JPS5950431B2 - Bonding material for Ni-based superalloys - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a bonding method used to bond heat engine parts made of Ni-based heat-resistant alloys, such as parts with complex shapes such as high-temperature gas turbine blades, by a diffusion bonding method. For more information on materials,
The metal structure of the joint is the same as that of the base material even for base materials of Ni and Al-γ' reinforced Ni-based superalloys with a γ' content of 55% or more, which is difficult to bond with conventional bonding materials. Therefore, the liquid phase diffusion bonding method (hereinafter referred to as TLP method) for Ni-based superalloys also improves joint efficiency.

) relating to a bonding material useful for application. [Technical background of the invention and its problems] Normally, Ni-based heat-resistant superalloy is used as a material for high-temperature gas turbine blades, but in order to increase the operating temperature, it requires complicated internal cooling passages. It has a cooling blade structure.

Typical structural examples include (A) a return flow type precision cast blade and (B) a wafer blade constructed by joining ten or more wafers in a plane.

In manufacturing gas turbine blades provided with these complicated cooling passages, a diffusion bonding method is usually applied. For example, in the case of (4), as shown in the cross-sectional view in Fig. 1, after precision casting the blade members 1 and 1'', which are divided into two parts in the blade span direction, insert filler metal is applied to the joint curved surface 2 of the two parts. The filler metal used in this case is preferably a quenched ribbon filler, which is easy to handle and has a high density, since the joining curved surface is wide. )In Case of,
Thin filler metal is used because there are many joint surfaces and the dimensional accuracy of the plane is strict. As the diffusion bonding method applied to manufacture (A) and (B), the TLP method is usually adopted.

This is because the TLP method increases the reliability of bonding.
When joining Ni-based heat-resistant alloys using the TLP method, conventional Ni-
Filler metals having compositions such as B, Ni-B-Si, Ni-Cr-B, etc. have been used.

This filler metal is made of Ni containing elements that lower the melting point, such as B and Si, and melts at a temperature several tens of degrees lower than the melting point of the base material (Ni-based heat-resistant alloy). Therefore, for joining, the filler metal is interposed between the base metals and the position corresponding to the joint is heated to a temperature above the melting point of the filler metal and below the melting point of the base metal to melt the filler metal, After the base material is wetted and brazed, the temperature is maintained for a longer period of time to diffuse B, Si, etc. into the base material. At this time, at the same time, the filler metal undergoes an isothermal solidification phenomenon in which it solidifies in the same manner as the base metal, forming a strong joint. The filler metal used in the TLP method is a chip-shaped piece made by slicing the Ni-based alloy solder as described above.
Alternatively, there are various types such as those made into a ribbon shape by applying a molten metal quenching method after melting a solder alloy.

When the composition of the filler alloy is the same, the ribbon filler produced by the molten metal quenching method has 100% density, can be punched into the required shape, is ductile, is easy to handle, and has the structure of the filler itself. Since the bond is uniform, highly reliable bonding can be achieved. For example, if a ribbon filler is used for a base material such as IN7l3C with a γ″ of 51%, it is possible to form a joint with almost the same creep bonding strength as the base material.Recently, for example, IN738LC, MAR-M
Strong Ni-based superalloys for precision casting, such as 247, have appeared.

In this Ni-based superalloy, γ in the metal structure is
In order to maximize the amount of material, the alloy composition range is set at the very limit based on alloy design, but that range is extremely narrow to begin with. When the TLP method is applied to materials using Ni alloy filler as described above, the metallographic structure of the joint will be different from the structure of the base metal, which makes it more difficult to obtain joint efficiency equal to that of the base metal. become.

In order to solve these problems, it is necessary to optimize the alloy composition of the filler metal in accordance with that of the base metal.

However, until now, such attempts have not been carried out systematically, and have only been carried out empirically through repeated trial and error.

Therefore, a filler metal with an alloy composition suitable for joining a base material of a Ni-based superalloy with a large amount of γ'', for example, 55% or more of γ″, by the TLP method has not yet been developed. <Object of the invention> The present invention solves the above-mentioned problems and reduces the amount of γ″ to 5.
Even when base metals of Ni-based superalloys with a content of 5% or more are joined by the TLP method, the metallographic structure of the joint becomes the same as that of the base metal, and as a result, we aim to provide a joint material that improves joint efficiency. purpose.

Summary of the Invention In order to achieve the above-mentioned object, the present inventors have carried out extensive research in consideration of metallographic principles, and have developed a method that can be used for joining Ni-based superalloys with a large amount of γ'' by the TLP method. We focused on the fact that the influencing factors that should be considered in optimizing the alloy composition of a ribbon filler fabricated by the molten metal quenching method can be roughly divided into bonding property factors and welding property factors.

First, the bonding characteristic factors to be considered in the present invention include the following.

In other words, 1) the type and amount of the solid solution strengthening element in the bonding material; 2) the type and amount of γ' that should be generated in the joint and the type and amount of the element necessary for this purpose; and 3) the oxidation protection that should be formed around the joint. 4) Types and amounts of elements that define the amount of grain boundary carbide reinforcement in the joint; 5) TCP (TOPOlOgical) in the joint;
These include the average number of electron vacancies (Nv) as a factor for preventing the generation of lyclOsedpackedphase), and the factor for preventing abnormal diffusion of the bonding material during 6 bonding.

In addition, as welding characteristic factors, the types and amounts of elements that define the molten metal formability or non-cholarization when forming the ribbon filler of the bonding material, and the melting point (Tm: ° C.) are to be considered.

The composition of the bonding material of the present invention is determined in consideration of each of the factors listed above.

The method for making this determination will be explained in detail below. First, before determining the alloy composition of the bonding material, the base material is analyzed and initial conditions are set.

In other words, the type and amount of each element constituting the base metal, the amount of primary γ' phase (coarse γ' phase) in the two base materials, and the amount of secondary γ' phase (fine γ' phase).
' phase), the amount of carbide in the base metal (MC type or M,,C).

Type: M represents a metal element. ), the Nv value of the base material, etc. are measured and used as main data. These data become the target tissue of the junction. In factor 1, CO, Ta, and W are selected as solid solution strengthening elements.

The CO is set to the same value as the weight percent CO in the base material. Ta
is less than or equal to the sum of Ta weight % and Nb weight % in the base material, that is, 0≦Tawt%≦(Ta+Nb) base material Wt%
Satisfies the relationship. is set to the value to be added. If the amount of Ta is outside this range, it will not contribute to solid solution strengthening when CO is set as above. W is also an element that defines factor 4, and its amount is 1/3 or more of the W weight% in the base material or the sum of the W weight% and MO weight% in the base material, that is, 1
/3W Base material Wt%≦Wwt%≦ (W+MO) Base material Wt
% relationship and the lower limit value of W weight % required to generate the same type and amount of grain boundary carbide as the grain boundary carbide in the base material in the joint. Set to a large value. If the amount of W is outside this range, the solid solution strengthening of the joint will decrease and at the same time the metal structure will not be the same as that of the base material, which is unsuitable. Next, regarding factor 2, the secondary γ' phase at the joint part diffuses from the base material during joining and becomes equivalent to the base material, so it may be left out of consideration.

Therefore, when considering the primary γ' phase, A1 is the element that produces the same primary γ' phase in the joint as the base metal.
is selected. Incidentally, Ti is also an element that generates the primary γ' phase, but at the same time, Ti is an element that causes abnormal diffusion phenomenon in the bonding portion and has an adverse effect on factor 6, so it is not contained in the bonding material of the present invention. Al is the main element that generates the primary γ' phase, and the amount of Al is the amount of Al necessary to generate the primary γ' phase in the base material at the joint.
If the amount is at least the lower limit of weight % and less than (the lower limit + 1) weight %, the necessary amount of primary γ' phase can be produced without adversely affecting the factor 6. Further, when the amount of Al is within the above range, when the diffusion bonding by TLP method is completed, the concentration of Al in the bonded part is Al≧14 when the Cr content in the base material is 8% by weight or less. 5/Cr (unit: weight %), and when Cr in the base material is greater than 8 weight %, the relationship of Al≧Cr/10+1 (unit: weight %) is satisfied.

Regarding factor 3, Al is used as an oxidation protective film.

O, is selected and the Al. O and Cr are selected as elements for forming a film around the joint portion. The amount of Cr is set to the same value as the weight percent of Cr in the base material. In the above manner, the types and amounts of elements that define each factor related to bonding characteristics are basically determined.

Note that the factor 5 will be described later. Next, considering the welding characteristic factors, first, regarding factor 1, B and Si are selected.

The amount of B and Si is such that the combined amount in the bonding material is 15 at% or more and 22 at% or more, that is, 15 at%≦B+Si.
≦22at%, and the amount of Si is set in the range of 5% by weight or less of soil in the bonding material, that is, 0≦Si≦1.5wt%. B +Si is less than 15 at% or 22 at%
In any case in which the Si content exceeds 1.5 wt%, the bonding material does not become amorphous, and if the Si content exceeds 1.5 wt%, Si remains in the bonded portion, which is disadvantageous because there is a risk of adverse effects. Although the types and amounts of the essential components of the bonding material of the present invention are basically determined as described above, in the present invention, the amounts of each component determined in this manner are further used. 5
The amount of each component is finally determined by feeding back the consideration to the factors 1 and 2.

That is, first, each component is readjusted based on the relationship of melting point (Tm). The formula for Tm to be applied is Tm=1433-(8
．． For 03×Al. 85+75.43×Bl. 2+56.
34×SiO. 7+60.8×C-2.4×W-Cr-
1.6XC0+MO), (however, each component represents weight %.

), and the values of each component described above are entered here, and it is verified whether the obtained Tm value (° C.) satisfies the relationship of 1050≦Tm≦1150. At Tm, Tm
The upper limit of 1150°C is a physically possible value for bonding and homogenization treatment, and the lower limit of 1050°C is for melting point depressing elements (B, S
This value is determined from the upper limit of i) and the lower limit of the solid solution strengthening elements (CO, Ta, W). If the value obtained from the Tm equation is outside the range of Tm above, depending on the type of bonding material, it may not be possible to perform uniformity treatment and the bonding material may not be usable.
The values of each component readjusted by this Tm formula are finally put into the formula for the average number of electron vacancies (Nv), and are adjusted again and again to satisfy the relationship of Nv≦2.2at%. factors are considered.

The formula for Nv is based on PHACOMP (PhasecOm), which is used to prevent strength deterioration due to TCP phase generation.
This is based on the putatiOn) method. That is, N
V=0.66×Ni+1.7×CO+2.66×Fe+
3.66×Mn+4.66×(Cr+MO+W)+6.
66×(Si+Zr) (however, each component represents atomic %) is used. Nv value is 2.2at%
If the temperature exceeds 100%, the TCP phase is likely to be generated. Each component determined by considering each factor as described above is blended in a predetermined amount, and a ribbon filler is formed by applying a commonly used molten metal quenching method. At this time, the cooling rate is set to 1×10 4 C/Sec or more. If the cooling rate is lower than this value, crystallization progresses, and intermetallic compounds that reduce the ductility of the ribbon filler tend to form, resulting in compositional fluctuations. Therefore, it is inappropriate. The bonding material of the present invention has an alloy composition optimized in accordance with the composition of the base material, and is particularly suitable for Ni-based superalloys with a γ'' content of 55% or more, such as IN738 and NAR-M247. It is useful as a bonding material.

It goes without saying that it is also useful for materials such as IN7l3C where the amount of .gamma.

First, Table 1 shows the composition of MAR-M247.

Next, various bonding materials having the compositions shown in Table 2 were prepared. In Table 2, sample numbers 1 and 2 are both commercially available fillers for Ni-based superalloys, with 1 being amorphous and 2 being powder.

For sample numbers 3 to 11, alloys blended with a predetermined composition were vacuum plasma melted in a water-cooled copper mold, and the molten metal was jetted onto a single roll and rapidly cooled at a cooling rate of approximately 3 x 10'°C/Sec. It's a ribbon. Note that both the Tm value and the Nv value are shown as calculated values. Test numbers 4, 5, 6 in Table 2
, 9 is a ribbon filler of the bonding material of the present invention. Using these bonding materials, the base materials of MAR-M247 were bonded by the TLP method.

Microscopic photographs of the metal structure of the joint are shown in Fig. 2 (magnification 5000) for sample number 1 (comparative example), Fig. 3 (magnification 500) for sample number 3 (comparative example), and Fig. 3 (magnification 500) for sample number 3 (comparative example).
Example) is shown in FIG. 4 (magnification 200), and FIG.
A further enlarged view of the joint is shown in FIG. 5 (magnification: 5000). In FIG. 2, the secondary γ'' phase is uniformly precipitated in the joint, but no primary γ'' phase is observed, and the metal structure is not the same as that of the base metal.

Furthermore, in the case where melting point lowering elements (B, Si) are simply added to the base material, as is clear from FIG. 3, the base material and the joint have distinctly different structures.

On the other hand, as is clear from Fig. 4, in the bonded part made of the bonding material of the present invention, both the primary γ'' phase and the secondary γ'' phase are precipitated in the same manner as the base metal, and the EPMA analysis results also show that The Al concentration in the sample was the same as that in the base material.

Furthermore, as is clear from Fig. 5, which shows a further enlargement of this joint, MC-type grain boundary carbides are precipitated at the joint, and the W concentration therein is also the same as that of the base metal according to the analysis results by E-PMA. Ta. [Effects of the Invention] As is clear from the above explanation, even if Ni-based superalloys with a γ″ content of 55% or more are joined by the TLP method using the joining material of the present invention, the joint will not be as strong as the base material. It has the same structure as the metal structure, making it possible to join with extremely high reliability.For example, even when manufacturing gas turbine cooling blades, which are used at high temperatures, the strength of the joint can be made equal to that of the base material, and it can be assembled in a split structure. Since it becomes possible to make the internal cooling method more efficient, its industrial value is extremely large.

Furthermore, by making full use of the method applied to determining the composition of the bonding material of the present invention, the conventional trial and error regarding bonding materials for various Ni-based superalloys can be eliminated, and ribbon fillers for wide bonding can be developed in an extremely systematic manner. Since it can be molded, its range of applications is extremely wide.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a gas turbine cooling blade.

Claims (1)

[Scope of Claims] 1 Ni_ in which the amount of γ′ of at least one is 55% or more
A ribbon-shaped bonding material for liquid phase diffusion bonding of a base material of a 3Al-γ' reinforced Ni-based superalloy, the bonding material comprising C.
An alloy whose essential components are O, Ta, W, Al, Cr, B and/or Si, and Ni, and its composition is (
I) Co is the same as the weight ratio (wt%) of Co in the base material; (II) Ta is 0 wt% or more and less than or equal to the sum of Ta weight% and Nb weight% in the base material; ( III) W is at least 1/3 of the W weight% in the base material and Mo weight% in the base material
or the lower limit of W weight % required to generate grain boundary carbides in the joint, whichever is greater; (IV) Al is present in the base material in the joint. Greater than or equal to the lower limit of Al weight % necessary to generate the primary γ' phase + 1
(V) Cr has the same value as the Cr weight % in the base material; (VI) B and Si have a value in which the combined amount of both is 15 atomic % or more and 22 atomic % or less; , and at least Si is 1.5% by weight or less; (VII) Moreover, the amount of each component in the bonding material has the following melting point (Tm) formula: T
m(℃)=1433-(8.03×Al^0.^8^5
+75.43×B^1. ^2+56.34×Si^0.
^7+60.8×C-2.4×W-Cr-1.6×Co
+Mo), (however, each component represents weight%), a value that satisfies the relationship 1050°C≦Tm≦1150°C; (VIII) Also, the amount of each component in the bonding material is
The following formula for the average number of electron vacancies (Nv); Nv=0.66
×Ni+1.71×Co+2.66×Fe+3.66×
Mn+4.66×(Cr+Mo+W)+6.66×(S
i+Zr) (however, each component represents atomic %), a value that satisfies the relationship Nv≦2.2 atomic %;
(X I) The balance is Ni; and a bonding material for a Ni-based superalloy, characterized in that it is produced by a molten metal rapid cooling method at a cooling rate of 10^4° C./sec or more.