JP3001781B2 - Composite heat-resistant material mainly composed of MoSi2 - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

This invention relates to MoSi ₂ or MoS
i ₂ relates composite refractory material mainly a substrate comprising 70% or more as a main component, in particular to a composite refractory material to form a protective coating on thereon to prevent oxidation of MoSi ₂ substrate.

[0002]

_2. Description of the Related Art MoSi ₂ is a high-temperature, high-temperature, 1000-1700 ° C., SiO.sub.
₂ Form a film and show excellent oxidation resistance. For this reason, it is attracting attention as an ultra-high temperature heat-resistant structural material. However, its oxidation behavior in some temperature ranges is different, 300-600
At a low temperature of ° C., the SiO ₂ film is not formed and oxidation proceeds rapidly, and what was originally bulk becomes oxide powder in a short time, which is called the plague phenomenon and is well known. .

[0003] For example, D. A. "Materials Science Engi" by Berztis et al.
nearing "A155 (1992) 165-181
Page papers published in the compares the oxidation behavior at 500 ° C. of MoSi ₂ material a MoSi ₂ Materials and MoSi ₂ powder produced was made by HIP at dissolution method. MoSi _{2 produced} by the dissolution method has small cracks and a low density, and has a higher oxidation rate than that produced by the HIP method. HI
MoSi ₂ obtained by the P method has a high density and a lower oxidation rate than that obtained by the dissolution method. From this fact, it has been widely proposed that a higher density is better to slow the low temperature oxidation. However, even with MoSi ₂ by the HIP method, oxidation proceeds even if it is slow, and unprotected MoO ₃ is formed. In addition, the higher the density, the lower the toughness and the lower the thermal shock resistance. Further evaluated the oxidation resistance of the SiO ₂ film formed at high temperature at 500 ° C.
_{(2) The} coating peels off and the antioxidant effect is not maintained.

[0004] Coatings by thermally sprayed Al is applied to the wide variety of materials as oxidation-resistant film, MoSi ₂ and M
Although a certain effect can be expected for a composite material containing 70% by volume or more of oSi ₂ , it is difficult to form a dense sprayed film, and it is not perfect. Pre-oxidation at high temperature
It has also been suggested that an iO ₂ film be applied, but it peels off in a short time, and its effect is not sufficient.

[0005]

SUMMARY OF THE INVENTION As described above, Mo
Since Si ₂ forms a protective SiO ₂ film in a high-temperature, oxidizing atmosphere and exhibits excellent oxidation resistance, it is attracting attention as an ultra-high-temperature heat-resistant structural material.
At a low temperature of -600 ° C., the SiO ₂ film is not formed, and oxidation proceeds rapidly, and what was originally bulk becomes oxide powder in a short time. Therefore, at least 300 to 600 ° C. of the ultra-high-temperature heat-resistant structure made of MoSi ₂
The parts exposed to low temperatures require some antioxidant treatment. Conventionally, for this purpose, techniques such as increasing the density of MoSi ₂ , forming a coating by Al spraying, and pre-oxidizing at a high temperature to form a SiO ₂ coating have been proposed. When the density is increased, the toughness decreases and the thermal shock resistance decreases. In addition, the manufacturing method is limited, which may increase the manufacturing cost. It is difficult to form a dense sprayed film by the Al sprayed film. SiO ₂ film by the preliminary oxidation will be peeled off in a short time, not effective for members such as used for a long time.

An object of the present invention is to establish a technique for imparting a long-term effective low-temperature oxidation preventing ability to MoSi ₂ material irrespective of its structure and manufacturing method.

[0007]

Means for Solving the Problems The present inventor has conducted intensive studies and found that the MoSi ₂ material has an oxidation resistance selected from Cr, Ni, Rh, Ir, Pt and Au having a thickness of 0.1 μm or more. It has been found that by forming a dense protective film of a metal having excellent resistance, a low-temperature antioxidant ability that is effective for a long period of time can be imparted. Based on this finding, the present invention provides Mo
A Si ₂ substrate or a substrate containing 70% or more of MoSi ₂ as a main component; and Cr, Ni, Rh, I formed on at least a part of the substrate and having a thickness of 0.1 μm or more.
Provided is a composite heat-resistant material comprising a metal selected from r, Pt, and Au, and a dense protective film having excellent oxidation resistance. It is also beneficial to form an Al sprayed coating on the protective coating. Preferably, the dense protective coating of a metal having excellent oxidation resistance is a thermal spray coating, a plating coating, or an ion plating coating.

[0008]

Effect: Cr, Ni, having a thickness of 0.1 μm or more
A dense protective film of a metal selected from Rh, Ir, Pt and Au, which has excellent oxidation resistance, cooperates with its thickness,
It acts as a barrier layer to prevent oxygen from penetrating into the substrate, preventing the plague phenomenon. By performing the treatment of the present invention, even at low density MoSi ₂ ,
MoO ₃ is not observed even if exposed for 0 hours or more.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a MoSi ₂ substrate or a substrate containing 70% or more of MoSi ₂ as a main component. In the present invention purposes, since the MoSi ₂ can be regarded as almost equally MoSi and characterization to _second substrate as long as it contains 70% or more, in this case also a substrate comprising 70% or more MoSi ₂ as a main component including . Mo as the main component
The density of Si ₂ does not matter. Even a low-density substrate can be sufficiently prevented from being oxidized by the protective film forming treatment.
The density of MoSi ₂ is appropriately determined according to the purpose of use and the manufacturing method. Therefore, any of a casting material, a material (HIP material) manufactured by a powder metallurgy method, and a single crystal material can be used as the base material. Also, MoSi
_Two coatings can also be used. The form of the substrate is also arbitrary as long as a protective film having a predetermined thickness can be formed thereon.

[0010] As stated earlier, MoSi ₂ is high temperature,
A protective SiO ₂ film is formed in an oxidizing atmosphere and exhibits excellent oxidation resistance.
At a low temperature of 0 ° C., the SiO ₂ film is not formed and the oxidation proceeds rapidly, and the original bulk becomes oxide powder in a short time. The protective coating according to the present invention is formed on the entire surface when the substrate is kept at a low temperature of 300 to 600 ° C. due to a periodic change in the temperature of the use environment or when there is a possibility of accidental occurrence. When only a part of the substrate is kept at such a low temperature, a protective film can be locally formed so as to cover the part. For example, the protective film may be formed only on the surface of the heat-resistant structural material opposite to the heating side, or the protective film may be formed only on the portion protruding outside the insert.

If necessary, before forming the metal film,
In order to increase the adhesion, MoSi ₂ may be subjected to a surface roughening treatment on the entire surface or on the portion where the metal film is formed.

The protective film is formed by a method such as plating, ion plating, thermal spraying, etc., for Cr, Ni, Rh, Ir, P
A single or multiple layer film of a metal selected from t and Au is formed. The coating must be as dense as possible. Therefore, it is necessary to control the process conditions so that the film becomes as dense as possible in plating, ion plating, thermal spraying, and the like. For example, the current density in plating, the voltage in ion plating, the temperature in thermal spraying, and the particle size of the powder used are controlled so as to form a denser film. When the thickness is 0.1 μm or less, there is no effect, and the thickness is desirably 1 to 30 μm. The denseness and thickness of the protective coating work together to form a barrier layer to the penetration of atmospheric oxygen. When it is 1 μm or more, an effect as a protective film is produced. On the other hand, if it exceeds 30 μm, the effect is saturated and the cost increases.

Further, 20 to 300 μm is formed on the formed film.
By forming an Al sprayed film having a thickness of m
1 Oxidation resistance is improved as compared with thermal spraying. It is advantageous in terms of cost to make the thickness of the expensive protective film relatively thin and form a relatively inexpensive Al sprayed film thereon.

[0014]

EXAMPLES holding the several kinds of metal plating, ion plating, a material obtained by coating the MoSi ₂ substrate at a film thickness of various by spraying a film forming method at 450 ° C. (Examples 1-8).
In the ninth embodiment, the Al sprayed film is thickened on the Ni plating film (20
0 μm). As Comparative Examples 1-4, film-free high density MoSi ₂ substrate, pre-oxidized film with a high density MoSi ₂ substrate, with Ni plating having a thickness of 0.05μm dense MoSi ₂ substrate and the thermally sprayed Al dense MoSi ₂ group An example in which the material was similarly maintained at 450 ° C. was also presented. 45
After maintaining at 0 ° C. for 3, 5, 10, 100 and 300 hours, the presence or absence of generation of MoO ₃ was examined from the surface condition by microscopic observation. Table 1 shows the film forming conditions and results.

[0015]

[Table 1]

[0016]

According to the treatment of the present invention, generation of MoO ₃ is not observed even when exposed to low-density MoSi ₂ at 450 ° C. in the air for 300 hours or more. Guarantees the reliability of MoSi ₂ material as an ultra-high temperature heat resistant structural material.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Atsushi Fukushima 187-4 Usuba, Hachikawa-cho, Kitaibaraki-shi, Ibaraki Japan Energy Isohara Plant (58) Field surveyed (Int.Cl. ⁷ , DB name) C23C 4 / 06,14 / 06,30 / 00 C22C 27/04

Claims (4)

(57) [Claims] 1. A MoSi ₂ substrate or a substrate containing 70% or more of MoSi ₂ as a main component, and a C formed on at least a part of the substrate and having a thickness of 0.1 μm or more.
A composite heat-resistant material comprising a metal selected from r, Ni, Rh, Ir, Pt and Au, and a dense protective film having excellent oxidation resistance. 2. The composite heat-resistant material according to claim 1, wherein the dense protective film made of a metal having excellent oxidation resistance is a thermal sprayed film, a plated film, or an ion-plated film. 3. A MoSi ₂ substrate or a substrate containing 70% or more of MoSi ₂ as a main component and a C formed on at least a part of the substrate and having a thickness of 0.1 μm or more.
A composite heat resistant material comprising a dense protective film of a metal selected from r, Ni, Rh, Ir, Pt and Au having excellent oxidation resistance and an Al sprayed film on the protective film. . 4. The composite heat-resistant material according to claim 3, wherein the dense protective film of the metal having excellent oxidation resistance is a thermal sprayed film, a plated film, or an ion-plated film.