Preparation method of interfacial diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating

Abstract

The present invention discloses a method for preparing an interface diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating, comprising the following steps: 1. cleaning and clamping a workpiece; 2. composite ion cleaning of the workpiece surface; 3. preparation of a Mo diffusion-resistant layer; 4. preparation of a Pt diffusion-resistant layer; 5. preparation of a nano-Cr layer; 6. preparation of a Cr coating; 7. preparation of a nano-Cr / Cr multilayer composite coating, and obtaining a Mo / Pt / nano-Cr / Cr multilayer composite coating on the surface of a zirconium alloy cladding. The present invention suppresses the bidirectional diffusion of Zr and Cr by prefabricating a highly chemically inert Mo / Pt layer on the surface of a Zr substrate, thereby ensuring the interface stability of the coating under service conditions, and improving the overall consistency and structural density of the coating through a multilayer composite structure of ion implantation and a Cr deposition layer, thereby obtaining an interface integrated coating, which meets the requirements of the zirconium alloy cladding for the corrosion resistance of the coating under nuclear working conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material surface treatment, and in particular relates to a method for preparing an interface diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating. Background Art

[0002] Zirconium alloy cladding material is a commonly used fuel cladding material in pressurized water reactors at home and abroad due to its "nuclear properties" such as good radiation resistance and low neutron absorption cross-section. However, the corrosion resistance of zirconium alloy under abnormal operating conditions is still insufficient, and even serious accidents can occur under extreme conditions. Functional coating technology can improve the corrosion resistance of zirconium alloy cladding by preparing a corrosion-resistant coating material on the surface of the zirconium alloy cladding without changing the existing nuclear reactor fuel structure system. This can address the performance shortcomings of zirconium alloy cladding under nuclear reaction accident conditions and improve the accident resistance of the entire reactor.

[0003] Among numerous candidate coating materials, Cr coatings, with their mature preparation technology, low cost, and excellent corrosion resistance, have become the most promising material for commercializing accident-resistant cladding coatings. The coating's excellent corrosion resistance in high-temperature, high-pressure water has attracted widespread attention from researchers. However, application evaluation has revealed that Cr coatings still face certain practical challenges. For example, the Zr / Cr interface formed during coating deposition is extremely unstable under high-temperature conditions, especially accident conditions, triggering irreversible interfacial diffusion and the formation of highly brittle ZrCr intermetallic compounds. This brittle phase formation can lead to brittle crack initiation at the Zr / Cr interface under the combined action of external forces and internal thermal stresses, further causing cracking of the Cr coating along the interface. Furthermore, Zr has a higher affinity for oxygen than Cr. Once microstructural defects are present in the coating, or if Cr is completely oxidized, oxygen preferentially reacts with the Zr substrate through the Cr layer, causing oxidative corrosion of the Zr substrate. Preventing interfacial diffusion and isolating oxygen from contact with the zirconium alloy substrate are key to improving the service performance of accident-resistant Cr coatings. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing an interface diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating in response to the deficiencies of the above-mentioned prior art. The method comprises the following steps: preparing a Mo / Pt diffusion-resistant layer, a Cr injection layer, and a Cr deposition layer on the surface of a Zr substrate in sequence, and realizing the alternating cycle preparation of the Cr injection layer and the Cr deposition layer. The highly chemically inert Mo / Pt diffusion-resistant layer prefabricated on the surface of the Zr substrate realizes the function of inhibiting the bidirectional diffusion of Zr into the interior of the coating, Cr, and external O elements into the interior of the substrate, thereby ensuring the interface stability of the coating under working conditions. The alternately prepared Cr injection layer and Cr deposition layer can also realize Cr ion pinning at the interface of the Cr deposition layer, stabilize the internal interface of the Cr coating, and the multilayer composite structure can simultaneously further improve the structural density of the coating, reduce the internal residual stress of the coating, realize the integration of the coating substrate, and meet the requirements of the zirconium or zirconium alloy cladding for the corrosion resistance of the coating under nuclear working conditions.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: an interface diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating and a preparation method thereof, characterized in that the method comprises the following steps:

[0006] Step 1: The nuclear fuel zirconium alloy cladding is acid-washed, rinsed with deionized water, dehydrated and dried in sequence, and then vertically hoisted into the vacuum chamber of the physical vapor deposition equipment, and the background vacuum degree of the vacuum chamber is made lower than 5×10 -3 Pa and heating to obtain a clean zirconium alloy cladding in a vacuum chamber;

[0007] Step 2: performing composite ion cleaning and activation on the clean zirconium alloy cladding obtained in step 1 to obtain an activated zirconium alloy cladding; the composite ion cleaning and activation process is as follows: first, sputtering and cleaning the zirconium alloy cladding using the gas glow generated by Ar gas discharge in a vacuum electric field, and then deeply activating and cleaning the zirconium alloy cladding using high-energy Mo ions generated by Mo target source discharge;

[0008] Step 3: Turn on the Mo target source of the physical vapor deposition equipment, and deposit a Mo diffusion barrier layer on the surface of the activated zirconium alloy cladding obtained in step 2 to obtain a zirconium alloy cladding having a Mo diffusion barrier layer;

[0009] Step 4: Turn off the Mo target source of the physical vapor deposition equipment and turn on the Pt target source, depositing a Pt diffusion barrier layer on the surface of the zirconium alloy cladding with the Mo diffusion barrier layer obtained in step 3 to obtain a zirconium alloy cladding with a Pt diffusion barrier layer;

[0010] Step 5: Turn off the Pt target source of the physical vapor deposition equipment and turn on the Cr metal ion source, and perform Cr ion implantation on the surface of the zirconium alloy cladding with the Pt diffusion barrier layer obtained in step 4 to obtain a zirconium alloy cladding with a nano-Cr ion implantation layer;

[0011] Step 6: Turn off the Cr metal ion source of the physical vapor deposition equipment and turn on the Cr target source, and deposit a Cr deposition layer on the surface of the zirconium alloy cladding with the nano-Cr ion implantation layer obtained in step 5 to obtain a zirconium alloy cladding with a Cr deposition layer;

[0012] Step 7: cyclically and alternately perform the ion implantation in step 5 and the Cr deposition layer deposition in step 6 to obtain a Mo / Pt / nano-Cr / Cr multilayer composite coating with a gradient transition on the surface of the zirconium alloy cladding.

[0013] The present invention uses the gas glow generated by Ar gas discharge in a vacuum electric field to sputter clean the zirconium alloy cladding to eliminate static electricity and adsorbed dust and other impurities on the workpiece surface. Then, the high-energy Mo ions generated by Mo target source discharge are used for deep activation and cleaning of the zirconium alloy cladding, removing surface micro-oxides and activating Zr atoms on the surface of the zirconium alloy cladding, creating the necessary conditions for the subsequent atomic bonding of the Mo coating and the substrate.

[0014] The present invention adopts a vacuum plasma physical vapor composite deposition method to design and prepare an accident-resistant multilayer composite coating with high-temperature interface diffusion resistance function on the surface of a zirconium alloy cladding. By utilizing the high chemical incompatibility of Zr, Mo, and Pt under normal and even accident conditions of the reactor, a Mo / Pt diffusion resistance barrier layer is designed to achieve mutual isolation between Zr and surface Cr and O. Furthermore, the Cr ion implantation layer and the Cr deposition layer are organically combined to simultaneously achieve triple control of the surface accident-resistant Cr coating structure density (multilayer composite structure), interface stability (interface Cr ion pinning), and internal low deposition thermal stress (injection effect introduces residual compressive stress), thereby obtaining a Mo / Pt / nano-Cr / Cr multilayer composite structure coating with diffusion resistance, high density, and low stress level, thereby eliminating the interface element interdiffusion defects that are prone to occur in existing accident-resistant Cr coatings under normal and accident conditions, suppressing the potential risks of coating spalling, substrate corrosion, etc., and further meeting the application requirements of zirconium alloy cladding for accident fault-tolerant functional coatings under nuclear operating conditions.

[0015] The above-mentioned method for preparing an interface diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating is characterized in that the temperature in the vacuum chamber after heating in step 1 is 200°C to 300°C.

[0016] The above-mentioned method for preparing an interface diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating is characterized in that the vacuum degree in the vacuum chamber during the sputtering cleaning process in step 2 is 1Pa~10Pa, the bias voltage is 800V~1200V, the duty cycle is 80%, and the time is 5min~15min. The vacuum degree in the vacuum chamber during the activation cleaning process is less than 5×10 -2 Pa, bias voltage is 600V~1000V, duty cycle is 80%, time is 3min~5min, current density of Mo target source is 0.5A / cm 2 ~2A / cm 2 During the composite ion cleaning and activation process, the temperature in the vacuum chamber is maintained at 200° C. to 300° C.

[0017] The above-mentioned method for preparing an interface diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating is characterized in that the vacuum degree in the vacuum chamber during the deposition of the Mo diffusion barrier layer in step 3, the deposition of the Pt diffusion barrier layer in step 4, and the deposition of the Cr deposition layer in step 6 are all no greater than 4×10 -1 Pa.

[0018] The above-mentioned method for preparing an interface diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating is characterized in that the process of depositing the Mo diffusion resistance layer in step 3 is: reducing the bias voltage to 200V~400V, the duty cycle is 80%, pre-deposition is 7min~15min, and then reducing the bias voltage to 50V~100V, the duty cycle is 80%, and deposition is 45min~90min; the Mo diffusion resistance layer is deposited by magnetron sputtering or arc ion plating, and the current density of the Mo target source is 0.5A / cm 2 ~2A / cm 2 The thickness of the Mo diffusion barrier layer is 1 μm to 3 μm. The Mo layer deposition process of the present invention includes bombardment at a high bias voltage greater than 500V, i.e., deep activation and cleaning using high-energy Mo ions in step 2, pre-deposition at a medium bias voltage of 200V to 400V, and deposition at a low bias voltage of less than 100V, resulting in a micro-gradient transition structure from the substrate to the Mo layer.

[0019] The above-mentioned method for preparing an interface diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating is characterized in that the process of depositing the Pt diffusion-resistant layer in step 4 is: increasing the bias voltage to 200V~400V, the duty cycle is 80%, pre-deposition is 7min~15min, and then reducing the bias voltage to 50V~100V, the duty cycle is 80%, and deposition is 45min~60min; the Pt diffusion-resistant layer is deposited by magnetron sputtering or arc ion plating, and the current density of the Pt target source is 0.5A / cm2 ~2A / cm 2 The thickness of the Pt diffusion barrier layer is 1 μm to 3 μm. The Pt diffusion barrier layer deposition process of the present invention includes bombardment at a high bias voltage greater than 500V, i.e., high-voltage bombardment activation before pre-deposition, pre-deposition at a medium bias voltage of 200V to 400V, and deposition at a low bias voltage of less than 100V, resulting in a micro-gradient transition structure from the Mo layer to the Pt layer.

[0020] The above-mentioned method for preparing an interface diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating is characterized in that the process of Cr ion implantation in step 5 is as follows: adjusting the vacuum degree to less than 2×10 -2 Pa, adjust the bias voltage to 150 V, the energy of the implanted ions to 10 keV to 120 keV, and the dose of the implanted ions to 1 × 10 10 ions / cm 2 ~7×10 15 ions / cm 2 .

[0021] The above-mentioned method for preparing an interface diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating is characterized in that the process of depositing the Cr deposition layer in step 6 is: adjusting the bias voltage to 50V~100V, the duty cycle to 80%, and depositing for 90min~150min; the Cr deposition layer is deposited by magnetron sputtering or arc ion plating, and the current density of the Cr target source is 1.0A / cm 2 ~1.5A / cm 2 The thickness of the Cr deposition layer is 2 μm to 5 μm.

[0022] The above-mentioned method for preparing a Mo / Pt / nano-Cr / Cr multilayer composite coating with interfacial diffusion resistance and accident resistance is characterized in that the ion implantation in step 5 and the Cr deposition layer in step 6 are alternately performed 3 to 5 times each. In the present invention, the nano-Cr / Cr layer is deposited on the surface of the Pt coating to form a multi-periodic composite structure with a total thickness of 10 μm to 15 μm.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. In order to solve the application defects of Zr, Cr and O interface diffusion in the existing zirconium alloy surface accident-resistant Cr coating under high-temperature working conditions, the present invention designs and prepares an interface diffusion-resistant composite functional coating with a multi-microlayer composite structure. The chemical stability of Mo and Pt under high temperature conditions is utilized to inhibit the bidirectional mutual diffusion of Zr and Cr at high temperature. On the other hand, the chemical inertness of Pt is utilized to avoid the diffusion of Cr oxides and O elements in the corrosive medium into the interior of the substrate, thereby achieving the purpose of interface diffusion resistance between the Zr substrate and the surface accident-resistant coating.

[0025] 2. The present invention introduces an ion implantation layer and a composite deposition structure effect in the structural design of the surface Cr coating. The Cr ion implantation layer can play an interface pinning effect, improve the stability of the internal interface of the coating at high temperature, and introduce residual compressive stress at the interface to avoid coating cracking caused by deposition thermal stress. The multi-layer composite structure of ion implantation and Cr deposition layer will greatly improve the overall consistency and structural density of the coating, weaken or even eliminate the internal interface of the coating, and obtain an interface-integrated functional coating on the surface of the zirconium alloy cladding, which meets the requirements of the zirconium alloy cladding for the corrosion resistance of the functional coating under nuclear working conditions.

[0026] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a cross-sectional microstructure of a Mo / Pt / nano-Cr / Cr multilayer composite coating obtained on the surface of a Zr-4 zirconium alloy cladding in Example 1 of the present invention.

[0028] Figure 2 This is a cross-sectional morphology of the Mo / Pt / nano-Cr / Cr multilayer composite coating obtained on the surface of the Zr-4 zirconium alloy cladding in Example 1 of the present invention after being subjected to high-temperature steam corrosion at 1200°C for 4 hours. DETAILED DESCRIPTION

[0029] Example 1

[0030] This embodiment includes the following steps:

[0031] Step 1: Workpiece cleaning and clamping: After surface pickling, deionized water rinsing, dehydration and drying, the Zr-4 zirconium alloy cladding is placed on the workpiece rack of the vacuum chamber of the vacuum plasma composite deposition equipment, and then the vacuum degree of the vacuum chamber is pumped to 5×10 -3 Pa and heated to 200°C; the cladding tube is vertically hoisted on the workpiece rack, and the revolution and rotation of the cladding tube can be realized synchronously;

[0032] Step 2: Composite ion cleaning of the workpiece surface: Ar is introduced into the vacuum chamber heated in step 1 and the vacuum degree is adjusted to 1 Pa. Under the conditions of bias voltage 1200 V and duty cycle 80%, Ar ion glow is excited to perform continuous discharge glow plasma sputtering cleaning on the workpiece surface for 5 minutes. After that, the Ar gas flow rate is controlled to adjust the vacuum degree to 5×10 -2 Pa, turn on the Mo target source, and perform Mo ion cleaning on the zirconium alloy clad workpiece after glow cleaning under the conditions of bias 800V and duty cycle 80%. The cleaning time is 3min, and the current density of the Mo target source is 1.5A / cm 2 , the temperature in the vacuum chamber is maintained at 200° C. during the cleaning process;

[0033] Step 3: Preparation of Mo diffusion barrier layer: After step 2, the Mo target source is kept on, the bias voltage is reduced to 200 V and the duty cycle is 80%, and a Mo layer is pre-deposited on the surface of the zirconium alloy cladding after Mo ion cleaning. The pre-deposition time is 7 minutes, and then the bias voltage is further reduced to 100 V and the duty cycle is 80%, and a Mo layer is deposited on the surface of the Mo pre-deposition layer to obtain a Mo diffusion barrier layer with a dense structure; the current density of the Mo target source is 1.5 A / cm 2 , the deposition time is 1 hour, and the thickness of the Mo diffusion barrier layer is 2 μm;

[0034] Step 4: Preparation of Pt diffusion barrier layer: After step 3, the Mo target source is turned off, the Pt target source is turned on, the bias voltage is increased to 200 V and the duty cycle is 80%, and a Pt layer is pre-deposited on the surface of the Mo diffusion barrier layer for 7 minutes. Then, the bias voltage is further reduced to 100 V and the duty cycle is 80%, and a Pt layer is deposited on the surface of the Pt pre-deposition layer to obtain a Pt diffusion barrier layer with a dense structure; the current density of the Pt target source is 1 A / cm 2 , deposition time 50min, the thickness of the Pt diffusion barrier layer is 2μm;

[0035] Step 5: Preparation of nano-Cr layer: Turn off the Pt target source in step 4 and adjust the vacuum degree to 2×10 - 2 Pa, adjust the bias voltage to 150 V, turn on the Cr metal ion source, and perform Cr ion implantation on the surface of the Pt diffusion barrier layer with an implantation dose of 5×10 12 ions / cm 2 ;

[0036] Step 6: Preparation of Cr coating: Turn off the Cr metal ion source, turn on the Cr target source, adjust the device bias voltage to 100V and the duty cycle to 80%, and deposit the Cr coating on the surface of the Cr ion implantation layer. The surface current density of the Cr target source is 1.5A / cm 2, the deposition time is 2 hours, and the thickness of the Cr coating is 3 μm;

[0037] Step 7. Preparation of nano-Cr / Cr multilayer composite coating: Repeat steps 5 and 6 5 times each to obtain a nano-Cr / Cr multilayer composite coating with a thickness of 15 μm and 5 periods of composite, and obtain a Mo / Pt / nano-Cr / Cr multilayer composite coating with a gradient transition on the surface of the zirconium alloy cladding.

[0038] Figure 1 The cross-sectional microstructure of the Mo / Pt / nano-Cr / Cr multilayer composite coating was obtained on the surface of the Zr-4 zirconium alloy cladding in this embodiment. Figure 1 It can be seen that the coating obtained on the surface of the Zr-4 zirconium alloy cladding in this embodiment has an obvious transition layer structure, an obvious multi-layer composite structure, a dense coating structure, and a thickness of about 15 μm.

[0039] The Mo / Pt / nano-Cr / Cr multilayer composite coating obtained on the surface of the Zr-4 zirconium alloy cladding in this embodiment was subjected to a steam corrosion test in 1200°C high temperature steam for 4 hours. The cross-sectional morphology of the coating after corrosion is shown in FIG. Figure 2 As shown in the figure, the test results show that there is no mutual diffusion of Zr, Cr and O at the Mo / Pt interface of the composite coating, the interface diffusion barrier effect is obvious, the interface stability is significantly improved, the coating does not fall off, and the Zr substrate does not show oxidation corrosion.

[0040] Example 2

[0041] This embodiment includes the following steps:

[0042] Step 1: Workpiece cleaning and clamping: After surface pickling, deionized water rinsing, dehydration and drying, the Zr-4 zirconium alloy cladding is placed on the workpiece rack of the vacuum chamber of the vacuum plasma composite deposition equipment, and then the vacuum degree of the vacuum chamber is pumped to 5×10 -3 Pa and heated to 250 ° C; the cladding tube is vertically hoisted on the workpiece rack, and the revolution and rotation of the cladding tube can be realized synchronously;

[0043] Step 2: Two-step ion cleaning of the workpiece surface: Ar is introduced into the vacuum chamber heated in step 1 and the vacuum degree is adjusted to 5 Pa. Under the conditions of bias voltage 1000 V and duty cycle 80%, Ar ion glow is excited to perform continuous discharge glow plasma cleaning on the workpiece surface for 7 minutes. After that, the vacuum degree is adjusted to 5×10 -2 Pa, turn on the Mo target source, and perform secondary Mo ion cleaning on the zirconium alloy clad workpiece after glow cleaning under the conditions of bias voltage 600V and duty cycle 80%. The cleaning time is 4min, and the current density of the Mo target source is 2A / cm 2, the temperature in the vacuum chamber is maintained at 250° C. during the cleaning process;

[0044] Step 3: Preparation of Mo diffusion barrier layer: After step 2, the Mo target source is kept on, the bias voltage is reduced to 300V and the duty cycle is 80%, and a Mo layer is pre-deposited on the surface of the Mo ion-cleaned zirconium alloy cladding for 10 minutes. The bias voltage is then further reduced to 80V and the duty cycle is 80%, and a Mo layer is deposited on the surface of the Mo pre-deposited layer to obtain a Mo diffusion barrier layer with a dense structure. The current density of the Mo target source is 2A / cm 2 , deposition time 90min, the thickness of the Mo diffusion barrier layer is 3μm;

[0045] Step 4: Preparation of Pt diffusion barrier layer: After step 3, the Mo target source was turned off, the Pt target source was turned on, the bias voltage was increased to 300V, the duty cycle was 80%, and a Pt layer was pre-deposited on the surface of the Mo diffusion barrier layer for 10 minutes. The bias voltage was then further reduced to 80V, the duty cycle was 80%, and a Pt layer was deposited on the surface of the Pt pre-deposited layer to obtain a Pt diffusion barrier layer with a dense structure. The current density of the Pt target source was 2A / cm 2 , deposition time 60min, the thickness of the Pt diffusion barrier layer is 3μm;

[0046] Step 5: Preparation of nano-Cr layer: Turn off the Pt target source in step 4 and adjust the vacuum degree to 2×10 - 2 Pa, adjust the bias voltage to 150 V, turn on the Cr metal ion source, and perform Cr ion implantation on the surface of the Pt diffusion barrier layer with an implantation dose of 1×10 10 ions / cm 2 ;

[0047] Step 6: Preparation of Cr coating: Turn off the Cr metal ion source, turn on the Cr target source, adjust the device bias voltage to 60V and the duty cycle to 80%, and deposit the Cr coating on the surface of the Cr ion implantation layer. The surface current density of the Cr target source is 2A / cm 2 , deposition time 150min, the Cr coating thickness is 5μm;

[0048] Step 7. Preparation of nano-Cr / Cr multilayer composite coating: Repeat steps 5 and 6 three times each to obtain a nano-Cr / Cr multilayer composite coating with a thickness of 15 μm and a three-period composite, and obtain a Mo / Pt / nano-Cr / Cr multilayer composite coating with a gradient transition on the surface of the zirconium alloy cladding.

[0049] The Mo / Pt / nano-Cr / Cr multilayer composite coating obtained in this example on the surface of a Zr-4 zirconium alloy cladding was subjected to a steam corrosion test in 1200°C high-temperature steam for 4 hours. The test results showed that there was no interdiffusion of Zr, Cr, and O at the Mo / Pt interface of the composite coating, resulting in a significant interfacial diffusion barrier effect and significantly improved interface stability. The coating did not fall off, and the Zr substrate showed no oxidative corrosion.

[0050] Example 3

[0051] This embodiment includes the following steps:

[0052] Step 1: Workpiece cleaning and clamping: After surface pickling, deionized water rinsing, dehydration and drying, the Zr-4 zirconium alloy cladding is placed on the workpiece rack of the vacuum chamber of the vacuum plasma composite deposition equipment, and then the vacuum degree of the vacuum chamber is pumped to 5×10 -3 Pa and heated to 300°C; the cladding tube is vertically hoisted on the workpiece rack, which can realize the revolution and rotation of the cladding tube synchronously;

[0053] Step 2: Two-step ion cleaning of the workpiece surface: Ar is introduced into the vacuum chamber heated in step 1 and the vacuum degree is adjusted to 10 Pa. Under the conditions of bias voltage 800 V and duty cycle 80%, Ar ion glow is excited to perform continuous discharge glow plasma cleaning on the workpiece surface for 15 minutes. After that, the vacuum degree is adjusted to 5×10 -2 Pa, turn on the Mo magnetron sputtering target source, and perform secondary Mo ion cleaning on the glow-cleaned zirconium alloy cladding workpiece under the conditions of bias voltage 1000V and duty cycle 80%. The cleaning time is 5min, and the current density of the Mo magnetron sputtering target source is 0.5A / cm 2 , the temperature in the vacuum chamber is maintained at 300° C. during the cleaning process;

[0054] Step 3: Preparation of Mo diffusion barrier layer: After step 2, the Mo magnetron sputtering target source is kept on and the vacuum is adjusted to 5×10 -1 Pa, the bias voltage is reduced to 400V and the duty cycle is 80%, and a Mo layer is pre-deposited on the surface of the Mo ion-cleaned zirconium alloy cladding for 15 minutes. Then the bias voltage is further reduced to 50V and the duty cycle is 80%, and a Mo layer is deposited on the surface of the Mo pre-deposition layer to obtain a Mo resistance diffusion layer with a dense structure; the Mo magnetron sputtering target source current density is 0.5A / cm 2 , deposition time 45min, the thickness of the Mo resistance diffusion layer is 1μm;

[0055] Step 4: Preparation of Pt diffusion barrier layer: After step 3, the vacuum level is maintained, the Mo magnetron sputtering target source is turned off, the Pt magnetron sputtering target source is turned on, the bias voltage is increased to 400V, the duty cycle is 80%, and a Pt layer is pre-deposited on the surface of the Mo diffusion barrier layer for 15 minutes. The bias voltage is then further reduced to 50V, the duty cycle is 80%, and a Pt layer is deposited on the surface of the Pt pre-deposited layer to obtain a Pt diffusion barrier layer with a dense structure; the current density of the Pt target source is 0.5A / cm 2 , deposition time 45min, the thickness of the Pt diffusion barrier layer is 1μm;

[0056] Step 5: Preparation of nano-Cr layer: Turn off the Pt target source in step 4 and adjust the vacuum degree to 2×10 - 2 Pa, adjust the bias voltage to 150 V, turn on the Cr metal ion source, and perform Cr ion implantation on the surface of the Pt diffusion barrier layer with an implantation dose of 7×10 15 ions / cm 2 ;

[0057] Step 6: Preparation of Cr coating: Turn off the Cr metal ion source, turn on the Cr target source, adjust the device bias voltage to 50V and the duty cycle to 80%, and deposit the Cr coating on the surface of the Cr ion implantation layer. The surface current density of the Cr target source is 1.0A / cm 2 , deposition time 90 min, the Cr coating thickness is 2 μm;

[0058] Step 7. Preparation of nano-Cr / Cr multilayer composite coating: Repeat steps 5 and 6 5 times each to obtain a nano-Cr / Cr multilayer composite coating with a thickness of 10 μm and 5 periods of composite, and obtain a Mo / Pt / nano-Cr / Cr multilayer composite coating with a gradient transition on the surface of the zirconium alloy cladding.

[0059] The Mo / Pt / nano-Cr / Cr multilayer composite coating obtained in this example on the surface of a Zr-4 zirconium alloy cladding was subjected to a steam corrosion test in 1200°C high-temperature steam for 4 hours. The test results showed that there was no interdiffusion of Zr, Cr, and O at the Mo / Pt interface of the composite coating, resulting in a significant interfacial diffusion barrier effect and significantly improved interface stability. The coating did not fall off, and the Zr substrate showed no oxidative corrosion.

[0060] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the technical essence of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing an interfacial diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating, characterized in that: The method comprises the following steps: Step 1: The nuclear fuel zirconium alloy cladding is acid-washed, rinsed with deionized water, dehydrated and dried in sequence, and then vertically hoisted into the vacuum chamber of the physical vapor deposition equipment, and the background vacuum degree of the vacuum chamber is made lower than 5×10 -3 Pa and heating to obtain a clean zirconium alloy cladding in a vacuum chamber; Step 2: performing composite ion cleaning and activation on the clean zirconium alloy cladding obtained in step 1 to obtain an activated zirconium alloy cladding; the composite ion cleaning and activation process is as follows: first, sputtering and cleaning the zirconium alloy cladding using the gas glow generated by Ar gas discharge in a vacuum electric field, and then deeply activating and cleaning the zirconium alloy cladding using high-energy Mo ions generated by Mo target source discharge; Step 3: Turn on the Mo target source of the physical vapor deposition equipment, and deposit a Mo diffusion barrier layer on the surface of the activated zirconium alloy cladding obtained in step 2 to obtain a zirconium alloy cladding having a Mo diffusion barrier layer, wherein the thickness of the Mo diffusion barrier layer is 1 μm to 3 μm; Step 4: Turn off the Mo target source of the physical vapor deposition equipment and turn on the Pt target source, depositing a Pt diffusion barrier layer on the surface of the zirconium alloy cladding with the Mo diffusion barrier layer obtained in step 3 to obtain a zirconium alloy cladding with a Pt diffusion barrier layer; the thickness of the Pt diffusion barrier layer is 1 μm to 3 μm; Step 5: Turn off the Pt target source of the physical vapor deposition equipment and turn on the Cr metal ion source. Perform Cr ion implantation on the surface of the zirconium alloy cladding with the Pt diffusion barrier layer obtained in step 4 to obtain a zirconium alloy cladding with a nano-Cr ion implantation layer. The dose of the implanted ions in the Cr ion implantation is 1×10 10 ions / cm 2 ~7×10 15 ions / cm 2 ; Step 6: Turn off the Cr metal ion source of the physical vapor deposition equipment and turn on the Cr target source, and deposit a Cr deposition layer on the surface of the zirconium alloy cladding with the nano-Cr ion implantation layer obtained in step 5 to obtain a zirconium alloy cladding with a Cr deposition layer; the thickness of the Cr deposition layer is 2 μm to 5 μm; Step 7: cyclically and alternately perform the ion implantation in step 5 and the Cr deposition layer deposition in step 6 to obtain a Mo / Pt / nano-Cr / Cr multilayer composite coating on the surface of the zirconium alloy cladding.

2. The method for preparing an interfacial diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating according to claim 1, characterized in that: After the heating in step 1, the temperature in the vacuum chamber is 200° C. to 300° C.

3. The method for preparing an interfacial diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating according to claim 1, characterized in that: The vacuum degree in the vacuum chamber during the sputtering cleaning process in step 2 is 1Pa~10Pa, the bias voltage is 800V~1200V, the duty cycle is 80%, and the time is 5min~15min. The vacuum degree in the vacuum chamber during the deep activation cleaning process using high-energy Mo ions generated by Mo target source discharge is less than 5×10 -2 Pa, bias voltage is 600V~1000V, duty cycle is 80%, time is 3min~5min, current density of Mo target source is 0.5A / cm 2 ~2A / cm 2 During the composite ion cleaning and activation process, the temperature in the vacuum chamber is maintained at 200° C. to 300° C.

4. The method for preparing an interfacial diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating according to claim 1, characterized in that: The vacuum degree in the vacuum chamber during the deposition of the Mo diffusion barrier layer in step 3, the deposition of the Pt diffusion barrier layer in step 4, and the deposition of the Cr deposition layer in step 6 is no greater than 4×10 -1 Pa.

5. The method for preparing an interfacial diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating according to claim 1, characterized in that: The process of depositing the Mo resistance diffusion layer in step 3 is as follows: reducing the bias voltage to 200V~400V, the duty cycle is 80%, pre-deposition for 7min~15min, then reducing the bias voltage to 50V~100V, the duty cycle is 80%, and deposition is 45min~90min; the Mo resistance diffusion layer is deposited by magnetron sputtering or arc ion plating, and the current density of the Mo target source is 0.5A / cm 2 ~2A / cm 2 .

6. The method for preparing an interfacial diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating according to claim 1, characterized in that: The process of depositing the Pt diffusion barrier layer in step 4 is as follows: increasing the bias voltage to 200V~400V, the duty cycle is 80%, pre-deposition is 7min~15min, then reducing the bias voltage to 50V~100V, the duty cycle is 80%, and deposition is 45min~60min; the Pt diffusion barrier layer is deposited by magnetron sputtering or arc ion plating, and the current density of the Pt target source is 0.5A / cm 2 ~2A / cm 2 .

7. The method for preparing an interfacial diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating according to claim 1, characterized in that: The process of Cr ion implantation in step 5 is as follows: adjust the vacuum degree to less than 2×10 -2 Pa, adjust the bias voltage to 150V, and the energy of the injected ions to 10keV~120keV.

8. The method for preparing an interfacial diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating according to claim 1, characterized in that: The process of depositing the Cr deposition layer in step 6 is as follows: adjusting the bias voltage to 50V~100V, the duty cycle to 80%, and depositing for 90min~150min; the Cr deposition layer is deposited by magnetron sputtering or arc ion plating, and the current density of the Cr target source is 1.0A / cm 2 ~1.5A / cm 2 .

9. The method for preparing an interfacial diffusion-resistant accident-resistant Mo / Pt / nano-Cr / Cr multilayer composite coating according to claim 1, characterized in that: The ion implantation in step five and the Cr deposition layer in step six are performed alternately in a cycle for 3 to 5 times.

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