Jet nozzle having an absorption portion for absorbing back-reflected radiation

Abstract

The present invention relates to a jet nozzle (1) for laser cladding along a direction of advance (2), comprising a light channel (3) for conducting at least one laser beam that is directed onto a workpiece; and an outer structure (5) surrounding the light channel (3) and extending from a flange portion (9) to a distal region (8) that is formed by a mouth (6) of the nozzle from which the laser beam exits; the light channel (3) having an absorption portion (40) for absorbing laser radiation back-reflected from the workpiece.

Description

[0001] Jet nozzle with an absorption section for absorbing reflected radiation

[0002] Technical area

[0003] The present invention relates to a jet nozzle for laser cladding along a feed direction.

[0004] State of the art

[0005] Laser cladding is used 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 extremely high-speed laser cladding (EHLA)). HS-LMD processes are described, for example, in published patent applications DE 10 2011 100 456 B4 and DE 10 2018 130 798 A1. Another laser cladding process is known from the Chinese patent application CN 109175372 A.

[0006] Laser cladding can be used to apply a functional layer to a workpiece. This layer generally increases the load-bearing capacity of the workpiece processed using laser cladding compared to an unmachined workpiece. The functional layer can serve, for example, as a wear-resistant layer. The application of the functional layer is based on melting a workpiece surface, applying a powdered filler material, and subsequent cooling, so that a matrix structure with hard material particles is firmly bonded to the material surface. Laser cladding thus intervenes in the internal material structure of the workpiece and changes it. This can potentially result in deficiencies in the internal material structure. These can impair the desired increase in load-bearing capacity. The deficiencies can be microscopic in nature, which is why they are only identifiable with great effort.

[0007] Description of the invention Starting from the known prior art, it is an object of the present invention to provide an improved jet nozzle for laser deposition welding 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 avoid deficiencies in a weld joint between a powdered filler material and a material surface. The deficiencies can be lack of bonding between the material surface and the applied functional layer or between individual applied functional layers. The deficiencies can also be pores, i.e. air inclusions, that occur within the applied functional layer or between the applied functional layer and the material surface.Pores may occur more frequently, particularly if the material surface is a cast material. The deficiencies may also include cracks, which run particularly vertically to the material surface within the applied functional layer. The deficiencies may also arise from powder particles, particularly carbides, of the powdered filler material dissolving in a matrix material of the powdered filler material, which leads to embrittlement of the matrix material. The invention further aims in particular to provide a reliable blasting nozzle that is resistant to thermal stress. The invention may further aim to design the blasting nozzle in such a way that it ensures reliable and precise laser cladding over very high cycle numbers.

[0008] The problem is solved by a jet nozzle having the features of claim 1. Advantageous further developments emerge from the subclaims, the description, and the figures.

[0009] Accordingly, a beam nozzle for laser material deposition along a feed direction is proposed, which has a light channel for guiding at least one laser beam directed at a workpiece. Laser material deposition can be a process for high-speed laser material deposition (HS-LMD). The feed direction is the direction along which the beam nozzle moves relative to the workpiece. It can result from a movement, in particular a rotational movement, of the workpiece, from a movement of the beam nozzle, or from a superposition of both movements. The feed direction and the correlating feed movement can be constant throughout the process. Alternatively, they can vary with the respective process stage. The workpiece can be a rotationally symmetrical workpiece, such as a brake disc, a hydraulic cylinder, a printing roller, or a plain bearing.The laser beam can pass through the light channel. It can be provided by a laser source, from which the laser beam is guided via a fiber optic cable to a laser system that splits the laser beam using a collimating lens and focuses it using laser optics for the process before it enters the jet nozzle. The light channel can be a hollow channel that runs longitudinally through the entire jet nozzle. In addition to the laser beam, a process gas can also be guided to the workpiece surface through the light channel.

[0010] The jet nozzle further has an outer structure surrounding the light channel, which extends from a flange section to a distal region formed by a nozzle mouth, from which the laser beam emerges. The outer structure can have a powder unit. The powder unit can be part of the nozzle mouth. The nozzle mouth is the part of the jet nozzle facing the workpiece. The end section of the nozzle mouth forms the distal region. This represents the part of the nozzle mouth closest to the workpiece. At the section facing away from the workpiece, the jet nozzle has a proximal region and the flange section. The proximal region and the flange section are the part of the jet nozzle facing away from the workpiece. The nozzle can be coupled to another component of the laser system, such as laser optics or a process unit, via the flange section.The outer structure can be a component made of a uniform material and can have a hollow channel along its longitudinal direction which represents the light channel.

[0011] The light channel forms an absorption section for absorbing reflected radiation from the laser beam from the workpiece. The absorption section can have a geometry that promotes the absorption of reflected radiation. The absorption section can extend variably in a circumferential direction around the light channel. It can also extend variably in a longitudinal direction of the light channel. In particular, no absorption section 40 is formed in the distal region of the nozzle mouth in order to better clean the nozzle mouth. Thus, the shape of the absorption section can be adapted to the expected reflected radiation. The absorption section can be formed from the same material as the remaining jet nozzle. It can also have a coating. The laser radiation absorbed by the absorption section can be dissipated by a cooling system that interacts with the absorption section.

[0012] The jet nozzle can thus provide 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 jet nozzle. It enables 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 be cleaning the material surface, preheating the material surface before the powdered filler material is applied, post-heating 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. The independent process zones can increase the weld quality and thus the resilience of the applied functional layer, especially the wear-resistant layer, and the workpiece as a whole. An additional process gas can stabilize the process zones and increase the precision of the laser cladding as well as the service life of the jet nozzle.

[0013] In particular, the jet nozzle can reduce the occurrence of fusion defects. Fusion defects can occur when the surface heated by the laser beam, such as the workpiece or a previously welded functional layer, has not been sufficiently heated. This insufficient heating can be the result of the laser power of a single laser beam being kept low to prevent overheating of the powdered filler material. Due to the increased variability of the laser beam guidance, the increased variability of the application of a powdered filler material, and / or the increased variability of the heat management of the jet nozzle, the occurrence of fusion defects can be reduced or even prevented, particularly because the jet nozzle with the absorption section contributes to the heat management and protection of the laser system in such a way that multiple process zones are possible.

[0014] In particular, the blasting nozzle can reduce the occurrence of pores between the welded functional layer and the surface heated by the laser beam. Pores can occur when lamellae in the workpiece, especially graphite lamellae, evaporate due to the laser radiation. Pores can also occur if the surface to be machined contains contaminants, for example, caused by oils, greases, cooling lubricants, or oxides, which cannot be completely removed by the welding process. The undesired evaporation of contaminants can be the result of the laser power of an individual laser beam being set so high that fusion defects due to insufficient heating can be avoided.Due to the increased variability of the laser beam guidance, the increased variability of the application of a powdered filler material and / or the increased variability of the thermal management of the jet nozzle, the occurrence of pores can be reduced or even avoided, in particular by the jet nozzle with the absorption section contributing to the thermal management and protection of the laser system in such a way that several process zones are possible.

[0015] In particular, the blasting nozzle can reduce the occurrence of cracks in the welded functional layer. Cracks can occur when the temperature gradient between the highly heated powdered filler material and the less heated workpiece surface is so strong that material shrinkage occurring during cooling leads to crack-causing stresses. Crack formation can be the result of setting the laser power of a single laser beam so high that fusion defects due to insufficient heating can be avoided.Due to the increased variability of the laser beam guidance, the increased variability of the application of a powdered filler material and / or the increased variability of the thermal management of the jet nozzle, the occurrence of cracks can be reduced or even avoided, in particular by the jet nozzle with the absorption section contributing to the thermal management and protection of the laser system in such a way that multiple process zones are possible.

[0016] Furthermore, the blasting nozzle can particularly reduce the dissolution of hard material particles, in particular carbides, in the matrix material. The powdered filler material can comprise hard material particles, in particular carbides, and a matrix material. The hard material particles should be present undissolved in the welded functional layer in order to increase the load-bearing capacity of the functional layer. However, hard material particles can dissolve if the powdered filler material is exposed to an excessively high irradiation intensity, causing the hard material particles to melt. Dissolved hard material particles cause the welded functional layer to become brittle because the matrix material is less ductile, meaning that stresses arising, for example, from shrinkage during cooling or loading of the workpiece cannot be absorbed by the matrix material.Due to the increased variability of the laser beam guidance, the increased variability of the application of a powdered filler material and / or the increased variability of the heat management of the blasting nozzle, the dissolution of hard material particles can be reduced or even avoided, in particular by the blasting nozzle with the absorption section contributing to the heat management and protection of the laser system in such a way that several process zones are possible.

[0017] In particular, the blasting nozzle can prevent powder particles from adhering to the nozzle orifice. Due to the high process heat, the reflected laser radiation and / or a metal vapor flare can cause filler material to adhere or even fuse to the nozzle orifice, which can disrupt the gas and powder flows and subsequently impair the process outcome. Metal vapor flare is a result of the partial evaporation of the material during laser cladding. It can lead to scattering and / or absorption of laser radiation and subsequently impair preheating of the workpiece. This can further promote the formation of fusion defects.Due to the increased variability of the laser beam guidance, the increased variability of the application of a powdered filler material and / or the increased variability of the heat management of the blasting nozzle, the undesired dissolution of hard material particles as well as the propagation of the metal vapor flare can be reduced or even avoided, in particular by the blasting nozzle with the absorption section contributing to the heat management and protection of the laser system in such a way that several process zones are possible.

[0018] The absorption section of the light channel absorbs reflected laser beam radiation from the workpiece back to the jet nozzle. Reflected radiation that could damage the jet nozzle can thus be efficiently dissipated. The reflected radiation is absorbed by the absorption section in such a way that the portion of radiation that penetrates other components of the laser system, such as the laser optics, is reduced or eliminated. This increases process reliability and the precision of the laser beam. The service life of the jet nozzle and the laser system is also increased. The improved properties of the jet nozzle due to the absorption surface enable welding behavior without the aforementioned deficiencies.

[0019] In one embodiment, the absorption section extends from above the distal region to a proximal region adjacent to the flange section. The absorption section can thus extend over the entire height of the jet nozzle, with the exception of the flange section and the distal region. Accordingly, reflected radiation is absorbed by the absorption section over a large part of the height of the jet nozzle, which contributes to efficient heat management and the protection of the laser system. The distal region can, for example, extend up to 10 mm along the height into the nozzle. The fact that no absorption section is formed in the distal region can facilitate cleaning of the jet nozzle.

[0020] In one embodiment, the absorption section has a serrated structure, in particular an irregularly serrated structure, which forms absorption surfaces facing the distal region. The serrated structure can have a Christmas tree contour along a longitudinal direction of the light channel. The absorption surfaces can run along a plane that is orthogonal to the longitudinal direction of the light channel. The serrated structure can be formed from the absorption surface and a support surface leading back to the wall of the light channel, such that each serration has a substantially triangular shape. The uniformly serrated structure can have uniform serrations from the distal region to the proximal region. Alternatively, the serrations can become larger from the distal region to the proximal region.

[0021] In one embodiment, a powder unit arranged radially outside the light channel is formed in the outer structure for guiding at least one powder jet to be applied to the workpiece. The powder unit forms a powder section at the nozzle mouth in a circumferential direction around the light channel, which is adjoined in the circumferential direction by a powder unit-free feed section. The feed section can be the section facing the feed direction, i.e., pointing in the direction of the feed direction. The feed section can extend along the circumferential direction around the light channel in an angular range. The area in which the feed section is formed can correlate with the position and orientation of the powder injectors that apply the powdered filler material to the workpiece. The powder section and the feed section together can form the entire circumference of the nozzle mouth around the light channel.For example, the powder section may be larger than the feed section. In plan view, the powder section and the feed section may extend contiguously along an opening of the light channel, for example, a slot-shaped opening.

[0022] In one embodiment, the absorption section is arranged at least in the feed section, in particular circumferentially. Due to the angle of incidence of the at least one laser beam, the feed section can be the part of the jet nozzle exposed to the highest thermal load. In this respect, the arrangement of the absorption section at least in the feed section can further contribute to efficient heat management and the protection of the laser system. The absorption section can be arranged, for example, only in the region of the feed section or also circumferentially, thus 360° along the circumferential direction.

[0023] In one embodiment, the absorption section extends completely around the light channel in a circumferential direction. In this way, absorption of the reflected radiation by the absorption section is guaranteed regardless of the arrangement of the jet nozzle relative to the workpiece and the reflected radiation resulting from the arrangement. This contributes to efficient heat management and the protection of the laser system. Alternatively, it can also be provided that a position of the absorption section correlates with an intended inclination of the jet nozzle relative to the workpiece. Thus, alternatively, the absorption section can not be designed to surround the light channel. Instead, it is specifically arranged in the area in which, due to the inclination of the jet nozzle relative to the workpiece, the reflected radiation is mostly directed onto the jet nozzle.

[0024] In one embodiment, a longitudinal axis of the light channel, along which the laser beam travels, is inclined relative to a normal to the workpiece surface to increase absorption of the reflected radiation by the absorption section. The laser beam is thus not aligned orthogonally to the workpiece in order to selectively absorb the reflected radiation via the absorption section.

[0025] In one embodiment, one end face of the jet nozzle is angled relative to the longitudinal axis of the light channel, along which the laser beam travels, so that the end face is designed to be plane-parallel to a workpiece surface. This allows for an increased distance between the nozzle orifice and the workpiece. This reduces the thermal load on the nozzle orifice. Furthermore, the angled end face enables improved shielding of the workpiece with a shielding gas stream. The plane-parallel surface of the end face allows for a shielding gas flow that exits orthogonally to the workpiece.

[0026] In one embodiment, the area of ​​the absorption section increases in a circumferential direction around the light channel, from the nozzle orifice to the flange section. This can correlate with the fact that the cross-section of the light channel increases toward the flange section, whereby the corresponding area of ​​the absorption section can also increase. This ensures that emissions in the proximal region are intercepted, which further contributes to thermal management by protecting the laser optics.

[0027] In one embodiment, the jet nozzle can be tilted relative to the workpiece, so that absorption of the reflected radiation by the absorption section can be controlled by means of an inclination. The orientation of the laser beam relative to the jet nozzle can be constant. Thus, the angle of reflection of the reflected radiation can be adjusted by tilting the jet nozzle. The inclination can interact with the absorption section to capture as much of the reflected radiation as possible from the absorption section.

[0028] In one embodiment, the absorption section is provided with an absorbent coating. This can contribute to increasing its thermal resilience. It can also increase the thermal conductivity of the absorption section. This helps ensure that the absorption section is not damaged even in the event of increased reflected radiation. In one embodiment, the jet nozzle is manufactured using an additive manufacturing process, in particular using powder bed melting. For this purpose, the jet nozzle can be made of copper or a copper alloy, more particularly a copper-chromium-zirconium alloy. This is suitable for the additive manufacturing process on the one hand and ensures sufficient strength, thermal conductivity, and heat resistance to withstand the process requirements on the other. In powder bed melting, the material to be processed is present in powder form.A laser beam heats the powder along the intended geometry, liquefying the powder and bonding it together. Powder bed melting can be implemented, for example, as Selective Laser Melting ("SLM") or Selective Laser Sintering ("SLS").

[0029] In one embodiment, the nozzle mouth has a bevel by which a portion of the nozzle mouth is cut off, wherein the bevel is essentially flat and runs in a plane that is inclined with respect to the longitudinal direction of the jet nozzle. The bevel can cut off the powder section and the feed section free of powder section in the circumferential direction around the light channel. The bevel reduces the volume of the nozzle mouth compared to the embodiment in which no bevel is provided. Thus, the nozzle mouth takes up less installation space. The jet nozzle with the bevel can be used, for example, to coat a brake disc that has a receptacle that protrudes axially relative to the functional surface to be coated. The bevel ensures that the jet nozzle can be flexibly moved on the functional surface to be coated and can be moved close to the receptacle.The bevel can run in the distal area like a passante on the elongated hole. The passante defines the orientation of the bevel at the nozzle mouth. The passante runs in the end face of the jet nozzle facing the workpiece along a straight line or an arc that neither intersects nor touches the elongated hole. The distance of the passante 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 passante and an outer edge of the elongated hole is selected such that the wall thickness in between ensures sufficient strength and load-bearing capacity of the jet nozzle.

[0030] In one embodiment, the disclosure further relates to a system comprising a jet nozzle according to the disclosure and a workpiece. The jet nozzle is inclined relative to the workpiece such that a longitudinal axis of the light channel, along which the laser beam travels, deviates from a normal to the workpiece surface, so that absorption of the reflected radiation by the absorption section is increased. The inclination can be realized by a relative movement of the jet nozzle to the workpiece or of the workpiece to the jet nozzle. For example, a workpiece support can be inclined relative to the jet nozzle. The inclination is adapted to the position of the absorption section.

[0031] In one embodiment, the inclination of the jet nozzle relative to the workpiece is between 2° and 45°, in particular between 3° and 10°. It has been found that at these inclination angles, an ideal compromise is achieved between the absorption of reflected radiation via the absorption section and the welding behavior of laser cladding.

[0032] In one embodiment, the jet nozzle is adapted to guide the laser beam along the longitudinal direction of the jet nozzle, so that the at least one laser beam runs orthogonally to the cross-sectional area. Furthermore, the light channel can be adapted to guide a protective gas at a radially outer portion for shielding a process zone.

[0033] The features disclosed contribute, partly individually and partly in combination, to overcoming the deficiencies in laser cladding mentioned at the outset.

[0034] Short description of the characters

[0035] Preferred further embodiments of the invention are explained in more detail in the following description of the figures. In the figures:

[0036] Figure 1 is a schematic view of a jet nozzle in laser cladding;

[0037] Figure 2 shows a jet nozzle in a side view;

[0038] Figure 3 shows the jet nozzle from Figure 2 in a perspective view;

[0039] Figure 4 shows the jet nozzle from Figure 2 connected to other components;

[0040] Figure 5 shows the jet nozzle from Figure 2 in a plan view of a distal region;

[0041] Figure 6 shows the jet nozzle from Figure 2 in a plan view of a flange section;

[0042] Figure 7 is a further perspective view of the jet nozzle from Figure 2;

[0043] Figure 8 is a perspective sectional view of the jet nozzle of Figure 2;

[0044] Figure 9 is a further perspective sectional view of the jet nozzle from Figure 2; Figure 10 is a further sectional view of the jet nozzle and the workpiece;

[0045] Figure 11 is a further perspective sectional view of the jet nozzle with an angled end face;

[0046] Figure 12 is a longitudinal sectional view through a jet nozzle with a smooth inner end section;

[0047] Figure 13 the jet nozzle with a process gas unit in a plan view of the distal area;

[0048] Figure 14 shows a further embodiment of the jet nozzle with a geometrically adapted nozzle mouth in a side view; and

[0049] Figure 15 shows a further embodiment of the jet nozzle with a geometrically adapted nozzle mouth in a plan view.

[0050] Detailed description of preferred embodiments

[0051] Preferred embodiments are described below with reference to the figures. Identical, similar, or equivalent elements in the different figures are provided with identical reference numerals, and a repeated description of these elements is partially omitted to avoid redundancies.

[0052] Figure 1 shows a jet nozzle 1 for laser material deposition along a feed direction 2. The feed direction 2 is the direction along which the jet 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 jet nozzle 1, or from a superposition of a movement of the workpiece 100 and the jet nozzle 1. The feed direction 2 and the correlating 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 printing roller, or a plain bearing. At least one laser beam 110 emerges from a light channel 3 with a lateral surface 4.The light channel 3 can also be adapted to guide a process protective gas 150 at a radially outer section to shield a process zone and prevent oxidation. The light channel 3 is surrounded by an outer structure 5 having a nozzle mouth 6, which in turn contains a powder unit 7. The powder unit 7 can, for example, have a plurality of injector guides 19 (see Figure 3), into each of which a powder injector 16 (see Figure 4) can be inserted. As an alternative to the individual injector guides 19, the powder unit 7 can have a powder annular gap channel. A powdery filler 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 filler material 120, which comprises hard material particles and a matrix material. For this purpose, the laser beam 110 can have a reduced core intensity. As the molten pool 130 cools, a welded functional layer 140, for example, a wear-resistant layer, forms from the hard material particles and the matrix material. The welded functional layer 140 makes the material surface more resistant and increases its load-bearing capacity.

[0053] Figure 2 shows the jet nozzle 1 in a side view, with the feed direction 2 pointing out of the plane of the drawing. The jet 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 of the jet nozzle 1 and which protrude radially from the jet nozzle 1, can be provided at least partially in the proximal region 10. A distal region 8 is formed at the end of the jet nozzle 1 opposite the proximal region 10. The distal region is a component of the funnel-shaped nozzle mouth 6. This has, in a circumferential direction around the light channel 3, a powder section 11 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 designed as a process gas section 61 (see, for example, Figure 9), which is part of a process gas unit 60.

[0054] Figure 3 shows the jet nozzle from Figure 2 in a perspective view. The light channel 3 is a hollow channel with the outer surface 4, within which the at least one laser beam 110 runs. The outer structure 5 surrounds the light channel 3 from the flange section 9 to the distal region 10. The nozzle mouth 6 is a substantially funnel-shaped region of the jet nozzle 1. The funnel shape of the nozzle mouth 6 serves, among other things, to enable the nozzle mouth 6 to form the plurality of injector guides 19 in the region of the powder unit 7. A powder injector 16 (see Figure 4) is inserted into each of these injector guides 19, which directs the powdered filler material 120 onto the at least one laser beam 110 and / or the workpiece 100 in a process-appropriate 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 it. In one embodiment, the feed section 12 can be shaped as a process gas section 61, so that a process gas is supplied via it. The jet nozzle 1 can be manufactured using additive manufacturing processes, in particular using powder bed melting. For this purpose, the jet nozzle 1 can be made of a copper-chromium-zirconium alloy. This is suitable for additive manufacturing processes on the one hand and ensures sufficient strength, thermal conductivity and heat resistance to withstand the process requirements on the other. In powder bed melting, the material to be processed is in powder form. A laser beam heats the powder along the intended geometry, whereby the powder liquefies and bonds firmly.Powder bed melting can be performed, for example, as Selective Laser Melting (“SLM”) or Selective Laser Sintering (“SLS”).

[0055] Figure 4 shows the blasting nozzle 1 with additional components attached. A coupling ring 15 is connected to the flange section 9, which secures the blasting 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 powder injectors 16 convey the powdered filler material 120 and apply it to the workpiece 100 with the intended focus. The individual powder injectors 16 can apply different powder foci. Alternatively, the powder injectors 16 can be directed at the same focal point. The powder injectors 16 are arranged in the injector guides 19 provided for this purpose in 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 is inserted into the coolant outlet 14.These connect the coolant inlet 13 and the coolant outlet 14 to a coolant circuit.

[0056] Figure 5 shows the jet nozzle 1 in a plan view of the distal region 8. The cross-sectional area of ​​the light channel 3, which runs orthogonally to the longitudinal direction of the jet 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 designed like an elongated hole, with a partial circular section adjoining 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 fiber optic cable. A provided laser light can be split into a parallel beam bundle via a collimating lens. The beam bundle can, for example, form the primary beam 111 and the secondary beam 112 from a single laser beam using a wedge plate.The respective centers of the primary beam 111 and the secondary beam 112 are offset in a line in the feed direction 2 to a center 20 of the light channel 3.

[0057] In this case, the secondary beam 112 is located in front of the primary beam 111 in the feed direction 2 and does not interact with a powder caustic. The secondary beam 112 can thus be used to preheat the workpiece 100 before the primary beam 111 and the powdered filler material 120 heated by the primary beam 111 strike the workpiece 100. The secondary beam 112 thus creates a first process zone that serves to preheat the workpiece 100, and the primary beam 111 creates a second process zone that serves to weld the powdered filler material 120 onto the workpiece 100. These different process zones enable defect-free welding in which no deficiencies, in particular no fusion defects, pores, cracks, and / or dissolution of carbides in the matrix material, occur. It is also possible to guide the secondary beam 112 in the feed direction 2 after the primary beam 111.Thus, the secondary beam 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 imperfections.

[0058] The primary beam 111 and the secondary beam 112 are arranged in close proximity to one another. The front partial circle section of the elongated hole in the feed direction 2 is concentric with the secondary beam 112, while the rear partial circle section of the elongated hole is concentric with the primary beam 111. A center of the cross-sectional area is eccentric to a center of the primary beam 111 and to a center of the secondary beam 112. A tertiary beam can also be provided, so that, for example, the secondary beam is arranged in front of the primary beam in the feed direction and the tertiary beam is arranged after the primary beam in the feed direction. The individual laser beams are guided unshielded from one another, so that there is exactly one light channel 3 with exactly one lateral surface 4, which results in minimal thermal losses.

[0059] Because the primary jet 111 in Figure 5 is arranged behind the secondary jet 112 in the feed direction 2 without any radial offset, 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 only heated by the primary jet 111 and not by the secondary jet 112. This is achieved by the jet nozzle 1 shaping the powder unit 7 in the region of the nozzle mouth 6 in such a way that it forms the powder section 11 in the circumferential direction around the light channel 3, to which the powder unit-free feed section 12 is connected in the circumferential direction.In addition to the powder unit 7, the process gas unit 60 can also be formed, which forms the process gas section 61, in which case the feed section 12 is formed as a 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 hole arc, in particular horseshoe-shaped, around the light channel 3. The powder section 11 therefore extends in the circumferential direction around the light channel 3 by a wrap angle of less than 360°, in particular between 90° and 330°, further in particular between 180° and 300°, relative to a center point of the light channel.This ensures that the powdered filler material flowing out of 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. The powder section 11 and the feed section 12 form a slotted hole in plan view. This further contributes to reducing or avoiding the deficiencies identified above.

[0060] Figure 6 shows the jet nozzle 1 in a plan view of the flange section 9. The cross-sectional area of ​​the light channel 3, which runs orthogonally to the longitudinal direction of the jet nozzle 1, also deviates from a circular shape in the region of the flange section 9 and is elongated in the feed direction 2. The extension of the cross-sectional area can decrease from the distal region 8 to the flange section 9. In the region of the nozzle mouth 6, the cross-sectional area can be elongated such that it is at least 1.5 times, in particular at least twice, as large in the feed direction as it is transverse to the feed direction. The flange section 9 has such a radial extension that the injector guides 19 are not visible from the plan view of the proximal region 10.

[0061] Figure 7 shows the jet nozzle 1 in a further perspective view. The nozzle mouth 6 has a curved funnel shape. The injector guides 19, into which the powder injectors 16 can be inserted, are formed within the individual curvatures. In the feed direction 2, the light channel is elongated in a manner deviating from a circular shape in order to achieve the advantages disclosed. In the circumferential direction around the light channel 3, the nozzle mouth 6 has the powder unit 7. This extends in the circumferential direction around the light channel 3 along the powder section 11, which is adjoined by the powder-free feed section 12. Figure 8 shows a perspective sectional view of the jet nozzle 1. The light channel 3 has a conical shape, so 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 arranged in the proximal region 10 of the jet nozzle 1 and protrude radially from the jet nozzle 1. Figure 8 shows a cross-sectional view of an injector guide 19. This is arranged in the powder section 11. In the feed section 12, no injector guide 19 is provided for guiding the powder jet. The jet nozzle 1 has a cooling system 30. A cooling medium, for example water, is fed back to a radially inner cooling chamber 31 via the coolant inlet 13 in the proximal region 10. The cooling medium can be distributed in the proximal region 10 in the circumferential direction around the light channel 3. From the proximal region 10, the cooling medium runs to the nozzle mouth 6. The radially inner cooling chamber 31 is formed at least in the nozzle mouth 6. It can run from the distal region 8 to the proximal region 10 and be designed in the manner of an annular gap segment that extends circumferentially around the light channel 3.In the region 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 region of the nozzle mouth 6 and is concentric to the light channel 3 in a cross-sectional area extending orthogonally to a longitudinal direction of the jet nozzle 1.

[0062] 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 in the radial direction in the region of the nozzle mouth 6 towards the distal region 8. 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 arranged in the feed section 12. The feed section 12 does not have any injector guides 19 for guiding the powder jet, whereby sufficient installation space is available for the transition 32.

[0063] The radially outer cooling chamber 33 has a cooling structure to increase the surface area. The cooling structure can be manufactured using an additive manufacturing process. It ensures that the cooling medium comes into contact with as much surface area as possible during the return from the distal region 8 to the proximal region 10 in order to promote heat dissipation. The cooling structure is optimized to cause the lowest possible pressure losses of the cooling medium. This can be achieved using a honeycomb structure 34, as shown in Figure 8. Figure 9 shows the jet nozzle 1 with an absorption section 40. This is designed to absorb reflected radiation of the laser beam from the workpiece. The absorption section 40 extends from the distal region 8 to the proximal region 10. It thus helps protect the laser optics from reflected radiation. The absorption section 40 has a serrated structure.This forms an absorption surface facing the distal region 8. The absorption section is provided in the region of the advance section 12. The absorption section 40 can be formed from the same material as the remaining jet nozzle 1. It can also have a coating. The laser radiation absorbed by the absorption section 40 can be dissipated by the cooling system 30 interacting with the absorption section 30.

[0064] Figure 10 shows the jet nozzle 1 with a workpiece 100. The laser beam 110 extends along a longitudinal axis 43 of the light channel 3. The longitudinal axis 43 of the light channel 3 is inclined relative to a normal of the workpiece surface 41. This inclination directs reflected laser radiation 150 onto the absorption section 40. The inclination of the longitudinal axis 43 of the light channel 3 relative to the normal of the workpiece surface 41 is selected such that the absorption section 40 absorbs as much reflected laser radiation as possible. The inclination is between 2° and 20°, in particular between 3° and 10°. To achieve the inclination, it is possible to incline the jet nozzle 1 relative to the workpiece 100 or to incline the workpiece 100 relative to the jet nozzle 1. A surface roughness of the absorption surfaces of the absorption section 40 is between 5 pm and 100 pm, in particular between 50 pm and 50 pm.The absorption section 40 may also be provided with an absorbent coating that promotes completion.

[0065] Figure 11 shows the jet nozzle 1, in which an end face 42 of the jet nozzle 1 is angled relative to the longitudinal axis 43 of the light channel 3, so that the end face 42 runs plane-parallel to the workpiece 100. Thus, the distance from the nozzle mouth 6 to the workpiece 100 is increased. This reduces the thermal load on the nozzle mouth 6. In addition, the angled end face 42 enables improved shielding of the workpiece 100 with the shielding gas. This is because the plane-parallel surface of the end face 42 enables a shielding gas flow exiting orthogonally to the workpiece 100.

[0066] Figure 12 shows a longitudinal sectional view through a jet nozzle 1 with a smooth inner end section 44. The jet nozzle 1 can form a smooth inner end section 44 as the distal surface of the light channel 3. The smooth inner end section 44 enables better cleaning of the inner nozzle mouth 6. The absorption section 40 extends proximally from the smooth inner end section 44. The absorption section 40 can also extend completely along the circumferential direction around the light channel 3, i.e., 360°. Thus, the absorption capacity of the jet nozzle 1 is not dependent on a specific feed direction.

[0067] In Figure 12, the powder unit 7, which forms the powder section 11 and through which the injector guides 19 extend, is provided at a rear region in the feed direction 2. The injector guides 19 are each adapted to accommodate a powder injector 16. The process gas unit 60, which forms the process gas section 61 and through which distribution arms for the process gas extend, can be provided at a front region in the feed direction 2. A distribution arm can accommodate an additional injector. Alternatively, the process gas is directed directly from the distribution arms to the material surface. The distribution arms have a curved shape along their longitudinal direction. The jet nozzle 1 has the cooling system 30 with the radially inner cooling chamber 31 and the radially outer chamber 33.Due to the design of the feed section 12 as a process gas section, the radially outer cooling chamber 33 surrounds the distribution arms 24 in the front area of ​​the nozzle mouth 6 in the feed direction 2. The process gas can thus contribute to the heat management of the jet nozzle 1.

[0068] Figure 13 shows the jet nozzle 1 in a plan 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 caustic, as described in more detail in connection with Figure 5. 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 vapor flare is not contained, it can interact in an undesirable manner with the at least one laser beam and / or the unprocessed and / or processed material surface. In the region adjoining the powder section 11, the feed section 12 can therefore be designed as a process gas section 61.This is formed by the process gas unit 60, which is arranged radially outside the light channel 3 and directs the process gas onto the workpiece. The process gas section 61 can prevent undesired propagation of the vapor flare and thus contribute to precise workpiece machining with a robust jet nozzle design. The process gas section 61 can form at least one, in this case three, outlet openings 62. The outlet openings 62 are formed on an end face of the jet nozzle 1. An additional injector for supplying the process gas without additional material can be inserted into the respective outlet opening 62. An inner diameter of the outlet opening 62 can be smaller than an inner diameter of the injector guides 19. The process gas section 61 also prevents powder particles from adhering to the end face of the jet nozzle 1. In this respect, the process gas section 61 also increases the service life of the jet nozzle 1.The process gas section 61 and the powder section 11 can be arranged circumferentially around the elongated hole formed by the light channel 3. Thus, the primary beam 111 and the secondary beam 112 are completely within the beams composed of the powder jet and the process gas jet.

[0069] Figure 14 shows a further embodiment of the jet nozzle 1. The nozzle mouth 6 has a bevel 50, by which a part of the nozzle mouth 6 is cut off. The bevel 50 has the effect that the powder section 11 and the powder-section-free feed section 12 are cut off in the circumferential direction around the light channel 3. The bevel 50 reduces the volume of the nozzle mouth 6 compared to the embodiment in which no bevel 50 is present. This ensures that the nozzle mouth 6 takes up less installation space. The jet nozzle 1 with the bevel 50 can be used, for example, to coat a brake disc. The brake disc can have a receptacle that protrudes axially relative to the functional surface to be coated. The bevel 50 ensures that the jet nozzle 1 can be flexibly moved on the functional surface to be coated and can be moved close to the receptacle.The bevel 50 can be substantially flat and extend in a plane that is inclined relative to the longitudinal direction of the jet nozzle. The bevel 50 represents a boundary surface of the nozzle orifice 6, in which no powder unit 7 is provided. In the distal region 8, the bevel 50 is arranged so close to the light channel 3 that no injector guides 19 are provided on an end face of the jet nozzle 1 facing the workpiece in the region of the bevel 50.

[0070] Figure 15 shows the jet nozzle 1 with the bevel 50 in a top view. The bevel 50 can run in the distal region 8 in the manner of a passante 51 on the elongated hole. The passante 51 defines the orientation of the bevel 50 on the nozzle mouth 6. The passante 51 runs in the end face of the jet nozzle 1 facing the workpiece along a straight line or an arc that neither intersects nor touches the elongated hole. The distance of the passante 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 passante 51 and an outer edge of the elongated hole is selected such that the wall thickness therebetween ensures sufficient strength and load-bearing capacity of the jet nozzle 1.

[0071] The orientation of the passante 51 and thus the orientation of the bevel 50 on the nozzle mouth 6 can be varied for different jet nozzles 1 depending on the respective field of application. For example, the passante 51 can run in the feed direction 2. In this case, the passante 51 runs along the extension of the cross-sectional area of ​​the light channel 3. The passante 51 thus runs along the long side of the elongated hole. Alternatively, the passante 51 can run, for example, transversely to the feed direction 2. In this case, the passante 51 runs transversely to the extension of the cross-sectional area of ​​the light channel 3. The passante 51 thus runs along the partial circle section of the elongated hole. Further alternatively, the passante 51 can, for example, run at an angle to the feed direction 2 that lies between a course along the feed direction 2 and a course transversely to the feed direction 2.In this case, the passante 51 runs along the transition section between the long side of the slot and the pitch circle section of the slot. The course of the passante 51 determines the orientation of the bevel 50.

[0072] In the embodiment shown in Figure 15, outlet openings 62 are provided on the front side of the jet nozzle. The process gas exits from the process gas unit 60 through these openings. In the present case, the

[0073] Chamfer 50 is designed such that the portion of the nozzle orifice 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 substantially the same. Where applicable, all individual features illustrated in the exemplary embodiments can be combined and / or interchanged with one another without departing from the scope of the invention.

[0074] List of reference symbols

[0075] 1 jet nozzle 25 32 transition

[0076] 2 Feed direction 33 radial outer cooling chamber

[0077] 3 Light channel 34 Honeycomb structure 4 Shell surface 35 Pin structure

[0078] 5 Outer structure 40 Absorption section

[0079] 6 Nozzle mouth 30 41 Solder of the workpiece surface

[0080] 7 Powder unit 42 front side

[0081] 8 distal area 43 longitudinal axis of the light channel 9 flange section 44 inner end section

[0082] 10 proximal area 50 bevel

[0083] 11 Powder Section 35 51 Passante

[0084] 12 Feed section 60 Process gas unit

[0085] 13 Coolant inlet 61 Process gas section 14 Coolant outlet 62 Outlet opening

[0086] 15 Coupling ring

[0087] 16 Powder injector 40 100 Workpiece

[0088] 17 Inlet nozzle 110 laser beam

[0089] 18 Drain nozzle 111 Primary jet 19 Injector guide 112 Secondary jet

[0090] 20 Center of the light channel 120 powdered filler material

[0091] 21 first powder focus 45 130 melt pool

[0092] 30 Cooling system 140 Functional layer

[0093] 150 reflected laser radiation

[0094] 31 radial inner cooling chamber

Claims

Claims 1. A jet nozzle (1) for laser cladding along a feed direction (2), comprising a light channel (3) for guiding at least one laser beam directed onto a workpiece; and an outer structure (5) which surrounds the light channel (3) at least in sections and extends from a flange section (9) to a distal region (8) formed by a nozzle mouth (6), from which the laser beam emerges; wherein the light channel (3) forms an absorption section (40) for absorbing reflection radiation of the laser beam from the workpiece.

2. Jet nozzle (1) according to claim 1, wherein the absorption section (40) extends from above the distal region (8) to a proximal region (10) adjacent to the flange section (9).

3. Jet nozzle (1) according to one of the preceding claims, wherein the absorption section (40) has a serrated structure which forms absorption surfaces facing the distal region (8).

4. Jet nozzle (1) according to one of the preceding claims, wherein a powder unit (7) arranged radially outside the light channel (3) for guiding at least one powder jet to be applied to the workpiece is formed in the outer structure (5), wherein the powder unit (7) forms a powder section (11) at the nozzle mouth (6) in a circumferential direction around the light channel (3), to which a powder unit-free feed section (12) adjoins in the circumferential direction.

5. Jet nozzle (1) according to claim 4, wherein the absorption section (40) is arranged at least in the feed section (12), in particular circumferentially in the circumferential direction.

6. Jet nozzle (1) according to one of the preceding claims, wherein the absorption section (40) extends completely around the light channel (3) in a circumferential direction.

7. Jet nozzle (1) according to one of the preceding claims, wherein a longitudinal axis (43) of the light channel (3), along which the laser beam runs, is inclined relative to a normal of the workpiece surface (41) in order to increase absorption of the reflected radiation by the absorption section (40).

8. Jet nozzle (1) according to claim 7, wherein an end face (42) of the jet nozzle (1) is angled relative to the longitudinal axis (43) of the light channel (3) along which the laser beam runs, so that the end face (42) is intended to run plane-parallel to a workpiece surface.

9. Jet nozzle (1) according to one of the preceding claims, wherein an area of ​​the absorption section (40) increases in a circumferential direction around the light channel (3) from the nozzle mouth (6) towards the flange section (9).

10. Jet nozzle (1) according to one of the preceding claims, wherein the jet nozzle (1) is inclinable relative to the workpiece, so that absorption of the reflected radiation by the absorption section (40) can be controlled by means of an inclination.

11. Jet nozzle (1) according to one of the preceding claims, wherein the absorption section (40) is provided with an absorbent coating.

12. Jet nozzle (1) 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, further in particular a copper-chromium-zirconium alloy.

13. Jet nozzle (1) according to one of the preceding claims, wherein the nozzle mouth (6) has a bevel (50) through 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).

14. System with a jet nozzle (1) according to one of the preceding claims and a workpiece (100), wherein the jet nozzle (1) is inclined relative to the workpiece (100) such that a longitudinal axis (43) of the light channel (3), along which the laser beam runs, deviates from a normal of the workpiece surface (41), so that absorption of the reflected radiation by the absorption section (40) is increased.

15. System according to claim 14, wherein the inclination of the jet nozzle (1) relative to the workpiece (100) is between 2° and 45°, in particular between 3° and 10°.

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