JPS6221856B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a Ni-based alloy that has particularly low deformation resistance during superplastic forging. Superplastic forging is a known method for forming large, complex-shaped products such as gas turbine disks using Ni-based superalloys. This utilizes the phenomenon of superplasticity, in which a metal material undergoes plastic deformation of several hundred percent or more with a small force, just like clay. Prior Art As conventional Ni-based alloys for superplastic forging, for example, Rene 95 (manufactured by GE) and Merl 76 (manufactured by Pratt & Whittney) are known.
However, as shown as comparative alloys in the Examples, these alloys also had a problem in that their crystal grain sizes were large and their deformation resistance was particularly large during superplastic forging. If the deformation resistance is too large, it will be difficult to mold large products or complex-shaped products, and even if molding is possible, a large press will be required, which is unfavorable from the viewpoint of productivity. It is known that making the crystal grains finer by extrusion is effective in reducing this superplastic deformation resistance, but in the existing Ni-based alloys, making the crystal grains smaller is effective. There was also a limit. Purpose of the Invention The present invention was made to solve the problems of existing Ni-based alloys for superplastic forging, and its purpose is to create a Ni-based alloy that has easy grain refinement and low superplastic deformation resistance. It is on offer. Structure of the Invention In order to achieve the above object, the present inventor first conducted studies to find the optimum alloy composition for refining crystal grains. What is important here is that no cracks occur during extrusion processing to refine the crystal grains. If cracks occur, it is impossible to form the material into a gas turbine disk or the like, even though the crystal grains are fine and the deformation resistance is low. As a result of studies from this viewpoint, the present inventors have found that an alloy having the composition described below is an optimal alloy that can refine crystal grains without causing cracks during extrusion processing. Furthermore, the present invention was completed by discovering an optimal method for refining crystal grains. The Ni-based alloy of the present invention has, in weight%, C0.02~0.12%, Co5~12%, Cr7~
9%, W10~14%, Al4.5~5.5%, Ti0.1~1.5
%, Ta3~5%, Hf0.3~1.3%, B0.005~0.018
%, Zr0.01-0.15%, and the balance is in a superplastic forging Ni-based alloy consisting essentially of Ni. The manufacturing method of the alloy is as follows: (1) In weight%, C0.02~0.12%, Co5~12%, Cr7
~9%, W10~14%, Al4.5~5.5%, Ti0.1~
1.5%, Ta3~5%, Hf0.3~1.3%, 0.005~
Put a Ni-based alloy powder containing 0.018% and 0.01 to 0.15% of Zr and the remainder substantially of Ni into a container,
A method for producing a Ni-based alloy for superplastic forging, characterized by extruding this at 1050-1225°C and an extrusion ratio of 4-15. (2) In weight%, C0.02~0.12%, Co5~12%, Cr7
~9%, W10~14%, Al4.5~5.5%, Ti0.1~
1.5%, Ta3~5%, Hf0.3~1.3%, B0.005~
Put a Ni-based alloy powder containing 0.018% and 0.01 to 0.15% of Zr and the remainder essentially of Ni into a container,
After solidifying by high temperature and high pressure treatment for 30 to 200 minutes at 1025 to 1250℃ and 800 to 2000 atm, 1050 to 1225℃,
A method for producing a Ni-based alloy for superplastic forging, characterized by extruding at an extrusion ratio of 4 to 15. The effects of the constituent elements of the Ni-based alloy of the present invention and the reasons for limiting their contents are as follows. C acts to strengthen grain boundaries and suppress cracks at grain boundaries during extrusion processing. To obtain this effect, the amount of C must be 0.02% by weight or more (hereinafter simply referred to as %). However, if the amount exceeds 0.12%, the entire alloy becomes brittle and cracks are likely to occur during extrusion processing, making it impossible to obtain a fine grain structure, so the amount of C must be between 0.02 and 0.12%. . Co increases the ductility of the alloy and suppresses cracking during extrusion processing. To get this effect 5
% or more is required. However, if the amount exceeds 12%, harmful precipitates are generated and cracks are likely to occur during extrusion processing, so the amount of Co must be 5 to 12%. Cr acts to soften the alloy and facilitate extrusion processing. If the amount is less than 7%, the effect will not be sufficient, and if it exceeds 9%, harmful phases such as sigma phase will occur in the alloy, which will cause cracks during extrusion processing, so the amount of Cr should be 7 to 9%. It is necessary that W is extremely effective in refining crystal grains. If the amount is less than 10%, the effect is not sufficient, and 14%
If it exceeds 10%, harmful phases such as alpha W phase and miu phase will be generated, and cracks will easily occur during extrusion processing, so the amount of W needs to be 10 to 14%. Al acts to generate a gamma prime phase. In order to make the crystal grains fine by extrusion processing, it is necessary that a sufficient amount of gamma prime phase be generated. For this purpose, an Al content of 4.5% or more is required. However, if the amount exceeds 5.5%, the amount of gamma prime phase becomes excessive and the pressure required for extrusion processing becomes too high.
%. Ti forms a gamma prime phase together with Al, and acts to promote grain refinement during extrusion processing.
If the amount is less than 0.1%, a sufficient effect will not be obtained, and if it exceeds 1.5%, eta phase will be generated and cracks will easily occur during extrusion processing, so the amount of Ti should be 0.1 to 1.5%.
%. Like W, Ta functions to refine crystal grains during extrusion processing. If the amount is less than 3%, the effect will not be sufficient, and if it exceeds 5%, a large amount of gamma prime phase will occur and the pressure required for extrusion will become too high, so the amount of Ta should be 3 to 5%. is necessary. Hf acts to suppress cracking at grain boundaries during extrusion processing. If the amount is less than 0.3%, the effect will not be sufficient, and if it exceeds 1.3%, harmful phases will be generated and cause cracks during extrusion processing, so the amount of Hf should be 0.3%.
~1.3% is required. Like C, B acts to suppress cracking at grain boundaries during extrusion processing. If the amount is less than 0.005%, the effect will not be sufficient, and if it exceeds 0.018%, the melting point of the alloy will decrease, causing partial melting and cracking during extrusion processing, so the amount of B should be between 0.005 and 0.018%. is necessary. Like C and B, Zr acts as a grain boundary strengthening element and prevents cracking during extrusion processing. The amount is 0.01
If the Zr content is less than 0.1%, the effect will not be sufficient, and if it exceeds 0.15%, a harmful phase will be produced and cracking during extrusion will be promoted. Next, a method for manufacturing the alloy of the present invention will be described.
The manufacturing method thereof can be carried out by two methods as described above. The first method is to place the alloy powder of the present invention in a container and extrude it. The extrusion temperature and extrusion ratio at this time are particularly important. Extrusion temperature is 1050~1225℃,
Most preferably, the extrusion ratio is in the range of 4 to 15. If the extrusion temperature is lower than 1050°C, cracks will occur during extrusion, making it impossible to obtain a practical superplastic Ni-based alloy for forging. If the temperature exceeds 1225°C, the crystal grains will not be refined enough, and the superplastic deformation resistance will not become small. If the extrusion ratio is smaller than 4, the crystal grains will not be refined enough to reduce the superplastic deformation resistance, and if the extrusion ratio is larger than 15, extrusion will not be possible. The second method is to perform high temperature and high pressure treatment (HIP treatment) prior to extrusion treatment. Although this HIP treatment does not directly lead to a reduction in superplastic deformation resistance,
Since the powder is sintered, there is an advantage that the subsequent extrusion processing operation is easy. For example, when inserting into an extrusion container, there is no need for depressurization treatment or encapsulation treatment, which improves work efficiency.
The conditions for HIP treatment are temperature 1025-1250℃ and pressure 800℃.
It is appropriate that the pressure is ~2000 atm and the time is 30~200 minutes. If the processing temperature is below 1025°C, the powder will not be sufficiently sintered, and if it exceeds 1250°C, the alloy will partially melt and form a harmful structure, which may cause cracks during extrusion processing. If the processing pressure is less than 800 atm, the powder will not be sufficiently sintered, and if it exceeds 2000 atm, a corresponding high-pressure device will be required, which is a substantial disadvantage. Furthermore, if the processing time is less than 30 minutes, the powder will not be sufficiently sintered, and if it exceeds 200 minutes, the production efficiency will be reduced. Extrusion temperature is 1050~1225℃, extrusion ratio is 4~15
The range shall be . The reasons are the same as above. Example The alloy of the present invention and existing Rene95 and Merl76 were manufactured under the conditions shown in Table 1. The results were as shown in Table 1. In addition, the superplastic deformation resistance values in Table 1 are for tensile test pieces (parallel part diameter 3.5 mm, parallel part length
20mm) and tensile deformation at 1050°C at a rate of 1.25mm/min.

【table】

[Table] As shown in the results, the alloy of the present invention made by the method of the present invention has a crystal grain size of 2 to 3 microns, which is less than half the grain size of existing Rene95 or Merl76. ing. As a result, the superplastic deformation resistance is significantly reduced. Effects of the Invention The Ni-based alloy of the present invention does not cause cracks during extrusion processing, has extremely fine grain size, has low superplastic deformation resistance, and can be forged into large products and complex-shaped products. Has excellent properties.

Claims (1)

[Claims] 1% by weight: C0.02~0.12%, Co5~12%, Cr7
~9%, W10~14%, Al4.5~5.5%, Ti0.1~1.5
%, Ta3~5%, Hf0.3~1.3%, B0.005~0.018
%, Zr0.01-0.15%, and the remainder is substantially Ni-based alloy for superplastic forging. 2 Weight%: C0.02-0.12%, Co5-12%, Cr7
~9%, W10~14%, Al4.5~5.5%, Ti0.1~1.5
%, Ta3~5%, Hf0.3~1.3%, B0.005~0.018
%, Zr0.01 to 0.15%, and the balance is essentially Ni, is placed in a container, and the powder is poured into a container.
A method for producing a Ni-based alloy for superplastic forging, characterized by extruding at 1050-1225°C and an extrusion ratio of 4-15. 3 Weight%: C0.02~0.12%, Co5~12%, Cr7
~9%, W10~14%, Al4.5~5.5%, Ti0.1~1.5
%, Ta3~5%, Hf0.3~1.3%, B0.005~0.018
%, Zr0.01~0.15%, and the balance is essentially Ni.
A method for producing a superplastic Ni-based alloy for forging, characterized by sintering by high temperature and high pressure treatment for 30 to 200 minutes at 800 to 2000 atm and extruding at 1050 to 1225°C at an extrusion ratio of 4 to 15. .