PROCEDE DE FABRICATION ADDITIVE

Abstract

Additive manufacturing method by laser fusion of a powder jet on a substrate, the powder jet comprising at least a first material (A) and a second material (B) according to a set total mass composition. Abstract figure: Figure 4

Description

Title of the invention: ADDITIVE MANUFACTURING PROCESS Technical field

[0001] The present description relates to an additive manufacturing method and an additive manufacturing device. Prior art

[0002] In the present text, "additive manufacturing process" has the meaning both of an initial manufacture of the part 40, and of a repair of a part 40 already manufactured (by any technique whatsoever) and of which an area is reloaded by "additive manufacturing", that is to say by an addition of material from metallic powder which can be carried out by a process of laser fusion of a powder jet or "LMD" as below.

[0003] An additive manufacturing process such as “Laser Metal Deposition” (LMD), consists of manufacturing a three-dimensional part 40 by a device 10 shown in [Fig.l]. The device 10 comprises a nozzle 20 from which a jet of metal powder is ejected, and a laser beam in order to achieve the fusion of the powder on a substrate. A succession of metal layers can thus be formed and secured to the substrate.

[0004] The device 10 may in particular comprise one or more reservoirs each comprising a metal powder. In the example shown in [Fig. 1], the device 10 comprises a first reservoir 12 comprising a metal powder of a first material A and a second reservoir 14 comprising a metal powder of a second material B different from the first material A.

[0005] The powder jet can therefore comprise either a single powder from one of the reservoirs, or a mixture of powders from several reservoirs. Thus, each metal layer can comprise 100% of the first material A, 100% of the second material B or a mixture of the first material A and the second material B.

[0006] As shown in Figure 2a, the manufacturing method may be of the type "multi-material" in that the part 40 obtained comprises a first part 42 adjacent to a second part 44, the first part 42 comprising 100% of the first material A and the second part 44 comprising 100% of the second material B. Alternatively, as shown in Figure 2b, the manufacturing method may be of the "gradient material" type in that the part 40 obtained comprises a first part 42 comprising 100% of the first material A and a second part 44 comprising 100% of the second material B and an intermediate part 46 between the first part 42 and the second part 44 which comprises a mixture of the first material A and the second material B. In particular, the intermediate portion 46 comprises a composition gradient between the first material A and the second material B (or, in other words, the intermediate portion 46 can form a “gradual” transition between the first portion 42 and the second portion 44).

[0007] The current manufacturing method as described above, however, has the disadvantage that it does not allow a deviation to be detected between the composition of the powder from the mixer and the desired composition. Such a deviation is in fact detrimental in that the part 40 obtained is not made in the desired alloy grade. However, the performance in terms of thermal and mechanical properties of the part 40 obtained depends directly on the composition of the material from which the part 40 is made.

[0008] Furthermore, when the composition of the powder from the mixer does not correspond to the desired composition, the manufacturing parameters, such as the power of the laser or the speed of advancement of the nozzle 20, may not be adapted to the desired part 40. Manufacturing defects may then result, such as an unstable deposit, increased porosity of the part 40 obtained, or even poor dimensions of the part 40 obtained.

[0009] Finally, a poor composition of the material from which the manufactured part 40 is made is difficult to identify once the part 40 is manufactured. Summary

[0010] A method of additive manufacturing by melting a powder jet onto a substrate is proposed, the powder jet comprising at least a first material and a second material according to a set total mass composition, the method comprising a manufacturing phase which comprises the steps: - delivering at least a first powder of the first material into a mixer according to a first mass flow rate; - delivering at least a second powder of the second material into the mixer according to a second mass flow rate; - mix the first powder and the second powder in the mixer; - conveying the mixture of the first powder and the second powder to a deposition nozzle; - take a portion of the mixture of the first powder and the second powder which is conveyed to the deposition nozzle; - determine a mass proportion of the first material and the second material in the mixture; - compare the mass proportion of the first material and the second material in the mixture with respect to the total mass composition setpoint of the powder jet; - modify at least one of the first mass flow rate and the second mass flow rate in the event of a discrepancy between the mass proportion of the first material and the second material in the mixture and the total mass composition setpoint of the powder jet.

[0011] Such a method makes it possible to detect a mass composition of the mixture (i.e. the mass proportion of the first material and the second material in the mixture), to compare it with the total set mass composition of the powder jet and to rectify, if necessary, the mass flow rate of the first powder and the second powder in the mixer so as to obtain a defined mass composition of the mixture. Thus, the method makes it possible to limit, or even prevent, the manufacture of a part in an undesired alloy grade. As a result, the manufactured part has better quality and better performance.

[0012] Furthermore, determining the mass proportion of the first material and the second material after mixing the first powder and the second powder makes it possible to detect a difference in mass composition which would be due to an anomaly during the supply of the first powder and / or the second powder to the mixer but also to an anomaly during the mixing in the mixer. Thus, the method makes it possible to ensure that the mixture arriving at the deposition nozzle has the total mass composition setpoint, especially since the sources of variations in the mass composition between the mixer and the deposition nozzle are limited.

[0013] Finally, the control and correction of the mass composition of the mixture are carried out during the manufacture of the part. Thus, the control and correction of the mass composition of the mixture is carried out in masked time, which makes it possible to avoid reducing the productivity of the process.

[0014] The melting of the powder jet can be carried out by means of a laser (high energy) or by an electron beam (also known as “Electron Beam Melting” or EBM).

[0015] A construction delay may also be provided upon detection of a difference between the mass composition of the mixture and the total set mass composition. This delay makes it possible to stabilize the adjusted mass flow rates of the first material and the second material, and to rehomogenize the mixture in the mixer before continuing the manufacturing.

[0016] Determining the mass proportion of the first material and the second material in the mixture may comprise: - measure the mass flow rate of the sampled portion of the mixture through a measuring orifice which has a predetermined diameter; - identify the mass proportion of the first material and the second material in the mixture from a comparison with a database that includes mass flow rate values through an orifice of diameter identical to that of the orifice measuring method for a powder comprising the first material and the second material whose mass composition varies between 100% first material and 100% second material.

[0017] Such a method for determining the mass proportion of the first material and the second material in the mixture has the advantage of being compatible with a wide range of materials. In addition, this allows rapid determination of the mass proportion of the first material and the second material in the mixture. Finally, the measurement of the mass flow rate of the sampled portion of the mixture through the measuring orifice and the identification of the mass proportion of the first material and the second material in the mixture in the database can be carried out in an automated manner, for example by an automaton.

[0018] The database may comprise the mass flow rate value through an orifice of diameter identical to that of the measuring orifice for a powder comprising the first material and the second material for each mass composition comprising x% of first material and (100-x)% of second material with x between 0 and 100 in an increment of 10%, preferably 5%, more preferably 1%.

[0019] The method may comprise a calibration phase for establishing the database, the calibration phase comprising the steps: i° provide a calibration powder comprising at least the first material and the second material according to a known mass composition of the first material and the second material; ii° measure a mass flow rate of a flow of the calibration powder through a calibration orifice which has a diameter identical to that of the measuring orifice; iii° repeat steps i° and ii° by varying the mass composition of the calibration powder between 100% of first material and 100% of second material.

[0020] Steps i° and ii° can be repeated for each mass composition of the calibration powder comprising x% of first material and (100-x)% of second material with x between 0 and 100 according to an increment of 10%, preferably 5%, more preferably 1%.

[0021] The diameter of the calibration orifice and the diameter of the measuring orifice can be adapted to the density of the mixed materials. The diameter of the calibration orifice and the diameter of the measuring orifice can be chosen so that the relative difference between the mass flow rate of the calibration powder whose mass composition comprises 100% of the first powder and the mass flow rate of the calibration powder whose mass composition comprises 100% of the second powder is greater than or equal to 10%. This allows a more precise determination and faster mass proportion of first material and second material in the mixture during the manufacturing phase.

[0022] The first mass flow rate and / or the second mass flow rate may be varied so as to maintain a constant mass flow rate of the powder jet.

[0023] The mixture may be delivered to the deposition nozzle via a transport gas stream and wherein the method comprises a step which comprises separating the withdrawn portion of the mixture from the transport gas.

[0024] According to another aspect, there is provided an additive manufacturing device comprising: - a first reservoir comprising a first powder of a first material; - a second reservoir comprising a second powder of a second material; - a mixer in communication with the first reservoir and the second reservoir, the mixer being adapted to form a mixture of the first powder and the second powder; - means for controlling a supply of first powder and second powder respectively according to a first mass flow rate and a second mass flow rate in the mixer; - a main conduit connecting the mixer to a deposition nozzle and through which the mixture is conveyed to the deposition nozzle; - a sampling conduit in communication with the main conduit, the sampling conduit being adapted to sample a portion of the mixture conveyed to the deposition nozzle; - determination means for measuring the mass proportion of the first material and the second material in the sampled portion of the mixture; - comparison means for comparing the mass proportion of first material and second material in the mixture with a set total mass composition and modification means for modifying the first mass flow rate and / or the second mass flow rate in the event of a difference between the mass proportion of first material and second material in the mixture and the set total mass composition.

[0025] The determining means for measuring the mass proportion of the first material and the second material in the mixture may comprise means for measuring a mass flow rate of the sampled portion of the mixture through a measuring orifice which has a predetermined diameter and a database which comprises the mass flow rate values through an orifice of diameter identical to that of the measuring orifice for a powder comprising the first material and the second material whose mass composition varies between 100% of first material and 100% of second material.

[0026] The means for measuring the mass flow rate of the sampled part of the mixture through the measuring orifice may comprise a member comprising the measuring orifice through which the sampled portion of the mixture can flow and a weighing system.

[0027] The device may comprise means for generating and / or managing a flow of transport gas for conveying the mixture from the mixer to the deposition nozzle, the device further comprising means for separating the withdrawn portion of the mixture from the transport gas. Brief description of the drawings

[0028] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which:

[0029] [Fig.l] schematically represents an additive manufacturing device according to the state of the art;

[0030] [Fig.2] comprises figures 2a and 2b which each schematically represent a multi-material or material gradient part manufactured by the device of [Fig.l];

[0031] [Fig.3] is a functional diagram of a manufacturing phase of an additive manufacturing process according to the present description;

[0032] [Fig.4] schematically represents a manufacturing device for implementing the method of [Fig.3].

[0033] [Fig.5] is a functional diagram of a calibration phase of the process of [Fig.3]

[0034] [Fig.6] is a graph which represents the evolution of mass flow rate through an orifice of predetermined diameter of a powder comprising a first material and a second material whose mass composition varies between 100% of the first material and 100% of the second material;

[0035] [Fig.7] is a graph which represents the evolution of the mass flow rate through an orifice of a powder comprising a first material and a second material according to different known mass compositions as a function of the diameter of the orifice. Description of the embodiments

[0036] Reference is now made to Figures 3 and 4. [Fig. 3] represents a functional diagram of a manufacturing phase 100 of an additive manufacturing process by melting a jet of powder onto a substrate. [Fig. 4] schematically represents an additive manufacturing device 10 suitable for implementing the manufacturing phase 100 of the process of [Fig. 3].

[0037] The powder jet here comprises a first material A and a second material B according to a total set mass composition. The total set mass composition corresponds to the desired alloy grade in which the part must be manufactured. Generally, the powder jet may comprise k materials with a integer greater than or equal to 2. Thus, according to alternatives not described, the powder jet may comprise more than two materials, for example the powder jet may comprise three or four materials. Also, the method may be of the “multi-material” type or of the “gradient material” type as described above.

[0038] The manufacturing phase 100 comprises a first step 110. The first step 110 of the manufacturing phase 100 comprises the supply of a first powder of the first material A into a mixer 16 according to a first mass flow rate Q1. In other words, the first powder has a mass composition comprising 100% of the first material A. The first step 110 further comprises the supply of a second powder of the second material B into the mixer 16 according to a second mass flow rate Q2. In other words, the second powder has a mass composition comprising 100% of the second material B. The supply of the first powder and the second powder can be carried out simultaneously in the mixer 16. The first mass flow rate Q1 and the second mass flow rate Q2 are determined so as to obtain the total mass composition setpoint.

[0039] For this purpose, the device 10 comprises a first reservoir 12 comprising the first powder of the first material A and a second reservoir 14 comprising the second powder of the second material B. Generally, the device 10 may comprise k reservoirs with k an integer greater than or equal to 2 with each reservoir comprising a specific material. The device 10 also comprises the mixer 16, the latter being in (fluidic) communication with the first reservoir 12 and the second reservoir 14. In addition, the device 10 comprises control means for controlling the supply of first powder and second powder respectively according to the first mass flow rate Q1 and the second mass flow rate Q2.

[0040] The manufacturing phase 100 comprises a second step 120. The second step 120 of the manufacturing phase 100 comprises the mixing of the first powder and the second powder in the mixer 16. For this purpose, the mixer 16 is adapted to form a mixture, preferably homogeneous, of the first powder and the second powder.

[0041] The manufacturing phase 100 comprises a third step 130. The third step 130 of the manufacturing phase 100 comprises conveying the mixture of the first powder and the second powder to a deposition nozzle 20 of the device 10. For this purpose, the device 10 comprises a main conduit 18 connecting the mixer 16 to the deposition nozzle 20 and through which the mixture is conveyed to the deposition nozzle 20. In particular, the mixture may be conveyed to the deposition nozzle 20 via a flow of transport gas. The device 10 may therefore further comprise means for generating the flow of transport gas in the main conduit 18. The deposition nozzle 20 generates the powder jet from the mixture. The nozzle 20 comprises furthermore a laser to heat the substrate and generate a melt pool locally on the substrate. The powder is directly projected into the melt pool so that it melts and bonds to the substrate. The nozzle can also be mobile. It is thus possible to form a succession of layers comprising the first material A and / or the second material B.

[0042] The manufacturing phase 100 comprises a fourth step 140. The fourth step 140 of the manufacturing phase 100 comprises the sampling of a portion of the mixture of the first powder and the second powder which is conveyed to the deposition nozzle 20. In other words, the sampling of the mixture is carried out at the main conduit. To do this, the device 10 comprises a sampling conduit 22 in (fluidic) communication with the main conduit 18, the sampling conduit 22 being adapted to sample a portion of the mixture conveyed to the deposition nozzle 20. The fourth step 140 may further comprise the separation of the sampled portion of the mixture from the transport gas by separation means 24.

[0043] The manufacturing phase 100 comprises a fifth step 150. The fifth step 150 of the manufacturing phase 100 comprises the determination of a mass proportion of the first material A and the second material B in the mixture. The device 10 here comprises determination means 26 for determining a mass proportion of the first material A and the second material B in the portion taken from the mixture.

[0044] First, the determination of the mass proportion of the first material A and the second material B in the mixture comprises a measurement of the mass flow rate of the portion taken from the mixture through a measuring orifice which has a predetermined diameter. For this purpose, the determination means 26 comprise means for measuring a mass flow rate of the portion taken from the mixture through the measuring orifice which comprise a member having the measuring orifice through which the portion taken from the mixture can flow and a weighing system. Thus, the measurement of the mass of the portion taken from the mixture which has flowed (under the effect of gravity) through the measuring orifice for a known period of time makes it possible to determine the mass flow rate of the portion taken from the mixture through the measuring orifice.

[0045] Then, the determination of the mass proportion of the first material A and the second material B in the mixture comprises the identification of the mass proportion of the first material A and the second material B in the mixture from a database (or an abacus) of the determination means 26. The database comprises the mass flow rate values through an orifice of diameter identical to that of the measuring orifice for a powder comprising the first material A and the second material B and whose mass composition varies between 100% of first material A and 100% of second material B. Such a method to determine the mass proportion of the first material A and the second material B in the mixture has the advantage of being compatible with a wide range of materials. In addition, this allows a rapid determination of the mass proportion of the first material A and the second material B in the mixture. Finally, the measurement of the mass flow rate of the sampled portion of the mixture through the measuring orifice and the identification of the mass proportion of the first material A and the second material B in the mixture in the database can be carried out in an automated manner, i.e. by an automaton for example.

[0046] The database may comprise the mass flow rate value through an orifice of diameter identical to that of the measuring orifice for a powder comprising the first material A and the second material B for each mass composition comprising x% of first material A and (100-x)% of second material B with x varying between 0 and 100 according to an increment of 10%, preferably 5%, more preferably 1%. In particular, the lower the percentage increment of the database, the more precise the determination of the mass proportion of first material A and second material B in the mixture will be.

[0047] [Fig.6] is a graph illustrating the database which includes the mass flow rate value through an orifice of diameter identical to that of the measuring orifice of a powder comprising the first material A and the second material B for each mass composition comprising x% of first material A and (100-x)% of second material B with x varying between 0 and 100 according to an increment of 10%, i.e. for the following mass compositions: 100%A; 90%A-10%B; 80%A-20%B; 70%A-30%B; 40%A-60%B; 50%A-50%B; 40%A-60%B; 30%A-70%B; 20%A-80%B; 10%A-90%B; 100%B. In the example graph in [Fig.6], the mass flow rate evolves linearly for a variation in mass composition between 100A% and 100%B. However, it is not excluded that the mass flow rate evolves non-linearly for a variation in mass composition between 100A% and 100%B.

[0048] The method further comprises a calibration phase 200 during which the database is established. [Fig.5] represents a functional diagram of the calibration phase 200 of the method.

[0049] The calibration phase 200 comprises a first step 210. The first step 210 of the calibration phase 200 comprises the provision of a calibration powder comprising at least the first material A and the second material B according to a known mass composition of the first material A and the second material B.

[0050] The calibration phase 200 comprises a second step 220. The second step 220 of the calibration phase 200 comprises the measurement of a mass flow rate of a flow of the calibration powder through a calibration orifice which has a diameter identical to that of the measuring orifice.

[0051] The first step 210 and the second step 220 are then repeated by varying the mass composition of the calibration powder between 100% of first material A and 100% of second material B. The first step 210 and the second step 220 can be repeated for each mass composition of the calibration powder comprising x% of first material A and (100-x)% of second material B with x varying between 0 and 100 according to an increment of 10%, preferably 5%, more preferably 1%. In the example of the database represented by the graph of [Fig.6], the first step 210 and the second step 220 are repeated 10 times.

[0052] With reference to [Fig.7], the diameter of the calibration orifice and the diameter of the measuring orifice may be chosen so as to be greater than or equal to a threshold diameter Ds for which the relative difference between the mass flow rate of the calibration powder whose mass composition comprises 100% of first powder and the mass flow rate of the calibration powder whose mass composition comprises 100% of second powder is greater than or equal to 10%. This allows a more precise and faster determination of the mass proportion of first material A and second material B in the mixture during the manufacturing phase 100.

[0053] The manufacturing phase 100 comprises a sixth step 160. The sixth step 160 of the manufacturing phase 100 comprises comparing the mass proportion of the first material A and the second material B in the mixture with respect to the total set mass composition of the powder jet and modifying at least one of the first mass flow rate Q1 and the second mass flow rate Q2 in the event of a difference between the mass proportion of the first material A and the second material B in the mixture and the total set mass composition of the powder jet.

[0054] To do this, the device 10 comprises comparison means 28 for comparing the mass proportion of first material A and second material B in the mixture with the total set mass composition and modification means 30 for modifying the first mass flow rate Q1 and / or the second mass flow rate Q2 in the event of a difference between the mass proportion of first material A and second material B in the mixture and the total set mass composition. The comparison means 28 and modification means 30 may in particular be in communication with the control means.

[0055] Such a method makes it possible to detect a mass composition of the mixture which does not correspond to the total mass composition setpoint of the powder jet and to rectify the mass flow rate of supply of first powder and second powder in the mixer 16 so as to obtain a correct mass composition of the mixture. Thus, the method makes it possible to limit, or even prevent, the manufacture of a part in an unwanted alloy grade. As a result, the manufactured part has better quality and performance.

[0056] Furthermore, determining the mass proportion of the first material A and the second material B after having mixed the first powder and the second powder makes it possible to detect a difference in mass composition which would be due to an anomaly during the supply of the first powder and / or the second powder to the mixer 16 but also to an anomaly during the mixing in the mixer 16. Thus, the method makes it possible to ensure that the mixture arriving at the deposition nozzle 20 has the total mass composition setpoint, all the more so since the sources of variations in the mass composition between the mixer 16 and the deposition nozzle 20 are limited, or even non-existent.

[0057] Finally, the control and correction of the mass composition of the mixture are carried out during the manufacture of the part. Thus, the control and correction of the mass composition of the mixture is carried out in masked time, which makes it possible to avoid reducing the productivity of the process.

[0058] Preferably, in the event of modification of the first mass flow rate Q1 and / or the second mass flow rate Q2, the first mass flow rate Q1 and / or the second mass flow rate Q2 can be modified so as to maintain a constant total mass flow rate of the powder jet.

[0059] According to a particular embodiment, a temporary shutdown of the laser may also be provided in response to the modification of the first mass flow rate Q1 and / or the second mass flow rate Q2 in the event of detection of a difference between the mass composition of the mixture and the total set mass composition. This makes it possible to rehomogenize the mixture in the mixer 16 before continuing the manufacturing. The laser can then be reactivated.

Claims

Claims

1. Additive manufacturing method by melting a powder jet onto a substrate, the powder jet comprising at least a first material (A) and a second material (B) according to a set total mass composition, the method comprising a manufacturing phase (100) which comprises the steps: - delivering at least a first powder of the first material (A) into a mixer (16) according to a first mass flow rate (Q1); - delivering at least a second powder of the second material (B) into the mixer (16) according to a second mass flow rate (Q2); - mixing the first powder and the second powder in the mixer (16); - conveying the mixture of the first powder and the second powder to a deposition nozzle (20); - taking a portion of the mixture of the first powder and the second powder which is conveyed to the deposition nozzle (20); - determine a mass proportion of the first material (A) and the second material (B) in the mixture; - compare the mass proportion of the first material (A) and the second material (B) in the mixture with respect to the total mass composition setpoint of the powder jet; - modify at least one of the first mass flow rate (Q1) and the second mass flow rate (Q2) in the event of a difference between the mass proportion of the first material (A) and the second material (B) in the mixture and the total mass composition setpoint of the powder jet.

2. Additive manufacturing method according to the preceding claim, in which the determination of the mass proportion of the first material (A) and the second material (B) in the mixture comprises: - measure the mass flow rate of the sampled portion of the mixture through a measuring orifice which has a predetermined diameter; - identify the mass proportion of the first material (A) and the second material (B) in the mixture from a comparison with a database which includes the mass flow rate values through an orifice of diameter identical to that of the measuring orifice for a powder comprising the first material (A) and the second material (B) whose mass composition varies between 100% of first material (A) and 100% of second material (B).

3. Additive manufacturing method according to the preceding claim, the method comprising a calibration phase (200) for establishing the database, the calibration phase (200) comprising the steps: i° providing a calibration powder comprising at least the first material (A) and the second material (B) according to a known mass composition of the first material (A) and the second material (B); ii° measuring a mass flow rate of a flow of the calibration powder through a calibration orifice which has a diameter identical to that of the measuring orifice; iii° repeating steps i° and ii° by varying the mass composition of the calibration powder between 100% of first material (A) and 100% of second material (B).

4. A method according to any preceding claim, wherein the first mass flow rate (A) and / or the second mass flow rate (B) are varied so as to maintain a constant total mass flow rate of the powder jet.

5. A manufacturing method according to any preceding claim, wherein the mixture is fed to the deposition nozzle (20) via a transport gas stream and wherein the method comprises a step which comprises separating the withdrawn portion of the mixture from the transport gas.

6. An additive manufacturing device (10) comprising: - a first reservoir (12) comprising a first powder of a first material (A); - a second reservoir (14) comprising a second powder of a second material (B); - a mixer (16) in communication with the first reservoir (12) and the second reservoir (14), the mixer being adapted to form a mixture of the first powder and the second powder; - control means for controlling a supply of first powder and second powder respectively according to a first mass flow rate (Q1) and a second mass flow rate (Q2) in the mixer (16); - a main conduit (18) connecting the mixer (16) to a deposition nozzle (20) and through which the mixture is conveyed to the deposition nozzle (20); - a sampling conduit (22) in communication with the main conduit (18), the sampling conduit (22) being adapted to sample a portion of the mixture conveyed to the deposition nozzle (20); - determination means (26) for determining a mass proportion of the first material and the second material in the sampled portion of the mixture; - comparison means (28) for comparing the mass proportion of the first material and the second material in the mixture with a set total mass composition and modification means (30) for modifying the first mass flow rate and / or the second mass flow rate in the event of a difference between the mass proportion of the first material and the second material in the mixture and the set total mass composition.

7. Device (10) according to the preceding claim, wherein the determining means (26) for determining a mass proportion of the first material (A) and the second material (B) in the mixture comprise means for measuring a mass flow rate of the sampled portion of the mixture through a measuring orifice which has a predetermined diameter and a database which comprises the mass flow rate values through an orifice of diameter identical to that of the measuring orifice for a powder comprising the first material (A) and the second material (B) whose mass composition varies between 100% of first material (A) and 100% of second material (B).

8. A device (10) according to claim 6 or 7, the device comprising means for generating a flow of transport gas for conveying the mixture from the mixer to the deposition nozzle (20), the device further comprising separation means (24) for separating the withdrawn portion of the mixture from the transport gas.

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