JP6865569B2 - Evaluation method and evaluation device for evaluating creep damage of metallic materials - Google Patents

Description

The present invention relates to a method of evaluating creep damage of a metallic material using electron backscatter diffraction imaging.

For example, a metal material constituting a gas turbine for power generation may be deformed or cracked by being loaded at a high temperature. If the gas turbine is continued to operate in a state where the material is damaged such as deformation or cracks, it may lead to operation troubles or damage to the equipment. Therefore, it is required to accurately evaluate the degree of damage to the material. .. As a method for evaluating creep damage of a metal material, observation of the structure of the material surface has been conventionally known.

Further, in recent years, as a method for evaluating creep damage of a hard metal material such as a nickel-based superalloy, there is a method using an electron backscatter diffraction image method. The method for evaluating damage to a metal material in Patent Document 1 includes measurement step S2 in which the crystal orientations of a plurality of measurement points in a sample of the metal material are measured by an electron backscattering diffraction image method, and measurement of a reference among the plurality of measurement points. Analysis step S3 to obtain the damage parameter of the sample by analyzing the average orientation difference function value defined by the average of the crystal orientation difference of each measurement point with respect to the point, and the damage rate formed from the same kind of metal material as the sample is known. By referring to the correlation between the damage rate and the damage parameter obtained in advance using another sample, the damage rate of the sample can be obtained from the damage parameter of the sample obtained as a result of the analysis in the analysis step. It has an evaluation step S4 for evaluation.

Japanese Unexamined Patent Publication No. 2012-2614

In the method described in Patent Document 1, the damage rate of the sample is evaluated based on the average value of the crystal orientation differences at each measurement point. This evaluation method is considered to be effective, for example, when stress is evenly applied to the sample when a load is applied at a high temperature, and the entire sample is creep-damaged.

However, for example, when a notch or a hole is present in a part of the sample, when a load is applied at a high temperature, stress is concentrated around the notch or the hole, so that the change in crystal orientation is locally caused at that part. growing. Therefore, when the damage rate of the sample is evaluated based on the average value of the crystal orientation differences of each measurement point as in the conventional case, it is difficult to accurately evaluate the damage rate of the sample because the error is large. ..

The present invention has been completed based on the above circumstances, and an object of the present invention is to enable accurate evaluation of the damage rate of a sample even if there are notches or holes in a part of the sample. To do.

The present invention is an evaluation method for evaluating creep damage of a metal material having a stress concentration portion, and an electron back scattering diffraction image of the crystal orientation of each measurement point in a predetermined region including the stress concentration portion of the metal material. A measurement step measured by the method, an orientation difference calculation step for calculating the crystal orientation difference with respect to the reference orientation of each measurement point, a total value calculation step for calculating the total value of the crystal orientation difference at each measurement point, and the crystal. It includes an evaluation step of evaluating the damage rate of the stress concentration portion based on the total value of the orientation differences.

The present invention is an evaluation device for evaluating creep damage of a metal material having a stress concentration portion, and an electron back scattering diffraction image of the crystal orientation of each measurement point in a predetermined region including the stress concentration portion of the metal material. The data processing unit includes a measurement unit for measuring by the method and a data processing unit, and the data processing unit includes an orientation difference calculation process for calculating a crystal orientation difference with respect to a reference orientation of each measurement point, and a crystal orientation difference of each measurement point. The total value calculation process for calculating the total value and the evaluation process for evaluating the damage rate of the stress concentration portion based on the total value of the crystal orientation differences are executed.

According to the present invention, the damage rate of a sample can be accurately evaluated even when a stress concentration portion such as a notch or a hole is present in a part of the sample.

Block diagram of the evaluation device according to the first embodiment Perspective view of gas turbine rotor Perspective view showing the state where the moving blades are attached to the turbine disk. Diagram summarizing the outline of the chemical composition of the test piece and the tensile properties Top view of the test piece Front view of creep tester The figure which showed the change of the crystal orientation around the notch part Diagram showing the evaluation area The figure which shows the relationship between the 1st damage parameter U1 and the damage rate Z Flow chart showing the evaluation method of the damage rate Z Diagram showing measurement point and crystal orientation difference The figure which shows the distribution of the crystal orientation difference H of the undamaged product about the same metal material as the evaluation target. The figure which shows the crystal orientation difference of each point in the fracture state of the sample which does not have a stress concentration part. Top view of the test piece according to the second embodiment The figure which compared the length in the stress direction about the stress concentration part of each test piece. The figure which shows the relationship between the 1st damage parameter U1 and the damage rate Z The figure which shows the relationship between the 2nd damage parameter U2 and the damage rate Z The figure which showed the change of the crystal orientation around a hole Flow chart showing the evaluation method of the damage rate Z

<Embodiment 1>
Hereinafter, an evaluation device for evaluating creep damage of a metal material will be described in detail with reference to FIGS. 1 to 13. In addition, creep damage means that the metal material is damaged by being used in a high temperature and stress load environment. Specifically, it means that the metal material is damaged by being used in an environment where the absolute temperature is more than half of the melting point and even a little stress is applied.

1. 1. Configuration of Evaluation Device 1 FIG. 1 shows a block diagram of an evaluation device for evaluating creep damage of a metal material. The evaluation device 1 includes a measurement unit 5 and a data processing device 20. The measuring unit 5 includes a scanning electron microscope (SEM) 10, an EBSD (Electron Back Scatter Diffraction) detector 14, and three control units 17, 18, and 19.

The scanning electron microscope 10 has a general configuration including a sample chamber 12 in which a sample stage 11 capable of fixing a sample W can be arranged therein, and an electron gun 13 capable of irradiating the sample W with an electron beam. Is. Further, the EBSD detector 14 includes a screen 15 for projecting an electron backscatter diffraction image generated by irradiating the sample W with an electron beam, and a high-sensitivity camera 16 for capturing the projected electron backscatter diffraction image. It has a general configuration.

The three control units 17, 18, and 19 are an electron beam control unit 17 that controls electron beam irradiation by an electron gun, a stage control unit 18 that controls the position and angle of a sample stage 11, and an image pickup by a high-sensitivity camera 16. It is composed of a camera control unit 19 for controlling. These control units 17, 18 and 19 are connected to the data processing device 20 and control the sample stage 11, the electron gun 13 and the high-sensitivity camera 16 according to a command from the CPU 21.

The data processing device 20 is composed of a computer, and includes a CPU 21 that executes a measurement / analysis program that controls electron beam irradiation, acquires a diffraction image, performs orientation analysis, and the like, and a hard disk 22. A data storage area 23 and a program storage area 24 are secured on the hard disk 22, respectively. The data storage area 23 stores data of the correlation curve L, which will be described later. Further, the program storage area 24 stores a program for analyzing the crystal orientation and evaluating the damage rate Z of the metal material.

In the present embodiment, the creep damage is evaluated for a metal material such as a nickel-based superalloy, and particularly a material having a stress concentration portion.
For example, the moving blade 30 of a gas turbine or the like is composed of a nickel-based superalloy. As shown in FIG. 2, the moving blade 30 is attached to the turbine disc 40, and as shown in FIG. 3, an air hole 35 for cooling is formed. When the gas turbine is driven, the rotor blades 30 rotate at a high speed and are in a state where a load is continuously applied at a high temperature. Therefore, stress is concentrated around the air holes 35 and the metal material is creep-damaged. ..

As the stress concentration portion, a notch portion or the like can be exemplified in addition to the holes such as the air hole 35.

2. Creep test and acquisition of correlation curve L The creep test is a test in which a constant stress is continuously applied to the test piece 100 under a high temperature state. The test piece 100 of the creep test is made of the same material as the sample for damage evaluation, and has a shape imitating the shape of the stress concentration portion.

Specifically, the material of the test piece 100 is a nickel-based superalloy, and the outline of the chemical composition and the tensile properties are as shown in FIG. Further, in the present embodiment, a notch shape is assumed as the shape of the stress concentration portion, and the test piece 100 has substantially V-shaped notch portions 120 on both sides of the central portion as shown in FIG. It has a shaped shape. FIG. 5A shows the entire test piece 100, and FIG. 5B shows the cutout portion 120 in an enlarged manner.

The dimensions of the test piece 100 are as follows.
The total length A of the test piece 100 is 68 mm, the length B of both ends 105 is 24 mm, and the length C of the central portion 110 is 20 mm.
The width W1 of the test piece 100 is 8 mm, the width W2 of the central portion 110 is 4 mm, and the plate thickness is 1.5 mm.
The notch portion 120 has a length Φ1 of 0.23 mm, a depth D of 0.25 mm, and an angle θ of 30 °.

FIG. 6 is a front view of the creep tester. The creep tester 70 has a heater 71 for raising the ambient temperature of the test piece 100 to a high temperature state, and a tension portion 75 for applying stress to the test piece 100.

Then, using the testing machine 70 shown in FIG. 6, a creep test was performed on the test piece 100. Specifically, at an ambient temperature of 880 ° C., a stress of 294 MPa was continuously applied to the test piece 100.

During the test, damage behavior such as crack formation and growth was constantly observed through an optical microscope. FIG. 7 is a diagram showing changes in crystal orientation around the notch, where (a) is the difference in crystal orientation at each point in the initial state, and (b) is each point in the state where the damage rate Z = 0.45. The crystal orientation difference of (c) is the crystal orientation difference of each point in the state of damage rate Z = 0.73, and (d) the crystal orientation difference of each point in the state immediately before fracture.

The damage rate Z is the degree of damage to the metal material in a creep environment (an environment in which stress is continuously applied at a high temperature), and is defined by the following equation (1) in the present specification.

Z = T / Tf ..... (1) Equation "T" is the elapsed time from the initial stage. “Tf” is the elapsed time from the initial stage to fracture, which is 156.8 hours in this test.

As shown in FIGS. 7 (b) to 7 (d), the change in crystal orientation is prominent around the notch 120. The change in crystal orientation increases as the damage rate Z increases, and the range expands around the notch 120, eventually leading to fracture.

During the creep test described above, as shown by the alternate long and short dash line frame shown in FIG. 8, the surface of the test piece is irradiated with an electron beam for the predetermined measurement area E including the notch 120, and each measurement point P The crystal orientation of was measured by electron backscatter diffraction. The measurement interval of the crystal orientation is 5 microns as an example. Then, for each damage rate Z, the crystal orientation difference H at each measurement point P was calculated. Then, further, the first damage parameter U1 corresponding to each damage rate Z was calculated from the obtained data.

The first damage parameter U1 is the total value of the crystal orientation difference H at each measurement point P, and is defined in the following equation (2) in the present specification.

U1 = ΣH ..... (2) Equation "H" is the crystal orientation difference at each measurement point (excluding those whose crystal orientation difference is smaller than the threshold value X).

The crystal orientation of each measurement point P, the calculation of the crystal orientation difference H at each measurement point P, and the calculation of the first damage parameter U1 by the electron backscatter diffraction method are performed in the same manner as in S20 to S60 described later. ing.

The correlation curve L shown in FIG. 9 is obtained from the above-mentioned creep test, and shows the relationship between the “first damage parameter U1” and the “damage rate Z of the test piece 100 having the notch 120”. There is. In the present embodiment, the data of the correlation curve L is stored in the hard disk 22, and the damage rate Z of the metal material having the notch portion 120 is evaluated by using the correlation curve L.

Hereinafter, a method for evaluating the damage rate Z due to creep damage of the metal material having the notch portion 120 will be described.
As shown in FIG. 10, the method for evaluating the damage rate Z comprises seven steps S10 to S70. In the following description, it is assumed that the metal material is a nickel-based superalloy like the test piece 100, and has the same shape as the test piece 100 and includes a notch 120 having the same dimensions.

In S10, the measurer prepares the sample. That is, a part including the notch 120 is collected as a sample from the metal material to be evaluated used in a high temperature and stress load environment. Then, it is prepared so that the surface state is suitable for the analysis by the electron backscatter diffraction method. Here, a sample for evaluation by the electron backscattering method can be prepared by using a general method such as mechanical polishing or electrolytic polishing.

Subsequently, in S20, the crystal orientation of each measurement point P is measured by the electron backscatter diffraction method for the sample to be evaluated set on the sample stage 11 of the scanning electron microscope 10. Specifically, first, an arbitrary measurement area E including a creep damage range is set. In this example, an arbitrary measurement area E including the notch 120 is set. Then, the sample surface is irradiated with an electron beam at a predetermined pitch in the set measurement area E.

The irradiation of the electron beam produces an electron backscatter diffraction image, which is projected onto the screen 15. The projected electron backscatter diffraction image is photographed by the high-sensitivity camera 16 and output to the data processing device 20 as image data.

Subsequently, in S30, the CPU 21 of the data processing device 20 analyzes the obtained electron backscatter diffraction image to obtain the crystal orientation at each measurement point P. This process can be performed by a known method using, for example, a measurement / analysis program such as "OIM" manufactured by TSL Solutions. The obtained crystal orientation is recorded in the data storage area 23 of the hard disk 22 together with the coordinate data of each measurement point P. The processing of S20 and S30 corresponds to the "measurement step" of the present invention. The measurement interval of the crystal orientation is 5 microns as an example.

Subsequently, in S40, the CPU 21 of the data processing device 20 determines the crystal orientation difference H at each measurement point P based on the crystal orientation of each measurement point P obtained in S30. Specifically, the difference between the crystal orientation of the target measurement point P and the reference orientation (grain average orientation) is calculated as the crystal orientation difference (GROD: Grain Reference Orientation Deviation) at the measurement point P. Similar to step S30, this process can be performed using a known measurement / analysis program such as “OIM” manufactured by TSL Solutions. The process of S40 corresponds to the "direction difference calculation process" and the "direction difference calculation step" of the present invention. Further, FIG. 11 shows the crystal orientation difference H between the reference point (reference orientation point) Po in the crystal grain and each measurement point P.

Subsequently, in S50, the CPU 21 of the data processing device 20 compares the crystal orientation difference H with the threshold value X for all the measurement points P obtained in S40, and extracts the measurement points P whose crystal orientation difference H is larger than the threshold value X. Perform the processing to be performed. The threshold value X is a boundary value between the crystal orientation difference H of the damaged portion and the crystal orientation difference H of the undamaged portion.

FIG. 12 shows the distribution of the crystal orientation difference H of the undamaged product for the same metal material as the evaluation target. As shown in FIG. 12, the crystal orientation difference H is present even when it is undamaged. In the case of FIG. 12, the crystal orientation difference H is 99% within 1 °, and in this example, the threshold value X of the crystal orientation difference H is set to 1 °.

As described above, by comparing the crystal orientation difference H with the threshold value X, the measurement point P of the damaged part can be extracted from all the measurement points P calculated in S30, and the measurement point P of the undamaged part can be extracted. Can be excluded from the subsequent processing.

After that, in S60, the CPU 21 of the data processing device 20 calculates the first damage parameter U1. The first damage parameter U1 is the total value of the crystal orientation difference H of each measurement point P extracted in S50. The processes of S50 and S60 correspond to the "total value calculation process" and the "total value calculation step" of the present invention.

Then, in S70, the CPU 21 of the data processing device 20 evaluates the damage rate Z of the cutout portion 120 of the metal material based on the first damage parameter U1 calculated in S60.

Specifically, the data of the correlation curve L shown in FIG. 9 is read from the hard disk 22. Then, the damage rate Z of the notch portion 120 is evaluated by referring to the first damage parameter U1 calculated in S60 with the correlation curve L shown in FIG. For example, when the value of the first damage parameter U1 calculated in S60 is "Ua", the damage rate Z of the notch portion 120 can be evaluated as "Za". The process of S70 corresponds to the "evaluation process" and "evaluation step" of the present invention.

As described above, in the evaluation device 1 of the present embodiment, the damage rate Z of the notch portion 120 of the metal material is evaluated based on the total value of the crystal orientation differences H of each measurement point P in the measurement area E. Therefore, the damage rate Z can be evaluated more accurately than the average value.

More specifically, FIG. 13 shows the crystal orientation difference H at each point in the fractured state (Z = 1.00) for a sample in which the stress concentration portion such as the notch portion 120 does not exist. As shown in FIG. 13, in the absence of the stress concentration portion, the change in crystal orientation appears almost uniformly throughout the sample. Therefore, when the stress concentration portion does not exist, it is possible to accurately estimate the damage rate Z of the metal material from the average value of the crystal orientation difference H.

On the other hand, in the metal material having the notch portion 120, as shown in FIGS. 7A to 7D, changes in the crystal orientation are concentrated around the notch portion 120, and the crystal orientation is concentrated in other portions. The change in is small. Therefore, when averaging is taken, the portion where the change in crystal orientation is large is averaged by the portion where the change in crystal orientation is small, so that the error becomes large and it is difficult to accurately estimate the damage rate Z of the metal material.

If it is the total value of the crystal orientation difference H, the portion where the change in crystal orientation is large is not averaged by the small portion, so that the error is small and the damage rate Z of the notch portion 120 can be estimated accurately. ..

Moreover, in the evaluation device 1, among the measurement points P included in the measurement area E, only those whose crystal orientation difference H is larger than the threshold value X are evaluated. That is, the crystal orientation difference H of the undamaged portion is excluded from the total, and the total value of the crystal orientation difference H is calculated only by the crystal orientation difference H of the damaged portion. By doing so, it is possible to accurately estimate the damage rate Z of the notch portion 120. That is, in this configuration, since the evaluation range (the range for obtaining the total crystal orientation difference) of the measurement area E can be narrowed down to the damaged part, it is possible to suppress an error due to the selection of the evaluation range. , It is possible to accurately estimate the damage rate Z of the notch portion 120.

<Embodiment 2>
In the first embodiment, as an example of the test piece 100, a double-sided notch type test piece having notches 120 on both upper and lower sides of the central portion 110 is shown. In the second embodiment, five types of test pieces shown in the following (a) to (e) are prepared for two patterns of the notch type shown in FIG. 5 and the hole type shown in FIG. 14 as the shape of the stress concentration portion. did. Note that FIG. 14A shows the entire test piece 100, and FIG. 14B shows the hole 130 in an enlarged manner.

Then, a creep test (stress load of 294 MPa at an ambient temperature of 880 ° C.) is performed on each test piece 100 with the testing machine 70 shown in FIG. 6 to evaluate the relationship between the damage rate Z and the first damage parameter U1. did. The first damage parameter U1 is the total value of the crystal orientation difference H as in the first embodiment.

(A) Product with notches on both sides (see Fig. 5)
(B) One-sided notch-shaped product (c) Hole-shaped product 1 (see FIG. 14)
(D) Hole-shaped product 2
(E) Hole-shaped product 3

FIG. 16 is a graph showing the relationship between the damage rate Z and the first damage parameter U1, where “◆” is the data of the notched product on both sides and “Δ” is the data of the notched product on one side. Further, "●" is the data of the hole-shaped product 1, and "□" is the data of the hole-shaped product 2.

The notched shape on both sides has the same shape as the test piece 100 described in the first embodiment. Further, the one-sided notch-shaped product has a shape in which the notch portion 120 is one of the upper and lower sides of the test piece shown in FIG.

The hole-shaped product 1 has a different shape of the stress concentration portion from the test piece 100 described in the first embodiment, and the hole-shaped product 1 has a central portion 110 of the test piece 100 as shown in FIG. It has a shape having holes 130. The diameter Φ of the hole 130 is 0.5 mm. The hole-shaped product 2 differs from the hole-shaped product 1 only in the width W2 of the central portion 110, and the hole-shaped product 1 has W2 = 4 mm, whereas the hole-shaped product 2 has W2 = 6 mm. Note that FIG. 15 summarizes the sizes of the notch portion 120 of each test piece 100, the length Φ1, and the diameter Φ2 of the hole 130.

As shown in FIG. 16, the two-sided notched product indicated by “◆” and the one-sided notched product indicated by “Δ” show substantially the same numerical value of the first damage parameter U1 for each damage rate Z. For the two-sided notched product indicated by "◆" and the one-sided notched product indicated by "Δ", the relationship between the damage rate Z and the first damage parameter U1 can be represented by a correlation curve La. The fact that the correlation curves of the two-sided notched product and the one-sided notched product are common is that the relationship between the damage rate Z and the first damage parameter U1 is almost the same regardless of the number of notched portions 120. Shown.

Further, also for the hole-shaped product 1 indicated by "●" and the hole-shaped product 2 indicated by "□", the numerical values of the first damage parameter U1 for each damage rate Z show substantially the same values, and the holes indicated by "●". In the shaped product 1 and the hole-shaped product 2 indicated by “□”, the relationship between the damage rate Z and the first damage parameter U1 can be represented by a correlation curve Lb. The fact that the correlation curves of the hole-shaped product 1 and the hole-shaped product 2 are common is that the relationship between the damage rate Z and the first damage parameter U1 does not change regardless of the width of the surplus portion around the hole. Is shown.

Therefore, the damage rate Z of the sample can be obtained from the first damage parameter U1 by selecting and using the correlation curves La and Lb according to the shape of the stress concentration portion. That is, in the case of the notch type, if the shape and size of the notch portions 120 are the same, the correlation curve La is used regardless of the number of the notch portions 120, and the first damage parameter U1 is used to determine the metal material. The damage rate Z can be obtained. Further, in the case of the hole type, if the sizes of the holes 130 are the same, the damage rate Z of the metal material is obtained from the first damage parameter U1 by using the correlation curve Lb regardless of the width of the surplus portion. Can be done.

The hole-shaped product 3 indicated by "○" has a different diameter Φ2 of the hole 130 from the hole-shaped product 1, and the hole-shaped product 1 has a Φ2 of 0.5 mm, whereas the hole-shaped product 3 has a hole-shaped product 3 of 0.5 mm. , Φ2 is 0.25 mm.

The data of the hole-shaped product 3 indicated by “◯” shows that the numerical value of the first damage parameter U1 for each damage rate Z is different from that of the hole-shaped product 1, and deviates from the correlation curve Lb.

This indicates that the correlation curve L differs due to the difference in the diameter Φ2 of the hole 130. Therefore, when the first damage parameter U1 is used, it is shown that the correlation curve L is required according to the diameter Φ2 of the hole 130.

FIG. 17 is a graph showing the relationship between the damage rate Z and the second damage parameter U2. “◆” is the data of the notched product on both sides, and “Δ” is the data of the notched product on one side. Further, "●" is the data of the hole-shaped product 1, "□" is the data of the hole-shaped product 2, and "◯" is the data of the hole-shaped product 3.

The second damage parameter U2 is a value obtained by dividing the total value ΣH of the crystal orientation difference H at each measurement point P by the length Φ in the stress direction of the stress concentration portion, and is expressed in the following equation (3) in the present specification. To define.

U2 = ΣH / Φ ... (3) Equation "H" is the crystal orientation difference at each measurement point (excluding those whose crystal orientation difference is smaller than the threshold value X).
"Φ" is the length of the stress concentration part in the stress direction

The stress direction is the direction in which stress acts on the sample. In this example, during the creep test, a load is applied to the test piece 100 in the longitudinal direction (R direction in FIGS. 5, 6 and 14). Therefore, the longitudinal direction (load direction) of the test piece 100 is the stress direction.

Therefore, the length Φ along the stress direction of the stress concentration portion is the length Φ1 of the notch type 120 in the case of the notch type test piece 100 shown in FIG. 5, and the hole type test piece shown in FIG. In the case of 100, the diameter of the hole 130 is Φ2.

As shown in FIG. 17, when the second damage parameter U2 is used, the correlation between the damage rate Z and the second damage parameter U2 can be represented by one correlation curve Ls for all five types of test pieces.

It can be inferred that this is due to the following reasons.
FIG. 7 is a diagram showing the change in crystal orientation of the notch type test piece 100 with the progress of damage, and FIG. 18 is a diagram showing the change of crystal orientation of the hole type test piece 100 with the progress of damage. ..

As shown in FIGS. 7 and 18, the change in crystal orientation is concentrated around the stress concentration portion such as the notch portion 120 and the hole 130, and the range is widened as the damage progresses. Specifically, the change in crystal orientation spreads in the stress direction (R direction shown in FIGS. 7 and 18) around the stress concentration portion. Therefore, when compared with the same damage rate Z, the total value of the crystal orientation difference H tends to increase in proportion to the length of the stress concentration portion along the stress direction (R direction).

Therefore, by dividing the total value of the crystal orientation difference H by the length Φ in the stress direction of the stress concentration portion and converting it into a numerical value per unit length, the difference in length Φ along the stress direction can be obtained. No damage parameter U is expected to be obtained (damage parameter normalization).

FIG. 19 is a flowchart of the evaluation method of the damage rate Z applied to the second embodiment. In the evaluation method of the second embodiment, the processes of S10 to S60 are common to the evaluation method of the first embodiment, and the process of S65 is added.

In S65, the total value ΣH of the crystal orientation difference H calculated in S60 is divided by the length Φ along the stress direction of the stress concentration portion to calculate the second damage parameter U2.

In the following S70, the damage rate Z of the sample is evaluated based on the second damage parameter U2 calculated in S65.

Specifically, the damage rate Z of the sample can be evaluated by referring to the second damage parameter U2 calculated in S65 with the correlation curve Ls shown in FIG. For example, when the second damage parameter U2 calculated in S65 is “Ub”, the damage rate Z of the sample can be evaluated as “Zb”.

As described above, in the configuration of the second embodiment, the damage rate Z of the metal material is calculated by using the second damage parameter U2. Therefore, there is an advantage that it is not necessary to provide the correlation curve Ls for each difference in the shape and dimensions of the stress concentration portion.

<Other Embodiments>
The present invention is not limited to the embodiments described in the above description and drawings, and for example, the following embodiments are also included in the technical scope of the present invention.

(1) In the first and second embodiments, "nickel-based superalloy" is exemplified as an example of the metal material. The metal material to be evaluated has a characteristic that the crystal orientation difference H is small in an undamaged state, such as "nickel-based alloy", "aluminum alloy", and "SUS", and the crystal orientation difference H increases as creep damage progresses. Any metal material (alloy-based metal material) having the above can be widely applied.

(2) In the first embodiment, "total ΣH of crystal orientation difference H" is set as the first damage parameter U1. In the second embodiment, "a numerical value obtained by subtracting the total ΣH of the crystal orientation difference H by the length Φ in the stress direction of the stress concentration portion" was set as the second damage parameter U2. In addition to this, as shown by the following equations (4) and (5), the measurement interval of the crystal orientation with respect to the first damage parameter U1 and the second damage parameter U2 (dimension Q shown in FIG. 11). The value obtained by multiplying the square of the third damage parameter U3 may be used as the third damage parameter U3. By doing so, it is possible to set the damage parameter regardless of the measurement interval Q of the crystal orientation. In FIG. 11, the measurement interval Q differs between the vertical direction and the horizontal direction, but in actual measurement, the measurement intervals in the vertical direction and the horizontal direction are substantially the same.

U3 = U1 x Q ² ... (4) formula U3 = U2 x Q ² ... (5) formula

The case where the third damage parameter U3 is used is the same as the case where the first damage parameter U1 and the second damage parameter U2 are used. First, the crystal orientation of each measurement point P is measured by the electron backscatter diffraction method. To do. Then, the crystal orientation difference H at each measurement point P is calculated from the measurement result, and the third damage parameter U3 described above is further calculated. After that, the damage rate Z of the sample can be evaluated by referring to the third damage parameter U3 to the correlation curve (correlation curve showing the relationship between the third damage parameter U3 and the damage rate Z).

(3) In the first embodiment, an example is shown in which the total value ΣH of the crystal orientation difference H is calculated by excluding the measurement points P whose crystal orientation difference H is smaller than the threshold value X from all the measurement points P in the measurement area. It was. In addition to this, the total value ΣH of the crystal orientation difference H may be calculated for all the measurement points P, including the measurement points P whose crystal orientation difference H is smaller than the threshold value X. Further, in the first embodiment, the threshold value X is set to 1 °, but the threshold value X may be a boundary value of the crystal orientation difference H between the “undamaged product” and the “damaged product”, and is not limited to the example of the embodiment.

1 ... Evaluation device 5 ... Measuring unit 10 ... Scanning electron microscope 11 ... Sample stage 13 ... Electron gun 14 ... EBSD detector 20 ... Data processing unit 30 ... Moving blade 40 ... Turbine disk 100 ... Test piece 120 ... Notch (corresponding to the "stress concentration part" of the present invention)
130 ... hole (corresponding to the "stress concentration portion" of the present invention)

Claims (8)

It is an evaluation method for evaluating creep damage of a metal material having a stress concentration portion.
A measurement step of measuring the crystal orientation of each measurement point in a predetermined region of the metal material including the stress concentration portion by an electron backscatter diffraction image method.
An orientation difference calculation step for calculating the crystal orientation difference with respect to the reference orientation of each measurement point, and
A total value calculation step for calculating the total value of the crystal orientation differences at each measurement point, and
An evaluation method including an evaluation step of evaluating the damage rate of the stress concentration portion based on the total value of the crystal orientation differences. The evaluation method according to claim 1.
In the total value calculation step,
An evaluation method for calculating the total value of the crystal orientation differences among the measurement points described above, with the measurement points having a crystal orientation difference larger than the threshold value. The evaluation method according to claim 1 or 2.
In the evaluation step,
An evaluation method for evaluating the damage rate of the stress-concentrated portion based on a value obtained by grading the total value of the crystal orientation differences with the length of the stress-concentrated portion in the stress direction. The evaluation method according to claim 1 or 2.
In the evaluation step,
Evaluation is performed to evaluate the damage rate of the stress-concentrated portion based on a value obtained by gradually increasing the total value of the crystal orientation differences by the length of the stress-concentrated portion in the stress direction and multiplying by the square of the measurement interval of the crystal orientation. Method. It is an evaluation device that evaluates creep damage of metal materials with stress concentration parts.
A measuring unit that measures the crystal orientation of each measurement point in a predetermined region including the stress concentration portion of the metal material by an electron backscatter diffraction image method, and a measuring unit.
Including data processing unit
The data processing unit
Orientation difference calculation processing for calculating the crystal orientation difference with respect to the reference orientation of each measurement point, and
A total value calculation process for calculating the total value of the crystal orientation differences at each measurement point, and
An evaluation device that executes an evaluation process for evaluating the damage rate of the stress concentration portion based on the total value of the crystal orientation differences. The evaluation device according to claim 5.
The data processing unit performs the total value calculation process.
An evaluation device that calculates the total value of the crystal orientation difference among the measurement points described above for the measurement points whose crystal orientation difference is larger than the threshold value. The evaluation device according to claim 5 or 6.
The data processing unit is subjected to the evaluation processing.
An evaluation device that evaluates the damage rate of the stress-concentrated portion based on a value obtained by grading the total value of the crystal orientation differences by the length of the stress-concentrated portion in the stress direction. The evaluation device according to claim 5 or 6.
The data processing unit is subjected to the evaluation processing.
Evaluation is performed to evaluate the damage rate of the stress concentration portion based on a value obtained by gradually increasing the total value of the crystal orientation differences by the length of the stress concentration portion in the stress direction and multiplying the measurement interval of the crystal orientation by the self-squared value. apparatus.

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