JP2018091720A - Evaluation method and evaluation device for evaluating creep damage of metallic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately evaluate the damage rate of a sample even when a notch or hole exists in a part of the sample.SOLUTION: An evaluation method of evaluating the creep damage of a metallic material having a stress concentration portion includes: a measurement step of measuring, by an electron backscattering diffraction image method, the crystal orientation of each measurement point in a prescribed area including the stress concentration portion in the metallic material; an orientation difference calculation step of calculating the crystal orientation difference with respect to the reference orientation of each measurement point; a total value calculation step of calculating the total value of the crystal orientation difference of each measurement point; and an evaluation step of evaluating the damage rate of the stress concentration portion on the basis of the total value of the crystal orientation difference.SELECTED DRAWING: Figure 10

Description

  The present invention relates to a method for evaluating creep damage of a metal material using an electron backscatter diffraction image method.

  For example, the metal material constituting the power generation gas turbine may be deformed or cracked when subjected to a load at a high temperature. Continued operation of the gas turbine while the material is damaged, such as deformation or cracking, can lead to operational troubles and 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.

  In recent years, for example, as a method for evaluating creep damage of a hard metal material such as a nickel-base superalloy, an electron backscatter diffraction image method is used. The damage evaluation method for a metal material disclosed in Patent Document 1 includes a measurement step S2 in which crystal orientations at a plurality of measurement points in a metal material sample are measured by an electron backscatter diffraction image method, and measurement of a reference among the plurality of measurement points. Analysis step S3 for obtaining a damage parameter of the sample by analyzing an average orientation difference function value defined by an average of crystal orientation differences at each measurement point with respect to the point, and a damage rate formed from the same metal material as the sample By referring to the correlation between the damage rate and damage parameters obtained in advance using other samples, the damage rate of the sample can be calculated from the damage parameters of the sample obtained as a result of the analysis in the analysis step. Evaluation step S4 for evaluation.

JP 2012-2614 A

  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 difference at each measurement point. This evaluation method is considered to be effective, for example, when stress is applied evenly 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 hole exists in a part of the sample, stress is concentrated around the notch or hole when a load is applied at a high temperature. growing. Therefore, when the damage rate of the sample is evaluated based on the average value of the crystal orientation difference at each measurement point as in the past, 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 make it possible to accurately evaluate the damage rate of a sample even when a notch or a hole exists in a part of the sample. To do.

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

  The present invention is an evaluation apparatus for evaluating creep damage of a metal material having a stress concentration portion, wherein the crystal orientation of each measurement point in a predetermined region including the stress concentration portion of the metal material is expressed by an electron backscatter diffraction image. A measurement unit for measuring by a method, and a data processing unit, the data processing unit, 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 A total value calculation process for calculating the total value and an 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, even when a stress concentration part such as a notch or a hole exists in a part of the sample, the damage rate of the sample can be accurately evaluated.

The block diagram of the evaluation apparatus in Embodiment 1. Gas turbine rotor perspective view The perspective view which shows the state which attached the rotor blade to the turbine disk A summary of the chemical composition and tensile properties of the specimen Top view of specimen Front view of creep testing machine Diagram showing the change in crystal orientation around the notch Diagram showing evaluation area The figure which shows the relationship between the 1st damage parameter U1 and the damage rate Z The flowchart figure which shows the evaluation method of damage rate Z Diagram showing measurement points and crystal orientation difference The figure which shows distribution of the crystal orientation difference H of an undamaged product about the same metal material as evaluation object The figure which shows the crystal orientation difference of each point in the fracture state of the sample where there is no stress concentration part Plan view of a test piece in Embodiment 2 Figure comparing the stress direction length 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 Diagram showing the change in crystal orientation around the hole The flowchart figure which shows the evaluation method of damage rate Z

<Embodiment 1>
Hereinafter, an evaluation apparatus for evaluating creep damage of a metal material will be described in detail with reference to FIGS. Note that creep damage means that the metal material is damaged when used under 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 the stress is applied even a little.

1. Configuration of Evaluation Apparatus 1 FIG. 1 shows a block diagram of an evaluation apparatus that evaluates creep damage of a metal material. The evaluation device 1 includes a measurement unit 5 and a data processing device 20. The measurement 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 is disposed, and an electron gun 13 capable of irradiating the sample W with an electron beam. It is. The EBSD detector 14 includes a screen 15 that projects an electron backscatter diffraction image generated by electron beam irradiation on the sample W, and a high-sensitivity camera 16 that captures the projected electron backscatter diffraction image. It has a general configuration.

  The three control units 17, 18, 19 are imaged by the electron beam control unit 17 that controls the electron beam irradiation by the electron gun, the stage control unit 18 that controls the position and angle of the sample stage 11, and the high sensitivity camera 16. The camera control unit 19 is controlled. 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 instructions from the CPU 21.

  The data processing device 20 is configured by a computer, and includes a CPU 21 that executes a measurement / analysis program for performing electron beam irradiation control, diffraction image acquisition, orientation analysis, and the like, and a hard disk 22. A data storage area 23 and a program storage area 24 are secured in the hard disk 22. The data storage area 23 stores data of a correlation curve L, which will be described later. 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 object of creep damage evaluation is a metal material such as a nickel-base superalloy, particularly a material having a stress concentration portion.
For example, the moving blade 30 such as a gas turbine is made of a nickel-base superalloy. As shown in FIG. 2, the rotor blade 30 is attached to the turbine disk 40, and as shown in FIG. 3, cooling air holes 35 are formed. Such a rotor blade 30 rotates at a high speed when the gas turbine is driven, and a load is continuously applied at a high temperature. Therefore, stress concentrates around the air hole 35 and the metal material is creep-damaged. .

  In addition, as a stress concentration part, a notch part etc. can be illustrated other than holes, such as the air hole 35. FIG.

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 condition. The specimen 100 for 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-base superalloy, and the outline and tensile properties of the chemical components are as shown in FIG. In this 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 center portion as shown in FIG. It has a shape. 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 end portions 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 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 test machine 70 includes a heater 71 for bringing the ambient temperature of the test piece 100 into a high temperature state, and a tension portion 75 that applies stress to the test piece 100.

  And the creep test was done with respect to the test piece 100 using the testing machine 70 shown in FIG. Specifically, a stress of 294 MPa was continuously applied to the test piece 100 at an ambient temperature of 880 ° C.

  During the test, damage behavior such as crack initiation and growth was always observed through an optical microscope. 7A and 7B are diagrams showing changes in crystal orientation around the notch, where FIG. 7A is a crystal orientation difference at each point in the initial state, and FIG. 7B is a point at a damage rate Z = 0.45. (C) is the crystal orientation difference of each point in the state where the damage rate Z = 0.73, and (d) is the crystal orientation difference of each point in the state immediately before the fracture.

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

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

  As shown in (b) to (d) of FIG. 7, the change in crystal orientation appears remarkably around the notch 120. The change in the crystal orientation is large as the damage rate Z is increased, and the range is expanded around the notch 120, and finally the fracture is reached.

  During the above-described creep test, 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 a predetermined measurement area E including the notch 120, and each measurement point P The crystal orientation of was measured by electron backscatter diffraction. The crystal orientation measurement interval is 5 microns as an example. Then, for each damage rate Z, the crystal orientation difference H at each measurement point P was calculated. Further, a first damage parameter U1 corresponding to each damage rate Z was calculated from the obtained data.

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

U1 = ΣH (2) Formula “H” is the difference in crystal orientation at each measurement point (however, the crystal orientation difference is smaller than the threshold value X)

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

  The correlation curve L shown in FIG. 9 is obtained from the above-described 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”. Yes. In the present embodiment, 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 120 is evaluated 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 120 will be described.
As shown in FIG. 10, the evaluation method of the damage rate Z includes seven steps S10 to S70. In the following description, it is assumed that the metal material is a nickel-base superalloy similar to the test piece 100 and has a shape including the notch 120 having the same shape and the same size as the test piece 100.

  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. And it prepares so that it may become a surface state suitable for the analysis by an electron backscattering diffraction method. Here, a sample for evaluation by an 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, for the set measurement area E, the sample surface is irradiated with an electron beam at a predetermined pitch.

  By electron beam irradiation, an electron backscattered diffraction image is generated and projected onto the screen 15. The projected electron backscattered diffraction image is captured 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 and obtains the crystal orientation at each measurement point P. This processing can be performed by a known method using 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. Moreover, the measurement interval of crystal orientation is 5 microns as an example.

  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 at 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 a crystal orientation difference (GROD) at the measurement point P. This processing can be performed using a known measurement / analysis program such as “OIM” manufactured by TSL Solutions, for example, as in step S30. The process of S40 corresponds to “azimuth difference calculation process” and “azimuth 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 point P where the crystal orientation difference H is greater than the threshold value X. Perform the process. The threshold value X is a boundary value between the crystal orientation difference H at the damaged site and the crystal orientation difference H at the undamaged site.

  FIG. 12 shows the distribution of the crystal orientation difference H of the undamaged product for the same metal material as the evaluation object. As shown in FIG. 12, the crystal orientation difference H exists even in the case of no damage. In the case of FIG. 12, the crystal orientation difference H is 99% within 1 ° or less. In this example, the threshold value X of the crystal orientation difference H is 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 further processing.

  Thereafter, 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 differences H of the measurement points P extracted in S50. The processes of S50 and S60 correspond to the “total value calculation process” and “total value calculation step” of the present invention.

  In S70, the CPU 21 of the data processing device 20 evaluates the damage rate Z of the notch 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. Then, the damage rate Z of the notch 120 is evaluated by referring to the correlation curve L shown in FIG. 9 with respect to the first damage parameter U1 calculated in S60. For example, when the value of the first damage parameter U1 calculated in S60 is “Ua”, it can be evaluated that the damage rate Z of the notch 120 is “Za”. The process of S70 corresponds to “evaluation process” and “evaluation step” of the present invention.

  As described above, in the evaluation apparatus 1 of the present embodiment, the damage rate Z of the notch 120 of the metal material is evaluated based on the total value of the crystal orientation differences H of the measurement points P in the measurement area E. Therefore, the damage rate Z can be evaluated with higher accuracy than the average value.

  Specifically, FIG. 13 shows the crystal orientation difference H at each point in a fractured state (Z = 1.00) for a sample in which no stress concentration portion such as the notch 120 exists. As shown in FIG. 13, when there is no stress concentration part, the change in crystal orientation appears almost uniformly throughout the sample. Therefore, if there is no stress concentration part, 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, as shown in FIGS. 7A to 7D, the metal material having the notch portion 120 concentrates the change in crystal orientation around the notch portion 120. The change is small. For this reason, if the average is taken, the portion where the change in crystal orientation is large is averaged by the small portion, so that the error becomes large and it is difficult to accurately estimate the damage rate Z of the metal material.

  If the total value of the crystal orientation difference H is used, 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 120 can be accurately estimated. .

  In addition, in the evaluation apparatus 1, among the measurement points P included in the measurement area E, only the crystal orientation difference H that is larger than the threshold value X is the object of evaluation. That is, the crystal orientation difference H of the undamaged part 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 part. By doing in this way, it is possible to estimate the damage rate Z of the notch 120 with high accuracy. In other words, in this configuration, since the range to be evaluated (the range in which the sum of crystal orientation differences is calculated) in the measurement area E can be narrowed down to the damaged part, errors due to selection of the range to be evaluated can be suppressed. It is possible to accurately estimate the damage rate Z of the notch 120.

<Embodiment 2>
In the first embodiment, as an example of the test piece 100, a both-side notch type test piece having the notch portions 120 on both upper and lower sides of the central portion 110 is shown. In Embodiment 2, 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. did. 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 differences H as in the first embodiment.

(A) Notched shape on both sides (see Fig. 5)
(B) One-side 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 data on both-side notches and “Δ” is data on one-side notches. Further, “●” is data of the hole-shaped product 1, and “□” is data of the hole-shaped product 2.

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

  The hole-shaped product 1 is different in the shape of the stress concentration portion from the test piece 100 described in the first embodiment, and the hole-shaped product 1 is formed in the central portion 110 of the test piece 100 as shown in FIG. The shape has a hole 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. The hole-shaped product 1 has W2 = 4 mm, whereas the hole-shaped product 2 has W2 = 6 mm. In FIG. 15, the length Φ1 of the notch 120 and the diameter Φ2 of the hole 130 of each test piece 100 are summarized.

  As shown in FIG. 16, the both-side notch product indicated by “♦” and the one-side notch product indicated by “△” show substantially the same value of the first damage parameter U1 for each damage rate Z. The relationship between the damage rate Z and the first damage parameter U1 can be represented by a correlation curve La for both-side notch products indicated by “◆” and one-side notch items indicated by “Δ”. It should be noted that the fact that the correlation curve of the notch on both sides and the notch on the one side is 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 notches 120. Show.

  Also, for the hole-shaped product 1 indicated by “●” and the hole-shaped product 2 indicated by “□”, the numerical value of the first damage parameter U1 with respect to each damage rate Z is substantially the same value, and the hole indicated by “●”. In the shape product 1 and the hole shape 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. It should be noted that the correlation curve of the hole-shaped product 1 and the hole-shaped product 2 is the same because 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, by selecting and using the correlation curves La and Lb corresponding to the shape of the stress concentration portion, the damage rate Z of the sample can be obtained from the first damage parameter U1. That is, in the case of the notch type, if the shape and size of the notch 120 are the same, the correlation curve La is used to calculate the metal material from the first damage parameter U1 regardless of the number of notches 120. The damage rate Z can be obtained. In the case of the hole type, if the size of the hole 130 is the same, the damage rate Z of the metal material is obtained from the first damage parameter U1 using the correlation curve Lb regardless of the width of the surplus portion. I can do it.

  The hole-shaped product 3 indicated by “◯” is different from the hole-shaped product 1 in the diameter Φ2 of the hole 130, whereas the hole-shaped product 1 has Φ2 of 0.5 mm, whereas the hole-shaped product 3 is , Φ2 is 0.25 mm.

  In the data of the hole-shaped product 3 indicated by “◯”, the numerical value of the first damage parameter U1 with respect to each damage rate Z indicates a value different from that of the hole-shaped product 1, and deviates from the correlation curve Lb.

  This indicates that the correlation curve L varies depending on the difference in the diameter Φ2 of the hole 130. For this reason, when the first damage parameter U1 is used, it is indicated that the correlation curve L is required according to the diameter Φ2 of the hole 130, respectively.

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

  The second damage parameter U2 is a numerical 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. In this specification, the following equation (3) is used. Define.

U2 = ΣH / Φ (3) Equation “H” is the crystal orientation difference at each measurement point (however, the 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, in the case of the notch type test piece 100 shown in FIG. 5, the length Φ along the stress direction of the stress concentration part is the length Φ1 of the notch part 120, and the hole type test piece shown in FIG. In the case of 100, it is the diameter Φ2 of the hole 130.

  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 expressed by one correlation curve Ls in all five types of test pieces.

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

  As shown in FIGS. 7 and 18, the change in crystal orientation is concentrated around the stress concentration portion such as the notch 120 and the hole 130, and the range expands as damage progresses. Specifically, the change in crystal orientation spreads around the stress concentration portion with respect to the stress direction (the R direction shown in FIGS. 7 and 18). Therefore, when compared at the same damage rate Z, the total value of the crystal orientation differences 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 to a numerical value per unit length, the difference in the length Φ along the stress direction It is considered that the damage parameter U is not obtained (normalization of the damage parameter).

  FIG. 19 is a flowchart of the damage rate Z evaluation method 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 second damage parameter U2 is calculated by dividing the total value ΣH of the crystal orientation difference H calculated in S60 by the length Φ along the stress direction of the stress concentration portion.

  In subsequent 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 correlation curve Ls shown in FIG. 17 with respect to the second damage parameter U2 calculated in S65. For example, when the second damage parameter U2 calculated in S65 is “Ub”, it can be evaluated that the damage rate Z of the sample is “Zb”.

  Thus, in the configuration of the second embodiment, the damage rate Z of the metal material is calculated 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 size of the stress concentration portion.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. 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 materials to be evaluated are, for example, “nickel-based alloy”, “aluminum alloy”, “SUS”, etc., in which the crystal orientation difference H is small in an undamaged state, and the crystal orientation difference H increases as creep damage progresses. If it is a metal material (alloy-type metal material) which has, it can apply widely.

  (2) In the first embodiment, “total ΣH of crystal orientation differences H” is set as the first damage parameter U1. In the second embodiment, “a numerical value obtained by grading the total ΣH of the crystal orientation differences H by the length Φ in the stress direction of the stress concentration portion” is set as the second damage parameter U2. In addition to this, as shown in the following equations (4) and (5), the crystal orientation measurement interval (dimension Q shown in FIG. 11) with respect to the first damage parameter U1 and the second damage parameter U2. A value obtained by multiplying the square of may be used as the third damage parameter U3. By doing in this way, it can be set as a damage parameter irrespective of the measurement interval Q of crystal orientation. In FIG. 11, the measurement interval Q is different between the vertical direction and the horizontal direction. However, in actual measurement, the measurement intervals in the vertical direction and the horizontal direction are substantially equal.

U3 = U1 × Q ² Equation (4) U3 = U2 × Q ² Equation (5)

  Note that 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 further, the above-described third damage parameter U3 is calculated. Thereafter, the damage rate Z of the sample can be evaluated by referring to the third damage parameter U3 with a correlation curve (correlation curve indicating the relationship between the third damage parameter U3 and the damage rate Z).

  (3) Embodiment 1 shows an example in which the total value ΣH of the crystal orientation difference H is calculated by excluding the measurement points P in which the crystal orientation difference H is smaller than the threshold value X among all the measurement points P in the measurement area. It was. In addition, 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. In the first embodiment, the threshold value X is 1 °. However, 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.

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

Claims (8)

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 including the stress concentration portion of the metal material by an electron backscatter diffraction image method;
An orientation difference calculating step for calculating a crystal orientation difference with respect to a reference orientation of each measurement point;
A total value calculating step for calculating a total value of crystal orientation differences at each measurement point;
And an evaluation step of evaluating a 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 calculating step,
An evaluation method in which a total value of crystal orientation differences is calculated for measurement points having a crystal orientation difference larger than a threshold among the measurement points. The evaluation method according to claim 1 or 2, wherein
In the evaluation step,
An evaluation method for evaluating a damage rate of the stress concentration portion based on a numerical value obtained by grading a total value of crystal orientation differences by a length in a stress direction of the stress concentration portion. The evaluation method according to claim 1 or 2, wherein
In the evaluation step,
Evaluating the damage ratio of the stress concentration portion based on a numerical value obtained by gradually grading the total value of the crystal orientation difference by the length in the stress direction of the stress concentration portion and multiplying by the square of the measurement interval of the crystal orientation. Method. An evaluation apparatus for evaluating creep damage of a metal material having a stress concentration portion,
A measurement 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,
Including a data processing unit,
The data processing unit
Orientation difference calculation processing for calculating a crystal orientation difference with respect to a reference orientation of each measurement point;
A total value calculation process for calculating the total value of the crystal orientation difference at each measurement point;
An evaluation apparatus that executes an evaluation process for evaluating a damage rate of the stress concentration portion based on the total value of the crystal orientation differences. An evaluation apparatus according to claim 5, wherein
The data processing unit, in the total value calculation process,
An evaluation apparatus that calculates a total value of crystal orientation differences for measurement points having a crystal orientation difference larger than a threshold among the measurement points. The evaluation device according to claim 5 or 6, wherein
In the evaluation process, the data processing unit
An evaluation apparatus that evaluates a damage rate of the stress concentration portion based on a numerical value obtained by grading a total value of crystal orientation differences by a length in a stress direction of the stress concentration portion. The evaluation device according to claim 5 or 6, wherein
In the evaluation process, the data processing unit
Evaluating the damage ratio of the stress concentration portion based on a numerical value obtained by gradually grading the total value of the crystal orientation difference by the length in the stress direction of the stress concentration portion and multiplying by the square of the measurement interval of the crystal orientation. apparatus.

Images