Laser deposition welding process for producing a coating layer on a component

Abstract

The invention relates to a laser deposition welding process for producing a coating layer (80) on a surface (74) of a component (70) by creating at least one coating track (86) with a predefined track width (B) on the surface (74) by applying an, in particular pulverulent, filler material (2) along a helix-shaped or spiral-shaped working trajectory (88), wherein the filler material (2) and the component (70) are heated along the working trajectory (88) by means of a laser beam (1) so that the at least one coating track (86) is formed when the filler material (2) impinges on the surface (74), wherein at least two, in particular at least three, turns (8) in the at least one coating track (86) at least partially overlap along a track width (B).

Description

[0001] Title: Laser cladding process for producing a

[0002] Coating layer on a component

[0003] Description

[0004] The invention relates to a laser cladding method for producing a coating layer on a surface of a component, a device for carrying out the laser cladding method and a component with at least one surface which is coated with a coating layer, wherein the coating layer is produced by means of the laser cladding method.

[0005] Conventional laser cladding is well known in the art. It involves melting a component's surface using a laser beam, and then adding a powdered filler material to the resulting melt pool. The powder is then melted in the melt pool, so that after the molten powder and the surface have solidified, a material layer is formed that is bonded, particularly by melt metallurgy.

[0006] Depending on the application, this process can be performed at various points on the surface or across a larger, contiguous area of ​​the workpiece surface, allowing 3D shapes to be applied using laser cladding. Furthermore, multiple layers of different materials can be built up on top of each other on the surface. When metallic material is applied, the deposition process is also referred to as "laser metal deposition" (LMD for short). Typical applications for laser cladding include repair, coating, and joining techniques.

[0007] So-called extreme high-speed laser cladding (EHLA for short) is already known from DE 10 2011 100 456 B4. According to this method, a significant increase in the achievable processing speed is achieved compared to conventional laser cladding by supplying at least one filler material in at least partially molten form to a process zone on a surface to be processed. For this purpose, the filler material, which is initially in powder form, is melted by means of a laser beam at a distance greater than zero, in particular to form a molten bath, and is then supplied to the molten bath in, in particular, completely liquid form. The melting of the filler material, in particular the powder, at the stated distance from the molten bath and the heating of the molten bath can be carried out by the same laser beam.The laser beam shining onto the molten bath also melts the filler material at the specified distance from the molten bath. This occurs by moving the molten bath and a focus of the laser beam parallel to each other relative to the surface at a speed of at least 20 m / min. Furthermore, in the case of a powdered filler material, the powder density can be adjusted so that the laser beam power in the molten bath is less than 60% of the laser power before the laser beam comes into contact with the powder. In this way, the EHLA process can significantly increase the processing speed of the laser cladding process.

[0008] A build-up of the coating layer, which can also be carried out on opposite surfaces of the component, in the range of 50 pm to 500 pm, preferably around 100 pm to 200 pm, layer thickness can be achieved in particular by repeatedly passing over a track width of tracks of the molten bath. In industrial research and development, ever higher laser powers are being used to increase productivity (per welded area per unit time), for example laser powers of up to 24 kW in one focal point. As the laser power increases, the coating spot size (laser focus diameter and powder focus diameter) must be or is increased. A larger area can be processed per unit time on the processing trajectory. Surprisingly, experimental practice has shown that with increasing irradiation spot diameters or laser power, the surface waviness on welded layers increases.As a result, a larger layer thickness allowance must be provided to ensure that the coating layer exhibits the desired surface finish (including roughness) after subsequent grinding. The coating layer must be ground down to the valleys created in the wavy coating layer.

[0009] The invention is based on the object of reducing the above-mentioned disadvantages in a laser deposition welding process, in particular of improving the component quality produced by reducing the surface waviness of the coating layer produced.

[0010] The object is achieved by a laser cladding method according to claim 1. Accordingly, a laser cladding method is proposed for producing a coating layer on a surface of a component, in that at least one coating track with a predetermined track width is produced on the surface by applying a, in particular powdered, filler material along a helical or spiral-shaped processing trajectory, wherein the filler material and the component are heated along the processing trajectory by means of a laser beam, so that when the filler material impacts the surface the at least one coating track is produced, wherein along a track width at least two, in particular at least three, turns of the at least one coating track at least partially overlap or are produced in an at least partially overlapping manner.In particular, a laser focus diameter of the laser beam can be greater than 1 mm, in particular 1.4 mm to 12 mm. By laser cladding in such a way that two, three or more turns of the at least one coating track are produced along a track width which forms the coating layer or parts thereof upon solidification, in particular next to one another such that they partially overlap one another, it has been shown that the surface waviness of the coating layer produced in this way can be effectively reduced. The turns are produced in particular next to one another and partially overlapping one another. Advantageously, particularly high laser powers can be implemented in this way, so that the productivity of the laser cladding process can be increased without reducing the quality of the components produced or requiring deep regrinding of the coating layer.It is particularly advantageous if, along the track width, on average over the entire at least one coating track for producing the coating layer on a component, at least four or more partially overlapping turns are produced next to one another. In particular, it is also possible to produce the entire coating layer with just a single coating track with a corresponding number of turns along the helical or spiral processing trajectory. In this respect, the coating track produced along the processing trajectory is in particular produced continuously and not interrupted. However, it is also possible to interrupt the processing and use two or more coating tracks, wherein the coating tracks can each adjoin one another.The indication of the at least partially overlapping turns along a track width refers to how many turns of the at least one coating track are applied per track width. In particular, the number of turns per track width of the at least one coating track that is visible in the plan view of the at least one coating track or coating layer produced in this way is counted. It is therefore not necessary for the partially overlapping turns to run completely within one track width, because then the turns would overlap one another completely instead of only partially. The fact that the turns partially overlap refers to the width of the overlap of the turns. In principle, the number of turns along a track width does not have to be a whole number, but can also comprise parts of whole numbers.For example, 4.1 or 4.6 turns along a track width may partially overlap each other and be arranged next to each other.

[0011] While it is proposed according to the invention that turns produced next to one another at least partially overlap one another, it can also be provided, as mentioned at the outset, that turns of the at least one coating track are produced one above the other by repeatedly traversing a track width in order to produce a coating layer of a certain thickness, for example in the range from 50 pm to 300 pm, preferably around 100 pm. Unlike when the at least partially overlapping turns are produced next to one another, the turns of the at least one coating track are not produced next to one another here. Instead, the track widths or turns already produced or traversed are typically only traversed again after an entire processing trajectory has been run through.

[0012] In particular, it can be provided that above turns in a start and / or end area of ​​the

[0013] Further turns can be generated along the machining trajectory's track width. In other words, particularly in the initial and / or final regions of the machining trajectory, a track width can be crossed multiple times, as explained above. This has the advantage of producing a constant coating layer thickness, e.g., in brake discs as components on the outer and / or inner circumference of the friction surface to be coated.

[0014] It can be provided that at least four at least partially overlapping turns are produced side by side along a track width. Surprisingly, it has been shown that starting with four partially overlapping turns, only a particularly slight surface waviness of the coating layer is produced, which therefore does not require any further processing or can be reworked by only minor regrinding.

[0015] It can also be provided that the partially overlapping turns overlap each other by at least 20%, in particular at least 40%, of the track width. In particular, the degrees of overlap, which are indicated here by way of example as a percentage of the track width, can be essentially the same for the turns. It has been found that these degrees of overlap also result in a particularly low

[0016] Surface waviness of the coating layer is generated.

[0017] Furthermore, it can be provided that the number of turns which at least partially overlap one another along the track width is varied during production of the processing layer. In particular, the number of turns can be varied by up to 50% of the average number of turns which partially overlap one another along a track width and / or the degree of overlap can be varied by up to 50% of the average degree of overlap across all turns. This has the advantage that the coating layer thickness can be adjusted during the laser deposition welding process. Furthermore, in a control mode of the laser deposition welding process, the coating layer thickness can be guided around a target value and, in the case of so-called shielded panes, opposing plane-parallel surfaces of the component can be produced by means of wedge-shaped coating layer thicknesses.

[0018] Furthermore, it can be provided that a height profile of the surface coated with the at least one coating track is generated by a measuring device. The measuring device can, for example, be set up for a light section. The measuring device can also be, for example, an optical coherence tomography or thermography measuring device. The advantage of such a measuring device is that the height profile generated can be used to monitor unwanted waviness in the coating layer. Furthermore, the height profile or a parameter derived therefrom, which is indicative of the waviness of the coating layer, can be compared with a predetermined limit value. If the predetermined limit value is exceeded, the manufacturing process can be stopped automatically or the laser deposition process can be regulated to reduce the waviness.

[0019] It can be provided that an irradiation point of the laser beams on the surface is moved along the surface at a relative speed of at least 20 m / min. The relative speed is the speed at which the surface to be coated moves relative to the irradiation point of the laser beam on the surface. The laser beam radiates onto the surface in such a way that a process zone is created on the surface, in particular at least partially a molten pool, on the surface. One could therefore also say that the irradiation point and thus the process zone are moved along the surface at a speed of at least 20 m / min. The advantage of this high relative speed lies primarily in the high achievable productivity. Laser cladding of this type can also be referred to as high-speed laser cladding.

[0020] Furthermore, it can be provided that the component is rotationally symmetrical, in particular as a disk, and is rotated about a rotation axis during the production of the coating layer, in particular so that the processing trajectory follows a spiral or helical shape. The component can be, for example, a brake disk, sliding disk, friction disk or similar, as can be used in various applications, for example in

[0021] Motor vehicles. The surface to be coated or opposing surfaces to be coated can each be circular ring-shaped surfaces. Accordingly, the rotation of the disk about its axis of rotation allows the disk to be coated all the way around. For this purpose, the disk can be attached to a shaft of a corresponding drive, for example an electric motor, which sets the disk in rotation. In addition, the point of incidence of the laser beam can of course be moved, in particular in a linear movement. In particular, it can be moved in a plane above the disk. This can be done, for example, by a linear drive on the processing heads which emits the laser beam. The orientation of the feed of the at least one additional material can also be moved together with the point of incidence of the laser beam.

[0022] Furthermore, it can be provided that the at least one filler material is in powder form before melting by means of the laser beam. The filler material can be metallic. In addition to a metallic filler material, other materials can also be present which are to be incorporated into the coating layer. Furthermore, different metals can also be processed. Alternatively, it is conceivable for the filler material to be in the form of wire, tape, or sheet metal strip. However, feeding powdered filler material to the laser beam for melting, so that it is fed to the process zone in essentially completely molten form, has proven to be particularly advantageous. Furthermore, it can be provided that the at least one filler material is made available to the respective laser beam by at least three injectors per surface of the component.Particularly preferred are 3 to 21 injectors, and most preferably 7 to 14 injectors per surface or side of the component. This allows a very symmetrical focus of the filler material, in particular powder focus, to be created on the surface, which can improve the quality of the resulting coating layer.

[0023] Furthermore, it can be provided that an average powder efficiency with powdered filler material of all injectors combined is at least 85%. The powder efficiency indicates how much of the supplied powder is melted. Powder loss can thus be reduced. This is made possible, among other things, by the use of injectors that can be used at an angle of 90° to the direction of gravity.

[0024] Furthermore, it can be provided that the injectors are supplied with powder from a corresponding powder conveyor via two or more supply lines, which can be directed from the injectors in two or more clusters via a distributor component. The required powder mass flow can thus be distributed among parallel powder feed lines. This achieves a particularly uniform powder mass flow and thus produces particularly uniform coating layers.

[0025] The injectors can advantageously be designed as tubes. In particular, they can be designed as hard metal tubes to provide high resistance to both the filler material and the high temperatures generated during machining. Another advantage of tubes is the particularly good flow of any conveying gas through them, allowing the filler material to be fed from a suitable conveyor or reservoir to the laser beam at a distance from the surfaces.

[0026] Furthermore, it can be provided that the exit angle of the injectors relative to a perpendicular to the respective surface of the component is less than 60°, in particular less than 50°, and most particularly less than 40°. It has been shown that surface waviness of the coating layer welded on in this way is particularly low.

[0027] Furthermore, it can be provided that the at least one additional material is supplied to the laser beam by means of a conveying gas, wherein the conveying gas has in particular a relative atomic mass of at least 4, in particular at least 14, and / or a specific volume flow of at least 3.2 Nl / min per mm 2 cross-sectional area. It has been shown that the conveying gas with the above parameters provides a sufficiently strong impulse and thus such a high filler material speed, in particular powder speed, that the filler material can be guided to the laser beam in an optimal manner without any significant influence from external factors, for example the gravity acting on the filler material.

[0028] It can also be provided that the coating layer of the component is produced in a direction from relatively inside the surface to relatively outside the surface. In the case of a disc as the component, the coating or the movement of the laser beam spot takes place from radially inside or the inner diameter to radially outside or the outer diameter. In this way, thermal expansion can be used to generate tensile stresses in the component, in particular the disc. When it cools, compressive stresses form in the welded coating layer. These are advantageous because compressive stresses counteract crack propagation in the welded coating layer.

[0029] Furthermore, it can be provided that a laser beam axis of the laser beam is inclined relative to the surface at an angle of incidence in the range from greater than 0° to 35°, in particular in the range from 5° to 30°. For this purpose, a main axis of a processing head from which the laser beam is emitted can be inclined correspondingly relative to the surface. Laser light reflected back from the component at the angle of incidence thus does not strike the processing head, but is deflected past it.

[0030] It is also possible for the intensity distribution of the laser beam to be generated at least approximately in the form of a so-called flat top. In comparison to a Gaussian laser power distribution, it has been shown that this produces lower roughness on the coating layer. Very particularly, the intensity distribution can be approximately in the form of a flat top with an area of ​​reduced intensity in the center (I_max (maximum intensity) > l_ core (intensity in the core) > 0). This opens up a particularly large process window for the laser deposition welding process. The object mentioned at the outset is further achieved by a component according to claim 14. The component has a surface which is coated with a coating layer, the coating layer being produced by means of a laser deposition welding process according to the invention.

[0031] In the cross-section of the component, the tracks partially overlapping each other along the track width can be seen under microscopic observation, so that the component manufactured by means of the laser deposition welding process can be clearly distinguished from components whose coating layer was manufactured by means of a different process.

[0032] In this case, features that are described herein with regard to the laser cladding process also apply with regard to the component and vice versa.

[0033] The object mentioned at the outset is also achieved by a device according to claim 15. The device is set up to carry out a laser deposition welding method according to the invention, wherein the device has at least one laser for generating the laser beam, and wherein the device has at least one filler material conveyor for conveying the at least one filler material at a distance from the surface of the component to the laser beam.

[0034] In this case, features described herein with respect to the laser deposition welding method and the component apply equally with respect to the device, and vice versa. In particular, the device can have a closed-loop and / or open-loop control device configured to close-loop and / or open-loop the laser deposition welding process such that at least two or at least three turns of the at least one coating track overlap along a track width. For this purpose, a closed-loop and / or open-loop control program with corresponding instructions can be provided in the closed-loop and / or open-loop control device.

[0035] The at least one laser can preferably have a laser power of more than 4 kW, in particular more than 12 kW and up to 24 kW. It can be a laser with a wavelength of approximately 1 pm (fiber laser, disk laser), approximately 0.8 pm (diode laser) or 0.5 pm (green converted). A laser light cable with a 2 inl fiber can be used, whereby a core diameter of 600 pm to 1000 pm or diameter ratios of 200 pm / 700 pm and 300 pm / 1000 pm can be implemented. An adjusting device (wedge switch) can also be used to adjust the core-cladding ratio of the 2 inl fiber. A processing head of the laser can have a focus of approximately 1.4 mm to approximately 8 mm for imaging the fiber end of the 2 inl fiber in the area of ​​a powder focus or onto the surfaces.

[0036] The at least one filler material conveyor can be designed as a powder conveyor and have a powder nozzle for forming a powder focus. The powder nozzle can be designed using injectors as described above, in particular with multiple injectors as a multi-jet nozzle. The conveying gas can be, for example, an inert gas such as argon or helium, or a gas mixture thereof.

[0037] A process protective gas can also be added to the process.

[0038] Furthermore, further devices can of course be provided in the device, such as the previously mentioned measuring device, a component holder, etc.

[0039] Further details and advantageous embodiments of the invention can be found in the following description, on the basis of which embodiments of the invention are described and explained in more detail.

[0040] It shows :

[0041] Figure 1 is a schematic view of a structure of a

[0042] Device for laser cladding;

[0043] Figure 2 is a plan view of a component according to a

[0044] From an exemplary embodiment of the invention;

[0045] Figure 3 is a top view of a component during

[0046] Coating by a laser cladding process according to an embodiment of the invention;

[0047] Figures 4a, 4b schematic views of the

[0048] Laser cladding process according to an embodiment of the invention;

[0049] Figure 5 , 6 Cross-sectional views of a part of the component during coating by different

[0050] Laser cladding process;

[0051] Figure 7 , 8 Top views of a part of the component during

[0052] Coating through the different

[0053] Laser deposition welding processes of Figures 5 and 6; and Figures 9-13 show cross sections through components which have been coated using different laser deposition welding processes.

[0054] In the following description and in the figures, the same reference symbols are used for identical or corresponding features.

[0055] Figure 1 shows an overall device 10 for laser cladding. The device 10 comprises a laser 12 for generating a laser beam 1. The laser beam 1 generated is fed to a light exit 16 via an optical fiber cable 14. The laser beam 1 generated in this way is then directed into parallel alignment in a collimating lens 18. The laser beam 1 then passes through a movable processing head 20 (incidentally, the light exit 16 and the collimating lens 18 can alternatively be arranged in the processing head 20 itself). A focusing lens (not shown) for concentrating the laser beam 1 is arranged within the processing head 20. After passing through the focusing lens, the laser beam 1 passes through a cylindrical section 22 and a funnel-shaped section 24 of the processing head 26, which also serve as a powder nozzle for a powdered filler material 2.

[0056] The entire assembly comprising light exit 16, collimation lens 18, and processing head 22 is arranged by means of a feed unit 30 so as to be movable linearly above a component 70 to be coated. To be precise, the feed unit 30 can be moved in the plane defined by an X-coordinate and a Y-coordinate above the component 70 (see Fig. 2). By way of example, the feed unit 30 in the present case comprises a linear drive 34 and an electric motor 32 which drives the linear drive 34. Furthermore, the device 10 comprises a rotation unit 90, which in the present case has a further electric motor 92 with a shaft 94 coupled thereto for rotating the component 70 attached thereto.The component 70 is designed here, for example, to be rotationally symmetrical, in particular as a brake disc, and is rotated about its axis of rotation 72, which coincides with the shaft 94, in the direction of rotation R shown during the coating of the component 70 with a coating layer 80, which will be explained in more detail later.

[0057] The device 10 further comprises a filler material conveyor 40 for conveying powdered filler material 2. In the filler material conveyor 40, the powder is mixed with a gas, in particular an inert gas such as nitrogen or argon, in order to generate a powder gas stream 4 for conveying the powder. In a distributor component 42, the powder gas stream 4 is distributed into several, in the present case, for example, three, feed lines 44, in particular feed hoses, and then flowed into the cylindrical section 22 of the machining head 20. The section 24 of the machining head 20 has a double wall, wherein the powder gas stream is guided through the annular gap thus created, so that the powder gas stream

[0058] 4 flows through the two walls. The laser beam 1 and the powder gas flow 4 therefore run coaxially to each other through the sections 22 and 24. In the funnel-shaped section 24, the annular gap between the two walls tapers, so that the powder gas flow 4 flows through a nozzle-like

[0059] Outlet of the funnel-shaped section 24 leaves.

[0060] The device 10 further comprises a sensory measuring device 50. The measuring device 50 can, for example, be configured to carry out the light-section method in order to generate a height profile of the surface 74. For example, a light-section scan can be performed at 4 kHz. In particular, a height profile can be generated along a schematically shown projected light line 52.

[0061] Finally, the device 10 comprises a control device 60. This serves, on the one hand, to control the laser 12 and the filler material conveyor 40. Furthermore, it serves to control a control unit 62 which is also part of the device 10 and is designed to control the electric motor 32 and the further electric motor 92. Furthermore, the control device 60 is set up to evaluate the measurement signals recorded by the measuring device 50. The control device 60 can, for example, measure the height profile of the coating layer 80 and compare it with a limit value for a predefined maximum waviness of the coating layer 80. If the limit value is exceeded, the control device 60 can intervene accordingly by means of control-related measures.

[0062] Figure 2 shows the component 70 in the form of a brake disc for a motor vehicle, wherein the surface 74 has the coating layer 80 produced by the method described below. Such a coating layer 80 can also be produced on the opposite surface 74 or side of the component 70.

[0063] Overall, the device 10 is designed to carry out the method described below:

[0064] The present circular surface 74 of the component 70 is subjected to extreme

[0065] High-speed laser deposition welding (EHLA) is used to coat the component. For this purpose, the component 70 is first set in rotation by driving the shaft 94 from the additional electric motor 92.

[0066] Furthermore, the laser beam 1 is generated and projected onto the surface 74, the laser beam 1 radiating onto the surface 74 at an incident point. As a result, a process zone 6 is generated on the surface 74. Furthermore, a powder gas stream 4 is generated. After leaving the cylindrical section 24, the powdered filler material 2 of the powder gas stream 4 strikes the light path of the laser beam 1 during its flight phase. As a result, the filler material 2 in the form of powder particles is at least partially or completely melted, specifically before these reach the process zone 6 on the component 70. The filler material 2 is therefore preferably fed to the process zone 6 in completely molten form. The filler material 2 melted by heating by means of the laser beam 1 is consequently applied to the surface 74 of the component 70.In this case, the component 70 is rotated about the rotation axis 72 so quickly that the point of incidence of the laser beam 1 is displaced along a predetermined processing trajectory 88 (see Fig. 3) on the surface 74 at a speed of at least 20 m / min, so that the aforementioned high-speed laser deposition welding can also be used. As a result, the process zone 6 created by means of the laser beam 1 is displaced along the surface 74 by at least 20 m / min. At least one coating track 86 is created along the processing trajectory 88 by means of the molten filler material 2, as will be explained in more detail below with reference to Fig. 3.

[0067] A coating layer 80 is gradually produced by the laser deposition welding process. As Fig. 3 shows purely by way of example, the laser beam 1 is moved bit by bit from radially outside to radially inside relative to the axis of rotation 72 by means of the linear drive 34, so that the incident point of the laser beam 1 is moved in a spiral-shaped processing trajectory 88 along the surface 74. Along the processing trajectory 88, at least one coating track 86 is created with a plurality of turns 8 which run around one another or around a center point of the component 70. The coating track 86 or the turns 8 is or are preferably produced continuously, that is to say without a processing stop and furthermore, in particular contrary to Fig. 3, essentially without a gap in between, which in Fig. 3 merely serves to improve understanding.Likewise, the process zone 6 is guided in a spiral from radially outside to radially inside (or vice versa) to produce the coating layer 80. As can be seen in Fig. 1, the surface 74 comprises a coated radially outer section 82 and an uncoated radially inner section 84. Figure 4a shows the laser deposition welding process for the.

[0068] Component 70 similar to Fig. 1 in a schematic cross-sectional view. Unlike in Fig. 1, no processing head 20, as described with reference to Fig. 1, is used here. Instead, several injectors 46, of which only two are shown here as an example, are used, by means of which the filler material 2, in particular as a powder gas stream 4, is fed directly to the laser beam 1. The injectors 46 are shown here as tubes, in particular hard metal tubes, by way of example. They can each be connected to the distributor component 42 by means of one, two or more feed lines 44. It is also possible for each injector 46 to have its own distributor component 42, wherein the distributor components 42 can in turn be connected to the filler material conveyor 40. As shown in Fig.As can also be seen in Figure 4a, laser beam 1 is moved with its laser beam axis LA, for example, in the X-direction as the feed direction, whereby its beam point is also shifted in this direction. This occurs during the rotation R of component 70 about the rotation axis 72.

[0069] In Fig. 4a, the exit angle a of the injectors 46 relative to a perpendicular to the respective surface 74, which here coincides, for example, with the longitudinal axis LA of the laser beams 1, is less than 60°. It has been shown that surface waviness of the coating layers 80 welded as a result is particularly low.

[0070] Figure 4b shows a modification of the beam guidance of the laser beam 1, in which the laser beam axis LA of the laser beam 1 is at an advantageous angle of incidence ß with respect to the surface 70, so that the laser beam 1 is incident on the surface 70 with its incident point at the angle of incidence ß. The angle of incidence ß here is, for example, 35°. The angle of incidence ß can be achieved in particular by appropriately arranging the processing head 20 relative to the surface 70, wherein the powder gas stream 4 can be guided in the processing head 20, as shown in Fig. 1, or can be guided outside the processing head 20, so that only the laser beam 1 is guided in the processing head 20 or exits therefrom.Advantageously, a laser beam 1 impinging on the surface 74 at the angle of incidence ß cannot be reflected back onto the processing head 20 as laser light, but is directed past it. The waviness of the coating layer 80 is also further reduced.

[0071] Figure 5 shows a cross-sectional view through a part of the component 70 during the execution of a conventional laser deposition welding process. In this case, a coating track 86 with the track width B is applied to the surface 74. In the laser deposition welding process known from the prior art, a next turn 8 of the coating track 86 in Fig. 5 (not shown) is applied to the right in relation to Fig. 5 or radially inward from the component 70 next to the shown turn 8. This leads to a high waviness of the coating layer 80 thus produced, in particular at high laser powers of the laser beam 1. This waviness can be reduced by later grinding of the

[0072] Coating layer 80 can be reduced, but this also reduces the usable coating layer 80. Figure 6 shows a cross-sectional view through part of the component 70 during the execution of a laser deposition welding process according to an embodiment of the invention. Along the track width B of a coating track 86, several turns 8 are applied next to one another and partially overlapping one another. In the present case, for example, approximately four turns 8 lie one above the other in one track width B. The number of partially overlapping turns 8 per track width B is determined in the plan view of the individual turns 8 per track width B. Therefore, only the part of the turns 8 that is visible on the surface is relevant.

[0073] Such an overlap significantly reduces the surface waviness of the coating layer 80, as will be explained in more detail later with reference to Figs. 9 to 13. Advantageously, regrinding with a corresponding removal of the usable coating layer 80 can thus be avoided.

[0074] Figure 7 shows the prior art once again in a plan view of a portion of the component 70. The turns 8 of the coating track 86 are applied side by side with their track width B defined by the focus diameter of the focusing lens of the laser beam 1, whereby only one turn 8 is shown here.

[0075] Figure 8, on the other hand, shows the overlap of several turns 8 of a coating track 86 in the region of a track width B, as provided in a laser deposition welding process according to an exemplary embodiment of the invention. Figures 9 to 13 show cross-sections through components 70 with coating layers 80. The cross-sections differ in the number of turns 8 of a coating track 86 that partially overlap (at least partially) across a track width B.

[0076] Fig. 9 shows the result of a coating layer 80 with a partial overlap of 3.3 adjacent turns 8 along a track width B and Fig. 10 shows the result of a coating layer 80 with a partial overlap of 3.7 adjacent turns 8 along a track width B. As can be seen, with this choice of parameters there is still a comparatively high waviness of the coating layer 80 compared to Figs. 11 to 13.

[0077] Fig. 11 shows the result of a coating layer 80 with a partial overlap of 4.1 turns 8 next to each other along a track width B. Fig. 12 shows the result of a coating layer 80 with a partial overlap of 4.7 turns 8 next to each other along a track width B. And, Fig. 13 shows the result of a coating layer 80 with a partial overlap of 5.5 turns 8 next to each other along a track width B. As can be seen, with this choice of parameters only a comparatively small waviness of the coating layer 80 is given.

[0078] It has accordingly been shown that with a partial overlap of approximately four turns 8 next to one another along a track width B, the waviness of the coating layer 80 is typically so low that regrinding is no longer necessary or only requires a very small removal of the usable coating layer 80 in order to achieve an optimal surface finish.

Claims

Claims: Laser cladding process for producing a coating layer (80) on a surface (74) of a component (70) by producing at least one coating track (86) with a predetermined track width (B) on the surface (74) by applying an, in particular powdered, filler material (2) along a helical or spiral processing path (88), wherein the filler material (2) and the component (70) are heated along the processing path (88) by means of a laser beam (1), such that when the filler material (2) hits the surface (74) the at least one coating track (86) is formed, characterized in that at least two, in particular at least three, turns (8) of the at least one coating track (86) overlap at least partially along a track width (B).Laser cladding method according to claim 1, wherein at least four turns (8) of the coating track (86) overlap at least partially along a track width (B). Laser cladding method according to claim 1 or 2, wherein the at least partially overlapping turns (8) overlap each other by at least 20%, in particular at least 40%, of the track width (B). Laser cladding method according to one of the preceding claims, wherein the number of windings (8) that at least partially overlap each other along the track width (B) is varied during the production of the processing layer (80). Laser cladding method according to one of the preceding claims, wherein above windings (8) in a start and / or end region of the processing path (88) further turns (8) of the at least one coating track (86) are generated across its track width (B). Laser cladding method according to one of the preceding claims, wherein a height profile of the surface (74) coated with the at least one coating track (86) is generated by a measuring device (50). Laser cladding method according to claim 6, wherein, based on the height profile, a total thickness and / or waviness of the at least one coating track (86) on the surface (74) is determined and compared with a predetermined limit value. Laser cladding method according to one of the preceding claims, wherein an incident point of the laser beam (1) on the surface (74) is moved along the surface (74) at a relative speed of at least 20 m / min along the processing trajectory (88). Laser cladding method according to one of the preceding claims, wherein the component (70) is rotationally symmetrical, in particular as a disk, and is rotated about a rotational axis (72) during the production of the coating layer (80). Laser cladding process according to one of the preceding claims, wherein the at least one filler material (2) is present as a powder before melting by means of the laser beams (1). Laser cladding process according to one of the preceding claims, wherein the at least one filler material (2) is supplied to the laser beam (1) by means of a conveying gas, wherein the conveying gas in particular has a relative atomic mass of at least 4 and / or a specific volume flow rate of at least 3.2 Nl / min per mm². 2 has a cross-sectional area. Laser cladding process according to one of the preceding claims, wherein the production of the coating layer (80) of the component (70) in the direction from relatively inside the surface (74) to relatively outside the surface (74). Laser cladding process according to one of the preceding claims, wherein a laser beam axis (LA) of the laser beam (1) is inclined at an angle of incidence (β) in the range of greater than 0° to 35° relative to the surface (74). Component (70) with at least one surface (74) which is coated with a coating layer (80), wherein the coating layer (80) is applied by means of a The device (10) is manufactured according to a laser cladding process as described in one of the preceding claims. The device (10) is for performing a laser cladding process as described in one of claims 1 to 13, wherein the device (10) comprises at least one laser. (12) for generating the laser beam (1), and wherein the device (10) has at least one additive material conveyor (40) for conveying the at least one additive material (2) at a distance from the surface (74) of the component (70) facing the laser beam (1) .

Images