Beam nozzle having absorption section for absorbing reflected radiation

Abstract

The invention relates to a beam nozzle (1) for laser cladding welding in 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) surrounding the light channel (3), which outer structure extends from the flange section (9) to a distal end region (8) formed by a nozzle opening (6) from which the laser beam exits; wherein the light channel (3) forms an absorption section (40) for absorbing reflected radiation of the laser beam reflected by the workpiece.

Description

Technical Field

[0001] The invention relates to a beam nozzle for laser cladding welding along a feed direction. Background Art

[0002] Laser cladding welding is used, for example, in the fields of repair, coating, and / or joining technology. A distinction can be made between conventional laser cladding welding techniques (laser metal deposition (LMD), direct metal deposition (DMD), or direct energy deposition (DED)) and so-called high-speed laser cladding welding (high-speed laser metal deposition (HS-LMD) or ultra-high-speed laser application (EHLA)). The HS-LMD method is described, for example, in publications DE 10 2011 100 456 B4 and DE 10 2018130 798 A1. Another method for laser cladding welding is known from Chinese patent application CN 109175372 A.

[0003] Laser cladding welding can be used to apply a functional layer to a workpiece. This generally results in an increase in the load-bearing capacity of a workpiece processed by laser cladding welding compared to an unprocessed workpiece. The functional layer can, for example, serve as a wear protection layer. Application of the functional layer is based on melting of the workpiece surface, application of a powdered additional material, and subsequent cooling, resulting in a material-to-material connection between the base structure with hard material particles and the workpiece surface. Laser cladding welding thus embeds itself into the internal material structure of the workpiece and alters it. In some cases, this can lead to defects in the internal material structure. These defects can be detrimental to the desired increase in load-bearing capacity. The defects can be microscopic in nature and can therefore only be detected with great effort. Summary of the Invention

[0004] Based on the known prior art, the present invention aims to provide an improved jet nozzle for laser cladding welding in the feed direction. The present invention is particularly intended to improve the weld quality of the applied functional layer and the entire workpiece, and to reduce or avoid defects in the welded connection between the powdered additional material and the material surface. Defects can be defects in the bond between the material surface and the applied functional layer, or between individual applied functional layers. Defects can also be pores, i.e., air pockets, that appear within the applied functional layer or between the applied functional layer and the material surface. Pores are particularly likely to occur when the material surface is a cast material. Defects can also be cracks within the applied functional layer that extend perpendicular to the material surface. Defects can also be caused by powder particles, particularly carbides, of the powdered additional material dissolving in the base material of the powdered additional material, which can lead to embrittlement of the base material. The present invention is also particularly intended to provide a reliable jet nozzle that is resistant to thermal stress. The present invention can also aim to design the jet nozzle so that it ensures reliable and precise laser cladding welding over a very high number of cycles.

[0005] This object is achieved by a jet nozzle having the features of claim 1. Advantageous developments result from the dependent claims, the description and the drawings.

[0006] Accordingly, a beam nozzle for laser cladding welding along a feed direction is proposed. The beam nozzle has an optical channel for guiding at least one laser beam, which is directed onto a workpiece. Laser cladding welding can be used for a high-speed laser metal deposition (HS-LMD) method. The feed direction is the direction of movement of the beam nozzle relative to the workpiece. This feed direction can be caused by: movement of the workpiece, in particular rotational movement; movement of the beam nozzle; or a combination of the two. The feed direction and the associated feed movement can be constant during the process flow. Alternatively, they can vary with the respective process phase. The workpiece can be rotationally symmetrical, such as a brake disk, hydraulic cylinder, pressure roller, or plain bearing. The laser beam can be irradiated through the optical channel. The laser beam can be provided by a laser source, which is guided from the laser source via a fiber optic cable to a laser system. The laser system splits the laser beam via a collimating lens and focuses the laser beam to the process requirements via laser optics before it enters the beam nozzle. The light channel can be a hollow channel extending through the entire jet nozzle in the longitudinal direction. In addition to the laser beam, process gas can also be guided to the workpiece surface through the light channel.

[0007] The beam nozzle also has an external structure that encloses the light channel, extending from the flange section to a distal region formed by the nozzle mouth, from which the laser beam emerges. The external structure may include a powder unit. The powder unit may be part of the nozzle mouth. The nozzle mouth is the portion of the beam nozzle that faces the workpiece. The end section of the nozzle mouth forms the distal region. This is the portion of the nozzle mouth closest to the workpiece. In the section facing away from the workpiece, the beam nozzle has a proximal region and a flange section. The proximal region and the flange section are the portions of the beam nozzle facing away from the workpiece. The nozzle can be connected to another component of the laser system, such as laser optics or a process unit, via the flange section. The external structure may be a component made of a uniform material and may have a hollow channel along its length that forms the light channel.

[0008] The light channel forms an absorption section, which is used to absorb reflected radiation of the laser beam that is reflected by the workpiece. The absorption section can have a geometry that is favorable for absorbing the reflected radiation. The absorption section can extend variably in the circumferential direction around the light channel. It can also extend variably in the longitudinal direction of the light channel. In particular, the absorption section 40 is not formed in the distal region of the nozzle opening to facilitate better cleaning of the nozzle opening. The shape of the absorption section can be adapted to the expected reflected radiation. The absorption section can be made of the same material as the rest of the beam nozzle. The absorption section 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.

[0009] The beam nozzle thus allows for greater variability in: (i) laser beam guidance; (ii) the use of powdered additive material; (iii) thermal management; and / or (iv) protection of the laser system, including the beam nozzle. The beam nozzle enables the establishment of multiple independent process zones with high precision. The process zone can be divided into a zone for laser cladding welding and a zone for pre-processing and / or post-processing. In the zone for laser cladding welding, at least one laser beam interacts with the powdered additive material. Pre-processing and / or post-processing can involve cleaning the material surface, pre-heating the material surface before applying the powdered additive material, post-heating the material surface after the powdered additive material has been applied, or a combination thereof. During pre-processing and / or post-processing, the laser beam can impinge on the workpiece without interacting with the powdered additive material. Independent process zones can improve weld quality and, therefore, the load-bearing capacity of the applied functional layer, particularly the wear protection layer, and the entire workpiece. Additional process gas can stabilize the process zone and increase the precision of the laser cladding welding and the service life of the beam nozzle.

[0010] In particular, the beam nozzle can reduce the occurrence of joining defects. This is because joining defects can occur if the surface heated by the laser beam (e.g., a workpiece or a previously welded functional layer) is not heated sufficiently. This insufficient heating can be caused by keeping the laser power of the individual laser beams low to avoid overheating of the powdered additive material. Increased variability in laser beam guidance, increased variability in the application of the powdered additive material, and / or increased variability in the thermal management of the beam nozzle can reduce or even prevent the occurrence of joining defects. In particular, a beam nozzle with an absorption section contributes to the thermal management and protection of the laser system by enabling multiple process zones.

[0011] In particular, the beam nozzle can further reduce the occurrence of holes between the welded functional layer and the surface heated by the laser beam. This is because holes can occur when lamellae in the workpiece, in particular graphite lamellae, are vaporized by the laser radiation. Holes can also occur if the surface to be processed has impurities, such as oil, grease, cooling lubricants or oxides, which cannot be completely removed by the welding process. The undesired vaporization of impurities can be caused by the laser power of a single laser beam being set too high in order to avoid joining defects caused by insufficient heating. Increased variability in the guidance of the laser beam, increased variability in the application of powdered additional material and / or increased variability in the thermal management of the beam nozzle can reduce or even avoid the occurrence of holes, in particular by a beam nozzle with an absorption section that contributes to the thermal management and protection of the laser system in such a way that multiple process zones can be implemented.

[0012] In particular, the beam nozzle can reduce the occurrence of cracks in the welded functional layer. This is because cracks can occur if the temperature gradient between the intensely heated powdered additive material and the less intensely heated workpiece surface is so great that the material contraction during cooling induces stresses that lead to cracks. Cracking can be caused by setting the laser power of a single laser beam too high to avoid joint defects caused by insufficient heating. Increased variability in laser beam guidance, increased variability in the application of powdered additive material, and / or increased variability in the thermal management of the beam nozzle can reduce or even prevent the occurrence of cracks. In particular, a beam nozzle with an absorption section contributes to the thermal management and protection of the laser system by enabling multiple process zones.

[0013] Furthermore, in particular, the jet nozzle can reduce the dissolution of hard material particles, in particular carbides, in the base material. The powdered additional material can contain hard material particles, in particular carbides, and a base material. The hard material particles should be present in the welded functional layer in an undissolved state to increase the load-bearing capacity of the functional layer. However, if the powdered additional material is exposed to excessively high radiation intensities, causing the hard material particles to melt, the hard material particles can dissolve. Due to the low ductility of the base material, the dissolved hard material particles can cause the welded functional layer to become brittle, so that, for example, stresses caused by contraction when the workpiece cools or is loaded cannot be absorbed by the base material. Increased variability in the guidance of the laser beam, increased variability in the application of the powdered additional material, and / or increased variability in the thermal management of the jet nozzle can reduce or even prevent the dissolution of hard material particles. In particular, a jet nozzle with an absorption section contributes to the thermal management and protection of the laser system by enabling the implementation of multiple process zones.

[0014] Furthermore, the jet nozzle can, in particular, prevent powder particles from adhering to the nozzle opening. In principle, due to the high process heat, reflected laser radiation and / or the metal vapor flame can cause additional material to adhere to or even weld to the nozzle opening, which can disrupt the gas and powder flow and subsequently negatively affect the process result. The metal vapor flame is the result of partial vaporization of the material caused by laser cladding welding. This can cause scattering and / or absorption of the laser radiation and thus affect the preheating of the workpiece. This can further promote the formation of joining defects. Increased variability in the laser beam guidance, increased variability in the application of powdered additional material, and / or increased variability in the thermal management of the jet nozzle can reduce or even avoid the undesirable dissolution of hard material particles and the spread of the metal vapor flame. In particular, a jet nozzle with an absorption section contributes to the thermal management and protection of the laser system by enabling the implementation of multiple process zones.

[0015] The absorption section of the light channel absorbs reflected radiation from the laser beam reflected from the workpiece back to the beam nozzle. This effectively dissipates reflected radiation that could damage the beam nozzle. The absorption section absorbs the reflected radiation, reducing or eliminating the amount of radiation that enters other components of the laser system, such as the laser optics. This improves process reliability and laser beam accuracy, and also increases the service life of the beam nozzle and laser system. The improved properties of the absorption surface of the beam nozzle enable welding behavior that is free of the aforementioned drawbacks.

[0016] In one embodiment, the absorption section extends from above the distal region to the proximal region adjacent to the flange section. Thus, the absorption section can extend across the entire height of the beam nozzle, excluding the flange section and the distal region. Accordingly, reflected radiation is absorbed by the absorption section over a significant portion of the height of the beam nozzle, contributing to effective thermal management and protection of the laser system. For example, the distal region can extend up to 10 mm into the nozzle. The absence of the absorption section in the distal region makes cleaning the beam nozzle easier.

[0017] In one embodiment, the absorption section has a sawtooth structure, in particular an uneven sawtooth structure, which forms an absorption surface facing the distal region. The sawtooth structure may have a Christmas tree-shaped profile along the longitudinal direction of the light channel. The absorption surface may extend along a plane orthogonal to the longitudinal direction of the light channel. The sawtooth structure may be formed by the absorption surface and a supporting surface returning to the wall of the light channel, so that each sawtooth portion has a substantially triangular shape. The uniform sawtooth structure may have a uniform sawtooth portion from the distal region to the proximal region. Alternatively, the sawtooth portion may become larger from the distal region to the proximal region.

[0018] In one embodiment, a powder unit is formed in the external structure and is arranged radially outside the light channel. The powder unit is used to guide at least one powder jet to be applied to the workpiece, wherein the powder unit forms a powder segment in the circumferential direction around the light channel on the nozzle mouth, and a feed segment without a powder unit is connected to the powder segment in the circumferential direction. The feed segment can be a segment facing the feed direction, that is, pointing in the feed direction. The feed segment can extend within an angular span along the circumferential direction around the light channel. The area forming the feed segment can be related to the position and orientation of the powder injector that applies the powdered additional material to the workpiece. The powder segment and the feed segment can together form the entire circumference of the light channel around the nozzle mouth. For example, the powder segment can occupy a larger portion than the feed segment. In a top view, the powder segment and the feed segment can extend in a closed manner along the opening of the light channel, for example, an opening in the form of a strip hole.

[0019] In one embodiment, the absorption section is arranged at least in the feed section, in particular, arranged circumferentially. Depending on the angle of incidence of the at least one laser beam, the feed section may be the part of the beam nozzle subject to the highest thermal load. In this regard, arranging the absorption section at least in the feed section can further contribute to effective thermal management and protection of the laser system. For example, the absorption section can be arranged only in the region of the feed section, or it can also be arranged circumferentially, i.e., 360°.

[0020] In one embodiment, the absorption section extends completely around the optical channel in the circumferential direction. This ensures that the absorption section absorbs the reflected radiation regardless of the arrangement of the beam nozzle relative to the workpiece and the resulting reflected radiation. This contributes to effective thermal management and protection of the laser system. Alternatively, the position of the absorption section can be dependent on the tilt of the beam nozzle relative to the workpiece. Therefore, the absorption section can alternatively be designed not to extend around the optical channel. Instead, it can be strategically positioned in an area where, due to the tilt of the beam nozzle relative to the workpiece, a large portion of the reflected radiation is directed toward the beam nozzle.

[0021] In one embodiment, the laser beam extends along the longitudinal axis of the optical channel, which is tilted relative to the vertical line of the workpiece surface to increase the absorption of reflected radiation by the absorption section. Therefore, the laser beam is not directed orthogonally toward the workpiece to achieve targeted absorption of reflected radiation by the absorption section.

[0022] In one embodiment, the end face of the beam nozzle extends at an angle relative to the longitudinal axis of the optical channel along which the laser beam extends, such that the end face is arranged to extend plane-parallel to the workpiece surface. This increases the distance from the nozzle opening to the workpiece, reducing the thermal load on the nozzle opening. Furthermore, the angled end face improves shielding gas coverage of the workpiece. This is because the plane-parallel surfaces of the end face enable a shielding gas stream to be ejected orthogonally to the workpiece.

[0023] In one embodiment, the surface area of ​​the absorption section increases in the circumferential direction around the light channel, starting from the nozzle opening toward the flange section. This can be related to the fact that the cross section of the light channel increases toward the flange section, so the corresponding surface area of ​​the absorption section can also increase. This ensures that the radiation is intercepted in the proximal region, which further contributes to thermal management by protecting the laser optics.

[0024] In one embodiment, the beam nozzle can be tilted relative to the workpiece, enabling the absorption of reflected radiation by the absorbing section to be controlled by tilting. The orientation of the laser beam relative to the beam nozzle can be constant. Thus, the exit angle of the reflected radiation can be adjusted by tilting the beam nozzle. This tilting can interact with the absorbing section to ensure that it captures as much reflected radiation as possible.

[0025] In one embodiment, the absorbing section is provided with an absorbing coating. The absorbing coating can help improve the thermal resistance of the absorbing section. The absorbing coating can also improve the thermal conductivity of the absorbing section. This helps prevent the absorbing section from being damaged even in the event of increased reflected radiation.

[0026] In one embodiment, the jet nozzle is manufactured by means of an additive manufacturing method, in particular by means of powder bed fusion. To this end, the jet nozzle can be made of copper or a copper alloy, further in particular a copper-chromium-zirconium alloy. This is suitable for additive manufacturing methods on the one hand and ensures sufficient strength, thermal conductivity and heat resistance to meet the process requirements on the other hand. In powder bed fusion, the material to be processed is in powder form. A laser beam heats the powder along the set geometry, whereby the powder liquefies and forms a material bond. For example, powder bed fusion can be achieved using selective laser melting (SLM) or selective laser sintering (SLS).

[0027] In one embodiment, the nozzle mouth has a beveled portion A portion of the nozzle opening is removed by the bevel, wherein the bevel is essentially planar and extends in a plane inclined relative to the longitudinal direction of the jet nozzle. The bevel can cut a powder section and a powder-free feed section circumferentially around the light channel. The bevel reduces the volume of the nozzle opening compared to embodiments without a bevel. This means that the nozzle opening takes up less construction space. A jet nozzle with a bevel can be used, for example, to coat brake disks having a receptacle that protrudes axially relative to the functional surface to be coated. The bevel ensures that the jet nozzle can be moved flexibly over the functional surface to be coated and can be moved close to the receptacle. In the distal region, the bevel can extend alongside the strip hole in the manner of a bypass. The bypass defines the orientation of the bevel on the nozzle opening. On the end face of the jet nozzle facing the workpiece, the bypass extends along a straight line or arc that neither intersects nor contacts the strip hole. The distance between the bypass line and the center point of the light channel is greater than the distance between the corresponding section of the strip hole and the center point of the light channel. The distance between the bypass line and the outer edge of the strip hole is selected so that the wall thickness therebetween ensures sufficient strength and load-bearing capacity of the jet nozzle.

[0028] In one embodiment, the present disclosure further relates to a system comprising a beam nozzle according to the present disclosure and a workpiece. The beam nozzle is tilted relative to the workpiece such that the longitudinal axis of the optical path, along which the laser beam extends, deviates from a perpendicular to the workpiece surface, thereby increasing absorption of reflected radiation by the absorption section. This tilting can be achieved by relative movement of the beam nozzle relative to the workpiece or the workpiece relative to the beam nozzle. For example, a workpiece support can be tilted relative to the beam nozzle. The tilting is adapted to the position of the absorption section.

[0029] In one embodiment, the beam nozzle is tilted relative to the workpiece by between 2° and 45°, in particular between 3° and 10°. It has been found that these tilt angles achieve an ideal compromise between absorption of reflected radiation by the absorption section and the welding behavior of laser cladding welding.

[0030] In one embodiment, the beam nozzle is adapted to guide the laser beam along its longitudinal direction so that the at least one laser beam extends orthogonally to the cross section. Furthermore, the light channel can be adapted to guide a shielding gas in a radially outer section to shield the process zone.

[0031] The features according to the present disclosure overcome the disadvantages of laser cladding welding mentioned at the outset partly individually and partly in combination. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The preferred further embodiments of the present invention are described in more detail by the following description of the accompanying drawings. In the accompanying drawings:

[0033] Figure 1 shows a schematic diagram of a beam nozzle during laser cladding welding;

[0034] Figure 2 A side view of the jet nozzle is shown;

[0035] Figure 3 Shown Figure 2 A perspective view of the jet nozzle in FIG.

[0036] Figure 4 Shows connections to other components Figure 2 The jet nozzle in

[0037] Figure 5 Shown Figure 2 A top view of the distal end region of the jet nozzle in FIG.

[0038] Figure 6 Shown Figure 2 A top view of a flange section of the jet nozzle in FIG.

[0039] Figure 7 Shown Figure 2 Another perspective view of the jet nozzle in FIG;

[0040] Figure 8 Shown Figure 2 A perspective cutaway view of the jet nozzle in FIG.

[0041] Figure 9 Shown Figure 2 Another perspective sectional view of the jet nozzle in;

[0042] Figure 10 Further cross-sectional views of the jet nozzle and the workpiece are shown;

[0043] Figure 11 A further perspective sectional view of the jet nozzle with an angled end face is shown;

[0044] Figure 12 shows a longitudinal section through a jet nozzle having a smooth inner end section;

[0045] Figure 13 A jet nozzle with a process gas unit is shown in a top view of the distal region;

[0046] Figure 14 A further embodiment of a jet nozzle with a geometrically adapted nozzle opening is shown in a side view; and

[0047] Figure 15 A further embodiment of a jet nozzle with a geometrically adapted nozzle opening is shown in a top view. DETAILED DESCRIPTION

[0048] The preferred embodiments are described below with reference to the accompanying drawings. In different figures, identical, similar or functional elements are provided with identical reference numerals, and repeated descriptions of these elements are partially omitted to avoid redundancy.

[0049] Figure 1 A beam nozzle 1 for laser cladding welding along a feed direction 2 is shown. The feed direction 2 is the direction along which the beam nozzle 1 moves relative to the workpiece 100. The feed direction can be caused by: a movement of the workpiece 100, in particular a rotational movement; a movement of the beam nozzle 1; or a superposition of movements of the workpiece 100 and the beam nozzle 1. The feed direction 2 and the associated feed movement can be constant during the process flow. Alternatively, they can vary with the respective process phase. 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 having a circumferential side 4. The light channel 3 can also be adapted to guide a process shielding gas 150 in a radially outer section in order to shield the process zone and avoid oxidation. The light channel 3 is surrounded by an outer structure 5, which has a nozzle mouth 6, which in turn contains a powder unit 7. For example, the powder unit 7 can have a plurality of injector guides 19 (see Figure 3 ), a powder injector 16 can be inserted into each of the plurality of injector guides (see Figure 4). As an alternative to the individual injector guides 19, the powder unit 7 can have a powder annular gap channel. Powdered additional material 120 is directed onto the workpiece 100 via the powder unit 7 and the powder injector 16 arranged in the powder unit 7. The laser beam 110 heats the workpiece 100, so that a molten pool 130 is formed on the material surface. In addition, the laser beam 110 heats the powdered additional material 120, which includes hard material particles and a base material. For this reason, the laser beam 110 can have a reduced core strength. Once the molten pool 130 cools, a welded functional layer 140, such as a wear protection layer, is formed from the hard material particles and the base material. The welded functional layer 140 makes the material surface more durable and improves the load-bearing capacity of the material surface.

[0050] Figure 2 The jet nozzle 1 is shown in a side view, wherein the feed direction 2 points out of the drawing plane. The jet nozzle 1 can be connected to other components of the laser system, such as laser optics or a process adapter, via a flange section 9. A proximal region 10 is connected to the flange section 9. A coolant inlet 13 and a coolant outlet 14 are part of the cooling system of the jet nozzle 1 and protrude radially from the jet nozzle 1, the coolant inlet and the coolant outlet being at least partially arranged 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. In the circumferential direction around the light channel 3, the nozzle mouth 6 partially has a powder section 11, in which the powder unit 7 is arranged. In the circumferential direction, a feed section 12 without a powder unit is connected to the powder section 11. The feed section 12 can be designed as a process gas section 61 (see, for example, Figure 9 ), the process gas section is a component of the process gas unit 60.

[0051] Figure 3 Shown Figure 2 1 . The light channel 3 is a hollow channel with a circumferential surface 4, within which the at least one laser beam 110 extends. The outer structure 5 surrounds the light channel 3 from the flange section 9 to the distal region 10. The nozzle opening 6 is a substantially funnel-shaped region of the jet nozzle 1. The funnel shape of the nozzle opening 6 serves in particular to enable the nozzle opening 6 to form a plurality of injector guides 19 in the region of the powder unit 7. Each powder injector 16 (see Figure 4) are inserted into these injector guides 19, and the powder injector 16 directs the powdered additional material 120 onto the at least one laser beam 110 and / or the workpiece 100 in accordance with the process requirements. The powder unit 7 extends along the powder section 11, and the feed section 12 without the powder unit is connected to the powder section in the circumferential direction. The feed section 12 is the following area of ​​the nozzle mouth 6 in which the injector guide 19 is not provided, so that the powdered additional material 120 is not supplied via this section. In one embodiment, the feed section 12 can be formed as a process gas section 61, so that the process gas is supplied via this process gas section. The jet nozzle 1 can be manufactured by means of an additive manufacturing method, 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 is suitable for additive manufacturing methods on the one hand, 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. The laser beam heats the powder along the set geometry, liquefies the powder and forms a material bond. For example, powder bed fusion can be achieved using selective laser melting (SLM) or selective laser sintering (SLS).

[0052] Figure 4 The jet nozzle 1 is shown with additional components attached. A coupling ring 15 is attached to the flange section 9 and secures the jet nozzle 1 to the attached unit, such as the laser optics system or a process adapter. A powder injector 16 is inserted into the injector guide 19 of the powder unit 7. Powdered additional material 120 is conveyed by means of the powder injectors 16 and applied to the workpiece 100 at a set focal point. Each powder injector 16 can use a different powder focal point relative to one another. Alternatively, the powder injectors 16 can be directed to the same focal point. In the powder section 11, the powder injectors 16 are arranged in the injector guide 19 of the powder unit 7 provided for this purpose. The feed section 12 does not have a powder injector 16. Furthermore, an inlet connection piece 17 is inserted into the coolant inlet 13, and an outlet connection piece 18 is inserted into the coolant outlet 14. These connections connect the coolant inlet 13 and the coolant outlet 14 to the coolant circuit.

[0053] Figure 5The jet nozzle 1 is shown in a top view of the distal region 8 . The cross section of the light channel 3 , which extends 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 section of the light channel 3 is designed as a strip-shaped hole, with a circular arc segment adjoining each of the two opposing ends of the rectangular section. Two laser beams, a primary beam 111 and a secondary beam 112, are guided within the light channel 3 . The primary beam 111 and the secondary beam 112 can originate from the same fiber optic cable. The provided laser light can be divided into parallel beam clusters using a collimating lens. For example, the beam clusters can be formed from a single laser beam into the primary beam 111 and the secondary beam 112 using a wedge plate. The respective center points of the primary beam 111 and the secondary beam 112 are aligned in the feed direction 2 , offset relative to the center point 20 of the light channel 3 .

[0054] In this example, secondary beam 112 is located upstream (downstream) of primary beam 111 in feed direction 2 and does not interact with the powder caustics. Consequently, secondary beam 112 can be used to preheat workpiece 100 before primary beam 111 and the powdered additional material 120 heated by primary beam 111 are directed onto workpiece 100. Thus, secondary beam 112 creates a first process zone for preheating workpiece 100, while primary beam 111 creates a second process zone for depositing powdered additional material 120 onto workpiece 100. These different process zones enable flawless welding without defects, particularly bonding defects, porosity, cracks, and / or dissolution of carbides in the base material. Alternatively, secondary beam 112 can be directed upstream (behind) primary beam 111 in feed direction 2. Thus, the secondary beam 112 may be used to provide additional heating to the workpiece 100, thereby facilitating more uniform cooling that avoids the formation of inclusions or other defects.

[0055] The main beam 111 and the secondary beam 112 are arranged in close proximity to each other. The arc segment of the strip-shaped hole in front in the feed direction 2 is concentric with the secondary beam 112, while the arc segment of the strip-shaped hole in the back is concentric with the main beam 111. The center point of the cross section is eccentric (non-concentric) with the center point of the main beam 111 and the center point of the secondary beam 112. A third beam can also be provided so that, for example, the secondary beam is arranged in front of the main beam in the feed direction and the third beam is arranged behind the main beam in the feed direction. The individual laser beams are guided without blocking each other, so that there is exactly one light channel 3 and exactly one circumferential side surface 4, thereby minimizing heat losses.

[0056] because Figure 5In the embodiment, primary beam 111 is arranged behind secondary beam 112 in feed direction 2 without radial offset, and secondary beam 112 is used to preheat the workpiece. Therefore, it is desirable that the powdered additional material does not interact with secondary beam 112. This ensures, on the one hand, that secondary beam 112 can perform only the function of preheating the workpiece, and, on the other hand, that the powdered additional material is heated only by primary beam 111 and not by secondary beam 112. This is achieved by forming the powder unit 7 in the region of the nozzle opening 6 such that the powder unit forms a powder section 11 circumferentially around the optical channel 3, with a feed section 12, which is free of powder units, adjoining the powder section 11 in the circumferential direction. In addition to the powder unit 7, a process gas unit 60 may also be provided, forming a process gas section 61, with the feed section 12 being formed as the process gas section 61. The feed section 12 is formed in the region of the nozzle opening 6 facing the feed direction 2. Powder segment 11 extends along the strip-shaped aperture that forms the cross-section of light channel 3 in distal region 8. Similar to a circular arc, powder segment 11 extends around light channel 3 along the strip-shaped aperture arc, particularly in the shape of a horseshoe. Consequently, powder segment 11 extends circumferentially around light channel 3 at a wrap angle that is less than 360°, particularly between 90° and 330°, and even more particularly between 180° and 300° relative to the center point of the light channel. This ensures that the powdered additional material flowing from injector 16 inserted into injector guide 19 interacts only with primary jet 111. Consequently, secondary jet 112 can form a process zone independent of primary jet 111. In a top view, powder segment 11 and feed segment 12 form a strip-shaped aperture. This also helps reduce or avoid the drawbacks mentioned above.

[0057] Figure 6 The jet nozzle 1 is shown in a top view of the flange section 9. The cross section of the light channel 3, which extends 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 elongation of the cross section can decrease from the distal region 8 to the flange section 9. In the region of the nozzle opening 6, the cross section can be elongated so that it is at least 1.5 times larger, in particular at least twice as large, in the feed direction transversely thereto. The flange section 9 has such a radial extent that the injector guide 19 is not visible from a top view of the proximal region 10.

[0058] Figure 7The jet nozzle 1 is shown in another perspective view. The nozzle mouth 6 has a domed funnel shape. Within each dome are formed injector guides 19, into which the powder injector 16 can be inserted. In the feed direction 2, the light channel is elongated, deviating from a circular shape, to achieve the advantages of the present disclosure. The nozzle mouth 6 includes a powder unit 7 circumferentially around the light channel 3. The powder unit 7 extends circumferentially around the light channel 3 along a powder section 11, which is joined by a powder-free feed section 12.

[0059] Figure 8 The figure shows a perspective sectional view of the jet nozzle 1. The light channel 3 has a conical shape, so that the cross section of the light channel 3, which extends 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 from the jet nozzle 1 in the radial direction. Figure 8 A cross-sectional view of an injector guide 19 is shown. The injector guide 19 is arranged in the powder section 11. No injector guide 19 for guiding the powder jet is provided in the feed section 12. The jet nozzle 1 has a cooling system 30. A cooling medium, such as water, is supplied back to a radially inner cooling chamber 31 via a coolant inlet 13 in the proximal region 10. The cooling medium can be distributed circumferentially around the light channel 3 in the proximal region 10. From the proximal region 10, the cooling medium flows to the nozzle mouth 6. The radially inner cooling chamber 31 is formed at least in the nozzle mouth 6. The radially inner cooling chamber 31 can extend from the distal region 8 to the proximal region 10 and be designed as an annular gap segment extending 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 opening 6 and is concentric with the light duct 3 in a cross section extending orthogonally to the longitudinal direction of the jet nozzle 1 .

[0060] A transition 32 between the radially inner cooling chamber 31 and the radially outer cooling chamber 33 is provided in the distal region 8. In the radial direction, the radially outer cooling chamber 33 has a radial width in the region of the nozzle opening 6 that decreases toward the distal region 8. The radially outer cooling chamber 33 extends from the distal region 8 to the proximal region 10, where it supplies 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 an injector guide 19 for guiding the powder jet, so there is sufficient space for the transition 32.

[0061] The radially outer cooling chamber 33 has a cooling structure for increasing the surface area. The cooling structure can be produced by means of additive manufacturing methods. It ensures that the cooling medium contacts the largest possible surface area when returning from the distal region 8 to the proximal region 10, thereby promoting heat dissipation. The cooling structure is optimized to cause the lowest possible pressure loss of the cooling medium. This can be achieved by means of a honeycomb structure 34, such as Figure 8 As shown in .

[0062] Figure 9 The jet nozzle 1 is shown with an absorption section 40. This absorption section is designed to absorb reflected radiation of the laser beam that is reflected from the workpiece. The absorption section 40 extends from the distal region 8 to the proximal region 10. Thus, it helps protect the laser optics from reflected radiation. The absorption section 40 has a sawtooth structure. This sawtooth structure forms an absorption surface facing the distal region 8. The absorption section is arranged in the region of the feed section 12. The absorption section 40 can be formed from the same material as the rest of the jet nozzle 1. The absorption section can also have a coating. The laser radiation absorbed by the absorption section 40 can be dissipated by the cooling system 30 that interacts with the absorption section 30.

[0063] Figure 10 The figure shows a jet nozzle 1 and a workpiece 100. A laser beam 110 extends along the longitudinal axis 43 of the optical channel 3. The longitudinal axis 43 of the optical channel 3 is tilted relative to the perpendicular 41 to the workpiece surface. Due to this tilt, reflected laser radiation 150 is directed onto the absorption section 40. The tilt of the longitudinal axis 43 of the optical channel 3 relative to the perpendicular 41 to the workpiece surface is selected so that the absorption section 40 absorbs as much of the reflected laser radiation as possible. The tilt is between 2° and 20°, particularly between 3° and 10°. To achieve this tilt, the jet nozzle 1 can be tilted relative to the workpiece 100, or the workpiece 100 can be tilted relative to the jet nozzle 1. The surface roughness of the absorption surface of the absorption section 40 is between 5 μm and 100 μm, particularly between 50 μm and 50 μm. The absorption section 40 can also be provided with an absorption coating to enhance absorption.

[0064] Figure 11 A jet nozzle 1 is shown in which the end side 42 of the jet nozzle 1 extends at an angle relative to the longitudinal axis 43 of the light tunnel 3, so that the end side 42 extends plane-parallel to the workpiece 100. This increases the distance from the nozzle opening 6 to the workpiece 100. This also reduces the thermal load on the nozzle opening 6. Furthermore, the angled end side 42 allows for improved coverage of the workpiece 100 with shielding gas. This is because the plane-parallel surfaces of the end side 42 enable a shielding gas stream to be ejected orthogonally to the workpiece 100.

[0065] Figure 12A longitudinal cross-section of a jet nozzle 1 having a smooth inner end section 44 is shown. The jet nozzle 1 can form a smooth inner end section 44 as the distal circumferential side of the light channel 3. The smooth inner end section 44 facilitates better cleaning of the interior of the nozzle opening 6. The absorption section 40 extends proximally from the smooth inner end section 44. The absorption section 40 can also extend completely around the light channel 3 in the circumferential direction, i.e., 360° around it. Therefore, the absorption capacity of the jet nozzle 1 is not dependent on a specific feed direction.

[0066] exist Figure 12 In the embodiment, the powder unit 7 is arranged in the rear region in the feed direction 2 , forming a powder section 11, through which an injector guide 19 extends. The injector guide 19 is adapted to accommodate a respective powder injector 16 . A process gas unit 60 can be arranged in the front region in the feed direction 2 , forming a process gas section 61, through which a distribution arm for the process gas extends. The distribution arm can accommodate additional injectors. Alternatively, the process gas is directed directly from the distribution arm to the material surface. The distribution arm has a curved shape along its longitudinal direction. The jet nozzle 1 has a cooling system 30 comprising a radially inner cooling chamber 31 and a radially outer cooling chamber 33 . Since the feed section 12 is designed as a process gas section, the radially outer cooling chamber 33 surrounds the distribution arm 24 in the front region of the nozzle opening 6 in the feed direction 2 . Thus, the process gas can contribute to thermal management of the jet nozzle 1 .

[0067] Figure 13 The jet nozzle 1 is shown in a top view of the distal region 8. A primary beam 111 and a secondary beam 112 are guided in the light channel 3. The secondary beam 112 is ahead of the primary beam 111 in the feed direction 2 and does not interact with the powder caustics, as with the Figure 5As described in more detail, when the laser beam interacts with the material surface and the powder jet, a vapor flame may form between the jet nozzle 1 and the workpiece 100. If this is not restricted, it may interact undesirably with the at least one laser beam and / or the unprocessed and / or processed material surfaces. Therefore, in the region adjoining the powder section 11, the feed section 12 may be designed as a process gas section 61. The process gas section 61 is formed by a process gas unit 60 arranged radially outside the light tunnel 3, which directs process gas onto the workpiece. The process gas section 61 prevents undesirable spread of the vapor flame and thus facilitates precise workpiece processing while maintaining a robust jet nozzle design. The process gas section 61 may form at least one, and in this example, three, outlet openings 62. The outlet openings 62 are formed on the end face of the jet nozzle 1. Additional injectors for supplying process gas rather than additional material may be inserted into the respective outlet openings 62. The inner diameter of the outlet openings 62 may be smaller than the inner diameter of the injector guide 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 around the strip-shaped opening formed by the light channel 3. Thus, the primary beam 111 and the secondary beam 112 are completely contained within the beam consisting of the powder beam and the process gas beam.

[0068] Figure 14 Another embodiment of the jet nozzle 1 is shown. The nozzle mouth 6 has a bevel 50, which cuts off a portion of the nozzle mouth 6. The bevel 50 causes the powder section 11 and the feed section 12, which does not have a powder section, to be cut circumferentially around the light channel 3. The bevel 50 reduces the volume of the nozzle mouth 6 compared to an embodiment without the bevel 50. This ensures that the nozzle mouth 6 takes up less construction space. For example, the jet nozzle 1 with the bevel 50 can be used to coat brake disks. The brake disk can have a receptacle that protrudes axially from the functional surface to be coated. The bevel 50 ensures that the jet nozzle 1 can be moved flexibly over the functional surface to be coated and can be moved close to the receptacle. The bevel 50 can be designed to be essentially planar and extend in a plane inclined relative to the longitudinal direction of the jet nozzle. The bevel 50 forms the boundary surface of the nozzle mouth 6 where the powder unit 7 is not located. In the distal end region 8 , the bevel 50 is arranged close to the light duct 3 , so that no injector guide 19 is provided in the region of the bevel 50 on the end face of the jet nozzle 1 facing the workpiece.

[0069] Figure 15The jet nozzle 1 is shown in a top view with a bevel 50. The bevel 50 can extend adjacent to the strip-shaped hole in the distal region 8 in the manner of a bypass path 51. The bypass path 51 defines the orientation of the bevel 50 at the nozzle opening 6. On the end face of the jet nozzle 1 facing the workpiece, the bypass path 51 extends along a straight line or arc that neither intersects nor touches the strip-shaped hole. The distance between the bypass path 51 and the center point 20 of the light channel 3 is greater than the distance between the corresponding section of the strip-shaped hole and the center point 20 of the light channel 3. The distance between the bypass path 51 and the outer edge of the strip-shaped hole is selected so that the wall thickness therebetween ensures sufficient strength and load-bearing capacity of the jet nozzle 1.

[0070] The orientation of the bypass path 51, and therefore the orientation of the bevel 50 at the nozzle opening 6, can vary depending on the application. For example, the bypass path 51 can extend in the feed direction 2. Here, the bypass path 51 runs along the elongation of the cross section of the light duct 3. Thus, the bypass path 51 runs along the long side of the strip-shaped hole. Alternatively, for example, the bypass path 51 can extend transversely to the feed direction 2. Here, the bypass path 51 runs transversely to the elongation of the cross section of the light duct 3. Thus, the bypass path 51 runs along a circular arc segment of the strip-shaped hole. Further alternatively, for example, the bypass path 51 can extend at an angle relative to the feed direction 2 that lies between a direction along the feed direction 2 and a direction transverse to the feed direction 2. Here, the bypass path 51 runs along the transition section between the long side of the strip-shaped hole and the circular arc segment of the strip-shaped hole. The orientation of the bypass path 51 predetermines the orientation of the bevel 50.

[0071] exist Figure 15 In the embodiment of FIG, the outlet opening 62 is provided on the end face of the jet nozzle. The process gas leaves the process gas unit 60 through the outlet opening 62. In this example, the chamfer 50 is designed so that the portion of the nozzle opening 6 removed by the chamfer is completely removed from the powder section 11. This means 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 unchanged.

[0072] Where applicable, all the individual features presented in the embodiments may be combined with one another and / or interchanged without departing from the scope of the present invention.

[0073] Reference Signs List

[0074] 1 Jet nozzle 32 Transition section

[0075] 2 Feed direction 33 radial external cooling chamber

[0076] 3 light channels 34 honeycomb structure

[0077] 4 Side surface 35 pin structure

[0078] 5 External structure 40 Absorption section

[0079] 6 Nozzle mouth 41 Vertical line of workpiece surface

[0080] 7 Powder unit 42 end side

[0081] 8 Distal region 43 Longitudinal axis of the optical channel

[0082] 9 Flange section 44 Inner end section

[0083] 10 proximal region 50 beveled portion

[0084] 11 Powder section 51 Bypass route

[0085] 12 Feed section 60 Process gas unit

[0086] 13 Coolant inlet 61 Process gas section

[0087] 14 Coolant outlet 62 outlet opening

[0088] 15 Coupling ring

[0089] 16 Powder Injector 100 Workpiece

[0090] 17 Inlet connection 110 Laser beam

[0091] 18 Outlet connector 111 Main beam

[0092] 19 Injector guide 112 secondary beam

[0093] 20 Center of light channel 120 Powdered additional material

[0094] 21 First powder focus 130 molten pool

[0095] 30 Cooling System 140 Functional Layer

[0096] 31 Radial inner cooling chamber 150 reflects laser radiation

Claims

1. A beam nozzle (1) for laser cladding welding along a feed direction (2), the beam nozzle comprising: - a light channel (3) for guiding at least one laser beam, which is directed onto the workpiece; and an outer structure (5) at least partially surrounding the light channel (3), said outer structure extending from a flange section (9) to a distal region (8) formed by a nozzle opening (6) from which the laser beam emerges; in, The light channel (3) forms an absorption section (40) for absorbing reflected radiation of the laser beam reflected by the workpiece.

2. The 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. The jet nozzle (1) according to claim 1, wherein: The absorption section (40) has a sawtooth structure, which forms an absorption surface facing the distal region (8).

4. The jet nozzle (1) according to claim 1, wherein: A powder unit (7) is formed in the external structure (5) and is arranged radially outside the light channel (3). The powder unit is used to guide at least one powder jet to be applied to the workpiece, wherein the powder unit (7) forms a powder section (11) in the circumferential direction around the light channel (3) on the nozzle mouth (6), and a feed section (12) without a powder unit is connected to the powder section in the circumferential direction.

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

6. The jet nozzle (1) according to claim 1, wherein: The absorption section (40) extends completely around the light channel (3) in the circumferential direction.

7. The jet nozzle (1) according to claim 1, wherein: The longitudinal axis of the light channel (3) is inclined relative to a vertical line (41) of the workpiece surface to increase the absorption of reflected radiation by the absorption section (40), and the laser beam extends along the longitudinal axis (43).

8. The jet nozzle (1) according to claim 7, wherein The end face (42) of the jet nozzle (1) extends at an angle to the longitudinal axis (43) of the light channel (3), so that the end face (42) is arranged to extend parallel to the workpiece surface plane, along which the laser beam extends.

9. The jet nozzle (1) according to claim 1, wherein: Starting from the nozzle opening (6) toward the flange section (9), the surface of the absorption section (40) increases in the circumferential direction around the light channel (3).

10. The jet nozzle (1) according to claim 1, wherein: The jet nozzle (1) can be tilted relative to the workpiece, so that the absorption of the reflected radiation by the absorption section (40) can be controlled by means of the tilting.

11. The jet nozzle (1) according to claim 1, wherein: The absorption section (40) is provided with an absorption coating. 12 . The jet nozzle ( 1 ) according to claim 1 , which is produced by means of an additive manufacturing method and contains, in particular, copper or a copper alloy, further in particular a copper-chromium-zirconium alloy.

13. The jet nozzle (1) according to any one of the preceding claims, wherein The nozzle opening (6) has a bevel (50), by which a part of the nozzle opening (6) is cut away, wherein the bevel (50) is substantially planar and extends in a plane which is inclined relative to the longitudinal direction of the jet nozzle (1).

14. A system comprising a jet nozzle (1) according to any one of the preceding claims and a workpiece (100), wherein: The jet nozzle (1) is tilted relative to the workpiece (100) such that a longitudinal axis (43) of the light channel (3) along which the laser beam extends deviates from a vertical line (41) to the workpiece surface, thereby increasing absorption of reflected radiation by the absorption section (40).

15. The 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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