JP6728282B2 - Ni-based alloy softening material manufacturing method and Ni-based alloy member manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a Ni-based alloy softening material and a method for manufacturing a Ni-based alloy member.

In order to improve the efficiency of gas turbines by raising the combustion temperature, it is required to improve the heat resistance temperature of turbine parts. For this reason, Ni-based alloys are widely used in gas turbine parts as materials having excellent high-temperature strength, including turbine disks, moving vanes, and combustors. The Ni-based alloy realizes high high-temperature strength by solid solution strengthening by adding solid solution strengthening elements such as W, Mo and Co and precipitation strengthening by adding precipitation strengthening elements such as Al, Ti, Nb and Ta. In a precipitation-strengthened Ni-based alloy, the lattice of the γ'phase (L12 structure), which is the precipitation-strengthening phase, is precipitated with continuity with the lattice of the γ-phase (FCC structure) of the parent phase to form a coherent interface. Contribute to strengthening. Therefore, in order to improve the high temperature strength, the amount of the γ'phase may be increased, but the workability deteriorates as the amount of the γ'phase increases. Therefore, there is a problem in that it is difficult to manufacture a large-sized forged product as the strength of the material is higher, and the forging cannot be performed due to an increase in the defect occurrence rate during forging.

As a technique for achieving both high temperature strength and hot forgeability of a Ni-based alloy, there is one described in Patent Document 1 (JP 2011-52308A). In patent document 1, C: 0.001-0.1%, Cr: 12-23%, Co: 15-25%, Al: 3.5-5.0%, Mo: 4-12 in mass reference. %, W: 0.1 to 7.0%, the total content of Ti, Ta and Nb is 0.5% or less on a mass basis, and the formula (1) (Ps=−7×(C content )−0.1×(Mo amount)+0.5×(Al amount)), the parameter Ps is 0.6 to 1.6, and a Ni-based alloy is disclosed.

JP, 2011-052308, A

Hot forging of a high-strength Ni-based alloy whose solid solution temperature of the γ'phase is 1050°C or higher is usually performed in the range of 1000 to 1250°C. This is because by raising the processing temperature to near the solid solution temperature of the γ'phase or higher, the amount of precipitation of the γ'phase, which is a strengthening factor, is reduced and the deformation resistance is reduced. However, in the case of forging at a temperature near the solid solution temperature or higher, the forging temperature is close to the melting point of the material to be processed, so that work cracking is likely to occur due to partial melting or the like. In addition, in a material in which the solid solution temperature of the γ′ phase is high as described above, when hot forging is performed at the solid solution temperature or higher, the γ′ phase that suppresses grain boundary migration and contributes to the refinement of crystal grains disappears. , The grain size of the γ phase becomes coarse, and the tensile strength and fatigue strength during use of the product decrease.

In view of the above circumstances, an object of the present invention is to achieve both excellent workability in the manufacturing process of a precipitation-strengthened Ni-based alloy member containing a large amount of γ′ phase and excellent high-temperature strength of the Ni-based alloy member. It is an object of the present invention to provide a method for producing a Ni-based alloy softening material and a method for producing a Ni-based alloy member that can be performed.

The present invention, in order to achieve the above objects, includes a softening treatment step of softening a Ni-based alloy material in a temperature region below the solid solution temperature of the γ'phase to improve workability, and the softening treatment step is a Ni-based alloy. The first step of hot forging the material at a temperature below the solid solution temperature of the γ'phase and at a temperature above the temperature at which the recrystallization of the γ phase proceeds rapidly to precipitate the unmatched γ'phase, and the solid solution of the γ'phase less than the temperature and then slowly cooled at a cooling rate of completion from the temperature above the temperature below 100 ° C. / h hot forging grown inconsistency γ'-phase, a second step of increasing the amount of non-alignment γ'-phase look including bets, the composition of the Ni-base alloy material, in mass%, 10% or more and 25% or less of Cr, 30% or less of Co, the sum of Ti and Nb and Ta 3% to 9% or less, 1% or more 1. Al less than 6%, Fe less than 10%, Mo less than 10%, W less than 8%, B less than 0.03%, C less than 0.1%, Zr less than 0.08%, 2. Provided is a method for producing a Ni-based alloy softening material, which contains 0% or less Hf and 5.0% or less Re, and the balance is Ni and inevitable impurities .

The present invention also includes a processing step of processing the Ni-based alloy softening material obtained by the method for manufacturing the Ni-based alloy softening material into a desired shape, and a mother phase of the Ni-based alloy material after the processing step. Solution treatment for solid solution of incoherent γ'phase precipitated on grain boundaries of γ-phase crystal grains and aging treatment for reprecipitation of coherent γ'phase to obtain Ni-based alloy members- An aging treatment step is provided, and a method for manufacturing a Ni-based alloy member is provided.

ADVANTAGE OF THE INVENTION According to this invention, the Ni base alloy softening which can make the outstanding workability in the manufacturing process of the precipitation strengthening type Ni base alloy member containing a large amount of (gamma)' phase, and the excellent high temperature strength of a Ni base alloy member compatible. It is possible to provide a method for manufacturing a material and a method for manufacturing a Ni-based alloy member.

It is a flow figure showing one embodiment of the manufacturing method of the Ni basis alloy member concerning the present invention. It is a figure which shows typically the temperature profile and crystal structure of the softening process process of FIG. It is a schematic diagram which shows the matching interface of (gamma) phase and (gamma)' phase. It is a schematic diagram which shows the non-coherent interface of (gamma) phase and (gamma)' phase. It is a figure which shows typically the temperature profile and crystal structure of the solution-aging treatment process of FIG. It is a schematic diagram which shows an example of the Ni-based alloy raw material for forging manufactured using the manufacturing method of the Ni-based alloy which concerns on this invention. It is a schematic diagram which shows an example of the Ni-based alloy thin plate manufactured by the manufacturing method of the Ni-based alloy member which concerns on this invention. It is a schematic diagram which shows an example of the Ni base alloy structure obtained by friction-stir welding the Ni base alloy member manufactured by the manufacturing method of the Ni base alloy member which concerns on this invention. It is a schematic diagram which shows an example of the boiler tube characterized by using the Ni-based alloy structure which concerns on this invention. It is a schematic diagram which shows an example of the combustor liner characterized by using the Ni-based alloy structure which concerns on this invention. It is a schematic diagram which shows an example of the gas turbine moving blade characterized by using the Ni base alloy structure which concerns on this invention. It is a schematic diagram which shows an example of the gas turbine disk characterized by using the Ni base alloy structure which concerns on this invention. It is a schematic diagram explaining the basic idea of the manufacturing method of the Ni-based alloy member which concerns on this invention.

Hereinafter, embodiments according to the present invention will be described in detail. However, the present invention is not limited to the embodiments described here, and various combinations and improvements can be made without departing from the scope of the invention.

[Basic idea of the present invention]
The inventors diligently studied a method for manufacturing a Ni-based alloy softening material and a Ni-based alloy member that can achieve the above object. As a result, paying attention to the fact that the γ'phase precipitated in a non-coherent manner with respect to the matrix γ phase (hereinafter referred to as "non-coherent γ'phase") does not contribute to strengthening, and the amount of the non-coherent γ'phase at the forging is Is increased to decrease the precipitation amount of the γ'phase (hereinafter referred to as the matched γ'phase) which is precipitated in a consistent manner with respect to the γ phase, and at the same time mainly consists of the γ phase and the unmatched γ'phase. It has been found that the workability during forging can be significantly improved by using a fine two-phase structure. Furthermore, after processing into the desired shape in this state, solution-aging treatment is performed to reduce the non-coherent γ′ phase and precipitate the coherent γ′ phase again, which is excellent for product use. It was found that high temperature strength can be realized. The present invention is based on this finding.

Hereinafter, the basic idea of the present invention will be described in more detail. FIG. 6 is a schematic diagram for explaining the basic idea of the method for manufacturing a Ni-based alloy member according to the present invention. In FIG. 6, the manufacturing process of the Ni-based alloy member according to the present invention will be described focusing on the material structure.

As shown in (I) of FIG. 6, the Ni-based alloy after the casting step or after the forging step includes a γ phase which is a mother phase and a matched γ′ phase which is precipitated in a consistent manner with respect to the γ phase. This Ni-based alloy is hot forged at a temperature below the solid solution temperature of the γ'phase and above the temperature at which recrystallization of the γ phase rapidly proceeds, and as shown in (II), precipitates the unmatched γ'phase. (First softening process step). Next, the temperature is lower than the solid solution temperature of the γ′ phase and is equal to or higher than the completion temperature of the hot forging, and the unmatched γ′ phase is grown as shown in (III) to obtain the unmatched γ′ phase. Increase the amount (second softening process step). At this time, the incoherent γ'phase does not contribute to strengthening, and since a fine two-phase structure mainly composed of the γ phase and the incoherent γ'phase is formed, the toughness is also high, which makes it very easy to process. It is in a state (softened state). In this softened state, a processing step of forming the Ni-based alloy into a desired shape is performed at a temperature lower than the solid solution temperature of the γ'phase. After the above processing steps, solution treatment is performed to re-dissolve the unmatched γ′ phase, and then aging treatment is performed to precipitate the matched γ′ phase (solution-aging treatment). Process). At this time, a large amount of the matched γ′ phase contributing to strengthening is precipitated, so that it is in a high strength state.

As described above, the present invention improves the workability by eliminating the strengthening function of the γ'phase, rather than processing in the state where the γ'phase is reduced or eliminated. According to the above manufacturing process, it is possible to obtain a Ni-based alloy member having a high temperature strength equal to or higher than that of the conventional one when used (when the product is completed), by softening the material at the time of processing and greatly improving the workability. It is possible to obtain a Ni-based alloy softening material and a Ni-based alloy member that can be obtained.

The “matched γ′ phase” and the “non-matched γ′ phase” in the present invention will be described. FIG. 3A is a schematic diagram showing a matching interface between the γ phase and the γ′ phase, and FIG. 3B is a schematic diagram showing a non-matching interface between the γ phase and the γ′ phase. As shown in FIG. 3A, when the atoms 7 forming the γ phase and the atoms 8 forming the γ′ phase form a matching interface 9 (lattice matching), this γ′ phase is referred to as a “matching γ′ phase”. .. Further, as shown in FIG. 3B, when the atoms 7 forming the γ phase and the atoms 8 forming the γ′ phase form a non-matching interface 10 (lattice mismatch), this γ′ phase is referred to as “non-matching γ”. This is referred to as "phase".

[Manufacturing method of Ni-based alloy softening material and Ni-based alloy member]
Next, a method for manufacturing a Ni-based alloy softening material and a method for manufacturing a Ni-based alloy member according to the present invention will be described. FIG. 1 is a flow chart showing an embodiment of a method for manufacturing a Ni-based alloy member according to the present invention. As shown in FIG. 1, the method for manufacturing a Ni-based alloy member according to the present invention is a raw material preparation step for obtaining a Ni-based cast alloy as a raw material or a Ni-based forged alloy obtained by forging after casting. (S1), a softening treatment step (S2) for softening the Ni-based alloy material to obtain a Ni-based alloy softening material, a processing step (S4) for processing the Ni-based alloy softening material into a desired shape, and a processing step. And a solution treatment-aging treatment step (S5) for obtaining a Ni-based alloy member by solution treatment and aging treatment. The softening treatment step (S2) includes a first softening treatment step (S21) and a second softening treatment step (S22). Further, the processing step (S4) may repeatedly include the softening processing step (S2) and a plurality of plastic working methods until the final shape is obtained, and is not limited to the final processing.

In the present invention, the material obtained by performing the material preparing step (S1) is referred to as “Ni-based alloy material”, and the material obtained by performing the softening treatment step (S2) is referred to as “Ni-based alloy softening material”. The one obtained by performing the solution treatment-aging treatment step (S5) is referred to as "Ni-based alloy member". In addition, after joining the Ni-based alloy softening material using friction stir welding or the like, the solution obtained by performing the solution treatment-aging treatment step (S5) is referred to as "Ni-based alloy structure (Ni-based alloy welded structure)". ". Further, in the present invention, the “Ni-based alloy” includes the above-mentioned “Ni-based alloy material” and “Ni-based alloy softening material”, and the processing step (S4) is performed once for the “Ni-based alloy softening material”. Or, it includes those applied multiple times.

Hereinafter, the steps S1 to S5 will be described in detail.

(S1: Material preparation process)
The method for preparing the Ni-based alloy material is not particularly limited, and a conventional method can be used. Specifically, using a ready-made alloy after casting or an alloy after forging, the steps after the softening treatment step described below are performed. As the composition of the Ni-based alloy material, one having a solid solution temperature of γ′ phase of 1050° C. or higher is used. The reason for this will be described later in detail.

(S2: Softening process step)
A method for manufacturing a Ni-based alloy softening material of the present invention for improving workability during a working step includes a first softening treatment step (S21) of hot forging at a temperature lower than a solution temperature of a γ'phase, and a first softening treatment step. And a second step (S22) of gradually cooling the Ni-based alloy after the softening treatment step from a temperature lower than the solid solution temperature of the γ'phase and equal to or higher than the hot forging completion temperature to increase the unmatched γ'phase. Including.

(S21: First softening process step)
FIG. 2 is a diagram schematically showing a temperature profile and a material structure in the softening treatment step of FIG. As described above, in the first softening treatment step, the Ni-based alloy material is hot forged at a temperature (T ₁ ) lower than the solid solution temperature of the γ'phase. When cooled after this hot forging, as shown in (I) of FIG. 2, the incoherent γ′ phase (reference numeral 6) is precipitated on the grain boundaries of the γ phase (reference numeral 4). The precipitate indicated by reference numeral 5 is a coherent γ'phase precipitated in the γ phase grains during cooling after the first softening treatment step. In the present invention, “on the grain boundary of the γ phase” means “the boundary between adjacent γ crystal grains”.

As described above, the strengthening mechanism of the precipitation-strengthened Ni-based alloy is that the γ phase and the γ′ phase contribute to strengthening by forming a coherent interface (reference numeral 9 in FIG. 3A). The sign 10) of 3B does not contribute to the strengthening. That is, by increasing the amount of the unmatched γ′ phase and decreasing the amount of the matched γ′ phase, it becomes possible to secure excellent workability during the working process. Therefore, in order to obtain the effect of the present invention, it is essential to precipitate the incoherent γ′ phase by hot forging in the first softening treatment step, and therefore, below the solid solution temperature of the γ′ phase, In addition, the Ni-based alloy must be capable of hot forging at a temperature above the temperature at which γ-phase recrystallization rapidly proceeds. Therefore, the solution temperature of the γ'phase of the Ni-based alloy material according to the present invention is most preferably 1050°C or higher. Although the effect of the present invention can be obtained even when the solid solution temperature of the γ'phase is 1000 to 1050°C, the unmatched γ'phase is hard to precipitate at 1000°C or lower, and the unmatched γ'phase can be precipitated at 950°C or lower. Therefore, the effect of the present invention cannot be obtained. Further, when the solid solution temperature of the γ'phase approaches the melting point of the Ni-based alloy material, cracking occurs during processing due to partial melting or the like. Therefore, the solid solution temperature of the γ'phase is preferably less than 1250°C.

The forging temperature T _{1 in} the first softening treatment step needs to be equal to or higher than the temperature at which the recrystallization of the γ phase rapidly proceeds as described above. More specifically, 1000° C. or higher is preferable, and 1050° C. or higher is more preferable. If T ₁ is less than 950° C., the incoherent γ′ phase cannot be precipitated and the effect of the present invention cannot be obtained. The upper limit temperature of T ₁ is lower than the solid solution temperature of the γ'phase as described above.

(S22: Second softening process step)
In the second softening treatment step, the temperature was raised to a temperature (T ₃ ) that was lower than the solid solution temperature of the γ′ phase and was equal to or higher than the hot forging completion temperature in the above-mentioned first softening treatment step, and precipitated in the γ phase. By making the matched γ′ phase a solid solution, a two-phase structure mainly composed of the γ phase and the unmatched γ′ phase is formed (FIG. 2(II)), and then gradually cooled to the temperature T ₂ to obtain the unmatched γ′ phase. By growing the phase, it is possible to reduce the matched γ′ phase which is mainly precipitated in the cooling process from the temperature at the end of slow cooling to room temperature, so that the workability can be improved (FIG. 2 (III)). At this time, it can slow cooling rate _(T A _{/ t)} is growing slowly that non-aligned γ'-phase, preferably not more than 50 ° C. / h, more preferably at most 10 ° C. / h. If it is faster than 100° C./h, the non-coherent γ′ phase cannot be sufficiently grown, and the coherent γ′ phase is precipitated during the cooling process, and the effect of the present invention cannot be obtained. Here, the hot forging completion temperature refers to the temperature at which the material to be forged is held at the final stage of forging.

The gradual cooling start temperature T ₃ of the second softening treatment step is lower than the solid solution temperature of the γ′ phase and the first softening temperature in order to have a two-phase structure mainly composed of the γ phase and the inconsistent γ′ phase. It is preferable to carry out at a temperature equal to or higher than the hot forging completion temperature in the treatment step. This is because when the temperature is lower than the forging temperature T1 in the first softening treatment step, the matched γ′ phase remains in the γ phase grains, and the unmatched γ′ phase disappears at the solid solution temperature of the γ′ phase or higher. Because it will be. However, the effect of the present invention can be obtained even when the slow cooling start temperature T3 is 100° C. lower than the hot forging completion temperature in the first softening treatment step described above.

In the second softening treatment step, as the unmatched γ'phase is increased as described above, the workability can be improved, so that the amount of the unmatched γ'phase is preferably 20% by volume or more, It is preferably at least 30% by volume. Here, the ratio (volume %) of the content of the incoherent γ′ phase is the ratio (absolute amount) to the entire alloy containing the parent phase and other precipitates. Regarding the amount of the non-matching γ'phase for obtaining the effect of the present invention, it is determined by the relative amount to which the ratio of the non-matching γ'phase can be increased with respect to the total amount of precipitable γ'phases. It is preferably 50% by volume or more of the total γ'phase amount, and more preferably 60% by volume or more of the total γ'phase amount. Further, the temperature (T ₂ ) at the end of the gradual cooling needs to be lowered to a temperature at which the amount of the unmatched γ′ phase is precipitated, and is preferably 1000° C. or lower, more preferably 900° C. or lower. Further, the cooling method from the slow cooling end temperature T ₂ to room temperature is better as the cooling rate is faster in order to suppress precipitation of the matched γ′ phase during cooling, and air cooling is preferable. More preferably, it is water cooled.

In order to obtain good workability, the Vickers hardness (Hv) at room temperature is preferably 400 or less, more preferably 370 or less, and the 0.2% proof stress at 900° C. is preferably 300 MPa or less, more preferably 250 MPa or less. 200 MPa is the most preferable.

By performing the second softening treatment step, the Ni-based alloy softening material obtained after the second softening treatment step has a Vickers hardness (Hv) at room temperature of 400 or less and a 0.2% proof stress at 900°C. It is possible to obtain a value of 250 MPa or less. By the above-mentioned softening treatment step, the lower limit of the processing temperature, which is a problem during hot working, can be lowered, and in the processing step described later, processing can be performed at a temperature lower than the solid solution temperature of the γ'phase by 100°C or more.

In FIG. 2, cooling is performed after the first softening treatment step and the second softening treatment step is performed, but the second softening treatment step may be performed without cooling after the first softening treatment step.

(S4: processing step)
The Ni-based softened material that has been softened in the softening process described above is processed. The processing method at this time is not particularly limited and can be applied to not only forging processing but also other plastic processing methods and joining methods, and repeated processing can be performed by combining with the above-mentioned softening treatment. Specifically, press work, rolling work, drawing work, extrusion work, cutting work, friction stir welding and the like can be applied. Furthermore, by combining the above-mentioned softening process and plastic working method, etc., for a boiler tube and a combustor liner using the high-strength Ni-based alloy according to the present invention, and for a thermal power plant such as a gas turbine rotor blade or a disk. It is also possible to provide members. Specific examples of the Ni-based alloy member or the Ni-based alloy structure that can be provided by the present invention will be described later in detail.

(S5: solution treatment-aging treatment process)
FIG. 4 is a diagram schematically showing a temperature profile and a material structure in the solution treatment-aging treatment process of FIG. After processing into a predetermined shape, it is possible to recover the high-temperature strength by subjecting the unmatched γ'phase to a solid solution and re-precipitating the matched γ'phase to recover high-temperature strength. It is desirable to deposit 30% by volume or more at 700°C.

In the present invention, the conditions of solution treatment and aging treatment are not particularly limited, and commonly used conditions can be applied.

(Composition of Ni-based alloy member)
Next, the composition of the Ni-based alloy material according to the present invention will be described.

The Ni-based alloy material according to the present invention contains, in mass%, 10% or more and 25% or less of Cr, 0% or more and 30% or less of Co, and the sum of Ti, Nb, and Ta is 3% or more and 9% or less, 1% or more. 1. Al less than 6%, Fe less than 10%, Mo less than 10%, W less than 8%, B less than 0.03%, C less than 0.1%, Zr less than 0.08%, 2. It is preferable to contain 0% or less of Hf and 5.0% or less of Re, with the balance being Ni and inevitable impurities.

One of the more preferable forms is, in mass %, 12.5% or more and 14.5% or less Cr, 24% or more and 26% or less Co, 5.5% or more and 7% or less Ti, and 1.5% or more. 3% or less of Al, 3.5% or less of Mo, 2% or less of W, 0.03% or less of B, 0.1% or less of C and 0.08% or less of Zr are contained, and the balance is Ni. And unavoidable impurities.

Further, one of other more preferable forms is, in mass %, 15% or more and 17% or less of Cr, 14% or more and 16% or less of Co, 4% or more and 6% or less of Ti, and 1.5% or more of 3. 5% or less Al, 0.5% or less Fe, 4% or less Mo, 2% or less W, 0.03% or less B, 0.1% or less C and 0.08% or less Zr. It is contained and the balance is Ni and inevitable impurities.

In addition, one of other more preferable forms is, in mass%, 15% or more and 17% or less of Cr, 7.5% or more and 9.5% or less of Co, 2.5% or more and 4.5% or less of Ti, The sum of Nb and Ta is 0.5% or more and 2.5% or less, 1.5% or more and 3.5% or less Al, 3% or more and 5% or less Fe, 4% or less Mo, and 4% or less W. , B of 0.03% or less, C of 0.1% or less and Zr of 0.08% or less, and the balance being Ni and inevitable impurities.

Below, the ratio of addition elements and the basis for selection are shown.

Cr is an element that improves oxidation resistance and high temperature corrosion resistance. In order to apply it to a high temperature member, addition of at least 10 mass% or more is essential. However, excessive addition promotes the formation of a harmful phase, so the content is made 25 mass% or less.

Co is a solid solution strengthening element that has the effect of strengthening the parent phase by addition. Further, it also has the effect of lowering the solid solution temperature of the γ'phase, and improves the high temperature ductility. Excessive addition promotes the formation of a harmful phase, so the content is made 30 mass% or less.

Al is an essential element that forms a γ′ phase that is a precipitation strengthening phase. It also has the effect of improving oxidation resistance. The addition amount is adjusted depending on the target precipitation amount of the γ'phase, but excessive addition deteriorates the workability because it raises the solid solution temperature of the γ'phase. Therefore, the amount is 1% by mass or more and 6% by mass or less.

Ti, Nb, and Ta are also important elements that stabilize the γ'phase like Al. However, excessive addition causes the formation of other intermetallic compounds containing a harmful phase, or causes the deterioration of workability due to an increase in the solid solution temperature of the γ'phase. Therefore, the sum of Ti, Nb, and Ta is set to 3% by mass or more and 9% by mass or less.

Fe can be replaced by expensive elements such as Co and Ni, reducing the cost of the alloy. However, excessive addition promotes the formation of a harmful phase, so the content is made 10 mass% or less.

Mo and W are important elements that form a solid solution in the matrix and strengthen the matrix. However, since these are elements having a high density, excessive addition causes an increase in density. In addition, the ductility also decreases, and the workability also deteriorates. Therefore, Mo is 10 mass% or less and W is 8 mass% or less.

C, B, and Zr are effective elements for strengthening the crystal grain boundaries and improving high temperature ductility and creep strength. However, since excessive addition deteriorates workability, C is 0.1 mass% or less, B is 0.03 mass% or less, and Zr is 0.08 mass% or less.

Hf is an element effective in improving the oxidation resistance. However, since excessive addition promotes the formation of a harmful phase, Hf is preferably 2.0% or less.

Re is an element that forms a solid solution in the matrix and strengthens the matrix. Further, it also has an effect of improving corrosion resistance. However, excessive addition promotes the formation of harmful phases. Moreover, since Re is an expensive element, an increase in the amount of addition causes an increase in the cost of the alloy. Therefore, Re is preferably 5.0 mass% or less.

[Example]
Examples of the present invention will be described below.

[Evaluation of hot workability]
Table 1 shows the composition of the test material.

With respect to the Ni-based alloy materials having the compositions shown in Table 1, test materials were produced under different manufacturing conditions, and the workability and high temperature strength of each test material were evaluated. In the production of each test material, 10 kg of each was melted by the vacuum induction heating melting method, subjected to homogenization treatment, and then hot forged at 1150 to 1250° C. to produce a round bar of φ15 mm, and the above-mentioned was performed. The first softening treatment step and the second softening treatment step were performed. Table 2 shows the conditions of the first softening treatment step. Further, the solid solution temperature of the γ'phase and the presence or absence of the γ'phase after the first softening treatment step were evaluated. The solid solution temperature of the γ'phase was calculated by a simulation based on thermodynamic calculation. Further, the presence or absence of the γ'phase was evaluated by observing the structure of the test material with an electron microscope. The results are also shown in Table 2.

In Table 2, regarding the temperature T ₁ (hot forging temperature) of the first softening treatment step, if a large crack occurs during hot forging in the above-described sample material production, the latter softening treatment step is not performed. It is described as "-", and when the hot forging of the first softening treatment step is not carried out, it is described as "not carried out", and when no crack is confirmed after the hot forging, it is The temperature is indicated.

As shown in Table 2, in Comparative Examples 1 and 2, large cracks occurred during hot forging in the production of the test material. The presence of the incoherent γ'phase was confirmed by observing the structure after hot forging, and therefore the effect of the present invention can be obtained, but most preferably, the solid solution temperature of the γ'phase is 1250°C or lower. Comparative Example 3 is a state immediately after the preparation of the test material and is not subjected to the hot forging in the softening treatment first step, but the hot forging temperature during the preparation of the test material is less than the solid solution temperature of the γ′ phase. Therefore, there is a non-matching γ′ phase. Further, in Comparative Example 4, since the hot forging was performed at the solid solution temperature of the γ'phase or higher, the non-matching γ'phase did not precipitate after the forging was completed. On the other hand, in Comparative Example 5, the hot forging was carried out at the solid solution temperature of the γ'phase or higher, but the unmatched γ'phase was precipitated due to the temperature decrease during the forging. In Comparative Examples 6 and 8 and Examples 1 to 9, since hot forging was performed at a temperature lower than the solid solution temperature of the γ'phase in any of the test materials, the γ phase of the softening treatment after the first step was finished. The existence of a non-coherent γ'phase was confirmed on the grain boundaries. In Comparative Example 7, the hot forging is performed at a temperature lower than the solid solution temperature of the γ′ phase, but since the forging is performed at a temperature lower than the temperature at which recrystallization of the γ phase rapidly proceeds (1000° C. or higher), No unmatched γ'phase was precipitated.

From the above results, the forging temperature T ₁ in the first softening treatment step for precipitating the incoherent γ′ phase is less than the solid solution temperature of the γ′ phase and the temperature at which the recrystallization of the γ phase rapidly proceeds. Has been shown to be preferred. More specifically, forging at 1000° C. or higher is preferable, and at 950° C. or lower, the inconsistent γ′ phase cannot be precipitated. Therefore, the solid solution temperature of the γ'phase needs to be higher than the temperature at which recrystallization rapidly proceeds, and is preferably 1050°C or higher.

Next, the test material is gradually cooled from the hot forging temperature T ₁ of each first softening process to the slow cooling end temperature T ₂ at a cooling rate T _A (° C./h), and then cooled to room temperature by water cooling. I did it later. Table 3 shows the conditions of the second softening treatment step. In addition, the amount of unmatched γ'phase and Vickers hardness at room temperature after cooling were evaluated. As for the amount of unmatched γ′ phase, the content ratio of unmatched γ′ phase was determined by observing the structure after casting, after hot forging, or after softening treatment. Specifically, the area ratio of the non-matching γ'phase was calculated from the observation photograph obtained with the electron microscope, and the content ratio of the non-matching γ'phase was calculated by converting the area ratio into the volume ratio. Further, in order to evaluate the hot workability after the softening treatment, each of the test materials was hot forged at 950° C., there were no problems with “○”, and those with slight cracks showed “△”. "For those with large cracks that were difficult to forge, we evaluated it as "x".

As shown in Table 3, in each of Examples 1 to 9, the amount of the non-matching γ′ phase after the softening treatment step exceeded 20% by volume in all the test materials, and the hardness also satisfied 400 Hv or less, and 950° C. Since hot forging could be performed without problems, improvement in workability was confirmed.

On the other hand, in Comparative Examples 3 to 6 in which the amount of the unmatched γ′ phase was less than 20% by volume and the hardness was more than 400 Hv, cracks were confirmed during or after forging. In Comparative Examples 5 and 6, the unmatched γ'phase was present after the softening treatment step, but the amount was not sufficient to suppress the amount of precipitation of the matched γ'phase during forging. In Comparative Example 7, the inconsistent γ′ phase was not precipitated, but the hardness was less than 400 Hv, and hot forging at 950° C. could be performed. However, the solid solution temperature of the γ′ phase of Comparative Example 7 is lower than 950° C., and the equilibrium precipitation amount of the γ′ phase at 700° C. calculated by a simulation based on thermodynamic calculation (stable in the thermodynamic equilibrium state is stable). The amount of precipitation of the γ'phase) is 22% by volume, which does not apply to the high-strength Ni-based alloy that is the target of the present invention. Therefore, in order to obtain the effect of the present invention sufficiently, it was confirmed that the amount of the unmatched γ′ phase after the softening treatment step was required to be 20% by volume or more.

Further, comparing Examples 1 and 2 or Examples 3 and 4, when the equilibrium precipitation amount of the equilibrium γ′ phase at 700° C. is the same and the annealing temperature range in the second softening treatment step is the same, The slower the cooling rate, the more the amount of unmatched γ'phase increases, and the hardness can be lowered. It is considered that this is because the larger amount of the unmatched γ′ phase was able to reduce the amount of the matched γ′ phase that was precipitated mainly during the cooling from the temperature at the end of slow cooling to room temperature. On the other hand, in Comparative Example 8, the incoherent γ′ phase is precipitated after the first softening treatment step and the second softening treatment step is performed, but the slow cooling rate is fast and the incoherent γ′ phase grows. Therefore, the effect of the present invention could not be sufficiently obtained.

From the above results, the slow cooling rate in the second step of softening treatment is preferably slower than 50° C./h, more preferably 10° C./h or less, and if faster than 100° C./h, the effect of the present invention is obtained. It was shown that it could not be obtained.

In each of Examples 1 to 9, the 0.2% proof stress at 900° C. is 250 MPa or less, and as an example, the 0.2% proof stress at 900° C. is 200 MPa in Example 7, which is an extremely excellent hot workability. showed that.

Therefore, by applying the present invention before hot forging of the Ni-based alloy, the forging temperature can be lowered by 100° C. or more than the conventional forging temperature, and the hot forging can be easily performed. In addition, if the above-mentioned excellent hot forgeability is seen, the processing step of the softened Ni-based alloy according to the present invention is not limited to hot forging, and pressing, rolling, drawing and extruding are performed. Needless to say, it exhibits excellent workability even in processing and cutting.

In Examples 1 to 9, by performing the solution aging treatment after hot forging at 950° C., the unmatched γ′ phase as shown in FIG. It has a large amount of precipitated structure, and the amount of the matched γ′ phase at 700° C. is 30% by volume or more. As an example, in Example 7, the tensile strength at 500° C. is 1518 MPa and the conventional high strength. It showed the same strength as the Ni-based alloy.

From the above results, it was shown that the hot workability of the high-strength Ni-based alloy, which is difficult to work, can be significantly improved by applying the Ni-based alloy member manufacturing method according to the present invention.

An example of a Ni-based alloy member manufactured by using the method for manufacturing a Ni-based alloy member according to the present invention is shown below.

FIG. 5A is a schematic view showing an example of a Ni-based alloy material for forging manufactured by using the method for manufacturing a Ni-based alloy according to the present invention. This Ni-based alloy material for forging is obtained after the above-described softening treatment step S2. Conventionally, in order to form a structure from a high-strength Ni-based casting alloy to a structure, in order to reduce the amount of the γ'phase which is a strengthening phase and reduce the strength, the final processing is performed in a high temperature range of 1000 to 1250°C. There was a need. By using the Ni-based alloy material 11 for forging produced by using the method for producing a Ni-based alloy according to the present invention, it becomes possible to exhibit extremely high formability during processing.

By using the above Ni-based alloy material 11 for forging, it becomes possible to manufacture a thin plate 12 (thickness of 3 mm or less) using a high-strength Ni-based alloy as shown in FIG. 5B by cold or hot rolling. ..

Further, in the friction stir welding, the temperature of the member during processing rises to about 900° C. Therefore, by applying the present invention, the 0.2% proof stress at the processing temperature can be set to 250 MPa or less, and thus the friction stir welding is also possible. Becomes This makes it possible to obtain a Ni-based alloy structure joined by friction stir welding as shown in FIG. 5C.

Further, by using the Ni-based alloy according to the present invention having high workability, it is possible to easily manufacture the boiler tube 15 as shown in FIG. 5D.

Further, since the thin plate 12 described above can be easily bent, by combining the friction stir welding, a combustor liner 16 having more excellent reliability and improved service temperature as shown in FIG. 5E can be obtained. It becomes possible to manufacture.

Further, since it is possible to easily perform die forging by using the Ni-based alloy material 11 for forging described above, by combining cutting work, the gas turbine dynamics excellent in high temperature strength as shown in FIG. 5F can be obtained. The wing 17 can be manufactured. In addition, it becomes possible to realize a high-efficiency thermal power plant using these gas turbine members.

Moreover, by using the Ni-based alloy material 11 for forging, it becomes possible to easily manufacture the gas turbine disk 18 as shown in FIG. 5G.

As described above, according to the present invention, both excellent workability in the production process of a precipitation-strengthened Ni-based alloy member containing a large amount of γ'phase and excellent high-temperature strength of the Ni-based alloy member are achieved. It was proved that a Ni-based alloy softening material and a method for manufacturing a Ni-based alloy member can be provided. Further, it has been proved that the Ni-based alloy softening material manufacturing method according to the present invention can be used to easily manufacture Ni-based alloy members, Ni-based alloy parts and Ni-based alloy structures having various shapes. It was

It should be noted that the above-described embodiments are specifically described to help understanding of the present invention, and the present invention is not limited to having all the configurations described. For example, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Furthermore, a part of the configuration of each embodiment can be deleted, replaced with another configuration, or added with another configuration.

4... γ phase, 5... Matched γ'phase, 6... Non-matched γ'phase, 7... Atoms that make up the γ phase, 8... Atoms that make up the γ'phase, 9... Matched between the γ phase and the γ'phase Interface, 10... Incoherent interface between γ phase and γ'phase, 11... Ni-based alloy material for forging manufactured by using the present invention, 12... Thin plate manufactured by using the present invention, 13... Friction stir welding Tool, 14... Joined part by friction stir welding, 15... Boiler tube produced by using the present invention, 16... Combustor liner produced by using the present invention, 17... Gas produced by using the present invention Turbine rear stage rotor blade, 18... Gas turbine disk manufactured by using the present invention.

Claims (4)

Including a softening treatment step of softening the Ni-based alloy material in a temperature range below the solid solution temperature of the γ'phase to improve workability,
In the softening treatment step, the Ni-based alloy material is hot forged at a temperature lower than the solid solution temperature of the γ′ phase and at a temperature equal to or higher than a temperature at which recrystallization of the γ phase rapidly proceeds to precipitate a non-matching γ′ phase . a first step, gradual cooling to grow a non-aligned γ'-phase in the γ'-phase is less than solid solution temperature and the hot 100 ° C. from completion temperature above the temperature of the forged / h following cooling rate, non a second step of increasing the amount of matching γ'-phase seen including,
The composition of the Ni-based alloy material is, in mass %, 10% or more and 25% or less of Cr, 30% or less of Co, and the sum of Ti, Nb, and Ta is 3% or more and 9% or less, 1% or more and 6% or less. Al, 10% or less Fe, 10% or less Mo, 8% or less W, 0.03% or less B, 0.1% or less C, 0.08% or less Zr, 2.0% or less A method for producing a Ni-based alloy softening material, which contains Hf and Re of 5.0% or less, and the balance is Ni and inevitable impurities . The Ni-based alloy softening material obtained by the softening treatment step has 20 volumes of unmatched γ′-phase crystal grains precipitated on the grain boundaries of the γ-phase crystal grains that are the parent phase of the Ni-based alloy material. % Or more, the method for manufacturing a Ni-based alloy softening material according to claim 1. The method for producing a Ni-based alloy softening material according to claim 1 or 2 , wherein the cooling rate of the slow cooling is 50°C/h or less. A processing step of processing the Ni-based alloy softening material obtained by the method for manufacturing the Ni-based alloy softening material according to any one of claims 1 to 3 into a desired shape, and the Ni after the processing step. The Ni-base alloy is subjected to solution treatment to form a solid solution of the incoherent γ'phase precipitated on the grain boundaries of the crystal grains of the γ-phase, which is the parent phase of the base alloy material, and aging treatment to reprecipitate the coherent γ'phase. A method for producing a Ni-based alloy member, which comprises a solution treatment for obtaining the member and an aging treatment step.

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