Method for preparing diamond coating on the surface of high-speed steel cutting tools and their products

Abstract

This invention provides a method for preparing a diamond coating on the surface of high-speed steel cutting tools and their products, belonging to the field of cutting tool surface coating modification technology. The method includes pretreatment of the high-speed steel substrate, low-temperature plasma carburizing, physical vapor deposition of a silicon transition layer on the substrate surface, and finally diamond coating deposition, resulting in an ultra-thin diamond coating on the cutting tool surface. This invention employs an integrated modification scheme of carburizing pretreatment and a composite silicon transition layer. First, carburizing forms a dense carbide barrier structure on the surface of the high-speed steel, inhibiting the diffusion of Fe and Co elements in the substrate and strengthening the surface mechanical properties. Then, silicon is used as a transition layer to achieve lattice adaptation and stress buffering, thereby inhibiting graphite phase formation, reducing internal stress in the coating, and significantly improving the bonding strength and coating uniformity between the subsequent diamond coating and the high-speed steel substrate.

Description

Technical Field

[0001] This invention relates to the field of surface coating modification technology for cutting tools, specifically to a method for preparing diamond coatings on the surface of cutting tools and their products made of high-speed steel. Background Technology

[0002] In existing diamond-coated high-speed steel tool manufacturing processes, relying solely on surface cleaning, conventional crystal implantation, or single barrier layer pretreatment methods cannot fundamentally solve the problems of Fe and Co elements in the high-speed steel substrate easily inducing the formation of graphite phases during diamond growth, weak interfacial bonding between the film and substrate, and easy peeling and cracking of the coating. Traditional carburizing / nitrocarburizing can only achieve shallow element diffusion barrier, but has limited effect on promoting diamond nucleation.

[0003] This invention employs an integrated modification scheme of carburizing pretreatment and composite silicon transition layer. First, a dense carbide barrier structure is formed on the surface of high-speed steel through carburizing, which inhibits the diffusion of Fe and Co elements in the matrix and strengthens the mechanical properties of the surface. Then, silicon is used as a transition layer to achieve lattice adaptation and stress buffering, thereby inhibiting the formation of graphite phase, reducing the internal stress of the coating, and significantly improving the bonding strength and coating uniformity between the diamond coating and the high-speed steel substrate. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing diamond coatings on the surface of high-speed steel cutting tools and their products. This method belongs to the field of cutting tool surface coating modification technology. It includes pretreatment of the high-speed steel substrate, low-temperature plasma carburizing, physical vapor deposition of a silicon transition layer on the substrate surface, and finally diamond coating deposition, resulting in an ultra-thin diamond coating on the cutting tool surface. This invention employs an integrated modification scheme of carburizing pretreatment and a composite silicon transition layer. First, carburizing forms a dense carbide barrier structure on the surface of the high-speed steel, inhibiting the diffusion of Fe and Co elements in the substrate and strengthening the surface mechanical properties. Then, silicon is used as a transition layer to achieve lattice adaptation and stress buffering, thereby inhibiting graphite phase formation, reducing internal stress in the coating, and significantly improving the bonding strength and coating uniformity between the subsequent diamond coating and the high-speed steel substrate.

[0005] To achieve the above technical effects, the following technical solution is adopted: A method for preparing a diamond coating on the surface of high-speed steel cutting tools and their products includes the following steps: Step S1: Pretreatment of high-speed steel substrate First, the high-speed steel substrate is immersed in degreasing agent and gently stirred to remove heavy oil stains, polishing paste and rust-preventive oil. Then, it is thoroughly rinsed with hot water. Next, it is subjected to high-power ultrasonic degreasing in acetone, ultrasonic displacement dehydration in anhydrous ethanol, and ultrasonic cleaning in deionized water to remove organic residues and ionic contaminants. After completion, it is immediately dried with circulating hot air and then quickly transferred to a desiccator for storage. Step S2: Low-temperature plasma carburizing The high-speed steel substrate pretreated in step S1 is loaded into a plasma carburizing furnace. The furnace is evacuated to a pressure of 10-20 Pa. Then, pure argon gas is introduced for ion bombardment cleaning to activate the surface. The heating rate is then controlled to stabilize the substrate temperature at 500-520°C. A mixed atmosphere of 60-70% nitrogen, 20-30% hydrogen, and 5-10% methane is introduced to maintain a total furnace pressure of 5-15 Pa and a workpiece bias voltage of -400 to -600 V. The heat treatment allows active carbon and nitrogen ions to penetrate into the surface of the high-speed steel to form a dense compound layer and diffusion layer. After the treatment is completed, the gas supply is stopped and the power is turned off. The furnace is slowly cooled under vacuum and then filled with nitrogen to break the vacuum and remove the substrate from the furnace. The temperature throughout the process does not exceed the tempering temperature of the high-speed steel to ensure that the hardness of the substrate does not decrease and that an effective diffusion barrier layer is formed on the surface. Step S3: Physical vapor deposition transition layer on substrate surface Using a Si target, a power of 100-150 W, a gas pressure of 1.0-1.5 Pa, an argon flow rate of 50-100 sccm, a sputtering temperature of 300-350℃, and a sputtering time of 0.5-1 h, a bias voltage of -100-200 V is applied to the substrate obtained in step S2 to improve the film-substrate adhesion and density. After deposition, the sputtering power supply is turned off, the argon atmosphere is maintained, the furnace is cooled, nitrogen is introduced to break the vacuum, and the substrate is removed. Step S4: Diamond coating deposition The deposition was carried out using hot filament chemical vapor deposition (HFCVD) with the following reaction gases: hydrogen 1000-2000 sccm, methane 20-100 sccm, and argon 500-1000 sccm. The deposition pressure was 1500-2500 Pa, the filament power was 3000-7000 W, and the filament spacing was 10-20 mm. An ultrathin diamond coating was deposited on the substrate surface obtained in step S3.

[0006] Furthermore, in step S1, the mixture is stirred for 5 to 10 minutes; and in step S1, the hot water temperature is above 60°C.

[0007] Furthermore, the ultrasound time in step S1 is 8-15 minutes.

[0008] Furthermore, in step S1, the temperature of the circulating hot air is 60–70°C.

[0009] Furthermore, the ultrasonic power in step S1 is 400W.

[0010] Furthermore, the specific method for ion bombardment cleaning and surface activation in step S2 is as follows: The surface is activated by ion bombardment cleaning for 10 to 20 minutes under a bias voltage of -600 to -900V and an air pressure of 1 to 3Pa.

[0011] Furthermore, in step S2, the heating rate is no higher than 5°C / min.

[0012] Furthermore, in step S2, the heat treatment lasts for 3 to 6 hours.

[0013] Furthermore, in step S2, the furnace is slowly cooled under vacuum to below 200°C; in step S3, the furnace is cooled to below 200°C.

[0014] Furthermore, the deposition time in step S4 is 5-10 hours.

[0015] The beneficial effects of this invention are as follows: This invention provides a method for preparing a diamond coating on the surface of high-speed steel cutting tools and their products, belonging to the field of cutting tool surface coating modification technology. The method includes pretreatment of the high-speed steel substrate, low-temperature plasma carburizing, physical vapor deposition of a silicon transition layer on the substrate surface, and finally diamond coating deposition, resulting in an ultra-thin diamond coating on the cutting tool surface. This invention employs an integrated modification scheme of carburizing pretreatment and a composite silicon transition layer. First, carburizing forms a dense carbide barrier structure on the surface of the high-speed steel, inhibiting the diffusion of Fe and Co elements in the substrate and strengthening the surface mechanical properties. Then, silicon is used as a transition layer to achieve lattice adaptation and stress buffering, thereby inhibiting graphite phase formation, reducing internal stress in the coating, and significantly improving the bonding strength and coating uniformity between the subsequent diamond coating and the high-speed steel substrate. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are only embodiments of the present invention. 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 SEM image of the surface morphology of the diamond coating prepared in Example 1 of the present invention; Figure 2 This is a high-resolution TEM image of the cross-section of the diamond coating prepared in Example 1 of the present invention; Figure 3This is an optical microscope image of the cross-sectional film thickness of the diamond coating prepared in Example 1 of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, 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.

[0020] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0021] In the following examples, unless otherwise specified, all reagents and consumables were purchased from conventional reagent manufacturers in the art; unless otherwise specified, the experimental methods and techniques used are conventional methods and techniques in the art.

[0022] The technical solutions provided by the present invention will be described below with reference to the embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0023] Example 1 1. Pretreatment of high-speed steel substrate: First, the high-speed steel substrate is immersed in an environmentally friendly alkaline degreasing agent and gently stirred for 5 minutes to remove heavy oil stains, polishing paste, and rust-preventive oil. Then, it is thoroughly rinsed with hot water above 60°C. Next, it is subjected to high-power ultrasonic degreasing in acetone for 10 minutes, ultrasonic displacement dehydration in anhydrous ethanol for 10 minutes, and ultrasonic cleaning in deionized water for 10 minutes to remove organic residues and ionic contaminants. After completion, it is immediately dried rapidly with circulating hot air at 60-70°C. After drying, it is quickly transferred to a desiccator for storage. When it enters the deposition furnace, it is then subjected to in-situ plasma cleaning by argon ion glow discharge.

[0024] 2. Low-temperature plasma carburizing: First, the tool, after fine grinding, deep degreasing and cleaning, and drying, is placed into a plasma carburizing furnace. The furnace is evacuated to a pressure of 15 Pa. Then, pure argon gas is introduced, and ion bombardment cleaning is performed for 10-20 minutes at a workpiece bias voltage of -600 to -900 V and a gas pressure of 1-3 Pa to activate the surface. Next, the heating rate is controlled to not exceed 5℃ / min, stabilizing the substrate temperature at 500-520℃. A mixed atmosphere consisting of 60%-70% nitrogen, 20%-30% hydrogen, and 5%-10% methane is introduced, maintaining a total furnace pressure of 5-15 Pa. The furnace is heated to 400-600V for 5 hours to allow active carbon and nitrogen ions to penetrate into the surface of the high-speed steel and form a dense compound layer and diffusion layer. After the treatment is completed, the gas supply is stopped and the power is cut off. The furnace is then slowly cooled under vacuum to below 200℃ before nitrogen is introduced to break the vacuum and the furnace is removed. The temperature throughout the process does not exceed the tempering temperature of the high-speed steel to ensure that the hardness of the substrate does not decrease and that an effective diffusion barrier layer is formed on the surface.

[0025] 3. PVD transition layer on substrate surface: PVD uses a Si target, a power of 100-150 W, a gas pressure of 1.0-1.5 Pa, an argon flow rate of 50-100 sccm, a sputtering temperature of 300-350 ℃, and a sputtering time of 0.5-1 h. Simultaneously, a bias voltage of -100-200 V is applied to the substrate to improve film adhesion and density. After deposition, the sputtering power is turned off, the argon atmosphere is maintained, and the furnace is cooled to below 200 ℃. Nitrogen gas is then introduced to break the vacuum, and the substrate is removed.

[0026] 4. Diamond Coating Deposition: Hot-Filament Chemical Vapor Deposition (HFCVD) was used for deposition. The reaction gases were hydrogen 1500 sccm, methane 45 sccm, and argon 500 sccm. The deposition pressure was 2000 Pa, the filament diameter was 0.5 mm, the filament power was 5000 W, the filament spacing was 20 mm, and the deposition time was 8 hours. Figure 1 and Figure 2 As shown, the intermediate transition layer of silicon is dense; as Figure 3 As shown, a diamond coating with a thickness of about 6 μm was deposited on the substrate surface, and the coating was dense.

[0027] Example 2 Other treatments were consistent with those in Example 1. The pretreated substrate was placed in a hot filament chemical vapor deposition (HFCVD) apparatus. The reaction gases were hydrogen 1500 sccm, methane 60 sccm, and argon 500 sccm. The deposition pressure was 2000 Pa, the filament diameter was 0.5 mm, the filament power was 4500 W, the filament spacing was 15 mm, and the deposition time was 8 h. A diamond coating with a thickness of about 7 μm was deposited on the substrate surface. The coating was dense.

[0028] Example 3 Other treatments were consistent with those in Example 1. The pretreated substrate was placed in a hot filament chemical vapor deposition (HFCVD) apparatus. The reaction gases were 1000 sccm of hydrogen, 45 sccm of methane, and 1000 sccm of argon. The deposition pressure was 2000 Pa, the filament diameter was 0.5 mm, the filament power was 5000 W, the filament spacing was 20 mm, and the deposition time was 10 h. A diamond coating with a thickness of about 7 μm was deposited on the substrate surface. The coating was dense.

[0029] Comparative Example 1 Based on Example 1, except that the low-temperature plasma carburizing process was omitted, all other steps were the same as in Example 1.

[0030] Experimental results: The coating peeled off due to low adhesion and poor wear resistance. The main reason is that carburizing is used to form carbides on the surface metal. This serves two purposes: firstly, it prevents the metal from precipitating to the surface during diamond growth at high temperatures (approximately 650℃-850℃). The Fe and Co elements in the matrix would cause the diamond to turn into graphite, preventing diamond growth and resulting in only graphite. Secondly, carburizing hardens the surface, reducing the hardness difference between the substrate and the coating, thus enhancing coating adhesion.

[0031] Comparative Example 2 Based on Example 1, except that there is no PVD transition layer on the substrate surface, all other steps are the same as in Example 1.

[0032] Experimental results show that the coating has no adhesion and almost all of it peels off. The main reason is that the PVD transition layer is to achieve lattice adaptation and stress buffering between the diamond coating and the substrate. Without the transition layer, the coating will peel off directly when the machine is turned off because the expansion coefficients of the two layers are large. During high-temperature growth, the substrate expands, and when cooled to room temperature, the substrate shrinks. The coating has a small expansion coefficient and basically does not change. Therefore, the substrate and coating are directly separated when cooled.

[0033] Therefore, those skilled in the art will recognize that although embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Therefore, the scope of the present invention should be understood and recognized as covering all such other variations or modifications.

Claims

1. A method for preparing a diamond coating on the surface of high-speed steel cutting tools and their products, characterized in that, Includes the following steps: Step S1: Pretreatment of high-speed steel substrate First, the high-speed steel substrate is immersed in degreasing agent and gently stirred to remove heavy oil stains, polishing paste and rust-preventive oil. Then, it is thoroughly rinsed with hot water. Next, it is subjected to high-power ultrasonic degreasing in acetone, ultrasonic displacement dehydration in anhydrous ethanol, and ultrasonic cleaning in deionized water to remove organic residues and ionic contaminants. After completion, it is immediately dried with circulating hot air and then quickly transferred to a desiccator for storage. Step S2: Low-temperature plasma carburizing The high-speed steel substrate pretreated in step S1 is loaded into a plasma carburizing furnace. The furnace is evacuated to a pressure of 10-20 Pa. Then, pure argon gas is introduced for ion bombardment cleaning to activate the surface. The heating rate is then controlled to stabilize the substrate temperature at 500-520°C. A mixed atmosphere of 60-70% nitrogen, 20-30% hydrogen, and 5-10% methane is introduced to maintain a total furnace pressure of 5-15 Pa and a workpiece bias voltage of -400 to -600 V. The heat treatment allows active carbon and nitrogen ions to penetrate into the surface of the high-speed steel to form a dense compound layer and diffusion layer. After the treatment is completed, the gas supply is stopped and the power is turned off. The furnace is slowly cooled under vacuum and then filled with nitrogen to break the vacuum and remove the substrate from the furnace. The temperature throughout the process does not exceed the tempering temperature of the high-speed steel to ensure that the hardness of the substrate does not decrease and that an effective diffusion barrier layer is formed on the surface. Step S3: Physical vapor deposition transition layer on substrate surface Using a Si target, a power of 100-150 W, a gas pressure of 1.0-1.5 Pa, an argon flow rate of 50-100 sccm, a sputtering temperature of 300-350℃, and a sputtering time of 0.5-1 h, a bias voltage of -100-200 V is applied to the substrate obtained in step S2 to improve the film-substrate adhesion and density. After deposition, the sputtering power supply is turned off, the argon atmosphere is maintained, the furnace is cooled, nitrogen is introduced to break the vacuum, and the substrate is removed. Step S4: Diamond coating deposition The deposition was carried out using hot filament chemical vapor deposition (HFCVD) with the following reaction gases: hydrogen 1000-2000 sccm, methane 20-100 sccm, and argon 500-1000 sccm. The deposition pressure was 1500-2500 Pa, the filament power was 3000-7000 W, and the filament spacing was 10-20 mm. An ultrathin diamond coating was deposited on the substrate surface obtained in step S3.

2. The method for preparing a diamond coating on the surface of a high-speed steel cutting tool and its products as described in claim 1, characterized in that, Stir for 5 to 10 minutes in step S1; the hot water temperature in step S1 is above 60°C.

3. The method for preparing a diamond coating on the surface of a high-speed steel cutting tool and its products as described in claim 1, characterized in that, The ultrasound time in step S1 is 8-15 minutes.

4. The method for preparing a diamond coating on the surface of a high-speed steel cutting tool and its products as described in claim 1, characterized in that, In step S1, the temperature of the circulating hot air is 60-70°C.

5. The method for preparing a diamond coating on the surface of a high-speed steel cutting tool and its products as described in claim 1, characterized in that, The ultrasonic power in step S1 is 400W.

6. The method for preparing a diamond coating on the surface of a high-speed steel cutting tool and its products as described in claim 1, characterized in that, The specific method for ion bombardment cleaning and surface activation in step S2 is as follows: The surface is activated by ion bombardment cleaning for 10 to 20 minutes under a bias voltage of -600 to -900V and an air pressure of 1 to 3Pa.

7. The method for preparing a diamond coating on the surface of a high-speed steel cutting tool and its products as described in claim 1, characterized in that, In step S2, the heating rate shall not exceed 5°C / min.

8. The method for preparing a diamond coating on the surface of a high-speed steel cutting tool and its products as described in claim 1, characterized in that, In step S2, the heat treatment lasts for 3 to 6 hours.

9. The method for preparing a diamond coating on the surface of a high-speed steel cutting tool and its products as described in claim 1, characterized in that, In step S2, the furnace is slowly cooled under vacuum to below 200°C; in step S3, the furnace is cooled to below 200°C.

10. The method for preparing a diamond coating on the surface of a high-speed steel cutting tool and its products as described in claim 1, characterized in that, The deposition time in step S4 is 5-10 hours.

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