JPH04332637A - High temperature heat resistant strength member - Google Patents

Abstract

PURPOSE:To provide high temperature heat resistant strength member excellent in heat resistance, oxidation resistance and resistance to deterioration by hydrogen. CONSTITUTION:The high temperature heat resistant strength member concerned is produced by forming covering layer 2 on the surface of C/SiC composite material 1. The covering layer 2 is impregnated with SiC or Si3N4 by vapor phase deposition in layer, which is made of at least one kind of powder selected from the group consisting of ceramic and heat resistant metal and/or short fibers. The front surface side of the covering layer 2 is dense while its base material 1 side is porous. Thus, the porous covering layer acts as stress relaxation layer, resulting in producing the covering layer, in which a few cracks develop. The resultant member is excellent in oxidation resistance and resistance to deterioration by hydrogen.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to high-temperature heat-resistant strength members, and more particularly to high-temperature heat-resistant strength members having outstanding heat resistance, oxidation resistance, and hydrogen deterioration resistance.

0002

[Prior Art] Although carbon fiber/carbon composite materials (hereinafter referred to as "CC composites") have extremely excellent heat resistance, they have no oxidation resistance and are also susceptible to hydrogen deterioration. The disadvantage is that the field of use is limited. 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, CC composites are permeable to gases and liquids, which also limits their uses.

[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-mentioned conventional problems and uses SiC or Si3 N4 with less cracking on the surface of the base material.
The object of the present invention is to provide a high-temperature heat-resistant strength member having improved oxidation resistance and hydrogen deterioration resistance by forming a layer thereon.

[0006]

[Means for Solving the Problems] The high temperature heat resistant strength member according to claim 1 is a carbon fiber/SiC composite material (hereinafter referred to as "C/SiC
"composite materials". ) A high temperature heat resistant strength member comprising a coating layer formed on the surface of a base material, the coating layer comprising:
Containing at least one kind of powder and/or short fibers selected from the group consisting of ceramics and heat-resistant metals, the powder and/or short fibers are selected from the group consisting of ceramics and heat-resistant metals.
Or SiC or S is applied to the gaps between the fibers by vapor deposition method.
The coating layer is impregnated with i3N4 and is characterized in that its surface side is dense and its base side is porous.

[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 porous 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.

In the present invention, the C/SiC composite material 1 serving as the base material has a carbon fiber content of 35 to 60% by volume, for example.
, the proportion of SiC as a matrix is 25 to 40% by volume
, those with a porosity of 10 to 30% by volume are preferred.

[0010] Such a C/SiC composite material can be manufactured, for example, as follows. (2) SiC is vapor-deposited into the pores of a porous body (preform) obtained by molding carbon fibers using a small amount of resin and then inorganicizing them using a CVD method or the like. ■ Sintering method. (2) Repeat the process of molding using a raw material resin for SiC fibers (polycarbosilane, etc.) and then mineralizing it. Depending on the case, SiC is further vapor-deposited into the holes by CVD or the like.

[0011] The coating layer 2 formed on the surface of the C/SiC composite material 1 contains at least one kind of powder and/or short fibers selected from the group consisting of ceramics and heat-resistant metals. Alternatively, the base layer 3 is formed by impregnating the gaps between the fibers with SiC or Si3N4 by vapor phase deposition.

In the present invention, the ceramic and heat-resistant metal constituting the powder and/or fiber of the base layer 3 include graphite, carbon, SiC, B4C, AlN, and TiB2.
, MoSi2, TaN, WC, W2C, and other ceramics; and W, Mo, and other heat-resistant metals. In addition, in the case of powder, the average particle size is 0.2 to 100μ
It is preferable to set it to about m. In addition, in the case of short fibers, the average fiber diameter is 0.2 to 30 μm, and the average fiber length is 20 to 30 μm.
Preferably, it is 200 μm.

In the present invention, it is particularly preferable that the powder and/or short fibers constituting the base layer 3 are made of a substance containing the boron (B) element. In other words, if the porous layer is made of a substance containing B, even if a crack occurs, the B contained in it will be oxidized by oxygen and become B2 O3.
(2B+2/3O2 → B2 O3), and this material becomes glassy, or borosilicate glass produced by oxidation of this material and SiC or Si3 N4 seals the crack. Therefore, the oxidation resistance and hydrogen deterioration resistance of the C/SiC composite material are more reliably improved. For this reason, it is preferable that the substance constituting the base layer 3 contains B, but if the content of B is too high, the heat resistance will decrease. Therefore, in the present invention, the B content (value before SiC or Si3 N4 impregnation) of the porous layer is preferably 1 to 30% by weight. In addition, as substances containing B, boron, boron carbide (B4C)
, boron nitride (BN), and the like.

[0014] In the present invention, the powder and/or
Alternatively, if the gap between the short fibers is too narrow, sufficient impregnation of SiC or Si3 N4 will not be achieved. Therefore, the porosity of the layer of powder and/or short fibers before impregnation (SiC or Si
3N4 value before impregnation) is preferably 40 to 99%. Furthermore, if the thickness of the coating layer 2 is too thin, a sufficient crack prevention effect cannot be obtained, and if it is too thick, it will reach the surface of the base material using SiC or S.
i3N4 cannot be vapor-deposited and impregnated, and the bond between the coating layer and the base material becomes insufficient, and the coating layer is likely to fall off or peel. Therefore, the thickness of the base layer 3 is preferably about 0.05 to 0.5 mm.

Such powder and/or short fibers can be prepared, for example, by applying an adhesive such as phenol resin to the surface of the C/SiC composite material using a spray gun or brush, and then applying the powder and/or short fibers to the surface of the C/SiC composite material.
Alternatively, it can be easily fixed to the C/SiC composite material by sprinkling short fibers, removing excess powder and/or short fibers with a brush or spatula, then curing the adhesive, and further mineralizing it ( (Hereinafter, this method will be referred to as the "adhesion method.")

In the high temperature heat resistant strength member of the present invention, this C/
SiC or Si3 N4 is applied to the gaps between the powder and/or short fibers fixed to the surface of the SiC composite material 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 porous. As in, impregnation and vapor deposition. Here, an example of suitable SiC deposition conditions for the CVI method or CVD method is shown in Table 1 below.

[0017]

[Table 1]

Under these conditions, SiC or Si3N
4, naturally a larger amount of SiC or Si3 N4 is deposited on the surface side, making it dense, and a smaller amount of SiC or Si3 N4 is deposited on the base material side, making it porous. A coating layer 2 is obtained in which the ratio increases in the thickness direction toward the surface.

If the SiC or Si3 N4 impregnation rate of the coating layer 2 is too low, the effect of improving oxidation resistance etc. by SiC or Si3 N4 will not be sufficiently obtained, and if it is too high, no further effect will be obtained and it is economical. Not the point. Therefore, SiC
Or Si3 N4 is 1 to 50% by volume in the coating layer
It is preferable to impregnate it so that it becomes.

In the present invention, the covering layer 2 may further have a vapor-deposited film 5 of SiC or Si3 N4 formed on its surface. By forming such a vapor-deposited film 5, the oxidation resistance and hydrogen deterioration resistance are further improved.

[0021] Such a high temperature heat resistant strength member of the present invention is as follows:
It is extremely useful for the following high-temperature component applications. ■ High-temperature parts such as rocket engine nozzles ■ Furnace tubes ■ Setters for heat treatment and sintering (stands for placing objects to be treated)

[
0022

[Function] The high-temperature heat-resistant strength member of the present invention has a layer made of at least one kind of powder and/or short fibers selected from the group consisting of ceramics and heat-resistant metals formed on the surface of the C/SiC composite material. In addition, the pores in this layer are impregnated with SiC or Si3 N4 produced by vapor phase deposition so that the surface side is dense and the base material side is porous.

[0023] Such a coating layer in which the SiC or Si3N4 content is graded and the porosity gradually changes in the thickness direction acts as a stress relaxation layer for the C/SiC composite material of the base material. Therefore, C/SiC composite material and SiC or S
The occurrence of cracks in the coating layer due to the difference in thermal expansion coefficient between i3 and N4 is reduced. Therefore, the C/SiC composite material is provided with good oxidation resistance, hydrogen deterioration resistance, gas and liquid impermeability due to the coating layer impregnated with SiC or Si3N4. Note that the C/SiC composite material has better compatibility with the surface coating layer than the CC composite material, and is less likely to cause cracks, so it is effective in the present invention.

In particular, when the substance constituting the coating layer contains B, even if a crack occurs in the coating layer, the deterioration of the base material is prevented due to the plugging effect of the vitrification of B.

[0025]

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

Example 1, Comparative Examples 1 and 2 A C/SiC composite material having a carbon fiber content of 40 volume %, a matrix SiC content of 40 volume %, and a porosity of 20 volume % was bonded using an adhesive method. A 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. Next, this porous layer was impregnated with SiC under the conditions of the CVI method shown in Table 1 above. The impregnation rate of SiC is 30% by volume with respect to the resulting coating layer, and a layer with a thickness of 5% is added to the surface.
A 0 μm SiC vapor deposited film was formed.

[0027] The obtained high temperature heat resistant strength member was heated in the atmosphere for 13 minutes.
When the weight loss rate was examined when heated to 00°C for 100 hours, the weight loss rate was 18%. On the other hand, Comparative Example 1
and to the same C/SiC composite material as Comparative Example 2, and to a CC composite (carbon content 40 vol%, matrix carbon content 35 vol%, porosity 25 vol%), respectively, with a thickness of 50 μm. When a similar heating test was conducted on the CVD-SiC coating film formed thereon, the carbon fibers and the CC composite in the C/SiC composite material were almost completely combusted.

Example 2 SiC powder with an average particle size of 2 μm and SiC powder with an average particle size of 3 μm were added to the same C/SiC composite material as used in Example 1 by an adhesive method.
A porous layer having a thickness of 0.3 mm, a B content of 20% by weight, and a porosity of 70% by volume was formed using B4C powder of 500 mL. Next, this porous layer was impregnated with SiC under the conditions of the CVI method shown in Table 1 above. The impregnation rate of SiC is 30% by volume with respect to the resulting coating layer, and a 50μ thick layer is added to the surface.
A SiC vapor deposited film of m was formed.

[0029] The obtained high-temperature heat-resistant strength member was heated in the atmosphere for 13 minutes.
When the weight loss rate was examined when heated to 00°C for 100 hours, the weight loss rate was 6%.

[0030]

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

[Brief explanation of drawings]

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

[Explanation of symbols]

1 C/SiC composite material 2 Coating layer 3 Base 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 a carbon fiber/SiC composite material, the coating layer comprising at least one member selected from the group consisting of ceramics and heat-resistant metals. The coating layer contains seed powder and/or short fibers, and the gaps between the powder and/or fibers are impregnated with SiC or Si3 N4 by vapor phase deposition, and the surface side of the coating layer is dense and has a base layer. A high-temperature heat-resistant strength member characterized by having a porous material side. 2. The high-temperature heat-resistant strength member according to claim 1, wherein the powder and/or short fibers constituting the porous layer are made of a boron-containing substance that generates B2O3 upon oxidation.