JPH1038853A - Material strength evaluation method of metal material and method and device for diffusion layer thickness evaluation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make possible evaluation of material strength by measuring conductivity of precipitation strengthened metal material strengthened by precipitating a precipitation phase in a parent phase and obtaining a mutual boundary length based on relationship between a predetermined conductivity and the mutual boundary length of the precipitation phase. SOLUTION: For a precipitation strengthened nickel group ultra-alloy IN 738 LC, a precipitation phase of a NI3 AI phase is dispersed in a parent phase of a Ni solid solution body, material strength of a material in which a fine precipitation phase is dispersed evenly is generally strong. This conductivity is measured by a tetra terminal method. The conductivity of this material varies depending upon a mutual boundary length L of the precipitation phase. That is, when the mutual boundary length L is long the conductivity is lowered, and when the mutual boundary length L is short the conductivity is higher. Assuming that an average mutual particle size of the precipitation phase is d and that a distance between crystal granules is λ, the result is L=πd/λ<2> and d/λ<2> has correlation with a creep strength. Consequently, the mutual boundary length L is obtained from correlation database predetermined by measuring conductivity and converted into d/λ<2> , making it possible to estimate the creep strength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for evaluating the strength of a metal material, and more particularly to a method for evaluating the strength of a precipitation-hardened metal material by performing electromagnetic nondestructive measurement. The present invention relates to a method and an apparatus for evaluating the strength of a material.

[0002]

2. Description of the Related Art FIG. 11 is a schematic diagram showing a metal material structure of IN738LC which is a typical precipitation strengthened metal material. This metal material has a form in which a Ni ₃ Al phase as an intermetallic compound is dispersed as a precipitation phase in a Ni solid solution as a matrix. The most important factor that governs the material strength of such a precipitation-strengthened metal material is the shape of the precipitate phase, and a material in which fine precipitate phases are uniformly dispersed is generally stronger. Therefore, it is important to know the shape of the precipitated phase in order to non-destructively estimate the material strength.

Conventionally, to know the shape of the precipitated phase of a precipitation-strengthened metallic material having a microstructure as shown in FIG.
For example, an observation method using a microscope is widely used. In this observation method, the surface of a mirror-polished subject is corroded using a specific corrosive liquid, and the extracted microstructure is observed under magnification using an optical microscope or an electron microscope.
Also, when the subject is large or the shape is complicated,
A replica method of transferring a microstructure to a film made of a resin and observing the film is also used.

[0004]

However, the conventional microstructure observation method described above is time-consuming and time-consuming, so that a large area cannot be observed at a time, and the method is limited when the subject has a large area. The whole was estimated by observing the microstructure of a part. According to this method, local inhomogeneity of the material unavoidable in the material manufacturing stage may be overestimated or underestimated, and in some cases, there is a great risk in using a metal material.

[0005] In particular, in the case of a precipitation-strengthened metal material used at a high temperature, the precipitated phase changes from a shape exhibited during production to a shape that is thermally stable during use. Recently, structural members that are used for a long time at high temperatures, such as gas turbines, are increasing their combustion gas inlet temperature for the purpose of improving thermal efficiency or protecting the global environment (such as reducing CO ₂ ). The environment in which they are placed is becoming increasingly harsh.

Therefore, the change in the shape of the precipitate phase in such a precipitation-strengthened metal material progresses in a shorter time than before, and it is necessary to know the change in the microstructure nondestructively for stable operation of the equipment. Is becoming indispensable.

Further, in the case of a structural member having a complicated curved surface, such as a blade of a gas turbine, the test environment of the material is slightly different for each position. It is difficult to represent as a microstructure.

In addition, these blades are provided with a coating for the purpose of oxidation resistance or heat shielding in order to prolong the life of the blade against oxidation and deterioration. Although these coatings extend the life of the substrate, it is not at all possible to observe the structure of the substrate by microstructure without removing the coating. Similarly, it cannot be applied to a part where surface treatment such as polishing and corrosion is prohibited, such as a part where the surface roughness is strictly defined.

As a method for non-destructively estimating the microstructure of a metal material, in addition to the above, there is an electromagnetic material evaluation method and apparatus described in Japanese Patent Application No. 7-267157 by the present applicant. Can be This is a method to evaluate the volume fraction of different materials contained in the base material from the eddy current intensity induced in the subject, and to measure the difference in the conductivity or magnetic permeability between the base material and the inclusion using an electromagnetic material measuring device. It measures the change in the eddy current amount that occurs from, and evaluates the volume ratio of different materials.

In other words, the method shown in this method and apparatus for evaluating electromagnetic properties is based on the difference in the electromagnetic constants such as the conductivity and the magnetic permeability between the mother phase and the precipitated phase. The volume ratio is non-destructively and easily estimated. In the case of the precipitation-strengthened metallic material to be a problem in the present invention,
If the volume fraction of the precipitated phase is manufactured under the same components and conditions, it will be almost the same due to the variation of the error range.

When the deterioration during use progresses, the shape of the precipitated phase changes greatly, but the volume ratio does not change much. That is, in the method described in Japanese Patent Application No. 7-267157, it is not possible to detect a change in the shape of the precipitation phase of the precipitation-strengthened metallic material, so that it is impossible to evaluate the material strength.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a method in which a metal matrix contains
Non-destructive measurement of the shape of the precipitated phase for precipitation-strengthened metallic materials that have been strengthened by precipitating metallic or non-metallic precipitated phases,
An object of the present invention is to provide a method and an apparatus for evaluating a material strength of a metal material, which can easily and accurately evaluate the material strength such as creep.

[0013] Another object of the present invention is as follows.
In a structural member in which a coating layer is applied to a surface of a metal material, a metal material diffusion layer thickness evaluation method and apparatus capable of evaluating a diffusion layer thickness existing between the coating layer and the metal material are provided. To provide.

[0014]

According to a first aspect of the present invention, there is provided a method for evaluating a material strength of a metal material, comprising the steps of: The conductivity is measured, and the phase boundary length of the precipitated phase in the material is determined based on the relationship between the conductivity and the phase boundary length of the precipitated phase, which are experimentally obtained in advance, and the material strength of the material is evaluated. It is characterized by doing.

According to a second aspect of the present invention, there is provided a method for evaluating the strength of a metal material, wherein the conductivity of each direction of a precipitation-strengthened metal material in which a precipitated phase of a metal or a nonmetal is precipitated and strengthened in a matrix of the metal. Is measured, and the phase boundary length of the precipitated phase in the material is obtained for each orientation based on the relationship between the conductivity and the phase boundary length of the precipitated phase that are experimentally obtained in advance, and the material strength of the material is obtained. Is characterized by evaluating the anisotropy of

According to a third aspect of the present invention, there is provided a method for evaluating a material strength of a metal material, wherein an eddy current generated in a precipitation-strengthened metal material in which a metal or non-metal precipitation phase is precipitated and strengthened in a metal matrix. The amount is measured under certain conditions, the conductivity of the test object is determined from the permeability measured in advance using a reference sample, and the relationship between the conductivity and the phase boundary length of the precipitate phase determined experimentally in advance is determined. The method is characterized in that a phase boundary length of a precipitated phase in the material is obtained based on the calculated value, and a material strength of the material is evaluated.

According to a fourth aspect of the present invention, there is provided a method for evaluating the strength of a metal material according to the third aspect, wherein the surface shape of the object is measured in advance or at the same time and the shape is corrected. It is characterized by doing.

According to a fifth aspect of the present invention, there is provided a method for evaluating the strength of a metal material, wherein the precipitation strengthening type metal material in which a metal or a non-metal precipitation phase is precipitated and strengthened in a metal matrix.
A first eddy current generated to a deeper position at a first frequency is measured, and then a second eddy generated only at a shallow position in the material at a second frequency higher than the first frequency. The amount of current was measured, the third eddy current amount only at a deep position was obtained from the first eddy current amount and the second eddy current amount, and the penetration depth of the magnetic field lines at each frequency was calculated in advance by electromagnetic analysis. The measurement depth of the third eddy current amount is quantitatively obtained from the result, converted into conductivity, and further measured from the relationship between the conductivity obtained experimentally and the phase boundary length of the precipitate phase. The method is characterized in that a phase boundary length of a precipitated phase is obtained and a material strength at a deep portion of the material is evaluated.

According to a sixth aspect of the present invention, there is provided the metal material strength evaluation method according to the fifth aspect, wherein the first frequency and the second frequency are changed a plurality of times. The eddy current amount is obtained, and the distribution of the material strength of the subject in the depth direction is evaluated based on the result of evaluating the material strength at each measurement depth.

According to a seventh aspect of the present invention, there is provided a method for evaluating the thickness of a diffusion layer of a metal material, comprising the steps of: The eddy current amount of the subject is measured, and the eddy current amount that occurs only at a certain depth is obtained from the result of calculating the penetration depth of the magnetic field lines at each frequency by electromagnetic analysis in advance, and the depth is converted to conductivity. The method is characterized in that a direction distribution is calculated, and a thickness of a diffusion layer existing between the coating layer and the metal material is evaluated from the change curve.

According to a eighth aspect of the present invention, there is provided an apparatus for evaluating a material strength of a metal material, wherein the apparatus comprises a coil having a known impedance,
The coil and the subject are brought close to or in contact with each other at a predetermined distance, an alternating current is applied to the coil to measure an eddy current amount induced in the subject, and the coil in an excited state is measured based on the measured eddy current amount. An impedance measuring unit for determining the impedance of the object, a database unit having data of the amount of eddy current generated in the subject and the phase boundary length of the precipitated phase,
An arithmetic unit that evaluates the eddy current amount from the impedance measurement result by the impedance measurement unit, calculates the phase boundary length of the precipitated phase with reference to the database unit, and evaluates the material strength. .

According to a ninth aspect of the present invention, there is provided an apparatus for evaluating the strength of a metal material according to the eighth aspect, further comprising a shape measuring section for measuring the shape of the object in advance or simultaneously. The apparatus is characterized in that a means for correcting the shape is provided in the apparatus.

According to a tenth aspect of the present invention, there is provided an apparatus for evaluating the thickness of a diffusion layer made of a metal material, comprising: a coil having a known impedance; An impedance measuring unit that measures an eddy current amount induced in the subject, and obtains an impedance of the coil in an excited state from the measured eddy current amount; a penetration depth analysis result of a magnetic field line at each frequency; and a diffusion of the subject. The database section of the layer thickness and the eddy current amount were evaluated from the impedance measurement result by the impedance measuring section, and the measurement depth of the eddy current amount was obtained by referring to the database, and the measurement was performed a plurality of times by changing the frequency. The distribution of the eddy current in the depth direction is calculated from the data, and the thickness of the diffusion layer existing between the coating layer and the metal material of the test object is evaluated from the change curve. Characterized by comprising an arithmetic unit section for.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment of Material Strength Evaluation Method]
FIG. 1 shows a first method of evaluating the strength of a metal material according to the present invention.
FIG. 1 shows an embodiment, and is an explanatory diagram for realizing material strength evaluation by obtaining a phase boundary length of a precipitated phase from conductivity measurement of an object.

In the present embodiment, a precipitation-strengthened metal material in which a metal or non-metal precipitation phase is precipitated and strengthened in a metal parent phase is used as the metal material. The article focuses on nickel-base superalloy IN738LC used for wings and the like.

This material has a form in which a Ni ₃ Al phase as an intermetallic compound is dispersed as a precipitated phase in a Ni solid solution as a parent phase. The most important factor that governs the material strength of such a precipitation strengthened metal material is
In the form of a precipitate phase, a material in which fine precipitate phases are uniformly dispersed is generally stronger.

FIG. 1 shows IN738L according to the present embodiment.
The evaluation results of the phase boundary length of the precipitated phase of C are shown. Here, the four-terminal method is used to measure the conductivity of the specimen, which is a precipitation-strengthened metal material. This material is made under specified manufacturing conditions, and its volume fraction hardly changes even if the shape of the precipitated phase changes. Therefore, the difference in conductivity due to volume fraction is so small as to be negligible. The conductivity σ of such a material changes depending on the length of the phase boundary in the subject.

That is, in the case of the nickel-base superalloy IN738LC, which is a precipitation-strengthened metal material, when the phase boundary length to be overcome is long, the resistance of the subject is inevitably increased and the conductivity is lowered. Conversely, when the phase boundary length is short, the conductivity increases. In other words, when scanning lines are drawn at regular intervals in one direction on the microstructure of the precipitation-strengthened metallic material, the conductivity decreases as the number of intersections between the scanning lines and the phase boundaries increases.

The shape of the precipitated phase of IN738LC according to the present embodiment has a cubic shape at the time of material production, but gradually becomes coarser and approaches a spherical shape when exposed to a high temperature for a long time. In other words, the shape of this precipitated phase has a close relationship with the number of phase boundaries, and the phase boundary length becomes larger when coarse and spheroidized than when the finely cubic precipitated phase is uniformly dispersed. It tends to be shorter and the electrical conductivity tends to be higher.

Now, assuming that the average phase grain size of the precipitated phase is d and the number of precipitated phases per unit area is ρ, the phase boundary length L is expressed by the following equation (1).

[0031]

L = πdρ (1) Here, the number ρ of the precipitated phases per unit area in the equation (1)
Is expressed as Equation (2), where the distance between crystal grains is a function of λ.

[0032]

Ρ = 1 / λ ² (2) From the equations (1) and (2), the phase boundary length L can be expressed as the equation (3).

[0033]

L = πd / λ ² (3) Therefore, it can be seen from equation (3) that the phase boundary length L is represented by the average phase grain size d of the precipitated phase and the intergranular distance λ.

By the way, this d / λ ² is determined by the Japanese Gas Turbine Society Journal Vol.No.85, p63-68, (published in 1994) “N
Effect of Material Deterioration on Mechanical Properties of i-Base Superalloy IN738LC ", a correlation with creep strength has been confirmed. From the measurement of conductivity, the phase boundary length of the precipitated phase was determined, and the value was calculated as d / when converted to λ ^2, it is possible to estimate the creep strength.

As described above, according to the present embodiment, the phase boundary length of the precipitated phase is determined by measuring the conductivity of the precipitation-strengthened metallic material, and the phase boundary length and creep strength determined experimentally in advance are determined. The creep strength of the test object can be estimated by referring to the database representing the relationship.

[Second Embodiment of Material Strength Evaluation Method] (Claim 2 and FIG. 2) FIGS. 2A and 2B show a second embodiment of a metal material strength evaluation method according to the present invention. (A) is a schematic diagram showing a microstructure of a precipitation-strengthened metallic material, and (B) is a diagram showing a relationship between a measurement direction and conductivity.

The present embodiment is a method for obtaining the shape of the precipitated phase for each direction from the conductivity measurement of the test object and realizing the anisotropy evaluation of the material strength. As an example of the precipitation strengthened metal material,
As in the first embodiment, a nickel-base superalloy IN738LC used for a moving blade of a gas turbine or the like is taken up.

When the nickel-base superalloy IN738LC is held in a high-temperature environment, the shape of Ni ₃ Al, which is a precipitated phase, gradually becomes coarser and spheroidized from the cubic shape at the beginning of production. As described. However, it is known that when used in a state where a stress load is applied, the coarsening and spheroidization of the precipitated phase are accompanied by anisotropy.

In this embodiment, the conductivity of the subject is measured by the method described in the first embodiment. At this time, the conductivity is, for example, 10 ° with one direction as a reference direction.
The measurement is performed at intervals of 0 ° to 180 °. In this case, if the shape of the precipitated phase has anisotropy, there is a difference in the conductivity for each direction.

This phenomenon will be described with reference to a schematic diagram of the microstructure of IN738LC having a flat precipitate phase as shown in FIG. 2A. When the conductivity measurement direction coincides with the longitudinal direction of the precipitate phase, the measurement is performed. The number of intersections between the scanning lines drawn in the direction and the phase boundaries is reduced. This means that there are fewer barriers to hinder conduction, so the longitudinal conductivity is higher.
Conversely, when the number of intersections between the scanning line drawn in the direction perpendicular to the longitudinal direction and the phase boundary increases, the conductivity decreases.

Therefore, if the conductivity of the precipitation-strengthened metal material as the test object is measured for each direction, a curve showing the relationship between the measurement direction and the conductivity as shown in FIG. 2B can be drawn. By converting the measurement results of the conductivity in each direction into the phase boundary length of the second phase of the subject by the method described in the first embodiment, it is possible to estimate the creep strength. That is, the material strength of each direction of the subject can be known from the conductivity measurement data of each direction.

As described above, according to the present embodiment, it is possible to evaluate the anisotropy of the material strength of the test object by measuring the conductivity of the precipitation-strengthened metal material in each direction.

[Third Embodiment of Material Strength Evaluation Method] (corresponding to claim 3 and FIG. 3) FIG. 3 shows a third embodiment of the material strength evaluation method for metal materials according to the present invention.
4 is a flowchart illustrating an embodiment. This embodiment is a method of realizing material strength evaluation by obtaining the shape of a precipitated phase from eddy current measurement of an object. In this embodiment, as in the first and second embodiments, a precipitation-enhanced metal material is used. As an example, a nickel-base superalloy IN738LC used for a moving blade of a gas turbine or the like is taken up.

In the present embodiment, the length of the phase boundary of the precipitation phase of the precipitation-strengthened metallic material as the specimen is estimated by measuring the intensity of the eddy current flowing through the specimen due to the electromagnetic induction phenomenon. This method (hereinafter referred to as an eddy current method) is a method in which an exciting coil is brought close to a subject, which is a conductor, and the amount of eddy current flowing in the subject is regarded as a change in coil impedance. Is determined by the magnetic permeability and conductivity of the subject, the magnetic flux density penetrating the conductor, and the like.
The method of determining the excitation coil impedance is described in detail in the Handbook of Nondestructive Inspection (Japanese Nondestructive Inspection: Nikkan Kogyo Shuppan), Vol.

The impedance of a coil close to a conductor can be determined by knowing the magnetic flux density and eddy current loss that vary with the conductivity and magnetic permeability of the conductor. The magnetic flux density and the eddy current loss can be estimated by eddy current analysis using the conductivity and the magnetic permeability of the conductor.

The probe coil impedance measured by the eddy current method is a value uniquely determined by the conductivity, magnetic permeability, shape, coil shape, and frequency of the subject. If the coil shape, frequency, and object shape are determined, the coil impedance changes depending on the conductivity and magnetic permeability of the object. Conversely, if the coil shape, frequency, and object shape can be specified, the coil From the value of the impedance, the conductivity of the subject and the magnetic permeability can be evaluated.

The i-based superalloy IN taken up in this embodiment
If 738LC is manufactured with the same components or conditions, the volume fraction of the precipitated phase will be almost the same due to the variation in the error range. Further, when the deterioration proceeds during use, the shape of the precipitated phase changes greatly, but the volume ratio does not change much. Therefore, the magnetic permeability, which has a characteristic that does not depend on the shape mainly depending on the volume ratio of the test object, hardly changes, and the measured value of the reference sample of the present alloy becomes a constant value that can be adopted for any test object. Therefore, in the case of the present material, since the conductivity of the subject can be determined independently by the eddy current method, the conductivity can be measured only by bringing the excitation coil into contact with or close to the subject.

As described above, the amount of eddy current generated in the Δi-base superalloy IN738LC under certain conditions is measured, and the conductivity of the subject is determined from the magnetic permeability measured using the reference sample in advance. The creep strength of the specimen can be evaluated by obtaining the phase boundary length of the precipitated phase in IN738LC from the relationship between the conductivity and the phase boundary length of the precipitated phase experimentally obtained.

As described above, according to this embodiment, it is possible to evaluate the material strength of the precipitation-strengthened metallic material only by bringing the excitation coil into contact with or close to the subject.

[Fourth Embodiment of Material Strength Evaluation Method] (corresponding to claim 4 and FIG. 4) FIG. 4 shows a fourth embodiment of the metal material strength evaluation method according to the present invention.
It is explanatory drawing which shows embodiment. This embodiment is a method for realizing material strength evaluation of a specimen having a curvature. In this embodiment, as in the first to third embodiments, as an example of a precipitation-strengthened metal material, a gas turbine is used. Nickel-base superalloy IN738L used for blades, etc.
C is taken up.

As described in the third embodiment, the material strength of the test object can be evaluated by measuring the amount of eddy current generated in the test object, which is a precipitation-strengthened metallic material, by the excitation coil. It is. However, when the subject has a complicated shape having a curvature, for example, it is necessary to correct the shape. The correction of the shape is performed by, for example, a laser oscillation probe close to the excitation coil.

The laser beam emitted from the laser oscillation probe is applied to a region of the subject where the magnetic field lines are generated, and the shape of the subject in the range is measured. The shape is a curvature, a distance to an end of the subject, or the like.

On the other hand, the eddy current amount of the subject is measured by the method described in the third embodiment. These two data are taken into an arithmetic unit, and the eddy current amount of the subject whose shape has been corrected in real time is calculated. From the measured data of the eddy current amount after this correction, the average phase boundary length of the precipitated phase in the range in which the lines of magnetic force are generated can be calculated, so that the material strength can be evaluated even when the specimen has a complicated shape. . In addition. This correction refers to the database of electromagnetic analysis. This shape database analyzes the state of occurrence of magnetic lines of force on a subject having various shapes by the finite element method, and selects a correction coefficient according to each shape by comparing with the case of a flat plate. is there.

As described above, according to the present embodiment, the eddy current amount measured from the precipitation-strengthened metal material having a complicated shape is corrected from the shape of the object measured in advance or simultaneously, and the phase boundary phase determined in advance is determined. The creep strength of the subject can be estimated by referring to a database representing the relationship between the length and the creep strength.

[Fifth Embodiment of Material Strength Evaluation Method] (corresponding to claim 5 and FIG. 5) FIG. 5 shows a fifth embodiment of the material strength evaluation method for metal materials according to the present invention.
It is explanatory drawing which shows embodiment. In this embodiment, the material strength evaluation is performed by obtaining the shape of the precipitate phase in the deep part of the subject from the eddy current measurement result at the first frequency and the eddy current measurement result at the second frequency higher than the first frequency. In this embodiment, as in the first to fourth embodiments, a nickel-base superalloy IN738LC used for a blade of a gas turbine or the like is used as an example of the precipitation-strengthened metal material in the same manner as in the first to fourth embodiments. I am taking it up.

The above-described eddy current method is a method in which an exciting coil is brought close to a conductor and the amount of eddy current flowing in a subject is detected as a change in coil impedance. The depth can be changed.

FIG. 5 shows a simulation result of an axially symmetric analysis model of the penetration depth of the magnetic field lines when the eddy current method is carried out at two kinds of frequencies. It is shallow. That is, the eddy current amount measured by selecting a low frequency includes information up to the deep part of the subject, and at a high frequency, includes only information of a shallow position of the subject.

First, a low frequency (500 kHz), which is the first frequency, is applied to the specimen which is a precipitation-strengthened metallic material.
In z), the first eddy current amount is measured, and the first eddy current amount is measured.
The first phase boundary length of the precipitated phase is determined by the method described in the embodiment. This phase boundary length is average value data from the surface layer to a depth of about 10 mm. The measurement frequency at this time was selected by calculating the penetration depth of the magnetic field lines by electromagnetic simulation for the purpose of measuring an average value up to a depth of 10 mm.

Next, the second frequency, the high frequency (1
MHz), the second eddy current generated in the subject is measured,
The second phase boundary length of the precipitated phase is determined by the method described in the first embodiment. This phase boundary length is average data from the surface layer to a depth of about 5 mm. The measurement frequency at this time was also selected by calculating the penetration depth of the magnetic field lines by electromagnetic simulation.

The first phase boundary length of the precipitated phase, which is the average up to the depth of 10 mm measured in this way, and the depth of 5 mm
From the second phase boundary length of the precipitated phase, which is the average of
The third phase boundary length of the precipitated phase at a depth of up to 10 mm is calculated. If this measurement operation is performed over the entire test object, it becomes possible to evaluate the material strength from the phase boundary length of the precipitated phase at a certain depth in a completely non-destructive manner.

That is, in this embodiment, the amount of the first eddy current generated to a deeper position in the material at the first frequency is measured, and then the amount of the eddy current in the material at the second frequency higher than the first frequency is measured. The second eddy current amount generated only at the shallow position of the eddy current is measured, and the third eddy current amount only at the deep position is obtained from the first eddy current amount and the second eddy current amount. From the result of calculating the penetration depth of the magnetic field lines at the frequency, the measurement depth of the third eddy current amount is quantitatively obtained, converted into electrical conductivity, and the phase boundary length between the electrical conductivity and the precipitate phase, which is experimentally obtained. From this relationship, the phase boundary length of the precipitated phase at the measurement depth of the specimen is determined, and the material strength at the deep portion of the material is evaluated.

As described above, according to the present embodiment, it is possible to evaluate the material strength such as creep in the deep part of the precipitation-strengthened metallic material.

[Sixth Embodiment of Material Strength Evaluation Method] (Claim 6, FIG. 6) FIG. 6 shows a sixth embodiment of the metal material strength evaluation method according to the present invention.
It is explanatory drawing which shows embodiment. In this embodiment, a third eddy current amount is obtained by changing the first frequency and the second frequency a plurality of times in the method described in the fifth embodiment, and the material strength evaluation in the depth direction of the subject is performed. This is a method for realizing, and in this embodiment, similarly to the first to fifth embodiments,
As an example of the precipitation-strengthened metal material, a nickel-base superalloy IN738LC used for a moving blade of a gas turbine or the like is taken up.

As described in the fifth embodiment, it is possible to evaluate the material strength of the deep part of the subject from the eddy current amounts measured at two different frequencies. FIG. 6 shows that the penetration depth of magnetic field lines is set to change to 10 mm at a pitch of 1 mm by electromagnetic simulation, the material strength of the deep part of the subject estimated by the method according to the fifth embodiment, and the penetration of magnetic field lines analyzed by electromagnetic simulation. This shows the relationship with the depth. That is, in the present embodiment, the material intensity distribution in the depth direction of the subject is evaluated by performing the eddy current amount measurement a plurality of times at the frequency at which the penetration depth of the magnetic field lines is changed.

For example, in the case of a turbine blade, environmental conditions such as temperature and stress are greatly different between the blade surface layer portion and the inside of the blade. This means that the degree of deterioration received by operation is different in the depth direction, and by evaluating the material strength distribution in the depth direction by the method described in this embodiment, the degree of deterioration of the material is non-destructively. Can be evaluated.

As described above, according to the present embodiment, the third eddy current amount is obtained by changing the first frequency and the second frequency a plurality of times in the method described in the fifth embodiment, and each measurement is performed. The material strength distribution in the depth direction of the precipitation-strengthened metal material can be evaluated based on the result of evaluating the material strength at the depth.

[One Embodiment of Diffusion Layer Thickness Evaluation Method] (Claim 7, FIG. 7) FIGS. 7A and 7B show one embodiment of a metal material diffusion layer thickness evaluation method according to the present invention. FIG. 4 is a process diagram showing the form, and a diagram showing the relationship between the distance from the surface layer and the conductivity. The present embodiment is a method for realizing the evaluation of the thickness of the diffusion layer of the subject from the measurement results of the eddy current of the subject using the exciting coil whose frequency is changed. In the present embodiment, a structural member in which a metal coating layer for improving oxidation resistance is provided on a base material of a nickel-base superalloy IN738LC as a precipitation-strengthened metal material.

As shown in FIG. 7 (A), this structural member is subjected to a diffusion heat treatment after coating to increase the adhesion. By this heat treatment, a diffusion layer is formed between the base material and the coating layer (coating layer) due to diffusion of both elements. The conditions of diffusion heat treatment are determined by temperature and time,
The higher the temperature and the longer the time, the thicker the diffusion layer formed. If this diffusion layer is thin,
If the adhesion between the base material and the coating layer is weak, and if the thickness of the diffusion layer is large, the effective area of the base material bearing the load becomes small, and none of them meets the design criteria. Therefore, it is necessary to manufacture a structural member having an appropriate diffusion layer thickness at the manufacturing stage.

In the above-described eddy current method, an exciting coil is brought close to a conductor, and the amount of eddy current flowing through the subject is regarded as a change in coil impedance. This is a method that can change the penetration depth.

First, the eddy current amount is measured a plurality of times while changing the frequency. The result of calculating the conductivity from this measurement result is combined with the results of the analysis of the penetration depth of the magnetic force lines at each frequency, and the relationship between the depth from the surface and the conductivity is shown in a graph.

FIG. 7B shows graphs before and after the diffusion heat treatment. Since the coating layer and the substrate have originally different electromagnetic characteristics, there is a difference in the electrical conductivity. That is, as shown in FIG. 7B, before the diffusion heat treatment, the conductivity changes rapidly when the distance from the surface layer becomes equal to the thickness of the coating layer. On the other hand, this change becomes gentle after the diffusion heat treatment. This is because the diffusion layer formed by mutual diffusion of the constituent elements of the base material and the coating layer has an intermediate property between the two layers when viewed from the viewpoint of electromagnetic characteristics. Therefore, the width of the transition region where the conductivity of the coating layer changes to the eddy current amount of the substrate becomes the thickness of the diffusion layer.

Therefore, in the present embodiment, in a structural member in which a coating layer is formed on the surface of a base material (metal material), the frequency flowing through the exciting coil is changed stepwise so that the eddy current From the result of calculating the penetration depth of the magnetic field lines at each frequency by electromagnetic analysis in advance, the amount of eddy current generated only at a certain depth is obtained, converted to conductivity, and the depth distribution is calculated. The thickness of the diffusion layer existing between the coating layer and the substrate is evaluated from the change curve.

As described above, according to the present embodiment, it is possible to non-destructively evaluate the thickness of the diffusion layer between the base material and the coating layer. Not only that, it is also possible to evaluate the thickness of the diffusion layer at each interface of the multilayer structure material.

[First Embodiment of Material Strength Evaluation Apparatus] (corresponding to claim 8 and FIG. 8) FIG. 8 shows a first embodiment of a metal material strength evaluation apparatus according to the present invention.
FIG. 1 is a block diagram illustrating an embodiment. This material strength evaluation apparatus includes a coil 1 excited at an AC angular frequency ω for flowing an eddy current through a precipitation-strengthened metal material as an object to measure the eddy current, and an impedance measuring unit for reading the impedance of the coil 1. 2 and a database that represents the relationship between the conductivity in the specimen calculated from the coil impedance and the phase boundary length of the precipitated phase of the specimen, and stores the phase boundary length of the precipitated phase and the material strength of the specimen. , An input device 4 for inputting initial information / setting signals, etc., and a coil impedance measured by the impedance measuring unit 2 and initial information generated in the subject from the initial information. An arithmetic unit 5 for estimating an eddy current amount, and further evaluating a phase boundary length of a precipitate phase of the specimen and a material strength of the specimen;
And an output device 7 for outputting measurement results and evaluations.

Next, the operation of the present embodiment will be described.

The material strength database section 3 stores simulation results as coil impedance matrices only with respect to commonly used coil shapes and frequencies. In other cases, a simulation is performed under each condition to create a matrix. The matrix once created can be stored and discarded at the discretion of the user according to conditions such as storage capacity. The database unit 3 can search (or create) an appropriate coil impedance matrix from the initial conditions, and evaluate the conductivity of the subject using this matrix.

The relationship between the eddy current amount and the phase boundary length of the precipitate phase of the specimen, and the relationship between the phase boundary length of the precipitate phase and the material strength of the specimen are determined by several types of precipitation strengthening experimentally determined. Each type metal material is memorized.

Therefore, in this embodiment, after the coil 1 is brought close to or brought into contact with the object at a predetermined distance, an alternating current is applied to the coil 1 to measure the amount of eddy current induced in the object. The impedance of the coil 1 in the excited state is obtained by the impedance measuring unit 2 from the eddy current amount obtained, and the data of the eddy current amount generated in the subject and the phase boundary length of the precipitated phase are stored in the material strength database unit 3. The arithmetic unit 5 evaluates the eddy current amount from the impedance measurement result by the impedance measuring unit 2, calculates the phase boundary length of the precipitated phase with reference to the material strength database unit 3, and evaluates the material strength. I have.

As described above, according to the apparatus for evaluating the strength of a metal material according to the present embodiment, by merely bringing the excited coil 1 into contact with or close to the subject, the amount of eddy current of the subject can be measured and the deposition of the subject can be determined. It is possible to estimate the length of the phase boundary length of the phase and evaluate the material strength. Since non-contact measurement is also possible, the evaluation time can be reduced by automatic scanning.

[Second Embodiment of Material Strength Evaluation Apparatus] (corresponding to claim 9 and FIG. 9) FIG. 9 shows a second embodiment of a metal material strength evaluation apparatus according to the present invention.
FIG. 1 is a block diagram illustrating an embodiment. Parts that are the same as or correspond to those in the first embodiment of the material strength evaluation device will be described with the same reference numerals as in FIG.

The material strength evaluation apparatus according to the present embodiment includes a coil 1 excited by an AC angular frequency ω for flowing an eddy current through a precipitation-enhanced metal material as an object to measure the same, and an impedance of the coil 1. An impedance measuring unit for reading, and a database storing a relationship between an eddy current amount in the subject calculated from the coil impedance and a phase boundary length of a precipitated phase of the subject, and further storing a phase boundary length of the precipitated phase. And a material strength database unit 3 for storing a database representing the relationship between the object strength and the material strength of the subject, an input device 4 for inputting initial information / setting signals, and the like, and an object generated from the measured coil impedance and the initial information. An arithmetic unit 5 for estimating the amount of eddy current to be generated, correcting the shape, and evaluating the phase boundary length of the precipitate phase of the specimen and the material strength of the specimen;
A storage device 6 for storing the calculation results of the calculation device 5 and the like
An output device 7 that outputs a measurement result and an evaluation, a shape measurement probe 8 of a subject arranged in close proximity to the coil 1,
An object shape measuring unit 9 for measuring the shape of the object from which the data of the shape measurement probe 8 is read, and a database that calculates the range of magnetic force lines generated in the object for various shapes of the object. Shape database part 1 to be stored
0.

Next, the operation of the present embodiment will be described.

The material strength database unit 3 stores simulation results as coil impedance matrices only for commonly used coil shapes and frequencies. In other cases, a matrix is created by performing simulation under each condition. Also, the matrix once created is stored at the discretion of the user according to conditions such as storage capacity, etc.
Enable disposal. The database unit 3 can search (or create) an appropriate coil impedance matrix from the initial conditions, and evaluate the conductivity of the subject using this matrix.

The relationship between the eddy current amount and the phase boundary length of the precipitate phase of the specimen, and the relationship between the phase boundary length of the precipitate phase and the material strength of the specimen are determined by several types of precipitation strengthening experimentally determined. Each type metal material is memorized.

The object shape measuring section 9 is provided with the selected coil 1
The range of the lines of magnetic force generated in the subject is calculated in advance in accordance with the frequency, and the shape of the range is measured based on the signal from the shape measurement probe 8.

The shape database unit 10 stores the results of analyzing the state of generation of the lines of magnetic force on the object having various shapes by the finite element method. Is to select a correction coefficient according to.

As described above, according to the apparatus for evaluating the strength of a metal material according to the present embodiment, the eddy current amount of the object can be measured and the deposition phase of the object can be measured simply by bringing the excitation coil into contact with or near the object. By estimating the phase boundary length, it is possible to evaluate the material strength. In addition, since non-contact measurement is possible, not only can the evaluation time be shortened by automatic scanning, but also the shape measurement probe 8, the object shape measurement unit 9, and the shape database unit 10 make the measurement complicated. The measurement of the shape of the object becomes possible, and the field applicability is high.

[One Embodiment of Diffusion Layer Thickness Evaluation Apparatus] (Corresponding to Claim 10 and FIG. 10) FIG. 10 is a block diagram showing an embodiment of a metal material diffusion layer thickness evaluation apparatus according to the present invention. is there. Parts that are the same as or correspond to those in the first embodiment of the material strength evaluation device will be described with the same reference numerals as in FIG.

The apparatus for evaluating the thickness of the diffusion layer according to the present embodiment reads the coil 1 excited by the AC angular frequency ω for flowing an eddy current through the metal material to be measured and measuring the eddy current, and the impedance of the coil 1. Measuring unit 2, a coil impedance data for each frequency, a diffusion layer thickness database unit 3a for storing a relationship between a conductivity change curve and a diffusion layer thickness, and an input device for inputting initial information / setting signals and the like. 4, a calculating device 5 for estimating the amount of eddy current generated in the deep part of the subject from the measured coil impedance and initial information, a storage device 6 for storing a calculation result of the calculating device 5, etc., a measurement result and an evaluation And an output device 7 for outputting the same.

Next, the operation of the present embodiment will be described.

The value of the eddy current amount measured a plurality of times while changing the frequency is stored in the storage device 6, and a curve is drawn on the relationship between the depth from the surface of the subject and the eddy current amount. The eddy current amount of the coating material only near the surface layer of the subject and the eddy current amount of the base material only in the deep part are measured. By measuring the width of the transition region existing between these two, the evaluation of the diffusion layer thickness can be made. It is possible, and based on the stored data, the arithmetic unit 5 evaluates the diffusion layer thickness with reference to the database unit 3a.

Therefore, in the present embodiment, the coil 1 is brought close to or in contact with the subject by a predetermined distance.
An eddy current induced in the subject is measured by passing an alternating current through the coil, and the coil 1 in the excited state is measured based on the measured eddy current.
Of the magnetic field lines at each frequency and the diffusion layer thickness of the subject are obtained by the diffusion layer thickness database unit 3.
a, the eddy current amount is evaluated from the impedance measurement result, and the measurement depth of the eddy current amount is determined with reference to the database 3a. The depth distribution of the eddy current amount is calculated, and the thickness of the diffusion layer existing between the coating layer of the subject and the base material (metal material) is evaluated from the change curve.

As described above, according to the apparatus for evaluating the thickness of the diffusion layer of a metal material according to the present embodiment, the eddy current amount of the object can be measured simply by bringing the excitation coil into contact with or near the object several times while changing the frequency. Thus, the thickness of the diffusion layer can be evaluated, and the measurement can be performed in a non-contact manner, so that the evaluation time can be reduced by automatic scanning.

[0094]

As described above, according to the method for evaluating the strength of a metallic material according to the first aspect of the present invention, the conductivity of a precipitation-strengthened metallic material is measured to determine the phase boundary length of a precipitated phase. By referring to a database representing the relationship between the phase boundary length and the material strength, which was obtained experimentally in advance,
For example, the strength of the material, such as creep, can be easily and accurately evaluated.

According to the method for evaluating the strength of a metal material according to the second aspect, the conductivity of the precipitation-strengthened metal material is measured in each direction, whereby the anisotropy of the material strength of the precipitation-strengthened metal material is measured. Can be evaluated.

According to the method for evaluating material strength of a metal material according to the third aspect, the eddy current amount of the precipitation-strengthened metal material is measured, and the conductivity of the subject is determined from the magnetic permeability measured in advance using a reference sample. The strength of the precipitation-strengthened metal material is determined by determining the phase boundary length of the precipitate phase in the precipitation-strengthened metal material from the relationship between the conductivity and the phase boundary length of the precipitate phase, which is determined experimentally in advance. Can be evaluated only by bringing the excitation coil into contact with or close to the subject.

According to the method for evaluating the material strength of a metal material according to the fourth aspect, the eddy current amount measured from the precipitation-strengthened metal material having a complicated shape is corrected from the shape of the object measured in advance or simultaneously, and The material strength of the subject can be evaluated by referring to the database representing the relationship between the determined phase boundary phase length and the material strength.

According to the material strength evaluation method of the fifth aspect, the eddy current measurement result at the first frequency and the eddy current measurement result at the second frequency higher than the first frequency are obtained from: By determining the shape of the precipitate phase in the deep part of the test object, it becomes possible to evaluate the material strength such as creep in the deep part of the precipitation-strengthened metallic material.

According to the material strength evaluation method for a metal material according to the sixth aspect, in the method of the fifth embodiment, the first frequency and the second frequency are changed a plurality of times to obtain the third eddy current amount. Is determined, and the material strength distribution in the depth direction of the precipitation-strengthened metal material can be evaluated based on the result of evaluating the material strength at each measurement depth.

According to the method for evaluating the thickness of a diffusion layer of a metal material according to the present invention, the thickness of the diffusion layer of the object is evaluated based on the measurement result of the eddy current of the object using the exciting coil whose frequency is changed. In addition, the thickness of the diffusion layer between the metal material and the coating layer can be non-destructively evaluated, and the diffusion at each interface of the multilayer structure material as well as the two-layer structure material including the coating layer and the metal material becomes possible. According to the material strength evaluation apparatus for a metal material according to claim 8, which can also evaluate the layer thickness, the coil is brought close to or in contact with the object at a predetermined distance, and an alternating current is passed through the coil to the object. The amount of induced eddy current is measured, and the impedance of the coil in the excited state is obtained from the measured amount of eddy current by the impedance measurement unit, while the data of the amount of eddy current generated in the subject and the phase boundary length of the precipitated phase are obtained. To The excited coil is covered by calculating the eddy current amount from the impedance measurement result by the impedance measurement unit using an arithmetic unit and calculating the phase boundary length of the precipitated phase by referring to the database unit. Just by contacting or approaching the specimen, it is possible to estimate the length of the phase boundary length of the precipitated phase of the specimen from the measurement of the eddy current amount of the specimen and evaluate the material strength. Since non-contact measurement is also possible, the evaluation time can be reduced by automatic scanning.

According to the material strength evaluation apparatus for a metal material according to the ninth aspect, in addition to the effect of the eighth aspect, a shape measuring unit for measuring the shape of the object in advance or simultaneously is provided. By providing the means for correcting the shape, it is possible to measure a subject having a complicated shape, and the field applicability is enhanced.

According to the apparatus for evaluating the thickness of a diffusion layer of a metal material according to the tenth aspect, the eddy current amount is evaluated from the impedance measurement result by the impedance measuring unit, and the measured eddy current amount depth is referred to a database. Is calculated, the depth distribution of the eddy current amount is calculated from data measured multiple times at different frequencies, and the thickness of the diffusion layer existing between the coating layer and the metal material of the subject is evaluated from the change curve. By doing so, it is possible to evaluate the thickness of the diffusion layer from the eddy current amount measurement of the subject simply by contacting or approaching the exciting coil to the subject a plurality of times while changing the frequency.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a first embodiment of a material strength evaluation method for a metal material according to the present invention.

FIGS. 2A and 2B show a second embodiment of the method for evaluating the strength of a metal material according to the present invention, and FIG. 2A is a schematic diagram showing the microstructure of a precipitation-strengthened metal material; The figure in parentheses) shows the relationship between the measurement direction and the conductivity.

FIG. 3 is a flowchart showing a third embodiment of the material strength evaluation method for a metal material according to the present invention.

FIG. 4 is an explanatory view showing a fourth embodiment of the material strength evaluation method for a metal material according to the present invention.

FIG. 5 is an explanatory view showing a fifth embodiment of the material strength evaluation method for a metal material according to the present invention.

FIG. 6 is an explanatory view showing a sixth embodiment of the material strength evaluation method for a metal material according to the present invention.

FIGS. 7A and 7B are a process chart showing one embodiment of a method for evaluating the thickness of a diffusion layer of a metal material according to the present invention, and a view showing the relationship between the distance from the surface layer and the conductivity.

FIG. 8 is a block diagram showing a first embodiment of a metal material strength evaluation apparatus according to the present invention.

FIG. 9 is a block diagram showing a second embodiment of the metal material strength evaluation apparatus according to the present invention.

FIG. 10 is a block diagram showing an embodiment of a metal material diffusion layer thickness evaluation apparatus according to the present invention.

FIG. 11 is a schematic view showing the shape of a precipitated phase of a precipitation strengthened alloy.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coil 2 Impedance measurement part 3 Material strength database part 3a Diffusion layer thickness database part 4 Input device 5 Calculation device 6 Storage device 7 Output device 8 Shape measurement probe 9 Subject shape measurement part 10 Shape database part

Claims (10)

[Claims] 1. A method for measuring the conductivity of a precipitation-strengthened metallic material in which a metallic or non-metallic precipitated phase is precipitated and strengthened in a metal matrix, and which is obtained by experimentation in advance. A method for evaluating the material strength of a metal material, comprising determining a phase boundary length of a precipitated phase in the material based on a relationship with the phase boundary length, and evaluating a material strength of the material. 2. Conductivity in each direction of a precipitation-strengthened metal material which is strengthened by precipitating a metallic or non-metallic precipitated phase in a metal matrix, and which is determined in advance by an experiment. And determining the phase boundary length of the precipitated phase in the material for each orientation based on the relationship between the phase boundary length of the material and the phase boundary length of the precipitated phase, and evaluating the anisotropy of the material strength of the material. Material strength evaluation method for materials. 3. An eddy current generated in a precipitation-strengthened metal material obtained by precipitating a metallic or non-metallic precipitated phase in a metallic matrix and measuring the eddy current amount under a certain condition, and a reference sample is prepared in advance. Determine the conductivity of the test object from the magnetic permeability measured by using, the phase boundary length of the precipitate phase in the material based on the relationship between the conductivity and the phase boundary length of the precipitate phase previously determined experimentally And evaluating the material strength of the metal material. 4. The method for evaluating the strength of a metal material according to claim 3, wherein the surface shape of the test object is measured in advance or simultaneously, and the correction based on the shape is performed. Strength evaluation method. 5. A first eddy current generated to a deeper position at a first frequency in a precipitation-strengthened metallic material in which a metallic or non-metallic precipitated phase is precipitated in a metallic matrix and strengthened. And measuring a second eddy current amount generated only at a shallow position in the material at a second frequency higher than the first frequency, and measuring the first eddy current amount and the second eddy current amount. The third eddy current amount at only a deep position is obtained from the eddy current amount of the eddy current, and the measured depth of the third eddy current amount is quantitatively obtained from the result of previously calculating the penetration depth of the magnetic field lines at each frequency by electromagnetic analysis. , Converted into conductivity, further obtained from the relationship between the experimentally determined conductivity and the phase boundary length of the precipitated phase, to determine the phase boundary length of the precipitated phase at the measured depth of the subject, the material of the material deep portion A method for evaluating the strength of a metal material, comprising evaluating the strength. 6. The method for evaluating a material strength of a metal material according to claim 5, wherein the first frequency and the second frequency are changed a plurality of times to obtain a third eddy current amount, and at each measurement depth. A material strength evaluation method for a metal material, comprising: evaluating a depth direction distribution of a material strength of a subject based on a result of evaluating the material strength. 7. In a structural member in which a coating layer is applied to the surface of a metal material, the amount of eddy current of the subject is measured a plurality of times by changing the frequency flowing through the exciting coil in a stepwise manner. From the result of calculating the penetration depth of the magnetic field lines at each frequency, the amount of eddy current generated only at a certain depth is calculated, the conductivity is converted into the depth direction distribution, and the coating layer and metal material are calculated from the change curve. A method for evaluating the thickness of a diffusion layer of a metal material, comprising: evaluating a thickness of a diffusion layer existing between the metal layers. 8. An apparatus for evaluating the strength of a precipitation-strengthened metallic material as a test object, comprising: a coil having a known impedance; An impedance measuring unit for measuring an amount of eddy current induced in the subject by flowing an electric current and obtaining an impedance of the coil in an excited state from the measured amount of eddy current; A database having phase boundary length data of a phase, and an eddy current amount is evaluated from impedance measurement results obtained by the impedance measuring unit, and a phase boundary length of a precipitated phase is calculated with reference to the database to obtain a material strength. And a calculating device for evaluating the strength of the metal material. 9. The apparatus for evaluating the strength of a metal material according to claim 8, further comprising a shape measuring unit for measuring the shape of the object in advance or simultaneously, and a means for correcting the shape in the arithmetic unit. A material strength evaluation device for a metal material, characterized in that: 10. An eddy current induced in the subject by measuring an impedance of the coil having a known impedance and bringing the coil and the subject close to or in contact with the subject at a predetermined distance to flow an alternating current through the coil. An impedance measuring unit for obtaining the impedance of the coil in the excited state from the eddy current amount obtained, a database unit for the analysis results of the penetration depth of the magnetic field lines at each frequency and a diffusion layer thickness of the subject, and impedance measurement by the impedance measuring unit. Evaluate the eddy current amount from the results, and determine the measurement depth of the eddy current amount by referring to the database, calculate the depth direction distribution of the eddy current amount from data measured a plurality of times by changing the frequency, A metal material comprising: a calculation unit for evaluating the thickness of a diffusion layer existing between the coating layer of the subject and the metal material from the change curve Diffusion layer thickness evaluation device.