JPS5916687A - Joining material for ni-base sintered alloy - Google Patents

Abstract

PURPOSE:To convert the metallic texture in a joint part to the texture resembling to that of a base material and to improve joint efficiency in the stage of subjecting Ni- base sintered alloys contg. much r' to liquid phase diffusion joining, by using an Ni alloy having the specific compsn. added with elements for decreasing m.p. CONSTITUTION:The joining material to be used in the stage of producing high temp. gas turbine blades, etc. made of an Ni3Al-r' reinforced type Ni-base sintered alloy of >=55% content of r' which is difficult to join from the parts thereof by a liquid phase diffusion joining method is formed of the following compsn.: Ni is used as an essential component. Co is contained at the same amt. as the amt. of Co contained in the Ni- base sintered alloy which is a base material. Ta is contained at (Ta+Nb) in the base material or below, W at 1/3 of the W-(W+Mo) in the base material, Al at the lower limit value-lower limit value+1% necessary for forming primary r' phase in the base material, Cr at the same amt. as that in the base material and B, Si are at 15- 22atom% total thereof and <1.5% Si. The m.p. expressed by the formula [ I ] is 1,050- 1,150 deg.C., and <=2.2atom% NV the average number of electron holes expressed by the formula [II] is satisfied. The joining material having such compsn. is used.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a bonding method used for bonding heat engine parts made of N1-based heat-resistant alloys, such as parts having a double-track shape such as high-temperature gas turbine blades, by a diffusion bonding method. For more information on materials,
Even for base materials of N1au-γ' reinforced N1 base superalloys with a γ' content of 55 inches or more, which is difficult to bond with conventional bonding materials,
The present invention relates to a bonding material useful for Ni-based superalloy liquid phase diffusion bonding (hereinafter referred to as TLP method), in which the metallographic structure of the bonded portion is the same as that of the base material, thereby improving joint efficiency.

[Technical background of the invention and its problems]

Generally, Nl-based heat-resistant superalloy is used as a material for high-temperature gas turbine blades, and in order to increase its operating temperature, it has a cooling blade structure with complicated cooling passages provided inside.

Typical structural examples include (A) a return flow complete precision casting unit and (B) a wafer wing constructed by joining more than ten wafers on a plane. When manufacturing gas turbine blades with these complicated cooling passages,
Usually, diffusion bonding method is applied. For example, in the case of (5), as shown in the cross-sectional view in Figure 1, 2
After precision casting the divided wing members 1.1', they are combined with an insert filler metal interposed on the joining curved surface 2 of the two parts, and are integrated by diffusion bonding. In this case, since the joining curved surface is wide, it is preferable that the filler metal used is a quenched ribbon filler that is easy to handle and has a high density. In the case of (B), there are many joint surfaces and the dimensional accuracy of the plane is strict, so a thin filler metal is used.

As the diffusion bonding method applied for manufacturing (4), 53), the TLP method is usually adopted. This is T
This is because the LP method increases the reliability of bonding.

When joining N1-base heat-resistant alloys by the TLP method, conventionally Ni
Filler metals having compositions such as -B, Ni-B-8t, and Ni-Cr-B have been used. This filler metal is N1 containing lower melting point elements such as B and 81, and melts at a temperature several tens of degrees lower than the melting point of the base material (Ni-based heat-resistant alloy). Therefore, in 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, and After wetting and brazing, a method is applied in which the temperature is maintained for a longer period of time to diffuse B, St, 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.

Filler metals used in the TLP method include various kinds of filler metals, such as chips made by slicing N1-based solder alloys as described above, or pieces made into bulges by melting a solder alloy and then applying the molten metal quenching method. There is something. If the composition of the filler alloy is the same, the resin filler made by the molten metal quenching method is
It has a density of 100 inches and can be punched into the required shape, is ductile, is easy to handle, and the structure of the filler itself is uniform, allowing for highly reliable joining. for example,
If a ribbon filler is used even for a base material such as IN713C, which has a γ' amount of 51 inches, it is possible to form a joint with almost the same creep bonding strength as the base material.

Recently, strong N1 base casting superalloys have appeared, such as IN738LC, MAN, and -M247. In this N1-based superalloy, in order to increase the amount of γ' in the metal structure at the outer corners as much as possible, the alloy composition range is set at the limit based on alloy design.
Its range is extremely narrow.

Therefore, for such a base material, the above-mentioned thicker Ni
If the TLP method is applied using a solder alloy, the metallographic structure of the joint will be different from that of the base metal, making it more difficult to obtain a joint power equal to that of the base metal.

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.0Therefore, when the amount of γ′ is large, for example, the amount of r′ A filler metal with an alloy composition suitable for joining base materials of N1-based superalloys with a content of 55% or more by the TLP method has not yet been developed. , and the amount of γ′ is 5.
Even when base metals of N1-based superalloys with a grade of 596 or higher are joined by the TLP method, the metallographic structure of the joint is not the same as that of the base metals.As a result, it is desirable to provide a joining material that improves joint efficiency purpose.

[Summary of the invention]

In order to achieve the above object, the present inventors have carried out extensive research in consideration of metallographic principles, and have found that the method can be used for joining Ni-based superalloys with a large amount of γ′ by the TLP method and that can be rapidly cooled by molten metal. Created by law? Regarding fillers, we focused on the fact that the influencing factors that should be taken into account when attempting to optimize the alloy composition are broadly classified 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, ■ the type and amount of the solid solution strengthening element in the bonding material; ■ the type of γ′ that should be generated in the joint;
■The type and amount of the oxidized protective film that should be formed around the joint, and the type and amount of the element necessary for it;■Elements that determine the amount of grain boundary carbide reinforcement in the joint. type and amount, ■ TCP phase at the joint (Top
olog1+-cal13' closed pack
These include the average number of electron vacancies (Nv) as a factor for preventing the generation of ed phase), and (2) a factor for preventing abnormal diffusion of the bonding material during bonding.

In addition, welding characteristic factors include O-joint, material resafety,
The types and amounts of elements that define the molten metal formability or amorphization when forming f-color, and the zero melting point (Tm:° C.) are subject to consideration.

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 types and amounts of each element constituting the base material, the amount of primary phase (coarse γ' phase) in the base material, the amount of secondary γ' phase (fine γ' phase), and the amount of carbides ( The amount of MC type or h'1xsca type (M represents a metal element), the Nv value of the base material, etc. are measured and used as main data. These data indicate that Co is the solid solution strengthening element at a factor of 0, which is the target structure of the joint.

Ta and W are selected. co is set to the same value as 00% by weight in the base material (Ta is less than or equal to the sum of T & weight% and depressed weight% in the base material, that is, 0≦'l'awt%
It is set to a value that satisfies the relationship: ≦(Ta+Nb) base material wt%.

If the amount of T& is outside this range, it will not contribute to solid solution strengthening when CO is set as described above. W is ■
It is also the element that defines the factor of
+Mo) Compare the value that satisfies the relationship of base material w t % with the lower limit value of W weight distribution required to generate the same type and amount of grain boundary carbide as the grain boundary carbide in the base material at the joint. and set to the greater of those values.

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 the factor (2), the secondary γI phase in the bonded portion diffuses from the base material during bonding and appears in the same manner as the base material, so it may be left out of consideration. Therefore, when considering the -order r' phase, AI is selected as the element that produces the same primary γ' phase as the base material at the joint. Incidentally, Tl is also an element that generates the primary γ' phase, but at the same time, Ti is an element that causes an abnormal diffusion phenomenon in the joint, and since it has an adverse effect on the factor (2), it is not contained in the mating material of the present invention. kl is the main element that generates the primary γ' phase, and its AI'iit is greater than or equal to the lower limit of M weight and It% required to generate the primary γ' phase in the base material at the joint. If it is below the lower limit + 1) weight -, the necessary amount of primary γ' phase can be produced without adversely affecting the factor (2).

Moreover, when the amount of M is within the above range, 1. The A concentration in the joint 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 AI≧Cr/10+1 (unit: weight %) is satisfied.

Regarding factor (2), N20° is selected as the oxidation protective film, and Cr is selected as the element necessary to form the JtO* film around the joint. The amount of Cr is set to the same value as the weight percent of Or 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 (■) will be described later.

Next, considering the welding characteristic factors, first, B and Si are selected as factors of 0. The amounts of B and St are
The combined amount is 15 atoms or more and 22 atoms or less in the bonding material, that is, 15 at%≦B+si≦22at,
and a range in which the amount of Sl in the bonding material is 1.5% by weight or less,
That is, it is set to OI≦81≦1.5wt%. B+
When Si is less than 15 at'% or more than 22 at'%, the bonding material does not become amorphous and S
If 1 exceeds 1.5 wt%, St will remain in the joint, which may have an adverse effect, which is disadvantageous.

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. Then, the amount of each component is finally determined by feeding back the consideration to the factor (2) and the factor (0). That is, first, the melting point (T
Each component is readjusted based on the relationship m ).

The bucket equation to be applied is = 1433-(8,03XJ5 Ag +75.43XB +56.34XSi
+60.8X C-2,4X W-Cr -1,6X
Co + Mo ), (however, each component represents weight %), and here, enter the value of each component above,
It is verified whether the obtained single value (° C.) satisfies the relationship 1050≦1≦1150. In rare cases, -
The upper limit of 1150°C is a physically possible value for bonding and uniformization treatment, and the lower limit of 1050°C is for melting point depressing elements (B, S
t) and the solid solution strengthening element (Co l Ta IW
) is the value determined from the lower limit value of If the value obtained from the Tm formula is outside the rare range mentioned 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 in this set are finally put into the formula for the average number of electron vacancies (Nv), and adjusted again and again to satisfy the relationship Nv≦2.2at. will be considered. The NvO formula is based on PHACOMP (phase
This method is based on the calculation method. That is, Nv = 0.66 XNi + 1.7 XCo
12, 66 XFe+3. ．． 66 XMn+ 4.66
X (Cr+Mo+W)+ 6.66 x (Si+
Zr), (However, each component represents an atom.)
is used (, when the Nv value exceeds 2.2 at%, T
CP phase is more likely to be generated.

Each component determined by considering each factor as described above is blended in a predetermined amount, and a reden filler is prepared by applying a commonly used molten metal quenching method. At this time, the cooling rate is I
It is set to 0'°C/sec or higher.

If the cooling rate is smaller than this value, (1) crystallization will proceed and The ductility of the filler decreases (11)
It is unsuitable because intermetallic compounds are not likely to be formed and compositional fluctuations occur.

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 I N738.
, MAR,-M247, which is useful as a bonding material for N1-based superalloys with an r' content of 55 inches or more, is also lN7
Even for those with a γ' amount of 55- or less, such as 13C,
It goes without saying that it is useful. [Examples of the Invention] MAR-N247 was joined to a base material.

First, the composition of MAR-N247 is shown in Table 1. 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 N1-based superalloys, with 1 being amorphous and 2 being powder. Sample numbers 3 to 11 were made by melting alloys blended at a predetermined composition ratio in a water-cooled steel mold using a vacuum plasma, and then spouting the molten metal onto a single roll to form a melt of approximately 3 X'10'' C/see. Rapid cooling with cooling speed? It is.

Note that both the - value and the Nv value are shown as calculated values. In Table 2, are test numbers 4, 5, and 6.9 the bonding material glue of the present invention?
It is a filler.

Using these bonding materials, iDMAR-M was fabricated by TLP method.
247 base materials were joined. A micrograph of the metal structure of the joint is shown in Figure 2 (magnification 50) for sample number 1 (comparative example).
00), sample number 3 (hikei II) in Figure 3 (magnification 500), and sample number 9 (example) in Figure 4 (
FIG. 5 (magnification: 5000) shows a further enlarged view of the joint in FIG. 4 (magnification: 200).

In FIG. 2, the secondary γ' phase is uniformly precipitated at the joint, but no -order γ' phase is observed, and the metal structure is not the same as that of the base metal.

Furthermore, in the case where the melting point lowering element (B, 81) was simply added to the base material, as is clear from FIG. 3, the base material and the bonded part have a distinctly different structure.

On the other hand, as is clear from Fig. 4, in the bonded part using the bonding material of the present invention, both the primary r' phase and the secondary γ' phase are precipitated in the same manner as the base metal. However, the A7 concentration in the joint was the same as that in the base metal.

Furthermore, as is clear from Figure 5, which shows a further enlargement of this joint, MC-type grain boundary carbides were precipitated at the joint, and the W concentration was also the same as that of the base metal according to the EPMA analysis results. .

[Effect of Qingming]

As is clear from the above explanation, even if the bonding material of the present invention is used to bond a Ni-based superalloy with a γ' content of 55q6 or more using the TLP method, the bonded portion will have the same metal structure as the base metal. This makes it possible to join with extremely high reliability.For example, even in the M construction of gas turbine cooling blades, which have high operating 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, which makes it possible to use the internal cooling method. Its industrial value is extremely great because it makes it possible to improve efficiency. Furthermore, by making full use of the method applied to determining the composition of the bonding material of the present invention, it is possible to
The conventional trial and error regarding base super superalloy bonding materials has been dispelled, and an extremely systematic and wide bonding glue has been developed. Since the filler can be molded, its range of applications is extremely wide.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a gas turbine cooling blade. Figure 2, Figure 3
2, 42 and 5 are microscopic photographs of the joints. Figure 1 Figure 2 Figure 3 ,・semi,

Claims (1)

[Claims] N15AA in which at least one of the γ′ amounts is 55% or more
- A tin-shaped bonding material for liquid phase diffusion bonding of a base material of a γ'-reinforced Ni-based alloy, the bonding material comprising Co + Ta g W s All g
Cr g An alloy containing either or both of B and SL and Ni as essential components, the composition of which is: (I) Co has the same value as the weight ratio (wt%) of Co in the base material; Q [) Ta is 0% by weight or more and less than or equal to the sum of Ta weight% in the base material and tooth profile amount%; ([) W is greater than or equal to the value of W weight in the base material - W weight% in the base material and Mo weight %, or the larger of the lower limit of W weight % necessary to generate grain boundary carbide at the joint; (EV) AJ is the joint A value that is greater than or equal to the lower limit of the AI weight percent necessary to generate the primary γ' phase in the base material and less than or equal to the armpit limit value + 1 weight percent; (V) A value where Cr is the same as the Cr weight percent in the base material; mB
15i is a value in which the combined amount of both is 15 atoms or more and 22 atoms or less, and at least Si is 1.5 weight or less; (2) Moreover, each of the The amount of each component in the bonding material satisfies the following formula for the melting point (Tkn); Formula for the number of vacancies (Nv): % formula % x (S1+Zr) (However, each component represents an atom -) A value that satisfies the relationship Nv ≦ 2.2 atoms; (IX') The remainder is A bonding material for an N1-based superalloy, characterized in that it is Ni; and is produced by a molten metal rapid cooling method at a cooling rate of 10"C/sec or more.