Thermal insulation copper-plating-free coating for underwater additive manufacturing and preparation method of thermal insulation copper-plating-free coating

Abstract

The invention provides a thermal insulation copper-plating-free coating for underwater additive manufacturing and a preparation method. The coating comprises the following components in percentage by weight: 1.0%-1.5% of carbon nanotubes, 50%-65% of porous diatomite, 1.0%-2.0% of gamma-MPS, 2.5%-3.5% of Zn3P2, 6%-10% of copper powder, 20%-30% of modified epoxy resin, 0.1%-0.3% of a stabilizing and leveling agent and inevitable impurities. The welding wire coating ensures the preheating effect of the welding wire before welding through good thermal insulation performance, slows down the cooling speed in the underwater welding process, effectively reduces the generation of quenched structures, has good environmental adaptability, ensures that the performance of the welding wire can be kept under diversified underwater environment conditions, and improves the reliability and efficiency of underwater additive repair.

Description

Technical Field

[0001] The present invention belongs to the field of metal welding, and particularly relates to a thermal insulation copper-free coating for underwater additive manufacturing and a preparation method thereof. Background Art

[0002] In the field of underwater additive repair, traditional welding techniques often result in the formation of hardened structures in the weld area due to rapid cooling, reducing material toughness and increasing the risk of brittle fracture. We can often adopt the method of preheating the welding wire before welding to increase the temperature of the welding wire reaching the welding molten pool to slow down the problem of too fast cooling rate in the weld area. However, at present, copper-coated coatings are mostly used in the market. Even if the welding wire is preheated before welding, when the welding wire is transported to the underwater additive repair area, under the limitation of high cooling rate underwater, the preheating heat of the welding wire will be exhausted. At the same time, due to serious pollution of the copper-coated coating, at present, developing a copper-free coating has always been a difficult problem that major welding wire manufacturers urgently need to overcome. Therefore, there is an urgent need in the market for a new type of welding wire coating that can, on the one hand, meet the requirements of preheating and heat preservation of the welding wire before welding, and on the other hand, solve the huge pollution problem of the traditional copper-coated coating.

[0003] In response to the above needs, a thermal insulation copper-free coating for underwater additive manufacturing and a preparation method thereof are proposed. Through reasonable material ratio and process flow, the coating achieves excellent thermal insulation performance, effectively slows down the problem of fast heat dissipation of the welding wire, reduces the cooling rate of the weld, reduces the generation of hardened structures, and thus significantly improves the toughness and crack resistance of the weld. At the same time, the coating shows good anti-peeling effect, and the high adhesion between the coating and the substrate and excellent wear resistance ensure the integrity and stability of the coating during the additive repair process. The coating has strong environmental adaptability and can work stably in a variety of underwater environments, ensuring the repair efficiency and quality.

[0004] The present invention brings a high-performance solution to the field of underwater additive repair, which not only improves the repair efficiency and the long-term stability of the structure, but also promotes the development of underwater additive repair technology, and has important practical application value and market prospects. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above problems and deficiencies and provide a thermal insulation copper-free coating for underwater additive manufacturing and a preparation method thereof that improve the repair efficiency and the long-term stability of the structure. This new type of welding wire coating for underwater additive repair slows down the heat dissipation of the welding wire during preheating before welding, reduces the cooling rate in the weld area, thereby reducing the proportion of brittle and hard structures, improving the toughness of the weld, and having good environmental adaptability, improving the quality of underwater welding.

[0006] The purpose of the present invention is achieved as follows:

[0007] A heat-insulating copper-free coating for underwater additive manufacturing. The composition of the coating is as follows by weight percentage: carbon nanotubes: 1.0% - 1.5%, porous diatomaceous earth: 50% - 65%, γ-MPS: 1.0% - 2.0%, Zn 3 P 2 : 2.5% - 3.5%, copper powder: 6% - 10%, modified epoxy resin: 20% - 30%, stabilizing and leveling agent: 0.1% - 0.3%, and inevitable impurities.

[0008] Furthermore, the thickness of the coating is 50 - 70μm.

[0009] The hardness value of the coating is 150 - 200HV, and the thermal conductivity is 0.1 - 1W / m·K.

[0010] Furthermore, the diameter of the carbon nanotubes is < 3nm, the length is < 10nm, and the purity is ≥ 95%.

[0011] Furthermore, the porosity of the porous diatomaceous earth is ≥ 80%, and the average particle size is 5 - 10μm.

[0012] Furthermore, the Zn 3 P 2 The purity is ≥ 98%, and the average particle size is 1 - 3μm.

[0013] The reasons for the design of the coating composition of the present invention are as follows:

[0014] Carbon nanotubes: As a wear resistance enhancer, carbon nanotubes have extremely high strength and toughness, can form a strong network structure in the coating, and significantly improve the wear resistance of the coating. When the content of carbon nanotubes is relatively high, it may cause the coating to become hard and brittle, reducing flexibility and impact resistance. When the content is relatively low, it is not sufficient to form an effective wear-resistant network, and the improvement of wear resistance is limited. Therefore, the content of carbon nanotubes is controlled at 1.0% - 1.5%; preferably, the diameter of the carbon nanotubes is < 3nm, the length is < 10nm, and the purity is ≥ 95%.

[0015] Porous diatomaceous earth: As a heat-insulating material, the high porosity of porous diatomaceous earth can effectively reduce heat transfer. Its natural porous structure provides excellent heat-insulating performance, while reducing the weight of the coating and helping to maintain the flexibility of the welding wire. However, when the content is too high, it may reduce the mechanical strength of the coating, making it more likely to be damaged under physical impact. When the content is insufficient, the heat-insulating effect will be weakened. Therefore, the content of porous diatomaceous earth is controlled at 50% - 65%, and preferably the porosity of porous diatomaceous earth is ≥ 80%, and the average particle size is 5 - 10μm.

[0016] γ-methacryloxypropyltrimethoxysilane (γ-MPS): As an adhesion promoter, the purity is ≥98%; γ-MPS reacts with the hydroxyl groups on the surface of the metal substrate to form covalent bonds, significantly improving the adhesion of the coating. At the same time, it promotes the cross-linking inside the coating and enhances the overall strength of the coating. When the content is too high, the surface of the coating becomes too hard, affecting its adaptability to the substrate and causing cracking. When the content is too low, it is not sufficient to form a strong bonding effect, and the coating is prone to peeling off; therefore, the content of γ-MPS is controlled at 1.0% - 2.0%.

[0017] Zinc phosphate (Zn 3 P 2 ): It has corrosion resistance. Zn 3 P 2 can form a dense protective film on the surface of the coating to prevent the penetration of corrosive substances in the underwater environment and extend the service life of the coating. However, when the content is too high, a too thick protective film may be formed, affecting the electrical conductivity and flexibility of the coating. When the content is too low, it cannot provide sufficient corrosion protection and reduces the durability of the coating. Therefore, the content of Zn 3 P 2 is controlled at 2.5% - 3.5%; preferably, the purity of Zn 3 P 2 is ≥98%, and the average particle size is 1 - 3μm.

[0018] Copper powder: It has electrical conductivity. As a conductive enhancer, copper powder provides necessary conductive channels to ensure the effective transmission of current during the welding process. However, when the content is too high, it may increase the thermal conductivity of the coating, reduce the heat insulation effect, and increase the cost at the same time. When the content is too low, the electrical conductivity is insufficient, affecting the welding quality and efficiency. Therefore, the content of copper powder is controlled at 6% - 10%; preferably, the purity of copper powder is ≥99.9%, and the average particle size is 300 - 500nm.

[0019] Modified epoxy resin: Modified epoxy resin provides the cohesion and adhesion required by the coating to ensure the stability and durability of the coating under various environmental conditions. When the content is too high, it may cause the coating to be too hard, reduce the flexibility, and increase the risk of cracking. When the content is too low, the bonding force is insufficient. Therefore, the content of modified epoxy resin is controlled at 20% - 30%, and the viscosity ≤500 cps.

[0020] Stabilizers and leveling agents: On the one hand, they help prevent the separation of coating components during storage and construction, ensuring the uniformity and stability of the coating. On the other hand, they can improve the surface leveling of the coating after construction, reducing surface defects such as orange peel and pinholes. When the content is too high, it will cause excessive surface smoothness and reduce the adhesion of the coating. When the content is too low, it cannot effectively improve the leveling of the coating, and surface defects may occur. Therefore, the content is controlled at 0.1% - 0.3%; preferably, the stabilizer and leveling agent is a silicone complex with a viscosity ≤ 1000 cps. The silicone complex is composed of polydimethylsiloxane, silicone-modified polyurethane, silicone oil, silicone resin, and a copolymer of polyethylene oxide and polypropylene oxide.

[0021] The second technical solution of the present invention is to provide a preparation method for a thermal insulation copper-free coating for underwater additive manufacturing, including the following steps: coating material mixing, wire surface pretreatment, coating spraying, coating curing,

[0022] (1) Coating material mixing:

[0023] Pretreatment and weighing of raw materials: Ensure that all solid raw materials are dried before mixing to remove surface moisture and ensure uniform mixing; use precise weighing equipment to accurately weigh each raw material according to the formula ratio;

[0024] First, disperse porous diatomaceous earth using a low-speed stirrer, and then sequentially add carbon nanotubes, copper powder, modified epoxy resin, γ-MPS, Zn 3 P 2 , deionized water, and stabilizer and leveling agent; strictly control the stirring speed during the addition and mixing of different substances; after the above substances are fully mixed and left standing for 20 - 40 min, ensure full mixing and no stratification or precipitation;

[0025] Low-speed stirring speed of porous diatomaceous earth: 50 - 70 rpm, stirring time: 5 - 10 min, to avoid destroying the pore structure of porous diatomaceous earth by high shear force and ensure the preliminary dispersion of large particles;

[0026] Stirring speed during the addition and mixing of carbon nanotubes and copper powder: 1500 - 2500 rmp, stirring time: 5 - 10 min; to refine and disperse carbon nanotubes and copper powder until uniform dispersion is achieved;

[0027] Stirring speed during the addition and mixing of the binder: 100 - 150 rpm, stirring time: 5 - 10 min, gradually add the binder to prevent air from mixing and generating bubbles, and ensure that the binder completely wets the solid particles;

[0028] Then add the adhesion promoter γ-MPS, and then add the corrosion resistance additive Zn 3 P 2 , γ-MPS and Zn3 P 2 Stirring speed during the addition and mixing stage: 300 - 500 rpm, stirring time: 10 - 15 min; Add the adhesion promoter γ-MPS under medium-speed stirring, and then add the corrosion-resistant additive zinc phosphate to ensure the uniform dispersion of the additives;

[0029] Adjustment of the coating carrier: Gradually add deionized water as the coating carrier according to the viscosity of the mixed system and the construction requirements; Viscosity adjustment range: 50 - 300 cP, measured using a rotational viscometer, and adjusted according to the actual construction equipment;

[0030] Final addition of the stabilizer and leveling agent: Add the silicone complex as the stabilizer and leveling agent in the final stage of the mixing process; Stirring speed: 200 - 300 rmp, time: 5 - 10 min, to ensure the uniform dispersion of the leveling agent and avoid surface defects of the coating;

[0031] (2) Pretreatment of the wire surface

[0032] Cleaning: After purging with high-pressure air, enter the ultrasonic cleaning tank, use isopropyl alcohol as the cleaning agent, ultrasonic frequency: 30 - 50 kHz, cleaning time 10 - 20 min, cleaning temperature 40 - 60 °C; Remove oil, dust and other contaminants on the wire surface;

[0033] Roughening: Use sandblasting treatment, use quartz sand or emery as the abrasive, sandblasting pressure 6 - 8 bar, distance 20 - 30 cm, sandblasting time 5 - 10 min; Increase the surface roughness of the wire and improve the coating adhesion;

[0034] Decontamination and passivation: Use chemical cleaning and passivation, immerse the wire in a dilute hydrochloric acid solution, hydrochloric acid concentration 5% - 10%, soaking time 1 - 3 min, then rinse with deionized water and dry to remove abrasive residues and oxide layers on the wire surface after sandblasting

[0035] (3) Coating spraying

[0036] Use an automated spraying system to spray the coating on the pretreated wire, and control the environmental conditions to ensure uniform coating coverage; Spraying: Use an automated spraying system, spraying speed 0.5 - 1 m / min, to ensure uniform coating coverage; Environmental control: Environmental humidity 40% - 50%;

[0037] (4) Coating curing

[0038] Initial drying: The welded wire after spraying is preliminarily dried at room temperature to remove most of the solvents, and the drying time is 30 - 60 min; preferably, during the initial drying of the coating, the coating thickness is regularly measured using a coating thickness gauge to ensure that the design requirements are met. It is measured every 10 - 20 min during the initial drying process until the coating is completely dry; the thickness of the dried coating is measured using a magnetic or eddy current coating thickness gauge to ensure uniformity and consistency. The film-forming thickness of the coating after initial drying is 50 - 70 μm;

[0039] Main curing: The welded wire is placed in an oven for thermal curing to complete the cross-linking reaction of the coating; the main curing temperature is 100 - 120 °C, and the main curing time is 1 - 2 hours. The main curing time is adjusted according to the coating thickness

[0040] Post-curing cooling: Naturally cool to room temperature.

[0041] The beneficial effects of the present invention are as follows:

[0042] 1. The coating of the welded wire ensures the preheating effect of the welded wire before welding through good thermal insulation performance, slows down the cooling rate during underwater welding, effectively reduces the formation of hardened structures, thereby significantly improving the toughness of the welded joint and the uniformity of the microstructure, and enhancing the toughness of the welded joint;

[0043] 2. The coating exhibits high adhesion and excellent wear resistance, ensuring stability and durability during the additive repair process;

[0044] 3. The coating has good environmental adaptability, ensuring that its performance can be maintained under diverse underwater environmental conditions, and improving the reliability and efficiency of underwater additive repair. Specific embodiments

[0045] The present invention will be further described below through examples;

[0046] In the embodiments of the present invention, according to the component ratios of the technical solutions, layer material mixing, surface pretreatment of the welded wire, coating spraying, and coating curing are carried out;

[0047] (1) Coating material mixing:

[0048] First, use a low-speed stirrer to disperse porous diatomaceous earth, and then sequentially add carbon nanotubes, copper powder, modified epoxy resin, γ-MPS, Zn 3 P 2 , deionized water, stabilizer and leveling agent; strictly control the stirring speed during the addition and mixing of different substances;

[0049] (2) Surface pretreatment of the welded wire

[0050] Cleaning: After purging with high-pressure air, it enters an ultrasonic cleaning tank. Isopropyl alcohol is used as the cleaning agent. Ultrasonic frequency: 30 - 50 kHz, cleaning time 10 - 20 min, cleaning temperature 40 - 60 °C;

[0051] Roughening: Sandblasting treatment is adopted. Quartz sand or emery is used as the abrasive. Sandblasting pressure 6 - 8 bar, distance 20 - 30 cm, sandblasting time 5 - 10 min;

[0052] Decontamination and passivation: The welding wire is immersed in a dilute hydrochloric acid solution with a hydrochloric acid concentration of 5% - 10%, soaking time 1 - 3 min, and then rinsed with deionized water and dried;

[0053] (3) Coating spraying

[0054] Spraying speed 0.5 - 1 m / min, ambient humidity 40% - 50%;

[0055] (4) Coating curing

[0056] Initial drying: The sprayed welding wire is preliminarily dried at room temperature, drying time 30 - 60 min;

[0057] Main curing: The welding wire is placed in an oven for thermal curing. Main curing temperature 100 - 120 °C, main curing time 1 - 2 hours;

[0058] Post-curing cooling: Naturally cool down to room temperature.

[0059] Furthermore; The low-speed stirring speed of porous diatomite: 50 - 70 rpm, stirring time: 5 - 10 min; The stirring speed during the addition and mixing stage of carbon nanotubes and copper powder: 1500 - 2500 rmp, stirring time: 5 - 10 min; The stirring speed during the addition and mixing stage of modified epoxy resin: 100 - 150 rpm, stirring time: 5 - 10 min; Then add γ-MPS, and then add Zn 3 P 2 and γ-MPS and Zn 3 P 2 The stirring speed during the addition and mixing stage: 300 - 500 rpm, stirring time: 10 - 15 min; The stirring speed during the addition and mixing stage of the leveling agent: 200 - 300 rmp, stirring time: 5 - 10 min.

[0060] Furthermore; In the coating material mixing step, the viscosity of the mixture after adding deionized water: 50 - 300 cP.

[0061] The composition of the wire coating in the embodiments of the present invention is shown in Table 1; the main process parameters of the wire coating and the wire surface treatment in the embodiments of the present invention are shown in Table 2; the main treatment process parameters of the wire and the coating in the embodiments of the present invention are shown in Table 3; the hardness value (HV) of the wire coating in the embodiments of the present invention is shown in Table 4; the thermal conductivity (W / m·K) of the wire coating in the embodiments of the present invention is shown in Table 5.

[0062] Table 1 Composition of the wire coating in the embodiments of the present invention (wt%)

[0063]

[0064] Table 2 Main process parameters of the wire coating and the wire surface treatment in the embodiments of the present invention

[0065]

[0066] Table 3 Main treatment process parameters of the wire and the coating in the embodiments of the present invention

[0067]

[0068] Table 4 Hardness value (HV) of the wire coating in the embodiments of the present invention

[0069] Example 1 2 3 4 5 6 7 8 Copper-plated coating on welding wire (pure copper) Hardness value 165 185 190 160 188 167 179 163 85

[0070] Table 5 Thermal conductivity (W / m·K) of the wire coating in the embodiments of the present invention

[0071] Example 1 2 3 4 5 6 7 8 Copper-plated coating on welding wire (pure copper) Thermal conductivity 0.67 0.70 0.54 0.53 0.65 0.56 0.68 0.65 400

[0072] For the wire coating produced by applying the present invention, the hardness value of the coating is 150 - 200 HV, and the thermal conductivity is 0.1 - 1 W / m·K; through good thermal insulation performance, the preheating effect of the wire before welding is ensured, the cooling rate during underwater welding is slowed down, the generation of hardened structures is effectively reduced, thereby significantly improving the toughness and the uniformity of the microstructure of the welded joint, and enhancing the toughness of the welded joint; at the same time, the coating exhibits high adhesion and excellent wear resistance, ensuring stability and durability during the additive repair process; it has good environmental adaptability, ensuring that its performance can be maintained under diverse underwater environmental conditions, and improving the reliability and efficiency of underwater additive repair.

[0073] In order to describe the present invention, the present invention has been appropriately and fully described by way of examples above. The above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Those of ordinary skill in the relevant technical fields can make various changes and modifications without departing from the spirit and scope of the present invention. Any modifications, equivalent replacements, improvements, etc. should be included within the protection scope of the present invention. The patent protection scope of the present invention shall be defined by the claims.

Claims

1. A thermally insulating copper-free coating for underwater additive manufacturing, characterized in that: The coating has the following components by weight percentage: carbon nanotubes: 1.0% to 1.5%, porous diatomaceous earth: 50% to 65%, γ-MPS: 1.0% to 2.0%, Zn3P2: 2.5% to 3.5%, copper powder: 6% to 10%, modified epoxy resin: 20% to 30%, stabilizer and leveling agent: 0.1% to 0.3%, and unavoidable impurities.

2. A thermal insulation copper-free coating for underwater additive manufacturing according to claim 1, characterized in that: The nano carbon tube has a diameter of less than 3 nm, a length of less than 10 nm, and a purity of ≥95%.

3. The thermal insulation copper-free coating for underwater additive manufacturing according to claim 1, characterized in that: The porous diatomaceous earth has a porosity of ≥80% and an average particle size of 5-10 μm.

4. The thermal insulation copper-free coating for underwater additive manufacturing according to claim 1, characterized in that: The average particle size of the Zn3P2 is 1~3µm.

5. The thermal insulation copper-free coating for underwater additive manufacturing according to claim 1, characterized in that: The coating thickness is 50-70 μm.

6. The thermal insulation copper-free coating for underwater additive manufacturing according to claim 1, characterized in that: The coating has a hardness value of 150-200 HV and a thermal conductivity of 0.1-1 W / m·K.

7. A method for preparing a thermal insulation copper-free coating for underwater additive manufacturing according to any one of claims 1 to 6, comprising mixing coating materials, pretreating the surface of welding wire, spraying the coating, and curing the coating; characterized in that: (1) Coating material mixing: First, use a low-speed stirrer to disperse porous diatomaceous earth, then add carbon nanotubes and copper powder, modified epoxy resin, γ-MPS, Zn3P2, deionized water, stabilizer and leveling agent in sequence; strictly control the stirring speed during the addition and mixing stages of different substances; (2) Surface pretreatment of welding wire Cleaning: After using high-pressure air to blow, enter the ultrasonic cleaning tank, ultrasonic frequency: 30~50kHz, cleaning time: 10~20min, cleaning temperature: 40~60℃; Roughening: Sandblasting is used, using quartz sand or corundum as abrasive, the sandblasting pressure is 6~8bar, the distance is 20~30cm, and the sandblasting time is 5~10min; Decontamination and passivation: Place the welding wire in a dilute hydrochloric acid solution with a concentration of 5% to 10% for 1 to 3 minutes, then rinse with deionized water and dry; (3) Coating spraying Spraying speed 0.5~1m / min, ambient humidity 40%~50%; (4) Coating curing Initial drying: The sprayed welding wire is initially dried at room temperature for 30 to 60 minutes; Main curing: put the welding wire into the oven for heat curing, the main curing temperature is 100~120℃, and the main curing time is 1~2 hours; Post-curing cooling: Cool down naturally to room temperature.

8. The method for preparing a thermally insulating copper-free coating for underwater additive manufacturing according to claim 7, characterized in that: In (1) the coating material mixing step, Porous diatomaceous earth low-speed stirring speed: 50~70rpm, stirring time: 5~10min; Stirring speed during the addition and mixing of carbon nanotubes and copper powder: 1500~2500rmp, stirring time: 5~10min; The stirring speed during the addition and mixing of modified epoxy resin is 100-150 rpm, and the stirring time is 5-10 min. Then add γ-MPS, and then add Zn3P2. The stirring speed during the addition and mixing of γ-MPS and Zn3P2 is 300-500 rpm, and the stirring time is 10-15 min. The stirring speed during the addition and mixing of the stabilizing and leveling agents is 200~300rmp, and the stirring time is 5~10min.

9. The method for preparing a thermally insulating copper-free coating for underwater additive manufacturing according to claim 8, characterized in that: In the (1) coating material mixing step, the viscosity of the mixture after adding deionized water is 50~300 cP.

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