JPH08217575A - Carbonaceous member and method for coating surface - Google Patents

Abstract

PURPOSE: To ensure superior corrosion resistance by coating the desired surface of a carbonaceous member with a surface coating film based on HfB2 and/or ZrB2 by applying a mixture of HfO2 and/or ZrO2 , with B4 C and firing it. CONSTITUTION: A powdery mixture of about 95-50 pts.wt. HfO2 powder and/or ZrO2 powder with about 5-50 pts.wt. B4 C powder is dispersed in an org. solvent such as ethanol. The resultant dispersion liq. is applied to a carbonaceous member of a graphite or carbon fiber reinforced carbon material, etc., by means of a spray gun, etc., and it is dried and fired at about 2,150-2,700 deg.C in an inert gaseous atmosphere to coat the desired surface of the member with a surface coating film based on HfB2 and/or ZrB2 . A carbonaceous member having superior durability such as a rocket nozzle is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a carbonaceous material forming a nozzle of a rocket, a combustion chamber and other members, and a part of a rocket nozzle and a combustion chamber where heat and corrosion resistance are required. The present invention relates to a surface coating method suitable for further improving the heat resistance and corrosion resistance of a carbonaceous member used as a material for parts.

[0002]

2. Description of the Related Art Conventionally, graphite (carbon fiber / carbon fiber) having excellent heat resistance has been used as a material for, for example, a rocket combustion chamber or a nozzle.
Including the case of carbon composite material. ) Is used,
In order to improve its corrosion resistance (erosion resistance),
In many cases, various surface coatings are applied.

As an example of this surface coating, for example, zirconium oxide (ZrO ₂ , melting point: about 2700 ° C.), aluminum oxide (Al ₂ O ₃ ,
There has been a method of coating oxide ceramics such as melting point: about 2050 ° C.) by plasma spraying, laser heating, sputtering or the like.

As another example, for example, zirconium carbide (ZrC, melting point: about 3) is formed on the inner surface of a graphite nozzle.
540 ℃, titanium carbide (TiC, melting point: about 3180
There was a method of coating carbide ceramics such as (° C.) by CVD (chemical vapor deposition) or the like.

[0005]

However, in such a conventional surface coating, since the surface coating is formed by depositing and adhering on the graphite as the base material, the base material There is a problem that the bonding strength between the surface coating and the surface coating is considerably low, and therefore there is a possibility that peeling may occur when an impact is applied.

[0006] Further, graphite which is a material of the nozzle (coefficient of thermal expansion is about 4.6 x 10 ^-6 / ° C) and zirconium oxide which is a surface film (coefficient of thermal expansion is about 10.5 x 10 ^-6 / ° C).
℃), aluminum oxide (coefficient of thermal expansion is about 8.1 × 10
^-6 / ° C), zirconium carbide (coefficient of thermal expansion is about 6.9)
× 10 ^-6 / ° C), titanium carbide (coefficient of thermal expansion is about 7.4)
X 10 ⁻⁶ / ° C.), the difference in the coefficient of thermal expansion is large, and therefore, for example, when heated rapidly, the surface coating may crack due to a sharp difference in the amount of thermal expansion, or the bonding strength as described above. In addition to this, there is a problem that peeling may occur.

Furthermore, zirconium oxide (melting point: about 2
700 ° C) and aluminum oxide (melting point: about 2070 ° C)
Since has a relatively low melting point, there is a problem that it is melted by the combustion gas of a rocket (temperature of about 3000 ° C.).

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and an object thereof is to provide a carbonaceous member having excellent heat resistance and corrosion resistance (erosion resistance), and In addition, the surface coating coated to improve corrosion resistance (erosion resistance) has a high bonding strength to the base material, and the surface is resistant to cracking or peeling even when subjected to mechanical shock or thermal shock. The purpose is to provide a coating method.

[0009]

The carbonaceous member according to the present invention has, as described in claim 1, hafnium diboride (HfB ₂ ) and zirconium diboride (ZrB ₂ ) on the required surface. Of these, at least one of them is the main component, and others are hafnium carbide (HfC) and zirconium carbide (Z
It is characterized in that a surface coating containing rC) or the like is coated.

In an embodiment of the carbonaceous member according to the present invention, as described in claim 2, the carbonaceous member is made of graphite or as described in claim 3. The carbonaceous member may be composed of carbon fiber / carbon, and in the same embodiment, the carbonaceous member is a rocket nozzle, and the inner surface of the nozzle is , Hafnium diboride (HfB ₂ ) and zirconium diboride (ZrB ₂ )
Of these, at least one of them may be the main constituent, and a surface coating containing hafnium carbide (HfC), zirconium carbide (ZrC), etc. may be covered.

Further, in the surface coating method according to the present invention, as described in claim 5, carbonization with hafnium oxide (HfO ₂ ) and / or zirconium oxide (ZrO ₂ ) is carried out on the required surface of the carbonaceous member. React with boron (B ₄ C), or in some cases, hafnium (Hf) and / or zirconium (Zr) and boron carbide (B
₄ C) and are reacted, the required surface of the carbonaceous member diboride hafnium (HfB ₂₎ and / or zirconium diboride (ZrB ₂₎ as a main component, other hafnium carbide (HfC), zirconium carbide ( It is characterized in that a surface film containing ZrC) or the like is coated.

In an embodiment of the surface coating method according to the present invention, as described in claim 6, hafnium oxide (HfO ₂ ) and / or zirconium oxide (ZrO ₂ ) are formed on the required surface of the carbonaceous member. ₂ ) and a mixture of boron carbide (B ₄ C), or optionally a mixture of hafnium (Hf) and / or zirconium (Zr) and boron carbide (B ₄ C), After firing, the required surface of the carbonaceous member is mainly composed of hafnium diboride (HfB ₂ ) and / or zirconium diboride (ZrB ₂ ) and other hafnium carbide (HfB).
fC), zirconium carbide (ZrC), and the like.

Also, in the embodiment of the surface coating method according to the present invention, as described in claim 7, the carbonaceous member is a rocket nozzle, and hafnium diboride is formed on the inner surface of the nozzle. A surface film mainly composed of (HfB ₂ ) and / or zirconium diboride (ZrB ₂ ) and also containing hafnium carbide (HfC), zirconium carbide (ZrC) and the like can be coated.

[0014]

The carbonaceous member according to the present invention is characterized by claim 1.
As described in, the required surface is mainly composed of at least one of hafnium diboride (HfB ₂ ) and zirconium diboride (ZrB ₂ ), and other hafnium carbide (HfC) and zirconium carbide (ZrC). Since it is assumed that the surface film containing such as is coated, it has excellent heat resistance of the base material and surface film as well as excellent corrosion resistance (erosion resistance), and the surface film has defects such as cracks and peeling. It becomes a high quality carbonaceous member that is hard to generate.

That is, hafnium diboride (HfB ₂ )
Has a very high melting point of about 3380 ° C., is excellent in heat resistance, does not melt even if it comes into contact with a high temperature combustion gas (about 3000 ° C.), and has excellent resistance to oxidation. The coefficient of thermal expansion of this hafnium diboride is about 5.
5 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of graphite (about 4.
6 × 10 ⁻⁶ / ° C.), the difference in the amount of thermal expansion or the amount of thermal contraction does not become so large even when rapidly heated or rapidly cooled. The film is difficult to crack or peel off.

Zirconium diboride (ZrB ₂ ) also has a remarkably high melting point of about 3245 ° C. and has excellent heat resistance so that it does not melt even if it comes into contact with high temperature combustion gas, and it has resistance to oxidation. The corrosion coefficient of hafnium diboride is about 6.0 × 1.
0 ⁻⁶ / ° C., and the thermal expansion coefficient of graphite (about 4.6 × 1
0 ^{-6 /} ° C.) and because there is no large difference, even when rapid heating or rapid cooling, because the thermal expansion amount or thermal contraction amount difference is not so large, the surface film mainly composed of the zirconium diboride It is difficult to crack or peel.

In an embodiment of the carbonaceous member according to the present invention, as described in claim 2, the carbonaceous member is made of graphite, or carbon as described in claim 3. The quality member is made of carbon fiber / carbon, which further improves the corrosion resistance (erosion resistance) of the member made of graphite or carbon fiber / carbon (parts, products and their materials, etc.). Will be things.

Further, as described in claim 4, the carbonaceous member is a rocket nozzle or a combustion chamber, and hafnium diboride (HfB ₂ ) and By using at least one of zirconium diboride (ZrB ₂ ) as a main component and a surface coating containing hafnium carbide (HfC), zirconium carbide (ZrC), etc., as a main component, rocket nozzles and combustion Room corrosion resistance (erosion resistance)
Is further improved.

Further, in the surface coating method according to the present invention, as described in claim 5, carbonization with hafnium oxide (HfO ₂ ) and / or zirconium oxide (ZrO ₂ ) is performed on the required surface of the carbonaceous member. Boron (B ₄ C), or in some cases, hafnium (Hf) and / or zirconium (Zr) is reacted with boron carbide (B ₄ C) to form a diboride on the required surface of the carbonaceous member. Hafnium (HfB ₂ ) and / or zirconium diboride (Zr
B ₂ ), other hafnium carbide (HfC),
Since the surface film containing zirconium carbide (ZrC) is coated, the component mainly composed of hafnium diboride and / or zirconium diboride is simply deposited by coating on the required surface of the carbonaceous member. Rather than forming a surface film, hafnium diboride and /
Alternatively, the surface coating mainly composed of zirconium diboride is metallurgically bonded to the carbonaceous material which is the base material, and hafnium diboride and / or zirconium diboride, and further hafnium carbide are formed inside the carbonaceous member. Since the zirconium carbide and / or the like penetrates deeply, the bonding strength between the base material and the surface coating is extremely high,
It is difficult for the surface coating to be easily peeled off from the surface of the substrate even by mechanical impact or thermal impact.

That is, in the surface coating method according to the present invention, instead of directly coating hafnium diboride, hafnium oxide (HfO ₂ ) is reacted with boron carbide (B ₄ C) at a high temperature and HfO ₂ is reacted. + 3C → HfC + 2CO ↑ HfO ₂ + B ₄ C + HfC → 2HfB ₂ + 2CO ↑ to produce a reaction of hafnium diboride (HfB ₂ , melting point: about 3380 ° C.) on the surface of the carbonaceous member.
And hafnium carbide (HfC, melting point: about 3890 ° C.) are produced, and the film mainly composed of hafnium diboride and the base material are metallurgically bonded to each other. Since hafnium and the like penetrate deeply, the bonding strength of the surface coating becomes extremely high.

Further, in the surface coating method according to the present invention,
Rather than simply coating zirconium diboride directly, zirconium oxide (ZrO ₂ ) is reacted with boron carbide (B ₄ C) at elevated temperature to produce ZrO ₂ + 3C → ZrC + 2CO ↑ ZrO ₂ + B ₄ C + ZrC → 2ZrB ₂ + 2CO ↑. By causing the above reaction, zirconium diboride (ZrB ₂ , melting point: about 3245 is formed on the surface of the carbonaceous member.
° C) and zirconium carbide (ZrC, melting point: about 3540)
(° C), the coating mainly composed of zirconium diboride and the base material are metallurgically bonded, and since zirconium diboride and the like penetrate deeply inside the base material, The bonding strength of the surface coating becomes extremely high.

In an embodiment of the surface coating method according to the present invention, as described in claim 6, hafnium oxide (HfO ₂ ) and / or zirconium oxide (ZrO ₂ ) is formed on the required surface of the carbonaceous member. And boron carbide (B
₄ C), or in some cases, a mixture of hafnium (Hf) and / or zirconium (Zr) and boron carbide (B ₄ C) is applied, followed by firing to give a carbonaceous member. On the required surface of, mainly hafnium diboride (HfB ₂ ) and / or zirconium diboride (ZrB ₂ ) and other hafnium carbide (HfB).
C), zirconium carbide (ZrC), etc. are coated, so that the surface of the carbonaceous member is mainly composed of hafnium diboride and / or zirconium diboride by a remarkably simple method. A film will be generated, and since this surface film has penetrated deeply from the base material surface and is metallurgically bonded,
The joint strength is remarkably high, and peeling hardly occurs. As described in claim 7, heat resistance, oxidation resistance, and corrosion resistance at a rocket nozzle, a combustion chamber, or a leading edge of a flying object are remarkably high. In addition to being improved, cracking and peeling of the surface film are less likely to occur.

[0023]

EXAMPLE In this example, according to the process shown in FIG.
The case where the surface coating is applied to the inner surface of the graphite nozzle as the carbonaceous member is shown.

First, 95 to 50 parts by weight of hafnium dioxide (HfO ₂ ) powder and 5 to 5 parts of boron carbide (B ₄ C) powder.
50 parts by weight were weighed and mixed together to obtain a mixed powder having different compounding ratios of hafnium dioxide powder and boron carbide powder, and then the mixed powder was dispersed in ethanol as an organic solvent to prepare HfO. _{A 2} + B ₄ C solution was prepared, and the HfO ₂ + B ₄ C solution 1 was placed in a spray gun 2 as shown in FIG.

On the other hand, after processing the graphite nozzle 3, HfO ₂ + B _{4 is applied} to the inner surface of the graphite nozzle 3 by the spray gun 2.
By spraying C solution 1 as spray stream 1a,
HfO ₂ + B ₄ C powder 4 was spray-coated on the inner surface of the graphite nozzle 3.

Next, after drying, as shown in FIG. 3, the graphite nozzle 3 is housed in a firing furnace 6 equipped with a heater 5, and 2150 to 27 in an Ar gas atmosphere of 1 atm.
Baking was performed at 00 ° C. for about 1 hour.

With respect to the graphite nozzle which was surface-coated at a baking temperature of 2600 ° C. for 1 hour, the compounding ratio of boron carbide was 23 parts by weight with respect to 77 parts by weight of the hafnium oxide powder, and the X-ray diffraction of the outermost surface of the surface coating After analysis,
As shown in FIG. 4, the outermost surface has hafnium diboride (melting point:
It was about 3380 ° C).

Further, when X-ray diffraction was performed on the intermediate portion of the surface coating, as shown in FIG. 5, hafnium diboride (melting point: about 3380 ° C.) and hafnium carbide (melting point: about 3) were found on the intermediate portion.
89 ° C.) was mixed.

Further, when the surface coating was observed with an optical microscope, the results shown in FIG. 6 were obtained. As shown in FIG. 6, HfC was sequentially deposited on the surface of the graphite nozzle (C) from the lower layer.
A surface coating having a thickness of about 20 to 40 μm and formed of + C layer, HfB ₂ + HfC layer, and HfB ₂ layer was formed.

Furthermore, hafnium oxide (HfO ₂ )
When the influence of the compounding ratio of the powder and the boron carbide (B ₄ C) powder and the firing temperature on the bonding condition of the surface coating was examined,
7 shows the results shown in FIG. 7, in which boron carbide (B
The compounding amount of ₄ C) is 20 to 35% by weight and the firing temperature is 2
It was possible to form a surface film having a sufficiently good bonding strength in the vicinity of 400 to 2700 ° C.

In the above-mentioned embodiments, the case where a film mainly containing hafnium diboride is formed on the surface of the graphite nozzle is shown. However, the case where a film mainly containing zirconium diboride is formed is almost the same. It can be carried out.

Next, a graphite carbon member (without surface coating)
The one having the conventional SiC coating formed on the surface of the graphite carbon member, the one having the same conventionally known tetraethyl orthosilicate impregnation treatment (TEOS treatment) applied to the SiC coating, and the surface HfB ₂ according to the present invention. Heat resistance was evaluated by performing burner heating and laser heating in the atmosphere for the coating formed by coating the main body and the coating coated by forming the coating mainly containing ZrB _{2 on the} surface according to the present invention. The results are shown in Table 1.

[0033]

[Table 1]

As shown in Table 1, HfB ₂ coating and Z
When the rB ₂ coating was performed, it was possible to remarkably improve the oxidation resistance of the graphite material.

Next, the sample material having zirconium oxide, aluminum oxide, zirconium carbide, titanium carbide, and hafnium diboride, zirconium diboride coatings formed on the surface of the graphite material was rapidly heated to give a surface coating. When the situation was examined, the results are shown in Table 2.

[0036]

[Table 2]

As shown in Table 2, according to the present invention, in the case where a film mainly composed of hafnium diboride or zirconium diboride is formed on the surface of a graphite substrate, the substrate and the film are metallurgically bonded. Therefore, cracking or peeling of the coating did not occur even by rapid heating, and the bonding strength of the coating was extremely high.

Furthermore, CVD-S is formed on the surface of the graphite base material.
S of the conventional X-ray diffraction result shown in FIG. 8 with the iC coating formed
When a combustion test was performed on the composite material having an iC film, after 10 seconds of the combustion test, the composition of the surface changed so that it was difficult to identify the composition, as shown in FIG. While the corrosion resistance (erosion resistance) was not very good, Hf was not formed on the surface of the graphite base material.
In the composite material of the present invention example in which the B ₂ coating was formed, the X-ray diffraction results shown in FIG. 10 were also obtained after the combustion test, and the composition before the combustion test shown in FIG. 4 and the combustion shown in FIG. The composition after the test was composed of only HfB ₂ and it was clear that the surface was not changed even by the combustion test, and it was recognized that the corrosion resistance (erosion resistance) was remarkably excellent. It was

[0039]

The carbonaceous member according to the present invention is characterized in that
As described above, since the required surface is covered with a surface film mainly containing at least one of hafnium diboride (HfB ₂ ) and zirconium diboride (ZrB ₂ ), Provide a high-quality carbonaceous member in which not only the heat resistance of the base material and surface coating is also excellent, but also the corrosion resistance (erosion resistance) is also outstanding, and the surface coating is resistant to defects such as cracking and peeling. It is possible to bring about a remarkable effect.

In the embodiment of the carbonaceous member according to the present invention, the carbonaceous member may be made of graphite as described in claim 2 or as described in claim 3. , The carbonaceous material is made of carbon fiber / carbon, which allows the use of graphite or carbon fiber / carbon.
Members made of carbon (parts, products and their materials, etc.)
The corrosion resistance (erosion resistance) can be further improved.

Further, as described in claim 4, the carbonaceous member is a rocket nozzle, and the inner surface of the nozzle is
Corrosion resistance (erosion resistance) of the rocket nozzle can be improved by using a surface film mainly containing at least one of hafnium diboride (HfB ₂ ) and zirconium diboride (ZrB ₂ ). It is possible to make it even more improved, and there is an excellent effect that it is possible to eliminate the risk that the nozzle is melted by the high temperature combustion gas.

Further, according to the surface coating method of the present invention, as described in claim 5, carbonization with hafnium oxide (HfO ₂ ) and / or zirconium oxide (ZrO ₂ ) is carried out on the required surface of the carbonaceous member. By reacting with boron (B ₄ C), hafnium diboride (HfB ₂ ) and / or zirconium diboride (Zr
Since the surface coating mainly composed of B ₂ ) is coated, the surface coating is formed by simply depositing hafnium diboride and / or zirconium diboride on the required surface of the carbonaceous member. Rather than being present, the surface coating mainly composed of hafnium diboride and / or zirconium diboride may be metallurgically bonded to the carbonaceous material that is the base material. Since hafnium diboride and / or zirconium diboride can be deeply penetrated into the substrate, the bonding strength between the base material and the surface coating can be made extremely high, and mechanical impact can be increased. It is possible to make the surface film extremely excellent in that the surface film is not easily peeled off from the surface of the substrate even by thermal shock.

In an embodiment of the surface coating method according to the present invention, as described in claim 6, hafnium oxide (HfO ₂ ) and / or zirconium oxide (ZrO ₂ ) is formed on the required surface of the carbonaceous member. ₂ ) and boron carbide (B ₄ C) are applied and then fired to deposit hafnium diboride (HfB ₂ ) and / or zirconium diboride (ZrB ₂ ) on the required surface of the carbonaceous member. Since the main surface film is coated, it is possible to form a surface film mainly containing hafnium diboride and / or zirconium diboride on the surface of the carbonaceous member by a remarkably simple method. Moreover, since this surface film is capable of being deeply penetrated from the surface of the base material and metallurgically bonded, the bonding strength is extremely high, It is possible to prevent peeling, and as described in claim 7, the heat resistance, oxidation resistance, and corrosion resistance of a rocket nozzle, a combustion chamber, or a leading edge of a flying object are remarkably improved. In addition to the above, it is possible to prevent cracking and peeling of the surface coating from occurring, which is a remarkable effect.

[Brief description of drawings]

FIG. 1 is an explanatory view showing steps of a surface coating method according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a procedure for applying HfO ₂ + B ₄ C powder on the inner surface of a graphite nozzle.

FIG. 3 is an explanatory diagram showing a procedure for firing a graphite nozzle having an inner surface coated with HfO ₂ + B ₄ C powder.

FIG. 4 is an explanatory diagram showing an X-ray diffraction result on the outermost surface of a surface coating mainly composed of HfB ₂ .

FIG. 5 is an explanatory diagram showing an X-ray diffraction result in an intermediate portion of a surface film mainly composed of HfB ₂ .

FIG. 6 is a copy of a photograph showing an optical microscope observation result of the surface of a graphite nozzle on which a surface film mainly composed of HfB ₂ is formed.

FIG. 7 is an explanatory diagram illustrating the results of examining the influence of the addition amount of B ₄ C and the generation temperature on the bonding state of the surface coating mainly composed of HfB ₂ .

FIG. 8 is an explanatory diagram showing an X-ray diffraction result before a combustion test of a surface coating of a composite material formed with a conventional CVD-SiC coating.

FIG. 9 is an explanatory diagram showing an X-ray diffraction result after a combustion test of a surface coating of a composite material having a conventional CVD-SiC coating formed thereon.

FIG. 10 is an explanatory diagram showing an X-ray diffraction result after a combustion test of a surface coating of a composite material having a HfB ₂ coating according to an example of the present invention.

Claims (7)

[Claims] 1. Hafnium diboride (HfB) on the required surface
₂ ) and zirconium diboride (ZrB ₂ ), a carbonaceous member characterized by being coated with a surface film mainly containing at least one of them. 2. The carbonaceous member according to claim 1, wherein the carbonaceous member is made of graphite. 3. The carbonaceous member according to claim 1, wherein the carbonaceous member is composed of carbon fiber / carbon. 4. The carbonaceous member is a rocket nozzle,
The carbon according to any one of claims 1 to 3, wherein an inner surface of the nozzle is coated with a surface film mainly containing at least one of hafnium diboride (HfB ₂ ) and zirconium diboride (ZrB ₂ ). Quality material. 5. Hafnium oxide (HfO ₂ ) and / or zirconium oxide (Zr) on the required surface of the carbonaceous member.
O ₂ ) and boron carbide (B ₄ C) are reacted to form a surface coating mainly containing hafnium diboride (HfB ₂ ) and / or zirconium diboride (ZrB ₂ ) on the required surface of the carbonaceous member. A method for coating a surface, comprising: 6. Hafnium oxide (HfO ₂ ) and / or zirconium oxide (Zr) is formed on a required surface of the carbonaceous member.
O ₂ ) and boron carbide (B ₄ C) are applied and then fired to form hafnium diboride (HfB ₂ ) and / or zirconium diboride (ZrB ₂ ) on the required surface of the carbonaceous member. 5. A surface film mainly composed of
The surface coating method according to. 7. The carbonaceous member is a rocket nozzle,
The surface coating method according to claim 5 or 6, wherein the inner surface of the nozzle is coated with a surface coating mainly containing hafnium diboride (HfB ₂ ) and / or zirconium diboride (ZrB ₂ ).