Marine-erosion-resistant composite coating and method for preparing the same

Abstract

The present application relates to the technical field of nuclear power, and especially relates to a seawater erosion resistant composite coating and a preparation method thereof. The composite coating comprises a high-entropy alloy layer and an epoxy resin layer coated on the high-entropy alloy layer. The preparation method comprises the following steps: step one, spraying a mixed powder coating on a substrate by using a low-pressure cold spraying method; step two, in-situ synthesizing a high-entropy alloy coating by remelting the mixed powder coating by induction; and step three, coating an epoxy resin layer on the high-entropy alloy layer. The coating formed by the present application has good sealing property and strong corrosion resistance, and is suitable for a seawater cooling system of a nuclear power plant.

Description

Technical Field

[0001] This invention relates to the field of nuclear power technology, and in particular to a seawater erosion resistant composite coating and its preparation method. Background Technology

[0002] Coatings are widely used in various fields, including nuclear power technology, electronics, industrial coatings, and marine coatings. Based on current theoretical calculations, the service life of polyethylene coatings is typically around 8-10 years, while that of polymer composite coatings can reach 12-15 years.

[0003] In practical applications, the service life of existing coatings is affected by a variety of factors. Although they play a significant role in practical applications, they also have some drawbacks. Certain types of coatings are prone to fading, peeling, or aging when exposed to harsh environmental conditions such as ultraviolet radiation, humidity, and high temperatures for extended periods, affecting the durability of the coating.

[0004] In the complex piping of the power plant's safety water system, existing coatings, after multiple coats, can reach a thickness of 500μm-1mm. Due to the multiple coats, the coating thickness becomes uneven, resulting in more stress points and accelerating peeling. The base material of existing coatings causes the peeled coating to coalesce into large clumps. These large clumps cannot be flushed out of the pipes with the liquid flow. After peeling, the pipes are not only prone to corrosion, but the complex piping system also makes it difficult to clean the peeled fragments. In particular, they are prone to getting stuck in the gaps of the heat exchanger plates, affecting the efficiency of the heat exchanger and ultimately impacting the operating efficiency of the nuclear power plant.

[0005] Cold spraying is a high-speed solid coating technology with the following characteristics:

[0006] 1. Low heat input: During cold spraying, powder particles are accelerated in a high-speed airflow and collide with the substrate in a solid form. High temperature or melting is not required, so thermal impact and deformation of the substrate can be avoided.

[0007] 2. Excellent adhesion: Because cold spraying achieves adhesion through solid mechanical anchoring, the coating has high bonding strength with the substrate, has good adhesion performance, and is not easy to peel or fall off.

[0008] 3. High-efficiency coverage: Cold spraying can propel metal powder onto the substrate surface at high speed, where it bonds with the substrate after impact, forming a uniform and dense coating. This process can be completed quickly, and the coating thickness is controllable.

[0009] 4. Provides excellent corrosion resistance and abrasion resistance: The cold spray coating has good sealing and density, which can effectively prevent external environmental media from entering the substrate and provide excellent corrosion resistance.

[0010] Cold spraying technology is becoming increasingly sophisticated. Applying high-entropy alloy coatings to the pipes of power plant safety water systems can effectively avoid various defects found in existing coatings. However, cold spray coatings also have some shortcomings; the surface may contain tiny pores or air bubbles. This is because some powder particles do not completely melt or solidify when the sprayed material bonds with the substrate under high-speed impact. The presence of pores may reduce the coating's sealing properties and mechanical performance. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to provide a seawater erosion resistant composite coating and its preparation method, which has good sealing performance and strong corrosion resistance.

[0012] The present invention provides a seawater erosion resistant composite coating, comprising: a high-entropy alloy layer and an epoxy resin layer applied above the high-entropy alloy layer.

[0013] In a specific embodiment of the present invention, the high-entropy alloy layer is formed by low-pressure cold spraying and then synthesized in situ by induction remelting.

[0014] In a specific embodiment of the present invention, the powder used in the low-pressure cold spraying method is composed of the following elemental powders by mass percentage: 10-15% Al powder, 8-12% Fe powder, 10% Al2O3 powder, 3-6% Mn powder, 2-5% Cr powder, and the balance Cu powder.

[0015] The particle size of the powder is in the range of 20 to 60 μm.

[0016] In a specific embodiment of the present invention, the thickness of the epoxy resin layer is less than 100 μm.

[0017] This invention also provides a method for preparing a seawater erosion-resistant composite coating, comprising the following steps:

[0018] Step 1: Apply a low-pressure cold spray to the substrate to form a mixed powder coating.

[0019] Step 2: Induction remelting is performed on the mixed powder coating to synthesize a high-entropy alloy coating in situ;

[0020] Step 3: Apply a layer of epoxy resin to the surface of the high-entropy alloy.

[0021] In a specific embodiment of the present invention, a preprocessing step is included before step one, specifically:

[0022] First, roughen the surface of the substrate by grinding and cleaning it. Then, use steel shot to sandblast the surface of the substrate.

[0023] In a specific embodiment of the present invention, in step one, the low-pressure cold spraying method is as follows:

[0024] Mechanically mix the metal powder mixture;

[0025] Low-pressure cold spraying is performed, with the following specific process parameters: compressed air is used as the working gas, the carrier gas temperature is in the range of 480 to 520℃, the carrier gas pressure is about 0.7MPa, the spraying distance is maintained at 8 to 15mm, and the spraying speed is maintained at 0.4 to 0.6m / s.

[0026] In a specific embodiment of the present invention, in step two, when synthesizing the high-entropy alloy coating, induction remelting is carried out by planar heating. The gap between the planar thin-film coil used and the workpiece should be 3-4 mm, the heating temperature should be controlled within the range of 700-1100℃, the heating power should be selected as 1.5-2.0 kW, the frequency is 175 kHz, and the heating time is 15 s.

[0027] In a specific embodiment of the present invention, in step three, the temperature during brushing is 10-40°C and the relative humidity is not greater than 80%.

[0028] In a specific embodiment of the present invention, the powder used in the low-pressure cold spraying method is composed of the following elemental powders by mass percentage: 10-15% Al powder, 8-12% Fe powder, 10% Al2O3 powder, 3-6% Mn powder, 2-5% Cr powder, and the balance Cu powder.

[0029] Compared with existing technologies, the seawater erosion-resistant composite coating and its preparation method of the present invention feature a high-entropy alloy coating with high-temperature stability and high-temperature oxidation resistance, making it suitable for use in extreme environments. Therefore, it will not peel off when applied to seawater cooling systems. The surface of the high-entropy alloy coating contains tiny pores or air pockets, which can be filled and sealed by applying an epoxy resin coating, improving the coating's sealing performance. The epoxy resin coating thickness is less than 100 μm. Even if peeling occurs in the pipes of the seawater cooling system, the peeled epoxy resin consists of small fragments that will be discharged from the pipes with the liquid flow, preventing blockage. Therefore, this composite coating can replace existing coatings in nuclear power plant seawater cooling systems. Experimental results show that the composite coating of the present invention exhibits strong corrosion and erosion resistance. Attached Figure Description

[0030] Figure 1 The cross section is a composite coating.

[0031] Figure 2 The surface is a high-entropy alloy coating;

[0032] Figure 3 The surface is coated with epoxy resin. Detailed Implementation

[0033] To further understand the present invention, embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the present invention.

[0034] An embodiment of the present invention discloses a seawater erosion resistant composite coating, comprising: a high-entropy alloy layer and an epoxy resin layer applied above the high-entropy alloy layer.

[0035] The high-entropy alloy layer is formed by low-pressure cold spraying and then synthesized in situ by induction remelting.

[0036] The powder used in the low-pressure cold spraying method consists of the following elemental powders by mass percentage: 10-15% Al powder, 8-12% Fe powder, 10% Al2O3 powder, 3-6% Mn powder, 2-5% Cr powder, and the balance Cu powder.

[0037] The particle size of the powder is in the range of 20 to 60 μm.

[0038] During the low-pressure cold spraying process, the powder particles in the high-entropy alloy layer undergo no phase transformation or oxidation; the powder particles undergo intense plastic deformation, resulting in a tight bond. Further induction remelting of the pre-formed mixed powder coating further reduces defects in the cold-sprayed coating, ensuring uniform element diffusion and a complete alloying reaction, leading to the formation of distinct dendritic structures, interdendritic structures, and metallic compound precipitates. After remelting, the cold-sprayed elemental powder coating undergoes an alloying reaction, resulting in uniform element diffusion and the formation of a high-entropy alloy coating. This reduces defects compared to the cold-sprayed state and significantly improves coating performance. The high-entropy alloy coating exhibits high-temperature stability and high-temperature oxidation resistance, making it suitable for extreme environments; therefore, it does not peel off when applied to seawater cooling systems. The surface of the high-entropy alloy coating contains minute pores or air pockets, which can be filled and sealed by applying an epoxy resin coating, improving the coating's sealing performance.

[0039] The epoxy resin layer is less than 100μm thick, so the peeled fragments will not form large pieces, but will be discharged out of the pipe with the liquid flow, thus avoiding the problem of pipe blockage.

[0040] The embodiments of the present invention also disclose a method for preparing a seawater erosion resistant composite coating, comprising the following steps:

[0041] Step 1: Apply a low-pressure cold spray to the substrate to form a mixed powder coating.

[0042] The low-pressure cold spraying method is as follows:

[0043] The metal powder mixture is mechanically mixed; the mixing time is preferably 4 to 10 hours.

[0044] The metal powder is composed of the following elemental powders by mass percentage: 10-15% Al powder, 8-12% Fe powder, 10% Al2O3 powder, 3-6% Mn powder, 2-5% Cr powder, and the balance Cu powder.

[0045] The preferred powder particle size is 20–60 μm;

[0046] Low-pressure cold spraying is performed, with the following specific process parameters: compressed air is used as the working gas, the carrier gas temperature is in the range of 480 to 520℃, the carrier gas pressure is about 0.7MPa, the spraying distance is maintained at 8 to 15mm, and the spraying speed is maintained at 0.4 to 0.6m / s.

[0047] Step 2: Induction remelting is performed on the mixed powder coating to synthesize a high-entropy alloy coating in situ;

[0048] When synthesizing high-entropy alloy coatings, induction remelting is carried out by planar heating. The gap between the planar thin-film coil and the workpiece should be 3-4 mm. The heating temperature should be controlled within the range of 700-1100℃. The heating power should be 1.5-2.0 kW, the frequency should be 175 kHz, and the heating time should be 15 s.

[0049] Step 3: Apply a layer of epoxy resin to the surface of the high-entropy alloy;

[0050] Before applying the coating, preferably, the surface of the high-entropy alloy should be cleaned, and the coating should be applied from top to bottom using a rubber scraper. The coating should be even, without dripping or air bubbles, and the resin layer should be full.

[0051] The temperature during application should be 10–40℃, and the relative humidity should not exceed 80%.

[0052] The thickness of the epoxy resin coating is no more than 100 μm.

[0053] Before step one, preprocessing is also included, specifically:

[0054] First, roughen the surface of the substrate by grinding and cleaning it. Then, use steel shot to sandblast the surface of the substrate.

[0055] Its advantages compared to existing technologies are:

[0056] (1) According to current data, the service life of polyethylene coatings is usually around 8-10 years, while that of polymer composite coatings can reach 12-15 years. In comparison, the high-entropy alloy and epoxy resin composite coating proposed in this invention has a longer service life, at least 50 years.

[0057] (2) Based on existing observations and research, existing coatings may gradually peel off after about one year of use. Due to uneven coating thickness, the peeled coating may exist in the form of blocks or long flakes, and these peelings are prone to getting stuck in heat exchanger pipes, especially in the gaps of heat exchanger fins in plate heat exchangers. However, the high-entropy alloy-epoxy resin composite coating provided by this invention has a special advantage: the high-entropy alloy coating will not peel off, and the epoxy resin coating is less than 100 μm thick. The peeled fragments will not form large pieces, but will be discharged out of the pipe with the liquid flow, thereby avoiding the problem of pipe blockage.

[0058] (3) According to experimental data and test results, the high-entropy alloy-epoxy resin coating prepared using this invention patent exhibits significantly better corrosion resistance compared to existing coatings. In existing coatings, the average corrosion rate of a single 201 pass followed by a second 202 pass is 567.65 g / m². 2 Over the years, the average corrosion rate of PPG850 was 528.81 g / m³. 2 • year. The average corrosion rate of the high-entropy alloy-epoxy resin composite coating is 128.05 g / m². 2 • year. The corrosive solutions used in the experiments were all 3.5% NaCl solutions.

[0059] (4) According to experimental data and test results, the high-entropy alloy-epoxy resin coating prepared using this patented invention exhibits significantly superior erosion resistance compared to existing coatings. Among existing coatings, the average erosion volume (one coat of 201 + two coats of 202) in a 30° erosion test is 0.009 g / cm³. 3 The average erosion volume (erosion volume) of PPG850 in the 30° erosion test was 0.040 / cm³. 3 The high-entropy alloy-epoxy resin composite coating showed an average erosion volume of 0.0012 / cm² in a 30° erosion test. 3 .

[0060] (5) By preparing a high-entropy alloy-epoxy resin composite coating, not only can the shortcomings of the two be overcome, but the advantages of the two can also be combined well, so that it can adapt to a more complex working environment and meet the actual industrial production needs.

[0061] The cross-section of the composite coating of the present invention is as follows: Figure 1 As shown, after being coated with an epoxy resin layer, the surface becomes denser and free of pores.

[0062] A single high-entropy alloy coating surface, such as Figure 2 As shown, the epoxy resin coating surface is as follows Figure 3 As shown.

[0063] To further understand the present invention, the following detailed description of the seawater erosion resistant composite coating and its preparation method provided by the present invention is provided in conjunction with embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0064] Example 1

[0065] (1) Preprocessing

[0066] First, roughen the surface of the substrate by grinding and cleaning it. Then, use steel shot to sandblast the surface of the substrate.

[0067] (2) Low-pressure cold spraying

[0068] The metal powders were mixed according to the following mass percentages:

[0069] 12% Al powder;

[0070] 10% Fe powder;

[0071] 10% Al2O3 powder;

[0072] 3% Mn powder;

[0073] Cr powder 5%;

[0074] Cu powder balance;

[0075] The powder has a particle size range of 20-60 μm and is mechanically mixed for 4 hours until homogeneous;

[0076] When performing low-pressure cold spraying, compressed air is used as the working gas, the carrier gas temperature is within the range of 500℃, the carrier gas pressure is about 0.7MPa, the spraying distance is maintained at 10mm, and the spraying speed is maintained at 0.5m / s.

[0077] (3) Induction remelting is performed on the mixed powder coating prepared by cold spraying to synthesize a high-entropy alloy coating in situ.

[0078] Induction remelting is performed using planar heating. The gap between the planar thin-film coil and the workpiece should be 3mm. The heating temperature should be controlled within the range of 900℃. The heating power should be 1.6kW, the frequency should be 175kHz, and the heating time should be 15s.

[0079] (4) Clean the surface of the high entropy alloy and apply epoxy resin from top to bottom with a rubber scraper;

[0080] The coating temperature is 20℃, the relative humidity is 40%, and the thickness of the epoxy resin layer is 50μm.

[0081] The composite coating prepared according to this invention was tested experimentally:

[0082] The table below shows the corrosion rate data of existing coatings, high-polymer ceramic repair agent coating (201), high-polymer ceramic fluid metal (202), high-polymer ceramic phenyl varnish (PPG850), and the high-entropy alloy-epoxy resin composite coating given in this invention, in 3.5% NaCl solution. The results show that the high-entropy alloy-epoxy resin composite coating exhibits superior corrosion resistance.

[0083] Table 1 Comparison of corrosion rates between existing coatings and high-entropy alloy-epoxy resin composite coatings

[0084]

[0085] The table below shows the data of existing coatings, high-polymer ceramic repair agent coating (201), high-polymer ceramic fluid metal (202), high-polymer ceramic phenyl varnish (PPG850), and the high-entropy alloy-epoxy resin composite coating given in this invention, under a 30° erosion test. The results show that the high-entropy alloy-epoxy resin composite coating exhibits superior erosion resistance.

[0086] Table 2 Comparison of erosion rates between existing coatings and high-entropy alloy-epoxy resin composite coatings

[0087]

[0088]

[0089] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0090] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A seawater erosion resistant composite coating, characterized in that, include: A high-entropy alloy layer and an epoxy resin layer coated on top of the high-entropy alloy layer; The high-entropy alloy layer is formed by low-pressure cold spraying and then synthesized in situ by induction remelting. The powder used in the low-pressure cold spraying method consists of the following elemental powders by mass percentage: 10-15% Al powder, 8-12% Fe powder, 10% Al2O3 powder, 3-6% Mn powder, 2-5% Cr powder, and the balance Cu powder. The particle size of the powder is between 20 and 60 μm; The thickness of the epoxy resin layer is less than 100 μm.

2. A method for preparing the seawater erosion resistant composite coating as described in claim 1, characterized in that, Includes the following steps: Step 1: Apply a low-pressure cold spray to the substrate to form a mixed powder coating. The powder used in the low-pressure cold spraying method consists of the following elemental powders by mass percentage: 10-15% Al powder, 8-12% Fe powder, 10% Al2O3 powder, 3-6% Mn powder, 2-5% Cr powder, and the balance Cu powder. The low-pressure cold spraying method is as follows: Mechanically mix the metal powder mixture; Low-pressure cold spraying is performed, with the following specific process parameters: compressed air is used as the working gas, the carrier gas temperature is in the range of 480~520℃, the carrier gas pressure is 0.7 MPa, the spraying distance is maintained at 8~15mm, and the spraying speed is maintained at 0.4~0.6 m / s. Step 2: Induction remelting is performed on the mixed powder coating to synthesize a high-entropy alloy coating in situ; Step 3: Apply a layer of epoxy resin to the surface of the high-entropy alloy.

3. The method for preparing the seawater erosion resistant composite coating according to claim 2, characterized in that, Before step one, preprocessing is also included, specifically: First, roughen the surface of the substrate by grinding and cleaning it. Then, use steel shot to sandblast the surface of the substrate.

4. The method for preparing the seawater erosion resistant composite coating according to claim 2, characterized in that, In step two, when synthesizing the high-entropy alloy coating, induction remelting is carried out by planar heating. The gap between the planar thin-film coil and the workpiece should be 3~4 mm, the heating temperature should be controlled within the range of 700~1100℃, the heating power should be selected as 1.5~2.0 kW, the frequency should be 175 kHz, and the heating time should be 15 s.

5. The method for preparing the seawater erosion resistant composite coating according to claim 2, characterized in that, In step three, the temperature during brushing is 10~40℃ and the relative humidity is no more than 80%.

Images