Spray nozzle having a powder section and a forward section

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 a powder unit (7) positioned radially outward of the optical channel (3) for guiding at least one powder injection applied to the workpiece, wherein the powder unit (7) forms a powder section (11) at the mouth (6) of the nozzle circumferentially around the optical channel (3), and a forward section (12) lacking the powder unit is circumferentially adjacent thereto.

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 German Patent Application Publication Nos. 10 2011 100 456 A and 10 2018 130 798 A1. Another laser cladding method is known from Chinese Patent Application No. 109175372A.

[0003] Laser cladding can be used to apply a functional layer to a workpiece. This generally increases the load-bearing capacity of the workpiece on which laser cladding has been performed compared to a workpiece on which it has not been performed. 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 powdery filler material, and subsequent cooling, so that a matrix structure with hard material particles is materially bonded to the material surface. Thus, laser cladding acts on 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 load-bearing capacity. Since the defects can be of a microscopic nature, it means that 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, in particular, when the material surface is a cast material. Defects may also be cracks that extend particularly 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. A further object of the present invention may also be to configure the injection nozzle 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 the two 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 be emitted through an 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 appropriately 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, the process gas can also be directed to the workpiece surface through the optical channel.

[0007] The injection nozzle has a powder unit positioned radially outward of 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 outward of 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 at least one powdery 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 powdery filler directly or indirectly. The powder unit may have an injector guide into which a powder injector can be inserted. It may also have an annular gap into which the powdery filler is guided.

[0008] The powder unit forms a powder section circumferentially at the nozzle opening around the optical channel, with a forward section lacking the powder unit circumferentially adjacent to it. The powder unit may be part of the nozzle opening. The nozzle opening is 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 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 away from the workpiece. The nozzle may be coupled via the flange section to another component of the laser system, such as a laser optical system or a process unit. The powder section and the forward section may together form the entire circumference of the nozzle opening around the optical channel. The powder section may constitute a larger portion, for example, than the forward section. In a plan view, the powder section and the forward section may extend in a closed manner along the opening of the optical channel.

[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 include cleaning the material surface, preheating the material surface before the powdered filler material is applied, post-heating the material surface after the powdered filler material is applied, or a combination thereof. During pre-treatment and / or post-treatment, the laser beam may strike the workpiece without interacting with the powdered filler material. Independent process zones can enhance the applied functional layer, particularly the wear protection layer and the overall weld quality of the workpiece, and therefore the load-bearing capacity. Additional process gases can stabilize the process zones and increase the accuracy of the laser cladding and the service life of the injection nozzle.

[0010] In particular, the injection nozzle 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 individual laser beams low to avoid overheating of the powdered filler material. Due to increased variability in laser beam guidance, increased variability in the application of powdered filler material, and / or increased variability in the thermal management of the injection nozzle, the occurrence of bonding failures can be reduced or further prevented, particularly by dividing the injection nozzle into a powder section and a forward section, thereby enabling the provision of 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 processed 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 individual laser beams being set very high to prevent bonding failures due to insufficient heating. Due to increased variability in laser beam guidance, increased variability in the application of powdered filler material, and / or increased variability in the thermal management of the injection nozzle, the occurrence of pores can be reduced or further prevented, in particular, by dividing the injection nozzle into a powder section and a forward section, thereby enabling the provision of multiple process zones.

[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 can cause cracks. Cracks may result from the laser power of the individual laser beams being set very high to prevent bonding failures due to insufficient heating. Due to increased variability in laser beam guidance, increased variability in the application of powdered filler and / or increased variability in the thermal management of the injection nozzle, the occurrence of cracks can be reduced or further prevented, in particular, by dividing the injection nozzle into a powder section and a forward section, thereby enabling the provision of multiple process zones.

[0013] Furthermore, the injection nozzle can also reduce the dissolution of hard material particles, particularly carbides, in the matrix material. The powdered filler material may contain hard material particles, particularly 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 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. Due to increased variability in laser beam guidance, increased variability in the application of the powdered filler material, and / or increased variability in the thermal management of the injection nozzle, the dissolution of hard material particles can be reduced or further prevented, in particular, by dividing the injection nozzle into a powder section and a forward section, thereby enabling the provision of multiple process zones.

[0014] Furthermore, the injection nozzle can prevent powder particles from adhering to the nozzle opening. In principle, high process heat can cause adhesion of the filler material to the nozzle opening, or even welding, due to reflected laser radiation and / or metal vapor plumes, which can disrupt the gas and powder flow and consequently impair the process results. Metal vapor plumes are the result of partial vaporization of the material due to laser cladding. They cause 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. Due to increased variability in laser beam guidance, increased variability in the application of powdered filler material and / or increased variability in the thermal management of the injection nozzle, unwanted melting of hard material particles and propagation of metal vapor flares can be reduced or further prevented, in particular, by dividing the injection nozzle into a powder section and a forward section, thereby enabling the provision of multiple process zones.

[0015] At least one laser beam, particularly at least one circular laser beam and / or one elliptical laser beam, can be guided into the nozzle opening to form two or more process zones in interaction with the powdered filler material, thereby facilitating welding behavior, reducing the occurrence of defects in welded joints, especially poor bonding, porosity, cracks, and / or carbide dissolution in the matrix material, and increasing the load-bearing capacity of the applied functional layer. This means that the melting behavior, powder ejection behavior, material bonding, and cooling behavior can be variably adapted to the respective application, material properties used, and process parameters. In particular, the powdered filler material can be prevented from being exposed to excessive laser power. Thus, the powdered filler material will not be overheated in interaction with the laser beam, thereby preventing, for example, vaporization and powder loss. Furthermore, the temperature gradient of the molten material is reduced by the forward section, resulting in reduced shrinkage and internal stress, thereby preventing crack formation in the functional layer. The division into powder and forward sections may also create gaps in the powder focal area, which further contributes to different process zones. The division into a powder section and a forward section enables the aforementioned defect-free welding behavior.

[0016] In one embodiment, the front section is formed in the region of the nozzle mouth facing forward. In a plan view, the region of the nozzle mouth facing forward is provided at the nozzle end on the side closer to the forward direction. One end face of the front section points in the direction of the workpiece. The front section may extend over a certain angular range along the circumferential direction around the optical channel. The angular range over which the front section extends may be smaller than the angular range over which the powder section extends. The region in which the front section is formed may correspond to the position and orientation of the powder injector that applies the powdered filler material to the workpiece.

[0017] In one embodiment, the powder section extends around the optical channel, particularly along a horseshoe-shaped elongated arc. Similar to a circular arc, the elongated arc represents a line enclosing the elongated hole in a given sector. The remaining portion of the elongated hole not occupied by the elongated arc on which the powder section extends may be occupied by the front section. The powder section may extend at least partially along two opposing linear ends and an intermediate circular segment section of the elongated hole to form a horseshoe shape. This further contributes to the possibility of providing two or more process zones.

[0018] In one embodiment, the powder section extends circumferentially around the optical channel with a winding angle of 45° to 330°, particularly 90° to 300°, and more specifically 180° to 300°, with respect to the center of the optical channel. The powder section can therefore extend around the optical channel with a larger section than the front section. In this way, satisfactory powder supply can be ensured by the powder unit, in particular by the injector located inside it. By precisely adapting the powder section and the front section to their respective process conditions, defect-free and efficient welding behavior is possible. In particular, if the nozzle opening has a chamfer that cuts off a portion of the nozzle opening, the winding angle of the powder section is 90° to 180°. If the nozzle opening does not have a chamfer, the nozzle opening is preferably greater than 180°.

[0019] In one embodiment, the powder section consists of a first powder section and a second powder section, the first powder section being separated from the second powder section by a powder section gap. The powder section gap may differ from that of the front section. The variability of the injection nozzle is further considered by the powder section consisting of a plurality of individual powder sections. The configuration of the powder section may be determined in interaction with the configuration of a laser beam or a plurality of laser beams.

[0020] In one embodiment, the gap in the powder section is formed in the region of the nozzle mouth away from the forward direction. The forward section may therefore be oriented forward, and the powder section gap may be oriented away from the forward direction. In particular, when the optical channel guides two or more, especially three, laser beams, the division of the powder section into multiple powder sections in interaction with the forward section and the powder section gap may further contribute to achieving defect-free and efficient welding behavior by the injection nozzle.

[0021] In one embodiment, the powder section has a plurality of injector guides into which a powder injector can be inserted. The injector guides may be cylindrical or conical through-openings in the mouth area of ​​the nozzle, into which a powder injector can be inserted. The injector guides may be introduced into the nozzle mouth by machining. However, preferably, they are provided at the additive manufacturing stage of the injection nozzle. The injector guides may be adapted to the powder injector used.

[0022] In one embodiment, a first powder injector is prepared to deliver a first powder mass flow, and a second powder injector is prepared to deliver a second powder mass flow, wherein the first powder mass flow is different from the second powder mass flow. The first powder injector may be provided within a first powder section, and the second powder injector may be provided within a second powder section. The first powder injector may be positioned to interact with the primary beam of a laser beam. The second powder injector may be positioned to interact with the secondary beam of a laser beam. The primary and secondary beams may be identical to each other or may deliver different energies. By providing a first powder mass flow and a second powder mass flow, the injection nozzle can realize two or more process zones, which further contributes to increased variability of the injection nozzle.

[0023] In one embodiment, the first powder mass flow delivers a different powder than the second powder mass flow. This allows for the application of a functional layer using a variable material to the workpiece. Alternatively, the first and second powder mass flows can direct the same powder onto the workpiece. Adapting each powder mass flow to its respective injector further contributes to increased variability.

[0024] In one embodiment, a first powder injector is prepared to form a first powder focus, and a second powder injector is prepared to form a second powder focus, wherein the first powder focus is distinct from the second powder focus. The powder focus may be the location where the powder jet strikes the workpiece. The powder focus is located radially within the cross-sectional area of ​​the optical channel. Multiple first powder injectors may be adapted to form a first powder focus, and similarly, multiple second powder injectors may be adapted to form a second powder focus. Therefore, for example, first and second laser depositions offset along the forward direction can be welded onto a workpiece. The adaptation of the powder focus may be performed according to the function of a particular workpiece or a particular process, further contributing to increased variability.

[0025] In one embodiment, the powder section forms an annular gap segment, particularly instead of an injector guide. The annular gap segment can form a uniform powder focus, for example, coinciding with the center of at least one laser beam. In the case of an annular gap segment, the powdery filler material is applied to the workpiece along a horseshoe-shaped jet.

[0026] In one embodiment, the injection nozzle is manufactured using an additive manufacturing process, particularly using 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 an intended geometric shape, thereby liquefying the powder and forming material bonds. Powder bed fusion may take the form of, for example, selective laser melting (SLM) or selective laser sintering (SLS).

[0027] In one embodiment, the nozzle opening has a chamfered portion where a portion of the nozzle opening is cut off, and the chamfered portion extends in a plane that is substantially flat and inclined with respect to the longitudinal direction of the spray nozzle. The chamfered portion can cut off a powder section and a forward section without a powder section in the circumferential direction around the light channel. The chamfered portion reduces the volume of the nozzle opening compared to embodiments in which the chamfer is not provided. This means that the nozzle opening occupies a smaller installation space. A spray nozzle with a chamfered portion may be used, for example, to coat a brake disc having a holder that protrudes axially from the functional surface to be coated. The chamfered portion ensures that the spray nozzle can move flexibly over the functional surface to be coated and can move in close proximity to the holder. In the distal region, the chamfered portion may pass through an elongated hole in the form of a through portion. The through portion defines the orientation of the chamfered portion at the nozzle opening. At the end face of the spray nozzle facing the workpiece, the through portion extends along a straight line or arc that neither intersects nor contacts the elongated hole. The distance from the center of the optical channel to the passage portion is greater than the distance from the center of the optical channel to the corresponding section of the elongated hole. The distance between the passage portion 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.

[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 may be adapted to guide the shielding gas along a radially outer section in order to shield the process zone.

[0029] The features according to the disclosure contribute, partly alone and partly in combination, to overcoming the deficiencies 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] 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 of FIG. 2 is shown. [Figure 4] The injection nozzle of FIG. 2 connected to other components is shown. [Figure 5] A plan view of the distal region of the injection nozzle of FIG. 2 is shown. [Figure 6] A plan view of the flange section of the injection nozzle of FIG. 2 is shown. [Figure 7] A further perspective view of the injection nozzle of FIG. 2 is shown. [Figure 8] A perspective cross-sectional view of the injection nozzle of FIG. 2 is shown. [Figure 9] A further plan view of the distal region of the injection nozzle of FIG. 2 is shown. [Figure 10] A plan view of the distal region of an injection nozzle having a process gas unit is shown. [Figure 11] A side view of a further embodiment of an injection nozzle having a geometrically adapted nozzle mouth is shown. [Figure 12] A plan view of a further embodiment of an injection nozzle having a geometrically adapted nozzle mouth is shown. [Modes 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 given the same reference numerals in different drawings, and repeated descriptions of these elements are 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, a plurality of injector guides 19 (see Figure 3), and a powder injector 16 may be inserted into each of the injector guides 19 (see Figure 4). As an alternative to individual injector guides 19, the powder unit 7 may have annular gap powder 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, which is, 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 a side view of the injection nozzle 1 with the forward direction 2 pointing outward from the drawing plane. The injection nozzle 1 may be coupled to other components of the laser system, such as a laser optical system or a process adapter, for example, via a flange section 9. The proximal region 10 is adjacent 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. It has a powder section 11 in which powder units 7 are arranged at fixed circumferential positions around the optical channel 3. Circumferentially, the powder section 11 is adjacent to a forward section 12 that lacks powder units. The forward section 12 may be configured 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 of 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. The powder unit 7 extends along the powder section 11, to which the front section 12, which lacks the powder unit, is circumferentially adjacent. 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 take the form of a process gas section 61, through which the process gas is supplied. The injection nozzle 1 may be manufactured using an additive manufacturing process, particularly using 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 represents a powder form. A laser beam heats the powder along an intended geometric shape, thereby liquefying the powder and forming material bonds. Powder bed fusion may take the form of, for example, selective laser melting (SLM) or selective laser sintering (SLS).

[0035] Figure 4 shows the injection nozzle 1 with additional components attached. For example, a connecting ring 15 for attaching the injection nozzle 1 to a connection unit such as a laser optical system or process adapter is connected to the flange section 9. 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 the intended focus. Individual powder injectors 16 may use different powder focuses from each other. Alternatively, the powder injectors 16 may be oriented to the same focus. The powder injectors 16 are located in the powder section 11 within the injector guide 19 provided for the powder unit 7. There are no powder injectors 16 in the front section 12. The intake connector 17 is further inserted into the coolant intake 13, and the discharge connector 18 is inserted into the coolant discharge port 14. These connect the coolant intake 13 and the coolant discharge port 14 to the coolant circuit.

[0036] Figure 5 shows a plan view of the distal region 8 of the injection nozzle 1. 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 takes the shape of an elongated hole, with in each case a circular segment section adjacent to two opposing ends of a rectangular 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 beams 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 collide with 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, defects such as poor bonding, porosity, cracks, and / or dissolution of carbides in the matrix material do not occur. It is also possible to guide the secondary beam 112 behind the primary beam 111 in the forward direction 2. Therefore, the secondary beam 112 can be used to reheat the workpiece 100, thereby contributing to more uniform cooling that prevents the formation of inclusions or other defects.

[0038] The primary beam 111 and the secondary beam 112 are positioned in close proximity to each other. The front circular segment section of the elongated hole in the forward direction 2 is concentric with the secondary beam 112, while the rear circular segment section of the elongated hole is concentric with the primary beam 111. The center of the cross-section 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 from 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 a powder unit 7 in the region of the nozzle mouth 6 such that the powder unit forms a powder section 11 in the circumferential direction around the optical channel 3, and this powder section is circumferentially adjacent by a forward section 12 that lacks a powder unit. In addition to the powder unit 7, a process gas unit 60 may also be formed, which forms a process gas section 61, in which case the forward section 12 takes the form of a 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 hole that forms 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 horseshoe-shaped elongated hole arc. Thus, the powder section 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°, 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 forward section 12 form an elongated hole shape when viewed in plan. This also helps to reduce or avoid the defects identified at the beginning.

[0040] Figure 6 shows a plan view of the flange section 9 of the injection nozzle 1. 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 extends 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 may extend to be at least 1.5 times larger in the forward direction and at least 2 times larger intersecting the forward direction in particular. The flange section 9 has such radial extensions that the injector guide 19 is not visible from the plan view of the proximal region 10.

[0041] Figure 7 shows a further perspective view of the injection nozzle 1. 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 extends 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 around the optical channel 3 along a powder section 11, which 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. A cooling medium, such as water, is returned 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 can take the shape of an annular gap segment that extends from the distal region 8 to the proximal region 10 and circumferentially 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 a cross-sectional area that extends 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 discharge port 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 lacks an injector guide 19 for powder injection guidance and provides sufficient installation space 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 using an additive manufacturing process. It ensures that heat dissipation is facilitated 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 produce the lowest possible pressure loss of the cooling medium. This can be achieved by a honeycomb structure 34, as shown in Figure 8.

[0045] Figure 9 illustrates the behavior described above, where the powder section 11 with the injector guide 19 forms a first powder focus 21 that coincides with the center of the primary beam 111. The injectors 16 have a common focus at the first powder focus 21. The individual injectors also face each other in a diametrically symmetrical manner at the first powder focus 21, in each case. This allows the injection nozzle 1 to efficiently apply the powdery filler material to the workpiece via the primary beam 111. In the region of the secondary beam 112, a gap 25 exists in the powder focus area, which is highlighted by hatching in Figure 9. The position of the first powder focus 21, and the position of the gap 25 in the powder focus area, can be adjusted through the arrangement of the powder unit 7 and its powder section 11, as well as the arrangement of the front section 12. The gap 25 in the powder focus area may be substantially half the size of the cross-sectional area of ​​the optical channel 3 in the distal region 8. This ensures that the secondary beam 112 does not interact with the powdery filler material 120. The relationship between the powder section 11 and the front section 12, and their arrangement in the circumferential direction of the optical channel 3, results in a winding angle 26 in which the powder section extends around the center point 20 of the optical channel 3. This is located between 90° and 330°, particularly between 180° and 300°, with respect to the center point 20 of the optical channel 3.

[0046] Figure 10 shows a plan view of the distal region 8 of the injection nozzle 1. 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, at least one laser beam and / or the raw and / or processed material surface may interact in an undesirable manner. In the region adjacent to the powder section 11, the forward section 12 may therefore be configured 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 discharge openings 62. The discharge openings 62 are formed on one end face of the injection nozzle 1. Additional injectors for supplying process gas can be inserted into each discharge opening 62 without additional filler material. The inner diameter of the discharge 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 fully contained within the injection consisting of the powder injection and the process gas injection.

[0047] Figure 11 shows a further embodiment of the injection nozzle 1. The nozzle opening 6 has a chamfered portion 50 that cuts off a portion of the nozzle opening 6. 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 light 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 injection nozzle 1 having the chamfered portion 50 can be used, for example, for coating brake discs. The brake disc may have a holder that projects axially with respect to 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 the holder. The chamfered portion 50 is substantially flat 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 positioned very close to the optical channel 3, and therefore, in the region of the chamfered portion 50, the end face of the injection nozzle 1 facing the workpiece is not provided with an injector guide 19.

[0048] Figure 12 shows a plan view of the injection nozzle 1 having a chamfered portion 50. The chamfered portion 50 can pass through the elongated hole in the distal region 8 in the form of a through portion 51. The through portion 51 defines the orientation of the chamfered portion 50 at 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.

[0049] 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 may 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 may 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 circular segment section of the elongated hole. Furthermore, alternatively, the through portion 51 may 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.

[0050] In the embodiment shown in Figure 12, the discharge opening 62 is provided on the end face of the injection nozzle. The process gas exits the process gas unit 60 through these discharge openings. In this example, the chamfered portion 50 is such that the portion of the nozzle opening 6 that is cut off by it is entirely derived from the powder section 11, and 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.

[0051] 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]

[0052] 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 discharge port 15 Connecting rings 16 Powder Injector 17. Intake Connection 18 Outlet connection 19 Injector Guide 20 Center of optical channels 21 First powder focus 25. Gap within the powder focus area 26 Turn angle 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 applied to the workpiece, The powder unit (7) forms a powder section (11) at the mouth portion (6) of the nozzle in a circumferential direction around the optical channel (3), and a front section (12) lacking the powder unit is located close to it in the circumferential direction, in the injection nozzle (1).

2. The spray nozzle (1) according to claim 1, wherein the front section (12) is formed in the region of the mouth portion (6) of the nozzle facing the forward direction (2).

3. The spray nozzle (1) according to claim 1 or 2, wherein the powder section (11) extends around the optical channel (3), particularly along a horseshoe-shaped elongated arc.

4. The spray nozzle (1) according to any one of claims 1 to 3, wherein the powder section (11) extends in the circumferential direction around the optical channel (3) with a winding angle (23) of 45° to 330°, particularly 90° to 300°, and more particularly 180° to 300°, with respect to the center (20) of the optical channel (3).

5. The spray nozzle (1) according to any one of claims 1 to 4, wherein the powder section (11) is composed of a first powder section and a second powder section, and the first powder section is separated from the second powder section by a powder section gap.

6. The spray nozzle (1) according to claim 5, wherein the powder section gap is formed in the region of the mouth portion (6) of the nozzle away from the forward direction (2).

7. The injection nozzle (1) according to any one of claims 1 to 6, wherein the powder section (11) has a plurality of injector guides (19), and a powder injector (16) can be inserted into each of the injector guides.

8. The injection nozzle (1) according to claim 7, wherein a first powder injector is prepared to deliver a first powder mass flow, and a second powder injector is prepared to deliver a second powder mass flow, wherein the first powder mass flow is different from the second powder mass flow.

9. The injection nozzle (1) according to claim 8, wherein the first powder mass flow conveys a powder different from the second powder mass flow.

10. The injection nozzle (1) according to any one of claims 7 to 9, wherein a first powder injector is prepared to form a first powder focus (20), and a second powder injector is prepared to form a second powder focus, wherein the first powder focus (20) is different from the second powder focus.

11. The spray nozzle (1) according to any one of claims 1 to 10, wherein the powder section (11) forms an annular gap segment.

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

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