Beam nozzle with elongated cross-section of light channel

Abstract

The invention relates to a beam nozzle (1) for laser cladding welding in a feed direction, comprising: a light channel for guiding at least one laser beam directed onto a workpiece; and a powder unit arranged radially outside the light channel for guiding at least one powder beam to be applied to the workpiece, the cross-section of the light channel orthogonal to the longitudinal direction of the beam nozzle being elongated in the feed direction deviating from the circular shape.

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 A and DE 10 2018 130 798 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 jet nozzle further comprises a powder unit arranged radially outside the light channel for directing at least one powder jet to be applied to the workpiece. The powder unit can be radially outside the light channel, relative to the longitudinal direction of the jet nozzle, and can be part of an outer structure that encloses the light channel in a closed manner. The powder jet can carry a powdered additional material comprising hard material particles, particularly carbides, and a matrix material. The powder unit can be a portion of the jet nozzle designed to directly or indirectly direct the powdered additional material. The powder unit can have an injector guide into which a powder injector can be inserted. The powder unit can also have an annular gap into which the powdered additional material is directed.

[0008] The cross-section of the light channel, which extends orthogonally to the longitudinal direction of the jet nozzle, is elongated in the feed direction (oblong), unlike a circular shape. The elongation can be in the feed direction or opposite to the feed direction. Due to the elongation, more than one process zone can be arranged on the workpiece in the feed direction. The jet nozzle is a widened, elongated component. The longitudinal direction can be the direction in which the jet nozzle points. The jet nozzle has a cross-section orthogonal to the longitudinal direction, a part of which has the shape of the light channel. In this case, this shape is elongated in the feed direction and can be axisymmetric along the feed direction and point-symmetrical about the center point of the cross-section of the light channel. The minimum cross-section of the light channel is predetermined by the size of the laser beam, in particular the diameter. Compared to the minimum size, the cross-section is elongated in the feed direction.

[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, particularly by guiding the primary and secondary beams via an elongated shape, which creates multiple process zones.

[0011] In particular, the beam nozzle can reduce the formation of holes between the welded functional layer and the surface heated by the laser beam. This is because holes can form when laminae in the workpiece, in particular graphite laminae, are vaporized by the laser radiation. Holes can also form if the surface to be processed has impurities, such as oil, grease, cooling lubricants, or oxides, that cannot be completely removed by the welding process. Undesirable vaporization of impurities can be caused by setting the laser power of a single laser beam too high 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 formation of holes, in particular by guiding the primary and secondary beams in an elongated shape, which form multiple process zones.

[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. Increasing the variability of laser beam guidance, the application of powdered additive material, and / or the thermal management of the beam nozzle can reduce or even prevent the occurrence of cracks, particularly by guiding the primary and secondary beams in an elongated shape, which creates multiple process zones.

[0013] Furthermore, in particular, the jet nozzle can reduce the dissolution of hard material particles, particularly carbides, in the base material. The powdered additional material can contain hard material particles, particularly 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 may dissolve. Due to the low ductility of the base material, the dissolved hard material particles can cause the welded functional layer to become brittle. As a result, for example, when the workpiece cools or is loaded, the stresses caused by contraction cannot be absorbed by the base material. Increased variability in laser beam guidance, 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, particularly by guiding the primary and secondary beams in an elongated shape, which creates multiple process zones.

[0014] Furthermore, in particular, the jet nozzle can prevent powder particles from adhering to the nozzle opening. 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 flows 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 lead to scattering and / or absorption of the laser radiation and thus affect the preheating of the workpiece. This can further contribute to the formation of joining defects. Increased variability in the guidance of the laser beam, in the application of the powdered additional material, and / or in the thermal management of the jet nozzle can reduce or even prevent the undesirable dissolution of hard material particles and the spread of the metal vapor flame, in particular by the jet nozzle guiding the primary and secondary beams in an elongated shape, which form multiple process zones.

[0015] At least one laser beam, in particular at least one circular laser beam and / or oval laser beam, can be guided along the elongated cross-section of the optical channel, resulting in more than one process zone. This facilitates welding behavior and reduces weld joint defects, particularly the occurrence of joint defects, pores, and cracks, and / or the dissolution of carbides in the base material, while also increasing the load-bearing capacity of the applied functional layer. The melting behavior, powder beam behavior, material joining, and cooling behavior can thus be variably adapted to the respective application and the prevailing material properties and process parameters. In particular, it is possible to avoid laser power being too high or too low in the region of the molten pool to achieve the desired process result, both for the workpiece and for the powdered additional material. For example, in addition to the main laser beam for laser cladding welding, a secondary laser beam for pre- or post-processing can be guided within the optical channel directly adjacent to the first process location. The secondary laser beam can be guided downstream or upstream of the main laser beam in the feed direction, depending on whether it is used for pre- or post-processing. The geometrically close arrangement of the secondary laser beam relative to the primary laser beam reduces heat losses due to heat conduction within the workpiece, thereby promoting the material connection between the powdered additional material and the workpiece. The elongated shape ensures that the welding process is free of the aforementioned defects.

[0016] In one embodiment, the cross section is configured in the form of a strip hole (Langloch) at the distal end region of the jet nozzle formed by the nozzle mouth, in which two opposite ends of a rectangular section are each connected to a circular arc section (Teilkreisabschnitt). 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 has a distal region. This is the part of the nozzle mouth closest to the workpiece. In the section facing away from the workpiece, the jet nozzle has a proximal region and a flange section. The proximal region and the flange section are the parts of the jet nozzle facing away from the workpiece. The nozzle can be connected to another component of the laser system, such as a laser optical device or a process unit, via the flange section.

[0017] In one embodiment, the cross section is elongated, particularly in the region of the nozzle opening, such that it is at least 1.5 times larger in the feed direction than transversely to the feed direction, and in particular at least twice as large transversely to the feed direction. In particular, the distance between the two circular arcs can be more than twice the distance between the two parallel flanks of the strip-shaped hole. This creates the prerequisite for guiding more than one laser beam in the light channel to provide the corresponding process zones. The cross section can increase further from the nozzle opening toward the proximal section. Thus, the cross section can reach its minimum dimension in the distal section. This minimum dimension can also be designed so that it is sufficient to guide multiple laser beams.

[0018] In one embodiment, the surface center point of the cross section is offset from at least one laser beam center point of the at least one laser beam. This allows the laser beam to be directed outside the center point, ensuring that the jet nozzle and the laser beam orientation caused thereby are divided into a plurality of process zones.

[0019] In one embodiment, the optical channel is adapted to guide a plurality of laser beams, wherein the plurality of laser beams includes a first laser beam as a primary beam and a second laser beam as a secondary beam. The primary beam and the secondary beam can originate from the same optical fiber cable. The provided laser light can be divided into parallel beam clusters via a collimating lens. For example, the beam cluster can be formed from a single laser beam into a primary beam and a secondary beam using a wedge plate. In this case, the primary beam and the secondary beam can have the same wavelength and transmit the same energy. Alternatively, the primary beam and the secondary beam can differ in their wavelength and energy. The respective center points of the primary beam and the secondary beam can be offset in a straight line with the center point of the optical channel in the feed direction. The provision of the plurality of laser beams facilitates the reliable implementation of multiple process zones.

[0020] In one embodiment, the secondary beam is adapted to interact less with the powder beam than the primary beam, wherein the secondary beam is downstream of the primary beam in the feed direction to preheat the workpiece. The interaction of the primary and secondary beams with the powder beam can be achieved by correspondingly directing the corresponding laser beams and / or the powder beam. For example, the powder cells can form a powder segment circumferentially around the optical channel at the nozzle mouth, with a feed segment without powder cells adjoining the powder segment circumferentially. The feed segment surrounds the portion of the optical channel facing the feed direction. Thus, the feed segment can ensure that the powder beam does not interact with the secondary beam, allowing the secondary beam to be used to preheat the workpiece rather than the powder particles.

[0021] In one embodiment, the secondary beam is adapted to interact less with the powder beam than the primary beam, with the secondary beam being upstream of the primary beam in the feed direction to provide additional heating of the workpiece. The interaction of the primary and secondary beams with the powder beam can be achieved by correspondingly directing the respective laser beams and / or the powder beam. Thus, a feed section without a powder unit can surround the portion of the optical channel facing away from the feed direction. This ensures that the powder beam does not interact with the secondary beam, allowing the secondary beam to be used for additional heating or cleaning of the workpiece.

[0022] In one embodiment, the plurality of laser beams includes a third laser beam as a third beam, which is adapted to interact less with the powder beam than the primary beam, wherein the primary beam is downstream of the third beam in the feed direction. The respective cross sections of the primary beam, the secondary beam, and the tertiary beam can extend along a line, i.e., their respective center points can be arranged along a line. This line can be aligned with the feed direction. This line can also coincide with the feed direction. At least three distinct process zones can be achieved via the primary beam, the secondary beam, and the tertiary beam, which facilitates the welding process.

[0023] In one embodiment, when multiple laser beams are used, a laser beam downstream in the feed direction, such as a secondary beam, is concentric with the front arc segment of the cross section in cross section, and / or a laser beam upstream in the feed direction, such as a third beam, is concentric with the rear arc segment of the cross section in cross section. This enables efficient use of the cross section of the optical channel when guiding multiple laser beams.

[0024] In one embodiment, for the multiple laser beams, the surface center of the cross section coincides with the surface center of the multiple laser beams. The surface center of the cross section may be the point about which the cross section is point-symmetric. The surface center of the multiple laser beams may be the point at which the corresponding laser beam has its surface center in its cross section. Since the surface centers coincide with each other, the spatial utilization of the cross section of the optical path is further optimized when guiding the multiple laser beams.

[0025] In one embodiment, the jet nozzle has exactly one optical channel, allowing the multiple laser beams to be guided within the jet nozzle without obstructing one another. Thus, the single optical channel guides the multiple laser beams without requiring a separate shield around each laser beam. This simplifies the nozzle design and facilitates heat dissipation.

[0026] In one embodiment, the jet nozzle is manufactured by means of an additive manufacturing method, in particular by means of powder bed fusion. For this purpose, the jet nozzle can be made of copper or a copper alloy, 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 a material bond is formed. 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 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.

[0029] 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

[0030] 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:

[0031] Figure 1 shows a schematic diagram of a beam nozzle during laser cladding welding;

[0032] Figure 2 A side view of the jet nozzle is shown;

[0033] Figure 3 Shown Figure 2 A perspective view of the jet nozzle in FIG.

[0034] Figure 4 Shows connections to other components Figure 2 The jet nozzle in

[0035] Figure 5 Shown Figure 2 A top view of the distal end region of the jet nozzle in FIG.

[0036] Figure 6 Shown Figure 2 A top view of a flange section of the jet nozzle in FIG.

[0037] Figure 7 Shown Figure 2 Another perspective view of the jet nozzle in FIG;

[0038] Figure 8 Shown Figure 2 A perspective cutaway view of the jet nozzle in FIG.

[0039] Figure 9 A jet nozzle in a further embodiment is shown in a top view of the distal region;

[0040] Figure 10 A jet nozzle with a process gas unit is shown in a top view of the distal region;

[0041] Figure 11 A further embodiment of a jet nozzle with a geometrically adapted nozzle opening is shown in a side view; and

[0042] Figure 12 A further embodiment of a jet nozzle with a geometrically adapted nozzle opening is shown in a top view. DETAILED DESCRIPTION

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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).

[0047] 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.

[0048] 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 .

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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 .

[0055] 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.

[0056] 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 .

[0057] Figure 9 A further embodiment of the 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 opposite ends of the rectangular section. A primary beam 111 and a secondary beam 112 are guided within the light channel 3 . 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 .

[0058] The primary beam 111 has a beam center point that coincides with the first powder focus 21. The first powder focus 21 is the point at which the ejector of the first powder section 22 is focused. The first powder section 22 forms a first powder caustic. Accordingly, the secondary beam 112 has a beam center point that coincides with the second powder focus 23. The second powder focus 23 is the point at which the ejector of the second powder section 24 is focused. The second powder section 24 forms a second powder caustic. The primary beam 111 and the secondary beam 112 are offset relative to each other in the feed direction 2. Accordingly, the first powder focus 21 is also offset relative to the second powder focus 23. Therefore, a powder unit 7 having a first powder section 22 and a second powder section 24 can form two different powder focuses. Furthermore, the powder mass flow delivered from the ejector of the first powder section 22 can differ from the powder mass flow delivered from the ejector of the second powder section 24. A gap may be provided between the first powder section 22 and the second powder section 24 so that the powder mass flow applied by the first powder section 22 interacts only with the primary beam 111 and the powder mass flow applied by the second powder section 24 interacts only with the secondary beam 112 .

[0059] The first and second powder sections 22 and 24 contribute to an increased application rate by creating at least two process zones within the jet nozzle 1. This increases the track width of the applied functional layer. Furthermore, since the shielding gas can be more localized, improved shielding gas coverage is achieved with lower shielding gas consumption.

[0060] The main beam 111 and the secondary beam 112 are arranged adjacent to each other. The leading arc section of the strip hole in the feed direction 2 is concentric with the secondary beam 112, while the trailing arc section of the strip hole is concentric with the main beam 111. The center point 20 of the cross section is eccentric to the center point of the main beam 111 and the center point of the secondary beam 112.

[0061] Figure 10 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 5 As 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. As a result, 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.

[0062] Figure 11Another 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.

[0063] Figure 12 The 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.

[0064] 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.

[0065] exist Figure 12 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.

[0066] 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.

[0067] Reference Signs List

[0068] 1 Jet nozzle 22 First powder section

[0069] 2 Feed direction 23 Second powder focus

[0070] 3 Light channel 24 Second powder section

[0071] 4-sided 30° cooling system

[0072] 5 External structure 31 Radial inner cooling chamber

[0073] 6 Nozzle mouth 32 Transition part

[0074] 7 Powder unit 33 Radial outer cooling chamber

[0075] 8 Distal region 34 Honeycomb structure

[0076] 9 Flange section 50 chamfer

[0077] 10 Proximal area 51 bypass route

[0078] 11 Powder section 60 Process gas unit

[0079] 12 Feed section 61 Process gas section

[0080] 13 Coolant inlet 62 Outlet opening

[0081] 14 Coolant outlet

[0082] 15 Coupling ring 100 Workpiece

[0083] 16 Powder injector 110 Laser beam

[0084] 17 Inlet pipe 111 Main beam

[0085] 18 outlets take over 112 beams

[0086] 19 Injector guide 120 Powdered additional material

[0087] 20 Center point of light channel 130 Molten pool

[0088] 21 First powder focus 140 Functional layer

Claims

1. A beam nozzle (1) for laser cladding welding along a feed direction (2), the beam nozzle comprising: - an optical channel (3) for guiding at least one laser beam, which is directed onto the workpiece; and a powder unit (7) arranged radially outside the light channel (3) and serving to guide at least one powder jet to be applied to the workpiece; in, A cross section of the light channel (3) extending orthogonally to the longitudinal direction of the jet nozzle (1) is elongated in the feed direction (2) in a manner deviating from a circular shape.

2. The jet nozzle (1) according to claim 1, wherein The cross section is configured in the distal region (8) of the jet nozzle (1) formed by the nozzle opening (6) in the manner of a strip hole, in which a circular arc section adjoins each of the two opposite ends of the rectangular section.

3. The jet nozzle (1) according to claim 1, wherein: The cross section is elongated, in particular in the region of the nozzle opening (6), such that the cross section in the feed direction (2) is at least 1.5 times larger, in particular at least twice as large, transversely to the feed direction (2).

4. The jet nozzle (1) according to claim 1, wherein: The surface center point of the cross-section is eccentric relative to at least one laser beam center point of the at least one laser beam.

5. The jet nozzle (1) according to claim 1, wherein: The optical channel (3) is adapted to guide a plurality of laser beams, wherein the plurality of laser beams comprises a first laser beam as a main beam (111) and a second laser beam as a secondary beam (112).

6. The jet nozzle (1) according to claim 5, wherein The secondary beam (112) is adapted to interact less with the powder beam than the primary beam (111), wherein the secondary beam (112) precedes the primary beam (111) in the feed direction (2) to preheat the workpiece.

7. The jet nozzle (1) according to claim 5, wherein The secondary beam (112) is adapted to interact less with the powder beam than the primary beam (111), wherein the secondary beam (112) is behind the primary beam (111) in the feed direction (2) for supplementary heating of the workpiece.

8. The jet nozzle (1) according to claim 5, wherein: The plurality of laser beams comprises a third laser beam as a third beam, which is adapted to interact less with the powder beam than the main beam (111), wherein the main beam (111) is ahead of the third beam in the feed direction (2).

9. The jet nozzle (1) according to claim 5, wherein: In the case of the multiple laser beams, the front laser beam in the feed direction (2) is concentric with the front circular arc segment of the cross section in the cross section; and / or the rear laser beam in the feed direction (2) is concentric with the rear circular arc segment of the cross section in the cross section.

10. The jet nozzle (1) according to any one of claims 5 to 9, wherein In the case of the plurality of laser beams, the surface center point of the cross section coincides with the surface center points of the plurality of laser beams. 11 . The jet nozzle ( 1 ) according to claim 5 , comprising precisely one light channel ( 3 ), so that the plurality of laser beams are guided within the jet nozzle without obstructing one another. 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 claim 1, 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).

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