JPH07197155A - Titanium aluminum base member and its production - Google Patents

Abstract

PURPOSE:To produce a Ti-Al base member consisting essentially of an intermetallic compd. of Ti and Al excellent in resistance to oxidation and high in dimensional accuracy by incorporating the third element other than Ti and Al at a surface of the member, where the content of the third element is higher than that at an inside of the member, in the member containing the third element other than Ti and Al. CONSTITUTION:In the Ti-Al base member containing at least one kind of the third element other than Ti and Al (e.g. Si, Nb, T, W, Mo, etc.), the content of the third element at the surface 3 of the member is made higher than that at the inside 2 of the member. In this way, the member consisting essentially of the intermetallic compd. of Ti and Al excellent in resistance to oxidation is produced.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an intermetallic compound TiAl.
The present invention relates to a member containing (titanium aluminum) as a main component, and more specifically to a member containing an intermetallic compound TiAl excellent in oxidation resistance as a main component. Furthermore, the present invention provides an intermetallic compound T
Regarding the surface treatment method of a member mainly composed of iAl,
More specifically, it relates to a surface treatment method for a member containing TiAl as a main component for improving the oxidation resistance.

[0002]

2. Description of the Related Art TiAl-based members have inferior toughness compared to general metal materials, but have toughness values an order of magnitude higher than those of ceramics. Furthermore, because of its small specific gravity and excellent strength at high temperatures, it is extremely promising as a high-temperature structural material, mainly for turbine materials such as gas turbines and turbochargers that rotate at high temperatures and high speeds. But T
Since the iAl-based member is inferior in oxidation resistance, a thick oxide scale is formed when it is used at a high temperature, and it cannot be put to practical use in a high temperature atmosphere. Generally, when a metal material is used in an oxidizing atmosphere, an oxide layer is formed on the surface. Often this oxide layer grows over time and erodes the matrix. That is, it is oxidative corrosion. However, in some cases, a thin oxide layer is formed on the surface and acts as a protective coating, which may increase the oxidation resistance of the base material. What acts as a protective film is, for example, NiO when Ni is contained in the base material, Al ₂ O ₃ when Al is contained, and the like. In the case of TiAl,
It is known that in an oxidizing atmosphere, a TiO ₂ (rutile) layer is formed on the surface of the base material, and then a TiO ₂ + Al ₂ O ₃ mixed layer is formed. Since this rutile layer does not act as a protective film, it has been a cause of reducing the oxidation resistance of TiAl. In recent years, since TiAl has poor oxidation resistance, various methods have been proposed for improving the oxidation resistance. For example, a method of coating the surface layer with a TiAl ₃ layer having excellent oxidation resistance (Japanese Patent Laid-Open No. 1111858),
Method of adding a third element such as Si, Y, Nb, W, Mo (Japanese Patent Publication No. 1-298858, JP-A-1-259)
No. 13, Japanese Patent Laid-Open No. 4-285138) and the like have been proposed.

[0003]

However, the above TiAl
_The method of coating ₃ has a relatively good oxidation resistance because it forms a protective Al ₂ O ₃ coating in an oxidizing atmosphere, but has the following problems. The coating (TiAl ₃ ) is the base material (TiA ₃
Al concentration is higher than that of l), but Al during use at high temperature
Will diffuse and penetrate into the substrate, and the coating will gradually become thinner. In the worst case, the film disappears and becomes a TiAl single phase. In this case, TiO ₂ (rutile) is produced by the oxidizing action in the oxidizing atmosphere, and so-called high temperature corrosion proceeds. On the other hand, T
Conventionally, the Al infiltration method has been used to generate the iAl ₃ layer. This is usually 600 ° C to 1000 ° C, 5 to 1 ° C by burying TiAl in an Al permeation material formed by mixing Al powder, alumina powder and ammonium chloride powder as a permeation accelerator.
It is carried out by heating for 5 hours. The problem with this Al infiltration method is that it takes a long time to process and is disadvantageous in terms of manufacturing cost. Furthermore, since the Al infiltration layer grows vertically outward with respect to the processing surface, in the case of a base material having corners, As shown in FIG. 6 (a), the coating of the corner portion 4 becomes extremely thin, or
That is, a crack is generated in the coating as in (b). Furthermore, for members that require high dimensional accuracy,
Since the Al permeation layer grows outward perpendicularly to the treated surface, it was difficult to control (control) the dimensions of the member after coating the Al permeation layer.

On the other hand, the method of adding the third element to TiAl does not cause the above problems, but the effect of improving the oxidation resistance does not reach that of the case of coating with TiAl ₃ . For example,
The oxidation test was performed at 900 ° C. for 100 hours, and TiAl ₃
In the case of coating with No. 3, the amount of oxidation increase can be reduced to 2% or less as compared with the case of not coating, but that with the addition of the third element is about 10 to 50%. The present invention has been made to solve these problems, excellent in oxidation resistance,
It provides a member whose main component is a high dimensional precision intermetallic compound TiAl, and further, Ti which improves the oxidation resistance.
The present invention provides a surface treatment method for a member containing Al as a main component.

[0005]

The first means is to use Ti
And a TiAl-based member containing at least one third element other than Al, wherein the content of the third element on the surface of the member is higher than the content of the third element inside the member.
It is a system member. The second means is that Al is formed on the base material containing at least one third element other than Ti and Al.
A TiAl-based member having a coating portion containing 60 to 70% by weight, wherein the content of the third element in the coating portion is higher than the content of the third element in the base material portion.
The third means is a TiAl-based member containing at least one kind of third element other than Ti and Al, and the thickness of the coating portion on the surface of the member is similar between the corners and the vicinity of the corners. It is a TiAl-based member. The fourth means is Ti and A.
A TiAl-based member having a coating portion made of TiAl ₃ on a base material portion containing at least one kind of third element other than 1, wherein the content of the third element in the coating portion is the base material portion. The TiAl-based member has a content higher than the content of the third element. The fifth means is the production of a surface-treated TiAl-based member in which a member containing at least one third element other than Ti and Al is heat-treated in an atmosphere that produces a reaction product with Ti of the base material. Is the way.

Here, the corner portion is a ridge line portion mainly formed by two surfaces, but even if the ridge line portion is smoothly continuous,
It doesn't matter whether they are sharply connected. Where Ti and A
The third element other than 1 is an element that improves oxidation resistance, not an unavoidable impurity. For example, Si, Nb,
Y, W, Mo and the like. The third element may be a single element or a plurality of elements depending on the conditions under which the member is used, and is appropriately selected. The atmosphere in which Ti of the base material and the reaction product is generated may be any atmosphere as long as it reacts with Ti of TiAl to reduce the content of Ti on the surface. And, the term "reducing a and atmosphere containing sulfur", for example, H ₂ S atmosphere, and the like H ₂ -H ₂ S mixed atmosphere, H ₂
The ratio of and S (sulfur) may be any ratio as long as it can react with TiAl to produce TiS. The "heat treatment" means heating at a temperature not lower than the temperature at which the reaction between the atmospheric components and TiAl starts and not higher than the melting point of TiAl (1460 ° C). 800 ℃ to obtain a stable effect
It is preferably about 1200 ° C, particularly preferably 900 ° C-
It is in the range of 1100 ° C. The treatment time varies depending on the temperature, but is preferably 10 minutes or longer.

[0007]

In the TiAl-based member of the present invention, the third oxidation resistance-improving element is present more on the surface of the member than inside the surface of the member. The oxidation resistance of the surface of the member can be improved while maintaining (FIG. 4). Also, the coating is Al60
Since it consists of ˜70 wt% or TiAl ₃ , the oxidation resistance is further improved (FIG. 4). The TiAl-based member of the present invention is
Since the thickness of the coating is similar at the corner and near the corner,
In general, even the corner portion 4 which is easily oxidized is difficult to be oxidized (FIG. 1). Furthermore, the TiAl ₃ layer on the surface forms an Al ₂ O ₃ layer on the surface in an oxidizing atmosphere, and no rutile layer is formed.
Therefore, the Al ₂ O ₃ coating on the surface acts as a protective coating and the oxidation resistance is improved.

According to the manufacturing method of the present invention, TiAl ₃ is coated on TiAl in a short time without easily reducing the content of the third element, and TiAl having a uniform thickness even at the corners. ₃ that produces TiA with excellent oxidation resistance
An l-based member can be obtained. The manufacturing method of the present invention is
A TiAl ₃ layer can be easily obtained on the surface of TiAl, and the content of the third element can be increased more on the outer surface of the member than on the inner surface of the member, or the content of the third element can be further reduced. The oxidation resistance of TiAl can be easily improved. Further, since TiAl ₃ is generated due to the lack of Ti, the growth of TiAl ₃ proceeds inward perpendicularly to the substrate surface. For this reason, there is no film deficiency in the corners, cracks, etc. seen in the Al diffusion infiltration method,
A coating of good thickness can be produced. Furthermore, it is easy to manage (control) the dimensions of the members. When heat-treated in a reducing sulfide atmosphere, Ti selectively diffuses on the surface and sulfides, and Ti sulfide (TiS) 5 (reactant) is generated on the surface (FIGS. 2 and 3). As a result, Ti near the surface of the TiAl base material
Deficiency, Al apparently moves from the inside of the base material, and Ti
Al3 3 is produced. Further, if the TiS layer remains adhered to the surface, it is not suitable for practical use, but TiS is brittle and adhesion is weak, so that it can be easily removed. For example, if it has a simple shape, it can be polished with sandpaper, and if it has a complicated shape, sulfide on the surface can be removed by sandblasting or the like. The intermediate composition layer 6 is formed from 36% by weight of Al in the TiAl base material portion to TiA.
13 Intermediate coating composition up to 60% by weight of Al
It is an alloy layer of 36% by weight to 60% by weight. 2 and 3
The left side of TiS is the embedded resin 7 used for sample observation. In addition, since the covering portion is formed inside the surface of the base material, it is suitable to obtain a member in which dimensional control of the member is easy and dimensional accuracy is highly required.

[0009]

Example An alloy having the composition shown in Table 1 was prepared by vacuum arc melting. In addition, in order to homogenize the composition, in vacuum 1100 ° C ×
Homogenized annealing was performed for 50 hours. A test piece of 10 mm × 10 mm × 1 mm was cut out from the obtained ingot,
It was an oxidation test piece. This was held at 1000 ° C. for 4 hours in a H ₂ —H ₂ S mixed gas (mixing ratio was H ₂ S 10 volume%) gas flow for heat treatment. The generated sulfide was removed with sandpaper.

[Table 1] The test piece thus obtained was placed in the atmosphere at 900 ° C x 1
It was kept for 00 hours, and the weight before and after it was measured to measure the increase in oxidation. As a comparative example, the same ingot as in the example, which was not subjected to the above treatment, was similarly subjected to the oxidation test. Further, after the completion of the oxidation test, the test piece of the example was cut and the element distribution of the cross section was measured by EPMA (Electron Probe Microanalyzer). The untreated test piece (No. 16) of the Ti-Al binary alloy had an extremely large amount of oxidation increase, and the test piece (No. 11 to No. 11) to which the third element was added.
16) also showed a large increase in oxidation. On the other hand, it is understood that the oxidation-treated (No. 1 to No. 6) increase in the sulfurized test piece is remarkably reduced, and that the sulfurized-treated test piece to which the third element is added has a smaller oxidation increase. No. 1 to N
The results of No. 6 are shown in FIGS. In both cases, the Al concentration was high in the outer layer, and the result of quantitative analysis was TiA.
It was confirmed that the phase was l ₃ . The concentration of the third element was also high in the outer layer portion, which contributed to the improvement of oxidation resistance. Moreover, when the edge of the sample was observed and analyzed, it was found that TiAl
_{The three} phases were evenly formed at the corners, and no deficiency, loss, or cracking of the film was observed.

[0010]

Industrial Applicability According to the present invention, it is possible to obtain a member having an intermetallic compound TiAl as a main component, which is excellent in oxidation resistance and has high dimensional accuracy, and further, TiAl which improves oxidation resistance.
It is possible to obtain a surface treatment method for a member containing as a main component.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a TiAl-based member of the present invention.

FIG. 2 shows a cross section of a TiAl-based member of the present invention in EPMA.
It is a photograph figure of a metal structure measured with (electron probe microanalyzer).

FIG. 3 is a schematic diagram of FIG.

FIG. 4 Ti and Al in the TiAl-based member of the present invention
It is a graph showing the distribution of.

FIG. 5 is a graph showing the distribution of Ti and Al of Examples No. 1 to No. 6.

FIG. 6 is a schematic sectional view of a TiAl-based member surface-treated by a conventional Al infiltration method.

[Explanation of symbols]

1 TiAl-based member 2 base section (TiAl), member 3 internal cover portion (TiAl _3, Al60~70 wt% of Ti
Al intermetallic compound) Member surface 4 Corner part (ridge line part formed from two surfaces) 5 Ti sulfide (TiS) 6 Intermediate composition layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaya Ito 14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi, Aichi Nihon Special Ceramics Co., Ltd.

Claims (8)

[Claims] 1. A TiAl-based member containing at least one third element other than Ti and Al, wherein the content of the third element on the surface of the member is greater than the content of the third element inside the member. A TiAl-based member characterized by a large amount. 2. A TiAl-based member having a coating portion containing 60 to 70% by weight of Al on a base material portion containing at least one third element other than Ti and Al, the third portion of the coating portion. A TiAl-based member characterized in that the content of the element is higher than the content of the third element in the base material portion. 3. The TiAl-based member according to claim 2, wherein the thickness of the coating portion containing 60 to 70% by weight of Al is similar at the corners of the TiAl-based member and near the corners. 4. A TiAl-based member containing at least one kind of a third element other than Ti and Al, wherein the thickness of the coating portion on the surface of the member is similar at the corners and near the corners. Characteristic TiAl-based member. 5. A TiAl-based member having a coating portion made of TiAl ₃ on a base material portion containing at least one third element other than Ti and Al, wherein the third portion of the coating portion is provided.
The content of the element of is larger than the content of the third element of the base material portion. 6. The thickness of the coating made of TiAl ₃ is T
The TiAl-based member according to claim 5, wherein the iAl-based member is approximated by the corners and the vicinity of the corners. 7. A surface-treated TiAl-based member, characterized in that a member containing at least one third element other than Ti and Al is heat-treated in an atmosphere that produces a reaction product with Ti of the member. Manufacturing method. 8. The method for producing a surface-treated TiAl-based member according to claim 7, wherein the atmosphere in which Ti and the reaction product of the base material are formed is a reducing atmosphere containing sulfur. .