Grey gold alloy

Abstract

A grey gold alloy which is nickel-free, cobalt-free, iron-free, silver-free, zirconium-free, niobium-free, chromium-free, indium-free, gallium-free and manganese-free and includes, expressed in weight percent, from 75.0 to 76.5% of Au, from 15 to 23% of Pd, from 1 to 7% of Cu, and from 0 to 5% of at least one of the alloying elements Ir, Ru, B and Re, the respective percentages of all the elements of the alloy adding up to 100%.

Claims

1. A grey gold alloy, which is nickel-free, cobalt-free, iron-free, silver-free, zirconium-free, niobium-free, chromium-free, indium-free, gallium-free and manganese-free, comprising, expressed in weight percent, the following elements: 75.0 to 76.5% of Au, 15 to 23% of Pd, 1 to 7% of Cu, 0 to 5% of at least one of the alloying elements Ir, Ru, B and Re, the respective percentages of all the elements of the alloy adding up to 100%.

2. The grey gold alloy according to claim 1, comprising, expressed in weight percent, from 75.0 to 76.5% of Au, from 17 to 22.5% of Pd, from 2 to 7% of Cu, and from 0 to 5% of at least one of the alloying elements Ir, Ru, B and Re, the respective percentages of all the elements of the alloy adding up to 100%.

3. The grey gold alloy according to claim 1, comprising, expressed in weight percent, from 75.0 to 76.5% of Au, from 18 to 22.5% of Pd, from 2 to 6.5% of Cu, and from 0 to 4% of at least one of the alloying elements Ir, Ru, B and Re, the respective percentages of all the elements of the alloy adding up to 100%.

4. The grey gold alloy according to claim 1, comprising, expressed in weight percent, from 75.0 to 76.5% of Au, from 18.5 to 22.5% of Pd, from 2 to 6.5% of Cu, and from 0 to 3% of at least one of the alloying elements Ir, Ru, B and Re, the respective percentages of all the elements of the alloy adding up to 100%.

5. The grey gold alloy according to claim 1, comprising, expressed in weight percent, from 75.0 to 76.5% of Au, from 18.5 to 21.5% of Pd, from 3 to 6% of Cu, and from 0 to 2.5% of at least one of the alloying elements Ir, Ru, B and Re, the respective percentages of all the elements of the alloy adding up to 100%.

6. The grey gold alloy according to claim 1, comprising, expressed in weight percent, from 75.0 to 76.5% of Au, from 19 to 21% of Pd, from 3.5 to 5.5% of Cu, and from 0 to 1.8% of at least one of the alloying elements Ir, Ru, B and Re, the respective percentages of all the elements of the alloy adding up to 100%.

7. The alloy according to claim 1, wherein the alloy comprises at least one of the elements Ir, B, each element being in a proportion comprised between 0.002 and 1% by weight.

8. The alloy according to claim 1, wherein the alloy comprises between 0.002 and 0.2% by weight of B.

9. The alloy according to claim 8, wherein the alloy comprises between 0.08 and 0.2% by weight of B.

10. The alloy according to claim 1, wherein the alloy comprises between 0.002 and 0.13% by weight of Ir.

11. The alloy according to claim 1, wherein the alloy comprises between 0.001 and 0.05% by weight of Re.

12. The alloy according to claim 1, wherein the alloy comprises between 0.002 and 1% by weight of Ru.

13. A timepiece or piece of jewellery comprising at least one component made of an alloy according to claim 1.

14. The timepiece or piece of jewellery according to claim 13, wherein the component is selected from the group constituted of a watch case, a dial, a bracelet or wristband, a bracelet clasp, a jewel and an accessory.

Description

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(1) The alloy of the present invention is a grey gold alloy which is nickel-free, cobalt-free, iron-free, silver-free, indium-free, gallium-free, manganese-free, zirconium-free, chromium-free and niobium-free.

(2) According to a first embodiment, the gold alloy is an 18 carat alloy and comprises, expressed in weight percent, from 75.0 to 76.5% of Au, from 15 to 23% of Pd, from 1 to 7% of Cu, and from 0 to 5% of at least one of the alloying elements Ir, Ru, B and Re, the respective percentages of all the elements of the alloy adding up to 100%.

(3) According to a second embodiment, the gold alloy is an 18 carat alloy and comprises, expressed in weight percent, from 75.0 to 76.5% of Au, from 17 to 22.5% of Pd, from 2 to 7% of Cu, and from 0 to 5% of at least one of the alloying elements Ir, Ru, B and Re, the respective percentages of all the elements of the alloy adding up to 100%.

(4) According to a third embodiment, the gold alloy is an 18 carat alloy and comprises, expressed in weight percent, from 75.0 to 76.5% of Au, from 18 to 22.5% of Pd, from 2 to 6.5% of Cu, and from 0 to 4% of at least one of the alloying elements Ir, Ru, B and Re, the respective percentages of all the elements of the alloy adding up to 100%.

(5) According to a fourth embodiment, the gold alloy is an 18 carat alloy and comprises, expressed in weight percent, from 75.0 to 76.5% of Au, from 18.5 to 22% of Pd, from 2.5 to 6.5% of Cu, and from 0 to 3% of at least one of the alloying elements Ir, Ru, B and Re, the respective percentages of all the elements of the alloy adding up to 100%.

(6) According to a fifth embodiment, the gold alloy is an 18 carat alloy and comprises, expressed in weight percent, from 75.0 to 76.5% of Au, from 18.5 to 21.5% of Pd, from 3 to 6% of Cu, and from 0 to 2.5% of at least one of the alloying elements Ir, Ru, B and Re, the respective percentages of all the elements of the alloy adding up to 100%.

(7) According to a sixth embodiment, the gold alloy is an 18 carat alloy and comprises, expressed in weight percent, from 75.0 to 76.5% of Au, from 19 to 21% of Pd, from 3.5 to 5.5% of Cu, and from 0 to 1.8% of at least one of the alloying elements Ir, Ru, B and Re, the respective percentages of all the elements of the alloy adding up to 100%.

(8) According to a variant of the above embodiments, the gold alloy may also be rhodium-free.

(9) According to any of the variants of the above embodiments, the gold alloy can comprise at least one of the elements Ir, B, with each element in a proportion comprised between 0.002 and 1% by weight.

(10) In any of the variants of the above embodiments where the alloy comprises B, the proportion of B is preferably comprised between 0.002 and 0.2%, and more preferably comprised between 0.08 and 0.2%.

(11) In any of the variants of the above embodiments where the alloy comprises Ir, the proportion of Ir is preferably comprised between 0.002 and 0.13% by weight.

(12) In any of the variants of the above embodiments where the alloy comprises Re, the proportion of Re is preferably comprised between 0.001 and 0.05% by weight, and more preferably comprised between 0.001 and 0.002% by weight.

(13) In any of the variants of the above embodiments where the alloy comprises Ru, the proportion of Ru is preferably comprised between 0.002 and 1% by weight, and more preferably comprised between 0.008 and 0.015% by weight.

(14) In a particularly preferred composition, the gold alloy according to the invention is an 18 carat alloy and comprises, expressed in weight percent, from 75.0 to 76.5% of Au, from 19 to 21% of Pd, from 3.5 to 5.5% of Cu, and from 0.08 to 0.2% of B, the respective percentages of all the elements of the alloy adding up to 100%.

(15) The gold alloys of the invention find particular application in the production of timepieces or pieces of jewelry. In this application, the alloy avoids the need for the electrodeposition of rhodium, which is commonly used in the fields of horology and jewelry to give the treated parts a brightness and colour of satisfactory whiteness.

(16) To prepare the grey gold alloy according to the invention, the procedure is as follows:

(17) The main elements involved in the composition of the alloy have a purity of between 999 and 999.9 per thousand and are deoxidised.

(18) The elements of the alloy composition are placed in a crucible and heated until the elements melt.

(19) Heating is performed in a sealed induction furnace under a partial pressure of nitrogen.

(20) The melted alloy is poured into an ingot mould.

(21) After solidifying, the ingot is water hardened.

(22) Next, the hardened ingot is cold rolled and then annealed. The rate of strain hardening between each annealing is from 66 to 80%.

(23) Each annealing operation lasts between 20 to 30 minutes and occurs at 900 C. in a reducing atmosphere constituted of N.sub.2 and H.sub.2.

(24) Cooling between each annealing is accomplished by water quenching.

(25) The following examples were produced in accordance with the conditions set out in Table 3 below and all relate to 18 carat grey gold alloys, made for comparative purposes (examples 1 to 3) and in accordance with the invention (examples 4 and 5). The proportions indicated are expressed in weight percent.

(26) TABLE-US-00003 TABLE 3 Au Pd B Cu N % % % % 1 (comp.) 75.1 15 0 9.9 2 (comp.) 75.1 17.5 0 7.4 3 (comp.) 75.1 24.9 0 0 4 (inv.) 75.2 20 0.13 4.67 5 (inv.) 75.1 19.5 0.08 5.31

(27) Table 4 below sets out different properties of the alloys obtained from examples No 1 to No 5 of Table 1.

(28) Table 4 provides, in particular, indications relating to the Vickers hardness of the alloy in the annealed state, and to the colour measured in a three-axis coordinate system.

(29) This three-dimensional measuring system known as CIELab, CIE being the acronym for the International Commission on Illumination and Lab the axes of the three coordinates; the L axis measures the white-black component (black=0; white=100), the a axis measures the red-green component (red=positive values +a; green=negative values a), and the b axis measures the yellow-blue component (yellow=positive values +b; blue=negative values b). (cf. International standard ISO 7724 established by the International Commission on Illumination).

(30) The colorimetric values are measured with a MINOLTA CM 3610 d apparatus in the following conditions: Illuminant: D65 Tilt: 100 Measurement: SCI+SCE (specular component included+excluded) UV: 100% Focal length: 4 mm Calibration standard: black body and white body

(31) TABLE-US-00004 TABLE 4 HV N L a* b* Hardness 1 (comp.) 80.15 1.72 6.28 128 2 (comp.) 80.31 1.50 5.79 122 3 (comp.) 80.44 1.19 4.41 117 4 (inv.) 80.49 1.46 5.21 174 5 (inv.) 80.70 1.41 5.25 163

(32) The 18 carat gold grey alloys of the invention (examples 4 and 5) were developed and tested for deformation to meet the triple constraint of brightness/whiteness, capacity for deformation and the production cost required for alloys intended to be used in the field of horology and jewelry. The alloys therefore present colour values such that L>80, a*<1.5 and b*<5.5, a hardness comprised between 140 HV and 225 HV, and preferably comprised between 140 HV and 180 HV, and a reduced production cost.

(33) The alloys of the prior art and of the comparative examples (examples 1 to 3) do not meet this triple constraint.