Method for predicting early stage oxide scale on nickel-base superalloy surfaces

Abstract

The application discloses a prediction method for early oxidation layer on the surface of nickel-based superalloy, which comprises the following steps: determining the phase composition of the nickel-based superalloy; obtaining the critical parameters of each phase of the nickel-based superalloy through numerical calculation by means of the density functional theory, and determining the chemical potential range of each element; establishing a surface model of the nickel-based superalloy and calculating the surface energy, selecting the surface model of the nickel-based superalloy with the lowest surface energy under the chemical potential value of each element, and determining the adsorption site; adding oxygen atoms on the adsorption site to establish an oxygen-nickel-based superalloy surface model and calculate the surface energy, selecting the model with the lowest surface energy under the chemical potential value of each element as the most stable model under the environment, and drawing a surface phase diagram of the nickel-based superalloy; and predicting the early oxidation layer on the surface of the nickel-based superalloy by means of the surface phase diagram of the nickel-based superalloy and in combination with the chemical potential change of each element. The application can predict the composition and continuity of the early oxidation layer on the surface of the nickel-based superalloy.

Description

Technical Field

[0001] This invention belongs to the field of nickel-based superalloy surface oxide layer prediction technology, specifically relating to a method for predicting early oxide layers on nickel-based superalloy surfaces. Background Technology

[0002] Nickel-based superalloys, due to their excellent physical, chemical, and mechanical properties, are widely used in industrial manufacturing and aerospace fields. The manufacturing and processing level of nickel-based superalloys has long been an important indicator of a country's technological development. In industrial production, the oxidation behavior of nickel-based superalloys is a common problem, and with technological advancements, increasingly complex and demanding operating conditions place higher requirements on their oxidation resistance. Improving the oxidation resistance of nickel-based superalloys can extend equipment lifespan, enhance system safety, and broaden the application range of materials; therefore, the oxidation resistance of nickel-based superalloys cannot be ignored.

[0003] When nickel-based superalloys are exposed to the environment, their surfaces undergo oxidation with oxygen, forming an oxide layer in the early stages of oxidation. Differences in the composition of the nickel-based superalloy and the oxidizing environment lead to significant variations in the composition, morphology, and continuity of the oxide layer. The structure and composition of the oxide layer directly affect the mechanical and chemical properties of the material. The properties of the initial oxide layer not only influence subsequent oxidation behavior but also directly determine whether the material can meet service requirements. A thorough understanding of the properties of the early oxide layer on nickel-based superalloys can optimize their performance, improve oxidation resistance, and extend service life; therefore, predictive analysis of the initial oxide layer on the surface of nickel-based superalloys is necessary.

[0004] Currently, some literature describes methods for predicting the mechanical properties of nickel-based superalloys, but there are very few methods for predicting the composition and continuity of the early oxide layer on the surface of nickel-based superalloys, and none of them consider the mechanism of the effect of microscopic atomic interactions on the early oxide layer. Therefore, it is necessary to develop a method for predicting the early oxide layer on the surface of nickel-based superalloys to solve the problems existing in the current technology.

[0005] Chinese patent application CN117457118A discloses a method for predicting the thickness of a high-temperature oxide layer on titanium alloys under forging temperatures. This method includes the following steps: obtaining the relationship between different high-temperature oxidation conditions and the high-temperature oxidation weight gain of titanium alloy samples; establishing the relationship between different high-temperature oxidation conditions and the high-temperature oxidation weight gain of titanium alloy samples; obtaining the relationship between the high-temperature oxide layer thickness and the oxidation weight gain of titanium alloy samples; establishing a model for the high-temperature oxide layer thickness and the oxidation weight gain per unit area, thereby calculating the predicted value of the high-temperature oxide layer thickness of titanium alloy samples under different high-temperature oxidation conditions. This method predicts the thickness of the high-temperature oxide layer on titanium alloys, not the oxide layer on the surface of nickel-based superalloys. Furthermore, it only considers the macroscopic reaction between titanium alloys and oxygen, without considering the microscopic mechanism of the effect of oxygen atoms on the surface of titanium alloys, and therefore cannot predict the composition and continuity of the oxide layer. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for predicting the early oxide layer on the surface of nickel-based superalloys. The prediction method includes the following steps in sequence:

[0007] Step 1: Test the unoxidized nickel-based superalloy target specimen to determine the phase composition of the nickel-based superalloy; Step 2: Based on the determined phase composition of the nickel-based superalloy, establish a unit cell model, perform numerical calculations using density functional theory to obtain relaxation results, obtain the critical parameters of each phase of the nickel-based superalloy based on the relaxation results, and determine the chemical potential range of each element on the surface of the nickel-based superalloy based on the chemical potential equilibrium theory.

[0008] Step 3: Establish several nickel-based superalloy surface models using a unit cell model, calculate the total energy of each nickel-based superalloy surface model, and then calculate the surface energy of each nickel-based superalloy surface model; select the nickel-based superalloy surface model with the lowest surface energy for each element's chemical potential value, and determine all possible adsorption sites on the selected nickel-based superalloy surface model; sequentially place oxygen atoms on different adsorption sites of different nickel-based superalloy surface models to establish oxygen-nickel-based superalloy surface models respectively;

[0009] Step 4: Based on several oxygen-nickel-based superalloy surface models, calculate the total energy of each oxygen-nickel-based superalloy surface model and the surface energy of each oxygen-nickel-based superalloy surface model; select the model with the lowest surface energy under each element's chemical potential value as the most stable model under this environment, and draw the nickel-based superalloy surface phase diagram based on the most stable model.

[0010] Step 5: By drawing the phase diagram of the nickel-based superalloy surface and combining it with the changes in the chemical potential of each element and oxygen element inside the nickel-based superalloy, the early oxide layer on the surface of the nickel-based superalloy is predicted.

[0011] Step Six: Conduct oxidation tests on the target nickel-based superalloy test piece, and compare the test results with the predicted early oxide layer on the surface of the nickel-based superalloy to verify the accuracy of the prediction method.

[0012] Preferably, in step one, the phase composition of the nickel-based superalloy includes at least the elemental composition and crystal structure of the nickel-based superalloy.

[0013] In any of the above schemes, it is preferred that, in step two, the critical parameter of each phase of the nickel-based superalloy is the total energy of each phase in the nickel-based superalloy.

[0014] In any of the above schemes, preferably, in step two, the chemical potential range of each element on the surface of the nickel-based superalloy should satisfy... In the formula,

[0015] —The chemical potential of a single i atom in the element i in its elemental form, in eV;

[0016] u bulk —The chemical potential of a single unit cell in a nickel-based superalloy, in eV;

[0017] u i —The chemical potential of a single i atom in a single unit cell of a nickel-based superalloy, in eV;

[0018] u j —The chemical potential of a single j atom in a single unit cell of a nickel-based superalloy, in eV;

[0019] M i —The number of i atoms in a single unit cell of a nickel-based superalloy;

[0020] M j —The number of j atoms in a single unit cell of a nickel-based superalloy;

[0021] i — Element type;

[0022] j — the types of elements other than i in a single unit cell.

[0023] In any of the above schemes, preferably, in step two, the chemical potential of atoms in a single unit cell of the nickel-based superalloy should satisfy the relationship u. bulk =∑ i M i u i In the formula,

[0024] ubulk —The chemical potential of a single unit cell in a nickel-based superalloy, in eV;

[0025] M i —The number of i atoms in a single unit cell of a nickel-based superalloy;

[0026] u i —The chemical potential of a single i atom in a single unit cell of a nickel-based superalloy, in eV;

[0027] i — Element type.

[0028] In any of the above schemes, preferably, in step three, the surface energy calculation formula for the nickel-based superalloy surface model is as follows: In the formula,

[0029] γ—Surface energy

[0030] E slab —Total energy of the surface model, eV;

[0031] N i —The number of i atoms in the surface model;

[0032] —The chemical potential of atom i in the surface model, in eV;

[0033] A – Total surface area of ​​the surface model. i — Element type.

[0034] Preferably, in any of the above schemes, in step four, the surface energy calculation formula for the oxygen-nickel-based superalloy surface model remains as follows: In the formula,

[0035] γ—Surface energy

[0036] E slab —Total energy of the surface model, eV;

[0037] N i —The number of i atoms in the surface model;

[0038] —The chemical potential of atom i in the surface model, in eV;

[0039] A – Total surface area of ​​the surface model. i — Element type.

[0040] In any of the above schemes, preferably, in step four, the chemical potential range of oxygen atoms in the oxygen-nickel-based superalloy surface model should satisfy... In the formula,

[0041] —The chemical potential of an oxygen molecule, eV;

[0042] u O —The chemical potential of a single oxygen atom in the surface model of an oxygen-nickel-based superalloy, in eV.

[0043] In any of the above schemes, it is preferred that, in step four, the model with the lowest surface energy under each element's chemical potential value is selected as the most stable model under this environment, and a phase diagram of the nickel-based superalloy surface is drawn based on the most stable model. This model includes a nickel-based superalloy surface model and an oxygen-nickel-based superalloy surface model.

[0044] In any of the above schemes, the preferred method for drawing the nickel-based superalloy surface phase diagram in step four is to calculate a certain chemical potential equilibrium state and select the nickel-based superalloy surface model with the lowest surface energy and the oxygen-nickel-based superalloy surface model as the most likely phases to appear.

[0045] This invention utilizes the CASTEP module of Materials Studio (MS) software to perform geometric optimization of a surface model based on first-principles calculations and calculate the surface energy. Then, by combining the chemical potential ranges of each element, a surface model with the lowest surface energy is obtained. The computational setup uses the Generalized Gradient Approximation Functional (GGA) as the exchange-correlation functional and the Perdew-Burke-Ernzerhof (PBE) functional as the exchange-correlation functional. The Grimme method is used to handle van der Waals forces and long-range interactions. A 7x7x1 k-point network is used for model optimization and electronic property calculation. The BFGS method is selected for optimization, with a convergence energy residual set to 1×10⁻⁵ eV / atom and a residual stress less than [value missing]. Offset residual less than The cutoff energy was set to 300 eV, and spin polarization was considered throughout the calculation.

[0046] The detailed scheme for establishing and validating the above-mentioned method for predicting the early oxide layer on the surface of nickel-based superalloys based on density functional theory and thermodynamic calculations is as follows:

[0047] X-ray diffraction (XRD) was used to determine the phase composition of nickel-based superalloys. A combination of density functional theory and thermodynamic calculations was employed, based on information such as the alloy element composition and crystal structure, to establish and calculate unit cell models, determining the critical parameters of each phase of the nickel-based superalloy. The chemical potential range of each element on the nickel-based superalloy surface was determined according to the chemical potential equilibrium theory. Surface models of the nickel-based superalloys were constructed based on the unit cell models, and energy calculations were performed to calculate the surface energy of each model. The nickel-based superalloy surface model with the lowest surface energy for each element's chemical potential value was selected, and all possible adsorption sites on the selected model were identified. Oxygen atoms were then placed on different adsorption sites in different nickel-based superalloy surface models to establish oxygen-nickel-based superalloy surface models. The total energy of each oxygen-nickel-based superalloy surface model was calculated, followed by the surface energy. The variation range of the chemical potential of each element was determined according to the chemical potential equilibrium theory, and the surface energy variation of the oxygen-nickel-based superalloy surface models was analyzed. Surface energy is negatively correlated with structural stability. Oxygen tends to combine with the alloy surface to form the structure with the lowest surface energy. This allows us to predict the most likely structure to appear under a given chemical potential state, and ultimately to predict the composition and continuity of the early oxide layer on the surface of nickel-based superalloys.

[0048] Nickel-based superalloys have complex and diverse grades and service conditions, making it difficult to predict and assess the early oxide layer that will form during their service. The structure and composition of the oxide layer directly affect the mechanical and chemical properties of the alloy, and also directly determine whether the alloy can continue to meet the service conditions. Therefore, the prediction and assessment of the initial oxide layer of nickel-based superalloys is essential for the safe and stable operation of equipment.

[0049] The method for predicting the early oxide layer on the surface of nickel-based superalloys of the present invention has the following beneficial effects:

[0050] (1) This invention proposes a method for predicting the early oxide layer on the surface of nickel-based superalloys based on density functional theory and thermodynamic calculations. This prediction method is based on density functional theory and thermodynamic calculations, and combines the variation range of chemical potential of each element in the oxidation behavior to establish a prediction phase diagram of the early oxide layer on the surface of nickel-based superalloys, providing a theoretical basis and methodological support for the prediction of the early oxide layer on the surface of nickel-based superalloys.

[0051] (2) The prediction method of the present invention can be used to qualitatively predict the composition and continuity of the early oxide layer on the surface of nickel-based superalloys, which is beneficial to the normal service of nickel-based superalloys.

[0052] (3) The method for predicting the early oxide layer on the surface of nickel-based superalloys of the present invention has been verified by the alloy oxidation test and has high accuracy. It provides technical support for the assessment of the early oxidation behavior of nickel-based superalloys. It can predict the early oxidation behavior of nickel-based superalloys under various environments, thereby avoiding economic losses caused by field experiments. Attached Figure Description

[0053] Figure 1 This is a flowchart of a preferred embodiment of the method for predicting early oxide layers on the surface of nickel-based superalloys according to the present invention;

[0054] Figure 2 for Figure 1 XRD detection results of the surface of nickel-based superalloy DD6 in the illustrated embodiment;

[0055] Figure 3 for Figure 1 The range of surface energy of the nickel-based superalloy surface model in the illustrated embodiment as a function of the chemical potential of Al.

[0056] Figure 4 for Figure 1 Microscopic model of the surface of nickel-based superalloy DD6 and possible adsorption sites in the illustrated embodiment;

[0057] Figure 5 for Figure 1 Elemental segregation determination phase diagram of the oxygen-nickel-based superalloy surface model in the embodiment shown;

[0058] Figure 6 for Figure 1 Phase diagram for determining oxygen element coverage of the oxygen-nickel based superalloy surface model in the illustrated embodiment;

[0059] Figure 7 for Figure 1 XRD detection results of the early oxide layer on the surface of the nickel-based superalloy in the illustrated embodiment;

[0060] Figure 8 for Figure 1 Super depth-of-field micrographs of the early oxide layer on the surface of a nickel-based superalloy in the illustrated embodiment.

[0061] The diagram shows the following labels: T - the top position of the surface atom, B - the middle position of the two closest atoms, and H - the middle position formed by multiple atoms. Detailed Implementation

[0062] To further understand the invention, the following detailed description of the invention will be provided in conjunction with specific embodiments.

[0063] like Figure 1As shown, in a preferred embodiment of the method for predicting the early oxide layer on the surface of nickel-based superalloys according to the present invention, the prediction method includes the following steps in sequence:

[0064] Step 1: Test the unoxidized nickel-based superalloy target specimen to determine the phase composition of the nickel-based superalloy; Step 2: Based on the determined phase composition of the nickel-based superalloy, establish a unit cell model, perform numerical calculations using density functional theory to obtain relaxation results, obtain the critical parameters of each phase of the nickel-based superalloy based on the relaxation results, and determine the chemical potential range of each element on the surface of the nickel-based superalloy based on the chemical potential equilibrium theory.

[0065] Step 3: Establish several nickel-based superalloy surface models using a unit cell model, calculate the total energy of each nickel-based superalloy surface model, and then calculate the surface energy of each nickel-based superalloy surface model; select the nickel-based superalloy surface model with the lowest surface energy for each element's chemical potential value, and determine all possible adsorption sites on the selected nickel-based superalloy surface model; sequentially place oxygen atoms on different adsorption sites of different nickel-based superalloy surface models to establish oxygen-nickel-based superalloy surface models respectively;

[0066] Step 4: Based on several oxygen-nickel-based superalloy surface models, calculate the total energy of each oxygen-nickel-based superalloy surface model and the surface energy of each oxygen-nickel-based superalloy surface model; select the model with the lowest surface energy under each element's chemical potential value as the most stable model under this environment, and draw the nickel-based superalloy surface phase diagram based on the most stable model.

[0067] Step 5: By drawing the phase diagram of the nickel-based superalloy surface and combining it with the changes in the chemical potential of each element and oxygen element inside the nickel-based superalloy, the early oxide layer on the surface of the nickel-based superalloy is predicted.

[0068] Step Six: Conduct oxidation tests on the target nickel-based superalloy test piece, and compare the test results with the predicted early oxide layer on the surface of the nickel-based superalloy to verify the accuracy of the prediction method.

[0069] In step one, the target test piece is made of second-generation nickel-based superalloy DD6, and its chemical composition is shown in Table 1. The XRD test results are as follows: Figure 2 As shown, by Figure 2 It is known that the main phase composition of the target test piece is Ni3Al. The phase composition of the nickel-based superalloy includes at least the elemental composition and crystal structure of the nickel-based superalloy.

[0070] Table 1 Chemical composition of the second-generation nickel-based superalloy DD6

[0071]

[0072]

[0073] In step two, the critical parameters of each phase of the nickel-based superalloy are the total energy of each phase in the nickel-based superalloy. The chemical potential range of each element on the surface of the nickel-based superalloy should satisfy... In the formula, —The chemical potential of a single i atom in the element i in its elemental form, in eV;

[0074] u bulk —The chemical potential of a single unit cell in a nickel-based superalloy, in eV;

[0075] u i —The chemical potential of a single i atom in a single unit cell of a nickel-based superalloy, in eV;

[0076] u j —The chemical potential of a single j atom in a single unit cell of a nickel-based superalloy, in eV;

[0077] M i —The number of i atoms in a single unit cell of a nickel-based superalloy;

[0078] M j —The number of j atoms in a single unit cell of a nickel-based superalloy;

[0079] i — Element type;

[0080] j — the types of elements other than i in a single unit cell.

[0081] The chemical potential of atoms in a single unit cell of the nickel-based superalloy should satisfy the relationship u. bulk =∑ i M i u i In the formula, u bulk —The chemical potential of a single unit cell in a nickel-based superalloy, in eV;

[0082] M i —The number of i atoms in a single unit cell of a nickel-based superalloy;

[0083] u i —The chemical potential of a single i atom in a single unit cell of a nickel-based superalloy, in eV;

[0084] i — Element type.

[0085] In step three, the spatial distribution of atoms on the relaxed nickel-based superalloy surface is determined based on the surface energy. The surface model with the lowest surface energy within the range of chemical potential variation is then identified. The range of surface energy variation with the change in the chemical potential of Al is as follows: Figure 3As shown. Possible adsorption sites for the nickel-based superalloy surface model are determined as follows. Figure 4 As shown, the top position T of the outermost atom, the middle position B between the two closest atoms in the outermost layer, and the middle position H formed by multiple atoms in the outermost layer are considered adsorption sites. The obtained bonding model between oxygen atoms and the nickel-based superalloy surface is geometrically optimized, and the most probable adsorption sites are determined based on the surface energy. The surface energy calculation formula for the nickel-based superalloy surface model is as follows: In the formula,

[0086] γ—Surface energy

[0087] E slab —Total energy of the surface model, eV;

[0088] N i —The number of i atoms in the surface model;

[0089] —The chemical potential of atom i in the surface model, in eV;

[0090] A – Total surface area of ​​the surface model. i — Element type.

[0091] In step four, the formula for calculating the surface energy of the oxygen-nickel-based superalloy surface model remains the same. In the formula,

[0092] γ—Surface energy

[0093] E slab —Total energy of the surface model, eV;

[0094] N i —The number of i atoms in the surface model;

[0095] —The chemical potential of atom i in the surface model, in eV;

[0096] A – Total surface area of ​​the surface model. i — Element type.

[0097] The chemical potential range of oxygen atoms in the oxygen-nickel based superalloy surface model should meet the following requirements: In the formula,

[0098] —The chemical potential of an oxygen molecule, eV;

[0099] u O —The chemical potential of a single oxygen atom in the surface model of an oxygen-nickel-based superalloy, in eV.

[0100] The model with the lowest surface energy for each element's chemical potential value is selected as the most stable model under this environment. The surface phase diagram of nickel-based superalloys is drawn based on the most stable model. The models mentioned here include nickel-based superalloy surface models and oxygen-nickel-based superalloy surface models.

[0101] The method for drawing the surface phase diagram of the nickel-based superalloy is as follows: under a certain chemical potential equilibrium state, the surface model of the nickel-based superalloy with the lowest surface energy and the surface model of the oxygen-nickel-based superalloy are selected as the most likely phases to appear.

[0102] In step five, the influence of oxygen on surface segregation of the nickel-based superalloy is determined using the surface phase diagram, and the continuity of the oxide layer is predicted. The phase diagram for elemental segregation determination is shown below. Figure 5 As shown, this phase diagram indicates that increasing the chemical potential of oxygen atoms favors the segregation of aluminum, and that the segregation behavior slows down as the chemical potential of aluminum decreases. The phase diagram for determining oxygen coverage is shown below. Figure 6 As shown in the diagram, the phase diagram indicates that as the chemical potential of oxygen increases, oxygen can completely cover the alloy surface, forming a continuous oxide layer.

[0103] In step six, the oxidation test results of nickel-based superalloy DD6 are compared with the predicted results. The XRD detection results and ultra-depth-of-field microscopic images of the oxide layer formed by oxidizing nickel-based superalloy DD6 at 1000℃ for 10 hours are shown below. Figure 7 and Figure 8 As shown, Figure 7 This indicates that the oxide layer of the nickel-based superalloy DD6 is mainly composed of Al2O3. Figure 8 This indicates that the morphology of the oxide layer is relatively continuous, which is consistent with the prediction results.

[0104] This embodiment utilizes the CASTEP module of Materials Studio (MS) software to perform geometric optimization of the surface model based on first-principles calculations and calculate the surface energy. Then, by combining the chemical potential ranges of each element, the surface model with the lowest surface energy is obtained. The computational setup uses the Generalized Gradient Approximation Functional (GGA) as the exchange-correlation functional and the Perdew-Burke-Ernzerhof (PBE) functional as the exchange-correlation functional. The Grimme method is used to handle van der Waals forces and long-range interactions. A 7x7x1 k-point network is used for model optimization and electronic property calculation. The BFGS method is selected for optimization, with a convergence energy residual set to 1×10⁻⁵ eV / atom and a residual stress less than [value missing]. Offset residual less than The cutoff energy was set to 300 eV, and spin polarization was considered throughout the calculation.

[0105] The detailed scheme for establishing and verifying the above-mentioned method for predicting the early oxide layer on the surface of nickel-based superalloys based on density functional theory and thermodynamic calculations is as follows: X-ray diffraction (XRD) experiments are used to determine the phase composition of the nickel-based superalloy; a unit cell model is established and calculated based on information such as the alloy element composition and crystal structure using a combination of density functional theory and thermodynamic calculations to determine the critical parameters of each phase of the nickel-based superalloy, and the chemical potential range of each element on the surface of the nickel-based superalloy is determined according to the chemical potential equilibrium theory; a surface model of the nickel-based superalloy is constructed based on the unit cell model, and energy calculations are performed to calculate the energy of each nickel-based superalloy surface. The surface energy of nickel-based superalloy surface models was determined by selecting the nickel-based superalloy surface model with the lowest surface energy for each element's chemical potential. All possible adsorption sites on the selected nickel-based superalloy surface model were identified, and oxygen atoms were sequentially placed on different adsorption sites of different nickel-based superalloy surface models to establish oxygen-nickel-based superalloy surface models. The total energy of each oxygen-nickel-based superalloy surface model was calculated, followed by the surface energy. The range of chemical potential variation for each element was determined based on the chemical potential balance theory, and the surface energy variation of the oxygen-nickel-based superalloy surface models was analyzed. Surface energy is negatively correlated with structural stability; oxygen elements tend to combine with the alloy surface to form structures with the lowest surface energy. Therefore, the most likely structure to occur under a given chemical potential state can be predicted, ultimately leading to the prediction of the composition and continuity of the early oxide layer on the nickel-based superalloy surface.

[0106] The method for predicting the early oxide layer on the surface of nickel-based superalloys in this embodiment has the following beneficial effects: (1) A method for predicting the early oxide layer on the surface of nickel-based superalloys based on density functional theory and thermodynamic calculations is proposed. This method is based on density functional theory and thermodynamic calculations, and combined with the variation range of the chemical potential of each element in the oxidation behavior, a prediction phase diagram of the early oxide layer on the surface of nickel-based superalloys is established, providing a theoretical basis and methodological support for the prediction of the early oxide layer on the surface of nickel-based superalloys. (2) This prediction method can qualitatively predict the composition and continuity of the early oxide layer on the surface of nickel-based superalloys, which is beneficial to the normal service of nickel-based superalloys. (3) The method for predicting the early oxide layer on the surface of nickel-based superalloys has been verified by alloy oxidation tests and has high accuracy. It provides technical support for the evaluation of the early oxidation behavior of nickel-based superalloys and can predict the early oxidation behavior of nickel-based superalloys under various environments, thereby avoiding economic losses caused by field experiments.

[0107] Special Note: The technical solution of this invention involves numerous parameters, and the synergistic effects between these parameters must be comprehensively considered to achieve the beneficial effects and significant progress of this invention. Furthermore, the value ranges of each parameter in the technical solution were obtained through extensive experimentation. For each parameter and the combinations thereof, the inventors have recorded a large amount of experimental data; however, due to space limitations, the specific experimental data is not disclosed here.

[0108] Those skilled in the art will readily understand that the method for predicting the early oxide layer on the surface of nickel-based superalloys of the present invention includes any combination of the inventive description and specific embodiments described in the above specification and the various parts shown in the accompanying drawings. Due to space limitations and for the sake of brevity, not all of these combinations have been described in detail. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for predicting the early oxide layer on the surface of a nickel-based superalloy, characterized in that: The prediction method includes the following steps in sequence. Step 1: Test the unoxidized nickel-based superalloy target specimen to determine the phase composition of the nickel-based superalloy; Step 2: Based on the determined phase composition of the nickel-based superalloy, establish a unit cell model, perform numerical calculations using density functional theory to obtain relaxation results, obtain the critical parameters of each phase of the nickel-based superalloy based on the relaxation results, and determine the range of chemical potentials of each element on the surface of the nickel-based superalloy based on the chemical potential equilibrium theory. Step 3: Establish several nickel-based superalloy surface models using a unit cell model, calculate the total energy of each nickel-based superalloy surface model, and then calculate the surface energy of each nickel-based superalloy surface model; select the nickel-based superalloy surface model with the lowest surface energy for each element's chemical potential value, and determine all possible adsorption sites on the selected nickel-based superalloy surface model; sequentially place oxygen atoms on different adsorption sites of different nickel-based superalloy surface models to establish oxygen-nickel-based superalloy surface models respectively; Step 4: Based on several oxygen-nickel-based superalloy surface models, calculate the total energy of each oxygen-nickel-based superalloy surface model and the surface energy of each oxygen-nickel-based superalloy surface model; select the model with the lowest surface energy under each element's chemical potential value as the most stable model under this environment, and draw the nickel-based superalloy surface phase diagram based on the most stable model. Step 5: By drawing the phase diagram of the nickel-based superalloy surface and combining it with the changes in the chemical potential of each element and oxygen element inside the nickel-based superalloy, the early oxide layer on the surface of the nickel-based superalloy is predicted. Step Six: Conduct oxidation tests on the target nickel-based superalloy test piece, and compare the test results with the predicted early oxide layer on the surface of the nickel-based superalloy to verify the accuracy of the prediction method.

2. The method for predicting the early oxide layer on the surface of nickel-based superalloys according to claim 1, characterized in that: In step one, the phase composition of the nickel-based superalloy includes at least the elemental composition and crystal structure of the nickel-based superalloy.

3. The method for predicting the early oxide layer on the surface of nickel-based superalloys according to claim 2, characterized in that: In step two, the critical parameter of each phase of the nickel-based superalloy is the total energy of each phase in the nickel-based superalloy.

4. The method for predicting the early oxide layer on the surface of nickel-based superalloys according to claim 3, characterized in that: In step two, the chemical potential range of each element on the surface of the nickel-based superalloy should meet the following requirements. In the formula, —The chemical potential of a single i atom in the element i in its elemental form, in eV; u bulk —The chemical potential of a single unit cell in a nickel-based superalloy, in eV; u i —The chemical potential of a single i atom in a single unit cell of a nickel-based superalloy, in eV; u j —The chemical potential of a single j atom in a single unit cell of a nickel-based superalloy, in eV; M i —The number of i atoms in a single unit cell of a nickel-based superalloy; M j —The number of j atoms in a single unit cell of a nickel-based superalloy; i — Element type; j — the types of elements other than i in a single unit cell.

5. The method for predicting the early oxide layer on the surface of nickel-based superalloys according to claim 4, characterized in that: In step two, the chemical potential of atoms in a single unit cell of the nickel-based superalloy should satisfy the relationship u. bulk =∑ i M i u i In the formula, u bulk —The chemical potential of a single unit cell in a nickel-based superalloy, in eV; M i —The number of i atoms in a single unit cell of a nickel-based superalloy; u i —The chemical potential of a single i atom in a single unit cell of a nickel-based superalloy, in eV; i — Element type.

6. The method for predicting the early oxide layer on the surface of nickel-based superalloys according to claim 5, characterized in that: In step three, the surface energy calculation formula for the nickel-based superalloy surface model is as follows: In the formula, γ — Surface energy E slab —Total energy of the surface model, eV; N i —The number of i atoms in the surface model; —The chemical potential of atom i in the surface model, in eV; A – Total surface area of ​​the surface model. i — Element type.

7. The method for predicting the early oxide layer on the surface of nickel-based superalloys according to claim 6, characterized in that: In step four, the formula for calculating the surface energy of the oxygen-nickel-based superalloy surface model remains the same. In the formula, γ is the surface energy. E slab —Total energy of the surface model, eV; N i —The number of i atoms in the surface model; —The chemical potential of atom i in the surface model, in eV; A – Total surface area of ​​the surface model. i — Element type.

8. The method for predicting the early oxide layer on the surface of nickel-based superalloys according to claim 7, characterized in that: In step four, the chemical potential range of oxygen atoms in the oxygen-nickel-based superalloy surface model should meet the following requirements: In the formula, —The chemical potential of an oxygen molecule, eV; u O —The chemical potential of a single oxygen atom in the surface model of an oxygen-nickel-based superalloy, in eV.

9. The method for predicting the early oxide layer on the surface of nickel-based superalloys according to claim 8, characterized in that: In step four, the model with the lowest surface energy for each element's chemical potential value is selected as the most stable model under this environment. The surface phase diagram of nickel-based superalloys is drawn based on the most stable model. This model includes a nickel-based superalloy surface model and an oxygen-nickel-based superalloy surface model.

10. The method for predicting the early oxide layer on the surface of a nickel-based superalloy according to claim 9, characterized in that: In step four, the method for drawing the phase diagram of the nickel-based superalloy surface is to calculate a certain chemical potential equilibrium state and select the nickel-based superalloy surface model with the lowest surface energy and the oxygen-nickel-based superalloy surface model as the most likely phases to appear.

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