Arrangement for coating metal workpieces by means of laser deposition welding, and method for coating metal workpieces by means of laser deposition welding

Abstract

The invention relates to an arrangement (1) and an associated method for coating metal workpieces by means of laser deposition welding with a powdered additive along a feed direction (VR), the arrangement comprising a nozzle device (2) and a laser device (3), wherein the laser device (3) has at least one beam-shaping laser optical unit (4) for generating a main laser radiation (HLS) and / or at least one secondary laser radiation (NLS1, NLS2) from laser radiation (LS) provided by means of a laser unit (5) with variably adjustable radiation power, wherein the nozzle device (2) has at least one laser guide channel (20) which extends along a longitudinal axis (LA) of the nozzle device (2) and is designed to guide the generated main and secondary laser radiation (HLS, NLS1, NLS2) through the nozzle device (2) and to apply the main laser radiation (HLS) to the metal workpiece in a main irradiation region (HB) and to apply the at least one secondary laser radiation (NLS1, NLS2) to the metal workpiece in at least one secondary irradiation region (NB1, NB2), wherein the nozzle device (2) has a plurality of powder guide channels (26, 27, 28, 29), arranged preferably point-symmetrically to the longitudinal axis (LA) of the nozzle device and concentrically around the at least one laser guide channel (20) for simultaneously applying the powdered additive to the metal workpiece in the main irradiation region (NB).

Description

[0001] Arrangement for coating metallic workpieces by means of laser cladding and method for coating metallic workpieces by means of laser cladding

[0002] The invention relates to an arrangement for coating metallic workpieces by means of laser cladding and an associated method for coating metallic workpieces by means of laser cladding.

[0003] Laser cladding allows functional layers to be applied to the surface of a metallic workpiece, increasing its load-bearing capacity or providing corrosion protection. Laser cladding is also used in the additive manufacturing of metallic workpieces.

[0004] Conventional laser cladding is also known as "Laser Metal Deposition" (LMD), "Direct Metal Deposition" (DMD) or "Direct Energy Deposition" (DED), and processes for so-called high-speed laser cladding (HS-LMD) are also known.

[0005] In laser cladding, the workpiece surface is exposed to laser radiation within a typically circular irradiation zone and melted accordingly. Simultaneously, the powdered filler material is applied to the workpiece surface using suitable nozzles. Shielding gas can also be used for deposition. The powdered filler material can be either a single powder or a mixture of a powder and hard particles forming a matrix structure. After solidification and cooling, the desired coating, called the functional or weld layer, is formed in the irradiation zone. The irradiation zone is guided along a feed direction across the workpiece surface to create a uniform coating.

[0006] Laser cladding creates a fusion metallurgical bond between the base material and the applied coating. This requires heating the base material. Insufficient heating can lead to bonding defects between the welded or coated material.

[0007] Functional layers and the material surface, or further weld layers, may form, potentially impairing the intended wear or corrosion protection. Cracks or pores may also form in the resulting weld or functional layer.

[0008] In the coating process, particularly in the production of coatings for wear or corrosion protection, it may also be necessary to heat the workpiece to be coated before laser coating, for example by means of additional heating elements or by induction heating. DE 10 2010 018 686 A1, for example, discloses a device and a method for laser cladding with powdered filler materials with additional heat input by means of an inductor.

[0009] Methods are also known in the field of additive manufacturing of metallic workpieces in which the material surface outside the current welding area is preheated with additional laser radiation. Such heating before and / or possibly also after the coating process by means of further irradiation areas from different laser beam sources is known, for example, from US 2021 / 0213565.

[0010] Furthermore, the use of laser units with beam-shaping laser optics in industrial material processing, as well as the design and operation of the beam-shaping laser optics, is well-known. For example, beam-shaping laser optics are used to shape the laser radiation generated by a laser unit, enabling the creation of a predefined focus geometry encompassing multiple processing areas within a single processing plane.

[0011] Such beam-shaping laser optics can include, among other things, rod lens arrays and / or wedge plate arrangements, by means of which a main laser beam and at least one secondary laser beam are generated from the laser radiation and which are focused and, if necessary, superimposed in the processing plane to generate the desired focus geometry. Beam-shaping laser optics for generating differently shaped focus geometries are known, for example, from DE 10 2015 112 537 Al or DE 10 2018 211 409 Al.

[0012] Based on this, the invention aims to provide an arrangement for coating metallic workpieces by means of laser cladding, as well as an associated method, by which the quality of the coating produced and / or its bond to the metallic workpiece and / or other previously produced layers can be improved. A further objective is, in particular, to reduce porosity, the tendency to bond defects, and the tendency to crack in the applied coating, especially when processing crack-sensitive and / or temperature-sensitive base materials.

[0013] The object of the invention is achieved by an arrangement for coating metallic workpieces by means of laser cladding according to the features of claim 1 and by an associated method according to claim 21. Advantageous further developments, details and embodiments of the invention will become apparent from the dependent claims, the description and the drawings.

[0014] The essential aspect of the arrangement according to the invention for coating metallic workpieces by means of laser cladding with a powdered filler material along a feed direction is that a nozzle device and a laser device are provided, wherein the laser device has at least one beam-shaping laser optic for generating a main laser beam and / or at least one secondary laser beam with variably adjustable radiation power from a laser beam provided by means of a laser unit, wherein the nozzle device has at least one laser guidance channel extending along a longitudinal axis of the nozzle device.the nozzle assembly is designed to guide the generated main and secondary laser radiation through the nozzle assembly and to impart the main laser radiation to the metallic workpiece in a main irradiation area and the at least one secondary laser radiation in at least one secondary irradiation area, and wherein the nozzle assembly is designed to simultaneously impart the powdered filler material to the metallic workpiece in the main irradiation area and / or in at least one secondary irradiation area.Preferably point-symmetric to the longitudinal axis of the nozzle assembly and having powder guide channels arranged concentrically around the at least one laser guide channel. Particularly advantageously, the laser radiation provided by a laser source is individually split into main and / or secondary laser radiation by means of the beam-shaping laser optics designed according to the invention and provided application-specifically for the laser cladding process. In particular, the resulting possibility of providing individual pre- and post-heating of the workpiece in the process area can improve the quality of the coating and reduce porosity, susceptibility to adhesion defects, and cracking in the applied coating.

[0015] Furthermore, the beam-shaping laser optics are advantageously configured to generate a circular, square, or rectangular main laser beam or a corresponding main irradiation area. Similarly, at least one circular, square, rectangular, or linear secondary laser beam or a corresponding secondary irradiation area can also be generated. The beam-shaping laser optics according to the invention can thus generate not only circular or oval irradiation areas, but also square, rectangular, and linear irradiation areas, the latter, for example, producing uniform heating across the entire width of the web-shaped weld layer. This allows for an advantageous increase in the track width of the coating and / or the coating volume.

[0016] In a preferred embodiment, the beam-shaping laser optics are configured to generate at least one secondary irradiation area leading and / or trailing the main beam area in the feed direction, and preferably at least one first and second secondary laser beam can be generated in addition to the main laser beam. This provides up to three irradiation areas for the laser cladding process, which, depending on the application, can be used for preheating and / or postheating or for coating. The beam-shaping laser optics are particularly advantageous for individually adjusting the distribution of the laser radiation power between the generated main laser beam and the at least one generated secondary laser beam.The laser radiation power can be distributed exclusively to the main laser beam, exclusively to at least one secondary laser beam (in particular the first and second), or uniformly or variably across the main laser beam and at least one secondary laser beam. This offers particularly advantageous new application possibilities and process variations for laser cladding; for example, two welding processes can be carried out consecutively, or separate pretreatments of the workpiece surface can be performed.

[0017] In a preferred embodiment, the beam-shaping laser optics comprise at least one collimation optic and one focusing optic, arranged sequentially in the laser beam path, with at least one wedge plate arrangement positioned at least partially between them. Preferably, at least one first and one second wedge plate arrangement are provided, arranged in a plane perpendicular to the propagation direction of the collimated laser radiation. Particularly preferably, the first and second wedge plate arrangements are each formed by a wedge plate array. The wedge plate arrays are preferably designed to be displaceable perpendicular to the longitudinal axis or propagation direction, so that the overlap area with the radiation cross-section of the collimated laser radiation can be varied.Accordingly, the power distribution between the generated main and secondary laser radiation can be adjusted almost arbitrarily.

[0018] In a further embodiment of the invention, the beam-shaping laser optics comprise a first and second rod lens arrangement downstream of the first and second wedge plate arrangements in the beam path. These rod lens arrangements preferably each comprise several rod lenses arranged in a plane perpendicular to the propagation direction. The rod lenses of the first and second rod lens arrangements are arranged relative to each other such that their longitudinal axes are parallel to each other, and the first and second rod lens arrangements are arranged in a crossed configuration. By means of the rod lens arrangement according to the invention, the intensity of the generated primary and secondary laser radiation is homogenized in the focal spot, and a square, rectangular, or linear beam distribution is additionally generated in the focal spot. This is particularly advantageous for a uniform coating process.

[0019] Advantageously, the laser guidance channel of the nozzle assembly opens at the outlet side into a first to third, preferably circular, nozzle opening, wherein the first nozzle opening is designed for the first secondary laser beam, the second nozzle opening for the main laser beam, and the third nozzle opening for the second secondary laser beam. This advantageously enables beam-specific guidance of the generated main and secondary laser beams and precise separation of the processing areas on the material surface. It also allows the powder guidance channels to be arranged in close proximity to the nozzle openings.

[0020] In an alternative embodiment, the laser guidance channel of the nozzle assembly can open into an elongated nozzle opening that deviates from a circular shape and is designed to guide the main and secondary laser beams. The cross-sectional shape of this elongated nozzle opening preferably corresponds to that of the partially overlapping first to third circular nozzle openings. This embodiment also achieves optimal beam guidance while simultaneously positioning the powder guidance channels as close as possible to the elongated nozzle opening. These channels are particularly advantageously arranged in the constricted sections of the elongated nozzle openings.

[0021] The powder guide channels and / or the nozzle openings can also be configured to supply shielding gas or a powder-shielding gas mixture to the main irradiation area and / or at least a secondary irradiation area, with the free ends of the powder guide channels preferably forming nozzle-shaped outlet openings. In a preferred embodiment, the powder guide channels are arranged point-symmetrically at the outlet end with respect to the longitudinal axis of the nozzle assembly or the nozzle opening of the laser guide channel. This results in a particularly uniform distribution of the powdered filler material in the process area.

[0022] The laser device can also include a laser unit for generating the laser radiation, and the beam-shaping laser optics can be arranged in the beam path of the laser unit. Alternatively, the laser unit can also be located upstream of the laser device. For example, the laser unit can be formed by a fiber-coupled laser beam source, in particular a fiber-coupled diode laser unit.

[0023] The invention also relates to a method for coating metallic workpieces by means of laser cladding with a powdered filler material along a feed direction using the aforementioned arrangement comprising a nozzle device and a laser device. Advantageously, a main laser beam and / or at least a secondary laser beam is generated by means of at least one beam-shaping laser optic of the laser device from a laser beam with variably adjustable radiation power provided by a laser unit, the generated main and secondary laser beams are guided through at least one laser guidance channel extending along a longitudinal axis of the nozzle device, and the metallic workpiece is exposed to the main laser beam in a main irradiation area and to the at least one secondary laser beam in at least one secondary irradiation area.Furthermore, the main irradiation area and / or at least one secondary irradiation area are simultaneously supplied with the powdered additive material, which is provided via several powder guide channels, preferably arranged point-symmetrically to the longitudinal axis of the nozzle assembly and concentrically around the at least one laser guide channel. Using the method according to the invention, pore formation, susceptibility to bonding defects, and cracking tendency in the applied coating can be reduced, especially when processing crack-sensitive and / or temperature-sensitive base materials.

[0024] Furthermore, it is advantageous to generate a circular, square or rectangular main laser beam or a corresponding main irradiation area and / or at least a circular, square, rectangular or linear secondary laser beam or a corresponding secondary irradiation area (NB1, NB2) by means of the beam-shaping laser optics.

[0025] This makes it possible to produce a particularly uniform coating of high quality.

[0026] Advantageously, the beam-shaping laser optics generate at least one secondary irradiation area leading and / or trailing the main beam area in the feed direction, by means of at least one first and second secondary laser beam in addition to the main laser beam. This provides individually adaptable processing areas on the material surface.

[0027] In a preferred embodiment, the beam-shaping laser optics are used to individually distribute the laser radiation power between the generated main laser beam and the at least one generated secondary laser beam. For example, the laser radiation power can be distributed exclusively to the main laser beam, exclusively to the at least one secondary laser beam (in particular the first and / or second), or evenly between the main laser beam and the at least one secondary laser beam. This allows the radiation power applied to the workpiece surface in the different processing areas to be individually adapted to the respective process requirements.

[0028] Further developments, advantages, and possible applications of the invention will also become apparent from the following description of exemplary embodiments and from the figures. All features described and / or illustrated are, individually or in any combination, fundamentally the subject matter of the invention, irrespective of their compilation in the claims or their cross-reference. The content of the claims is also incorporated into the description.

[0029] Brief description of the drawings: The invention will be explained in more detail below with reference to exemplary embodiments in conjunction with the drawings. They show...

[0030] Fig. 1 shows an exemplary schematic sectional view through an arrangement according to the invention for coating metallic workpieces by means of laser cladding;

[0031] Fig. 2 shows an example of a perspective view of a nozzle assembly;

[0032] Fig. 3 shows an exemplary front view of the nozzle assembly according to Figure 2;

[0033] Fig. 4 shows an exemplary schematic sectional view through an arrangement according to the invention for coating metallic workpieces by means of laser cladding according to Figure 1 with an alternative nozzle device;

[0034] Fig. 5 shows an example of a perspective view of an alternative nozzle arrangement;

[0035] Fig. 6 shows an exemplary front view of the nozzle assembly according to Figure 5,

[0036] Fig. 7 shows an exemplary schematic sectional view through an arrangement according to the invention for coating metallic workpieces by means of laser cladding according to Figure 1 with an alternative laser device;

[0037] Fig. 8 shows, by way of example, a schematic top view of the layers produced in a machining plane on a workpiece surface and the machining areas exposed to the main and secondary laser radiation;

[0038] Fig. 9 shows an exemplary schematic top view of the processing area with the main irradiation area activated but without secondary irradiation areas; Fig. 10 shows an exemplary schematic top view of the processing area with the leading secondary irradiation area activated but without an active main irradiation area and without an active trailing secondary irradiation area;

[0039] Fig. 11 shows an exemplary schematic side view of the processing area with activated leading secondary irradiation area without active main irradiation area and without active trailing secondary irradiation area;

[0040] Fig. 12 shows an exemplary schematic top view of the processing area with activated trailing secondary irradiation area without active main irradiation area and without active leading secondary irradiation area;

[0041] Fig. 13 shows an exemplary schematic side view of the processing area with activated trailing secondary irradiation area without active main irradiation area and without active leading secondary irradiation area;

[0042] Fig. 14 shows an exemplary schematic top view of the processing area with a radiation power evenly distributed over the preceding and following secondary irradiation areas without an active main irradiation area;

[0043] Fig. 15 shows an exemplary schematic side view of the processing area with a radiation power evenly distributed over the preceding and following secondary irradiation areas without an active main irradiation area;

[0044] Fig. 16 shows an exemplary schematic top view of the processing area with radiation power distributed across the preceding and following secondary irradiation areas and the main irradiation area; Fig. 17 shows an exemplary schematic side view of the processing area with radiation power distributed across the preceding and following secondary irradiation areas and the main irradiation area;

[0045] Fig. 18 shows an exemplary schematic top view of the processing area with a radiation power distributed across the preceding and following secondary irradiation areas and the main irradiation area, each with a square cross-section; and

[0046] Fig. 19 shows an exemplary schematic side view of the processing area with a radiation power distributed over the preceding and following secondary irradiation areas and the main irradiation area, each with a square cross-section.

[0047] Ways to implement the invention

[0048] Identical reference numerals are used in the figures for identical or similarly functioning elements of the invention. Furthermore, for the sake of clarity, only those reference numerals necessary for describing the respective figure are shown in the individual figures.

[0049] Figure 1 shows an exemplary arrangement 1 according to the invention for coating metallic workpieces with a powdered filler material by means of laser cladding, wherein the metallic workpiece itself is not shown in the figures.

[0050] Such a metallic workpiece can be, for example, a metal component such as a brake disc of a vehicle or another industrially manufactured metallic component such as a shaft or a cylinder with a surface suitable for coating. The arrangement 2 according to the invention is particularly suitable for coating metallic workpieces made of materials susceptible to cracking and / or temperature sensitivity by means of laser cladding.

[0051] The powdered filler material used in laser cladding can either be a powdered material or a mixture of a powdered material and hard material particles, wherein the hard material particles are added to the powdered material to create a matrix composite consisting of a metallic matrix and hard material particles.

[0052] The arrangement 1 comprises a nozzle assembly 2 and a laser assembly 3, wherein the nozzle assembly 2 extends along a longitudinal axis LA and the beam path of the laser assembly 3 is also oriented in or along the longitudinal axis LA in a propagation direction PR. The laser assembly 3 is configured to generate at least one main laser beam HLS and at least one, preferably a first and second, secondary laser beam NLS1, NLS2 from a laser beam LS and for this purpose comprises at least one beam-shaping laser optic 4, which preferably includes several optical components. The nozzle assembly 2 is configured to guide the generated main and secondary laser beams HLS, NLS1, NLS2 and to deliver the powdered additive material to the workpiece surface and can therefore also be referred to as a powder nozzle assembly.

[0053] The generated secondary laser radiation NLS1, NLS2 is positioned upstream and / or downstream of the generated primary laser radiation HLS in a feed direction VR, wherein the feed direction VR preferably runs perpendicular to the longitudinal axis LA of the nozzle assembly 2 or approximately perpendicular to the propagation direction PR. This direction indicates the direction in which the laser cladding process progresses, whereby either the workpiece and / or the nozzle assembly 2 can be moved. For example, the nozzle assembly 2 can be integrated into a processing head, which can be connected to the laser assembly 3 via an optical fiber for transmitting the primary and secondary laser radiation HLS, NLS1, NLS2. Thus, the workpiece surface can be irradiated along the feed direction VR with both the primary laser radiation HLS and the at least one secondary laser radiation NLS1, NLS2.A laser unit 5, which forms a laser source, is provided for generating the laser radiation LS. The laser unit 5 can, for example, be a fiber-coupled laser source connected to the beam-shaping laser optics 4 via an optical fiber. This means that the generated laser radiation LS is coupled into the beam-shaping laser optics 4 via the optical fiber, and the resulting main and secondary laser radiations HLS, NLS1, NLS2 are guided to the nozzle assembly 2 in the beam path. The laser unit 5 can also be part of or integrated into the laser assembly 3. For example, the laser unit 5 is designed as a diode laser unit.

[0054] In a preferred embodiment of the arrangement 1 according to the invention, the beam-shaping laser optics 4 are configured to generate the main laser beam HLS as well as the first and second secondary laser beams NLS1, NLS2, and for this purpose comprise a collimation optics 4.1 on the input side and a focusing optics 4.2 on the output side. The collimation optics 4.1 can be formed by a collimation lens and the focusing optics 4.2 by a focusing lens, as shown, for example, in Figures 1, 4, and 7. By means of the collimation optics 4.1, the coupled laser beam LS is expanded, and a collimated laser beam LS' is generated. The collimated laser beam LS' preferably has a round or circular beam cross-section.

[0055] Between the collimation optics 4.1 and the focusing optics 4.2, at least one, preferably a first and second, wedge plate arrangement 4.3, 4.4 is included in the beam path. These wedge plates generate, in addition to a main laser beam HLS, at least one secondary laser beam NLS1, NLS2 from the laser radiation LS' collimated by the collimation optics 4.1. According to the invention, this secondary laser beam is focused by the focusing optics 4.2 into a processing area on the workpiece surface, guided for this purpose by the nozzle device 2. Accordingly, the metallic workpiece is irradiated on its surface in a main irradiation area HB with the main laser beam HLS and in at least one, preferably a first and second secondary irradiation area NB1, NB2 with the at least one, or the first and second, secondary laser beam NLS1, NLS2, respectively. In the embodiment according to Figures 1 and 4, wedge plates are arranged between the collimation optics 4.1 and the focusing optics 4.2.Figure 2 incorporates the first and second wedge plate arrangements 4.3, 4.4 in the beam path, wherein the first wedge plate arrangement 4.3 and the second wedge plate arrangement 4.4 are spaced apart from each other and are positioned at least partially within the beam path of the collimated laser radiation LS, in order to form a first and second secondary laser radiation NLS1, NLS2 from the collimated laser radiation LS' in addition to the skin laser radiation HLS. An alternative embodiment of a beam-shaping laser optic 4, also with a first and second wedge plate arrangement 4.3, 4.4, is shown in Figure 7.

[0056] The first and second wedge plate arrangements 4.3, 4.4 can be formed by a wedge plate array, i.e., several wedge plates directly adjoining one another, each extending in a plane perpendicular to the longitudinal axis LA or the propagation direction PR, respectively, and directly adjoining each other. A wedge plate is essentially rod-shaped, and a wedge plate array forms an approximately plate-shaped component with a square or rectangular cross-sectional area. Using the wedge plate arrays 4.3, 4.4, the collimated laser radiation LS' with a circular radiation cross-section is deflected from the central axis or longitudinal axis LA, thus generating the secondary laser radiation NLS1, NLS2, which is laterally or laterally shifted with respect to the main laser radiation HLS. The generated secondary laser radiation NLS1, NLS2 therefore forms an approximately acute angle with the longitudinal axis LA.The generated main and secondary laser radiation HLS, NLS1, NLS2 also exhibits a circular or oval radiation cross-section.

[0057] The positioning of the wedge plate arrays 4.3, 4.4 allows the radiation cross-section overlapping with collimated laser radiation LS' to be changed, and thus also the distribution of the radiation energy of the collimated laser radiation LS' between the generated main and secondary laser radiation HLS, NLS1, NLS2. Therefore, the first and second wedge plate arrangements 4.3, 4.4 are preferably positioned along the feed direction VR and thus perpendicular to the longitudinal axis LS and LS, respectively.

[0058] The propagation direction PR is movably mounted in the beam-shaping laser optics 4, so that its overlap area with the circular radiation cross-section of the collimated laser radiation LS', and thus the distribution of the radiation energy or the radiation power of the generated first and second secondary laser radiations NLS1, NLS2, relative to the main laser radiation HLS, can be adjusted. This makes it particularly advantageous to adapt the energy distribution between the main and secondary laser radiations HLS, NLS1, NLS2 to the required process parameters.

[0059] According to the invention, the nozzle assembly 2 for guiding the generated main and secondary laser radiation HLS, NLS1, NLS2 through the nozzle assembly 2 has at least one laser guidance channel 20, which extends along a longitudinal axis LA of the nozzle assembly 2. By means of this, the generated main and secondary laser radiation HLS, NLS1, NLS2 can penetrate the nozzle assembly 2 unhindered and thus be directed onto the material surface.

[0060] The nozzle assembly 2 comprises a nozzle section 2.1 at the end face and a feed section 2.2 adjoining it, wherein a laser guidance channel 20 extends along the longitudinal axis LA over both the nozzle section 2.1 and the feed section 2.2. An inlet opening 21 is provided in the feed section 2.2, which forms the open inlet end of the laser guidance channel 20. The inlet opening 21 preferably has a circular cross-section, the diameter of which corresponds to the diameter of the laser guidance channel 20 at the inlet end of the feed section 2.2.

[0061] The outlet end of the laser guide channel 20, opposite the inlet opening 21, opens into a first to third nozzle opening 22, 23, 24, which are arranged in the region of a free-end end face 2.11 of the nozzle section 2.1 along the feed direction VR. The first to third nozzle openings 22, 23, 24 preferably have a circular or semicircular cross-section, wherein the first nozzle opening 22 is provided for the main laser beam HLS, the second nozzle opening 23 for the first secondary laser beam NLS1, and the third nozzle opening 24 for the second secondary laser beam NLS2. The free-end end face 2.11 of the nozzle section 2.1 forms a flat surface section that runs perpendicular to the longitudinal axis LA of the nozzle device 2, wherein the adjoining outer surface sections of the nozzle section 2.1 extend funnel-shaped from the feed section 2.2 to the free-end end face 2.11 approach.

[0062] The first to third nozzle openings 22, 23, 24 can form independent, separate passage openings to the laser guide channel 20, as shown, for example, in Figures 1 to 3. In this embodiment, the first to third nozzle openings 22, 23, 24 are spaced apart from each other in the free-end end face 2.11 along the feed direction VR and form a row of openings.

[0063] Alternatively, the first to third nozzle openings 22, 23, 24 can be partially overlapping and form an elongated passage opening 25 with a correspondingly shaped opening contour for the laser guide channel 20, as shown, for example, in Figures 4 to 6. In this configuration, the first to third nozzle openings 22, 23, 24 overlap in such a way that an elongated passage opening or nozzle opening 25 is formed, extending along the feed direction VR. The lateral edge of this opening, running along the feed direction VR, is wavy. This edge is formed by two opposing constriction sections 25.1, 25.2, which partially reduce the opening width of the elongated passage opening or nozzle opening, thus dividing the passage opening 25 into three overlapping, semicircular opening sections.

[0064] According to the invention, the nozzle assembly 2 for simultaneously supplying the metallic workpiece in the main irradiation area HB with the powdered filler material comprises several powder guide channels 26, 27, 28, 29, preferably arranged point-symmetrically to the longitudinal axis LA of the nozzle assembly 2 and concentrically around the at least one laser guide channel 20. In the present embodiment, a first, second, third, and fourth powder guide channel 26, 27, 28, 29 are provided, which preferably have the same radial distance to the longitudinal axis LA of the nozzle assembly 2. The first to fourth powder guide channels 26, 27, 28, 29 thus serve to preferably uniformly supply the powdered filler material into the main irradiation area HB for heating it via the main laser radiation HLS and carrying out the laser cladding process.

[0065] Furthermore, the first to fourth powder guide channels 26, 27, 28, 29 are arranged laterally along the feed direction VR to the first to third nozzle openings 22, 23, 24 or elongated nozzle opening 25 in the free-end end face 2.11. The end-face free ends of the powder guide channels 26, 27, 28, 29 are in the form of nozzle-like openings for generating a powder jet with which the workpiece surface in the machining area is cleaned.

[0066] The main irradiation area HB is acted upon. The first to fourth powder guide channels 26, 27, 28, 29 each extend from the free-end end face 2.11 along the longitudinal axis LA via the nozzle section 2.1 into the feed section 2.2. There, the powdered additive material is fed to the nozzle assembly 2 and into the first to fourth powder guide channels 26, 27, 28, 29 in a manner known in itself. For conveying the powdered additive material through the first to fourth powder guide channels 26, 27, 28, 29, a gas or gas mixture, in particular comprising a protective gas, can be used, for example. In the present embodiment, four powder guide channels 26, 27, 28, 29 and corresponding nozzle-like outlet openings are provided. It is understood that deviations from the number are permissible without abandoning the inventive concept.For example, two, three, six, or eight powder guide channels 26, 27, 28, 29, or a corresponding number of nozzle-like outlet openings, can be provided, preferably concentrically and approximately uniformly distributed around the longitudinal axis LA. In the present embodiment, the first to fourth powder guide channels 26, 27, 28, 29, or the nozzle-like outlet openings formed thereby, are arranged not only point-symmetrically with respect to the longitudinal axis LA, but also mirror-symmetrically with respect to a plane that accommodates the feed direction VR and the longitudinal axis LA.

[0067] In an alternative embodiment of the beam-shaping laser optics 4 according to Figure 7, a first and second rod lens arrangement 4.5, 4.6 are arranged in the beam path following the first and second wedge plate arrangements 4.3, 4.4. These rod lens arrangements are preferably designed in the form of a rod lens array. The first and second rod lens arrangements 4.5, 4.6 comprise several rod lens elements arranged side by side in a plane, the longitudinal axes of which are parallel to each other. The rod lens elements in the first and second rod lens arrangements 4.5, 4.6 are positioned in the beam path of the collimated laser radiation LS' such that the longitudinal axes of the rod lenses in the first rod lens arrangement 4.5 are perpendicular to the longitudinal axes of the rod lenses in the second rod lens arrangement 4.6, i.e., they are arranged crosswise to each other. In the present embodiment, the first rod lens arrangement 4.The first rod lens array 4.5 is mounted in the beam-shaping laser optics 4 such that its longitudinal axes are parallel to the feed direction VR and perpendicular to the propagation direction PR of the laser radiation LS. The second rod lens array 4.6 is rotated 90° relative to the first rod lens array 4.5 and positioned downstream of the laser radiation LS in the beam path. The beam cross-section of the generated main and / or secondary laser radiation HLS, NLS1, NLS2 can be adjusted by means of the first and second rod lens arrays 4.5, 4.6. For example, the rod lens arrays of the first and second rod lens arrays 4.5, 4.6 are configured and dimensioned such that the circular or oval beam cross-section of the generated main and / or secondary laser radiation HLS is shaped into a square, rectangular, or linear beam cross-section.Accordingly, square, rectangular, or linear main and / or secondary irradiation areas HB, NB1, NB2 can be generated on the workpiece surface within the processing area. Using the first and second rod lens arrangements 4.5, 4.6, the intensity of the generated main and secondary laser radiation HLS, NLS1, NLS2 can additionally be homogenized within the focal spot, resulting in an approximately constant intensity distribution within the focal spot and thus enabling a uniform coating.

[0068] In one embodiment, the first and second wedge plate arrangements 4.3, 4.4 can be completely removed from the beam path, so that only the first and second rod lens arrangements 4.5, 4.6 remain in the beam path between the collimation optics 4.1 and the focusing optics 4.2. This merely transforms the circular or oval radiation cross-section of the main laser beam HLS into a square, rectangular, or linear main laser beam HLS. No further secondary laser beams NLS1, NLS2 are generated; that is, the radiant power of the main laser beam HLS corresponds approximately to the total radiant power of the laser beam LS.

[0069] By appropriately shifting the first and second wedge plate arrangements 4.3, 4.4 into the beam path of the collimated laser radiation LS', the proportion of the radiation power of the first and / or second secondary laser radiation NLS1, NLS2 can be increased at the expense of the radiation power of the main laser radiation HLS, depending in each case on the overlap area of ​​the first and second wedge plate arrangements 4.3, 4.4 with the radiation cross-section of the collimated laser radiation LS'.

[0070] Figures 8 and 9 show, by way of example, a schematic top and side view of the different processing areas on the workpiece surface W, where at least one track-shaped weld layer SS has already been produced on the workpiece surface by means of laser cladding. The beam-shaping laser optics 2 are configured such that a main laser beam HLS is generated from the laser beam LS, which has 100% of the radiation power, whereas no secondary laser beams NLS1, NLS2 are generated, i.e., the secondary radiation areas NB1, NB2 indicated in the figure have a radiation power of 0%.To generate the further path-shaped weld layer SS', the first secondary irradiation area NB1, which advances in the feed direction VR, and the second secondary irradiation area NB2, which trails in the feed direction VR, are not supplied with secondary laser radiation NSL1, NSL2. Instead, only the main irradiation area HB is supplied with the main laser radiation HLS, which, for example, has the maximum achievable radiation power of 100%. The main irradiation area HB is circular, meaning that the main laser radiation HLS was generated by the beam-shaping laser optics 2 shown in Figures 1 and 4 without rod lens arrangements 4.5, 4.6. In this configuration of the beam-shaping laser optics 4, laser cladding can be carried out without pre- or post-heating of the processing area.

[0071] Figures 10 and 11 again show, by way of example, a schematic top and side view of the processing areas on the workpiece surface W, in which the beam-shaping optical laser optics 4 exhibit an alternative operating mode. In this embodiment, the first secondary irradiation area NB1, which advances in the feed direction VR, is activated and provides the full radiation power. The main laser radiation HLS and the trailing second secondary laser radiation NLS2 are inactive, i.e., their radiation power is 0%. Thus, the workpiece surface W is only exposed to the first secondary laser radiation NLS1 in the first secondary irradiation area NB1 and heated accordingly. In the first secondary irradiation area NB1, a further coating process can therefore be carried out, either in addition to or as an alternative to the main coating process in the main irradiation area HB.If the application of powdered additive material is required, the direction of the jet of at least individual powder guide channels 26, 27, 28, 29 can be adjusted accordingly.

[0072] Similarly, Figures 12 and 13 show a variant in which the second secondary irradiation area NB2, which trails in the feed direction VR, is exclusively activated and thus provides a radiation power of 100%. The main laser radiation HLS and the first secondary laser radiation BLS2 are inactive and have a radiation power of 0%.

[0073] Alternatively, the radiation power can be divided equally between the first and second secondary irradiation areas NB1 and NB2, as can be seen, for example, in the top view of Figure 14 and the side view of Figure 15. This generates a first and second secondary laser beam NLS1 and NLS2, each with a radiation power of 50% of the total power of the laser beam LS, without the need for a main laser beam HLS. The available radiation energy is thus distributed evenly between the two secondary irradiation areas NB1 and NB2. For example, this allows two coatings to be applied consecutively. The beam direction of at least some of the powder guide channels 26, 27, 28, 29 can be adjusted accordingly for the application of any required powdered additive material.Figures 16 and 17 again show a further embodiment by way of example in a schematic top and side view of the processing areas on the workpiece surface W. In this embodiment, a main laser beam HLS with a radiation power of 60% of the radiation power of the laser beam LS provided by the laser unit 5 and a first and second secondary laser beam NLS1, NLS2 with a radiation power of 20% each are generated via the beam-shaping laser optics 4. The welding process is thus carried out in the main beam area HB and the workpiece surface W is heated by means of the first and second secondary laser beam NLS1, NLS2 in the secondary beam areas NB1, NB2, which precede and lag behind in the feed direction VR.

[0074] It is also possible to integrate a heating process between two coating processes, or to implement two preceding or two following heating processes before or after a coating process, each with a radiation output adapted to the individual process requirements.

[0075] In Figures 16 and 17, circular main and secondary radiation zones HB, NB1, NB2 are used. Similarly, square main and secondary radiation zones HB, NB1, NB2 can also be provided to ensure uniform heating. Figures 18 and 19 show a schematic top and side view of such square processing areas on the workpiece surface W. Square main and secondary radiation zones HB, NB1, NB2 enable the production of larger track widths and / or coatings with higher volumes. This also results in uniform interaction times between the workpiece and the secondary radiation zones NB1, NB2. The power output of the main and secondary radiation zones HB, NB1, NB2 is also variably adjustable.

[0076] The invention has been described above using exemplary embodiments. It is understood that numerous modifications and adaptations are possible within the scope of protection of the following claims without departing from the underlying inventive concept. List of reference numerals

[0077] 1. Arrangement

[0078] 2 nozzle assembly

[0079] 2.1 Nozzle section

[0080] 2.11 Free-end end face

[0081] 2.2 Feed section

[0082] 3 Laser device

[0083] 4 beam-shaping laser optics

[0084] 4.1 Collimation Optics

[0085] 4.2 Focusing optics

[0086] 4.3 First wedge plate arrangement

[0087] 4.4 Second wedge plate arrangement

[0088] 4.5 First rod lens arrangement

[0089] 4.6 Second rod lens arrangement

[0090] 5 laser units

[0091] 20 laser guide channel

[0092] 21 Entrance

[0093] 22 first nozzle opening

[0094] 23 second nozzle opening

[0095] 24 third nozzle opening

[0096] 25 elongated nozzle openings

[0097] 26 first powder guide channel

[0098] 27 second powder guide channel

[0099] 28 third powder guide channel

[0100] 29 fourth powder guide channel

[0101] HB Main irradiation area

[0102] HLS main laser radiation

[0103] LA Longitudinal axis

[0104] LS Laser radiation

[0105] LS' collimated laser radiation

[0106] NB1 first side radiation area NB2 second side radiation area NLS1 first side laser radiation NLS2 second side laser radiation

[0107] PR Propagation Direction

[0108] SS sheet-like weld layer

[0109] SS' further web-shaped weld layer VR feed direction

[0110] W workpiece surface

Claims

- 25 - Patent claims 1. Arrangement (1) for coating metallic workpieces by means of laser cladding with a powdered filler material along a feed direction (VR) comprising a nozzle device (2) and a laser device (3), wherein the laser device (3) has at least one beam-shaping laser optic (4) for generating a main laser radiation (HLS) and / or at least one secondary laser radiation (NLS1, NLS2) with variably adjustable radiation power from a laser radiation (LS) provided by means of a laser unit (5), wherein the nozzle device (2) has at least one laser guidance channel (20) extending along a longitudinal axis (LA) of the nozzle device (2), which guides the generated main and secondary laser radiation (HLS, NLS1, NLS2) through the nozzle device (2) and acts upon the metallic workpiece with the main laser radiation (HLS) in a main irradiation area (HB) and with the at least one secondary laser radiation (NLS1, NLS2).NLS2) is formed in at least one secondary irradiation area (NB1, NB2), wherein the nozzle device (2) for simultaneously applying the powdered additive material to the metallic workpiece in the main irradiation area (NB) and / or in the at least one secondary irradiation area (NB1, NB2) has several powder guide channels (26, 27, 28, 29) arranged preferably point-symmetric to the longitudinal axis (LA) of the nozzle device (2) and concentrically around the at least one laser guide channel (20).

2. Arrangement according to claim 1, characterized in that the beam-shaping laser optics (4) is designed to generate a circular or square or rectangular main laser radiation (HLS) or a corresponding main irradiation area (HB).

3. Arrangement according to claim 1, characterized in that the beam-shaping laser optics (4) are configured to generate at least one circular, square, rectangular or linear side laser beam (NLS1, NLS2) or a corresponding side irradiation area (NB1, NB2).

4. Arrangement according to any one of the preceding claims, characterized in that the beam-shaping laser optics (4) are configured to generate at least one side irradiation area (NB1, NB2) that precedes and / or trails the main beam area (HB) in the feed direction (VR).

5. Arrangement according to one of the preceding claims, characterized in that the beam-shaping laser optics (4) are designed to generate at least one first and second secondary laser radiation (NLS1, NLS2) in addition to the main laser radiation (HLS).

6. Arrangement according to one of the preceding claims, characterized in that the beam-shaping laser optics (4) is designed for individually adjustable distribution of the radiant power of the laser radiation (LS) onto the generated main laser radiation (HLS) and the at least one generated secondary laser radiation (NLS1, NLS2).

7. Arrangement according to one of the preceding claims, characterized in that the radiant power of the laser radiation (LS) can be distributed exclusively to the main laser radiation (HLS) or exclusively to at least one, in particular a first and second secondary laser radiation (NLS1, NLS2) or uniformly to the main laser radiation (HLS) and at least one secondary laser radiation (NLS1, NLS2) by means of the beam-shaping laser optics (4).

8. Arrangement according to one of the preceding claims, characterized in that the beam-shaping laser optics (4) comprises at least a collimation optics (4.1) and a focusing optics (4.2) which are arranged one behind the other in the beam path of the laser radiation (LS) and between which at least a wedge plate arrangement (4.3, 4.4) is included at least sectionally in the beam path of the collimated laser radiation (LS').

9. Arrangement according to claim 8, characterized in that the beam-shaping laser optics (4) has at least a first and second wedge plate arrangement (4.3, 4.4) which are preferably displaceably arranged in a plane perpendicular to the propagation direction (PR) of the collimated laser radiation (LS').

10. Arrangement according to claim 9, characterized in that the first and second wedge plate arrangement (4.3, 4.4.) are each formed by a wedge plate array, wherein the respective wedge plate array is designed to be displaceable perpendicular to the propagation direction (PR).

11. Arrangement according to claim 9 or 10, characterized in that the beam-shaping laser optics (4) comprises a first and second rod lens arrangement (4.5, 4.6) downstream of the first and second wedge plate arrangement (4.3, 4.4) in the beam path.

12. Arrangement according to claim 11, characterized in that the first and second rod lens arrangement (4.5, 4.6) each have several rod lenses arranged in a plane perpendicular to the propagation direction (PR), wherein the rod lenses of the first and second rod lens arrangement (4.5, 4.6) are each arranged to each other such that their rod lens longitudinal axes run parallel to each other, wherein the first and second rod lens arrangement (4.5, 4.6) are arranged crossed to each other.

13. Arrangement according to one of the preceding claims, characterized in that the laser guidance channel (20) of the nozzle device (2) opens on the output side into a first to third, preferably circular nozzle opening (22, 23, 24), wherein the first nozzle opening (22) is designed for the passage of the first secondary laser radiation (NLS1), the second nozzle opening (23) for the passage of the main laser radiation (HLS) and the third nozzle opening (24) for the passage of the second secondary laser radiation (NLS2).

14. Arrangement according to one of the preceding claims, characterized in that the laser guidance channel (20) of the nozzle device (2) extends on the outlet side into an elongated shape deviating from the circular shape- 28 - The nozzle opening (25) opens, which is designed to carry out the main and secondary laser radiation (HLS, NLS1, NLS2).

15. Arrangement according to one of claims 13 and 14, characterized in that the cross-sectional shape of the elongated nozzle opening (25) corresponds to that of partially overlapping first to third circular nozzle openings (22, 23, 24).

16. Arrangement according to one of the preceding claims, characterized in that the powder guide channels (26, 27, 28, 29) and / or the nozzle openings (22, 23, 24, 25) are designed for supplying protective gas to the main irradiation area (HB) and / or at least one secondary irradiation area (NB1, NB2).

17. Arrangement according to one of the preceding claims, characterized in that the free ends of the powder guide channels (26, 27, 28, 29) form nozzle-shaped outlet openings.

18. Arrangement according to one of the preceding claims, characterized in that the powder guide channels (26, 27, 28, 29) are arranged point-symmetrically to the longitudinal axis (LA) of the nozzle device (2) on the outlet side.

19. Arrangement according to one of the preceding claims, characterized in that the laser device (3) has a laser unit (5) for generating the laser radiation (LS) and the beam-shaping laser optics (4) is arranged in the beam path of the laser unit (5).

20. Arrangement according to claim 19, characterized in that the laser unit is formed by a fiber-coupled laser beam source, in particular a fiber-coupled diode laser unit.

21. Method for coating metallic workpieces by means of laser cladding with a powdered filler material along a feed direction (VR) using an arrangement according to one of the preceding claims comprising a nozzle device (2) and- 29 - A laser device (3) in which a main laser radiation (HLS) and / or at least one secondary laser radiation (NLS1, NLS2) is generated from a laser radiation (LS) with variably adjustable radiation power provided by a laser unit (5) by means of at least one beam-shaping laser optic (4) of the laser device (3), in which the generated main and secondary laser radiation (HLS, NLS1, NLS2) is guided through at least one laser guidance channel (20) extending along a longitudinal axis (LA) of the nozzle device (2) and the metallic workpiece is irradiated in a main irradiation area (HB) with the main laser radiation (HLS) and in at least one secondary irradiation area (NB1, NB2) with the at least one secondary laser radiation (NLS1, NLS2), wherein the main irradiation area (NB) and / or at least one secondary irradiation area (NB1, NB2) is simultaneously irradiated with the powdered filler material, which is applied via several,preferably point-symmetric to the longitudinal axis (LA) of the nozzle device (2) and concentric around the at least one laser guide channel (20) powder guide channels (26, 27, 28, 29) are provided.

22. Method according to claim 21, characterized in that a circular or square or rectangular main laser radiation (HLS) or a corresponding main irradiation area (HB) is generated by means of the beam-shaping laser optics (4).

23. Method according to claim 21, characterized in that at least one circular, square, rectangular or linear side laser radiation (NLS1, NLS2) or a corresponding side irradiation area (NB1, NB2) is generated by means of the beam-shaping laser optics (4).

24. Method according to one of claims 21 to 23, characterized in that at least one secondary irradiation area (NB1, NB2) is generated by means of the beam-shaping laser optics (4) which precedes and / or follows the main radiation area (HB) in the feed direction (VR).

25. Method according to one of claims 21 to 24, characterized in that at least one first and second secondary laser radiation (NLS1, NLS2) are generated in addition to the main laser radiation (HLS).- 30 - 26. Method according to one of claims 21 to 25, characterized in that the radiant power of the laser radiation (LS) is individually distributed to the generated main laser radiation (HLS) and the at least one generated secondary laser radiation (NLS1, NLS2) by means of the beam-shaping laser optics (4).

27. Method according to one of claims 21 to 25, characterized in that the radiant power of the laser radiation (LS) is distributed exclusively to the main laser radiation (HLS) or exclusively to the at least one, in particular the first and second secondary laser radiation (NLS1, NLS2) or uniformly to the main laser radiation (HLS) and the at least one secondary laser radiation (NLS1, NLS2) by means of the beam-shaping laser optics (4).

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