Method and device for coating a workpiece surface

Abstract

The invention relates to a method for coating a workpiece surface (133), in which an atmospheric plasma beam (26) is generated by means of a plasma nozzle (2), a coating material is supplied to the generated plasma beam (26) and the plasma beam, with the coating material, is directed to the workpiece surface (133) to be coated, wherein the coating material is supplied to the generated plasma beam (26) in that a filament (34) is supplied to the generated plasma beam (26), said filament containing or consisting of the coating material. The invention also relates to a device (100, 200, 300, 400) for coating a workpiece surface (133), having a plasma nozzle (2) which is designed to generate an atmospheric plasma beam (26), wherein the plasma nozzle (2) has a nozzle opening (6) from which the plasma beam (26) exits during operation, and having a filament supply element (124) which is arranged and designed to supply a filament (34) to the generated plasma beam (26) during operation, and to a use of the device (100, 200, 300, 400).

Description

[0001] Method and device for coating a workpiece surface

[0002] The present invention relates to a method for coating a workpiece surface, in which an atmospheric plasma jet is generated by means of a plasma nozzle, in which a coating material is supplied to the generated plasma jet, and in which the plasma jet containing the coating material is directed onto the workpiece surface to be coated. The present invention further relates to a device for coating a workpiece surface and the use of the device.

[0003] Various atmospheric coating processes are known from the state of the art.

[0004] In cold gas spraying, coating material in powder form is applied at very high speeds to the workpiece surface to be coated. The powders used in this process have very small particle sizes, some of which are even respirable, and therefore require a high level of safety. Furthermore, the gases (such as helium) used for the supersonic gas jets used in these processes are quite expensive. Furthermore, this process requires a certain degree of ductility in the powder particles and the workpiece surface to be coated, which results in material limitations.

[0005] In atmospheric plasma spraying, powder is introduced into a high-temperature plasma generated by DC discharge or low-frequency discharge and directed onto the workpiece surface to be coated. These powders, in turn, require safety precautions during handling. Furthermore, the high temperatures are unsuitable for certain coating materials and workpieces, which in turn results in material limitations. Coating processes using an atmospheric plasma jet generated by high-frequency, high-voltage discharges are also known. Compared to plasma spraying, these processes operate at lower temperatures and are therefore also suitable for more temperature-sensitive workpieces. However, the liquids, gases, or powders used as precursors require very strict safety precautions.In addition, the deposition rates in such a process are quite low, so that it is particularly suitable for thin layer thicknesses.

[0006] Feeding a precursor in powder form also requires a sophisticated transport mechanism to achieve uniform and reliable powder feeding, making the coating equipment more complex and expensive.

[0007] WO 2011 / 042459 A1 discloses an atmospheric-pressure plasma process in which a precursor in a gaseous, liquid, or solid, powdered state is introduced into an atmospheric plasma jet, thereby depositing a coating on a workpiece surface. Such precursors may require quite stringent safety precautions. At the same time, a sputter electrode is used as the inner electrode of the plasma nozzle. High-frequency discharges between the sputter electrode and a counter electrode release particles that become embedded in the coating.

[0008] Against this background, the present invention is based on the object of providing a method and a device for coating a workpiece surface that reduce or overcome one or more of the aforementioned disadvantages of the prior art methods. In particular, the invention is based on the object of providing a method and a device for coating a workpiece surface that are also suitable for temperature-sensitive workpiece surfaces, have lower

[0009] Require security requirements and / or enable higher order rates.

[0010] The aforementioned object is achieved according to the invention by a method for coating a workpiece surface, in which an atmospheric plasma jet is generated by means of a plasma nozzle, in which a coating material is supplied to the generated plasma jet, and in which the plasma jet containing the coating material is directed onto the workpiece surface to be coated, wherein the coating material is supplied to the generated plasma jet by feeding a filament containing the coating material or consisting of it to the generated plasma jet. In this way, a coating of a workpiece surface is achieved with a lower risk potential for the operator of the coating device. In addition, relatively high deposition rates and thus high layer thicknesses can be achieved with this method.

[0011] In the process, an atmospheric plasma jet is generated using a plasma nozzle.

[0012] By using an atmospheric plasma jet, negative pressure environments can be eliminated. An atmospheric plasma jet is defined as a plasma jet that operates at atmospheric pressure, i.e., particularly when exiting the plasma nozzle, for example, with a slight overpressure, into an environment near atmospheric pressure. The plasma jet can, for example, have a pressure in the range of + / - 300 mbar, preferably + / - 200 mbar, around the ambient atmospheric pressure.

[0013] The use of a plasma jet generated by a plasma nozzle also allows for targeted application of the plasma to the workpiece surface to be coated. In particular, the coating can be applied precisely to the desired areas of the workpiece surface. Furthermore, the coating thickness can be easily adjusted.

[0014] Furthermore, the plasma nozzle can be moved relative to the workpiece surface, for example, using a dedicated traversing device. This allows a larger area of ​​the workpiece surface to be exposed to the plasma jet.

[0015] In this process, coating material is fed into the generated plasma beam by adding a filament containing or consisting of the coating material. Compared to gaseous, liquid, and powdered precursors, the use of a filament has the advantage that safety requirements can be met more easily and cost-effectively. For example, the storage and use of potentially reactive precursor gases and / or precursor liquids and / or potentially respirable precursor powders can be dispensed with. Unlike conventional gaseous, liquid, or powdered precursors, filaments can be procured and stored without any safety-related effort. Furthermore, it has been determined that vapors and particles generated when a filament is fed into the plasma beam can be shielded using relatively simple means to protect the health of users.In addition, suitable filaments are generally readily available on the market, for example, due to the proliferation of 3D printers. Furthermore, filaments can be easily and controlledly fed into the plasma jet.

[0016] The coating material of the filament can, in particular, be melted, fragmented, and / or vaporized by the plasma jet. Furthermore, the coating material can be at least partially activated by the plasma jet, allowing it to better form a layer on the workpiece surface. For example, the coating material can be partially ionized by the plasma jet, or the plasma jet can form reactive compounds or groups, for example by breaking down chemical bonds, which enable better layer formation on the workpiece surface, for example, through crosslinking or polymerization of the coating material.

[0017] The filament can be fed into the plasma jet, for example, in the area where it is generated. If the plasma nozzle has electrodes, such as an inner electrode and an outer electrode, between which discharges are generated in a discharge zone, the filament can be fed into the plasma jet, for example, in the discharge zone. In particular, higher temperatures prevail in the discharge zone than downstream of the discharge zone, which allows for a higher filament throughput and higher deposition rates during coating.

[0018] The plasma jet generation area, where electrical discharges are generated in the plasma nozzle, is also referred to as the primary plasma area. The filament can therefore be introduced into the plasma jet particularly in the primary plasma area.

[0019] If the plasma nozzle has an internal electrode, the filament is preferably fed into the plasma jet at a distance from the inner electrode of the plasma nozzle. This reduces the direct impact of electrical discharges on the filament.

[0020] In one embodiment, the filament has electrically insulating properties. This prevents direct electrical discharges to the filament in the plasma nozzle. Preferably, the filament has a resistivity of at least 10 kΩ-cm, preferably at least 100 kΩ-cm, and in particular at least 1 mΩ-cm at 20°C.

[0021] The filament can also be fed into the plasma jet downstream of its generation, particularly downstream of the discharge area. This exposes the filament to lower temperatures, allowing for easier adjustment of lower deposition rates. Furthermore, more temperature-sensitive filaments can be used. When using electrically conductive filaments, feeding them downstream of the discharge area is advantageous to avoid electrical discharges to the filaments.

[0022] The region of the plasma jet in which no electrical discharges are generated in the plasma nozzle is also called the secondary plasma region or the relaxing plasma region. In this region, the plasma of the plasma jet begins to relax, particularly to recombine. The temperature and electrical potential of the plasma jet are lower in the relaxing region, or secondary plasma region, than in the generation region, or primary plasma region. The filament can therefore also be introduced into the plasma jet, particularly in the secondary plasma region.

[0023] The plasma nozzle can have a discharge catcher that separates the discharge region or the region of the primary plasma from a region downstream of the discharge region or from the region of the secondary plasma. The discharge catcher can be, for example, an electrically conductive grid or perforated plate, which is preferably conductively connected to the counter electrode and / or grounded. Such a discharge catcher can prevent discharges, for example discharge streamers, from extending downstream far beyond the discharge region. In this way, a plasma jet with a low electrical potential can be provided downstream of the discharge catcher. This is advantageous for certain applications, such as battery production.

[0024] If the plasma nozzle has a discharge catcher, the filament is preferably introduced into the plasma jet downstream of the discharge catcher. This prevents the coating material from clogging the discharge catcher, in particular the grid or perforated plate. Furthermore, the filament downstream of the discharge catcher can be protected from direct contact with electrical discharges, which is particularly advantageous for temperature-sensitive and / or electrically conductive filaments.

[0025] In this process, the plasma jet containing the coating material is directed at the workpiece surface to be coated. This way, the coating material is transported to the workpiece surface by the plasma jet, where it forms a coating on the workpiece surface.

[0026] The aforementioned object is further achieved according to the invention by a device for coating a workpiece surface, comprising a plasma nozzle configured to generate an atmospheric plasma jet, wherein the plasma nozzle has a nozzle opening from which the plasma jet emerges during operation, and a filament feed arranged and configured to feed a filament to the plasma jet generated during operation. The device can be used in particular when carrying out the aforementioned method or an embodiment thereof.

[0027] The above-mentioned object is further achieved according to the invention by the use of the above-described device or an embodiment thereof for coating a workpiece surface, in particular for carrying out the above-described method or an embodiment thereof.

[0028] Various embodiments of the method, device, and use are described below, with each individual embodiment applying independently to the method, device, and use. Furthermore, the individual embodiments can be combined with one another as desired.

[0029] In one embodiment, the plasma jet is generated by means of electrical discharges in a working gas, in particular by means of high-frequency, high-voltage discharges, in particular between at least two electrodes of the plasma nozzle. In a corresponding embodiment of the device, the plasma nozzle is configured to generate the plasma jet by means of electrical discharges in a working gas, in particular by means of high-frequency, high-voltage discharges, in particular between at least two electrodes of the plasma nozzle. In this way, a plasma jet is generated that is easy to focus and well-suited for plasma coating.

[0030] In particular, the atmospheric plasma jet can be generated by means of an arc-like discharge in a working gas, wherein the arc-like discharge is generated by applying a high-frequency high voltage between electrodes.

[0031] To generate the arc-like electrical discharge, at least two electrodes are provided, as well as a voltage source for applying a high-frequency high voltage to the electrodes. The high-frequency high voltage for generating a high-frequency arc-like discharge has, in particular, a voltage in the range of 1-100 kV, preferably 1-50 kV, more preferably 10-50 kV, and a frequency of 1-300 kHz, in particular 1-100 kHz, preferably 10-100 kHz, more preferably 10-50 kHz.

[0032] The plasma nozzle can, in particular, have an internal electrode. In this case, the filament feed is preferably arranged at a distance from the internal electrode. In this way, direct contact of the filament with electrical discharges from or to the internal electrode can be reduced or avoided, for example, in the case of temperature-sensitive or electrically conductive filaments.

[0033] In one embodiment, the filament contains at least one plastic. In another embodiment, the filament is based on at least one plastic. In another embodiment, the filament is made of plastic. The plastic contains, in particular, one or more polymers. The one or more polymers can, in particular, be homopolymers and / or copolymers. Furthermore, the plastic can, in particular, be a thermoplastic and / or an elastomer. The plastic can, in particular, be a thermoplastic elastomer, a thermoplastic vulcanizate, or a thermoplastic urethane.For example, the plastic can be polypropylene (PP), polylactide (PLA), polyethylene (PE), polyethylene terephthalate (PET), polycarbonate (PC), polypropylene-polyethylene copolymer, polyamide (PA), such as polyamide 6 (PA6), acrylonitrile-butadiene-styrene copolymer (ABS), acrylonitrile-styrene-acrylate (ASA), polyvinyl acetate (PVA), polyvinyl chloride (PVC), polystyrene (PS), polyetheretherketone (PEEK), polyvinyl butyral (PVB), polyvinylidene fluoride (PVDF), polyphenylene sulfide (PPS), polymethyl methacrylate (PMMA) or mixtures thereof.

[0034] The polymer can also be a thermoset, such as thermosetting polyurethane (PU). It has been found that the plasma jet can break some of the crosslinks in thermoset materials, making the thermoset material suitable for forming a coating on a workpiece surface when exposed to the plasma jet.

[0035] By using a polymer filament, a plastic coating can be created on the workpiece surface. It has been found that this method can be used to coat workpieces made of a variety of materials. In particular, the process can also be used to coat temperature-sensitive workpieces.

[0036] In one embodiment, the filament contains additives such as fillers, primers, or functional substances. For example, the use of fillers can increase the deposition rate. Flame-retardant fillers also enable the application of flame-retardant coatings. The use of primers as additives enables the application of coatings with adhesion-promoting properties. Furthermore, the use of other functional substances can influence the properties of the coating, for example, its optical, electrical, or antimicrobial properties.

[0037] Examples of additives that can be considered are metallic particles, in particular metal powder, glassy particles, in particular glass particles, stone powder, carbon-based particles, reinforcing fibers, in particular glass and / or carbon fibers, wood fibers, fluorescent substances, or mixtures thereof.

[0038] When using a polymer-based filament, the additives can be embedded in the polymer matrix formed by the polymer. This allows for a uniform distribution of the additives throughout the filament. Furthermore, particulate additives, in particular, can be bound within the filament, thereby reducing the safety risks posed by the particles' binding in the matrix.

[0039] In one embodiment of the device, the filament feed has a receptacle for a filament supply, in particular for a filament spindle. Filaments are readily available commercially as spindles and can thus be stored easily and safely. Providing a receptacle for a filament supply, in particular in the form of a filament spindle, allows for uninterrupted coating operation over an extended period of time, as well as easy refilling or replacing of the filament.

[0040] In one embodiment, the filament is guided into the plasma nozzle, in particular in the region of a nozzle opening of the plasma nozzle. In a corresponding embodiment of the device, the filament feed is configured to guide the filament into the plasma nozzle, in particular in the region of the nozzle opening of the plasma nozzle. In this way, feeding of the filament into the plasma jet under controlled conditions, for example controlled flow and / or temperature conditions, is enabled, so that, for example, a desired deposition rate can be better adjusted. Furthermore, more efficient operation is enabled because the plasma jet within the plasma nozzle has an even higher temperature, thus achieving more efficient melting and / or evaporation of the filament, whereby higher deposition rates can be achieved.

[0041] In one embodiment, the filament is fed to the plasma jet outside the plasma nozzle, in particular in the area in front of a nozzle opening of the plasma nozzle. In a corresponding embodiment of the device, the filament feed is configured to introduce the filament outside the plasma nozzle into the plasma jet generated by the plasma nozzle during operation, in particular in the area in front of the nozzle opening of the plasma nozzle. This is particularly advantageous if the plasma nozzle has a discharge catcher, such as a metal grid or perforated plate, at the nozzle opening. By feeding the filament outside the plasma nozzle, clogging of the openings of such a metal grid or perforated plate is avoided. Furthermore, a greater distance between the discharge and filament introduction is advantageous for temperature-sensitive filaments or when low deposition rates are desired during coating.

[0042] In one embodiment, the filament feed comprises a filament transport device configured to feed the filament to the generated plasma jet at a predetermined speed. In a corresponding embodiment of the method, the filament is fed to the plasma jet at a predetermined speed. The predetermined speed can be constant or variable. A variable speed, for example, allows the deposition rate to be changed over time, so that, for example, different deposition rates can be set for different areas of the workpiece surface. The filament transport device can, in particular, comprise a controllable motor, preferably a stepper motor, which drives one or more drive rollers to transport the filament.

[0043] In one embodiment, the filament is cooled before entering the plasma jet, in particular before entering the plasma nozzle. In a corresponding embodiment of the device, the filament feed comprises a cooling device configured to cool the filament and / or a portion of the filament feed in the region of the plasma nozzle. This prevents the filament from melting prematurely and clogging the filament feed. The cooling device can, for example, comprise a heat sink for air cooling. Liquid-cooled cooling devices are also conceivable.

[0044] In one embodiment, the device comprises a control device configured to control the operation of the device. The control device can, in particular, be configured to control the operation of the filament feed and / or the operation of the plasma nozzle. For example, the control device can be configured to control the filament transport device such that the filament is fed to the plasma jet at a predetermined speed.

[0045] Furthermore, the control device can be configured to monitor the operation of the device, for example, using one or more provided sensors. For example, a sensor can be provided that monitors the advance of the filament. In this way, it can be detected, for example, if the filament feed becomes clogged, for example, due to premature melting of the filament, so that such a blockage can be counteracted.

[0046] The control device can, for example, be configured to perform a cleaning process, for example, upon corresponding user input at a designated user interface or automatically, for example, at predetermined times or when a blockage in the filament feed is detected. For the cleaning process, the control device can be configured to allow the plasma jet to burn for a predetermined period of time without advancing the filament through the filament feed. In this way, the plasma jet can burn the plasma nozzle clean, in particular of coating material, without requiring disassembly and mechanical removal of the coating material.

[0047] Further features and advantages of the method and the device and the use will become apparent from the following description of embodiments, with reference to the accompanying drawings.

[0048] In the drawing show

[0049] Fig. 1 a plasma nozzle for generating an atmospheric plasma jet by means of a high-frequency arc-like discharge,

[0050] Fig. 2 shows an embodiment of the method and device for coating a workpiece surface,

[0051] Fig. 3 shows a second embodiment of the method and device for coating a workpiece surface,

[0052] Fig. 4 shows a third embodiment of the method and device for coating a workpiece surface and

[0053] Fig. 5 shows a fourth embodiment of the method and device for coating a workpiece surface.

[0054] Fig. 1 shows a schematic sectional view of a plasma nozzle 2 for generating an atmospheric plasma jet 26 by means of a high-frequency arc-like discharge. The plasma nozzle 2 has a nozzle tube 4 made of metal, to which a preferably replaceable outlet nozzle 25 with a nozzle opening 6 is connected at one end, to which the nozzle tube 4 and the outlet nozzle 25 taper.

[0055] At the end opposite the nozzle opening 6, the nozzle tube 4 has a swirl device 8 with an inlet 10 for a gas flow, in particular a working gas, for example air or nitrogen.

[0056] An intermediate wall 12 of the swirl device 8 has a ring of circumferentially inclined bores 14 through which the gas flow is guided. The downstream, conically tapered portion of the nozzle tube is therefore flowed through by the gas flow in the form of a vortex 16, the core of which runs along the longitudinal axis of the nozzle tube. An internal electrode 18 is arranged centrally on the underside of the intermediate wall 12 and projects coaxially into the nozzle tube in the direction of the tapered section. The electrode 18 is electrically connected to the intermediate wall 12 and the remaining parts of the swirl device 8. The swirl device 8 is electrically insulated from the nozzle tube 4 by a ceramic or quartz glass tube 20. A high-frequency high voltage, generated by a transformer 22, is applied to the electrode 18 via the swirl device 8.The inlet 10 is connected via a hose (not shown) to a working gas source, upstream of which the plasma nozzle 2 is supplied with a working gas stream 23 during operation. The nozzle tube 4 and the connected outlet nozzle 25 are grounded. The applied voltage generates a high-frequency discharge in the form of an arc 24 between the electrode 18 and the nozzle tube 4.

[0057] The terms "arc," "arc discharge," and "arc-like discharge" are used here as a phenomenological description of the discharge, since the discharge occurs in the form of an arc. The term "arc" is also used elsewhere as a discharge form for DC discharges with essentially constant voltage values. In this case, however, it is a high-frequency discharge in the form of an arc, i.e., a high-frequency, arc-like discharge.

[0058] However, due to the swirling flow of the working gas, this arc is channeled in the vortex core on the axis of the nozzle tube 4, so that it only branches out in the area of ​​the outlet nozzle 25 to the wall of the nozzle tube 4 or the outlet nozzle 25.

[0059] The working gas, which rotates at a high flow velocity in the region of the vortex core and thus in the immediate vicinity of the arc 24, comes into intimate contact with the arc 24 and is thereby partially converted into the plasma state, so that a plasma jet 26 is created in the plasma nozzle 2 at a pressure close to atmospheric pressure, for example in the pressure range 800 - 1300 mbar, and exits through the nozzle opening 6.

[0060] In the wall of the outlet nozzle 25, a bore 30 is provided, to which a supply line 32 is connected, through which a filament 34 can be guided into the outlet nozzle 25 into the area of ​​the plasma jet 26.

[0061] In Fig. 1, the filament 34 is introduced into the plasma jet 26 downstream of the discharge region. The plasma nozzle 2 can optionally have a discharge catcher, for example a metal grid, that separates the discharge region from the region downstream of the discharge region. If such a discharge catcher is provided, the filament 34 is preferably introduced into the plasma jet 26 downstream of the discharge catcher.

[0062] The filament 34 can also be introduced into the discharge area, i.e., in the immediate area of ​​the arc 24 and thus in the area where the plasma jet 26 is generated, for example, through a correspondingly provided bore in the nozzle tube 4. Furthermore, it is conceivable for the filament to be introduced into the plasma jet only outside the plasma nozzle 2, for example, by a feed device arranged in front of the nozzle opening 6. This is particularly advantageous if the plasma nozzle 2 has a discharge catcher, in particular a metal grid, in the area of ​​the nozzle opening 6.

[0063] Furthermore, it can be provided that a secondary nozzle with an enlarged cross-section is connected to the nozzle opening 6 and the filament is introduced into the plasma jet 26 in the region of the secondary nozzle.

[0064] Fig. 2 now shows an embodiment of a device for coating a workpiece surface in a schematic representation.

[0065] The device 100 has the plasma nozzle 2 from Fig. 1 and a filament feed 110. The filament feed 110 comprises a receptacle 112 for a filament supply, into which a filament supply 113 in the form of a spindle filament 34 can be inserted. The filament feed 110 further comprises a filament transport device 116 with a filament propulsion unit 120 driven by a stepper motor 118. The filament feed 110 further comprises a cooling device 122 and a filament guide 124 for guiding the filament 34 through the filament transport device 116 and the cooling device 122 into the feed line 32.

[0066] The filament drive unit 120 is formed in Fig. 2 by two rollers 120a-b driven in opposite directions by the stepper motor 118, between which the filament 34 is guided. The cooling device 122 is designed in Fig. 2 as a heat sink with cooling fins for air cooling. Additionally or alternatively, a cooling device with liquid cooling, for example, water cooling, can also be provided.

[0067] The filament guide 124 in Fig. 2 comprises respective openings and channels, such as the supply line 32, through which the filament 34 runs from the filament supply 113 to the plasma jet 26.

[0068] Furthermore, the device 100 preferably has a displacement device (schematically illustrated by arrows 130) for displacing the plasma nozzle 2 relative to a workpiece 132 to be coated. Additionally or alternatively, a movable workpiece holder may also be provided to displace the workpiece relative to the plasma nozzle 2.

[0069] The device 100 further comprises a control device 136 which is configured to control the plasma nozzle 2, the filament transport device 116 and the displacement device 130 and is connected to them for this purpose via wired or wireless communication connections (not shown).

[0070] Furthermore, sensors, such as sensors for determining the transport speed of the filament or temperature sensors for determining the temperature of the supply line to the cooling device, can be provided and connected to the control device 136 via communication links, so that the control device 136 can monitor and regulate the operation of the device 100.

[0071] The operation of the device 100 and thus an embodiment of the method for coating a workpiece surface using the device 100 is described below.

[0072] An atmospheric plasma jet 26 is generated by the plasma nozzle 2. For this purpose, a high-frequency high voltage is applied between the inner electrode 18 and the nozzle tube 4 or the outlet nozzle 25 using the transformer 22, while a working gas stream 23 is introduced into the plasma nozzle 2, so that, as described above in connection with Fig. 1, a plasma jet 26 is formed, which exits from the nozzle opening 6 of the plasma nozzle 2 and is directed onto a workpiece surface 133 of a workpiece 132 to be coated.

[0073] By controlling the filament transport device 116, in particular the stepper motor 118, filament 34 is fed through the cooling device 122 to the outlet nozzle 25 of the plasma nozzle 2 and thus introduced into the plasma jet 26. The filament 34, which may be a polypropylene filament, for example, is partially melted and / or fragmented in the plasma jet 26 and, together with the plasma jet 26, reaches the workpiece surface 133, where it forms a coating 134.

[0074] Fig. 3 shows a second embodiment of a device for coating a workpiece surface in a schematic representation.

[0075] The device 200 has a similar structure to the device 100 of Fig. 2 and differs from it essentially only in the design of the lower part of the plasma nozzle 2 and the arrangement of the supply line 32 to the plasma nozzle 2, which are shown schematically in Fig. 3.

[0076] Components corresponding to the components in Fig. 1 and 2 are provided in Fig. 3 with the associated reference numerals from Fig. 1 and 2, even if they may be partially structurally different and / or arranged differently in Fig. 3 than in Fig. 1 and 2. In this respect, reference is made to the associated description of Fig. 1 and 2.

[0077] In the device 200, the outlet nozzle 25 has, downstream of the section 202 in which the interior of the plasma nozzle 2 tapers, an adjoining section 204 with a substantially constant cross-section with the bore 30 to which the supply line 32 is connected.

[0078] Between the first section 202 and the bore 30, a discharge catcher 206, preferably a metal grid or perforated metal sheet, is preferably arranged, which separates the discharge region (upstream of the discharge catcher 206) from the region downstream of the discharge region (downstream of the discharge catcher 206).

[0079] In this way, the filament can be introduced into the plasma jet 26 in a region where no discharges occur between the inner electrode 18 and the nozzle tube 4 or the outlet nozzle 25. In this way, direct discharges onto the filament 34 can be prevented, for example, in the case of a conductive filament 34. Furthermore, the filament 34 can be introduced into a region of lower temperature within the plasma jet 26, which can be advantageous, for example, with temperature-sensitive filaments 34 or when low deposition rates are desired.

[0080] Fig. 4 shows a second embodiment of a device for coating a workpiece surface in a schematic representation.

[0081] The device 300 has a similar structure to the device 200 of Fig. 3 and differs from it only in the design of the outlet nozzle 25 at the lower part of the plasma nozzle 2, which is shown schematically in Fig. 3.

[0082] Components corresponding to the components in Fig. 1 - 3 are provided in Fig. 4 with the associated reference numerals from Fig. 1 - 3, even if they may be structurally different in some cases and / or arranged differently in Fig. 4 than in Fig. 1 - 3. In this respect, reference is made to the associated description of Fig. 1 - 3. In the device 300, the outlet nozzle 25 has the section 202, in which the interior of the plasma nozzle 2 tapers, as well as an adjoining section 304, the cross-section of which is enlarged compared to the smallest cross-section of section 202. The section can increase in size abruptly from section 202 to section 304, as shown in Fig. 4, or continuously. The cross-section can remain the same in the further course of section 304 (as in Fig. 4) or increase further.

[0083] In section 304, the bore 30 is located, to which the supply line 32 is connected.

[0084] Due to the cross-sectional expansion in section 304, a stronger relaxation and / or cooling of the plasma jet 26 can be achieved already in the plasma nozzle 2. In this way, the filament 34 can be introduced into a cooler region of the plasma jet 26, which is advantageous, for example, for temperature-sensitive filaments or when low deposition rates are desired.

[0085] Furthermore, the cross-sectional expansion in section 304 can widen the plasma jet 26 so that, for example, a larger surface area of ​​a workpiece can be coated simultaneously.

[0086] Fig. 5 shows a second embodiment of a device for coating a workpiece surface in a schematic representation.

[0087] The device 400 has a similar structure to the device 100 from Fig. 2 and differs from it only in the design of the lower part of the plasma nozzle 2 and the arrangement of the feed line 32 to the plasma nozzle 2, which are shown schematically in Fig. 3. Components corresponding to the components from Figs. 1 and 2 are provided in Fig. 3 with the associated reference numerals from Figs. 1 and 2, even if they may be partially structurally designed and / or arranged differently in Fig. 3 than in Figs. 1 and 2. In this respect, reference is made to the associated description of Figs. 1 and 2.

[0088] In the device 400, the supply line 32 is arranged such that the filament 34 is introduced into the plasma jet 26 after it has exited the plasma nozzle 2 through the nozzle opening 6. The bore 30 is accordingly unnecessary in the device 400.

[0089] Outside the plasma nozzle 2, the plasma jet 26 relaxes and / or cools down, so that the filament 34 can be introduced into a cooler region of the plasma jet 26, which is advantageous for temperature-sensitive filaments 34 or when lower deposition rates are desired.

[0090] Furthermore, the embodiment in Fig. 4 allows for more flexible adjustment of the position at which the filament 34 is introduced into the plasma jet 26 by adjusting the distance between the nozzle opening 6 and the feed line 32. The distance can be adjusted, for example, to the filament material used or the desired deposition rate.

[0091] List of reference symbols:

[0092] 2 plasma nozzles

[0093] 4 nozzle pipe

[0094] 6 nozzle opening

[0095] 8 Swirl device

[0096] 10 Entrance

[0097] 12 Partition wall

[0098] 14 holes 16 vertebrae

[0099] 18 Internal electrode

[0100] 20 quartz glass tubes

[0101] 22 Transformer

[0102] 23 Working gas flow

[0103] 24 arc

[0104] 25 Outlet nozzle

[0105] 26 Plasma beam

[0106] 30 holes

[0107] 32 supply line

[0108] 34 filament, 200, 300, 400 device

[0109] 110 Filament feeder

[0110] 112 Holder for filament supply

[0111] 113 filament stock

[0112] 116 Filament transport device

[0113] 118 Stepper motor

[0114] 120 Filament propulsion unit

[0115] 120a-b roles

[0116] 122 Cooling device

[0117] 124 Filament guide

[0118] 130 Traversing device

[0119] 132 Workpiece

[0120] 133 Workpiece surface

[0121] 134 Coating

[0122] 136 Control device

[0123] 202 Section of the outlet nozzle with tapered cross-section

[0124] 204 Section of the outlet nozzle with constant cross-section

[0125] 304 Section of the outlet nozzle with extended cross-section

[0126] 206 discharge catcher

Claims

Patent claims 1. A method for coating a workpiece surface (133), in particular using a device (100, 200, 300, 400) according to one of claims 7 to 12, in which an atmospheric plasma jet (26) is generated by means of a plasma nozzle (2), in which a coating material is supplied to the generated plasma jet (26), and in which the plasma jet (26) with the coating material is directed onto the workpiece surface (133) to be coated, characterized in that the coating material is supplied to the generated plasma jet (26) by supplying a filament (34) which contains or consists of the coating material to the generated plasma jet (26).

2. Method according to claim 1, characterized in that the plasma jet (26) is generated by means of electrical discharges in a working gas, in particular by means of high-frequency high-voltage discharges, in particular between at least two electrodes of the plasma nozzle.

3. Method according to claim 1 or 2, characterized in that the filament (34) contains at least one plastic, is based on a plastic or consists of a plastic.

4. Method according to one of claims 1 to 3, characterized in that the filament (34) contains additives which are preferably embedded in a polymer matrix.

5. Method according to one of claims 1 to 4, characterized in that the filament (34) is guided into the plasma nozzle (2), in particular in the region of a nozzle opening (6) of the plasma nozzle (2), or that the filament (34) is fed to the plasma jet (26) outside the plasma nozzle (2), in particular in the region in front of a nozzle opening (6) of the plasma nozzle (2).

6. Method according to one of claims 1 to 5, characterized in that the filament (34) is cooled before entering the plasma jet (26), in particular before entering the plasma nozzle (2).

7. Device (100, 200, 300, 400) for coating a workpiece surface (133), with a plasma nozzle (2) which is designed to generate an atmospheric plasma jet (26), wherein the plasma nozzle (2) has a nozzle opening (6) from which the plasma jet (26) emerges during operation, and with a filament feed (124) which is arranged and designed to feed a filament (34) to the plasma jet (26) generated during operation.

8. Device according to claim 7, characterized in that the plasma nozzle (2) is designed to generate the plasma jet (26) by means of electrical discharges in a working gas, in particular by means of high-frequency high-voltage discharges, in particular between at least two electrodes of the plasma nozzle (2).

9. Device according to claim 7 or 8, characterized in that the filament feed (124) has a receptacle (112) for a filament supply (113), in particular for a filament spindle.

10. Device according to one of claims 7 to 9, characterized in that the filament feed (110) is designed to guide the filament (34) into the plasma nozzle (2), in particular in the region of the nozzle opening (6) of the plasma nozzle (2).

11. Device according to one of claims 7 to 10, characterized in that the filament feed (110) has a filament transport device (116) which is designed to feed the filament (34) to the generated plasma jet at a predetermined speed.

12. Device according to one of claims 7 to 11, characterized in that the filament feed (110) has a cooling device (122) which is designed to cool the filament (34) and / or a part of the filament feed (110) in the region of the plasma nozzle (2).

13. Device according to one of claims 7 to 12, characterized in that the device (100, 200, 300, 400) has a control device which is designed to control the operation of the device (100, 200, 300, 400), in particular the filament feed (110) and / or the plasma nozzle (2).

14. Use of the device (100, 200, 300, 400) according to one of claims 7 to 13 for coating a workpiece surface (133).

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