JPH08127833A - Nickel-base heat resistant alloy excellent in weldability - Google Patents

Abstract

PURPOSE: To produce an Ni-base heat resistant alloy used as the forming mate rial for the turbine stationary blade of a gas turbine and the other high temp. parts. CONSTITUTION: In the case the compsn. of this alloy is constituted of 0.05 to 0.25% C, 18 to 25% Cr, 15 to 25% Co, <=3.5% Mo, 5 to 10% W, 5 to 10% W+1/2Mo, 1.0 to 5.0% Ti, 1.0 to 4.0% Al, 0.5 to 4.5% Ta, 0.2 to 3.0% Nb, 0.005 to 0.10% Zr, 0.001 to 0.01% B, and the balance Ni, the range of ABCDE shown in the figure 1 is satisfied, or in the same, in the case of 10 to 20% Cr, the range of ABCFGHE shown in the figure is satisfied. Thus, the Ni-base heat resistant alloy having high temp. strength higher than that of the conventional Ni-base heat resistant alloy and excellent in weldability can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel-base heat-resistant alloy used as a material for forming turbine vanes and other high-temperature parts of gas turbines.

[0002]

2. Description of the Related Art Heat-resistant alloys that have hitherto been used as materials for high-temperature parts such as turbine vanes of gas turbines include intermetallic compounds Ni ₃ (Al, Ti), that is, precipitation strengthening by the γ'phase and Mo, W, etc. There are Ni-based alloys which also have solid solution strengthening by Co and alloys which are precipitation strengthened by carbides. In Ni-based alloys, generally, when the precipitation amount of the γ'phase is increased, the high temperature strength is improved, but the weldability tends to decrease. For example, an alloy in which the precipitation amount of the γ'phase is increased to improve the high temperature strength (special characteristics It is also apparent from JP 54-6968) that the weldability is extremely poor, and the alloy (JP-A-1-104738) in which the weldability is improved by reducing the γ'phase has a remarkably low high temperature strength. On the other hand, Co-based alloys generally have good weldability, but their high-temperature strength is low and significant improvement cannot be expected. From the above, since the high temperature strength of the Co-based alloy is limited, its weldability must be improved without impairing the high-temperature strength of the Ni-based alloy.

[0003]

In order to improve the weldability without impairing the high temperature strength of the Ni-based alloy, A
L, Ti, and other elements such as W, C, and Zr are adjusted without lowering the content of the γ′-phase forming element, and the intended purpose, for example, a welded structure, is used at high temperature. To obtain an alloy that can be used for gas turbine vanes and welded structural equipment. The performance of such an alloy is 900 ° C. × 20 kgf /
mm ² creep rupture time of 110 hours or more and 5 × 6
TIG welding was performed under the welding conditions of welding current 100A, welding voltage 12V, and welding speed 1.67 mm / S using a 0 × 100 mm test piece, and the additional strain amount (total strain amount) was 0.25% or 0.77%. It is characterized in that the maximum crack length in the Balestrain test is 0.8 mm or less.

[0004]

Means for Solving the Problems As a result of earnest studies, the present inventors have added Cr and Co in a range such that alloy phases described later do not produce harmful phases such as σ phase and μ phase, and The high temperature strength is increased by the addition of Al, Ti, Nb, Ta, etc., which are phase forming elements, and the addition of W, Mo, etc., of solid solution strengthening elements, while C, Zr, B, which easily segregate at grain boundaries, are added in appropriate amounts. By adding it to improve the weldability, an alloy with excellent high-temperature strength and weldability was obtained. Furthermore, it can be used as a material for high temperature parts used under low-grade fuel such as heavy oil, that is,
The inventors have found that a Ni-based alloy having excellent oxidation resistance and corrosion resistance can be prepared, and have completed the present invention.

That is, the present invention, in% by weight, is 0.0
5 to 0.25% C, 18 to 25% Cr, 15 to 25
% Co, one or two of up to 3.5% Mo and 5-10% W in an amount such that the value of W + 1 / 2Mo is 5-10%, 1.0-5.0% Ti, 1.0-4.0% Al, 0.5-4.5% Ta, 0.2-3.0% N
b, 0.005 to 0.10% Zr and 0.001 to 0.
01% B is contained, the balance is Ni and unavoidable impurity elements, and (Al + Ti) amount and (W + 1 / 2M)
o) The amount is point A (Al + Ti: 3%, W + 1) in FIG.
/ 2Mo: 10%), point B (Al + Ti: 5%, W + 1)
/ 2Mo: 7.5%), point C (Al + Ti: 5%, W +
1 / 2Mo: 5%), point D (Al + Ti: 7%, W + 1
/ 2Mo: 5%), point E (Al + Ti: 7%, W + 1 /
2Mo: 10%), a nickel-base heat-resistant alloy having a composition within a range surrounded by a line sequentially connecting each point,
And 0.05 to 0.25% by weight of C, 10
~ 20% Cr, 15-25% Co, W + 1 / 2Mo
One or two of Mo up to 3.5% and W up to 0.5-10% in an amount whose value of 0.5-10%, 1.0-
5.0% Ti, 1.0-4.0% Al, 0.5-
4.5% Ta, 0.2-3.0% Nb, 0.005
.About.0.10% Zr and 0.001 to 0.01% B, with the balance being Ni and inevitable impurity elements,
The amounts of (Al + Ti) and (W + 1 / 2Mo) are shown in FIG.
At point A (Al + Ti: 3%, W + 1 / 2Mo:
10%), point B (Al + Ti: 5%, W + 1 / 2Mo:
7.5%), point C (Al + Ti: 5%, W + 1 / 2M
o: 5%), point F (Al + Ti: 4%, W + 1 / 2M)
o: 5%), point G (Al + Ti: 4%, W + 1 / 2M)
o: 0.5%), point H (Al + Ti: 7%, W + 1/2)
Mo: 0.5%) Point E (Al + Ti: 7%, W + 1/2)
Mo: 10%) is a nickel-base heat-resistant alloy having a composition within a range surrounded by a line sequentially connecting the respective points.

Next, the reasons for limiting the action of each element and the addition amount (weight basis) in the alloy composition of the Ni-base heat resistant alloy of the present invention will be described. C forms carbides, especially grain boundaries,
Precipitates at dendrite boundaries and strengthens grain boundaries and resinous boundaries. If it is less than 0.05%, there is no strengthening effect, and it is 0.25.
If it exceeds%, the ductility and creep strength will decrease. A particularly preferable range is 0.09 to 0.23%. Although Cr was set to 18 to 25% in Claim 1 and 10 to 20% in Claim 2, Cr is an element that imparts oxidation resistance and corrosion resistance at high temperatures, and if each is less than the lower limit, its effect is small, while If the respective upper limits are exceeded, there is a risk of σ phase formation during long-term high temperature service. It should be noted that the alloy of claim 1 takes special consideration of corrosion resistance and oxidation resistance, and the alloy of claim 2 takes high temperature strength into consideration.

Co has the effect of increasing the limit of solid solution of Ti, Al, etc., which form the γ'phase, to the substrate at high temperature (solid solution limit). It is necessary to adopt 15.0% or more. on the other hand,
In order to avoid the risk of σ phase formation, it was set to 25.0% or less. T
i is an element necessary for the precipitation of the γ'phase for increasing the high temperature strength. If it is less than 1.0%, the required strength cannot be satisfied, and if it is added in too large an amount, ductility and weldability are reduced. Since it inhibits, it was set to 5.0% or less. Al, like Ti, forms a γ ′ phase, increases high-temperature strength, and contributes to impart oxidation resistance and corrosion resistance at high temperatures. The amount is required to be 1.0% or more, and if added too much, the ductility and weldability are impaired, so 4.0%.
Below. Particularly, Al + Ti is preferably in the range of 3.0 to 7.0%. W and Mo have effects of solid solution strengthening and weak precipitation strengthening, and contribute to impart high temperature strength. To obtain this effect, W + 1 / 2Mo needs to be 0.5% or more, and if added too much, ductility is impaired, so W is 10% or less, Mo is 3.5% or less, and W + 1 / 2Mo is 10%. Below.

Ta and Nb contribute to the improvement of high temperature strength by solid solution strengthening and γ'phase precipitation strengthening. Ta is 0.5% or more and Nb is 0.2% or more. On the other hand, if too much is added, the ductility decreases, so Ta is 4.5% or less
b was 3.0% or less. Especially Ta is 1.0 to 4.2%
The range of Nb is preferably 0.5 to 1.5%.
Zr has the effect of increasing the bond strength at the grain boundaries and strengthening the grain boundaries, but if it is less than 0.005%, no improvement in creep strength is seen, and if it exceeds 0.10%, the weldability is reversed. Must be present in the range of 0.005 to 0.10%. A particularly preferred range is 0.01
Is about 0.10%. B, like Zr, strengthens the grain boundaries by increasing the bond strength of the grain boundaries. However, if it is less than 0.001%, the creep strength is not improved, and if it exceeds 0.01%, the weldability is reversed. B content is 0.001
It was set to a range of 0.01%.

The reason why the range is limited to the range surrounded by the line in FIG. 1 is as follows. Al and Ti increase the high temperature strength by precipitating the γ'phase, which is the strengthening factor of Ni-based alloys, that is, Ni ₃ (Al, Ti), but if added excessively, the weldability and ductility deteriorate, so Al + Ti is 7% or less. And If the addition amount is small, the effect of increasing the high temperature strength will be small, so
As shown in the figure, it was set to 3% or more. Since the amount of Cr also affects the high temperature strength, Al + T
The lower limit of i was set to 4% as shown in the figure. W and Mo have the effects of solid solution strengthening and precipitation strengthening by carbide, and have the effect of increasing high temperature strength. To get that effect, W + 1 /
2Mo must be 0.5% or more, and if added too much,
The upper limit of W + 1 / 2Mo is set to 10% because it promotes precipitation of harmful phases such as σ phase and reduces ductility and strength.

[0010]

EXAMPLES The present invention will be described in more detail with reference to specific examples. Example 1 Tables 1 and 2 show chemical compositions (% by weight) of alloys invented for typical gas turbine vanes. In addition, Tables 3 and 4 show the chemical compositions of comparative alloys which are conventional alloys. For each composition, 20 kg of steel ingots were melted in a vacuum high frequency melting furnace. The samples were made by casting them as master ingots and lost wax precision casting, 1160 ℃ × 4hr + 1000 ℃ × 6hr +
Heat treatment was performed at 800 ° C. for 4 hours. Then, by mechanical processing, a creep rupture test piece having a parallel portion of 6.25φ × 25 mm, a 5 × 60 × 100 mm Balestrain test piece, and the like were produced. Nos. 1 to 18 in Table 1 are alloys of the present invention.
X, Y, Z, 19-36 are comparative alloys. Note that X,
Y is an example of the aforementioned Japanese Examined Patent Publication No. 54-6968, and Z is an example of JP-A-1-104738.

[0011]

[Table 1]

[0012]

[Table 2]

[0013]

[Table 3]

[0014]

[Table 4]

FIG. 1 shows (Al + Ti) for each sample.
The relationship between the amount and the amount of (W + 1 / 2Mo) is shown. In addition, in () of each sample number, 900 ° C., 20 kgf / mm
² shows the creep rupture time. In FIG. 1, the alloys of the present invention are indicated by white circles (◯), and the comparative alloys are indicated by black circles (●). Al + Ti and W within the line connecting the points ABCDE
The alloy of the present invention having a high + 1 / 2Mo (1, 4, 11, 12,
13, 14, 15, 16) show high strength,
Particularly, No. 11 shows high strength. Also, Al + Ti, W +
1/2 Mo is within the line connecting the points FGHD, and the alloy of the present invention having a low Cr content (2, 3, 5, 6, 7, 8, 9, 10, 1)
7, 18) shows particularly high strength. FIG. 2 shows the representative alloys Y, Z and 20 of Table ² and the alloys 9 and 11 of the present invention of Table 1 at 900 ° C., 20 kgf / mm ² and 98, respectively.
A comparison of creep rupture strength at 0 ° C and 10 kgf / mm ² is shown. Larson Miller parameter P = T on the horizontal axis
_k (20 + logt) × 10 ⁻³ , T _k : test temperature (°
K), t: breaking time (Hr) is used. The test results at 900 ° C and 980 ° C show that the stress on the vertical axis is 20 kgf each
/ Mm ² and 10 kgf / mm ² . The larger the parameter P on the horizontal axis, the higher the strength. The alloys of the present invention Nos. 9 and 11 have larger Larson-Miller parameters under the same test stress as those of the comparative alloys No. Y, Z and No. 20. This is an effect (No. 11) of increasing the amounts of Al + Ti and W + 1 / 2Mo and lowering the amount of Cr. On the other hand, the amount of Al + Ti is slightly higher than that of No. 9, but the comparative alloy No.Y, which also has a large amount of Cr, and the amount of Al + Ti is low, but W + 1 / 2Mo
Large amount of comparative alloy No.20, Al + Ti amount, W + 1/2
The Larson-Miller parameters such as the comparative alloy No. Z, which has a low Mo content, are on the lower side of the alloy of the present invention at the same test stress.

The weldability was evaluated by the Balestrain test (FIG. 6). That is, the welding current 100
A, welding voltage 12V, welding speed TIG welding under welding conditions of 1.67 mm / s, total strain of 0.25% or 0.77% is applied, and an index of the embrittlement region at the time of welding that occurs The length of the maximum crack which becomes is measured. This maximum crack length and creep rupture time (900 ° C × 20 kgf / m
The relationship of m ² ) is shown in FIG. The vertical axis in the figure indicates that the smaller the value, the better the weldability. Therefore, the lower the right side of the figure, the better the weldability and the higher the high temperature strength.
Inventive alloys Nos. 3, 7, 9, 10, 11, 12, and 15 in which Zr is 0.1% or less and B is 0.01% or less, all have a small maximum crack length. Especially No.9,
Nos. 11 and 12 have a target of 0.3 mm or less and a creep rupture time of 185 hours or more, which are excellent properties. On the other hand, in the comparative alloy, No. X, Y, 25, 27, 28,
33 and 35 showed a creep rupture time of 110 hours or more, but the maximum crack length of the vale train was 0.
The target was not satisfied when it was 8 mm or more. From the above results, Z
Al + Ti and W + 1 / 2Mo even if the amount of r and B are lowered
The relationship between A and B in the range of ABCDE or Cr
By setting the relationship between l + Ti and W + 1 / 2Mo within the range of ABCFGHE, it is possible to improve the weldability and increase the creep strength.

Example 2 Using a No. 11 alloy shown in Table 1 of Example 1, a gas turbine stationary blade shown in FIG. 4 was manufactured by the lost wax precision casting method, and solution heat treatment was performed at 1160 ° C. for 4 hours. After that, a welding test was conducted. This vane has a width of about 200 mm,
The height is about 200 mm, and the inside is a casting having a hollow structure with an air passage for cooling. The positions 1, 2, 3, 4 on the ventral side of the wing shown in FIG. 4, the positions 5, 6 of the leading edge and the position 7 of the trailing edge are overlay welded, and the inner shroud 8 is shown in FIG. As described above, the shroud portion 8 (invention alloy No. 11) and the cover plate 10 (Hastelloy X alloy) are welded with Hastelloy W alloy 11 to fillet the weld with TIG.
I went in. After welding, visual inspection at each position, fluorescence penetration deep scratch test, and microstructure observation of the cross section at the position shown in FIG. 5 were performed, but no crack was observed at any position. A comparative turbine Y (Japanese Patent Publication No. Sho 54-6968) was used to manufacture the same vane for a gas turbine as described above, and a welding test was conducted. A crack having a length of about 1 mm was recognized.

[0018]

As described above, according to the present invention, it is possible to obtain a Ni-base heat-resistant alloy having higher high-temperature strength and excellent weldability than conventional Ni-base heat-resistant alloys. This Ni-base heat-resistant alloy is particularly suitable for a gas turbine stationary blade material that requires reliability as the temperature of the gas turbine rises.

[Brief description of drawings]

FIG. 1 is a diagram showing the test results of the range of the alloy of the present invention and creep rupture time.

FIG. 2 is a diagram showing a comparison of creep rupture strength of match money.

FIG. 3 is a diagram showing the relationship between the maximum crack length and creep rupture time in the Balestrain test.

FIG. 4 is a perspective view of a gas turbine stationary blade on which a welding test is performed by applying the alloy of the present invention.

FIG. 5 is an explanatory diagram of a welded portion in a welding test.

FIG. 6 is an explanatory view of the procedure of a Varestraint test carried out to evaluate the weldability of the alloy of the present invention and the comparative alloy.

[Explanation of symbols]

 1 to 7 Weld beads 8 Inner shroud 9 Outer shroud 10 Cover plate 11 Hastelloy W alloy 12 Balestrain test piece (before bending strain addition) 13 Yoke 14 Bead 15 Welding torch 16 Balestrain test piece (after bending strain addition) 17 Bending block

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Kawabata 1 Hiraide Industrial Park, Utsunomiya City, Tochigi Prefecture Utsunomiya Manufacturing Co., Ltd. (72) Inventor Takemi Kokubu 1 Hiide Industrial Park, Utsunomiya City, Tochigi Prefecture Mitsubishi Steel Corporation Company Utsunomiya Works (72) Inventor Toshio Mochizuki 1 Hiraide Industrial Park, Utsunomiya City, Tochigi Prefecture Mitsubishi Steel Corporation Utsunomiya Works (72) Inventor Shuichi Sakashita 1 Hitsuide Industrial Park, Utsunomiya City, Tochigi Prefecture Mitsubishi Steel Corporation Utsunomiya Manufacturing Co., Ltd. (72) Inventor Hisataka Kawai 2-1-1, Niihama, Arai-cho, Takasago-shi, Hyogo, Takasago Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Ikuo Okada 2-1-1, Niihama, Arai-cho, Takasago, Hyogo Mitsubishi Heavy Industries, Ltd. In the laboratory (72) Inventor Ichiro Tsuji 2-1-1, Niihama, Arai-cho, Takasago-shi, Hyogo Mitsubishi Heavy Industries, Ltd., Takasago Plant (72) Inventor, Koji Takahashi, 2-1-1 Nihama, Arai-cho, Takasago-shi, Hyogo Prefecture Mitsubishi Heavy Industries, Ltd., Takasago Plant, (72) In-house, Taiji, Taiji, Niihama, Arai-cho, Hyogo Prefecture No. 1 Mitsubishi Heavy Industries, Ltd. Takasago Plant

Claims (2)

[Claims] 1. A weight percentage of 0.05 to 0.25% C,
18-25% Cr, 15-25% Co, W + 1/2
One or two of up to 3.5% Mo and 5-10% W in an amount with a Mo value of 5-10%, 1.0-5.
0% Ti, 1.0-4.0% Al, 0.5-4.5
% Ta, 0.2-3.0% Nb, 0.005-0.
Containing 10% Zr and 0.001-0.01% B,
The balance consists of Ni and unavoidable impurity elements, and (Al
+ Ti) amount and (W + 1 / 2Mo) amount are points A (Al + Ti: 3%, W + 1 / 2Mo: 10%) in FIG.
Point B (Al + Ti: 5%, W + 1 / 2Mo: 7.5
%), Point C (Al + Ti: 5%, W + 1 / 2Mo: 5)
%), Point D (Al + Ti: 7%, W + 1 / 2Mo: 5)
%), Point E (Al + Ti: 7%, W + 1 / 2Mo: 10)
%), A nickel-base heat-resistant alloy having excellent weldability, characterized in that it has a composition within a range surrounded by a line that sequentially connects the respective points (%). 2. 0.05 to 0.25% C by weight,
10-20% Cr, 15-25% Co, W + 1/2
M up to 3.5% of the amount where Mo value is 0.5-10%
o and one or two of W up to 0.5-10%;
0-5.0% Ti, 1.0-4.0% Al, 0.5
~ 4.5% Ta, 0.2-3.0% Nb, 0.00
5 to 0.10% of Zr and 0.001 to 0.01% of B are contained, the balance is Ni and unavoidable impurity elements, and the amount of (Al + Ti) and (W + 1 / 2Mo) is
In FIG. 1, point A (Al + Ti: 3%, W + 1 / 2M
o: 10%), point B (Al + Ti: 5%, W + 1 / 2M)
o: 7.5%), point C (Al + Ti: 5%, W + 1/2)
Mo: 5%), point F (Al + Ti: 4%, W + 1 / 2M
o: 5%), point G (Al + Ti: 4%, W + 1 / 2M)
o: 0.5%), point H (Al + Ti: 7%, W + 1/2)
Mo: 0.5%) Point E (Al + Ti: 7%, W + 1/2)
Mo: 10%) is a nickel-base heat-resistant alloy having excellent weldability, characterized by having a composition within a range surrounded by a line sequentially connecting each point.