Beam nozzle for laser build-up welding in feed direction

Abstract

The utility model relates to a beam nozzle for laser build-up welding in a feed direction, having a light channel for guiding at least one laser beam directed onto a workpiece, the light channel being configured to direct a first laser beam onto the workpiece in order to produce a first irradiation zone and to direct a second laser beam onto the workpiece in order to produce a second irradiation zone, the beam nozzle has a first irradiation zone, which is located in front of the first irradiation zone in the feed direction, and a second irradiation zone, which is located in front of the first irradiation zone in the feed direction, and has a powder unit, which is arranged outside the light channel, for guiding at least one filling material to be applied to the workpiece, the powder unit being configured to introduce the filling material into the first irradiation zone. The second laser beam is introduced into the second irradiation zone such that the filler enters at least partially into the first laser beam and is thereby at least partially heated before impacting the workpiece, a secondary laser energy of the second laser beam introduced into the second irradiation zone being greater than a primary laser energy of the first laser beam introduced into the first irradiation zone.

Description

Technical Field

[0001] This application relates to a beam nozzle for laser surfacing along the feed direction. Background Technology

[0002] Laser cladding is commonly used in repair, coating, and / or joining techniques. It can be distinguished between conventional laser cladding (laser metal deposition (LMD), direct metal deposition (DMD), or direct energy deposition (DED)) and so-called high-speed laser cladding (HS-LMD or ultra-high-speed laser cladding (EHLA)). HS-LMD methods are described, for example, in publications DE 10 2011 100456 A and DE 10 2018 130 798 A1. Furthermore, publication DE 10 2022 100 173 A1 discloses an additive manufacturing method in which a first laser beam originates from a nozzle unit and a second laser beam originates from a separate head and is directed onto the workpiece to apply powdered structural material in an additive manner.

[0003] Laser cladding can be used to apply functional layers to workpieces. These functional layers typically improve the load-bearing capacity of the laser-clad workpiece relative to the unprocessed workpiece. Functional layers can be used, for example, as wear-protective layers. The application of functional layers can be based on diffusion processes, welding and / or melting of the workpiece surface, application of fillers, and subsequent cooling, resulting in a substrate structure with hard particles bonded to the workpiece surface material. Laser cladding affects and alters the internal material structure of both the workpiece and the material to be applied. In some cases, this can lead to deficiencies in the internal material structure, such as cracks and / or bonding defects. It is also possible that the hard particles form alloys with the substrate material, leading to embrittlement of the substrate structure and thus the applied functional layer. Therefore, these deficiencies can impair the efforts made to achieve improved load-bearing capacity. These deficiencies are often microscopic and thus only become apparent through significant expenditure of resources. Summary of the Invention

[0004] Based on known prior art, the objective of this application is to provide an improved method for laser surfacing along the feed direction and an improved beam nozzle. The object of this application is particularly to apply filler to the workpiece in such a way that deficiencies in the internal material structure are reduced or even avoided, and the overall weld quality of the applied functional layer and the workpiece is improved. The deficiencies can be bonding defects between the workpiece surface and the applied functional layer, or between the individual applied functional layers. The deficiencies can also be voids, i.e., air inclusions, which appear within the applied functional layer or between the applied functional layer and the workpiece surface. In particular, voids may increase when the workpiece surface is a cast material. The deficiencies can also be cracks, which extend, particularly perpendicular to the workpiece surface, within the applied functional layer. The deficiencies can also arise from the dissolution of powdered filler particles, especially carbides, in the base material of the powdered filler, thereby forming an alloy, which leads to embrittlement of the base material. The object of this application is also particularly to provide a reliable beam nozzle capable of achieving the application of the functional layer in accordance with process requirements. This application can also achieve a beam nozzle configuration that ensures reliable and precise laser welding over very high cycle times.

[0005] The task is solved by a method and beam nozzle having the features of the independent claims. Advantageous extensions are derived from the dependent claims, the specification, and the drawings.

[0006] Accordingly, a method for laser cladding along a feed direction using a beam nozzle is proposed. The laser cladding can be a method for high-speed laser cladding (HS-LMD). The feed direction is the direction in which the beam nozzle moves relative to the workpiece. This feed direction can be formed by the movement of the workpiece, particularly rotational movement, the movement of the beam nozzle, or a combination of both. The workpiece can be rotationally symmetric, such as a brake disc, hydraulic cylinder, pressure roller, or sliding bearing. The beam nozzle has an optical channel for guiding at least one laser beam directed toward the workpiece. The optical channel can be a hollow channel that extends longitudinally through the entire beam nozzle. Process gas, in addition to the laser beam, can also be guided to the workpiece surface through the optical channel. The beam nozzle also has powder units, particularly arranged radially outside the optical channel, for guiding at least one filler, particularly powder, or alternatively, welding wire, wherein the filler is to be applied to the workpiece. The powder units can originate radially outside the optical channel from the longitudinal direction of the beam nozzle and can be part of an outer structure that closes around the optical channel. A powder beam can guide powdered filler composed of hard particles, particularly carbides, and a base material. The powder unit can be a component of the beam nozzle, configured to guide the powdered filler directly or indirectly. The powder unit may have an injector guide into which a powder injector can be inserted. The powder unit may also have an annular gap within which the powdered filler is guided.

[0007] The method includes the step of directing a first laser beam onto a workpiece to create a first irradiation zone. The first laser beam can be used to heat and, in particular, at least partially melt the filler and the workpiece. Therefore, the thermal energy delivered by the first laser beam, i.e., the primary laser energy, can be used to melt the filler and the workpiece in a manner desired for laser welding. Thus, the first irradiation zone can be referred to as the process zone because the process of applying a functional layer to the workpiece is carried out here.

[0008] The method further includes the step of directing a second laser beam onto the workpiece to create a second irradiation zone. The second laser beam can be used to preheat the workpiece. Therefore, the thermal energy delivered by the second laser beam, i.e., secondary laser energy, can be used to preheat the workpiece or the substrate to be coated before melting. Thus, the second irradiation zone can be called a preheating zone because preheating of the substrate to be coated occurs here. The second laser beam can be directed such that it does not interact with the filler or interacts only to a negligible degree before the filler impacts the workpiece.

[0009] The second irradiation zone is positioned ahead of the first irradiation zone in the feed direction, causing the first irradiation zone to follow the second irradiation zone. Alternatively, the second irradiation zone can be positioned directly ahead of the first irradiation zone, minimizing the time required between preheating and melting.

[0010] The method further includes the step of introducing filler into a first irradiation zone, wherein the filler is at least partially introduced into the first laser beam and thereby at least partially heated before impacting the workpiece. Heating of the filler by the first laser beam can improve its melting behavior on the workpiece. The filler may be introduced around the first laser beam, for example, along a semi-circular shape or a partially elongated hole shape.

[0011] According to this application, the secondary laser energy introduced into the second irradiation area by the second laser beam is greater than the primary laser energy introduced into the first irradiation area by the first laser beam. The higher secondary laser energy can be achieved by a higher irradiation intensity (W / cm²) of the laser beam. 2 This is caused by the higher secondary laser energy, which can also be caused by the laser wavelength having higher absorption on the workpiece. This can be achieved, in particular, by means of diode laser radiation, which is approximately 800 nm in the case of aluminum and approximately 515 nm or 450 nm in the case of copper. Therefore, the thermal energy introduced into the preheating zone exceeds the thermal energy introduced into the process zone. Thus, this application deviates from the fundamental principle widely adopted in the current field: the energy applied to the actual process is greater than the energy applied to the accompanying phenomena, i.e., the preheating application. In this way, the heat input to the filler can be large enough to facilitate melting without the risk of hard particles forming alloys with the substrate, which has been proven to be a cause of substrate embrittlement and cracking.

[0012] Therefore, this application is based on thermal management in which the energy applied to heat and partially melt the filler before it impacts the workpiece is less than the energy applied to preheat the workpiece. The workpiece is preheated relatively strongly by means of a secondary laser energy higher than the primary laser energy, thereby reducing heat transfer from the heated filler to the workpiece after the filler is applied. This reduced heat transfer from the filler, for example, in the form of molten liquid powder, to the workpiece can result in a molten pool, especially a uniform molten pool, not being required in either the first or second irradiation zone, to ensure adequate application of the functional layer to the workpiece. In the case of a correspondingly high secondary laser energy, it is also possible that a molten pool can be generated on the workpiece surface in the second laser beam, i.e., before the powder beam impacts the workpiece. Furthermore, the reduced primary laser energy can result in the filler undergoing only partial preheating in the process zone. Therefore, the direct energy input to the filler and the hard particles contained therein is relatively small compared to the indirect energy input from the preheated workpiece to the filler. The indirect energy input enables a smooth and uniform fabrication of the connection between the filler and the workpiece and any previously applied layers, thus providing a smaller temperature gradient. This smooth and uniform manufacturing process reduces the risk that hard particles can alloy with the base material and thus contribute to the formation of embrittled and / or cracked functional layers.

[0013] The first and / or second laser beams can be sourced using disk lasers or fiber lasers. Diode lasers can also be used. In this way, laser beams with wavelengths of approximately 450 nm, approximately 515 nm, between approximately 800 nm and approximately 1000 nm, or approximately 1030 nm, 1060 nm, or 1070 nm can be generated, for example. The corresponding laser beams can be guided to the processing head via optical fibers. With a large usable fiber diameter, the laser beams can be satisfactorily coupled to relatively large loop and core portions of multi-clad optical fibers, for example, within the limitations of the brightness of diode emitters or barren emitters or stacks, as described in detail below. The laser source can have a laser power between 2 kW and 100 kW. When the workpiece is a brake disc, the laser power can particularly be between 8 kW and 50 kW, and when the workpiece is a sliding bearing, the laser power can particularly be 2 kW. The laser beam can be pointed substantially perpendicularly to the surface of the workpiece to be processed. The powder beam can be tilted relative to the laser beam to create an interaction zone between the powder beam and the laser beam above the workpiece surface. This interaction zone enables more efficient application of powdered material to the workpiece.

[0014] In this embodiment, the second laser beam has an increased laser power relative to the first laser beam and / or a higher power measured in W / cm².2 The unit for irradiation intensity and / or increase is cm. 2 The cross-sectional area. The secondary laser energy, which is increased relative to the primary laser energy, can be geometrically achieved by dividing the laser output beam into a larger area for the second laser beam. This secondary laser energy can also be achieved by having different laser sources for the first and second laser beams. The cross-sectional areas of the first and / or second laser beams can be adapted using a suitable focusing lens. This helps to avoid crack formation and / or adhesion defects through optimized heat treatment.

[0015] In this embodiment, the ratio of secondary laser energy to primary laser energy is greater than 11:10, particularly greater than 5:4, and even more particularly greater than 3:2. It has been demonstrated that this ratio provides optimized characteristics between sufficient heating and subsequent melting of the filler by the first laser beam and sufficient thermal energy in the second irradiation zone. This avoids alloying of hard particles in the surrounding metallic material.

[0016] In one embodiment, the method further includes the step of manipulating a workpiece receiving unit on which the workpiece is arranged, such that rotational motion causes the workpiece to move about a rotational axis. This manipulation can occur between a central control unit of the laser system and a local control unit of the processing unit. The workpiece receiving unit can clamp the workpiece such that if the workpiece receiving unit itself rotates, the workpiece is fixedly supported within it. The rotational axis can correspond to the rotational symmetry axis of a rotationally symmetric workpiece. The beam nozzle can be pointed at a position on the workpiece that is radially outside the workpiece's rotational symmetry axis. Therefore, rotation about the rotational axis causes a powder layer trace to follow a path on the workpiece. The rotational motion of the workpiece receiving unit can be driven by a separate drive.

[0017] The method further includes the step of manipulating the translation unit such that the translational motion moves the beam nozzle and / or workpiece receiving unit in an offset direction substantially perpendicular to the axis of rotation. The translational motion can be driven by a drive component separate from the workpiece receiving unit. Alternatively, the translational motion can be driven by the same drive component as the rotational motion. The offset direction of the translational motion can cause a translation perpendicular to the axis of rotation, which can correspondingly affect the trajectory of the powder layer trace. Compared to the translational motion, the rotational motion can be very high-speed.

[0018] Rotational and translational motions are superimposed to form a feed motion, applying a powder layer with a radial trace width onto the workpiece along a helical trajectory. This enables planar powder coating in the radial direction of the workpiece. The geometry of the helical trajectory is predefined by the feed motion. The feed motion can influence process parameters, such as the interaction time between the powder beam, laser beam, and workpiece, to achieve a robust bond between the powder particles and the workpiece. The helical trajectory extends along a curve around the axis of rotation, wherein the distance relative to the axis of rotation increases if applied from the radial inward to the radial outward, or decreases if applied from the radial outward to the radial inward. The rotational motion is caused by the rotational speed, and the translational motion by the translational speed. When the processing parameter is a feed motion, these variables are caused by variations in the rotational speed and / or translational speed.

[0019] The offset between two adjacent helical surfaces of the helical trajectory is less than the trace width, causing the powder layer traces to form a radial overlap along the helical trajectory. Therefore, when applied from the radial interior to the radial exterior, the radially interior powder layer trace is positioned below at least the immediately adjacent radially exterior powder layer trace. Specifically, the first single trace (Einzelspur) of the powder layer can be formed by superimposing multiple, for example, three, four, five, or six additional traces. Correspondingly, when applied from the radial exterior to the radial interior, the radially exterior powder layer trace is positioned below the immediately adjacent radially interior powder layer trace. This radial overlap increases the powder layer thickness because the powder layer traces that are at least partially superimposed on each other, i.e., the superimposed powder layer traces, have a greater powder layer thickness than the two powder layer traces whose offset is greater than their radial trace width.

[0020] In this implementation, the ratio of trace width to offset is greater than 2:1, particularly greater than 5:1, or even greater than 15:1. This ensures the appropriate layer thickness of the applied functional layer. The ratio of trace width to offset also allows for adaptation to the laser welding process speed, in addition to the layer thickness caused by the functional layer. The aforementioned ratio enables a reliable and sufficiently thick functional layer within an effective processing time.

[0021] In this implementation, the radial overlap and feed motion are such that the second laser beam, when applied along the helical trajectory, reheats the previously applied powder layer marks, thereby improving its weldability through reprocessing, particularly reheating. Therefore, the second irradiation zone, i.e., the preheating zone, caused by the second laser beam, can simultaneously achieve a reheating zone for adjacent helical surfaces. Thus, the second irradiation zone not only facilitates the application of individual marks but also promotes a gentle cooling phase for adjacent helical surfaces, i.e., a cooling phase with a small temperature gradient.

[0022] In this implementation, the first and / or second laser beams have reduced intensity in the core region of their respective laser beams compared to the edge region. The core intensity may, for example, be less than 90% of the edge intensity. Therefore, the laser beams have an intensity in the edge region, at least within the interaction zone, that is higher than the intensity in the core region, such that the powdered filler is loaded with higher intensity in the edge region as it enters the interaction zone. The interaction distance (Wechselwirkungsstrecke) with the laser beam changes across the cross-section of the powder beam due to the tilted orientation of the at least one powder beam relative to the laser beam. This varying intensity in the core region results in a substantially uniform energy supply to each powder particle as the interaction distance changes. In other words, the maximum intensity in the edge region of the laser beam leads to a more uniform distribution of energy density per powder particle and thus results in an expanded process window toward higher laser power while maintaining stable welding quality. The intensity distribution of the laser beam suitable for the focal plane is: I Rand ≥I Zentrum ≥0.

[0023] In the implementation, the first laser beam and / or the second laser beam has a plateau-shaped intensity distribution. The plateau shape can also be referred to as a top-hat. A plateau-shaped or top-hat-shaped intensity distribution describes a step increase in intensity at the edge of the laser beam to its maximum value, which is maintained substantially across the entire width of the edge region before a step decrease in intensity towards the core region of the laser beam. Compared to a Gaussian-shaped intensity distribution, a plateau-shaped or top-hat-shaped intensity distribution in the edge region of the laser beam is advantageous for reducing the roughness of the applied material layer. At at least one location within the interaction zone, the intensity in the core region of the laser beam can be up to 90%, preferably up to 50%, and more preferably up to 10% of the maximum intensity in the edge region of the laser beam. An intensity distribution with a decreasing intensity in the core region of the laser beam can increase the process window in terms of the variability of the laser power used. In particular, with the intensity distribution described in the focusing plane, laser power greater than 4 kW can be used while maintaining weld quality, because more laser power is used for preheating and / or melting the powder used for coating the workpiece. The power in the core region of the laser beam can be at least between 7% and 9% of the total laser beam power at one location within the interaction zone. The power in the core region can also be between 5% and 7% of the total laser beam power, particularly about 6%. According to alternative variations, the power in the core region can be reduced to a minimum, specifically 0% of the total laser power.

[0024] In this embodiment, the first and second laser beams are generated from a common laser output beam in a common optical device by beam splitting. This simplifies the construction of the laser system and enables space-saving structural arrangements. The beam splitting is achieved, in particular, by means of optical wedges, cylindrical lenses, and / or diffractive optical elements (DOEs). Faceted optics or microlens arrays can also be used as beam splitter elements. Independent partial beams can be generated by means of optical wedges and DOEs, as well as by means of faceted optics or microlens arrays, and these partial beams are applied to the workpiece surface in corresponding irradiation areas. An elliptical beam profile can be generated by means of cylindrical lenses, such that the laser beam irradiates the corresponding irradiation areas on the workpiece surface with a continuous spot. Furthermore, a shifting unit can be included, by means of which the optical element configured as an optical wedge or DOE for distributing laser power to the generated laser beam can be moved laterally along the beam path of the laser output beam.

[0025] In this embodiment, the first and second laser beams can be provided by two separate laser beam sources, particularly by means of two separate laser optics, wherein the second laser beam is supplied to a second irradiation area outside the optical channel. Thus, the supply of the laser beams can take into account a predetermined irradiation energy for the corresponding irradiation area.

[0026] In one embodiment, a protective gas is supplied in the optical channel to protect the first and / or second irradiation areas from ambient oxygen. The protective gas may be arranged in a ring around the first and / or second laser beams to prevent undesirable oxidation in the first and / or second irradiation areas.

[0027] In this embodiment, the filler is introduced into the first irradiation zone by means of a powder injector. The powder injector can enter a corresponding injector guide in the powder unit of the beam nozzle. The powder injector enables high precision in the supply of filler that meets process requirements. The separation achieved through the powder focusing and preheating efforts of the second laser beam can be achieved particularly effectively by the powder injector.

[0028] This application also relates to a beam nozzle for laser surfacing along the feed direction. The beam nozzle has an optical channel for guiding at least one laser beam directed onto a workpiece. The workpiece can be rotationally symmetric, such as a brake disc, hydraulic cylinder, pressure roller, or sliding bearing. The optical channel can be a hollow channel that extends longitudinally through the entire beam nozzle. Through the optical channel, process gas can also be guided to the workpiece surface in addition to the laser beam. The beam nozzle also has a powder unit, particularly arranged radially outside the optical channel, for guiding at least one filler, particularly powder or welding wire, to be applied to the workpiece. The powder unit can extend radially outside the optical channel from the longitudinal direction of the beam nozzle and can be part of an outer structure that closes around the optical channel. The powder beam can guide powdered filler composed of hard particles, particularly carbides, and a base material. The powder unit can be a component of the beam nozzle, configured to guide the powdered filler directly or indirectly. The powder unit can have an ejector guide into which a powder ejector can be inserted. The powder unit may also have an annular gap, within which powdered filler is guided.

[0029] The beam nozzle is configured and set up for implementing the method according to this disclosure. The beam nozzle is coupled by means of a control unit that pre-sets primary and secondary laser energies such that the application of filler can be achieved through optimized thermal management according to this disclosure.

[0030] In this embodiment, the beam nozzle is manufactured using additive manufacturing methods, particularly powder bed melting. For this purpose, the beam nozzle can be composed of copper or copper alloys, especially copper-chromium-zirconium alloys. This is suitable for additive manufacturing methods and ensures sufficient strength, thermal conductivity, and heat resistance to meet process requirements. In powder bed melting, the material to be processed exists in powder form. A laser beam heats the powder along a set geometry, thereby liquefying the powder and bonding the materials together. Powder bed melting can be performed, for example, as selective laser melting (“SLM”) or selective laser sintering (“SLS”). The beam nozzle can be composed of non-ferromagnetic and / or non-ferromagnetic materials.

[0031] The features of this disclosure are used individually or in combination to overcome the aforementioned deficiencies in laser cladding. Attached Figure Description

[0032] The preferred embodiments of this application are illustrated in detail below with reference to the accompanying drawings. As shown herein:

[0033] Figure 1 A schematic view of the beam nozzle during laser surfacing, showing a first irradiation zone and a second irradiation zone;

[0034] Figure 2 Schematic view of the laser optics used to generate the first and second irradiation areas;

[0035] Figure 3 Microscopic view of a functional layer applied by means of a conventional method for laser cladding, and a functional layer applied by means of a method according to this disclosure;

[0036] Figure 4 A schematic top view of the brake disc, showing powder layer traces applied to the brake disc along a spiral trajectory;

[0037] Figure 5 A schematic cross-section of the brake disc, with a first powder layer mark (above) or another powder layer mark (below) applied to the brake disc;

[0038] Figure 6. Schematic top view of the brake disc, with a first powder layer mark (left) or another powder layer mark (right) applied to the brake disc;

[0039] Figure 7 A perspective view of the beam nozzle from above, showing the powder injector being inserted into the beam nozzle;

[0040] Figure 8 A perspective view of the beam nozzle from below; and

[0041] Figure 9 A schematic view of the interaction between the packing material and the first laser beam, and the lack of interaction between the packing material and the second laser beam. Detailed Implementation

[0042] Preferred embodiments are described below with reference to the accompanying drawings. Here, the same, similar, or equivalent elements are given the same reference numerals in different drawings, and some repetitive descriptions of these elements are omitted to avoid redundancy.

[0043] Figure 1 A beam nozzle 1 for laser welding along a feed direction 2 is shown. The feed direction 2 is the direction in which the beam nozzle 1 moves relative to the workpiece 100. This feed direction can be generated by the movement of the workpiece 100, particularly rotational movement, by the movement of the beam nozzle 1, or by the superposition of the movements of the workpiece 100 and the beam nozzle 1. The feed direction 2 and the associated feed motion can be constant during the process. Alternatively, the feed direction can change with corresponding process stages. The workpiece 100 can be a rotationally symmetric workpiece, such as a brake disc, hydraulic cylinder, pressure roller, or sliding bearing.

[0044] The beam nozzle 1 has an optical channel 3 for guiding a laser output beam 50, which consists of a first laser beam 51 and a second laser beam 52. The first laser beam 51 and the second laser beam 52 can be traced back to the same laser source or alternatively to two different laser sources. The optical channel 3 has a side 4, within which the laser output beam 50 is guided. Radially outside the optical channel 3 is an outer structure 5. In the region of the end of the beam nozzle 1 facing the workpiece 100, a nozzle orifice 6 forms a powder unit 7. Multiple ejector guides 8 can be constructed within the powder unit 7, each containing a powder ejector 9.

[0045] A first laser beam 51 is directed onto the workpiece 100 and forms a first irradiation zone 101. A second laser beam 52 is also directed onto the workpiece 100 and creates a second irradiation zone 102. The second irradiation zone 102 is located ahead of the first irradiation zone 101 in the feed direction 2. A filler 60 is introduced into the first irradiation zone 101 via a powder unit 7, wherein the filler 60 is at least partially introduced into the first laser beam 51 before impacting the workpiece 100 and is thereby partially heated. The secondary laser energy introduced by the second laser beam 52 into the second irradiation zone 102 is greater than the primary laser energy introduced by the first laser beam 51 into the first irradiation zone 101.

[0046] Therefore, the laser output beam 50, composed of the first laser beam 51 and the second laser beam 52, can be emitted from the beam nozzle 1. The first laser beam 51 creates a first irradiation zone 101 on the workpiece surface when irradiating (not shown) the workpiece surface, and the second laser beam 52 creates a second irradiation zone 102 in a similar manner. Through the relative movement of the workpiece 100 to be coated and the beam nozzle 1, the laser beams 51 and 52 move along a predetermined processing trajectory on the workpiece surface in the feed direction 2. Furthermore, powdered filler 60 is injected into the first laser beam 51 through the beam nozzle 1, causing the powder particles to be heated by the first laser beam 51 and impact the workpiece surface in the first irradiation zone 101 along the processing trajectory; this first irradiation zone is also referred to as the process zone. Through the simultaneous heating of the powder particles and the workpiece surface in the process zone 101, a fixed connection is generated very quickly when the powder particles impact the workpiece surface. Here, a partial molten pool, different from a fully molten pool, can be constructed. The partially molten material deposited in the process zone 101 solidifies in subsequent processes into a mark in the form of a weld bead 61. To accelerate the coating process and simultaneously minimize adhesion defects, the workpiece surface is preheated in a second irradiation zone 102 by a second laser beam 52 before reaching process zone 101; this second irradiation zone is also referred to as the preheating zone. To further improve the adhesion of the filler 60 material deposits on the workpiece 100, or the adhesion of overlapping material deposits, the weld bead 61 can also be heated in a third irradiation zone after process zone 101, which is generated by irradiation with a third laser beam (not shown). The first laser beam 51 and / or the second laser beam 52 may have reduced core strength.

[0047] exist Figure 2The diagram schematically illustrates the construction of a laser optics device 110, which can be used in a laser system having a beam nozzle 1. The laser optics device 110 can be particularly arranged in the processing head of a laser system. The laser output beam 50 is aligned to a collimating unit 112, particularly a collimating lens, via an optical fiber cable 111, for example, with a two-in-one fiber. A beam splitter element 113, particularly in the form of an optical wedge, is arranged in the beam path of the collimated laser output beam 50. The beam splitter element 113 can be moved laterally to the propagation direction of the laser output beam 50 and thus divides the laser output beam 50 into a first laser (part) beam 51 and a second laser (part) beam 52 according to process requirements. For example, by laterally positioning the beam splitter element 113 within the laser output beam 50, the total power of the laser output beam 50 can be selectively distributed to the laser part beams 51 and 52. The first laser beam 51 can deliver, for example, 30% of the energy of the laser output beam 50, while the second laser beam 52 delivers 70% of the energy of the laser output beam 50. Subsequently, the laser beams 51 and 52 are focused onto the surface of the workpiece 100 to be coated by a focusing unit 114, which is in the form of a focusing lens, and thereby generate corresponding irradiation areas 101 and 102 on the workpiece surface, respectively.

[0048] exist Figure 3 The image shows a cross-section of a coating on a workpiece 100 applied by means of laser overlay welding. The workpiece 100 includes a substrate 80 and an intermediate layer 81 applied to the substrate 80. A functional layer 82 is applied to the intermediate layer 81, the functional layer having powder particles embedded in the substrate material. The functional layer 82 includes multiple powder layer traces superimposed on each other, as further described below. Figure 3 The functional layer 82 in the diagram above shows adhesion defects 83 between the powder particles and the substrate. In the diagram above, the primary laser energy exceeds the secondary laser energy during laser welding. The coating method proposed herein should resist the formation of adhesion defects, such as in... Figure 3 As shown in the diagram below, in which the secondary laser energy exceeds the primary laser energy during laser welding.

[0049] Figure 4A workpiece 100 is shown in the form of a brake disc with a hub housing. The brake disc is mounted on a workpiece receiving unit, which moves the workpiece 100 along a rotational motion 115. Furthermore, the workpiece receiving unit and / or the beam nozzle 1 are provided with a translational unit, which causes a translational motion 116 of the beam nozzle and / or the workpiece receiving unit. The rotational motion 115 and the translational motion 116 are superimposed to form a feed motion along the feed direction 2. Here, a powder layer trace 62 is applied to the workpiece along a helical trajectory 63. An offset 64 exists between two adjacent helical surfaces of the helical trajectory 63 due to the feed motion. The dimensions of the offset 64 are combined with… Figure 5 Further processing is needed.

[0050] Figure 5 Workpiece 100 is shown. In the figure above, a first powder layer trace 62 with a trace width 65 has been applied as a single trace. In a further process of laser welding, the powder layer trace 62 is applied to workpiece 100 along a helical trajectory 63. Here, the offset 64 of two adjacent helical surfaces is selected such that the offset is less than the trace width 65, thereby forming a radial superposition 66 of the powder layer trace 62 along the helical trajectory 63. The ratio of the trace width 65 to the offset 64 is 4:1 in the present example, such that four partial traces in the figure below are applied to the single trace in the figure above. The radial superposition 66, combined with the division of primary and secondary laser energies according to this disclosure, has the advantage that the first applied powder layer trace 62, such as the single trace in the figure above, is reheated when the superimposed trace is applied. This reheating is beneficial to the solidification behavior of the applied functional layer 82 and produces higher weld quality. Through the superposition 66, the previously welded trace is covered by the weld and is beneficial for remelting.

[0051] Figure 6a and 6b The workpiece 100, in the form of a brake disc, is shown in a top view. Figure 6a In the middle, powder layer trace 62 is still a single trace. Powder layer trace 62 has a trace width of 65. Figure 6b The laser welding process continues in the middle. Besides... Figure 6aIn addition to the single mark, three additional marks are marked on the workpiece 100 along a helical trajectory 63. The offset 64 between two adjacent helical surfaces of the helical trajectory 63 is less than the mark width 65. Accordingly, a radial overlap 66 is formed between adjacent helical surfaces, and the ratio of the mark width 65 to the offset 64 can be greater than 2:1, for example, 3:1 or 4:1. Once the entire helical trajectory 63 is applied, the functional layer 82 covers the substrate 80. In the case of a brake disc, the friction surface, as the substrate 80, is provided with an HS-LMD coating as the functional layer. This reduces the fine dust load associated with the braking process.

[0052] Figure 7 and 8 An embodiment of a laser nozzle 1 for laser surfacing along the feed direction 2 is shown. A laser output beam 50 exits from an optical channel 3 having side surfaces 4. Furthermore, the optical channel 3 can be adapted to guide process protective gas in radially outer sections for protecting the process zone and preventing oxidation. The optical channel 3 is surrounded by an outer structure 5 having a nozzle orifice 6, which in turn contains a powder unit 7. The powder unit 7 may, for example, have multiple ejector guides 8, each into which a powder ejector 9 can be respectively inserted. Instead of the individual ejector guides 8, the powder unit 7 may have a powder annular channel (not shown). The filler 60 is aligned onto the workpiece 100 via the powder unit 7 and, for example, the powder ejector 9 arranged therein. The laser output beam 50 heats the workpiece 100 in such a way that a molten pool is at least partially formed on the workpiece surface. Here, the division between the primary and secondary laser energies according to this disclosure helps to avoid deficiencies in the functional layer 82. Here, the first laser beam 51 heats the filler 60. Once the molten pool cools, a functional layer 82 of the weld is formed by hard particles and a base material, such as a weld abrasion protection layer. The functional layer 82 of the weld makes the workpiece surface more resistant and improves its load-bearing capacity.

[0053] A flange section with a coupling ring 10 can be joined to the beam nozzle 1, which secures the beam nozzle 1 to the joined unit, such as the laser optics 110 or process adapter. A powder ejector 9 is inserted into the ejector guide 8 of the powder unit 7. The filler 60 is delivered by means of the powder ejector 9 and applied to the workpiece 100 with a particularly adjustable focus. Each powder ejector 9 can apply a different powder focus to each other. Alternatively, the powder ejectors 9 can be pointed to the same focal point. The powder ejectors 9 are arranged in the powder section 11 within the ejector guide 8 of the powder unit 7 for this purpose. A feed section 12 without a powder unit is joined to the powder section 11 in the circumferential direction; this feed section does not have powder ejectors 9. Furthermore, an inlet sleeve 13 is inserted into the coolant inlet and an outlet sleeve 14 is inserted into the coolant outlet. These sleeves connect the coolant inlet and outlet of the beam nozzle to the coolant circuit of the laser system. The nozzle orifice 6 has an arched funnel shape. An ejector guide 8 is formed inside each arch, into which the powder ejector 9 can be inserted. In the feed direction 2, the optical channel 3 is elongated differently from a circular shape to guide the first laser beam 51 and the second laser beam 52 according to this disclosure and to contribute to the advantages of this disclosure.

[0054] Figure 9 A beam nozzle 1 is shown, from which a first laser beam 51 and a second laser beam 52 are emitted. A powder beam, each emitted from an ejector guide 8, interacts with the first laser beam 51. According to this disclosure, the second laser beam 52 is used to preheat the workpiece surface. The second laser beam 52 is positioned ahead of the first laser beam 51 in the feed direction 2. To avoid interaction between the powder beam and the second laser beam 52, a powder-free feed section 12 is provided in the region of the nozzle orifice 6, in which no filler 60 is conveyed to the workpiece surface. The cross-section of the optical channel 3, extending orthogonally to the longitudinal direction of the beam nozzle 1, is not circularly elongated in the feed direction 2. This elongation facilitates the configuration of the first irradiation zone 101 as a process zone and the second irradiation zone 102 as a preheating zone. In other words, a portion of the cross-section, orthogonal to the longitudinal direction of the beam nozzle 1, is the shape of the optical channel 3. The cross-section can be elongated in feed direction 2 and can be axially symmetrical along feed direction 2 and about the center point of the cross-section of optical channel 3. The minimum cross-section of the optical channel is predetermined by the size of the laser beam, especially its diameter. The cross-section elongates along the feed direction relative to the minimum size.

[0055] Where applicable, all individual features shown in the embodiments may be combined and / or substituted with each other without departing from the scope of this application.

[0056] List of reference numerals

[0057] 1. Beam nozzle

[0058] 2. Feed direction

[0059] 3 optical channels

[0060] 4. Side view

[0061] 5. External Structure

[0062] 6 Nozzle opening

[0063] 7 Powder Unit

[0064] 8. Injector guide

[0065] 9. Powder injector

[0066] 10 Coupling ring

[0067] 11 Powder Section

[0068] 12 feed sections

[0069] 13 Entering the casing

[0070] 14 Discharge sleeve

[0071] 50 laser output beams

[0072] 51 First laser beam

[0073] 52 Second laser beam

[0074] 60 packing

[0075] 61 weld beads

[0076] 62 Powder layer traces

[0077] 63 Spiral Trajectory

[0078] 64 offset

[0079] 65 Trace width

[0080] 66 Radial superposition part

[0081] 80 matrix

[0082] 81 Intermediate Layer

[0083] 82 Functional Layer

[0084] 83 Adhesion defects

[0085] 100 workpieces

[0086] 101 First Irradiation Zone

[0087] 102 Second Irradiation Zone

[0088] 110 Laser Optical Devices

[0089] 111 Optical fiber cable

[0090] 112 Collimation Unit

[0091] 113 Beam Splitter Components

[0092] 114 Focusing Units

[0093] 115 Rotational motion

[0094] 116 Translational motion

Claims

1. Beam nozzle (1) for laser deposition welding along a feed direction (2), characterized in that The beam nozzle has - a light channel (3) for guiding at least one laser beam, which is directed onto a workpiece (100), wherein the light channel (3) is configured for directing a first laser beam (51) onto the workpiece (100) to produce a first irradiation zone (101) and for directing a second laser beam (52) onto the workpiece (100) to produce a second irradiation zone (102), wherein the second irradiation zone (102) is located in front of the first irradiation zone (101) in the feed direction (2); and - a powder unit (7) arranged outside the light channel (3) for guiding at least one filler material (60) to be applied to the workpiece (100), wherein the powder unit (7) is configured for introducing the filler material (60) into the first irradiation zone (101) such that the filler material (60) at least partially enters into the first laser beam (51) and is thereby at least partially heated before impinging on the workpiece (100); wherein the secondary laser energy introduced by the second laser beam (52) into the second irradiation zone (102) is greater than the primary laser energy introduced by the first laser beam (51) into the first irradiation zone (101).

2. Beam nozzle (1) according to claim 1, characterized in that the second laser beam (52) has an increased laser power and / or a higher irradiation intensity and / or an increased cross-sectional area relative to the first laser beam (51).

3. Beam nozzle (1) according to claim 1 or 2, characterized in that the ratio of the secondary laser energy relative to the primary laser energy is greater than 11:

10.

4. Beam nozzle (1) according to claim 1 or 2, characterized in that The filler material (60) is a powder.

5. Beam nozzle (1) according to claim 3, characterized in that the ratio of the secondary laser energy relative to the primary laser energy is greater than 5:

4.

6. Beam nozzle (1) according to claim 3, characterized in that the ratio of the secondary laser energy relative to the primary laser energy is greater than 3:

2.

7. Beam nozzle (1) according to claim 1 or 2, characterized in that the first laser beam (51) and / or the second laser beam (52) has a reduced intensity in a core region relative to a peripheral region.

8. Beam nozzle (1) according to claim 1 or 2, characterized in that the first laser beam (51) and / or the second laser beam (52) has a plateau-shaped intensity profile.

9. Beam nozzle (1) according to claim 1 or 2, characterized in that the first laser beam (51) and the second laser beam (52) are produced in the same optical device from the same laser output beam by beam splitting.

10. Beam nozzle (1) according to claim 9, characterized in that the beam splitting is produced by means of a light wedge, a cylindrical lens and / or a diffractive optical element (DOE).

11. Beam nozzle (1) according to claim 1 or 2, characterized in that The first laser beam (51) and the second laser beam (52) are supplied by two separate laser beam sources, wherein the second laser beam (52) is supplied to the second irradiation zone (102) outside the light tunnel (3).

12. Beam nozzle (1) according to claim 11, characterized in that The laser beam sources are configured as laser optics.

13. Beam nozzle (1) according to claim 1 or 2, characterized in that In A protective gas is guided in the light tunnel (3), by means of which the first irradiation zone (101) and / or the second irradiation zone (102) are protected from ambient oxygen.

14. Beam nozzle (1) according to claim 1 or 2, characterized in that The introduction of the filler material (60) into the first irradiation zone (101) is effected by means of a powder jet.

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