Cr-based protective coating with multi-layer structure and preparation method of Cr-based protective coating

Abstract

The invention belongs to the field of protective coatings, and relates to a Cr-based protective coating with a multi-layer structure and a preparation method of the Cr-based protective coating. The Cr-based protective coating comprises a plurality of periodic layers, and each periodic layer is composed of a Cr layer and a Cr-Al-Si-N layer. The element composition of the Cr-Al-Si-N layer is CrxAlySizN1-x-y-z, x, y and z are atomic ratios, x is larger than or equal to 0.33 and smaller than or equal to 0.43, y is larger than or equal to 0.20 and smaller than or equal to 0.27, and z is larger than or equal to 0.04 and smaller than or equal to 0.08; and the Cr-Al-Si-N layer is of a two-phase composite structure in which nanocrystals are dispersed and distributed in compact noncrystals. The multi-layer structure coating provided by the invention combines the double advantages of radiation resistance and high-temperature oxidation resistance, shows good comprehensive protection performance, and can provide effective protection for the nuclear fuel cladding tube in a complex and severe reactor environment.

Description

Technical Field

[0001] The invention belongs to the field of protective coatings and relates to a Cr-based protective coating with a multi-layer structure and a preparation method thereof. Background Art

[0002] Nuclear energy is a clean energy that occupies an important position in the world's energy structure, showing great potential and attractive prospects. Nuclear energy will play an increasingly important role in my country's energy system. At present, nuclear safety issues are a major factor restricting the development and application of nuclear power, which has attracted great attention and strategic deployment from nuclear units at home and abroad. Nuclear fuel cladding tubes are the first barrier to prevent nuclear fuel leakage. Therefore, nuclear fuel cladding tubes with accident tolerance (ATFC) are generally considered to be the core component of nuclear safety engineering. The development direction of ATFC includes: finding new cladding tube materials (such as silicon carbide and iron-chromium-aluminum alloy) to replace zirconium alloy, and improving the accident tolerance of existing zirconium alloy cladding tubes through surface coating technology. The latter is not only compatible with existing nuclear systems and cladding tube processing and production technologies, but also has the advantages of short R&D cycle, high feasibility and low cost. Therefore, it has also become the key deployment direction of nuclear energy agencies at home and abroad. After extensive preliminary screening, metal chromium (Cr)-based coatings have excellent resistance to supercritical water corrosion and high-temperature steam oxidation, and are recognized as the candidate coating material with the most application potential.

[0003] At present, many universities and research institutes at home and abroad have carried out the research and development and application of Cr-based coated cladding tubes, but they are more concerned with the protective behavior of cladding tube coatings under the action of single factors such as corrosion, oxidation, and irradiation. In fact, cladding tubes face a more complex and severe service environment in reactors. The inventors found in early research that after low doses (0.26dpa) of xenon ions (Xe 20+ ) After irradiation, the Cr coating will undergo obvious radiation hardening and embrittlement behavior; and because the radiation defects will provide a rapid diffusion channel for the diffusion of oxygen elements, the oxidation mechanism of the coating in high-temperature water vapor will change from external oxidation to internal oxidation, and it is difficult to form a continuous and complete oxide isolation layer on the surface, which ultimately leads to a significant reduction in its protective ability or even failure. It can be seen that the high-temperature oxidation process of the coating is very sensitive to radiation defects.

[0004] Therefore, how to suppress the accelerated element diffusion induced by irradiation defects is the key to further improve the protective performance of Cr-based coatings after irradiation. The solution to this problem is of great significance to the design and development of cladding tube protective coatings and the development and application of ATFC. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a multi-layered Cr-based protective coating and a preparation method thereof.

[0006] One object of the present invention is achieved by the following technical solutions:

[0007] A multi-layer Cr-based protective coating, wherein the Cr-based protective coating is a plurality of periodic layers, each periodic layer is composed of a Cr layer and a Cr-Al-Si-N layer; the element composition of the Cr-Al-Si-N layer is Cr x Al y Si z N 1-x-y-z , where x, y, and z are atomic ratios, 0.33≤x≤0.43, 0.20≤y≤0.27, and 0.04≤z≤0.08; the Cr-Al-Si-N layer is a two-phase composite structure of dispersed nanocrystals in dense amorphous materials.

[0008] Preferably, the Cr-based protective coating has 1 to 100 periodic layers; more preferably, it has 1 to 20 periodic layers.

[0009] Preferably, the thickness of the Cr—Al—Si—N layer in each periodic layer is 100 to 500 nm, and more preferably 100 to 300 nm.

[0010] Preferably, in each periodic layer, the thickness ratio of the Cr layer to the Cr-Al-Si-N layer is 1-5:1.

[0011] Preferably, the growth structure of the Cr layer is a single-phase structure of columnar crystals.

[0012] Preferably, the width of the columnar crystal is 20 to 500 nm, more preferably 20 to 200 nm.

[0013] Preferably, the density of the Cr layer is 6.0-7.0 g / cm 3 .

[0014] Preferably, the size of the nanocrystals in the Cr-Al-Si-N layer is 1 to 50 nm, and more preferably 5 to 20 nm. The nanocrystals are evenly distributed in the dense amorphous.

[0015] Preferably, the density of the Cr-Al-Si-N layer is 6.2-7.5 g / cm 3 More preferably, it is 6.5 to 7.5 g / cm 3 .

[0016] Preferably, the outermost layer of the Cr-based protective coating is a Cr-Al-Si-N layer.

[0017] Preferably, the Cr layer and the Cr—Al—Si—N layer are prepared by physical vapor deposition, which includes magnetron sputtering, cathode arc deposition, and the like.

[0018] The growth structure of the physical vapor deposition coating will present a typical columnar crystal structure, in which the column boundary is a very effective radiation-resistant interface. Generally speaking, the Cr coating on the zirconium alloy substrate grows competitively and presents a "V"-shaped columnar crystal structure. The coarsening and growth of columnar crystals means that the interface / grain boundary density decreases, which reduces the radiation resistance of the coating as its thickness increases. Therefore, inhibiting the coarsening and growth of grains / crystal columns and increasing the size and density of interfaces / grain boundaries become the key to improving the radiation resistance of the coating. The present invention can effectively interrupt the coarsening and growth of Cr grains by periodically introducing a Cr-Al-Si-N intermediate layer with an optimized atomic ratio into the traditional Cr coating, prompting the grains to re-nucleate to increase the density of the interface / grain boundary, and the formed Cr / Cr-Al-Si-N interlayer interface can also be used as an anti-radiation medium, which is beneficial to improving the overall radiation resistance of the system. Secondly, the Cr-Al-Si-N layer with an optimized atomic ratio is also beneficial to improving the oxidation resistance of the coating system. Oxidation resistance mainly depends on whether a dense and stable oxide isolation layer can be quickly formed on the surface. Based on the "third element" effect, a small amount of anti-oxidation elements Al and Si doping helps the external oxidation mechanism to proceed. The oxide layer formed by the Cr-Al-Si-N coating in high-temperature water vapor is dense and thin, which can effectively reduce the growth stress in the oxide layer and is conducive to its structural stability and integrity. Combining the above two approaches, the multilayer structure composed of a Cr layer and a nitride Cr-Al-Si-N layer proposed in the present invention exhibits good comprehensive radiation resistance and oxidation resistance.

[0019] The second object of the present invention is achieved by the following technical solutions:

[0020] A method for preparing a multi-layer Cr-based protective coating comprises the following steps:

[0021] (1) Install the target and substrate;

[0022] (2) evacuating the deposition chamber and heating the substrate;

[0023] (3) Set the experimental parameters and alternately deposit Cr layers and Cr-Al-Si-N layers on the substrate.

[0024] The present invention preferably uses magnetron sputtering to deposit the Cr layer and the Cr-Al-Si-N layer.

[0025] Preferably, the substrate is a zirconium alloy.

[0026] Before installing the substrate, the substrate surface needs to be polished and cleaned. The polishing is further preferably mechanical polishing, and the cleaning includes chemical cleaning and / or plasma glow cleaning.

[0027] The following is an example of mechanical polishing process, which is not intended to limit the present invention. The mechanical polishing is: using sandpapers of 100-500 mesh, 700-1500 mesh, 2000-3000 mesh, 4000-6000 mesh, 7000-9000 mesh and polishing paste of 9500-11000 mesh in sequence, and using a metallographic polishing machine to polish the substrate coating surface to a mirror surface with a roughness Ra≤10nm.

[0028] The following are chemical cleaning methods, which are not intended to limit the present invention. The chemical cleaning method is as follows: the substrate or workpiece is sequentially placed in acetone and anhydrous ethanol for ultrasonic treatment for 1 to 10 minutes each, and then air-dried in a drying oven at a temperature of 70 to 90° C. for 1 to 5 hours, or blown dry with high-purity N2 having a purity of ≥99.99%.

[0029] The following is an example of plasma glow cleaning, which is not intended to limit the present invention. The plasma glow cleaning is as follows: the chemically cleaned substrate is fixed on a rotatable sample plate in a vacuum chamber. The background vacuum is pumped down to less than 1×10 -3 After 30 min, Ar gas is introduced and the working gas pressure is maintained at 0.1-10 Pa. Then, the power is turned on and a negative bias is applied to the substrate. The plasma generated by the ionization of Ar gas is used to sputter-etch the substrate for 3-20 min, so that the water molecules, gas molecules or dust particles adsorbed on the surface of the substrate are completely bombarded and cleaned.

[0030] Preferably, the target material includes a Cr target and a Cr a Al b Si 1-a-b Target, wherein 0.45≤a≤0.60, 0.25≤b≤0.32, a and b are both atomic ratios. Preferably, the purity of each target material is ≥99.9%.

[0031] Preferably, in step (2), the vacuuming refers to pumping the background vacuum of the deposition chamber to less than 1.0×10 -4 Pa; the substrate heating temperature is 450-550°C.

[0032] Preferably, in step (3), the process of depositing the Cr layer includes: applying a radio frequency-assisted DC power supply to the Cr target, introducing Ar gas, adjusting the gas pressure to 0.1 to 2 Pa (more preferably 0.5 to 1.0 Pa), and controlling the sputtering negative bias voltage to 0 to 30 V, and then depositing the Cr layer.

[0033] Preferably, in step (3), the process of depositing the Cr-Al-Si-N layer comprises: applying a radio frequency power supply to the Cr target, applying a DC power supply to the Cr a Al b Si 1-a-b Then, a mixed gas of Ar and N2 is introduced onto the target, the gas pressure is adjusted to 0.1-2 Pa (more preferably 0.5-1.0 Pa), and the sputtering negative bias voltage is controlled to 5-10 V, and then the Cr-Al-Si-N layer is deposited.

[0034] Preferably, in the process of depositing the Cr layer, the power density of the Cr target is 6.4 to 8.7 W / cm 2 .

[0035] Preferably, in the process of depositing the Cr-Al-Si-N layer, the power density of the Cr target is 5.6-7.5 W / cm 2 ,Cr a Al b Si 1-a-b The power density of the target is 7.2~9.6W / cm 2 .

[0036] Preferably, in the process of depositing the Cr—Al—Si—N layer, the flow ratio of Ar to N2 is 8 to 13:1.

[0037] In the present invention, the key to obtaining the coating structure is to use appropriate experimental parameters such as substrate heating temperature, selection of working gas with appropriate flow rate, working gas pressure, use of direct current, radio frequency assisted direct current power supply, power density of each target, etc. for sputtering. The direct current power supply can generate sufficiently strong medium energy ions (~60eV), and the radio frequency power supply can generate a higher plasma flux. Through the bombardment of a small amount of medium energy ions and a large amount of low energy plasma, not only can the diffusion of sputtered atoms be promoted, but also the stress accumulation in the coating deposition process can be reduced, and the formation of defects such as penetrating pores and cracks in the coating growth process can be reduced.

[0038] By magnetron sputtering with appropriate experimental parameters, the alternating deposition of a Cr layer with a single-phase structure of columnar crystals and a two-phase composite structure of nanocrystals dispersed in dense amorphous materials was obtained. x Al y Si z N 1-x-y-z layer (wherein x, y, z are atomic ratios, 0.33≤x≤0.43, 0.20≤y≤0.27, 0.04≤z≤0.08).

[0039] The third object of the present invention is achieved by the following technical solutions:

[0040] A zirconium alloy workpiece comprises a zirconium alloy substrate and a multi-layered Cr-based protective coating located on the surface of the zirconium alloy substrate.

[0041] Preferably, the zirconium alloy workpiece is exposed to 5 MeV Xe 20+ Ion, irradiation dose is 1.0×10 15 ions / cm 2 After irradiation treatment, the zirconium alloy matrix did not show oxidation phenomenon when oxidized in water vapor at 1200°C for 6 to 10 hours.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. The present invention periodically introduces a Cr-Al-Si-N layer with an optimized atomic ratio and containing nanocrystals into the Cr coating, and combines the columnar crystal structure of the Cr layer with the two-phase composite structure of dispersed nanocrystals in the dense amorphous Cr-Al-Si-N layer to form a unique multilayer periodic structure, thereby significantly improving the overall radiation resistance of the coating.

[0044] 2. The multilayer protective structure of the alternately deposited Cr coating and the Cr-Al-Si-N layer with optimized atomic ratio and containing nanocrystals formed by the present invention has excellent radiation resistance. After irradiation treatment, the multilayer protective structure can still form a dense and stable oxide isolation layer, reducing the growth stress in the oxide layer, making the oxide layer structure more stable and complete, and improving the oxidation resistance of the coating.

[0045] 3. The multilayer structure coating provided by the present invention combines the dual advantages of radiation resistance and high temperature oxidation resistance, exhibits good comprehensive protection performance, and can provide effective protection for nuclear fuel cladding tubes in complex and harsh reactor environments.

[0046] 4. The present invention uses magnetron sputtering to deposit the Cr layer and the Cr-Al-Si-N layer, which can accurately control the composition and structure of the coating and ensure high quality and high efficiency production of the coating.

[0047] 5. The present invention applies an improved multi-layer coating to the surface of the zirconium alloy cladding tube, which can improve the ability of the traditional coating to resist high-temperature water vapor oxidation after irradiation. On the one hand, it can significantly extend the service life of the fuel cladding tube, and on the other hand, it can provide nuclear power unit personnel with longer accident response time under accident conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 A schematic diagram of the structure of a multi-layer Cr-based protective coating provided by the present invention;

[0049] Figure 2 This is a cross-sectional morphology diagram of the Cr-based protective coating prepared in Example 1 of the present invention;

[0050] Figure 3 This is a cross-sectional morphology diagram of the Cr-based protective coating prepared in Example 2 of the present invention;

[0051] Figure 4 The cross-sectional morphology and corresponding element surface distribution diagram of the Cr-based protective coating prepared in Example 2 of the present invention after ion irradiation and oxidation in high-temperature water vapor at 1200° C. for 10 hours;

[0052] Figure 5 This is a cross-sectional morphology diagram of the Cr-based protective coating prepared in Example 3 of the present invention;

[0053] Figure 6 This is a cross-sectional morphology diagram of the Cr-based protective coating prepared in Example 4 of the present invention;

[0054] Figure 7 This is a cross-sectional morphology diagram of the Cr-based protective coating prepared in Example 5 of the present invention;

[0055] Figure 8 This is a transmission electron microscopic image of the Cr-Al-Si-N layer in the Cr-based protective coating prepared in Example 5 of the present invention, showing a morphology of dispersed nanocrystals in dense amorphous materials;

[0056] Fig. 9 This is a cross-sectional morphology diagram and corresponding element surface distribution diagram of the Cr-based single-layer protective coating prepared in Comparative Example 1 after ion irradiation and oxidation in high-temperature water vapor at 1200°C for 1 hour. DETAILED DESCRIPTION

[0057] The technical scheme of the present invention is further described below by specific examples and accompanying drawings. It should be understood that the specific examples described herein are only used to help understand the present invention and are not intended for specific limitations of the present invention. The accompanying drawings used herein are only for better illustrating the disclosure of the present invention and do not have a limiting effect on the scope of protection. If not otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used raw materials in the art, and the methods used in the embodiments are all conventional methods in the art.

[0058] The coatings in the following examples and comparative examples were prepared on a single-chamber dual-target co-sputtering magnetron coating device.

[0059] Table 1 and Table 2 respectively show the preparation process parameters of the Cr layer and the preparation process parameters of the Cr-Al-Si-N layer in each embodiment and comparative example.

[0060] Table 1 Preparation process parameters of Cr layer

[0061]

[0062] Table 2 Preparation process parameters of Cr-Al-Si-N layer

[0063]

[0064] Cr a Al b Si 1-a-b The purity of the target and the Cr target was 99.95%.

[0065] The structural characterization and performance testing of the coatings in the following embodiments and comparative examples were all measured according to the following methods:

[0066] 1. Physical phase of coating

[0067] The physical phases of the coatings of each example were analyzed using a Brucker AXSD8 Advance X-ray diffractometer (XRD), and the coatings in the prepared state and after irradiation / high-temperature steam oxidation were characterized. The physical phases of the prepared coatings and the physical phases of the oxidation products formed after high-temperature steam oxidation were determined, and the high-temperature steam oxidation resistance of the coatings was judged based on the physical phases.

[0068] 2. Morphology and composition of coating

[0069] The ZEISS G300 scanning electron microscope (SEM) and its equipped X-ray energy dispersive spectrometer (EDS) were used to observe the structure of the prepared coating and analyze its composition and element distribution. The cross-sectional morphology of the coating after high-temperature steam oxidation was observed and the composition was measured to determine the morphological characteristics and oxidation products of the coating after steam oxidation, and then the high-temperature steam oxidation resistance of the coating was qualitatively judged based on the morphological characteristics.

[0070] 3. Ion irradiation of coating

[0071] The ion irradiation experiments of each embodiment were conducted using the Lanzhou Heavy Ion Research Facility (HIRFL) of the Lanzhou Heavy Ion Accelerator National Laboratory of the Institute of Modern Physics, Chinese Academy of Sciences, and the ions used were Xe with an energy of 5 MeV. 20+ ions, the irradiation dose is 1.0×10 15 ions / cm 2 .

[0072] 4. High temperature steam oxidation of coating

[0073] The high-temperature steam oxidation experiment was carried out in a tubular furnace with a steam generator at one end, and the temperature of the tubular furnace was set to 1200°C. After the temperature of the furnace tube reached the set temperature, the steam generator was turned on, and steam with a uniform flow rate was introduced into the furnace tube. When the steam flow rate was stable, the sample was sent from the open end of the furnace tube to the center of the furnace tube, and the port was sealed with a corundum furnace plug for insulation. After continuous oxidation for different times, the sample was slowly taken out and cooled to room temperature in the air. After the sample was cooled, it was sealed with epoxy resin, and the cross section was polished. Its cross-sectional morphology and composition were analyzed under SEM to evaluate the high-temperature steam oxidation resistance of the coating.

[0074] 5. Coating hardness test

[0075] The hardness test was carried out using a Brucker TI980 nanoindenter and a Berkovich diamond indenter. In order to eliminate the influence of substrate effect and surface roughness, the maximum indentation depth was 1 / 10 of the coating thickness. Ten test points were measured for each sample and the average value was taken to avoid the randomness of the experimental results.

[0076] Figure 1 A schematic diagram of the structure of a multi-layer Cr-based protective coating provided by the present invention, comprising Figure 1 It can be seen that each periodic layer λ is composed of a Cr layer and a Cr-Al-Si-N layer, and n periodic layers λ constitute the multi-layered Cr-based protective coating of the present invention.

[0077] The zirconium alloy substrates in the following examples and comparative examples were mechanically polished, chemically cleaned, and plasma glow cleaned before installation.

[0078] The mechanical polishing process is as follows: select sandpapers of 200 mesh, 1000 mesh, 2500 mesh, 5000 mesh, 8000 mesh and polishing paste of 10000 mesh in sequence, and use a metallographic polishing machine to polish the substrate coating surface to a mirror surface with a roughness Ra of 10 nm.

[0079] The chemical cleaning is as follows: the substrate is placed in acetone and anhydrous ethanol in turn and ultrasonicated for 5 minutes each, and then dried in a drying oven at a temperature of 780°C for 2 hours, or blown dry with high-purity N2 with a purity of 99.99%.

[0080] Plasma glow cleaning is as follows: fix the chemically cleaned substrate on a rotatable sample holder in a vacuum chamber. Pump down the background vacuum to 1×10 -4 After 1 Pa, Ar gas is introduced and the working gas pressure is maintained at 1 Pa. Then the power is turned on and a negative bias is applied to the substrate. The plasma generated by the Ar gas ionization is used to sputter-etch the substrate for 10 minutes, so that the water molecules, gas molecules or dust particles adsorbed on the surface of the substrate are completely bombarded and cleaned.

[0081] Example 1

[0082] Install the target material and the pretreated zirconium alloy substrate; pump the background vacuum of the deposition chamber to 1.0×10 -5 Pa, start heating the sample stage, and keep it warm for 2 hours when the temperature rises to the target temperature. Then, deposit the Cr layer and the Cr-Al-Si-N layer according to the requirements. The Cr layer is deposited using the parameter No. 1-1, and a RF-assisted DC power supply is applied to the Cr target. Ar gas is introduced, the gas pressure is adjusted to 0.7 Pa, and the sputtering negative bias voltage is controlled to deposit the Cr layer. The Cr-Al-Si-N layer is deposited using the parameter No. 2-1, and a RF power supply is applied to the Cr target, and a DC power supply is applied to the Cr target. a Al b Si 1-a-b Then, a mixed gas of Ar gas and N2 is introduced onto the target, and the flow ratio of the two is controlled to be Ar / N2=Q, the gas pressure is adjusted to 0.7Pa, and a Cr-Al-Si-N layer is deposited; Cr layer and Cr-Al-Si-N layer are deposited alternately in sequence.

[0083] like Figure 2 As shown in the figure, the prepared Cr coating has a loose columnar crystal structure, the columnar crystal width is about 150nm, and the density is 6.2g / cm 3 , the composition of Cr-Al-Si-N coating is Cr 37.2 Al 20.6 Si 5.0 N 37.2 The coating is a two-phase composite structure of dispersed nanocrystals in dense amorphous materials. The size of the nanocrystals is 5-10nm and the density is 6.8g / cm 3 . The coating thickness in one periodic layer λ is 1μm (the Cr coating thickness is 750nm, and the Cr-Al-Si-N coating thickness is 250nm), the total coating thickness is 4μm, and the coating has n=4 periodic layers. The hardness of the coating was measured to be 11.2GPa. After ion irradiation and oxidation in high-temperature water vapor at 1200℃ for 6 hours, it was found that the zirconium alloy substrate was not oxidized, indicating that the coating played a protective role. A 150-320nm thick uniform, dense and continuous α-Al2O3 / Cr2O3 double-layer oxide layer was found at the top of the coating. Among them, α-Al2O3 has a more negative Gibbs free energy and is the most thermodynamically stable. It can inhibit the further diffusion of oxygen and corrosive media, prevent further oxidation of residual coatings and zirconium alloy substrates, and play an excellent protective role.

[0084] Example 2

[0085] Install the target material and the pretreated zirconium alloy substrate; pump the background vacuum of the deposition chamber to 1.0×10 -5Pa, start heating the sample stage, and keep it warm for 2 hours when the temperature rises to the target temperature. Then, deposit the Cr layer and the Cr-Al-Si-N layer according to the requirements. The Cr layer is deposited using the parameters No. 1-2, and a RF-assisted DC power supply is applied to the Cr target. Ar gas is introduced, the gas pressure is adjusted to 0.7 Pa, and the sputtering negative bias voltage is controlled to deposit the Cr layer. The Cr-Al-Si-N layer is deposited using the parameters No. 2-2, and a RF power supply is applied to the Cr target, and a DC power supply is applied to the Cr target. a Al b Si 1-a-b Then, a mixed gas of Ar gas and N2 is introduced onto the target, and the flow ratio of the two is controlled to be Ar / N2=Q, the gas pressure is adjusted to 0.7Pa, and a Cr-Al-Si-N layer is deposited; Cr layer and Cr-Al-Si-N layer are deposited alternately in sequence.

[0086] like Figure 3 As shown in the figure, the prepared Cr coating has a loose columnar crystal structure, the columnar crystal width is about 30-50nm, and the density is 6.8g / cm 3 The composition of the prepared Cr-Al-Si-N coating is Cr 36.4 Al 26.9 Si 4.5 N 32.2 The coating is a two-phase composite structure of dispersed nanocrystals in dense amorphous materials. The size of the nanocrystals is 5-10nm and the density is 7.2g / cm 3 The coating thickness in one periodic layer λ is 1.2μm (the Cr coating thickness is 1000nm, and the Cr-Al-Si-N coating thickness is 200nm), the total coating thickness is 10.8μm, and the coating has n=9 periodic layers. The hardness of the coating was measured to be 13.7GPa. After ion irradiation and oxidation in high-temperature water vapor at 1200℃ for 6 hours, its morphology is as follows Figure 4 As shown in the figure, the zirconium alloy substrate is not oxidized, indicating that the coating plays a protective role, and there are obvious holes in the coating after oxidation. Secondly, it can be found that there is a 5μm thick uniform, dense and continuous Al2O3 / Cr2O3 oxide layer at the top of the coating. The presence of this oxide layer can inhibit the further diffusion of oxidation and corrosive media, prevent further oxidation of the residual coating and the zirconium alloy substrate, and play an excellent protective role.

[0087] Example 3

[0088] Install the target material and the pretreated zirconium alloy substrate; pump the background vacuum of the deposition chamber to 1.0×10 -5Pa, start heating the sample stage, and keep it warm for 2 hours when the temperature rises to the target temperature. Then, deposit the Cr layer and the Cr-Al-Si-N layer according to the requirements. The Cr layer is deposited using the parameters No. 1-3, and a RF-assisted DC power supply is applied to the Cr target. Ar gas is introduced, the gas pressure is adjusted to 0.7 Pa, and the sputtering negative bias voltage is controlled to deposit the Cr layer. The Cr-Al-Si-N layer is deposited using the parameters No. 2-3, and a RF power supply is applied to the Cr target, and a DC power supply is applied to the Cr target. a Al b Si 1-a-b Then, a mixed gas of Ar gas and N2 is introduced onto the target, and the flow ratio of the two is controlled to be Ar / N2=Q, the gas pressure is adjusted to 0.7Pa, and a Cr-Al-Si-N layer is deposited; Cr layer and Cr-Al-Si-N layer are deposited alternately in sequence.

[0089] like Figure 5 As shown in the figure, the prepared Cr coating has a dense columnar crystal structure, the columnar crystal width is about 70-80nm, and the density is 6.7g / cm 3 The composition of the prepared Cr-Al-Si-N coating is Cr 42.9 Al 26.0 Si 4.8 N 26.3 The coating is a two-phase composite structure of dispersed nanocrystals in dense amorphous materials. The size of the nanocrystals is 5-10nm and the density is 6.8g / cm 3 . The coating thickness in one periodic layer λ is 500nm (the Cr coating thickness is 250nm, and the Cr-Al-Si-N coating thickness is 250nm), the total coating thickness is 3μm, and the coating has n=6 periodic layers. The hardness of the coating was measured to be 14.1GPa. After ion irradiation and oxidation in high-temperature water vapor at 1200℃ for 6 hours, it was found that the zirconium alloy substrate was not oxidized, indicating that the coating played a protective role, and there were obvious holes in the coating after oxidation. Secondly, it can be found that there is a 200-400nm thick uniform, dense and continuous α-Al2O3 / Cr2O3 double-layer oxide layer at the top of the coating. The presence of this oxide layer can inhibit the further diffusion of oxygen and corrosive media, prevent further oxidation of the residual coating and the zirconium alloy substrate, and play an excellent protective role.

[0090] Example 4

[0091] Install the target material and the pretreated zirconium alloy substrate; pump the background vacuum of the deposition chamber to 1.0×10 -5Pa, start heating the sample stage, and keep it warm for 2 hours when the temperature rises to the target temperature. Then, deposit the Cr layer and the Cr-Al-Si-N layer according to the requirements. The Cr layer is deposited using the parameters No. 1-4, and a RF-assisted DC power supply is applied to the Cr target. Ar gas is introduced, the gas pressure is adjusted to 0.7 Pa, and the sputtering negative bias voltage is controlled to deposit the Cr layer. The Cr-Al-Si-N layer is deposited using the parameters No. 2-4, and a RF power supply is applied to the Cr target, and a DC power supply is applied to the Cr target. a Al b Si 1-a-b Then, a mixed gas of Ar gas and N2 is introduced onto the target, and the flow ratio of the two is controlled to be Ar / N2=Q, the gas pressure is adjusted to 0.7Pa, and a Cr-Al-Si-N layer is deposited; Cr layer and Cr-Al-Si-N layer are deposited alternately in sequence.

[0092] like Figure 6 As shown in the figure, the prepared Cr coating has a dense columnar crystal structure, the columnar crystal width is about 50-60nm, and the density is 6.8g / cm 3 The composition of the prepared Cr-Al-Si-N coating is Cr 33.7 Al 24.6 Si 4.5 N 37.2 The coating is a two-phase composite structure of dispersed nanocrystals in dense amorphous materials. The size of the nanocrystals is 5-10nm and the density is 7.1g / cm 3 . The coating thickness in one periodic layer λ is 300nm (the Cr coating thickness is 200nm, and the Cr-Al-Si-N coating thickness is 100nm), the total coating thickness is 3.3μm, and the coating has n=11 periodic layers. The hardness of the coating was measured to be 13.5GPa. After ion irradiation and oxidation in high-temperature water vapor at 1200℃ for 6 hours, it was found that the zirconium alloy substrate was not oxidized, indicating that the coating played a protective role, and there were obvious holes in the coating after oxidation. Secondly, it can be found that there is a 100-200nm thick uniform, dense and continuous α-Al2O3 / Cr2O3 double-layer oxide layer at the top of the coating. The presence of this oxide layer can inhibit the further diffusion of oxygen and corrosive media, prevent further oxidation of the residual coating and the zirconium alloy substrate, and play an excellent protective role.

[0093] Example 5

[0094] Install the target material and the pretreated zirconium alloy substrate; pump the background vacuum of the deposition chamber to 1.0×10 -5Pa, start heating the sample stage, and keep it warm for 2 hours when the temperature rises to the target temperature. Then, deposit the Cr layer and the Cr-Al-Si-N layer according to the requirements. The Cr layer is deposited using the parameters No. 1-5, and a RF-assisted DC power supply is applied to the Cr target. Ar gas is introduced, the gas pressure is adjusted to 0.7 Pa, and the sputtering negative bias voltage is controlled to deposit the Cr layer. The Cr-Al-Si-N layer is deposited using the parameters No. 2-5, and a RF power supply is applied to the Cr target, and a DC power supply is applied to the Cr target. a Al b Si 1-a-b Then, a mixed gas of Ar gas and N2 is introduced onto the target, and the flow ratio of the two is controlled to be Ar / N2=Q, the gas pressure is adjusted to 0.7Pa, and a Cr-Al-Si-N layer is deposited; Cr layer and Cr-Al-Si-N layer are deposited alternately in sequence.

[0095] like Figure 7 As shown in the figure, the prepared Cr coating has a dense columnar crystal structure, the columnar crystal width is about 100nm, and the density is 6.5g / cm 3 The composition of the prepared Cr-Al-Si-N coating is Cr 38.0 Al 26.8 Si 5.2 N 30 ,from Figure 8 It can be seen that the Cr-Al-Si-N layer is a two-phase composite structure with dispersed nanocrystals in dense amorphous phase. The size of the nanocrystals is 5-10nm and the density is 6.6g / cm 3 . The coating thickness in one periodic layer λ is 1.1μm (the Cr coating thickness is 800nm, and the Cr-Al-Si-N coating thickness is 300nm), the total coating thickness is 4.4μm, and the coating has n=4 periodic layers. The hardness of the coating was measured to be 13.4GPa. After ion irradiation and oxidation in high-temperature water vapor at 1200℃ for 6 hours, it was found that the zirconium alloy substrate was not oxidized, indicating that the coating played a protective role. A uniform, dense and continuous α-Al2O3 oxide layer with a thickness of 100 to 300nm was found at the top of the coating, which can inhibit the further diffusion of oxygen and corrosive media, prevent further oxidation of the residual coating and the zirconium alloy substrate, and play an excellent protective role.

[0096] Comparative Example 1

[0097] Install the target material and the pretreated zirconium alloy substrate; pump the background vacuum of the deposition chamber to 1.0×10 -5Pa, start heating the sample stage, and when the temperature reaches the target temperature and keeps warm for 2 hours, use parameters numbered 1-5 to deposit the Cr layer, apply RF-assisted DC power to the Cr target, introduce Ar gas, adjust the gas pressure to 0.7 Pa, control the sputtering negative bias, and adjust the deposition time to obtain a Cr coating thickness of 9 μm.

[0098] The Cr coating structure is a dense columnar crystal structure with a columnar crystal width of about 70 to 80 nm. There are no through-holes, cracks, or other defects along the coating growth direction. The hardness of the coating is 4 GPa after being irradiated with ions and oxidized in high-temperature water vapor at 1200 ° C for 1 hour. Fig. 9 As shown, the zirconium substrate has been oxidized, indicating that the coating has failed at this time, and there are a large number of obvious holes in the coating after oxidation. Although there is a Cr2O3 oxide layer on the top of the coating, the oxide layer is discontinuous and bulges, and there are many pores in the residual coating, which cannot play a protective role.

[0099] Comparative Example 2

[0100] Install the target material and the pretreated zirconium alloy substrate; pump the background vacuum of the deposition chamber to 1.0×10 -5 Pa, start heating the sample stage, and keep it warm for 2 hours when the temperature rises to the target temperature. Then, deposit the Cr layer and the Cr-Al-Si-N layer according to the requirements. Among them, the Cr layer is deposited using the parameters No. 1-5, and the RF-assisted DC power supply is applied to the Cr target, Ar gas is introduced, the gas pressure is adjusted to 0.7 Pa, and the sputtering negative bias voltage is controlled to deposit the Cr layer; the Cr-Al-Si-N layer is deposited using the parameters No. 2-6, and the RF power supply is applied to the Cr target, and the DC power supply is applied to the Cr target. a Al b Si 1-a-b Then, a mixed gas of Ar gas and N2 is introduced onto the target, and the flow ratio of the two is controlled to be Ar / N2=Q, the gas pressure is adjusted to 0.7Pa, and a Cr-Al-Si-N layer is deposited; Cr layer and Cr-Al-Si-N layer are deposited alternately in sequence.

[0101] The prepared Cr coating has a dense columnar crystal structure with a columnar crystal width of about 100nm and a density of 6.5g / cm 3 The composition of the prepared Cr-Al-Si-N coating is Cr 53 Al 16.6 Si 5.2 N 25.2 It is a two-phase composite structure of dispersed nanocrystals in dense amorphous materials. The size of the nanocrystals is 5-10nm and the density is 6.8g / cm 3. The coating thickness in one periodic layer λ is 1.1μm (the Cr coating thickness is 800nm, and the Cr-Al-Si-N coating thickness is 300nm), the total coating thickness is 4.4μm, and the coating has n=4 periodic layers. The hardness of the coating was measured to be 12.6GPa. After ion irradiation and oxidation in high-temperature water vapor at 1200℃ for 6 hours, it was found that the zirconium alloy substrate was oxidized, indicating that the coating had failed at this time. After ion irradiation, the coating's resistance to high-temperature water vapor oxidation was reduced, and it could not provide protection for the zirconium alloy substrate after ion irradiation.

[0102] Comparative Example 3

[0103] Install the target material and the pretreated zirconium alloy substrate; pump the background vacuum of the deposition chamber to 1.0×10 -5 Pa, start heating the sample stage, keep the temperature for 2 hours after the temperature rises to the target temperature, and then deposit the Cr layer and the Cr-Al-Si-N layer according to the requirements, wherein the Cr layer is deposited using the parameters numbered 1-5, a RF-assisted DC power supply is applied to the Cr target, Ar gas is introduced, the gas pressure is adjusted to 0.7 Pa, and the sputtering negative bias voltage is controlled to deposit the Cr layer; the Cr-Al-Si-N layer is deposited using the parameters numbered 2-7, a RF power supply is applied to the Cr target, and a DC power supply is applied to the Cr target. a Al b Si 1-a-b Then, a mixed gas of Ar gas and N2 is introduced onto the target, and the flow ratio of the two is controlled to be Ar / N2=Q, the gas pressure is adjusted to 0.7Pa, and a Cr-Al-Si-N layer is deposited; Cr layer and Cr-Al-Si-N layer are deposited alternately in sequence.

[0104] The prepared Cr coating has a dense columnar crystal structure with a columnar crystal width of about 100nm and a density of 6.5g / cm 3 The composition of the prepared Cr-Al-Si-N coating is Cr 29.6 Al 28.5 Si 6.8 N 35.1 It is a two-phase composite structure of dispersed nanocrystals in dense amorphous materials. The size of the nanocrystals is 5-10nm and the density is 6.7g / cm 3. The coating thickness in one periodic layer λ is 1.1μm (Cr coating thickness is 800nm, Cr-Al-Si-N coating thickness is 300nm), the total coating thickness is 4.4μm, and the coating has n=4 periodic layers. The hardness of the coating was measured to be 13.7GPa. After ion irradiation and oxidation in high-temperature water vapor at 1200℃ for 5 hours, it was found that the zirconium alloy substrate was oxidized, indicating that the coating had failed at this time. After ion irradiation, the high-temperature water vapor oxidation resistance of the coating was greatly reduced, and it could not provide protection for the zirconium alloy substrate after ion irradiation.

[0105] Comparative Example 4

[0106] Install the target material and the pretreated zirconium alloy substrate; pump the background vacuum of the deposition chamber to 1.0×10 -5 Pa, start heating the sample stage, and keep it warm for 2 hours when the temperature rises to the target temperature. Then, deposit the Cr layer and the Cr-Al-Si-N layer according to the requirements. The Cr layer is deposited using the parameters No. 1-5, and a RF-assisted DC power supply is applied to the Cr target. Ar gas is introduced, the gas pressure is adjusted to 0.7 Pa, and the sputtering negative bias voltage is controlled to deposit the Cr layer. The Cr-Al-Si-N layer is deposited using the parameters No. 2-8, and a RF power supply is applied to the Cr target, and a DC power supply is applied to the Cr target. a Al b Si 1-a-b Then, a mixed gas of Ar gas and N2 is introduced onto the target, and the flow ratio of the two is controlled to be Ar / N2=Q, the gas pressure is adjusted to 0.7Pa, and a Cr-Al-Si-N layer is deposited; Cr layer and Cr-Al-Si-N layer are deposited alternately in sequence.

[0107] The prepared Cr coating has a dense columnar crystal structure with a columnar crystal width of about 100nm and a density of 6.5g / cm 3 The composition of the prepared Cr-Al-Si-N coating is Cr 25.7 Al 53.5 Si 4.9 N 22.9 , which is a dense amorphous structure without nanocrystals and has a density of 6.7g / cm 3 . The coating thickness in one periodic layer λ is 1.1μm (Cr coating thickness is 800nm, Cr-Al-Si-N coating thickness is 300nm), the total coating thickness is 4.4μm, and the coating has n=4 periodic layers. The hardness of the coating was measured to be 14.2GPa. After ion irradiation and oxidation in high-temperature water vapor at 1200℃ for 4 hours, it was found that the zirconium alloy substrate was oxidized, indicating that the coating had failed at this time. After ion irradiation, the high-temperature water vapor oxidation resistance of the coating was greatly reduced, and it could not provide protection for the zirconium alloy substrate after ion irradiation.

[0108] The various aspects, embodiments, and features of the present invention should be considered to be illustrative in all aspects and not limiting of the present invention, the scope of which is defined solely by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.

[0109] In the preparation method of the present invention, the order of each step is not limited to the order listed. For those skilled in the art, without creative work, the order of each step is also within the protection scope of the present invention. In addition, two or more steps or actions can be performed simultaneously.

[0110] Finally, it should be noted that the specific embodiments described herein are merely examples of the present invention, and are not intended to limit the implementation methods of the present invention. A person skilled in the art of the present invention may make various modifications or supplements to the specific embodiments described, or replace them in a similar manner. It is not necessary and impossible to provide all examples of all implementation methods here. However, these obvious changes or modifications derived from the essential spirit of the present invention still fall within the scope of protection of the present invention, and interpreting them as any additional limitation is contrary to the spirit of the present invention.

Claims

1. A multi-layer Cr-based protective coating, characterized in that: The Cr-based protective coating is a plurality of periodic layers, each of which is composed of a Cr layer and a Cr-Al-Si-N layer; the element composition of the Cr-Al-Si-N layer is Cr x Al y Si z N 1-x-y-z , where x, y, and z are atomic ratios, 0.33≤x≤0.43, 0.20≤y≤0.27, and 0.04≤z≤0.08; the Cr-Al-Si-N layer is a two-phase composite structure of dispersed nanocrystals in dense amorphous materials.

2. The multi-layer Cr-based protective coating according to claim 1, characterized in that: The Cr-based protective coating is 1 to 100 periodic layers; and / or, in each periodic layer, the thickness of the Cr-Al-Si-N layer is 100 to 500 nm; And / or, in each periodic layer, the thickness ratio of the Cr layer to the Cr-Al-Si-N layer is 1 to 5:

1.

3. The multi-layered Cr-based protective coating according to claim 1, characterized in that: The growth structure of the Cr layer is a single-phase structure of columnar crystals, and the width of the columnar crystals is 20 to 500 nm; And / or, the size of the nanocrystals in the Cr-Al-Si-N layer is 1-50 nm.

4. The multi-layered Cr-based protective coating according to claim 1, characterized in that: The density of the Cr layer is 6.0-7.0 g / cm 3 The density of the Cr-Al-Si-N layer is 6.2-7.5 g / cm 3 .

5. The method for preparing a multi-layer Cr-based protective coating according to claim 1, characterized in that: The following steps are involved: (1) Install the target and substrate; (2) evacuating the deposition chamber and heating the substrate; (3) Set the experimental parameters and alternately deposit Cr layers and Cr-Al-Si-N layers on the substrate.

6. The preparation method according to claim 5, characterized in that: Target materials include Cr target and Cr a Al b Si 1-a-b target, wherein 0.45≤a≤0.60, 0.25≤b≤0.32, a and b are both atomic ratios; And / or, the vacuuming refers to pumping the background vacuum of the deposition chamber to less than 1.0×10 -4 Pa, the substrate heating temperature is 450 ~ 550 ℃.

7. The preparation method according to claim 5, characterized in that: In step (3), the process of depositing the Cr layer includes: applying a radio frequency-assisted direct current power supply to the Cr target, introducing Ar gas, adjusting the gas pressure to 0.1-2 Pa, and controlling the sputtering negative bias voltage to 0-30 V, and then depositing the Cr layer; And / or, the process of depositing the Cr-Al-Si-N layer comprises: applying a radio frequency power supply to the Cr target, applying a direct current power supply to the Cr a Al b Si 1-a-b Then, a mixed gas of Ar and N2 is introduced onto the target, the gas pressure is adjusted to 0.1-2 Pa, and the sputtering negative bias voltage is controlled to 5-10 V, and then the Cr-Al-Si-N layer is deposited.

8. The preparation method according to claim 7, characterized in that: In the process of depositing the Cr layer, the power density of the Cr target is 6.4-8.7 W / cm 2 ; And / or, in the process of depositing the Cr-Al-Si-N layer, the power density of the Cr target is 5.6-7.5 W / cm 2 ,Cr a Al b Si 1-a-b The power density of the target is 7.2~9.6W / cm 2 ; And / or, in the process of depositing the Cr—Al—Si—N layer, the flow ratio of Ar to N2 is 8 to 13:

1.

9. A zirconium alloy workpiece, characterized in that: The invention comprises a zirconium alloy substrate and a Cr-based protective coating having a multi-layer structure as claimed in claim 1 and located on the surface of the zirconium alloy substrate.

10. The zirconium alloy workpiece according to claim 9, characterized in that: The zirconium alloy workpiece is heated to 5 MeV Xe 20+ Ion, irradiation dose is 1.0×10 15 ions / cm 2 After irradiation treatment, the zirconium alloy matrix did not show oxidation phenomenon when oxidized in water vapor at 1200°C for 6 to 10 hours.

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