Device for laser cladding comprising a beam nozzle with an elongated cross-sectional area of ​​a light channel

Abstract

Device for laser cladding comprising a jet nozzle (1), and a rotationally symmetrical workpiece (100), wherein the beam nozzle (1) has a light channel (3) for guiding at least one laser beam directed at the workpiece (100); and a powder unit (7) arranged radially outside the light channel (3) for guiding at least one powder jet to be applied to the workpiece (100); has wherein a cross-sectional area of ​​the light channel (3) extending orthogonally to a longitudinal direction of the jet nozzle (1) is stretched, deviating from a circular shape, essentially parallel to the circumference of the workpiece (100).

Description

Technical area

[0001] The present invention relates to a device for laser cladding comprising a beam nozzle for laser cladding along a feed direction. State of the art

[0002] Laser cladding is used, for example, in repair, coating, and / or joining technology. A distinction can be made between conventional laser cladding (Laser Metal Deposition (LMD), Direct Metal Deposition (DMD), or Direct Energy Deposition (DED)) and so-called high-speed laser cladding (HS-LMD or extreme high-speed laser cladding (EHLA)). HS-LMD processes are described, for example, in German patent applications DE 10 2011 100 456 A and DE 10 2018 130 798 A1. Another laser cladding process is known from Chinese patent application CN 109175372 A.

[0003] Laser cladding allows a functional layer to be applied to a workpiece. Compared to an untreated workpiece, this generally increases the load-bearing capacity of the workpiece treated by laser cladding. The functional layer can, for example, serve as a wear-resistant coating. The application of the functional layer is based on melting the workpiece surface, applying a powdered filler material, and subsequent cooling, resulting in a matrix structure with hard particles that is metallurgically bonded to the material surface. Thus, laser cladding affects and modifies the internal material structure of the workpiece. This can potentially lead to imperfections in the internal material structure, which can impair the desired increase in load-bearing capacity. These imperfections can be microscopic in nature, making them difficult to identify.. Description of the invention

[0004] Based on the known prior art, an object of the present invention is to provide an improved beam nozzle for laser cladding along a feed direction. The invention aims in particular to increase the weld quality of an applied functional layer and of the workpiece as a whole, and to reduce or eliminate deficiencies in a weld joint between a powdered filler material and a material surface. These deficiencies may include bonding defects between the material surface and the applied functional layer or between individual applied functional layers. The deficiencies may also include pores, i.e., air inclusions, that occur within the applied functional layer or between the applied functional layer and the material surface.Particularly when the material surface is a cast material, pores can occur more frequently. Defects can also include cracks, especially those running vertically to the material surface within the applied functional layer. Furthermore, defects can arise from powder particles, particularly carbides, of the powdered filler material dissolving into a matrix material of the powdered filler material, leading to embrittlement of the matrix material. The invention further aims, in particular, to provide a reliable blast nozzle that is resistant to thermal stress. The invention can also aim to design the blast nozzle in such a way that it ensures reliable and precise laser cladding over very high cycle counts.

[0005] The problem is solved by a device for laser cladding comprising a beam nozzle with the features of claim 1. Advantageous embodiments are described in the dependent claims, the description, and the figures.

[0006] Accordingly, a beam nozzle for laser cladding is proposed, featuring a feed direction and a light channel for guiding at least one laser beam directed at a workpiece. The laser cladding process can be a high-speed laser cladding (HS-LMD) method. The feed direction is the direction along which the beam nozzle moves relative to the workpiece. It can result from a movement, particularly a rotational movement, of the workpiece, from a movement of the beam nozzle, or from a combination of both. The feed direction and the corresponding feed motion can remain constant throughout the process. Alternatively, they can vary with each process stage. The workpiece can be rotationally symmetrical, such as a brake disc, a hydraulic cylinder, a pressure roller, or a plain bearing.The laser beam can pass through the light channel. It can be supplied by a laser source, from which the laser beam is guided via a fiber optic cable to a laser system. This system splits the laser beam using a collimating lens and focuses it according to the process requirements before it enters the beam nozzle via laser optics. The light channel can be a hollow channel that runs the entire length of the beam nozzle. In addition to the laser beam, a process gas can also be guided to the workpiece surface through the light channel.

[0007] The blast nozzle further comprises a powder unit arranged radially outside the light channel for guiding at least one powder jet to be applied to the workpiece. The powder unit can extend radially outside the light channel from the longitudinal direction of the blast nozzle and can be part of an outer structure that completely surrounds the light channel. The powder jet can carry a powdered filler material consisting of hard particles, particularly carbides, and a matrix material. The powder unit can be the part of the blast nozzle designed to guide the powdered filler material directly or indirectly. The powder unit can include injector guides into which powder injectors can be inserted. It can also have an annular gap within which the powdered filler material is guided.

[0008] A cross-sectional area of ​​the light channel, extending orthogonally to a longitudinal direction of the nozzle, is elongated in the feed direction, deviating from a circular shape. This elongation can point in the feed direction or opposite to it. Due to this elongation, more than one process zone can be provided on the workpiece in the feed direction. The nozzle is, in its extended form, an elongated component. The longitudinal direction can be the direction in which the nozzle is oriented. Orthogonal to this longitudinal direction, the nozzle has a cross-section, part of which is the shape of the light channel. This section is elongated in the feed direction and can be axially symmetric along the feed direction and point-symmetric about a center point of the light channel's cross-section. A minimum cross-sectional area of ​​the light channel is determined by a dimension, particularly a diameter, of the laser beam.Compared to the minimum dimension, the cross-sectional area is stretched along the feed direction.

[0009] The beam nozzle can thus enable increased variability in (i) laser beam guidance, (ii) the application of a powdered filler material, (iii) thermal management, and / or (iv) the protection of the laser system, including the beam nozzle. It allows for the provision of multiple independent process zones with high precision. The process zones can be divided into zones for laser cladding and zones for pre- and / or post-processing. In the laser cladding zones, an interaction takes place between at least one laser beam and a powdered filler material. The pre- and / or post-processing can consist of cleaning the material surface, preheating the material surface before the powdered filler material is applied, reheating the material surface after the powdered filler material has been applied, or a combination thereof.During pre- and / or post-processing, the laser beam can strike the workpiece without interacting with the powdered filler material. These independent process zones can improve weld quality and thus the durability of the applied functional layer, especially the wear-resistant layer, and of the workpiece as a whole. An additional process gas can stabilize the process zones and increase the precision of the laser cladding process as well as the service life of the beam nozzle.

[0010] In particular, the blast nozzle can reduce the occurrence of bonding defects. Bonding defects can occur when the surface heated by the laser beam, such as the workpiece or a previously welded functional layer, is not heated sufficiently. This insufficient heating can result from keeping the laser power of a single laser beam low to prevent overheating of the powdered filler material. Increased variability in laser beam guidance, increased variability in the application of a powdered filler material, and / or increased variability in the thermal management of the blast nozzle can reduce or even prevent the occurrence of bonding defects, especially by using an elongated nozzle shape that directs a primary and a secondary beam, creating multiple process zones.

[0011] Furthermore, the beam nozzle can, in particular, reduce the occurrence of pores between the welded functional layer and the surface heated by the laser beam. Pores can occur when lamellae within the workpiece, especially graphite lamellae, vaporize due to the laser radiation. Pores can also occur if the surface being processed contains contaminants, such as oils, greases, cooling lubricants, or oxides, which cannot be completely removed by the welding process. The undesirable vaporization of these contaminants can result from setting the laser power of a single laser beam so high that fusion defects due to insufficient heating are avoided.The increased variability of the laser beam guidance, the increased variability of the application of a powdered additive material and / or the increased variability of the heat management of the blast nozzle can reduce or even prevent the occurrence of pores, especially by guiding a primary beam and a secondary beam through the elongated shape of the blast nozzle, which create several process zones.

[0012] Furthermore, the blast nozzle can, in particular, reduce the occurrence of cracks in the welded functional layer. Cracks can occur when a temperature gradient between the intensely heated powdered filler material and the less heated workpiece surface is so pronounced that material shrinkage during cooling leads to stresses that cause cracking. Crack formation can also result from setting the laser power of a single laser beam so high that bonding defects due to insufficient heating are avoided.The increased variability of the laser beam guidance, the increased variability of the application of a powdered additive material and / or the increased variability of the heat management of the blast nozzle can reduce or even prevent the occurrence of cracks, especially by guiding a primary beam and a secondary beam through the elongated shape of the blast nozzle, which create several process zones.

[0013] Furthermore, the blasting nozzle can, in particular, reduce the dissolution of hard particles, especially carbides, in the matrix material. The powdered filler material can contain hard particles, especially carbides, and a matrix material. The hard particles should be present undissolved in the welded functional layer to increase its load-bearing capacity. However, hard particles can dissolve if the powdered filler material is exposed to excessive irradiance, causing the hard particles to melt. Dissolved hard particles lead to embrittlement of the welded functional layer because the matrix material becomes less ductile. This means that stresses occurring during cooling or when the workpiece is loaded, for example, cannot be absorbed by the matrix material.The increased variability of the laser beam guidance, the increased variability of the application of a powdered additive material and / or the increased variability of the heat management of the blast nozzle can reduce or even prevent the dissolution of hard particles, especially by guiding a primary and a secondary beam through the elongated shape of the blast nozzle, which creates several process zones.

[0014] Furthermore, the nozzle can prevent powder particles from adhering to the nozzle mouth. Due to the high process heat, the reflected laser radiation and / or a metal vapor flare can cause the filler material to adhere to or even weld to the nozzle mouth, disrupting the gas and powder flows and consequently impairing the process result. The metal vapor flare is a result of the partial vaporization of the material during laser cladding.

[0015] It can lead to scattering and / or absorption of laser radiation, consequently impairing the preheating of the workpiece. This can further promote the formation of bonding defects. Increased variability in laser beam guidance, the application of powdered filler material, and / or the thermal management of the blast nozzle can reduce or even prevent the undesirable dissolution of hard particles and the spread of the metal vapor flare, particularly by using an elongated nozzle shape that directs a primary and a secondary beam, creating multiple process zones.

[0016] Along the elongated cross-sectional area of ​​the light channel, at least one laser beam, in particular at least one circular and / or oval laser beam, can be guided in such a way that more than one process zone is formed. This promotes welding behavior and reduces the deficiencies of the weld joint, especially the occurrence of fusion defects, pores, cracks, and / or the dissolution of carbides in the matrix material, and increases the load-bearing capacity of the applied functional layer. Thus, the melting behavior, the powder jet behavior, the metallurgical bond, and the cooling behavior can be variably adapted to the respective application and the prevailing material properties and process parameters.In particular, it can be avoided that the laser power supplied to the workpiece in the weld pool area and to the powdered filler material is too high or too low to achieve the desired process result. For example, in addition to a primary laser beam for laser cladding, a secondary laser beam for pre- or post-processing can be guided within the light channel in close proximity to a first processor. The secondary laser beam can be positioned in the feed direction before or after the primary laser beam, depending on whether it is used for pre- or post-processing. A geometrically close arrangement of the secondary laser beam to the primary laser beam reduces thermal losses due to heat conduction within the workpiece, which promotes the metallurgical bond between the powdered filler material and the workpiece material. The elongated shape enables welding behavior without the aforementioned shortcomings.

[0017] In one embodiment, the cross-sectional area at a distal region of the blast nozzle formed by a nozzle opening is shaped like an elongated slot, with a partial circular segment adjoining each of two opposite ends of a rectangular section. The powder unit can be part of the nozzle opening. The nozzle opening is the part of the blast nozzle facing the workpiece. The end section of the nozzle opening has a distal region. This is the part of the nozzle opening that is closest to the workpiece. On the section facing away from the workpiece, the blast nozzle has a proximal region and a flange section. The proximal region and the flange section constitute the part of the blast nozzle facing away from the workpiece. The nozzle can be coupled to another component of the laser system, such as laser optics or a processing unit, via the flange section.

[0018] In one embodiment, the cross-sectional area, particularly in the region of the nozzle opening, is elongated such that it is at least 1.5 times, and in particular at least twice, larger in the feed direction than transversely to the feed direction. Specifically, the distance between the two pitch circles can be more than twice the distance between the two parallel flanks of the elongated hole. This creates the prerequisite for guiding more than one laser beam in the light channel to provide corresponding process zones. The cross-sectional area can increase even further from the nozzle opening towards the proximal section. Thus, the cross-sectional area can reach its smallest dimension in the region of the distal section. This smallest dimension can also be sufficient for guiding multiple laser beams.

[0019] In one embodiment, the center point of the cross-sectional area is eccentric to the center point of the at least one laser beam. This allows the laser beam to be guided outside a central point, enabling the division of the nozzle and the resulting laser beam orientations into multiple process zones.

[0020] In one embodiment, the light channel is adapted to guide a plurality of laser beams, each having a first laser beam as the primary beam and a second laser beam as the secondary beam. The primary and secondary beams can originate from the same optical fiber. A supplied laser light can be split into a parallel beam bundle using a collimating lens. The beam bundle can, for example, be formed from a single laser beam by a wedge plate to create the primary and secondary beams. In this case, the primary and secondary beams can have the same wavelength and carry the same energy. Alternatively, the primary and secondary beams can differ in their wavelength and energy. The respective centers of the primary and secondary beams can be offset in the feed direction from a center point of the light channel.Providing a majority of laser beams facilitates the reliable implementation of multiple process zones.

[0021] In one embodiment, the secondary beam is adapted to interact less with the powder jet than the primary beam, with the secondary beam positioned ahead of the primary beam in the feed direction to preheat the workpiece. The interaction of the primary and secondary beams with the powder jet can be achieved by appropriately guiding the respective laser beams and / or the powder jet. For example, the powder unit at a nozzle opening can form a powder section circumferentially around the light channel, to which a powder-free feed section is attached circumferentially. The feed section surrounds the portion of the light channel facing the feed direction. Thus, the feed section can ensure that the powder jet does not interact with the secondary beam, allowing the secondary beam to be used to preheat the workpiece and not the powder particles.

[0022] In one embodiment, the secondary beam is adapted to interact less with the powder jet than the primary beam, with the secondary beam positioned behind the primary beam in the feed direction to reheat the workpiece. The interaction of the primary and secondary beams with the powder jet can be achieved by appropriately guiding the respective laser beams and / or the powder jet. For example, a powder-free feed section can surround the portion of the light channel that faces away from the feed direction. This feed section can thus ensure that the powder jet is not integrated with the secondary beam, allowing the secondary beam to be used for reheating or cleaning the workpiece.

[0023] In one embodiment, the majority of laser beams include a third laser beam, a tertiary beam, which is adapted to interact less with the powder jet than the primary beam, with the primary beam positioned ahead of the tertiary beam in the feed direction. The respective cross-sections of the primary, secondary, and tertiary beams can run along a line, meaning their respective centers lie along a line. This line can be aligned with the feed direction or be coincident with it. At least three different process zones, which promote welding behavior, can be realized via the primary, secondary, and tertiary beams.

[0024] In one embodiment, when multiple laser beams are present, the laser beam that is at the front in the feed direction, for example the secondary beam, is concentric in cross-section to a front partial circular segment of the cross-sectional area, and / or the laser beam that is at the rear in the feed direction, for example the tertiary beam, is concentric in cross-section to a rear partial circular segment of the cross-sectional area. This enables efficient use of the cross-sectional area of ​​the light channel when guiding multiple laser beams.

[0025] In one embodiment, the center of the cross-sectional area of ​​the majority of laser beams coincides with the center of the area of ​​the majority of laser beams. The center of the cross-sectional area can be the point about which the cross-section is point-symmetric. The center of the area of ​​the majority of laser beams can be the point at which the respective laser beams have their center of area in the cross-section. Because these are congruent, the spatial utilization of the cross-sectional area of ​​the light channel is further optimized when guiding multiple laser beams.

[0026] In one embodiment, the nozzle has exactly one light channel, so that the majority of laser beams are guided within the nozzle without any shielding from each other. The single light channel thus guides the majority of laser beams without requiring separate shielding around each individual laser beam. This simplifies the nozzle design and facilitates heat dissipation.

[0027] In one embodiment, the nozzle is manufactured using an additive manufacturing process, in particular powder bed fusion. For this purpose, the nozzle can be made of copper or a copper alloy, especially a copper-chromium-zirconium alloy. This material is suitable for additive manufacturing processes and, on the other hand, ensures sufficient strength, thermal conductivity, and heat resistance to meet the process requirements. In powder bed fusion, the material to be processed is in powder form. A laser beam heats the powder along the intended geometry, causing the powder to liquefy and bond together. Powder bed fusion can be implemented, for example, as selective laser melting (“SLM”) or selective laser sintering (“SLS”).

[0028] In one embodiment, the nozzle opening has a chamfer that cuts off a portion of the opening. The chamfer is essentially planar and runs in a plane inclined relative to the longitudinal direction of the nozzle. The chamfer can cut off the powder section and the powder-free feed section circumferentially around the light channel. The chamfer reduces the volume of the nozzle opening compared to the embodiment without a chamfer, thus requiring less installation space. The nozzle opening with the chamfer can be used, for example, to coat a brake disc that has a recess projecting axially from the functional surface to be coated. The chamfer ensures that the nozzle can move flexibly on the surface to be coated and can be positioned close to the recess.The chamfer can run along the distal end of the elongated hole in the manner of a bypass. The bypass defines the orientation of the chamfer at the nozzle opening. On the workpiece-facing end face of the blast nozzle, the bypass runs along a straight line or arc that neither intersects nor touches the elongated hole. The distance of the bypass from the center of the light channel is greater than the distance of the corresponding section of the elongated hole from the center of the light channel. The distance between the bypass and an outer edge of the elongated hole is chosen such that the intervening wall thickness ensures sufficient strength and load-bearing capacity of the blast nozzle.

[0029] In one embodiment, the nozzle is adapted to guide the laser beam along its longitudinal direction, such that at least one laser beam is orthogonal to the cross-sectional area. Furthermore, the light channel can be adapted to guide a protective gas along a radially outer section to shield a process zone.

[0030] The disclosed features contribute, partly on their own and partly in combination, to overcoming the shortcomings in laser cladding mentioned at the outset. Short description of the characters

[0031] Preferred further embodiments of the invention are explained in more detail by the following description of the figures. These show: Fig. 1 A schematic view of a beam nozzle in laser cladding; Fig. 2 a jet nozzle in a side view; Fig. 3. Turn off the jet nozzle Fig. 2 in a perspective view; Fig. 4. Turn off the jet nozzle Fig. 2 connected to other components; Fig. 5 the jet nozzle off Fig. 2 in a top view of a distal area; Fig. 6. Turn off the jet nozzle Fig. 2 in a top view of a flange section; Fig. 7 another perspective view of the jet nozzle Fig. 2; Fig. 8 a perspective sectional view of the jet nozzle Fig. 2; Fig. 9 the jet nozzle in a further embodiment in a top view of a distal area; Fig. 10 the jet nozzle with a process gas unit in a top view of the distal area; Fig. 11 Another embodiment of the jet nozzle with a geometrically adapted nozzle mouth in a side view; and Fig. 12 Another embodiment of the jet nozzle with a geometrically adapted nozzle mouth in a top view. Detailed description of preferred embodiments

[0032] Preferred embodiments are described below with reference to the figures. Identical, similar, or equivalent elements in the different figures are designated with identical reference numerals, and repeated descriptions of these elements are sometimes omitted to avoid redundancy.

[0033] Fig. Figure 1 shows a beam nozzle 1 for laser cladding along a feed direction 2. The feed direction 2 is the direction along which the beam nozzle 1 moves relative to a workpiece 100. It can result from a movement, in particular a rotational movement, of the workpiece 100, from a movement of the beam nozzle 1, or from a superposition of movements of the workpiece 100 and the beam nozzle 1. The feed direction 2 and the corresponding feed movement can be constant throughout the process. Alternatively, they can vary with the respective process stage. The workpiece 100 can be a rotationally symmetrical workpiece, such as a brake disc, a hydraulic cylinder, a pressure roller, or a sliding bearing. At least one laser beam 110 emerges from a light channel 3 with a cylindrical surface 4.The light channel 3 can also be adapted to guide a process protective gas 150 along a radially outer section to shield a process zone and prevent oxidation. The light channel 3 is surrounded by an outer structure 5 which has a nozzle opening 6, which in turn contains a powder unit 7. The powder unit 7 can, for example, have a plurality of injector guides 19 (see ). Fig. 3), each containing a powder injector 16 (to which Fig. 4) can be used. As an alternative to the individual injector guides 19, the powder unit 7 can have a powder annular gap channel. A powdered additive material 120 is directed onto the workpiece 100 via the powder unit 7 and the powder injectors 16 arranged therein. The laser beam 110 heats the workpiece 100 such that a melt pool 130 forms on a material surface. In addition, the laser beam 110 heats the powdered additive material 120, which has hard particles and a matrix material. For this purpose, the laser beam 110 can have a reduced core intensity. As soon as the melt pool 130 cools, a welded-on functional layer 140, for example a wear-resistant layer, forms from the hard particles and the matrix material. The welded-on functional layer 140 makes the material surface more resistant and increases its load-bearing capacity.

[0034] Fig. Figure 2 shows the blast nozzle 1 in a side view, with the feed direction 2 pointing out of the plane of the drawing. The blast nozzle 1 can be coupled to other components of a laser system, such as laser optics or a process adapter, via a flange section 9. A proximal region 10 adjoins the flange section 9. A coolant inlet 13 and a coolant outlet 14, which are part of a cooling system for the blast nozzle 1 and project radially from the blast nozzle 1, can be provided, at least partially, in the proximal region 10. A distal region 8 is formed at the end of the blast nozzle 1 opposite the proximal region 10. The distal region is part of the funnel-shaped nozzle mouth 6. This has a powder section 11 in a circumferential direction around the light channel 3, in which the powder unit 7 is arranged.A powder-unit-free feed section 12 adjoins the powder section 11 in the circumferential direction. The feed section 12 can be designated as a process gas section 61 (see, for example, ). Fig. 9) be designed to be part of a process gas unit 60.

[0035] Fig. Figure 3 shows the jet nozzle. Fig. 2 in a perspective view. The light channel 3 is a hollow channel with the lateral surface 4, within which at least one laser beam 110 passes. The outer structure 5 surrounds the light channel 3 from the flange section 9 to the distal region 10. The nozzle mouth 6 is an essentially funnel-shaped region of the jet nozzle 1. The funnel shape of the nozzle mouth 6 serves, among other things, to allow the nozzle mouth 6 to form the majority of injector guides 19 in the region of the powder unit 7. A powder injector 16 is inserted into each of these injector guides 19 (see Fig. 4) is used, which directs the powdered filler material 120 towards the at least one laser beam 110 and / or the workpiece 100 in a process-oriented manner. The powder unit 7 extends along the powder section 11, to which the powder unit-free feed section 12 adjoins in the circumferential direction. The feed section 12 is the area of ​​the nozzle mouth 6 in which no injector guides 19 are provided, so that no powdered filler material 120 is supplied via this section. In one embodiment, the feed section 12 can be configured as a process gas section 61, so that a process gas is supplied via this section. The jet nozzle 1 can be manufactured by means of additive manufacturing processes, in particular by means of powder bed fusion. For this purpose, the jet nozzle 1 can be made of a copper-chromium-zirconium alloy.This material is suitable for additive manufacturing processes on the one hand, and on the other hand ensures sufficient strength, thermal conductivity, and heat resistance to withstand the process requirements. In powder bed melting, the material to be processed is in powder form. A laser beam heats the powder along the intended geometry, causing the powder to liquefy and bond together. Powder bed melting can be implemented, for example, as Selective Laser Melting (SLM) or Selective Laser Sintering (SLS).

[0036] Fig. Figure 4 shows the jet nozzle 1, to which additional components are attached. A coupling ring 15 is connected to the flange section 9, which secures the jet nozzle 1 to the connected unit, for example, the laser optics or the process adapter. Powder injectors 16 are inserted into the injector guides 19 of the powder unit 7. The powdered additive material 120 is conveyed by the powder injectors 16 and applied to the workpiece 100 with the intended focus. The individual powder injectors 16 can apply different powder foci to each other. Alternatively, the powder injectors 16 can be directed at the same focal point. The powder injectors 16 are arranged in the designated injector guides 19 of the powder unit 7 in the powder section 11. The feed section 12 is free of powder injectors 16. Furthermore, an inlet nozzle 17 is inserted into the coolant inlet 13 and an outlet nozzle 18 into the coolant outlet 14.These connect the coolant inlet 13 and the coolant outlet 14 to a coolant circuit.

[0037] Fig. Figure 5 shows the nozzle 1 in a top view of the distal region 8. The cross-sectional area of ​​the light channel 3, which runs perpendicular to the longitudinal direction of the nozzle 1, deviates from a circular shape and is elongated in the feed direction 2. In the distal region 8, the cross-sectional area of ​​the light channel 3 is shaped like an elongated slot, with a partial circular segment attached to each of the two opposite ends of a rectangular section. Two laser beams are guided within the light channel 3: a primary beam 111 and a secondary beam 112. The primary beam 111 and the secondary beam 112 can originate from the same optical fiber. A supplied laser light can be split into a parallel beam using a collimating lens. The beam can be formed, for example, from a single laser beam by a wedge plate to create the primary beam 111 and the secondary beam 112.The respective centers of the primary beam 111 and the secondary beam 112 are offset in the feed direction 2 in a line to a center point 20 of the light channel 3.

[0038] In this case, the secondary jet 112 is positioned in the feed direction 2 upstream of the primary jet 111 and does not interact with a powder caustic. The secondary jet 112 can therefore be used to preheat the workpiece 100 before the primary jet 111 and the powdered filler material 120, heated by the primary jet 111, strike the workpiece 100. The secondary jet 112 thus creates a first process zone for preheating the workpiece 100, and the primary jet 111 creates a second process zone for welding the powdered filler material 120 onto the workpiece 100. These different process zones enable a defect-free weld in which no deficiencies occur, in particular no lack of fusion, pores, cracks, and / or dissolution of carbides in the matrix material. It is also possible to guide the secondary beam 112 in the feed direction 2 after the primary beam 111.Thus, the secondary jet 112 can be used to reheat the workpiece 100 and thus contribute to a more uniform cooling, which prevents the occurrence of inclusions or other deficiencies.

[0039] The primary beam 111 and the secondary beam 112 are arranged in close proximity to each other. The leading partial circular segment of the elongated hole in the feed direction 2 is concentric with the secondary beam 112, while the trailing partial circular segment of the elongated hole is concentric with the primary beam 111. A surface center of the cross-sectional area is eccentric to a center point of the primary beam 111 and to a center point of the secondary beam 112. A tertiary beam can also be provided, such that, for example, the secondary beam is arranged in front of the primary beam in the feed direction and the tertiary beam is arranged behind the primary beam in the feed direction. The individual laser beams are guided without shielding from each other, so that there is exactly one light channel 3 with exactly one surface area 4, resulting in minimal thermal losses.

[0040] Because the primary beam 111 in Fig. Since the primary jet 111 is arranged radially offset behind the secondary jet 112 in the feed direction 2, and the secondary jet 112 serves to preheat the workpiece, it is desirable that the powdered filler material does not interact with the secondary jet 112. This ensures that, on the one hand, the secondary jet 112 can exclusively perform the function of preheating the workpiece, and on the other hand, the powdered filler material is heated only by the primary jet 111 and not by the secondary jet 112. This is achieved by shaping the powder unit 7 in the nozzle 1 in the region of the nozzle mouth 6 such that it forms the powder section 11 around the light channel 3 in the circumferential direction, to which the powder-free feed section 12 adjoins in the circumferential direction.In addition to the powder unit 7, the process gas unit 60 can also be formed, which constitutes the process gas section 61, in which case the feed section 12 is formed as the process gas section 61. The feed section 12 is formed in a region of the nozzle mouth 6 facing the feed direction 2. The powder section 11 extends along the elongated hole that forms the cross-sectional area of ​​the light channel 3 in the distal region 8. Analogous to a circular arc, the powder section 11 extends along an elongated arc, in particular horseshoe-shaped, around the light channel 3. The powder section 11 therefore extends circumferentially around the light channel 3 by a wrap angle of less than 360°, in particular between 90° and 330°, and furthermore in particular between 180° and 300°, with respect to a center point of the light channel.This ensures that the powdered additive material flowing from the injectors 16, which are inserted into the injector guides 19, interacts only with the primary jet 111. The secondary jet 112 can thus form a process zone independent of the primary jet 111. In plan view, the powder section 11 and the feed section 12 form an elongated shape. This further contributes to reducing or avoiding the deficiencies identified at the outset.

[0041] Fig. Figure 6 shows the nozzle 1 in a top view of the flange section 9. The cross-sectional area of ​​the light channel 3, which runs orthogonally to the longitudinal direction of the nozzle 1, deviates from a circular shape even in the region of the flange section 9 and is elongated in the feed direction 2. The elongation of the cross-sectional area can decrease from the distal region 8 to the flange section 9. In the region of the nozzle orifice 6, the cross-sectional area can be elongated such that it is at least 1.5 times, and in particular at least twice, larger in the feed direction than transversely to the feed direction. The flange section 9 has such a radial extension that the injector guides 19 are not visible from the top view of the proximal region 10.

[0042] Fig. Figure 7 shows the nozzle 1 in another perspective view. The nozzle opening 6 has a curved, funnel-shaped form. Within the individual curves, the injector guides 19 are formed, into which the powder injectors 16 can be inserted. In the feed direction 2, the light channel is elongated, deviating from a circular shape, in order to achieve the advantages disclosed. In the circumferential direction around the light channel 3, the nozzle opening 6 has the powder unit 7. This extends in the circumferential direction around the light channel 3 along the powder section 11, to which the powder-free feed section 12 is attached.

[0043] Fig. Figure 8 shows a perspective sectional view of the jet nozzle 1. The light channel 3 has a conical shape, such that the cross-sectional area of ​​the light channel 3, which runs orthogonally to the longitudinal direction of the jet nozzle 1, is smaller in the distal region 8 than in the proximal region 10. The coolant inlet 13 and the coolant outlet 14 are located in the proximal region 10 of the jet nozzle 1 and project radially from the jet nozzle 1. Fig. Figure 8 shows a cross-sectional view of an injector guide 19. This is located in the powder section 11. No injector guide 19 is provided in the feed section 12 for guiding the powder jet. The jet nozzle 1 has a cooling system 30. A cooling medium, for example water, is returned to a radially inner cooling chamber 31 via the coolant inlet 13 in the proximal region 10. The cooling medium can spread circumferentially around the light channel 3 in the proximal region 10. From the proximal region 10, the cooling medium flows to the nozzle opening 6. The radially inner cooling chamber 31 is formed at least in the nozzle opening 6. It can extend from the distal region 8 to the proximal region 10 and be designed as an annular gap segment that extends circumferentially around the light channel 3. In the area of ​​the nozzle mouth 6, the radially inner cooling chamber 31 extends circumferentially around the light channel 3.The radially inner cooling chamber 31 has a constant width in the radial direction in the area of ​​the nozzle mouth 6 and is concentric to the light channel 3 in a cross-sectional area running orthogonally to a longitudinal direction of the jet nozzle 1.

[0044] In the distal region 8, a transition 32 is provided between the radially inner cooling chamber 31 and a radially outer cooling chamber 33. The radially outer cooling chamber 33 has a radial width that decreases towards the distal region 8 in the region of the nozzle orifice 6. The radially outer cooling chamber 33 extends from the distal region 8 to the proximal region 10, where it supplies the heated coolant to the coolant outlet 14. The transition 32 between the radially inner cooling chamber 31 and the radially outer cooling chamber 33 is located in the feed section 12. The feed section 12 does not have injector guides 19 for powder jet guidance, thus providing sufficient installation space for the transition 32.

[0045] The radially outer cooling chamber 33 features a cooling structure to increase the surface area. This cooling structure can be manufactured using an additive manufacturing process. It ensures that the cooling medium, when recirculated from the distal region 8 to the proximal region 10, comes into contact with as much surface area as possible to promote heat dissipation. The cooling structure is optimized to minimize pressure losses of the cooling medium. This can be achieved by a honeycomb structure 34, as described in Fig. As shown in 8, it can be achieved.

[0046] Fig. Figure 9 shows a top view of the distal region 8 of the nozzle 1 of a further embodiment. The cross-sectional area of ​​the light channel 3, which runs orthogonally to the longitudinal direction of the nozzle 1, deviates from a circular shape and is elongated in the feed direction 2. In the distal region 8, the cross-sectional area of ​​the light channel 3 is shaped like an elongated slot, with a partial circular segment attached to each of the two opposite ends of a rectangular section. The primary beam 111 and the secondary beam 112 are guided within the light channel 3. The respective centers of the primary beam 111 and the secondary beam 112 are offset in the feed direction 2 from the center point 20 of the light channel 3.

[0047] The primary beam 111 has a beam center that coincides with a first powder focus 21. The first powder focus 21 is the point on which the injectors of a first powder section 22 are focused. The first powder section 22 forms a first powder caustic. Similarly, the secondary beam 112 has a beam center that coincides with a second powder focus 23. The second powder focus 23 is the point on which the injectors of a second powder section 24 are focused. The second powder section 24 forms a second powder caustic. The primary beam 111 and the secondary beam 112 are offset from each other in the feed direction 2. The first powder focus 21 is also offset from the second powder focus 23. The powder unit 7, which has the first powder section 22 and the second powder section 24, can thus form two different powder foci.Furthermore, the powder mass flow rate delivered from the injectors of the first powder section 22 can differ from the powder mass flow rate delivered from the injectors of the second powder section 24. A gap can be provided between the first powder section 22 and the second powder section 24, such that the powder mass flow rate applied by the first powder section 22 interacts exclusively with the primary jet 111, and the powder mass flow rate applied by the second powder section 24 interacts exclusively with the secondary jet 112.

[0048] The first powder section 22 and the second powder section 24 contribute to an increase in the deposition rate by creating at least two process zones within the jet nozzle 1. This can increase the track width of the applied functional layer. Furthermore, improved protective gas coverage is achieved with lower protective gas consumption, as the protective gas injection can be more precisely localized.

[0049] The primary beam 111 and the secondary beam 112 are arranged in close proximity to each other. The front partial circular segment of the elongated hole in the feed direction 2 is concentric with the secondary beam 112, while the rear partial circular segment of the elongated hole is concentric with the primary beam 111. The center point 20 of the cross-sectional area is eccentric with respect to the center point of the primary beam 111 and the center point of the secondary beam 112.

[0050] Fig. Figure 10 shows the jet nozzle 1 in a top view of the distal region 8. The primary beam 111 and the secondary beam 112 are guided within the light channel 3. The secondary beam 112 is in front of the primary beam 111 in the feed direction 2 and does not interact with a powder cautery, as described in connection with Fig. 5 is described in more detail. During the interaction of the laser beams with the material surface and the powder jet, a vapor flare can form between the jet nozzle 1 and the workpiece 100. If this is not contained, it can interact undesirably with the at least one laser beam and / or the unprocessed and / or the processed material surface. Therefore, in the area adjoining the powder section 11, the feed section 12 can be designed as a process gas section 61. This is formed by the process gas unit 60, arranged radially outside the light channel 3, which directs the process gas towards the workpiece. The process gas section 61 can prevent undesired propagation of the vapor flare and thus contribute to precise workpiece processing with a robust jet nozzle design. The process gas section 61 can form at least one, and in this case three, outlet opening 62.The outlet openings 62 are formed on an end face of the blast nozzle 1. An additional injector for supplying the process gas without filler material can be inserted into each outlet opening 62. The inner diameter of the outlet opening 62 can be smaller than the inner diameter of the injector guides 19. The process gas section 61 also prevents powder particles from adhering to the end face of the blast nozzle 1. In this respect, the process gas section 61 also increases the service life of the blast nozzle 1. The process gas section 61 and the powder section 11 can be arranged around the entire perforation formed by the light channel 3. Thus, the primary jet 111 and the secondary jet 112 are completely within the jets that are composed of the powder jet and the process gas jet.

[0051] Fig. Figure 11 shows a further embodiment of the blast nozzle 1. The nozzle mouth 6 has a chamfer 50, which cuts off a portion of the nozzle mouth 6. The chamfer 50 causes the powder section 11 and the powder-free feed section 12 to be cut off circumferentially around the light channel 3. The chamfer 50 reduces the volume of the nozzle mouth 6 compared to the embodiment without a chamfer 50. This ensures that the nozzle mouth 6 occupies a smaller installation space. The blast nozzle 1 with the chamfer 50 can, for example, be used to coat a brake disc. The brake disc can have a receptacle that protrudes axially from the functional surface to be coated. The chamfer 50 ensures that the blast nozzle 1 can move flexibly on the functional surface to be coated and can be positioned close to the receptacle.The chamfer 50 can be essentially planar and extend in a plane inclined relative to the longitudinal direction of the blast nozzle. The chamfer 50 forms an interface of the nozzle mouth 6 in which no powder unit 7 is provided. In the distal region 8, the chamfer 50 is arranged so close to the light channel 3 that no injector guides 19 are provided on an end face of the blast nozzle 1 facing the workpiece in the region of the chamfer 50.

[0052] Fig. Figure 12 shows the blast nozzle 1 with the chamfer 50 in a top view. The chamfer 50 can extend along the elongated hole in the distal region 8 in the manner of a flanking edge 51. The flanking edge 51 defines the orientation of the chamfer 50 at the nozzle opening 6. The flanking edge 51 runs along a straight line or arc on the end face of the blast nozzle 1 facing the workpiece, neither intersecting nor touching the elongated hole. The distance of the flanking edge 51 from the center point 20 of the light channel 3 is greater than the distance of the corresponding section of the elongated hole from the center point 20 of the light channel 3. The distance between the flanking edge 51 and an outer edge of the elongated hole is selected such that the intervening wall thickness ensures sufficient strength and load-bearing capacity of the blast nozzle 1.

[0053] The orientation of the guide edge 51, and thus the orientation of the chamfer 50 at the nozzle opening 6, can be varied for different jet nozzles 1 depending on the specific application. For example, the guide edge 51 can run in the feed direction 2. In this case, the guide edge 51 runs along the elongation of the cross-sectional area of ​​the light channel 3. The guide edge 51 thus runs along the long side of the elongated hole. Alternatively, the guide edge 51 can, for example, run perpendicular to the feed direction 2. In this case, the guide edge 51 runs perpendicular to the elongation of the cross-sectional area of ​​the light channel 3. The guide edge 51 thus runs along the partial circular segment of the elongated hole. Another alternative is that the guide edge 51 can run at an angle to the feed direction 2 that lies between a path along the feed direction 2 and perpendicular to the feed direction 2.In this case, the guide 51 runs along the transition section between the long side of the elongated hole and the partial circular section of the elongated hole. The course of the guide 51 determines the orientation of the chamfer 50.

[0054] In the embodiment in Fig. Outlet openings 62 are provided on the front face of the jet nozzle. The process gas from the process gas unit 60 exits through these openings. In this case, the chamfer 50 is such that the portion of the nozzle mouth 6 cut off by it originates entirely from the powder section 11, so that the angle along which the powder section 11 extends is reduced by the chamfer 50, while the angle along which the process gas unit 60 extends remains essentially the same.

[0055] Where applicable, all individual features shown in the exemplary embodiments can be combined and / or exchanged without leaving the scope of the invention. Reference symbol list 1 jet nozzle 2 Feed direction 3 light channel 4 Surface area 5 External structure 6 nozzle mouth 7 powder units 8 distal area 9 Flange section 10 proximal area 11 Powder section 12 Feed section 13 Coolant inlet 14 Coolant outlet 15 coupling ring 16 powder injectors 17 inlet nozzles 18 drain spouts 19 Injector guide 20 Center of the light channel 21 first powder focus 22 first powder section 23 second powder focus 24 second powder section 30 Cooling system 31 radial inner cooling chamber 32 Transition 33 radial outer cooling chamber 34 honeycomb structure 50 Bevel 51 passers-by 60 process gas unit 61 Process gas section 62 Exit opening 100 workpieces 110 laser beam 111 Primary beam 112 Secondary beam 120 powdered additive material 130 Melt bath 140 functional layer QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] FROM 10 2011 100 456 A

[0002] DE 10 2018 130 798 A1

[0002] CN 109175372 A

[0002]

Claims

[1] Device for laser cladding comprising a jet nozzle (1), and a rotationally symmetrical workpiece (100), wherein the jet nozzle (1) has a light channel (3) for guiding at least one laser beam directed onto the workpiece (100); and a powder unit (7) arranged radially outside the light channel (3) for guiding at least one powder jet to be applied to the workpiece (100); wherein a cross-sectional area of ​​the light channel (3) extending orthogonally to a longitudinal direction of the jet nozzle (1) is stretched substantially parallel to the circumference of the workpiece (100) in a manner deviating from a circular shape. [2] Device according to claim 1, wherein the cross-sectional area at a distal region (8) of the jet nozzle (1) formed by a nozzle mouth (6) is designed in the manner of an elongated hole, in which a partial circular section adjoins two opposite ends of a rectangular section. [3] Device according to one of the preceding claims, wherein the cross-sectional area, in particular in the region of the nozzle mouth (6), is stretched such that it is at least 1.5 times, in particular at least twice as large in the feed direction (2) as transverse to the feed direction (2). [4] Device according to one of the preceding claims, wherein a center point of the cross-sectional area is eccentric to the at least one laser beam center point of the at least one laser beam. [5] Device according to one of the preceding claims, wherein the light channel (3) is adapted to guide a plurality of laser beams, the plurality having a first laser beam as a primary beam (111) and a second laser beam as a secondary beam (112). [6] Apparatus according to claim 5, wherein the secondary jet (112) is adapted to interact less with the powder jet than the primary jet (111), the secondary jet (112) being in front of the primary jet (111) in the feed direction (2) in order to preheat the workpiece. [7] Apparatus according to claim 5, wherein the secondary jet (112) is adapted to interact less with the powder jet than the primary jet (111), the secondary jet (112) being behind the primary jet (111) in the feed direction (2) in order to reheat the workpiece. [8] Apparatus according to any one of claims 5 to 7, wherein the plurality of laser beams has a third laser beam as a tertiary beam adapted to interact less with the powder jet than the primary beam (111), the primary beam (111) being in front of the tertiary beam in the feed direction (2). [9] Device according to one of claims 5 to 8, wherein in the plurality of laser beams, the laser beam which is at the front in the feed direction (2) is concentric in cross section to a front pitch circle section of the cross-sectional area and / or the laser beam which is at the rear in the feed direction (2) is concentric in cross section to a rear pitch circle section of the cross-sectional area. [10] Device according to one of claims 5 to 9, wherein in the plurality of laser beams a center point of the cross-sectional area is congruent with a center point of the plurality of laser beams. [11] Device according to one of claims 5 to 10, which has exactly one light channel (3), so that the plurality of laser beams are guided to one another within the beam nozzle without shielding. [12] Device according to one of the preceding claims, which is produced by means of an additive manufacturing process and consists in particular of copper or a copper alloy, more particularly a copper-chromium-zirconium alloy. [13] Device according to one of the preceding claims, wherein the nozzle mouth (6) has a bevel (50) by which a part of the nozzle mouth (6) is cut off, wherein the bevel (50) is substantially flat and extends in a plane which is inclined with respect to the longitudinal direction of the jet nozzle (1).

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