Method of producing sintered body

Abstract

To provide a production method capable of suppressing lowering of yield in a method of producing a sintered body consisting of a sintered body of zirconia including titanium and containing not less than 5 mol% and not more than 10 mol% of yttrium in terms of Y2O3, and a sintered body of zirconia including iron / cobalt composite oxide and titanium and containing not less than 2 mol% and less than 5 mol% of yttrium in terms of Y2O3, as an opaque zirconia segment.SOLUTION: There is provided a production method including a sintering step of sintering a secondary molding formed by laminating a zirconia molding including titanium and containing not less than 5 mol% and not more than 10 mol% of yttrium in terms of Y2O3 and a zirconia molding including iron / cobalt composite oxide and titanium and containing not less than 2 mol% and less than 5 mol% of yttrium in terms of Y2O3. The method of producing a sintered body consisting of a sintered body of zirconia including titanium and containing not less than 5 mol% and not more than 10 mol% of yttrium in terms of Y2O3 and a sintered body of zirconia including iron / cobalt composite oxide and titanium and containing not less than 2 mol% and less than 5 mol% of yttrium in terms of Y2O3, is characterized by including a defatting step of defatting the secondary molding in a pressurized nitrogen atmosphere prior to the sintering step.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a sintered body. [Background technology]

[0002] A zirconia sintered body having a transparent zirconia portion and a zirconia portion and having a biaxial bending strength of 300 MPa or more is known as a zirconia sintered body that can be used in a wider range of applications than conventional ceramic joined bodies containing transparent zirconia (Patent Document 1). Patent Document 1 discloses a sintered body consisting of a zirconia sintered body containing titanium and 10 mol % yttrium calculated as Y2O3 as the transparent zirconia portion, and a zirconia sintered body containing titanium and a composite oxide of iron and cobalt as the opaque zirconia portion, and 4 mol % yttrium calculated as Y2O3. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-121576 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the sintered body of Patent Document 1 is prone to defects when repeatedly produced, resulting in a low final yield.

[0005] An object of the present disclosure is to provide a manufacturing method capable of suppressing a decrease in yield in a manufacturing method for a sintered body including a zirconia sintered body containing titanium and 5 mol % to 10 mol % of yttrium calculated as Y2O3, and a zirconia sintered body containing, as an opaque zirconia portion, a composite oxide of iron and cobalt and titanium and 2 mol % to less than 5 mol % of yttrium calculated as Y2O3. [Means for solving the problem]

[0006] This disclosure investigates a method for producing a sintered body consisting of a zirconia sintered body containing titanium and 5 mol% to 10 mol% yttrium in terms of Y2O3, and a zirconia sintered body containing a composite oxide of iron and cobalt and titanium, and 2 mol% to less than 5 mol% yttrium in terms of Y2O3. As a result, it was found that the yield in the debinding process significantly affects the yield of the final sintered body, and that the debinding atmosphere affects the debinding behavior. In addition, it was found that the air atmosphere promotes the generation of defects during debinding. Furthermore, it was found that the generation of defects during the debinding process can be significantly suppressed by controlling the debinding atmosphere.

[0007] That is, the present invention is as described in the claims, and the gist of the present disclosure is as follows. [1] A manufacturing method including a sintering step of sintering a degreased body of a secondary molded body formed by stacking a zirconia molded body containing titanium and 5 mol% to 10 mol% of yttrium calculated as Y2O3, and a zirconia molded body containing a composite oxide of iron and cobalt and titanium and containing 2 mol% to less than 5 mol% of yttrium calculated as Y2O3, characterized in that prior to the sintering step, a degreasing step of degreasing the secondary molded body in a pressurized nitrogen atmosphere to form a degreased body is included. [Effects of the Invention]

[0008] The present disclosure can provide a manufacturing method capable of suppressing a decrease in yield in a manufacturing method for a sintered body including a zirconia sintered body containing titanium and 10 mol % of yttrium calculated as Y2O3, and a zirconia sintered body containing a composite oxide of iron and cobalt and titanium and 4 mol % of yttrium calculated as Y2O3. DETAILED DESCRIPTION OF THE INVENTION

[0009] The manufacturing method of the present disclosure will be described below with reference to an example embodiment. The present disclosure also includes any combination of the configurations and parameters disclosed herein, and any combination of the upper and lower limits of the values ​​disclosed herein.

[0010] The present embodiment is a manufacturing method for a sintered body including a zirconia sintered body containing titanium and containing 5 mol % to 10 mol % of yttrium calculated as Y2O3, and a zirconia sintered body containing a composite oxide of iron and cobalt and titanium and containing 2 mol % to less than 5 mol % of yttrium calculated as Y2O3, which includes a sintering step of sintering a degreased body of a secondary molded body formed by stacking these bodies, characterized in that the sintering step further includes a degreasing step of degreasing the secondary molded body in a pressurized nitrogen atmosphere to obtain a degreased body.

[0011] The compact to be subjected to the sintering step is a degreased secondary compact (hereinafter also simply referred to as "secondary compact") in which a zirconia compact containing titanium and 5 mol% to 10 mol% of yttrium calculated as Y2O3 and a zirconia compact containing a composite oxide of iron and cobalt and titanium and 2 mol% to less than 5 mol% of yttrium calculated as Y2O3 are laminated together. The secondary compact contains a binder to improve its formability and shape retention. The secondary compact undergoes a degreasing step prior to the sintering step, whereby the binder is removed from the secondary compact, making it a so-called degreased compact.

[0012] The manufacturing method of this embodiment includes a degreasing step of degreasing the secondary compact in a nitrogen atmosphere prior to the sintering step. The degreasing step is a step of heat-treating the compact (powder compact) to remove the binder. This results in a degreased body. Therefore, the secondary compact subjected to the degreasing step is a laminated compact of a zirconia compact containing titanium and 5 mol% to 10 mol% of yttrium calculated as Y2O3, and a zirconia compact containing a composite oxide of iron and cobalt and titanium and 2 mol% to less than 5 mol% of yttrium calculated as Y2O3, and also containing a binder.

[0013] In the degreasing process of this embodiment, the degreasing atmosphere is a pressurized nitrogen atmosphere. One of the reasons why using a nitrogen atmosphere for the degreasing improves yield is thought to be the following. Conventional degreasing processes, including those described in Patent Document 1, are performed in an air atmosphere. However, degreasing in an air atmosphere causes thermal oxidative decomposition due to a reaction between the binder and oxygen. Because thermal oxidative decomposition is an exothermic reaction, localized heat is generated throughout the secondary molded body during the degreasing process, rapidly promoting localized reactions such as further volatilization and decomposition of the binder. As a result, degreasing in an air atmosphere is thought to cause defects such as cracks due to the occurrence of localized reactions. In contrast, degreasing in a nitrogen atmosphere does not cause thermal oxidative decomposition, making it less likely to generate localized heat and less likely to cause defects such as cracks.

[0014] Furthermore, one of the reasons why using a pressurized nitrogen atmosphere as the debinding atmosphere is effective in improving yield is thought to be the following. Specifically, when debinding is performed in a pressurized atmosphere, the number of surrounding gas molecules that collide with the green body per unit time is greater than when debinding is performed in an atmospheric pressure atmosphere. As a result, the amount of heat that propagates from the green body to the surrounding gas increases, making it easier for the green body's heat to diffuse. This makes it easier for the heat generated by the debinding to be released into the surrounding gas (gas molecules). As a result, it is thought that sudden volatilization and decomposition reactions of the binder are less likely to occur, suppressing defects such as cracks.

[0015] The conditions for the degreasing step include the following.

[0016] Heating rate: 0.5℃ / hour to 200℃ / hour Degreasing temperature: 150℃ or higher and 800℃ or lower Degreasing pressure: 1.5 atmospheres or more and 50 atmospheres or less The holding time at the debinding temperature may be adjusted appropriately depending on the shape and size of the compact to be subjected to the debinding step and the characteristics of the heat treatment furnace to be used, and may be, for example, from 0.5 hours to 5 hours.

[0017] For the sintering in the sintering step, any known sintering method can be applied except that the secondary molded body (degreased body) obtained in the above-mentioned degreasing step is used, and it is preferable to apply the sintering method disclosed in Patent Document 1. [Example]

[0018] The present disclosure will be described below with reference to examples, but the present disclosure is not limited to the following examples.

[0019] Example 1 A ceramic composition containing 5.5 mol% yttrium-containing zirconia powder (product name: Zpex-Smile, manufactured by Tosoh Corporation) and a binder was injection molded at an injection pressure of 120 MPa to obtain a cylindrical compact (green compact; injection molded body) with a diameter of 10 mm and a height of 10 mm. Next, a ceramic composition containing 4 mol% yttrium-containing zirconia powder (product name: Zpex4.m, manufactured by Tosoh Corporation) and a binder was injection molded at an injection pressure of 120 MPa to cover the periphery of the primary compact, to obtain a cylindrical compact (green compact; injection molded body) with a diameter of 40 mm and a height of 10 mm. Nine secondary compacts were produced by repeating the same procedure. Each of the obtained secondary compacts was heat-treated (degreased) under the following conditions to obtain the degreased body of this example. Degreasing atmosphere: Nitrogen atmosphere Pressure: 2 atmospheres Heating rate: 5°C / hour Degreasing temperature: 450℃ Holding time: 2 hours

[0020] The obtained degreased bodies were subjected to pre-sintering, hot isostatic pressing (HIP) treatment, and annealing under the following conditions respectively to obtain the sintered bodies of this example. <Pre-sintering> Pre-sintering method: Sintering under normal pressure Atmosphere: Air atmosphere Heating rate: 100 °C / hour Pre-sintering temperature: 1350 °C Holding time: 2 hours <HIP treatment> Atmosphere: Argon atmosphere Heating rate: 600 °C / hour HIP treatment temperature: 1525 °C Holding time: 1 hour <Annealing> Atmosphere: Air atmosphere Heating rate: 100 °C / hour Annealing temperature: 900 °C Holding time: 1 hour

[0021] Comparative Example 1 The degreased bodies and sintered bodies of this comparative example were obtained in the same manner as in Example 1, except that the pressure in the heat treatment (degreasing) was set to atmospheric pressure (1 atm), and 10 formed bodies were produced.

[0022] The obtained degreased bodies and sintered bodies were visually inspected, cracks and interfacial cracks between two materials were regarded as defects, and the percentage of the number of non-defective parts to the total number [pieces] produced was taken as the yield. The results are shown in the following table.

[0023]

Table 1

[0024] From the above table, it was confirmed that degreasing in a pressurized nitrogen atmosphere significantly improved the yield of the degreased body itself, and as a result, the yield of the sintered body also improved. Furthermore, the yield of the sintered body from the degreased body was 100%, and in the manufacturing method of the example, no defects were observed during the HIP treatment and the subsequent annealing treatment.

Claims

[Request 1] Contains titanium, Y ２ O ３ A zirconia molded body containing 5 mol % to 10 mol % of yttrium in terms of yttrium conversion, a composite oxide of iron and cobalt, and titanium, ２ O ３ A manufacturing method for a zirconia molded body containing 2 mol % or more and less than 5 mol % of yttrium in terms of yttrium content, and a sintering step of sintering a laminated secondary molded body, characterized in that prior to the sintering step, a degreasing step of degreasing the secondary molded body in a pressurized nitrogen atmosphere is carried out. ２ O ３ A zirconia sintered body containing 5 mol % to 10 mol % of yttrium in terms of yttrium conversion, a composite oxide of iron and cobalt, and titanium, ２ O ３ A method for producing a sintered body made of zirconia containing 2 mol% or more and less than 5 mol% of yttrium in terms of yttrium content.

Images