JPH05186270A - Production of silicon nitride-silicon carbide composite sintered material - Google Patents
Production of silicon nitride-silicon carbide composite sintered materialInfo
- Publication number
- JPH05186270A JPH05186270A JP4023206A JP2320692A JPH05186270A JP H05186270 A JPH05186270 A JP H05186270A JP 4023206 A JP4023206 A JP 4023206A JP 2320692 A JP2320692 A JP 2320692A JP H05186270 A JPH05186270 A JP H05186270A
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- composite powder
- silicon nitride
- silicon
- sintering
- carbon
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、自動車部品や機械部
品、耐摩工具等に使用される構造用セラミックス材料と
して優れた性能を有する窒化ケイ素系焼結体に関するも
のであり、特にその強度と破壊靭性値を共に向上させた
窒化ケイ素−炭化ケイ素複合焼結体の製造方法に関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon nitride-based sintered body having excellent performance as a structural ceramic material used for automobile parts, machine parts, wear resistant tools, etc., and particularly its strength and fracture. The present invention relates to a method for producing a silicon nitride-silicon carbide composite sintered body having both improved toughness values.
【０００２】[0002]
【従来の技術】窒化ケイ素は強度、破壊靭性、耐食性、
耐摩耗性、耐熱衝撃性、耐酸化性等においてバランスの
とれた材料であるため、切削工具からエンジン部品、核
融合炉材等の広い範囲で利用されている。特に最近で
は、自動車エンジンやガスタービン等の高温構造用材料
として注目を集めている。2. Description of the Related Art Silicon nitride has strength, fracture toughness, corrosion resistance,
Since it is a material with well-balanced wear resistance, thermal shock resistance, oxidation resistance, etc., it is used in a wide range from cutting tools to engine parts, fusion furnace materials, and the like. In particular, it has recently attracted attention as a material for high temperature structures such as automobile engines and gas turbines.
【０００３】しかしながら、自動車エンジン等のように
材料に対して高い信頼性が要求される分野に窒化ケイ素
系焼結体を使用するためには、破壊靭性を更に向上させ
て脆さを克服し、且つ同時に強度向上も図ることが必要
不可欠である。その一つの高強度化策として、多結晶体
である窒化ケイ素系焼結体の個々の結晶粒を微細化する
方法が従来からとられて来たが、この方法では高強度化
は達成できるものの破壊靭性が低下し、より一層脆くな
るという欠点があった。However, in order to use the silicon nitride-based sintered body in a field where high reliability is required for a material such as an automobile engine, the fracture toughness is further improved to overcome brittleness, At the same time, it is essential to improve the strength. As one of the measures for increasing the strength, a method of refining individual crystal grains of a silicon nitride-based sintered body that is a polycrystalline body has been conventionally taken, but although this method can achieve high strength, There was a drawback that the fracture toughness was lowered and the material became more brittle.
【０００４】一方、破壊靭性を向上させる方法として、
例えば特開昭６２−２６５１７３号公報等に示されるよ
うに、窒化ケイ素マトリックスに炭化ケイ素ウイスカー
を分散、複合化させる方法がある。この方法によれば、
破壊の際に進展する亀裂がウイスカーによってディフレ
クションしたり、ウイスカーの引き抜きや架橋により破
壊靭性が向上すると考えられる。しかし、添加するウイ
スカーのサイズが約１〜１０μｍのオーダーである上、
その凝集を機械的に完全に取り除くことは事実上困難で
あるため、これが粗大欠陥となって破壊起点として作用
するので、強度の向上が期待できない。On the other hand, as a method of improving fracture toughness,
For example, as disclosed in JP-A-62-265173, there is a method in which silicon carbide whiskers are dispersed and compounded in a silicon nitride matrix. According to this method
It is considered that the cracks that develop during fracture are deflected by the whiskers, and that the fracture toughness is improved by pulling out or crosslinking the whiskers. However, the size of the added whiskers is on the order of about 1 to 10 μm, and
Since it is practically difficult to completely remove the agglomerates mechanically, these act as coarse defects and act as fracture initiation points, so that improvement in strength cannot be expected.
【０００５】このような問題点を解決するための新しい
材料組織の概念として、ナノコンポジット材料がある。
例えば、特開平２−１６０６６９号公報に示されるよう
に、窒化ケイ素中に数ナノメーターから数百ナノメータ
ーの大きさの炭化ケイ素の微粒子が分散し、窒化ケイ素
の粒界に平均粒径１μｍ以下の炭化ケイ素が分散した構
造をもつ窒化ケイ素−炭化ケイ素複合焼結体が提案さ
れ、この窒化ケイ素−炭化ケイ素複合焼結体は窒化ケイ
素単味の焼結体に比べて高い強度と破壊靭性を持つこと
が知られている。As a concept of a new material structure for solving such problems, there is a nanocomposite material.
For example, as disclosed in JP-A-2-160669, fine particles of silicon carbide having a size of several nanometers to several hundreds of nanometers are dispersed in silicon nitride, and an average particle diameter of 1 μm or less at a grain boundary of silicon nitride. A silicon nitride-silicon carbide composite sintered body having a structure in which silicon carbide is dispersed is proposed, and this silicon nitride-silicon carbide composite sintered body has higher strength and fracture toughness than a silicon nitride-only sintered body. Known to have.
【０００６】しかしながら、従来の複合焼結体の製造プ
ロセスのように、母相である窒化ケイ素粉末と分散相で
ある炭化ケイ素粉末とを機械的に混合し焼結する方法で
は、原料粉末の平均粒径自体がミクロンオーダーかせい
ぜい小さくても数百ナノメーターであるため、焼結体中
の分散粒子の平均粒径をナノメーターオーダーにするこ
とは事実上不可能であり、従って従来のプロセスで得ら
れる複合焼結体の高強度化は期待できない。However, in the method of mechanically mixing and sintering the silicon nitride powder as the mother phase and the silicon carbide powder as the dispersed phase as in the conventional manufacturing process of the composite sintered body, the average of the raw material powders is The average particle size of dispersed particles in a sintered body is practically impossible to reach the nanometer order because the particle size itself is several hundred nanometers, even if it is as small as micron order. Higher strength of the obtained composite sintered body cannot be expected.
【０００７】そこで、よりファインなナノコンポジット
材料を焼結体として得るためには、原料粉末自体を複合
化し、焼結中にその場で分散粒子が生成する製造プロセ
スを採用することが有効である。例えば、前記特開平２
−１６０６６９号公報にも記載されているように、主に
ケイ素と窒素と炭素からなる有機ケイ素化合物をアンモ
ニアを含む非酸化性ガス中で加熱し、得られる非晶質複
合粉末に焼結助剤を加えて焼結し、焼結中にその場で炭
化ケイ素を結晶化させることによって、より一層微細な
炭化ケイ素粒子を析出させることが可能である。Therefore, in order to obtain a finer nanocomposite material as a sintered body, it is effective to employ a manufacturing process in which the raw material powder itself is compounded and dispersed particles are generated in situ during sintering. .. For example, the above-mentioned Japanese Patent Laid-Open No. 2
As described in Japanese Patent Publication No. 160669, an organosilicon compound mainly composed of silicon, nitrogen and carbon is heated in a non-oxidizing gas containing ammonia to obtain an amorphous composite powder and a sintering aid. It is possible to precipitate finer silicon carbide particles by adding and sintering and crystallizing silicon carbide in situ during sintering.
【０００８】[0008]
【発明が解決しようとする課題】上記のごとく窒化ケイ
素系焼結体の高強度化及び高靭性化には、ナノコンポジ
ット材料の窒化ケイ素−炭化ケイ素複合焼結体とするこ
とが有効であるが、従来の方法で原料粉末として使用さ
れてきた主にケイ素と窒素と炭素からなる非晶質複合粉
末では、焼結中に局所的に１０μｍ以上の極端に大きな
炭化ケイ素の粗大凝集組織が生成してしまい、これが破
壊起点となって材料本来の強度より低いレベルで破壊し
てしまうことが分かった。As described above, in order to increase the strength and toughness of the silicon nitride-based sintered body, it is effective to use the silicon nitride-silicon carbide composite sintered body of the nanocomposite material. In the amorphous composite powder mainly composed of silicon, nitrogen and carbon which has been used as a raw material powder in the conventional method, an extremely large coarse aggregate structure of silicon carbide of 10 μm or more is locally generated during sintering. It has been found that this becomes the starting point of fracture and causes fracture at a level lower than the original strength of the material.
【０００９】即ち、主にケイ素と窒素と炭素からなる非
晶質複合粉末を焼結すると、α相の窒化ケイ素及びβ相
の炭化ケイ素への結晶化が起こり、更には高温域で最終
的な緻密化が行われるが、その際に下記に示すような気
相−固相反応が同時に起こるため、局所的な炭化ケイ素
の粗大凝集組織が生成する。 (1)粉末中の遊離炭素と粉末表面の酸化層又は焼結助剤
の酸化物の酸素との反応によるＣＯガスの生成： Ｃ（固）＋Ｏ（固）→ＣＯ（気） (2)粉末中のケイ素−窒素結合の解離によるケイ素の生
成： Ｓｉ3Ｎ4（固）→Ｓｉ（固）＋Ｎ2（気） (3)生成したＣＯガスとケイ素との反応による炭化ケイ
素の生成： ＣＯ（気）＋Ｓｉ（固）→ＳｉＣ（固）＋Ｏ2（気） (4)生成したＣＯガスと窒化ケイ素との反応による炭化
ケイ素の生成： ＣＯ（気）＋Ｓｉ3Ｎ4（固）→ＳｉＣ（固）＋ＮＯ
x（気）That is, when an amorphous composite powder mainly composed of silicon, nitrogen and carbon is sintered, crystallization into α-phase silicon nitride and β-phase silicon carbide occurs, and further, finally in a high temperature range. Although densification is performed, a vapor-solid reaction as shown below occurs at the same time, so that a local coarse aggregate structure of silicon carbide is generated. (1) Generation of CO gas by reaction of free carbon in powder with oxygen of oxide layer on powder surface or oxide of sintering aid: C (solid) + O (solid) → CO (gas) (2) powder Of silicon by dissociation of silicon-nitrogen bond in: Si 3 N 4 (solid) → Si (solid) + N 2 (gas) (3) Generation of silicon carbide by reaction of generated CO gas with silicon: CO ( Gas) + Si (solid) → SiC (solid) + O 2 (gas) (4) Formation of silicon carbide by reaction of generated CO gas with silicon nitride: CO (gas) + Si 3 N 4 (solid) → SiC (solid) ) + NO
x
【００１０】本発明はかかる従来の事情に鑑み、炭化ケ
イ素の粗大欠陥の生成を抑制し、強度並びに破壊靭性が
共に優れた窒化ケイ素−炭化ケイ素複合焼結体の製造方
法を提供することを目的とする。In view of such conventional circumstances, it is an object of the present invention to provide a method for producing a silicon nitride-silicon carbide composite sintered body which suppresses the generation of coarse defects of silicon carbide and is excellent in both strength and fracture toughness. And
【００１１】[0011]
【課題を解決するための手段】上記目的を達成するた
め、本発明の窒化ケイ素−炭化ケイ素複合焼結体におい
ては、ケイ素と窒素と炭素を主成分とし、結晶化率が６
５％以上で且つ結晶相がα相の窒化ケイ素である結晶質
複合粉末に、焼結助剤を加えて焼結することを特徴とす
る。To achieve the above object, the silicon nitride-silicon carbide composite sintered body of the present invention contains silicon, nitrogen and carbon as main components and has a crystallization rate of 6%.
It is characterized in that a sintering aid is added to the crystalline composite powder which is 5% or more and the crystal phase is silicon nitride of α phase and is sintered.
【００１２】本発明方法の好ましい態様としては、主に
ケイ素と窒素と炭素とからなる非晶質複合粉末を、窒素
雰囲気中において１５５０〜１７００℃で少なくとも３
時間熱処理することにより、ケイ素と窒素と炭素を主成
分とし、結晶化率が６５％以上で且つ結晶相がα相の窒
化ケイ素である結晶質複合粉末を製造し、この結晶質複
合粉末に焼結助剤を加えて焼結する方法がある。In a preferred embodiment of the method of the present invention, an amorphous composite powder composed mainly of silicon, nitrogen and carbon is used in a nitrogen atmosphere at 1550 to 1700 ° C. for at least 3 times.
By heat treatment for a period of time, a crystalline composite powder containing silicon, nitrogen, and carbon as main components and having a crystallization rate of 65% or more and a crystalline phase of α-phase silicon nitride is produced, and this crystalline composite powder is burned. There is a method of adding a sintering aid and sintering.
【００１３】[0013]
【作用】本発明においては、窒化ケイ素−炭化ケイ素複
合焼結体の焼結原料粉末として結晶質の複合粉末を用い
るので、従来使用していた非晶質粉末よりも酸化に対し
て安定であり、又非晶質粉末中に余分に含まれる炭素や
窒素等が揮発除去されている。従って、粉末中の遊離炭
素と粉末表面の酸化層との反応によるＣＯガスの生成が
少なくなるので、ＣＯガスとＳｉ及びＳｉ3Ｎ4との気相
−固相反応が抑制されて炭化ケイ素の粗大凝集組織の生
成が減少し、最終焼結体の強度を向上させることができ
る。In the present invention, since the crystalline composite powder is used as the sintering raw material powder of the silicon nitride-silicon carbide composite sintered body, it is more stable against oxidation than the conventionally used amorphous powder. In addition, excess carbon, nitrogen, etc. contained in the amorphous powder are removed by volatilization. Therefore, CO gas generation due to the reaction between the free carbon in the powder and the oxide layer on the surface of the powder is reduced, so that the gas-solid reaction between the CO gas and Si and Si 3 N 4 is suppressed and silicon carbide Generation of a coarse agglomerate structure is reduced, and the strength of the final sintered body can be improved.
【００１４】又、本発明における結晶質複合粉末では、
α相の窒化ケイ素への結晶化率が最終焼結体の強度や靭
性に大きく影響する。即ち、α相の窒化ケイ素への結晶
化率が高くなるほど、前記したＣＯガスとの気相−固相
反応の影響が少なくなり、炭化ケイ素の粗大凝集による
欠陥の発生を低減できるのであり、非晶質相による欠陥
発生の影響をなくすために結晶化率は６５％以上必要で
あって、８５％以上が好ましい。更に、その結晶相はα
相の窒化ケイ素であって炭化ケイ素の結晶相又は結晶粒
子を含まないから、焼結中に炭化ケイ素が粒成長して粗
大欠陥となることも防止できる。尚、非晶質複合粉末中
にβ相の窒化ケイ素が生成すると、焼結性の低下及び異
常粒成長の原因となるので好ましくない。In the crystalline composite powder of the present invention,
The crystallization rate of α phase into silicon nitride has a great influence on the strength and toughness of the final sintered body. That is, the higher the crystallization rate of the α phase to silicon nitride, the less the influence of the gas phase-solid phase reaction with the CO gas described above, and the more the generation of defects due to coarse agglomeration of silicon carbide can be reduced. The crystallization rate must be 65% or more, and preferably 85% or more, in order to eliminate the influence of the occurrence of defects due to the crystalline phase. Furthermore, its crystalline phase is α
Since the phase is silicon nitride and does not include the crystal phase or crystal particles of silicon carbide, it is also possible to prevent the silicon carbide from growing into coarse defects during sintering. If β-phase silicon nitride is generated in the amorphous composite powder, it is not preferable because it causes deterioration of sinterability and abnormal grain growth.
【００１５】かかる本発明における結晶質複合粉末は、
主にケイ素と窒素と炭素からなる非晶質粉末を窒素雰囲
気中で熱処理することにより製造できる。その原料とな
る非晶質粉末は特に限定されず、例えばＣＶＤ法やＰＶ
Ｄ法等の気相析出法により合成した主にケイ素と窒素と
炭素からなる非晶質複合粉末、ポリシラザン等のケイ素
と窒素と炭素を含む有機ケイ素化合物とアンモニアの気
相反応で得られる非晶質複合粉末、有機ケイ素化合物又
は炭素粉末を混合した非晶質窒化ケイ素粉末等を使用す
ることが可能である。The crystalline composite powder according to the present invention is
It can be produced by heat treating an amorphous powder mainly composed of silicon, nitrogen and carbon in a nitrogen atmosphere. The amorphous powder used as the raw material is not particularly limited, and may be, for example, a CVD method or PV.
Amorphous composite powder mainly composed of silicon, nitrogen and carbon synthesized by a vapor deposition method such as method D, amorphous obtained by a vapor phase reaction of ammonia with an organosilicon compound containing silicon, nitrogen and carbon such as polysilazane It is possible to use a fine composite powder, an amorphous silicon nitride powder mixed with an organic silicon compound or a carbon powder, or the like.
【００１６】中でも気相析出法により合成した主にケイ
素と窒素と炭素からなる非晶質複合粉末の熱処理による
製造が好ましいが、非晶質複合粉末に含まれる炭素の量
が多い程、α相窒化ケイ素への結晶化速度が遅くなるの
で注意を要する。例えば、炭素を含まない窒化ケイ素非
晶質粉末は、１５００℃で１２時間の熱処理により８５
％がα相窒化ケイ素に結晶化するが、炭素含有量が９重
量％になると１５００℃では殆ど結晶化しない。炭素含
有量９重量％の非晶質複合粉末では、１６００℃で１６
時間の熱処理でも結晶化率は３４％のみであり、更に温
度を上げて１７５０℃で熱処理すると好ましくないβ相
の窒化ケイ素及びβ相の炭化ケイ素が生成してしまう。Above all, it is preferable to produce the amorphous composite powder mainly composed of silicon, nitrogen and carbon by the heat treatment, which is synthesized by the vapor phase precipitation method. However, as the amount of carbon contained in the amorphous composite powder increases, the α phase Care must be taken because the rate of crystallization into silicon nitride becomes slow. For example, a carbon-free silicon nitride amorphous powder is subjected to a heat treatment at 1500 ° C. for 12 hours to 85
% Crystallizes into α-phase silicon nitride, but when the carbon content becomes 9 wt%, it hardly crystallizes at 1500 ° C. With an amorphous composite powder having a carbon content of 9% by weight, 16 at 1600 ° C.
The crystallization rate is only 34% even after the heat treatment for a long time, and further heat treatment at 1750 ° C. further produces undesirable β-phase silicon nitride and β-phase silicon carbide.
【００１７】従って、結晶化率が６５％以上且つ結晶相
がα相の窒化ケイ素である結晶質複合粉末を製造するた
めには、主にケイ素と窒素と炭素とからなる非晶質複合
粉末の炭素含有量に応じて、窒素雰囲気中での熱処理温
度を１５５０〜１７００℃とし、少なくとも３時間熱処
理することが必要である。尚、非晶質複合粉末中の炭素
含有量は、１０重量％を越えると結晶質複合粉末の焼結
の際に緻密化せず、又１重量％未満では最終焼結体にお
ける炭化ケイ素粒子の生成が不十分で高強度化の効果が
ないので、１〜１０重量％の範囲が好ましい。Therefore, in order to produce a crystalline composite powder having a crystallization ratio of 65% or more and a crystal phase of α-phase silicon nitride, an amorphous composite powder mainly composed of silicon, nitrogen and carbon is used. Depending on the carbon content, it is necessary to set the heat treatment temperature in a nitrogen atmosphere to 1550 to 1700 ° C. and perform the heat treatment for at least 3 hours. If the carbon content in the amorphous composite powder exceeds 10% by weight, the crystalline composite powder will not be densified during sintering, and if it is less than 1% by weight, the content of silicon carbide particles in the final sintered body will increase. Since the formation is insufficient and there is no effect of increasing the strength, the range of 1 to 10% by weight is preferable.
【００１８】この様に非晶質複合粉末の炭素含有量は重
要であるが、非晶質複合粉末を熱処理して得られた結晶
質複合粉末、又は焼結助剤を加えた結晶質複合粉末若し
くはその圧粉体を、大気中において４００〜１０００℃
で０.５〜５０時間熱処理することにより、遊離炭素の
残渣を酸化除去することができる。従って、この処理に
より不要な炭素が除去され、より一層微細で強度及び靭
性に優れた最終焼結体の製造が可能である。As described above, the carbon content of the amorphous composite powder is important, but the crystalline composite powder obtained by heat-treating the amorphous composite powder or the crystalline composite powder to which a sintering aid is added is added. Alternatively, the green compact is heated to 400 to 1000 ° C in the atmosphere.
It is possible to oxidize and remove the free carbon residue by heat treatment for 0.5 to 50 hours. Therefore, unnecessary carbon is removed by this treatment, and it is possible to manufacture a finer final sintered body having excellent strength and toughness.
【００１９】本発明における結晶質複合粉末は、非晶質
複合粉末に比べて焼結性に富み、これにＹ2Ｏ3、Ａｌ2
Ｏ3、ＭｇＯ、ＡｌＮ等の焼結助剤を加えて、窒素雰囲
気中において焼結すれば、緻密な窒化ケイ素−炭化ケイ
素複合焼結体を得ることができる。焼結方法としても、
ホットプレス法のほか、ガス圧焼結や常圧焼結等も適用
することができる。この焼結中において、前記のごとく
非晶質粉末に由来する気相−固相反応が抑制され、局所
的な粗大欠陥の生成がなくなるので、ナノメーターサイ
ズの微細な炭化ケイ素粒子が分散、析出したナノコンポ
ジット材料の焼結体となり、高強度化及び高靭性化が達
成される。The crystalline composite powder of the present invention is more sinterable than the amorphous composite powder, and Y 2 O 3 , Al 2
A dense silicon nitride-silicon carbide composite sintered body can be obtained by adding a sintering aid such as O 3 , MgO or AlN and sintering in a nitrogen atmosphere. As a sintering method,
In addition to the hot pressing method, gas pressure sintering, atmospheric pressure sintering and the like can be applied. During this sintering, the gas phase-solid phase reaction derived from the amorphous powder is suppressed as described above, and the generation of local coarse defects is eliminated, so that nanometer-sized fine silicon carbide particles are dispersed and precipitated. It becomes a sintered body of the nanocomposite material, and high strength and high toughness are achieved.
【００２０】[0020]
【実施例１】公知のＣＶＤ法により合成した炭素含有量
の異なるＳｉ−Ｎ−Ｃ非晶質複合粉末を、窒素雰囲気中
において表１に示す条件でそれぞれ熱処理した。得られ
た結晶質複合粉末のα相窒化ケイ素への結晶化率を測定
した後、各粉末に焼結助剤として５wt％Ｙ2Ｏ3と２wt％
Ａｌ2Ｏ3を加えて混合し、窒素雰囲気中において２００
kg／cm2の圧力にて１８５０℃で２時間のホットプレス
焼結を行った。得られた各焼結体について、曲げ強度
（σ）と破壊靭性（ＫIC）を測定し、結果を非晶質粉末
の炭素含有量、熱処理条件及び結晶化率と共に表１に示
した。Example 1 Si-N-C amorphous composite powders having different carbon contents synthesized by a known CVD method were heat-treated in a nitrogen atmosphere under the conditions shown in Table 1. After measuring the crystallization rate of the obtained crystalline composite powder into α-phase silicon nitride, each powder was mixed with 5 wt% Y 2 O 3 and 2 wt% as a sintering aid.
Al 2 O 3 is added and mixed, and the mixture is heated to 200 in a nitrogen atmosphere.
Hot press sintering was performed at 1850 ° C. for 2 hours at a pressure of kg / cm 2 . The bending strength (σ) and fracture toughness (K IC ) of each of the obtained sintered bodies were measured, and the results are shown in Table 1 together with the carbon content of the amorphous powder, the heat treatment conditions and the crystallization rate.
【００２１】[0021]
【表１】 Ｃ含有量 熱 処 理 条 件 結晶化率 曲げ強度 破壊靭性 試料 (wt％) 温度(℃) 時間(hr) (％) (kg／mm2) (MPam1/2) A−0＊ 1.7 熱処理なし 0 101 5.81 1 1.7 1550 8 70 125 6.33 2 1.7 1550 16 88 148 6.94 3 1.7 1600 16 95 152 7.13 B−0＊ 2.8 熱処理なし 0 112 5.95 1 2.8 1550 10 66 138 6.06 2 2.8 1600 16 87 158 7.02 C−0＊ 5.6 熱処理なし 0 120 5.85 1 5.6 1600 8 70 139 6.11 2 5.6 1600 24 81 155 6.89 3 5.6 1650 8 86 159 6.77 4 5.6 1650 16 97 178 8.97 5 5.6 1700 16 100 189 9.57 D−0＊ 8.7 熱処理なし 0 136 6.38 1＊ 8.7 1600 7 7 95 6.20 2＊ 8.7 1600 16 15 101 6.16 3 8.7 1600 50 92 198 9.28 4 8.7 1700 16 96 201 10.1 5 8.7 1700 30 100 210 11.5 （注）＊を付した試料は比較例である。[Table 1] C content Heat treatment Condition Crystallization rate Bending strength Fracture toughness Sample (wt%) Temperature (℃) Time (hr) (%) (kg / mm 2 ) (MPam 1/2 ) A-0 * 1.7 No heat treatment 0 101 5.81 1 1.7 1550 8 70 125 6.33 2 1.7 1550 16 88 148 6.94 3 1.7 1600 16 95 152 7.13 B-0 * 2.8 No heat treatment 0 112 5.95 1 2.8 1550 10 66 138 6.06 2 2.8 1600 16 87 158 7.02 C-0 * 5.6 No heat treatment 0 120 5.85 1 5.6 1600 8 70 139 6.11 2 5.6 1600 24 81 155 6.89 3 5.6 1650 8 86 159 6.77 4 5.6 1650 16 97 178 8.97 5 5.6 1700 16 100 189 9.57 D-0 * 8.7 No heat treatment 0 136 6.38 1 * 8.7 1600 7 7 95 6.20 2 * 8.7 1600 16 15 101 6.16 3 8.7 1600 50 92 198 9.28 4 8.7 1700 16 96 201 10.1 5 8.7 1700 30 100 210 11.5 (Note) * marked The prepared sample is a comparative example.
【００２２】[0022]
【実施例２】炭素含有量が１０wt％以上のＳｉ−Ｎ−Ｃ
非晶質複合粉末を、結晶化率が９５％以上になるように
窒素雰囲気中にて１７００℃で５〜１０時間熱処理し、
得られた結晶質複合粉末を更に大気中にて表２に示す条
件で熱処理して遊離炭素の残渣を酸化除去した。その
後、各結晶質複合粉末を実施例１と同様に焼結助剤を加
えてホットプレス焼結し、得られた各焼結体について曲
げ強度（σ）と破壊靭性（ＫIC）を測定し、結果を非晶
質複合粉末の炭素含有量、大気中での熱処理条件と共に
表２に示した。Example 2 Si-N-C having a carbon content of 10 wt% or more
The amorphous composite powder is heat-treated at 1700 ° C. for 5 to 10 hours in a nitrogen atmosphere so that the crystallization rate is 95% or more,
The obtained crystalline composite powder was further heat-treated in the atmosphere under the conditions shown in Table 2 to remove the free carbon residue by oxidation. Thereafter, each crystalline composite powder was hot-press sintered by adding a sintering aid in the same manner as in Example 1, and bending strength (σ) and fracture toughness (K IC ) of each obtained sintered body were measured. The results are shown in Table 2 together with the carbon content of the amorphous composite powder and the heat treatment conditions in the atmosphere.
【００２３】[0023]
【表２】 Ｃ含有量 大気中熱処理条件 曲げ強度 破壊靭性 試料 (wt％) 温度(℃) 時間(hr) (kg／mm2) (MPam1/2) E−0＊ 15 熱処理なし 86 4.56 1＊ 15 200 2 94 5.12 2 15 500 2 142 7.41 3 15 800 5 187 8.25 F−0＊ 20 熱処理なし 65 4.80 1＊ 20 200 2 75 4.98 2 20 500 2 138 6.63 3 20 800 5 179 7.89 （注）＊を付した試料は比較例である。[Table 2] C content Heat treatment condition in air Bending strength Fracture toughness Sample (wt%) Temperature (℃) Time (hr) (kg / mm 2 ) (MPam 1/2 ) E-0 * 15 No heat treatment 86 4.56 1 * 15 200 2 94 5.12 2 15 500 2 142 7.41 3 15 800 5 187 8.25 F−0 * 20 No heat treatment 65 4.80 1 * 20 200 2 75 4.98 2 20 500 2 138 6.63 3 20 800 5 179 7.89 (Note) * The sample marked with is a comparative example.
【００２４】[0024]
【発明の効果】本発明によれば、強度及び破壊靭性とも
に従来のものよりも優れた窒化ケイ素系セラミックスを
得ることができ、高強度且つ高靭性で高い信頼性が要求
される自動車エンジンをはじめとする各種の高温構造用
材料として有用である。EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain silicon nitride-based ceramics which are superior in strength and fracture toughness to the conventional ones, and it is possible to obtain an automobile engine which requires high strength, high toughness and high reliability. It is useful as various high temperature structural materials.
Claims (4)
化率が６５％以上で且つ結晶相がα相の窒化ケイ素であ
る結晶質複合粉末に、焼結助剤を加えて焼結することを
特徴とする窒化ケイ素−炭化ケイ素複合焼結体の製造方
法。1. A sintering aid is added to a crystalline composite powder containing silicon nitride, nitrogen, and carbon as main components and having a crystallization rate of 65% or more and a crystal phase of α phase silicon nitride, and sintering the mixture. A method for producing a silicon nitride-silicon carbide composite sintered body, comprising:
質複合粉末を、窒素雰囲気中において１５５０〜１７０
０℃で少なくとも３時間熱処理することにより、ケイ素
と窒素と炭素を主成分とし、結晶化率が６５％以上で且
つ結晶相がα相の窒化ケイ素である結晶質複合粉末を製
造し、この結晶質複合粉末に焼結助剤を加えて焼結する
ことを特徴とする窒化ケイ素−炭化ケイ素複合焼結体の
製造方法。2. Amorphous composite powder mainly composed of silicon, nitrogen and carbon in a nitrogen atmosphere at 1550 to 170.
By heat-treating at 0 ° C. for at least 3 hours, a crystalline composite powder containing silicon, nitrogen and carbon as main components and having a crystallization ratio of 65% or more and a crystal phase of α-phase silicon nitride is produced. A method for producing a silicon nitride-silicon carbide composite sintered body, which comprises adding a sintering aid to a high-quality composite powder and performing sintering.
１０重量％であることを特徴とする、請求項２に記載の
窒化ケイ素−炭化ケイ素複合焼結体の製造方法。3. The carbon content of the amorphous composite powder is from 1 to 1.
It is 10 weight%, The manufacturing method of the silicon nitride silicon carbide compound sintered compact of Claim 2 characterized by the above-mentioned.
えた結晶質複合粉末若しくはその圧粉体を、大気中にお
いて４００〜１０００℃で０.５〜５０時間熱処理する
ことにより、遊離炭素の残渣を酸化除去することを特徴
とする、請求項１又は２に記載の窒化ケイ素−炭化ケイ
素複合焼結体の製造方法。4. A crystalline composite powder, or a crystalline composite powder containing a sintering aid or a powder compact thereof is heat-treated in the atmosphere at 400 to 1000 ° C. for 0.5 to 50 hours to release the crystalline composite powder. The method for producing a silicon nitride-silicon carbide composite sintered body according to claim 1, wherein the carbon residue is removed by oxidation.
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4023206A JPH05186270A (en) | 1992-01-13 | 1992-01-13 | Production of silicon nitride-silicon carbide composite sintered material |
| DE69225304T DE69225304T2 (en) | 1991-08-13 | 1992-08-12 | Sintered silicon nitride composite and its manufacture |
| PCT/JP1992/001032 WO1993004012A1 (en) | 1991-08-13 | 1992-08-12 | Composite silicon nitride sinter and production thereof |
| US07/956,887 US5352641A (en) | 1991-08-13 | 1992-08-12 | Silicon nitride composite sintered body and process for producing same |
| EP92917816A EP0552381B1 (en) | 1991-08-13 | 1992-08-12 | Composite silicon nitride sinter and production thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4023206A JPH05186270A (en) | 1992-01-13 | 1992-01-13 | Production of silicon nitride-silicon carbide composite sintered material |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH05186270A true JPH05186270A (en) | 1993-07-27 |
Family
ID=12104197
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP4023206A Pending JPH05186270A (en) | 1991-08-13 | 1992-01-13 | Production of silicon nitride-silicon carbide composite sintered material |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH05186270A (en) |
-
1992
- 1992-01-13 JP JP4023206A patent/JPH05186270A/en active Pending
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