JPH0826815A - Rare earth compound oxide-based sintered compact and its production - Google Patents

Abstract

PURPOSE:To obtain a rare earth compound oxide-based sintered compact, excel lent in antioxidant properties at a high temperature and causing extremely small deterioration in mechanical strength from ambient temperature up to a high temperature of 1400 deg.C by compounding a disilicate or a monosilicate containing a group IIIa element of the periodic table with a compound oxide comprising the group IIIa element and a specific element. CONSTITUTION:This rare earth compound oxide-based sintered compact comprises one or more of a disilicate (RE2Si2O7) and a monosilicate (RE2SiO5) containing a group IIIa element (RE) of the periodic table and 0.1-95mol% (expressed in terms of oxides) one or more compound oxides (RExMOz; M is Al, Cr, Hf, Nb, Zr, Ti, V and Ta) comprising the group IIIa element (RE) of the periodic table and any of Al, Cr, Hf, Nb, Zr, Ti, V and Ta. This method for producing the sintered compact is to mix an oxide (RE2O3) of the group IIIa element of the periodic table with powder comprising silicon dioxide and one or more of oxides of the Al, Cr, Hf, Nb, Zr, Ti, V and Ta, forming the resultant mixture and baking the resultant formed compact.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a suitable high temperature strength and excellent high temperature stability as a heat resistant structural member for aerospace industry, metal industry, chemical industry, power generation, automobile ceramic gas turbine and the like. The present invention relates to a rare earth compound 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) alloys have been used as heat resistant structural members. I couldn't be satisfied.

Therefore, ceramics, which have a much smaller coefficient of thermal expansion than conventional metallic materials, are excellent in mechanical strength, heat resistance, and wear resistance, and have a small specific gravity and which can be made light and compact, have been attracting attention. Alumina (Al
₂ O ₃ ), zirconia (ZrO ₂ ), magnesia (Mg
Oxide ceramics such as O), silicon carbide (S
Carbide-based and nitride-based ceramics such as iC) and silicon nitride (Si ₃ N ₄ ), or non-oxide-based ceramics such as boride-based ceramics have been investigated.

As a result, the oxide-based ceramics and the non-oxide-based ceramics have good mechanical strength and oxidation resistance at a much higher temperature than other conventional materials. Various studies have been made and proposed for use as the various heat-resistant structural members (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, since dislocation motion easily occurs at high temperature, it softens and plastically deforms, and generally mechanical strength sharply decreases at a temperature around 900 ° C. Although it can be practically used as a member that does not add much, it cannot be used as a structural member under the condition that it is exposed to high temperature and stress acts, and there is a problem that it lacks reliability.

On the other hand, the non-oxide ceramic sintered body such as the above-mentioned carbide type, nitride type, or boride type material has excellent mechanical properties even at high temperatures, but it is oxidized by interaction with the atmosphere, or Since decomposition occurs, mechanical strength deteriorates significantly from room temperature, and various adjustments of the type and amount of addition aid and sintering conditions have been studied so far, although some improvement in material properties was observed. However, it is still insufficient, and as a heat-resistant structural member for high temperature, it is still required to satisfy the characteristic that mechanical strength is less 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 excellent resistance to oxidation at high temperatures, and also to cause deterioration of mechanical strength from room temperature to a high temperature of 1400 ° C. It is an object of the present invention to provide a rare earth compound oxide-based sintered body much smaller than the sintered body and a method for producing the same.

[0008]

Means for Solving the Problems The present inventors have found that even if used at high temperature for a long period of time, oxidation or decomposition does not occur, and an oxide having excellent oxidation resistance can be provided with mechanical strength at a temperature exceeding 900 ° C. As a result of repeated studies from the viewpoint that increasing the plastic deformation resistance at high temperature may maintain high mechanical strength even at high temperature in order to prevent deterioration, crystal symmetry is low among oxides. Periodic table Group 3a element (RE) disilicate (RE ₂ Si ₂ O ₇ ) and monosilicate (R)
We have found that E ₂ SiO ₅ ) is promising.

Further, the disilicate (RE ₂ Si ₂
O ₇ ), monosilicate (RE ₂ SiO ₅ ), and at least one group 3a element (RE) and A
l, Cr, Hf, Nb, Zr, Ti, V, or more comprising a composite oxide of _{Ta (RE x M y O z} , M is Al, C
The rare-earth composite oxide in which the plastic deformation of the crystal is further suppressed by mainly dispersing the refractory substance such as r, Hf, Nb, Zr, Ti, V, and Ta) from room temperature to 1400
It became clear that it showed excellent mechanical properties up to a high temperature of ℃.

That is, the rare earth compound oxide-based sintered body of the present invention comprises a group 3a element (RE) of the periodic table and Al, Cr, H.
A refractory substance made of one or more complex oxides (RE _x M _y O _z ) made of any one of f, Nb, Zr, Ti, V, and Ta contains an element (RE) of Group 3a of the periodic table. Disilicate (RE ₂ Si ₂ O ₇ ), Monosilicate (R
E ₂ SiO ₅ ), which is mainly dispersed in one or more crystals in a total amount of 0.1 to 95 mol% in terms of oxide,
It is characterized by suppressing the plastic deformation of the disilicate (RE ₂ Si ₂ O ₇ ) or monosilicate (RE ₂ SiO ₅ ).

Further, the method for producing such a rare earth compound oxide-based sintered body is based on an oxide (RE) of a Group 3a element of the periodic table.
₂ O ₃ ) and silicon dioxide (SiO ₂ ) and Al, Cr, H
A molded body obtained from a molding material prepared by mixing powders of one or more oxides of f, Nb, Zr, Ti, V, and Ta as a raw material is 1100 to 1850 ° C.
Of a disilicate (RE ₂ Si ₂ O ₇ ) and a monosilicate (RE ₂ SiO ₅ ) containing a Group 3a element (RE) of the Periodic Table, which are synthesized by firing at the temperature of One or more, and a Group 3a element (RE) of the periodic table and Al, Cr, Hf, Nb, Zr, Ti,
V, or more comprising a composite oxide of Ta (RE _x M _y O
One or more of _z ) is subjected to a crushing, mixing, and molding manufacturing process, and the molded body is fired at a temperature of 1100 to 1850 ° C.

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

[0013]

According to the rare earth compound oxide-based sintered body and the method for producing the same of the present invention, a disilicate (RE ₂ Si ₂ O ₇ ) and a monosilicate (RE) containing a group 3a element (RE) of the Periodic Table. ₂ SiO ₅ ) mainly has a monoclinic crystal structure, and is difficult to be plastically deformed because the crystal structure has low symmetry.
The decrease in mechanical strength is small even at a high temperature of about 1400 ° C.

Furthermore, a group 3a element (RE) of the periodic table and A
l, Cr, Hf, Nb, Zr, Ti, V, or more comprising a composite oxide of _{Ta (RE x M y O z} ) has a high melting point, is stable at high temperatures, they said disilicate (RE ₂ Si ₂ O ₇ ) and monosilicate (RE ₂ Si
Dispersion in O ₅ ) suppresses plastic deformation due to the movement of dislocations and significantly improves the mechanical strength at high temperatures above 900 ° C., especially the deterioration of mechanical strength at high temperatures around 1400 ° C. It becomes smaller, and the effect of preventing deterioration becomes more remarkable.

The oxidation resistance of alumina (Al
₂ O ₃ ), zirconia (ZrO ₂ ), magnesia (Mg
It is equivalent to oxide-based ceramics such as O).

[0016]

EXAMPLES The rare earth compound oxide-based sintered body of the present invention and the method for producing the same will be described in detail below with reference to Examples.

The rare earth compound oxide-based sintered body of the present invention comprises a disilicate (RE ₂ Si ₂ O ₇ ) and a monosilicate (RE ₂ Si) containing a group 3a element (RE) of the periodic table.
One or more of O ₅ ) and the total amount is 0.1 to 9 in terms of oxide.
5 mol% of Group 3a element (RE) and A of the periodic table
and one or more complex oxides (RE _x M _y O _z ) made of any one of 1, Cr, Hf, Nb, Zr, Ti, V, and Ta, which is a disilicate (RE ₂ Si ₂
The crystal structure of O ₇ ) is triclinic, monoclinic or oblique α, β, γ,
Either δ or y type may be used, but β, γ and δ phases which are stable phases at high temperature are particularly preferable.

The Group 3a element (RE) of the periodic table
And Al, Cr, Hf, Nb, Zr, Ti, V, or more comprising a composite oxide of _{Ta (RE x M y O z} ) is 1
Since it is a compound that has a melting point of 700 ° C. or higher and is stable at high temperatures, it is suitable as a compound that does not deteriorate the mechanical strength up to high temperatures, but M is particularly preferably Al, Cr, Hf, or Zr.

Therefore, the total amount of the complex oxide is 0.1
If it is less than mol%, there is no compound strengthening effect and conversely 95mo
If it exceeds 1%, the excellent characteristics of disilicate (RE ₂ Si ₂ O ₇ ) or monosilicate (RE ₂ SiO ₅ ) cannot be obtained, so it is limited to the range of 0.1 to 95 mol% and the improvement of high temperature strength. 5-80m from the point of effect
ol% is more desirable.

The elements of Group 3a (RE) of the periodic table used in the present invention include Sc, Y and lanthanoid elements, but especially Sc, Y and Dy, Er, Ho,
Heavy rare earth elements such as Yb and Lu have a strong bond strength between the silicate formed and the complex oxide crystal due to their small ionic radius, and therefore have excellent mechanical properties at high temperatures.
More preferable.

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

As the starting raw material, metal element powders may be mixed in a predetermined ratio and then oxidized in an oxygen atmosphere, and the particle diameter of the raw material powders is 0.3 to 2.0 μm.
Is appropriate.

The rare earth compound oxide-based sintered body produced by using the above-mentioned raw material powder is a disilicate (RE ₂ Si ₂ O ₇ ) or a monosilicate (R ₂ Si ₂ O ₇ ) of a group 3a element of the periodic table.
E ₂ SiO ₅ ), converted into Eq.
Group element (RE) and Al, Cr, Hf, Nb, Zr, T
i, V, the total amount in terms of the composite oxide (RE _x M _y O _z) consisting of Ta, 0.1~95mol% as described above,
It is particularly important that the amount is 5 to 80 mol%.

The raw material powders mixed in the above proportions are molded into a desired shape by a desired molding means such as a die press, cast molding, extrusion molding, injection molding, cold isostatic pressing and the like.

Next, this molded body is subjected to a known sintering method, for example, a hot pressing method, a normal pressure firing method, a nitrogen gas pressure firing method, or hot isostatic treatment (HIP) after these firing steps.
Or after glass sealing, hot isostatic treatment (HI
P) is performed to obtain a dense sintered body having a theoretical density ratio of 95% or more.

The firing temperature is high in mechanical strength, and in order to obtain a dense sintered body, it is desirable to perform firing at a temperature of 1100 to 1850 ° C, particularly 1300 to 1750 ° C.

On the other hand, one or more of disilicate (RE ₂ Si ₂ O ₇ ) and monosilicate (RE ₂ SiO ₅ ) containing a Group 3a element (RE) of the Periodic Table, and a Group 3a element of the Periodic Table (RE RE) and Al, Cr, Hf, Nb, Z
A complex oxide (R) composed of any of r, Ti, V, and Ta
One or more of E _x M _y O _z ) are respectively calcined, pulverized and mixed, and then the pulverized mixed powder is molded in the same manner as above to obtain a molded body, which is fired at a temperature of 1100 to 1850 ° C. It is also possible to produce a rare earth complex oxide-based sintered body.

The composite oxide (RE _x M _y O _z ) obtained by the above-mentioned calcination is generally more stable and less reactive than the raw material oxide powder constituting the composite oxide, so that it is It suppresses abnormal grain growth and glass phase formation, and further improves the high temperature strength characteristics of the material.

Further, the periodic table contains a Group 3a element (RE).
Own disilicate (RE₂Si ₂O₇) And Monosiri
Kate (RE₂SiO_Five) Si in Al, Cr, H
A certain amount of f, Nb, Zr, Ti, V, or Ta
As a result, a solid solution type composite oxide is formed.
It

That is, the rare earth complex oxide-based sintered body obtained by the above-mentioned manufacturing method was heated to a temperature not higher than the firing temperature thereof at 1000 ° C.
After heat treatment in the above temperature range, supersaturated solid solution atoms are converted into disilicate (RE ₂ Si ₂ O ₇ ) and monosilicate (R
E ₂ SiO ₅ ) compound oxide (R
E _x M _y O _z in the form of) can be finely precipitated by the precipitation process, the nanocomposite is formed not only to improve the high temperature strength of the material, it becomes possible to realize improvement in fracture toughness.

The precipitation treatment, that is, the heat treatment, is 1000 ° C.
At a lower temperature, it is not practical because the precipitation treatment requires a long time from the viewpoint of the diffusion rate of atoms, while on the other hand, grain treatment of crystal grains occurs when treated at a temperature higher than the firing temperature, and the properties of the material deteriorate, It is important that the heat treatment temperature is 1000 ° C. or higher and the firing temperature or lower.

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

In order to evaluate the rare earth compound oxide-based sintered body of the present invention and the manufacturing method thereof, rare earth oxide (RE ₂ O ₃ ) and SiO ₂ and Al ₂ O ₃ and Cr ₂ are used as raw material powders.
O ₃ , HfO ₂ , Nb ₂ O ₅ , ZrO ₂ , TiO ₂ , V
The powder of each oxide prepared by using ₂ O ₅ and Ta ₂ O _{5 so as} to have a predetermined composition ratio was first press-molded at a pressure of 1 t / cm ² , and further 3 t / cm was added to the sample fired in the air. cm ²
While making a hydrostatic pressure treatment with the pressure of
At the same time, the respective oxides were blended so as to have the composition ratios shown in Table 1 and Table 2, and calcined at a temperature of 1300 ° C. for 1 hour, and a pulverized composite oxide was used to prepare a molded body in the same manner as described above. Next, as shown in Tables 1 and 2, when the formed body is fired at atmospheric pressure in the atmosphere, it is held at each firing temperature for 5 hours,
When hot-press firing, nitrogen (N ₂ ) at atmospheric pressure is used.
In the 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., 1
A heat treatment of 0 hours was applied to some of the samples.

The sintered body thus obtained was subjected to JIS-R16.
A bending test piece was prepared by polishing to a predetermined size in accordance with the 01 standard, and the bending test piece was subjected to 4 at room temperature and 1400 ° C.
A point bending bending test was carried out.

In addition, RE ₂ O ₃ / SiO ₂ / M _m O
_n (M is Al, Cr, Hf, Nb, Zr, Ti, V, T
a) composition ratio, and Group 3a element (RE) and A of the periodic table
l, Cr, Hf, Nb, Zr, Ti, V, Ta is a composite oxide (RE _x M _y O _z ) of which mol% is the weight of RE, Si and M by the ICP method after crushing the sintered body. Measure the ratio,
It was calculated in terms of oxide.

Furthermore, when the rare earth complex oxide-based sintered body for evaluation was subjected to X-ray diffraction measurement to identify the crystal phase, disilicate (RE ₂ Si ₂ O ₇ ) and monosilicate (R) were identified.
E ₂ SiO ₅ ), Group 3a element (RE) of the periodic table and A
l, Cr, Hf, Nb, Zr, Ti, V, or more comprising a composite oxide of _{Ta (RE x M y O z} , M is Al, C
r, Hf, Nb, Zr, Ti, V, 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, 7, 10, 16, 21, 27, 29, 32, 35 containing no complex oxide or a predetermined amount
Nos. 41, 49, 60, 64, 66 and 69 have a bending strength at RT as low as 390 MPa or less, and the bending strength at 1400 ° C. also shows an extremely large deterioration of up to 120 MPa, whereas the rare earths of the present invention All of the composite oxide-based sintered bodies have a high bending strength at RT of 400 MPa or more, which is 1
It can be seen that the deterioration in bending strength at 400 ° C. is 30 MPa or less, which is very small.

[0043]

As described above, according to the rare earth compound oxide-based sintered body of the present invention and the method for producing the same, a disilicate (RE ₂ Si ₂ ) containing a group 3a element (RE) of the periodic table is used.
O ₇ ), monosilicate (RE ₂ SiO ₅ ) and one or more elements of the Periodic Table Group 3a (RE) and Al, Cr, H
The total amount of composite oxide (RE _x M _y O _z ) with any element of f, Nb, Zr, Ti, V, and Ta is 0.
1 to 95 mol% dispersed, and an oxide (RE ₂ O ₃ ) of a group 3a element of the periodic table and silicon dioxide (S
iO ₂ ) and one or more oxides of the above elements, or a disilicate (RE ₂ S) containing one or more elements of Group 3a (RE) of the periodic table synthesized by calcination.
and i ₂ O ₇₎ and monosilicate (RE ₂ SiO _5), the periodic table group 3a elements (RE) and complex oxides of the respective elements (RE _x M _y O _z) molded body using one or more 1
Since it is densified by firing at a temperature of 100 to 1850 ° C, plastic deformation due to movement of dislocations is suppressed, mechanical strength at a high temperature exceeding 900 ° C is significantly improved, and plastic deformation from room temperature to a high temperature of 1400 ° C is achieved. It is difficult to do so, deterioration of mechanical strength is much smaller than that of a conventional ceramic sintered body, and a rare earth complex oxide-based sintered body excellent in stability at high temperature and a manufacturing method thereof can be obtained.

Claims (4)

[Claims] 1. One or more disilicate (RE ₂ Si ₂ O ₇ ) and monosilicate (RE ₂ SiO ₅ ) containing a group 3a element (RE) of the Periodic Table, and the total amount thereof is 0. 1-95 mol% Periodic Table Group 3a element (R
E) and Al, Cr, Hf, Nb, Zr, Ti, V, Ta
Any more made composite oxide _{(RE x M y O z,} M is Al, Cr, Hf, Nb, Zr, Ti, V, Ta) rare earth composite oxide sintered, characterized in that it consists of one or more Union. 2. An oxide of a Group 3a element of the periodic table (RE ₂ O
₃ ) and silicon dioxide (SiO ₂ ) and Al, Cr, Hf,
A rare earth compound oxide-based calcining method, comprising: mixing a powder of one or more oxides of Nb, Zr, Ti, V, and Ta, and then firing the molded body obtained by shaping the mixed powder. A method for producing a bound body. 3. One or more of a disilicate (RE ₂ Si ₂ O ₇ ) and a monosilicate (RE ₂ SiO ₅ ) containing a group 3a element (RE) of the periodic table, and an element 3a group (a) of the periodic table (RE ₂ Si ₂ O ₇ ). RE) and Al, Cr, Hf, Nb, Zr, Ti,
V, or more comprising a composite oxide of Ta (RE _x M _y O
_z and M are Al, Cr, Hf, Nb, Zr, Ti, V and T
A method for producing a rare earth complex oxide-based sintered body, which comprises calcining and pulverizing and mixing one or more kinds of a), and then firing a compact obtained by shaping the pulverized mixed powder. 4. The super-saturated solid solution atom is precipitated by heat-treating the rare earth complex oxide-based sintered body at a temperature not higher than the firing temperature and not lower than 1000 ° C. Of the rare earth compound oxide-based sintered body according to claim 1.