JPH0633701A - Single crystal moving blade for gas turbine and production thereof - Google Patents

Abstract

PURPOSE:To provide, a single crystal moving blade for a gas turbine which is excellent in creep strength and creep fatigue resistance, and a production thereof. CONSTITUTION:A seed crystal is set on the bottom of a mold, in such a way as a complicated cooling hole is formed inside a moving blade, longitudinal crystal orientation upon which centrifugal stress acts is <001> orientation 1 and <100> orientation 2 perpendicular to longitudinal <001> orientation 1 becomes normal direction to a face where maximum thermal stress of the blade is generated, and a single crystal moving blade is produced by an one-way solidification method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas turbine rotor blade, and more particularly to a single crystal rotor blade excellent in creep fatigue strength and a method for manufacturing the same.

[0002]

2. Description of the Related Art Ni-based superalloys have been mainly used as the moving blade material for gas turbines, but the combustion gas temperature has been increasing year by year in order to improve the thermal efficiency of the gas turbine. In order to increase the heat-resistant strength of the rotor blade, along with this, the equiaxed crystal blade formed by normal casting is changed to a columnar crystal blade formed by unidirectional solidification, and further a single crystal blade is formed. , I tried to cool it from the inside.

Most of the single crystal castings are made in Japanese Patent Publication No. 45-40.
No. 661 and Japanese Unexamined Patent Publication No. 59-42171, a unidirectional solidification method using a selector, and a unidirectional solidification method using a seed shown in Japanese Patent Publication No. 60-44168 and Japanese Patent Publication No. 1-26796. ing. This method is a method in which a mold is pulled out from a heated furnace and gradually solidified upward from the lower end. By this method, a single crystal blade having a crystal orientation of the longitudinal Z axis acting on centrifugal stress of <001> was manufactured, and creep strength characteristics and thermal fatigue strength characteristics have been dramatically improved.

[0004]

However, when the combustion gas temperature is raised and the internal cooling is strengthened in order to further improve the efficiency, a large thermal stress has been generated due to the temperature difference between the inside and outside of the blade. This stress becomes a compressive stress on the outside where the combustion gas hits and becomes high temperature, and a tensile stress on the inside where it is cooled, with the center of the blade thickness as the boundary.
When used for a long time in this state, the outside undergoes compressive creep deformation. On the other hand, the inside is in a tensile creep state, but creep deformation hardly occurs because the temperature is low.
When the operation is stopped while in this state,
The blade temperature decreases and heat shrinkage occurs. At this time, the outer side having a higher temperature has a larger contraction amount than the inner side having a lower temperature, so that tensile stress occurs. When this is repeated, cracks will eventually occur. The tensile stress generated at this time increases as the creep deformation during use increases. Further, cracks occur in a shorter time than general thermal fatigue, and are more likely to occur as the temperature difference between the outer side and the inner side of the blade in use increases. In the blade in which the combustion gas temperature is increased and the internal cooling is strengthened in this manner, creep fatigue, which is a combination of creep deformation and fatigue, causes cracks in the gas turbine and has become a major factor in determining blade life. The characteristics of a single crystal change greatly depending on the crystal orientation, and the creep strength is highest in the <111> orientation, next in the <100> orientation, and then in the <110> orientation. On the other hand, since the thermal stress decreases as the elastic modulus decreases, the <100> orientation has the smallest thermal stress, the <110> orientation is next, and the <111> orientation is next, for the same temperature difference. In order to increase the creep fatigue strength, it is effective to increase the creep strength and reduce the thermal stress, and the azimuth satisfying the above two requirements is the <100> azimuth.

However, conventionally, since the thermal stress is small and the temperature at which the blade is used is low, it is not necessary to consider the creep fatigue. Therefore, only the creep characteristics are considered, and the longitudinal Z-axis in which the centrifugal stress acts is taken into consideration. The crystal orientation of is only the <001> orientation, and the lateral orientation is not particularly considered. Therefore, in the single crystal moving blade manufactured by the conventional technique, the crystal orientation in the lateral direction is not constant and the characteristics vary, so that the thermal fatigue strength in the weakest orientation must be used as a reference. Even when the orientation in the lateral direction was taken into consideration, it was intended to simply improve the thermal fatigue strength, and it was insufficient to improve the creep fatigue strength.

As described above, the above-mentioned conventional single crystal moving blade is intended to improve the characteristics in the longitudinal direction under the action of centrifugal stress and the thermal fatigue life, and the creep due to the thermal stress in the blade cross section is caused. Fatigue was not taken into consideration, and the lateral orientation was not optimized, so it was not possible to extend the life of the moving blade and improve the thermal efficiency.

An object of the present invention is to provide a single crystal moving blade for a gas turbine which is excellent in creep strength and creep fatigue strength, and a method for manufacturing the same.

[0008]

In order to achieve the above object, a gas turbine rotor blade according to the present invention has a complicated cooling hole inside the rotor blade, and crystals in the longitudinal Z-axis on which centrifugal stress acts. The azimuth is the <001> direction, and the <0> direction of the longitudinal Z axis is <0>.
The <100> orientation, which is perpendicular to the 01> orientation, is the normal direction of the cross section where the thermal stress is maximum on the plane parallel to the Z axis of the blade.

Further, in the gas turbine blade according to the present invention, the crystal orientation of the longitudinal Z-axis is the <001> orientation,
The <100> orientation perpendicular to the <001> orientation of the longitudinal Z-axis has an angular difference of 20 ° or less from the normal direction of the cross section where the thermal stress is maximum on the plane parallel to the Z-axis of the blade. It is a thing.

In the gas turbine moving blade according to the present invention, the position where the maximum thermal stress is generated is approximately in the middle between the blade tip portion and the platform portion, and is the blade leading edge portion.

The blade for a gas turbine according to the present invention has cooling holes inside the blade, and the cooling holes are divided into several passages.

Further, in the method for manufacturing a single crystal blade according to the present invention, the lateral direction of the seed is set to the <100> orientation at the bottom of the mold, and the <100> orientation is a plane parallel to the Z axis of the blade portion. The step of setting the seed crystal so as to match the normal direction of the cross section where the thermal stress of the maximum is, the step of casting the casting raw material into the mold after melting, and the mold is relatively pulled out from the high-temperature heating furnace. The step of gradually unidirectionally solidifying from one end side to the other end side is included.

[0013]

In the rotor blade for a gas turbine according to the present invention, the crystal orientation of the longitudinal Z axis on which the centrifugal stress acts is the <001> orientation, and the <10 1> orientation of the longitudinal Z axis is <10>.
Since the 0> orientation is the normal direction of the cross section where the thermal stress is maximized on the plane parallel to the Z axis of the blade, the blade should have high creep strength and high creep fatigue strength. You can

[0014]

1 is a perspective view of a single crystal moving blade for a gas turbine according to the present invention, and FIG. 2 is a sectional view showing an outline of a method for manufacturing the moving blade according to the method of the present invention.

In FIG. 2, first, on the water-cooled copper chill 4, the lateral direction of the seed is defined as a <100> direction, and this <1>
00> orientation is fixed by fixing the ceramic mold 6 containing alumina as a main component in which the seed crystal 5 is set so as to match the normal direction of the cross section in which the thermal stress is maximum on the plane parallel to the Z axis of the blade,
It is set in a mold heating heater 7 and the ceramic mold 6 is heated above the melting point of the Ni-based superalloy. Next, the melted Ni-base superalloy was cast into a ceramic mold 6, and then the water-cooled copper chill 4 was drawn out downward and solidified in one direction. When it is unidirectionally solidified, it grows epitaxially from the seed crystal 5 and becomes a large single crystal in the expanded portion, and the crystal orientation of the longitudinal Z axis is the <001> orientation, and the <100> orientation perpendicular to the <001> orientation of the longitudinal Z axis is , A single crystal rotor blade having a cross-section in which the thermal stress is maximum on a plane parallel to the Z-axis of the blade portion is the normal direction. In this case, the mold heating heater 7 is the ceramic mold 6
Was pulled out completely and kept at high temperature until the solidification was completed.
In addition, all the above steps were performed in vacuum.

Table 1 shows the casting conditions for the above-mentioned single crystal moving blade.
Table 2 shows the chemical composition of the Ni-based superalloy used for casting.
The single crystal rotor blade cast by the above method was
At ˜1350 ° C., a solution treatment is performed in vacuum for 2 to 20 hours to change the eutectic γ ′ phase formed by solidification and the precipitated γ ′ phase formed in the cooling process after solidification to the γ phase, After that, at 980 to 1080 ° C for 4 to 20 hours and 800 to 900
Aging heat treatment was performed at 10 ° C. for 10 to 30 hours to precipitate a γ ′ phase with an average of 0.3 to 2 μm in the γ phase.

[0017]

[Table 1]

[0018]

[Table 2]

FIG. 3 shows the maximum thermal stress generation region 8 in the transverse section of the blade tip of the single crystal moving blade shown in FIG. 1 and the intermediate portion of the platform. Results of inelastic stress analysis using the finite element method,
In the blade shown in FIG. 1, it was found that the maximum thermal stress generation region 8 was the leading edge portion. Therefore, the tangent direction of the leading edge arc at the center position of the maximum thermal stress generation region 8 (the portion having the smallest radius of curvature) is defined as the <100> orientation. As a result, the crystallographic orientation of the longitudinal Z axis on which the centrifugal stress of the present invention acts is <00.
1> orientation, and the <100> orientation, which is perpendicular to the <001> orientation of the longitudinal Z-axis, is aligned with the normal direction of the cross section where the thermal stress is maximum on the plane parallel to the Z-axis of the blade. Crystal blades
The creep fatigue life was improved from 2000 times to 8000 times, which is about 4 times that of the conventional single crystal blade that does not control the lateral direction. Incidentally, the azimuth in the normal direction of the conventional single crystal moving blade is <1
10> azimuth was assumed.

On the other hand, in the case of a blade whose shape is three-dimensionally changed, <10> perpendicular to the <001> direction of the longitudinal Z-axis.
In many cases, it is difficult to perfectly match the 0> orientation with the normal direction of the cross section where the thermal stress is maximum on the plane parallel to the Z axis of the blade. In this case, it is necessary to allow some angular difference. FIG. 4 shows the relationship between the deviation from the <100> direction and the creep fatigue characteristics. 20 ° deviation from <100> direction
Within the range, the creep fatigue property is not significantly deteriorated. Therefore, the crystal orientation of the longitudinal Z-axis is the <001> orientation, and the <100> orientation perpendicular to the <001> orientation of the longitudinal Z-axis.
If the angle difference between the azimuth and the normal direction of the cross section where the thermal stress is maximum on the plane parallel to the Z axis of the blade portion is within 20 °, the life will be significantly longer than that of the conventional single crystal rotor blade. It is possible.

Further, in the embodiment, the position where the maximum thermal stress is generated is the leading edge, but the position where the maximum thermal stress is generated naturally varies depending on the blade shape and the cooling system. However, even in this case, the <001>
By aligning the <100> azimuth, which is perpendicular to the azimuth, with the normal direction of the cross section where the thermal stress is maximum on the plane parallel to the Z axis of the blade, the life is extended as in the case of the embodiment. Can be planned.

[0022]

According to the gas turbine rotor blade of the present invention, since a rotor blade having high creep strength and high creep fatigue strength can be obtained, the life of the rotor blade is extended and the combustion gas temperature is increased. This is effective in improving the thermal efficiency of the gas turbine.

According to the method for manufacturing a gas turbine moving blade of the present invention, the above moving blade can be easily manufactured.

[Brief description of drawings]

FIG. 1 is a perspective view of a single crystal moving blade for a gas turbine according to the present invention.

FIG. 2 is a configuration diagram showing an outline of a method for manufacturing the single crystal moving blade for gas turbine shown in FIG.

FIG. 3 is an explanatory diagram showing a relationship between a maximum thermal stress generation position and a <100> direction.

FIG. 4 is a diagram showing the relationship between deviation from <100> orientation and creep fatigue characteristics.

[Explanation of symbols]

 1 <001> orientation 2 <100> orientation 3 <010> orientation 4 water-cooled copper chill 5 seed crystal 6 ceramic mold 7 mold heating heater 8 maximum thermal stress generation position

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsumi Iijima 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture Hitachi Research Institute Ltd. (72) Tadami Ishida 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Hitsuryu Corporation Hitachi, Ltd. (72) Akira Okayama, Akira Okayama 4026, Kuji-machi, Hitachi, Hitachi, Ibaraki Hitachi, Ltd., Hitachi Research Institute (72) Teruo Hirane 4026, Kuji, Hitachi, Ibaraki, Hitachi, Ltd., Hitachi, Ltd. (72) Inventor Kimio Kano 3-7-1, Ichibancho, Aoba-ku, Sendai-shi, Miyagi Tohoku Electric Power Co., Inc. (72) Hiroyuki Matsuzaki 3-7-1, Ichibancho, Aoba-ku, Sendai, Miyagi Prefecture Tohoku Electric power company

Claims (5)

[Claims] 1. A rotor blade used in a gas turbine for power generation, wherein the crystallographic orientation of the longitudinal Z axis on which centrifugal stress acts is the <001> orientation, and the <001> orientation of the longitudinal Z axis is perpendicular to the <001> orientation. A single crystal moving blade for a gas turbine, wherein the 100> orientation is a normal direction of a cross section in which a thermal stress is maximum in a plane parallel to the Z axis of the blade portion. 2. The single crystal moving blade for a gas turbine according to claim 1, wherein heat is generated in a <100> orientation perpendicular to the <001> orientation of the longitudinal Z axis and in a plane parallel to the Z axis of the blade portion. A single-crystal moving blade for a gas turbine having an angle difference of 20 ° or less with a normal line direction of a cross section having the maximum stress. 3. The single crystal moving blade for a gas turbine according to claim 1, wherein the position where the maximum thermal stress is generated is approximately in the middle between the blade tip portion and the platform portion, and at the blade leading edge portion. A single crystal rotor blade for a gas turbine. 4. The single crystal moving blade for a gas turbine according to claim 1, 2 or 3, wherein the single crystal moving blade has a cooling hole inside the blade, and the cooling hole is divided into several passages. Single crystal rotor blade for a gas turbine. 5. A step of setting a seed crystal on the bottom of the mold,
Manufacture of single-crystal blades for gas turbines, including the steps of melting the casting raw material into the mold and then relatively withdrawing the mold from a high-temperature heating furnace to gradually and unidirectionally solidify from one end to the other end. In the method, the lateral orientation of the seed is <100>
The relative positional relationship between the seed and the mold was fixed so that the <100> orientation coincided with the normal direction of the cross section in which the thermal stress on the plane parallel to the Z axis of the blade was the maximum. Manufacturing method of single crystal moving blade for gas turbine.