WO2019103210A1 - Nickel-based single crystal superalloy and manufacturing method for same - Google Patents

Abstract

The present invention provides a nickel-based single crystal superalloy and a manufacturing method for same, the nickel-based single crystal superalloy comprising: 4.0-6.0 wt% of aluminum (Al); 10.5-12.5 wt% of cobalt (Co); 2.65-4.65 wt% of chromium (Cr); at most 2.0 wt% (over 0 wt%) of molybdenum (Mo); 1.0-1.7 wt% of rhenium (Re); 6.0-8.0 wt% of tantalum (Ta); 1.8-2.5 wt% of titanium (Ti); 6.9-8.9 wt% of tungsten (W); and the remainder in nickel (Ni) and other unavoidable impurities.

Description

Nickel-base single-crystal superalloy alloy and method for manufacturing the same

The present invention relates to a nickel-based single-crystal super-high-temperature alloy and a method of manufacturing the same, and more particularly, to a nickel-based single crystal super-high-temperature alloy excellent in high-temperature creep characteristics and a method of manufacturing the same.

Super heat resistant alloys can be classified into a group of nickel (Ni), iron (Fe), and cobalt (Co) based alloys. Among these, the most important and widely used in the industry is a nickel-base superalloy. Nickel (Ni) -based superalloys use nickel (Ni) as a matrix and are made of chromium (Cr), cobalt (Co), aluminum (Al), tungsten (W), tantalum (Ta), molybdenum ), Carbon (C), and rhenium (Re) are added to optimize high temperature mechanical properties and environmental characteristics. Nickel (Ni) base superalloys are applied in many industries requiring high temperature corrosion resistance and heat resistance, but the most important applications are aircraft engines and power generation gas turbines.

Recently, as environmental problems such as global warming are emerging, there is a growing need for new ways to reduce or eliminate carbon dioxide (CO ₂ ) generation and to improve the efficiency of existing methods. As a result, the operating temperature of the gas turbine is continuously increasing to improve the efficiency. The gas turbine combusts the compressed air in the compressor with the fuel so that the expanded combustion gas rotates the turbine to generate power or to produce power.

Therefore, turbine blades, vanes, and the like have a three-dimensionally complicated aerodynamic design including a complicated cooling passage inside a component to obtain higher efficiency under a given condition. For this reason, turbine blades, vanes and the like are manufactured by a casting process which is easy to shape. Also, the turbine blades of a gas turbine operating at a high temperature are subject to centrifugal force due to high-speed rotation of the turbine, and creep characteristics for enduring centrifugal force at high temperatures are very important.

Since grain boundaries of cast alloy produced by general casting process are vulnerable to high temperature creep characteristics, unidirectional solidification casting process which improves creep characteristics of alloy by eliminating grain boundaries having direction perpendicular to stress and single crystal casting process which completely eliminates grain boundaries Has been developed and is being used to manufacture turbine blades. As described above, alloys that are specially developed for process development, respective polycrystalline, one-way solidification and single crystal casting processes have been developed and used. The nickel-base superalloy has been continuously studied for designing alloy compositions having excellent properties because the characteristics of alloys exhibited vary depending on the kind, content and specific combination of alloying elements to be added.

Meanwhile, in order to satisfy the necessity of an alloy excellent in temperature water solubility and creep characteristics of alloys, it has been devised to control addition amounts of other alloying elements while suppressing addition of high-priced alloying elements as much as possible.

As described above, in the case of a component used at a high temperature, the creep life to reach the creep rupture is also important. However, if the shape of the component is changed, the original use is impossible or the efficiency is low. It is a very important factor to consider in design.

Accordingly, efforts have been made to obtain alloys excellent in tensile strength and creep characteristics at high temperatures by controlling the amount of alloying elements. However, since it contains expensive rhenium (Re) and ruthenium (Ru), alloys containing rhenium (Re) and ruthenium (Ru) have difficulties in suppressing price increase. The prior art is an alloy designed only considering the creep characteristics. It is an alloy designed to contact with corrosive gas at a high temperature and to apply high stress due to centrifugal force of thousands or tens of thousands of rpm. Corrosion problems can shorten component life.

Therefore, in order to design the material for the first stage of the gas turbine for power generation, alloy design should be made considering not only creep characteristics but also various material characteristics such as high temperature corrosion resistance, oxidation resistance, casting of large parts, do. In particular, a TCP phase (topologically close packed phase) is formed in the base of a nickel-base superalloy. The TCP phase is a brittle structure. As the content in the matrix increases, the creep life is shortened. Alloy design is needed.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a nickel-based single crystal super-high temperature alloy capable of suppressing the fraction of TCP that deteriorates mechanical properties while improving the creep characteristics of a super- And to provide the above objects. However, these problems are exemplary and do not limit the scope of the present invention.

According to one aspect of the present invention, there is provided a nickel-based single crystal superalloy alloy. The nickel-based single crystal superalloy article of claim 1, wherein the nickel-based single crystal superalloy alloy comprises 4.0 to 6.0 aluminum (Al), 10.5 to 12.5 cobalt (Co), 2.65 to 4.65 chromium (Cr), 2.0 or less molybdenum (Mo) , Rhenium (Re) of 1.0 to 1.7, tantalum (Ta) of 6.0 to 8.0, titanium (Ti) of 1.8 to 2.5, tungsten (W) of 6.9 to 8.9 and the balance nickel and other unavoidable impurities .

The content of rhenium (Re), tungsten (W), and chromium (Cr) in the nickel-based single crystal superalloy is controlled by the following Equation 1, and the equilibrium TCP fraction parameter value (Not less than 0) of not more than 19.12%.

[Equation 1]

Equilibrium TCP fraction parameter = 2.00 [Re] + 1.45 [W] + 0.60 [Cr]

(Where Re, W and Cr are the weight percentages of Re, W and Cr, respectively)

The Ni-based single-crystal super-high-temperature alloy according to claim 1, wherein the super-high-temperature alloy has a range of high temperature compatibility represented by the following formula (2): 502 to 592.

&Quot; (2) "

High temperature compatibility = Creep life x Phase stability

(Wherein the phase stability is the ratio of the fraction of TCP over the commercial alloy (CMSX4) over the TCP of the manufacturing alloy)

According to the embodiment of the present invention as described above, the creep property of the super-heat-resistant alloy is improved and the fraction of the TCP phase, which deteriorates the mechanical properties, is suppressed. As a result, the cost is low and the high temperature corrosion resistance, A single-crystal, super-high-temperature alloy of nickel, which is superior in high-temperature fatigue characteristics and high-temperature creep characteristics, and a method of manufacturing the same. Of course, the scope of the present invention is not limited by these effects.

1 is a schematic cross-sectional view of a member having a ceramic heat-resistant coating on a nickel-based single crystal superalloy using as a base material.

FIG. 2 is a photograph showing a result of a micro fatigue test cycle and a thermal fatigue test cycle of a nickel-based single crystal superalloy according to an experimental example of the present invention.

FIG. 3 is a graph showing the relationship between the amount of TCP phase and the amount of each element in the nickel-based single crystal superalloy according to the present invention.

FIGS. 4 to 8 are SEM micrographs of the interfacial microstructure of the nickel-based single crystal superalloy according to the present invention. FIG.

9 is a graph showing the creep characteristics of nickel-based single-crystal superalloys according to Experimental Examples of the present invention.

10 is a graph showing the results of analysis of creep life, room temperature stability, and high temperature compatibility of the nickel-based single crystal superalloy according to Experimental Example of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, Is provided to fully inform the user. Also, for convenience of explanation, the components may be exaggerated or reduced in size.

1 is a schematic cross-sectional view of a member having a ceramic heat-resistant coating on a nickel-based single crystal superalloy using as a base material.

Nickel single crystal super heat resistant alloys are mainly used in aircraft engines and power generation gas turbines, and the super heat resistant alloys are exposed to high temperature / high pressure corrosive environments. In this case, in order to lower the exposure temperature of the super-heat-resistant alloy material to a temperature lower than the service temperature at which the component is used, a thermal barrier coating layer is formed by spraying powder on the surface of the super- Make it corrosive.

As shown in Fig. 1 (a), a nickel-based single crystal superalloy alloy 10 is provided. The single crystal can be manufactured by using the nickel-based single crystal super-heat-resistant alloy one-way casting method or the like.

A bond coat layer (20) is formed on the super heat resistant alloy (10). Since the bond coat layer 20 is difficult to directly bond the super-high temperature resistant alloy 10 and the ceramic layer 40 to be formed later, the bond coat layer 20 is positioned between the two layers so that the super heat resistant alloy 10 and the ceramic layer 40 are bonded And a coating layer of a metal material used for making the coating film. For example, MCrAlY (M, Ni, Co, etc.) coating powder is widely used as the bond coat layer 20.

The bond coat layer 20 may be formed using various methods such as APS (air plasma spray), HVOF (high velocity oxygen fuel spray), and VPS (vacuum plasma spray). However, in order to deposit the bond coat powder on the surface of the super-high temperature alloy 10 regardless of the spraying process, the bond coat layer 20 must have a certain degree of surface roughness on the surface of the super heat resistant alloy 10 . 1 (b), before the bond coat layer 20 is formed, the surface of the super heat resistant alloy 10 is subjected to grit blasting treatment with alumina (Al ₂ O ₃ ) or the like Thereby forming a surface roughness. The grit blasting has been already commercialized, and a detailed description thereof will be omitted.

A TGO layer (thermally grown oxide layer) 30 is formed on the bond coat layer 20. The TGO layer 30 is a dense oxide film and has a function of preventing the oxidation of the super heat resistant alloy 10 by blocking oxygen penetration into the super heat resistant alloy 10 and dissipation of metal components from the super heat resistant alloy 10 .

Thereafter, the ceramic layer 40 is formed on the TGO layer 30. The ceramic layer 40 is a heat shielding film having a lot of pores to block heat flow from the high temperature gas in the turbine to the super heat resistant alloy 10 So that the temperature of the base material does not rise excessively. The ceramic layer 40 is used, for example, by coating ceramics of zirconia (ZrO ₂ ).

A recrystallization layer is formed at the interface due to the residual stress on the surface of the super-high-temperature alloy 10 and the mutual diffusion between the super-heat-resistant alloy 10 and the bond coat layer 20 by grit blasting during the coating process. Hereinafter, the recrystallized layer can be understood as a secondary reaction zone (SRZ).

Generally, in the case of a nickel-based single crystal superalloy, it is known that the mechanical properties are reduced when the second reaction layer is formed. Particularly, a TCP topologically close packed phase formed in the second reaction layer is mainly composed of a refractory element such as rhenium (Re), tantalum (Ta), and tungsten (W) As shown in FIG. The TCP phase decreases the intensity of gamma phase, which is a matrix, and gamma prime phase, which is a precipitation phase, and degrades the properties.

In order to solve this problem, in the present invention, the content of refractory elements controlling the formation of TCP is controlled, and the content of titanium (Ti) is controlled, whereby nickel-based monocrystalline super heat resistance exhibiting superior creep characteristics and phase stability Alloy.

Specifically, the nickel-based single crystal super-high temperature alloy according to an embodiment of the present invention includes aluminum (Al) of 4.0 to 6.0, cobalt (Co) of 10.5 to 12.5, chromium (Cr) of 2.65 to 4.65, (Re) of 1.0 to 1.7, tantalum (Ta) of 6.0 to 8.0, titanium (Ti) of 1.8 to 2.5, tungsten (W) of 6.9 to 8.9, and the balance nickel (Ni) and other unavoidable impurities.

In the present invention, the composition of aluminum (Al) may be in the range of 4.0 wt% to 6.0 wt%. Since aluminum (Al) is a constituent element of the gamma prime phase (? ') Which is the primary strengthening phase of the nickel-based single crystal superalloy, it is an element required for improving the high temperature creep property and also contributes to improvement of oxidation resistance. However, when the content is less than 4.0% by weight, the creep strength is lowered. On the other hand, when the content exceeds 6.0% by weight, excess gamma prime phase (γ ') may precipitate and mechanical properties may be deteriorated. In the case of aluminum (Al), the absolute amount of the composition is also important, but the relationship with the titanium (Ti) content, which is another element of gamma prime phase (γ '), is also important.

The composition of cobalt (Co) may satisfy 10.5 wt% to 12.5 wt%. Cobalt (Co) has a role of strengthening the solid solution, and the solid phase of gamma prime phase (γ '), which is the primary strengthening phase of nickel single crystal superalloy, and the solidus of gamma phase (γ) It also improves high temperature corrosion resistance. If the content of cobalt (Co) is less than 10.5% by weight, the creep property is lowered. On the other hand, if the content exceeds 12.5% by weight, the temperature range in which the solution treatment is possible becomes small.

The composition of molybdenum (Mo) may be 2.0 wt% or less (more than 0). Molybdenum (Mo) is a solid solution strengthening element and plays a role in improving the high-temperature characteristics of a nickel-base single crystal superalloy. However, when it is more than 2.0% by weight, the density becomes high and a TCP phase can be produced. In the absence of molybdenum (Mo), it is difficult to expect an employment strengthening effect.

The composition of tantalum (Ta) may be from 6.0 wt% to 8.0 wt%. Tantalum (Ta) is incorporated into the gamma prime phase (γ '), which is the main strengthening phase, and serves to strengthen the gamma prime phase (γ') phase. This contributes to the improvement of the creep strength and segregation in the dendritic region to increase the density of this region, thereby suppressing the formation of freckle which is a casting defect. If the content of tantalum (Ta) is less than 6.0 wt%, the above effect can not be expected. If the content of tantalum (Ta) exceeds 8.0 wt%, the delta phase (δ)

Titanium (Ti) is a member of the gamma prime phase (γ ') like aluminum (Al) and helps to improve creep strength. Particularly, addition of titanium (Ti) increases the lattice mismatch, and the lamination defect energy becomes small, so that creep characteristics can be improved.

The present inventors have added titanium (Ti) to improve creep characteristics, and found that the creep is improved as the content of titanium (Ti) increases, but the fraction of the TCP phase is increased. As described above, the TCP phase is a brittle phase and deteriorates the mechanical properties of the super-heat-resistant alloy, so it should be suppressed as much as possible.

Therefore, in order to control the TCP phase fraction while maintaining the creep characteristics due to the addition of titanium (Ti), the contents of tungsten (W), chromium (Cr) and rhenium (Re) .

Here, an appropriate content of the main elements can be derived by the following equation (the concrete content of the balanced TCP fractional parameter will be described later). At this time, Equation 1 should satisfy the equilibrium TCP fraction parameter value of 19.12% or less (more than 0). The criterion for the 19.12% is the equilibrium TCP fraction parameter value calculated using the composition of commercial alloy (CMSX4). The equilibrium TCP fraction parameter value is the result of thermodynamic calculation according to the content of each element.

[Equation 1]

Equilibrium TCP fraction parameter = 2.00 [Re] + 1.45 [W] + 0.60 [Cr]

[Re] is the content (% by weight) of rhenium (Re), [W] is the content (wt%) of tungsten (W) and [Cr] is the content (wt%) of chromium (Cr).

According to the above equations, the content of rhenium (Re), tungsten (W), and chromium (Cr) is important in addition to the content of titanium (Ti). The rhenium (Re), tungsten (W), and chromium (Cr) are solved to improve the creep characteristics. The rhenium (Re) It is technically meaningful.

The composition ranges of titanium (Ti), rhenium (Re), tungsten (W) and chromium (Cr) under the condition that the equilibrium TCP fraction parameter value has a value of 19.12% or less and the reasons for the limitation are as follows.

The composition of rhenium (Re) may satisfy 1.0 wt% to 1.7 wt%. Rhenium (Re) is a solid solution strengthening element and its diffusion rate is very slow, which contributes greatly to improvement of creep characteristics. By adding rhenium (Re), the nickel-based single-crystal superalloy has remarkably improved not only the creep life required for use at high temperatures but also resistance to creep deformation. However, if the content of rhenium (Re) is less than 1.0% by weight, it is difficult to expect the above effect. On the other hand, when the content exceeds 1.7% by weight, a large amount of the TCP phase is generated, the phase stability is lowered, the density is increased, and the price is high, which raises the process cost.

The composition of tungsten (W) can satisfy 6.9 wt% to 8.9 wt%. Tungsten (W) is an element that increases creep strength by solid solution strengthening. However, when the content of tungsten (W) is less than 6.9% by weight, the effect of high temperature strength can not be obtained. On the other hand, when the content of tungsten exceeds 8.9% by weight, the density is increased and toughness and corrosion resistance are lowered. . In addition, when single crystal and one-direction solidification are performed, the possibility of occurrence of casting defects such as freckles increases.

The composition of chromium (Cr) may be 2.65 wt% to 4.65 wt%. Chromium (Cr) increases the corrosion resistance of nickel-base single-crystal superalloys, but it can produce carbides and TCP phases, and its amount is limited because it does not contribute to heat resistance. If the content of chromium (Cr) is less than 2.65% by weight, corrosion resistance may occur. On the other hand, if it exceeds 4.65% by weight, creep characteristics may be deteriorated.

The composition of titanium (Ti) may satisfy 1.8 wt% to 2.5 wt%, preferably 2.0 wt% to 2.5 wt%.

If the titanium (Ti) content is less than 1.8 wt%, the desired creep characteristics are not exhibited. If the titanium (Ti) content is more than 2.5 wt%, a large amount of TCP phase is generated and the phase stability is lowered. The optimum range of such titanium (Ti) can be expressed by the high temperature compatibility expressed by the following formula (2), and the nickel-based single crystal superalloy according to the embodiment of the present invention can have a high temperature compatibility range of 502 to 592 .

&Quot; (2) "

High temperature compatibility = Creep life x Phase stability

(Wherein the phase stability is the ratio of the fraction of TCP over the commercial alloy (CMSX4) over the TCP of the manufacturing alloy.)

Hereinafter, experimental examples for understanding the characteristics of the nickel-based single-crystal super-heat-resistant alloy realized by the method for manufacturing a nickel-based single crystal superalloy according to the present invention will be described. It should be understood, however, that the following examples are for the purpose of promoting understanding of the present invention and that the present invention is not limited to the following examples.

In order to suppress the formation of TCP phase due to the addition of titanium (Ti) elements, parameters related to TCP stability were derived as a first step for alloy design. Hereinafter, the process of deriving the parameters will be described in detail.

FIG. 2 is a photograph showing a result of a micro fatigue test cycle and a thermal fatigue test cycle of a nickel-based single crystal superalloy according to an experimental example of the present invention. First, a bond coat layer was formed on a sample of Experimental Example 1 which is a commercial alloy, and a thermal fatigue test was repeatedly performed 100 times at 1100 ° C. FIG. 2 (a) shows a thermal fatigue cycle thereof, and FIG. 2 (b) shows a microstructure analysis photograph. The component analysis results at points 1, 2, and 3 shown in FIG. 2 (b) are summarized in Table 1 below.

weight%	Al	Ti	Cr	Co	Ni	Ta	W	Re	Mo	Total
Branch 1	2.85	0.42	10.7	5.32	32.6	-	27.2	20.5	0.41	100
Branch 2	0.82	-	14.2	4.99	19.4	-	29.0	30.8	0.87	100
Branch 3	1.46	-	11.6	5.91	24.2	1.77	29.9	24.5	0.69	100

 Referring to FIG. 2 and Table 1, TCP analysis of the sample of Experimental Example 1, which is a commercial alloy, showed that the contents of nickel (Ni), chromium (Cr), tungsten (W) and rhenium there was. In particular, the content of rhenium (Re) is 10 wt% or more. Therefore, the optimum alloy design must be performed using chromium (Cr), tungsten (W), and rhenium (Re) elements except for the content of nickel, which is the main element. The amount of each alloy element was changed based on the sample of Experimental Example 1 which is a commercial alloy, and the equilibrium TCP phase fraction at 1100 ° C was calculated with JMatPro and summarized in Table 2.

Alloying element		Tungsten (W)	Rhenium (Re)	Chromium (Cr)
D comp. (weight%)	-2	0	0	0.741099
	-One	0.774395	0.101992	1.508807
	0	2.201801	2.201801	2.201801
	+1	3.678606	4.170176	2.541609
	+2	5.130768	6.115098	3.226059

FIG. 3 is a graph showing the relationship between the amount of TCP phase and the amount of each element in the nickel-based single crystal superalloy according to the present invention.

Referring to FIG. 3 and Table 2, plotting TCP fraction according to composition change of rhenium (Re), tungsten (W) and chromium (Cr) and then leaner fitting, . 3 (a), 3 (b) and 3 (c) are graphs respectively showing rhenium (Re), tungsten (W) and chromium (Cr). The slope in each graph can be calculated as a fraction parameter on the balanced TCP to yield the following equation (1).

[Equation 1]

Equilibrium TCP fraction parameter = 2.00 [Re] + 1.45 [W] + 0.60 [Cr]

[Re] is the content (% by weight) of rhenium (Re), [W] is the content (wt%) of tungsten (W) and [Cr] is the content (wt%) of chromium (Cr).

From this, the compositions of rhenium (Re), tungsten (W) and chromium (Cr) satisfying the equilibrium TCP fractional parameters of the above formula (1) were derived while varying the content of titanium (Ti).

Table 3 below shows alloy compositions derived using the equilibrium TCP fraction parameters derived in the first step. FIG. 3 is a table summarizing experimental examples for finding an optimum composition capable of effectively controlling the TCP phase generated in a matrix of a super-heat-resistant alloy as a nickel-based single crystal superalloy alloy sample according to an experimental example of the present invention.

Alloys	Al	Co	Cr	Mo	Re	Ta	Ti	W	Hf	Ni
Experimental Example 1	5.6	9.0	6.4	0.6	3.0	6.5	1.0	6.4	0.1	61.4
Experimental Example 2	5.5	11.5	4.0	1.0	1.5	7.0	1.0	8.5	0.0	60.0
Experimental Example 3	5.0	11.5	4.0	1.0	1.5	7.0	2.0	8.5	0.0	59.5
Experimental Example 4	5.0	11.5	4.0	1.0	1.5	7.0	2.5	8.5	0.0	59.0
Experimental Example 5	4.5	11.5	4.0	1.0	1.5	7.0	3.0	8.5	0.0	59.0

(AMDRY 9624, Ni-22Cr-10Al-1.0Y) was coated on the surface of the alloy by applying a conventional VPS coating process, Was formed to a thickness of 250 +/- 50 mu m. Five kinds of samples with bond coat layer were exposed at about 1100 ℃ for 30 hours and the area fraction of TCP formed near bond coat layer and base metal interface was measured to compare phase stability of each alloy sample. The average fraction of TCP was calculated by SEM-BEI (Scanning Electron Microscopy - Backscattered Electron Image) for each type of alloy using image analyzing program. The average fractions are summarized in Table 4 below. The photographic magnification used was 1,000 times, the area per one photograph was about 128 × 96 μm ² , and the average fraction was arithmetically averaged for each area fraction obtained from the photograph. Here, the base material of the sample of Experimental Example 1 is the composition of CMSX4 which is a commercial single crystal super heat resistant alloy. FIGS. 4 to 8 are SEM micrographs of the interfacial microstructure of the nickel-based single crystal superalloy according to the present invention. FIG.

	Experimental Example 1	Experimental Example 2	Experimental Example 3	Experimental Example 4	Experimental Example 5
Ti content	1.0%	1.0%	2.0%	2.5%	3.0%
Average TCP area fraction	1.42 ± 0.20%	0.39 ± 0.05%	0.63 + 0.11%	0.67 + 0.08%	1.52 + 0.22%

Referring to FIGS. 4 to 8, it can be seen that as the content of titanium (Ti) increases, a large amount of TCP phase is generated at the interface. In particular, in the case of the sample of Experimental Example 5 in which the content of titanium (Ti) was 3% by weight, the TCP phase was distributed in a considerably large amount and formed into a long elongated shape.

Referring to Table 4, it can be seen that the average TCP area fraction is smaller in Experimental Examples 2 to 4 as compared with Experimental Example 1, which is CMSX4, which is a commercial single crystal superalloy, although the content of Ti is 1.0 wt% or more. However, in the case of Experimental Example 5 in which the Ti content is 3.0 wt%, it can be confirmed that the average TCP area fraction is larger than that in Experimental Example 1. [ From this, according to the alloy design according to the technical idea of the present invention, it can be seen that even if the composition of Ti is added at 1% or more, the generation of TCP can be suppressed, but it should be controlled to less than 3.0%.

9 is a graph showing creep characteristics of a nickel single crystal super-superalloy according to an experimental example of the present invention under a condition of 982 ° C and 248 MPa. Table 5 summarizes the creep life according to the content of titanium (Ti).

Single crystal alloy	Experimental Example 1	Experimental Example 2	Experimental Example 3	Experimental Example 4	Experimental Example 5
Ti content (% by weight)	1.0	1.0	2.0	2.5	3.0
Life time (hours)	204	132	223	279	300

9 and Table 5, it can be seen that the creep life tends to increase with an increase in the content of titanium (Ti). In case of Experimental Example 1 which is a commercial alloy, the creep life is 205 hours, Was lower than the samples of Experimental Examples 3 to 5 having a content of more than 2.0% by weight.

10 is a graph showing the results of analysis of creep life, room temperature stability, and high temperature compatibility of the nickel-based single crystal superalloy according to Experimental Example of the present invention.

Referring to FIGS. 10 and 5, it can be seen that, in the case of the samples of Experimental Examples 2 to 5 of the present invention, as the content of titanium (Ti) increases, the creep life also increases. On the other hand, the fraction on TCP increased, and thus the phase stability showed a tendency to decrease as the content of titanium (Ti) increased.

The phase stability refers to the TCP phase fraction of the commercial alloy (CMSX4) relative to the TCP of the manufacturing alloy. Here, it means the TCP fraction fraction of the sample of Experimental Example 1 relative to the fraction of TCP of the Experimental Examples 2 to 5. For example, the fraction of TCP in the sample of Experimental Example 2 is 0.39%, and the fraction of TCP in the sample of Experimental Example 1 is 1.42%. Therefore, when the content of titanium (Ti) is 1% by weight, the phase stability is about 364 .

The high temperature compatibility according to the titanium (Ti) content shown in FIG. 9C is obtained by multiplying the creep life shown in FIG. 9A (a) and the phase stability shown in FIG. The high temperature compatibility values are graphically displayed.

It was found that the high temperature compatibility value becomes higher as the characteristics are better at high temperature and that the samples of Experimental Examples 2 to 5 are higher in temperature than those of Experimental Example 1 which is a commercial alloy at high temperature compatibility. However, in the case of the sample of Experimental Example 5, as the content of titanium (Ti) increases to 3% by weight, it is not suitable because the high temperature compatibility decreases due to the increase of the TCP phase. Referring to FIG. 9 (c), it can be seen that an optimum range of 2.0% by weight to 2.5% by weight, which is a titanium composition having a high temperature compatibility in the range of 502 to 592, is considered in consideration of both creep life and phase stability.

As described above, the inventors of the present invention have found that by controlling the content of titanium (Ti) primarily through various experimental examples, it is possible to improve the creep lifetime and to reduce the content of chromium (Cr), rhenium ) And tungsten (W) can be effectively controlled by selecting the parameters that can effectively control the content and shape of the precipitate.

 While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Claims (3)

1. (Al) of 4.0 to 6.0, cobalt (Co) of 10.5 to 12.5, chromium (Cr) of 2.65 to 4.65, molybdenum (Mo) of 2.0 or less and molybdenum of 1.0 to 1.7 Tantalum (Ta) of 6.0 to 8.0, titanium (Ti) of 1.8 to 2.5, tungsten (W) of 6.9 to 8.9 and the balance nickel (Ni) and other unavoidable impurities.

   Nickel group single crystal super heat resistant alloy.
2. The method according to claim 1,

   The content of rhenium (Re), tungsten (W) and chromium (Cr) is controlled by the following equation (1), and the equilibrium TCP fraction parameter value calculated by the following formula (1) satisfies 19.12% doing,

   Nickel group single crystal super heat resistant alloy.

   [Equation 1]

   Equilibrium TCP fraction parameter = 2.00 [Re] + 1.45 [W] + 0.60 [Cr]

   (Where Re, W and Cr are the weight percentages of Re, W and Cr, respectively)
3. The method according to claim 1,

   Wherein the super-heat-resistant alloy has a range of high temperature compatibility represented by the following formula (2): 502 to 592,

   Nickel group single crystal super heat resistant alloy.

   &Quot; (2) "

   High temperature compatibility = Creep life x Phase stability

   (Wherein the phase stability is the ratio of the fraction of TCP over the commercial alloy (CMSX4) over the TCP of the manufacturing alloy)

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