CH719782A2 - Metal-ceramic hybrid part. - Google Patents

Abstract

The present invention describes a method for manufacturing a composite part comprising a metallic material (100) and a ceramic material (200) forming an inseparable whole and in which the metallic material remains distinct from the ceramic material. Metallic and ceramic materials are selected in the form of separate powders and then arranged in an orderly manner in a mold before being subjected to a sintering operation. The resulting part may be involved in one or more other machining, grinding, finishing and packing steps. The present invention also covers a composite part resulting from such a process, for example a watch movement part.

Description

Technical area

[0001] The present invention relates to a composite part consisting of, or comprising, one or more ceramic materials and at least one metal, in which the metal and the ceramic material(s) form an inseparable whole while remaining distinct from each other. the other. The composite part consists for example of a watch movement part such as a balance bridge, but can designate any other part having a dual mechanical and aesthetic function, particularly in the field of watchmaking, medical devices or aeronautics. The present invention further relates to a method of manufacturing such a part.

State of the art

[0002] In the watchmaking field, the mechanical performance of parts and their aesthetic quality are often two closely linked aspects. Concerning aesthetic characteristics, mixtures of shapes and colors can be obtained in ceramic materials thanks to a metallic coating. Patent CH707121, for example, describes a process in which a ceramic body is coated with a metallic material which can then be machined to perfect its aesthetic appearance. This process can, however, lead to materials of great hardness and whose impact resistance and elasticity may not meet mechanical requirements. In addition, such a process only allows thin metal layers, which limits its functionality. In addition, the entire surface of the ceramic body must be treated as a whole, which prohibits any decorative pattern located only on part of its surface.

[0003] Document US2019302697 describes a method based on the use of one or more sacrificial layers requiring chemical ablation of part of the coating.

[0004] There are so-called ceramization processes, consisting of depositing a layer of ceramic on a body made of another material. In this case, the aesthetic effects are limited due to the impossibility of using pigments.

[0005] Steel hardening treatments, used to give a part the required mechanical properties, are most often limited to the surface of the part and also do not offer a choice of colors.

[0006] It is often useful to obtain parts having locally specific characteristics different from the rest of the part, and which do not affect the overall properties of the part in question, whether they are mechanical or aesthetic. This is particularly the case for ceramic parts in which a decorative element or a rolling axis must be embedded. Existing processes, such as those mentioned above, suffer from the shortcomings mentioned. The addition of decorative or functional elements to such parts is usually carried out by gluing, which lacks precision and resistance over time. In the case where a material less hard than ceramic is used, such as a metallic material, making it possible to embed a decorative or functional element, coloring of this material is necessary, which can be carried out via different processes such as such as ALD, PVD, galvano, anodizing (anodizing) or oxidation. These processes are not conducive to localized aesthetic effects. In addition, the final appearance of the piece is not identical to the appearance of ceramic and certain colors, such as white, cannot be obtained.

[0007] Existing composite materials, known under the term cermet, involve the mixing of ceramic and metallic materials in the form of powders. The mixture obtained is homogeneous and does not allow the different constituents to be distinguished. Localized aesthetic effects are then impossible or very difficult. In addition, their mechanical properties are close to those of ceramics. The hardness of the parts obtained on the basis of such composite materials limits their applications, particularly when it comes to embedding other elements such as a ruby, or a rolling axle.

Brief summary of the invention

[0008] There is therefore scope for developing new processes making it possible to produce mechanical parts with a greater variety of aesthetic effects, without affecting their mechanical properties, or even improving them. In particular, it is a question of proposing a process allowing localized aesthetic effects, on a portion of a surface of the part.

Another aim of the present invention is to propose a method making it possible to produce a mechanical part made of distinct materials. In particular, the process makes it possible to obtain a mechanical part having locally mechanical properties different from its overall properties, particularly in terms of hardness, elasticity and impact resistance.

Another aim of the present invention is to propose a process for manufacturing mechanical parts containing several distinct materials without using sacrificial layers or chemical ablation.

Another aim of the present invention is to provide a mechanical part, such as a part of a watch movement, having mechanical and aesthetic properties locally distinct from its global properties.

[0012] According to the invention, these goals are achieved in particular by means of the method and the part which is the subject of the independent claims and described in more detail in the claims which depend thereon.

[0013] This solution has the particular advantage compared to the prior art of allowing a greater diversity of decoration, in particular on a portion of the surfaces of the parts considered. It also makes it possible to produce composite parts locally presenting distinct mechanical and/or aesthetic properties.

Brief description of the figures

[0014] Examples of implementation of the invention are indicated in the description illustrated by the following figures: • Figure 1: Schematic view of part of the process according to the present invention • Figure 2: Schematic view of additional steps which can be involved in the process according to the present invention • Figures 3a, 3b, 3c, 3d, 3e: examples of composite parts produced according to the invention, based on a ceramic material and a metallic material • Figures 4a, 4b: Examples of composite parts produced according to the present invention, based on a metallic material and two distinct ceramic materials • Figures 5a, 5b: Examples of composite parts produced according to the present invention, based on a ceramic material and two materials distinct metallic

Example(s) of embodiment of the invention

[0015] The process of the present description is illustrated in Figures 1 and 2. The process is characterized by an ordered assembly, such as a juxtaposition and/or stacking, of different materials, each of the materials being in powder form , followed by a sintering step of all the different powders. The aforementioned assembly taking place in a mold in which each of said powder materials is directly in contact with at least one other powder material. In this case, the different materials are not previously formed and then deposited one on top of the other or assembled in their rigid state, but produced simultaneously during the sintering operation so as to give a hybrid part, or composite, forming an inseparable set of materials and where these materials remain distinct from each other.

[0016] In the present description the terms “hybrid” and “composite” are equivalent and apply to the parts of the present invention, comprising several different materials assembled in an inseparable manner while remaining distinct from each other, i.e. i.e. not mixed. The different materials designate at least one ceramic material and at least one metallic material, preferably one or more ceramic materials and a single metallic material.

The method comprises a step S1 of selecting one or more metallic materials 100, 110, in the form of one or more first powders 10. A metal material100,110 can be selected from all metals and alloys commonly used in the field of watchmaking or other fields depending on the needs. It can for example be selected from titanium, stainless steel, inconel, or any equivalent. Preferably, the present method comprises a step of selecting a single metallic material. Preferably, the only metallic material selected in step S1 is grade 5 titanium, or comprises grade 5 titanium.

[0018] The metallic material(s) selected in step S1 may be supplemented with non-metallic elements as required. Such non-metallic additives are preferably also non-ceramic. In particular, pigments or mineral additives may be included. Any additives are then preferably incorporated into the first powder(s)10 so as to form a homogeneous mixture.

[0019] The present method comprises a step S2 of selecting one or more ceramic materials 200, 210, in the form of one or more second powders 20. The ceramic material(s) may for example be of the zirconia type, which may or may not be doped with yttrium. The zirconia can for example be of the Y-TPZ type. They can be chosen from an alumina or a mixture of aluminas, or from other ceramic powders. It is also not excluded that a mixture of different types of ceramic constitute the second powder(s)20. Depending on the needs, the second powder(s)20 may be supplemented with non-ceramic elements, such as pigments, metal oxides or any other component deemed useful. Preferably the non-ceramic elements added to the second powder(s) are also non-metallic.

[0020] According to one embodiment, a single ceramic material or mixture of ceramic materials200 is selected during step S2 in the form of a second powder20. According to another embodiment, a first ceramic material or mixture of ceramic materials200 and a second ceramic material or mixture of ceramic materials210 different from the first ceramic material, are selected during step S2. In this case, they are each distributed into a separate powder, thus forming a first second powder20 and a second second powder20'. Either or both of these second powders may be independently additived as indicated above. It is understood that more than two different powders can be considered for ceramic materials. For example, 3 or 4 different second powders can be considered.

[0021] According to one embodiment, the metallic material 100 is titanium, grade 5, and the ceramic material 200 is Y-TPZ type zirconia.

The present process comprises a step S3 of orderly arrangement of the different powders. An ordered arrangement means that the different powders are juxtaposed or stacked, so as to come into contact with each other without mixing. Thus, a first powder10 can be placed in a mold30, typically a sintering mold. A second powder20 can be placed on top of the first powder10, or contiguously, or in a mixed arrangement in which the second powder20 is both partly contiguous to the first powder10 and superimposed on the latter, so as to produce an assembly powders2.

[0023] In the case where a first powder 10 and a second powder 20 are superimposed, they can completely cover each other, to produce a final part 1 whose two opposite faces are entirely made up of two different materials, as illustrated in Figures 3a and 3b. Alternatively, two layers can be superimposed so as to only partially overlap, which makes it possible to obtain final parts1 as shown in Figure 3c. Preferably, a second powder20 is placed on the first powder10 so as to only partially cover it, or placed next to a first powder10, so as to only adjoin part of its height. Thus, at least part of the first powder10 remains not obscured by the second powder20. The properties of the final part will thus be modified only on a portion of its exterior surface. A first powder10 may be sandwiched between two layers of a second powder20, or conversely, a second powder20 may be sandwiched between two layers of a first powder10. The intermediate layer can extend over the entire surface so as to remain visible on the edge of the powder assembly2 then on that of the final part1. Alternatively, the intermediate layer can be limited to part of the surface so as to be completely included inside the assembly of powders2, then inside the final part1, as shown in Figure 3d. In this case, the material corresponding to this powder, whether metallic or ceramic, remains distinct from the material forming the outer layers, although no longer visible from outside the part1. According to a possible embodiment, one or more steps can be provided, aimed at compacting one powder or several of the powders placed in the mold30. In particular, a powder used in the present process can be subject to local compaction, so as to create a relief, which can be filled with another powder. For example, a hollow can be printed in a powder using a suitable tool. The shape of the hollow can also be predetermined by the tool used. Alternatively or in addition to a compression step, reliefs can be created in a powder by digging using a suitable tool, such as a spatula, a point or any other relevant tool. Free figures can thus be produced there before sintering.

[0024] According to one embodiment, a first powder10 corresponding to a first metallic material 100 is combined with a first second powder20 and a second second powder20', each corresponding to a different ceramic material, in the assembly of powders2. The final part1 which results from such an assembly is represented for example in Figure 4a or Figure 4b. In the case of Figure 4a, the surface of a first powder 10 is partially covered by a first second powder 20 and partially covered by a second second powder 20'. The final part 1 then comprises two distinct ceramic materials 200 and 210 combined with a metallic material 100. In the case of Figure 4b, the surface of a first powder 10 is completely covered with a first second powder 20, which is completely covered with a second second powder 20'. The final part1 which results then comprises a stack of a metallic material 100, a first ceramic material 200 and a second ceramic material 210.

The powders can be juxtaposed. For example, a first powder10 can be placed in the mold30 and flanked on either side by one or more second powders20. An example of a part1 that could result is shown in Figure 3e, in which a metallic material 100 is flanked on either side by a ceramic material 200.

[0026] Alternatively or in addition, several metallic materials100,110 can be used. Figure 5a shows a final part1 resulting from an assembly of powders2 comprising a first metal powder10 and a second metal powder10' both flanked by a ceramic powder20. The final part 1 is thus a part made of a ceramic material 200 into which a first metallic material 100 and a second metallic material 110 are inserted. Alternatively, a second first powder 10' can be placed on a first first powder 10, so as to cover it entirely or only partially, and be covered with a second powder 20 to lead to a final part 1 illustrated by Figure 5b.

[0027] Those skilled in the art understand that all of the above arrangements can be combined and that other arrangements can be considered depending on the needs. It is also possible to repeat the operations described below one or more times with the same powders or different powders so as to obtain a repeated alternation of one or more of the powders used.

The present process comprises a step S4 of sintering the assembly of powders2 to produce a sintered part3, corresponding to a raw part, prefiguring the final part1. In other words, the sintering step S4 gives the powders placed in the mold their cohesion necessary to produce a rigid part, having its own shape. Sintering is carried out according to the usual practices known to those skilled in the art. The temperature and pressure conditions can be adapted depending on the nature of the powders and/or the expected final properties of the part1. According to one embodiment, the sintering step involves a temperature between 500°C and 2000°C, or between 600°C and 1600°C, or between 800°C and 1300°C. The process can be isothermal or include one or more temperature variations.

[0029] The sintering step S4 is preferably carried out under primary vacuum, i.e. at pressures of the order of 100 Pa to 300 Pa. The vacuum can be of constant value or include controlled variations, such as different thresholds or ramps of increasing or decreasing values.

[0030] The sintering step further comprises a mechanical pressure of between 10 N/mm<2> and 200 N/mm<2>, or between 20 N/mm<2> and 120 N/mm<2>, or around 50 to 80 N/mm<2>. The mechanical pressure can be constant or include controlled variations such as different thresholds or ramps of increasing or decreasing values.

[0031] Sintering is preferably carried out at a constant temperature of 600°C to 1600°C, under constant primary vacuum with a pressure of the order of 20 N/mm<2> to 120 N/mm<2>. Sintering can for example be carried out at 1000°C for 12 minutes under a primary vacuum and a mechanical pressure of 100 N/mm<2>.

The sintering conditions are those of Flash sintering, SPS (Spark Plasma Sintering).

[0033] The method includes a step of demolding S5 of the part thus obtained making it possible to dispose of the demolded sinter4. The part is removed from the mold according to the usual practices of those skilled in the art.

[0034] The process according to the present description may include one or more other stages of transforming the demolded sinter4 to result in a final part1. If the demolded frit4 has all the expected characteristics, it corresponds to the final part1 and does not require any additional steps.

[0035] Among the additional steps, the rectification step S6 makes it possible to rectify the dimensions of the part obtained after sintering or after another step of the process. In this case, the demolded sinter4 is characterized by the presence of at least one metallic material 100 having a dimension e1 and at least one ceramic material 200 having a dimension e2. The dimensionse1ete2 are taken from at least one external surface of the demolded frit4. For example, the demolded sinter 4 represented in Figure 1 comprises a metallic material 100 having an external surface 101 and a ceramic material 200 having an external surface 201, the two metallic 100 and ceramic 200 materials being joined by an interface 202. The dimensione1 then corresponds to the thickness of the metallic material100, taken between the interface202 and its surface101. The dimension2corresponds to the thickness of the ceramic material200, taken between the interface202and its surface201. The rectification step S6 leads to a variation, generally a reduction, of one and/or the other of the dimensions e1, e2 to lead to rectified dimensions se1', e2'. Grinding is not systematically necessary but can be useful for example if the desired thicknesses cannot be obtained in the assembly of powders2. This is particularly the case for thicknesses less than 0.5 mm.

The machining step S7 is an independent step, making it possible to transform the demolded sinter4 into a semi-finished part 5 comprising one or more machined portions40,50. Machining includes all the usual means such as grinding, mechanical machining, laser machining, water jet machining, drilling. The shape of the semi-finished part5 may then be different from that of the demolded sinter4.

The finishing step S8, consisting of finishing the part, is also independent. Finishing may involve one or more processes such as satin finishing, mirror polishing, guilloché, Côte de Genève, perlage, hammering and any other applicable procedure. Different processes can be applied to different materials of the part. For example, satin finishing can be carried out on the surface201 of the ceramic material200 and the Côte de Genève on the surface101 of the metallic material100, in particular where the metallic material is grade 5 titanium.

[0038] The filling step S9 makes it possible to fill the room 1 with at least one additional element, whether decorative and/or functional. The filling may consist, for example, of driving out a ruby in the metallic material 100 of part 1, in order to accommodate a mobile axis, particularly in the case where the metallic material is grade 5 titanium.

The different steps S6, S7, S8 and S9 can be applied independently of each other and according to needs.

[0040] The present description further covers a composite part1, comprising at least one metallic material 100 and at least one ceramic material 200 distinct from at least one metallic material 100 and combined in an inseparable manner. Preferably, the at least one metallic material 100 is limited to titanium, in particular grade 5 titanium. Alternatively, the at least one metallic material comprises titanium, in particular grade 5 titanium.

[0041] The at least one metallic material 100 and the at least one ceramic material 200 are in contact with each other via an interface 202. According to one embodiment, the interface 202 extends over an entire surface of each of the two metallic 100 and ceramic 200 materials in contact with each other. According to another embodiment, the interface 202 extends only over a reduced portion of a surface of one of the two metallic materials 100 and ceramic 200 and over an entire surface of the other of the materials in contact with each other. . According to another embodiment, the interface 202 corresponds only to a portion of a surface of each of the metallic 100 and ceramic 200 materials in contact with each other. The interface202 can be rectilinear or planar (Figure 3a) or present a three-dimensional surface (Fig 3b). The interface 202 may be parallel or generally parallel to one of the exterior surfaces 101,201. Alternatively, the interface 202 can be inclined relative to at least one of the exterior surfaces 101, 201 of the part 1. Preferably, at least one of the metallic100 and ceramic200 materials has at least one external surface101,201. The metallic material 100 has a dimension e1, e1', taken from its at least one external surface 101 and the ceramic material 200 has a dimension e2, e2' taken from its at least one external surface 201. The dimension e1, e1' of the metallic material 100 and the dimension e2, e2' of the ceramic material 200 preferably designate the thickness of the corresponding material.

[0042] A composite part 1 according to the present description may comprise one or more metallic materials 100, 110 included in one or more ceramic materials 200a, 200b, 200c, the metallic material(s) 100, 110 forming with the ceramic material(s) 200a, 200b, 200c several interfaces 202a, 202b, 204b, 204c (figures 3e, 5a). According to one embodiment, only a metallic material 100 is included in the ceramic material 200 at one location or at several different locations. For example, the only metallic material 100 inserted into the ceramic material is grade 5 titanium. The ceramic material(s) 200a, 200b can form several external surfaces 201a, 201b on either side of the metallic material(s) 100. Preferably, the metallic material(s) 100 comprise at least one external surface 101.

[0043] A composite part 1 according to the present description may comprise one or more metallic materials 100, 110 superimposed on one or more ceramic materials 200, 210 (Figures 4a, 4b). Preferably, a composite part1 comprises a single metallic material100, such as grade 5 titanium superimposed on one or two or more ceramic materials200,210. For example, a metallic material 100 may share a surface with two ceramic materials 200, 210 (Figure 4a) so as to establish a first interface 202 between the metallic material 100 and the first ceramic material 200 and a second interface 212 between the metallic material 100 and the second ceramic material 210. The first ceramic material has at least one external surface 201 and the second ceramic material 210 has at least one external surface 211. The first200and second210ceramic materials form an interface203between them.

[0044] Alternatively, the metallic material 100 and the first 200 and second 210 ceramic materials are all superimposed. The metallic material 100 forms an interface 202 with one of the first 200 and second ceramic material, which forms an interface 203 with the other of the first 200 and second 210 ceramic material (FIG. 4b). One or more of the interfaces 203 and 202 preferably extend only over a portion of the surfaces of the corresponding materials.

Preferably, in the embodiments presented above, the interface(s) extend over a restricted portion of a surface of one of the two corresponding materials in contact with one another, or on a restricted surface of the two corresponding materials in contact with each other. A restricted surface area designates for example less than two thirds, or less than half or less than a third or a surface area of the order of 10% or 20% of the surface area of the corresponding material. Thus, according to a first possible arrangement, part of the surface 130 of the metallic material(s) 100 remains free while another part of this surface is obscured by at least one other material. According to another possible arrangement, part of the surface 230 of the ceramic material(s) 200 remains free while another part of this surface 230 is obscured by at least one other material. Another arrangement consists of a combination of the two previous arrangements, where the two materials metallic100 and ceramic200 partially overlap.

Reference numbers used in the figures

[0046] 1 Composite part 2 Powder assembly 3 Sintered 4 Unmolded sintered 5 Semi-finished part 10 First powder 20, 20' Second powder 30 Sintering mold 40, 50 Machined portion 60 Trim element 100 Metallic material 101 External surface of the first metallic material 110 Second metallic material 101 First external surface 200, 200a, 200b Ceramic material 201, 201a, 201b External surface of the first ceramic material 202, 202a, 202b Interface between the first metallic material and the first ceramic material 203 Interface between the first and second ceramic materials 210 Second ceramic material 212 Interface between the second ceramic material and the first metallic material e1 Thickness of the metallic material e2 Thickness of the ceramic material e1' Rectified thickness of the metallic material e2' Rectified thickness of the ceramic material 51 Selection of one or more metallic materials 52 Selection of one or more ceramic materials S3 Orderly arrangement S4 Sintering S5 Demolding S6 Grinding S7 Machining S8 Finishing S9 Filling

Claims (10)

1. Method for manufacturing a composite part (1) comprising at least one metallic material (100) and at least one ceramic material (200) forming an inseparable whole in which the at least one metallic material remains distinct from the at least one ceramic material, comprising the steps of: – S1: selecting one or more metallic materials in the form of one or more first powders (10); – S2: select one or more ceramic materials in the form of one or more second powders (20); – S3: arrange in a mold (30) the one or more first powders (10) and the one or more second powders (20) so as to form an assembly of powders (2), in which the one or more first powders and one or more second powders are in contact with each other without being mixed; – 54: carry out flash sintering under conditions making it possible to obtain cohesion of said at least one or more first powders (10) so as to produce the one or more metallic materials (100) and to obtain cohesion of said at least one or more second powders (20) so as to produce the one or more ceramic materials (200) and to combine the one or more metallic materials (100) and the one or more ceramic materials (200) so as to form said composite part (1); – 55: unmold said composite part (1). 2. The method of claim 1, wherein said one or more metallic materials comprises, or consists of, titanium, such as grade 5 titanium. 3. Method according to one of claims 1 or 2, wherein said one or more second powders (20) are placed on said one or more first powders (10) so as to cover it at least partially, or are placed next to it. of one or more first powder (10), so as to adjoin at least part of its height. 4. Method according to one of claims 1 to 3, in which steps S1, S2 and S3 can be the subject of one or more iterations before proceeding to sintering step S4. 5. Method according to one of claims 1 to 4, wherein said one or more ceramic material is selected from zirconia, an alumina or a mixture of the two. 6. Method according to one of claims 1 to 5, wherein at least one of said one or more first powders (10) and one or more second powders (20) comprises one or more additives. 7. Method according to one of claims 1 to 6, in which the conditions necessary for sintering include a temperature between 600°C and 1600°C, a mechanical pressure between 20 and 120 N/mm<2>and, preferably, a primary vacuum. 8. Method according to one of claims 1 to 7, further comprising one or more of the steps – S6 for grinding the composite part (1) to the desired thicknesses, – S7 for machining the composite part (1), – S8 to complete the composite part (1), – S9 to fill the composite part (1). 9. Composite part (1), preferably timepiece, comprising at least one metallic material (100), preferably a single metallic material, and at least one ceramic material (200) forming an inseparable whole in which the at least one metallic material remains distinct from at least one ceramic material. 10. Composite part according to claim 9, in which the at least one metallic material and the at least one ceramic material form one or more interfaces (202, 202a, 202b, 212, 203) extending over a restricted portion of a surface (130, 230) of one of the corresponding materials or of two corresponding materials, in contact with one another so as to leave part of this surface (130, 230) free.