JP2003074376A - Temperature estimation method for thermal barrier coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To nondestructively inspect an operating temperature of such a high temperature part with a thermal barrier coating (TBC) applied to a surface as a gas turbine component part. SOLUTION: A correlation is computed between a secular change in thermal conductivity of a TBC applied to a surface of a high temperature part, an operating time t (exposure time) and an operating temperature T (exposure temperature), and according to the correlation, the operating temperature T of the TBC is estimated from measured values of thermal conductivity before and after an operation and the operating time t. An expression of a Larson- Miller parameter (LMP) type is used to represent a unique correlation between the thermal conductivity, the operating time t and the operating temperature T.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature estimation method for a thermal barrier coating (hereinafter referred to as "TBC"). More specifically, the present invention relates to a technique for estimating the temperature of a component, such as a gas turbine high temperature component, for which the surface of the component is subjected to TBC and it is difficult to measure the temperature during operation.

[0002]

2. Description of the Related Art Operated at a high temperature like a gas turbine,
Moreover, it is generally difficult to actually measure the component temperature during operation in a power generator having a rotating body. So conventionally,
During the test run, attempts have been made to measure the temperature with a thermocouple for stationary components and a telemeter or radiation thermometer for rotating bodies.

However, such a measuring method requires a great deal of labor because it involves modification of the casing and attachment of a thermometer, and has the drawback that it cannot be measured from the viewpoint of safety during commercial operation.

Therefore, instead of such an actual measurement method, a method of estimating the temperature of components during operation is adopted. For example, for a moving blade, the component temperature is estimated by utilizing the property that the γ ′ phase existing in the material structure of the component gradually increases in size in correlation with the operating time t and the operating temperature T of the component. . In this case, the components are exposed to a high temperature atmosphere, and the size of the γ'phase in the blade material and the exposure conditions (exposure time,
Correlation formula with exposure temperature) is obtained in a laboratory, and the operating temperature T of the relevant part is estimated by inputting the size of the γ'phase and the component operation time t obtained from the destructive inspection of the actual machine parts to this correlation formula. The method is being tried.

[0005]

However, according to such an estimation method, expensive parts must be destroyed, resulting in high parts cost and inspection cost.

Therefore, an object of the present invention is to provide a TBC (thermal barrier coating) temperature estimation method capable of nondestructively examining the operating temperature of a high temperature component such as a gas turbine component having TBC on its surface. And

[0007]

The inventors of the present invention have found that TBC, which is applied to the surface of high temperature parts for the purpose of heat resistance, has large and small pores inside in the initial working state, but is used at high temperature. As a result, we focused on the property that the sintering progresses, the internal pores decrease, and the thermal conductivity and porosity change over time. As a result of various experiments, the higher the exposure temperature is, the larger the reduction rate of the porosity is, the porosity tends to decrease with the increase of the exposure time, and as with the case of the thermal conductivity, 200%. It was found that the porosity changes rapidly by the time and then gradually changes.The decrease in non-welded parts due to sintering and the change in the crystal structure due to heating also deteriorate the heat shielding performance over time. It was also found to cause. Furthermore, when exposed to high temperatures, the aged material (deteriorated material) has a higher thermal conductivity than the initial material under any of the exposure conditions. It was found that the rate of increase in conductivity was large. It was also considered that the increase in thermal conductivity due to sintering occurred at 1000 ° C or higher. As a result of various studies, it has been found from these properties that a change in the thermal conductivity (or a change in the porosity) with respect to the initial state and a correlation between the operating time t and the operating temperature T can be obtained.

The present invention is based on such knowledge, and the temperature estimation method of the thermal barrier coating (TBC) according to claim 1 is the thermal conductivity of the thermal barrier coating applied to the surface of a high temperature component such as a gas turbine component. Of the thermal barrier coating from the measured values of the thermal conductivity before and after the operation and the operating time t based on this correlation. It is an estimate.

In this case, the operating temperature T can be estimated based on the correlation between the thermal conductivity and the operating time t and the operating temperature T from the thermal conductivity and the operating time t obtained from the measurement of the actual machine parts. Therefore, by combining the present invention with a known or novel nondestructive TBC thermal conductivity measurement method (for example, photothermal infrared detection method), the operating temperature of a gas turbine high temperature component, which has been difficult to measure up to now, can be obtained. It enables non-destructive inspection and enables low-cost maintenance of parts.

Further, the correlation is a linear expression λ / λ _{as sprayed} = a × LMP + b (where λ is the heat conduction after the operation), which represents the relationship between the change in the thermal conductivity and the LMP, as in the second aspect of the invention. Rate, λ _{as sprayed}
Is the thermal conductivity before operation, a and b are constants determined by the sintering condition of the TBC (thermal barrier coating) material, and LMP is the Larson Miller parameter LMP = (T + 273.15) (log
₁₀ t + C), T is operating temperature, t is operating time, and C is constant). In this case, the correlation between the thermal conductivity and the operating time t and the operating temperature T is uniquely expressed, and the thermal conductivity obtained from the measurement of the actual machine parts is input to this correlation formula, and the operating time t is also input. By doing so, the remaining operating temperature T can be calculated and estimated.

According to the third aspect of the present invention, the correlation between the secular change in the porosity of the thermal barrier coating applied to the surface of the high temperature component such as the gas turbine component and the operating time t and the operating temperature T is obtained. Based on the correlation, the operating temperature T of the thermal barrier coating is estimated from the measured porosity values before and after the operation and the operating time t.

In this case, the operating temperature T can be estimated from the porosity and the operating time t obtained from the measurement of the actual machine parts based on the correlation between the porosity and the operating time t and the operating temperature T.

The correlation equation is the linear expression P / P _{as sprayed} = c × LMP + d (where P is the porosity after the operation), which represents the relationship between the change in the porosity and the LMP, as in the invention of claim 4. , P _{as sprayed} is the porosity before operation, c and d are constants determined by the sintering condition of the TBC (thermal barrier coating) material, and LMP is the Larson Miller parameter LMP = (T + 273.15) (log ₁₀ t
+ C), T is an operating temperature, t is an operating time, and C is a constant). In this case, the correlation between the porosity and the operating time t and the operating temperature T is uniquely expressed, and the porosity obtained from the measurement of the actual machine parts is input to this correlation formula, and the operating time t is also input. Can calculate and estimate the remaining operating temperature T.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below based on an example of an embodiment shown in the drawings.

1 to 4 are diagrams for explaining the temperature estimating method of the TBC according to the present invention. This temperature estimation method is based on the TB applied to the surface of high temperature parts such as gas turbine components.
The correlation between the secular change in the thermal conductivity (or porosity) at C and the operating time t and the operating temperature T is obtained, and the thermal conductivity (or porosity) before and after the operation is calculated based on this correlation.
The operating temperature T of the TBC is calculated and estimated from the measured value and the operating time t.

In this case, the correlation equation can be expressed as Equation 1 or Equation 2 as a linear equation showing the relationship between the change in thermal conductivity (or porosity) and the LMP (Larson Miller parameter).

[ _Formula 1] λ / λ _{as sprayed} = a × LMP + b

_Where P / P _{as sprayed} = c × LMP + d, where λ / λ _{as sprayed} is the change in thermal conductivity, P / P _{as sprayed} is the change in porosity, a, b, c,
d is a constant determined by the sintering condition of the TBC material, LMP = (T + 273.15) (log ₁₀ t + C) LMP: Larson Miller parameter C: constant (14 when the thermal conductivity changes, when the porosity changes) 32) The subscript as sprayed indicates that it is an initial material (or a state before operation). Further, in the present embodiment, the change in thermal conductivity (or change in porosity) is expressed as the ratio of the thermal conductivity (or change in porosity) after operation and before operation.

According to these linear expressions, the correlation between the thermal conductivity (or porosity) and the operating time t and the operating temperature T is uniquely expressed on a straight line graph, and the thermal conductivity (or porosity) is obtained.
The operating temperature T can be calculated and estimated from the operating time t and the operating time t.

Here, the correlation equation using LMP is obtained by using samples as follows, for example. First, a TBC for measuring thermal conductivity and porosity in the same manner as TBC applied to an actual machine (for example, a gas turbine rotor blade).
Make a sample. Then, the thermal conductivity and the porosity of the TBC sample before use were measured and the exposed material exposed under several conditions in an electric furnace using the exposure conditions (exposure time and exposure temperature) as parameters, respectively. A correlation equation between the change in the thermal conductivity and the porosity of the exposed material with respect to the initial material and the exposure time t and the exposure temperature T is obtained.

The term "exposure" as used herein means exposing a TBC sample whose surface is TBC to a high temperature atmosphere in a furnace or the like. The exposure conditions (exposure time, exposure temperature) are set according to the operating conditions of.

Since it is considered that the change in the thermal conductivity of TBC is caused by the change in the porosity due to the progress of sintering, it is assumed that the behavior in TBC follows the Arrhenius type equation, and the exposure to the initial material is assumed. The rate of change of the thermal conductivity of the material is expressed using the following mathematical formula 3.

[Equation 3] However, A and Q are a frequency factor and an apparent activation energy, respectively, and both are constants specific to the reaction conditions.
Further, T is the exposure temperature [° C].

Next, by modifying Equation 3,

[Equation 4]

Here, considering that the rate of change of the thermal conductivity of the exposed material with respect to the initial material is proportional to 1 / t, Equation 4
By transforming, the following formula 5 is obtained.

## EQU5 ## Q / R = (T + 273.15) (log ₁₀ t + C) where C is a constant.

The right side of the equation (5) is in agreement with the Larson-Miller parameter which is generally used for arranging the relationship between creep rupture strength, exposure temperature and rupture time for metallic materials. Therefore, by using this Larson-Miller parameter to represent the thermal conductivity ratio at a certain temperature (for example, 950 ° C.), the correlation between the temporal change of the thermal conductivity and the operating time t and the operating temperature T is expressed by a linear expression. be able to. In this case, the operating temperature T in the TBC can be uniquely estimated by inputting (substituting) the measured value of the thermal conductivity and the operating time t to the correlation expression thus obtained. . As for the porosity, the change in porosity, the operating time t, and the operating temperature T are similar to the thermal conductivity.
The correlation with and is expressed by a linear expression, and the measured porosity and the operating time t
By inputting (substituting) and calculating, the operating temperature T in the TBC can be uniquely estimated.

According to the temperature estimation method of this embodiment, the local operating temperature T of the target component can be obtained by applying it to any part of the high temperature component such as the gas turbine component, and further, It is also possible to obtain the temperature distribution of the parts by obtaining the operating temperature T at a plurality of points.

In this embodiment, the correlation is calculated under the assumption that the behavior in the TBC follows the Arrhenius type equation, but this is only a preferable example. Although not mentioned in detail here, if other equations that can well organize the relationship between the sintering rate, the exposure temperature T, and the exposure time t are obtained, the correlation equation can be obtained using these equations.

[0026]

EXAMPLE An example in which the above-mentioned temperature estimation method is applied to the measurement of the thermal conductivity before and after the operation of the TBC actually applied to the gas turbine combustor will be shown below with specific numerical values. Here, 8 wt% yttria partially stabilized zirconia (8 wt%
The TBC prepared by atmospheric pressure plasma spraying from the thermal sprayed powder of (YSZ) was exposed to the assumed temperature of the actual machine, the correlation equation was obtained, and the operating temperature T of the TBC used for 12000 hours in the actual machine combustor was estimated by calculation. First, using the Larson-Miller parameters expressed in the above-mentioned mathematical expression 5, correlation equations (mathematical expressions 6 and 7) at an exposure temperature of 950 ° C. were obtained.

(6) λ / λ _{as sprayed} = 1.25 × 10 ^-4 LMP-1.40

## _EQU7 ## P / P _{as sprayed} = -1.89 × 10 ^-5 LMP + 1.80, where λ: thermal conductivity (value at 950 ° C.) P: porosity T: exposure temperature (or operating temperature) t: exposure time ( Or operating time) C: Constant (14 in case of change in thermal conductivity, 32 in case of change in porosity) LMP: Larson-Miller parameter In addition, exposure time and exposure at the stage of obtaining the correlation equations (6, 7) The temperature becomes the algebra t and T, and the operation time and the operation temperature in the actual machine become t and T at the stage of applying the obtained correlation equation to the actual machine.

As a result of _{obtaining the} mathematical formulas as described above, as shown in FIG. 1 for thermal conductivity and FIG. 2 for porosity, LMP and change in thermal conductivity λ / λ _{as sprayed} (or LMP and porosity). The relationship of change P / P _{as sprayed} ) could be expressed as a linear function.

Further, when the correlation between the thermal conductivity and the porosity obtained in the initial material and the exposed material is obtained by regression analysis or the like, and the correlation equation is obtained, the equation 8 is obtained, and as a linear function as shown in FIG. I was able to represent it.

[Equation 8] λ = -0.383P + 4.42

Next, using these three equations (Equation 6 to Equation 8), the operating temperature of the TBC of the gas turbine (temperature of the TBC portion during operation) according to the flow shown in FIG.
T was estimated. In this case, if a known or new non-destructive thermal conductivity measurement method is used, the thermal conductivity λ of the component subjected to the actual TBC before being operated in the gas turbine (initial material)
It is possible to measure the thermal conductivity λ after _{as sprayed} and after operation (aged material) as shown in Step 1 and Step 2. However, in reality, the thermal conductivity was measured using a TBC test piece simulating TBC. It was measured. Although only the thermal conductivity is measured here, the porosity (P _{as sprayed} ) of the TBC of the initial material is also measured when the operating temperature T is obtained by utilizing the change in the porosity of TBC (step 3).

After completing these measurements, the first method is
And the thermal conductivity of the initial material λ_{as sprayed} And thermal conductivity of aged wood
Substituting λ into Equation 6 (step 4), and further operating time t
Was substituted to estimate the operating temperature T (step 5). Na
When using the change in porosity, use the second method.
Substituting the thermal conductivity λ of the aged material into Equation 8
Calculate the porosity P (step 6, step 7)
Porosity P of material, Porosity P of initial material_{as sprayed}, While driving
Substituting the time t into Equation 7 (steps 8 and 9)
The temperature T is estimated. Also, the porosity of the initial material
P_{as sprayed}If is not measurable, thermal conductivity before and after operation
Substituting the thermal conductivity λ of the part that has no change into Equation 7,
This can be done by assuming that the porosity P is the porosity P of the initial material.
Noh.

Here, by plotting how the thermal conductivity λ changes depending on the temperature, the initial material, the combustor inlet portion (low temperature portion), and the combustor intermediate portion (high temperature portion) are almost linear. I found that they line up. However, this result is not a non-destructive measurement, but a measurement result of a test piece obtained by destruction. Table 1 shows the calculation results by the first method.
Table 2 shows the calculation results obtained by the second method. Since the porosity P before operation is unknown, it was determined by the above-mentioned method (assumed method).

[Table 1]

[Table 2]

As a result, as the estimated value of the middle part of the combustor,
Almost equivalent values were obtained by the first method and the second method.
As for the applicable temperature range of the formulas 6 to 8, sintering starts 1000
Considering that the temperature is higher than or equal to ℃, it has been confirmed that it is possible to accurately estimate the actual operating temperature T of the TBC by the method of the present application, especially in a usage environment of higher than or equal to 1000 ℃.

The above-described embodiment is an example of the preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention. For example, in the present embodiment, the thermal conductivity measured by the photothermal infrared detection method or the like is used, but in some cases, the thermal diffusivity, the low-pressure specific heat, and the thermal expansion coefficient are measured by a known measuring device, and the You may use the thermal conductivity calculated | required by calculation. When the thermal conductivity of the initial material is known, the operating temperature T can be estimated by using this known value. Further, in the above description, the gas turbine is described as a specific application example, but the present invention is also applicable to high temperature components other than the gas turbine component.

[0034]

[Comparative Example] 6 wt% YSZ, 20 wt% YSZ, 8 wt
Table 3 for three types of TBC of% YSZ (hollow powder)
The relationship between the thermal conductivity ratio of the deteriorated material to the initial material of each TBC and the exposure condition was obtained by using the exposure condition and the measured value of the thermal conductivity shown in (4) and the same value of C as used in Equation 6. . The result is shown in FIG. From this figure, 8 wt% YS
It was found that Z and 8 wt% YSZ (hollow powder) showed almost the same tendency, and that the heat shield performance after exposure was the least.

[Table 3] Thus, by using the Larson-Miller parameter type formula, it is possible to compare changes in the heat shield performance of various TBC candidate materials, and this method can be used as a judgment criterion when selecting a new TBC candidate material. It is considered to be a thing.

[0035]

As is apparent from the above description, according to the method of estimating the temperature of the thermal barrier coating (TBC) according to the first aspect, the change of the thermal conductivity, the operating time t and the operating temperature T.
Based on the correlation with, the operating temperature T of the high temperature component can be accurately estimated in a non-destructive manner. According to this, reliable temperature information can be obtained, so maintenance of high-temperature parts such as gas turbine components can be appropriately performed at low cost to maintain soundness, and operational reliability of gas turbines can be maintained. It is possible to improve.

Further, the operating temperature of the gas turbine high temperature component, which has been difficult to measure up to now, can be inspected nondestructively, and the maintenance management of the component can be performed at low cost.

According to the temperature estimating method for TBC of the second aspect, the operating temperature T can be estimated by using a specific correlation equation and substituting the thermal conductivity and the operating time t into this equation.

Further, according to the temperature estimating method of the TBC of the third aspect, the operating temperature T of the high temperature component can be accurately estimated nondestructively based on the correlation between the change in the porosity and the operating time t and the operating temperature T. be able to. According to this, reliable temperature information can be obtained, so maintenance of high-temperature parts such as gas turbine components can be appropriately performed at low cost to maintain soundness, and operational reliability of gas turbines can be maintained. It is possible to improve.

Further, it becomes possible to nondestructively check the operating temperature of the gas turbine high temperature component which has been difficult to measure up to now, and the maintenance management of the component can be performed at low cost.

According to the temperature estimating method of the TBC described in claim 4, the operating temperature T can be estimated by using a specific correlation equation and substituting the porosity and the operating time t into this equation.

[Brief description of drawings]

FIG. 1 is a graph showing an example of the correlation between changes in thermal conductivity and exposure conditions.

FIG. 2 is a graph showing an example of correlation between changes in porosity and exposure conditions.

FIG. 3 is a graph showing an example of correlation between thermal conductivity λ and porosity P.

FIG. 4 is a flowchart showing a flow of operating temperature estimation of TBC.

FIG. 5 is a graph showing a result of measuring the thermal conductivity λ of TBC of the gas turbine combustor.

FIG. 6 is a graph showing a comparison of heat shield performance deterioration states of TBCs.

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Claims (4)

[Claims] 1. A correlation between a secular change in thermal conductivity of a thermal barrier coating applied to the surface of a high temperature component such as a gas turbine component and an operating time t and an operating temperature T is obtained, and operation is performed based on this correlation. A method for estimating the temperature of a thermal barrier coating, comprising estimating an operating temperature T of the thermal barrier coating from the measured values of the thermal conductivity before and after the operation and the operating time t. 2. The correlation is a change in the thermal conductivity and the LM.
A linear expression λ / λ _{as sprayed} = a × LMP + b (where λ is the thermal conductivity after operation, λ _{as sprayed)}
Is the thermal conductivity before operation, a and b are constants determined by the sintering condition of the thermal barrier coating material, LMP is the Larson Miller parameter, LMP = (T + 273.15) (log ₁₀ t + C),
The method of claim 1, wherein T is an operating temperature, t is an operating time, and C is a constant. 3. The correlation between the secular change in the porosity of the thermal barrier coating applied to the surface of a high temperature component such as a gas turbine component and the operating time t and the operating temperature T is calculated,
A temperature estimation method for a thermal barrier coating, wherein the operating temperature T of the thermal barrier coating is estimated from the measured porosity values before and after the operation and the operating time t based on this correlation. 4. The correlation is the change in porosity and LMP.
P / P _{as sprayed} = c × LMP + d (where P is the porosity after the operation, P _{as sprayed} is the porosity before the operation, and c and d are determined by the sintering condition of the thermal barrier coating material) 4. The intercept according to claim 3, wherein LMP is a Larson Miller parameter, LMP = (T + 273.15) (log ₁₀ t + C), T is operating temperature, t is operating time, and C is constant. Thermal coating temperature estimation method.