Apparatus and method for plasma treating metal surfaces

Abstract

An apparatus and method for stable plasma treatment of parts, particularly large parts, with individual weights of 500 kg to 40 tons. The apparatus includes a treatment chamber in the form of a horizontal cylinder with at least one lateral cylinder cover and a special sealing system. The apparatus and method enable stable plasma treatment of such parts, particularly large tool parts such as large forming tools.

Description

[Technical Field]

[0001] The present invention relates to plasma treating metal surfaces, particularly metal surfaces of large components, to produce large components with modified metal surfaces.

[0002] In the context of the present invention, a component is generally understood to be any component or substrate having a metal surface, and a large component is defined in particular as a component having a weight in the range of 500 kg to 40 tonnes (500 kilograms to 40 tons).

[0003] The term part is therefore used in the context of this specification in particular for tools and tool parts as well as workpieces. [Background technology]

[0004] The plasma treatment according to the invention can be used in particular to modify the metal surfaces of tools used in manufacturing processes such as molding and plastic processing, such as injection molding (known in German as "Kunststoffverarbeitung" or "Spritzgiessen") and extrusion molding (in the extrusion molding process, long-fiber reinforced thermosetting semi-finished products with modified metal surfaces can be used, which are also called "Sheet Molding Compound" in German-speaking countries, and are simply called SCM).

[0005] A wide field of application for such parts with modified metal surfaces is found in forming technology, in particular in the processing of products for the automotive industry. Known products processed in this way include, for example, outer panels and structural parts for the automotive industry (doors, flaps, side walls, hoods, etc.). Such forming tools (hereinafter also referred to as tool parts) can, for example, have individual tool part weights of 500 kg to 40 tons. Therefore, such forming tools are also referred to herein as large parts.

[0006] The metal surface modified parts or large parts are also molded for use in the plastics industry, such as for the processing of bumpers, car headlights, interior and exterior plastic parts for automobiles, and home appliances.

[0007] Within the scope of this specification, larger parts such as gears, rollers and discs may also be treated to produce modified metal surfaces.

[0008] However, the above-mentioned metal surface modified parts or large parts should be understood as merely examples of large parts within the scope of the present invention and should not be considered as limiting the use of the apparatus or method of the present invention for plasma treating metal surfaces.

[0009] Depending on the application, different requirements are placed on the surface of the component.

[0010] For example, in the case of forming tools for metal forming, the requirements are considerable and must at least meet the following requirements: ·High hardness, High corrosion and wear resistance, Low coefficient of friction, Fatigue resistance, ·Polishing ability, · Repairability (overhaul).

[0011] The general trend in the automotive body manufacturing industry is towards reducing lubricants (especially with regard to the use of lubricants in the forming process) and vehicle weight. As a result, the use of lubricants in production has been limited and high-strength sheet materials (known in German as "hochfester Blechwerkstoff") and ultra-high-strength sheet materials (known in German as "hochstfester Blechwerkstoff") have been introduced, which places continuously increasing demands on forming tools in terms of improved wear resistance.

[0012] Until now, wear in press shops has been reduced by increasing the amount of lubricant (using additional lubricant) in addition to the oil lubrication of the coil or sheet to protect against wear, especially adhesive wear.

[0013] However, effective lubricants often contain chlorinated kerosene as an extreme pressure additive, which is relatively toxic and harmful to the environment, so the trend today is to further restrict its use and minimize lubrication (maximum reduction of additional lubricants).

[0014] Therefore, it is desirable to provide a suitable surface treatment to protect the tool surface from wear.

[0015] In sheet metal forming, adhesive wear is the main wear mechanism. This type of wear basically has the following stages: The sheet metal material begins to transfer locally to the tool surface. The transferred layer grows (wear of the sheet metal material onto the tool surface during the sheet metal forming process), followed by abrasive wear of the sheet metal. -Transition to strong adhesive wear.

[0016] Zumkeller et al. disclose in WO 2012 / 072209 A1 that an excellent solution for increasing the corrosion resistance of metal surfaces and protecting them from wear is to nitriding these metal surfaces.

[0017] WO 2012 / 072209 A1 mentions a special nitriding process marketed as the PPD® process, in particular Zumkeller et al. in WO 2012 / 072209 A1 describe a special embodiment of this PPD® process, which can improve the performance of plastic processed parts.

[0018] In this regard, reference is made to WO 2012 / 072209 A1, the contents of which are incorporated herein by reference.

[0019] It is known that improved corrosion and wear resistance can be achieved by plasma nitriding, in which the substrate to be nitrided is exposed to a plasma containing hydrogen and nitrogen ions under vacuum conditions. Nitriding using pulsed plasma is also known. Pulsing has several advantages. On the one hand, by controlling the pulse duration, a wide range of processing temperatures can be selected via the power combiner, without the need to change other processing parameters such as the voltage between the electrodes. On the other hand, pulsing largely prevents sparks from occurring during the nitriding process.

[0020] Nitriding occurs when nitrogen diffuses into the surface of the substrate, forming a nitride zone where it either forms compounds with the workpiece material near the surface or, deeper down, where nitrogen (in addition to forming nitrides with alloying elements) forms a solid solution with the substrate, interposing between them. This nitride zone therefore usually contains a compound layer and a diffusion zone. The compound layer therefore mainly contains nitride compounds. In the case of an iron substrate, for example, the compound layer contains ε-nitrides (=Fe 2(3) N) and / or γ-nitrides (=FeN) may be formed.

[0021] The present invention relates to an improved plasma nitriding process for efficiently and reliably producing parts with optimally modified metal surfaces for a variety of applications.

[0022] This improvement represents a further development of the PPD® Plasma Nitridation method described in WO 2012 / 072209 A1. [Prior art documents] [Patent documents]

[0023] [Patent Document 1] International Publication No. 2012 / 072209A1 Summary of the Invention [Problem to be solved by the invention]

[0024] One object of the present invention is to provide an apparatus (hereinafter also referred to as equipment) for plasma surface treatment (particularly nitriding) of parts, suitable for treating large parts, which has a treatment chamber that avoids or completely eliminates problems that often occur when sealing large treatment chambers.

[0025] This is particularly challenging because very large processing chambers 200 require large openings 250 to accommodate correspondingly large components (see FIGS. 1 and 3). For example, the plant constructed by the applicant is in the shape of a horizontal cylinder, 10 meters long and 4.2 meters in diameter. The heaviest components, such as sidewall tools containing cast iron or steel with dimensions of length × width (L × W) = ≦ 10 meters × ≦ 2.9 meters and element weights of up to 40 tons, can be introduced into the processing plant through the cylinder's base surface 100, configured as a retractable cover 150 (see FIG. 3). When the cover is closed, a vacuum-tight seal must be created over a circumference of π × D, i.e., approximately 3.14 × 4.2 meters = 13 meters. The applicant has protected the appearance of such a system in a European design under application number 002071415.

[0026] The present invention is intended to address and solve this sealing problem.

[0027] It is yet another object of the present invention to provide a method for avoiding or substantially controlling the occurrence of arcing or arcing (also known in German as "Lichtbogenentladungen" or "Funkendurschlage") that is often associated with plasma processing methods.

[0028] The plasma treatment method can be carried out, for example, at an operating voltage of up to about 1000 V (up to about one thousand volts), and the pressure typically set to carry out the method is, for example, between 0.5 mbar and 4.5 mbar, for example 1.9 mbar.

[0029] With these method parameters, depending inter alia on the geometry of the part to be treated, the temperature distribution, as well as gas emissions, which are not always unavoidable due to the presence of contaminants that cannot be removed, plasma breakdowns can occur in the form of localized flashes, which can damage the part to be treated, for example, at the point of impact.

[0030] This problem can also be addressed by the present invention. [Means for solving the problem]

[0031] It is therefore an object of the present invention to provide a surface treatment system (in particular an apparatus for plasma treatment of substrates) capable of subjecting large workpieces (also referred to as large components) to be treated to a plasma treatment, the system comprising: the negative pressure required for the process can be generated and kept stable by the means according to the invention; The process / steps according to the invention can be carried out to prevent increased occurrence of plasma damage to the parts being treated.

[0032] The solution according to the present invention The problem of the present invention is solved by providing an apparatus according to claim 1 and a method according to claims 2-7. [Brief explanation of the drawings]

[0033] [Figure 1] 1 is a view showing the exterior of a system constructed by the applicant from a certain viewpoint with the processing chamber closed. [Figure 2] 1 is a schematic diagram of the inventive solution to the sealing problem described above; FIG. [Figure 3] 2 is a view of the same system shown in FIG. 1 from a perspective with the processing chamber open and the processing chamber cover therefore removed from the remainder of the processing chamber. [Explanation of symbols]

[0034] 1 Seal (inner seal ring of inner seal groove 3 and outer seal ring 1 of outer seal groove 2) 2 Outer seal groove 3 Inner seal groove 4 central groove 6. The sealing lip of the outer sealing ring 1 (in the outer sealing groove 2) facing the external ambient atmosphere 10, and the sealing lip of the inner sealing ring 1 (in the inner sealing groove 3) facing the interior of the processing chamber 20 7 sealing lip of the outer seal ring 1 (in the outer seal groove 2) and the sealing lip of the inner seal ring (in the inner seal groove 3) facing the support vacuum space 40 8 Circular ring surface of the chamber against which the front face of the corresponding seal 1 presses 10 External environment (also called external environment atmosphere or outer surroundings) 20 Processing chamber interior 30 Pressurized chamber (inner groove area of ​​seal groove) 40 Vacuum space or support vacuum space within the seal system 100 Base surface on which the parts to be processed are placed 150 Retractable cylinder cover for processing chamber 200 Cylindrical horizontal processing chamber 250 Processing chamber opening DETAILED DESCRIPTION OF THE INVENTION

[0035] Special seals 1 are placed in the outer seal groove 2 and the inner seal groove 3. The seals are not inflatable seals; the rear seal lips 6 and 7 of seal 1 are simply pressed against the seal walls of the grooves and the system flange (or the circular ring surface 8 of the system flange) at the front by pressurizing with a gas such as nitrogen.

[0036] A vacuum is created in the support vacuum space 40 or vacuum space 40. This space is called a support vacuum because it supports the sealing of the sealing lips 7. Each sealing lip 7 is further pulled against the groove by the vacuum in the vacuum space 40, thereby supporting the sealing of the vacuum space 40.

[0037] The apparatus (facility) according to the present invention comprises a cylindrical treatment chamber for plasma-assisted treatment of the surface of a large component, the cylindrical treatment chamber having a base surface on which a large component to be treated can be placed and fixed, the treatment chamber constructed in the form of a horizontal cylinder with a cylinder cover on at least one side, the cylinder cover being openable and closable in a vacuum-tight manner, the cylinder cover being arranged on either end of the horizontal cylinder, the circumference of the cylinder cover being at least 8 m, preferably 10 m to 15 m, so that when the cylinder cover is open, the component to be treated can be loaded into the treatment chamber through the opening in the side, the cylinder cover having a circular ring-shaped cover sealing surface arranged opposite to the remaining cylinder part, the remaining cylinder part having a circular ring-shaped remaining cylinder part sealing surface arranged opposite to the cover sealing surface, and a sealing system for vacuum-tight closure is provided in which a groove (preferably a total of three grooves) is machined in one of the sealing surfaces, and the following conditions are satisfied: A first circumferential groove is provided, which will be hereinafter also referred to as outer groove 2 (or seal groove 2). A second circumferential groove is provided, which will be hereinafter also referred to as inner groove 3 (or seal groove 3). 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 is provided between the outer groove 2 and the inner groove 3, and will be hereinafter also referred to as a central groove 4. The circle described by the central sulcus is smaller than the circle described by the outer sulcus. However, the circle described by the central sulcus is larger than the circle described by the medial sulcus. The three grooves are each centered on a central point, preferably the same central point, and do not intersect. · A seal ring 1 is provided in each of the outer and inner grooves. At least one, and preferably both, of the sealing rings 1 are shaped in such a way that when the cover is pressed against the circular ring surface of the remaining chamber part, a flat sealing surface presses against the cover, and at the same time, in the groove depth direction, the sealing ring has an outward-facing sealing lip (also referred to as the outward-facing side of the sealing ring) and an inward-facing sealing lip (also referred to as the inward-facing side of the sealing ring) that seal against the groove wall, and this arrangement is configured so that when the sealing surfaces of the cover and the sealing surfaces of the remaining cylinder part are pressed together, an intermediate space system is formed that is sealed off from the external environment 10 and the cylinder interior 20 of the system (i.e. the chamber, processing chamber or vacuum processing chamber), the intermediate space system having two pressurized chambers 30 and one vacuum space 40 in which a so-called support vacuum is generated, and the sealing system includes elements for applying an overpressure to the pressurized chamber 30 of at least 0.1 mbar to 1 mbar (i.e. between 0.1 mbar and 1 mbar), preferably at least 0.1 bar, particularly preferably at least 0.2 bar and very particularly preferably at least 0.3 bar.

[0038] A pneumatic system (compressed air) is not used for pressurization, since such a system can have many adverse effects, such as the intrusion of atmospheric oxygen into the treatment chamber, which can lead to poor nitriding results. Therefore, according to the present invention, the pressurization chamber is pressurized with a predetermined gas (or gas mixture), which gas or gas mixture does not contain oxygen. Preferably, the pressurization chamber is pressurized with nitrogen at a pressure between 0.1 mbar and 1 mbar.

[0039] According to a first aspect of the present invention, the apparatus of the present invention includes a cover sealed by the above-described sealing system. When the cover is pressed against the processing chamber, the chamber has a circular ring-shaped surface against which the cover is provided with a mating surface. A first circumferential groove is machined in this surface of the cover, also referred to herein as outer groove 2 (also referred to as seal groove 2). A second circumferential groove is also machined in this surface of the cover, also referred to herein as inner groove 3 (also referred to as seal groove 3). 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 is provided between the outer and inner grooves, also referred to herein as central groove 4. The circle described by the central groove is smaller than the circle described by the outer groove. However, the circle described by the central groove is larger than the circle described by the inner groove. All three grooves (respectively the inner groove, central groove, and outer groove) are centered on essentially the same center point and do not intersect.

[0040] A seal ring 1 is provided in each of the outer and inner grooves. At least one, but preferably both, of the seal rings 1 is shaped so that when the cover is pressed against the circular ring surface of the remaining chamber portion, a flat sealing surface is pressed against the cover, and the seal ring is formed in the groove depth direction so that it has outward and inward side surfaces that come into close contact with the groove wall.

[0041] 2 shows a cross section of a portion of such a cover and processing chamber combination. It can be seen that the seal 1 is located in an outer groove 2 and an inner groove 3, creating a spatial system between these grooves that is isolated and sealed from both the external environment 10 and the chamber interior 20, and has three spaces (two pressurized chambers 30 and one vacuum space 40), with the vacuum space 40 having a central groove 4.

[0042] In this specification, the vacuum space 40 is also referred to as the support vacuum space 40 .

[0043] According to an important feature of this aspect of the invention, the processing plant includes an element for applying gas at an overpressure to each pressurization chamber. According to the invention, the element has at least one gas supply, preferably a nitrogen gas supply, and can apply an overpressure of 0.1 mbar to 1 mbar, e.g., 0.3 bar, to each pressurization chamber with gas, preferably nitrogen gas. By applying pressure to the special seals 1 (not inflatable seals, but seals preferably having the above-described shape and arranged in the outer seal groove 2 and the inner seal groove 3), the rear seal lips 6 and 7 of the seal rings 1 are pressed against the seal walls 10 of the respective grooves 2 and 3, and the seals 1 are simultaneously pressed toward the processing chamber, thereby pressing the seal rings 1 against the circular ring surface 8 of the chamber in a much more favorable and effective manner.

[0044] The side of the sealing ring (sealing lip) prevents the nitrogen from continuing to flow further, like a valve flap.

[0045] In each case, the pressurized space is preferably pressurized at least twice, i.e., at the beginning of the evacuation phase in order to essentially pre-position the sealing ring, and at the end of the evacuation phase, i.e., at the point when the mechanical displacements due to the forces acting on the system during evacuation have ceased and the seal, in particular the flanks (sealing lips) and / or flat parts, are finally positioned. A vacuum, a so-called support vacuum, is created in the central groove.

[0046] Nitrogen is applied only to the pressurized chamber 30 (the seals 1 in the outer groove 2 and the inner groove 3), and the space within the groove 4 is in a vacuum state.

[0047] According to another aspect of the present invention, a method is proposed for preventing or at least reducing the occurrence of spark discharges that are harmful to the substrate as described above.

[0048] The method is carried out in the above-mentioned equipment (also referred to as apparatus or plasma processing equipment), which includes a powerful pulsed plasma generator with an integrated automatic safety control system to ensure precise control of the process and safe treatment of the parts being treated.

[0049] Despite extremely high processing powers of up to 1,000 kW, the temperature increase during heating (up to 530°C) and cooling can be adjusted as needed, ensuring extremely low and even uniform stresses on the part (or tool, in the case of tools) even at their largest dimensions. And despite extremely high pulse powers for optimal processing results, the incredibly fast plasma control, in the range of a few millionths of a second, ensures particularly gentle interactions between the high-energy plasma and the part's functional surfaces (such as those of the tool). The plasma source's arc management (management of arc or spark discharges) combined with adaptive system control ensures a reliable reaction when spark discharges occur, thereby protecting the surface of the processed substrate (such as the forming tool) from damage.

[0050] The system operates at a predetermined typical operating voltage, which in this case is typically up to 1000 V. If these spark discharges occur frequently (e.g., between 7 and 25 spark discharges at 250 millisecond intervals), the inventors have surprisingly found that in many cases, abruptly reducing the operating voltage (e.g., by 50 V) by a voltage value in the range of 10 V to 100 V, preferably 10 V to 70 V, will stop the spark discharges, even if the operating voltage is then gradually (e.g., over a period of more than one minute) returned to its original operating voltage value. The system operates at a predetermined operating pressure of X mbar, which in this example is typically 1.9 mbar. The inventors have further surprisingly found that incremental pressure increases or decreases can also contribute to further reducing the occurrence of spark discharges. For example, the pressure can be increased from 1.9 mbar to 2.5 mbar in six 0.1 mbar steps, or decreased from 1.9 mbar to 1.0 mbar in nine 0.1 mbar steps. The system continues to operate stably even with changing parameters, and can then be slowly returned to the typical operating pressure.

[0051] The inventors have found that a rapid reduction in the operating voltage, particularly by a voltage value in the preferred range (10 V to 70 V) described above, has the advantage of reducing the risk of plasma extinction (which depends on the load and process parameters).

[0052] The inventors hypothesized that the conditions within the system, at least with regard to voltage and pressure, change so suddenly that the preconditions for spark discharge to occur are eliminated, and therefore spark discharge does not occur.

[0053] According to another aspect of the invention, the method is further developed to include a cleaning step under pre-vacuum conditions before plasma ignition, the cleaning step comprising high temperature heating without plasma, which is carried out to decompose oils and impurities from the substrate before plasma ignition, thereby eliminating the need for prior annealing of the component.

[0054] This is primarily due to the avoidance of the essential but fundamentally harmful prior annealing treatment (also known as pre-annealing), which often involves too steep heating and cooling gradients and the associated risk of residual stresses. But above all, it also avoids harmful surface and intergranular oxidation, which results from pre-annealing (which is always done in air) and can only be partially removed by thorough intermediate polishing. Furthermore, omitting pre-annealing reduces the risk of material growth, which can be particularly important for cast irons containing thermally unstable pearlite.

[0055] For optimal processing results, this advanced method is implemented in such a way that oil, paint and plastic residues on the parts being treated (e.g., forming tools) are decomposed during high-temperature heating without plasma and condense in cooler areas.

[0056] By measuring the temperature of the part to be treated and implementing an optimized ramp function, the tool can be heated gently and in a controlled manner. This is followed by a plasma stage, which can be easily initiated by an upstream stage of the invention (a cleaning stage when heating without plasma) and which acts immediately and evenly on the tool, ensuring an even heat input.

[0057] In accordance with yet another aspect of the present invention, the method has been further developed to significantly reduce the occurrence of hydrogen embrittlement by adjusting the composition of the process gas.

[0058] An important aspect of plasma surface treatment of metal surfaces is the issue of hydrogen embrittlement, which is the change in the strength of the metal due to the penetration and incorporation of hydrogen into the metal lattice. Large components to be treated, such as forming tools, are usually pre-modified by welding, and hydrogen embrittlement can lead to delamination, especially at interfaces that may define favorable diffusion paths. This, combined with thermal stresses, can lead to premature failure of the material. Surprisingly, the inventors found that this risk can be significantly reduced by changing the process gas composition (precursor composition) from N2 / H2 = 1:3 to N2 / H2 = 1:1 or from N2 / H2 = 1.15:1 to 1:1.15.

[0059] A particularly preferred method according to the invention for producing a part with a modified metal surface preferably comprises the following steps: a. Preparing at least one substrate surface to be processed (at least one part, e.g., a large molding tool) for at least one substrate to be processed. b. Optionally, polishing the surface of the substrate to be processed (pre-polishing). c. Loading at least one substrate to be processed into a vacuum chamber (of a plasma processing system), wherein the at least one substrate is held in electrical isolation from the walls of the vacuum chamber, such that the walls of the vacuum chamber form an anode and the at least one substrate forms at least a portion of a cathode. d. Closing the vacuum chamber by sealing one or more openings through which the vacuum chamber is loaded with at least one substrate to be processed. e. Evacuate the vacuum chamber to operating pressure (preferably up to 0.05 mbar). f. Heating the substrate in a pre-vacuum state by means of an electric heater, until the substrate reaches a substrate temperature of 100°C to 300°C, thereby carrying out a cleaning step of decomposing oils and impurities from the substrate before plasma ignition (this treatment step should also be understood in the context of the present invention as an integrated cleaning step or cleaning step of the substrate when heating without plasma, said heating being preferably carried out to a temperature of 100°C to 300°C, or 220°C to 300°C, for example up to 250°C). g. Injecting a gas mixture into the vacuum chamber, the gas mixture containing both hydrogen and nitrogen in elemental and / or combined forms, preferably with a process gas composition in the vacuum chamber of N2 / H2 in the range of 1.15:1 to 1:1.15 or N2 / H2=1:1. h. Ignite the plasma at a substrate temperature of 100℃~300℃. i. Nitriding is performed by applying a pulsed voltage between the anode and cathode, which ionizes the gas mixture and forms a plasma in the vacuum chamber. Pulsed DC plasma nitriding is preferably performed at a substrate temperature of 300-560°C depending on the type, size, weight, and material of the substrate (e.g., steel or cast iron). j. Cooling. k. Optionally, polishing (regrinding).

[0060] The present invention makes it possible to treat forming tools for metal forming in such a way that all of the above requirements are met. Therefore, it is also possible to realize overhaul (local welding) of tools treated according to the present invention, i.e., forming tools, without the need for a prior denitrification treatment. Furthermore, the present invention makes it possible to treat tools or forming tools in such a way that the use of lubricants, which are normally added, can be substantially omitted, thereby achieving maximum lubrication with minimal lubrication.

[0061] More particularly, the present invention relates primarily to an apparatus and method for plasma processing of components, the apparatus being particularly suitable for plasma processing of large components, and the method being suitable for plasma processing of components with good stability, in particular the following components:

[0062] 1. An apparatus for plasma processing a component in a plasma processing chamber, the apparatus comprising: a cylindrical processing chamber for plasma-assisted processing of a surface of the component, the cylindrical processing chamber having a base surface on which a component to be processed can be placed and fixed; the processing chamber constructed in the form of a horizontal cylinder having at least one side cylinder cover that can be opened and closed vacuum-tight, the cylinder cover being arranged at either end of the horizontal cylinder, the cylinder cover having a circumference of at least 8 mm, through which the component to be processed can be loaded into the processing chamber when the cylinder cover is open, the cylinder cover having a circular ring-shaped cover sealing surface that is arranged opposite to a remaining cylinder portion, the remaining cylinder portion having a circular ring-shaped sealing surface that is arranged opposite to the cover sealing surface, a sealing system is provided for sealing the sealing surfaces to close vacuum-tightly, one of the sealing surfaces is machined with a groove, and the following conditions are satisfied: A first circumferential groove is provided, which will be referred to hereinafter as outer groove 2; A second circumferential groove is provided, which will be referred to hereinafter as inner groove 3. 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 is provided between the outer groove 2 and the inner groove 3, which will be hereinafter also referred to as the central groove 4. The circle described by the central groove is smaller than the circle described by the outer groove. However, the circle described by the central sulcus is larger than the circle described by the inner sulcus. The three grooves are each centered on a central point, preferably the same central point, and do not intersect; The outer and inner grooves are each provided with a seal ring 1; at least one, and preferably both, of the sealing rings 1 is shaped in such a way that when the cover is pressed against the circular ring surface 8 of the remaining chamber part, a flat sealing surface is pressed against the cover, while in the groove depth direction, the sealing ring has an outwardly facing sealing lip 6 (the "outwardly facing" element being either towards the outer periphery 10 or towards the cylinder interior 20 as shown in FIG. 2b) and an inwardly facing sealing lip 7 (the "inwardly facing" element being towards the support vacuum space 40 as shown in FIG. 2b) that seals tightly against the groove wall, The arrangement is such that when the sealing surfaces of the cover and the remaining cylinder part are pressed together, an intermediate space system is formed that is sealed from the external environment 10 and the cylinder interior 20 of the system, the intermediate space system having two pressurized chambers 30 and one supporting vacuum space 40, the sealing system including means for applying an overpressure of 0.1 to 1 mbar to the pressurized chambers 30 by gas, preferably nitrogen gas.

[0063] A method of plasma treating a component in a plasma treatment chamber to produce a component having a modified metal surface, the method comprising the steps of: a. Providing at least one substrate to be processed (at least one part, eg, a large molding tool) having at least one substrate surface to be processed. b. Optionally, polishing the substrate surface to be processed (ie, pre-polishing if necessary). c. Loading at least one substrate to be processed into a vacuum chamber (of a plasma processing system), wherein the at least one substrate is held in electrical isolation from the walls of the vacuum chamber, the walls of the vacuum chamber forming an anode and the at least one substrate forming at least a portion of a cathode. d. Closing the vacuum chamber by sealing one or more openings through which the vacuum chamber is loaded with at least one substrate to be processed. e. Evacuate the vacuum chamber to operating pressure (preferably up to 0.05 mbar). f. Heating the substrate in a pre-vacuum state using an electric heater until the substrate reaches a substrate temperature of 100°C to 300°C, thereby performing a cleaning step to decompose oil and impurities from the substrate before plasma ignition. g. Injecting a gas mixture into the vacuum chamber, the gas mixture preferably containing both hydrogen and nitrogen in elemental and / or combined form, and preferably the composition of the process gas in the vacuum chamber is N2 / H2 in the range of 1.15:1 to 1:1.15 or N2 / H2=1:1. h. Ignite plasma at a substrate temperature of 100°C to 300°C. i. Carrying out a plasma treatment (wherein the plasma treatment is in particular or at least includes nitriding) by applying a pulsed voltage between an anode and a cathode, whereby the gas mixture is ionized and a plasma is formed in the vacuum chamber. The nitriding is preferably carried out via pulsed DC plasma, and also at a substrate temperature of preferably 300-560°C, which varies depending on the type, size, weight and material of the substrate (e.g., steel or cast iron). j. Cooling. k. Optionally, polishing (i.e., re-polishing as necessary).

[0064] According to a preferred embodiment, in carrying out step i. above, a method is used that allows the plasma treatment to be carried out in a stable manner.

[0065] According to the present invention, one such method for enabling stable plasma processing is a method for plasma processing a component in a plasma processing chamber at a predetermined operating voltage and a predetermined process pressure, wherein, in the event of arcing accumulation, the operating voltage is abruptly reduced by an absolute voltage amount ranging from 10 V to 100 V to suppress the arcing, and the operating voltage is then reset to the original operating voltage in a stepwise process lasting at least 1 minute, wherein an accumulation is recognized as an arcing occurrence ranging from 7 to 25 occurrences in a time interval of 250 ms. According to a preferred embodiment of the method, the operating pressure is increased, preferably in 0.1 mbar steps, to a maximum value of 2.5 mbar and / or the operating pressure is decreased in 0.1 mbar steps to a minimum value of 0.5 mbar, wherein the original operating pressure is between 0.5 mbar and 4.5 mbar.

[0066] Preferably, the above-described method of the present invention is carried out in the above-described device of the present invention.

[0067] According to the invention, the substrate to be treated is preferably a tool for molding or plastics processing.

[0068] However, the present invention is not limited to plasma treatment of these tools.

Claims

1. 1. An apparatus for plasma processing of a component in a plasma processing chamber, the apparatus comprising: a cylindrical processing chamber for plasma-assisted processing of a component surface, the cylindrical processing chamber having a base surface on which the component to be processed can be placed and fixed; the processing chamber constructed in the form of a horizontal cylinder with at least one openable and vacuum-tight closable lateral cylinder cover, the cylinder cover being arranged at either end of the horizontal cylinder, the cylinder cover having a circumference of at least 8 mm, through which the component to be processed can be loaded into the processing chamber when the cylinder cover is open, the cylinder cover having a circular ring-shaped cover sealing surface arranged opposite the remaining cylinder part, a sealing system for sealing the sealing surface to close vacuum-tightly, one of the sealing surfaces being machined with a groove, and the following conditions: - a first circumferential groove is provided, which will be referred to below as the outer groove (2), - a second circumferential groove is provided, hereinafter also referred to as inner groove (3), 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 is provided between the outer groove (2) and the inner groove (3), which will be referred to hereinafter as a central groove (4). The circle described by the central groove is smaller than the circle described by the outer groove; provided that the circle described by the central groove is larger than the circle described by the inner groove; the three grooves are each centered on a central point, preferably the same central point, and do not intersect; - Providing a seal ring (1) in each of the outer groove and the inner groove; At least one, and preferably both, of the sealing rings (1) are shaped so that when the cover is pressed against the circular ring surface (8) of the remaining chamber portion, a flat sealing surface is pressed against the cover, and at the same time, in the groove depth direction, the sealing ring has an outward-facing sealing lip (6) and an inward-facing sealing lip (7) that fit tightly against the groove wall. the arrangement is such that when the sealing surfaces of the cover and the remaining cylinder part are pressed together, an intermediate space system is formed that is sealed from the external environment (10) and from the cylinder interior (20) of the system, the intermediate space system comprising two pressurized chambers (30) and one supporting vacuum space (40), the sealing system including means for applying an overpressure of 0.1 to 1 mbar to the pressurized chambers 30 by gas, preferably nitrogen gas; A device that satisfies the above requirements.

2. 1. A method for plasma processing a component in a plasma processing chamber at a predetermined operating voltage and a predetermined process pressure, wherein, when arcing occurrences accumulate, the operating voltage is abruptly reduced by an absolute voltage amount in a range of 10V to 100V to suppress the arcing, and the operating voltage is then returned to the original operating voltage in a stepwise process lasting at least one minute, wherein an arcing occurrence is recognized when arcing occurrences range from 7 to 25 within a time interval of 250 ms.

3. 3. The method according to claim 2, further characterized in that the operating pressure is temporarily increased in steps, preferably by 0.1 mbar up to a maximum value of 2.5 mbar, and / or the operating pressure is decreased in steps by 0.1 mbar down to a minimum value of 0.5 mbar, the original operating pressure being between 0.5 mbar and 4.5 mbar.

4. 1. A method of plasma processing a component in a plasma processing chamber to produce a component having a modified metal surface, the method comprising the steps of: a. providing at least one substrate surface to be processed; b. optionally pre-polishing the surface of the substrate to be processed; c. loading the at least one substrate to be processed into a vacuum chamber of a plasma processing system, the at least one substrate being held in electrical isolation from walls of the vacuum chamber, the walls of the vacuum chamber forming an anode and the at least one substrate forming at least a portion of a cathode; d. closing said vacuum chamber by sealing one or more openings through which said vacuum chamber is loaded with at least one substrate to be processed; e. Evacuating the vacuum chamber to operating pressure (preferably up to 0.05 mbar); f. Heating the substrate under pre-vacuum conditions by an electric heater, until the substrate reaches a substrate temperature of 100°C to 300°C, thereby performing a cleaning step of decomposing oil and impurities from the substrate before plasma ignition; g. injecting a gas mixture into said vacuum chamber, said gas mixture containing both hydrogen and nitrogen in elemental and / or combined forms; h. igniting said plasma at a substrate temperature between 100°C and 300°C; i. performing a plasma process of nitriding or including nitriding by applying a pulse voltage between an anode and a cathode, whereby the gas mixture is ionized to form a plasma within the vacuum chamber; j. Cooling; k. Regrinding as necessary A method comprising:

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

6. A method according to any one of claims 2 to 5, characterized in that it is carried out in an apparatus according to claim 1.

7. 8. The method according to claim 4, wherein the substrate to be treated is a tool for molding or plastics processing.

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