Manufacture of multicoloured ceramic component

Abstract

SOLUTION: A method for manufacturing a ceramic timepiece component includes the steps of: manufacturing an intermediate component (E1) in the form of a green body based on ceria-zirconia; totally or partially debinding (E2) the intermediate component to obtain a debound intermediate component; partially impregnating (E3) the debound intermediate component with at least one solution comprising at least one metal salt, on one portion only of its surface, to obtain an impregnated debound intermediate component; sintering and thermally treating (E4) the impregnated debound intermediate component by performing at least one heat treatment under a reducing atmosphere (E42; E41').SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a watch part made of a zirconia-based, two-color or multicolor ceramic, more particularly a watch part made of a sintered technical ceramic. The invention also relates to a watch comprising said watch part. The invention finally relates to a method for producing a watch part made of a zirconia-based, two-color or multicolor ceramic. [Background technology]

[0002] In the field of watchmaking, as in jewellery, it is known to use components made of technical ceramics, also called more simply ceramics. The adjective "technical" refers to the high performance properties of the selected ceramic. In particular, these technical ceramics are capable of achieving very high mechanical, thermal or electrical and / or biochemical properties, as well as chemical inertia and diamagnetic properties, which make them suitable for forming watch components, in particular watch movement components, but also small watch external components. Technical ceramics differ from conventional ceramics by reason of their composition, since they are derived from purified synthetic powders, rather than natural mineral powders, such as feldspar or kaolin.

[0003] Among technical ceramics, zirconia-based ceramics are commonly used due to their high mechanical properties. However, one drawback of zirconia-based ceramics is that they are naturally in the form of white bodies. One of the requirements in watchmaking is an attractive appearance of the material used, which necessarily includes color. In the prior art, there are several steps to color such ceramics, for example with color pigments, which complicates the manufacturing process while adding other drawbacks. Among other things, limitations in the use of these ceramic components are due to the difficulty or impossibility of obtaining certain colors and especially some color combinations, for example red and black. More generally, there is a difficulty in obtaining the same uniform, predictable and reproducible color. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Swiss Patent Application Publication No. 707424 [Non-patent literature]

[0005] [Non-Patent Document 1] "Technical Report of Colorimetry", CIE 15, 2004 Summary of the Invention [Problem to be solved by the invention]

[0006] A general object of the present invention is therefore to propose a solution for manufacturing ceramic components, in particular for watches, which does not have the drawbacks of the prior art.

[0007] More specifically, a first object of the invention is to propose a solution for the production of ceramic parts, which makes it possible to obtain ceramics with a controlled colour, in particular multicoloured, in particular bicoloured, in particular red and black results.

[0008] A second object of the invention is to propose a solution for the production of ceramic components with a reliable and reproducible color.

[0009] A third object of the invention is to propose a solution for the production of ceramic components which is simplified as much as possible and makes it possible to obtain ceramics with suitable technical properties compatible with their use as watch components. [Means for solving the problem]

[0010] To this end, the present invention provides Producing an intermediate part in the form of a ceria-zirconia based green body; fully or partially debinding said intermediate part to obtain a debound (sometimes also referred to as "debound") intermediate part; impregnating said debinding intermediate part locally, only on a part of its surface, with at least one solution comprising at least one metal salt to obtain an impregnated debinding intermediate part, sintering and heat treating the impregnated and debound intermediate part by at least one heat treatment step in a reducing atmosphere, Including steps, Based on the manufacturing method of ceramic watch parts.

[0011] The invention also relates to a ceramic watch part which is based on ceria-zirconia, is a monolithic, cast, one-piece part and comprises at least a first portion of a first colour and a second portion of a second colour different from said first colour, in particular being bicoloured, comprising a first colour of red and a second colour of black, or multicoloured.

[0012] The invention is more particularly defined in the claims.

[0013] The subject matter, features and advantages of the present invention will be explained in more detail in the following non-limiting description of one particular embodiment, given with reference to the accompanying drawings. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a flow chart of the steps of a method for manufacturing a ceramic watch component according to one embodiment of the present invention. [Diagram 2] 2a to 2c illustrate the evolution of temperature as a function of time for three examples of heat treatment according to three variants of embodiment of the invention. [Diagram 3] FIG. 3 illustrates a bezel disc obtained after a step of sintering in an oxidizing atmosphere, corresponding to a first sub-step of heat treatment, according to a first example of an embodiment of the present invention. [Figure 4]FIG. 4 illustrates the bezel disk of FIG. 3 obtained after a step of heat treatment under a reducing atmosphere, corresponding to the second sub-step of heat treatment according to a first example embodiment of the present invention. [Diagram 5] FIG. 5 includes two tables detailing several ceramic properties obtained from various exemplary embodiments of the present invention. [Figure 6] FIG. 6 illustrates bezel discs obtained according to an embodiment of the invention from raw materials containing different proportions of cerium oxide and alumina. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, a ceramic part means an element made of a material that mainly comprises at least one high density ceramic. A "high density" ceramic is understood to mean a ceramic whose density is between 95% and 100% of the theoretical density of the material under consideration. In this specification, "ceramic" or "technical ceramic" means a high density material based on stabilized zirconium oxide.

[0016] Furthermore, "zirconia-based" is understood to mean a material that contains a predominantly zirconia component, in all cases at least 50%, or at least 75%, or at least 90% by weight. For example, the ceramic material according to the invention contains at least 50% by weight zirconia.

[0017] In all cases, the ceramics according to the invention (i.e., dense) are free of organic compounds. Thus, the general term "binder-added ceramic" (or sometimes "binder-added ceramic") refers to a composite material consisting of a ceramic and a binder, which generally consists of one or more organic compounds in various proportions. The term "green body" refers to a ceramic that has been binder-added and shaped. At this stage, the ceramic has not been fired.

[0018] A method for making a ceramic body according to an embodiment of the present invention includes the steps outlined below.

[0019] The first step of the manufacturing method according to one embodiment consists of producing an intermediate part E1 in the form of a ceria-zirconia based green body, said intermediate part being in its final or quasi-final shape. At this stage, the part is not sintered.

[0020] This first step may include the sub-steps described below.

[0021] In a first substep, the method for manufacturing a ceramic component comprises the preparation E11 of a raw material, namely a ceramic powder based on zirconia. According to one embodiment, the zirconia-based powder is made of cerium oxide CeO 2 Thus, the term "ceria-zirconia" is used to mean a zirconia-based ceramic powder or ceramic that contains at least 50% by weight of zirconia and cerium oxide. According to one embodiment, the cerium oxide is present in a weight percentage of between 3% and 6%, or between 3% and 5% of the total. Furthermore, the zirconia-based powder may contain yttria (or yttrium oxide) (Y 2 O 3 ) for example, yttrium oxide Y in a proportion between 1.4 mol % and 4 mol %, calculated relative to zirconia. 2 O 3 The proportion of yttria is stabilized by n(Y 2 O 3 ) / [n(Y 2 O 3 )+n(ZrO 2 ) where n is the amount of material. Finally, advantageously, the powder contains alumina, which is advantageous due to its effect on the final color. It may be introduced later in the process, as an alternative or in addition to its introduction into the zirconia-based powder at this stage. The proportion of alumina can vary, for example, between 0.1% and 1% by weight. This proportion influences the final color obtained, especially the hue and opacity.

[0022] A second substep of the manufacturing method consists of introducing E12 into the ceramic powder obtained in the first substep a binder, generally consisting of one or more organic compounds, thereby obtaining a binder-doped ceramic powder.

[0023] The third substep consists of the shaping of the ceramic part E13, making it possible to obtain an intermediate part. For this purpose, the first approach comprises a step of pressing the clusters of binder-added particles obtained at the end of the second substep. In such a method, the second substep prepares the binder-added ceramic powder in the form of spray-dried granules for pressing. The second approach consists of shaping by injection into a mould. In this case, the preparation obtained from the second substep is a binder-added ceramic powder, called "feedstock". The third approach consists of shaping by casting into a mould and subsequent drying, usually called slip casting. In this case, the preparation obtained from the second substep is a binder-added ceramic powder in a suspension, called slurry or slip. At the end of the third substep, a ceramic part is obtained, called green body as defined above, with a shape approaching the final shape and containing both ceramic powder and binder. Alternatively, other shaping techniques can be used, such as gel casting, freeze casting or other solidification casting techniques.

[0024] A second step of the embodiment consists of a total or partial debinding E2 of the intermediate part to obtain a debound intermediate part. The debinding applied to the intermediate part is - Heat treatment, or by treatment with a solution (solvent), which may for example be aqueous, or by combining a solution (solvent) and a heat treatment, in a mixed manner; This can be done in several ways. This step causes extraction of at least a part of the binder. For this reason, this step is full debinding or partial debinding. For further notational simplicity, this step is called "debinding". The resulting part is at least partially debinding. At this stage, the part forms a monolithic body, called debinding intermediate part. In addition to debinding, step E2 may optionally include a "pre-sintering" heat treatment that allows the start of densification (porosity reduction) of the part in order to reduce its brittleness during handling operations. During such a single heat treatment, debinding is carried out up to 450°C, and pre-sintering is considered to be carried out at a higher temperature. The term debinding is used in a broad sense, including additional pre-sintering.

[0025] A third step consists of locally impregnating E3 the debindered intermediate part with at least one solution comprising at least one metal salt, only on a part of its surface, in order to obtain a (locally) impregnated debindered intermediate part. The location of the impregnated area on the surface of the part is determinative of the aesthetics of the final result. The impregnated area may represent a geometrical part of the surface. The impregnated area may also completely cover one surface of the part or completely cover all surfaces of the part.

[0026] The impregnation step is carried out, for example, according to the method described in US Pat. No. 5,399,633. The impregnation step may include the use of an aqueous solution in which the additional element is present in the form of a metal salt. The impregnation step may be applied in various ways, for example manually or by inkjet printing. To obtain different colors, various aqueous solutions of salts (nitrates, chlorides, etc.) and metals (nickel, iron, cobalt, aluminum, etc.) can be used. For example, the metal salts may be selected from the elements Co, Fe, Mn, Ni, Al. In particular, the impregnation introduces salts into the ceramic, which then form reducible pigments. These pigments, depending on their nature, obtain different colors when reduced, as will be explained below based on certain exemplary embodiments. In particular, the pigments are colored orange, brown-gray and advantageously black. According to observations, the elements Co, Fe, Mn, Ni make it possible to obtain the black color. It has been observed that alumina, which was foreseen in the composition of the original ceramic powder for its effect on color, may alternatively or additionally be introduced into the debinding intermediate composition via the impregnation step, for example by using an aluminum salt. It has been observed that one or more different metal salts may be used for impregnation during the impregnation step. It has also been observed that the impregnation step may be carried out on an intermediate part that has not been completely debinding, where the final stage of debinding is carried out thereafter.

[0027] The fourth step of the method consists of heat treating E4 the (locally) impregnated, debindered intermediate part, sintering and reducing the intermediate part, in order to obtain a final or nearly final part.

[0028] As is known, sintering makes it possible to densify the part by removing the pores resulting from the debinding (or by continuing the removal of the pores, if step E2 comprises a presintering). Sintering consists of a heat treatment, more particularly a high-temperature firing.

[0029] The final mechanical properties and the final color of the part only appear at the end of the fourth step E4 and are the result of reactions between the various constituents of the part and the gases present in the furnace acting during the heat treatment. These reactions are complex.

[0030] According to a first embodiment, the fourth step of the heat treatment advantageously comprises at least two sub-steps carried out under different conditions.

[0031] In particular, the first substep consists of oxidative sintering E41, preferably in air. For this, a heat treatment is advantageously carried out at a temperature between 1400° C. and 1650° C. or between 1450° C. and 1550° C., with a thermal hold of at least 30 minutes. Alternatively, a heat treatment in any other oxidizing atmosphere may be carried out. It is noted that at the end of this first step, the impregnated and non-impregnated areas of the debindered intermediate part have different colors from each other. Moreover, these colors are neutral.

[0032] The method then comprises at least a second sub-step of heat treatment E42 of the part under a reducing atmosphere, which makes it possible to modify the color of at least one of the areas of the part. In particular, the complete or partial reduction of cerium oxide (from Ce+IV to Ce+III) makes it possible to form a brilliant red to orange color in at least one non-impregnated area of ​​the part. Furthermore, it has been observed that it is possible to obtain very dark colors in the impregnated areas, in particular black colors (in particular after impregnation with cobalt salts). Alternatively, it has also been observed that it is possible to obtain lighter colors in the impregnated areas, in particular orange colors (in particular after impregnation with aluminum salts). For this reason, the method according to the invention is particularly suitable for obtaining ceramics of a very attractive appearance, in two colors, in particular red and black or red and orange. In the second sub-step of heat treatment E42 of the part under a reducing atmosphere, a heat treatment is advantageously carried out at a temperature between 1200 ° C and 1550 ° C, or between 1350 ° C and 1500 ° C, with a thermal hold of at least 30 minutes. In E42, the atmosphere advantageously comprises hydrogen, in particular pure, or hydrogen as a mixture with, for example, nitrogen, or hydrogen together with an inert gas, such as argon. At the end of the second sub-step of the reduction heat treatment, a final color is obtained, which differs from the intermediate color.

[0033] Figure 2a illustrates the temperature evolution as a function of time for the two sub-steps E41 and E42 according to the first embodiment described above. At the end of the first sub-step E1, the part is cooled down to room temperature RT before the start of the second sub-step E42.

[0034] It has been observed that alternatively, the two sub-steps E41 (oxidative sintering) and E42 (reducing heat treatment) may follow each other without the need to cool the part down to room temperature. For this reason, the entire step E4 can be carried out in the same furnace, where the gas can be exchanged (from an oxidizing atmosphere to a reducing atmosphere). This variant is shown in FIG. 2b.

[0035] It has been observed that, according to another variant, the two sub-steps E41 (with sintering objective) and E42 (with reduction heat treatment objective) can be combined into a single step of reduction sintering E41', which variant is illustrated in Fig. 2c. In the reduction sintering step E41', a heat treatment is advantageously carried out at a temperature between 1400°C and 1650°C, or between 1450°C and 1550°C, with a thermal hold of at least one hour. Furthermore, the atmosphere advantageously comprises hydrogen, in particular pure, or hydrogen as a mixture, for example with nitrogen, or hydrogen together with an inert gas, such as argon.

[0036] In three variants of this embodiment, it is possible to obtain components or parts of components made of two-tone ceramic.

[0037] Optionally, the method for manufacturing a part may comprise an additional step consisting of creating recesses in the surface of the watch part (obtained from steps E2, E3 or E4), for example by means of a laser or a conventional tool. Optionally, the method may comprise an additional step consisting of coating all or part of the surface of the watch part obtained from the sintering step, in order to deposit a coating on all or part of the surface, for example in the recesses. Said coating step may be carried out by the physical vapour deposition (PVD) technique. The step makes it possible to deposit a metal, for example platinum, advantageously with an adhesion layer. Finally, the method may comprise other, optional, finishing steps, for example grinding and / or polishing and / or sandblasting and / or satin finishing steps.

[0038] Finally, the manufacturing method of the watch component according to the present invention has the following advantages. - The impregnation carried out makes it possible to obtain a coloration not only superficially, but throughout a considerable depth of the part, so that in the event of surface wear there is no influence on the color of the part. - at least two differently colored parts of the part are produced from one piece, in one piece cast form, in other words there is no weak joint or boundary between the two parts, as would be the case if the two colors were obtained by elements that were at least partly produced separately and then assembled. - Components made from zirconia-based sintered technical ceramics have high mechanical properties compatible with watchmaking applications, in particular high toughness and high fracture stress. Furthermore, ceramic components of various colors can be obtained in a simple and easily reproducible manner. - The impregnation with salts does not form a solid solution but a pigment during sintering, which allows to obtain a color opacity, so that the method is suitable for obtaining dark areas, more particularly black areas. In addition, the method works with several ceria-zirconia compositions, making it possible to obtain areas of red color, the precise color of which is controllable, depending notably on the proportion of cerium oxide and alumina used. As a result of this, the method is particularly suitable for producing zirconia-based ceramics that contain at least a black portion and a red portion. In addition, the method makes it possible to obtain sharp boundaries between areas of different colour.

[0039] The invention also relates to the material itself obtained by the manufacturing method according to the invention, and to a watch part made of a ceramic based on ceria-zirconia, i.e. a sintered technical ceramic based on ceria-zirconia, the material and the watch part comprising the material advantageously comprising at least a first part of a first colour and a second part of a second colour different from the first colour, in particular a first part of red and a second part of black.

[0040] By observation, the color of technical ceramics is measured by spectrophotometry. The measurements are performed in reflection with an aperture of 7 mm for a measurement diameter of 4 mm. The geometry of the measuring device corresponds to diffuse illumination and to the measurement of the spectrum at 8°. If the part does not have a sufficient planar area, a control pellet is used to perform the measurements. The reflection measurements are performed between 360 nm and 740 nm, and the color is evaluated with the assumption that the observer uses illuminant D65 at 10°. The lightness L* and the chromaticity values ​​a* and b*, the chroma C* and the hue angle h* are evaluated in the space defined by the International Commission on Illumination, CIE L*a*b*, as shown in [1]. The measurements are performed in the SCI (specular component included) and SCE (specular component excluded) modes. Furthermore, the spectrophotometric measurements are performed on parts with a polished surface finish, with a roughness defined by a normalized roughness parameter Ra, preferably equal to 2 nm ± 0.2 nm. By observation, the parameter Ra is measured according to the ISO 4287 standard.

[0041] Thus, more particularly, according to the above mentioned standardized approach, the invention makes it possible to form a multicolored ceramic watch part, which can include at least a portion of red color, defined by the following colorimetric parameters in SCI mode: L* between 47.5 and 54.1, or L* between 47.8 and 49.5, or L* between 48.0 and 49.2, and a* between 11.7 and 25.1, or a* between 14.4 and 17.7, or a* between 13.4 and 16.4, and b* between 5.2 and 15.5, or b* between 5.8 and 8.8, or b* between 5.9 and 8.0. Furthermore, the part can include at least a portion of dark color, in particular black color, defined by the following colorimetric parameters in SCI mode: L* between 47.5 and 54.1, or L* between 47.8 and 49.5, or L* between 48.0 and 49.2, and a* between 11.7 and 25.1, or a* between 14.4 and 17.7, or a* between 13.4 and 16.4, and b* between 5.2 and 15.5, or b* between 5.8 and 8.8, or b* between 5.9 and 8.0. L* less than 47.0, or L* less than 45.6, or L* less than 45.4, or L* between 43.0 and 47.0, or L* between 44.3 and 45.6, or L* between 45.0 and 45.4, and a* between -0.5 and 1, or a* between -0.1 and 1.0, or a* between 0.3 and 0.9, and b* between -1 and 1.6, or b* between -0.8 and 1.4, or b* between 0.3 and 1.1.

[0042] Moreover, the watch component comprising said material on a technical ceramic basis forms a one-piece cast shape and / or a one-piece moulding. The watch component is a one-piece part. In particular, there is no mechanical physical discontinuity between two parts of different colours, which may lead to fragility, as would be the case if two separate parts were assembled, for example by overmolding or bi-injection moulding or co-pressing methods, and if the two separate parts are assembled, there would still be a risk of unexpected separation of the two assembled separate parts, but this is not the case with the component of the present invention. The watch component has, in particular, a series of concentrations or chemical compositions of cerium, in addition to a series of zirconia. The component has a series of concentrations of at least these two elements (Zr and Ce) in its core, but not of additional elements, which is identical and continuous with respect to the different coloured parts of the watch component and is made of one-piece part. The core may be considered as an area of ​​sufficient depth in the material that is not affected by the above-mentioned colouring methods. Alternatively, impregnation parameters may be implemented that color the entire depth of the thin part. In addition, the watch part is shaped in a single manufacturing phase, so that the final shape can be achieved simultaneously for at least two different colored parts from the same raw material, for example the same ceramic part, and during the same sintering operation.

[0043] The ceria-zirconia based material of the invention advantageously contains a percentage by weight (meaning percentage by weight) of cerium oxide between 3% and 5%.

[0044] The invention naturally also relates to a watch component comprising said technical ceramic, sintered on a ceria-zirconia basis. The watch component may be a small watch bezel, a dial, a scale, a winding crown, a push piece or any other small watch external part or accessory for any watch movement. The watch component may be entirely made of a ceria-zirconia-based ceramic material or alternatively partially. For example, the watch component may comprise a body entirely made of a ceria-zirconia-based ceramic according to the invention, on which other separate elements are attached.

[0045] The invention also relates to a timepiece, in particular a wristwatch, comprising the sintered technical ceramic according to the invention or at least one timepiece component as described above.

[0046] Several examples of the practice of the present invention are described below.

[0047] According to a first embodiment, the watch part produced is a bezel disc.

[0048] The first step of the method includes the sub-steps described below, which correspond to the more general method described above. The first substep consists of selecting the raw materials: according to the present embodiment, the selection is directed to a zirconia-based ceramic powder stabilized with yttria (3 mol%) and containing cerium oxide (3 wt%) and alumina (0.1 wt%). A second substep of the method consists of incorporating a binder into the ceramic powder obtained in the first substep to obtain a feedstock material. The third substep consists of shaping the ceramic part by injection into a mould, obtaining a bezel disk made of ceria-zirconia, binder-doped, unsintered, constituting a green body, corresponding to the intermediate part according to the above nomenclature.

[0049] The second step consists in debinding the green body by heat treatment, in this case involving pre-sintering. Debinding and pre-sintering are carried out in a single heat treatment. The intermediate part is heated to at least 750° in an ambient air furnace for one hour.

[0050] The third step of the present invention is the impregnation step. For this purpose, an aqueous solution is used in which the additional element is present in the form of a metal salt. The impregnation can be carried out, for example, with 1 M Al(NO 3 ) 3 and 0.5 M Co(NO 3 ) 2 In order to obtain a solution with the composition 3 ) 3· 9H 2O, Co(NO 3 ) 2 6H 2 Impregnation is carried out here manually (alternatively it can be carried out by inkjet) using an aqueous solution of aluminum and cobalt salts obtained by dissolving O. The impregnation is carried out on one half of the ring that will form the future bezel disc.

[0051] Finally, the fourth heat treatment step involves sintering, first in ambient air, at 1480° C. with a thermal hold of 2 hours. At the end of this first heat treatment (forming the first sub-step of oxidation sintering), the bezel disc 1, shown diagrammatically in FIG. 3, is yellow in the non-impregnated locations 2 and blue in the impregnated locations 3 (the blue color is due to the presence of CoAl 2 O 3 formed from the cobalt salt introduced by impregnation). 2 O 4 In this embodiment, the bezel disc is then ground. The fourth heat treatment step then includes a second sub-step including a heat treatment in a reducing atmosphere. The bezel disc is then ground in a hydrogen atmosphere. 2 The ceria-zirconia is subjected to a heat treatment at 1400° in a reducing atmosphere consisting of argon and Argon (Ar) with a heat hold of 1 hour. The ceria-zirconia turns red at the end of the reducing heat treatment in the non-impregnated area 2. The impregnated area 3, which was blue at the end of the sintering in air, turns black, as shown in FIG.

[0052] Thus, at the end of the method according to the invention, the ceria-zirconia bezel disc is two-coloured: red in the non-impregnated areas and black in the impregnated areas.

[0053] In this embodiment, the bezel disc with the recesses 4 (see figures 3 and 4) (notably formed during injection) is then sandblasted and coated with a platinum deposition by PVD and then polished, so that the recesses have the colour of platinum and the bezel disc is bi-coloured, black and red.

[0054] Of course, the present invention is not limited to the aforementioned examples. To that end, the table shown in FIG. 5 illustrates additional examples (numbered 2 through 12) corresponding to various embodiments of the present invention. The differences between these examples are the composition of the ceramic powder and impregnation solution (nature, concentration, etc. of the metal salts), the temperature of debinding, the temperature of sintering in air (forming gas (hydrogen H ) for samples 2 through 5 and 12), and the temperature of sintering in air (forming gas (hydrogen H ) for samples 2 through 5 and 12). 2 and nitrogen N 2 The different parameters were modified, including the temperature of the reduction (for samples 6 to 11, it is carried out under a mixture of 20% hydrogen and 80% nitrogen) and for samples 7 to 10, in a mixture of 20% hydrogen and 80% nitrogen). The resulting color is measured by spectrophotometry, as described above. The results show that it is possible to obtain ceria-zirconia parts in two colors, here red (with several hues, even orange), on the one hand, and black (with several L*a*b*C*h* values), on the other hand. By observation, the surface of the part is polished. For this reason, the roughness of said polished surface is defined by the normalized roughness parameter Ra, which is equal to 2 nm ± 0.2 nm. Said parameter Ra is measured according to the ISO 4287 standard. The parameter indicates the (arithmetic) mean height of the roughness. Reference sample 12 is monochromatic, since it is not impregnated. The method may result in an embodiment of a two-color part, where the red portion is characterized by an L* between 48.3 and 49.4, an a* between 14.4 and 17.6, and a b* between 6.3 and 8.8 in SCI mode, and an L* between 20.5 and 24.0, an a* between 34.5 and 38.1, and a b* between 28.3 and 37.9 in SCE mode, and the black portion is characterized by an L* between 45 and 45.6, an a* between 0.3 and 0.9, and a b* between 0.3 and 1.3 in SCI mode, and an L* between 5.0 and 12.0, an a* between 1.4 and 5.7, and a b* between 5.5 and 10.8 in SCE mode.

[0055] In all examples, the zirconia used was stabilized with yttrium oxide with a proportion of 3 mol% yttrium oxide. This proportion can vary, for example between 1.4 mol% and 4 mol% without departing from the invention. Furthermore, the proportion of cerium oxide in the yttria stabilized zirconia can also vary. In these examples, a proportion of 3% by weight was chosen. The proportion of alumina in the matrix can also vary. In these examples, proportions of 0.1% and 0.5% by weight were chosen.

[0056] Figure 6 illustrates an example of the effect of varying the proportion of cerium oxide and alumina in the selected raw materials on the red color obtained after sintering in air with a thermal hold of 1470 °C for 2 hours, followed by reduction in a reducing atmosphere of forming gas with a thermal hold of 1400 °C for 1 hour. The part located on the left side of Figure 6 is a cerium oxide CeO with 5% by weight, which corresponds to Example 12 in the table of Figure 5. 2 and 1 wt% alumina Al 2 O 3 The part located on the right side of FIG. 6 is an orange-ish colored bezel disk 11 made of yttria-stabilized zirconia containing 3% by weight of cerium oxide CeO (which corresponds in terms of composition and heat treatment to the red areas of the parts constituting Examples 2 to 5 in the table of FIG. 5). 2 and 0.1% by weight of alumina Al 2 O 3 The bezel disc 12 is red and made of yttria stabilized zirconia containing .Observation showed that neither of the two parts was impregnated.

[0057] In addition to the elements mentioned above, several other production parameters also influence, in particular the color. The person skilled in the art can define these parameters depending on the result desired. The main ones are: - the gas atmosphere used for the reduction process, which may for example contain hydrogen in various proportions (from 5% to 100%) and various additional gases, in particular argon Ar and / or nitrogen N 2 The flow of gas within the chamber may also be variable. - sintering in air, or more generally in an oxidizing atmosphere, or alternatively in a reducing atmosphere (step E41'), advantageously at a temperature between 1400°C and 1650°C, and more particularly between 1450°C and 1550°C, and / or a heat hold of at least 30 minutes for E41, or at least 1 hour for E41'. - Duration of the sintering heat hold, which can vary from 30 minutes to several hours. a temperature of the reduction in the second heat treatment substep E42 in a reducing atmosphere, advantageously between 1200°C and 1550°C, and more particularly between 1350°C and 1500°C. The duration of the thermal hold for reduction is advantageously between 30 minutes and several hours for E42. - Molding method (injection, pressing, etc.). [Explanation of symbols]

[0058] 1 bezel disc 2 Non-impregnated area 3 Impregnation area 4 Recess 11 Bezel disc 12 Bezel disc

Claims

1. To manufacture an intermediate component in the form of a green body of ceria-zirconia groups (E1), To obtain a binder-free intermediate component, all or part of the intermediate component is binder-free (E2). To obtain an impregnated debinder intermediate component, a portion of the surface of the debinder intermediate component is locally impregnated with at least one solution containing at least one metal salt (E3). The impregnation debinder intermediate component is sintered and heat-treated by performing at least one heat treatment step (E42; E41') in a reducing atmosphere (E4). Steps including A method for manufacturing ceramic watch components.

2. The step of sintering and heat-treating the impregnation de-binder intermediate component (E4) is as follows: A first substep involves sintering the impregnation debinder intermediate component under an oxidizing atmosphere (E41), and thereafter, The second substep (E42) of heat treatment under a reducing atmosphere, including The method according to claim 1.

3. (E1) The step of manufacturing an intermediate component in the form of a green body made of ceria-zirconia uses ceramic powder of yttria-stabilized zirconia groups. The method according to claim 1.

4. The zirconia-based ceramic powder contains alumina in a weight proportion ranging from 0.1% to 1%. The method according to claim 3.

5. The step of sintering and heat-treating the impregnation de-binder intermediate component (E4) is as follows: A first substep involves sintering the impregnation debinder intermediate component under an oxidizing atmosphere (E41), and thereafter, The second substep involves heat treatment under a reducing atmosphere (E42), Includes, The first substep (E41) sintersects the impregnation debinding intermediate component in an oxidizing atmosphere, and / or heat-treats the impregnation debinding intermediate component by exposing it to a heat-hold at a temperature in the range of 1400°C to 1650°C for at least 30 minutes, and / or heat-treats it in a reducing atmosphere, and / or heat-treats it in a reducing atmosphere, and / or heat-treats it in a reducing atmosphere, The method according to claim 1.

6. The step of sintering and heat-treating the impregnation de-binder intermediate component (E4) includes a single step of reduction sintering (E41'), in which the impregnation de-binder intermediate component is subjected to heat holding for at least one hour in a reducing atmosphere at a temperature in the range of 1400°C to 1650°C. The method according to claim 1.

7. The step of partially impregnating the debinder intermediate component (E3) is performed using a solution containing at least one metal salt selected from the group consisting of Co, Fe, Mn, Ni, and Al. The method according to claim 1.

8. The step of sintering and heat-treating the impregnation de-binder intermediate component (E4) is as follows: Defined by the first colorimetric analysis parameter in SCI mode, L* in the range of 47.5 to 54.1, a* in the range of 11.7 to 25.1 5.2 to 15.5, a first non-impregnated surface portion having at least one red color, and / or Defined by the second colorimetric analysis parameter in SCI mode, L* smaller than 47.0, a* in the range of -0.5 to 1, The second dark portion within at least one impregnated surface area is b* in the range of -1 to 1.6, It is possible to form multi-colored ceramic watch components, Spectrophotometric values ​​are based on measurements performed on parts with a polished surface finish. The method according to claim 7.

9. An additional step of covering all or part of the surface of the watch component obtained from the sintering step, and / or Additional steps of grinding and / or polishing, and / or Additional steps of sandblasting, and / or Satin finish additional step including, The method according to claim 1.

10. At least a first portion of the first color, Including at least a second part of a second color different from the first color, It is a ceria-zirconia base, a single-piece cast part, and a two-color or multi-color ceramic watch component. A ceramic watch component in which the first color is red and the second color is black.

11. comprising at least one continuous core portion in a mechanical and / or concentration sense, wherein the core portion extends from the at least one first portion to the at least one second portion. The ceramic watch component according to claim 10.

12. The first part and the second part are obtained from the same powder formed by the same operation and heat-treated by the same operation. The ceramic watch component according to claim 10.

13. Contains cerium oxide in a weight percentage ranging from 3% to 5%. The ceramic watch component according to claim 10.

14. The first part is defined by the first colorimetric analysis parameter of the SCI mode, L* in the range of 47.5 to 54.1, a* in the range of 11.7 to 25.1 The red portion is b* in the range of 5.2 to 15.5, and / or The second part is defined by the second colorimetric analysis parameter of the SCI mode, L* smaller than 47.0, a* in the range of -0.5 to 1, The black area is b* in the range of -1 to 1.

6. Spectrophotometric values ​​are based on measurements performed on parts with a polished surface finish. The ceramic watch component according to claim 10.

15. Small watch bezels, dials, markings, winding crowns, push pieces, or other small external watch parts or replacement parts for watch movements. The ceramic watch component according to claim 10.

16. A watch or jewelry part, including the ceramic watch component described in claim 10.

17. The step of sintering and heat-treating the impregnation debinder intermediate component (E4) comprises a single step of reduction sintering (E41'), The method according to claim 1.

18. The ceramic powder of yttria-stabilized zirconia groups comprises yttrium oxide Y₂O₃ in a calculated proportion ranging from 1.4 mol% to 4 mol% relative to zirconia, and cerium oxide in a weight proportion ranging from 3% to 6%. The method according to claim 3.

19. The first substep of sintering the impregnation debinder intermediate component in an oxidizing atmosphere (E41) is to expose the impregnation debinder intermediate component to heat holding at a temperature in the range of 1450°C to 1550°C for at least 30 minutes. The method according to claim 5.

20. The second substep of heat treatment in a reducing atmosphere (E42) is to expose the impregnation debinder intermediate component to heat holding for at least 30 minutes in a reducing atmosphere containing H2 at a temperature in the range of 1350°C to 1500°C. The method according to claim 5.

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