FR2648068A1 - LASER WELDING METHOD AND APPARATUS - Google Patents

Abstract

According to the invention, the laser welding apparatus comprises a laser 12, the beam 13 of which is focused at a focusing point 15 located above, below or at the level of the surface of the substrate 16 to be welded and has a density d 'energy large enough to split part of the substrate and form a weld bead 22, a laser welding nozzle which delivers powder onto the weld bead evenly around its circumference, a powder feed system 50, 52 which supplies the powder to the welding nozzle, and an axial gas flow system 60 which flows gas through the nozzle to the substrate to modify the flow of the powder and protect the apparatus from damage due to intense heat. The laser welding nozzle preferably comprises frustoconical outer and inner shells which define an annular space between them, the powder mixed with a fluidized gas being metered through the annular space and being directed to the welding zone 62 where it is obtained. then solidifies to form the weld bead 22.

Description

LASER SCUDING PROCESS AND APPARATUS

  The present invention relates to welding processes

  in which filler material is added to the support region

  dage, and relates more particularly to such methods in which the energy for melting the substrate and the filler material is supplied by a laser. Welding is a process in which at least two pieces of a material are assembled. In a conventional type of welding, a welding torc2 is used to melt the surfaces facing the two pieces, and to melt together the facing surfaces. Filler metal or filler material can be added to the welded area to give properties

  or to constitute part of the Sou-

  dage. In its most general sense, welding can also be accomplished by solid state processes such as diffusion bonding, but in a narrower sense of the term as used here, the two materials intended for to be connected must

  be at least partially melted.

  In another type of welding, a surface layer is added to the substrate by melting a region of the surface of the substrate, by adding a filler material to the molten assembly, from which results an interpenetration and a fusion of the filler material and the substrate, and then allowing the molten material to solidify. This technique is widely used in n apliations, often to reinforce hard layers, such as wear-resistant coatings, on duller substrate materials and to build and repair defective, deteriorated or inferior parts at the price originally planned. The present invention primarily relates to surface welding, although it

  piss be used in other welding applications.

  A lot of different types of sources have been

  used to supply the necessary energy to melt the subs-

  trat and filler material in welding processes. Of

  electric arcs and torches are in common use.

  The heat generated by friction is used in welding

by friction.

  More recently, the intense heat generated by a laser was used for welding operations in order to melt the substrates and the filler materials. US Patents 4,200,669, 4,730,093, and 4,743,733 show welding techniques by

  laser. In each case, the output beam of an industrial laser

  triel is focused at a point close to the substrate or located in the substrate, so that the surface regimes of the substrate are heated and melted by the focused laser beam. A filler material can be introduced into the laser beam or into the

  fcndue zone, if necessary. The great flexibility that allows

  The use of laser heating has resulted in the use of

  widespread use of lasers in welding and

  other metalworking operations.

  It has been shown that laser welding can be used, but that it sometimes has drawbacks in certain practical applications. The apparatus illustrated in US Pat. No. 4,200,669 injects a stream of powdered filler material into the beam, and precise control of the powder in relation to the beam is difficult. The approach illustrated in US Pat. Nos. 4,730,093 and 4,743,733 proposes a major improvement in the possibility of control, but uses a directional camper for the feeding of the powder. In these

  conditions, if the relative movement of the laser beam and the

  Ltrat is as illustrated in FIG. 5 of patent 4,730,093, the powder is fed from the rear of the welding region. If a relative noavemnt happens to be out of the drawing plane, the powder is fed from the side of the welding region, unless a special support is provided to rotate the

  leads powder. The result is that a sub region

  dage has characteristics which vary depending on the relative directions of movement of the substrate and the hot mouse. There is therefore a need for a device and

  an improved laser welding process, which combines the advantages

  stages of laser welding techniques of the prior art while providing improved control of the powder introduction system and improved quality of the structure obtained. The present invention fulfills this need and also provides

other advantages.

  The present invention provides a laser welding apparatus in which the heating of the substrate can be controlled and the introduction of the filler metal is not directional. The characteristic of the welded construction is therefore unchanged when the direction of relative movement of the welding apparatus and the substrate is changed. There is no need to stop at the corners or change the speed of movement of the welding head, thus avoiding the use of other variables which are known to affect the quality of the welding. The device is optional and allows you to slip inside tight spaces. The introduction of the filler material is controlled and

  modified if necessary, and the intro point

  powder performance in relation to the welding kit and

  focal point of the laser beam is easily checked.

  According to the invention, the laser welding device intended for depositing a filler material on a substrate cred a laser; a beam of fol cation of the beam will be at a focal point sufficiently close to the surface of the substrate to merge a region of the substrate, thus forming a zoe of

  welding; and means for supplying filler material to the material

  seems to weld uniformmenet around its circumference. Befor-

  ference, the means for bringing the filler material comprises a nozzle having an outer casing and an inner casing which define between them a convergent annular passage, the

  filler material being brought to the nozzle at the level of the

  divergent half of the passage and being drawn towards the end

  converging of the passage. In this way, the filler material -

  is brought uniformly around the circumference of the welding zone and there is no directional effect observed in the welding when the direction of the relative movement of the device

and the substrate is changed.

  More specifically, according to a particular characteristic

  As is clear from the invention, the laser welding apparatus comprises a nozzle having an outer casing in the form of a trc de c = ne and an inner casing in the form of a barter cane of smaller cone size than the outer casing and threaded in the latter, the axes of the trunk of the outer and inner envelopes being combined, the outer envelope and the inner envelope defining a circular passage therebetween; a laser; a. an optical system configured to direct the laser beam along the axis of the cone of the cone of the outer and inner envelopes towards a focal point located outside the nozzle; a gas supply system communicating with the interior of the interior envelope, creating a flow of gas from the interior envelope to the focal point of the laser; and a omnicient feeding system with the

  annular passage located between the inner envelope and the envelope

  external lopPe and suitable for introducing a flow of a

  finely divided filler material mixed with carrier gas.

  The present invention also extends to a laser smear process using a filler material. According to this aspect of the IRTIOM, the process for depositing a card of a filler material on a substrate includes the following steps:

  to provide a laser and an optical system to carry out the

  laser beam at a focal point close enough to the surface of the substrate for a region of the substrate to melt to form a weld zone; and adding a filler material divided sharply to the assembly to be sced, the filler material being added uniformly around the circumference of

the welding area.

  The present invention provides a laser and a system

  optic which focuses the laser beam at a focal point

  The region is sufficiently narrow at the surface of the substrate so that the regions on the surface are melted in order to form a weld zone. The effective focal point of the laser may be below, in co-incidence, coinciding with, or above the surface of the substrate, but in all cases the power density in the region of the focal point must be sufficient to melt the material. of the substrate. A circumferential envelope fixed to the end of the enclosure of the optical system encircles the laser beam. The envelope comprises an inner envelope and an outer envelope defining between them an annular passage narrowing downwards. The

  powder fluidized in a gas flow is brought to the

  upper part of the annular space through separate orifices, and is distributed around the annular space during its descent. An inner wall in the annular space can be provided to improve the ciroonferential distribution of the powder. At the place where such a wall or barrier is provided, the powder is introduced through the orifices into one space located at the rear of the barrier, and then spreads over the barrier uniformly cironferentially. The convergent cover located at the lower end of the annular passage directs the powder towards the molten sodage zone. The powder can enter the lar beam before reaching the welding zone, the filler material being added uniformly around the circumference of the welding zone. An axial flow of gas passes through the inner shell and towards the substrate. The axial gas flow avoids the erndiaIEng t of the optical system and the laser by acting oeiw

  a barrier for welding spatter and smoke.

  The axial flow of gas can also contribute to the formation of a plasma in the vicinity of the laser focal point, if the power density of the laser beam is large enough to create such a plasma by icization of the atoms of the gas and of the vaporized atoms. from the filler material and the substrate material. The axial gaw eoArulation also directs the filler material towards the substrate and the scxdage zone where the metal is deposited. The heated and melted droplets of the material

  filler mixes with the molten material of the support zone

  dage, and the solder mixture solidifies in the form of a bead which typically protrudes from the initial surface of the substrate

  due to the mass of added filler material.

  The nozzle assembly according to the present invention allows the introduction of a controlled flow of powder into the welding zone. The mass flow rate of the powder is modulated by controlling the flow rate of the powder and of the fluidizing gas

  in the powder feed system. The powder is intro-

  picks up in the welding area evenly around its circumference

  ference due to the annular passage. Normally, the laser beam is perpendicular to the substrate. With a nozzle according to the invention, a change in the direction of the relative movement of the beam and the surface of the substrate does not require any adjustment of the powder feed mechanism nor modification of the speed of the relative movement in order to allow the adjustment of the feeding mechanism. The present apparatus is also very compact and is contained within a structure which can be easily grasped and manipulated, thus improving the ease

  of using laser welding in a workshop event.

  Other characteristics and advantages of the present invention will appear during the detailed description of an exemplary embodiment, taken in conjunction with 'the appended figures, among figure i is an elevation view of an apparatus according to the invention, in which the passage of the laser beam is shown in section; Figure 2 is a sectional side view of the welding nozzle of the apparatus; and Figure 3 is a view similar to Figure 2 of another embodiment of the invention, including a barrier

  powder flow control system.

  The present invention is implemented in a laser welding apparatus 10, illustrated generally in FIG. 1. The apparatus 10 co-operates a laser 12 having a beam 13 which, when it is focused using an optical system 14, has a sufficient power density to melt a

  part of the adjacent substrate 16 and melt (or heat) a material

  flow of fiúmiently divided contribution. The beam 13 of the laser 12, defi-

  at the end of a beam axis 18, is focused in a convergent way

  using an optical system 14 at a focal point 15.

  (In the system illustrated in Figure 1, the focusing focus -

  gente is obtained with a sharp mirror 17, but a lens can be used). After leaving the optical system 14, the beam 13 enters a soda nozzle 20 whose structure and function are described in more detail below. The nozzle 20 introduces divided filler material into the ford part of the substrate where the finely divided filler material is melted. The filler material mixes with the material of the molten substrate and rapidly solidifies in the form of a bead 22, because the heat is evacuated towards the underlying non-faded substrate. The distric of fcrticrient separating 1 the end of the nozzle 20 and the

  suJbstat 16 is typically around 5 min. The removal of the material

  riau d'aehot is shrunk, unidirectio l and collimated, and the

  nozzle 20 ends towards the substrate 16.

  E re re as in Figure 2, the nozzle 20 includes an outer cover 30 which is screwed to the end of the optical system 14 as the central axis 32 of the envelope which is cincrid with the axis of the beam 18 of the laser. The envelope 30 is hollow so that the laser beam 13 can enter between

  the extremity linked to the optical system 14, to pass through the envelope

  lcppe along the central axis 32, and exit by the other end

  moth. The screw connection allows the outer casing 30 to be moved relative to the optical system 14 by rebinding or moving away, in an adjustable manner, from the central axis

  32 of the envelope 30 remaining in incidentoe with the axis of the beam

  ceau 18 of the laser 12. This adjustment possibility allows the position of the fc / read point 15 of the laser to be adjusted by a relative axial displacement relative to the casing 30, without changing the optical system. The outer surface of the envelope

  outer 30 generally has a trocoic regu-

  lière. Preferably, several turns 36 of a tube scnt fixed on the external surface of the external envelope 30, and cooling water is errvyée in the tube via cooling water pipes 37. The surf the interior of the outer casing 30 includes a trar.-ic surface 34 at its end remote from the point of attachment with the

optical system 14.

  An inner envelope 40 is disposed inside

  of the outer casing 30 and is screwed thereon. The env-

  the inner envelope 40 is also hollow, and has the same central axis 32 as the outer envelope 30. The laser beam 13 also passes through the inner envelope 40 along

  the central axis 32. The connection by screwing the inner casing

  40 on the outer casing 30 allows the axial positioning of the two envelopes in order to adjust them relative to each other, thereby changing the size of the annular passage which will be described below. The inner envelope 40 corend a risk surface 42 located at the remote end of the system

  optic 14 and adjacent to the surface taz = xr-ique 34 of 1 '-

  l1ppe outside 30. The two tzanic surfaces 34 and 42 are generally opposite one another, and define a converging ancillary passage 44 ente them. The relative axial movement of the inner casing 40 and the outer casing 30 causes the passage area to be enlarged or reduced

ring finger 44.

  As a prefix, the half angle of o & r- of the surface = rctxrnique 34 of the outer envelope is 2 & 10 degrees

  greater than the half angle of o-ne oerrespdant sure ae tron-

  o: iique 42 of the inner envelope, so that the passage

  annular slightly converges to its exit point 46.

  In a particular embodiment, the half angle of the surface of the surface 34 is between approximately 20 and 45 degrees, from

  preferably between 30 and 35 degrees, and half

  o * -e arnle of the surface 42 is coepris between erniron 20 and 35 degrees but about 2 to 10 degrees less than the half angle of c of the surface 34. The nvergent character of the annular passage 44 causes a focusing of the the powder in the successive parts of the annular space, towards a common point of convexency located at the center of the central axis 32

  and which incidentally coincide with the axis of the laser beam 18.

  One of the controllable parameters of the apparatus 10 is the relative position of the focal point of the beam 15 and of the point where the flow of powder intersects the central axis 32. In certain cases, for partial operating conditions, it it is desirable that the focal point of the laser beam 15 coincides with the point of convergence of the powder flow,

  but under other conditions, we can not make them corner-

  cider. In normal fonting, the powder is directed towards the region of the substrate, and the laser beam is focused.

  above, below, or at the surface of the substrate.

2648 0'68

  The divided firneent filler material, of Prefrenoe in the form of a podre urea, is introduced into the apparatus 10 through the annular passage 44 in its upper or divergent extremity. An ali / mntati o of the powder comprises a powder source and a fluidization pipe (na shown) which deliver powder through a powder feed tube 50 to several powder discharge tubes 53. The powder fluidized flows from the tubes 53 to the annular passage 44 through a number, typically 2 or 4, of separate injection orifices 54, arranged symmetrically at the head of the annular passage 44, upstream from the point of

  outlet 46. The powder introduced is distributed around the cirotn-

  ference from passage 44, flows towards the exit point 46 under the action of gravity and under the pressure of the carrier gas flow, then leaves passage 44 towards the focal point of

the powder.

  It has been found that, for certain types of powder and filler materials, the circumferential distribution of the powder around the annular passage 44 is not as uniform as would be desired. To increase the uniformity of the circumferential distribution, a barrier for the powder 56 is added on the internal wall of the traxnic surface 34 of the external envelope 30, while being directed towards the interior, just above the point of introduction. of the powder through the injection orifices 54. FIG. 3 illustrates this embodiment in which the other elements are arranged as described, pl'y d, enEt. In this embodiment, the fluidized powder filler material is introduced through injection orifices 54 into the volume located behind the barrier 56. This volume fills, and the powder pours over the barrier 56, into the lower part of the annular passage 44, then towards the exit point 46, in the manner described above. ' The rate of discharge of the powder is equal to the rate of total flow of the powder through the powder supply tube 50, during a stabilized fanctiamement. The spill is uniform cirmféentiella ent, cxuiisant a uniform flow circferentiell.ment of powder through the outlet point 46. A ioulemrnt of axial gas is provided in the nozzle 20 at the middle of a nalisatia of axial gas flow 60 which is connected with the interior of the nozzle 20, either dirt and through the wall of the nozzle 20, or through the wall of the

  optical system 14, as is the case in the embodiment

  tion illustrated in figure 1. Axial gas flows from the cana-

  Lization 60 through the interior of the optical system 14 and of the nozzle 20, towards the substrate 16. The axial gas flow protects the optical system and the nozzle from damage originating from a return of droplets of solder, of smoke and heat, cools the nozzle and also helps direct filler material to the

substrate.

  In another approach, the surface of the substrate 16 is

  protected during welding by a protective gas which envelops it

  coats and prevents oxidation. The protective gas is typically an inert gas such as argon and is supplied by different sources. The axial gas and the fluidizing gas provide a

  part of the shielding gas, since they are generally made up of

  partly or entirely inert gas. An external gas flow all around the nozzle 20 can be provided by an external tube (not shown). A shielding gas flow can be provided through the apparatus 10 itself. Cam illustrated in FIG. 3, one or more protective gas tubes 70 can be fixed on the outer surface of the outer casing 30,

  the flow of the protective gas being directed towards the support zone

  age 62 as well as in neighboring scn. The inert gas flows are intended to prevent oxidation or other defects due to the environment of the metal in the weld zone and the crdon

when it is hot.

  The laser beam 13 is focused by the optical system 14 at a focus point 15 on the axis of the beam 18. The focus point 15 can be located above, below or at the surface of the substrate 16. The positicns of the nozzle 20 with respect to the substrate 16 and the positions of the focal point of the beam 13 by comparison with the nozzle 20 scnt adjusted so that the volumic power of the laser beam Near the focal point 15 is sufficient to shape the region of the sitube substrate = = ius the nozzle 20, forming a molten or welded area 62. the filler material, which can be fcdu or partially formed before it reaches the welding zo 62, is directed into this zore 62 and mixes with this zone material. As the substrate 16 is moved relative to the apparatus 10 in the direction indicated by the arrow 64, the welding zone 62 moves on the surface of the substrate 16, forming the oerdon 22 which extends and which follows

the path of the device 10.

  The beam power of the beam 13 is most varied at the level of the focus point 15. If the energy density is sufficiently high At this place or any other place, the interaction between the axial gas, the carrier gas, the powder and the energy of the laser beam causes the formation of a plasna. Plasma is a highly ionized medium containing ions and electrons which reach an extremely high temperature

  high in a limited volume. In this volune, the part of the material

  The feed line is normally provided. The energy of the laser beam removes electrons from the gas atoms making up the plasma and vaporized atoms from the filler material. Plasma, once

  initiated or "switched on", continues to maintain itself if the listening

  The gas and the filler material, as well as the laser beam, are maintained. The apparatus 10 can be used either with

either without the formation of a plasna.

  Preferably, the finely divided filler material forms an inverted cone when it leaves the nozzle 20. This filler material has a fooelization point which can be adjusted, i.e. the point of focusing of the filler material can be brought closer or further away from the nozzle 20. Such an adjustment of the focal point of the filler material is obtained by turning the inner th 40, relative to the outer th 30. Such a rotation qoe the axial displacement of one outer casing 30 and either increases or decreases the size of the annular passage 44, in particular at the level of the lower extremity. When the passage 44 is adjusted with a smaller size, the aoMe of filler material and its point of functionning also changed. The focal point of the filler material and the focal point of the laser beam

  can be adjusted so as to coincide, in order to frame the material

feed line.

  At least part of the divided firnemnt filler material is generally partly or wholly formed by the laser beam, and other parts may remain free of

  intentional or unintentional. In oertairnes useful

  sations, such as the application of wear-resistant coatings, it may be desirable for some of the filler material to remain unfinished. For example, the filler material may include a finely divided ceramic powder which, when deposited in particles on the surface of the substrate, increases the

wear resistance of the substrate.

  The structural and functional details that go

  follow, cocexrnant a mode of realization of the present invention

  ticn scnt obtained with additional information and does not constitute a limitation. The maximum external diameter of the external envelope is approximately 63 mm, and the diameter of an ejection opening 24 is approximately 3.2 mmn. The nozzle is used with casings 30 and 40 adjusted so that the width of the annular passage 44, at the outlet point 46, is about 1.5 mm. The axial gas flow rate is between 0.056

  and 0.42 me per hour. Under typically fncrticon conditions

  ques, the powder flow is about 7 granmmes per minute. The

  focal point of the powder 48 is adjusted so as to cAin-

  cider with the substrate at the weld bead 62. The width of the nozzle is approximately 102 mm, but this dimension is not critical. The laser is an oerbone dioxide laser operating at a power between 100 and 5000 watts

  fcrctionnant in inpulsion or in crntinu.

  Either the substrate, the nozzle, or both, scnt

  moved so that there is a relative movement between the sub-

  trat and the nozzle. Preferably, the nozzle is fixed and the sub-

  tat is moved automatically by uz table l / Loà rr-

  having axes of iveent X and Y, the measurements, for example the speed or the direction of movement, being controlled by a

computer progrm m. A number of different gases and gas mixtures have been used

  for axial gas flow, among others argon, nitrogen, hel / um, hydrogen and mixtures of these gases. Argon was used for the carrier gas

  powder. Varied filler materials, metallic and rno metal-

  ligques, were deps, among these, ceramics. Such materials which can be deposited in the welded structure

  These include titanium alloys, such as Ti-6At-4V, tungs-

  tne, cobalt alloys, nickel alloys such as

IN 718, as well as ceramics.

  The present invention provides a multi-purpose tool for depositing materials on substrates. Although the present invention has been described in relation to embodiments given by way of example, this invention is not limited to these examples and may extend to any modifications to it.

the scope of the art hymn.

RE VENDICATIO NS

  1. A scuaglase apparatus, characterized in that it has a nozzle having an outer casing trcrx niqoe (30) and an inner frustoconical casing (42) whose cane is smaller than that of the outer casing and

  embedded in it, the axes (32) of the trunk of cme des env-

  interior and exterior loppers (30, 42) being combined, the envelope

  inner lamp (42) being axially adjustable relative to

  1 'outer casing (30),' outer casing and the casing

  inner lope defining, between them, an onvergent annular passage (44); a laser (12); an optical system (14) arranged to direct the beam

  laser along the axis of the tr. rope (32) of the outer envelopes

  lower and inner towards a focal point (15) located outside of the nozzle (10); a gas amerne system (60) communicating with the interior of the interior envelope (42), creating an exhaust

  gas inside the envelope towards the focal point

  saticn (15) of the laser; and a supply system (50, 52) immunizing with the annular passage (44) located between the inner casing (42) and the outer casing (30) and adapted to introduce into it a burst of material of split split contribution

mixed with a carrier gas.

  2. Apparatus according to claim 1, characterized in that the laser beam (13) passes along the central axis (32) of

1 '' inner envelope.

  3. Apparatus according to claim 1, characterized in that

  that the laser is a carbon dioxide laser.

26 48068

  4. Apparatus according to reverdicatio 1, characterized in that the optical system (14) comprises a mirror (17) intended to

focus the laser beam.

  5. Apparatus according to reverdication 1, characterized in that it cu orte further ure barrier for pEcdre (56)

  available inside the arlar passage (44).

  6. A method for depositing a filler material on a substrate, characterized in that it comprises the following steps: supplying a laser (12) and an optical system (14) which

  focus the laser beam at a sufficient focal point

  fisamnent close to the surface of the substrate so that an area of the substrate is melted to form a welding area; and add finely divided filler material to the area

  welding, the filler material being added uniformly around -

  the circumference of the welding area;

  in which the adjunction step is obtained by providing

  forming a laser welding nozzle comprising an outer casing (30) and an inner casing (42) which define a convergent and adjustable annular passage between them, the filler material being brought into the nozzle at

  the divergent end of the passage and being drawn towards the end

converging half of the passage.

  7. Method according to claim 6, characterized in that the finely divided filler material is mixed with a gas

  fluidizing before being admitted into the nozzle.

  8. Method according to claim 6, characterized in that an axial gas flow is directed through the interior of

  1 inner envelope (42) towards the substrate.

  9. Method according to claim 8, characterized in that the axial gas is selected from the group of gases consisting of argcon, nitrogen, helium, hydrogen and mixtures of these gases. 10. Proé according to reveication 6, characterized in that the filler material is selected from the group consisting of a titanium alloy, a nickel alloy, an alloy of

cabt and an iron alloy.

  11. Pro according to claim 6, characterized in oe

  that the laser focal point is located in the substrate.

  12. Procd according to claim 6, characterized in that the laser fcaliticm point is located above the substrate.

  13. Installation of laser spray nozzle, characteristic

  terized in that it comprises: a nozzle coips (40) provided with a trap and an end-spaced apart from each other and with a beam passage extending between those -this to allow the laser beam to enter the passage through the first end and exit through the end secode; an envelope (30) surrounding the spaced end and spaced therefrom, forming an annular passage (44) therewith and carrying an opening (46) coaxial with the beam passage to allow the laser beam to pass therethrough; and means intended to be associated with the passage (44) for

  feed powder into it so that the powder and make it

  this converge in a common place.

  14. Assembly according to the claim 13, characterized in that the means is associated with the passage (44) for distributing

  evenly the powder in the passage.

  15. An assembly according to claim 13, characterized in that the end sx is of trcx shape: urch (42) and the envelope (30) has a lower part which tapers towards the opening and has a shape in relation to the dry end (42) to fit therewith a

uniform size space.

  16. Assembly according to claim 15, characterized in that a mKyen is associated functionally with the Corlps to allow the movement of the oerps and thus positions the

  dry end with respect to the lower part.

  17. Assembly according to claim 13, characterized in that the first means is associated fcrcticnnellement with

  the envelope (30) to cool down this envelcwppe.

  18. Compensation according to claim 17, created in that a second means (60) is associated with the

  first end to cool this first end.

  19. Assembly seloe reverdication 13, cratered

  in that a means (14) is associated with the nozzle cxrps for foca-

read the beam.

  20. An assembly according to claim 19, characterized

  in that the laser beam constitutes a means coupled to the body.

  21. Nozzle for a typical laser plating system

  terized in that it includes: means generating a laser beam (12);

  an open casing (30) of general cylindrical form

  drique having a first end associated with the laser beam generating means for receiving a laser beam and a second end which can be arranged adjacent to a work piece so that the laser beam exciting the second end is directed onto the work piece ; a recess in the second end coaxial with the opening forming a powder distribution chamber, this chamber having a coxial outlet with this opening; an open nozzle body (40) arranged coxially in the casing and including a passage receiving the beam, through which the beam passes; and powder dispensing means (53, 54) positioned inside the chamber for dispensing powder into

  so that the beam and the powder come out of the envelope

  lcpe and converge in a cmmn place.

  22. Pipe according to reverdicatian 21, characterized

  that the body (40) has a trcxonic part (42) already

  cante at said exit; the second end tapers towards said outlet to form a space with said frustoconical part; and a means of refridisst associated foctiroellent to

se oe etréité.

  23. Nozzle according to Reveditic 21, rised in that means are asscièces with the body (40) to deplete the crps the loEg of his soul in order to adjust the crtement and control the.scrte the olunlent of the powder to at the exit. 24. A method of laser plating, characterized in that it comprises the following steps: providing a laser nozzle assembly having an oentral beam passage and a chamber for dispersing the arrular and coaxial powder; placing a work piece (16) at the outlet of the nozzle assembly; if necessary, direct the beam and the pider in a common place on the work piece so that the beam fcrde on a thin edge of the work piece and that the powder is dispersed inside the fcndue layer; and advance the nozzle assembly with respect to the pin

working (16).

  25. Assembly selo la reverdicaticn 15, characterized in that a means is associated fncticniellement to the nozzle body to move the body the lncrg of its axis in order to adjust the gap between the trcrrmique part and the line part and to regulate the the flow of powder through the outlet.