WO2016107837A1 - Method for preventative treatment against the release of nickel ions from a part made of a nickel and chromium alloy - Google Patents

Method for preventative treatment against the release of nickel ions from a part made of a nickel and chromium alloy Download PDF

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Publication number
WO2016107837A1
WO2016107837A1 PCT/EP2015/081273 EP2015081273W WO2016107837A1 WO 2016107837 A1 WO2016107837 A1 WO 2016107837A1 EP 2015081273 W EP2015081273 W EP 2015081273W WO 2016107837 A1 WO2016107837 A1 WO 2016107837A1
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laser
nickel
alloy
chromium
release
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PCT/EP2015/081273
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French (fr)
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Wilfried PACQUENTIN
Nadège CARON
Lucille GOUTON
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Commissariat à l'énergie atomique et aux énergies alternatives
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Publication of WO2016107837A1 publication Critical patent/WO2016107837A1/en

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    • CCHEMISTRY; METALLURGY
    • C23COATING 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
    • C23CCOATING 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
    • C23C8/00Solid 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
    • C23C8/06Solid 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
    • C23C8/08Solid 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
    • C23C8/10Oxidising
    • C23C8/12Oxidising using elemental oxygen or ozone
    • CCHEMISTRY; METALLURGY
    • C23COATING 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
    • C23CCOATING 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
    • C23C8/00Solid 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
    • C23C8/02Pretreatment of the material to be coated

Definitions

  • the present invention relates to the field of metal surface treatment processes.
  • the invention more particularly relates to a treatment method for limiting the effects of the relaxation of the nickel ions of a part made of a nickel-chromium alloy, in particular alloy A690.
  • nickel ions in solution are all areas where it is necessary to limit the content of nickel ions in solution by loosening. Indeed, nickel being classified as carcinogenic and mutagenic reprotoxic, it is important to limit the solution content. In addition, the presence of nickel ions can cause contamination, as is the case in nuclear reactors, where they cause radioactive contamination. Again, it will be important to limit the solution content.
  • water circulates in a closed circuit (called the primary circuit) and is used as a coolant to bring the heat produced in the reactor core to a steam generator, where a heat transfer of the heat takes place at the wall of a multitude of tubes located inside the steam generator, between the water of the primary circuit, circulating inside the tubes, and the water contained in the steam generator outside the tubes, causing the transformation into steam of the water contained in the steam generator.
  • the primary circuit a closed circuit
  • the tubes being generally made of an alloy containing a percentage by weight of nickel of between 60 and 75%, the consequence of these conditions is mainly reflected by a relaxation of Ni 2+ metal cations in the water of the primary circuit.
  • Ni 2+ metal cations Once released into the primary circuit water, these Ni 2+ metal cations will be transported to the reactor core, where they will be irradiated and produce radioactive cobalt 58 and cobalt 60.
  • the release of Ni 2+ cations in the primary circuit water is thus at the origin of a contamination of the entire primary circuit up to a few kilograms per operating cycle of the reactor.
  • This radioactive cobalt contamination requires waiting several days, after the shutdown of the reactor, the radioactivity has sufficiently decreased before carrying out maintenance operations of the primary circuit, which results in a loss of time and operating income.
  • a solution proposed in the document [1] consists in limiting the release of the tubes of the steam generator by performing an electropolishing of their inner surface in order to remove the surface hardened layer, then to induce the formation of a layer Passive protection rich in chrome.
  • the protective layer thus obtained contains, in addition to chromium, nickel and iron.
  • Another solution proposed in document [2] also makes it possible to limit the release of the tubes of the steam generator, but is implemented during the operation of the reactor. It consists in introducing magnetite (Fe3 ⁇ 4) in the water of the primary circuit when it is at a temperature between 80 ° C and 180 ° C and to circulate this treated water in the primary circuit, so that it is in contact with the inner surface of the tubes. An oxide protective layer having a spinel type structure, for example a NiCr 2 0 4 layer, is then formed on the inner surface of the tubes.
  • the aim of the inventors is therefore to find out how to proceed in order to easily form a chromine layer on the surface of nickel and chromium alloy parts, and in particular A690 alloy parts.
  • the laser irradiation is performed with a laser so as to obtain a pfd absorbed by the workpiece between 2.4 ⁇ 10 7 W / cm 2 and 2.7 ⁇ 10 7 W / cm 2 .
  • the laser irradiation is produced by a nanosecond pulsed pulsed laser, preferably having pulses of a duration between 100 ns and 180 ns.
  • the laser used has a pulse frequency of between 15 and 25 kHz, a wavelength of between 1060 and 1064 nm and a duration at half-height of the pulses of between 100 and 180 nm. .
  • the properties of the chromine layer formed by this process are governed by the laser parameters; the use of these parameters in the preferred range of values indicated above makes it possible to obtain a layer of chromine (thus having a fixed chromium content) having, for the desired thickness, a good adhesion on the surface of the treated tube .
  • the use of a laser according to the invention makes it possible to obtain a surface treatment of the part. This is particularly interesting because the formation of the chromine layer must not alter the core properties of the constituent material of the part, in particular to not modify its mechanical properties.
  • the preferred use of a nanosecond pulsed laser makes it possible to deliver a large amount of energy over a very short period of time, which has the advantage of being able to perform the surface treatment on a very small thickness: the surface treatment then does not affect than the extreme surface of the room.
  • the laser surface treatment according to the invention preferably using a nanosecond pulsed laser, thus improves the surface properties of a piece of nickel alloy and chromium, while maintaining the volume properties of the alloy of the piece.
  • Another advantage of the method that is the subject of the invention is that the use of a laser makes it possible to form a chromine layer without contact (the laser as a device does not touch the surface of the part, the contact being made with the focused beam produced by the laser) and without adding material, which limits the risks of separation of the layer formed because the metallurgical bond is in continuity with the surface of the part, and limits the risk of pollution of the layer of chromine thus formed
  • the laser irradiation is obtained by scanning the surface of the part with a non-zero laser impact coating, preferably covering between 66% and 74%.
  • a non-zero laser impact coating preferably covering between 66% and 74%.
  • Such a covering makes it possible to treat the surface in its entirety and to obtain adequate thermal cycles for the formation of chromine.
  • a lower overlap would have the effect of limiting the final chromium content in the oxide layer, while a greater overlap would result in forming a cracked oxide layer with a risk of delamination and a depletion of chromium at the metal-oxide interface.
  • the method further comprises, prior to formation of the chromine surface layer, polishing of the workpiece surface to a surface roughness of less than or equal to 50 nm.
  • the parts to be treated are typically made of an alloy comprising at least 59% by weight of nickel and at least 29% by weight of chromium; preferably, the parts are made of an A690 alloy of chemical formula NiCr 2 9Fe.
  • Figures 1a, 1b and 1c show schematically, respectively, 0%, 50% and 90% overlaps of round shaped laser impacts.
  • the laser can be equipped with a galvanometric head that allows the laser beam to accurately perform a desired trajectory in two directions x and y through two mirrors, whose movement is managed by computer. By moving the galvanometric head parallel to the surface to be treated, it can then be treated in its entirety.
  • the characteristics of the laser must be carefully considered because they will directly affect the properties of the barrier layer that will be formed.
  • the frequency, the wavelength, the duration of the pulses and the power flux-density of the laser are parameters which depend on each other and which must be perfectly adjusted, in order to obtain the most adequate laser-material interaction.
  • FIGS. 1a, 1b and 1c are respectively round shaped laser impacts having a 0%, 50% and 90% overlap (the 50% and 90% overlaps being located in the dashed rectangles).
  • the horizontal recovery Rh is preferably chosen equal to the vertical recovery R v in order to obtain a homogeneous layer.
  • a chromine layer on plates of alloy A690 alloy A690 (alloy sheet 690 from Valinox Nucléaire) of dimensions 24 ⁇ 50 ⁇ 1 mm 3 .
  • the surface to be treated of the sample is previously polished up to a particle size of 1200, in order to limit the surface pollution and to obtain a roughness of around 50 nm.
  • This approach is similar to the absorptivity of the internal part of the steam generator tubes whose characteristics are to be mimicked.
  • the inventors plan to transpose the method that is the subject of the invention to the treatment of the internal part of the nickel alloy tubes of a steam generator of a nuclear reactor.
  • the surface to be treated is polished under water with a polishing machine and polishing cloth with fixed abrasive particles (SiC) of decreasing grain size (400, 800 and 1200).
  • SiC fixed abrasive particles
  • the sample is cleaned with ethanol in an ultrasonic bath for 10 minutes to remove impurities produced during polishing.
  • a treatment is applied to the surface of the sample, focusing a laser beam, the surface to be treated being located at the focal plane of the laser.
  • IPG Ytterbium doped fiber
  • the diameter of the Gaussian distribution beam in energy is equal to 125 ⁇ at 1 / e 2 at the focal plane of the laser.
  • the laser treatment is carried out at a power density of 2.56 ⁇ 10 7 W / cm 2 .
  • a laser with a pfd of 2.56 ⁇ 10 7 W / cm 2 and a beam diameter of 125 ⁇ this equates to an average power of 8.8 W with a power tolerance of less than +/- 0.5 W on each laser impact.
  • the sample was tested in an experimental installation that recreates the conditions of the primary medium of a water-cooled nuclear reactor and tracks the release of nickel. This facility, known as the PETER loop, is located in AREVA's Le Creusot facility in France.

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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)
  • Laser Beam Processing (AREA)

Abstract

The invention relates to a method for preventative treatment against the release of nickel ions from a part made of a nickel and chromium alloy, the method comprising the formation of a surface layer of chromium(III) oxide (Cr2O3) by laser irradiation of the surface of the part, the laser irradiation being performed with a laser so as to obtain a power flux density absorbed by the part to be treated of between 2.107 W/cm2 and 2,7.107 W/cm2, and the part being made of an alloy comprising at least 59 wt. % of nickel and at least 29 wt. % of chromium.

Description

PROCÉDÉ DE TRAITEMENT PRÉVENTIF CONTRE LE RELACHEMENT D'IONS NICKEL D'UNE PIÈCE EN ALLIAGE DE NICKEL ET DE CHROME  PREVENTIVE TREATMENT METHOD FOR RELEASING NICKEL IONS OF A NICKEL AND CHROME ALLOY PART
DESCRIPTIONDESCRIPTION
DOMAINE TECHNIQUE TECHNICAL AREA
La présente invention concerne le domaine des procédés de traitement de surface de pièces métalliques. The present invention relates to the field of metal surface treatment processes.
L'invention concerne plus particulièrement un procédé de traitement visant à limiter les effets du relâchement des ions nickel d'une pièce en un alliage à base de nickel et de chrome, en particulier en alliage A690.  The invention more particularly relates to a treatment method for limiting the effects of the relaxation of the nickel ions of a part made of a nickel-chromium alloy, in particular alloy A690.
Les domaines d'application de ce procédé sont tous les domaines où il est nécessaire de limiter la teneur des ions nickel en solution par relâchement. En effet, le nickel étant classé comme produit cancérigène et mutagène reprotoxique, il est important d'en limiter la teneur en solution. Par ailleurs, la présence d'ions nickel peut être à l'origine d'une contamination, comme c'est le cas dans les réacteurs nucléaires, où ils provoquent une contamination radioactive. Là encore, il sera important d'en limiter la teneur en solution.  The fields of application of this process are all areas where it is necessary to limit the content of nickel ions in solution by loosening. Indeed, nickel being classified as carcinogenic and mutagenic reprotoxic, it is important to limit the solution content. In addition, the presence of nickel ions can cause contamination, as is the case in nuclear reactors, where they cause radioactive contamination. Again, it will be important to limit the solution content.
ÉTAT DE LA TECHNIQUE ANTÉRIEURE STATE OF THE PRIOR ART
Comme nous l'avons précisé ci-dessus, il y a de nombreux domaines dans lesquels il est important de limiter la teneur des ions nickel en solution par relâchement. Pour illustrer les problématiques de l'invention, nous allons prendre l'exemple du relâchement se produisant dans un réacteur nucléaire, étant entendu que le procédé objet de l'invention peut s'appliquer à tous les domaines où on chercherait à limiter ce relâchement. As noted above, there are many areas in which it is important to limit the content of nickel ions in solution by loosening. To illustrate the problems of the invention, let us take the example of relaxation occurring in a nuclear reactor, it being understood that the method which is the subject of the invention can be applied to all areas where this relaxation would be limited.
Dans un réacteur nucléaire en fonctionnement, de l'eau circule dans un circuit fermé (appelé circuit primaire) et est utilisé comme caloporteur pour amener la chaleur produite dans le cœur du réacteur jusqu'à un générateur de vapeur, où un transfert thermique de la chaleur s'opère, au niveau de la paroi d'une multitude de tubes situés à l'intérieur du générateur de vapeur, entre l'eau du circuit primaire, circulant à l'intérieur des tubes, et l'eau contenue dans le générateur de vapeur à l'extérieur des tubes, provoquant la transformation en vapeur de l'eau contenue dans le générateur de vapeur. In a functioning nuclear reactor, water circulates in a closed circuit (called the primary circuit) and is used as a coolant to bring the heat produced in the reactor core to a steam generator, where a heat transfer of the heat takes place at the wall of a multitude of tubes located inside the steam generator, between the water of the primary circuit, circulating inside the tubes, and the water contained in the steam generator outside the tubes, causing the transformation into steam of the water contained in the steam generator.
Au cours du fonctionnement du réacteur, la surface des tubes du générateur de vapeur en contact avec le milieu primaire sont soumises à des conditions sévères du fait des conditions élevées de température et de pression qui régnent au sein du circuit primaire. Les tubes étant généralement réalisés en un alliage contenant un pourcentage en poids de nickel compris entre 60 et 75%, la conséquence de ces conditions se traduit principalement par un relâchement de cations métalliques Ni2+ dans l'eau du circuit primaire. During operation of the reactor, the surface of the tubes of the steam generator in contact with the primary medium are subjected to severe conditions due to the high temperature and pressure conditions that prevail within the primary circuit. The tubes being generally made of an alloy containing a percentage by weight of nickel of between 60 and 75%, the consequence of these conditions is mainly reflected by a relaxation of Ni 2+ metal cations in the water of the primary circuit.
Une fois relâchés dans l'eau du circuit primaire, ces cations métalliques Ni2+ vont être transportés jusqu'au cœur du réacteur, où ils vont être irradiés et produire du cobalt 58 et du cobalt 60 radioactifs. Le relâchement de cations Ni2+ dans l'eau du circuit primaire est ainsi à l'origine d'une contamination de l'ensemble du circuit primaire à hauteur de quelques kilogrammes par cycle de fonctionnement du réacteur. Once released into the primary circuit water, these Ni 2+ metal cations will be transported to the reactor core, where they will be irradiated and produce radioactive cobalt 58 and cobalt 60. The release of Ni 2+ cations in the primary circuit water is thus at the origin of a contamination of the entire primary circuit up to a few kilograms per operating cycle of the reactor.
Cette contamination au cobalt radioactif nécessite d'attendre plusieurs jours, après la mise à l'arrêt du réacteur, que la radioactivité ait suffisamment baissée avant de procéder à des opérations de maintenance du circuit primaire, ce qui se traduit par une perte de temps et de revenus d'exploitation.  This radioactive cobalt contamination requires waiting several days, after the shutdown of the reactor, the radioactivity has sufficiently decreased before carrying out maintenance operations of the primary circuit, which results in a loss of time and operating income.
Il est donc important de limiter au maximum la quantité de cobalt radioactif présente au sein du circuit primaire.  It is therefore important to limit as much as possible the amount of radioactive cobalt present in the primary circuit.
A cette fin, une solution proposée dans le document [1] consiste à limiter le relâchement des tubes du générateur de vapeur en réalisant un électropolissage de leur surface interne afin de supprimer la couche écrouie superficielle, puis à y induire la formation d'une couche passive de protection riche en chrome. La couche protectrice ainsi obtenue contient, en plus du chrome, du nickel et du fer.  To this end, a solution proposed in the document [1] consists in limiting the release of the tubes of the steam generator by performing an electropolishing of their inner surface in order to remove the surface hardened layer, then to induce the formation of a layer Passive protection rich in chrome. The protective layer thus obtained contains, in addition to chromium, nickel and iron.
Une autre solution proposée dans le document [2] permet elle aussi de limiter le relâchement des tubes du générateur de vapeur, mais est mise en œuvre pendant le fonctionnement du réacteur. Elle consiste à introduire de la magnétite (Fe3Û4) dans l'eau du circuit primaire lorsque celle-ci est à une température située entre 80°C et 180°C et à faire circuler cette eau traitée dans le circuit primaire, afin qu'elle soit en contact avec la surface internes des tubes. I l se forme alors, sur la surface interne des tubes, une couche protectrice d'oxyde ayant une structure de type spinelle, par exemple une couche NiCr204. Another solution proposed in document [2] also makes it possible to limit the release of the tubes of the steam generator, but is implemented during the operation of the reactor. It consists in introducing magnetite (Fe3Û 4) in the water of the primary circuit when it is at a temperature between 80 ° C and 180 ° C and to circulate this treated water in the primary circuit, so that it is in contact with the inner surface of the tubes. An oxide protective layer having a spinel type structure, for example a NiCr 2 0 4 layer, is then formed on the inner surface of the tubes.
Ces deux solutions sont intéressantes et permettent effectivement de réduire la formation de cobalt radioactif dans le circuit primaire.  These two solutions are interesting and effectively reduce the formation of radioactive cobalt in the primary circuit.
Les I nventeurs ont toutefois cherché à encore améliorer ces résultats et notamment à concevoir un procédé de traitement plus efficace.  The inventors, however, have sought to further improve these results and in particular to design a more efficient treatment method.
Par ailleurs, au cours d'études antérieures, il a été déterminé que la diffusion du nickel dans une couche de chromine (Cr203) était de plusieurs ordres de grandeur plus lente que dans une couche d'oxyde de type spinelle NiCr204 (document On the other hand, in previous studies it has been determined that the diffusion of nickel into a chromine layer (Cr 2 O 3) was several orders of magnitude slower than in a NiCr 2 spinel oxide layer. 4 (document
[3]). Les I nventeurs ont donc supposé que la formation d'une couche de chromine pourrait constituer une barrière vis-à-vis de la diffusion des cations Ni2+ dans le milieu primaire et ainsi permettre de diminuer considérablement le temps d'arrêt du réacteur nucléaire. [3]). The inventors have therefore assumed that the formation of a chromine layer could constitute a barrier against the diffusion of Ni 2+ cations in the primary medium and thus make it possible to considerably reduce the downtime of the nuclear reactor. .
Les I nventeurs se sont donc fixé comme but de trouver comment procéder pour former de manière simple une couche de chromine sur la surface de pièces en alliage à base de nickel et de chrome, et notamment des pièces en alliage A690. EXPOSÉ DE L'INVENTION  The aim of the inventors is therefore to find out how to proceed in order to easily form a chromine layer on the surface of nickel and chromium alloy parts, and in particular A690 alloy parts. STATEMENT OF THE INVENTION
I ls y sont parvenu en proposant un procédé de traitement préventif contre le relâchement d'ions nickel d'une pièce en un alliage de nickel et de chrome, le procédé comprenant la formation d'une couche superficielle de chromine (Cr203) par irradiation laser de la surface de la pièce, l'irradiation laser étant réalisée avec un laser de manière à obtenir une puissance surfacique absorbée par la pièce à traiter comprise entre 2.107 W/cm2 et 2,7.107 W/cm2 et la pièce étant en un alliage qui comprend au moins 59 % en poids de nickel et au moins 29% en poids de chrome. They did this by proposing a preventive treatment method against the release of nickel ions from a piece of a nickel-chromium alloy, the process comprising the formation of a surface layer of chromine (Cr 2 O 3) by laser irradiation of the workpiece surface, the laser irradiation being performed with a laser so as to obtain a power flux absorbed by the workpiece between 2.10 7 W / cm 2 and 2.7 × 10 7 W / cm 2 and the piece being an alloy which comprises at least 59% by weight of nickel and at least 29% by weight of chromium.
La focalisation du faisceau laser sur la surface de la pièce à traiter provoque sa fusion quasi instantanée sur quelques micromètres d'épaisseur, immédiatement suivie d'une solidification ultra-rapide allant jusqu'à 1010K/s. La combinaison de ces deux processus permet : Focusing the laser beam on the surface of the workpiece causes its almost instantaneous melting on a few micrometers thick, immediately followed by ultra-fast solidification up to 10 10 K / s. The combination of these two processes allows:
- la modification de la composition chimique de la surface de la pièce en une couche de chromine ;  the modification of the chemical composition of the surface of the part into a layer of chromine;
- la modification de la microstructure et de la structure cristallographique sur les premiers micromètres de la pièce ;  the modification of the microstructure and of the crystallographic structure on the first micrometers of the part;
- l'élimination des défauts présents en surface de la pièce par évaporation ou redistribution ;  the elimination of defects present on the surface of the part by evaporation or redistribution;
- une modification de la topographie.  - a modification of the topography.
De préférence, l'irradiation laser est réalisée avec un laser de manière à obtenir une puissance surfacique absorbée par la pièce à traiter comprise entre 2,4.107 W/cm2 et 2,7.107 W/cm2. Preferably, the laser irradiation is performed with a laser so as to obtain a pfd absorbed by the workpiece between 2.4 × 10 7 W / cm 2 and 2.7 × 10 7 W / cm 2 .
De préférence, l'irradiation laser est produite par un laser puisé à impulsions nanosecondes, de préférence ayant des impulsions d'une durée comprise entre 100 ns et 180 ns. Selon une variante préférée de l'invention, le laser utilisé a une fréquence d'impulsions comprise entre 15 et 25 kHz, une longueur d'onde comprise entre 1060 et 1064 nm et une durée à mi-hauteur des impulsions comprise entre 100 et 180ns.  Preferably, the laser irradiation is produced by a nanosecond pulsed pulsed laser, preferably having pulses of a duration between 100 ns and 180 ns. According to a preferred variant of the invention, the laser used has a pulse frequency of between 15 and 25 kHz, a wavelength of between 1060 and 1064 nm and a duration at half-height of the pulses of between 100 and 180 nm. .
Les propriétés de la couche de chromine formée par ce procédé (teneur en chrome, épaisseur, adhérence) sont gouvernées par les paramètres du laser ; l'utilisation de ces paramètres dans les gammes de valeurs préférées indiquées ci-dessus permettent d'obtenir une couche de chromine (ayant donc une teneur en chrome fixée) ayant, pour l'épaisseur souhaitée, une bonne adhérence sur la surface du tube traité.  The properties of the chromine layer formed by this process (chromium content, thickness, adhesion) are governed by the laser parameters; the use of these parameters in the preferred range of values indicated above makes it possible to obtain a layer of chromine (thus having a fixed chromium content) having, for the desired thickness, a good adhesion on the surface of the treated tube .
L'utilisation d'un laser selon l'invention permet d'obtenir un traitement en surface de la pièce. Cela est particulièrement intéressant car la formation de la couche de chromine ne doit pas altérer les propriétés de cœur du matériau constitutif de la pièce, notamment pour ne pas modifier ses propriétés mécaniques. L'utilisation préférée d'un laser à impulsions nanosecondes permet de délivrer une énergie importante sur une très courte durée, ce qui présente l'avantage de pouvoir réaliser le traitement de surface sur une très faible épaisseur : le traitement de surface n'affecte alors que l'extrême surface de la pièce. Le traitement de surface par laser selon l'invention, de préférence à l'aide d'un laser à impulsions nanosecondes, permet donc d'améliorer les propriétés de surface d'une pièce en alliage de nickel et de chrome, tout en conservant les propriétés volumiques de l'alliage de la pièce. The use of a laser according to the invention makes it possible to obtain a surface treatment of the part. This is particularly interesting because the formation of the chromine layer must not alter the core properties of the constituent material of the part, in particular to not modify its mechanical properties. The preferred use of a nanosecond pulsed laser makes it possible to deliver a large amount of energy over a very short period of time, which has the advantage of being able to perform the surface treatment on a very small thickness: the surface treatment then does not affect than the extreme surface of the room. The laser surface treatment according to the invention, preferably using a nanosecond pulsed laser, thus improves the surface properties of a piece of nickel alloy and chromium, while maintaining the volume properties of the alloy of the piece.
Un autre avantage du procédé objet de l'invention est que l'utilisation d'un laser permet de former une couche de chromine sans contact (le laser en tant qu'appareil ne touche pas la surface de la pièce, le contact se faisant avec le faisceau focalisé produit par le laser) et sans apport de matière, ce qui limite les risques de décollement de la couche formée car la liaison métallurgique se fait en continuité avec la surface de la pièce, et limite les risques de pollution de la couche de chromine ainsi formée  Another advantage of the method that is the subject of the invention is that the use of a laser makes it possible to form a chromine layer without contact (the laser as a device does not touch the surface of the part, the contact being made with the focused beam produced by the laser) and without adding material, which limits the risks of separation of the layer formed because the metallurgical bond is in continuity with the surface of the part, and limits the risk of pollution of the layer of chromine thus formed
Avantageusement, l'irradiation laser est obtenue en procédant à un balayage de la surface de la pièce avec un recouvrement des impacts laser non nul, de préférence un recouvrement compris entre 66% et 74%. Un tel recouvrement permet de traiter la surface dans son intégralité et d'obtenir des cycles thermiques adéquats pour la formation de chromine. Un recouvrement plus faible aurait pour conséquence de limiter la teneur finale en chrome dans la couche d'oxyde, tandis qu'un recouvrement plus important aurait pour conséquence de former une couche d'oxyde fissurée présentant un risque de décollement et un appauvrissement en chrome à l'interface métal-oxyde.  Advantageously, the laser irradiation is obtained by scanning the surface of the part with a non-zero laser impact coating, preferably covering between 66% and 74%. Such a covering makes it possible to treat the surface in its entirety and to obtain adequate thermal cycles for the formation of chromine. A lower overlap would have the effect of limiting the final chromium content in the oxide layer, while a greater overlap would result in forming a cracked oxide layer with a risk of delamination and a depletion of chromium at the metal-oxide interface.
De préférence, le procédé comprend en outre, avant la formation de la couche superficielle de chromine, un polissage de la surface de la pièce jusqu'à obtenir une rugosité de surface inférieure ou égale à 50 nm.  Preferably, the method further comprises, prior to formation of the chromine surface layer, polishing of the workpiece surface to a surface roughness of less than or equal to 50 nm.
Les pièces à traiter sont typiquement constituées d'un alliage comprenant au moins 59 % en poids de nickel et au moins 29% en poids de chrome ; de préférence, les pièces sont en un alliage A690 de formule chimique NiCr29Fe. BRÈVE DESCRIPTION DES DESSINS The parts to be treated are typically made of an alloy comprising at least 59% by weight of nickel and at least 29% by weight of chromium; preferably, the parts are made of an A690 alloy of chemical formula NiCr 2 9Fe. BRIEF DESCRIPTION OF THE DRAWINGS
Les figures la, lb et le représentent respectivement, de manière schématique, des recouvrements à 0 %, à 50 % et à 90 % d'impacts laser de forme ronde. EXPOSÉ DÉTAILLÉ D'UN MODE DE RÉALISATION PARTICULIERS Figures 1a, 1b and 1c show schematically, respectively, 0%, 50% and 90% overlaps of round shaped laser impacts. DETAILED DESCRIPTION OF A PARTICULAR EMBODIMENT
Selon un exemple possible de montage du laser, le laser peut être équipé d'une tête galvanométrique qui permet au faisceau laser d'effectuer précisément une trajectoire voulue selon deux directions x et y grâce à deux miroirs, dont le déplacement est géré par ordinateur. En déplaçant la tête galvanométrique parallèlement à la surface à traiter, celle-ci peut alors être traitée dans son intégralité. According to a possible example of mounting the laser, the laser can be equipped with a galvanometric head that allows the laser beam to accurately perform a desired trajectory in two directions x and y through two mirrors, whose movement is managed by computer. By moving the galvanometric head parallel to the surface to be treated, it can then be treated in its entirety.
Les caractéristiques du laser doivent être considérées avec soin, car elles vont directement influées sur les propriétés de la couche barrière qui va être formée.  The characteristics of the laser must be carefully considered because they will directly affect the properties of the barrier layer that will be formed.
La fréquence, la longueur d'onde, la durée des impulsions et la puissance surfacique du laser sont des paramètres qui dépendent les uns des autres et qui doivent être parfaitement ajustés, afin d'obtenir l'interaction laser-matière la plus adéquate.  The frequency, the wavelength, the duration of the pulses and the power flux-density of the laser are parameters which depend on each other and which must be perfectly adjusted, in order to obtain the most adequate laser-material interaction.
De même, le recouvrement des impacts laser, inévitable pour traiter de larges surfaces, doit être pris en considération : plus le recouvrement sera faible, et moins la surface de l'alliage sera traitée de façon homogène, impactant directement la qualité de la couche barrière formée.  Similarly, the recovery of laser impacts, inevitable to treat large areas, must be taken into consideration: the lower the coverage, and the less the surface of the alloy will be treated homogeneously, directly impacting the quality of the barrier layer formed.
Le calcul du taux de recouvrement horizontal Rh est donné par l'équation 1 ci-dessous, où Vh correspond à la vitesse de balayage en mm/s, d au diamètre du faisceau laser à 1/e2 au plan focal et f la fréquence du laser en Hz. The calculation of the horizontal recovery rate Rh is given by equation 1 below, where Vh corresponds to the scanning speed in mm / s, d to the laser beam diameter at 1 / e 2 in the focal plane and f the frequency of the laser in Hz.
Rh = l - Vb / (d x f) (équation 1) R h = l - Vb / (dxf) (Equation 1)
Le recouvrement vertical Rv est donné par l'équation 2 ci-dessous, où d, est la distance entre deux lignes horizontales de traitement en millimètres. The vertical overlap R v is given by equation 2 below, where d, is the distance between two horizontal treatment lines in millimeters.
Rv = 1 - di / d (équation 2)  Rv = 1 - di / d (equation 2)
Dans les figures la, lb et le sont représentés respectivement des impacts laser de forme ronde ayant un recouvrement à 0 %, à 50 % et à 90 % (les recouvrements à 50% et 90% étant situés dans les rectangles en pointillés).  In FIGS. 1a, 1b and 1c are respectively round shaped laser impacts having a 0%, 50% and 90% overlap (the 50% and 90% overlaps being located in the dashed rectangles).
Pour chaque traitement laser, le recouvrement horizontal Rh est de préférence choisi égal au recouvrement vertical Rv afin d'obtenir une couche homogène. Afin d'illustrer le procédé selon l'invention, nous avons réalisé une couche de chromine sur des plaquettes en alliage A690 (Tôle en alliage 690 de chez Valinox Nucléaire) de dimensions 24 x 50 x 1 mm3. For each laser treatment, the horizontal recovery Rh is preferably chosen equal to the vertical recovery R v in order to obtain a homogeneous layer. In order to illustrate the process according to the invention, we have produced a chromine layer on plates of alloy A690 (alloy sheet 690 from Valinox Nucléaire) of dimensions 24 × 50 × 1 mm 3 .
La surface à traiter de l'échantillon est préalablement polie jusqu'à une granulométrie de 1200, afin de limiter la pollution surfacique et d'obtenir une rugosité avoisinant les 50 nm. On se rapproche ainsi de l'absorptivité de la partie interne des tubes de générateurs de vapeur dont on cherche à mimer les caractéristiques. En effet, à terme, les Inventeurs envisagent de transposer le procédé objet de l'invention au traitement de la partie interne des tubes en alliage de nickel d'un générateur de vapeur d'un réacteur nucléaire. Par exemple, la surface à traiter est polie sous eau à l'aide d'une polisseuse et de draps de polissage à particules abrasives fixes (SiC) de granulométrie décroissante (400, 800 et 1200). Puis, l'échantillon est nettoyé à l'éthanol dans un bain à ultrasons pendant 10 minutes afin d'éliminer les impuretés produites au cours du polissage.  The surface to be treated of the sample is previously polished up to a particle size of 1200, in order to limit the surface pollution and to obtain a roughness of around 50 nm. This approach is similar to the absorptivity of the internal part of the steam generator tubes whose characteristics are to be mimicked. Indeed, in the long term, the inventors plan to transpose the method that is the subject of the invention to the treatment of the internal part of the nickel alloy tubes of a steam generator of a nuclear reactor. For example, the surface to be treated is polished under water with a polishing machine and polishing cloth with fixed abrasive particles (SiC) of decreasing grain size (400, 800 and 1200). Then, the sample is cleaned with ethanol in an ultrasonic bath for 10 minutes to remove impurities produced during polishing.
Puis, un traitement est appliqué à la surface de l'échantillon, en y focalisant un faisceau laser, la surface à traiter étant située au niveau du plan focal du laser.  Then, a treatment is applied to the surface of the sample, focusing a laser beam, the surface to be treated being located at the focal plane of the laser.
Dans cet exemple de réalisation, nous utilisons un laser nano- impulsionnel à fibre dopée Ytterbium (IPG), dont les caractéristiques sont les suivantes :  In this embodiment, we use a Ytterbium doped fiber (IPG) nano-pulse laser, whose characteristics are as follows:
- fréquence des impulsions laser : 20 kHz ;  frequency of the laser pulses: 20 kHz;
- longueur d'onde : 1060 nm ;  wavelength: 1060 nm;
- durée des impulsions : 140 ns à mi-hauteur ;  pulse duration: 140 ns at mid-height;
- puissance surfacique maximale : 5,8.107 W/cm2. - maximum pfd: 5.8.10 7 W / cm 2 .
Le diamètre du faisceau à distribution gaussienne en énergie est égal à 125 μιη à 1/e2 au niveau du plan focal du laser. The diameter of the Gaussian distribution beam in energy is equal to 125 μιη at 1 / e 2 at the focal plane of the laser.
Dans cet exemple de réalisation, nous avons choisi d'avoir un recouvrement des impacts laser de 70%, avec une tolérance inférieure à +/- 4%. Le traitement laser est effectué à une puissance surfacique de 2,56.107 W/cm2. Pour un laser ayant une puissance surfacique de 2,56.107 W/cm2 et un diamètre du faisceau de 125 μιη, cela équivaut à une puissance moyenne de 8,8 W avec une tolérance sur la puissance inférieure à +/- 0,5 W sur chaque impact laser. Après traitement laser, l'échantillon a été testé dans une installation expérimentale qui permet de recréer les conditions du milieu primaire d'un réacteur nucléaire refroidi par eau et de suivre le relâchement du nickel. Cette installation, nommée boucle PETER, est située dans les locaux d'AREVA, le Creusot, en France. In this exemplary embodiment, we have chosen to have a laser impact coverage of 70%, with a tolerance of less than +/- 4%. The laser treatment is carried out at a power density of 2.56 × 10 7 W / cm 2 . For a laser with a pfd of 2.56 × 10 7 W / cm 2 and a beam diameter of 125 μιη, this equates to an average power of 8.8 W with a power tolerance of less than +/- 0.5 W on each laser impact. After laser treatment, the sample was tested in an experimental installation that recreates the conditions of the primary medium of a water-cooled nuclear reactor and tracks the release of nickel. This facility, known as the PETER loop, is located in AREVA's Le Creusot facility in France.
Afin d'avoir un point de comparaison, nous avons choisi comme échantillon témoin une plaquette en alliage A690, de mêmes dimensions que l'échantillon traité, qui n'a pas subi de traitement laser.  In order to have a point of comparison, we chose as a control sample an alloy plate A690, of the same dimensions as the treated sample, which has not undergone laser treatment.
Les résultats sont présentés dans le tableau ci-dessous.  The results are shown in the table below.
Figure imgf000009_0001
Figure imgf000009_0001
Ces résultats montrent que, pendant la montée en température, l'échantillon traité relâche environ 8 fois moins de nickel que l'échantillon non traité laser, et environ 3 fois moins pendant la descente en température. Pendant la phase nominale, le relâchement du nickel a lieu indépendamment du traitement appliqué. La stabilisation de la vitesse de relâchement est observée après 200 heures. These results show that, during the rise in temperature, the treated sample releases about 8 times less nickel than the untreated laser sample, and about 3 times less during the temperature decrease. During the nominal phase, nickel relaxation takes place independently of the applied treatment. Stabilization of the release rate is observed after 200 hours.
REFERENCES CITEES [1] Guinard et al. REFERENCES CITED [1] Guinard et al.
"Effect of surface passivation of inconel 690 on oxidation in primay circuit conditions", Water Chemistry of Nuclear Reactor Systems 8, BNES (2000), p. 67-72  "Effect of surface passivation of inconel 690 on oxidation in primary circuit conditions", Water Chemistry of Nuclear Reactor Systems 8, BNES (2000), p. 67-72
[2] WO 2013/093382 Al  [2] WO 2013/093382 A1
[3] Sabioni et al. "Diffusion of nickel in single- and polycrystalline Cr2C>3", Philosophical Magazine, Vol. 88, No. 3, 21 January 2008, p. 391-405 [3] Sabioni et al. "Diffusion of nickel in single and polycrystalline Cr2C>3", Philosophical Magazine, Vol. 88, No. 3, 21 January 2008, p. 391-405

Claims

REVENDICATIONS
1. Procédé de traitement préventif contre le relâchement d'ions nickel d'une pièce en un alliage de nickel et de chrome, le procédé comprenant la formation d'une couche superficielle de chromine (Cr203) par irradiation laser de la surface de la pièce, l'irradiation laser étant réalisée avec un laser de manière à obtenir une puissance surfacique absorbée par la pièce à traiter comprise entre 2.107 W/cm2 et 2,7.107 W/cm2 et la pièce étant en un alliage qui comprend au moins 59 % en poids de nickel et au moins 29% en poids de chrome. A method of preventive treatment against the release of nickel ions from a nickel-chromium alloy part, the method comprising forming a surface layer of chromine (Cr 2 O 3) by laser irradiation of the surface of the piece, the laser irradiation being performed with a laser so as to obtain a pfd absorbed by the workpiece between 2.10 7 W / cm 2 and 2.7 × 10 7 W / cm 2 and the part being made of an alloy which comprises at least 59% by weight of nickel and at least 29% by weight of chromium.
2. Procédé selon la revendication 1, dans lequel l'irradiation laser est réalisée avec un laser de manière à obtenir une puissance surfacique absorbée par la pièce à traiter comprise entre 2,4.107 W/cm2 et 2,7.107 W/cm2. 2. Method according to claim 1, wherein the laser irradiation is performed with a laser so as to obtain a pfd absorbed by the workpiece between 2.4 × 10 7 W / cm 2 and 2.7 × 10 7 W / cm. 2 .
3. Procédé selon la revendication 1 ou la revendication 2, dans lequel l'irradiation laser est produite par un laser puisé à impulsions nanosecondes. The method of claim 1 or claim 2, wherein the laser irradiation is produced by a nanosecond pulse pulsed laser.
4. Procédé selon la revendication 3, dans lequel le laser utilisé a une fréquence d'impulsions comprise entre 15 et 25 kHz, une longueur d'onde comprise entre 1060 nm et 1064 nm, et une durée à mi-hauteur des impulsions comprise entre 100 ns et 180 ns. 4. The method of claim 3, wherein the laser used has a pulse frequency between 15 and 25 kHz, a wavelength between 1060 nm and 1064 nm, and a half-time duration of the pulses between 100 ns and 180 ns.
5. Procédé selon l'une quelconque des revendications 1 à 4, dans lequel l'irradiation laser est obtenue en procédant à un balayage de la surface de la pièce avec un recouvrement des impacts laser compris entre 66% et 74%. 5. Method according to any one of claims 1 to 4, wherein the laser irradiation is obtained by scanning the surface of the workpiece with an overlap of laser impacts of between 66% and 74%.
6. Procédé selon l'une quelconque des revendications 1 à 5, comprenant en outre, avant la formation de la couche superficielle de chromine, un polissage de la surface de la pièce jusqu'à obtenir une rugosité de surface inférieure ou égale à 50 nm. The method according to any one of claims 1 to 5, further comprising, prior to formation of the chromine surface layer, polishing of the workpiece surface to a surface roughness of 50 nm or less .
7. Procédé selon la revendication 1, dans lequel la pièce est en un alliage A690 de formule chimique NiCr29Fe. 7. The method of claim 1, wherein the part is an alloy A690 chemical formula NiCr 2 9Fe.
PCT/EP2015/081273 2014-12-30 2015-12-28 Method for preventative treatment against the release of nickel ions from a part made of a nickel and chromium alloy WO2016107837A1 (en)

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Citations (4)

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JPS6353210A (en) * 1986-08-22 1988-03-07 Sumitomo Metal Ind Ltd Method for improving stress corrosion cracking resistance of stainless steel
JPH0565530A (en) * 1991-09-10 1993-03-19 Hitachi Ltd Stress corrosion cracking resistant austenitic material and its manufacture
JPH08104949A (en) * 1994-10-05 1996-04-23 Hitachi Ltd Formation of structure having surface treated layer and surface treated layer
US20080020216A1 (en) * 2005-05-10 2008-01-24 Bagnoli Kenneth E High performance coated material with improved metal dusting corrosion resistance

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6353210A (en) * 1986-08-22 1988-03-07 Sumitomo Metal Ind Ltd Method for improving stress corrosion cracking resistance of stainless steel
JPH0565530A (en) * 1991-09-10 1993-03-19 Hitachi Ltd Stress corrosion cracking resistant austenitic material and its manufacture
JPH08104949A (en) * 1994-10-05 1996-04-23 Hitachi Ltd Formation of structure having surface treated layer and surface treated layer
US20080020216A1 (en) * 2005-05-10 2008-01-24 Bagnoli Kenneth E High performance coated material with improved metal dusting corrosion resistance

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