A method for preparing a silicon steel annealing furnace roller surface coating based on a double hollow graphite electrode plasma arc melting diamond-graphite composite coating and application thereof

Abstract

The present application relates to the field of steel metallurgy and high-temperature material engineering, in particular to a silicon steel annealing furnace roller surface coating preparation method based on double hollow graphite electrode plasma arc melting diamond-graphite composite coating and application thereof, which comprises the following steps: adopting double hollow graphite electrode as cathode and roller as anode to form a current loop and generate plasma arc between the electrodes; mixing diamond powder, graphite powder and modified zirconia powder, adding nickel-based self-fluxing alloy powder to obtain mixed powder; sending the mixed powder into the plasma arc area through the double hollow graphite electrode with argon as carrier gas; using high temperature and high energy generated by the plasma arc to activate the surface of the mixed powder particles and cause metallurgical bonding with the surface of the partially molten roller base material to form diamond-graphite composite coating on the roller surface by cladding; and performing post-treatment on the diamond-graphite composite coating according to requirements.

Description

Technical Field

[0001] This invention relates to the fields of iron and steel metallurgy and high-temperature materials engineering, and more specifically, to a method for preparing a coating on the surface of a silicon steel annealing furnace roller based on a diamond-graphite composite coating formed by plasma arc melting with double hollow graphite electrodes, and its application. Background Technology

[0002] Silicon steel undergoes high-temperature treatment in the annealing furnace, and the support rollers are directly eroded by molten steel, slag, and the high-temperature environment, often resulting in wear, oxidation, and material degradation. This seriously affects the production efficiency and product quality of the annealing furnace. Traditional support roller coating technologies, such as spraying and welding, can improve the wear resistance of the coating, but they usually have problems such as weak adhesion, uneven coating, and insufficient high-temperature resistance. In view of this, we propose a method for preparing a coating on the surface of silicon steel annealing furnace rollers based on a diamond-graphite composite coating obtained by plasma arc melting with double hollow graphite electrodes, and its application. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing a coating on the surface of a silicon steel annealing furnace roller based on a diamond-graphite composite coating formed by plasma arc melting with double hollow graphite electrodes and its application, so as to solve the problems of traditional support roller coating technologies such as spraying and welding mentioned in the background art. Although these methods can improve the wear resistance of the coating, they usually have problems such as weak adhesion, uneven coating, and insufficient high temperature resistance.

[0004] This invention provides a method for preparing a coating on the surface of a silicon steel annealing furnace roller based on a diamond-graphite composite coating formed by plasma arc melting with double hollow graphite electrodes, comprising the following steps:

[0005] S1.1. Double hollow graphite electrodes are used as cathodes and rollers are used as anodes to form a current loop, so that a plasma arc is generated between the electrodes.

[0006] S1.2. Titanium-plated diamond powder, graphite powder, and modified zirconia powder are mixed, and nickel-based self-fluxing alloy powder accounting for 30%-60% of the total mass of diamond powder, graphite powder, and modified zirconia powder is added to obtain a mixed powder. The titanium-plated layer on the diamond surface is used as a thermal barrier and diffusion barrier layer to prevent the diamond from graphitizing or dissolving in the high-temperature plasma arc and molten pool. High-speed argon gas is used to transport the powder, so that the residence time of the particles in the high-temperature region of the plasma arc core is extremely short. The titanium-plated layer reacts with the nickel-based alloy and the substrate to form a TiC transition layer, which achieves a strong metallurgical bond with the substrate.

[0007] Among them, the modified zirconium oxide powder is prepared by using zirconium oxychloride and yttrium nitrate as raw materials, using chemical co-precipitation method and adding ammonia water to prepare a precursor, and then calcining it;

[0008] S1.3 Using argon as the carrier gas, the mixed powder is fed into the plasma arc region through a double hollow graphite electrode;

[0009] S1.4. The high temperature and high energy generated by the plasma arc are used to activate the surface of the mixed powder particles and metallurgically bond them with the surface of the partially molten roller substrate, forming a diamond-graphite composite coating on the roller surface.

[0010] S1.5. Perform post-treatment on the diamond-graphite composite coating as required.

[0011] High-speed argon gas is used to transport the powder, resulting in an extremely short residence time for diamond particles in the high-temperature region of the plasma arc core, far shorter than the time required for a complete phase transformation from diamond to graphite, thus achieving instantaneous cladding. Only the surface layer of the diamond particles is instantaneously activated or undergoes slight amorphization / graphitization at high temperatures. This, in turn, facilitates the formation of a strong metallurgical / ceramic interface between the diamond particles and the molten metal substrate and other powder components, while the core of the particles retains its intact diamond crystal structure. Therefore, the final coating is a composite material with diamond as the core hard phase, dispersed in the graphite and zirconium oxide matrix.

[0012] Preferably, in step S1.2, the mass percentages of diamond powder, graphite powder, and modified zirconia powder are: 30%-60% diamond powder, 25%-55% graphite powder, and 5%-25% modified zirconia powder.

[0013] The particle size of diamond powder is 45-150 micrometers, and the particle size of graphite powder is 0.5-5.0 micrometers.

[0014] Preferably, in step S1.2, the modified zirconium oxide powder is prepared using the following method:

[0015] Zirconium oxychloride was dissolved in deionized water at a mass ratio of 1:5 and stirred at 300-400 rpm until clear. Yttrium nitrate was added, and stirring continued to dissolve, yielding a zirconium-yttrium ion mixed solution. Ammonia was added dropwise to the mixed solution under vigorous stirring to make the pH value greater than 9, resulting in a mixed hydroxide gel. The gel was aged for 12-24 hours to allow the precipitate particles to grow uniformly. Subsequently, it was filtered and washed until no chloride ions were detected in the filtrate using silver nitrate solution, yielding a hydroxide precipitate. The washed hydroxide precipitate was dried at 100-120℃ to obtain a precursor powder. The precursor powder was calcined in air at 600-850℃ for 1-2 hours to form yttrium-stabilized zirconia primary powder. The calcined powder was ball-milled at a ball-to-powder ratio of 10:1 at 350 rpm for 4-6 hours, and finally spray-dried to obtain modified zirconia powder.

[0016] Preferably, the mass ratio of zirconium oxychloride to yttrium nitrate is 4.8-5.0:1.

[0017] Preferably, the mass concentration of the ammonia water is 25-28%.

[0018] Preferably, in step S1.3, the powder feeding speed of the mixed powder is 5-30 g / min, the powder feeding distance is 5-20 mm, and the carrier gas flow rate is 10 L / min-30 L / min.

[0019] Preferably, in step S1.3, the power of the plasma arc is 1000W-5000W, and the operating voltage is 20V-40V.

[0020] Preferably, in step S1.4, the thickness of the diamond-graphite composite coating is 0.1 mm to 1.0 mm.

[0021] Preferably, in step S1.5, the post-treatment is annealing under vacuum conditions at a temperature of 600-900°C for 2 hours, followed by furnace cooling to room temperature.

[0022] On the other hand, the present invention provides a method for preparing a coating on the surface of a silicon steel annealing furnace roller based on a diamond-graphite composite coating formed by plasma arc melting of double hollow graphite electrodes, for use in support rollers operating under various high-temperature conditions.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] The present invention relates to a method for preparing a silicon steel annealing furnace roller surface coating based on a double hollow graphite electrode plasma arc melting diamond-graphite composite coating and its application. Modified zirconia powder is introduced into the diamond-graphite composite coating. Through its phase transformation toughening effect and thermal expansion coefficient between the matrix and the carbon phase, a good thermal stress buffer gradient is constructed, suppressing cracks and spalling caused by thermal mismatch during high-temperature cycling. The diamond-graphite-zirconia three-phase system retains the ultra-high hardness of diamond and the self-lubricating properties of graphite, while using zirconia to enhance the coating's toughness and interfacial stability. This synergistic effect enables the coating to exhibit superior thermal shock resistance, high-temperature dimensional stability, and bonding strength under the harsh environment of the silicon steel annealing furnace, thereby significantly extending the service life of the furnace roller, reducing unplanned downtime, and improving the continuity and economy of the production line. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] Diamond powder (titanium-plated diamond) and graphite powder were purchased from Xi'an Qiyue Biotechnology Co., Ltd.

[0027] Zirconium oxychloride (CAS No.: 13520-92-8) was purchased from Shanghai Yuanye Biotechnology Co., Ltd.

[0028] Yttrium nitrate (CAS No.: 13494-98-9) was purchased from Jining Maikerui Rare Earth Co., Ltd.

[0029] Example 1: A method for preparing a coating on the surface of a silicon steel annealing furnace roller based on a plasma arc melting diamond-graphite composite coating using double hollow graphite electrodes, comprising the following steps:

[0030] S1.1. Double hollow graphite electrodes are used as cathodes and rollers are used as anodes to form a current loop, so that a plasma arc is generated between the electrodes.

[0031] S1.2. Mix diamond powder, graphite powder and modified zirconium oxide powder, and add nickel-based self-fluxing alloy powder accounting for 50% of the total mass of diamond powder, graphite powder and modified zirconium oxide powder to obtain mixed powder.

[0032] The mass percentages of diamond powder, graphite powder, and modified zirconia powder are as follows: diamond powder 45%, graphite powder 40%, and modified zirconia powder 15%.

[0033] The particle size of diamond powder is 100 micrometers, and the particle size of graphite powder is 2.5 micrometers.

[0034] S1.3 Using argon as the carrier gas, the mixed powder is fed into the plasma arc region through a double hollow graphite electrode; the powder feeding speed is 15g / min, the powder feeding distance is 12mm, the carrier gas flow rate is 20L / min, the plasma arc power is 3000W, and the working voltage is 30V.

[0035] S1.4. The high temperature and high energy generated by the plasma arc are used to activate the surface of the mixed powder particles and metallurgically bond them with the surface of the partially molten roller substrate, forming a diamond-graphite composite coating with a thickness of 0.3 mm on the roller surface.

[0036] S1.5 The diamond-graphite composite coating is annealed under vacuum conditions at a temperature of 750℃ for 2 hours, and then cooled to room temperature in the furnace.

[0037] The preparation method of modified zirconia powder is as follows:

[0038] Zirconium oxychloride was dissolved in deionized water at a mass ratio of 1:5 and stirred at 350 rpm until clear. Yttrium nitrate (mass ratio of zirconium oxychloride to yttrium nitrate was 4.9:1) was added, and stirring continued to dissolve, resulting in a zirconium-yttrium ion mixed solution. Under vigorous stirring, 26% ammonia solution was added dropwise to the mixed solution to make the pH value greater than 9, resulting in a mixed hydroxide gel. The gel was aged for 20 h to allow the precipitate particles to grow uniformly. Then, it was filtered and washed until no chloride ions were detected in the filtrate using silver nitrate solution, resulting in a hydroxide precipitate. The washed hydroxide precipitate was dried at 110 °C to obtain a precursor powder. The precursor powder was calcined in air at 700 °C for 2 h to form yttrium-stabilized zirconia primary powder. The calcined powder was ball-milled at a ball-to-powder ratio of 10:1 at 350 rpm for 5 h, and finally spray-dried to obtain modified zirconia powder.

[0039] Example 2: A method for preparing a coating on the surface of a silicon steel annealing furnace roller based on a plasma arc melting diamond-graphite composite coating using double hollow graphite electrodes, comprising the following steps:

[0040] S1.1. Double hollow graphite electrodes are used as cathodes and rollers are used as anodes to form a current loop, so that a plasma arc is generated between the electrodes.

[0041] S1.2. Mix diamond powder, graphite powder and modified zirconium oxide powder, and add nickel-based self-fluxing alloy powder accounting for 50% of the total mass of diamond powder, graphite powder and modified zirconium oxide powder to obtain mixed powder.

[0042] The mass percentages of diamond powder, graphite powder, and modified zirconia powder are as follows: diamond powder 40%, graphite powder 55%, and modified zirconia powder 5%.

[0043] The particle size of diamond powder is 100 micrometers, and the particle size of graphite powder is 2.5 micrometers.

[0044] S1.3 Using argon as the carrier gas, the mixed powder is fed into the plasma arc region through a double hollow graphite electrode; the powder feeding speed is 15g / min, the powder feeding distance is 12mm, the carrier gas flow rate is 20L / min, the plasma arc power is 3000W, and the working voltage is 30V.

[0045] S1.4. The high temperature and high energy generated by the plasma arc are used to activate the surface of the mixed powder particles and metallurgically bond them with the surface of the partially molten roller substrate, forming a diamond-graphite composite coating with a thickness of 0.5 mm on the roller surface.

[0046] S1.5 The diamond-graphite composite coating is annealed under vacuum conditions at a temperature of 750℃ for 2 hours, and then cooled to room temperature in the furnace.

[0047] The preparation method of modified zirconia powder is as follows:

[0048] Zirconium oxychloride was dissolved in deionized water at a mass ratio of 1:5 and stirred at 350 rpm until clear. Yttrium nitrate (mass ratio of zirconium oxychloride to yttrium nitrate was 4.9:1) was added, and stirring continued to dissolve, resulting in a zirconium-yttrium ion mixed solution. Under vigorous stirring, 26% ammonia solution was added dropwise to the mixed solution to make the pH value greater than 9, resulting in a mixed hydroxide gel. The gel was aged for 20 h to allow the precipitate particles to grow uniformly. Then, it was filtered and washed until no chloride ions were detected in the filtrate using silver nitrate solution, resulting in a hydroxide precipitate. The washed hydroxide precipitate was dried at 110 °C to obtain a precursor powder. The precursor powder was calcined in air at 700 °C for 2 h to form yttrium-stabilized zirconia primary powder. The calcined powder was ball-milled at a ball-to-powder ratio of 10:1 at 350 rpm for 5 h, and finally spray-dried to obtain modified zirconia powder.

[0049] Example 3: A method for preparing a coating on the surface of a silicon steel annealing furnace roller based on a plasma arc melting diamond-graphite composite coating using double hollow graphite electrodes, comprising the following steps:

[0050] S1.1. Double hollow graphite electrodes are used as cathodes and rollers are used as anodes to form a current loop, so that a plasma arc is generated between the electrodes.

[0051] S1.2. Mix diamond powder, graphite powder and modified zirconium oxide powder, and add nickel-based self-fluxing alloy powder accounting for 50% of the total mass of diamond powder, graphite powder and modified zirconium oxide powder to obtain mixed powder.

[0052] The mass percentages of diamond powder, graphite powder, and modified zirconia powder are as follows: diamond powder 50%, graphite powder 25%, and modified zirconia powder 25%.

[0053] The particle size of diamond powder is 100 micrometers, and the particle size of graphite powder is 2.5 micrometers.

[0054] S1.3 Using argon as the carrier gas, the mixed powder is fed into the plasma arc region through a double hollow graphite electrode; the powder feeding speed is 15g / min, the powder feeding distance is 12mm, the carrier gas flow rate is 20L / min, the plasma arc power is 3000W, and the working voltage is 30V.

[0055] S1.4. The high temperature and high energy generated by the plasma arc are used to activate the surface of the mixed powder particles and metallurgically bond them with the surface of the partially molten roller substrate, forming a diamond-graphite composite coating with a thickness of 0.5 mm on the roller surface.

[0056] S1.5 The diamond-graphite composite coating is annealed under vacuum conditions at a temperature of 750℃ for 2 hours, and then cooled to room temperature in the furnace.

[0057] The preparation method of modified zirconia powder is as follows:

[0058] Zirconium oxychloride was dissolved in deionized water at a mass ratio of 1:5 and stirred at 350 rpm until clear. Yttrium nitrate (mass ratio of zirconium oxychloride to yttrium nitrate was 4.9:1) was added, and stirring continued to dissolve, resulting in a zirconium-yttrium ion mixed solution. Under vigorous stirring, 26% ammonia solution was added dropwise to the mixed solution to make the pH value greater than 9, resulting in a mixed hydroxide gel. The gel was aged for 20 h to allow the precipitate particles to grow uniformly. Then, it was filtered and washed until no chloride ions were detected in the filtrate using silver nitrate solution, resulting in a hydroxide precipitate. The washed hydroxide precipitate was dried at 110 °C to obtain a precursor powder. The precursor powder was calcined in air at 700 °C for 2 h to form yttrium-stabilized zirconia primary powder. The calcined powder was ball-milled at a ball-to-powder ratio of 10:1 at 350 rpm for 5 h, and finally spray-dried to obtain modified zirconia powder.

[0059] Example 4: A method for preparing a coating on the surface of a silicon steel annealing furnace roller based on a diamond-graphite composite coating formed by plasma arc melting with double hollow graphite electrodes, comprising the following steps:

[0060] S1.1. Double hollow graphite electrodes are used as cathodes and rollers are used as anodes to form a current loop, so that a plasma arc is generated between the electrodes.

[0061] S1.2. Mix diamond powder, graphite powder and modified zirconium oxide powder, and add nickel-based self-fluxing alloy powder accounting for 50% of the total mass of diamond powder, graphite powder and modified zirconium oxide powder to obtain mixed powder.

[0062] The mass percentages of diamond powder, graphite powder, and modified zirconia powder are as follows: diamond powder 45%, graphite powder 40%, and modified zirconia powder 15%.

[0063] The particle size of diamond powder is 100 micrometers, and the particle size of graphite powder is 2.5 micrometers.

[0064] S1.3 Using argon as the carrier gas, the mixed powder is fed into the plasma arc region through a double hollow graphite electrode; the powder feeding speed is 15g / min, the powder feeding distance is 12mm, the carrier gas flow rate is 20L / min, the plasma arc power is 3000W, and the working voltage is 30V.

[0065] S1.4. The high temperature and high energy generated by the plasma arc are used to activate the surface of the mixed powder particles and metallurgically bond them with the surface of the partially molten roller substrate, forming a diamond-graphite composite coating with a thickness of 0.1 mm on the roller surface.

[0066] S1.5 The diamond-graphite composite coating is annealed under vacuum conditions at a temperature of 750℃ for 2 hours, and then cooled to room temperature in the furnace.

[0067] The preparation method of modified zirconia powder is as follows:

[0068] Zirconium oxychloride was dissolved in deionized water at a mass ratio of 1:5 and stirred at 350 rpm until clear. Yttrium nitrate (mass ratio of zirconium oxychloride to yttrium nitrate was 4.9:1) was added, and stirring continued to dissolve, resulting in a zirconium-yttrium ion mixed solution. Under vigorous stirring, 26% ammonia solution was added dropwise to the mixed solution to make the pH value greater than 9, resulting in a mixed hydroxide gel. The gel was aged for 20 h to allow the precipitate particles to grow uniformly. Then, it was filtered and washed until no chloride ions were detected in the filtrate using silver nitrate solution, resulting in a hydroxide precipitate. The washed hydroxide precipitate was dried at 110 °C to obtain a precursor powder. The precursor powder was calcined in air at 700 °C for 2 h to form yttrium-stabilized zirconia primary powder. The calcined powder was ball-milled at a ball-to-powder ratio of 10:1 at 350 rpm for 5 h, and finally spray-dried to obtain modified zirconia powder.

[0069] Example 5: A method for preparing a coating on the surface of a silicon steel annealing furnace roller based on a plasma arc melting diamond-graphite composite coating using double hollow graphite electrodes, comprising the following steps:

[0070] S1.1. Double hollow graphite electrodes are used as cathodes and rollers are used as anodes to form a current loop, so that a plasma arc is generated between the electrodes.

[0071] S1.2. Mix diamond powder, graphite powder and modified zirconium oxide powder, and add nickel-based self-fluxing alloy powder accounting for 50% of the total mass of diamond powder, graphite powder and modified zirconium oxide powder to obtain mixed powder.

[0072] The mass percentages of diamond powder, graphite powder, and modified zirconia powder are as follows: diamond powder 45%, graphite powder 40%, and modified zirconia powder 15%.

[0073] The particle size of diamond powder is 100 micrometers, and the particle size of graphite powder is 2.5 micrometers.

[0074] S1.3 Using argon as the carrier gas, the mixed powder is fed into the plasma arc region through a double hollow graphite electrode; the powder feeding speed is 15g / min, the powder feeding distance is 12mm, the carrier gas flow rate is 20L / min, the plasma arc power is 3000W, and the working voltage is 30V.

[0075] S1.4. The high temperature and high energy generated by the plasma arc are used to activate the surface of the mixed powder particles and metallurgically bond them with the surface of the partially molten roller substrate, forming a diamond-graphite composite coating with a thickness of 2.5 mm on the roller surface.

[0076] S1.5 The diamond-graphite composite coating is annealed under vacuum conditions at a temperature of 750℃ for 2 hours, and then cooled to room temperature in the furnace.

[0077] The preparation method of modified zirconia powder is as follows:

[0078] Zirconium oxychloride was dissolved in deionized water at a mass ratio of 1:5 and stirred at 350 rpm until clear. Yttrium nitrate (mass ratio of zirconium oxychloride to yttrium nitrate was 4.9:1) was added, and stirring continued to dissolve, resulting in a zirconium-yttrium ion mixed solution. Under vigorous stirring, 26% ammonia solution was added dropwise to the mixed solution to make the pH value greater than 9, resulting in a mixed hydroxide gel. The gel was aged for 20 h to allow the precipitate particles to grow uniformly. Then, it was filtered and washed until no chloride ions were detected in the filtrate using silver nitrate solution, resulting in a hydroxide precipitate. The washed hydroxide precipitate was dried at 110 °C to obtain a precursor powder. The precursor powder was calcined in air at 700 °C for 2 h to form yttrium-stabilized zirconia primary powder. The calcined powder was ball-milled at a ball-to-powder ratio of 10:1 at 350 rpm for 5 h, and finally spray-dried to obtain modified zirconia powder.

[0079] Example 6: A method for preparing a coating on the surface of a silicon steel annealing furnace roller based on a plasma arc melting diamond-graphite composite coating using double hollow graphite electrodes, comprising the following steps:

[0080] S1.1. Double hollow graphite electrodes are used as cathodes and rollers are used as anodes to form a current loop, so that a plasma arc is generated between the electrodes.

[0081] S1.2. Mix diamond powder, graphite powder and modified zirconium oxide powder, and add nickel-based self-fluxing alloy powder accounting for 30% of the total mass of diamond powder, graphite powder and modified zirconium oxide powder to obtain mixed powder.

[0082] The mass percentages of diamond powder, graphite powder, and modified zirconia powder are as follows: diamond powder 45%, graphite powder 40%, and modified zirconia powder 15%.

[0083] The particle size of the diamond powder is 45 micrometers, and the particle size of the graphite powder is 0.5 micrometers.

[0084] S1.3 Using argon as the carrier gas, the mixed powder is fed into the plasma arc region through a double hollow graphite electrode; the powder feeding speed is 15g / min, the powder feeding distance is 12mm, the carrier gas flow rate is 10L / min, the plasma arc power is 3000W, and the working voltage is 20V.

[0085] S1.4. The high temperature and high energy generated by the plasma arc are used to activate the surface of the mixed powder particles and metallurgically bond them with the surface of the partially molten roller substrate, forming a diamond-graphite composite coating with a thickness of 0.5 mm on the roller surface.

[0086] S1.5 The diamond-graphite composite coating is annealed under vacuum conditions at a temperature of 600℃ for 2 hours, and then cooled to room temperature in the furnace.

[0087] The preparation method of modified zirconia powder is as follows:

[0088] Zirconium oxychloride was dissolved in deionized water at a mass ratio of 1:5 and stirred at 300-400 rpm until clear. Yttrium nitrate (mass ratio of zirconium oxychloride to yttrium nitrate was 4.9:1) was added, and stirring continued to dissolve, yielding a zirconium-yttrium ion mixed solution. Under vigorous stirring, ammonia solution with a mass concentration of 25-28% was added dropwise to the mixed solution to adjust the pH to greater than 9, resulting in a mixed hydroxide gel. The gel was aged for 12-24 hours to allow for uniform precipitate growth, followed by pressure filtration and... Wash until no chloride ions are detected in the filtrate using silver nitrate solution to obtain a hydroxide precipitate; dry the washed hydroxide precipitate at 100-120℃ to obtain a precursor powder; calcine the precursor powder in air at 600-850℃ for 1-2 hours to form yttrium-stabilized zirconia primary powder; ball mill the calcined powder at a ball-to-powder ratio of 10:1 and a rotation speed of 350 rpm for 4-6 hours, and finally spray dry to obtain modified zirconia powder.

[0089] Example 7: A method for preparing a coating on the surface of a silicon steel annealing furnace roller based on a plasma arc melting diamond-graphite composite coating using double hollow graphite electrodes, comprising the following steps:

[0090] S1.1. Double hollow graphite electrodes are used as cathodes and rollers are used as anodes to form a current loop, so that a plasma arc is generated between the electrodes.

[0091] S1.2. Mix diamond powder, graphite powder and modified zirconium oxide powder, and add nickel-based self-fluxing alloy powder accounting for 60% of the total mass of diamond powder, graphite powder and modified zirconium oxide powder to obtain mixed powder.

[0092] The mass percentages of diamond powder, graphite powder, and modified zirconia powder are as follows: diamond powder 45%, graphite powder 40%, and modified zirconia powder 15%.

[0093] The particle size of the diamond powder is 150 micrometers, and the particle size of the graphite powder is 5.0 micrometers.

[0094] S1.3 Using argon as the carrier gas, the mixed powder is fed into the plasma arc region through a double hollow graphite electrode; the powder feeding speed is 15g / min, the powder feeding distance is 12mm, the carrier gas flow rate is 30L / min, the plasma arc power is 3000W, and the working voltage is 40V.

[0095] S1.4. The high temperature and high energy generated by the plasma arc are used to activate the surface of the mixed powder particles and metallurgically bond them with the surface of the partially molten roller substrate, forming a diamond-graphite composite coating with a thickness of 0.5 mm on the roller surface.

[0096] S1.5 The diamond-graphite composite coating is annealed under vacuum conditions at a temperature of 900℃ for 2 hours, and then cooled to room temperature in the furnace.

[0097] The preparation method of modified zirconia powder is as follows:

[0098] Zirconium oxychloride was dissolved in deionized water at a mass ratio of 1:5 and stirred at 300-400 rpm until clear. Yttrium nitrate (mass ratio of zirconium oxychloride to yttrium nitrate was 4.9:1) was added, and stirring continued to dissolve, yielding a zirconium-yttrium ion mixed solution. Under vigorous stirring, ammonia solution with a mass concentration of 25-28% was added dropwise to the mixed solution to adjust the pH to greater than 9, resulting in a mixed hydroxide gel. The gel was aged for 12-24 hours to allow for uniform precipitate growth, followed by pressure filtration and... Wash until no chloride ions are detected in the filtrate using silver nitrate solution to obtain a hydroxide precipitate; dry the washed hydroxide precipitate at 100-120℃ to obtain a precursor powder; calcine the precursor powder in air at 600-850℃ for 1-2 hours to form yttrium-stabilized zirconia primary powder; ball mill the calcined powder at a ball-to-powder ratio of 10:1 and a rotation speed of 350 rpm for 4-6 hours, and finally spray dry to obtain modified zirconia powder.

[0099] The method for determining wear resistance (μm / 1000 friction cycles) is as follows: Fix the coating sample to be tested on the test platform of the friction and wear testing machine and apply a certain load; select an appropriate friction material (such as cemented carbide, steel ball, etc.) and rub it against the coating surface; set the specified number of friction cycles (usually 1000 cycles) and load (generally 5-10N) and start the friction test; after the test, measure the depth of coating wear or the amount of surface wear (in μm), and calculate the wear resistance based on the depth of wear.

[0100] Method for determining high temperature resistance: Prepare the coating sample to be tested and place it in a high temperature furnace; set the furnace temperature, generally select a high temperature environment of 800℃ to 1000℃ for testing, and maintain it for a certain time (e.g., 4 hours); under high temperature environment, record whether the coating has any peeling, cracking or deformation; after the test, check the appearance, thickness and structure of the coating to evaluate the high temperature resistance performance of the coating.

[0101] Methods for determining antioxidant properties (oxidation rate): Place the coating sample in an oxidation furnace or high-temperature environment, and select an oxidizing atmosphere (such as air, oxygen, etc.); set the temperature, generally between 650℃ and 800℃, and start the oxidation test; periodically sample and measure the change in oxidation mass of the sample, usually by mass change method or surface morphology analysis method (such as scanning electron microscopy or X-ray photoelectron spectroscopy) to determine the thickness of the oxide layer; calculate the oxidation rate based on the change in oxidation mass, with the unit being g / m²·h.

[0102] Method for determining thermal stability (number of temperature fluctuations): Place the coating sample in a thermal cycling test chamber and set an appropriate temperature range (e.g., from -50°C to 800°C); set a temperature fluctuation cycle (e.g., the temperature rises from a low temperature to a high temperature and then drops back to a low temperature, with each cycle lasting 2-3 hours); perform multiple temperature fluctuation cycles (generally set to 10-50 cycles), observe the surface changes of the coating after each cycle, such as cracks, peeling, or other physical changes; record the performance of the coating after thermal cycling, evaluate the thermal stability of the coating, and calculate the number of temperature fluctuations it can withstand.

[0103] Table 1 Performance data of the coating

[0104] Abrasion resistance (μm / 1000 cycles of friction) High temperature resistance Antioxidant properties (oxidation rate) Thermal stability (number of temperature fluctuations) Example 1 10 820℃ 0.04 g / m²·h 65 Example 2 12 780℃ 0.05g / m²·h 52 Example 3 9 750℃ 0.07 g / m²·h 45 Example 4 7 850℃ 0.04 g / m²·h 72 Example 5 22 700℃ 0.09 g / m²·h 28 Example 6 13 780℃ 0.07 g / m²·h 55 Example 7 10 820℃ 0.02 g / m²·h 63

[0105] Comparing Examples 1, 2, and 3, according to the data in Table 1, the antioxidant properties of Example 1 (oxidation rate 0.04 g / m²·h) are better than those of Example 2 (0.05 g / m²·h) and Example 3 (0.07 g / m²·h). This indicates that in the system, higher graphite content does not necessarily lead to better antioxidant properties. In Example 1, 40% graphite and 15% zirconium oxide formed a synergistic protective effect, constructing a denser antioxidant barrier. However, in Example 2, the excessively high graphite content (55%) and the excessively low zirconium oxide content (5%) may result in poor interfacial bonding or insufficient toughness, making it prone to microcracks at high temperatures, thereby reducing the overall antioxidant performance.

[0106] Comparing Examples 1, 4, and 5, it can be seen that coating thickness affects performance; thicker coatings do not necessarily mean better wear resistance. When the coating thickness increases to 2.5 mm (Example 5), the wear amount reaches 22 μm / 1000 friction cycles, exhibiting the worst wear resistance, and the high-temperature resistance also drops to 700°C. This is because the ultra-thick coating accumulates huge thermal mismatch internal stress during preparation and cooling, leading to microcracks invisible to the naked eye inside the coating, making it more prone to brittle spalling during wear and high-temperature tests. Conversely, the thinner coating (Example 4, 0.3 mm) exhibits excellent wear resistance (wear amount 7 μm / 1000 friction cycles) and good high-temperature resistance (850°C), thanks to its lower internal stress and better heat conduction.

[0107] Based on the above measurements, Example 1 achieved excellent wear resistance (wear amount 10μm / 1000 friction cycles) while maintaining extremely low oxidation rate (0.04g / m²·h) and high temperature resistance (820℃). It exhibited the most balanced and comprehensive performance in all aspects. Therefore, Example 1 was selected as the optimal example.

[0108] Comparative Example 1: The difference between this example and Example 1 is that the traditional silicon carbide coating replaces the diamond-graphite composite coating.

[0109] Comparative Example 2: The difference between this example and Example 1 is that no diamond powder was added.

[0110] Comparative Example 3: The difference between this example and Example 1 is that no modified zirconium oxide powder was added.

[0111] Table 2 Performance data of the coating

[0112] Abrasion resistance (μm / 1000 cycles of friction) High temperature resistance Antioxidant properties (oxidation rate) Thermal stability (number of temperature fluctuations) Example 1 10 820℃ 0.04 g / m²·h 65 Comparative Example 1 18 800℃ 0.06 g / m²·h 42 Comparative Example 2 45 750℃ 0.12 g / m²·h 35 Comparative Example 3 18 760℃ 0.09 g / m²·h 15

[0113] Compared with the optimal Example 1 of the present invention, Comparative Example 1 (conventional silicon carbide coating) has significantly inferior wear resistance (wear amount 18μm / 1000 friction cycles), high temperature resistance (800℃), oxidation resistance (0.06g / m²·h), and thermal stability (42 cycles) compared with Example 1 (65 cycles). This is because although the silicon carbide coating has high hardness, its toughness under extreme thermal cycling is not as good as the multiphase composite structure of the present invention.

[0114] Compared with Example 1, Comparative Example 2 (pure graphite coating) has the worst performance in all aspects; in particular, its wear resistance is extremely poor, with a wear rate as high as 45 μm / 1000 friction cycles. This is because the hardness of pure graphite is too low to resist abrasive wear. In addition, its oxidation resistance is also the worst, with an oxidation rate of 0.12 g / m²·h. This indicates that the structure of the pure graphite coating is not stable under high-temperature oxidation conditions. Its high-temperature resistance and thermal stability are also far inferior to those of the embodiments of the present invention.

[0115] The wear rate of Comparative Example 3 was 80% higher than that of Example 1, and it could only withstand 15 temperature fluctuations. This was because it lacked the phase transformation toughening and thermal expansion coefficient buffering effect of zirconium oxide. Under frictional stress or thermal cycling, high stress was generated between the diamond hard phase and the steel matrix due to the huge difference in thermal expansion coefficients, which directly led to the early failure of the coating due to insufficient toughness. The high temperature resistance and oxidation resistance were greatly reduced: the temperature resistance of Comparative Example 3 decreased by about 60°C, and the oxidation rate increased to more than twice that of Example 1. Since the addition of zirconium oxide is not only a stable high temperature oxide, it can also form a denser composite structure with the carbon phase at the interface. In the absence of zirconium oxide, the coating mainly relies on graphite for oxidation resistance at high temperatures, but the stability of the pure graphite layer is insufficient in long-term high temperature and oxidizing atmosphere, resulting in a rapid decline in protective performance.

[0116] In summary, the diamond-graphite composite coating of the present invention exhibits advantages over traditional silicon carbide coatings and pure graphite coatings in four key indicators: wear resistance, high temperature resistance, oxidation resistance, and thermal stability. This fully demonstrates that the present invention scientifically combines the hardness of diamond with the lubricity and chemical stability of graphite, synergistically improving the overall performance of the coating and achieving technical effects that single-component coatings or traditional coatings cannot achieve.

[0117] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a coating on the surface of a silicon steel annealing furnace roller based on a diamond-graphite composite coating obtained by plasma arc melting using double hollow graphite electrodes, characterized in that, Includes the following steps: S1.

1. Double hollow graphite electrodes are used as cathodes and rollers are used as anodes to form a current loop, so that a plasma arc is generated between the electrodes. S1.2 A mixture of surface-coated titanium-diamond powder, graphite powder, and modified zirconia powder is prepared. Nickel-based self-fluxing alloy powder, comprising 30%-60% of the total mass of the diamond powder, graphite powder, and modified zirconia powder, is added to obtain a mixed powder. The mass percentages of diamond powder, graphite powder, and modified zirconia powder are: diamond powder 30%-60%, graphite powder 25%-55%, and modified zirconia powder 5%-25%. The particle size of the diamond powder is 45-150 micrometers, and the particle size of the graphite powder is 0.5-5.0 micrometers. The modified zirconia powder is prepared as follows: Zirconium oxychloride is dissolved in deionized water at a mass ratio of 1:5, stirred at 300-400 rpm until clear, yttrium nitrate is added, and stirring continues to dissolve, yielding a zirconium-yttrium ion mixed solution. Ammonia water is added dropwise to the mixed solution under vigorous stirring to make its pH value greater than 9, yielding a mixed hydroxide gel. The gel is then... The precipitate is aged for 12-24 hours to allow for uniform growth of the precipitate particles. It is then filtered and washed until no chloride ions are detected in the filtrate using silver nitrate solution, yielding a hydroxide precipitate. The washed hydroxide precipitate is dried at 100-120℃ to obtain a precursor powder. The precursor powder is calcined in air at 600-850℃ for 1-2 hours to form yttrium-stabilized zirconia primary powder. The calcined powder is ball-milled at a ball-to-powder ratio of 10:1 at 350 rpm for 4-6 hours, and finally spray-dried to obtain modified zirconia powder. S1.3: Using argon as the carrier gas, the mixed powder is fed into the plasma arc region through a double hollow graphite electrode. S1.4: Utilizing the high temperature and energy generated by the plasma arc, the surface of the mixed powder particles is activated and metallurgically bonded to the partially molten roller substrate surface, forming a diamond-graphite composite coating on the roller surface. S1.

5. Perform post-treatment on the diamond-graphite composite coating as required.

2. The method for preparing a coating on the surface of a silicon steel annealing furnace roller based on a double hollow graphite electrode plasma arc melting diamond-graphite composite coating according to claim 1, characterized in that, The mass ratio of zirconium oxychloride to yttrium nitrate is 4.8-5.0:

1.

3. The method for preparing a coating on the surface of a silicon steel annealing furnace roller based on a double hollow graphite electrode plasma arc melting diamond-graphite composite coating according to claim 1, characterized in that, The mass concentration of the ammonia water is 25-28%.

4. The method for preparing a coating on the surface of a silicon steel annealing furnace roller based on a double hollow graphite electrode plasma arc melting diamond-graphite composite coating according to claim 1, characterized in that, In step S1.3, the powder feeding speed of the mixed powder is 5-30 g / min, the powder feeding distance is 5-20 mm, and the carrier gas flow rate is 10 L / min-30 L / min.

5. The method for preparing a coating on the surface of a silicon steel annealing furnace roller based on a double hollow graphite electrode plasma arc melting diamond-graphite composite coating according to claim 1, characterized in that, In S1.3, the power of the plasma arc is 1000W-5000W, and the operating voltage is 20V-40V.

6. The method for preparing a coating on the surface of a silicon steel annealing furnace roller based on a double hollow graphite electrode plasma arc melting diamond-graphite composite coating according to claim 1, characterized in that, In step S1.4, the thickness of the diamond-graphite composite coating is 0.1mm-1.0mm.

7. The method for preparing a coating on the surface of a silicon steel annealing furnace roller based on a double hollow graphite electrode plasma arc melting diamond-graphite composite coating according to claim 1, characterized in that, In S1.5, the post-treatment is to perform annealing under vacuum conditions at a temperature of 600-900℃ for 2 hours, followed by furnace cooling to room temperature.

8. The application of the coating prepared by the method for preparing a silicon steel annealing furnace roller surface coating based on a double hollow graphite electrode plasma arc melting diamond-graphite composite coating as described in any one of claims 1-7 in support rollers operating under various high-temperature conditions.