watch parts
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- ROLEX SA
- Filing Date
- 2020-11-04
- Publication Date
- 2026-08-03
Smart Images
Figure 0007898827000004 
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Abstract
Description
Technical Field
[0001] The present invention relates to a timepiece part for a timepiece and a method for manufacturing the part. The present invention also relates to a surface treatment method used in the method for manufacturing the part. The present invention further relates to a timepiece including the timepiece part.
Background Art
[0002] In the field of timepiece manufacturing, the manufacturing of parts, especially for the function of decorating timepieces, is subject to numerous constraints. First, the parts must respect specific mechanical constraints due to their expected functionality. In addition, the parts must achieve an impeccable aesthetic appearance. Finally, it is often necessary to give the timepiece parts specific and often complex shapes in order to achieve a novel and overall aesthetic result and / or effectively fulfill specific functionality. Furthermore, it is always desirable to propose a solution that enables the manufacturing of such timepiece parts in a way that can handle mass production and sales, including those made of alloy compositions that are difficult to obtain using conventional casting techniques. Finally, it is also advantageous to provide lighter parts, especially for precious metals with high density.
[0003] Ultimately, existing solutions attempt to achieve a compromise of all the above-mentioned requirements. Existing solutions generally rely on traditional metallurgy, using metallic materials or metal alloys, especially those based on precious metals, or using ceramics. However, there is a need to improve existing solutions to meet the various requirements described above.
Summary of the Invention
Problems to be Solved by the Invention
[0004] Therefore, a general object of the present invention is to propose a solution for manufacturing a timepiece part that achieves a better compromise satisfying all the above-mentioned requirements.
[0005] More specifically, the first objective of the present invention is to propose a flexible solution for manufacturing watch components that allows for the formation of complex shapes while accommodating the use of a wide range of materials.
[0006] A second objective of the present invention is to propose a solution for manufacturing watch components that have an impeccable aesthetic appearance.
[0007] A third objective of this invention is to propose a solution for manufacturing watch components suitable for large-scale production.
[0008] A fourth objective of the present invention is to propose a solution for manufacturing lightweight watch components. [Means for solving the problem]
[0009] Therefore, the present invention relates to a surface treatment method for manufacturing metal and / or cermet-based watch parts from parts containing pores and / or precipitates and / or scratches, obtained by powder metallurgy or additive manufacturing methods, the method comprising a step of improving the surface finish of the part by surface remelting of the surface area of the part. The method further comprises a step of finishing the surface of the surface area of the part, the finishing step being performed after the step of improving the surface finish of the part by surface remelting.
[0010] The present invention also relates to watch components for watches, based on metal and / or cermet, comprising a core having irregularities such as pores and / or precipitates, and including a surface region having less irregularity than the core as a result of a surface treatment involving surface remelting. The surface region may have a lower porosity than the core. The present invention further relates to watches, particularly wristwatches.
[0011] The present invention is defined in more detail in the claims.
[0012] The object, features, and advantages of the present invention are described in the following detailed description relating to specific embodiments, which are not limited to those given in connection with the accompanying drawings. [Brief explanation of the drawing]
[0013] [Figure 1] Figure 1 is a schematic diagram illustrating the implementation of a process for improving the surface of a component by the LSM method according to an embodiment of the present invention. [Figure 2] Figure 2 shows several examples of the absorptivity of various materials as a function of specific wavelengths. [Figure 3] Figure 3 shows several examples of the reflectivity of various materials as a function of specific wavelengths. [Figure 4] Figure 4 shows the reflectivity of three white gold samples with different surface treatments. [Figure 5] Figure 5 is a schematic diagram showing a process for improving surface finish by an LSM process according to a modified embodiment of the present invention. [Figure 6] Figure 6 shows an example in which the present invention is implemented on a white gold body. [Figure 7] Figure 7 shows an example in which the present invention is implemented on a plate based on 316L steel. [Figure 8] Figure 8 is an enlarged view in the thickness direction of the plate based on 316L steel shown in Figure 7 according to the present invention. [Figure 9] Figure 9 shows an example of the present invention being implemented on a plate based on Grade 5 titanium. [Figure 10] Figure 10(a) shows the surface area of a Grade 5 titanium-based plate shown in Figure 9, which has been treated according to an embodiment of the present invention. Figure 10(b) shows a Grade 5 titanium-based plate similar to the one shown in Figure 10(a), but without the treatment according to an embodiment of the present invention. [Modes for carrying out the invention]
[0014] The present invention is based on a first choice, comprising using powder metallurgy or additive manufacturing techniques as the first step in a method for manufacturing watch components. Such a choice has the primary advantage of enabling the formation of complex and diverse shapes, including shapes that cannot be achieved by traditional metallurgical processes, for example. On the other hand, this first choice has the secondary advantage of enabling the use of a large number of materials, including alloys and combinations of components that cannot be obtained by other traditional processes, such as certain metal alloys that are unsuitable for traditional metallurgy. The first choice according to the present invention can address some of the multiple objectives of the present invention.
[0015] However, these selected techniques are characterized by forming porous and often heterogeneous parts that have visible or perceptible surface defects, such as pores and / or precipitates and / or streaks. Therefore, it is difficult to satisfy watchmaking requirements with these selected techniques. Furthermore, it is extremely difficult, almost impossible, to remove these defects present in parts with complex shapes using conventional finishing techniques such as grinding, polishing, and electropolishing. Therefore, the present invention includes a surface treatment that performs a step to improve parts obtained by the powder metallurgy or additive manufacturing techniques described above, in order to finally define an improved manufacturing method that meets all watchmaking requirements.
[0016] A method for manufacturing watch components according to an embodiment of the present invention will be described in detail below.
[0017] According to an embodiment of the present invention, in the first step, a blank of a part is prepared by a known additive manufacturing or powder metallurgy process. This blank has a shape very close to the final shape of the final part. However, additional operations such as threading and / or reworking can be optionally performed before or after the surface improvement process described later in detail. Therefore, all parts or all blanks, regardless of whether they have been reworked or not, on which the surface improvement treatment described later is to be performed, are intentionally referred to as members. This part may be made of a metal such as stainless steel, aluminum alloy, titanium, gold, silver, etc. Alternatively, it may be made of a cermet. The whole part may be made of the same material among the materials described above. Alternatively, it may include a combination of different materials. A "part made of a specific material" means a part containing at least 50% by weight of the material or at least 80% by weight of the material.
[0018] In powder metallurgy, the powder can be obtained, for example, by spraying, milling, or a combination of these techniques. The obtained powder can then be compressed, for example, by cold pressing, hot pressing, isostatic pressing, and / or sintering. Known powder metallurgy methods include metal powder injection molding (MIM) and spark plasma sintering (SPS).
[0019] Examples of known additive manufacturing techniques include selective laser melting (SLM), direct metal laser sintering (DMLS), electron beam melting (EBM), nanoparticle jetting (NPJ), metal binder jetting, laser engineered net shaping, and electron beam additive manufacturing (EBAM).
[0020] By applying powder metallurgy and additive techniques to metals and cermets, as described above, it becomes possible to obtain parts having various shapes. They provide the advantage of enabling alloy compositions, combinations of multiple components, and even combinations of different materials within the same part that were impossible to synthesize by conventional techniques. For example, with this technology, it becomes possible to use a white gold alloy containing at least 75 wt% Au, 13 to 17 wt% Cr, 5 to 10 wt% Pd, and 1 to 5 wt% Fe. Therefore, the colorimetric parameter b* of this alloy according to the CIE1976L*a*b* model is less than 10.
[0021] Furthermore, with this technology, it becomes possible to use a composition containing 90 to 98 wt% WC and 2 to 10 wt% nickel or an 18-karat gold composition having 2 to 25 wt% TiN. This technology further enables the creation of parts consisting of a core of an aluminum alloy and an outer layer of 316L stainless steel or a composition with different outer layers depending on the surface position, for example, forming the body, horns, case band, bezel ring, etc. from different alloys and / or cermets. Thereby, it becomes possible to obtain, for example, a color gradient or juxtaposition of different colors and different mechanical resistances.
[0022] However, all parts obtained by these techniques are porous and thus have a lower density than that of solid parts made of the same material. As a result, these parts generally do not have a satisfactory surface finish that would permit their use in the field of watchmaking. In fact, as a result of the very nature of these techniques, visible or at least perceptible irregularities appear on the surface of the parts in the form of, for example, pores, ridges, depressions, precipitates, and / or streaks. The porosity ratio, i.e., the amount of defects, depends on the materials used and the manufacturing techniques. However, none of the current techniques are capable of manufacturing completely defect-free parts.
[0023] However, these defects negatively affect the appearance of the parts, particularly surfaces that are desirable to be smooth, such as those finished by mirror polishing. In addition, pores, precipitates, and / or streaks with dimensions of 1 μm (or 0.5 μm) or more in at least one direction are especially troublesome, because surface finishing processes such as shot peening, mechanical polishing, and / or chemical or electrolytic polishing cannot remove them. In practice, pores and precipitates with a diameter of 500 μm or less become visible on polished surfaces, resulting in comet-tail-like holes, pitting, and other aesthetic defects. More generally, in mirror polishing, pores and / or precipitates and / or streaks with dimensions of 0.5 μm or more are likely to be perceived. As a result, despite their advantages, parts obtained by the aforementioned techniques remain unsatisfactory in their current state for forming watch components, and traditional finishing processes are not suitable for reliably removing all of these defects.
[0024] The present invention proposes to eliminate the above-mentioned defects resulting from the manufacturing of the part by the first step described above, and to perform a surface treatment method that includes a step of improving the surface finish of the part as described in detail below.
[0025] According to one embodiment, the process of improving the surface finish of a part involves surface remelting, in particular, by a laser, for example, by a method known as laser surface melting (LSM). Alternatively, energy can be supplied to the part by laser light, plasma beam, electron or ion beam, or arc. For example, a surface made of Ti-6Al-4V material can be remelted. -1 The sample is processed in a Pa helium atmosphere by a 60 kV electron beam with a current of 1 to 50 mA, a spot size of 10 to 100 μm, and a scanning speed of 0.1 to 1 m / s.
[0026] The process of improving the surface finish of a part by surface remelting may involve the use of a laser in which the cross-section of the laser beam has a substantially uniform energy distribution. Alternatively, this may include the use of a plasma beam, electron beam, ion beam, or arc.
[0027] These processes share the common characteristic of inducing surface remelting of the part by applying energy, thereby removing pores and / or precipitates and / or streaks from the part's surface while having only a small impact on the overall density of the part. These processes act only on the surface area of the part. Advantageously, these processes can simultaneously reduce the roughness of the part.
[0028] More precisely, laser processing using the LSM method is based on the interaction between electromagnetic radiation and the component material. Due to the energy density of the laser light, i.e., energy per unit area, the focus / focus misalignment of the laser light on or near the component surface, and the duration of the interaction, some of the energy is absorbed into the surface region of the component. The component material in this surface region is thus heated until the material melts.
[0029] Figure 1 is a schematic diagram illustrating the surface treatment of a component by the LSM method. As described above, component 1 is formed, and component 1 includes pores 2 that form surface defects 3 and surface scratches 4. A laser L moves across the surface at a certain velocity v (from right to left in Figure 1) to melt the component material in the surface area and form a solution bath 11. This method thus effectively remelts the surface area of component 1. Pores and / or precipitates are removed within this solution bath 11. As a result, a treated surface area 12 with higher density and improved quality is obtained, with its surface 13 having only very few defects, if any. The treatment has only a slight effect on the core 15 of the component, and therefore, after the laser passes, the core retains the pores 2 that were originally there. Finally, in the intermediate area 14 between the surface area 12 and the core 15, the material is not melted, but its structure is altered by temperature diffusion during the cooling and solidification of the solution bath 11.
[0030] The thickness of the solution bath 11, which substantially corresponds to the thickness of the surface region 12, is between 10 μm and 1 mm. Preferably, this thickness is 50 μm or more, or 100 μm or more. Also preferably, this thickness is 1000 μm or less, or 500 μm or less, or 200 μm or less, or 100 μm or less.
[0031] In this LSM method, the laser velocity v is optimized to obtain a solution bath 11 with predetermined dimensions and to ensure controlled solidification of the material. The surface region 12 of the component is thus densified by the surface remelting process. The intermediate layer 14 is a region potentially affected by the surface remelting process. Even if the material is not completely melted, the microstructure of the material may have changed.
[0032] The laser energy and wavelength are preferably matched to the properties of the part being processed, particularly the absorptivity and conductivity of its constituent materials, and the shape of the object being processed. If the laser energy is insufficient, the local temperature will not be sufficient to obtain a suitable solution bath, and all perceptible defects cannot be removed. If the size of the solution bath or the duration of the liquid phase before solidification is insufficient, the pores may not rise properly to the surface, and / or the thickness of the layer without perceptible pores will not be satisfactory. Furthermore, if the absorbed energy is too high, the shape of the processed part may change, leading to significant deformation that will be discovered during subsequent polishing and / or the formation of additional pores (keyholes) at the interface between the solution and the material. Moreover, once the material becomes liquid, the absorptivity increases significantly, and if the energy is too high, it will lead to the formation of keyholes.
[0033] Therefore, by controlling the temperature gradient of the solution bath and its cooling rate by the laser power distribution and / or scanning and / or screening speed, it is possible to obtain the desired results and remove contents from the pores and / or treated surface region 12.
[0034] According to this embodiment, the scanning speed is selected to be lower than that typically used by the LSM method, for example, at least 10 times slower than the commonly used speed, between 500 and 2000 mm / s, allowing the pores to move to the surface. Finally, the output as a function of material and laser wavelength, the space-time power distribution, the laser scanning speed, and the screening are optimized to define the shape of the solution bath and the thickness of the resulting surface area being treated, with minimal impact on the part shape.
[0035] As an example, a 2kW IPG® laser with a 3x3 square spot and Trumpf® optics and ILT nozzle is used. Other similar devices employing red or infrared lasers, such as CO2 lasers, can also be used. Alternatively, blue, green, UV, and other lasers can also be used.
[0036] Beam focusing and homogenization are advantageously adjusted based on a “top-hat” type spatial power distribution, which is particularly advantageous. A “top-hat” beam is characterized in that the edges of the beam's cross-section have the same energy at every point in the cross-section. In other words, the cross-section of the edges of the laser beam has a substantially uniform energy distribution. In addition, the laser speed and screening are set based on the energy required to obtain a solution bath of the desired dimensions and to control the cooling rate of the solution bath. Finally, the laser power is selected to obtain a solution bath whose depth is equal to or slightly greater than the thickness of the layer formed by the desired densified surface region 12. Such optimization of the process, in particular the laser starting point, scanning pattern, scanning speed, number of optical paths, etc., makes it possible to eliminate defects present in the material and to limit or completely prevent the laser from generating new defects such as deformation, distortion, and scattering.
[0037] Advantageously, this optimization takes into account the material and shape of the part being processed. Furthermore, advantageously, the laser parameters are adapted to the shape and / or surface finish and / or composition of the part. The speed and / or power and / or number of optical paths and / or screening can be adjusted to take into account the shape or composition of a particular part. Alternatively, it is possible to select a laser with a wavelength corresponding to the specific reflectivity of the material being processed, for example, a laser with a wavelength of 500 nm or less for gold and silver, and a laser with a wavelength of 350 nm for each.
[0038] Advantageously, the part may also be tempered or cooled on its surface or as a whole, for example by using a temperature-controlled support, to control the direction of solidification. Advantageously, the conditions are selected to promote a particle orientation substantially perpendicular to the outer surface of the treated part.
[0039] In one variation, the component is cooled using a liquid or gas, such as a fluid flow suitable for a given temperature, during or after the laser pass-through, or throughout the process. Cooling is performed immediately after the laser treatment or with a delay.
[0040] The table below shows some examples of IPG laser parameters for performing the surface treatment described above by injecting shielding gas.
[0041] [Table 1]
[0042] In another variation, the laser parameters are servo-controlled to measure the temperature of the work surface of the part, for example, using an optical temperature sensor or other suitable sensor.
[0043] Finally, the surface treatment method is advantageous in that it is - Use of liquids or gases, or —In particular, temperature control of the entire component using a temperature control support, or —Servo control for measuring the temperature of the processed surface of a component This includes a controlled cooling process for the components.
[0044] As mentioned above, the interaction between lasers and materials is a complex phenomenon. The interaction between laser irradiation and the component being processed is influenced not only by the properties of the laser and the parameters of the laser process, but also by the characteristics of the component's constituent material, particularly its reflectivity, conductivity, and absorptivity. The absorptivity of the material at the laser wavelength is one of the most important parameters. The lower the absorptivity, the less laser energy is "absorbed," making it more difficult to melt the material.
[0045] This invention considers that the absorption rate of the material being processed directly affects the dimensions of the solution bath and the required energy to be supplied.
[0046] However, in some cases, the absorption rate of the material was insufficient for optimal surface remelting.
[0047] For example, if the components are prepared from metals or alloys with low absorptivity, such as gold, copper, silver, platinum, palladium, or aluminum-based metals, which are typically used in watchmaking, you may face a difficult problem. In fact, the absorptivity of these materials at wavelengths above 700 nm generally does not allow for optimal interaction with lasers having wavelengths such as 1064 nm.
[0048] However, as mentioned above, increasing the laser power or interaction time to compensate for the low absorption rate of the material can lead to deformation of the surface dimensions, such as deformation of the part due to overall heating. This effect is unacceptable in the manufacture of watch components, and therefore increasing the laser power or changing other laser parameters is not always possible.
[0049] The graphs in Figures 2 and 3 show some examples of material absorptivity and reflectivity as functions of specific wavelengths.
[0050] These figures show, for example, that in a YAG laser with a wavelength of 1064 nm, the average absorption rate of copper (Cu) is 10%, while that of nickel (Ni) is 28%. In a CO2 laser with a wavelength of approximately 10 μm, the average absorption rate of copper is 1%, while that of nickel is 4%.
[0051] According to the present invention, the absorption rate of a material at a given wavelength is an extremely surface phenomenon, essentially relating to the first atomic layer, and is dependent on the properties of the first atomic layer and / or the surface finish of the material. Therefore, differences in surface finish, such as the presence of a certain degree of roughness and / or porosity, or differences in the composition of the component surface, can affect the process.
[0052] Based on the above considerations, if the material has a low absorption rate and the supplied energy may not be sufficient to melt the material, this may manifest as insufficient melting of the material or insufficient dimensions of the solution bath, and may not adequately remove pores and / or precipitates and / or streaks that are perceptibly present on the surface of the part.
[0053] For example, in a white gold alloy (75.2 wt% Au, 13.9 wt% Pd, 3 wt% Ag, and 7.9 wt% Cu, with a reflectivity of approximately 75%), the dimensions of the solution bath were not optimal when processing with a 2 kW output IPG (registered trademark) type 1500 W laser beam having a 3x3 square spot with a Trumpf (registered trademark) optical system and ILT nozzle at an operating speed of 500 mm / min.
[0054] In response to these circumstances, this embodiment proposes the implementation of a preliminary step to modify the absorptivity of the surface region of the component. This preliminary step is performed to pre-treat the component surface to reduce its reflectivity for energy absorption in the surface region of the component to be subsequently treated. Thus, this surface pre-treatment has the effect of changing the behavior of the surface to laser light during the subsequent LSM treatment. Optionally, surface absorption mapping may be performed to correlate laser parameters in advance. Optionally, this surface pre-treatment is localized at the start spot of the surface treatment method to subsequently utilize the change in the absorptivity of the solution bath relative to the solid surface.
[0055] According to a first modification of the embodiment, the pre-treatment step of the surface preparation includes a step of depositing a chemical element in the form of a coating. This deposit advantageously gives the chemical element an amount of 5 atomic percent or less with respect to the overall composition of the surface area. The surface coating can alter the chemical properties and / or color of the surface. Alternatively or simultaneously, the surface coating can alter the topology of the surface. The surface coating can be deposited, for example, by PVD, CVD, ALD, electroplating, sol-gel or SAM. The thickness of the surface coating may be 0.1 nm or more, or 0.5 nm or more, or 1 nm or more, and 10 μm or less, or 1 μm or less.
[0056] The table below shows several examples produced by the first modification (for a YAG laser with a wavelength of 1064 nm).
[0057] [Table 2]
[0058] Surface coatings can be applied by physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), electrodeposition, sol-gel treatment, or self-assembled film (SAM).
[0059] This surface pretreatment can temporarily or permanently alter the color of the surface.
[0060] Advantageously, the thickness of the applied coating is 0.1 nm or more, or 0.5 nm or more, or 1 nm or more. In addition, it is preferable that this thickness is 10 μm or less, or 1 μm or less.
[0061] In all cases, this coating alters the initial absorption rate of the component material and facilitates future processes that improve the surface finish. The effect of the coating remains relatively minor on the material properties of the component; in particular, the added material does not significantly alter the composition of the treated surface area and does not change the mechanical properties of the material.
[0062] According to a second variation of this preliminary surface pretreatment process, chemical or electrolytic etching of the component surface can be carried out. For example, nitrate-hydrochloric acid etching (aqua regia) on a gold alloy reduces the reflectivity of the surface. The layer modified by this preparation process advantageously includes thicknesses between 0.1 nm and 10 μm, or between 0.5 nm and 1 μm.
[0063] According to a third modification of this preliminary surface pretreatment process, microtexturing of the surface by, for example, sandblasting, bead blasting, grinding, laser treatment or other suitable techniques is performed to reduce the surface reflectivity.
[0064] According to a fourth variation of this preliminary surface pretreatment process, the initial solid-state absorption rate of the component material surface can be altered by performing oxidation, nitriding, borization, chlorination, fluorination, or sulfidation. Such pretreatment may, for example, increase surface roughness or change color. In this fourth variation, the thickness of the altered layer is similar to that of the coating described above. In addition, the contribution of chemical elements remains very low. In fact, the contribution of these chemical elements is less than 5 atomic percent of the total composition of the surface layer, i.e., the surface area being treated.
[0065] For example, the surface of a gold alloy-based component can be oxidized. For instance, a white gold component (75.0 wt% Au, 7.0 wt% Pd, 15.0 wt% Cr, and 3.0 wt% Fe) may be pre-oxidized by heating it in an air furnace at 700°C for 15 minutes. An oxide layer of approximately 100 nm can be obtained.
[0066] Three samples of 18-karat white gold were tested using standard techniques, polished with P320 sandpaper (polished surface) and then with P4000 sandpaper (mirror polish). One of the mirror-polished samples was then oxidized in air at 700°C for 15 minutes. The reflectance of the three samples was then measured using a UV-Vis IR spectrophotometer. The results are detailed in the table and Figure 4 below.
[0067] [Table 3]
[0068] These tests demonstrate that oxidation can reduce the reflectivity of a metal from 70% or 75% in its non-oxidized state to less than 30% by creating a 100 nm thick oxide layer.
[0069] Furthermore, on a pre-oxidized surface of a white gold alloy (75.2 wt% Au, 13.9 wt% Pd, 3 wt% Ag, and 7.9 wt% Cu), a 1500 W laser at 500 mm / min removes perceptible pores without affecting the shape of the object, whereas the same treatment appears to have little effect on pores present in non-oxidized materials. Advantageously, this treatment is carried out in the presence of a gas or gas mixture, such as a reducing gas or a mixture of reducing gases (which may be weakly reducing), to remove oxygen from the surface layer of the precious metal alloy. This makes it possible to avoid changing the final composition of the part.
[0070] As a final variation, the different variations described above can be combined with each other.
[0071] This preliminary surface pretreatment step, while optional, always provides a highly desirable effect to subsequent steps that improve the surface finish of the part. In fact, the increase in absorptiveness promotes the initiation of surface remelting from the initial solid state. Furthermore, it has been confirmed that by increasing the initial absorptiveness on the surface of the part material, a deeper solution bath can be obtained with a given laser (e.g., a 1064 nm laser) compared to an unpretreated surface of the same part. This pretreatment step therefore increases the efficiency of the surface improvement process, enabling the removal of surface defects to an appropriate depth without introducing excess energy that could affect the shape of the part.
[0072] Figure 5 schematically illustrates a process for improving the surface finish by the LSM process, which is performed after a surface pretreatment step by coating or oxidation. Part 1 includes a surface coating or oxide layer 16 superimposed on the surface region 12 intended to be treated, which is superimposed on an intermediate region 14 located between the surface region 12 and the core 15 of the part. During treatment with the laser L, the coating or oxide layer 16 and the surface region 12 are simultaneously melted, accelerated by the coating or oxide layer 16, while the intermediate region 14 is affected by the heat but does not melt. Note that after the surface improvement treatment, the coating or oxide layer 16 disappears and melts into the surface region 12.
[0073] Such surface pretreatment is particularly suitable for parts based on gold, copper, silver, platinum, palladium, aluminum, or alloys thereof.
[0074] Naturally, in the modified examples, the preliminary pretreatment steps may be applied only to a portion of the surface of the part, particularly to the starting area of the treatment.
[0075] The process of improving the surface of the parts, as described above, ultimately yields the following two advantageous effects. - The surface of porous parts is processed to correspond to traditional finishing processes, thereby further improving the appearance of the surface finish. - This provides the possibility of making the surface of the part denser than its core, and therefore lighter than parts made from solid materials.
[0076] Preferably, the surface treatment method according to the embodiment of the present invention may include a subsequent finishing step. This step is particularly suitable for manufacturing decorative watch components that have very high surface finish requirements.
[0077] In particular, the finishing process includes grinding, machining, or polishing the surface of the surface area of the part. Preferably, this finishing process consists of polishing.
[0078] It should be noted that polishing may be required several times, not only during manufacturing but also during subsequent maintenance work, to remove scratches. This polishing also has very demanding requirements to ultimately achieve a mirror finish, and depending on the depth of the scratches, it may be necessary to remove material to a thickness of 50 μm or more. Therefore, the treated surface area of the part must have sufficient thickness to allow for such subsequent finishing processes. This thickness can be predetermined according to the desired final surface finish and to accommodate normal maintenance work. Advantageously, the thickness of the treated surface area may be 100 μm or more, or 200 μm or more, or 500 μm or more, or 1000 μm or more.
[0079] In all cases, the surface treatment method described above may be used to treat the entire surface of the part or to treat only a portion of its surface.
[0080] The present invention has described a method for manufacturing watch parts, comprising a first step of manufacturing a metal or cermet-based part by powder metallurgy or an additive manufacturing method, and then carrying out a process of surface treatment of the part obtained in the first step. The present invention also relates to such a surface treatment method.
[0081] Therefore, the manufacturing method described above makes it possible to obtain watch components having the advantages described above. Such components are particularly lightweight, can take on complex shapes, and / or may be based on original combinations of components or materials. For example, the manufacturing method can reduce the weight of watch components that can also be manufactured by existing traditional methods while maintaining a high-density surface layer with the same appearance. Thus, depending on the alloy and / or shape of the component, a significant weight reduction of, for example, 20%, 30%, or more can be achieved.
[0082] Accordingly, the present invention relates to such watch components. Such watch components for a watch are based on metal and / or cermet and include a core having irregularities such as pores and / or precipitates as a result of being manufactured by powder metallurgy or an additive manufacturing method, and also include a surface area having fewer irregularities than the core as a result of a surface treatment that involves surface remelting.
[0083] According to embodiments of the present invention, the core and surface regions of a watch component are composed of substantially the same chemical composition.
[0084] Therefore, the surface region may have a lower porosity than the core. Furthermore, the surface region may contain precipitates with a lower density and / or smaller dimensions than the core precipitates.
[0085] The core of a watch component may be porous and have a density of 99.5% or less, while the surface area may have a strictly higher porosity and / or a density of 99.9% or more than that of the core. Density represents a percentage of the density of the same solid material.
[0086] The surface region may have a porosity of 0.1% or less for dimensions greater than 0.5 μm.
[0087] The surface region may extend to a depth of 20 μm or more, or 50 μm or more, or 100 μm or more. This depth corresponds to the thickness of the layer formed by the surface region. This is understood to be a minimum or average value.
[0088] The surface region may extend to a depth of 1000 μm or less, or 500 μm or less, or 200 μm or less, or 100 μm or less.
[0089] The surface area of the component may extend to only a portion or all of the surface of the watch component.
[0090] Watch components may be based on austenitic stainless steel, titanium alloy, precious metal alloy, or copper alloy.
[0091] Watch components may be based on metals having a low absorption rate of 30% or less and / or high thermal conductivity, such as metals and alloys thereof, such as Au, Al, Cu, Pt, Pd, etc.
[0092] Watch components may include the case, case back, bezel, crown, bracelet links, clasp, hands, or inlays.
[0093] The present invention also relates to a clock, in particular a miniature clock, such as a wristwatch, which includes at least one of the clock components described above.
[0094] Advantageously, the initial porosity of the part is selected to obtain a part with a predetermined density. The method according to the present invention makes it possible to increase the density of only the surface layer, i.e., the aforementioned surface region, making it possible to obtain a lighter part with improved aesthetics. Furthermore, since the surface layer is made of the same material as the porous core, interface problems that can occur with traditional coatings such as plating do not occur.
[0095] The present invention is illustrated by three examples that enable the manufacture of the following watch components.
[0096] According to the first embodiment, a white gold body (72.5 wt% Au, 13.9 wt% Pd, 3 wt% Ag, and 7.9 wt% Cu) is manufactured using the SLM process described above. Before processing, the surface of the SLM-treated body has 0.5 to 2% porosity consisting of pores larger than 0.5 μm and an absorptivity of approximately 20%. The body is then oxidized in air at 700°C for 15 minutes, thereby creating an oxide layer of approximately 100 nm. This step corresponds to the pre-treatment step of the processing method according to the present invention described above. Next, a 2 kW output IPG laser with a 3 × 3 square spot and Trumpf® optics and an ILT nozzle is used to scan the surface of the body at an average scanning speed of 500 mm / min and under argon flux at an output of 1500 W (top hat). The distance between the laser and the surface to be processed is adjusted so that the surface is at the focal plane height. This final step corresponds to improving the surface finish of the part by surface remelting of the surface area of the part according to the present invention. A body free of perceptible pores and / or precipitates is obtained. The thickness of the densified layer is 200 μm, and the porosity consisting of pores of 0.5 μm or larger is 0.1% or less.
[0097] Figure 6 shows an embodiment of the present invention by comparing the untreated area of the body with the treated area. The enlarged view of the untreated area shows the defects 20 that disappeared after performing the surface treatment method according to the embodiment of the present invention.
[0098] In this second embodiment, a 316L steel plate manufactured by selective laser melting (SLM) is processed according to the present invention. Prior to processing, the surface of the 316L steel plate has a porosity of 0.5 to 2%, consisting of pores of 0.5 μm or larger. A 2 kW IPG laser with a 3 × 3 square spot and Trumpf® optics and an ILT nozzle is used, and the plate surface is scanned at an average scanning speed of 1000 mm / min and under a nitrogen flow at an output of 1500 W (top hat). The distance between the laser and the surface to be processed is adjusted so that the surface is at the focal plane. A plate without perceptible pores and / or precipitates is obtained. The thickness of the densified layer is approximately 200 μm, and the porosity consisting of pores of 0.5 μm or larger is 0.1% or less. This embodiment is shown in Figures 7 and 8.
[0099] Figure 7 shows the surface of a plate based on 316L steel. This surface has an untreated area with several visible defects 20. It also includes an area 13 treated by the surface treatment method according to the present invention, which no longer has these defects 20. Figure 8 is an enlarged view in the thickness direction of a plate based on 316L steel according to the present invention. This part includes a dense, defect-free surface area 12 and a core 15 that is less dense and contains porosity 2.
[0100] In the third embodiment, a Grade 5 titanium plate manufactured by selective laser melting (SLM) is treated according to the present invention. Prior to this treatment, the surface of the Grade 5 titanium plate has a porosity of 0.2 to 1%, consisting of pores of 0.5 μm or larger. A 2 kW IPG laser with a 3 × 3 square spot and Trumpf® optics and an ILT nozzle is used, and the plate surface is scanned at an average scanning speed of 1000 mm / min and under argon flux at an output of 1500 W (top hat). The distance between the laser and the surface to be treated is adjusted so that the surface is at the focal plane height. A plate without perceptible pores and / or precipitates is obtained. The thickness of the densified layer is 300 μm, and the porosity consisting of pores of 0.5 μm or larger is 0.1% or less. This embodiment is shown in Figures 9 and 10.
[0101] Figure 9 shows the surface of a plate based on Grade 5 titanium. This surface has an untreated area with several visible defects 20. It also includes an area 13 treated by the surface treatment method according to the present invention, which no longer has these defects 20. Figures 10a and 10b show enlarged views, respectively, of the surface area of the Grade 5 titanium plate treated according to the present invention and the untreated surface area. The surface area 12 treated according to the present invention, shown in Figure 10a, does not contain defects in the thickness direction or on the surface 13. In contrast, the untreated area, shown in Figure 10b, contains defects such as surface pores 3 and streaks 4. [Explanation of symbols]
[0102] 1 part 2 pores 3. Surface defects 4. Scars 11 Solution bath 12 Surface area 13 Surface 14 Intermediate area 15 cores 20 defects
Claims
1. A surface treatment method for manufacturing metal and / or cermet-based watch parts from parts containing pores and / or precipitates and / or scratches, obtained by powder metallurgy or addition processes, The process includes a step of improving the surface finish of the part by surface remelting of the surface region of the part, and a step of finishing the surface of the surface region of the part, wherein the finishing step is performed after the step of improving the surface finish of the part by surface remelting. In order to absorb energy in the aforementioned surface region, the process includes a pre-processing step to change the absorption rate of the surface region of the component by performing a surface pre-treatment to reduce the reflectance, The preceding step includes a step of depositing a chemical element in the form of a surface coating, wherein the surface coating is deposited by physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), electrodeposition, sol-gel treatment, or self-assembled film (SAM), the thickness of the deposited coating is 0.1 nm or more and 1 μm or less, and the surface coating is a surface treatment method that changes the color of the surface.
2. The surface region of the aforementioned part includes a depth of 50 μm or more. The surface treatment method according to claim 1.
3. The surface region of the component includes an average depth of 1000 μm or less, or 500 μm or less, or 200 μm or less, or 100 μm or less. The surface treatment method according to claim 1 or 2.
4. The aforementioned adhesion step provides a chemical element amount of 5 atomic percent or less with respect to the overall composition of the surface region. A surface treatment method according to any one of claims 1 to 3.
5. The process includes a first step of manufacturing a metal or cermet-based component by powder metallurgy or an additive manufacturing method, wherein the component obtained by the first step is subjected to a surface treatment method according to any one of claims 1 to 4. A method for manufacturing watch parts.
6. The component includes a core (15) having irregularities such as pores and / or precipitates, and as a result of a surface treatment involving surface remelting by the method of any one of claims 1 to 4, it includes an irregularity-reducing surface region (12) having fewer irregularities than the core (15). A method for manufacturing the watch component described in claim 5.
7. The surface region (12) with reduced unevenness has a lower porosity than the core (15), and / or the surface region (12) has precipitates with a lower density and / or smaller dimensions than the precipitates of the core (15), and / or the core (15) is porous and has a density of 99.5% or less, and the surface region (12) with reduced unevenness has a density of 99.9% or more. A method for manufacturing a watch component as described in claim 6.
8. The surface region (12) with reduced unevenness contains a porosity of 0.1% or less for dimensions greater than 0.5 μm. A method for manufacturing a watch component according to claim 6 or 7.
9. The surface region (12) with reduced unevenness extends to a depth of 50 μm or more. A method for manufacturing a watch component according to any one of claims 6 to 8.
10. The surface region with reduced unevenness extends to an average depth of 1000 μm or less, or 500 μm or less, or 200 μm or less, or 100 μm or less. A method for manufacturing a watch component according to any one of claims 6 to 9.
11. The surface area of the component with reduced unevenness extends over the entire or partial surface of the watch component. A method for manufacturing a watch component according to any one of claims 6 to 10.
12. The aforementioned watch components are based on austenitic stainless steel, titanium alloy, precious metal alloy, or copper alloy. A method for manufacturing a watch component according to any one of claims 6 to 11.
13. The aforementioned watch component is based on a metal or alloy thereof having a low absorption rate of 30% or less and / or a high thermal conductivity. A method for manufacturing a watch component according to any one of claims 6 to 12.
14. The aforementioned watch components include the case, case back, bezel, crown, bracelet links, clasp, hands, or inlays. A method for manufacturing a watch component according to any one of claims 6 to 13.