WO1997019203A1 - Procede de traitement de surface thermochimique au plasma, installation correspondante et utilisation du procede et de l'installation - Google Patents

Procede de traitement de surface thermochimique au plasma, installation correspondante et utilisation du procede et de l'installation Download PDF

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Publication number
WO1997019203A1
WO1997019203A1 PCT/CH1996/000307 CH9600307W WO9719203A1 WO 1997019203 A1 WO1997019203 A1 WO 1997019203A1 CH 9600307 W CH9600307 W CH 9600307W WO 9719203 A1 WO9719203 A1 WO 9719203A1
Authority
WO
WIPO (PCT)
Prior art keywords
discharge
workpieces
workpiece
anode
cathode
Prior art date
Application number
PCT/CH1996/000307
Other languages
German (de)
English (en)
Other versions
WO1997019203A9 (fr
Inventor
Norbert Marie Dingremont
Erich Bergmann
Pierre Collignon
Original Assignee
Balzers Aktiengesellschaft
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 Balzers Aktiengesellschaft filed Critical Balzers Aktiengesellschaft
Priority to EP96928307A priority Critical patent/EP0862662A1/fr
Publication of WO1997019203A1 publication Critical patent/WO1997019203A1/fr
Publication of WO1997019203A9 publication Critical patent/WO1997019203A9/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/36—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases using ionised gases, e.g. ionitriding

Definitions

  • the present invention relates to a method for plasma-thermochemical surface treatment of workpieces, in which a gas with a connecting element, namely in particular with at least one of the elements C, N, O, B, Si, S, is excited and thermally by at least one low-voltage discharge -
  • a gas with a connecting element namely in particular with at least one of the elements C, N, O, B, Si, S
  • the workpiece surface is chemically changed, a plant for this and preferred uses of this method or this plant and a workpiece preferably produced therewith.
  • Thermochemical, plasma-assisted surface treatment processes for workpieces are used industrially on a large scale. Compared to surface treatments using salt baths or in gas phases, they offer the possibility of realizing a large variety of different surface coatings, while varying the resulting properties as a function of the treatment parameters.
  • an abnormal glow discharge in which the workpieces to be treated are set to cathodic potential.
  • the ion current density on the cathode surface is uniform and increases with the discharge voltage applied.
  • the electrical generators used for the discharge must supply high voltages can, with adjustable and constantly stable power, to ignite the discharge and then maintain it according to the surface to be treated, the working pressure in the treatment recipient and the desired treatment temperature.
  • Power densities of 0.1 to 4W / cm 2 are used (see T. Lampe and S. Eisenberg, Z. Maschinenstofftech. 17, 183-193 (1986)), and a working pressure is between 1 and 10 ohmPa.
  • the plasmas used are referred to as so-called "weakly ionized plasmas" due to the relationship between the density of electrically charged particles, electrons or ions, and the amount of neutral particles present.
  • These ratios are of the order of 10 10 particles / cm 3 in terms of electrons and ions, at an operating pressure of 4 hPa and a total density of 5.8 10 10 particles / cm 3 (see JL Marchand et al., Proc. Of International Conference on Ion Nitriding, Cleveland, USA, 1986).
  • generators were used which are capable of delivering variable, pulsed currents with regard to repetition frequency and duty cycle, and thus pulsed plasmas were used.
  • the technological interest in this regard is based on the reduction of arcing and on the fact that the outputs to which the workpieces are exposed - heating output, discharge loading - can be easily adjusted.
  • the ion density is several orders of magnitude higher than with high-voltage plasma discharges, but at the same time the ion impact energy on the workpieces is lower due to the reduced acceleration field.
  • the workpieces can be heated with the aid of an additional heating device or by the discharge itself.
  • the treatment is carried out by nitriding in a process atmosphere with N, H and C in the form of CH compounds, additionally with argon or a noble gas in general.
  • the present invention relates to a method or a plant, the plasma-thermochemical surface treatment being implemented with the aid of a low-voltage discharge.
  • An independent low-voltage discharge preferably with a hot cathode, is preferably used.
  • Another object of the present invention is to achieve that the surface microstructure on the finished workpiece remains essentially identical to the surface microstructure on the workpiece that has not yet been treated.
  • a system according to the invention is specified in claim 6, preferred embodiments in claims 7 to 11, preferred uses of both the system and the method in claims 12 and 13.
  • a workpiece according to the invention with preferred embodiments is in claims 14 to 19 specified.
  • FIG. 1 schematically shows a system according to the invention in a first variant for carrying out the method according to the invention in a first embodiment
  • FIG. 2 shows a representation analogous to that of FIG. 1, a second variant of the system according to the invention for carrying out the method according to the invention in a second, preferred form;
  • the present invention is preferably used to treat the surfaces of structural steels or tool steels, hot work steels or cold work steels, martensitic stainless steels, austenitic stainless steels or Ti alloys, in particular under Installation of at least one of the elements C, N, O, B, Si or S, or a combination of these elements, but in particular with the participation of N.
  • a cathode chamber 5 is flanged to a vacuum recipient 1, connected via a diaphragm 3, in which a thermally electron-emitting cathode turn 17 is stored, which, as a directly heated cathode, is preferably connected to a high-current generator 9 for the heating current I H.
  • a gas feed line 11 for the discharge working gas, preferably for argon, opens into the cathode chamber 5.
  • the vacuum recipient 1 is evacuated via a pump connection 13.
  • the gas tank 17 contains reactive gas with at least one compounding agent, namely with at least one of the elements C, N, O, B, Si, S, preferably at least with N.
  • the diaphragm 3 opposite is a workpiece carrier anode 21 provided, which is cooled via a cooling medium circuit 23, preferably a water circuit.
  • the workpiece carrier anode 21 is electrically insulated from the recipient 1, which is preferably held at reference potential, preferably at ground potential.
  • the DC voltage source 25 is connected for the operation of the dependent low-voltage discharge 27, whereby, by definition, the workpiece carrier anode 21 is set to a positive potential with respect to the cathode 7.
  • a heating arrangement 29 is provided in the recipient 1, preferably along the recipient wall, enclosing the workpiece carrier anode 21, with heat shields 31a or 31i preferably being provided in this regard on the outside and / or inside.
  • the workpieces 33 are arranged on the workpiece carrier arrangement.
  • the invention can also be used without the provision of the heating device 29, and then the 9 -
  • Workpieces 33 are heated by the electron current, which can be adjusted by setting the heating circuit I H at the heating current source 9.
  • the workpieces 33 are placed on the potential of the discharge anode.
  • the workpieces are operated at floating potential in the discharge. According to the invention, they also remain at a potential which is more positive than the potential of the cathode 7.
  • FIG. 1 shows the preferred embodiment variant of a system according to the invention for carrying out the process according to the invention with several variants.
  • the same reference numerals as in FIG. 1 are used for the same parts in FIG. 2. Only the deviations are also described with reference to FIG. 1.
  • the anode is formed with respect to the cathode 7 by at least a part 21a of the inner heat shield cylinder 31i, as a cylinder anode.
  • electrical insulation sections 43 any cylinder part that is electrically active for the anode function can be separated from the rest of the cylinder part, which is only thermally active.
  • the entire heat shield inner cylinder 3li according to FIG. 1 can also be used as anode 21a.
  • a tool carrier 39 is provided which, as shown with the electrically insulating holder 41, is held at floating potential in the process space 27. Its potential, in any case higher than that of the cathode 7, is set automatically depending on the electrical conditions in the process space 27.
  • the cylinder anode 21a in any of the mentioned 10 -
  • one or more ring anodes 21b can be provided, the position of which, as shown by the double arrow z, is chosen along the discharge axis A as required.
  • the discharge direct voltage source 25 applies the cathode 7, on the other hand the cylinder anode 21a and / or the at least one ring anode 21b, which may be provided, to the respective potentials.
  • This option is shown schematically with the selection unit 40.
  • the workpiece carrier 39 can also be tied to a potential that is independent of the anode potential, positive with respect to the potential of the cathode 7, such as by means of a preferably adjustable voltage source 26.
  • a cooling medium circuit (not shown) can also be provided for the workpiece carrier 39 according to FIG. 2, as has already been illustrated with reference to FIG. 1.
  • the discharge cross section is spread, by providing the cylinder and / or ring anode 21a, 21b, which is the area provided for receiving the workpieces 33 - left
  • the operation of the workpieces at floating potential has the further advantage that the heating takes place indirectly in that no discharge current flows over the workpieces. For a given plasma power, a relatively balanced temperature distribution on the workpieces can therefore be achieved, regardless of the plasma density distribution.
  • the heating devices 29 By providing the heating devices 29, the workpieces are heated, the influence of the plasma discharge on the workpieces being reduced with respect to homogeneous temperature distribution. This means that plasma performance can also be optimized with regard to the density of reactive species, regardless of the temperature of the workpieces, i.e. an additional degree of freedom is obtained.
  • the thermal characteristics and the characteristics of the plasma reactivity, necessary to carry out a specific treatment, are decoupled.
  • the nitriding mentioned results in a nitriding depth of approx. 170 ⁇ m.
  • the preparation phase for the thermochemical surface treatments mentioned is always chemical.
  • an argon / hydrogen plasma is used in order to prepare the surfaces to be treated with respect to diffusion, for example of nitrogen, into the material.
  • the workpieces are usually kept at floating potential. This makes it possible in the treatment according to the invention with workpieces kept at floating potential to go directly from the pretreatment phase into the treatment phase.
  • ion bombardment of the workpieces, as is otherwise customary, is not necessary even for rustproof austenitic steels of the types AISI316L. The system costs are thus reduced by the costs of an additional generator in order to put the workpieces on potential.
  • the discharge operating sources are considerably less expensive than those necessary for independent discharges, whether the latter are pulsed or not.
  • the reactive gas consumption is considerably lower, due to lower working pressures. Furthermore, according to the invention, there are no interference problems on the workpieces.
  • the kinetics, i.e. the treatment effect resulting per unit of treatment time is significantly increased, for example by a factor of 2 to 3 for the nitriding of steel during floating operation of the workpieces.
  • the procedure according to the invention makes it possible to implement novel coatings according to the invention, such as single-phase iron e-nitrate, Fe 2 -3 N6, essentially free of carbon.
  • This type of layer has an increased corrosion resistance, generally compared to layers which can be produced under substantial ion bombardment.
  • the resistance to salt spray according to the DIN 50021 standard of steel 35CD4, treated in an arrangement with ion bombardment, is only 5 hours, while the same steel, treated according to the invention in a floating manner, resists 24 hours.
  • the treatment was carried out with a system according to FIG. 3, the workpieces were operated at floating potential.
  • the vacuum recipient After the workpieces have been introduced into the vacuum recipient, the latter is evacuated to 0.02 Pa and the workpieces are heated to the necessary treatment temperature with the aid of the heating system 29 shown in FIG. 3. After a few minutes, argon is let in at a pressure of 0.3 Pa and the hot cathode 7 is heated. The discharge is then created between the hot cathode 7 and the anode 21a. The discharge current is 200A. Hydrogen is now let into the recipient with 100ccm, in addition to the argon. The chemical pretreatment, mentioned above, is carried out while the workpieces are being heated.
  • the hydrogen flow is reduced to 10cc and then nitrogen is introduced until a total pressure of 0.8Pa is obtained.
  • the workpiece nitriding temperature is then regulated with the help of the heating devices 29 as an actuator during the nitriding treatment.
  • the total pressure should be between 0.5 and - 15th
  • the reactive gas mass flow in this case the nitrogen mass flow, is also regulated.
  • 35NCD16 aeronautical construction steel, tool steel for mold making,
  • Z2CND17-13 stainless austenitic steel.
  • the bodies treated according to the invention subsequently survive the salt spray test according to DIN 50021 for longer than 10 hours, even longer than 20 hours or 24 hours, compared to bodies treated by conventional treatment methods under ion bombardment, which no longer meet the test mentioned resisted than 5.5 hours.
  • FIG. 6a and 6b show the micrographs of the base bodies according to the invention on 35NCD16 steel on the one hand (FIG. 6a) and on Z38CDV5 steel on the other, with a magnification of 500 times each.
  • the nitrogen concentration N in the e-zone is substantially higher than this concentration in the conventional manner, i.e. Diffusion zones generated under ion bombardment, namely higher than 24at%, in particular in a range between 25at% to 30at% (both limits included).
  • the N concentration is at most 20at% to 22at%.
  • the ratio of the diffusion zone thickness to the e-zone thickness is 2 ⁇ 10 to 3 ′ IO “6 , preferably approx. 2.5 ⁇ IO “ 6 .
  • the diffusion zone on the 35CD4 workpiece treated according to the invention was 0.2 mm, while the e-zone was approximately 8 ⁇ m thick.
  • the formation of a zone which at least predominantly has the Fe 2 _ 3 Ne compound is to be regarded as an essential advantage and leads in particular to the increase mentioned with regard to mechanical and chemical wear resistance.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)

Abstract

Pour améliorer le rapport 'efficacité du traitement de surface/unité du temps de traitement' lors du traitement de surface thermochimique au plasma de pièces (33) tout en obtenant que la microstructure superficielle de la pièce traitée soit identique à celle de la pièce non traitée, il est proposé, selon l'invention, de produire une décharge basse tension (27) et de conférer aux pièces (33) un potentiel électrique positif (25) par rapport à la cathode (7) de décharge (27).
PCT/CH1996/000307 1995-11-22 1996-09-06 Procede de traitement de surface thermochimique au plasma, installation correspondante et utilisation du procede et de l'installation WO1997019203A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP96928307A EP0862662A1 (fr) 1995-11-22 1996-09-06 Procede de traitement de surface thermochimique au plasma, installation correspondante et utilisation du procede et de l'installation

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR95/13843 1995-11-22
FR9513843A FR2741361B3 (fr) 1995-11-22 1995-11-22 Procede pour traitement thermochimique de surface par immersion dans un plasma, installation pour ce procede, utilisations et pieces obtenues

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WO1997019203A1 true WO1997019203A1 (fr) 1997-05-29
WO1997019203A9 WO1997019203A9 (fr) 1998-05-14

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EP (1) EP0862662A1 (fr)
FR (1) FR2741361B3 (fr)
WO (1) WO1997019203A1 (fr)

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3394066A (en) * 1962-09-20 1968-07-23 Little Inc A Method of anodizing by applying a positive potential to a body immersed in a plasma
FR2332336A1 (fr) * 1975-11-21 1977-06-17 Vide & Traitement Sa Procede et four pour la realisation de traitements de metaux par bombardement ionique
JPS5568636A (en) * 1978-11-20 1980-05-23 Nippon Telegr & Teleph Corp <Ntt> Anodic oxidation method of compound semiconductor by plasma
JPS55117244A (en) * 1979-03-05 1980-09-09 Nippon Telegr & Teleph Corp <Ntt> Method of plasma anodizing third to fifth group compound semiconductor
WO1987001738A1 (fr) * 1985-09-24 1987-03-26 Centre National De La Recherche Scientifique (Cnrs Procede et dispositif de traitement chimique, notamment de traitement thermochimique et de depot chimique dans un plasma homogene de grand volume
EP0394159A1 (fr) * 1989-04-18 1990-10-24 USINOR SACILOR Société Anonyme Procédé de coloration de la surface de matériaux métalliques et produits obtenus par sa mise en oeuvre
EP0461011A1 (fr) * 1990-06-05 1991-12-11 Ugine Aciers De Chatillon Et Gueugnon Procédé de coloration d'une bande d'un matériau métallique en défilement par plasma basse température
FR2666821A1 (fr) * 1990-09-19 1992-03-20 Ugine Aciers Dispositif de traitement superficiel d'une plaque ou d'une tole d'un materiau metallique par plasma basse temperature.
EP0583473A1 (fr) * 1991-04-29 1994-02-23 Scientific-Industrial Enterprise NOVATECH Procede et dispositif de traitement d'articles dans du plasma a decharge de gaz
EP0645461A1 (fr) * 1993-08-27 1995-03-29 Hughes Aircraft Company Procédé et dispositif de traitement thermique par réchauffage au moyen de plasma et d'électrons et au moyen d'un jet de refroidissement solide/gazeux

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3394066A (en) * 1962-09-20 1968-07-23 Little Inc A Method of anodizing by applying a positive potential to a body immersed in a plasma
FR2332336A1 (fr) * 1975-11-21 1977-06-17 Vide & Traitement Sa Procede et four pour la realisation de traitements de metaux par bombardement ionique
JPS5568636A (en) * 1978-11-20 1980-05-23 Nippon Telegr & Teleph Corp <Ntt> Anodic oxidation method of compound semiconductor by plasma
JPS55117244A (en) * 1979-03-05 1980-09-09 Nippon Telegr & Teleph Corp <Ntt> Method of plasma anodizing third to fifth group compound semiconductor
WO1987001738A1 (fr) * 1985-09-24 1987-03-26 Centre National De La Recherche Scientifique (Cnrs Procede et dispositif de traitement chimique, notamment de traitement thermochimique et de depot chimique dans un plasma homogene de grand volume
EP0394159A1 (fr) * 1989-04-18 1990-10-24 USINOR SACILOR Société Anonyme Procédé de coloration de la surface de matériaux métalliques et produits obtenus par sa mise en oeuvre
EP0461011A1 (fr) * 1990-06-05 1991-12-11 Ugine Aciers De Chatillon Et Gueugnon Procédé de coloration d'une bande d'un matériau métallique en défilement par plasma basse température
FR2666821A1 (fr) * 1990-09-19 1992-03-20 Ugine Aciers Dispositif de traitement superficiel d'une plaque ou d'une tole d'un materiau metallique par plasma basse temperature.
EP0583473A1 (fr) * 1991-04-29 1994-02-23 Scientific-Industrial Enterprise NOVATECH Procede et dispositif de traitement d'articles dans du plasma a decharge de gaz
EP0645461A1 (fr) * 1993-08-27 1995-03-29 Hughes Aircraft Company Procédé et dispositif de traitement thermique par réchauffage au moyen de plasma et d'électrons et au moyen d'un jet de refroidissement solide/gazeux

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 4, no. 109 (E - 020) 6 August 1980 (1980-08-06) *
PATENT ABSTRACTS OF JAPAN vol. 4, no. 170 (E - 035) 22 November 1980 (1980-11-22) *

Also Published As

Publication number Publication date
EP0862662A1 (fr) 1998-09-09
FR2741361A1 (fr) 1997-05-23
FR2741361B3 (fr) 1998-04-17

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