JPH04286636A - High temperature heat-resistant strength member - Google Patents

Abstract

PURPOSE:To improve heat resistance, oxidation resistance and resistance to hydrogen deterioration of a CC composite. CONSTITUTION:A coated layer 2 is formed on the surface of a CC composite 1. Said coated layer 2 is provided with a porous intermediate layer 3 containing SiC or Si3N4 long fiber or short fiber and a surface layer 4 composed of at least one kind of powder and/or short fiber selected out of a group composed of ceramic and heat-resistant metal. Both layers are impregnated with SiC or Si3N4 by means of the gas phase deposition method. The surface side of the coated layer 2 is of dense quality, while the side of a base 1 is porous.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to high-temperature heat-resistant strength members, and in particular, it provides oxidation resistance,
The present invention relates to a high temperature heat resistant strength member with improved hydrogen deterioration resistance.

0002

BACKGROUND OF THE INVENTION Although CC composites have extremely excellent heat resistance, they have no oxidation resistance and are also susceptible to hydrogen deterioration, which limits their field of use. For example, it is unsuitable for applications such as rocket engine nozzles that are exposed to high temperature oxidizing atmospheres. Furthermore, in furnace tubes, heat treatment, and sintering setters, there is a problem of carbon deterioration in an inert atmosphere, especially due to hydrogen. Furthermore, C.C.
Composites are permeable to gases and liquids, which also limits their applications.

[0003] For this reason, various surface treatment methods have been proposed in the past for the purpose of improving the thermal oxidation properties of CC composites. For example, there are the following methods. ■
Silicification of the surface by impregnation with Si vapor or molten Si. That is,
Form SiC on the surface. ■ Apply SiC coating to the surface by CVD method. ■ After the above treatment, impregnate with various types of molten glass (for example, borosilicate glass) to seal the cracks.

0004

[Problems to be Solved by the Invention] However, since the thermal expansion coefficients of CC composites and SiC are significantly different, as shown in (1) and (2) above, in the case of a material with a SiC layer formed on the surface, Cracks occur and CC
Composite cannot be adequately protected. Although cracks can be sealed by performing the treatment (2), they cannot be fundamentally solved.

The present invention solves the above conventional problems and
The object of the present invention is to form a SiC or Si3 N4 layer with less cracking on the surface of a composite, and to provide a high-temperature heat-resistant strength member with improved oxidation resistance and hydrogen deterioration resistance.

[0006]

[Means for Solving the Problems] A high temperature heat resistant strength member according to claim 1 is a high temperature heat resistant strength member comprising a base material made of carbon fiber/carbon composite material and a coating layer formed on the surface of the base material, the coating layer being a high temperature heat resistant strength member. contains at least one kind of powder and/or short fibers selected from the group consisting of ceramics and heat-resistant metals, and S is added to the gaps between the powders and/or short fibers by vapor deposition.
a surface layer impregnated with iC or Si3N4;
or containing long fibers and/or short fibers of Si3N4,
SiC or Si3 is deposited in the gaps between the fibers by vapor phase deposition.
an intermediate layer impregnated with N4 and interposed between the surface layer and the base material, and the coating layer is characterized in that the surface side thereof is dense and the base material side is porous. That is.

[0007] The high temperature heat resistant strength member according to claim 2 is the high temperature heat resistant strength member according to claim 1.
The high temperature heat-resistant strength member is characterized in that the powder and/or short fibers constituting the front layer are made of a boron-containing substance that generates B2 O3 upon oxidation.

The present invention will be explained in detail below with reference to the drawings. FIG. 1 is a schematic sectional view showing an embodiment of the high temperature heat resistant strength member of the present invention.

[0009] In the present invention, the CC composite 1 serving as the base material may be one that is normally provided, for example, the carbon fiber ratio is 35 to 60% by volume and the matrix carbon (or black smoke) ratio is 25 to 40% by volume. %, porosity is 10-30
% CC composite by volume can be used.

The coating layer 2 formed on the surface of the CC composite 1 includes long fibers and/or short fibers of SiC or Si3 N4, and SiC or Si3 N4 is deposited in the gaps between the fibers by vapor deposition. an intermediate layer 3 impregnated with at least one kind of powder and/or short fibers selected from the group consisting of ceramics and heat-resistant metals formed on the intermediate layer 3; It has a front side layer 4 impregnated with SiC or Si3 N4 by vapor phase deposition in the gap.

In the present invention, the following combinations of powders and fibers for the front layer 4 and the intermediate layer 3 are possible. ■
When the surface layer consists only of powder. In this case, as the intermediate layer, only short fibers; only long fibers; or both short fibers and long fibers can be employed.

(2) When the surface layer consists only of short fibers. In this case, the intermediate layer consists of only long fibers; short fibers and long fibers; and only short fibers (however, they differ from the short fibers in the front layer in at least one characteristic of material, diameter, and length); Either can be adopted.

[0013] ■ When the surface layer consists of short fibers and powder. In this case, the intermediate layer includes only short fibers; only long fibers;
Both short fibers and long fibers can be used.

In the present invention, Si constituting the intermediate layer 3
As long fibers of C or Si3N4, the average fiber diameter is 5~
Preferably, the thickness is 30 μm. In addition, the short fibers of the intermediate layer 3 have an average fiber diameter of 0.2 to 30 μm and an average fiber length of 20 μm.
~200 μm is preferred.

If the intermediate layer 3 is too thin, a sufficient crack prevention effect cannot be obtained, and if it is too thick, the cost becomes high, which is not economical. Therefore, the thickness of the intermediate layer 3 is 0.1
It is preferable to set it to about 1.0 mm. Note that this intermediate layer 3 preferably has a fiber content of 2 to 70% by volume. If this fiber content is less than 2% by volume, sufficient crack prevention effect cannot be obtained, and if it exceeds 70% by volume,
SiC or Si3 N4 cannot be vapor-deposited and impregnated to the surface of the base material, resulting in insufficient bonding between the intermediate layer 3 and the base material, and the coating layer is likely to peel off or fall off.

Such an intermediate layer can be formed, for example, by the following method (1) or (2). ■ Fabrics made of short or long fibers (matte, plain weave, twill weave, etc.) are
After bonding to the surface of the composite with resin, it is mineralized. (2) A resin mixed with short fibers or long fibers is applied to the surface of the CC composite, and after being molded to a predetermined thickness using a press, spatula, etc., it is mineralized.

In the present invention, the ceramic and heat-resistant metal constituting the front layer 4 include graphite, carbon, and Si.
C, B4 C, AlN, TiB2, MoSi2, Ta
Examples include one or more powders and/or short fibers selected from the group consisting of ceramics such as N, WC, and W2C, and heat-resistant metals such as W and Mo. In addition, in the case of powder,
The average particle size is preferably about 0.2 to 100 μm. In addition, in the case of short fibers, the average fiber diameter is 0.2 to 30μ
m, the average fiber length is preferably 20 to 200 μm.

In the present invention, it is particularly preferable that the powder and/or short fibers constituting the front layer 4 are made of a boron (B)-containing substance that generates B2 O3 upon oxidation. In other words, if the surface layer is made of such a B-containing substance, even if a crack occurs, the B contained in it will be oxidized by oxygen and become B2 O3 (2B+2/3O2
→B2O3), borosilicate glass produced by this B2O3 reacting with surrounding substances seals the crack. Therefore, the oxidation resistance and hydrogen deterioration resistance of the CC composite are improved more reliably. For this reason, it is preferable that the substance constituting the front layer contains B, but if the content of B is too high, the heat resistance will decrease. Therefore, in the present invention, the B content of the front layer is 1 to 30
Preferably, it is % by weight. In addition, such B-containing substances include boron, boron carbide (B4C
), boron nitrite (BN), and the like.

In the present invention, if the porosity of the layer of powder and/or short fibers in the front layer is too low, sufficient Si
No C or Si3 N4 impregnation is done. Therefore, the porosity of this accumulated layer of powder and/or short fibers is 50 to 99.
% is preferable. In addition, if the thickness of the surface layer is too thin, sufficient crack prevention and corrosion prevention effects cannot be obtained.
If it is too thick, SiC or Si3N4 cannot be deposited and impregnated to the surface of the base material, resulting in insufficient bonding between the intermediate layer 3 and the base material.
The coating layer is likely to peel off and fall off, and the cost is also high. Therefore, the thickness of the stacked layer of powder and/or short fibers in the front layer is preferably about 0.05 to 0.5 mm.

[0020] To form such a coating layer, for example, after applying an adhesive such as a phenol resin to the surface of the CC composite using a spray gun or brush, short fibers and/or long fibers forming the intermediate layer are applied. After applying the adhesive in the same way, powder and/or short fibers forming the front layer are sprinkled, excess powder or short fibers are removed with a brush or spatula, the adhesive is cured, and an inorganic (hereinafter, this method will be referred to as the "adhesion method").

[0021] In the high temperature heat-resistant strength member of the present invention, SiC or Si3 N4 is applied to the layer made of such powder or fiber by a vapor phase deposition method such as CVD or CVI, so that the coating layer surface side is dense and the base material side is dense. Impregnation and vapor deposition to make it porous.

[0022] Here, suitable S of the CVI method or CVD method
An example of the iC deposition conditions is shown in Table 1 below.

[0023]

[Table 1]

By depositing SiC or Si3 N4 from the surface side of the layer made of powder or fibers under these conditions, a large amount of SiC or Si3 N4 is naturally deposited on the surface side.
N4 is evaporated to become dense, and a small amount of Si is deposited on the base material side.
C or Si3 N4 is deposited to make it porous. As a result, a coating layer 2 is obtained in which the SiC or Si3 N4 concentration changes in the thickness direction so that it becomes higher toward the surface.

[0025] Si in the surface portion of the front layer 4 of the coating layer 2
If the C or Si3 N4 impregnation rate is too small, the improvement effect of SiC or Si3 N4, such as oxidation resistance, cannot be sufficiently obtained, so at least the surface portion is made dense so that there are no pores. If a crack should occur in the front layer 4, if the SiC or Si3 N4 impregnation rate of the front layer 4 is too small, the effect of improving oxidation resistance or the like by SiC or Si3 N4 will not be sufficiently achieved. Therefore, in the front layer 4, SiC or Si3N4 is contained in a volume% of 1 to 50%.
%.

In the present invention, the covering layer 2 may further have a vapor-deposited film 6 of SiC or Si3 N4 formed on its surface. By forming such a vapor-deposited film 6, the oxidation resistance and hydrogen deterioration resistance are further improved.

[0027] Such a high temperature heat resistant strength member of the present invention is as follows:
It is extremely useful for the following uses. High-temperature parts■ High-temperature parts such as rocket engine nozzles■ Furnace tubes■ Setters for heat treatment and sintering (stands for placing objects to be processed)■
High-temperature parts such as gas turbines and jet engine combustor inner tubes, transition tubes, stator vanes, etc. ■ Thermocouple protection tubes ■ Corrosion-resistant parts for burner nozzles ■ Containers for hydrogen fluoride, aqua regia, etc. ■ High-temperature hydrogen fluoride, aqua regia, chloride Core tube and vessel wear-resistant parts for hydrogen and other steam■ Powder injection nozzle

[0028]

[Operation] The high-temperature heat-resistant strength member of the present invention is made of a ceramic and a heat-resistant metal on the surface of a CC composite through a porous intermediate layer made of SiC or Si3N4 containing long or short fibers of SiC or Si3N4. At least one powder and/or short fiber selected from the group and Si
It is made of C or Si3 N4, and at least the surface is covered with a dense front layer.

[0029] The intermediate layer on the surface of the CC composite acts as a stress relaxation layer and a crack propagation prevention layer for the base CC composite, and the coating layer with a graded SiC or Si3N4 concentration acts on the base CC composite. CC composite and Si
Cracks in the coating layer due to the difference in thermal expansion coefficient with C or Si3 N4 are prevented. Therefore, the CC composite is reliably held by the coating layer impregnated with SiC or Si3N4, and good oxidation resistance, hydrogen deterioration resistance, airtightness, and watertightness are obtained.

In particular, when the material constituting the front layer contains B, even if a crack occurs in the coating layer, the vitrification of B prevents deterioration of the base material.

[0031]

[Examples] The present invention will be explained in more detail with reference to Examples below.

Example 1, Comparative Example 1 SiC long fibers (average fiber diameter 15 μm ) of 2-
2 twill fabric (thickness 0.4mm, SiC content 30% by volume)
) was bonded with resin and then mineralized to form a long fiber layer. Next, a powder layer having a thickness of 0.3 mm and a porosity of 70% by volume was formed using SiC powder with an average particle size of 2 μm by an adhesion method. Next, the above-mentioned Table 1 was applied to the long fiber layer and the powder layer.
SiC was impregnated under the following CVI method conditions. The impregnation rate of SiC is 30% by volume with respect to the powder layer and fiber layer,
Furthermore, a 50 μm thick SiC vapor deposition film was formed on the surface.

[0033] The obtained high-temperature heat-resistant strength member was heated in the atmosphere for 13 minutes.
When the weight loss rate of the CC composite was examined when heated to 00°C for 100 hours, the weight loss rate was 0.0%.

[0034] Furthermore, when the density of the surface coating layer of this high-temperature heat-resistant strength member was examined by the following method, it was confirmed that the density was extremely good. Test method■ As shown in Figure 2, N2 introduction pipe 21 and pressure gauge 2
2 and an exhaust valve 27, a SUS lid 24 is attached to the SUS flange 23 at one end of the SUS cylinder 20 using bolts and nuts 25 and sealed, and a sample 26 on which a coating layer 26A is formed is inserted into the other end. Put on the lid. Sample 26 is
After adhering to SUS cylinder 20 with epoxy adhesive, at room temperature.
Dry at normal pressure, and further dry at room temperature and 1 Torr for 24 hours. ■ N2 0.1 from the introduction pipe 21 into the SUS cylinder 20
Fill with kgf/cm2 of N2. ■ Check for pressure changes. ■ Evaluate compactness based on the presence or absence of pressure drop. That is,
If there is a pressure drop, there is a slight problem with the density, and if there is no pressure drop, the density can be evaluated as being good. on the other hand,
When a heating test was conducted in the same manner as above on a CC composite in which a 50 μm thick CVD-SiC coating film was directly formed on the CC composite without forming an intermediate layer or a front layer, the CC composite was completely burned.

[0035]

Effects of the Invention As detailed above, the high-temperature heat-resistant strength member of the present invention has the excellent heat resistance of a CC composite, and also has excellent oxidation resistance, hydrogen deterioration resistance, and gas and liquid impermeability. A significantly improved high temperature heat resistant strength member is provided. In particular, the high temperature heat resistant strength member according to claim 2 provides more excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing one embodiment of the high temperature heat resistant strength member of the present invention.

FIG. 2 is a schematic cross-sectional view showing the test apparatus used in Example 1.

[Explanation of symbols]

1 CC composite 2 Coating layer 3 Middle class 4. Front layer

Claims (2)

[Claims] 1. A high-temperature heat-resistant strength member comprising a coating layer formed on the surface of a base material made of carbon fiber/carbon composite material, the coating layer comprising at least one member selected from the group consisting of ceramics and heat-resistant metals. A surface layer containing seed powder and/or short fibers and impregnating the gaps between the powders and/or short fibers with SiC or Si3 N4 by vapor deposition, and a long fiber of SiC or Si3 N4 and/or Contains short fibers, and SiC is deposited in the gaps between the fibers by vapor phase deposition.
or an intermediate layer impregnated with Si3N4 and interposed between the surface layer and the base material, the coating layer comprising:
A high temperature heat resistant strength member characterized in that its surface side is dense and its base side is porous. 2. The high-temperature heat-resistant strength member according to claim 1, wherein the powder and/or short fibers constituting the front layer are made of a boron-containing substance that generates B2O3 upon oxidation.