Magnetron sputtering preparation method of diamond-like composite coating on surface of crystallizer copper plate

Abstract

The invention belongs to the technical field of metallurgy, and particularly relates to a magnetron sputtering preparation method of a diamond-like composite coating on the surface of a crystallizer copper plate. Comprising the following steps: S1, pretreatment of a copper plate: sequentially carrying out surface cleaning, grinding and polishing and acid etching treatment on the crystallizer copper plate; s2, a transition layer is deposited, specifically, a chromium transition layer is deposited on the surface of the pretreated copper plate through the non-equilibrium plasma magnetron sputtering technology; s3, composite coating deposition: depositing a diamond-like coating on the surface of the transition layer to form a composite coating; and S4, post-treatment: carrying out annealing and surface polishing treatment on the crystallizer copper plate deposited with the composite coating. The composite coating has the comprehensive performance of high hardness, low friction, high wear resistance and high thermal conductivity, and the preparation method is controllable in parameter, good in repeatability, uniform in coating thickness and suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, and in particular relates to a magnetron sputtering method for preparing a diamond-like composite coating on the surface of a crystallizer copper plate. Background Technology

[0002] In continuous steel casting processes, the crystallizer is one of the core pieces of equipment, and the surface properties of its copper plate directly affect the quality of the cast billet and production efficiency. During operation, the copper plate of the crystallizer is exposed to a high-temperature, high-friction, and corrosive environment for extended periods, which easily leads to wear, thermal fatigue, and surface oxidation. This results in increased surface roughness and decreased thermal conductivity, ultimately affecting the surface quality of the cast billet and the service life of the crystallizer.

[0003] Currently, electroplating and thermal spraying are commonly used in industry to treat the surface of copper plates for crystallizers. However, these methods have the following drawbacks:

[0004] 1. Electroplated coating: The adhesion to the copper substrate is weak, and it is easy to peel off under high temperature and high stress conditions;

[0005] 2. Thermal spray coating: The coating thickness is difficult to control precisely, and the porosity is high, which affects the density and protective performance of the coating;

[0006] 3. Existing magnetron sputtered diamond-like carbon coatings: have high internal stress and poor thermal expansion coefficient matching with the copper substrate, which easily leads to coating cracking and peeling.

[0007] Therefore, developing a method for preparing a coating on the surface of a crystallizer copper plate that has strong adhesion, low internal stress, and stable performance has significant industrial application value. Summary of the Invention

[0008] The purpose of this invention is to provide a magnetron sputtering method for preparing a diamond-like composite coating on the surface of a crystallizer copper plate, so as to solve the problems existing in the prior art.

[0009] The technical solution adopted by this invention to solve its technical problem is:

[0010] A magnetron sputtering method for preparing a diamond-like carbon composite coating on the surface of a crystallizer copper plate includes the following steps:

[0011] S1. Copper plate pretreatment: The copper plate of the crystallizer is cleaned, polished, and acid-etched in sequence.

[0012] S2. Transition layer deposition: A chromium transition layer is deposited on the pretreated copper plate surface using non-equilibrium plasma magnetron sputtering technology.

[0013] S3. Composite coating deposition: A diamond-like coating is deposited on the surface of the transition layer to form a composite coating;

[0014] S4. Post-treatment: Annealing and surface polishing are performed on the copper plate of the crystallizer with the composite coating deposited.

[0015] Furthermore, in step S1, surface cleaning is performed by placing the copper plate of the crystallizer in an acetone solution and ultrasonically cleaning it for 15-20 minutes to remove surface oil stains; then rinsing it with anhydrous ethanol 2-3 times, each rinsing time being 5-10 minutes, to ensure that there are no residual organic substances on the surface.

[0016] Furthermore, in step S1, the grinding and polishing process involves sequentially grinding the surface of the copper plate with sandpaper of 200 grit, 400 grit, 600 grit, and 800 grit to remove the surface oxide layer and scratches, so that the surface roughness Ra reaches 0.2~0.5μm.

[0017] Furthermore, in step S1, the acid etching process is as follows: the polished copper plate is placed in a 10%~15% dilute sulfuric acid solution and soaked at room temperature for 30~60 seconds to remove surface oxides and impurities. Then it is rinsed with clean water and placed in an ultrasonic cleaner to be cleaned with deionized water for 10~15 minutes to remove residual acid.

[0018] Furthermore, in step S2, the method for depositing the transition layer specifically involves using a chromium target with a purity of 99.95% or higher as the target material for the transition layer deposition, placing the pretreated copper plate into the magnetron sputtering chamber, and evacuating the vacuum level to below 5 × 10⁻⁶. -3 Pa, then argon gas with a purity of 99.999% is introduced as the working gas, with the flow rate controlled at 20~30 sccm. After ignition, the power is adjusted to 100~150W and the bias voltage to -100~-150V to begin depositing the transition layer. The deposition time is 10~15 minutes, so that the thickness of the transition layer reaches 50~100nm. During the deposition process, the gas pressure in the sputtering chamber is kept stable at 0.5~1.0Pa, and the temperature of the copper substrate is controlled at 20~30℃ through the circulating water cooling system.

[0019] Furthermore, in step S3, the method for depositing the composite coating is as follows: a graphite target with a purity of 99.99% is selected as the target material, and a titanium sheet is used as the auxiliary target material. After the transition layer is deposited, without disrupting the vacuum environment, the working gas is directly switched to a mixture of methane and argon. The flow rate of the mixed gas is controlled at 30~50 sccm, the power is adjusted to 200~300W, and the bias voltage is -50~-100V. The deposition of the diamond-like carbon composite coating begins, and the deposition time is 60~90 minutes, so that the thickness of the diamond-like carbon composite coating reaches 1~3μm. During the deposition process, the temperature of the copper substrate is controlled at 200~300℃ through the heating system.

[0020] Furthermore, the flow ratio of methane to argon is controlled at 1:5 to 1:10.

[0021] Furthermore, in step S4, the annealing process specifically involves placing the copper plate with the composite coating into a vacuum annealing furnace and evacuating it to a vacuum level below 1×10⁻⁶. -3 Pa, heat to 400~500℃, hold for 30~60 minutes, then cool to room temperature with the furnace, and then lightly polish the surface of the annealed copper plate to remove the small protrusions and defects on the coating surface, so that the surface roughness Ra reaches 0.1~0.3μm.

[0022] The present invention has the following beneficial effects:

[0023] 1. This invention forms a gradient transition composite coating by non-equilibrium plasma deposition of a chromium transition layer and a diamond-like carbon layer. The bonding strength between the composite coating and the substrate reaches 35-48 MPa, which is much higher than the 12-25 MPa of the traditional method, thus solving the problem of easy peeling of the coating.

[0024] 2. The optimized deposition process and annealing treatment of this invention effectively reduce the internal stress of the coating. After the thermal shock test, the coating is free of cracks, overcoming the defect of easy cracking of diamond-like coatings prepared by conventional magnetron sputtering methods.

[0025] 3. The composite coating has a hardness of 7500-8800 HV, a wear rate that is 82%-88% lower than that of uncoated copper plates, a friction coefficient of 0.12-0.18, and a thermal conductivity of 350-420 W / (m·K). It also has comprehensive properties of high hardness, low friction, high wear resistance, and high thermal conductivity.

[0026] 4. The parameters of this invention are controllable, have good repeatability, and produce uniform coating thickness, making it suitable for large-scale industrial production. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0028] Example 1:

[0029] A magnetron sputtering method for preparing a diamond-like carbon composite coating on the surface of a crystallizer copper plate includes the following steps:

[0030] S1. Copper plate pretreatment: The copper plate of the crystallizer is cleaned, polished and acid-etched in sequence.

[0031] The copper plate of the crystallizer was ultrasonically cleaned in acetone solution for 18 minutes to remove surface oil. It was then rinsed twice with anhydrous ethanol for 8 minutes each time to ensure that there was no residual organic matter on the surface. The surface of the copper plate was then polished step by step with 200-grit, 400-grit, 600-grit, and 800-grit sandpaper to remove the surface oxide layer and scratches, so that the surface roughness Ra reached 0.3μm. The polished copper plate was then immersed in a 10% dilute sulfuric acid solution at room temperature for 40 seconds to remove surface oxides and impurities. It was then rinsed with clean water and placed in an ultrasonic cleaner to be cleaned with deionized water for 13 minutes to remove residual acid.

[0032] S2. Transition layer deposition: A chromium transition layer is deposited on the pretreated copper plate surface using non-equilibrium plasma magnetron sputtering technology.

[0033] A chromium target with a purity of 99.95% or higher was used as the target material for the transition layer deposition. The pretreated copper plate was placed in the magnetron sputtering chamber and the vacuum was evacuated to a level below 5 × 10⁻⁶. -3 Pa, then argon gas with a purity of 99.999% is introduced as the working gas, with the flow rate controlled at 25 sccm. After ignition, the power is adjusted to 120W and the bias voltage to -120V, and the deposition of the transition layer begins. The deposition time is 12 minutes, so that the thickness of the transition layer reaches 80nm. During the deposition process, the gas pressure in the sputtering chamber is kept stable at 0.8Pa, and the temperature of the copper substrate is controlled at 25℃ through the circulating water cooling system. Low-temperature deposition is beneficial to maintain the fine grain structure and avoid softening of the copper substrate.

[0034] S3. Composite coating deposition: A diamond-like coating is deposited on the surface of the transition layer to form a composite coating;

[0035] A graphite target with a purity of 99.99% was selected as the target material, and a titanium sheet was used as the auxiliary target material. After the transition layer deposition was completed, without disrupting the vacuum environment, the working gas was directly switched to a mixture of methane and argon, with the flow ratio of methane to argon controlled at 1:8 and the mixed gas flow rate controlled at 40 sccm. The power was adjusted to 250W and the bias voltage to -80V, and the deposition of the diamond-like carbon composite coating began. The deposition time was 75 minutes, achieving a diamond-like carbon composite coating thickness of 2μm. During the deposition process, the temperature of the copper substrate was controlled at 250℃ using a heating system. The deposition temperature of 200-300℃ provides sufficient surface migration energy, allowing atoms to arrange themselves into a more ordered structure, while also preventing excessively high temperatures from causing carbon graphitization.

[0036] S4. Post-treatment: Annealing and surface polishing are performed on the copper plate of the crystallizer with the composite coating deposited.

[0037] A copper plate with a composite coating is placed in a vacuum annealing furnace and evacuated until the vacuum level is below 1×10⁻⁶. -3Pa, heat to 450℃, hold for 45 minutes, then cool to room temperature with the furnace, and then lightly polish the surface of the annealed copper plate to remove the small protrusions and defects on the coating surface, so that the surface roughness Ra reaches 0.2μm.

[0038] Example 2:

[0039] A magnetron sputtering method for preparing a diamond-like carbon composite coating on the surface of a crystallizer copper plate includes the following steps:

[0040] S1. Copper plate pretreatment: The copper plate of the crystallizer is cleaned, polished and acid-etched in sequence.

[0041] The copper plate of the crystallizer was ultrasonically cleaned in acetone solution for 15 minutes to remove surface oil. It was then rinsed twice with anhydrous ethanol for 5 minutes each time to ensure that no organic matter remained on the surface. The surface of the copper plate was then polished step by step with 200-grit, 400-grit, 600-grit, and 800-grit sandpaper to remove the surface oxide layer and scratches, so that the surface roughness Ra reached 0.5μm. The polished copper plate was then immersed in a 10% dilute sulfuric acid solution at room temperature for 30 seconds to further remove surface oxides and impurities. It was then rinsed with clean water and placed in an ultrasonic cleaner to be cleaned with deionized water for 10 minutes to remove residual acid.

[0042] S2, Transition Layer Deposition: A chromium transition layer is deposited on the pretreated copper plate surface using non-equilibrium plasma magnetron sputtering technology.

[0043] A chromium target with a purity of 99.95% or higher was used as the target material for the transition layer deposition. The pretreated copper plate was placed in the magnetron sputtering chamber and the vacuum was evacuated to 5 × 10⁻⁶. -3 Pa, then argon gas with a purity of 99.999% is introduced as the working gas, with the flow rate controlled at 20. After ignition, the power is adjusted to 100W and the bias voltage to -100V, and the deposition of the transition layer begins. The deposition time is 10 minutes, so that the thickness of the transition layer reaches 50nm. During the deposition process, the gas pressure in the sputtering chamber is kept stable at 0.5Pa, and the temperature of the copper substrate is controlled at 20℃ through the circulating water cooling system.

[0044] S3. Composite coating deposition: A diamond-like coating is deposited on the surface of the transition layer to form a composite coating;

[0045] A graphite target with a purity of 99.99% was selected as the target material, and a titanium sheet was used as the auxiliary target material. After the transition layer was deposited, without disrupting the vacuum environment, the working gas was directly switched to a mixture of methane and argon. The flow ratio of methane to argon was controlled at 1:5, and the flow rate of the mixed gas was controlled at 30 sccm. The power was adjusted to 200V and the bias voltage to -50V, and the deposition of the diamond-like carbon composite coating began. The deposition time was 60 minutes, so that the thickness of the diamond-like carbon composite coating reached 1μm. During the deposition process, the temperature of the copper substrate was controlled at 200℃ through the heating system.

[0046] S4. Post-treatment: Annealing and surface polishing are performed on the copper plate of the crystallizer with the composite coating deposited.

[0047] A copper plate with a composite coating is placed in a vacuum annealing furnace and evacuated to a vacuum level of 1×10⁻⁶. -3 Pa, heat to 400℃, hold for 30 minutes, then cool to room temperature with the furnace, and then lightly polish the surface of the annealed copper plate to remove the small protrusions and defects on the coating surface, so that the surface roughness Ra reaches 0.3μm.

[0048] Example 3:

[0049] A magnetron sputtering method for preparing a diamond-like carbon composite coating on the surface of a crystallizer copper plate includes the following steps:

[0050] S1. Copper plate pretreatment: The copper plate of the crystallizer is cleaned, polished and acid-etched in sequence.

[0051] The copper plate of the crystallizer was ultrasonically cleaned in acetone solution for 20 minutes to remove surface oil. Then it was rinsed three times with anhydrous ethanol for 10 minutes each time to ensure that there was no residual organic matter on the surface. The surface of the copper plate was then polished step by step with 200-grit, 400-grit, 600-grit, and 800-grit sandpaper to remove the surface oxide layer and scratches, so that the surface roughness Ra reached 0.2μm. The polished copper plate was then immersed in a 15% dilute sulfuric acid solution at room temperature for 60 seconds to remove surface oxides and impurities. Then it was rinsed with clean water and placed in an ultrasonic cleaner to be cleaned with deionized water for 15 minutes to remove residual acid.

[0052] S2. Transition layer deposition: A chromium transition layer is deposited on the pretreated copper plate surface using non-equilibrium plasma magnetron sputtering technology.

[0053] A chromium target with a purity of 99.95% or higher was used as the target material for the transition layer deposition. The pretreated copper plate was placed in the magnetron sputtering chamber and the vacuum was evacuated to a level below 5 × 10⁻⁶. -3Pa, then argon gas with a purity of 99.999% is introduced as the working gas, with a flow rate controlled at 30 sccm. After ignition, the power is adjusted to 150W and the bias voltage to -150V, and the deposition of the transition layer begins. The deposition time is 15 minutes, so that the thickness of the transition layer reaches 100nm. During the deposition process, the gas pressure in the sputtering chamber is kept stable at 1.0Pa, and the temperature of the copper substrate is controlled at 30℃ through a circulating water cooling system.

[0054] S3. Composite coating deposition: A diamond-like coating is deposited on the surface of the transition layer to form a composite coating;

[0055] In step S3, the specific method for composite coating deposition is as follows: a graphite target with a purity of 99.99% is selected as the target material, and a titanium sheet is used as the auxiliary target material. After the transition layer deposition is completed, without disrupting the vacuum environment, the working gas is directly switched to a mixture of methane and argon. The flow ratio of methane to argon is controlled at 1:10, the flow rate of the mixed gas is controlled at 50 sccm, the power is adjusted to 300W, the bias voltage is -100V, and the deposition of diamond-like carbon composite coating begins. The deposition time is 90 minutes, so that the thickness of the diamond-like carbon composite coating reaches 3μm. During the deposition process, the temperature of the copper substrate is controlled at 300℃ through the heating system.

[0056] S4. Post-treatment: Annealing and surface polishing are performed on the copper plate of the crystallizer with the composite coating deposited.

[0057] A copper plate with a composite coating is placed in a vacuum annealing furnace and evacuated until the vacuum level is below 1×10⁻⁶. -3 Pa, heat to 500℃, hold for 60 minutes, then cool to room temperature in the furnace, and then lightly polish the surface of the annealed copper plate to remove the small protrusions and defects on the coating surface, so that the surface roughness Ra reaches 0.1μm.

[0058] The tests conducted on Examples 1-3 are shown in Table 1 below:

[0059] Table 1: Summary of Test Results for Examples 1-3

[0060]

[0061] The comparison item for the wear rate reduction ratio in Table 1 is the uncoated copper plate. As can be seen from Table 1, the composite coating prepared by the method of the present invention has strong coating bonding strength, reaching 35~48MPa, coating hardness above 7500HV, and a friction coefficient below 0.18, indicating low friction. Furthermore, it has a thermal conductivity higher than 350W / (m·K), exhibiting good thermal conductivity, good internal stress release, and no cracks.

[0062] Comparative Example 1:

[0063] Taking Example 1 as an example, a comparison was made with existing copper plate coatings and magnetron sputtering single coatings. The experimental setup is as follows:

[0064] Comparison Sample 1: Chromium plating was performed on the surface of the copper plate of the crystallizer using a conventional electroplating process, with a thickness of approximately 10 μm;

[0065] Comparative Sample 2: WC-Co coating with a thickness of approximately 100 μm was prepared by supersonic flame spraying;

[0066] Comparative Sample 3: A diamond-like coating prepared using existing magnetron sputtering methods, with no transition layer and a thickness of approximately 2 μm.

[0067] Test sample: The composite coating obtained in Example 1 of this invention.

[0068] The comparison results are shown in Table 2 below:

[0069] Table 2: Comparison Experiment of Composite Coating of the Present Invention with Single Coatings by Electroplating, Thermal Spraying and Magnetron Sputtering

[0070]

[0071] As shown in Table 2 above, the bonding strength of Comparative Sample 1 is only 12 MPa, making it prone to peeling; although Comparative Sample 2 has a certain bonding strength (25 MPa), its high porosity leads to poor long-term stability; the bonding strength of this invention reaches 42 MPa, an improvement of more than 250%, and the gradient transition layer design eliminates interface abrupt changes, significantly improving the bonding strength. Comparative Sample 3 directly deposits diamond-like carbon (DLC) onto a copper plate. Due to the large difference in thermal expansion coefficients, the internal stress is high, and microcracks appear after the thermal shock test; this invention, through a chromium transition layer + gradient design + annealing treatment, effectively releases internal stress. Examples 1-3 showed no cracks after 50 thermal shocks, indicating good coating integrity.

[0072] Compared with the electroplated coating of the control sample 1 and the control sample 2, the hardness of the coating is low; compared with the thermal spray coating of the control sample 2, the thermal conductivity is poor; compared with the control sample 3, although the hardness is high, the bonding force is insufficient; the present invention ensures high hardness, low friction, high thermal conductivity and high bonding force, and has excellent comprehensive performance.

[0073] The problem of uneven coating thickness in thermal spraying has always existed. Compared with thermal spraying, magnetron sputtering technology has a significant technical advantage in terms of coating thickness uniformity. Although electroplating coatings have better thickness uniformity than thermal spraying coatings, the environmental problems of electroplating solutions are prominent. The composite coating of this invention has uniform thickness, good performance, and good repeatability, making it suitable for industrial production.

[0074] The working principle of this invention is:

[0075] The coefficient of thermal expansion of the copper substrate is approximately 17 × 10⁻⁶. -6 / K, the coefficient of thermal expansion of diamond-like carbon coating is approximately 2-3×10⁻⁶. -6The coefficient of thermal expansion of the chromium transition layer is approximately 6 × 10⁻⁶ K, which varies considerably. Direct deposition of diamond-like carbon coatings can lead to significant thermal and internal stresses. -6 / K, situated between the two, serves as a gradient transition and buffers thermal stress. Chromium and copper have good metallurgical compatibility; under non-equilibrium plasma bombardment, chromium atoms can form a diffusion interface or pseudo-diffusion layer with the copper matrix, enhancing mechanical and chemical bonding and preventing interface peeling. The chromium layer can also, to some extent, block the diffusion of copper atoms into the diamond-like carbon coating, preventing copper-catalyzed carbon graphitization and protecting the high-hardness structure of the diamond-like carbon coating.

[0076] Unlike traditional balanced magnetron sputtering, unbalanced magnetron sputtering uses a magnetic field design that causes some plasma to overflow from the target area and extend to the vicinity of the substrate. This results in high-density ion bombardment of the substrate, significantly increasing ion energy and flux. In the early stages of transition layer deposition, high-energy ions, such as Ar... + The ion bombardment further removes residual contaminants and oxide layers from the copper plate surface, while simultaneously generating surface defects and active sites, which facilitates the adsorption and nucleation of subsequent atoms. At the same time, high-energy ion bombardment provides additional energy to the deposited atoms, promoting surface migration and interfacial diffusion of chromium atoms on the copper surface, forming a stronger interfacial bond. Ion bombardment continuously rearranges the deposited atoms, eliminating porosity and defects, resulting in a dense transition layer.

[0077] During the deposition of diamond-like carbon (DLC) composite coatings, methane is dissociated by high-energy electron collisions in plasma, generating various active groups and atoms such as CH3, CH2, CH, C, and H. These active groups adsorb, migrate, and react on the substrate surface, forming an amorphous carbon network structure. The addition of argon enhances the ion bombardment effect, contributing to the formation of more sp(s). 3 Hybridization enhances coating hardness. During sputtering, titanium sheets are dissociated, generating titanium atoms or ions that are incorporated into the diamond-like carbon coating. The introduction of titanium forms TiC nanocrystals, dispersed within the amorphous carbon network, acting as a second-phase reinforcement. Furthermore, the incorporation of titanium alters the connection mode of the carbon network, mitigating structural distortion and reducing internal stress. The resulting nanocrystalline / amorphous composite structure helps inhibit crack propagation and improves toughness. Methane provides a sufficient carbon source, while argon enhances ion bombardment and promotes sputtering. 3 Bond formation. The ratio of the two is controlled at 1:5 to 1:10, so as to achieve the best balance between hardness, toughness and internal stress.

[0078] Deposited diamond-like carbon (DLC) composite coatings exhibit significant compressive stress, primarily stemming from ion bombardment and the non-equilibrium state of atomic arrangement. During vacuum annealing at 400-500℃, atoms gain sufficient energy for local rearrangement and relaxation, eliminating the metastable structure and releasing the internal stress. Since the annealing temperature is lower than the graphitization transition temperature, it does not damage the high-hardness structure of the DLC composite coating.

[0079] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the concept and scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the design concept of the present invention should fall within the protection scope of the present invention.

[0080] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A magnetron sputtering method for preparing a diamond-like carbon composite coating on the surface of a crystallizer copper plate, characterized in that, Includes the following steps: S1. Copper plate pretreatment: The copper plate of the crystallizer is cleaned, polished, and acid-etched in sequence. S2. Transition layer deposition: A chromium transition layer is deposited on the pretreated copper plate surface using non-equilibrium plasma magnetron sputtering technology. S3. Composite coating deposition: A diamond-like coating is deposited on the surface of the transition layer to form a composite coating; S4. Post-treatment: Annealing and surface polishing are performed on the copper plate of the crystallizer with the composite coating deposited.

2. The magnetron sputtering preparation method for a diamond-like carbon composite coating on the surface of a crystallizer copper plate according to claim 1, characterized in that, In step S1, the surface cleaning is as follows: the copper plate of the crystallizer is placed in an acetone solution and ultrasonically cleaned for 15-20 minutes to remove surface oil stains; then it is rinsed with anhydrous ethanol 2-3 times, each rinsing time is 5-10 minutes, to ensure that there are no residual organic substances on the surface.

3. The magnetron sputtering preparation method for a diamond-like carbon composite coating on the surface of a crystallizer copper plate according to claim 2, characterized in that, In step S1, the grinding and polishing process involves sequentially grinding the surface of the copper plate with 200-grit, 400-grit, 600-grit, and 800-grit sandpaper to remove the surface oxide layer and scratches, so that the surface roughness Ra reaches 0.2~0.5μm.

4. The magnetron sputtering preparation method for the diamond-like carbon composite coating on the surface of a crystallizer copper plate according to claim 3, characterized in that, In step S1, the acid etching process is as follows: the polished copper plate is placed in a 10%~15% dilute sulfuric acid solution and soaked at room temperature for 30~60 seconds to remove surface oxides and impurities. Then it is rinsed with clean water and placed in an ultrasonic cleaner and cleaned with deionized water for 10~15 minutes to remove residual acid.

5. The magnetron sputtering preparation method of the diamond-like carbon composite coating on the surface of the crystallizer copper plate according to claim 1, characterized in that, In step S2, the method for depositing the transition layer specifically involves: using a chromium target with a purity of 99.95% or higher as the target material for the transition layer deposition; placing the pretreated copper plate into the magnetron sputtering chamber; and evacuating the chamber to a vacuum level below 5 × 10⁻⁶. -3 Pa, then argon gas with a purity of 99.999% is introduced as the working gas, with the flow rate controlled at 20~30 sccm. After ignition, the power is adjusted to 100~150W and the bias voltage to -100~-150V to begin depositing the transition layer. The deposition time is 10~15 minutes, so that the thickness of the transition layer reaches 50~100nm. During the deposition process, the gas pressure in the sputtering chamber is kept stable at 0.5~1.0Pa, and the temperature of the copper substrate is controlled at 20~30℃ through the circulating water cooling system.

6. The method for preparing a diamond-like carbon composite coating on the surface of a crystallizer copper plate by magnetron sputtering according to claim 1, characterized in that, In step S3, the method for depositing the composite coating is as follows: a graphite target with a purity of 99.99% is selected as the target material, and a titanium sheet is used as the auxiliary target material. After the transition layer is deposited, without disrupting the vacuum environment, the working gas is directly switched to a mixture of methane and argon. The flow rate of the mixed gas is controlled at 30~50 sccm, the power is adjusted to 200~300W, and the bias voltage is -50~-100V. The deposition of the diamond-like carbon composite coating begins, and the deposition time is 60~90 minutes, so that the thickness of the diamond-like carbon composite coating reaches 1~3μm. During the deposition process, the temperature of the copper substrate is controlled at 200~300℃ through the heating system.

7. The magnetron sputtering preparation method for a diamond-like carbon composite coating on the surface of a crystallizer copper plate according to claim 6, characterized in that, The flow ratio of methane to argon is controlled at 1:5 to 1:

10.

8. The method for preparing a diamond-like carbon composite coating on the surface of a crystallizer copper plate by magnetron sputtering according to claim 1, characterized in that, In step S4, the annealing process specifically involves placing the copper plate with the composite coating into a vacuum annealing furnace and evacuating it to a vacuum level below 1×10⁻⁶. -3 Pa, heat to 400~500℃, hold for 30~60 minutes, then cool to room temperature with the furnace, and then lightly polish the surface of the annealed copper plate to remove the small protrusions and defects on the coating surface, so that the surface roughness Ra reaches 0.1~0.3μm.

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