KR20180081313A - Directional solidification ni base superalloy and manufacturing method therefor - Google Patents

Abstract

The present invention relates to a steel sheet comprising, by weight%, 9.5 to 12.5% of Cr, 9.0 to 9.5% of Co, 0.4 to 0.6% of Mo, 9.3 to 9.7% of W, 5.2 to 5.9% of Al, 0.6 to 0.9% of Ti, 3.0 to 3.5% Wherein the alloy contains 0.04 to 0.08% of B, 0.01 to 0.02% of B and the balance of Ni and other impurities, and further comprises a metal of Hf, Re and Ru, and a process for producing the same, And corrosion resistance. However, it is possible to improve both the high temperature strength (creep characteristic) and the high temperature oxidizing property of the conventional alloy by complementing the weakness.

Description

TECHNICAL FIELD [0001] The present invention relates to a directionally solidified Ni-base superalloy and a method for manufacturing the same,

The present invention relates to a directionally solidified Ni-base superalloy, and a method of manufacturing the same. More specifically, the present invention relates to a directionally solidified Ni-base superalloy having improved high-temperature oxidation and creep characteristics and a method for manufacturing the same.

Gas turbine engines operate in extreme environments, and engine components, especially turbine components, are exposed to high operating temperatures and stresses. In particular, the blades of the power generating turbines may be of a length of about 36 inches or more and a weight of about 40 pounds or more, and are not particularly limited, but may include casting crack resistance, tensile strength, ductility, creep resistance, It is necessary to balance the properties starting from low-feel sensitivity, low enough density, reasonable cost and moderately large heat treatment windows.

Superalloys have been used for the rigorous use of the same demands described above in that they can maintain moderately high strength up to about 75% of their melting temperature with good environmental resistance. Ni-based superalloys are widely used particularly in applications such as turbine blades and nozzles all over the gas turbine engine. However, the conventional Ni-based superalloy used for the rear end blade may be difficult to cast and yield may be lowered. Historically, a steady rise in gas turbine combustion temperature conditions has been attributed to improvements in mechanical performance and environmental material performance in these applications.

Directional solidification is successfully used because it optimizes creep and fracture behavior in Ni-based superalloy applications. The crystal grains are selectively oriented in the direction of the main axis of the stress (generally in the longitudinal direction) to bring the columnar crystal grain structure to eliminate the grain boundary across the growth direction. The oriented orientation also brings about a desirable longitudinal modulus of elasticity, which is advantageous for the fatigue performance of the member.

Compared with conventional alloy castings, when directional solidification is used, an article having greatly improved strength, ductility and thermal fatigue resistance can be obtained. However, in such articles, low strength and ductility characteristics may still be seen in the lateral direction for the presence of columnar crystal grain boundaries. Hafnium, carbon and boron are used as additional alloying elements, such as U.S. Pat. No. 6,908,818, as an attempt to improve the lateral grain boundary strength of the articles being hung. However, the addition of other elements may deteriorate other desirable properties (for example, melting point), and development of a Ni-base superalloy in order to balance the characteristics is urgently required.

The present invention relates to a directionally solidified Ni-base superalloy alloy and a method of manufacturing the same.

An object of the present invention is to provide a directionally solidified Ni-base superalloy having high-temperature oxidation and corrosion resistance at the same time, containing Cr in an amount of 10% or more, and a method for producing the same.

It is another object of the present invention to provide a directionally solidified Ni-base superalloy having improved high-temperature strength (creep characteristics) and high-temperature oxidizing ability at the same time by adding Re and Ru at the same time, and a method for producing the same.

It is another object of the present invention to provide a single-crystal Ni-base superalloy capable of being used as a material for a boiler, a steam turbine and a gas turbine, and a method of manufacturing the same.

Other objects and advantages of the present invention will become more apparent from the following detailed description of the invention and claims.

The embodiments of the present invention are described in order to more fully explain the present invention to those skilled in the art, and the following embodiments may be modified into various other forms, It is not limited to the embodiment. Rather, these embodiments are provided so that this disclosure will be more faithful and complete, and will fully convey the scope of the invention to those skilled in the art.

In the drawings, the thickness and the size of each layer are assumed for convenience and clarity of description, and the same reference numerals denote the same elements in the drawings. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" include singular forms unless the context clearly dictates otherwise. Also, " comprise "and / or" comprising "when used herein should be interpreted as specifying the presence of stated shapes, numbers, steps, operations, elements, elements, and / And does not preclude the presence or addition of one or more other features, integers, operations, elements, elements, and / or groups.

In one embodiment of the present invention, the present invention provides a method of manufacturing a semiconductor device, comprising: 9.5 to 12.5% of Cr, 9.0 to 9.5% of Co, 0.4 to 0.6% of Mo, 9.3 to 9.7% of W, 5.2 to 5.9% of Al, , 3.0 to 3.5% of Ta, 0.04 to 0.08% of C, 0.01 to 0.02% of B, balance Ni and other impurities.

In one embodiment of the present invention, the directionally solidified Ni-based superalloy of the present invention may further include Hf, Re and Ru.

In one embodiment of the present invention, the directionally solidified Ni-base superalloy can further contain Hf 1.2 to 1.6%, Re 0.6 to 1.6%, and Ru 0.5 to 1.5%.

In one embodiment of the present invention, the directionally solidified Ni-base superalloy of the present invention may have a mixed structure of? (Gamma) phase and? 'Phase.

In one embodiment of the present invention, the directionally solidified Ni-based superalloy of the present invention may have a fraction of? 'Phase of 50 to 70%.

In one embodiment of the present invention, the present invention provides a method for producing an aluminum alloy comprising the steps of: 1) mixing 9.5 to 12.5% of Cr, 9.0 to 9.5% of Co, 0.4 to 0.6% of Mo, 9.3 to 9.7% of W, 5.2 to 5.9% of Al, 0.9 to 0.9% of Ta, 3.0 to 3.5% of Ta, 0.04 to 0.08% of C, 0.01 to 0.02% of B, remaining Ni and other impurities; And 2) introducing the molten steel in step 1) into a ceramic shell mold for manufacturing a one-way alloy by precision casting; And

3) A step of drawing a chill plate, which is mounted on a shell mold of the step 2), at a rate of 3 to 5 mm / min, to prepare a directionally solidified Ni-base superalloy ≪ / RTI >

In one embodiment of the present invention, the steel of step 1) of the present invention may further comprise Hf, Re and Ru.

In one embodiment of the present invention, it may further include 1.2 to 1.6% of Hf, 0.6 to 1.6% of Re, and 0.5 to 1.5% of Ru in step 1) of the present invention.

In one embodiment of the present invention, step (1) of the present invention may be a step of heating and melting at 1400 to 1600 占 폚 in a vacuum induction melting process.

In one embodiment of the present invention, the ceramic shell mold for manufacturing the unidirectional alloy of the present invention may be preheated to 1400 to 1600 占 폚 before the molten steel is introduced.

The present invention relates to a directionally solidified Ni-base superalloy having improved high-temperature strength (creep characteristics) and high-temperature oxidizing ability as compared with conventional alloys, .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a method for producing a directionally solidified Ni-based superalloy according to an embodiment of the present invention;
100: melting furnace
110: induction coil
200: alloy composition
300: Ceramic shell casting for manufacturing unidirectional alloy
400: cooling plate

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood that both the foregoing description and the following detailed description are exemplary, explanatory and are intended to be illustrative, and not restrictive. The scope of the invention is defined by the appended claims rather than by the foregoing description. will be.

In one embodiment of the present invention, the present invention provides a method of manufacturing a semiconductor device, comprising: 9.5 to 12.5% of Cr, 9.0 to 9.5% of Co, 0.4 to 0.6% of Mo, 9.3 to 9.7% of W, 5.2 to 5.9% of Al, , 3.0 to 3.5% of Ta, 0.04 to 0.08% of C, 0.01 to 0.02% of B, balance of Ni and other impurities, and may further include Hf, Re and Ru. More specifically, Hf is 1.2 to 1.6% , Re 0.6-1.6% and Ru 0.5-1.5%, but is not limited to the examples.

The directional solidification Ni - base superalloy has a Cr content of 8% and is vulnerable to high temperature oxidation and corrosion resistance. In order to solve the problem of the conventional alloy, the Cr content was increased to 9.5% or more, thereby improving the high temperature oxidation and corrosion resistance.

Further, the content of the γ 'phase was controlled to be between 50 and 70% by finely adjusting the contents of Al and Ti as compared with the conventional single crystal Ni-base superalloy.

Further, it will be further characterized by including Re and Ru in order to improve high-temperature strength (creep characteristics) in comparison with existing alloys. In order to solve the problem of the conventional alloy, although Hf is included in the alloy composition, Hf and Re are included, or Hf and Ru are included, according to one embodiment of the present invention, Hf, Re and Ru Is added at the same time. In addition to the simultaneous addition of Hf, Re and Ru, the optimal range of content that can be used as a material for boilers, steam turbines, and gas turbines is set.

Due to the above characteristics, the directionally solidified Ni-base superalloy according to an embodiment of the present invention has high oxidizing property and creep property at the same time as the conventional alloy due to the simultaneous addition of Hf, Re and Ru, .

Hf : 1.2 to 1.6%

Hf is segregated at the grain boundaries during casting to prevent hot cracking, contributes to improvement of grain boundary ductility and improvement of casting, and is effective in preventing casting crack due to difference of thermal expansion coefficient between ceramic mold / core and alloy. In addition, it is preferentially segregated on γ ', and when it is added less than 1.2%, resistance to oxidation is decreased, but when it is more than 1.6%, MC carbide coarsening and HfO 2 oxide and process compound formation are accelerated to lower creep and TMF properties.

Re: 0.6 to 1.6%

Re is γ-based solid solution strengthening element, which contributes to improvement of creep strength and improvement of high temperature corrosion due to slow diffusion at high temperature. If it is less than 0.6%, the strengthening effect is insignificant, and if it is 1.6% or more, the formation of the TCP phase is promoted and the creep and TMF strength are lowered. The price per kilogram is about 2.9 million won, which is very expensive and can be included in the range of 0.6-1.6% in order to obtain the maximum effect with minimum addition, but is not limited to the examples.

Ru : 0.5 to 1.5%

Ru acts to reverse segregate the γ phase element to γ 'phase to inhibit the formation of SRZ (secondary reaction zone) between the TCP phase and the base / coating layer and to increase the solubilization range of γ' phase. When added at less than 0.5%, the suppression effect on the TCP is insignificant, and the addition of 2% or more increases the segregation of Re and Ta to thereby form a TCP phase and an ε-phase to lower the high temperature strength . The price per kilogram is about 1.7 million, which is quite expensive and can be included in the range of 0.5 to 1.5%, but is not limited to the example.

Co: 9.0 to 9.5%

Co can replace the Ni in the γ phase phase to enhance solubility and increase the solution temperature range by reducing the solidus temperature on γ 'phase. When the solution temperature is less than 9%, the solution temperature range is narrowed. When the solution temperature is more than 9.5%, the amount of the γ 'phase is decreased to lower the strength.

Cr : 9.5 to 12.5%

Creation characteristics are lowered when Cr is more than 5%, and formation of topollogically close packed (TCP) phase is more than 7.5%. The corrosion resistance is significantly reduced when the content is less than 10%, but the higher the corrosion resistance, the higher the addition amount.

Mo : 0.4 to 0.6%

Mo enhances the high temperature strength by increasing the lattice misfit between γ / γ 'phases as an element promoting the Raft effect. Mo is employed in the base to increase the high temperature strength and improve the high temperature strength through the Raft effect and precipitation hardening. If it is less than 0.4%, the high-temperature strength is lowered, but when it exceeds 0.6%, there arises a problem of precipitating a harmful phase to mechanical properties.

W: 9.3 to 9.7%

W can be added to increase the creep strength and the TMF strength as solid solution strengthening and precipitation strengthening elements like Mo.

Al: 5.2 to 5.9%,

Al forms Ni < ₃ > Al intermetallic compounds with Ni to precipitate at the [gamma] base and optimize the creep strength and TMF (Thermo-Mechanical Fatigue) strength when the fraction of the y 'phase is 50 to 70% have. When the content is less than 5.2%, there is a problem that the fraction of the? 'Phase decreases and it is difficult to satisfy the required high temperature strength.

Ti : 0.6 to 0.9%

Ti, like Al, improves creep strength as an element forming γ 'phase, but when added at 5% or more, lattice misfit is increased, while SFE (Stacking fault energy) is decreased to lower creep strength .

Ta : 3.0 to 3.5%

Ta is an effective element for strengthening the? 'Phase to increase the creep strength and TMF strength, but when added in large amounts, the formation of the process?' Phase may be promoted, thereby reducing the solutioning effect.

B: 0.01 to 0.02%

B enhances the grain boundaries by reducing grain boundary diffusion and changes the shape of the y 'phase and carbide. As the addition amount is increased, the liquidus temperature and the liquidus / solidus temperature of the carbide are decreased.

C: 0.04 to 0.08%

C is a crystal grain strengthening element. C is combined with Ti, Cr, Zr, Nb and W to form carbides such as MC, M6C and M23C6. When C is 0.08% or more, MC carbide can be formed. As the amount of addition increases, the liquidus temperature may be decreased and the segregation of Re may be reduced. In addition, it can reduce the incidence of casting defects such as freckles, misoriented grains and reduce the formation of surface scales.

As an example of the melting apparatus used in the embodiment of the present invention, an induction type melting furnace employing the eddy current loss heat of the material itself is adopted.

Since each of the additive elements has different melting points and evaporation temperatures, it is very difficult to control the alloy composition because a metal having a low melting point first evaporates when a high temperature heat source is suddenly supplied. Therefore, it is preferable to dissolve the molten metal in a vacuum atmosphere so that the components of the alloy are not oxidized, and a vacuum induction melting furnace can be used for this purpose.

In one embodiment of the present invention, the vacuum induction melting furnace is characterized in that the weight of the vacuum induction melting furnace is 9.5 to 12.5% of Cr, 9.0 to 9.5% of Co, 0.4 to 0.6% of Mo, 9.3 to 9.7% of W, 5.2 to 5.9% of Al, (VIM, Vacuum induction melting) was performed by adding a steel containing 0.9% of Sn, 3.0 to 3.5% of Ta, 0.04 to 0.08% of C, 0.01 to 0.02% of B and the remaining Ni and other impurities, Dissolve well to mix. The steel composition may further include Hf 1.2 to 1.6%, Re 0.6 to 1.6%, and Ru 0.5 to 1.5%. In order to prepare a single crystal specimen after completion of the vacuum induction melting, the molten alloy composition is injected into a ceramic shell mold for manufacturing a precise casting alloy. The ceramic shell casting for alloy manufacture has the shape of the product. It can be manufactured by withdrawing a chill plate mounted at a shell mold at a constant speed. The molten alloy composition charged into the ceramic shell casting is brought into contact with the cooling plate, and the alloy composition in contact with the cooling plate forms a fine polycrystalline phase. The cooling rate of the cooling plate is 3 to 5 mm / , And have a directional structure due to the temperature difference. That is, when the temperature gradient between the portion of the melted alloy composition injected into the shell casting and the other portion contacting the cooling plate is maintained, the particles grow in a direction perpendicular to the heat-releasing direction.

1, a method of manufacturing a directionally solidified Ni-base superalloy according to an embodiment of the present invention is shown. The outer side of the melting furnace 100 is positioned with an induction coil 110 , The temperature of the inside of the melting furnace is raised to 1400 to 1600 ° C so that the components of the alloy can be dissolved well by the vacuum induction melting method. The alloy composition 200 dissolved by the vacuum induction melting method is introduced into a ceramic shell casting 300 for manufacturing a unidirectional alloy and the melted alloy composition 200 is cooled by a cooling plate 400 located at a lower end of the cell casting 300 As mentioned above, the molten alloy composition that forms a fine polycrystal, but does not touch, has a temperature difference between the cooling plate 400 and the molten alloy composition in contact therewith, and the heat of the molten alloy composition in the direction of the cooling plate 400 As the release proceeds, particles having directionality grow.

Claims (10)

Wherein the alloy contains 9.5 to 12.5% of Cr, 9.0 to 9.5% of Co, 0.4 to 0.6% of Mo, 9.3 to 9.7% of W, 5.2 to 5.9% of Al, 0.6 to 0.9% of Ti, 3.0 to 3.5% of Ta, %, B 0.01 ~ 0.02%, the balance Ni and other impurities. The method according to claim 1,
The directionally solidified Ni-base superalloy has further a directionally solidified Ni-base superalloy including Hf, Re and Ru. The method according to claim 1,
Wherein said directionally solidified Ni-based superalloy further comprises Hf 1.2 to 1.6%, Re 0.6 to 1.6% and Ru 0.5 to 1.5%. The method according to claim 1,
Wherein the directionally solidified Ni-based superalloy has a mixed structure of? Phase and? 'Phase. The method according to claim 1,
Wherein the directionally solidified Ni-based superalloy has a fraction of? 'Phase of 50 to 70%. 1) by weight of at least one of Cr 9.5 to 12.5%, Co 9.0 to 9.5%, Mo 0.4 to 0.6%, W 9.3 to 9.7%, Al 5.2 to 5.9%, Ti 0.6 to 0.9%, Ta 3.0 to 3.5% To 0.08%, B 0.01 to 0.02%, remaining Ni and other impurities; And
2) introducing the molten steel in step 1) into a ceramic shell mold for manufacturing a one-way alloy by precision casting; And
3) A step of drawing a chill plate, which is mounted on a shell mold of the step 2), at a rate of 3 to 5 mm / min, to prepare a directionally solidified Ni-base superalloy Way. The method according to claim 6,
Wherein the steel of step 1) further comprises Hf, Re and Ru. The method according to claim 6,
Wherein the steel of step 1) further comprises Hf 1.2 to 1.6%, Re 0.6 to 1.6%, and Ru 0.5 to 1.5%. The method according to claim 6,
Wherein the step (1) is carried out by raising the temperature to 1400 to 1600 占 폚 in a vacuum induction melting process to dissolve the oriented solidified Ni-base superalloy. The method according to claim 6,
Wherein the ceramic shell mold for manufacturing the unidirectional alloy is preheated at 1400 to 1600 占 폚 before the dissolution of the molten steel.

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