JPS60215571A - Manufacturing method for high-strength zirconia-based sintered bodies - 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 The present invention relates to a method for producing an extremely high-strength zirconia sintered body made of zirconia containing a small amount of a stabilizer and alumina, an alumina-magnesia oxide, or an alumina-silica oxide.

In recent years, zirconia sintered bodies (hereinafter abbreviated as Y-PSZ sintered bodies) containing square pieces to which a small amount of IJA (IJA) has been added as a stabilizer have been developed to be used in mechanical structures because they exhibit high strength and toughness. Development of its use as a material is becoming more active. On the other hand, regarding the Y-PSZ-Al, O, based sintered body,
Literature (Journal Materials Science 17, 24
7-254 (1982)) and Japanese Unexamined Patent Publication No. 58-32066, the bending strength of these reported sintered bodies is at most about 1200 MPa, and it is difficult to define a sufficiently satisfactory strength. Good and difficult. Therefore, by making these strengths even higher, the uses of the sintered body can be greatly expanded, and sintered bodies for this purpose are being sought.

In view of these circumstances, the present inventors have conducted extensive research in order to further improve the strength characteristics of Y-PSZ sintered bodies. By hot isostatic pressing using zirconia powder obtained by thermally decomposing precipitate, a zirconia sintered body with much higher strength than conventional Y-PSZ sintered body is produced. Find out what you can get,
The present invention has now been completed.

That is, the present invention provides salts, organometallic compounds, or Ammonium carbonate is added to an aqueous solution containing an oxide, the resulting precipitate is thermally decomposed to obtain a zirconia-based powder, and the powder is further heated at a pressure of 50 MPa or more for 1
The present invention provides a method for producing a high-strength zirconia-based sintered body by hot isostatic pressing at a temperature of 300 to 1700°C.

The present invention will be explained in more detail below.

The sintered body obtained by the method of the present invention is yttrium.

Zirconia 50-98 containing 1.5-5 mol% of lanthanum or lanthanum-based rare earth element oxide as a stabilizer
% by weight and 50 to 2% by weight of alumina, alumina-magnesia-based oxide or alumina-silica-based oxide,
Moreover, it is a high-strength zirconia-based sintered body with a three-point bending strength of 1700 MPa or more.

In order to obtain the high-strength zirconia-based sintered body, raw material powder with excellent sinterability must be used. This is because the strength of the sintered body depends extremely sensitively on the sinterability of the raw material powder. For this purpose, (a) zirconium, (b)
) and (c) a salt, organometallic compound or oxide of aluminum, ammonium carbonate is added to an aqueous solution, a precipitate is formed, and then thermally decomposed, the resulting product has excellent sinterability. Obtain zirconia powder.

Further, as the aqueous solution (c), an aqueous solution containing a magnesium or silicon salt, an organometallic compound, or an oxide in addition to aluminum may be used.

As the starting material compound, chlorides such as zirconium oxychloride, aluminum chloride, magnesium chloride, and yttrium chloride, as well as nitrates, sulfates, and the like can be used. Furthermore, silicon oxides and stabilizer oxides can also be used.

These starting material compounds are used as zirconia-based sintered bodies.
An aqueous solution is prepared by dissolving an appropriately selected amount to achieve the above-mentioned composition ratio.

Although ammonium carbonate may be added as it is, it is preferable to form it into an aqueous solution. The addition method is based on the pH of the solution.
It is preferable to add it all at once to the solution while stirring vigorously so that the ratio is around 9.

In addition, as a thermal decomposition method, after separating and drying the precipitated product produced by the addition of ammonium carbonate, the
Preferably, the temperature is 1150°C.

If it is carried out at a temperature of 1150° C. or higher, strong bonds between powder particles will occur, and the powder will not have excellent sinterability.

According to the method of the invention, the precipitated product contains carbonate radicals,
Furthermore, during the thermal decomposition process, the contained carbonate radicals are violently scattered, so that it is possible to obtain a zirconia-based powder in which bonding between powder particles is difficult to occur, so-called weak secondary aggregation.

The average primary particle size of the zirconia-based powder is preferably [L1 μm or less].

Furthermore, the zirconia powder obtained by the method of the present invention is
Compared to powders obtained by evaporating an aqueous solution containing metal ions of each constituent component to dryness and then thermally decomposing it, or by thermally decomposing a precipitate produced by adding aqueous ammonia to a similar aqueous solution, When put together, it makes a decisive difference. That is, the powder produced by the method of the present invention yields a dense sintered body having a bulk density of 98% or more of the theoretical density at a sintering temperature of 1400° C. under normal pressure, whereas powder produced by other methods produces a bulk density of 95% or less. Therefore, the sintered body contains many crack-like cavities. These crack-like cavities cause a significant decrease in the strength of the sintered body. Therefore, even in the case of pressureless sintering, the bending strength of the powder produced by the method of the present invention is 1000 MP.
However, other method powders give only about 600 MPa.

In the present invention, the powder is further subjected to hot isostatic pressing (
(hereinafter abbreviated as H-P). H
Processing methods include vacuum sealing the powder compact in a capsule made of glass, metal, etc., and press sintering; or pre-sintering the powder compact under normal pressure, and then re-sintering it using a press machine. There are two known methods for doing this. Although either method is possible in the method of the present invention, the latter method does not require an encapsulation operation and is advantageous in terms of productivity. The conditions for the H-P treatment are a pressure of 50 MPa or more and a temperature of 1300 to 1700°C.
It is necessary to do so. Under these conditions, 1700 MPa
A zirconia-based sintered body having a strength of the above can be obtained. If the pressure is 50 MPa or less and the temperature is 1300° C. or less, the expected high strength sintered body will not be obtained.

Even if powder obtained by other methods is treated with H-P according to the present invention, 1
Only a sintered body of about 200 MPa can be obtained.

In the preliminary sintering, a compact preliminary sintered body is obtained by forming the zirconia-based powder into a compact by a rubber pressing method or the like, and then sintering it at 1200 to 1500°C.

The stabilizer in the present invention is an oxide of yttrium, lanthanum, or a lanthanum-based rare earth element, and the amount thereof may be in the range of 1.5 to 5 mol% relative to zirconia.

In addition, zirconia and alumina containing other stabilizers, alumina
The proportion of magnesia-based brew or alumina-silica-based oxide must be 50,150 to 98/2 (wt%); outside this range, it is not possible to obtain an unprecedented bending strength of 1700 MPa or more.

Furthermore, in the zirconia-based sintered body obtained by the method of the present invention, the crystalline phase of zirconia must be mainly tetragonal or a mixed phase of tetragonal and cubic crystals. However, monoclinic crystals may coexist as other phases as long as they are 60% by weight or less. Further, the average particle diameter of the sintered crystals is 2 μm or less. The presence of crystal grains of 2 μm or more is not preferable because it becomes thermally unstable and tends to transition from tetragonal crystal to monoclinic crystal. In other words, 200-300℃
If the sintered body is kept at a relatively low temperature for a long period of time, the sintered body will crack and break due to volume expansion due to the transition from tetragonal to monoclinic. By setting the thickness to 2 μm or less, it becomes possible to suppress the phenomenon of thermal deterioration over time.

When a compound of aluminum laminate and magnesium is used as the starting material, spinel is the main crystalline phase in the alumina-magnesia-based oxide, and when a compound of aluminum and silicon is used, mullite is the main crystal phase in the alumina-silica-based oxide, and zirconia is used as the main crystal phase. This is the form that exists in the system sintered body.

As explained above, the sintered body obtained by the method of the present invention is a zirconia-based sintered body with a high strength of 1700 MPa or more, which has not been seen before, and is a mechanical structural material (cutting tool,
useful as dies, nozzles, bearings, etc.).

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited thereto.

Raw material powder production example 1 Zirconium oxychloride solution (zroJl !l O1
9/I 788rrLl and aluminum chloride solution (A-
A solution of 560 rrtl (box concentration 10'', 59/1) and 96 g of ittria dissolved in hydrochloric acid was placed in a container and stirred vigorously, and ammonium carbonate (Nl (, ), 0
035009 to ammonia water (NH3 content 13%) 14
00m/ solution was added at once. The obtained precipitate was filtered, dried in a vacuum dryer, and then calcined at a temperature of 1000°C for 1 hour to obtain lh500! ;1 of zirconia-alumina powder (zro2:Al, os weight ratio = 80:20 ZrO,:Y2os molar ratio = 98:2) was obtained.

Powders having zirconia and alumina weight ratios of 98:2, 90:10, and 60:40 were prepared by similar operations. Powders were also obtained in the same manner with different amounts of alumina added for powders in which the mole percent of Y and O5 in ZrO2 was 5 mole percent and 4 mole percent. In order to examine the sinterability of these powders, the powders were molded by an all-powder rubber press method and then fired at 1400° C. for 2 hours to obtain sintered bodies. All sintered compact densities have reached 98% or more of the theoretical density,
It was found that it had excellent sinterability.

Raw material powder production example 2 Zirconium oxychloride solution used in Example 1.

Aluminum chloride solution 1 Add a magnesium chloride solution (MgO concentration 40-4
9/1) Add 5BOrttl and add fla while stirring.
By adding 1400 ml of ammonia water (NH5 content 12%) containing ammonium 5009, filtering and drying the resulting precipitate, and calcining it at 1050°C for 1 hour, approximately 6
009 zirconia-spinel powder (ZrO2: A
1tMgo4 weight ratio = 75:25) was obtained.

Also, instead of the magnesium chloride solution, zirconia-mullite powder (ZrO2: 3A120.2SiO2 weight ratio =
75:25) was obtained. Further, powders having different contents of spinel and mullite were synthesized by changing the amounts added and repeating the above operation.

The sinterability of the powders was examined by the method described in Example 1, and the sintered body densities all reached 98% or more of the theoretical density.

Raw material powder production example 3 Zirconium oxychloride solution, aluminum chloride solution I
Aqueous ammonia containing ammonium carbonate is added to a solution in which a predetermined amount of D72'/' hydrochloric acid solution is mixed to obtain a precipitate.
After filtering and drying it, it was calcined at 950°C for 3 hours to obtain a zirconia-alumina powder. Also, D7
A powder of the present invention was obtained by the above operation using a hydrochloric acid solution of YbA instead of tOs. In order to examine the sinterability of these powders, sintered bodies were prepared by the method described in Example 1, and their densities were measured. All densities reached 98% or more of the theoretical density.

Production Example of Sintered Body Raw Material Powder Production Using the powders obtained in Examples 1 to 6, the powders obtained in Examples 1 to 6 were made into sintered bodies with a thickness of 9 widths and a length of 4 tons each.
nm, 40ms+, 56mm, and pre-sintered this molded body at 1400°C for 2 hours to form H-P.
This was used as a preliminary sintered body for processing. This preliminary sintered body was subjected to H-P treatment in Ar gas for 0.5 hours under the conditions of 1300 to 1700°C and 250 to 200M a as shown in Table 1 to obtain the zirconia-based sintered body of the present invention. Regarding the sintered body thus produced, the crystal phase, average particle diameter, and bending strength of Zr11)2 were measured. These results are shown in Table 1.

In addition, the measurement of 5-point bending strength is 'JIF3 R1601
- Based on 1981, a test specimen with a width of 4 mm, a thickness of 5 mm, a length of 40 mm, a span length of 30 mm, and a crosshead speed of Q
, 5 ram/min, and the values in Table 1 are the average values of 10 or more specimens.

Claims (3)

[Claims] (1) Salts, organometallic compounds, or oxides of (a) zirconium, (b) yttrium, lanthanum, or lanthanum-based rare earth elements as stabilizers, and (C) aluminum, aluminum and magnesium, or aluminum and silicon. ammonium carbonate is added to an aqueous solution containing , the resulting precipitate is thermally decomposed to obtain a zirconia powder, and the powder is further heated under a pressure of 50 MPa or more. A method for producing a zirconia-based sintered body, characterized by hot isostatic pressing at a temperature of 1300 to 1700°C. (2) The zirconia-based sintered body contains a stabilizer of 1.5 to 5
Claim No. 1, comprising 50 to 98% by weight of zirconia containing mol% and 50 to 2% by weight of alumina, alumina-magnesia-based oxide, or alumina-silica-based oxide (
1) A method for producing a zirconia-based sintered body as described in section 1). (3) Three-point bending strength of zirconia-based sintered body is 1700
Claims (1) or (2) which is MPa or more
2) A method for producing a zirconia-based sintered body as described in section 2). (Claim No. 1) in which the zirconia crystal phase constituting the zirconia-based sintered body is mainly tetragonal or consists of tetragonal and cubic crystals, and the average particle size of the sintered body crystals is 2 μm or less. A method for producing a zirconia-based sintered body according to any one of paragraphs to (3).