JP2708136B2 - Silicon nitride sintered body and method for producing the same - Google Patents
Silicon nitride sintered body and method for producing the sameInfo
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- JP2708136B2 JP2708136B2 JP2410989A JP41098990A JP2708136B2 JP 2708136 B2 JP2708136 B2 JP 2708136B2 JP 2410989 A JP2410989 A JP 2410989A JP 41098990 A JP41098990 A JP 41098990A JP 2708136 B2 JP2708136 B2 JP 2708136B2
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- oxide
- silicon nitride
- sintered body
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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】近時、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
５８−５１９０号にて検討されている。Recently, it has been known 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 (JP-B-52-3649, JP-B-58-5190). Is being considered.
【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、室温強度の向上は認められるが、高温
強度の向上に関してはその検討がなされていない。[0006] In the method of adding Ta, Nb, Ti or the like to the sintered body, improvement in room temperature strength is recognized, but no study has been made on improvement in high temperature strength.
【０００７】[0007]
【発明の目的】本発明の目的は、室温から高温まで自動
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。SUMMARY OF THE INVENTION An object of the present invention is to provide a strength characteristic sufficient for use in automobile parts and gas turbine engine parts from room temperature to high temperature, and particularly to a bending strength from room temperature to high temperature of 1000 ° C. An object of the present invention is to provide an excellent silicon nitride sintered body 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、窒化珪素を主体し、これ
に希土類元素酸化物、酸化アルミニウムならびに酸化珪
素を添加した系に対して、さらに周期律表第５ａ族元素
酸化物を添加し、これを成形焼成し、得られる焼結体中
に珪素、酸素および窒素から構成される結晶質の粒界相
を析出させるとともに、周期律表第５ａ族元素の酸窒化
物からなる相を析出させることによって優れた高温特性
を有する焼結体が得られることを知見した。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 view that it is important to control the sub-phases present at the grain boundaries of the phase, as a result of repeated investigations, a system in which silicon nitride is the main component, and rare earth element oxides, aluminum oxide and silicon oxide are added thereto Is further added with a Group 5a element oxide of the periodic table, which is formed and fired to precipitate a crystalline grain boundary phase composed of silicon, oxygen and nitrogen in the obtained sintered body. It has been found that a sintered body having excellent high-temperature characteristics can be obtained by precipitating a phase composed of an oxynitride of a Group 5a element of the periodic table.
【０００９】以下、本発明を詳述する。本発明の窒化珪
素質焼結体は、窒化珪素を主成分とし、これに添加成分
として希土類元素、アルミニウムおよび過剰酸素、さら
に周期律表第５ａ族元素を含むものである。Hereinafter, the present invention will be described in detail. The silicon nitride-based sintered body of the present invention contains silicon nitride as a main component, and further contains a rare earth element, aluminum, excess oxygen, and a Group 5a element of the periodic table as additional components.
【００１０】ここで、過剰酸素とは焼結体の全酸素量か
ら焼結助剤中、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除く残りの酸素量であり、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。Here, the excess oxygen is defined as a rare earth element oxide, aluminum oxide, or a Group 5a element oxide of the periodic table in the sintering aid based on the total oxygen content of the sintered body. The remaining amount of oxygen excluding the bound oxygen, most of which is contained in the silicon nitride raw material, or
It is mixed as an additive such as SiO 2 , and is considered in the present invention as being present as all SiO 2 .
【００１１】本発明の焼結体は、窒化珪素結晶相を主相
とするものであり、そのほとんどはβ−Ｓｉ3 Ｎ4 結晶
からなるが、場合によっては少量の酸化アルミニウム
（Ａｌ2 Ｏ3 ）が固溶し、Ｓｉ−Ａｌ−Ｏ−Ｎ（サイア
ロン）を形成することもある。また、この主相は一般に
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 sintered body of the present invention has a silicon nitride crystal phase as a main phase, and most of the sintered body is composed of β-Si 3 N 4 crystals. In some cases, a small amount of aluminum oxide (Al 2 O 3) is used. ) May form a solid solution to form Si-Al-ON (Sialon). The main phase generally has a columnar shape, and has an average crystal grain size (short diameter) of 1.5 μm.
Hereinafter, it is preferable that the aspect ratio is 2 to 15 from the viewpoint of improving strength and toughness.
【００１２】本発明によれば、上記主相の粒界に副相と
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、Ｓｉ2 Ｎ
2 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 at a grain boundary of the main phase. This crystal phase is, for example, Si 2 N
It consists of a silicon oxynitride crystal phase represented by 2 O, and the high temperature strength can be increased by the presence of this crystal phase.
【００１３】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、室温および高温における強度が向上する。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 suppresses abnormal grain growth of the silicon nitride crystal phase and improves strength at room temperature and high temperature.
【００１４】本発明の焼結体中には上記３種の結晶相が
生成されるが、これらの結晶相の粒界には珪素、アルミ
ニウム、酸素、希土類元素からなる粒界相が形成され
る。この粒界相は、それ自体非晶質、結晶相のいずれで
あっても差し支えない。The above three types of crystal phases are formed in the sintered body of the present invention, and a grain boundary phase composed of silicon, aluminum, oxygen and a rare earth element is formed at the grain boundaries of these crystal phases. . The grain boundary phase may be either an amorphous phase or a crystalline phase.
【００１５】また、本発明の焼結体は、窒化珪素が６０
〜９３モル％、特に６８〜８５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％、特に１4.２〜３1.８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％、特に0.２〜0.８モル％の組成からなるこ
とも重要である。Further, the sintered body of the present invention has a silicon nitride of 60%.
-93 mol%, especially 68-85 mol%,
The total of the oxide equivalent of the Group 3a element of the periodic table, the oxide equivalent of aluminum and the excess oxygen equivalent of SiO 2 is 6.0 to 39.9 mol%, particularly 14.2 to 31.8 mol%. And the group 5a element of the periodic table is 0.1% in terms of oxide.
It is also important to have a composition of .about.1.0 mol%, especially 0.2-0.8 mol%.
【００１６】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、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成長が
起こるために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。This is because 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, and it is necessary to raise the firing temperature. Particle 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 the high-temperature strength is reduced and the oxidation resistance at high temperatures is further deteriorated. For the reason, Periodic Table No. 5a
When the group-group element is less than 0.1 mol%, the growth of silicon nitride particles occurs, causing a decrease in strength. When the group element is more than 1.0 mol%, needle-like formation of the silicon nitride particles is suppressed, and the fracture toughness decreases. It is because.
【００１７】また、本発明によれば、周期律表第３ａ族
元素の酸化物換算量をＲＥ2 Ｏ3 、アルニウムの酸化物
換算量をＡｌ2 Ｏ3 とした時、過剰酸素のＳｉＯ2 換算
量とのＳｉＯ2 ／ＲＥ2 Ｏ3 で表されるモル比が２以
上、特に２〜２５、および、Ａｌ2 Ｏ3 ／（ＳｉＯ2 ＋
ＲＥ2 Ｏ3 ）で表されるモル比が１／１５〜５／４、特
に0.１〜1.０であることが望ましい。これは、ＳｉＯ2
／ＲＥ2 Ｏ3 モル比が２以下では、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、また、Ａｌ2 Ｏ3 ／（ＳｉＯ2 ＋ＲＥ2 Ｏ3 ）
モル比が１／１５より小さいと焼結性が低下し高密度の
焼結体を得ることが難しく、５／４より大きいと、Ａｌ
2 Ｏ3 により低融点物質の生成が多くなり高温における
強度および耐酸化特性が劣化してしまうからである。According to the present invention, when the oxide equivalent of Group 3a element of the periodic table is RE 2 O 3 and the oxide equivalent of alnium is Al 2 O 3 , the excess oxygen is equivalent to SiO 2. The molar ratio expressed by SiO 2 / RE 2 O 3 with respect to the amount is 2 or more, especially 2 to 25, and Al 2 O 3 / (SiO 2 +
It is desirable that the molar ratio represented by RE 2 O 3 ) is 1/15 to 5/4, particularly 0.1 to 1.0. This is SiO 2
When the / RE 2 O 3 molar ratio is 2 or less, a crystal phase composed of silicon, oxygen and nitrogen is hardly generated, which causes a decrease in strength. Al 2 O 3 / (SiO 2 + RE 2 O 3 )
If the molar ratio is less than 1/15, the sinterability deteriorates, and it is difficult to obtain a high-density sintered body.
This is because 2 O 3 increases the generation of low-melting-point substances and deteriorates the strength and oxidation resistance at high temperatures.
【００１８】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挙げられるが、これらの中でもＹ
ｂ2 Ｏ3 、Ｅｒ2 Ｏ3 、Ｈｏ2 Ｏ3 、Ｄｙ2 Ｏ3 が焼結
体の均一性および、強度の点から好ましい。The rare earth element used in the present invention is Y
And lanthanoid elements, among which Y
b 2 O 3 , Er 2 O 3 , Ho 2 O 3 , and Dy 2 O 3 are preferable in terms of uniformity and strength of the sintered body.
【００１９】また、周期律表第５ａ族元素としては、Ｎ
ｂ、Ｖ、Ｔａが挙げられるが、これらの中でもＮｂが最
も効果が大きい。In addition, as an element of Group 5a of the periodic table, N
Among them, b, V, and Ta are listed, and among these, Nb is the most effective.
【００２０】本発明の窒化珪素質焼結体の製造方法によ
れば、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。According to the method for producing a silicon nitride-based sintered body of the present invention, silicon nitride powder, rare earth element oxide powder, aluminum oxide powder and group 5a element oxide powder of the periodic table are used as raw material powders. In some cases, a silicon oxide powder is further used.
【００２１】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。The silicon nitride powder itself is α-Si
3 N 4, can be used either in β-Si 3 N 4, it is desirable that their particle size is 0.4～1.2Myuemu.
【００２２】本発明によれば、これらの粉末を用いて窒
化珪素（Ｓｉ3Ｎ4 ）が６０乃至９３モル％、特に６８
乃至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（ＳｉＯ2 ）とは、窒
化珪素粉末に含まれる不純物酸素をＳｉＯ2 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, silicon nitride (Si 3 N 4 ) is used in an amount of 60 to 93 mol%, particularly 68
To 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 to 31.8 mol%, and an oxide of a Group 5a element of the periodic table in an amount of 0.1 to 3
It is prepared and mixed so as to be 1.0 mol%, especially 0.2 to 0.8 mol%. The excess oxygen (SiO 2 ) at this time is the total amount of the amount of impurity oxygen contained in the silicon nitride powder in terms of SiO 2 and the amount of the silicon oxide powder to be added.
【００２３】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, casting molding, extrusion molding, injection molding, cold isostatic pressing and the like.
【００２４】次に、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、これらの焼成後のＨＩＰ焼成、および、
ガラスシ−ルＨＩＰ焼成等で焼成し、緻密な焼結体を得
る。この時の焼成温度は、高温しぎると窒化珪素結晶が
粒成長し強度が低下するため、１９００℃以下、特に１
７００〜１８００℃の窒素ガス含有非酸化性雰囲気であ
ることが望ましい。Next, the obtained molded body is fired by a known firing method,
For example, hot press method, normal pressure firing, nitrogen gas pressure firing, and further, HIP firing after firing, and
It is fired by glass seal HIP firing or the like to obtain a dense sintered body. The firing temperature at this time is 1900 ° C. or less, particularly 1
A non-oxidizing atmosphere containing nitrogen gas at 700 to 1800 ° C. is desirable.
【００２５】この焼成によれば、添加成分のほとんどは
窒化珪素結晶相の粒界に存在するが、これらのうち周期
律表第５ａ族元素は酸化物の一部が窒素置換されること
により酸窒化物が生成される。一方、その他の添加物に
より、珪素、窒素、酸素からなる結晶相と、珪素、アル
ミニウム、酸素、窒素からなる粒界相が形成されるが、
条件によって珪素、窒素、酸素からなる結晶相が生成さ
れない場合には、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。According to this calcination, most of the added components are present at the grain boundaries of the silicon nitride crystal phase, and among these, the Group 5a element of the periodic table has an oxide obtained by partially substituting the oxide with nitrogen. Nitride is produced. On the other hand, other additives form a crystal phase composed of silicon, nitrogen and oxygen, and a grain boundary phase composed of silicon, aluminum, oxygen and nitrogen.
When a crystal phase consisting of silicon, nitrogen and oxygen is not generated depending on the conditions, the obtained sintered body is 1000 to 1500
By treating in a non-oxidizing atmosphere at a temperature of ° C., a crystalline phase can be generated.
【００２６】[0026]
【作用】窒化珪素結晶粒子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、窒化珪素粒子の成長を抑制でき、微細な組織を形
成することができる。The silicon nitride crystal grains have an appropriate aspect ratio and size, and in order to obtain high reliability, it is necessary that no abnormally grown grains exist. For that purpose, an appropriate amount of the grain boundary phase is necessary, and the melting point of the liquid phase generated in the sintering process is lowered by adding SiO 2 in addition to the conventional rare earth element oxide and aluminum oxide. In addition, low-temperature sintering becomes possible, growth of silicon nitride particles can be suppressed, and a fine structure can be formed.
【００２７】さらに、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。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窒化
珪素結晶相以外の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を高めるととも
に靱性をも高めることができる。Further, 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 is not dissolved in the grain boundary phase composed of other components, but as 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. Further, silicon in the sintered body,
By forming a crystal phase composed of oxygen and nitrogen, components other than the silicon nitride crystal phase are stabilized at a high temperature, whereby the strength and the toughness of the sintered body at room temperature and high temperature can be increased.
【００２８】[0028]
【実施例】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
示す組成なるように調合して混合後、１ｔ／ｃｍ2 で金
形プレス成形した。EXAMPLES Example 1 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 powders, aluminum oxide powders and Group 5a element oxide powders of the periodic table. After mixing and mixing, the mixture was subjected to die press molding at 1 t / cm 2 .
【００２９】[0029]
【表１】 [Table 1]
【００３０】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。The obtained compact 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. .
【００３１】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.
【００３２】[0032]
【表２】 [Table 2]
【００３３】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,１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,１０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0.１モル％未満のＮo,６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,９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 shown in 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, 1 in which the total amount of No. 2 exceeds 39.9 mol% has a low high-temperature strength, and the content of Si 3 N 4 exceeds 93 mol%.
The sintered body of No. 10 in which the total amount of RE 2 O 3 , Al 2 O 3 , and SiO 2 was less than 6 mol% was insufficient in densification and the strength was reduced. Further, the sintered body of No.6 containing less than 0.1 mol% of the group 5a element has reduced room temperature strength, and the sintered body of No.9 containing more than 1.0 mol% of the group 5a element has a fracture toughness. And the room temperature strength was reduced.
【００３４】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６８より大きく８５
以下で、Ａｌ2 Ｏ3 ／（ＳｉＯ2 ＋ＲＥ2 Ｏ3 ）モル比
が０．１より大きく、１．０以下のＮo,２、Ｎo,５、Ｎ
o,７、Ｎo,８、Ｎo,１１、Ｎo,１４、Ｎo,１５、Ｎo,１
６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, the molar ratio of SiO 2 / RE 2 O 3 is more than 68 and 85
In the following, the Al 2 O 3 / (SiO 2 + RE 2 O 3 ) molar ratio is larger than 0.1, and is 1.0 or less.
o, 7, No, 8, No, 11, No, 14, No, 15, No, 1
The sintered compact of No. 6 showed further excellent bending strength and fracture toughness.
【００３５】実施例２ 実施例１の表１の試料のうち、Ｎo,３、Ｎo,１０、Ｎo,
１２、Ｎo,１３の焼結体について、さらに、窒素ガス含
有アルゴンガス２０００気圧、１８５０℃、１時間の条
件で熱間静水圧処理を行った。なお、ＨＩＰ時での組成
変動は認められなかった。得られた焼結体に対し、実施
例１と同様の評価を行い、結果を表４に示した。Example 2 Of the samples in Table 1 of Example 1, No, 3, No, 10, No,
The sintered bodies No. 12 and No. 13 were further subjected to hot isostatic pressure treatment at 2,000 atm of nitrogen gas-containing argon gas at 1850 ° C. for 1 hour. It should be noted that no composition change was observed during HIP. The same evaluation as in Example 1 was performed on the obtained sintered body, and the results are shown in Table 4.
【００３６】[0036]
【表３】 [Table 3]
【００３７】表３の結果によると、ＨＩＰ処理によりい
ずれも焼結体の密度は向上したが、Ｓｉ3 Ｎ4 量が少な
い試料Ｎo,１０ではＨＩＰ処理しても強度を回復するこ
とはできなかった。According to the results shown in Table 3, although the density of the sintered body was improved by the HIP treatment, the strength could not be recovered by the HIP treatment in Sample No. 10 having a small amount of Si 3 N 4. Was.
【００３８】[0038]
【発明の効果】以上詳述した通り、本発明によれば、Ｓ
ｉ3 Ｎ4 −ＲＥ2 Ｏ3 −Ａｌ2 Ｏ3 −ＳｉＯ2 系に対し
て周期律表第５ａ族元素酸化物を添加し、焼結体中に第
５ａ族酸窒化物および珪素、酸素、窒素からなる結晶相
を析出させることにより、窒化珪素結晶粒の粒成長を抑
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, S
To the i 3 N 4 —RE 2 O 3 —Al 2 O 3 —SiO 2 system, a Group 5a element oxide of the periodic table is added, and a Group 5a oxynitride and silicon, oxygen, By precipitating a crystal phase composed of nitrogen, it is possible to suppress the growth of silicon nitride crystal grains and to stabilize additives such as a sintering aid in a high-temperature region. Strength and toughness can be obtained.
【００３９】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 (5)
からなる結晶質の粒界相と、少なくとも希土類元素およ
びアルミニウムを含む粒界相と、周期律表第５ａ族元素
の酸窒化物相から構成されることを特徴とする窒化珪素
質焼結体。1. A silicon nitride crystal phase, a crystalline grain boundary phase comprising silicon, oxygen and nitrogen, a grain boundary phase containing at least a rare earth element and aluminum, and an oxynitride phase of a Group 5a element of the periodic table A silicon nitride-based sintered body characterized by comprising:
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乃至1.０モ
ル％の割合で存在する請求項１記載の窒化珪素質焼結
体。(2) a total amount of silicon nitride of 60 to 93 mol%, a rare earth element oxide equivalent, aluminum oxide equivalent, and excess oxygen equivalent of SiO 2 equivalent of 6 to 39.9 mol%;
2. The silicon nitride sintered body according to claim 1, wherein the Group 5a element of the periodic table is present in an amount of 0.1 to 1.0 mol% in terms of oxide.
と、過剰酸素のＳｉＯ2 換算量と、アルミニウムの酸化
物換算量（Ａｌ2 Ｏ3 ）において、ＳｉＯ2 ／ＲＥ2 Ｏ
3 で表されるモル比が２を越え、且つＡｌ2 Ｏ3 ／（Ｒ
Ｅ2 Ｏ3 ＋ＳｉＯ2 ）で表されるモル比が１／１５〜５
／４である請求項１記載の窒化珪素質焼結体。3. An amount of rare earth element in terms of oxide (RE 2 O 3 )
And SiO 2 / RE 2 O in terms of SiO 2 in terms of excess oxygen and aluminum oxide in terms of oxide (Al 2 O 3 ).
The molar ratio represented by 3 exceeds 2, and Al 2 O 3 / (R
E 2 O 3 + SiO 2 ) in a molar ratio of 1/15 to 5
The silicon nitride sintered body according to claim 1, wherein the ratio is / 4.
酸化物、酸化アルミニウムおよび酸化珪素の合量が６〜
３9.９モル％と、周期律表第５ａ族元素酸化物を0.１〜
1.０モル％になるように調合した混合物を成形後、窒素
を含む非酸化性雰囲気中で焼結し、窒化珪素結晶相と、
珪素、酸素および窒素からなる結晶質の粒界相と、少な
くとも希土類元素およびアルミニウムを含む粒界相と、
周期律表第５ａ族元素の酸窒化物相を生成させることを
特徴とする窒化珪素質焼結体の製造方法。4. A total amount of 60 to 93 mol% of silicon nitride and 6 to 93 mol% of rare earth oxide, aluminum oxide and silicon oxide.
39.9% by mole of the Group 5a element oxide in the periodic table
After molding the mixture prepared to be 1.0 mol%, the mixture is sintered in a non-oxidizing atmosphere containing nitrogen, and a silicon nitride crystal phase,
Silicon, a crystalline grain boundary phase composed of oxygen and nitrogen, and a grain boundary phase containing at least a rare earth element and aluminum,
A method for producing a silicon nitride-based sintered body, comprising generating an oxynitride phase of a Group 5a element of the periodic table.
3 ）と、前記酸化珪素の添加量（ＳｉＯ2 ）と、前記酸
化アルミニウムの添加量（Ａｌ2 Ｏ3 ）において、Ｓｉ
Ｏ2 ／ＲＥ2 Ｏ3 で表されるモル比が２を越え、且つＡ
ｌ2Ｏ3 ／（ＲＥ2 Ｏ3 ＋ＳｉＯ2 ）で表されるモル比
が１／１５〜５／４である請求項４記載の窒化珪素質焼
結体の製造方法。5. The amount of said rare earth element oxide added (RE 2 O
3 ), the addition amount of silicon oxide (SiO 2 ), and the addition amount of aluminum oxide (Al 2 O 3 )
The molar ratio represented by O 2 / RE 2 O 3 exceeds 2, and A
l 2 O 3 / molar ratio represented by (RE 2 O 3 + SiO 2 ) is 1 / 15-5 / 4 in the manufacturing method according to claim 4 silicon nitride sintered body, wherein.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2410989A JP2708136B2 (en) | 1990-12-14 | 1990-12-14 | Silicon nitride sintered body and method for producing the same |
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| Publication Number | Publication Date |
|---|---|
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| JP2708136B2 true JP2708136B2 (en) | 1998-02-04 |
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