JPH06269957A - Jointed body of lightweight heat resistant material and its production - Google Patents

Abstract

PURPOSE:To suppress the formation of a brittle intermetallic compd. at the boundary and to improve joint strength by joining a Ti-Al member and a W- base or Mo-base high melting metal base material via an insert material, such as Ta or Nb, in a solid phase. CONSTITUTION:The insert material consisting of the Ta or Nb is interposed between the first member consisting of the intermetallic compd. of the Ti-Al system and the second member consisting of the W-base or Mo-base high melting metal base materia. Both members are butted and joined against and to each other in the solid phase state by an HIP treatment, by which these members are combined and the joined body of the lightweight heat resistant materials is obtd. The thickness of the insert material is preferably >=10mum in terms of preventing the interdiffusion between Ti or Al and the high melting metal. The intermetallic compd. of the Ti-Al system is for example, Ti3Al, TiAl, TiAl3, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightweight heat-resistant material joined body suitable for space / aircraft engine members and the like, and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a new material expected to be applied to members requiring high strength in a high temperature environment such as space and aircraft engine members, Ti--Al based intermetallic compounds (Ti ₃ A
1, TiAl, TiAl _3, etc.). This new material is
As is the case with common intermetallic compounds, it has poor ductility and extremely low workability, but it is also excellent in high-temperature strength, and is lighter and more heat-resistant than general intermetallic compounds. Therefore, T
The i-Al intermetallic compound is expected as a new material applicable to space / aircraft engine members.

[0003]

However, the use limit temperature of the Ti-Al intermetallic compound is about 1273K. On the other hand, as the operating environment temperature of the turbine of a jet engine, the outer wall of a spacecraft, etc., a temperature higher than the melting point of Ti-Al-based intermetallic compounds (about 1773 K for TiAl) is expected. Therefore, Ti-Al-based intermetallic compounds cannot be used for members such as the turbine of a jet engine and the outer wall of a spacecraft, and a material having higher heat resistance than this is required.

An object of the present invention is to provide a lightweight heat resistant material joined body having heat resistance superior to that of a Ti--Al based intermetallic compound and a method for producing the same.

[0005]

[Means for Solving the Problems] If attention is paid only to heat resistance, high-melting-point metals such as Mo and W have high melting points exceeding 2000 K, and are superior in heat resistance to Ti-Al-based intermetallic compounds. Have However, since these high-melting-point metals have a large specific gravity, it is difficult to apply them individually to the space and aircraft fields where weight reduction is particularly required. Therefore, it is conceivable to develop a lightweight material having excellent heat resistance by joining a high melting point metal and a Ti—Al-based intermetallic compound to form a composite.

However, up to now, no detailed study has been found on the joining of dissimilar materials, and only joining of Ti—Al-based intermetallic compounds has been studied (JP-A-3-226387). , Welding Society National Convention Lecture Summary No. 50 No. 313-315, Welding Metallurgical Commission Material WU
-1378-91).

In the dissimilar material joining of a Ti--Al based intermetallic compound and a refractory metal such as W or Mo, a fragile intermetallic compound layer is formed at the joining interface, so that a sound dissimilar material joint cannot be obtained. Can be considered. Friction welding, hot rolling, diffusion bonding, brazing and the like are generally used for the dissimilar material bonding of the combination in which the bonding materials react with each other to form a brittle intermetallic compound layer. There is such a problem.

In friction welding, the joint is limited to one having a good rotational symmetry. The hot rolling method requires large plastic deformation of the material, and thus Ti-Al having poor deformability.
Not suitable for joining intermetallic compounds and refractory metals. In diffusion bonding, the melting points of both are W: 3683K, Mo: 28.
It is difficult to select the bonding conditions because it is significantly different from 93K for TiAl: about 1773K. Since brazing uses a low melting point brazing material, it is difficult to apply it to a member that is particularly required to have heat resistance at high temperatures.

Further, in the diffusion bonding, since the bonding is usually performed at a temperature of ½ or more of the melting point (K) of the bonding material, a bonding temperature of 1800K or higher for W bonding and 1400K or higher for Mo bonding is required. However, the melting point of TiAl is 1773K.
And the melting points of Mo and W are low,
When the joining by diffusion joining is performed under the condition of (1), TiAl is largely deformed by the pressure applied during joining, and there is also a problem that a sound shaped joint cannot be obtained.

On the other hand, fusion welding such as arc welding and electron beam welding is carried out for joining refractory metals to each other, but brittleness may occur due to coarsening of crystal grains due to exposure to high temperature during welding. This is a problem, and the same problem is feared even when diffusion bonding is performed at a high temperature.

The inventors of the present invention have found that T
a and Nb are Ti-Al based intermetallic compounds and Mo and W
It has been confirmed that it is difficult to form a brittle intermetallic compound against any of the refractory metals such as. Further, since the HIP process can apply pressure from all directions, it is possible to prevent deformation of the materials to be joined.

From these points, the present inventors have joined by HIP treatment using a Ta insert material developed for joining Ti-based or Zr-based metal and stainless steel (JP-A-4-46685). I focused on. And
In addition to Ta, Nb as an insert material, TiAl and M
The joining of O, TiAl and W was carried out by HIP treatment under the conditions of heating temperature of 1473 K, pressure of 100 kgf / cm ² , and holding for 1 hour. As a result, it was confirmed that the embrittlement layer was not formed at the joint interface, and Ta and Nb were found to be effective insert materials for joining the Ti—Al-based metal compound and the refractory metal (Mo, W). Got

Further, in the joining by the HIP treatment, not only the deformation is suppressed but also the pressurizing force can be increased by suppressing the deformation, so that the joining can be performed at a relatively low temperature, and as a result, Mo and The growth of W crystal grains is suppressed,
It was also found that it is possible to manufacture a joined body without embrittlement on the side of the Mo base material or the W base material.

The present invention has been made on the basis of these findings. A first member made of a Ti--Al intermetallic compound and a second member made of a W-based or Mo-based refractory metal-based material are used.
The first gist is a lightweight heat-resistant material joined body characterized by being solid-phase joined with the member of No. 1 through an insert material made of Ta or Nb. And a second member made of a W-based or Mo-based refractory metal-based material with an insert material made of Ta or Nb interposed therebetween so that both members are HIPed.
A second gist is a method of manufacturing a lightweight heat-resistant material joined body, which is characterized by joining and compounding in a solid phase state by treatment.

[0015]

[Function] The insert material made of Ta or Nb suppresses the formation of brittle intermetallic compounds at the joint interface and enables the formation of a composite of Ti-Al-based intermetallic compounds with excellent joint strength and refractory metal-based materials. To

The thickness of the insert material is preferably 10 μm or more from the viewpoint of preventing mutual diffusion of Ti and Al and the refractory metal, but from the viewpoint of weight reduction, it is better not to increase the thickness of the insert material.

Examples of the Ti-Al intermetallic compound include Ti ₃ Al, TiAl, and TiAl ₃ .

The refractory metal-based material includes, in addition to Mo and W, binary and ternary Mo-based alloys and W-based alloys to which Re or the like is added as an additive element.

The joining form may be such that the Ti--Al based intermetallic compound and the refractory metal-based material are simply joined together, or that the refractory metal based material and the Ti--Al-based intermetallic compound are sandwiched.

Such a joined body is expected to exceed the melting point of the Ti-Al intermetallic compound by exposing the refractory metal-based material side to a high-temperature use environment, and is expected to exceed the melting point of a jet engine turbine or a spacecraft. It exhibits high strength even under ultra-high temperature use environment such as outer wall, and the reduction in weight is minimized.

The bonding temperature in the HIP process is T
Since the melting point of the i-Al-based intermetallic compound is lower than the melting points of Mo and W, 1673K is the maximum limit, preferably 1500K or less, and particularly preferably about 1273K.

When the HIP process is used, the applied pressure can be increased without considering the deformation of the materials to be joined, so that the joining interface can be sufficiently adhered, and a Mo or W joint of about 1273K can be obtained. As a result, it is possible to join at a low temperature, and it is possible to prevent embrittlement of Mo and W at a high temperature.

It is preferable that the pressing force is large in order to enhance the adhesiveness of the joint surface, and especially 50 kgf / cm ² or more is preferable in the case of joining in the vicinity of 1273K.

The joining time is preferably 5 minutes to 3 hours for the purpose of causing diffusion at the joining interface and preventing a decrease in strength due to coarsening of the crystal grains of the Ti--Al intermetallic compound.

[0025]

EXAMPLES Examples and comparative examples of the present invention will be described below.

Using industrial pure Ti and pure Al as raw materials, Ti
-25 to 75 at% Al intermetallic compound is melted to produce a round bar having an outer diameter of 10 mm and a length of 30 mm, and a round bar made of W and Mo having the same shape as that of the round bar, and further inserted. Ta, Nb, Zr, N with a thickness of 0.1 mm
i foil was prepared. Then, with an insert material interposed between both round bar materials, a joining temperature of 1073K to 1573K, a pressing force of 10 to 2000 kg / cm ² , and a holding time of 0.1 to 5 h.
Butt joining was performed by HIP treatment under the condition of r.

The tensile strength of the joint portion of the joined body obtained by butt joining was investigated. The results are shown in Tables 1-5.

Tables 1 to 3 show that TiAl is Ti-50 at%.
As Al, the result of the investigation when the joining conditions are changed is shown. Good joining strength was obtained even when the joining temperature was 1273 K, which was relatively low for W and Mo, and this prevented embrittlement of W and Mo.

Table 4 shows the joining conditions of 1273K-100kg.
The results are shown when the composition of TiAl is changed by fixing the pressure / cm ² pressure to 1 hr. Good bonding strength was obtained regardless of the composition of TiAl.

Table 5 shows the joining conditions of 1273K-100kg.
/ Cm ² Pressurization-holding for 1 hr holding, the result of investigation when changing the insert material is shown. Good joining was performed only when the insert material was Ta or Nb, and it became possible to manufacture a lightweight heat-resistant material joined body that could be put to practical use.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

[Table 4]

[0035]

[Table 5]

[0036]

As is apparent from the above description, the lightweight heat-resistant material joined body of the present invention is obtained by joining a TiAl-based intermetallic compound and a Mo-based or W-based refractory metal-based material. It can be used even at an ultrahigh temperature exceeding the limit temperature of use of the intermetallic compound. In addition, since the use of the high melting point metal-based material is limited to a part, it is excellent in lightness. Therefore, it exerts a great effect on weight reduction of members in the space and aircraft fields.

Further, the method for producing a joined body of a lightweight heat-resistant material of the present invention is a method of joining a TiAl-based intermetallic compound and a Mo-based or W-based refractory metal-based material with sufficient strength, thereby It is possible to manufacture a lightweight heat-resistant material joined body having high strength up to an extremely high temperature exceeding the use limit temperature of a compound, and it exerts a great effect on weight reduction of members in the space and aircraft fields.

Claims (2)

[Claims] 1. A first member made of a Ti--Al-based intermetallic compound and a second member made of a W-based or Mo-based refractory metal-based material, with an insert material made of Ta or Nb interposed therebetween. A lightweight heat-resistant material joined body characterized by being solid-phase joined together. 2. An insert material made of Ta or Nb between a first member made of a Ti—Al-based intermetallic compound and a second member made of a W-based or Mo-based refractory metal-based material. A method for manufacturing a lightweight heat-resistant material joined body, characterized in that both members are joined in a solid state by HIP treatment to form a composite by interposing the above.