JPS63162570A - Thermal degradation-resistant high strength zirconia-alumina ceramics and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to high-strength, high-toughness ceramics with excellent heat deterioration resistance, and more specifically to zirconia ceramics containing α-alumina and partially stabilized zirconia as main components. Regarding alumina ceramics.

The zirconia-alumina ceramic of the present invention is a sintered body with high strength and toughness, and excellent wear resistance and heat deterioration resistance. It can be used as a structural material for mechanical parts, etc.

[Conventional technology]

As a means to improve the toughness of alumina sintered bodies, zirconia-alumina ceramics in which tetragonal zirconia containing or not containing a stabilizer is dispersed in an alumina structure ([Ceramics J Vol, 17. No. 2. P1064
11 (1982), JP-A-54-25908, etc.), or zirconia-alumina ceramics with improved heat deterioration resistance and hardness by adding alumina to partially stabilized zirconia (JP-A-60-86073). )It has been known.

Problems to be solved by invention C] Conventionally known zirconia-alumina ceramics have excellent hardness and heat deterioration resistance, but it is difficult to make a sintered body dense, so it is difficult to create a stable sintered body. In order to obtain this, sintering at high temperature or sintering under high pressure (HIP treatment) is required, which is industrially unfavorable. Furthermore, high-temperature sintering is unfavorable in terms of strength because it involves grain growth of alumina and zirconia.

Further, in order to prevent thermal deterioration of the zirconia component in a low temperature range, there are usually methods of increasing the amount of stabilizer, but this method has the disadvantage of decreasing toughness and hardness.

An object of the present invention is to provide a high-strength zirconia-alumina ceramic with improved heat deterioration resistance, and a method for producing the same.

[Means for solving the invention]

The present invention is characterized in that A component mainly composed of zirconia is 5 to 99 mol%, A1g is 031 to 95 mol%, and transition metal oxide is 0.
In the zirconia-alumina ceramics consisting of ~1 mol%, the A component consists of v, o, 0-3 mol% Ti (h 0.5-30 mol% Zr0i 67-99 mol%, Y2O3 and T
This is a composite sintered body characterized in that iO□ is dissolved in ZrO□.

In the present invention, the crystal structure of component A of the sintered body is 80% or more tetragonal, and A f , 0. The crystal structure of l is 95
More than % is corundum.

In component A, the proportion of Y2O is more than 3.0 mol%,
Alternatively, if the TiO□ content exceeds 30 mol%, the toughness decreases, and if the TiO□ content is less than 0.5 mol%, the effect of improving the heat deterioration resistance of Zr0z is insufficient. According to the present invention, A component and A1□0. Regardless of the ratio, there is an effect of improving heat deterioration resistance, but zirconia-alumina ceramics with a content of component A of less than 5 mol% have insufficient toughness, and the effects of the present invention are not noticeable. So I don't like it. ^120. Zirconia-alumina ceramics with a content of less than 1 mol % do not have high heat deterioration resistance, and are therefore not preferred as high-strength, high-toughness ceramics. If the content of the transition metal oxide exceeds 1 mol %, the sintering properties will deteriorate.

Y2O in component A is Ah (if h is the main component, it does not necessarily need to be added, but when component A becomes the main component, it is added to stabilize the tetragonal crystal of ZrO□. Also, Ti0z can be used alone or together with Y2O and ZrO□
By dissolving it in solid solution, the heat deterioration resistance of the tetragonal crystal of z'Ot is improved.

Although the transition metal oxide is not essential to the present invention, it is desirable to add it to achieve more stable sintering at low temperatures.

The zirconia-alumina ceramics of the present invention is 'It
030-3 mol%, TiO□0.5-30 mol% and Z
r (h Consisting of 61 to 99 mol%, Y2O, and Ti
l□ is ZrO! After filtering, washing, and drying the powder obtained from the mixture consisting of component A powder or its precursor powder, α-alumina powder or its precursor powder, and, if necessary, a transition metal oxide precursor solution, which are solid-dissolved in It is manufactured by sintering the powder obtained by calcination. In the present invention, the term "precursor" refers to something that produces the oxide through calcination.

A component, Z in which Y20□ and/or TiO□ is solid-dissolved
The preparation of rO□ is obtained by mixing a mixed solution of a yttrium compound and/or a titanium compound and a zirconium compound with a precipitate forming liquid such as ammonia or nia water, and calcining the resulting mixed coprecipitated powder. The raw material compound may be any compound that is water-soluble, forms a precipitate upon pH adjustment, and becomes an oxide upon calcination. Specifically, examples of the zirconium compound include oxychlorides, oxynitrates, oxyacetates, oxysulfates, and the like. Examples of yttrium compounds include chlorides, nitrates, carboxylates, metal alkoxides, and the like. Examples of the titanium compound include titanium tetrachloride, titanyl sulfate, titanyl acetate, and the like.

＾１□0． The mixing of Al2O. and Zr
This is preferable in order to improve the dispersibility with O2 and obtain a powder with excellent sinterability.

In addition, when obtaining a sintered body containing transition metal oxides,
A mixed powder of component A powder or its precursor powder and ^1□03 or its precursor powder is mixed with a solution of a transition metal compound, and then the solvent is removed by complete drying or spray drying, and then calcined. This makes a sintered raw material powder. The transition metal compound to be used is not particularly limited as long as it produces an oxide by thermal decomposition (it can be used, but a compound that is soluble in water or an organic solvent is used as a solution. Specific examples include nitrates, etc.) Examples include inorganic compounds and organic acid salts such as carboxylic acid salts.

Although it is sufficient to compact the powder by ordinary molding, it is preferable to hydrostatically press the compact in order to improve the density, mechanical strength, etc. of the final sintered compact.

Although any known method may be used for sintering the molded body, normal pressure sintering in an air atmosphere can sufficiently achieve the purpose.

[Effect]

As mentioned above, high-temperature sintering is necessary to sinter the zirconia-alumina composite to a high density, and high-temperature sintering progresses grain growth and reduces the dispersibility of zirconia and alumina. Since the square yield rate of steel decreases, it is necessary to increase the amount of stabilizer, but in this case, the toughness value decreases. Furthermore, )11P processing has the disadvantage of high cost.

On the other hand, the stabilizer (Y
If zOi) is kept low, the heat deterioration resistance of zirconia decreases.

In the present invention, the solid solution effect of TiOz and Y2O on ZrO□ and 7. The dispersion sintering effect of rOt particles and 41201 particles and the low-temperature sintering promotion effect of transition metal oxides act synergistically to obtain a zirconia-alumina sintered body with high toughness and high strength with excellent heat deterioration resistance. I can do it.

〔Example〕

The present invention will be explained in more detail with reference to Examples.

(1) Production of raw material powder (1-1) The alumina powder shown in Table 1 was added to a mixed aqueous solution of ZrOCb, YCIz and TiC1m, or a mixed aqueous solution of Zr0C1z and TiC1a, stirred and dispersed, and then mixed with ammonia water. The pH was adjusted to obtain a coprecipitation mixture containing alumina. The coprecipitate was calcined at a predetermined temperature for 1 hour, and Y
ZrO□ in which 2O3 and or TiO□ are dissolved in ZrO2
・A1□0. A composite powder was obtained. The properties of the obtained powders are shown in Table 2 (powder numbers 1-1 to 1-3).

(]-2) Zirconia/alumina powder prepared in the same manner as above was added to an ethanol solution in which nitrates of various transition metals were dissolved and mixed by milling, then the ethanol was evaporated and dried, and the transition metal-added ZrO2/A1□ 03 composite powder was obtained. The properties of the obtained powders are shown in Table 2 (powder numbers 2-1 to 2-6).

(Comparative Example) In Comparative Examples 1 to 4, powders were obtained in the same manner as in the Example except that the composition was outside the range of the present invention. In Comparative Example 5, titanium tetrachloride was not added, but TiO□ particles were added to the calcined powder obtained by the same operation as in the example, and mixed by milling to obtain a sintered raw material powder.

Ti0t is not dissolved in ZrO2.

Table 1: Powder properties of raw material alumina (2) Production of sintered body After the raw material powder was pressure-molded, an additional 2t/cm
A molded body was obtained by isostatic pressing at a pressure of 100 ml. This molded body was sintered under normal pressure at the temperature shown in Table 3 for 3 hours to obtain a zirconia-alumina sintered body.

[Measurement of characteristics of raw material powder and sintered body] (A) BET specific surface area Micromeritics
(manufactured by Shimadzu Corporation).

(B) Fracture toughness value A via-curse indenter is driven into the mirror-polished surface of the sample.
It was calculated from the size of the obtained indentation and the length of the crack generated from the indentation using the following formula proposed by Shinryo et al. The driving load of the indenter was 30 kgf.

(Ko, φ/Ha' ”) (H/Eφ)0・4=
0.035 (1/a) -””Φ: Restraint coefficient (~3) H: Via-curse indenter E: Elastic modulus a: 1/2 of the diagonal length of the indentation 1: Length from the center of the indentation to the tip of the crack C) Bending strength 3 x 4 x 40m + m sample, JIS-160
Measurements were made based on the provisions of 1. Span: 301 IIm, crosshead speed: 0.5 mm/l1in. The average value of 5 samples manufactured under the same conditions was determined.

(F) Tetragonal phase content The surface of the sample was polished with a 3 μm diamond slurry, then subjected to X-ray diffraction, and calculated using the following formula.

(111)t+(111)m+(lli)m(111)
t: Tetragonal (111) plane diffraction intensity (111) w: Monoclinic (111) plane diffraction intensity (111) + m: Monoclinic (
The (111) plane diffraction intensity (111) diffraction peak includes the cubic (111) c diffraction peak, but all calculations were made assuming a square product.

It was confirmed that the tetragonal phase content of Zr0z in the sintered body was 95% or more in all samples except the comparative example.

(D) If a sample of a heat-resistant deterioration-resistant sintered body finished to a mirror finish with 3 μm of diamond slurry is held at 200°C for 200 hours, if the rate of decrease in the tetragonal crystal content of the mirror is within 5z (○), 5-2
If it was 0χ, it was marked (△), and if it was more than that, it was marked (×).

〔Effect of the invention〕

The heat deterioration resistant, high strength zirconia/alumina sintered body of the present invention has excellent heat deterioration resistance, high sintered density, fracture toughness value, high bending strength, and high hardness, as shown in the above examples.
It is a highly tough sintered body.

In the present invention, the heat deterioration resistance of zirconia is increased without impairing toughness by solid solution of a small amount of Y2O and/or TiO2 in ZrO□, and densification is promoted. Due to the dispersion effect and the sintering promotion effect of the transition metal, sintering progresses at low temperatures without grain growth, resulting in a low Y20. A high-strength, high-toughness sintered body with little thermal deterioration can be obtained while maintaining the high toughness of zirconia.

Therefore, it is expected to be applied to mechanical parts and the like as high-strength functional ceramics that require heat resistance.

Furthermore, since Y2O is an expensive material, reducing the Y2O content is economically effective.

The present invention provides a zirconia-alumina sintered body having high toughness and high strength and excellent heat deterioration resistance, and has great industrial significance.

Claims (6)

[Claims] (1) 5 to 99 mol% of A component whose main component is zirconia
, Al_2O_31-95 mol% and transition metal oxide 0
In the zirconia alumina ceramics consisting of ~1 mol%, the A component consists of Y_2O_30-3 mol%, TiO_20.5-30 mol%, ZrO_267-99 mol%, and Y_2O_3 and TiO_2 are dissolved in ZrO_2. Composite sintered body. (2) The composite sintered body according to claim (1), wherein 80% or more of the crystal structure of the A component particles is tetragonal, and 95% or more of the crystal structure of Al_2O_3 is corundum. (3) The transition metal oxide is MnO_2, Fe_2O_3,
The composite sintered body according to claim (1), which is at least one selected from the group consisting of CoO, NiO, CuO, and ZnO. (4) Y_2O_30~3 mol%, TiO_20.5~
Consisting of 30 mol% and ZrO_267-99 mol%,
A powder obtained from a mixture consisting of A component powder or its precursor powder in which Y_2O_3 and TiO_2 are dissolved in ZrO_2, α-alumina powder or its precursor powder, and if necessary a transition metal oxide precursor solution is sintered. 5 to 99 mol% of A component mainly composed of zirconia, A
l_2O_31-95 mol% and transition metal oxide 0-1
A method for manufacturing a composite sintered body, characterized by manufacturing a zirconia-alumina ceramic comprising mol%. (5) A component precursor and Al_2O_3 or Al_2O_3 precursor are co-precipitated from a dispersion of α-alumina powder or its precursor powder in a mixed solution of a titanium compound and a zirconium compound containing or not containing an yttrium compound. 4. A method according to claim 4, characterized in that a mixture with the body is obtained. (6) A component precursor and Al_2O_3 or Al_2O_
After calcining the mixture with 3 precursors, the powder is dispersed in a transition metal compound solution and the solvent is removed to obtain a mixed powder of component A, Al_2O_3, and transition metal oxide precursor. A method according to claim (5).