CH714796B1 - Brown-colored article and its manufacturing process. - Google Patents

Abstract

The invention relates to a method of manufacturing a decorative article, in particular a watch component, of brown color, comprising the successive steps consisting in: Performing a first mixture with a powder of Si 3 N 4, a powder of Y 2 O 3, an Al 2 O 3 powder and a TiO 2 powder, said first mixture comprising by weight between 79 and 91% of Si 3 N 4, between 3 and 7% of Y 2 O 3, between 3 and 7% Al 2 O 3, between 3 and 7% TiO 2, Produce a second mixture comprising the first mixture and a binder, Form a blank by giving this second mixture the desired shape of the article, Debinding the 'blank, Sinter the debonded blank at a temperature of between 1650 and 1850 ° C. under a pressure of between 20 and 80 bars of nitrogen for a period of between 30 minutes and 3 hours.

Description

TECHNICAL AREA

The present invention relates to a method of manufacturing a decorative article, in particular a watch component, brown in color based on silicon nitride. It also relates to the decorative article.

PRIOR ART

In the watchmaking field, it is known to produce trim components such as ceramic watch cases based on zirconium oxide, otherwise called zirconia, with a color which can be adjusted according to the composition. ceramics. Thus, documents EP 3 012 239 and CH 708 030 respectively disclose ceramics based on zirconia of gray color and orange color.

Another ceramic which is silicon nitride is also used in watch components. This ceramic has the advantage of being less dense than zirconia, which makes it possible to manufacture components which are light while being hard. For example, document CH 699 793 discloses a ceramic material based on silicon nitride used as a substrate for watch case middle parts or bracelet links.

Silicon nitride is gray in color. For aesthetic reasons, other colors may be desired.

SUMMARY OF THE INVENTION

The object of the present invention is thus to provide a method of manufacturing a sintered article based on silicon nitride which is colored throughout and, in particular, which is brown in color.

For this purpose, the composition of the ceramic powder based on silicon nitride (Si3N4) is suitable. It contains oxides of titanium (TiO2), yttrium (Y2O3) and aluminum (Al2O3). The titanium oxide imparts the brown color to the product resulting from the process. The oxides of yttrium and aluminum form a liquid phase during sintering which acts as a binder for the Si3N4 grains while making it possible to shade the brown color of the final product. The various oxides are thus present in percentages chosen to obtain a very specific brown color which qualitatively can be qualified as chocolate brown. The percentage by weight of TiO2 is maintained in a range of between 3 and 7%, preferably between 4 and 6% and more preferably between 4.5 and 5.5%. The percentages by weight of Y2O3 and Al2O are maintained between 3 and 7% and, preferably, between 4 and 6%.

[0007] Other characteristics and advantages of the present invention will become apparent from the following description of a preferred embodiment, presented by way of non-limiting example with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE FIGURE

[0008] FIG. 1 represents a watch case produced with the ceramic material based on silicon nitride according to the invention.

DETAILED DESCRIPTION

The present invention relates to a brown article made of a ceramic material based on silicon nitride and its manufacturing process. This item can be a component of watches, jewelry, bracelets, brooches, necklaces, handbags, etc. In the watchmaking field, this article can be a caseband, a caseback, a bezel, a push-piece, a bracelet link, a dial, a hand, a dial index, etc. By way of illustration, a watch case 1 made with the ceramic material according to the invention is shown in FIG. 1.

The article is manufactured by sintering with the process consisting of: First mix with Si3N4 powder, Y2O3 powder, Al2O3 powder and TiO2 powder. The mixture comprises by weight between 3 and 7%, preferably between 4 and 6%, of Y2O3, between 3 and 7%, preferably between 4 and 6% of Al2O3, between 3 and 7%, preferably between 4 and 6%, and more preferably between 4.5 and 5.5% of TiO2, the remainder being Si3N4 powder. Particularly preferably, the mixture comprises by weight 85% of Si3N4, 5% of Y2O3, 5% of Al2O3 and 5% of TiO2. Grind the first mixture to obtain a particle diameter d100 less than or equal to 5 μm if the first mixture has a diameter d100 greater than this value. Preferably, the diameter d100 of the particles is less than or equal to 3 μm to ultimately obtain a very dense sintered product with a very fine microstructure. The grinding time can be of the order of an hour with, for example, a time of 2 hours. Make a second mixture comprising the first mixture and an organic binder system (paraffin, polyethylene, etc.). Form a blank by shaping this second mixture into the shape of the desired article, for example, by injection or pressing. Unbind the blank, for example with a solvent. Sinter the debonded blank at a temperature between 1650 and 1850 ° C, preferably between 1700 and 1800 ° C, under a pressure between 20 and 80, preferably between 50 and 70, bars of nitrogen for a period between 30 minutes and 3 hours and preferably between 1 and 2 hours.

The article resulting from the process has a brown color imparted by titanium oxide. More specifically, it has a chocolate brown color when the starting powder contains 85% Si3N4, 5% Y2O3, 5% Al2O3 and 5% TiO2. The shade of brown can be modulated by adjusting the TiO2 content as well as the Y2O3 content which tends to change the intensity of the color and the Al2O3 content which tends to provide shades of green. The oxides of yttrium and aluminum act as a binder for the silicon nitride grains and form a glassy phase in the final product.

For example, the method according to the invention was implemented to manufacture a watch case back from a powder comprising by weight 85% of Si3N4 (UBE SNE10), 5% of Y2O3 (Starck Grade C), 5% Al2O3 (Sumitomo AKP 50) and 5% TiO2 (US Research Nanomaterials 300 nm), the mixture of powders being passed through an attritor for 1 hour in order to obtain a d100 of less than 3 µm . Measurements of hardness (HV30), toughness (Kic), colorimetry (CIELab in accordance with standards CIE No. 15, ISO 7724/1, DIN 5033 Teil 7, ASTM E-1164) were carried out.

Table 1 below shows the results of the hardness and toughness measurements. The hardness measurements were carried out on a cross section of the bottom with respectively three measurements under the surface and three measurements at the core of the sample. The toughness was determined on the basis of the measurements of the lengths of the cracks at the four ends of the diagonals of the hardness indentation according to the formula: with P which is the applied load (N), a which is the half-diagonal (m) and / which is the length of the measured crack (m).

The hardness is greater than 1500 Vickers and the toughness is greater than 4 MPa √m. Surface 1514 9.2 5.3 0.1 Core 1509 8 4.8 0.2

Table 1

The Lab colorimetric values were measured with a KONICA MINOLTA CM-5 spectrophotometer under the following conditions: SCI (specular reflection included) and SCE (specular reflection excluded) measurements, inclination of 8 °, MAV measurement area of 8 mm of diameter. The L * a * b * values are 43.32 0.42 and 2.42 respectively.

Claims (10)

1. A method of manufacturing a decorative article, in particular a watch component, of brown color, comprising the successive steps consisting in: - Perform a first mixture with a Si3N4 powder, a Y2O3 powder, an Al2O3 powder and a TiO2 powder, said first mixture comprising by weight between 79 and 91% of Si3N4, between 3 and 7% of Y2O3, between 3 and 7% of Al2O3 and between 3 and 7% of TiO2, - making a second mixture comprising the first mixture and a binder, - forming a blank by giving this second mixture the desired shape of the article, - unbind the blank, sintering the debonded blank at a temperature of between 1650 and 1850 ° C. under a pressure of between 20 and 80 bars of nitrogen for a period of between 30 minutes and 3 hours. 2. Method according to claim 1, characterized in that the first mixture comprises by weight between 82 and 88% of Si3N4, between 4 and 6% of Y2O3, between 4 and 6% of Al2O3 and between 4 and 6%, of preferably, between 4.5 and 5.5% TiO2. 3. Method according to claim 2, characterized in that the first mixture comprises by weight 85% of Si3N4, 5% of Y2O3, 5% of Al2O3 and 5% of TiO2. 4. Method according to any one of the preceding claims, characterized in that it comprises, before the step of producing the second mixture, a step of grinding the first mixture to obtain a diameter d100 of the particles less than or equal to 5. μm and, preferably, less than or equal to 3 μm. 5. Method according to any one of the preceding claims, characterized in that the step of sintering the debonded blank is carried out at a temperature between 1700 and 1800 ° C under a pressure between 50 and 70 bars of nitrogen. for a period of between 1 and 2 hours. 6. Decorative article, in particular watch component, brown in color, made of a sintered material from a base powder comprising a silicon nitride Si3N4, an yttrium oxide Y2O3, an aluminum oxide Al2O3 and a titanium oxide. TiO2 with by weight a percentage of Si3N4 between 79 and 91%, a percentage of Y2O3 between 3 and 7%, a percentage of Al2O3 between 3 and 7% and a percentage of TiO2 between 3 and 7%. 7. Article according to claim 6, characterized in that the base powder comprises by weight between 82 and 88% of Si3N4, between 4 and 6% of Y2O3, between 4 and 6% of Al2O3 and between 4 and 6%, preferably, between 4.5 and 5.5% of TiO2. 8. Article according to claim 7, characterized in that the base powder comprises 85% of Si3N4, 5% of Y2O3, 5% of Al2O3 and 5% of TiO2. 9. Article according to claim 8, characterized in that it has an L * a * b * colorimetry of 43.32 0.42 and 2.42. 10. Article according to any one of claims 6 to 9, characterized in that it is a watch component chosen from a caseband, a back, a bezel, a push-piece, a bracelet link, a dial, a hand and a dial index.