JPS6357388B2 - - Google Patents
Info
- Publication number
- JPS6357388B2 JPS6357388B2 JP59011061A JP1106184A JPS6357388B2 JP S6357388 B2 JPS6357388 B2 JP S6357388B2 JP 59011061 A JP59011061 A JP 59011061A JP 1106184 A JP1106184 A JP 1106184A JP S6357388 B2 JPS6357388 B2 JP S6357388B2
- Authority
- JP
- Japan
- Prior art keywords
- silicon nitride
- sintered body
- oxide
- powder
- nitride sintered
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 29
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 29
- 239000000843 powder Substances 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 12
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 10
- 239000011521 glass Substances 0.000 claims description 9
- 238000004519 manufacturing process Methods 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 9
- 229910052751 metal Inorganic materials 0.000 claims description 6
- 239000002184 metal Substances 0.000 claims description 6
- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 claims description 6
- 230000000737 periodic effect Effects 0.000 claims description 6
- 238000000465 moulding Methods 0.000 claims description 4
- 239000002775 capsule Substances 0.000 claims description 3
- 238000010304 firing Methods 0.000 claims description 2
- 239000002994 raw material Substances 0.000 claims 1
- 238000005245 sintering Methods 0.000 description 8
- 239000011230 binding agent Substances 0.000 description 5
- 239000013078 crystal Substances 0.000 description 5
- 238000000280 densification Methods 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 229910044991 metal oxide Inorganic materials 0.000 description 4
- 150000004706 metal oxides Chemical class 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 2
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 description 2
- 239000007858 starting material Substances 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 229910000420 cerium oxide Inorganic materials 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 229910003440 dysprosium oxide Inorganic materials 0.000 description 1
- NLQFUUYNQFMIJW-UHFFFAOYSA-N dysprosium(iii) oxide Chemical compound O=[Dy]O[Dy]=O NLQFUUYNQFMIJW-UHFFFAOYSA-N 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000003779 heat-resistant material Substances 0.000 description 1
- 238000001746 injection moulding Methods 0.000 description 1
- 238000000462 isostatic pressing Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000005121 nitriding Methods 0.000 description 1
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 1
- 239000012188 paraffin wax Substances 0.000 description 1
- 238000013001 point bending Methods 0.000 description 1
- 238000007788 roughening Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229920005992 thermoplastic resin Polymers 0.000 description 1
- -1 yttrium oxide Chemical class 0.000 description 1
Landscapes
- Ceramic Products (AREA)
Description
〔発明の技術分野〕
本発明は窒化ケイ素焼結体の製造方法に関し、
特に高温静水圧プレス（HIP）焼結法を用いた窒
化ケイ素焼結体の製造方法の改良に関する。
〔発明の技術的背景とその問題点〕
一般に窒化ケイ素はその結合様式が共有的であ
るために、耐熱性，耐食性，高強度の特長を有す
る。しかしながら、窒化ケイ素は安定な物質であ
ることから焼結が難しいため、多孔質の状態で合
成するか、もしくは焼結助剤を使つて緻密化する
ことが行なわれている。
例えば既にα型窒化ケイ素粉末に周期律表第
ａ族金属の酸化物（例えば酸化イツトリウム等）
とアルミナを加えたものをベースにし、必要に応
じて窒化アルミニウムや他の酸化物を加えた組成
物を出発物質として焼結し、強度の高い材料を得
る方法が知られている（特公昭49−21091号、特
公昭52−3649号等）。
ところで、窒化ケイ素などの耐熱材料はより高
温で使用することを期待する分野も少なくない。
特に、高温熱機関に用いる場合は1200℃以上の高
い温度での耐熱性が要求され、しかもかなりの熱
応力或いは機械的応力が必要とされているものが
多い。こうした要求に対して従来の窒化ケイ素焼
結体はかならずしも十分満足するものでなく、よ
り優れた機械的強度、特に高靭性の窒化ケイ素焼
結体の出現が要望されていた。
〔発明の目的〕
本発明は上記要望を満足すべくなされたもの
で、高緻密性で、かつ機械的強度、特に靫性の優
れた窒化ケイ素焼結体を簡単に製造し得る方法を
提供しようとするものである。
〔発明の概要〕
本発明者らは、窒化ケイ素粉末に周期律表第
ａ族金属の酸化物粉末とアルミナ粉末を添加した
組成物を出発原料として用いて成形し、この成形
体を常圧下にて熱処理し、熱処理した成形体をガ
ラスカプセルにて高温静水圧プレス焼成する工程
を具備した製造方法によつて、結晶粒径が柱状化
し、高靭性の窒化ケイ素焼結体を得られることを
見い出したものである。
以下、本発明を詳細に説明する。
まず、α含有量が65％以上の窒化ケイ素粉末に
周期律表第ａ族金属の酸化物粉末4.2〜12重量
％及びアルミナ粉末0.01〜８重量％添加して出発
原料である組成物を調製した。ここに用いる窒化
ケイ素粉末のα含有量を限定した理由は、α含有
量を65％未満にすると、十分な緻密化は可能であ
るが高強度化が困難となる。前記第ａ族金属酸
化物粉末は結晶粒の長柱状化に寄与するもので、
その添加量を4.2重量％未満にすると結晶粒の長
柱状化をかならずしも十分達成できず、かといつ
て12重量％を越えると、本来の窒化ケイ素に比べ
て第２，第３の反応生成物の量が増すため、焼結
体としての特性が低下してしまう。かかる第ａ
族金属酸化物としては、例えば酸化イツトリウ
ム，酸化セリウム，酸化ランタン，酸化ジスプロ
シウム等を挙げることができる。また、前記アル
ミナは焼結体の緻密化に寄与するもので、その添
加量を0.01重量％未満にすると、十分な緻密化を
達成できず、かといつて８重量％を越えると、窒
化ケイ素に比べて耐熱性、強度の低いアルミナ性
質が顕在化する。なお、第ａ族金属酸化物／ア
ルミナの比率は1.2以上にすることが望ましい。
次いで、前記組成物を均一に混合し、これにバ
インダを加えて成形する。バインダの種類と量は
成形方法に応じて適宜選定されるもので、通常の
金型成形では数％程度、射出成形では多量の例え
ば熱可塑性樹脂が用いられる。但し、このバイン
ダは成形後除去されるので直接焼結組成として関
与しない。つづいて、この成形体中のバインダを
除去する。
次いで、前記成形体を常圧下で1600〜1750℃の
範囲にて熱処理する。このように熱処理温度を限
定した理由は上記温度範囲を逸脱すると、この熱
処理工程において、密度を85％以上とする事がで
きず、また結晶粒の柱状化を充分達成できなくな
り、最終的な焼結体の靫性向上を図ることが難し
くなるからである。
次いで、熱処理した成形体をガラスカプセルの
中に入れて脱気して焼成し、成形体表面にガラス
を被覆するか、もしくは成形体表面にガラス成分
物質をコートして焼成し、ガラス層で成形体を覆
うか、いずれかにより成形体を外部環境から遮断
する。つづいて、1700〜2000℃，1000〜3000気圧
を条件でHIP焼結を行なつた後、ガラスを除去し
て窒化ケイ素焼結体を製造する。しかして、本発
明によれば高靭性化された緻密な窒化ケイ素焼結
体を得ることができる。このような優れた特性を
有する窒化ケイ素焼結体が得られるのは次のよう
な機構によるものと推定される。即ち、前述した
窒化ケイ素粉末，酸化イツトリウム等の第ａ族
金属酸化物及びアルミナからなる成形体をHIP焼
結する前に常圧もしくは減圧下で熱処理すると、
酸化イツトリウム濃度の高い粒界相を作り、その
結果、結晶粒の柱状化を顕著にもたらし、ひいて
は高靭性の焼結体が得られるものと推定される。
〔発明の実施例〕
次に、実施例の実施例を説明する。
実施例 １
まず、平均粒径1μm、α含有量95％の窒化ケイ
素粉末に平均粒径0.5μmの試薬級の酸化イツトリ
ウム粉末７重量％及び粒径0.3μm以下の試薬級の
アルミナ粉末２重量％を加え、これを充分に混合
した後、パラフイン（バインダ）を５重量％加え
て500Kg／cm2の条件で成形し、脱脂して37×37×
８mmの寸法の成形体を作製した。つづいて、この
成形体を窒化ガス300／hrの気流中にて常圧で
1650℃、２時間の熱処理を行なつた。次いで、こ
れをシリカガラス中に入れて脱気し、加熱してガ
ラスを被覆した後、1750℃、1000気圧の条件で２
時間のHIP焼結を行ない、更にガラスを回収して
窒化ケイ素焼結体を製造した。
得られた窒化ケイ素焼結体は焼結密度3.31ｇ／
c.c.、室温３点曲げ強度98Kg／mm2、破壊靭性値
（K1c）8.2MN／m3/2を示した。これに対し、実
施例１と同一組成で熱処理を行なわない場合（比
較例１）は緻密化については同等であつたもの
の、強度は87Kg／mm2、K1cは6.5MN／m3/2であつ
た。微構造観察では実施例１の焼結体は柱状結晶
粒の成長が認められたが、比較例１の焼結体は不
十分であつた。
実施例 ２〜５
実施例１の方法において、下記表に示す如く粗
成，製造条件を変えて５種の窒化ケイ素焼結体を
製造した。得られた焼結体の焼結密度及びK1cを
同表に併記した。なお、表中には比較例２，３，
４を併記した。
[Technical field of the invention] The present invention relates to a method for manufacturing a silicon nitride sintered body,
In particular, it relates to improvements in the manufacturing method of silicon nitride sintered bodies using the high temperature isostatic pressing (HIP) sintering method. [Technical Background of the Invention and Problems Therewith] In general, silicon nitride has a covalent bonding mode, and therefore has the features of heat resistance, corrosion resistance, and high strength. However, since silicon nitride is a stable substance, it is difficult to sinter it, so silicon nitride is synthesized in a porous state or densified using a sintering aid. For example, α-type silicon nitride powder already contains oxides of metals from group a of the periodic table (such as yttrium oxide, etc.).
A method is known in which a high-strength material is obtained by sintering a composition based on aluminum nitride and alumina, with aluminum nitride and other oxides added as needed. -21091, Special Publication No. 52-3649, etc.). By the way, there are many fields in which heat-resistant materials such as silicon nitride are expected to be used at higher temperatures.
In particular, when used in high-temperature heat engines, heat resistance at temperatures as high as 1200° C. or higher is required, and many require considerable thermal or mechanical stress. Conventional silicon nitride sintered bodies do not necessarily fully satisfy these demands, and there has been a demand for a silicon nitride sintered body with better mechanical strength, particularly high toughness. [Objective of the Invention] The present invention has been made to satisfy the above-mentioned needs, and it is an object of the present invention to provide a method for easily manufacturing a silicon nitride sintered body that is highly dense and has excellent mechanical strength, especially toughness. That is. [Summary of the Invention] The present inventors molded a composition obtained by adding silicon nitride powder, oxide powder of a group a metal of the periodic table, and alumina powder as a starting material, and molded the molded body under normal pressure. We have discovered that a silicon nitride sintered body with columnar grain size and high toughness can be obtained by a manufacturing method that includes the steps of heat-treating the molded body and firing the heat-treated molded body using a high-temperature isostatic press in a glass capsule. It is something that The present invention will be explained in detail below. First, a starting material composition was prepared by adding 4.2 to 12% by weight of an oxide powder of a Group A metal in the periodic table and 0.01 to 8% by weight of alumina powder to silicon nitride powder having an α content of 65% or more. . The reason for limiting the α content of the silicon nitride powder used here is that if the α content is less than 65%, sufficient densification is possible, but high strength is difficult to achieve. The Group A metal oxide powder contributes to making the crystal grains long columnar,
If the amount added is less than 4.2% by weight, it will not necessarily be possible to sufficiently form crystal grains into long columnar shapes, while if it exceeds 12% by weight, the amount of secondary and tertiary reaction products compared to the original silicon nitride will increase. As the amount increases, the properties of the sintered body deteriorate. Such a
Examples of group metal oxides include yttrium oxide, cerium oxide, lanthanum oxide, and dysprosium oxide. In addition, the alumina contributes to densification of the sintered body, and if the amount added is less than 0.01% by weight, sufficient densification cannot be achieved, while if it exceeds 8% by weight, silicon nitride In comparison, the properties of alumina, which have lower heat resistance and strength, become apparent. Note that the ratio of group a metal oxide/alumina is desirably 1.2 or more. Next, the composition is uniformly mixed, a binder is added thereto, and the mixture is molded. The type and amount of the binder are appropriately selected depending on the molding method; for example, a thermoplastic resin is used in an amount of about several percent in ordinary mold molding, and a large amount in injection molding. However, since this binder is removed after molding, it does not directly participate in the sintering composition. Subsequently, the binder in this molded body is removed. Next, the molded body is heat treated at a temperature of 1600 to 1750°C under normal pressure. The reason for limiting the heat treatment temperature in this way is that if the temperature exceeds the above temperature range, it will not be possible to achieve a density of 85% or more in this heat treatment process, and it will not be possible to achieve sufficient columnarization of crystal grains, resulting in the final sintering. This is because it becomes difficult to improve the viscosity of the body. Next, the heat-treated molded body is placed in a glass capsule, degassed and fired, and the surface of the molded body is coated with glass, or the surface of the molded body is coated with a glass component and fired, and molded with a glass layer. The molded body is shielded from the external environment by either covering the body or shielding the molded body from the external environment. Subsequently, HIP sintering is performed under the conditions of 1700 to 2000°C and 1000 to 3000 atmospheres, and then the glass is removed to produce a silicon nitride sintered body. Therefore, according to the present invention, a dense silicon nitride sintered body with high toughness can be obtained. The reason why a silicon nitride sintered body having such excellent properties is obtained is presumed to be due to the following mechanism. That is, if the molded body made of the silicon nitride powder, Group A metal oxide such as yttrium oxide, and alumina described above is heat treated under normal pressure or reduced pressure before HIP sintering,
It is presumed that a grain boundary phase with a high concentration of yttrium oxide is created, resulting in significant columnarization of crystal grains, and as a result, a highly tough sintered body is obtained. [Embodiments of the Invention] Next, embodiments of the invention will be described. Example 1 First, 7% by weight of reagent-grade yttrium oxide powder with an average particle size of 0.5 μm and 2% by weight of reagent-grade alumina powder with a particle size of 0.3 μm or less are added to silicon nitride powder with an average particle size of 1 μm and α content of 95%. After thoroughly mixing this, 5% by weight of paraffin (binder) was added and molded at 500Kg/ cm2 , degreased and 37x37x
A molded body with a size of 8 mm was produced. Next, this molded body was placed in a nitriding gas flow of 300/hr at normal pressure.
Heat treatment was performed at 1650°C for 2 hours. Next, this was placed in silica glass, degassed, heated to coat the glass, and then heated at 1750℃ and 1000 atm for 2 hours.
HIP sintering was performed for several hours, and the glass was recovered to produce a silicon nitride sintered body. The obtained silicon nitride sintered body has a sintered density of 3.31g/
cc, room temperature three-point bending strength of 98 Kg/mm 2 , and fracture toughness value (K 1c ) of 8.2 MN/m 3/2 . On the other hand, when the composition was the same as in Example 1 but no heat treatment was performed (Comparative Example 1), the densification was the same, but the strength was 87 Kg/mm 2 and the K 1c was 6.5 MN/m 3/2 . It was hot. Microstructural observation showed that the sintered body of Example 1 had grown columnar crystal grains, but the sintered body of Comparative Example 1 had insufficient growth. Examples 2 to 5 Using the method of Example 1, five types of silicon nitride sintered bodies were manufactured by changing the roughening and manufacturing conditions as shown in the table below. The sintered density and K 1c of the obtained sintered bodies are also listed in the same table. In addition, in the table, Comparative Examples 2, 3,
4 is also listed.
以上詳述した如く、本発明によれば高緻密性
で、かつ機械的強度、特に靭性に優れ高温熱機関
部材等に好適な窒化ケイ素焼結体の製造方法を提
供できる。
As detailed above, according to the present invention, it is possible to provide a method for manufacturing a silicon nitride sintered body that is highly dense, has excellent mechanical strength, particularly toughness, and is suitable for high-temperature heat engine parts.
Claims (1)
律表第ａ族金属の酸化物粉末4.2〜12重量％と
アルミナ粉末0.01〜８重量％を添加した組成物を
出発原料として用いて成形する工程と、この成形
体を常圧下で1600℃を越え1750℃までの範囲にて
熱処理する工程と、熱処理した成形体をガラスカ
プセルにて高温静水圧プレス焼成する工程とを具
備した事を特徴とする高靭性窒化ケイ素焼結体の
製造方法。 ２ 周期律表第ａ族金属の酸化物として酸化イ
ツトリウムを用いることを特徴とする特許請求の
範囲第１項記載の高靭性窒化ケイ素焼結体の製造
方法。 ３ 組成物中の周期律表第ａ族金属の酸化物／
アルミナの比を1.2以上にすることを特徴とする
特許請求の範囲第１項記載の高靭性窒化ケイ素焼
結体の製造方法。[Claims] 1 Starting from a composition in which 4.2 to 12% by weight of an oxide powder of a Group A metal of the periodic table and 0.01 to 8% by weight of alumina powder are added to silicon nitride powder with an α content of 65% or more. A process of molding using it as a raw material, a process of heat-treating the molded body under normal pressure at a temperature exceeding 1600℃ to 1750℃, and a process of firing the heat-treated molded body in a glass capsule using a high-temperature isostatic press. A method for manufacturing a high-toughness silicon nitride sintered body, characterized by the following: 2. The method for producing a high-toughness silicon nitride sintered body according to claim 1, characterized in that yttrium oxide is used as the oxide of a group a metal of the periodic table. 3 Oxide of group a metal of the periodic table in the composition/
2. The method for producing a high toughness silicon nitride sintered body according to claim 1, characterized in that the ratio of alumina is set to 1.2 or more.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59011061A JPS60155576A (en) | 1984-01-26 | 1984-01-26 | Manufacture of silicon nitride sintered body |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59011061A JPS60155576A (en) | 1984-01-26 | 1984-01-26 | Manufacture of silicon nitride sintered body |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS60155576A JPS60155576A (en) | 1985-08-15 |
| JPS6357388B2 true JPS6357388B2 (en) | 1988-11-11 |
Family
ID=11767487
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP59011061A Granted JPS60155576A (en) | 1984-01-26 | 1984-01-26 | Manufacture of silicon nitride sintered body |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS60155576A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4892848A (en) * | 1985-07-30 | 1990-01-09 | Kyocera Corporation | Silicon nitride sintered body and process for preparation thereof |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57123865A (en) * | 1981-01-27 | 1982-08-02 | Kobe Steel Ltd | Manufacture of high density silicon nitride sintered body |
| JPS5891074A (en) * | 1981-11-26 | 1983-05-30 | 株式会社東芝 | Manufacture of silicon nitride sintered body |
-
1984
- 1984-01-26 JP JP59011061A patent/JPS60155576A/en active Granted
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57123865A (en) * | 1981-01-27 | 1982-08-02 | Kobe Steel Ltd | Manufacture of high density silicon nitride sintered body |
| JPS5891074A (en) * | 1981-11-26 | 1983-05-30 | 株式会社東芝 | Manufacture of silicon nitride sintered body |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS60155576A (en) | 1985-08-15 |
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