EP0171793B1 - Plasma spray torch with cooled electrode and nozzle - Google Patents

Plasma spray torch with cooled electrode and nozzle Download PDF

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Publication number
EP0171793B1
EP0171793B1 EP85110152A EP85110152A EP0171793B1 EP 0171793 B1 EP0171793 B1 EP 0171793B1 EP 85110152 A EP85110152 A EP 85110152A EP 85110152 A EP85110152 A EP 85110152A EP 0171793 B1 EP0171793 B1 EP 0171793B1
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EP
European Patent Office
Prior art keywords
electrode
burner
plasma spray
nozzle
burner nozzle
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EP85110152A
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German (de)
French (fr)
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EP0171793A2 (en
EP0171793A3 (en
Inventor
Heiko Dr. Dipl.-Phys. Gruner
Markus Müller
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Plasmainvent AG
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Plasmainvent AG
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/32—Plasma torches using an arc
    • H05H1/42—Plasma torches using an arc with provisions for introducing materials into the plasma, e.g. powder, liquid
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/32—Plasma torches using an arc
    • H05H1/34—Details, e.g. electrodes, nozzles
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/32—Plasma torches using an arc
    • H05H1/34—Details, e.g. electrodes, nozzles
    • H05H1/3463—Oblique nozzles
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/32—Plasma torches using an arc
    • H05H1/34—Details, e.g. electrodes, nozzles
    • H05H1/3478—Geometrical details

Definitions

  • the invention relates to a plasma spray gun with a cooled electrode and burner nozzle for insertion into pipes and bores of workpieces and coating of inner surfaces of these workpieces.
  • a preferred area of application for such plasma spray burners is the coating of the contact surfaces of the blade root and turbine disk within the retaining grooves of the turbine disk in turbine wheels.
  • the spraying distance between plasma spray gun and substrate surface as well as the geometrical dimensions of the entire inner gun limit the minimum pipe or bore diameter at which coating can still be carried out with the same spray coating quality; the latter is thus predetermined by the normal design of the plasma spray gun. It would be possible to reduce the plasma flame length and thus the spraying distance by lowering the plasma energy, the amount of plasma gas and the amount of powder injected, so as to also coat holes of smaller diameter; however, this would only be possible at the expense of spray coating quality.
  • US-A-4,140,892 discloses a plasma spray burner with a cooled electrode and burner nozzle, in which the electrode is in the shape of a truncated cone with a rounded tip.
  • the burner nozzle in which the electrode is inserted partially and coaxially, has a minimum diameter which is smaller than the maximum outer diameter of the electrode and which extends to the outlet opening of the burner nozzle in the region from which a plurality of radial powder injector tubes of circular cross section open.
  • US Pat. No. 4,127,760 discloses a plasma spray burner which differs from the plasma spray burner according to US Pat. No. 4,140,892 in that the powder injector tubes open tangentially into the region of the minimum inner diameter of the burner nozzle and the burner nozzle has an outer partial area facing away from the electrode. whose inside diameter is larger than its smallest diameter.
  • EP-A-0 106 091 discloses a plasma spray burner whose electrode is formed in the shape of a truncated cone with a flattened tip.
  • the burner nozzle in which the electrode is inserted partially and coaxially, has a minimum inner diameter which is equal to or larger than the maximum outer diameter of the electrode, and the outer portion of the burner nozzle which faces away from the electrode can have an inner diameter which is larger than the smallest Inside diameter of the burner nozzle.
  • the invention has for its object to provide a plasma spray gun of the type described above, which enables a coating of high quality on the inner surfaces of pipes and bores with minimal inner diameters of up to about 25 mm with increased spray efficiency.
  • the burner nozzle-electrode pairing according to the invention causes the injected powder particles to be melted over a very short flame length and thus flight distance. Not only is the flame length shortened, but the plasma flame is also elliptically deformed, which leads to an increase in the geometric spraying efficiency in relation to the spray jet diameter as well as to a uniform thickness of the sprayed-on layer with each spraying pass.
  • the electrode expediently has two diametrically opposed flats on its hemispherical head.
  • the torch nozzle is advantageous, starting from its smallest inside diameter from the electrode expanded conically into an exit area with an inner ring surface of larger diameter.
  • the longitudinal axis of the flat outlet cross section of the powder injector is expediently arranged perpendicular to a connecting line between the flats of the electrode.
  • the electrode and the burner nozzle are expediently cooled by two separate water circuits.
  • a nozzle ring for cooling the surface and blowing out spray dust can additionally be provided by an annular gas protection jacket.
  • a separate line can be provided through which gas cooling and spray dust blow-out take place directly at the burner nozzle.
  • the burner advantageously consists of a stably cast part with all the elements not subject to wear and an openable part which carries the parts, which are subject to wear, easily replaceable, such as the electrode, the burner nozzle and the powder injector. All components, which are naturally subject to a wear process during burner operation, can thus be replaced simply and easily.
  • the openable part expediently has two hinged half-shells which are separated by an insulation plate.
  • the exchangeable burner nozzle is sealed against the cooling channel by O-rings and the seat of the O-rings is designed such that they are directly on at most one of four sealing surfaces on the burner nozzle and at least on two of the four sealing surfaces are good heat conductors , cooled components.
  • Channels for direct coolant access from the cooling channel to the O-rings are also advantageously provided.
  • the injected powder particles are distributed and melted in a wide coating spot, as a result of which the substrate material can be coated without excessive thermal stress despite the very short spraying distance, which is particularly important for thin-walled tubes.
  • the additional gas cooling supports this effect.
  • the plasma spray gun 1 for internal coatings shown in FIGS. 1 and 2 has a stably cast part 2 with all the elements not subject to wear and an openable part 3.
  • the openable part 3 consists of a cathode half-shell 4 and an anode half-shell 5, which are separated by an insulation plate 6, designed to be foldable and held together by a clamp 7.
  • On the stably cast part 2 there is a nozzle ring 8 with nozzle openings 9, through which a gas protection jacket around the plasma spray gun can be generated for surface cooling and spray dust blowing.
  • a separate line 31 can be led directly into the area of the burner nozzle.
  • An electrode 10 is fastened in the cathode half-shell 4 in an easily replaceable manner.
  • An insulating and replaceable gas distribution ring 11 is inserted into the insulation plate 6.
  • a burner nozzle 12 fixed with an extension tab, is easily replaced.
  • a powder injector 13 with a flat outlet cross section is also interchangeably inserted in the anode half-shell 5.
  • a cooling channel 14 for cooling the electrode 10 is provided in the cathode half-shell 4 and a cooling channel 14 for cooling the burner nozzle 12 in the anode half-shell 5. Both cooling channels are fed in parallel with coolant, for example water, gas or liquid carbon dioxide.
  • Part 2 represents the burner shaft, part 3 the burner head.
  • the cathode half-shell 4 and the anode half-shell 5 can be unfolded in order to have access to the gas distribution ring 11, if necessary, to replace it together with the insulation plate 6.
  • the electrode 10 has a hemispherical head 15 with diametrically opposite Flattenings 16 on.
  • the diameter of the electrode 10 is smaller than the smallest inside diameter of the burner nozzle 12. Starting from its smallest inside diameter, the burner nozzle 12 is flared away from the electrode 10 into an exit area with an inner ring surface 17 of a larger inside diameter.
  • the arc 18 that arises between the electrode 10 and the torch nozzle 12 is suppressed and concentrated on the undisturbed spherical surface of the head 15. This creates a flattened plasma flame 19.
  • the conical extension of the burner nozzle 12 to the inner ring surface 17 significantly reduces the length of the plasma flame 19.
  • the flat outlet cross section of the powder injector 13 ensures a powder injection corresponding to the flattened plasma flame 19.
  • zone I of the spray jet there is a high coating efficiency with a practically constant growth rate per unit of coating time, in zone 11 a coating efficiency which decreases sharply with the distance from the center and in zone III practically no coherent spray layer.
  • Zones I and II are delimited by concentric circles.
  • Zones I and 11 are flattened here in a strongly elliptical manner, the width of zone II being very small.
  • the layer thickness is practically constant within zone I and drops to zero over zone II over a small width. This results in a strong increase in the geometric spraying efficiency in relation to the spray jet diameter.
  • FIG. 7 shows that the burner nozzle 10 is sealed off from its associated cooling duct 20 by two O-rings 21, 22. Both O-rings 21, 22 each abut only one of their four sealing surfaces on the burner nozzle 12. A second sealing surface of the O-rings 21, 22 is formed on the insulation plate 6 or on an insulation body 23 for their thermal protection, while the O-rings 21, 22 rest on their further two sealing surfaces on components which are good heat conductors and are cooled by the cooling channel 20 . Additional channels 24, 25 are also provided from the cooling channel 20 for direct coolant access to the O-rings 21, 22. This results in particularly good thermal protection of the endangered O-rings 21, 22.
  • Coolant is fed in via a water inlet 26 parallel to the cooling channels 14 and 20 and discharged again via a water outlet 27.
  • the positive pole is connected to the water inlet 26 and the negative pole is connected to the water outlet 27.
  • Insulating tubes 28 are provided in the line guides for appropriate insulation of the cooling circuit flows from the electrical lines.
  • Plasma gas is supplied via a connection 29, wettable powder via a connection 30. Air or gas can be supplied into the area of the burner via an additional line 31.
  • Blade feet 34 of turbine blades 35 are inserted into holding grooves 32 of a turbine disk 33.
  • Coatings 36 with the plasma spray torch according to the invention are provided on the contact surfaces of blade root 34 and holding groove 32.
  • the purpose of the coatings 36 is to prevent fretting, friction welding and / or knocking out of the groove walls during operation of the turbine.
  • a CuNiln spray coating is used as the coating.
  • the coatings 36 are applied flat and broadly in three segments, preferably each with one burner passage.

Description

Die Erfindung betrifft einen Plasmaspritzbrenner mit gekühlter Elektrode und Brennerdüse zum Einführen in Rohre und Bohrungen von Werkstücken und Beschichten von Innenflächen dieser Werkstücke.The invention relates to a plasma spray gun with a cooled electrode and burner nozzle for insertion into pipes and bores of workpieces and coating of inner surfaces of these workpieces.

Ein bevorzugtes Anwendungsgebiet derartiger Plasmaspritzbrenner ist die Beschichtung der Berührungsflächen von Schaufelfuß und Turbinenscheibe innerhalb der Haltenuten der Turbinenscheibe bei Turbinenrädern.A preferred area of application for such plasma spray burners is the coating of the contact surfaces of the blade root and turbine disk within the retaining grooves of the turbine disk in turbine wheels.

Bei einem bekannten Plasmaspritzbrenner dieser Art wurde durch Verkleinerung der geometrischen Abmessungen der Brennerdüsen-Elektrodenpaarung erreicht, die Beschichtung der Innenflächen in der erforderlichen Spritzschichtqualität in Bohrungen bis zu einem minimalen Innendurchmesser von 70 mm durchzuführen. Bei dem bekannten Innenbrenner sind Plasmastrahlenergie, Plasmagasfördermenge und Spritzpulverinjektion auf der einen Seite sowie geometrische Verkleinerung der Brennerdüsen-Elektrodenpaarung auf der anderen Seite derart aufeinander abgestimmt, daß praktisch jedes Spritzpulver, für dessen -Aufschmelzung Standardbrenner eine Flugstrecke innerhalb der Plasmaflamme bis zu 150 mm benötigten, schon nach einer Flugstrecke von etwa 35 mm aufgeschmolzen ist. Der Spritzabstand zwischen Plasmaspritzbrenner und Substratoberfläche sowie die geometrischen Abmessungen des gesamten Innenbrenners begrenzen den minimalen Rohr- oder Bohrungsdurchmesser, bei welchem noch mit gleicher Spritzschichtqualität beschichtet werden kann; letztere ist somit von der Normalkonstruktion des Plasmaspritzbrenners vorgegeben. Es wäre möglich, durch Absenkung der Plasmaenergie, der Plasmagasmenge und der injektierten Pulvermenge die Plasmaflammlänge und damit den Spritzabstand zu verkleinern, um so auch Bohrungen geringeren Durchmessers zu beschichten; dies wäre jedoch nur auf Kosten der Spritzschichtqualität möglich.In a known plasma spray burner of this type, by reducing the geometric dimensions of the burner nozzle-electrode pair, it was possible to coat the inner surfaces in the required spray layer quality in bores up to a minimum inner diameter of 70 mm. In the known internal burner, plasma jet energy, plasma gas flow rate and spray powder injection on the one hand and geometric reduction of the burner nozzle-electrode pair on the other hand are coordinated with one another in such a way that practically any spray powder, for the melting of which standard burners require a flight path up to 150 mm within the plasma flame, already melted after a flight distance of about 35 mm. The spraying distance between plasma spray gun and substrate surface as well as the geometrical dimensions of the entire inner gun limit the minimum pipe or bore diameter at which coating can still be carried out with the same spray coating quality; the latter is thus predetermined by the normal design of the plasma spray gun. It would be possible to reduce the plasma flame length and thus the spraying distance by lowering the plasma energy, the amount of plasma gas and the amount of powder injected, so as to also coat holes of smaller diameter; however, this would only be possible at the expense of spray coating quality.

In der US-A-4,140,892 ist ein Plasmaspritzbrenner offenbart mit gekühlter Elektrode und Brennerdüse, bei welchem die Elektrode kegelstumpfförmig mit abgerundeter Spitze ausgebildet ist. Die Brennerdüse, in welche die Elektrode teilweise und gleichachsig eingesetzt ist, hat einen minimalen Durchmesser, der kleiner als der maximale Außendurchmesser der Elektrode ist und der sich bis zur Austrittsöffnung der Brennerdüse erstreckt, im Bereich von welcher eine Mehrzahl von radialen Pulverinjektorrohren kreisförmigen Querschnittes mündet.US-A-4,140,892 discloses a plasma spray burner with a cooled electrode and burner nozzle, in which the electrode is in the shape of a truncated cone with a rounded tip. The burner nozzle, in which the electrode is inserted partially and coaxially, has a minimum diameter which is smaller than the maximum outer diameter of the electrode and which extends to the outlet opening of the burner nozzle in the region from which a plurality of radial powder injector tubes of circular cross section open.

In der US-A-4,127,760 ist ein Plasmaspritzbrenner offenbart, der sich von dem Plasmaspritzbrenner gemäß US-A-4,140,892 dadurch unterscheidet, daß die Pulverinjektorrohre in den Bereich minimalen Innendurchmessers der Brennerdüse tangential münden und die Brennerdüse einen äußeren, der Elektrode abgewandten Teilbereich hat, dessen Innendurchmesser größer als ihr kleinster Durchmesser ist.US Pat. No. 4,127,760 discloses a plasma spray burner which differs from the plasma spray burner according to US Pat. No. 4,140,892 in that the powder injector tubes open tangentially into the region of the minimum inner diameter of the burner nozzle and the burner nozzle has an outer partial area facing away from the electrode. whose inside diameter is larger than its smallest diameter.

Aus der EP-A-0 106 091 ist schließlich ein Plasmaspritzbrenner bekannt, dessen Elektrode kegelstumpfförmig mit abgeflachter Spitze gebildet ist. Die Brennerdüse, in welche die Elektrode teilweise und gleichachsig eingesetzt ist, hat einen minimalen Innendurchmesser, der gleich oder größer als der maximale Außendurchmesser der Elektrode ist, und der äußere, der Elektrode abgewandte Teilbereich der Brennerdüse kann einen Innendurchmesser haben, der größer als der kleinste Innendurchmesser der Brennerdüse ist.Finally, EP-A-0 106 091 discloses a plasma spray burner whose electrode is formed in the shape of a truncated cone with a flattened tip. The burner nozzle, in which the electrode is inserted partially and coaxially, has a minimum inner diameter which is equal to or larger than the maximum outer diameter of the electrode, and the outer portion of the burner nozzle which faces away from the electrode can have an inner diameter which is larger than the smallest Inside diameter of the burner nozzle.

Der Erfindung liegt die Aufgabe zugrunde, einen Plasmaspritzbrenner der eingangs beschriebenen Art zu schaffen, welcher eine Beschichtung hoher Qualität der Innenflächen von Rohren und Bohrungen mit minimalen Innendurchmessern von bis zu etwa 25 mm mit erhöhter Spritzeffizienz ermöglicht.The invention has for its object to provide a plasma spray gun of the type described above, which enables a coating of high quality on the inner surfaces of pipes and bores with minimal inner diameters of up to about 25 mm with increased spray efficiency.

Durch die Erfindung ist ein Plasmaspritzbrenner mit gekühlter Elektrode und Brennerdüse zum Einführen in Rohre und Bohrungen von Werkstücken und Beschichten von Innenflächen dieser Werkstücke geschaffen, wobei

  • a) die Elektrode mit Bezug auf ihre Längsachse rotationssymmetrisch ausgebildet ist und im Bereich ihres Kopfes diametral gegenüberliegende Abweichungen von der rotationssymmetrischen Gestalt hat, an denen der zwischen der Elektrode und der Brennerdüse entstehende Lichtbogen unterdrückt wird, so daß er auf die verbleibende ungestörte Oberfläche des Kopfes der Elektrode konzentriert ist, wodurch eine flachgedrückte Plasmaflamme entsteht,
  • b) die Brennerdüse, in welche die Elektrode teilweise und gleichachsig eingesetzt ist, einen minimalen Innendurchmesser hat, der größer als der maximale Außendurchmesser der Elektrode ist,
  • c) die Brennerdüse einen äußeren, der Elektrode abgewandten Teilbereich hat, dessen Innendurchmesser größer als ihr kleinster Innendurchmesser ist, wodurch die Länge der Plasmaflamme erheblich verkürzt wird, und
  • d) ein Pulverinjektorrohr vorgesehen ist, welches an einer in den äußeren Teilbereich der Brennerdüse mündenden Austrittsöffnung einen lang gestreckten Querschnitt hat.
The invention provides a plasma spray burner with a cooled electrode and burner nozzle for insertion into pipes and bores of workpieces and coating of inner surfaces of these workpieces, wherein
  • a) the electrode is rotationally symmetrical with respect to its longitudinal axis and has diametrically opposite deviations from the rotationally symmetrical shape in the region of its head, at which the arc which arises between the electrode and the burner nozzle is suppressed, so that it impinges on the remaining undisturbed surface of the head the electrode is concentrated, creating a flattened plasma flame,
  • b) the burner nozzle, in which the electrode is inserted partially and coaxially, has a minimum inside diameter which is larger than the maximum outside diameter of the electrode,
  • c) the burner nozzle has an outer portion facing away from the electrode, the inside diameter of which is larger than its smallest inside diameter, as a result of which the length of the plasma flame is considerably shortened, and
  • d) a powder injector tube is provided which has an elongated cross section at an outlet opening which opens into the outer partial region of the burner nozzle.

Mit einem derartigen Aufbau des Plasmaspritzbrenners bewirkt die erfindungsgemäße Brennerdüsen-Elektrodenpaarung, daß die injektierten pulverpartikel auf sehr kurzer Flammlänge und damit Flugstrecke aufgeschmolzen werden. Dabei ist nicht nur die Flammlänge verkürzt, sondern auch die Plasmaflamme elliptisch verformt, was sowohl zu einer Erhöhung der geometrischen Spritzeffizienz bezogen auf den Spritzstrahldurchmesser als auch zu einer vergleichmäßigten Dicke der aufgespritzten Schicht bei jedem Spritzdurchgang führt.With such a structure of the plasma spray burner, the burner nozzle-electrode pairing according to the invention causes the injected powder particles to be melted over a very short flame length and thus flight distance. Not only is the flame length shortened, but the plasma flame is also elliptically deformed, which leads to an increase in the geometric spraying efficiency in relation to the spray jet diameter as well as to a uniform thickness of the sprayed-on layer with each spraying pass.

Die Elektrode weist zweckmäßig zwei diametral gegenüberliegende Abflachungen an ihrem halbkugelförmigen Kopf auf.The electrode expediently has two diametrically opposed flats on its hemispherical head.

Vorteilhaft ist die Brennerdüse ausgehend von ihrem kleinsten Innendurchmesser von der Elektrode weg konisch in einen Ausgangsbereich mit einer Innenringfläche größeren Durchmessers erweitert.The torch nozzle is advantageous, starting from its smallest inside diameter from the electrode expanded conically into an exit area with an inner ring surface of larger diameter.

Die Längsachse des flachen Austrittsquerschnitts des Pulverinjektors ist dabei zweckmäßig senkrecht zu einer Verbindungslinie zwischen den Abflachungen der Elektrode angeordnet.The longitudinal axis of the flat outlet cross section of the powder injector is expediently arranged perpendicular to a connecting line between the flats of the electrode.

Um die Wärmeabfuhr von dem Plasmaspritzbrenner zu optimieren und damit sowohl die für die geforderte Spritzschichtqualität notwendige Dauerbrennerleistung zu erhalten als auch die Lebensdauer der Brennerbauelemente zu vergrößern, sind die Elektrode und die Brennerdüse zweckmäßig durch zwei getrennte Wasserkreisläufe gekühlt.In order to optimize the heat dissipation from the plasma spray burner and thus to maintain both the long-term burner output required for the required spray layer quality and to extend the life of the burner components, the electrode and the burner nozzle are expediently cooled by two separate water circuits.

Zur Unterstützung dieser Wirkung kann zusätzlich ein Düsenring zur Oberflächenkühlung und Spritzstaubausblasung durch einen ringförmigen Gasschutzmantel vorgesehen sein. Alternativ kann eine separate Leitung vorgesehen sein, durch die eine Gaskühlung und Spritzstaubausblasung unmittelbar an der Brennerdüse erfolgt. Durch derartige Ausbildungen des Plasmaspritzbrenners erfolgt eine zusätzliche Abfuhr des reflektierten Spritzstaubs von der zu beschichtenden Bohrungsoberfläche, was zu einer Erhöhung der Qualität der Beschichtung führt.To support this effect, a nozzle ring for cooling the surface and blowing out spray dust can additionally be provided by an annular gas protection jacket. Alternatively, a separate line can be provided through which gas cooling and spray dust blow-out take place directly at the burner nozzle. Such designs of the plasma spray gun additionally remove the reflected spray dust from the bore surface to be coated, which leads to an increase in the quality of the coating.

Weiter besteht der Brenner vorteilhaft aus einem stabil vergossenen Teil mit allen nicht dem Verschleiß unterworfenen Elementen und einem öffenbaren Teil, der die verschleißbehafteten Teile Elektrode, Brennerdüse und Pulverinjektor leicht auswechselbar trägt. Alle Bauteile, welche während des Brennerbetriebs naturgemäß einem Abnützungsprozeß unterworfen sind, können damit einfach und leicht ausgewechselt werden.Furthermore, the burner advantageously consists of a stably cast part with all the elements not subject to wear and an openable part which carries the parts, which are subject to wear, easily replaceable, such as the electrode, the burner nozzle and the powder injector. All components, which are naturally subject to a wear process during burner operation, can thus be replaced simply and easily.

Der öffenbare Teil weist zweckmäßig zwei aufklappbare Halbschalen auf, die durch eine Isolationsplatte getrennt sind.The openable part expediently has two hinged half-shells which are separated by an insulation plate.

Zur weiteren Erhöhung der Standzeit der auswechselbaren Brennerdüse ist diese durch O-Ringe gegen den Kühlkanal abgedichtet und der Sitz der O-Ringe derart ausgebildet, daß diese an höchstens einer von vier Dichtflächen an der Brennerdüse direkt und wenigstens an zwei der vier Dichtflächen an gut wärmeleitenden, gekühlten Bauteilen anliegen. Vorteilhaft sind weiter Kanäle für den direkten Kühlmittelzutritt aus dem Kühlkanal zu den O-Ringen vorgesehen.To further increase the service life of the exchangeable burner nozzle, it is sealed against the cooling channel by O-rings and the seat of the O-rings is designed such that they are directly on at most one of four sealing surfaces on the burner nozzle and at least on two of the four sealing surfaces are good heat conductors , cooled components. Channels for direct coolant access from the cooling channel to the O-rings are also advantageously provided.

Mit dem erfindungsgemäßen Plasmaspritzbrenner erfolgt die Verteilung und Aufschmelzung der injektierten Pulverpartikel in einem breiten Beschichtungsfleck, wodurch das Substratmaterial trotz des sehr geringen Spritzabstandes ohne übermäßige thermische Belastung beschichtbar ist, was insbesondere für dünnwandige Rohre wichtig ist. Die zusätzliche Gaskühlung unterstützt diese Wirkung.With the plasma spray torch according to the invention, the injected powder particles are distributed and melted in a wide coating spot, as a result of which the substrate material can be coated without excessive thermal stress despite the very short spraying distance, which is particularly important for thin-walled tubes. The additional gas cooling supports this effect.

Die Erfindung ist im folgenden an Ausführungsbeispielen und anhand der Zeichnungen näher erläutert. In den Zeichnungen zeigen

  • Fig. 1 einen Längsschnitt durch ein Ausführungsbeispiel eines erfindungsgemäßen Plasmaspritzbrenners für Innenbeschichtungen,
  • Fig. 2 einen vergrößerten Teilausschnitt des Brennerkopfes in Fig. 1 in schematischer Darstellung,
  • Fig. 3 eine schematische Seitenschnittansicht von Elektrode und Brennerdüse des Plasmaspritzbrenners,
  • Fig. 4 eine schematische Vorderansicht der Anordnung in Fig. 3,
  • Fig. 5 eine schematische Darstellung der Beschichtungseffizienz und Schichtdickenverteilung im statischen Spritzbild bei einer rotationssymmetrischen Brennerdüsen-Elektrodenkonfiguration,
  • Fig. 6 eine schematische Darstellung der Beschichtungseffizienz und Schichtdickenverteilung im statischen Spritzbild bei einer Brennerdüsen-Elektrodenkonfiguration gemäß der Erfindung,
  • Fig. 7 eine schematische Darstellung der Brennerdüsenhalterung und -abdichtung,
  • Fig. 8 ein Beispiel für die Zuführung getrennter Kühlwasserkreisläufe, und
  • Fig. 9 eine schematische Darstellung einer Turbinenscheibe mit Turbinenschaufel und innenbeschichteter Haltenut.
The invention is explained below using exemplary embodiments and with reference to the drawings. Show in the drawings
  • 1 shows a longitudinal section through an embodiment of a plasma spray torch according to the invention for internal coatings,
  • 2 shows an enlarged partial section of the burner head in FIG. 1 in a schematic representation,
  • 3 is a schematic side sectional view of the electrode and burner nozzle of the plasma spray gun,
  • 4 shows a schematic front view of the arrangement in FIG. 3,
  • 5 shows a schematic representation of the coating efficiency and layer thickness distribution in the static spray pattern in the case of a rotationally symmetrical burner nozzle electrode configuration,
  • 6 shows a schematic illustration of the coating efficiency and layer thickness distribution in the static spray pattern in a burner nozzle electrode configuration according to the invention,
  • 7 is a schematic representation of the burner nozzle holder and seal,
  • Fig. 8 shows an example of the supply of separate cooling water circuits, and
  • 9 shows a schematic illustration of a turbine disk with a turbine blade and an internally coated holding groove.

Der in den Fig. 1 und 2 dargestellte Plasmaspritzbrenner 1 für Innenbeschichtungen weist ein stabil vergossenes Teil 2 mit allen nicht dem Verschleiß unterworfenen Elementen und ein öffenbares Teil 3 auf. Das öffenbare Teil 3 besteht aus einer Kathodenhalbschale 4 und einer Anodenhalbschale 5, die durch eine Isolationsplatte 6 getrennt, aufklappbar gestaltet und durch eine Klammer 7 zusammengehalten sind. Auf dem stabil vergossenen Teil 2 sitzt ein Düsenring 8 mit Düsenöffnungen 9, durch die ein Gasschutzmantel um den Plasmaspritzbrenner zur Oberflächenkühlung und Spritzstaubausblasung erzeugbar ist. Statt des Düsenrings 8 oder auch zusätzlich zu ihm kann eine separate Leitung 31 unmittelbar in den Bereich der Brennerdüse geführt werden.The plasma spray gun 1 for internal coatings shown in FIGS. 1 and 2 has a stably cast part 2 with all the elements not subject to wear and an openable part 3. The openable part 3 consists of a cathode half-shell 4 and an anode half-shell 5, which are separated by an insulation plate 6, designed to be foldable and held together by a clamp 7. On the stably cast part 2 there is a nozzle ring 8 with nozzle openings 9, through which a gas protection jacket around the plasma spray gun can be generated for surface cooling and spray dust blowing. Instead of the nozzle ring 8 or in addition to it, a separate line 31 can be led directly into the area of the burner nozzle.

In der Kathodenhalbschale 4 ist eine Elektrode 10 leicht auswechselbar befestigt. In die Isolationsplatte 6 ist ein isolierender und auswechselbarer Gasverteilungsring 11 eingesetzt. In die Anodenhalbschale 5 ist eine Brennerdüse 12, fixiert mit einer Verlängerungslasche, leicht auswechselbar eingesetzt. Ein Pulverinjektor 13 mit flachem Austrittsquerschnitt ist ebenfalls auswechselbar in die Anodenhalbschale 5 eingesetzt.An electrode 10 is fastened in the cathode half-shell 4 in an easily replaceable manner. An insulating and replaceable gas distribution ring 11 is inserted into the insulation plate 6. In the anode half-shell 5, a burner nozzle 12, fixed with an extension tab, is easily replaced. A powder injector 13 with a flat outlet cross section is also interchangeably inserted in the anode half-shell 5.

In der Kathodenhalbschale 4 ist ein Kühlkanal 14 zur Kühlung der Elektrode 10 und in der Anodenhalbschale 5 ein Kühlkanal 14 zur Kühlung der Brennerdüse 12 vorgesehen. Beide Kühlkanäle werden parallel mit Kühlmittel, beispielsweise Wasser, Gas oder flüssigem Kohlendioxid beschickt.A cooling channel 14 for cooling the electrode 10 is provided in the cathode half-shell 4 and a cooling channel 14 for cooling the burner nozzle 12 in the anode half-shell 5. Both cooling channels are fed in parallel with coolant, for example water, gas or liquid carbon dioxide.

Der Teil 2 stellt den Brennerschaft dar, der Teil 3 den Brennerkopf. Nach Lösen der Klammer 7 können die Kathodenhalbschale 4 und die Anodenhalbschale 5 auseinandergeklappt werden, um Zugang zu dem Gasverteilungsring 11 gegebenenfalls zu dessen Auswechselung zusammen mit der Isolationsplatte 6 zu haben. Die Elektrode 10 weist einen halbkugelförmigen Kopf 15 mit diametral gegenüberliegenden Abflachungen 16 auf. Der Durchmesser der Elektrode 10 ist kleiner als der kleinste Innendurchmesser der Brennerdüse 12. Die Brennerdüse 12 ist, ausgehend von ihrem kleinsten Innendurchmesser, von der Elektrode 10 weg konisch in einen Ausgangsbereich mit einer Innenringfläche 17 größeren Innendurchmessers erweitert.Part 2 represents the burner shaft, part 3 the burner head. After loosening the clamp 7, the cathode half-shell 4 and the anode half-shell 5 can be unfolded in order to have access to the gas distribution ring 11, if necessary, to replace it together with the insulation plate 6. The electrode 10 has a hemispherical head 15 with diametrically opposite Flattenings 16 on. The diameter of the electrode 10 is smaller than the smallest inside diameter of the burner nozzle 12. Starting from its smallest inside diameter, the burner nozzle 12 is flared away from the electrode 10 into an exit area with an inner ring surface 17 of a larger inside diameter.

An den Abflachungen 16 wird der zwischen Elektrode 10 und Brennerdüse 12 entstehende Lichtbogen 18 unterdrückt und auf die ungestörte Kugeloberfläche des Kopfes 15 konzentriert. Dadurch entsteht eine flachgedrückte Plasmaflamme 19. Durch die konische Erweiterung der Brennerdüse 12 zur Innenringfläche 17 wird die Länge der Plasmaflamme 19 erheblich verkürzt. Der flache Austrittsquerschnitt des Pulverinjektors 13 sorgt für eine der abgeflachten Plasmaflamme 19 entsprechende Pulverinjektion.At the flats 16, the arc 18 that arises between the electrode 10 and the torch nozzle 12 is suppressed and concentrated on the undisturbed spherical surface of the head 15. This creates a flattened plasma flame 19. The conical extension of the burner nozzle 12 to the inner ring surface 17 significantly reduces the length of the plasma flame 19. The flat outlet cross section of the powder injector 13 ensures a powder injection corresponding to the flattened plasma flame 19.

Fig. 5 zeigt schematisch die Beschichtungseffizienz verteilt über den Plasmastrahlquerschnitt, aufgenommen durch ein statisches Spritzbild auf einer Substratschicht und die entsprechende Schichtdicke bei einer konventionellen, rotationssymmetrischen Elektroden-Brennerdüsenkonfiguration. In einer Zone I des Spritzstrahls ergibt sich eine hohe Beschichtungseffizienz mit praktisch konstanter Aufwachsrate pro Beschichtungszeiteinheit, in einer Zone 11 eine mit dem Abstand vom Zentrum stark abnehmende Beschichtungseffizienz und in einer Zone III praktisch keine zusammenhängende Spritzschicht mehr. Die Zonen I und II sind durch konzentrische Kreise begrenzt.5 shows schematically the coating efficiency distributed over the plasma jet cross section, recorded by a static spray pattern on a substrate layer and the corresponding layer thickness in a conventional, rotationally symmetrical electrode-torch nozzle configuration. In zone I of the spray jet there is a high coating efficiency with a practically constant growth rate per unit of coating time, in zone 11 a coating efficiency which decreases sharply with the distance from the center and in zone III practically no coherent spray layer. Zones I and II are delimited by concentric circles.

In Fig. 6 ist die Beschichtungseffizienz und Schichtdikkenverteilung für eine erfindungsgemäße rotationsunsymmetrische Elektroden-Brennerdüsenkonfiguration dargestellt. Die Zonen I und 11 sind hier stark elliptisch abgeflacht, wobei die Breite der Zone II sehr gering ist. Die Schichtdicke ist innerhalb der Zone I praktisch konstant und fällt in der Zone II über geringe Breite auf Null ab. Hierdurch ergibt sich eine starke Erhöhung der geometrischen Spritzeffizienz bezogen auf den Spritzstrahldurchmesser.6 shows the coating efficiency and layer thickness distribution for a rotationally asymmetrical electrode-torch nozzle configuration according to the invention. Zones I and 11 are flattened here in a strongly elliptical manner, the width of zone II being very small. The layer thickness is practically constant within zone I and drops to zero over zone II over a small width. This results in a strong increase in the geometric spraying efficiency in relation to the spray jet diameter.

Fig. 7 zeigt, daß die Brennerdüse 10 durch zwei O-Ringe 21, 22 gegenüber ihrem zugehörigen Kühlkanal 20 abgedichtet ist. Beide O-Ringe 21, 22 liegen jeweils nur an einer ihrer vier Dichtflächen an der Brennerdüse 12 an. Eine zweite Dichtfläche der O-Ringe 21, 22 wird zu deren Wärmeschutz an der Isolationsplatte 6 bzw. an einem Isolationskörper 23 gebildet, während die O-Ringe 21, 22 an ihren weiteren zwei Dichtflächen an gut wärmeleitenden, über den Kühlkanal 20 gekühlten Bauteilen anliegen. Von dem Kühlkanal 20 sind außerdem zusätzliche Kanäle 24, 25 für direkten Kühlmittelzutritt zu den O-Ringen 21, 22 vorgesehen. Damit ergibt sich ein besonders guter Wärmeschutz der gefährdeten O-Ringe 21, 22.7 shows that the burner nozzle 10 is sealed off from its associated cooling duct 20 by two O-rings 21, 22. Both O-rings 21, 22 each abut only one of their four sealing surfaces on the burner nozzle 12. A second sealing surface of the O-rings 21, 22 is formed on the insulation plate 6 or on an insulation body 23 for their thermal protection, while the O-rings 21, 22 rest on their further two sealing surfaces on components which are good heat conductors and are cooled by the cooling channel 20 . Additional channels 24, 25 are also provided from the cooling channel 20 for direct coolant access to the O-rings 21, 22. This results in particularly good thermal protection of the endangered O-rings 21, 22.

Fig. 8 zeigt die Leitungszuführung zu dem Plasmaspritzbrenner 1. Über einen Wassereingang 26 wird Kühlmittel parallel zu den Kühlkanälen 14 und 20 zugeführt und über einen Wasserausgang 27 wieder abgeführt. Am Wassereingang 26 ist der Pluspol und am Wasserausgang 27 der Minuspol angeschlossen. Zur entsprechenden Isolierung der Kühlkreisfläufe von den elektrischen Leitungen sind in den Leitungsführungen Isolierrohre 28 vorgesehen. Plasmagas wird über einen Anschluß 29 zugeführt, Spritzpulver über einen Anschluß 30. Über eine zusätzliche Leitung 31 kann Luft oder Gas in den Bereich des Brenners zugeführt werden.8 shows the line feed to the plasma spray burner 1. Coolant is fed in via a water inlet 26 parallel to the cooling channels 14 and 20 and discharged again via a water outlet 27. The positive pole is connected to the water inlet 26 and the negative pole is connected to the water outlet 27. Insulating tubes 28 are provided in the line guides for appropriate insulation of the cooling circuit flows from the electrical lines. Plasma gas is supplied via a connection 29, wettable powder via a connection 30. Air or gas can be supplied into the area of the burner via an additional line 31.

Fig. 9 zeigt ein bevorzugtes Anwendungsgebiet für den erfindungsgemäßen Plasmaspritzbrenner. In Haltenuten 32 einer Turbinenscheibe 33 werden Schaufelfüße 34 von Turbinenschaufeln 35 eingesetzt. An den Berührungsflächen von Schaufelfuß 34 und Haltenut 32 werden Beschichtungen 36 mit dem erfindungsgemäßen Plasmaspritzbrenner vorgesehen. Zweck der Beschichtungen 36 ist es, Reibverschleiß, Reibverschweißung und/oder Ausschlagen der Nutwandungen im Betrieb der Turbine zu verhindern. Diese Beanspruchungen der Haltenut 32 entstehen durch den notwendigerweise nicht spielfreien Einbau der Turbinenschaufeln 35 in den Haltenuten 32. Die Beanspruchungen treten vor allem beim Anlauf und Abstellen der Turbine auf. Sie sind auch deshalb relativ groß, weil meist aus Gewichtsgründen Titan oder Titanlegierungen verwendet werden.9 shows a preferred area of application for the plasma spray torch according to the invention. Blade feet 34 of turbine blades 35 are inserted into holding grooves 32 of a turbine disk 33. Coatings 36 with the plasma spray torch according to the invention are provided on the contact surfaces of blade root 34 and holding groove 32. The purpose of the coatings 36 is to prevent fretting, friction welding and / or knocking out of the groove walls during operation of the turbine. These stresses on the holding groove 32 arise from the necessarily not clearance-free installation of the turbine blades 35 in the holding grooves 32. The stresses occur especially when the turbine is started and stopped. They are also relatively large because mostly titanium or titanium alloys are used for weight reasons.

Als Beschichtung kommt beispielsweise eine CuNiln-Spritzschicht zum Einsatz. Die Beschichtungen 36 werden flach und breitspurig in drei Segmenten, vorzugsweise jeweils mit einem Brennerdurchgang, aufgetragen.For example, a CuNiln spray coating is used as the coating. The coatings 36 are applied flat and broadly in three segments, preferably each with one burner passage.

Im folgenden sind als Anwendungsbeispiel für die Verwendung eines Maschinenbrenners nach dem Stand der Technik, eines Innenbrenners nach dem Stand der Technik und eines erfindungsgemäß ausgebildeten Innenbrenners die einzelnen Leistungs- und Spritzdaten angegeben:

  • Spritzpulver: NiAl 95/5% Kornfraktionierung: - 325 mesh Kornkonfiguration: Ni-Kugel mit außen aufgesetzten AI-Partikeln Plasmaflamme: Ar/H2-Gemisch
The individual performance and spray data are given below as an application example for the use of a machine burner according to the prior art, an internal burner according to the prior art and an internal burner designed according to the invention:
  • Wettable powder: NiAl 95/5% grain fractionation: - 325 mesh grain configuration: Ni ball with externally placed AI particles plasma flame: Ar / H 2 mixture

Beschichtungsparameter für dicht gespritzte, haftfeste Plasmaspritzschicht:

  • A. Maschinanhranner nach dem Stand der Technik:
    Figure imgb0001
  • B. Innenbrenner nach dem Stand der Technik:
    Figure imgb0002
  • C. Erfindungsgemäß ausgebildeter Innenbrenner:
    Figure imgb0003
Coating parameters for tightly sprayed, adhesive plasma spray coating:
  • A. Machine scanner according to the state of the art:
    Figure imgb0001
  • B. State of the art internal burner:
    Figure imgb0002
  • C. Internal burner designed according to the invention:
    Figure imgb0003

Claims (11)

1. Plasma spray burner with a cooled electrode and a burner nozzle for introduction into pipes and drillings of workpieces and for coating the inner surfaces of these workpieces, in which
a) the electrode (10) is rotationally symmetrical with respect to its longitudinal axis has variations in shape (16) diametrically opposite to the rotationally symmetrical shape in the region of its head (15) which suppress the arcing formed between the electrode (10) and the burner nozzle (12) so that the arcing is concentrated on the remaining undisturbed surface of the head (15) of the electrode (10), resulting in a flattened plasma flame (19),
b) the burner nozzle (12), in which the electrode (10) is partially and uniaxially inserted, has a minimum internal diameter which is greater than the maximum external diameter of the electrode,
c) the burner nozzle (12) has an outer partial region (17) facing away from the electrode (10) whose internal diameter is greater than its smallest internal diameter, whereby the length of the plasma flame (19) is considerably reduced, and
d) a powder injection pipe (13) is provided whose outlet opening has an elongated cross-section which opens into the outer partial region (17) of the burner nozzle (12).
2. Plasma spray burner according to claim 1, characterized in that the semi-spherical head (15) of the electrode (10) has two flattened portions (16) arranged diametrically opposite each other.
3. Plasma spray burner according to claim 1 or 2, characterized in that starting from its smallest internal diameter, the burner nozzle (12) is conically enlarged away from the electrode (10) into an outlet region with an internal annular surface (17) of larger diameter.
4. Plasma spray burner according to claim 2 or 3, characterized in that the longitudinal axis of the flat outlet cross-section of the powder injector (13) is arranged perpendicularly to a connecting line between the flattened portions (16) of the electrode (10).
5. Plasma spray burner according to one of the preceding claims, characterized in that the electrode (10) and the burner nozzle (12) are cooled by two separate cooling circuits (14, 20).
6. Plasma spray burner according to one of the preceding claims, characterized in that a nozzle ring (8) is provided for the surface cooling and the blowing out of spray powder by means of an annular protective gas envelope.
7. Plasma spray burner according to one of the claims 1 to 5, characterized in that a separate pipe (31) is provided by means of which a gas cooling and a blowing out of spray powder is effected directly at the burner nozzle.
8. Plasma spray burner according to one of the preceding claims, characterized in that the burner (1) consists of a rigidly cast part (2) containing all the components which are not subjected to wear, and a part (13) which can be opened containing all the parts which are subjected to wear, such as the electrode (10), burner-nozzle (12) and powder injector (13), which can be easily exchanged.
9. Plasma spray burner according to claim 8, characterized in that the accessible part (3) has two mutually hingeable half shells (4, 5) which are separated by an insulation plate (6).
10. Plasma spray burner according to any one of the preceding claims, characterized in that the burner nozzle (12) is sealed by 0-rings (21, 22) relative to its cooling channel (20), and in that the mounting of the 0-rings (20, 21) is constructed in such a manner that no more than one of four sealing surfaces makes direct contact with the burner nozzle (12) and at least two of the four sealing surfaces contact cooled components which are good heat conductors.
11. Plasma spray burner according to claim 10, characterized in that channels (24, 25) are provided for direct coolant access from the cooling channel (20) to the O-rings (21, 22).
EP85110152A 1984-08-17 1985-08-13 Plasma spray torch with cooled electrode and nozzle Expired - Lifetime EP0171793B1 (en)

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DE19843430383 DE3430383A1 (en) 1984-08-17 1984-08-17 PLASMA SPRAY BURNER FOR INTERNAL COATINGS
DE3430383 1984-08-17

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EP0171793A2 EP0171793A2 (en) 1986-02-19
EP0171793A3 EP0171793A3 (en) 1987-09-23
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JPS61133158A (en) 1986-06-20
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US4661682A (en) 1987-04-28
JPH0357833B2 (en) 1991-09-03
EP0171793A3 (en) 1987-09-23
DE3581014D1 (en) 1991-02-07

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