CH717261A2 - Non-magnetic watch component with wear resistance - Google Patents

Abstract

The present invention relates to a non-magnetic watch component comprising a substrate (4) made of a copper alloy, characterized in that at least part of the substrate (4) comprises on the surface a layer (5) comprising intermetallics Cu x Ti y. It also relates to the method of manufacturing this watch component.

Description

Field of the invention

The invention relates to a non-magnetic watch component intended for the movement or the dressing as well as to its manufacturing process.

Background of the invention

[0002] Hard and non-ferromagnetic metal alloys find applications in many fields, mainly for components subjected to strong mechanical and / or tribological stresses and having to remain insensitive to magnetic fields. This is particularly the case for many watch components, such as for example wheels, pinions, axles or even springs at the level of the movement. For the external cladding, it is also advantageous to obtain high hardnesses, for example for the caseband, the bezel, the back or even the crown. Indeed, a high hardness generally makes it possible to obtain better resistance to scratches and wear and therefore good durability of these components exposed to the external environment.

In metallurgy, different mechanisms make it possible to harden the alloys, depending on their chemical compositions and their thermomechanical histories. Thus, solid solution hardening, structural hardening, work hardening, martensitic transformation in steels, spinodal decomposition, or even hardening by reduction of the grain size (Hall Petch) are known. In the most remarkable alloys, several of these hardening mechanisms are taken advantage of simultaneously. However, non-ferromagnetic alloys which have hardnesses greater than 500 HV are rare. Moreover, such alloys are difficult to machine and almost impossible to deform, owing to their very high hardnesses and their very low ductilities.

[0004] Document EP 3 273 304 discloses a watch component, and more particularly a pivot axis, comprising at least a part made of a non-magnetic copper alloy comprising by weight between 10 and 20% Ni and between 6 and 12% of Sn. This alloy has a low intrinsic hardness of the order of 350HV. In order to increase the hardness, the external surface of the component is hardened by atom diffusion or by depositing a layer of TiN, diamond, etc., or even by an ion implantation process.

[0005] To date, there is still a need for new non-magnetic watch components exhibiting improved wear resistance and, where appropriate depending on the type of component, also improved tribological properties.

Aims of the invention

The aim of the present invention is to provide a watch component making it possible both to limit the sensitivity to magnetic fields and to obtain an improved hardness compatible with the requirements of resistance to wear and to shocks in the watchmaking field. while exhibiting improved tribological properties for components such as pivot pins, wheels, etc.

[0007] To this end, the invention relates to a watch component intended for the movement or for the dressing comprising a substrate made of a copper alloy, with at least part of the substrate comprising on the surface a layer of intermetallic CuxTiY . This component combines the advantages of the non-magnetic copper alloy and the hardness of the outer intermetallic layer for the most stressed parts resulting in improved wear resistance. In addition, the presence of the layer of intermetallics on the surface makes it possible to reduce the coefficient of friction in use.

The present invention also relates to the method of manufacturing said component which comprises the following steps: a) Provision of a substrate made of a copper alloy, at least part of said substrate already having substantially the final shape of the non-magnetic watch component, b) Depositing a layer of titanium on said part of the substrate, c) Diffusion heat treatment of titanium in the copper alloy to form a layer of Cux, Tiys intermetallics on said part.

This diffusion treatment makes it possible to obtain a hard outer layer which adheres perfectly to the substrate. Indeed, the layer of intermetallics forms a layer which is continuous with the substrate thanks to the diffusion of the titanium in the copper alloy of the substrate.

Brief description of the drawings

Other features and advantages will emerge clearly from the description which is given below, by way of indication and in no way limiting, with reference to the accompanying drawings, in which: FIG. 1 is a representation of a watch component, and more precisely of a balance axis, according to the invention; and FIG. 2 is a partial section of one of the pivots of the axis according to FIG. 1 coated with an outer layer of intermetallics.

Description of the invention

In the present description, the term “non-magnetic” alloy means a paramagnetic or diamagnetic or antiferromagnetic alloy, the magnetic permeability of which is less than or equal to 1.01.

[0012] The invention relates to a watch component intended for the movement or the covering. Thus, it may be a covering component chosen from the non-exhaustive list comprising a caseband, a back, a bezel, a push-piece, a bracelet link, a bracelet, a pin buckle and a crown. For the movement, there may be mentioned in a non-exhaustive manner an anchor board, a wheel board, a cog, an axle, an anchor rod and a pinion. More specifically, the horological component may be a pivot axis with at least a part of said axis such as a pivot, a screw, a winding stem or a stud having improved wear resistance and tribological properties thanks to the method. according to the invention.

The invention will be described below in the context of an application to a non-magnetic balance axis, generally referenced 1 for a watch component, as shown in Figure 1. The parts of this type present in body level with diameters less than 2 mm, and pivots with a diameter of less than 0.2 mm, with an accuracy of a few microns.

Referring to Figure 1, one can see the balance axis 1 according to the invention which comprises a plurality of sections 2 of different diameters, preferably formed by bar turning or any other machining technique by removing chips, and conventionally defining bearing surfaces 2a and shoulders 2b arranged between two end portions defining two pivots 3. These pivots are each intended to pivot in a bearing, typically in an orifice of a stone or ruby.

According to the invention and as shown in Figure 2, at least part of the watch component 1 and, in the example illustrated at least one pivot 3, is formed of a substrate 4 made of a non-magnetic metal alloy in order to limit its sensitivity to magnetic fields. This alloy is any copper alloy such as, by way of example, a CuNi, CuSn, CuZn, CuNiZn, CuNiSn, CuAI, CuAINi, CuAINiFe, CuBe or CuBePb alloy. More specifically, still by way of example, one can choose a CuNi15Sn8, CuNi9Sn6 or CuNi7.5Sn5 alloy from the CuNiSn and CuBe2 or CuBe2Pb alloys from the CuBe alloys. According to the invention, at least part of the substrate 4 comprises on the surface a layer of intermetallics CuxTiy, referenced 5. This layer of intermetallics comprises one or more of the following compounds: Cu4Ti, Cu2Ti, CuTi, Cu3Ti2, CuTi2, Cu4Ti3. It has a thickness of between 20 nm and 10 μm, preferably between 500 nm and 2.5 μm.

According to the invention, the layer of intermetallic has a hardness HV0.01 (load of 10g) greater than 400 HV0.01 and preferably greater than 500 HV0.01. As for the substrate, it has a hardness less than or equal to 400 HV0.01.

The method of manufacturing the watch component according to the invention comprises the following steps: Provision of the substrate in the copper (Cu) alloy with at least part of said substrate already having substantially the final shape of the watch component, Deposit of a layer of titanium (Ti) on said part, Diffusion heat treatment to at least partially transform said titanium layer into a CuxTiy intermetallic layer,

According to the invention, the substrate can be produced by any suitable technique: casting, rolling, powder metallurgy, additive manufacturing, etc., followed, if required to scale, by machining. It can be fully dimensioned before depositing the titanium layer. It is also conceivable that only a part of the substrate is dimensioned before the deposition of the titanium layer and that the rest of the component is dimensioned after the diffusion heat treatment. More specifically for a balance axis, at least the pivot is dimensioned by bar turning or any other machining technique by removing chips from copper alloy bars with a diameter of less than 3 mm, and preferably less than 2 mm before depositing the titanium layer.

The contribution of the titanium layer around the substrate can be achieved by galvanic route, PVD, CVD, ALD or any other suitable process. The deposited layer has a thickness of between 20 nm and 10 μm, preferably between 500 nm and 2.5 μm. The diffusion heat treatment is carried out in a temperature range of between 600 and 900 ° C for a time of between 30 minutes and 10 hours, preferably between 1 and 6 hours. According to a variant of the invention, the entire titanium layer is transformed into intermetallics. According to another variant of the invention, the titanium layer is only partially transformed into intermetallics, a titanium layer then remaining around the intermetallic layer. This residual titanium layer has a thickness of between 1 nm and 5 μm. It can be retained on the final product or removed by selective chemical attack or polishing.

[0020] The method may further comprise a heat treatment of volume hardening of the substrate, such as, for example, a hardening of spinodal decomposition for the alloys of the CuNiSn family or a structural hardening for the alloys of the CuBe family, in a temperature range of between 300 and 500 ° C, preferably between 320 ° C to 450 ° C, for a time of between 30 minutes and 3 hours, more particularly between 30 minutes and 1 hour 30 minutes. The hardening heat treatment first requires dissolving at high temperature the elements involved in hardening, Ni and Sn for a CuNiSn or Be alloy for a CuBe or CuBePb alloy, followed by quenching to keep the elements in solution before to carry out the hardening heat treatment. According to the invention, the diffusion heat treatment between 600 and 900 ° C. can be used to effect the dissolution. By way of example, for a CuBe2Pb alloy, the treatment of diffusion of Ti and of dissolving of Be is carried out at 800 ° C, the substrate is then rapidly cooled to a temperature below 200 ° C before be treated at 325 ° C for 3 hours for the precipitation of CuBe2. In general, the manufacturing process thus comprises, following the step of depositing a layer of titanium, the steps of: Heat treatment of diffusion of Ti and dissolution, for example of Ni and Sn for a CuNiSn alloy or of Be for a CuBe or CuBePb alloy, at a temperature between 600 and 900 ° C for a time of between 30 minutes and 10 hours, preferably between 1 and 6 hours, Quench to a temperature below 200 ° C, Curing heat treatment at a temperature between 300 and 500 ° C, preferably between 320 ° C to 450 ° C, for a time between 30 minutes and 3 hours, preferably between 30 and 90 minutes.

The manufacturing process can be finalized after the heat treatment of surface diffusion or hardening in volume if necessary, by a surface finishing step such as polishing or rolling.

Claims (20)

1. Non-magnetic watch component (1) comprising a substrate (4) made of a copper alloy, characterized in that at least part of the substrate (4) comprises on the surface a layer (5) comprising intermetallics CuxTiy. 2. Non-magnetic watch component (1) according to claim 1, characterized in that the copper alloy is chosen from the group comprising the alloys CuNi, CuSn, CuZn, CuNiZn, CuNiSn, CuBe, CuBePb, CuAI, CuAINi or CuAINiFe. 3. Non-magnetic watch component (1) according to one of the preceding claims, characterized in that the intermetallic layer (5) has a thickness between 20 nm and 10 microns, preferably between 500 nm and 2.5 microns. 4. Non-magnetic watch component (1) according to one of the preceding claims, characterized in that the intermetallic layer (5) has a hardness greater than 400 HV0.01, preferably greater than 500 HV0.01. 5. Non-magnetic watch component (1) according to one of the preceding claims, characterized in that the intermetallic layer (5) comprises one or more compounds chosen from the group comprising Cu4Ti, Cu2Ti, CuTi, Cu3Ti2, CuTi2 and Cu4Ti3 . 6. Non-magnetic watch component (1) according to one of the preceding claims, characterized in that the intermetallic layer (5) has on its outer surface a residual titanium layer. 7. Non-magnetic watch component (1) according to the preceding claim, characterized in that the residual titanium layer has a thickness between 1 nm and 5 microns. 8. Non-magnetic watch component (1) according to one of the preceding claims, characterized in that it is a component of the movement or of the casing. 9. Non-magnetic watch component (1) according to one of the preceding claims, characterized in that it is chosen from the group comprising an anchor plate, a wheel plate, a cog, an axis, an anchor rod. and a pinion. 10. Non-magnetic watch component (1) according to the preceding claim, characterized in that it consists of a pivot axis, said part being a pivot (3), a screw, a winding stem or a stud. 11. Non-magnetic horological component (1) according to one of claims 1 to 9, characterized in that it is chosen from the group comprising a caseband, a back, a bezel, a pusher, a bracelet link, a bracelet and a crown. 12. A method of manufacturing a non-magnetic watch component (1) comprising the following steps: a) Provision of a substrate (4) made of a copper alloy, at least part of said substrate (4) already having substantially the final shape of the non-magnetic watch component (1), b) depositing a layer of titanium on said part of the substrate (4), c) Diffusion heat treatment of titanium in the copper alloy to form a layer of intermetallics (5) Cux, Tiysur said part. 13. Manufacturing process according to the preceding claim, characterized in that the diffusion heat treatment is carried out at a temperature between 600 and 900 ° C for a time between 30 minutes and 10 hours, preferably between 1 and 6 hours. 14. The manufacturing method according to claim 12 or 13, characterized in that the substrate (4) is manufactured by casting, rolling, powder metallurgy or additive manufacturing optionally followed by machining. 15. The manufacturing method according to one of claims 12 to 14, characterized in that the titanium layer is deposited by galvanic route, by PVD, by ALD or by CVD. 16. Manufacturing process according to one of claims 12 to 15, characterized in that the titanium layer deposited has a thickness between 20 nm and 10 microns, preferably between 500 nm and 2.5 microns. 17. The manufacturing method according to one of claims 12 to 16, characterized in that it comprises a step of selective removal of the residual titanium layer remaining around the intermetallic layer (5) after the heat treatment of diffusion. 18. The manufacturing method according to one of claims 12 to 17, characterized in that it comprises a step of heat treatment of volume hardening of the substrate (4) carried out at a temperature between 300 and 500 ° C, preferably between 320 ° C to 450 ° C, for a time of between 30 minutes and 3 hours, preferably between 30 and 90 minutes, said step being carried out after step c). 19. The manufacturing method according to the preceding claim, characterized in that it comprises a quenching step to a temperature below 200 ° C between step c) of diffusion heat treatment and the heat treatment step of volume hardening. 20. Manufacturing process according to the preceding claim, characterized in that step c) of diffusion heat treatment is used to dissolve Ni and Sn for a CuNiSn alloy or Be for a CuBe or CuBePb alloy. .