Powder feed nozzle device for a powder build-up welding process

Abstract

The invention relates to a powder feed nozzle device (1) for a powder build-up welding process, comprising at least the following components: - a plurality of feed lines (2, 3, 4); and - a number of outlets (5, 6, 7) corresponding to the number of feed lines, each of the outlets (5, 6, 7) being directed towards a focal point of the powder (8). The powder feed nozzle device (1) is primarily characterized in that it also comprises a control device (9) which is designed to adjust the speed of the gas flow (10) in at least one of the feed lines (2, 3, 4), and in that differing powder conveying speeds can be set at at least two of the outlets (5, 6, 7). A powder material having a wide range of particle sizes can be used with the powder feed nozzle device according to the invention.

Description

[0001] Powder feed nozzle device for a powder build-up welding process

[0002] The invention relates to a powder feed nozzle device for a powder build-up welding process, a powder build-up welding process with such a powder feed nozzle device, and a powder build-up welding process with such a powder build-up welding process.

[0003] Various powder deposition welding processes are known in the prior art. Typically, a powdered welding consumable, hereinafter referred to as the powder material, is injected into a welding device, such as an arc, flame, or laser beam, by means of a powder feed nozzle device. The powder material is melted or partially melted and thus applied to a surface of a component, possibly to a molten pool created thereon. A powder deposition welding process using a laser is known, for example, in DE 102011 100 456 A1 as so-called extremely high-speed laser deposition welding (EHLA).Using these special powder deposition welding processes, very high feed rates can be achieved because the powder material is already melted or partially melted in a powder focus above the surface to be coated before reaching the melt pool and is also connected to an already created melt pool.

[0004] In all powder build-up welding processes known in the prior art, the powder nozzle device typically comprises a feed line in which the powder material is fed to one or more outlets by means of a gas stream, forming a powder focus at a defined angle and a powder conveying speed generated by the speed of the (carrier) gas stream in the feed line. This powder focus is aligned with the provided welding energy (e.g., the laser focus of a laser optics in a laser build-up welding process) according to the respective powder build-up welding process. Currently, considerable costs of powder build-up welding are associated with the fact that only a powder material with high technical purity in terms of its composition and / or with a small grain size range can be used to achieve a satisfactory result with minimal post-processing requirements.For example, when coating a brake disc, a generally very hard or abrasion-resistant coating is applied using powder deposition welding. The subsequent grinding process is time-consuming and results in high wear on the abrasives, thus resulting in high costs.

[0005] Based on this, the present invention is based on the object of at least partially overcoming the disadvantages known from the prior art. The features of the invention are derived from the independent claims, for which advantageous embodiments are presented in the dependent claims. The features of the claims can be combined in any technically reasonable manner, whereby the explanations from the following description as well as features from the figures, which comprise additional embodiments of the invention, can also be consulted for this purpose.

[0006] The invention relates to a powder feed nozzle device for a powder build-up welding process, comprising at least the following components:

[0007] - a plurality of supply lines; and

[0008] - a number of outlets corresponding to the number of supply lines, each of the outlets being directed towards a powder focus.

[0009] The powder feed nozzle device is characterized in particular in that it further comprises a control device which is designed to adjust the speed of the gas flow in at least one of the feed lines, and wherein different powder feed speeds can be adjusted at at least two of the outlets.

[0010] Unless explicitly stated otherwise, ordinal numbers used in the preceding and following descriptions serve only to clearly distinguish them and do not reflect the order or ranking of the designated components. An ordinal number greater than one does not necessarily imply that another such component must be present.

[0011] The individual particles (or grains) of a powder material are arranged in a roughly Gaussian distribution with regard to their diameter and / or mass. The heat capacity (C) of the individual particles is the ratio of the heat supplied to the particle (Q) to the resulting temperature increase (AT), which, for approximately homogeneous bodies, can also be calculated as the product of the specific heat capacity (c) and the mass (m) of the particle's body (C=cxm). This effect can be exploited because the residence time of the powder material in the (spatially) limited area of ​​the supply of welding energy can be adjusted, firstly by the path, for example the angle at which the powder material is sprayed, and secondly by the speed of the powder material.A smaller included angle between the powder material and the limited area of ​​the provision of the welding energy and / or a slower powder feed rate lead (each independently of each other) to a longer residence time in the area of ​​the welding energy and thus cause a higher energy input into the powder material compared to a larger angle or faster powder feed rate.

[0012] Here, it is proposed that the speed of the gas flow, which is used as a carrier or conveying means for the powder material, is adjusted depending on the grain size present. It is further proposed that different grain size windows are provided via a plurality of outlets and thus different powder conveying speeds are set at at least two of the outlets. This means that a grain size window with an optimal powder conveying speed can be guided through the limited range of the provided welding energy via the respective outlet. In other words, a powder material with a significantly larger grain size window, namely divided into several smaller grain size windows at the majority of outlets, can be used.This allows the use of a significantly more cost-effective powder material or, in addition, the portion of the powder material currently arising as scrap or as a further grain size window that needs to be processed during the production of a powder material with a defined grain size distribution can be used.

[0013] It should be noted that in another or overlapping aspect, powder materials can also be used simultaneously and / or without adjustments to the supplied welding energy and / or feed rate, which preferably also sets the properties of a molten pool to be produced, different powder materials with different heat capacities (C) by spraying them out at different speeds at the respective outlet, i.e. (assuming the same degree of melting or always complete melting) a powder material with high heat capacity is supplied to the area of ​​the provided welding energy at a lower powder feed rate and a powder material with lower heat capacity is supplied to the area of ​​the provided welding energy at a comparatively higher powder feed rate.

[0014] It should be noted that it is currently partly accepted that parts of the powder material with a common (large) grain size window evaporate due to the small grain size and are therefore not only not added to the coating, but also form a gaseous pollutant which must be treated and removed separately.

[0015] In one embodiment, each supply line has an outlet. Alternatively, one supply line has multiple outlets and / or one outlet has multiple supply lines.

[0016] The feed lines are configured to feed the powder material into a powder focus. Preferably, each individual outlet is aligned with a single powder focus or the trajectory of the conveyed powder material. In one embodiment, multiple outlets are aligned with the same or different powder focuses. In one embodiment, such a powder focus of an outlet is set so that it lies in the laser focus and / or in the molten pool. It should be noted that the extent of the spatially limited area in which the welding energy is provided (focus area) is greater than the (spatial) extent of the powder focus and / or that at least enough welding energy is provided in an edge area around this focus area for the powder material to be significantly heated there too.In one embodiment, the trajectory of the powder gas flow is deflected by the means for providing the welding energy, for example in so-called powder spraying or high velocity oxygen fuel spraying [HVOF]. Alternatively, the trajectory of the powder gas flow is not influenced or only negligibly influenced by the means for providing the welding energy, for example in arc welding or extremely high speed laser cladding [EHLA].

[0017] In one embodiment, at least one of the outlets is formed in a circumferential ring, preferably arranged around the outlet of the welding device. In one embodiment, at least one of the outlets is designed as an opening arranged laterally to the welding device, for example with the same (hydraulic) diameter as the associated supply line or a diameter that is reduced compared to that. Preferably, a plurality of such lateral openings are arranged in a ring, preferably around the outlet of the welding device. In many applications, the speed of the (carrier) gas flow corresponds to the respective powder conveying speed. It should be noted that in one embodiment, the gas flow deviates from the powder conveying speed at the respective outlet in the area of ​​​​a regulation or measurement for a control in a supply system, wherein such a relationship is known at least empirically.

[0018] Preferably, a powder outflow direction has an included angle of less than 45° [forty-five degrees out of 360°], preferably less than 30°, with a main axis of the limited area of ​​provision of the welding energy, for example of a laser beam or its laser focus. In this context, the included angle is understood to be the angle enclosed by the powder outflow direction and the main laser axis in their main vector direction (i.e., in the direction of travel). In a preferred embodiment of the powder feed nozzle device, the feed lines have different (hydraulic) diameters; preferably, at least two of the feed lines have different diameters. The feed lines are preferably dimensioned with regard to their diameter in such a way that this is advantageous for the powder materials used in the feed line with a defined grain size window.The diameter of a supply line determines, depending on the selected gas flow velocity, the powder conveying velocity at which a powder material particle leaves the outlet corresponding to the supply line. This also determines the residence time of the powder material particles in the welding energy range (focus area) and thus the energy input of the welding device into the powder material particles. In one embodiment, the resistance of the supply line, for example, within the applicable Reynolds number range, is decisive for the gas flow. For example, in this embodiment, the diameters are then adjusted for a constant and / or common pressure at which the carrier gas is supplied, for the desired gas flow velocity.

[0019] In an advantageous embodiment, the entire welding filler material required for a build-up welding is supplied as powder material, particularly preferably via the aforementioned supply lines and outlets, to the focus area of ​​a powder build-up welding device.

[0020] It is further proposed in an advantageous embodiment of the powder feed nozzle device that the following feed lines are arranged for feeding a powder material:

[0021] - at least one first feed line for feeding powder materials with a first grain size window; and

[0022] - at least one further feed line for feeding powder materials with a second grain size window, wherein the first grain size window is smaller than the second grain size window.

[0023] In one embodiment, the first grain size window is configured for grain sizes equal to or less than 53 pm [fifty-three micrometers], and the second grain size window is configured for grain sizes equal to or greater than 53 pm. In a preferred embodiment of the powder feed nozzle device, at least one first feed line is configured for conveying a powder material with a first grain size window of 10 pm [ten micrometers] to 53 pm.In a preferred embodiment of the powder feed nozzle device, at least one further feed line is set up for guiding a powder material with a further grain size window of 53 pm to 90 pm [ninety micrometers], and / or preferably at least one (optionally still) further feed line is set up for guiding a powder material with a (still) further grain size window of more than 90 pm, preferably from 90 pm to 120 pm, more preferably from 90 pm to 150 pm [one hundred and fifty micrometers].

[0024] It is further proposed in an advantageous embodiment of the powder feed nozzle device that a control device is further included which is designed to adjust the feed of the powder quantity into the feed line.

[0025] With such a control device for, preferably variable, adjusting the gas flow velocity, the powder feed rate in a supply line or at the respective outlet can be adjusted depending on the respective grain size range of the powder material being fed in. This allows the speed at which a particle of the powder material leaves the corresponding outlet to be adjusted, and thus the residence time of the respective particle in the focus area of ​​the welding energy. As explained above, the energy input to the particles of the powder material can thus be adjusted.

[0026] In such a control device, for example, the pressure at which the carrier gas is provided for the gas flow is controlled. In one embodiment, a gas flow is variably throttled by means of a control valve. In one embodiment, a control loop with a measured variable related to the velocity of the gas flow is provided.

[0027] Preferably, the control device of the powder feed nozzle device can independently adjust the gas flow velocity in each individual or at least one of the feed lines. Thus, the gas flow velocity for the respective feed line can be adjusted depending on the grain size range of the powder material to be fed in the respective feed line.

[0028] In a further preferred embodiment of the powder feed nozzle device, a control device (additional to or the same as the one mentioned above) is included, which is designed to variably adjust the supply of the powder quantity into the feed line.

[0029] This allows the amount of powder material fed into the supply line and thus the amount of welding energy available per particle of powder material to be adjusted; because a high density of particles leads to mutual shading and thus to a reduced energy input per particle.

[0030] It should be noted that with variable adjustment, such a wide range can be set that, according to the description here, the powder material can be adequately fed to the focus area (of the welding energy) and the surface to be coated for different requirements, such as different powder materials (e.g., with different grain size windows). Alternatively, (simple) adjustment is possible solely for setting a speed within a tolerance window. It should also be noted that such a control device is not absolutely necessary; manual adjustment is also possible, possibly only by checking the welding result and without additional measured values.

[0031] It is further proposed in an advantageous embodiment of the powder feed nozzle device that a separating device for separating a powder material into at least two grain size windows is also included, wherein the separating device is connected to the feed lines of the powder feed nozzle device in such a way that separated powder materials are fed to an associated one of the feed lines depending on a respective grain size window.

[0032] In this embodiment, a powder material comprising particles of different sizes within a very large grain size window can be directly introduced into the powder feed nozzle device (and preferably without a prior separation step). The separation device enables the provided grain size window to be separated into at least two grain size windows. These separated powder materials with different grain size windows then comprise an approximately Gaussian distribution of particles with a size corresponding to the respective set grain size window.

[0033] In one embodiment, sieving and / or centripetal force can be used for separation.

[0034] In one embodiment, the separating device is formed separately from the supply lines, for example, for filling a corresponding number of storage containers. In a preferred embodiment of the powder feed nozzle device according to the invention, a device for separating powder materials is connected to the supply lines of the powder feed nozzle device in such a way that separated powder materials of specific grain size ranges are each provided to a corresponding supply line.

[0035] It should be noted that the cost aspect is only one possible advantage, and possibly (for example instead) a very high quality requirement is placed on the welding result, whereby the powder material is supplied with precisely the welding energy that leads to a satisfactory welding result by evaporating no or a smaller portion of the powder material and / or melting (at least almost) all portions of the powder material or (at least sufficiently) melting them. For this purpose, it is advantageous, for example, to use a more precisely adjusted, and thus generally more expensive, powder material, for example with a narrower grain size window or a plurality of such powder materials, for example with different

[0036] Material composition and heat capacity of the respective particles.

[0037] According to a further aspect, a powder build-up welding method is proposed which is carried out by means of a powder feed nozzle device according to an embodiment as described above, comprising the following steps: a. Providing a powder material with a first grain size window to a first feed line of the powder feed nozzle device and a powder material with a second grain size window to a second feed line of the powder feed nozzle device; and b. Feeding the powder material with the first grain size window by means of the first feed line to the powder focus and the powder material with the second grain size window by means of the second feed line to the powder focus, wherein the first grain size window is different from the second grain size window.

[0038] Reference is made to the above description insofar as it describes necessary features for implementing the powder feeding method proposed here, or at least optional features relating to the powder feeding method. This method enables powder build-up welding to be carried out simultaneously with at least two powder materials of different grain size ranges or with at least two powder materials of different grain size ranges.

[0039] In a preferred embodiment of the powder feeding method, the powder material with a first grain size window and the powder material with a second grain size window are the same powder material. It should be understood that the same powder material has particles of different diameters and / or masses and that at least two different grain size windows of the same powder material are used in the powder feeding method. It should be noted that the different grain size windows may overlap with one another, and not only at the negligible edges of the approximately Gaussian distribution of the respective grain size windows. The grain size windows are preferably selected to be immediately adjacent to one another. The boundaries are selected based on cost, availability, and / or optimal exposure to the welding energy.

[0040] It should be noted that the powder feeding process for coating a surface is carried out in conjunction with powder build-up welding. For example, for testing purposes, preferably during adjustment, or during breaks in the coating process, the powder feeding process can also be carried out without powder build-up welding.

[0041] It is further proposed in an advantageous embodiment of the powder feeding method that at least the following steps are further included: in step a.: providing at least one powder material with at least one further grain size window to at least one further feed line of the powder feed nozzle device; and in step b.: feeding the powder material with the at least one further grain size window by means of a respective further feed line to the powder focus, wherein the third grain size window is different from the first grain size window and the second grain size window.

[0042] It is further proposed in an advantageous embodiment of the powder feeding method that the powder materials of a respective grain size window have a certain heat capacity, wherein at least two, preferably all, of the heat capacities are different from one another.

[0043] This powder feeding method is carried out alternatively or in addition to the powder feeding method with the different grain size windows. For example, as described above, a plurality of different powder materials, each with a different heat capacity of the material composition, is used. Furthermore, in an advantageous embodiment of the powder feeding method, it is proposed that the powder material with the different grain size windows be a technically homogeneous material.

[0044] A technically homogeneous material is a powder material that can be produced using economically feasible measures that, within this limitation, are considered to have no or sufficiently minimal impact on the material composition. For example, it is acceptable for one grain size window to contain less of an element, such as less hard material, than another. This may or may not necessarily be compensated for, for example, by a different mass input per unit time to the individual grain size windows.Especially in the case of a grain size window with on average smaller particles than the other grain size windows, depending on the design of the powder feeding process during powder build-up welding, the influence on the weld quality is lower due to the lower mass than with a larger grain size window, because good mixing with the other applied (melted and / or partially melted) particles can be expected during the welding process.

[0045] It is further proposed in an advantageous embodiment of the powder feeding method that step b. is carried out at a predetermined powder conveying speed, wherein at least two, preferably all, of the powder conveying speeds at the respective outlets are different from one another.

[0046] In this embodiment, as already described above in connection with the powder feed nozzle device, at least two of the grain size windows are sprayed at different powder feed rates. Due to the different (average) heat capacities, the above-mentioned advantages with regard to weld quality and / or the usability of one powder material with a comparatively large and / or multiple powder materials with the corresponding grain size windows can be achieved. In an advantageous embodiment, all outlets are operated with different grain size windows and corresponding (i.e., different) powder feed rates.

[0047] In a preferred embodiment, at least two, preferably all, of the outlets in step b. are operated in a controlled manner at a powder conveying speed adapted to the respective grain size range, whereby the powder conveying speed is thus measured directly or indirectly and taken into account as a measured variable in a control loop. An indirect measurement is, for example, the inspection of the coating applied to a surface to be coated.

[0048] It should be noted that in an advantageous embodiment, the powder feed rate is constant during operation, i.e., both during a welding process and before or between two welding processes. Particularly preferably, the powder feed rate of each outlet of a powder feed nozzle device, once installed, is constant (apart from any necessary adjustments).

[0049] It is further proposed in an advantageous embodiment of the powder feeding method that at least two, preferably all, of the powder materials with different grain size windows are fed to the respective outlet and / or powder focus in steps b. at least partially overlapping in time or simultaneously.

[0050] In one embodiment, the supply lines and outlets are operated at different times. Preferably, they are operated simultaneously, at least during the build-up welding process, meaning that the powder material with the different grain size windows is simultaneously provided and welded to the surface to be coated.

[0051] It is further proposed in an advantageous embodiment of the powder feeding method that a step c. is carried out before step a., in which a powder material is separated into at least two grain size windows, preferably by means of a separation device according to an embodiment according to the above description.

[0052] In this powder feeding method, a powder material is provided with a grain size window that is larger than the powder feeding method proposed here, for example, encompassing the entire range of grain sizes to be welded. This powder material is then divided into the desired grain size windows, preferably as described above, using a separating device (preferably as described above) either integrated into the build-up welding process or separately beforehand.

[0053] According to a further aspect, a powder build-up welding method is proposed, wherein, in addition to the powder feed nozzle device, a powder build-up welding device is further comprised for carrying out the powder build-up welding method, which comprises a welding device with a focus area for welding energy and a workpiece holder for fixing and aligning a workpiece with a surface to be coated, wherein the powder build-up welding method comprises at least the following steps: i. by means of the powder feed nozzle device, carrying out a powder feed method according to an embodiment as described above; ii. by means of the workpiece holder fixed and aligned, providing a workpiece with a surface to be coated; and iii.by means of the welding device, providing welding energy in a predetermined focus area, wherein the focus area and the at least one powder focus spatially overlap, wherein preferably the focus area and / or at least one of the powder focuses are arranged above the surface to be coated.

[0054] Here, a powder deposition welding device is proposed, which is configured to use the powder material supplied by means of the powder supply nozzle device and according to an embodiment of the powder supply method described above. The powder material is melted or partially melted in the (spatially limited) focus area by means of the welding energy of the welding device and applied to the surface to be coated, in which a molten pool is preferably formed.

[0055] The workpiece holder is designed to clamp, i.e., fix, a workpiece (i.e., a base body), whereby a defined spatial axis, for example, a central rotational axis, of the workpiece can be precisely aligned. As a rule, the base body is already finished, except for the coating to be applied or, if necessary, other minor post-processing steps. Precise positioning is therefore necessary. This is preferably supported by a gripper arm and defined gripping surfaces on the workpiece and / or appropriate measuring technology. For example, the workpiece holder comprises a device for detecting imbalances, whereupon clamping can be corrected or, if balancing of the workpiece has not yet been carried out or may still be added (e.g., within the scope of admissibility), at least appropriate material removal or material addition is carried out.For a rotating workpiece, the workpiece holder could be a chuck, for example. For a workpiece without a rotational axis or one that is unsuitable for rotary machining, the workpiece holder could be a tool table with appropriate fixing elements, for example. The workpiece holder itself is preferably integrated into a fixed, possibly adjustable, machine coordinate system (at least within the scope of an adjustment tolerance).

[0056] The powder deposition welding device further comprises a welding device which comprises a locally limited high-temperature source, for example a torch (in high-velocity oxygen fuel (HVOF) spraying) or a laser (in laser deposition welding, preferably in extremely high-speed laser deposition welding (EHLA)).

[0057] The welding device is designed in such a way that the powdery

[0058] Welding filler material (the powder material) can be melted or melted in the focus area (and optionally in an area around the focus area) so that the powder material impacts the surface of the workpiece to be coated in a partially melted state (i.e. with a melted surface) or completely melted state. In one embodiment, the welding device is set up such that in a region close to the focus area, i.e. generally along the axis of the welding device in the direction of the surface to be coated behind the focus of the supplied powder material, the surface of the workpiece to be coated is melted to a desired depth (i.e. a melt pool is formed) so that the powder material is absorbed into the surface to be coated.In a particularly preferred embodiment, the powder material is melted or molten and a molten pool is created in the region near the focus area in the surface of the workpiece to be coated.

[0059] It is further proposed in an advantageous embodiment of the powder deposition welding process that the powder deposition welding process is a laser deposition welding process, preferably an extremely high-speed laser deposition welding process, wherein, preferably in a step b., a quantity of the supplied powder material is also controllable.

[0060] Such powder deposition welding using a laser deposition welding process is carried out using a welding device comprising at least one laser optic.

[0061] The laser optics are fed from and / or comprise one or more laser sources. The laser beam or the multiple laser beams of the laser optics are bundled onto one or more laser focuses (forming a focus area), wherein the energy density (intensity) for the desired (maximum) thermal input is preferably present only in this area when, controlled by a control device, a predetermined power limit or more power is emitted by means of the laser optics. The laser focus has a spatial extent, for example with a diameter (in a plane parallel to the surface to be coated) of 1 mm [one millimeter] to 12 mm, for example of 1.2 mm to 8 mm, particularly preferably of 3 mm to 4 mm.It should be noted that the area depends on the power of the laser beam used and should have an increasing diameter with increasing power for a desired energy density on the surface to be coated.

[0062] According to a further aspect, a powder build-up welding device is proposed, wherein the powder build-up welding device is configured to carry out a powder build-up welding method according to an embodiment as described above.

[0063] The invention described above is explained in detail below against the relevant technical background with reference to the accompanying drawings, which show preferred embodiments. The invention is in no way limited by the purely schematic drawings, whereby it should be noted that the drawings are not to scale and are not suitable for defining proportions. It is shown in

[0064] Fig. 1 : a powder feed nozzle device for a powder build-up welding process; and

[0065] Fig. 2: A flow chart showing a powder deposition welding process for coating a workpiece.

[0066] Fig. 1 shows a schematic representation of a powder feed nozzle device 1 for a powder build-up welding process using extremely high-speed laser build-up welding [EHLA]. On the left in the illustration, a powder build-up welding device 13 with a welding device 14 comprising laser optics is shown. The powder material 12 is fed here by means of a carrier gas via three outlets 5, 6, 7 to a powder focus 8, which is located in the focus area 15 of the laser beam 21 of the welding device 14. The powder material 12 melted or partially melted therein is bonded to the surface 18 to be coated of the workpiece 17 held in a workpiece holder 16, wherein the surface 18 to be coated is preferably melted or partially melted in the focus area 15 of the laser beam 21.

[0067] On the right of the illustration, a separating device 11 is shown, which is supplied with a powder material 12 from a (here purely optionally single) storage container 22. The powder material 12 in this storage container 22 has a large grain size window, in which the later grain size windows of the (here purely optionally three) supply lines 2, 3, 4 are contained. Furthermore, a gas source 23 is shown, from which a gas stream 10 can be injected into the separating device 11. The speed of the respective gas stream 10 is adjustable in this embodiment via controllable throttle valves, specifically by means of a control device 9 (here symbolically indicated by a processor 19 and a memory unit 20). In this simple embodiment of the separating device 11, the powder material 12 supplied from the storage container 22 is distributed between the supply lines 2, 3, 4 via the gas streams 10 due to its different masses.Thus, the lightest powder grains and thus the smallest grain size range are fed into the first feed line 2, the heaviest powder grains and thus the largest grain size range are fed into the third feed line 4, and the medium-heavy powder grains and thus the medium grain size range are fed into the second feed line 3. Alternatively or additionally, the powder material 12 provided from the storage container 22 is divided into the desired grain size ranges by sieving. Alternatively, the grain size ranges are made available separately to the respective feed lines 2, 3, and 4 via separate storage containers 22.

[0068] The first supply line 2 is connected to the first outlet 5, the second supply line 3 to the second outlet 6, and the third supply line 4 to the third outlet 7. The desired conveying speed of the powder material 12 with the respective grain size window is preferably already set in the supply lines 2, 3, 4, but at the latest at the outlets 5, 6, 7. In this illustration, the outlets 5, 6, 7 (e.g., rotating ring nozzles) have very different angles to one another and impinge on a common powder focus 8. Alternatively, the angles are the same or only slightly different. Irrespective of this, the powder focuses 8 of the outlets 5, 6, 7 diverge, meaning that the outlets 5, 6, 7 then do not have a common powder focus 8.

[0069] Fig. 2 shows a flowchart of a powder deposition welding process for coating a workpiece 17. In step i., the following powder feeding process is carried out by means of a powder feed nozzle device 1, whereby reference is made to the illustration in Fig. 1 purely for the sake of clarity without excluding generality:

[0070] First, in a (purely optional) step c., a powder material 12 is separated into at least two grain size windows, for example as shown in Fig. 1 or as described alternatively.

[0071] Subsequently, in step a., a powder material 12 with a first grain size window is provided to a first feed line 2 of the powder feed nozzle device 1 and a powder material 12 with a second grain size window is provided to a second feed line 3 of the powder feed nozzle device 1 and, if necessary, further grain size windows are provided to further feed lines 4.

[0072] Subsequently, in step b, the powder material 12 with the first grain size window is fed to the powder focus 8 via the first feed line 2, and the powder material 12 with the second grain size window is fed to the powder focus 8 via the second feed line 3, and optionally further grain size windows are fed to the powder focus 8 via further feed lines 4. The grain size windows are (preferably all) different from one another.

[0073] In a step ii., a workpiece 17 with a surface 18 to be coated is fixed and aligned by means of a workpiece holder 16 and thus prepared for a coating process. Then, in step iii., welding energy is provided in a predetermined focus area 15 by means of a welding device 14, for example in the form of a laser beam 21. The focus area 15 and the at least one powder focus 8 spatially overlap. In a preferred embodiment, the powder deposition welding process is so-called extremely high-speed laser deposition welding [EHLA], wherein the focus area 15 and the at least one powder focus 8 are arranged above the surface 18 to be coated of the provided workpiece 17.

[0074] With the powder feed nozzle device proposed here, a powder material with a large grain size window can be used.

[0075] List of reference symbols

[0076] Powder feed nozzle device first supply line second supply line third supply line first outlet second outlet third outlet

[0077] Powder Focus

[0078] Control device

[0079] Gas flow

[0080] Separating device

[0081] Powder material

[0082] Powder deposition welding device

[0083] Welding device

[0084] Focus area

[0085] Workpiece holder

[0086] Workpiece surface to be coated

[0087] processor

[0088] storage unit

[0089] laser beam

[0090] storage container

[0091] Gas source

Claims

Patent claims 1 . Powder feed nozzle device (1) for a powder build-up welding process, comprising at least the following components: - a plurality of supply lines (2,3,4); and - a number of outlets (5, 6, 7) corresponding to the number of supply lines, wherein each of the outlets (5, 6, 7) is directed towards a powder focus (8), characterized in that it further comprises a control device (9) which is designed to adjust the speed of the gas flow (10) in at least one of the supply lines (2, 3, 4), and wherein different powder conveying speeds can be adjusted at at least two of the outlets (5, 6, 7).

2. Powder feed nozzle device (1) according to claim 1, further comprising a control device (9) which is designed to adjust the feed of the powder quantity into the feed line.

3. Powder feed nozzle device (1) according to claim 1 or claim 2, further comprising a separating device (11) for separating a powder material (12) into at least two grain size windows, wherein the separating device (11) is connected to the feed lines (2, 3, 4) of the powder feed nozzle device (1) in such a way that separated powder materials (12) are fed to an associated one of the feed lines (2, 3, 4) depending on a respective grain size window.

4. Powder build-up welding method, which is carried out by means of a powder feed nozzle device (1) according to one of claims 1 to 3, comprising the following steps: a. Providing a powder material (12) with a first grain size window to a first feed line (2) of the powder feed nozzle device (1) and a powder material (12) with a second grain size window to a second Feed line (3) of the powder feed nozzle device (1); and b. feeding the powder material (12) with the first grain size window by means of the first feed line (2) to the powder focus (8) and the powder material (12) with the second grain size window by means of the second feed line (3) to the powder focus (8), wherein the first grain size window is different from the second grain size window.

5. Powder feeding method according to claim 4, wherein the powder material (12) with the different grain size windows is a technically homogeneous material.

6. Powder feeding method according to claim 4 or claim 5, wherein step b. is carried out at a predetermined powder feed rate, wherein at least two, preferably all, of the powder feed rates at the respective outlets (5, 6, 7) are different from each other.

7. Powder feeding method according to one of claims 4 to 6, wherein at least two, preferably all, of the powder materials (12) with different grain size windows are fed to the respective outlet (5, 6, 7) and / or powder focus (8) in steps b. at least partially overlapping in time or simultaneously.

8. Powder feeding method according to one of claims 4 to 7, further comprising a step c. carried out before step a., in which a powder material (12) is separated into at least two grain size windows, preferably by means of a separating device (11) according to claim 3.

9. Powder build-up welding method, wherein, in order to carry out the powder build-up welding method, in addition to the powder feed nozzle device (1), a powder build-up welding device (13) is further comprised, which comprises a welding device (14) with a focus area (15) for welding energy and a workpiece holder (16) for fixing and aligning a workpiece (17) with a surface (18) to be coated, wherein the powder build-up welding method comprises at least the following steps: i. by means of the powder feed nozzle device (1), carrying out a powder feed method according to one of the preceding claims; ii. by means of the workpiece holder (16) fixed and aligned, providing a workpiece (17) with a surface (18) to be coated; and iii. by means of the welding device (14), providing welding energy in a predetermined focus area (15), wherein the focus area (15) and the at least one powder focus (8) spatially overlap, wherein preferably the focus area (15) and / or at least one of the powder focuses (8) are arranged above the surface (18) to be coated.

10. Powder deposition welding method according to claim 9, wherein the powder deposition welding method is a laser deposition welding method, preferably an extremely high-speed laser deposition welding method, wherein, preferably in a step b., a quantity of the supplied powder material (12) is also controllable.

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