A corrosion resistant coating and preparation method thereof

Abstract

The present invention belongs to the technical field of coatings, and specifically relates to a corrosion-resistant coating and a preparation method thereof. The present invention performs sandblasting on the surface of a zirconium alloy to obtain a rough surface; performs supersonic plasma spraying on the rough surface to prepare a chromium coating layer, and then uses a chromium powder jet to impact the chromium coating layer for compaction treatment; the chromium powder jet is not heated; the process of preparing a chromium coating layer by supersonic plasma spraying and the process of compaction treatment by impacting the chromium coating layer with a chromium powder jet are performed alternately to obtain a corrosion-resistant coating. The present invention combines the supersonic plasma spraying process with the solid powder impact compaction process, and the prepared chromium coating layer has high density, can prevent corrosive substances in a high-temperature environment from diffusing inward, and makes the chromium coating layer have high corrosion resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and in particular relates to a corrosion-resistant coating and a preparation method thereof. Background Art

[0002] Nuclear power generation can convert nuclear energy into electrical energy, and there is no carbon dioxide emission in the process of generating electricity. Zirconium alloy is a commonly used nuclear fuel cladding material. Zirconium alloy has insufficient high temperature oxidation corrosion resistance, and improving the high temperature oxidation corrosion resistance of zirconium alloy is of great significance.

[0003] Chromium coating has high resistance to high temperature oxidation corrosion. The preparation of chromium coating on the surface of zirconium alloy can improve the resistance to high temperature oxidation corrosion of zirconium alloy. In addition, the thermal neutron absorption cross section of chromium is moderate, and chromium has little effect on the neutron economy of zirconium alloy cladding. Therefore, chromium coating is a suitable protective coating for zirconium alloy surface.

[0004] Supersonic plasma spraying is a method for preparing chromium coatings, but there are pores and cracks in the chromium coatings prepared by supersonic plasma spraying, resulting in low density of the chromium coatings. In a high temperature (1200°C) oxidative corrosion environment, corrosive substances diffuse inward through the pores and cracks, causing the chromium coating to corrode quickly and fail. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a corrosion-resistant coating and a preparation method thereof. The corrosion-resistant coating provided by the present invention has high density and can prevent corrosive substances from diffusing inward in a high-temperature environment, so that it has high corrosion resistance.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a corrosion-resistant coating, comprising the following steps:

[0008] The surface of the zirconium alloy is subjected to sandblasting to obtain a rough surface;

[0009] A chromium coating is prepared by supersonic plasma spraying on the rough surface, and then a chromium powder jet is used to impact the chromium coating to perform compaction treatment; the chromium powder jet is not heated;

[0010] The process of preparing a chromium coating layer by supersonic plasma spraying and the process of compacting the chromium coating layer by impacting the chromium powder jet are performed alternately to obtain a corrosion-resistant coating.

[0011] Preferably, the spraying powder used in the supersonic plasma spraying is spherical chromium powder; the particle size of the spherical chromium powder is 30 to 70 μm.

[0012] Preferably, the power of the supersonic plasma spraying is 60-70 kW.

[0013] Preferably, the working gas used for the supersonic plasma spraying includes argon and hydrogen; the flow rate of the argon is 90 to 110 L / min; the flow rate of the hydrogen is 20 to 30 L / min.

[0014] Preferably, the spraying distance of the supersonic plasma spraying is 90 to 110 mm.

[0015] Preferably, the powder feeding rate of the supersonic plasma spraying is 20 to 30 g / min.

[0016] Preferably, the distance between the spray gun used for the compaction treatment and the chromium coating is 8 to 12 mm.

[0017] Preferably, the powder feeding rate of the compaction treatment is 10 to 16 g / min.

[0018] Preferably, the working gas used in the compaction treatment is argon; the gas pressure of the argon is 1.8-2 MPa.

[0019] The present invention also provides a corrosion-resistant coating prepared by the preparation method described in the above technical solution, comprising a chromium coating; the thickness of the corrosion-resistant coating is 80 to 120 μm; and the density of the corrosion-resistant coating is 99.4 to 99.7%.

[0020] The invention provides a method for preparing a corrosion-resistant coating, comprising the following steps: sandblasting a zirconium alloy surface to obtain a rough surface; performing supersonic plasma spraying on the rough surface to prepare a chromium coating layer, and then using a chromium powder jet to impact the chromium coating layer for compaction treatment; the chromium powder jet is not heated; the process of preparing a chromium coating layer by supersonic plasma spraying and the process of using a chromium powder jet to impact the chromium coating layer for compaction treatment are alternately performed to obtain a corrosion-resistant coating.

[0021] The present invention combines the supersonic plasma spraying process with the solid powder impact compaction process. First, a layer of chromium coating is prepared by supersonic plasma spraying. Then, the chromium powder is not heated, and the solid chromium powder is accelerated by the high-speed airflow generated by the same device. Since the thickness of a layer of chromium coating is very small, the high-speed chromium powder jet can compact the chromium coating after impacting the surface of the chromium coating, remove the pores and cracks in the chromium coating, and improve the density of the chromium coating. Then, the next layer of chromium coating is prepared, and then the chromium coating is further compacted. The spraying process and the compaction process of each layer of chromium coating are alternately performed until a dense chromium coating of a certain thickness is obtained. The dense chromium coating can hinder the inward diffusion of corrosive substances, reduce the diffusion rate of corrosive substances into the coating, improve the corrosion resistance of the coating, and make the chromium coating have high corrosion resistance. DETAILED DESCRIPTION

[0022] The present invention provides a method for preparing a corrosion-resistant coating, comprising the following steps:

[0023] The surface of the zirconium alloy is subjected to sandblasting to obtain a rough surface;

[0024] A chromium coating is prepared by supersonic plasma spraying on the rough surface, and then a chromium powder jet is used to impact the chromium coating to perform compaction treatment; the chromium powder jet is not heated;

[0025] The process of preparing a chromium coating layer by supersonic plasma spraying and the process of compacting the chromium coating layer by impacting the chromium powder jet are performed alternately to obtain a corrosion-resistant coating.

[0026] Unless otherwise specified, the present invention has no special requirements on the sources of the raw materials used in the preparation, and commercially available products known to those skilled in the art can be used.

[0027] The present invention performs sandblasting on the surface of the zirconium alloy to obtain a rough surface.

[0028] In the present invention, the conditions for the sandblasting treatment include: the type of abrasive is preferably aluminum oxide particles, the abrasive particle size is preferably 110-190 μm, more preferably 140-160 μm, the spraying distance is preferably 120-180 mm, more preferably 140-160 mm, the spraying angle is preferably 60-90°, more preferably 70-80°, the spraying time is preferably 30-60s, more preferably 40-50s, and the compressed air pressure is preferably 0.2-0.5 MPa, more preferably 0.3-0.4 MPa.

[0029] In the present invention, the roughness of the rough surface is preferably 3 to 7 μm, more preferably 4 to 6 μm.

[0030] The present invention increases the surface roughness of the zirconium alloy through sandblasting, thereby improving the bonding strength between the zirconium alloy and the chromium coating.

[0031] After obtaining the rough surface, the present invention performs supersonic plasma spraying on the rough surface to prepare a chromium coating.

[0032] In the present invention, the spraying powder used in the supersonic plasma spraying is preferably spherical chromium powder; the particle size of the spherical chromium powder is preferably 30 to 70 μm, more preferably 40 to 60 μm.

[0033] In the present invention, the power of the supersonic plasma spraying is preferably 60-70kW, more preferably 65kW; the working gas used for the supersonic plasma spraying preferably includes argon and hydrogen; the flow rate of the argon is preferably 90-110L / min, more preferably 100L / min; the flow rate of the hydrogen is preferably 20-30L / min, more preferably 25L / min; the spraying distance of the supersonic plasma spraying is preferably 90-110mm, more preferably 100mm; the powder feeding rate of the supersonic plasma spraying is preferably 20-30g / min, more preferably 25g / min.

[0034] In the present invention, the thickness of the chromium coating is preferably 8-12 μm, more preferably 10 μm.

[0035] After the chromium coating is obtained, the present invention utilizes a chromium powder jet to impact the chromium coating for compaction treatment.

[0036] In the present invention, the chromium powder in the chromium powder jet is preferably spherical chromium powder; the particle size of the spherical chromium powder is preferably 30 to 70 μm, more preferably 40 to 60 μm.

[0037] In the present invention, the chromium powder jet is preferably generated by a supersonic plasma spraying device; the chromium powder jet is not heated.

[0038] In the present invention, the distance between the spray gun used for the compaction treatment and the chromium coating is preferably 8-12 mm, more preferably 10 mm; the powder feeding rate of the compaction treatment is preferably 10-16 g / min, more preferably 12-14 g / min; the working gas used for the compaction treatment is argon; the gas pressure of the argon is preferably 1.8-2 MPa, more preferably 1.9 MPa.

[0039] The process of preparing a chromium coating layer by supersonic plasma spraying and the process of compacting the chromium coating layer by impacting the chromium powder jet are performed alternately to obtain a corrosion-resistant coating.

[0040] In the present invention, the total number of alternating steps is preferably 10 times.

[0041] The present invention combines the process of preparing a chromium coating by supersonic plasma spraying with the process of impact compaction of a chromium powder jet. First, a layer of chromium coating is prepared by supersonic plasma spraying. Then, the chromium powder is not heated, and a high-speed airflow is generated by the same device to accelerate the solid chromium powder. Since the thickness of a layer of chromium coating is very small, the high-speed chromium powder jet can compact the chromium coating after impacting the surface of the chromium coating, remove the pores and cracks in the chromium coating, and improve the density of the chromium coating. Then, the next layer of chromium coating is prepared, and then the chromium coating is compacted. The spraying process and the compaction process of each layer of chromium coating are alternately performed until a dense chromium coating of a certain thickness is obtained. The dense chromium coating can prevent the corrosive substances in the high-temperature environment from diffusing inward, so that the chromium coating has high corrosion resistance.

[0042] The present invention also provides a corrosion-resistant coating prepared by the preparation method described in the above technical solution, including a chromium coating.

[0043] In the present invention, the thickness of the corrosion-resistant coating is preferably 80 to 120 μm, more preferably 90 to 110 μm, and most preferably 100 μm; the density of the corrosion-resistant coating is preferably 99.4 to 99.7%, and more preferably 99.5 to 99.6%.

[0044] The technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention, but they should not be understood as limiting the protection scope of the present invention.

[0045] Example 1

[0046] The zirconium alloy surface was sandblasted, and the sandblasting conditions were as follows: the abrasive type was aluminum oxide particles, the abrasive particle size was 150 μm, the blasting distance was 150 mm, the blasting angle was 75°, the blasting time was 45 s, and the compressed air pressure was 0.35 MPa, and a rough surface with a roughness of 5 μm was obtained;

[0047] The zirconium alloy after sandblasting was placed in the spraying room, and the spraying distance was adjusted to 100mm. The working gas was a mixture of argon and hydrogen, the argon flow rate was 100L / min, the hydrogen flow rate was 25L / min, the spraying powder was spherical chromium powder with a particle size of 30-70μm, the powder feeding rate was 25g / min, and supersonic plasma spraying was performed at a power of 65kW to prepare a first layer of chromium coating with a thickness of 10μm on the surface of the zirconium alloy. Then, the chromium powder was not heated, and the distance between the spray gun and the chromium coating was adjusted to 10mm. The powder rate is 13 g / min, and under the condition of argon pressure of 1.9 MPa, a high-speed chromium powder jet is generated by supersonic plasma spraying equipment, and the high-speed chromium powder is used to impact the first chromium coating to remove pores and cracks in the chromium coating, so that the first chromium coating has a high density. The process of preparing a layer of chromium coating by supersonic plasma spraying and the process of compacting the chromium coating by impacting the chromium powder jet are alternately performed for a total of 10 times, and finally a dense chromium coating (corrosion-resistant coating) with a thickness of 100 μm is prepared on the surface of the zirconium alloy.

[0048] The porosity of the cross section of the corrosion-resistant chromium coating was tested by image grayscale analysis, and the cross section porosity of the prepared chromium coating was 0.5%. The prepared chromium coating was placed in a 1200°C water vapor environment to test the corrosion resistance. After 2 hours of high-temperature corrosion, the thickness of the corrosion layer of the chromium coating was tested. The corrosion resistance was compared according to the thickness of the corrosion layer. The smaller the thickness of the corrosion layer, the higher the corrosion resistance. The test results show that the thickness of the corrosion layer of the chromium coating is 13μm after 2 hours of corrosion.

[0049] Example 2

[0050] The zirconium alloy surface was sandblasted, and the sandblasting conditions were as follows: the abrasive type was aluminum oxide particles, the abrasive particle size was 190 μm, the blasting distance was 180 mm, the blasting angle was 90°, the blasting time was 60 s, and the compressed air pressure was 0.5 MPa, and a rough surface with a roughness of 7 μm was obtained;

[0051] The zirconium alloy after sandblasting was placed in the spraying room, and the spraying distance was adjusted to 100mm. The working gas was a mixture of argon and hydrogen, the argon flow rate was 110L / min, the hydrogen flow rate was 30L / min, the spraying powder was spherical chromium powder with a particle size of 30-70μm, the powder feeding rate was 30g / min, and supersonic plasma spraying was performed at a power of 70kW to prepare a first layer of chromium coating with a thickness of 12μm on the surface of the zirconium alloy. Then, the chromium powder was not heated, and the distance between the spray gun and the chromium coating was adjusted to 12mm. The powder feeding rate is 16 g / min. Under the condition of argon gas pressure of 2 MPa, a high-speed chromium powder jet is generated by supersonic plasma spraying equipment. The high-speed chromium powder is used to impact the first chromium coating to remove pores and cracks in the chromium coating, so that the first chromium coating has a high density. The process of preparing a layer of chromium coating by supersonic plasma spraying and the process of compacting the chromium coating by impacting the chromium powder jet are alternately performed for a total of 10 times, and finally a dense chromium coating (corrosion-resistant coating) with a thickness of 120 μm is prepared on the surface of the zirconium alloy.

[0052] The porosity of the cross section of the corrosion-resistant chromium coating was tested by image grayscale analysis, and the cross section porosity of the prepared chromium coating was 0.3%. The prepared chromium coating was placed in a 1200℃ water vapor environment to test the corrosion resistance. After 2 hours of high-temperature corrosion, the thickness of the corrosion layer of the chromium coating was tested. The corrosion resistance was compared according to the thickness of the corrosion layer. The smaller the thickness of the corrosion layer, the higher the corrosion resistance. The test results show that the thickness of the corrosion layer of the chromium coating is 10μm after 2 hours of corrosion.

[0053] Example 3

[0054] The zirconium alloy surface was sandblasted, and the sandblasting conditions were as follows: the abrasive type was aluminum oxide particles, the abrasive particle size was 110 μm, the blasting distance was 120 mm, the blasting angle was 60°, the blasting time was 30 s, and the compressed air pressure was 0.2 MPa, and a rough surface with a roughness of 3 μm was obtained;

[0055] The sandblasted zirconium alloy was placed in the spraying room, the spraying distance was adjusted to 90 mm, the working gas was a mixture of argon and hydrogen, the argon flow rate was 90 L / min, the hydrogen flow rate was 20 L / min, the spraying powder was spherical chromium powder with a particle size of 30 to 70 μm, the powder feeding rate was 20 g / min, and supersonic plasma spraying was performed at a power of 60 kW to prepare a first layer of chromium coating with a thickness of 8 μm on the surface of the zirconium alloy. Then, the chromium powder was not heated, the distance between the spray gun and the chromium coating was adjusted to 8 mm, and the powder was fed. The rate is 10 g / min, and under the condition of argon pressure of 1.8 MPa, a high-speed chromium powder jet is generated by supersonic plasma spraying equipment, and the high-speed chromium powder is used to impact the first chromium coating to remove pores and cracks in the chromium coating, so that the first chromium coating has a high density. The process of preparing a layer of chromium coating by supersonic plasma spraying and the process of compacting the chromium coating by impacting the chromium powder jet are alternately performed for a total of 10 times, and finally a dense chromium coating (corrosion-resistant coating) with a thickness of 80 μm is prepared on the surface of the zirconium alloy.

[0056] The porosity of the cross section of the corrosion-resistant chromium coating was tested by image grayscale analysis, and the cross section porosity of the prepared chromium coating was 0.6%. The prepared chromium coating was placed in a 1200℃ water vapor environment to test the corrosion resistance. After 2 hours of high-temperature corrosion, the thickness of the corrosion layer of the chromium coating was tested. The corrosion resistance was compared according to the thickness of the corrosion layer. The smaller the thickness of the corrosion layer, the higher the corrosion resistance. The test results show that the thickness of the corrosion layer of the chromium coating is 15μm after 2 hours of corrosion.

[0057] Comparative Example 1

[0058] The chromium coating was prepared on the surface of the zirconium alloy by supersonic plasma spraying. The surface of the zirconium alloy was sandblasted. The sandblasting conditions were as follows: the abrasive type was aluminum oxide particles, the abrasive particle size was 150 μm, the spray distance was 150 mm, the spray angle was 75°, the spray time was 45 s, and the compressed air pressure was 0.35 MPa. A rough surface with a roughness of 5 μm was obtained.

[0059] The zirconium alloy after sandblasting is placed in the spraying chamber, the spraying distance is adjusted to 100 mm, and then argon and hydrogen are introduced into the spraying chamber. The argon flow rate is 100 L / min, the hydrogen flow rate is 25 L / min, the spraying power is adjusted to 65 kW, the spraying powder is spherical chromium powder with a particle size of 30 to 70 μm, the powder feeding rate is 25 g / min, and a chromium coating with a thickness of 100 μm is prepared on the surface of the zirconium alloy substrate by supersonic plasma spraying.

[0060] The porosity of the cross section of the chromium coating was tested by image grayscale analysis. The cross section porosity of the prepared chromium coating was 2.8%. The prepared chromium coating was placed in a 1200°C water vapor environment to test the corrosion resistance. After 2 hours of high temperature corrosion, the thickness of the corrosion layer of the chromium coating was tested. The corrosion resistance was compared according to the thickness of the corrosion layer. The test results show that the thickness of the corrosion layer of the chromium coating is 32μm after 2 hours of corrosion.

[0061] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention rather than all the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a corrosion-resistant coating, characterized in that: The following steps are involved: The zirconium alloy surface was sandblasted, and the sandblasting conditions were as follows: the abrasive type was aluminum oxide particles, the abrasive particle size was 190 μm, the blasting distance was 180 mm, the blasting angle was 90°, the blasting time was 60 s, and the compressed air pressure was 0.5 MPa, and a rough surface with a roughness of 7 μm was obtained; The sandblasted zirconium alloy was placed in a spraying chamber, the spraying distance was adjusted to 100 mm, the working gas was a mixture of argon and hydrogen, the argon flow rate was 110 L / min, the hydrogen flow rate was 30 L / min, the spraying powder was spherical chromium powder with a particle size of 30 to 70 μm, the powder feeding rate was 30 g / min, and supersonic plasma spraying was performed at a power of 70 kW to prepare a first layer of chromium coating with a thickness of 12 μm on the surface of the zirconium alloy, and then the chromium powder was not heated, and the distance between the spray gun and the chromium coating was adjusted. The thickness of the chromium coating is 12 mm, the powder feeding rate is 16 g / min, and under the condition of argon pressure of 2 MPa, a high-speed chromium powder jet is generated by supersonic plasma spraying equipment, and the high-speed chromium powder is used to impact the first chromium coating to remove pores and cracks in the chromium coating, so that the first chromium coating has a high density. The process of preparing a chromium coating by supersonic plasma spraying and the process of compacting the chromium coating by impacting the chromium powder jet are alternately performed for a total of 10 times, and finally a corrosion-resistant coating with a thickness of 120 μm is prepared on the surface of the zirconium alloy.