EP2546371B1 - 18-carat grey gold - Google Patents

18-carat grey gold Download PDF

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Publication number
EP2546371B1
EP2546371B1 EP12176002.9A EP12176002A EP2546371B1 EP 2546371 B1 EP2546371 B1 EP 2546371B1 EP 12176002 A EP12176002 A EP 12176002A EP 2546371 B1 EP2546371 B1 EP 2546371B1
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Prior art keywords
gold
alloy
essentially
composition
component
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German (de)
French (fr)
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EP2546371A1 (en
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Niklaus Baltzer
Thierry Copponnex
Kangping Huang Guo
Laurence Simonet
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Cendres and Metaux SA
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Cendres and Metaux SA
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C5/00—Alloys based on noble metals
    • C22C5/02—Alloys based on gold
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/14—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of noble metals or alloys based thereon

Definitions

  • the present invention relates to an 18-carat white gold having a white color comparable to that of rhodium-plated gold and having good polishing ability for applications in jewelery, watchmaking, jewelery, or for writing instruments.
  • 18ct white gold alloys also known as white gold usually consist of gold, copper and elements that have the power to whiten gold. These whitening elements are often found in group VIII of the periodic table of the elements, such as Ni, Pd, Co and Fe. The whitening effect of certain metals on gold has been the subject of studies since the 1970s. as described in reference 1: " Improvement of 18 carat white gold alloys ", GP O'Connor, Gold Bull 11, 2 (1978) ).
  • gray gold alloys are distinguished into two categories: palladium gold and nickel gold.
  • Nickel brings an interesting color and is economically advantageous, but its allergenic effect has almost proscribed luxury applications (jewelry, watchmaking).
  • the Applicant has studied various metallurgical systems in order to develop an 18-carat gray gold.
  • the alloys studied are based on the Au-Pd system with usual additive elements such as Ag, Ga, Zn, Sn, Fe and Rh, but without nickel and without copper. This is a classic composition for a jewelery alloy.
  • the whitest alloy obtained consists of 75% Au, 21% Pd, 2% Ag and 2% Rh.
  • Table 1 gives the colorimetric measurements on the L * a * b * scale, according to the CIE 1976 model, of different compositions of 18cts gray alloys on the market.
  • the value of the Yellowness Index (YI), or yellow index is also specified.
  • This parameter is commonly used to characterize the white color of an alloy (What is a white gold? Progress on the issues! Dr. Christopher W. Corti, Santa Fe Symposium Proceedings, May 2005 ).
  • the World Gold Council has defined several grades of gray gold: Non-White (YI>32); Off-White (24.5 ⁇ YI ⁇ 32); Standard-White (19 ⁇ YI ⁇ 24.5); Premium-White (YI ⁇ 19).
  • the Applicant has also studied the development of a gray gold in the Au-In system.
  • it has studied the feasibility of industrial exploitation of the Au75In25 alloy as an alloy for jewelery.
  • Au75In25 is in the zone ( ⁇ ) which is an intermetallic phase (Au3In2).
  • Au3In2 an intermetallic phase
  • This alloy gives the alloy an extraordinarily white color, but its intermetallic structure gives it a very great fragility.
  • This alloy is unfortunately practically unusable.
  • the addition of elements like Sn, Al, Zn, Cr and Nb has also been considered in order to obtain 18-carat gold ternary alloys based on the Au-In system. It has been shown that the addition of an element comprising one of: Sn, Al, Zn, Cr and Nb, however, gives rise to either a loss of color or an inhomogeneous structure, and does not sufficiently improve the ductility of the alloy.
  • the whitening power of chromium on gold is a known feature which is cited in a number of publications such as reference 1, reference 2: " Mechanical properties of Au-Fe-Cr white gold, T. Suzuki, Y. Kaneko, S. Hashimoto, J. Japan Inst Metals, 67, No. 11 (2003) ); and reference 3: " White gold alloys for investment casting ", M. Poliero, Gold Technology, No. 31 (2001) ). From this observation, the plaintiff chose to direct her research towards the Au-Cr system.
  • the patent application WO2009 / 092920 also cites the use of Cr to whiten gold.
  • it discloses the combination of gold with a refractory metal of columns IVB, VB and VIB of the periodic table (including Cr), without specifying the contents of refractory element.
  • the patent application JPH0657356 discloses a decorative gold alloy containing, by weight, 75% Au, 15 to 24% of at least one of Fe and Cr, and 1 to 10% of Ni.
  • the alloy is subjected to a treatment at a temperature between 250 and 500 ° C with an oxidizing flame so as to obtain a color ranging from yellow, red, purple, blue, green to gray.
  • the whitening power of Cr has already been demonstrated, its use is limited because of its partial miscibility with gold. Indeed, if the limit of solubility of Cr in Au is exceeded, the alloy becomes inhomogeneous. The Cr precipitates present in the material deteriorate the polishing ability of the alloy, which then becomes unusable for an application in jewelery / watchmaking. The difficulty of developing a gray gold at Cr then consists in introducing additional alloying elements making it possible to increase the solubility of Cr in gold, without altering the white color.
  • An object of the present invention is to provide an 18-carat gray gold alloy free from the limitations of known gray gold.
  • Another object of the invention is to obtain an alloy of 18 carat gold of white color, in the mass, comparable to that of a gold rhodium, and having a good surface quality after a mirror polishing.
  • gray gold alloy comprising by weight: essentially 75% of gold; between 13% and 17% of Cr; between 5% and 10% of Pd; and between 1% and 5% Fe.
  • the alloy comprises by weight 75% Au, 17% Cr, and 8% Pd.
  • This alloy is characterized by a color L * a * b * having the component L * of about 82, the component a * of about 0.56 and the component b * of about 3.7.
  • the Cr composition is between 13% and 16%; the composition of the Pd is between 5% and 8%; and the composition of the Fe is between 1% and 4%.
  • the alloy comprises by weight essentially 75% Au, essentially 15% Cr, essentially 7% Pd, and essentially 3% Fe.
  • This alloy is characterized by a color The color L * a * b * with a component L * of about 82, a component a * of about 0.45 and a component b * of about 3.0 .
  • the present disclosure also relates to a timepiece, jewelery, jewelery or writing instrument, comprising at least one component made with the alloy of the invention.
  • This solution has the particular advantage over the prior art of obtaining an 18-carat gold alloy making it possible to produce compositions combining a color close to rhodium-plated gold and a polishing ability that makes it possible to produce jewelery pieces. watchmaking, jewelery, or writing instruments.
  • the good surface quality is directly related to the homogeneity of the alloy. If the alloy has a multiphase structure, inhomogeneities will appear on the surface of the mirror-polish.
  • an 18-carat white gold alloy comprising by weight: at least 75% gold; between 13% and 23% of Cr; between 2% and 12% of at least one element selected from: Pd, Fe, Ru, Pt, Co, Ga, Ge, Mn, V, Ni.
  • the composition of Cr may be between 15% and 20% and the composition of said at least one element chosen from: Pd, Fe, Ru, Pt, Co, Ga, Ge, Mn, V, Ni is between 5% and 10%.
  • the alloy comprises between 2% and 12% of Pd and at most 5% of at least one element chosen from Fe, Ru, Pt, Co, Ga, Ge and Mn.
  • the composition of the Cr can be between 13% and 18%.
  • the composition of the Pd can be between 5% and 10%.
  • the good surface quality is directly related to the homogeneity of the alloy. If the alloy has a multiphase structure, inhomogeneities will appear on the surface of the mirror-polish.
  • an 18-carat white gold alloy comprising by weight: at least 75% gold; between 13% and 23% of Cr; between 2% and 12% of at least one element selected from: Pd, Fe, Ru, Pt, Co, Ga, Ge, Mn, V, Ni.
  • the composition of Cr may be between 15% and 20% and the composition of said at least one element chosen from: Pd, Fe, Ru, Pt, Co, Ga, Ge, Mn, V, Ni is between 5% and 10%.
  • the alloy comprises between 2% and 12% of Pd and at most 5% of at least one element chosen from Fe, Ru, Pt, Co, Ga, Ge and Mn.
  • the composition of the Cr can be between 13% and 18%.
  • the composition of the Pd can be between 5% and 10%.
  • the alloy further comprises at most 1% of an element chosen from refining elements: Ir, Rh, Re, W, Mo, among the neutral elements: Nb, Ta, Ni, V , Ti, Zn, and among the deoxidizing elements: Zr, Si and B.
  • refining elements Ir, Rh, Re, W, Mo
  • neutral elements means elements that have no significant effect on the main characteristics of the alloy as described herein. above and including these neutral elements.
  • the 18-carat white gold alloy comprises by weight: at least 75% Au, essentially 17% Cr, and essentially 8% Pd.
  • the whitening effect of Pd is widely used in conventional 18K gray golds.
  • Cr having a significant solubility in Pd this element has been introduced as a secondary addition element in different proportions in order to improve the homogeneity of the material.
  • the use of this element makes it possible, in fact, to maintain high levels of Cr without altering the white color.
  • the polishing ability has been improved but is not optimal because Cr precipitates are sometimes present from the casting.
  • the most favorable composition contains essentially 17% Cr and essentially 8% Pd (see Table 2).
  • the Au-Cr-Pd-Fe system has also been studied.
  • Fe has indeed a high solubility in Cr and Pd at high temperature.
  • it is a known element for bleaching gold (see references 2 and 3).
  • the substitution of a few mass percents of Cr in favor of Fe has considerably improved the homogeneity of the material and thus the polishing ability, while maintaining a very interesting color.
  • the 18-carat white gold alloy comprises by weight: at least 75% gold; between 13% and 17% of Cr; between 5% and 10% of Pd; and between 1% and 5% Fe.
  • the Cr composition is between 13% and 16%; and the composition of the Pd is between 5% and 8%.
  • the gold alloy comprises by weight: at least 75% Au, essentially 15% Cr, and essentially 7% Pd and essentially 3% Fe. This latter alloy has the best compromise between color and polishing ability. .
  • Table 2 reports results of measurements on the L * a * b * scale according to the CIE 1976 model. and the Yellowness Index (YI), or yellow index, measured according to ASTM D-1925 for each of these alloys, as well as observations on the quality of the polishing.
  • Table 2 reports colorimetric measurements and observations on the polishing quality of four conventional gray gold alloys (Nos. 1 to 4) and seven examples of gold alloys according to the invention (Nos. 5 to 11). The compositions are expressed in% by weight.
  • the measurements have shown in particular that the alloy comprises by weight: at least 75% of gold; between 13% and 23% of Cr; between 2% and 12% of at least one element selected from: Pd, Fe, Ru, Pt, Co, Ga, Ge, Mn, V, Ni, is characterized by a yellow index being less than 10. a yellow index of less than 10 for the other alloys of the invention.
  • the color is in the mass of the alloy and can not be damaged by surface wear.
  • a color L * a * b * is measured with the L * component of about 82, the component a * d about 0.56 and the b * component about 3.7.
  • a color L * a * b * is measured with the L * component of about 82%. , the component a * of about 0.45 and the component b * of about 3.0.
  • compositions AuCr17Pd8 at least 75% Au, essentially 17% Cr, and essentially 8% Pd
  • AuCr15Pd7Fe3 at least 75% Au, essentially 15% Cr, essentially 7% Pd, and essentially 3% Fe
  • the composition containing Fe has the most promising characteristics for an application in the field of luxury (jewelery, watchmaking) because it combines both a very white color and good polishing ability.
  • Corrosion test results according to the dental standard were performed on seven alloys to evaluate the release rate (in ⁇ g / cm 2 x7d) of the ions of sensitive elements such as Ni and Cr (Table 3).
  • the ISO 10271-2001 standard limits the total release rate to 200 ⁇ g / cm 2 x 7d. According to these tests, the two alloys AuCr17Pd8 and AuCr15Pd7Fe have a very good resistance to corrosion.
  • Table 4 gives a summary of our studies in the Au-Cr-X and Au-Cr-Pd-Fe systems as well as the characteristics of the two preferred alloys.
  • X corresponds to at least one element chosen from: Pd, Fe, Ru, Pt, Co, Ga, Ge, Mn, V, Ni.
  • the study of the Au-Cr-Pd ternary system has made it possible to develop 18-carat alloys with a white color comparable to that of rhodium-plated gold.
  • the best composition corresponds to: at least 75% Au, essentially 17% Cr and essentially 8% Pd.
  • the Au-Cr-Pd-Fe quaternary system made 18cts alloys with even more attractive properties in terms of color, polishing ability, ductility and price.
  • the best composition corresponds to: at least: 75% Au, essentially 15% Cr, essentially 7% Pd and essentially 3% Fe.
  • Cr is introduced as the main bleaching element.
  • Pd and Fe are introduced to improve the solubility of chromium in gold, without altering the desired white color. Only the combination of the three elements of alloy Cr, Pd and Fe has made it possible to develop compositions combining a color close to rhodium-plated golds and a polishing ability allowing the production of pieces of jewelery, timepieces, jewelery, or jewelry. writing instruments.

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Description

Domaine techniqueTechnical area

La présente invention concerne un or gris 18 carats présentant une couleur blanche comparable à celle des ors rhodiés et possédant une bonne aptitude au polissage pour des applications en bijouterie, en horlogerie, en joaillerie, ou pour des instruments d'écriture.The present invention relates to an 18-carat white gold having a white color comparable to that of rhodium-plated gold and having good polishing ability for applications in jewelery, watchmaking, jewelery, or for writing instruments.

Etat de la techniqueState of the art

Les alliages d'or gris (également dénommés or blanc) 18 carats se composent habituellement d'or, de cuivre et d'éléments qui ont le pouvoir de blanchir l'or. Ces éléments blanchissants se trouvent souvent dans le groupe VIII du tableau périodique des éléments, comme Ni, Pd, Co et Fe. L'effet blanchissant de certains métaux sur l'or a fait l'objet d'études dès les années 70, tel que décrit dans la référence 1: " Improvement of 18 carat white gold alloys", G.P. O'Connor, Gold Bull. 11, 2 (1978 ).18ct white gold alloys (also known as white gold) usually consist of gold, copper and elements that have the power to whiten gold. These whitening elements are often found in group VIII of the periodic table of the elements, such as Ni, Pd, Co and Fe. The whitening effect of certain metals on gold has been the subject of studies since the 1970s. as described in reference 1: " Improvement of 18 carat white gold alloys ", GP O'Connor, Gold Bull 11, 2 (1978) ).

Sur le marché actuel, les alliages d'or gris se distinguent en deux catégories: les ors au palladium et les ors au nickel. Le nickel apporte une couleur intéressante et est économiquement avantageux, mais son effet allergisant l'a quasiment proscrit des applications de luxe (bijouterie, horlogerie).In the current market, gray gold alloys are distinguished into two categories: palladium gold and nickel gold. Nickel brings an interesting color and is economically advantageous, but its allergenic effect has almost proscribed luxury applications (jewelry, watchmaking).

Pour blanchir l'or sans nickel, différentes pistes sont explorées avec leurs inconvénients. Par exemple, on peut augmenter la teneur en éléments platineux. Cette solution est chère et ne permet pas d'obtenir un or assez blanc. Une autre solution consiste à rhodier la surface du produit final. Dans ce cas, une couleur blanche est bien obtenue mais comme il s'agit d'un traitement superficiel, la couche colorée est sensible à l'usure due au frottement et la couleur blanche est susceptible d'être détériorée avec le temps.To whiten nickel-free gold, different tracks are explored with their disadvantages. For example, the platinum content can be increased. This solution is expensive and does not get a pretty white gold. Another solution is to rhodium the surface of the final product. In this case, a white color is well obtained but as it is a surface treatment, the colored layer is sensitive to wear due to friction and the white color is likely to be deteriorated with time.

Dès 2003, la demanderesse a étudié différents systèmes métallurgiques dans le but de développer un or gris 18 carats. Les alliages étudiés sont basé sur le système Au-Pd avec des éléments additifs habituels tels que Ag, Ga, Zn, Sn, Fe et Rh, mais sans nickel et sans cuivre. Il s'agit d'une composition classique pour un alliage de joaillerie. Dans cette première étude, l'alliage le plus blanc obtenu se compose de 75%Au, 21 %Pd, 2%Ag et 2%Rh. Le Tableau 1 donne les mesures colorimétriques sur l'échelle L*a*b*, selon le modèle C.I.E. 1976, de différentes compositions d'alliages 18cts gris présents sur le marché. La valeur du Yellowness Index (YI), ou indice de jaune, est également précisée. Ce paramètre, calculé à partir des trois coordonnées L*a*b*, est couramment employé pour caractériser la couleur blanche d'un alliage (What is a white gold ? Progress on the issues !", Dr Christopher W. Corti, Santa Fe Symposium Proceedings, May 2005 ). Sur la base de ce paramètre, le World Gold Council a défini plusieurs grades d'or gris : Non-White (YI>32) ; Off-White (24.5<YI<32) ; Standard-White (19<YI<24.5) ; Premium-White (YI<19). Tableau 1 Composition d'alliage L* a* b* YI Situation du marché Au750, Ni155, Cu40,Zn55 85 0.4 5.9 12.2 Produit du marché Au750, Ni50, Pd50, Ag110, Cu40 78.2 0.7 5.9 14.1 Produit du marché Au750, Pd120, Ag40, Cu90 80 2.8 8.2 20.6 Produit courant du marché Au750, Pd120, Ag40, Cu90 ; rhodié 90 1.0 2.2 5.6 Produit le plus courant du marché Au750, Pd210, In35, Ga5 79 1.6 6.1 15.2 Produit du marché Au750, Pd210, Ag20, Rh20 79.4 1.4 5.2 13.1 CM prototype 2003, trop cher Since 2003, the Applicant has studied various metallurgical systems in order to develop an 18-carat gray gold. The alloys studied are based on the Au-Pd system with usual additive elements such as Ag, Ga, Zn, Sn, Fe and Rh, but without nickel and without copper. This is a classic composition for a jewelery alloy. In this first study, the whitest alloy obtained consists of 75% Au, 21% Pd, 2% Ag and 2% Rh. Table 1 gives the colorimetric measurements on the L * a * b * scale, according to the CIE 1976 model, of different compositions of 18cts gray alloys on the market. The value of the Yellowness Index (YI), or yellow index, is also specified. This parameter, calculated from the three coordinates L * a * b *, is commonly used to characterize the white color of an alloy (What is a white gold? Progress on the issues! Dr. Christopher W. Corti, Santa Fe Symposium Proceedings, May 2005 ). On the basis of this parameter, the World Gold Council has defined several grades of gray gold: Non-White (YI>32); Off-White (24.5 <YI <32); Standard-White (19 <YI <24.5); Premium-White (YI <19). Table 1 Alloy composition L * at* b * YI Market situation Au750, Ni155, Cu40, Zn55 85 0.4 5.9 12.2 Market product Au750, Ni50, Pd50, Ag110, Cu40 78.2 0.7 5.9 14.1 Market product Au750, Pd120, Ag40, Cu90 80 2.8 8.2 20.6 Current product of the market Au750, Pd120, Ag40, Cu90; rhodium 90 1.0 2.2 5.6 Most common product on the market Au750, Pd210, In35, Ga5 79 1.6 6.1 15.2 Market product Au750, Pd210, Ag20, Rh20 79.4 1.4 5.2 13.1 CM prototype 2003, too expensive

La demanderesse a également étudié le développement d'un or gris dans le système Au-In. Elle a notamment étudié la faisabilité d'une exploitation industrielle de l'alliage Au75In25 comme alliage pour la bijouterie. Selon le diagramme de phases du système Au-In, Au75In25 se trouve dans la zone (Ψ) qui est une phase intermétallique (Au3In2). Cette composition donne à l'alliage une couleur extraordinairement blanche, mais sa structure intermétallique lui confère une très grande fragilité. Cet alliage est malheureusement pratiquement inexploitable. L'ajout d'éléments comme Sn, Al, Zn, Cr et Nb a également été considéré de sorte à obtenir des alliages d'or ternaires 18 carats basés sur le système Au-In. Il a été montré que l'ajout d'un élément comprenant l'un de: Sn, Al, Zn, Cr et Nb engendre cependant, soit une perte de couleur, soit une structure inhomogène, et n'améliore pas suffisamment la ductilité de l'alliage.The Applicant has also studied the development of a gray gold in the Au-In system. In particular, it has studied the feasibility of industrial exploitation of the Au75In25 alloy as an alloy for jewelery. According to the Au-In phase diagram, Au75In25 is in the zone (Ψ) which is an intermetallic phase (Au3In2). This The composition gives the alloy an extraordinarily white color, but its intermetallic structure gives it a very great fragility. This alloy is unfortunately practically unusable. The addition of elements like Sn, Al, Zn, Cr and Nb has also been considered in order to obtain 18-carat gold ternary alloys based on the Au-In system. It has been shown that the addition of an element comprising one of: Sn, Al, Zn, Cr and Nb, however, gives rise to either a loss of color or an inhomogeneous structure, and does not sufficiently improve the ductility of the alloy.

Le pouvoir blanchissant du chrome sur l'or est une caractéristique connue qui est citée dans un certain nombre de publications telles que la référence 1, la référence 2: " Mechanical properties of Au-Fe-Cr white gold", T. Suzuki, Y. Kaneko, S. Hashimoto, J. Japan Inst. Metals, Vol. 67, No. 11 (2003 ); et la référence 3: " White gold alloys for investment casting", M. Poliero, Gold Technology, No 31 (2001 ). A partir de ce constat, la demanderesse a choisi d'orienter ses recherches vers le système Au-Cr.The whitening power of chromium on gold is a known feature which is cited in a number of publications such as reference 1, reference 2: " Mechanical properties of Au-Fe-Cr white gold, T. Suzuki, Y. Kaneko, S. Hashimoto, J. Japan Inst Metals, 67, No. 11 (2003) ); and reference 3: " White gold alloys for investment casting ", M. Poliero, Gold Technology, No. 31 (2001) ). From this observation, the plaintiff chose to direct her research towards the Au-Cr system.

L'emploi de Cr pour blanchir l'or (combiné à Ag, Cu, Ni et Fe) a notamment connu de la demande de brevet DE10027605 . Ce document décrit des teneurs en Cr n'excédant pas 14% en poids.The use of Cr for bleaching gold (combined with Ag, Cu, Ni and Fe) has, for example, been known from the patent application. DE10027605 . This document describes contents of Cr not exceeding 14% by weight.

La demande de brevet WO2009/092920 cite également l'utilisation de Cr pour blanchir l'or. En particulier, il divulgue la combinaison de l'or à un métal réfractaire des colonnes IVB, VB et VIB de la classification périodique (dont le Cr), sans préciser les teneurs en élément réfractaire.The patent application WO2009 / 092920 also cites the use of Cr to whiten gold. In particular, it discloses the combination of gold with a refractory metal of columns IVB, VB and VIB of the periodic table (including Cr), without specifying the contents of refractory element.

La demande de brevet JPH0657356 décrit un alliage d'or décoratif contenant, en poids, 75% Au, 15 à 24% d'au moins l'un de Fe et Cr, et 1 à 10% de Ni. L'alliage est soumis à un traitement à une température comprise entre 250 et 500 °C avec une flamme oxydante de sorte à obtenir une couleur allant de jaune, rouge, pourpre, bleu, vert à gris.The patent application JPH0657356 discloses a decorative gold alloy containing, by weight, 75% Au, 15 to 24% of at least one of Fe and Cr, and 1 to 10% of Ni. The alloy is subjected to a treatment at a temperature between 250 and 500 ° C with an oxidizing flame so as to obtain a color ranging from yellow, red, purple, blue, green to gray.

Si le pouvoir blanchissant du Cr a déjà été démontré, son emploi est limité étant donné sa miscibilité partielle avec l'or. En effet, si la limite de solubilité du Cr dans l'Au est dépassée, l'alliage devient inhomogène. Les précipités de Cr présents dans la matière détériorent l'aptitude au polissage de l'alliage qui devient alors inexploitable pour une application en bijouterie/horlogerie. La difficulté du développement d'un or gris au Cr consiste alors à introduire des éléments d'alliage additionnels permettant d'augmenter la solubilité du Cr dans l'or, sans altérer la couleur blanche.If the whitening power of Cr has already been demonstrated, its use is limited because of its partial miscibility with gold. Indeed, if the limit of solubility of Cr in Au is exceeded, the alloy becomes inhomogeneous. The Cr precipitates present in the material deteriorate the polishing ability of the alloy, which then becomes unusable for an application in jewelery / watchmaking. The difficulty of developing a gray gold at Cr then consists in introducing additional alloying elements making it possible to increase the solubility of Cr in gold, without altering the white color.

Bref résumé de l'inventionBrief summary of the invention

Un but de la présente invention est de proposer un alliage d'or gris 18 carats exempt des limitations des ors gris connus.An object of the present invention is to provide an 18-carat gray gold alloy free from the limitations of known gray gold.

Un autre but de l'invention est d'obtenir un alliage d'or 18 carats de couleur blanche, dans la masse, comparable à celle d'un or rhodié, et ayant une bonne qualité de surface après un polissage miroir.Another object of the invention is to obtain an alloy of 18 carat gold of white color, in the mass, comparable to that of a gold rhodium, and having a good surface quality after a mirror polishing.

Selon l'invention, ces buts sont atteints notamment au moyen d'un alliage d'or gris comprenant en poids: essentiellement 75% d'or; entre 13% et 17% de Cr; entre 5% et 10% de Pd; et entre 1 % et 5% de Fe.According to the invention, these objects are achieved in particular by means of a gray gold alloy comprising by weight: essentially 75% of gold; between 13% and 17% of Cr; between 5% and 10% of Pd; and between 1% and 5% Fe.

Dans un mode de réalisation, l'alliage comprend en poids 75% Au, 17%Cr, et 8%Pd. Cet alliage est caractérisé par une couleur L*a*b* ayant la composante L* d'environ 82, la composante a* d'environ 0.56 et la composante b* d'environ 3.7.In one embodiment, the alloy comprises by weight 75% Au, 17% Cr, and 8% Pd. This alloy is characterized by a color L * a * b * having the component L * of about 82, the component a * of about 0.56 and the component b * of about 3.7.

Encore dans un autre mode de réalisation, la composition du Cr est comprise entre 13% et 16%; la composition du Pd est comprise entre 5% et 8%; et la composition du Fe est comprise entre 1 % et 4%.In yet another embodiment, the Cr composition is between 13% and 16%; the composition of the Pd is between 5% and 8%; and the composition of the Fe is between 1% and 4%.

Encore dans un autre mode de réalisation, l'alliage comprend en poids essentiellement 75% Au, essentiellement 15% Cr, essentiellement 7% Pd, et essentiellement 3% Fe. Cet alliage est caractérisé par une couleur La couleur L*a*b* avec une composante L* d'environ 82, une composante a* d'environ 0.45 et une composante b* d'environ 3.0.In yet another embodiment, the alloy comprises by weight essentially 75% Au, essentially 15% Cr, essentially 7% Pd, and essentially 3% Fe. This alloy is characterized by a color The color L * a * b * with a component L * of about 82, a component a * of about 0.45 and a component b * of about 3.0 .

La présente divulgation concerne également une pièce d'horlogerie, de bijouterie, de joaillerie ou un instrument d'écriture, comportant au moins un composant réalisé avec l'alliage de l'invention.The present disclosure also relates to a timepiece, jewelery, jewelery or writing instrument, comprising at least one component made with the alloy of the invention.

Cette solution présente notamment l'avantage par rapport à l'art antérieur d'obtenir un alliage d'or 18 carats permettant d'élaborer des compositions combinant une couleur proche des ors rhodiés et une aptitude au polissage permettant la réalisation de pièces de bijouterie, d'horlogerie, joaillerie, ou d'instruments d'écriture.This solution has the particular advantage over the prior art of obtaining an 18-carat gold alloy making it possible to produce compositions combining a color close to rhodium-plated gold and a polishing ability that makes it possible to produce jewelery pieces. watchmaking, jewelery, or writing instruments.

Exemple(s) de mode de réalisation de l'inventionExample (s) of embodiment of the invention

La bonne qualité de surface est directement liée à l'homogénéité de l'alliage. Si l'alliage présente une structure multiphasée, des inhomogénéités apparaîtront en surface du poli-miroir.The good surface quality is directly related to the homogeneity of the alloy. If the alloy has a multiphase structure, inhomogeneities will appear on the surface of the mirror-polish.

Dans un mode de réalisation, un alliage d'or gris 18 carats comprenant en poids: au moins 75% d'or; entre 13% et 23% de Cr; entre 2% et 12% d'au moins un élément choisi parmi: Pd, Fe, Ru, Pt, Co, Ga, Ge, Mn, V, Ni. Dans une variante, la composition du Cr peut être comprise entre 15% et 20% et la composition dudit au moins un élément choisi parmi: Pd, Fe, Ru, Pt, Co, Ga, Ge, Mn, V, Ni est comprise entre 5% et 10%.In one embodiment, an 18-carat white gold alloy comprising by weight: at least 75% gold; between 13% and 23% of Cr; between 2% and 12% of at least one element selected from: Pd, Fe, Ru, Pt, Co, Ga, Ge, Mn, V, Ni. In a variant, the composition of Cr may be between 15% and 20% and the composition of said at least one element chosen from: Pd, Fe, Ru, Pt, Co, Ga, Ge, Mn, V, Ni is between 5% and 10%.

Dans un autre mode de réalisation, l'alliage comprend entre 2% et 12% de Pd et au maximum 5% d'au moins un élément choisi parmi: Fe, Ru, Pt, Co, Ga, Ge et Mn. Dans ce cas, la composition du Cr peut être comprise entre 13% et 18%. La composition du Pd peut être comprise entre 5% et 10%.In another embodiment, the alloy comprises between 2% and 12% of Pd and at most 5% of at least one element chosen from Fe, Ru, Pt, Co, Ga, Ge and Mn. In this case, the composition of the Cr can be between 13% and 18%. The composition of the Pd can be between 5% and 10%.

Exemple(s) de mode de réalisation de l'inventionExample (s) of embodiment of the invention

La bonne qualité de surface est directement liée à l'homogénéité de l'alliage. Si l'alliage présente une structure multiphasée, des inhomogénéités apparaîtront en surface du poli-miroir.The good surface quality is directly related to the homogeneity of the alloy. If the alloy has a multiphase structure, inhomogeneities will appear on the surface of the mirror-polish.

Dans un mode de réalisation, un alliage d'or gris 18 carats comprenant en poids: au moins 75% d'or; entre 13% et 23% de Cr; entre 2% et 12% d'au moins un élément choisi parmi: Pd, Fe, Ru, Pt, Co, Ga, Ge, Mn, V, Ni. Dans une variante, la composition du Cr peut être comprise entre 15% et 20% et la composition dudit au moins un élément choisi parmi: Pd, Fe, Ru, Pt, Co, Ga, Ge, Mn, V, Ni est comprise entre 5% et 10%.In one embodiment, an 18-carat white gold alloy comprising by weight: at least 75% gold; between 13% and 23% of Cr; between 2% and 12% of at least one element selected from: Pd, Fe, Ru, Pt, Co, Ga, Ge, Mn, V, Ni. In a variant, the composition of Cr may be between 15% and 20% and the composition of said at least one element chosen from: Pd, Fe, Ru, Pt, Co, Ga, Ge, Mn, V, Ni is between 5% and 10%.

Dans un autre mode de réalisation, l'alliage comprend entre 2% et 12% de Pd et au maximum 5% d'au moins un élément choisi parmi: Fe, Ru, Pt, Co, Ga, Ge et Mn. Dans ce cas, la composition du Cr peut être comprise entre 13% et 18%. La composition du Pd peut être comprise entre 5% et 10%.In another embodiment, the alloy comprises between 2% and 12% of Pd and at most 5% of at least one element chosen from Fe, Ru, Pt, Co, Ga, Ge and Mn. In this case, the composition of the Cr can be between 13% and 18%. The composition of the Pd can be between 5% and 10%.

Encore dans un autre mode de réalisation, l'alliage comprend en outre au maximum 1 % d'un élément choisi parmi les éléments affineurs: Ir, Rh, Re, W, Mo, parmi les éléments neutres: Nb, Ta, Ni, V, Ti, Zn, et parmi les éléments désoxydants: Zr, Si et B. Ici, l'expression "éléments neutre" signifie des éléments qui n'ont pas d'effet notable sur les principales caractéristiques de l'alliage tel que décrit ci-dessus et comprenant ces éléments neutres.In yet another embodiment, the alloy further comprises at most 1% of an element chosen from refining elements: Ir, Rh, Re, W, Mo, among the neutral elements: Nb, Ta, Ni, V , Ti, Zn, and among the deoxidizing elements: Zr, Si and B. Here, the expression "neutral elements" means elements that have no significant effect on the main characteristics of the alloy as described herein. above and including these neutral elements.

De façon encore préférée, l'alliage d'or gris 18 carats comprend en poids: au moins 75% Au, essentiellement 17%Cr, et essentiellement 8%Pd.More preferably, the 18-carat white gold alloy comprises by weight: at least 75% Au, essentially 17% Cr, and essentially 8% Pd.

L'effet blanchissant du Pd est largement employé dans les ors gris 18 carats conventionnels. Aussi, le Cr présentant une solubilité importante dans le Pd, cet élément a été introduit en tant qu'élément d'addition secondaire dans différentes proportions afin d'améliorer l'homogénéité de la matière. L'emploi de cet élément permet, en effet, de maintenir des teneurs élevées en Cr sans altérer la couleur blanche. L'aptitude au polissage s'est vue améliorée mais n'est pas optimale car des précipités de Cr sont parfois présents dès la coulée. Dans ce système Au-Cr-Pd, la composition la plus favorable contient essentiellement 17% Cr et essentiellement 8% Pd (voir Tableau 2).The whitening effect of Pd is widely used in conventional 18K gray golds. Also, Cr having a significant solubility in Pd, this element has been introduced as a secondary addition element in different proportions in order to improve the homogeneity of the material. The use of this element makes it possible, in fact, to maintain high levels of Cr without altering the white color. The polishing ability has been improved but is not optimal because Cr precipitates are sometimes present from the casting. In this Au-Cr-Pd system, the most favorable composition contains essentially 17% Cr and essentially 8% Pd (see Table 2).

Le système Au-Cr-Pd-Fe a également été étudié. Dans ce système, le Fe présente en effet une solubilité importante dans le Cr et le Pd à haute température. De plus, c'est un élément connu pour blanchir l'or (voir références 2 et 3). La substitution de quelques pourcents massiques de Cr au profit du Fe a permis d'améliorer notablement l'homogénéité de la matière et ainsi l'aptitude au polissage, tout en conservant une couleur très intéressante.The Au-Cr-Pd-Fe system has also been studied. In this system, Fe has indeed a high solubility in Cr and Pd at high temperature. In addition, it is a known element for bleaching gold (see references 2 and 3). The substitution of a few mass percents of Cr in favor of Fe has considerably improved the homogeneity of the material and thus the polishing ability, while maintaining a very interesting color.

Dans un autre mode de réalisation, l'alliage d'or gris 18 carats comprend en poids: au moins 75% d'or; entre 13% et 17% de Cr; entre 5% et 10% de Pd; et entre 1 % et 5% de Fe. De façon préférée, la composition du Cr est comprise entre 13% et 16%; et la composition du Pd est comprise entre 5% et 8%. De façon encore préférée, l'alliage d'or comprend en poids: au moins 75 % Au, essentiellement 15% Cr, et essentiellement 7% Pd et essentiellement 3% Fe. Ce dernier alliage présente le meilleur compromis entre couleur et aptitude au polissage.In another embodiment, the 18-carat white gold alloy comprises by weight: at least 75% gold; between 13% and 17% of Cr; between 5% and 10% of Pd; and between 1% and 5% Fe. Preferably, the Cr composition is between 13% and 16%; and the composition of the Pd is between 5% and 8%. More preferably, the gold alloy comprises by weight: at least 75% Au, essentially 15% Cr, and essentially 7% Pd and essentially 3% Fe. This latter alloy has the best compromise between color and polishing ability. .

Des exemples de compositions d'alliages conventionnels et de l'alliage selon l'invention sont mentionnés dans le Tableau 2. En particulier, le Tableau 2 rapporte des résultats de mesures sur l'échelle L*a*b* selon la modèle C.I.E. 1976 et le Yellowness Index (YI), ou indice de jaune, mesuré selon la norme ASTM D-1925 pour chacun de ces alliages, ainsi que des observations sur la qualité du polissage. Plus particulièrement, le tableau 2 rapporte des mesures colorimétriques et observations sur la qualité du polissage de quatre alliages d'or gris conventionnels (nos. 1 à 4) et sept exemples d'alliages d'or selon l'invention (nos. 5 à 11). Les compositions sont exprimées en % en poids. Par exemple, les mesures ont montré notamment que l'alliage comprenant en poids: au moins 75% d'or; entre 13% et 23% de Cr; entre 2% et 12% d'au moins un élément choisi parmi: Pd, Fe, Ru, Pt, Co, Ga, Ge, Mn, V, Ni, est caractérisé par un indice de jaune étant inférieur à 10. On obtient également un indice de jaune inférieur à 10 pour les autres alliages de l'invention. Ici, la coloration est dans la masse de l'alliage et ne peut être détériorée par l'usure en surface. Tableau 2 Compositions des alliages (% en poids) L a* b* YI Aptitude au polissage et observations diverses 1 Au75.0, Ni15.5, Cu4.0, Zn5.5 85 0.1 5.9 12.2 Produit du marché, avec nickel 2 Au75.0, Pd12.0, Ag4.0, Cu9.0 80 2.8 8.2 20.6 Produit du marché, pas assez blanc 3 Au75.0, Pd12.0, Ag4.0, Cu9.0 ; rhodié 90 1.0 2.2 5.6 Produit du marché, avec rhodiage 4 Au75.0, In25.0 85.7 0.13 2.58 5.9 Bonne aptitude au polissage, très fragile 5 Au75.0, Cr20.0, Pd5.0 80.9 0.35 3.4 8.1 Difficile à polir 6 Au75.0, Cr17.0, Pd8.0 81.8 0.56 3.7 8.9 Aptitude au polissage dépendante de la coulée 7 Au75.0, Cr17.0, Ni8.0 81 0.25 3.8 8.9 Aptitude au polissage dépendante de la coulée 8 Au75.0, Cr17.0, Pd5.0, Fe3.0 82.5 0.27 2.7 6.4 Difficile à polir 9 Au75.0, Cr15.0, Pd7.0, Fe3.0 82 0.45 3.0 7.2 Bonne aptitude au polissage 10 Au75.0, Cr15.0, Ni7.0, Fe3.0 80.7 0.30 4.2 9.8 Bonne aptitude au polissage 11 Au75.0, Cr13.0, Pd7.0, Fe5.0 83.5 0.70 4.1 9.7 Bonne aptitude au polissage Examples of conventional alloy compositions and the alloy according to the invention are given in Table 2. In particular, Table 2 reports results of measurements on the L * a * b * scale according to the CIE 1976 model. and the Yellowness Index (YI), or yellow index, measured according to ASTM D-1925 for each of these alloys, as well as observations on the quality of the polishing. In particular, Table 2 reports colorimetric measurements and observations on the polishing quality of four conventional gray gold alloys (Nos. 1 to 4) and seven examples of gold alloys according to the invention (Nos. 5 to 11). The compositions are expressed in% by weight. For example, the measurements have shown in particular that the alloy comprises by weight: at least 75% of gold; between 13% and 23% of Cr; between 2% and 12% of at least one element selected from: Pd, Fe, Ru, Pt, Co, Ga, Ge, Mn, V, Ni, is characterized by a yellow index being less than 10. a yellow index of less than 10 for the other alloys of the invention. Here, the color is in the mass of the alloy and can not be damaged by surface wear. Table 2 Compositions of alloys (% by weight) The at* b * YI Ability to polish and various observations 1 Au75.0, Ni15.5, Cu4.0, Zn5.5 85 0.1 5.9 12.2 Market product, with nickel 2 Au75.0, Pd12.0, Ag4.0, Cu9.0 80 2.8 8.2 20.6 Market product, not white enough 3 Au75.0, Pd12.0, Ag4.0, Cu9.0; rhodium 90 1.0 2.2 5.6 Market product, with rhodium 4 Au75.0, In25.0 85.7 0.13 2.58 5.9 Good polishing ability, very fragile 5 Au75.0, Cr20.0, Pd5.0 80.9 0.35 3.4 8.1 Hard to polish 6 Au75.0, Cr17.0, Pd8.0 81.8 0.56 3.7 8.9 Polishing ability dependent on casting 7 Au75.0, Cr17.0, Ni8.0 81 0.25 3.8 8.9 Polishing ability dependent on casting 8 Au75.0, Cr17.0, Pd5.0, Fe3.0 82.5 0.27 2.7 6.4 Hard to polish 9 Au75.0, Cr15.0, Pd7.0, Fe3.0 82 0.45 3.0 7.2 Good polishing ability 10 Au75.0, Cr15.0, Ni7.0, Fe3.0 80.7 0.30 4.2 9.8 Good polishing ability 11 Au75.0, Cr13.0, Pd7.0, Fe5.0 83.5 0.70 4.1 9.7 Good polishing ability

Pour l'alliage comprenant en poids: au moins 75% Au, essentiellement 17% Cr, et essentiellement 8% Pd, une couleur L*a*b* est mesurée avec la composante L* d'environ 82, la composante a* d'environ 0.56 et la composante b* d'environ 3.7.For the alloy comprising by weight: at least 75% Au, essentially 17% Cr, and essentially 8% Pd, a color L * a * b * is measured with the L * component of about 82, the component a * d about 0.56 and the b * component about 3.7.

Pour l'alliage comprenant en poids: au moins: 75% Au, essentiellement 15%Cr, essentiellement 7%Pd, et essentiellement 3% Fe, une couleur L*a*b* est mesurée avec la composante L* d'environ 82, la composante a* d'environ 0.45 et la composante b* d'environ 3.0.For the alloy comprising by weight: at least 75% Au, essentially 15% Cr, essentially 7% Pd, and essentially 3% Fe, a color L * a * b * is measured with the L * component of about 82%. , the component a * of about 0.45 and the component b * of about 3.0.

Parmi les alliages testés, les compositions AuCr17Pd8 (au moins 75% Au, essentiellement 17%Cr, et essentiellement 8%Pd) et AuCr15Pd7Fe3 (au moins 75% Au, essentiellement 15%Cr, essentiellement 7%Pd, et essentiellement 3% Fe) sont les plus intéressantes. La composition contenant du Fe (AuCr15Pd7Fe3) présente cependant les caractéristiques les plus prometteuses pour une application dans le domaine du luxe (bijouterie, horlogerie) car elle associe à la fois une couleur très blanche et une bonne aptitude au polissage.Of the alloys tested, compositions AuCr17Pd8 (at least 75% Au, essentially 17% Cr, and essentially 8% Pd) and AuCr15Pd7Fe3 (at least 75% Au, essentially 15% Cr, essentially 7% Pd, and essentially 3% Fe ) are the most interesting. The composition containing Fe (AuCr15Pd7Fe3), however, has the most promising characteristics for an application in the field of luxury (jewelery, watchmaking) because it combines both a very white color and good polishing ability.

Des résultats de tests de corrosion selon la norme dentaire (ISO 10271-2001) ont été effectués sur sept alliages pour évaluer le taux de libération (en µg/cm2x7d) des ions des éléments sensibles comme Ni et Cr (Tableau 3). Pour une application dentaire, la norme ISO 10271-2001 limite le taux de libération total à 200 µg/cm2x7d. D'après ces essais, les deux alliages AuCr17Pd8 et AuCr15Pd7Fe présentent une très bonne résistance à la corrosion. Tableau 3 Alliage µg/cm2x7d AuCr17Pd8 0.22 AuCr15Pd7Fe3 0.44 AuCr14Pd6Fe5 0.63 AuNi25 6.08 AuNi20Pd5 10.00 AuNi20Fe5 468.08 AuPd21Fe3Ge 54.93 Corrosion test results according to the dental standard (ISO 10271-2001) were performed on seven alloys to evaluate the release rate (in μg / cm 2 x7d) of the ions of sensitive elements such as Ni and Cr (Table 3). For a dental application, the ISO 10271-2001 standard limits the total release rate to 200 μg / cm 2 x 7d. According to these tests, the two alloys AuCr17Pd8 and AuCr15Pd7Fe have a very good resistance to corrosion. Table 3 Alloy μg / cm 2 x7d AuCr17Pd8 0.22 AuCr15Pd7Fe3 0.44 AuCr14Pd6Fe5 0.63 AuNi25 6.08 AuNi20Pd5 10.00 AuNi20Fe5 468.08 AuPd21Fe3Ge 54.93

Le Tableau 4 donne un résumé de nos études dans les systèmes Au-Cr-X et Au-Cr-Pd-Fe ainsi que les caractéristiques des deux alliages préférés. Ici, X correspond à au moins un élément choisi parmi: Pd, Fe, Ru, Pt, Co, Ga, Ge, Mn, V, Ni. Tableau 4 Système Ternaire : Au-Cr-X Quaternaire : Au-Cr-Pd-Fe Variations de compositions 13-23wt%Cr, 2-12wt%X 13-17wt%Cr, 5-10wt%Pd, 1-5wt%Fe Compositions préférées 15-20wt%Cr, 5-10wt%X 13-16wt%Cr, 5-8wt%Pd, 1-5wt%Fe Meilleures compositions et leurs caractéristiques Composition, wt% 75%Au, 17%Cr, 8%Pd 75%Au, 15%Cr, 7%Pd, 3%Fe Couleur, L*/a*/b*, YI 82/0.56/3.7,8.9 83/0.45/3.0, 7.2 Corrosion, µg/cm2x7d 0.22 0.44 Dureté, HV 400HV 270HV Aptitude au polissage oui oui, bonne Applications envisageables Casting joaillerie Semi- produits horlogerie, joaillerie Procédés de fabrication de type additif (Selective Laser Melting, ...) horlogerie, joaillerie Table 4 gives a summary of our studies in the Au-Cr-X and Au-Cr-Pd-Fe systems as well as the characteristics of the two preferred alloys. Here, X corresponds to at least one element chosen from: Pd, Fe, Ru, Pt, Co, Ga, Ge, Mn, V, Ni. Table 4 System Ternary: Au-Cr-X Quaternary: Au-Cr-Pd-Fe Variations of compositions 13-23wt% Cr, 2-12wt% X 13-17wt% Cr, 5-10wt% Pd, 1-5wt% Fe Favorite compositions 15-20wt% Cr, 5-10wt% X 13-16wt% Cr, 5-8wt% Pd, 1-5wt% Fe Best compositions and their characteristics Composition, wt% 75% Au, 17% Cr, 8% Pd 75% Au, 15% Cr, 7% Pd, 3% Fe Color, L * / a * / b *, YI 82 / 0.56 / 3.7,8.9 83 / 0.45 / 3.0, 7.2 Corrosion, μg / cm 2 x7d 0.22 0.44 Hardness, HV 400HV 270HV Polishing ability Yes yes, good Possible applications Casting jewelry Semi-products watchmaking, jewelery Additive manufacturing processes (Selective Laser Melting, ...) watchmaking, jewelery

L'étude du système ternaire Au-Cr-Pd a permis d'élaborer des alliages 18 carats présentant une couleur blanche comparable à celle des ors rhodiés. La meilleure composition correspond à: au moins 75%Au, essentiellement 17%Cr et essentiellement 8%Pd.The study of the Au-Cr-Pd ternary system has made it possible to develop 18-carat alloys with a white color comparable to that of rhodium-plated gold. The best composition corresponds to: at least 75% Au, essentially 17% Cr and essentially 8% Pd.

Le système quaternaire Au-Cr-Pd-Fe a permis de réaliser des alliages 18cts avec des propriétés encore plus attractives en termes de couleur, aptitude au polissage, ductilité et prix. La meilleure composition correspond à: au moins: 75%Au, essentiellement 15%Cr, essentiellement 7%Pd et essentiellement 3%Fe.The Au-Cr-Pd-Fe quaternary system made 18cts alloys with even more attractive properties in terms of color, polishing ability, ductility and price. The best composition corresponds to: at least: 75% Au, essentially 15% Cr, essentially 7% Pd and essentially 3% Fe.

Le Cr est introduit comme élément blanchissant principal. Le Pd et le Fe sont introduits afin d'améliorer la solubilité du chrome dans l'or, sans altérer la couleur blanche recherchée. Seule la combinaison des trois éléments d'alliage Cr, Pd et Fe a permis d'élaborer des compositions combinant une couleur proche des ors rhodiés et une aptitude au polissage permettant la réalisation de pièces de bijouterie, d'horlogerie, de joaillerie, ou d'instruments d'écriture.Cr is introduced as the main bleaching element. Pd and Fe are introduced to improve the solubility of chromium in gold, without altering the desired white color. Only the combination of the three elements of alloy Cr, Pd and Fe has made it possible to develop compositions combining a color close to rhodium-plated golds and a polishing ability allowing the production of pieces of jewelery, timepieces, jewelery, or jewelry. writing instruments.

Claims (8)

  1. Grey gold alloy comprising by weight: at least 75% Au; and between 13% and 17% of Cr; characterized in that it further comprises between 5% and 10% of Pd; and between 1 % and 5% of Fe; so that the alloy is characterized by a yellowness index of less than 10.
  2. Alloy according to claim 1, wherein the composition of the Cr is comprised between 13% and 16%; the composition of the Pd is comprised between 5% and 8%; and the composition of the Fe is comprised between 1 % and 4%.
  3. Alloy according to claim 1 or 2, comprising by weight: at least 75% Au, essentially 15% Cr, essentially 7% Pd and essentially 3% Fe.
  4. Alloy according to one of the claims 1 or 2, comprising by weight: at least 75% Au, essentially 17% Cr and essentially 8% Pd.
  5. Alloy according to claim 4, characterized by a colour L*a*b* having the component L* of approximately 82, the component a* of approximately 0.56 and the component b* of approximately 3.7.
  6. Alloy according to claim 3, characterized by a colour L*a*b* having a component L* of approximately 82, a component a* of approximately 0.45 and a component b* of approximately 3.0.
  7. Alloy according to one of the claims from 1 to 6, used for applications in watchmaking, jewellery and gems or writing implements.
  8. Item of watchmaking, jewellery, gems or writing implements comprising at least one component made with the alloy according to one of the claims from 1 to 6.
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EP3020835B1 (en) 2014-11-17 2021-04-21 Omega SA Piece of watchmaking, bijouterie or jewelry comprising a component made of a palladium-based alloy
EP3040790A1 (en) * 2014-12-29 2016-07-06 Montres Breguet S.A. Timepiece or piece of jewellery made of a light titanium-based precious alloy
EP3070182B1 (en) 2015-03-17 2017-08-30 The Swatch Group Research and Development Ltd. White-gold alloy
EP3339455B1 (en) 2016-12-20 2020-02-05 Montres Breguet S.A. Grey-gold alloy
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JP2002256360A (en) * 2001-03-01 2002-09-11 Ijima Kingin Kogyo Kk White gold alloy
FR2923492A1 (en) 2007-11-12 2009-05-15 Gerard Bienvenu White gold alloy, useful to prepare materials for optoelectronics and in jewelry, where the gold is combined with at least one refractory metal of IVB, VB and VIB column of periodic table

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