METHOD FOR THE PRODUCTION OF PARTS MADE FROM METAL OR METAL MATRIX COMPOSITE AND RESULTING FROM ADDITIVE MANUFACTURING FOLLOWED BY AN OPERATION INVOLVING THE FORGING OF SAID PARTS

Abstract

A method of manufacturing a piece of metal alloy or of metal matrix composite materials includes making a preform by additive manufacturing by adding material in successive layers, and subjecting the preform to a forging operation taking place in a single step and between two dies with a view to obtaining the final shape of the piece.

Claims

1- A method of manufacturing a piece of metal alloy or of metal matrix composite materials, comprising: making a preform by additive manufacturing by adding material in successive layers; and subjecting the preform to a forging operation taking place in a single step and between two dies with to obtain a final shape of the piece.

2- The method according to claim 1, wherein the piece of metal alloy comprises an alloy based on iron, aluminum, nickel, titanium, chromium, or cobalt.

3- The method according to claim 1, wherein the piece of composite materials comprises a titanium-titanium carbide alloy, an aluminum-alumina alloy, or an aluminum-silicon carbide alloy.

4- The method according to claim 1, wherein the forging operation is performed semi-hot or cold or hot.

5- The method according to claim 1, wherein the preform contains zones in which a powder is not bonded or is partially consolidated.

6- Pieces or parts obtained by implementing the method according to claim 1.

Description

[0013] In entirely unexpected manner, and on the basis of tests conducted by the Applicant, it has appeared that implementing a combination of the two technologies is capable of responding to and of remedying the drawbacks observed in additive manufacturing.

[0014] In accordance with the invention, the solution that has been developed consists in obtaining a piece of metal alloy or of metal matrix composite materials by additive manufacturing so as to form a preform, and then in forging said preform while it is hot, semi-hot, or cold, in a single step implemented between two dies with a view to obtaining the final shape for the piece to be obtained.

[0015] The resulting piece thus has its final shape, and, after deburring or without deburring, has the functional dimensions to be fit for purpose without requiring additional machining other than of the functional zones with limited tolerance ranges.

[0016] In entirely unexpected mariner, this method makes it possible to overcome the above-mentioned drawbacks and the limits observed with pieces obtained by additive manufacturing.

[0017] The forging step that consists in deforming the material makes it possible to reclose and to re-bond the microporosities with uniform boding of the various layers of the additive structure. This gives improved ductility and fatigue strength.

[0018] This step of forging between two polished dies also enables the surface roughness to be drastically reduced, thereby making it possible to improve the fatigue strength and the surface appearance.

[0019] The tests that have been conducted appear very promising. No indication of either of the technologies known since 1983-1984 could have suggested combining them because the state in which the preform was obtained was different, the preform being obtained by casting in the cast-and-forged technology, whereas it is obtained by fusing (melting together) or sintering successive layers in additive manufacturing.

[0020] In the context of implementing the invention, the piece may be a piece of metal alloy (based on steel, iron, aluminum, Inconel, nickel, titanium, chromium-cobalt, etc.) or of metal matrix composite materials (titanium-titanium carbide, aluminum-alumina, aluminum-silicon carbide, etc.).

[0021] The forging second step of the invention for forging the preform obtained by additive manufacturing may be performed hot, semi-hot, or cold. The dies may optionally be polished.

[0022] This technology of die forging a preform obtained by additive manufacturing may also be applied to preforms that have non-bonded or partially consolidated powder zones that are then deformed and bonded during the forging step. Forging powder preforms manufactured by uniaxial or isostatic compaction is already a known method. The technique used in the invention is novel in that the powder is held captive within the preform that has a bonded periphery. The fact that not all of the powder is bonded makes it possible to save a considerable amount of cycle time during the manufacturing. In order to sinter or melt the powder during additive manufacturing, the laser or the electron beam needs to sweep the entire surface of the piece for each layer. By performing the powder fusion optimally on the outside outline of the preform only, the preform thus being constituted by a solid bonded shell holding the partially consolidated or non-consolidated powder captive inside it, a preform is obtained that is in the form of a solid shell filled with non-bonded powder. Forging this preform makes it possible to obtain the end piece or part. Bonding the powder during the hot deformation is particularly effective on preforms manufactured by EBM due to such manufacturing taking place in a vacuum, which makes it possible to trap any gas inside the material.

[0023] This technique also offers the advantage of obtaining a microstructure having fine particles due to the fact that there is no fusion of the powder. Epitaxial growth of the particles on the lower layer has been observed during additive manufacturing of titanium alloy. Such growth gives rise to a microstructure with rather course particles, which is not good for the mechanical properties. With no fusion of the powder, the fineness of the microstructure is preserved. The non-bonded zones of the preform thus give zones with a very fine microstructure on the final piece or part because the bonding takes place in solid phase during the forging step. Such a fine structure that does not have any crystallographic texture is very good for the static and cyclic mechanical properties of the piece or part.

[0024] The above-highlighted advantages and unexpected results with implementing the invention constitute a considerable development in processing pieces of metal or of metal matrix composite that are obtained by additive manufacturing.