Method for producing a ceramic component

Abstract

The invention relates to a method for producing a technical ceramic component (10). The method comprises, inter alia, the following steps: i) arranging in a mould at least one ceramic powder composition (p1; p1, p2; p1, p2, p3); ii) carrying out an SPS sintering cycle to obtain a blank (12) of the ceramic component having at least one gray hue (n1; n1, n2; n1, n2, n3); iii) machining the rough blank (12) to obtain a rough blank (14) of a predetermined shape; characterised in that, after step iii), there is also an additional step iv) comprising subjecting the blank (14) of a predetermined shape to an oxidation operation in order to obtain, at least on the surface of the first portion of the ceramic part (10), at least one colour (c1; c1, c2; c1, c2, c3), the surface of the second portion of the ceramic component (10) exhibiting said at least one gray hue.

Description

Field of the Invention

[0001] The present invention relates to a method for producing technical ceramic components, in particular for producing decorative components in the field of clocks or jewelry. The method includes steps such as an oxidation operation, which can produce ceramic components with more aesthetic effects without affecting their mechanical properties. Background Art

[0002] In the field of clocks, the mechanical properties of clock components (especially a watch case middle (une carrure de montre)) are crucial because it can withstand accidental impacts. However, due to its structure, ceramic materials have the disadvantage of being fragile. Currently, there are various methods to produce ceramic-based components with better mechanical properties.

[0003] CH718069 discloses a method for producing ceramic decorative elements, which makes the decorative components substantially uniform in terms of structure and mechanical properties while maintaining the original appearance. The method includes the following steps:

[0004] i) Prepare a first base composition, which contains powders for sintering operations to form ceramics;

[0005] ii) Prepare a second base composition, which contains powders for sintering operations to form ceramics;

[0006] iii) Before the sintering operation, process at least one of the first base composition and the second base composition to introduce at least one pigment and respectively define a first reactant and a second reactant;

[0007] iv) Place the first reactant and the second reactant at least partially adjacent to each other in the form of at least two layers in a mold to define an interface with a predetermined shape between them; and

[0008] v) Perform a sintering operation on the mold containing the first reactant and the second reactant.

[0009] The method also includes at least one processing step for the ceramic product obtained after the sintering operation, including at least one material removal operation along a path intersecting the interface, such that at least a part of the interface is visible on the surface of the decorative element, and the element exhibits a change in shade (teinte) and / or color on its surface.

[0010] The disadvantage of this method is that it is relatively complex to implement because it involves multiple steps, including preparing powders containing binders and stabilizers, and a debinding step. Therefore, the complexity of this method has a significant impact on the cost of the produced components. Summary of the Invention

[0011] Accordingly, an object of the present invention is to provide a method for producing a technical ceramic component, which is simpler to implement compared to the above-mentioned prior art.

[0012] Another object of the present invention is to provide a method for producing a technical ceramic component with enhanced mechanical properties.

[0013] Another object is to provide a method for producing a technical ceramic component (in particular, a middle case of a watch), which allows the production of components with more aesthetic effects without compromising their mechanical properties.

[0014] Another object of the present invention is to provide a method for producing a technical ceramic component (in particular, a middle case of a watch), which includes a decoration step without adding new materials.

[0015] These objects are achieved at least in part, in particular by a method for producing a technical ceramic component, comprising the following steps:

[0016] i) arranging at least one ceramic powder composition containing at least one metal oxide in a mold;

[0017] ii) performing an SPS sintering cycle to obtain a green body of the ceramic component in a reduced state, having at least one gray tone on its surface; and

[0018] iii) machining the green body to obtain a green body of a predetermined shape. After step iii), there is an additional step iv), namely oxidizing the green body of the predetermined shape to present at least one color generated by the oxidation of the at least one metal oxide on at least the surface of the first part of the ceramic component, and the surface of the second part of the ceramic component presents the at least one gray tone.

[0019] According to one embodiment, step i) includes arranging a first and a second composition in the mold, each composition containing ceramic powder and different metal oxides, so as to obtain a first and a second gray tone after step ii).

[0020] According to one embodiment, step i) includes filling the mold with at least three compositions, each composition containing ceramic powder and different metal oxides, so as to obtain three gray tones after step ii).

[0021] According to one embodiment, the oxidation operation in step iv) is carried out by a laser beam or a plasma jet supplied by an oxygen stream.

[0022] According to one embodiment, at least one of the laser beam and the plasma jet is used to create a pattern with a certain level of detail, the resolution of which depends on the beam diameter or the effective diameter of the plasma jet, respectively.

[0023] According to one embodiment, the oxidation operation includes oxidizing at least on the surfaces of selected one or more different regions of the ceramic component.

[0024] According to one embodiment, the selection of the one or more different regions of the ceramic component for oxidation results in the formation of one or more patterns of a predetermined shape, presenting at least one color according to the metal oxides contained in the oxidized regions of the ceramic component.

[0025] According to one embodiment, the method further includes performing a surface treatment operation on at least one region of the green body of the predetermined shape between steps iii) and iv) to obtain at least one treated surface, wherein the oxidation operation is performed on one or more regions where the surface has been pre-treated.

[0026] According to one embodiment, a relative movement is generated between the plasma jet or laser beam and the green body of the predetermined shape, while respectively changing the distance between the plasma jet and the green body and the power of the laser beam to obtain a change in the degree of oxidation on the first part of the ceramic component, making it show a color gradient.

[0027] According to one embodiment, the oxidation operation in step iv) is carried out by placing the green body of the predetermined shape in an oxygen furnace or an air furnace and maintaining a predetermined duration and temperature cycle. The duration and temperature cycle are set such that, on the one hand, oxidation occurs on at least a part of the surface of the green body to obtain a color depending on the metal oxides present on the surface of the green body, and on the other hand, oxidation occurs inside the body of the green body to a predetermined depth to obtain a color. After the oxidation operation, an operation of selectively removing an oxide layer is carried out to show at least one gray tone and / or a gradient color.

[0028] According to one embodiment, the predetermined temperature cycle includes a heating cycle with a temperature rising from about 20°C to between 800°C and 1200°C over a time interval of 3 to 5 hours. After the heating cycle, it is followed by a cooling cycle with a temperature dropping to about 20°C over a time interval of 2 hours 30 minutes to 3 hours 30 minutes. On the one hand, this enables oxidation of at least a part of the surface of the green body to obtain a color depending on the metal oxides present on the surface, and on the other hand, oxidizes the underlying material to a depth of 50 to 300 microns.

[0029] According to one embodiment, the material is removed according to a predetermined pattern to a depth exceeding the depth of the oxidized body of the green body to expose one or more gray tones.

[0030] According to one embodiment, the material is removed along a trajectory within the oxidized body according to a predetermined pattern and variable depth to show a color gradient.

[0031] According to one embodiment, the SPS sintering cycle is carried out at a temperature between 1100 °C and 1300 °C within a time interval of 10 to 45 minutes.

[0032] Another aspect of the present invention relates to a component of a timepiece or jewelry item obtained by the above method, in particular a middle case or bezel of a watch case. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Examples of embodiments of the present invention are provided in the specification and are described in conjunction with the accompanying drawings, wherein:

[0034] - Figures 1a to 1e is a schematic diagram of each stage in the manufacturing process of a middle case of a watch case according to one embodiment;

[0035] - Figures 2a to 2e is a schematic diagram of each stage in the manufacturing process of a middle case of a watch case according to another embodiment;

[0036] - Figures 3a to 3d is a schematic diagram of each stage in the manufacturing process of a middle case of a watch case according to another embodiment, and Figure 4a and 4b is a schematic diagram of the final decoration step according to two embodiments;

[0037] - Figures 5a to 5d is a schematic diagram of each stage in the manufacturing process of a middle case of a watch case according to another embodiment;

[0038] - Figures 6a to 6e is a schematic diagram of each stage in the manufacturing process of a middle case of a watch case according to another embodiment;

[0039] - Figure 7 is Figure 6e a top view schematic diagram of the middle case of [] during the oxidation process, and the oxidation process generates a color gradient by spraying oxygen plasma with a plasma jet of a nozzle;

[0040] - Figure 8 is a graph exemplifying the relationship between the oxidation degree of the middle case of a watch case and the distance between the nozzle and the middle case of the watch case;

[0041] - Figure 9 is Figure 7 the middle case of [], and the color of the central part shows a gradient with the oxidation degree and the distance between the nozzle and the central part of the middle case of the watch case. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] The following description focuses on a method for manufacturing a technical ceramic component for the watchmaking or jewelry field, and will be illustrated based on a plurality of selected embodiments (non-limiting examples). More specifically, the ceramic component manufactured by implementing the method according to any of the following embodiments is a watch case middle. Of course, those skilled in the art can apply the same method to the manufacturing methods of other ceramic components without departing from the scope of the present invention.

[0043] In the present invention, the term "color" refers to colors other than combinations of gray shades (couleurs autres que la palette de nuances de gris). In the present invention, a color or color combination (palette de couleurs) refers to the visual appearance imparted to the surface or visible part of the ceramic component through an oxidation operation. The colors obtainable depend on the metal oxides present in the ceramic powder. In addition, the term "at least one gray shade" refers to the visual appearance imparted to the surface of the ceramic component blank in a reduced state obtained after the SPS sintering cycle of the ceramic powder without performing an oxidation operation. A gray shade is one of the shades between white and black as seen by the human eye.

[0044] Generally, the method for manufacturing a watch case middle comprises two steps identical to those described below. The first step is to place at least one ceramic powder composition containing at least one metal oxide into a mold. This step is followed by a second step involving a flash sintering operation, or "field-assisted sintering technology / discharge plasma sintering (FAST / SPS)". This operation is commonly referred to as SPS sintering and is a method similar to hot isostatic pressing, but utilizes the Joule effect to heat the pre-pressed powder placed in a mold between two graphite electrodes under an inert gas or vacuum condition. Under the action of a hydraulic press, the mold contains the pre-pressed powder and is subjected to a pressure of several megapascals. A continuous or alternating current (pulsed or non-pulsed current) of several kiloamperes is applied between the electrodes, with a voltage of several volts.

[0045] During sintering, the plasma ionizes the residual gas between the powder particles and generates negative ions, thereby consuming all the oxygen in the metal oxides contained in the ceramic powder. Although the sintering operation is usually carried out in a vacuum or inert gas environment, the ionization of the residual gas forms a so-called reducing atmosphere within the plasma. Due to this reducing atmosphere, after the flash sintering operation is completed, the final component is necessarily in a reduced state.

[0046] SPS sintering is carried out at a determined sintering temperature and pressure to ensure that all the powder does not melt. In this case, the sintering pressure can be mechanical pressure. Preferably, the sintering temperature should be determined to be lower than the lowest melting point of the powder under the sintering conditions. The appropriate sintering temperature can be evaluated based on the sintering pressure to avoid reaching or exceeding, or maintaining below, the melting point of the powder under the sintering pressure.

[0047] According to one embodiment, the SPS sintering temperature is below 2000 °C, even below 1500 °C. For example, the SPS sintering temperature is between 1000 °C and 1300 °C, and the sintering time interval is 10 to 45 minutes.

[0048] The SPS sintering pressure ranges from 20 to 180 N / mm 2 or from 50 to 100 N / mm 2 . Depending on the selected part and / or the quality requirements of the final mechanical part, other pressure values can also be preferably used.

[0049] The SPS sintering operation produces a sintered part that retains the fine grain size of the ceramic. Compared with the traditional sintering cycle, its advantage lies in the optimized mechanical properties, especially hardness and toughness. Since the sintering is carried out under an inert gas or vacuum condition, the resulting sintered part is in a reduced state, and its shape is determined by the final shape of the part.

[0050] Taking the middle frame of a watch case as an example, the shape of the sintered blank is basically cylindrical, and its diameter range can be between 40 mm and 60 mm, for example, about 50 mm, and the thickness range is between 15 mm and 20 mm, for example, 18 mm.

[0051] According to the first embodiment, with reference to Figures 1a to 1e , the method for manufacturing the ceramic watch case middle frame 10 includes a first step S1, which includes putting the first and second compositions p1, p2 into a mold (not shown), and each composition contains ceramic powder (preferably zirconia, especially yttria-stabilized zirconia) and at least one different metal oxide (preferably selected from iron oxide, alumina, bismuth oxide, and chromium oxide).

[0052] The first and second compositions p1, p2 are distributed in the mold in a non-mixed manner, as Figure 1a shown. More specifically, the first and second compositions p1, p2 are placed adjacent to each other to form an interface between them, and the direction in which the interface extends is basically perpendicular to the bottom of the mold.

[0053] In the second step S2, an SPS sintering operation is carried out to obtain the rough blank 12 of the watch case middle frame, as Figure 1b shown, whose surface has two gray tones n1, n2, which meet at an interface that may be basically perpendicular to the overall middle plane of the watch case middle frame 10. In a variant (not shown), three, four, or even five or more different compositions are arranged side by side so that after the SPS sintering operation, the rough blank of the watch case middle frame is obtained, and its surface has the same number or more gray tones, so that their respective interfaces preferably extend basically perpendicular to the overall middle plane of the watch case middle frame.

[0054] In another variant, not shown, at least two different compositions, for example three, four or even five or more compositions, are distributed in the mold to form the same number or more different superposed layers. Thus, after the SPS sintering operation, a rough blank of the case middle part with two, three, four or even five or more grey shades can be obtained, and these grey shades meet at their respective interfaces, which may be substantially parallel. These interfaces can be substantially parallel to the general plane of the case middle part or inclined to the general plane of the case middle part.

[0055] Each composition p1, p2 can contain one or more different metal oxides, such as iron oxide, aluminum oxide, cerium oxide, bismuth oxide and chromium oxide. The volumes of the two compositions p1, p2 can be substantially the same. According to the desired positions of the different grey shades n1, n2 on the finished part, the compositions p1, p2 are placed relative to each other in the mold. The ceramic powders of the compositions p1, p2 may also be different. For example, composition p1 is based on zirconia, while composition p2 is based on alumina or other materials.

[0056] After the SPS sintering operation is completed, the method includes a third step S3: machining the rough blank 12 to obtain a rough blank 14 with a predetermined shape, which generally corresponds to the final dimensions of the ceramic part, and in this example, it is the shape of the case middle part, as Figure 1c shown. The machining is carried out by conventional methods, especially milling and / or grinding.

[0057] The method may include a surface treatment step S4 as Figure 1d shown. This step is an optional step and includes decorating one or more areas of the surface of the part (especially the side surface of the case middle part) by mechanical and / or chemical operations. The mechanical operations can especially include polishing (polissage), sandblasting (sablage), straight-line satin finish (satinage dutyperectiligne), circular or spiral satin finish (circulaire ou ), microbeading (microbillage), guillochage, circular graining (perlage), Geneva ripple finish (finition de Genève) or hand engraving (gravure main). In this example, the machined rough blank 14 is surface-treated to make it include one or more surfaces 16 and obtain a decoration by one of the above mechanical operations.

[0058] In the case of a part comprising several separate and surface-treated areas, all areas may be subjected to the same type of treatment, for example sandblasting, or, according to a variant, the different areas may be treated differently, for example a first area may be sandblasted, a second area may be satin-finished and a third area may be polished. According to another variant, these different areas may be adjacent.

[0059] The method comprises a final step S5, comprising decorating the rough blank, such as Figure 1e The decoration step S5 includes oxidizing at least a portion of the case middle frame (especially the side thereof) to reveal the color of the metal oxide on the surface of the component. Figure 1e The oxidation operation consists in selectively oxidizing the surface of the case middle frame 10, for example to a depth of 50 microns, so that the shape of the oxidized surface matches the desired pattern. This operation triggers a chemical reaction caused by the contact of oxygen with one or more metal oxides present on the surface of the component. This reaction causes the different oxides to show their bright colors. This final operation is therefore a chemical transformation of the material, which is different from the method described in CH718069, where the final step is to remove the material using a CNC machine or a laser.

[0060] Patterns 18a, 18b, and 18c are represented by three stars in this example, showing different colors. The first star 18a shows a color specific to one or more metal oxides present in the first composition p1; the second star 18b shows two different colors, corresponding to the colors of one or more metal oxides present in the first composition p1 and the second composition p2; the third star 18c shows another color specific to one or more metal oxides present in the second composition p2.

[0061] For example, compositions p1 and p2 may contain bismuth oxide and aluminum oxide, respectively, to obtain Figure 1b The rough blank shown, wherein the compositions p1 and p2 in the reduced state have a dark grey tone and a light grey tone respectively. The dark grey and light grey tones vary depending on the concentration of oxides in the two compositions. Figure 1e After the oxidation step shown, the first pattern 18a will present a uniform color c1, tending towards blue, whose intensity will vary according to the concentration of bismuth oxide. The third pattern 18c will present a color c3, tending towards white, whose intensity will vary according to the concentration of aluminum oxide; and the second two-color pattern will present a combination of the two colors mentioned above.

[0062] Thus, the surface of the watch case middle part 10 obtained according to the first embodiment presents two gray shades n1 and n2 and is provided with different decorations 18a, 18b, 18c, which are represented by star patterns in this example, and the bright colors thereof depend on one or more oxides present on the surface where the star patterns are located. The star patterns 18 are preferably made in the area of the watch case middle part that has been surface-treated 16 (as described above) to form an additional contrast with the decorations 18a, 18b, 18c. According to a variant not shown in the figures, these decorations can also be applied to the area of the watch case middle part that has not been surface-treated.

[0063] For example, the oxidation operation can be carried out using a laser source, and local heating can form a local oxide layer. The laser source can be controlled so that the laser reproduces a pattern, such as a repeating pattern or even text, along a predetermined path on the surface of the watch case middle part 10.

[0064] According to the second embodiment and with reference to Figures 2a to 2e , the manufacturing method of the ceramic component includes a first step S1, which includes filling a mold (not shown in the figures) with a single composition p1 containing one or more metal oxides; subsequently, in a second step S2, an SPS sintering operation as described in the first embodiment is carried out to obtain a rough blank 12 of the disc-shaped watch case middle part in a reduced state. At this time, the appearance of the ceramic only presents a single uniform gray shade n1, as Figure 2b shown.

[0065] As shown in the first embodiment, the method includes a third step S3, which includes machining the rough blank 12 of the watch case middle part to its final dimensions after the sintering operation is completed, as Figure 2c shown.

[0066] In this embodiment, the operation of decorating the machined rough blank 14 includes two steps. The preparatory step S4 includes oxidizing at least a part of the surface of the rough blank. Preferably, the entire surface of the rough blank is oxidized.

[0067] To this end, the machined rough blank 14 is placed in a furnace with an oxygen or air atmosphere and maintained for a predetermined duration and temperature cycle for oxidation: on the one hand, oxidation occurs on the surface of the component rough blank to obtain a color related to one or more types of metal oxides present on the surface of the component; on the other hand, oxidation occurs inside the component body, that is, oxidation reaches at least a certain depth so that it is no longer regarded as a part of the surface of the component. Step S4 is a chemical transformation of the material, especially on the surface of the rough blank. This step is different from the previous step S3, which includes machining the rough blank 12 of the watch case middle part to its final dimensions. This is different from the method described in CH718069, the last step of which is to remove material using a CNC numerical control machine tool or a laser.

[0068] The predetermined temperature cycle usually includes a temperature rise cycle, from about 20° C. to between 800° C. and 1200° C., preferably about 1000° C., within a time interval of 3 to 5 hours (preferably about 4 hours). The temperature rise cycle is followed by a temperature drop cycle, with the temperature dropping to about 20° C. within a time interval of 2.5 to 3.5 hours (preferably about 3 hours). This temperature cycle can, on the one hand, oxidize the rough surface so that it obtains a single uniform color c1 related to one or more types of metal oxides present on the rough surface; on the other hand, oxidize the underlying material to a thickness of preferably 50 to 300 μm.

[0069] The oxidation operation is followed by a step S5, the purpose of which is to selectively remove the entire thickness of the oxide layer on and near the surface of the part, following one or more arbitrary decorative shapes, in this case three stars 18a, 18b, 18c, so as to reveal the ceramic in a reduced state beneath the oxide layer, corresponding to the grey tone n1.

[0070] For example, the oxide layer can be selectively removed by conventional machining, or for highly detailed patterns, a laser source can be used as a machining tool.

[0071] Therefore, the case middle frame 10 obtained by the method of this embodiment has an overall visual appearance, including a substantially uniform surface, which presents a bright color according to the presence of one or more metal oxides on the surface of the component, and one or more decorations 18a, 18b, 18c presenting a gray tone n1, which corresponds to the underlying ceramic in a reduced state.

[0072] According to a variant not shown, the depth of material removal varies along the trajectory over the thickness of the oxide layer so as to display a color gradient corresponding to the different degrees of oxidation of the oxide or oxides present in the composition p1 .

[0073] According to the third embodiment, referring to Figures 3a to 3d The method for manufacturing a ceramic component comprises a first step S1, comprising filling a mold (not shown) with three compositions p1, p2, p3, each of which comprises a ceramic powder (preferably zirconium oxide, in particular yttrium stabilized zirconium oxide) and at least one different metal oxide. The three compositions p1, p2, p3 are distributed in the mold without mixing with each other. Each composition p1, p2, p3 may comprise one or more different metal oxides.

[0074] According to the method described in the first embodiment, the SPS sintering operation S2 is performed to obtain Figure 3bThe case middle frame blank 12 in the reduced state as shown. The SPS sintering operation presents three uniform gray tones n1, n2, n3, which converge at two interfaces. A machining operation S3 is performed on the sintered part to obtain the final dimensions of the case middle frame blank 14 of a predetermined shape, as Figure 3c shown.

[0075] Then, as Figure 3d shown, an oxidation operation S4 is performed on the entire surface of the blank 14. The oxidation of the regions presenting three different gray tones results in three different bright colors c1, c2, c3. As described in the previous two embodiments, step S4 is a chemical conversion of the surface material of the blank. This step is different from the previous step S3, which machines the case middle frame blank 12 to its final dimensions.

[0076] After the oxidation operation is operation S5, which includes selectively removing the oxide layer to form a decoration including one or more patterns. Figure 4a and 4b show the case middle frame 10 obtained by the method according to this embodiment, having three different bright colors and two decoration examples on its overall surface. Figure 4a The case middle frame 10 shown includes a decoration in the form of a groove 18 on its side, and the three gray tones n1, n2, n3 appear in sequence along the groove 18. Figure 4b The case middle frame 10 shown includes a decoration in the form of three different patterns on its side, such as three star patterns 18a, 18b, 18c, presenting the three gray tones n1, n2, n3 respectively.

[0077] Figures 5a to 5d A fourth embodiment is shown, where the first three steps S1, S2, and S3 are the same as the first three steps of the previous embodiments. As Figure 5c shown, the surface of the blank 14 of a predetermined shape is then selectively oxidized in step S4 according to one or more arbitrary patterns 18 to form a decoration within the regions containing the three gray tones n1, n2, n3. The oxidation can present three bright colors c1, c2, c3, which are specific to one or more types of metal oxides present in different compositions p1, p2, p3. This chemical transformation of the surface material of the blank 14 is also different from the previous step S3, which machines the case middle frame blank to its final dimensions.

[0078] The case middle frame 10 obtained by the method according to this embodiment has an overall visual appearance, including a surface having three gray tones n1, n2, n3 and one or more decorations presenting three bright colors c1, c2, c3.

[0079] According to Figures 6a to 6eIn another embodiment shown, the first three steps S1, S2, and S3 are the same as the first three steps of the method of the second embodiment. After the machining step S3, an optional step S4 can be carried out, including surface treatment (as described above), to obtain one or more surfaces with a specific finition type on the side of the middle case of the watch case. After the machining step S3 or the surface treatment step S4, an oxidation step S5 is carried out on the central part 20 of the middle case of the watch case by spraying an oxygen plasma jet. The overall surface of the obtained middle case 10 of the watch case presents a bright color c1, while the part 22 (a part 22 including the lugs) presents a gray tone n1.

[0080] Reference Figures 7 - 9 , the spraying of the oxygen plasma jet is carried out using a nozzle that generates the plasma jet 30. The middle case 10 of the watch case or the plasma jet 30, particularly the nozzle of the spraying jet, can be moved, thereby causing a relative movement of the plasma jet on the central part 20 of the middle case of the watch case. In a preferred embodiment, the nozzle or the middle case 10 of the watch case can be moved to change the distance between the plasma jet 30 and the middle case of the watch case. More specifically, the distance between the effective diameter of the plasma jet (which is basically conical) and the middle case of the watch case is changed, and actually the distance d between the nozzle and the middle case of the watch case is changed. This change in distance can, on the one hand, change the degree of oxidation of the central part 20 to present a color gradient, and on the other hand, make the part 22 including the lugs present a gray tone.

[0081] It should be noted that regardless of the envisioned embodiment, the oxidation operation using a laser beam and / or the plasma jet 30 can be used to obtain a selected or even random pattern on the surface of the blank 14 with a predetermined shape, or to obtain flat areas. These flat areas can consist of uniform, gradient, or mixed surfaces or regions. The above-mentioned patterns also apply, and they can also be formed entirely or partially outside or inside these regions.

[0082] Although the method is mainly described for manufacturing the middle case of a technical ceramic watch case, it can also be applied to other ceramic components without departing from the invention defined by the claims. For example, the method can be applied to any type of watch component, particularly to the movement components visible from the back of the watch case through a sapphire glass, or to the decorative components in the fields of watches and jewelry.

Claims

1. A method for producing a technical ceramic component (10), comprising the following steps: i) disposing in a mold at least one ceramic powder composition (p1; p1, p2; p1, p2, p3) comprising at least one metal oxide; ii) performing an SPS sintering cycle to obtain a green body (12) of the ceramic component, the green body having at least one grey shade (n1; n1, n2; n1, n2, n3) on the surface of the component; iii) machining the green body (12) to obtain a green body (14) of a predetermined shape; characterized in that after step iii) there is an additional step iv) comprising an oxidizing operation on the green body (14) of the predetermined shape to obtain on the surface of at least a first part of the ceramic component (10) at least one color (c1; c1, c2; c1, c2, c3) resulting from the oxidation of the at least one metal oxide, the surface of a second part of the ceramic component (10) presenting the at least one grey shade.

2. The method according to claim 1, wherein step i) comprises disposing a first composition and a second composition (p1, p2) in the mold, the compositions each comprising ceramic powder and different metal oxides, so as to obtain a first grey shade and a second grey shade (n1, n2) after step ii).

3. The method according to claim 1, wherein step i) comprises filling the mold with at least three compositions (p1, p2, p3), each composition comprising ceramic powder and different metal oxides, so as to obtain three grey shades (n1, n2, n3) after step ii).

4. The method according to any one of the preceding claims, wherein the oxidizing operation in step iv) is carried out by a laser beam or a plasma jet (30) supplied with an oxygen stream.

5. According to the method described in the preceding claim, wherein, At least one of the laser beam and the plasma jet (30) is used to implement a pattern with a certain level of detail, the resolution of the pattern depending respectively on the beam diameter or the effective diameter of the plasma jet (30).

6. The method according to claim 4 or 5, wherein the oxidizing operation comprises oxidizing at least on the surface of one or more selected different regions of the ceramic component.

7. According to the method described in the foregoing claims, wherein, Oxidizing the said selected one or more different regions of the ceramic component results in the formation of one or more patterns (18) of a predetermined shape, the patterns presenting at least one color (c1, c2, c3), depending on the metal oxides comprised in the oxidized regions of the ceramic component.

8. The method according to any one of claims 5 to 7, further comprising a surface treatment operation on at least one region of the green body (14) of the predetermined shape between steps iii) and iv) to obtain at least one treated surface (16), wherein the oxidizing operation is carried out on one or more regions (16) on which the surface has been pre-treated.

9. The method according to claim 4, wherein a relative movement is caused between the plasma jet (30) or the laser beam and the blank (14) of a predetermined shape, while changing the distance between the plasma jet (30) and the blank or the power of the laser beam, to obtain a change in the degree of oxidation of the first part of the ceramic component, so as to exhibit a color gradient.

10. The method according to any one of claims 1 to 3, wherein the oxidation operation in step iv) is carried out by placing the blank (14) of a predetermined shape in an oxygen furnace or an air furnace and subjecting it to a predetermined duration and temperature cycle, such that on the one hand, oxidation occurs on at least a part of the surface of the blank (14) to obtain a color that depends on the metal oxides present on the surface of the blank (14), and on the other hand, oxidation occurs to a predetermined depth within the body of the blank. After the oxidation operation, an operation of selectively removing the oxide layer is carried out to reveal at least one gray tone (n1, n2, n3) and / or a color gradient (c1, c2, c3).

11. The method according to the preceding claims, wherein the predetermined temperature cycle includes a heating cycle in which the temperature rises from about 20 °C to between 800 °C and 1200 °C within a time interval of 3 to 5 hours, and then a cooling cycle in which the temperature is lowered to about 20 °C within a time interval of 2 hours 30 minutes to 3 hours 30 minutes, so as to oxidize on the one hand at least a part of the surface of the blank (14) to obtain a color that depends on the metal oxides present on the surface, and on the other hand, oxidize the underlying material to a thickness of 50 to 300 microns.

12. The method according to claim 10 or 11, wherein the material is removed according to a predetermined pattern, and the depth of removal exceeds the depth of the oxidized body of the blank (14) to expose one or more gray tones (n1, n2, n3).

13. The method according to claim 10 or 11, wherein the material is removed along a trajectory in the oxidized body according to a predetermined pattern and variable depth to display a color gradient (c1, c2, c3).

14. The method according to any one of the preceding claims, wherein the SPS sintering cycle is carried out at a temperature between 1100 and 1300 °C and within a time interval of 10 to 45 minutes.

15. A component for a timepiece or a jewelry item, which is obtained by the method according to any one of the preceding claims.

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