【０００１】[0001]
【発明の属する技術分野】本発明は、破壊靱性に優れ、
特にピストン、シリンダー、バルブ、カムローラー、ロ
ッカーアーム、ピストンリング、ピストンピンなどの自
動車用部品や、タービンロータ、タービンブレード、ノ
ズル、コンバスタ、スクロール、ノズルサポート、シー
ルリング、スプリングリング、ディフューザ、ダクト、
シュラウドなどのガスタービンエンジン用部品に好適に
使用される高靭性窒化珪素質焼結体に関する。TECHNICAL FIELD The present invention relates to a method for producing a steel sheet having excellent fracture toughness,
In particular, automotive parts such as pistons, cylinders, valves, cam rollers, rocker arms, piston rings, piston pins, turbine rotors, turbine blades, nozzles, combustors, scrolls, nozzle supports, seal rings, spring rings, diffusers, ducts,
The present invention relates to a high-toughness silicon nitride sintered body suitably used for a gas turbine engine component such as a shroud.
【０００２】[0002]
【従来技術】従来から、窒化珪素質焼結体は、強度、硬
度、熱的化学的安定性に優れることからエンジニアリン
グセラミックスとして、特に熱機関構造用材料としてそ
の応用が進められている。このような窒化珪素質焼結体
は、窒化珪素粉末に対して周期律表第３ａ族元素酸化物
等の焼結助剤を添加混合し、成形後、非酸化性雰囲気中
で１５００〜２０００℃の温度にて焼成することにより
得られている。2. Description of the Related Art Conventionally, silicon nitride based sintered bodies have been applied as engineering ceramics, particularly as heat engine structural materials, because of their excellent strength, hardness and thermal and chemical stability. Such a silicon nitride-based sintered body is obtained by adding and mixing a sintering aid such as an oxide of a Group 3a element in the periodic table to silicon nitride powder, forming the mixture, and then forming the mixture at 1500 to 2000 ° C. in a non-oxidizing atmosphere. At the following temperature.
【０００３】ところが、窒化珪素質焼結体は、優れた特
性を有する反面、靱性は他のセラミック材料よりは高い
ものの、金属材料に比べると低いという問題を有してい
る。そこで、この破壊靭性を高めるために、これまで窒
化珪素結晶を針状、柱状化し、クラックの伸展を抑制す
る方法、あるいはウィスカーや微小粒子を添加し複合化
する方法がとられてきた。[0003] Although silicon nitride-based sintered bodies have excellent characteristics, they have a problem that the toughness is higher than that of other ceramic materials, but lower than that of metal materials. Therefore, in order to enhance the fracture toughness, a method of forming a silicon nitride crystal into a needle-like or columnar shape and suppressing the extension of cracks, or a method of adding whiskers or fine particles to form a composite has been employed.
【０００４】[0004]
【発明が解決しようとする課題】上記の従来技術によれ
ば、窒化珪素結晶を成長させ粗大化することにより、プ
ルアウト、クラックディフレクション、ボンディング等
の効果により破壊靭性が向上するとされている。しかし
ながら、従来の方法では、クラックの進行に対し柱状化
した粗大粒子のみではその存在量が少ないために前述す
る効果が得られにくいために、破壊靱性の向上効果が不
十分であり、場合によっては、粗大粒を起点としたクラ
ックが発生しやすいために強度が低下するという問題が
あった。According to the above-mentioned prior art, it is said that by growing silicon nitride crystals and making them coarse, the fracture toughness is improved by the effects of pull-out, crack deflection, bonding and the like. However, in the conventional method, the effect described above is hardly obtained because only the coarse particles that have been columnarized with respect to the progress of the cracks have a small abundance, and the effect of improving the fracture toughness is insufficient. In addition, there is a problem that cracks starting from coarse grains are likely to occur, resulting in a decrease in strength.
【０００５】また同様に、ＳｉＣなどの微小粒子を分散
させる方法も、ＳｉＣ粒子を多量に配合しないとその効
果が得られにくく、またＳｉＣ量が多いと焼結性が低下
するために高密度の焼結体が得られにくく、いずれも破
壊靱性の向上効果が不十分である。また、焼結性の低下
により強度が劣化する等の問題があり決定的な対策には
到っていないのが現状である。Similarly, in the method of dispersing fine particles such as SiC, it is difficult to obtain the effect unless a large amount of SiC particles are blended, and when the amount of SiC is large, the sinterability is reduced, so that the high density It is difficult to obtain a sintered body, and in each case, the effect of improving the fracture toughness is insufficient. In addition, there is a problem that the strength is deteriorated due to a decrease in sinterability, and no definitive measures have been reached at present.
【０００６】[0006]
【課題を解決するための手段】本発明者は、破壊靱性及
び組織に対して検討を加えたところ、破壊靱性の対して
窒化珪素粒子の柱状化した粗大粒子のみならず、粗大粒
子をとりまくマトリックス粒子を適量存在させ、そのマ
トリックスを形成する結晶粒子の粒径を制御し、同時に
柱状の粗大粒子の粒径およびその量を制御することによ
り、高い強度を有したまま、破壊靭性を大きく向上でき
ることを見いだし、本発明に至った。The inventors of the present invention have studied the fracture toughness and the microstructure, and found that not only the columnar coarse particles of silicon nitride particles but also the matrix surrounding the coarse particles are suitable for the fracture toughness. By having an appropriate amount of particles and controlling the particle size of the crystal particles forming the matrix, and simultaneously controlling the particle size and the amount of the columnar coarse particles, the fracture toughness can be greatly improved while maintaining high strength. And have led to the present invention.
【０００７】即ち、本発明の高靱性窒化珪素質焼結体に
よれば、窒化珪素を６０〜９９モル％と、周期律表第３
ａ族元素を酸化物換算で１〜１０モル％と、Ａｌを酸化
物換算で０〜１０モル％と、不純物的酸素をＳｉＯ2換
算で１〜３０モル％の割合で含有するとともに、平均長
径が５〜５０μｍ、平均アスペクト比が５以上の窒化珪
素柱状結晶粒子からなるマトリックス中に、長径が８０
μｍ以上、アスペクト比が５以上の窒化珪素柱状結晶粒
子が３〜１５体積％の割合で分散してなることを特徴と
するものである。That is, according to the high toughness silicon nitride sintered body of the present invention, the content of silicon nitride is 60 to 99 mol%,
It contains a group a element in an amount of 1 to 10 mol% in terms of oxide, Al in an amount of 0 to 10 mol% in terms of oxide, and oxygen in an amount of 1 to 30 mol% in terms of SiO2. Is 5 to 50 μm and the average aspect ratio is 5 or more.
It is characterized in that silicon nitride columnar crystal grains having a size of at least 5 μm and an aspect ratio of at least 5 are dispersed at a rate of 3 to 15% by volume.
【０００８】また、かかる焼結体においては、さらに、
窒化珪素以外の平均粒径が１〜５μｍの硬質粒子を０．
５〜２５重量部の割合で分散含有してもよく、その場
合、前記硬質粒子としては、Ｔａ、Ｎｂ、Ｍｏ、Ｗのシ
リサイド及びＳｉＣの中から選ばれる少なくとも１種以
上が好適である。[0008] Further, in such a sintered body,
Hard particles having an average particle size of 1 to 5 μm other than silicon nitride are added in an amount of 0.
The hard particles may be dispersed and contained at a ratio of 5 to 25 parts by weight. In this case, the hard particles are preferably at least one selected from silicides of Ta, Nb, Mo, W and SiC.
【０００９】さらに、組成上、高温での耐酸化性を重視
する場合には、前記不純物的酸素の二酸化珪素換算（Ｓ
ｉＯ2）の前記周期律表第３ａ族元素の酸化物換算量
（ＲＥ2Ｏ3）に対するモル比（ＳｉＯ2／ＲＥ
2Ｏ3）が２以上であることが望ましく、その場合、前
記不純物的酸素及び周期律表第３ａ族元素が前記窒化珪
素の結晶粒子の粒界に主として存在し、該粒界にはシリ
コンオキシナイトライド、モノシリケート及び、ダイシ
リケートからなる群より選ばれた少なくとも１種以上の
結晶相が析出していることが望ましい。Further, when importance is attached to oxidation resistance at high temperatures in terms of composition, the above-mentioned impurity oxygen is converted into silicon dioxide (S
The molar ratio (SiO2 / RE) of iO2 ) to the oxide equivalent (RE2 O3 ) of the Group 3a element of the periodic table.
2 O3 ) is preferably 2 or more. In this case, the impurity oxygen and the Group 3a element of the periodic table mainly exist at the grain boundaries of the silicon nitride crystal grains, and the silicon oxy It is desirable that at least one crystal phase selected from the group consisting of nitride, monosilicate, and disilicate is precipitated.
【００１０】また、高温強度を重視する場合には、前記
ＳｉＯ2／ＲＥ2Ｏ3のモル比が２未満であることが望
ましく、その場合、前記不純物的酸素及び周期律表第３
ａ族元素が窒化珪素の結晶粒子の粒界に主として存在
し、該粒界にはＹＡＭ、アパタイト、メリライト及び、
ワラストナイトからなる群より選ばれた少なくとも１種
以上の結晶相が析出していることが望ましい。When importance is placed on high-temperature strength, the molar ratio of SiO2 / RE2 O3 is desirably less than 2, in which case the impurity oxygen and the third element of the periodic table are required.
Group a elements are mainly present at grain boundaries of crystal grains of silicon nitride, and YAM, apatite, melilite and
It is desirable that at least one crystal phase selected from the group consisting of wollastonite is precipitated.
【００１１】[0011]
【発明の実施の形態】本発明の窒化珪素質焼結体は、窒
化珪素結晶を主成分として、その結晶の粒界を構成する
主成分として、周期律表第３ａ族元素、不純物的酸素、
場合によっては、Ａｌを含む。ここで不純物的酸素と
は、焼結体中の全酸素量から添加物として周期律表第３
ａ族元素化合物とＡｌ中に化学量論的に含まれる酸素を
差し引いた残りの酸素の意であり、そのほとんどは窒化
珪素原料に含まれる酸素、あるいは添加される酸化珪素
として混入するものであり、これらは全てＳｉ−Ｏの化
学結合を含む、例えばＳｉＯ2として存在すると考えら
れる。BEST MODE FOR CARRYING OUT THE INVENTION The silicon nitride sintered body of the present invention comprises a silicon nitride crystal as a main component, a main element constituting a grain boundary of the crystal, a Group 3a element of the periodic table, impurity oxygen,
In some cases, it contains Al. Here, the term “impurity oxygen” refers to the third oxygen content in the periodic table as an additive based on the total oxygen content in the sintered body.
The meaning of the remaining oxygen after subtracting the oxygen stoichiometrically contained in the group a element compound and Al, most of which is mixed as oxygen contained in the silicon nitride raw material or added silicon oxide. , all containing chemical bonds of SiO, for example, is believed to be present as SiO2.
【００１２】本発明によれば窒化珪素質焼結体は、組織
的には、窒化珪素結晶を主結晶相とするものであるが、
本発明の特徴は、この窒化珪素結晶粒子が、微小柱状結
晶粒子（以下、単に微小粒子という。）からなるマトリ
ックス中に、粗大柱状結晶粒子（以下、単に粗大粒子と
いう。）からなる分散相が存在することが重要である。
そして、このマトリックスを構成する微小粒子は、平均
長径が５〜５０μｍ、特に１０〜４０μｍ、平均アスペ
クト比が５以上、特に１０以上であり、この微小粒子か
らなるマトリックス中に、長径が８０μｍ以上、特に１
００μｍ以上、アスペクト比が５以上、特に１０以上の
粗大粒子が３〜１５体積％、特に５〜１０体積％の割合
で存在することが重要である。According to the present invention, the silicon nitride based sintered body has a structure in which a silicon nitride crystal is a main crystal phase.
A feature of the present invention is that a dispersed phase composed of coarse columnar crystal particles (hereinafter simply referred to as coarse particles) is contained in a matrix in which the silicon nitride crystal particles are composed of fine columnar crystal particles (hereinafter simply referred to as fine particles). It is important to be present.
The fine particles constituting the matrix have an average major axis of 5 to 50 μm, particularly 10 to 40 μm, and an average aspect ratio of 5 or more, particularly 10 or greater. Especially 1
It is important that coarse particles having a size of 00 μm or more and an aspect ratio of 5 or more, particularly 10 or more are present in a proportion of 3 to 15% by volume, particularly 5 to 10% by volume.
【００１３】このマトリックスの微小粒子の形状を上記
に限定したのは、平均長径が５μｍよりも小さい、また
は平均アスペクト比が５よりも小さいと、高い破壊靱性
が得られず、５０μｍよりも大きいと、強度が低下する
ためである。The reason why the shape of the fine particles of the matrix is limited to the above is that if the average major axis is smaller than 5 μm or the average aspect ratio is smaller than 5, high fracture toughness cannot be obtained, and if it is larger than 50 μm. This is because the strength is reduced.
【００１４】一方、長径が８０μｍ以上、アスペクト比
が５以上の粗大粒子の量が３体積％よりも少ないと、破
壊靱性の向上効果が得られず、１５体積％よりも多い
と、これらの粗大粒子が破壊源となり、強度が劣化する
ためである。On the other hand, if the amount of the coarse particles having a major axis of 80 μm or more and the aspect ratio of 5 or more is less than 3% by volume, the effect of improving fracture toughness cannot be obtained. This is because the particles are a source of destruction and the strength is deteriorated.
【００１５】なお、この粗大粒子の存在割合は、焼結体
の断面による走査型電子顕微鏡写真（ＳＥＭ）から、長
径が８０μｍ以上、アスペクト比が５以上の粗大粒子の
占める面積比率を体積比率として求めることができる。The existence ratio of the coarse particles is determined from the scanning electron micrograph (SEM) of the cross section of the sintered body, where the area ratio of the coarse particles having a major axis of 80 μm or more and an aspect ratio of 5 or more is defined as a volume ratio. You can ask.
【００１６】マトリックスとは、上記長径が８０μｍ以
上、アスペクト比が５以上の粗大粒子以外の粒子群の総
称であって、上記粗大粒子以外の結晶粒子の長径の平均
値およびアスペクト比の平均値を求めたものである。The matrix is a general term for particles other than the coarse particles having a major axis of 80 μm or more and an aspect ratio of 5 or more. The matrix refers to the average value of the major axis of the crystal particles other than the coarse particles and the average value of the aspect ratio. It is what I sought.
【００１７】本発明における焼結体の具体的組成として
は、窒化珪素を６０〜９９モル％と、周期律表第３ａ族
元素を酸化物換算で１〜１０モル％と、Ａｌを酸化物換
算で０〜１０モル％と、不純物的酸素をＳｉＯ2換算で
１〜３０モル％の割合で含有する。これは、窒化珪素量
が６０モル％より少ないと高温強度が発揮されず、周期
律表第３ａ族元素が１モル％未満では緻密化が不十分で
あり、１０モル％を越えると高温強度及び高温耐クリー
プ性が劣化する。Ａｌも同様に１０モル％を越えると高
温強度及び高温耐クリープ性が劣化する。また、不純物
的酸素が１モル％よりも少ないと、焼結性が劣化し、緻
密化不足となり、３０モル％よりも多いと高温強度及び
高温耐クリープ性が劣化するためである。The specific composition of the sintered body in the present invention is as follows: silicon nitride is 60 to 99 mol%, Group 3a element of the periodic table is 1 to 10 mol% in terms of oxide, and Al is oxide in terms of oxide. In an amount of 0 to 10 mol%, and impurity oxygen in a ratio of 1 to 30 mol% in terms of SiO2 . This is because when the amount of silicon nitride is less than 60 mol%, high-temperature strength is not exhibited, and when the element of Group 3a of the periodic table is less than 1 mol%, densification is insufficient. High temperature creep resistance deteriorates. Similarly, when Al exceeds 10 mol%, the high-temperature strength and the high-temperature creep resistance deteriorate. On the other hand, if the amount of impurity oxygen is less than 1 mol%, the sinterability deteriorates and the densification becomes insufficient. If the amount exceeds 30 mol%, the high temperature strength and the high temperature creep resistance deteriorate.
【００１８】また、かかる焼結体において、高温での耐
酸化性を重視する場合には、前記不純物的酸素の二酸化
珪素換算（ＳｉＯ2）の前記周期律表第３ａ族元素の酸
化物換算量（ＲＥ2Ｏ3）に対するモル比（ＳｉＯ2／
ＲＥ2Ｏ3）が２以上、特に２．１以上であることが望
ましく、その場合、前記不純物的酸素及び周期律表第３
ａ族元素が窒化珪素の結晶粒子の粒界に主として存在
し、該粒界にはモノシリケート、ダイシリケート、およ
びシリコンオキシナイトライドの群から選ばれる少なく
とも１種の結晶相が析出していることが望ましい。In the sintered body, when importance is placed on the oxidation resistance at high temperatures, the amount of the impurity oxygen in terms of silicon dioxide (SiO2 ) in terms of the oxide of the Group 3a element of the Periodic Table is calculated. (RE2 O3 ) molar ratio (SiO2 /
RE2 O3 ) is desirably 2 or more, particularly 2.1 or more, in which case, the impurity oxygen and the third element in the periodic table
The group a element is mainly present at the grain boundaries of silicon nitride crystal grains, and at least one crystal phase selected from the group consisting of monosilicate, disilicate, and silicon oxynitride is precipitated at the grain boundaries. Is desirable.
【００１９】但し、シリコンオキシナイトライド結晶相
は窒化珪素結晶と類似の特性を有するが、その量が多く
なると窒化珪素の柱状化を阻害し、破壊靱性値を低下さ
せる恐れがあることから、さらに望ましくは、モノシリ
ケートあるいはダイシリケート相が主として析出するの
がよい。However, the silicon oxynitride crystal phase has similar characteristics to the silicon nitride crystal. However, if the silicon oxynitride crystal phase is too large, the silicon oxynitride crystal phase may hinder the columnarization of the silicon nitride and lower the fracture toughness. Preferably, a monosilicate or disilicate phase is mainly deposited.
【００２０】また、高温強度を重視する場合には、前記
ＳｉＯ2／ＲＥ2Ｏ3のモル比が２未満、特に１．８以
下であることが望ましく、その場合、前記不純物的酸素
及び周期律表第３ａ族元素が窒化珪素結晶粒子の粒界に
主として存在し、該粒界にはＹＡＭ、アパタイト、メリ
ライト及び、ワラストナイトの群から選ばれる少なくと
も１種の結晶相が析出していることが望ましい。When importance is placed on high-temperature strength, the molar ratio of SiO2 / RE2 O3 is desirably less than 2, especially 1.8 or less. The Group 3a element is mainly present at the grain boundaries of the silicon nitride crystal grains, and at least one crystal phase selected from the group consisting of YAM, apatite, melilite and wollastonite is precipitated at the grain boundaries. Is desirable.
【００２１】さらに、本発明によれば、破壊靱性や強度
の改善のために、さらには、前記窒化珪素、周期律表第
３ａ族元素酸化物、酸化アルミニウム、酸化珪素からな
る窒化珪素成分１００重量部に対して、平均粒径が１〜
５μｍのＴａ、Ｎｂ、Ｍｏ、Ｗのシリサイド及びＳｉＣ
の中から選ばれる少なくとも１種以上の硬質粒子を０．
５〜２５重量部の割合で分散含有することもできる。Further, according to the present invention, in order to improve the fracture toughness and the strength, a silicon nitride component consisting of silicon nitride, an oxide of a Group 3a element of the periodic table, aluminum oxide and silicon oxide is added in an amount of 100% by weight. Parts, the average particle size is 1 to
5 μm Ta, Nb, Mo, W silicide and SiC
At least one hard particle selected from
It may be dispersed and contained at a ratio of 5 to 25 parts by weight.
【００２２】本発明によれば、上記のように、窒化珪素
質焼結体の粗大粒子及びマトリックスの粒子の粒径及び
アスペクト比を制御することにより、粗大粒子のみでは
効果が少なかったクラックディフレクション等の効果
が、柱状の微小粒子からなるマトリックスにより増大さ
れる結果、強度を低下させることなく、破壊靭性を改善
することができる。さらに、前記硬質粒子はクラックの
進展を妨げる効果があることから、さらに破壊靱性を向
上できる。According to the present invention, as described above, by controlling the particle size and aspect ratio of the coarse particles and the matrix particles of the silicon nitride-based sintered body, the effect of crack deflection is small with only the coarse particles. As a result, the fracture toughness can be improved without lowering the strength. Further, since the hard particles have an effect of preventing the propagation of cracks, the fracture toughness can be further improved.
【００２３】次に、本発明の窒化珪素質複合材料を製造
する場合の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、周期律表第３ａ族元素酸化物、ある
いは場合により酸化アルミニウム、酸化珪素粉末を添加
してなる。また添加形態として周期律表第３ａ族元素酸
化物とＳｉＯ2からなる化合物、または窒化珪素と周期
律表第３ａ族元素酸化物とＳｉＯ2の化合物粉末を用い
ることもできる。用いられる窒化珪素粉末は、α型、β
型のいずれでも使用することができ、その平均粒子径は
０．４〜１．２μｍが適当であり、直接窒化法、イミド
分解法などのいずれの製法によるものであってもかまわ
ない。また、粗大粒子形成用として、平均粒径が３〜５
μｍの粉末を混合することも可能である。Next, the method for producing the silicon nitride composite material of the present invention will be described. First, as a starting material, silicon nitride powder, an oxide of a Group 3a element of the periodic table, or aluminum oxide, It is obtained by adding silicon powder. As an addition form, a compound composed of an oxide of an element belonging to Group 3a of the periodic table and SiO2 , or a compound powder of silicon nitride, an oxide of an element belonging to Group 3a of the periodic table and SiO2 can be used. The silicon nitride powder used is α-type, β
Any type can be used, and the average particle diameter is suitably 0.4 to 1.2 μm, and any method such as a direct nitriding method or an imide decomposition method may be used. Further, for forming coarse particles, the average particle diameter is 3-5.
It is also possible to mix μm powder.
【００２４】本発明によれば、これらの粉末を用いて、
前述したような組成を満足するように調合する。調合に
際して前述したＳｉＯ2／ＲＥ2Ｏ3比を制御する場
合、窒化珪素中に不可避に含まれる酸素をＳｉＯ2分あ
るいは製造過程で吸着される酸素分等を考慮して周期律
表第３ａ族元素酸化物量を決定するが、場合によっては
ＳｉＯ2粉末を添加して調整すればよい。さらには、平
均粒径が１〜５μｍのＴａ、Ｎｂ、Ｍｏ、Ｗのシリサイ
ド及びＳｉＣの中から選ばれる少なくとも１種以上の硬
質粒子粉末を前記窒化珪素、周期律表第３ａ族元素酸化
物、酸化アルミニウム、酸化珪素からなる窒化珪素成分
１００重量部に対して、０．５〜２５重量部の割合で添
加する。According to the present invention, using these powders,
It is prepared so as to satisfy the composition as described above. When controlling the above-mentioned ratio of SiO2 / RE2 O3 at the time of mixing, oxygen inevitably contained in silicon nitride is taken into account in terms of SiO2 or oxygen adsorbed in the production process, and the like. The amount of elemental oxide is determined, but may be adjusted by adding SiO2 powder in some cases. Further, at least one hard particle powder selected from Ta, Nb, Mo, W silicide and SiC having an average particle diameter of 1 to 5 μm is mixed with the silicon nitride, the oxide of a Group 3a element of the periodic table, It is added at a ratio of 0.5 to 25 parts by weight based on 100 parts by weight of a silicon nitride component composed of aluminum oxide and silicon oxide.
【００２５】上記の割合で各粉末を秤量後、振動ミル、
回転ミル、バレルミルなどで十分に混合した後、混合粉
末を所望の成形手段、例えば、金型プレス、鋳込み成
形、排泥成形、押し出し成形、射出成形、冷間静水圧プ
レス（ＣＩＰ）等により任意の形状に成形する。After weighing each powder at the above ratio,
After being sufficiently mixed by a rotary mill, a barrel mill, etc., the mixed powder is optionally mixed by desired molding means, for example, a die press, a casting molding, a sludge molding, an extrusion molding, an injection molding, a cold isostatic press (CIP), or the like. Mold into the shape of
【００２６】この成形体を窒素ガス加圧焼成法（ＧＰ
Ｓ）により焼成することによって相対密度９５％以上に
緻密化することが出来る。本発明によれば、マトリック
スの柱状化を促進し、アスペクト比を高めるとともに、
さらに適量の粗大粒子を生成させるためには、まず一次
焼成として、０．５〜２．０気圧の窒素雰囲気中におい
て、１６００〜１８００℃で３時間以上保持して一次焼
成して、緻密化を抑制しつつ窒化珪素のα→β転移を行
って粗大粒子の核となる長径２μｍ以上のβ型窒化珪素
を析出させる。This compact was fired under a nitrogen gas pressurized firing method (GP
By firing in S), it is possible to make the relative density 95% or more. According to the present invention, while promoting columnarization of the matrix and increasing the aspect ratio,
In order to further generate an appropriate amount of coarse particles, first, as a primary firing, a primary firing is performed in a nitrogen atmosphere of 0.5 to 2.0 atm at 1600 to 1800 ° C. for 3 hours or more to perform densification. While suppressing the silicon nitride, the α → β transition is performed to precipitate β-type silicon nitride having a major axis of 2 μm or more, which serves as a core of coarse particles.
【００２７】次いで、一次焼成後の焼結体をＳｉＯ、Ａ
ｌ（ｇ）、Ａｌ2Ｏ等の焼結促進ガスを含有する窒素ガ
ス圧２．０〜１００気圧の雰囲気中にて、１８００〜２
０００℃の温度で二次焼成する方法が有効である。この
時のＳｉＯガスは、成形体とともにＳｉ粉末とＳｉＯ2
粉末との混合粉末を配置することによりＳｉＯガスを発
生できる。また、Ａｌ、Ａｌ2Ｏガスは、Ａｌ2Ｏ3粉
末あるいはＡｌ2Ｏ3＋Ｙ2Ｏ3など混合粉末を配置す
ることにより発生できる。Next, the sintered body after the primary firing is made of SiO, A
1 (g) in a nitrogen gas pressure of 2.0 to 100 atm containing a sintering promoting gas such as Al2 O,
The method of secondary firing at a temperature of 000 ° C. is effective. At this time, the SiO gas was mixed with Si powder and SiO2 together with the compact.
By arranging the mixed powder with the powder, SiO gas can be generated. Al and Al2 O gas can be generated by arranging Al2 O3 powder or mixed powder such as Al2 O3 + Y2 O3 .
【００２８】このＳｉＯガスやＡｌ、Ａｌ2Ｏガスが存
在しないと、液相成分の分解が多くなり、特に、焼成時
にＳｉＯガスがない場合、焼結体外周部のシリコンオキ
シナイトライド結晶が分解しやすくなり、表層より数ｍ
ｍ程度の部分に分解層が生成し色調差が生じる場合があ
る。If this SiO gas, Al, or Al2 O gas does not exist, the decomposition of the liquid phase component increases. In particular, when there is no SiO gas at the time of firing, the silicon oxynitride crystals on the periphery of the sintered body are decomposed. Several meters above the surface
In some cases, a decomposition layer is formed in a portion of about m and a color tone difference occurs.
【００２９】ここで一次焼成の焼成温度が１６００℃よ
り低いと組織全体が粗大化し緻密化せず、１８００℃よ
りも高いと分解が多く緻密化を阻害する。特に１６３０
〜１７７０℃で焼成することが望ましい。また、窒素圧
が２．０気圧よりも高いと、高圧のガスが試料内部に閉
じ込められ、焼結を阻害する。Here, if the firing temperature of the primary firing is lower than 1600 ° C., the entire structure becomes coarse and does not become dense. If it is higher than 1800 ° C., the decomposition is increased and the densification is hindered. Especially 1630
It is desirable to bake at １７1770 ° C. On the other hand, if the nitrogen pressure is higher than 2.0 atm, a high-pressure gas is confined inside the sample and hinders sintering.
【００３０】また、二次焼成の焼成温度が１８００℃よ
りも低いと、緻密化を促進することができず、焼成温度
が２０００℃を越えると窒化珪素結晶が粒成長し、強度
劣化を引き起こす。この時の窒素圧が２．０気圧よりも
低いと分解が生じＳｉが析出する。On the other hand, if the firing temperature of the secondary firing is lower than 1800 ° C., the densification cannot be promoted. If the firing temperature exceeds 2000 ° C., the silicon nitride crystal grains grow and the strength is deteriorated. If the nitrogen pressure at this time is lower than 2.0 atm, decomposition occurs and Si is deposited.
【００３１】さらには、上記のようにして作製した焼結
体をＮ2ガスやＡｒガスなどによる１０００気圧以上の
圧力下で１５００〜１９００℃の温度で熱間静水圧焼成
（ＨＩＰ）法により処理することによりさらに緻密化を
高めることができる。Further, the sintered body produced as described above is treated by hot isostatic sintering (HIP) at a temperature of 1500 to 1900 ° C. under a pressure of 1000 atm or more with N2 gas or Ar gas. By doing so, the densification can be further improved.
【００３２】さらに、上記の焼成後の冷却過程で焼成温
度から１０００℃までの温度範囲を２００℃／ｈｒ以下
の速度で徐冷するか、または焼結体をＮ2雰囲気中で１
０００〜１７００℃で熱処理することにより粒界相の結
晶化を促進し特性のさらなる改善を行うことができる。Further, in the cooling process after the above-mentioned firing, the temperature range from the firing temperature to 1000 ° C. is gradually cooled at a rate of 200 ° C./hr or less, or the sintered body is cooled in an N2 atmosphere for 1 hour.
By performing the heat treatment at 000 to 1700 ° C., the crystallization of the grain boundary phase can be promoted, and the characteristics can be further improved.
【００３３】さらに高い寸法精度が要求される場合に
は、窒化珪素粉末の一部または全部をＳｉ粉末に置き換
えて成形体を作製し、これを窒素含有雰囲気中、８００
〜１５００℃で窒化処理してＳｉ3Ｎ4に変換して成形
体密度を高めたうえで、前述した焼成条件で焼成するこ
とにより、焼成時の収縮を小さくすることが出来る。If higher dimensional accuracy is required, a part of or all of the silicon nitride powder is replaced with Si powder to produce a compact, which is then placed in a nitrogen-containing atmosphere at 800
After nitriding at ５００1,500 ° C. to convert to Si3 N4 to increase the density of the compact, and then sintering under the above sintering conditions, shrinkage during sintering can be reduced.
【００３４】[0034]
【実施例】原料粉末として窒化珪素粉末Ａ（平均粒径
０．７μｍ、ＢＥＴ比表面積９ｍ2／ｇ、α率９８％以
上、酸素量１．１重量％）と、窒化珪素粉末Ｂ（平均粒
径４μｍ、ＢＥＴ比表面積３ｍ2／ｇ、α率９８％以
上、酸素量１．１重量％）と、周期律表第３ａ族元素酸
化物（ＲＥ2Ｏ3）粉末および酸化珪素（ＳｉＯ2）粉
末、酸化アルミニウム（Ａｌ2Ｏ3）粉末、平均粒径が
２〜３μｍの炭化珪素粉末、ＴａＳｉ2、ＮｂＳｉ2、
ＭｏＳｉ2、ＷＳｉ2、ＳｉＣの各粉末を用いて、これ
らを適量混合しメタノールを溶媒として窒化珪素ボール
を用いて１２０時間回転ミルで混合粉砕し、スラリーを
乾燥後、直径６０ｍｍ、厚み２０ｍｍの形状に３ｔ／ｃ
ｍ2の圧力でラバープレス成形した。EXAMPLES Silicon nitride powder A (average particle diameter 0.7 μm, BET specific surface area 9 m2 / g, α rate 98% or more, oxygen content 1.1% by weight) and silicon nitride powder B (average particle diameter) A diameter of 4 μm, a BET specific surface area of 3 m2 / g, an α ratio of 98% or more, an oxygen content of 1.1% by weight), a powder of a Group 3a element oxide (RE2 O3 ) of the periodic table, and silicon oxide (SiO2 ) Powder, aluminum oxide (Al2 O3 ) powder, silicon carbide powder having an average particle size of 2 to 3 μm, TaSi2 , NbSi2 ,
Using MoSi2 , WSi2 , and SiC powders, mixing them in appropriate amounts, mixing and pulverizing with a rotary mill for 120 hours using silicon nitride balls with methanol as a solvent, drying the slurry, and then forming a slurry having a diameter of 60 mm and a thickness of 20 mm. 3t / c
Rubber press molding was performed at a pressure of m2 .
【００３５】そしてかかる成形体を表１、２、３に示す
温度にて一次焼成および二次焼成を行った。なお焼成に
あたっては、一次焼成は、窒素１気圧とし、その焼成炉
内に、Ｓｉ／ＳｉＯ2混合粉末を配置してＳｉＯガスを
発生させた。また、二次焼成は、窒素１０気圧中でＳｉ
／ＳｉＯ2混合粉末を配置してＳｉＯガスを発生させ、
窒素ガス加圧焼成（ＧＰＳ）を行った。The compact was subjected to primary firing and secondary firing at the temperatures shown in Tables 1, 2 and 3. In the firing, the primary firing was performed at 1 atm of nitrogen, and a Si / SiO2 mixed powder was arranged in the firing furnace to generate SiO gas. In addition, the secondary firing is performed under a pressure of nitrogen of 10 atm.
/ SiO2 mixed powder is arranged to generate SiO gas,
Nitrogen gas pressure firing (GPS) was performed.
【００３６】なお、表１中のＧＰＳ＋ＨＩＰは、上記Ｇ
ＰＳ条件で焼成後、１７００℃、窒素圧２０００ａｔｍ
で１時間熱間静水圧焼成したものである。Note that GPS + HIP in Table 1 is the above G
After firing under PS condition, 1700 ° C, nitrogen pressure 2000atm
For one hour under hot isostatic pressure.
【００３７】得られた焼結体に対してアルキメデス法に
よる比重から対理論密度比を算出するとともに３×４×
４０ｍｍのテストピース形状に切断研磨し、ＪＩＳ−Ｒ
１６０１に基づき室温強度およびＪＩＳ−Ｒ１６０４に
基づき１５００℃での４点曲げ抗折強度試験を実施し、
ＪＩＳ−Ｒ１６０７に基づき破壊靭性値の測定を実施し
た。破壊靱性またＸ線回折測定により焼結体の粒界相の
結晶を同定し、主結晶相および副結晶相を決定した。The theoretical density ratio was calculated from the specific gravity of the obtained sintered body by the Archimedes method, and 3 × 4 ×
Cut and polished into a test piece shape of 40 mm, JIS-R
1601 based on JIS-R1604 based on the room temperature strength and the 4-point bending strength test at 1500 ° C.
Fracture toughness was measured based on JIS-R1607. The crystal of the grain boundary phase of the sintered body was identified by the fracture toughness and X-ray diffraction measurement, and the main crystal phase and the sub crystal phase were determined.
【００３８】なお、表１、２、３中の不純物的酸素量
は、焼結体を粉砕し化学分析によって酸素量を求め、添
加した周期律表第３ａ族元素酸化物中の酸素量及びＡｌ
2Ｏ3の酸素量を除いた酸素量をＳｉＯ2換算したもの
である。また大気中１５００℃で１００時間放置した前
後の重量変化を測定し酸化重量増を測定した。但し、室
温強度が６００ＭＰａ以下のものについては、１５００
℃強度、破壊靱性の測定および酸化重量増の測定は目的
に適さないため省略した。The oxygen content in Tables 1, 2 and 3 was determined by crushing the sintered body and obtaining the oxygen content by chemical analysis, and determining the oxygen content and Al content in the added Group 3a element oxide of the periodic table.
The oxygen content excluding the oxygen content of2 O3 is converted into SiO2 . The weight change before and after standing at 1500 ° C. for 100 hours in the atmosphere was measured to determine the increase in oxidized weight. However, for those having a room temperature strength of 600 MPa or less, 1500
The measurement of the ° C strength, the fracture toughness, and the measurement of the increase in oxide weight were omitted because they were not suitable for the purpose.
【００３９】また、組織については、各焼結体の断面を
エッチングした後、走査型電子顕微鏡写真から、長径が
８０μｍ以上、アスペクト比が５以上の窒化珪素粒子の
面積比率を求め、これを体積比率とした。そして、それ
ら粗大粒子の平均長径と平均アスペクト比を計算した。
さらに、上記長径が８０μｍ以上、アスペクト比が５以
上の結晶粒子以外の窒化珪素結晶粒子について平均長径
と平均アスペクト比を計算した。また、焼成前と焼成後
の寸法差から収縮率を求めた。Regarding the structure, after the cross section of each sintered body was etched, the area ratio of silicon nitride particles having a major axis of 80 μm or more and an aspect ratio of 5 or more was determined from a scanning electron micrograph, and the volume ratio was determined. The ratio was used. Then, the average major axis and the average aspect ratio of the coarse particles were calculated.
Furthermore, the average major axis and the average aspect ratio were calculated for silicon nitride crystal particles other than the crystal particles having the major axis of 80 μm or more and the aspect ratio of 5 or more. The shrinkage was determined from the dimensional difference before and after firing.
【００４０】[0040]
【表１】[Table 1]
【００４１】[0041]
【表２】[Table 2]
【００４２】[0042]
【表３】[Table 3]
【００４３】[0043]
【表４】[Table 4]
【００４４】[0044]
【表５】[Table 5]
【００４５】[0045]
【表６】[Table 6]
【００４６】表１〜６の結果によれば、周期律表第３ａ
族元素酸化物量が１モル％より少ない試料Ｎo.５、３５
では緻密化不足となり、機械的特性が劣化する。また周
期律表第３ａ族元素酸化物量が１０モル％を超える試料
Ｎo.６、３６及びアルミニウム含有量が１０モル％を超
える試料Ｎo.１０、４０では所望の組織が得られず破壊
靭性が劣化した。焼成条件においては、一次焼成温度が
１６００℃より低い試料Ｎo.２３では全体が粗大化し緻
密体が得られなかった。一方、一次焼成温度が１８００
℃より高い試料Ｎo.２６では、分解が激しく緻密体が得
られなかった。また二次焼成温度が１８００℃より低い
試料Ｎo.２７では緻密体が得られなかった。一方、二次
焼成温度が２０００℃より高い試料Ｎo.２９では窒化珪
素の粒成長が激しく強度劣化した。According to the results of Tables 1 to 6, the periodic table 3a
Samples Nos. 5 and 35 containing less than 1 mol% of group oxides
In this case, the densification becomes insufficient, and the mechanical characteristics deteriorate. In Samples Nos. 6 and 36 in which the amount of Group 3a element oxide in the periodic table exceeds 10 mol% and in Samples Nos. 10 and 40 in which the aluminum content exceeds 10 mol%, the desired structure cannot be obtained and the fracture toughness deteriorates. did. Regarding the firing conditions, the sample No. 23 having a primary firing temperature lower than 1600 ° C. was coarsened as a whole, and a dense body could not be obtained. On the other hand, the primary firing temperature is 1800
In Sample No. 26 higher than ℃, the decomposition was so severe that a dense body could not be obtained. In the case of Sample No. 27 in which the secondary firing temperature was lower than 1800 ° C., no dense body was obtained. On the other hand, in Sample No. 29, in which the secondary sintering temperature was higher than 2000 ° C., the grain growth of silicon nitride was severe and the strength was deteriorated.
【００４７】これらの比較例に対して本発明の窒化珪素
質焼結体は、常温強度６００ＭＰａ以上、破壊靭性値８
ＭＰａ・ｍ1/2 以上の優れた特性が達成された。なお、
Ａｌ2Ｏ3量が１モル％を超える試料は、１５００℃の
高温強度および１５００℃酸化重量増の測定ができず、
高温強度の観点からはＡｌ2Ｏ3量は少ない方が望まし
く、粒界相にメリライト、ＹＡＭ、アパタイトなどが析
出しているもの、また高温での耐酸化性の観点からは粒
界相にダイシリケートが析出している方がよいことがわ
かる。In contrast to these comparative examples, the silicon nitride of the present invention
The sintered body has a normal temperature strength of 600 MPa or more and a fracture toughness value of 8
MPa ・ m1/2 The above excellent characteristics were achieved. In addition,
AlTwoOThreeThe sample whose amount exceeds 1 mol%
High temperature strength and 1500 ° C oxidation weight increase cannot be measured.
From the viewpoint of high temperature strength, AlTwoOThreeThe smaller the amount, the better
In addition, melilite, YAM, apatite, etc. precipitate in the grain boundary phase
From the viewpoint of oxidation resistance at high temperatures.
It is better to have disilicate precipitated in the interphase.
Call
【００４８】[0048]
【発明の効果】以上の通り、本発明の高靱性窒化珪素質
焼結体によれば、窒化珪素粒子の柱状化した粗大粒子の
みならず、微細な柱状粒子からなるマトリックス中に、
適量の柱状の粗大粒子を分散させ、それらの結晶粒子の
長径およびアスペクト比を制御することにより、高い強
度を有したまま、破壊靭性を大きく向上できることがで
きる。As described above, according to the high toughness silicon nitride-based sintered body of the present invention, not only the columnar coarse particles of silicon nitride particles, but also the matrix composed of fine columnar particles,
By dispersing an appropriate amount of columnar coarse particles and controlling the major axis and aspect ratio of the crystal particles, the fracture toughness can be greatly improved while maintaining high strength.
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11043863AJP2000247748A (en) | 1999-02-22 | 1999-02-22 | High toughness silicon nitride sintered body |
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11043863AJP2000247748A (en) | 1999-02-22 | 1999-02-22 | High toughness silicon nitride sintered body |
| Publication Number | Publication Date |
|---|---|
| JP2000247748Atrue JP2000247748A (en) | 2000-09-12 |
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP11043863APendingJP2000247748A (en) | 1999-02-22 | 1999-02-22 | High toughness silicon nitride sintered body |
| Country | Link |
|---|---|
| JP (1) | JP2000247748A (en) |
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002265273A (en)* | 2001-03-09 | 2002-09-18 | Ngk Spark Plug Co Ltd | Silicon nitride sintered body and method for producing the same |
| WO2005009920A1 (en)* | 2003-07-15 | 2005-02-03 | Honeywell International Inc. | Sintered silicon nitride |
| JP2011014924A (en)* | 2010-09-22 | 2011-01-20 | Hitachi Metals Ltd | Silicon nitride substrate |
| US8039412B2 (en)* | 2005-12-20 | 2011-10-18 | Momentive Performance Materials Inc. | Crystalline composition, device, and associated method |
| JP2016050137A (en)* | 2014-08-29 | 2016-04-11 | 京セラ株式会社 | Silicon nitride-based sintered body, and abrasion-resistant member including the same |
| WO2024204262A1 (en)* | 2023-03-27 | 2024-10-03 | デンカ株式会社 | Biological material, powder composition, bone prosthetic material, and method for using composition containing composite compound as biological material |
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| JPH03218974A (en)* | 1990-01-23 | 1991-09-26 | Ngk Insulators Ltd | Silicon nitride sintered body and production thereof |
| JPH0465362A (en)* | 1990-06-29 | 1992-03-02 | Kyocera Corp | Method for manufacturing silicon nitride sintered body |
| JPH04238868A (en)* | 1990-12-28 | 1992-08-26 | Kyocera Corp | Production of silicon nitride-silicon carbide compounded sintered material |
| JPH0834670A (en)* | 1994-07-26 | 1996-02-06 | Natl Inst For Res In Inorg Mater | Silicon nitride sintered body and method for producing the same |
| JPH08175873A (en)* | 1994-12-27 | 1996-07-09 | Kyocera Corp | Silicon nitride sintered body and method for manufacturing the same |
| JPH09268069A (en)* | 1996-03-29 | 1997-10-14 | Kyocera Corp | High thermal conductivity material and method of manufacturing the same |
| JPH10182237A (en)* | 1996-12-26 | 1998-07-07 | Kyocera Corp | Silicon nitride composite sintered body and method for producing the same |
| JPH10212167A (en)* | 1997-01-31 | 1998-08-11 | Kyocera Corp | Silicon nitride composite sintered body and method for producing the same |
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH03218974A (en)* | 1990-01-23 | 1991-09-26 | Ngk Insulators Ltd | Silicon nitride sintered body and production thereof |
| JPH0465362A (en)* | 1990-06-29 | 1992-03-02 | Kyocera Corp | Method for manufacturing silicon nitride sintered body |
| JPH04238868A (en)* | 1990-12-28 | 1992-08-26 | Kyocera Corp | Production of silicon nitride-silicon carbide compounded sintered material |
| JPH0834670A (en)* | 1994-07-26 | 1996-02-06 | Natl Inst For Res In Inorg Mater | Silicon nitride sintered body and method for producing the same |
| JPH08175873A (en)* | 1994-12-27 | 1996-07-09 | Kyocera Corp | Silicon nitride sintered body and method for manufacturing the same |
| JPH09268069A (en)* | 1996-03-29 | 1997-10-14 | Kyocera Corp | High thermal conductivity material and method of manufacturing the same |
| JPH10182237A (en)* | 1996-12-26 | 1998-07-07 | Kyocera Corp | Silicon nitride composite sintered body and method for producing the same |
| JPH10212167A (en)* | 1997-01-31 | 1998-08-11 | Kyocera Corp | Silicon nitride composite sintered body and method for producing the same |
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002265273A (en)* | 2001-03-09 | 2002-09-18 | Ngk Spark Plug Co Ltd | Silicon nitride sintered body and method for producing the same |
| WO2005009920A1 (en)* | 2003-07-15 | 2005-02-03 | Honeywell International Inc. | Sintered silicon nitride |
| US6977233B2 (en) | 2003-07-15 | 2005-12-20 | Honeywell International, Inc. | Sintered silicon nitride |
| US8039412B2 (en)* | 2005-12-20 | 2011-10-18 | Momentive Performance Materials Inc. | Crystalline composition, device, and associated method |
| JP2011014924A (en)* | 2010-09-22 | 2011-01-20 | Hitachi Metals Ltd | Silicon nitride substrate |
| JP2016050137A (en)* | 2014-08-29 | 2016-04-11 | 京セラ株式会社 | Silicon nitride-based sintered body, and abrasion-resistant member including the same |
| WO2024204262A1 (en)* | 2023-03-27 | 2024-10-03 | デンカ株式会社 | Biological material, powder composition, bone prosthetic material, and method for using composition containing composite compound as biological material |
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