JP2783711B2 - Silicon nitride sintered body - Google Patents
Silicon nitride sintered bodyInfo
- Publication number
- JP2783711B2 JP2783711B2 JP3284473A JP28447391A JP2783711B2 JP 2783711 B2 JP2783711 B2 JP 2783711B2 JP 3284473 A JP3284473 A JP 3284473A JP 28447391 A JP28447391 A JP 28447391A JP 2783711 B2 JP2783711 B2 JP 2783711B2
- Authority
- JP
- Japan
- Prior art keywords
- sintered body
- silicon nitride
- oxygen
- silicon
- phase
- 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 - Fee Related
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Description
【０００１】[0001]
【産業上の利用分野】本発明は、室温から高温までの強
度特性に優れ、特に、自動車用部品やガスタ−ビンエン
ジン用部品等に使用される窒化珪素質焼結体およびその
製造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon nitride sintered body having excellent strength characteristics from room temperature to a high temperature and particularly used for parts for automobiles and parts for gas turbine engines, and a method for producing the same.
【０００２】[0002]
【従来の技術】従来から、窒化珪素質焼結体は、耐熱
性、耐熱衝撃性および耐酸化性に優れることからエンジ
ニアリングセラミックス、特にターボロータ等の熱機関
用として応用が進められている。2. Description of the Related Art Hitherto, silicon nitride sintered bodies have been applied to engineering ceramics, particularly for heat engines such as turbo rotors, because of their excellent heat resistance, thermal shock resistance and oxidation resistance.
【０００３】窒化珪素は、それ自体難焼結性を有するこ
とから高密度で高強度の焼結体を作製するために焼結助
剤として希土類元素酸化物や酸化アルミニウムを添加す
ることが特公昭５２−３６４９号、特公昭５８−５１９
０号にて提案されている。[0003] Since silicon nitride itself has difficulty in sintering, it is necessary to add a rare earth element oxide or aluminum oxide as a sintering aid in order to produce a high density and high strength sintered body. No. 52-3649, JP-B-58-519
No. 0 is proposed.
【０００４】また、最近では、窒化珪素質焼結体中にＮ
ｂ、Ｔａ、Ｔｉ、Ｗ等の金属の化合物を添加することに
より焼結体の強度や靱性を高める方法等が特開昭６４−
８７５６８号にて提案されている。Recently, silicon nitride based sintered bodies have
A method of increasing the strength and toughness of a sintered body by adding a compound of a metal such as b, Ta, Ti, W, etc.
No. 87568.
【０００５】[0005]
【発明が解決しようとする問題点】しかしながら、焼結
助剤として酸化イットリウムと酸化アルミニウムを用い
た場合、その焼結性が高められ、高密度化できることに
より室温および高温における強度をある程度は向上する
ことができるが、実用的には未だ不十分であり、さらに
強度の改良が要求される。However, when yttrium oxide and aluminum oxide are used as sintering aids, their sinterability is enhanced and their densities can be increased, so that the strength at room temperature and high temperature is improved to some extent. However, it is still insufficient for practical use, and further improvement in strength is required.
【０００６】また、焼結体中にＴａ、Ｎｂ、Ｔｉ等を添
加する方法では、室温強度の向上を主たる目的とするも
ので、一般に室温で用いられる産業用構造材料として開
発されているのみで、高温特性についてはその検討がほ
とんどなされていないのが現状である。Further, the method of adding Ta, Nb, Ti, etc. to a sintered body has a main purpose of improving the strength at room temperature, and has been developed only as an industrial structural material generally used at room temperature. At present, little consideration has been given to high-temperature characteristics.
【０００７】よって、本発明の目的は、室温から高温域
まで自動車用部品やガスタ−ビンエンジン用部品等で使
用されるに充分な強度特性、特に、室温から１０００℃
の高温までの抗折強度に優れた窒化珪素質焼結体および
その製造方法を提供するにある。Accordingly, an object of the present invention is to provide strength characteristics sufficient for use in automobile parts and gas turbine engine parts from room temperature to a high temperature range, particularly from room temperature to 1000 ° C.
Another object of the present invention is to provide a silicon nitride based sintered body having excellent bending strength up to a high temperature and a method for producing the same.
【０００８】[0008]
【問題点を解決するための手段】本発明者等は、焼結体
の高温特性を高めるためには、焼結体の組成および焼結
体中の窒化珪素結晶相の形状や、窒化珪素結晶相の粒界
に存在する副相を制御することが重要であるという見地
に基づき、検討を重ねた結果、珪素が窒化物換算で６０
〜９３モル％、希土類元素の酸化物換算量、アルミニウ
ムの酸化物換算量および過剰酸素のＳｉＯ2 換算量の合
計量が６〜３９．９モル％、周期律表第５ａ族元素が酸
化物換算量で０．１〜１．０モル％の割合で存在するよ
うに制御するとともに、かかる焼結体を少なくともβ相
の窒化珪素結晶格子からなり該格子内で珪素の一部がア
ルミニウムにより置換され、且つ窒素の一部が酸素によ
り置換された主結晶相と、珪素、酸素および窒素からな
る結晶相と、周期律表第５ａ族元素の酸窒化物相よりな
る結晶相により構成することにより前述した目的が達成
されることを見出したものである。Means for Solving the Problems In order to enhance the high-temperature characteristics of the sintered body, the present inventors have studied the composition of the sintered body, the shape of the silicon nitride crystal phase in the sintered body, and the silicon nitride crystal. Based on the observation that it is important to control the sub-phases present at the grain boundaries of the phases, as a result of repeated studies, it was found that silicon
９３93 mol%, the total amount of rare earth elements in terms of oxides, the amount in terms of oxides of aluminum and the amount of excess oxygen in terms of SiO 2 is 6〜39.9 mol%, and the elements of Group 5a of the periodic table are in terms of oxides. The sintered body is made of at least a β-phase silicon nitride crystal lattice, and a part of silicon is replaced by aluminum in the lattice. And a crystal phase composed of a main crystal phase in which a part of nitrogen is replaced by oxygen, a crystal phase composed of silicon, oxygen and nitrogen, and a crystal phase composed of an oxynitride phase of a group 5a element in the periodic table. It has been found that the purpose achieved is achieved.
【０００９】以下、本発明を詳述する。本発明の窒化珪
素質焼結体を構成する元素は、珪素、希土類元素、アル
ミニウム、周期律表第５ａ族元素の金属成分と、酸素、
窒素の非金属元素よりなる。また本発明の窒化珪素質焼
結体中の酸素は、希土類元素、アルミニウムおよび周期
律表第５ａ族元素に化学量論量で結合している酸素の他
に過剰に存在する酸素（過剰酸素）が存在する。この過
剰酸素は、通常、焼結体の全酸素量から焼結助剤中、即
ち希土類元素酸化物、酸化アルミニウムさらに周期律表
第５ａ族元素酸化物として化学量論的に各元素に結合し
ている酸素を差し引くことにより算出される酸素量であ
り、そのほとんどは窒化珪素原料に含まれる酸素、ある
いは、ＳｉＯ2 等の添加物として混入するものであり、
本発明では全てＳｉＯ2 として存在するものとして考慮
する。Hereinafter, the present invention will be described in detail. Elements constituting the silicon nitride sintered body of the present invention include silicon, a rare earth element, aluminum, a metal component of a 5a group element of the periodic table, oxygen,
Consists of a non-metallic element of nitrogen. The oxygen in the silicon nitride-based sintered body of the present invention is oxygen present in excess (excess oxygen) in addition to oxygen stoichiometrically bonded to the rare earth element, aluminum and the group 5a element of the periodic table. Exists. Usually, this excess oxygen is stoichiometrically bonded to each element in the sintering aid, that is, as a rare earth element oxide, aluminum oxide and a Group 5a element oxide of the periodic table, based on the total oxygen content of the sintered body. It is the amount of oxygen calculated by subtracting the oxygen that is present, most of which is mixed with oxygen contained in the silicon nitride raw material or as an additive such as SiO 2 ,
In the present invention, all of them are considered as existing as SiO 2 .
【００１０】本発明の焼結体の結晶組織は、β相窒化珪
素結晶格子からなり該格子内で珪素の一部がアルミニウ
ムにより置換され、且つ、窒素の一部が酸素により置換
されたβ型ＳｉＡｌＯＮ（サイアロン）結晶相を主結晶
相とするものであり、さらに場合によってはこの結晶格
子中に希土類元素が一部混入する場合もある。また、こ
の主結晶相は一般に柱状形状を成すがその平均結晶粒径
（短径）が１．５μｍ以下、アスペクト比２〜１５であ
ることが強度、靱性向上の点から好ましい。The crystal structure of the sintered body of the present invention comprises a β-phase silicon nitride crystal lattice in which a part of silicon is replaced by aluminum and a part of nitrogen is replaced by oxygen. The SiAlON (Sialon) crystal phase is used as the main crystal phase, and in some cases, a rare earth element may be partially mixed in the crystal lattice. The main crystal phase generally has a columnar shape, but preferably has an average crystal grain size (short diameter) of 1.5 μm or less and an aspect ratio of 2 to 15 from the viewpoint of improving strength and toughness.
【００１１】本発明によれば、上記主結晶相の他に、副
相として珪素、酸素および窒素からなる結晶相が存在す
ることが大きな特徴である。この結晶相は例えば、Ｓｉ
2 Ｎ2 Ｏで表されるシリコンオキシナイトライド結晶相
からなるもので、この結晶相の存在により高温強度を高
めることができる。According to the present invention, a major feature is that a crystal phase composed of silicon, oxygen and nitrogen exists as a sub-phase in addition to the main crystal phase. This crystal phase is, for example, Si
Made of silicon oxynitride crystal phase represented by 2 N 2 O, it is possible to enhance the high-temperature strength due to the presence of the crystal phase.
【００１２】また本発明によれば、上記の結晶相の他に
周期律表第５ａ族元素の酸窒化相が存在することも重要
である。この結晶相は、窒化珪素結晶相の異常粒成長を
抑制し、微細な組織を生成するとともに特性的に焼結体
の室温および高温における強度を向上させることができ
る。According to the present invention, it is also important that an oxynitride phase of a Group 5a element of the periodic table exists in addition to the above-mentioned crystal phase. This crystal phase can suppress abnormal grain growth of the silicon nitride crystal phase, generate a fine structure, and characteristically improve the strength of the sintered body at room temperature and high temperature.
【００１３】なお、本発明の焼結体は、少なくとも上記
３種の結晶相により構成されるが、これらの結晶相以外
に、珪素、アルミニウム、酸素、希土類元素および窒素
からなるガラスよりなる粒界相が形成される場合がある
が、極力少ない方がよい。The sintered body of the present invention is composed of at least the above three crystal phases. In addition to these crystal phases, a grain boundary made of glass composed of silicon, aluminum, oxygen, a rare earth element and nitrogen is used. A phase may be formed, but it is better to minimize the phase.
【００１４】また、本発明の焼結体は、それぞれ珪素を
窒化物換算、周期律表第３ａ族元素を酸化物換算、アル
ミニウムを酸化物換算、周期律表第５ａ族元素を酸化物
換算過剰酸素をＳｉＯ2 換算した時、これらの合量を１
００モル％とした時に、珪素が窒化珪素換算で６０〜９
３モル％の割合で存在し、周期律表第３ａ族元素の酸化
物換算量、アルミニウムの酸化物換算量ならびに過剰酸
素のＳｉＯ2 換算量の合計が６．０〜３９．９モル％か
らなり、さらに周期律表第５ａ族元素が酸化物換算で
０．１〜１．０モル％の組成からなることも重要であ
る。In the sintered body of the present invention, silicon is converted into nitride, element of group 3a of the periodic table is converted into oxide, aluminum is converted into oxide, and element of group 5a of the periodic table is converted into oxide. When oxygen is converted to SiO 2 , the total amount of these is 1
When the molar ratio is set to 00 mol%, silicon is 60 to 9 in terms of silicon nitride.
It is present at a ratio of 3 mol%, and the total of the oxide equivalent of Group 3a element of the periodic table, the oxide equivalent of aluminum and the SiO 2 equivalent of excess oxygen is 6.0 to 39.9 mol%. It is also important that the Group 5a element of the periodic table has a composition of 0.1 to 1.0 mol% in terms of oxide.
【００１５】これは、希土類元素、アルミニウム、過剰
酸素の合量が６．０モル％より小さいと焼結過程で液相
が不足するために焼成温度を高くする必要があり、その
ために窒化珪素結晶粒子の成長が起こり強度の低下を引
き起こし、３９．９モル％より大きいと焼結体中の粒界
相が多くなり、高温強度が低下するとともにさらには高
温での耐酸化特性が劣化してしまうためである。また、
周期律表第５ａ族元素が０．１モル％より小さいと窒化
珪素粒子の粒成長を抑制することができず、強度低下を
引き起こし、１．０モル％より大きいと窒化珪素粒子の
針状化が抑制され、破壊靱性が低下してしまうからであ
る。If the total amount of the rare earth element, aluminum and excess oxygen is less than 6.0 mol%, the liquid phase becomes insufficient during the sintering process, so that it is necessary to raise the firing temperature. Grain growth occurs, causing a decrease in strength. If it exceeds 39.9 mol%, the number of grain boundary phases in the sintered body increases, so that high-temperature strength decreases and oxidation resistance at high temperatures deteriorates. That's why. Also,
If the Group 5a element of the periodic table is less than 0.1 mol%, the grain growth of the silicon nitride particles cannot be suppressed, causing a decrease in strength. If the element is more than 1.0 mol%, the silicon nitride particles become acicular. Is suppressed, and the fracture toughness is reduced.
【００１６】また、本発明によれば、前記主結晶相以外
の成分中、即ち珪素−希土類元素−アルミニウム−酸素
−窒素からなる粒界中の周期律表第３ａ族元素の酸化物
換算量（ＲＥ2 Ｏ3 ）と、過剰酸素の換算量（Ｓｉ
Ｏ2 ）のＳｉＯ2 ／ＲＥ2 Ｏ3 で表されるモル比が２以
上、特に４以上であることが望ましい。これは、ＳｉＯ
2 ／ＲＥ2 Ｏ3 モル比が２より低いと、珪素、酸素およ
び窒素からなる結晶相が生成されにくく、強度の低下を
招くためである。Further, according to the present invention, the oxide equivalent of the Group 3a element of the periodic table in the components other than the main crystal phase, that is, in the grain boundary composed of silicon-rare earth element-aluminum-oxygen-nitrogen ( RE 2 O 3 ) and the amount of excess oxygen (Si
It is preferable that the molar ratio of O 2 ) expressed by SiO 2 / RE 2 O 3 is 2 or more, particularly 4 or more. This is SiO
When the 2 / RE 2 O 3 molar ratio is lower than 2, a crystal phase composed of silicon, oxygen and nitrogen is hardly generated, and the strength is reduced.
【００１７】本発明に用いられる希土類元素としてはＹ
やランタノイド系元素が挙げられるが、これらの中でも
Ｙｂ2 Ｏ3 、Ｅｒ2 Ｏ3 、Ｈｏ2 Ｏ3 、Ｄｙ2 Ｏ3 を用
いると焼結体の均一性および強度等の特性の改善効果が
特に優れている。また、周期律表第５ａ族元素として
は、Ｎｂ、Ｖ、Ｔａが挙げられるが、これらの中でもＮ
ｂが最も効果が大きい。The rare earth element used in the present invention is Y
And lanthanoid elements. Among them, when Yb 2 O 3 , Er 2 O 3 , Ho 2 O 3 , and Dy 2 O 3 are used, the effect of improving properties such as uniformity and strength of the sintered body is particularly improved. Are better. Examples of Group 5a elements in the periodic table include Nb, V, and Ta.
b is the most effective.
【００１８】本発明の窒化珪素質焼結体を製造するため
の一例を説明すると、まず、原料粉末として窒化珪素粉
末、希土類元素酸化物粉末、酸化アルミニウム粉末およ
び周期律表第５ａ族元素酸化物粉末を用い、場合によっ
てはさらに酸化珪素粉末を用いる。An example for producing the silicon nitride sintered body of the present invention will be described. First, silicon nitride powder, rare earth element oxide powder, aluminum oxide powder and group 5a element oxide of the periodic table are used as raw material powders. A powder is used, and in some cases, a silicon oxide powder is further used.
【００１９】窒化珪素粉末は、それ自体α−Ｓｉ
3 Ｎ4 、β−Ｓｉ3 Ｎ4 のいずれでも用いることがで
き、それらの粒径は０．４〜１．２μｍであることが望
ましい。また、窒化珪素粉末には不純物酸素が不可避的
に含有されるが、この酸素は過剰酸素形成成分として考
慮する。The silicon nitride powder itself is α-Si
Either 3 N 4 or β-Si 3 N 4 can be used, and their particle diameter is desirably 0.4 to 1.2 μm. Although silicon nitride powder inevitably contains impurity oxygen, this oxygen is considered as an excess oxygen forming component.
【００２０】本発明によれば、これらの粉末を用いて窒
化珪素（Ｓｉ3 Ｎ4 ）が６０〜９３モル％、特に６８〜
８５モル％、希土類元素酸化物（ＲＥ2 Ｏ3 ）、酸化ア
ルミニウム（Ａｌ2 Ｏ3 ）、過剰酸素（ＳｉＯ2 換算
量）の合量が６．０乃至３９．９モル％、特に１４．２
乃至３１．８モル％、周期律表第５ａ族元素酸化物を
０．１乃至１．０モル％、特に０．２乃至０．８モル％
になるように調製、混合する。この時の過剰酸素（Ｓｉ
Ｏ2 ）とは、窒化珪素粉末に含まれる不純物酸素をＳｉ
Ｏ2 換算した量と添加する酸化珪素粉末との合量であ
る。According to the present invention, using these powders, silicon nitride (Si 3 N 4 ) is contained in an amount of 60 to 93 mol%, especially 68 to 93 mol%.
85 mol%, the total amount of rare earth element oxide (RE 2 O 3 ), aluminum oxide (Al 2 O 3 ) and excess oxygen (SiO 2 equivalent) is 6.0 to 39.9 mol%, especially 14.2
0.1 to 1.0 mol%, particularly 0.2 to 0.8 mol% of the Group 5a element oxide of the periodic table.
Prepare and mix so that At this time, excess oxygen (Si
O 2 ) means that the impurity oxygen contained in the silicon nitride powder is converted to Si
It is the total amount of the O 2 converted amount and the silicon oxide powder to be added.
【００２１】また、上記配合組成において、過剰酸素
（ＳｉＯ2 換算量）の希土類元素酸化物（ＲＥ2 Ｏ3 ）
に対するモル比（ＳｉＯ2 ／ＲＥ2 Ｏ3 ）を２以上、特
に４以上に設定する。In the above composition, a rare earth element oxide (RE 2 O 3 ) containing excess oxygen (equivalent to SiO 2 )
The molar ratio (SiO 2 / RE 2 O 3 ) is set to 2 or more, especially 4 or more.
【００２２】このようにして得られた混合粉末を公知の
成形方法、例えば、プレス成形、鋳込み成形、押出し成
形、射出成形、冷間静水圧成形などにより所望の形状に
成形する。The mixed powder thus obtained is formed into a desired shape by a known molding method, for example, press molding, cast molding, extrusion molding, injection molding, cold isostatic pressing and the like.
【００２３】そして、得られた成形体を公知の焼成方
法、例えば、ホットプレス方法、常圧焼成、窒素ガス圧
力焼成、さらにはこれら焼成後の焼結体を１０００気圧
以上の高圧中で熱間静水圧焼成するか、あるいは焼結体
の表面にガラスシールを形成して前記と同様に熱間静水
圧焼成し高緻密化を図ることができる。この時の焼成温
度は、高温すぎると窒化珪素結晶が粒成長し強度が低下
するために１９００℃以下、特に１６５０〜１８００℃
の窒素ガス含有非酸化性雰囲気であることが望ましい。The obtained compact is fired in a known firing method, for example, a hot pressing method, normal pressure firing, nitrogen gas pressure firing, and further, the fired sintered body is subjected to hot pressing at a pressure of 1000 atm or more. Either isostatic firing or forming a glass seal on the surface of the sintered body and hot isostatic firing in the same manner as described above to achieve high density. If the firing temperature at this time is too high, the silicon nitride crystal grows grains and the strength is reduced.
It is desirable to use a non-oxidizing atmosphere containing nitrogen gas.
【００２４】この焼成によれば、酸化アルミニウムと窒
化珪素の反応によりβ相の窒化珪素格子からなり、該格
子内で珪素の一部がアルミニウムにより置換され、且つ
窒素の一部が酸素により置換された結晶が生成する。ま
た、その粒界には未反応の酸化アルミニウム、Ｓｉ
Ｏ2 、希土類元素酸化物および窒化ケイ素が存在する
が、焼成後の冷却過程で珪素、窒素および酸素よりなる
結晶相が析出し、この結晶化に寄与しなかった成分が、
ガラス相として残存する。一方、周期律表第５ａ族元素
は酸化物の一部が焼結過程で窒素置換されることにより
酸窒化物結晶が生成される。According to this firing, a β-phase silicon nitride lattice is formed by the reaction between aluminum oxide and silicon nitride, in which part of silicon is replaced by aluminum and part of nitrogen is replaced by oxygen. Crystals are formed. In addition, unreacted aluminum oxide, Si
O 2 , a rare earth oxide and silicon nitride are present, but a crystal phase consisting of silicon, nitrogen and oxygen precipitates in the cooling process after firing, and a component that has not contributed to this crystallization is
It remains as a glass phase. On the other hand, in the Group 5a element of the periodic table, an oxynitride crystal is generated by part of the oxide being replaced with nitrogen in the sintering process.
【００２５】また、焼結−冷却過程で珪素、窒素および
酸素よりなる結晶相の析出が不十分である場合には得ら
れた焼結体を１０００〜１５００℃の非酸化性雰囲気中
で処理することにより結晶相を生成することができる。If the precipitation of the crystal phase composed of silicon, nitrogen and oxygen during the sintering and cooling process is insufficient, the obtained sintered body is treated in a non-oxidizing atmosphere at 1000 to 1500 ° C. Thereby, a crystal phase can be generated.
【００２６】[0026]
【作用】窒化珪素質焼結体を構成する主結晶相は、適当
なアスペクト比と大きさをもち、高信頼性を得るために
は異常成長粒子が存在しない事が必要である。その為に
は、適当量の粒界相が必要で、かつ従来の希土類元素酸
化物と酸化アルミニウムの添加だけではなく、ＳｉＯ2
を所定の割合で添加することで焼結過程で生成する液相
の融点が低下し、低温焼成が可能となり、それにより窒
化珪素粒子の高温での粒成長を抑制でき、微細な針状組
織を形成することができる。The main crystal phase constituting the silicon nitride sintered body has an appropriate aspect ratio and size, and it is necessary that no abnormally grown particles exist in order to obtain high reliability. For that purpose, an appropriate amount of the grain boundary phase is necessary, and not only the addition of the conventional rare earth element oxide and aluminum oxide, but also SiO 2
By adding at a predetermined ratio, the melting point of the liquid phase generated in the sintering process is lowered, and low-temperature sintering becomes possible, whereby the grain growth of silicon nitride particles at a high temperature can be suppressed, and a fine needle-like structure Can be formed.
【００２７】また、周期律表第５ａ族元素酸化物の添加
により、焼結過程で酸化物が酸窒化物に変化することに
より他の成分からなる粒界相に溶解せず酸窒化物相とし
て残存するために、この酸窒化物相が窒化珪素粒子の成
長を更に抑制し、微細でアスペクト比の揃った均一な組
織を形成することができる。The addition of the Group 5a element oxide of the periodic table changes the oxide into an oxynitride during the sintering process, so that the oxide does not dissolve in the grain boundary phase composed of other components but forms an oxynitride phase. Since the oxynitride phase remains, the oxynitride phase further suppresses the growth of silicon nitride particles, and a fine and uniform structure having a uniform aspect ratio can be formed.
【００２８】さらに焼結体中に珪素、酸素、窒素からな
る結晶相を形成させることにより主結晶相以外の粒界成
分の高温安定化が図られ、これにより焼結体の室温およ
び高温における強度とともに靱性をも高めることができ
る。Further, by forming a crystal phase composed of silicon, oxygen, and nitrogen in the sintered body, high-temperature stabilization of the grain boundary components other than the main crystal phase is achieved, whereby the strength of the sintered body at room temperature and high temperature is achieved. In addition, the toughness can be increased.
【００２９】[0029]
実施例１ 原料粉末として窒化珪素粉末（ＢＥＴ比表面積８ｍ2 ／
ｇ、α率９８％、酸素量１．２重量％）と各種希土類元
素酸化物粉末、酸化珪素粉末、酸化アルミニウム粉末な
らびに周期律表第５ａ族元素酸化物粉末を用いて、表１
に示す組成になるように調合して混合後、１ｔ／ｃｍ2
で金形プレス成形した。得られた成形体を炭化珪素質の
匣鉢に入れて、カ−ボンヒ−タ−を用い、常圧にて窒素
ガス気流中１７５０℃で４時間焼成し、焼結体を得た。Example 1 A silicon nitride powder (BET specific surface area 8 m 2 /
g, α ratio of 98%, oxygen content of 1.2% by weight) and various rare earth element oxide powders, silicon oxide powder, aluminum oxide powder and Group 5a element oxide powder of the periodic table.
After mixing and mixing to obtain the composition shown in (1), 1 t / cm 2
Was press-molded. The obtained molded body was placed in a silicon carbide sagger and fired at 1750 ° C. for 4 hours in a nitrogen gas stream at normal pressure using a carbon heater to obtain a sintered body.
【００３０】得られた焼結体の組成を、酸素窒素分析及
びＩＣＰ分析によるＳｉ、ＲＥ、Ａｌ量から求めた。
又、焼結体の粒界相の組成は得られた焼結体から薄片を
切出しアトムシンイング後、分析顕微鏡を用い、ＵＴＷ
−ＥＤＸ法により求めた。結果を表１に示した。The composition of the obtained sintered body was determined from the amounts of Si, RE and Al by oxygen nitrogen analysis and ICP analysis.
Further, the composition of the grain boundary phase of the sintered body was determined by cutting a thin slice from the obtained sintered body, performing atom thinning, and using an analytical microscope to measure the UTW.
-Determined by the EDX method. The results are shown in Table 1.
【００３１】[0031]
【表１】 [Table 1]
【００３２】得られた焼結体をＪＩＳ−Ｒ１６０１にて
指定される形状まで研磨し試料を作成した。この試料に
ついてアルキメデス法に基づく比重測定、窒化珪素結晶
の平均結晶粒径（短径）およびその平均アスペクト比を
電子顕微鏡写真から測定し、ＪＩＳ−Ｒ１６０１に基づ
く室温および１０００℃での４点曲げ抗折強度試験を実
施し、さらに破壊靱性の測定を行った。またＸ線回折測
定により焼結体中の結晶を同定した。結果は表２に示し
た。The obtained sintered body was polished to a shape specified by JIS-R1601 to prepare a sample. The specific gravity of this sample was measured based on the Archimedes method, the average crystal grain size (short diameter) of the silicon nitride crystal and the average aspect ratio thereof were measured from an electron micrograph. A bending strength test was performed, and the fracture toughness was measured. Further, crystals in the sintered body were identified by X-ray diffraction measurement. The results are shown in Table 2.
【００３３】[0033]
【表２】 [Table 2]
【００３４】表１および表２の結果によると、Ｓｉ3 Ｎ
4 が６０モル％未満でＲＥ2 Ｏ3 、Ａｌ2 Ｏ3 、ＳｉＯ
2 の合量が３９．９モル％を越えるＮo,２の焼結体は高
温強度が低下しており、Ｓｉ3 Ｎ4 が９３モル％を越
え、ＲＥ2 Ｏ3 、Ａｌ2 Ｏ3 、ＳｉＯ2 の合量が６モル
％未満のＮo,８の焼結体は緻密化不足で強度も低下して
いた。また、第５ａ族元素が無添加のＮo,１の焼結体は
室温強度が低下し、第５ａ族元素が１．０モル％を越え
るＮo,１２の焼結体は破壊靱性と室温強度が低下してい
た。According to the results of Tables 1 and 2, Si 3 N
4 is less than 60 mol%, and RE 2 O 3 , Al 2 O 3 , SiO
The sintered body of No, 2 having a total amount of more than 39.9 mol% of 2 has a low high-temperature strength, and the content of Si 3 N 4 exceeds 93 mol%, and RE 2 O 3 , Al 2 O 3 , SiO 2 The sintered body of No, 8 having a total amount of 2 less than 6 mol% had a low strength due to insufficient densification. In addition, the sintered body of No, 1 containing no Group 5a element has a reduced room temperature strength, and the sintered body of No, 12 containing a Group 5a element exceeding 1.0 mol% has fracture toughness and room temperature strength. Had declined.
【００３５】これらの比較例に対し、本発明の焼結体は
いずれも優れた抗折強度、破壊靱性を示していた。さら
に、ＳｉＯ2 ／ＲＥ2 Ｏ3 モル比が４以上のＮo,３、Ｎ
o,４、Ｎo,５、Ｎo,７、Ｎo,１３〜Ｎo,１７の焼結体は
さらに優れた抗折強度、破壊靱性を示していた。In contrast to these comparative examples, all of the sintered bodies of the present invention exhibited excellent bending strength and fracture toughness. Further, when the SiO 2 / RE 2 O 3 molar ratio is 4 or more,
The sintered bodies of o, 4, No, 5, No, 7, and No. 13 to No. 17 exhibited more excellent bending strength and fracture toughness.
【００３６】[0036]
【発明の効果】以上詳述した通り、本発明によれば、周
期律表第５ａ族元素酸化物の添加および周期律表第５ａ
族元素酸窒化物相の生成により主結晶相の粒成長を抑制
するとともに、高温域での焼結助剤等の添加物を安定化
することができ、これにより室温から高温において高い
強度と靱性を得ることができる。As described in detail above, according to the present invention, the addition of an element oxide of Group 5a of the Periodic Table and the addition of 5a
Generation of group oxynitride phase suppresses the grain growth of the main crystal phase and stabilizes additives such as sintering aids at high temperatures, thereby achieving high strength and toughness from room temperature to high temperature. Can be obtained.
【００３７】よって、ガスタービンやターボロータ等の
熱機関用構造材料をはじめとし、各種の室温や高温にて
使用される構造用材料として用いることができる。Therefore, it can be used as a structural material used at various room temperatures or high temperatures, including structural materials for heat engines such as gas turbines and turbo rotors.
Claims (2)
土類元素の酸化物換算量、アルミニウムの酸化物換算量
および過剰酸素のＳｉＯ2 換算量の合計量が６〜３９．
９モル％、周期律表第５ａ族元素が酸化物換算量で０．
１〜１．０モル％の割合で存在し、且つβ相の窒化珪素
結晶格子からなり該格子内で珪素の一部がアルミニウム
により置換され、且つ窒素の一部が酸素により置換され
た主結晶相と、珪素、酸素および窒素からなる結晶相
と、周期律表第５ａ族元素の酸窒化物相よりなる結晶相
を含むことを特徴とする窒化珪素質焼結体。(1) The silicon content is 60 to 93 mol% in terms of nitride, and the total amount of oxides of rare earth elements, oxides of aluminum and SiO 2 of excess oxygen is 6 to 39.
9 mol%, the element of Group 5a of the periodic table being 0.1% in terms of oxide.
A main crystal which is present at a ratio of 1 to 1.0 mol% and comprises a β-phase silicon nitride crystal lattice in which a part of silicon is substituted by aluminum and a part of nitrogen is substituted by oxygen in the lattice. A silicon nitride-based sintered body comprising a phase, a crystal phase composed of silicon, oxygen and nitrogen, and a crystal phase composed of an oxynitride phase of a Group 5a element of the periodic table.
元素の酸化物換算量 (ＲＥ2 Ｏ3 ）と、過剰酸素のＳｉ
Ｏ2 換算量（ＳｉＯ2 ）とのＳｉＯ2 ／ＲＥ2 Ｏ3で表
されるモル比が２以上である請求項１記載の窒化珪素質
焼結体。2. The amount of the rare earth element in terms of oxide (RE 2 O 3 ) in the components other than the main crystal phase, and the excess oxygen Si
O 2 equivalent amount (SiO 2) and SiO 2 / RE 2 molar ratio represented by O 3 is larger than 2, claim 1 of silicon nitride sintered body according to.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3284473A JP2783711B2 (en) | 1991-10-30 | 1991-10-30 | Silicon nitride sintered body |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3284473A JP2783711B2 (en) | 1991-10-30 | 1991-10-30 | Silicon nitride sintered body |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05117031A JPH05117031A (en) | 1993-05-14 |
| JP2783711B2 true JP2783711B2 (en) | 1998-08-06 |
Family
ID=17678983
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3284473A Expired - Fee Related JP2783711B2 (en) | 1991-10-30 | 1991-10-30 | Silicon nitride sintered body |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2783711B2 (en) |
-
1991
- 1991-10-30 JP JP3284473A patent/JP2783711B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH05117031A (en) | 1993-05-14 |
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