EP0500492A1 - Plasma spray gun for spraying powdered or gaseous materials - Google Patents

Plasma spray gun for spraying powdered or gaseous materials Download PDF

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Publication number
EP0500492A1
EP0500492A1 EP92810095A EP92810095A EP0500492A1 EP 0500492 A1 EP0500492 A1 EP 0500492A1 EP 92810095 A EP92810095 A EP 92810095A EP 92810095 A EP92810095 A EP 92810095A EP 0500492 A1 EP0500492 A1 EP 0500492A1
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EP
European Patent Office
Prior art keywords
cathode
plasma
spraying device
nozzle
channel
Prior art date
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Granted
Application number
EP92810095A
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German (de)
French (fr)
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EP0500492B1 (en
Inventor
Klaus Dr.-Ing. Landes
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Oerlikon Metco AG
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Sulzer Metco AG
Plasma Tecknik AG
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Publication of EP0500492A1 publication Critical patent/EP0500492A1/en
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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
    • H05H1/3452—Supplementary electrodes between cathode and anode, e.g. cascade
    • 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
    • H05H1/3484—Convergent-divergent 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
    • H05H1/44—Plasma torches using an arc using more than one torch
    • 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
    • H05H1/3468—Vortex generators

Definitions

  • the invention relates to a plasma spraying device for spraying powdery or gaseous material according to the preamble of claim 1.
  • a plasma spraying device of this type is known from EP 0 249 238 A2.
  • the cathode arrangement consists of a rod cathode, and the spray material is supplied at the anode-side end of the plasma guide channel through a tube inserted laterally into this channel, the end part of which is bent into the channel axis.
  • the invention seeks to avoid these disadvantages by moving the spray material supply to the cathode-side end of the plasma channel. Proposals in this direction are known per se; However, their use in connection with a plasma spraying device of the type mentioned at the outset has not led to satisfactory results.
  • DE-GM 1 932 150 shows a plasma spraying device with an indirect plasmatron that works with a short arc.
  • a hollow cylindrical cathode works together with a likewise hollow cylindrical, nozzle-shaped anode, the cathode protruding into the anode arranged coaxially to this.
  • the hollow cathode also serves as a feed pipe for the spray material, which is introduced axially into the arc space in this way.
  • the plasma gas passes through the annular gap between the cathode and anode into the arc space and then into the anode nozzle, through which the plasma jet is constricted.
  • DE-OS 33 12 232 A1 shows an example of such a solution on a plasma spraying device with a direct plasmatron, i.e. with an arc transferred to the workpiece.
  • Auxiliary anodes for igniting pilot arcs are assigned to the cathodes, from which individual arcs are drawn to the anode nozzle under the action of the plasma gas flowing along the cathodes and which generate a plasma stream combined in the center of the anode nozzle.
  • the spray material is introduced axially into the arc space through a tube located in the center of the cathode arrangement, specifically directly at the point of union of the individual plasma flows.
  • the invention aims to achieve the highest possible energy concentration that begins in the vicinity of the cathode arrangement and extends to the anode or even beyond.
  • the selected cathode arrangement in an indirect plasmatron working with a long arc, in connection with the constriction formed by the inlet nozzle, ensures the greatest possible energy concentration in the nozzle cavity.
  • the spray material which is introduced through the feed pipe arranged in the central axis, usually with the aid of a carrier gas, penetrates into the hot core of the plasma jet near the cathode, in which the spray material, for example the powder particles, is melted and further accelerated.
  • the carrier gas flow By varying the carrier gas flow, the initial speed of the powder particles and thus also the technically important residence time of the powder particles can be set in a simple manner. With these sizes, in combination with a suitable choice of plasma gas flow and arc current, optimal operating conditions can be achieved.
  • the central insulation body not only serves to electrically insulate the rod cathodes from one another and from the feed tube, but also has the task of forming an annular channel together with the inlet nozzle, through which the plasma gas flows into the cathode space in the most laminar form possible. It is also important that the plasma gas flows along the cathode tips protruding from the insulating body, which tips are additionally cooled as a result. This leads to an increase in cathode life.
  • the insulation body directly adjoins the arcing space and is therefore highly thermally stressed. It is therefore preferably made of a high-melting material, e.g. made of ceramic or boron nitride.
  • the cathodes preferably have a water-cooled cathode shaft and at their active end a cathode pin made of a high-melting material and inserted into the cathode shaft.
  • the cathode shaft can be made of copper and the cathode pin of thoriated tungsten.
  • the active ends of the cathodes should be as close together as possible in operational terms so that the arc branches emanating from them come together as close as possible to the arc attachment points.
  • the cathode shafts have a relatively large diameter due to the cavities for water cooling and must have a minimum mutual spacing for insulation reasons, the desired small mutual spacing of the cathode pins cannot be achieved when the cathode pin is arranged coaxially with the cathode shaft.
  • the arrangement could be such that the cathode pins run obliquely towards one another; however, such a solution is unsatisfactory from a manufacturing standpoint.
  • a preferred solution therefore consists in inserting the cathode pin eccentrically into the cathode shaft, so that the longitudinal axis of the cathode pin is closer to the central longitudinal axis than that of the cathode shaft.
  • a gas distribution arrangement with a plurality of nozzles.
  • a gas distribution ring with a plurality of through holes for the inlet of the plasma gas into the ring channel can be arranged in front of the ring channel between the insulation body and the inlet nozzle.
  • the insulation body is preceded by a gas distribution disk, which extends radially from the central tube for supplying the spray material to the wall of the inlet nozzle and which has a plurality of circular bores arranged for the inlet of the plasma gas the ring channel is provided in the inlet nozzle.
  • the through holes have the same effect here as those in the gas distribution ring mentioned above.
  • this gas distribution disk shields the entire front side of the insulation body against the action of the arc heat, so that the insulation body no longer has to be made of relatively expensive high-melting material.
  • the gas distribution disk should have a corresponding heat resistance, but for the gas distribution disk considerably less of the refractory material is required than otherwise for the insulating body and, moreover, it has a less complicated shape than that, which leads to a simpler and cheaper solution.
  • the gas distribution disk has further through bores through which the cathode pins extend. These through bores preferably have a larger diameter than the cathode pins. This enables a part of the plasma gas to be passed through the annular gap along the cathode pins due to the difference in diameter, which further improves the cooling thereof.
  • the through holes for the plasma gas can run both in the gas distribution ring and in the gas distribution disk, instead of axially, tangentially to virtual, central-axis helical lines. This allows a vortex flow of the plasma gas to be achieved, which has proven to be advantageous under certain operating conditions.
  • the paths of the molten powder particles are subject to the shot effect, ie they run in a cone which must lie along the plasma channel up to the mouth of the ring-shaped anode within the channel cross section so that no molten particles can be deposited on the channel wall.
  • This condition can also be determined by suitable selection of the operating parameters and by achieve the corresponding longitudinal profile of the plasma channel, for example by continuously expanding the plasma channel towards the anode following the inlet nozzle.
  • the plasma channel 4 is formed by a number of ring-shaped neutrodes 6 to 12 which are electrically insulated from one another and the ring-shaped anode 3.
  • the cathodes 1 each have a cathode shaft consisting of two parts 51 and 52, e.g. made of copper, which is anchored in a cathode support 13 made of insulating material. This is followed by a sleeve-shaped anode carrier 14 made of insulating material, which surrounds the neutrodes 6 to 12 and the anode 3.
  • the whole is held together by three metal sleeves 15, 16, 17, the first sleeve 15 being screwed to the end on the end face and the second sleeve 16 being screwed to the first circumference, while the third sleeve 17 is loosely anchored on the one hand to the second sleeve 16 and on the other hand is screwed circumferentially to the anode carrier 14.
  • the third sleeve 17 also presses with an inwardly directed flange 18 against the anode ring 3 and thus holds the elements forming the plasma channel 4 together, the neutrode 6 closest to the cathodes 1 being supported on an inner collar 19 of the anode carrier 4.
  • the cathodes 1 carry at their ends cathode pins 20, which are made of an electrically and thermally particularly conductive and also high-melting material, e.g. Tungsten.
  • the cathode pins 20 are arranged eccentrically to the respective axis of the cathode shafts 51, 52 in such a way that their longitudinal axes are closer to the central longitudinal axis 2 than those of the cathode shafts.
  • a central insulating body 21 made of refractory material, e.g. Ceramic or boron nitride, which is arranged in a fixed position to the first neutrode 6 and from which the cathode pins 20 protrude into the cavity 22 of the inlet nozzle formed by the first neutrode 6.
  • the exposed part of the outer circumferential surface of the insulating body 21 lies radially opposite a part of the nozzle wall and forms with this wall part an annular channel 23 for the inlet of the plasma gas into the nozzle cavity 22.
  • the supply of the spray material SM, e.g. Metal or ceramic powder into the plasma jet is carried out with the aid of a carrier gas TG at the cathode-side end of the plasma channel 4.
  • a pipe 24 running in the longitudinal axis 2 and held by the insulating body 21 is provided, which likewise opens into the nozzle cavity 22, whereby the cathode pins 20 extend beyond the mouth 25 of the tube 24.
  • the plasma gas PG is fed through a transverse channel 26 provided in the cathode carrier 13, which crosses into a longitudinal channel 27 from which the plasma gas reaches an annular space 28 and from there into the annular channel 23.
  • a gas distribution ring 29 is provided on the insulating body 21 and has a plurality of through bores 30 which connect the annular space 28 to the annular channel 23.
  • the elements forming the plasma channel 4, namely the anode 3 and the neutrodes 6 to 12, are electrically insulated from one another by ring disks 31 made of insulating material, for example boron nitride, and are gas-tightly connected to one another by sealing rings 32.
  • the plasma channel 4 has a constriction zone 33 in the vicinity of the cathode and, following this constriction zone 33, widens towards the anode 3 to a diameter which is at least 1.5 times the channel diameter at the narrowest point of the constriction zone 33 this expansion, the plasma channel 4 runs cylindrical to its anode-side end.
  • the neutrodes 6 to 12 consist of copper
  • the anode 3 is made of an outer ring 34, for example made of copper, and an inner ring 35 made of an electrically and thermally particularly conductive and also high-melting material, such as tungsten.
  • the neutrode 6 closest to the cathode rods 1 extends over the entire constriction zone 33, so that the channel wall 5 unites beyond the narrowest point of the constriction zone has a steady course.
  • the parts directly exposed to the arc and plasma heat are largely water-cooled.
  • different cavities for the circulation of the cooling water KW are provided in the cathode holder 13, in part 52 of the cathode shaft and in the anode holder 14.
  • the cathode holder 13 has three annular spaces 36, 37 and 38, which are connected to connecting lines 39, 40 and 41, and the anode holder 14 has an annular space 42 in the region of the anode 3 and all neutrodes in the region of the neutrodes 6 to 12 surrounding cavity 43.
  • Cooling water KW is supplied via the connecting lines 39 and 41.
  • the cooling water of the connecting line 39 first passes through a longitudinal channel 44 to the annular space 42 surrounding the most thermally stressed anode 3.
  • the cooling water flows through the cavity 43 of the lateral surface of the neutrodes 6 to 12 back through a longitudinal channel 45 into the annular space 37
  • the cooling water of the connecting line 41 flows into an annular space 38 and out of this into a cavity 46 of the cathode shaft part 52, which is divided by a cylindrical partition wall 47.
  • the cooling water finally arrives from the cathode shafts into the annular space 37, from which it flows out via the connecting line 40.
  • FIG. 3 shows the approximate course of the arc 48 during operation of the plasma spraying device according to FIGS. 1 and 2, as well as the flow course of the plasma gas PG and the trajectory of the spraying material SM.
  • the effect of the constriction zone 33 and the subsequent expansion of the plasma channel 4 can be clearly seen.
  • the distance between the channel wall 50 and the plasma beam is relatively large. Under these circumstances, the channel wall 50 is subjected to less thermal stress in this area, and the cooling capacity can be reduced accordingly.
  • FIG. 4 and 5 show an embodiment of the plasma spraying device which has been modified in the region of the cathode space and which can otherwise be of the same design as that of FIG. 1.
  • the same reference numerals as in FIG. 1 are used for the constant parts of the device been.
  • the gas distribution ring 29 in FIG. 1 is replaced by a gas distribution disk 53, which is located in front of the central insulation body 54 and extends radially from the central tube 24 for the supply of the spray material to the wall 55 of the inlet nozzle 6 extends.
  • This gas distribution disk 53 is provided with a plurality of through bores 56 arranged in a circle for the inlet of the plasma gas from the ring channel 57 into the nozzle cavity 22 of the inlet nozzle 6.
  • the passage bores 56 have a tangential directional component, so that the plasma gas flows into the inlet nozzle 6 in a vortex around the central longitudinal axis 2.
  • the same measure can of course also be provided for the gas distribution ring 29 according to FIG. 1.
  • the front surface of the insulating body 54 facing the gas distribution disk 53 is set back in some areas, so that a sector-shaped cavity 58 results in these areas, which is delimited by the parts 59 reaching as far as the gas distribution disk 53 (chain-dotted lines in FIG. 5).
  • the through bores 60, through which the cathode pins 20 extend, have a somewhat larger diameter than the cathode pins 20. Due to the gap and the cavity 58 due to the diameter difference, part of the plasma gas flows from the annular space 57 directly along the cathode pins 20 into the nozzle cavity 22.
  • the flow pattern is indicated by arrows 61.
  • FIG. 6 to 8 show a further variant of the means for supplying the plasma gas into the cathode compartment.
  • the parts that remain the same as in FIG. 4 are provided with the same reference numerals.
  • a e.g. copper guide sleeve 70 is provided, which occupies the annular space between the central insulation body 71 and the cathode near the neutrode 72 and has continuous longitudinal grooves 73 on the outside for the gas passage.
  • the longitudinal grooves 73 run in a helical shape, so that the plasma gas flowing from the annular space 57 in the direction of the arrow 74 into the longitudinal grooves 73 exits the guide sleeve 70 in a vortex shape.
  • the guide sleeve 70 extends to close to the wall 75 of the neutrode 72 delimiting the constriction area.
  • sector-shaped cavities 76 are provided in the insulating body 71 on the front side of the cathode shaft parts 52, from which part of the plasma gas flows along the same in the nozzle cavity 22 for additional cooling of the cathode pins 20.
  • the plasma gas enters each of these sector-shaped cavities 76 through a longitudinal gap 77, which is connected to a radial inlet bore 78 in the insulating body 71.
  • the flow pattern is indicated by arrow 79.

Abstract

The plasma spray gun contains an indirect plasmatron for generating a long arc, having a plasma channel (4) between the cathode arrangement (1, 20) and the anode ring (3). The cathode arrangement has a central insulation body (21) which projects into the cavity (22) of an inlet nozzle (5) of the plasma channel (4). The plasma gas is introduced into the inlet nozzle (5) through an annular channel (23) between the insulation body (21) and the nozzle wall. A plurality of rod-shaped cathodes (1) which are embedded in the insulation body (21) run parallel to one another and are arranged distributed in the circle around a central axis (2) whose active ends (63) project out of the insulation body (21) into the nozzle cavity. The spray material (SM) is supplied to the cathode-side end of the plasma channel (4) through a tube (24) which extends along the central axis (2) through the insulation body (21) and opens into the nozzle cavity, the cathode ends (20) projecting beyond the mouth (25) of the tube. By means of a high energy concentration in the nozzle cavity, energy is supplied to the spray material in this region and through the long arc along the entire plasma channel, so that the spray material emerges from the gun in the fused state with high acceleration. The anode ring has no nozzle function and can therefore be wide enough for the spray material not to impinge on it. <IMAGE>

Description

Die Erfindung betrifft ein Plasmaspritzgerät zum Versprühen von pulverförmigem oder gasförmigem Material nach dem Oberbegriff des Patentanspruchs 1.The invention relates to a plasma spraying device for spraying powdery or gaseous material according to the preamble of claim 1.

Ein Plasmaspritzgerät dieser Art ist aus der EP 0 249 238 A2 bekannt. Die Kathodenanordnung besteht bei diesem Gerät aus einer Stabkathode, und die Zufuhr des Spritzmaterials erfolgt am anodenseitigen Ende des Plasmaführungskanals durch ein seitlich in diesen Kanal eingeführtes Rohr, dessen Endpartie in die Kanalachse umgebogen ist.A plasma spraying device of this type is known from EP 0 249 238 A2. In this device, the cathode arrangement consists of a rod cathode, and the spray material is supplied at the anode-side end of the plasma guide channel through a tube inserted laterally into this channel, the end part of which is bent into the channel axis.

Der Wirkungsgrad eines derartigen Plasmaspritzgeräts ist ziemlich gering, da ein erheblicher Teil der Lichtbogenenergie durch Wärmeübergang an die gekühlte Wandung des verhältnismässig engen Plasmaführungskanals vorlorengeht und für das Aufschmelzen und Beschleunigen des Spritzmaterials nur die verbleibende Energie des freien Plasmastrahls zur Verfügung steht. Ausserdem führt die gewählte Anordnung der Austrittsdüse für die Zufuhr des Spritzmaterials innerhalb des Plasmaführungskanals zu Schwierigkeiten, weil die Austrittsdüse und der Plasmastrahl sich gegenseitig ungünstig beeinflussen. Einerseits wird die Strömung des Plasmastrahls durch die Austrittsdüse mechanisch behindert, andererseits wird die Austrittsdüse im Zentrum des Plasmastrahls thermisch ausserordentlich stark beansprucht.The efficiency of such a plasma spraying device is quite low, since a considerable part of the arc energy is transferred to the cooled wall of the relatively narrow plasma guide channel due to heat transfer and only the remaining energy of the free plasma jet is available for melting and accelerating the spray material. In addition, the chosen arrangement of the outlet nozzle for the supply of the spray material within the plasma guide channel leads to difficulties because the outlet nozzle and the plasma jet adversely affect one another. On the one hand, the flow of the plasma jet through the outlet nozzle is mechanically impeded, on the other hand, the outlet nozzle in the center of the plasma jet is subjected to extremely high thermal stress.

Die Erfindung sucht diese Nachteile durch eine Verlegung der Spritzmaterialzufuhr an das kathodenseitige Ende des Plasmakanals zu vermeiden. Vorschläge in dieser Richtung sind zwar an sich bekannt; deren Anwendung in Verbindung mit einem Plasmaspritzgerät der eingangs genannten Art haben aber bisher zu keinen befriedigenden Ergebnissen geführt.The invention seeks to avoid these disadvantages by moving the spray material supply to the cathode-side end of the plasma channel. Proposals in this direction are known per se; However, their use in connection with a plasma spraying device of the type mentioned at the outset has not led to satisfactory results.

Das DE-GM 1 932 150 zeigt ein Plasmaspritzgerät mit einem indirekten Plasmatron, das mit einem Kurzlichtbogen arbeitet. Eine hohlzylindrische Kathode arbeitet mit einer ebenfalls hohlzylindrischen, düsenförmig ausgebildeten Anode zusammen, wobei die Kathode in die koachsial zu dieser angeordneten Anode hineinragt. Die Hohlkathode dient zugleich als Zuführrohr für das Spritzmaterial, das auf diese Weise achsial in den Lichtbogenraum eingeführt wird. Das Plasmagas gelangt durch den Ringspalt zwischen Kathode und Anode in den Lichtbogenraum und anschliessend in die Anodendüse, durch welche der Plasmastrahl eingeschnürt wird.DE-GM 1 932 150 shows a plasma spraying device with an indirect plasmatron that works with a short arc. A hollow cylindrical cathode works together with a likewise hollow cylindrical, nozzle-shaped anode, the cathode protruding into the anode arranged coaxially to this. The hollow cathode also serves as a feed pipe for the spray material, which is introduced axially into the arc space in this way. The plasma gas passes through the annular gap between the cathode and anode into the arc space and then into the anode nozzle, through which the plasma jet is constricted.

Die Anwendung einer Hohlkathode in einem Plasmatron mit Langlichtbogen bereitet jedoch, insbesondere bei hohen Lichbogenströmen, enorme technische Schwierigkeiten, da wegen des meist lokalen kathodischen Lichtbogenansatzes (Brennfleck) eine thermische Überlastung und damit eine vorzeitige Abnützung der Kathode eintreten kann. Durch elektromagnetisch bewirkte Rotation des Lichtbogenansatzes entlang des Kathodenrands lässt sich diese Gefahr zwar vermindern. Auch kann durch Nachführen der Kathode, wie z.B. im Falle der längsbeweglichen Stabkathode nach der EP 0 249 238 A2 eine Abnützung derselben kompensiert werden. Beide Lösungen sind aber mit erhöhtem Aufwand verbunden.However, the use of a hollow cathode in a plasmatron with a long arc causes enormous technical difficulties, especially with high arc currents, since thermal overloading and thus premature wear of the cathode can occur due to the mostly local cathodic arc approach (focal spot). This risk can be reduced by electromagnetically caused rotation of the arc attachment along the edge of the cathode. Also by tracking the cathode, e.g. in the case of the longitudinally movable rod cathode according to EP 0 249 238 A2, wear thereof can be compensated. Both solutions are associated with increased effort.

Eine Verbesserung in dieser Hinsicht ergibt sich, wenn die zentrale Hohlkathode durch eine Mehrzahl von Stabkathoden ersetzt wird und das Spritzmaterial durch ein im Zentrum der Kathoden angeordnetes Rohr zugeführt wird. Ein Beispiel für eine solche Lösung zeigt die DE-OS 33 12 232 A1 an einem Plasmaspritzgerät mit einem direkten Plasmatron, d.h. mit einem auf das Werkstück übertragenen Lichtbogen.An improvement in this regard results if the central hollow cathode is replaced by a plurality of rod cathodes and the spray material is fed through a tube arranged in the center of the cathodes. DE-OS 33 12 232 A1 shows an example of such a solution on a plasma spraying device with a direct plasmatron, i.e. with an arc transferred to the workpiece.

Ein anderes Plasmaspritzgerät der genannten Art, mit einem indirekten Plasmatron, das mit einem Kurzlichtbogen arbeitet, besitzt ebenfalls eine Mehrzahl von Stabkathoden, welche im Kreis um die Achse einerAnodendüse parallel zueinander angeordnet sind. Den Kathoden sind Hilfsanoden zur Zündung von Pilotlichtbögen zugeordnet, von denen aus unter der Einwirkung des längs der Kathoden strömenden Plasmagases Einzellichtbögen zur Anodendüse gezogen werden, welche einen im Zentrum der Anodendüse vereinigten Plasmastrom erzeugen. Durch ein im Zentrum der Kathodenanordnung befindliches Rohr wird das Spritzmaterial achsial in den Lichtbogenraum eingeführt, und zwar direkt an den Vereinigungspunkt der einzelnen Plasmaströme. Zwar lässt sich durch die Stromaufteilung auf mehrere Kathoden deren Standzeit infolge geringerer thermischer Belastung erhöhen. Da sich aber die drei Einzellichtbögen nicht zwangsläufig im Zentrum derAnodendüse vereinigen und nicht in den Plasmaführungskanal eindringen, sondern an Anodenpartien ansetzen, die den Kathoden näher liegen, findet keine höchstmögliche Energiekonzentration im Zentrum des Lichtbogenraums statt, d.h. dort wo das Spritzmaterial aus dem zentralen Zuführrohr hingelangt. Somit ist davon auszugehen, dass auch in diesem Fall dem Spritzmaterial die zum Aufschmelzen der Partikel erforderliche Energie grösstenteils erst im freien Plasmastrahl zugeführt wird. Dies dürfte sogar erwünscht sein, weil unter diesen Umständen die Pulverteilchen bis zum Austritt aus der Anodendüse noch nicht aufgeschmolzen sind und sich daher nicht an der Wandung derselben niederschlagen können.Another plasma spraying device of the type mentioned, with an indirect plasma matron, which works with a short arc, also has a plurality of rod cathodes, which are arranged parallel to one another in a circle around the axis of an anode nozzle. Auxiliary anodes for igniting pilot arcs are assigned to the cathodes, from which individual arcs are drawn to the anode nozzle under the action of the plasma gas flowing along the cathodes and which generate a plasma stream combined in the center of the anode nozzle. The spray material is introduced axially into the arc space through a tube located in the center of the cathode arrangement, specifically directly at the point of union of the individual plasma flows. It is true that by dividing the current over several cathodes, their service life can be increased due to the lower thermal load. However, since the three individual arcs do not necessarily merge in the center of the anode nozzle and do not penetrate into the plasma guide channel, but instead attach to anode parts that are closer to the cathodes, there is no maximum possible energy concentration in the center of the arc space, i.e. where the spray material comes from the central feed pipe. It can therefore be assumed that in this case too, the spray material is largely supplied with the energy required to melt the particles only in the free plasma jet. This may even be desirable because, in these circumstances, the powder particles have not yet melted until they exit the anode nozzle and therefore cannot be deposited on the wall of the same.

Demgegenüber bezweckt die Erfindung, eine höchstmögliche Energiekonzentration, die bereits im Nahbereich der Kathodenanordnung beginnt und sich bis zur Anode bzw. noch darüber hinaus erstreckt, zu erzielen.In contrast, the invention aims to achieve the highest possible energy concentration that begins in the vicinity of the cathode arrangement and extends to the anode or even beyond.

Dieses Ziel lässt sich durch die im Kennzeichen des Patentanspruchs 1 genannten Massnahmen erreichen.This goal can be achieved by the measures mentioned in the characterizing part of patent claim 1.

Die gewählte Kathodenanordnung in einem mit Langlichtbogen arbeitenden, indirekten Plasmatron, in Verbindung mit der durch die Einlaufdüse gebildeten Einschnürung, gewährleistet eine grösstmögliche Energiekonzentration im Düsenhohlraum. Das Spritzmaterial, welches durch das in der zentralen Achse angeordnete Zuführrohr, normalerweise mit Hilfe eines Trägergases, eingebracht wird, dringt bereits in Kathodennähe in den heissen Kern des Plasmastrahls ein, in welchem das Sprühmaterial, z.B. die Pulverteilchen aufgeschmolzen und weiterbeschleunigt werden. Durch Variation des Trägergasflusses lässt sich in einfacher Weise die Anfangsgeschwindigkeit der Pulverteilchen und damit auch die technisch wichtige Verweilzeit derselben im Plasma einstellen. Mit diesen Grössen können in Verbindung mit einer geeigneten Wahl des Plasmagasflusses und des Lichtbogenstroms optimale Betriebsbedingungen erreicht werden.The selected cathode arrangement in an indirect plasmatron working with a long arc, in connection with the constriction formed by the inlet nozzle, ensures the greatest possible energy concentration in the nozzle cavity. The spray material, which is introduced through the feed pipe arranged in the central axis, usually with the aid of a carrier gas, penetrates into the hot core of the plasma jet near the cathode, in which the spray material, for example the powder particles, is melted and further accelerated. By varying the carrier gas flow, the initial speed of the powder particles and thus also the technically important residence time of the powder particles can be set in a simple manner. With these sizes, in combination with a suitable choice of plasma gas flow and arc current, optimal operating conditions can be achieved.

Der zentrale Isolationskörper dient nicht nur dazu, die Stabkathoden untereinander und gegenüber dem Zuführrohr elektrisch zu isolieren, sondern hat auch die Aufgabe, zusammen mit der Einlaufdüse einen Ringkanal zu bilden, durch welchen das Plasmagas in möglichst laminarer Form in den Kathodenraum einströmt. Wichtig ist dabei auch, dass das Plasmagas den aus dem Isolierkörpervorstehenden Kathodenspitzen entlang strömt, welche dadurch zusätzlich gekühlt werden. Dies führt zu einer Erhöhung der Kathodenstandzeit.The central insulation body not only serves to electrically insulate the rod cathodes from one another and from the feed tube, but also has the task of forming an annular channel together with the inlet nozzle, through which the plasma gas flows into the cathode space in the most laminar form possible. It is also important that the plasma gas flows along the cathode tips protruding from the insulating body, which tips are additionally cooled as a result. This leads to an increase in cathode life.

In einer der möglichen Ausführungsformen grenzt der Isolationskörper unmittelbar an den Lichtbogenraum an und ist daher thermisch stark belastet. Er besteht deshalb vorzugsweise aus einem hochschmelzenden Material, z.B. aus Keramik oder Bornitrid.In one of the possible embodiments, the insulation body directly adjoins the arcing space and is therefore highly thermally stressed. It is therefore preferably made of a high-melting material, e.g. made of ceramic or boron nitride.

Mit Rücksicht auf die thermische Belastung der Kathoden weisen diese vorzugsweise einen wassergekühlten Kathodenschaft und an ihrem aktiven Ende einen in den Kathodenschaft eingesetzten Kathodenstift aus einem hochschmelzenden Material auf. Z.B. kann der Kathodenschaft aus Kupfer und der Kathodenstift aus thoriertem Wolfram bestehen.With regard to the thermal load on the cathodes, they preferably have a water-cooled cathode shaft and at their active end a cathode pin made of a high-melting material and inserted into the cathode shaft. E.g. the cathode shaft can be made of copper and the cathode pin of thoriated tungsten.

Die aktiven Enden der Kathoden sollten so nahe wie betriebsmässig möglich beieinander liegen, damit die Vereinigung der von diesen ausgehenden Lichtbogenäste möglichst nahe der Bogenansatzstellen stattfindet. Da aber die Kathodenschäfte aufgrund der Hohlräume für die Wasserkühlung einen verhältnismässig grossen Durchmesser aufweisen und aus Isolationsgründen einen minimalen gegenseitigen Abstand haben müssen, lässt sich bei koaxialer Anordnung des Kathodenstifts zum Kathodenschaft nicht der gewünschte geringe gegenseitige Abstand der Kathodenstifte erreichen. Die Anordnung könnte zwar so getroffen sein, dass die Kathodenstifte schräg aufeinander zulaufen; eine solche Lösung ist jedoch vom Gesichtspunkt der Herstellung aus nicht befriedigend. Eine bevorzugte Lösung besteht deshalb darin, den Kathodenstift exzentrisch in den Kathodenschaft einzusetzen, so dass die Längsachse des Kathodenstifts der zentralen Längsachse näher liegt als diejenige des Kathodenschafts.The active ends of the cathodes should be as close together as possible in operational terms so that the arc branches emanating from them come together as close as possible to the arc attachment points. However, since the cathode shafts have a relatively large diameter due to the cavities for water cooling and must have a minimum mutual spacing for insulation reasons, the desired small mutual spacing of the cathode pins cannot be achieved when the cathode pin is arranged coaxially with the cathode shaft. The arrangement could be such that the cathode pins run obliquely towards one another; however, such a solution is unsatisfactory from a manufacturing standpoint. A preferred solution therefore consists in inserting the cathode pin eccentrically into the cathode shaft, so that the longitudinal axis of the cathode pin is closer to the central longitudinal axis than that of the cathode shaft.

Zur Erzielung einer laminaren Einströmung des Plasmagases in die Einlaufdüse hat es sich als zweckmässig erwiesen, eine Gasverteilanordnung mit einer Mehrzahl von Düsen vorzusehen. Beispielsweise kann dem zwischen dem Isolationskörper und der Einlaufdüse vorhandenen Ringkanal ein auf dem Isolationskörper sitzender Gasverteilring mit einer Mehrzahl von Durchgangsbohrungen für den Einlass des Plasmagases in den Ringkanal vorgelagert sein.In order to achieve a laminar inflow of the plasma gas into the inlet nozzle, it has proven to be expedient to provide a gas distribution arrangement with a plurality of nozzles. For example, a gas distribution ring with a plurality of through holes for the inlet of the plasma gas into the ring channel can be arranged in front of the ring channel between the insulation body and the inlet nozzle.

Eine noch vorteilhaftere Lösung besteht allerdings darin, dass dem Isolationskörper eine Gasverteilscheibe vorgelagert ist, welche sich radial vom zentralen Rohr für die Zufuhr des Spritzmaterials bis an die Wandung der Einlaufdüse erstreckt und welche mit einer Mehrzahl von im Kreis angeordneten Durchlassbohrungen für den Einlass des Plasmagases aus dem Ringkanal in die Einlaufdüse versehen ist. Die Durchlassbohrungen haben hier die gleiche Wirkung wie diejenigen bei dem vorher erwähnten Gasverteilring. Diese Gasverteilscheibe schirmt jedoch die ganze Frontseite des Isolationskörpers gegen die Einwirkung der Lichtbogenwärme ab, so dass nunmehr der Isolationskörper nicht mehr aus verhältnismässig teurem hochschmelzenden Material bestehen muss. Dagegen soll die Gasverteilscheibe eine entsprechende Wärmebeständigkeit aufweisen, wobei jedoch fürdie Gasverteilscheibe erheblich wenigervon dem hochschmelzenden Material benötigtwird als sonst für den Isolationskörper und im übrigen eine weniger komplizierte Form hat als jener, was zu einer einfacheren und billigeren Lösung führt.An even more advantageous solution, however, is that the insulation body is preceded by a gas distribution disk, which extends radially from the central tube for supplying the spray material to the wall of the inlet nozzle and which has a plurality of circular bores arranged for the inlet of the plasma gas the ring channel is provided in the inlet nozzle. The through holes have the same effect here as those in the gas distribution ring mentioned above. However, this gas distribution disk shields the entire front side of the insulation body against the action of the arc heat, so that the insulation body no longer has to be made of relatively expensive high-melting material. On the other hand, the gas distribution disk should have a corresponding heat resistance, but for the gas distribution disk considerably less of the refractory material is required than otherwise for the insulating body and, moreover, it has a less complicated shape than that, which leads to a simpler and cheaper solution.

Aufgrund ihrer Plazierung unmittelbar vor dem Isolationskörper besitzt die Gasverteilscheibe weitere Durchgangsbohrungen, durch welche sich die Kathodenstifte erstrecken. Vorzugsweise haben diese Durchgangsbohrungen einen grösseren Durchmesser als die Kathodenstifte. Dies ermöglichtes, einen Teil des Plasmagases durch den aufgrund der Durchmesserdifferenz bestehenden Ringspalt entlang der Kathodenstifte zu leiten, womit die Kühlung derselben weiter verbessert wird.Because of its placement directly in front of the insulation body, the gas distribution disk has further through bores through which the cathode pins extend. These through bores preferably have a larger diameter than the cathode pins. This enables a part of the plasma gas to be passed through the annular gap along the cathode pins due to the difference in diameter, which further improves the cooling thereof.

Im übrigen können die Durchlassbohrungen für das Plasmagas sowohl bei dem Gasverteilring als auch bei der Gasverteilscheibe, anstatt achsial, tangential zu virtuellen, zentralachsigen Schraubenlinien verlaufen. Dadurch lässt sich eine Wirbelströmung des Plasmagases erreichen, was sich unter gewissen Betriebsbedingungen als vorteilhaft erwiesen hat.Otherwise, the through holes for the plasma gas can run both in the gas distribution ring and in the gas distribution disk, instead of axially, tangentially to virtual, central-axis helical lines. This allows a vortex flow of the plasma gas to be achieved, which has proven to be advantageous under certain operating conditions.

Die Bahnen der geschmolzenen Pulverteilchen unterliegen dem Schroteffekt, d.h. sie verlaufen in einem Kegel, der längs des Plasmakanals bis zur Mündung desselben an der ringförmigen Anode innerhalb des Kanalquerschnitts liegen muss, damit sich keine geschmolzenen Teilchen an der Kanalwandung ablagern können. Diese Bedingung lässt sich ebenfalls durch geeignete Wahl der Betriebsparameter sowie durch ein entsprechendes Längsprofil des Plasmakanals erreichen, z.B. dadurch, dass sich der Plasmakanal im Anschluss an die Einlaufdüse zur Anode hin stetig erweitert.The paths of the molten powder particles are subject to the shot effect, ie they run in a cone which must lie along the plasma channel up to the mouth of the ring-shaped anode within the channel cross section so that no molten particles can be deposited on the channel wall. This condition can also be determined by suitable selection of the operating parameters and by achieve the corresponding longitudinal profile of the plasma channel, for example by continuously expanding the plasma channel towards the anode following the inlet nozzle.

In der Zeichnung sind Ausführungsbeispiele der Erfindung dargestellt, und zwar zeigen:

  • Fig. 1 ein Plasmaspritzgerät nach der Erfindung im Längs schnitt;
  • Fig. 2 einen auf den Kathodenraum beschränkten Querschnitt nach den Linien 11-11 in Fig. 1, in grösserem Mass stab;
  • Fig. 3 eine schematische Schnittansicht des Plasmakanals gemäss der Ausführungsform nach Fig. 1 in grösserem Massstab, mit eingezeichneter Plasma- und Spritz materialströmung;
  • Fig. 4 einen auf den Kathodenraum beschränkten Teillängs schnitt einer in diesem Bereich abgeänderten Ausfüh rungsform des erfindungsgemässen Plasmaspritzgeräts;
  • Fig. 5 eine Ansicht auf die den Lichtbogenraum rückseitig abschliessenden Teile aus der Richtung X in Fig. 4;
  • Fig. 6 einen auf den Kathodenraum beschränkten Teillängs schnitt mit einer weiteren Variante der Mittel zur Gasführung in diesem Bereich;
  • Fig. 7 eine Ansicht auf die den Lichtbogenraum rückseitig anschliessenden Teile aus der Richtung X in Fig. 6; und
  • Fig. 8 eine Seitenansicht der in der Ausführungsform nach den Fig. 6 und 7 vorgesehenen Gasführungshülse.
Exemplary embodiments of the invention are shown in the drawing, namely:
  • Figure 1 is a plasma spray device according to the invention in longitudinal section.
  • Figure 2 is a cross-section limited to the cathode space along the lines 11-11 in Figure 1, to a greater extent rod.
  • Fig. 3 is a schematic sectional view of the plasma channel according to the embodiment of Figure 1 on a larger scale, with the plasma and spray material flow shown.
  • 4 shows a partial longitudinal section, restricted to the cathode compartment, of a modified embodiment of the plasma spraying device according to the invention in this area;
  • 5 shows a view of the parts closing off the arc chamber on the rear from the direction X in FIG. 4;
  • 6 shows a partial longitudinal section restricted to the cathode compartment with a further variant of the means for gas guidance in this area;
  • FIG. 7 shows a view of the parts adjoining the back of the arc chamber from the direction X in FIG. 6; and
  • Fig. 8 is a side view of the gas guide sleeve provided in the embodiment of FIGS. 6 and 7.

Das Plasmaspritzgerät nach den Fig. 1 und 2 besitzt drei stabförmige Kathoden 1, welche parallel zueinander verlaufen und im Kreis um die zentrale Längsachse 2 des Geräts gleichmässig verteilt angeordnet sind, ferner eine von den Kathoden 1 distanzierte ringförmige Anode 3 und einen von den Kathoden 1 zur Anode 3 sich erstreckenden Plasmakanal 4. Der Plasmakanal 4 ist durch eine Anzahl ringförmiger, voneinander elektrisch isolierter Neutroden 6 bis 12 und die ringförmige Anode 3 gebildet.1 and 2 has three rod-shaped cathodes 1, which run parallel to one another and are evenly distributed in a circle around the central longitudinal axis 2 of the device, furthermore an annular anode 3 distanced from the cathodes 1 and one from the cathodes 1 to the anode 3 extending plasma channel 4. The plasma channel 4 is formed by a number of ring-shaped neutrodes 6 to 12 which are electrically insulated from one another and the ring-shaped anode 3.

Die Kathoden 1 weisen je einen aus zwei Teilen 51 und 52 bestehenden Kathodenschaft z.B. aus Kupfer auf, welcher in einem Kathodenträger 13 aus Isoliermaterial verankert ist. An diesen schliesst sich ein hülsenfönniger Anodenträger 14 aus Isoliermaterial an, der die Neutroden 6 bis 12 und die Anode 3 umgibt. Das Ganze wird zusammengehalten durch drei Metallhülsen 15, 16, 17, wobei die erste Hülse 15 mit dem Kathodenträger 13 stirnseitig und die zweite Hülse 16 mit der ersten umfänglich verschraubt ist, während die dritte Hülse 17 einerseits an der zweiten Hülse 16 lose verankert und andererseits mit dem Anodenträger 14 umfänglich verschraubt ist. Die dritte Hülse 17 drückt ausserdem mit einem nach innen gerichteten Flanschrand 18 gegen den Anodenring 3 und hält damit die den Plasmakanal 4 bildenden Elemente zusammen, wobei sich die den Kathoden 1 am nächsten liegende Neutrode 6 an einem Innenbund 19 des Anodenträgers 4 abstützt.The cathodes 1 each have a cathode shaft consisting of two parts 51 and 52, e.g. made of copper, which is anchored in a cathode support 13 made of insulating material. This is followed by a sleeve-shaped anode carrier 14 made of insulating material, which surrounds the neutrodes 6 to 12 and the anode 3. The whole is held together by three metal sleeves 15, 16, 17, the first sleeve 15 being screwed to the end on the end face and the second sleeve 16 being screwed to the first circumference, while the third sleeve 17 is loosely anchored on the one hand to the second sleeve 16 and on the other hand is screwed circumferentially to the anode carrier 14. The third sleeve 17 also presses with an inwardly directed flange 18 against the anode ring 3 and thus holds the elements forming the plasma channel 4 together, the neutrode 6 closest to the cathodes 1 being supported on an inner collar 19 of the anode carrier 4.

Die Kathoden 1 tragen an ihren Enden Kathodenstifte 20, welche aus einem elektrisch und thermisch besonders gut leitenden und zudem hochschmelzenden Material, z.B. Wolfram, bestehen. Dabei sind die Kathodenstifte 20 derart exzentrisch zur jeweiligen Achse der Kathodenschäfte 51, 52 angeordnet, dass deren Längsachsen der zentralen Längsachse 2 näher liegen als diejenigen der Kathodenschäfte.The cathodes 1 carry at their ends cathode pins 20, which are made of an electrically and thermally particularly conductive and also high-melting material, e.g. Tungsten. The cathode pins 20 are arranged eccentrically to the respective axis of the cathode shafts 51, 52 in such a way that their longitudinal axes are closer to the central longitudinal axis 2 than those of the cathode shafts.

An den Kathodenträger 13 ist auf der dem Plasmakanal 4 zugewandten Seite ein zentraler Isolierkörper 21 aus hochschmelzendem Material, z.B. Keramik oder Bornitrid, angesetzt, welcher in fester Position zur ersten Neutrode 6 angeordnet ist und aus dem die Kathodenstifte 20 heraus in den Hohlraum 22 der durch die ersten Neutrode 6 gebildeten Einlaufdüse ragen. Der freiliegende Teil der äusseren Mantelfläche des Isolierkörpers 21 liegt einem Teil der Düsenwandung radial gegenüber und bildet mit diesem Wandungsteil einen Ringkanal 23 für den Einlass des Plasmagases in den Düsenhohlraum 22.On the cathode support 13, on the side facing the plasma channel 4, there is a central insulating body 21 made of refractory material, e.g. Ceramic or boron nitride, which is arranged in a fixed position to the first neutrode 6 and from which the cathode pins 20 protrude into the cavity 22 of the inlet nozzle formed by the first neutrode 6. The exposed part of the outer circumferential surface of the insulating body 21 lies radially opposite a part of the nozzle wall and forms with this wall part an annular channel 23 for the inlet of the plasma gas into the nozzle cavity 22.

Die Zufuhr des Spritzmaterials SM, z.B. Metall- oder Keramikpulver, in den Plasmastrahl erfolgt mit Hilfe eines Trägergases TG am kathodenseitigen Ende des Plasmakanals 4. Zu diesem Zweck ist ein in der Längsachse 2 verlaufendes und vom Isolierkörper 21 gehaltenes Rohr 24 vorgesehen, das ebenfalls in den Düsenhohlraum 22 mündet, wobei sich die Kathodenstifte 20 über die Mündung 25 des Rohrs 24 hinaus erstrecken.The supply of the spray material SM, e.g. Metal or ceramic powder into the plasma jet is carried out with the aid of a carrier gas TG at the cathode-side end of the plasma channel 4. For this purpose, a pipe 24 running in the longitudinal axis 2 and held by the insulating body 21 is provided, which likewise opens into the nozzle cavity 22, whereby the cathode pins 20 extend beyond the mouth 25 of the tube 24.

Das Plasmagas PG wird durch einen im Kathodenträger 13 vorgesehenen Querkanal 26 zugeführt, welcher in einen Längskanal 27 übergeht, aus dem das Plasmagas in einen Ringraum 28 und von da in den Ringkanal 23 gelangt. Zur Erzielung einer möglichst laminaren Einströmung des Plasmagases in den Düsenhohlraum 22 ist ein auf dem Isolierkörper 21 sitzender Gasverteilring 29 mit einer Mehrzahl von Durchgangsbohrungen 30 vorgesehen, welche den Ringraum 28 mit dem Ringkanal 23 verbinden.The plasma gas PG is fed through a transverse channel 26 provided in the cathode carrier 13, which crosses into a longitudinal channel 27 from which the plasma gas reaches an annular space 28 and from there into the annular channel 23. In order to achieve a flow of the plasma gas into the nozzle cavity 22 that is as laminar as possible, a gas distribution ring 29 is provided on the insulating body 21 and has a plurality of through bores 30 which connect the annular space 28 to the annular channel 23.

Die den Plasmakanal 4 bildenden Elemente, nämlich die Anode 3 und die Neutroden 6 bis 12, sind durch Ringscheiben 31 aus Isoliermaterial, z.B. Bornitrid, gegeneinander elektrisch isoliert und durch Dichtungsringe 32 gasdicht miteinander verbunden. Der Plasmakanal 4 weist im kathodennahen Bereich eine Einschnürungszone 33 auf und erweitert sich im Anschluss an diese Einschnürungszone 33 zur Anode 3 hin auf einen Durchmesser, welcher mindestens 1,5-mal so gross ist wie der Kanaldurchmesser an der engsten Stelle der Einschnürungszone 33. Nach dieser Erweiterung verläuft der Plasmakanal 4 zylindrisch bis an sein anodenseitiges Ende. Während die Neutroden 6 bis 12 z.B. aus Kupfer bestehen, ist die Anode 3 aus einem Aussenring 34, z.B. aus Kupfer, und einem Innenring 35 aus einem elektrisch und thermisch besonders gut leitenden und zudem hochschmelzenden Material, z.B. Wolfram, aufgebaut.The elements forming the plasma channel 4, namely the anode 3 and the neutrodes 6 to 12, are electrically insulated from one another by ring disks 31 made of insulating material, for example boron nitride, and are gas-tightly connected to one another by sealing rings 32. The plasma channel 4 has a constriction zone 33 in the vicinity of the cathode and, following this constriction zone 33, widens towards the anode 3 to a diameter which is at least 1.5 times the channel diameter at the narrowest point of the constriction zone 33 this expansion, the plasma channel 4 runs cylindrical to its anode-side end. While the neutrodes 6 to 12 consist of copper, for example, the anode 3 is made of an outer ring 34, for example made of copper, and an inner ring 35 made of an electrically and thermally particularly conductive and also high-melting material, such as tungsten.

Um die Plasmaströmung, insbesondere im Düsenbereich, nicht durch Spalte in der Wandung des Plasmakanals 4 zu behindern, erstreckt sich die den Kathodenstäben 1 am nächsten liegende Neutrode 6 über die ganze Einschnürungszone 33, damit die Kanalwandung 5 bis über die engste Stelle der Einschnürungszone hinaus einen stetigen Verlauf aufweist.In order not to impede the plasma flow, in particular in the nozzle area, by gaps in the wall of the plasma channel 4, the neutrode 6 closest to the cathode rods 1 extends over the entire constriction zone 33, so that the channel wall 5 unites beyond the narrowest point of the constriction zone has a steady course.

Die der Lichtbogen- und Plasmawärme unmittelbar ausgesetzten Teile sind weitgehend wassergekühlt. Zu diesem Zweck sind im Kathodenhalter 13, im Teil 52 des Kathodenschafts und im Anodenhalter 14 verschiedene Hohlräume für die Zirkulation des Kühlwassers KW vorgesehen. Der Kathodenhalter 13 weist drei Ringräume 36, 37, und 38 auf, die mit Anschlussleitungen 39, 40 bzw. 41 verbunden sind, und der Anodenhalter 14 weist im Bereich der Anode 3 einen Ringraum 42 und im Bereich der Neutroden 6 bis 12 einen alle Neutroden umgebenden Hohlraum 43 auf. Kühlwasser KW wird über die Anschlussleitungen 39 und 41 zugeführt. Das Kühlwasser der Anschlussleitung 39 gelangt durch einen Längskanal 44 zunächst zu dem die thermisch am stärksten belastete Anode 3 umgebenden Ringraum 42. Von da strömt das Kühlwasser durch den Hohlraum 43 der Mantelfläche der Neutroden 6 bis 12 entlang zurück durch einen Längskanal 45 in den Ringraum 37. Das Kühlwasser der Anschlussleitung 41 fliesst in einen Ringraum 38 und aus diesem in je einen Hohlraum 46 des Kathodenschaftteils 52, welcher durch eine zylindrische Trennwand 47 unterteilt ist. Aus den Kathodenschäften gelangt das Kühlwasser schliesslich in den Ringraum 37, aus dem es über die Anschlussleitung 40 abfliesst.The parts directly exposed to the arc and plasma heat are largely water-cooled. For this purpose, different cavities for the circulation of the cooling water KW are provided in the cathode holder 13, in part 52 of the cathode shaft and in the anode holder 14. The cathode holder 13 has three annular spaces 36, 37 and 38, which are connected to connecting lines 39, 40 and 41, and the anode holder 14 has an annular space 42 in the region of the anode 3 and all neutrodes in the region of the neutrodes 6 to 12 surrounding cavity 43. Cooling water KW is supplied via the connecting lines 39 and 41. The cooling water of the connecting line 39 first passes through a longitudinal channel 44 to the annular space 42 surrounding the most thermally stressed anode 3. From there, the cooling water flows through the cavity 43 of the lateral surface of the neutrodes 6 to 12 back through a longitudinal channel 45 into the annular space 37 The cooling water of the connecting line 41 flows into an annular space 38 and out of this into a cavity 46 of the cathode shaft part 52, which is divided by a cylindrical partition wall 47. The cooling water finally arrives from the cathode shafts into the annular space 37, from which it flows out via the connecting line 40.

Die Fig. 3 zeigt den ungefähren Verlauf des Lichtbogens 48 beim Betrieb des Plasmaspritzgeräts nach den Fig. 1 und 2, sowie den Strömungsverlauf des Plasmagases PG und die Flugbahn des Spritzmaterials SM. Man erkennt deutlich die Wirkung der Einschnürungszone 33 und der anschliessenden Erweiterung des Plasmakanals 4. Die von den einzelnen Kathodenstiften 20 ausgehenden Lichtbogenäste 49 vereinigen sich in unmittelbarer Nähe der Bogenansatzstellen, und zwar einerseits aufgrund des geringen gegenseitigen Abstands der Kathodenstifte 20 und andererseits wegen der kathodennahen Einschnürungszone 33, welche das Plasma und die Stromlinien derart einengen, dass sich im Zentrum des Plasmakanals 4 bereits an der Stelle der Spritzmaterialzufuhreine hohe Energiekonzentration ergibt und keine kalte Seele im Plasmastrahl auftritt. Im erweiterten Teil des Plasmakanals 4 ist der Abstand der Kanalwandung 50 zum Plasmastrahl verhältnismässig gross. Unter diesen Umständen wird die Kanalwandung 50 in diesem Bereich thermisch weniger beansprucht, und die Kühlleistung lässt sich dementsprechend verringern.3 shows the approximate course of the arc 48 during operation of the plasma spraying device according to FIGS. 1 and 2, as well as the flow course of the plasma gas PG and the trajectory of the spraying material SM. The effect of the constriction zone 33 and the subsequent expansion of the plasma channel 4 can be clearly seen. The arc branches 49 emanating from the individual cathode pins 20 unite in the immediate vicinity of the arc attachment points, on the one hand because of the small mutual spacing of the cathode pins 20 and on the other hand because of the constriction zone near the cathode 33, which constrict the plasma and the streamlines in such a way that a high energy concentration results in the center of the plasma channel 4 already at the point of the spray material feed and no cold soul occurs in the plasma jet. In the expanded part of the plasma channel 4, the distance between the channel wall 50 and the plasma beam is relatively large. Under these circumstances, the channel wall 50 is subjected to less thermal stress in this area, and the cooling capacity can be reduced accordingly.

Die Fig. 4 und 5 zeigen eine im Bereich des Kathodenraums abgeänderte Ausführungsform des Plasmaspritzgeräts, welche im übrigen gleich ausgebildet sein kann als dasjenige nach Fig. 1. Im vorliegenden Beispiel sind für die gleichbleibenden Teile des Geräts die gleichen Bezugszeichen wie in Fig. 1 verwendet worden.4 and 5 show an embodiment of the plasma spraying device which has been modified in the region of the cathode space and which can otherwise be of the same design as that of FIG. 1. In the present example, the same reference numerals as in FIG. 1 are used for the constant parts of the device been.

Der Unterschied zur ersten Ausführungsform besteht darin, dass der Gasverteilring 29 in Fig. 1 durch eine Gasverteilscheibe 53 ersetzt ist, welche dem zentralen Isolationskörper 54 vorgelagert ist und sich radial vom zentralen Rohr 24 für die Zufuhr des Spritzmaterials bis an die Wandung 55 der Einlaufdüse 6 erstreckt. Diese Gasverteilscheibe 53 ist mit einer Mehrzahl von im Kreis angeordneten Durchlassbohrungen 56 für den Einlass des Plasmagases aus dem Ringkanal 57 in den Düsenhohlraum 22 der Einlaufdüse 6 versehen. Wie in Fig. 5 angedeutet ist, haben die Durchlassbohrungen 56 eine tangentiale Richtungskomponente, so dass das Plasmagas in einem Wirbel um die zentrale Längsachse 2 in die Einlaufdüse 6 einströmt. Die gleiche Massnahme kann selbstverständlich auch bei dem Gasverteilring 29 nach Fig. 1 vorgesehen sein.The difference from the first embodiment is that the gas distribution ring 29 in FIG. 1 is replaced by a gas distribution disk 53, which is located in front of the central insulation body 54 and extends radially from the central tube 24 for the supply of the spray material to the wall 55 of the inlet nozzle 6 extends. This gas distribution disk 53 is provided with a plurality of through bores 56 arranged in a circle for the inlet of the plasma gas from the ring channel 57 into the nozzle cavity 22 of the inlet nozzle 6. As indicated in FIG. 5, the passage bores 56 have a tangential directional component, so that the plasma gas flows into the inlet nozzle 6 in a vortex around the central longitudinal axis 2. The same measure can of course also be provided for the gas distribution ring 29 according to FIG. 1.

Die der Gasverteilscheibe 53 zugewandte Frontfläche des Isolationskörpers 54 ist bereichsweise zurückgesetzt, so dass sich in diesen Bereichen ein sektorförmiger Hohlraum 58 ergibt, welcher durch die bis an die Gasverteilscheibe 53 reichenden Teile 59 (strickpunktiert in Fig. 5) begrenzt sind. Die Durchgangsbohrungen 60, durch welche sich die Kathodenstifte 20 erstrecken, haben einen etwas grösseren Durchmesser als die Kathodenstifte 20. Durch den aufgrund der Durchmesserdifferenz bestehenden Spalt und den Hohlraum 58 strömt ein Teil des Plasmagases aus dem Ringraum 57 unmittelbar den Kathodenstiften 20 entlang in den Düsenhohlraum 22. Der Strömungsverlauf ist durch die Pfeile 61 angedeutet.The front surface of the insulating body 54 facing the gas distribution disk 53 is set back in some areas, so that a sector-shaped cavity 58 results in these areas, which is delimited by the parts 59 reaching as far as the gas distribution disk 53 (chain-dotted lines in FIG. 5). The through bores 60, through which the cathode pins 20 extend, have a somewhat larger diameter than the cathode pins 20. Due to the gap and the cavity 58 due to the diameter difference, part of the plasma gas flows from the annular space 57 directly along the cathode pins 20 into the nozzle cavity 22. The flow pattern is indicated by arrows 61.

Die Fig. 6 bis 8 zeigen eine weitere Variante der Mittel für die Zufuhr des Plasmagases in den Kathodenraum. Die im Vergleich zu Fig. 4 gleichbleibenden Teile sind mit gleichen Bezugszeichen versehen.6 to 8 show a further variant of the means for supplying the plasma gas into the cathode compartment. The parts that remain the same as in FIG. 4 are provided with the same reference numerals.

Anstelle des Gasverteilrings 29 in Fig. 1 bzw. der Gasverteilscheibe 53 in Fig. 4 ist bei der weiteren Variante eine z.B. aus Kupfer bestehende Führungshülse 70 vorgesehen, welche den Ringraum zwischen dem zentralen Isolationskörper 71 und der kathodennahen Neutrode 72 einnimmt und an ihrerAussenseite durchgehende Längsnuten 73 für den Gasdurchtritt aufweist. Wie aus Fig. 8 deutlich hervorgeht, verlaufen die Längsnuten 73 schraubenlinienförmig, so dass das aus dem Ringraum 57 in Richtung des Pfeils 74 in die Längsnuten 73 einströmende Plasmagas wirbeiförmig aus der Führungshülse 70 austritt. Damit diese Wirbelströmung möglichst bis zum Erreichen der Lichtbogenzone erhalten bleibt, erstreckt sich die Führungshülse 70 bis nahe an die den Einschnürungsbereich begrenzende Wandung 75 der Neutrode 72.Instead of the gas distribution ring 29 in FIG. 1 or the gas distribution disk 53 in FIG. 4, in the further variant a e.g. copper guide sleeve 70 is provided, which occupies the annular space between the central insulation body 71 and the cathode near the neutrode 72 and has continuous longitudinal grooves 73 on the outside for the gas passage. As is clear from FIG. 8, the longitudinal grooves 73 run in a helical shape, so that the plasma gas flowing from the annular space 57 in the direction of the arrow 74 into the longitudinal grooves 73 exits the guide sleeve 70 in a vortex shape. In order that this eddy flow is maintained as far as possible until the arc zone is reached, the guide sleeve 70 extends to close to the wall 75 of the neutrode 72 delimiting the constriction area.

Auch in diesem Ausführungsbeispiel sind an der Frontseite der Kathodenschaftteile 52 sektorförmige Hohlräume 76 im Isolierkörper 71 vorgesehen, aus denen ein Teil des Plasmagases zur zusätzlichen Kühlung der Kathodenstifte 20 entlang derselben in den Düsenhohlraum 22 strömt. In diese sektorförmigen Hohlräume 76 gelangt das Plasmagas durch je einen Längsspalt 77, der mit einer radialen Einlassbohrung 78 im Isolierkörper 71 verbunden ist. Der Strömungsverlauf ist durch den Pfeil 79 angedeutet.In this exemplary embodiment, too, sector-shaped cavities 76 are provided in the insulating body 71 on the front side of the cathode shaft parts 52, from which part of the plasma gas flows along the same in the nozzle cavity 22 for additional cooling of the cathode pins 20. The plasma gas enters each of these sector-shaped cavities 76 through a longitudinal gap 77, which is connected to a radial inlet bore 78 in the insulating body 71. The flow pattern is indicated by arrow 79.

Claims (20)

1. Plasmaspritzgerät zum Versprühen von pulverförmigem oder gasförmigem Material, mit einem indirekten Plasmatron zur Erzeugung eines Langlichtbogens, welches eine Kathodenanordnung (1), eine von der Kathodenanordnung distanzierte ringförmige Anode (3) und einen zwischen der Kathodenanordnung (1) und der Anode (3) sich erstreckenden Plasmakanal (4) aufweist, welcher durch den Anodenring und eine Anzahl ringförmiger, voneinander elektrisch isolierter Neutroden (6-12) gebildet ist, wobei die der Kathodenanordnung (1) am nächsten liegende Neutrode eine Einlaufdüse (6) mit zur Kathodenanordnung hin erweitertem Querschnitt bildet, und mit einer Einrichtung (24) für die achsiale Zufuhr des Spritzmaterials in den Plasmastrahl, dadurch gekennzeichnet, dass die Kathodenanordnung (1) einen zentralen Isolationskörper (21) aufweist, welcher in fester Position zur Einlaufdüse (6) angeordnet ist und in den Hohlraum (22) derselben hineinragt, dass die Kathodenanordnung (1) mehrere stabförmige, in den Isolationskörper(21) eingebettete Kathoden (1) aufweist, welche im Kreis um eine zentrale, auf die Längsachse des Plasmakanals (4) ausgerichtete und parallel zu dieser verlaufenden Längsachse (2) verteilt angeordnet sind und deren aktive Enden (63), an welchen der Lichtbogen entsteht, aus dem Isolationskörper (21) hervor in den Hohlraum (22) der Einlaufdüse (6) ragen, und dass ein in der zentralen Achse des Isolationskörpers (21) verlaufendes und von diesem gehaltenes Rohr (24) für die Zufuhr des Spritzmaterials in den Düsenhohlraum (22) mündet.1. Plasma spraying device for spraying powdery or gaseous material, with an indirect plasmatron for generating a long arc, which has a cathode arrangement (1), an annular anode (3) spaced from the cathode arrangement and one between the cathode arrangement (1) and the anode (3 ) extending plasma channel (4) which is formed by the anode ring and a number of ring-shaped neutrodes (6-12) which are electrically insulated from one another, the neutrode closest to the cathode arrangement (1) having an inlet nozzle (6) with the cathode arrangement forms an enlarged cross section, and with a device (24) for the axial supply of the spray material into the plasma jet, characterized in that the cathode arrangement (1) has a central insulation body (21) which is arranged in a fixed position relative to the inlet nozzle (6) and protrudes into the cavity (22) of the same, so that the cathode arrangement (1) has a plurality of rods Mige, in the insulation body (21) embedded cathodes (1), which are arranged in a circle around a central, aligned to the longitudinal axis of the plasma channel (4) and extending parallel to this longitudinal axis (2) and the active ends (63) , on which the arc arises, protrude from the insulation body (21) into the cavity (22) of the inlet nozzle (6), and that a pipe (24) running in the central axis of the insulation body (21) and held by the latter Feed of the spray material opens into the nozzle cavity (22). 2. Plasmaspritzgerät nach Anspruch 1, dadurch gekennzeichnet, dass sich die Endbereiche (20) der Kathoden (1) über die Mündung (25) des Rohrs (24) für die Zufuhr des Spritzmaterials hinaus erstrecken,2. Plasma spraying device according to claim 1, characterized in that the end regions (20) of the cathodes (1) extend beyond the mouth (25) of the tube (24) for the supply of the spray material, 3. Plasmaspritzgerät nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass der Isolationskörper (21) aus hochschmelzendem Material besteht.3. Plasma spray gun according to claim 1 or 2, characterized in that the insulating body (21) consists of high-melting material. 4. Plasmaspritzgerät nach Anspruch 3, dadurch gekennzeichnet, dass der Isolationskörper (21) aus Keramik oder Bornitrid besteht.4. Plasma spray gun according to claim 3, characterized in that the insulating body (21) consists of ceramic or boron nitride. 5. Plasmaspritzgerät nach Anspruch 3, dadurch gekennzeichnet, dass der Isolationskörper (21) mit die Kathodenendbereiche (20) umgebenden Bohrungen versehen ist, die einen grösseren Durchmesser aufweisen als die Kathodenendbereiche (20), um den Durchtritt von Gas, welches in Strömungsrichtung von der Kathode zur Anode fliesst, zu gewährleisten.5. Plasma spraying device according to claim 3, characterized in that the insulation body (21) with the cathode end regions (20) surrounding holes which have a larger diameter than the cathode end regions (20) to the passage of gas, which in the flow direction of the To ensure cathode flows to the anode. 6. Plasmaspritzgerät nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass die Kathoden (1) einen wassergekühlten Kathodenschaft (52) und an ihren Endbereichen einen in den Kathodenschaft eingesetzten Kathodenstift (20) aus einem hochschmelzenden Material aufweisen.6. Plasma spraying device according to claim 1 or 2, characterized in that the cathodes (1) have a water-cooled cathode shaft (52) and at their end regions a cathode pin (20) inserted into the cathode shaft and made of a high-melting material. 7. Plasmaspritzgerät nach Anspruch 6, dadurch gekennzeichnet, dass der Kathodenschaft (51,52) aus Kupfer und der Kathodenstift (20) aus thoriertem Wolfram besteht.7. Plasma spraying device according to claim 6, characterized in that the cathode shaft (51, 52) consists of copper and the cathode pin (20) consists of thoriated tungsten. 8. Plasmaspritzgerät nach Anspruch 6, dadurch gekennzeichnet, dass der Kathodenstift (20) exzentrisch in den Kathodenschaft (51,52) eingesetzt ist, so dass die Längsachse des Kathodenstiftes (20) der zentralen Längsachse (2) näher liegt als diejenige des Kathodenschaftes (51, 52).8. Plasma spray gun according to claim 6, characterized in that the cathode pin (20) is eccentrically inserted in the cathode shaft (51, 52), so that the longitudinal axis of the cathode pin (20) is closer to the central longitudinal axis (2) than that of the cathode shaft ( 51, 52). 9. Plasmaspritzgerät nach Anspruch 1, dadurch gekennzeichnet, dass die Mantelfläche des Isolationskörpers (21) einem Teil der Düsenwandung (5) radial gegenüberliegt und mit diesem Wandungsteil einen Ringkanal (23) für den Einlass des Plasmagases in die Einlaufdüse (6) bildet.9. Plasma spray gun according to claim 1, characterized in that the outer surface of the insulating body (21) radially opposite part of the nozzle wall (5) and forms an annular channel (23) with this wall part for the inlet of the plasma gas into the inlet nozzle (6). 10. Plasmaspritzgerät nach Anspruch 1, dadurch gekennzeichnet, dass zur Erzielung einer laminaren Einströmung des Plasmagases in die Einlaufdüse (6) eine Gasverteilanordnung mit einer Mehrzahl von Düsen vorgesehen ist.10. Plasma spraying device according to claim 1, characterized in that a gas distribution arrangement with a plurality of nozzles is provided in order to achieve a laminar inflow of the plasma gas into the inlet nozzle (6). 11. Plasmaspritzgerät nach Anspruch 10, dadurch gekennzeichnet, dass dem zwischen dem Isolationskörper (21) und der Einlaufdüse (6) vorhandenen Ringkanal (23) ein auf dem Isolationskörper sitzender Gasverteilring (29) mit einer Mehrzahl von Durchgangsbohrungen (30) für den Einlass des Plasmagases in den Ringkanal vorgelagert ist.11. Plasma spraying device according to claim 10, characterized in that between the insulating body (21) and the inlet nozzle (6) existing ring channel (23) on the insulating body seated gas distribution ring (29) with a plurality of through holes (30) for the inlet of the Plasma gas is upstream in the ring channel. 12. Plasmaspritzgerät nach Anspruch 10, dadurch gekennzeichnet, dass dem Isolationskörper (21) eine Gasverteilscheibe (53) vorgelagert ist, welche sich radial vom zentralen Rohr (24) für die Zufuhr des Spritzmaterials bis an die Wandung (55) der Einlaufdüse (6) erstreckt und welche mit einer Mehrzahl von im Kreis angeordneten Durchlassbohrungen (56) für den Einlass des Plasmagases aus dem Ringkanal in die Einlaufdüse versehen ist.12. Plasma spraying device according to claim 10, characterized in that the insulating body (21) is preceded by a gas distribution disk (53) which extends radially from the central tube (24) for the supply of the spray material up to the wall (55) of the inlet nozzle (6). extends and which is provided with a plurality of through holes (56) arranged in a circle for the inlet of the plasma gas from the annular channel into the inlet nozzle. 13. Plasmaspritzgerät nach Anspruch 12, dadurch gekennzeichnet, dass die Gasverteilscheibe (53) aus einem hochschmelzenden Material besteht.13. Plasma spray gun according to claim 12, characterized in that the gas distribution disk (53) consists of a high-melting material. 14. Plasmaspritzgerät nach Anspruch 13, dadurch gekennzeichnet, dass die Gasverteilscheibe (53) aus Keramik oder Bornitrid besteht.14. Plasma spraying device according to claim 13, characterized in that the gas distribution disk (53) consists of ceramic or boron nitride. 15. Plasmaspritzgerät nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass die Durchgangsbohrungen (56) tangential zu virtuellen, zentralachsigen Schraubenlinien verlaufen.15. Plasma spraying device according to one of the preceding claims, characterized in that the through holes (56) are tangential to virtual, central-axis helical lines. 16. Plasmaspritzgerät nach Anspruch 11, dadurch gekennzeichnet, dass die Gasverteilscheibe (53) weitere Durchgangsbohrungen aufweist, durch welche sich die Kathodenstifte (20) erstrecken und deren Durchmesser grösser ist als derjenige der Kathodenstifte.16. Plasma spraying device according to claim 11, characterized in that the gas distribution disk (53) has further through bores through which the cathode pins (20) extend and whose diameter is larger than that of the cathode pins. 17. Plasmaspritzgerät nach Anspruch 9, dadurch gekennzeichnet, dass eine Gasführungshülse (70) vorgesehen ist, welche den Ringraum zwischen dem zentralen Isolationskörper (71) und der kathodennahen Neutrode (72) einnimmt und welche an ihrer Aussenseite durchgehende Längsnuten (73) für den Gasdurchtritt aufweist.17. The plasma spraying device according to claim 9, characterized in that a gas guide sleeve (70) is provided which occupies the annular space between the central insulation body (71) and the neutrode (72) near the cathode and which has continuous longitudinal grooves (73) on the outside for the gas passage having. 18. Plasmaspritzgerät nach Anspruch 17, dadurch gekennzeichnet, dass die Längsnuten (73) schraubenlinienförmig verlaufen.18. Plasma spray gun according to claim 17, characterized in that the longitudinal grooves (73) run helically. 19. Plasmaspritzgerät nach Anspruch 17 oder 18, dadurch gekennzeichnet, dass sich die Führungshülse (70) bis nahe an die den Einschnürungsbereich begrenzende Wandung (75) der Neutrode (72) erstreckt.19. Plasma spray gun according to claim 17 or 18, characterized in that the guide sleeve (70) extends up to close to the wall (75) of the neutrode (72) delimiting the constriction area. 20. Plasmaspritzgerät nach Anspruch 1, dadurch gekennzeichnet, dass sich der Plasmakanal (4) im Anschluss an die Einlaufdüse (6) stetig erweitert.20. Plasma spraying device according to claim 1, characterized in that the plasma channel (4) is continuously widened following the inlet nozzle (6).
EP92810095A 1991-02-21 1992-02-10 Plasma spray gun for spraying powdered or gaseous materials Expired - Lifetime EP0500492B1 (en)

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DE4105407A DE4105407A1 (en) 1991-02-21 1991-02-21 PLASMA SPRAYER FOR SPRAYING SOLID, POWDER-SHAPED OR GAS-SHAPED MATERIAL
DE4105407 1991-02-21

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WO1996012390A1 (en) * 1994-10-14 1996-04-25 The University Of British Columbia Plasma torch electrode structure
WO2018035619A1 (en) 2016-08-26 2018-03-01 Amt Ag Plasma spraying device
CN112647037A (en) * 2020-12-17 2021-04-13 青岛科技大学 Four-cathode plasma spraying spray gun device
CN114059024A (en) * 2022-01-17 2022-02-18 北京航空航天大学 Spray gun for plasma physical vapor deposition and thermal barrier coating preparation method
CN114059024B (en) * 2022-01-17 2022-04-08 北京航空航天大学 Spray gun for plasma physical vapor deposition and thermal barrier coating preparation method

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US5332885A (en) 1994-07-26
ATE136190T1 (en) 1996-04-15
EP0500492B1 (en) 1996-03-27
DE59205803D1 (en) 1996-05-02
CA2061181A1 (en) 1992-08-22
DE4105407C2 (en) 1993-02-11
DE4105407A1 (en) 1992-08-27
CA2061181C (en) 1998-06-30
JP3131001B2 (en) 2001-01-31
JPH0584455A (en) 1993-04-06

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