Method for producing component based on plurality of noble metals and component obtained thereby

Abstract

The invention relates to a method for producing a mechanical part on the basis of at least two precious metals or alloys thereof, comprising a step of atomizing the various precious metals or precious metals, a step of placing the resulting powders in a mould to form an assembly of unmixed powders, and a step of sintering at a temperature below the melting temperature of the metals used. The invention also encompasses a mechanical part produced by such a method and a timepiece comprising such a mechanical part.

Description

Technical Field

[0001] The present invention relates to a method for preparing watch parts based on a plurality of precious or noble metals or alloys of these metals, which are individually atomized into individual powders and then jointly participate in a sintering operation, in particular SPS (spark plasma sintering), also known as flash sintering. In the resulting watch parts, the various precious or noble metals can be distinguished from each other. The present description also covers watch parts made of a plurality of different precious or noble metals, and watches comprising such parts. Prior art

[0002] The principle of sintering metal material powders is known and is often used to prepare metal alloys. For example, document EP3766997 describes the use of this method to form noble or precious metal alloys. However, such alloys require homogenization or at least mixing of the powders. This method cannot produce components whose local compositions differ from each other.

[0003] Document EP3822712 gives an example of a method for designing watch parts using metal powders. The metals involved in this method are not limited to precious or noble metals, including, for example, stainless steel or aluminum. Therefore, the sintering conditions are not suitable for producing parts made of precious metals, which are distributed alone in the final part.

[0004] Document EP 2728422 describes the preparation of a bimetallic component comprising a base to which a cover plate is welded. This method requires at least partial melting of the metals involved. This method is also limited to the use of metal plates, which limits the variety of effects obtained.

[0005] Document CH715336 focuses on the production of two-color components in which the boundaries between the colors are clear. To achieve this, subcomponents of amorphous materials of different colors must be produced separately and then assembled under stress. This method requires meticulous machining operations to assemble the subcomponents, as well as to connect the elements used as decoration.

[0006] Sintering technology is an alternative to brazing or welding, with the advantage of limiting or avoiding the addition of material at the interface, as well as mixing of the materials involved. It also enables the production of monolithic parts. However, this method is not yet popular for precious metals. Therefore, there is room to develop a method specifically suitable for precious metal materials to achieve a wider range of uses and assemblies.

[0007] Brief description of the invention

[0008] One object of the present invention is to propose a method particularly suitable for precious metals and their alloys, making it possible to produce metal parts, such as watch parts, whose various metals are different from each other. In particular, the method of the present description proposes to assemble different precious metals without mixing them. In addition, the method proposes to avoid local changes in composition during the production of the parts.

[0009] Another object of the invention is to produce a monolithic or monobloc mechanical part, in particular a watch part, comprising or consisting of two or more noble metals or noble metal alloys that are different from each other. In particular, such a mechanical part or watch part preferably has no or minimal concentration gradients of the various components at its interface, for example at a thickness of less than 10 microns, or less than 5 microns or less than 1 micron. The term "monolithic" or "monobloc" is used to indicate a part consisting of a single block, i.e., it is not the result of an assembly of prefabricated subassemblies.

[0010] According to the invention, these objects are achieved in particular by methods and components which are the subject matter of the independent claims, details of which are the subject matter of the dependent claims.

[0011] In particular, this solution offers the advantage over the prior art of producing precious metal-based timepiece components having a specific aesthetic appearance and / or mechanical properties due to the local distribution of the various metals that compose them. In particular, local variations in color and / or hardness can be produced directly in the mass of the component without the need for additional steps. In particular, the components produced in this way are monolithic, which makes them more durable and / or easier to produce.

[0012] BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Embodiments of the present invention are described in the following drawings:

[0014] · Figure 1 : A method according to one embodiment of the present invention.

[0015] · Figure 2 : A method according to another embodiment of the present invention.

[0016] · Figure 3 : Schematic diagram of the post-demolding steps that may be involved in the method according to the present invention.

[0017] Detailed description of the invention

[0018] Figure 1 and 2The method described herein is shown. In a first step S1, a material M1 constituting one of the mechanical parts is atomized into a first powder P1. In this specification, the term "atomization" refers to any suitable operation for reducing the material under consideration to a powder. This may consist of or include a grinding step. The powder obtained may consist of particles of different fineness. For example, the size of the particles is micron-sized, with an average diameter in the range of 1 μm to 500 μm or 10 to 100 μm. Alternatively, the particles may be submicron-sized, i.e. with an average diameter of less than 1 micron.

[0019] The average particle size of the powder can be adjusted depending on the material and / or the result to be achieved.

[0020] The method comprises a step S2 for atomizing the second material M2 to produce a second powder P2. The atomization conditions may be the same or different from the conditions for atomizing the first material M1. The average particle size forming the second powder P2 may be the same or similar to the average particle size forming the first powder P1. Alternatively, different particle sizes may form the first powder P1 and the second powder P2. It is understood that the atomization steps of the first material M1 and the second material M2 are performed separately from each other, thereby obtaining different powders P1 and P2. In particular, the method according to the present invention does not include any mixing steps of these first powders P1 and second powders P2. More specifically, the method according to the present invention includes all measures for not mixing the first powder P1 and the second powder. It may even be provided that the first material M1 and the second material M2 are atomized at different locations to avoid or limit contamination between each other. A device for tracking or tracing different materials and powders may also be provided. According to these arrangements, the method may include steps for separately packaging, tracking and separately storing materials and / or powders.

[0021] The atomization step of the first material M1 and the atomization step of the second material M2 may be performed in parallel or sequentially.

[0022] According to one embodiment, one or more materials used in the present method can be directly selected in powder form, thus eliminating the need for the corresponding atomization steps S1, S2, Si described herein.

[0023] Both the first material M1 and the second material M2 are selected from noble or precious metals, or alloys based on such noble or precious metals.

[0024] Precious or noble metals according to the present specification include gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), scandium (Sc), ruthenium (Ru), osmium (Os) and iridium (Ir). In particular, precious metals refer to corrosion-resistant metals. In the context of the present specification, the terms "precious metal" and "noble metal" are interchangeable and equivalent, so that either of the two terms refers to the metals listed above.

[0025] In the context of this specification, the alloy of these precious metals contains at least 50% by mass, or 80% by mass or more, or even 95% by mass of one of these precious metals or a combination of these precious metals. The alloy according to this specification may include a mixture of gold and silver, which together constitute at least 50% by mass, or 80% by mass or more of the mechanical part. This does not exclude the combination of more than two precious metals to form an alloy. According to a specific embodiment, the alloy may consist only of a combination of two or more of the precious metals listed above.

[0026] According to one embodiment, the alloy according to the invention comprises one or more of the noble metals listed above and one or more other non-noble metals, such as copper, tin, aluminum, zinc, titanium or nickel.

[0027] Different materials M1, M2 may refer to different alloys based on the same precious metal. For example, the first material M1 may represent a first gold alloy, and the second material M2 may represent a second gold alloy. One or both of the first material M1 and the second material M2 may be selected from the following gold alloys, for example:

[0028] - White gold: 75% gold, 19% copper, 6% silver,

[0029] - White gold: 75% gold, 25% palladium or 25% nickel,

[0030] -Red gold: 75% gold, 25% copper,

[0031] -Pink gold: 75% gold, 20% copper, 5% silver,

[0032] -Green Gold: 75% gold, 25% silver.

[0033] All 18 ct gold alloys from 1N to 5N can be considered as different materials M1, M2 and assembled in the same component. Other gold alloys can be considered as required. In addition, various alloys based on precious metals other than gold can also be considered, such as platinum-based alloys or palladium-based alloys.

[0034] The precious metals may be used independently in different amounts, such as 9 ct, 12 ct, 18 ct or 24 ct, or in other amounts.

[0035] The first material M1 and the second material M2 are characterized by their own melting temperatures T1, T2. For example, the melting temperature of gold at atmospheric pressure is about 1064°C. The melting temperature of gold alloys is usually higher than this value. The melting temperature of palladium is about 1554°C, the melting temperature of platinum is about 1768°C, the melting temperature of rubidium is about 39°C, the melting temperature of scandium is about 1541°C, the melting temperature of rhodium is about 1964°C, the melting temperature of iridium is about 2446°C, the melting temperature of ruthenium is about 2333°C, and the melting temperature of osmium is about 3033°C.

[0036] The method according to the present specification comprises a step S3 of arranging the first powder P1 and the second powder P2 in the sintering mold 2. The first powder P1 and the second powder P2 are arranged in sequence so that they do not mix. They can be arranged individually to form a powder bed or a powder pile, or arranged in different arrangements, such as in a linear arrangement, or in a geometric pattern or a random pattern. As required, one or more of the first powder P1 and the second powder P2 and any additional powder Pi (see below) can be reused, for example to form multiple clusters, or multiple lines or multiple layers, alternating with other powders.

[0037] In one embodiment, if necessary, the powders may be vibrated or subjected to any other operation to make them more compact or more evenly distributed. It must then be ensured that the first powder P1 and the second powder P2 do not mix during these operations, if they occur.

[0038] The first powder P1 and the second powder P2 can be used in different proportions, for example in equal amounts, so that the final mechanical component contains the same amount of the first material M1 and the second material M2, regardless of their distribution. The M1 / M2 ratio of the first material M1 and the second material M2 can vary, for example, from 10 / 90 to 90 / 10 or from 20 / 80 to 80 / 20. Of course, a ratio between 30 / 70 and 70 / 30 or between 40 / 60 and 60 / 40 is also feasible.

[0039] The powders combine to form an unmixed powder assembly A. The first powder P1 and the second powder P2 are in contact with each other, but each remains located at a specific point determined when it is placed in the mold 2 .

[0040] The method described here does not exclude the use of powder mixtures to produce in-situ alloys. For example, in addition to the first powder P1 and the second powder P2, a third powder consisting of a combination of the first powder P1 and the second powder P2 or other powders may be added. Under these conditions, the third powder corresponds to a noble or precious metal alloy as defined in this specification.

[0041] Once the unmixed powder component A is produced, it is sintered in step S4. The sintering conditions include the sintering temperature Tfri. They also include the sintering pressure Pfri, which can be a mechanical pressure.

[0042] The sintering temperature Tfri is determined in such a way that none of the powders in the powder assembly A melts under the sintering conditions. The appropriate sintering temperature Tfri can be evaluated based on the sintering pressure Pfri so that the melting temperatures T1 and T2 of the first material M1 and the second material M2 under the sintering pressure Pfri are not reached or exceeded or are kept below the melting temperatures T1 and T2 of the first material M1 and the second material M2 under the sintering pressure Pfri. Preferably, the sintering temperature is determined in such a way that it is kept below the lowest value of the melting temperatures T1, T2 of the first material M1 and the second material M2 under the sintering conditions. It is understood that the sintering temperature varies depending on the first and second materials used and / or their alloys. In this case, the sintering temperature is defined based on the physical properties of the materials involved.

[0043] Preferably, the sintering conditions are those of flash sintering, also known as SPS (spark plasma sintering).Using electrodes to heat the unmixed powder assembly A allows very short heating times to be achieved while maintaining particle fineness.

[0044] In one embodiment, the sintering temperature Tfri is less than 2000° C., or even less than 1500° C., or even less than 1000° C. For example, the sintering temperature is between 600° C. and 1600° C.

[0045] The sintering pressure Pfri can be between 20 and 180 N / mm 2 Between or between 50 and 100 N / mm 2 Other pressure values ​​may be preferred depending on the components selected and / or the quality required of the final mechanical part.

[0046] Once sintering is complete, a solid component B is obtained from the powder assembly A. The solid component B is inhomogeneous and therefore locally contains different components, each corresponding to the first material M1 and the second material M2 used. The local components can therefore correspond independently of each other to a pure noble metal or a specific noble metal alloy.

[0047] Once the solid component B is obtained, it is demoulded in step S5 in order to recover the demoulded solid component C.

[0048] The demoulded solid part C may correspond to the final part. However, the demoulded part C may require one or more subsequent operations to improve its quality or aesthetic appearance, or to modify the obtained part to obtain the final part 1. For example, a correction step S6 can be used to adjust the size of the demoulded solid part C. A processing step S7 can be performed to modify the solid part C, thereby producing one or more holes, or grooves, or ridges or any other material ablation. Processing can be performed by any suitable technology, whether mechanical, laser, water jet or equivalent technology. One or more S8 finishing steps can also be envisioned. Other post-sintering transformations can be provided as required.

[0049] Although a method using two materials is described above, this by no means excludes the use of more than two materials, for example three or more materials, in an arrangement identical or similar to that already described. Figure 2 A method using an additional material Mi is shown, which is atomized into an additional powder Pi in an additional atomization step Si. The one or more additional materials Mi are different from the first material M1 and the second material M2. However, they are selected from the above-mentioned noble or precious metals or combinations thereof. The one or more additional powders Pi obtained are processed and treated under the conditions already described for the first powder P1 and the second powder P2. In particular, sufficient measures are taken to ensure that they are not mixed with other powders. One or more additional materials can be directly selected in powder form. In this case, one or more corresponding atomization steps may not be necessary.

[0050] A collection of the first powder P1, the second powder P2 and one or more additional Pi powders are separately arranged in a mold to form at least three unmixed powder components A', and a sintering operation is performed under the desired conditions to obtain a solid part B' comprising the first material M1, the second material M2 and one or more additional materials Mi (although different from each other but combined together). The temperature and pressure conditions for sintering are those already mentioned for the component A of at least two powders. Specifically, the sintering temperature Tfri is set to a temperature at which none of the first material M1, the second material M2 or the additional material Mi melts during sintering. The solid part B' can be demolded to obtain a demolded solid part C'. One or more of the above-mentioned post-demolding operations S6, S7, S8 can be performed, such as Figure 3 shown.

[0051] According to one embodiment, other materials, such as pigments, may be added to any of the first powder P1, the second powder P2 and the additional powders Pi. If such additives are present, the amount is preferably less than 5 wt% or even less than 1 wt%.

[0052] Thus, the component obtained by the method described herein is produced by a single sintering operation, even if it contains a variety of materials or alloys. The method has the advantages of being simple and direct. In this case, it eliminates the assembly phase of different sub-assemblies that is usually required for components of this type. The division of colors and geometric patterns also remains clear and distinct. In particular, the concentration gradient at the junction of different materials is zero or limited to less than 10 microns or 5 microns, or even less than 1 micron. The pattern produced is realized directly in the body (mass) of the component. A pattern is understood here as any change in color or hue, any two-dimensional or three-dimensional shape obtained from the body of the component, or any other visual and / or aesthetic or decorative aspect. The pattern coincides with the interface of the various materials of the component. Due to changes in the local composition, these patterns may be accompanied by local changes in mechanical properties, especially in terms of hardness.

[0053] This specification also covers a mechanical part 1 prepared according to the above method. In particular, this is a metal part based on at least two precious or noble metals or their alloys or a metal part based on at least three precious or noble metals or their alloys. In the context of this specification, a part based on precious or noble metals contains one or more precious or noble metals, the mass of which accounts for at least half of the mass of the part. According to one embodiment, the mechanical part contains 80% by mass or more, or 95% by mass of one or more precious or noble metals, or their alloys. The various precious or noble metals of such a part are different from each other. In this way, the mechanical part 1 can be characterized by the different color characteristics of the different precious or noble metals used to prepare it. Patterns, such as camouflage effects or geometric patterns, may also appear. Alternatively, or in addition, the mechanical part can be characterized by different local mechanical properties, which are specific to the different precious or noble metals used to prepare the mechanical part.

[0054] The distribution of various precious or noble metals in a mechanical component is not restricted. Different precious or noble metals may be distributed in a mechanical component in the form of superimposed layers, or in the form of clusters, or in any other arrangement determined during the preparation process. One of the precious or noble metals may be completely hidden from view, especially if it forms the core or inner part of the component, and is covered by another precious or noble metal. Nevertheless, the boundaries of the different materials within the component remain clear and distinct. The resulting visual effect is of the highest quality.

[0055] Thus, the mechanical component 1 according to the present description comprises at least one first material M1 and a second material M2, which form an inseparable whole, such as a monolithic or integral one, wherein at least the first material M1 and the second material M2 remain different from each other. In addition to the first material M1 and the second material M2, the mechanical component 1 may also comprise one or more other additional materials Mi, which are different from the first material M1 and the second material M2 and from other materials. The first material M1 and the second material M2 and any additional material Mi are selected from one of the above-mentioned noble or precious metals or their alloys.

[0056] The mechanical part 1 may be, for example, a watch component, such as a gear train or any other part of a watch movement. Alternatively, the mechanical part 1 is a decorative or finishing part. It may be, for example, a watch case or a dial or any other element visible to the user. In this respect, the mechanical part 1 exploits the advantages of the above-described method, which is particularly suitable for combining different precious metals in a single part, thereby producing a wide variety of aesthetic effects.

[0057] Example 1

[0058] The first 5N 18ct gold powder and the second 2N 18ct gold powder are stacked in the SPS sintering mold. Sintering is performed at a sintering temperature of 800°C and a pressure of 100 MPa, and the resulting pellets are demolded to form a watch case. Since all materials are 18ct, the final case middle is also 18ct.

[0059] Example 2

[0060] The first 18ct 5N gold powder and the second 18ct yellow gold powder were stacked in sequence in an SPS sintering mold. The third 950 / 1000 platinum powder was placed on top of the first two powders. Sintering was carried out at a sintering temperature of 860°C and a pressure of 130MPa, and the resulting beads were demoulded and processed into a bezel. The part was then completed by decorating a 950 / 1000 platinum surface layer, which is softer than the layer below. The final part was not titrated.

[0061] Example 3

[0062] The first 18ct 5N gold powder, the second 18ct 2N gold powder and the 18ct grey gold powder are randomly distributed in the SPS sintering mold to form powder clusters. Sintering is carried out at a sintering temperature of 790°C and a pressure of 80MPa. The resulting beads are demolded to produce a bezel with a yellow, pink and grey camouflage pattern. Since all materials are 18ct, the final element is also 18ct.

[0063] Reference numerals used in the drawings

[0064] 1 Mechanical parts

[0065] M1 First Material

[0066] M2 Second Material

[0067] Mi Additional materials (one or more)

[0068] P1 First Powder

[0069] P2 Second Powder

[0070] Pi additional powder (one or more)

[0071] S1 Atomization step of the first material

[0072] Atomization steps of Si additive materials

[0073] S2 Atomization step of the second material

[0074] S3 Steps for arranging powder in the mold

[0075] S4 Sintering step

[0076] S5 demoulding step

[0077] S6 Calibration Procedure

[0078] S7 processing steps

[0079] S8 finishing step

Claims

1. A method for producing a timepiece component (1) based on at least two noble or precious metals or noble or precious metal alloys which remain different from one another, the timepiece component containing at least 50% by mass or 80% by mass or more of these metals and / or alloys, the method comprising: choose a first material (M1) in the form of a first powder (P1), said first material (M1) having a first melting temperature (T1) at atmospheric pressure, a second material (M2) in the form of a second powder (P2), said second material (M2) having a second melting temperature (T2) at atmospheric pressure, - and optionally, one or more additional materials (Mi) different from the first material (M1) and the second material (M2), in the form of the same amount of corresponding additional powders (Pi), - step S3, arranging said material in powder form in a mould (2) to form an assembly (A, A') of at least two unmixed powders, wherein said powders are in contact, - step S4 of sintering under conditions such as to produce a solid part (B, B') from the assembly (A, A') of unmixed powders, - step S5, demoulding the solid part (B, B') to obtain a demoulded part (C, C'), Characterized in that the material (M1, M2, Mi) represents the precious or noble metal or precious or noble metal alloy contained in the watch component (1), and the sintering of step S4 is flash sintering or SPS type sintering, operated at a sintering temperature (Tfri) and a sintering pressure (Pf), and the sintering temperature (Tfri) and pressure (Pfri) are determined so that none of the materials melt.

2. The method according to claim 1, wherein the material (M1, M2, Mi) is selected from gold (Au), silver, platinum (Pt), palladium (Pd), osmium (Os) and alloys thereof.

3. A method according to any one of claims 1 or 2, wherein the alloy comprises at least 50 mass %, or 80 mass % or more, or even 95 mass % of a noble or precious metal or a combination of noble or precious metals.

4. The method according to any one of claims 1 to 3, wherein the powder is arranged in step S4 to independently form one or more clusters, one or more rows or a plurality of alternating layers.

5. Method according to any one of claims 1 to 4, wherein one or more of the powders (P1, P2, Pi) comprises one or more additives.

6. The method according to any one of claims 1 to 5, wherein the sintering temperature (Tf) is between 600°C and 1600°C.

7. The method according to any one of claims 1 to 6, wherein the sintering pressure (Pfri) is between 20 and 180 N / mm 2 Mechanical pressure between.

8. The method according to any one of claims 1 to 7, further comprising one or more steps selected from step S1, step S2 and step Si, step S1 atomizing the first material (M1) to produce the first powder (P1), step S2 atomizing the second material (M2) to produce the second powder (P2), and step Si atomizing the additional material to produce corresponding one or more powders (Pi).

9. The method according to any one of claims 1 to 8, further comprising one or more of the following steps: -S6, correct the solid parts (C, C') after demoulding to the required thickness, - S7, processing of the demoulded solid parts (C, C'), - S8, finishing of the solid parts (C, C') after demoulding, Thereby, the timepiece component is obtained.

10. A watch component comprising at least two materials selected from a first material (M1), a second material (M2) and optionally one or more additional materials (Mi), forming an integral component, wherein the materials (M1, M2, Mi) remain different from each other and form a pattern in the body of the component, and the materials are selected from precious or noble metals and their alloys.

11. The timepiece component according to claim 10, the pattern comprising one or more of a local colour change, a local hue change, a two-dimensional shape, a three-dimensional shape and combinations thereof.

12. A timepiece component according to any one of claims 10 and 11, wherein the interface of the at least two materials has a zero concentration gradient or a concentration gradient reduced to a thickness of less than 10 microns, or less than 5 microns or less than 1 micron, so that the distinction of the materials is clear and obvious.

13. Timepiece component according to any one of claims 10 to 12, obtained by a method according to any one of claims 1 to 9.

14. A timepiece component according to any one of claims 10 to 13, said component being a decorative finish or a movement component.

15. Timepiece comprising a timepiece component according to any one of claims 10 to 13.

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