JPH11350094A - Gas turbine moving blade - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the tensile strength of the areas of moving blades of a gas turbine of which temperature is low during operation by subjecting the blades made of Ni-based alloy to a multi-stage heat treatment at specified temperatures to increase creep rupture strength and subsequently subjecting them to aging treatment at a temperature range lower than in the heat treat ment. SOLUTION: This gas turbine blade consisting of the Ni base alloy whose 100,000 hour creep rupture strength at 825 deg.C is controlled to >=10 kgf/mm<2> by multistage heat treatment at >=800 deg.C is subjected to aging treatment within the temp. range of 700 to 800 deg.C successively to the multistage heat treatment at >=800 deg.C to improve the tensile strength of the part where using temp. is <=700 deg.C. In the gas turbine moving blade consisting of the Ni base alloy treated in this way, the strength of the part where the using temp. reaches >=800 deg.C by multastage heat treatment at >=800 deg.C is improved, and moreover, by applying aging treatment within the temp. range of 700 to 800 deg.C, the tensile strength of the part where the using temp. is <=700 deg.C is improved without impairing its creep strength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving blade for a high-temperature and high-efficiency gas turbine.

[0002]

2. Description of the Related Art A moving blade of a gas turbine operates at a temperature of 1000 ° C.
Even if it is exposed to a 400 ° C. high-temperature gas and performs advanced cooling, the temperature in the high-temperature portion becomes 800 ° C. or more. To withstand such an environment, the gas turbine is required to have a γ 'phase (Ni3Al)
Is used.

[0003]

Gas turbine blade materials have been developed with the aim of improving the characteristics of the first stage blade at the maximum temperature in order to improve the operating temperature. Since the Ni-based alloy has a creep strength lower than the tensile strength at 700 ° C. or higher, the existing developed material has been developed with an emphasis on the high-temperature creep strength. However, due to the increase in the size of the blades accompanying the increase in the capacity of gas turbines, the stress applied to the roots of the blades at low temperatures increases, and not only high-temperature creep strength but also high-temperature tensile strength are required to be high. ing.

[0004] The three-stage and four-stage blades of gas turbines are large in size and therefore have high centrifugal stress, but due to the low operating temperature, alloys developed for the first stage are generally diverted. Was. In recent years, the combustion temperature has been increasing in order to increase efficiency,
The operating temperature of the three-stage bucket is also high. Correspondingly, the first stage blade material with higher service temperature may be used,
Among the first-stage blade materials having a high service temperature with an emphasis on creep strength, there are those having a low-temperature tensile strength lower than that of the existing three-stage blade material.

[0005] The strength of a γ 'phase strengthened Ni-based alloy largely depends on the structure of the γ' phase. The morphology of the γ 'phase is highly dependent on the chemical composition of the alloy, so one of the methods is to adjust the chemical composition of the alloy.However, such attempts have been made for a long time, and the creep strength and tensile strength It is not easy to find a higher compromise between strengths.

[0006]

As described above, gas turbine blades are required to have high creep resistance and tensile properties.
However, the part where high creep resistance is required is different from the part where tensile properties are required. High creep resistance is required from the center to the upper end of the blade where the temperature is high. Further, the tensile properties are required from the wing root side to the center. Therefore, when it is desired to improve the tensile characteristics of the blade, the structure of only the lower part of the blade may be set as the structure for improving the tensile characteristics. Further, in order to maintain the creep resistance at the conventional level, the structure of the upper part of the wing needs to be the same as the conventional one.

Since the γ 'phase, which is the reinforcing phase, is stable at a lower temperature than the γ phase of the parent phase, lowering the final aging temperature increases the content of the γ' phase and improves the tensile strength. However, if the operating temperature is higher than the final aging temperature, the γ 'phase decreases during use and the structure becomes unstable, so the final aging temperature is generally set to be equal to or higher than the operating temperature. The final aging temperature of many alloys developed for the first stage rotor blades is 840 ° C
That is all.

When such alloys are further aged at about 700 ° C. to 800 ° C. after the usual final aging, the γ ′ phase increases as described above, and
The tensile strength up to about 00 ° C. is improved. In the part where the temperature rises to 800 ° C. or higher during use, the γ ′ phase increased by aging at 700 ° C. to 800 ° C. decreases again and returns to the structure after the conventional final aging, so that there is no effect. This effect is maintained during use in the low temperature portion on the wing root side where high tensile strength is required. In addition, the structure from the center to the tip of the blade, which becomes hot during use, returns to the structure after final aging during use as described above, so that the creep strength is also at the conventional level. The tensile properties can be improved without impairing the creep resistance of the steel.

[0009] If the aging temperature after the usual final aging is too low, the precipitation rate of the γ 'phase is too slow to be effective, and if it is too close to the usual final heat treatment temperature, the increase in the γ' phase is small. Not effective. Therefore, the aging temperature is 7
About 00-800 degreeC is desirable.

[0010] Some alloys having a low high-temperature creep strength have a low use temperature and a low final aging temperature. Therefore, even if the present invention is applied to a gas turbine blade using this alloy, significant results can be obtained. I can't. The present invention is effective for a gas turbine blade using an alloy having a final aging temperature of 825 ° C. or higher, particularly a Ni-base cast material having a creep rupture strength at 825 ° C. for 100,000 hours of 10 kgf / mm ² or more.

That is, for a gas turbine blade, 800
After performing a multi-stage heat treatment at a temperature of 800 ° C. or higher to improve the strength of a portion where the temperature during use is 800 ° C. or higher,
By adding the aging treatment in the temperature range of 00 ° C to 800 ° C, the tensile strength of the blade is improved without impairing the creep resistance.

[0012]

(Embodiment 1)

[0013]

[Table 1]

The alloys of the three compositions shown in Table 1 were melted,
A round bar having a diameter of 15 mm and a length of 150 mm was manufactured by a precision casting method. Heat treatment was performed on a part of each sample under the conditions shown in heat treatment A in Table 2, and this was used as a conventional blade simulation material. The creep rupture strength of the conventional simulated wing material at 825 ° C. for 100,000 hours is 16, 14.8 kgf / mm ² , respectively.
The remaining samples were subjected to the heat treatment B following the heat treatment A, and these samples were used as simulated materials of the present invention. Table 1
The creep strength inside is the creep rupture strength at 835 ° C for 100,000 hours extrapolated from the creep rupture data of the conventional simulated wing material.

For these simulation materials, the parallel part length 32
A precision tensile test piece having a diameter of 6 mm and a diameter of 6 mm was prepared, and a tensile test was performed at 650 ° C. and 850 ° C. to simulate a blade root portion having a low temperature during use and a blade upper portion having a high use temperature. The test started after holding at the test temperature for 15 minutes. FIG.
(A), (b), (c) are the results of the tensile test of each alloy.
Samples I and II having high creep strength and high final aging temperature have improved tensile strength at 650 ° C. and 0.2% proof stress, indicating that the present invention is effective. The tensile strength at 850 ° C. where creep strength is more important than tensile strength is about the same as that of the conventional simulated material. In Sample III, no improvement in strength due to the application of the present invention was observed at any temperature, because the creep strength, that is, the service temperature of creep was low, and the final aging temperature was low. The present invention is not effective for a blade using such an alloy. FIG.
(A) and (b) show the results of creep rupture tests at 900 ° C. of the conventional simulated materials of Samples I and II and the simulated material of the present invention in which the tensile strength in the low temperature region is improved by applying the present invention. In any of the simulated materials of the present invention, no deterioration in the high-temperature creep strength was observed with respect to the simulated materials of the related art, indicating that the present invention is effective.

[0016]

[Table 2]

FIG. 3 shows the results of hardness measurement of sample I when the heat treatment temperature of heat treatment B in Table 2 was changed. The heat treatment time was 8, 16, 24, and 48 hours, and the measurement was performed five times at each time, and the average value was regarded as the hardness. As described above, the resin is not cured at 800 ° C. or higher because the difference from the final aging temperature (843 ° C.) is small and the amount of the γ ′ phase precipitated is small. Below 700 ° C, the deposition rate is slow,
In about 8 hours, large hardening cannot be obtained, and strength cannot be improved under any conditions. The present invention is effective when the aging temperature is 70
This is the case where the temperature is set to about 0 to 800 ° C.

(Example 2) Using the alloy of the composition of Sample I (Rene 80 type), two gas turbine rotor blades 1 having the shapes shown in FIGS. 4A and 4B were produced by precision casting.
One of them was subjected to heat treatment A of Example 1 and the other two were subjected to heat treatment A and heat treatment B to obtain a conventional blade (Rene80 type) and a blade of the present invention (Rene80 type), respectively. Tensile test pieces were cut out from the lower part 2 of these wings and subjected to a tensile test at 650 ° C. in the same manner as in Example 1.

FIG. 5 shows the test results. The blade of the present invention is superior to the conventional blade in tensile strength at 650 ° C. In addition, three creep test pieces were taken from the upper part 3 of the wing of the present invention and the conventional wing, and a creep rupture test was performed at 925 ° C. FIG. 6 shows the result. The wing according to the present invention has substantially the same creep strength as the conventional wing, although the tensile strength is improved.

Next, one gas turbine rotor blade was manufactured in the same manner as in Sample I, using the alloy having the composition of Sample II (IN738LC type). This blade was subjected to the heat treatment A of Example 1 to obtain a conventional blade (IN738LC type). A test piece was taken from the lower wing 2 and a tensile test was performed. Using a test piece taken from the upper part 3 of the wing, the temperature was 935 ° C., the stress was 14 kgf / mm.
^The creep rupture test was performed in ² . The conventional wing (Rene80
Type) and the wing of the present invention (Rene80 type) were also subjected to creep tests under the same conditions.

FIG. 7 compares the characteristics of the conventional blade and the blade of the present invention based on the test results. Conventional wing using Rene80 type alloy has creep strength of IN738LC
Creep strength is higher than conventional wings using a type of alloy,
It has the advantage that it can be used up to higher temperatures, but its tensile strength is I
There is a problem that it is lower than the N738LC type. Rene80
The wing of the present invention using a type alloy has a creep strength of Rene80
While maintaining the same tensile strength as that of the conventional blade using the alloy of the type 7, the tensile strength is comparable to that of the conventional blade using the alloy of the IN738LC type.

[0022]

As described above, according to the present invention, the tensile strength of a blade can be improved without impairing creep resistance.

[Brief description of the drawings]

FIGS. 1A to 1C are characteristic diagrams showing tensile test results of a simulated wing material of the present invention and a simulated conventional wing material.

FIGS. 2A and 2B are characteristic diagrams showing creep test results of the simulated wing material of the present invention and the simulated conventional wing material.

FIG. 3 is a characteristic diagram showing a hardness measurement result of the simulated wing material of the present invention.

FIGS. 4A and 4B are schematic perspective views showing the shape of a manufactured wing.

FIG. 5 is a characteristic diagram showing tensile test results of the wing of the present invention and the conventional wing.

FIG. 6 is a characteristic diagram showing creep test results of the wing of the present invention and the conventional wing.

FIG. 7 is a characteristic diagram showing a characteristic comparison between the wing of the present invention and a conventional wing.

[Explanation of symbols]

 1. Turbine blades, 2. Lower part, 3. Upper part.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C22F 1/00 691 C22F 1/00 691C (72) Inventor Isao Takehara 3-1-1 Kochicho, Hitachi-shi, Hitachi, Ibaraki Pref. Inside Hitachi, Ltd. Hitachi Plant (72) Inventor Ken Kudo 3-1-1, Sachimachi, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Plant

Claims (3)

[Claims] By 1. A is subjected to multi-stage heat treatment above 800 ° C., 100,000 hours creep rupture strength at 825 ° C. for a gas turbine blade made of a Ni-based alloy was 10 kgf / mm ² or more, the multi-stage heat treatment above 800 ° C. A gas turbine rotor blade characterized by improving the tensile strength of a portion where the temperature during use is 700 ° C. or less by successively performing aging treatment in a temperature range of 700 ° C. to 800 ° C. 2. A gas turbine blade made of an alloy having a chemical composition of Rene 80 type, after a creep rupture strength at 825 ° C. for 100,000 hours of 10 kgf / mm ² or more at 825 ° C. by a multi-stage heat treatment at 700 ° C. to 800 ° C. ° C
The gas turbine rotor blade according to claim 1, wherein the aging treatment in the temperature range of (1) improves the tensile strength of a portion where the temperature during use is 700 ° C or lower. 3. A gas turbine blade made of an alloy having a chemical composition of Rene 80 type, which is subjected to an aging treatment in a temperature range of 700 ° C. to 800 ° C., following the four-stage standard heat treatment of Rene 80 type, to thereby increase the temperature during use. 2. The tensile strength of a part at a temperature of 700 ° C. or lower has been improved.
A gas turbine blade as described.