CH706408A2 - Component, useful for applications in e.g. watch industry, comprises metal substrate, coating including metal valve covering whole or a part of substrate, and oxide layer obtained by anodization of coating - Google Patents

Abstract

The component (1) comprises a metal substrate (2), a coating (3) including a metal valve covering whole or a part of the substrate, and an oxide layer (4) obtained by an anodization of the coating to generate a color of the coating by interference. The substrate includes the metal valve. The coating has a thickness of greater than 1 mu m. An independent claim is included for a method for manufacturing a component.

Description

Technical area

The invention relates to a component based on a valve metal that can be colored, including a decorative item such as a dressing room for watches, jewelery or eyewear. The invention also relates to the same article for biomedical applications.

State of the art

[0002] The coloring of a titanium or titanium alloy piece may find application in various fields. Thus, in the medical field, titanium screws are often used, intended to be screwed inside the human body. Such screws may, by way of example, be used for fixing a pin to a bone. These screws can be of different shapes and sizes, the differences between the screws can be very small for a high accuracy in the choice of screws. Because of this precision, the differences between the screws are not necessarily easily visible to the naked eye. This is why it is known to provide titanium screws for surgical use of different colors depending on their shape and their dimensions, in other words their ribs; the color makes it possible to differentiate the screws between them. Such colored screws can be obtained by a coloring process.

The cladding parts for the watch in titanium or titanium alloy, such as boxes, squares, bracelet links, watch dials or the like, can also be colored for aesthetic reasons.

The coloring of a titanium or titanium alloy piece can be obtained by an anodic oxidation process. In such a process, the piece to be colored forms the anode of an electrolysis device. Potential is applied between this anode and a cathode and current is passed between the two. This results in an oxidation reaction at the anode, which results in the formation of a thin layer of oxide (from the metal of the part) on the surface of the part. Such an oxide layer has the property of being stained with light by diffraction; the nature of the diffraction depends in particular on the thickness of the oxide layer, which depends on the potential difference applied to the electrodes and the duration during which this potential difference is applied. Thus, depending on the potential difference and its duration of application, it is possible to form pieces of different colorations when exposed to visible light.

The oxide layers thus formed are however fragile and can be removed at least partially from the treated part, with a loss of the color of the part. In order to overcome this disadvantage, the colored oxide layers may be coated with a protective film comprising, for example, oxides such as SiOx, AlO and MnO.

In JP 62 284 097, a portion of a watchmaking piece is coated with titanium which is subsequently anodized to obtain a colored oxide film on the surface of the titanium coated portion. A transparent film is then coated on the colored piece to protect the colored oxide film. Such protective films can, however, alter the color of the oxide layer. Irregularities in color are also possible in the case where the protective film is not uniform in thickness.

Brief summary of the invention

An object of the present invention is to provide a colored component free of known limitations of the state of the art.

Another object of the invention is to provide colored component having good wear resistance and good tribological properties.

According to the invention, these objects are achieved in particular by means of the subject of the claims in the corresponding categories.

These objects are also achieved in particular by means of a component comprising a metal substrate, a layer comprising a valve metal coating all or part of the substrate, and an oxide film obtained by anodizing the layer, so as to generate a coloration of the layer by interference.

In one embodiment, the valve metal may comprise one of the metals: Ta, Ti, Al, Hf, Mg, Zr, Nb and W or an alloy of one or a combination of these metals. Preferably, the valve metal comprises Ta or a Ta alloy.

In another embodiment, the substrate may comprise a valve metal which may comprise one of the metals: Ta, Ti, Al, Hf, Mg, Zr, Nb and W, or an alloy of one or two a combination of these metals. The coating may have a thickness of between 0.05 μm and 10 μm, but preferably between 0.1 μm and 5 μm, or between 0.1 μm and 1 μm.

In yet another embodiment, the substrate comprises a stainless steel, brass or aluminum or an aluminum alloy, a plastic or a ceramic. The coating may have a thickness of greater than 1 μm.

The present invention also relates to a method of manufacturing the component, comprising: forming the coating on the substrate by a PVD, CVD, cathodic sputtering, thermal spraying, plasma spraying, or an electroplating method; and forming an oxide layer so that the thickness of the oxide layer is controlled.

The component according to the invention has a very good wear resistance, has good tribological properties and is biocompatible. The colored coating will retain its original appearance and original color even under conditions of use where the component is stressed in friction and is subjected to corrosive environments.

Brief description of the figures

Examples of implementation of the invention are indicated in the description illustrated by the attached figure schematically illustrating a section of the article according to one embodiment.

Example (s) of embodiment of the invention

In one embodiment, a component 1 is formed of a metal substrate 2 and a colored coating 3 coating all or part of the substrate 2. The colored coating 3 comprises a valve metal of which at least a portion comprises a layer of oxide 4. The thickness of the oxide layer 4 is adjusted so as to obtain an interferential coloration of the coating 3. The coating 3 may comprise a valve metal such as tantalum (Ta), zirconium (Zr), niobium (Nb), titanium (Ti), aluminum (Al), hafnium (Hf), magnesium (Mg) and tungsten (W). The valve metal may also comprise an alloy of one or a combination of at least one of the above metals. The substrate 2 also comprises a valve metal such as one of the above metals, or an alloy of one or a combination of the above metals. It goes without saying that the composition of the substrate is not limited to the metals and alloys mentioned above but may also include other metals, a plastic or a ceramic. Preferably, the coating 3 comprises Ta or a Ta alloy. Still more preferably, the coating 3 comprising Ta or a Ta alloy is formed on the titanium substrate 2 or an alloy of this metal.

The coating 3 may be formed on the substrate 2 by means of a suitable deposition process, such as a physical vapor deposition (PVD) method, chemical vapor deposition (CVD), CVD assisted by plasma, cathodic sputtering, thermal spraying, plasma spraying, or by a process of electrodeposition in an ionic liquid medium or sol-gel deposition.

The oxide layer 4 can be obtained by an anodizing or thermal oxidation process, the coating 3, so that the thickness of the layer 4 can be controlled sufficiently accurately to ability to obtain predefined interference colors.

By way of example, the anodizing process may comprise a step of preparing an electrolyte containing a polar solvent (such as water or an organic solvent) and a solute (salt, acid or base). The piece to be colored (substrate 2 and coating 3) forms the anode of an electrolysis device and a potential is applied between this anode and a cathode. An oxidation reaction at the anode results in the formation of a thin oxide layer 4 (from the valve metal of the coating 3) to the surface of the coating 3. Such an oxide layer 4 has the property of stain with light, by diffraction. The nature of the diffraction depends in particular on the thickness of the oxide layer 4, which depends on the potential difference applied to the electrodes and the duration during which this potential difference is applied. Thus, depending on the potential difference and its duration of application, it is possible to form pieces of different colorations when exposed to visible light. The anodizing voltage can therefore be controlled so as to control the thickness of the oxide layer 4.

The oxide layer 4 gives the coating 3 a coloration, by diffraction of the incident light in the oxide layer 4. The coloring is a function of the voltage applied during the anodic oxidation step. For example, in the case of an electrolyte containing 5% sulfuric acid, a voltage of 22V makes it possible to obtain a blue color, a voltage of 30V makes it possible to obtain a light blue color, etc .; that is to say, can produce an oxide layer with a thickness of about 2.5 nm per volt.

The anodizing step (oxidation reaction) may be preceded by a degreasing step to remove impurities on the surface of the coating 3 and a rinsing step. The anodizing process may also include a pickling step to remove a pre-existing oxide layer on the surface of the coating 3, possibly followed by a rinsing step to remove any residues from the pickling bath. The anodizing step may be followed by a rinsing step to remove any residues from the oxidation bath.

Alternatively, the oxide layer 4 can be obtained by a thermal oxidation process of the substrate 2 with the coating 3. In this case, the color of the oxidized coating will depend on the composition of the gas in the enclosure, the temperature of the heat treatment and the duration of this treatment.

When the substrate 2 comprises a valve metal such as titanium, the coating 3 may have a thickness which is between 0.05 microns and 10 microns. Preferably, on such a substrate, the coating 3 has a thickness of between 0.1 μm and 5 μm, or between 0.1 μm and 1 μm. For example, the coating 3 may have a thickness of 3.5 microns.

The coating 3 Ta or Ta alloy with the colored oxide layer 4 has a very good wear resistance. The component comprising the Ta or Ta alloy coating with the colored oxide layer 4, will retain its original appearance and its original color even under conditions of use where the coating 3 is stressed in friction and / or even subjected to corrosive environments. The coating 3 of the invention thus lends itself well to applications in the watch industry, such as dressing, as well as jewelery and eyewear. The coating 3 Ta or Ta alloy not only has good tribological properties, but is also biocompatible. Component 1 coated with such a coating 3 will therefore be suitable for biomedical applications. For example, in the case of a titanium screw comprising the tantalum coating 3 with the oxide layer 4, the friction between the screw and a plate of the implant will be facilitated.

In another embodiment, the substrate 2 comprises a stainless steel, brass, aluminum or an aluminum alloy, or a plastic or a ceramic. In this case, the coating 3 preferably has a thickness greater than 1 micron. On such a substrate, a thickness of the coating 3 greater than 1 μm is necessary in order to obtain a good seal of the coating vis-à-vis the substrate 2, and make the coating 3 sufficiently conductive so as to bring the anodizing current over the entire surface of the substrate. In the case of stainless steel, brass, aluminum or aluminum alloy, such a thickness of the coating 3 is also necessary in order to minimize the corrosion of the substrate.

In another embodiment, the coating 3 comprises a succession of layers of the valve metal 3 alternating with the oxide layer 4.

In yet another embodiment, the coating may comprise several oxide layers 4 of different thicknesses so that the coating comprises several colors. For example, the anodizing process may comprise at least two anodizing steps, the first of which is carried out under a relatively high voltage so as to form a first relatively thick oxide layer, and the subsequent steps under a lower voltage, after at least a portion of the previous oxide layer has been masked. In the unmasked portions thus form thinner oxide layers which make them appear in different colors.

Claims (12)

1. Component (1) comprising a metal substrate (2), a coating 3 comprising a valve metal coating all or part of the substrate (2), and an oxide layer (4) obtained by anodizing the coating (3), such as to generate a coloration of the coating (3) by interference. 2. The component (1) according to claim 1, wherein the valve metal comprises one of the metals: Ta, Ti, Al, Hf, Mg, Zr, Nb and W, or an alloy of one or one combination of these metals. 3. The component (1) according to claim 1 or 2, wherein the valve metal comprises Ta or a Ta alloy. 4. The component (1) according to one of claims 1 to 3, wherein the substrate (2) comprises a valve metal. 5. The component according to claim 4, wherein the substrate (2) comprises one of the metals: Ta, Ti, Al, Hf, Mg, Zr, Nb and W, or an alloy of one or a combination of these metals. 6. The component (1) according to claim 4 or 5, wherein the coating (3) has a thickness of between 0.05 microns and 10 microns, but preferably between 0.1 microns and 5 microns, or between 0.1 microns and 1 micron. 7. The component (1) according to one of claims 1 to 3, wherein the substrate (2) comprises a stainless steel, brass or aluminum, an aluminum alloy, a plastic or a ceramic. 8. The component (1) according to claim 7, wherein the coating (3) has a thickness greater than 1 micron. 9. The component (1) according to one of claims 1 to 8, for applications in watchmaking, jewelry, eyewear, and medical. 10. A method of manufacturing a component (1) according to one of claims 1 to 9, comprising: forming the coating (3) on the substrate (2) by a PVD, CVD, cathodic sputtering, thermal spraying, plasma spraying, or electroplating method; and forming an oxide layer (4) so that the thickness of the oxide layer is controlled. The method of claim 10, wherein forming an oxide layer (4) comprises anodizing the coating (3); the anodizing voltage being controlled so as to control the thickness of the oxide layer. The method of claim 10, wherein forming an oxide layer (4) comprises a thermal oxidation process.