Method for manufacturing a part based on multiple precious metals, and resulting part

Abstract

The present invention relates to a method for manufacturing a mechanical part based on at least two precious or noble metals or alloys thereof, the method comprising a step of atomizing the various precious metals, positioning the resulting powders in a mold, so as to form a blend of unmixed powders, and a step of sintering at temperatures below the melting temperatures of the metals used. The invention also covers a mechanical part produced by such a method, and a timepiece comprising such a mechanical part.

Description

Process for manufacturing a part from several precious metals and the resulting part technical field

[0001] The present invention relates to a method for manufacturing a watch component based on several precious or noble metals or alloys of such metals, which are individually atomized into separate powders before being jointly involved in a sintering operation, in particular spark plasma sintering (SPS), also known as flash sintering. The different precious or noble metals can be distinguished from one another in the watch component thus obtained. This description further covers a watch component made of several distinct precious metals, as well as a timepiece incorporating such a component. State of the art

[0002] The principle of sintering metallic powders is well-known and frequently used to manufacture metal alloys. Document EP3766997, for example, describes the formation of precious metal alloys using such a process. However, such alloys require that the powders be homogenized or at least thoroughly mixed. These processes do not allow for the production of components with distinct local compositions.

[0003] Document EP3822712 provides an example of a metal powder-based process for designing a watch component. The metals involved in the process are not limited to precious or noble metals and include, for example, stainless steel or aluminum. Consequently, the sintering conditions are not suitable for producing components made of precious metals distributed throughout the final part. AUDEMA-19-PCT

[0004] Document EP 2728422 describes the manufacture of a bimetallic component comprising a base onto which a cover plate is welded. This process requires at least partial melting of the metals involved. Furthermore, the use of metal plates limits the range of effects that can be achieved.

[0005] Document CH715336 focuses on producing two-tone components with a clear color separation. This requires the separate production of amorphous materials in different colors, followed by assembly under stress. The process necessitates meticulous machining operations to join the sub-assemblies, as well as the use of decorative connecting elements.

[0006] Sintering is an alternative to brazing or welding that offers the advantage of limiting or eliminating material buildup at interfaces, as well as mixing of the materials present. It also allows for the production of monolithic parts. However, this process is not currently favored for precious metals. Therefore, there is potential to develop a process specifically adapted to precious materials, enabling a greater variety of uses and assembly possibilities. Brief summary of the invention

[0007] One object of the present invention is to provide a process specifically adapted to precious metals and their alloys, enabling the manufacture of a metal part, such as a watch component, in which the different metals are distinct from one another. In particular, the process described herein aims to assemble different precious metals without mixing them. Furthermore, the present process aims to avoid localized alterations to the compositions during the production of the part.

[0008] Another objective of the invention is to produce a monolithic or monobloc mechanical part, in particular, a watch component, AUDEMA-19-PCT comprising or made of two or more precious metals or precious metal alloys, which are distinct from one another. In particular, such a mechanical part or watch component preferably exhibits no concentration gradient of the different constituents at their interfaces or a minimal concentration gradient, for example, over a thickness of less than 10 micrometers, or less than 5 micrometers, or less than 1 micrometer. The terms "monolithic" or "monobloc" are understood to designate a part made from a single block, that is to say, it does not result from an assembly of prefabricated sub-assemblies.

[0009] According to the invention, these goals are achieved in particular by means of the method and component which are the subject of the independent claims, and whose details are the subject of the dependent claims.

[0010] This solution offers a significant advantage over previous methods in producing watch components made from precious metals with a distinctive aesthetic appearance and / or specific mechanical properties due to the localized distribution of the various metals that constitute them. In particular, local variations in color and / or hardness can be achieved directly within the component itself, without any additional steps. Furthermore, the resulting parts are made from a single piece of metal, making them more durable and / or simpler to manufacture. Brief description of the figures

[0011] Examples of implementation of the invention are shown in the description illustrated by the following figures: Figure 1: Method according to an embodiment of the present invention. AUDEMA-19-PCT Figure 2: Method according to another embodiment of the present invention. • Figure 3: Schematic representation of post-demolding steps that may be involved in the process according to the present invention. Example(s) of an embodiment of the invention

[0012] The process described herein is illustrated in Figures 1 and 2. In a first step S1, one of the materials M1 constituting the mechanical part is atomized into a first powder P1. In this description, the term "atomize" refers to any suitable operation that reduces the material in question to a powder. It may consist of, or include, a grinding step. The resulting powder may consist of particles of varying fineness. For example, the particles may be micrometer-sized, with an average diameter on the order of 1 µm to 500 µm, or 10 to 100 µm. Alternatively, the particles may be sub-micrometer-sized, with an average diameter of less than one micrometer.

[0013] The average particle size of the powder can be adapted according to the material considered and / or the result to be obtained.

[0014] The process includes a step S2 of atomizing a second material M2 to produce a second powder P2. The atomization conditions may be identical or different from those of the atomization of the first material M1. The average size of the particles forming the second powder P2 may be identical or similar to that forming the first powder P1. Alternatively, particles of different sizes may constitute the first P1 and second P2 powders. It is understood that the atomization steps of the first M1 and second M2 materials are carried out separately from each other, so that distinct powders P1 and P2 are obtained. In particular, the process according to the present invention does not include any step of mixing these first P1 and second P2 powders. More particularly, the process according to the present AUDEMA-19-PCT The invention includes all provisions for preventing the mixing of the first P1 and second P2 powders. It may even be provided that the first M1 and second M2 materials are atomized in different locations to avoid or limit cross-contamination. A system for tracing or monitoring the different materials and powders may also be implemented. According to these provisions, the process may include steps of separate packaging, tracing, and separate storage of the materials and / or powders.

[0015] The atomization step of the first material M1 can be carried out in parallel with that of the second material M2 or sequentially.

[0016] According to one embodiment, one or more of the materials used in the present process can be selected directly in powder form so that the corresponding atomization steps S1, S2, Si described herein are not necessary.

[0017] The first M1 and second M2 materials are both selected from precious or noble metals, or alloys based on such precious or noble metals.

[0018] Precious or noble metals, as defined herein, include gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), scandium (Sc), ruthenium (Ru), osmium (Os), and iridium (Ir). In particular, noble metals are those that are highly resistant to corrosion. For the purposes of this description, the terms "precious" and "noble" are interchangeable and equivalent, so either term refers to the metals listed above.

[0019] For the purposes of this description, alloys of these precious metals comprise at least 50% by mass, or 80% or more, or even 95% by mass of one of these precious metals or a combination thereof. An alloy as described herein may comprise a mixture of gold and silver forming together at least 50% by mass or 80% AUDEMA-19-PCT in mass or more, of the mechanical part. This does not preclude more than two precious metals from being combined to form an alloy. According to a particular embodiment, an alloy may consist exclusively of a combination of two or more of the precious metals listed above.

[0020] According to one embodiment, an alloy according to the present invention comprises one or more of the precious metals listed above and one or more other non-precious metals such as copper, tin, aluminum, zinc, titanium or nickel.

[0021] The different materials M1 and M2 can refer to different alloys based on the same precious metal. For example, the first material M1 could refer to a first gold alloy, and the second material M2 could refer to a second gold alloy. One or both of the first M1 and second M2 materials could, for example, be selected from the following gold alloys: - White gold: 75% gold, 19% copper, 6% silver, - White gold: 75% gold, 25% palladium or 25% nickel, - Red gold: 75% gold, 25% copper, - Rose gold: 75% gold, 20% copper, 5% silver, - Green gold: 75% gold, 25% silver.

[0022] All 18-karat gold alloys, such as golds ranging from 1N to 5N, can be considered as different materials (M1, M2) and assembled into a single component. Other gold alloys can be considered depending on the requirements. Furthermore, various alloys based on precious metals other than gold can be considered, such as platinum-based or palladium-based alloys. AUDEMA-19-PCT

[0023] Precious metals can independently be used in different grades, such as 9 and, 12 and, 18 and or 24 and or other grades.

[0024] The first M1 and second M2 materials are characterized by their own specific melting temperatures, T1 and T2. For example, the melting temperature of gold at atmospheric pressure is approximately 1064°C. The melting temperatures of gold alloys are generally higher than this value. The melting temperature of palladium is around 1554°C, that of platinum around 1768°C, that of rubidium around 39°C, that of scandium around 1541°C, that of rhodium around 1964°C, that of iridium around 2446°C, that of ruthenium around 2333°C, and that of osmium around 3033°C.

[0025] The process described herein includes a step S3 of arranging the first P1 and second P2 powders in a sintering mold 2. The first P1 and second P2 powders are arranged sequentially so as not to mix. They can each be arranged to form a powder bed, a powder cluster, or in various arrangements such as lines, geometric shapes, or random patterns. Depending on requirements, one or more of the first P1 and second P2 powders, and optionally additional powders Pi (see below), can be used repeatedly, for example, to form several clusters, lines, or layers alternating with other powders.

[0026] In one embodiment, the powders may be subjected to vibration or any other operation to densify them or improve their distribution if necessary. It is then important to ensure that the first P1 and second P2 powders do not mix during these operations, if they occur.

[0027] The first P1 and second P2 powders can be used in varying proportions, for example in equal quantities so that the AUDEMA-19-PCT The final mechanical part comprises equal amounts of the first material M1 and the second material M2, regardless of their proportions. The M1 / M2 ratio of the first and second materials M2 can, for example, vary from 10 / 90 to 90 / 10 or from 20 / 80 to 80 / 20. Ratios between 30 / 70 and 70 / 30 or 40 / 60 and 60 / 40 are, of course, also possible.

[0028] The combination of powders forms an assembly A of unmixed powders. The first P1 and second P2 powders are in contact with each other while each remaining localized in the specific locations determined during their arrangement in the mold 2.

[0029] The process described here does not preclude the use of additional powder mixtures to produce an alloy in situ. For example, in addition to the first powder P1 and the second powder P2, a third powder consisting of a combination of the first P1 and second P2 powders, or other powders, may be added. Under these conditions, the third powder corresponds to an alloy of precious or noble metals as defined in this description.

[0030] Once the unmixed powder assembly A is formed, it is subjected to sintering in step S4. The sintering conditions involve a sintering temperature Tfri. They also include a sintering pressure Pfri, which can be a mechanical pressure.

[0031] The sintering temperature Tfri is determined so 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 as not to reach, not to exceed, or to remain below the melting temperatures T1 and T2 of the first M1 and second M2 materials at the sintering pressure Pfri. Preferably, the sintering temperature is determined so as to remain below the lower of the melting temperatures T1 and T2 of the first M1 and second M2 materials under the sintering conditions. It is understood that the sintering temperature varies depending on the first and second materials. AUDEMA-19-PCT used and / or their alloys. In this case, the sintering temperature is defined in relation to the physical properties of the materials involved.

[0032] Preferably, the sintering conditions are those of flash sintering, also known as SPS (spark plasma sintering). The use of electrodes to heat the unmixed powder assembly A allows for very short heating times and preserves grain fineness.

[0033] According to one embodiment, the sintering temperature Tfri is less than 2000°C, or even less than 1500°C, or even less than 1000°C. The sintering temperature is, for example, between 600°C and 1600°C.

[0034] The sintering pressure Pfri can be between 20 and 180 N / mm² 2 or between 50 and 100 N / mm 2 Other pressure values ​​may be preferred depending on the components selected and / or the required quality of the final mechanical part.

[0035] Once sintering is complete, a solid part B is obtained based on the assembly of powders A. Solid part B is inhomogeneous and therefore locally exhibits different compositions, each corresponding to the first M1 and second M2 materials used. These local compositions can thus independently correspond to pure precious metals or specific precious metal alloys.

[0036] The solid part B, once obtained, is demolded in a step S5, so as to recover a demolded solid part C.

[0037] The solid part removed from the mold C may correspond to the final component. However, it may be necessary for the part removed from the mold C to require one or more subsequent interventions to improve its quality or aesthetic appearance, or to modify the part obtained to produce the final component 1. A grinding step S6, for example, may allow for AUDEMA-19-PCT Resize the demolded solid part C. A machining step S7 can be performed to modify the solid part C, resulting in one or more holes, grooves, striations, or any other material removal. Machining can be carried out using any suitable technique, whether mechanical, laser, waterjet, or equivalent. One or more finishing steps S8 may also be considered. Other post-sintering transformations may be planned as required.

[0038] Although the process is described above with two materials, this does not preclude the use of more than two, such as three or more, following the same or similar arrangements already described. Figure 2 schematically illustrates the process with an additional material Mi, atomized into an additional powder Pi in an additional atomization step Si. The additional material(s) Mi are different from the first M1 and second M2 materials. They are, however, selected from among the precious or noble metals mentioned above, or their combination. The resulting additional powder(s) Pi are processed and handled under the conditions already described for the first P1 and second P2 powders. In particular, appropriate measures are taken to prevent them from mixing with other powders. The additional material(s) can be selected directly in powder form.In this case, the corresponding atomization step(s) may not be useful.

[0039] The first powders P1 and P2, along with one or more additional powders Pi, arranged separately in a mold to form an assembly of at least three unmixed powders A', are subjected to a sintering operation under the required conditions to obtain a solid part B' comprising the first M1, the second M2, and one or more additional materials Mi, combined but distinct from one another. The temperature and pressure conditions for sintering are those already mentioned for the assembly of at least two powders A. In particular, the sintering temperature Tfri is determined so that none of the first M1, second M2, or additional materials Mi melts during sintering. The solid part B' can be demolded to obtain a demolded solid part C'. One or more of the following operations... AUDEMA-19-PCT Demolding procedures S6, S7, S8 described above can be implemented, as illustrated in figure 3.

[0040] According to one embodiment, either of the first P1, second P2 powders and additional powders Pi may be additively mixed with other materials such as pigments. Such additives, if present, are preferably in quantities of less than 5%, or even less than 1% by mass.

[0041] The part resulting from the process described here is thus produced by a single sintering operation, even though it comprises several materials or alloys. This process has the advantage of being simple and direct. In this case, it eliminates the assembly steps of different sub-assemblies often required for this type of component. Furthermore, the demarcation of colors and geometric patterns remains clear and distinct. In particular, concentration gradients at the junctions of the different materials are minimized or limited to less than 10 micrometers, 5 micrometers, or even less than 1 micrometer. The patterns produced are directly embedded within the component. Here, "patterns" is understood to mean any variation in color or shade, any two- or three-dimensional shape within the component, or any other visual and / or aesthetic or ornamental feature. The patterns coincide with the interfaces of the different materials in the component.Due to variations in local composition, these patterns can be accompanied by local variations in mechanical properties, particularly in terms of hardness.

[0042] This description also covers a mechanical part 1 manufactured according to the process described above. In particular, it refers to a metal part made of at least two precious or noble metals, or their alloys, or at least three precious or noble metals, or their alloys. For the purposes of this description, a part made of precious or noble metals contains at least half of its mass of one or more precious or noble metals. In one embodiment, the mechanical part comprises 80% or more of its mass, or 95% of its mass, of a metal component made of precious or noble metals. AUDEMA-19-PCT A component is made of one or more precious or noble metals, or their alloys. The different precious or noble metals in such a component are distinct from one another. Thus, the mechanical component 1 can be characterized by different colors, each characteristic of the different precious or noble metals that constitute it. Patterns such as camouflage or geometric designs may appear. Alternatively, or in addition, it may be characterized by different local mechanical properties, specific to the different precious or noble metals that compose it.

[0043] The distribution of different precious or noble metals within a mechanical part is not limited. These metals can be arranged in superimposed layers, clusters within the part, or any other configuration determined during its manufacture. One of the precious or noble metals may remain completely hidden from view, particularly if it forms the core of the part or its internal structure, which is covered by another precious or noble metal. Nevertheless, the boundaries between the different materials within the part remain sharp and distinct. The resulting visual effects are of high quality.

[0044] Thus, a mechanical part 1 according to this description comprises at least a first material M1 and a second material M2 forming an inseparable unit, either monolithic or monobloc, in which the at least first M1 and second M2 materials remain distinct from each other. In addition to the first M1 and second M2 materials, the mechanical part 1 may comprise one or more other additional materials Mi, different from the first M1 and second M2 materials and also distinct from the other materials. The first M1 and second M2 materials, as well as any additional materials Mi, are selected from among one of the precious or noble metals mentioned above or their alloys.

[0045] Mechanical part 1 could be, for example, a watch component such as a gear or any other part of a watch movement. Alternatively, mechanical part 1 could be an ornamental component or AUDEMA-19-PCT of the casing. It can be, for example, a watch case, a dial, or any other element visible to the user. As such, mechanical part 1 fully benefits from the advantages of the process described above, which is particularly well-suited for arranging different precious metals within the same part and thus producing a wide variety of aesthetic effects.

[0046] Example 1 A first 5N 18-karat gold powder and a second 2N 18-karat gold powder are successively stacked in an SPS sintering mold. Sintering is carried out at a temperature of 800°C and a pressure of 100 MPa. The resulting pellet is demolded to obtain a blank. Since all the materials together have a 18-karat gold content, the resulting blank also has a 18-karat gold content.

[0047] Example 2 A first layer of 18-karat 5N gold powder and a second layer of 18-karat yellow gold powder are successively stacked in an SPS sintering mold. A third layer of 950 / 1000 platinum powder is then placed on top of the first two layers. Sintering is carried out at a temperature of 860°C and a pressure of 130 MPa. The resulting pellet is removed from the mold and then machined to create a bezel. A finishing step is performed, during which the 950 / 1000 platinum surface layer, which is less hard than the underlying layers, is decorated. The final piece is not hallmarked.

[0048] Example 3 A first 5N 18 gold powder, a second 2N 18 gold powder, and an 18-karat white gold powder are randomly distributed in an SPS sintering mold to form powder clusters. Sintering is carried out at a temperature of 790°C and a pressure of 80 MPa. The resulting pellet is demolded to obtain a bezel with a pattern resembling a AUDEMA-19-PCT Camouflage composed of yellow, pink and grey colors. All materials are 18ct, the final piece is also 18ct. AUDEMA-19-PCT Reference numbers used in the figures 1 Mechanical part M1 First material M2 Second material Additional material(s) P1 First powder P2 Second powder Pi Additional Powder(s) S1 Atomization stage of the first material 51 Atomization stage of additional materials 52 Atomization step of the second material 53. Stage of arranging the powders in a mold 54 Sintering stage 55 Demolding stage 56. Rectification Step 57 Machining stage 58 Finishing Stage AUDEMA-19-PCT

Claims

Demands 1. A method for manufacturing a watch component (1) based on at least two precious or noble metals or alloys of precious or noble metals, remaining distinct from one another, said watch component comprising at least 50% or 80% or more, by mass, of these metals and / or alloys, the method comprising: the selection - of 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, - of a second material (M2) in the form of a second powder (P2), said second material (M2) having a second melting point (T2) at atmospheric pressure, - and optionally one or more additional materials (Mi) different from the first (M1) and second (M2) materials, in the form of as many corresponding additional powders (Pi), - A step S3 of arranging said materials in powder form in a mold (2), so as to form an assembly (A, A') of at least two unmixed powders, in which said powders are in contact, - A step S4 to carry out sintering under conditions allowing the production of a solid part (B, B') from the assembly (A, A') of unmixed powders, AUDEMA-19-PCT A step S5 of demolding said solid part (B, B') to obtain a demolded part (C, C'), characterized in that said materials (M1, M2, Mi) designate said precious or noble metals or alloys of precious or noble metals contained in the watch component (1), and in that the sintering of step S4 is a flash or SPS type sintering, carried out at a sintering temperature (Tfri) and a sintering pressure (Pf), said sintering temperatures (Tfri) and pressure (Pfri) being determined so that none of said materials melts.

2. A method according to claim 1, wherein said materials (M1, M2, Mi) are selected from gold (Au), silver, platinum (Pt), palladium (Pd), osmium (Os) and their alloys.

3. A process according to any one of claims 1 or 2, wherein said alloys comprise at least 50% by mass, or 80% or more, or even 95% by mass of a precious or noble metal or a combination of precious or noble metals.

4. A method according to any one of claims 1 to 3, wherein the powders are arranged during step S4 so as to independently form one or more clusters, one or more lines, or several alternating layers.

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

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

7. A method according to any one of claims 1 to 6, wherein the sintering pressure (Pfri) is a mechanical pressure between 20 and 180 N / mm² 2 . AUDEMA-19-PCT 8. A method according to any one of claims 1 to 7, further comprising one or more steps from a step S1 of atomizing said first material (M1) so as to produce said first powder (P1), a step S2 of atomizing said second material (M2) so as to produce said second powder (P2) and a step S1 of atomizing said additional materials so as to produce the corresponding powder(s) (Pi).

9. A method according to any one of claims 1 to 8, further comprising one or more of the steps: - S6 for rectifying the demolded solid part (C, C') to the desired thicknesses, - S7 machining of the demolded solid part (C, C'), - S8 to finish the solid demolded part (C, C'), so as to obtain said watch component.

10. 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 a single block in which the materials (M1, M2, Mi) remain distinct from each other and form a pattern in the mass of said component, said materials being selected from the group of precious or noble metals and their alloys.

11. Watch component according to claim 10, said motif comprising one or more of a local color variation, local hue variation, a two-dimensional shape, a three-dimensional shape, as well as their combination. AUDEMA-19-PCT 12. Watch component according to any one of claims 10 and 11, wherein the interface of said at least two materials has a zero concentration gradient or a concentration gradient reduced to a thickness of less than 10 micrometers, or less than 5 micrometers, or less than 1 micrometer, so that the distinction of said materials is clear and distinct.

13. Watch component according to any one of claims 10 to 12, said component being obtained by the process according to any one of claims 1 to 9.

14. Watch component according to any one of claims 10 to 13, said component being a case or movement part.

15. Timepiece comprising a timepiece component according to any one of claims 10 to 13. AUDEMA-19-PCT

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