A method and system for accurately predicting the creep strength and life of superalloys

Abstract

The present invention belongs to the technical field of materials science and engineering applications, and particularly relates to a method and system for accurately predicting the creep rupture strength and life of superalloys. This method conducts creep and rupture tests on superalloy materials at different temperatures and stresses to obtain the material life under different conditions; predicts the C value by using two methods, namely surface fitting and the intersection point of isostress lines, and takes the average value of the two as the actual C value; substitutes the C value and then conducts surface fitting to obtain the fitting relationship among temperature, stress, and life; predicts the strength or life of superalloy materials according to the obtained relationship. The method of the present invention uses the surface fitting method, which is both simple and fast, and can comprehensively and intuitively reflect the variation law of material performance data; it will provide an important method for accurately predicting the creep rupture strength or life of superalloy materials and has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of materials science and engineering applications, and particularly relates to a method and system for accurately predicting the creep rupture strength and life of superalloys. Background Art

[0002] Superalloys are in a harsh service environment. Under the action of temperature and stress for a long time, creep rupture is the main failure form of the material. Therefore, it is particularly important to determine the creep rupture strength or life under corresponding conditions according to the actual service environment of superalloy materials, which has always been the focus of superalloy research. The service time of some superalloy components is very long, reaching tens of thousands or even hundreds of thousands of hours. It is really not easy to conduct ultra-long-term creep rupture tests. Generally, the strength or life of a long time is extrapolated based on short-term test data. Therefore, it is very necessary to adopt a suitable method to accurately predict the creep rupture strength and life of superalloys.

[0003] At present, the Larson-Miller parameter method is a relatively commonly used prediction method. The selection of the C value has a great influence on the prediction result. However, at present, the C value is mostly determined by the empirical value of the alloy material, which will definitely affect the prediction result. The traditional Larson-Miller parameter method needs to calculate the P value corresponding to each data point, and uses the surface fitting method to fit the P parameter, and fits the relationship between P and stress σ. Then, the relationship formula between temperature, stress and life is derived, which is relatively cumbersome and it is not easy to see the overall relationship change trend of the three. Therefore, it is very necessary to determine a C value that conforms to the actual situation according to the test data to improve the prediction accuracy of superalloy materials; at the same time, optimizing and improving the traditional Larson-Miller prediction method to improve the prediction efficiency and visualization degree is also very beneficial for actual prediction operations. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and system for accurately predicting the creep rupture strength and life of superalloys. The method is based on the relationship formula of the Larson-Miller parameter method, predicts and determines the C value by various methods according to the test data, and uses the surface fitting method to obtain the relationship formula among temperature, stress and life to predict the strength or life of superalloy materials.

[0005] The technical solution of the present invention is as follows: A method for accurately predicting the creep rupture strength and life of superalloys, characterized in that creep and creep rupture tests are carried out on superalloy materials at different temperatures and stresses to obtain the material life under different conditions; based on the relationship formula of the Larson-Miller parameter method, the C value is predicted by two methods of surface fitting and the intersection point of isostress lines respectively, and the average value of the two is used as the actual C value; the C value is substituted and then surface fitting is carried out to obtain the fitting relationship formula among temperature, stress and life; the strength or life of the superalloy material is predicted according to the obtained relationship formula.

[0006] Further, the method includes the following steps:

[0007] S1) Creep and creep rupture tests are carried out on superalloy materials at different temperatures and stresses to obtain multiple test data points of the superalloy material, including temperature, stress and life;

[0008] S2) The data obtained in S1) is subjected to surface fitting through a mathematical analysis software, and the fitting formula is to obtain the fitting result C1 of the C value;

[0009] Then, multiple groups of data points under isostress conditions are selected from the obtained data, and the C value is obtained by linear fitting through a mathematical analysis software. The fitting formula is The average value of the C values obtained under each stress condition is used as the fitting result C2 of the C value;

[0010] The average value of the obtained C1 and the obtained C2 is taken to obtain as the final C value;

[0011] S3) Substitute the C value obtained in S2) into the formula to obtain Then, surface fitting is carried out on the data in S1) to obtain A0, A1…A n , to obtain the fitting relationship formula among temperature, stress and life;

[0012] S4) Predict the strength or life of the superalloy according to the relationship formula obtained in S3).

[0013] Further, the tests in S1) include at least 3 temperatures, each temperature includes at least 3 stresses, at least 9 valid test data points are obtained, and each data point includes temperature, stress and life.

[0014] Further, the fitting formula in S2) is transformed from the relationship formula of the Larson-Miller parameter method, where t r is the life (unit: h), σ is the test stress (unit: MPa), T is the test temperature (unit: K), A0, A1…An are coefficients to be determined, and C is also a coefficient to be determined;

[0015] Fitting formula is transformed from the relational expression of the Larson-Miller parameter method, where t r is the life (unit: h), T is the test temperature (unit: K), P is a function of stress (under the condition of equal stress, P can be regarded as a constant, which is a coefficient to be determined), and C is a coefficient to be determined.

[0016] It also includes data under equal stress. At least two stress conditions need to be selected, and there are at least two data points at different temperatures under the selected stress conditions. If there is no test data point at the required temperature under the selected stress condition, the isothermal line method is used to find this data point.

[0017] Furthermore, the formula of the isothermal line method is lgt r = A - Blgσ, which gives the relationship between t r and σ under the isothermal condition. Here, t r is the life (unit: h), σ is the test stress (unit: MPa), and A and B are coefficients to be determined. The isothermal line formula can be fitted according to the existing test data points at this temperature, and then the required data points can be obtained.

[0018] Furthermore, for the fitting formula in the step S3) where t r is the life (unit: h), σ is the test stress (unit: MPa), T is the test temperature (unit: K), A0, A1... A n are coefficients to be determined, is a known constant.

[0019] Furthermore, for the selection of the polynomial degree during fitting, generally quadratic or cubic is selected, and it can be flexibly adjusted according to the fitting results specifically.

[0020] The beneficial effects of the present invention are as follows:

[0021] (1) According to the actually measured data of the test, the present invention combines multiple methods to determine the value of C. Compared with the traditional method of selecting the value of C according to experience, a more accurate and more suitable value of C can be obtained, improving the prediction accuracy;

[0022] (2) Different from the traditional surface fitting, the present invention adopts the method of surface fitting, which is not only simple and fast, but also can comprehensively and intuitively reflect the change law of the performance data of the material. The present invention will provide important help in the accurate prediction of the creep rupture strength or life of superalloy materials and has a wide application prospect. Brief description of the drawings

[0023] Figure 1Schematic flow chart of a method for accurately predicting the creep rupture strength and life of superalloys according to the present invention.

[0024] Figure 2 Creep rupture data surface fitting graph of Example 1 of the present invention.

[0025] Figure 3 Creep rupture data surface fitting graph of Example 2 of the present invention.

[0026] Figure 4 Logic block diagram of a system for accurately predicting the creep rupture strength and life of superalloys according to the present invention. Detailed implementation manners

[0027] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0028] As Figure 1 shown, a method for accurately predicting the creep rupture strength and life of superalloys according to the present invention is as follows: First, collect the material life data of superalloy materials at different temperatures and stresses; use two methods, namely surface fitting and intersection points of isostress lines, to predict the C value for the collected material life data respectively, and then take the average value of the two predicted C values as the final C value; substitute the final C value into the surface fitting again to obtain the fitting relationship among temperature, stress, and life, and predict the strength or life of the superalloy material according to the obtained relationship.

[0029] The method includes the following steps:

[0030] S1) Conduct creep and creep rupture tests on superalloy materials at different temperatures and stresses to obtain multiple test data points of the superalloy materials;

[0031] S2) First, perform surface fitting and linear fitting on the data obtained in S1) respectively, and take the average value of the obtained fitting values as the final C value;

[0032] S3) Substitute the C value obtained in S2) into the surface fitting formula to find A0, A1... A in the surface fitting formula n , and obtain the fitting relationship among temperature, stress, and life;

[0033] S4) Predict the strength or life of the superalloy respectively according to the fitting relationship among temperature, stress, and life obtained in S3).

[0034] The data points in S1) include temperature, stress, and life.

[0035] The specific steps of S2) are as follows:

[0036] S2.1) Perform surface fitting on the data points obtained in S1) through mathematical analysis software to obtain the fitting result C1 of the C value;

[0037] S2.2) Then select multiple groups of data points under equal stress conditions from the data obtained in S1), perform linear fitting through mathematical analysis software to find the C value, and take the average of the C values obtained under each stress condition as the fitting result C2 of the C value;

[0038] S2.3) Take the average of C1 obtained in S2.1) and C2 obtained in S2.2) to obtain as the final C value.

[0039] The fitting formula in S2.1) is:

[0040] In the formula, t r is the life, with the unit of h; σ is the test stress, with the unit of MPa; T is the test temperature, with the unit of K); A0, A1…A n are undetermined coefficients, and C is also an undetermined coefficient.

[0041] The fitting formula in S2.2) is:

[0042] In the formula, t r is the life, with the unit of h; T is the test temperature, with the unit of K; P is a function of stress, and under equal stress conditions, P can be regarded as a constant, which is an undetermined coefficient; C is an undetermined coefficient.

[0043] For the data under equal stress in S2.2), at least two stress conditions need to be selected, and there are at least two data points at different temperatures under the selected stress conditions. If there are no test data points at the required temperature under the selected stress conditions, the isothermal line method is used to find this data point.

[0044] The formula of the isothermal line method is:

[0045] lgt r = A - Blgσ,

[0046] Given the relationship between t r and σ under isothermal conditions, in the formula, t r is the life, with the unit of h; σ is the test stress, with the unit of MPa, and A, B are undetermined coefficients.

[0047] A system for implementing the method for accurately predicting the creep strength and life of superalloys described above. The system includes:

[0048] A data acquisition module, which is used to adopt a plurality of test data points obtained from creep and stress rupture tests of superalloy materials at different temperatures and stresses;

[0049] A data fitting calculation module, which is used to predict the C value by using two methods of surface fitting and intersection points of isostress lines for the data points collected by the data acquisition module, and then calculate the average value of the two predicted C values to obtain the final C value;

[0050] A prediction module, which is used to perform surface fitting on the C value obtained by the data fitting calculation module again to obtain a fitting relationship among temperature, stress and life, and finally predict the strength or life of the superalloy material.

[0051] A readable storage medium, including a memory, where the memory stores a program, and a processor, and the processor executes the method for accurately predicting the stress rupture strength and life of superalloys described above.

[0052] Example 1: Taking the stress rupture data of Waspaloy alloy as an example, the specific implementation manner of this method is described as follows:

[0053] (1) Obtain the stress rupture test data of Waspaloy alloy as shown in Table 1.

[0054] Table 1:

[0055]

[0056]

[0057] (2) In this case, the origin software is used for data fitting. Substitute the data in Table 1 into the formula for surface fitting, and select cubic polynomial fitting. The fitted result is C = C1 = 23.47;

[0058] (3) Select the data under the isostress condition, use the isothermal line method to find the missing data points under this stress, and use the formula to fit the C values under each stress and take the average value to obtain C = C2 = 23.51, as shown in Table 2.

[0059] Table 2:

[0060]

[0061] (4) Determine the final C value as and substitute it into the formula.

[0062] (5) Use the formula to perform surface fitting on the data again. The fitting result is as shown in Figure 2 , and the fitting relationship is as follows:

[0063]

[0064] (6) Predict the creep rupture lives at 650 °C / 580 MPa and 760 °C / 280 MPa according to the fitted relational expression, and compare them with the traditional Larson-Miller method (C = 20). As shown in Table 3, it can be seen that compared with the traditional Larson-Miller method, the error of the prediction results by this method is significantly reduced.

[0065] Table 3:

[0066] Temperature T / °C 650 760 Stress σ / MPa 580 280 <![CDATA[Actual life t r / h]]> 6509 1373 <![CDATA[Larson-Miller method for predicting life t r / h]]> 3671 1127 Relative error of Larson-Miller method 43.60％ 17.92％ <![CDATA[This method predicts the life t r / h]]> 5419 1470 Relative error of this method 16.75％ 7.06％

[0067] Example 2: Taking the creep rupture data of K452 alloy as an example, illustrate the specific implementation method of this method:

[0068] (1) Obtain the creep rupture test data of K452 alloy as shown in Table 4.

[0069] Table 4:

[0070] Temperature T / °C Stress σ / MPa <![CDATA[Service life t r / h]]> 750 490 153 750 470 262 750 450 544 850 300 98 850 260 243 850 230 493 900 190 209 900 170 323 900 150 699

[0071] (2) In this case, use the origin software for data fitting. Substitute the data in Table 4 into the formula for surface fitting, and select the cubic polynomial fitting. The fitted result is C = C1 = 20.06;

[0072] (3) Select the data under the equal stress condition, use the isothermal line method to find the missing data points under this stress, and use the formula to fit the C values under each stress and take the average value to obtain C = C2 = 17.57, as shown in Table 5.

[0073] Table 5:

[0074]

[0075] (4) Determine the final C value as and substitute it into the formula.

[0076] (5) Use the formula to perform surface fitting on the data again. The fitting result is as shown in Figure 3 , and the fitted relational expression is as follows:

[0077]

[0078] (6) Predict the creep rupture life at 750 °C / 400 MPa and 850 °C / 185 MPa according to the fitted relational expression, and compare it with the traditional Larson - Miller method (C = 20). As shown in Table 6, it can be seen that compared with the traditional Larson - Miller method, the error of the prediction results by this method is significantly reduced.

[0079] Table 6:

[0080]

[0081]

[0082] The above has introduced in detail a method and system for accurately predicting the creep strength and life of superalloys provided by the embodiments of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present application.

[0083] As used in the specification and claims, certain terms are used to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. The specification and claims do not use the difference in names as a way to distinguish components, but use the difference in functions of components as the criterion for distinction. As mentioned throughout the specification and claims, "comprising" and "including" are open - ended terms, so they should be interpreted as "including / including but not limited to". "Roughly" means within an acceptable error range. Those skilled in the art can solve the technical problem within a certain error range and basically achieve the technical effect. The subsequent description in the specification is the preferred implementation manner for implementing the present application, but the description is for the purpose of explaining the general principles of the present application and is not used to limit the scope of the present application. The protection scope of the present application shall be subject to what is defined by the appended claims.

[0084] It should also be noted that the term "including", "comprising" or any other variant thereof is intended to cover non - exclusive inclusion, so that a commodity or system including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such a commodity or system. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the commodity or system including the said element.

[0085] It should be understood that the term "and / or" used herein is merely a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0086] The above description shows and describes several preferred embodiments of the present application. However, as mentioned above, it should be understood that the present application is not limited to the forms disclosed herein, should not be regarded as an exclusion of other embodiments, but can be used in various other combinations, modifications, and environments, and can be changed within the scope of the application concept described herein through the above teachings or the technology or knowledge in the relevant field. And the changes and variations made by those skilled in the art that do not depart from the spirit and scope of the present application shall fall within the protection scope of the appended claims of the present application.

Claims

1. A method for accurately predicting the creep strength and life of superalloys, characterized in that, The method is specifically as follows: First, collect the material life data of superalloy materials at different temperatures and stresses; calculate the predicted values of the collected material life data by using two methods, namely surface fitting and the intersection points of isostress lines, and then take the average value of the two obtained predicted values as the final C value; perform surface fitting on the final C value to obtain the fitting relationship among temperature, stress, and life, and predict the strength or life of the superalloy material according to the obtained fitting relationship. The method includes the following steps: S1) Conduct creep and stress rupture tests on superalloy materials at different temperatures and stresses to obtain multiple test data points of the superalloy materials; S2) First, perform surface fitting and linear fitting on the data obtained in S1) respectively, and take the average value of the obtained fitting values as the final C value; The specific steps are as follows: S2.1) Perform surface fitting on the data points obtained in S1) through mathematical analysis software to obtain the fitting result C1; The surface fitting formula is as follows: where t r is the life, in hours; σ is the test stress, in MPa; T is the test temperature, in K; A0, A1…A n are all undetermined coefficients, and C is an undetermined coefficient; S2.2) Then select multiple groups of data points under equal stress conditions from the data obtained in S1), perform linear fitting through mathematical analysis software, and take the average value of the values obtained under each stress condition as the fitting result C2; The fitting formula is as follows: where t r is the life in hours; T is the test temperature in K; P is a function of stress; S2.3) Take the average of C1 obtained in S2.1) and C2 obtained in S2.2) to get the final value of C; S3) Substitute the C value obtained in S2) into the surface fitting formula to find A0, A1... A in the surface fitting formula n , and obtain the fitting relationship among temperature, stress, and life S4) Predict the strength or life of the superalloy respectively according to the fitting relationship among temperature, stress, and life obtained in S3).

2. The method according to claim 1, wherein The data points in the S1) include temperature, stress, and life.

3. The method according to claim 1, wherein For the data points under equal stress in the S2.2), at least two stress conditions need to be selected, and there are at least two data points at different temperatures under the selected stress conditions. If there are no test data points at the required temperature under the selected stress conditions, the isotherm method is used to obtain the data points.

4. The method according to claim 3, wherein The formula of the isotherm method is: lgt r = A - Blgσ, where t r is the life in hours; σ is the test stress in MPa, and A and B are undetermined coefficients.

5. A system for implementing the method of accurately predicting the creep strength and life of a superalloy as described in any one of claims 1-4, characterized in that, The system includes: A data acquisition module, which is used to acquire multiple test data points obtained from creep and stress rupture tests of superalloy materials at different temperatures and stresses; A data fitting calculation module, which is used to predict the C value by using two methods, namely surface fitting and the intersection points of isostress lines, for the data points collected by the data acquisition module, and then calculate the average value of the two predicted C values to obtain the final C value; A prediction module, which is used to perform surface fitting on the C value obtained by the data fitting calculation module again to obtain the fitting relationship among temperature, stress, and life, and finally predict the strength or life of the superalloy material.

6. A readable storage medium, including a memory which stores a program, and a processor, characterized in that, The processor executes the method for accurately predicting the creep rupture strength and life of superalloys according to any one of claims 1-4.

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