JP2003065978A - Method for assessing remaining life of heat resisting material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for surely estimating a life consumption rate and a remaining life at high temperatures for a heat resisting material. SOLUTION: A positron annihilation life of the heat resisting material undergoing an aged damage at high temperatures is measured, and a relation curve between a positron annihilation mean lifetime and the life consumption rate of the material is formed. It is detected whether the damage is in a transition creep region or reaches an acceleration creep region. When the damage is in the acceleration creep region, a life value of the material is estimated by extrapolating the curve up to a positron annihilation life value of a full annealed pure iron (approximately 110 psec). A degree of the damage, the life consumption rate or the remaining life is detected in this manner by the remaining life assessment method for the heat resisting material (for high temperature structure devices).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for diagnosing the remaining life of heat-resistant materials, and more particularly to a method for diagnosing the remaining life of heat-resistant materials used in high temperature structural equipment.

[0002]

2. Description of the Related Art Boilers and turbines for power generation, nuclear power generation equipment, chemical industrial equipment and other equipment are used for a long time under high temperature and high pressure. Therefore, the heat-resistant material used in these devices is required to have excellent strength at high temperature, corrosion resistance, oxidation resistance, toughness at room temperature, and the like. For these applications, conventionally, austenitic stainless steel (for example, JIS-SUS321H steel, SUS347H steel), low alloy steel (for example, JIS-STBA24 steel (2.25% Cr-1% Mo steel)), 9-12% Cr high Cr ferritic steel (for example, JIS-
STBA26 steel (9% Cr-1% Mo steel), recently STBA-28 steel (improved
9% Cr-1% Mo steel)) has been used.

In recent years, in thermal power plants, it is necessary to improve the thermal efficiency in order to reduce the emission of CO ₂ etc. from the viewpoint of preventing global warming, and the steam conditions of the boiler are set to high temperature and high pressure (for example, exceeding 600 ° C.). , 300 bar) new plants are being built one after another. On the other hand, whether or not existing plants, which were constructed in the high growth period, will reach their planned life one by one and will be replaced by new plants with high thermal efficiency, or if their life will be extended by partial repair, etc. is related to Japan's energy policy. Is becoming a big social problem.

In the new plant of high temperature and high pressure, newly developed materials having higher strength and higher corrosion resistance than conventional ones are used. However, since they are new, a long time database in an actual plant like conventional steel is established. No, and a follow-up survey of changes over time is needed. Further, in the existing plant, it is necessary to accurately evaluate the life consumption rate (ratio to the planned life) of the heat-resistant material used and accurately diagnose the remaining life.

Many studies have been made in the past as a method of performing aged deterioration diagnosis and residual life evaluation of materials incorporated in a plant as non-destructively as possible. For example,
Method to measure the hardness change of aged damage material (hardness measurement method),
Similarly, a replica is collected and the number and amount (area ratio, etc.) of creep voids are observed by SEM (scanning electron microscope) (void method), or a replica is collected and TEM-EDX (transmission electron microscope) is also used. A method (carbide method) for quantifying the type, size and amount of carbides with a microscope-energy dispersive X-ray analyzer) has been proposed.

[0006] These methods have been used to some extent in conventional low alloy steels, but any of these methods are prone to measurement accuracy problems and experimental variations, and can be highly accurate life diagnosis methods. Not not.

Further, in a new heat resistant material used in a new plant, for example, in a high Cr ferritic steel (STBA28 steel) having a tempered martensitic structure, carbides are stable and creep voids are hard to form. For the reason, it has been clarified that the conventional low alloy steel (STBA24 steel) cannot be applied with the void method and the carbide method, which have been effective to some extent.

In such a case, the member is destructively taken from a part of the high-temperature structural equipment, a tensile test or a creep test is performed, and the property is evaluated before use without damage. The most reliable method is to evaluate how much deterioration has occurred and to estimate how much creep damage has occurred.

However, deterioration of mechanical properties obtained by this method is often indistinguishable from deterioration due to softening due to simple heating, and corresponds to the original creep damage in which damage due to heat softening and creep deformation are superimposed. It is impossible to accurately estimate the lifespan consumption rate and the remaining lifespan.

In recent years, a new method has been proposed for estimating creep strain by applying the positron annihilation method to a heat-resistant material having a tempered martensite structure (Japanese Patent Laid-Open No. 2000-242242).
2000-171418, reference).

In the positron annihilation method, when a positron (elementary particle having the same mass as an electron and having a positive charge) is incident on a substance and pair annihilation occurs with the electron, the annihilation process is a lattice defect (vacancy) in the substance. It is a method of finding lattice defects in a material by utilizing the fact that it changes according to the state of holes and dislocations. The positron annihilation method is a method of measuring the time from the incidence to the annihilation (annihilation lifetime) (called lifetime measurement method), and the change in kinetic energy of gamma rays (511 keV, two rays emitted in the 180 degree direction) emitted at the time of annihilation. There is a method of measuring (Doppler spread method, angle correlation method) and the like. However, due to the difficulty of measurement and the difficulty of analysis, only laboratory-scale research has been conducted on highly crystalline semiconductor materials, pure metals, and simple alloy systems.

However, in the invention disclosed in Japanese Patent Laid-Open No. 2000-171418, positron annihilation measurement is performed on aged heat-resistant material of the new heat-resistant material STBA-28 steel, and the S parameter (described later) is measured by the Doppler spread method. It is proposed that, when calculated, the creep strain amount of the damaged material can be estimated from the correspondence relationship between the S parameter and the known creep strain amount of the same composition material that is obtained in advance.

Here, the S parameter is an index of the spread of the energy spectrum of gamma rays emitted at the time of positron annihilation, and is defined as the ratio of the count number in the central part of the peak to the count number of the entire energy peak. It is generally known that, in the absence of defects, this S parameter becomes small, but as point defects such as vacancies are introduced, the S parameter becomes larger and the peak becomes sharper.

Further, in Japanese Patent Laid-Open No. 2000-266699, the Doppler spread method is used in the same manner as described above, and gamma rays at the time of positron annihilation are simultaneously measured by two detectors, thereby mainly measuring deterioration of reactor materials. As such, a method and apparatus for evaluating the state of point defects and the aggregate of elements (precipitate having a composition different from that of the matrix) with higher accuracy have been proposed.

[0015]

In the Doppler broadening method of the positron annihilation method described above, it is known that the S parameter is sharpened when the number of voids, which is an aggregate of point defects, is large. However, point defects interact with crystal grain boundaries, dislocations, and precipitates in practical materials, and disappear or are newly generated. Therefore, it is difficult to conclude that the measured S-parameter corresponds to the true creep damage when the changes in the microstructure and defect structure during the damage deterioration of the practical material are not clear.

By the Doppler spread method of simultaneous measurement,
It is possible to measure with higher accuracy, but it is still difficult to capture changes in the structure and defect structure during creep damage process. Therefore, a method for accurately diagnosing the remaining life by measuring the life consumption rate due to creep damage of the heat resistant material has not been obtained.

The object of the present invention is to improve the high Cr content from conventional low alloy steels.
The object of the present invention is to provide a method for accurately estimating the life consumption rate and the remaining life of a ferritic steel, and also for all heat-resistant materials including new heat-resistant materials, by measuring the damage deterioration process mainly due to creep deformation at high temperature.

[0018]

DISCLOSURE OF THE INVENTION The inventors have studied in detail the relationship between the high temperature long-time creep deformation characteristics, the chemical composition of the material, and the metal structure (microstructure) of various heat resistant materials. As a result, the following new findings were obtained.

(1) The shape of the creep deformation curve is similar regardless of the microstructure, there is a transition creep region where the creep speed gradually decreases, and then the minimum creep speed is shown. Later, on the contrary, there is an accelerating creep region where the creep speed increases with time, which eventually leads to rupture, and (2) the amount of strain that transitions from the transition creep region to the accelerating creep region is about several% to 10%. Even so,
Some materials have a gradual increase in creep speed in the accelerated creep region, or some materials undergo rapid creep deformation after entering the accelerated creep region, even though this strain amount is as small as 1% or less. Therefore, it may be difficult to estimate the degree of damage to the material, in other words, the life consumption rate, only from the magnitude of creep strain.

In view of such a situation, the inventors have conducted various studies, and as a result, found that the change in positron annihilation lifetime is most suitable for expressing the creep deformation process of such a complicated heat-resistant material. The invention was completed.

The gist of the present invention resides in the following method for diagnosing the remaining life of heat resistant materials.

The positron annihilation lifetime of a heat-resistant material which has been aged at high temperature is measured, and a relationship curve (FIG. 6 and FIG. 10) between the positron annihilation average lifetime and the life consumption rate of the material is prepared to show that the heat-resistant material is A method for diagnosing the remaining life of a heat-resistant material for determining whether it is in a transition creep region or in an accelerated creep region.

The positron annihilation lifetime of a heat-resistant material that has been aged at high temperature is measured, and a master curve (FIG. 6 and FIG. 10) of a relationship curve between the positron annihilation average lifetime and the lifetime consumption rate of the material obtained in advance is obtained. A method for diagnosing the remaining life of a heat-resistant material, by which the life consumption rate or the remaining life of the heat-resistant material is determined by comparison.

The positron annihilation lifetime of a heat-resistant material that has been aged at high temperature is measured, and a relationship curve between the positron annihilation average lifetime and the life consumption rate of the material is created to determine whether the heat-resistant material is in the transition creep region or at an accelerated rate. It is determined whether the creep region has been reached, and if it is in the accelerated creep region, extrapolation of the curve up to the positron annihilation lifetime value (105 to 110 psec) of completely annealed pure iron indicates the damage of the heat resistant material. degree,
A method for diagnosing the remaining life of a heat-resistant material for determining the life consumption rate or the remaining life.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors examined in detail the relationship between high temperature long-time creep deformation characteristics and positron annihilation life for various heat resistant materials. As a result, we have obtained a new finding that there is a certain relationship between the creep deformation characteristics and the positron annihilation lifetime, which change intricately depending on the chemical composition of materials and the microstructure.

That is, in the new heat-resistant material, in order to obtain high strength, excessive dislocations are introduced as a martensite structure, or fine precipitates are deposited. However, as described above, the shape of the creep deformation curve is similar regardless of the structure, there is a transition creep region where the creep speed gradually decreases, and after that, after showing the minimum creep speed, On the contrary, there is an accelerating creep region where the creep speed increases with time, which eventually leads to fracture.

FIG. 1 is a schematic diagram showing a creep deformation curve.

Creep strain increases with time, leading to fracture. Inflection point of curve (position of creep strain ε _min )
There is a transition creep region where the gradient of the curve gradually becomes gentle and a accelerating creep region where the gradient becomes large again.

FIG. 2 is a schematic diagram showing the relationship between creep speed and time. This figure is a curve in which the creep speed (rate of change of creep strain with time) is obtained from the creep deformation curve and plotted against time. From FIG. 2, the creep speed becomes the minimum at the inflection point of the creep deformation curve, and the creep speed gradually decreases in the transition creep region and the creep speed gradually increases in the accelerated creep region.

The relationship curve (FIG. 2) between the creep rate and the time of the heat resistant material basically shows the same form even if the microstructure and the strength are different. However, there are cases in which the slope of the curve changes, the transition from the transition creep region to the acceleration creep region is rapid or gentle, and the acceleration appears in two stages. In the material of martensite structure,
Excessive dislocations in martensite disappear in the transition creep region. In austenitic alloys and annealed ferritic steels, dislocations are introduced by work hardening, but in the transition creep region, the mobility of dislocations decreases and the creep rate decreases. Further, in any case, the fine precipitate acts as a dislocation movement barrier and has an effect of increasing creep resistance.
This strengthening action gradually weakens with the passage of time, depletion of solid solution strengthening elements, decrease in effect due to coarsening of precipitate precipitates, and local deformation progress in weaker areas than other areas such as near grain boundaries. By moving to the accelerated creep area,
The creep speed increases at an accelerating rate.

FIG. 3 is a diagram showing the relationship between creep speed and creep strain. This figure is a plot of creep rate against creep strain, and it became clear that the material exhibits a very characteristic curve shape.
In other words, with some materials, the amount of strain that transitions from the transition creep region to the accelerated creep region is several percent to 10%, and the increase in creep speed is slow even in the accelerated creep region, while another material has Despite the extremely small strain amount of 1% or less, creep deformation rapidly progresses after shifting to the accelerated creep region. Therefore, estimating the degree of damage to the material, in other words, the life consumption rate, from only the magnitude of creep strain is
Have difficulty.

In view of such a situation, the inventors have conducted various studies, and as a result, have found that the change in the positron annihilation lifetime is most suitable for expressing the creep deformation process of such a complicated heat-resistant material.

A creep deformation test was carried out until breakage of a heat-resistant material which undergoes complex creep deformation.

FIG. 4 is a diagram showing the relationship between the creep speed and the test time. In this figure, a creep test was conducted at a temperature of 650 ° C. and a stress of 118 MPa using the test steel A shown in Table 1, and the creep rate was plotted corresponding to the elapsed test time.

FIG. 5 is a diagram showing the relationship between creep speed and creep strain. This figure shows the temperature of 6
FIG. 3 is a plot of the creep rate and creep strain obtained by performing a creep test at 50 ° C. and a stress of 118 MPa.

FIG. 6 is a diagram showing the relationship between the positron annihilation average lifetime and the lifetime consumption rate of the material. This figure shows that for test steel A, an interrupted test material was created from the life consumption rate of 0% (before the test) to 100% (rupture) during the creep test, and the positron annihilation life was measured. This is a plot in which the annihilation average life and the life consumption rate of the material are associated with each other.

FIG. 7 is a diagram showing the relationship between the positron annihilation average lifetime and creep strain. This figure is a plot in which the positron annihilation average life and creep strain are associated with each other for the test steel A.

FIG. 8 is a diagram showing the relationship between the creep speed and the test time. This figure is a plot of the creep rate in the creep test using the test steel B shown in Table 1 at a temperature of 650 ° C. and a stress of 118 MPa in accordance with the elapsed test time.

FIG. 9 is a diagram showing the relationship between creep speed and creep strain. This figure shows that using test steel B at a temperature of 6
FIG. 3 is a plot of the creep rate and creep strain obtained by performing a creep test at 50 ° C. and a stress of 118 MPa.

FIG. 10 is a diagram showing the relationship between the positron annihilation average lifetime and the lifetime consumption rate of the material. This figure shows that for steel B under test, a suspended test material was created between the life consumption rate of 0% (before the test) and 100% (breakage) during the creep test, and the positron annihilation life was measured. This is a plot in which the annihilation average life and the life consumption rate of the material are associated with each other.

FIG. 11 is a diagram showing the relationship between the positron annihilation average lifetime and creep strain. This figure is a plot in which the positron annihilation average lifetime and creep strain are made to correspond to each other for sample steel B.

As a result, in martensitic steels, the positron annihilation average life decreases (as shown in FIG. 10) as the degree of creep damage increases, and conversely in materials that undergo work hardening (austenitic steels and ferritic steels). At the initial stage, the positron annihilation average lifetime becomes large as shown in FIG. In any case, when the transitional creep region transitions to the accelerated creep region, the positron annihilation average lifetime shows an inflection point or maximum point, then there is a stable period in which it gradually decreases, and then it rapidly decreases again. Finally, it approaches the positron annihilation average lifetime (105 to 110 psec) of fully annealed pure iron. The relationship curve between the obtained positron annihilation lifetime and the material lifetime consumption rate (Fig. 6)
And FIG. 10), the relationship curve between positron annihilation lifetime and creep strain (FIGS. 7 and 11) is the relationship curve between creep speed and test time (FIGS. 4 and 8), and the relationship curve between creep speed and creep strain. Corresponding very well with the changes in (FIGS. 5 and 9), it became clear that the positron annihilation lifetime is very suitable for expressing the creep deformation process.

From the above, it is also possible to conduct a positron annihilation test on the aged damage material of the heat-resistant material used in the actual plant, either onsite or destructively for detailed investigation. It is understood that the remaining life of the material can be predicted.

In this case, although data on creep strain may not be available, test materials are sampled onsite or destructively for detailed investigation, and the positron annihilation average life with respect to the elapsed time of use is calculated. , It is possible to easily determine whether the material is still in the transition creep region or has already reached the accelerated creep region by plotting it as a relationship curve between the positron annihilation average life and the life consumption rate of the material. . In addition, for those that have reached the accelerated creep region, extrapolation of the curve up to the positron annihilation lifetime value (105 to 110 psec) of pure iron without complete burning allows for extremely accurate material life consumption rate and residual life. Can be estimated.

Hereinafter, further details will be described with reference to examples.

[0046]

EXAMPLE Two types of heat-resistant steels having different chemical compositions shown in Table 1 were used as test materials.

[0047]

[Table 1]

The test steel A is a type of work-hardening steel and has a two-phase mixed structure of a tempered martensite structure and a δ ferrite structure before use. Test Steel B has a tempered martensite single phase structure. The sample steel is a tube material (outer diameter 70 mm, wall thickness 10 mm) manufactured on an industrial scale.
Normal normalizing (1050 ℃), tempering (780
(° C.) treatment, and then a creep test material was collected. For each steel, a creep deformation test was performed up to breaking to obtain a relationship curve between creep speed and time and a relationship curve between creep speed and creep strain (FIGS. 4, 5, 8 and 9). Furthermore, a creep interruption test material was prepared from the material with a life consumption rate of 0% (before the test) to 100% (breakage), and the positron annihilation life was measured. From the results of the creep test and the positron annihilation test, a relationship curve between the positron annihilation average life and the life consumption rate of the material and a relationship curve between the positron annihilation average life and the creep strain were created (FIGS. 6, 7, and 10).
And 11).

For the positron annihilation lifetime measurement, two plate materials each having a thickness of 0.5 mm, a width of 7 mm and a length of 10 mm were sampled from each test material, and one surface thereof was mirror-polished to obtain a test material. The radiation source is sealed
^{A 22} Na radiation source (50 microcuries, encapsulated with polyimide) was used, and a sandwich method was used in which the radiation source was sandwiched between two test materials. The number of positron measurements per measurement was about 2 million, and the time resolution of the measurement system was about 230 psec. The positron annihilation lifetime of the completely annealed pure iron sample was determined by this measurement system to be 110 ± 0.5 psec. The start signal for the lifetime measurement was the primary gamma ray (1.28 MeV) emitted from the radiation source, and the stop signal was the 511 KeV gamma ray emitted when the positrons disappeared in the test material.

The positron annihilation lifetime was calculated by the following method.

In a perfect crystal, the positron annihilation lifetime spectrum T (t) is expressed by the equation (1). T (t) = exp (−t / τ ₁ ) (1) where τ ₁ is the positron annihilation lifetime of a perfect crystal, and t is time.

When defects are introduced into the material, some of the positrons are trapped in the defects, so the positron annihilation lifetime spectrum has two components, a defect-free part and a defect part (or multi-component if there are many defect species). ). T (t) = (I ₀ / τ ₀ ) exp (-t / τ ₀ ) + (I _d / τ _d ) exp (-t / τ _d ) ・ ・ ・ (2) where τ ₀ is the mother phase (Bulk) positron annihilation lifetime, τ _d
Is the positron annihilation lifetime of the defect and is a value specific to the defect species. At that time, the relative intensity I _d of the defect is as follows using the trapping speed κ that is proportional to the concentration of the defect. I _d = κ / ((1 / τ ₁ ) + κ- (1 / τ _d )) (3) Further, τ ₀ is also κ, and τ ₀ = 1 / ((1 / τ ₁ ) + κ) (4), and the positron annihilation lifetime is shorter than in the case of perfect crystal.

Positron annihilation average lifetime τ of interest in the present invention
_M is represented below. τ _M = I ₀ τ ₀ + I _d τ _d (5) Positron annihilation by one-component analysis by removing the lifetime component of the polyimide shielding the positron from the positron lifetime spectrum obtained in the measurement. The average life was calculated.

Relationship curves between positron annihilation average life and material life consumption rate obtained for each steel (FIG. 6 and FIG.
10), looking at the relationship curves between positron annihilation average life and creep strain (Figs. 7 and 11), the relationship curves between creep speed and time (Figs. 4 and 8), and the relationship curves between creep velocity and creep strain The changes in (Figs. 5 and 9) are reproduced very well, and by measuring the positron annihilation average life, whether the damage of the aged material is in the transition creep region,
Alternatively, it can be easily determined whether the acceleration creep region has been reached.

FIG. 12 is a diagram showing a relationship curve between positron annihilation average life and material life consumption rate of two steels having different structures. As is clear from this figure, in the test steels A and B,
As mentioned above, the behaviors in the transition creep region tend to be quite opposite, but the behaviors in the accelerated creep region are very similar.

FIG. 13 is a diagram for explaining a method of predicting the life of a material by using the relationship curve between the positron annihilation average life and the material life consumption rate as a master curve. This figure shows a creep rupture test at 700 ° C and a stress of 50MPa using test steel A.
FIG. 7 is a diagram in which a positron annihilation test was performed on a test piece interrupted for time, a test piece interrupted for 300 hours, and a test piece fractured for 1982 hours, and the results are plotted as a master curve in FIG. 6.

As is clear from FIG. 13, when the positron annihilation average life of the test material is plotted against the material life consumption rate, it is shown on a curve substantially similar to the master curve. From this, the life consumption rate of the material can be estimated by performing several similar measurements on the aged material and comparing it with the master curve. It is also possible to estimate the remaining life of the material from the actual elapsed time.

FIG. 14 is a diagram for explaining a method of predicting the life of a material by performing a test simulating a material used over time for steel having a tempered martensite structure.

With respect to the sample steel C (Table 1) having a tempered martensite structure, the positron annihilation average life was measured up to the accelerated creep region in the creep interruption test material (675 ° C, 88 MPa) simulating the material used over time (Fig. Then 5 points).
The data obtained was subjected to curve regression to estimate the time to reach the positron annihilation lifetime value (110 psec) of the pure iron annealed material. Although the estimated life of the obtained material was 5780 hours, the actual breaking time was 5222 hours, and the difference was extremely small within 10%. Therefore, even if there is no master curve, the lifetime value can be estimated accurately by measuring the positron annihilation average lifetime up to the accelerated creep region multiple times. Further, it becomes possible to accurately diagnose the degree of material damage, the life consumption rate, or the remaining life.

[0060]

According to the residual life diagnosis method of the present invention, the positron annihilation life of a heat-resistant material that has been aged at high temperature is measured, and a relationship curve between the average positron annihilation life and the life consumption rate of the material is created. Thus, it is possible to diagnose whether the damage of the material is in the transition creep region or in the accelerated creep region. Further, by comparing the relationship curve between the positron annihilation average lifetime and the material lifetime consumption rate obtained in advance with the master curve, the degree of damage to the material, the lifetime consumption rate or the remaining lifetime can be diagnosed. Furthermore, when the material is in the accelerated creep region, the positron annihilation lifetime value of fully annealed pure iron (105-110
By extrapolating the curve up to psec), the life value of the material can be estimated to diagnose the degree of damage, life consumption rate or remaining life.

Using the method of the present invention, aging damage due to creep deformation of heat-resistant materials used in high-temperature structural equipment such as boilers and turbines for power generation, nuclear power generation equipment, and chemical industrial equipment is evaluated, and The remaining life can be predicted with high accuracy, and the timing of plant renewal or material replacement can be accurately diagnosed. This makes it possible to achieve both safety and economy.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a creep deformation curve.

FIG. 2 is a schematic diagram showing the relationship between creep speed and time.

FIG. 3 is a diagram showing a relationship between creep speed and creep strain.

FIG. 4 is a diagram showing the relationship between creep speed and test time.

FIG. 5 is a diagram showing a relationship between creep speed and creep strain.

FIG. 6 is a diagram showing a relationship between a positron annihilation average lifetime and a lifetime consumption rate of a material.

FIG. 7 is a diagram showing a relationship between positron annihilation average lifetime and creep strain.

FIG. 8 is a diagram showing the relationship between creep speed and test time.

FIG. 9 is a diagram showing the relationship between creep speed and creep strain.

FIG. 10 is a diagram showing a relationship between a positron annihilation average lifetime and a lifetime consumption rate of a material.

FIG. 11 is a diagram showing the relationship between positron annihilation average lifetime and creep strain.

FIG. 12 is a diagram showing a relationship curve between a positron annihilation average life and a material life consumption rate of two steels having different structures.

FIG. 13 is a diagram for explaining a method of predicting the life of a material by using a relationship curve between a positron annihilation average life and a material life consumption rate as a master curve.

FIG. 14 is a diagram for explaining a method of predicting the life of a material by performing a test simulating an aged material on steel having a tempered martensite structure.

Continued front page    F-term (reference) 2G001 AA03 BA01 CA02 FA01 KA20                       LA02                 2G050 AA01 BA10 BA12 EA01 EB10

Claims (3)

[Claims] 1. A positron annihilation lifetime of a heat-resistant material that has been aged at high temperature is measured, and a relationship curve between the positron annihilation average lifetime and the life consumption rate of the material is created to determine whether the heat-resistant material is in the transition creep region. , A method for diagnosing the remaining life of a heat-resistant material, characterized by determining whether it is in an accelerated creep region. 2. A positron annihilation lifetime of a heat-resistant material that has been aged at high temperature is measured and compared with a master curve of a relationship curve between the positron annihilation average lifetime and the material lifetime consumption rate which is obtained in advance. Degree of damage to the heat resistant material,
A method for diagnosing the remaining life of a heat-resistant material, characterized by determining the life consumption rate or the remaining life. 3. The positron annihilation lifetime of a heat-resistant material that has been aged at high temperature is measured, and a relationship curve between the positron annihilation average lifetime and the life consumption rate of the material is created to determine whether the heat-resistant material is in the transition creep region. , The acceleration creep region is judged, and if it is in the accelerated creep region, by extrapolating the curve up to the positron annihilation life value of completely annealed pure iron, the degree of damage of the heat resistant material and the life consumption rate Alternatively, a method for diagnosing the remaining life of a heat-resistant material is characterized by determining the remaining life.