JP2001172085A - Silicon nitride sintered compact, production process therefor, and silicon nitride abrasion-resistant material using the same - Google Patents
Silicon nitride sintered compact, production process therefor, and silicon nitride abrasion-resistant material using the sameInfo
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- JP2001172085A JP2001172085A JP35915399A JP35915399A JP2001172085A JP 2001172085 A JP2001172085 A JP 2001172085A JP 35915399 A JP35915399 A JP 35915399A JP 35915399 A JP35915399 A JP 35915399A JP 2001172085 A JP2001172085 A JP 2001172085A
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- silicon nitride
- grain boundary
- boundary phase
- sintered body
- oxide
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、窒化珪素質焼結体
からなる耐摩耗性部材およびその製造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wear-resistant member made of a silicon nitride sintered body and a method for manufacturing the same.
【０００２】[0002]
【従来の技術】窒化珪素質焼結体は、高強度で耐摩耗性
や剛性に優れているため構造用機械部品の材料として期
待されており、近年ではこれらの特性を利用してベアリ
ングの転動体であるボールやローラーに使用されてい
る。2. Description of the Related Art A silicon nitride sintered body is expected to be used as a material for structural mechanical parts because of its high strength and excellent wear resistance and rigidity. Used for moving balls and rollers.
【０００３】上記窒化珪素質焼結体の焼結に際しては、
上記窒化珪素質焼結体の原材料である窒化珪素に自己焼
結性がないため焼結助剤を添加して焼結を行っている。
上記焼結助剤としては、一般にＹ2Ｏ3などの希土類酸化
物や、Ａｌ2Ｏ3、ＭｇＯ、ＣａＯなどの酸化物が組み合
わされて用いられている。そして、窒化珪素粉末にこれ
らの焼結助剤を混合して成形した後、焼結を行うことに
より窒化珪素質焼結体を得ている。上記焼結する方法と
しては、常圧下で行う常圧焼結や窒素等による雰囲気加
圧焼結などがあり、さらに、上記常圧焼結により得られ
る焼結体においては、焼結体内部の残留気孔を排除する
ために高温で高いガス圧力で処理して機械的強度を向上
させるために、ＨＩＰ（熱間静水圧加圧）処理を行って
いる。In sintering the above silicon nitride sintered body,
Since silicon nitride as a raw material of the silicon nitride-based sintered body has no self-sintering property, sintering is performed by adding a sintering aid.
As the sintering aid, rare earth oxides such as Y 2 O 3 and oxides such as Al 2 O 3 , MgO and CaO are generally used in combination. Then, after mixing these sintering aids with silicon nitride powder and molding, sintering is performed to obtain a silicon nitride-based sintered body. Examples of the sintering method include atmospheric pressure sintering performed under normal pressure and atmospheric pressure sintering with nitrogen or the like, and further, in a sintered body obtained by the normal pressure sintering, HIP (Hot Isostatic Pressing) processing is performed to improve mechanical strength by processing at high temperature and high gas pressure to eliminate residual pores.
【０００４】特に、軸受材料として用いる場合は、材料
に内在する微少な欠陥（気孔等）が転がり疲労によって
表面で剥離を起こす原因となるため、雰囲気加圧焼結や
ＨＩＰ処理が用いられている。このようにして得られた
焼結体は、製品として精密加工された後、軸受部品とし
て使用される。[0004] In particular, when used as a bearing material, atmospheric pressure sintering or HIP processing is used because minute defects (pores and the like) inherent in the material cause peeling on the surface due to rolling fatigue. . The sintered body thus obtained is used as a bearing component after precision processing as a product.
【０００５】転動体は、表面ないしはその近傍の表層に
高い引っ張り応力を受けるために、表面ないしはその近
傍の表層に欠陥が存在しないことが重要であり、軸受部
品材料として用いる焼結体には、特に、欠陥（気孔、介
在物、組織の異常など）がないことが要求されている。[0005] Since the rolling element receives a high tensile stress on the surface or in the vicinity of the surface layer, it is important that no defects exist on the surface or in the vicinity of the surface layer. In particular, it is required that there be no defects (pores, inclusions, abnormalities in tissue, etc.).
【０００６】さらに、近年はセラミックベアリングの主
用途である工作機械の高速化、及び、航空機、宇宙産業
への市場展開により、より高温環境化での高負荷用セラ
ミック軸受けのニーズが高まっている。また、軽量であ
ることから高速回転のＨＤＤ用としてセラミック軸受け
のニーズが高まっている。Further, in recent years, with the increase in speed of machine tools, which are the main applications of ceramic bearings, and the market development in the aviation and space industries, the need for high-load ceramic bearings in higher temperature environments has been increasing. In addition, the need for ceramic bearings for high-speed HDDs is increasing because of their light weight.
【０００７】[0007]
【発明が解決しようとする課題】しかしながら、上述の
ようにして得られる窒化珪素質焼結体を用いた軸受材料
は、摩擦熱の発生による機械的特性の低下が発生すると
いう問題点があった。特に、光学顕微鏡で観察したとき
に焼結体内に白い模様が発生し、製品に加工するまでに
除去できずに製品の表面に残った場合、機械的特性の低
下が顕著であった。この白い模様は粒界の欠落によるも
のであり、表面に残った模様は、製品表面の蛍光探傷検
査において明確な欠陥指示模様ではないが微弱に発色す
る。However, the bearing material using the silicon nitride-based sintered body obtained as described above has a problem that the mechanical properties are reduced due to the generation of frictional heat. . In particular, when a white pattern was generated in the sintered body when observed with an optical microscope and could not be removed before being processed into a product and remained on the surface of the product, the mechanical characteristics were significantly reduced. This white pattern is due to the lack of grain boundaries, and the pattern remaining on the surface is not a clear defect indication pattern in the fluorescence inspection inspection of the product surface, but develops a weak color.
【０００８】特開平６−３２９４７２号公報でも、この
ような模様を有する窒化珪素質焼結体は、軸受材料とし
て要求されている転がり寿命に対して、下記に示すよう
な問題が記載されている。[0008] Japanese Patent Application Laid-Open No. 6-329472 also describes the following problem with respect to the rolling life required for a bearing material of a silicon nitride sintered body having such a pattern. .
【０００９】上記表面からの深さが１ｍｍを越えると、
該模様を構成している粒界相欠落部の大きさが０. ３μ
ｍを越える傾向があり、転がり疲労による剥離を起こ
す。また、窒化珪素質焼結体が有する上記模様を構成し
ている上記粒界相欠落部の集合体の大きさは、０. ３μ
ｍ以下であっても使用温度が高い軸受けについてはその
粒界相欠落部の集合体の大きさが０．５ｍｍ以上になる
と、短時間で転がり疲労による剥離を生じるという問題
があった。When the depth from the surface exceeds 1 mm,
The size of the grain boundary phase missing part constituting the pattern is 0.3 μm.
m, and causes peeling due to rolling fatigue. Further, the size of the aggregate of the grain boundary phase lacking portions constituting the pattern of the silicon nitride based sintered body is 0.3 μm.
However, if the size of the aggregate at the grain boundary phase-missing portion is 0.5 mm or more, there is a problem in that a bearing that is used at a high operating temperature even if the temperature is not more than 0.5 m causes peeling due to rolling fatigue in a short time.
【００１０】特開平６−３２９４７２号公報の中には、
上記のような問題も示されているが、欠陥サイズを０．
３μｍ以下のマイクロボイドの集合体であると規定した
のみで根本対策には至っていない。[0010] In Japanese Patent Application Laid-Open No. 6-329472,
Although the above-mentioned problem is also shown, the defect size is set to 0.
Only the definition of the aggregate of microvoids of 3 μm or less has not been taken as a fundamental measure.
【００１１】[0011]
【課題を解決するための手段】本発明者は前記課題に鑑
み、種々検討した結果、結晶粒界相の少なくとも一部が
結晶化している窒化珪素質焼結体であって、前記粒界相
の結晶最大径が１００μｍ以下とすることにより上記課
題を解決できることを見出した。Means for Solving the Problems In view of the above problems, the present inventor has made various studies and as a result, has found that a silicon nitride based sintered body in which at least a part of a crystal grain boundary phase is crystallized, It has been found that the above problem can be solved by setting the maximum crystal diameter to 100 μm or less.
【００１２】また、かかる焼結体を作製する方法とし
て、窒化珪素を主成分とし、焼結助剤として希土類元素
酸化物粉末および酸化アルミニウム粉末を添加した混合
物を成形した後、非酸化物雰囲気中で１６００℃〜２０
００℃の温度で焼成し緻密化し、急速に冷却した後、９
００℃〜１２００℃の温度で熱処理することが有効であ
ることを見出した。摩擦熱による高温耐久性を向上させ
るために粒界を結晶化させて熱伝導率を向上させること
が重要であり、さらに、その粒界相の結晶の大きさが粒
界相欠落部の発生に影響し、ひいては高温耐久性に影響
することを発見し、本発明に至ったのである。As a method of producing such a sintered body, a mixture containing silicon nitride as a main component and a rare earth element oxide powder and an aluminum oxide powder as sintering aids is formed, and then molded in a non-oxide atmosphere. 1600 ℃ ～ 20
After sintering at a temperature of 00 ° C. for densification and rapid cooling, 9
It has been found that heat treatment at a temperature of 00 ° C to 1200 ° C is effective. It is important to improve the thermal conductivity by crystallizing the grain boundaries in order to improve the high-temperature durability due to frictional heat.Furthermore, the crystal size of the grain boundary phase causes The present invention was found to have an effect on the high-temperature durability, thereby leading to the present invention.
【００１３】また、粒界相欠落部は粒界相の最大結晶径
に起因することが判明した。したがって、粒界相の最大
結晶径を小さくすることで粒界相欠落部の発生を小さく
し、粒界相欠落部の集合である樹枝状白色模様が生じに
くくなることを見いだし、本発明に至ったのである。It has also been found that the grain boundary phase lacking portion is caused by the maximum crystal diameter of the grain boundary phase. Therefore, by reducing the maximum crystal diameter of the grain boundary phase, the occurrence of the grain boundary phase lacking portion is reduced, and it is found that a dendritic white pattern, which is a collection of the grain boundary phase lacking portion, is less likely to occur. It was.
【００１４】ここで、粒界結晶相と示しているものは、
従来指摘されている窒化珪素結晶相に囲まれるように存
在する欠陥としての粒界結晶相ではなく、一群の窒化珪
素結晶相を内部に分散した粒界相のまとまりを意味する
ものであり、セラミックスを研磨し偏光顕微鏡で観察す
ることにより、観察できるものである。こうして観察さ
れる粒界結晶相は、結晶がある一点から放射状に並んで
いるので、他の部分と識別することができる。Here, what is indicated as a grain boundary crystal phase is as follows:
It does not mean the grain boundary crystal phase as a defect existing so as to be surrounded by the silicon nitride crystal phase that has been pointed out conventionally, but means a group of grain boundary phases in which a group of silicon nitride crystal phases are dispersed. Can be observed by polishing and observing with a polarizing microscope. The grain boundary crystal phases thus observed can be distinguished from other parts because the crystals are arranged radially from one point.
【００１５】[0015]
【発明の実施の形態】以下、本発明を詳細に説明する。BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
【００１６】まず、本発明の窒化珪素質焼結体について
説明する。本発明の窒化珪素は焼結助剤として、酸化物
換算で１〜３０重量％の希土類元素化合物や、他に酸化
珪素、酸化アルミニウムを含有するものである。また、
上記の焼結助剤により形成される粒界相は、少なくとも
一部が結晶化しており、その粒界相の最大結晶径が１０
０μｍ以下であることを特徴とする。First, the silicon nitride sintered body of the present invention will be described. The silicon nitride of the present invention contains a rare earth element compound in an amount of 1 to 30% by weight in terms of oxide, as well as silicon oxide and aluminum oxide, as a sintering aid. Also,
At least a part of the grain boundary phase formed by the sintering aid is crystallized, and the maximum crystal diameter of the grain boundary phase is 10%.
It is not more than 0 μm.
【００１７】ここで、まず、従来の窒化珪素質焼結体の
粒界結晶相の模式図を図２を用いて説明する。従来の窒
化珪素質焼結体は、表面ないしは破面を研磨し偏光顕微
鏡でその組織を観察すると、偏光の角度を調整した場合
に図２に示したように、光る集合部分が見える。これ
が、粒界結晶相１である。その大きさにより、１０〜２
００倍程度の倍率で観察することができる。この粒界結
晶相１が１００μｍより大きくなると、その周囲に、粒
界相欠落層２である樹脂状白色模様が発生しているのが
判る。これに対し、本発明の窒化珪素質焼結体の粒界結
晶相は、図１に示すように粒界結晶相１の大きさが１０
０μｍ以下と小さく、その周囲に粒界相欠落部である樹
脂状白色模様がみえないことが特徴である。First, a schematic diagram of a grain boundary crystal phase of a conventional silicon nitride sintered body will be described with reference to FIG. When a conventional silicon nitride sintered body is polished on its surface or fractured surface and its structure is observed with a polarizing microscope, when the angle of polarization is adjusted, as shown in FIG. This is the grain boundary crystal phase 1. Depending on its size, 10-2
It can be observed at a magnification of about 00. When the grain boundary crystal phase 1 is larger than 100 μm, it can be seen that a resinous white pattern as the grain boundary phase lacking layer 2 is generated around the grain boundary crystal phase 1. On the other hand, the grain boundary crystal phase of the silicon nitride sintered body of the present invention has a grain boundary crystal phase 1 having a size of 10 as shown in FIG.
It is characterized by a small size of 0 μm or less, and no resin-like white pattern, which is a grain boundary phase missing portion, is not observed around it.
【００１８】本発明者等は、この粒界結晶相１をよく観
察することにより、これらが、結晶相がある起点から放
射状に結晶化した粒界結晶相１であり、これらの組織の
中に窒化珪素の結晶が内包されている組織であることが
判った。また、これらの磁器が焼成後冷却され、前記粒
界結晶相１が生成する際に大きく収縮するため、残留し
ている液層成分との間に隙間が生成し、前記結晶化した
粒界結晶相１の周囲に隙間を生成させたものが、粒界相
欠落部２であることを見出した。By observing the grain boundary crystal phases 1 well, the present inventors have found that they are the grain boundary crystal phases 1 which are crystallized radially from a certain starting point. It was found that the structure contained silicon nitride crystals. In addition, since these porcelains are cooled after firing and greatly shrink when the grain boundary crystal phase 1 is formed, a gap is formed between the liquid phase components remaining and the crystallized grain boundary crystal. It was found out that a gap formed around the phase 1 was the grain boundary phase missing part 2.
【００１９】しかしながら、本発明の窒化珪素質焼結体
は、粒界相の少なくとも一部が結晶化していることが重
要である。その理由は、窒化珪素質焼結体の用途として
軸受け部品があるが、使用中の摩擦熱の発生により機械
的特性の低下が発生するという問題点があったからであ
る。そこで発生する摩擦熱を効率よく逃がしてやる必要
がある。窒化珪素には自己焼結性がないために焼結助剤
を添加して焼結を行っている。一般に、熱伝導率は金属
や結晶性の良い物質が優れているが、窒化珪素粒子の間
の粒界相が非晶質であると、非晶質の部分は熱伝導率が
低いために摩擦熱が効率よく逃がされない。ところが粒
界相が結晶化していると熱伝導率が高く、摩擦熱を効率
よく逃がすことができ、窒化珪素質焼結体を軸受け部品
として用いたときに機械的特性の低下が発生しないこと
を見出した。However, it is important for the silicon nitride sintered body of the present invention that at least a part of the grain boundary phase is crystallized. The reason for this is that although there is a bearing component as an application of the silicon nitride-based sintered body, there is a problem that mechanical properties are deteriorated due to generation of frictional heat during use. It is necessary to efficiently release the friction heat generated there. Since silicon nitride has no self-sintering property, sintering is performed by adding a sintering aid. In general, metals and substances with good crystallinity are excellent in thermal conductivity, but if the grain boundary phase between silicon nitride particles is amorphous, the amorphous portion has low thermal conductivity, so friction is low. Heat is not efficiently dissipated. However, when the grain boundary phase is crystallized, the thermal conductivity is high, frictional heat can be efficiently released, and there is no decrease in mechanical properties when using a silicon nitride sintered body as a bearing component. I found it.
【００２０】粒界相の欠陥に関しては、特開平２−１４
１４７４号公報に１００μｍ以上の粒界析出部が存在し
ないことが必要であることが示されているが、前記特許
公報で示されている粒界析出部は、窒化珪素の粒子間に
形成される欠陥であり、本発明で捕らえている粒界析出
部は、ある一点から放射状に粒界結晶相が並んだ、一群
の窒化珪素の粒子を包含する粒界相のまとまりを意味す
る点で、基本的に異なるものである。前記特許公報で示
されている欠陥には、内部に窒化珪素の結晶を内部に分
散した粒界相の最大結晶径が１００μｍ以下であること
を示唆する記述はない。また、粒界相の結晶化につい
て、特願昭６３−４４００１号公報に粒界相の５０％以
下が結晶化している窒化珪素材料とすることが必要であ
るとの記載があるが、ここでも、本発明のように、内部
に窒化珪素の結晶を内部に分散した最大結晶径について
はしめされていない。Regarding defects in the grain boundary phase, see JP-A No. 2-14 / 1990.
Japanese Patent No. 1474 discloses that it is necessary that there is no grain boundary precipitation portion of 100 μm or more. However, the grain boundary precipitation portion described in the above patent publication is formed between silicon nitride particles. The grain boundary precipitation portion, which is a defect and is trapped in the present invention, is basically a group of grain boundary phases including a group of silicon nitride particles in which grain boundary crystal phases are arranged radially from a certain point. Are different. There is no description in the patent document indicating that the maximum crystal diameter of the grain boundary phase in which silicon nitride crystals are dispersed is 100 μm or less. Regarding the crystallization of the grain boundary phase, Japanese Patent Application No. 63-44001 discloses that it is necessary to use a silicon nitride material in which 50% or less of the grain boundary phase is crystallized. However, as in the present invention, the maximum crystal diameter in which silicon nitride crystals are dispersed is not described.
【００２１】また、本発明は、粒界相の最大結晶径を小
さくすることで粒界相欠落部２の発生を小さくし、粒界
相欠落部２の集合である樹枝状白色模様が生じにくくす
ることができる。すなわち、粒界相欠落部の発生は次の
ように説明される。Further, according to the present invention, by reducing the maximum crystal diameter of the grain boundary phase, the occurrence of the grain boundary phase lacking portion 2 is reduced, and a dendritic white pattern, which is a collection of the grain boundary phase lacking portion 2, is less likely to occur. can do. That is, the occurrence of the grain boundary phase missing portion is explained as follows.
【００２２】焼成中に液相となっている焼結助剤を主と
する成分が冷却に伴い熱収縮するが、その一部または全
てが結晶化すると、結晶化に伴う急激な体積収縮（体積
収縮で数％）が生じ、隣接する粒界の結晶あるいは過冷
却状態の非晶質部との間に隙間が生じ粒界相の欠落部が
発生するのである。このとき粒界相の最大結晶径が大き
く、その数が少ないほど結晶化に伴う体積収縮により発
生する隙間が大きくなり、より大きな粒界相欠落部が発
生する。そこで粒界相欠落部２の発生を抑えるために
は、粒径の小さい粒界の結晶が数多くあればよい。During sintering, components mainly including the sintering aid which is in a liquid phase undergo thermal contraction with cooling, but when a part or all of the components crystallize, rapid volume contraction (volume) accompanying crystallization occurs. (Several% by shrinkage), a gap is formed between the crystal at the adjacent grain boundary or the amorphous portion in the supercooled state, and a missing part of the grain boundary phase is generated. At this time, the maximum crystal diameter of the grain boundary phase is large, and the smaller the number is, the larger the gap generated due to volume shrinkage accompanying crystallization becomes, and a larger grain boundary phase lacking part is generated. Therefore, in order to suppress the generation of the grain boundary phase lacking portion 2, it is sufficient that there are many crystals at the grain boundaries having a small grain size.
【００２３】最大粒径が１００μｍ以下の小さい粒界の
結晶を数多く発生させるためには、焼成後に急激に冷却
することにより粒界を非晶質化させてやり、その後、結
晶の核生成温度で熱処理を行い多くの核を生成させたの
ち結晶化させることが必要である。ただし、焼成後に急
冷を行わないと、冷却過程でサイズの大きい結晶が生成
してしまい、そのとき起こる体積収縮により粒界相欠落
部が発生する。そのために、焼成後に急冷して粒界相を
一旦非晶質化させてやる必要があり、そうすることによ
り焼成後に行う９００℃〜１２００℃の温度での熱処理
により１００μｍ以下の小さな結晶核が数多く析出し、
粒界の結晶相は１００μｍ以上の大きさには成長しな
い。In order to generate a large number of crystals having small grain boundaries having a maximum grain size of 100 μm or less, the grain boundaries are made amorphous by rapidly cooling after firing, and thereafter, at the nucleation temperature of the crystals. It is necessary to crystallize after heat treatment to generate many nuclei. However, if the quenching is not performed after firing, crystals having a large size are generated in the cooling process, and the grain boundary phase missing portions are generated due to the volume shrinkage occurring at that time. Therefore, it is necessary to quench after firing and to make the grain boundary phase amorphous once, so that a large number of small crystal nuclei of 100 μm or less are obtained by heat treatment at 900 ° C. to 1200 ° C. performed after firing. Precipitate,
The crystal phase at the grain boundary does not grow to a size of 100 μm or more.
【００２４】このときの粒界相の最大結晶径について説
明する。The maximum crystal diameter of the grain boundary phase at this time will be described.
【００２５】通常、粒界が結晶化した場合、その最大結
晶径は、サブμｍから数ｍｍの大きさであると考えられ
ていた。通常走査型電子顕微鏡などによって観察される
粒界相は、二つの窒化珪素粒子に挟まれた２面間領域
や、三つの窒化珪素粒子に挟まれた３重点領域などを指
し、その大きさはせいぜい大きくても十数μｍ（偏析が
ある場合数十μｍ）の様に観察される。しかし、実際に
は窒化珪素粒子の２面間領域や３重点領域は立体的に連
結しているため、結晶化した場合、１つの結晶は立体的
に連結した広い領域（例えば数ｍｍ）に及ぶ事がある。
これは、窒化珪素焼結体を薄片化し、偏光顕微鏡などで
観察すると、数ｍｍの領域に渡って粒界相が同一方位を
有して結晶化している場合があることからも明らかであ
る。Usually, when a grain boundary is crystallized, the maximum crystal diameter has been considered to be a size of sub-μm to several mm. The grain boundary phase usually observed by a scanning electron microscope or the like refers to a region between two planes sandwiched between two silicon nitride particles, a triple junction region sandwiched between three silicon nitride particles, and the like. At most, it is observed as large as tens of μm (several tens of μm if there is segregation). However, since the two-plane region and the triple point region of the silicon nitride particles are actually connected three-dimensionally, when crystallized, one crystal extends over a wide three-dimensionally connected region (for example, several mm). There are things.
This is clear from the fact that when the silicon nitride sintered body is sliced and observed with a polarizing microscope or the like, the grain boundary phase may be crystallized with the same orientation over a region of several mm.
【００２６】数ｍｍの最大結晶径となる場合は、数ｍｍ
の結晶相（例えばＲＥ2Ｓｉ2Ｏ7結晶など）の中に窒化
珪素粒子が密に分散した形態となっているのである。本
発明で定義する粒界相の最大結晶径は、１０〜１００μ
ｍの厚さ、または粒界結晶相が確認される程度の厚さま
で薄片加工した窒化珪素質焼結体を偏光顕微鏡で観察し
たときに、ある一点から放射状に成長した白く光る結晶
群が確認できた場合、この結晶群の大きさを粒界相の最
大結晶径と判断した。顕微鏡で観察する場合の倍率は、
粒界結晶相の大きさに応じて２０〜２００倍程度で観察
することが可能である。本発明では、ひとつの試料につ
き５ｍｍ角の部分を５箇所づつ観察した。この大きさ
は、顕微鏡写真から測定した。When the maximum crystal diameter is several mm, several mm
Is a form in which silicon nitride particles are densely dispersed in a crystal phase (for example, RE 2 Si 2 O 7 crystal or the like). The maximum crystal diameter of the grain boundary phase defined in the present invention is 10 to 100 μm.
When observed with a polarizing microscope, a silicon nitride-based sintered body sliced to a thickness of about m or a thickness at which a grain boundary crystal phase was confirmed, a group of white-shining crystals that grew radially from one point could be confirmed. In this case, the size of this crystal group was determined to be the maximum crystal diameter of the grain boundary phase. When observing with a microscope,
Observation can be made at about 20 to 200 times depending on the size of the grain boundary crystal phase. In the present invention, 5 mm square portions were observed at five locations per sample. This size was measured from a micrograph.
【００２７】このようにして観察すると、粒界相の最大
結晶径が１００μｍ以下、望ましくは１０μｍ以下であ
れば、結晶化による体積収縮量が小さく、粒界結晶間ま
たは、一部結晶化せずに残存する非晶質間との隙間に生
じる粒界欠落部が小さくなる。粒界相の最大結晶径を上
記のように管理すると、粒界相欠落部の集合である樹枝
状白色模様の大きさについては３００μｍ以下、望まし
くは１００μｍ以下、さらに望ましくは１０μｍ以下と
なり、転がり疲労による剥離が生じないことが判明し
た。According to the observation in this manner, when the maximum crystal diameter of the grain boundary phase is 100 μm or less, preferably 10 μm or less, the volume shrinkage due to crystallization is small, and the space between the grain boundary crystals or partial crystallization does not occur. The grain boundary missing portions generated in the gaps between the amorphous portions remaining in the crystal grains are reduced. When the maximum crystal diameter of the grain boundary phase is controlled as described above, the size of the dendritic white pattern, which is a set of the grain boundary phase-missing portions, becomes 300 μm or less, preferably 100 μm or less, and more preferably 10 μm or less. It was found that no peeling was caused by the peeling.
【００２８】さらには、セラミック部品、特に軸受け材
等の耐摩耗性部品は表面を研削したり、研削しない場合
でも表面近傍に応力がかかるため、表面より１ｍｍの範
囲内の粒界相欠落部が１μｍ以下、かつ１μｍ以下の粒
界相欠落部の集合である樹枝状白色模様の大きさが３０
０μｍ以下であることが特に重要である。Furthermore, ceramic parts, especially wear-resistant parts such as bearings, are subjected to stress in the vicinity of the surface even when the surface is ground or not ground, so that a grain boundary phase missing portion within 1 mm from the surface is formed. The size of a dendritic white pattern, which is a set of grain boundary phase missing portions of 1 μm or less and 1 μm or less, is 30
It is particularly important that the thickness be 0 μm or less.
【００２９】また、焼結助剤としては希土類元素酸化物
を用いた場合の方が、酸化マグネシウムや酸化カルシウ
ムなどを用いる場合より粒界相欠落部の生成が少ない。
理由は明確でないが、粒界相の性質が異なるものと思わ
れる。Further, when a rare earth element oxide is used as a sintering aid, generation of grain boundary phase missing portions is smaller than when magnesium oxide or calcium oxide is used.
Although the reason is not clear, it seems that the properties of the grain boundary phase are different.
【００３０】特に希土類元素酸化物は焼結助剤として重
要であり、その量は１〜３０重量％が望ましい。この範
囲を選んだ理由は、１重量％未満では緻密化させるため
に焼成温度を高温にする必要があるため、機械的特性が
低下する傾向にあるからであり、また、３０重量％を越
えると窒化珪素の本来の特性、即ち機械的特性が低下す
る傾向にあるからである。Particularly, the rare earth element oxide is important as a sintering aid, and its amount is desirably 1 to 30% by weight. The reason for selecting this range is that if it is less than 1% by weight, the firing temperature must be high in order to densify it, so that the mechanical properties tend to deteriorate, and if it exceeds 30% by weight, This is because the intrinsic properties of silicon nitride, that is, mechanical properties, tend to decrease.
【００３１】また、窒化珪素質磁器を分析する事によっ
て求めた酸素量から、添加した希土類元素酸化物の含有
する酸素量を差し引き、残りの酸素がＳｉＯ2となって
いると仮定して計算したときに、ＳｉＯ2：希土類元素
酸化物の重量比が１：０．３〜１：１５となるようにす
ると、耐摩耗性が良好な窒化珪素質セラミック焼結体を
得ることができる。Further, the amount of oxygen contained in the added rare earth element oxide was subtracted from the amount of oxygen obtained by analyzing the silicon nitride-based porcelain, and calculation was performed assuming that the remaining oxygen was SiO 2 . In some cases, when the weight ratio of SiO 2 : rare earth element oxide is 1: 0.3 to 1:15, a silicon nitride ceramic sintered body having good wear resistance can be obtained.
【００３２】これは、重量比が１：０．３未満であれ
ば、粒界相がＳｉＯ2に富んだ相を分離して白い模様
（粒界の脱落した組織）が発生しやすい傾向にあり、ま
た、１：１５以上であれば、ＳｉＯ2−希土類元素酸化
物の反応による低融点組成から大幅に外れるため液相生
成が十分ではなく、焼結不良が発生して機械的特性の低
い焼結体になる傾向にあるためである。If the weight ratio is less than 1: 0.3, the grain boundary phase tends to separate a phase rich in SiO 2 , and a white pattern (structure with grain boundaries dropped out) tends to be generated. If the ratio is 1:15 or more, the composition deviates significantly from the low-melting point composition due to the reaction of SiO 2 -rare earth element oxide. This is because they tend to be united.
【００３３】なお、ＳｉＯ2は窒化珪素原料中に最初か
ら含まれていたものに加え、場合によっては焼結助剤と
して加えてもかまわないし、製造工程中で原料の酸化等
による増加や焼成分解等による減少が生じてもかまわな
い。It is to be noted that SiO 2 may be added as a sintering aid in addition to the one originally contained in the silicon nitride raw material, and may be added during the manufacturing process due to oxidation of the raw material or decomposition by firing. Such a decrease may occur.
【００３４】なお、本発明に用いられる希土類元素とし
ては、Ｙ、Ｅｒ、Ｙｂ、Ｌｕが望ましい。これらの元素
中で、白い模様（粒界の脱落した組織）が発生し難くな
る点で特にＹｂ、Ｅｒ等の重希土類元素を用いることが
最も望ましい。The rare earth elements used in the present invention are preferably Y, Er, Yb, and Lu. Among these elements, it is most preferable to use a heavy rare earth element such as Yb or Er, since a white pattern (a structure in which grain boundaries have fallen off) hardly occurs.
【００３５】さらに、副成分として酸化アルミニウムを
添加する方が、焼結性の面および粒界相を一旦非晶質化
させる点で望ましい。粒界相の最大結晶径を１００μｍ
以下にするためには、焼成後に急冷して粒界相を一旦非
晶質化させてやる必要があり、そうすることにより焼成
後に行う９００℃〜１２００℃の温度での熱処理により
１００μｍ以下の小さな結晶核が数多く析出し、粒界相
の結晶相は１００μｍ以上の大きさに成長しない。好ま
しい酸化アルミニウム量は、酸化アルミニウム：希土類
元素酸化物の重量比が１：０．５〜１：１０、さらに好
ましくは、１：１〜１：５の範囲に選ばれる。Further, it is desirable to add aluminum oxide as a subcomponent in that the sintering surface and the grain boundary phase are once made amorphous. Maximum grain size of grain boundary phase is 100μm
In order to reduce the temperature to below, it is necessary to rapidly cool the grain boundary phase after firing and to make the grain boundary phase amorphous once. Many crystal nuclei are precipitated, and the crystal phase of the grain boundary phase does not grow to a size of 100 μm or more. The preferred amount of aluminum oxide is selected so that the weight ratio of aluminum oxide to the rare earth element oxide is 1: 0.5 to 1:10, and more preferably 1: 1 to 1: 5.
【００３６】その理由は、酸化アルミニウム：希土類元
素酸化物比が１：０．５より酸化アルミニウムが過剰に
なると、破壊靭性値が低下する傾向にある。また、酸化
アルミニウム：希土類元素酸化物比が１：１０より酸化
アルミニウムが少なくなると、焼結性が悪くなり、圧砕
荷重が低くなる傾向にある。また、粒界相が非晶質化し
にくくなり、粒界相欠落部が発生しやすくなる。The reason for this is that when the ratio of aluminum oxide: rare earth element oxide is 1: 0.5 or more, the fracture toughness tends to decrease. Further, when the ratio of aluminum oxide: rare earth element oxide is less than 1:10, the sinterability is poor and the crushing load tends to be low. In addition, the grain boundary phase is less likely to become amorphous, and the grain boundary phase missing portion is more likely to occur.
【００３７】また、上記の焼結体中に、平均粒径が３μ
ｍ以下であるタングステン珪化物を含有させることが好
ましい。もともと窒化珪素原料中には微量のＦｅが不純
物として含まれており、焼成後Ｆｅが偏在して破壊源と
なることがあり、強度低下が生じ、また耐摩耗性部材と
して用いたときに、圧砕荷重が低下し、転がり寿命が短
くなる。タングステン珪化物はＦｅを固溶する性質を持
つため、焼成後のＦｅの偏在を少なくし、機械的特性を
向上させる。In the above sintered body, the average particle size is 3 μm.
It is preferable to contain a tungsten silicide of m or less. Originally, a small amount of Fe was contained as an impurity in the silicon nitride raw material, and Fe was unevenly distributed after firing, which might be a source of destruction, resulting in a decrease in strength and crushing when used as a wear-resistant member. The load is reduced and the rolling life is shortened. Since tungsten silicide has the property of dissolving Fe, the uneven distribution of Fe after firing is reduced, and the mechanical properties are improved.
【００３８】ここで、これらのＷ珪化物の粒径を３μｍ
以下に限定したのは、タングステン珪化物が３μｍより
大きいと粒界相中での分散が不十分となり、それ自身が
破壊源となり焼結体の強度を低下させてしまい、目的の
強度が得られないためである。Here, the particle size of these W silicides is 3 μm
The reason for the limitation is that if the tungsten silicide is larger than 3 μm, the dispersion in the grain boundary phase becomes insufficient, and the tungsten silicide itself becomes a fracture source and lowers the strength of the sintered body, and the desired strength is obtained. Because there is no.
【００３９】また、窒化珪素質焼結体中にＷ5Ｓｉ3やＷ
Ｓｉ2を生成させるには、平均粒径が３μｍ以下のＷの
珪化物、炭化物、酸化物、窒化物の１種類以上を０. １
〜１０．０重量％を添加する。これらのＷ化合物は焼成
中に窒化珪素やＳｉＯ2と反応し、３μｍ以下のＷ5Ｓｉ
3やＷＳｉ2を生成する。In addition, W 5 Si 3 or W
In order to generate Si 2 , one or more types of W silicides, carbides, oxides, and nitrides having an average particle size of 3 μm or less are added in 0.1%.
Add 〜10.0% by weight. These W compounds react with silicon nitride or SiO 2 during firing and form W 5 Si of 3 μm or less.
3 and WSi 2 are generated.
【００４０】なお、本発明の焼結体においては、Ｗ成分
以外に、Ｔｉ、Ｔａ、Ｍｏ、Ｎｂ、Ｖ、Ｍｎなどの周期
率第４ａ、５ａ、６ａ族金属や、それらの珪化物、炭化
物、酸化物、窒化物、また、ＳｉＣなどの分散粒子やウ
イスカーとして本発明の焼結体に分散させても特性を劣
化させるような影響が少ないことから、これらを周知技
術に基づき、適量添加して複合材料として特性の改善を
行うことも当然可能である。In the sintered body of the present invention, in addition to the W component, metals having periodicity of groups 4a, 5a and 6a such as Ti, Ta, Mo, Nb, V and Mn, and silicides and carbides thereof. , Oxides, nitrides, and also dispersed particles or whiskers of SiC or the like in the sintered body of the present invention have little effect of deteriorating the properties. Of course, it is also possible to improve the characteristics as a composite material.
【００４１】さらに、Ｗの珪化物のうち、Ｗ5Ｓｉ3粒子
はＷＳｉ2粒子よりも耐熱性が高いと考えられるためＷ5
Ｓｉ3粒子を含有する場合の方が、転がり寿命が優れ
る。Ｗ 5Ｓｉ3とＷＳｉ2との比率（Ｗ5Ｓｉ3／ＷＳｉ2）
が０．１以上で構成されるセラミック焼結体とすること
が好適である。さらに好ましくは、上記比率が０．３〜
１．５とするのが望ましい。Further, among the silicides of W, WFiveSiThreeparticle
Is WSiTwoW is considered to have higher heat resistance than particles.Five
SiThreeRolling life is better when particles are included
You. W FiveSiThreeAnd WSiTwoAnd the ratio (WFiveSiThree/ WSiTwo)
Ceramic sintered body composed of 0.1 or more
Is preferred. More preferably, the ratio is 0.3 to
It is desirably 1.5.
【００４２】次に、本発明の窒化珪素質焼結体の製造方
法を説明する。Next, a method for producing the silicon nitride sintered body of the present invention will be described.
【００４３】原料粉末を所定量秤量し、公知の混合方
法、例えば回転ミルや振動ミル、バレルミルでＩＰＡや
メタノール、水等を溶媒として混合する。場合によって
は、溶媒を使わない乾式混合でもかまわない。A predetermined amount of the raw material powder is weighed and mixed by a known mixing method, for example, a rotary mill, a vibration mill, or a barrel mill using IPA, methanol, water or the like as a solvent. In some cases, dry mixing without using a solvent may be used.
【００４４】できあがった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、押し出し成
形、射出成形、鋳込み成形等により任意の形状にする。
成型手段によっては、スプレードライ等による造粒や、
水、有機バインダーと共にある一定粘度の杯土を作製す
るなどの準備も必要であるが、通常のセラッミクスの成
形手順に従えばよい。[0044] The mixed powder thus obtained is subjected to desired molding means,
For example, an arbitrary shape is formed by a die press, a cold isostatic press, an extrusion molding, an injection molding, a casting molding, or the like.
Depending on the molding method, granulation by spray drying or the like,
Preparations such as preparation of a clay having a certain viscosity together with water and an organic binder are also required, but a normal ceramics molding procedure may be used.
【００４５】成形後、乾燥、脱脂が必要な場合、窒素中
や真空中、大気中で、５０℃〜１４００℃の温度で加熱
処理する。If drying and degreasing are required after molding, heat treatment is performed at a temperature of 50 ° C. to 1400 ° C. in nitrogen, vacuum, or air.
【００４６】焼成は、窒素を含有した非酸化物雰囲気中
において１６００℃〜２０００℃で行う。１８００℃以
上で焼成を行う場合は、窒化珪素の分解が生じるので、
１気圧以上の窒素分圧を必要とする。さらにこれらの焼
成後、熱間静水圧焼成（ＨＩＰ）等で焼成することによ
り、より緻密な焼結体を得る。焼成温度は、高すぎると
主相である窒化珪素結晶が粒成長し強度が低下するた
め、１６５０〜１９５０℃で行うことが望ましい。The firing is performed at 1600 ° C. to 2000 ° C. in a nitrogen-containing non-oxide atmosphere. When firing at 1800 ° C. or higher, decomposition of silicon nitride occurs,
Requires a partial pressure of nitrogen of at least one atmosphere. Further, after sintering, sintering is performed by hot isostatic pressing (HIP) or the like to obtain a denser sintered body. If the firing temperature is too high, the main phase, silicon nitride crystal, grows to reduce the strength, so that the firing temperature is desirably 1650 to 1950 ° C.
【００４７】また、成形体をガラス浴ＨＩＰ法で焼成す
ると低温短時間で緻密な焼結体が作製できるので、特に
高強度を必要とするセラミック部品や、耐摩耗性部品に
は好適である。Further, when the molded body is fired by the glass bath HIP method, a dense sintered body can be produced in a short time at a low temperature, so that it is particularly suitable for ceramic parts requiring high strength and wear-resistant parts.
【００４８】また、粒界相の結晶最大径を１００μｍ以
下にするためには、粒界相を一旦非晶質化させる必要が
あるが、粒界相を一旦非晶質化させるためには冷却速度
が速いほうが良く、特に１６００〜８００℃の温度領域
を３時間、望ましくは１時間、さらに望ましくは３０分
以内で冷却させる方がよい。In order to reduce the maximum crystal diameter of the grain boundary phase to 100 μm or less, it is necessary to make the grain boundary phase amorphous once. The higher the speed, the better. In particular, it is better to cool the temperature range of 1600 to 800 ° C. for 3 hours, preferably 1 hour, and more preferably within 30 minutes.
【００４９】さらに、非晶質化した粒界相を結晶径の小
さい結晶として析出させるために、９００℃〜１２００
℃の温度で熱処理し結晶核を生成させる。この熱処理は
焼成後完全に冷却した後、炉から取り出して別の炉で個
々に行う単独熱処理としてもかまわないし、冷却に続く
焼成パターンとして同一の炉で行う連続熱処理としても
構わない。この焼成により窒化珪素は、原料がα、βの
いずれの場合においてもβ−Ｓｉ3Ｎ4となる。Further, in order to precipitate the amorphized grain boundary phase as crystals having a small crystal diameter, 900 ° C. to 1200 ° C.
Heat treatment at a temperature of ° C. to generate crystal nuclei. This heat treatment may be a single heat treatment that is completely cooled after firing and then taken out of the furnace and individually performed in another furnace, or may be a continuous heat treatment performed in the same furnace as a firing pattern following cooling. By this firing, silicon nitride becomes β-Si 3 N 4 regardless of whether the raw material is α or β.
【００５０】この焼成により、最終的にはβ−窒化珪素
主結晶相と粒界相を含む焼結体が得られる。特に希土類
元素酸化物、酸化アルミニウムを焼結助剤として用いた
場合は、希土類元素、アルミニウム、酸素および窒素を
含む粒界相からなり、その粒界中に平均粒径が３μｍ以
下であるＷ5Ｓｉ3あるいはＷ5Ｓｉ3＋ＷＳｉ2を含有し
た焼結体を得ることができる。ここで結晶化する部分
は、希土類元素酸化物、酸化アルミニウム、酸化珪素等
のセラミックス成分を主成分とする粒界部分である。By this firing, a sintered body containing a β-silicon nitride main crystal phase and a grain boundary phase is finally obtained. In particular, when a rare earth element oxide or aluminum oxide is used as a sintering aid, W 5, which is composed of a grain boundary phase containing a rare earth element, aluminum, oxygen and nitrogen, and has an average particle size of 3 μm or less in the grain boundary. A sintered body containing Si 3 or W 5 Si 3 + WSi 2 can be obtained. The portion to be crystallized here is a grain boundary portion mainly composed of a ceramic component such as a rare earth oxide, aluminum oxide, and silicon oxide.
【００５１】さらにＷＳｉ2またはＷ5Ｓｉ3は粒界に単
分散し、外部より応力がかかった際に、応力を緩和する
効果があり、また、同時に焼結助剤としても効果があ
り、その結果、破壊靭性が５．６ＭＰａ√ｍ以上、か
つ、Ｈｖ１０硬度が１４．５以上の高靭性、かつ、高硬
度の機械的特性を有することができる。つまり、本発明
によると、白い樹枝状に観察される模様がなくなり、高
信頼性であり、変質層が少ないため研削代が少なく、か
つ高破壊靭性、高硬度である窒化珪素質焼結体を得るこ
とが可能となる。Further, WSi 2 or W 5 Si 3 is monodispersed at the grain boundaries and has an effect of relaxing the stress when an external stress is applied, and also has an effect as a sintering aid. As a result, it is possible to have high toughness having a fracture toughness of 5.6 MPa√m or more and an Hv10 hardness of 14.5 or more and high mechanical properties of high hardness. In other words, according to the present invention, there is no white dendritic pattern observed, the silicon nitride sintered body is highly reliable, has a small amount of alteration, has a small grinding allowance, and has high fracture toughness and high hardness. It is possible to obtain.
【００５２】以上の本発明の窒化珪素質焼結体は種々の
セラミックス部品、特に、転動体、ピストンピン、ロー
ラーピン、ロッカーアームチップ、ローラーブッシュ、
カムローラー、バルブ等の耐摩耗性部品に使用する事が
可能である。The above-mentioned silicon nitride sintered body of the present invention is made of various ceramic parts, especially rolling elements, piston pins, roller pins, rocker arm chips, roller bushes,
It can be used for wear-resistant parts such as cam rollers and valves.
【００５３】[0053]
【実施例】実施例 １ 以下、実施例を説明する。Embodiment 1 An embodiment will be described below.
【００５４】まず窒化珪素粉末（ＢＥＴ比表面積９ｍ2
／ｇ）粉末に表１に示す焼結助剤を添加し、ＩＰＡとと
もにバレルミルで４０Ｈｒ混合した。混合後＃５００メ
ッシュを通してスラリーから異物を除去後、乾燥した。
この混合粉末に水、有機バインダーを加え、２０Ｈｒ混
合後、スプレードライにより原料顆粒を得た。この原料
顆粒を用いて、プレス成形により球状成形体及び強度測
定用の試験片を作製した。First, silicon nitride powder (BET specific surface area 9 m 2
/ G) The sintering aids shown in Table 1 were added to the powder and mixed with IPA in a barrel mill for 40 hours. After mixing, foreign matter was removed from the slurry through a # 500 mesh and dried.
Water and an organic binder were added to this mixed powder, and after mixing for 20 hours, raw material granules were obtained by spray drying. Using the raw material granules, a spherical molded body and a test piece for measuring the strength were prepared by press molding.
【００５５】次にこの成形体を１０Ｔｏｒｒ以下の減圧
中８００〜１４００℃の温度域で加熱後、１７５０〜１
８５０℃で窒素雰囲気の下、相対比重９９％以上まで緻
密化させた。さらに、２０００気圧の加圧下にて１６０
０℃でＨＩＰ処理を施し、１６００〜８００℃までの冷
却時間を１または６時間とし、９００℃〜１２００℃の
温度域で熱処理して直径３／８インチの本発明球状セラ
ミックス焼結体および強度測定用試験片を得た。Next, this compact was heated in a temperature range of 800 to 1400 ° C. under a reduced pressure of 10 Torr or less, and then heated at 1750 to 1400 ° C.
It was densified at 850 ° C. under a nitrogen atmosphere to a relative specific gravity of 99% or more. In addition, under a pressure of 2000 atm.
The spherical ceramic sintered body of the present invention having a diameter of 3/8 inch is subjected to a HIP treatment at 0 ° C., and a heat treatment in a temperature range of 900 ° C. to 1200 ° C. with a cooling time of 1600 to 800 ° C. for 1 or 6 hours. A test piece for measurement was obtained.
【００５６】球状セラミックスの圧砕荷重は、同じ寸法
の２個の球を重ねて圧縮荷重を加えるもので、ＪＩＳ−
Ｂ−１５０１に準じ、インストロン万能試験機によりク
ロスヘッドスピード５ｍｍ／分で測定した。The crushing load of the spherical ceramic is obtained by superposing two balls of the same size and applying a compressive load.
The measurement was performed at a crosshead speed of 5 mm / min using an Instron universal testing machine according to B-1501.
【００５７】強度測定は、３×４×３５ｍｍの形状に加
工した試験片をＪＩＳ Ｒ１６０１に準じた四点曲げ試
験にて行った。The strength was measured by a four-point bending test according to JIS R1601 on a test piece processed into a shape of 3 × 4 × 35 mm.
【００５８】粒界相欠落部のサイズは光学顕微鏡１００
倍で観察した後、ＳＥＭ像によって測定した。粒界相欠
落部の集合体である樹枝状白色模様のサイズは、光学顕
微鏡１００倍の写真より測定した。The size of the grain boundary phase missing portion was determined by using an optical microscope 100.
After observation at × 2, it was measured by an SEM image. The size of the dendritic white pattern, which is an aggregate of the grain boundary phase-missing portions, was measured from a photograph taken with an optical microscope (× 100).
【００５９】粒界相の最大結晶径の判断は、結晶の有無
を焼結体を粉砕した粉末のＸ線回折により判断し、さら
に同一ロットの球状セラミックス体を２０μｍに薄片加
工し、偏光顕微鏡によって粒界相の最大結晶径の確認を
行った。試料は、各条件５ｍｍ角の部分を５箇所づつ調
査した。偏光顕微鏡に試料をセットし、試料を回転して
いくと、方位があった時点で白く見える部分がある。こ
のとき白く見える部分が一つの粒界相の結晶であり、こ
れらの評価結果を表１にまとめた。The maximum crystal diameter of the grain boundary phase is determined by determining the presence or absence of crystals by X-ray diffraction of a powder obtained by pulverizing a sintered body. Further, a spherical ceramic body of the same lot is sliced to 20 μm and subjected to a polarizing microscope. The maximum crystal diameter of the grain boundary phase was confirmed. As for the sample, a 5 mm square portion under each condition was examined at five locations. When the sample is set on the polarizing microscope and the sample is rotated, there is a part that looks white when there is an orientation. At this time, the portion that looks white is a crystal of one grain boundary phase, and the evaluation results are summarized in Table 1.
【００６０】[0060]
【表１】 [Table 1]
【００６１】表１から明らかなように、粒界相の最大結
晶径が１００μｍより大きい試料２、３は強度が劣る。
これに対して本発明の請求範囲内である粒界相の結晶サ
イズが１００μｍ以下である試料１、４〜６は高強度で
あり、かつ圧砕荷重に優れていた。As is clear from Table 1, the strength of Samples 2 and 3 in which the maximum crystal diameter of the grain boundary phase is larger than 100 μm is inferior.
On the other hand, Samples 1, 4 to 6 in which the crystal size of the grain boundary phase within the scope of the present invention is 100 μm or less were high in strength and excellent in crushing load.
【００６２】実施例 ２ 実施例１と同様の手法を用いて、焼結体を作製した。結
晶化条件を表２に示した冷却時間、熱処理温度とし、得
られた各々の焼結体を実施例１と同様の手法により評価
した。Example 2 A sintered body was produced in the same manner as in Example 1. The crystallization conditions were set to the cooling time and heat treatment temperature shown in Table 2, and each of the obtained sintered bodies was evaluated in the same manner as in Example 1.
【００６３】破壊靭性値はＪＩＳ Ｒ１６０７に準じ
た。これらの評価結果を表２にまとめた。The fracture toughness value was in accordance with JIS R1607. Table 2 summarizes the results of these evaluations.
【００６４】[0064]
【表２】 [Table 2]
【００６５】表２から明らかなように、希土類元素酸化
物であるＹｂ2Ｏ3を４０重量％含有しＳｉＯ2：希土類
元素酸化物比が１：２０である試料７は、焼結不足とな
った。また、前記Ｙｂ2Ｏ3を０．５重量％含有しＳｉＯ
2：希土類元素酸化物比が１：０．２である試料３は、
粒界相の最大結晶径が１４０μｍとなり、強度および圧
砕荷重、Ｋ１ｃが低い値となった。As is clear from Table 2, Sample 7 containing 40% by weight of Yb 2 O 3 which is a rare earth element oxide and having a SiO 2 : rare earth element oxide ratio of 1:20 was insufficiently sintered. Was. Further, 0.5% by weight of the aforementioned Yb 2 O 3
2 : Sample 3 having a rare earth element oxide ratio of 1: 0.2,
The maximum crystal diameter of the grain boundary phase was 140 μm, and the strength, crushing load, and K1c were low.
【００６６】これに対し、希土類元素酸化物が１〜３０
重量％で、ＳｉＯ2：希土類元素酸化物の重量比が１：
０．３〜１：１５である試料１、２、４〜６、８は粒界
相の結晶サイズが１００μｍ以下であって、機械的特性
が優れていた。On the other hand, the rare earth element oxide is 1 to 30
In weight%, the weight ratio of SiO 2 : rare earth element oxide is 1:
Samples 1, 2, 4 to 6, and 8 having a grain size of 0.3 to 1:15 had a crystal size of the grain boundary phase of 100 μm or less, and were excellent in mechanical properties.
【００６７】また、同じ重量比の希土類元素酸化物を添
加した試料１、２、５において、Ｅｒ、Ｙｂを使用した
試料２、５は強度が特に優れていた。In Samples 1, 2, and 5 to which the same weight ratio of rare earth oxide was added, Samples 2 and 5 using Er and Yb were particularly excellent in strength.
【００６８】実施例 ３ 実施例１と同様の手法を用いて、焼結体を作製した。表
３に示した冷却時間、熱処理温度で粒界相を結晶化さ
せ、得られた焼結体を実施例１と同様の手法により評価
した。Example 3 A sintered body was produced in the same manner as in Example 1. The grain boundary phase was crystallized at the cooling time and heat treatment temperature shown in Table 3, and the obtained sintered body was evaluated in the same manner as in Example 1.
【００６９】破壊靭性値はＪＩＳ Ｒ１６０７に準じ
た。これらの評価結果を表３にまとめた。The fracture toughness value was in accordance with JIS R1607. Table 3 summarizes the results of these evaluations.
【００７０】[0070]
【表３】 [Table 3]
【００７１】表３から明らかなように、試料１〜１１に
おいて、酸化アルミニウム：希土類元素酸化物比が１：
１０より酸化アルミニウムが少ない試料１、３、５は焼
結不足であり、酸化アルミニウム：希土類元素酸化物比
が１：０．５より酸化アルミニウムが過剰な試料１１は
破壊靱性値および圧砕荷重が劣っていたが、酸化アルミ
ニウム：希土類元素酸化物が１：０．５〜１：１０の試
料２、４、６〜１０は、焼結性に優れており、かつ、粒
界相の最大結晶径が１００μｍ以下であって、かつ粒界
相欠落部が１μｍ以下で、粒界相欠落部の集合である樹
枝状白色模様が３００μｍ以下であり、優れた機械的特
性を有していた。As is clear from Table 3, in Samples 1 to 11, the aluminum oxide: rare earth element oxide ratio was 1: 1.
Samples 1, 3, and 5 with less aluminum oxide than 10 had insufficient sintering, and Sample 11 with an aluminum oxide: rare earth element oxide ratio of more than 1: 0.5 aluminum oxide was inferior in fracture toughness value and crushing load. However, Samples 2, 4, 6 to 10 in which the ratio of aluminum oxide: the rare earth element oxide was 1: 0.5 to 1:10 had excellent sinterability, and the maximum crystal diameter of the grain boundary phase was large. It was 100 μm or less, the grain boundary phase missing part was 1 μm or less, and the dendritic white pattern, which is a set of grain boundary phase missing parts, was 300 μm or less, and had excellent mechanical properties.
【００７２】[0072]
【発明の効果】以上詳述した通り、本発明によれば、粒
界相を有する窒化珪素質焼結体において、表面より１ｍ
ｍの範囲内にある結晶粒界相の最大結晶径が１００μｍ
以下であり、かつ窒化珪素粒子間から欠落した粒界相欠
落部の大きさが１μｍ以下であり、かつ１μｍ以下の粒
界相欠落部の集合である樹枝状白色模様の大きさが３０
０μｍ以下であることを特徴とするものが得られ、高い
機械的特性を有する窒化珪素質焼結体と、研削代の少な
い長寿命の耐摩耗性部材を提供することができる。As described above in detail, according to the present invention, in a silicon nitride sintered body having a grain boundary phase, 1 m
m is within 100 μm.
And the size of the grain boundary phase missing portion between the silicon nitride particles is 1 μm or less, and the size of the dendritic white pattern which is a set of the grain boundary phase missing portions of 1 μm or less is 30 μm or less.
A silicon nitride-based sintered body having high mechanical properties and a long-wearing wear-resistant member with a small grinding allowance can be provided.
【図１】本発明の窒化珪素質焼結体における粒界結晶相
を示す模式図である。FIG. 1 is a schematic diagram showing a grain boundary crystal phase in a silicon nitride based sintered body of the present invention.
【図２】従来の窒化珪素質焼結体における粒界結晶相を
示す模式図である。FIG. 2 is a schematic view showing a grain boundary crystal phase in a conventional silicon nitride based sintered body.
１：粒界結晶相 ２：粒界相欠落部 1: grain boundary crystal phase 2: grain boundary phase missing part
Claims (5)
いる窒化珪素質焼結体であって、前記粒界相の最大結晶
径が１００μｍ以下であることを特徴とする窒化珪素質
焼結体。1. A silicon nitride sintered body in which at least a part of a crystal grain boundary phase is crystallized, wherein a maximum crystal diameter of the grain boundary phase is 100 μm or less. Union.
〜３０重量％の希土類元素化合物を含み、酸化物換算し
た酸化珪素：希土類元素酸化物の重量比が１：０．３〜
１：１５であることを特徴とする請求項１記載の窒化珪
素質焼結体。2. As an additive component, at least 1 in terms of oxide.
-30% by weight of a rare earth element compound, and the weight ratio of silicon oxide: rare earth element oxide in terms of oxide is 1: 0.3-
The silicon nitride based sintered body according to claim 1, wherein the ratio is 1:15.
み、酸化物換算した酸化アルミニウム：希土類元素酸化
物の重量比が１：０．５〜１：１０であることを特徴と
する請求項２記載の窒化珪素質焼結体。3. The nitride according to claim 2, wherein an aluminum compound is contained as an additional component, and the weight ratio of aluminum oxide to rare earth element oxide in terms of oxide is 1: 0.5 to 1:10. Silicone sintered body.
なることを特徴とする窒化珪素質耐摩耗性部材。4. A silicon nitride-based wear-resistant member comprising the silicon nitride-based sintered body according to claim 1.
後、非酸化物雰囲気中で１６００℃〜２０００℃の温度
で焼成し、１６００℃〜８００℃の温度領域を３時間以
内で冷却し、その後９００℃〜１２００℃の温度で熱処
理することを特徴とする窒化珪素質焼結体の製造方法。5. After forming a powder containing silicon nitride as a main component, the powder is fired at a temperature of 1600 ° C. to 2000 ° C. in a non-oxide atmosphere, and cooled in a temperature range of 1600 ° C. to 800 ° C. within 3 hours. And a subsequent heat treatment at a temperature of 900 ° C. to 1200 ° C.
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| JP35915399A JP4822573B2 (en) | 1999-12-17 | 1999-12-17 | Method for producing silicon nitride sintered body |
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| WO2008114752A1 (en) * | 2007-03-22 | 2008-09-25 | Ngk Spark Plug Co., Ltd. | Insert and cutting tool |
| JP2011140416A (en) * | 2010-01-07 | 2011-07-21 | Nikkato:Kk | Silicon nitride sintered compact and abrasion resistant member |
| US9719942B2 (en) | 2010-01-07 | 2017-08-01 | Nikkato Corporation | Sintered ceramic and ceramic sphere |
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| JPH0959069A (en) * | 1995-08-21 | 1997-03-04 | Mitsubishi Heavy Ind Ltd | Boron nitride sintered compact and its production |
| JPH1017368A (en) * | 1996-06-28 | 1998-01-20 | Kyocera Corp | Low-loss dielectric material for high-frequency wave |
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| JP2003063872A (en) * | 2001-08-28 | 2003-03-05 | Toshiba Corp | Abrasion-resistant part for electronic instrument and its manufacturing method, and bearing for electronic instrument using it |
| WO2008114752A1 (en) * | 2007-03-22 | 2008-09-25 | Ngk Spark Plug Co., Ltd. | Insert and cutting tool |
| US8492300B2 (en) | 2007-03-22 | 2013-07-23 | Ngk Spark Plug Co., Ltd. | Insert and cutting tool |
| JP2011140416A (en) * | 2010-01-07 | 2011-07-21 | Nikkato:Kk | Silicon nitride sintered compact and abrasion resistant member |
| US9719942B2 (en) | 2010-01-07 | 2017-08-01 | Nikkato Corporation | Sintered ceramic and ceramic sphere |
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| Publication number | Publication date |
|---|---|
| JP4822573B2 (en) | 2011-11-24 |
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