Jet nozzle with an elongated cross-sectional area of ​​a light channel

Abstract

Beam nozzle (1) for laser cladding along a feed direction (2), comprising - a light channel (3) for guiding at least one first laser beam as primary beam (111) and one second laser beam as secondary beam (112), which are directed towards a workpiece; and - a powder unit (7) arranged radially outside the light channel (3) for guiding at least one powder jet to be applied to the workpiece; wherein the powder unit (7) has a first powder section (22) forming a first powder focus (21), and the primary jet (111) has a jet center that coincides with the first powder focus (21), and the powder unit (7) has a second powder section (24) forming a second powder focus (23), and the secondary jet (112) has a jet center that coincides with the second powder focus (23).

Description

Technical area

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

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

[0003] Laser cladding can be used to apply a functional layer to a workpiece. This layer generally increases the load-bearing capacity of the workpiece processed by laser cladding compared to an unprocessed workpiece. The functional layer can serve, for example, as a wear-resistant layer. The application of the functional layer is based on melting a workpiece surface, applying a powdered filler material, and subsequent cooling, so that a matrix structure with hard material particles is firmly bonded to the material surface. Thus, laser cladding intervenes in the internal material structure of the workpiece and changes it. This can potentially result in deficiencies in the internal material structure. These can impair the desired increase in load-bearing capacity. The deficiencies can be microscopic in nature, which is why they are only identifiable with considerable effort. Description of the invention

[0004] Based on the known prior art, it is an object of the present invention to provide an improved jet nozzle for laser cladding along a feed direction.

[0005] The invention aims in particular at improving the weld quality of an applied functional layer and the workpiece as a whole, and at reducing or avoiding deficiencies in a weld joint between a powdered filler material and a material surface. These deficiencies may be lack of fusion between the material surface and the applied functional layer or between individual applied functional layers. These deficiencies may also be pores, i.e., air inclusions, that occur within the applied functional layer or between the applied functional layer and the material surface. Pores may occur more frequently, particularly when the material surface is a cast material.The deficiencies may also include cracks, particularly those running vertically to the material surface within the applied functional layer. The deficiencies may also result from powder particles, particularly carbides, of the powdered filler material dissolving in a matrix material of the powdered filler material, leading to embrittlement of the matrix material. The invention further aims, in particular, to provide a reliable jet nozzle that is resistant to thermal stress. The invention may further aim to design the jet nozzle in such a way that it ensures reliable and precise laser cladding over very high cycle numbers.

[0006] The problem is solved by a jet nozzle having the features of claim 1. Advantageous further developments emerge from the subclaims, the description, and the figures.

[0007] Accordingly, a beam nozzle for laser cladding along a feed direction is proposed, which has a light channel for guiding at least two laser beams directed onto a workpiece. Laser cladding can be a high-speed laser cladding (HS-LMD) process.

[0008] The feed direction is the direction in which the jet nozzle moves relative to the workpiece. It can result from a movement, particularly a rotational movement, of the workpiece, a movement of the jet nozzle, or a combination of both movements.

[0009] The feed direction and the corresponding feed motion can be constant throughout the process. Alternatively, they can vary depending on the process stage.

[0010] The workpiece can be a rotationally symmetrical workpiece, such as a brake disc, a hydraulic cylinder, a printing roller, or a plain bearing. The laser beam can shine through the light channel. It can be provided by a laser source, from which the laser beam is guided via a fiber optic cable to a laser system that splits the laser beam using a collimating lens and focuses it using laser optics for the process before it enters the jet nozzle. The light channel can be a hollow channel that runs longitudinally through the entire jet nozzle. In addition to the laser beam, a process gas can also be guided to the workpiece surface through the light channel.

[0011] The blasting nozzle further comprises a powder unit arranged radially outside the light channel for guiding at least one powder jet to be applied to the workpiece. The powder unit may be arranged radially outside the light channel, starting from the longitudinal direction of the blasting nozzle, and may be part of an external structure that encloses the light channel. The powder jet may guide a powdered filler material consisting of hard material particles, in particular carbides, and a matrix material. The powder unit may be the part of the blasting nozzle intended to guide the powdered filler material directly or indirectly. The powder unit may comprise injector guides into which powder injectors can be inserted. It may also comprise an annular gap within which the powdered filler material is guided.

[0012] A cross-sectional area of ​​the light channel running orthogonally to a longitudinal direction of the jet nozzle is designed in the manner of an elongated hole at a distal region of the jet nozzle formed by a nozzle mouth, in which a partial circular section adjoins two opposite ends of a rectangular section. By designing it in the manner of an elongated hole, more than one process zone can be provided on the workpiece. The jet nozzle is an elongated component in the expanded form. The longitudinal direction can be the direction in which the jet nozzle is aligned. The jet nozzle has a cross-section orthogonal to the longitudinal direction, part of which is the shape of the light channel. In this case, this is designed in the manner of an elongated hole.

[0013] The light channel can be axially symmetric along the feed direction and point-symmetric about a center point of the light channel's cross-section. A minimum cross-sectional area of ​​the light channel is defined by a dimension, in particular a diameter, of the laser beam. Compared to the minimum dimension, the cross-sectional area is elongated along the feed direction.

[0014] The light channel is adapted to guide a first laser beam as the primary beam and a second laser beam as the secondary beam.

[0015] The respective centers of the primary beam and the secondary beam can be offset in a line from a center point of the light channel. In other words, the centers of the primary beam and the secondary beam are spaced apart from each other.

[0016] The primary beam may be concentric in cross-section to a front partial circle section of the cross-sectional area of ​​the light channel and the secondary beam may be concentric in cross-section to a rear partial circle section of the cross-sectional area of ​​the light channel.

[0017] The jet nozzle can thus provide increased variability in (i) laser beam guidance, (ii) the application of powdered filler material, (iii) thermal management, and / or (iv) the protection of the laser system including the jet nozzle. It enables the provision of multiple independent process zones with high precision. The process zones can be divided into zones for laser cladding and zones for pre- and / or post-processing.

[0018] In the laser cladding zones, an interaction takes place between at least one laser beam and a powdered filler material. Pre- and / or post-processing can include cleaning the material surface, preheating the material surface before the powdered filler material is applied, post-heating the material surface after the powdered filler material has been applied, or a combination thereof. During pre- and / or post-processing, the laser beam can strike the workpiece without interacting with the powdered filler material. The independent process zones can increase the weld quality and thus the load-bearing capacity of the applied functional layer, in particular the wear-resistant layer, and of the workpiece as a whole. An additional process gas can stabilize the process zones and increase the precision of the laser cladding as well as the service life of the beam nozzle.

[0019] In particular, the blasting nozzle can reduce the occurrence of fusion defects. Fusion defects can occur when the surface heated by the laser beam, such as the workpiece or a previously welded functional layer, has not been sufficiently heated. This insufficient heating can be the result of the laser power of a single laser beam being kept low in order to prevent overheating of the powdered filler material. The increased variability of the laser beam guidance, the increased variability of the application of a powdered filler material, and / or the increased variability of the heat management of the blasting nozzle can reduce or even prevent the occurrence of fusion defects, particularly when the blasting nozzle guides a primary beam and a secondary beam through its elongated shape, creating multiple process zones.

[0020] In particular, the blasting nozzle can reduce the occurrence of pores between the welded functional layer and the surface heated by the laser beam. Pores can occur when lamellae in the workpiece, especially graphite lamellae, evaporate due to the laser radiation. Pores can also occur if the surface to be machined contains contaminants, for example, caused by oils, greases, cooling lubricants, or oxides, which cannot be completely removed by the welding process. The undesired evaporation of contaminants can be the result of the laser power of an individual laser beam being set so high that fusion defects due to insufficient heating can be avoided.Due to the increased variability of the laser beam guidance, the increased variability of the application of a powdered filler material and / or the increased variability of the heat management of the blasting nozzle, the occurrence of pores can be reduced or even avoided, in particular by the blasting nozzle guiding a primary beam and a secondary beam through the elongated shape, which result in several process zones.

[0021] In particular, the blasting nozzle can reduce the occurrence of cracks in the welded functional layer. Cracks can occur when the temperature gradient between the highly heated powdered filler material and the less heated workpiece surface is so strong that material shrinkage occurring during cooling leads to crack-causing stresses. Crack formation can be the result of setting the laser power of a single laser beam so high that fusion defects due to insufficient heating can be avoided.Due to the increased variability of the laser beam guidance, the increased variability of the application of a powdered filler material and / or the increased variability of the heat management of the blasting nozzle, the occurrence of cracks can be reduced or even avoided, in particular by the blasting nozzle guiding a primary beam and a secondary beam through the elongated shape, which create several process zones.

[0022] Furthermore, the blasting nozzle can reduce the dissolution of hard material particles, especially carbides, in the matrix material. The powdered filler material can comprise hard material particles, especially carbides, and a matrix material. The hard material particles should be present undissolved in the welded functional layer to increase the load-bearing capacity of the functional layer. However, hard material particles can dissolve if the powdered filler material is exposed to excessive irradiation intensity, causing the hard material particles to melt.

[0023] Dissolved hard material particles cause embrittlement of the welded functional layer because the matrix material is less ductile, meaning that stresses caused, for example, by shrinkage during cooling or loading of the workpiece cannot be absorbed by the matrix material. Through increased variability of the laser beam guidance, increased variability in the application of a powdered filler material, and / or increased variability in the heat management of the blasting nozzle, the dissolution of hard material particles can be reduced or even prevented, particularly by guiding the blasting nozzle through its elongated shape with a primary beam and a secondary beam, which create multiple process zones.

[0024] In particular, the blasting nozzle can prevent powder particles from adhering to the nozzle orifice. Due to the high process heat, reflected laser radiation and / or metal vapor flare can cause filler material to adhere or even fuse to the nozzle orifice, disrupting the gas and powder flows and subsequently impairing the process outcome. Metal vapor flare is a result of the partial evaporation of the material during laser cladding. It can lead to scattering and / or absorption of laser radiation and subsequently impair preheating of the workpiece. This can further promote the formation of fusion defects.Due to the increased variability of the laser beam guidance, the increased variability of the application of a powdered filler material and / or the increased variability of the heat management of the blasting nozzle, the undesirable dissolution of hard material particles as well as the propagation of the metal vapor flare can be reduced or even avoided, in particular by the blasting nozzle guiding a primary beam and a secondary beam through the elongated shape, which create several process zones.

[0025] At least two laser beams are guided along the cross-sectional area of ​​the light channel, which is designed like an elongated hole, in such a way that more than one process zone is formed. This promotes the welding behavior and reduces deficiencies in the weld joint, in particular the occurrence of lack of fusion, pores, cracks and / or the dissolution of carbides in the matrix material, and increases the load-bearing capacity of the applied functional layer. This allows the melting behavior, the powder jet behavior, the material bond, and the cooling behavior to be variably adapted to the respective application and the prevailing material properties and process parameters. In particular, it can be avoided that the laser power supplied to the workpiece in the area of ​​the melt pool and to the powdered filler material is too high or too low to achieve the desired process result.

[0026] For example, in addition to a primary laser beam for laser material deposition, a secondary laser beam for pre- or post-processing can be guided within the light channel in close proximity to a first processing location. The secondary laser beam can be guided before or after the primary laser beam in the feed direction, depending on whether it is used for pre- or post-processing. A geometrically close arrangement of the secondary laser beam to the primary laser beam reduces thermal losses due to heat conduction within the workpiece, which promotes the bond between the powdered filler material and the material. The elongated shape enables welding behavior without the aforementioned deficiencies.

[0027] In one embodiment, the cross-sectional area at a distal region of the jet nozzle formed by a nozzle mouth is designed in the manner of an elongated hole, in which a partial circular section is connected to two opposite ends of a rectangular section. 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 represents the part of the nozzle mouth closest to the workpiece. At the section facing away from the workpiece, the jet nozzle has a proximal region and a flange section. The proximal region and the flange section are the part of the jet nozzle facing away from the workpiece. The nozzle can be coupled to another component of the laser system, such as laser optics or a process unit, via the flange section.

[0028] In one embodiment, the cross-sectional area, particularly in the region of the nozzle mouth, is elongated such that it is at least 1.5 times, and in particular at least twice, as large in the feed direction as it is transverse to the feed direction. In particular, the distance between the two partial circles can be more than twice the distance between the two parallel flanks of the elongated hole. This creates the prerequisite for more than one laser beam to be guided in the light channel in order to provide corresponding process zones. The cross-sectional area can increase even further, starting from the nozzle mouth in the direction of the proximal section. In this way, the cross-sectional area can reach its smallest dimension in the region of the distal section. This smallest dimension can also be such that it is sufficient for guiding several laser beams.

[0029] In one embodiment, a center point of the cross-sectional area is eccentric to the at least one laser beam center point of the at least one laser beam. Thus, the laser beam can be guided outside of a center point to ensure a division of the jet nozzle and the laser beam orientations it generates into multiple process zones.

[0030] The primary beam and the secondary beam can originate from the same fiber optic cable. A supplied laser light can be split into a parallel beam bundle using a collimating lens. The beam bundle can, for example, form the primary beam and the secondary beam from a single laser beam using a wedge plate. In this case, the primary beam and the secondary beam can have the same wavelength and carry the same energy. Alternatively, the primary beam and the secondary beam can differ in terms of their wavelength and energy. The respective centers of the primary beam and the secondary beam can be offset in the feed direction in a line from a center of the light channel. Providing a plurality of laser beams facilitates the reliable implementation of multiple process zones.

[0031] In one embodiment, the secondary beam is adapted to interact less with the powder jet than the primary beam, wherein the secondary beam is located ahead of the primary beam in the feed direction in order to preheat the workpiece. The interaction of the primary beam and the secondary beam with the powder jet can be achieved by appropriately guiding the respective laser beam and / or by appropriately guiding the powder jet. For example, the powder unit can form a powder section at a nozzle mouth in a circumferential direction around the light channel, which is adjoined in the circumferential direction by a powder unit-free feed section. The feed section surrounds the part of the light channel facing the feed direction. Thus, the feed section can ensure that the powder jet does not interact with the secondary beam, so that the secondary beam can be used to preheat the workpiece and not the powder particles.

[0032] In one embodiment, the secondary beam is adapted to interact less with the powder jet than the primary beam, wherein the secondary beam is located behind the primary beam in the feed direction in order to reheat the workpiece. The interaction of the primary beam and the secondary beam with the powder jet can be realized via appropriate guidance of the respective laser beam and / or via appropriate guidance of the powder jet. For example, a powder unit-free feed section can surround the part of the light channel that faces away from the feed direction. Thus, the feed section can ensure that the powder jet is not integrated with the secondary beam, so that the secondary beam can be used for reheating or cleaning the workpiece.

[0033] The powder unit may have a first powder section forming a first powder focus, and the primary jet may have a jet center coincident with the first powder focus.

[0034] The powder unit may further comprise a second powder section forming a second powder focus, and the secondary jet may have a jet center coincident with the second powder focus.

[0035] In one embodiment, the plurality of laser beams has a third laser beam as a tertiary beam, which is adapted to interact less with the powder jet than the primary beam, wherein the primary beam is located in front of the tertiary beam in the feed direction. The respective cross-sections of the primary beam, the secondary beam, and the tertiary beam can run along a line, i.e., have their respective centers along a line. This line can be aligned with the feed direction. It can also be congruent with it. At least three different process zones can be realized using the primary beam, the secondary beam, and the tertiary beam, which favor the welding behavior.

[0036] In one embodiment, with the plurality of laser beams, the laser beam that is at the front in the feed direction, for example, the secondary beam, is concentric in cross-section with a front partial circular section of the cross-sectional area, and / or the laser beam that is at the rear in the feed direction, for example, the tertiary beam, is concentric in cross-section with a rear partial circular section of the cross-sectional area. This enables efficient spatial utilization of the cross-sectional area of ​​the light channel when guiding multiple laser beams.

[0037] In one embodiment, for the plurality of laser beams, a center point of the cross-sectional area is congruent with a center point of the plurality of laser beams. The center point of the cross-sectional area can be the point at which the cross section is point-symmetric. The center point of the plurality of laser beams can be the point at which the respective laser beams have their center point in the cross section. By congruently matching these points, the spatial utilization of the cross-sectional area of ​​the light channel is further optimized when guiding multiple laser beams.

[0038] In one embodiment, the jet nozzle has exactly one light channel, so that the plurality of laser beams within the jet nozzle are guided to one another without shielding. The one light channel thus guides the plurality of laser beams without the need for separate shielding around each laser beam. This simplifies the nozzle design and facilitates heat dissipation.

[0039] In one embodiment, the jet nozzle is manufactured using an additive manufacturing process, in particular powder bed melting. 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 processes on the one hand and ensures sufficient strength, thermal conductivity, and heat resistance to withstand the process requirements on the other. In powder bed melting, the material to be processed is in powder form. A laser beam heats the powder along the intended geometry, liquefying the powder and bonding it together. Powder bed melting can, for example, be implemented as selective laser melting ("SLM") or selective laser sintering ("SLS").

[0040] In one embodiment, the nozzle mouth has a bevel by which a portion of the nozzle mouth is cut off, wherein the bevel is essentially flat and runs in a plane that is inclined with respect to the longitudinal direction of the jet nozzle. The bevel can cut off the powder section and the feed section free of powder section in the circumferential direction around the light channel. The bevel reduces the volume of the nozzle mouth compared to the embodiment in which no bevel is provided. Thus, the nozzle mouth takes up less installation space. The jet nozzle with the bevel can be used, for example, to coat a brake disc that has a receptacle that protrudes axially relative to the functional surface to be coated. The bevel ensures that the jet nozzle can be flexibly moved on the functional surface to be coated and can be moved close to the receptacle.The bevel can run in the distal area like a passante on the elongated hole. The passante defines the orientation of the bevel at the nozzle mouth. The passante runs in the end face of the jet nozzle facing the workpiece along a straight line or an arc that neither intersects nor touches the elongated hole. The distance of the passante from the center of the light channel is greater than the distance of the corresponding section of the elongated hole from the center of the light channel. The distance between the passante and an outer edge of the elongated hole is selected such that the wall thickness in between ensures sufficient strength and load-bearing capacity of the jet nozzle.

[0041] In one embodiment, the jet nozzle is adapted to guide the laser beam along the longitudinal direction of the jet nozzle, so that the at least one laser beam runs orthogonally to the cross-sectional area. Furthermore, the light channel can be adapted to guide a protective gas at a radially outer portion for shielding a process zone.

[0042] The features disclosed contribute, partly individually and partly in combination, to overcoming the deficiencies in laser cladding mentioned at the outset. Short description of the characters

[0043] Preferred further embodiments of the invention are explained in more detail in the following description of the figures. In the figures: Fig. 1 a schematic view of a jet nozzle in a laser cladding process; Fig. 2 a jet nozzle in a side view; Fig. 3 the jet nozzle Fig. 2 in a perspective view; Fig. 4 the jet nozzle Fig. 2 connected to other components; Fig. 5 the jet nozzle Fig. 2 in a plan view of a distal region; Fig. 6 the jet nozzle Fig. 2 in a plan view of a flange section; Fig. 7 another perspective view of the jet nozzle from Fig. 2; Fig. 8 a perspective sectional view of the jet nozzle from Fig. 2; Fig. 9 the jet nozzle in a further embodiment in a plan view of a distal region; Fig. 10 the jet nozzle with a process gas unit in a plan view of the distal area; Fig. 11 shows a further embodiment of the jet nozzle with a geometrically adapted nozzle mouth in a side view; and Fig. 12 a further embodiment of the jet nozzle with a geometrically adapted nozzle mouth in a plan view. Detailed description of preferred embodiments

[0044] Preferred embodiments are described below with reference to the figures. Identical, similar, or equivalent elements in the different figures are provided with identical reference numerals, and a repeated description of these elements is partially omitted to avoid redundancies.

[0045] Fig. 1 shows a jet nozzle 1 for laser material deposition along a feed direction 2. The feed direction 2 is the direction along which the jet nozzle 1 moves relative to a workpiece 100. It can result from a movement, in particular a rotational movement, of the workpiece 100, from a movement of the jet nozzle 1, or from a superposition of a movement of the workpiece 100 and the jet nozzle 1. The feed direction 2 and the correlating feed movement can be constant throughout the process. Alternatively, they can vary with the respective process stage. The workpiece 100 can be a rotationally symmetrical workpiece, such as a brake disc, a hydraulic cylinder, a printing roller, or a plain bearing. At least one laser beam 110 emerges from a light channel 3 with a lateral surface 4.The light channel 3 can also be adapted to guide a process protective gas 150 at a radially outer portion to shield a process zone and prevent 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. The powder unit 7 can, for example, have a plurality of injector guides 19 (see . Fig. 3), into each of which a powder injector 16 (for this Fig. 4). As an alternative to the individual injector guides 19, the powder unit 7 can have a powder annular gap channel. A powdered filler material 120 is directed onto the workpiece 100 via the powder unit 7 and the powder injectors 16 arranged therein. The laser beam 110 heats the workpiece 100 such that a melt pool 130 forms on a material surface. In addition, the laser beam 110 heats the powdered filler material 120, which comprises hard material particles and a matrix material. For this purpose, the laser beam 110 can have a reduced core intensity. As soon as the melt pool 130 cools, a welded functional layer 140, for example a wear-resistant layer, forms from the hard material particles and the matrix material. The welded functional layer 140 makes the material surface more resistant and increases its load-bearing capacity.

[0046] Fig. 2 shows the jet nozzle 1 in a side view, with the feed direction 2 pointing out of the plane of the drawing. The jet nozzle 1 can be coupled to other components of a laser system, such as laser optics or a process adapter, via a flange section 9. A proximal region 10 adjoins the flange section 9. A coolant inlet 13 and a coolant outlet 14, which are part of a cooling system of the jet nozzle 1 and which protrude radially from the jet nozzle 1, can be provided at least partially in the proximal region 10. A distal region 8 is formed at the end of the jet nozzle 1 opposite the proximal region 10. The distal region is a component of the funnel-shaped nozzle mouth 6. This nozzle mouth has, in a circumferential direction around the light channel 3, a powder section 11 in which the powder unit 7 is arranged.A powder unit-free feed section 12 adjoins the powder section 11 in the circumferential direction. The feed section 12 can be used as a process gas section 61 (see, for example, . Fig. 9) which is part of a process gas unit 60.

[0047] Fig. 3 shows the jet nozzle from Fig. 2 in a perspective view. The light channel 3 is a hollow channel with the lateral surface 4, within which the at least one laser beam 110 runs. The outer structure 5 surrounds the light channel 3 from the flange section 9 to the distal region 10. The nozzle mouth 6 is a substantially funnel-shaped region of the jet nozzle 1. The funnel shape of the nozzle mouth 6 serves, among other things, to enable the nozzle mouth 6 to form the plurality of injector guides 19 in the region of the powder unit 7. In each of these injector guides 19, a powder injector 16 (see Fig. 4) is used, which directs the powdered filler material 120 onto the at least one laser beam 110 and / or the workpiece 100 in a process-appropriate manner. The powder unit 7 extends along the powder section 11, which is adjoined in the circumferential direction by the powder unit-free feed section 12. The feed section 12 is the region of the nozzle mouth 6 in which no injector guides 19 are provided, so that no powdered filler material 120 is supplied via it. In one embodiment, the feed section 12 can be shaped as a process gas section 61, so that a process gas is supplied via it. The jet nozzle 1 can be manufactured using additive manufacturing methods, in particular using powder bed melting. For this purpose, the jet nozzle 1 can be made of a copper-chromium-zirconium alloy.This is suitable for additive manufacturing processes and, on the other hand, ensures sufficient strength, thermal conductivity, and heat resistance to withstand the process requirements. In powder bed melting, the material to be processed is in powder form. A laser beam heats the powder along the intended geometry, liquefying the powder and bonding it together. Powder bed melting can be implemented, for example, as Selective Laser Melting ("SLM") or Selective Laser Sintering ("SLS").

[0048] Fig. 4 shows the blasting nozzle 1 with additional components attached. A coupling ring 15 is connected to the flange section 9, which secures the blasting nozzle 1 to the connected unit, for example, the laser optics or the process adapter. Powder injectors 16 are inserted into the injector guides 19 of the powder unit 7. The powder injectors 16 convey the powdered filler material 120 and apply it to the workpiece 100 with the intended focus. The individual powder injectors 16 can apply different powder foci. Alternatively, the powder injectors 16 can be directed at the same focus point. The powder injectors 16 are arranged in the designated injector guides 19 of the powder unit 7 in the powder section 11. The feed section 12 is free of powder injectors 16. Furthermore, an inlet nozzle 17 is inserted into the coolant inlet 13 and an outlet nozzle 18 is inserted into the coolant outlet 14.These connect the coolant inlet 13 and the coolant outlet 14 to a coolant circuit.

[0049] Fig. Figure 5 shows the jet nozzle 1 in a plan view of the distal region 8. The cross-sectional area of ​​the light channel 3, which runs orthogonally to the longitudinal direction of the jet nozzle 1, deviates from a circular shape and is elongated in the feed direction 2. In the distal region 8, the cross-sectional area of ​​the light channel 3 is designed like an elongated hole, with a partial circular section adjoining two opposite ends of a rectangular section. Two laser beams are guided within the light channel 3: a primary beam 111 and a secondary beam 112. The primary beam 111 and the secondary beam 112 can originate from the same fiber optic cable. A provided laser light can be split into a parallel beam bundle via a collimating lens. The beam bundle can, for example, form the primary beam 111 and the secondary beam 112 from a single laser beam using a wedge plate.The respective centers of the primary beam 111 and the secondary beam 112 are offset in a line in the feed direction 2 to a center 20 of the light channel 3.

[0050] In this case, the secondary beam 112 is located in front of the primary beam 111 in the feed direction 2 and does not interact with a powder caustic. The secondary beam 112 can thus be used to preheat the workpiece 100 before the primary beam 111 and the powdered filler material 120 heated by the primary beam 111 strike the workpiece 100. The secondary beam 112 thus creates a first process zone that serves to preheat the workpiece 100, and the primary beam 111 creates a second process zone that serves to weld the powdered filler material 120 onto the workpiece 100. These different process zones enable defect-free welding in which no deficiencies, in particular no fusion defects, pores, cracks, and / or dissolution of carbides in the matrix material, occur. It is also possible to guide the secondary beam 112 in the feed direction 2 after the primary beam 111.Thus, the secondary beam 112 can be used to reheat the workpiece 100 and thus contribute to a more uniform cooling, which prevents the occurrence of inclusions or other imperfections.

[0051] The primary beam 111 and the secondary beam 112 are arranged in close proximity to one another. The front partial circle section of the elongated hole in the feed direction 2 is concentric with the secondary beam 112, while the rear partial circle section of the elongated hole is concentric with the primary beam 111. A center of the cross-sectional area is eccentric to a center point of the primary beam 111 and to a center point of the secondary beam 112. A tertiary beam can also be provided, so that, for example, the secondary beam is arranged in front of the primary beam in the feed direction and the tertiary beam is arranged after the primary beam in the feed direction. The individual laser beams are guided unshielded from one another, so that there is exactly one light channel 3 with exactly one lateral surface 4, which results in minimal thermal losses.

[0052] Because the primary beam 111 in Fig. 5 is arranged behind the secondary jet 112 in the feed direction 2 without radial offset and the secondary jet 112 serves to preheat the workpiece, it is desirable that the powdered filler material does not interact with the secondary jet 112. This ensures that, on the one hand, the secondary jet 112 can exclusively perform the function of preheating the workpiece and, on the other hand, the powdered filler material is only heated by the primary jet 111 and not by the secondary jet 112. This is achieved by the jet nozzle 1 shaping the powder unit 7 in the region of the nozzle mouth 6 in such a way that it forms the powder section 11 in the circumferential direction around the light channel 3, to which the powder unit-free feed section 12 is connected in the circumferential direction.In addition to the powder unit 7, the process gas unit 60 can also be formed, which forms the process gas section 61, in which case the feed section 12 is formed as a process gas section 61. The feed section 12 is formed in a region of the nozzle mouth 6 facing the feed direction 2. The powder section 11 extends along the elongated hole that forms the cross-sectional area of ​​the light channel 3 in the distal region 8. Analogous to a circular arc, the powder section 11 extends along an elongated hole arc, in particular horseshoe-shaped, around the light channel 3. The powder section 11 therefore extends in the circumferential direction around the light channel 3 by a wrap angle of less than 360°, in particular between 90° and 330°, further in particular between 180° and 300°, relative to a center point of the light channel.This ensures that the powdered filler material flowing out of the injectors 16, which are inserted into the injector guides 19, interacts only with the primary jet 111. The secondary jet 112 can thus form a process zone independent of the primary jet 111. The powder section 11 and the feed section 12 form a slotted hole in plan view. This further contributes to reducing or avoiding the deficiencies identified above.

[0053] Fig. 6 shows the jet nozzle 1 in a plan view of the flange section 9. The cross-sectional area of ​​the light channel 3, which runs orthogonally to the longitudinal direction of the jet nozzle 1, also deviates from a circular shape in the region of the flange section 9 and is elongated in the feed direction 2. The elongation of the cross-sectional area can decrease from the distal region 8 to the flange section 9. In the region of the nozzle mouth 6, the cross-sectional area can be elongated such that it is at least 1.5 times, in particular at least twice, as large in the feed direction as it is transverse to the feed direction. The flange section 9 has such a radial extension that the injector guides 19 are not visible from the plan view of the proximal region 10.

[0054] Fig. Figure 7 shows the jet nozzle 1 in a further perspective view. The nozzle mouth 6 has a curved funnel shape. The injector guides 19, into which the powder injectors 16 can be inserted, are formed within the individual curvatures. In the feed direction 2, the light channel is elongated in a manner deviating from a circular shape in order to achieve the advantages disclosed. In the circumferential direction around the light channel 3, the nozzle mouth 6 has the powder unit 7. This extends in the circumferential direction around the light channel 3 along the powder section 11, which is adjoined by the powder-free feed section 12.

[0055] Fig. 8 shows a perspective sectional view of the jet nozzle 1. The light channel 3 has a conical shape, so that the cross-sectional area of ​​the light channel 3 running 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 in the radial direction from the jet nozzle 1. Fig. Figure 8 shows a section through an injector guide 19. This is arranged in the powder section 11. In the feed section 12, no injector guide 19 is provided for guiding the powder jet. The jet nozzle 1 has a cooling system 30. A cooling medium, for example water, is returned to a radially inner cooling chamber 31 via the coolant inlet 13 in the proximal region 10. The cooling medium can be distributed in the proximal region 10 in the circumferential direction around the light channel 3. The cooling medium runs from the proximal region 10 to the nozzle mouth 6. The radially inner cooling chamber 31 is formed at least in the nozzle mouth 6. It can run from the distal region 8 to the proximal region 10 and be designed in the manner of an annular gap segment that extends circumferentially around the light channel 3. In the area of ​​the nozzle mouth 6, the radially inner cooling chamber 31 extends in the circumferential direction around the light channel 3.The radially inner cooling chamber 31 has a constant width in the radial direction in the region of the nozzle mouth 6 and is concentric to the light channel 3 in a cross-sectional area extending orthogonally to a longitudinal direction of the jet nozzle 1.

[0056] In the distal region 8, a transition 32 is provided between the radially inner cooling chamber 31 and a radially outer cooling chamber 33. The radially outer cooling chamber 33 has a radial width that decreases in the radial direction in the region of the nozzle mouth 6 towards the distal region 8. The radially outer cooling chamber 33 extends from the distal region 8 to the proximal region 10, where it supplies the heated coolant to the coolant outlet 14. The transition 32 between the radially inner cooling chamber 31 and the radially outer cooling chamber 33 is arranged in the feed section 12. The feed section 12 does not have any injector guides 19 for guiding the powder jet, which means that there is sufficient installation space for the transition 32.

[0057] The radially outer cooling chamber 33 has a cooling structure for surface enlargement. The cooling structure can be manufactured using an additive manufacturing process. It ensures that the cooling medium comes into contact with as much surface area as possible during the return from the distal region 8 to the proximal region 10 in order to promote heat dissipation. The cooling structure is optimized to cause the lowest possible pressure losses of the cooling medium. This can be achieved by a honeycomb structure 34, as shown in Fig. 8 can be achieved.

[0058] Fig. Figure 9 shows the jet nozzle 1 of a further embodiment in a plan view of the distal region 8. The cross-sectional area of ​​the light channel 3, which runs orthogonally to the longitudinal direction of the jet nozzle 1, deviates from a circular shape and is elongated in the feed direction 2. In the distal region 8, the cross-sectional area of ​​the light channel 3 is designed like an elongated hole, in which a partial circular section adjoins two opposite ends of a rectangular section. The primary beam 111 and the secondary beam 112 are guided within the light channel 3. The respective centers of the primary beam 111 and the secondary beam 112 are offset in the feed direction 2 in a line from the center point 20 of the light channel 3.

[0059] The primary beam 111 has a beam center that coincides with a first powder focus 21. The first powder focus 21 is the point on which the injectors of a first powder section 22 are focused. The first powder section 22 forms a first powder caustic. Accordingly, the secondary beam 112 has a beam center that coincides with a second powder focus 23. The second powder focus 23 is the point on which the injectors of a second powder section 24 are focused. The second powder section 24 forms a second powder caustic. The primary beam 111 and the secondary beam 112 are offset from one another in the feed direction 2. Accordingly, the first powder focus 21 is also offset from the second powder focus 23. The powder unit 7, which has the first powder section 22 and the second powder section 24, can thus form two different powder foci.In addition, a powder mass flow delivered from the injectors of the first powder section 22 can differ from a powder mass flow delivered from the injectors of the second powder section 24. A gap can be provided between the first powder section 22 and the second powder section 24, so that the powder mass flow delivered by the first powder section 22 interacts exclusively with the primary jet 111 and the powder mass flow delivered by the second powder section 24 interacts exclusively with the secondary jet 112.

[0060] The first powder section 22 and the second powder section 24 contribute to an increase in the deposition rate by creating at least two process zones within the jet nozzle 1. This can increase the track width of the applied functional layer. Furthermore, improved shielding gas coverage with lower shielding gas consumption is achieved, as the shielding gas can be more localized.

[0061] The primary beam 111 and the secondary beam 112 are arranged in close proximity to each other. The front pitch circle section of the elongated hole in the feed direction 2 is concentric with the secondary beam 112, while the rear pitch circle section of the elongated hole is concentric with the primary beam 111. The center point 20 of the cross-sectional area is eccentric to the center point of the primary beam 111 and the center point of the secondary beam 112.

[0062] Fig. 10 shows the jet nozzle 1 in a plan view of the distal area 8. The primary beam 111 and the secondary beam 112 are guided within the light channel 3. The secondary beam 112 is in front of the primary beam 111 in the feed direction 2 and does not interact with a powder caustic, as in connection with Fig. 5. During the interaction of the laser beams with the material surface and the powder jet, a vapor flare can form between the jet nozzle 1 and the workpiece 100. If this is not contained, it can interact in an undesirable manner with the at least one laser beam and / or the unprocessed and / or the processed material surface. In the area adjacent to the powder section 11, the feed section 12 can therefore be designed as a process gas section 61. This is formed by the process gas unit 60 arranged radially outside the light channel 3, which directs the process gas onto the workpiece. The process gas section 61 can prevent an undesirable spread of the vapor flare and thus contribute to precise workpiece processing with a robust jet nozzle design. The process gas section 61 can form at least one, in this case three, outlet opening 62.The outlet openings 62 are formed on an end face of the jet nozzle 1. An additional injector for supplying the process gas without additional material can be inserted into the respective outlet opening 62. The inner diameter of the outlet opening 62 can be smaller than the inner diameter of the injector guides 19. The process gas section 61 also prevents powder particles from adhering to the end face of the 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 provided circumferentially around the elongated hole formed by the light channel 3. Thus, the primary jet 111 and the secondary jet 112 are completely within the jets composed of the powder jet and the process gas jet.

[0063] Fig. 11 shows a further embodiment of the jet nozzle 1. The nozzle mouth 6 has a bevel 50, by which a portion of the nozzle mouth 6 is cut off. The bevel 50 causes the powder section 11 and the powder-section-free feed section 12 to be cut off in the circumferential direction around the light channel 3. The bevel 50 reduces the volume of the nozzle mouth 6 compared to the embodiment in which no bevel 50 is present. This ensures that the nozzle mouth 6 occupies a smaller installation space. The jet nozzle 1 with the bevel 50 can be used, for example, to coat a brake disc. The brake disc can have a receptacle that protrudes axially relative to the functional surface to be coated. The bevel 50 ensures that the jet nozzle 1 can be flexibly moved on the functional surface to be coated and can be moved close to the receptacle.The bevel 50 can be substantially flat and extend in a plane that is inclined relative to the longitudinal direction of the jet nozzle. The bevel 50 represents a boundary surface of the nozzle orifice 6, in which no powder unit 7 is provided. In the distal region 8, the bevel 50 is arranged so close to the light channel 3 that no injector guides 19 are provided on an end face of the jet nozzle 1 facing the workpiece in the region of the bevel 50.

[0064] Fig. 12 shows the jet nozzle 1 with the bevel 50 in a top view. The bevel 50 can run in the distal region 8 in the manner of a passante 51 on the elongated hole. The passante 51 defines the orientation of the bevel 50 on the nozzle mouth 6. The passante 51 runs in the end face of the jet nozzle 1 facing the workpiece along a straight line or an arc that neither intersects nor touches the elongated hole. The distance of the passante 51 from the center point 20 of the light channel 3 is greater than the distance of the corresponding section of the elongated hole from the center point 20 of the light channel 3. The distance between the passante 51 and an outer edge of the elongated hole is selected such that the wall thickness therebetween ensures sufficient strength and load-bearing capacity of the jet nozzle 1.

[0065] The orientation of the passante 51 and thus the orientation of the bevel 50 on the nozzle orifice 6 can be varied for different jet nozzles 1 depending on the respective application. For example, the passante 51 can run in the feed direction 2. In this case, the passante 51 runs along the extension of the cross-sectional area of ​​the light channel 3.

[0066] The passante 51 thus runs along the long side of the elongated hole. Alternatively, the passante 51 can, for example, run transversely to the feed direction 2. In this case, the passante 51 runs transversely to the extension of the cross-sectional area of ​​the light channel 3. The passante 51 thus runs along the partial circle section of the elongated hole. Further alternatively, the passante 51 can, for example, run at an angle to the feed direction 2 that lies between a course along the feed direction 2 and a course transversely to the feed direction 2. In this case, the passante 51 runs along the transition section between the long side of the elongated hole and the partial circle section of the elongated hole. The course of the passante 51 determines the orientation of the bevel 50.

[0067] In the embodiment in Fig.12, outlet openings 62 are provided on the end face of the jet nozzle. The process gas exits from the process gas unit 60 through these outlet openings. In the present case, the bevel 50 is such that the portion of the nozzle mouth 6 cut off by it originates entirely from the powder section 11, so that the angle along which the powder section 11 extends is reduced by the bevel 50, while the angle along which the process gas unit 60 extends remains essentially the same.

[0068] Where applicable, all individual features presented in the embodiments may be combined and / or exchanged without departing from the scope of the invention. List of reference symbols 1 jet nozzle 2 Feed direction 3 light channels 4 Shell surface 5 External structure 6 nozzle mouth 7 powder unit 8 distal area 9 Flange section 10 proximal area 11 Powder section 12 Feed section 13 Coolant inlet 14 Coolant outlet 15 Coupling ring 16 Powder injector 17 inlet nozzles 18 drain outlets 19 Injector guide 20 Center of the light channel 21 first powder focus 22 first powder section 23 second powder focus 24 second powder section 30 Cooling system 31 radial inner cooling chamber 32 Transition 33 radial outer cooling chamber 34 Honeycomb structure 50 bevel 51 passersby 60 process gas unit 61 Process gas section 62 Exit opening 100 workpieces 110 laser beam 111 Primary beam 112 Secondary beam 120 powdered filler material 130 melt pool 140 functional layer QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 10 2011 100 456 A

[0002] DE 10 2018 130 798 A1

[0002] CN 109175372 A

[0002]

Claims

[1] Jet nozzle (1) for laser deposition welding along a feed direction (2), comprising - a light channel (3) for guiding at least a first laser beam as a primary beam (111) and a second laser beam as a secondary beam (112), which are directed onto a workpiece; and - a powder unit (7) arranged radially outside the light channel (3) for guiding at least one powder jet to be applied to the workpiece; wherein the powder unit (7) has a first powder section (22) forming a first powder focus (21), and the primary jet (111) has a jet center that coincides with the first powder focus (21), and the powder unit (7) has a second powder section (24) forming a second powder focus (23), and the secondary jet (112) has a jet center that coincides with the second powder focus (23). [2] Jet nozzle (1) according to claim 1, wherein a cross-sectional area of ​​the light channel (3) extending orthogonally to a longitudinal direction of the jet nozzle (1) is designed in the manner of an elongated hole at a distal region (8) of the jet nozzle (1) formed by a nozzle mouth (6), in which a partial circular section adjoins two opposite ends of a rectangular section, and the light channel (3) is adapted to guide a first laser beam as a primary beam (111) and a second laser beam as a secondary beam (112). [3] Jet nozzle (1) according to claim 1 or 2, wherein the respective centers of the primary beam (111) and the secondary beam (112) are offset in a line from a center point (20) of the light channel (3). [4] Jet nozzle (1) according to claim 2 or 3, wherein the primary jet (111) is concentric in cross-section to a front partial circle section of the cross-sectional area of ​​the light channel (3), and the secondary jet (112) is concentric in cross-section to a rear partial circle section of the cross-sectional area of ​​the light channel (3). [5] Blasting nozzle (1) according to one of claims 1 to 4, wherein the secondary jet (112) is adapted to interact less with the powder jet than the primary jet (111), the secondary jet (112) being located in front of the primary jet (111) in the feed direction (2) in order to preheat the workpiece. [6] Blasting nozzle (1) according to one of claims 1 to 4, wherein the secondary jet (112) is adapted to interact less with the powder jet than the primary jet (111), the secondary jet (112) being located behind the primary jet (111) in the feed direction (2) in order to reheat the workpiece. [7] Jet nozzle (1) according to one of the preceding claims, which is produced by means of an additive manufacturing process and consists in particular of copper or a copper alloy, further in particular a copper-chromium-zirconium alloy. [8] Jet nozzle (1) according to one of the preceding claims, wherein the nozzle mouth (6) has a bevel (50) by which a part of the nozzle mouth (6) is cut off, wherein the bevel (50) is substantially flat and extends in a plane which is inclined with respect to the longitudinal direction of the jet nozzle (1).

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