Tungsten carbide-based anti-sticking coating for coating roller as well as preparation method and application of tungsten carbide-based anti-sticking coating

Abstract

The invention provides a tungsten carbide-based coating roller anti-sticking coating and a preparation method and application thereof, and relates to the technical field of anti-sticking composite coatings, and the preparation method comprises the following steps: (1) carrying out particle size screening on tungsten carbide powder, and selecting particles with the particle size of 1-5 [mu] m to ensure the uniformity and compactness of the coating; (2) carrying out high-temperature calcination treatment on the oxide ceramic powder, controlling the temperature at 1200-1500 DEG C, and carrying out heat preservation for 2-4 hours so as to remove impurities and improve the activity; (3) the nickel-based alloy powder is prepared through a chemical reduction method, it is guaranteed that the particle size of the nickel-based alloy powder is small and evenly distributed, and the average particle size ranges from 0.5 micrometer to 2 micrometers; and (4) rare earth oxide is added and fully mixed with the powder in a ball milling mode, the ball milling time is 12-24 hours, and the ball-to-material ratio is (5-10): 1. According to the coating, tungsten carbide forms a continuous framework, oxide ceramic is filled in the framework, nickel-based alloy wraps and bonds all phases, and when the coating is applied to the coating roller, the adhesive force between materials and the surface of the coating is effectively reduced, and the transfer printing rate and the coating effect are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of anti - sticking composite coatings, in particular to a tungsten carbide - based anti - sticking coating for a coating roll, its preparation method and application. Background Art

[0002] The coating roll is a core component in a coating machine. Its main function is to evenly cover materials such as coatings on the surfaces of objects such as films, papers, and printed products to achieve effects such as aesthetics and anti - corrosion. It helps with uniform coating. Through appropriate rotation speed and pressure, the coating is evenly covered on the surface of the roll body and transferred to the surface of the object to be coated, ensuring uniform coating quality. The texture or grooves on the surface of the coating roll can control the thickness and uniformity of the coating material. Through extrusion, the excess coating on the surface of the object can be removed, making the surface of the product smoother. Since the pressure exerted by the coating roll on the surface of the product is consistent, the coating can be more evenly distributed, which can achieve the effect of saving coating costs.

[0003] The surface coating of the coating roll needs to meet the following requirements: First, it should have good anti - sticking property, which can effectively prevent the coating from adhering to the roll surface, ensure the smooth progress of the coating process, enable the coating to be evenly transferred to the object to be coated, and avoid problems such as uneven coating and adhesion. Second, it should have a low surface tension, which helps the coating to spread better on the roll surface and the surface of the object to be coated, reducing the interfacial tension between the coating and the roll surface as well as between the coating and the object to be coated, thereby improving the coating effect of the coating and the transfer rate of the material. Third, it should have high hardness and wear resistance. During the coating process, the coating will generate friction with the coating and the surface of the object to be coated. The coating with high hardness and wear resistance can ensure that during long - term use, the coating will not be easily worn, maintain its stable performance, ensure the consistency of coating quality, and extend the service life of the coating roll. Fourth, it should have good chemical stability, be able to resist the erosion of various chemical components in the coating, not react chemically with the coating, ensure that the coating performance is not affected, and at the same time prevent the coating from corroding the roll body, ensuring that the coating roll can work normally under different coating systems. Finally, it should have good bonding force with the roll body. The coating and the surface of the roll body need to be closely combined, not easily fall off or peel off, so as to ensure that the coating can firmly adhere to the roll body during use and fully exert its various performance advantages.

[0004] Therefore, in the material coating process, the surface properties of the coating roller have a crucial impact on the transfer effect of the material. According to relevant research data, for every 1 dyne / cm reduction in surface tension, the material transfer rate can be increased by approximately 5%. The traditional coating roller coatings have significant limitations in reducing surface tension, making it difficult to achieve an ideal level of material transfer rate. For example, although some organic polymer anti-sticking coatings can achieve anti-sticking effects to a certain extent, their surface tension reduction is limited, only able to be reduced to approximately 30 dyne / cm, and their strength is low, being easily damaged under some working conditions. According to statistics, after such coatings are damaged, the coating quality decreases by approximately 30% and the efficiency decreases by approximately 20%, seriously affecting the overall coating quality and efficiency. Summary of the Invention

[0005] The present invention overcomes the deficiencies in the prior art and provides a tungsten carbide-based anti-sticking coating for a coating roller, its preparation method and application.

[0006] To solve the above technical problems, the present invention is realized through the following technical solutions:

[0007] A preparation method of a tungsten carbide-based anti-sticking coating for a coating roller, comprising the following steps:

[0008] (1) Screen the tungsten carbide powder by particle size, and select particles with a particle size between 1 - 5 μm to ensure the uniformity and denseness of the coating;

[0009] (2) Conduct high-temperature calcination treatment on the oxide ceramic powder, control the temperature at 1200 - 1500 °C, and keep it warm for 2 - 4 hours to remove impurities and improve activity;

[0010] (3) Prepare the nickel-based alloy powder by chemical reduction method to ensure its fine particle size and uniform distribution, with an average particle size between 0.5 - 2 μm;

[0011] (4) Add rare earth oxides, and mix them thoroughly with the tungsten carbide powder, oxide ceramic powder, and nickel-based alloy powder by ball milling. The ball milling time is 12 - 24 hours, and the ball-to-material ratio is 5 - 10:1;

[0012] (5) Put the pretreated tungsten carbide powder, oxide ceramic powder, nickel-based alloy powder, and the mixed powder containing rare earth oxides into a three-dimensional mixer, and mix them for 8 - 12 hours under the condition of a rotation speed of 60 - 100 revolutions per minute to ensure the uniform distribution of each component;

[0013] (6) Add the diluted binder, set the rotation speed and mixing time of the ball mill, control the rotation speed at 100 - 300 revolutions per minute, and the mixing time is 2 - 4 hours to ensure the full and uniform mixing of each component.

[0014] Further, the method for preparing nickel-based alloy powder by chemical reduction in step (3) includes the following steps:

[0015] (1) Preparation of mixed solution: Add appropriate amount of deionized water into a three-necked flask, dissolve nickel sulfate, cobalt sulfate, chromium sulfate, and ammonium molybdate in a certain amount of deionized water according to the ratio of 50:20:15:15, turn on the magnetic stirrer, and stir to make them fully dissolve to form a uniform mixed salt solution;

[0016] Add an appropriate amount of dispersant polyvinylpyrrolidone PVP, continue to stir to make the dispersant evenly dispersed in the solution, and prevent particle agglomeration during the subsequent reaction process;

[0017] (2) Reduction reaction: Set the temperature of the constant temperature water bath to 60 - 80 °C, and slowly drip the reducing agent sodium borohydride solution into the three-necked flask through a reflux condenser; during the dripping process, continuously stir and observe the reaction situation of the solution. Black precipitate will gradually form, which is the process of nickel ions being reduced to metallic nickel;

[0018] After the dripping is completed, keep the reaction temperature and continue to stir and react for a period of 1 - 2 hours to ensure that the reduction reaction proceeds fully;

[0019] (3) Product separation and washing: After the reaction is completed, stop stirring, transfer the mixed solution in the three-necked flask to a suction filtration device for suction filtration to obtain a solid product;

[0020] Wash the solid product with deionized water multiple times until no relevant impurity ions can be detected in the washing solution to remove the adsorbed impurities on the surface;

[0021] (4) Drying and calcination: Place the washed solid product in an oven and dry it at a temperature of 80 - 100 °C to remove moisture;

[0022] Transfer the dried product to a high-temperature furnace and calcine it at a temperature of 800 - 1000 °C to further improve the crystallinity and purity of the powder, and at the same time make the particle size more uniform. The calcination time is 1 - 2 hours;

[0023] (5) Ball milling and refinement: Subject the powder after calcination to ball milling treatment. Add the powder and stainless steel balls as the grinding medium into the ball milling tank, and ball mill at a speed of 200 - 300 revolutions per minute on the ball mill for 8 - 12 hours. During the ball milling process, the powder particles are continuously impacted and rubbed by the grinding medium, thereby refining the particle size;

[0024] (6) Screening and classification: Conduct screening and classification through a screening device, and select nickel-based alloy powder with a particle size between 0.5 - 2 μm for subsequent use.

[0025] Further, oleic acid is added during the ball milling and mixing process of the rare earth oxide with tungsten carbide powder, oxide ceramic powder, and nickel-based alloy powder. The addition amount of oleic acid is 0.1-1% of the total mass of the mixed powder to improve the dispersion of the rare earth oxide in the mixed powder.

[0026] Further, the binder is transferred to a vacuum degassing device before dilution and degassed for 1-2 hours under a vacuum degree of -0.08 to -0.1 MPa to remove the air bubbles in the system and perform degassing treatment.

[0027] Further, the dilution method of the binder is as follows: in a well-ventilated environment, a diluent composed of low-boiling ethers and high-boiling esters mixed in a ratio of 3-4:6-7 is slowly added to the binder while continuously stirring; the stirring speed is controlled at 200-300 revolutions per minute to ensure that the diluent and the binder are fully mixed evenly to form a diluted binder with appropriate viscosity to meet the requirements of the coating preparation process.

[0028] The present invention also claims protection for a tungsten carbide-based anti-sticking coating for a coating roller, which is prepared by using the preparation method of the tungsten carbide-based anti-sticking coating for a coating roller described above. Among them, calculated based on the total preparation amount of 100%, the tungsten carbide powder accounts for 30-50%, the oxide ceramic powder accounts for 20-30%, the nickel-based alloy powder accounts for 20-30%, and the balance is rare earth oxide.

[0029] The present invention also claims protection for the application of a tungsten carbide-based anti-sticking coating for a coating roller. The tungsten carbide-based anti-sticking coating for a coating roller is prepared by using the preparation method of the tungsten carbide-based anti-sticking coating for a coating roller described above, or is the tungsten carbide-based anti-sticking coating for a coating roller described above;

[0030] This coating is applied by spraying on the coating roller;

[0031] Specifically, it includes the following steps:

[0032] Pretreat the coating roller: clean, degrease, and roughen the surface of the coating roller;

[0033] Spraying: Use a plasma spraying device to spray the coating; convey the mixed powder to the plasma spray gun, heat the powder to a molten or semi-molten state through a high-temperature plasma flame, and spray it at high speed onto the surface of the preheated coating roller substrate;

[0034] The thickness of each layer of the coating is controlled at 50-100 μm, and the number of spray coating layers is set to 3-5 layers according to the required total thickness of the coating;

[0035] Heat preservation treatment: After spraying is completed, the coating roller is subjected to heat preservation treatment in a furnace. The heat preservation temperature is 500 - 600 °C, and the heat preservation time is 2 - 3 hours, so that the components in the coating can further diffuse and densify, improving the performance of the coating;

[0036] Cooling treatment: Cool the coating roller after heat preservation. The cooling rate is controlled at 5 - 10 °C / min to avoid cracks in the coating caused by too fast cooling;

[0037] Surface processing: Finally, finish machining the surface of the coating, such as grinding, polishing, etc., so that the surface roughness of the coating reaches Ra0.8 - 1.6 μm to meet the requirements of the coating process for the flatness of the roller surface.

[0038] Furthermore, the pre - treated coating roller refers to: cleaning the surface of the coating roller substrate to remove oil stains, impurities and oxide layers on the surface; cleaning with a chemical degreasing agent and then sanding the surface to make its roughness reach Ra3.2 - 6.3 μm.

[0039] Furthermore, the pre - treated coating roller also includes pre - heating the coating roller substrate after degreasing and roughening, heating it to 150 - 200 °C and keeping it warm for 1 - 2 hours to remove the moisture on the substrate surface and improve the surface activity of the substrate, which is beneficial to the adhesion of the coating.

[0040] Furthermore, during spraying, spraying parameters should be controlled. The power of the plasma spray gun is 30 - 50 kW, the spraying distance is 100 - 150 mm, the spraying angle is perpendicular to the roller surface, and the roller body rotates at a constant speed during spraying, so that the coating evenly covers the roller surface.

[0041] Compared with the prior art, the beneficial effects of the present invention are:

[0042] The anti - sticking coating of the present invention is applied to the coating roller, which can effectively prevent the adhesion and drying of coating liquid, glue, paint, etc. on the surface of the coating roller, ensure the smooth coating process, make the coating thickness uniform and continuous, and improve the product quality; in addition, it helps to reduce the cleaning frequency and difficulty, reduce the manual cleaning workload and time cost, and improve the production efficiency.

[0043] In the formula of the anti - sticking coating, the combination of tungsten carbide and oxide ceramics is organically adopted. Among them, tungsten carbide provides hardness and wear resistance, and oxide ceramics fill the voids and optimize the densification. The two cooperate with each other, so that the coating has both a high - strength wear - resistant skeleton and a smooth surface with low surface energy, thus effectively reducing the adhesion force between the material and the coating surface.

[0044] The addition of nickel - based alloy can ensure the firm bonding between the coating and the substrate, and the addition of rare earth oxides helps to improve the tissue uniformity, jointly enhancing the overall performance of the coating and ensuring the stability and anti - sticking effect of the coating during long - term use.

[0045] The above components act synergistically to form an integrated whole with complementary properties. From a microscopic structure perspective, tungsten carbide forms a continuous framework, oxide ceramics are filled therein, nickel-based alloy wraps and bonds each phase, and rare earth elements are distributed at grain boundaries to improve properties. This structure endows the coating with good wear resistance, corrosion resistance, low surface tension, and high bonding strength with the substrate, comprehensively achieving an excellent anti-sticking effect. Specific Embodiments

[0046] The following is an illustration in conjunction with the preferred embodiments of the present invention. It should be understood that the preferred embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.

[0047] The present invention claims a method for preparing an anti-sticking coating for a tungsten carbide-based coating roll, comprising the following steps:

[0048] (1) Screen the particle size of tungsten carbide powder, and select particles with a particle size between 1 - 5 μm to ensure the uniformity and denseness of the coating;

[0049] (2) Conduct high-temperature calcination treatment on the oxide ceramic powder, control the temperature at 1200 - 1500 °C, and keep it warm for 2 - 4 hours to remove impurities and improve activity;

[0050] (3) Prepare the nickel-based alloy powder by chemical reduction method to ensure that its particle size is fine and evenly distributed, with an average particle size between 0.5 - 2 μm;

[0051] (4) Add rare earth oxides, and fully mix them with tungsten carbide powder, oxide ceramic powder, and nickel-based alloy powder by ball milling. The ball milling time is 12 - 24 hours, and the ball-to-material ratio is 5 - 10:1;

[0052] (5) Put the pretreated tungsten carbide powder, oxide ceramic powder, nickel-based alloy powder, and the mixed powder containing rare earth oxides into a three-dimensional mixer, and mix them for 8 - 12 hours under the condition of a rotation speed of 60 - 100 revolutions per minute to ensure the uniform distribution of each component;

[0053] (6) Add the diluted binder, set the rotation speed and mixing time of the ball mill, control the rotation speed at 100 - 300 revolutions per minute, and the mixing time is 2 - 4 hours to ensure the full and uniform mixing of each component.

[0054] Among them, the method for preparing the nickel-based alloy powder by chemical reduction method in step (3) includes the following steps:

[0055] (1) Preparation of mixed solution: Add an appropriate amount of deionized water into a three-necked flask. Dissolve nickel sulfate, cobalt sulfate, chromium sulfate, and ammonium molybdate in a certain amount of deionized water according to the ratio of 50:20:15:15. Turn on the magnetic stirrer and stir to fully dissolve them to form a uniform mixed salt solution;

[0056] Add an appropriate amount of dispersant polyvinylpyrrolidone PVP and continue stirring to evenly disperse the dispersant in the solution to prevent particle agglomeration during the subsequent reaction process;

[0057] (2) Reduction reaction: Set the temperature of the constant temperature water bath to 60 - 80 °C, and slowly drip the reducing agent sodium borohydride solution into the three-necked flask through a reflux condenser; during the dripping process, continuously stir and observe the reaction situation of the solution. Black precipitate will gradually form, which is the process of nickel ions being reduced to metallic nickel;

[0058] After the dripping is completed, maintain the reaction temperature and continue stirring for a period of 1 - 2 hours to ensure the full progress of the reduction reaction;

[0059] (3) Product separation and washing: After the reaction is completed, stop stirring, transfer the mixed liquid in the three-necked flask to a suction filtration device for suction filtration to obtain a solid product;

[0060] Wash the solid product with deionized water multiple times until no relevant impurity ions can be detected in the washing liquid to remove the adsorbed impurities on the surface;

[0061] (4) Drying and calcination: Place the washed solid product in an oven and dry it at a temperature of 80 - 100 °C to remove moisture;

[0062] Transfer the dried product to a high-temperature furnace and calcine it at a temperature of 800 - 1000 °C to further improve the crystallinity and purity of the powder, and at the same time make the particle size more uniform. The calcination time is 1 - 2 hours;

[0063] (5) Ball milling and refinement: Perform ball milling on the powder after calcination. Add the powder and stainless steel balls as the grinding medium into the ball milling tank and ball mill at a rotational speed of 200 - 300 revolutions per minute for 8 - 12 hours. During the ball milling process, the powder particles are continuously impacted and rubbed by the grinding medium, thereby refining the particle size;

[0064] (6) Screening and classification: Perform screening and classification through a screening device, and select nickel-based alloy powder with a particle size between 0.5 - 2 μm for subsequent use.

[0065] The above nickel-based alloy powder is prepared by the chemical reduction method, which can precisely control the content of each element in the nickel-based alloy powder. Compared with the traditional melting method, it can more accurately reach the preset alloy composition ratio, which is beneficial to preparing nickel-based alloy powder with stable performance and meeting specific requirements.

[0066] In addition, during the reduction reaction process, due to the action of the reducing agent and the characteristics of the reaction system, it is possible to form nickel-based alloy nanoparticles at the nanoscale. Nanoparticles have a large specific surface area and special physical and chemical properties, which bring new application potential to the nickel-based alloy powder.

[0067] Compared with some traditional high-temperature melting methods, the reaction temperature of the chemical reduction method is relatively low, and large-scale equipment such as high-temperature furnaces is not required. The preparation process is relatively mild. This not only reduces the equipment cost and energy consumption, but also reduces problems such as impurity introduction and composition segregation that may occur during the high-temperature process, which is beneficial to preparing high-quality nickel-based alloy powder.

[0068] Among them, oleic acid is added during the ball milling and mixing process of rare earth oxides with tungsten carbide powder, oxide ceramic powder, and nickel-based alloy powder. The addition amount of oleic acid is 0.1-1% of the total mass of the mixed powder to improve the dispersibility of rare earth oxides in the mixed powder; surfactant molecules will adsorb on the surface of rare earth oxide particles, reducing the surface energy between particles and preventing particle agglomeration.

[0069] The binder is transferred to a vacuum degassing device before dilution and degassed for 1-2 hours under a vacuum degree of -0.08 to -0.1 MPa to remove the bubbles in the system and perform degassing treatment.

[0070] Rare earth oxides are added to be fully mixed with tungsten carbide powder, oxide ceramic powder, and nickel-based alloy powder, laying a good foundation for the subsequent preparation of a high-performance anti-sticking coating for tungsten carbide-based coating rollers. By adding rare earth oxides in this way, the role of rare earth elements in the coating can be better exerted, realizing the synergistic effect between various components, thereby significantly improving the comprehensive properties such as anti-sticking performance, wear resistance, and corrosion resistance of the coating.

[0071] The dilution method of the binder is to slowly add a diluent composed of low-boiling ethers and high-boiling esters in a ratio of 3-4:6-7 to the binder in a well-ventilated environment while continuously stirring; the stirring speed is controlled at 200-300 revolutions per minute to ensure that the diluent and the binder are fully mixed evenly to form a diluted binder with appropriate viscosity to meet the requirements of the coating preparation process.

[0072] Performance Test 1:

[0073] To verify the influence of the addition of rare earth oxides on the anti-sticking coating, an example (with rare earth oxides) and a test example (without rare earth oxides) were designed.

[0074] 1. The anti - sticking coating of the embodiment adopts the following steps. Calculated based on the total preparation amount of 100%, tungsten carbide powder accounts for 45%, oxide ceramic powder accounts for 25%, nickel - based alloy powder accounts for 20%, and the balance is rare - earth oxide:

[0075] (1) Screen the particle size of tungsten carbide powder and select particles with a particle size between 2.5μm to ensure the uniformity and density of the coating;

[0076] (2) Conduct high - temperature calcination treatment on the oxide ceramic powder. Control the temperature at 1300°C and keep it warm for 2.5 hours to remove impurities and improve activity;

[0077] (3) The nickel - based alloy powder is prepared by chemical reduction method to ensure that its particle size is fine and evenly distributed, with an average particle size between 0.8μm;

[0078] (4) Add rare - earth oxide and mix it fully with tungsten carbide powder, oxide ceramic powder, and nickel - based alloy powder by ball - milling. The ball - milling time is 16 hours and the ball - to - material ratio is 8:1;

[0079] (5) Put the pretreated tungsten carbide powder, oxide ceramic powder, nickel - based alloy powder, and the mixed powder containing rare - earth oxide into a three - dimensional mixer and mix them for 9 hours under the condition of a rotation speed of 65 revolutions per minute to ensure the uniform distribution of each component;

[0080] (6) Add the diluted binder, set the rotation speed and mixing time of the ball mill. The rotation speed is controlled at 150 revolutions per minute and the mixing time is 3 hours to ensure the full and uniform mixing of each component.

[0081] Furthermore, the method for preparing the nickel - based alloy powder by chemical reduction method in step (3) includes the following steps:

[0082] (1) Preparation of the mixed solution: Add appropriate amount of deionized water into a three - necked flask, dissolve nickel sulfate, cobalt sulfate, chromium sulfate, and ammonium molybdate in a certain amount of deionized water according to the ratio of 50:20:15:15, turn on the magnetic stirrer, and stir to make it fully dissolve to form a uniform mixed salt solution;

[0083] Add an appropriate amount of dispersant polyvinylpyrrolidone PVP, and continue stirring to make the dispersant evenly dispersed in the solution to prevent particle agglomeration during the subsequent reaction process;

[0084] (2) Reduction reaction: Set the temperature of the constant - temperature water bath at 70°C, and slowly drip the reducing agent sodium borohydride solution into the three - necked flask through a reflux condenser; during the dripping process, continuously stir and observe the reaction situation of the solution. Black precipitates will gradually form, which is the process of nickel ions being reduced to metallic nickel.

[0085] After the dropping is completed, keep the reaction temperature and continue stirring for a period of time, 2 hours, to ensure that the reduction reaction proceeds fully;

[0086] (3) Product separation and washing: After the reaction is completed, stop stirring, transfer the mixed solution in the three-necked flask to a suction filtration device for suction filtration to obtain a solid product;

[0087] Wash the solid product with deionized water multiple times until no relevant impurity ions can be detected in the washing liquid to remove the adsorbed impurities on the surface;

[0088] (4) Drying and calcination: Place the washed solid product in an oven and dry it at a temperature of 95 °C to remove moisture;

[0089] Transfer the dried product to a high-temperature furnace and calcine it at a temperature of 900 °C to further improve the crystallinity and purity of the powder, and at the same time make the particle size more uniform. The calcination time is 1.5 hours;

[0090] (5) Ball milling and refinement: Subject the powder after calcination to ball milling. Add the powder and stainless steel balls as the grinding medium to the ball milling tank and ball mill at a speed of 250 revolutions per minute for 10 hours. During the ball milling process, the powder particles are continuously impacted and rubbed by the grinding medium, thereby refining the particle size;

[0091] (6) Screening and classification: Perform screening and classification through a screening device, and select nickel-based alloy powder with a particle size between 1.5 μm for subsequent use.

[0092] Among them, oleic acid is added during the ball milling and mixing process of the rare earth oxide with tungsten carbide powder, oxide ceramic powder, and nickel-based alloy powder. The addition amount of oleic acid is 0.5% of the total mass of the mixed powder to improve the dispersion of the rare earth oxide in the mixed powder.

[0093] Among them, the binder is transferred to a vacuum degassing device before dilution and degassed at a vacuum degree of -0.09 MPa for 1.5 hours to remove the bubbles in the system and perform degassing treatment.

[0094] Second, the anti-sticking coating of the test example adopts the following steps. Calculated based on the total preparation amount of 100%, the tungsten carbide powder accounts for 50%, the oxide ceramic powder accounts for 25%, and the nickel-based alloy powder accounts for 25%:

[0095] (1) Perform particle size screening on the tungsten carbide powder and select particles with a particle size between 2.5 μm to ensure the uniformity and density of the coating;

[0096] (2) The oxide ceramic powder is subjected to high-temperature calcination treatment at a temperature controlled at 1300 °C for 2.5 hours to remove impurities and improve activity;

[0097] (3) The nickel-based alloy powder is prepared by chemical reduction method to ensure that its particle size is fine and evenly distributed, and the average particle size is between 0.8 μm;

[0098] (4) The mixed powder of pretreated tungsten carbide powder, oxide ceramic powder, and nickel-based alloy powder is put into a three-dimensional mixer and mixed for 9 hours at a rotation speed of 65 revolutions per minute to ensure that the components are evenly distributed;

[0099] (5) Add the diluted binder, set the rotation speed and mixing time of the ball mill. The rotation speed is controlled at 150 revolutions per minute, and the mixing time is 3 hours to ensure that the components are fully and evenly mixed.

[0100] Furthermore, the method for preparing the nickel-based alloy powder by chemical reduction method in step (3) includes the following steps:

[0101] (1) Preparation of the mixed solution: Add an appropriate amount of deionized water to a three-necked flask, dissolve nickel sulfate, cobalt sulfate, chromium sulfate, and ammonium molybdate in a certain amount of deionized water according to the ratio of 50:20:15:15, turn on the magnetic stirrer, and stir to make it fully dissolve to form a uniform mixed salt solution;

[0102] Add an appropriate amount of dispersant polyvinylpyrrolidone PVP, and continue to stir to make the dispersant evenly dispersed in the solution to prevent particle agglomeration during the subsequent reaction process;

[0103] (2) Reduction reaction: Set the temperature of the constant-temperature water bath to 70 °C, and slowly drip the reducing agent sodium borohydride solution into the three-necked flask through a reflux condenser; during the dripping process, continuously stir and observe the reaction of the solution. Black precipitates will gradually form, which is the process of nickel ions being reduced to metallic nickel;

[0104] After the dripping is completed, keep the reaction temperature and continue to stir and react for a period of time of 2 hours to ensure that the reduction reaction proceeds fully;

[0105] (3) Product separation and washing: After the reaction is completed, stop stirring, transfer the mixed solution in the three-necked flask to a suction filtration device for suction filtration to obtain a solid product;

[0106] Wash the solid product with deionized water multiple times until no relevant impurity ions can be detected in the washing solution to remove the impurities adsorbed on the surface;

[0107] (4) Drying and calcination: Place the washed solid product in an oven and dry it at a temperature of 95 °C to remove moisture;

[0108] Transfer the dried product to a high-temperature furnace and calcine it at 900 °C to further improve the crystallinity and purity of the powder, and at the same time make the particle size more uniform. The calcination time is 1.5 hours;

[0109] (5) Ball milling and refinement: The calcined powder is subjected to ball milling. The powder and stainless steel balls used as grinding media are added to the ball mill tank and ball milled at a speed of 250 revolutions per minute for 10 hours. During the ball milling process, the powder particles are continuously impacted and rubbed by the grinding media, thereby refining the particle size;

[0110] (6) Screening and classification: Screening and classification are carried out through a screening device, and nickel-based alloy powder with a particle size between 1.5 μm is selected for subsequent use.

[0111] Among them, the binder is transferred to a vacuum degassing device before dilution and degassed for 1.5 hours under a vacuum degree of -0.09 MPa to remove the bubbles in the system and perform degassing treatment.

[0112] The wear resistance of the examples and test examples is tested. According to the standard test method for rubber wear resistance in ASTM D1630, during the wear resistance test, through a friction and wear experiment, the friction situation between the material and the coating roller during the coating process is simulated, and the wear resistance of the coating roller sprayed with the examples and test examples is tested.

[0113] Taking the wear amount as an index, after a certain period of friction, the wear amount of the coating roller of this example is 0.05 - 0.08 mm 3 , and the wear amount of the test example is 0.1 - 0.15 mm 3 .

[0114] This shows that the coating of this example with rare earth oxides added has better wear resistance, can ensure the integrity of the coating during long-term use, and maintain a good anti-sticking effect.

[0115] That is, under the same friction conditions, the wear resistance of the coating roller using the example is improved, effectively extending the service life of the coating roller and meeting the high-performance requirements of the coating roller in industrial production.

[0116] The present invention also claims a tungsten carbide-based anti-sticking coating for a coating roller, which is prepared by using the preparation method of the tungsten carbide-based anti-sticking coating for a coating roller described above. Among them, calculated based on the total preparation amount of 100%, the tungsten carbide powder accounts for 30 - 50%, the oxide ceramic powder accounts for 20 - 30%, the nickel-based alloy powder accounts for 20 - 30%, and the balance is rare earth oxides.

[0117] The present invention also claims protection for an application of a tungsten carbide-based coating roller anti-stick coating, wherein the tungsten carbide-based coating roller anti-stick coating is prepared by the above-mentioned preparation method of the tungsten carbide-based coating roller anti-stick coating, or is the above-mentioned tungsten carbide-based coating roller anti-stick coating;

[0118] The coating is applied by spraying onto a coating roller;

[0119] Specifically, the steps include:

[0120] Pre-treatment of coating roller: cleaning, degreasing and roughening of the coating roller surface;

[0121] Spraying: Plasma spraying equipment is used for coating spraying; the mixed powder is conveyed to the plasma spray gun, the powder is heated to a molten or semi-molten state by a high-temperature plasma flame flow, and then sprayed at high speed onto the preheated coating roller substrate surface;

[0122] The thickness of each coating layer is controlled at 50-100 μm, and the number of spray layers is set to 3-5 layers according to the required total coating thickness;

[0123] Controlling the thickness and number of layers of the coating as mentioned above can avoid problems caused by the coating being too thick or too thin. If the thickness is greater than 100 μm, it may be too thick, which may lead to an uneven surface, affect coating accuracy, and even increase material costs. If the thickness is less than 50 μm, it may be too thin, and the anti-sticking function may not be effectively achieved, reducing the protective effect of the coating.

[0124] The above-mentioned multi-layer spraying helps to make the overall coating cover the surface of the coating roller more evenly. Through each thinner layer of spraying, the microscopic unevenness of the roller surface can be better filled, reducing the possibility of defects such as uneven thickness and sagging in the coating, thereby ensuring the performance consistency of the anti-stick coating.

[0125] In addition, the multi-layer structure can provide a denser and continuous anti-stick barrier, improve the coating's ability to isolate materials, reduce adhesion, make the coating process smoother, and enhance the anti-stick effect; and increasing the number of spray layers can make the coating stronger, enhance its ability to resist friction and wear, extend the service life of the coating roller, maintain stable anti-stick performance, and improve wear resistance.

[0126] Easy process control and adjustment: In actual production, the number of spray layers is determined to be 3-5 layers according to the required total coating thickness. This setting makes the coating process easier to control and adjust. If the total thickness needs to be fine-tuned, it can be achieved by increasing or decreasing the number of layers without significantly changing the thickness of each layer, thereby more accurately meeting the requirements of different production processes for the performance of the anti-stick coating.

[0127] Heat preservation treatment: After spraying is completed, the coating roller is subjected to heat preservation treatment in a furnace. The heat preservation temperature is 500 - 600 °C, and the heat preservation time is 2 - 3 hours, enabling the components in the coating to further diffuse and densify, thereby improving the performance of the coating;

[0128] At a heat preservation temperature of 500 - 600 °C, various components in the coating can obtain sufficient energy, thus diffusing more fully. This helps different components interact and fuse better with each other, making the chemical composition of the coating more uniform, and further optimizing the performance of the coating, thereby promoting component diffusion.

[0129] Then, high-temperature heat preservation for 2 - 3 hours allows the molecules or atoms in the coating to have sufficient time for rearrangement and densification processes. This makes the coating structure more compact, reduces pores and defects, and improves the density of the coating. A dense coating has better barrier properties, wear resistance, corrosion resistance, etc., can better meet the performance requirements of the anti-sticking coating of the coating roller, extend the service life of the coating roller, ensure the stability of the coating quality, and achieve densification.

[0130] Cooling treatment: The heat-preserved coating roller is cooled, and the cooling rate is controlled at 5 - 10 °C / min to avoid cracks in the coating caused by too fast cooling;

[0131] Surface processing: Finally, the surface of the coating is finely processed, such as grinding, polishing, etc., so that the surface roughness of the coating reaches Ra0.8 - 1.6 μm to meet the requirements of the coating process for the flatness of the roller surface.

[0132] If the roughness is less than 0.8 μm, the roller surface is too smooth, which may cause the coating liquid to slide on the roller surface, making it difficult to adhere evenly to the substrate, resulting in difficulty in controlling the coating thickness and affecting product quality; if the roughness is greater than 1.6 μm, the surface is too rough, and the coating material is likely to accumulate or flow away at the rough places, causing uneven coating thickness and possibly coating defects, affecting the appearance and performance of the product. When the surface roughness of the coating reaches Ra0.8 - 1.6 μm, it can reduce the frictional resistance between the coating material and the roller surface, reduce the loss of the coating material, avoid damage, improve the coating efficiency and reduce costs. When the roughness is less than 0.8 μm, although the friction can be reduced, the coating liquid may not adhere firmly due to excessive smoothness; when it is greater than 1.6 μm, the frictional resistance will increase, which is not conducive to the coating process.

[0133] The pre-treated coating roller refers to: cleaning the surface of the coating roller substrate to remove oil stains, impurities, and oxide layers on the surface; cleaning with a chemical degreaser and then sanding the surface to make its roughness reach Ra3.2 - 6.3 μm.

[0134] Furthermore, the pre-treatment coating roll further includes preheating the degreased and roughened coating roll substrate, heating it to 150 - 200 °C, and holding for 1 - 2 hours to remove the moisture on the substrate surface and improve the surface activity of the substrate, which is beneficial to the adhesion of the coating.

[0135] The above heating range helps to activate the atoms or molecules on the substrate surface, increasing their activity. After the surface activity is improved, it is easier for the substrate surface to undergo chemical reactions or physical adsorption with the coating material, enhancing the interaction force between the coating and the substrate, such as chemical bonding, van der Waals force, etc. Consequently, the adhesion strength of the coating is significantly improved, ensuring that the coating will not easily peel off during use, extending the service life of the coating roll, and guaranteeing its stable and reliable operation in the coating process.

[0136] During spraying, the spraying parameters should be controlled. The power of the plasma spray gun is 30 - 50 kW, the spraying distance is 100 - 150 mm, the spraying angle is perpendicular to the roll surface, and the roll body rotates at a constant speed during spraying to ensure that the coating evenly covers the roll surface.

[0137] Performance Test 2:

[0138] To further verify the effect of the coating in reducing the surface tension, the tungsten carbide-based anti-sticking coating of this embodiment, a traditional organic polymer anti-sticking coating, and a commonly used inorganic metal oxide coating are specifically selected. Then, multiple coating rolls of the same material and size are prepared and different coatings are sprayed on them respectively.

[0139] A surface tension tester is used to measure the static surface tension of the surface of each coated roll. Each coating is measured 5 times, and the average value is taken as the surface tension data of the coating.

[0140] Under the same coating process conditions, each coated roll is used to coat the same material, and the transfer rate of the material is recorded. The transfer rate is calculated by measuring the ratio of the adhesion amount of the material on the roll surface after coating to the initial coating amount. Each coating is subjected to 3 coating tests, and the average value is taken as the transfer rate data of the coating.

[0141] The test results are as follows:

[0142]

[0143] It can be clearly seen from the test data that the tungsten carbide-based anti-sticking coating of the present invention has the lowest surface tension and the highest transfer rate. Compared with the traditional organic polymer anti-sticking coating, the surface tension is reduced by 3.5 dynes / cm, and the transfer rate is increased by 7%; compared with the inorganic metal oxide coating, the surface tension is reduced by 1.5 dynes / cm, and the transfer rate is increased by 4%. This fully demonstrates that the tungsten carbide-based anti-sticking coating of the present invention has significant advantages in reducing the surface tension and improving the material transfer rate.

[0144] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. However, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of an anti-sticking coating for a tungsten carbide-based coating roll, characterized in that, It includes the following steps: (1) Screen the tungsten carbide powder by particle size, and select particles with a particle size between 1 - 5 μm to ensure the uniformity and density of the coating; (2) Conduct high-temperature calcination treatment on the oxide ceramic powder, control the temperature at 1200 - 1500 °C, and keep it warm for 2 - 4 hours to remove impurities and improve activity; (3) Prepare the nickel-based alloy powder by chemical reduction method to ensure that its particle size is fine and evenly distributed, and the average particle size is between 0.5 - 2 μm; (4) Add rare earth oxides, and mix them with tungsten carbide powder, oxide ceramic powder, and nickel-based alloy powder fully by ball milling. The ball milling time is 12 - 24 hours, and the ball-to-material ratio is 5 - 10:1; (5) Put the pretreated tungsten carbide powder, oxide ceramic powder, nickel-based alloy powder, and the mixed powder containing rare earth oxides into a three-dimensional mixer, and mix them for 8 - 12 hours under the condition of a rotation speed of 60 - 100 revolutions per minute to ensure the uniform distribution of each component; (6) Add the diluted binder, set the rotation speed and mixing time of the ball mill. The rotation speed is controlled at 100 - 300 revolutions per minute, and the mixing time is 2 - 4 hours to ensure the full and uniform mixing of each component.

2. The preparation method of the anti-sticking coating for the tungsten carbide-based coating roll according to claim 1, wherein: The method for preparing the nickel-based alloy powder by chemical reduction method in step (3) includes the following steps: (1) Preparation of the mixed solution: Add an appropriate amount of deionized water into a three-necked flask, dissolve nickel sulfate, cobalt sulfate, chromium sulfate, and ammonium molybdate in a certain amount of deionized water according to the ratio of 50:20:15:15, turn on the magnetic stirrer, and stir to make it fully dissolve to form a uniform mixed salt solution; Add an appropriate amount of dispersant polyvinylpyrrolidone PVP, and continue to stir to make the dispersant evenly disperse in the solution to prevent particle agglomeration during the subsequent reaction process; (2) Reduction reaction: Set the temperature of the constant temperature water bath at 60 - 80 °C, and slowly drip the reducing agent sodium borohydride solution into the three-necked flask through a reflux condenser; during the dripping process, continuously stir and observe the reaction situation of the solution. Black precipitates will gradually form, which is the process of nickel ions being reduced to metallic nickel; After the dripping is completed, keep the reaction temperature and continue to stir and react for a period of time of 1 - 2 hours to ensure the full progress of the reduction reaction; (3) Product separation and washing: After the reaction is completed, stop stirring, transfer the mixed solution in the three-necked flask to a suction filtration device for suction filtration to obtain a solid product; Wash the solid product with deionized water multiple times until no relevant impurity ions are detected in the washing solution to remove the adsorbed impurities on the surface; (4) Drying and calcination: Place the washed solid product in an oven and dry it at a temperature of 80 - 100 °C to remove moisture; transfer the dried product to a high-temperature furnace and calcine it at a temperature of 800 - 1000 °C to further improve the crystallinity and purity of the powder, and at the same time make the particle size more uniform. The calcination time is 1 - 2 hours; (5) Ball milling: The calcined powder is subjected to ball milling treatment. The powder and stainless steel balls as grinding media are added to a ball mill and milled at a speed of 200-300 rpm for 8-12 hours. During the ball milling process, the powder particles are continuously impacted and rubbed by the grinding media, thereby refining the particle size. (6) Screening and grading: Screening and grading are performed by a screening device to select nickel-based alloy powder with a particle size between 0.5 and 2 μm for subsequent use.

3. The preparation method of the anti-sticking coating for the tungsten carbide-based coating roll according to claim 2, wherein: Oleic acid is added to the rare earth oxide during the ball milling and mixing process with tungsten carbide powder, oxide ceramic powder and nickel-based alloy powder. The amount of oleic acid added is 0.1-1% of the total mass of the mixed powder to improve the dispersibility of the rare earth oxide in the mixed powder.

4. The preparation method of the anti-sticking coating for the tungsten carbide-based coating roll according to claim 3, wherein: The binder is transferred to a vacuum degassing device before dilution, and degassed for 1-2 hours at a vacuum degree of -0.08 to -0.1 MPa to remove bubbles in the system and perform a degassing treatment.

5. The preparation method of the anti-sticking coating for the tungsten carbide-based coating roll according to claim 4, wherein: The dilution method of the binder is to slowly add a diluent prepared by mixing low-boiling-point ethers and high-boiling-point esters in a ratio of 3-4:6-7 into the binder in a well-ventilated environment while continuously stirring; the stirring speed is controlled at 200-300 rpm to ensure that the diluent and the binder are fully and evenly mixed to form a diluted binder with a suitable viscosity to meet the coating preparation process requirements.

6. A tungsten carbide-based anti-sticking coating for a coating roll, characterized in that: The anti-stick coating of a tungsten carbide-based coating roller is prepared by the preparation method of any one of claims 1 to 5, wherein, based on the total preparation amount as 100%, the tungsten carbide powder accounts for 30-50%, the oxide ceramic powder accounts for 20-30%, the nickel-based alloy powder accounts for 20-30%, and the remainder is rare earth oxide.

7. Application of an anti-sticking coating for a tungsten carbide-based coating roll, characterized in that: The tungsten carbide-based coating roller anti-stick coating is prepared by the preparation method of the tungsten carbide-based coating roller anti-stick coating according to any one of claims 1 to 5, or is the tungsten carbide-based coating roller anti-stick coating according to claim 6; The coating is applied by spraying onto a coating roller; Specifically, the steps include: Pre-treatment of coating roller: cleaning, degreasing and roughening of the coating roller surface; Spraying: Plasma spraying equipment is used for coating spraying; the mixed powder is conveyed to the plasma spray gun, the powder is heated to a molten or semi-molten state by a high-temperature plasma flame flow, and then sprayed at high speed onto the preheated coating roller substrate surface; The thickness of each coating layer is controlled at 50-100 μm, and the number of spray layers is set to 3-5 layers according to the required total coating thickness; Insulation treatment: After spraying, the coating roller is placed in a furnace for insulation treatment at a temperature of 500-600°C for 2-3 hours to further diffuse and densify the components in the coating and improve the performance of the coating; Cooling treatment: Cool the coating roller after heat preservation, and control the cooling rate at 5-10℃ / min to avoid cracks in the coating caused by too fast cooling; Surface processing: Finally, the coating surface is finely processed, such as grinding and polishing, so that the coating surface roughness reaches Ra0.8-1.6μm to meet the requirements of the coating process for roller surface flatness.

8. Use of the anti-sticking coating for the tungsten carbide-based coating roll according to claim 7, characterized in that: The pre-treatment coating roll refers to: cleaning the surface of the coating roll substrate to remove oil stains, impurities and oxide layers on the surface; cleaning with a chemical degreasing agent and then sanding the surface to make its roughness reach Ra3.2 - 6.3μm.

9. The application of the anti-sticking coating for the tungsten carbide-based coating roll according to claim 8, characterized in that: The pre-treatment coating roll further includes preheating the coating roll substrate after degreasing and roughening, heating it to 150 - 200°C and keeping it warm for 1 - 2 hours to remove the moisture on the substrate surface and improve the surface activity of the substrate, which is beneficial to the adhesion of the coating.

10. The application of the anti-sticking coating for the tungsten carbide-based coating roll according to claim 7, characterized in that: During spraying, spraying parameters should be controlled. The power of the plasma spray gun is 30 - 50kW, the spraying distance is 100 - 150mm, the spraying angle is perpendicular to the roll surface, and the roll body rotates at a constant speed during spraying to make the coating evenly cover the roll surface.

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