JP3339111B2 - Single crystal nickel base super heat resistant alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single crystal nickel-base superalloy used for high-speed moving and stationary blades of aircraft, gas turbines and the like.

[0002]

2. Description of the Related Art Typical compositions of single crystal nickel-base superalloys conventionally developed as materials for moving and stationary blades at high temperatures such as aircraft and gas turbines are shown in Table 1. .

[0003]

[Table 1]

[0004] The above heat-resistant alloy is subjected to a solution treatment at a predetermined temperature and then to an aging treatment to obtain a single crystal nickel-based super heat-resistant alloy.

[0005]

SUMMARY OF THE INVENTION In Table 1, Alloy-45
4 has an excessive amount of Ta, so that the amount of eutectic γ 'is large, the amount of eutectic γ' remains large even after high-temperature solution treatment, and the high-temperature strength is low. CMSX-2 alloy is an excellent alloy in the first generation, but it has few solid solution strengthening elements such as W, Mo, Ta, etc.
Aiming for higher temperatures results in insufficient strength. The CMSX-4 alloy is a second-generation alloy that aims to increase strength and is excellent in strength. However, since it uses a lot of high-priced raw materials such as Re and Ta, it is expensive and, in addition, has high Re. It contains a large amount (1.5 to 4.0% by weight), so that it is 6% for homogenization (disappearance of dendrite pattern and disappearance of eutectic γ 'amount)
Since it requires a solution treatment over several stages, it cannot be said that it is simple for practical use, and it is practically difficult to apply the above heat treatment to the moving and stationary blades.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a single crystal nickel-base super heat-resistant alloy having excellent high-temperature strength and capable of easily performing heat treatment.

[0007]

Means for Solving the Problems In order to achieve the above object, a single crystal nickel-base superalloy according to the present invention has a composition in which the content is wt. 0 to 6.5, Mo: 2.0 to
5.0, W: 2.0-6.0, Co: 4.5-5.5.
5, Ta: 4.0 to 6.0, Al: 4.0 to 6.0.
0, Ti: 0.8 to 1.2, Re: 0.8 to 1.2,
Ni: balance, W + Mo + Re = 6 to 12, A
to l + Ti = 5 to 7 of the alloy, of 1 28 from 0 to 1,330 ° C. temperature
After facilities the two-step solution heat treatment in degrees range, 760-11
Aging treatment was performed in a temperature range of 00 ° C.

[0008]

According to the above construction, W, M contributing to solid solution strengthening.
o, Re, and Ta are added in the above-mentioned solid solution range to optimize so as not to be too large or too small, and at the same time, phase stability (α,
(σ, μ phase) and excellent corrosion resistance and castability, and low cost of high cost raw materials such as Ta and Re. Further, since Re is added in a small amount, the solution treatment step can be reduced.

[0009] In the component, Cr has a function of improving corrosion resistance, 5. 0 wt% to below the its effect is insufficient, since the 6.5 wt% is exceeded and strength improvement can not be expected, 5. The range is 0 to 6.5% by weight.

Mo is a solid solution in Ni, and is an element effective for solid solution strengthening. When it exceeds 5.0% by weight, a harmful phase is precipitated, and when it is less than 2.0% by weight, especially 1% by weight. Since it is not effective in improving the strength, the content is set in the range of 2.0 to 5.0% by weight.

W has the same effect as Mo, and when W exceeds 6% by weight, especially 10% by weight, harmful phases are easily precipitated.
If the content is less than 2% by weight, no improvement in strength can be expected.
To 6.0% by weight.

[0012] Co has the effect of increasing the solid solubility of Mo and W. When the content is less than 4.5% by weight, the effect is insufficient.
Further, it is not enough to exceed 5.5% by weight.
It is in the range of 5.5% by weight.

[0013] Ta forms a solid solution in the γ 'phase to increase and strengthen the γ' phase, but has no effect if the content is less than 4.0% by weight, and if it exceeds 6.0% by weight, especially 8% by weight. Since the amount of the eutectic γ 'phase is excessive and the merit of improving the strength is reduced, it is not preferable, so that the range is 4.0 to 6.0% by weight.

Al and Ti have the same effect as Ta. Al is in the range of 4.0 to 6.0% by weight.
Is preferably in the range of 0.8 to 1.2% by weight,
The total of the two needs to be such that Al + Ti is in the range of 5 to 7% by weight, and if it is out of this range, no improvement in strength can be expected, which is not preferable.

Re has the effect of solid solution strengthening similarly to W and Mo. However, if it is less than 0.8% by weight, it has no effect of solid solution strengthening. Although the disappearance and the disappearance of the eutectic γ ′ phase are desirable, the solution treatment for the treatment is performed in several stages, and the heat treatment becomes difficult.
It is in the range of 1.2% by weight.

The sum of W, Mo, and Re is W + Mo +
When Re is in the range of 6 to 12% by weight, the effect of solid solution strengthening is improved.

The single-crystal nickel-base superalloy of the present invention comprises:
Single crystallization by the unidirectional solidification method is possible, the γ ′ solubility temperature is 1200 to 1260 ° C., and the solidus temperature is about 13 ° C.
Was 40 ° C., the solution treatment temperature is 1 28 0-1,330 ° C.
2-step line a solution treatment without melting portion in the range of
By performing aging treatment in the temperature range of 760 to 1100 ° C., the γ ′ phase is aligned, the alloy has high temperature strength, and can be an alloy having good oxidation resistance and castability.

[0018]

EXAMPLES Examples of the present invention will be described below together with comparative examples.

First, the alloy compositions of Examples 1 to 3 of the present invention are as shown in Table 2.

[0020]

[Table 2]

Next, Table 3 shows the heat treatment conditions of the alloy of the present invention shown in Table 2 and the alloys shown in Table 1 (Comparative Examples 1 to 3).

[0022]

[Table 3]

As can be seen from Table 3 , the solution treatment of the alloys of Examples 1 to 3 was performed in two stages, and Comparative Example 1 (Alloy454)
And Comparative Example 2 (CMSX-2) first-generation solution treatment of the alloy of
More than (1 step), but less than the solution treatment (6 steps) of the second generation alloy of (CMSX-4) in Comparative Example 3.
I am . This is due to the difference in the amounts of Re, W, and Mo added. Re, W, and Mo are elements having relatively similar physical properties. In particular, Re has a larger atomic radius and a larger diffusion coefficient than W and Mo, and has a segregation coefficient of W, Mo.
More differently, Re is likely to concentrate around the dendrite core of the solidified structure, and therefore
Requires a number of stages of heat treatment for the solution treatment to make the surface uniform. Because in the first-generation alloy, but because soluble conjugated treatment additives were not of Re is only once, in the second-generation alloy, which has a 3.0 wt% addition amount of Re,
The solution treatment requires as many as six steps . On the contrary,
In the present invention, the amount of Re added is made smaller than that of the second generation alloy.
And 0.8% to 1.2% by weight, the solution treatment can be performed in two stages .

Next, the results of creep life tests of the alloys of Examples 1 to 3 and Comparative Examples 1 to 3 obtained in Table 2 are shown in Table 4.

[0025]

[Table 4]

In this creep test, the test piece was heated at 1000 ° C.
At a high temperature of 250 MPa, a tensile strength of 250 MPa was given, and the time required for the test piece to undergo creep rupture was determined as the life.

As can be seen from Table 4, the alloys of Examples 1 to 3 of the present invention have a longer creep life than the first generation alloy and a shorter life than the second generation alloy. Considering the complexity, the high-temperature strength can be sufficiently practical.

That is, Re, W, and Mo are all high-melting metals called refractory metals, and this kind of alloy (single crystal-dedicated alloy) acts as solid solution strengthening of the matrix (γ phase). In the first generation alloy, these addition amounts are 9
% By weight, and 10% by weight or more for the second generation alloy. Therefore, the creep life of the second generation alloy can be remarkably improved. However, in the case of the second-generation alloy, the amount of Re added becomes large, so that the solution treatment becomes a problem. However, in the present invention, the amount of Re is reduced, and instead, the amount of Mo is increased to increase the total amount of the refractory metal. Is increased so that high-temperature strength can be improved.

[0029]

In summary, according to the present invention, heat treatment is easy , specifically, two-step solution treatment is sufficient for practical use.
Single-crystal nickel-base super heat-resistant alloy with rich high-temperature strength
It is possible to obtain.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-59474 (JP, A) JP-A-4-124237 (JP, A) JP-A-1-255636 (JP, A) 9349 (JP, A) JP-A-63-118037 (JP, A) JP-A-60-177160 (JP, A) JP-A-63-24029 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) C22C 19/05 C22F 1/10 C30B 29/52

Claims (1)

(57) [Claims] (1) Cr: 5. 0 to 6.5, Mo: 2.0 to 5.0,
W: 2.0 to 6.0, Co: 4.5 to 5.5, Ta: 4.0 to 6.0, A
l: 4.0 to 6.0, Ti: 0.8 to 1.2, Re: 0.8 to 1.2, N
i: The remainder, and W + Mo + Re = 6 to 12, Al + Ti = 5 to 7
The alloys 1 28 0-1330 2-step solution heat treatment at a temperature range of ℃
After facilities and aging treatment in the temperature range of 760-1,100 ° C.
A single crystal nickel-based super heat-resistant alloy characterized by being subjected to a heat treatment .