Surface treatment of a glass mold by cold spraying of a metallic powder

Abstract

This document describes a surface treatment process for treating a molding surface (2) of a glass mold (1). This surface treatment process includes a step of cold spraying a solid metal powder (4) onto the molding surface (2) of the glass mold (1) to obtain a solid deposit (5). It also includes a step of machining the solid deposit (5) to obtain a coating. This document also relates to a metal powder, a surface treatment machine, and a surface treatment installation for carrying out such a process, as well as a glass mold obtained by such a process. Figure for the abstract: Fig. 1

Description

Title of the invention: Surface treatment of a glass mold by cold spraying of a metallic powder. Field of the invention

[0001] This application relates generally to foundry parts in the field of glassmaking, in particular cast iron, brass, bronze (and other alloys including copper and tin) or steel molds used to make glass objects such as bottles.

[0002] The present application relates more particularly to the surface treatment of the metal molding surface of these molds which comes into contact with the parison during the manufacture of glass objects during the roughing and finishing phase in order to improve the thermal and / or mechanical properties of the molds. State of the art

[0003] The manufacture of a glass object, in particular a hollow glass object such as a bottle, is done in several stages.

[0004] In a first step called the roughing stage, viscous glass is melted (at a temperature between 700 °C and 1200 °C) and poured in the form of a parison (drop) into a mold, called a roughing mold. The viscous glass is compressed in the roughing mold and then pierced to bring it into contact with the walls of the roughing mold and obtain a rough shape. The rough shape then has a temperature that can reach 900 °C, depending on the area and thickness of the rough shape.

[0005] Then, during a second stage called the finishing stage, the blank thus formed is transferred into a finishing mold to be blown and given its final shape. Upon contact between the blank and the finishing mold, a significant decrease in temperature occurs, as well as an elongation of the glass. The final product is obtained after this blowing stage. It then has a temperature of approximately 600°C.

[0006] Glass molds thus have several functions.

[0007] First, glass molds have a thermal function by allowing the glass to cool. Indeed, upon exiting the rough mold, the blank must be sufficiently cooled to retain its shape. To this end, the blank must remain in the rough mold for a sufficient time to allow the dissipation of a quantity of heat enabling the glass to reach the desired viscosity. It is easy to understand that this quantity of heat increases with the weight of the blank, which, at constant thermal conductivity, normally leads to a longer residence time in the rough mold. In addition, during the finishing stage, the molding surface of the mold will heat up. via heat transfer between the core of the blank and its surface. To avoid both excessive cooling time in the blank mold becoming incompatible with an industrial production rate and excessive temperature of the finishing mold surface leading to structural changes, the mold material must be carefully selected to ensure sufficient thermal conductivity.

[0008] For large objects such as sparkling wine and champagne bottles, molds made of copper and tin alloy, particularly bronze, have been proposed, as they offer good thermal conductivity. However, these molds are very expensive.

[0009] It is therefore desirable to have glass molds which, while exhibiting good thermal conductivity, are less expensive than molds made of copper and tin alloy.

[0010] Furthermore, glass molds have a geometric function since they give the article its final shape. This function is, however, compromised by mold wear problems. These molds, most often made of cast iron, bronze (and other alloys containing copper and tin), or steel (particularly iron-carbon steels, stainless steels, and refractory steels), tend to wear rapidly, especially in areas such as the parting line (or seam), the base, the ring, or the neck of the mold, due to abrasion and / or corrosion caused by the presence of silica in the glass. In order to avoid having to replace the entire mold, torch-based, Plasma Transfer Arc (PTA), or laser-based cladding techniques have been proposed, in which a layer of metallic alloy is fused onto the surface of the mold, at the edges.The resulting mold is then machined after cooling to obtain the desired geometry.

[0011] However, known overlay techniques are not entirely satisfactory, as they only allow treatment of the edges and not the entire molding surface. Indeed, treating the entire molding surface with these known techniques carries a high risk of mold cracking. Therefore, known overlay techniques do not completely prevent mold wear, which consequently requires regular replacement.

[0012] It is therefore desirable to have new resurfacing techniques that allow the entire molding surface to be treated. Exposed

[0013] One purpose of the present application is to remedy at least some of the aforementioned disadvantages.

[0014] To this end, the invention relates, according to a first aspect, to a surface treatment process for treating a molding surface of a glass mold, the surface treatment process comprising the following steps: - cold projection of a solid metallic powder onto the molding surface of the glass mold to obtain a solid deposit; and - machining of the solid deposit to obtain a coating.

[0015] According to particular embodiments of the invention, the surface treatment process also has one or more of the following characteristics, taken individually or in any technically possible combination(s): - the metal powder is projected using a projection gas subjected to a pressure greater than thirty bars, for example between forty bars and seventy bars, for example about fifty bars; - the metal powder is projected using a projection gas heated to a temperature greater than or equal to 750°C, in particular greater than or equal to 900°C, for example between 990°C and 1010°C; - during the projection stage, a projection distance, corresponding to a distance between a metal powder projection nozzle and the molding surface, is between 15 millimeters and 60 millimeters, preferably between 15 and 35 millimeters, for example equal to about 20 millimeters or about 30 millimeters; - during the projection stage, the speed of movement of a projection nozzle of the metal powder during projection is between 500 millimeters per second and 1000 millimeters per second, for example equal to about 800 millimeters per second; - the projection step is carried out for a sufficient duration to obtain a solid deposit with a thickness between 0.3 millimeters and 3 millimeters, preferably between 0.5 millimeters and 1 millimeter; - an injection rate of the metal powder into the projection gas is between 5.936 and 17.808 cm3 / min, preferably between 8.904 and 14.840 cm3 / min, for example in the order of 11.872 cm3 / min; - the coating has better mechanical resistance than the molding surface, in particular better resistance to abrasion; - the metallic powder comprises and is advantageously essentially made up of NiCr powder; - the glass mold is a mold for borosilicate glasses or a mold made of copper and tin alloy, for example bronze; - the coating has a thermal conductivity higher than that of the molding surface; - the metallic powder comprises and is advantageously essentially composed of, by mass relative to the total mass of the powder: • between 60 and 70%, preferably between 62 and 68%, of copper; • between 7 and 17%, preferably between 10 and 15%, of nickel; • between 5 and 15%, preferably between 8 and 12%, of aluminium; • between 5 and 15%, preferably between 8 and 12%, of zinc; - the glass mold is a mold for soda-lime glasses; and - the glass mold is made of graphite cast iron with a micrographite structure lamellar, vermicular or spheroid, in iron-carbon steel, refractory steel or stainless steel.

[0016] The invention also relates, according to a second aspect, to a metallic powder for the surface treatment of a glass mold in accordance with a surface treatment process according to the first aspect.

[0017] According to particular embodiments of the invention, the metal powder has one or more of the following characteristics, taken individually or in any technically possible combination(s): - said metallic powder comprises and is advantageously essentially made up of NiCr powder; - the nickel content in the NiCr powder is between 40 and 50% by mass and the chromium content is between 50% and 60% by mass, relative to the total mass of the NiCr powder; - the nickel content in the NiCr powder is between 55 and 85% by mass and the chromium content is between 15% and 45% by mass, relative to the total mass of the NiCr powder; - the particle size of the NiCr powder is between 10 and 40 micrometers; - said metallic powder comprises and is advantageously essentially composed of, by mass relative to the total mass of the powder: • between 60 and 70%, preferably between 62 and 68%, of copper; • between 7 and 17%, preferably between 10 and 15%, of nickel; • between 5 and 15%, preferably between 8 and 12%, of aluminium; • between 5 and 15%, preferably between 8 and 12%, of zinc. - the particle size of the metal powder is greater than or equal to 15 microns and less than or equal to 45 microns.

[0018] The invention also relates, according to a third aspect, to a glass mold comprising: - a molding surface; and - a coating covering all or part of the molding surface and comprising a metallic alloy obtained by cold spraying a metallic powder onto the molding surface in accordance with a surface treatment process according to the first aspect.

[0019] According to particular embodiments of the invention, the glass mold also has one or more of the following characteristics, taken individually or in any technically possible combination(s): - the metal powder is made up essentially of nickel and chromium; - the molding surface comprises at least one of the following materials: graphite cast iron with a lamellar, vermicular or spheroidal micrographitic structure, a copper and tin-based alloy such as bronze, iron-carbon steel, refractory steel or stainless steel, brass; - the coating is obtained by cold spraying a metallic powder according to the second aspect.

[0020] Finally, the invention relates, according to a fourth and a fifth aspect, to a surface treatment machine for a glass mold, comprising a support configured to receive a glass mold having a molding surface and a projection nozzle configured to cold project a solid metallic powder onto the molding surface so as to obtain a solid deposit, and an installation comprising a surface treatment machine according to the fourth aspect and a machining station configured to machine the solid deposit and obtain a coating. Description of the figures

[0021] Other features, purposes and advantages will become apparent from the following description, which is purely illustrative and not limiting and is given with reference to the accompanying drawings, on which: - Fig. 1 schematically illustrates an example of an installation for the surface treatment of a glass mold according to an embodiment; - [Fig.2] is a flowchart illustrating the steps of a surface treatment process for a glass mold conforming to an embodiment; - [Fig.3] is a schematic cross-sectional view of a glass mold comprising a coating conforming to an embodiment;

[0022] Throughout the figures, similar elements bear identical references. Detailed description

[0023] With reference to [Fig. 1], the present application relates to the surface treatment of all or part of the molding surface 2 of a glass mold 1. The glass mold 1 may, in particular, include a blank mold 1 configured to receive a drop of glass (parison) and form a blank. The molding surface 2 corresponds to the surface of the mold 1 that is likely to come into contact with the parison during the molding process. The molding surface 2 may, in particular, comprise at least one of the following materials: graphite cast iron with a lamellar, vermicular, or spheroidal micrographitic structure; bronze (and other alloys including copper and tin); iron-carbon steel, refractory steel, or stainless steel; or brass. Preferably, the glass mold 1 is formed entirely from the same constituent material as the molding surface 2.

[0024] In order to treat the molding surface 2 of a glass mold 1, it is proposed to cold-project, at a very high speed, a metallic powder 4 onto all or part of the molding surface 2 by means of a high-pressure projection gas 3 transporting it.

[0025] Cold spraying, also known as high-pressure cold spray, allows for a deposition density very close to the theoretical density of the solid metallic material constituting the powder, without heating the molding surface 2 during deposition. This avoids altering the metallurgical quality of the molding surface 2 and the solid deposit 5. Furthermore, it allows for thick deposits (up to several millimeters) with low roughness and a material yield of over 90%, as well as high interparticle cohesion. In addition, this cold spraying process does not require any prior preparation of the molding surface 2 or masking of the mold 1 to be treated. SURFACE TREATMENT INSTALLATION 9

[0026] An installation 9 for treating all or part of the molding surface 2 of a glass mold 1 is shown in [Fig. 1]. This installation 9 comprises a surface treatment machine 10 and a machining station 11.

[0027] The surface treatment machine 10 is configured to cold-spray the metal powder 4, in solid form, onto the molding surface 2 of the mold 1. For this purpose, it includes a spray nozzle 7, preferably made of ceramic, comprising: - a heating and pressurization system for a projection gas 3, typically nitrogen or helium, in a pressurization chamber 12; - a powder dispenser 13 to supply the metal powder 4; - an injection system 18 to inject the metal powder 4 into the projection gas 3 downstream of the pressurization chamber 12 so that it is not heated by the surface treatment machine 10 and therefore remains in a solid state; - a transport system 19 for transporting the metal powder 4 from the powder dispenser 13 to the injection system 18 by means of a carrier gas (typically identical to the projection gas 3); - a convergent-divergent nozzle 8 placed downstream of the injection system 18 and configured to accelerate the blasting gas 3 when it carries the metal powder 4, the divergent part of the nozzle 8 forming a deposition tube 14; and - a cooling system 15 which may include a conduit which surrounds the deposition tube 14 in order to cool the blasting gas 3, which carries the metal powder 4, by conduction by circulating a cooling fluid around the deposition tube 14; the cooling fluid may in particular include distilled water at a temperature lower than the temperature of the blasting gas 3, typically at a temperature between 8 and 20°C.

[0028] The projection nozzle 7 has an outlet diameter (at the free end of the deposition tube 14) between two and ten millimeters, for example on the order of six millimeters.

[0029] The surface treatment machine 10 further includes a support 17 configured to fix the glass mold 1 relative to the spray nozzle and actuators (not shown) configured to move the spray nozzle 7 relative to the molding surface 2 in the three spatial directions. These actuators can move the spray nozzle 7, the support 17 on which the mold 1 is mounted, or both the spray nozzle 7 and the support 17. The actuators are configured to move the nozzle 7 relative to the molding surface 2 at a speed between 600 millimeters per second (mm / s) and 1000 millimeters per second (mm / s), for example, on the order of 800 millimeters per second (mm / s) (to within 5%). The actuators are further configured to offset the impact zone by a distance of between 0.5 millimeters and two millimeters (no projection between two adjacent cords), for example on the order of one millimeter (to within 10%).

[0030] The heating system is configured to heat the projection gas 3 to a temperature greater than or equal to 750°C, in particular greater than or equal to 900°C, for example between 990°C and 1010°C. The projection gas 3 is also pressurized in the pressurization chamber to a pressure greater than or equal to thirty-five bar, preferably between forty bar and seventy bar, for example in the order of fifty bar.

[0031] The projection nozzle 7 can be controlled by a remote control station 16, located near the surface treatment machine 10 or at a distance.

[0032] The machining station 11 includes a support configured to receive the mold 1 coated with the solid deposit 5 and a machining tool, such as a milling machine, configured to machine the solid deposit 5 and obtain the coating 6. The machining tool can be manipulated by an operator or mounted on the installation 8 and controlled by a remote control station, for example the same control station 16 of the projection nozzle 7. SURFACE TREATMENT PROCESS 100

[0033] A process 100 for treating the molding surface 2, implemented by the surface treatment installation 9, is shown in [Fig. 2]. It comprises the following steps: - cold projection 110 of a solid metallic powder 4 onto the molding surface 2 of the glass mold 1 so as to obtain a solid deposit 5; and - machining 120 of the solid deposit 5 so as to obtain a coating 6 ([Fig.3]).

[0034] The process 100 can be applied to the entire molding surface 2 of the mold 1 or to only a part of this surface 2.

[0035] During the projection step 110, a high-temperature (typically nitrogen or helium) and high-pressure projection gas 3 is used to propel the metal powder 4 at supersonic speed (greater than 300 m / s) onto the molding surface 2 to create a solid deposit 5 intended to form the coating 6 by impact of the metal powder 4 onto the molding surface 2, the impact force ensuring the quality of the deposit. In the present application, the deposit is referred to as "solid" insofar as the grains of the metal powder 4 remain in a solid state throughout the projection and adhesion step 110 to the molding surface 2, as opposed to processes in which the temperature of the metal powder 4 exceeds its melting point so that all or part of the powder 4 melts at some point during the process.When the metal powder 4 comes into contact at high speed with the molding surface 2, it mechanically adheres to the molding surface 2 through plastic deformation with strong adhesion, thus preventing high-temperature defects such as oxidation, residual stresses, phase transformations, etc. The solid deposit 5 is then bonded to the molding surface 2; that is, it can only be separated from the molding surface 2 by being wholly or partially damaged.

[0036] The projection step 110 is said to be cold insofar as the metal powder 4 is not heated before or during deposition, other than by its contact with the projection gas 3 or the molding surface 2.

[0037] During the projection step 110, the projection gas 3 is heated and pressurized to ensure that the metal powder 4 is projected at a projection velocity (velocity of the metal powder 4 exiting the nozzle 7) sufficient to allow the metal powder 4 to undergo plastic deformation upon impact with the contact surface. It should be noted that the gas is heated and pressurized before the solid powder is injected into the gas and projected onto the molding surface 2 to ensure that the metal powder 4 remains in a solid state. For this purpose, said projection velocity is greater than or equal to the critical velocity of the metal powder 4. This critical velocity corresponds to the speed at which the adhesion of the solid deposit 5 is possible: when the impact velocity is less than the critical velocity of the material, then the metal powder particles 4 do not deform plastically and can rebound and / or erode the molding surface 2. The critical velocity depends on the nature of the material and the grain size of the metal powder 4. The critical velocity is, for example, higher in the case of a metal powder 4 comprising a hard material, such as a titanium dioxide-based material (above 1250 m / s), than in the case of a metal powder 4 comprising a ductile material, such as a copper-based material (on the order of 600 m / s). An equation El for determining the critical velocity of a material was developed by T. Schmidt, F. Gartner, H. Assadi, H.Kreye, “Development of a generalized parameter window for cold spray deposition”, Acta Mater. 54 (2006) 729-742; https: / / doi.org / 10.1016 / j.actamat.2005.10.005): . LC \ „ / „ ZïŒl) vcr = y~~p~ | 1 -7-77 ) + F^^Tm- T}j where: or is the breaking stress of the material; p is the density of the material to be characterized; T; is the initial temperature of the material to be characterized; Tm is the melting temperature of the material to be characterized; cp is the specific heat; Tr is a reference temperature equal to 293 K; and Fi and F2 are calibration coefficients used to recalibrate the calculated value on measured speed values.

[0038] The pressure applied to the projection gas 3 is therefore chosen so as to exceed the critical velocity of the metal powder 4 used for the solid deposition 5. A pressure greater than or equal to thirty-five bars, preferably greater than or equal to forty bars, for example equal to fifty bars, is suitable for most metal powders that can be used in the surface treatment of a glass mold.

[0039] Furthermore, the temperature to which the projection gas 3 is heated is typically greater than or equal to 750°C, in particular greater than or equal to 900°C, for example between 990°C and 1010°C. This heating temperature is advantageously at least 300°C below the melting temperature of the constituent of the metal powder 4 with the lowest melting temperature and for example between 300 and 700°C below this melting temperature.

[0040] Where appropriate, the projection gas 3 can further be accelerated by the configuration of the projection nozzle 7 (modification of the gas passage cross-section, for example in a convergent-divergent nozzle 8, etc.).

[0041] For a nickel chromium based powder as described below, the critical velocity is for example on the order of 574 m / s.

[0042] If necessary, the projection gas 3 can be cooled downstream of the point of injection of the metal powder 4 into the gas in order to ensure that the metal powder 4 remains solid without reducing the projection velocity of the powder.

[0043] The projection step 110 is carried out so as to obtain a solid deposit 5 of sufficient thickness to allow machining of the solid deposit 5 and obtaining the coating 6. This thickness of the solid deposit 5 is typically between 0.3 millimeters and 3 millimeters, preferably between 0.5 millimeters and 1 millimeter. The thickness of the coating 6 (after machining) can thus be between 0.1 millimeters and 1.5 millimeters.

[0044] For this purpose, the molding surface 2 is moved relative to the surface treatment machine 10 during the projection step 110 in order to deposit the material onto all or part of the molding surface 2. The projection nozzle 7 can be moved while the glass mold 1 is stationary, or alternatively the glass mold 1 can be moved while the projection nozzle 7 is stationary, or both the projection nozzle 7 and the glass mold 1 are moved. The relative speed of movement and the number of passes over a given surface determine the thickness of the deposit. For example, the relative speed of movement of the projection nozzle 7 and the molding surface 2 of the glass mold 1 can be between 600 millimeters per second (mm / s) and 1000 millimeters per second (mm / s), for example on the order of 800 millimeters per second (mm / s) (to within 5%).

[0045] The supply rate of the metal powder 4 by the distributor 13 is between 5,936 and 17,808 cm³ / min, preferably between 8,904 and 14,840 cm³ / min, for example on the order of 11,872 cm³ / min. The metal powder 4 thus supplied is entirely transported by the carrier gas to the injection system 18, so that this supply rate also constitutes an injection rate of the metal powder 4 into the projection gas 3 by the injection system 18. For this purpose, the carrier gas flow rate is typically between 3 and 6 cubic meters per hour (m³ / h), for example on the order of 4.5 cubic meters per hour (m³ / h).

[0046] The size (bead width) of the solid deposit 5 is preferably between 0.5 millimeters and two millimeters, for example on the order of one millimeter (to within 10%). This size depends on the distance between the outlet of the spray nozzle 7 of the surface treatment machine 10 and the molding surface 2 and on the outlet diameter of the spray nozzle 7. In order to obtain the aforementioned solid deposit size, said distance is typically between fifteen millimeters and sixty millimeters, preferably between fifteen millimeters and thirty-five millimeters, for example equal to about twenty millimeters or about thirty millimeters, for an outlet diameter of the projection nozzle 7 between two and ten millimeters, for example on the order of six millimeters.

[0047] The projection pitch (distance between the centers of two adjacent solid deposit beads 5) is between 0.5 millimeters and two millimeters, for example on the order of one millimeter (to within 10%). It is preferably substantially equal to the size of the solid deposit 5. METALLIC POWDER 4

[0048] The metal powder 4 preferably comprises 75% by mass or more, advantageously at least 80% by mass, of spherical grains, relative to the total mass of the powder.

[0049] Laser particle size is measured according to ISO 13320:2019.

[0050] The diameter of the powder grains is advantageously between 10 and 50 pm, in particular between 12 and 45 pm, and preferably has a D50 value between 20 and 30 pm.

[0051] The melting temperature of the powder components is typically higher than the parison temperature—which can reach 1100 °C—in order to prevent thermal degradation of the coating 6 during molding. Preferably, the melting temperature of the powder component with the lowest melting temperature is 300 °C higher than the parison temperature.

[0052] The "tamped density" is evaluated according to the basis of standard NF EN ISO 3923 (2018) relating to "Metal powders - Determination of apparent density after tamping". Typically, a 25 cm³ volume test specimen and a KERN SEAL balance with a maximum capacity of 6000 g and a resolution of 0.1 g are used. The tamping is stopped after 3000 blows.

[0053] The "true density" is evaluated according to the basis of standard NF EN ISO 8130-2 (2011) relating to "Coating powders - Determination of density using a gas pycnometer (reference method)". A helium pycnometer (Quantachrome Upyc 1200 e) with a 10 cm³ cell is used. The mass of the powder is measured with a balance, for example METTLER TOLEDO AB 104 with a maximum capacity of 110 g and a resolution of 0.1 mg.

[0054] The packed density of the metal powder is typically between 3 and 7 g / cm3

[0055] The true density is typically between 6 and 10 g / cm3, preferably with a low standard deviation, for example of 0.001. Metallic powders having such a true density make it possible to obtain a denser solid deposit.

[0056] For the purposes of the present invention, a powder is "essentially made up" of a compound A when the powder comprises at least 99% by mass of compound A, relative to the total mass of the powder.

[0057] Metallic powder comprising a NiCr alloy

[0058] According to a first embodiment, the metal powder 4 comprises or is essentially composed of a nickel-chromium alloy (called a nickel-chromium alloy and denoted NiCr). This makes it possible to obtain a NiCr coating 6 that provides thermomechanical protection to the mold 1. In particular, a NiCr coating 6 gives the mold 1 better abrasion resistance, which is especially useful in the case of molds for borosilicate glasses and in the case of copper-tin alloy molds. Indeed, borosilicate glasses are particularly abrasive and generally lead to premature wear of the molds. As for copper-tin alloy molds, they have good thermal conductivity and are generally very expensive, so it is advantageous to lose some of the mold's thermal conductivity if this allows it to last longer.

[0059] Thus, according to an advantageous variant of this first embodiment, the glass mold 1 is a mold for borosilicate glasses or a mold made of a copper and tin alloy, for example bronze.

[0060] The nickel content in the NiCr alloy is advantageously between 40% and 85% by mass, preferably between 45% and 80% by mass, relative to the total mass of the NiCr alloy, the remainder being essentially made up of chromium.

[0061] According to a first embodiment, the nickel content in the NiCr alloy is between 40 and 50% by mass, while the chromium content is between 50 and 60% by mass, relative to the total mass of the NiCr alloy. For example, the nickel content in the NiCr alloy is approximately 50% by mass, and the chromium content is also approximately 50% by mass, relative to the total mass of the NiCr alloy. According to a second embodiment, the nickel content in the NiCr alloy is about 80% by mass, while the chromium content is about 20% by mass, relative to the total mass of the NiCr alloy.

[0062] The particle size of the NiCr powder is advantageously between 10 and 50 µm. The D50 value of the NiCr powder is typically between 20 and 30 µm, preferably between 25 and 27 µm, for example, approximately 26.1 µm. The D10 value of the NiCr powder is typically between 10 and 20 µm, preferably between 14 and 16 µm, for example, approximately 14.7 µm. The D90 value of the NiCr powder is typically between 40 and 50 µm, preferably between 43 and 45 µm, for example, approximately 44.0 µm.

[0063] The packed density of NiCr powder is typically between 4 and 5 g / cm³, in particular between 4.3 and 4.8 g / cm³, for example on the order of 4.7 g / cm³. The true density of NiCr powder is typically between 7.5 and 8.5 g / cm³, in particular between 7.6 and 8.0 g / cm³, for example on the order of 7.71 g / cm³.

[0064] Metallic powder comprising a cupronickel-type alloy

[0065] According to a second embodiment, the metal powder 4 comprises or is essentially composed of a copper, nickel, aluminum, and zinc alloy, which, for the sake of simplicity, will be referred to hereafter as "cupronickel." This makes it possible to obtain a coating 6 comprising a so-called "cupronickel" alloy that gives the mold better thermal conductivity, which allows the glass to cool more homogeneously upon contact with the coated mold. Such a coating is particularly advantageous in the case of molds for soda-lime glasses.

[0066] Thus, according to an advantageous variant of this first embodiment, the glass mold 1 is a mold for soda-lime glasses. The material of the mold 1 is typically a cast iron, for example a graphite cast iron with a lamellar, vermicular or spheroidal micrographitic structure, an iron-carbon steel, a refractory steel or a stainless steel.

[0067] According to this second embodiment, the metal powder 4 comprises or is essentially composed of a powder of an alloy comprising, by mass relative to the total mass of the alloy: • between 60 and 70%, preferably between 62 and 68%, of copper; • between 7 and 17%, preferably between 10 and 15%, of nickel; • between 5 and 15%, preferably between 8 and 12%, of aluminium; • between 5 and 15%, preferably between 8 and 12%, of zinc; • the possible supplement preferably consisting primarily of chromium, manganese and / or iron.

[0068] Typically, the additive represents at most 3% by mass relative to the total mass of the alloy. Preferably, the additive comprises, by mass relative to the total mass of the alloy: • at most 1% chromium; • at most 1% manganese; and • at most 1% iron.

[0069] The packed density of the "cupronickel" powder is typically between 1 and 6 g / cm3, particularly between 4.5 and 5.5 g / cm3. The true density of the powder of " "cupronickel" is typically between 4 and 9 g / cm3, especially between 7.5 and 9.0 g / cm3.

[0070] The particle size of the "cupronickel" powder is advantageously between 15 and 45 µm. The D50 value of the "cupronickel" powder is typically between 20 and 30 µm. ADVANTAGES OF THE INVENTION

[0071] Thus, thanks to the invention described above, it is possible to improve both the abrasion resistance and the thermal conductivity of the glass mold 1. It is therefore possible to reduce the frequency of replacement of glass molds, by coating their molding surface entirely with a coating having good abrasion resistance, such as a NiCr coating, or to use for the molding of large volumes of glass or soda-lime glasses less expensive molds whose molding surface is simply coated with a coating having good thermal conductivity, such as a "cupronickel" alloy coating.

[0072] The costs of purchasing and replacing molds can thus be reduced.

Claims

Demands

1. Surface treatment method (100) for treating a molding surface (2) of a glass mold (1), the surface treatment method (100) comprising the following steps: - cold spraying (110) of a solid metallic powder (4) onto the molding surface (2) of the glass mold (1) so as to obtain a solid deposit (5); and - machining (120) of the solid deposit (5) so as to obtain a coating (6).

2. A surface treatment method (100) according to claim 1, wherein the metal powder (4) is projected using a projection gas (3) subjected to a pressure greater than thirty bars, for example between forty bars and seventy bars, for example about fifty bars.

3. A surface treatment method (100) according to any one of claims 1 or 2, wherein the metal powder (4) is projected using a projection gas (3) heated to a temperature greater than or equal to 750°C, in particular greater than or equal to 900°C, for example between 990°C and 1010°C.

4. A surface treatment method (100) according to any one of claims 1 to 3, wherein during the projection step (110), a projection distance, corresponding to a distance between a projection nozzle (7) of the metal powder (4) and the molding surface (2), is between 15 millimeters and 60 millimeters, preferably between 15 and 35 millimeters, for example about 20 millimeters or about 30 millimeters.

5. Surface treatment method (100) according to any one of claims 1 to 4, wherein during the projection step (110), a displacement speed of a projection nozzle (7) of the metal powder (4) during projection is between 500 millimeters per second (mm / s) and 1000 millimeters per second (mm / s), for example equal to about 800 millimeters per second (mm / s).

6. Surface treatment method (100) according to any one of claims 1 to 5, wherein the projection step (110) is carried out for a sufficient duration to obtain a solid deposit (5) having a thickness of between 0.3 millimeters and 3 millimeters, preferably between 0.5 millimeters and 1 millimeter.

7. Surface treatment method (100) according to any one of claims 1 to 6, wherein an injection flow rate of the metal powder (4) into the projection gas (3) is between 5,936 and 17,808 cm3 / min, preferably between 8,904 and 14,840 cm3 / min, for example in the order of 11,872 cm3 / min.

8. Surface treatment method (100) according to any one of claims 1 to 7, wherein the coating (6) has better mechanical strength than the molding surface (2), in particular better abrasion resistance.

9. Surface treatment method (100) according to any one of claims 1 to 7, wherein the coating (6) has a thermal conductivity greater than that of the molding surface (2).

10. Surface treatment method (100) according to any one of claims 1 to 9, wherein the metal powder (4) comprises and is advantageously essentially made up of NiCr powder.

11. A surface treatment process (100) according to any one of claims 1 to 9, wherein the metal powder (4) comprises and is advantageously essentially made up of, by mass relative to the total mass of the powder: • between 60 and 70%, preferably between 62 and 68%, of copper; • between 7 and 17%, preferably between 10 and 15%, of nickel; • between 5 and 15%, preferably between 8 and 12%, of aluminum; • between 5 and 15%, preferably between 8 and 12%, of zinc.

12. Glass mold (1) comprising: - a molding surface (2); and - a coating (6) covering all or part of the molding surface (2) and comprising a metallic alloy obtained by cold spraying a metallic powder (4) onto the molding surface (2) in accordance with a surface treatment process (100) according to any one of claims 1 to 9.

13. Glass mold (1) according to claim 12, wherein the molding surface (2) comprises at least one of the following materials: graphite cast iron with a lamellar, vermicular, or spheroidal micrographite structure, a copper-tin alloy such than bronze, iron-carbon steel, refractory steel or stainless steel, brass.

14. Glass mold (1) according to any one of claims 12 and 13, wherein the metal powder (4) is essentially made up of nickel and chromium.

15. Glass mold (1) according to any one of claims 12 and 13, wherein the coating (6) is obtained by cold spraying a metal powder comprising and advantageously consisting mainly of NiCr powder or a metal powder comprising and advantageously consisting mainly of, by mass relative to the total mass of the powder: • between 60 and 70%, preferably between 62 and 68%, of copper; • between 7 and 17%, preferably between 10 and 15%, of nickel; • between 5 and 15%, preferably between 8 and 12%, of aluminum; • between 5 and 15%, preferably between 8 and 12%, of zinc.

16. Installation comprising: - a surface treatment machine (10) for a glass mold (1) comprising: - a support (17) configured to receive a glass mold (1) having a molding surface (2); and - a projection nozzle (7) configured to cold project a solid metallic powder (4) onto the molding surface (2) so as to obtain a solid deposit (5), and - a machining station (11) configured to machine the solid deposit (5) and obtain a coating (6).

Images