Injection nozzle having an absorbing portion for absorbing reflected radiation

Abstract

The present invention relates to an injection nozzle (1) for laser cladding along a forward direction (2), the injection nozzle (1) comprising an optical channel (3) for guiding at least one laser beam directed onto a workpiece, and an external structure (5) which surrounds the optical channel (3) and extends from a flange portion (9) to a distal region (8) formed by the nozzle opening (6) from which the laser beam is emitted, wherein the optical channel (3) has an absorbing portion (40) for absorbing back-reflected laser radiation from the workpiece.

Description

Technical Field

[0001] The present invention relates to an injection nozzle for laser cladding along a forward direction.

Background Art

[0002] Laser cladding is used, for example, in the fields of repair, coating and / or joining techniques. A distinction can be made between conventional laser cladding techniques (laser metal deposition (LMD), direct metal deposition (DMD) or direct energy deposition (DED)) and high-speed laser cladding (high-speed laser metal deposition (HS-LMD) or extreme high-speed laser applications (EHLA)). The HS-LMD method is described, for example, in the published brochures DE 10 2011 100 456 B4 and DE 10 2018 130 798 A1. Another method related to laser cladding is known from Chinese Patent Application No. CN 109175372 A.

[0003] A functional layer can be applied to a workpiece by laser cladding. This generally increases the load-bearing capacity of the workpiece processed by laser cladding compared to the untreated workpiece. The functional layer can function, for example, as a wear protection layer. The application of the functional layer is based on the melting of the workpiece surface, the application of a powdered filler material, and subsequent cooling, so that a matrix structure with hard material particles is material-bonded to the material surface. Thus, laser cladding engages with the internal material structure of the workpiece and changes it. In certain environments, this can lead to defects in the internal material structure. These can potentially impair the desired increase in durability. Since the defects can be of a microscopic nature, they can only be identified with great effort.

[0004] Summary of the Invention Based on known prior art, the object of the present invention is to provide an improved injection nozzle for forward-oriented laser cladding. The present invention particularly aims to increase the weld quality of the deposited functional layer and the overall weld quality of the workpiece, and to reduce or avoid defects in the weld joint between the powdered filler and the material surface. Defects may be poor bonding between the material surface and the applied functional layer, or between individual applied functional layers. Defects may also be pores, i.e., air inclusions occurring within the applied functional layer or between the applied functional layer and the material surface. Pores may occur more frequently, especially when the material surface is a cast material. Defects may also be cracks extending perpendicular to the material surface within the applied functional layer. Defects may also arise from the fact that powder particles of the powdered filler, particularly carbides, dissolve into the matrix material of the powdered filler, which leads to embrittlement of the matrix material. The present invention also aims particularly to provide a reliable injection nozzle that is resistant to thermal stress. The present invention may also aim to design injection nozzles to ensure reliable and precise laser cladding over a very large number of cycles.

[0005] The objective is achieved by an injection nozzle having the features of claim 1. Advantageous developments arise from the dependent claims, the detailed description of the invention, and the drawings.

[0006] Therefore, a jet nozzle for laser cladding along the forward direction is proposed, which has an optical channel for guiding at least one laser beam directed onto the workpiece. Laser cladding can be a method for high-speed laser metal deposition (HS-LMD). The forward direction is the direction in which the jet nozzle moves relative to the workpiece. It can result from the movement of the workpiece, particularly rotational movement, the movement of the jet nozzle, or a superposition of both movements. The forward direction and the corresponding forward movement can be constant throughout the process. Alternatively, they can vary at each process stage. The workpiece can be a rotationally symmetric workpiece such as a brake disc, hydraulic cylinder, pressure roller, or sliding bearing. The laser beam can shine through the optical channel. The laser beam can be provided by a laser light source, from which the laser beam is guided to a laser system by an optical fiber cable, which splits the laser beam through a collimator lens, focuses it through a laser optical system along the process, and then directs it into the jet nozzle. The optical channel may be a hollow channel that extends longitudinally through the entire injection nozzle. In addition to the laser beam, the process gas can also be directed to the workpiece surface through the optical channel.

[0007] The injection nozzle further comprises an external structure surrounding the optical channel, the external structure extending from a flange portion to a distal region formed by the nozzle opening from which the laser beam is emitted. The external structure may include a powder unit, which may be part of the nozzle opening. The nozzle opening is the part of the injection nozzle facing the workpiece. The end portion of the nozzle opening forms the distal region, which is the part of the nozzle opening closest to the workpiece. In the portion facing away from the workpiece, the injection nozzle has a proximal region and a flange portion. The proximal region and flange portion are the parts of the injection nozzle facing away from the workpiece. The nozzle may be coupled via the flange portion to further components of the laser system, such as a laser optical system or a process unit. The external structure may be a component made of a homogeneous material and may have a hollow channel forming the optical channel along its longitudinal direction.

[0008] The optical channel forms an absorptive portion for absorbing the back-reflected radiation of the laser beam from the workpiece. The absorptive portion may have a geometric shape that promotes the absorption of back-reflected radiation. The absorptive portion can extend in various ways circumferentially around the optical channel. It can also extend in various ways longitudinally around the optical channel. In particular, the absorptive portion 40 is not formed in the distal region of the nozzle opening to facilitate cleaning of the nozzle opening. The shape of the absorptive portion can be adapted to the expected back-reflected radiation. The absorptive portion can be formed from the same material as the rest of the injection nozzle. It may also have a coating. The laser radiation absorbed by the absorptive portion can be dissipated by a cooling system that interacts with the absorptive portion.

[0009] The injection nozzle can therefore offer increased versatility in (i) laser beam guidance, (ii) use of powdered filler material, (iii) thermal management, and / or (iv) protection of the laser system including the injection nozzle. This makes it possible to provide multiple independent process zones with high precision. The process zones can be divided into zones for laser cladding and zones for pre-treatment and / or post-treatment. In the zone for laser cladding, interaction occurs between at least one laser beam and the powdered filler material. Pre-treatment and / or post-treatment may be cleaning of the material surface, preheating of the material surface before application of the powdered filler material, post-heating of the material surface after application of the powdered filler material, or a combination thereof. During pre-treatment and / or post-treatment, the laser beam may be irradiated onto the workpiece without interaction with the powdered filler material. Independent process zones can increase the weld quality, and therefore durability, of the applied functional layers, particularly the wear protection layer and the overall workpiece. Additional process gases can stabilize the process zones and increase the accuracy of laser cladding and the service life of the injection nozzle.

[0010] In particular, injection nozzles can reduce the occurrence of bonding failures. This is because bonding failures can occur if the surface heated by the laser beam, such as the workpiece or a previously welded functional layer, is not sufficiently heated. This insufficient heating may result from keeping the laser power of a single laser beam low to avoid overheating of the powdered filler material. Increasing the diversity of laser beam induction, increasing the diversity of powdered filler material applications, and / or increasing the diversity of thermal management of injection nozzles can reduce or even prevent bonding failures, particularly by enabling multiple process zones, as injection nozzles with absorbent portions contribute to thermal management and protection of the laser system.

[0011] In particular, injection nozzles can also reduce the occurrence of pores between the welded functional layer and the surface heated by the laser beam. This is because pores can occur when lamellae in the workpiece, especially graphite lamellae, vaporize due to laser radiation. Pores can also occur if the surface being machined has impurities, such as oil, grease, coolant lubricant, or oxides, which cannot be completely removed by the welding process. The vaporization of unwanted impurities may result from the laser power of a single laser beam being set very high to avoid bonding failures due to insufficient heating. Increasing the diversity of laser beam induction, increasing the diversity of powdered filler application, and / or increasing the diversity of thermal management of the injection nozzle can also reduce or further prevent pore occurrence, in particular, as injection nozzles with absorbent portions contribute to thermal management and protection of the laser system, enabling multiple process zones.

[0012] In particular, injection nozzles can also reduce the occurrence of cracks in the welded functional layer. This is because when the temperature gradient between the strongly heated powdered filler and the weakly heated workpiece surface is very large, the shrinkage of the material during cooling creates stress that can cause cracks. Cracks may result from the laser power of a single laser beam being set very high to avoid bonding failures due to insufficient heating. Increasing the diversity of laser beam guidance, increasing the diversity of powdered filler application and / or increasing the diversity of thermal management of injection nozzles can reduce or further prevent crack occurrence, in particular, as injection nozzles with absorption portions contribute to thermal management and protection of the laser system, enabling multiple process zones.

[0013] In particular, the injection nozzle can also reduce the dissolution of hard material particles, especially carbides, in the matrix material. Powdered filler may contain hard material particles, especially carbides, and matrix material. The hard material particles should exist in an undissolved state within the welded functional layer to increase the load-bearing capacity of the functional layer. However, if the powdered filler is exposed to excessively high radiation intensity, the hard material particles will dissolve, causing melting of the hard material particles. The melted hard material particles make the welded functional layer brittle due to the low ductility of the matrix material, meaning that, for example, stress caused by shrinkage cannot be absorbed by the matrix material when the workpiece is cooled or subjected to load. Increasing the diversity of laser beam guidance, increasing the diversity of powdered filler application, and / or increasing the diversity of thermal management of the injection nozzle can reduce or further prevent the undesirable dissolution of hard material particles, in particular, by allowing multiple process zones, as injection nozzles with absorption portions contribute to thermal management and protection of the laser system.

[0014] In particular, the injection nozzle can prevent powder particles from adhering to the nozzle opening. In principle, high process heat, reflected laser radiation, and / or metal vapor plume can cause the filler material to adhere to the nozzle opening, or even weld, which can disrupt the gas and powder flow and consequently impair the process results. The metal vapor plume is a result of the partial vaporization of the material due to laser cladding. It causes scattering and / or absorption of laser radiation, which can consequently impair the preheating of the workpiece. This can further promote the formation of poor bonding. Increasing the diversity of laser beam induction, increasing the diversity of application of powdered filler materials, and / or increasing the diversity of thermal management of the injection nozzle can reduce or further prevent undesirable dissolution of hard material particles and metal vapor plume, in particular, by allowing multiple process zones, as injection nozzles with absorption portions contribute to thermal management and protection of the laser system.

[0015] The absorbing portion of the optical channel absorbs the back-reflected radiation of the laser beam returning from the workpiece to the injection nozzle. This back-reflected radiation, which could damage the injection nozzle, can therefore be efficiently dissipated. The back-reflected radiation is absorbed by the absorbing portion in such a way that a portion of the radiation entering other components of the laser system, such as the laser optics, is reduced or eliminated. This increases process reliability and laser beam accuracy. The lifespan of the injection nozzle and laser system is also increased. The improved characteristics of the injection nozzle due to the absorbing surface enable the aforementioned defect-free welding behavior.

[0016] In one embodiment, the absorbing portion extends from the distal region to the proximal region adjacent to the flange portion. The absorbing portion can therefore extend across the entire height of the jet nozzle, excluding the flange portion and the distal region. Thus, the reflected radiation is absorbed by the absorbing portion over most of the height of the jet nozzle, contributing to efficient thermal management and protection of the laser system. For example, the distal region can extend up to 10 mm along the height within the nozzle. The absence of an absorbing portion in the distal region makes cleaning the jet nozzle easier.

[0017] In one embodiment, the absorbing portion has a serrated structure, particularly an irregular serrated structure, forming an absorbing surface facing the distal region. The serrated structure may have a Christmas tree-like contour along the longitudinal direction of the optical channel. The absorbing surface may extend along a plane perpendicular to the longitudinal direction of the optical channel. The serrated structure can be formed from the absorbing surface and a supporting surface returning to the wall of the optical channel, so that each sawtooth has a substantially triangular shape. A uniform serrated structure may have uniform sawtooth from the distal region to the proximal region. Alternatively, the sawtooth may increase in size from the distal region to the proximal region.

[0018] In one embodiment, a powder unit positioned radially outside the optical channel is formed within an external structure to guide the injection of at least one powder to be applied to the workpiece. The powder unit forms a powder portion at the nozzle opening in the circumferential direction around the optical channel, followed by a forward portion without the powder unit in the circumferential direction. The forward portion may be oriented forward, i.e., directed in the forward direction. The forward portion may extend along the circumferential direction around the optical channel over a range of angles. The region in which the forward portion is formed can correlate with the position and orientation of the powder injector that applies the powdery filler to the workpiece. Both the powder portion and the forward portion may form the entire circumference of the nozzle opening around the optical channel. For example, the powder portion may occupy a larger portion than the forward portion. In a top view, the powder portion and the forward portion may extend in a closed manner along the opening of the optical channel, for example, in the form of an elongated hole.

[0019] In one embodiment, the absorbing portion is located at least in the forward portion, particularly in the circumferential direction. Due to the incidence angle of at least one laser beam, the forward portion may be the part of the injection nozzle that is subjected to the highest thermal load. In this respect, locating the absorbing portion at least in the forward portion can further contribute to the effective thermal management and protection of the laser system. For example, the absorbing portion may be located only in the region of the forward portion, or it may be located circumferentially, i.e., 360° along the circumferential direction.

[0020] In one embodiment, the absorbing portion extends circumferentially around the entire perimeter of the optical channel. In this way, absorption of back-reflected radiation by the absorbing portion is ensured in any case of back-reflected radiation resulting from any arbitrary placement of the injection nozzle relative to the workpiece. This contributes to efficient thermal management and protection of the laser system. Alternatively, the position of the absorbing portion may be set to correlate with the inclination of the injection nozzle relative to the workpiece. Therefore, the absorbing portion does not necessarily have to be designed to extend around the entire perimeter of the optical channel. Instead, the absorbing portion is specifically positioned in a region where, due to the inclination of the injection nozzle relative to the workpiece, most of the back-reflected radiation is directed toward the injection nozzle.

[0021] In one embodiment, the longitudinal axis of the optical channel from which the laser beam extends is inclined with respect to the perpendicular to the workpiece surface in order to increase the absorption of back-reflected radiation by the absorbing portion. Therefore, the laser beam is not aligned perpendicular to the workpiece in order to specifically absorb back-reflected radiation through the absorbing portion.

[0022] In one embodiment, the end face of the injection nozzle extends at an angle to the longitudinal axis of the optical channel through which the laser beam extends, and so the end face is provided to extend in a manner parallel to the surface of the workpiece. This means that the distance from the nozzle opening to the workpiece can be increased. This reduces the thermal load on the nozzle opening. In addition, the angled end face allows for an improved range of application of the shielding gas to the workpiece. This is because the plane-parallel surface of the end face allows the flow of the shielding gas to flow perpendicular to the workpiece.

[0023] In one embodiment, the surface area of ​​the absorbing portion increases circumferentially around the optical channel from the nozzle opening to the flange portion. This can correlate with the fact that the optical channel increases toward the flange portion, thereby increasing the surface area of ​​the corresponding absorbing portion. This further contributes to thermal management by blocking radiation in the proximal region and protecting the laser optical system.

[0024] In one embodiment, the injection nozzle can be tilted relative to the workpiece, so that the absorption of back-reflected radiation by the absorbing portion can be controlled by the tilt. The alignment of the laser beam relative to the injection nozzle can be constant. Therefore, the reflection angle of back-reflected radiation can be adjusted by the tilt of the injection nozzle. The tilt interacts with the absorbing portion to capture as much back-reflected radiation as possible from the absorbing portion.

[0025] In one embodiment, the absorbent portion is provided with an absorbent coating. This may help increase the heat resistance of the absorbent portion. It may also increase the thermal conductivity of the absorbent portion. This helps ensure that the absorbent portion is not damaged even if the back reflected radiation increases.

[0026] In one embodiment, the injection nozzle is manufactured by an additive manufacturing process, particularly by powder bed fusion. For this purpose, the injection nozzle may be made from 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 hand. In powder bed fusion, the material to be processed is in powder form. A laser beam heats the powder along a provided geometry, thereby liquefying the powder and forming material bonds. Powder bed fusion may be formed using, for example, selective laser melting (SLM) or selective laser sintering (SLS).

[0027] In one embodiment, the mouth of the nozzle has a chamfered portion where a part of the mouth of the nozzle is cut off, the chamfered portion is essentially planar and extends in a plane that is inclined with respect to the longitudinal direction of the injection nozzle. The chamfered portion can cut off the powder portion and the front portion without the powder portion in the circumferential direction around the optical channel. The chamfered portion reduces the volume of the mouth of the nozzle compared to embodiments without chamfering. This means that the mouth of the nozzle takes up a smaller installation space. The injection nozzle having the chamfered portion can be used, for example, to coat a brake disk having an attachment portion that axially protrudes from the functional surface to be coated. The chamfered portion ensures that the injection nozzle can move flexibly on the functional surface to be coated and can move close to the holder. The chamfered portion can extend into the distal region in the form of a passage portion on the slot. The passage portion defines the orientation of the chamfered portion on the mouth of the nozzle. At the end face of the injection nozzle facing the workpiece, the passage portion extends along a straight line or an arc that does not intersect or contact the slot. The distance of the passage portion from the center of the optical channel is greater than the distance of the corresponding portion of the slot from the center of the optical channel. The distance between the passage portion and the outer edge of the slot is selected such that the wall thickness therebetween ensures sufficient robustness and stress resistance of the injection nozzle.

[0028] In one embodiment, the present disclosure further relates to a system comprising an injection nozzle according to the present disclosure and a workpiece. The injection nozzle is inclined with respect to the workpiece, and as a result, the longitudinal axis of the optical channel along which the laser beam extends extends deviating from the perpendicular to the workpiece surface, so that the absorption of the retroreflected radiation by the absorption portion increases. The inclination can be achieved by the relative movement of the injection nozzle with respect to the workpiece or the relative movement of the workpiece with respect to the injection nozzle. For example, the workpiece support can be inclined with respect to the injection nozzle. The inclination is adapted to the position of the absorption portion.

[0029] In one embodiment, the inclination of the nozzle with respect to the workpiece is 2° to 45°, particularly 3° to 10°. These inclination angles have been found to achieve an ideal compromise between the absorption of reflected radiation through the absorption portion and the welding behavior of laser cladding.

[0030] In one embodiment, the injection nozzle is adapted to guide the laser beam along the longitudinal direction of the injection nozzle such that at least one laser beam is orthogonal to the cross-sectional area. Further, the optical channel can be adapted to guide the shielding gas along the radially outer portion to shield the process zone.

[0031] The features according to the disclosure contribute, alone and in combination, to overcoming the deficiencies of laser cladding mentioned at the beginning.

Brief Description of the Drawings

[0032] Preferred further embodiments of the present invention are described in more detail by the following description of the drawings. [Figure 1] A schematic view of an injection nozzle during laser cladding is shown. [Figure 2] A side view of the injection nozzle is shown. [Figure 3] A perspective view of the injection nozzle from FIG. 2 is shown. [Figure 4] The injection nozzle from FIG. 2 connected to other components is shown. [Figure 5] A top view of the distal region of the injection nozzle from FIG. 2 is shown. [[ID=3?]] [Figure 6] A top view of the flange portion of the injection nozzle from FIG. 2 is shown. [Figure 7] Another perspective view of the injection nozzle from FIG. 2 is shown. [Figure 8] A perspective cross-sectional view of the injection nozzle from FIG. 2 is shown. [Figure 9] A further perspective cross-sectional view of the injection nozzle from FIG. 2 is shown. [Figure 10] A further cross-sectional view of the injection nozzle and the workpiece is shown. [Figure 11] A further perspective cross-sectional view of an injection nozzle with an angled end face is shown. [Figure 12] This shows a longitudinal cross-sectional view through an injection nozzle having a smooth inner end portion. [Figure 13] This is a top view of the distal region, showing an injection nozzle with a process gas unit. [Figure 14] A side view shows a further embodiment of an injection nozzle having a geometrically adapted nozzle opening. [Figure 15] A top view shows a further embodiment of an injection nozzle having a geometrically adapted nozzle opening. [Modes for carrying out the invention]

[0033] Preferred exemplary embodiments are described below with reference to the drawings. In these cases, elements that are the same, similar, or have the same effect are given the same reference numerals in different drawings, and repeated descriptions of these elements are omitted in some cases to avoid redundancy.

[0034] Figure 1 shows an injection nozzle 1 for laser cladding along a forward direction 2. The forward direction 2 is the direction in which the injection nozzle 1 moves relative to the workpiece 100. It can result from the movement of the workpiece 100, particularly rotational movement, the movement of the injection nozzle 1, or a superposition of the movement of the workpiece 100 and the injection nozzle 1. The forward direction 2 and its corresponding forward movement may be constant throughout the process. Alternatively, they may vary at each process stage. The workpiece 100 may be a rotationally symmetric workpiece such as a brake disc, hydraulic cylinder, pressure roller, or sliding bearing. At least one laser beam 110 is emitted from an optical channel 3 having a transverse surface 4. The optical channel 3 may also be adapted to guide a shielding gas 150 along its radially outward portion to shield the process zone and prevent oxidation. The optical channel 3 is surrounded by an external structure 5, which has a nozzle opening 6 and subsequently houses a powder unit 7. The powder unit 7 may have, for example, multiple injector guides 19 (see Figure 3), into which a powder injector 16 (see Figure 4) can be inserted. As an alternative to individual injector guides 19, the powder unit 7 may have powder ring gap channels. The powdered filler material 120 is directed onto the workpiece 100 via the powder unit 7 and the powder injectors 16 located inside it. 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 filler material 120, which includes hard material particles and matrix material. For this purpose, the laser beam 110 may have reduced core strength. As soon as the molten pool 130 cools, a welded functional layer 140, for example, a wear protection layer, is formed from the hard material particles and matrix material. The welded functional layer 140 makes the material surface more resistant and increases its load-bearing capacity.

[0035] Figure 2 shows the injection nozzle 1 in a side view with the forward direction 2 pointing outward from the drawing plane. The injection nozzle 1 may be coupled via a flange portion 9 to other components of the laser system, such as a laser optical system or a process adapter. The proximal region 10 is attached to the flange portion 9. Coolant inlet 13 and coolant outlet 14, which are part of the cooling system of the injection nozzle 1 and project radially from the injection nozzle 1, may be provided at least partially within the proximal region 10. The distal region 8 is formed at the end of the injection nozzle 1 opposite to the proximal region 10. The distal region is part of the funnel-shaped opening 6 of the nozzle. It has a powder portion 11 within the section, in which powder units 7 are arranged circumferentially around the optical channel 3. Following the powder portion 11 is a forward portion 12 without powder units, which follows circumferentially. The forward portion 12 may be designed as a process gas portion 61, which is part of a process gas unit 60 (see, for example, Figure 9).

[0036] Figure 3 shows a perspective view of the injection nozzle from Figure 2. The optical channel 3 is a hollow channel having a transverse surface 4 into which at least one laser beam 110 extends. The external structure 5 surrounds the optical channel 3 from the flange portion 9 to the distal region 10. The nozzle mouth 6 is essentially a funnel-shaped region of the injection nozzle 1. The funnel shape of the nozzle mouth 6 functions, among other things, to allow the nozzle mouth 6 to form a plurality of injector guides 19 in the region of the powder unit 7. Powder injectors 16 (see Figure 4) are inserted into each of these injector guides 19 and direct the powdered filler material 120 onto at least one laser beam 110 and / or the workpiece 100 according to the process. The powder unit 7 extends along the powder portion 11, followed circumferentially by a forward portion 12 without the powder unit. The front portion 12 is the area of ​​the nozzle opening 6, where no injector guide 19 is provided, and therefore no powdered filler material 120 is supplied through this portion. In one embodiment, the front portion 12 may be formed as a process gas portion 61, through which the process gas is supplied. The injection nozzle 1 is manufactured by an additive manufacturing process, in particular by powder bed fusion. For this purpose, the injection nozzle 1 may be made from 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 hand. In powder bed fusion, the material to be processed is in powder form. A laser beam heats the powder along a provided geometry, thereby liquefying the powder and forming material bonds. Powder bed fusion may be formed using, for example, selective laser melting (SLM) or selective laser sintering (SLS).

[0037] Figure 4 shows the injection nozzle 1 to which additional components are attached. The connecting ring 15 is connected to the flange portion 9 and attaches the injection nozzle 1 to a connecting unit, such as a laser optical system or process adapter. The powder injector 16 is inserted into the injector guide 19 of the powder unit 7. The powdered filler material 120 is transported by the powder injector 16 and applied to the workpiece 100 at a predetermined focus. Individual powder injectors 16 can use different powder focuses with respect to each other. Alternatively, the powder injectors 16 can be oriented to the same focus. The powder injector 16 is located in the powder portion 11 within the provided injector guide 19 of the powder unit 7. There is no powder injector 16 in the front portion 12. The intake connector 17 is also inserted into the coolant intake 13, and the discharge connector 18 is inserted into the coolant outlet 14. These connect the coolant intake 13 and the coolant outlet 14 to the coolant circuit.

[0038] Figure 5 shows the injection nozzle 1 in a top view of the distal region 8. The cross-sectional area of ​​the optical channel 3, which is perpendicular to the longitudinal direction of the injection nozzle 1, is deviated from a circular shape and extends in the forward direction 2. In the distal region 8, the cross-sectional area of ​​the optical channel 3 is designed in the shape of an elongated hole, in which the two opposite ends of a rectangular portion are joined by a partially circular portion. Two laser beams, a primary beam 111 and a secondary beam 112, are guided into the optical channel 3. The primary beam 111 and the secondary beam 112 may originally originate from the same optical fiber cable. The supplied laser light can be split into parallel beams via a collimator lens. The beam bundles can be formed from a single laser beam, for example, using a wedge plate to form the primary beam 111 and the secondary beam 112. The centers of the primary beam 111 and the secondary beam 112 are located in the forward direction 2 on a line offset from the center 20 of the optical channel 3.

[0039] In this example, the secondary beam 112 is located in front of the primary beam 111 in the forward direction 2 and does not interact with the powder's focal area. The secondary beam 112 can therefore be used to preheat the workpiece 100 before the primary beam 111 and the powdery filler material 120 heated by the primary beam 111 are irradiated onto the workpiece 100. The secondary beam 112 therefore creates a first process zone that functions to preheat the workpiece 100, and the primary beam 111 creates a second process zone that functions to weld the powdery filler material 120 onto the workpiece 100. These different process zones enable defect-free welding, and in particular, do not result in defects such as poor bonding, porosity, cracks, and / or dissolution of carbides in the matrix material. It is also possible to direct the secondary beam 112 in the forward direction 2 after the primary beam 111. Therefore, the secondary beam 112 can be used to reheat the workpiece 100, thereby contributing to more uniform cooling that prevents the occurrence of traps or other defects.

[0040] The primary beam 111 and the secondary beam 112 are positioned in close proximity to each other. The front circular portion of the elongated hole in the forward direction 2 is concentric with the secondary beam 112, and the rear circular portion of the elongated hole is concentric with the primary beam 111. The center of the cross-sectional area is eccentric with respect to the center of the primary beam 111 and the center of the secondary beam 112. A tertiary beam may also be provided, for example, the secondary beam being positioned in front of the primary beam in the forward direction, and the tertiary beam being positioned behind the primary beam in the forward direction. The individual laser beams are guided without shielding each other, so there is exactly one optical channel 3 with exactly one transverse surface 4, thereby minimizing heat loss.

[0041] In Figure 5, the primary beam 111 is positioned behind the secondary beam 112 in the forward direction 2 without radial offset, and the secondary beam 112 functions to preheat the workpiece. Therefore, it is desirable that the powdery filler material does not interact with the secondary beam 112. This ensures that, on the one hand, the secondary beam 112 performs only the function of preheating the workpiece, and on the other hand, that the powdery filler material is heated only by the primary beam 111 and not by the secondary beam 112. This is achieved by the injection nozzle 1 forming the powder unit 7 in the region of the nozzle mouth 6 such that it forms a powder portion 11 circumferentially around the optical channel 3, and a forward portion 12 without the powder unit follows the powder portion 11 circumferentially. In addition to the powder unit 7, a process gas unit 60 may also be formed, thereby forming a process gas portion 61, in which case the forward portion 12 is formed as the process gas portion 61. The forward portion 12 is formed in the region of the nozzle mouth 6 facing the forward direction 2. The powder portion 11 extends along the elongated pores that form the cross-sectional area of ​​the optical channel 3 in the distal region 8. Similar to a circular arc, the powder portion 11 extends around the optical channel 3, particularly along the elongated pore-like arc of a horseshoe shape. Thus, the powder portion 11 extends circumferentially around the optical channel 3 with a winding angle of less than 360°, particularly 90° to 330°, and even more particularly 180° to 300°, with respect to the center point of the optical channel. This ensures that the powdery filler material flowing out from the injector 16 inserted into the injector guide 19 interacts only with the primary beam 111. Therefore, the secondary beam 112 can form a process zone independent of the primary beam 111. The powder portion 11 and the forward portion 12 form an elongated pore shape when viewed from above. This also helps to reduce or avoid the defects identified at the beginning.

[0042] Figure 6 shows the injection nozzle 1 in a top view of the flange portion 9. The cross-sectional area of ​​the optical channel 3, perpendicular to the longitudinal direction of the injection nozzle 1, is also deviated from a circular shape in the region of the flange portion 9 and extends in the forward direction 2. The extension of the cross-sectional area may decrease from the distal region 8 to the flange portion 9. In the region of the nozzle mouth 6, the cross-sectional area can be extended to be at least 1.5 times larger in the forward direction, and at least 2 times larger intersecting the forward direction. The flange portion 9 has such a radial extension that the injector guide 19 is not visible from the top view of the proximal region 10.

[0043] Figure 7 shows the injection nozzle 1 in a further perspective view. The nozzle opening 6 has a curved funnel shape. Injector guides 19 into which a powder injector 16 can be inserted are formed within the individual curves. In the forward direction 2, the optical channel is extended in a manner that deviates from a circular shape to achieve the advantages of this disclosure. Circumferentially around the optical channel 3, the nozzle opening 6 has a powder unit 7. This extends circumferentially along the powder portion 11 around the optical channel 3, and the powder portion 11 is adjacent to a powder-free forward portion 12.

[0044] Figure 8 shows a perspective cross-sectional view of the injection nozzle 1. The optical channel 3 has a conical shape, and therefore the cross-sectional area of ​​the optical channel 3 extending perpendicular to the longitudinal direction of the injection nozzle 1 is smaller in the distal region 8 than in the proximal region 10. The coolant inlet 13 and coolant outlet 14 are located within the proximal region 10 of the injection nozzle 1 and project radially from the injection nozzle 1. Figure 8 shows a cross-sectional view of the injector guide 19, which is located within the powder section 11. The injector guide 19 for guiding powder injection is not provided within the forward section 12. The injection nozzle 1 has a cooling system 30. A cooling medium, such as water, is supplied back to the radially inward cooling chamber 31 via the coolant inlet 13 in the proximal region 10. The cooling medium can be distributed circumferentially around the optical channel 3 in the proximal region 10. The cooling medium extends from the proximal region 10 to the nozzle opening 6. The radially inward cooling chamber 31 is formed at least within the nozzle opening 6. It may be designed in the shape of an annular gap segment extending from the distal region 8 to the proximal region 10 and extending around the optical channel 3. In the region of the nozzle opening 6, the radially inward cooling chamber 31 extends circumferentially around the optical channel 3. The radially inward cooling chamber 31 has a constant width in the radial direction in the region of the nozzle opening 6 and is concentric with the optical channel 3 in cross-sectional area extending perpendicular to the longitudinal direction of the injection nozzle 1.

[0045] The transition section 32 between the radially inner cooling chamber 31 and the radially outer cooling chamber 33 is provided in the distal region 8. The radially outer cooling chamber 33 has a radial width that decreases radially toward the distal region 8 in the region of the nozzle mouth 6. The radially outer cooling chamber 33 extends from the distal region 8 to the proximal region 10, where it supplies the heated coolant to the coolant outlet 14. The transition section 32 between the radially inner cooling chamber 31 and the radially outer cooling chamber 33 is located within the front section 12. The front section 12 does not have an injector guide 19 for guiding the ejection of the powder beam, so sufficient space is provided for the transition section 32.

[0046] The radially outer cooling chamber 33 has a cooling structure to increase its surface area. The cooling structure can be manufactured by an additive manufacturing process. As the cooling medium returns from the distal region 8 to the proximal region 10, it is ensured that it comes into contact with as much surface area as possible to promote heat dissipation. The cooling structure is optimized to keep the pressure loss of the cooling medium as low as possible. This can be achieved by a honeycomb structure 34, as shown in Figure 8.

[0047] Figure 9 shows a jet nozzle 1 having an absorbing portion 40. This is designed to absorb the reflected radiation of the laser beam from the workpiece. The absorbing portion 40 extends from the distal region 8 to the proximal region 10. Therefore, it helps protect the laser optics from reflected radiation. The absorbing portion 40 has a serrated structure. This forms an absorbing surface facing the distal region 8. The absorbing portion is provided over the area of ​​the front portion 12. The absorbing portion 40 can be formed from the same material as the rest of the jet nozzle 1. It may also have a coating. The laser radiation absorbed by the absorbing portion 40 can be dissipated by a cooling system 30 that interacts with the absorbing portion 30.

[0048] Figure 10 shows a jet nozzle 1 with a workpiece 100. A laser beam 110 extends along the longitudinal axis 43 of an optical channel 3. The longitudinal axis 43 of the optical channel 3 is inclined with respect to a perpendicular 41 to the workpiece surface. Due to this inclination, the reflected laser radiation 150 is directed onto the absorption portion 40. The inclination of the longitudinal axis 43 of the optical channel 3 with respect to the perpendicular 41 to the workpiece surface is selected so that the absorption portion 40 absorbs as much reflected laser radiation as possible. The inclination is 2° to 20°, particularly 3° to 10°. To achieve the inclination, it is possible to incline the jet nozzle 1 with respect to the workpiece 100, or to incline the workpiece 100 with respect to the jet nozzle 1. The surface roughness of the absorption surface of the absorption portion 40 is 5 μm to 100 μm, particularly 50 μm to 50 μm. The absorption portion 40 may also be provided with an absorbent coating to enhance absorption.

[0049] Figure 11 shows the injection nozzle 1, where the end face 42 of the injection nozzle 1 extends at an angle with respect to the longitudinal axis 43 of the optical channel 3, so that the end face 42 extends parallel to the workpiece 100. This increases the distance from the nozzle opening 6 to the workpiece 100. This also reduces the thermal load on the nozzle opening 6. In addition, the angled end face 42 allows for an improved range of application of the shielding gas to the workpiece 100. This is because the plane-parallel surface of the end face 42 allows the flow of the shielding gas to flow perpendicular to the workpiece 100.

[0050] Figure 12 shows a longitudinal cross-sectional view through the injection nozzle 1 having a smooth inner end portion 44. The injection nozzle 1 can form the smooth inner end portion 44 as the distal surface of the optical channel 3. The smooth inner end portion 44 makes cleaning the inner opening 6 of the nozzle easier. The absorbent portion 40 extends proximal to the smooth inner end portion 44. The absorbent portion 40 can extend further and completely circumferentially, i.e., 360°, around the optical channel 3. The absorbent capability of the injection nozzle 1 is therefore independent of any particular forward direction.

[0051] In Figure 12, the powder unit 7 is provided in the rear region in the forward direction 2, forming a powder section 11 through which an injector guide 19 extends. Each injector guide 19 is adapted to accommodate a powder injector 16. The process gas unit 60 may be provided in the front region in the forward direction 2, forming a process gas section 61 through which a distribution arm for process gas extends. The distribution arm can accommodate additional injectors. Alternatively, the process gas is directed directly from the distribution arm to the material surface. The distribution arm has a curved shape along its longitudinal direction. The injection nozzle 1 has a cooling system 30 comprising a radially inward cooling chamber 31 and a radially outward chamber 33. Due to the design of the front section 12 as the process gas section, the radially outward cooling chamber 33 surrounds the distribution arm 24 in the front region of the nozzle opening 6 in the forward direction 2. The process gas can therefore contribute to the thermal management of the injection nozzle 1.

[0052] Figure 13 shows the injection nozzle 1 in a top view of the distal region 8. The primary beam 111 and secondary beam 112 are guided within the optical channel 3. The secondary beam 112 is ahead of the primary beam 111 in the forward direction 2 and does not interact with the powder focal area, as will be described in more detail in relation to Figure 5. When the laser beam interacts with the material surface and the injection of powder, a vapor plume may form between the injection nozzle 1 and the workpiece 100. If this is not suppressed, it may interact with at least one laser beam and / or the raw and / or processed material surface in an undesirable manner. In the region adjacent to the powder portion 11, the forward portion 12 can therefore be designed as a process gas portion 61. This is formed by positioning a process gas unit 60 radially outside the optical channel 3 and directing the process gas toward the workpiece. The process gas portion 61 can prevent undesirable diffusion of the vapor plume and therefore contribute to precise workpiece machining with a robust injection nozzle design. The process gas portion 61 can form at least one, in this example, three, exhaust openings 62. The exhaust openings 62 are formed on one end face of the injection nozzle 1. Additional injectors for supplying process gas can be inserted into each exhaust opening 62 without additional material. The inner diameter of the exhaust openings 62 may be smaller than the inner diameter of the injector guide 19. The process gas portion 61 also prevents powder particles from adhering to the end face of the injection nozzle 1. In this respect, the process gas portion 61 also increases the service life of the injection nozzle 1. The process gas portion 61 and the powder portion 11 may be provided circumferentially around an elongated hole formed by the optical channel 3. Thus, the primary beam 111 and the secondary beam 112 are entirely contained within the beam consisting of the powder injection and the process gas injection.

[0053] Figure 14 shows a further embodiment of the spray nozzle 1. The nozzle opening 6 has a chamfered portion 50, which cuts off a portion of the nozzle opening 6. The chamfered portion 50 has the effect of cutting off the powder portion 11 and the front portion 12 without the powder portion in the circumferential direction around the optical channel 3. The chamfered portion 50 reduces the volume of the nozzle opening 6 compared to embodiments without the chamfered portion 50. This ensures that the nozzle opening 6 occupies a smaller installation space. The spray nozzle 1 having the chamfered portion 50 can be used, for example, for coating brake discs. The brake disc may have mounting portions that project axially from the functional surface to be coated. The chamfered portion 50 ensures that the spray nozzle 1 can move flexibly on the functional surface to be coated and can move in close proximity to the holder. The chamfered portion 50 is essentially flat and can extend in a plane inclined with respect to the longitudinal direction of the spray nozzle. The chamfered portion 50 represents the boundary surface of the nozzle opening 6 where the powder unit 7 is not provided. In the distal region 8, the chamfered portion 50 is located very close to the optical channel 3, and therefore, in the region of the chamfered portion 50, the injector guide 19 is not provided on the end face of the injection nozzle 1 facing the workpiece.

[0054] Figure 15 shows a top view of an injection nozzle 1 having a chamfered portion 50. The chamfered portion 50 may extend into the distal region 8 in the form of a through portion 51 on an elongated hole. The through portion 51 defines the orientation of the chamfered portion 50 on the mouth portion 6 of the nozzle. At the end face of the injection nozzle 1 facing the workpiece, the through portion 51 extends along a straight line or arc that neither intersects nor contacts the elongated hole. The distance of the through portion 51 from the center 20 of the optical channel 3 is greater than the distance of the corresponding section of the elongated hole from the center 20 of the optical channel 3. The distance between the through portion 51 and the outer edge of the elongated hole is selected so that the wall thickness between them ensures sufficient robustness and stress load capacity of the injection nozzle 1.

[0055] The orientation of the through portion 51, and therefore the orientation of the chamfered portion 50 at the nozzle opening 6, can be changed for each different spray nozzle 1 according to its respective application. For example, the through portion 51 can extend in the forward direction 2. In this case, the through portion 51 extends along the extension of the cross-sectional area of ​​the optical channel 3. Therefore, the through portion 51 extends along the long side of the elongated hole. Alternatively, the through portion 51 can extend, for example, intersecting the forward direction 2. In this case, the through portion 51 extends intersecting the extension of the cross-sectional area of ​​the optical channel 3. Therefore, the through portion 51 extends along the partial circular section of the elongated hole. Furthermore, alternatively, the through portion 51 can extend at an angle to the forward direction 2, located between a path along the forward direction 2 and a path intersecting the forward direction 2. In this case, the through portion 51 extends along the transition section between the long side of the elongated hole and the partial circular section of the elongated hole. The path of the through portion 51 determines the orientation of the chamfered portion 50.

[0056] In the embodiment shown in Figure 15, the discharge opening 62 is provided on the front of the injection nozzle. From here, the process gas exits the process gas unit 60. In this example, the chamfered portion 50 is designed so that the portion of the nozzle opening 6 cut off by the chamfered portion is entirely derived from the powder portion 11. Therefore, the angle at which the powder portion 11 extends is reduced by the chamfered portion 50, while the angle at which the process gas unit 60 extends remains substantially the same.

[0057] To the extent applicable, all individual features presented in the exemplary embodiments may be combined with and / or substituted for each other without departing from the scope of the invention. [Explanation of Symbols]

[0058] 1. Spray nozzle 2 Forward direction 3 optical channels 4. Side surface 5 External structure 6. Nozzle opening 7 Powder Unit 8. Distal region 9. Flange section 10 Proximal region 11 Powder part 12 Front part 13 Coolant intake 14 Coolant outlet 15 Connecting rings 16 Powder Injector 17. Intake Connection 18 Outlet connection 19 Injector Guide 20 Center of optical channels 21 First powder focus 30 Cooling Systems 31 Radially inward cooling chamber 32 Transition Section 33 Radially outer cooling chamber 34 Honeycomb structure 35-pin structure 40 Absorbent portion 41 Perpendicular line to the surface of the workpiece 42 End face 43 Longitudinal axis of the optical channel 44 Inner end part 50 Chamfered section 51 Passage section 60 Process Gas Units 61 Process gas section 62 Discharge opening 100 Workpiece 110 laser beams 111 Primary beam 112 Secondary beam 120 Powdered filling material 130 Melting Pools 140 Functional Layers 150 Reflected laser radiation

Claims

1. A jet nozzle (1) for laser cladding along the forward direction (2), - An optical channel (3) for guiding at least one laser beam directed onto the workpiece, - An external structure (5) that surrounds the optical channel (3) in at least one section and extends from the flange portion (9) to the distal region (8) formed by the mouth portion (6) of the nozzle from which the laser beam is emitted, The injection nozzle (1) has an optical channel (3) that forms an absorption portion (40) for absorbing the back reflected radiation of the laser beam from the workpiece.

2. The injection nozzle (1) according to claim 1, wherein the absorbing portion (40) extends from above the distal region (8) to the proximal region (10) adjacent to the flange portion (9).

3. The injection nozzle (1) according to claim 1 or 2, wherein the absorbing portion (40) has a sawtooth structure that forms an absorbing surface facing the distal region (8).

4. A powder unit (7) positioned radially outward of the optical channel (3) is formed within the external structure (5) to guide the ejection of at least one powder to be applied to the workpiece, wherein the powder unit (7) forms a powder portion (11) at the mouth portion (6) of the nozzle in a circumferential direction around the optical channel (3), and thereafter a forward portion (12) without the powder unit follows in the circumferential direction, the injection nozzle (1) according to any one of claims 1 to 3.

5. The injection nozzle (1) according to claim 4, wherein the absorbing portion (40) is arranged circumferentially in at least the front portion (12), particularly in the circumferential direction.

6. The injection nozzle (1) according to any one of claims 1 to 5, wherein the absorbing portion (40) extends circumferentially around the entire periphery of the optical channel (3).

7. The injection nozzle (1) according to any one of claims 1 to 6, wherein the longitudinal axis (43) of the optical channel (3) from which the laser beam extends is inclined with respect to a perpendicular (41) to the surface of the workpiece in order to increase the absorption of reflected radiation by the absorbing portion (40).

8. The injection nozzle (1) according to claim 7, wherein the end face (42) of the injection nozzle (1) extends at a certain angle with respect to the longitudinal axis (43) of the optical channel (3) from which the laser beam extends, and so the end face (42) is provided to extend parallel to the surface of the workpiece.

9. The injection nozzle (1) according to any one of claims 1 to 8, wherein the surface of the absorbing portion (40) increases in the circumferential direction around the optical channel (3) from the mouth portion (6) of the nozzle toward the flange portion (9).

10. The injection nozzle (1) according to any one of claims 1 to 9, wherein the injection nozzle (1) can be tilted with respect to the workpiece, and so that the absorption of the back reflected radiation by the absorption portion (40) can be controlled by the tilt.

11. The spray nozzle (1) according to any one of claims 1 to 10, wherein the absorbent portion (40) is provided with an absorbent coating.

12. An injection nozzle (1) according to any one of claims 1 to 11, manufactured by an additive manufacturing process and comprising, in particular, copper or a copper alloy, in particular, a copper-chromium-zirconium alloy.

13. The injection nozzle (1) according to any one of claims 1 to 12, wherein the mouth portion (6) of the nozzle has a chamfered portion (50) from which a part of the mouth portion (6) of the nozzle has been cut off, and the chamfered portion (50) is substantially flat and extends in a plane inclined with respect to the longitudinal direction of the injection nozzle (1).

14. A system comprising a spray nozzle (1) and a workpiece (100) according to any one of claims 1 to 13, wherein the spray nozzle (1) is inclined with respect to the workpiece (100), and as a result, the longitudinal axis (43) of the optical channel (3) from which the laser beam extends extends off from the perpendicular (41) to the surface of the workpiece, thereby increasing the absorption of the reflected radiation by the absorbing portion (40).

15. The system according to claim 14, wherein the inclination of the injection nozzle (1) with respect to the workpiece (100) is 2° to 45°, particularly 3° to 10°.

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