Injection nozzle with optical channel having elliptical cross-sectional area

Abstract

The present invention relates to a jet nozzle (1) for laser cladding along a forward direction, the jet nozzle (1) comprising an optical channel for guiding at least one laser beam directed onto a workpiece, and a powder unit positioned radially outward of the optical channel for guiding at least one powder jet to be applied to the workpiece, wherein the cross-sectional area of ​​the optical channel perpendicular to the longitudinal direction of the jet nozzle is deviated from a circular shape and is elliptical in the forward direction.

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 technologies. 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 A and DE 10 2018 130 798 A1. Another method for 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 result in 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 that occur 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 that extend 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 collimating lens, focuses it along the process through a laser optical system, 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, process gases can also be directed to the workpiece surface through the optical channel.

[0007] The injection nozzle also has a powder unit located radially outside the optical channel for guiding at least one powder spray to be applied to the workpiece. Starting from the longitudinal direction of the injection nozzle, the powder unit may be radially outside the optical channel and may be part of an external structure that encloses the optical channel in a closed state. The powder spray may carry powdered filler consisting of hard material particles, particularly carbides and matrix materials. The powder unit may be part of the injection nozzle provided to guide the powdered filler directly or indirectly. The powder unit may have an injector guide into which a powder injector can be inserted. It may have an annular gap into which the powdered filler is guided.

[0008] The cross-sectional area of ​​the optical channel perpendicular to the longitudinal direction of the injection nozzle is deviant from a circular shape and is elliptical in the forward direction. The extension can be directed in the forward direction or in the opposite direction. Due to the extension, two or more process zones may be provided on the workpiece in the forward direction. The injection nozzle is an extended, elongated component. The longitudinal direction can be the direction in which the injection nozzle is oriented. Perpendicular to the longitudinal direction, the injection nozzle has a cross-section, part of which is the shape of the optical channel. In this example, this is elliptical in the forward direction, can be axially symmetric along the forward direction, and can be point-symmetric with respect to the center of the cross-section of the optical channel. The minimum cross-sectional area of ​​the optical channel is determined by its dimensions, in particular the diameter of the laser beam. Compared to the minimum dimensions, the cross-sectional area is elliptical along the forward direction.

[0009] The injection nozzle can therefore provide increased variability in (i) guiding the laser beam, (ii) using powdered filler material, (iii) thermal management, and / or (iv) protecting 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 applied functional layer, in particular the wear protection layer and the overall weld quality of the workpiece, and therefore its durability. 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 variability of laser beam guidance, increasing the variability of powdered filler application, and / or increasing the variability of thermal management of the injection nozzle can reduce or even prevent bonding failures, particularly by guiding primary and secondary beams due to the elongated shape, and thus providing multiple process zones.

[0011] In particular, the injection nozzle 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 variability of laser beam guidance, increasing the variability of the application of powdered filler material, and / or increasing the variability of the thermal management of the injection nozzle can reduce or even prevent pore occurrence by guiding primary and secondary beams, and thus providing multiple process zones, particularly due to the elongated shape.

[0012] In particular, the injection nozzle 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 causes cracks. Cracks may result from the laser power of a single laser beam being set very high to avoid poor bonding due to insufficient heating. Increasing the variability of laser beam guidance, increasing the variability of powdered filler application and / or increasing the variability of thermal management of the injection nozzle can reduce or even prevent crack occurrence by guiding primary and secondary beams, and thus providing multiple process zones, particularly due to the elongated shape.

[0013] In particular, the injection nozzle can also reduce the dissolution of hard material particles, especially carbides, in the matrix material. The powdered filler material may contain hard material particles, especially carbides, and the 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 material is exposed to excessively high radiation intensity, the hard material particles will dissolve, causing the hard material particles to melt. 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 variability of laser beam guidance, increasing the variability of the application of the powdered filler material, and / or increasing the variability of the thermal management of the injection nozzle can reduce or even prevent the dissolution of hard material particles by guiding primary and secondary beams, and thus providing multiple process zones, particularly due to the elongated shape.

[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 variability of laser beam induction, increasing the variability of the application of powdered filler material, and / or increasing the variability of the thermal management of the injection nozzle can reduce or even prevent the dissolution of unwanted hard material particles and the diffusion of metal vapor plume, particularly due to the elongated shape, by inducing primary and secondary beams and thus providing multiple process zones.

[0015] At least one laser beam, particularly at least one circular and / or elliptical laser beam, can be guided along the elliptical cross-sectional area of ​​the optical channel, resulting in the formation of two or more process zones, which favorably influence the welding behavior, reducing the occurrence of defects in the weld joint, especially poor bonding, porosity, cracks, and / or dissolution of carbides in the matrix material, and increasing the load-bearing capacity of the applied functional layer. This means that the melting behavior, powder jetting behavior, material bonding, and cooling behavior can be variably adapted to the respective application, material properties used, and process parameters. In particular, it can be avoided that the area of ​​the molten pool and the laser power supplied to the workpiece in the powdered filler material are too high or too low to achieve the desired process results. For example, in addition to the primary laser beam for laser cladding, a secondary laser beam for pre-treatment or post-treatment can be guided into the optical channel adjacent to the first treatment area. The secondary laser beam can be guided in the forward direction, either in front of or behind the primary laser beam, depending on whether it is for pre-treatment or post-treatment. The geometrically high-density arrangement of the secondary laser beam relative to the primary laser beam reduces heat loss due to heat conduction within the workpiece, thereby promoting material bonding between the powdered filler and the material. The elongated shape enables the aforementioned defect-free welding behavior.

[0016] In one embodiment, the cross-sectional area of ​​the distal region of the injection nozzle, formed by the nozzle opening, is designed in the style of an elongated hole, with two opposite ends of a rectangular section joined by a partial circular section. The powder unit may be part of the nozzle opening. The nozzle opening is the part of the injection nozzle facing the workpiece. The end section of the nozzle opening has a distal region, which is the part of the nozzle opening closest to the workpiece. In the section facing away from the workpiece, the injection nozzle has a proximal region and a flange section. The proximal region and flange section are the parts of the injection nozzle facing away from the workpiece. The nozzle may be coupled via the flange section to another component of a laser system, such as a laser optical system or a process unit.

[0017] In one embodiment, particularly in the region of the nozzle opening, the cross-sectional area is extended to be at least 1.5 times larger in the forward direction, and at least twice as large in the forward direction, especially intersecting the forward direction. In particular, the distance between two subcircles can be more than twice the distance between two parallel sides of the elongated hole. This creates a prerequisite for two or more laser beams to be guided into the optical channel to provide the corresponding process zone. The cross-sectional area may further increase from the nozzle opening toward the proximal section. Thus, the cross-sectional area may reach a minimum dimension in the distal section. Even this minimum dimension may be sufficient to guide several laser beams.

[0018] In one embodiment, the center of the cross-sectional area is eccentric with respect to at least one laser beam center of at least one laser beam. This allows the laser beam to be guided outward from the center, ensuring that the alignment of the injection nozzle and the resulting laser beam is divided into multiple process zones.

[0019] In one embodiment, the optical channel is adapted to guide multiple laser beams, the multiple laser beams having a first laser beam as a primary beam and a second laser beam as a secondary beam. The primary and secondary beams may originally originate from the same optical fiber cable. The supplied laser light can be split into parallel beams via a collimating lens. The beam bundle can be formed from a single laser beam into primary and secondary beams, for example, using a wedge plate. In this case, the primary and secondary beams may have the same wavelength and transmit the same energy. Alternatively, the primary and secondary beams may differ in terms of their wavelength and energy. The centers of the primary and secondary beams may be offset forward along the center of the optical channel. Providing multiple laser beams is advantageous for the reliable implementation of multiple process zones.

[0020] In one embodiment, the secondary beam is adapted to have less interaction with the powder ejection than the primary beam, and the secondary beam is located in front of the primary beam in the forward direction for preheating the workpiece. The interaction of the primary and secondary beams with the powder ejection can be achieved by appropriate guidance of each laser beam and / or appropriate guidance of the powder ejection. For example, the powder unit may form a powder section at the nozzle opening in the circumferential direction around the optical channel, followed by a forward section without the powder unit in the circumferential direction. The forward section surrounds the portion of the optical channel facing forward. Therefore, the supply section can ensure that the powder ejection does not interact with the secondary beam, and thus the secondary beam can be used to preheat the workpiece rather than the powder particles.

[0021] In one embodiment, the secondary beam is adapted to have less interaction with the powder jet than the primary beam, and the secondary beam is located behind the primary beam in the forward direction for reheating the workpiece. The interaction of the primary and secondary beams with the powder jet can be achieved by proper guidance of each laser beam and / or proper guidance of the powder jet. Therefore, the forward section without the powder unit can enclose the portion of the optical channel facing away from the forward direction. Thus, the supply section can ensure that the powder jet does not merge with the secondary beam, and the secondary beam can therefore be used for reheating or cleaning the workpiece.

[0022] In one embodiment, a plurality of laser beams have a third laser beam as a tertiary beam adapted to have less interaction with the powder jet than the primary beam, with the primary beam located ahead of the tertiary beam in the forward direction. The cross-sections of the primary, secondary, and tertiary beams can each extend along a straight line, i.e., have their respective centers aligned along a line. This line can be aligned with the forward direction. The line can also be congruent with the forward direction. At least three different process zones can be realized through the primary, secondary, and tertiary beams, which works favorably for the welding behavior.

[0023] In one embodiment, among multiple laser beams, the laser beam on the front side in the forward direction, for example, the secondary beam, is concentric in the cross-section with respect to the front subcircular section of the cross-sectional area, and / or the laser beam on the rear side in the forward direction is concentric in the cross-section with respect to the rear subcircular section of the cross-sectional area. This makes it possible to efficiently use the cross-sectional area of ​​the optical channel when guiding multiple laser beams.

[0024] In one embodiment, the center of the cross-sectional area of ​​multiple laser beams is congruent to the centers of the multiple laser beams. The center of the cross-sectional area may be a point where the cross-section is point-symmetric. The centers of the multiple laser beams may be points where each laser beam has its center in its cross-section. Since these are congruent to each other, the spatial utilization of the optical channel's cross-sectional area is further optimized when guiding multiple laser beams.

[0025] In one embodiment, the injection nozzle has exactly one optical channel, so that multiple laser beams are guided within the injection nozzle without being shielded from one another. One optical channel thus guides multiple laser beams without providing separate shields around each laser beam. This simplifies the nozzle design and facilitates heat dissipation.

[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 substantially planar, and extends in a plane inclined with respect to the longitudinal direction of the injection nozzle. The chamfered portion can cut off a powder section and a front section without a powder section in the circumferential direction around the optical channel. The chamfered portion reduces the volume of the mouth of the nozzle compared to an embodiment without chamfering. This means that the mouth of the nozzle takes up a smaller installation space. The injection nozzle having a chamfered portion can be used, for example, to coat a brake disk having a mounting portion protruding axially from a 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 long hole. 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 long hole. The distance of the passage portion from the center of the optical channel is greater than the distance of the corresponding section of the long hole from the center of the optical channel. The distance between the passage portion and the outer edge of the long hole is selected such that the wall thickness therebetween ensures sufficient robustness and stress resistance of the injection nozzle.

[0028] In one embodiment, the injection nozzle is adapted to guide at least one laser beam along the longitudinal direction of the injection nozzle such that the laser beam is orthogonal to the cross-sectional area. Further, the optical channel can be adapted to guide shielding gas along a radially outer section to shield the process zone.

[0029] The features according to the disclosure contribute, alone and in combination, in part to overcoming the defects of the laser cladding mentioned at the beginning.

Brief Description of the Drawings

[0030] Preferred further embodiments of the present invention are explained in more detail by the following description of the drawings. [Figure 1] Shows a schematic diagram of an injection nozzle during laser cladding. [Figure 2] Shows a side view of the injection nozzle. [Figure 3] Shows a perspective view of the injection nozzle of the injection from FIG. 2. [Figure 4] Shows the injection nozzle from FIG. 2 connected to other components. [Figure 5] Shows a top view of the distal portion of the injection nozzle of the injection from FIG. 2. [Figure 6] Shows a top view of the flange section of the injection nozzle from FIG. 2. [Figure 7] Shows another perspective view of the injection nozzle from FIG. 2. [Figure 8] Shows a perspective cross-sectional view of the injection nozzle from FIG. 2. [Figure 9] Shows an injection nozzle in a further embodiment in a top view of the distal region. [Figure 10] Shows an injection nozzle having a process gas unit in a top view of the distal region. [Figure 11] Shows a further embodiment of an injection nozzle having a geometrically adapted nozzle mouth in a side view. [Figure 12] Shows a further embodiment of an injection nozzle having a geometrically adapted nozzle mouth in a top view.

Mode for Carrying Out the Invention

[0031] Preferred exemplary embodiments are described below with reference to the drawings. In this case, elements that are the same, similar, or have the same effect are provided with the same reference numerals in different drawings, and the repeated description of these elements is omitted in some cases to avoid redundancy.

[0032] 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 a radially external section 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.

[0033] 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 section 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 section 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. The section has a powder section 11 in which powder units 7 are arranged circumferentially around the optical channel 3. Following the powder section 11 is a forward section 12 without powder units, which follows circumferentially. The forward section 12 may be designed as a process gas section 61, which is part of a process gas unit 60 (see, for example, Figure 9).

[0034] 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 section 9 to the distal region 10. The nozzle mouth 6 is substantially the 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 section 11, followed circumferentially by a forward section 12 without powder units. The front section 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 section. In one embodiment, the front section 12 may be formed as a process gas section 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).

[0035] Figure 4 shows the injection nozzle 1 to which additional components are attached. The connecting ring 15 is connected to the flange section 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. Each individual powder injector 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 injectors 16 are located in the predetermined injector guide 19 of the powder unit 7 in the powder section 11. There are no powder injectors 16 in the front section 12. The intake connector 17 is also inserted into the coolant intake 13, and the outlet connector 18 is inserted into the coolant outlet 14. These connect the coolant intake 13 and the coolant outlet 14 to the coolant circuit.

[0036] 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, perpendicular to the longitudinal direction of the injection nozzle 1, is deviated from a circular shape and is elliptical 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, where the two opposite ends of a rectangular cross-section are joined by a partial circular cross-section. 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 collimating lens. The beam bundles can be formed from a single laser beam, for example, using a wedge plate. 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.

[0037] 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.

[0038] The primary beam 111 and the secondary beam 112 are positioned in close proximity to each other. The front circular section of the elongated hole in the forward direction 2 is concentric with the secondary beam 112, and the rear circular section 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.

[0039] In Figure 5, the primary beam 111 is positioned behind the secondary beam 112 in the forward direction 2 without radial offset, and since the secondary beam 112 functions to preheat the workpiece, 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 section 11 in the circumferential direction around the optical channel 3, and a forward section 12 without a powder unit is connected to the powder section 11 in the circumferential direction. In addition to the powder unit 7, a process gas unit 60 may also be formed, thereby forming a process gas section 61, in which case the forward section 12 is formed as the process gas section 61. The forward section 12 is formed in the region of the nozzle mouth 6 facing the forward direction 2. The powder section 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 section 11 extends around the optical channel 3, particularly along the elongated pore-like arc of a horseshoe shape. Thus, the powder section 11 extends in the central direction around the optical channel 3 with a winding angle of less than 360°, particularly 90° to 330°, and even more particularly 180° to 300°, relative to the center 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 section 11 and the front section 12 form an elongated pore shape when viewed from above. This also helps to reduce or avoid the defects identified at the beginning.

[0040] Figure 6 shows the injection nozzle 1 in a top view of the flange section 9. The cross-sectional area of ​​the optical channel 3 perpendicular to the longitudinal direction of the injection nozzle 1 is also deviate from a circular shape in the region of the flange section 9 and is elliptical in the forward direction 2. The elongation of the cross-sectional area may 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 larger in the forward direction and at least 2 times larger intersecting the forward direction. The flange section 9 has a radial extension in which the injector guide 19 is not visible from the top view of the proximal region 10.

[0041] 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. In the circumferential direction around the optical channel 3, the nozzle opening 6 has a powder unit 7. This extends along the powder section 11 in the circumferential direction around the optical channel 3, and the powder section 11 is adjacent to a powder-free forward section 12.

[0042] 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 in the forward section 12. The injection nozzle 1 has a cooling system 30. For example, a cooling medium such as water is supplied back to the cooling chamber 31 radially inward 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 flows 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 radial width in the region of the nozzle opening 6 and is concentric with the optical channel 3 in a cross-sectional area perpendicular to the longitudinal direction of the injection nozzle 1.

[0043] 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 forward section 12. The forward 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.

[0044] 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. It ensures that heat dissipation is promoted by contacting as much surface area as possible as the cooling medium returns from the distal region 8 to the proximal region 10. 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.

[0045] Figure 9 shows an injection nozzle 1 of a further embodiment 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 is elliptical in the forward direction 2. In the distal region 8, the cross-sectional area of ​​the optical channel 3 is designed to be elongated, with the two opposite ends of a rectangular cross-section joined by a partial circular cross-section. The primary beam 111 and the secondary beam 112 are guided within the optical channel 3. The centers of the primary beam 111 and the secondary beam 112 are aligned with the center 20 of the optical channel 3 and offset in the forward direction 2.

[0046] The primary beam 111 has a beam center that coincides with the first powder focus 21. The first powder focus 21 is the point where the injector of the first powder section 22 is focused. The first powder section 22 forms the focal area of ​​the first powder. Thus, the secondary beam 112 has a beam center that coincides with the second powder focus 23. The second powder focus 23 is the point where the injector of the second powder section 24 is focused. The second powder section 24 forms the focal area of ​​the second powder. The primary beam 111 and the secondary beam 112 are offset from each other in the forward direction 2. Thus, the first powder focus 21 is also offset from the second powder focus 23. The powder unit 7 having the first powder section 22 and the second powder section 24 can therefore form two powder focuses that are different from each other. In addition, the powder mass flow delivered from the injector of the first powder section 22 may differ from the powder mass flow delivered from the injector of the second powder section 24. A gap may be provided between the first powder section 22 and the second powder section 24, so that the powder mass flow applied by the first powder section 22 interacts exclusively with the primary beam 111, and the powder mass flow applied by the second powder section 24 interacts exclusively with the secondary beam 112.

[0047] The first powder section 22 and the second powder section 24 contribute to increasing the application speed by realizing at least two process zones within the injection nozzle 1. This can increase the track width of the applied functional layer. In addition, shielding gas consumption is reduced and an improved shielding gas coverage is achieved because the shielding gas can be more localized.

[0048] The primary beam 111 and the secondary beam 112 are positioned close to each other. The front circular section of the elongated hole in the forward direction 2 is concentric with the secondary beam 112, and the rear circular section of the elongated hole is concentric with the primary beam 111. The center 20 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.

[0049] Figure 10 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 section 11, the forward section 12 can therefore be designed as a process gas section 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 section 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 section 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 section 61 also prevents powder particles from adhering to the end face of the injection nozzle 1. In this respect, the process gas section 61 also increases the service life of the injection nozzle 1. The process gas section 61 and the powder section 11 can 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.

[0050] Figure 11 shows a further embodiment of the injection nozzle 1. The nozzle opening 6 has a chamfered portion 50, which is a portion of the nozzle opening 6 that has been cut off. The chamfered portion 50 has the effect of cutting off the powder section 11 and the forward section 12 without a powder section in the circumferential direction around the optical channel 3. The chamfered portion 50 reduces the volume of the nozzle opening 6 compared to embodiments in which the chamfered portion 50 is not provided. This ensures that the nozzle opening 6 occupies a smaller installation space. The injection nozzle 1 having the chamfered portion 50 can be used, for example, for coating brake discs. The brake disc may have a mounting portion that protrudes axially from the functional surface to be coated. The chamfered portion 50 ensures that the injection nozzle 1 can move flexibly on the functional surface to be coated and can move in close proximity to a holder. The chamfered portion 50 is substantially planar and may extend in a plane inclined with respect to the longitudinal direction of the injection 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, the injector guide 19 is not provided on the end face of the injection nozzle 1 facing the workpiece in the region of the chamfered portion 50.

[0051] Figure 12 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. On 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.

[0052] 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.

[0053] In the embodiment shown in Figure 12, 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 section 11. Therefore, the angle at which the powder section 11 extends is reduced by the chamfered portion 50, while the angle at which the process gas unit 60 extends remains substantially the same.

[0054] 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]

[0055] 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 Section 12 Front Section 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 22 First Powder Section 23 Second powder focus 24. Second powder section 30 Cooling Systems 31 Radially inward cooling chamber 32 Transition Section 33 Radially outer cooling chamber 34 Honeycomb structure 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 pool 140 Functional Layers

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, - comprising a powder unit (7) positioned radially outward of the optical channel (3) to guide at least one powder jet to be applied to the workpiece, The injection nozzle (1) is such that the cross-sectional area of ​​the optical channel (3), which is perpendicular to the longitudinal direction of the injection nozzle (1), is not circular and is elliptical in the forward direction (2).

2. The injection nozzle (1) according to claim 1, wherein the cross-sectional area of ​​the distal region (8) of the injection nozzle (1) formed by the nozzle opening (6) is designed in the style of an elongated hole, and the two opposite ends of the rectangular section are joined by a partial circular section.

3. The spray nozzle (1) according to claim 1 or 2, wherein, in particular in the region of the nozzle mouth (6), the cross-sectional area extends to be at least 1.5 times larger in the forward direction (2), and at least 2 times larger intersecting the forward direction (2).

4. The injection nozzle (1) according to any one of claims 1 to 3, wherein the center of the cross-sectional area is eccentric with respect to the center of at least one laser beam of the at least one laser beam.

5. The injection nozzle (1) according to any one of claims 1 to 4, wherein the optical channel (3) is adapted to guide a plurality of laser beams, and the plurality of laser beams have a first laser beam as a primary beam (111) and a second laser beam as a secondary beam (112).

6. The injection nozzle (1) according to claim 5, wherein the secondary beam (112) is adapted to have less interaction with the powder injection than the primary beam (111), and the secondary beam (112) is located in front of the primary beam (111) in the forward direction (2) for preheating the workpiece.

7. The injection nozzle (1) according to claim 5, wherein the secondary beam (112) is adapted to have less interaction with the powder injection than the primary beam (111), and the secondary beam (112) is located behind the primary beam (111) in the forward direction (2) for reheating the workpiece.

8. The injection nozzle (1) according to any one of claims 5 to 7, wherein the plurality of laser beams have a third laser beam as a tertiary beam which is adapted to have less interaction with the powder injection than the primary beam (111), and the primary beam (111) is located in front of the tertiary beam in the forward direction (2).

9. The injection nozzle (1) according to any one of claims 5 to 8, wherein, among the plurality of laser beams, the laser beam located on the front side in the forward direction (2) is concentric in cross-section with respect to the front partial circular section of the cross-sectional area, and / or the laser beam located on the rear side in the forward direction (2) is concentric in cross-section with respect to the rear partial circular section of the cross-sectional area.

10. The injection nozzle (1) according to any one of claims 5 to 9, wherein the center of the cross-sectional area of ​​the plurality of laser beams is contiguous with the center of the plurality of laser beams.

11. The injection nozzle (1) according to any one of claims 5 to 10, having strictly one optical channel (3), so that the plurality of laser beams are guided within the injection nozzle without being shielded from one another.

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 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 is 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).

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