Method for predicting influence of striped crystal on creep life of nickel-based single crystal superalloy

Abstract

The invention provides a method for predicting the influence of striped crystals on the creep life of a nickel-based single crystal superalloy. The method comprises the following steps: S1, constructing a creep damage equation and a creep constitutive equation of a nickel-based single crystal superalloy material without striped crystals; s2, acquiring creep curve parameters and critical slitting stress of the nickel-based single-crystal high-temperature alloy material without streak crystals; s3, constructing a creep life prediction model based on the creep curve parameters, the critical slitting stress, the creep damage equation and the creep constitutive equation; s4, the slip system slitting stress of the nickel-based single-crystal high-temperature alloy material containing the striped crystals is obtained; and S5, predicting the creep life of the nickel-based single-crystal high-temperature alloy material containing the striped crystals based on the slip system slitting stress of the nickel-based single-crystal high-temperature alloy material containing the striped crystals and the creep life prediction model. The problems that in the prior art, quantitative evaluation of the influence of different striped crystals on the creep life of blades is lacked, and the qualified rate of blade castings is low are solved.

Description

Technical Field

[0001] The invention relates to the technical field of nickel-based high-temperature alloys, and in particular to a method for predicting the influence of striped crystals on the creep life of nickel-based single crystal high-temperature alloys. Background Art

[0002] Nickel-based single crystal alloys have excellent creep, fatigue and oxidation resistance mechanical properties at high temperatures and are widely used in the manufacture of aircraft engine turbine blades. Streaky crystals are common casting defects in the preparation of single crystal blades for aircraft engines, which seriously affect the high-temperature mechanical properties of the blades and may cause blade failure. Streaky crystal defects appear as striped morphology and generally appear on the shallow surface of the blade. Streaky crystals will introduce unnecessary grain boundaries, thus significantly affecting the performance and life of the blades. In the prior art, if streaky crystals appear in blade castings, they are all treated as scrapped, which seriously reduces the qualified rate of blade castings. The orientation and width of streak crystal defects are important indicators for measuring the severity of streak crystal defects. Quantitative evaluation of the influence of streak crystals of different widths and orientations on the creep life of blades can provide technical guidance for the quality assessment of aircraft engine blades. Summary of the invention

[0003] The main purpose of the present invention is to provide a method for predicting the influence of streak crystals on the creep life of nickel-based single crystal high-temperature alloys, so as to solve the problems in the prior art of lack of quantitative evaluation of the influence of streak crystals on the creep life of blades and low qualified rate of blade castings.

[0004] In order to achieve the above object, according to one aspect of the present invention, a method for predicting the influence of striped crystals on the creep life of a nickel-based single crystal high-temperature alloy is provided, comprising the following steps:

[0005] Step S1, constructing a creep damage equation and a creep constitutive equation of a nickel-based single crystal high-temperature alloy material without striated crystals based on crystal plasticity theory;

[0006] Step S2, obtaining creep curve parameters and critical shear stress of a nickel-based single crystal high-temperature alloy material without stripe crystals;

[0007] Step S3, constructing a creep life prediction model based on creep curve parameters, critical shear stress, creep damage equation and creep constitutive equation;

[0008] Step S4, obtaining the shear stress of the slip system of the nickel-based single crystal high-temperature alloy material containing stripe crystals;

[0009] Step S5, predicting the creep life of the nickel-based single crystal high-temperature alloy material containing stripe crystals based on the slip system shear stress and creep life prediction model of the nickel-based single crystal high-temperature alloy material containing stripe crystals;

[0010] Wherein, the nickel-based single crystal high-temperature alloy material without stripe crystals and the nickel-based single crystal high-temperature alloy material without stripe crystals have the same composition;

[0011] The creep damage equation is:

[0012]

[0013] The creep constitutive equation is:

[0014]

[0015] The creep life prediction model is:

[0016]

[0017] Among them, α is the slip system, A is the first temperature creep parameter, n is the second temperature creep parameter, α (α) is the α slip system damage, is the creep shear strain rate, is the steady-state creep rate, is the initial creep shear strain rate, is the initial damage rate, is the slip system damage rate, τ c is the critical shear stress, τ (α) is the shear stress of the slip system, χ is the third temperature creep parameter, is the fourth temperature creep parameter, β0 is a constant, t f is the creep life, and N is the number of sliding surface movement directions in a slip system.

[0018] Furthermore, in step S1, a creep damage equation of a nickel-based single crystal high-temperature alloy material without stripe crystals is established based on crystal plasticity theory, comprising the following steps:

[0019] Based on the crystal plasticity theory, the corresponding relationship between the shear stress and damage of the slip system is established through creep tests on nickel-based single crystal high-temperature alloy materials without stripe crystals.

[0020] The creep damage equation is established according to the corresponding relationship between the shear stress of the slip system and the damage.

[0021] Furthermore, in step S1, a creep constitutive equation of a nickel-based single crystal high-temperature alloy material without stripe crystals is constructed based on the crystal plasticity theory, comprising the following steps:

[0022] Based on the crystal plasticity theory, the relative relationship between creep strain and time is established through the test of nickel-based single crystal high-temperature alloy materials without stripe crystals.

[0023] The creep constitutive equation is established according to the relative relationship between creep strain and time.

[0024] Furthermore, in step S2, the critical shear stress of the nickel-based single crystal high-temperature alloy material without stripe crystals is obtained through a tensile test.

[0025] Furthermore, the step of obtaining creep curve parameters of the nickel-based single crystal high-temperature alloy material without stripe crystals in step S2 is as follows:

[0026] A creep test was conducted on a nickel-based single crystal high-temperature alloy material without stripe crystals to obtain a creep curve.

[0027] The creep curve parameters of nickel-based single crystal high-temperature alloy materials without stripe crystals are obtained based on the creep curve.

[0028] Furthermore, the shear stress τ of the slip system of the nickel-based single crystal high-temperature alloy material containing striped crystals in step S4 is (α) Obtained by the following formula:

[0029] τ (α) =σ:P (α) ;

[0030]

[0031] P (α) is the orientation factor, σ is the stress tensor under the crystal axis system, m (α) is the slip direction of the slip system, and n (α) is the unit normal vector of the slip plane in the slip system.

[0032] Further, the slip system is selected from an octahedral slip system.

[0033] Furthermore, N is 12.

[0034] Furthermore, the nickel-based single crystal high-temperature alloy material without streak crystals and the nickel-based single crystal high-temperature alloy material without streak crystals are prepared by the same process.

[0035] By applying the technical solution of the present invention, a creep life prediction model is constructed based on the creep curve parameters, creep damage equation and creep constitutive equation of a nickel-based single crystal high-temperature alloy material without streak crystals. The creep life can be obtained by inputting the shear stress of the slip system of the test sample. The method based on the present invention can be used not only to predict the creep life of samples without streak crystals, but also to predict the creep life of samples containing streak crystals, thereby providing a reference for the life assessment of single crystal high-temperature alloy blades in industrial production. DETAILED DESCRIPTION

[0036] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0037] As described in the background technology, the prior art lacks a quantitative evaluation of the effect of streak crystals of different widths and orientations on the creep life of blades, and the qualified rate of blade castings is low. In order to solve the above problems, the present invention provides a method for predicting the effect of streak crystals on the creep life of nickel-based single crystal high-temperature alloys, comprising the following steps:

[0038] Step S1, constructing a creep damage equation and a creep constitutive equation of a nickel-based single crystal high-temperature alloy material without striated crystals based on crystal plasticity theory;

[0039] Step S2, obtaining creep curve parameters and critical shear stress of a nickel-based single crystal high-temperature alloy material without stripe crystals;

[0040] Step S3, constructing a creep life prediction model based on creep curve parameters, critical shear stress, creep damage equation and creep constitutive equation;

[0041] Step S4, obtaining the shear stress of the slip system of the nickel-based single crystal high-temperature alloy material containing stripe crystals;

[0042] Step S5, predicting the creep life of the nickel-based single crystal high-temperature alloy material containing stripe crystals based on the slip system shear stress and creep life prediction model of the nickel-based single crystal high-temperature alloy material containing stripe crystals;

[0043] The nickel-based single crystal high-temperature alloy material without stripe crystals has the same composition as the nickel-based single crystal high-temperature alloy material without stripe crystals;

[0044] The creep damage equation is:

[0045]

[0046] The creep constitutive equation is:

[0047]

[0048] The creep life prediction model is:

[0049]

[0050] Among them, α is the slip system, the slip system of nickel-based single crystal alloy includes hexahedral slip system, octahedral slip system and dodecahedral slip system, A is the first temperature creep parameter, n is the second temperature creep parameter, ω (α) is the α slip system damage, is the creep shear strain rate, is the steady-state creep rate, which is 10. is the initial creep shear strain rate, is the initial damage rate, is the slip system damage rate, τ c is the critical shear stress, τ(α) is the shear stress of the slip system, χ is the third temperature creep parameter, is the fourth temperature creep parameter, β0 is a constant with a value of 2.5, t f is the creep life, and N is the number of sliding surface movement directions in a slip system.

[0051] In order to measure the severity of streak crystal defects, the present invention provides a method for predicting the influence of streak crystals on the creep life of nickel-based single crystal high-temperature alloys. A creep life prediction model is constructed based on creep curve parameters, creep damage equation and creep constitutive equation of nickel-based single crystal high-temperature alloy materials without streak crystals. The creep life can be obtained by inputting the shear stress of the slip system of the test sample. The method based on the present invention can be used not only to predict the creep life of samples without streak crystals, but also to predict the creep life of samples containing streak crystals, providing a reference for the life evaluation of single crystal high-temperature alloy blades in industrial production.

[0052] In a preferred embodiment, in step S1, a creep damage equation for a nickel-based single crystal high-temperature alloy material free of striated crystals is established based on the crystal plasticity theory, including the following steps: establishing a corresponding relationship between the shear stress of the slip system and the damage through a creep test of the nickel-based single crystal high-temperature alloy material free of striated crystals based on the crystal plasticity theory; establishing a creep damage equation based on the corresponding relationship between the shear stress of the slip system and the damage.

[0053] In a preferred embodiment, in step S1, a creep constitutive equation of a nickel-based single crystal high-temperature alloy material without striated crystals is constructed based on the crystal plasticity theory, including the following steps: establishing the relative relationship between creep strain and time through experiments on nickel-based single crystal high-temperature alloy materials without striated crystals based on the crystal plasticity theory; establishing a creep constitutive equation based on the relative relationship between creep strain and time.

[0054] The critical shear stress refers to the maximum stress at which a material will not break without cracking due to the action of an external load. In a preferred embodiment, the critical shear stress of a nickel-based single crystal high-temperature alloy material free of streak crystals is obtained by a tensile test in step S2.

[0055] In a preferred embodiment, the steps of obtaining creep curve parameters of the nickel-based single crystal high-temperature alloy material without streak crystals in step S2 are as follows: a creep test is performed on the nickel-based single crystal high-temperature alloy material without streak crystals to obtain a creep curve; based on the creep curve, creep curve parameters of the nickel-based single crystal high-temperature alloy material without streak crystals are obtained. Specifically, the creep curve parameters include a first temperature creep parameter A, a second temperature creep parameter n, an initial damage rate The third temperature creep parameter χ, the fourth temperature creep parameter

[0056] In a preferred embodiment, the shear stress τ of the slip system of the nickel-based single crystal high-temperature alloy material containing striped crystals in step S4 is (α) Obtained by the following formula:

[0057] τ (α) =σ:P (α) ;

[0058]

[0059] P (α) is the orientation factor, σ is the stress tensor under the crystal axis system, m (α) is the slip direction of the slip system, and n (α) is the unit normal vector of the slip plane in the slip system. Both can be derived from the slip system activation law of nickel-based single crystal alloys and will not be described in detail here.

[0060] The constitutive model of nickel-based single crystal superalloy containing stripe crystals can be characterized by the creep deformation strain rate, which can be expressed as And satisfy the following relationship:

[0061]

[0062] In the formula, is the macroscopic strain rate, and is the strain rate of the elastic part, is the strain rate of the inelastic part, and

[0063] Then the creep strain is decomposed into:

[0064]

[0065] in, corresponds to the creep strain of the hexahedral slip system, corresponds to the creep strain of the octahedral slip system, The corresponding value is zero if one of the slip systems is not activated.

[0066] In addition, C e is the anisotropic elastic tensor, which can be expressed in matrix form:

[0067]

[0068] For nickel-based single crystal alloy materials, C11, C12 and C44 are three independent elastic constants, and C 11 =1 / E,C 12 =-μ / E, C 44 =1 / G, E is the elastic modulus, μ is the Poisson's ratio, and G is the shear modulus.

[0069] In a preferred embodiment, the slip system is selected from the octahedral slip system.

[0070] In a preferred embodiment, N is 12.

[0071] In a preferred embodiment, a nickel-based single crystal high-temperature alloy material without streak crystals and a nickel-based single crystal high-temperature alloy material without streak crystals are prepared by the same process, and a creep life prediction model is constructed using the nickel-based single crystal high-temperature alloy material without streak crystals as the material. Then, the life of the nickel-based single crystal high-temperature alloy material with streak crystals and the same composition prepared by the same process is predicted, and the predicted value is closer to the true value and has higher accuracy.

[0072] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0073] Example 1

[0074] A sample of a nickel-based single crystal high-temperature alloy material without stripe crystals was prepared for constructing a model (referred to as a model sample), and creep curve parameters of the model sample of the nickel-based single crystal high-temperature alloy material without stripe crystals under specific conditions were obtained. The creep curve parameters are shown in Table 1 below. The critical shear stress τ of the model sample of the nickel-based single crystal high-temperature alloy material without stripe crystals was obtained by a tensile test. c , then based on the first temperature creep parameter A, the second temperature creep parameter n, the initial damage rate The third temperature creep parameter χ, the fourth temperature creep parameter Critical shear stress τ c As well as the above creep damage equation and constitutive equation (where the slip system is an octahedral slip system, N is 12, The value of β0 is 10, and the value of β0 is 2.5), and a creep life prediction model is constructed in the finite element simulation software ABAQUS; then two test samples are prepared by the same process as the model sample, including a test sample 1 of a nickel-based single crystal high-temperature alloy material without streak crystals and a test sample 2 of a nickel-based single crystal high-temperature alloy material with streak crystals. For the nickel-based single crystal high-temperature alloy material with streak crystals and the nickel-based single crystal high-temperature alloy material without streak crystals, their elastic modulus E, Poisson's ratio, and shear modulus are not much different, and are approximately the same, as shown in Table 2. The streak crystal width and streak crystal orientation of the test sample 1 and the test sample 2 are shown in Table 3 respectively; then The ABAQUS software is used to calculate the slip system shear stress of the test sample through the stripe crystal width, stripe crystal orientation, elastic modulus E, Poisson's ratio and shear modulus of the test sample. Finally, the creep life prediction model obtains the creep life of the test sample according to the slip system shear stress and records it as the creep life prediction value. At the same time, the creep curves of the two test samples under specific conditions (the same conditions as the model sample) are measured through experimental measurement to obtain the true value of the creep life. The creep life prediction values ​​and the true values ​​of the creep life of the two test samples are shown in Table 3. Among them, the composition of the model sample, the test sample 1 and the test sample 2 are the same, as shown in Table 4.

[0075] Table 1. Creep curve parameters and critical shear stress of nickel-based single crystal superalloy materials without stripe crystals

[0076]

[0077] Table 2. Physical parameters of nickel-based single crystal high-temperature alloy materials without stripe crystals

[0078]

[0079] Table 3. Physical parameters of nickel-based single crystal high-temperature alloy materials

[0080]

[0081] Table 4. Chemical composition of nickel-based single crystal high-temperature alloy materials

[0082]

[0083] It can be seen from Table 3 that the relative error between the predicted value and the true value of the creep life of sample 1 of the nickel-based single crystal high-temperature alloy material without streak crystals is -2.7%, and the relative error between the predicted value and the true value of the creep life of sample 2 of the nickel-based single crystal high-temperature alloy material with streak crystals is 0.95%. The absolute values ​​of the relative errors of the two are both less than 3%. The creep life prediction model can be used not only to predict the creep life of samples without streak crystals, but also to predict the creep life of samples with streak crystals, and both have high accuracy.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for predicting the effect of streak crystals on the creep life of nickel-based single crystal high-temperature alloys, characterized in that: The steps include: Step S1, constructing a creep damage equation and a creep constitutive equation of a nickel-based single crystal high-temperature alloy material without striated crystals based on crystal plasticity theory; Step S2, obtaining creep curve parameters and critical shear stress of a nickel-based single crystal high-temperature alloy material without stripe crystals; Step S3, constructing a creep life prediction model based on the creep curve parameters, the critical shear stress, the creep damage equation and the creep constitutive equation; Step S4, obtaining the shear stress of the slip system of the nickel-based single crystal high-temperature alloy material containing stripe crystals; Step S5, predicting the creep life of the nickel-based single crystal high-temperature alloy material containing striated crystals based on the slip system shear stress of the nickel-based single crystal high-temperature alloy material containing striated crystals and the creep life prediction model; The nickel-based single crystal high-temperature alloy material without stripe crystals has the same composition as the nickel-based single crystal high-temperature alloy material without stripe crystals; The creep damage equation is: The creep constitutive equation is: The creep life prediction model is: Among them, α is the slip system, A is the first temperature creep parameter, n is the second temperature creep parameter, ω (α) is the α slip system damage, is the creep shear strain rate, is the steady-state creep rate, is the initial creep shear strain rate, is the initial damage rate, is the slip system damage rate, τ c is the critical shear stress, τ (α) is the shear stress of the slip system, χ is the third temperature creep parameter, is the fourth temperature creep parameter, β0 is a constant, t f is the creep life, and N is the number of sliding surface movement directions in a slip system.

2. The method for predicting the influence of stripe crystals on the creep life of nickel-based single crystal high-temperature alloy according to claim 1, characterized in that: The step S1 of establishing the creep damage equation of the nickel-based single crystal high-temperature alloy material without striated crystals based on the crystal plasticity theory comprises the following steps: Based on the crystal plasticity theory, a corresponding relationship between the shear stress of the slip system and the damage is established through a creep test of the nickel-based single crystal high-temperature alloy material without stripe crystals; The creep damage equation is established according to the corresponding relationship between the shear stress of the slip system and the damage.

3. The method for predicting the influence of stripe crystals on the creep life of nickel-based single crystal high-temperature alloy according to claim 1, characterized in that: The step S1 of constructing the creep constitutive equation of the nickel-based single crystal high-temperature alloy material without striated crystals based on the crystal plasticity theory comprises the following steps: Based on the crystal plasticity theory, the relative relationship between creep strain and time is established through the nickel-based single crystal high-temperature alloy material test without stripe crystals; The creep constitutive equation is established according to the relative relationship between the creep strain and time.

4. The method for predicting the influence of streak crystals on the creep life of nickel-based single crystal high-temperature alloy according to claim 1, characterized in that: In the step S2, the critical shear stress of the nickel-based single crystal high-temperature alloy material free of striped crystals is obtained by a tensile test.

5. The method for predicting the influence of streak crystals on the creep life of nickel-based single crystal high-temperature alloy according to claim 1, characterized in that: The steps of obtaining creep curve parameters of the nickel-based single crystal high-temperature alloy material without stripe crystals in step S2 are as follows: Conducting a creep test on the nickel-based single crystal high-temperature alloy material without stripe crystals to obtain a creep curve; The creep curve parameters of the nickel-based single crystal high-temperature alloy material free of stripe crystals are obtained based on the creep curve.

6. The method for predicting the influence of streak crystals on the creep life of nickel-based single crystal high-temperature alloy according to claim 1, characterized in that: The shear stress τ of the slip system of the nickel-based single crystal high-temperature alloy material containing striped crystals in step S4 (α) Obtained by the following formula: t (α) =s:P (α) ; P (α) is the orientation factor, σ is the stress tensor under the crystal axis system, m (ω) is the slip direction of the slip system, and n (α) is the unit normal vector of the slip plane in the slip system.

7. The method for predicting the influence of stripe crystals on the creep life of nickel-based single crystal high-temperature alloy according to claim 1, characterized in that: The slip system is selected from an octahedral slip system.

8. The method for predicting the influence of streak crystals on the creep life of nickel-based single crystal high-temperature alloy according to claim 7, characterized in that: The N is 12.

9. The method for predicting the influence of streak crystals on the creep life of nickel-based single crystal high-temperature alloy according to claim 1, characterized in that: The nickel-based single crystal high-temperature alloy material without streak crystals and the nickel-based single crystal high-temperature alloy material without streak crystals are prepared by adopting the same process.

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