Robus timepiece component

Abstract

Disclosed is a method for manufacturing the surface of a timepiece component, in particular an external timepiece component, the method being characterized in that it includes the following steps: - taking a timepiece component blank forming a core of the timepiece component; - depositing a surface coating on said core, the coating being made of a ceramic-metal composite material in order to form a hard surface of the timepiece component, having a hardness greater than or equal to 500 HV, or even greater than or equal to 600 HV, or even greater than or equal to 750 HV, or even greater than or equal to 900 HV.

Description

[0001] Robust watch component

[0002] The present invention relates to a watch component, in particular a watch component for displaying. It also relates to a timepiece, in particular a wristwatch, comprising at least one such watch component. It also relates to a method for manufacturing such a watch component.

[0003] A watch component must achieve numerous mechanical properties, particularly at the level of its visible external surface, which are sometimes contradictory. Among these sought-after properties, we can mention:

[0004] - A very attractive appearance, free from defects, compatible with the aesthetic requirements of luxury watchmaking;

[0005] - Robustness, to withstand the external constraints to which a timepiece is subjected, so that the watch component retains the same appearance over time, for example avoiding as much as possible its external surface degrading through the appearance of scratches over time, and more generally retains all of its mechanical properties over time.

[0006] In practice, existing solutions represent compromises between these properties. However, these existing solutions have limitations, and there is a need to identify new solutions that optimize the properties and / or appearance of watch components, and more generally of watch components.

[0007] An object of the present invention is therefore to propose a solution for obtaining a watch component in an improved manner compared to the state of the art.

[0008] More specifically, the present invention has as its first object to propose a solution for forming a watch component whose surface is sufficiently hard to resist external aggressions. A second object of the invention is to propose a solution for forming a watch component whose surface has an attractive and robust appearance.

[0009] To this end, the invention is based on a watch component, in particular a watch component for displaying, characterized in that it comprises a core covered by a surface coating of ceramic-metal composite material, in particular based on tungsten carbide and cobalt-chromium or based on tungsten carbide and iron-chromium, this coating comprising a hard surface with a hardness greater than or equal to 500 HV, or even greater than or equal to 600 HV, or even greater than or equal to 750 HV, or even greater than or equal to 900 HV.

[0010] The invention is also based on a method for manufacturing the surface of a watch component, in particular a watch exterior component, characterized in that it comprises the following steps:

[0011] Obtain a rough watch component forming the heart of the watch component;

[0012] Depositing a surface coating on said core, this coating being in ceramic-metal composite material to form a hard surface of the watch component with a hardness greater than or equal to 500 HV, or even greater than or equal to 600 HV, or even greater than or equal to 750 HV, or even greater than or equal to 900 HV.

[0013] The invention is more precisely defined by the claims.

[0014] These objects, characteristics and advantages of the present invention will be explained in detail in the following description of particular embodiments made without limitation.

[0015] The concept of the invention consists in providing a watch component comprising a very hard surface, which can optionally be finished by a surface structuring step by a laser, to form reliefs and / or coloring. This very hard surface is formed by adding a very hard and thick surface coating on a blank of the watch component.

[0016] As a note, throughout the text, we will use the expression "based on a material" to designate the fact that said material is the main or majority element. In particular, we will use the expression "based on a material" to designate the fact of comprising at least 50% by weight of said material. In addition, we will sometimes use the simplified expression "component" to designate a watch component, or even abusively a nearly finalized rough part. The invention will be particularly described in the context of a watch component for exterior use, but it may be implemented for any other watch component, as will be specified.

[0017] A method of manufacturing a watch component, according to one embodiment of the invention, will now be detailed.

[0018] The manufacturing method first comprises a first step of producing a blank of a watch exterior component, forming a core of the watch exterior component. This blank may have different mechanical properties. According to a first approach, it may be a relatively porous blank, with a low relative density, to be advantageously light. According to a second approach, it may be a core made of a first rigid and / or dense material. This first material may be identical to or different from the second material of the coating which will be described later. According to yet another approach, which may be combined with the previous approaches, the core of the watch exterior component may be made of a single or several different materials.

[0019] The method then comprises a second step of depositing a surface coating, so as to form a very hard surface of the exterior watch component. Note that this very hard surface may extend over all or part of the exterior watch component. Thus, this coating comprises a second very hard material, preferably different from the first material forming the core of the exterior watch component. According to one embodiment, the surface coating has a density greater than the density of the core, and / or said second material has a density greater than that of the first material forming this core.

[0020] In other words, the first material may have a lower density than that of the second material. More generally, the second step may comprise the deposition of at least one layer of a surface coating with a density greater than the density of the at least one core of the component. This second step may also in particular form a surface having a porosity rate lower than that of the at least one core of the component, ideally a surface having a zero porosity rate. This second step makes it possible to obtain a watch component having in particular a high surface hardness, this surface in question being formed by said coating. This hardness is greater than or equal to 500 HV, or even greater than or equal to 600 HV, or even greater than or equal to 750 HV, or even greater than or equal to 900 HV.

[0021] Advantageously, in this embodiment, the deposition of a surface coating is carried out by thermal spraying, in particular at high temperature, which may be greater than or equal to 800°C. Such an embodiment variant uses, for example, the spraying at high temperature, for example at 900°C, of ​​ceramic and / or metal particles, such as, for example, tungsten carbide WC and cobalt-chromium CoCr particles (the cobalt-chromium CoCr playing, within the coating, the role of binder between the WC particles), with WC particles possibly having an average diameter of 40 μm, or even a smaller average diameter. Alternatively, other binders could be envisaged, such as iron-chromium (Fe-Cr).As a note, in the examples mentioned above, the surface coating layer therefore comprises particles of a first material, such as for example tungsten carbide WC, and particles of a second material, such as for example cobalt-chromium CoCr, which fulfill the function of binder. This second material remains optional, the binder not being essential. The thermal spraying could for example be of the plasma type (known by its acronym "VPS" for the English name "Vacuum Plasma Spraying"), which has many advantages, such as allowing adjustment of the chemistry of the material, being able to spray many different materials, such as ceramics, oxides, metals.

[0022] To minimize the porosity of the coating layer, the particle size distribution of the powders is important and must be adjusted for each layer composition and each application, as is known to those skilled in the art. The use of particles with a bimodal or multimodal size distribution is particularly favorable.

[0023] This approach has the advantage of making it possible to obtain a thick layer, in particular with a thickness greater than or equal to 80 pm, or even greater than or equal to 100 pm, or even greater than or equal to 150 pm, or even greater than or equal to 200 pm, or even greater than or equal to 250 pm, or even greater than or equal to 300 pm, or even greater than or equal to 350 pm. Advantageously, the second step consisting of depositing a surface coating deposits a thickness of material of between 20 pm and 400 pm, or even between 80 pm and 400 pm, or even between 150 pm and 350 pm, in a single layer of the same material or in several layers of different materials.

[0024] Alternatively, other spraying or deposition techniques are possible. In particular, anodizing, especially electrolytic arc anodizing, can be used. Cold spray is also possible. In the latter case, a cold spray technique is carried out at a temperature below the melting point of the powder and / or below the phase transition temperature (for example, below 900°C), to form said high-hardness layer. This cold spray technique makes it possible to coat blanks of temperature-sensitive components and / or to deposit powders while preserving their structure. The spraying technique will be adapted to the materials used. In all cases, the coating technique chosen has the advantage of allowing the deposition of a thick coating, particularly according to the thickness values ​​mentioned above.

[0025] Projection therefore makes it possible to obtain a thick layer of a coating. Advantageously, the particles are projected in combination with a binder, in the form of simultaneous projection of powders of different materials, which makes it possible to obtain a layer of a particularly qualitative surface coating. Alternatively, it is also possible to project particles devoid of binder. Alternatively again, it is possible to use a black cermet, for example of the AI2O3-Ti or AI2O3-Cr type, in order to obtain polishable, black samples with a hardness of approximately 500HV. Alternatively, other materials can be used, such as carbides, nitrides and / or oxides of metallic elements such as Ti, Al, Cr, Zr. Thus, projection makes it possible to obtain, for example, a thick layer formed among others of TiN or TiC or TiCN, of Cr2O3, AI2O3, or even of ZrO2.Advantageously, the oxide, carbide, or nitride particles are sprayed in combination with a binder. More typically, the coating is a ceramic-metal composite material. There is the ability to vary the coating material properties, such as toughness and hardness, by adjusting the relative ceramic and metal ratios. An advantage of this approach is that the spraying techniques are compatible with many materials.

[0026] The projected particles are moreover advantageously in a semi-pasty state, in the case of thermal projection, to spread out upon impact and form a regular and dense layer. By semi-pasty state is meant a semi-solid or semi-liquid state, as opposed to solid grains (or "cold grains") which would produce an irregular structure, in the case of the aforementioned "cold" projection, which is particularly suitable for material blanks formed from a first material sensitive to high temperatures. The coating layer obtained can thus be not very rough and compact, with low porosity.

[0027] The core of the exterior watch component thus forms a substrate for receiving the surface coating. Said first material of this core (or of the substrate that it forms) may be made of a metal alloy, such as a steel (for example a 904L steel or any other stainless steel), or a magnesium alloy (for example ZK60) or a titanium alloy (for example Ti grade 5) or an aluminum alloy. It may be a metal or a metal alloy or a metal superalloy, in particular comprising elements such as Fe, Mg, Al, Ti, Au, Pd, Pt, Ni, Si, and / or Co, and / or an amorphous or partially amorphous alloy, or a ceramic, in particular an alumina-based or zirconia-based ceramic.

[0028] The difference in thermal expansion coefficient between certain materials, such as metals and ceramics, induces stresses during temperature changes. The choice of the first core material, as well as the geometry and surface condition of the core, advantageously takes this aspect into account. Optionally, it is possible to heat the core to a certain temperature to minimize the occurrence of stresses during the projection of the surface coating (temperature varies depending on the composition of the core, the atmosphere and the pressure of the deposition chamber).

[0029] According to another embodiment, the second step of depositing at least one surface coating layer can be carried out by additive manufacturing.

[0030] Thus, the second step of depositing at least one layer of a surface coating makes it possible to form at least one layer of high hardness.

[0031] According to one embodiment, the second step of depositing at least one layer of a surface coating may comprise several sub-steps of producing a deposit of a coating, that is to say it may comprise the production of superimposed layers, resulting in a surface coating composed of several distinct layers. In such a case, these layers may be produced by the same variant embodiment among the variants explained above, or by different variant embodiments. In addition, these layers may be in the same material, or in different materials.For example, it is possible to combine in the same coating a first thick layer which ensures the hardness and protection of the substrate (for example 250 pm thick WC+Co-Cr, providing a hardness of 900 to 1200HV), then a second layer for the appearance or the color in another material (for example, up to 20 pm thick Ti grade 5, or more generally a thickness between 500 nm and 20 pm of a metal or a metal alloy, for example of the Au, Ag, Pt, Pd type).

[0032] In any case, the second step allows the formation of at least one layer of a high-hardness coating, which can represent the surface coating on its own.

[0033] Naturally, it is possible to combine the various embodiments described above to obtain a component of which at least one first surface achieves a high hardness. For example, a first surface can be coated according to one of the described variants and a second distinct surface can be coated according to another of these described variants, these two distinct surfaces being able to have different hardnesses and / or materials. In all cases, the resulting exterior watch component is provided with a high-hardness surface, this surface extending over all or part of the component. This high-hardness surface is formed by a ceramic-metal composite material coating.

[0034] Furthermore, as mentioned, it is possible to treat only part of the surface of a component according to the invention. For example, certain surfaces of a component with a very complex geometry may not be treated. According to another example, certain surfaces of a component intended to fulfill particular functions, for example surfaces for assembly with another component, or surfaces for gripping by a user, may also not be treated by the invention. For example, these untreated surfaces may be assembly surfaces of a caseband or a bezel or a back or a crown or a push-piece or a bracelet element, such as for example threads or lug holes, or an assembly surface of an oscillating weight or a pocket on a movement blank. They may also be surfaces forming interfaces with a user such as those of a push-piece or a crown.

[0035] According to an advantageous embodiment variant, the structure of the core, in particular at its outer surface forming a substrate intended to receive the surface coating, is shaped to optimize this adhesion. For this, the method may comprise an optional intermediate step of preparing the surface of the blank of the exterior watch component by forming a roughness of this surface, in particular by sandblasting, or by forming a favorable chemical composition, before the step consisting of depositing a surface coating. Sandblasting is for example possible, in order to obtain a roughness Ra of between 3 and 10 pm, with a target value of 5 pm. On a less hard substrate, very light sandblasting may be favorable.It is therefore favorable to prepare the surface of the substrate by an appropriate treatment, for example by mechanical treatment (sandblasting, for example), and / or by localized heating (laser, electron beam), to obtain a particularly suitable roughness and / or chemical composition of the surface.

[0036] Thus, in all cases, the method comprises a first step consisting of providing a watchmaking exterior component forming a core of the watchmaking exterior component, then a second step consisting of depositing a surface coating on said core, this coating being in ceramic-metal composite material based on tungsten carbide and cobalt-chromium, or based on tungsten carbide and iron-chromium, to form a hard surface of the watchmaking exterior component with a hardness greater than or equal to 500 HV, or even greater than or equal to 600 HV, or even greater than or equal to 750 HV, or even greater than or equal to 900 HV. More generally, in all cases, said hard surface may be based on a ceramic-metal composite material or may consist of a ceramic-metal composite material.

[0037] The method then comprises an optional intermediate step comprising grinding and / or polishing and / or texturing and / or micro-blasting of the hard surface of the exterior watch component. Such an optional step may have the advantages of removing surface roughness and oxidation following projection and / or correcting geometric defects induced by deposition and / or reducing surface roughness. It can be carried out by any traditional means, mechanical or chemical. It is also possible to directly carry out the laser treatment which will be detailed subsequently after deposition, depending on the final rendering which is targeted.

[0038] Such an optional intermediate step can also contribute to the formation of the final geometry of the component blank in a simpler and / or more precise manner. For example, it is possible to machine a component with a deliberate undercut, for example a middle part with a undercut of approximately 200 μm. The deposition of a surface coating as described above comprises a thickness which largely exceeds the undercut made. Finally, part of the thickness of this surface coating is removed by mechanical grinding with special grinding wheels. For example, in the case of the middle part comprising a undercut of 200 μm, a 400 μm thick coating is produced, then a thickness of approximately 200 μm is removed.

[0039] According to a variant of this approach, one can take advantage of this to define the final geometry of the component blank, by applying this process unevenly on the different treated surfaces of the component, so that the coating produced modifies the shape of the blank, thus making it possible to arrive at the final shape of the component, in a simpler way than if it had been necessary to obtain the same shape directly on the blank, without using the coating. For example, it is possible to produce the simplest possible component blank by stamping, to apply a surface coating, and then to machine this surface coating so as to obtain a final surface of the component more complex than that obtained by stamping. The aforementioned reduction of the component blank is therefore not necessarily a homothety. It is also possible to deposit a variable thickness of the surface coating and / or to remove a variable thickness of surface coating.The optional grinding and / or polishing step in this case helps to achieve the final geometry of the component.

[0040] The manufacturing process then includes a third optional step consisting of structuring the hard surface of the component using a laser, to form reliefs and / or coloring of this hard surface. Indeed, depending on the laser setting, it is possible to form reliefs on the hard surface, and / or even to generate coloring of this hard surface.

[0041] According to one embodiment, this third step of structuring by a laser comprises carrying out satin finishing, spraying or sandblasting on said hard surface.

[0042] The deposits obtained in the case of a surface coating as described above have the particularity of forming in certain cases a surface whose roughness is significant. The third stage of completion of the method of the invention makes it possible, thanks to the use of a laser, to achieve a satisfactory surface state, without porosity, and roughness in the technical and aesthetic target, with an interesting aesthetic rendering. A particularly delicate technical problem consists in fact in obtaining such an acceptable surface rendering. The production of a thick coating according to embodiments of the invention, even if it has advantages, in particular of being robust with regard to possible delaminations, presents the risk of having microporosities or surface defects, which are generally encountered after certain mechanical treatments of such a surface.Surprisingly, laser structuring can solve this technical problem. In addition to achieving the desired roughness, more precisely the desired structuring and / or coloring through laser treatment, this laser treatment also allows residual porosities to be filled and / or closed, probably through localized fusion of one or more components of the coating.

[0043] The invention also allows several different structures to be formed, through specific uses of a laser, depending on the desired final result. Several different laser treatments can be combined on the same hard surface of the component.

[0044] For example, tests were carried out internally on steel and magnesium alloy blanks, known by its reference ZK60, coated with a layer of WC+CoCr produced by thermal spraying, as mentioned above, with grinding and polishing of the surface. Other tests were carried out using blanks coated with a layer of WC+CoCr material, which were then textured by a fairly advanced satin finish, and then subjected to different laser terminations. These terminations made it possible to form laser spraying, laser sandblasting and laser satin finish terminations. Other tests were carried out with an additional laser treatment in order to form a coloring, thus illustrating the wide variety of renderings obtained with this approach according to embodiments of the invention.Different plates, each with an initial texture respectively microblasted or satin, were produced with a coloring that varies from gray to brown through gold. Other colors can alternatively be obtained while maintaining the structure, such as deep blue (aubergine), blue, or green.

[0045] These tests of structuring and coloring the hard surface of these blanks were carried out by two successive laser treatments, the first to obtain a surface structure and a termination, and the second to obtain a coloring. Surprisingly, the second laser treatment does not significantly affect or degrade the structuring obtained by the first laser treatment, that is to say that any change in this structuring is not visible to the naked eye. According to embodiment variants, it is therefore possible to combine several sub-steps of laser termination treatments, to form several surface structurings whose effects combine, in particular a structuring and a coloring. The person skilled in the art will be able to optimize the laser parameters to obtain the desired result.

[0046] Another technical problem arises in the case of a watch component with a complex geometry, such as a case middle. Indeed, a complementary object of the invention in such a case is to obtain a uniform rendering on all the surfaces of the component, and in particular at the joints between the different surfaces (for example between the side of a case middle and the top of the case middle). For this, the processing equipment used in the context of the invention makes it possible to manage the tracking of complex surfaces, as well as the connection between two surfaces. The method according to one embodiment notably implements tracking of the laser focal point during the third step of the method, either from the 3D geometry of the component as defined by a digital CAD file, or from a 3D surface measurement.

[0047] The invention also relates to a component, in particular a watch component for display, obtained by a manufacturing method according to the invention, which is naturally not limited to the preceding description.

[0048] Thus, the invention makes it possible to form any watch component, characterized in that it comprises a core covered by a surface coating of ceramic-metal composite material based on tungsten carbide and cobalt-chromium, or based on tungsten carbide and iron-chromium, this coating comprising a hard surface with a hardness greater than or equal to 500 HV, or even greater than or equal to 600 HV, or even greater than or equal to 750 HV, or even greater than or equal to 900 HV. Such a watch component may comprise a core made of a first material covered by a coating comprising the hard surface made of a second material different from the first material. In such a case, the coating may have a thickness of between 20 pm and 400 pm, or even between 80 pm and 400 pm, or even between 150 pm and 350 pm, or even between 20 and 200 pm, or even between 60 pm and 100 pm. The coating may have a porosity rate of less than or equal to 0.5%, or less than or equal to 0.1%, or less than or equal to 0.05%, or less than or equal to 0.01% and / or the core may have a porosity rate greater than that of the coating, and / or the porosity rate of the core may be less than or equal to 0.5%.

[0049] The invention is particularly suitable for manufacturing a watch component which is a case middle, a bezel, a back, a crown, a pusher, a clasp element, a bracelet element, in particular a mesh or a link or a fixing or an oscillating weight or a plate or a bridge.

[0050] Furthermore, according to a particular embodiment of the invention, at least one portion or region of the component, in particular the watch component, could comprise a structured hard surface, the remainder of the component being able to comprise any other architecture, in particular conventional. Thus, the invention also relates to a watch component which comprises a structured hard surface only in certain portions. Alternatively, the watch component could comprise several different portions, each comprising different structured hard surfaces.

[0051] The invention also relates to a timepiece, in particular a wristwatch, which comprises at least one such timepiece component.

[0052] Ultimately, the invention therefore makes it possible to combine two major objectives for a watch component, which were not achieved until now. It makes it possible to form a component having a hard, resistant and thick surface layer, in particular one which does not scratch easily, while being aesthetically attractive, with a robust external appearance, which lasts over time and which can have a multitude of aspects.

[0053] By depositing a coating, particularly by spraying, a hard and thick surface coating is obtained, this thickness being perfectly resistant to delamination, presenting a lasting aesthetic, and with great flexibility on the chemistry of the coating, in fact compatible with a wide variety of powders and chemistries. It is also possible to functionalize the coating, for example using laser structuring, and / or to obtain surface conditions and finishes such as sprayed, sandblasted or satin.

Claims

CLAIMS 1. Method for manufacturing the surface of a watch component, in particular a watch exterior component, characterized in that it comprises the following steps: Obtain a rough watch component forming the heart of the watch component; Depositing a surface coating on said core, this coating being in ceramic-metal composite material to form a hard surface of the watch component with a hardness greater than or equal to 500 HV, or even greater than or equal to 600 HV, or even greater than or equal to 750 HV, or even greater than or equal to 900 HV.

2. Manufacturing method according to the preceding claim, characterized in that said ceramic-metal composite material is based on tungsten carbide and cobalt-chromium, or based on tungsten carbide and iron-chromium.

3. Manufacturing method according to one of the preceding claims, characterized in that the step of depositing a surface coating is carried out by thermal spraying, in particular at a high temperature greater than or equal to 800°C, or by cold spraying.

4. Manufacturing method according to one of the preceding claims, characterized in that the step of depositing a surface coating deposits a thickness of material of between 20 pm and 400 pm, or even of between 80 pm and 400 pm, or even of between 150 pm and 350 pm, or deposits a thickness of material greater than or equal to 80 pm, or even greater than or equal to 100 pm, or even greater than or equal to 150 pm, or even greater than or equal to 200 pm, or even greater than or equal to 250 pm, or even greater than or equal to 300 pm, or even greater than or equal to 350 pm, in a single layer of the same material or in several layers of different materials.

5. Manufacturing method according to one of the preceding claims, characterized in that it comprises a preliminary step of preparing the surface of the blank of the watch component by forming a roughness of this surface, in particular by sandblasting, or by forming a favorable chemical composition, before the step consisting of depositing a surface coating.

6. Manufacturing method according to one of the preceding claims, characterized in that it comprises a step of grinding and / or polishing and / or texturing and / or micro-blasting of said hard surface.

7. Manufacturing method according to one of the preceding claims, characterized in that it comprises a step consisting of carrying out a structuring of the hard surface by a laser, to form reliefs and possibly a coloring of this hard surface.

8. Manufacturing method according to one of the preceding claims, characterized in that the step of depositing a surface coating is not carried out over the entire surface of the blank, surfaces of complex geometry and / or intended to fulfill functions such as assembly with another component or gripping by a user, such as threads or bar holes, not being coated by the step of depositing a coating.

9. Watch component, in particular a watch component for display, characterized in that it comprises a core covered by a surface coating of ceramic-metal composite material, in particular based on tungsten carbide and cobalt-chromium or based on tungsten carbide and iron-chromium, this coating comprising a hard surface with a hardness greater than or equal to 500 HV, or even greater than or equal to 600 HV, or even greater than or equal to 750 HV, or even greater than or equal to 900 HV.

10. Watch component according to the preceding claim, characterized in that said core is made of a first solid material, or with a porosity rate of less than or equal to 0.5%, or even less than or equal to 0.1%.

11. Watch component according to claim 8 or 9, characterized in that the coating has a thickness of between 20 pm and 400 pm, or even between 80 pm and 400 pm, or even between 150 pm and 350 pm, or even between 20 and 200 pm, or even between 60 pm and 100 pm.

12. Watch component according to one of claims 9 to 11, characterized in that the coating has a porosity rate less than or equal to 0.5%, or even less than or equal to 0.1%, or even less than or equal to 0.05%, or even less than or equal to 0.01%, and / or in that the core has a porosity rate greater than that of the coating.

13. Watch component according to one of claims 9 to 12, characterized in that said hard surface comprises a structuring obtained by a laser, forming reliefs and possibly a coloring of the surface.

14. Watch component according to one of claims 9 to 13, characterized in that it is a watch component chosen from a case middle, a bezel, a back, a crown, a pusher, a clasp element, or a bracelet element, in particular a mesh or a link or a fixing, or in that it is a watch movement component such as an oscillating weight or a movement blank such as a plate or a bridge.

15. Timepiece, characterized in that it comprises at least one component according to one of claims 9 to 14.

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