JP3358796B2 - Method for modifying surface of Ti-Al alloy and Ti-Al alloy having modified layer on surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method for modifying the surface of a Ti-Al alloy and a Ti-Al alloy having a modified layer on the surface.

[0003]

2. Description of the Related Art Ti-Al alloys are lighter than Ni-base superalloys, which are typical heat-resistant metal materials currently in practical use, and are superior in terms of high-temperature specific strength.
It is expected to be applied to materials requiring high heat resistance and high strength, such as turbine wheel materials. However, this Ti-Al-based alloy has a problem in that at high temperatures of 800 ° C. or higher, the oxidation resistance is significantly lower than that of a Ni-based superalloy (for example, Inconel 713C). Therefore, T
In order to use an i-Al-based alloy as a heat-resistant material, improvement in oxidation resistance is indispensable, and addition of a third element, surface treatment, and the like have been studied.

[0004] As a method of improving the oxidation resistance of a Ti-Al alloy by adding a third element, for example, molybdenum (Mo), niobium (Nb), silicon (Si), tantalum ( There is a method of adding a third element such as Ta) and tungsten (W). Thereby, the oxidation resistance is improved. However, in the atmosphere at 900 ° C. or higher, there is a problem that sufficient oxidation resistance cannot be obtained because the oxidation rate is high.

On the other hand, examples of the improvement of oxidation resistance by the surface treatment method include (1) aluminizing treatment method, (2) chromizing treatment method, and (3) low oxygen partial pressure treatment method.
In any case, from the viewpoint of adhesion to the base material and long-term stability of the coating,
It is not always an effective measure.

In order to solve these problems, sputtering and diffusion heat treatment or Mo and / or
Alternatively, heat treatment is performed in the presence of an oxide of W and, if necessary, by diffusion heat treatment, Mo and / or W is concentrated to a thickness of 0.5 μm or more in the depth direction on the surface of the Ti—Al-based intermetallic compound material. A "Ti-Al-based intermetallic compound excellent in oxidation resistance and a method for producing the same" characterized by forming a layer has been proposed (JP-A-5-78817). It is stated that the provision of the Mo or W enriched layer promotes the formation of an Al ₂ O ₃ layer in the lateral direction, and significantly improves the oxidation resistance.

[0007] Further, the present invention is characterized in that TiAl is packed in a container with niobium oxide powder, and the container is kept in a low vacuum and high temperature atmosphere to form an alumina film on the surface of TiAl. Surface treatment method ”(JP-A-8-41654) has been proposed. Thus, a protective film of alumina is formed on the TiAl surface.

[0008] A method for modifying the surface of an aluminum alloy member by subjecting the surface of the aluminum alloy member to shot peening, wherein the shot material includes fine particles in the shot material when the surface of the aluminum alloy member is shot. "A method for modifying the surface of an aluminum alloy member", wherein the fine particles are dispersed and embedded in the surface of the aluminum alloy member by performing a shot peening treatment in a state accompanied by a crack. 864
No. 43) has been proposed. Thus, during the shot peening process on the surface of the aluminum alloy member, fine particles for improving the strength reliability such as abrasion resistance and corrosion resistance are embedded in the surface portion of the aluminum alloy member, so that the residual by the shot peening process. In addition to the generation of stress, it is stated that fine particles embedded by the shot can improve strength reliability such as wear resistance and corrosion resistance.

[0009]

However, in the Ti-Al-based intermetallic compound disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 5-78817, Mo and / or W may be present because a large amount of Ti exists near the surface. The formation of a suppuration phase on the surface alone cannot form a protective film that can secure sufficient oxidation resistance. Therefore, in an oxidizing atmosphere in the air, not only a protective film of alumina is formed but also TiO ₂ is formed. When this TiO ₂ is formed, it grows to the inside of the base material, and the oxidation resistance is significantly deteriorated. Therefore,
A protective film that can secure sufficient oxidation resistance cannot be formed.
In addition, Mo and / or W is deposited, and
It is necessary to perform a diffusion treatment in a temperature range of 00 to 1450 ° C., and there is a possibility that these metal powders may be sintered and solidified, and there is a problem that they adhere to the Ti—Al-based intermetallic compound material. Furthermore, when both the Mo oxide and / or the W oxide are heated in a closed container, the Ti-Al-based intermetallic compound material may be sintered and solidified in the same manner as the above-mentioned metal powder. There is a problem of adhesion to the intermetallic compound material. These deposits may form a reaction product having a low melting point with the Ti-Al intermetallic compound material in an oxidizing atmosphere, and the oxidation resistance is rather reduced. Further, the treatment method of performing the heat treatment in the closed container has a problem also in terms of productivity.

The "method of surface treatment of TiAl" described in JP-A-8-41654 has the following problems. That is, (1) it is necessary to perform heat treatment in a closed container in a vacuum, which is problematic in terms of productivity. Also, (2) there is a problem that the treated powder is solidified and sintered, and the powder adheres to the treated material. Therefore, it is necessary to prevent the treatment agent from solidifying during the treatment, to fluidize the treatment agent, and to sublimate and evaporate the treatment agent at a treatment temperature or lower.

The "method of modifying the surface of an aluminum alloy member" described in Japanese Patent Application Laid-Open No. 5-86443 has the following problems. In other words, (1) simply embedding fine particles having an effect on abrasion resistance, corrosion resistance, etc. on the surface by shot peening treatment results in T near the surface.
i is present and TiO
₂ is formed, and the oxidation resistance is deteriorated. Further, (2) Ti is still present in the vicinity of the surface by merely diffusing the fine particles after the particles are dispersed on the surface by the shot peening treatment, and has little effect on the improvement of oxidation resistance, corrosion resistance and the like. (3) Mechanically embedded particles are weakly bonded to the base material, causing cracking and falling off,
Strength reliability such as wear resistance and corrosion resistance cannot be sufficiently secured. In order to increase the interfacial bond between the embedded particles and the base material, it is necessary to perform a treatment for secondarily increasing the bonding force.
(4) The degree of improvement in corrosion resistance and wear resistance is determined by the inherent characteristics of the embedded fine particles. (5) It has a layer structure in which particles mechanically embedded in the substrate are dispersed on the surface of the substrate, and corrosion progresses from an exposed portion of the substrate composition, and it is difficult to obtain sufficient environmental resistance.

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems of the prior art, and have conducted various systematic experiments. As a result, the present invention has been accomplished.

(Object of the Invention) The object of the present invention is to provide Ti-A
An object of the present invention is to provide a method for modifying the surface of a Ti-Al alloy which imparts excellent oxidation resistance to an l-alloy. Another object of the present invention is to provide a Ti-Al having a modified layer having excellent oxidation resistance on the surface.
System alloy.

[0014]

[Means for Solving the Problems]

(First Invention) In the method for modifying the surface of a Ti—Al alloy according to the present invention,
5 atomic% to 55 atomic% of Ti-Al alloy
In a state where a substance containing an oxide having a smaller absolute value of standard free energy of formation than alumina exists on the surface of the Al-based alloy base material, mechanical energy is applied to the base surface to form a mechanical alloy. It is characterized by forming a layer. In the present invention, the step of “providing mechanical energy in the presence of a substance containing an oxide having a smaller absolute value of standard free energy of formation than alumina” is performed in the step of providing an oxide having a smaller absolute value of standard free energy of formation than alumina. In the presence of a substance containing, the step of applying mechanical energy (apart from the substance), the mechanical energy is imparted by applying a substance containing an oxide having an absolute value of the standard free energy of formation smaller than that of alumina. (Hereinafter the same).

(Second Invention) In the Ti-Al based alloy having a modified layer on the surface according to the present invention, the Al content is 15 atomic% to 55 atomic%.
A Ti-Al-based alloy base material comprising a Ti-Al-based alloy of
A modified layer formed on the surface of the substrate, wherein the modified layer is formed of at least one of Si, Nb, Ta, Cr, Mo, and W.
It is characterized by comprising a mechanical alloying layer obtained by applying mechanical energy to the surface of the substrate in a state where a substance containing at least one kind of element is present.

[0017]

【The invention's effect】

(Effect of the First Invention) According to the surface modification method of the present invention, excellent oxidation resistance can be imparted to a Ti-Al alloy.

(Effect of the Second Invention) Since the Ti—Al alloy of the present invention has a modified layer having excellent oxidation resistance on the surface,
Excellent oxidation resistance.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention, which is more specific, and embodiments of the present invention will be described.

(Points of Interest) The present inventors have focused on the following with respect to the above-mentioned problems of the prior art. That is, in order to achieve the above-described object, at least one of niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), and tungsten (W) is formed on the surface of the Ti-Al-based alloy base material. Fine particles containing the above elements are provided, and Ti
-Forming an oxide film mainly composed of elements (at least one of Nb, Ta, Cr, Mo, W) constituting the fine particles provided on the surface portion of the Al-based alloy material;
The oxidation resistance of the i-Al-based alloy is improved. Further, the oxide film changes into a stable oxide in a high-temperature oxidizing atmosphere to form a layer having excellent oxidation resistance at a high temperature.
The oxidation resistance of the i-Al alloy is significantly improved.

[First Embodiment of the Invention]

The method for modifying the surface of a Ti—Al alloy according to the present invention is characterized in that the surface of a Ti—Al alloy base material composed of a Ti—Al alloy containing 15 to 55 atomic% of Al In a state in which a substance having a small absolute value of free energy of formation exists, mechanical energy is applied to the Ti-
It is characterized in that a mechanical alloying layer is formed on the surface of the Al-based alloy base material. Although the mechanism by which the method for modifying the surface of a Ti—Al-based alloy of the present invention exerts an excellent effect is not yet clear, it is considered as follows. The method for modifying the surface of a Ti-Al-based alloy according to the present invention comprises the steps of first forming a standard part from alumina on the surface of a Ti-Al-based alloy base material composed of a Ti-Al-based alloy containing 15 to 55 atomic% of Al. In a state where a substance having a small absolute value of free energy exists, mechanical energy is applied. Thereby, the surface of the Ti-Al-based alloy substrate undergoes plastic deformation,
A clean surface that is prone to sticking is formed. At the same time, a clean surface is formed on the substance, which is liable to adhere during the course of pulverization or exfoliation. Further, by applying mechanical energy, by repeating shearing and friction, fineness and mixing progress, and mixing at the atomic level on the substrate and the material surface is promoted. In a mixed state at the atomic level, a reaction can be performed even at a low temperature. Therefore, when the phase formation is more energetically stable than in the mixed state, alloying is promoted even at a low temperature.
In addition, even in a phase having a high energy order, by the application of mechanical energy, the energy is accumulated inside the material,
A non-equilibrium phase and a metastable phase can be formed. This allows
A mechanical alloying layer mainly composed of an element containing the substance is formed. Since the mechanical alloying layer has a smaller absolute value of the standard free energy of formation than alumina, it is reduced by the aluminum in the base material to metal. On the other hand, aluminum in the base material is oxidized to form an alumina film on the surface. Thereby, it is considered that a mechanical alloying layer having excellent oxidation resistance can be formed on the surface of the Ti—Al-based alloy base material. It is also considered that this modified layer can be formed easily and inexpensively.

(Ti-Al-based alloy base material) The Ti-Al-based alloy base material applicable in the present invention has an Al content of 15 atomic%.
５５55 atomic% of a Ti—Al alloy. Al: Al
Is contained in an amount of 15 to 55 atomic%, thereby obtaining a Ti-Al alloy having ductility at room temperature and excellent high-temperature strength. When the Al content is less than 15 atomic%, a mixed structure of the α-Ti alloy and the Ti ₃ Al phase is formed, and the high-temperature strength is reduced. When the content of Al exceeds 55 atomic%,
It becomes a mixed phase of the TiAl phase and the Al ₃ Al phase, and becomes very brittle. The Ti-Al-based alloy applied to the present invention is obtained by subjecting the raw material to any melting process or sintering process,
It may be one having an appropriate shape such as forging, cutting, or rolling.

(Material Containing an Oxide with a Smaller Standard Free Energy of Formation than Alumina) Materials that can be used in the method for modifying the surface of a Ti—Al-based alloy of the present invention have a larger absolute value of the standard free energy of formation than alumina. A substance containing a small oxide (hereinafter, simply referred to as an oxide-containing substance).
Note that the smaller the absolute value of the standard free energy of formation of the oxide is, the more easily the metal is reduced, and the larger the absolute value is, the more stable the oxide is. Specifically, Ti, V, Cr, Mn, F
e, Co, Ni, Cu, Nb, Mo, Ta, W, Si,
A substance containing an oxide of at least one element of Ce (of course, a substance composed of the oxide) may be used. This substance is, for example, JFElliot, M. Gleiser: Thermo
chemistry for Steelmaking, vol.I (1960), Addison-We
Introduced by sley. Note that the oxide-containing substance can take a form of powdered solid, gas, liquid, or the like. The substance is composed of Nb, Ta, Cr, Mo, W, S
It is preferable that the powder is mainly composed of an oxide of at least one element of i. By using these powders, oxidation / reduction reactions at high temperatures are likely to occur, and an alumina coating excellent in oxidation resistance is formed.

(Form of oxide-containing substance, application condition, applied energy, etc.) The oxide-containing substance may be present in the vicinity of the surface of the Ti—Al alloy base material, Alternatively, the substance may be applied (along with mechanical energy) to the surface of the Ti-Al-based alloy substrate. The application form of the oxide-containing substance may be a form that achieves the object of the present invention.
Any method and conditions may be used, and there is no particular limitation.
As a method of applying the substance, a method of colliding the powder at a high speed is most preferable. The atmosphere during the treatment is preferably performed in an inert gas such as Ar, but may be performed in the air.
The substance may be an alloy powder, an oxide powder, or a composite powder thereof. The size of the substance is 5
Preferably it is 300 μm. When the size of the above substance is less than 5 μm, it is difficult to handle the powder, and when it exceeds 300 μm, the surface reaction hardly occurs. The atmosphere during the application of the substance may be air, but is preferably performed in an inert gas. The above substance is Ti-A
After the reaction with the surface of the l-based alloy substrate, it is preferable to perform a heat treatment. Thereby, the oxidation resistance can be further improved. Note that the heating temperature is a temperature range of 1450 ° C. or less. This is because if the temperature is 1450 ° C. or higher, the Ti—Al-based alloy as the base material is melted.
The energy for applying the applied substance is 20 in terms of the ejection speed.
３００300 m / sec is preferred. If the ejection speed is less than 20 m / sec, it is difficult to cause a surface reaction, and the ejection speed is 300 m / se.
If it exceeds c, the surface condition may be impaired.

(Applying mechanical energy) In the method for applying mechanical energy, plastic flow is developed to enable mechanical alloying between the Ti-Al-based alloy base material and the oxide-containing substance. Any method may be used as long as the method is performed. In order to efficiently express plastic flow,
It is preferable to reduce the application area of the shear stress and increase the number of repetitions. For example, the stress application area is 0.5 mm ² or less, and the number of times of applying the stress per 1 mm ² is 50 or more, preferably 100 or more. Specifically, a method of repeatedly colliding particles at a high speed, a method of rotating a metal member and a material for alloying and a hard ball in a container, or a method of repeatedly hitting with a highly rigid brush-like material Method.

In the case where energy is applied mechanically by repeatedly colliding particles, the oxide-containing substance may be used as particles for applying energy. In this case, the hardness of the powder is desirably equal to or higher than that of the Ti-Al alloy base material. When the hardness of the oxide-containing material is lower than the Ti-Al-based alloy base material,
This is because the powder is only deformed and adheres to the surface of the base material, and does not reach plastic flow for developing mechanical alloying with the base material. When the hardness of the oxide-containing material is lower than the Ti-Al-based alloy base material,
A method may be used in which irregularities are given to the surface of the base material in advance, the powder is caused to collide at a high speed and adhered, and then mechanical energy is applied.

When the oxide-containing substance is a gas or a liquid, it may be used as a medium for transporting energy imparting particles. For example, when the form of the oxide-containing substance is a gas, a gas composed of the oxide-containing substance may be used instead of compressed air in shot peening, and the form of the oxide-containing substance is a liquid. In some cases, a method of spraying with the energy imparting particles may be used.

Although the magnitude of the mechanical energy varies depending on the material of the Ti-Al-based alloy base material, applying a shear stress at least 50% higher than the 0.2% proof stress of the base material causes plastic deformation. Desirable to get up. It is preferable that the shear stress is repeatedly applied in order to promote a solid phase reaction between the substrate and the oxide-containing substance.

As a method for accelerating the formation of the mechanical alloying layer, the substrate may be heated from room temperature to a temperature lower than the recrystallization temperature when applying mechanical energy. Heating is
Not only to make it easier to generate plastic flow by reducing the deformation resistance of the surface of the Ti-Al alloy base material,
Mechanical energy for developing mechanical alloying can be reduced. As a heating method, a method may be used in which the entire substrate is heated or the surface of the substrate is heated simultaneously with a mechanical energy applying process.

(Suitable Surface Modification Method 1 of Ti-Al Alloy) The preferred method of modifying the surface of Ti-Al alloy of the present invention is as follows.
Fine particles containing an oxide having an absolute value of standard free energy of formation smaller than that of alumina are applied to the surface of a Ti-Al-based alloy base material composed of a Ti-Al-based alloy having 1 to 15 at% to 55 at%, The oxide in the fine particles is composed on the surface of the base material.
It is characterized by forming an oxide film mainly composed of the element to be formed. The mechanism by which the preferred method for modifying the surface of a Ti-Al-based alloy according to the present invention exhibits an excellent effect is not necessarily clear yet, but is considered as follows. The method for modifying the surface of a Ti-Al-based alloy according to the present invention comprises the steps of first forming a standard part from alumina on the surface of a Ti-Al-based alloy base material composed of a Ti-Al-based alloy containing 15 to 55 atomic% of Al. A substance containing an oxide having a small absolute value of free energy is provided. As a result, an oxide layer mainly composed of the element containing the fine particles is formed on the surface of the Ti—Al-based alloy substrate by impact compression of the fine particles. Since this oxide has a smaller absolute value of the standard free energy of formation than alumina, it is reduced by aluminum in the base material to metal. On the other hand, aluminum in the base material is oxidized to form an alumina film on the surface. Thereby, Ti-A
It is considered that an oxide film having excellent oxidation resistance can be formed on the surface of the l-based alloy substrate. It is also considered that this modified layer can be formed easily and inexpensively. According to the preferred surface modification method of the present invention, T
Excellent oxidation resistance can be imparted to the i-Al alloy.

(Suitable Surface Modification Method for Ti-Al Alloy 2) The preferred method for modifying the surface of Ti-Al alloy of the present invention is as follows.
The silicon (S) is formed on the surface of a Ti-Al-based alloy base material composed of a Ti-Al-based alloy in which 1 is 15 to 55 atomic%.
i), niobium (Nb), tantalum (Ta), chromium (C
r), molybdenum (Mo) and tungsten (W) in the presence of a substance containing at least one element, applying mechanical energy to the element (Si) constituting the substance on the surface of the substrate. , Nb, Ta, Cr, M
and at least one of o and W). As a result, the alloy coating functions as a protective coating, and further forms an alumina coating in a layered form in a high-temperature oxide atmosphere. These coatings have good adhesion to the base material, function as a protective coating stably over a long period of time, and significantly improve oxidation resistance. The mechanism by which the present surface modification method exhibits an excellent effect is not necessarily clear yet, but is considered as follows. In this surface modification method, first, Al is 15 atomic% to 5 atomic%.
In a state where a substance containing at least one or more elements of Si, Nb, Ta, Cr, Mo, and W is present on the surface of a Ti-Al-based alloy base material composed of 5 atomic% of a Ti-Al-based alloy, Apply mechanical energy. Thereby, Ti
Forming a reaction layer between the base material and one or more of the above-mentioned elements on the surface of the Al-based alloy; The above substance may be formed only from a metal element, but is preferably a thermally stable oxide, and may be changed to an oxide. Therefore, the elements (Si, Nb, Ta, C) constituting the substance are provided on the surface of the Ti-Al alloy material.
An oxide film mainly composed of at least one of r, Mo, and W) is formed. This oxide film changes into a stable oxide under a high-temperature oxidizing atmosphere and becomes a layer having excellent oxidation resistance at high temperature.
It becomes an alloy. As described above, Ti-Al having excellent oxidation resistance
It is considered that the base alloy can be easily and inexpensively manufactured.

(Suitable Surface Modification Method for Ti-Al Alloy 3) The preferred method for modifying the surface of Ti-Al alloy of the present invention is as follows.
The silicon (S) is formed on the surface of a Ti-Al-based alloy base material composed of a Ti-Al-based alloy in which 1 is 15 to 55 atomic%.
i), niobium (Nb), tantalum (Ta), chromium (C
r), molybdenum (Mo) and tungsten (W) in the presence of a substance containing an oxide of at least one element, applying mechanical energy to the element constituting the substance on the surface of the substrate. (Si, Nb, Ta, C
(at least one of r, Mo, and W). Thus, the oxide film functions as a protective film, and further forms an alumina film in a high-temperature oxidizing atmosphere. These oxide films have good adhesion to the base material, act as a protective film stably for a long time, and significantly improve oxidation resistance.

(Suitable Surface Modification Method for Ti-Al Alloy 4) The preferred method for modifying the surface of Ti-Al alloy of the present invention is the method for modifying the surface of Ti-Al alloy described above and the preferred method. In the method for modifying a surface of a Ti-Al-based alloy,
-The film formed on the surface of the Al-based alloy base material is characterized by forming a layer having excellent oxidation resistance at high temperatures containing a stable oxide in a high-temperature oxidizing atmosphere. This suppresses internal oxidation and acts as a protective coating for a long time, so that a Ti-Al-based alloy having excellent oxidation resistance can be easily obtained.

(Suitable surface modification method for Ti-Al alloy 5) The preferred method for modifying the surface of Ti-Al alloy according to the present invention is a Ti-Al alloy containing 15 to 55 atomic% Al. Niobium (N)
b) or tantalum (Ta) in the presence of a substance containing at least one element, applying mechanical energy to the substrate (at least one of Nb or Ta) constituting the substance. A method for modifying the surface of a Ti-Al-based alloy formed by forming an oxide film mainly comprising at least one of a base material and an oxide film under a high-temperature oxidizing atmosphere due to the presence of the oxide film. Al-
A stable oxide layer mainly composed of O is formed to form a layer having excellent oxidation resistance at high temperatures. Thereby, since a stable oxide-resistant layer mainly composed of Al-O is provided between the base material and the oxide film, generation of TiO ₂ causing internal oxidation is suppressed, and Even if the oxide film is lost, the oxidation resistance at high temperatures is not impaired.

(Suitable Ti-Al-based alloy surface modification method 6) The preferred Ti-Al-based alloy surface modification method of the present invention is a Ti-Al-based alloy containing 15 to 55 atomic% of Al. Chromium (C
r) Ti-Al formed by applying mechanical energy in the presence of a substance containing an element to form an oxide film mainly composed of the element (Cr) constituting the substance on the surface of the substrate. A method for modifying a surface of a system alloy, characterized in that the oxide film forms a layer having excellent oxidation resistance as a stable oxide in a high-temperature atmosphere. Accordingly, the oxide film functions as a protective film and forms a layer having excellent oxidation resistance as a stable oxide under a high-temperature atmosphere, thereby becoming a protective film that is more stable at a higher temperature.

(Preferred Surface Modification Method 7 of Ti-Al Alloy) The preferred surface modification method of the Ti-Al alloy according to the present invention comprises the present invention and the preferred Ti-Al alloy according to the present invention. In the surface modification methods 1 to 6, the content of Al is 15 atomic% to 5 atomic%.
A material containing an oxide having an absolute value of standard free energy of formation smaller than that of alumina is applied to the surface of a Ti-Al-based alloy base material composed of 5 atomic% of a Ti-Al-based alloy. Thereby, since the oxide-containing substance is provided on the surface of the base material, excellent oxidation resistance can be easily provided to the Ti-Al-based alloy.

(Preferred Ti-Al-based alloy base material) The method for modifying the surface of a Ti-Al-based alloy of the present invention and a suitable Ti-A
Suitable Ti-Al Applicable in Surface Modification Method of l-based Alloy
The Ti-based alloy base material contains 15 to 55 atomic% of Al, and contains 0.1 to 10 atomic% in total of at least one of Group Va element or Group VIa element.
It is an Al-based alloy. Group Va element and / or VI
By including a group a element, the ductility or high-temperature strength of the base material can be improved. When the Group Va element and / or the Group VIa element is contained in an amount exceeding 10 atomic%, the lightness of the Ti-Al alloy is impaired.

(Preferred Ti-Al-based Alloy Substrate) The method for modifying the surface of a Ti-Al-based alloy of the present invention and the preferred Ti-A
Suitable Ti-Al Applicable in Surface Modification Method of l-based Alloy
The base alloy base material is a Ti-Al base alloy containing 15 to 55 atomic% of Al and further containing 1 to 10 atomic% of boron. Further, when boron is contained in an amount of 1 at% to 10 at%, the solidified structure becomes finer, and the normal temperature ductility of the base material can be secured. If it is contained more than this, the ductility will decrease.

(Preferred Ti-Al-based Alloy Substrate) The method for modifying the surface of a Ti-Al-based alloy of the present invention and a suitable Ti-A
Suitable Ti-Al Applicable in Surface Modification Method of l-based Alloy
The base alloy base material contains 15 to 55 atomic% of Al, 0.1 atomic% to 10 atomic% in total of one or more of the Group Va element or Group VIa element, and further contains 1 atomic% to 10 atomic% of boron. It is a Ti-Al-based alloy containing at. By containing a Group Va element and / or a Group VIa element, the base material can be improved in ductility or high-temperature strength. Further, when boron is contained in an amount of 1 at% to 10 at%, the solidified structure becomes finer, and the normal temperature ductility of the base material can be secured.

According to the method for modifying the surface of a Ti—Al alloy of the present invention and the preferred method for modifying the surface of a Ti—Al alloy,
It is considered that a Ti-Al-based alloy having excellent oxidation resistance can be easily obtained. Thereby, the oxidation resistance of the Ti—Al-based alloy is improved, and the Ni-based heat-resistant alloy Inconel 7 is used.
It exceeds the oxidation resistance of 13C, and has heat resistance even at a high temperature of 900 ° C. or more. Therefore, the present invention can be applied not only to materials for turbochargers for automobiles, but also to materials for gas turbines for power generation and materials for jet engines. In addition, there is no need for a complicated apparatus such as a closed container, and no heat treatment is involved, so that the processing material powder does not adhere to the base material, and the processing powder does not sinter or solidify. Further, when the fine particles of the present invention are used at the time of unmolding a casting after casting, an oxidation resistance improving treatment can be provided in the manufacturing process.

[Embodiment of the Second Invention]

The Ti-Al having a modified layer on the surface according to the present invention
Ti-Al containing 15 atomic% to 55 atomic% of Al
And a modified layer formed on the surface of the substrate, wherein the modified layer is composed of Si, N
a mechanical alloying layer obtained by applying mechanical energy to the surface of the substrate in a state where a substance containing at least one element of b, Ta, Cr, Mo, and W is present. I do. The mechanism by which the Ti-Al-based alloy of the present invention exerts an excellent effect is not necessarily clear yet, but is considered as follows. That is, in the Ti-Al-based alloy of the present invention, the base material has Al of 15 atomic% or more.
It consists of 55 atomic% Ti-Al alloy. Thus, a Ti-Al-based alloy having normal temperature ductility and excellent high-temperature strength is obtained. Further, the Ti-Al-based alloy of the present invention is characterized in that a mechanical alloying layer mainly composed of a substance containing at least one or more elements of Si, Nb, Ta, Cr, Mo and W is provided on the surface of the substrate. have. Since the mechanical alloying layer has a smaller absolute value of the standard free energy of formation than alumina, it is reduced by the aluminum in the base material to metal. on the other hand,
Aluminum in the base material is oxidized to form an alumina film on the surface. From the above, it is considered that the Ti-Al-based alloy of the present invention was able to be an alloy having excellent oxidation resistance.

(Preferred Ti-Al-based alloy 1) The preferred Ti-Al-based alloy having a modified layer on its surface according to the present invention is a Ti-Al-based alloy containing 15 to 55 atomic% of Al.
An i-Al alloy base material and a silicon (S)
i), niobium (Nb), tantalum (Ta), chromium (C
r), molybdenum (Mo), tungsten (W) in the presence of a substance containing at least one or more elements, a surface portion made of an alloy coating obtained by applying mechanical energy to the Ti-Al Alloy, wherein the surface portion comprises the element (Si, Nb, T
a, Cr, Mo, W). The oxide film has a high oxidation resistance at high temperatures containing a stable oxide in a high-temperature oxidizing atmosphere. It is characterized by forming an excellent layer. Although the mechanism by which the Ti-Al-based alloy having excellent oxidation resistance of the present invention exerts an excellent effect is not yet clearly understood,
It is considered as follows. That is, the Ti—Al of the present invention
As for the base alloy, the base material is made of T of 15 atomic% to 55 atomic% of Al.
It is made of a Ti-Al alloy made of an i-Al alloy. From this, Ti-Al which has room temperature ductility and excellent high temperature strength
It becomes a system alloy. Further, the Ti-Al-based alloy of the present invention has a structure in which silicon (Si), niobium (Nb),
Tantalum (Ta), chromium (Cr), molybdenum (M
o) In the state where a substance containing at least one or more elements of tungsten (W) exists, it has a surface portion having excellent oxidation resistance formed by applying mechanical energy. This surface portion corresponds to the element (S
(i.e., at least one of i, Nb, Ta, Cr, Mo, and W). For this reason, the formation of TiO ₂ which proceeds inside is suppressed, and the oxidation resistance is significantly improved. Further, in the Ti-Al-based alloy of the present invention, the oxide film changes into a stable oxide in a high-temperature oxidizing atmosphere, and a layer having excellent oxidation resistance at a high temperature is formed. That is, Si,
An oxide film mainly containing at least one element of Nb, Ta, Cr, Mo, and W is changed into an oxide film that is stable at a high temperature in a high-temperature oxidizing atmosphere, and has a function of improving oxidation resistance. is there. From the above, it is considered that the Ti-Al-based alloy of the present invention could be made an alloy having excellent oxidation resistance.

(Preferred Ti-Al-based alloy 2) A preferred Ti-Al-based alloy of the present invention is a Ti-Al-based alloy base material composed of a Ti-Al-based alloy containing 15 to 55 atomic% of Al. And niobium (N) on the surface of the Ti-Al alloy base material.
b) or a surface portion made of an oxide film obtained by applying mechanical energy in a state where at least one kind of substance such as b) or tantalum (Ta) is present. A portion having an oxide film mainly composed of an element (at least one of Nb and Ta) constituting the substance, and at the surface portion under a high-temperature oxidizing atmosphere due to the presence of the oxide film. A stable oxide layer mainly composed of Al-O is formed between the substrate and the oxide film to form a layer having excellent oxidation resistance at high temperatures. Thereby, even if the oxide film loses its function as a protective film in a high-temperature oxidizing atmosphere, the stable oxide layer mainly composed of Al-O has an effect as a protective film, Since the adhesion is good, a Ti-Al-based alloy having excellent oxidation resistance is obtained.

(Preferred Ti-Al-based alloy 3) A preferred Ti-Al-based alloy of the present invention is a Ti-Al-based alloy base material composed of a Ti-Al-based alloy containing 15 to 55 atomic% of Al. And chromium (C) on the surface of the Ti-Al alloy base material.
r) a Ti-Al-based alloy comprising a surface portion made of an oxide film obtained by applying mechanical energy in a state where a substance containing the element is present, wherein the surface portion constitutes the substance It has an oxide film mainly composed of element (Cr), and the oxide film forms a layer having excellent oxidation resistance as a stable oxide in a high-temperature oxidizing atmosphere. I do. Thereby, the oxide film acts as a protective film, and furthermore, forms a layer having excellent oxidation resistance as a stable oxide in a high-temperature oxidizing atmosphere. Ti-Al based alloy.

(Ti-Al-based alloy base material) In the present invention, the Ti-Al-based alloy base material described in the first embodiment of the present invention and a suitable Ti-Al-based alloy base material can be applied. it can.

[0050]

Embodiments of the present invention will be described below.

(First Embodiment)

99.9% pure titanium sponge and 9 pure
9.99% aluminum was weighed to the target composition and 10 ^-4
After evacuating to torr, it was cast into a mold by high frequency melting under an Ar atmosphere, and about 1 kg of ingot (Ti-47 atomic%
Al). Next, a plate-like test piece was cut from the ingot to a size of 10 mm × 15 mm × 3 mm. The surface of the obtained test piece was polished with a No. 1500 SiC paper and then degreased with acetone.

Using a test peening apparatus, SiO ₂ , Cr having a particle size of 5 to 100 μm
Particles of ₂ O ₃ , MoO ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , and WO ₃ were repeatedly impacted in the air to perform a surface modification treatment. The injection pressure was 4 kgf / cm ² .

An evaluation test of the obtained plate-shaped test piece was performed by an oxidation resistance evaluation test. In this test, an oxidation test was performed by heating at 900 ° C. for 200 hours in the air using a resistance heating electric furnace. The test piece was heated while being placed in the Al ₂ O ₃ crucible, all the peeled coatings were collected, the weight increase due to oxidation was measured, and the oxidation resistance was evaluated based on the weight increase.
Table 1 shows the results.

[0055]

[Table 1]

(Second Embodiment) In this embodiment, in order to investigate the influence of the Al content, the Al content of the Ti-Al-based alloy was set to 1
5%, 47%, and 55%, 3 types are changed.
High frequency melting was performed in an Ar atmosphere. Ingot weight is 1
kg. Oxidation test piece from this ingot 10mm
It was cut into dimensions of × 15mm × 3mm. Next, SiO ₂ , Cr ₂ O ₃ , MoO ₃ , Nb ₂ O ₅ , Ta ₂ having a particle size of 5 to 200 μm were added to the prepared test pieces in the same manner as in the first embodiment.
After performing surface modification treatment using O ₅ and WO ₃ powder,
An oxidation test was performed in the same manner as in the first embodiment. Table 2 shows the results. As shown in Table 2, when the Al content of the Ti-Al-based alloy was set to 15 at%, 47 at%, and 55 at%, it was found that the alloy was effective.

[0057]

[Table 2]

(Third Embodiment) In this embodiment, V, Cr,
Ti-47 atomic% Al containing Nb, Mo, Ta, W
Was considered. A test piece was prepared by high-frequency melting in Ar in the same manner as in the second embodiment, and a surface modification treatment was performed using WO ₃ powder in the same manner as in the second embodiment. The oxidation test was performed in the same manner as in the second embodiment. The test results are shown in Table 3.

[0059]

[Table 3]

Generally, an alloy containing V and Cr has lower oxidation resistance than an alloy not containing these elements. However, as shown in Table 3, it can be seen that the surface modification treatment of the present invention is also effective for alloys containing these alloys. Furthermore, it can be seen that the effect of the surface treatment of the present invention is also effective for alloys containing Nb, Mo, Ta, and W.

(Fourth Embodiment) The alloy of the third embodiment was further examined for Ti-47 atomic% Al containing B. As in the third embodiment, high-frequency melting in Ar
A test piece was prepared and subjected to a surface modification treatment. The oxidation test was performed in the same manner as in the third embodiment. Test results
It is shown in Table 4.

[0062]

[Table 4]

In general, an alloy containing B has lower oxidation resistance than an alloy containing no B. However, Table 4
As shown in Table 2, the surface modification treatment of the present invention is also effective for alloys containing these alloys.

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Taku Saito 41 Toyota Chuo R & D Co., Ltd., 41, Okucho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture (56) References JP-A-3-75385 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 24/08 B24C 1/10 C21D 1/76 C22C 14/00

Claims (17)

(57) [Claims] 1. The method according to claim 1, wherein the Al—15 atomic% to 55 atomic% Ti—
On the surface of a Ti-Al-based alloy substrate made of an Al-based alloy,
In a state where a substance containing an oxide having a smaller absolute value of standard free energy of formation than alumina is present, mechanical energy is applied to form a mechanical alloying layer on the surface of the base material. A method for modifying the surface of a Ti-Al alloy. 2. The method according to claim 1, wherein the Al—15 atomic% to 55 atomic% of Ti—
On the surface of a Ti-Al-based alloy substrate made of an Al-based alloy,
The microparticles were applied, including the absolute value is less oxides of standard free energy than alumina, the substrate surface portion, the fine particle
A method for modifying the surface of a Ti-Al-based alloy, comprising forming an oxide film mainly composed of an element constituting an oxide in a particle. 3. The method according to claim 1, wherein the Al—15 atomic% to 55 atomic% Ti—
On the surface of a Ti-Al-based alloy substrate made of an Al-based alloy,
Silicon (Si), niobium (Nb), tantalum (T
a), in the presence of a substance containing at least one element of chromium (Cr), molybdenum (Mo), and tungsten (W), mechanical energy is applied to form the substance on the surface of the substrate. The elements (Si, Nb,
Characterized by forming an alloy coating mainly composed of at least one of Ta, Cr, Mo and W).
A method for modifying the surface of an Al-based alloy. 4. The method according to claim 1, wherein said Al—containing 15 to 55 atomic% of Ti—
On the surface of a Ti-Al-based alloy substrate made of an Al-based alloy,
Silicon (Si), niobium (Nb), tantalum (T
a), in the presence of a substance containing an oxide of at least one element of chromium (Cr), molybdenum (Mo), and tungsten (W), applying mechanical energy to the surface of the base material. The element (S
i. Nb, Ta, Cr, Mo, W or at least one of them). 5. A film formed on the surface of the Ti—Al alloy base material, comprising a layer containing an oxide stable in a high-temperature oxidizing atmosphere and having excellent oxidation resistance at a high temperature. The method for modifying the surface of a Ti-Al-based alloy according to any one of claims 1 to 4, wherein 6. The Ti—Al-based alloy base material contains at least one of a Group Va element or a Group VIa element in a total amount of 0.1%.
The method for modifying the surface of a Ti-Al-based alloy according to any one of claims 1 to 4, wherein the method comprises at least 10 atomic%. 7. The Ti—Al-based alloy base material contains at least one of a Group Va element or a Group VIa element in a total amount of 0.1%.
Atomic% to 10 atomic%, and further contains 1 atomic% to 1 atomic% of boron.
The method for modifying the surface of a Ti-Al-based alloy according to any one of claims 1 to 4, wherein 0% by atom is contained. 8. A Ti— alloy containing 15 to 55 atomic% of Al.
On the surface of a Ti-Al-based alloy substrate made of an Al-based alloy,
At least one of niobium (Nb) and tantalum (Ta)
In a state where a substance containing at least one kind of element is present, mechanical energy is applied to the element (at least one kind of Nb or Ta) constituting the substance on the surface of the base material.
A method for modifying the surface of a Ti-Al-based alloy formed by forming an oxide film mainly comprising: a method for forming a layer between the substrate and the oxide film under a high-temperature oxidizing atmosphere due to the presence of the oxide film. A stable oxide layer mainly composed of Al-O is formed to form a layer having excellent oxidation resistance at high temperatures.
A method for modifying the surface of an i-Al alloy. 9. Ti-containing aluminum containing 15 to 55 atomic% of Al.
On the surface of a Ti-Al-based alloy substrate made of an Al-based alloy,
In a state where a substance containing a chromium (Cr) element is present, Ti is formed by applying mechanical energy to form an oxide film mainly composed of the element (Cr) constituting the substance on the surface of the base material. A method for modifying the surface of an Al-based alloy, characterized in that the oxide film forms a layer having excellent oxidation resistance as a stable oxide under a high-temperature atmosphere. Surface modification method. 10. Ti containing 15 to 55 atomic% of Al.
A material containing an oxide having an absolute value of standard free energy of formation smaller than that of alumina is applied to the surface of a Ti-Al alloy base material composed of an Al alloy, and a mechanical alloying layer is formed on the surface of the base material. The method for modifying the surface of a Ti-Al-based alloy according to claim 1, wherein the surface is formed. 11. Ti containing 15 to 55 atomic% of Al.
And a modified layer formed on the surface of the substrate, wherein the modified layer is composed of
a material containing at least one element of i, Nb, Ta, Cr, Mo, and W; and a mechanical alloying layer obtained by applying mechanical energy to the surface of the base material. Ti-Al having a modified layer on its surface
System alloy. 12. Ti containing 15 to 55 atomic% of Al.
-Al-based alloy base material, and silicon (Si), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W) A) a Ti—Al-based alloy comprising: a surface portion made of an alloy coating obtained by applying mechanical energy in a state where a substance containing at least one or more elements of (a) is present; An oxide film mainly composed of the above-mentioned elements (at least one of Si, Nb, Ta, Cr, Mo and W) constituting the substance is formed, and the oxide film is formed under a high-temperature oxidizing atmosphere. A Ti-Al-based alloy having a modified layer on its surface, characterized by forming a layer having excellent oxidation resistance at a high temperature containing a stable oxide. 13. The method according to claim 13, wherein the Ti—Al-based alloy base material is
Group element or one or more group VIa element in a total amount of 0.
請 characterized by containing% 1 atom% to 10 atom
The T having the modified layer on the surface according to claim 11 or claim 12.
i-Al alloy. 14. The Ti-Al having a modified layer on its surface according to claim 13, wherein the Ti-Al-based alloy base material further contains 1 to 10 atomic% of boron.
System alloy. 15. Ti containing 15 to 55 atomic% of Al.
A Ti-Al-based alloy base material comprising an Al-based alloy;
An oxide film obtained by applying mechanical energy in a state where a substance containing at least one element of niobium (Nb) or tantalum (Ta) is present on the surface of the Al-based alloy base material; A Ti-Al-based alloy comprising a surface portion, wherein the surface portion has an oxide coating mainly containing an element (at least one of Nb and Ta) constituting the substance; Forming a stable oxide layer mainly composed of Al-O between the base material and the oxide film under a high-temperature oxidizing atmosphere due to the presence of the oxide film to provide oxidation resistance at a high temperature. A Ti-Al-based alloy having a modified layer on the surface, which is an excellent layer. 16. Ti containing 15 to 55 atomic% of Al.
A Ti-Al-based alloy base material comprising an Al-based alloy;
Ti-A comprising a surface portion of an oxide film obtained by applying mechanical energy in a state where a substance containing chromium (Cr) element is present on the surface portion of the Al-based alloy base material
an l-based alloy, wherein the surface portion has an oxide film mainly composed of an element (Cr) constituting the substance, and the oxide film is a stable oxide under a high-temperature oxidizing atmosphere. A Ti-Al-based alloy having a modified layer on the surface, characterized by forming a layer having excellent oxidation resistance. 17. Ti containing 15 to 55 atomic% of Al.
And a modified layer formed on the surface of the substrate, wherein the modified layer is composed of
a Ti-Al-based material having a modified layer on the surface, comprising a mechanical alloying layer obtained by applying a substance containing at least one element of i, Nb, Ta, Cr, Mo, and W; alloy.