24 are made of the same material as the material of the envelope 12, for example a metal alloy commonly referred to by the trademark Inconel ™. Inconel is later referred to as an alloy based on iron alloyed with nickel and chromium.

The enlargement of the internal mesh structure 24 shows a structure having a three-dimensional network 26 of the material of the envelope 12 as well as an empty three-dimensional network 28.

In addition, the envelope 12 also comprises a cavity 30 which communicates with the filling funnel 14 and the empty three-dimensional network 28 of the internal mesh structure 24.

FIG. 2 represents the part 10 after filling the envelope 12, that is to say the empty three-dimensional network 28 of the internal structure 24, of the cavity 30 and the filling funnel 14, by a powder 32. This powder 32 may or may not be of the same material as the material of the envelope 12, this powder may for example be a powder of titanium.

In Figure 2, the part 10 also comprises a plug 34 disposed in the filling funnel 14 so as to close the envelope 12 before isostatic pressing, for example hot. This plug may be an outer part attached to the casing 12, it may also be formed by welding the edges of the filling funnel 14 and / or by crushing the filling funnel 14 on itself or any other suitable technique.

Figure 3 shows the part 10 after a hot isostatic pressing step during which the titanium powder has been densified. Figure 4 shows the part 10 after a machining step during which the envelope 12 has been removed. Part 10 can also be densified by cold isostatic pressing and / or vacuum densification isostatic pressing. It will then generally be desirable to subject the part to heat treatment.

In the embodiment of FIG. 4, the part 10 comprises three regions: the first region 18 having the full internal structure 20 in Inconel, the second region 22 having the three-dimensional network 26 in Inconel is a three-dimensional titanium network. and the third region 36 having a solid internal structure 38 of titanium.

Through the combined use of an additive manufacturing process and hot isostatic pressing, the part 10 comprises two different materials which are intimately connected to one another through the second region 22 having two networks. three-dimensional intimately interconnected. In particular, the second region having the two closely interconnected three-dimensional networks could not have been obtained using additive manufacturing alone or hot isostatic pressing alone. Furthermore, the production time of the part 10 is reduced because only the Inconel part is produced by the additive manufacturing process.

In what follows, the elements common to the various embodiments are identified by the same reference numerals. Figures 5 to 14 illustrate different stages of a second embodiment of the method of manufacturing a part 10.

The envelope 12 of the part 10 is manufactured by an additive manufacturing process, for example on a bed of powder. Also, as the envelope 12 is made from the powder of the powder bed, the envelope 12 is also filled with the same powder. The manufacturing steps of the envelope 12 by the process of additive manufacturing and filling of the envelope 12 are therefore simultaneous.

In the embodiment of Figure 5, the casing 12 comprises an internal structure 16 formed of a cylindrical partition 38 present over the entire height of the casing 12. This cylindrical partition 38 is in the extension of the filling funnel 14. The cylindrical partition 38 defines in the casing 12 a first cavity 40 and a second cavity 42 disposed around the first cavity 40. The first cavity 40 is thus in communication with the filling funnel 14.

The envelope 12 also comprises a secondary filling chimney 40 which is in communication with the second cavity 42.

It is understood that the circular partition 38 may have a diameter greater than that of the filling funnel 14 and / or have another shape that may be different from a regular shape.

FIG. 6 represents the step during which the envelope 12 of the powder coming from the powder bed is emptied. In this particular example, the two cavities 40, 42 are emptied.

As shown in Figure 7, once the envelope 12 completely emptied, it is ready to be filled. Each cavity 40, 42 may be filled with a powder or a mixture of powders, a liquid or a gas. It is also conceivable to insert an electromechanical system in one of the cavities 40, 42 and then fill it with a powder or a mixture of powders, a liquid or a gas. Each cavity 40, 42 may be filled with materials of different nature.

FIG. 8 represents the part 10 in which the cavity 42 has been filled with a first powder 46 by the secondary filling chimney 44. FIG. 9 represents the part 10 in which the secondary filling chimney 44 has been closed by a first plug 48 before a first step of hot isostatic pressing. The envelope 12 is thus partially closed.

As in the first embodiment, this first cap 48 may be an outer part attached to the casing 12, it may also be formed by welding the edges of the secondary filler pipe 44 and / or by crushing the secondary filling funnel 44 on itself or any other suitable technique.

Figure 10 shows the part 10 after densification of the first powder 46 by hot isostatic pressing. Since the filling funnel 14 has not been closed, the pressure applied to the workpiece 10 during the hot isostatic pressing step is also applied to the first powder 46 on the side of the first cavity 40 of the workpiece 10. An isotropic densification of the first powder 46 is thus obtained.

As shown in FIG. 11, after the first hot isostatic pressing step, the first cavity 40 is filled with a second powder 50 by the filling funnel 14. FIG. filling 14 was closed by means of a second plug 52, similar to the first plug 48, and this, prior to the second step of hot isostatic pressing.

Figure 13 shows the part 10 after the second hot isostatic pressing step during which the second powder 50 has been densified. FIG. 14 shows the part 10 after machining the filling funnel 14 and the secondary filling funnel 44.

In the embodiment of FIG. 14, the part 10 comprises the envelope 12 made in the material of the powder bed and a solid cylinder corresponding to the volume of the first cavity 40. This solid cylinder is produced in the material of the second powder 50. The part 10 also comprises an annular section volume made in the material of the first powder 46. This annular section volume is interposed between the casing 12 and the solid cylinder.

FIG. 15 represents a part 10 obtained by additive manufacturing of the envelope 12, the envelope 12 comprising a structure internal mesh 24 having a three-dimensional network 26 and a two-dimensional vacuum network 54 which has been filled with a different powder or not powder powder bed.

Although the present invention has been described with reference to a specific embodiment, it is obvious that various modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In addition, individual features of the various embodiments mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

For simplification, the envelope 12 of the part 10 has been shown in Figures 1 to 15 in the form of a cylinder, it is understood that the envelope may be more complex shape, for example have the shape of a turbine blade or a crankcase. It is the same for the cylindrical partition 38. It is also understood that the cylindrical partition is shown centered with respect to the envelope 12, it may not be. The envelope 12 could also include a plurality of internal partitions each defining a separate cavity. Moreover, one can also consider making mesh structures within the different cavities. These mesh structures may be different from each other. The meshed structures may be regular or have a gradient, that is to say for example that the thickness of the three-dimensional network structure produced by additive manufacturing may change from one area to another of the mesh internal structure. It is thus possible to produce parts comprising gradients of materials.

In the embodiment of Figures 5 to 14, one could consider, for example at the end of the additive manufacturing step, to partially close the casing 12 by closing the filling stack 14 or the filling chimney secondary 44, by additive manufacturing process or by a plug. Also, only the cavity that has not been closed is emptied of the powder from the powder bed. This reduces the manufacturing time by additive manufacturing of the part of the envelope that has not been emptied. Indeed, after hot isostatic pressing the part of the envelope which comprises the powder of the powder bed is densified without having been produced by additive manufacturing. Additive manufacturing can of course be carried out by any additive manufacturing process.

Claims

A method of manufacturing a workpiece (10), comprising the steps of:

- manufacturing an envelope (12) of the part (10) by an additive manufacturing process;

filling the envelope (12);

- isostatic pressing of the part;

the method being characterized in that at least one cavity (30; 40,42) of the envelope is filled with a powder different from the powder used for the envelope.

2. The manufacturing method according to claim 1, wherein, the manufacture of the envelope (12) comprises the manufacture of an internal structure (16) to the envelope.

3. The manufacturing method according to claim 2, wherein the internal structure (16) comprises a mesh internal structure (24).

4. The manufacturing method according to claim 2 or 3, wherein the envelope (12) produced by the additive manufacturing process comprises at least two regions (18, 22) each having a different internal structure.

5. Manufacturing process according to any one of the preceding claims, wherein prior to the isostatic pressing is at least partially closed envelope (12).

6. Manufacturing process according to the preceding claim, wherein the at least partial closure of the casing (12) is performed by additive manufacturing.

7. Method according to any one of the preceding claims, wherein, prior to filling the envelope (12), the envelope (12) of the unfused powder is emptied during additive manufacturing.

8. Manufacturing process according to any one of the preceding claims, comprising a step of machining the workpiece (10).

9. Manufacturing method according to any one of the preceding claims, wherein the part comprises a metal alloy and / or a ceramic material.