JPS6043422B2 - Ni-based heat-resistant alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a N
This invention relates to an i-based heat-resistant alloy.

The most effective way to increase the output and thermal efficiency of gas turbines used in jet engines, power generation equipment, etc. is to increase the combustion gas temperature.

For this purpose, a moving blade material with high creep rupture strength is required. Additionally, the rotor blade material needs to withstand thermal fatigue associated with starting and stopping the gas turbine. For this purpose, it must have excellent ductility at high temperatures. Currently, -7 brightness degree Celsius (manufactured by Inco Corporation, composition listed below) is used for large gas turbine rotor blade materials for power generation, and MarM200 (manufactured by Martin Murrieta Corporation, composition listed below) is used for jet engine rotor blade materials. ) is used as an excellent one, and also MarM247
(manufactured by Martin Murrieta, composition listed below) is being considered for practical use.

However, since these alloys do not have excellent creep rupture strength, there is a limit to their ability to increase output and thermal efficiency.

NAS is an existing alloy with excellent creep rupture strength.
There is an A■-A alloy (manufactured by NASA, USA, composition listed below).

However, this alloy has extremely low high temperature tensile ductility;
It has the disadvantage of being weak against thermal fatigue. Furthermore, since expensive Re is used, there is a problem that the alloy is expensive. The object of the present invention is to provide a Ni-based heat-resistant alloy that has excellent creep rupture strength and high-temperature ductility without using JRe as in the NASA ■-A alloy. The Ni-based heat-resistant alloy of the present invention has C05 to 1
2%, Cr7-9%, Wll, 5%-15%, A14.
2-5.8%, Ti 0.1-1.5%, Ta 4-6%,
Hf0.5-1.5%, C0.05-0.15%, B0
．． 005 to 0.02%, Zr0.01 to 0.15%, and the remainder substantially consists of Ni, and at the same time, +Ti<6
．． It is a Ni-based heat-resistant alloy that satisfies the following: 5% W + Ta 16-19%.

The effects of the compositional components of the Ni-based heat-resistant alloy of the present invention and the reason for limiting the composition ratio are as follows.

Co dissolves in the γ phase and the γ' phase stoichiometrically represented by Ni and Al, contributing to the solid solution of these phases and increasing the amount of γ' phase precipitated in the γ phase. This acts to promote precipitation strengthening. If the amount is less than 5%, the above effects cannot be sufficiently obtained. Also, the amount is 12%
If it exceeds this, harmful precipitates such as σ phase appear, resulting in a decrease in creep rupture strength. Cr has the effect of improving the sulfide corrosion resistance of the alloy.

However, if the amount exceeds 9%, harmful phases such as σ phase and μ phase are formed on the plate, resulting in a disadvantage that the creep rupture strength decreases. If it is less than 7%, the above effect cannot be obtained sufficiently.

W forms a solid solution in the γ and γ″ phases and significantly strengthens these phases.

For that purpose, it is necessary to contain 11.5% or more,
If it exceeds 15%, harmful precipitates such as μ phase are produced, resulting in a shortened creep rupture life. A1 is an element necessary to generate the γ'' phase, and in order to sufficiently precipitate the γ'' phase, it must be contained in an amount of 4.2% or more.

However, if it exceeds 5.8%, the amount of coarse γ'' phase called eutectic γ″ becomes too large, resulting in a disadvantage that the creep rupture strength decreases. Most of Ti is dissolved in the γ″ phase, and the γ
“Contributes to strengthening the phase.

At least 0.1% is required to obtain this effect. However, if it exceeds 1.5%, an n-phase is formed, resulting in cracks that reduce creep rupture strength. Most of Ta dissolves in the γ'' phase and significantly strengthens the steel as a solid solution, and also increases the amount of the γ'' phase to contribute to precipitation strengthening.

In order to obtain this effect with the alloy of the present invention, a content of 4% or more is required. However, when it exceeds 6%, harmful precipitates such as σ phase are generated, resulting in a decrease in creep rupture life and a decrease in high-temperature ductility. As is well known, C is MC type, M
Three types of carbides, 23C6 type and M6C type, are made to mainly strengthen the grain boundaries of the alloy crystals. To obtain this effect, 0.05% or more of C is required. However, if it exceeds 0.15%, a large amount of coarse carbides will crystallize, which will actually reduce the creep rupture strength. B segregates at grain boundaries, improves grain boundary strength at high temperatures, and functions to increase creep rupture strength and fracture elongation.

In order to obtain this effect, 0.005% or more is required. However, if it exceeds 0.02%, a low melting point eutectic is generated at the grain boundaries, resulting in the disadvantage that the alloy is more likely to be damaged by melting. Like B, Zr also acts to strengthen grain boundaries.

To obtain this effect, 0.01% or more is required. However, if it exceeds 0.15%, intermetallic compounds are formed at the grain boundaries, resulting in a disadvantage of lowering the creep rupture strength. H
f acts to strengthen grain boundaries. To get this effect, 0.5
% or more is required. However, if the content exceeds 1.5%, harmful intermetallic compounds will be produced and the creep rupture life will be reduced.
The composition ratios of each element have been explained above, but in order to obtain an alloy that is excellent in both creep rupture strength and high-temperature ductility, conditions related to a plurality of elements are required.

That is, in the case of the alloy of the present invention, the total amount of W.5Ta, which is an element effective for solid solution strengthening of the γ phase or γ'' phase, must be 16% or more.

When W+Ta is less than 16%, the amount of solid solution strengthening is insufficient,
If the sorb strength is insufficient, it will not be possible to obtain sufficient sorb rupture strength. On the other hand, if the total amount exceeds 19%, harmful precipitates such as σ phase and μ phase are formed, resulting in a disadvantage that the creep rupture strength decreases. In addition, in the case of the alloy of the present invention, when A1+Ti is 6.5% or more, the amount of γ'' becomes excessive and the high temperature ductility decreases.
+Ti must be less than 6.5. Preferably 6
% or less. Examples are given below, and conventional N1
A comparison with base heat-resistant alloys is shown.

EXAMPLE Four types of alloys of the present invention and four types of existing alloys were melted and cast, and creep rupture tests were conducted.

Melting was carried out in a high frequency vacuum melting furnace, and the temperature was kept at 800°C.
W! One Lφ creep rupture test piece was cast into a potted Stowwax mold. The test piece was heat treated at 1080'C x 4 hours, air-cooled + 870°C x 20 hours;
It was subjected to a creep rupture test (JISZ-2272) and a high temperature tensile test (JISG-0567). The test results were as shown in Table 1. This is illustrated in Figure 1, which compares the performance of the existing alloy and the alloy of the present invention. As is clear from the figure, the creep rupture life of the alloy of the present invention is
IN-738LC. ．． To MarM20 ■ It can be seen that it is larger than RM247, which is currently considered the strongest alloy.

This is mainly due to the amount of solid solution strengthening (W+MO+Ta+Nb
) can be explained by (MO here (5N
Since b has the same solid solution strengthening effect as WNTa per 1%, W+MO+Ta+Nb can be regarded as the solid solution strengthening amount. )
As shown in Table 1, the amount of solid solution strengthening of KO-738LC is significantly smaller than that of the alloy of the present invention, and the amount of W is also small, and the amount of Cr is large. MarM2OO@-gold and MarM247 alloy also have a smaller amount of W+MO+Ta+Nb than the alloy of the present invention, and C
The amount of r is large.

Therefore, the above three types of alloys have lower creep rupture strength than the alloy of the present invention. The NASA ■-A alloy exhibits a creep rupture life equal to or better than that of the alloy of the present invention. but,
Low high temperature tensile ductility. This is because Cri is low at 5.8% and ]a is high at 9%. Compared to these existing alloys, the alloy of the present invention is an alloy superior in both creep rupture strength and high-temperature ductility, and has extremely high practical value. Furthermore, the NASA ■-A alloy has γ″ due to Ta.
In contrast, the alloy of the present invention does not use expensive Re and uses only a small amount of Ta, and is mainly an inexpensive alloy. This utilizes the solid solution strengthening of W. Therefore, the alloy of the present invention can be produced at a much lower cost than the NASA 1-A alloy. In addition, the alloy of the present invention has excellent effects such as being more advantageous in the production control of manufacturing in factories, for example in the conversion of scrap to other alloys. By using the alloy of the present invention as a rotor blade material, it is possible to improve the efficiency of various gas turbines such as jet engines and power generation equipment.

At the same time, a gas turbine with sufficiently high reliability against thermal fatigue can be obtained.

This alloy can also be used with oxidation-resistant or sulfur-resistant coatings.

Furthermore, it can be used as a directionally solidified material or a single crystal material, which provides improved strength and ductility at high temperatures. In addition, it can also be used as a base for particle dispersion strengthened alloys.

[Brief explanation of the drawing]

FIG. 1 shows a comparison diagram of the tensile rupture elongation and creep rupture life of a known alloy and an alloy of the present invention.

Claims (1)

[Claims] 1% by weight: Co5-12%, Cr7-9%, W1
1.5% to 15%, Al4.2 to 5.8%, Ti0.1
~1.5%, Ta4~6%, Hf0.5~1.5%, C
0.05-0.15%, B0.005-0.002%,
A Ni-based heat-resistant alloy containing 0.01 to 0.15% of Zr, the remainder substantially consisting of Ni, and at the same time satisfying the following conditions: Al+Ti<6.5% W+Ta=16 to 19%.