WO1998038841A1 - Torche a plasma pour installation de projection au plasma et son anode - Google Patents

Torche a plasma pour installation de projection au plasma et son anode Download PDF

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Publication number
WO1998038841A1
WO1998038841A1 PCT/DE1998/000599 DE9800599W WO9838841A1 WO 1998038841 A1 WO1998038841 A1 WO 1998038841A1 DE 9800599 W DE9800599 W DE 9800599W WO 9838841 A1 WO9838841 A1 WO 9838841A1
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WO
WIPO (PCT)
Prior art keywords
electrode
plasma
anode
plasma torch
elements
Prior art date
Application number
PCT/DE1998/000599
Other languages
German (de)
English (en)
Inventor
Oliver Prause
Original Assignee
Oliver Prause
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Oliver Prause filed Critical Oliver Prause
Priority to EP98914832A priority Critical patent/EP1013155A1/fr
Publication of WO1998038841A1 publication Critical patent/WO1998038841A1/fr

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Classifications

    • 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

Definitions

  • the present invention relates to a plasma torch for a thermal plasma spray system, comprising a first electrode which can be connected as an anode to an associated current source and a second cathode which can be connected to the current source as a cathode.
  • Thermal plasma spraying systems generally have a so-called plasma torch.
  • the plasma torch essentially consists of a cathode and an anode.
  • the arrangement of the cathode and anode and the entire arrangement of the plasma torch is generally carried out in such a way that an electric current flows between the cathode and anode via an arc.
  • a hot plasma is generated by supplying a gas flow to the arc.
  • the plasma generated is used, for example, to coat any surface with or without filler materials (e.g. ceramic thermal barrier coatings on turbine blades) or to treat it thermally (e.g. surface hardening).
  • a suitable supply and discharge of a cooling medium e.g. water
  • the electrodes for plasma torches are usually formed from a high-melting metal with one or more dopants that promote electron emissions, ie material additives with low electron work function.
  • a metallic powder is usually mixed with the dopants, in bars or rods. be pressed and sintered. After sintering, the bars are formed several times until the required diameter is reached. The bars are then sanded and cut.
  • the electrodes are in a heat-conducting connection with a further metal (eg copper), which has good thermal conductivity, in order to dissipate the heat that occurs during operation to a cooling medium.
  • the cut electrode blanks are placed in a graphite mold and cast in copper in an oven. Finally, this composite material is machined, whereby the added doping leads to improved machinability (eg drilling) of the high-melting metal (eg tungsten).
  • machinability eg drilling
  • high-melting metal eg tungsten
  • the high-current cathodes are compared with a comparison cathode made of pure tungsten and with a conventional sintered cathode in order to demonstrate improved burn-off properties.
  • the sintered electrode has an electrode body made of tungsten and added to the tungsten. doping which reduces the electron work function (2nd
  • Laid open a value customary in plasma technology in order to reduce the electron work function in tungsten from 4.4 eV to approximately 2.63 to 2.86 eV).
  • the invention has for its object to provide a plasma torch of the type specified in such a way that a long service life is achieved both for the first electrode serving as the anode and for the second electrode serving as the cathode.
  • the second electrode serving as the cathode (more precisely: its active electrode section interacting with the arc, which is made of a high-melting metal electrode material and preferably comprises tungsten and / or molybdenum), according to the invention - like cathodes of the prior art - has one with regard to the electron work function we- substantial proportion of material additives in the form of doping with low electron work function (or - in other words - with energetically unstable electron configuration).
  • elements with incompletely occupied d or f electrode shells, or / and with electron donor action for example oxides and borides of the elements of the IIIb to IVb subgroup of the periodic table of the elements and the first three elements from the lanthanoid and actinide group, such as ThO 2 , La 2 O 3 , CeO 2 , Y 2 O 3 and LaB 6 can be used.
  • the first electrode serving as the anode (more precisely: its active electrode section interacting with the arc, which is made of a high-melting metal electrode material and preferably comprises tungsten and / or molybdenum) has no material additions in the form of dopants with regard to the electron work function with a low electron work function (or - in other words - with an energetically unstable electron configuration).
  • the result of increasing the service life by dispensing with doping can possibly be explained by the fact that in the first place A high thermal stability of the anode material is of crucial importance for the service life. Tungsten with the highest melting point of all metals is particularly suitable. Furthermore, it may be that the theoretically explainable low amount of energy practically does not occur when the electrons re-enter the anode due to the low ionization energy caused by the doping. This could be explained by the fact that, due to the high temperature and the sputtering effect of the arc, no layer near the surface with a low electron work function can form on the anode.
  • the following material-related causes may also have an adverse effect on the anode life: formation of microcracks due to evaporation of doping (eg ThO 2 , La 2 O 3 ) that promotes electron emission;
  • sinter-activating material additives can thus be added to the metal powder both in the case of the first electrode serving as an anode and in the case of the second electrode serving as cathode, since sinter-activating material additives if they contain a small amount Make up the proportion of the electrode or the electrode material, have no significant influence on the service life.
  • the sintering temperature or sintering time can be reduced and / or the workability (e.g. drilling) of the high-melting sintered material (preferably sintered from high-melting tungsten powder) can be improved.
  • Good results have been achieved with a weight fraction of the sinter-activating material additives, in particular nickel, in the metal powder of up to 1 weight percent. In particular, contents of approximately 0.12 to 0.5 percent by weight are recommended.
  • the electrodes according to the invention in particular anodes, can be produced, for example, by the method known from German patent DE 44 42 161 C1 (cf. in particular Their claims 1 1 to 18), but in the case of the first electrode or anode, according to the invention, no or only an insignificant proportion of doping to promote electron emission is to be provided and under certain circumstances (possibly in deviation from claim 1 of DE 44 42 161 C1) a post-processing of the electrode surface interacting with the arc is indicated.
  • first electrode or anode for the doping Since additions of materials that require electron emissions (doping) have a greater effect on the service life of the first electrode or anode than sinter-activating additions of material If the first electrode or anode for the doping is as small as possible, a maximum value of 1.0 percent by weight, preferably a maximum of 0.1 percent by weight, most preferably a maximum of 0.01 percent by weight is suggested, or it is best to dispense with it entirely.
  • the invention further relates to an anode for a plasma torch according to the invention, namely an electrode serving as an anode, the electrode section of which, when interacting with an arc, directly interacts with an electrode (active electrode section; in particular in contrast to an optionally provided holding section of the electrode, for example made of copper, which is the active one Holds electrode section and can serve for cooling) consists predominantly or completely of at least one high-melting metallic electrode material.
  • the active electrode section or the electrode material has no material additives or only a small proportion of material additives, in particular no or only an insignificant proportion - in particular insignificant with regard to the electron work function - of doping with low electron work function or energetically unstable electron configuration, such as Elements with incompletely occupied d- or f-electron shells, or / and with electron donor action, for example oxides and borides of the elements of the 111 ____ to IVb subgroup of the periodic table of the elements and the first three elements from the lanthanide and actinide groups, such as ThO 2 , La 2 O 3 , CeO 2 , Y 2 O 3 and LaB 6 .
  • the anode according to the invention can have the features specified above and in the claims with respect to the first electrode. As a rule, the anode will have a plasma passage channel.
  • the anode is preferably a sintered electrode.
  • an anode according to the invention can optionally also be composed of several sections. With regard to the plasma torch, it goes without saying that this may also have multiple anodes or / and multiple cathodes.
  • the invention also relates to a thermal plasma spray system with an anode according to the invention.
  • an electrode with electron-emitting doping according to the prior art is preferably to be provided as the cathode. It is therefore preferred that the plasma spraying system has a plasma torch according to the invention.
  • Figure 1 is a schematic sectional view of a plasma torch according to the invention with two electrodes: a cathode and an anode; and
  • Fig. 2 is a schematic sectional view of the anode according to
  • FIG. 1 shows a longitudinal section of a cathode 22 and an anode 20 according to the invention as parts of a plasma torch 10.
  • the cathode 22 and the anode 20 as part of the plasma torch 10 are geometrically designed so that a cooling medium 40 (for example water) can be brought up to a material 32 with high thermal conductivity (for example copper), which with the actual electrode material 30 (which in operation with a cooling medium 40 (for example water) can be brought up to a material 32 with high thermal conductivity (for example copper), which with the actual electrode material 30 (which in operation with a cooling medium 40 (for example water) can be brought up to a material 32 with high thermal conductivity (for example copper), which with the actual electrode material 30 (which in operation with a
  • a cooling medium 40 for example water
  • a material 32 with high thermal conductivity for example copper
  • Arc directly interacting electrode section of the anode - here referred to as "active" electrode section) is in a thermally conductive connection.
  • the cathode 22 and the anode 20 are arranged in such a way that an arc can form between the cathode 22 and the anode 20 (more precisely: between their "active" electrode sections which interact directly with the arc) in order to use a gas flow to introduce a plasma into the To produce an arc.
  • the generated plasma is conducted via the plasma passage channel 50 in the direction of the surface to be treated.
  • the anode designated 20, also called a plasma nozzle is shown as a composite of the electrode material 30 and the material 32 with high thermal conductivity.
  • the electrode material 30 of an anode 20 produced in the described embodiment using a sintering process consists of metal powder which essentially consists only of chemically pure tungsten or from 95.5 to 98.8% by weight chemically pure tungsten with a sinter-activating material additive, namely in the case of the here described example 0, 12 to 0.5 weight percent nickel, is composed.
  • a sinter-activating material additive namely in the case of the here described example 0, 12 to 0.5 weight percent nickel
  • the metal powder in elastic, cylindrical hoses filled and sealed watertight.
  • the metal powder is then compressed in a cold isostatic press at 2000 to 3000 bar.
  • the metal powder can also be placed in a correspondingly shaped press die and then compressed mechanically and hydraulically.
  • the pressed metal powder is sintered in a direct current passage - Coolidge process - at approx. 2600 ° to 3200 ° C and a holding time of 15 to 30 minutes in a hydrogen atmosphere.
  • the sintered rod or the electrode material 30 is usually shaped at temperatures of 900 ° to 1600 ° C., the temperature depending on the degree of deformation, for example by hammering.
  • the metal powder and the sinter-activating material additive are prepared by dry mechanical mixing or by a wet chemical hydrometallurgical process. In the latter case, a liquid nickel nitrate solution is sprayed into tungsten trioxide and mixed, and subjected to a drying, reducing and sieving process.
  • the prepared metal powder with the material additive is filled into elastic, cylindrical hoses, sealed watertight and cold isostatically compressed at 2000 to 3000 bar.
  • the compacted metal powder is sintered in a furnace at temperatures of 1400 ° to 1600 ° C and holding times of 30 to 180 minutes in a hydrogen atmosphere. By sintering, the pressed metal powder becomes the metallic state of the electrode material 30 transferred, densities from 80 to 97% of theoretical
  • Density can be achieved.
  • the electrode material 30 made of chemically pure tungsten or of tungsten with sinter-activating material additive can be machined after the sintering process (for example, rotating and / or grinding and / or eroding), in particular by drilling and / or eroding the plasma passage 50 as Plasma nozzle serving anode 20 are introduced.
  • the appropriately prepared electrode material 30 is finally placed in a suitably designed graphite mold. After adding copper as material 32 with high thermal conductivity to the graphite mold, it is placed in a lowering or gradient furnace. At temperatures of 1050 ° to 1200 ° C, the copper is completely melted in a hydrogen atmosphere and then continuously cooled in order to obtain a non-porous composite.
  • the cathode 22 can be produced in the same way using the two processing methods mentioned, although preferably additions of materials (doping) which require electron emissions are introduced, as is known in the prior art for anodes and cathodes for plasma burners. Such electron emission-requiring material additives are not provided according to the invention for the anode 20.
  • the anode 20 can be installed in a plasma torch 10 as part of a plasma spraying system.
  • the cathode 22 and the anode 20 are electrically connected to a current source, the cathode 22 being connected to the negative pole and the anode 20 being connected to the positive pole of the current source.
  • the arc between cathode 22 and anode 20 is ignited by a high-frequency voltage superposition or capacitor discharge. Electrons emerge from the cathode 22, are accelerated by an electrical voltage in the direction of the anode 20 and reenter the electrode material 30 of the anode 20, as a result of which the electrical circuit is closed.
  • the invention relates to an electrode, in particular anode, made of a high-melting metal electrode material for plasma spraying systems, in particular plasma torches.
  • the electrode has no or only a small proportion of material additives, especially no or only a small proportion of doping, so that an improvement in the service life properties is achieved.
  • the invention relates to a plasma torch with an electrode according to the invention, connected as an anode, and to a corresponding plasma spraying system.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Plasma Technology (AREA)
  • Powder Metallurgy (AREA)

Abstract

L'invention concerne une électrode (20), notamment une anode (20), constituée d'un matériau métallique réfractaire pour installations de projection au plasma, notamment des torches à plasma (10). Cette électrode (20) présente peu ou pas d'additifs matière, notamment peu ou pas d'agents dopants, permettant ainsi une amélioration des caractéristiques de longévité. L'invention concerne également une torche au plasma (10) pourvue d'une électrode (20) raccordée comme anode, ainsi qu'une installation de projection au plasma correspondante.
PCT/DE1998/000599 1997-02-26 1998-02-26 Torche a plasma pour installation de projection au plasma et son anode WO1998038841A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP98914832A EP1013155A1 (fr) 1997-02-26 1998-02-26 Torche a plasma pour installation de projection au plasma et son anode

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19707699A DE19707699C1 (de) 1997-02-26 1997-02-26 Plasmabrenner für Plasmaspritzanlagen
DE19707699.8 1997-02-26

Publications (1)

Publication Number Publication Date
WO1998038841A1 true WO1998038841A1 (fr) 1998-09-03

Family

ID=7821552

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/DE1998/000599 WO1998038841A1 (fr) 1997-02-26 1998-02-26 Torche a plasma pour installation de projection au plasma et son anode

Country Status (3)

Country Link
EP (1) EP1013155A1 (fr)
DE (1) DE19707699C1 (fr)
WO (1) WO1998038841A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105899297A (zh) * 2013-12-19 2016-08-24 欧瑞康美科（美国）公司 具有衬里的长寿命等离子体喷嘴
EP3118339A1 (fr) * 2015-07-17 2017-01-18 Gesellschaft für Wolfram Industrie mbH Alliage de molybdene, electrode comprenant un alliage de molybdene et utilisation d'une electrode
WO2023046223A1 (fr) * 2021-09-24 2023-03-30 Thermacut, K.S. Buse pour torche à plasma et torche à plasma

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2602812A1 (de) * 1975-01-27 1976-07-29 Villamos Ipari Kutato Intezet Verfahren zum anschmelzen der oberflaeche von festen materialien beziehungsweise koerpern, insbesondere bauelementen, und plasmagenerator zur durchfuehrung desselben
DE3544657A1 (de) * 1985-12-17 1987-06-19 Plasmainvent Ag Hochstromelektrode
EP0334981A1 (fr) * 1987-02-14 1989-10-04 Toho Kinzoku Co., Ltd. Matériau d'électrode à décharge
US5004888A (en) * 1989-12-21 1991-04-02 Westinghouse Electric Corp. Plasma torch with extended life electrodes
US5296670A (en) * 1992-12-31 1994-03-22 Osram Sylvania Inc. DC plasma arc generator with erosion control and method of operation
EP0713738A1 (fr) * 1994-11-27 1996-05-29 Bayerische Metallwerke GmbH Corps fritté à partir de poudre métallique à point de fusion élevé avec dopants

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2755213C2 (de) * 1977-12-10 1982-05-06 Fa. Dr. Eugen Dürrwächter DODUCO, 7530 Pforzheim Nichtabschmelzende Elektrode und Verfahren zu ihrer Herstellung
US4392047A (en) * 1980-05-14 1983-07-05 Bykhovskij David G Non-consumable electrode
SE452862B (sv) * 1985-06-05 1987-12-21 Aga Ab Ljusbagselektrod
NO163412B (no) * 1988-01-25 1990-02-12 Elkem Technology Plasmalanse.

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2602812A1 (de) * 1975-01-27 1976-07-29 Villamos Ipari Kutato Intezet Verfahren zum anschmelzen der oberflaeche von festen materialien beziehungsweise koerpern, insbesondere bauelementen, und plasmagenerator zur durchfuehrung desselben
DE3544657A1 (de) * 1985-12-17 1987-06-19 Plasmainvent Ag Hochstromelektrode
EP0334981A1 (fr) * 1987-02-14 1989-10-04 Toho Kinzoku Co., Ltd. Matériau d'électrode à décharge
US5004888A (en) * 1989-12-21 1991-04-02 Westinghouse Electric Corp. Plasma torch with extended life electrodes
US5296670A (en) * 1992-12-31 1994-03-22 Osram Sylvania Inc. DC plasma arc generator with erosion control and method of operation
EP0713738A1 (fr) * 1994-11-27 1996-05-29 Bayerische Metallwerke GmbH Corps fritté à partir de poudre métallique à point de fusion élevé avec dopants

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105899297A (zh) * 2013-12-19 2016-08-24 欧瑞康美科（美国）公司 具有衬里的长寿命等离子体喷嘴
EP3083064A4 (fr) * 2013-12-19 2017-08-16 Oerlikon Metco (US) Inc. Buse à plasma à longue durée de vie comportant une chemise conductrice
US10898913B2 (en) 2013-12-19 2021-01-26 Oerlikon Metco (Us) Inc. Long-life plasma nozzle with liner
EP3118339A1 (fr) * 2015-07-17 2017-01-18 Gesellschaft für Wolfram Industrie mbH Alliage de molybdene, electrode comprenant un alliage de molybdene et utilisation d'une electrode
WO2023046223A1 (fr) * 2021-09-24 2023-03-30 Thermacut, K.S. Buse pour torche à plasma et torche à plasma

Also Published As

Publication number Publication date
DE19707699C1 (de) 1998-07-23
EP1013155A1 (fr) 2000-06-28

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