CH721902A2 - Process for manufacturing a ceramic watch component - Google Patents

Abstract

The present invention relates to a method for manufacturing a watch component (10) made of ceramic material. The method comprises the following steps: a step (S3) consisting of depositing at least two ceramic powders (P1, P2) of different compositions into a mold (M), arranging them in a desired configuration to form an assembly (A) of at least two unmixed powders, in which said powders are in contact; a step (54) consisting of performing sintering under conditions enabling the production of a solid part (B) from the assembly (A) of unmixed powders such that said solid part (B) has several visible zones comprising ceramics (C1, C2) of different compositions, providing a distinct visual appearance to each of the zones with a clear visual demarcation between each of said zones; a step (S5) consisting of demolding said solid part (B) to obtain a demolded part; and a machining step to obtain the watch component (10).

Description

technical field

[0001] The present invention relates to a method for manufacturing a watch component based on several ceramics of different compositions and comprising, in particular, a sintering operation. The method is adapted so that the resulting watch component has several visible zones of different colors with clear demarcations between these zones.

State of the art

[0002] Processes using, in particular, a sintering operation of ceramic powders for the manufacture of ceramic watch components are well known. For example, obtaining a watch case requiring a sintering step is described in publication CH718069.

Brief summary of the invention

[0003] An object of the present invention is to propose a method for manufacturing a watch component made up of several ceramics of different compositions, according to an alternative solution.

[0004] This objective is at least partly achieved in particular by a process for manufacturing a watch component made of ceramic material comprising the following steps:

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a step consisting of depositing at least two ceramic powders of different compositions into a mold, arranging them in a desired configuration to form an assembly of at least two unmixed powders, in which said powders are in contact,

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a step consisting of carrying out sintering, under conditions of temperature and pressure determined so that none of the ceramic powders are calcined, making it possible to produce a solid part from the assembly of unmixed powders so that said solid part has several visible zones comprising ceramics of different compositions providing a distinct visual appearance to each of the zones with a clear visual demarcation between each of said zones,

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a step consisting of removing the solid part from the mold to obtain a demolded part, and

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a machining step to obtain the watch component.

[0005] In one embodiment, the sintering is of the flash or SPS type.

[0006] In one embodiment, said clear visual demarcation at the junction of the different zones has a concentration gradient of zero or limited to less than 10 micrometers or 5 micrometers, or even less than 1 micrometer.

[0007] In one embodiment, at least one of the ceramic powders is chosen from a powder based on alumina, zirconia, silicon carbide, silicon nitride, boron nitride and aluminum nitride.

[0008] In one embodiment, at least one of the ceramic powders is a composite selected from the following three composites: Alumina matrix zirconia (ZTA), Zirconia matrix alumina (ATZ) and Yttrium-stabilized zirconia (Y-TZP).

[0009] In one embodiment, at least one of the ceramic powders is composed of a mixture of alumina matrix zirconia (ZTA), zirconia matrix alumina (ATZ), and zirconia stabilized at least partially with yttrium (Y-TZP).

[0010] In one embodiment, each ceramic powder comprises at least one pigment preferably selected from preferably an iron oxide, an aluminum oxide, a bismuth oxide, a cobalt oxide and a chromium oxide.

[0011] In one embodiment, the ceramic powders are arranged in the mold so as to form several alternating layers.

[0012] In one embodiment, the ceramic powders are arranged in the mold so that one or more ceramic powders are embedded in a main powder.

[0013] In one embodiment, the step of depositing said at least two ceramic powders in the mold is preceded by a step of atomizing a first ceramic material in order to obtain one of the two ceramic powders and by a second step of atomizing a second ceramic material in order to obtain the other of the two ceramic powders of different composition.

[0014] Another aspect of the invention relates to a timepiece comprising at least one timepiece component obtained by the process according to one of the aforementioned embodiments.

[0015] In one embodiment, the watch component is a finishing part, preferably a case, a bezel or a case back of a watch.

Brief description of the figures

[0016] Examples of implementation of the invention are shown in the description illustrated by the following figures:

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Figure 1 illustrates a schematic view of the different stages of the process according to one embodiment of the present invention.

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Figure 2 illustrates a schematic view of the process according to another embodiment of the present invention.

Examples of embodiments of the invention

[0017] The process for manufacturing a watch component 10 from ceramic material, according to a first embodiment illustrated in Figure 1, comprises a first step S1 consisting of atomizing one of the ceramic materials C1' into a first powder P1. In this description, the term "atomize" refers to any suitable operation that reduces the ceramic 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.

[0018] Depending on the ceramics selected, the P1 ceramic powder obtained by atomization can, for example, be alumina, zirconia, silicon carbide, silicon nitride, boron nitride, or aluminum nitride powder. The P1 ceramic powder can also be a composite selected, in particular, from alumina matrix zirconia.

[0019] (ZTA), zirconia matrix alumina (ATZ) and yttrium-stabilized zirconia (Y-TZP).

[0020] The process includes a step S2 of atomizing a second ceramic material C2' to produce a second powder P2 with a composition different from that of the first powder P1. The second ceramic material C2' can, for example, be chosen to obtain one of the aforementioned powders. The atomization conditions can be identical or different from those of the atomization of the first ceramic material C1'. The average particle size of the second ceramic powder P2 can be identical or similar to that of the first powder P1. Alternatively, the first and second powders P1 and P2 can be composed of particles of different sizes.

[0021] It is understood that the atomization steps of the first and second ceramic materials are carried out separately, so that distinct powders P1, P2 are obtained. In particular, the process according to the present invention does not include any mixing step of these first and second powders P1, P2. More specifically, the process according to the present invention includes all the provisions necessary to prevent the first and second powders P1, P2 from mixing. It may even be provided that the first and second ceramic materials C1', C2' are atomized in different locations so as to avoid or limit contamination from one to the other.

[0022] 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 S1, S2 atomization steps are not necessary.

[0023] The process according to this description includes a step S3 consisting of arranging the first and second powders P1, P2 in a sintering mold M. The first and second powders P1, P2 are arranged sequentially so as not to mix. These powders can each be arranged to form a powder bed, a powder cluster, or in various arrangements such as layers, geometric shapes, or random patterns. Depending on requirements, one or more of the first and second powders P1, P2, and optionally additional powders Pi, can be used repeatedly, for example, to form several clusters or several layers alternating with other powders.

[0024] According to the embodiment illustrated in Figure 1, the two powders P1, P2 are distributed in the mold M to obtain an assembly A of unmixed powders. The two powders can, for example, be distributed so as to have an inclination or complementary shapes in order to form an interface with no (or almost no) concentration gradient between the two powders P1, P2.

[0025] The first and second powders P1, P2 can be used in varying proportions, for example in equal quantities so that the watch component 10 obtained by the process, typically the watch case in the illustrated example, comprises as much of the first ceramic material C1 as of the second ceramic material C2, regardless of their distribution.

[0026] Once the assembly A of unmixed powders has been made, it is subjected to sintering in a step S4. The sintering conditions involve a sintering temperature Tf. They also include a sintering pressure Pf, which can be a mechanical pressure.

[0027] The sintering temperature Tf is determined so that none of the powders in the powder assembly A are calcined under the sintering conditions. The appropriate sintering temperature can be evaluated as a function of the sintering pressure Pf, so as not to reach, not to exceed, or to remain below the calcination temperatures of the first and second ceramic powders P1, P2 at the sintering pressure. Preferably, the sintering temperature is determined so as to remain below the lowest of the calcination temperatures of the first and second ceramic powders P1, P2 under the sintering conditions.

[0028] Preferably, the sintering conditions are those of flash sintering, also known as spark plasma sintering (SPS). This operation is a process similar to hot isostatic pressing but uses the Joule effect to heat a pre-compacted powder in a mold between two electrodes. The mold containing the pre-compacted powder is subjected to a pressure of several megapascals by a hydraulic press. A direct or alternating current of several kiloamperes, pulsed or non-pulsed, is applied between the electrodes with a voltage of a few volts.

[0029] Typically, the SPS sintering operation lasts between 2 and 60 minutes, preferably between 5 and 30 minutes, depending on the nature of the reagents and the operating conditions used. It can be carried out while the mold is maintained under vacuum or under a controlled atmosphere (for example, under argon, hydrogen, or nitrogen).

[0030] The SPS sintering temperature is less than 2000°C, or even less than 1500°C, for example between 1000°C and 1300°C.

[0031] The SPS sintering pressure can be between 20 and 180 N/mm² or between 50 and 100 N/mm². Other pressure values may be preferred depending on the components selected and/or the required quality of the watch component.

[0032] The SPS sintering operation makes it possible to obtain a sintered part with a density between 98 and 100%, preferably between 99% and 99.99%, preserving the fineness of the granularity of the ceramic, which has the advantage of optimizing the mechanical properties, in particular the hardness and toughness compared to a conventional sintering cycle.

[0033] It should be noted that in the case of SPS sintering, the use of binders is not necessary.

[0034] Once sintering is complete, a solid part B, obtained from the assembly of powders A, is demolded in step S5. The solid part B is inhomogeneous and therefore comprises different compositions, each corresponding to the first and second ceramics C1, C2 used. It should also be noted that the term composition refers not only to the nature of the materials or powders used but also to their proportions. Thus, two compositions will remain different if they use materials or powders of the same nature but in different proportions.

[0035] According to one embodiment, the ceramic powders may include pigments of different kinds so that the SPS sintering process can reveal different colors or shades distributed according to the arrangement of the different ceramics in the assembly.

[0036] For example, but not limited to, iron oxide (red colour, or brown to black colour depending on the degree of oxidation of the iron), aluminium oxide (white colour), bismuth or cobalt oxide (blue colour) and/or chromium oxide (green colour) may be used.

[0037] The solid part removed from the mold may correspond to the final component. However, it may be necessary for the molded part to require one or more subsequent interventions to improve its quality or aesthetic appearance, or to modify the part obtained to produce the watch component 10. A machining step S6 may, for example, allow the solid part removed from the mold to be resized. Machining may be carried out by any suitable technique, whether mechanical, laser, waterjet, or any equivalent.

[0038] The watch component 10 may, in particular, be a casing component, such as a watch case, a bezel, a watch case back, a dial, or any other element visible to a user. The watch component may also be part of the watch movement, such as a gear train.

[0039] One or more finishing steps (not illustrated) may also be considered. These optional steps consist of applying a decoration to one or more areas of the surface of the watch component, particularly on the side of a case 10, by means of a mechanical and/or chemical operation. The mechanical operation may include, in particular, polishing, sandblasting, satin finishing (straight, circular, or spiral), microblasting, guilloché work, perlage, Côtes de Genève finishing, or hand engraving.

[0040] According to a second embodiment illustrated in Figure 2, the process uses at least one additional ceramic C3', atomized into an additional powder P3 in an additional atomization step S3. In one variant, the process may include several additional ceramics C3'...Ci. These are selected from, in particular, the ceramics mentioned above, or a combination thereof. The additional powder(s) Pi obtained are processed and handled under the conditions already described for the first and second powders P1, P2. In particular, appropriate measures are taken to prevent them from mixing with other powders.

[0041] In the case at hand, three ceramic powders P1, P2, P3 are arranged in a mold M so that one or more ceramic powders, for example two ceramic powders P2, P3 of the same or different compositions, are embedded in a main or predominant ceramic powder P1 in order to obtain a powder assembly A. The embedded ceramic powders P2, P3 are therefore not mixed with the base powder P1, i.e. the gradient at the interface of the different powders is zero or almost zero.

[0042] A sintering operation of the powder assembly A is then carried out in step S4 under the required conditions, so as to obtain a solid part B comprising the different ceramics C2, C3 embedded in the main ceramic C1. The temperature and pressure conditions for sintering are those already mentioned for the assembly A of at least two ceramics of different compositions of the embodiment illustrated in Figure 1. In particular, the sintering temperature Tf is determined so that none of the ceramic powders C1, C2, C3 are calcined during sintering. The solid part B can be demolded to obtain a solid part. One or more of the post-demolding operations described above can be implemented.

[0043] The part resulting from the process described herein is thus produced by a single sintering operation, even though it comprises several ceramics of different compositions. Furthermore, the demarcation of colors and geometric patterns remains clear and distinct. In particular, the concentration gradients at the junction of the different ceramics are zero or limited to less than 10 micrometers or 5 micrometers, or even less than 1 micrometer. The patterns produced are directly embedded in the mass of the component.

[0044] Patterns are understood here to mean any variation in color or shade, any two- or three-dimensional shape incorporated into the mass of the component, or any other visual and/or aesthetic or ornamental feature. The patterns coincide with the interfaces of the different materials of the component. Due to variations in local composition, these patterns may be accompanied by local variations in mechanical properties, particularly in terms of hardness.

Claims (12)

1. A method for manufacturing a watch component (10) from ceramic material comprising the following steps: - a step (S3) of depositing at least two ceramic powders (P1, P2; P1, P2, P3) of different compositions into a mold (M), arranging them in a desired configuration to form an assembly (A) of at least two unmixed powders, in which said powders are in contact, - a step (S4) of performing sintering, under temperature and pressure conditions determined so that none of the ceramic powders are calcined, producing a solid part (B) from the assembly (A) of unmixed powders such that said solid part (B) has several visible zones comprising ceramics (C1, C2; C1, C2, C3) of different compositions, providing a distinct visual appearance to each of the zones with a clear visual demarcation between each of said zones, - a step (S5) of to demold said solid part (B) to obtain a demolded part, and - a machining step to obtain the watch component (10). 2. A method according to claim 1, wherein the sintering is of the flash or SPS type. 3. Method according to claim 1 or 2, wherein said clear visual demarcation at the junction of the different zones has a concentration gradient of zero or limited to less than 10 micrometers or 5 micrometers, or even less than 1 micrometer. 4. A method according to any one of the preceding claims, wherein at least one of the ceramic powders (P1, P2; P1, P2, P3) is selected from a powder based on alumina, zirconia, silicon carbide, silicon nitride, boron nitride and aluminum nitride. 5. A method according to any one of the preceding claims, wherein at least one of the ceramic powders (P1, P2; P1, P2, P3) is a composite selected from the following three composites: Alumina matrix zirconia (ZTA), Zirconia matrix alumina (ATZ) and Yttrium-stabilized zirconia (Y-TZP). 6. A method according to any one of the preceding claims, wherein at least one of the ceramic powders (P1, P2; P1, P2, P3) is composed of a mixture of alumina matrix zirconia (ZTA), zirconia matrix alumina (ATZ), and zirconia stabilized at least partially with yttrium (Y-TZP). 7. A method according to any one of the preceding claims, wherein at least one of the ceramic powders (P1, P2; P1, P2, P3) comprises at least one pigment preferably selected from an iron oxide, an aluminum oxide, a bismuth oxide and a chromium oxide. 8. A method according to any one of the preceding claims, wherein the ceramic powders are arranged in the mold (M) so as to form several alternating layers. 9. A method according to any one of the preceding claims, wherein the ceramic powders (P1, P2, P3) are arranged in the mold (M) so that one or more ceramic powders (P2, P3) are embedded in a main powder (P1). 10. A method according to any one of the preceding claims, wherein the step (S3) of depositing said at least two ceramic powders (P1, P2; P1, P2, P3) into the mold (M) is preceded by a step (S1) of atomizing a first ceramic material (C1') in order to obtain one of the two ceramic powders and by a second step (S2) of atomizing a second ceramic material (C2') in order to obtain the other of the two ceramic powders of different composition. 11. Timepiece comprising at least one timepiece component (10) obtained by the process according to one of the preceding claims. 12. A watch part according to claim 11, wherein the watch component is a casing part, preferably a case, a bezel or a case back of a watch.