JP2003261381A - Ceramic-base composite member and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic-base composite member less liable to lowering of strength due to repetitive thermal shocks and capable of ensuring airtightness in a few steps, thereby capable of shortening the manufacturing time and capable of lowering costs and to provide a method for manufacturing the same. <P>SOLUTION: The method for producing a ceramic-base composite member has a CVI treatment step (A) in which an SiC matrix layer is formed on the surface of a shaped woven fabric of fibers, a PIP treatment step (B) in which a thermosetting polymer is impregnated as a base material into the matrix layer and fired, and a slurry impregnating step (C) in which a slurry containing SiC particles is further impregnated into the matrix layer. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic-based composite member having excellent airtightness and thermal shock resistance, and a method for producing the same.

[0002]

_2. Description of the Related Art In order to improve the performance of a rocket engine using NTO / N ₂ H ₄ , NTO / MMH or the like as a propellant, it is required to increase the heat resistant temperature of a combustor (thrust chamber). Therefore, a coated niobium alloy having a heat resistant temperature of about 1500 ° C. has been conventionally used as a chamber material for many rocket engines. However, this material has drawbacks that it is heavy due to its high density, its high temperature strength is low, and the life of the coating is short.

On the other hand, ceramics have a high heat resistance but have a drawback of being brittle. Therefore, a ceramic matrix composite member (Ceramic Matrix) reinforced with ceramic fibers is used.
Composite: Hereinafter, abbreviated as CMC) has been developed. That is, the ceramic matrix composite member (CMC) is composed of ceramic fibers and a ceramic matrix. Note that CMC is generally expressed as ceramic fiber / ceramic matrix (for example, SiC / SiC when both are made of SiC) depending on its material.

Since CMC is lightweight and has high strength at high temperature,
In addition to the above-described rocket engine combustor (thrust chamber), it is a very promising material for high-temperature fuel pipes, jet engine turbine blades, combustors, afterburner parts, and the like.

[0005]

[Problems to be Solved by the Invention] However, the conventional CMC
Had a problem that it could not maintain airtightness and had low thermal shock resistance. That is, in the conventional CMC, after a predetermined shape is made of ceramic fibers, the so-called C
VI processing (Chemical Vapor Infil)
A matrix is formed in the interstices of the fibers by the (translation: vapor phase impregnation method), but there is a problem that it takes an impractical long time (for example, one year or longer) to completely fill the interstices between the fibers with this CVI. . Further, when the conventional CMC thus formed is tested at a high temperature or the like, when a strong thermal shock (for example, a temperature difference of 900 ° C. or more) is applied, there is a problem that the strength is severely reduced and the reuse is hardly possible. . Therefore, it has been considered that the conventional ceramics-based composite member (CMC) cannot be practically used for parts that require airtightness and thermal shock resistance, such as a combustor (thrust chamber) and a fuel pipe.

In order to solve the above-mentioned problems, the inventors of the present invention previously created and applied for "Ceramics-based composite member and its manufacturing method" (Japanese Patent Laid-Open No. 2000-21).
9576). This manufacturing method is a process (hybrid processing) in which the CVI processing and the PIP processing are combined, and the airtightness and the thermal shock resistance can be remarkably enhanced, which makes it practically applicable to the thrust chamber and the like.

However, the conventional SiC / SiC (CMC) manufactured by the above-described manufacturing method has a problem that its strength becomes half or less when repeatedly subjected to a thermal shock of about 10 times. In addition, in order to ensure airtightness, P
It is necessary to perform the IP treatment about 30 to 40 times, resulting in a problem that the manufacturing period is prolonged and the cost is high.

The present invention was devised to solve such problems. That is, the object of the present invention is to reduce the strength due to repeated thermal shock, to ensure the airtightness in a small number of steps, thereby shortening the manufacturing period and greatly reducing the cost, and the manufacturing thereof. To provide a method.

[0009]

According to the present invention, C forming a SiC matrix layer on the surface of a formed fiber fabric is described.
VI treatment step (A) and PIP in which the gap between the matrix layers is impregnated with a thermosetting polymer as a base material and fired
In the processing step (B), and further in the gap between the matrix layers, S
and a slurry impregnation step (C) of impregnating a slurry containing iC particles.

According to this method of the present invention, after the SiC matrix layer is formed on the surface of the fiber fabric in the CVI treatment step (A), the thermosetting polymer (for example, in the gap between the matrix layers is formed in the PIP treatment step (B). PVS)
Since PVS is impregnated as a base material and fired, PVS can be easily impregnated to the inside, and the filling rate can be efficiently obtained. Further, in the slurry impregnation step (C), since the slurry containing the SiC particles is impregnated, the filling rate can be increased more efficiently.

According to a preferred embodiment of the present invention, in the CVI treatment step (A), there is a surface film removal treatment for removing the SiC film on the surface blocking the gas path between the fibers in the middle of the plurality of CVI treatments. By this method, it is possible to remove the SiC film by the CVI treatment that blocks the gas path on the surface and increase the impregnation efficiency by the CVI treatment.

In the step (B) of PIP treatment, PVS (polyvinyl silane) is used as the thermosetting polymer, and in order to reduce the viscosity, it is about 30-
Heat to 40 ° C to impregnate, then 800-1300 ° C
Heat treatment. By heating to about 30 to 40 ° C. and impregnating, the viscosity of PVS can be reduced, and PVS can be efficiently filled in the gaps in the matrix layer. Also, 8
By heat treatment at 00 to 1300 ° C, low molecular weight components, hydrogen, methane, etc. contained in PVS are evaporated and released, and the polymer is further thermally decomposed into ceramics (SiC
Can be changed).

In the slurry impregnation step (C), SiC particles having an average particle size of 0.1 to 5 μm are mixed and impregnated with a volatile liquid having a low viscosity such as ethanol, and then the volatile liquid is evaporated. And then SiC by CVI treatment
Fix the particles. By mixing it with a low-viscosity volatile liquid such as ethanol, the viscosity of the slurry itself can be lowered and the slurry can be efficiently filled in the gaps in the matrix layer. Further, since this slurry contains only the volatile liquid, the SiC particles are not fixed to the fibers. However, the CVI treatment is performed after evaporating the volatile liquid.
It is possible to fix the SiC particles filled with the SiC film by the VI treatment.

Further, it is preferable to provide a PIP treatment step (D) of impregnating a gap between the matrix layers with a thermoplastic polymer as a base material and baking the same. By this PIP treatment step (D), the thermoplastic PCS (polycarbosilane) is attached to the fibers so as to cling to the fibers, so that the bonding force between the matrix and the fibers can be increased and the initial strength of the CMC itself can be increased.

Further, according to the present invention, a SiC matrix layer formed on the surface of the molded fiber woven fabric and a matrix layer made of PVS (polyvinylsilane) formed in the gap between the matrix layers are provided. A featured ceramic-based composite member is provided. With this configuration, the binding force between the matrix layer made of PVS (polyvinylsilane) and the ceramic fiber is weak, so that a kind of flexible structure is formed, the Young's modulus is reduced, the thermal stress is reduced, and the thermal shock resistance is improved.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing a conventional method for manufacturing a ceramic-based composite member. This figure shows a method for manufacturing a ceramic-based composite member disclosed in Japanese Patent Laid-Open No. 2000-219576.

When manufacturing a chamber requiring air tightness by this method, (1) first, a mandrel (weaving jig)
Is used to weave a woven fabric into a chamber shape by braid weaving or the like. (2) Next, the fabric is subjected to interface coating. This coating serves as a layer that separates the fiber from the matrix and also serves as a sliding layer for developing strength as SiC / SiC. C (carbon) is mainly used for this interface coating. (3) After that, CVI (Chemical Vap)
or Infiltration, vapor phase impregnation)
Attach a SiC matrix. (4) After that, P
IP (Polymer Implementation a)
nd Pyrolysis, liquid phase impregnation) is repeatedly performed to increase the filling rate of the chamber, and (5) finally, a shape is formed by machining. After that, CVI coating is performed on the surface, and a leak test is further performed to complete a CMC such as an airtight chamber. If there is a leak in the leak inspection, the above (3) to (5) are repeated.

FIG. 2 is a flowchart specifically showing the conventional manufacturing method. The SiC fiber 1 is used as a fiber forming the woven fabric 2, and a woven fabric having an axially symmetrical shape such as a thrust chamber is manufactured.

In the IF coating treatment 11, a raw material gas is caused to flow and decomposed in a furnace to coat carbon or boron nitride on the surface of the fiber of the woven fabric. As described above, this coating is a layer (interface) that separates the fiber from the matrix, and also serves as a sliding layer for expressing strength as SiC / SiC. That is, I
The F coating treatment 11 is a step of coating the formed fiber fabric with carbon (preferably graphite carbon) or BN. The coating thickness is
It is preferably about 0.1 to 1.0 μm. As disclosed in JP-A-63-12671, such a coating layer plays a role of separating the matrix and the ceramic fiber and strengthening the toughness of the fiber. In addition, generally, a desizing process is performed before the IF coating process. In this desizing treatment, the sizing agent (polymer) attached to the surface of the SiC fiber is heat-treated in vacuum to be removed.

In the CVI process 12, the CVI process (Che
medical Vapor Information:
A SiC matrix is formed in the interstices between the fibers by the vapor phase impregnation method. This SiC matrix has a function of preventing the coating layer (interface) from reacting with PIP or the like performed in a later step, and a role of protecting the interface and the fiber from oxidation during use. In the conventional method of FIG. 2, after the CVI process 12 achieves a predetermined density, the next PCS-PIP process 13 is performed.

The PIP treatment is a step of impregnating a polymer which is pyrolyzed into SiC and heat-treating it in Ar to attach a SiC matrix. Thermoplastic PCS (polycarbosilane) is mainly used for the polymer. PIP processing using PCS is referred to as PCS-PIP processing in this application. In the PCS-PIP treatments 13 and 16, since PCS is a powder, it is used by dissolving it in a solvent (for example, xylene). The impregnation is performed, for example, in a depressurized environment by expelling bubbles inside the fabric, and then heat-treated at about 900 ° C. to thermally decompose the polymer into SiC. In the process of FIG. 2, in order to secure the airtightness of the chamber, the PCS
-PIP processing is performed 30 times or more in total.

Further, as the polymer, thermosetting PVS is used.
(Polyvinylsilane) may be used. PIP processing using PVS is referred to as PVS-PIP processing in this application. PVS is a highly viscous liquid and cannot be used as it is because the viscosity is too high. Therefore, PVS is used after being heated to about 30 to 40 ° C. The impregnation is performed, for example, in a depressurized environment by expelling bubbles inside the fabric, and then heat-treated at about 900 ° C. to thermally decompose the polymer into SiC. PCS
The thermal decomposition processes of (polycarbosilane) and PVS (polyvinylsilane) are similar, low molecular weight components evaporate at about 400 to 550 ° C, and methane and hydrogen are released at about 550 to 1000 ° C to form a ceramic, Form a SiC matrix.

In the machining 14 shown in FIG. 2, the PCS-PIP is used.
The inner and outer surfaces of the treated fabric 2 are ground. Also, CVI
In coating 17, the entire fabric is coated with a SiC layer by CVI treatment.

CMC having improved airtightness and thermal shock resistance by the above-mentioned conventional method for producing a ceramic-based composite member.
(Thrust chamber etc.) can be manufactured. However, the CMC manufactured by the above-described method has a severe thermal shock equivalent to the thermal shock received by the rocket nozzle (for example, 900 ° C in the atmosphere, it is dropped in ice water for 1 hour, and ΔT =
As a result of the test, it became clear that the strength is halved when subjected to a temperature difference of about 400 ° C.) about 10 times. In addition, as described above, in order to ensure airtightness,
It is necessary to perform the PIP process about 30 to 40 times, and as a result, there is a problem that the manufacturing period becomes long and the cost is too high.

FIG. 3 is a flow chart showing the first embodiment of the method for producing a ceramics-based composite member of the present invention. As shown in this figure, the ceramic-based composite member of the present invention and its manufacturing method include a CVI treatment step (A), a PIP treatment step (B), and a slurry impregnation step (C).

In this example, the CVI treatment step (A) consists of two CVI treatments 21a and 21b and a surface film removal treatment 22 between them, and the SVI treatment is performed on the surface of the formed fiber fabric.
An iC matrix layer is formed. CVI processing 21a, 2
In 1b, the matrix of SiC is formed in the interstices between the fibers by the CVI treatment described above. In addition, in this CVI processing step (A), a plurality (two times in this example) of CVI processing 2 is performed.
A surface film removal treatment 22 is provided between 1a and 21b to remove the SiC film on the surface blocking the gas path between the fibers.

In this example, the PIP treatment step (B) consists of two PVS-PIP treatments 23, in which the gaps in the matrix layer are impregnated with a thermosetting polymer as a base material and fired. In this PIP treatment step (B), PVS (polyvinylsilane) is used as the thermosetting polymer, and this is impregnated by heating at about 30 to 40 ° C. to reduce the viscosity, and then heat treatment at about 900 ° C. . The heat treatment temperature may be 800 ° C. or higher and lower than 1300 ° C.

In this example, the slurry impregnation step (C) consists of two CVI treatments 21c and 21d and a slurry impregnation treatment 24 between them, and the S in the gap between the matrix layers.
Impregnate a slurry containing iC particles. In this slurry impregnation step (C), SiC having an average particle size of 1 to 3 μm
The particles are mixed with ethanol for impregnation, then the ethanol is evaporated and the SiC particles are fixed by CVI treatment. In FIG. 3, the other processes 11, 14, and 17 are
It is similar to FIG. The average particle size of SiC particles is 0.1 to 5
It may be μm, and ethanol may be another volatile liquid having a low viscosity.

According to the method of the present invention shown in FIG. 3, CV
After the SiC matrix layer is formed on the surface of the textile fabric in the treatment step (A), the gap between the matrix layers is impregnated with the thermosetting polymer (for example, PVS) as the base material in the PIP treatment step (B) and then fired. PVS can be easily impregnated into the inside, and the filling rate can be efficiently obtained. In the slurry impregnation step (C), S
Since the slurry containing the iC particles is impregnated, the filling rate can be increased more efficiently.

Further, since the surface film removing process 22 is provided between the plurality of CVI processes 21a and 21b, the SiC film by the CVI process blocking the gas path on the surface is removed to remove C
Impregnation efficiency can be increased by VI treatment.

Further, in the PIP treatment step (B), the P is treated by heating at about 30 to 40 ° C. to impregnate it.
Decrease the viscosity of VS, PVS in the gap of the matrix layer
Can be efficiently filled. Also, 800 to 13
By heat treatment at 00 ° C., low molecular weight components, hydrogen, methane, etc. contained in PVS can be vaporized and released, and the polymer can be thermally decomposed into a ceramic (SiC).

In the slurry impregnation step (C), the viscosity of the slurry itself is lowered by mixing SiC particles having an average particle diameter of 0.1 to 5 μm with ethanol having a low viscosity, and the slurry is filled in the gaps of the matrix layer. It can be filled efficiently. Also, since this slurry is only ethanol, SiC particles are not fixed to the fibers,
Next, CVI treatment is performed after evaporating the ethanol to obtain Si filled with the SiC film by the CVI treatment.
C particles can be fixed.

FIG. 4 is a photomicrograph of the ceramic-based composite member according to the conventional example (A) and the present invention (B). Figure 4
As shown in (A), C according to the conventional method shown in FIG.
In MC, the matrix of PCS (S decomposed by PCS
It can be seen that the iC matrix) is attached so as to cling to the fibers, and the voids (black portions) are rounded. This indicates that the matrix of PCS binds the fibers tightly. In contrast, FIG. 4 (B)
As shown in FIG. 3, CMC according to the method of the present invention shown in FIG.
Then, PVS matrix (PVS decomposed SiC
The matrix) has an angular shape and is almost independent of the fibers. Also, the PVS matrix is bound to the fibers by the surrounding CVI matrix (white layer).

That is, the CMC of the present invention comprises a SiC matrix layer (CV) formed on the surface of a molded fiber fabric.
I matrix), and a matrix layer (PVS matrix) made of PVS (polyvinylsilane) formed in the gap between the matrix layers, and further comprising PV
The matrix of S is bound to the fibers by the matrix of CVI around it.

FIG. 5 is a graph showing the relationship between the number of thermal shocks and the tensile strength according to the conventional example and the present invention. In this figure, the horizontal axis represents the number of thermal shocks and the vertical axis represents the tensile strength. Further, in the figure, ● represents the conventional CMC (PCS matrix), and ◆ represents the CMC (PVS matrix) of the present invention. This thermal shock test was carried out 10 times, which is equivalent to the thermal shock received by the rocket nozzle and was dropped into ice water from 900 ° C. for 1 hour in the atmosphere. From FIG. 5, the initial tensile strength of the CMC of the present invention is about 200 MPa, which is about 80% that of the conventional CMC. This is because the PVS matrix does not bond directly to the fibers, as shown in FIG.
It is considered that they are linked by the matrix. However, the tensile strength after 10 thermal shock tests was C of the present invention.
In MC, approximately 200 MPa, which is almost equal to the initial tensile strength
On the other hand, in the conventional CMC, about 180 MPa
Has fallen to. Although the binding force between the matrix layer made of PVS (polyvinyl silane) and the ceramic fiber is weak, this is a kind of flexible structure, the Young's modulus is lowered, the thermal stress is reduced, and the thermal shock resistance is improved. Conceivable.

Table 1 shows a comparison between the matrix structures of the conventional example and the CMC of the present invention.

[0037]

[Table 1]

In the conventional CMC, the volume ratio of CVI to PIP was 1: 1, but in the present invention, the ratio of CVI is increased up to 4: 1. The porosity is 14 vol in the conventional example.
%, But in the present invention, it is as low as about 6.4 vol%. Therefore, the airtightness is improved accordingly. P
The number of IPs is reduced to 4 in the example of FIG. 3 including the slurry impregnation, compared to about 30 in the conventional case. That is, according to the present invention, it is understood that the number of steps for achieving the airtightness is significantly reduced and a high filling rate is obtained, and the impregnation efficiency of the matrix is high.

FIG. 6 is a flow chart showing a second embodiment of the method for manufacturing a ceramics-based composite member of the present invention. In addition to the first embodiment of FIG. 3, the second embodiment further includes a PIP processing step (D) of impregnating the gaps of the matrix layer with a thermoplastic polymer as a base material and firing the same. This PIP processing step (D), in this example,
It consists of two PCS-PIP treatments 25 and two slurry impregnation treatments 26. Other processes are the same as those in FIG.
By adding the PIP treatment step (D), the thermoplastic PCS (polycarbosilane) is attached to the fibers so as to cling to the fibers to enhance the bonding force between the matrix and the fibers and further enhance the initial strength of the CMC itself. You can

The present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[0041]

As described above, in the present invention, the thermosetting polymer is used for the PIP instead of the thermoplastic polymer as the main component. Further, since SiC made of a thermosetting polymer lacks adhesion to fibers, CVI is performed for fixing the SiC. This CVI also helps improve the oxidation resistance of the PIP matrix. In addition, this may be followed by further filling with a thermoplastic polymer.

That is, by using a thermosetting polymer, SiC having less cracks inside and excellent in oxidation resistance as compared with a thermoplastic one can be obtained. Further, since it is thermosetting, individual SiC is independent and a large gap is likely to be formed. Therefore, the fixed CVI can efficiently enter, and the surroundings can be completely wrapped with the CVI. Further, even if the coating on the surface of CMC is cracked by thermal shock, the PIP matrix is not immediately oxidized, so that the strength hardly decreases even after 10 thermal shocks.

Therefore, the ceramic-based composite member of the present invention and the method for manufacturing the same have little strength reduction due to repeated thermal shocks, and can secure airtightness in a small number of steps, thereby shortening the manufacturing period and greatly reducing the cost. It has an excellent effect such as being possible.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a conventional method for manufacturing a ceramic-based composite member.

FIG. 2 is a flow chart showing a conventional method for manufacturing a ceramic-based composite member.

FIG. 3 is a flow chart showing a first embodiment of a method for manufacturing a ceramics-based composite member of the present invention.

FIG. 4 is a micrograph of a ceramic-based composite member according to a conventional example and the present invention.

FIG. 5 is a diagram showing the relationship between the number of thermal shocks and the tensile strength according to the conventional example and the present invention.

FIG. 6 is a flowchart showing a second embodiment of the method for manufacturing a ceramics-based composite member of the present invention.

[Explanation of symbols]

1 SiC fiber, 2 woven fabric, 3 CMC (ceramic matrix composite member), 11 IF coating treatment, 12 C
VI treatment, 13 PCS-PIP treatment, 14 machining, 15 PVS-PIP treatment, 16 PCS-PIP
Treatment, 17 CVI-Coating Treatment, 21a-21
d CVI treatment, 22 surface film removal treatment, 23 PVS
-PIP treatment, 24, 26 slurry impregnation treatment, 25
PCS-PIP processing

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02C 7/00 D06M 15/21 A C04B 35/80 G F02K 9/62 L D06M 11/00 Z F term ( Reference) 3G002 EA08 EA09 4G001 BA22 BA33 BA60 BA77 BA86 BB22 BB86 BC22 BC33 BC47 BC52 BC54 BD07 BD15 BE11 BE39 4L031 AA29 AB32 BA19 DA11 4L033 AA09 AB05 AC15 CA59 DA03

Claims (6)

[Claims] 1. A CVI treatment step (A) for forming a SiC matrix layer on the surface of a molded fiber woven fabric, and a PIP treatment step (B) for impregnating a gap between the matrix layers with a thermosetting polymer as a base material and firing the same. And a slurry impregnation step (C) of impregnating a slurry containing SiC particles in the gaps between the matrix layers. 2. In the CVI treatment step (A), there is a surface film removal treatment for removing the SiC film on the surface blocking the gas path between the fibers in the middle of the plurality of CVI treatments.
The method for producing a ceramics-based composite member according to claim 1, wherein. 3. In the PIP processing step (B), PVS (polyvinylsilane) is used as the thermosetting polymer, and about 30 to 4 is used to reduce the viscosity.
2. The method for producing a ceramics-based composite member according to claim 1, wherein the impregnation is carried out by heating to 0 [deg.] C., followed by heat treatment at 800-1300 [deg.] C. 4. In the slurry impregnation step (C), SiC particles having an average particle diameter of 0.1 to 5 μm are mixed and impregnated with a volatile liquid having a low viscosity, and then the volatile liquid is evaporated. The method for producing a ceramics-based composite member according to claim 1, wherein the SiC particles are fixed by CVI treatment. 5. The production of a ceramic-based composite member according to claim 1, further comprising a PIP treatment step (D) of impregnating a gap between the matrix layers with a thermoplastic polymer as a base material and firing the same. Method. 6. S formed on the surface of a molded fiber woven fabric
A ceramics-based composite member comprising an iC matrix layer and a matrix layer made of PVS (polyvinylsilane) formed in a gap between the matrix layers.