JPH04280938A - Production of ni-base superalloy member - Google Patents

Abstract

PURPOSE:To improve the ductility, etc., of an Ni-base superalloy member by specifying the relationship between the solidification velocity of a molten metal and the temp. gradient at the solidification boundary at the time of casting a member composed of an Ni-base superalloy with a specific composition. CONSTITUTION:A member of an Ni-base superalloy which has a composition containing, by weight, 11-23% Cr and 0.5-4.0% Ti as essential elements, containing one or two kinds among <=20% Co, <=6% W, and <=10% Mo, and also 1.0-6.5% Nb, <=2.0% Ta, 0.2-4.0% Al and <=37% Fe as selective elements, and having the balance Ni with impurities is produced by means of casting. At this time, casting is performed under the condition where the relationship between the solidification rate Rcm/h of the molten Ni-base superalloy and the temp. gradient G deg.C/cm at the solidification boundary satisfies G/R>=0.5 deg.C.h/ cm<2>. By this method, the ductility, etc., of the Ni-base superalloy member (stock, parts, product, etc.) can be improved to a greater extent.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to materials, parts, or products that are required to have excellent strength, toughness, heat resistance, and corrosion resistance at high temperatures, such as aircraft engine turbine parts and fastenings in nuclear reactor vessels. The present invention relates to a method for manufacturing a Ni-based superalloy member that is used to manufacture a Ni-based superalloy member suitable for use as a heat-resistant or corrosion-resistant member such as a bolt.

0002

[Background Art] In recent years, in order to improve the performance and efficiency of power engines such as jet engines and gas turbines, it has become essential to raise the temperature of each part of the turbine. There is a growing need to develop durable turbine components.

Characteristics required for this type of turbine member are excellent creep rupture strength that can withstand centrifugal force at high temperatures;
These include fatigue strength, toughness, heat resistance to high-temperature combustion gas atmospheres, and corrosion resistance.

Conventionally, Ni-based superalloys have been widely used as materials suitable for such uses, and they have been manufactured by casting a molten Ni-based superalloy.

[0005]

[Problems to be Solved by the Invention] However, in the conventional production of Ni-based superalloy members by casting, casting was performed without particularly controlling the solidification conditions of the molten Ni-based superalloy, so that the casting structure , due to solidification segregation, (Fe, Cr, Ni)2 (Mo, Ti, Nb)
Laves, a hexagonal intermetallic compound represented by
(Laves) phase may be formed at dendrite boundaries, and when such a Laves phase is formed, N
There is a problem that the ductility etc. of the i-based superalloy member may be reduced, and it has been a problem to solve this problem.

[0006]

[Object of the Invention] The present invention has been made to solve the above-mentioned conventional problems, and prevents a decrease in ductility etc. of Ni-based superalloy members (materials, parts, products, etc.) manufactured by casting. The purpose of the present invention is to manufacture a Ni-based superalloy member that can further improve ductility and the like.

[0007]

[Means for Solving the Problems] A method for manufacturing a Ni-based superalloy member according to the present invention is such that when manufacturing a Ni-based superalloy member by casting, the solidification rate Rcm/
The relationship between h and the temperature gradient G°C/cm at the solidification interface is G/cm.
It is characterized by a configuration in which casting is performed in a state that satisfies R≧0.5°C・h/cm2, and in an embodiment, the solidification rate Rcm/h of the Ni-based superalloy molten metal and the temperature gradient at the solidification interface are The relationship with G℃/cm is G/R≧1.0℃
・It is characterized by having a configuration in which casting is performed in a state that satisfies N.
It is characterized in that the i-based superalloy is an alloy for single crystals, or an alloy for equiaxed crystals or an alloy for unidirectionally solidified columnar crystals, and in the same embodiment, the Ni-based superalloy contains Cr: 11 to 23% by weight, Ti: 0.5 to 4.0% by weight, as essential elements, Co: 20% by weight or less, W: 6% by weight or less, and Mo: 10% by weight or less. One or two of the following, Nb: 1.0 to 6.5% by weight, Ta: 2.0% by weight or less, Al: 0.2 to 4.0% by weight, Fe: 37% by weight or less, select elements C: 0.15% by weight or less, B: 0.01% by weight. Hereinafter, Zr: 0.30% by weight or less is characterized by a structure regulated to below, and the structure of the invention related to the method for manufacturing the above-mentioned Ni-based superalloy member is to solve the above-mentioned conventional problems. It is used as a means.

In the method for manufacturing a Ni-based superalloy member according to the present invention, the relationship between the solidification rate Rcm/h of the molten Ni-based superalloy and the temperature gradient G°C/cm at the solidification interface is such that G/R≧0.
5℃・h/cm2, more preferably G/R≧1.0℃
・We try to perform casting under conditions that satisfy h/cm2, but the reason for this is that the above G/R value is 0.5℃・
hcm2, (Fe, Cr, Ni)2 (Mo, Ti,
La, a hexagonal intermetallic compound represented by Nb)
This is because the possibility that the Laves phase will be formed at the dendrite boundary increases, and as a result, problems such as a decrease in ductility and the like will occur due to the formation of the Laves phase.

In addition, in the method for producing a Ni-based superalloy member according to the present invention, it is preferable that the Ni-based superalloy be a single crystal alloy, or an alloy that has been frequently used in the past. It is also possible to use an alloy for axial crystals or an alloy for unidirectionally solidified columnar crystals.

Unlike the conventional normally cast equiaxed crystal alloys and unidirectionally solidified columnar crystal alloys, the single crystal body made of the Ni-base superalloy for single crystals shown in the former example has no grain boundaries, so the temperature is just below the melting point. γ phase (matrix alloy phase consisting of irregular face-centered cubic lattice), γ' phase (intermetallic compound phase consisting of L12 type ordered lattice), and Since it is possible to obtain a homogeneous structure consisting of the γ'' phase (an intermetallic compound phase consisting of a DO22-type regular lattice), it has excellent heat resistance and corrosion resistance without reducing creep rupture strength or fatigue strength at high temperatures. This is advantageous in that it is possible to further improve the

[0011] Examples of the Ni-based superalloy used in the method for manufacturing a Ni-based superalloy member according to the present invention include:
Cr, Co, Mo, W, Nb, T in the Ni matrix
There are products containing a, Ti, Al, etc., and the product names include Incoloy, Inconel, M252, N
imonic, Pyromet, Refractory
, Rene, Udimet, Unitemp, Wasp
There is something called alloy.

As a specific example of the alloy composition, those having the following chemical compositions are used.

Cr: 11 to 23% by weight Cr is an effective element for improving the heat resistance and corrosion resistance of alloys at high temperatures.
It is desirable that the content be 1% by weight or more. The effect increases as the Cr content increases, but if the Cr content increases too much, the solid solubility limit of the solid solution strengthening element will be lowered, and the TCP phase, which is a brittle phase, will precipitate, impairing high-temperature strength. Therefore, it is desirable that the content be 23% by weight or less.

Co: 20% by weight or less Co is an effective element for improving the heat resistance and corrosion resistance of Ni-based superalloy members, so it is also desirable to include it in a range of 20% by weight or less.

W: 6% by weight or less and Mo: 10% by weight
One or two of the following W, Mo are mainly dissolved in the γ phase which is the matrix,
It is an effective element for increasing creep strength and fatigue strength through solid solution strengthening. When it is necessary to sufficiently obtain such effects, it is desirable that W be at least 1.0% by weight and Mo be at least 2.5% by weight. However, W,
Mo may reduce the corrosion resistance of the member at high temperatures, and acicular α-(W, Mo) may precipitate, reducing creep strength, fatigue strength, and toughness.
It is desirable that Mo be 10% by weight or less.

[0016] Nb: 1.0 to 6.5% by weight Ta: 2.0
Nb and Ta in weight% or less are added to [Ni3 (A
Creep strength and fatigue strength are improved by solid solution strengthening in the form of Nb (Nb, Nb, Ta)], but when it is necessary to obtain such effects, the amount of Nb is increased to 1.0% by weight or more. It is desirable to do so. However, if the content is too large, creep strength and fatigue strength tend to decrease, so it is desirable that Nb be 6.5% by weight or less and Ta be 2.0% by weight or less.

Ti: 0.5 to 4.0% by weight Ti not only strengthens the alloy by forming a solid solution in the γ' phase and γ'' phase in the form of [Ni3 (Al, Ti)], but also strengthens the alloy at high temperatures. It is also desirable to contain 0.5% by weight or more since it has the effect of improving the corrosion resistance of. However, when added in large quantities,
Since corrosion resistance tends to deteriorate, the content is preferably 4.0% by weight or less.

Al: 0.2 to 4.0% by weight Al is a constituent element of the γ′ phase [Ni3Al], which is a precipitation strengthening phase,
When it is necessary to obtain the effect of Al addition, 0.2~
A desirable range is 4.0% by weight.

Fe: 37% by weight or less Fe is an element that can be added as a substitute element for Ni.
It is possible to contain up to 7% by weight without significantly deteriorating the properties of the Ni-based superalloy.

C: 0.15% by weight or less B: 0.01% by weight or less Zr: 0.30% by weight or less These elements strengthen grain boundaries in conventional normally cast equiaxed crystal alloys and directionally solidified columnar crystal alloys. These grain boundary strengthening elements are used as elements, but when single crystallized, these grain boundary strengthening elements are not necessary, but rather become harmful elements as shown below, so it is desirable to regulate them appropriately.

C is a carbide (TiC, NbC, TaC, etc.)
It forms and precipitates in lumps. This carbide has a low melting temperature compared to the melting point of the alloy, and local melting occurs when solution treatment is performed just below the melting point of the alloy, making it impossible to raise the temperature of the solidification treatment, which limits the temperature range of single crystal solidification. In order to narrow the range, it is also desirable that the C content be 0.15% by weight or less in the case of single crystallization.

B is a boride [(Cr, Ni, Ti, Mo
)3B2] and precipitates at the grain boundaries of the alloy. Like carbides, borides have a lower melting point than that of alloys, lowering the solution treatment temperature of single crystals and narrowing the solution treatment temperature range, so when forming single crystals, reduce B by 0.01 It is also desirable that the amount is less than % by weight.

Zr lowers the solidus temperature of the alloy and widens the solidification temperature range, so it is harmful to single crystallization.
In the case of single crystallization, it is also desirable that Zr be 0.30% by weight or less.

The method for manufacturing a Ni-based superalloy member according to the present invention can be applied to the above-mentioned Ni-based superalloy. For example, when applied to an Inconel alloy,
When considering an alloy based on nconel 718 with relaxed regulations on grain boundary strengthening elements etc. in consideration of single crystallization, Cr: 15.0 to 23.0% by weight, Mo: 2
．． 5-3.5% by weight, Nb: 4.5-5.5% by weight, T
i: 0.5-1.5% by weight, Al: 0.2-0.9% by weight, Fe: 13.0-25.0% by weight, Ta: 1.0% by weight or less, Zr: 0.3 A Ni-based superalloy consisting of C: 0.15% by weight or less, B: 0.01% by weight or less, and the balance being Ni and impurities can be used.

[0025]

According to the method for manufacturing a Ni-based superalloy member according to the present invention, when manufacturing a Ni-based superalloy member by casting, the solidification rate Rcm/h of the molten Ni-based superalloy and the temperature of the solidification interface are controlled. The relationship with the gradient G°C/cm is G/R≧0.
5℃・h/cm2, and the solidification rate R of the molten alloy was not too large with respect to the temperature gradient G at the solidification interface. Since the harmful Laves phase, which causes a decrease in ductility, is less likely to be formed at dendrite boundaries, the ductility, etc. of the Ni-based superalloy member is further improved.

[0026]

[Example] In this example, Table 1 was prepared by vacuum induction melting.
A Ni-based superalloy having the chemical composition shown below was prepared.

[0027]

[Table 1]

Next, the above Ni-base superalloy material was cut out and placed in a single crystal mold with a diameter of 20 mm, vacuum induction melting was performed, and a single crystal was produced by unidirectional solidification during casting. At this time, the solidification conditions expressed by the relationship between the solidification rate Rcm/h and the temperature gradient G°C/cm at the solidification interface were controlled.

As a result, the relationship between solidification conditions and Laves phase was as shown in FIG. 1.

As shown in FIG. 1, it is recognized that the amount of Laves phase produced tends to increase as the value of G/R decreases, and it is recommended that G/R≧0.5°C·h/cm2. It was confirmed that the Laves phase was 2% by volume or less, and the ductility could be improved by about 20% compared to the conventional case where the solidification conditions were not controlled.

[0031] Furthermore, the method for producing a Ni-base superalloy member according to the present invention is applicable not only to single crystallization but also to formation of equiaxed or unidirectionally solidified columnar crystal structures using the above G/R casting conditions. It was recognized that ductility could be improved by

[0032]

Effects of the Invention In the method for manufacturing a Ni-based superalloy member according to the present invention, when manufacturing a Ni-based superalloy member by casting, the solidification rate Rcm/h of the molten Ni-based superalloy and the temperature gradient G at the solidification interface are controlled. The relationship with ℃/cm is G/R≧0.5℃
・Since casting is performed under conditions that satisfy h/cm2, it is possible to further improve the ductility of Ni-based superalloy members (materials, parts, products, etc.), which is a remarkable advantage. This will bring about a positive effect.

[Brief explanation of the drawing]

[Figure 1] G/ which is the ratio between the solidification rate R (cm/h) of the Ni-based superalloy molten metal and the temperature gradient G (°C/cm) at the solidification interface.
It is a graph illustrating the results of investigating the relationship between R (°C·h/cm 2 ) and the amount of Laves phase formed.

Claims (5)

[Claims] [Claim 1] When manufacturing a Ni-based superalloy member by casting, the solidification rate Rcm/h of the Ni-based superalloy molten metal,
The relationship with the temperature gradient G°C/cm at the solidification interface is G/R≧0.
．． A method for producing a Ni-based superalloy member, characterized in that casting is performed under conditions that satisfy a temperature of 5° C./h/cm2. [Claim 2] Solidification rate Rcm/of Ni-based superalloy molten metal
The relationship between h and the temperature gradient G°C/cm at the solidification interface is G/cm.
The method for manufacturing a Ni-based superalloy member according to claim 1, wherein casting is performed in a state satisfying R≧1.0°C·h/cm2. 3. The method for producing a Ni-based superalloy member according to claim 1, wherein the Ni-based superalloy is a single crystal alloy. 4. The Ni-based superalloy contains Cr: 11 to 23% by weight and Ti: 0.5 to 4.0% by weight as essential elements,
Co: 20% by weight or less, W: 6% by weight or less, and Mo: 1 or 2 types from 10% by weight or less, Nb: 1.0 to 6.5% by weight, Ta: 2.0% by weight or less, Contains Al: 0.2 to 4.0% by weight, Fe: 37% by weight or less as selected elements, and the balance is N.
The method for producing a Ni-based superalloy member according to claim 1, 2 or 3, comprising i and an impurity. 5. The Ni-based superalloy member according to claim 4, wherein the impurities are regulated as follows: C: 0.15% by weight or less, B: 0.01% by weight or less, Zr: 0.30% by weight or less. manufacturing method.