JP2017179592A - MANUFACTURING METHOD OF Ni-BASED HEAT-RESISTANT SUPERALLOY - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a Ni-based heat-resistant superalloy having high gamma prime mole ratio and easily conducting hot processing of a raw material thereof.SOLUTION: There is provided a manufacturing method of a Ni-based heat-resistant superalloy by conducting plasticity processing at a temperature Tp of (Ts-200°C)≤Tp≤(Ts-20°C), where Ts is gamma prim solid solution temperature, and strain rate Vs of over 1.0/sec. on a raw material of the Ni-based heat-resistant superalloy having C amount of 0.12 mass% or less and equilibration deposition amount of the gamma prime at 700°C of 40 mol% or more. There is provided a manufacturing method of a Ni-based heat-resistant superalloy by a heat treatment including heating the raw material of the Ni-based heat-resistant superalloy before conducting the above described plastic processing at a temperature Th of Ts or more and cooling the raw material of the Ni-based heat-resistant superalloy heated to the temperature of Th to at least (Ts-300°C) at cooling rate of less than 5°C/min.SELECTED DRAWING: Figure 1

Description

  The present invention provides a method for producing a Ni-based superalloy, particularly a difficult-to-workable Ni-based superalloy having a high gamma prime molar ratio.

As heat-resistant parts used in aircraft engines and gas turbines for power generation, for example, Ni-based super heat-resistant alloys such as 718 alloy are often used. With the improvement in performance and fuel efficiency of gas turbines, heat-resistant parts having a high heat-resistant temperature are required. In order to improve the heat resistance of the Ni-base superalloy, it is most effective to increase the amount of gamma prime (hereinafter also referred to as “γ ′”) which is a precipitation strengthening phase. In the future, in order to satisfy high heat resistance and high strength, the γ 'molar ratio of Ni-base superalloys will be increasingly required. The “γ ′ molar ratio” is the amount of γ ′ that the Ni-base superalloy can precipitate in an equilibrium state at 700 ° C.
However, when γ ′ increases, the deformation resistance during hot working increases. Therefore, when performing plastic working such as hot forging on a material such as an ingot, this hot forging becomes difficult. Moreover, the higher the γ ′ molar ratio, the stronger the segregation tendency at the time of casting solidification, the higher the number of unstable phases and casting defects in the material, and the lower the hot forgeability of the material. In addition, addition of a large amount of Al and Ti, which are γ′-forming elements, causes a decrease in the solidus temperature of the alloy and an increase in the recrystallization temperature, thereby narrowing the hot forging temperature region (in general, hot forging is the solidus temperature). This is performed at a temperature higher than the recrystallization temperature). Conventionally, when the γ ′ molar ratio is 40% or more, the temperature range in which forging is practically close to zero, and hot forging is difficult. Therefore, in the production of Ni-base superalloys with a high γ 'molar ratio, proposals have been made such as castings that are used as-cast, avoiding the difficulty of forging, and powder metallurgy methods that produce initial ingots by powder sintering. (For example, JP-A-10-46278 (Patent Document 1)).

Japanese Patent Laid-Open No. 10-46278

As in the method of Patent Document 1 described above, a cast material used as a part as cast has a coarse cast structure, casting segregation of alloy elements, and casting defects, so that mechanical performance and reliability are limited. For example, it cannot be applied to a component such as a turbine disk that requires high reliability. Powder metallurgy can produce alloys with a high γ 'molar ratio as a fired material, but the process is more complex than melting and forging methods, and advanced management is indispensable to prevent contamination by impurities in the manufacturing process. There is a problem that the manufacturing cost is high. Therefore, casting materials and fired materials are limited to some special applications.
An object of the present invention is to provide a method for producing a Ni-base superalloy that facilitates hot working of a Ni-base superalloy having a high γ ′ molar ratio.

As a result of systematically studying the processing conditions affecting the work ductility using a high γ ′ content Ni-base superalloy, the present inventors have found that a high strain rate (unit: Is 1 / second.), It has been found that the plastic working ductility can be drastically improved, and the present invention has been achieved.
That is, according to the present invention, the gamma prime solid solution temperature of a Ni-based superalloy having a C content of 0.12% by mass or less and an equilibrium precipitation amount of gamma prime at 700 ° C. of 40 mol% or more is expressed as Ts. Is a manufacturing method of a Ni-base superalloy that performs plastic working at a strain rate Vs exceeding 1.0 / sec at a temperature Tp of (Ts−200 ° C.) ≦ Tp ≦ (Ts−20 ° C.).

  In the above-described method for producing a Ni-base superalloy according to the present invention, preferably, the Ni-base superheat-resistant alloy material before the plastic working is heated to a temperature Th equal to or higher than Ts and heated to this temperature Th. This is a method for producing a Ni-base superheat-resistant alloy, in which a heat treatment is performed to cool a Ni-base superheat-resistant alloy material to at least (Ts-300 ° C) at a cooling rate of less than 5 ° C / min.

  Moreover, in the manufacturing method of the Ni-base superalloy according to the present invention described above, the component composition of the material of the Ni-base superalloy is preferably mass%, C: 0.12% or less, Cr: 8. 0 to 22.0%, Mo: 2.0 to 7.0%, Al: 2.0 to 8.0%, Ti: 0.5 to 7.0%, the balance being over Ni and consisting of Ni and impurities It is a manufacturing method of a heat-resistant alloy. More preferably, the component composition of the material of the Ni-based superalloy is, by mass, Co: 28.0% or less, W: 6.0% or less, Nb: 4.0% or less, Ta: 3.0% or less, Fe: 10.0% or less, V: 1.2% or less, Hf: 1.0% or less, B: 0.300% or less, Zr: 0.300% or less Containing one or more elemental species.

  According to the present invention, it is possible to easily perform plastic working of a hard-working Ni-base superalloy having a γ ′ molar ratio of 40% or more, which has been conventionally difficult to perform hot plastic working such as hot forging. .

Product No. evaluated in the examples. 2 is a drawing-substituting photograph showing the appearance of Ni-based superalloy (No. 2) according to the present invention. Product No. evaluated in the examples. 11 is a drawing-substituting photograph showing the appearance of 11 Ni-base superalloy (comparative example). Product No. evaluated in the examples. It is a drawing substitute photograph which shows the external appearance of 12 Ni-base superalloys (comparative example). Product No. evaluated in the examples. 2 is a crystal orientation diagram obtained from a cross-sectional structure of Ni-based superalloy (No. 2) according to the present invention. Product No. evaluated in the examples. 11 is a crystal orientation diagram obtained from a cross-sectional structure of 11 Ni-base superalloy (comparative example). It is a figure explaining the point of the compression test performed in the Example.

Below, each process which concerns on the manufacturing method of the Ni-base superalloy of this invention, and the reason for limitation of the conditions are described.
Ni-base superalloys tend to be more difficult to plastically work as the “γ ′ molar ratio” determined by the composition of the Ni-based superheat-resistant alloy increases. In this case, the present invention is effective for plastic working of a Ni-base alloy having a low γ ′ mole ratio, but the γ ′ mole ratio, which was difficult to be plastically processed by a conventional processing technique, is “40% or more”. Targets difficult-to-work Ni-base superalloys. The material of the Ni-base superalloy used in the present invention may be an ingot, billet, or other starting form. Moreover, it is preferable that the raw material of the Ni-base superalloy used as the object of the present invention is obtained by a melting method in which molten metal is poured into a mold to produce an ingot. In this case, the ingot may be manufactured by combining, for example, vacuum melting and conventional methods such as vacuum arc remelting and electroslag remelting.

The reason why the plastic working temperature Tp is “(Ts−200 ° C.) ≦ Tp ≦ (Ts−20 ° C.)” and the plastic working strain rate Vs is “over 1.0 / second” when performing the plastic working of the present invention. Is as follows.
First, the plastic working temperature Tp is set to 20 ° C. or lower than the γ ′ solid solution temperature Ts. This γ ′ solid solution temperature Ts is usually referred to as “Solvus temperature”. And in the temperature range exceeding this solvus temperature, (gamma) 'dissolves and it becomes a single phase organization only of (gamma). Further, in a temperature range below this solvus temperature, a structure in which two phases of γ ′ and γ coexist is obtained.
In the case of the present invention, in the temperature range below the solvus temperature, a two-phase structure in which a small amount and an appropriate amount of γ ′ are dispersed in a γ matrix is superior in ductility compared to a single-phase structure containing only γ. I stopped. And the temperature range which produces the two-phase structure | tissue excellent in this ductility is a temperature range of "(Ts-20 degreeC or less)." Therefore, the upper limit of the plastic working temperature Tp is (Ts-20 ° C.). About this upper limit, Preferably it is (Ts-30 degreeC). More preferably (Ts-50 ° C).
On the other hand, when the temperature is further decreased in the temperature range of “(Ts−20 ° C.) or lower”, the amount of γ ′ precipitated from the matrix increases with the temperature decrease, and the amount of γ decreases. Become. When the amount of γ ′ increases, the deformation resistance increases, and plastic working of the material becomes difficult. In addition, the application of a small amount of γ ′ is effective for improving the ductility of the material, but if the amount of γ ′ is excessively increased, the ductility is lowered. Therefore, the lower limit of the plastic working temperature Tp is (Ts−200 ° C.). The lower limit is preferably (Ts−150 ° C.). More preferably (Ts-100 ° C.).

And about the ductility of the raw material of the Ni-based superalloy described above, the ductility of the raw material being plastically processed in the above temperature range is affected by the “strain rate” at this time, and the greater the strain rate, the higher the ductility. The present inventors have found out. In other words, it was found that “dynamic recrystallization” is promoted in the structure of the material when the strain rate is increased during plastic working in a temperature range below the solvus temperature. Specifically, by setting the strain rate Vs during the plastic working to a large value “exceeding 1.0 / second”, dynamic recrystallization is sufficiently generated, and a fine recrystallized structure is generated. We found that the ductility during plastic working increased dramatically. Thereby, it is also possible to process a material of a difficult-to-process Ni-base superalloy having a gamma prime of 40 mol% or more into a shape such as a fine wire. When the strain rate Vs is “0.1 / second or less”, dynamic recrystallization hardly occurs in the structure during plastic deformation.
The strain rate Vs is preferably 2.0 / second or more. More preferably, it is 3.0 / second or more. More preferably, it is 5.0 / second or more. Particularly preferably, it is 8.0 / second or more. By increasing the strain rate, this also leads to an improvement in the production rate of the Ni-base superalloy (as a whole) (that is, a reduction in production time), and is effective in increasing production efficiency.
On the other hand, although it is not necessary to provide an upper limit of the strain rate Vs, about 300.0 / sec is realistic considering the equipment capacity for hot plastic working. Preferably, it is 200.0 / second or less. More preferably, it is 100.0 / second or less. More preferably, it is 70.0 / sec or less. Particularly preferably, it is 30.0 / second or less.
As a plastic working method capable of achieving the plastic working temperature Tp and the strain rate Vs of the present invention, press, extrusion, forging, swaging, roll rolling, die drawing, and the like can be applied.

Moreover, in the manufacturing method of the Ni-base superalloy according to the present invention, the material before the plastic working is heated to a temperature Th equal to or higher than the above temperature Ts, and the material heated to this temperature Th is 5 ° C / It is preferable to perform a heat treatment to cool to at least (Ts-300 ° C.) at a cooling rate of less than a minute.
By holding the raw material before plastic working at a temperature Th equal to or higher than the γ ′ solid solution temperature Ts, γ ′ in the structure is once dissolved, and the heated structure is converted into a single phase of γ. To do. Next, the heated material is cooled under the slow cooling conditions described later, so that γ ′ is precipitated in the structure to obtain a structure in which γ ′ is uniformly coarsened. Although the mechanism is unknown, the material of the Ni-base superalloy having γ ′ uniformly coarsened becomes more dynamic with the above-described large strain rate in the next plastic working as the degree of coarsening becomes significant. Recrystallization is promoted and the effect of improving plastic workability is remarkable.
In order to obtain a structure in which γ ′ is coarsened uniformly, it is effective to completely dissolve γ ′ by heating and holding. Therefore, the heating and holding temperature Th is preferably Ts or higher. More preferably, the temperature is higher by 10 ° C. than Ts. It is not necessary to provide an upper limit for the heating and holding temperature Th, and the heating and holding temperature Th is theoretically lower than the temperature at which the Ni-based superalloy material starts to melt (solidus temperature). In this heat treatment, the material holding time after reaching the heating holding temperature Th is preferably 2 hours or more. And 10 hours or less is realistic. Preferably, it is 7 hours or less. More preferably, it is 4 hours or less. As a result, in addition to the coarsening of γ ′, there is an effect (soaking effect) in uniformizing the component composition.

In the above heat treatment, the cooling after the Ni-based superalloy material is heated and held at “temperature Th” may be cooled to at least (Ts−300 ° C.) at a cooling rate of “less than 5 ° C./min”. preferable. In other words, by “slowly cooling” the “high temperature region” in the cooling process, the diffusion of γ′-generating elements such as Ni and Al becomes active, and the nucleation and grain growth of precipitated γ ′ can be promoted. . In the cooling process of the Ni-base superalloy having a γ ′ (gamma prime) of 40 mol% or more, the high temperature range from the heating holding temperature Th to (Ts−300 ° C.) is the temperature at which the γ ′ coarsening occurs exclusively. This is because γ ′ becomes coarser as the cooling rate in this temperature range is slower. About the temperature range which adjusts this cooling rate, More preferably, it is to (Ts-350 degreeC), More preferably, it is to (Ts-400 degreeC).
In the case of the present invention, it is more effective to improve the plastic workability of the present invention that at least the cooling in the above temperature range is set to a slow cooling rate of “less than 5 ° C./min”. More preferably, it is 3 degrees C / min or less, More preferably, it is 1 degrees C / min or less.
The cooling rate does not require a special lower limit. However, if the cooling rate is extremely slow, the cooling time becomes long, which is disadvantageous in terms of production efficiency. Further, when the cooling rate is slowed down to around 0.1 ° C./min, the coarsening effect of γ ′ tends to be saturated. Therefore, the lower limit of the cooling rate can be set to 0.1 ° C./min, for example.

Next, the preferable component composition of the Ni-base superalloy used in the present invention will be described. In the present invention, any component composition having a γ ′ molar ratio of 40% or more can be widely applied. However, C (carbon) that can be contained in the Ni-base superalloy used in the present invention needs to be regulated to 0.12% by mass or less.
<C: 0.12 mass% or less>
C has the effect of enhancing the castability of the Ni-base superalloy and increasing the strength of the grain boundaries. However, when C increases, it precipitates as coarse eutectic carbide in the final solidified part of the cast ingot. As the amount of C increases, the number of eutectic carbides increases and the size of the carbides also increases. And when C exceeds about 0.12 mass%, a coarse eutectic carbide will become a form connected with each other in a rod shape. Since carbide is brittle and serves as a starting point for cracks in plastic working, the connected carbide greatly impairs the ductility of plastic working. Therefore, C has an upper limit of 0.12% by mass. Preferably it is 0.05 mass% or less, More preferably, you may be 0.03 mass% or less. More preferably, it is 0.025 mass% or less. Most preferably, it is 0.02 mass% or less. For the present invention, C is a regulatory element and is preferably managed lower. In addition, when it is good also as C not adding (it is an inevitable impurity level of a raw material), the minimum of C shall be 0 mass%.

And about the element seed | species except C, the component composition shown below is especially suitable. The unit of component composition is “mass%”.
<Cr: 8.0 to 22.0%>
Cr is an element that improves oxidation resistance and corrosion resistance. In order to obtain the effect, 8.0% or more is necessary. If Cr is contained excessively, an embrittlement phase such as a σ phase is formed and the strength and hot workability are lowered, so the upper limit is made 22.0%. A preferable lower limit is 9.0%, and more preferably 9.5%. More preferably, it is 10.0%. Moreover, a preferable upper limit is 18.0%, More preferably, it is 16.0%. More preferably, it is 14.0%.

<Mo: 2.0 to 7.0%>
Mo contributes to the solid solution strengthening of the matrix and has the effect of improving the high temperature strength. In order to obtain this effect, 2.0% or more is necessary. However, if Mo is excessive, an intermetallic compound phase is formed and high temperature strength is impaired, so the upper limit is made 7.0%. A preferred lower limit is 2.5%, more preferably 3.0%. More preferably, it is 3.5%. Moreover, a preferable upper limit is 6.0%, More preferably, it is 5.0%.

<Al: 2.0 to 8.0%>
Al is an element that forms a strengthening phase γ ′ (Ni ₃ Al) phase and improves high-temperature strength. In order to obtain the effect, at least 2.0% is necessary. However, excessive addition reduces hot workability and causes material defects such as cracks during processing, so it is limited to 8.0% or less. A preferred lower limit is 2.5%, more preferably 3.0%. More preferably, it is 4.0%, and particularly preferably 4.5%. Moreover, a preferable upper limit is 7.5%, More preferably, it is 7.0%. More preferably, it is 6.5%.

<Ti: 0.5 to 7.0%>
Ti is also an element that forms γ ′ like Al and enhances high-temperature strength by solid-solution strengthening γ ′. In order to obtain the effect, at least 0.5% is necessary. However, excessive addition causes the gamma prime phase to become unstable at high temperatures and cause coarsening at high temperatures, and forms a harmful η (eta) phase, thereby impairing hot workability. Therefore, the upper limit of Ti is set to 7.0%. Considering the balance of other γ ′ forming elements and the matrix, the preferable lower limit of Ti is 0.6%, more preferably 0.7%. More preferably, it is 0.8%. Moreover, a preferable upper limit is 6.5%, More preferably, it is 6.0%. More preferably, it is 4.0%, and particularly preferably 2.0%.

The preferred component composition of the Ni-base superalloy used for the material of the present invention is a Ni-base superalloy having a C content of 0.12% or less and containing the above element species, the balance being Ni and impurities. It can be set as the component composition. In addition to the above element species, the following element species can also be contained.
<Co: 28.0% or less>
Co improves the stability of the structure and makes it possible to maintain hot workability even when a large amount of Ti as a strengthening element is contained. It is one of the selective elements that can be contained in the range of 28.0% or less in combination with other elements. Increasing the Co content improves the hot workability. In particular, in the difficult-to-work Ni-base superalloy, the addition of Co is effective. On the other hand, since Co is expensive, the cost increases. The preferable lower limit when Co is added for the purpose of improving hot workability is preferably 8.0%. More preferably, it is 10.0%. The preferable upper limit of Co is 18.0%. More preferably, it is 16.0%. If the Co addition level (the inevitable impurity level of the raw material) may be set due to the balance between the γ ′ generation element and the Ni matrix generation, the lower limit of Co is set to 0%.

<W: 6.0% or less>
W, like Mo, is one of the selective elements that contribute to the solid solution strengthening of the matrix. If W is excessive, a harmful intermetallic compound phase is formed and the high temperature strength is impaired, so the upper limit is made 6.0%. A preferable upper limit is 5.5%, and more preferably 5.0%. In order to exhibit the effect of W more reliably, the lower limit of W is preferably set to 1.0%. Moreover, the solid solution strengthening effect can be exhibited more by adding W and Mo in combination. In the case of composite addition, W is preferably 0.8% or more. In addition, when it is good also considering W as an additive-free level (inevitable impurity level of a raw material) by sufficient addition of Mo, the minimum of W shall be 0%.

<Nb: 4.0% or less>
Nb is one of the selective elements that forms γ ′ in the same manner as Al and Ti and enhances high-temperature strength by solid-solution strengthening γ ′. In order to exhibit the above-described effect of Nb more reliably, the lower limit of Nb is preferably set to 1.0%. Preferably it is 2.0%. However, excessive addition of Nb forms a harmful δ (delta) phase and impairs hot workability, so the upper limit of Nb is 4.0%. A preferable upper limit is 3.5%, more preferably 2.5%. In the case where Nb may be made non-addition level (inevitable impurity level of the raw material) by adding other γ ′ forming elements, the lower limit of Nb is set to 0%.

<Ta: 3.0% or less>
Ta, like Al and Ti, is one of the selective elements that forms γ ′ and enhances γ ′ by solid solution strengthening to increase the high-temperature strength. In order to exhibit the above Ta effect more reliably, the lower limit of Ta is preferably set to 0.3%. However, excessive addition of Ta causes the gamma prime phase to become unstable at a high temperature and cause coarsening at a high temperature, and forms a harmful η (eta) phase and impairs hot workability. Therefore, the upper limit of Ta is set to 3.0%. Preferably it is 2.5% or less. On the other hand, if Ta is allowed to be at the non-added level (the inevitable impurity level of the raw material) due to the addition of γ ′ forming elements such as Ti and Nb and the balance of the matrix, the lower limit of Ta is set to 0%.

<Fe: 10.0% or less>
Fe is one of the selective elements used as an alternative to expensive Ni and Co, and is effective in reducing alloy costs. In order to acquire this effect, it is good to determine whether to add with the combination of another element. However, if Fe is contained excessively, an embrittlement phase such as a σ phase is formed and the strength and hot workability are lowered, so the upper limit of Fe is 10.0%. A preferable upper limit is 9.0%, more preferably 8.0%. On the other hand, if the Fe addition level (inevitable impurity level of the raw material) is allowed due to the balance of the γ ′ generating element and the Ni matrix generation, the lower limit of Fe is 0%.

<V: 1.2% or less>
V is one of the selective elements useful for strengthening the solid solution of the matrix and strengthening the grain boundaries by forming carbides. In order to exhibit the effect of V more reliably, the lower limit of V is preferably set to 0.5%. However, excessive addition of V leads to generation of a high-temperature unstable phase in the production process and adversely affects manufacturability and high-temperature dynamic performance, so the upper limit of V is set to 1.2%. A preferable upper limit is 1.0%, and more preferably 0.8%. In addition, when it is good also considering V as an additive-free level (inevitable impurity level of a raw material) by balance with the other alloy element in an alloy, the minimum of V shall be 0%.

<Hf: 1.0% or less>
Hf is one of the selective elements useful for improving the oxidation resistance of alloys and strengthening grain boundaries by forming carbides. In order to exhibit the effect of Hf more reliably, the lower limit of Hf is preferably set to 0.1%. However, excessive addition of Hf leads to production of oxides and high temperature unstable phases in the production process, and adversely affects manufacturability and high temperature dynamic performance, so the upper limit of Hf is 1.0%. If the Hf may be a non-additive level material (inevitable impurity level) due to the balance with other alloy elements in the alloy, the lower limit of Hf is set to 0%.

<B: 0.300% or less>
B is an element that improves the grain boundary strength and improves the creep strength and ductility. In order to obtain this effect, a content of at least 0.001% is preferable. On the other hand, B has a large effect of lowering the melting point, and when coarse boride is formed, workability is hindered. Therefore, it is preferable to control B not to exceed 0.300%. A more preferred lower limit is 0.003%, and even more preferably 0.005%. Particularly preferred is 0.010%. Moreover, a preferable upper limit is 0.200%, More preferably, it is 0.100%. More preferably, it is 0.050%, Most preferably, it is 0.020%. In addition, when B may be a non-additive level raw material (inevitable impurity level) due to balance with other alloy elements in the alloy, the lower limit of B is set to 0%.

<Zr: 0.300% or less>
Zr has the effect of improving the grain boundary strength in the same manner as B, and a content of at least 0.001% is preferable for obtaining this effect. On the other hand, if Zr is excessive, the melting point is lowered and the high temperature strength and hot workability are hindered, so the upper limit is made 0.300%. A more preferable lower limit is 0.005%, and further preferably 0.010%. Moreover, a preferable upper limit is 0.250%, More preferably, it is 0.200%. More preferably, it is 0.100%, Most preferably, it is 0.050%. In addition, when Zr may be used as an additive-free raw material (inevitable impurity level) due to the balance with other alloy elements in the alloy, the lower limit of Zr is set to 0%.
As described above, the balance other than the elements to be described is Ni, but naturally unavoidable impurities are included.

The “γ ′ molar ratio” according to the present invention is the equilibrium precipitation amount of gamma prime (γ ′) at 700 ° C. In the case of the present invention, it is possible to process a difficult-to-process Ni-base superalloy material having a γ ′ molar ratio of 40 mol% or more into a shape such as a thin wire. Preferably, it is 50 mol% or more. More preferably, it is 60 mol% or more. It is not particularly necessary to provide an upper limit for the value of this γ ′ molar ratio. However, about 75 mol% is realistic.
The value of the γ ′ mole ratio expressed in the above “mol%” is a value that can be determined by the component composition of the Ni-base superalloy. The value of “mol%” of the equilibrium precipitation amount can be obtained by analysis by thermodynamic equilibrium calculation. In the case of analysis by thermodynamic equilibrium calculation, it can be obtained accurately and easily by using thermodynamic equilibrium calculation software.

  According to the present invention, a high-performance turbine disk for aircraft or power generation can be manufactured using a high γ′-containing Ni-base superalloy, for example. Furthermore, according to the present invention, it becomes possible to process a difficult-to-process Ni-base superalloy having a γ ′ molar ratio of 40% or more into a shape such as a wire fine wire, and to provide it for use in overlay welding or 3D modeling. It becomes possible.

Ingots A and B of cylindrical Ni-base superalloys having a diameter of 100 mm and a length of 110 mm were prepared by casting a molten metal having a predetermined component composition prepared by vacuum melting. Table 1 shows the composition of the ingots A and B. Regarding element types other than those shown in Table 1, Co: 28.0% or less, W: 6.0% or less, Ta: 3.0% or less, V: 1.2% or less, Hf: 1.0% It was the following.
Table 1 also shows “γ ′ molar ratio” and “γ ′ solid solution temperature (solvus temperature) Ts” of these ingots A and B. These values were calculated using a commercially available thermodynamic equilibrium calculation software “JMatPro (Version 8.0.1, product of Senté Software Ltd.)”. The content of each element listed in Table 1 was input to this thermodynamic equilibrium calculation software, and the above-mentioned “γ ′ molar ratio” and “γ ′ solid solution temperature Ts” were obtained.

An ingot piece having a diameter of 10 mm and a length of 14 mm was collected from the produced Ni-base superheat-resistant alloys ingots A and B in a direction parallel to the length direction of the ingot. The ingot piece was subjected to the heat treatment shown in Table 2 (holding temperature Th × holding time, and cooling rate from the holding temperature Th to (Ts−300 ° C.)), and then machined to have a diameter of 8 mm × length. Finished into a cylinder with a size of 12 mm, a material for compression test was obtained. And this material was subjected to plastic working by the following compression test to produce a Ni-based super heat-resistant alloy product.
The compression test was conducted with a hot working reproduction test device in accordance with ASTM D3410. The point of the compression test is that the above material is compressed in the length (axis) direction at a compression rate of 60% calculated by the following equation (1) (FIG. 6). At this time, the “plastic working temperature Tp” during the compression test and the “strain rate Vs” calculated by the following equation (2) are changed. And the quality of plastic workability was judged by the presence or absence of the "crack" in the external appearance of the raw material (namely, product) after compression. These numbers and results are shown in Table 2.
・ Compression rate (%) = [(L0−L1) / L0] × 100 (1)
Strain rate Vs (s ⁻¹ ) = (L0−L1) / (t × L0) (2)
Where t: compression time (s).

Product No. 1 to 5 are temperatures Tp that satisfy (Ts−200 ° C.) ≦ Tp ≦ (Ts−20 ° C.) with respect to the “γ ′ solid solution temperature Ts” of the material, and a strain rate exceeding 1.0 / second. This is obtained by plastic processing of Vs. Product No. In Nos. 1 to 5, “crack” was not confirmed in the appearance, and excellent plastic workability was achieved. And product no. Among the products Nos. 1 to 5, the product No. 1 was subjected to heat treatment on the material before the compression test. 2 to 5, the surface of the product No. Compared to 1, it was smooth with less irregularities.
FIG. The external appearance of 2 is shown. In FIG. 1, the diagram on the left side is an observation of the product from the surface to which the compressive load is applied (that is, corresponding to the upper surface of the columnar material before the compression test). The figure on the right is an observation of the product from its side (that is, corresponding to the side of the cylindrical material before the compression test). From FIG. It can be seen that the appearance of 2 is free of cracks and has a smooth surface.
4 shows the product No. 2 is a crystal orientation diagram obtained by observing a cross-sectional structure of 2 and analyzing a diffraction pattern obtained by EBSD (electron beam backscatter diffraction analysis). The position of the observed cross section is the center position of the cut surface when the product is cut along its compression axis (center line). The cut surface was polished for micro observation and then OPS polished. From FIG. In 2, a fine complete recrystallized structure was observed.

On the other hand, product no. 11 and 12, although the plastic working was performed at a temperature Tp that satisfies (Ts−200 ° C.) ≦ Tp ≦ (Ts−20 ° C.) with respect to the “γ ′ solid solution temperature Ts” of the material, The strain rate Vs was small. And product no. 11 and 12, a “crack” was confirmed in the appearance.
FIG. 11 shows the external appearance. Also, FIG. The external appearance of 12 is shown. 2 and 3, the form of the product shown on the right and left sides is the same as that in FIG. 1. From the comparison between FIG. 2 and FIG. It can be seen that cracks generated in the appearance of No. 11 (FIG. 2) are prominent.
Further, FIG. 11 is a crystal orientation diagram obtained by observing 11 cross-sectional structures and analyzing a diffraction pattern obtained by EBSD. The procedure for observation is the same as in FIG. From FIG. 11 was an unrecrystallized structure.

Product No. Reference numerals 13 and 14 indicate that the amount of C contained in the material was large at the time of the material before the plastic working. In the case of such a material, even if the plastic working temperature Tp and the strain rate Vs were appropriately adjusted, and even if heat treatment was performed before the plastic working, cracks occurred in the product after the plastic working.
For such materials, product no. 15 and 16 are obtained by further reducing the strain rate Vs. And product no. 14 compared with product No. 15 and 16 were markedly cracked.
For such materials, product no. No. 17 is a value in which the plastic working temperature Tp is higher than the “γ ′ solid solution temperature Ts”. In this case, in addition to the fact that the material itself contains a large amount of C, the ductility during the plastic working is considerably reduced. Compared to 14 again, a remarkable crack occurred.

Claims (4)

When the amount of C is 0.12% by mass or less and the equilibrium precipitation amount of gamma prime at 700 ° C. is 40 mol% or more and the Ni-base superheat-resistant alloy material is Ts, A method for producing a Ni-base superalloy, characterized by performing plastic working at a strain rate Vs exceeding 1.0 / sec at a temperature Tp of −200 ° C. ≦ Tp ≦ (Ts−20 ° C.). The Ni-base superheat-resistant alloy material before the plastic working is heated to a temperature Th equal to or higher than Ts, and the Ni-base superheat-resistant alloy material heated to this temperature Th is cooled at a cooling rate of less than 5 ° C / min. 2. The method for producing a Ni-base superalloy according to claim 1, wherein a heat treatment is performed to cool to at least (Ts−300 ° C.). The component composition of the material of the Ni-based superalloy is, by mass, C: 0.12% or less, Cr: 8.0-22.0%, Mo: 2.0-7.0%, Al: 2 The method for producing a Ni-based superalloy according to claim 1 or 2, wherein 0.0 to 8.0%, Ti: 0.5 to 7.0%, and the balance is made of Ni and impurities. The component composition of the material of the Ni-based superalloy is, by mass, Co: 28.0% or less, W: 6.0% or less, Nb: 4.0% or less, Ta: 3.0% or less Fe: 10.0% or less, V: 1.2% or less, Hf: 1.0% or less, B: 0.300% or less, Zr: 0.300% or less The method for producing a Ni-base superalloy according to claim 3, comprising at least elemental species.