JP3273099B2 - Rare earth composite oxide-based sintered body and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is applicable to a heat-resistant structural member such as aerospace industry, metal industry, chemical industry, power generation, ceramic gas turbine for automobiles, etc. The present invention relates to a rare earth composite oxide-based sintered body having oxidation resistance and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, various heat-resistant alloys such as nickel (Ni) / cobalt (Co) -based alloys have been used as heat-resistant structural members. I was no longer satisfied.

[0003] Therefore, ceramics that have a much lower coefficient of thermal expansion than conventional metal materials, have excellent mechanical strength, heat resistance, and wear resistance, and have a small specific gravity and are capable of reducing the size and weight of products have been attracting attention. Alumina (Al ₂ O ₃ )
And zirconia (ZrO _2), magnesia (MgO) including oxide-based ceramics such as silicon carbide (SiC) and silicon nitride (Si ₃ N ₄₎ carbide and nitride of the like, or boride-based, etc. Non of Oxide-based ceramics have been studied.

As a result, the oxide ceramics and the non-oxide ceramics have much higher mechanical strength and oxidation resistance at a much higher temperature than other conventional materials. Utilization as the above-mentioned various heat-resistant structural members has been variously studied and proposed (see JP-A-6-157126).

[0005]

However, when the ceramic sintered body is used as a heat-resistant structural member, the oxide ceramic sintered body has stable mechanical properties at room temperature especially in an oxidizing atmosphere. However, at high temperatures, dislocation motion is likely to occur, so the material softens and plastically deforms, and the mechanical strength generally drops sharply at a temperature around 900 ° C. Although it can be used practically as a member that does not add much, it cannot be used as a structural member under conditions where it is exposed to a high temperature and a stress acts, and there is a problem that reliability is lacking.

On the other hand, non-oxide ceramic sintered bodies such as carbide, nitride and boride are materials having excellent mechanical properties even at high temperatures, but are oxidized or Since decomposition occurs, the mechanical strength is significantly deteriorated from room temperature, and until now, various studies have been made on adjusting the type and amount of the additive aid and the sintering conditions, and although some improvement in material properties was observed, However, the heat-resistant structural member for high temperature is still required to satisfy the characteristic that the mechanical strength is not deteriorated at room temperature.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a conventional ceramic which is excellent in oxidation resistance at a high temperature and has a mechanical strength which is deteriorated from room temperature to a high temperature of 1400 ° C. An object of the present invention is to provide a rare earth composite oxide-based sintered body much smaller than a sintered body and a method for producing the same.

[0008]

Means for Solving the Problems The present inventors have developed an oxide having excellent oxidation resistance which does not undergo oxidation or decomposition even when used for a long time at a high temperature, and has a mechanical strength even at a temperature exceeding 900 ° C. As a result of repeated studies based on the view that increasing plastic deformation resistance at high temperatures may maintain high mechanical strength even at high temperatures in order to prevent deterioration, the crystal symmetry is low even among oxides Disilicate (RE ₂ Si ₂ O ₇ ) and monosilicate (RE ₂ ) of Group 3a element (RE) of the periodic table
SiO ₅ ) has been found to be promising.

Further, the above-mentioned disilicate (RE ₂ Si ₂ O)
₇ ) and / or a crystal composed of monosilicate (RE ₂ SiO ₅ ), a group 3a element (RE) of the periodic table and Al, C
any one of r, Hf, Nb, Zr, Ti, V and Ta
Composite oxide consisting of seeds (RE _x M _y O _z, where x, y, z
Does not include 0, and M is Al, Cr, Hf, Nb, Zr, T
i, V and Ta), the rare-earth composite oxide which further suppresses plastic deformation of the crystal by exhibiting high mechanical properties from room temperature to a high temperature of 1400 ° C. It became clear.

That is, the rare earth composite oxide-based sintered body of the present invention comprises a disilicate (RE ₂ Si ₂ O ₇ ) and / or a monosilicate (RE ₂ SiO) containing a Group 3a element (RE) of the periodic table. ₅ ) and the total amount is ₅ to 80 mo in terms of oxide
Group 3a element (RE) in the periodic table of 1% and Al, C
any one of r, Hf, Nb, Zr, Ti, V and Ta
Composite oxide consisting of seeds (RE _x M _y O _z, where x, y, z
Does not include 0, and M is Al, Cr, Hf, Nb, Zr, T
i, V, and Ta).

In addition, the method for producing such a rare earth composite oxide-based sintered body is based on the group 3a of the periodic table of disilicate (RE ₂ Si ₂ O ₇ ) and / or monosilicate (RE ₂ SiO ₅ ). Element (RE) and Al, Cr, Hf, Nb, Z
r, excluding Ti, composite oxide consisting of any one of V and _{Ta (RE x M y O z} , where x, y, z is a 0, M is Al, Cr, Hf, Nb, Zr, Ti , V and Ta) so that the total amount is 5 to 80 mol%,
Oxide (RE ₂ O ₃ ) of Group 3a element of the periodic table, silicon dioxide (SiO ₂ ), Al, Cr, Hf, Nb, Zr, T
After mixing a powder comprising at least one of oxides of i, V and Ta, a compact obtained by molding the mixed powder is fired, or a Group 3a element (RE) of the periodic table is removed. Containing disilicate (RE ₂ Si ₂ O ₇ ) and / or monosilicate (RE ₂ SiO ₅ ) and a group 3a element of the periodic table (R
E) and a composite oxide (RE _x M) composed of any one of Al, Cr, Hf, Nb, Zr, Ti, V and Ta
_y O _z , where x, y, and z do not include 0, and M is Al, Cr,
Any one of Hf, Nb, Zr, Ti, V and Ta)
Is calcined, pulverized and mixed, and then a molded body obtained by molding the pulverized mixed powder is calcined.

In particular, it is desirable that the rare earth composite oxide-based sintered body obtained by the above-mentioned manufacturing method is heat-treated at a temperature of 1000 ° C. or more and a firing temperature thereof or less to precipitate supersaturated solid solution atoms.

[0013]

According to the rare earth composite oxide-based sintered body of the present invention and the method for producing the same, disilicate (RE ₂ Si ₂ O ₇ ) and / or monosilicate containing a Group 3a element (RE) of the periodic table (RE ₂ SiO ₅ ) mainly has a monoclinic crystal structure and is less likely to be plastically deformed due to the low symmetry of the crystal structure, and the decrease in mechanical strength is small even at a high temperature of about 1400 ° C.

Further, an element (RE) belonging to Group 3a of the periodic table and A
l, Cr, Hf, Nb, Zr, Ti, composite oxide consisting of any one of V and _{Ta (RE x M y O z} ) has a high melting point, is stable at high temperatures, they and the disilicate ( RE ₂ Si ₂ O ₇ ) and / or monosilicate (RE ₂ S)
In the rare-earth composite oxide-based sintered body of the present invention comprising iO ₅ ), plastic deformation due to dislocation movement is suppressed, and mechanical strength at a high temperature exceeding 900 ° C. is remarkably improved. The deterioration of the mechanical strength below becomes smaller, and the effect of preventing the deterioration becomes more remarkable.

Also, the oxidation resistance is alumina (Al ₂ O ₃ ),
This is equivalent to oxide ceramics such as zirconia (ZrO ₂ ) and magnesia (MgO).

[0016]

EXAMPLES The rare earth composite oxide-based sintered body of the present invention and a method for producing the same will now be described in detail with reference to examples.

The rare earth complex oxide sintered body of the present invention is a disilicate (RE ₂ Si ₂ O ₇ ) and / or monosilicate (RE ₂ S) containing a Group 3a element (RE) of the periodic table.
iO ₅ ), a group 3a element (RE) of the periodic table having a total amount of ₅ to 80 mol% in terms of oxide, Al, Cr, Hf,
Nb, Zr, Ti, and consisted of a 1 or more composite oxides made of any one of V and _{Ta (RE x M y O z} ), disilicate of (RE ₂ Si ₂ O ₇₎ The crystal structure may be any of triclinic, monoclinic, and oblique α, β, γ, δ, and y forms, but the β, γ, and δ phases, which are high-temperature stable phases, are particularly preferred.

Further, the element (RE) of Group 3a of the periodic table
And Al, Cr, Hf, Nb, Zr, Ti, V and Ta
Composite oxide consisting of any one of (RE _x M _y O _z)
Is a compound that has a melting point of 1700 ° C. or higher and is stable at high temperatures, and thus is suitable as a material that does not deteriorate mechanical strength up to high temperatures. In particular, M is most preferably any one of Al, Cr, Hf, and Zr. desirable.

Therefore, the total amount of the composite oxide is excellent in the properties of disilicate (RE ₂ Si ₂ O ₇ ) or monosilicate (RE ₂ SiO ₅ ), and the effect of strengthening the composite is sufficient, 5 to improve strength
80 mol% is important.

The Group 3a element (RE) of the Periodic Table used in the present invention includes Sc, Y and lanthanoid elements, and particularly Sc, Y and Dy, Er, Ho,
Heavy rare earth elements such as Yb and Lu have a small ionic radius, so that the bond strength between the silicate formed and the composite oxide crystal is strong, and therefore, the mechanical properties at high temperatures are excellent.
More preferred.

Next, a method for producing the rare earth composite oxide-based sintered body of the present invention will be described. According to the present invention, as starting materials, oxides (RE ₂ O ₃ ) and silicon dioxide (SiO ₂ ) of rare earth elements, which are Group 3a elements of the periodic table, and Al, Cr, Hf, Nb, Zr, Ti, Each powder of an oxide of either V or Ta is used.

The starting material may be mixed with a metal element powder at a predetermined ratio and then oxidized in an oxygen atmosphere. The particle diameter of the material powder is 0.3 to 2.0 μm.
Is appropriate.

Further, the rare earth complex oxide-based sintered body produced using the raw material powder is a disilicate (RE ₂ Si ₂ O ₇ ) or a monosilicate (RE ₂
SiO ₅ ), Al, Cr, Hf, Nb, Zr, Ti, V
And the total amount in terms of the composite oxide (RE _x M _y O _z) made of Ta, it is important to be 5～80Mol% as described above.

The raw material powder mixed in the above ratio is formed into an arbitrary shape by a desired molding means, for example, a die press, a casting molding, an extrusion molding, an injection molding, a cold isostatic pressing and the like.

Next, the compact is sintered by a known sintering method, for example, a hot pressing method, a normal pressure sintering method, a nitrogen gas pressurizing sintering method, and a hot isostatic pressure treatment (HIP) after these sintering.
Or after glass sealing, hot isostatic pressure treatment (HI
P) to obtain a dense sintered body having a theoretical density ratio of 95% or more.

The firing temperature is preferably high at 1100 to 1850 ° C., particularly 1300 to 1750 ° C., in order to obtain a dense sintered body with high mechanical strength.

On the other hand, at least one of a disilicate (RE ₂ Si ₂ O ₇ ) and / or a monosilicate (RE ₂ SiO ₅ ) containing a Group 3a element (RE) of the periodic table and the periodic table 3a Group element (RE) and Al, Cr, Hf, Nb, Z
r, Ti, was crushed and mixed with one or more calcined respective composite oxide consisting of any one of V and _{Ta (RE x M y O z} ), molding the pulverized mixture powder in the same manner the It is also possible to produce a rare earth composite oxide-based sintered body by firing the molded body obtained at a temperature of 1100 to 1850 ° C.

[0028] Incidentally, the calcined by the resulting composite oxide (RE _x M _y O _z) generally the composite oxide more stable than the raw material oxide powder constituting the, due to low reactivity, at the time of firing Abnormal grain growth and generation of a glass phase are suppressed, and the high-temperature strength characteristics of the material are further improved.

Further, Si in a disilicate (RE ₂ Si ₂ O ₇ ) or monosilicate (RE ₂ SiO ₅ ) containing a Group 3a element (RE) of the periodic table is converted to Al, Cr, Hf,
By substituting a certain amount of any one of Nb, Zr, Ti, V and Ta, a solid solution type composite oxide is formed.

That is, the rare-earth composite oxide-based sintered body obtained by the above-mentioned manufacturing method is heated to a temperature of 1000 ° C. or lower at a firing temperature or lower.
The heat treatment is performed in the above temperature range, and the atoms dissolved in supersaturation are converted into disilicate (RE ₂ Si ₂ O ₇ ) or monosilicate (RE ₂
In a crystal grain of SiO ₅ ) or in a crystal grain boundary, a composite oxide (RE _x M
_y O _z ), and the precipitation process forms a nanocomposite, which not only improves the high-temperature strength of the material but also improves the fracture toughness.

The above-mentioned precipitation treatment, that is, heat treatment is performed at 1000 ° C.
At lower temperatures, the precipitation process takes a long time in terms of the diffusion rate of atoms, which is not practical.On the other hand, if the treatment is performed at a temperature higher than the firing temperature, crystal grains will grow and the properties of the material will decrease, It is important that the heat treatment temperature is not lower than 1000 ° C. and not higher than the firing temperature.

By the above manufacturing method, a homogeneous, fine-grained and dense rare earth composite oxide-based sintered body can be obtained.

In order to evaluate the rare-earth composite oxide-based sintered body of the present invention and the method for producing the same, rare-earth oxide (RE ₂ O ₃ ) and SiO ₂ and Al ₂ O ₃ , Cr ₂ O ₃ ,
HfO ₂ , Nb ₂ O ₅ , ZrO ₂ , TiO ₂ , V ₂ O ₅ , Ta ₂
Each oxide powder prepared to have a predetermined composition ratio using O ₅ was first press-molded at a pressure of 1 t / cm ² ,
The sample fired in the air is further subjected to hydrostatic pressure treatment at a pressure of 3 t / cm ² to produce a molded body, and the above oxides are also prepared so as to have the composition ratios shown in Tables 3 and 4. The composite oxide was calcined at a temperature of 1300 ° C. for 1 hour, and a compact was produced in the same manner as described above using the pulverized composite oxide. Next, as shown in Tables 1 and 2, when the molded body is fired at normal pressure in the air, the temperature is maintained at each firing temperature for 5 hours. In a (N ₂ ) atmosphere, firing was performed at a pressure of 0.3 t / cm ² at each firing temperature for 1 hour.

Further, at temperatures of 1400 ° C. and 1500 ° C.,
A 0 hour heat treatment was applied to some of the samples.

The sintered body thus obtained was subjected to JIS-R16
The specimen was polished to a predetermined size in accordance with the standard of No. 01 to prepare a bending test piece, and the bending test piece was subjected to 4 ° C at room temperature and 1400 ° C.
A point bending bending test was performed.

Further, the composition of _{RE 2 O 5 / SiO 2 /} M m O n (M is free Al, Cr, Hf, Nb, Zr, Ti, or V and Ta, m, n is 0) Ratio, element of group 3a (RE) of the periodic table and Al, Cr, Hf, Nb, Z
r, a composite oxide of any one of Ti, V and Ta (R
Mol% of E _x M _y O _z) after pulverizing the sintered body, ICP
The weight ratio of RE, Si and M was measured by the method and calculated in terms of oxide.

Further, when the crystal phase was identified by X-ray diffraction measurement of the rare earth composite oxide-based sintered body for evaluation, disilicate (RE ₂ Si ₂ O ₇ ) and monosilicate (RE ₂
SiO ₅ ), Group 3a element (RE) of the periodic table and Al,
Cr, Hf, Nb, Zr, Ti, composite oxide consisting of any one of V and _{Ta (RE x M y O z} , where x, y,
z does not include 0, and M is Al, Cr, Hf, Nb, Zr,
Ti, V, and Ta). The above results are shown in Tables 1 to 4.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3]

[0041]

[Table 4]

As is clear from the results of Tables 1 to 4,
Sample Nos. 1, 6, 9, 14, 19, 24, 26, 29, 32, 3 containing no complex oxide or containing a predetermined amount
In 7, 45, 56, 60, 62, and 65, the flexural strength at RT was as low as 390 MPa or less, and the flexural strength at 1400 ° C. showed extremely large deterioration of up to 120 MPa. Each of the composite oxide-based sintered bodies has a high bending strength at RT of 400 MPa or more,
It can be seen that the flexural strength degradation at 00 ° C. is very small, 30 MPa or less.

[0043]

As described above, the rare earth composite oxide-based sintered body of the present invention is a disilicate (RE ₂ Si ₂ O ₇ ) and / or monosilicate containing a Group 3a element (RE) in the periodic table. (RE ₂ SiO ₅ ) and the total amount is 5 to 8 in terms of oxide.
An element (RE) Al of Group 3a of the Periodic Table which is 0 mol%,
Cr, Hf, Nb, Zr, Ti, composite oxide consisting of any one of V and _{Ta (RE x M y O z} , where x, y,
z does not include 0, and M is Al, Cr, Hf, Nb, Zr,
Ti, V, and Ta), which suppresses plastic deformation due to dislocation movement.
The mechanical strength at high temperatures exceeding 900 ° C is remarkably improved, it is difficult to plastically deform from room temperature to a high temperature of 1400 ° C, the deterioration of mechanical strength is much smaller than the conventional ceramic sintered body, and the stability at high temperatures is improved. An excellent rare earth composite oxide-based sintered body can be obtained.

Claims (4)

(57) [Claims] A total amount of disilicate (RE ₂ Si ₂ O ₇ ) and / or monosilicate (RE ₂ SiO ₅ ) containing a Group 3a element (RE) of the periodic table is 5 to 8 in terms of oxide.
Group 3a element (RE) of the periodic table which is 0 mol% and A
l, Cr, Hf, Nb, Zr, Ti, composite oxide consisting of any one of V and _{Ta (RE x M y O z} , where x,
y and z do not include 0, and M is Al, Cr, Hf, Nb, Z
a rare earth composite oxide-based sintered body comprising at least one of r, Ti, V and Ta). 2. Disilicate (RE ₂ Si ₂ O ₇ ) and / or
Or, for a monosilicate (RE ₂ SiO ₅ ), a group 3a element (RE) of the periodic table and Al, Cr, Hf, Nb, Z
r, excluding Ti, composite oxide consisting of any one of V and _{Ta (RE x M y O z} , where x, y, z is a 0, M is Al, Cr, Hf, Nb, Zr, Ti , V and Ta) so that the total amount is 5 to 80 mol%,
Oxide (RE ₂ O ₃ ) of Group 3a element of the periodic table, silicon dioxide (SiO ₂ ), Al, Cr, Hf, Nb, Zr, T
a powder of at least one of oxides of i, V, and Ta is mixed, and then a molded body obtained by molding the mixed powder is fired; Production method. 3. A disilicate (RE ₂ Si ₂ O ₇ ) and / or monosilicate (RE ₂ SiO ₅ ) containing a Group 3a element (RE) of the periodic table, and a Group 3a element (R) of the periodic table.
E) and a composite oxide (RE _x M) composed of any one of Al, Cr, Hf, Nb, Zr, Ti, V and Ta
_y O _z , where x, y, and z do not include 0, and M is Al, Cr,
Any one of Hf, Nb, Zr, Ti, V and Ta)
A method for producing a rare earth composite oxide-based sintered body, comprising calcining and pulverizing and mixing each of at least one of the above, and then baking a compact obtained by molding the pulverized mixed powder. 4. A super-saturated solid solution atom is precipitated by heat-treating said rare earth composite oxide-based sintered body at a temperature not higher than its firing temperature and not lower than 1000 ° C.
A method for producing the rare earth composite oxide-based sintered body according to the above.