FR3058341A1 - METHOD FOR MANUFACTURING PARTS ACCORDING TO ADDITIVE MANUFACTURING OPERATION FOLLOWED BY HOT ISOSTATIC COMPACTION OPERATION - Google Patents

Abstract

The present invention relates to a method for manufacturing a metal alloy piece or metal matrix composite material, according to which: a preform (10) is produced according to an additive manufacturing operation by adding material in powder form, with stacking successive layers of powder, and partial melting of at least some layers of powder, the preform (10) thus consisting of predefined solid parts (11) and residual powder areas (12), said residual powder being unwelded or partially consolidated; and subjecting the preform (10) to a hot isostatic compaction operation to obtain the final shape of the workpiece.

Description

(57) The present invention relates to a method of manufacturing a part made of a metal alloy or of a metal matrix composite material, according to which: a preform (10) is produced according to an additive manufacturing operation by adding material in powder form , with stacking of successive layers of powder, and partial melting of at least certain layers of powder, the preform (10) thus being constituted by solid parts (11) and by zones of residual powder (12) predefined, said residual powder being not welded or partially consolidated; and subjecting the preform (10) to a hot isostatic compaction operation so as to obtain the final shape of the part.

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METHOD FOR MANUFACTURING PARTS ACCORDING TO AN ADDITIVE MANUFACTURING OPERATION FOLLOWED BY A HOT ISOSTATIC COMPACTION OPERATION

The invention relates to the technical field of the manufacture of metal or composite parts with a metal matrix for the production in particular and without limitation of components and equipment for the automotive, aeronautical or medical sector.

Additive manufacturing which makes it possible to manufacture parts by melting or sintering several successive layers is developing, the basic concept being defined in US Pat. No. 4,575,330 dated 1984.

Additive manufacturing is defined by ASTM as a process for shaping a part by adding material by stacking successive layers, in opposition to shaping by removing material such as machining. It is also the name given to three-dimensional printing technology.

This technology has been developed to produce metal alloy parts as well by melting or sintering powder beds or by welding wires. Tests on composite materials with metallic matrices have shown great promise.

The technologies used to cite them in a non-exhaustive manner range from selective laser sintering (Selecting Laser Sintering) to electron beam fusion (Electron Beam Melting) through metal laser sintering (Direct Métal Laser Sintering) as well as metal deposition by laser (Laser Métal Déposition) or laser fusion (Selective Laser Melting).

These technologies make it possible to manufacture parts which have great geometric complexity with satisfactory mechanical properties at the cost of a cycle time which often turns out to be long. Indeed, for each successive layer a roller must spread the powder and the electron beam or laser must scan the entire surface of each layer to obtain good cohesion of the powder.

To reduce this cycle time, the manufacturers' strategy is to increase the power and the number of beams to be able to melt or sinter each layer more quickly, thus increasing the price of the manufacturing machine.

The object of the present invention is to provide an improved manufacturing process for parts made of metal alloy or composite material with a metal matrix, overcoming the known drawbacks of additive manufacturing.

To this end, the subject of the present invention is a method of manufacturing a part made of a metal alloy or of a metal matrix composite material, according to which:

a preform is produced according to an additive manufacturing operation by adding material in powder form, with stacking of successive powder layers, and partial melting of at least certain powder layers, the preform thus being made up of solid parts and zones predefined residual powder, said residual powder being unwelded or partially consolidated; and the preform is subjected to a hot isostatic compaction operation so as to obtain the final shape of the part.

By reducing the scanning time of the layers during the additive manufacturing operation, the overall manufacturing time of the part is reduced and its manufacturing cost is improved.

According to other advantageous characteristics of the process according to the invention, taken individually or in combination:

- The solid parts of the preform include external walls surrounding the areas of residual powder.

- The solid parts of the preform include an internal lattice structure, in which the areas of residual powder are included.

- The trellis structure forms an alveolar network.

- The lattice structure has areas of different lattice densities.

- The hot isostatic compaction operation is carried out with the following parameters: a temperature between 850 and 1000 ° C, preferably between 900 and 950 ° C; a pressure between 900 and 1100 MPa, preferably of the order of 1000 MPa. ; and a duration of between 1 and 3 hours, preferably of the order of 2 hours in an inert atmosphere.

The invention also relates to a part obtained according to the implementation of the process mentioned above.

The invention also relates to a preform produced according to an additive manufacturing operation, characterized in that the preform consists of solid parts and predefined residual powder zones, said residual powder being unwelded or partially consolidated.

The invention will be better understood on reading the description which follows, given solely by way of nonlimiting example and made with reference to the appended drawings in which:

Figure 1 is an elevational view of a preform obtained by implementing the manufacturing method according to the invention; Figure 2 is a section of the preform, taken along the line II-II in Figure 1; Figures 3 and 4 are other sections of the preform, respectively along the lines III-III and IV-IV in Figure 2;

Figure 5 is a perspective view, partially broken away, of the preform of Figures 1 to 4;

Figure 6 is an enlarged view, with an electron microscope, of the detail VI of Figure 4;

Figure 7 is a section of the preform, at the start of the hot isostatic compaction operation;

Figure 8 is a section of the part obtained from the preform, at the end of the hot isostatic compaction operation; and Figures 9 and 10 are views similar to Figure 3, showing variants of preforms according to the invention.

In Figures 1 to 8 is illustrated the method of manufacturing a part 1 according to the invention.

The part 1 can be made of a metal alloy, for example based on iron, aluminum, nickel, titanium, chromium or cobalt. Alternatively, the part 1 may be made of a metal matrix composite material, for example titanium alloy-titanium carbide, aluminum alloy-alumina, or aluminum alloy silicon carbide.

The method according to the invention comprises an additive manufacturing operation, then a hot isostatic compaction operation.

In Figures 1 to 6 is illustrated a preform 10 obtained at the end of the additive manufacturing operation.

In FIGS. 7 and 8 is illustrated the isostatic compaction operation of this preform 10 to obtain the part 1.

The additive manufacturing operation consists in producing the preform 10, by adding material in powder form, with stacking of successive layers of powder, and partial melting of at least certain layers of powder. This accelerates the production of the preform 10 and reduces the cost of the additive manufacturing operation, and therefore the cost of the final part 1.

Thus, the preform 10 consists of solid parts 11 and areas of residual powder 12, not welded or partially consolidated. More specifically, the solid parts 11 include external walls 13 and an internal structure 14 shaped as a trellis. The walls 13 form a solid shell around the zones 12 and of the structure 14. In addition, there is inclusion of zones 12 within the structure 14. The solid parts 11 and zones of residual powder 12 are predefined during the definition. the process for obtaining the desired part 1. In other words, the distribution of parts 11 and zones 12 within part 1 is not obtained accidentally or randomly.

The hot isostatic compaction operation consists in deforming the preform 10, in order to densify and sinter the non-consolidated powder within the preform 10, in the zones 12.

In practice, the preform 10 is placed in an enclosure 20 of hot isostatic compaction. The preform 10 is subjected to temperature and pressure constraints for a certain period of time, until the final shape of the part 1 is obtained. In other words, compaction forces F are exerted over the entire periphery of the preform 10.

The hot isostatic compaction operation makes it possible to weld the powder in zones 12 with the solid parts, with a homogeneous connection of the different layers of the preform. This gives a gain in ductility and fatigue resistance.

As an example, the hot isostatic compaction operation can be performed with the following parameters:

a temperature between 850 and 1000 ° C, preferably between 900 and 950 ° C;

a pressure between 900 and 1100 MPa, preferably of the order of 1000 MPa. ; and a duration of between 1 and 3 hours, preferably of the order of 2 hours in an inert atmosphere.

During the compaction operation, the lattice structure 14 makes it possible to avoid buckling of the walls 13 and to facilitate the conduction of heat to the heart of the preform 10, so as to fuse the powder in the zones 12.

The technique used in the invention is advantageous in the sense that the powder is trapped in the predefined zones 12 within the preform 10, the external walls 13 of which are welded.

Failure to weld all of the powder provides significant savings in cycle time during manufacturing. Indeed, to sinter or melt the powder during additive manufacturing, the laser or the electron beam must scan the entire surface of the preform 10 for each layer. By optimally performing powder melting only on the outer contour of the preform 10 to form the walls 13 and on certain internal lines of the preform 10 to form the structure 14, the solid parts 11 of the preform 10 partially trap the powder consolidated or unconsolidated inside the preform 10.

The compaction of this preform 10 then makes it possible to obtain the final part 1. After deburring or without deburring, part 1 has the functional dimensions to meet the need, without requiring additional machining other than in the functional areas, with restricted tolerance intervals.

Welding the powder during hot deformation is all the more effective on preforms produced in EBM (Electron Beam Melting) due to vacuum manufacturing which makes it possible not to trap gas within the material.

This technique also advantageously makes it possible to obtain a fine-grain microstructure in a large part of the part 1, due to the replacement of the melting of the powder by a solid phase sintering in the zones 12.

Indeed, grain growth by epitaxy on the lower layer was observed during the additive manufacturing of titanium alloy. This growth results in a microstructure with fairly coarse grains which is not good for mechanical properties.

Without melting the powder, we keep the fineness of the microstructure. The non-welded zones 12 of the preform 10 therefore give zones with a very fine microstructure on the final part 1 since the welding takes place in the solid phase during the compaction step. This fine structure which has no crystallographic texture is very good for the static and cyclic mechanical properties of the part.

The grains have a size which is easier to control than for the processes which incorporate a step of melting the material. The microstructure is also equiaxed and without texture, which allows an isotropic mechanical behavior of the part.

In addition, residual manufacturing constraints should be minimized. In fact, the internal stresses are generally lower in a lattice or lattice structure, in comparison with a part of equivalent but massive external geometry. Subsequently, the compaction operation also tends to limit, or even decrease, the residual stresses

The advantages and the unexpected results in the implementation of the invention, thus highlighted, constitute a considerable development in the treatment of metal parts or in metal matrix composites resulting from additive manufacturing.

Other embodiments of a preform 10 according to the invention are shown in FIGS. 9 and 10. Certain constituent elements of the preform 10 are comparable to those of the first embodiment described above and, for the purpose of simplification, have the same reference numbers.

In FIG. 9, the lattice structure 14 forms an alveolar network 15, in honeycomb. The zones 12 are included in this network 15. Such a structure 14 makes it possible to strengthen the resistance of the preform 10, while retaining maximum lightness.

In FIG. 10, the lattice structure 14 has zones 16, 17 and 18 of different lattice densities. The peripheral zone 16, formed against the external walls 16, has a maximum mesh density. The intermediate zone 17, formed between zones 16 and 18, has an average lattice density. The central zone 18, formed at the heart of the preform 10, has a minimum mesh density.

Furthermore, the method, the part 1 and / or the preform 10 may be different from FIGS. 1 to 10 without departing from the scope of the invention.

In addition, the technical characteristics of the various embodiments and variants mentioned above may be, in whole or for some of them, combined together.

Thus, the part 1 can be adapted in terms of cost, functionalities and performance.

Claims (8)

1- Method for manufacturing a part (1) made of a metal alloy or a metal matrix composite material, according to which: a preform (10) is produced according to an additive manufacturing operation by adding material in powder form, with stacking of successive powder layers, and partial melting of at least certain powder layers, the preform (10) thus being constituted solid parts (11) and predefined residual powder zones (12), said residual powder being unwelded or partially consolidated; and the preform (10) is subjected to a hot isostatic compaction operation so as to obtain the final shape of the part (1). 2- Method according to claim 1, characterized in that the solid parts (11) of the preform (10) comprise external walls (13) surrounding the areas of residual powder (12). 3- Method according to any one of claims 1 or 2, characterized in that the solid parts (11) of the preform (10) comprise an internal structure (14) in lattice, in which are included the zones of residual powder ( 12). 4- A method according to claim 3, characterized in that the lattice structure (14) forms an alveolar network (15). 5- Method according to any one of claims 3 or 4, characterized in that the lattice structure (14) has zones (16, 17, 18) of different lattice densities. 6- A method according to any one of claims 1 to 5, characterized in that the hot isostatic compaction operation is carried out with the following parameters: a temperature between 850 and 1000 ° C, preferably between 900 and 950 ° C; a pressure between 900 and 1100 MPa, preferably of the order of 1000 MPa. ; and a duration of between 1 and 3 hours, preferably of the order of 2 hours in an inert atmosphere. 7 - Piece (1) obtained according to the implementation of the method according to any one of claims 1 to 6. 8- Preform (10) produced according to an additive manufacturing operation, characterized in that the preform (10) consists of solid parts (11) and predefined residual powder zones (12), said residual powder being unwelded or partially consolidated. VI