Preparation method of gamma ray shielding coating

Abstract

The present invention discloses a method for preparing a gamma-ray shielding coating, which includes cleaning, sandblasting, spraying and sealing steps in sequence; the spraying step is: using a plasma thermal spraying process, planning a spraying path according to the surface shape of the coating equipment component to be prepared, and preparing tungsten powder or tungsten-based metal ceramics to form a shielding coating; in the plasma thermal spraying process, the current during plasma thermal spraying is kept unchanged, the plasma arc voltage is increased, and the output power is increased. The preparation method of the present application uses tungsten or tungsten-based metal ceramics as shielding raw materials, avoiding the pollution and secondary bremsstrahlung problems caused by lead shielding, and compared with the existing shielding materials, adding organic-based flexible materials increases the effective shielding volume and improves the shielding effect; using plasma thermal spraying technology to heat, melt and atomize the above materials, and prepare the shielding coating on the surface of the equipment or component, solving the problems of high hardness and high melting point of tungsten and difficult processing of bulk materials.

Description

[0001] This application is a divisional application of the invention patent application with application date of November 4, 2020, application number 202011214424X, and invention name “Gamma ray shielding coating and preparation method thereof”. Technical Field

[0002] The patent of this invention belongs to the technical field of shielding and protection of ionizing radiation, and specifically relates to a method for preparing a gamma-ray shielding coating. Background Art

[0003] With the rapid development and widespread application of nuclear energy technology, radiation sources generate increasing electromagnetic radiation energy, causing radiation damage to humans or equipment components, affecting human health and the stable operation of equipment. X / γ-ray radiation is common in the nuclear industry, and has received widespread attention in industrial fields such as nuclear medicine, scientific research synchrotron radiation accelerators, aviation, national defense, and non-destructive testing. Traditional shielding materials include lead, heavy concrete containing metal oxides, etc. However, lead has poor mechanical properties and poor corrosion resistance, and cannot be used as a structural member alone. It is usually used to hang lead plates or fill lead blocks in the interlayer. In addition, heavy metal lead is harmful to the human body and is prone to heavy metal pollution in the environment. Heavy concrete has certain strength and durability, but its shielding ability is relatively weak.

[0004] Japanese scholars have found that tungsten has a better shielding effect on gamma rays than lead, and is the most promising radiation shielding material to replace lead. Chen Xin compared the absorption changes of lead and tungsten-nickel alloy to different gamma rays and found that tungsten-nickel alloy absorbs gamma rays much better than traditional shielding material - lead. With the same shielding effect, the thickness of tungsten-nickel alloy is only 2 / 3 of that of lead. In some cases, such as 60 When Co is 1332kev, the semi-absorption thickness d of tungsten-nickel alloy 1 / 2 Than the half absorption thickness of lead d 1 / 2 Less than half of what it was.

[0005] Due to the high hardness and melting point of tungsten, bulk materials are difficult to process and shape. The current preparation method is to add shielding materials such as tungsten powder and lead powder to organic adhesives such as epoxy resin and polyurethane, and solidify them on the surface of equipment or components to form a radiation shielding layer. However, the limited specific gravity of heavy metals leads to a small effective shielding volume ratio and weak shielding effect. On the other hand, adhesives are prone to aging after irradiation, have a short lifespan, and the radiation shielding effect is unstable and difficult to guarantee. Summary of the invention

[0006] In view of this, in order to overcome the defects of the prior art and achieve the above-mentioned purpose, the purpose of the present invention is to provide a method for preparing a gamma-ray shielding coating, which can prepare a coating from raw materials of tungsten powder or tungsten-based metal ceramics.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for preparing a gamma-ray shielding coating comprises the following steps: cleaning and sandblasting the surface of a component to be sprayed, and then using a plasma thermal spraying process to prepare a shielding coating from tungsten powder or tungsten-based metal ceramics; in the plasma thermal spraying process, after each stroke of the plasma thermal spraying gun is completed, a pulsed laser shot blasting method is used to laser shot blast the formed coating to eliminate stress.

[0009] Using plasma thermal spraying equipment, a manipulator or other motion mechanism grasps the plasma thermal spraying gun, and after planning the spraying path according to the surface shape of the coating equipment component to be prepared, the shielding coating is sprayed and prepared. Each time the plasma thermal spraying gun completes a stroke, the coating thickness increases by about 30μm-50μm. Because the spray powder droplets splash onto the substrate during the stroke coating process, a certain compressive stress will be generated. When the coating reaches a certain thickness (generally 1mm-2mm), the accumulated stress will cause the coating to peel or crack. Therefore, after each stroke of the plasma thermal spraying gun, the present application uses a pulsed laser shot peening method to perform laser shot peening to eliminate stress on the formed coating, so that the thickness of the final prepared coating can reach more than 5mm. Therefore, compared with traditional plasma spraying, the present application increases the power of the plasma spray gun by increasing the arc voltage, and can spray tungsten powder or tungsten-based metal ceramics using a plasma thermal spraying process. In addition, by controlling the stress using laser shot peening technology during the process, the thickness of the traditional plasma thermal spray coating can be increased from 1mm-2mm to more than 5mm.

[0010] According to some preferred embodiments of the present invention, the tungsten powder is cast tungsten powder and / or agglomerated tungsten powder, the particle size range of the cast tungsten powder is 45 μm-90 μm; the particle size range of the agglomerated tungsten powder is 15 μm-45 μm.

[0011] According to some preferred embodiments of the present invention, the particle size range of the tungsten-based metal ceramic is 15μm-90μm; the tungsten-based metal ceramic includes the following components by mass: 4wt%-6wt% B; 8wt%-16wt% Ni; ≦1.0wt% Fe; ≦0.5wt% O; the balance is W.

[0012] That is, in this application, the raw materials used to prepare the tungsten-based shielding coating are the following three:

[0013] ① Cast tungsten powder: cast spherical tungsten powder, the purity of cast tungsten powder is 99.7%, and the particle size range is 45μm-90μm;

[0014] ② Agglomerated tungsten powder: after the ammonium paratungstate is reduced to submicron tungsten powder, it is agglomerated and sintered to form spherical agglomerated sintered tungsten powder. The purity of the agglomerated tungsten powder is 99.7%, and the particle size range is 15μm-45μm;

[0015] ③ Tungsten-based metal ceramics: tungsten boride-nickel metal ceramics, in which tungsten boride is the main ceramic phase and nickel is the metal bonding phase; in the formed shielding coating, tungsten mainly plays the role of shielding gamma rays and slowing down fast neutrons, boron mainly plays the role of absorbing thermal neutrons, and the metal phase nickel mainly plays the role of bonding tungsten boride ceramics to form a coating. In addition, nickel also has a certain shielding effect on gamma rays.

[0016] In some embodiments of the present invention, the tungsten boride-nickel metal ceramic is agglomerated and sintered spherical powder with a particle size range of 15μm-90μm, and the contents of various components are as follows: B: 4wt%-6wt%; Ni: 8wt%-16wt%; Fe: ≦1.0wt%; O: ≦0.5wt%; W: balance.

[0017] According to some preferred implementation aspects of the present invention, in the plasma thermal spraying process, argon is used as the main gas and hydrogen is used as the auxiliary gas to increase the plasma arc voltage in the plasma thermal spraying process. The current during plasma thermal spraying is kept unchanged, and after the plasma arc voltage is increased, the output power is increased, and the energy and calorific value are increased, which facilitates the melting of the spray powder.

[0018] According to some preferred implementation aspects of the present invention, the parameters in the plasma thermal spraying process are: argon pressure is 100Psi-150Psi, flow rate is 100SCFH-120SCFH, hydrogen pressure is 100Psi-150Psi, flow rate is 10SCFH-14SCFH; current is 680A-750A, and plasma arc voltage is 48V-60V. Powder is fed into the side powder feeding hole of the anode of the plasma spray gun using argon gas, and the argon gas pressure is 100Psi-150Psi and the flow rate is 8SCFH-12SCFH.

[0019] According to some preferred implementation aspects of the present invention, in the laser shot peening treatment, a pulsed laser is used, with laser energy: 1-3J; pulse width: 5-15ns; spot size: (2-5)×(2-5)mm; laser pulse frequency: 5-10HZ; scanning speed: 800-1200mm / min. In some embodiments of the present invention, the preferred parameters are as follows: laser energy: 2J; pulse width: 10ns; spot size: 3*3mm; laser pulse frequency: 10HZ; scanning speed: 800-1200mm / min.

[0020] According to some preferred implementation aspects of the present invention, the surface roughness of the component to be sprayed after the sandblasting treatment reaches 6 μm or more, so as to improve the bonding strength between the coating and the component substrate.

[0021] According to some preferred implementation aspects of the present invention, the sandblasting process is as follows: abrasive particle size: 250 μm-750 μm; compressed air pressure: 0.5 MPa-0.8 MPa; sandblasting distance: 150 mm-500 mm.

[0022] According to some preferred implementation aspects of the present invention, the preparation method further includes a sealing step: applying a sealing agent to the surface of the coating, leaving it to stand or placing the workpiece in a vacuum container to evacuate, wiping off the sealing agent remaining on the surface, and placing it at room temperature to solidify the sealing agent. The sealing agent is a styrene-based sealing agent or an epoxy resin-based sealing agent. Specifically, a liquid resin (sealing agent) such as styrene or epoxy resin is used, and after being prepared, it is applied to the surface of the coating with a brush, or sprayed to the surface of the coating after being atomized using a compressed air spray bottle, and left to stand for 30 minutes or the component is placed in a vacuum container to evacuate for 30 minutes. After the liquid resin is infiltrated into the tiny pores of the coating, the liquid resin remaining on the surface is wiped clean, and placed for 24 hours to 72 hours to solidify the liquid resin to form a sealing effect.

[0023] According to some preferred embodiments of the present invention, the preparation method further comprises a finishing step: using a grinder and a grinding tool to grind or polish the coating so that the coating reaches the set required surface roughness and size.

[0024] In some embodiments of the present invention, the preparation method of the gamma ray shielding coating mainly includes cleaning, sandblasting and plasma thermal spraying, as follows:

[0025] Step 1: Cleaning: Use a clean cotton cloth to wipe the surface of the component to be coated, preliminarily clean the surface stains, and then use organic solvents such as ethanol or thinner to clean and degrease the surface of the component.

[0026] Step 2: Sandblasting: Use white corundum or brown corundum abrasive to sandblast the surface of the component to be coated, roughen and clean the surface of the component to be coated, and the surface meets the standard requirements of ISO8501-1SA-3, so that the surface roughness Ra after sandblasting reaches more than 6μm.

[0027] The parameters of the sandblasting process are as follows:

[0028] White corundum or brown corundum particle size: 250μm-750μm

[0029] Compressed air pressure: 0.5MPa-0.8MPa

[0030] Sandblasting distance: 150mm-500mm

[0031] Step 3: Spraying: Use plasma thermal spraying process to prepare the coating. Use plasma thermal spraying equipment, a manipulator or other motion mechanism to hold the plasma thermal spraying gun, plan the spraying path according to the shape of the surface of the coating equipment component to be prepared, and then spray the shielding coating to prepare the shielding coating.

[0032] In plasma thermal spraying, a high-energy plasma spray gun is used, with argon as the main gas and hydrogen as the auxiliary gas to increase the arc pressure.

[0033] The coating prepared by plasma thermal spraying process has a porosity of 1%-8%. Corrosive ions may slowly penetrate into the interface between the coating and the component substrate through these pores, corrode the component substrate, and the corrosion products expand in volume, causing the coating to bubble and fall off. Therefore, it is necessary to seal the pores of the coating to close the tiny pores of the coating. Therefore, when the coated component is used in a corrosive environment, the preparation method also includes step 4, sealing:

[0034] The specific steps of sealing are: use liquid resin (sealing agent) such as styrene or epoxy resin, mix it according to the following conditions, apply it to the coating surface with a brush, or use a compressed air spray bottle to atomize it and spray it to the coating surface, let it stand for 30 minutes or place the component in a vacuum container and evacuate it for 30 minutes. After the liquid resin penetrates into the tiny pores of the coating, wipe off the liquid resin remaining on the surface and leave it for 24 to 72 hours to allow the liquid resin to solidify and form a seal.

[0035] For some components that have requirements on surface roughness and assembly dimensions, the preparation method of some embodiments of the present invention also includes step five after step three or step four, coating finishing: using a grinder and grinding tools to grind or polish the coating so that the component meets the preset surface roughness and size requirements.

[0036] The present invention also provides a gamma-ray shielding coating prepared according to the above preparation method. The shielding coating uses tungsten, tungsten-based metal ceramics, etc. as shielding raw materials, avoiding the pollution and secondary bremsstrahlung problems caused by lead shielding, and adding organic-based flexible materials to existing shielding materials increases the effective shielding volume and improves the shielding effect.

[0037] Due to the adoption of the technical scheme as described above, compared with the prior art, the advantages of the present invention are as follows: the preparation method of the gamma-ray shielding coating of the present application uses tungsten or tungsten-based metal ceramics as the shielding raw material, thereby avoiding the pollution and secondary bremsstrahlung radiation problems caused by lead shielding, and adding organic-based flexible materials relative to the existing shielding materials increases the effective shielding volume and improves the shielding effect; high-energy plasma thermal spraying technology is used to heat, melt and atomize the above-mentioned materials to prepare a shielding coating on the surface of the equipment or component, thereby solving the problems of high hardness and high melting point of tungsten and difficult processing and molding of bulk materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0039] Figure 1 A cross-sectional schematic diagram of a gamma-ray shielding coating in a preferred embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram of shielding effect detection in a preferred embodiment of the present invention;

[0041] In the attached drawings, there are radiation source-1, sample to be tested-2, shielding coating-21, component substrate-22, and measuring instrument-3. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0043] The method for preparing the gamma-ray shielding coating 21 in this embodiment mainly includes the following steps:

[0044] Step 1: Cleaning

[0045] Use a clean cotton cloth to wipe the surface of the component substrate 22 to be coated to preliminarily clean the surface stains, and then use an organic solvent such as ethanol or thinner to clean and degrease the component surface.

[0046] Step 2: Sandblasting

[0047] The surface of the component substrate 22 to be coated is sandblasted using white corundum or brown corundum abrasives, and the surface of the component substrate 22 to be coated is roughened and cleaned, so that the surface meets the standard requirements of ISO8501-1SA-3, and the surface roughness Ra after sandblasting reaches more than 6μm.

[0048] The parameters of the sandblasting process are as follows:

[0049] White corundum or brown corundum particle size: 500μm

[0050] Compressed air pressure: 0.6MPa

[0051] Sandblasting distance: 300mm

[0052] Step 3: Spraying

[0053] The coating is prepared using a plasma thermal spraying process. Using plasma thermal spraying equipment, a manipulator or other motion mechanism holds a plasma thermal spraying gun, and after planning a spraying path according to the shape of the surface of the coating equipment component to be prepared, the shielding coating 21 is sprayed and prepared.

[0054] In plasma thermal spraying, a high-energy plasma spray gun is used, with argon as the main gas and hydrogen as the auxiliary gas to increase the arc pressure. The argon pressure is 130Psi, the flow rate is 110SCFH, the hydrogen pressure is 130Psi, the flow rate is 12SCFH; the current is 720A, and the plasma arc voltage is 55V. The powder is fed into the side powder feeding hole of the plasma spray gun anode using argon gas, and the argon gas pressure is 130Psi and the flow rate is 10SCFH.

[0055] After each stroke of the plasma thermal spray gun, the formed coating is subjected to laser shot peening to eliminate stress using the pulsed laser shot peening method, so that the thickness of the final prepared coating can reach more than 5mm.

[0056] In the present embodiment, the preferred parameters are as follows: laser energy: 2J; pulse width: 10ns; spot size: 3*3mm; laser pulse frequency: 10HZ; scanning speed: 1000mm / min.

[0057] Using plasma thermal spraying equipment, a manipulator or other motion mechanism grasps the plasma thermal spraying gun, and after planning the spraying path according to the surface shape of the coating equipment component to be prepared, the shielding coating is sprayed and prepared. Each time the plasma thermal spraying gun completes a stroke, the coating thickness increases by about 30μm-50μm. Because the spray powder droplets splash onto the substrate during the stroke coating process, a certain compressive stress will be generated. When the coating reaches a certain thickness (generally 1mm-2mm), the stress accumulation will cause the coating to peel or crack. Therefore, after each stroke of the plasma thermal spraying gun, the present application uses a pulsed laser shot peening method to perform laser shot peening to eliminate stress on the formed coating, so that the thickness of the final prepared coating can reach more than 5mm. Therefore, compared with traditional plasma spraying, this embodiment increases the power of the plasma spray gun by increasing the arc voltage, and can spray tungsten powder or tungsten-based metal ceramics using a plasma thermal spraying process. In addition, by controlling the stress using laser shot peening technology during the process, the thickness of the traditional plasma thermal spray coating can be increased from 1mm-2mm to more than 5mm.

[0058] Step 4: Sealing

[0059] The coating prepared by plasma thermal spraying process has a porosity of 1%-8%. Corrosive ions may slowly penetrate into the interface between the coating and the component substrate 22 through these pores, corrode the component substrate 22, and the corrosion products expand in volume, thus causing the coating to bubble and fall off. Therefore, it is necessary to seal the pores of the coating to close the tiny pores of the coating. Therefore, when the coated component is used in a corrosive environment, it is also necessary to seal the shielding coating 21.

[0060] The specific steps of sealing are: use liquid resin (sealing agent) such as styrene or epoxy resin, mix it according to the following conditions, apply it to the coating surface with a brush, or use a compressed air spray bottle to atomize it and spray it to the coating surface, let it stand for 30 minutes or place the component in a vacuum container and evacuate it for 30 minutes. After the liquid resin penetrates into the tiny pores of the coating, wipe off the liquid resin remaining on the surface and leave it for 24 to 72 hours to allow the liquid resin to solidify.

[0061] In this embodiment, the two sealing liquid resin components are specifically:

[0062] (1) Styrene sealant

[0063] Main agent: styrene, 30wt%;

[0064] Modified epoxy resin, 70wt%;

[0065] Curing agent: modified aliphatic polyamine

[0066] The addition ratio of main agent to hardener is 4:1 (mass ratio)

[0067] (2) Epoxy resin sealant;

[0068] Main agent: epoxy resin;

[0069] Curing agent: Tetrahydrophthalic anhydride

[0070] The addition ratio of main agent to hardener is 4:1 (mass ratio)

[0071] Step 5: Finishing of coating

[0072] For some components that have requirements on surface roughness and assembly dimensions, this embodiment also includes a coating finishing step after step three or step four: using a grinder and grinding tools to grind or polish the coating so that the component meets the preset surface roughness and dimensional requirements.

[0073] Step 4 and step 5 are not necessary steps for preparing the shielding coating 21. Step 4 is only required when the coating component or equipment is used in a corrosive environment, and step 5 is only required when preparing components or equipment with requirements for surface roughness and assembly dimensions. And step 5 can be after step 3 or after step 4. Therefore, the order of the above steps 4 and 5 is only for the convenience of understanding and explanation, and there is no certain correspondence between the order of front and back.

[0074] Effect verification:

[0075] Use Co 60 As a radiation source, Figure 2 In the schematic diagram of shielding effect detection shown in the figure, the center of the radiation source 1, the center of the test sample 2 and the measuring instrument 3 are installed on the same axis. The radiation source and the measuring instrument are remotely controlled and monitored in real time through a remote monitoring device.

[0076] 1. Use a stainless steel sample with a specification of 200mm×200mm×23mm as a comparison sample; the coating shielding effect test sample uses a stainless steel sample with the same specification (200mm×200mm×23mm), prepare a 1mm thick shielding coating on the stainless steel sample, and test the shielding effect of the 1mm thick shielding coating.

[0077] First, a stainless steel plate without shielding coating is installed on the test platform to test the gamma ray count rate (mSv / h) passing through the stainless steel plate. Then the shielding sample with coating is tested in two ways: the shielding coating surface faces the radiation source and the shielding layer faces the back of the radiation source, and the gamma ray count rate (mSv / h) passing through the shielding sample is obtained respectively. The test results are shown in Table 1 below.

[0078] Table 1 Test results

[0079]

[0080] Table 1 shows that the uncoated stainless steel plate was tested 5 times, and the count rate (mSv / h) was 112mSv / h. The shielding coating surface was tested five times facing the radiation source, and the measurement was 98.4mSv / h-98.9mSv / h, with an average of 98.7mSv / h. The shielding coating surface was tested five times with its back to the radiation source, and the measurement was 97.4mSv / h-97.8mSv / h, with an average of 97.6mSv / h. It was found that the shielding effect of the coating facing away from the radiation source was better than that of the coating facing the radiation source. It is considered that when the coating faces away from the radiation source, the high-energy gamma rays are partially blocked by the front stainless steel. Due to Compton scattering, the proportion of low energy in the beam passing through the steel plate will increase (the energy spectrum becomes "soft"), so it is easier to be shielded.

[0081] Taking the shielding effect of the stainless steel plate without shielding coating as the comparison benchmark, the attenuation ratio is set to 1. The attenuation ratio of the coating facing the radiation source is calculated to be (98.7-112) / 98.7=-13.5%, and the attenuation ratio of the coating facing away from the radiation source is (97.6-112) / 97.6=-14.8%.

[0082] 2. Shielding effect of tungsten shielding coating and lead plate of the same thickness on gamma rays

[0083] A stainless steel plate with a size of 200mm×200mm×8mm was used as the substrate. Tungsten shielding coatings with thicknesses of 1mm, 2mm, 3mm, and 4mm were prepared on four stainless steel plates. Lead plates with thicknesses of 1mm, 2mm, 3mm, and 4mm were fixed on the other four stainless steel plates. An Ir192 radiation source was used, and the sample under test was 1m away from the radiation source. The test diagram is shown in the figure below. Figure 2 As shown, the shielding effect of gamma rays obtained by the test is as follows:

[0084] Table 2 Test results

[0085]

[0086] Table 2 shows that the gamma ray shielding effect of tungsten shielding coatings of the same thickness is significantly greater than that of lead plates, and the gamma ray shielding effect is increased by 4.65%-26.87% compared with lead plates of the same thickness.

[0087] 3. Shielding effect of tungsten shielding coating and lead plate of the same thickness on X-rays

[0088] A stainless steel plate with a specification of 200mm×200mm×8mm was used as the substrate. Tungsten shielding coatings with thicknesses of 1mm, 2mm, 3mm, and 4mm were prepared on four stainless steel plates. Lead plates with thicknesses of 1mm, 2mm, 3mm, and 4mm were fixed on the other four stainless steel plates. An Ir192 radiation source was used, and the sample under test was 1m away from the radiation source. The test diagram is shown in the figure below. Figure 2 As shown, the test results show that the shielding effect of X-rays is as follows:

[0089] Table 3 Test results

[0090]

[0091] Table 3 shows that the X-ray shielding effect of tungsten shielding coatings of the same thickness is significantly greater than that of lead plates, and the X-ray shielding effect is increased by 65.87%-666.67% compared with lead plates of the same thickness.

[0092] The fields of nuclear industry, nuclear medicine, radiation accelerators, aviation, nuclear-powered ships, non-destructive testing, etc. will produce ionizing radiation that is highly harmful to the human body and the environment. Among them, gamma rays and X-ray radiation need to be protected because of their high energy and strong penetration. The existing technology has the following disadvantages: 1. At present, gamma ray shielding mostly uses the method of hanging lead plates or filling lead blocks to shield gamma rays. Lead, as a radiation protection material, is easy to produce secondary bremsstrahlung and heavy metal pollution; 2. Due to the high hardness and high melting point of tungsten, the block material is difficult to process and form. Tungsten powder and other shielding materials are added to organic adhesives such as epoxy resin and polyurethane, and solidified on the surface of equipment or components, and combined with the equipment to form a ray shielding coating. However, the limited addition of heavy metals leads to a small effective shielding volume ratio and an unsatisfactory shielding effect; and the adhesive is prone to aging after irradiation and has a poor life. On the other hand, for tungsten materials, general machining, casting, etc. are difficult to form.

[0093] In order to solve the above-mentioned technical problems, the present invention uses high-energy plasma technology and a plasma thermal spraying process to prepare a shielding coating on the surface of equipment, components or buildings that need to shield gamma rays using tungsten powder, tungsten-based metal ceramics and other powders. The tungsten material is prepared into a coating to facilitate combination with mechanical equipment components to form equipment components with shielding functions, thereby achieving a ray shielding effect.

[0094] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a gamma-ray shielding coating, characterized in that: The preparation method comprises cleaning, sandblasting, spraying and sealing steps in sequence; The spraying step comprises: using a plasma thermal spraying process, planning a spraying path according to the surface shape of the coating equipment component to be prepared, and preparing tungsten powder or tungsten-based metal ceramics to form a shielding coating; In the plasma thermal spraying process, the current during plasma thermal spraying is kept unchanged, the plasma arc voltage is increased, and the output power is increased; in the plasma thermal spraying process, the coating thickness increases by 30μm-50μm each time the spray gun completes a stroke; in the plasma thermal spraying process, after each spray gun completes a stroke, the formed coating is laser shot peened using a pulsed laser shot peening method to eliminate stress; The sealing step is: applying the sealing agent to the surface of the coating, leaving it to stand or placing the workpiece in a vacuum container to evacuate, wiping off the sealing agent remaining on the surface, and leaving it at room temperature to solidify the sealing agent.

2. The preparation method according to claim 1, characterized in that: In the plasma thermal spraying process, argon is used as the main gas and hydrogen is used as the auxiliary gas to increase the plasma arc voltage in the plasma thermal spraying process.

3. The preparation method according to claim 2, characterized in that: The parameters of the plasma thermal spraying process are: argon pressure is 100Psi-150Psi, flow rate is 100SCFH-120SCFH, hydrogen pressure is 100Psi-150Psi, flow rate is 10SCFH-14SCFH; current is 680A-750A, and plasma arc voltage is 48V-60V.

4. The preparation method according to claim 2, characterized in that: The powder is fed into the side powder feeding hole of the anode of the plasma spray gun using argon gas. The pressure of the powder feeding argon gas is 100Psi-150Psi, and the flow rate is 8SCFH-12SCFH.

5. The preparation method according to claim 1, characterized in that: In the laser shot blasting treatment, the pulse laser energy used is: 1-3J; pulse width: 5-15ns; spot size: (2-5)×(2-5)mm; laser pulse frequency: 5-10HZ; scanning speed: 800-1200mm / min.

6. The preparation method according to claim 1, characterized in that: The tungsten powder is cast spherical tungsten powder, and its particle size range is 45 μm-90 μm.

7. The preparation method according to claim 1, characterized in that: The tungsten powder is agglomerated tungsten powder, which is obtained by reducing ammonium paratungstate to submicron tungsten powder and then agglomerating and sintering to form spherical agglomerated sintered tungsten powder. The particle size of the agglomerated tungsten powder ranges from 15 μm to 45 μm.

8. The preparation method according to claim 1, characterized in that: The tungsten-based metal ceramic is tungsten boride-nickel metal ceramic, which is agglomerated and sintered spherical powder with a particle size range of 15μm-90μm; the content of each component is as follows by mass: 4wt%-6wt% boron; 8wt%-16wt% nickel; ≦1.0wt% iron; ≦0.5wt% oxygen; the balance is tungsten.

9. The preparation method according to claim 1, characterized in that: The sealing steps are as follows: use a styrene-based sealing agent or an epoxy resin sealing agent, mix it, brush it on the coating surface, or use compressed air to atomize it and then spray it on the coating surface, let it stand for 30 minutes or place the component in a vacuum container and evacuate it for 30 minutes. After the liquid resin penetrates into the tiny pores of the coating, wipe off the liquid resin remaining on the surface, and let it stand for 24 hours to 72 hours to allow the liquid resin to solidify and form a sealing effect.

10. The preparation method according to claim 9, characterized in that: The styrene-based sealing agent comprises a main agent and a curing agent, wherein the main agent is styrene and modified epoxy resin, and the curing agent is modified aliphatic polyamine.

11. The preparation method according to claim 9, characterized in that: The epoxy resin sealing agent comprises a main agent and a curing agent, wherein the main agent is epoxy resin and the curing agent is tetrahydrophthalic anhydride.

12. The preparation method according to claim 1, characterized in that: The cleaning step is: first wipe the surface of the component to be coated to preliminarily clean the surface stains, and then use ethanol or thinner to clean and degrease the surface of the component.

13. The preparation method according to claim 1, characterized in that: The sandblasting step comprises: using abrasives to sandblast the surface of the component to be coated, roughening and cleaning the surface of the component to be coated, so that the surface roughness Ra after sandblasting reaches more than 6 μm.

14. The preparation method according to claim 1, characterized in that: The preparation method further comprises a finishing step after the spraying or sealing step: grinding or polishing the coating to make the coating reach the set required surface roughness and size.

15. The preparation method according to any one of claims 1 to 14, characterized in that: The shielding effect of the shielding coating with the same thickness on gamma rays is increased by 4.65%-26.87% compared with the lead plate; the shielding effect of the shielding coating with the same thickness on X-rays is increased by 65.87%-666.67% compared with the lead plate.

Images