Method for predicting different crack tip driving forces in double-layer environmental barrier coating

Abstract

The invention relates to a method for predicting different crack tip driving forces in a double-layer environmental barrier coating, which belongs to the field of material science and comprises the following steps: modeling a coating crack propagation behavior through finite element analysis (FEM), quantitatively analyzing the driving forces of crack tips and evaluating crack propagation trends under different working conditions. The mechanical property and the thermal behavior of the coating material are simulated through the system, and the crack propagation path and the possible failure mode can be predicted. According to the method, a scientific basis is provided for design optimization of the environmental barrier coating, and potential crack propagation risks can be identified in the design stage, so that material selection and the coating structure are optimized, the crack propagation resistance is improved, the service life is prolonged, and the reliability and safety of high-temperature parts are improved.

Description

Technical Field

[0001] This invention belongs to the field of materials science, and specifically relates to a method for predicting the driving force of different crack tips in a double-layer environmental barrier coating. Background Technology

[0002] Environmental barrier coatings (EBCs) are important protective materials widely used in critical components operating in high-temperature environments, such as turbine inlets, including aero engines. Their primary function is to protect the base material from corrosion by high-temperature gases, oxidation, and water vapor, thereby improving engine lifespan and performance.

[0003] As the performance and fuel efficiency requirements of aero engines continue to increase, the maximum inlet temperature of the turbine inlet is gradually rising. However, the high-temperature tolerance of traditional superalloy materials is nearing its limit, and even with cooling systems and thermal barrier coatings, it is difficult to meet the demands of even higher temperatures. Therefore, ceramic matrix composites (CMCs) such as SiC are being used... f SiC has become a growing trend as a replacement material for high-temperature components. f / SiC materials have low density and excellent high-temperature strength, enabling them to provide better performance in high-temperature environments.

[0004] However, SiC f When SiC materials are exposed to oxygen, a protective SiO2 oxide film forms to prevent further oxidation. However, the presence of water vapor reacts with SiO2 to generate volatile Si(OH)4, accelerating its degradation and affecting its long-term performance. Therefore, using EBCs to protect CMC materials has become an effective way to extend their service life.

[0005] To meet long-term effective protection requirements, EBC materials must possess good high-temperature phase stability, excellent water vapor corrosion resistance, and, crucially, thermal compatibility with the matrix material. Rare earth silicate materials are ideal for EBCs due to their good chemical compatibility with CMC. Among them, Yb₂SiO₅ exhibits strong water vapor corrosion resistance, while Yb₂Si₂O₇ is widely used in EBC design due to its good thermal expansion matching. By designing the intermediate layer of a composite structure and adjusting the phase ratio of Yb₂SiO₅ to Yb₂Si₂O₇, the thermal expansion matching and corrosion resistance of the coating can be further optimized.

[0006] However, crack propagation frequently occurs in coated systems during thermal cycling tests. Studies have shown that the propagation and bifurcation of surface cracks have a significant impact on the failure mechanism of coatings, and crack density and crack propagation behavior are directly related to the durability and thermal shock resistance of the coating. Therefore, studying the driving force of crack propagation, crack density, and their impact on coating performance has become an important direction for coating design optimization.

[0007] This invention systematically studies the influence of different crack distributions in coatings on crack propagation behavior using the finite element method (FEM), providing a theoretical basis for the performance optimization and design of EBCs. Summary of the Invention

[0008] The purpose of this invention is to provide a method for predicting the driving force of different crack tips in a double-layer environmental barrier coating, so as to optimize the coating design and improve its performance and durability in high-temperature and corrosive environments.

[0009] This invention provides a method for predicting the driving force of different crack tips in a double-layer environmental barrier coating, the method comprising the following steps: (1) Establishment of geometric model: In the modeling module of finite element software, establish a geometric model of the environmental barrier coating system including the substrate, adhesive layer, intermediate layer and surface layer; (2) Define material properties: In the material module of the finite element software, define the elastic modulus, Poisson's ratio, coefficient of thermal expansion and other material parameters for the matrix, adhesive layer, intermediate layer and surface layer respectively; (3) Set the analysis step and boundary conditions: Set up a static universal analysis step to simulate the response of the environmental barrier coating system; Set mechanical boundary conditions to constrain the rigid body displacements of the model; Set thermal boundary conditions to simulate the actual service temperature environment of the coating system; (4) Perform grid division; (5) Calculation and result analysis: Submit the finite element software calculation task to obtain the stress field and strain field distribution, and analyze the propagation driving force of crack tips located in different parts; based on the calculated crack propagation driving force, determine the crack propagation trend, and thus predict the dangerous area of ​​the environmental barrier coating system.

[0010] The present invention provides a method for predicting the driving force of different crack tips in a double-layer environmental barrier coating, wherein the coating is a double-layer coating consisting of Yb2SiO5 as the top layer and Yb2Si2O7 as the intermediate layer.

[0011] The present invention provides a method for predicting the driving force at the tip of different cracks in a double-layer environmental barrier coating, wherein the crack propagation trend is determined by calculating the change in the driving force at the crack tip.

[0012] The present invention provides a method for predicting the driving force of different crack tips in a double-layer environmental barrier coating, wherein the crack location is one of the following regions: the surface layer, the interface between the surface layer and the intermediate layer, and the intermediate layer.

[0013] The method for predicting the driving force of different crack tips in a double-layer environmental barrier coating provided by this invention uses a finite element model with a width range of 0.04~0.5 mm when predicting the crack driving force.

[0014] The method provided by this invention for predicting the driving force of different crack tips in a double-layer environmental barrier coating, when the research object is a bifurcated crack located in the middle layer, the bifurcation angle of the bifurcated crack is in the range of 5~90°.

[0015] The beneficial effects of this invention are as follows: By calculating the driving force at the tip of a bifurcated crack in a double-layer environmental barrier coating, this invention can accurately assess the key factors of crack propagation, providing a scientific basis for the optimized design of the coating. This technology, by quantifying the driving force of crack propagation, helps predict the crack development trend of the coating under different operating conditions, revealing the relationship between crack propagation and coating materials, structure, and external environmental factors. This analysis can effectively guide the selection of coating materials and the optimization of coating structures, improving the coating's resistance to crack propagation and reducing the risk of coating failure. Furthermore, the technical method provided by this invention helps to identify potential failure modes in advance during the coating design stage, ensuring the coating operates stably for a long time in harsh environments such as high temperature and corrosion, thereby significantly extending the service life of the coating and improving the reliability and safety of high-temperature components. Attached Figure Description

[0016] Figure 1 The model is an overall model of an environmental barrier coating with surface cracks. (a) shows the structure of the environmental barrier coating, which consists of a top layer, an intermediate layer, an adhesive layer, and a substrate, arranged from top to bottom. (b) shows the environmental barrier coating model after meshing. (c) shows a partial enlarged schematic diagram of the top layer mesh. Figure 2 The model is an overall model of an environmental barrier coating containing interface cracks. (a) shows the structure of the environmental barrier coating, which consists of a top layer, an intermediate layer, an adhesive layer, and a substrate, arranged from top to bottom. (b) shows the environmental barrier coating model after meshing. (c) shows a magnified view of a part of the mesh containing interface cracks. Figure 3 The model is an overall model of an environmental barrier coating containing bifurcated cracks in the intermediate layer. (a) shows the structure of the environmental barrier coating, which consists of a top layer, an intermediate layer, an adhesive layer, and a substrate, arranged from top to bottom. (b) shows the environmental barrier coating model after meshing. (c) and (d) are enlarged schematic diagrams of the mesh containing bifurcated cracks. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0018] To simplify the description, the present invention makes the following assumptions: (1) each coating layer, substrate and bottom layer material are uniform and isotropic; (2) each coating layer has uniform thickness; (3) an ideal elastic model is used; (4) this method only describes the finite element analysis of a single environmental barrier coating system.

[0019] Example 1: Predicted driving force of surface crack tips when crack density is 5 cracks / mm (1) Establishment of the preliminary geometric model In this embodiment, the layers of the environmental barrier coating are defined as follows: top layer (TC), intermediate layer (IC), adhesive layer (BC), and substrate (SUB). The thickness of the top layer is... h TC The thickness of the intermediate layer is h IC The thickness of the adhesive layer is h BC The thickness of the substrate is h SUB The model width is w The vertical crack length is l In the component module of the finite element software, the sketch tool is used to create and divide the structure of each layer of the environmental barrier coating, and the meshing tool is used to add surface cracks of different lengths. The finite element model of the environmental barrier coating containing surface cracks is shown below. Figure 1 As shown, surface cracks can be observed. h TC It is 0.1 mm, the h IC It is 0.1 mm, the h BC It is 0.08 mm, the h SUB It is 2 mm, the w It is 0.2 mm, the l It is 0.005~0.08 mm.

[0020] (2) Assigning material properties Assign material properties to the topcoat, intermediate layer, adhesive layer, and substrate. Assume that the material properties do not change with temperature; specific values ​​are shown in Table 1 below. Table 1 Material Properties

[0021] (3) Setting of mechanical and thermal boundary conditions In the interaction module of the finite element software, set the mechanical boundary conditions for the coating system: Set symmetrical boundary conditions on the left side; The right side sets the continuity boundary conditions, which are implemented through multi-point constraints (MPC). The lower boundary has a fixed vertical displacement. The upper boundary is free.

[0022] In the boundary conditions module of the finite element software, set the temperature conditions for the coating system: the entire coating system is cooled from 1350 ℃ to 25 ℃.

[0023] (4) Analysis step settings In the analysis step module of the finite element software, a static general analysis step is created, and the implicit calculation method is used for solving.

[0024] (5) Grid division The model is meshed, especially at the interface, to improve computational accuracy.

[0025] (6) Submission of computation task After completing the model setup, submit the calculation task to solve the problem and analyze the change in driving force at the crack tip. The results of the surface crack tip driving force when the crack density is 5 cracks / mm are as follows: Figure 2 As shown, the greater the driving force at the crack tip, the easier it is for the coating to be damaged. Figure 2 The results can predict the hazardous areas of the coating system.

[0026] Example 2: Predicted driving force of interface crack tip when crack density is 5 cracks / mm (1) Establishment of the preliminary geometric model In this embodiment, the layers of the environmental barrier coating are defined as follows: top layer (TC), intermediate layer (IC), adhesive layer (BC), and substrate (SUB). The thickness of the top layer is... h TC The thickness of the intermediate layer is h IC The thickness of the adhesive layer is h BC The thickness of the substrate is h SUB The model width is w The deflection length of the interface deflection crack is d d The penetration depth of the interface penetration crack is d p In the component module of the finite element method software, the sketching tool is used to create and divide the structure of each layer of the environmental barrier coating, and the meshing tool is used to add interface cracks. The finite element model of the environmental barrier coating containing interface cracks is shown below. Figure 2 As shown, the presence of interface cracks can be observed. hTC It is 0.1 mm, the h IC It is 0.1 mm, the h BC It is 0.08 mm, the h SUB It is 2 mm, the w It is 0.2mm, the d d The value is 0.001 mm. d p It is 0.001 mm.

[0027] (2) Assigning material properties Assign material properties to the topcoat, intermediate layer, adhesive layer, and substrate. Assume these material properties do not change with temperature; specific values ​​are shown in Table 2 below. Table 2 Material Properties

[0028] (3) Setting of mechanical and thermal boundary conditions In the interaction module of the finite element software, set the mechanical boundary conditions for the coating system: Set symmetrical boundary conditions on the left side; The right side sets the continuity boundary conditions, which are implemented through multi-point constraints (MPC). The lower boundary has a fixed vertical displacement. The upper boundary is free.

[0029] In the boundary conditions module of the finite element software, set the temperature conditions for the coating system: the entire coating system is cooled from 1350 ℃ to 25 ℃.

[0030] (4) Analysis step settings In the analysis step module of the finite element software, a static general analysis step is created, and the implicit calculation method is used for solving.

[0031] (5) Grid division The model is meshed, especially at the interface, to improve computational accuracy.

[0032] (6) Submission of computation task After completing the model setup, submit the calculation task to solve the problem, analyze the changes in the driving force at the crack tip, and predict the dangerous areas of the coating system.

[0033] Example 3: Predicted driving force at the tip of a bifurcated crack when the crack density is 5 cracks / mm (1) Establishment of the preliminary geometric model In this embodiment, the layers of the environmental barrier coating are defined as follows: top layer (TC), intermediate layer (IC), adhesive layer (BC), and substrate (SUB). The thickness of the top layer is... h TC The thickness of the intermediate layer is h IC The thickness of the adhesive layer is h BC The thickness of the substrate is h SUB The model width is w The bifurcation angle of the bifurcation crack is α In the component module of the finite element software, the sketch tool is used to create and divide the structure of each layer of the environmental barrier coating, and the partitioning tool is used to add bifurcated cracks. The finite element model of the environmental barrier coating containing bifurcated cracks is shown below. Figure 3 As shown, the presence of bifurcated cracks can be observed. h TC It is 0.1mm, the h IC It is 0.1mm, the h BC It is 0.08mm, the h SUB It is 2mm, the w It is 0.2mm, the α The range is 5 to 90 degrees.

[0034] (2) Assigning material properties Assign material properties to the topcoat, intermediate layer, adhesive layer, and substrate. Assume these material properties do not change with temperature; specific values ​​are shown in Table 3 below. Table 3 Material Properties

[0035] (3) Setting of mechanical and thermal boundary conditions In the interaction module of the finite element software, set the mechanical boundary conditions for the coating system: Set symmetrical boundary conditions on the left side; The right side sets the continuity boundary conditions, which are implemented through multi-point constraints (MPC). The lower boundary has a fixed vertical displacement. The upper boundary is free.

[0036] In the boundary conditions module of the finite element software, set the temperature conditions for the coating system: the entire coating system is cooled from 1350 ℃ to 25 ℃.

[0037] (4) Analysis step settings In the analysis step module of the finite element software, a static general analysis step is created, and the implicit calculation method is used for solving.

[0038] (5) Grid division The model is meshed, especially at the interface, to improve computational accuracy.

[0039] (6) Submission of computation task After completing the model setup, submit the calculation task to solve the problem, analyze the changes in the driving force at the crack tip, and predict the dangerous areas of the coating system.

Claims

1. A method for predicting the driving force at different crack tips in a double-layer environmental barrier coating, characterized in that: The steps of this method are as follows: (1) Establishment of geometric model: In the modeling module of finite element software, establish a geometric model of the environmental barrier coating system including the substrate, adhesive layer, intermediate layer and surface layer; (2) Define material properties: In the material module of the finite element software, define the elastic modulus, Poisson's ratio, coefficient of thermal expansion and other material parameters for the matrix, adhesive layer, intermediate layer and surface layer respectively; (3) Set the analysis step and boundary conditions: Set up a static universal analysis step to simulate the response of the environmental barrier coating system; Set mechanical boundary conditions to constrain the rigid body displacements of the model; Set thermal boundary conditions to simulate the actual service temperature environment of the coating system; (4) Perform grid division; (5) Calculation and result analysis: Submit the finite element software calculation task to obtain the stress field and strain field distribution, and analyze the propagation driving force of crack tips located in different parts; based on the calculated crack propagation driving force, determine the crack propagation trend, and thus predict the dangerous area of ​​the environmental barrier coating system.

2. The method for predicting the driving force of different crack tips in a double-layer environmental barrier coating according to claim 1, characterized in that: The coating is a two-layer coating consisting of Yb2SiO5 as the top layer and Yb2Si2O7 as the intermediate layer.

3. The method for predicting the driving force of different crack tips in a double-layer environmental barrier coating according to claim 1, characterized in that: The crack propagation trend is determined by calculating the change in the driving force at the crack tip.

4. The method for predicting the driving force of different crack tips in a double-layer environmental barrier coating according to claim 1, characterized in that: The crack location is one of the following regions: the surface layer, the interface between the surface layer and the intermediate layer, and the intermediate layer.

5. The method for predicting the driving force of different crack tips in a double-layer environmental barrier coating according to claim 1, characterized in that: When predicting crack driving force, the width of the finite element model used is in the range of 0.04~0.5 mm.

6. The method for predicting the driving force of different crack tips in a double-layer environmental barrier coating according to claim 1, characterized in that: When the research object is a bifurcated crack located in the middle layer, the bifurcation angle of the bifurcated crack ranges from 5 to 90°.

Images