EP2925471A1

EP2925471A1 - Method for manufacturing a part by melting powder, the powder particles reaching the bath in a cold state

Info

Publication number: EP2925471A1
Application number: EP13808135.1A
Authority: EP
Inventors: Christophe Colin; Julie MAISONNEUVE; Gérard Saussereau
Original assignee: MBDA France SAS; SNECMA SAS
Current assignee: Safran Aircraft Engines SAS; MBDA France SAS
Priority date: 2012-11-30
Filing date: 2013-11-29
Publication date: 2015-10-07
Also published as: US20150298259A1; WO2014083291A1; CN104903030A; JP2019064268A; JP6480341B2; RU2678619C2; CN104903030B; JP2016504215A; CA2892848C; SG10201703930VA; RU2015125712A; CA2892848A1; FR2998818A1; SG11201504105YA; US10967460B2; FR2998818B1; BR112015012278A2

Abstract

The invention relates to a method of manufacturing a part, involving the following steps: (a) providing a material in the form of powder particles (60), (b) heating a first quantity of the powder to a temperature higher than the melting point T_F of said layer using a high energy beam (95) and forming, at the surface of a support member (80) a first bath comprising this melted powder and a portion of the support member (80), (c) heating, likewise, a second quantity of the powder and forming, at the surface of the support member (80) a second bath comprising this melted powder downstream of the first bath, (d) repeating step (c) until a first layer (10) of the part is formed on the support member (80), (e) heating, likewise, an [n]^th quantity of the powder, and forming an [n]^th bath comprising in part this melted powder above a portion of the first layer (10), (f) heating, likewise, an [n+1]^th quantity of powder, and forming an [n+1]^th bath comprising in part this melted powder downstream of the [n]^th bath above a portion of the first layer (10), (g) repeating step (f) in order to form a second layer (20) of the part above the first layer (10), (h) repeating steps (e) to (g) for each layer located above an already formed layer until the part has reached substantially the final form thereof. The particles (60) of powder reach each of the baths at a temperature signficantly lower than the bath temperature.

Description

PROCESS FOR MANUFACTURING A PIECE BY POWDER FUSION, POWDER PARTICLES ENTERING THE COLD IN THE BATH

The present invention relates to the field of manufacturing parts by melting powder by means of a high energy beam (laser beam, electron beam, etc.).

The invention more particularly relates to a method comprising the following steps:

(a) A material is provided in the form of powder particles forming a powder bundle,

(b) A first quantity of this powder is heated to a temperature above the melting point T _F of this powder using a high energy beam, and a first bath is formed on the surface of a support. comprising this melted powder and a portion of this support,

(c) A second quantity of this powder is heated to a temperature above its melting point T _F with the aid of this high energy beam, and a second bath comprising this melted powder and a second bath is formed on the surface of the support. portion of this support downstream of this first bath,

(d) repeating step (c) until forming a first layer of this part on this support,

(e) An [n] th quantity of this powder is heated to a temperature above its melting temperature T _F by means of a high energy beam, and an [n] th bath is formed comprising part this melted powder over a portion of this first layer,

(0) An [n + 1] th quantity of this powder is heated to a temperature above its melting temperature T _F using this high energy beam, and a [n + 1] bath is formed. comprising in part this melted powder downstream of said [n] -th bath over a portion of this first layer,

(g) repeating step (f) so as to form a second layer of the workpiece above said first layer, (h) Steps (e) to (g) are repeated for each layer above an already formed layer until the part is substantially in its final form.

In the above process, [n-1] amounts of powder are required to form the first layer.

Methods are known that make it possible to obtain mechanical parts of complex three-dimensional (3D) shape. These methods construct a layer-by-layer piece to reconstruct the desired shape of that piece. Advantageously, the part can be reconstituted directly from the CAD / CAM file deduced from the data processing of its 3D CAD graphic file by means of a computer control of the machine which thus forms one on the other of the successive layers of melted then solidified, each layer consisting of juxtaposed cords having a size and a geometry defined from the CFAO file.

The particles constituting the powder are, for example, metal, intermetallic, ceramic, or polymer.

In the present application, in the case where the powder is a metal alloy, the melting temperature T _F is a temperature between the liquidus temperature and the solidus temperature for the given composition of this alloy.

The construction support may be a part of another room on which it is desired to add an additional function. Its composition may be different from that of the powder particles and thus have a different melting temperature.

These methods include laser projection (in English "Direct Metal Deposition" or DMD), "Selective Laser Melting" (SLM), and "electron beam fusion" (in English). English "Electron Beam Melting" or EBM).

The operation of the DMD process is explained below with reference to Figures 2, 4, and 5.

A first layer 10 of material is formed, under local protection or in a chamber under pressure or regulated depression of inert gas, by spraying particles of powder of this material on a support 80, through a nozzle 190. This nozzle 190 emits, simultaneously with the projection of particles 60 of powder, a beam laser 95 which comes from a generator 90. The first orifice 191 of the nozzle 190 through which the powder is projected onto the support 80 is coaxial with the second orifice 192 through which the laser beam 95 is emitted, so that the powder is projected in the laser beam 95. The powder forms a cone of particles, this cone being hollow and having a certain thickness (powder beam 94 in Figure 4), and the laser beam 95 is conical.

The work plane P is defined as the plane containing the surface on which the layer is under construction / formation.

For the construction of the first layer, this surface is the (free) upper face S ₀ of the support 80. For the construction of the [n + 1] layer, this surface is the (free) upper face of the [n + 1] layer. ] -th layer (with n integer, n≥l).

The laser beam 95 forms a bath 102 on the support 80 by melting the region of the support 80 exposed to the laser beam. The powder feeds the bath 102 in which it reaches the molten state, the powder having melted during its journey in the laser beam before arriving in the bath.

Alternatively, the nozzle 190 and the laser focal point can be adjusted and / or positioned so that the given size distribution powder does not spend enough time, for example, in the laser beam 95 so that all of its particles of different sizes are completely melted, and melt on arriving in the bath 102 previously formed on the surface of the support 80 by melting the region of the support 80 exposed to the laser beam 95.

The working distance WD is defined as the distance between the outlet of the nozzle 190 and the work plane P.

Over the working distance WD considered, the powder may also not be melted by the laser beam 95 or be only partially because the size of all or some of the particles constituting the powder is too important for them to be fondues. In fact, according to FIG. 3, the lower the average diameter D _p of the powder particles, the greater their heating rate, but the shorter their maintenance at the melting stage and the faster their cooling. In addition, Figure 3 demonstrates that the smaller the size distribution, the more all the particles of the powder arrive melted in the bath for a given work configuration.

In all cases, the powder particles are heated by their passage in the laser beam 95 before feeding the bath.

As the laser beam 95 (or the support 80) moves downstream, the bath 102 is maintained and solidifies step by step to form a bead of solidified material 105 on the support 80. The process is continued to form another cord solidified on the support 80, this other cord being for example juxtaposed to the first bead. Thus, by displacement of the nozzle 190 or the support 80 in a plane parallel to the previous working plane P, a first layer 10 of material is deposited on the support 80 which solidifies a first element 15 in one piece with the geometry conforms to that defined by the CAD / CAM file.

A second scan of the nozzle assembly 190 / laser beam 95 is then performed to similarly form a second layer 20 of material above the first element 15. This second layer 20 forms a second consolidated element 25, the entire of these two elements 15 and 25 forming a block in one piece. The baths 102 formed on the first element 15 during the construction of this second layer 20 generally comprise at least a portion of the first element 15 which has been melted by exposure to the laser beam 95, and the particles of the powder feed the baths 102. .

Consider the reference mark consisting of the vertical axis Z ₀ perpendicular to the upper surface So of the support, and by the surface So of the support. This mark is attached to the support 80 or more exactly to the part in construction whose working plane P is defined by the surface S ₀ of the support during the deposition of the first layer of material or by the upper surface of the last layer which comes to be filed.

For a layer in general, the work plane P is not necessarily parallel to the surface S ₀ . The Z axis defined as being perpendicular to the work plane P, is not necessarily parallel to the Z ₀ axis.

Between two successive layers, the nozzle moves along the Z axis by a value ΔΖ theoretically equal to the height of material H _app actually deposited which must be constant (independently of the trajectory of the nozzle) and sufficiently important in the case of an optimal and stable construction (Figures 4 and 5). Figure 5 is a cross section of the liquid bath formed in part in the support, and shows the shape of this bath.

The surface S ₀ of the support 80 is the plane of zero height. Also, during the construction of the first layer, a plane parallel to So, a part of which is contained in this support or below this support (with reference to the axis Z ₀ ) is of negative height, and a parallel plane at S ₀ , a part of which is above the surface S ₀ of the support (with reference to the axis Z ₀ ) is of positive height.

A given work plane P for the construction of one [n] -th layer will be above another worktop attached to a lower layer if it has a positive height, greater than the height of that other plan.

In this reference linked to the support 80 and to the part, the second layer

20 is constructed on a work plane P which is located above the working plane of the first layer 10, these two planes being distant from ΔΖ measured along the Z axis perpendicular to the work plane P.

In the general case, the working plane of an upper layer may not be parallel to the working plane of the previous lower layer, in this case the Z axis of the upper layer makes a non-zero angle with the axis. Z of the working plane of the lower layer, and the distance ΔΖ, measured along the latter axis Z above each point of the lower layer, is a mean value.

This process of building the part layer by layer is then continued by adding additional layers above the already formed assembly.

FIG. 4, which represents the prior art, shows in more detail the configuration of the laser beam 95 and the powder beam 94. The laser beam 95 leaves the nozzle 190 diverging at a 2 β angle from its focal point F _L (located in the lower part of the nozzle 190) and illuminates a region of the support 80, thereby creating a bath 102.

The powder bundle 94 leaves the nozzle 190 converging at an angle δ 2 to its focal point F _P which lies inside the laser beam 95, and just on (or above) the surface of the support 80 (P worktop), so that the powder particles 60 pass a maximum time in the laser beam 95 to be heated. The advantage of a wide laser / powder interaction upstream of the bath is to generate both a high deposition rate and a low dilution which are frequently sought in the case of reloading (surface repair of worn parts) and the coating of hard deposits.

The theoretical melting efficiency is defined as the ratio of the diameter 0 _L of the laser beam 95 to the diameter _P of the powder bundle 94, these two diameters being determined at the right of the worktop P.

Alternatively, 0 _L can be replaced by the diameter of the liquid bath 0BL (see FIG. 4) in order to evaluate the yield, which depends inter alia on the parameterization chosen, in particular on the laser power, P _L , on the scanning speed of the laser beam, V and the mass flow D _m of powder.

Since the laser focal point laser diameter (ie 0 _L o) is often much smaller than the diameter 0 _P o of the powder beam at the focal point powder, the working configuration according to the prior art requires logically that the laser beam either defocused (its focal point F _L is above the work plane P) for a focused powder beam (its focal point Fp is located on the work plane P) or a defocused powder beam whose focal point F _P is above the work plane P and below the focal point F _L , failing to generate an unstable construction and moreover not guaranteeing an acceptable melting efficiency. As indicated above, as a rule the diameter of the laser beam 0 _L measured at right of the plane P, does not correspond to the diameter of the liquid bath 0 _B L which is, meanwhile, approximated to the width (denoted e _app ) the cord after solidification (Figures 4 and 5).

This diameter of the liquid bath 0 _B L is supposed to be a function of 0 _L and thus of 0 _L o but also of the parametrium defined by the triplet (P _L , V, D _m ) and moreover of the size D _p of the different particles of powder and their Vp speeds in addition to depend on their thermo-physical properties.

During the process of building the part layer by layer, the nozzle 190 moves in particular in height, and maintaining constant the distance between the points F _L and F _P (Defoc _L - defocus _P = constant) where Defoc _L and Defoc _P represent respectively the defocus laser and that of the powder defined by Défoq. = {distance between point F _L and work plane P} and Defoc _P = {distance between point F _P and work plane P} and are visible in FIG. 4).

Thus, the focal point F _P of the powder beam 94 remains inside the laser beam 95, and just on (or above) the surface of the previously constructed layer (work plane P).

We therefore have a defocused laser beam (defocus _L > 0) and a focused powder beam (defocus _P = 0) on the plane P or defocused (defocus _P > 0) above the plane P, and the two angles 2β and 2d must be configured so that on the one hand the working distance WD between the outlet of the nozzle and this plane P is large enough to prevent degradation of the bottom of the nozzle by the radiation of the bath and secondly that the opening of the laser beam at the exit of the nozzle remains smaller than the diameter of the inner cone.

Moving the support 80 or scanning the nozzle assembly

190 / laser beam 95 makes it possible to give each layer a form independent of the adjacent layers. The lower layers of the room are annealed and cool as the top layers of the room are formed.

There is, however, a need to improve the melt mass efficiency R _m (i.e., the ratio of the amount of material forming the finished part to the amount of material projected by the nozzle to form this part). mass efficiency of recycled powder _re cy (that is to say the ratio of the amount of powder intact in morphology and agglomerates obtained for example after sieving the amount of material sprayed), the stability of the baths formed on the surface of the part and the material health of the fabricated part, for a given non-exhaustive set of parameters (size distribution D _P of the powder particles, nature of the powder material, mass flow rate D _m of powder, speed of displacement V of the nozzle / laser beam assembly, power P _L provided by the laser, distribution of the power density on the work plane P, type of laser source (solid or gas), mode (pulsed or continuous), coaxial nozzle, nature and gas flow po D _gp powder particles, nature and flow rate of the protective gas D _gl through the axis of the nozzle, the angles 2 β and 2 δ and the diameters 0 _L o and 0 _PO defined above, etc.). The aim of the invention is to propose a method and more particularly an optimized working configuration (defined by: Defoc _L , defocus _P , WD) for the DMD process which makes it possible firstly to improve the stability of the bath and in a second time to mass melting efficiency, the recycled powder mass yield, the material health and the construction speed (maximizing the Z-riser increment of the nozzle noted ΔΖ).

This goal is achieved by virtue of the fact that the powder particles arrive in each bath at a cold temperature relative to the temperature of the bath.

Thanks to these arrangements, the mass yield of _η ρ process defined as the sum of the mass of fusion yields (R _m) and recycled fe _re cy powder) is greater than the mass yield of the process in the case where the powder particles arrive hot partially or totally melted in the bath. In addition, the powder particles, arriving in the bath, will temper the temperature of the liquid bath TBL (because they are much colder than this bath, the latter being substantially at room temperature before entering the bath), while by increasing the volume of the bath and in particular that above the plane P without increasing the width and the height of the diluted zone (volume of the bath which is below the plane P). This inevitably leads to a rapid increase in the liquid / vapor surface tension of the bath, and consequently generates a better stability of the bath.

In addition, thus promoting a significant dilution to each deposited layer minimizes manufacturing defects.

Advantageously, the focal point F _L of the high energy beam is above the working plane P or on this plane, and the focal point F _P of the powder bundle is below the working plane P, such that so that the powder particles do not intersect at any time the high energy beam between the outlet of the nozzle and the working plane P. In particular, the focal point F _P of the powder bundle can be located inside the support , especially when depositing the first layers. After the deposition of a number of layers, the focal point F _P of the powder bundle may lie within the previously deposited layers. Thus, a majority of powder particles arrive cold in the previously formed bath on part of the already constructed part.

These particles then enter a bath that is sufficiently wide (0 _B L> 0P) and deep (H _Z > H _ap p: see definitions below with reference to Figure 5) to integrate a maximum amount and proportion of the set of particles projected by the nozzle during the laser / bath interaction time, defined by the ratio of 0 _L to V.

In addition, the rest of the powder particles being intact, unheated by the high energy beam, are perfectly recyclable.

In addition, the powder bundle and the high energy beam may be substantially coaxial, that is to say that their axes form between them an angle of less than 30 °, preferably less than 20 °, more preferably less than 10 °, more preferably less than 5 °. Thus, the high energy beam can easily follow the powder beam when making parts with complex geometry. Tracking the shape of the part to be manufactured is much more difficult in the case of a remote projection or melting, that is to say when the powder beam and the high energy beam are not substantially coaxial.

The invention will be better understood and its advantages will appear better on reading the detailed description which follows, of an embodiment shown by way of non-limiting example. The description refers to the accompanying drawings in which:

FIG. 1 is a diagram showing a possibility of positioning the high energy beam and the powder bundle in the case of the method according to the invention,

FIG. 2, already described, is an explanatory diagram of the method according to the prior art illustrating the device of the DMD method,

FIG. 3, already described, shows the effect of the diameter D _P of the Ti-6Al-4V powder particles on their temperature from the outlet of the nozzle on arrival in the liquid bath,

FIG. 4, already described, is a diagram showing the positioning of the high energy beam and the powder bundle in the case of the method according to the prior art,

- Figure 5, already described, is a schematic representation of a cross section of the liquid bath formed in the support. According to the invention, the powder particles arrive cold in the bath formed on the surface of the previous layer (or support). The term "cold" means that the temperature of the particles is much lower than the temperature of the bath. Indeed, the temperature of the particles, before entering the bath, is substantially equal to the ambient temperature, for example of the order of 20 ° C.

In comparison, the temperature of the liquid bath T _B L is greater than the melting temperature T _F of the material constituting the powder but lower than the boiling point _{T e} of this material. This melting temperature is greater than 550 ° C for aluminum alloys, 1300 ° C for nickel bases, 1450 ° C for steels and 1550 ° C for titanium alloys.

Figure 1 illustrates an embodiment of the invention that allows the powder particles to arrive cold in the bath formed on the surface of the previous layer (or support). Such an embodiment also has the advantage of facilitating the coaxial vision of the bath by among other things a CCD (Charge Coupled Device) camera to allow control of the on-line process, useful for the industrialization of the process.

FIG. 1 shows a sectional view of a support 80 and a first layer 10 of material already deposited on this support 80. A second layer 20 is then deposited on this first layer 10. A bead 105 of this second layer 20 is under construction, the progression of the cord 105 from left to right, from upstream to downstream (direction of advance of the cord 105, or, equivalently, the liquid bath 102). The bath 102 is thus located immediately downstream of the bead 105, under the nozzle 190 from which the laser beam 95 and the powder bundle 94 exit. The upper surface of the first layer 10 then constitutes the work plane P relative to the second layer under construction and from which defocus laser defocus _L , defocus powder defocus _P , working distance WD, laser beam diameter 0 _L , and powder beam diameter 0 _P are measured.

The nozzle 190 emits, simultaneously with the projection of particles 60 of powder, a laser beam 95 which comes from a generator 90. The first orifice 191 of the nozzle 190 through which the powder is projected on the support 80 is coaxial with the second orifice 192 by which the laser beam 95 is emitted, so that the powder is projected into the laser beam 95. The powder forms a cone of particles, this hollow cone having a certain thickness (powder beam 94), and the laser beam is conical.

According to the invention, the nozzle 190 is configured and positioned so that the focal point F _L of the high energy beam 95 is above the working plane P or on this plane, and the focal point F _P of the beam powder 94 is located below the working plane P, so that the powder particles 60 do not intersect at any time the high energy beam between the outlet of the nozzle and the work plane P.

According to another embodiment than that of FIG. 1, the focal point F _P of the powder bundle may be located inside the support. In this case, Defoc _P powder defocusing is smaller than that shown in FIG. 1. Thus, the diameter of the laser beam 0 _L at the plane P is close to the diameter of the powder bundle 0 _P at the plane P, for parameterization (P _{L /} V, D _m ) considered.

For example, the diameter of the laser beam 0 _L in line with the plane P is slightly smaller than the diameter of the powder beam 0 _P at the right plane P.

Such a configuration is obtained, as represented in FIG. 1, by bringing the nozzle 190 closer to the working plane P of the configuration according to the prior art (FIG. 4), that is by decreasing the working distance WD.

Such a working configuration is particularly suitable for producing large cords 105, that is cords 105 whose width is greater than the diameter 0 _L o of the high energy beam 95 at the laser focal point.

Indeed, the diameter of the liquid bath 0 _B L is then wider and more powder particles arrive cold in the liquid bath 102, which is beneficial as explained above.

The focal point F _L of the high energy beam (95) may alternatively be located on the working plane P, which is preferable in the production of thin cords whose width is smaller. In this case, the focal point F _P of the powder bundle 94 can be located on the work plane P. The focal point F _P of the powder bundle 94 can also be located below the work plane P. To optimize the method according to the invention, certain parameters can be adapted accordingly, in particular the laser power P _L , the scanning speed V and / or the mass flow rate D _m of powder.

However, in this embodiment shown in FIG. 1, an (additional) cooling of the nozzle 190 may be necessary, since the nozzle 190 heats up by radiation due to its proximity to the liquid bath 102. Such cooling requires a expensive device.

To overcome this problem and thus maintain a working distance WD (distance from the bath nozzle) sufficient while avoiding that the powder beam crosses the high energy beam, the inventors have developed an embodiment which advantageously consists either in to decrease the distance Defoq, or to decrease the divergence half-angle β of the laser beam 95 with respect to the Z axis, returning in both cases to decrease 0 _L so that it is lower than 0 _P.

Alternatively, the defocus distance _P of the powder beam 94 is increased in order to compensate for the decrease of 0 _P in the event of an increase in WD and thus maintain 0 _P greater than 0 _L.

This decrease in the distance Defoc _L and angle β and this increase in distance Defoc _P can be performed jointly.

These variations of these three variables may be performed independently or in addition to an increase in the working distance WD. In practice, the nozzle 190 is thus configured and positioned so that the powder particles 60 reach the working plane P just outside the area of the working plane P covered by the laser beam 95.

Thus, since the liquid bath 102 extends by conduction a little beyond this zone, the majority of the powder particles 60 fall into the bath 102 without having interacted with the laser beam 95. The powder particles 60 are therefore still cold before entering the bath 102. An advantage of this absence of laser-powder interaction upstream of the bath 102 is to avoid the change of shape, the formation of agglomerates and the harmful oxidation of the powder particles 60.

This explains that the tests carried out by the inventors show that the mass melting efficiency R _m in the process according to the invention is higher than the mass melting efficiency in the case where the powders arrive hot, even partially or completely melted, in the bath.

In addition, the bath 102 is more thermally stable because the powder particles 60 rapidly cool the bath 102 (which results in an increase in the liquid / vapor surface tension of the bath, and certainly also a variation of the convective movements at the bath. in the bath because of the variation of the density of the liquid by the addition of "cold" powders and a change of the thermal gradient in the bath).

An additional advantage of the process according to the invention is that the powder particles 60 which did not participate in the formation of the liquid bath (because fallen outside the bath 102) remained cold and are therefore recyclable almost completely. . The total mass yield of the process (melting + recycling) according to the invention is therefore much higher than the total mass yield of the process according to the prior art.

Advantageously, for greater stability of the bath 102 and better material health after the local establishment of a stationary thermal regime around the bath of the room under construction, the bath has an oblong shape defined by θ <90 °, H _a pp / e _at pp <1 and H _ZR / H _app ≥0.6, where Θ is the angle of the upper surface of the bath 102 with the worktop P, H _ap p the apparent height of the bead (part of the bath 102 above worktop P), e _app its width, and H _Z R the height of the remelted zone or diluted zone (part of the bath below worktop P) (see Figure 5).

Preferably, the three quantities Θ, H _app / e _app , and H _Z R / H _app satisfy the relationships: ^ο ≤ θ = 60 °, 0.04≤H _ap p / e _app ≤0.75, and 1 <H _ZR / H _ap p≤6.

In the case of a material reloading on a part, these quantities preferably check the relations:

30 ° ≤θ≤60 °, 0.15≤H _app / e _ap p≤0.25, and 0.01 <H _ZR / H _app <0.025.

Advantageously, the size distribution of the powder particles 60 is narrow (which corresponds to particles all having substantially the same size, which size is in agreement with the temperature and the volume of the liquid bath to be melted at any moment during the duration of the laser / bath interaction). Indeed, in this case, the probability is high for all the powder particles 60 to have time to melt in the bath 102 before the laser beam 95 is moves (and therefore stops heating this bath 102). The process of feeding the bath of cold powder particles and of narrow size distribution will then be more effective in terms of stability and speed of construction because the temperature of the bath decreases more rapidly and the apparent height of the cords becomes larger. This apparent height is even greater than the particles are fine because the bath temperature will gradually decrease and then remain constant (solidification plateau reached) as the particles enter the bath 102.

For example, the powder particles 60 have sizes ranging from 25 to 75 μm (microns). Preferably, these sizes are between 25 and 45 μm.

In the method according to the prior art, a wider distribution of powder particles 60 is more detrimental. Indeed, in the presence of laser / powder interaction, the powder particles 60, having different sizes, arrive in the bath at different temperatures, and consequently the temperature of the bath fluctuates, which is likely to lead to instability of the bath.

Advantageously, the positioning of the nozzle 190, namely the working distance WD, is slaved to the spatial variations of the working plane P (variations in the height of consolidated material H _app of a layer of the part to be constructed whereas the Z-rise increment ΔΖ of the nozzle 190 is kept constant by pre-programming) so that, for each layer, the focal point F _L of the laser beam 95 is at the same height above the work plane P and the focal point F _P of the powder bundle 94 is at the same height below the work plane P.

Alternatively, the increment ΔΖ can be enslaved to changes in the height of consolidated matter H _app of a layer.

These servocontrols are performed using a known type of process control program, which need not be described here.

Claims

14/083291 15 CLAIMS

A method of manufacturing a part comprising the following steps:

(a) A powder particle material (60) is provided as a powder bundle (94),

(b) a first quantity of said powder is heated to a temperature above the melting temperature T _F of this powder by means of a high energy beam (95), and is formed on the surface of a support (80) a first bath comprising said molten powder and a portion of said support (80),

(c) a second amount of said powder is heated to a temperature above its melting temperature T _F with the aid of said high energy beam (95), and a second bath comprising this melted powder and a portion of this support (80) downstream of said first bath,

(d) step (c) is repeated until a first layer (10) of said workpiece is formed on said support (80),

(e) Heat a [n] ^'th amount of said powder at a temperature above its melting temperature T _F with the aid of a high energy beam (95), and forming a [n]' ^th bath comprising in part this melted powder over a portion of said first layer (10),

(f) Heat a [n + l] ^'th amount of said powder at a temperature above its melting temperature T _F with the aid of said high energy beam (95), and forming a [n + l] ^th bath comprising in part this melted powder downstream of said [n] ^th bath over a portion of said first layer (10),

(g) repeating step (f) so as to form a second layer (20) of said piece above said first layer (10),

(h) Steps (e) to (g) are repeated for each layer above an already formed layer until said part is substantially in its final form,

said method being characterized in that the powder beam (94) and the high energy beam (95) are substantially coaxial and in that 14/083291

16

the particles (60) of powder arrive in each of the baths at a cold temperature relative to the temperature of said bath.

2. A method of manufacturing a part according to claim 1 characterized in that the focal point F _L of the high energy beam (95) is above the working plane P or on this plane, and the focal point F _P of the powder bundle (94) lies below the working plane P, so that the powder particles do not intersect at any time the high energy beam (95) between the outlet of a nozzle (190) and the work plane P, the work plane P being defined as the plane containing the surface on which one of said layers is forming.

3. A method of manufacturing a part according to claim 2 characterized in that to obtain the arrangement of the focal point FL of the high energy beam (95) and the focal point F _P of the powder bundle (94) according to claim 2. the defocus distance Defocp of the powder beam (94) is increased, and / or the divergence half-angle β of the laser beam (95) relative to the perpendicular to said working plane P is reduced or the distance of defocus Defoq. high energy beam (95).

4. A method of manufacturing a part according to any one of claims 1 to 3 characterized in that the size distribution of the powder particles 60 is narrow.

5. A method of manufacturing a part according to any one of claims 1 to 4 characterized in that each of said baths has a shape defined by θ <90 °, H _ap p / e _has pp <1 and H _ZR / H _app > 0.6, where Θ denotes the angle of the upper surface of said bath with said working plane P, H _app the apparent height of the bead, e _app its width and H _Z R the height of the recast area.

6. A method of manufacturing a part according to claim 5 characterized in that the three quantities Θ, H _aP p / e _app and H _ZR / H _app verify the relations: 15 ° ≤θ≤60 °, 0.04 < H _app / e _app <0.75, and 1 <H _ZR / H _app <6.