Mold and mold protective coating for high temperature forming

Abstract

The utility model discloses a mold for high-temperature forming and a mold protective coating. The protective coating comprises a chromium / platinum layer and a ruthenium layer, wherein the chromium / platinum layer is arranged on the surface of a mold substrate of the mold in an attached mode, and the ruthenium layer is arranged on the chromium / platinum layer in an attached mode. Preferably, the die further comprises a titanium layer arranged between the die substrate and the chromium / platinum layer; the ruthenium layer can resist oxidation and is good in adhesion performance, and chromium / platinum is prevented from being transported outwards; a small amount of oxygen entering through the ruthenium layer can be absorbed by the chromium / platinum layer, and chromium / platinum oxidation can form a compact oxide film at the grain boundary with ruthenium to prevent oxygen from entering an oxidation mold substrate; moreover, when the mold is used for high-temperature forming, chromium / platinum atoms can diffuse, pass through a grain boundary and reach the surface of the ruthenium layer to react with oxygen left in the surrounding atmosphere to form a compact oxide thin film, and the thin film can improve the anti-adhesion performance of the surface of the mold and can also prevent oxygen from entering the coating. Titanium is used as the middle layer, so that the adhesive force of the whole protective coating can be improved.

Description

Technical Field

[0001] This utility model relates to the field of glass processing, and in particular to a mold and mold protective coating for high-temperature forming. Background Technology

[0002] With the popularity of curved-screen smartphones, VR devices, and other electronic products, different requirements have arisen for product appearance to provide consumers with a better user experience, leading to various demands on screens. The use of 3D curved screens has become a development trend. 3D curved glass is mainly produced through hot bending. During the hot bending process, the mold needs to transfer heat and force to the glass without affecting the forming accuracy of the finished glass. This requires the mold to have properties such as high temperature resistance, thermal conductivity, and low expansion rate. Currently, most hot bending molds use graphite materials. Due to the poor oxidation resistance of graphite, it is easily oxidized at high temperatures. Direct contact between the mold and the heated glass at elevated forming temperatures leads to a decrease in glass accuracy. Furthermore, graphite molds have low strength, resulting in powdering and edge chipping with long-term use, ultimately leading to a short mold lifespan. Therefore, protective coatings have become indispensable. Existing protective coatings for graphite molds mostly use hard coatings such as titanium N, titanium NC, and Al titanium N. Hard coatings provide multiple functions, such as appropriate adhesion, high thermal stability, and high hardness, thus basically meeting the needs of surface protective coatings. However, these materials have a high coefficient of surface friction, making them prone to adhesion to the glass. In addition, the working environment of the molds for 3D glass hot bending is harsh, usually requiring operation at temperatures close to 800°C. At high temperatures, these common hard coatings may oxidize or thermally mismatch, causing them to peel off and lose their original properties. Utility Model Content

[0003] The technical problem to be solved by this utility model is to provide a mold and mold protective coating for high-temperature molding, which addresses the shortcomings of existing technologies such as glass easily adhering to the mold cavity and poor high-temperature resistance during annealing at high forming temperatures.

[0004] The technical solution adopted by this utility model to solve its technical problem is:

[0005] On the one hand, a mold protective coating for high-temperature molding is constructed, comprising a chromium / platinum layer attached to the surface of the mold substrate of the mold, and a ruthenium layer attached to the chromium / platinum layer.

[0006] The mold protective coating described in this utility model also includes a titanium layer disposed between the mold substrate and the chromium / platinum layer.

[0007] In the mold protective coating described in this utility model, the deposition thickness of the titanium layer is within a thickness range centered at 50 nm and fluctuating within a range of ±20%, the deposition thickness of the chromium / platinum layer is within a thickness range centered at 200 nm and fluctuating within a range of ±20%, and the deposition thickness of the ruthenium layer is within a thickness range centered at 500 nm and fluctuating within a range of ±20%.

[0008] In the mold protective coating described in this utility model, the mold substrate is graphite.

[0009] Secondly, a mold protective coating for high-temperature molding is constructed, comprising: a chromium / platinum layer attached to the surface of the mold substrate of the mold, a ruthenium layer attached to the chromium / platinum layer, and a thin film formed outside the ruthenium layer to improve anti-adhesion and anti-oxidation properties.

[0010] In the mold protective coating described in this utility model, the film is specifically a chromium / platinum oxide film formed by the oxidation of the chromium / platinum of the chromium / platinum layer after it reaches the outer surface of the ruthenium layer.

[0011] The mold protective coating described in this utility model also includes a titanium layer disposed between the mold substrate and the chromium / platinum layer.

[0012] In the mold protective coating described in this utility model, the deposition thickness of the titanium layer is within a thickness range centered at 50 nm and fluctuating within a range of ±20%, the deposition thickness of the chromium / platinum layer is within a thickness range centered at 200 nm and fluctuating within a range of ±20%, and the deposition thickness of the ruthenium layer is within a thickness range centered at 500 nm and fluctuating within a range of ±20%.

[0013] In three aspects, a mold for high-temperature molding is constructed, which includes a mold base and a mold protective coating as described above, attached to the surface of the mold base.

[0014] The mold and mold protective coating for high-temperature molding of this invention have the following beneficial effects: A chromium / platinum layer is attached to the surface of the mold substrate, and a ruthenium layer is attached to the chromium / platinum layer. Thus, the ruthenium layer itself is oxidation-resistant, and the ruthenium above the chromium / platinum acts as a diffusion barrier, hindering the outward transport of chromium / platinum, making it less prone to oxidation. Furthermore, ruthenium has good anti-adhesion properties. Small amounts of oxygen penetrating through the ruthenium layer are absorbed by the chromium / platinum layer, preventing direct oxidation of the mold substrate. Moreover, the oxidation of chromium / platinum can form a dense oxide film at the grain boundaries with ruthenium, blocking oxygen from entering and oxidizing the mold substrate. Furthermore, when the mold is used for high-temperature molding... Chromium / platinum atoms gain enough thermal energy to overcome the activation energy barrier, which allows them to diffuse through the grain boundaries and reach the ruthenium layer surface. Once the chromium / platinum reaches the metal surface, it reacts with residual oxygen in the surrounding atmosphere, causing chromium / platinum oxides to grow on the surface of the ruthenium layer until a critical thickness (which is very thin) is reached, eventually forming a dense, continuous and stable oxide film. This oxide film also keeps the mold from adhering to the glass surface, improving the anti-adhesion performance of the mold surface. It also blocks oxygen from entering the coating, enhances the oxidation resistance of the mold, extends the service life of the graphite mold, improves the production yield, and reduces production costs.

[0015] Furthermore, a titanium layer can be attached to the surface of the mold substrate before setting the chromium / platinum layer, and then the chromium / platinum layer can be set on the titanium layer. Titanium is used as an intermediate layer because it has good adhesion and is therefore very uniform, which can improve the adhesion of the entire protective coating. This will reduce the stress inside the film and promote the uniform growth of the film. It can help regulate the growth rate and uniformity of the film, thereby optimizing the quality and performance of the film layer in the entire film production process. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0017] Figure 1 This is a schematic diagram illustrating the composition of the mold according to Embodiment 1 of this utility model;

[0018] Figure 2 This is a schematic diagram of the composition of the mold of the present invention, according to Embodiment 2. Detailed Implementation

[0019] To facilitate understanding of this utility model, a more comprehensive description will be given below with reference to the accompanying drawings. The drawings illustrate typical embodiments of this utility model. However, this utility model can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of this utility model more thorough and complete. It should be understood that the embodiments of this utility model and the specific features thereof are detailed descriptions of the technical solutions of this application, and not limitations thereof. Where there is no conflict, the embodiments of this utility model and the technical features thereof can be combined with each other.

[0020] Example 1

[0021] refer to Figure 1 This is a schematic diagram of the composition of the mold protective coating according to an embodiment of the present invention. The diagram shows the state in use, with glass 5 placed outside the coating.

[0022] The mold of this utility model embodiment is a graphite mold for hot bending of glass. The mold protective coating includes a titanium layer 2 attached to the surface of the graphite substrate 1 of the mold, a chromium layer 3 attached to the titanium layer 2, and a ruthenium layer 4 attached to the chromium layer 3.

[0023] Because the ruthenium layer 4 itself is oxidation-resistant, the overall oxidation resistance of the protective coating is ensured, and ruthenium also has good anti-adhesion properties. Ruthenium acts as a diffusion barrier above chromium, hindering the outward transport of chromium and making it less prone to oxidation. Any small amount of oxygen that penetrates through the ruthenium layer 4 is absorbed by the chromium layer 3, preventing direct oxidation of the mold substrate 1. Furthermore, chromium oxidation can form a dense oxide film at the grain boundaries with ruthenium, blocking oxygen from entering and oxidizing the mold substrate 1. Thus, this embodiment can improve the anti-adhesion properties of the mold surface, prevent oxygen from entering the coating, enhance the oxidation resistance of the mold, extend the service life of the graphite mold, improve production yield, and reduce production costs.

[0024] This mold can be used directly for glass hot bending. During long-term use, high-temperature annealing will cause a thin film to form on the outer surface of the ruthenium layer 4, which improves its anti-adhesion and anti-oxidation properties. Specifically, this film is a chromium oxide film formed by the oxidation of chromium from the chromium layer 3 to the outer surface of the ruthenium layer 4, typically a Cr2O3 film. Furthermore, after high-temperature annealing, a titanium-chromium alloy will form between the titanium layer 2 and the chromium layer 3.

[0025] Precision glass forming typically requires high-temperature conditions. Chromium (Cr) has a limited ability to form a dense Cr₂O₃ film directly from chromium at high temperatures; ruthenium (Ru) acts as a barrier to Cr diffusion in this coating. During high-temperature annealing, a very small number of Cr atoms gain enough thermal energy to overcome the activation barrier, allowing them to diffuse through the upper Ru layer, usually via grain boundaries, and reach the Ru metal surface. High temperatures facilitate this diffusion process. Once Cr reaches the Ru metal surface, it reacts with residual oxygen (O) in the surrounding atmosphere to form CrO, as shown in reaction (1):

[0026] Cr + O → CrO (1)

[0027] The reaction between the outwardly diffusing Cr and O continues, causing CrO to grow on the surface of the Ru layer. CrO gradually thickens until a critical thickness is reached. At this point, CrO may undergo structural transformation and atomic rearrangement, resulting in the formation of a continuous CrO2 layer. In addition, the CrO2 layer can undergo oxidation in the presence of excess oxygen, leading to the formation of Cr2O3. The oxidation process from CrO2 to Cr2O3 is faster than the formation of CrO2. See reaction (2):

[0028] 4CrO2 + 3O2 → 2Cr2O3 + 2O2 (2);

[0029] In summary, during later use, this protective coating for the mold will inevitably form a dense Cr2O3 film on its outermost layer. This Cr2O3 film will not only prevent it from adhering to the glass surface, but also block oxygen from entering the coating, enhance the mold's oxidation resistance, and extend the service life of the graphite mold.

[0030] In this embodiment, titanium is used as the intermediate layer. Due to its good adhesion, the titanium layer 2 itself will be very uniform, thereby improving the adhesion of the entire protective coating. This results in lower internal stress in the film, promoting uniform film growth and helping to regulate the film's growth rate and uniformity, thus optimizing the quality and performance of the film layer throughout the entire film production process. It is understood that the titanium layer 2 disposed between the graphite substrate 1 and the chromium layer 3 in this embodiment is a preferred method, but in practice, the titanium layer 2 is not mandatory.

[0031] In this embodiment, the titanium layer 2, chromium layer 3, and ruthenium layer 4 can be configured using magnetron sputtering technology. The deposition thickness of the titanium layer 2 is within a range of ±20% centered at 50 nm, the chromium layer 3 is within a range of ±20% centered at 200 nm, and the ruthenium layer 4 is within a range of ±20% centered at 500 nm. It is understood that the ±20% fluctuation range is only a preferred range; theoretically, the range can be expanded to 10 times, but the larger the thickness error, the weaker the effect.

[0032] It should be noted that the graphite used in this embodiment is a 2D planar shape. In practice, different graphite molds can be designed according to the product shape, and then the thin film can be deposited using magnetron sputtering. Furthermore, the application scenarios of this mold are not limited. In this embodiment, it is used as a graphite mold for hot-bending glass, but it can also be used in metal molds, ceramic molds, other molds, jigs, and other applications. Additionally, chromium can be replaced with platinum.

[0033] The following section uses a graphite mold for hot bending of glass as an example to detail its preparation process and steps:

[0034] 1. Use chromium (Cr), ruthenium (Ru), and titanium (Ti) metal targets on a graphite substrate (i.e., the graphite base of the mold). Mount the sputtering targets in a vacuum chamber, which is evacuated to 8 × 10⁻⁶. -7 The pressure on To.

[0035] For Ru and Cr, the measured diameter is 50.8 mm, and for Ti, the measured diameter is 76.2 mm.

[0036] Before deposition, the following preparations are required: all targets are pre-sputtered to ensure surface cleanliness; the graphite substrate with dimensions of (2×7×7) mm is metallographically ground and polished with diamond gypsum to obtain an ultra-smooth surface. The benefits of this smoothness are:

[0037] First, a smooth substrate surface ensures that the coating evenly covers the entire surface, avoiding uneven coating thickness or insufficient coverage in some areas.

[0038] Secondly, it reduces defects and bubbles. A smooth surface reduces surface defects and minor unevenness, which can become sources of bubbles and other defects in the coating. If the substrate surface is not smooth, bubbles and other defects are more likely to form, affecting the quality and stability of the coating.

[0039] Third, it improves adhesion: A smooth surface helps improve the adhesion between the coating and the substrate. Coatings are usually deposited onto the substrate surface by chemical or physical methods, and a smooth surface can provide a larger contact area and stronger bonding force.

[0040] 2. Place the graphite substrate sample on the substrate support and adjust the rotation speed to 50 revolutions per minute (rpm).

[0041] 3. Argon (Ar) gas was introduced as a plasma source at a flow rate of 50 sccm.

[0042] 4. A 50 nm thick titanium layer was deposited on the graphite substrate using a DC power of 150 W. Next, a 200 nm thick chromium layer was deposited. Finally, a 500 nm thick ruthenium layer was deposited.

[0043] 5. Place the aluminosilicate glass slide (Tg≈630℃) on the prepared coated sample.

[0044] 6. Annealing is carried out in a tube furnace under a vacuum of approximately 1 mbar.

[0045] 7. Heat the prepared coated sample from room temperature to 750°C at a heating rate of 5°C / min and hold for 10 hours and 20 hours.

[0046] 8. After annealing, the sample is cooled to room temperature in a quartz tube furnace.

[0047] The coating thickness can be used to distinguish between graphite and glass, which facilitates a series of subsequent tests.

[0048] To test the solution of this utility model, we deposited protective coatings with six different Ru thicknesses, subjected them to annealing at 750°C for different durations, and conducted the following tests before annealing (the protective coating at this point is temporarily referred to as the deposited coating) and after annealing (the protective coating at this point is temporarily referred to as the annealed coating):

[0049] 1. Phase identification of the developed coating was performed using X-ray diffraction.

[0050] After annealing, no significant changes in the peak positions of Ru or Cr were observed. However, the peak intensity of Ru showed a slight increase with increasing Ru thickness. Furthermore, it should be noted that the formation of a chromium oxide film was evident in the transmission electron microscopy (TEM) results. However, due to its extremely low thickness, this phase could not be detected by XRD measurements using parallel beam mode.

[0051] 2. Use a scanning electron microscope to examine the surface morphology and surface roughness of the Ru and Cr layers respectively.

[0052] After annealing, slight changes in surface characteristics were observed compared to the deposited state. The annealed coating showed the presence of newly grown nano-sized particles, indicating the formation of an oxide layer on the surface of the protective coating. EDS spectroscopy of the annealed coating confirmed the presence of oxygen (O), indicating the formation of an oxide layer on the coating surface.

[0053] A slight increase in surface roughness was observed after annealing. This phenomenon can be attributed to the formation of a slightly roughened chromium oxide scale on the coated sample surface. However, it is noteworthy that the increase in surface roughness is not significant. The results obtained indicate that the developed coating exhibits good surface characteristic stability and maintains its desired surface characteristics even after prolonged annealing.

[0054] 3. Use X-ray photoelectron spectroscopy to study the surface chemical state of coating elements.

[0055] After the annealing process, only Cr was observed. 3+ Valence state. In addition, trace amounts of free chromium are sometimes detected. This is because during annealing, chromium diffuses outward to the surface, where it oxidizes and forms an oxide layer. Therefore, XPS analysis performed on the annealed coating confirms the outward diffusion of Cr and its subsequent oxidation to Cr. 3+ This ultimately leads to the formation of a stable Cr2O3 layer on the surface.

[0056] 4. Use a nanoindentation tester to perform nanoindentation tests to measure nanohardness and Young's modulus.

[0057] The mechanical properties of the deposited coating are affected by variations in the Ru layer thickness. The hardness of the annealed coating initially shows an increase, which can be attributed to the formation of Cr₂O₃. However, with prolonged annealing time, the hardness decreases, indicating changes in grain size (grain growth) and microstructure. The elastic modulus follows a similar trend to the hardness. Initially, a lower value is observed in the coating before annealing. Subsequently, annealing at higher temperatures leads to an increase in the elastic modulus, while prolonged annealing results in a slight decrease.

[0058] 5. Use scanning / transmission electron microscopy to examine the nanostructure of the coating.

[0059] The Ru coating exhibits a nanoscale columnar structure with a discernible preferred orientation. The presence of distinct polyhedral apexes indicates a preferred growth direction, as atoms tend to diffuse towards energy-favorable sites upon surface absorption. Grain growth begins with thin columnar structures and remains cylindrical, gradually widening slightly as the film continues to grow. Similarly, the Cr layer beneath the Ru layer also exhibits an ordered columnar structure. These observations are consistent with earlier XRD results, further confirming that Ru film deposition on Cr film can enhance crystallinity.

[0060] After numerous experimental tests, it was determined that increasing the Ru thickness hindered the outward transport of Cr, resulting in the formation of a thin but stable oxide surface that remained non-adhesive to the glass surface. Furthermore, due to the annealing effect, the thickness of the Cr and Ti interlayer increased, while the Cr-Ti interface disappeared, leading to interdiffusion and alloy formation; however, the thickness of the ruthenium layer remained unchanged.

[0061] Example 2

[0062] As mentioned in Example 1, when the mold of Example 1 is used later, a thin film will be formed on the outside of the ruthenium layer 4 due to the high temperature annealing process during the glass hot bending process. In fact, the cover film can also be generated before the mold is put into use, as is the case in this example.

[0063] refer to Figure 2 The difference between this embodiment and Embodiment 1 is that a thin film 6, which improves anti-adhesion and anti-oxidation properties, is formed outside the ruthenium layer 4. Correspondingly, in this embodiment, after attaching a titanium layer 2, a chromium layer 3, and a ruthenium layer 4 to the surface of the graphite substrate 1, the mold is not directly used. Instead, a thin film 6, which improves anti-adhesion and anti-oxidation properties, is formed outside the ruthenium layer 4 through high-temperature annealing. Specifically, the thin film 6 is a chromium oxide film formed by the oxidation of chromium from the chromium layer 3 upon reaching the outer surface of the ruthenium layer 4. The formation principle of this film is similar to that of the Ru surface film mentioned in Embodiment 1, except that this film is not generated during the hot bending of glass products, but is prepared during mold making through a high-temperature annealing process.

[0064] Similarly, chromium can be replaced with platinum. For more details, please refer to Example 1, which will not be repeated here.

[0065] In summary, the mold and protective coating for high-temperature molding of this invention have the following beneficial effects: This invention attaches a chromium / platinum layer to the surface of the mold substrate, and a ruthenium layer is attached to the chromium / platinum layer. Thus, the ruthenium layer itself is oxidation-resistant, and the ruthenium above the chromium / platinum acts as a diffusion barrier, hindering the outward transport of chromium / platinum, making it less prone to oxidation. Furthermore, ruthenium has good anti-adhesion properties. Small amounts of oxygen penetrating through the ruthenium layer are absorbed by the chromium / platinum layer and will not directly oxidize the mold substrate. Moreover, chromium / platinum oxidation can form a dense oxide film at the grain boundaries with ruthenium, preventing oxygen from entering and oxidizing the mold substrate. Furthermore, when the mold is used for high-temperature molding, chromium / platinum atoms gain sufficient thermal energy to overcome the activation energy barrier, allowing them to diffuse through the grain boundaries and reach the ruthenium layer surface. Once the chromium / platinum reaches the metal surface, it reacts with residual oxygen in the surrounding atmosphere, leading to… Chromium / platinum oxide grows on the surface of the ruthenium layer until a critical thickness (very thin) is reached, ultimately forming a dense, continuous, and stable oxide film. This oxide film also prevents the mold from adhering to the glass surface, improving the mold's anti-adhesion properties. It also blocks oxygen from entering the coating, enhancing the mold's oxidation resistance, extending the lifespan of the graphite mold, increasing production yield, and reducing production costs. Furthermore, a titanium layer can be attached to the surface of the mold substrate before the chromium / platinum layer is applied, and then the chromium / platinum layer is applied on top of the titanium layer. Using titanium as an intermediate layer, its good adhesion ensures uniformity, thereby improving the adhesion of the entire protective coating. This reduces the internal stress of the film, promoting uniform film growth and helping to regulate the film's growth rate and uniformity, thus optimizing the quality and performance of the film layer throughout the entire film production process.

[0066] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0067] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A mold protective coating for high-temperature molding, characterized in that, include: A chromium / platinum layer is attached to the surface of the mold base of the mold, a ruthenium layer is attached to the chromium / platinum layer, and a thin film is formed on the outside of the ruthenium layer to improve the anti-adhesion and anti-oxidation properties; the thin film is a chromium / platinum oxide film formed by the oxidation of chromium / platinum from the chromium / platinum layer to the outer surface of the ruthenium layer.

2. The mold protective coating according to claim 1, characterized in that, It also includes a titanium layer disposed between the mold base and the chromium / platinum layer.

3. The mold protective coating according to claim 2, characterized in that, The deposition thickness of the titanium layer is within a range of ±20% centered at 50 nm, the deposition thickness of the chromium / platinum layer is within a range of ±20% centered at 200 nm, and the deposition thickness of the ruthenium layer is within a range of ±20% centered at 500 nm.

4. The mold protective coating according to claim 1, characterized in that, The mold substrate is graphite.

5. A mold for high-temperature molding, characterized in that, Includes a mold base and a mold protective coating as described in any one of claims 1-4, which is attached to the surface of the mold base.

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