GRADED COATING OF ELEMENT DIFFUSION INHIBITION AND ADHESION RESISTANCE ON MOLD FOR GLASS MOLDING

Abstract

Disclosed are coatings made of inorganic materials on molds for glass molding, particularly, a graded coating of element diffusion inhibition and adhesion resistance on molds for glass molding. The graded coating includes a Cr adhesion layer which is bonded with a substrate, a CrN intermediate layer and a Cr.sub.xW.sub.yN.sub.(1-x-y) surface layer, where 0.15<x<0.4, and 0.2y<0.45. The graded coating has excellent crack growth suppression and adhesion resistance.

Claims

1. A graded coating on a mold for glass molding, comprising: a Cr adhesion layer which is bonded with a substrate; a CrN intermediate layer; and a Cr.sub.xW.sub.yN.sub.(1-x-y) surface layer, wherein 0.15<x<0.4, and 0.2y<0.45.

2. The graded coating of claim 1, wherein a thickness of the Cr adhesion layer is 50-100 nm; a thickness of the CrN intermediate layer is 150-300 nm; and a thickness of the Cr.sub.xW.sub.yN.sub.(1-x-y) surface layer is 1300-1500 nm.

3. The graded coating of claim 1, wherein a wetting angle of the graded coating at 1000 C. is 125.

4. A method for preparing the graded coating of claim 1, comprising: (A) performing sputter cleaning on the substrate and target materials in a vacuum and an inert gas; (B) in a vacuum and an inert gas, depositing, with a Cr target and a W target, the Cr adhesion layer, the CrN intermediate layer and the Cr.sub.xW.sub.yN.sub.(1-x-y) surface layer successively on a surface of the substrate treated in step (A).

5. The method of claim 4, wherein the inert gas is selected from argon, nitrogen or a mixture thereof.

6. The method of claim 4, wherein in step (A), a flow rate is 100-180 sccm; a vacuum degree for the sputter cleaning is 0.4-0.5 Pa; the substrate is preheated to 200-400 C.; a bias voltage for deposition is 3070 V; a time for the sputter cleaning of the substrate is 30-120 min; and a time for the sputter cleaning of target materials is 1-5 min.

7. The method of claim 4, wherein in step (B), when depositing the Cr adhesion layer, a vacuum degree for the substrate in a vacuum chamber is 310.sup.3-610.sup.3 Pa; a working gas is argon; a vacuum degree of a reaction chamber is 0.4-0.5 Pa; a bias voltage for deposition is 3070 V; a power for the Cr target is 3-6 kW; a deposition temperature is 300-400 C.; a deposition time is 2-5 min.

8. The method of claim 4, wherein in step (B), when depositing the CrN intermediate layer, a working gas is a mixture of argon and nitrogen; a vacuum degree for the sputter cleaning is 0.4-0.5 Pa; a bias voltage is 3070 V; a power for the Cr target is 3-6 kW; a deposition temperature is 300-400 C.; and a deposition time is 20-40 min.

9. An application of the graded coating of claim 1, comprising applying the graded coating to the preparation of a mold for glass molding.

10. A mold for glass molding, comprising: a graded coating comprising a Cr adhesion layer which is bonded with a substrate, a CrN intermediate layer and a Cr.sub.xW.sub.yN.sub.(1-x-y) surface layer, wherein 0.15<x<0.4, and 0.2y<0.45.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 is a schematic diagram of a graded coating on a mold for glass molding according to an embodiments of the present invention.

[0040] FIGS. 2A-2B are SEM images showing a surface and a cross section of a coating according to a first embodiment.

[0041] FIG. 3 shows a test result of hardness of the graded coating according to the first embodiment.

[0042] FIG. 4 shows a test result of surface roughness of the graded coating according to the first embodiment.

[0043] FIG. 5 is an image showing morphologies of surfaces of the graded coating and the glass according to the first embodiment, in which the glass has been molded.

[0044] FIG. 6 shows an XRD result of elements of the graded coating according to the first embodiment.

[0045] FIG. 7 shows a test result of phase composition of the graded coating according to the first embodiment.

[0046] FIG. 8 shows a test result of wettability of the graded coating at high temperature according to the first embodiment.

[0047] FIG. 9A shows a test result of crack growth suppression of the graded coating according to the first embodiment; FIG. 9B shows a test result of crack growth suppression of the graded coating according to a second embodiment; FIG. 9C shows a test result of crack growth suppression of the graded coating according to a third embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

[0048] The embodiments are intended to better illustrate but not to limit the present invention. Therefore, non-substantial improvements and adjustments to the embodiments based on above-mentioned inventions by those skilled in the art shall fall within the scope of the present invention.

EXAMPLE 1

[0049] In this embodiment, illustrated is a method for preparing the graded coating on a mold of glass molding, comprising the following steps.

[0050] (1) Pre-treatment

[0051] The substrate (a tungsten carbide mold doped with 8% by mass of Co) was mechanically ground and polished, then was ultrasonically cleaned in deionized water, acetone and ethanol in turn for 20 min, respectively, and finally was dried in an oven at 80 C. for 30 min.

[0052] (2) Sputter cleaning

[0053] The treated substrate was placed in a vacuum chamber which was pre-vacuumized to a vacuum degree of 510.sup.3 Pa and heated to 300 C. High-purity argon (purity>99.99%, known from outer packing) was added to perform the ion sputter etching cleaning on the substrate and target materials with a flow rate of 120 sccm, a vacuum degree of 0.4 Pa and a bias voltage of 70 V. A time for the sputter cleaning of the substrate is 5 min, and a time for the sputter cleaning of the target materials is 5 min. The target materials were covered by a lining board during the sputter cleaning.

[0054] (3) Deposition of Cr adhesion layer

[0055] The Cr adhesion layer was deposited on the substrate using a plasma enhanced magnetron sputtering system. During the sputter cleaning, the vacuum degree of the substrate in the vacuum chamber was 510.sup.3 Pa; the working gas was argon (purity>99.99%, known from outer packing); the target material was a high-purity Cr target (purity>99.9%, known from outer packing); the vacuum degree was 0.4 Pa; the bias voltage was 30 V; the power for the Cr target was 5 kW; the deposition temperature was 300 C.; and the deposition time was 5 min.

[0056] (4) Deposition of CrN intermediate layer

[0057] The CrN intermediate layer was deposited on a surface of the substrate deposited with the Cr adhesion layer using the plasma enhanced magnetron sputtering system. During the sputter cleaning, the working gas was a mixture of argon (purity>99.99%, known from outer packing) and nitrogen (purity>99.99%, known from outer packing); the target material was a high-purity Cr target (purity>99.9%, known from outer packing); the vacuum degree was 0.4 Pa; the bias voltage for deposition was 30 V; the power for the Cr target was 5 kW; the deposition temperature was 300 C.; and the deposition time was 20 min.

[0058] (5) Deposition of Cr.sub.xW.sub.yN.sub.(1-x-y) surface layer

[0059] The Cr.sub.xW.sub.yN.sub.(1-x-y) surface layer was deposited on surface of the substrate deposited with the Cr adhesion layer and the CrN intermediate layer using the plasma enhanced magnetron sputtering system. During the sputter cleaning, the working gas was a mixture of argon (purity>99.99%, known from outer packing) and nitrogen (purity>99.99%, known from outer packing), the target materials were a high-purity Cr target (purity>99.9%, known from outer packing) and a high-purity W target (purity>99.6%, known from outer packing); the vacuum degree was 0.4 Pa, the bias voltage was 30 V; the power for the Cr target was 3 kW; the power for the W target was 4 kW; the deposition temperature was 300 C.; and the deposition time was 60 min.

EXAMPLE 2

[0060] In this embodiment, provided is a method for preparing the graded coating on a mold for glass molding, comprising the following steps.

[0061] (1) Pre-treatment

[0062] The substrate (a tungsten carbide mold doped with 8% by mass of Co) was mechanically ground and polished, then was ultrasonically cleaned in deionized water, acetone and ethanol solution in turn for 20 min, respectively, and finally was dried in an oven at 80 C. for 30min.

[0063] (2) Sputter cleaning

[0064] The treated substrate was placed in a vacuum chamber which was pre-vacuumized to a vacuum degree of 510.sup.3 Pa and heated to 300 C. High-purity argon (purity>99.99%, known from outer packing) was added to perform the ion sputter etching cleaning on the substrate and target materials with a flow rate of 120 sccm, a vacuum degree of 0.4 pa, a bias voltage of 70 V. A time for the sputter cleaning of the substrate is 60 min, and a time for the sputter cleaning of the target materials is 5 min. The target materials were covered by a lining board during the sputter cleaning.

[0065] (3) Deposition of Cr adhesion layer

[0066] The Cr adhesion layer was deposited on the substrate using a plasma enhanced magnetron sputtering system. During the sputter cleaning, the vacuum degree of the substrate in the vacuum chamber was 510.sup.3 Pa; the working gas was argon (purity>99.99%, known from outer packing); the target material was a high-purity Cr target (purity>99.9%, known from outer packing); the vacuum degree was 0.4 Pa; the bias voltage was 30 V; the power for the Cr target was 5 kW, the deposition temperature was 300 C., and the deposition time was 5 min.

[0067] (4) Deposition of Cr.sub.xW.sub.yN.sub.(1-x-y) surface layer

[0068] The Cr.sub.xW.sub.yN.sub.(1-x-y) surface layer was deposited on a surface of the substrate deposited with the Cr adhesion layer using the plasma enhanced magnetron sputtering system. During the sputter cleaning, the working gas was a mixture of argon (purity>99.99%, known from outer packing) and nitrogen (purity>99.99%, known from outer packing); the target materials were a high-purity Cr target (purity>99.9%, known from outer packing) and a high-purity W target (purity>99.6%, known from outer packing); the vacuum degree was 0.4 Pa; the bias voltage for deposition was 30 V; the power for the Cr target was 3 kW; the power for the W target was 4 kW; the deposition temperature was 300 C.; and the deposition time was 60 min.

EXAMPLE 3

[0069] In this embodiment, illustrated is a method for preparing a graded coating on a mold for glass molding, comprising the following steps.

[0070] (1) Pre-treatment

[0071] The substrate (a tungsten carbide mold doped with 8% by mass of Co) was mechanically ground and polished, then was ultrasonically cleaned in deionized water, acetone and ethanol in turn for 20 min, respectively, and finally was dried in an ovan at 80 C. for 30 min.

[0072] (2) Sputter cleaning

[0073] The substrate was placed in a vacuum chamber which was pre-vacuumized to a vacuum degree of 510-3 Pa and heated to 300 C. During sputter cleaning, high-purity argon (purity>99.99%, known from outer packing) was added to perform the ion sputter etching cleaning on the substrate and target materials with a flow rate of 120 sccm, a vacuum degree of 0.4 Pa, a bias voltage of 70 V. A time for the sputter cleaning of the substrate was 60 min, and a time for the sputter cleaning of the target materials was 5 min. The target materials were covered by a lining board during sputter cleaning.

[0074] (3) Deposition of Cr.sub.xW.sub.yN.sub.(1-x-y) surface layer

[0075] The Cr.sub.xW.sub.yN.sub.(1-x-y) surface layer was deposited on a surface of the substrate deposited with the Cr adhesion layer using the plasma enhanced magnetron sputtering system. During the sputter cleaning, the working gas was a mixture of argon (purity>99.99%, known from outer packing) and nitrogen (purity>99.99%, known from outer packing); the target materials were a high-purity Cr target (purity>99.9%, known from outer packing) and a high-purity W target (purity>99.6%, known from outer packing); the vacuum degree was 0.4 Pa; the bias voltage for deposition was 30 V; the power for the Cr target was 4 kW; the power for the W target was 4 kW; the deposition temperature was 300 C., and the deposition time was 60 min.

Performance Test

[0076] The coating in the first embodiment is tested in terms of performance such as morphologies of surface and cross section of the coating, hardness, surface roughness, surface elements, phase compositions and wetability at high temperature, and the results are shown in FIGS. 2-8.

[0077] The hardness of the coating is tested by nanoindentors using the continuous stiffness measurement (CSM). The depth of nano-indentation is set to 110 nm so as to eliminate the substrate factor on the test result. Five different areas on the sample are selected for testing, and then the hardness and elastic modulus are averaged, so that the accuracy and reliability of the data are ensured.

[0078] The roughness of the surface was tested by an atomic force microscope with a sample area of 22 m.

[0079] The molding pressure is tested by molding the BK7 optical glass using the self-designed mold for optical non-spherical glass molding (Chinese Patent Application No. 201710124489.7; Chinese Patent Publication No. 106946441 A), where the molding pressure is 0.5 kN; and the molding temperature is 650 C. The morphologies and colors of the BK7 glass and the coating on the mold are observed.

[0080] Elements of the coating surface are tested via qualitative analysis using X-ray energy dispersive spectrometer (EDS) of the field emission scanning electron microscope (FESEM).

[0081] Phase structure of the coating is tested by an X-ray diffractometer, and the crystal structure of the coating is analyzed with small angle diffraction to avoid the factor of the substrate.

[0082] Through a high-temperature wetting test, the wettability of the coating at high temperature is examined at a temperature of 1000 C. by using a modified sessile drop method, where the vacuum is 510.sup.3 Pa, and the glass is BK7 optical glass.

[0083] The property of crack growth suppression of the coating is tested by applying a load of 60 N to the coating via a diamond indenter with a conical angle of 120 of a Rockwell hardness tester, and then the surface of the pressed coating was observed by a microscope with ultra depth of field.

[0084] As shown in FIGS. 2A-B, the surface morphology of the graded coating in Example 1 presents cauliflower clusters of different sizes, and the surface exhibits defects such as small cracks and holes. It is observed from the cross section of the coating that the coating grows in columnar crystal structure, with layers tightly bound together, where the Cr adhesion layer has a thickness of 96 nm; the CrN intermediate layer has a thickness of 297 nm and the Cr.sub.xW.sub.yN.sub.(1-x-y) layer has a thickness of 1375 nm.

[0085] As shown in FIG. 3, the coating prepared in Example 1 has a hardness of 16 GPa. Thus, the coating of the invention having good mechanical properties reaches the hardness standard of the coating on the mold for glass molding.

[0086] As shown in FIG. 4, the roughness of the graded coating in Example 1 is 4 nm, representing an excellent surface quality and meeting the use requirements of coating on the mold for precision glass molding.

[0087] As shown in FIG. 5, after the thermoforming, the glass and the surface of the mold coating have no significant changes. Further, the color of the glass is not changed and no bubble is generated, and the mold surface has no adhered glass. no no peeling appears on the contacting part between the coating surface and the glass. The graded coating in Example 1 shows excellent properties of high temperature resistance and adhesion resistance during molding.

[0088] As shown in FIG. 6, the graded coating in Example 1 mainly comprises Cr, W and N elements.

[0089] As shown in FIG. 7, the surface layer of the graded coating in Example 1 has significant CrN phase, with main crystal orientations of (111), (200), (220), (311) and (222), containing 35% by mass of Cr, 40% by mass of W, 45% by mass of N.

[0090] As shown in FIG. 8, when the coating prepared in Example 1 is in an environment temperature of 1000 C. and a vacuum of 510 Pa, no spread appears on the surfaces of the molten glass and the coating, and contact angles between the molten glass and the coating at high temperature are 125. Therefore, the coating of the invention has excellent properties of high temperature resistance and adhesion resistance.

[0091] As shown in FIG. 9, compared to the coatings prepared in Examples 2-3, the number of cracks of the graded coating in Example 1 was significantly reduced, demonstrating that the property of crack growth suppression of the graded coating in this invention was significantly improved.

[0092] It should be understood that although the embodiments are illustrated in the description for clarity, each embodiment may include more than one technical solution. It is noted that the description should be taken as a whole, and various embodiments can be appropriately combined to form other embodiments that can be understood by those skilled in the art.