JP2002293672A - Corrosion-resistant ceramic and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide corrosion-resistant ceramic which has excellent adherence even at 800-1,600 deg.C and a long-lived surface-coated layer, consists of a nonoxide ceramic sintered compact and is manufactured easily at a low cost. SOLUTION: A layer of the multiple oxide of the element of group 3a in the periodic table and a transition metal element, for example, the layer of the multiple oxide shown by the formula: RE2 (Six M1-x )2 O7 (wherein RE is the element of group 3a in the periodic table; M is the transition metal element; 0<=x<1) is formed on the surface of the nonoxide ceramic sintered compact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-temperature member,
In particular, the present invention relates to a corrosion-resistant ceramic suitably used as a component for a heat engine such as a component for a vehicle such as a piston pin or an engine valve or a component for a gas turbine engine, and a method for producing the same.

[0002]

2. Description of the Related Art Non-oxide ceramic sintered bodies such as silicon nitride based sintered bodies, silicon carbide based sintered bodies, and sialon based sintered bodies are known as engineering ceramics and are used for various purposes. . For example, a silicon nitride-based sintered body and a sialon-based sintered body have excellent heat resistance, thermal shock resistance, wear resistance, and oxidation resistance.
Applications as heat engine components such as heat pumps are being promoted. Silicon carbide sintered bodies are widely used for mechanical parts and the like because of their high strength and excellent heat resistance. As for such ceramics, further improvement in strength, oxidation resistance, and corrosion resistance at high temperatures is required when the usage conditions are further increased. In response to such demands, improvement has been promoted by producing an oxide protective film having a high adhesion in addition to various improvements such as examination of sintering aids and grain boundary phases and improvement of firing conditions. .

For example, in Japanese Patent Application Laid-Open No. 9-183676, the surface of a sintered body mainly composed of silicon nitride or sialon is coated with a glass layer mainly composed of SiO ₂ , so that the mechanical strength and acid resistance at high temperatures are increased. The improvement of the chemical nature is aimed at. Japanese Patent Application Laid-Open No. Hei 5-238855 discloses that a silicon nitride-based sintered body is coated with Al ₂ O having good oxidation resistance.
_3, ZrO ₂ and the like were coated with CVD and thermal spraying technique a protective film is formed, oxidation resistance, erosion, it is possible to improve the corrosion resistance has been proposed. Further, Japanese Patent Application Laid-Open No. 2000-007472 discloses that silicide ceramics such as silicon nitride and silicon carbide are made of RE ₂ SiO ₅ or R ₂ SiO _5.
It has been proposed to improve oxidation resistance and corrosion resistance by laminating E ₂ Si ₂ O ₇ (RE = rare earth element).

[0004]

However, in the method of forming a glass layer on the surface as disclosed in Japanese Patent Application Laid-Open No. 9-183676, there is an effect of improving the characteristics under static conditions. When exposed to a high-temperature, high-pressure, high-speed gas, the surface coating layer is rapidly consumed by evaporation, resulting in a short life. In addition, the method described in Japanese Patent Application Laid-Open No. 5-238855 has a problem that it is easily peeled off due to a difference in thermal expansion coefficient from a substrate, and the surface coating layer is rapidly consumed due to high-temperature corrosion. Further, JP-A-2000-00
According to the method described in Japanese Patent No. 7472, when used in a higher temperature, higher pressure, and highly corrosive environment such as an industrial large gas turbine engine, the protection film is greatly deteriorated due to corrosion. However, there is a problem that the length is shortened.

Accordingly, the present invention has excellent adhesive force even in a high temperature range around 800 to 1600 ° C.,
An object of the present invention is to provide a corrosion-resistant ceramic made of a non-oxide ceramic sintered body having a long-life surface coating layer simply and at low cost.

[0006]

According to the present invention, a composite oxide layer containing a Group 3a element of the periodic table and a transition metal element is provided on the surface of a non-oxide ceramic sintered body. A characteristic corrosion resistant ceramic is provided. According to the present invention, further, on the surface of the non-oxide ceramics sintered body,
After applying a composite oxide of a transition metal element and a Group 3a element of the periodic table, heat-treating at a temperature of 1300 to 1900 ° C.
A method for producing a corrosion-resistant ceramic, comprising forming a composite oxide layer, is provided.

An important feature of the corrosion-resistant ceramic of the present invention is that a composite oxide layer of a Group 3a element of the periodic table and a transition metal element is provided on the surface of the non-oxide ceramic sintered body. Due to the formation of the composite oxide layer, exfoliation and consumption are suppressed even when exposed to high temperature, high pressure and high speed gas,
As a result, remarkable improvements in oxidation resistance, erosion resistance and corrosion are realized.

In the present invention, it is most preferable that the non-oxide ceramic sintered body as the base material contains at least one of silicon nitride, silicon carbide and sialon as a main component. That is, by providing a layer of the composite oxide on the surface of such a non-oxide ceramic sintered body, it is possible to maintain the original high-temperature characteristics of the non-oxide ceramic and obtain a corrosion-resistant ceramic which is resistant to corrosion. it can.

In the present invention, from the viewpoint of reducing the difference in thermal expansion with the non-oxide ceramic sintered body as the base material and effectively preventing the composite oxide layer as the protective layer from peeling off, The thickness of the layer is preferably from 30 to 300 μm. The transition metal element constituting the composite oxide is preferably at least one of Zr, Hf and Ti. Thereby, even when exposed to a high-temperature, high-pressure, and high-speed gas, peeling and consumption can be suppressed, and oxidation resistance, erosion resistance, and corrosion can be significantly improved. Further, in view of the fact that the composite oxide is thermally stable, the following formula (1): RE ₂ M ₂ O ₇ (1) wherein RE is a Group 3a element of the periodic table, M is preferably a transition metal element. Further, in the present invention, a composite oxide having a structure in which a part of the transition metal element M of the composite oxide of the above formula (1) is substituted with a silicon atom can also be used. Such silicon-substituted compound oxide represented by the following formula _(2): RE in _{2 (Si x M 1-x} ) 2 O 7 ... (2) Equation, RE is a periodic table Group 3a element, M Is a transition metal element, and x is a number satisfying 0 <x <1. That is, such a silicon-substituted composite oxide is chemically more stable, and by providing such a composite oxide layer, further improvement in corrosion resistance can be realized. Further, in the above formula (2), it is preferable that the number x indicating the replacement ratio of silicon atoms satisfies 0.5 ≦ x <0.9. Thereby, the difference in thermal expansion between the non-oxide ceramics sintered body and the composite oxide layer can be reduced, so that peeling of the composite oxide layer formed on the surface can be effectively prevented.

The corrosion-resistant ceramic of the present invention can be produced by applying the composite oxide to the surface of a non-oxide ceramic sintered body and heat-treating the composite oxide at a temperature of 1000 to 1900 ° C. The surface roughness Ra (JIS B0601) of the sintered body on which the material is applied is 0.7 μm.
It is preferably in the range of m to 3 μm. This allows
Increases the bonding strength between the non-oxide ceramic sintered body and the composite oxide layer coated on its surface, effectively exfoliating and eroding the composite oxide layer even when exposed to high-temperature, high-pressure, high-speed gas. Can be suppressed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION (Non-Oxide Ceramic Sintered Body) The non-oxide ceramic sintered body forming a composite oxide protective layer, which will be described in detail later, includes metal carbides, nitrides, borides and the like. Various substances such as silicides are known, and in the present invention, any of these can be used.
The present invention is most effective when a silicon nitride based sintered body, a silicon carbide based sintered body, and a sialon based sintered body are used.

For example, a silicon nitride-based sintered body has high density, high strength, high toughness and high mechanical reliability, but has poor corrosion resistance in a high-temperature combustion gas atmosphere. By coating with a protective layer, the corrosion resistance can be improved and the life as a high-temperature structural component can be prolonged. In the present invention, among such silicon nitride-based sintered bodies, oxides of a Group 3a element of the periodic table (or carbonates, nitrates, etc., which can form oxides by firing) and Si as sintering aids are particularly preferred.
Those obtained by firing using O ₂ are preferred.
That is, in such a silicon nitride-based sintered body, the same crystal phase as that of the composite oxide protective layer formed on the surface is precipitated at the grain boundary, and as a result, oxidation resistance and corrosion resistance are further improved. This is because it is possible to improve. In addition, the content of the component derived from such a sintering aid in terms of oxide is preferably 20 mol% or less in total. If the content of these components is too large, the excellent characteristics of the silicon nitride sintered body may be impaired.

Further, the silicon carbide sintered body is excellent in high temperature strength, but is inferior in corrosion resistance in a high temperature combustion gas atmosphere.
Therefore, by coating the surface with a composite oxide protective layer described later, oxidation resistance and corrosion resistance can be improved, and the life as a high-temperature structural component can be extended.

Further, the sialon-based sintered body has been put to practical use as a wear-resistant tool, a turbine blade or an engine component due to its excellent mechanical strength, toughness and thermal shock resistance. However, sialon also has poor corrosion resistance and degrades high-temperature characteristics in a high-temperature combustion gas atmosphere.However, by providing a composite oxide protective layer described later on the surface, corrosion resistance and oxidation resistance in a high-temperature combustion gas atmosphere are reduced. Can improve and prolong life. In the above-mentioned silicon carbide-based sintered body and sialon-based sintered body, as long as the excellent properties are not impaired, for example, as long as the silicon carbide or sialon as the main crystal is contained in an amount of 80% by weight or more. Of course, it may contain a component derived from a sintering aid or the like or another crystal.

(Composite Oxide Layer) In the present invention, a protective layer of a composite oxide of a transition metal element and a Group 3a element of the periodic table is provided on the surface of the non-oxide ceramic sintered body described above. While maintaining the properties of the non-oxide ceramic sintered body, it can suppress peeling and wear even when exposed to high temperature, high pressure and high speed gas, and can significantly improve corrosion resistance such as oxidation resistance, erosion resistance, corrosion resistance, etc. .

That is, SiO ₂ , ZrO ₂ , Al ₂ O ₃ ,
It is conventionally known that a protective film such as mullite, cordierite, or YAG is provided on the surface of a non-oxide ceramic sintered body, but the crystal phase of a composite oxide of a transition metal element and a Group 3a element in the periodic table is known. Has a characteristic that it is very stable even in a high-temperature oxidizing atmosphere as compared with these protective films, and thus exhibits excellent oxidation resistance and corrosion resistance. In addition, since it has a high melting point, it has excellent heat resistance and has a long life at high temperatures.

In the present invention, the Group 3a element of the periodic table constituting the composite oxide is a so-called rare earth element,
c, Y, La, Ce, Pr, Nd, Pm, Sm, Eu,
Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Among these, Yb, Er, and Lu are particularly high in the bonding strength of the crystal formed, and are thermally stable and high melting point compounds. Y is preferable from the viewpoint of low cost and easy availability. Further, the transition metal element refers to a group 4a to 7a group element, a group 8 element,
Group 1b and 2b elements are meant. Specifically, 4a
Ti, Zr, Hf, V, Nb, T
a, Cr, Mo, W, Mn, etc.
e, Co, Ni, etc.
And Zn and the like. In the present invention, among these, at least one of Zr, Hf and Ti is particularly preferable from the viewpoint of being thermally stable and a high melting point compound.

In the present invention, the above-mentioned transition metal element
Examples of complex oxides of silicon and elements of group 3a of the periodic table
The following formula (1): RE₂M₂O₇ (1) wherein RE is an element of Group 3a of the periodic table, and M is
A transfer metal element, for example, Gd₂Z
r₂O₇, La₂Hf₂O₇, LuTi₂O ₇Examples
can do. That is, it is expressed by such an equation (1).
Complex oxide crystals having a composition that is thermally stable
It has the feature of.

In the present invention, a complex oxide in which part of the transition element M in the complex oxide represented by the above formula (1) is substituted by a silicon atom, for example, the following formula (2): RE ₂ ( _{Si x M 1-x) 2} O 7 ... (2) wherein, RE is a periodic table group 3a element, M is a transition metal element, x is satisfies 0 <x <1 A silicon-substituted composite oxide represented by the following formula can also be used. Such a silicon-substituted composite oxide is chemically more stable, and by providing a protective layer of such a composite oxide, further improvement in corrosion resistance can be realized. This is advantageous in that the difference in the coefficient of thermal expansion between the body and the protective layer can be reduced. In particular, x in equation (2)
But 0.5 ≦ x <0.9, and further 0.6 ≦ x ≦ 0.8
Providing a protective layer of silicon-substituted composite oxide is
It is suitable for remarkably improving oxidation resistance, erosion resistance and corrosion resistance. That is, a part of the transition element M is changed to S
By substituting with i (silicon), diffusion between non-oxide ceramics such as silicon nitride, silicon carbide and sialon or the grain boundary phase of the particles and the protective layer of the composite oxide proceeds with each other. As a result, the chemical bonding force between the non-oxide ceramic sintered body and the surface protective layer is strengthened, and even when exposed to high-temperature, high-pressure, high-speed gas, peeling and wear of the surface protective layer are effectively suppressed, and acid resistance is reduced. , Erosion resistance and corrosion can be remarkably improved. In addition, since the difference in thermal expansion between the non-oxide ceramic sintered body and the composite oxide can be reduced, peeling of the surface protective layer can be more effectively prevented.

In the present invention, the thickness of the protective layer of the composite oxide is 30 to 300 μm, preferably 50 to 300 μm.
The thickness is preferably 250 μm, most preferably 80 to 180 μm. This is to reduce the difference in thermal expansion between the composite oxide and the non-oxide ceramic sintered body constituting the protective layer, prevent the protective layer from peeling off, and prolong the life of the corrosion-resistant ceramic.

The corrosion-resistant ceramics configured as described above have high corrosion resistance and oxidation resistance, and are therefore used in automobile parts such as pistons and cylinders, and gas turbine engine parts such as turbine rotors and nozzles. In particular, it is suitably used for parts and the like which are brought into a combustion gas atmosphere.

(Production of Corrosion-Resistant Ceramics) The corrosion-resistant ceramics of the present invention are produced by preparing a non-oxide ceramic sintered body and forming the above-mentioned composite oxide protective layer on the surface of the sintered body. .

The non-oxide ceramic sintered body on which the protective layer is formed is manufactured by a method known per se. here,
The method will be described taking a silicon nitride based sintered body as an example.
As a starting material, a powder of silicon oxide of a Group 3a element of the periodic table (RE ₂ O ₃ ) and a powder of SiO _{2 if} desired
A mixed powder obtained by mixing powders at a predetermined ratio is used.
_A composite oxide powder composed of ₂ O ₃ and SiO ₂ can be mixed with silicon nitride powder, or a composite compound powder of silicon nitride, RE ₂ O ₃ and SiO ₂ can be used. After the above powder is prepared to a desired composition, and the mixed powder is sufficiently mixed and / or pulverized by a ball mill or the like, an appropriate amount of an organic binder or an organic solvent is added to prepare a molding slurry. A molded body having a desired shape is produced by a technique such as mold pressing, casting, cold isostatic pressing, or extrusion. These compacts are vacuum or Ar, N
1,700-1,900 ° C. in an inert gas atmosphere of ₂ such as, preferably by sintering about 1 to 10 hours at a temperature range of 1,750 to 1,850 ° C., for example a porosity of 5% or less dense silicon nitride sintered The body is obtained. As the firing method, for example, a hot pressing method, normal pressure firing, nitrogen gas pressure firing, or the like can be used. Further, after these firing, hot isostatic pressure firing under a high pressure of 1000 atm or more can also be used. In the grain boundary phase of the silicon nitride based sintered body thus obtained, a crystal phase composed of a complex oxide containing a Group 3a element of the periodic table and silicon is formed. Is advantageous.

The non-oxide ceramic sintered body manufactured as described above has a surface roughness Ra (JIS
B0601) is from 0.7 μm to 3 μm, especially from 0.8 μm to 3 μm.
It is preferably 2.5 μm, more preferably 1-2 μm. Of course, if the surface roughness of the burnt surface (unpolished) is within the above range, it is not particularly necessary to perform polishing or the like. This surface roughness has the effect of improving the adhesion between the composite oxide and the non-oxide ceramic sintered body by the anchor effect. For example, high temperature, high pressure, and suppresses peeling even when exposed to high-speed gas,
Oxidation resistance, erosion resistance and corrosion resistance can be remarkably improved.

As a starting material for forming the protective layer of the composite oxide, for example, a composite oxide having a composition represented by the above formula (1) or (2) can be used. More simply, a mixed powder of a Group 3a element oxide (RE ₂ O ₃ ) powder of the periodic table and a transition metal oxide (MO ₂ ) or a mixed powder further added with a SiO ₂ powder can be used. . In these mixed powders, the mixing ratio of each powder is adjusted according to the desired composition of the composite oxide. For example, in the case of the composite oxide layer represented by the formula (2), the MO ₂ / RE ₂ O ₃ ratio (molar ratio) is 1 to 3,
In particular, it is preferable that the amount is adjusted to be 1.5 to 2.5, more preferably 1.8 to 2.2. In the case of the composite oxide represented by the formula (1), the ratio of MO ₂ / RE ₂ O ₃ is preferably closer to 2.

A binder and a solvent are added to the above raw material powder, and the mixture is sufficiently mixed by a ball mill or the like to prepare a slurry. As the binder, polyvinyl alcohol or the like having good adhesion and easy to handle after drying is preferable.
Examples of the solvent include an organic solvent and water (distilled water), and water (distilled water) is preferable in consideration of safety, volatility, and the like.

The composite oxide slurry prepared by the above method is applied to the surface of the non-oxide ceramic sintered body.
For the coating, a known method such as coating with a brush, spraying with a spray, or dipping can be used. If the protective layer is required only on a part of the surface, the slurry can be applied only to a desired portion by a method using screen printing or the like or spraying using a mask. The thickness of the coating layer is preferably such that a layer having a thickness of 30 to 300 μm is formed by a subsequent heat treatment.
It is preferable to set the thickness to 500 μm. In this case, it is possible to adjust the thickness of the coating layer to a target range by performing the coating at once, or to form a thin layer of about several μm by one coating and repeat the process many times. Thereby, the thickness of the coating layer can be adjusted to a target range. In this way, it is possible to reduce the difference in thermal expansion from the non-oxide ceramic sintered body as the base material, and to form a coating layer having a thickness suitable for forming a protective layer having a thickness effective for suppressing peeling. it can.

The sintered body coated with the slurry coating layer of a predetermined thickness as described above is dried, and then heat-treated in a nitrogen atmosphere of 1 atm or less to have a protective layer of a composite oxide on the surface. The corrosion resistant ceramic of the present invention is obtained. Heat treatment is generally between 1300 ° C. and 1900
° C, especially 1400-1800 ° C, furthermore 1450-1
The heat treatment is performed at 700 ° C., particularly when forming a protective layer of the silicon-substituted composite oxide represented by the formula (2), the heat treatment temperature is set at 1300 to 1800 ° C., particularly 1400 to 17 ° C.
Preferably, the temperature is set to 00 ° C.

The composite oxide slurry is applied to the surface of the unfired non-oxide ceramic molded body, and the molded body and the composite oxide slurry are simultaneously fired to form a protective layer of the composite oxide on the surface. It is also possible to obtain a corrosion-resistant ceramic provided.

Although the above description has been made using the coating method for forming the protective layer, the protective layer may be formed using a known method such as plasma spraying, sputtering or PVD. For example, RE ₂ O ₃ consisting of a predetermined amount
A mixed powder of powder, SiO ₂ and MO ₂ powder, or a mixed powder once treated at a high temperature to synthesize a composite oxide having a predetermined composition, and then subjected to a known plasma spraying method or a sputtering method to synthesize the composite oxide. It is also possible to form a protective layer by attaching an object to the surface of the sintered body.

[0031]

EXPERIMENTAL EXAMPLE 1 Silicon nitride having a BET specific surface area of 9 m ² / g, an α ratio of silicon nitride of 99%, an oxygen content of 1.1% by weight, and a cation metal impurity content of 30 ppm or less such as Al, Mg, Ca, Fe, etc. Rare earth oxide powder having a purity of 99% and an average particle size of 1.5 μm, and silicon oxide having a purity of 99.9% and an average particle size of 0.5 μm, if desired, a purity of 99% and an average particle size of 5.0 μm. Were mixed as shown in Table 1 to prepare a raw material powder for a silicon nitride sintered body. To this raw material powder, a binder and methanol as a solvent are added, and 4
The mixture was pulverized by a rotary mill for 8 hours, dried, and then subjected to rubber press molding at a pressure of 1 t / cm ² into a shape having a diameter of 60 mm and a thickness of 30 mm. Then, the obtained molded body is
It was fired at 1850 ° C. in a nitrogen gas atmosphere at atmospheric pressure to obtain a silicon nitride sintered body. The average surface roughness Ra of the obtained sintered body was measured according to JIS B0601, and the results are shown in Table 1. The surface roughness of some of the sintered bodies was adjusted by surface polishing.

Next, the purity is 99% and the average particle size is 1.5 μm.
Rare earth oxide powder, purity 99.9%, average particle size 0.5
μm silicon oxide, zirconium oxide powder and purity 9
9.9%, average particle size 1 μm titanium oxide, hafnium oxide
Was used as a raw material powder for the composite oxide. These powders
The composition ratio at which the composite oxide having the composition shown in Table 1 is formed
, And dispersed in methanol to form a slurry,
Sprayed uniformly to the sintered body to a predetermined thickness by spraying
After drying, heat treatment at the temperature shown in Table 1
Preparation of sintered body with surface coating layer (protective layer) of composite oxide
(Sample Nos. 1 to 21). For comparison, Y
b₂Si₂O₇, Lu₂Si₂O₇, Er₂Si
₂O ₇, Y₂Si₂O₇, SiO₂, ZrO₂, Murai
Powder (or these oxides are formed by heat treatment)
Same as above using a mixed powder with a composition
Slurry, apply it to the surface of the sintered body, dry and heat
Performing a sintering with a surface coating layer of these oxides
A body was prepared (Sample Nos. 22 to 28).

With respect to the sintered body of each sample obtained above,
The theoretical density ratio of the surface coating layer was calculated from the specific gravity by the Archimedes method. Further, the crystal of the grain boundary phase of the sintered body and the crystal of the surface coating layer were identified by X-ray diffraction measurement. Furthermore, J
Room temperature and high temperature (1500 based on IS-R1601)
° C), and an average value of 30 test results was calculated. Further, as the oxidation resistance, a weight increase after the sintered body was kept in the air at 1500 ° C. for 100 hours was measured. In addition, kerosene is burned to a temperature of 120
The sintered body was exposed to a combustion gas stream at 0 ° C., a pressure of 0.4 MPa, and a gas flow rate of 50 m / s for 500 hours, and the thickness reduction, which is the amount of reduction in the thickness of the surface coating layer, was measured from the change in weight. The results are shown in Table 1.

[0034]

[Table 1]

Sample No. of the present invention 1 to 21 have a room temperature strength of 620 MPa or more, a high temperature strength of 450 MPa or more, an oxidation weight gain of 0.03 mg / cm ² or less, and a wall thickness reduction of 1.5
μm or less. In particular, Sample No. 1 provided with a protective layer (surface coating layer) of a silicon-substituted composite oxide represented by Formula (2). 7 to 10 and 18 to 21 have a room temperature strength of 620.
The high-temperature strength was 450 MPa or more, the oxidation weight gain was 0.02 mg / cm ² or less, and the wall thinning amount was 1 μm or less. On the other hand, the sample No. in which the composite oxide of the surface coating layer does not contain a transition metal element and is outside the scope of the present invention. In Nos. 22 to 25, the room temperature strength was 600 MPa or more and the high temperature strength was 400 MPa or more, but the oxidation weight gain was 0.04 mg / cm ² or more, and the wall thickness reduction was 2 μm or more. In addition, the sample No. in which the surface coating layer was formed of SiO ₂ , ZrO ₂ and mullite and which was outside the scope of the present invention. In Nos. 26 to 28, the oxidation weight increase was 1.21 mg / cm ² or more, and the wall thickness reduction was 110 μm or more.

EXPERIMENTAL EXAMPLE 2 A BET specific surface area of 7 m ² / g, an amount of cationic metal impurities such as Al, Mg, Ca and Fe of 30 ppm or less, and a purity of 99.99% with respect to silicon carbide powder containing 100 ppm or less of free carbon. An alumina powder having an average particle size of 0.5 μm and a powder of yttrium oxide having a purity of 99.9% and an average particle size of 1.5 μm were mixed to prepare a raw material powder for a silicon carbide sintered body. To the above raw material powder, a binder and methanol as a solvent were added, and mixed and pulverized for 48 hours using a silicon nitride ball in a rotary mill.
m, and was subjected to rubber press molding at a pressure of 1 t / cm ² into a shape having a thickness of 30 mm, followed by firing to obtain silicon carbide sintered bodies (Sample Nos. 29 to 33). Further, silicon nitride having a purity of 99.999% and an average particle size of 0.7 μm, alumina powder having a purity of 99.99% and an average particle size of 0.5 μm, and a purity of 99.9
%, An aluminum nitride powder having an average particle size of 0.5 μm was mixed to prepare a raw material powder for a sialon sintered body. Using this raw material powder, a sialon sintered body was obtained in the same manner as described above (Sample Nos. 34 to 36).

Next, the purity is 99% and the average particle size is 1.5 μm.
Rare earth oxide powder, silicon oxide having a purity of 99.9% and an average particle size of 0.5 μm, and titanium oxide having a purity of 99.9% and an average particle size of 1 μm were mixed, calcined at 1500 ° C., and then pulverized. Thus, a raw material powder of the composite oxide having the composition shown in Table 2 was obtained. Prepare a slurry in which the raw material powder is dispersed in methanol, apply uniformly to the sintered body by spraying,
After a coating layer having a predetermined thickness was formed, the coating layer was dried and heat-treated at a temperature shown in Table 2 to form a surface coating layer of a composite oxide having a composition shown in Table 2 on the surface of each sample sintered body. In Table 2,
The Yb ₂ (Si _0.8 Ti _0.2 ) ₂ O ₇ coating layer was produced in the same manner as in Experimental Example 1. The obtained sintered body was evaluated in the same manner as in Experimental Example 1. The results are shown in Table 2.

[0038]

[Table 2]

Sample No. of the present invention In Nos. 29 to 36, the oxidation weight increase is 0.03 mg / cm ² or less, and the wall thickness reduction is 1.5 μm.
It was below.

[0040]

According to the corrosion-resistant ceramic of the present invention, a protective layer of a composite oxide containing a Group 3a element of the periodic table and a transition element is formed on the surface of the non-oxide ceramic sintered body,
This protective layer is firmly attached to the surface of the sintered body,
It shows a large adhesive force even in a high temperature range of about 0 to 1500 ° C., and can be used for a long time in a high temperature range, and the oxidation resistance, corrosion resistance and erosion resistance of the non-oxide ceramic sintered body are remarkably improved. ing.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 35/58 302C 302Z (72) Inventor Isao Yuri 2-6-1 Nagasaka, Yokosuka City, Kanagawa Pref. 4G001 BA03 BA04 BA08 BA09 BA22 BA32 BA36 BA52 BB03 BB04 BB08 BB09 BB22 BB32 BB36 BB52 BC13 BC23 BC52 BC54 BC72 BD11 BD14 BD37 BE35

Claims (9)

[Claims] 1. A corrosion-resistant ceramic comprising a non-oxide ceramic sintered body provided on a surface thereof with a composite oxide layer containing a Group 3a element of the periodic table and a transition metal element. 2. The composite oxide layer has a thickness of 30 to 300.
2. The corrosion-resistant ceramic according to claim 1, which has a thickness of μm. 3. The method according to claim 2, wherein the transition metal element is Zr, Hf or Ti.
The corrosion-resistant ceramic according to claim 1, wherein the ceramic is at least one of the following. 4. The composite oxide is represented by the following formula (1): RE ₂ M ₂ O ₇ (1) wherein RE is a Group 3a element in the periodic table, and M is a transition metal element. 4. A method according to claim 1, wherein
The corrosion resistant ceramic according to any one of the above. Wherein said composite oxide is represented by the following formula _(2): RE in _{2 (Si x M 1-x} ) 2 O 7 ... (2) Equation, RE is a periodic table Group 3a elements, The corrosion-resistant ceramic according to claim 1, wherein M is a transition metal element, and x is a number satisfying 0 <x <1. 6. x in the formula (2) is 0.5 ≦ x
The corrosion-resistant ceramic according to claim 5, wherein the number satisfies <0.9. 7. The corrosion resistance according to claim 1, wherein the non-oxide ceramic sintered body contains at least one of silicon nitride, silicon carbide and sialon as a main component. Ceramics. 8. The surface of a non-oxide ceramic sintered body,
After applying a composite oxide of a transition metal element and a Group 3a element of the periodic table, heat-treating at a temperature of 1300 to 1900 ° C.
A method for producing a corrosion-resistant ceramic, comprising forming a composite oxide layer. 9. The method according to claim 8, wherein the surface of the non-oxide ceramic sintered body has a surface roughness Ra of 0.7 μm to 3 μm.