EP0079007A1 - Method of sealing a porous coating - Google Patents

Method of sealing a porous coating Download PDF

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Publication number
EP0079007A1
EP0079007A1 EP82110003A EP82110003A EP0079007A1 EP 0079007 A1 EP0079007 A1 EP 0079007A1 EP 82110003 A EP82110003 A EP 82110003A EP 82110003 A EP82110003 A EP 82110003A EP 0079007 A1 EP0079007 A1 EP 0079007A1
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EP
European Patent Office
Prior art keywords
plastic
coating
workpiece
layer
lacquer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP82110003A
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German (de)
French (fr)
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EP0079007B1 (en
Inventor
Winfried Heinzel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Oerlikon Friction Systems Germany GmbH
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PTG Plasma Oberflaechentechnik GmbH
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Publication of EP0079007A1 publication Critical patent/EP0079007A1/en
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/06—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by exposure to radiation
    • B05D3/068—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by exposure to radiation using ionising radiations (gamma, X, electrons)
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/62—Plasma-deposition of organic layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D2350/00—Pretreatment of the substrate
    • B05D2350/60—Adding a layer before coating
    • B05D2350/63—Adding a layer before coating ceramic layer

Definitions

  • the invention relates to a method for sealing a porous coating made of hard material, such as aluminum oxide, tungsten carbide, chromium, applied to a body in the plasma spraying method.
  • hard material such as aluminum oxide, tungsten carbide, chromium
  • metallic objects which must have a very high resistance to abrasion, in the plasma to provide the spraying method with a coating of a hard material, suitable metals, oxides and carbides being suitable as hard materials.
  • the coating material is fed to the plasma spray nozzle in the form of a powder, melted in the plasma jet on the surface of the individual grains and thus reaches the surface to be coated, where the hard material forms a more or less porous coating.
  • the cavities contained in this coating are generally to a greater or lesser extent capillaries. While the resistance of metallic bodies that have been coated in this way to purely mechanical wear is generally good, the resistance to chemical attacks is often inadequate, since acids can reach the metallic body through the cavities of the coating, for example. attack it and cause the coating to peel
  • the object of the invention is to close the voids in the coating so that chemically aggressive substances cannot reach the surface of the metallic body.
  • This object is achieved according to the invention in that the coating is impregnated with a liquid curable, in particular crosslinkable, plastic or lacquer, and in that this plastic layer or lacquer layer is crosslinked, at least in its outwardly facing region, by irradiation with electrons.
  • the advantage of the invention is that a completely closed layer of the cured, in particular cross-linked plastic or lacquer is created within the porous coating, which prevents the entry of acids or other aggre sensitive substances to the surface of the metallic body with suitable selection of the plastic with certainty prevented. It is not absolutely necessary that the plastic or lacquer layer, which is simply referred to as a plastic layer in the following, is cross-linked to its full depth, but it is sufficient if the cross-linking takes place only in an outer region.
  • Another advantage of the invention is that the crosslinking by means of electron radiation can take place very quickly, in the presence of suitable systems, for example in a few seconds or at most a few minutes, and that the plastic layer and thus the body carrying the coating are not noticeably heated as a result of the electron radiation . It is therefore also possible to treat bodies sensitive to temperature increases with the method according to the invention. If it is intended to subject the body to processing after crosslinking, for example grinding the coated surface, then the crosslinking is carried out in such a way that the crosslinking in the applied plastic layer extends at least so deep that no areas which have not yet been crosslinked in the subsequent processing the plastic layer can be reached.
  • the coated bodies can be processed further immediately after the electron irradiation. Depending on the type of the coated object, it may then be sufficient if areas of the plastic which are not yet crosslinked in the depth are still completely crosslinked under the influence of a sufficiently high ambient temperature in the course of the following days or weeks.
  • the body is heated to approximately 80 ° C. before the liquid plastic is applied, and that the plastic subsequently applied to the heated body, in particular sprayed on.
  • the relatively low temperature for example, 80 ° C, which can be withstood even by sensitive bodies without danger
  • the air contained in the cavities of the hard material coating is largely expelled and the liquid plastic penetrates into it Depth of the porous layer is facilitated.
  • the plastic is applied while the body is still warm, so that the liquid plastic can penetrate into deeper areas of the porous layer when the air still contained in the pores cools.
  • the amount of liquid plastic applied can be adapted to the particular requirements in a particularly simple manner by spraying.
  • a liquid plastic of low viscosity preferably a plastic that is more liquid than water. This facilitates the penetration of the plastic into the cavities in the hard material coating.
  • the method is applied in such a way that only a single plastic coating is provided, which then generally takes up the entire thickness of the hard material coating.
  • the porous coating is first soaked only in its area adjacent to the metallic body, and that after curing by electron radiation the body is in turn soaked with a plastic which is also crosslinked by electron radiation.
  • the same plastic can be used here if, in special cases, for example, a desired crosslinking to a relatively great depth cannot take place in a single irradiation process because the plastic layer is too thick for this; however, different plastics are used in other embodiments of the invention.
  • the outer plastic layer can be chosen so that a particularly low coefficient of friction of the body results; in this case the outer, fully crosslinked plastic layer can in particular be polytetrafluoroethylene.
  • the penetration of the plastic can only be brought about into the area of the porous coating adjacent to the metallic body by applying only a limited amount of plastic required to fill the capillaries adjacent to the metallic body, which is then heated by appropriate heating as a result of gravity seeps down, being due to the limited amount of the liquid plastic, the upper areas can be cleared of the plastic again and can be filled with another plastic after the plastic has hardened.
  • the entire coating can be filled with a certain plastic and the workpiece heated to a temperature at which the liquid plastic evaporates from the area near the surface, at which temperature the remaining plastic is already cured can.
  • Another plastic can then be introduced into the area of the porous layer which has become free due to evaporation of the plastic and can be cured by electron radiation.
  • the heating can be carried out in such a way that this area of the layer located on the surface heats up more than the area of the porous layer adjacent to the metallic body.
  • An important advantage of the invention lies in the following: If a body coated with hard material, for example a cylinder of a printing press, has to be ground to achieve a sufficiently smooth surface, whole grains of the coating material are often torn out of the coating, so that a certain amount of Roughing depth cannot be fallen below.
  • the body is in accordance with the invention Provided sealer, the cross-linked plastic layer holds the grains of the hard material coating firmly, especially if it extends to greater depths of the coating, so that individual grains that protrude too far outward are partially removed as desired, but not completely be torn out of the coating.
  • a metallic body which in the exemplary embodiment is a printing cylinder of a printing press, and which consists of steel and has dimensions of 180 cm in length and 85 cm in diameter, is coated with a layer of tungsten carbide in the plasma spraying process. This coating has a thickness of approximately 100 pm.
  • the plasma spraying process or, as it is also called, plasma spraying, and the devices required for this are known.
  • a gas is fed to an arc plasma torch and dissociated and ionized in the arc depending on the type of gas. Shortly before the nozzle emerges, the pulverized spray material, i.e. the hard material, is fed to the plasma flowing out at high speed with the aid of a carrier gas. Argon is often used as the plasma gas.
  • the body provided with the hard material coating is then heated in such a way that the temperature of the body decreases somewhat from the inside to the outside.
  • the heating causes most of the air contained in the pores of the surface layer to escape.
  • the coated body with a liquid Sprayed plastic which is specified below. This plastic is drawn into the pores of the coating, at least in part also as a result of capillary action, not least because the liquid plastic penetrates into the warmer areas of the coating, that is to say inside, with further liquefaction.
  • Spraying takes place immediately after the workpiece has been heated to approximately 80 ° C., so that the air that has escaped from the pores of the coating does not penetrate again in the meantime.
  • the workpiece is irradiated by electrons.
  • a system suitable for such radiation is sold by Otto Dürr Anlagenbau GmbH, D-7000 Stuttgart under the type designation ESH 150.
  • This system generates electrons with an energy of 150 keV, whereby the body to be irradiated can be in the free atmosphere and is only flushed with a suitable inert gas to keep out the oxygen in the air in the area in which the electrons strike the body .
  • Nitrogen is an example of an inert gas.
  • the power of the electron beam available for irradiation is 7.5 KW.
  • the sealing by the plastic cross-linked or hardened by means of electron bombardment is extremely effective.
  • An unsealed, plasma sprayed layer is removed, for example, in a single operation by sandblasting with corundum. If a hardened plastic layer according to the invention is introduced into the hard material layer, about six such sandblasting processes are required to remove this combined layer.
  • the cross-linked plastic layer makes it possible for the first time to use workpieces with surfaces sprayed with a plasma spray in the chemical sector, where without the hardened plastic layer the hard material coating would be damaged by corrosion of the metal body supporting this layer. An impregnation of the hard material layer with an uncured plastic, however, could not prevent corrosion of the metal body with certainty.
  • a high-molecular plastic which essentially consists of polyethylene glycol dimethacrylate or trimethylol propane trimethacrylate with the addition of aliphatic and / or aromatic hydrocarbons, especially amines, and which contains the usual additives of plasticizer, polymer Thickener, peroxide, toluidine, saccharin, fillers, pigments, stabilizers and the like, some based on Si.

Abstract

1. A method of surface treatment of a porous coating applied to a workpiece, in which the coating gets soaked with a plastics which seals the pores, characterized in that the workpiece is a highly abrasion-resistant machine part, that the workpiece first of all gets provided by the plasma spray method with a coating of a hard substance such as aluminium oxide, tungsten carbide or chromium, that then for the soaking a crosslinkable plastics or varnish is employed, that the plastics at least in the region pointing outwards is hardened by electron radiation and in particular is cross-linked, and that subsequently the surface directly after the cross-linking gets further processed and in particular is ground.

Description

Die Erfindung betrifft ein Verfahren zum Versiegeln einer im Plasmasprühverfahren auf einen Körper aufgebrachten porösen Beschichtung aus Hartstoff, wie Aluminiumoxid, Wolframcarbid, Chrom. Es ist bekannt, metallische Gegenstände, die eine sehr hohe Widerstandsfähigkeit gegen Abrieb aufweisen müssen, im Plasmasprühverfahren mit einer Beschichtung aus einem Hartstoff zu versehen, wobei als Hartstoffe u.a. geeignete Metalle, Cxide und Carbide in Frage kommen. Das Be- schichtune:smaterial wird der Plasmasprühdüse in Form eines Pulvers zugeführt, im Plasmastrahl an der Oberfläche der einzelnen Körner geschmolzen und gelangt so zu der zu beschichtenden Oberfläche, wo der Hartstoff einen mehr oder weniger porösen Überzug bildet. Die in dieser Beschichtung enthaltenen Hohlräume sind im allgemeinen zu einem mehr oder weniger großen Teil Kapillaren. Während die Widerstandsfähigkeit metallischer Körper, die in dieser Weise beschichtet worden sind, gegen rein mechanische Abnutzung in der Regel gut ist, ist die Widerstandsfähigkeit gegen chemische Angriffe häufig ungenügend, denn es können durch die Hohlräume der Beschichtung beispielsweise Säuren bis zu dem metallischen Körper gelangen, diesen angreifen und dadurch ein Ablösen der Beschichtung verursachen.The invention relates to a method for sealing a porous coating made of hard material, such as aluminum oxide, tungsten carbide, chromium, applied to a body in the plasma spraying method. It is known that metallic objects, which must have a very high resistance to abrasion, in the plasma to provide the spraying method with a coating of a hard material, suitable metals, oxides and carbides being suitable as hard materials. The coating material is fed to the plasma spray nozzle in the form of a powder, melted in the plasma jet on the surface of the individual grains and thus reaches the surface to be coated, where the hard material forms a more or less porous coating. The cavities contained in this coating are generally to a greater or lesser extent capillaries. While the resistance of metallic bodies that have been coated in this way to purely mechanical wear is generally good, the resistance to chemical attacks is often inadequate, since acids can reach the metallic body through the cavities of the coating, for example. attack it and cause the coating to peel off.

Der Erfindung liegt die Aufgabe zugrunde, die Hohlräume in der Beschichtung zu schließen, so daß chemisch aggresive Stoffe nicht bis zur Oberfläche des metallischen Körpers gelangen können. Diese Aufgabe wird gemäß der Erfindung dadurch gelöst, daß die Beschichtung mit einem flüssigen aushärtbaren, insbesondere vernetzbaren Kunststoff oder Lack getränkt wird und daß diese Kunststoffschicht bzw. Lackschicht zumindest in ihrem nach außen weisenden Bereich durch Bestrahlung mit Elektronen vernetzt wird.The object of the invention is to close the voids in the coating so that chemically aggressive substances cannot reach the surface of the metallic body. This object is achieved according to the invention in that the coating is impregnated with a liquid curable, in particular crosslinkable, plastic or lacquer, and in that this plastic layer or lacquer layer is crosslinked, at least in its outwardly facing region, by irradiation with electrons.

Der Vorteil der Erfindung liegt darin, daß innerhalb der porösen Beschichtung eine vollkommen geschlossene Schicht des ausgehärteten, insbesondere vernetzten Kunststoffs oder Lacks geschaffen wird, die den Zutritt von Säuren oder sonstigen aggresiven Stoffen zur Oberfläche des metallischen Körpers bei geeigneter Auswahl des Kunststoffes mit Sicherheit verhindert. Es ist dabei nicht unbedingt erforderlich, daß die Kunststoff- oder Lackschicht, die im folgenden der Einfachheit halber lediglich als Kunststoffschicht bezeichnet wird, in inrer vollen Tiefe vernetzt wird, sondern es genügt, wenn das Vernetzen lediglich in einem äußeren Bereich erfolgt. Von Vorteil ist bei der Erfindung weiterhin, daß das Vernetzen mittels Elektronenbestrahlung sehr schnell erfolgen kann, bei Vorhandensein geeigneter Anlagen beispielsweise in wenigen Sekunden oder allenfalls wenigen Minuten, und daß eine merkliche Erwärmung der Kunststoffschicht und somit des die Beschichtung tragenden Körpers infolge der Elektronenbestrahlung nicht erfolgt. Es können daher auch gegen Temperaturerhöhungen empfindliche Körper mit dem erfindungsgemäßen Verfahren behandelt werden. Wenn vorgesehen ist, den Körper nach dem Vernetzen einer Bearbeitung zu unterziehen, beispielsweise die beschichtete Oberfläche zu schleifen, so wird die Vernetzung so durchgeführt, daß die Vernetzung in der aufgebrachten Kunststoffschicht zumindest so tief reicht, daß bei der nachfolgenden Bearbeitung keine noch nicht vernetzten Bereiche der Kunststoffschicht erreicht werden. Da zumindest der äußere Bereich der Kunststoffschicht in äußerst kurzer Zeit vernetzt und somit trocken ist, können die beschichteten Körper unmittelbar nach der Elektronenbestrahlung weiter bearbeitet werden. Je nach der Art des beschichteten Gegenstands mag es dann ausreichend sein, wenn in der Tiefe vorhandene, noch nicht vernetzte Bereiche des Kunststoffs unter dem Einfluß einer ausreichend hohen Umgebungstemperatur im Lauf der folgenden Tage oder Wochen noch vollständig vernetzen.The advantage of the invention is that a completely closed layer of the cured, in particular cross-linked plastic or lacquer is created within the porous coating, which prevents the entry of acids or other aggre sensitive substances to the surface of the metallic body with suitable selection of the plastic with certainty prevented. It is not absolutely necessary that the plastic or lacquer layer, which is simply referred to as a plastic layer in the following, is cross-linked to its full depth, but it is sufficient if the cross-linking takes place only in an outer region. Another advantage of the invention is that the crosslinking by means of electron radiation can take place very quickly, in the presence of suitable systems, for example in a few seconds or at most a few minutes, and that the plastic layer and thus the body carrying the coating are not noticeably heated as a result of the electron radiation . It is therefore also possible to treat bodies sensitive to temperature increases with the method according to the invention. If it is intended to subject the body to processing after crosslinking, for example grinding the coated surface, then the crosslinking is carried out in such a way that the crosslinking in the applied plastic layer extends at least so deep that no areas which have not yet been crosslinked in the subsequent processing the plastic layer can be reached. Since at least the outer area of the plastic layer is cross-linked and therefore dry in an extremely short time, the coated bodies can be processed further immediately after the electron irradiation. Depending on the type of the coated object, it may then be sufficient if areas of the plastic which are not yet crosslinked in the depth are still completely crosslinked under the influence of a sufficiently high ambient temperature in the course of the following days or weeks.

Für den beabsichtigten Korrosionsschutz der metallischen Oberfläche des beschichteten Körpers ist es nicht unbedingt erforderlich, daß der Kunststoff überall bis zur metallischen Oberfläche vordringt.For the intended corrosion protection of the metallic surface of the coated body, it is not absolutely necessary for the plastic to penetrate all the way to the metallic surface.

Da es jedoch für viele Fälle vorteilhaft ist, wenn die Kunststoffschicht möglichst tief in die poröse Beschichtung eindringt, ist gemäß einer Ausführungsform der Erfindung vorgesehen, daß der Körper vor dem Aufbringen des flüssigen Kunststoffes auf etwa 80°C erwärmt wird, und daß der Kunststoff anschließend auf den erwärmten Körper aufgebracht, insbesondere aufgesprüht wird. Durch das Erwärmen auf die verhältnismäßig niedrige Temperatur von beispielsweise 80°C, die auch von empfindlichen Körpern ohne Gefahr ausgehalten wird, wird die in den Hohlräumen der Hartstoffbeschichtung enthaltene Luft zu einem großen Teil ausgetrieben und es wird daher das Eindringen des flüssigen Kunststoffs bis in die Tiefe der porösen Schicht erleichtert. Der Kunststoff wird dabei aufgebracht, solange der Körper noch warm ist, so daß der flüssige Kunststoff bei der Abkühlung der in den Poren noch enthaltene Luft in tiefere Bereiche der porösen Schicht eindringen kann. Durch Aufsprühen kann die Menge des aufgebrachten flüssigen Kunststoffs besonders einfach den jeweiligen Erfordernissen angepaßt werden.However, since it is advantageous in many cases if the plastic layer penetrates as deeply as possible into the porous coating, it is provided according to one embodiment of the invention that the body is heated to approximately 80 ° C. before the liquid plastic is applied, and that the plastic subsequently applied to the heated body, in particular sprayed on. By heating to the relatively low temperature of, for example, 80 ° C, which can be withstood even by sensitive bodies without danger, the air contained in the cavities of the hard material coating is largely expelled and the liquid plastic penetrates into it Depth of the porous layer is facilitated. The plastic is applied while the body is still warm, so that the liquid plastic can penetrate into deeper areas of the porous layer when the air still contained in the pores cools. The amount of liquid plastic applied can be adapted to the particular requirements in a particularly simple manner by spraying.

Vorteilhaft ist es, gemäß einer Ausführungsform der Erfindung einen flüssigen Kunststoff geringer Viskosität zu verwenden, vorzugsweise einen Kunststoff, der flüssiger als Wasser ist. Dadurch wird das Eindringen des Kunststoffs in die Hohlräume der Hartstoffbeschichtung erleichtert.According to one embodiment of the invention, it is advantageous to use a liquid plastic of low viscosity, preferably a plastic that is more liquid than water. This facilitates the penetration of the plastic into the cavities in the hard material coating.

Bei Ausführungsformen der Erfindung wird das Verfahren so angewandt, daß lediglich eine einzige Kunststoffbeschichtung vorgesehen wird, die dann im allgemeinen die gesamte Dicke der Hartstoffbeschichtung einnimmt. Bei anderen Ausführungsformen der Erfindung ist jedoch vorgesehen, daß die poröse Beschichtung zunächst nur in ihrem dem metallischen Körper benachbarten Bereich getränkt wird, und daß nach dem Aushärten durch Elektronenbestrahlung der Körper wiederum mit einem Kunststoff getränkt wird, der ebenfalls durch Elektronenbestrahlung vernetzt wird. Es kann hierbei bei Ausführungsformen der Erfindung der gleiche Kunststoff verwendet sein, wenn in besonderen Fällen beispielsweise eine gewünschte Vernetzung bis in relativ große Tiefe nicht in einem einzigen Bestrahlungsvorgang erfolgen kann, weil die Kunststoffschicht hierzu zu dick ist; bei anderen Ausführungsformen der Erfindung sind jedoch unterschiedliche Kunststoffe verwendet. Insbesondere kann die äußere Kunststoffschicht so gewählt sein, daß sich ein besonders niedriger Reibungskoeffizient des Körpers ergibt; die äußere fertig vernetzte Kunststoffschicht kann in diesem Falle insbesondere Polytetrafluoräthylen sein.In embodiments of the invention, the method is applied in such a way that only a single plastic coating is provided, which then generally takes up the entire thickness of the hard material coating. In other embodiments of the invention, however, it is provided that the porous coating is first soaked only in its area adjacent to the metallic body, and that after curing by electron radiation the body is in turn soaked with a plastic which is also crosslinked by electron radiation. In the case of embodiments of the invention, the same plastic can be used here if, in special cases, for example, a desired crosslinking to a relatively great depth cannot take place in a single irradiation process because the plastic layer is too thick for this; however, different plastics are used in other embodiments of the invention. In particular, the outer plastic layer can be chosen so that a particularly low coefficient of friction of the body results; in this case the outer, fully crosslinked plastic layer can in particular be polytetrafluoroethylene.

Bei ebenen Werkstücken kann das Eindringen des Kunststoffes nur in den dem metallischen Körper benachbarten Bereich der porösen Beschichtung dadurch bewirkt werden, daß auf die poröse Schicht nur eine beschränkte zur Füllung der dem metallischen Körper benachbarten Kapillaren erforderliche Menge Kunststoff aufgebracht wird, der dann durch entsprechende Erwärmung in Folge der Schwerkraft nach unten sickert, wobei wegen der begrenzten Menge des flüssigen Kunststoff die oberen Bereiche vom Kunststoff wieder frei werden und nach dem Aushärten des eingebrachten Kunststoffes mit einem anderen Kunsstoff gefüllt werden können. Wo ein derartiges Verfahren nicht möglich ist, kann die ganze Beschichtung mit einem bestimmten Kunststoff angefüllt werden und das Werkstück auf eine Temperatur erwärmt werden, bei der der flüssige Kunststoff aus dem oberflächennahen Bereich verdampft, wobei dann bei dieser Temperatur bereits eine Aushärtung des verbleibenden Kunststoffes erfolgen kann. In den durch Verdampfung des Kunststoffes frei gewordenen Bereich der porösen Schicht kann dann ein anderer Kunststoff eingebracht und durch Elektronenbestrahlung ausgehärtet werden. Um die Verdampfung des Kunststoffes an der Oberfläche zu erreichen, kann die Erwärmung so vorgenommen werden, daß sich dieser an der Oberfläche befindliche Bereich der Schicht stärker erwärmt als der dem metallischen Körper benachbarten Bereich der porösen Schicht.In the case of flat workpieces, the penetration of the plastic can only be brought about into the area of the porous coating adjacent to the metallic body by applying only a limited amount of plastic required to fill the capillaries adjacent to the metallic body, which is then heated by appropriate heating as a result of gravity seeps down, being due to the limited amount of the liquid plastic, the upper areas can be cleared of the plastic again and can be filled with another plastic after the plastic has hardened. Where such a method is not possible, the entire coating can be filled with a certain plastic and the workpiece heated to a temperature at which the liquid plastic evaporates from the area near the surface, at which temperature the remaining plastic is already cured can. Another plastic can then be introduced into the area of the porous layer which has become free due to evaporation of the plastic and can be cured by electron radiation. In order to achieve the evaporation of the plastic on the surface, the heating can be carried out in such a way that this area of the layer located on the surface heats up more than the area of the porous layer adjacent to the metallic body.

Ein wichtiger Vorteil der Erfindung liegt noch in folgendem: Muß ein mit Hartstoff beschichteter Körper, beispielsweise ein Zylinder einer Druckmaschine, zur Erzielung einer ausreichend glatten Oberfläche geschliffen werden, so werden häufig ganze Körner des Beschichtungsstoffs aus der Beschichtung gerissen, so daß ein bestimmtes Maß der Rauhtiefe nicht unterschritten werden kann. Ist der Körper dagegen mit der erfindungsgemäßen Versiegelung versehen, so hält die vernetzte Kunststoffschicht insbesondere dann, wenn sie bis in größere Tiefen der Beschichtung reicht, die Körner der Hartstoffbeschichtung fest, so daß beim Schleifvorgang einzelne zu weit nach außen ragende Körner teilweise abgetragen werden, wie dies erwünscht ist, aber nicht vollständig aus der Beschichtung herausgerissen werden.An important advantage of the invention lies in the following: If a body coated with hard material, for example a cylinder of a printing press, has to be ground to achieve a sufficiently smooth surface, whole grains of the coating material are often torn out of the coating, so that a certain amount of Roughing depth cannot be fallen below. In contrast, the body is in accordance with the invention Provided sealer, the cross-linked plastic layer holds the grains of the hard material coating firmly, especially if it extends to greater depths of the coating, so that individual grains that protrude too far outward are partially removed as desired, but not completely be torn out of the coating.

Die Erfindung wird im folgenden anhand eines Ausführungsbeispieles beschrieben. Ein metallischer Körper, bei dem es sich im Ausführungsbeispiel um einen Druckzylinder einer Druckmaschine handelt, und der aus Stahl besteht und Abmessungen von 180 cm Länge und 85 cm Durchmesser aufweist, wird im Plasmasprühverfahren mit einer Schicht aus Wolframkarbid überzogen. Diese Beschichtung hat eine Dicke von etwa 100 pm. Das Plasmasprühverfahren oder, wie es auch genannt wird, Plasmaspritzen, und die hierfür erforderlichen Vorrichtungen sind bekannt. Dabei wird ein Gas einem Lichtbogen-Plasmabrenner zugeführt und in dem Lichtbogen je nach Art des Gases dissoziiert und ionisiert. Kurz vor dem Düsenaustritt wird dem unter hoher Geschwindigkeit ausströmenden Plasma das pulverisierte Spritzgut, also der Hartstoff, mit Hilfe eines Trägergases zugeführt. Als Plasmagas wird häufig Argon verwendet.The invention is described below using an exemplary embodiment. A metallic body, which in the exemplary embodiment is a printing cylinder of a printing press, and which consists of steel and has dimensions of 180 cm in length and 85 cm in diameter, is coated with a layer of tungsten carbide in the plasma spraying process. This coating has a thickness of approximately 100 pm. The plasma spraying process or, as it is also called, plasma spraying, and the devices required for this are known. A gas is fed to an arc plasma torch and dissociated and ionized in the arc depending on the type of gas. Shortly before the nozzle emerges, the pulverized spray material, i.e. the hard material, is fed to the plasma flowing out at high speed with the aid of a carrier gas. Argon is often used as the plasma gas.

Anschließend wird der mit der Hartstoffbeschichtung versehene Körper so erwärmt, daß die Temperatur des Körpers von innen nach außen etwas abnimmt. Die Erwärmung bewirkt, daß die in den Poren der Oberflächenschicht enthaltene Luft großenteils entweicht. Hierauf wird der beschichtete Körper mit einem flüssigen Kunststoff besprüht, der unten näher angegeben ist. Dieser Kunststoff zieht, zumindest teilweise auch infolge von Kapillarwirkung, in die Poren der Beschichtung ein, nicht zuletzt deshalb, weil der flüssige Kunststoff unter weiterer Verflüssigung in die wärmeren Bereiche der Beschichtung, also nach innen, vordringt.The body provided with the hard material coating is then heated in such a way that the temperature of the body decreases somewhat from the inside to the outside. The heating causes most of the air contained in the pores of the surface layer to escape. Then the coated body with a liquid Sprayed plastic, which is specified below. This plastic is drawn into the pores of the coating, at least in part also as a result of capillary action, not least because the liquid plastic penetrates into the warmer areas of the coating, that is to say inside, with further liquefaction.

Das Besprühen erfolgt unmittelbar nach dem Erwärmen des Werkstücks auf etwa 80°C, damit die aus den Poren der Beschichtung ausgetretene Luft nicht inzwischen wieder eindringt.Spraying takes place immediately after the workpiece has been heated to approximately 80 ° C., so that the air that has escaped from the pores of the coating does not penetrate again in the meantime.

Anschließend an das Besprühen wird das Werkstück durch Elektronen bestrahlt. Eine für eine derartige Bestrahlung geeignete Anlage wird von der Firma Otto Dürr Anlagenbau GmbH, D-7000 Stuttgart unter der Typenbezeichnung ESH 150 vertrieben. Diese Anlage erzeugt Elektronen mit einer Energie von 150 keV, dabei kann der zu bestrahlende Körper sich an der freien Atmosphäre befinden und wird lediglich zum Fernhalten des Sauerstoffs der Luft in dem Bereich, in dem die Elektronen auf den Körper auftreffen, mit einem geeigneten Inertgas gespült. Als Inertgas kommt beispielsweise Stickstoff in Frage. Von der genannten Anlage gibt es mehrere Ausführungsformen, die sich in der Breite des erzeugten Elektronenstrahls unterscheiden. Bei einer derartigen Anlage beträgt die Leistung des zum Bestrahlen zur Verfügung stehenden Elektronenstrahls 7,5 KW.After spraying, the workpiece is irradiated by electrons. A system suitable for such radiation is sold by Otto Dürr Anlagenbau GmbH, D-7000 Stuttgart under the type designation ESH 150. This system generates electrons with an energy of 150 keV, whereby the body to be irradiated can be in the free atmosphere and is only flushed with a suitable inert gas to keep out the oxygen in the air in the area in which the electrons strike the body . Nitrogen is an example of an inert gas. There are several embodiments of the system mentioned, which differ in the width of the electron beam generated. In such a system, the power of the electron beam available for irradiation is 7.5 KW.

Es ist ansich nicht erforderlich, daß die gesamte Hartstoffschicht von dem Elektronenstrahl durchdrungen wird, es genügt vielmehr, wenn die vom Elektronenstrahl durchdrungene Schicht so tief ist, daß sie bei einer nachfolgenden Bearbeitung nicht ganz abgetragen wird, so daß auch nach einer nachfolgenden Bearbeitung die Oberfläche des Werkstücks mit ausgehärtetem Kunststoff bedeckt ist. Der unterhalb dieser ausgehärteten Kunststoffschicht befindliche Kunststoff härtet dann im Laufe der Zeit aus, beispielsweise innerhalb von etwa 2 bis 10 Wochen.It is not in itself necessary that the entire hard material layer is penetrated by the electron beam, rather it is sufficient if that by the electron beam third layer is so deep that it is not completely removed during subsequent processing, so that the surface of the workpiece is covered with hardened plastic even after subsequent processing. The plastic located below this hardened plastic layer then hardens over time, for example within about 2 to 10 weeks.

Die Versiegelung durch den mittels Elektronenbeschuß vernetzten oder ausgehärteten Kunststoff ist außerordentlich wirksam. Eine unversiegelte, im Plasmaspritzverfahren aufgebrachte Schicht wird beispielsweise bei einem einzigen Arbeitsgang durch Sandstrahlen mit Korund entfernt. Ist eine erfindungsgemäße ausgehärtete Kunststoffschicht in die Hartstoffschicht eingebracht, so sind zum Entfernen dieser kombinierten Schicht etwa sechs derartige Sandstrahlvorgänge erforderlich.The sealing by the plastic cross-linked or hardened by means of electron bombardment is extremely effective. An unsealed, plasma sprayed layer is removed, for example, in a single operation by sandblasting with corundum. If a hardened plastic layer according to the invention is introduced into the hard material layer, about six such sandblasting processes are required to remove this combined layer.

Durch die vernetzte Kunststoffschicht ist es erstmals möglich, Werkstücke mit im Plasmasprühverfahren vergüteten Oberflächen im chemischen Bereich zu verwenden, wo ohne Vorhandensein der gehärteten Kunststoffschicht die Hartstoffbeschichtung durch Korrosion des diese Schicht tragenden Metallkörpers Schaden nehmen würde. Eine Tränkung der Hartstoffschicht mit einem nicht ausgehärteten Kunststoff könnte dagegen die Korrosion des Metallkörpers nicht mit Sicherheit verhindern.The cross-linked plastic layer makes it possible for the first time to use workpieces with surfaces sprayed with a plasma spray in the chemical sector, where without the hardened plastic layer the hard material coating would be damaged by corrosion of the metal body supporting this layer. An impregnation of the hard material layer with an uncured plastic, however, could not prevent corrosion of the metal body with certainty.

Wollte man die in die Hartstoffschicht eingebrachte flüssige Kunststoffschicht durch Anwendung erhöhter Temperaturen innerhalb relativ kurzer Zeit vernetzen, so müßten hierfür Temperaturen zwischen 1300C und 250°C, je nach der Art des verwendeten Kunststoffs, angewendet werden.If one wanted to the introduced in the hard material coating liquid plastic layer by use of elevated temperatures crosslinking within a relatively short period of time, so would have to be applied for this purpose temperatures between 130 0 C and 250 ° C, depending on the type of plastic used.

Es hat sich überraschend gezeigt, daß die Elektronenbestrahlung trotz der durch die einzelnen Partikel der Hartstoffschicht zu erwartenden Abschattung eine wirkungsvolle schnelle Aushärtung der Kunststoffschicht bewirkt. Dabei kann eine Aushärtung bis in eine Tiefe von 300µm erzielt werden. Demgegenüber sind bei vielen Anwendungen die Hartstoffschichten nur etwa 100µm dick, so daß in einem einzigen Bestrahlungsgang die Kunststoffschicht vollständig ausgehärtet werden kann.It has surprisingly been found that, despite the shading to be expected from the individual particles of the hard material layer, the electron irradiation brings about an effective rapid hardening of the plastic layer. Curing down to a depth of 300 µm can be achieved. In contrast, in many applications the hard material layers are only about 100 µm thick, so that the plastic layer can be fully cured in a single radiation cycle.

Zur Zeit wird als günstig die Verwendung eines hochmolekularen Kunststoffes angesehen, der im wesentlichen aus Polyäthylen-Glycol-Dimethacrylat oder Trimetylol-Propan-Trimethacrylat unter Beimengung von aliphatischen und/oder aromatischen Kohlenwasserstoffen, insbesondere Aminen besteht, und der die üblichen Zusätze von Weichmacher, Polymer-Verdicker, Peroxid, Toluidin, Saccharin, Füllstoffen, Pigmenten, Stabilisatoren und dgl., z.T. auf Si-Basis aufweist.At present, the use of a high-molecular plastic is considered favorable, which essentially consists of polyethylene glycol dimethacrylate or trimethylol propane trimethacrylate with the addition of aliphatic and / or aromatic hydrocarbons, especially amines, and which contains the usual additives of plasticizer, polymer Thickener, peroxide, toluidine, saccharin, fillers, pigments, stabilizers and the like, some based on Si.

Claims (6)

1. Verfahren zum Versiegeln einer im Plasmasprühverfahren auf einem Werkstück aufgebrachten porösen Beschichtung aus Hartstoff, wie Aluminiumoxid, Wolframkarbid, Chrom, dadurch gekennzeichnet, daß die Beschichtung mit einem flüssigen vernetzbaren Kunststoff oder Lack getränkt wird, und die Kunststoff- bzw. Lackschicht zumindest in ihrem nach außen weisenden Bereich durch Bestrahlung mit Elektronen ausgehärtet insbesondere vernetzt wird.1. A method for sealing a porous coating of hard material such as aluminum oxide, tungsten carbide, chromium applied to a workpiece in the plasma spraying process, characterized in that the coating is impregnated with a liquid crosslinkable plastic or lacquer, and the plastic or lacquer layer at least in its outward-pointing area is cured, in particular crosslinked, by irradiation with electrons. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß das Werkstück vor dem Aufbringen des flüssigen Kunststoffs oder Lacks auf etwa 80°C erwärmt wird, und daß der Kunststoff bzw. Lack auf das erwärmte Werkstück aufgebracht wird.2. The method according to claim 1, characterized in that the workpiece is heated to about 80 ° C before the application of the liquid plastic or lacquer, and that the plastic or lacquer is applied to the heated workpiece. 3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß der Kunststoff auf die Beschichtung aufgesprüht wird.3. The method according to claim 1 or 2, characterized in that the plastic is sprayed onto the coating. 4. Verfahren nach einem der vorhergehenden Ansprüche dadurch gekennzeichnet, daß ein Kunststoff oder Lack geringer-Viskosität verwendet wird.4. The method according to any one of the preceding claims, characterized in that a plastic or low-viscosity paint is used. 5. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Menge des flüssigen Kunststoffs oder Lacks derart bemessen ist, daß die poröse Beschichtung nur in ihren unteren Bereichen getränkt wird, und daß nach dem Vernetzen dieser Kunststoffschicht das Werkstück wiederum mit einem flüssigen Kunststoff oder Lack getränkt wird, der ebenfalls durch Elektronenbestrahlung vernetzt wird.5. The method according to any one of the preceding claims, characterized in that the amount of liquid plastic or lacquer is dimensioned such that the porous coating is impregnated only in its lower regions, and that after the crosslinking of this plastic layer, the workpiece in turn with a liquid plastic or lacquer is soaked, which is also cross-linked by electron radiation. 6. Verfahren nach Anspruch 5, dadurch gekennzeichnet, daß unterschiedliche Kunststoffe bzw. Lacke für die unterschiedlichen Tränkungsvorgänge verwendet werden.6. The method according to claim 5, characterized in that different plastics or paints are used for the different impregnation processes.
EP19820110003 1981-11-05 1982-10-29 Method of sealing a porous coating Expired EP0079007B1 (en)

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DE3143874 1981-11-05
DE19813143874 DE3143874C2 (en) 1981-11-05 1981-11-05 Method for coating a workpiece with a coating made of hard material

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CN112713072A (en) * 2019-10-24 2021-04-27 中微半导体设备(上海)股份有限公司 Plasma processing chamber internal components and methods of making the same
CN115558319A (en) * 2022-10-10 2023-01-03 佛山桃园先进制造研究院 Porous hydrophobic anti-sticking coating for metal matrix and preparation method thereof

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DE3842673A1 (en) * 1988-12-19 1990-06-21 Atilla Dipl Chem Dr Ing Akyol Process for producing wear-resistant coats
SG106041A1 (en) * 2000-03-21 2004-09-30 Nanyang Polytechnic Plastic components with improved surface appearance and method of making the same

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FR1438594A (en) * 1964-04-29 1966-05-13 Boeing Co Improvements to methods of applying a fluorinated hydrocarbon coating to an article, and to articles so treated
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US9943838B2 (en) 2013-07-24 2018-04-17 Basf Se Regeneration of a titanium containing zeolite
CN112713072A (en) * 2019-10-24 2021-04-27 中微半导体设备(上海)股份有限公司 Plasma processing chamber internal components and methods of making the same
CN112713072B (en) * 2019-10-24 2024-03-12 中微半导体设备(上海)股份有限公司 Internal parts of plasma processing chamber and method for manufacturing the same
CN115558319A (en) * 2022-10-10 2023-01-03 佛山桃园先进制造研究院 Porous hydrophobic anti-sticking coating for metal matrix and preparation method thereof

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DE3143874A1 (en) 1983-05-11
DE3143874C2 (en) 1988-12-22

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