JP3237963B2 - 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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- JP3237963B2 JP3237963B2 JP18787493A JP18787493A JP3237963B2 JP 3237963 B2 JP3237963 B2 JP 3237963B2 JP 18787493 A JP18787493 A JP 18787493A JP 18787493 A JP18787493 A JP 18787493A JP 3237963 B2 JP3237963 B2 JP 3237963B2
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- sio
- silicon nitride
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Description
【０００１】[0001]
【産業上の利用分野】本発明は、ガスタービンなどの熱
機関用構造材料として有用な窒化珪素質焼結体およびそ
の製法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon nitride sintered body useful as a structural material for heat engines such as gas turbines and a method for producing the same.
【０００２】[0002]
【従来技術】従来から、窒化珪素質焼結体は、高温にお
ける強度、硬度、熱的化学的安定性に優れた材料として
注目され、エンジニアリングセラミックスとして、特に
熱機関用構造材料としての応用が進められている。2. Description of the Related Art Conventionally, silicon nitride sintered bodies have been attracting attention as materials having excellent strength, hardness and thermochemical stability at high temperatures, and have been applied as engineering ceramics, particularly as structural materials for heat engines. Have been.
【０００３】一般に、窒化珪素は、それ自体、難焼結性
であるために焼結助剤としてＹ2 Ｏ3 などの周期律表第
３ａ族元素酸化物や、Ａｌ2 Ｏ3 などを添加し、それを
成形後、窒素を含む非酸化性雰囲気中で１５００〜２０
００℃の温度で焼成することにより高密度の焼結体が得
られている。[0003] In general, silicon nitride itself is difficult to sinter, so that an oxide of a Group 3a element in the periodic table, such as Y 2 O 3 , or Al 2 O 3 is added as a sintering aid. After molding, in a non-oxidizing atmosphere containing nitrogen
By firing at a temperature of 00 ° C., a high-density sintered body is obtained.
【０００４】[0004]
【発明が解決しようとする問題点】通常の焼結体を製品
化する場合には、その表面を研磨加工を施すが、例えば
タービンロータなどの複雑形状品を作製する場合には、
焼結体の表面すべてを研磨することができず、未研磨部
分、いわゆる焼き肌面が残存することとなる。Problems to be Solved by the Invention When a normal sintered body is commercialized, its surface is polished. However, when a complex shaped article such as a turbine rotor is manufactured,
The entire surface of the sintered body cannot be polished, and an unpolished portion, a so-called burnt surface, remains.
【０００５】前述したような従来の方法で作製する場合
には、焼成中に非酸化性雰囲気中での窒化珪素と各種焼
結助剤との反応などにより分解が生じやすいため、焼き
肌面近傍では靱性や強度が低下し、複雑形状品の機械的
特性の安定化を阻害するという問題がある。In the case of manufacturing by the conventional method as described above, decomposition tends to occur due to the reaction between silicon nitride and various sintering aids in a non-oxidizing atmosphere during firing, so that the area near the burning surface In this case, there is a problem that toughness and strength are reduced, and stabilization of mechanical properties of a product having a complicated shape is hindered.
【０００６】焼成時の窒化珪素と焼結助剤成分との反応
による分解を抑制する方法として、例えば、特開昭６３
−１９０７５９号では、焼成中の雰囲気をＳｉＯを含む
窒素雰囲気にすることが提案されているが、焼き肌面近
傍における強度や靱性を実用的なレベルまで高めるには
至っていないのが現状である。As a method of suppressing decomposition due to the reaction between silicon nitride and a sintering aid component during firing, for example, Japanese Patent Application Laid-Open
In -190759, it is proposed that the atmosphere during firing be a nitrogen atmosphere containing SiO, but at present the strength and toughness in the vicinity of the baked surface have not yet been raised to practical levels.
【０００７】[0007]
【発明が解決しようとする問題点】本発明者らは、焼き
肌面近傍における強度や靱性の劣化の原因について詳細
に検討を行ったところ、焼結体表面における酸素量が分
解により低下することに起因して焼結体表面の組成、具
体的にはＳｉＯ2 ／ＲＥ2 Ｏ3 （ＲＥ：周期律表第３ａ
族元素）の比が内部の比より低下しているためであるこ
とを突き止めた。DISCLOSURE OF THE INVENTION The present inventors have studied in detail the cause of the deterioration of the strength and toughness in the vicinity of the burnt surface, and found that the oxygen amount on the surface of the sintered body is reduced by decomposition. Of the sintered body surface, specifically, SiO 2 / RE 2 O 3 (RE: 3a of the periodic table)
Group element) is lower than the internal ratio.
【０００８】そこで、本発明によれば、成形体における
表面の組成に対して焼結後の焼結体表面の組成の変動幅
を特定の範囲内となるように焼成雰囲気を制御すること
により焼結体の焼き肌面近傍の靱性および強度を実用的
なレベルにまで高めることができることを見出し本発明
に至った。Therefore, according to the present invention, the firing atmosphere is controlled by controlling the variation range of the composition of the sintered body surface after sintering with respect to the surface composition of the molded body within a specific range. The present inventors have found that the toughness and strength in the vicinity of the baked surface of the sintered body can be increased to a practical level, and have reached the present invention.
【０００９】即ち、本発明の窒化珪素質焼結体は、窒化
珪素を主成分とし、周期律表第３ａ族元素（ＲＥ）およ
び過剰酸素を含有し、焼結体表面部の前記周期律表第３
ａ族元素の酸化物換算量（ＲＥ2Ｏ3）と過剰酸素のＳｉ
Ｏ2換算量のＳｉＯ2／ＲＥ2Ｏ3で表されるモル比を
Ｉ1、焼結体中心部の前記モル比をＩ2とした時、Ｉ1＜
２．３、Ｉ2＜１．９、−０．３≦Ｉ1−Ｉ2≦０．４を
満足するとともに、焼結体表面を０．０５ｍｍ研磨した
鏡面における破壊靱性（Ｋ1c）が５．５ＭＰａｍ1/2以
上であることを特徴とするものである。また、本発明の
窒化珪素質焼結体の製造方法は、窒化珪素に対して、周
期律表第３ａ族元素酸化物（ＲＥ2Ｏ3）、あるいは周期
律表第３ａ族元素酸化物（ＲＥ2Ｏ3）およびＳｉＯ2を
含有する成形体を窒素含有雰囲気中で１６００〜２００
０℃の温度で焼成するに当たり、焼成炉内に、成形体と
ともに雰囲気制御剤を配置し、前記成形体におけるＳｉ
Ｏ2／ＲＥ2Ｏ3で表されるモル比をＩ3、最終焼結体の表
面部における前記モル比をＩ1とした時、Ｉ3＜１．９、
Ｉ3−Ｉ1≦０．６を満足するように前記雰囲気制御剤の
量を調整しながら焼成することを特徴とするものであ
る。That is, the silicon nitride-based sintered body of the present invention contains silicon nitride as a main component, contains a Group 3a element (RE) of the periodic table and excess oxygen, and forms a surface of the sintered body on the periodic table. Third
Group a element oxide equivalent (RE 2 O 3 ) and excess oxygen Si
When the molar ratio expressed by SiO 2 / RE 2 O 3 in terms of O 2 is I 1 , and the molar ratio at the center of the sintered body is I 2 , I 1 <
2.3, I 2 <1.9, −0.3 ≦ I 1 −I 2 ≦ 0.4, and the fracture toughness (K 1c ) on the mirror-finished surface of the sintered body 0.05 mm was 5 It is characterized by being not less than 0.5 MPam 1/2 . In addition, the method for producing a silicon nitride-based sintered body of the present invention provides a method for producing a silicon nitride based on Group 3a element oxide (RE 2 O 3 ) or Group 3a element oxide (RE The molded body containing 2 O 3 ) and SiO 2 is placed in a nitrogen-containing atmosphere at 1600 to 200
In firing at a temperature of 0 ° C. , the molded body and
In both cases, an atmosphere control agent is arranged, and Si
When the molar ratio represented by O 2 / RE 2 O 3 is I 3 and the molar ratio on the surface portion of the final sintered body is I 1 , I 3 <1.9,
Of the atmosphere control agent so as to satisfy I 3 −I 1 ≦ 0.6 .
It is characterized by baking while adjusting the amount .
【００１０】以下、本発明を詳述する。本発明における
窒化珪素質焼結体は、組成上、窒化珪素を主成分とし、
望ましくは７０〜９９モル％の割合で含まれるものであ
り、他の成分として周期律表第３ａ族元素（ＲＥ）およ
び過剰酸素を含有するものである。ここで、過剰酸素と
は、焼結体中に含まれる全酸素量から周期律表第３ａ族
元素酸化物として化学量論量で混入した酸素を除いた残
りの酸素量であり、実際には窒化珪素原料中の不純物酸
素あるいはＳｉＯ2 として添加された酸素から構成され
るものである。Hereinafter, the present invention will be described in detail. The silicon nitride-based sintered body in the present invention is mainly composed of silicon nitride,
Desirably, it is contained at a ratio of 70 to 99 mol%, and contains, as other components, a Group 3a element (RE) of the periodic table and excess oxygen. Here, the excess oxygen is the amount of oxygen remaining after removing stoichiometric oxygen mixed as a Group 3a element oxide of the periodic table from the total amount of oxygen contained in the sintered body. It is composed of impurity oxygen in silicon nitride raw material or oxygen added as SiO 2 .
【００１１】本発明によれば、焼結体中に含まれる周期
律表第３ａ族元素の酸化物（ＲＥ2Ｏ3 ）換算量と、過
剰酸素をＳｉＯ2 として換算した時の焼結体表面部のＳ
ｉＯ2 ／ＲＥ2 Ｏ3 で表されるモル比をＩ1 、焼結体中
心部の前記モル比をＩ2 とした時、Ｉ1 ＜２．３、Ｉ2
＜１．９、−０．３≦Ｉ1 −Ｉ2 ≦０．４を満足するこ
とが重要である。According to the present invention, the amount of oxide (RE 2 O 3 ) of a Group 3a element of the periodic table contained in the sintered body and the surface of the sintered body when the excess oxygen is converted to SiO 2 Department of S
When the molar ratio represented by iO 2 / RE 2 O 3 is I 1 and the molar ratio at the center of the sintered body is I 2 , I 1 <2.3 and I 2
It is important to satisfy <1.9, -0.3 ≦ I 1 −I 2 ≦ 0.4.
【００１２】本発明において、Ｉ1 およびＩ2 を上記の
範囲に限定したのは、Ｉ1 が２．３より大きかったり、
Ｉ2 が１．９より大きいと１４００℃の高温強度が十分
でなく、またＩ1 −Ｉ2 が−０．３より小さいと焼結体
表面の特に焼き肌面の靱性および強度の向上がなく、
０．４を越えると、焼結体の内部の高温強度が低下する
ためであり、またＩ1 −Ｉ2 の値が上記範囲を逸脱する
と内外差での組成差が大きいことに起因して内部応力が
発生しクラックなどが生じる場合もある。In the present invention, the reason why I 1 and I 2 are limited to the above range is that I 1 is larger than 2.3,
If I 2 is greater than 1.9, the high-temperature strength at 1400 ° C. is not sufficient, and if I 1 -I 2 is less than -0.3, the toughness and strength of the surface of the sintered body, in particular, the surface of the burnt surface are not improved. ,
When the ratio exceeds 0.4, the high-temperature strength inside the sintered body decreases, and when the value of I 1 -I 2 is out of the above range, the composition difference between the inside and outside is large, so that the internal In some cases, stress is generated to cause cracks.
【００１３】さらに、本発明の焼結体は、その焼結体表
面、例えば焼成後の焼き肌面を０．０５ｍｍ研磨した鏡
面における破壊靱性（Ｋ1c）が５．５ＭＰａ・ｍ1/2 以
上であることも重要である。これは、少なくとも焼き肌
面の機械的強度を高める上で重要な要素であり、上記破
壊靱性値が５．５ＭＰａ・ｍ1/2 より低いと、焼き肌面
に不可避的に存在するボイドなどの欠陥によって容易に
破壊に至り、焼き肌面の高強度化を達成できないためで
ある。Further, the sintered body of the present invention has a fracture toughness (K 1 c) of 5.5 MPa · m 1/2 on the surface of the sintered body, for example, a mirror surface obtained by polishing the burnt surface after firing to 0.05 mm. It is also important that this is done. This is an important factor at least in increasing the mechanical strength of the burnt surface, and when the fracture toughness value is lower than 5.5 MPa · m 1/2, voids and the like inevitably exist on the burnt surface. This is because the defect easily causes destruction, and it is not possible to achieve high strength of the burnt skin surface.
【００１４】本発明における上記Ｉ1 、Ｉ2 の望ましい
範囲は、Ｉ1 ≦１．８、Ｉ2 ≦１．８、０≦Ｉ1 −Ｉ2
≦０．３である。In the present invention, the desirable ranges of I 1 and I 2 are as follows: I 1 ≦ 1.8, I 2 ≦ 1.8, 0 ≦ I 1 −I 2
≦ 0.3.
【００１５】次に、本発明における窒化珪素質焼結体の
製造方法について説明すると、まず出発原料として、窒
化珪素粉末を主成分とし、添加成分として周期律表第３
ａ族元素酸化物粉末、場合により酸化珪素粉末を用い
る。なお、上記粉末の他に周期律表第３ａ族元素酸化物
と酸化珪素との複合化合物粉末や、窒化珪素−周期律表
第３ａ族元素酸化物−酸化珪素の複合化合物粉末の形態
で添加することもできる。用いる窒化珪素粉末は、α
型、β型のいずれでもよく、それらの平均粒子径は０．
４〜１．２μｍが適当である。Next, the method for producing a silicon nitride sintered body according to the present invention will be described. First, a silicon nitride powder is used as a main component as a starting material, and the third component of the periodic table is used as an additional component.
A group a element oxide powder, and in some cases, a silicon oxide powder are used. In addition, in addition to the above powder, a compound compound powder of a Group 3a element oxide of the periodic table and silicon oxide or a compound compound powder of silicon nitride-oxide of a Group 3a element of the periodic table-silicon oxide is added. You can also. The silicon nitride powder used is α
Type and β type, and their average particle size is 0.3.
4-1.2 μm is appropriate.
【００１６】その後、これらの粉末を用いて所定の割合
で混合する。混合する割合としては窒化珪素成分を７０
〜９９モル％、周期律表第３ａ族元素酸化物および酸化
珪素などの添加成分を１〜３０モル％の割合となるよう
に調製する。そして、この混合粉末を所望の成形手段、
例えば、金型プレス，冷間静水圧プレス，押出し成形等
により任意の形状に成形する。Thereafter, these powders are mixed at a predetermined ratio. The mixing ratio is 70% for the silicon nitride component.
An additive component such as an oxide of Group 3a element of the periodic table and silicon oxide is prepared so as to have a ratio of 1 to 30 mol%. Then, the mixed powder is formed into desired molding means,
For example, it is formed into an arbitrary shape by a die press, a cold isostatic press, an extrusion molding or the like.
【００１７】その後、かかる成形体を窒素を含む非酸化
性雰囲気中で焼成する。焼成方法としては、普通焼成、
ホットプレス法の他、１気圧を越える、望ましくは５気
圧以上の窒素ガス加圧雰囲気中で焼成する方法、あるい
は前記焼成方法で得た焼結体を不活性ガス５００〜２０
００気圧下で焼成する熱間静水圧焼成法などが採用でき
る。Thereafter, the compact is fired in a non-oxidizing atmosphere containing nitrogen. As the firing method, normal firing,
In addition to the hot press method, a method of firing in a nitrogen gas pressurized atmosphere exceeding 1 atm, desirably 5 atm or more, or a method using an inert gas of 500 to 20
A hot isostatic firing method of firing at 00 atm can be employed.
【００１８】本発明によれば、上記焼結過程において、
成形体における周期律表第３ａ族元素の酸化物換算量
（ＲＥ2 Ｏ3 ）と過剰酸素のＳｉＯ2 換算量とのＳｉＯ
2 ／ＲＥ2 Ｏ3 で表される比率をＩ3 、最終焼結体の表
面部における前記モル比をＩ1とした時、Ｉ3 ＜１．
９、Ｉ3 −Ｉ1 ≦０．６を満足するように焼成すること
が重要である。特に望ましくは、Ｉ3 ≦１．８、Ｉ3 −
Ｉ1 ≦０である。According to the present invention, in the sintering process,
The amount of the oxide of the Group 3a element of the periodic table (RE 2 O 3 ) in terms of oxide and the amount of excess oxygen in terms of SiO 2 in the molded product are expressed as SiO.
When the ratio represented by 2 / RE 2 O 3 is I 3 and the molar ratio on the surface of the final sintered body is I 1 , I 3 <1.
9. It is important to bake so as to satisfy I 3 −I 1 ≦ 0.6. Particularly preferably, I 3 ≦ 1.8, I 3 −
I 1 ≦ 0.
【００１９】成形体および焼結体表面部のＳｉＯ2 ／Ｒ
Ｅ2 Ｏ3 比Ｉ1 、Ｉ3 を上記の範囲に限定したのは、Ｉ
3 が１．９以上では、焼結過程では最終焼結体のＳｉＯ
2 ／ＲＥ2 Ｏ3 比Ｉ1 が２．３を越えてしまう場合があ
り、高強度の焼結体を安定して作製することができない
ためであり、Ｉ3 −Ｉ1 が０．６を越えると、焼結過程
での分解揮散が激しいことを意味し、ＳｉＯ2 ／ＲＥ2
Ｏ3 比の変動幅が大きくなり焼結体表面近傍の靱性が低
下し焼結体の高温強度の向上が見られないためである。SiO 2 / R on Surface of Molded and Sintered Body
The reason why the E 2 O 3 ratios I 1 and I 3 were limited to the above range was that
If the value of 3 is 1.9 or more, the final sintered body SiO
May 2 / RE 2 O 3 ratio of I 1 may exceed 2.3, and due to the inability to stably produce a sintered body of high strength, I 3 -I 1 0.6 If it exceeds, it means that the decomposition and volatilization during the sintering process are severe, and SiO 2 / RE 2
This is because the fluctuation range of the O 3 ratio becomes large, the toughness near the surface of the sintered body is reduced, and no improvement in the high-temperature strength of the sintered body is observed.
【００２０】また、上記のように、成形体から焼結体に
なる過程においてＳｉＯ2／ＲＥ2Ｏ3比の変動を上記範
囲に抑制する方法としては、雰囲気を細かく制御するこ
とが必要である。具体的には、雰囲気中にＳｉ3Ｎ4の分
解を抑制するためにＳｉ3Ｎ4の分解平衡圧以上の窒素ガ
スを導入するとともに、添加成分の分解を抑制するため
に、焼成炉内に、雰囲気制御剤を成形体とともに配置す
るが、上記関係を満足するように雰囲気制御剤の量を調
整する。雰囲気制御剤としては、窒化珪素粉末、周期律
表第３ａ族元素酸化物粉末やＳｉＯ2粉末、Ｓｉ粉末と
ＳｉＯ2粉末の混合粉末など、あるいはＡｌ2Ｏ3などの
不可避的に成形体中に含まれ低融点物質として揮散され
やすいため、これら不純物成分も雰囲気制御剤として焼
成炉内に配置することも有効である。Further, as described above, as a method of suppressing the variation of the SiO 2 / RE 2 O 3 ratio in the process of forming a sintered body into a sintered body, it is necessary to precisely control the atmosphere. . More specifically, the introducing decomposition equilibrium pressure more nitrogen gas the Si 3 N 4 in order to suppress the decomposition the Si 3 N 4 in an atmosphere, in order to suppress the decomposition of the additive components, in a firing furnace , Place the atmosphere control agent together with the compact
However, the amount of the atmosphere control agent was adjusted to satisfy the above relationship.
Adjust. The atmosphere control agent, silicon nitride powder, the periodic table group 3a element oxide powder or SiO 2 powder, a mixed powder of Si powder and SiO 2 powder, or inevitably molded body of Al 2 O 3 or the like Since it is contained and is easily volatilized as a low-melting substance, it is also effective to dispose these impurity components in a firing furnace as an atmosphere control agent .
【００２１】[0021]
【作用】通常、焼成後の焼結体の表面には、焼結体成分
の分解や揮散などに起因して表面の荒れが生じており、
研磨面に比較して機械的特性が低下するという現象があ
る。単純な形状品においては、表面を研磨加工すること
により焼成時の荒れによる特性の劣化を防止することが
できるが、複雑形状品では研磨することができない箇所
が不可避的に存在するため、焼き肌面の機械的特性は避
けられないものであった。このように焼き肌面の機械的
特性が劣化する原因について検討したところ、焼結過程
でＳｉＯ2 成分が主として分解し焼結体表面の組成、具
体的にはＳｉＯ2 ／ＲＥ2 Ｏ3 （ＲＥ：周期律表第３ａ
族元素）の比が内部組成より低下していることによるこ
とを突き止めた。[Action] Usually, the surface of the sintered body after firing has been roughened due to decomposition or volatilization of the sintered body components,
There is a phenomenon that the mechanical properties are lower than that of the polished surface. In the case of simple shaped products, the surface can be polished to prevent deterioration of characteristics due to roughness during firing. The mechanical properties of the surface were inevitable. As a result of examining the cause of the deterioration of the mechanical properties of the burnt surface, the SiO 2 component was mainly decomposed during the sintering process and the composition of the surface of the sintered body, specifically, SiO 2 / RE 2 O 3 (RE : Periodic table 3a
Group element) was found to be lower than the internal composition.
【００２２】さらに、本発明によれば、この焼き肌面の
強度を高めることのできる要因について検討したとこ
ろ、焼き肌面近傍の靱性が高いと、焼き肌面を通じて発
生したクラックが焼き肌面直下の高靱性領域でその進展
を抑制し、焼結体の破壊を食い止める作用をなすことが
わかった。このことは、図１の焼き肌面近傍の靱性値と
高温強度との関係から明らかである。図１から明らかな
ように焼き肌面の強度が６００ＭＰａ以上を達成するた
めには、焼き肌面近傍の靱性を５．５ＭＰａ・ｍ1/2 以
上とすることが必要であることがわかる。Further, according to the present invention, the factors that can enhance the strength of the baked surface were examined. If the toughness near the baked surface was high, cracks generated through the baked surface would be directly below the baked surface. It has been found that it suppresses the progress in the high toughness region and suppresses the fracture of the sintered body. This is apparent from the relationship between the toughness value near the burnt surface and the high temperature strength in FIG. As is clear from FIG. 1, in order to achieve the strength of the burnt surface of 600 MPa or more, it is necessary to set the toughness near the burnt surface to 5.5 MPa · m 1/2 or more.
【００２３】本発明によれば、焼成過程において、成形
体のＳｉＯ2 ／ＲＥ2 Ｏ3 比を変動が小さくなるように
して焼成すると、焼結体内部と焼き肌面におけるＳｉＯ
2 ／ＲＥ2 Ｏ3 比の差も小さくなり、それと同時に焼き
肌面近傍の靱性の低下がなく、靱性が向上し、結果とし
て焼き肌面を有する焼結体の機械的特性を高めることが
できる。According to the present invention, in the firing step, if the SiO 2 / RE 2 O 3 ratio of the molded body is fired so that the fluctuation is small, the SiO 2 in the sintered body and the burnt surface can be obtained.
The difference in the 2 / RE 2 O 3 ratio is also reduced, and at the same time, there is no decrease in toughness near the burnt surface, and the toughness is improved. As a result, the mechanical properties of the sintered body having the burnt surface can be enhanced. .
【００２４】また、実用的な強度を得るためには、Ｓｉ
Ｏ2 ／ＲＥ2 Ｏ3 比は特定の範囲に制御される必要があ
り、焼結体表面部の比Ｉ1 ＜２．３、焼結体内部の比Ｉ
2 ＜１．９、−０．３≦Ｉ1 −Ｉ2 ≦０．４、成形体に
おける比Ｉ3 ＜１．９、Ｉ3−Ｉ1 ≦０．６とすること
により１４００℃における抗折強度６００ｋｇ／ｍｍ2
以上が達成される。さらに、上記構成によれば、１４０
０℃における耐酸化性も向上し、後述する実施例から明
らかなように０．１５ｍｇ／ｃｍ2 以下が達成できる。In order to obtain practical strength, Si
The O 2 / RE 2 O 3 ratio needs to be controlled to a specific range, and the ratio I 1 <2.3 of the surface of the sintered body and the ratio I inside the sintered body
2 <1.9, −0.3 ≦ I 1 −I 2 ≦ 0.4, and the ratio I 3 <1.9, I 3 −I 1 ≦ 0.6 in the molded body, so that the bending at 1400 ° C. Strength 600 kg / mm 2
The above is achieved. Further, according to the above configuration, 140
Oxidation resistance at 0 ° C. is also improved, and 0.15 mg / cm 2 or less can be achieved as is apparent from the examples described later.
【００２５】なお、本発明における周期律表第３ａ族元
素とは、Ｙ、Ｙｂ、Ｅｒ、Ｌｕ、Ｈｏ、Ｄｙなどが適当
である。The element of Group 3a of the periodic table in the present invention is suitably Y, Yb, Er, Lu, Ho, Dy and the like.
【００２６】また、本発明の窒化珪素質焼結体によれ
ば、不純物としてＡｌ、Ｍｇ、Ｃａ、Ｆｅなどが含まれ
る場合があるが、これらの成分は低融点物質を生成しや
すいために、高温強度を高める上では、これらの成分量
を０．５重量％以下、特に０．１重量％以下に制御する
ことが望ましい。According to the silicon nitride sintered body of the present invention, Al, Mg, Ca, Fe and the like may be contained as impurities in some cases. In order to enhance the high-temperature strength, it is desirable to control the amounts of these components to 0.5% by weight or less, particularly 0.1% by weight or less.
【００２７】さらに、本発明の窒化珪素質焼結体は上記
組成以外に、Ｗ、Ｔｉ、Ｎｂ、Ｖ、Ｍｏなどの金属の炭
化物、窒化物、炭窒化物、硼化物などを１０重量％以下
の割合で含んでいてもよい。Further, in addition to the above composition, the silicon nitride-based sintered body of the present invention contains not more than 10% by weight of carbides, nitrides, carbonitrides, borides and the like of metals such as W, Ti, Nb, V and Mo. May be included.
【００２８】[0028]
【実施例】出発原料として、窒化珪素粉末（平均粒径
０．５μｍ、不純物酸素量１重量％、純度９９％）と、
純度９５％以上の周期律表第３ａ族元素酸化物粉末、お
よび酸化珪素粉末を準備し、これらを表１の組成になる
ように秤量混合した。なお、表１中の調合組成における
ＳｉＯ2 量は添加したＳｉＯ2 量と窒化珪素粉末中の不
純物酸素をＳｉＯ2 換算した量の合計量である。そし
て、この混合粉末をプレス成形した。得られた成形体に
対してＩＣＰ分析により組成を分析したところ、調合組
成とほとんどかわらないものであった。EXAMPLES As starting materials, silicon nitride powder (average particle size: 0.5 μm, impurity oxygen amount: 1% by weight, purity: 99%)
A powder of a Group 3a element of the periodic table having a purity of 95% or more and a silicon oxide powder were prepared, and they were weighed and mixed so as to have the composition shown in Table 1. The amount of SiO 2 in the composition shown in Table 1 is the total amount of the added SiO 2 and the amount of impurity oxygen in the silicon nitride powder in terms of SiO 2 . And this mixed powder was press-molded. When the composition of the obtained molded body was analyzed by ICP analysis, it was almost the same as the prepared composition.
【００２９】次に、この成形体をカーボンヒータを配置
した焼成炉内で炭化珪素質の匣鉢内に入れ、成形体と一
緒に雰囲気制御剤としてＳｉ粉末とＳｉＯ2粉末とを
１：１．５の重量比で混合した混合粉末および窒化珪素
粉末を表１に示すような量で配合し、１８００℃、窒素
ガス圧力１０気圧の雰囲気で５時間焼成した。Next, the compact was placed in a silicon carbide sagger in a firing furnace provided with a carbon heater, and together with the compact , Si powder and SiO 2 powder were used as an atmosphere control agent in a ratio of 1: 1. The mixed powder and the silicon nitride powder mixed at a weight ratio of 5 were blended in amounts as shown in Table 1 and fired in an atmosphere of 1800 ° C. and a nitrogen gas pressure of 10 atm for 5 hours.
【００３０】得られた焼結体に対して、厚さ１０ｍｍの
平板を焼結体内部および焼き肌面を含む表面から切り出
し、その試験についてＳｉＯ2 ／ＲＥ2 Ｏ3 比、抗折強
度、酸化重量増、破壊靱性を測定した。From the obtained sintered body, a flat plate having a thickness of 10 mm was cut out from the inside including the inside of the sintered body and the surface including the burning surface, and the SiO 2 / RE 2 O 3 ratio, bending strength, oxidation Weight increase and fracture toughness were measured.
【００３１】ＳｉＯ2 ／ＲＥ2 Ｏ3 比Ｉ1 、Ｉ2 は、上
記の試験片を用いて、ＩＣＰ分析および窒素酸素同時分
析を行い、ＳｉＯ2 量は、全酸素量からＩＣＰ分析によ
り定量した周期律表第３ａ族元素量に対して酸化物とし
て結合する量の酸素量を差し引いた残りの酸素量をＳｉ
Ｏ2 換算したものである。The SiO 2 / RE 2 O 3 ratios I 1 and I 2 were subjected to ICP analysis and nitrogen-oxygen simultaneous analysis using the above test pieces, and the amount of SiO 2 was quantified from the total oxygen amount by ICP analysis. The amount of oxygen remaining after subtracting the amount of oxygen that binds as an oxide from the amount of Group 3a element in the periodic table is expressed as Si.
It is converted to O 2 .
【００３２】抗折強度はＪＩＳＲ１６０１に基づき、上
記試験片よりＪＩＳによる試験片を切り出し（表面の試
験片では焼き肌面を含む）、室温での抗折強度を測定し
た。The flexural strength was measured in accordance with JIS R1601 by cutting out a JIS test piece from the above test piece (including the burnt surface in the case of the surface test piece) and measuring the flexural strength at room temperature.
【００３３】また、内部試験片については１４００℃の
高温における抗折強度も測定した。The flexural strength of the internal test piece at a high temperature of 1400 ° C. was also measured.
【００３４】また、焼き肌面を含む試験片による強度測
定後、その試験片を用いて焼き肌面を０．０１〜０．０
５ｍｍ研磨して鏡面出しを行い、ＩＭ法により破壊靱性
Ｋ1ｃを測定した。さらに、酸化重量増は、大気中で１
４００℃で２４時間の酸化処理をして重量変化から算出
した。結果は、表１に示した。After measuring the strength of the test piece including the burnt surface, the burnt surface is measured for 0.01 to 0.0
Mirror polishing was performed after polishing by 5 mm, and fracture toughness K 1 c was measured by IM method. Furthermore, the oxidation weight increase is 1 in air.
The oxidation treatment was performed at 400 ° C. for 24 hours, and the weight was calculated from the change in weight. The results are shown in Table 1.
【００３５】[0035]
【表１】 [Table 1]
【００３６】表１から明らかなように、最終焼結体にお
ける表面部のＳｉＯ2 ／ＲＥ2 Ｏ3比Ｉ1 が２．３以
上、あるいは内部における比Ｉ2 が１．９以上の試料Ｎ
o.７，８，９，１７はいずれも１４００℃における強度
が低く、またＩ1 −Ｉ2 が−０．３より小さい試料Ｎo.
１では焼き肌面近傍の靱性および強度が低く、Ｉ1 −Ｉ
2 が０．４を越える試料Ｎo.８，１０では、焼結体の内
部の高温強度が低下した。なお、試料Ｎo.１〜９，１２
について、焼き肌面近傍の靱性と焼き肌面強度とを図１
にプロットした。この図１から明らかなように焼き肌面
近傍の靱性が高いほど焼き肌面強度が高いことがわか
る。As is clear from Table 1, the sample N having a SiO 2 / RE 2 O 3 ratio I 1 of 2.3 or more or a ratio I 2 of 1.9 or more in the surface of the final sintered body was obtained.
Samples Nos. 7, 8, 9, and 17 all had low strength at 1400 ° C., and I 1 -I 2 was smaller than -0.3.
In No. 1, the toughness and strength near the baked surface were low, and I 1 -I
In Samples Nos. 8 and 10, where 2 exceeded 0.4, the high-temperature strength inside the sintered body was reduced. Sample Nos. 1 to 9, 12
Fig. 1 shows the toughness near the burnt surface and the strength of the burnt surface.
Are plotted. As is apparent from FIG. 1, the higher the toughness near the burnt surface, the higher the burnt surface strength.
【００３７】また、成形体のＳｉＯ2 ／ＲＥ2 Ｏ3 比Ｉ
3 が１．９以上では、試料Ｎo.１７のように焼結過程で
最終焼結体のＩ1 が２．３を越えてしまい高温強度が低
くかったり、試料Ｎo.１８のように所望の特性が発揮さ
れなかった。Ｉ3 −Ｉ1 が０．６を越える試料Ｎo.１，
２，１１，１８では、焼結体表面近傍の靱性が低下し焼
結体の高温強度の向上が見られなかった。Further, the SiO 2 / RE 2 O 3 ratio I
3 is a least 1.9, or bought high-temperature strength is low I 1 of the final sintered body will exceed the 2.3 sintering process as in Sample No.17, desired as in Sample No.18 The properties were not exhibited. Sample No. 1 in which I 3 −I 1 exceeds 0.6
In Nos. 2, 11, and 18, the toughness near the surface of the sintered body was reduced, and no improvement in the high-temperature strength of the sintered body was observed.
【００３８】これらの比較例に対して、本発明の試料
は、いずれも焼き肌面靱性が５．５ＭＰａ・ｍ1/2 以上
で、焼結体の焼き肌面の室温強度６００ＭＰａ以上、内
部６５０ＭＰａ以上、１４００℃の内部強度６００ＭＰ
ａ以上が達成された。In contrast to these comparative examples, all of the samples of the present invention had a burnt surface toughness of 5.5 MPa · m 1/2 or more, a room temperature strength of the burnt surface of the sintered body of 600 MPa or more, and an internal 650 MPa. Above, internal strength of 600MP at 1400 ° C
a or more was achieved.
【００３９】[0039]
【発明の効果】以上、詳述したように、本発明によれ
ば、成形体の焼結過程および得られた焼結体におけるＳ
ｉＯ2 ／ＲＥ2 Ｏ3 比を特定の条件を満足するように制
御するとともに焼結体の表面近傍の靱性を高めることに
より、焼き肌面における強度を高めることができる。こ
れにより、複雑形状品で表面研磨ができないような製品
においても高い強度を付与することができ、信頼性の高
い製品を提供することができる。As described above in detail, according to the present invention, the sintering process of the compact and the S
By controlling the iO 2 / RE 2 O 3 ratio so as to satisfy specific conditions and increasing the toughness in the vicinity of the surface of the sintered body, the strength on the burnt surface can be increased. Thereby, high strength can be imparted even to a product having a complicated shape and whose surface cannot be polished, and a highly reliable product can be provided.
【図１】焼き肌面近傍の靱性と焼き肌面強度との関係を
示した図である。FIG. 1 is a diagram showing the relationship between the toughness near the burnt surface and the burnt surface strength.
───────────────────────────────────────────────────── フロントページの続き (58)調査した分野(Int.Cl.7，ＤＢ名) C04B 35/584 - 35/596 ──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. 7 , DB name) C04B 35/584-35/596
Claims (2)
元素（ＲＥ）および過剰酸素を含有し、焼結体表面部の
前記周期律表第３ａ族元素の酸化物換算量（ＲＥ2Ｏ3）
と過剰酸素のＳｉＯ2換算量のＳｉＯ2／ＲＥ2Ｏ3で表さ
れるモル比をＩ1、焼結体中心部の前記モル比をＩ2とし
た時、Ｉ1＜２．３、Ｉ2＜１．９、−０．３≦Ｉ1−Ｉ2
≦０．４を満足するとともに、焼結体表面を０．０５ｍ
ｍ研磨した鏡面における破壊靱性（Ｋ1c）が５．５ＭＰ
ａ・ｍ1/2以上であることを特徴とする窒化珪素質焼結
体。The present invention is characterized in that it contains silicon nitride as a main component, contains a Group 3a element (RE) of the periodic table, and excess oxygen, and the oxide equivalent of the Group 3a element of the periodic table (RE) on the surface of the sintered body. 2 O 3 )
When the molar ratio represented by SiO 2 / RE 2 O 3 in SiO 2 equivalent amount of excess oxygen and I 1, the molar ratio of the sintered body center and I 2 and, I 1 <2.3, I 2 <1.9, −0.3 ≦ I 1 −I 2
Satisfies ≦ 0.4 and the surface of the sintered body is 0.05 m
The fracture toughness (K 1c ) on the polished mirror surface is 5.5MP.
A silicon nitride-based sintered body having a diameter of at least a · m 1/2 .
酸化物（ＲＥ2Ｏ3）、あるいは周期律表第３ａ族元素酸
化物（ＲＥ2Ｏ3）およびＳｉＯ2を含有する成形体を窒
素含有雰囲気中で１６００〜２０００℃の温度で焼成す
るに当たり、焼成炉内に、成形体とともに窒化珪素粉
末、周期律表第３ａ族元素酸化物粉末、ＳｉＯ 2 粉末、
Ｓｉ粉末とＳｉＯ 2 粉末の混合粉末及びＡｌ 2 Ｏ 3 のうち
少なくとも１種からなる雰囲気制御剤を配置し、前記成
形体におけるＳｉＯ2／ＲＥ2Ｏ3で表されるモル比を
Ｉ3、最終焼結体の表面部における前記モル比をＩ1とし
た時、Ｉ3＜１．９、Ｉ3−Ｉ1≦０．６を満足するよう
に前記雰囲気制御剤の量を調整しながら焼成することを
特徴とする窒化珪素質焼結体の製法。 2. A molding containing silicon nitride containing a Group 3a element oxide of the periodic table (RE 2 O 3 ) or a Group 3a element oxide of the periodic table (RE 2 O 3 ) and SiO 2. When the green body is fired at a temperature of 1600 to 2000 ° C. in a nitrogen-containing atmosphere, the silicon nitride powder is placed in a firing furnace together with the compact.
Powder of a Group 3a element of the periodic table, SiO 2 powder,
Of mixed powder of Si powder and SiO 2 powder and Al 2 O 3
At least one type of atmosphere control agent is disposed, and the molar ratio represented by SiO 2 / RE 2 O 3 in the molded body is I 3 , and the molar ratio in the surface portion of the final sintered body is I 1 And baking while adjusting the amount of the atmosphere control agent so as to satisfy I 3 <1.9 and I 3 −I 1 ≦ 0.6.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18787493A JP3237963B2 (en) | 1993-07-29 | 1993-07-29 | Silicon nitride sintered body and method for producing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18787493A JP3237963B2 (en) | 1993-07-29 | 1993-07-29 | Silicon nitride sintered body and method for producing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0741367A JPH0741367A (en) | 1995-02-10 |
| JP3237963B2 true JP3237963B2 (en) | 2001-12-10 |
Family
ID=16213726
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP18787493A Expired - Fee Related JP3237963B2 (en) | 1993-07-29 | 1993-07-29 | Silicon nitride sintered body and method for producing the same |
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| Country | Link |
|---|---|
| JP (1) | JP3237963B2 (en) |
-
1993
- 1993-07-29 JP JP18787493A patent/JP3237963B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0741367A (en) | 1995-02-10 |
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