KR102340057B1 - Ni base single crystal superalloy and Method of manufacturing thereof - Google Patents

Abstract

The present invention is, by weight%, 4.0 to 6.0 of aluminum (Al), 10.5 to 12.5 of cobalt (Co), 2.65 to 4.65 of chromium (Cr), 2.0 or less (greater than 0) of molybdenum (Mo), 1.0 to 1.7 Nickel-based single crystal candle containing rhenium (Re), tantalum (Ta) of 6.0-8.0, titanium (Ti) of 1.8-2.5, tungsten (W) of 6.9-8.9, and the balance containing nickel (Ni) and other unavoidable impurities Provided are a heat-resistant alloy and a method for manufacturing the same.

Description

Nickel-based single crystal superalloy and manufacturing method thereof

The present invention relates to a nickel-based single-crystal superalloy and a method for manufacturing the same, and more particularly, to a nickel-based single-crystal superalloy having excellent high-temperature creep properties and a method for manufacturing the same.

The superalloy may be classified into a nickel (Ni) group, an iron (Fe) group, and a cobalt (Co) group alloy group. Among them, the most important and widely used industrially is a nickel (Ni)-based superalloy. Nickel (Ni)-based superalloys use nickel (Ni) as a matrix, chromium (Cr), cobalt (Co), aluminum (Al), tungsten (W), tantalum (Ta), molybdenum (Mo) ), carbon (C), and rhenium (Re) are added to optimize high-temperature mechanical properties and environmental resistance properties by adding about 10 alloying elements. Nickel (Ni)-based superalloys are applied in many industrial fields requiring high temperature corrosion resistance and heat resistance, but the most important application fields are aircraft engines and gas turbines for power generation.

Recently, as environmental problems such as global warming have emerged, there is a growing need for methods to increase the efficiency of existing power generation methods along with research on new power generation methods to reduce or eliminate _{carbon dioxide (CO 2 ) generation.} As a result, in the case of gas turbines, the operating temperature is continuously increasing to improve efficiency. A gas turbine burns compressed air in a compressor with fuel, and the expanded combustion gas rotates the turbine to generate output or electricity.

Accordingly, turbine blades or vanes have a three-dimensionally complex aerodynamic design including a cooling passage having a complex shape inside the component to obtain higher efficiency under a given condition. For this reason, turbine blades, vanes, etc. are manufactured by a casting process that facilitates shape manufacturing. In addition, the turbine blades of a gas turbine operating at a high temperature receive a centrifugal force according to the high-speed rotation of the turbine, and creep characteristics to withstand the centrifugal force at a high temperature are very important.

Since the grain boundaries of cast alloys manufactured by the general casting process are vulnerable to high temperature creep characteristics, the unidirectional solidification casting process that improves the creep properties of the alloy by removing the grain boundaries having a direction perpendicular to the stress, and the single crystal casting process that completely eliminates the grain boundaries It has been developed and used for the manufacture of turbine blades. As such, alloys specialized for process development, polycrystalline, unidirectional solidification, and single crystal casting processes have been developed and used. Nickel-based superalloys are constantly being studied for the design of alloy compositions with excellent properties because the properties of the alloy exhibited greatly change depending on the type, content, and combination of specific elements added.

On the other hand, recently, in order to satisfy the need for an alloy having excellent temperature solubility and creep properties of the alloy, a method of controlling the addition amount of other alloying elements while suppressing the additional addition of expensive alloying elements as much as possible has been devised.

As described above, in the case of parts used at high temperatures, the creep life to reach creep failure is also important, but if the shape of the part changes, continuous use for its original purpose is impossible or the efficiency is lowered, so the resistance to initial creep deformation is also the alloy It is a very important factor to consider in design.

Accordingly, efforts are being made to obtain an alloy having excellent tensile strength and creep properties at high temperatures by controlling the amount of alloying elements. However, since it contains expensive rhenium (Re) and ruthenium (Ru), it is difficult to suppress the price increase of alloys containing rhenium (Re) and ruthenium (Ru). In addition, the prior art is an alloy designed in consideration of creep characteristics only, and when applied to parts such as the first stage blade of a gas turbine for power generation that comes in contact with high temperature corrosive gas and high stress is added due to centrifugal force of thousands or tens of thousands of rpm, high temperature oxidation and Corrosion problems can shorten component life.

Therefore, in order to design a material for the first stage blade of a gas turbine for power generation, an alloy design should be made in consideration of various material characteristics and economic feasibility such as creep characteristics, high temperature corrosion characteristics, oxidation resistance, castability of large parts, price, high temperature fatigue characteristics, etc. do. In particular, a topologically close packed phase (TCP) is formed in the matrix of the nickel-based superalloy, and the TCP phase is a brittle structure, and as the content in the matrix increases, the creep life can be shortened. An alloy design that can do this is necessary.

Domestic Registered Patent No. 10-0725624

The present invention is to solve various problems including the above problems, and a nickel-based single-crystal superalloy capable of suppressing the fraction of TCP phase that deteriorates mechanical properties while improving creep properties of the superalloy, and a method for manufacturing the same is intended to provide However, these problems are exemplary, and the scope of the present invention is not limited thereto.

According to one aspect of the present invention, there is provided a nickel-based single crystal superalloy. The nickel-based single crystal superalloy is, by weight, of 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 (more than 0) molybdenum (Mo) , 1.0 to 1.7 rhenium (Re), 6.0 to 8.0 tantalum (Ta), 1.8 to 2.5 titanium (Ti), 6.9 to 8.9 tungsten (W), and the balance contains nickel (Ni) and other unavoidable impurities. can

In the nickel-based single crystal superalloy, the contents of rhenium (Re), tungsten (W) and chromium (Cr) are controlled by Equation 1 below, and the equilibrium TCP fraction parameter value calculated by Equation 1 below 19.12% or less (greater than 0) can be satisfied.

[Equation 1]

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

(where [Re], [W] and [Cr] are weight % of Re, W and Cr, respectively)

The nickel-based single crystal superalloy according to claim 1, wherein the superalloy may have a high temperature suitability range of 502 to 592 expressed by Equation 2 below.

[Equation 2]

High Temperature Compatibility = Creep Life × Phase Stability

(Here, the phase stability is the ratio of the fraction of the TCP phase of the commercial alloy (CMSX4) to the TCP phase of the manufactured alloy.)

According to the embodiment of the present invention made as described above, by suppressing the fraction of the TCP phase that deteriorates the mechanical properties while improving the creep properties of the superalloy, the price is low, the high temperature corrosion property, the oxidation resistance, and the main component of large parts A nickel-based single-crystal superalloy having excellent composition, high-temperature fatigue characteristics and high-temperature creep characteristics and a manufacturing method thereof can be realized. Of course, the scope of the present invention is not limited by these effects.

1 is a cross-sectional view schematically illustrating a member using a nickel-based single-crystal superalloy as a base material and having a ceramic heat-resistant coating thereon.
2 is a photograph showing the microstructure analysis results observed after a thermal fatigue test cycle and a thermal fatigue test of a nickel-based single crystal superalloy according to an experimental example of the present invention.
3 is a graph showing the amount of TCP phase production and the correlation of each element of the nickel-based single-crystal superalloy according to an experimental example of the present invention.
4 to 8 are photographs of the microstructure of the interface of the nickel-based single-crystal superalloy according to the experimental example of the present invention analyzed with a scanning electron microscope.
9 is a graph showing the results of testing the creep characteristics of the nickel-based single-crystal superalloy according to the experimental example of the present invention.
10 is a graph showing the results of analyzing the creep life, room temperature stability, and high temperature suitability of a nickel-based single crystal superalloy according to an experimental example of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms. It is provided to fully inform the In addition, in the drawings for convenience of description, the size of the components may be exaggerated or reduced.

1 is a cross-sectional view schematically illustrating a member using a nickel-based single-crystal superalloy as a base material and having a ceramic heat-resistant coating applied thereon.

The nickel-based single crystal superalloy is mainly used in aircraft engines and gas turbines for power generation, and the superalloy is exposed to a corrosive environment of high temperature/high pressure. At this time, in order to lower the exposure temperature of the superalloy material than the service temperature at which the component is used, powder is sprayed on the surface of the superalloy to form a thermal barrier coating layer, so that high temperature oxidation resistance and resistance make it corrosive.

As shown in Fig. 1 (a), a nickel-based single crystal superalloy 10 is provided. The nickel-based single crystal superalloy may be manufactured as a single crystal by using a unidirectional casting method or the like.

A bond coating layer 20 is formed on the superalloy 10 . Since it is difficult to directly bond the superalloy 10 and the ceramic layer 40 to be formed later, the bond coating layer 20 is positioned between the two layers to bond the superalloy 10 and the ceramic layer 40 to each other. It is a coating layer of a metal material used to The bond coating layer 20 is, for example, MCrAlY (M is Ni, Co, etc.) a lot of coating powder is used.

The bond coating layer 20 may be formed using various methods such as air plasma spray (APS), high velocity oxygen fuel spray (HVOF), and vacuum plasma spray (VPS). However, for the bond coating layer 20 to deposit the bond coating powder on the surface of the superalloy 10 regardless of the thermal spraying process, a certain degree of surface roughness must be formed on the surface of the superalloy 10. . To this end, as shown in (b) of Figure 1, before forming the bond coating layer 20, the surface of the superalloy 10 is grit blasting (grit blasting) treatment with _{alumina (Al 2} O _{3), etc.} to form a surface roughness; As for the grit blasting, a detailed description will be omitted as it is a technology that has already been commercialized.

In addition, a thermally grown oxide layer (30) is formed on the bond coating layer (20). The TGO layer 30 is a dense oxide film, and prevents oxidation of the superalloy 10 by blocking oxygen penetration into the superalloy 10 and the elution of metal components from the superalloy 10 . carry out

Thereafter, a ceramic layer 40 is formed on the TGO layer 30 . The ceramic layer 40 is a thermal barrier film with many pores and blocks the heat flow from the high temperature gas in the turbine to the superalloy 10 . By doing so, it performs the function of preventing the temperature of the base material from rising too much. The ceramic layer 40 is used, for example, by coating a ceramic made of _{zirconia (ZrO 2 ).}

A recrystallized layer is formed at the interface due to residual stress on the surface of the superalloy 10 and interdiffusion between the superalloy 10 and the bond coating layer 20 by grit blasting during the coating process. Hereinafter, the recrystallization layer may be understood as a secondary reaction zone (SRZ).

In general, in the case of a nickel-based single-crystal superalloy, it is known that mechanical properties decrease when a secondary reaction layer is formed. In particular, the TCP phase (topologically close packed phase) formed in the secondary reaction layer is a refractory element such as rhenium (Re), tantalum (Ta) and tungsten (W) mainly included for the purpose of improving the strength of the alloy. contains a large amount of The TCP phase reduces the strength of a gamma phase, which is a matrix, and a gamma prime phase, which is a precipitated phase, thereby reducing properties.

In order to solve this problem, in the present invention, by controlling the content of refractory elements that control the generation of the TCP phase and at the same time controlling the content of titanium (Ti), a nickel-based single crystal super heat-resistance that exhibits superior creep properties and phase stability compared to commercial superalloys. alloy is provided.

Specifically, the nickel-based single-crystal superalloy according to an embodiment of the present invention is, by weight, 4.0 to 6.0 aluminum (Al), 10.5 to 12.5 cobalt (Co), 2.65 to 4.65 chromium (Cr), 2.0 Molybdenum (Mo) of less than (greater than 0), 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 (Ni) and other unavoidable impurities.

In the present invention, the composition of aluminum (Al) may satisfy 4.0 wt% to 6.0 wt%. Since aluminum (Al) is a constituent element of the gamma prime phase (γ'), which is the main strengthening phase of a nickel-based single crystal superalloy, it is a necessary element for improving high-temperature creep properties and also contributes to improvement of oxidation resistance. However, if it is less than 4.0% by weight, the creep strength is lowered, whereas if it exceeds 6.0% by weight, the mechanical properties may be deteriorated due to the precipitation of excessive gamma prime phase (γ′). In addition, in the case of aluminum (Al), the absolute amount of the composition is important, but the relationship with the content of titanium (Ti), which is another gamma prime phase (γ') generating element, is also important.

The composition of cobalt (Co) may satisfy 10.5 wt% to 12.5 wt%. In addition to the role of solid solution strengthening, cobalt (Co) changes the solidus line of the gamma prime phase (γ'), the main strengthening phase of the nickel-based single crystal superalloy, and the solidus line of the gamma phase (γ), which is the base, at a temperature where solution treatment is possible. It also improves the high temperature corrosion resistance. If the content of cobalt (Co) is less than 10.5% by weight, the creep characteristics are lowered, whereas when it exceeds 12.5% by weight, the temperature range in which the solution heat treatment is possible becomes small, so it is difficult to determine the heat treatment conditions.

The composition of molybdenum (Mo) may satisfy 2.0 wt% or less (greater than 0). Molybdenum (Mo) is a solid solution strengthening element and serves to improve the high temperature characteristics of a nickel-based single crystal superalloy. However, if it exceeds 2.0 wt%, the density may increase and a TCP phase may be formed, and in the absence of molybdenum (Mo), it is difficult to expect a solid solution strengthening effect.

The composition of tantalum (Ta) may satisfy 6.0 wt% to 8.0 wt%. Tantalum (Ta) is dissolved in the gamma prime phase (γ′), which is the main strengthening phase, and serves to strengthen the gamma prime phase (γ′) phase. Through this, it contributes to the improvement of creep strength, and it segregates in the interdendritic region and increases the density of this region, thereby suppressing the formation of freckles, which are casting defects. If the content of tantalum (Ta) is less than 6.0% by weight, the above effect cannot be expected, and if it exceeds 8.0% by weight, delta phase (δ) may be precipitated, thereby deteriorating properties.

Like aluminum (Al), titanium (Ti) is a component of the gamma prime phase (γ′) and helps to improve creep strength. In particular, since the lattice misfit increases and the stacking fault energy decreases according to the addition of titanium (Ti), creep characteristics can be improved.

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

Therefore, in order to control the fraction of the TCP phase while maintaining the creep characteristics due to the addition of titanium (Ti), the contents of tungsten (W), chromium (Cr) and rhenium (Re), which are the main elements of the TCP phase, among the added component elements are appropriately adjusted. should be regulated

Here, the appropriate content of the main elements can be derived by the following Equation 1 (the detailed content of the equilibrium TCP fraction parameter will be described later). At this time, in Equation 1 below, the equilibrium TCP fraction parameter value must satisfy 19.12% or less (more than 0). The reference for the 19.12% is an equilibrium TCP fraction parameter value calculated using the composition of a commercial alloy (CMSX4). The equilibrium TCP fraction parameter value is a 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]

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

According to the above formula, in the production of the TCP phase, the contents of rhenium (Re), tungsten (W) and chromium (Cr) are important in addition to the content of titanium (Ti). The rhenium (Re), tungsten (W) and chromium (Cr) are elements necessary to improve creep properties by being dissolved in solid solution, and as factors that can effectively control the amount of TCP phase generation while maintaining creep properties due to titanium (Ti), I would say it has technical significance.

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 limitation thereof 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 since its diffusion rate is very slow, it greatly contributes to the improvement of creep properties. By adding rhenium (Re), the resistance to creep deformation as well as the creep life required for use at high temperatures of the nickel-based single-crystal superalloy is greatly improved. 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 it exceeds 1.7% by weight, a large amount of TCP phase is generated and phase stability is lowered, the density is increased, and the process cost is increased because the price is high.

The composition of tungsten (W) may satisfy 6.9 wt% to 8.9 wt%. Tungsten (W) is an element that increases creep strength by solid solution strengthening. However, if the content of tungsten (W) is less than 6.9% by weight, high-temperature strength effect cannot be obtained. On the other hand, if it exceeds 8.9% by weight, the density increases, toughness and corrosion resistance decrease, and a large amount of TCP phase is generated, thereby reducing phase stability. . In addition, when single crystals and unidirectional solidification are performed, the possibility of occurrence of casting defects such as freckles increases.

The composition of chromium (Cr) may satisfy 2.65 wt% to 4.65 wt%. While chromium (Cr) improves corrosion resistance in nickel-based single crystal superalloy, it can form carbide or TCP phase, 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 occurs, whereas if it exceeds 4.65% by weight, creep properties are deteriorated, and when exposed for a long time at high temperature, a large amount of TCP phase is generated, thereby reducing phase stability.

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

When the composition of titanium (Ti) is less than 1.8% by weight, the desired creep characteristics do not appear, and when it exceeds 2.5% by weight, a large amount of TCP phase is generated and phase stability is deteriorated. The optimum range of titanium (Ti) may be expressed by the high temperature compatibility expressed by Equation 2 below, and the high temperature compatibility of the nickel-based single crystal superalloy according to the embodiment of the present invention may be in the range of 502 to 592. .

[Equation 2]

High Temperature Compatibility = Creep Life × Phase Stability

(Here, the phase stability is the ratio of the fraction of the TCP phase of the commercial alloy (CMSX4) to the TCP phase of the manufactured alloy.)

Hereinafter, experimental examples for understanding the characteristics of a nickel-based single-crystal superalloy implemented by the method for manufacturing a nickel-based single-crystal superalloy of the present invention will be described. However, the following experimental examples are only for helping the understanding of the present invention, and the embodiments of the present invention are not limited to the following experimental examples only.

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

2 is a photograph showing the microstructure analysis results observed after the thermal fatigue test cycle and the thermal fatigue test of a nickel-based single crystal superalloy according to an experimental example of the present invention. Referring to this, first, a bond coating layer was formed on the sample of Experimental Example 1, which is a commercial alloy, and the thermal fatigue test was repeatedly performed 100 times at 1100°C. The thermal fatigue cycle for this is shown in Fig. 2 (a), and the microstructure analysis picture is shown in Fig. 2 (b). The component analysis results at point 1, point 2, and point 3 shown in FIG. 2(b) are summarized in Table 1 below.

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

2 and Table 1, as a result of analyzing the TCP phase of the sample of Experimental Example 1, which is a commercial alloy, it can be confirmed that the content of nickel (Ni), chromium (Cr), tungsten (W) and rhenium (Re) is large. there was. In particular, the content of rhenium (Re) is contained as much as 10% by weight or more. Therefore, it is necessary to design an optimal alloy using elements of chromium (Cr), tungsten (W) and rhenium (Re) except for the content of nickel (Ni), which is the main element. Accordingly, after changing the amount of each alloy element based on the sample of Experimental Example 1, which is a commercial alloy, the equilibrium TCP phase fraction at 1100° C. was calculated with JMatPro and summarized in Table 2.

alloy 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

3 is a graph showing the amount of TCP phase production and the correlation of each element of the nickel-based single-crystal superalloy according to an experimental example of the present invention.

Referring to Figure 3 and Table 2, after plotting the fraction of the TCP phase according to the compositional change of rhenium (Re), tungsten (W), and chromium (Cr) and fitting (leaner fitting), a graph of a one-dimensional linear form is formed 3 (a), 3 (b) and 3 (c) are graphs of rhenium (Re), tungsten (W) and chromium (Cr), respectively. Equation 1 below can be derived by calculating the slope in each graph as a fraction parameter on the equilibrium TCP.

[Equation 1]

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

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

From this, the composition of rhenium (Re), tungsten (W) and chromium (Cr) satisfying the equilibrium TCP fraction parameter of Equation 1 was derived while changing the titanium (Ti) content.

Table 3 below shows the alloy composition derived using the equilibrium TCP fraction parameters derived in the first step. As a nickel-based single-crystal superalloy sample according to an experimental example of the present invention, a table summarizing experimental examples for finding an optimal composition that can effectively control the TCP phase generated in the matrix of the superalloy.

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

The experimental example is a commercial NiCrAlY bond coating layer (AMDRY 9624, Ni-22Cr-10Al-1.0Y) on the alloy surface by applying a conventional VPS coating process after processing to the same size (Φ: 13 mm, L: 5 mm) was formed to a thickness of 250±50 μm. After exposing five types of samples with a bond coating layer to about 1100° C. for 30 hours, the area fraction of the TCP phase formed near the interface between the bond coating layer and the base material was measured to compare the phase stability of each alloy sample. The average fraction of the TCP phase was calculated by using an image analyzing program for photos taken with SEM-BEI (Scanning Electron Microscopy - Back scattered Electron Image) for each type of alloy. The average fraction is summarized in Table 4 below. The used photographic magnification was 1,000 times, the area per photograph was about 128 × 96 μm ² , and the average fraction was an arithmetic average of each area fraction obtained from the photograph. Here, the base material of the sample of Experimental Example 1 has a composition of CMSX4, which is a commercial single-crystal superalloy. 4 to 8 are photographs of the microstructure of the interface of the nickel-based single-crystal superalloy according to the experimental example of the present invention analyzed with a scanning electron microscope.

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 %

4 to 8 , as the content of titanium (Ti) increased, it was confirmed that a large amount of TCP phase was generated at the interface. In particular, in the case of the sample of Experimental Example 5 in which the content of titanium (Ti) is 3% by weight, the TCP phase is formed in an elongated shape while being distributed quite a lot, so the possibility of fracture at the interface is very high compared to the sample of Experimental Example 1.

Referring to Table 4, it can be seen that when compared with Experimental Example 1, which is a commercial single-crystal superalloy CMSX4, Experimental Examples 2 to 4 exhibited a smaller average TCP area fraction even though the Ti content was 1.0% by weight 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 shows a larger value than in Experimental Example 1. From this, it can be seen that according to the alloy design according to the technical idea of the present invention, the generation of TCP can be suppressed even when the composition of Ti is added to 1% or more, but it should be controlled to be less than 3.0%.

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

single crystal alloy Experimental Example 1 Experimental Example 2 Experimental Example 3 Experimental Example 4 Experimental Example 5 Ti content
(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 as the content of titanium (Ti) increases, and in the case of Experimental Example 1, which is a commercial alloy, the creep life is 205 hours for titanium (Ti). It could be confirmed that the content of was lower than the samples of Experimental Examples 3 to 5 exceeding 2.0% by weight.

10 is a graph showing the results of analyzing the creep life, room temperature stability, and high temperature suitability of a nickel-based single crystal superalloy according to an experimental example of the present invention.

10 and Table 5, in the case of the samples of Experimental Examples 2 to 5 of the present invention, as the content of titanium (Ti) increased, it was confirmed that the creep life was also increased. On the other hand, the fraction of the TCP phase increased, and thus the phase stability showed a trend of decreasing as the content of titanium (Ti) increased.

Phase stability is the fraction of the TCP phase of the commercial alloy (CMSX4) with respect to the TCP phase of the manufactured alloy, and here, it means the fraction of the TCP phase of the sample of Experimental Example 1 compared to the fraction of the TCP phase of the samples of Experimental Examples 2 to 5. For example, since the fraction of the TCP phase of the sample of Experimental Example 2 is 0.39%, and the fraction of the TCP phase of the sample of Experimental Example 1 is 1.42%, the phase stability when the content of titanium (Ti) is 1% by weight is about 364. indicates.

The high temperature suitability according to the titanium (Ti) content shown in (c) of FIG. 9 is derived by multiplying the creep life shown in (a) of FIG. 9A and the phase stability value shown in (b) of FIG. The high temperature compatibility values are plotted.

The higher the characteristic at high temperature, the higher the high temperature compatibility value, and it was found that the samples of Experimental Examples 2 to 5 were suitable for high temperature because the high temperature compatibility value was higher than that of the Experimental Example 1 sample, which is a commercial alloy. However, in the case of the sample of Experimental Example 5, as the content of titanium (Ti) is increased to 3% by weight, it is not appropriate because the high temperature compatibility is decreased due to the increase of the TCP phase. Referring to FIG. 9(c), it can be seen that 2.0 wt% to 2.5 wt%, which is a titanium composition having a high temperature compatibility in a range of 502 to 592, is the optimal range when considering both creep life and phase stability.

As described above, the present inventors improve creep life by primarily controlling the content of titanium (Ti) through various experimental examples, and chromium (Cr), rhenium (Re) alloy elements that can control the TCP phase fraction ) and found that it is possible to effectively control the shape and size of precipitates by selecting parameters that can efficiently control the content of tungsten (W).

Although the present invention has been described with reference to the embodiments shown in the drawings, which are merely exemplary, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

10: super heat-resistant alloy
20: bond coating layer
30: TGO layer (thermally grown oxide layer)
40: ceramic layer
50: alumina

Claims (3)

In wt%, 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 (greater than 0) molybdenum (Mo), 1.0 to 1.7 rhenium (Re ), 6.0-8.0 tantalum (Ta), 1.8-2.5 titanium (Ti), 6.9-8.9 tungsten (W), and the balance contains nickel (Ni) and other unavoidable impurities,
Nickel-based single crystal superalloy. The method of claim 1,
The content of rhenium (Re), tungsten (W) and chromium (Cr) is controlled by Equation 1 below, and the equilibrium TCP fraction parameter value calculated by Equation 1 below satisfies 19.12% or less (more than 0) do,
The equilibrium TCP fraction is compared by measuring the area fraction of the TCP phase formed near the interface of the bond coating layer and the superalloy base material when the bond coating layer is formed on the surface of the superalloy.
Nickel-based single crystal superalloy.
[Equation 1]
Equilibrium TCP fraction parameter = 2.00 [Re] + 1.45 [W] + 0.60 [Cr]
(where [Re], [W] and [Cr] are the weight % of Re, W and Cr, respectively) The method of claim 1,
The superalloy has a high temperature suitability range of 502 to 592 expressed by Equation 2 below,
Nickel-based single crystal superalloy.
[Equation 2]
High Temperature Compatibility = Creep Life × Phase Stability
(Here, the phase stability is the ratio of the fraction of the TCP phase of the commercial alloy (CMSX4) to the TCP phase of the manufactured alloy, and the TCP phase is the bond coating layer and the super alloy when a bond coating layer is formed on the surface of the superalloy. It is formed near the interface of the heat-resistant alloy base material)

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