JPH08209273A - Nickel based alloy for heat resistant material - Google Patents

Abstract

PURPOSE: To prevent the rupture of Ni based alloy due to the decrease of strength at the time of using by preventing the generation of anisotropic structural change (rafting) of γ'-phase at the time of using the Ni based alloy composed of γ-phase and γ' phase. CONSTITUTION: The width of the variation of stress generated in the γ-phase of the Ni based alloy is controlled to a value less than the nominal value of stress due to external force applied to the Ni based alloy. As a result, the reliability of a device such as a gas turbine using the Ni based alloy is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Ni-based alloy used in a high temperature environment, and in particular, it has excellent thermal stability and creep rupture strength of a metal structure when subjected to a load in a high temperature environment, and a gas turbine blade The present invention relates to a Ni-base superalloy single crystal material suitable as a material, a single crystal component for a gas turbine produced by using the single crystal casting, and a high efficiency gas turbine produced by using the single crystal component, and more particularly The present invention relates to a combined cycle power generation system for power generation and having high thermal efficiency.

[0002]

2. Description of the Related Art In gas turbines, turbine blades that are exposed to extremely harsh thermodynamically and mechanically are made from polycrystalline ordinary casting alloys to unidirectional columnar solidified alloys that have no grain boundaries in the stress loading direction. In addition, it has become a single-crystal alloy with no grain boundaries. The history of such development is mainly centered on aircraft gas turbines, and continuous operation time is relatively short, but high low cycle fatigue strength has been emphasized. Alloy 444 (U.S. Pat. No. 4,116,72) is an example of an alloy that has been developed from this viewpoint.
3, JP-B-59-34776), PWA1484 (US Pat. No. 4,71)
9,080, JP 61-284545), CMSX-4 ((US Pat. No. 4,643,782, JP 60-211031), SC-
83 (US Pat. No. 4,976,791, JP-A-2-138431) and the like.

On the other hand, the operating temperature of the blade of the gas turbine for terrestrial power generation has not been so high as that for aircraft, and ordinary cast alloy has been mainly used. However, recent global environmental pollution problems have been highlighted, and There is an urgent need to improve the efficiency of gas turbines for terrestrial power generation, and the combustion temperature of gas turbines has risen. In response to this, it has become necessary to shift turbine blade materials from ordinary cast alloys to single crystal cast alloys. However, in gas turbines for terrestrial power generation, the continuous operating time is significantly longer than that for aircraft, and the turbine blade inspection interval is also longer, so the stability of the turbine alloy structure during long-term operation is dependent on the reliability of the entire turbine system. It has become extremely important for sex. That is, the microstructure of the alloy needs to be stable even under an operating environment at a higher temperature than before, but an alloy satisfying such a need has not yet been put into practical use. The current situation.

[0004]

Ni-based alloys for heat-resistant materials are composed of an ordered phase called γ'phase and an irregular phase called γ phase. Has a cubic shape with one side of about 0.5 micron and is regularly arranged in the matrix γ phase. It is empirically known that such a microscopic metal structure has high creep strength and toughness, but normally, such an alloy structure is stable up to about 950 ° C. under load. When the temperature becomes higher than that, there is a problem that the γ'phase usually grows in the direction perpendicular to the stress loading direction with creep deformation. That is, at a high temperature of about 950 ° C. or higher, the structure of the Ni-based superalloy single crystal is unstable under load. Such an anisotropic growth phenomenon of the γ ′ phase is called a Rafting phenomenon, but this Rafting phenomenon occurs at an extremely high speed,
At high temperatures above a certain level, it becomes clearly observed during the initial creep period of several hours to several tens of hours after the start of deformation.

It has been confirmed that such a change in the microstructure of the metal reflects on the creep strength of the Ni-base alloy, and that the creep rupture time is remarkably shortened in the alloy having Rafting. In addition, by observing the fracture surface with an electron microscope, it is possible to observe how fracture occurs along the thinned γ'phase. Therefore, if it is possible to suppress such a Rafting phenomenon and prevent the alloy structure from changing even under high temperature creep conditions of about 950 ° C. or higher, a creep rupture strength higher than conventional can be obtained.

A prominent feature of the Rafting phenomenon is that this phenomenon occurs perpendicularly to the stress loading direction (or parallel to the stress loading direction depending on the material), and the γ'phase grows rapidly. The fact that the growth occurs according to the stress loading direction suggests that the anisotropy of deformation caused by stress is important for the growth direction of the γ ′ phase, and the extremely fast growth indicates that γ ′ It also shows that the mass transfer that leads to phase growth is also very fast. In other words, it can be seen that the Rafting phenomenon is caused by anisotropic deformation in the microstructure of the alloy, and occurs in the process of high-speed mass transfer.

The problem to be solved by the present invention is to control the mass transfer by making the deformation occurring in the microstructure of the alloy uniform and isotropic, thereby controlling the mass transfer in the high temperature region above 950 ° C. It is to improve the creep strength.

[0008]

In order to achieve the above object, according to the present invention, the width of the spatial variation of the stress value generated in the γ phase of the Ni-based alloy is controlled by the external force applied to the Ni-based alloy. By designing the stress generated by the stress to be sufficiently smaller than the nominal value, a material designing method for preventing anisotropic growth of the γ ′ phase due to creep deformation is provided.

Further, the width of the spatial variation of the stress value generated in the γ phase of the Ni-based alloy is sufficiently smaller than the nominal value of the stress generated by the external force applied to the Ni-based alloy. Provided is a method of designing a material having a combination of elastic constants and lattice constants of the phase and γ ′ phase.

Further, by making the plastic deformation occurring in the γ phase of the Ni-base alloy spatially uniform, it is possible to prevent the anisotropic growth of the γ'phase due to creep deformation from occurring in the material. Design methods are provided.

Further, there is provided a method of designing a material having a combination of elastic constants and lattice constants of the γ phase and the γ ′ phase such that the plastic deformation occurring in the γ phase of the Ni-based alloy becomes substantially spatially uniform. It

Further, the width of the spatial variation of the stress value generated in the γ phase of the Ni-based alloy is sufficiently smaller than the nominal value of the stress generated by the external force applied to the Ni-based alloy, Provided is a Ni-base alloy for heat-resistant materials, which does not cause anisotropic growth of the γ'phase due to creep deformation.

Further, the width of the spatial variation of the stress value generated in the γ phase of the Ni-based alloy is sufficiently smaller than the nominal value of the stress generated by the external force applied to the Ni-based alloy, Provided is a Ni-base alloy for heat-resistant materials, which has a combination of elastic constants and lattice constants of the γ phase and the γ ′ phase such that anisotropic growth of the γ ′ phase due to creep deformation does not occur.

Further, N for heat resistant materials having a combination of elastic constants and lattice constants of the γ phase and the γ ′ phase such that the plastic deformation occurring in the γ phase of the Ni-based alloy becomes substantially uniform in space.
An i-based alloy is provided.

Further, there is provided a material designing method for designing using the elastic constants and lattice constants of the γ phase and the γ ′ phase in the temperature range of 800 to 1200 ° C.

There is also provided a Ni-base alloy for heat resistant materials designed by using the elastic constants and lattice constants of the γ phase and γ'phase in the temperature range of 800 to 1200 ° C.

Also, a dimensionless quantity

[0018]

(Equation 6)

A method for designing a material having a value of 0.05 or less is provided.

However, the symbol used in the calculation of d corresponds to the following physical quantity.

Σ: Nominal value of stress applied to the gas turbine blade Eγ: Young's modulus of γ phase in the stress loading direction Eγ ′: Young's modulus of γ ′ phase in the stress loading direction

[0022]

(Equation 7)

Aγ: lattice constant of γ phase aγ ′: lattice constant of γ ′ phase D: spacing of misfit dislocations introduced at the γ-γ ′ interface.

[0024]

(Equation 8)

There is provided a Ni-based alloy for heat-resistant materials having a value of 0.05 or less.

Also, a dimensionless quantity

[0027]

[Equation 9]

A method for designing a material for adjusting the composition ratio of elements constituting a Ni-based alloy is provided so that the value becomes 0.05 or less.

Also, a dimensionless quantity

[0030]

[Equation 10]

There is provided a Ni-base alloy for heat-resistant materials, in which the component ratio of the elements constituting the Ni-base alloy is adjusted so that the value becomes 0.05 or less.

Further, there is provided a method of designing a material having a two-phase structure consisting of a γ ′ phase having a cubic shape and a shape corresponding thereto and a γ phase surrounding the γ ′ phase.

There is also provided a Ni-base alloy for heat-resistant materials having a two-phase structure composed of a γ'phase having a cubic shape and a shape similar thereto and a γ phase surrounding the γ'phase.

The alloys described above are Ni, Al, T
i, Cr, Co, Rh, W, Ta, Mo, Nb, Hf, which is composed of at least two kinds of components, and when used as a component for machine structure, only a single crystal or a small number of small-angle grain boundaries are used. Provided is a Ni-based alloy for a heat-resistant material having a metal structure containing.

There is also provided a gas turbine blade, a gas turbine nozzle, or a gas turbine using the alloy described above.

Further, in the gas turbine in which the fuel gas compressed by the compressor is made to collide with the blade implanted in the disk through the nozzle to rotate the blade, the combustion gas temperature is 1500 ° C. or higher, and the first stage blade inlet The combustion gas temperature is 1300 ° C. or higher, the blade is made of a Ni-based alloy single crystal casting, and the total length is 1
A gas turbine with a power generation capacity of 250,000 kW or more with a diameter of 500 mm or more is provided.

[0037]

The deformation state of a material is generally described by the strain generated in the material. Strain is usually the sum of elastic strain and plastic strain. Elastic strain is the response that a material first exhibits when a load is applied to the material. The magnitude of elastic strain corresponds to the stress generated in the material through Hooke's law in a one-to-one correspondence. Plastic strain occurs when the stress generated in a material exceeds a certain limit value. At this time, many crystal defects called dislocations propagate and move in the material. Dislocation growth and migration are driven by stress. It is known that such a dislocation becomes one of the diffusion paths in the crystal.

From the above, to eliminate the anisotropy of deformation and create a uniform deformed state in the microstructure is the same as to make the distribution of elastic strain and plastic strain uniform. For that purpose, it is necessary to make the distribution of the stress generated in the microstructure uniform. Also,
The main mass transfer mechanism is pipe diffusion using dislocations as diffusion paths, and interface diffusion using γ-γ ′ interfaces as diffusion paths.
Although it is a body diffusion mediated by atomic vacancies, the density of dislocations and vacancies is closely related to plastic strain. Therefore, homogeneity of the plastic strain distribution is the most important from the viewpoint of uniforming the spatial distribution of the crystal defects that act as the path of mass transfer and mediation, and the homogeneity of the stress distribution that determines the plastic strain distribution. Sex is needed here as well. That is, controlling the distribution of stress in the structure so that the plastic strain that occurs in the microstructure of the material is isotropic becomes the basic design guideline for an alloy with a thermally stable structure, and The alloy material designed in this way has high structural stability under high temperature creep conditions.

The microstructure of the Ni-base alloy for heat-resistant materials has a geometry such that cubic γ'phases with a side of about 0.5 micron are regularly arranged in the matrix γ phase. Have unique characteristics. A microstructure having such geometrical characteristics can be obtained by subjecting a cast alloy to an appropriate aging treatment. FIG. 1 is a schematic drawing of such a structure, and the hatched region represents the γ'phase. Since the resistance of the γ'phase to plastic deformation is sufficiently larger than that of the γ phase, plastic deformation usually occurs only in the γ phase part. If an external force is applied in the direction shown in Fig. 1, Raftin
It is known that the phenomenon of g proceeds such that the V region shown in FIG. 1 becomes narrower and the H region becomes wider. The microstructure during the Rafting process is shown schematically in FIG. When the region H in FIG. 1 is called a horizontal channel and the region V is called a vertical channel, the Rafting phenomenon is a phenomenon in which the shape of the γ ′ phase becomes flat and the vertical channel disappears, and the width of the horizontal channel widens. Can be said.

The main causes of stress in γ-γ 'microstructure are (1) externally applied load and object force,
(2) Difference in crystal lattice constant between γ phase and γ ′ phase. Of the load and the object force applied from the outside of (1), the main one is the centrifugal force, and hereinafter, the sum of this centrifugal force and the load applied from the outside will be simply referred to as an external force.

Assuming that the direction of the external force coincides with the <100> direction of the crystal, the stress caused by the difference between the crystal lattice constants and the external force is numerically obtained using the finite element method and summarized. The following results were obtained: (1) Stress field generated by external force i) Both lateral and longitudinal channels are uniaxial vertical stress fields in the direction of external force. ii) The stress value in the lateral channel is almost the nominal stress value even if the elastic constants of the γ and γ ′ phases are different.

Here, the nominal stress is a value obtained by dividing the external force value by the cross-sectional area of the sample. Iii) The stress value in the longitudinal channel is almost equal to the nominal stress value (Eγ
/ Eγ ′) times.

(2) Stress field caused by difference in lattice constant i) Biaxial vertical stress field in a direction parallel to the interface between the γ phase and the γ ′ phase is roughly obtained for both the lateral channel and the longitudinal channel.

Ii) The stress value is approximately Eγε *.

The physical substance of plastic deformation occurring in the longitudinal and transverse channels is the growth and movement of dislocations occurring at those locations. Propagation and movement of dislocations are driven by shear stress applied to the dislocations. Therefore, in order to cause the same amount of plastic deformation in the longitudinal channel and the transverse channel, the shear stresses applied to the dislocations at those locations should be equal. The well-known generalized Schmid factor can be used to calculate the shear stress applied to dislocations from the stress values mentioned in the previous section. The shear stress applied to the dislocations in the horizontal and vertical channels is τH and τV, respectively.
Then

[0046]

[Expression 11] τH = | σ−Eγε * | (3)

[0047]

(Equation 12)

It becomes When the magnitude relationship between τH and τV is displayed in the space with Eγ / Eγ ′ and 2Eγ′ε * as the coordinate axes, τH is larger than τV in the hatched area in FIG. 3 and τH is in the unhatched area. It becomes smaller than τV, and τH = τV holds on the thick line of the boundary. E
Under the condition of γ / Eγ ′> 0, τH = τV is defined by the following equation.

[0049]

(Equation 13)

Only when is zero. By designing the material for the combination of the elastic constant and the lattice constant of the crystal depending on the stress applied to the material so that δ becomes 0, the plastic deformation generated in the γ phase can be made uniform. However, it may be practically impossible to completely set the δ value to 0 in material design. However, τH in each region shown in Fig. 3
Since the difference between τV and τV is continuous, the intended purpose of homogenizing the plastic deformation that occurs in the γ phase is to position the combination of the elastic constant and the lattice constant near the straight line of δ = 0. To be achieved. For example, Journal of Materia
Numerical simulation using the crystal plasticity analysis program described in ls Research, Volume7, 1992, p3032-3038 was performed to calculate the spatial non-uniformity of the plastic deformation occurring in the γ phase, and the theory of the material flow rate caused by it was calculated. According to the evaluation result, the deviation from the straight line of δ = 0 is 5% of the σ value.
It has been clarified that the growth rate of the γ ′ phase due to the spatial variation of the amount of plastic deformation occurring in the γ phase is sufficiently longer than the turbine blade operating time within the range. Therefore, as a material design guideline

[0051]

[Equation 14]

It suffices to make the value 0.05 or less. At this time, γ
The combination of the elastic constants and lattice constants of the phase and γ ′ phase satisfies the condition that the plastic deformations that occur in the vertical and horizontal channels are almost equal.

[0053]

【Example】

(Example 1) A typical value of the design stress assumed for the Ni-based alloy turbine rotor blade according to the present invention is 100 to 250M.
Pa. In such an environment, the conditions under which the alloy structure does not become raft during creep deformation can be determined as follows.

That is, when σ = 200 MPa, ε * is 0.1
Estimating%, and using Eγ′≈1 × 10 ¹¹ / Pa, Eγ = 0.5 × 10 ¹¹ / Pa. That is, the material composition ratio is determined so that the Young's modulus of the γ phase and the γ ′ phase is 0.5.

In this case, changing the composition ratio causes a change in the ε * value as well as a change in the Young's modulus, so that the combination of the two values should be satisfied, that is, the non-raft with respect to the stress required in the design. The value of the material constant is determined within a practical range so that the conversion condition is almost satisfied. However, it is necessary to use the value of the material constant illustrated here in the temperature range in which the material is assumed to be used.

(Embodiment 2) Under the same design stress as in Embodiment 1, if ε * is estimated to be −0.05%, Eγ′≈1 ×
The Eγ = 2 × 10 ¹¹ / Pa to 10 ¹¹ / Pa. That is, the material composition ratio is determined so that the Young's modulus ratio of the γ phase and the γ ′ phase is 2.

(Embodiment 3) FIG. 4 is a sectional view of a gas turbine apparatus having a turbine blade and a nozzle using the Ni-based single crystal alloy of the present invention. This example is a three-stage turbine, and the Ni-based single crystal alloy, which is the material having the material constant described in Example 1, was used in the first stage. According to this embodiment,
Since the combustion gas temperature at the turbine inlet can be made higher than in the conventional case, it is possible to provide a gas turbine with high thermal efficiency.

[0058]

According to the present invention, it becomes possible to prevent the anisotropic growth of the γ'phase due to the creep deformation of the Ni-base alloy for heat-resistant materials, and the creep deformation of the Ni-base alloy for heat-resistant materials. The characteristics can be improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a microstructure before a Ni-based alloy for heat-resistant material undergoes creep deformation.

FIG. 2 is a schematic diagram of anisotropic growth of a γ ′ phase accompanying creep deformation of a Ni-based alloy for heat resistant materials.

FIG. 3 is a diagram showing the magnitude relationship of plastic deformation occurring in a vertical channel and a horizontal channel of a γ ′ phase.

FIG. 4 is a cross-sectional view of a gas turbine device that is an embodiment of the present invention.

[Explanation of symbols]

1 ... Turbine stub shaft, 2 ... Distant piece, 3 ... Turbine blade, 4 ... Turbine disk, 5
... Turbine stacking bolts, 6 ... Compressor disk, 7 ... Compressor blade, 8 ... Turbine spacer, 9 ... Compressor stub shaft, 10 ... Nozzle,
11 ... Compressor stacking bolt.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinya Konno 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Masakazu Saito 7-chome, Omika-cho, Hitachi City, Ibaraki Prefecture No. 1 in Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Hiroshi Miyata No. 1-1, Omika-cho, Hitachi, Hitachi, Ibaraki (1) In Hitachi Research Laboratory, Hitachi, Ltd. (72) Osamu Ito Hitachi, Ibaraki Prefecture 7-1, Omika-cho, Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor, Akira Yoshinari 7-1, 1-1, Omika-cho, Hitachi, Ibaraki Prefecture, Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor, Hideki Tamaki Hitachi 1-1, Omika-cho, Hitachi City, Ibaraki Prefecture

Claims (19)

[Claims] 1. A width of spatial variation in stress value generated in the γ phase of a Ni-based alloy is set to be sufficiently smaller than a nominal value of stress generated by an external force applied to the Ni-based alloy. This prevents the anisotropic growth of the γ'phase due to creep deformation. 2. The value of the spatial variation of the stress value generated in the γ phase of the Ni-based alloy is sufficiently smaller than the nominal value of the stress generated by the external force applied to the Ni-based alloy according to claim 1. A method for designing a material characterized by having a combination of elastic constants and lattice constants of the γ phase and γ ′ phase such that 3. An anisotropic growth of the γ'phase due to creep deformation is prevented by making the plastic deformation occurring in the γ phase of a Ni-based alloy spatially uniform. Characteristic material design method. 4. A combination of elastic constants and lattice constants of a γ phase and a γ ′ phase such that the plastic deformation occurring in the γ phase of the Ni-based alloy becomes substantially spatially uniform. Material design method characterized by that. 5. The width of the spatial variation of the stress value generated in the γ phase of the Ni-based alloy is sufficiently smaller than the nominal value of the stress generated by the external force applied to the Ni-based alloy, An Ni-based alloy for heat-resistant materials, characterized in that anisotropic growth of the γ'phase does not occur due to creep deformation. 6. The width of the spatial variation of the stress value generated in the γ phase of the Ni-based alloy is sufficiently smaller than the nominal value of the stress generated by the external force applied to the Ni-based alloy, Ni for heat resistant materials, characterized by having a combination of elastic constants and lattice constants of the γ phase and the γ ′ phase such that anisotropic growth of the γ ′ phase due to creep deformation does not occur.
Base alloy. 7. A heat-resistant material having a combination of elastic constants and lattice constants of a γ phase and a γ ′ phase such that the plastic deformation occurring in the γ phase of a Ni-based alloy is spatially substantially uniform. Ni-based alloy for use. 8. The method according to claim 1, wherein 800
A design method for materials characterized by designing using elastic constants and lattice constants of the γ phase and γ ′ phase in the temperature range from 1 to 1200 ° C. 9. The dimensionless quantity according to claim 5, wherein Is 0.05 or less, a material design method. However, the symbol used in the calculation of d corresponds to the following physical quantity. σ: Nominal value of stress applied to gas turbine blade Eγ: Young's modulus of γ phase in stress loading direction Eγ ′: Young's modulus of γ ′ phase in stress loading direction [Equation 2] aγ: lattice constant of γ phase aγ ′: lattice constant of γ ′ phase D: spacing of misfit dislocations introduced at the γ-γ ′ interface 10. The non-dimensional quantity according to claim 6, wherein Of less than 0.05 is Ni for heat resistant materials
Base alloy. 11. The non-dimensional quantity according to claim 5, wherein A method of designing a material, characterized in that the component ratio of the elements constituting the Ni-based alloy is adjusted so that the value becomes 0.05 or less. 12. The non-dimensional quantity according to claim 6, wherein A Ni-based alloy for heat-resistant materials, characterized in that the component ratio of the elements constituting the Ni-based alloy is adjusted so that the value becomes 0.05 or less. 13. A method of designing a material having a two-phase structure comprising a γ'phase having a cubic shape and a shape corresponding thereto and a γ phase surrounding the γ'phase according to claim 7 or 9. 14. The γ ′ phase having a cubic shape and a shape conforming thereto, and γ ′ according to claim 8 or 10.
A Ni-based alloy for a heat-resistant material, which has a two-phase structure composed of a γ phase surrounding a phase. 15. The alloy according to any one of claims 1 to 12 is Ni, Al, Ti, Cr, Co, Rh, W, Ta,
Ni-base for heat-resistant materials, which is composed of at least two kinds of components selected from Mo, Nb, and Hf, and has a metallographic structure including a single crystal or a small number of small-angle grain boundaries when it is used as a machine structural part. alloy. 16. A gas turbine blade using the alloy according to any one of claims 1 to 13. 17. A gas turbine nozzle using the alloy according to any one of claims 1 to 13. 18. A gas turbine using the alloy according to any one of claims 1 to 13. 19. A gas turbine in which fuel gas compressed by a compressor is caused to collide with a blade embedded in a disk through a nozzle to rotate the blade, the combustion gas temperature is 1500 ° C. or higher, and The combustion gas temperature is 1300 ° C or higher, and the blade is made of a single crystal cast of Ni-based alloy and has a total length of 1500.
A gas turbine having a power generation capacity of 250,000 kW or more in mm or more.