PLATINUM ALLOY

Abstract

A platinum alloy consisting, by weight, of the following elements: 95.00 to 96.00% of Pt, 1.00 to 4.95% of Ru, 0.05 to 2.00% of Ge, 0 to 2.00% of Au, any impurities with a total content≤0.50%.

Claims

1. A platinum alloy consisting, by weight, of the following elements: 95.00 to 96.00% of Pt, 1.00 to 4.95% of Ru, 0.05 to 2.00% of Ge, 0 to 2.00% of Au, and any impurities with a total content≤0.50%.

2. The platinum alloy according to claim 1, wherein the Ru content is between 2.00 and 4.95% by weight.

3. The platinum alloy according to claim 1, wherein the Ru content is between 3.00 and 4.95% by weight.

4. The platinum alloy according to claim 1, wherein the Ru content is between 3.50 and 4.80% by weight.

5. The platinum alloy according to claim 1, wherein the Ge content is between 0.05 and 1.50% by weight.

6. The platinum alloy according to claim 1, wherein the Ge content is between 0.05 and 1.00% by weight.

7. The platinum alloy according to claim 1, wherein the Ge content is between 0.07 and 0.70% by weight.

8. The platinum alloy according to claim 1, wherein the Au content is between 0.05 and 1.50% by weight.

9. The platinum alloy according to claim 1, wherein the Au content is between 0.10 and 1.00% by weight.

10. The platinum alloy according to claim 1, wherein the Au content is between 0.10 and 0.70% by weight.

11. The platinum alloy according to claim 1, wherein the alloy consists, by weight, of 95.00 to 96.00% of Pt, of 2.00 to 4.90% of Ru, of 0.05 to 1.50% of Ge, of 0.05 to 1.50% of Au and of any impurities with a total content≤0.50%.

12. The platinum alloy according to claim 1, wherein the alloy consists, by weight, of 95.00 to 96.00% of Pt, of 3.00 to 4.85% of Ru, 0.05 and 1.00% of Ge, of 0.10 to 1.00% of Au and of any impurities with a total content≤0.50%.

13. The platinum alloy according to claim 1, wherein the alloy consists, by weight, of 95.00 to 96.00% of Pt, of 3.50 to 4.83% of Ru, 0.07 and 0.70% of Ge, of 0.10 to 0.70% of Au and of any impurities with a total content≤0.50%.

14. The platinum alloy according to claim 1, wherein the alloy has a HV2 hardness between 140 and 230 and a yellowness index Yi10° between 7 and 8.

15. The platinum alloy according to claim 1, wherein its structure is face-centred cubic single-phased, free of intermetallic precipitations.

16. An item made of platinum alloy according to claim 1.

17. The item according to claim 16, wherein the item is a decorative item.

18. The item according to claim 16, wherein the item is a timepiece component selected from the group comprising a middle, a back, a bezel, a push-piece, a crown, a bracelet link, a bracelet clasp, a dial, a hand and a dial index.

19. The platinum alloy according to claim 1, wherein the alloy has a HV2 hardness between 150 and 210 and a yellowness index Yi10° between 7 and 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0015] The alloy of the present invention is a platinum alloy at the grade of 95% by weight.

[0016] According to the invention, the platinum alloy consists by weight, of 95.00 to 96.00% of Pt, of 1.00 to 4.95% of Ru, of 0.05 to 2.00% of Ge, of 0 to 2.00% of Au and of any impurities with a total content≤0.50%. The alloy consists of these various elements and impurities, that is to say that all of the Pt, Ru, Ge, Au and any impurities reach the percentage of 100%.

[0017] Preferably, the Ru content is between 2.00 and 4.95% by weight. More preferably, it is between 3.00 and 4.95% by weight. Particularly preferably, the Ru content is between 3.50 and 4.80% by weight.

[0018] Preferably, the Ge content is between 0.05 and 1.50% by weight. More preferably, it is between 0.05 and 1.00% by weight. Particularly preferably, the Ge content is between 0.07 and 0.70% by weight.

[0019] Preferably, the Au content is between 0.05 and 1.50% by weight. More preferably, the Au content is between 0.10 and 1.00% by weight. Particularly preferably, the Au content is between 0.10 and 0.70% by weight.

[0020] Advantageously, according to a first variant, the platinum alloy consists, by weight, of 95.00 to 96.00% of Pt, of 2.00 to 4.90% of Ru, of 0.05 to 1.50% of Ge, of 0.05 to 1.50% of Au and of any impurities with a total content≤0.50%.

[0021] Advantageously, according to a second variant, the platinum alloy consists, by weight, of 95.00 to 96.00% of Pt, of 3.00 to 4.85% of Ru, of 0.05 to 1.00% of Ge, of 0.10 to 1.00% of Au and of any impurities with a total content≤0.50%.

[0022] Advantageously, according to a third variant, the platinum alloy consists, by weight, of 95.00 to 96.00% of Pt, of 3.50 to 4.83% of Ru, of 0.07 to 0.70% of Ge, of 0.10 to 0.70% of Au and of any impurities with a total content≤0.50%.

[0023] The platinum alloy according to the invention particularly applies to the production of a timepiece component and more specifically of an external part timepiece component such as a middle, a back, a bezel, a push-piece, a crown, a bracelet link, a bracelet clasp, a dial, a hand and a dial index. Generally, this alloy may be used for any item and more specifically any decorative item, for example, in the field of jewellery.

[0024] The alloy according to the invention has a HV2 hardness between 140 and 230, and optionally between 150 and 210 and a yellowness index Yi10° such as defined hereafter between 7 and 8.

[0025] Advantageously, the alloy according to the invention has a face-centred cubic type single-phased structure, free of intermetallic precipitations such as GePt3, GePt2, Ge2Pt3, GePt, Ge3Pt2, GeRu.

[0026] To prepare the platinum alloy according to the invention, the procedure is as follows: [0027] The main elements incorporated into the composition of the alloy have a purity between 999 and 999.9 per thousand and are deoxidised. [0028] The elements of the composition of the alloy are placed in a crucible that is heated until the elements melt. [0029] The heating is carried out in an airtight induction furnace under partial pressure of argon [0030] The molten alloy is cast in an ingot-mould. [0031] After solidification, the ingot is optionally subjected to water quenching. [0032] The cooled ingot is subsequently cold rolled then annealed. The degree of cold-working between each annealing is 40 to 80%. [0033] Each annealing lasts 20 to 120 minutes and is carried out between 900° C. and 1100° C. under a reducing atmosphere consisting of pure H2 or of a mixture of H.sub.2 and N.sub.2. [0034] The cooling after the annealing operations is carried out by water quenching or open-air cooling.

[0035] The colorimetric values and the hardness of various alloys according to the invention prepared with the method described above are given in Table 1 with a comparative example. The composition of Comparative Example No. 1 is devoid of germanium and includes gold and ruthenium. Samples No. 2 to No. 11 include gold and germanium while Samples No. 12 and No. 13 do not include gold. The measurements are taken on annealed and polished samples.

[0036] The L*a*b* colorimetric values in the CIELAB colorimetric space (in accordance with IEC No.15, ISO 7724/1, DIN 5033 Teil 7, ASTM E-1164) have been measured with a KONICA MINOLTA Cm-2600d spectrophotometer with a D65 illuminant and a viewing angle of 10°. The Yellowness index Yi10° which is an indicator of the whiteness of the alloy has been calculated based on L*a*b* values according to ASTM E313. The lower this index, the whiter the alloy.

[0037] A significant and almost linear increase of the hardness is observed with the addition of germanium in Alloys No. 2 to No. 13 while maintaining a similar yellowness index that is between the 7 to 8 range. The alloys according to the invention have a hardness between 150 and 196 HV2 in relation to 138 HV2 for the Reference Alloy No. 1 without germanium. The addition of a low content of germanium with a content of 0.1% by weight in Alloys No. 5 and 7 already has a significant effect with a hardness value reaching 150 HV2. With an addition of 0.5% by weight of germanium, the hardness rises to 196 HV2. It can be observed that the addition of germanium has a significant effect on the hardness whether or not the alloy includes gold.

TABLE-US-00001 TABLE 1 (% by weight) Composition Colorimetry No. Pt Ru Au Ge L a* b* Yi10° HV2 Comparative 1 95.3 4.2  0.5 / 88.2 0.8 3.5 7.6 138 Invention 2 95.3 3.7  0.5 0.5  87.9 0.8 3.5 7.8 196 3 95.3 4.0  0.5 0.2  88.3 0.7 3.4 7.4 166 4 95.3 4.0  0.4 0.3  88.3 0.7 3.3 7.2 181 5 95.3 4.2  0.4 0.1  88.3 0.7 3.4 7.4 150 6 95.3 4.2  0.2 0.3  88.3 0.7 3.3 7.2 171 7 95.3 4.2  0.4 0.1  88.3 0.7 3.3 7.3 150 9 95.3 4.2  0.3 0.2  88.2 0.7 3.3 7.2 159 10 95.3 4.2  0.2 0.3  88.1 0.7 3.4 7.4 172 11 95.3 4.2  0.1 0.4  88.2 0.7 3.3 7.2 186 12 95.3 4.45 / 0.25 88.0 0.7 3.4 7.5 169 13 95.3 4.55 / 0.15 88.4 0.7 3.2 7.1 153