Method for manufacturing an impeller with a shroud

Abstract

The method includes a preliminary step of coaxially arranging a disk and a shroud relative to each other, one of the disk and the shroud including a plurality of blades protruding toward the other of the disk and the shroud, each blade having a base and a tip, the other of the disk and the shroud including a plurality of grooves in an outer surface facing the opposite side of the blade, each groove having a side surface and a bottom surface, the shroud and the disk being arranged in contact with each other along the blades, each of the plurality of grooves extending along one of the plurality of blades. Next, each blade is welded to the other of the disk and the shroud along each respective groove by a wobbling laser beam that is irradiated from outside the impeller and moves along the groove.

Description

Technical Field

[0001] The present disclosure relates to the field of turbomachinery. Embodiments disclosed herein specifically relate to a method for manufacturing a shrouded impeller for a turbomachine.

Background Art

[0002] Some types of turbomachines use a rotating impeller to convert mechanical power into pressure power of a gas flow or vice versa. Specifically, a turboexpander includes an impeller mounted on a shaft for expanding a compressed gas flow and converting the energy of the compressed fluid into mechanical power available on the rotating shaft of the expander. Centrifugal compressors and centrifugal pumps include a rotating impeller for compressing a gas flow using mechanical power applied to the rotary shaft of the compressor.

[0003] Generally, an impeller includes a disk, also known as a hub, and has a plurality of blades integral with the disk. The blades may have a so-called three-dimensional shape or twist. Some impellers specifically referred to in the present disclosure further include a shroud. The disk, the shroud, and the blades disposed therebetween define a flow path through which a gas flow passes and exchanges energy with the rotating impeller. Usually, the blades are formed by machining a blank and forming the disk and the blades as a single monolithic body. The shroud is then welded to the tips of the blades, usually by arc welding (U.S. Patent No. 42302657). Attempts have also been made in the past to use laser welding for the purpose of reducing the thermal distortion and stress induced in the impeller by conventional arc welding techniques (U.S. Patent No. 8408873).

[0004] Laser welding has proven to have severe limitations, particularly with respect to the maximum dimensions of shrouded impellers that can be manufactured with such techniques.

[0005] Therefore, there remains a need for improvement in the field of laser welding of shrouded impellers. SUMMARY OF THE INVENTION

[0006] According to the present disclosure, a method for manufacturing a shrouded impeller is provided, the method including a preliminary step of coaxially arranging a disk and a shroud relative to each other. One of the disk and the shroud includes a plurality of blades protruding toward the other of the disk and the shroud, each blade having a base and a tip. The other of the disk and the shroud includes a plurality of grooves on an outer surface facing the opposite side of the blades, each groove having a side surface and a bottom. The shroud and the disk are arranged in contact with each other along the blades, and each of the plurality of grooves extends along one of the plurality of blades. The method further includes welding each blade to the other of the disk and the shroud along each groove by a wobbling laser beam irradiated from outside the impeller and moving along the groove, i.e., using a laser beam having a wobbling motion.

[0007] In some embodiments, the step of welding each blade to the other of the disk and the shroud along each groove may include: passing a laser beam with a wobbling motion at least once along each groove to melt the bottom of the groove and then solidifying the melted bottom to weld the disk and the shroud along the groove; and filling the groove with a metal filler material by generating a series of overlapping layers of a metal material, each layer being melted by a laser beam with a wobbling motion and then solidified.

[0008] In a particularly preferred embodiment, after the disk and the shroud are coaxially arranged with respect to each other in order to temporarily connect the shroud and the disk to each other at the correct mutual angular position, preliminary circumferential welding can be performed. Next, each blade provided on one of the shroud and the disk is welded to the other of the disk and the shroud along the respective grooves by performing the following steps. a) Passing a laser beam with a wobbling motion along a first track extending along the groove to locally weld the disk and the shroud along the first track. b) If required by the width of the groove, passing a laser beam with a wobbling motion along a further track that is parallel to the first track and laterally offset from the first track in the direction of the width of the groove. c) Optionally, repeating step (b) until the entire bottom of the groove is welded to the respective blade. d) Forming a layer of metal filler material in the groove, d1. While supplying metal filler material into the groove, passing a laser beam with a wobbling motion along a first filling track extending along the groove to melt the metal filler material with the laser beam; d2. If required by the width of the groove, passing a laser beam with a wobbling motion along a further filling track that is parallel to the first track and laterally offset from the first track in the direction of the width of the groove; d3. Optionally, repeating step (d2) until the entire width of the groove is filled with a layer of melted and solidified metal filler material. e) Repeating step (d) for subsequent layers of metal filler material until the height of the groove is filled with a plurality of layers of melted and solidified metal filler material.

[0009] Once steps (a), (b), and (c) are completed for one blade, step (d) can be executed. However, preferably, the next blade is welded along its respective groove by performing steps (a), (b), and (c). Preferably, steps (a), (b), and (c) are performed for all blades, and only then are steps (d) and (e) executed starting from one of the blades. Similarly, steps (d) and (e), which are necessary to fill the grooves with a metal filling material, can be performed for one blade at a time. However, preferably, step (d) is performed once for each blade and then repeated in sequence for different blades, such that all the grooves are gradually filled with subsequent layers of the metal filling material.

[0010] Generally, the shroud and the disk welded to each other in the steps outlined above can be semi-finished, i.e., they may require additional machining and possible hardening or finishing steps to achieve the shape and structure of the final impeller. As will become apparent from the detailed description of the embodiments, the shroud and the disk can have a thickness and diameter much larger than the final disk and shroud after the impeller has achieved its final shape. The large allowance in both the shroud and the disk is useful for reducing thermal distortion during welding. This additional metal material is removed by machining in one or more steps, optionally in combination with heat treatment aimed at modifying the mechanical properties of the impeller, for example, for hardening purposes, and / or for reducing internal stresses, or for other reasons, to obtain the final shape of the impeller.

[0011] Further features and embodiments of the method of the present disclosure are described in more detail below with reference to the accompanying drawings and are set forth in the appended claims.

Brief Description of the Drawings

[0012] Here, briefly refer to the accompanying drawings.

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[0013] The following description relates in particular to a shrouded impeller for a centrifugal compressor. However, the method disclosed herein can also be used to manufacture impellers for pumps or turboexpanders.

[0014] In short, the method provides for welding blades to the shroud (or disk) of an impeller by providing a plurality of grooves in the shroud (or disk), each groove having a spread substantially the same as that of each blade. Each blade is then welded to the shroud (or disk) of the impeller from the outside of the impeller by using a wobbling laser that executes one or more passes along the groove to melt the bottom of each groove and then solidify the molten material. When the bottom of the groove is melted and solidified, thus forming a first layer of weld material, the groove is filled with additional metallic material, which is supplied into the groove (e.g., in powder or wire form) and melted by multiple passes of a laser beam. The wobbling motion of the laser beam creates a pool of molten metal larger than the laser spot. This enables the groove to be rapidly filled with melted and then solidified metallic material by creating overlapping layers of melted and then solidified metallic material. Each layer is formed, in turn, by at least one strip, preferably by a plurality of strips of melted and solidified metallic material arranged side by side. Each strip is formed by passing a wobbling laser along a track following the longitudinal extension of the groove.

[0015] Referring now to the drawings, FIG. 1 shows the impeller in an axonometric projection. The impeller 1 includes a disk, or hub 3, and a shroud 5. A plurality of blades 7 are disposed between the disk 3 and the shroud 5. The blades 7 may be three-dimensional blades. Each blade includes a base 7.1 connected to the disk and a tip 7.2 connected to the shroud.

[0016] In some embodiments, the disk 3 and the blades 7 can be machined by milling from a single blank, while the shroud is manufactured separately and then connected by laser welding to the blade tips, thereby forming the final impeller 1 with the shroud. Specifically, the disk 3 has an inner surface 3.1 (see also FIG. 10), to which the base 7.1 of the blade 7 is connected, from which the blade 7 projects towards the shroud 5. The outer surface on the opposite side of the disk 3 is labeled 3.2. The shroud 5 has an inner surface 5.1 facing the inside of the impeller 1 and connected to the tip 7.2 of the blade 7. The outer surface on the opposite side of the shroud 5 is labeled 5.2. The flow path 9 is formed between the inner surface 3.1 of the disk 3 and the inner surface 5.1 of the shroud 5 and between adjacent blades 7.

[0017] In other embodiments, the blades and the shroud can be manufactured by machining a blank, e.g., by milling, and the disk can be manufactured separately and then welded to the blade bases to form an impeller with a shroud.

[0018] In a presently preferred embodiment, the shroud 5 is manufactured separately and welded to the tip 7.2 of the blade 7 machined from a single blank together with the disk 5.

[0019] When the shroud 5 is welded to the tip 7.2 of the blade 7 extending from the inner surface 5.1 of the disk 5, the outer surface 5.2 of the shroud 5 is machined to provide a plurality of grooves 11 therein. Each groove has a bottom 11.1 and sides 11.2 and extends longitudinally along a curve that extends along the tip 7.2 of each blade 7 when the shroud 5 is welded to the blade 7.

[0020] Welding of the shroud to the blade tip 7.2 is performed using a wobbling laser as will be described in more detail below. The welding process includes two steps for each blade 7 and each respective groove 11. In the first step, the metal material forming the bottom of the groove and the metal material forming the tip 7.2 of each blade 7 are melted by heating with a laser output and then solidified to form a welded connection between the shroud 5 and the disk 3. In the second step, the groove 11 is gradually filled with a metal material which is supplied in powder form or wire form, melted by the laser output and then solidified within the groove.

[0021] The following detailed description refers to the laser welding process summarized above as being performed along a single groove. The same process is repeated for each groove until the shroud 5 is welded to the disk 3 along a number of weld lines equal to the number of blades 7. For the sake of explanation, the process is described below as being performed for a single groove and the first and second steps are performed sequentially along the same groove. After both steps of the process have been performed for the first groove, the next groove and blade are processed and the process continues in the same manner until the shroud 5 is fully welded to all of the blades 7. However, it should be understood that the bottom welding of the first step can be performed sequentially for all of the grooves and the groove filling of the second step can be performed after the bottom of each groove 11 has been welded to the respective blade tip 7.2.

[0022] In some embodiments, the grooves are in a sequence adapted to reduce the risk of thermal deformation of the impeller, for example starting with a first groove and then a second groove arranged at an angle of 180° with respect to the first groove and welded to each blade, the third groove to be welded is offset by 90° with respect to the second groove, the fourth groove to be welded is offset by 180° with respect to the third groove, and so on. To fill each groove, the same sequence is continued in the second stage.

[0023] A laser device for performing the welding process is schematically shown in FIG. 2. Generally, the device includes a support for the impeller 1 and a laser head. The laser head and the impeller are provided with movement along numerical control axes such that the laser beam generated by the laser head can scan each groove 11 of the shroud 5.

[0024] More specifically, in the embodiment schematically shown in FIG. 2, the device 21 includes an inclined table 23 on which the disk 3 of the impeller 1 can be blocked. The inclined table 23 can preferably provide numerical control motion around one or two numerical control rotation axes oriented at 90° to each other. The device 21 further includes a laser head 25 which can be provided with movement by numerical control translation axes, for example two numerical control translation axes orthogonal to each other. In different embodiments not shown, the laser head 25 can be attached to a robotic arm, for example a humanoid robotic arm.

[0025] A schematic view of the laser head 25 and the impeller 1 during the welding step of the welding process is shown in FIG. 3. The laser head 25 includes a wobbling laser, that is, a laser light source, and an associated optical system that imparts a wobbling motion to the laser beam generated by the laser light source. The wobbling laser light source is disclosed, for example, in U.S. Patent Application Publication No. 2020 / 0376594.

[0026] In some embodiments, the laser head includes a laser light source 25.1, a collimator 25.2, a set of movable mirrors 25.3, and a focusing optical system 25.4. The movable mirror 25.3 can be controlled by a suitable actuator for generating a wobbling motion.

[0027] The wobbling laser light source can be moved relative to the impeller such that the laser spot generated by the laser optical systems 25.2 - 25.4 moves along a main trajectory T, for example parallel to the groove 11, and is further given a wobbling motion around a center point. The center point moves along the main trajectory. The trajectory of the laser spot resulting on the metal material to be welded is a continuous line along the main direction, combined with a periodic motion. If the wobbling motion is, for example, a circular motion around the center point and the main trajectory is a continuous line along which the center point moves, the laser spot moves along a line as shown in FIG. 4.

[0028] The wobbling motion combined with the main motion of the laser spot along the main trajectory of the laser spot results in a pool of molten metal that is larger in size than the laser spot and is given by the diameter of the circular wobbling motion. In FIG. 4, the reference symbol S represents the laser spot and W is the width of the pool of molten metal.

[0029] As will become apparent from the following detailed description of the welding process, the wobbling motion of the laser spot S enables the welding of large impellers, which can have a thickness that is a multiple of the diameter of the laser spot S and thus a relatively wide groove 11, with a relatively small number of laser passes.

[0030] To better understand the welding process, FIG. 5 shows a cross-sectional view of the semi-finished shroud before welding to the disk of the impeller. The impeller is symmetric with respect to the axis of rotation A-A, and thus only half of the impeller is shown in the cross-sectional view of FIG. 5. The contour of the final impeller shape is shown by a dotted line. As can be understood from the overlapping dotted-line final contour of the impeller, the shroud is semi-finished in that its thickness is substantially greater than the thickness of the final impeller shroud shown by the dotted line. Further, the semi-finished shroud 5 includes a circumferential protrusion 5.3, which is removed in a final machining step and is used during the welding process to temporarily couple the semi-finished shroud to the semi-finished disk.

[0031] The semi-finished disk 3 is shown in FIG. 6 in a partial cross-sectional view along a radial plane including the axis of rotation of the impeller.

[0032] The final impeller is shown in a partial cross-sectional view along the radial plane of FIG. 10. Reference numeral 1.1 indicates the impeller eye.

[0033] As best shown in FIGS. 7 and 9, the grooves 11 provided on the outer surface of the semi-finished shroud 5 have longitudinal extensions that extend and have a shape corresponding to the shape of the tip 7.2 of each blade 7, such that when the shroud 7 and the disk 5 are stacked in sequence, the grooves 11 have the same spread as the blade tip 7.2, i.e., extend along the tip 7.2 of the corresponding blade 7.

[0034] As shown in the cross-sectional view of FIG. 8, each groove 11 has a bottom 11.1 and two side walls 11.2. When the shroud 5 is placed on top of the disk 3, the outer surface of the bottom 11.1 contacts the tip 7.2 of the corresponding blade 7 machined on the disk 3.

[0035] Before welding the blade 7 to the shroud 5, a preliminary welding step is performed to temporarily connect the semi-finished shroud to the semi-finished disk 3. The tack welding is performed along a circumferential line connecting the circular protrusion 5.3 (Fig. 5) of the semi-finished shroud 5 and the circular edge 3.5 (Fig. 6) of the semi-finished disk 3. The correct mutual angular positions of the semi-finished shroud 5 and the semi-finished disk 3 can be determined by the stop holes at the tips 7.2 of some of the blades 7 formed monolithically with the semi-finished disk 3 and the respective through holes at the bottoms 11.1 of some of the grooves 11. Dowels are introduced into the through holes at the bottoms 11.1 of the grooves and the corresponding stop holes of the blades 7.

[0036] When the semi-finished shroud 5 and the semi-finished disk 3 are temporarily assembled and welded to each other along the circumferential protrusion 5.3 to form the semi-finished impeller 1, this semi-finished impeller is mounted on the inclined table 23 for welding along each blade 7.

[0037] The sequence of FIGS. 11A - 11J is the steps of the welding process for welding one of the blades 7 to the shroud 5. As described above, the process is divided into two stages, namely, a first stage including melting the groove bottom 11.1 and the blade tip 7.1 and then solidifying the molten material, and a second stage of filling the groove 11 with additional filler metal material supplied in powder or wire form. As described above, the two stages are not normally performed in sequence on the same groove 11. Rather, the welding of the groove bottoms is first performed on all the grooves 11, and then the filling with additional metal material is performed.

[0038] In the sequence of FIGS. 11A - 11J, the groove 11 and the blade tip 7.2 are shown in a cross-sectional view taken along line VIII - VIII of FIG. 7.

[0039] When the semi-finished impeller 1 is locked onto the inclined table 23, in the first step, the laser head 25 is moved to one end of the groove 11 so that the laser beam B generates a laser spot located at one end of the groove 11, which is close to one of the side walls 11.2 of the groove 11. The laser head 25 is moved according to a wobbling motion combined with a main motion along an orbit extending from one end of the groove 11 to the opposite end. The main motion can be imparted to the laser head 25, the impeller 1, or both, that is, it can be obtained by combining the motion of the inclined table 23 and the motion of the laser head 25 with respect to a stationary structure that supports the laser head 25 and the table 23.

[0040] In some embodiments, the motion can start at the radially outermost end of the groove 11. A combination of a linear motion along the main orbit T (Figure 4) and a wobbling motion of the laser B melts the metallic material that constitutes the shroud 5 and the blade 7. Figure 11A shows the step before melting. More specifically, the bottom 11.1 of the groove 11 and the uppermost part of the blade tip 7.2 melt. The width W of the melting region (pool of molten metal) in the transverse direction of the groove 11 depends on the diameter of the circular wobbling motion and can be a multiple of the diameter of the laser spot S. The width of the melting pool, that is, the pool of molten metal, is usually smaller than the width W of the groove 11.

[0041] As the laser spot S moves along the linear orbit T along the longitudinal extension of the groove 11, the molten metal behind the laser spot S gradually solidifies, generating a weld bead formed by the melted and solidified material at the bottom 11.1 of the groove 11 and by the melted and solidified material at the blade tip 7.2. The bead is shown in Figure 11B.

[0042] As described above, since the diameter of the melting pool (W in FIG. 4) is usually smaller than the width of the groove 11, the above-described steps can be repeated two or more times using two or more passes of the laser beam along the groove 11. Each pass is shifted laterally with respect to the previous pass along the transverse direction of the groove 11. If the width of the groove 11 is equal to the diameter of the melting pool, one pass is sufficient.

[0043] For example, as shown in FIG. 11C, by moving the laser beam B along an additional track offset from the first track in the transverse direction of the groove 11, a further melting pool is formed that moves from one end of the groove 11 to the opposite end in the longitudinal direction of the groove 11. Thereafter, the molten material solidifies. Optionally, the wobbling laser beam can move along a plurality of further tracks along the groove 11, each track being offset from the previous track in the transverse direction, i.e., in the direction of the width of the groove 11, until the entire bottom of the groove 11 and the entire tip 7.2 of each blade 7 are melted and then solidified (FIG. 11D). Thereby, a weld bead of the same size as the groove 11 is formed. The groove 11 has a width that substantially corresponds to the width of the blade 7, or preferably a width greater than the width of the blade 7, such that the resulting weld layer has a width greater than or equal to the thickness of the blade 7.

[0044] Thanks to the use of a wobbling laser, i.e., a laser beam B having a wobbling motion combined with a main motion along the longitudinal welding track T, the number of laser passes required to generate a weld layer of the same size as the width of the groove is substantially smaller than the ratio between the width of the groove 11 and the laser spot diameter. The time required to generate the weld layer is short, and this welding method can also be used for large-sized impellers with a relatively large thickness of the blade 7.

[0045] Next, a further step of welding and filling the groove 11 with a metallic material is performed (Figs. 11E to 11J). As described above, the further step can be performed after welding and solidification of the groove bottom 11.1, or after the bottom 11.1 of one, several, or all of the other grooves 11 has been melted and welded to the tip 7.2 of the corresponding blade 2. This second approach is preferred as it reduces the risk of thermal deformation of the semi-finished impeller 1.

[0046] The welding of the second step involves adding a metallic material to the groove 11 in order to fill the groove. The metallic material can be dispensed, for example, in wire form or powder form. The added metallic material is placed under the wobbling laser beam B, which is moved along a trajectory T along each groove 11, and the linear motion along the main trajectory T is combined with the wobbling motion of the laser beam B to generate a molten pool having a width greater than the diameter of the laser spot S.

[0047] Fig. 3 schematically shows, as an exemplary embodiment of a metal dispensing device, a nozzle 31 for dispensing metal powder towards the molten pool formed along the bottom of the groove 11 during this welding step. As described above, the metallic material can also be supplied in other forms, for example in wire form.

[0048] Fig. 11E shows a first bead formed by melting and solidifying the added metallic material along the side of the groove 11. This step is repeated two or more times until a layer of molten and then solidified added metallic material is formed, as shown in the sequence of Figs. 1F, 11G. The number of laser passes required to complete the layer depends on the diameter of the laser spot S, the width of the wobbling motion (for example, the diameter of a circular wobbling motion), and the width of the groove 11. If the width of the groove 11 is very small and equal to the diameter of the pool of molten metallic material formed by the wobbling laser, one pass is sufficient to generate a layer of molten and then solidified metallic material.

[0049] This process is repeated the number of times necessary to form a sufficient fill for subsequent machining of the impeller 11 (see FIGS. 11H - 11J). In some examples, the entire groove 11 can be filled until the last layer of molten and solidified additional metallic material reaches the outer surface 5.2 of the semi - finished shroud.

[0050] The multi - pass process, in combination with the wobbling motion of the laser beam B, will quickly fill the entire groove 11, or a portion thereof as required, even in the case of large impellers 1 where the thickness of the blade tip 7.2, and thus the width of the groove 11, requires several passes of the laser beam along a laterally offset main track T. Optionally, the diameter of the wobbling motion can be adapted to the cross - sectional dimension of the groove, such that for larger blades 7, a wider wobbling motion is used to create a larger melt pool with each laser pass.

[0051] The above procedure results in an efficient welding process even for large - sized impellers, avoiding the use of arc welding and thus reducing the thermally induced stresses and deformations in the resulting impeller.

[0052] As described above, in the preferred embodiment, the semi - finished shroud 5 and the semi - finished disk are welded to each other as described above, and as a result, the thermally induced impeller deformation is reduced due to the thickness of the semi - finished shroud 5 and the disk 3. The excess material is then removed by machining, for example, by milling, until the final impeller shown in the cross - section of FIG. 10 is obtained. The chip - removal process also removes the excess material around the circumference of the impeller and thus removes the temporary weld beads formed along the circular protrusion 5.3 of the shroud 5.

[0053] In the above description and the accompanying drawings, the blade 7 is formed by machining the disk 3, and the groove 11 is machined on the outer surface 5.2 of the shroud. However, as described above, an opposite approach can be used in which the blade 7 is machined starting from a blank as a monolithic part of the shroud 5, such that the blade 7 projects from the inner surface 5.1 of the shroud while the disk 3 comprises a smooth inner surface 3.1 and the groove 11 machined on its outer surface 3.2.

[0054] Exemplary embodiments are disclosed above and shown in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions, and additions may be made to what is specifically disclosed herein without departing from the scope of the invention as defined in the following claims.

Claims

1. A method for manufacturing an impeller with a shroud, the method comprising: placing a disk and a shroud coaxially with each other, one of the disk and the shroud including a plurality of blades protruding toward the other of the disk and the shroud, each blade having a base and a tip, the other of the disk and the shroud including a plurality of grooves on an outer surface facing the opposite side of the blade, each groove having a side surface and a bottom, the shroud and the disk being arranged in contact with each other along the blade, and each groove of the plurality of grooves extending along one of the plurality of blades; welding each blade to the other of the disk and the shroud along each respective groove by a wobbling laser beam irradiated from outside the impeller and moving along the groove; The step of welding each blade to the other of the disk and the shroud along each respective groove includes passing the laser beam with a wobbling motion along each groove at least once to melt the bottom of the groove and then solidifying the melted bottom to weld the disk and the shroud along the groove; filling the groove with a metal filling material by generating a series of superimposed layers of a metal material, each layer being melted by the laser beam with a wobbling motion and then solidified, a method for manufacturing an impeller with a shroud.

2. The step of welding each blade to the other of the disk and the shroud along each respective groove a) passing a laser beam with a wobbling motion along a first track extending along the groove to locally weld the disk and the shroud along the first track; b) repeating step (a) along a further track parallel to the first track and laterally offset from the first track in the direction of the width of the groove until the entire bottom of the groove is welded to the respective blade; c) forming a layer of metal filling material in the groove, c1. While supplying a metal filling material into the groove, passing the laser beam with wobbling motion along a first filling track extending along the groove, and melting the metal filling material with the laser beam; c2. Repeating step (c1) along a further filling track that is parallel to the first filling track and laterally offset from the first filling track in the direction of the width of the groove until the entire width of the groove is filled with a layer of melted and solidified metal filling material; and forming by; d) Repeating step (c) for subsequent layers of the metal filling material until the height of the groove is filled with a plurality of layers of melted and solidified metal filling material. The method according to claim 1, comprising.

3. The method according to claim 2, wherein step (c) is repeated until the groove is completely filled with the metal filling material.

4. The method according to any one of claims 1 to 3, wherein the blade protrudes from the disk and the groove is formed on the outer surface of the shroud facing the opposite side of the disk.

5. The method according to any one of claims 1 to 3, wherein the blade protrudes from the shroud and the groove is formed on the outer surface of the disk facing the opposite side of the shroud.

6. The method according to any one of claims 1 to 5, wherein the metal filling material is supplied to the groove in powder form and melted by the laser beam.

7. The method according to any one of claims 1 to 5, wherein the metal filling material is melted from a bar or wire by the laser beam.

8. The method according to any one of claims 1 to 7, comprising machining the blade by milling one of the disk and the shroud.

9. The method according to any one of claims 1 to 8, comprising machining the groove by milling.

10. The method according to any one of claims 1 to 9, further comprising machining the shroud and the disk to the final shape of the impeller after filling the groove.

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