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FR2993578A1 - Protective plating, useful for magnet of neodymium-iron-boron, nickel layer and titanium nitride layer, where chromium layer is disposed between nickel layer and titanium nitride layer and titanium nitride layer is covered by lacquer layer - Google Patents

Protective plating, useful for magnet of neodymium-iron-boron, nickel layer and titanium nitride layer, where chromium layer is disposed between nickel layer and titanium nitride layer and titanium nitride layer is covered by lacquer layer Download PDF

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FR2993578A1
FR2993578A1 FR1256956A FR1256956A FR2993578A1 FR 2993578 A1 FR2993578 A1 FR 2993578A1 FR 1256956 A FR1256956 A FR 1256956A FR 1256956 A FR1256956 A FR 1256956A FR 2993578 A1 FR2993578 A1 FR 2993578A1
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titanium nitride
neodymium
magnet
iron
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FR2993578B1 (en
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Claude Boursse
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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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • 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
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/02—Pretreatment of the material to be coated
    • C23C14/024—Deposition of sublayers, e.g. to promote adhesion of the coating
    • C23C14/025—Metallic sublayers
    • 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
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/0641—Nitrides
    • 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
    • C23C28/32—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer
    • 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
    • C23C28/32—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer
    • C23C28/322—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer only coatings of metal elements only
    • 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
    • C23C28/34—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/10—Electroplating with more than one layer of the same or of different metals
    • C25D5/12—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium
    • C25D5/14—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium two or more layers being of nickel or chromium, e.g. duplex or triplex layers
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D7/00—Electroplating characterised by the article coated
    • C25D7/001—Magnets
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/14—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates
    • H01F41/24—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates from liquids
    • H01F41/26—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates from liquids using electric currents, e.g. electroplating

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Electrochemistry (AREA)
  • Power Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Magnetic Treatment Devices (AREA)

Abstract

Placage protecteur pour aimant en néodyme-fer-bore à usage thérapeutique L'objet de l'invention est de remplacer le placage habituel en or des aimants thérapeutiques par un placage donnant le même aspect, tout en étant biocompatible, plus résistant et moins couteux. Ce placage comprend, de l'intérieur vers l'extérieur en partant de l'aimant en alliage néodyme-fer-bore, une couche de nickel, éventuellement une couche de chrome, et une couche de nitrure de titane. L'invention concerne aussi le procédé de fabrication consistant : immédiatement après réalisation de chaque aimant par frittage d'un mélange de poudre de néodyme, de fer et de bore, à déposer électrolytiquement sur lui une couche de nickel, et éventuellement une couche de chrome, puis à l'envelopper par évaporation en phase gazeuse d'une couche de nitrure de titane.The object of the invention is to replace the usual gold plating of therapeutic magnets with a veneer giving the same appearance, while being biocompatible, more resistant and less expensive. This veneer comprises, from the inside to the outside starting from the neodymium-iron-boron alloy magnet, a nickel layer, possibly a chromium layer, and a titanium nitride layer. The invention also relates to the manufacturing method consisting of: immediately after making each magnet by sintering a mixture of neodymium powder, iron and boron, electrolytically depositing on it a layer of nickel, and optionally a layer of chromium and then wrap it with gas phase evaporation of a layer of titanium nitride.

Description

L'invention concerne un placage protecteur pour aimant en alliage néodyme-fer-bore et son procédé de réalisation. Le domaine technique de l'invention est donc le placage de métaux sur d'autres matières pour en améliorer les qualités. Elle concerne plus spécialement 5 le placage réalisé par du nitrure de titane. L'état de la technique fourni de nombreux procédés de protection d'articles métalliques divers par une couche de métal, tel que nickel, chrome, zinc, or et argent, cette couche étant déposée par électrolyse, galvanoplastie, transfert gazeux, ou manuellement au tampon. 10 Dans la bijouterie et dans les articles de traitement du corps humain ou animal venant en contact avec la peau, le placage est réalisé avec des métaux anallergiques ou biocompatibles tels que l'or et l'argent et en aucun cas avec du nickel, dont le contact direct avec la peau est interdit depuis longtemps. L'invention concerne plus spécialement la protection des aimants en 15 alliage néodyme-fer-bore. Le néodyme est un métal gris argent de la famille des lanthanides, et qui, allié au fer et au bore est utilisé pour réaliser des aimants permanents puissants. Cet alliage présente l'inconvénient de s'oxyder rapidement à l'air et à température ambiante notamment à cause de la présence du fer. Pour éviter cette oxydation détériorant l'aspect de l'aimant avant d'en réduire la 20 puissance et le rendre inapte, chaque aimant est traditionnellement recouvert par un placage en nickel ou en zinc. Ce placage peut-être aussi recouvert d'une peinture de type époxy. Dans le cadre d'utilisation industrielle ces revêtements peuvent être suffisants. Dans le cadre d'un usage thérapeutique et surtout lorsqu'ils sont 25 directement placés en contact avec la peau, ces revêtements ne sont plus adaptés. Dans l'utilisation thérapeutique en contact avec la peau, on utilise des aimants en alliage néodyme-fer-bore revêtus de nickel pour réaliser ensuite un placage d'or afin d'éviter les allergies au nickel. On trouve aussi des aimants qui en plus du placage d'or sont enrobés d'un vernis de type polyuréthane transparent 30 pour renforcer la barrière au nickel. A l'usage, il se révèle que les frottements contre la peau, de même que la répétition des collages et décollages de l'adhésif de fixation sur la peau, parviennent à user la couche de vernis et permettent à la couche d'or de venir en contact avec la peau. Le vernis polyuréthane présente une tension de surface moyenne très adhérente à l'adhésif. Il en résulte des résidus d'adhésifs sur la surface de l'aimant à la suite des collages et décollages successifs ainsi qu'une altération rapide de la couche de vernis. La grande sensibilité de l'or à l'oxydation par l'air, la faible épaisseur de son placage, de l'ordre de trois micromètres, et les mêmes phénomènes d'usure par frottement, auxquels s'ajoutent les effets de l'acidité de certaines peaux humaines, permettent rapidement d'éliminer localement l'or au profit du nickel sous-jacent, puis du néodyme encore plus sensible à l'oxydation. Il en résulte que l'oxydation détruit l'aspect esthétique de l'aimant, le rend impropre à son usage, et oblige à le remplacer.The invention relates to a protective coating for a neodymium-iron-boron alloy magnet and to its method of production. The technical field of the invention is therefore the plating of metals on other materials to improve their qualities. It more particularly relates to the veneer made by titanium nitride. The state of the art provides numerous methods of protecting various metal articles with a layer of metal, such as nickel, chromium, zinc, gold and silver, this layer being deposited by electrolysis, electroplating, gas transfer, or manually at buffer. In the jewelery and in the articles of treatment of the human or animal body coming into contact with the skin, the plating is carried out with anallergic or biocompatible metals such as gold and silver and in no case with nickel, of which direct contact with the skin has been banned for a long time. The invention relates more particularly to the protection of neodymium-iron-boron alloy magnets. Neodymium is a silver gray metal of the lanthanide family, which, together with iron and boron, is used to make strong permanent magnets. This alloy has the disadvantage of rapidly oxidizing in air and at room temperature, particularly because of the presence of iron. To avoid this oxidation deteriorating the appearance of the magnet before reducing its power and rendering it unsuitable, each magnet is traditionally covered by a nickel or zinc plating. This veneer may also be covered with an epoxy type paint. In the context of industrial use these coatings can be sufficient. In the context of a therapeutic use and especially when they are placed directly in contact with the skin, these coatings are no longer suitable. In therapeutic use in contact with the skin, neodymium-iron-boron alloy magnets coated with nickel are used to then carry out gold plating in order to avoid nickel allergies. Magnets are also found which, in addition to the gold plating, are coated with a clear polyurethane varnish to reinforce the nickel barrier. In use, it turns out that the friction against the skin, as well as the repetition of gluing and take-off of the fixing adhesive on the skin, manage to wear the layer of varnish and allow the gold layer to come into contact with the skin. The polyurethane varnish has a medium surface tension very adherent to the adhesive. This results in adhesive residues on the surface of the magnet following successive collages and takeoffs as well as a rapid deterioration of the varnish layer. The high sensitivity of gold to oxidation by air, the small thickness of its plating, of the order of three micrometers, and the same phenomena of frictional wear, to which are added the effects of acidity of some human skins, quickly allow the local elimination of gold in favor of the underlying nickel, then neodymium even more sensitive to oxidation. As a result, oxidation destroys the aesthetic appearance of the magnet, renders it unfit for use, and requires replacement.

L'objet de l'invention est de remédier à ces inconvénients en fournissant un placage garantissant la protection de l'aimant mais aussi de la personne utilisant son champ magnétique permanent par contact direct contre la peau. Parmi les matières utilisées pour constituer des placages sur des surfaces métalliques on connait le nitrure de titane (Ti N) se caractérisant par sa résistance à l'oxydation, par sa biocompatibilité, par son faible coefficient de frottement et par sa dureté. Cette matière est par exemple déposée sur les zones coupantes des outils de coupe pour en améliorer le tranchant, la force de frottement et la résistance à l'usure. C'est cette couche qui donne localement aux outils une couleur dorée caractéristique. Pour résoudre le problème à la base de l'invention, il vient immédiatement à l'esprit de remplacer le placage à l'or par un revêtement au nitrure de titane, mais faut il encore pouvoir assurer sa liaison avec l'alliage néodyme-fer-bore de manière à former une couche homogène, résistante et s'accrochant au substrat. C'est donc par sélection de diverses combinaisons qu'a été retenue la solution consistant à déposer la couche de nitrure de titane sur une couche de nickel enveloppant l'aimant en alliage néodyme-fer-bore. Grace à cet aménagement, l'alliage à base de néodyme est protégé par deux couches métalliques, dont celle extérieure en nitrure de titane est peu sensible à l'usure, en raison de son faible coefficient de frottement. De la sorte, il est improbable que les frottements sur la peau, de même que les collages et décollages des adhésifs, usent localement cette couche en nitrure de titane. Il n'y a donc aucun risque que le nickel vienne en contact avec la peau et que l'alliage néodyme-fer-bore puisse venir en contact avec l'air par usure successive de chacune de ses couches protectrices. Par ailleurs, l'aspect économique a aussi une importance indéniable dans l'apport de la présente invention. En effet, l'or étant un matériau dont le prix ne cesse d'augmenter, son remplacement par le nitrure de titane présente un intérêt économique incontestable, même si la mise en oeuvre du traitement par évaporation gazeuse est d'un coût supérieur à l'électrolyse. Dans une forme d'exécution de l'invention, une couche de chrome est interposée entre la couche de nitrure de titane et la couche de nickel enveloppant l'aimant. Cette couche intercalaire augmente la protection des couches qu'elle enveloppe et accroit la brillance du nitrure de titane qui se rapproche alors de celle de l'or. Avantageusement, la couche de nitrure de titane est recouverte par une couche de vernis.The object of the invention is to overcome these disadvantages by providing a veneer guaranteeing the protection of the magnet but also the person using his permanent magnetic field by direct contact against the skin. Among the materials used to form veneers on metal surfaces is known titanium nitride (Ti N) characterized by its resistance to oxidation, its biocompatibility, its low coefficient of friction and its hardness. This material is for example deposited on the cutting areas of the cutting tools to improve the cutting edge, the friction force and the wear resistance. It is this layer that locally gives the tools a characteristic golden color. To solve the problem underlying the invention, it immediately comes to mind to replace the gold plating with a titanium nitride coating, but must still be able to ensure its connection with the neodymium-iron alloy -bore so as to form a homogeneous layer, resistant and clinging to the substrate. It is therefore through the selection of various combinations that the solution consisting in depositing the titanium nitride layer on a layer of nickel enveloping the neodymium-iron-boron alloy magnet was chosen. Thanks to this arrangement, the neodymium alloy is protected by two metal layers, the outer layer of titanium nitride is insensitive to wear, due to its low coefficient of friction. In this way, it is unlikely that the friction on the skin, as well as the collages and take-offs of the adhesives, locally use this layer of titanium nitride. There is therefore no risk that the nickel comes into contact with the skin and that the neodymium-iron-boron alloy can come into contact with the air by successive wear of each of its protective layers. Moreover, the economic aspect also has undeniable importance in providing the present invention. Indeed, gold being a material whose price continues to increase, its replacement by titanium nitride has an undeniable economic interest, even if the implementation of gas evaporation treatment is of a cost greater than 'electrolysis. In one embodiment of the invention, a chromium layer is interposed between the titanium nitride layer and the nickel layer surrounding the magnet. This interlayer increases the protection of the layers it envelops and increases the brightness of the titanium nitride which is close to that of gold. Advantageously, the titanium nitride layer is covered by a layer of varnish.

Cette couche améliore la protection de l'aimant et de l'utilisateur. Elle permet aussi d'utiliser cet aimant dans les applications dans lesquelles chaque aimant est maintenu par collage au moyen d'un adhésif contre un support, textile ou autre. En effet, sans le vernis enveloppant le nitrure de titane, le caractère anti adhésif de ce dernier rendrait très aléatoire son collage contre un adhésif et s'opposerait à son utilisation dans les applications mettant en oeuvre des aimants amovibles. L'invention concerne aussi le procédé de fabrication du placage. Dans une forme de réalisation de la présente invention, chaque aimant est en forme de disque de 2 à 6 millimètres d'épaisseur pour un diamètre de 10, 15, 25 ou 32 millimètres de diamètre. Ce disque présente un bord arrondi pour ne pas marquer la peau à cause d'une arête vive. Il est formé par frittage de poudre d'alliage néodyme-fer-bore sous haute température. Immédiatement après son frittage, l'aimant est enveloppé par un dépôt électrolytique de nickel avec une épaisseur de l'ordre de 3 micromètres et, dans 30 une réalisation, par un dépôt électrolytique de chrome de la même épaisseur. Ces dépôts électrolytiques sont des procédés bien connus par l'homme de métier. Ensuite, chaque aimant reçoit par évaporation en phase gazeuse une couche enveloppante en nitrure de titane, à une température contrôlée. La température de traitement ne doit pas modifier l'alliage néodyme-fer-bore pour ne pas altérer ses propriétés magnétiques. Le traitement est interrompu quand la couche a une épaisseur de l'ordre de 3 micromètres. C'est à la fin de cette opération que les futures faces nord des aimants reçoivent le marquage du fabricant. Cette opération est réalisée par gravure laser 5 superficielle de la couche de nitrure de titane. A ce stade les aimants sont prêts pour l'usage thérapeutique en contact avec la peau. Le revêtement titane révèle ses multiples avantages : la biocompatibilité, la faible adhérence, et pour l'aspect marketing la couleur or et la belle apparence de la gravure laser sur le nitrure de titane.This layer improves the protection of the magnet and the user. It also allows the use of this magnet in applications in which each magnet is held by gluing by means of an adhesive against a support, textile or other. Indeed, without the enamel surrounding the titanium nitride, the anti-adhesive nature of the latter would make it very random sticking against an adhesive and oppose its use in applications using removable magnets. The invention also relates to the method of manufacturing the plating. In one embodiment of the present invention, each magnet is disk-shaped 2 to 6 millimeters thick for a diameter of 10, 15, 25 or 32 millimeters in diameter. This disc has a rounded edge to not mark the skin because of a sharp edge. It is formed by sintering neodymium-iron-boron alloy powder under high temperature. Immediately after sintering, the magnet is enveloped by electrolytic nickel deposition with a thickness of the order of 3 microns and, in one embodiment, electrolytic deposition of chromium of the same thickness. These electrolytic deposits are methods well known to those skilled in the art. Then, each magnet receives by evaporation in the gas phase a surrounding layer of titanium nitride, at a controlled temperature. The treatment temperature must not modify the neodymium-iron-boron alloy in order not to alter its magnetic properties. The treatment is interrupted when the layer has a thickness of the order of 3 microns. It is at the end of this operation that the future north faces of the magnets receive the marking of the manufacturer. This operation is carried out by superficial laser etching of the titanium nitride layer. At this stage the magnets are ready for therapeutic use in contact with the skin. The titanium coating reveals its many advantages: biocompatibility, low adhesion, and for the marketing aspect the gold color and the beautiful appearance of laser engraving on titanium nitride.

10 Dans une autre réalisation de l'invention, la couche de nitrure de titane est recouverte par une couche de vernis déposée au trempé ou par tout autre moyen connu de l'homme de métier. Ce vernis peut-être un vernis polyuréthane transparent contact cutané avec un additif de type silicone pour abaisser l'adhérence.In another embodiment of the invention, the titanium nitride layer is covered by a layer of varnish deposited by dipping or by any other means known to those skilled in the art. This varnish may be a clear polyurethane skin contact with a silicone type additive to lower the adhesion.

15 Dans une autre version de réalisation, le vernis polyuréthane est utilisé sans additif de façon à conserver une tension de surface élevée et favoriser le collage de l'aimant sur des supports, par exemple textiles ou en matières plastiques. Dans ces applications l'usage de colles de type cyanoacrylate est privilégié.In another embodiment, the polyurethane varnish is used without additive so as to maintain a high surface tension and promote the bonding of the magnet on supports, for example textile or plastic. In these applications, the use of cyanoacrylate adhesives is preferred.

20 Dans d'autres variantes de réalisation de l'invention, la couleur du dépôt de nitrure de titane peut être modifiée et différente de la couleur or, comme par exemple de teintes bleues, argentées ou grises. Le marquage laser reste toujours possible sur ces couleurs.In other embodiments of the invention, the color of the titanium nitride deposit may be varied and different from the gold color, such as, for example, blue, silver or gray tints. Laser marking is still possible on these colors.

Claims (8)

REVENDICATIONS1.) Placage protecteur pour aimant en alliage néodyme-fer-bore, caractérisé en ce qu'il comprend, de l'intérieur vers l'extérieur en partant de l'aimant, une couche de nickel et un couche de nitrure de titane.CLAIMS1.) Protective veneer for a neodymium-iron-boron alloy magnet, characterized in that it comprises, from the inside towards the outside, starting from the magnet, a layer of nickel and a layer of titanium nitride. 2.) Placage protecteur pour aimant néodyme-fer-bore selon la revendication 1 caractérisé en ce qu'une couche de chrome est interposée entre la couche de nickel et la couche de nitrure de titane.2.) Protective veneer for neodymium-iron-boron magnet according to claim 1 characterized in that a chromium layer is interposed between the nickel layer and the titanium nitride layer. 3.) Placage protecteur pour aimant néodyme-fer-bore selon la revendication 1 caractérisé en ce que la couche de nitrure de titane est recouverte 10 par une couche de vernis.3.) Protective veneer for neodymium-iron-boron magnet according to claim 1 characterized in that the titanium nitride layer is covered by a layer of varnish. 4.) Placage protecteur pour aimant néodyme-fer-bore selon les revendications 1 et 3 prises ensemble caractérisé en ce que le vernis est un vernis polyuréthane sans additif pour conserver une tension de surface élevée favorisant le collage ultérieur de l'aimant.. 154.) Protective veneer for neodymium-iron-boron magnet according to claims 1 and 3 taken together characterized in that the varnish is a polyurethane varnish without additive to maintain a high surface tension favoring the subsequent bonding of the magnet. 5.) Placage protecteur pour aimant néodyme-fer-bore selon les revendications 1 et 3 prises ensemble caractérisé en ce que le vernis est un vernis polyuréthane comportant un additif abaissant l'adhérence de surface.5.) Protective veneer for neodymium iron boron magnet according to claims 1 and 3 taken together characterized in that the varnish is a polyurethane varnish comprising an additive reducing the surface adhesion. 6.) Procédé de fabrication d'un placage protecteur pour aimant néodyme-fer-bore selon la revendication 1 caractérisé en ce qu'il consiste, 20 immédiatement après réalisation de chaque aimant par frittage d'un mélange de poudre de néodyme, fer et bore, à envelopper cet aimant par dépôt électrolytique sur lui, d'une couche de nickel, puis à l'envelopper, par évaporation en phase gazeuse, par une couche de nitrure de titane.6. A method of manufacturing a protective coating for neodymium iron boron magnet according to claim 1, characterized in that it consists, immediately after completion of each magnet by sintering a mixture of neodymium powder, iron and boron, to wrap this magnet by electrolytic deposition on it, a layer of nickel, and then wrap, by gas phase evaporation, with a layer of titanium nitride. 7.) Procédé de fabrication d'un placage protecteur pour aimant 25 néodyme-fer-bore selon la revendication 6 caractérisé en ce qu'il comprend, entre la phase de dépôt de la couche de nickel et la phase de dépôt de nitrure de titane, une phase de dépôt d'une couche de chrome enveloppant la couche de nickel.7.) A method of manufacturing a protective coating for neodymium iron boron magnet according to claim 6 characterized in that it comprises, between the deposition phase of the nickel layer and the titanium nitride deposition phase , a phase of deposition of a layer of chromium enveloping the nickel layer. 8.) Procédé de fabrication selon l'une quelconque des revendications 6 30 ou 7 caractérisé en ce qu'il comprend, après réalisation de la couche de nitrure de titane, et avant recouvrement par un vernis, à réaliser l'identification de la face Nord de l'aimant par gravure au laser dans l'épaisseur de cette couche.8.) The manufacturing method according to any one of claims 6 or 7 characterized in that it comprises, after production of the titanium nitride layer, and before coating with a varnish, to perform the identification of the face North of the magnet by laser etching in the thickness of this layer.
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