FR2980380A1 - Manufacturing metal part such as blade of turboshaft engine, comprises performing two successive sweepings of same zone of metal powder layer by laser beam or electron beam, where metal powder layer is coated with deposit on support - Google Patents

Abstract

The method comprises performing two successive sweepings of a same zone of a metal powder layer (2) by a laser beam or an electron beam (11) of different energies, where the metal powder layer is coated with a deposit on a support (6), a selective fusion is performed in the metal powder layer by sweeping a surface of the metal powder layer by the laser beam or the electron beam, and a coating part is obtained after solidification of the metal powder layer. A periphery of the part is swept by the laser beam or electron beam whose energy is lower than that used to sweep the core of the part. The method comprises performing two successive sweepings of a same zone of a metal powder layer (2) by a laser beam or an electron beam (11) of different energies, where the metal powder layer is coated with a deposit on a support (6), a selective fusion is performed in the metal powder layer by sweeping a surface of the metal powder layer by the laser beam or the electron beam, and a coating part is obtained after solidification of the metal powder layer. The first sweeping is carried out with a laser beam or an electron beam whose energy is lower or higher than that of the laser beam or the electron beam during the second sweeping. A periphery of the part is swept by the laser beam or electron beam whose energy is lower than that used to sweep the core of the part. The first complete sweeping of the metal powder layer is carried out using the laser beam or the electron beam before carrying out the second complete sweeping of the zone previously swept using the laser beam or the electron beam. The sweeping of the metal powder layer is carried out using first and second beams that are simultaneously moved and shifted one compared to the other so that a trajectory of the second beam follows that of the first beam. The first and second beams are produced by a same source whose beam was divided into two parts or produced by two distinct sources (9). The metal powder layer comprises superalloy of nickel. An average granulometry of the metal powder layer is 40-45 mu m. The first sweeping of the metal powder layer is realized using the laser beam with an energy of 0.22-0.26 Watt.s/mm. The second sweeping is realized using the laser beam with an energy of 0.11-0.13 Watt.s/mm. The periphery of the part is swept by a first laser beam whose energy is 0.14-0.18 Watt.s/mm, and by a second laser beam whose energy is 0.09-0.11 20 Watt.s/m.

Description

The present invention relates to a method of manufacturing layer by layer of a metal part by selective melting of a powder with the aid of a laser beam or a laser beam. an electron beam, such a process also being known as Direct Metal Laser Sintering or Electron Beam Melting. A technique is known which consists in making a part by melting successive layers of powder by means of a laser beam or an electron beam controlled by an information processing system in which the three-dimensional coordinates have been recorded. points of successive layers to achieve. Conveniently, in a vessel whose bottom is formed by a movable plate in translation, a first layer of powder is provided with a scraper. The layer then has a lower surface corresponding to the surface of the plate and an upper surface on which is directed and displaced the laser beam or the electron beam. The energy provided by this beam causes the local melting of the powder which, solidifying, forms a first layer of the metal part. After forming this first layer, the plate is lowered by a distance corresponding to the thickness of a layer, then a second layer of powder is fed by the scraper on the previous layer. In the same way as before, a second layer of the metal part is formed using the beam. These operations are repeated until complete production of the part. Such a method makes it possible to reduce the manufacturing times of the parts by approximately 30% compared with conventional machining.

However, it has been found that parts made using such a process may not have the desired mechanical characteristics. Studies conducted by the Applicant have found that the material of these parts is not always dense enough and can be cracked and / or may have too much porosity. The size of these pores must be as small as possible to reduce the risk of crack initiation they constitute. The larger the crack initiators, the more the cracks generated can spread and seriously damage the part, especially if the latter is subjected to stresses such as vibratory or oligocyclic fatigue. In the case of selective fusion using a laser beam or an electron beam, the higher the energy of the beam, the more the material obtained after solidification of the molten powder bath is dense. However, a beam whose energy is high generates significant thermal gradients ahead and behind the melt liquid bath, which can generate cracks that degrade the mechanical properties of the part, especially if the material is sensitive to cracking such as René 77, TiAI, etc ... The material of the parts obtained by such a process can also have a relatively large heterogeneity, which is unfavorable in terms of mechanical properties.

The objective is to obtain parts whose material is as dense as possible, with the smallest possible porosities, without presenting cracks. The invention aims in particular to provide a simple, effective and economical solution to these problems.

For this purpose, it proposes a method of manufacturing a metal part, carried out layer by layer by depositing a layer of metal powder on a support or on a part already made of the part, then by selective melting of the layer of powder by scanning the surface of the powder layer by a laser beam or an electron beam, a layer of the part being obtained after solidification of the layer of melted powder, characterized in that for each layer of the piece and realized, the method comprises at least two successive scans of the same area of the powder layer by a laser beam or an electron beam. Whereas before, the powder layer was scanned only once by the beam, the invention therefore proposes to perform two successive scans of this layer. This allows better control of the manufacturing process, reduce the risk of cracking and generate layers of higher density material without causing excessive thermal gradients, as well as to homogenize the material of the parts thus manufactured. Preferably, the two successive scans of the same area are made with laser beams or electrons of different energy. In particular, the first scan may be performed with a laser beam or an electron beam whose energy is, relative to that of said beam which provides the following scan: - is lower, in order to preheat the powder to reduce the gradient thermal at the passage of the second sweep that creates the fusion; - higher, in order to obtain a double fusion.

Each scan can thus be performed using a beam having an energy adapted to the desired effect. The first scan makes it possible, for example, to obtain the right density of the material as well as the desired porosity size. The second scan can then be performed with less energy, without destroying the effect of the first scan because the powder has already been melted. This second scan makes it possible to increase the homogeneity of the material and lowers the level of residual stresses of the material. According to another characteristic of the invention, in order to obtain a rougher surface condition, the periphery of the part is scanned twice by a laser beam or an electron beam whose energy is less than that used to scan the core. of the room.

In a first embodiment of the method according to the invention, a first complete scan of the powder layer is carried out using a laser beam or an electron beam before carrying out at least a second complete scanning of the previously scanned area using the laser beam or the electron beam. This first mode makes it possible to use only one laser source which carries out two complete sweeps, one after the other. In a second embodiment of this method, the powder layer is scanned using a first and a second beam, at least, moved in synchronism and offset with respect to the other so that the trajectory of the second beam follows, at least partially, that of the first beam. This second embodiment makes it possible to produce parts with a very short cycle time.

In the context of the second embodiment, the two beams may be produced by the same source, whose beam has been divided into at least two parts, or by two separate sources. It should be noted that the use of a single source makes it possible to obtain two beams of different energies.

Advantageously, the powder is made of nickel-based superalloy, the mean particle size of the powder being between 40 and 45 μm, the first scan of the powder layer being made using a laser beam of linear energy between 0.22 and 0.26 Watt s / mm, the second scan being performed using a laser energy beam of between 0.11 and 0.13 Watt s / mm. In addition, to improve the surface condition, the periphery of the part can be scanned by a first laser beam whose linear energy is between 0.14 and 0.18 Watt s / mm, then by a second beam laser whose energy is between 0.09 and 0.11 Watts / mm.

The invention will be better understood and other details, features and advantages of the invention will become apparent on reading the following description given by way of non-limiting example with reference to the accompanying drawings, in which: FIG. 1 is a view schematic diagram of a selective powder melting plant; - Figures 2 to 4 are seen from a portion of the installation, according to three embodiments of the invention. FIG. 1 represents a selective powder melting installation used for the manufacture of parts such as, for example, turbomachine blades. This installation comprises a tank 1 containing a metal powder 2 and whose bottom 3 is movable and movable in vertical translation by a rod 4 of a jack, and a neighboring tank 5 whose bottom is constituted by a movable plate 6, also movable in vertical translation by a rod 7 of a jack. The installation further comprises a scraper 8 for feeding powder from the tank 1 to the tank 5, by displacement in a horizontal plane A, and means 9 for generating a laser beam or a beam of electrons, coupled to a computer controlled device 10 for orienting and moving the beam 11. A receiving tray 12 of the excess powder 13, adjacent to the tank 5, can also be provided.

The operation of this installation is as follows. First, the bottom 3 of the tank 1 is moved upwards so that a certain amount of powder 2 is located above the horizontal plane A. The scraper 8 is moved from left to right, in order to scrape said powder layer 2 in the reservoir 1 and deposit a thin layer of metal powder on the horizontal flat surface of the plate 6. The quantity of powder 2 and the position of the plate 6 are determined so as to form a layer of powder of a chosen and constant thickness.

In a first embodiment of the method, a laser beam 11 or an electron beam, perpendicular to the plane A, scans for a first time a determined zone of the powder layer formed in the tank 5, so as to preheat it or melt it locally. The melted zones then solidify by forming a first layer of material 14, this layer having, for example, a thickness of the order of 10 to 200 μm. This layer is then scanned a second time by the laser beam 11 or by the electron beam. In this case, a first complete scan of the powder layer with a laser beam or an electron beam is then performed before performing at least a second complete scan of the previously scanned area. using a laser beam or an electron beam. A single laser or electron source 9 can be used for the implementation of such a method, as shown schematically in FIG. 2.

Alternatively, it is also possible to scan the powder layer using a first and a second beam 11a, 11b, moved simultaneously in synchronism and offset with respect to each other so that the trajectory of the second beam 11b follows, at least partially, that of the first beam 11a.

In such a case, the two beams 11a, 11b may be produced by two separate sources 9 (FIG. 3), or by a single source 9 whose beam has been divided into two parts by a bifocal optical system 15 or by any other means beam separation (Figure 4), each of the two beams being then controlled by a scanning device and / or by a separate optical arrangement 16 to obtain the expected scan and energy. According to the invention, the two successive scans of the same zone are advantageously made with laser beams or electrons of different energies. In particular, the first scan is performed with a laser beam or an electron beam whose energy is, relative to that of said beam during the next scan, either lower (preheating) or higher (double melting). In addition, the periphery of the part is advantageously scanned successively by a laser beam or an electron beam whose energy is less than that used to scan the heart of the part. By way of example, in the case where the powder is made of nickel-based superalloy and the mean particle size of the powder is between 40 and 45 μm, the first sweep of the powder layer is carried out using an energy laser beam of between 0.22 and 0.26 Watt s / mm, the second scan of the powder layer being carried out using an energy laser beam of between 0.11 and 0.13 Watt s / mm. In this case also, the periphery of the part is scanned by a first laser beam whose energy is between 0.14 and 0.18 Watt s / mm, then by a second laser beam whose energy is included. between 0.09 and 0.11 Watt s / mm. The periphery has for example a width of between 50 and 100 lm. The thickness of each layer of the part is between 10 and 45 μm, respectively between 45 and 150 μm, when the powder is melted with the aid of a laser beam or with a laser beam respectively. electrons. Thin films are preferred because they control the roughness. Once a first layer of the piece has been made, the plate 6 is lowered and then a second layer of powder is fed, in the same manner as before, onto the first layer of powder. These operations are repeated until the complete formation of the piece. The layers have substantially the same thickness. In the case where the part is built layer by layer by selective melting of the powder by means of a laser beam, the powder has an average grain size of between 10 and 50 μm, preferably between 40 and 45 μm. . In the case where the part is built layer by layer by selective melting of the powder with the aid of an electron beam, the powder has an average grain size of between 50 and 100 μm. The method according to the invention makes it possible to generate parts of greater density without causing excessive thermal gradients, and to homogenize the material of the parts thus produced. In addition, the parts made using this method do not necessarily need to undergo an additional heat treatment operation and / or hot isostatic compaction, which is an obvious gain in terms of time and cost of the process. manufacturing cycle.

Claims (10)

REVENDICATIONS1. Process for manufacturing a metal part, carried out layer by layer by depositing a layer of metal powder (2) on a support (6) or on a part already made of the part, then by selective melting of the powder layer by scanning the surface of the powder layer by a laser beam or an electron beam (11), a layer of the part being obtained after solidification of the molten powder layer, characterized in that, for each layer of the piece thus produced, the method comprises at least two successive scans of the same area of the powder layer by a laser beam or an electron beam (11). 2. Manufacturing process according to claim 1, characterized in that the two successive scans of the same area are made with laser beams or electrons (11) of different energies. 3. Method according to claim 1 or 2, characterized in that the first scan is performed with a laser beam or an electron beam (11) whose energy is, according to the desired effect, either less than or greater than that of said beam (11) during the next scan. 4. Method according to one of claims 1 to 3, characterized in that the periphery of the part is scanned by a laser beam or an electron beam (11) whose energy is less than that used to scan the heart of the room. 5. Method according to one of claims 1 to 4, characterized in that a first complete scan of the powder layer is carried out using a laser beam or an electron beam (11) before performing at least a second complete scan of the previously scanned area with a laser beam or an electron beam (11). 6. Method according to claim 1 to 4, characterized in that a scanning of the powder layer is carried out using a first and a second beam (11a, 11b), at least, simultaneously moved ensynchronism and offset with respect to each other so that the path of the second beam (11b) follows, at least partially, that of the first beam (11a). 7. Method according to claim 6, characterized in that the two beams are produced by the same source (9), the beam of which has been divided into at least two parts. 8. Method according to claim 6, characterized in that the two beams (11a, 11b) are produced by two separate sources (9). 9. Method according to one of claims 1 to 8, characterized in that the powder (2) is nickel-based superalloy, the average particle size of the powder (2) being between 40 and 45 lm, the first sweep the powder layer is produced using a laser beam (11) of energy between 0.22 and 0.26 Watt s / mm, the second scan being carried out using a beam laser (11) with a power of 0.11 and 0.13 watts. s / mm. 10. Method according to claims 4 and 9, characterized in that the periphery of the part is scanned by a first laser beam (11) whose energy is between 0.14 and 0.18 Watt s / mm, then by a second laser beam (11) whose energy is between 0.09 and 0.11 Watt. s / m m.