A method for preparing a surface gradient composite coating of a nuclear zirconium alloy

Abstract

The application discloses a preparation method of a surface gradient composite coating of a nuclear zirconium alloy, and comprises the following steps: 1, performing pickling activation treatment on the surface of the zirconium alloy, and then placing the zirconium alloy after the pickling activation into a physical vapor deposition device to perform vacuum pumping and heating treatment; 2, performing glow cleaning and secondary ion cleaning activation treatment on the surface of the zirconium alloy sample; 3, depositing a CrAlTiNiVSi coating; 4, depositing a CrAlTiNiVSi-N coating; 5, repeating the step 3 and the step 4 to alternately deposit the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating on the surface of the zirconium alloy. The CrAlTiNiVSi coating and the CrAlTiNiVSi-N coating are alternately deposited in the application, so that the formation of columnar crystals can be inhibited, a dense coating with excellent high-temperature corrosion resistance can be prepared on the surface of the zirconium alloy substrate, and the service performance of the fuel cladding material is effectively improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nuclear reactor accident-tolerant fuel coating, and particularly relates to a preparation method of a nuclear zirconium alloy surface gradient composite coating. BACKGROUND

[0002] Nuclear energy is a world-recognized clean energy for sustainable development. With the rapid development of nuclear power technology, the installed capacity of nuclear power in China is continuously expanding. It is predicted that by 2030, the development scale of nuclear power in China will reach 131 million kilowatts, and the power generation proportion will reach 10.0%. It is predicted that by 2035, the development scale of nuclear power in China will reach 169 million kilowatts, and the power generation proportion will reach 13.5%. The service life of nuclear power reactor fuel cladding material is of great significance to the development of nuclear power in China. Zirconium alloy has become the preferred material for nuclear power plant reactor fuel cladding due to its excellent processing performance, low thermal neutron absorption cross-section, and good corrosion resistance.

[0003] Under accident conditions, long-term irradiation damage of zirconium alloy leads to hardening and embrittlement of the cladding material, accelerating the corrosion of the cladding material. In a loss of coolant accident environment, poor cooling of the reactor core material can cause the cladding temperature to rise sharply. When the temperature reaches 1000℃, zirconium alloy will rapidly react with water vapor, causing severe zirconium-water reaction, producing a large amount of hydrogen and heat (Zr+2H2O(g)→ZrO2+2H2(g)), and the accumulation of a large amount of hydrogen and high heat environment can easily cause a reactor core explosion, posing a serious threat to the safety of the reactor. Therefore, how to improve the service performance of fuel cladding materials under accident conditions is a problem that needs to be solved in the world nuclear power field.

[0004] Therefore, the development of accident-tolerant fuel cladding materials has become a research hotspot at home and abroad. Accident-tolerant fuel cladding materials not only need to withstand neutron irradiation and water corrosion under normal service conditions, but also can withstand high-temperature water vapor corrosion above 1000℃ under loss of coolant accident conditions, delaying the occurrence of accidents and gaining valuable time for artificial intervention. The most economical and effective accident-tolerant fuel cladding material is a layer of accident-tolerant cladding protective coating with high-temperature corrosion resistance and radiation resistance deposited on the surface of the zirconium alloy substrate.

[0005] At present, the research is more on the preparation of metal protective coating and ceramic protective coating on the surface of zirconium alloy. The metal protective coating is mainly Cr coating, but above 1200℃ in high temperature environment, Cr coating is easy to form Zr-Cr eutectic with zirconium matrix, which reduces the melting point of the matrix, and its wear resistance is poor. The ceramic protective coating is mainly carbide ceramic coating, and the carbide ceramic coating on the surface of zirconium alloy has excellent high temperature corrosion resistance, but the interface bonding performance of the ceramic coating is poor, and the peeling phenomenon is easy to occur. It can be seen that a single coating cannot comprehensively protect the zirconium alloy. Therefore, it is urgent to develop a new type of accident-resistant protective coating with good high temperature corrosion resistance, oxidation resistance, wear resistance and excellent bonding performance. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a preparation method of a nuclear zirconium alloy surface gradient composite coating to solve the above problems of the prior art. The CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating prepared on the surface of the zirconium alloy by the method has excellent compactness, and the alternating deposition of the CrAlTiNiVSi coating and the CrAlTiNiVSi-N coating hinders the formation of columnar crystals, effectively improves the high temperature corrosion resistance of the zirconium alloy, and prolongs the service life of the cladding material.

[0007] To solve the above technical problems, the technical scheme adopted by the present application is: a preparation method of a nuclear zirconium alloy surface gradient composite coating, characterized in that the method comprises the following steps:

[0008] Step one, the surface of the zirconium alloy is activated by acid pickling, and then the zirconium alloy after acid pickling is activated is placed in the vacuum chamber of the physical vapor deposition equipment for vacuumizing and heating treatment; the process of the acid pickling activation treatment is: the zirconium alloy is placed in the acid pickling liquid for acid pickling, and then is sequentially rinsed with room temperature deionized water, boiled with deionized water, ultrasonically cleaned and dehydrated and dried;

[0009] Step two, when the vacuum degree of the vacuum chamber in step one is better than 5*10 -3 Pa, and the temperature reaches 200℃, Ar is introduced into the vacuum chamber, the Ar ions generated by ion discharge are used to glow clean the surface of the zirconium alloy, and then the CrAlTiNiVSi ion source is opened, and the CrAlTiNiVSi ions are used to perform secondary ion cleaning and activation treatment on the surface of the zirconium alloy;

[0010] Step three, after the ion cleaning and activation treatment in step two, the Ar gas flow, bias voltage and current are adjusted, and the CrAlTiNiVSi coating is deposited on the zirconium alloy surface after ion bombardment activation;

[0011] Step four, after the CrAlTiNiVSi coating deposition in step three is completed, N2 gas is introduced to deposit a CrAlTiNiVSi-N coating on the surface of the CrAlTiNiVSi coating;

[0012] Step five, steps three and four are alternately cycled to prepare a CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating on the surface of the zirconium alloy substrate.

[0013] In the present application, a CrAlTiNiVSi ion source is used, which is a high-entropy alloy ion source. The high-entropy alloy contains a large number of element types, at least 5 elements. By appropriate control, it can have excellent corrosion resistance, oxidation resistance, wear resistance, and radiation resistance, etc. Cr, Al, and other elements can easily form a dense oxide film at high temperatures, which can hinder further corrosion. The addition of Ti element can reduce the hydrogen absorption of the zirconium alloy substrate, to a certain extent, reducing the probability of hydrogen explosion. The addition of Ni, V, and Si elements can help improve the high-temperature oxidation resistance of the substrate. The addition of N element can effectively improve the high-temperature steam corrosion resistance of the substrate. Therefore, the present application selects Cr, Al, Ti, Ni, V, Si, and N elements as effective element selection for high-entropy alloy coating. The CrAlTiNiVSi coating and the CrAlTiNiVSi-N coating are alternately deposited on the surface of the zirconium alloy substrate, which can effectively inhibit the formation of columnar crystals, improve the density of the coating, improve the high-temperature corrosion resistance of the coating, and prolong the service life of the cladding material.

[0014] The preparation method of the nuclear zirconium alloy surface gradient composite coating, characterized in that, the room temperature deionized water washing time in step one is not less than 3 min, the deionized water boiling temperature is 60-90℃, the time is 10-30 min, the ultrasonic cleaning time is not less than 10 min, the heating treatment is started after the vacuum degree is better than 5*10 -3 Pa. The present application controls the deionized water washing time to dilute the concentration of the zirconium alloy surface pickling solution, removes the residual pickling solution on the surface, controls the deionized water boiling temperature and time to further remove the pickling solution on the surface of the zirconium alloy, reduces the residual pickling solution on the surface of the zirconium alloy, and controls the ultrasonic cleaning time to accelerate the cleaning degree of the zirconium alloy, remove the surface contaminants to a greater extent, and ensure the cleanliness of the zirconium alloy surface.

[0015] The preparation method of the nuclear zirconium alloy surface gradient composite coating, characterized in that, the CrAlTiNiVSi ion source in step two is a magnetron target source, and the magnetron target source is prepared by uniformly mixing Cr, Al, Ti, Ni, V, and Si raw materials in an equal molar ratio and smelting.

[0016] The preparation method of the nuclear zirconium alloy surface gradient composite coating has the characteristics that, in the glow cleaning process in step two, the substrate bias is 600V-1200V, and the time is 5min-10min, and the activation treatment time is 5min-10min.

[0017] The preparation method of the nuclear zirconium alloy surface gradient composite coating has the characteristics that, in the deposition of the CrAlTiNiVSi coating in step three, the deposition of the pre-plating layer and the deposition of the deposition layer are included, the deposition time of the pre-plating layer is 2min-10min, the substrate bias is 150V-500V, the deposition time of the deposition layer is not less than 80min, the substrate bias is 50V-200V, and the target current is not less than 0.1A.

[0018] The preparation method of the nuclear zirconium alloy surface gradient composite coating has the characteristics that, in the deposition of the CrAlTiNiVSi coating in step three, the deposition of the pre-plating layer and the deposition of the deposition layer are included, the deposition time of the pre-plating layer is 2min-10min, the substrate bias is 150V-500V, the deposition time of the deposition layer is not less than 80min, the substrate bias is 50V-200V, and the target current is not less than 0.1A.

[0019] Compared with the prior art, the present application has the following advantages:

[0020] 1. The CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating prepared on the surface of the nuclear zirconium alloy of the present application is prepared by alternately depositing the CrAlTiNiVSi coating and the CrAlTiNiVSi-N coating, the alternate deposition of the coating can inhibit the formation of columnar crystals, improve the compactness of the coating, and improve the high-temperature corrosion resistance of the coating; the composite coating is uniform and consistent in surface, and has low surface roughness, and the low surface roughness can reduce the frictional resistance of the surface of the cladding material, effectively avoid the problem of uneven heat dissipation caused by local protrusions on the surface, and prolong the service life of the cladding coating material in the service environment.

[0021] 2. The CrAlTiNiVSi coating and the CrAlTiNiVSi-N coating are alternately deposited in the present application, which can inhibit the formation of columnar crystals, prepare a dense coating with excellent high-temperature corrosion resistance on the surface of the zirconium alloy substrate, and effectively improve the service performance of the fuel cladding material, which has great significance for the development of China's energy strategy and nuclear industry.

[0022] 3. The zirconium alloy substrate is ion bombarded and activated before the preparation of the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating in the present application, so that the fresh surface of the zirconium alloy substrate is exposed, the deposition efficiency of the subsequent coating is improved, the interface bonding performance between the coating and the nuclear zirconium alloy substrate is enhanced, and the service life of the cladding coating under working conditions is prolonged.

[0023] 4. The preparation method of the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating on the surface of the nuclear zirconium alloy of the present application is a magnetron sputtering method, which is simple and convenient in process, has good uniformity and strong reliability, and is suitable for large-scale batch production.

[0024] The technical solutions of the present application will be further described in detail below with the help of the drawings and examples. DESCRIPTION OF DRAWINGS

[0025] Figure 1 The surface morphology diagram of the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating prepared on the surface of the zirconium alloy of Example 1 of the present application.

[0026] Figure 2 The atomic force microscope diagram of the surface of the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating prepared on the surface of the zirconium alloy of Example 1 of the present application.

[0027] Figure 3 The cross-sectional morphology diagram of the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating prepared on the surface of the zirconium alloy of Example 1 of the present application.

[0028] Figure 4 The cross-section energy spectrum of the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating prepared on the surface of the zirconium alloy in Example 1 of the present application.

[0029] Figure 5 The morphology of the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating prepared on the surface of the zirconium alloy in Example 1 of the present application after high-temperature environment corrosion at 1200℃. DETAILED DESCRIPTION

[0030] Example 1

[0031] The present example comprises the following steps:

[0032] Step one, the surface of the zirconium alloy is subjected to pickling activation treatment, and then the zirconium alloy is placed in a mixed and uniform pickling solution for pickling. The pickled zirconium alloy is sequentially subjected to room temperature deionized water rinsing for 5 min, 80℃ hot deionized water boiling for 15 min, ultrasonic cleaning for 25 min, and anhydrous ethanol dehydration drying treatment on the surface of the zirconium alloy by using a clean silk cloth dipped in anhydrous ethanol. Then, the treated zirconium alloy is placed in a physical vapor deposition device for vacuumizing. When the vacuum degree of the vacuum chamber reaches 4×10 -3 Pa, the temperature starts to rise;

[0033] Step two, when the vacuum degree of the vacuum chamber in step one reaches 3.8×10 -3 Pa, and the temperature reaches 235℃, Ar gas is introduced into the vacuum chamber to make the vacuum degree of the vacuum chamber 5×10 -1 Pa, the substrate bias is adjusted to 1000V, the Ar ions generated by ion discharge are used to perform glow cleaning on the surface of the zirconium alloy, the bombardment time of the Ar ions is 6 min, the temperature is 260℃, the CrAlTiNiVSi magnetron target ion source made by uniformly mixing and smelting Cr, Al, Ti, Ni, V and Si raw materials in equal molar ratio in a powder metallurgy way is opened, the CrAlTiNiVSi ions overflowing from the surface of the target are used to perform secondary ion cleaning and activation treatment on the surface of the zirconium alloy by bombarding the target with Ar ions, the bombardment activation time of the CrAlTiNiVSi ions is 6 min, and the temperature is 280℃;

[0034] Step three, after the ion cleaning and activation treatment in step two, the Ar gas flow is adjusted, and the gas pressure of the vacuum chamber is controlled to 4×10 -1Pa, the base body bias is adjusted to 370 V, the target current is 0.6 A, the CrAlTiNiVSi pre-coating layer is deposited on the surface of the zirconium alloy after ion bombardment activation, the deposition time of the pre-coating layer is 5 min, then the base body bias is adjusted to 150 V, the target current is 0.5 A, the CrAlTiNiVSi deposition layer is deposited on the surface of the pre-coating layer, the deposition time of the deposition layer is 130 min, and the vacuum chamber temperature is 265℃;

[0035] Step four: after the deposition of the CrAlTiNiVSi coating is completed, the N2 gas flow meter is opened, N2 gas is introduced, the N2 gas flow is adjusted to 80 sccm, the CrAlTiNiVSi-N coating is deposited on the surface of the CrAlTiNiVSi coating, the deposition time is 120 min, and the vacuum chamber temperature is 273℃;

[0036] Step five: the steps three and four are alternately cycled for a total of 6 times to prepare the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating on the surface of the zirconium alloy substrate.

[0037] It is detected that the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating prepared on the surface of the zirconium alloy in the embodiment is uniform on the surface, the surface roughness is 47.6 nm, which is lower than the surface roughness of the zirconium alloy substrate, the surface roughness of the substrate is about 74.2 nm, and the deposition of the coating reduces the surface roughness of the substrate; the total thickness of the composite coating is about 2.93 μm, the thickness of the CrAlTiNiVSi single layer is about 406 nm, and the thickness of the CrAlTiNiVSi-N single layer is about 158 nm, the coating thickness is uniformly distributed and has no columnar crystal, and the coating has good compactness; the mass content of each element in the CrAlTiNiVSi coating is Cr: Al: Ti: Ni: V: Si = 21.13: 12.74: 16.23: 23.34: 16.27: 10.29, the mass content of each element in the CrAlTiNiVSi-N coating is Cr: Al: Ti: Ni: V: Si: N = 18.38: 11.51: 14.97: 19.94: 14.20: 9.05: 11.95; the average microhardness of the coating is about 273 HV, which is higher than the microhardness of the substrate, and the average microhardness of the substrate is about 217 HV; the coating sample does not have obvious cracks, bulges and other defects under the condition of 1200℃ thermal shock, and has good thermal shock resistance; the coating does not have obvious cracks, bulges, peeling and other defects under the condition of 1200℃ high-temperature steam environment, and has good high-temperature corrosion resistance.

[0038] Figure 1 The surface morphology of the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating prepared on the surface of the zirconium alloy in the embodiment is shown in the following figure:Figure 1 As can be seen from the figure, the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating prepared on the surface of the zirconium alloy is uniform and consistent, and the coating is sputter-deposited by particles with uniform size.

[0039] Figure 2 The atomic force microscope image of the surface of the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating prepared on the surface of the zirconium alloy in this example is shown in the figure, and the Element 1 and Element 2 points in the figure are analyzed for element mass content. Figure 2 As can be seen from the figure, the coating surface has uniform and consistent particle size, and as can be seen from the three-dimensional AFM micrograph, the coating surface has certain height difference in the microscopic scale. In the test area, the highest position of the coating is 200.6 nm above the center line, the lowest position of the coating is 8.8 nm below the center line, the coating surface has certain roughness, the test result shows that the average height of the coating surface is 47.6 nm, and the roughness of the coating surface is 47.6 nm.

[0040] Figure 3 The cross-sectional morphology of the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating prepared on the surface of the zirconium alloy in this example is shown in the figure. Figure 3 As can be seen from the figure, the coating and the substrate, and the interface between the CrAlTiNiVSi coating and the CrAlTiNiVSi-N coating are tightly combined, the coating cross-section is dense and uniform, no columnar crystal is formed, the coating cross-section has no obvious defects such as cracks and holes, and the thickness of the gradient composite coating is about 2.93 μm.

[0041] Figure 4 The cross-sectional energy spectrum of the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating prepared on the surface of the zirconium alloy in this example is shown in the figure, and the element mass content of the Element 1 and Element 2 points in the figure is analyzed. Figure 3 As can be seen from the figure, the single-layer thickness of the CrAlTiNiVSi coating is about 406 nm; the element composition and content of the CrAlTiNiVSi-N coating are Cr: Al: Ti: Ni: V: Si: N = 18.38: 11.51: 14.97: 19.94: 14.20: 9.05: 11.95, as shown in Table 1, in combination with Figure 3 As can be seen from the figure, the single-layer thickness of the CrAlTiNiVSi coating is about 406 nm; the element composition and content of the CrAlTiNiVSi-N coating are Cr: Al: Ti: Ni: V: Si: N = 18.38: 11.51: 14.97: 19.94: 14.20: 9.05: 11.95, as shown in Table 1, in combination with

[0042] Table 1

[0043] Element 1 Wt% Element 2 Wt% N / N 11.95 Al 12.74 Al 11.51 Si 10.29 Si 9.05 Ti 16.23 Ti 14.97 V 16.27 V 14.20 Cr 21.13 Cr 18.38 Ni 23.34 Ni 19.94 Total 100.00 Total 100.00

[0044] Figure 5 The CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating prepared on the surface of the zirconium alloy in this embodiment has a morphology after high-temperature environment corrosion at 1200℃, as shown in FIG. 6. Figure 5 As can be seen from FIG. 6, the gradient composite coating maintains good coating integrity at 1200℃ high-temperature environment, and no obvious cracks, bulges, peeling and other defects appear on the surface of the coating, which shows good high-temperature corrosion resistance.

[0045] Embodiment 2

[0046] This embodiment includes the following steps:

[0047] Step one, the surface of the zirconium alloy is subjected to pickling activation treatment, the zirconium alloy is placed in a mixed and uniform pickling solution for pickling, and then the pickled zirconium alloy is sequentially subjected to room temperature deionized water rinsing for 6min, 90℃ hot deionized water boiling for 10min, ultrasonic cleaning for 30min, anhydrous ethanol dehydration drying treatment on the surface of the zirconium alloy by using a clean silk cloth to dip anhydrous ethanol, and then the treated zirconium alloy is placed in a physical vapor deposition device for vacuumizing, and when the vacuum degree of the vacuum chamber reaches 4.9×10 -3 Pa, the temperature starts to rise;

[0048] Step two, when the vacuum degree of the vacuum chamber reaches 4.3×10 -3 Pa and the temperature reaches 227℃, Ar gas is introduced into the vacuum chamber to make the vacuum degree of the vacuum chamber 7×10 -1 Pa, the substrate bias is adjusted to 800V, the Ar ions generated by ion discharge are used for glow cleaning of the surface of the zirconium alloy, the bombardment activation time of the Ar ions is 8min, the temperature is 210℃, the CrAlTiNiVSi magnetron target ion source made by uniformly mixing and smelting Cr, Al, Ti, Ni, V and Si raw materials in equal molar ratio in a powder metallurgy way is opened, the CrAlTiNiVSi ions overflowing from the surface of the target are used for secondary ion cleaning and activation treatment of the surface of the zirconium alloy by bombarding the target with Ar ions, the bombardment activation time of the CrAlTiNiVSi ions is 8min, and the temperature is 240℃;

[0049] Step three, after the ion cleaning and activation treatment in step two, the Ar gas flow is adjusted to control the gas pressure of the vacuum chamber to 6×10 -1Pa, the base body bias is adjusted to 260 V, the target current is 1.2 A, the CrAlTiNiVSi pre-coating layer is deposited on the surface of the zirconium alloy after ion bombardment activation, the deposition time of the pre-coating layer is 8 min; then the base body bias is adjusted to 100 V, the target current is 0.85 A, the CrAlTiNiVSi deposition layer is deposited on the surface of the pre-coating layer, the deposition time of the deposition layer is 150 min, and the vacuum chamber temperature is 225℃;

[0050] Step four, after the deposition of the CrAlTiNiVSi coating is completed, the N2 gas flow meter is opened, N2 gas is introduced, the N2 gas flow is adjusted to 100 sccm, the CrAlTiNiVSi-N coating is deposited on the surface of the CrAlTiNiVSi coating, the deposition time is 80 min, and the vacuum chamber temperature is 230℃;

[0051] Step five, the steps three and four are alternately cycled for a total of 6 times to prepare the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating on the surface of the zirconium alloy substrate.

[0052] It is detected that the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating prepared on the surface of the zirconium alloy in the embodiment is uniform on the surface, the surface roughness is 52.8 nm, which is lower than the surface roughness of the zirconium alloy substrate, the surface roughness of the substrate is about 74.2 nm, and the deposition of the coating reduces the surface roughness of the substrate; the total thickness of the composite coating is about 3.07 μm, the thickness of the CrAlTiNiVSi single layer is about 456 nm, and the thickness of the CrAlTiNiVSi-N single layer is about 158 nm, the coating thickness is uniformly distributed, there is no columnar crystal, and the coating has good compactness; the content of each element in the CrAlTiNiVSi coating is Cr: Al: Ti: Ni: V: Si = 20.75: 13.19: 16.98: 22.75: 16.05: 10.28, the content of each element in the CrAlTiNiVSi-N coating is Cr: Al: Ti: Ni: V: Si: N = 18.08: 11.05: 14.56: 19.73: 14.24: 8.70: 13.64; the average microhardness of the coating is about 289 HV, which is higher than the microhardness of the substrate, and the average microhardness of the substrate is about 217 HV; the coating sample does not have obvious cracks, bulges and other defects under the condition of 1200℃ thermal shock, and has good thermal shock resistance; the coating does not have obvious cracks, bulges, peeling and other defects under the condition of 1200℃ high-temperature steam environment, and has good high-temperature corrosion resistance.

[0053] Embodiment 3

[0054] The embodiment includes the following steps:

[0055] Step one, the surface of the zirconium alloy is activated by pickling, the zirconium alloy is placed in the mixed and uniform pickling solution for pickling, then the pickled zirconium alloy is sequentially rinsed with room temperature deionized water for 4 min, boiled with 70℃ hot deionized water for 20 min, cleaned with ultrasonic wave for 20 min, and dried with anhydrous ethanol on the surface of the zirconium alloy by using a clean silk cloth dipped with anhydrous ethanol, and then the treated zirconium alloy is placed in a physical vapor deposition device for vacuumizing, when the vacuum degree of the vacuum chamber reaches 4.3*10 -3 Pa, the temperature starts to rise;

[0056] Step two, when the vacuum degree of the vacuum chamber reaches 3.5*10 -3 Pa and the temperature reaches 240℃, Ar gas is introduced into the vacuum chamber to make the vacuum degree of the vacuum chamber 3*10 -1 Pa, the substrate bias is adjusted to 1200V, the Ar ions generated by ion discharge are used to perform glow cleaning on the surface of the zirconium alloy, the bombardment activation time of the Ar ions is 5 min and the temperature is 300℃, the CrAlTiNiVSi magnetron target ion source made by uniformly mixing and smelting Cr, Al, Ti, Ni, V and Si raw materials in equal molar ratio in a powder metallurgy way is opened, the CrAlTiNiVSi ions overflowing from the surface of the target are used to perform secondary ion cleaning and activation treatment on the surface of the zirconium alloy by bombarding the target with Ar ions, the bombardment activation time of the CrAlTiNiVSi ions is 5 min and the temperature is 350℃;

[0057] Step three, after the ion cleaning and activation treatment in step two, the Ar gas flow is adjusted to control the gas pressure of the vacuum chamber to 4*10 -1 Pa, the substrate bias is adjusted to 500V and the target current is 0.3A, the CrAlTiNiVSi pre-plating layer is deposited on the surface of the zirconium alloy after ion bombardment and activation, the deposition time of the pre-plating layer is 2 min, then the substrate bias is adjusted to 200V and the target current is 0.1A, the CrAlTiNiVSi deposition layer is deposited on the surface of the pre-plating layer, the deposition time of the deposition layer is 80 min, and the temperature of the vacuum chamber is 320℃;

[0058] Step four, after the deposition of the CrAlTiNiVSi coating is completed, the N2 gas flow meter is opened to introduce N2 gas, the N2 gas flow is adjusted to 60sccm, the CrAlTiNiVSi-N coating is deposited on the surface of the CrAlTiNiVSi coating, the deposition time is 60 min, and the temperature of the vacuum chamber is 338℃;

[0059] Step five, steps three and four are alternately cycled for a total of 6 times to prepare the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating on the surface of the zirconium alloy substrate.

[0060] It is detected that the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating prepared on the surface of the zirconium alloy in the embodiment is uniform on the surface, the surface roughness is 41.1 nm, which is lower than the surface roughness of the zirconium alloy substrate, the surface roughness of the substrate is about 74.2 nm, and the deposition of the coating reduces the surface roughness of the substrate; the total thickness of the composite coating is about 2.0 μm, the thickness of the CrAlTiNiVSi single layer is about 306 nm, and the thickness of the CrAlTiNiVSi-N single layer is about 79 nm, the coating thickness is uniformly distributed, and there is no columnar crystal, and the coating has good compactness; the content of each element in the CrAlTiNiVSi coating is Cr:Al:Ti:Ni:V:Si = 20.40:12.72:17.12:22.09:16.99:10.68, and the content of each element in the CrAlTiNiVSi-N coating is Cr:Al:Ti:Ni:V:Si:N = 17.14:10.04:14.23:19.05:14.30:8.75:16.49; the average microhardness of the coating is about 269 HV, which is higher than the microhardness of the substrate, and the average microhardness of the substrate is about 217 HV; the coating sample does not have obvious cracks, bulges and other defects under the condition of 1200℃ thermal shock, and has good thermal shock resistance; the coating does not have obvious cracks, bulges, peeling and other defects under the condition of 1200℃ high temperature steam environment, and has good high temperature corrosion resistance.

[0061] Embodiment 4

[0062] The embodiment includes the following steps:

[0063] Step one, the surface of the zirconium alloy is subjected to pickling activation treatment, the zirconium alloy is placed in the mixed and uniform pickling solution for pickling, then the pickled zirconium alloy is sequentially subjected to room temperature deionized water washing for 3 min, 60℃ hot deionized water boiling for 30 min, ultrasonic cleaning for 10 min, anhydrous ethanol dehydration drying treatment on the surface of the zirconium alloy by using a clean silk cloth dipped in anhydrous ethanol, and then the treated zirconium alloy is placed in a physical vapor deposition device for vacuumizing, and when the vacuum degree of the vacuum chamber reaches 4.1×10 -3 Pa, the temperature starts to rise;

[0064] Step two, when the vacuum degree of the vacuum chamber in step one reaches 4.9×10 -3 Pa, and the temperature reaches 200℃, Ar gas is introduced into the vacuum chamber, so that the vacuum degree of the vacuum chamber is 9×10 -1Pa, the substrate bias is adjusted to 600 V, the zirconium alloy surface is cleaned by glow discharge generated Ar ions, the Ar ion bombardment activation time is 10 min, the temperature is 180°C, the CrAlTiNiVSi magnetron target ion source made of Cr, Al, Ti, Ni, V, Si raw materials mixed and melted in equal molar ratio by powder metallurgy is opened, the CrAlTiNiVSi ions overflowing from the surface of the target are used to perform secondary ion cleaning and activation treatment on the zirconium alloy surface by Ar ion bombardment of the target, the CrAlTiNiVSi ion bombardment activation time is 10 min, the temperature is 210°C;

[0065] Step three, after the ion cleaning and activation treatment in step two, the Ar gas flow is adjusted, the gas pressure in the vacuum chamber is controlled to 8x10 -1 Pa, the substrate bias is adjusted to 150 V, the target current is 1.1 A, the CrAlTiNiVSi pre-plating layer is deposited on the zirconium alloy surface activated by ion bombardment, the deposition time of the pre-plating layer is 10 min, then the substrate bias is adjusted to 50 V, the target current is 0.75 A, the CrAlTiNiVSi deposition layer is deposited on the surface of the pre-plating layer, the deposition time of the deposition layer is 120 min, and the vacuum chamber temperature is 200°C;

[0066] Step four, after the CrAlTiNiVSi coating is deposited, the N2 gas flow meter is opened, N2 gas is introduced, the N2 gas flow is adjusted to 120 sccm, the CrAlTiNiVSi-N coating is deposited on the surface of the CrAlTiNiVSi coating, the deposition time is 180 min, and the vacuum chamber temperature is 217°C;

[0067] Step five, the steps three and four are alternately cycled for a total of 6 times to prepare a CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating on the surface of the zirconium alloy substrate.

[0068] It is detected that the CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating prepared on the surface of the zirconium alloy in the embodiment is uniform on the surface, the surface roughness is 61.3 nm, which is lower than the surface roughness of the zirconium alloy substrate, the surface roughness of the substrate is about 74.2 nm, and the deposition of the coating reduces the surface roughness of the substrate; the total thickness of the composite coating is about 3.30 μm, the thickness of the CrAlTiNiVSi single layer is about 385 nm, and the thickness of the CrAlTiNiVSi-N single layer is about 237 nm, the coating thickness is uniformly distributed, there is no columnar crystal, and the coating has good compactness; the content of each element in the CrAlTiNiVSi coating is Cr:Al:Ti:Ni:V:Si=20.19:13.90:16.80:21.56:16.49:11.06, the content of each element in the CrAlTiNiVSi-N coating is Cr:Al:Ti:Ni:V:Si:N=17.21:11.06:14.41:18.63:14.26:9.01:15.42; the average microhardness of the coating is about 326 HV, which is higher than the microhardness of the substrate, and the average microhardness of the substrate is about 217 HV; the coating sample does not have obvious cracks, bulges and other defects under the condition of thermal shock at 1200℃, and has good thermal shock resistance; the coating does not have obvious cracks, bulges, shedding and other defects in the high-temperature steam environment at 1200℃, and has good high-temperature corrosion resistance.

[0069] The above merely describes preferred embodiments of the present application, but does not limit the present application in any way. Any simple modification, change and equivalent variation of the above embodiments according to the technical essence of the present application are still within the protection scope of the technical solution of the present application.

Claims

1. A method for producing a surface gradient composite coating of a zirconium alloy for nuclear use, characterized by, The method comprises the following steps: Step one, the surface of zirconium alloy is activated by pickling, and then the zirconium alloy after pickling activation is placed in the vacuum chamber of physical vapor deposition equipment for vacuumizing and heating treatment; the process of pickling activation is that the zirconium alloy is pickled in pickling solution, and then is sequentially rinsed with room temperature deionized water, boiled with deionized water, cleaned by ultrasonic wave and dried by dehydration; Step two, when the vacuum degree of the vacuum chamber in step one is better than 5x10 -3 Pa, and the temperature reaches 200℃, Ar is introduced into the vacuum chamber, the zirconium alloy surface is glow cleaned by Ar ions generated by ion discharge, then the CrAlTiNiVSi ion source is opened, and the zirconium alloy surface is activated by secondary ion cleaning by CrAlTiNiVSi ions. Step three, after the ion cleaning activation treatment in step two, the Ar gas flow, bias voltage and current are adjusted to deposit CrAlTiNiVSi coating on the surface of zirconium alloy after ion bombardment activation; the deposition of CrAlTiNiVSi coating comprises the deposition of pre-plating layer and the deposition of deposition layer, the deposition time of pre-plating layer is 2 min to 10 min, the substrate bias voltage is 150 V to 500 V, the deposition time of deposition layer is not less than 80 min, the substrate bias voltage is 50 V to 200 V, and the target current is not less than 0.1 A; Step four, after the CrAlTiNiVSi coating deposition in step three is completed, N2 gas is introduced to deposit CrAlTiNiVSi-N coating on the surface of CrAlTiNiVSi coating; Step five, steps three and four are alternately cycled to prepare CrAlTiNiVSi / CrAlTiNiVSi-N gradient composite coating on the surface of zirconium alloy substrate.

2. The method of claim 1, wherein the method comprises the steps of: The time of the room temperature deionized water flushing in step one is not less than 3 minutes, the temperature of the deionized water boiling is 60-90℃, the time is 10-30 minutes, the time of the ultrasonic cleaning is not less than 10 minutes, the heating treatment is in the vacuum degree better than 5×10 -3 Pa after starting to raise the temperature. ​ 3. The method of claim 1, wherein the method comprises the steps of: (a) preparing a Zr alloy substrate; (b) preparing a Zr alloy surface gradient composite coating on the Zr alloy substrate; and (c) performing a heat treatment on the Zr alloy surface gradient composite coating. The CrAlTiNiVSi ion source in step two is a magnetron target source, and the magnetron target source is made by uniformly mixing Cr, Al, Ti, Ni, V and Si raw materials in equal molar ratio and smelting.

4. The method of claim 1, wherein the method comprises the steps of: (a) preparing a Zr alloy substrate; (b) preparing a Zr alloy surface gradient composite coating on the Zr alloy substrate; and (c) performing a heat treatment on the Zr alloy surface gradient composite coating. In the glow cleaning process in step two, the substrate bias voltage is 600 V to 1200 V, and the time is 5 min to 10 min, and the activation treatment time is 5 min to 10 min.

5. The method for preparing a gradient composite coating on the surface of a nuclear-grade zirconium alloy according to claim 1, characterized in that, In the deposition of CrAlTiNiVSi-N coating in step four, the flow rate of N2 gas is 60 sccm to 120 sccm, and the deposition time is not less than 60 min.

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