JPH07247803A - Manufacture of turbine blade - Google Patents

Abstract

PURPOSE:To provide such a single crystal turbine blade as being free from high temperature strength reduction even if it is under existence of crystal grain boundary, being healthy, having hight reliability and improved productivity. CONSTITUTION:After a single crystal turbine blade raw material is manufactured by means of precision cast, either one kind of C, B, Zr, and Hf for reinforcing grain boundary or a plurality of elements thereof is/are allowed to invade from the surface of a turbine blade by means of dispersion treatment and ion filling, and those elements are dispersed through dispersion treatment at a high temperature, or they are stuck on the surface by means of a physical evaporation method or an ion plating method, and after that, they are allowed to invade and to be dispersed by means of dispersion treatment. It is thus possible to reinforce crystal grain boundary and sub-boundary which are formed at the time of precision casting, or crystal grain boundary which is generated by means of heating treatment after that.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a highly reliable single crystal turbine blade used in aircraft engines and gas turbines, which is excellent in productivity.

[0002]

2. Description of the Related Art Aircraft engines and gas turbines tend to have a higher turbine inlet temperature due to higher efficiency and higher power output. Unidirectionally solidified alloys and single crystals of Ni-based alloys, which have higher high-temperature strength such as creep rupture strength than ordinary casting turbine blades of Ni-based alloys manufactured by conventional manufacturing methods Alloy blades have come into use. In particular, since the single crystal blade has no crystal grain boundaries at all, it does not contain trace elements such as carbon, boron, and zirconium that strengthen the crystal grain boundaries, so the solution temperature can be raised to just below the melting point, and Since it can be subjected to various solution treatments, the high temperature strength is further enhanced, and it is optimal for higher temperature turbine blades.

[0003]

However, since the single crystal turbin blade does not contain a trace element that strengthens the grain boundary as described above, if the grain boundary exists, the grain boundary is changed. Since it is extremely weak, the expected high temperature strength cannot be obtained. An example of forming a grain boundary with a single crystal turbine blade is the formation and direction of a grain boundary due to the growth of a different crystal that tends to occur when a single crystal turbine blade is manufactured by directional solidification in precision casting. The grain boundaries such as sub-grain boundaries (low-angle grain boundaries) due to a slight shift in the crystal growth direction of the dendrites that grow during solidification, and the high temperature heat treatment after precision casting of the turbine blades, the turbine blades The typical example is the formation of new crystal grains called recrystallization that occur in the corners and stress concentration areas where the cross-sectional area changes rapidly. Therefore, it is necessary to strictly control the precision casting and the directional solidification process in order to completely suppress the formation of the grain boundaries as described above when manufacturing the single crystal turbine blade. It costs a lot of money. Even if such strict control is carried out, it is actually difficult to completely prevent the formation of the above-mentioned crystal grain boundaries, and the single crystal turbin blur containing crystal grain boundaries or sub-grain boundaries is actually difficult to prevent. -Do castings must be discarded. For this reason, the product yield is increased by the conventional turbine
It is significantly worse than that of the single crystal, significantly increasing the cost, and significantly impairing the reliability of the single crystal turbine blade.

The object of the present invention is to obtain a single crystal turbine blade which is sound, reliable and excellent in productivity without deterioration of high temperature strength even in the presence of grain boundaries. It is to provide a manufacturing method of a cord.

[0005]

A means for solving the problems of the present invention
The manufacturing method of the carbon C is a single crystal turbine blade, in which a single crystal turbine blade material is manufactured by precision casting and then carbon grain boundaries are strengthened from the surface of the turbine blade. , Boron B, zirconium Zr, and hafnium Hf, or a plurality of elements are infiltrated by a method such as diffusion treatment or ion implantation, and these elements are dispersed by high-temperature diffusion treatment, or physically. After adhering to the surface by dynamic vapor deposition or ion plating, it is infiltrated and dispersed by diffusion treatment to strengthen the crystal grain boundaries, sub-grain boundaries formed during precision casting, or crystal grain boundaries generated by subsequent heat treatment. It is characterized by doing.

The single crystal turbine blade is characterized by being made of a Ni-base alloy or a Co-base alloy strengthened by fine precipitation of the γ'phase of the intermetallic compound Ni ₃ (Al, Ti).

As a method of invading or adhering each element of carbon C, boron B, zirconium Zr, and hafnium Hf from the surface of the turbine blade, pack diffusion method, molten salt diffusion method, vapor phase diffusion method Synthetic CVD,
It is characterized by high temperature treatment such as CVI, high energy implantation method such as ion implantation method, physical vapor deposition method PVD, ion plating method, plating method and the like, or a combination thereof.

In addition, carbon C, boron B, zirconium Zr, and hafnium Hf are single-crystal turbine alloys.
After infiltrating the surface of the substrate, the diffusion treatment is performed at a temperature between 1000 ° C and 1150 ° C.

In the portion including the crystal grain boundaries of the single crystal turbine blade manufactured as described above, 0.01 to
Carbon C up to 0.08% by weight, 0.005 to 0.05% by weight boron B, 0.01 to 0.08% by weight zirconium Z
r, 0.01 to 0.5% by weight of hafnium Hf.

[0010]

[Effect] As a result, even if a grain boundary is formed during the production of a single crystal turbine blade, the high temperature strength does not decrease, and the single crystal turbine is sound, reliable and excellent in productivity. A method for manufacturing a bottle blade can be provided.

[0011]

EXAMPLES The manufacturing method and diffusion heat treatment of the present invention, and the addition amount of the constituent elements for strengthening the grain boundaries formed as a result of the production method and the high temperature strength of the single crystal turbine blade are focused on. Selected.

Grain boundaries or sub-grain boundaries that may be formed in the process of producing a single crystal turbine blade are during precision casting by directional solidification and subsequent high temperature heat treatment called solution treatment. . The solution treatment may be combined with the treatment of uniformly diffusing the invaded elements of carbon, boron, zirconium, and hafnium to the crystal grain boundaries. Therefore, it is optimal to infiltrate the grain boundary strengthening elements such as boron, zirconium, and hafnium after precision casting by directional solidification. However, when the treatment for uniformly diffusing each element into the crystal grain boundaries is preferably lower than the solution heat treatment temperature, the treatment for invading each element may be performed after the solution heat treatment.

The method of infiltrating each element of carbon, boron, zirconium, and hafnium from the surface of the single crystal turbine blade is a pack diffusion method called a powder pack method or a molten salt diffusion method using a salt of an element to be diffused, or A high temperature treatment method in which a diffusion treatment such as vapor phase synthesis method CVD or CVI is simultaneously performed is preferable because it can also be used as a diffusion treatment for each element thereafter. Since it is not always possible to use the same method for invading each element, a required crystal grain boundary strengthening element is invaded and diffused by combining an optimal treatment method for each element. In addition, a high energy implantation method such as an ion implantation method can inject each element into the surface of the turbine blade alone or in duplicate. In this case, if the required amount of added elements can be obtained by implantation, the subsequent diffusion heat treatment can be omitted. Furthermore, first, each element can be deposited on the surface of the single crystal turbine blade by physical vapor deposition PVD or plating, and then each element can be diffused and penetrated to a required depth from the surface by diffusion heat treatment. The method of invading each element from the surface of the turbine blade does not necessarily have to be the same method when injecting a plurality of necessary elements, and each element is most effectively treated in a short time. Can be performed in combination with the methods that can be performed in. Although typical processing methods among various methods have been described here, similar methods not described here are of course applicable as long as they do not impair the high temperature strength of the base material of the single crystal turbine blade. .

The content of each element in the region is as follows from its effect and harmfulness. Carbon C exists in the grain boundaries and is necessary to precipitate carbides to increase the intergranular cracking resistance. It must be at least 0.01% by weight, but if it exceeds 0.08% by weight, the grain boundaries are increased. Not only this, but also carbide precipitates inside the crystal, and it aggregates and coarsens during long-term use, reducing the creep rupture life and fatigue life.

Boron B is an element which exists in the grain boundaries and enhances the bonding force of the grain boundaries, and 0.005% by weight is necessary for producing this effect. However, if contained in a large amount, boride is formed and the fatigue life is adversely affected. Therefore, the content should be 0.05% by weight or less.

Zirconium Zr exists in the crystal grain boundaries and strengthens the grain boundaries. For this purpose, 0.01% by weight is necessary, but when contained in excess, it forms a compound such as zirconium carbide, which reduces ductility and
The creep rupture life is also shortened, so 0.08% by weight is the limit.

Hafnium Hf is also an element necessary for strengthening the crystal grain boundaries, but when carbon is present,
Since it does not act effectively as a hafnium carbide, 0.01 to 0.5% by weight is optimal.

In order to make the above-mentioned respective elements for strengthening the crystal grain boundaries effectively act, it is necessary to use a turbine bin
After each element is infiltrated into the oxide, a heat treatment for diffusion can be performed while holding at a high temperature so that the element is dispersed at a sufficient depth in the region where the grain boundary exists. In this case, the treatment temperature for diffusion is determined from the depth of the region and the industrial treatment time, but at the same time, the high temperature strength of the turbine blade substrate should not be impaired. For this purpose, the temperature of the diffusion treatment is optimally in the range of 1000 to 1150 ° C.

It is the Ni-based alloy single crystal turbine blades that the high temperature strength is significantly adversely affected by the formation of grain boundaries during the production of the turbine blades.
A similar adverse effect occurs in a turbine blade made of unidirectionally solidified columnar crystals. That is, unidirectionally solidified columnar turbine blades grow columnar crystals in parallel along the longitudinal direction of the blade so as to eliminate grain boundaries in the direction perpendicular to the direction in which stress acts, but precision casting Often, new grain boundaries and sub-grain boundaries are formed as with single crystal turbine blades during and after high temperature heat treatment. Since the unidirectionally solidified columnar crystal originally has a grain boundary, the grain boundary strengthening element described in the present invention is contained, but the amount is not always sufficient, and a new grain boundary is formed. As in the case of the single crystal, the high temperature strength including the creep rupture strength generated at the position perpendicular to the stress is drastically reduced and the turbine blade must be discarded. Therefore, the manufacturing method according to the present invention is also effective for a turbine blade made of unidirectionally solidified columnar crystals.

Further, as the single crystal and unidirectional columnar crystal turbine blades, the one which is mainly used at present is Ni strengthened by fine precipitation of the γ ′ phase of the intermetallic compound Ni ₃ (Al, Ti). Although it is a base alloy, it is a high temperature material similar to that of a Ni base alloy, and the above manufacturing method is applied to a single crystal and a unidirectionally solidified columnar turbine blade made of a Co base alloy used for a stationary blade. Can be applied in terms of securing high temperature strength and productivity.

The embodiments of the present invention will be described below.
A single crystal material test piece 1 made of a Ni-based single crystal alloy for a turbine blade was manufactured by precision casting by a rapid solidification method. The chemical composition of the single-use alloy used here is an alloy reinforced by fine precipitation of the γ ′ phase of the intermetallic compound Ni ₃ (Al, Ti) as shown in Table 1, and carbon, boron, zirconium, and hafnium are used. It is a typical Ni-based single crystal alloy that does not contain.

[0022]

[Table 1]

At the same time, a bicrystal test piece 2 having a grain boundary formed in a part across the longitudinal direction was cast. The single crystal test piece was precision cast, blasted with alumina particles on the surface, and then subjected to the standard solution treatment of the single crystal alloy at 1315 ° C for 4 hours to obtain a surface layer with a depth of about 100 μm. A test piece 3 containing recrystallized grains was produced. Twin crystals consisting of single crystal alloy prepared in this way, or single crystal alloy test piece having recrystallized grains, carbon, boron by various methods,
Zirconium and hafnium were introduced, and appropriate diffusion heat treatment was performed to diffuse each element inside. Here, for the invasion and diffusion of carbon, carburizing treatment by the pack diffusion method was performed, and for boron, the boron was infiltrated by the boration treatment with a molten salt. After that, zirconium and hafnium were deposited on the surface by physical vapor deposition PVD and then subjected to a diffusion heat treatment to promote the diffusion of each element into the inside. The diffusion treatment was carried out by holding the bicrystal test piece 2-1 at 1150 ° C for 16 hours, and the recrystallization test piece 3-1 at 1050 ° C.
Therefore, it was held for 4 hours. In addition to the above, a test piece in which only carbon and boron were diffused and penetrated was prepared for the bicrystal test piece and the recrystallized test piece. The single crystal alloy test pieces 2-1 and 2-2 and 3-1 according to the present invention manufactured in this manner
A creep rupture test was conducted together with untreated test pieces using 3-2. The results are summarized in Table 2.

[0024]

[Table 2]

As is clear from Table 2, when the single crystal alloy contains grain boundaries, the creep rupture life is remarkably shortened from several tenths to tenths. On the other hand, in the single crystal test pieces 2-1 and 3-1 including the crystal grain boundaries according to the present invention, the decrease is very small and the effect is clear. Also,
Even when not containing all of the grain boundary strengthening elements like the test pieces 2-2 and 3-2, the decrease in creep rupture life is reduced to such an extent that it does not pose a practical problem. The effect is fully observed.

Next, the manufacturing method according to the present invention was applied to a single crystal turbine blade. FIG. 1 shows the appearance of a general gas turbine blade, which comprises an effective part 1, a platform part 2, and an implant part 3. Recrystallized grains were formed in this effective portion by the same alumina blast as above and the subsequent solution treatment. First, carbon was diffused and infiltrated into this turbine blade by a carburizing method. Then, a predetermined amount of boron was diffused by a boration treatment using a molten salt method. Subsequently, zirconium and hafnium were coated on the surface layer by an ion plating method and subjected to a diffusion treatment at 1080 ° C. for 8 hours to diffuse the zirconium and hafnium inside and homogenize carbon and boron. As shown in FIG. 2, a plate-shaped test piece 4 including the surface layer was sampled from the effective portion of the turbine blade thus manufactured. A creep rupture test was conducted with a test piece cut out from a turbine blade as a single crystal, and a cut-out plate test piece containing recrystallization but not subject to this production method. Even if recrystallized grains are present in the turbine blade manufactured by the manufacturing method according to the invention, the creep rupture life is equivalent to that of a test piece cut out from a healthy single crystal turbine blade. Was confirmed to have.

[0027]

[Table 3] FIG. 1 shows the results of EPMA analysis of the element distribution in the vicinity of the grain boundaries of a test piece cut out from the turbine blade according to the present invention. As can be seen from this analysis result, carbon and boron, which originally existed only in the degree of unavoidable impurities in the single crystal alloy, or zirconium or hafnium penetrated and diffused at a predetermined concentration to strengthen the crystal grain boundary. You can see that

[0028]

The manufacturing method of the present invention can provide a manufacturing method which has a practically sufficient high temperature strength as a single crystal turbine blade even when it contains a grain boundary, and has a good productivity.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing analysis results of grain boundary strengthening elements in a turbine blade manufactured according to the present invention.

[Fig. 2] Perspective view of the turbine blade

[Explanation of symbols]

 1 Effective part 2 Platform 3 Implanted part 4 Creep test piece

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location F01D 5/14 F02C 7/00 D

Claims (5)

[Claims] 1. A method for producing a single crystal turbine blade, wherein a single crystal turbine blade material is produced by precision casting, and then grain boundaries are strengthened from the surface of the turbine blade. Any one or more of carbon C, boron B, zirconium Zr, and hafnium Hf is introduced by diffusion treatment or ion implantation, and these elements are dispersed by high-temperature diffusion treatment or physically. After adhering to the surface by the vapor deposition method or ion plating method, it is infiltrated and dispersed by diffusion treatment to strengthen the crystal grain boundaries, sub-grain boundaries formed during precision casting or the crystal grain boundaries generated by the subsequent heat treatment. A method for manufacturing a turbine blade, which is characterized in that 2. A single crystal Turbin blade is made of a Ni-base alloy strengthened by fine precipitation of a γ'phase of an intermetallic compound Ni ₃ (Al, Ti). The method for manufacturing the turbine blade described in 1. 3. Carbon C, boron B, zirconium Z
As a method for invading or adhering each element of r and hafnium Hf from the surface of the turbine blade, high temperature treatment such as pack diffusion method, molten salt diffusion method, vapor phase synthesis method, high ion treatment method, etc. 2. The method for manufacturing a turbine blade according to claim 1, wherein one type of energy injection method, physical vapor deposition method, ion plating method, plating method, or a combination thereof is used. 4. Carbon C, boron B, zirconium Zr,
The hafnium Hf and the hafnium Hf are infiltrated from the surface of the single crystal turbine blade, and then diffusion treatment is performed at a temperature between 1000 ° C and 1150 ° C. Production method. 5. A turbine single crystal finally made of a single crystal.
In the relevant part including the crystal grain boundary of C, 0.01 to 0.08% by weight of carbon C, 0.005 to 0.05% by weight of boron B, 0.01 to 0.08% by weight of zirconium Zr, 0.0
The method for producing a turbine blade according to claim 1, which contains 1 to 0.5% by weight of hafnium Hf.