PLATINUM ALLOY

Description

Technical field of the invention

[0001] The present invention relates to a platinum alloy. The invention also relates to an article, in particular a decorative article, and more specifically to a watch component, made from this alloy. Technological background

[0002] There are several families of platinum-based alloys on the market used in watchmaking and jewelry. These alloys have the particularity of being mainly used by an internationally recognized fineness of 95% by weight, which severely limits the content of additional elements. The additional elements will therefore meet a technical constraint specific to the element. The first classic additional elements are ruthenium, cobalt, copper, iridium. Ruthenium platinum alloys have universal use for jewelry and watchmaking, particularly for machined products. The platinum-ruthenium alloy has the characteristic of being the whitest platinum alloy on the market. Unfortunately, this alloy is difficult to cast due to its high casting temperature and relatively low melting range.Furthermore, this alloy is not very suitable for traditional machining techniques such as turning, milling and drilling.

[0003] Also known from WO 2015 / 193659 is a platinum-based alloy comprising 95% Pt, 2.5% Cu, 1% Ge and 1.5% Ru. Summary of the invention

[0004] The object of the present invention is to overcome the aforementioned drawbacks by proposing a new platinum alloy which is brightly white, easy to cast while having good machinability.

[0005] For this purpose, the present invention relates to a platinum alloy as defined by claim 1 of the patent.

[0006] Preferably, the Ru content is between 2.00 and 4.80% by weight. More preferably, it is between 3.00 and 4.80% by weight. Particularly preferably, the Ru content is between 3.50 and 4.80% by weight.

[0007] 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.

[0008] 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. More preferably, the Au content is between 0.10 and 0.70% by weight.

[0009] Ruthenium brings some hardening and whiteness to the alloy. The addition of germanium significantly increases the hardness of the alloy. In addition, the addition of germanium increases the machinability of the alloy and allows the melting range to be increased while reducing the casting temperature. The addition of gold has this same beneficial effect on machinability and castability.

[0010] Typically, the alloy according to the invention has a yellowness index Yi10° between 7 and 8 and a hardness HV2 between 140 and 230.

[0011] Advantageously, the alloy according to the invention has a single-phase structure of the face-centered cubic type, free from precipitation of intermetallics such as GePt3, GePt2, Ge2Pt3, GePt, Ge3Pt2, GeRu, which would reduce solid solution hardening and could generate defects during the polishing steps (presence of hard spots).

[0012] The composition of this alloy therefore makes it possible to achieve an excellent compromise between hardness, machinability and castability without negatively impacting the white color of the alloy.

[0013] The present invention also relates to an article and in particular a watch component made from this alloy. Detailed description of the invention

[0014] The alloy of the present invention is a platinum alloy with a content of 95% by weight.

[0015] According to the invention, the platinum alloy consists by weight of 95.00 to 96.00% Pt, 1.00 to 4.80% Ru, 0.05 to 2.00% Ge, 0.05 to 1.50% Au and any impurities with a total content ≤ 0.50%. The alloy consists of these different elements and impurities, i.e. the total Pt, Ru, Ge, Au and any impurities reaches the percentage of 100%.

[0016] Preferably, the Ru content is between 2.00 and 4.80% by weight. More preferably, it is between 3.00 and 4.80% by weight. Particularly preferably, the Ru content is between 3.50 and 4.80% by weight.

[0017] 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.

[0018] According to the invention, 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. In a particularly preferred manner, the Au content is between 0.10 and 0.70% by weight.

[0019] Advantageously, according to a first variant, the platinum alloy is made up, by weight, of 95.00 to 96.00% of Pt, of 2.00 to 4.80% of Ru, of 0.05 to 1.50% of Ge, of 0.05 to 1.50% of Au and possible impurities with a total content ≤ 0.50%.

[0020] Advantageously, according to a second variant, the platinum alloy is made up, by weight, of 95.00 to 96.00% of Pt, 3.00 to 4.80% of Ru, 0.05 and 1.00% of Ge, 0.10 to 1.00% of Au and possible impurities with a total content ≤ 0.50%.

[0021] Advantageously, according to a third variant, the platinum alloy is made up, by weight, of 95.00 to 96.00% of Pt, 3.50 to 4.80% of Ru, 0.07 and 0.70% of Ge, 0.10 to 0.70% of Au and possible impurities with a total content ≤ 0.50%.

[0022] The platinum alloys according to the invention find a particular application for the production of a watch component and more specifically of a watch component for display purposes such as a case middle, a back, a bezel, a pusher, a crown, a bracelet link, a bracelet clasp, a dial, a hand and a dial index. In general, this alloy can be used for any article and more specifically any decorative article, for example, in the field of jewelry or jewelry.

[0023] The alloy according to the invention has a hardness HV2 of between 140 and 230, and possibly between 150 and 210 and a yellowness index Yi10° as defined below of between 7 and 8.

[0024] Advantageously, the alloy according to the invention has a single-phase structure of the face-centered cubic type, free from precipitation of intermetallics such as GePt3, GePt2, Ge2Pt3, GePt, Ge3Pt2, GeRu.

[0025] To prepare the platinum alloy according to the invention, the procedure is as follows: The main elements used in the composition of the alloy have a purity between 999 and 999.9 per thousand and are deoxidized. The elements of the alloy composition are placed in a crucible and heated until the elements melt. Heating is carried out in a sealed induction furnace under partial argon pressure. The molten alloy is poured into an ingot mold. After solidification, the ingot is optionally water quenched. The cooled ingot is then cold rolled and annealed. The work hardening rate between each annealing is 40 to 80%. Each annealing lasts 20 to 120 minutes and is carried out between 900°C and 1100°C under a reducing atmosphere composed of pure H 2 or a mixture of H 2 and N 2 . Cooling after annealing is carried out by water quenching or cooling in the open air.

[0026] The colorimetric values ​​and hardness of different 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 free of germanium and comprises gold and ruthenium. Samples No. 2 to No. 11 comprise gold and germanium and are alloys according to the invention, while samples No. 12 and No. 13 do not comprise gold and are reference alloys which are not part of the invention. The measurements were carried out on annealed and polished samples.

[0027] The L*a*b* colorimetric values ​​in the CIELAB color space (compliant with CIE No. 15, ISO 7724 / 1, DIN 5033 Teil 7, ASTM E-1164) were measured with a KONICA MINOLTA CM-2600d spectrophotometer with a D65 illuminant and an observation angle of 10°. The Yellowness index Yi10°, which is an indicator of the whiteness of the alloy, was calculated based on the L*a*b* values ​​according to ASTM E313. The lower this index, the whiter the alloy.

[0028] A significant and almost linear increase in hardness is observed with the addition of germanium in alloys No. 2 to No. 13 while maintaining a similar yellowness index which is in the range 7 to 8. The alloys according to the invention have a hardness between 150 and 196 HV2 compared 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 increases to 196 HV2. It is observed that the addition of germanium has a significant effect on the hardness whether the alloy contains gold or not. Table 1 (% by weight) Composition Colorimetry HV2 N° Pt Ru At Ge L a* b* Yi10° Comparative 1 95.3 4.2 0.5 / 88.2 0.8 3.5 7.6 138 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

Claims

1. Platinum alloy consisting, by weight, of the following elements: - 95.00 to 96.00% of Pt, - 1.00 to 4.80% of Ru, - 0.05 to 2.00% of Ge, - 0.05 and 1.50% of Au, - any impurities with a total content ≤ 0.50%.

2. Platinum alloy according to claim 1, characterised in that the Ru content is between 2.00 and 4.80% by weight.

3. Platinum alloy according to one of the preceding claims, characterised in that the Ru content is between 3.00 and 4.80% by weight.

4. Platinum alloy according to one of the preceding claims, characterised in that the Ru content is between 3.50 and 4.80% by weight.

5. Platinum alloy according to one of the preceding claims, characterised in that the Ge content is between 0.05 and 1.50% by weight.

6. Platinum alloy according to one of the preceding claims, characterised in that the Ge content is between 0.05 and 1.00% by weight.

7. Platinum alloy according to one of the preceding claims, characterised in that the Ge content is between 0.07 and 0.70% by weight.

8. Platinum alloy according to one of the preceding claims, characterised in that the Au content is between 0.10 and 1.00% by weight.

9. Platinum alloy according to one of the preceding claims, characterised in that the Au content is between 0.10 and 0.70% by weight.

10. Platinum alloy according to claim 1, characterised in that it consists, by weight, of 95.00 to 96.00% of Pt, of 2.00 to 4.80% 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%.

11. Platinum alloy according to claim1, characterised in that it consists, by weight, of 95.00 to 96.00% of Pt, of 3.00 to 4.80% 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%.

12. Platinum alloy according to claim1, characterised in that it consists, by weight, of 95.00 to 96.00% of Pt, of 3.50 to 4.80% 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%.

13. Platinum alloy according to one of the preceding claims, characterised in that it has a HV2 hardness between 140 and 230, preferably between 150 and 210 and a yellowness index Yi10° measured according to ASTM E313, between 7 and 8.

14. Platinum alloy according to one of the preceding claims, characterised in that its structure is face-centred cubic type single-phased, free of intermetallic precipitations such as GePt3, GePt2, Ge2Pt3, GePt, Ge3Pt2, GeRu.

15. Item made of platinum alloy according to one of the preceding claims.

16. Item according to the preceding claim, characterised in that it concerns a decorative item.

17. Item according to claim 15 or 16, characterised in that it concerns 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.