Device and method for the plasma treatment of metal surfaces

Abstract

A device and method for a stable plasma treatment of components, in particular of large components of individual weights between 500 kg and 40 t, the device comprising a treatment chamber in the form of a lying cylinder with at least one lateral cylinder cover, and a special sealing system, the device and method allowing a stable plasma treatment of such components, in particular of large tools such as for example large forming tools.

Description

[0001] Device and method for plasma treatment of metal surfaces

[0002] The present invention relates to the plasma treatment of metal surfaces, in particular metal surfaces of large components, in order to produce large components with modified metal surfaces.

[0003] Components in the context of the present invention are generally understood to mean any parts or substrates with metal surfaces, with large components being referred to in particular as those having weights in the range of 500 kg to 40 t (between five hundred kilograms and forty tonnes).

[0004] Accordingly, the term components is used in this description in particular for tools and tool parts as well as for components.

[0005] The plasma treatment according to the present invention can be used in particular for the modification of metal surfaces of tools which are used in manufacturing processes, such as forming and plastics processing, such as injection moulding (called "Plastic Injection" or "Injection Moulding" in English), and extrusion processes (in the extrusion process, long fibre-reinforced thermosetting semi-finished products with modified metal surfaces can be used, which due to their name in English "Sheet Molding Compound", are also simply referred to as SCM in German-speaking countries).

[0006] A major application area for such components with modified metal surfaces lies in forming technology, especially in the processing of products for the automotive industry. Well-known products processed in this way include outer skin and structural parts for the automotive industry (e.g., doors, flaps, side panels, hoods). Such forming tools (hereinafter also referred to as tool parts) can, for example, have individual tool part weights of 500 kg up to 40 t. Accordingly, such forming tools are also referred to as large components in this description. Components or large components with modified metal surfaces are also molds that are treated for use in the plastics industry, for example, for the processing of bumpers, car headlights, plastic parts for the interior and exterior of automobiles, and household appliances.

[0007] Within the scope of the present description, for example, large components such as gears, rollers and discs can also be treated to produce modified metal surfaces.

[0008] However, the above-mentioned components or large components with modified metal surfaces are merely examples of large components within the scope of the present invention and should therefore not be considered as a limitation of the use of the inventive device or the inventive method for the plasma treatment of metal surfaces.

[0009] Depending on the application, different requirements are placed on the surfaces of components.

[0010] For example, in the case of forming tools for metal forming, the requirements are considerable, so that at least the following requirements should be met:

[0011] • High hardness,

[0012] • High corrosion and wear resistance,

[0013] • Low friction coefficient,

[0014] • Fatigue resistance,

[0015] • Polishing ability

[0016] • Repairability (maintenance).

[0017] In the body shop industry, the general trend is toward reducing lubricants (particularly with regard to lubricant use in the forming process) and vehicle weight. The resulting limited use of lubricants, combined with the introduction of high-strength sheet materials (so-called "high-strength sheet materials") and ultra-high-strength sheet materials (so-called "ultra-high-strength sheet materials"), is leading to a continuous increase in the requirements for forming tools with regard to improved abrasion resistance. Previously, wear in press shops was limited by increasing the amount of lubricant (using additional lubricant) in addition to the coil or sheet lubrication to protect against wear (particularly adhesive wear).

[0018] However, efficient lubricating oils often contain chlorinated paraffin as an extreme-pressure additive, which is relatively toxic and has negative environmental impacts. Therefore, its use is now even more limited, and the trend is toward minimal lubrication (maximum reduction of additional lubricant).

[0019] Therefore, a suitable surface treatment is advisable to protect the tool surfaces from wear.

[0020] In sheet metal forming, adhesive wear is the main wear mechanism. This type of wear generally includes the following phases:

[0021] • Initiation of a local transfer of sheet material to the tool surface.

[0022] • Growth of the transfer layer (abrasion from sheet material that occurs on the tool surface during the sheet metal forming process) and subsequent abrasive wear on the sheet.

[0023] • Transition to severe adhesive wear.

[0024] Zumkeller et al. disclose in WO 2012 / 072209 A1 that a good solution to increase the corrosion resistance of metal surfaces and to protect them against wear is to nitride these metal surfaces.

[0025] WO 2012 / 072209 A1 mentions special nitriding processes marketed as PPD® processes. In particular, Zumkeller et al. describe in WO 2012 / 072209 A1 a special implementation of this PPD® process that can lead to improved performance of plastics processing components.

[0026] In this respect, reference is made to application WO 2012 / 072209 A1 , the content of which is hereby incorporated into this application.

[0027] It is known that increased corrosion and wear resistance can be achieved through plasma nitriding, in which the substrates to be nitrided are exposed to a plasma containing hydrogen and nitrogen ions under vacuum conditions. Nitriding with a pulsed plasma is also known. Pulsing offers several advantages: firstly, the process temperature can be selected within a wide range via power coupling by controlling the pulse duration, without having to change other process parameters such as the voltage between the electrodes. Secondly, pulsing can largely prevent sparking during the nitriding process.

[0028] Nitriding occurs through the diffusion of nitrogen into the surface of the base material, creating a nitriding zone in which, near the surface, the nitrogen bonds with the workpiece materials, or slightly deeper, the nitrogen (along with nitride formation with the alloying elements) forms an intercalated solid solution with the base material. Therefore, this nitriding zone is typically composed of a compound layer and a diffusion zone. Accordingly, the compound layer primarily contains nitride compounds. In the case of iron-containing substrates, for example, s-nitride (=Fe2(3)N) and / or y-nitride (=Fe4N) can form in the compound layer.

[0029] The present invention is concerned with the improvement of plasma nitriding processes in order to produce components efficiently and reliably with optimally modified metal surfaces for various applications.

[0030] The present improvement represents a further development of the PPD® plasma nitriding process described in WO 2012 / 072209 A1.

[0031] Object of the present invention

[0032] An object of the present invention is to provide a device (hereinafter also referred to as a system) for the plasma surface treatment (in particular for nitriding) of components, which is suitable for the treatment of large components, wherein the device should comprise a treatment chamber in which the frequently occurring problem with the sealing of large treatment chambers is avoided or completely eliminated. This is particularly difficult because a very large treatment chamber 200, in order to be able to equip it with correspondingly large components to be treated, must have a large opening 250 (see Figures 1 and 3). For example, the system built by the applicant has the shape of a horizontal cylinder with a length of 10 meters and a diameter of 4.2 meters. This allows the heaviest components, e.g.Sidewall tools made of cast iron or steel with dimensions of length by width (L x W) = < 10 meters by < 2.9 meters and a unit weight of up to 40 tons are introduced into the treatment plant via the base area 100 of the cylinder, which is designed as a retractable lid 150 (see Figure 3). When the lid is closed, a circumference of IT x D, i.e., approximately 3.14 x 4.2 meters = 13 meters, must be vacuum-sealed. The applicant has protected the appearance of such a system in the European design application number 002071415.

[0033] The present invention aims to address and solve this sealing problem.

[0034] Yet another object of the present invention is to provide a method for avoiding or satisfactorily controlling the occurrence of arc discharges or spark leaks (also called "plasma leaks" or "arcing") frequently associated with plasma treatment processes.

[0035] A plasma treatment process can, for example, be carried out at an operating voltage of up to approximately 1000 V (up to approximately one thousand volts), whereby the pressure typically set for carrying out the process is, for example, a value between 0.5 mbar and 4.5 mbar, e.g. 1.9 mbar.

[0036] With such process parameters, depending, among other things, on the geometry of the component to be treated, its temperature distribution, as well as outgassing due to contamination that cannot always be avoided, plasma breakdowns sometimes occur in the form of local lightning, which can damage the component to be treated, for example at the point of impact.

[0037] This problem is also addressed by the present invention. The present invention is therefore based on the object of providing a surface treatment system (in particular, a device for plasma treatment of substrates) with which it is possible to subject large workpieces (also called large components) to a plasma treatment, wherein in this system: the negative pressure required for the treatment can be generated and maintained stable due to the inventive measures, and

[0038] - steps according to the invention can be carried out to prevent an increased occurrence of plasma breakdowns on the components to be treated.

[0039] Solution according to the present invention

[0040] The object of the present invention is achieved by providing a device according to claim 1 and methods according to claims 2 to 7.

[0041] Figure 1 shows the external appearance of a plant built by the applicant from a perspective with the treatment chamber closed.

[0042] Figure 2 shows a schematic representation of the inventive solution to the sealing problem mentioned above.

[0043] Figure 3 shows the appearance of the same system shown in Figure 1 from a perspective where the treatment chamber is open and the lid of the treatment chamber is accordingly removed from the rest of the treatment chamber.

[0044] Legend of the figures:

[0045] 1 Seals (inner sealing ring in the inner sealing groove 3 and outer sealing ring 1 in the outer sealing groove 2)

[0046] 2 outer sealing groove

[0047] 3 inner sealing groove

[0048] 4 middle groove

[0049] 6 Sealing lip on the outer sealing ring 1 (in the outer sealing groove 2) facing the external environmental atmosphere 10, and sealing lip on the inner sealing ring 1 (in the inner sealing groove 3) facing the treatment chamber interior 20

[0050] 7 Sealing lip on the outer sealing ring 1 (in the outer sealing groove 2) and sealing lip on the inner sealing ring (in the inner sealing groove 3) pointing towards the support vacuum chamber 40

[0051] 8 Circular surface of the chamber against which the front of the respective seals 1 is pressed

[0052] 10 external environment (also called external environmental atmosphere or external surroundings)

[0053] 20 Treatment chamber interior

[0054] 30 pressure chambers (inner groove areas of the sealing grooves)

[0055] 40 Vacuum space in the sealing system or support vacuum space

[0056] 100 Base area on which the components to be treated are mounted

[0057] 150 retractable cylinder cover of the treatment chamber

[0058] 200 cylindrical, horizontal treatment chamber

[0059] 250 Opening of the treatment chamber

[0060] The special seals 1 are located in the outer seal groove 2 and the inner seal groove 3. These seals are not inflatable seals. The rear seal lips 6 and 7 of the seals 1 are simply pressed against the seal wall of the groove by the application of gas, e.g., nitrogen, and, on the front side, against the system flange (or against the annular surface 8 of the system flange).

[0061] In the support vacuum chamber 40, or vacuum chamber 40, a vacuum is created, which is called a support vacuum because it supports the tightness of the sealing lips 7. The sealing lips 7 are each additionally pulled against the groove by the vacuum in the vacuum chamber 40, thus supporting the tightness in the vacuum chamber 40.

[0062] The device (plant) according to the present invention comprises a cylindrical treatment chamber for plasma-assisted surface treatment of large components, wherein the cylindrical treatment chamber has base surfaces over which the large components to be treated can be loaded and secured, and the treatment chamber is constructed in the form of a horizontal cylinder with at least one lateral cylinder cover that can be opened and sealed vacuum-tight, wherein the cylinder cover is arranged at one of the two ends of the horizontal cylinder and the cylinder cover circumference is at least 8 m, preferably between 10 m and 15 m, so that when the cylinder cover is open, the components to be treated can be loaded into the treatment chamber through this lateral opening, and comprises an annular cover sealing surface on the cylinder cover that is opposite the rest of the cylinder,and the residual cylinder comprises a circular ring-shaped residual cylinder sealing surface to be positioned opposite the lid sealing surface, wherein a sealing system is provided for sealing the sealing surfaces for vacuum-tight closure, such that grooves (preferably a total of three grooves) are milled into one of the sealing surfaces, so that the following conditions are met:

[0063] • a first circumferential groove is realized, which is also called outer groove

[0064] 2 (or sealing groove 2)

[0065] • a second circumferential groove is realized, which is also called inner groove

[0066] 3 (or sealing groove 3)

[0067] • the diameter of the circle described by the inner groove is smaller than the diameter of the circle described by the outer groove,

[0068] • between the outer groove 2 and the inner groove 3 there is a third groove, which is also called middle groove 4 in the following,

[0069] • the circle described by the middle groove is smaller than the circle described by the outer groove,

[0070] • the circle described by the middle groove is larger than the circle described by the inner groove,

[0071] • the three grooves are each centered around a center point, preferably the same center point, so that they do not intersect,

[0072] • A sealing ring 1 is provided in each of the outer and inner grooves,

[0073] • at least one of the sealing rings 1, but preferably both, have a shape such that when the cover is pressed onto the circular ring surface of the remaining chamber, a flat sealing surface is pressed, while in the direction of the groove depth, the sealing ring has an outwardly facing sealing lip (also called the outwardly facing flank of the sealing ring) and an inwardly facing sealing lip (also called the inwardly facing flank of the sealing ring), which nestle against the groove walls, and the arrangement is designed such that when the cover sealing surface and the remaining cylinder sealing surface are pressed against one another, an intermediate space system is created which is insulated from the external environment 10 and from the cylinder interior 20 of the system (iethe chamber or the treatment chamber or the vacuum treatment chamber), wherein the intermediate space system comprises two pressurization spaces 30 and a vacuum space 40 in which a so-called supporting vacuum is generated, wherein the sealing system comprises means for pressurizing the pressurization spaces 30 with an overpressure of at least 0.1 mbar to 1 mbar (ie between 0.1 mbar and 1 mbar), preferably of at least 0.1 bar, particularly preferably of at least 0.2 bar and most preferably of at least 0.3 bar.

[0074] No pneumatic systems (no compressed air) are used for the pressurization, as such systems can have numerous adverse effects, such as the penetration of atmospheric oxygen into the treatment chamber, which can lead to poor nitriding results. Accordingly, according to the invention, the pressurization chambers are pressurized with a defined gas (or gas mixture), whereby the gas or gas mixture does not contain oxygen. Preferably, the pressurization chambers are pressurized with nitrogen at a pressure between 0.1 mbar and 1 mbar.

[0075] According to a first aspect of the present invention, the inventive device thus comprises a lid which, as mentioned above, is sealed by means of a sealing system. Where the lid is pressed against the treatment chamber, the chamber has an annular surface for which a counter-surface is provided in the lid. Milled into this surface of the lid is a first circumferential groove, which is also referred to as the outer groove 2 (also referred to as the sealing groove 2) in the present description. Also milled into this surface of the lid is a second circumferential groove, which is also referred to as the inner groove 3 (also referred to as the sealing groove 3) in the present description. The diameter of the circle described by the inner groove is smaller than the diameter of the circle described by the outer groove. A third groove, which is also referred to as the middle groove 4 in the present description, is provided between the outer groove and the inner groove.The circle described by the middle groove is smaller than the circle described by the outer groove. However, the circle described by the middle groove is larger than the circle described by the inner groove. All three grooves (the inner, middle, and outer grooves) are essentially centered around the same center point, so they do not intersect.

[0076] A sealing ring 1 is provided in each of the outer and inner grooves. At least one of the sealing rings 1, but preferably both, is shaped such that when the lid is pressed against the annular surface of the remaining chamber, a flat sealing surface is pressed against it, while, in the direction of the groove depth, the sealing ring has an outward-facing flank and an inward-facing flank that conform to the groove walls.

[0077] The schematic representation in Figure 2 shows a cross-section through part of such a lid-treatment chamber combination. It is clear that, due to the seals 1 in the outer groove 2 and the inner groove 3, a space system is created between these grooves that is separated and sealed from both the external environment 10 and the chamber interior 20. This system comprises three spaces (two pressurization spaces 30 and one vacuum space 40), with the vacuum space 40 encompassing the central groove 4.

[0078] In the present description, the vacuum space 40 is also called the support vacuum space 40.

[0079] According to a feature which is essential with regard to this aspect of the present invention, the treatment plant comprises means for pressurising each pressurisation chamber with gas. According to the invention, the above-mentioned means comprise at least one gas supply, preferably a nitrogen gas supply, so that each pressurisation chamber can be pressurised by means of gas, preferably by means of nitrogen gas, to an overpressure of 0.1 mbar to 1 mbar, e.g. 0.3 bar. Due to the pressurisation of the special seals 1 (seals which are not inflatable seals and preferably have a shape as described above), which are placed in the outer sealing groove 2 and in the inner sealing groove 3, the respective rear sealing lips 6 and 7 of the sealing rings 1 are pressed against the sealing wall 10 of the respective groove 2 and3 and the seals 1 are simultaneously pressed towards the treatment chamber, whereby these sealing rings 1 are pressed much more effectively and better against the circular ring surface 8 of the chamber.

[0080] The flanks (sealing lips) of the sealing rings prevent the nitrogen from flowing further, like valve flaps.

[0081] In each case, the overpressure in the pressurization chamber is applied at least twice according to a preferred procedure: at the beginning of the evacuation step, essentially to properly position the sealing rings in advance, and at the end of the evacuation process, i.e., when mechanical displacements due to the forces acting on the system during the evacuation no longer occur, and the seals, and in particular the flanks (sealing lips) and / or flat components, are to be finally brought into the correct position. A vacuum is created in the central groove, the so-called support vacuum.

[0082] Then only the pressurization spaces 30 (the seals 1 in the outer groove 2 and inner groove 3) are pressurized with nitrogen, while the space in the groove 4 is under vacuum.

[0083] According to a further aspect of the present invention, a method is proposed to suppress or at least reduce the occurrence of spark discharges which are harmful to the substrate and which are described above.

[0084] The process is carried out in the system described above (also called device or plasma treatment system), which includes a powerful pulsed plasma generator integrated with an automatic safety control system, so that precise control of the process and safe treatment of the components to be treated are ensured.

[0085] Despite the unusually high process power of up to 1,000 kW, the temperature ramps during heating (up to 530 °C) and cooling can be adjusted as required to keep stresses in the components (in the case of tools, tool stresses) very low, even with the largest dimensions, and even compensate for them. And despite the extremely high pulse power, which ensures optimal treatment results, the incredibly fast-responding plasma control system, which reacts within a few millionths of a second, ensures particularly gentle interactions between the high-energy plasma and the functional surfaces of the components (e.g., tool functional surfaces). The combination of arc management (management of arc discharges or spark penetration) of the plasma source and the adapted system control system reacts reliably when spark discharges occur, thus protecting the surfaces of the treated substrates (e.g., forming tools) from damage.

[0086] The system operates at a predetermined typical operating voltage. In our case, this is typically up to 1000 V. When these spark discharges occur frequently (for example, when spark discharges occur in a number m range from 7 to 25 spark discharges in a time interval of 250 milliseconds), the inventors discovered to their astonishment that in many cases a sudden reduction in the operating voltage by a voltage value, for example in the range from 10 V to 100 V, preferably in the range from 10 V to 70 V (e.g. a sudden reduction in the operating voltage by 50 V), brings the occurrence of spark discharges to a halt, even if the operating voltage is subsequently slowly (i.e. over a period of longer than one minute) and gradually returned to the original value of the operating voltage. The system also operates under a predetermined working pressure of X mbar.In this example, this is typically 1.9 mbar. To their further surprise, the inventors discovered that a gradual increase or decrease in pressure can also contribute to a reduction in the occurrence of spark discharges. For example, the pressure can be increased from 1.9 mbar to 2.5 mbar in a total of six steps of 0.1 mbar, or reduced from 1.9 mbar to 1.0 mbar in a total of nine steps of 0.1 mbar. Despite the changed parameters, the system continues to operate stably. Later, the typical operating pressure can be slowly returned to.

[0087] The inventors have determined that a sudden reduction in the operating voltage by one voltage value, particularly in the above-mentioned preferred range (from 10 V to 70 V), has the advantage of reducing the risk of plasma extinction (depending on the load and process parameters). The inventors have developed the hypothesis that a sudden change in the conditions in the system, at least with regard to voltage and pressure, removes the conditions for the established occurrence of spark discharges, thus preventing them from occurring.

[0088] According to yet another aspect of the present invention, the method has been further developed such that a cleaning step is integrated before the plasma ignition, in the pre-vacuum, wherein the cleaning step consists of heating up without plasma, which is carried out in such a way that oils and contaminants are cracked from the substrates before the plasma ignition, so that a prior annealing treatment of the components is not necessary.

[0089] This is primarily to avoid an otherwise indispensable, but fundamentally harmful, upstream annealing treatment (also called pre-annealing), with additional, often excessively steep heating and cooling ramps and the associated risks of residual stresses. Above all, however, it is also to avoid harmful surface and grain boundary oxidation, which, due to the pre-annealing (which always takes place in air), can only be partially eliminated even by complex intermediate polishing. Furthermore, the elimination of pre-annealing reduces the risk of material growth, which can be particularly significant for cast iron grades with thermally unstable pearlite.

[0090] In the interest of ensuring the best possible treatment results, the advanced process is carried out in such a way that oils in the components to be treated (e.g. forming tools) and residues of paints and plastics are cracked during heating without plasma and condense in cold spots.

[0091] The tools can be heated up gently and in a controlled manner by measuring the temperature of the components to be treated and implementing an optimized ramp function. This is followed by the plasma step, which can be easily initiated thanks to the upstream inventive step (cleaning step during heating without plasma) and is immediately and evenly applied to the tools, resulting in a homogeneous heat input. According to yet another aspect of the present invention, the process has been further developed in such a way that the occurrence of hydrogen embrittlement has been massively reduced by adjusting the process gas composition.

[0092] A significant aspect of plasma surface treatments of metallic surfaces is the problem of hydrogen embrittlement. This refers to the change in the strength of metals due to the penetration and deposition of hydrogen into their metal lattice. Since the large components to be treated, such as forming tools, usually have areas that have been previously modified by welding, potential hydrogen embrittlement poses the risk of spalling, especially since preferred diffusion paths can be determined by the existing interface. In conjunction with thermal stresses, this creates a tendency for premature material failure. The inventors have surprisingly discovered that by changing the process gas composition (precursor composition) from N2 / H2 = 1:3 to N2 / H2 = 1:1 or N2 / H2 between 1:15:1 and 1:1:15, this risk was massively reduced.

[0093] A particularly preferred method according to the present invention for producing components with modified metal surfaces preferably comprises the following steps: a. Providing at least one substrate to be treated (at least one component, e.g. a large forming tool) with at least one substrate surface to be treated. b. Optionally - polishing the substrate surface to be treated (pre-polishing). c. Loading a vacuum chamber (from a plasma treatment system) with the at least one substrate to be treated, wherein the at least one substrate is held electrically insulated from the vacuum chamber wall in such a way that the vacuum chamber wall can form an anode and the at least one substrate can form at least part of a cathode. d. Closing the vacuum chamber by sealing one or more openings through which the vacuum chamber was loaded with the at least one substrate to be treated, e.Evacuating the vacuum chamber to a working pressure (preferably down to 0.05 mbar). f. Heating the substrate in a pre-vacuum using electric heaters, whereby the substrates are heated up to a substrate temperature between 100°C and 300°C, so that a cleaning step is carried out in this way in which oils and contaminants are cracked from the substrates before plasma ignition (this process step is also to be understood within the scope of the present invention as an integrated cleaning step or cleaning step of the substrate during heating without plasma, whereby the heating, as mentioned above, is preferably heated up to a temperature between 100°C and 300°C, or between 220°C and 300°C, for example up to 250°C). g.Admitting a gas mixture into the vacuum chamber, wherein the gas mixture contains both hydrogen and nitrogen in elemental and / or bound form and the process gas composition in the vacuum chamber is preferably in the N2 / H2 range between 1.15:1 and 1:1.15 or at N2 / H2 = 1:1. h. Igniting the plasma at a substrate temperature between 100°C and 300°C. i. Carrying out the nitriding by applying a pulsed voltage between the anode and cathode in such a way that the gas mixture is ionized and a plasma forms in the vacuum chamber. Nitriding via pulsed DC plasma is preferably carried out at a substrate temperature between 300-560°C depending on the type, dimensions, weight and material of the substrate (e.g. whether steel or cast iron). j. Cooling k. Optional - polishing (post-polishing).

[0094] The present invention enables the treatment of tools in such a way that all of the above-mentioned requirements for metal forming tools can be met. Thus, it is also possible to carry out repairs (local welding) of the tools or forming tools treated according to the invention without having to perform prior denitration. Furthermore, the present invention enables the treatment of tools or forming tools in such a way that the usual use of additional lubricant can be practically dispensed with, thus achieving maximum minimal lubrication. Specifically, the present invention primarily relates to a device and method for plasma treatment of components, wherein the device is particularly suitable for plasma treatment of large components, and the methods are suitable for excellent and stable plasma treatment of components, in particular components:

[0095] A device for plasma treatment of components in a plasma treatment chamber comprising a cylindrical treatment chamber for plasma-assisted surface treatment of components, wherein the cylindrical treatment chamber has base surfaces over which the components to be treated can be loaded and secured, and the treatment chamber is constructed in the form of a horizontal cylinder with at least one lateral cylinder cover that can be opened and closed in a vacuum-tight manner, wherein the cylinder cover is arranged at one of the two ends of the horizontal cylinder and the cylinder cover circumference is at least 8 m, so that when the cylinder cover is open, the components to be treated can be loaded into the treatment chamber through this lateral opening, and comprises an annular cover sealing surface on the cylinder cover that is opposite the rest of the cylinder,and the residual cylinder comprises a circular ring-shaped residual cylinder sealing surface to be positioned opposite the lid sealing surface, wherein a sealing system is provided for sealing the sealing surfaces for vacuum-tight closure, such that grooves are milled into one of the sealing surfaces so that the following conditions are met:

[0096] • a first circumferential groove is realized, which is also called outer groove

[0097] 2 is called

[0098] • a second circumferential groove is realized, which is also called inner groove

[0099] 3 is called

[0100] • the diameter of the circle described by the inner groove is smaller than the diameter of the circle described by the outer groove,

[0101] • between the outer groove 2 and the inner groove 3 there is a third groove, which is also called middle groove 4 in the following,

[0102] • the circle described by the middle groove is smaller than the circle described by the outer groove, • the circle described by the middle groove is larger than the circle described by the inner groove,

[0103] • the three grooves are each centered around a center point, preferably the same center point, so that they do not intersect,

[0104] • A sealing ring 1 is provided in each of the outer and inner grooves,

[0105] • at least one of the sealing rings 1, but preferably both, have a shape such that when the cover is pressed against the circular ring surface 8 of the remaining chamber, a flat sealing surface is pressed, while in the direction of the groove depth, the sealing ring has an outwardly facing sealing lip 6 (where "outwardly facing" means either towards the external environment 10 or towards the cylinder interior 20, as shown in Figure 2b) and an inwardly facing sealing lip 7 (where "inwardly facing" means towards the supporting vacuum space 40, as shown in Figure 2b), which nestle against the groove walls,

[0106] • the arrangement is designed in such a way that when pressing together

[0107] Cover sealing surface and remaining cylinder sealing surface, an intermediate space system is created which is closed off from the external environment 10 and from the cylinder interior 20 of the system, whereby the intermediate space system comprises two loading spaces 30 and one

[0108] Support vacuum chamber 40, and wherein the sealing system comprises means for pressurizing the pressurizing chambers 30 by means of a gas, preferably nitrogen gas with an overpressure of between 0.1 and 1 mbar.

[0109] A method for plasma treating components in a plasma treatment chamber, wherein for producing components with modified metal surfaces the method comprises the following steps: a. Providing at least one substrate to be treated (at least one component, e.g. a large forming tool) with at least one substrate surface to be treated. b. Optionally - polishing the substrate surface to be treated (i.e. if necessary pre-polishing). c. Loading a vacuum chamber (from a plasma treatment system) with the at least one substrate to be treated, wherein the at least one substrate is held electrically insulated from the vacuum chamber wall in such a way that the vacuum chamber wall can form an anode and the at least one substrate can form at least part of a cathode. d. Closing the vacuum chamber by sealing one or more openings through which the vacuum chamber was loaded with the at least one substrate to be treated, e.Evacuating the vacuum chamber to a working pressure (preferably down to 0.05 mbar). f. Heating the substrate in a pre-vacuum using electrical heaters, whereby the substrates are heated to a substrate temperature of between 100°C and 300°C, so that a cleaning step is carried out in which oils and impurities are cracked from the substrates before plasma ignition. g. Admitting a gas mixture into the vacuum chamber, whereby the gas mixture preferably contains both hydrogen and nitrogen in elemental and / or bound form and the process gas composition in the vacuum chamber is preferably in the N2 / H2 range between 1.15:1 and 1:1.15 or at N2 / H2 = 1:1. h. Igniting the plasma at a substrate temperature of between 100°C and 300°C. i.Carrying out the plasma treatment (wherein the plasma treatment is in particular a nitriding or at least comprises a nitriding) by applying a pulsed voltage between the anode and the cathode in such a way that the gas mixture is ionized and a plasma forms in the vacuum chamber. Nitriding is preferably carried out using pulsed DC plasma and likewise preferably at a substrate temperature of between 300 and 560 °C, whereby the substrate temperature depends on the type, dimensions, weight and material of the substrate (e.g. whether steel or cast iron). j. Cooling. k. Optionally - polishing (i.e., re-polishing if necessary). According to a preferred embodiment, when carrying out step i. listed above, a method is used which enables stable implementation of the plasma treatment.

[0110] One such method, which enables stable plasma treatment, is according to the present invention a method for plasma treatment of components in a plasma treatment chamber with a predetermined operating voltage and a predetermined treatment pressure, wherein in the event of a frequent occurrence of arc discharges, the operating voltage is suddenly reduced by a voltage amount in the range of 10 V to 100 V to suppress said discharges and then, via a step-by-step process lasting at least one minute, the operating voltage is readjusted to the original operating voltage, wherein an occurrence of arc discharges from a number in the range of 7 to 25 arc discharges in a time interval of 250 ms is recognized as a frequent occurrence. According to a preferred embodiment of this method, the operating pressure is additionally reduced step by step, preferably in 0.1 mbar steps up to a maximum value of 2.5 mbar and / or the operating pressure is gradually reduced in 0.1 mbar steps down to a minimum value of 0.5 mbar, whereby the original operating pressure is between 0.5 mbar and 4.5 mbar.

[0111] Preferably, the inventive methods described above are carried out in a device according to the invention as described above.

[0112] According to the present invention, the substrates to be treated are preferably tools for forming or for plastics processing.

[0113] However, the present invention is not limited to the plasma treatment of these tools.

Claims

Claims 1. A device for plasma treatment of components in a plasma treatment chamber, the device comprising a cylindrical treatment chamber for plasma-assisted surface treatment of components, wherein the cylindrical treatment chamber has base surfaces over which the components to be treated can be loaded and secured, and the treatment chamber is constructed in the form of a horizontal cylinder with at least one lateral cylinder cover that can be opened and sealed vacuum-tight, wherein the cylinder cover is arranged at one of the two ends of the horizontal cylinder and the cylinder cover circumference is at least 8 m, so that when the cylinder cover is open, the components to be treated can be loaded into the treatment chamber through this lateral opening, and the cylinder cover comprises an annular cover sealing surface that is opposite the rest of the cylinder,and the residual cylinder comprises a circular ring-shaped residual cylinder sealing surface to be positioned opposite the lid sealing surface, wherein a sealing system is provided for sealing the sealing surfaces for vacuum-tight closure, such that grooves are milled into one of the sealing surfaces so that the following conditions are met: • a first circumferential groove is realized, which is also called outer groove (2) is called • a second circumferential groove is realized, which is also called inner groove (3) is called • the diameter of the circle described by the inner groove is smaller than the diameter of the circle described by the outer groove, • between the outer groove (2) and the inner groove (3) there is a third groove, which is also called the middle groove (4) below, • the circle described by the middle groove is smaller than the circle described by the outer groove, • the circle described by the middle groove is larger than the circle described by the inner groove, • the three grooves are each centered around a center point, preferably the same center point, so that they do not intersect, • a sealing ring (1 ) is provided in each of the outer and inner grooves, • at least one of the sealing rings (1), but preferably both, have a shape such that when the cover is pressed against the circular ring surface (8) of the remaining chamber, a flat sealing surface is pressed, while in the direction of the groove depth, the sealing ring has an outwardly facing sealing lip (6) and an inwardly facing sealing lip (7), which nestle against the groove walls, • the arrangement is designed such that when the cover sealing surface and the remaining cylinder sealing surface are pressed together, an intermediate space system is created which is closed off from the external environment (10) and from the cylinder interior (20) of the system, wherein the intermediate space system comprises two pressurization spaces (30) and a supporting vacuum space (40), and wherein the sealing system comprises means for pressurizing the pressurization spaces (30) by means of a gas, preferably nitrogen gas with an overpressure of between 0.1 and 1 mbar.

2. Method for the plasma treatment of components in a plasma treatment chamber with a predetermined operating voltage and a predetermined treatment pressure, characterized in that in the event of an increased occurrence of arc discharges, in order to suppress them, the operating voltage is suddenly reduced by a voltage amount in the range from 10 V to 100 V and then, via a step-by-step process lasting at least one minute, the operating voltage is readjusted to the original operating voltage, wherein an occurrence of arc discharges from a number in the range from 7 to 25 arc discharges in a time interval of 250 ms is recognized as an increased occurrence.

3. Method according to claim 2, characterized in that in addition the operating pressure is temporarily increased stepwise, preferably in 0.1 mbar steps up to a value of maximum 2.5 mbar and / or the operating pressure is gradually reduced in 0.1 mbar steps up to a value of minimum 0.5 mbar, wherein the original operating pressure is between 0.5 mbar and 4.5 mbar.

4. A method for the plasma treatment of components in a plasma treatment chamber, characterized in that for the production of components with modified metal surfaces the method comprises the following steps: a. Providing at least one substrate to be treated with at least one substrate surface to be treated. b. Optionally pre-polishing the substrate surface to be treated. c. Loading a vacuum chamber of a plasma treatment system with the at least one substrate to be treated, wherein the at least one substrate is held electrically insulated from the vacuum chamber wall in such a way that the vacuum chamber wall can form an anode and the at least one substrate can form at least part of a cathode. d. Closing the vacuum chamber by sealing one or more openings through which the vacuum chamber was loaded with the at least one substrate to be treated, e. Evacuating the vacuum chamber to a working pressure (preferably down to 0.05 mbar). f. Heating the substrate in a pre-vacuum using electric heaters, whereby the substrates are heated to a substrate temperature of between 100 °C and 300 °C, so that a cleaning step is carried out in which oils and impurities are cracked from the substrates before the plasma is ignited. g. Admitting a gas mixture into the vacuum chamber, wherein the gas mixture contains both hydrogen and nitrogen in elemental and / or bound form. h. Igniting the plasma at a substrate temperature of between 100 °C and 300 °C i. Carrying out the plasma treatment, which is or comprises nitriding, by applying a pulsed voltage between the anode and cathode in such a way that the gas mixture is ionized and a plasma forms in the vacuum chamber, whereby . j. Cooling k. If necessary, re-polishing.

5. The method according to claim 4, characterized in that when carrying out step i. a method according to claim 2 or 3 is carried out.

6. Method according to one of the preceding claims 2 to 5, characterized in that the method is carried out in a device according to claim 1.

7. Method according to one of the preceding claims 4 to 7, characterized in that the substrates to be treated are tools for forming or for plastics processing.

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