JP3883461B2 - Iridium-hafnium-coated nickel-base superalloy - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The invention of this application relates to an iridium-hafnium-coated nickel-base superalloy. More specifically, the invention of this application is expected to improve the high-temperature oxidation resistance, high-temperature corrosion resistance and base metal structure stability of a member formed of a nickel-base superalloy, and extend the base material life. It relates to an iridium-hafnium-coated nickel-base superalloy.
[0002]
[Prior art and its problems]
Nickel-based superalloys (Ni-based superalloys) are used as materials for jet engines, gas turbine turbine blades, and turbine vanes that are exposed to high temperatures and high stresses. One of the effective means for reducing carbon dioxide gas is to increase the efficiency of the internal combustion engine. As the operating temperature rises, the high temperature oxidation resistance and high temperature corrosion resistance required for the base metal are severe. It has become.
[0003]
To improve oxidation resistance, the base metal surface is coated with an alloy rich in aluminum (Al) and chromium (Cr), and oxides such as alumina (Al ₂ O ₃ ) and chromia (Cr ₂ O ₃ ). In general, a passive state is formed or Al and Cr are diffused and penetrated into the surface of the base material.
[0004]
However, the current situation is that it is difficult to cope with the surface modification method.
[0005]
This is because as the temperature rises, Al and Cr in the coating diffuse into Ni in the base material, and the oxidation resistance of the coating is weakened, and a harmful phase is precipitated in the base material. This is because it deteriorates.
[0006]
The invention of this application was made in view of such circumstances, and the high-temperature oxidation resistance of members formed of a nickel-base superalloy, high-temperature corrosion resistance, and improvement in the structural stability of the base material, and An object to be solved is to provide an iridium-hafnium-coated nickel-base superalloy whose lifetime of the base material is expected to be extended.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the invention of this application is directed to an iridium-hafnium-coated nickel in which an iridium- hafnium alloy film is formed on the surface of a nickel-base superalloy and an aluminum film is formed on the surface of the iridium-hafnium alloy film. iridium aluminum-based superalloys is characterized by being diffused and penetrated - providing hafnium coated nickel-base super alloys and (claim 1).
[0008]
In the invention of this application, the thickness of the iridium-hafnium alloy film is 5 μm to 100 μm (Claim 2), and the iridium content in the iridium-hafnium alloy film is 50 atomic% to 98 atomic% ( According to a third aspect of the present invention, the iridium content in the iridium-hafnium alloy film is 75 atomic%, and the hafnium content is 25 atomic% (claim 4 ), respectively.
[0009]
Hereinafter, the iridium-hafnium-coated nickel-base superalloy according to the present invention will be described in more detail with reference to examples.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In the iridium-hafnium-coated nickel-base superalloy of the invention of this application, as described above, the iridium-hafnium alloy film is formed on the surface of the nickel-base superalloy.
[0011]
Iridium (Ir) and hafnium (Hf) form an intermetallic compound phase Ir ₃ Hf. This intermetallic compound phase Ir ₃ Hf can suppress diffusion into a base material formed from a nickel-base superalloy, which is a problem with aluminum (Al) and chromium (Cr), and Ir—Hf The alloy coating functions as a diffusion barrier layer of these Al and Cr. In addition, both Ir and Hf have stable oxides, which improves the oxidation resistance of the nickel-base superalloy. Therefore, precipitation of a harmful phase in the base material is suppressed, and the structure of the base material is stabilized. Moreover, Ir is excellent in corrosion resistance, and it is possible to improve the corrosion resistance.
[0012]
The Ir—Hf alloy coating is less likely to exhibit its performance as a diffusion barrier layer when the thickness is less than 5 μm. When the thickness exceeds 100 μm, the thermal expansion coefficient of the Ir—Hf alloy coating is higher than that of the Ni-base superalloy. Therefore, the Ir—Hf alloy coating is easily peeled off due to thermal fatigue caused by the difference in thermal expansion coefficient, which affects the life of the base material. Therefore, the thickness of the Ir—Hf alloy coating is preferably 5 μm to 100 μm.
[0013]
Further, as described above, in order to precipitate the intermetallic compound phase Ir ₃ Hf in the Ir—Hf alloy coating, the Ir content in the Ir—Hf alloy coating is 50 atomic% or more and 98 atomic% or less. Is preferred.
[0014]
Iridium of the invention of this application - hafnium coated nickel-base superalloy, after Ir-Hf alloy coating formed, including multi-layer coating of Al to its surface, further, by applying the diffusion penetration treatment of Al, resistance It is possible to improve the high temperature oxidation resistance, the high temperature corrosion resistance, the structural stability of the base material, and extend the life of the base material.
[0015]
【Example】
TMS-75 (Ni-12.6Co-3.5Cr-1.3Mo-2W-13.7Al-2Ta-0.04Hf-1.67Re, the number indicates atomic%) is selected as the Ni-base superalloy and used as a base material. An Ir 75 atomic% -Hf 25 atomic% alloy (purity of raw materials is 99.99% for both Ir and Hf) and a thickness of about 2 μm and an Al film of about 2 μm are formed on the surface of the base material. The layers were sequentially formed by electron beam physical vapor deposition. At this time, an AMF-1050SB type vapor deposition apparatus manufactured by Shinko Seiki Co., Ltd. was used, and the film forming conditions were a vacuum degree of 1.2 to 3.5 × 10 ⁻³ Pa and an electron beam voltage of 10 kV.
[0016]
After this, the sample was washed with acetone, and then placed in a mixed powder of Al, Al ₂ O ₃ , iron (Fe), and ammonium chloride (NH ₄ Cl). Diffusion penetration treatment was performed.
[0017]
And the oxidation resistance of the produced sample was evaluated. Specifically, the process of holding the sample in the atmosphere at 1100 ° C. for 20 hours and then cooling to room temperature was defined as one cycle, and the oxidation test was repeated 6 times.
[0018]
The obtained results were obtained by coating Hf alone on the surface of the base material, then coating Al, and further performing Al diffusion and permeation treatment, without directly forming the Ir-Hf alloy film, and diffusing Al directly into the base material. It compared with the result of having done the same test about what performed the osmosis | permeation process.
[0019]
FIG. 1 is a graph showing the results of repeated oxidation tests.
[0020]
During the oxidation test, the sample increases in weight as it oxidizes, and then loses weight due to volatilization or delamination. Therefore, it is concluded that the one with the smallest amount of weight change has the best oxidation resistance. From the results shown in FIG. 1, it was confirmed that an Ir—Hf alloy film formed on a base material and Al film was coated with multiple layers and then Al diffusion diffusion treatment was most excellent in oxidation resistance. The The oxidation resistance is improved by alloying Ir and Hf, which can be said to be a demonstration of the function of the Ir—Hf alloy coating as a diffusion barrier layer.
[0021]
In addition to such a function as a diffusion barrier layer, as described above, Ir is also excellent in corrosion resistance. Therefore, it is reasonable that iridium-hafnium-coated nickel-base superalloys are effective in improving corrosion resistance. Can be considered.
[0022]
Of course, the invention of this application is not limited by the above embodiments. It goes without saying that various modes are possible for details such as the type and composition of the Ni-base superalloy forming the base material, the composition of the Ir—Hf alloy coating, the forming method, and the thickness.
[0023]
【The invention's effect】
As described above in detail, the invention of this application can improve the high-temperature oxidation resistance, high-temperature corrosion resistance and structural stability of the base material formed of the nickel-base superalloy, and extend the life of the base material. Expected.
[Brief description of the drawings]
FIG. 1 is a graph showing the results of a repeated oxidation test.

Claims (4)

The iridium-hafnium alloy film is formed on the surface of the nickel-base superalloy, and aluminum is diffused and penetrated into the iridium-hafnium-coated nickel-base superalloy in which the aluminum film is formed on the surface of the iridium-hafnium alloy film. Iridium-hafnium-coated nickel-base superalloy.   The iridium-hafnium-coated nickel-base superalloy according to claim 1, wherein the thickness of the iridium-hafnium alloy coating is 5 µm to 100 µm.   The iridium-hafnium-coated nickel-base superalloy according to claim 1 or 2, wherein the iridium content in the iridium-hafnium alloy film is 50 atomic percent to 98 atomic percent. The iridium- hafnium-coated nickel-base superalloy according to claim 3 , wherein the iridium-hafnium alloy film has an iridium content of 75 atomic% and a hafnium content of 25 atomic% .

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