Zirconium alloy cladding high-temperature oxidation resistant composite coating for nuclear and preparation method of zirconium alloy cladding high-temperature oxidation resistant composite coating

Abstract

The invention discloses a nuclear zirconium alloy cladding high-temperature oxidation resistant composite coating and a preparation method thereof, and belongs to the technical field of nuclear zirconium alloy coatings. According to the preparation method disclosed by the invention, through component gradient structure design, Cr ion pretreatment activation, deposition of a pure Cr inner coating, deposition of a Cr70Al30 intermediate coating and deposition of a Cr50Al50 outer coating are sequentially carried out on the surface of a nuclear zirconium alloy cladding, and the Cr-Cr70Al30-Cr50Al50 composite coating zirconium alloy cladding with a three-layer structure is obtained. According to the method, outward migration of the Al element is effectively limited while the excellent anti-oxidation characteristics of the Cr and Al elements are fully utilized, the coating has the excellent high-temperature oxidation performance, and the requirement for the service performance of the surface coating of the zirconium alloy cladding at the extremely high temperature is met.

Description

Technical Field

[0001] The present invention belongs to the technical field of nuclear zirconium alloy coatings, and particularly relates to a high-temperature oxidation-resistant composite coating for nuclear zirconium alloy cladding and a preparation method thereof. Background Art

[0002] Due to its low thermal neutron absorption cross-section and good corrosion resistance, zirconium alloy is widely used as the cladding material for fuel rods. Widely used zirconium alloys include Zr-2 and Zr-4, as well as later improved Zr-Sn-Nb alloys such as ZIRLO. These alloys show stability in high-temperature and high-pressure water environments, but under accident conditions, they will undergo an oxidation exothermic reaction, leading to the risk of hydrogen explosion. This problem has been paid more attention after the Fukushima accident. Therefore, it is necessary to consider methods to inhibit the reaction between the cladding and high-temperature steam and improve the safety margin. The accident-tolerant coating for zirconium alloy can not only not change the existing reactor structure and fuel system, but also directly improve the accident tolerance of the cladding tube under loss-of-coolant conditions, which is one of the most popular research directions among many ATF technologies at present.

[0003] The Cr coating has characteristics such as high melting point, good thermal conductivity, and similar thermal coefficient to Zr, and is one of the most widely studied ATF coating materials at present. However, in an oxidation environment above 1000 °C, the Cr2O3 antioxidant layer formed on the surface of the metal Cr coating will be further oxidized into volatile substances (such as CrO3, CrO2(OH), etc.), thereby reducing its utilization rate. Compared with metal Cr, metal Al also has excellent antioxidant properties, and its oxide α-Al2O3 shows a lower growth rate and better thermodynamic stability in high-temperature steam. However, Al is extremely easy to form oxides with different structures below 1000 °C, and there is also an obvious outward diffusion problem at high temperatures, which has an adverse effect on its oxidation behavior. How to give full play to the excellent antioxidant characteristics of Cr and Al elements while restricting the weakening of oxidation performance caused by the migration of Al elements is the key to improving the service performance of the accident-tolerant CrAl coating. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-temperature oxidation-resistant composite coating for nuclear zirconium alloy cladding and a preparation method thereof to solve the technical problem of poor service performance of the existing CrAl coating.

[0005] To achieve the above object, the present invention adopts the following technical solutions: The present invention discloses a preparation method of a high-temperature oxidation-resistant composite coating for nuclear zirconium alloy cladding, including the following steps: Perform surface pretreatment on the nuclear zirconium alloy cladding, and then perform Cr ion pretreatment activation on the surface to obtain the pretreated nuclear zirconium alloy cladding; Deposit a pure Cr inner coating on the surface of the pre-treated zirconium alloy cladding for nuclear use to obtain a zirconium alloy cladding with a Cr coating; Deposit Cr 70 Al 30 intermediate coating on the surface of the zirconium alloy cladding with a Cr coating to obtain a zirconium alloy cladding with a double-layer structure of Cr-Cr 70 Al 30 composite coating; Deposit Cr 70 Al 30 on the surface of the zirconium alloy cladding with a double-layer structure of Cr-Cr 50 Al 50 outer coating to obtain a high-temperature oxidation-resistant composite coating.

[0006] Furthermore, the surface pretreatment includes grinding, polishing, pickling treatment, cleaning, and drying treatment carried out in sequence; the pickling treatment is carried out by soaking in pickling solution; the pickling solution is a mixture of nitric acid, hydrofluoric acid, and water with a volume ratio of 45%:8%:47%; the time of pickling treatment is 40 - 60 s; The cleaning is carried out by cleaning with ethanol in an ultrasonic cleaner for 10 - 20 min.

[0007] Furthermore, the specific steps for Cr ion pretreatment activation are as follows: Place the pre-treated zirconium alloy cladding for nuclear use in the vacuum chamber of a vapor deposition device, introduce argon and adjust the vacuum degree, and perform Cr ion pretreatment activation on its surface using Cr ions; The pressure in the vacuum chamber is 0.01 - 0.1 Pa; the Cr ions are generated by discharging a Cr target source, the applied voltage is 800 - 1000 V, and the pretreatment activation temperature is 150 - 350 °C.

[0008] Furthermore, the specific steps for depositing a pure Cr inner coating on the surface of the pre-treated zirconium alloy cladding for nuclear use are as follows: Deposit a pure Cr inner coating on the pre-treated zirconium alloy cladding for nuclear use using a vapor deposition device. The pressure during the deposition process is 0.5 - 1.5 Pa, the temperature is 250 - 350 °C, and the deposition time is 4 - 6 h; the Cr coating is deposited by Cr ions generated by discharging a Cr target source, and the loading current density of the Cr target source is 0.5 - 1.0 A / cm 2 , and the applied bias voltage is - 100 - 150 V.

[0009] Furthermore, the thickness of the pure Cr inner coating exceeds 7.0 μm.

[0010] Furthermore, deposit Cr 70 Al30 The specific steps of the intermediate coating are as follows: Continuously deposit Cr on the zirconium alloy cladding with a Cr coating using a vapor deposition device 70 Al 30 Intermediate coating, the pressure during the deposition process is 0.5 - 1.5 Pa, the temperature is 250 - 350 °C, and the deposition time is 3 - 5 h; the Cr 70 Al 30 Intermediate layer is deposited by Cr 70 Al 30 ions generated by the discharge of the Cr and Al target sources, and the loading current density of the Cr 70 Al 30 target source is 0.5 - 1.0 A / cm 2 , and the loading bias voltage is -100 - -150 V.

[0011] Furthermore, the deposition thickness of the Cr 70 Al 30 intermediate coating exceeds 10.0 μm.

[0012] Furthermore, on the surface of the zirconium alloy cladding with a double-layer Cr-Cr 70 Al 30 composite coating, deposit Cr 50 Al 50 The specific steps of the outer coating are as follows: On the zirconium alloy cladding with a double-layer Cr-Cr 70 Al 30 composite coating, continuously deposit Cr 50 Al 50 Outer coating, the pressure during the deposition process is 0.5 - 1.5 Pa, the temperature is 250 - 350 °C, and the deposition time is 3 - 5 h; the Cr 50 Al 50 Outer coating is deposited by Cr 50 Al 50 ions generated by the discharge of the Cr and Al target sources, and the loading current density of the Cr 50 Al 50 target source is 0.5 - 1.0 A / cm 2 , and the loading bias voltage is -100 - -150 V.

[0013] Furthermore, the deposition thickness of the Cr 50 Al 50 outer coating exceeds 10.0 μm.

[0014] The present invention also discloses a high-temperature oxidation-resistant composite coating for nuclear-use zirconium alloy cladding prepared by the above preparation method.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a preparation method of a high-temperature oxidation-resistant composite coating for nuclear zirconium alloy cladding. Through the design of a composition gradient structure, Cr ion pretreatment activation, deposition of a pure Cr inner coating, deposition of Cr 70 Al 30 intermediate coating, and deposition of Cr 50 Al 50 outer coating are successively carried out on the surface of the nuclear zirconium alloy cladding to obtain a Cr-Cr 70 Al 30 -Cr 50 Al 50 composite coating zirconium alloy cladding (high-temperature oxidation-resistant composite coating for nuclear zirconium alloy cladding). On the one hand, the introduction of Al element improves the oxidation resistance of the coating. On the other hand, it effectively restricts the outward migration of Al element, thus improving the coating quality, reducing the thermal expansion stress between the coatings during the deposition process, avoiding quality problems such as coating cracking caused by deposition thermal stress, enhancing the overall consistency and structural compactness of the coating, weakening or even eliminating the internal interface of the coating, obtaining a zirconium alloy cladding composite coating with good interface quality, and meeting the requirements of the surface coating service performance of zirconium alloy cladding under extreme high temperature.

[0016] The present invention also discloses a high-temperature oxidation-resistant composite coating for nuclear zirconium alloy cladding prepared by the above preparation method. Through the design of a composition gradient structure, while making full use of the excellent oxidation resistance characteristics of Cr and Al elements, it effectively restricts the outward migration of Al element, and the coating has excellent high-temperature oxidation performance, meeting the requirements of the surface coating service performance of zirconium alloy cladding under extreme high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is the cross-sectional microstructure morphology diagram and line scan result of the Cr-Cr 70 Al 30 -Cr 50 Al 50 composite coating prepared in Example 1 of the present invention; Wherein: a - cross-sectional microstructure morphology diagram; b - line scan result; Figure 2 is the cross-sectional morphology diagram of the Cr-Cr 70 Al 30 -Cr 50 Al 50 composite coating after high-temperature oxidation at 1200 °C for 3 h prepared in Example 1 of the present invention; Figure 3 is the Cr-Cr 70 Al30 -Cr 50 Al 50 Cross-sectional morphology of the composite coating after high-temperature oxidation at 1200 °C for 3 h; Figure 4 This is the Cr-Cr prepared in Example 3 of the present invention 70 Al 30 -Cr 50 Al 50 Cross-sectional morphology of the composite coating after high-temperature oxidation at 1200 °C for 3 h; Figure 5 This is the cross-sectional microstructure morphology and line scan results of the pure Cr coating deposited on the surface of the nuclear-grade zirconium alloy cladding in Comparative Example 1 of the present invention. Detailed implementation manners

[0018] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art for the present invention. In case of conflict, the definition in this specification shall prevail.

[0019] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0020] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges shall be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values (including integers and fractions) within the range.

[0021] In this article, unless otherwise specified, the terms "comprising", "including", "containing", "having" or similar terms cover the meanings of "consisting of" and "consisting essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A consists only of a".

[0022] In this article, for the sake of brevity of description, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope described in this specification.

[0023] The present invention provides a method for preparing a high-temperature oxidation-resistant composite coating for a nuclear-grade zirconium alloy cladding, comprising the following steps: Step 1: Grind and polish the surface of the zirconium alloy cladding for nuclear use, then soak it in the pickling solution for pickling, and then clean and dry it for standby; Step 2: Place the pickled zirconium alloy cladding after Step 1 in the vacuum chamber of the vapor deposition equipment, introduce argon and adjust the vacuum degree, and pre-treat and activate the zirconium alloy cladding with Cr ions to obtain the pre-treated zirconium alloy cladding for nuclear use; Step 3: Deposit a pure Cr inner coating on the pre-treated zirconium alloy cladding for nuclear use in Step 2 with the vapor deposition equipment to obtain a zirconium alloy cladding with a Cr coating; Step 4: Continuously deposit a Cr 70 Al 30 intermediate coating on the zirconium alloy cladding with a Cr coating in Step 3 to obtain a zirconium alloy cladding with a double-layer Cr-Cr 70 Al 30 composite coating; Step 5: Continuously deposit a Cr 70 Al 30 outer coating on the zirconium alloy cladding with a double-layer Cr-Cr 50 Al 50 composite coating in Step 4 to obtain a zirconium alloy cladding with a three-layer Cr-Cr 70 Al 30 -Cr 50 Al 50 composite coating.

[0024] Preferably, in Step 1, the ratio of the pickling solution is nitric acid: hydrofluoric acid: water = 45%: 8%: 47%; the pickling time is 40 - 60 s; the cleaning is carried out in an ultrasonic cleaner with ethanol for 10 - 20 min.

[0025] Preferably, in Step 2, the pressure in the vacuum chamber is 0.01 - 0.1 Pa; the Cr ions are generated by the discharge of the Cr target source, the loading voltage is 800 - 1000 V, and the pre-treatment activation temperature is 150 - 350 °C.

[0026] Preferably, in Step 3, the pressure during the deposition process is 0.5 - 1.5 Pa, the temperature is 250 - 350 °C, and the deposition time is 4 - 6 h; the Cr coating is deposited by Cr ions generated by the discharge of the Cr target source, the loading current density of the Cr target source is 0.5 - 1.0 A / cm 2 ², the loading bias voltage is -100 - -150 V; the thickness of the deposited Cr inner coating exceeds 7.0 μm.

[0027] Preferably, in the deposition process of step 4, the pressure is 0.5~1.5 Pa, the temperature is 250~350 °C, and the deposition time is 3~5 h; the Cr 70 Al 30 The intermediate layer is formed by depositing Cr 70 Al 30 ions generated by the discharge of the Cr and Al targets. The loading current density of the Cr 70 Al 30 target is 0.5~1.0 A / cm 2 , and the loading bias voltage is -100~-150 V; the thickness of the deposited Cr 70 Al 30 intermediate layer exceeds 10.0 μm.

[0028] Preferably, in the deposition process of step 5, the pressure is 0.5~1.5 Pa, the temperature is 250~350 °C, and the deposition time is 3~5 h; the Cr 50 Al 50 The outer coating is formed by depositing Cr 50 Al 50 ions generated by the discharge of the Cr and Al targets. The loading current density of the Cr 50 Al 50 target is 0.5~1.0 A / cm 2 , and the loading bias voltage is -100~-150 V; the thickness of the deposited Cr 50 Al 50 outer coating exceeds 10.0 μm.

[0029] Preferably, the above gas-phase deposition equipment is a magnetron sputtering equipment, an arc ion plating equipment, etc.

[0030] The following is a further elaboration of the present invention in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0031] Conventional instrument equipment in the art is used in the following embodiments. For the experimental methods without specific conditions noted in the following embodiments, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Various raw materials are used in the following embodiments. Unless otherwise stated, commercially available products are used, and their specifications are conventional specifications in the art. In the specification of the present invention and the following embodiments, unless otherwise specified, "%" all represents weight percentage, "parts" all represents weight parts, and the ratio all represents weight ratio.

[0032] Example 1 A preparation method of a high-temperature oxidation-resistant composite coating for nuclear zirconium alloy cladding, comprising the following steps: Step 1: Surface grinding and pickling of nuclear zirconium alloy cladding: The nuclear zirconium alloy cladding is surface-ground and polished to a mirror surface, then immersed in pickling solution for 45 s of pickling, and then cleaned with ethanol in an ultrasonic cleaner for 10 min and dried for later use; Step 2: Surface pretreatment activation: The pickled zirconium alloy cladding after Step 1 is placed in the vacuum chamber of a vapor deposition device, argon is introduced, and the pressure of the vacuum chamber is adjusted to 0.01 Pa. Under the condition of a bias voltage of 1000 V, the zirconium alloy cladding is pretreated and activated with Cr ions, and the temperature is maintained at 350 °C during the pretreatment activation process; Step 3: Deposition of pure Cr inner coating: The zirconium alloy cladding after surface pretreatment activation in Step 2 is placed in the vacuum chamber of a vapor deposition device, argon is introduced, and the pressure of the vacuum chamber is adjusted to 1 Pa. The Cr target source is turned on, and a pure Cr inner coating is deposited on the surface of the pretreated and activated zirconium alloy cladding under the conditions of a bias voltage of -100 V and a current density of 0.5 A / cm 2 The deposition time is 6 h, and the deposition temperature is 320 °C to obtain a zirconium alloy cladding with a Cr coating; Step 4: Deposition of Cr 70 Al 30 intermediate coating: The zirconium alloy cladding deposited with a Cr coating in Step 3 is placed in the vacuum chamber of a vapor deposition device, argon is introduced, and the pressure of the vacuum chamber is adjusted to 1 Pa. The Cr 70 Al 30 target source is turned on, and a Cr 2 Al 70 intermediate coating is deposited on the surface of the zirconium alloy cladding deposited with a Cr coating under the conditions of a bias voltage of -100 V and a current density of 0.5 A / cm 30 The deposition time is 3 h, and the deposition temperature is 320 °C to obtain a zirconium alloy cladding with a double-layer structure of Cr-Cr 70 Al 30 composite coating; Step 5: Deposition of Cr 50 Al 50 outer coating: The zirconium alloy cladding deposited with a Cr 70 Al 30 intermediate coating in Step 4 is placed in the vacuum chamber of a vapor deposition device, argon is introduced, and the pressure of the vacuum chamber is adjusted to 1 Pa. The Cr 50 Al 50 target source is turned on, and a Cr 2 Al 50 outer coating is deposited on the surface of the zirconium alloy cladding deposited with a Cr coating under the conditions of a bias voltage of -100 V and a current density of 0.5 A / cm 50The intermediate coating was deposited for 3 h at a deposition temperature of 320 °C to obtain a Cr-Cr 70 Al 30 -Cr 50 Al 50 composite coating zirconium alloy cladding.

[0033] Figure 1 This is the Cr-Cr deposited on the surface of the nuclear-grade zirconium alloy cladding in this example 70 Al 30 -Cr 50 Al 50 cross-sectional microstructure morphology diagram and line scan results of the composite coating; From Figure 1 it can be seen that the coating obtained on the surface of the nuclear-grade zirconium alloy cladding in this example has a clear coating interface and a dense coating structure; among them, the thickness of the Cr coating is about 7.5 μm, and the Cr 70 Al 30 intermediate coating thickness is about 10 μm, and the Cr 50 Al 50 outer coating thickness is about 10.5 μm. The overall thickness of the coating exceeds 25 μm.

[0034] Figure 2 This is the Cr-Cr deposited on the surface of the nuclear-grade zirconium alloy cladding in this example 70 Al 30 -Cr 50 Al 50 cross-sectional morphology diagram of the composite coating after high-temperature oxidation at 1200 °C for 3 h. The high-temperature oxidation test results show that the coating interface is tightly bonded, the coating interface can be clearly observed, and no other defects are found except for a very small number of micropores. The presence of the composite coating significantly improves the oxidation resistance of the coating.

[0035] Example 2 A preparation method of a high-temperature oxidation-resistant composite coating for nuclear-grade zirconium alloy cladding, comprising the following steps: Step 1: Surface grinding and pickling of the nuclear-grade zirconium alloy cladding: The surface of the nuclear-grade zirconium alloy cladding was ground and polished to a mirror surface, then immersed in the pickling solution for pickling for 60 s, and then cleaned with ethanol in an ultrasonic cleaner for 15 min and dried for use; Step 2: Surface pretreatment activation: The pickled zirconium alloy cladding in Step 1 was placed in the vacuum chamber of the vapor deposition equipment, argon was introduced and the pressure of the vacuum chamber was adjusted to 0.01 Pa, and the zirconium alloy cladding was pretreated and activated with Cr ions under a bias voltage of 800 V. During the pretreatment activation process, the temperature was maintained at 300 °C; Step 3: Depositing a pure Cr inner coating: Place the zirconium alloy cladding after surface pretreatment and activation in Step 2 in the vacuum chamber of the vapor deposition equipment. Introduce argon and adjust the pressure in the vacuum chamber to 0.5 Pa. Turn on the Cr target source and deposit a pure Cr inner coating on the surface of the pretreated and activated zirconium alloy cladding under the conditions of a bias voltage of -150 V and a current density of 1.0 A / cm 2 for 5 h at a deposition temperature of 350 °C to obtain a zirconium alloy cladding with a Cr coating; Step 4: Depositing a Cr 70 Al 30 intermediate coating: Place the zirconium alloy cladding with a Cr coating deposited in Step 3 in the vacuum chamber of the vapor deposition equipment. Introduce argon and adjust the pressure in the vacuum chamber to 0.5 Pa. Turn on the Cr 70 Al 30 target source and deposit a Cr 2 Al 70 intermediate coating on the surface of the zirconium alloy cladding with a Cr coating deposited under the conditions of a bias voltage of -150 V and a current density of 1.0 A / cm 30 for 4 h at a deposition temperature of 350 °C to obtain a zirconium alloy cladding with a double-layer Cr-Cr 70 Al 30 composite coating; Step 5: Depositing a Cr 50 Al 50 outer coating: Place the zirconium alloy cladding with a Cr 70 Al 30 intermediate coating deposited in Step 4 in the vacuum chamber of the vapor deposition equipment. Introduce argon and adjust the pressure in the vacuum chamber to 0.5 Pa. Turn on the Cr 50 Al 50 target source and deposit a Cr 2 Al 50 intermediate coating on the surface of the zirconium alloy cladding with a Cr coating deposited for 4 h at a deposition temperature of 350 °C to obtain a zirconium alloy cladding with a three-layer Cr-Cr 50 Al 70 -Cr 30 Al 50 composite coating; 50

[0036] Figure 3 The Cr-Cr 70 Al 30 -Cr 50 Al 50 ​Cross-sectional morphology diagram of the composite coating after high-temperature oxidation at 1200 °C for 3 h; The results of the high-temperature oxidation test show that the coating interface is tightly bonded, and there are no other structural defects except for a very small number of micropores. The presence of the composite coating significantly improves the oxidation resistance of the coating.

[0037] Example 3 A preparation method of a high-temperature oxidation-resistant composite coating for nuclear zirconium alloy cladding, comprising the following steps: Step 1: Surface grinding and pickling of the nuclear zirconium alloy cladding: The nuclear zirconium alloy cladding is surface-ground and polished to a mirror finish, then immersed in the pickling solution for 50 s for pickling, and then cleaned with ethanol in an ultrasonic cleaner for 10 min and dried for use; Step 2: Surface pretreatment activation: The pickled zirconium alloy cladding after Step 1 is placed in the vacuum chamber of the vapor deposition equipment, argon is introduced, and the pressure of the vacuum chamber is adjusted to 0.01 Pa. Under the condition of a bias voltage of 900 V, the zirconium alloy cladding is pretreated and activated with Cr ions, and the temperature is maintained at 300 °C during the pretreatment activation process; Step 3: Deposition of a pure Cr inner coating: The zirconium alloy cladding after surface pretreatment activation in Step 2 is placed in the vacuum chamber of the vapor deposition equipment, argon is introduced, and the pressure of the vacuum chamber is adjusted to 1.5 Pa. The Cr target source is turned on, and a pure Cr inner coating is deposited on the surface of the pretreated and activated zirconium alloy cladding under the conditions of a bias voltage of -150 V and a current density of 0.5 A / cm 2 The deposition time is 5 h, and the deposition temperature is 320 °C to obtain a zirconium alloy cladding with a Cr coating; Step 4: Deposition of a Cr 70 Al 30 intermediate coating: The zirconium alloy cladding with a Cr coating deposited in Step 3 is placed in the vacuum chamber of the vapor deposition equipment, argon is introduced, and the pressure of the vacuum chamber is adjusted to 1 Pa. The Cr 70 Al 30 target source is turned on, and a Cr 2 Al 70 intermediate coating is deposited on the surface of the zirconium alloy cladding with a Cr coating under the conditions of a bias voltage of -150 V and a current density of 0.5 A / cm 30 The deposition time is 4 h, and the deposition temperature is 340 °C to obtain a zirconium alloy cladding with a double-layer structure of Cr-Cr 70 Al 30 composite coating; Step 5: Deposition of a Cr 50 Al 50 outer coating: The zirconium alloy cladding with a Cr 70 Al 30 intermediate coating deposited in Step 4 is placed in the vacuum chamber of the vapor deposition equipment, argon is introduced, and the pressure of the vacuum chamber is adjusted to 1 Pa. The Cr50 Al 50 The target source deposits Cr on the surface of the zirconium alloy cladding with a Cr coating under the conditions of a bias voltage of -150 V and a current density of 0.5 A / cm 2 and obtains a zirconium alloy cladding with a Cr-Cr 50 Al 50 intermediate coating. The deposition time is 4 h and the deposition temperature is 340 °C 70 Al 30 -Cr 50 Al 50 composite coating.

[0038] Figure 4 This is the cross-sectional morphology diagram of the Cr-Cr 70 Al 30 -Cr 50 Al 50 composite coating deposited on the surface of the zirconium alloy cladding for nuclear use after high-temperature oxidation at 1200 °C for 3 h. The results of the high-temperature oxidation test show that the overall surface of the coating is intact, the interface combination is tight, and there are no other structural defects except for a very small number of micropores. The existence of the composite coating significantly improves the oxidation resistance of the coating.

[0039] Comparative Example 1 A high-temperature oxidation-resistant composite coating for nuclear zirconium alloy cladding and its preparation method include the following steps: Step 1: Surface grinding and pickling of the nuclear zirconium alloy cladding: The surface of the nuclear zirconium alloy cladding is ground and polished to a mirror surface, then soaked in the pickling solution for 60 s for pickling, and then cleaned with ethanol in an ultrasonic cleaner for 10 min and dried for use; Step 2: Surface pretreatment activation: The pickled zirconium alloy cladding after Step 1 is placed in the vacuum chamber of the vapor deposition equipment, argon is introduced and the pressure of the vacuum chamber is adjusted to 0.01 Pa, and the zirconium alloy cladding is pretreated and activated with Cr ions under the condition of a bias voltage of 1000 V; the temperature is maintained at 300 °C during the pretreatment activation process; Step 3: Deposition of a pure Cr inner coating: The zirconium alloy cladding after surface pretreatment activation in Step 2 is placed in the vacuum chamber of the vapor deposition equipment, argon is introduced and the pressure of the vacuum chamber is adjusted to 1.5 Pa, the Cr target source is turned on, and a pure Cr inner coating is deposited on the surface of the pretreated and activated zirconium alloy cladding under the conditions of a bias voltage of -100 V and a current density of 0.5 A / cm 2 and the deposition time is 18 h and the deposition temperature is 320 °C to obtain a zirconium alloy cladding with a pure Cr coating with a coating thickness of 27 μm.

[0040] Figure 5This is the cross-sectional morphology diagram of the pure Cr coating deposited on the surface of the nuclear-grade zirconium alloy cladding in this comparative example after high-temperature oxidation at 1200 °C for 3 hours; the high-temperature oxidation test results show that there are obvious defects on the coating surface, a large number of cracks appear inside the specimen, and the protective effect of the Cr coating on the specimen at high temperature is limited.

[0041] In summary, for a nuclear-grade zirconium alloy cladding high-temperature oxidation-resistant composite coating and its preparation method of the present invention, by introducing Al element and designing a composition gradient structure, on the one hand, it solves the gasification loss of the Cr2O3 antioxidant layer on the surface of the traditional Cr coating in an oxidation environment above 1000 °C; on the other hand, it effectively restricts the outward migration of the Al element, thereby improving the coating quality; at the same time, it also reduces the thermal expansion stress between the coatings during the deposition process, avoiding quality problems such as coating cracking caused by deposition thermal stress; the composition gradient composite coating improves the service performance and safety margin of the zirconium alloy cladding at extremely high temperatures.

[0042] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A preparation method of a high-temperature oxidation-resistant composite coating for nuclear zirconium alloy cladding, characterized in that, It includes the following steps: Perform surface pretreatment on the nuclear-grade zirconium alloy cladding, and then perform Cr ion pretreatment activation on the surface to obtain the pretreated nuclear-grade zirconium alloy cladding; Deposit a pure Cr inner coating on the surface of the pretreated nuclear-grade zirconium alloy cladding to obtain a zirconium alloy cladding with a Cr coating; Depositing Cr on the surface of a zirconium alloy cladding with a Cr coating 70 Al 30 Intermediate coating to obtain a Cr-Cr composite coating zirconium alloy cladding with a double-layer structure 70 Al 30 Composite coating zirconium alloy cladding; On the surface of a zirconium alloy cladding with a double-layer structure of Cr-Cr 70 Al 30 a Cr 50 Al 50 outer coating is deposited to obtain a high-temperature oxidation-resistant composite coating.

2. The preparation method of a high-temperature oxidation-resistant composite coating for nuclear zirconium alloy cladding according to claim 1, characterized in that, The surface pretreatment includes grinding, polishing, pickling treatment, cleaning, and drying treatment performed in sequence; the pickling treatment is carried out by soaking in pickling solution; the pickling solution is nitric acid, hydrofluoric acid, and water with a volume ratio of 45%:8%:47%; the pickling treatment time is 40 - 60 s; The cleaning is carried out in an ultrasonic cleaner with ethanol for 10 - 20 min.

3. The preparation method of a high-temperature oxidation-resistant composite coating for nuclear zirconium alloy cladding according to claim 1, characterized in that, The specific steps for performing Cr ion pretreatment activation are as follows: Place the surface-pretreated nuclear-grade zirconium alloy cladding in the vacuum chamber of a vapor deposition device, introduce argon and adjust the vacuum degree, and perform Cr ion pretreatment activation on its surface using Cr ions; The pressure of the vacuum chamber is 0.01 - 0.1 Pa; the Cr ions are generated by the discharge of a Cr target source, the applied voltage is 800 - 1000 V, and the pretreatment activation temperature is 150 - 350 °C.

4. The preparation method of a high-temperature oxidation-resistant composite coating for nuclear zirconium alloy cladding according to claim 1, characterized in that, The specific steps for depositing a pure Cr inner coating on the surface of the pretreated nuclear-grade zirconium alloy cladding are as follows: Deposit a pure Cr inner coating on the pre-treated zirconium alloy cladding for nuclear use with a vapor deposition device. The pressure during the deposition process is 0.5 - 1.5 Pa, the temperature is 250 - 350 °C, and the deposition time is 4 - 6 h. The Cr coating is deposited by Cr ions generated by the discharge of a Cr target source, and the loading current density of the Cr target source is 0.5 - 1.0 A / cm 2 , and the loading bias voltage is -100 - -150 V.

5. The preparation method of a high-temperature oxidation-resistant composite coating for nuclear zirconium alloy cladding according to claim 1, characterized in that, The thickness of the pure Cr inner coating exceeds 7.0 μm.

6. The preparation method of a high-temperature oxidation-resistant composite coating for nuclear zirconium alloy cladding according to claim 1, characterized in that, Depositing Cr on the surface of a zirconium alloy cladding with a Cr coating 70 Al 30 The specific steps of the intermediate coating are as follows: Continuously deposit Cr on the zirconium alloy cladding with a Cr coating using a vapor deposition device 70 Al 30 Intermediate coating, the pressure during the deposition process is 0.5 - 1.5 Pa, the temperature is 250 - 350 °C, and the deposition time is 3 - 5 h; the Cr 70 Al 30 The intermediate layer is deposited by Cr 70 Al 30 ions and Al ions generated by the discharge of the target source, and the loading current density of the Cr 70 Al 30 target source is 0.5 - 1.0 A / cm 2 , and the loading bias voltage is -100 - -150 V.

7. The preparation method of a high-temperature oxidation-resistant composite coating for nuclear zirconium alloy cladding according to claim 1, characterized in that The Cr 70 Al 30 The deposition thickness of the intermediate coating exceeds 10.0 μm.

8. The preparation method of a high-temperature oxidation-resistant composite coating for nuclear zirconium alloy cladding according to claim 1, characterized in that The Cr-Cr with a double-layer structure 70 Al 30 deposit Cr 50 Al 50 on the surface of the composite coating zirconium alloy cladding. The specific steps for the outer coating are as follows: On the Cr-Cr 70 Al 30 composite-coated zirconium alloy cladding, continue to deposit Cr 50 Al 50 outer coating with a vapor deposition device. The pressure during the deposition process is 0.5 to 1.5 Pa, the temperature is 250 to 350 °C, and the deposition time is 3 to 5 h; the 50 Al 50 outer coating is deposited by Cr 50 Al 50 ions generated by the discharge of the target source. The loading current density of the 50 Al 50 target source is 0.5 to 1.0 A / cm 2 , and the loading bias voltage is -100 to -150 V.

9. The preparation method of a high-temperature oxidation-resistant composite coating for nuclear zirconium alloy cladding according to claim 1, characterized in that, The Cr 50 Al 50 The deposition thickness of the outer coating exceeds 10.0 μm.

10. A high-temperature oxidation-resistant composite coating for nuclear zirconium alloy cladding, characterized in that, It is prepared by using the preparation method described in any one of claims 1 - 9.

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