A multi-gradient Al 2 O 3 / Simulation Method of Tritium Barrier Coating System for Low Activity Martensitic Steel

Abstract

The present invention belongs to the technical field of tritium retention coating systems in experimental fusion reactors, and particularly relates to a simulation method for an Al2O3 / low-activity martensitic steel tritium retention coating system with multiple gradients; it is an effective method to alleviate the excessively high internal thermal stress in the system caused by the Al2O3 tritium retention coating in a high-temperature environment during the operation of a fusion reactor; based on the Ansys workbench software, the present invention simplifies the substrate surface of the tritium retention coating system with a rough substrate and designs a gradient tritium retention coating; effectively solves the problems of high stress and low bonding strength of the tritium retention coating in a high-temperature service environment; reduces stress concentration in the coating system, improves the bonding strength between the coating and the substrate, and increases the service life of the coating.

Description

Technical Field

[0001] The invention belongs to the technical field of tritium barrier coating system in experimental fusion reactor, and particularly relates to a multi-gradient Al 2 O 3 / Simulation method for tritium barrier coating system of low-activity martensitic steel. Background Art

[0002] After decades of unremitting efforts in controlled nuclear fusion, experimental fusion reactors are now under construction. In addition, with the implementation and development of the International Thermonuclear Experimental Reactor (ITER) program, the study of tritium barrier coatings that meet the requirements of ITER's future advanced fusion reactors is a hot topic.

[0003] The tritium produced by the proliferation of tritium in the fusion reactor blanket can easily penetrate outward through the blanket structural material. This will not only cause the loss of tritium and cause radioactive contamination, but also cause the blanket structural material to become brittle and swollen, bringing disastrous consequences to the fusion reactor. Studies have shown that in order to prevent the penetration of tritium while maintaining the overall performance of the structural material, the most effective method is to deposit a ceramic tritium barrier coating on the surface of the structural material. Among many ceramics, Al 2 O 3 It has good tritium permeability, excellent corrosion resistance and thermal stability, and is considered to be one of the promising candidate materials for tritium barrier coatings. At the same time, low-activity martensitic steel has the advantages of low tritium permeability, high strength and good plasticity. Therefore, Al is deposited on the surface of low-activity martensitic steel. 2 O 3 , as a tritium barrier coating system is the focus of current research.

[0004] Due to Al 2 O 3 The coating lattice constant and thermal expansion coefficient are quite different from those of the low-activity martensitic steel substrate material, and the heterogeneous interface between the coating and the substrate material is discontinuous and incoherent. Under the coupling of multiple physical fields such as high temperature, alternating thermal field, and alternating irradiation field, high thermal stress will inevitably be caused at the interface between the coating and the substrate. High thermal stress will induce cracks on the coating surface, which will cause the coating to fall off, indicating the characteristics of insufficient film-substrate bonding strength.

[0005] In addition, most of the current theoretical research work on coating / substrate systems focuses on tritium barrier systems with smooth substrate surfaces. However, in actual processing and production, the roughness of the substrate surface cannot be avoided due to the influence of the polishing process. Studies have shown that in tritium barrier coating systems, a rough substrate surface is detrimental to the stability of the overall system. It not only affects the thermodynamic properties of the coating, but also aggravates the stress concentration at the interface between the coating and the substrate, inducing multiple cracks on the coating surface. As the cracks expand, catastrophic failure of the coating and low-activity martensitic steel may occur. Therefore, how to effectively reduce Al 2 O 3 / Thermal stress in the low-activity martensitic steel system is the key to improving the service life of the coating. However, due to the complex preparation process of tritium barrier coatings, the complexity of the working environment, and the huge financial and material investment required for the experiment, there are still certain defects in the development of high-performance tritium barrier coatings through experimental methods.

[0006] In contrast, in the field of coatings and thermodynamics, the use of finite element simulation methods can effectively shorten experimental time, improve work efficiency, save experimental costs, and provide efficient design guidance for later experimental research and development. At present, in the field of tritium barrier coatings, some finite element research has been carried out, mainly focusing on the measurement of temperature field and thermal deformation. However, there are few reports on the design of coatings with rough substrates. There are only studies on the structural analysis of single coatings and double-layer tritium barrier coatings with intermediate slow-heat layers. This is mainly because in the design of the coating, the transition layer material must meet the strict requirements of good compatibility with the liquid Li-Pb in the cladding and matching the performance of the top coating and substrate materials. In addition, in the simulation of real working conditions in the later stage, there are problems such as complex calculations and non-convergence. Therefore, it is urgent to develop a simple new design method based on finite element technology to solve this problem. Summary of the invention

[0007] The object of the present invention is to provide an Al 2 O 3 / A method for simulating a tritium barrier coating system for low-activity martensitic steel, comprising the following steps:

[0008] (1) Model establishment

[0009] A relatively regularly distributed area on the rough substrate surface of the low-activity martensitic steel is selected for analysis, and the rough contour line of the low-activity martensitic steel substrate surface is simplified as an isosceles triangle; the distance h between the peak and the trough and the length L between the peaks in the rough contour line of the low-activity martensitic steel substrate surface are determined, and the height and base length of the isosceles triangle are set respectively;

[0010] In the Geometry module, Al 2 O 3 / The tritium barrier coating system of low-activity martensitic steel is simplified into a two-dimensional model in the XY plane; (2) Design of gradient coating

[0011] ①Model design

[0012] An isosceles triangle unit is established in the XOY coordinate system; the isosceles triangle unit is copied by a mode command; and the isosceles triangle unit is cut into a gradient intermediate coating by a slice command;

[0013] ②Material design

[0014] Based on Al 2 O 3 / Material properties of low activity martensitic steel tritium barrier system, Al 2 O 3 The transition area from the coating to the low-activity martensitic steel substrate is set as a gradient coating, forming an Al 2 O 3 / low-activity martensitic steel tritium-blocking coating; along the positive direction of the Y axis, the gradient coating includes a plurality of sub-coatings, and the plurality of sub-coatings are respectively defined as the first layer, the second layer, the third layer ... the Kth layer, where K is greater than or equal to 4;

[0015] (3) Grid division

[0016] Divide the short sides of the gradient coating obtained in step (2) into M segments, and divide the remaining sides into N segments, where M≥3 and N≥6; obtain the gradient coating grid design;

[0017] (4) Boundary conditions

[0018] The leftmost boundary line of the gradient coating model in step (3) is selected as the symmetry axis. In the displacement command, the displacement of all nodes on the symmetry axis in the X direction is set to be free, and the displacement in the Y direction is set to be 0; the displacement of all nodes on the bottom edge of the substrate of the low-activity martensitic steel in the X direction is selected to be 0, and the displacement in the Y direction is set to be free; and the ambient temperature of the gradient coating model is limited to 400° C.-600° C.;

[0019] (5) Results analysis

[0020] Based on the above steps (1) to (4), the Al with multiple gradients is obtained. 2 O 3 / The low-activity martensitic steel tritium barrier coating system is at an ambient temperature of 400°C-600°C, the thermal stress and thermal strain distribution of the gradient coating model at the ambient temperature, and the thermal stress and deformation distribution of the gradient coating along the substrate interface direction.

[0021] In some embodiments, the parameters of the model in step (1) are: the type mode is selected as linear, the geometry is selected as the line body Line1 established in the previous step; the offset is set to the length of the triangle base 2 μm, the number of copies is set to 9, and the direction is along the positive direction of the X axis;

[0022] Further, the parameters of the model in step (1) are: 2 O 3 The coating thickness is ≥2μm, the low-activity martensitic steel substrate thickness is ≥25μm, and the low-activity martensitic steel radius is ≥20μm; characterized in that the material properties of the sub-coating of each layer in the gradient coating are calculated according to the following formula:

[0023]

[0024] Y i =Y c (V c ) i +Y s (1-(V c ) i ) (2)

[0025] E i =E c (V c ) i +E s (1-(V c ) i ) (3)

[0026] α i =α c (V c ) i +α s (1-(V c ) i ) (4)

[0027] In the formula (V c ) i represents the volume fraction of the coating in the i-th layer; n represents the number of layers of the gradient coating; Y C , Y S , Y i Represent the yield strength of coating, substrate and i-th gradient coating respectively; E C , E S , E i Represent the elastic modulus of the coating, substrate, and i-th layer respectively; α c , α s , α i represent the Poisson’s ratio of the coating, substrate, and the i-th layer, respectively.

[0028] In some embodiments, the modeled Al 2 O 3 The coating model, the gradient coating unit obtained after cutting, and the substrate model are combined to form an overall model.

[0029] In some embodiments, the grid division method of the gradient coating in step (3) adopts a division quantity method, the performance is set to straight, and the bias form is set to unbiased.

[0030] Furthermore, the surface roughness contour line in step (1) is composed of the waists of 10 groups of isosceles triangle units with a base length of 2 μm and a height of 1.5 μm.

[0031] Further, in step (2), Al 2 O 3 In the material property settings for the coating, gradient coating, and low-activity martensitic steel substrate, select isotropic mode, select solid in the creation range, and select uniform in the type.

[0032] In some embodiments, in step (2), the 10 groups of isosceles triangles representing the roughness of the substrate previously established are moved 25 μm along the positive direction of the Y axis through a transformation command.

[0033] In some embodiments, in step (2) of modeling the intermediate gradient coating, a slice command is selected, the slice type is selected as cutting through a plane, and the reference plane is plane 3. Through the generation option, 10 groups of isosceles triangles are each cut into 10 groups of isosceles triangle units with a height of 0.375 μm and 10 groups of isosceles trapezoidal units with a height of 1.125 μm.

[0034] The beneficial effect of the present invention is to provide an Al2O3 having multiple gradients. 2 O 3 / Low activity martensitic steel tritium barrier coating system simulation method. A material property along the substrate to Al 2 O 3 The intermediate gradient coating with gentle distribution of the coating was then placed in a 400℃ to 600℃ environment for finite element simulation, and the system thermal stress, thermal strain, and thermal stress and deformation distribution diagram along the rough contour of the substrate surface were obtained. This method overcomes the previous complicated and expensive tritium barrier coating experimental design method, and can directly obtain the analysis results of the main parameters under the working temperature. The design process is convenient and fast, the design ideas are clear, and the use process is convenient and simple.

[0035] The present invention is achieved by 2 O 3 / The gradient coating is designed in the coating model of low-activity martensitic steel tritium barrier, which significantly reduces the maximum thermal stress and maximum thermal strain of the system at a temperature of 400℃ to 600℃. In addition, the thermal stress and thermal deformation along the rough contour of the substrate surface in the system containing the gradient coating are small. Therefore, the introduction of the gradient coating effectively alleviates the phenomenon of thermal stress concentration in the system and improves the stability of the tritium barrier system. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] This specification includes the following drawings, which show the following contents:

[0037] Figure 1 The present invention provides an Al 2 O 3 Material properties of the coating.

[0038] Figure 2 The present invention provides a material property of a low-activity martensitic steel.

[0039] Figure 3 The present invention provides a simplified principle of a rough substrate surface profile.

[0040] Figure 4 A model design of a gradient coating provided by the present invention.

[0041] Figure 5 The present invention provides a kind of gradient coating.

[0042] Figure 6 A gradient coating material coefficient is provided by the present invention.

[0043] Figure 7 A model grid division situation provided by the present invention.

[0044] Figure 8 The present invention provides a boundary condition of a model.

[0045] Fig. 9 The present invention provides a system thermal stress distribution of a gradient coating and a non-gradient coating at 400°C-600°C.

[0046] Fig.10 The present invention provides a system thermal strain distribution of a gradient coating and a non-gradient coating at 400°C-600°C.

[0047] Fig.11 The thermal stress distribution along the rough contour of the substrate surface in the system with / without gradient coating provided by the present invention.

[0048] Fig.12 The present invention provides a system with or without gradient coating, and provides deformation distribution along the roughness profile of the substrate surface. DETAILED DESCRIPTION

[0049] The specific implementation methods of the present invention are further described in detail below with reference to the accompanying drawings through the description of embodiments, with the aim of helping those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solution of the present invention and to facilitate its implementation.

[0050] A multi-gradient Al 2 O 3 / A method for simulating a tritium barrier coating system for low-activity martensitic steel, comprising the following steps:

[0051] (1) Preliminary establishment of the model

[0052] like Figure 3 As shown, a relatively regular area on the rough substrate surface of the low-activity martensitic steel in the experimental sample is selected for analysis, and the rough contour line of the low-activity martensitic steel substrate surface is simplified as an isosceles triangle; the distance h between the peak and the trough in the rough contour line of the low-activity martensitic steel substrate surface and the length L between the peaks are determined. The above-measured h and L are respectively set as the height and base length of the isosceles triangle.

[0053] Due to Al 2 O 3 The tritium barrier coating system model of low-activity martensitic steel has an axisymmetric type, so it can be simplified into a two-dimensional model in the XOY plane in the geometry module. 2 O 3 The coating thickness is ≥2μm, the low-activity martensitic steel substrate thickness is ≥25μm, and the radius of the low-activity martensitic steel is ≥20μm. 2 O 3 The coating thickness is 2 μm, the low-activity martensitic steel substrate thickness is 25 μm, and the radius is 20 μm. Based on this method, the preliminary modeling of the tritium barrier coating was completed.

[0054] (2) Design of gradient tritium barrier coating

[0055] ①Model design

[0056] Create a sketch in the XOY coordinate system. In this sketch, use the line command in the drawing interface to draw an isosceles triangle unit with a base length of 2μm and a height of 1.5μm. Through the concept module, select the sketch created above in the base object in the sketch generation line command, click the generation operation, and complete the creation of the isosceles triangle line Line1.

[0057] In the mode command, select the mode type as linear, and select the line body Line1 created in the above steps. Set the deviation to the length of the triangle base 2μm, set the number of copies to 9, and the direction along the positive direction of the X axis. Through the above steps, 9 additional triangle units are copied on the basis of the original model. Through the transformation command, move the 10 groups of isosceles triangle units created above by 25μm along the positive direction of the Y axis.

[0058] Click the Create New Plane module, select the Type as From Plane, and select the Base Plane as XOY Plane, and generate a new coordinate system plane 1. Right-click Plane 1 and select the Sketch Projection command from the Insert option. In this command, select the waist of the 10 groups of isosceles triangles completed in the above steps in the Geometry module, and click the Form operation to complete the new sketch. Figure 2 Create new grass in plane 1 Figure 3 In the grass Figure 3 In the sketch, select the Create Sketch command, take (0,25μm) as the starting point, and use the Create Line command to create a rectangle with a height of 2μm and a length of 20μm. Then delete the bottom edge of the rectangle, which is used as the Al 2 O 3 Coated wire model. Create a new grass in plane 1 Figure 4 , use the Create Line command to create a rectangle with a height of 25μm and a length of 20μm. Then delete the top edge of the rectangle to use it as the base line model. In the Concept module, click the Line from Sketch command and select the Base object. Figure 2 Click the Form operation to generate the interface line Line2. Continue to select the Line from Sketch command in the Concept Options and select Sketch as the Base Object. Figure 3 , Al is generated by forming 2 O 3 Coating width and length line Line3. Then, in the concept module, click the Line from Sketch command and select the Base object as Sketch. Figure 4 This step completes the creation of the rough contour line model Line4 on the upper surface of the base. Select the Line from Sketch command in the concept module again, and select the base object as Sketch. Figure 4 Through this operation, the base width and length line Line5 are generated. The above steps complete the modeling of the model line.

[0059] Use the edge-construct surface command in the concept module and select the top Al in the edge module. 2 O 3 The coating model is generated by the generation option, which includes the two wide edges, the top edge, and the rough contour lines on the upper surface of the substrate. Again, the surface form of the edge in the concept module is formed, and the two wide edges, the bottom edge, and the rough contour lines on the upper surface of the substrate are selected in the edge option, and the substrate model is established by the generation option. According to the above steps, the pre-modeling of the model is completed.

[0060] In the XOY coordinate system, establish a new coordinate plane 2 with the vertex position of the first triangle on the left (1μm, 23μm). In plane 2, set the type to originate from the centroid, and set the transfer module to rotate around the X axis. Establish a new coordinate plane 3. In plane 3, set the type to originate from the plane, set the base plane to plane 2, set the transfer to deviate from the Z axis, and set the deviation value to 0.375μm. Establish a new coordinate plane 4. In plane 4, set it to originate from the plane, set the base plane to plane 3, set the transfer module to deviate from the Z axis, and set the deviation value to 0.375μm. Establish a new coordinate plane 5. In plane 5, set the type to originate from the plane, set the base plane to plane 4, set the transfer to deviate from Z, and set the deviation value to 0.375μm. Establish a new coordinate plane 6. In plane 6, set the type to originate from the plane, set the base plane to plane 5, set the transfer to deviate from the Z axis, and set the deviation value to 0.375μm. Select the slice command, select the slice type as cutting through the plane, and select plane 3 as the base plane. Through the generation option, cut the 10 groups of isosceles triangle units into 10 groups of isosceles triangle units with a height of 0.375μm and 10 groups of isosceles trapezoidal units with a height of 1.125μm. Select the slice command, select the slice type as the cutting method through the plane, and select plane 4 as the reference plane. Through the generation option, cut the 10 groups of isosceles trapezoidal units with a height of 1.125μm cut out in the previous step into two isosceles trapezoidal parts with heights of 0.375μm and 0.75μm. Select the slice command, select the slice type as the cutting method through the plane, and select plane 5 as the reference plane. Through the generation option, cut the 10 groups of isosceles trapezoidal units with a height of 0.75μm obtained in the previous step into two isosceles trapezoidal parts with heights of 0.375μm and 0.375μm. The Al 2 O 3 The coating model, the gradient coating model unit obtained after cutting and the substrate model are combined to form an overall model. Figure 4 As shown, the 4-layer gradient coating model design is completed through the above steps.

[0061] ②Material design

[0062] Assume that the coating and substrate have isotropic and perfect elastic-plastic properties. 2 O 3 Material properties of coatings and low-activity martensitic steels, Al 2 O 3The transition area from the coating to the low-activity martensitic steel substrate is set as a gradient coating. Along the positive direction of the Y axis, the gradient coating includes a plurality of sub-coatings, which are defined as the first layer, the second layer, the third layer, ... the Kth layer, respectively, where K is greater than or equal to 4. For further example, the material design is performed with K equal to 4 layers. Figure 5 As shown, along the positive direction of the Y axis, the gradient coating is named as the 1st layer, the 2nd layer, the 3rd layer, and the 4th layer. It is characterized in that the material properties of the sub-coating of each layer in the gradient coating are calculated according to the following formula:

[0063]

[0064] Y i =Y c (V c ) i +Y s (1-(V c ) i ) (2)

[0065] E i =E c (V c ) i +E s (1-(V c ) i ) (3)

[0066] α i =α c (V c ) i +α s (1-(V c ) i ) (4)

[0067] In the formula (V c ) i represents the volume fraction of the coating in the i-th layer, n represents the number of layers of the gradient coating; Y C , Y S , Y i Represent the yield strength of coating, substrate and i-th gradient coating respectively; E C , E S , E i Represent the elastic modulus of the coating, substrate, and i-th layer respectively; α c , α s , α i represent the Poisson’s ratio of the coating, substrate, and the i-th layer, respectively.

[0068] According to the above coating property design method, the following Figure 6The material coefficients of each layer of the gradient coating are shown. In the material module of the engineering data, create 1-intermediate layer, 2-intermediate layer, 3-intermediate layer, and 4-intermediate layer respectively. Enter the thermal expansion coefficient corresponding to the four gradient coatings in the physical properties. In the linear elastic module, enter the elastic modulus and Poisson's ratio corresponding to each layer. In the strength module, enter the yield strength of the corresponding gradient coating.

[0069] In the Performance module, create Al 2 O 3 Material properties of coating, gradient coating and low-activity martensitic steel. Set the elastic modulus and Poisson's ratio in the Mechanical Elasticity module. Select Isotropic in the Elasticity module. In the Create Interface module, select Solid in the Create Range and Uniform in the Type. 2 O 3 The material properties of the gradient coating and the low-activity martensitic steel material are respectively assigned to the top coating, the 1st to 4th intermediate layers and the substrate.

[0070] (3) Grid division

[0071] like Figure 7 The figure shows the mesh division of the model. 2 O 3 The short side of the coating is divided into 6 segments by the number of divisions, the performance is set to straight, and the bias type is set to no bias. The long side is also divided into 60 segments by the number of divisions, the performance is set to straight, and the bias type is set to no bias. 2 O 3 The boundary line between the coating and the gradient coating is the 10 groups of unit cells obtained by the above slicing command. The bottom edge of each unit cell is divided into 6 segments using the number of divisions. The performance is set to straight and the bias type is set to no bias. 2 O 3 Coating added surface mesh to Al 2 O 3 According to the above steps, complete the Al 2 O 3 Mesh design of the coating model.

[0072] The short side of the gradient coating is divided into M segments and the remaining sides are divided into N segments, where M≥3 and N≥6, to obtain the gradient coating model. For further example, the short side is divided into 3 segments and the remaining sides are divided into 6 segments, the performance is set to straight, and the bias type is set to no bias. And the surface mesh is scanned for each layer in the gradient coating. According to the above steps, the meshing of the intermediate gradient coating model is completed.

[0073] The long side of the substrate is divided into 75 segments using the number of divisions, the performance is set to straight, and the bias type is set to no bias. The short side of the substrate is divided into 60 segments using the number of divisions, and the bias type is set to no bias. The leftmost boundary line of the coating model system is used as the symmetry axis for later analysis. According to the above steps, the grid design of the substrate model is completed.

[0074] (4) Boundary conditions

[0075] like Figure 8 As shown, it is the boundary condition of the model. Select the leftmost boundary line of the gradient coating model in step (3) as the symmetry axis. In the displacement command, set the displacement of all nodes on the symmetry axis along the X direction to free, and the displacement in the Y direction to 0. Continue to insert the displacement command, and select the bottom node of the low-activity martensitic steel substrate in the geometry module. The displacement of these nodes along the X direction is 0, and the displacement in the Y direction is free. Finally, insert the thermal boundary condition and limit the ambient temperature of the gradient coating model to 400℃-600℃.

[0076] (5) Results characterization

[0077] Based on the above steps (1) to (4), the Al with multiple gradients is obtained. 2 O 3 / The low-activity martensitic steel tritium barrier coating system is at an ambient temperature of 400°C-600°C, the thermal stress and thermal strain distribution of the gradient coating model at the ambient temperature, and the thermal stress and deformation distribution of the gradient coating along the substrate interface direction.

[0078] The parameters of the model in step (1) are: the type mode is selected as linear, the geometry is selected as the line body Line1 established in the above steps; the offset is set to the length of the triangle base 2μm, the number of copies is set to 9, and the direction is along the positive direction of the X axis; the parameters of the model in step (1) are: limit Al 2 O 3 The coating thickness is ≥2μm, the low-activity martensitic steel substrate thickness is ≥25μm, and the low-activity martensitic steel radius is ≥20μm; characterized in that the material properties of the sub-coating of each layer in the gradient coating are calculated according to the following formula:

[0079]

[0080] Y i =Y c (V c ) i +Y s (1-(V c ) i ) (2)

[0081] E i=E c (V c ) i +E s (1-(V c ) i ) (3)

[0082] α i =α c (V c ) i +α s (1-(V c ) i ) (4)

[0083] In the formula (V c ) i represents the volume fraction of the coating in the i-th layer; n represents the number of layers of the gradient coating; Y C , Y S , Y i Represent the yield strength of coating, substrate and i-th gradient coating respectively; E C , E S , E i Represent the elastic modulus of the coating, substrate, and i-th layer respectively; α c , α s , α i represent the Poisson’s ratio of the coating, substrate, and the i-th layer, respectively.

[0084] The modeled Al 2 O 3 The coating model, the gradient coating model obtained after cutting, and the substrate model are combined to form an overall model; the grid division method of the gradient coating in the step (3) adopts the division number method, the performance is set to straight, and the bias form is set to unbiased. The grid division method is to adopt the division number method, the performance is set to straight, and the bias form is set to unbiased.

[0085] The surface roughness contour line in step (1) is composed of 10 groups of isosceles triangle units with a base length of 2 μm and a height of 1.5 μm; in step (2), the Al 2 O 3 In the material property settings for the coating, gradient coating, and low-activity martensitic steel substrate, select isotropic mode, select solid in the creation range, and select uniform in the type.

[0086] In step (2), the 10 groups of isosceles triangle elements representing the roughness of the substrate established previously were moved 25 μm along the positive direction of the Y axis through the transformation command; in step (2) of modeling the intermediate gradient coating, the slice command was selected, the slice type was selected as cutting through a plane, and the reference plane was selected as plane 3. Through the generation option, the 10 groups of isosceles triangle elements were each cut into 10 groups of isosceles triangle elements with a height of 0.375 μm and 10 groups of isosceles trapezoidal elements with a height of 1.125 μm.

[0087] Fig. 9 As shown in Figure 2, the thermal stress distribution of the system with gradient coating and without gradient coating at 400℃ to 600℃. Fig. 9 (a) contains Al 2 O 3 Thermal stress distribution in gradient barrier tritium system. Fig. 9 (b) Single Al 2 O 3 Thermal stress distribution of tritium barrier coating system. Comparison of the two figures shows that the maximum thermal stress of the system has been significantly reduced by the introduction of gradient coating. Fig. 9 (a) The thermal stress of the coating and the interface has obvious uniform stratification, which indicates that the thermal stress in the coating decreases slowly along the substrate. Fig. 9 In (b), the thermal stress distribution at the interface is uneven, and there is obvious stress concentration at the tip of the base triangle. Stress concentration will induce microcracks in the coating. Under the action of temperature load, microcracks are prone to expand, causing macro cracking and shedding of the coating, which will pose a safety hazard to the service of the tritium barrier coating. Therefore, the introduction of the gradient coating effectively alleviates the stress concentration, reduces the thermal stress of the system, and improves the thermal stability of the coating.

[0088] Fig.10 Shown is the thermal strain distribution of the system with and without gradient coating at 400°C to 600°C. Fig.10 (a) Strain of the system containing gradient tritium barrier coating. Fig.10 (b) Single Al 2 O 3 Strain of the coating tritium barrier system. By comparison, it can be found that with the introduction of the interface gradient coating, the maximum strain of the system has been effectively reduced. In the gradient coating system, the strain distribution is uniform, the strain distribution along the interface is more continuous, and the strain change is small. This shows from the side that the introduction of the gradient coating effectively reduces the deformation of the system and thus improves the thermal stability of the coating.

[0089] Fig.11The distribution of thermal stress along the rough contour of the substrate surface with / without gradient coating system. Due to the difference in thermal properties of the materials on both sides of the interface, this area is prone to stress concentration. When the stress concentration reaches a certain level, it will cause cracking between the coating and the substrate. Therefore, the interface position is a dangerous area for the coating system. As can be seen from the figure, compared with a single Al 2 O 3 The introduction of gradient coating significantly reduces the thermal stress at the interface, thereby improving the stability of the overall coating system.

[0090] like Fig.12 The deformation distribution of the system with gradient coating and without gradient coating along the rough contour of the substrate surface. 2 O 3 The coating, which contains a gradient coating, has a small deformation along the interface direction and high stability.

[0091] In summary, the present invention provides a multi-gradient Al 2 O 3 / Low-activity martensitic steel tritium barrier coating system simulation method. On the premise that the model is closer to the actual substrate morphology, a material property is designed along the substrate to Al 2 O 3 The intermediate gradient coating with gentle distribution of the coating was then placed in an environment of 400℃ to 600℃ for finite element simulation, and the system thermal stress, thermal strain and thermal stress and deformation distribution diagram along the rough contour of the substrate surface were obtained. This method overcomes the previous complicated and high-cost experimental design method of tritium barrier coating, and can directly obtain the thermal stress and thermal strain analysis results of the entire system and along the interface at the working temperature. 2 O 3 A comparative study of thermal stress and strain of coatings and tritium barrier systems containing gradient coatings was conducted, and the analysis results provide theoretical guidance for the design of tritium barrier coatings with high thermal stability.

[0092] The present invention is described above by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-mentioned methods. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention; or the above concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for simulating a multi-gradient Al2O3 / low-activity martensitic steel tritium barrier coating system, characterized in that: The following steps are involved: (1) Model establishment The relatively regular distribution area on the rough substrate surface of the low-activity martensitic steel was selected for analysis, and the rough contour line of the substrate surface of the low-activity martensitic steel was simplified as an isosceles triangle; Determine the distance h between the peak and the trough in the rough contour line of the low-activity martensitic steel substrate surface, and the length L between the peaks, and set them as the height and base length of the isosceles triangle respectively; In the geometry module, the Al2O3 / low-activity martensitic steel tritium barrier coating system is simplified into a two-dimensional model in the XY plane; (2) Design of gradient coating ①Model design An isosceles triangle unit is established in the XOY coordinate system; the isosceles triangle unit is copied by a mode command; and the isosceles triangle unit is cut into a gradient intermediate coating by a slice command; ②Material design Based on the material properties of the Al2O3 / low-activity martensitic steel tritium barrier system, the transition area from the Al2O3 coating to the low-activity martensitic steel substrate is set as a gradient coating to form an Al2O3 / low-activity martensitic steel tritium barrier coating with multiple gradients; along the positive direction of the Y axis, the gradient coating includes a plurality of sub-coatings, and the plurality of sub-coatings are respectively defined as the first layer, the second layer, the third layer ... the Kth layer, where K is greater than or equal to 4; (3) Grid division Divide the short sides of the gradient coating obtained in step (2) into M segments, and divide the remaining sides into N segments, where M≥3 and N≥6; obtain the gradient coating grid design; (4) Boundary conditions The leftmost boundary line of the gradient coating model in step (3) is selected as the symmetry axis. In the displacement command, the displacement of all nodes on the symmetry axis in the X direction is set to be free, and the displacement in the Y direction is set to be 0; the displacement of all nodes on the bottom edge of the substrate of the low-activity martensitic steel in the X direction is selected to be 0, and the displacement in the Y direction is set to be free; and the ambient temperature of the gradient coating model is limited to 400° C.-600° C.; (5) Results characterization Based on the above steps (1) to (4), the Al2O3 / low-activity martensitic steel tritium barrier coating system with multiple gradients is obtained at an ambient temperature of 400°C-600°C, the thermal stress and thermal strain distribution of the gradient coating model at the ambient temperature, and the thermal stress and deformation distribution of the gradient coating along the substrate interface direction.

2. The method for simulating a multi-gradient Al2O3 / low-activity martensitic steel tritium barrier coating system according to claim 1, characterized in that: The parameters of the model in step (1) are: the type mode is selected as linear, the geometry selects the line body Line1 established in the above steps; the offset is set to the length of the triangle base 2μm, the number of copies is set to 9, and the direction is along the positive direction of the X-axis.

3. The method for simulating a multi-gradient Al2O3 / low-activity martensitic steel tritium barrier coating system according to claim 1, characterized in that: The parameters of the model in step (1) are as follows: the thickness of the Al2O3 coating is limited to ≥2 μm, the thickness of the low-activity martensitic steel substrate is ≥25 μm, and the radius of the low-activity martensitic steel is ≥20 μm.

4. A method for simulating a multi-gradient Al2O3 / low-activity martensitic steel tritium barrier coating system according to any one of claims 1 to 3, characterized in that: The material properties of the sub-coating of each layer in the gradient coating are calculated according to the following formula: AND i =And c (V c ) i +Y s (1-(V c ) i ) (2) E i =E c (V c ) i +E s (1-(V c ) i ) (3) a i =a c (V c ) i +a s (1-(V c ) i ) (4) In the formula (V c ) i represents the volume fraction of the coating in the i-th layer, n represents the number of layers of the gradient coating; Y C , Y S , Y i Represent the yield strength of coating, substrate and i-th gradient coating respectively; E C , E S , E i Represent the elastic modulus of the coating, substrate, and i-th layer respectively; α c , α s , α i represent the Poisson’s ratio of the coating, substrate, and the i-th layer, respectively.

5. A method for simulating a multi-gradient Al2O3 / low-activity martensitic steel tritium barrier coating system as claimed in claim 1 or 2, characterized in that: After the design of the gradient coating in step (2) is completed, the Al2O3 coating that has been modeled, the gradient coating unit obtained after cutting, and the substrate model are combined to form an overall model.

6. A method for simulating a multi-gradient Al2O3 / low-activity martensitic steel tritium barrier coating system as claimed in claim 1 or 2, characterized in that: The grid division method of the gradient coating in the step (3) adopts the division quantity method, the performance is set to straight, and the bias form is set to unbiased.

7. A method for simulating a multi-gradient Al2O3 / low-activity martensitic steel tritium barrier coating system according to any one of claims 1 or 2, characterized in that: The surface roughness contour line in the step (1) is composed of the waists of 10 groups of isosceles triangle units with a base length of 2 μm and a height of 1.5 μm.

8. A method for simulating a multi-gradient Al2O3 / low-activity martensitic steel tritium barrier coating system according to any one of claims 1 to 3, characterized in that: In step (2), in the material property settings involving the Al2O3 coating, gradient coating and low-activity martensitic steel substrate, select the isotropic method, select solid in the creation range, and select uniform in the type.

9. The method for simulating a multi-gradient Al2O3 / low-activity martensitic steel tritium barrier coating system according to claim 7, characterized in that: In step (2), the 10 groups of isosceles triangle elements representing the surface roughness of the substrate previously established are moved 25 μm along the positive direction of the Y axis through the transformation command.

10. The method for simulating a multi-gradient Al2O3 / low-activity martensitic steel tritium barrier coating system according to claim 7, characterized in that: In step (2) of modeling the intermediate gradient coating, select the slice command, select the slice type as cutting through a plane, and select plane 3 as the reference plane; through the generation option, cut each of the 10 groups of isosceles triangles into 10 groups of isosceles triangles with a height of 0.375 μm and 10 groups of isosceles trapezoids with a height of 1.125 μm.

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