EP0707661B1 - Procede pour la nitruration a basse pression d'une piece metallique et four pour la mise en uvre dudit procede - Google Patents

Procede pour la nitruration a basse pression d'une piece metallique et four pour la mise en uvre dudit procede Download PDF

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Publication number
EP0707661B1
EP0707661B1 EP95918040A EP95918040A EP0707661B1 EP 0707661 B1 EP0707661 B1 EP 0707661B1 EP 95918040 A EP95918040 A EP 95918040A EP 95918040 A EP95918040 A EP 95918040A EP 0707661 B1 EP0707661 B1 EP 0707661B1
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EP
European Patent Office
Prior art keywords
treatment
gas
phase
parts
depassivation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP95918040A
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German (de)
English (en)
French (fr)
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EP0707661A1 (fr
Inventor
Jean-Pierre Souchard
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Innovatique SA
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Innovatique SA
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Filing date
Publication date
Priority claimed from FR9405062A external-priority patent/FR2719057B1/fr
Priority claimed from FR9411483A external-priority patent/FR2725015B1/fr
Application filed by Innovatique SA filed Critical Innovatique SA
Publication of EP0707661A1 publication Critical patent/EP0707661A1/fr
Application granted granted Critical
Publication of EP0707661B1 publication Critical patent/EP0707661B1/fr
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    • 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
    • C23C8/08—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 only one element being applied
    • C23C8/24—Nitriding
    • C23C8/26—Nitriding of ferrous surfaces
    • 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
    • C23C8/38—Treatment of ferrous surfaces

Definitions

  • the present invention relates to a method for nitriding at low pressure of a metal part, by steel example, to improve its properties mechanical on the surface and, in particular, its resistance to wear.
  • nitriding in salt baths we know that it exists on time current at least three types of treatment allowing to carry out this nitriding, namely: nitriding in salt baths, ionic nitriding and gas nitriding.
  • Nitriding in a salt bath is a technique particularly polluting and dangerous due to toxic gas discharges and rinsing water it generates. In addition, it imposes on the workforce difficult working conditions. This is the reason which this technique tends to disappear.
  • Ion nitriding involves an installation relative vacuum heat treatment, specially equipped so as to generate on the parts to be treated a glow discharge in a gas atmosphere nitriding.
  • This technique has the disadvantage of being relatively expensive and not suitable for parts of complex shape and, in particular, of shape tubular, due to cathode phenomena dig.
  • Gas nitriding involves bringing the parts to a treatment temperature of the order of 500 ° C to 600 ° C, and sweep them with nitriding gas, such as ammonia, associated with a compound accelerating the catalytic dissociation of ammonia, at pressure atmospheric.
  • nitriding gas such as ammonia
  • Such treatment which is described in European patent application No. 0 089 885, presents the disadvantage of being relatively long and consuming large amounts of process gas. For this same reason, this type of treatment is also polluting.
  • the invention more particularly aims to eliminate these drawbacks.
  • the above-mentioned catalyst may consist of nitrous oxide (N 2 O), carbon monoxide (CO), or even their hydrocarbon such as methane or propane.
  • the nitriding power of mixture and, therefore, the type or nature of the nitrided combination layer obtained, as well as the quality of the diffusion layer can be checked by diluting the gas mixture with an amount of nitrogen molecular variable depending on the desired result (elimination of iron carbonitrides in the network which weaken the room). This dilution allows in particular avoid or limit the formation of a layer of so-called white layer combination.
  • the process of diffusion of nitrogen in the layer surface of the metal constituting the parts to be treated is further improved by the depassivation phase prior.
  • This depassivation phase can be obtained by injecting a passivation gas composed for example of ammonia and / or hydrogen, the room temperature then being greater than one threshold temperature of the order of 400 ° C.
  • the depassivation treatment may start during the temperature rise phase of parts and may continue during the keeping parts at processing temperature (between 500 ° C and 600 ° C).
  • this depassivation could be performed by generating a discharge on the parts luminescent in an atmosphere of hydrogen and argon at low pressure.
  • the oven allowing the implementation of the process previously described preferably consists of an oven of the type used for low carburization pressure which includes an enclosure, for example double walls, constantly cooled, a refractory flask, housed inside the enclosure, which delimits a laboratory inside which the parts to be treated can be placed, heating means by radiation arranged inside the laboratory and process gas injectors passing through the enclosure and the muffle to lead inside the laboratory.
  • an enclosure for example double walls, constantly cooled, a refractory flask, housed inside the enclosure, which delimits a laboratory inside which the parts to be treated can be placed
  • heating means by radiation arranged inside the laboratory and process gas injectors passing through the enclosure and the muffle to lead inside the laboratory.
  • means are also provided for generate in the enclosure a relative vacuum and means for adjusting the process gas flow.
  • this type of oven provides surprising results mainly due to the fact that it allows to generate a flow inside the laboratory continuous and homogeneous process gas arriving on the parts to be treated at a relatively temperature low, below the dissociation temperature. This is due to the fact that between the cooled wall of the enclosure and the muffle, the temperature stays at a level relatively low and that intense heat exchange which are mainly effected by radiation affect only the interior volume of the laboratory, i.e. areas relatively close to the parts to be treat.
  • the process gases do not reach the processing temperature when in contact with the parts to treat. Therefore, a significant part of the nitrogen active released during this dissociation acts on parts to be treated even before the phenomenon of recombination of active nitrogen into molecular nitrogen could happen.
  • the gases resulting from this dissociation are then sucked up by the means used to generate the relative vacuum inside the oven.
  • the oven used is of the "cold wall” type, that is to say that it comprises a sealed enclosure 1 with double walls 2, 3 between which circulates a cooling fluid such as water. Thanks to this feature, the oven has low thermal inertia and therefore cooling rates significantly higher than those obtained in an oven with hot walls. This point is essential when dealing with nuances of steel susceptible to precipitation corrosion intergranular.
  • a muffle 4 of refractory material which delimits a volume V constituting the laboratory, inside from which the parts 5 are placed on a support 6 carried through the bottom of the enclosure 1.
  • the rooms can be arranged in bulk on several mesh elements arranged one above the other.
  • the heating of 5 pieces inside the laboratory is provided by heating resistors 7 connected to a circuit external power supply.
  • the oven is also equipped a gas circulation turbine which can be used in particular to accelerate the cooling of the interior volume of enclosure 1. This cooling is usually obtained by introduction of an inert gas (nitrogen or nitrogen hydrogenated) at a pressure below the pressure atmospheric, the convection of this gas being ensured by the turbine 8.
  • an inert gas nitrogen or nitrogen hydrogenated
  • the admission of the treatment gases inside the oven is ensured by a gas injection circuit 11 supplied from gas sources S 1 , S 2 , S 3 by means of a mixer-regulator of flow 12.
  • the oven can also be equipped with treatment means by ion bombardment involving for example a high voltage electric generator connected to the enclosure wall and the support structure of the parts to be treated.
  • treatment means by ion bombardment involving for example a high voltage electric generator connected to the enclosure wall and the support structure of the parts to be treated.
  • these processing means can be used to perform plasma assisted stripping.
  • the invention is not limited to such a provision: Indeed, the injection could be performed in another location, inside the laboratory, possibly inside the rooms to treat (tubular).
  • the conduit injection can pass into the support structure 6, aspiration then takes place at another location from the oven, preferably in a location where to obtain an axial flow of process gas.
  • the injection pipe or the suction pipe may be extended by an injection nozzle or a suction nozzle of suitable shape for example for inject or aspirate inside a tubular.
  • the nitriding gas mixture used may consist of a mixture consisting of ammonia (NH 3 ), nitrous oxide (N 2 O) and nitrogen (N 2 ).
  • NH 3 ammonia
  • N 2 O nitrous oxide
  • N 2 nitrogen
  • hydrogen (H2) and argon (Ar) can also be used.
  • the base mixture consists of 95% to 97% NH 3 and 5 to 3% N 2 O, depending on the grades of steel treated.
  • the processing temperature can vary between 500 and 600 ° C depending on the nuances treated and the specifications charges.
  • Figure 2 shows the different successive phases a nitriding treatment at low pressure, according to the method according to the invention.
  • a high vacuum is applied to the oven at a pressure of the order of 10 -2 mbar, in order to obtain purging of the oven.
  • the parts are then heated to a pressure of 10 -2 mbar (temperature rise phase) for a period T 1 .
  • the actual depassivation phase is then carried out by maintaining the parts at the treatment temperature, under this partial pressure of ammonia for a period T 2 .
  • the nitriding phase itself is started by injecting the treatment gas onto the parts to be treated. During this nitriding phase which continues during the period T 3 , the temperature and pressure conditions are maintained.
  • the nitriding cycle ends with a rapid cooling phase, thanks to an injection of inert cooling gas (nitrogen or hydrogenated nitrogen), the circulation of this gas being ensured by the turbine (period T 4 ).
  • inert cooling gas nitrogen or hydrogenated nitrogen
  • An important advantage of the process described above is that, thanks to the fact that the treatment is performed at low pressure, it is possible to obtain a rapid regulation of the nitriding potential: effect, to purge the oven and inject a different mixture (more or less rich in nitrogen) for vary this potential in a few minutes, which is not possible with conventional methods.
  • gaseous releases caused by the nitriding at low pressure are very low and are easily treatable compared to releases generated by salt baths and rinsing water necessary for nitriding treatments in salt baths.
  • working conditions as well as job security work are of better quality.
  • the process according to the invention uses less expensive means. he allows, in particular on tubulars, treatments that cannot be carried out ionically due to hollow cathode phenomena. It also allows the carrying out bulk treatments (impossible in ionic) thereby reducing the cost of preparing the charge.
  • the process according to the invention improves the treatment of very long tubulars by injecting the mixture gas directly into the tubulars.

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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)
EP95918040A 1994-04-22 1995-04-21 Procede pour la nitruration a basse pression d'une piece metallique et four pour la mise en uvre dudit procede Expired - Lifetime EP0707661B1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
FR9405062 1994-04-22
FR9405062A FR2719057B1 (fr) 1994-04-22 1994-04-22 Procédé pour la nitruration à bsase pression d'une pièce métallique et four pour la mise en Óoeuvre dudit procédé.
FR9411483 1994-09-23
FR9411483A FR2725015B1 (fr) 1994-09-23 1994-09-23 Four utilisable pour la nitruration a basse pression d'une piece metallique
PCT/FR1995/000522 WO1995029269A1 (fr) 1994-04-22 1995-04-21 Procede pour la nitruration a basse pression d'une piece metallique et four pour la mise en ×uvre dudit procede

Publications (2)

Publication Number Publication Date
EP0707661A1 EP0707661A1 (fr) 1996-04-24
EP0707661B1 true EP0707661B1 (fr) 2000-03-15

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP95918040A Expired - Lifetime EP0707661B1 (fr) 1994-04-22 1995-04-21 Procede pour la nitruration a basse pression d'une piece metallique et four pour la mise en uvre dudit procede

Country Status (4)

Country Link
EP (1) EP0707661B1 (bg)
DE (2) DE707661T1 (bg)
TW (1) TW279902B (bg)
WO (1) WO1995029269A1 (bg)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19947381B4 (de) * 1999-10-01 2011-06-22 METAPLAS IONON Oberflächenveredelungstechnik GmbH, 51427 Vorrichtung zur Wärmebehandlung von Werkstücken, insbesondere zum Gasnitrieren, Nitrocarburieren und Oxidieren
DE10118494C2 (de) * 2001-04-04 2003-12-11 Aichelin Gesmbh Moedling Verfahren zur Niederdruck-Carbonitrierung von Stahlteilen
DE102009002985A1 (de) * 2009-05-11 2010-11-18 Robert Bosch Gmbh Verfahren zur Carbonitrierung
GB2497354B (en) * 2011-12-07 2014-09-24 Solaris Holdings Ltd Method of improvement of mechanical properties of products made of metals and alloys
DE102014213510A1 (de) 2014-07-11 2016-02-18 Robert Bosch Gmbh Verfahren zum Nitrieren eines Bauteils eines Kraftstoffeinspritzsystems
CN110747430B (zh) * 2019-10-25 2020-12-15 西南交通大学 一种低压气体快速渗氮方法

Family Cites Families (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB564841A (en) * 1943-02-13 1944-10-16 John Fallon Improvements in furnaces heated by gaseous or liquid fuels
DE1933439A1 (de) * 1968-07-01 1970-01-15 Gen Electric Nitrierverfahren
FR2264891B1 (bg) * 1974-03-19 1977-10-07 Michel Henri
SE7700229L (sv) * 1976-01-22 1977-07-23 Western Electric Co Forfarande for beleggning av substrat genom utfellning fran ett plasma
FI63783C (fi) * 1981-09-30 1983-08-10 Kymin Oy Kymmene Ab Foerfarande foer nitrering vid laogt tryck med hjaelp av glimurladdning
FR2524006B1 (fr) * 1982-03-23 1985-10-11 Air Liquide Procede de durcissement superficiel de pieces metalliques
JPS60211061A (ja) * 1984-04-05 1985-10-23 Toyota Central Res & Dev Lab Inc アルミニウム材のイオン窒化方法
DE3705710A1 (de) * 1986-02-24 1987-08-27 Ohara Co Verfahren zum nitrieren der oberflaeche von formteilen aus titan und vorrichtung zur nitrierbehandlung
GB8608717D0 (en) * 1986-04-10 1986-05-14 Lucas Ind Plc Metal components
US4926793A (en) * 1986-12-15 1990-05-22 Shin-Etsu Handotai Co., Ltd. Method of forming thin film and apparatus therefor
US5039357A (en) * 1990-06-15 1991-08-13 Dynamic Metal Treating, Inc. Method for nitriding and nitrocarburizing rifle barrels in a fluidized bed furnace
FR2674618B1 (fr) * 1991-03-27 1998-03-13 Etudes Const Mecaniques Procede et four de nitruration.
DE4208848C2 (de) * 1991-12-04 2001-08-30 Ald Vacuum Techn Ag Verfahren zur thermochemischen Nachbehandlung von Stählen und Metallen

Also Published As

Publication number Publication date
DE69515588D1 (de) 2000-04-20
TW279902B (bg) 1996-07-01
DE707661T1 (de) 1996-10-10
DE69515588T2 (de) 2000-09-07
EP0707661A1 (fr) 1996-04-24
WO1995029269A1 (fr) 1995-11-02

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