JPH0941058A - Nickel base single crystal alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an Ni base single crystal alloy excellent in high temp. strength and easily capable of solution treatment. SOLUTION: An alloy having a compsn. contg., by weight, 8.0 to 11.5% Mo, 4.5 to 6.5% Ta, 2.0 to 4.0% Re, 5.5 to 6.5% Al, 0.5 to 1.5% Ti, and the balance Ni with inevitable impurities is prepd. This alloy is subjected to solution treatment at 1,300 to 1,350 deg.C and is successively subjected to aging treatment at 850 to 1,100 deg.C, by which the Ni base single crystal alloy excellent in high temp. strength and easily capable of solution treatment can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant alloy which is required to have high strength at high temperature, such as a blade of an aircraft or a gas turbine for power generation, and more particularly to a Ni-based single crystal alloy. .

[0002]

2. Description of the Prior Art γ'precipitation-strengthened Ni-based alloys are widely used as super heat-resistant alloys required to have high strength at high temperatures, such as blades of aircraft and gas turbines for power generation.

FIG. 2 shows the solid solution behavior when the third element (C) is added to γ '(Ni ₃ Al).

The reason why Ni-based alloys have become the mainstream of super-heat-resistant alloys is that first, Ni can dissolve many kinds of elements in solid solution, and secondly, as shown in FIG. The strengthening phase γ '(Ni ₃ Al) also forms a solid solution with many kinds of elements,
Moreover, this γ'is maintained in a fine state relatively stably for a long time even at a high temperature. γ ′ has a unique property that strength increases with increasing temperature (positive temperature dependence), which cannot be found in ordinary metals and alloys, and precipitation strengthening of this phase is the basis of Ni-based heat-resistant alloys. Has become.

In FIG. 2, a solid solution is formed with an element such as Co that substitutes for the Ni site of Ni ₃ Al, an element that substitutes for the Al site such as Ti, Ta, Mo, or an element that substitutes for both sites such as Cr. There are various methods for controlling the high temperature strength of the γ'precipitation strengthened Ni-based alloy, and the strength of γ and γ ', as well as the amount of γ'precipitated in the γ matrix while maintaining consistency. These include dimensions and misfit (difference in lattice constant). In other words, it can be said that the history of performance improvement of Ni-based heat-resistant alloys was to change the type and amount of additive elements.

The main point of strengthening the Ni-based single crystal alloy is γ '.
It is precipitation strengthening by the phase (Ni ₃ Al) and solid solution strengthening of the γ phase which is the parent phase.

Regarding the precipitation strengthening by the γ'phase, the volume amount of the γ'phase is 60 to 60 even in the case of the existing Ni-based single crystal alloy.
The strength has reached 65%, and even if the volume is larger than this, the strength is leveled off or lowered due to the precipitation of a coarse eutectic γ'phase, etc., so that the strength improvement by precipitation strengthening has reached the limit.

On the other hand, regarding solid solution strengthening of the γ phase, it seems that there is still room for improvement in strength by adding an element effective for strengthening the γ phase while suppressing precipitation of harmful phases (α, μ, σ, etc.). Be done.

Representative existing Ni developed so far
The base single crystal alloy is shown in Table 1.

[0010]

[Table 1]

Table 1 also shows the chemical composition and heat treatment conditions of each Ni-based single crystal alloy.

As shown in Table 1, Alloy 454 (Un
ited Technology), CMSX-2 (Cannon-Muskego
n-made) is a Ni-based single crystal alloy called the first generation,
The chemical composition of loy454 is wt%, Co: 5.0, C
r: 10.0, Al: 5.0, Ti: 1.5, Ta: 12.0, W:
9.0, the balance consisting of Ni and unavoidable impurities, and the heat treatment condition was 1316 ° C. for 3 hours, followed by rapid cooling, then 9
After being held at 82 ° C. for 5 hours, it was rapidly cooled and finally air-cooled at 871 ° C. for 20 hours. The chemical composition of CMSX-2 is wt%: Co: 4.6, Cr: 7.8, Al: 5.6, T
i: 1.0, Ta: 6.0, W: 8.0, Mo: 0.5, balance of Ni and inevitable impurities, heat treatment condition is 128
Hold at 8 ° C for 4 hours, then quench, then at 1080 ° C for 4 hours.
After holding for an hour, it was rapidly cooled, and finally air-cooled at 871 ° C. for 20 hours.

CMSX-4 is a Ni-based single crystal alloy called the second generation, whose chemical composition is wt%, Co: 9.6,
Cr: 6.5, Al: 5.6, Ti: 1.0, Ta: 6.5,
W: 6.4, Mo: 0.6, Re: 3.0, Hf: 0.1, balance of Ni and inevitable impurities, heat treatment condition is 12
Hold at 77 ° C for 2 hours, hold at 1288 ° C for 2 hours, hold at 1296 ° C for 3 hours, and hold at 1304 ° C for 3 hours.
After holding for 1 hour, at 1313 ° C for 2 hours, then 13
After being held at 16 ° C. for 2 hours, held at 1080 ° C. for 4 hours, rapidly cooled, and finally air-cooled at 870 ° C. for 20 hours.

[0014]

However, All
In oy454, the amount of Ta is too large, so that the eutectic γ '
Of eutectic γ'remains after the solid solution treatment, and the high temperature strength is lowered. Since CMSX-2 has a small amount of W, Mo and Ta contributing to solid solution strengthening, it does not exhibit sufficient strength.

As described above, since the first-generation Ni-based single crystal alloy was insufficient in strength, the second-generation Ni-based single crystal alloy was developed.

CMSX-4 is an alloy aiming at improvement of high temperature strength and is excellent in strength, but as shown in Table 1, the combination of additional elements is complicated, and homogenization of W and Re ( Due to the disappearance of the dendrite pattern and the solid solution of eutectic γ ′), solution treatment of up to 6 steps is required, and the temperature gradient conditions are finely defined, so that the production is not easy.

As described above, the second-generation Ni-based single crystal alloy has advantages and disadvantages, but in order to attain high-temperature strength, Re, which has poor homogeneity but is particularly excellent in high-temperature strength, cannot be excluded.

According to the study by the present inventors, it has been found that Cr and Co should be eliminated in order to facilitate the solution treatment without eliminating Re.

An object of the present invention is to solve the above problems and to provide a Ni-based single crystal alloy which is excellent in high-temperature strength and easy to undergo solution treatment.

[0020]

In order to achieve the above object, the invention of claim 1 has a weight percentage of Mo: 8.0 to 11.5%.
, Ta: 4.5 to 6.5%, Re: 2.0 to 4.0%, Al: 5.5
-6.5%, Ti: 0.5-1.5%, the balance consisting of Ni and unavoidable impurities.
The aging treatment is performed at 0 ° C. and subsequently at 850 to 1100 ° C.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION A feature of the Ni-based single crystal alloy according to the present invention is that only elements such as Ti, Ta, and Mo that substitute for Al sites are added, and Cr and Co are not added. This is because it is possible to increase the amount of addition of Mo, which contributes to solid solution strengthening and has higher high-temperature strength than Cr, and facilitates solution treatment while maintaining high-temperature strength.

The reason for adding only the element substituting to the Al site, that is, the element showing a similar solid solution, is that the solution treatment is considered to be easy.

Among the additive elements, W and Re are elements that have poor homogeneity and complicate the solution treatment, but Re is one of refractory metals that has excellent tensile strength at high temperature ( In order to have a tensile strength of about 580 MPa at 1000 ° C., it was decided to add about the same amount as the existing Ni-based single crystal alloy (second generation), but W is the tensile strength at high temperature (1000
(About 230 MPa at ℃) is not very good, so it was decided to eliminate it.

According to the above constitution, the elements added to the Ni-based single crystal alloy are simplified, Cr is not added so much that it does not contribute so much to the strengthening of the γ phase, and the solid solution to the γ phase is dominant. And Mo, Ta, and Re that contribute to strengthening the γ phase are
A large amount can be added so as not to become too large or too small within the solid solution range, and the decrease in corrosion resistance due to the addition of no Cr is suppressed by the addition of Re and Ti.
It is possible to produce a Ni-based single crystal alloy that is excellent in high-temperature strength and that can be easily solution-treated without impairing the characteristics of the base single-crystal alloy.

The reason why the composition range of the Ni-based single crystal alloy according to the present invention is limited is as follows.

Mo is an element effective for solid solution strengthening. Mo
If the addition amount exceeds 11.5%, harmful phases such as α phase are precipitated, and if it is less than 8.0%, strength becomes ineffective.

Re, like Mo, is effective for solid solution strengthening. If the added amount of Re is less than 2.0%, the solid solution strengthening effect is not obtained, and if it exceeds 4.0%, the solid solution amount is exceeded. Re also contributes to the improvement of corrosion resistance and high temperature strength. Mo
It is possible to increase the added amount of Re by decreasing the added amount of Re, but since Re is an expensive metal element, 4.
It is not preferable to exceed 0%.

Ta increases the volume of the γ'phase and contributes to solid solution strengthening. If the addition amount of Ta exceeds 6.5%, the eutectic γ'phase becomes too large, and if it is less than 4.5%, the volume amount of the γ'phase becomes too small to contribute to precipitation strengthening.

Al is an element necessary for producing the γ'phase. When the added amount of Al exceeds 6.5%, eutectic γ ′
If the phase becomes too large and is less than 5.5%, the volume of the γ'phase becomes too small to contribute to precipitation strengthening.

Ti also has the same effect as Al, and contributes to the improvement of corrosion resistance when the amount of Ti added is in the range of 0.5 to 1.5%.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The inventors of the present invention produced test materials of the Ni-based single crystal alloys of the present invention having different chemical compositions by the unidirectional solidification method, heat-treated them, and then conducted characteristic tests.

Table 2 shows an example of the chemical composition of each test material used in the test.

[0034]

[Table 2]

Table 2 also shows the heat treatment conditions for each test material.

In Table 2, the chemical composition of NA-1 is wt.
%, Mo: 11.1, Re: 3.9, Ta: 5.2,
Ti: 1.0, Al: 5.9, the balance being Ni and inevitable impurities. The chemical composition of NA-2 is wt
%, Mo: 10.1, Re: 4.0, Ta: 5.2
Ti: 1.0, Al: 5.9, the balance being Ni and inevitable impurities. The chemical composition of NA-3 is wt
%, Mo: 10.3, Re: 3.0, Ta: 5.2,
Ti: 1.1, Al: 5.8, and the balance Ni and unavoidable impurities.

The heat treatment condition of NA-1 is 1320 ° C. and 4
After being held for an hour, it is rapidly cooled, then held at 1080 ° C. for 2 hours, then rapidly cooled, and finally air-cooled at 870 ° C. for 20 hours. The heat treatment conditions for NA-2 and NA-3 are 1
Hold at 300 ° C for 4 hours, then quench, then 1080 ° C
Hold for 2 hours, then cool rapidly, and finally at 870 ° C for 20 hours
r It is cooled by air.

Tables 3 and 4 are examples of the results of the characteristic test.

[0039]

[Table 3]

Table 3 shows the present embodiment (NA-
1, NA-2, NA-3), Comparative Example 1 shown in Table 1 (Alloy 454 which is a first generation alloy, CMSX-2),
Comparative Example 2 (CM, which is a second generation alloy, also shown in Table 1)
The result of the high temperature tensile test (0.2% proof stress at 900 ° C., tensile strength, breaking elongation, breaking reduction) in SX-4) is shown.

As shown in Table 3, it goes without saying that the high temperature tensile properties of this example are considerably superior to those of Comparative Example 1,
Even when compared with Comparative Example 2, the elongation at break in NA-3 is slightly inferior and almost equal or higher.

[0042]

[Table 4]

Table 4 shows the present embodiment (NA-shown in Table 2).
1, NA-2, NA-3), Comparative Example 1 shown in Table 1 (Alloy 454 which is a first generation alloy, CMSX-2),
Comparative Example 2 (CM, which is a second generation alloy, also shown in Table 1)
SX-4) high temperature creep strength test (900
The results of creep rupture life, elongation, and reduction at 400 ° C., 400 MPa, 1050 ° C., and 160 MPa are shown.

As shown in Table 4, 900 ° C, 400MP
Regarding the high temperature creep strength of this example in a, NA-3 of this example is superior to Comparative Example 1 and is substantially the same in characteristics as Comparative Example 2. But the higher temperature of 1050
At 160 ° C. and 160 ° C., it is needless to say that the present example is considerably superior to Comparative Example 1, and even when compared with Comparative Example 2, the elongation and drawing at NA-1 are slightly inferior.
It shows excellent characteristics that are almost equal or better.

The Ni-based single crystal alloy of the present invention has a significantly increased addition amount of Mo, which is a refractory metal, as compared with the existing Ni-based single crystal alloy, and therefore has excellent creep strength particularly at high temperatures. The result is shown.

Next, another embodiment of the present invention will be described.

FIG. 1 shows the result of an oxidation test in the atmosphere. Oxidation test is conducted at 1100 ° C in the atmosphere at 200
I went for an hour. The upper bar graph in FIG. 1 indicates the thickness of the oxygen permeation layer (μm), and the lower bar graph indicates the decrease in weight (mg).
/ Cm ² ).

As shown in FIGS. 1A and 1B, the oxidation resistance of the Ni-based single crystal alloy (B) of the present invention is as follows. It is slightly inferior to the crystalline alloy (A), but there is not much difference.

However, when the oxidation resistance is strongly required, Y is added to the Ni-based single crystal alloy of the present invention in order to improve the oxidation resistance. Since Y has a strong bond with O ₂ , its content in the alloy of 100 to 300 ppm contributes to the improvement of oxidation resistance, but the yield is about 1
Since it is as bad as / 10, 0.1 to 0.3 wt% is added. Y
In addition to Y alone, a mother alloy such as Ni-Y may be added.

As shown in FIGS. 1 (A) and 1 (C), a Ni-based single crystal alloy (C) in which Cr is not added by adding Y is added.
Also, in this case, it has the same oxidation resistance as the Ni-based single crystal alloy (A) to which Cr is added.

[0051]

As described above, the Ni-based single crystal alloy according to the present invention exhibits the following excellent effects.

(1) After preparing a single crystal sample by the unidirectional solidification method, heat treatment was performed, and the characteristics of the high temperature tensile test and the high temperature creep strength test were compared under the same conditions as the existing alloy. As a result, the characteristics of the Ni-based single crystal alloy of this example at high temperature were superior to those of the first-generation alloy, and were substantially equal to or higher than those of the second-generation alloy.

(2) The Ni-based single crystal alloy of this example is
Partial melting (Incipi
The solution treatment was easy without causing ent Melting). Further, by aging treatment at 850 to 1100 ° C., fine precipitation of γ ′ was possible.

(3) The Ni-based single crystal alloy of this example is
Although Cr, which has excellent oxidation resistance, was not added in order to direct the high temperature strength, the addition of Re and Ta did not make a big difference although the high temperature oxidation characteristics were slightly inferior to the existing alloys. In addition, since it is practically used after being subjected to coating treatment, there is no problem at all.

(4) The Ni-based single crystal alloy of this example is
Since the upper limit was set for the total amount of solid solution strengthening elements such as Mo, Re, and Ta, no precipitation of harmful phase was observed even after heating for a long time.

(5) The Ni-based single crystal alloy of this example is
Since Mo is mainly added as a solid solution strengthening element, the specific strength (value obtained by dividing strength by density) is excellent.

(6) Since the Ni-based single crystal alloy of this embodiment has good castability, it can be single-crystallized even when used in a turbine rotor blade having a complicated shape.

[Brief description of drawings]

FIG. 1 is a diagram showing the results of an oxidation test in the atmosphere of this example.

FIG. 2 is a diagram showing a solid solution behavior when a third element is added to γ ′ which is a precipitation phase of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshio Ota 3-1-1-15 Toyosu, Koto-ku, Tokyo Ishikawajima Harima Heavy Industries Ltd. Technical Research Institute (72) Inventor Oi Adult 3-5 Mukaidaicho, Tanashi City, Tokyo No. 1 Ishikawa Shima Harima Heavy Industries Ltd. Tanashi Factory (72) Inventor Hiroshi Hattori 3-5-1, Mukaidaicho, Tanashi City, Tokyo Ishikawa Shima Harima Heavy Industries Ltd. Tanashi Factory

Claims (1)

[Claims] 1. Mo: 8.0 to 11.5% by weight percentage, T
a: 4.5 to 6.5%, Re: 2.0 to 4.0%, Al: 5.5 to 6.5
%, Ti: 0.5 to 1.5%, the balance consisting of Ni and unavoidable impurities, and solution treatment at 1300 to 1350 ° C.
And a subsequent aging treatment at 850 to 1100 ° C.