Method and device for surface treatment

Abstract

The invention relates to a method and a device (1) for processing surfaces (3, 4, 5), wherein an electric field is applied between at least two surfaces (3, 4, 5) in a common, gas-tight housing (2), with a gas pressure in the housing (2) lower than the ambient pressure of the housing (2). The energy of the electric field supplied to each of the surfaces (3, 4, 5) is regulated or controlled.

Description

[0001] The invention relates to a method and a device for processing surfaces, wherein an electric field is applied between at least two surfaces in a common, gas-tight housing, at a gas pressure in the housing less than the ambient pressure of the housing.

[0002] Surfaces, such as metallic and ceramic surfaces, are modified, for example, by mechanical polishing and / or electric fields. Analogous to electropolishing in liquids, as described, for example, in G. Yang et al., Electropolishing of surfaces: theory and applications, Surface Engineering 33 (2017), pp. 149–166, electric fields also enable surface modification in gases, for example, with regard to roughness and / or structure. At low gas pressures, down to vacuum pressure, electric fields improve a surface, for example, by locally melting and / or rearranging the atoms on the surface, which, for example, allows for the smoothing of a flat surface. For this purpose, the surface is subjected to a field; that is, an electrical voltage is applied between the surface and a counter electrode, which generates an electric field between the surface (acting as an electrode) and the counter electrode. At high voltages, or...Field strengths can cause electrical discharges between the electrodes, which can migrate, for example, across the surface of the electrodes.

[0003] Unordered passes, particularly those with irregularly fluctuating fields caused by the passes, remove peaks or raised areas from the surface being processed. Large surfaces require longer processing times, up to minutes for surfaces measuring a few square centimeters. Achieving a uniform surface finish is difficult.

[0004] The invention is based on the objective of solving the problems described above. In particular, the invention is based on the objective of providing a method and a device for surface treatment which enables surface treatment via an electric field, especially in a short time.

[0005] The problem is solved according to the invention by a method for processing surfaces with the features of claim 1 and / or by a device for carrying out the previously described method according to claim 11. Advantageous embodiments of the method for processing surfaces according to the invention are specified in the dependent claims. The subject matter of the main claim can be combined with features of the dependent claims, and features of the dependent claims can be combined with each other.

[0006] A method according to the invention for surface treatment comprises applying an electric field between at least two surfaces in a common, gas-tight housing, with a gas pressure in the housing lower than the ambient pressure of the housing. The energy of the electric field supplied to each surface is regulated or controlled.

[0007] By regulating or controlling the energy of the electric field that is supplied to the surfaces, This enables regulated or controlled, and in particular ordered, arcing processes, without the irregular, locally fluctuating fields caused by the arcing. This allows, for example, peaks or elevations on the surface to be processed to be defined, and in particular, to be removed in a predetermined, ordered manner within a short time. For large surfaces, shorter processing times are possible compared to unregulated or uncontrolled energy. Furthermore, a uniform surface finish is achieved.

[0008] The at least two surfaces can be metallic and / or ceramic. Metallic surfaces are electrically conductive and well-suited as electrodes for applying electric fields. At very high voltages, such as those exceeding 50 kV, even non-conductive surfaces, such as ceramic surfaces, can be treated by electrical discharges when an electric field is applied. Applying an electric field with regulated or controlled energy enables defined surface treatment or tempering, particularly of non-conductive surfaces.

[0009] The pressure inside the housing can be less than 1 bar, particularly less than 1 mbar. At low pressures, especially in the vacuum range, surface treatment by electrical discharges under an applied electric field is readily possible, offering the advantages described above for regulated or controlled electric field energies.

[0010] An alternating electric field with a frequency in the range of 10 Hz to 100 kHz can be used, particularly in the range of 16 Hz to 16 kHz. At the frequencies described above, surface treatment or surface coating is readily possible, especially on metallic and ceramic surfaces, within a manageable timeframe, particularly in the range of seconds to minutes.

[0011] An electric field with a field strength greater than 1 kV / mm, particularly greater than 10 kV / mm, and especially greater than 100 kV / mm, can be used. At such field strengths, metallic and / or ceramic surfaces in particular can be readily processed or tempered by electrical discharges, with the advantages described above.

[0012] The energy supplied to the surfaces can be automatically regulated or controlled, leading to surface treatment, particularly through pre-programmed automation. This automated regulation or control, especially pre-programmed automation, e.g., computer-controlled or regulated according to a predetermined program, enables surface treatment and coating with predetermined final surface properties, requiring minimal personnel and costs, and in a short time, particularly within seconds or minutes.

[0013] The electric field between at least two surfaces allows for electrical discharges, and the energy of the electric field supplied to each surface can be regulated or controlled with respect to the number of discharges per unit of time and / or a predetermined total number of discharges. Such parameters enable the regulation or control of surface treatment or tempering, with a predictable result. A specific degree of surface tempering, as the final result, can be predetermined, in particular, by terminating the process at a specific number of discharges per unit of time and / or a predetermined total number of discharges.

[0014] The electric field between at least two surfaces allows electrical discharges to occur, and the energy of the electric field supplied to each surface can be regulated or controlled such that the number of discharges per unit of time at the end of the process is 80% or less than the number of discharges per unit of time at the beginning of the process, and / or the number of discharges per unit of time remains constant over a time interval in the range of seconds or minutes, particularly in the range of 30 seconds. This allows for the production of well-coated surfaces in a manageable time, at low cost, and with the advantages described above.

[0015] An electric field can be applied between more than two surfaces in a common housing, whereby the surfaces are particularly grouped and subjected to an electrical voltage. This allows several surfaces to be processed simultaneously, especially with comparable surface coatings, resulting in cost and time savings compared to processing a single surface and enabling the use of identical surface coatings on multiple surfaces.

[0016] The gas-tight housing can have electrically insulating areas, in particular comprising glass and / or ceramic, through which metal surfaces are dielectrically separated. This makes it possible to apply an electric field to surfaces inside the housing from the outside, for processing surfaces inside the housing, in particular from opposite sides of the housing.

[0017] An apparatus according to the invention for carrying out a previously described method comprises at least one device for generating an electric field between the surfaces to be processed, and comprises a control device which regulates or controls the energy of the electric field supplied to the surfaces. The advantages previously mentioned for the method are analogous to the advantages of the apparatus according to the invention.

[0018] In the following, exemplary embodiments of the invention are schematically illustrated in the single figure and subsequently described in more detail.

[0019] This shows Figure schematically shows a device 1 according to the invention for processing surfaces 3, 4, 5 with the method according to the invention, with a device 7 for generating an electric field between the surfaces 3, 4, 5 to be processed and with a control device 8 which regulates or controls the energy of the electric field which is supplied to the surfaces 3, 4, 5.

[0020] The single figure schematically shows a device 1 according to the invention for processing surfaces 3, 4, 5 from the side. The device 1 comprises a gas-tight housing 2 with a gas pressure lower than the ambient pressure, e.g., a pressure less than 1 bar, in particular less than 1 mbar. especially with a vacuum inside. The surfaces 3, 4, 5 are arranged in the housing 2. In the embodiment shown in the single figure, three surfaces 3, 4, 5 are depicted, wherein two surfaces 4 and 5 are arranged side by side in one plane for processing, grouped together, and the surface 3 is arranged opposite them, in particular parallel to the two grouped surfaces 4 and 5.

[0021] Surfaces 3, 4, and 5 are electrically connected. Surface 3 serves as the counter electrode to surfaces 4 and 5. An electric field is applied between surface 3 and surfaces 4 and 5. The energy of the electric field supplied to surfaces 4 and 5 is regulated or controlled. For this purpose, a device for generating an electric field 7 and an associated control device 8 are provided, which are electrically connected to surfaces 3, 4, and 5, for example, via cables, in particular copper cables. The device for generating an electric field 7 and the control device 8 are arranged in separate devices or housings, or can be enclosed by a single device or housing, and may be located outside or inside the housing 2.

[0022] The surfaces 3, 4, 5 to be processed are, for example, metallic, glass-like, and / or ceramic surfaces, in particular copper, aluminum, steel, glass, and / or ceramic. When an electric field, in particular an alternating field with a frequency in the range of 10 Hz to 100 kHz or in the range of 16 Hz to 16 kHz, and / or a field strength greater than 1 kV / mm, in particular greater than 10 kV / mm, in particular greater than 100 kV / mm, is applied between surface 3 and the grouped surfaces 4 and 5, electrical discharges occur between the surfaces 3, 4, 5. The discharges have, for example, the form of electric arcs. The discharges process the surfaces 3, 4, 5.

[0023] Particularly in areas of high roughness or at peaks on surfaces 3, 4, 5, overvoltages arise, triggering arcing. These arcs cause local heating in these areas or at the peaks, especially at temperatures above the melting point of the surface material, e.g., greater than 1000 degrees Celsius. The local melting, or even the increase in the mobility of surface atoms and molecules below the melting temperature on surfaces 3, 4, 5, leads to a smoothing and tempering of these surfaces. Rough areas or peaks on surfaces 3, 4, 5 are removed. If a housing 2 is located near surfaces 3, 4, 5, areas of the housing can also be processed, in particular smoothed or tempered.In the case of high potential differences between housing 2 and surfaces 3, 4, 5, arcing can occur between housing 2 and surfaces 3, 4, 5, which leads to the machining of the inner surface of housing 2.

[0024] During the coating process, contaminants, especially organic substances and / or dust particles, can also be locally desorbed or "burned off." Evaporated substances and / or particles can be removed from the housing 2 via an externally connected pump, particularly a vacuum pump, which is not shown in the single figure for the sake of simplicity. To enable uniform surface treatment, the energy supplied to surfaces 3, 4, 5 via the electric field is automatically regulated or controlled, in particular by pre-programming. Predefined programs can be set for this purpose, according to which the energy supplied via the field is changed. This prevents random, disordered surface treatment and instead produces uniform surfaces 3, 4, 5 with, in particular, predetermined coating properties.Disordered rollovers, especially those with irregularly fluctuating fields due to the rollovers, are avoided.

[0025] For large surfaces, especially those measuring several square centimeters, longer processing times are avoided or the processing time is reduced compared to unregulated or uncontrolled processing, often to just a few seconds or minutes. Uniform surface finishing is achieved.

[0026] The energy of the electric field is supplied by the device 7 for generating an electric field between the surfaces 3, 4, 5 to be processed and is regulated or controlled by the control device 8. Regulation or control is carried out, for example, with regard to the number of flashovers 6 per unit of time and / or with regard to a predetermined total number of flashovers 6, after which the surface processing is terminated, e.g., by switching off the electric field. Regulation or control can be implemented, for example, such that the number of flashovers 6 per unit of time at the end of the process is 80% or less than the number of flashovers 6 per unit of time at the beginning of the process. Alternatively, regulation or control can be implemented with a constant number of flashovers 6 per unit of time over a time interval in the range of seconds or minutes, particularly in the range of 30 seconds.

[0027] The embodiments described above can be combined with one another and / or with the prior art. For example, the housing 2 can be made of a material, in particular a homogeneous material such as a homogeneous insulator, or the gas-tight housing 2 can have electrically insulating areas, in particular comprising glass and / or ceramic, which dielectrically separate the metal surfaces. For processing, high voltages, in particular voltages greater than 52 kV, are applied between the surfaces 3, 4, 5 and / or between the surfaces 3, 4, 5 and the housing 2. The housing 2 can, for example, have a hollow cylindrical shape with a circular or elliptical base, or other shapes such as a cuboid. Reference symbol list 1 Device for surface processing 2 cases 3 first surface 4 second surface 5 third surface 6. Overlap between the surfaces 7 Device for generating an electric field 8 Control or regulating device

Claims

[1] Method for processing surfaces (3, 4, 5) wherein an electric field is applied between at least two surfaces (3, 4, 5) in a common, gas-tight housing (2), at a gas pressure in the housing (2) less than the ambient pressure of the housing (2), characterized by , that the energy of the electric field supplied to each of the surfaces (3, 4, 5) is regulated or controlled. [2] Method according to claim 1, characterized by that at least two surfaces (3, 4, 5) include metallic and / or ceramic surfaces. [3] Method according to any one of the preceding claims, characterized by , that the pressure used in the housing (2) is less than 1 bar, in particular less than 1 mbar. [4] Method according to any one of the preceding claims, characterized by, that an alternating field with a frequency in a range of 10 Hz to 100 kHz is used as the electric field, in particular in a range of 16 Hz to 16 kHz. [5] Method according to any one of the preceding claims, characterized by , that the electric field used is a field with a field strength greater than 1 kV / mm, in particular greater than 10 kV / mm, in particular greater than 100 kV / mm. [6] Method according to any one of the preceding claims, characterized by , that the energy supplied to the surfaces (3, 4, 5) leads to a surface coating, wherein the energy is automatically regulated or controlled, in particular pre-determined automatically. [7] Method according to any one of the preceding claims, characterized by, that electrical discharges (6) occur through the electric field between the at least two surfaces (3, 4, 5), and the energy of the electric field supplied to each of the surfaces (3, 4, 5) is regulated or controlled with respect to the number of discharges (6) per unit of time and / or with respect to a predetermined total number of discharges (6). [8] Method according to any one of the preceding claims, characterized by, that electrical discharges (6) occur through the electric field between the at least two surfaces (3, 4, 5), and the energy of the electric field supplied to each of the surfaces (3, 4, 5) is regulated or controlled such that the number of discharges (6) per unit of time at the end of the process is 80% or less than the number of discharges (6) per unit of time at the beginning of the process, and / or the number of discharges (6) per unit of time is constant over a time interval in the range of seconds or minutes, in particular in the range of 30 seconds. [9] Method according to any one of the preceding claims, characterized by , that an electric field is applied between more than two surfaces (3, 4, 5) in a common housing (2), wherein surfaces (4, 5) are in particular grouped together and subjected to an electric voltage. [10] Method according to any one of the preceding claims, characterized by, that the gas-tight housing (2) has electrically insulating areas, in particular comprising glass and / or ceramic, through which metal surfaces are dielectrically separated. [11] Device (1) for carrying out a method according to any of the preceding claims, characterized by , that the device (1) comprises at least one device (7) for generating an electric field between the surfaces to be processed, and that the device comprises a control or regulating device (8) which regulates or controls the energy of the electric field which is supplied to the surfaces (3, 4, 5) respectively.

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