JP4122431B2 - Aluminum oxide wear-resistant member having a layered structure and method for producing the same - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、層状構造を有する耐摩耗性酸化アルミニウム部材の製造方法に関するものであり、更に詳しくは、部材の表面層の、粒径の小さな等軸晶の結晶からなる耐摩耗層と、内部の、異方性を有する結晶から構成される高破壊靱性層との少なくとも２層構造を有する耐摩耗／高破壊靱性の複層酸化アルミニウム部材の製造方法及び該方法により作製された耐摩耗層／高破壊靱性層の複層酸化アルミニウム焼結体に関するものである。本発明により作製された酸化アルミニウム耐摩耗性部材は、例えば、耐摩耗性と高い破壊靱性が要求される機械の摺動部品、鉱石や粉体、あるいは、スラリー等の移送管内張、ブラストノズル、メカニカルシール、切削工具、金型、粉砕機部品などの構造材料のみならず、高い機械的信頼性と耐摩耗性、及び生体的、化学的に不活性なことが要求される人工関節、歯科材料などの生体代替部品や半導体製造装置等の構造部材として有用である。
【０００２】
【従来の技術】
一般に、酸化アルミニウムは、化学的に安定であり、優れた硬さと適度な機械的強度を有しており、かつ資源が豊富で安価であるとともに、他の構造用セラミックスと比べて耐摩耗性に優れている。また、酸化アルミニウムは、生体毒性が無く、食品工業用機械部材、人工関節等の生体材料としても問題がない。また、酸化アルミニウムは、極めて安定な化合物であるため、半導体製造用機械部品などの極端に活性不純物を嫌う用途にも使用可能である。更に、酸化アルミニウムは、窯業製品などの製造機械部品としても、酸化アルミニウムが若干混入しても着色等の欠陥の原因とならないため、使用することができる。金属工業においても、酸化アルミニウムは、鉱石中の不純物として多量に含有されているため、鉱石に混入しても容易に除去可能である。
【０００３】
以上のような理由により、酸化アルミニウムは、多種の耐摩耗材料として広く使用されている。しかし、酸化アルミニウム焼結体は、材料の信頼性の指標である破壊靱性が劣るため、大きな衝撃の加わる部材や高い信頼性を要求される部材には、耐摩耗性は、酸化アルミニウムよりも劣るものの、窒化ケイ素や酸化ジルコニウムなどの構造用セラミックスが使用されてきている。
【０００４】
酸化アルミニウム焼結体の耐摩耗性を更に向上させる手段として、例えば、焼結体全体に添加物を加えた材料が報告されている（例えば、特許文献１〜３参照）が、これらは、耐摩耗性に主眼を置いたものであり、材料の信頼性の指標である破壊靱性を考慮していない。
【０００５】
一方、破壊靱性の向上を目的とし、例えば、焼結体の微細組織を制御した材料が報告されている（例えば、特許文献４〜９参照）。また、異常粒成長抑制の目的で、市販の多くの酸化アルミニウム焼結体に酸化マグネシウムが添加されているが、逆に、マグネシウム無添加で異常粒を均一に生成させた焼結体は、強度は低いが、破壊靱性が大幅に向上し、欠陥許容性の向上のみならず、加工の際の欠け、チッピングが減少することが知られている（非特許文献１参照）。しかし、これらの材料は、アスペクト比が大きく、かつ粒径の比較的大きな結晶粒から構成される組織を特徴とするため、比較的高い温度での焼結が必要となり、耐摩耗性が悪化する。
【０００６】
また、耐摩耗性と破壊靱性の両立を目指した材料として、例えば、酸化アルミニウム焼結体の表面から周期律表の３ａ、４ａ、５ａ、６ａ族元素、Ｆｅ、Ｎｉ、Ｃｏ、Ｓｉなどの元素を拡散させた材料（特許文献１０参照）、焼結体全体に鉄等を添加し、雰囲気制御下での熱処理により、表面改質層を形成した材料（特許文献１１、１２参照）などが知られている。また、表面層と内部層で異なる酸化物を添加した粉末を積層し、同時に焼結する方法（特願平２００２−１７３１８８）が知られている。しかし、これらは、表面改質処理の工程数の増加や高価な雰囲気制御を必要とする。酸化アルミニウム焼結体は、構造用セラミックスとしては比較的安価な材料であるため、当該技術分野では、簡便、かつ安価な方法により作製できる、耐摩耗性と高い破壊靱性を同時に満足する構造部材の開発が強く求められていた。
【０００７】
【特許文献１】
特開平７−２０６５１４号公報
【特許文献２】
特開平７−２３７９６１号公報
【特許文献３】
特開２００１−３０２３３６号公報
【特許文献４】
特開平７−２５７９６３号公報
【特許文献５】
特開平７−２７７８１４号公報
【特許文献６】
特開平１０−１５８０５５号公報
【特許文献７】
特開平１１−０７１１６８号公報
【特許文献８】
特開平１１−１３６５号公報
【特許文献９】
特開２００１−３２２８６５号公報
【特許文献１０】
特開平６−１６４６８号公報
【特許文献１１】
特開平９−３２８４４７号公報
【特許文献１２】
特開２００１−３１６１７１号公報
【非特許文献１】
Y. Yoshizawa et. al., J. Ceram. Soc. Jpn., 108 (2000) 558
【０００８】
【発明が解決しようとする課題】
このような状況の中で、本発明者らは、上記従来技術に鑑みて、上記従来技術の諸問題を抜本的に解決することを可能とする新しい酸化アルミニウム部材の製造方法を開発することを目標として鋭意研究を積み重ねた結果、部材の表面層と内部層に対する要求特性の違いに着目し、耐摩耗性や強度が要求される表面層には、微細な結晶粒から構成される微細組織を有し、内部層には、高い破壊靱性が得られる、アスペクト比が大きく、かつ粒径の比較的大きな結晶粒から構成される微細組織を有する耐摩耗部材を開発し、種々実験を試みた結果、結晶粒成長抑制剤をほとんど含有しない酸化アルミニウム成形体、又は、その仮焼結体の耐摩耗性を付与したい部分に、安価なマグネシウムイオンを塗布した後、通常の焼結を行うという極めて簡便な操作のみで、高い耐摩耗性と破壊靱性を高いレベルで両立させることが可能であることを見い出し、本発明を完成するに至った。
【０００９】
すなわち、本発明は、安価で耐摩耗性と破壊靱性が高いレベルで両立した酸化アルミニウム耐摩耗性部材の製造方法を提供することを目的とするものである。また、本発明は、優れた耐摩耗性を有する表面層と破壊靱性が５ＭＰａ・ｍ1/2以上の内部層との少なくとも２層からなる酸化アルミニウムを主成分とする耐摩耗部材であって、マグネシウムをほとんど含有しない酸化アルミニウム成形体、又は仮焼結体に、マグネシウムを塗布した後、本焼結を行うことによって作製される酸化アルミニウムを主成分とする耐摩耗部材を提供することを目的とするものである。
【００１０】
【課題を解決するための手段】
上記課題を解決するための本発明は、以下の技術的手段から構成される。
（１）異方性を有する結晶から構成される高破壊靱性材料の表面に、粒径の小さな等軸晶の結晶からなる耐摩耗層を配した少なくとも２層構造を有する耐摩耗層／高破壊靱性層の複層酸化アルミニウム焼結体を製造する方法であって、（ａ）不純物レベルを上回る酸化マグネシウムを含有しない酸化アルミニウム分が少なくとも９０％の酸化アルミニウム粉末を、成形、又は、成形の後、仮焼結することにより成形体を作製する、（ｂ）耐摩耗層形成部分に、マグネシウムイオン、又はマグネシウム化合物の少なくとも１種類を含む成分を付着させる、（ｃ）これらを本焼結する、ことを特徴とする複層酸化アルミニウム焼結体の製造方法。
（２）酸化アルミニウム粉末の成形体、又は、仮焼結体をマグネシウム化合物を含む粉末に埋没させ、本焼結を行うことを特徴とする前記（１）記載の複層酸化アルミニウム焼結体の製造方法。
（３）酸化アルミニウム粉末の成形体、又は、仮焼結体に、マグネシウムイオン、又はマグネシウム化合物の少なくとも１種類を含む溶液、又はスラリーを塗布、又は含浸させることを特徴とする前記（１）記載の複層酸化アルミニウム焼結体の製造方法。
（４）酸化アルミニウム粉末の成形体、又は仮焼結体に、加速器を用いてマグネシウムイオンを打ち込むことを特徴とする前記（１）記載の複層酸化アルミニウム焼結体の製造方法。
（５）上記マグネシウムイオン、又はマグネシウム化合物を付着させた成形体、又は仮焼結体を、常圧焼結、ホットプレス、又は熱間静水圧プレスの内から選ばれた１種類以上の方法によって焼結することを特徴とする前記（１）記載の複層酸化アルミニウム焼結体の製造方法。
（６）前記（１）から（５）のいずれかに記載の方法で作製された、乾式のピン・オン・ディスク法で測定される比摩耗量が１×１０−９ｍｍ２／Ｎまでの高い耐摩耗性を有する表面層と、破壊靱性が少なくとも５ＭＰａ・ｍ１／２の内部層との少なくとも２層からなる耐摩耗層／高破壊靱性層の複層酸化アルミニウム焼結体を構成要素として含む耐摩耗性構造部材。
（７）切断面の組織観察において、結晶粒のアスペクト比が１．５までで粒径が３μｍまでの結晶粒が少なくとも８０面積％を占める表面層と、アスペクト比が少なくとも１．５で粒径が少なくとも３μｍの粒子が少なくとも３０面積％含まれる内部層とを有する前記（６）記載の複層酸化アルミニウム焼結体を構成要素として含む耐摩耗性構造部材。
【００１１】
【発明の実施の形態】
次に、本発明について更に詳細に説明する。
本発明は、材料の表面と内部に要求される特性を考慮し、材料表面は、耐摩耗性に優れる、アスペクト比が小さく微細な結晶粒組織とし、内部は、破壊靱性に優れる、アスペクト比が大きく、かつ粒径の大きな結晶粒から構成される微細組織としたことを特徴とする複層酸化アルミニウム焼結体の製造方法に係るものである。通常、単一組成の焼結体では、微細な結晶粒から構成される組織が得られる焼結温度と、アスペクト比が大きく、かつ粒径の大きな結晶粒から構成される組織が得られる焼結温度は、大きく異なっており、これらを同一焼結温度で同時に焼結することは困難である。
このため、本発明では、通常、高強度酸化アルミニウム焼結体の作製の際に添加される結晶粒成長抑制剤を含有しない酸化アルミニウム分が９０％以上の粉末を使用する。本発明において、原料の酸化アルミニウム材料としては、高純度酸化アルミニウム粉末、低ソーダ酸化アルミニウム粉末、普通純度酸化アルミニウム粉末などが使用されるが、望ましくは、焼結体にアスペクト比の大きな粒子が生成するための酸化物を添加した高純度酸化アルミニウム粉末、あるいは、マグネシウム分を含有しない低ソーダ酸化アルミニウム粉末を使用する。
【００１２】
上記の粉末を、金型成形、冷間静水圧成形、鋳込み成形、排泥成形、ドクターブレード、押し出し等によって成形、又は、成形の後、仮焼結することにより成形体を作製する。このようにして作製した成形体、生加工を施した成形体、脱脂した成形体、あるいは、アスペクト比の大きな粒子が生成する温度以下で仮焼結した成形体に対し、表面耐摩耗層を形成したい箇所、又は全体に、高温での焼結過程で酸化マグネシウムとなる化合物、イオンを含有する成分を適宜の手段で付着させるが、好適には、これらの溶液、イオン、ガス、スラリー、あるいは粉末を塗布、打ち込み、あるいは含浸させる。成形体、仮焼結体の気孔率は、特に限定されず、内部層にアスペクト比の大きな粒子が生成する温度以下の仮焼結であれば良い。溶液、スラリーとしては、塩化マグネシウム水溶液、硝酸マグネシウム水溶液、マグネシウムエトキシドアルコール溶液、微粒酸化マグネシウム粉末のスラリーなどが例示される。しかし、本発明は、これらの材料に制限にされるものではなく、これらと同効のものであれば同様に使用することができる。
【００１３】
上記の溶液、スラリーの塗布、含浸方法としては、例えば、噴霧、刷毛塗り、ディッピング、スクリーン印刷、インクジェット印刷、滴下等の方法が例示される。しかし、本発明は、これらの方法に制限にされるものではなく、これらと同効のものであれば同様に使用することができる。マグネシウム化合物、ないしイオンを含有する溶液、あるいはスラリーを塗布あるいは含浸させる方法以外にも、成形体、仮焼結体に加速器を用いてマグネシウムイオンを打ち込んだもの、マグネシウムを含有するガス中で処理し、成形体、あるいは、仮焼結体の表面層に、高温で処理することで酸化マグネシウムとなる化合物などを析出したものも同様に使用することができる。また、酸化アルミニウム粉末とマグネシウム化合物、あるいは、イオンを含有するスラリーを塗布し、成形体表面に肉盛りすることも可能である。焼結後の耐摩耗性表面層に含有されるマグネシウム量が少なすぎると十分な結晶粒成長抑制効果が出現しないため、焼結後の耐摩耗性表面層に含有されるマグネシウム量が、酸化マグネシウム換算で０．００５重量％以上になるように溶液などの濃度、粘性、粒子径、塗布量、含浸量、塗布回数、含浸回数、本焼結条件などで調整する。表面層の厚さも、同様に調整可能である。
【００１４】
上記の方法でマグネシウムを表面に塗布、あるいは、表面層に含浸させた成形体、仮焼結体を、内部層にアスペクト比の大きな粒子が十分に生成する温度で常圧焼結、ホットプレス、又は熱間静水圧プレスの内から選ばれた１種類以上の方法によって焼結することにより、表面層の、粒径の小さな等軸晶の結晶からなる耐摩耗層と、内部の、異方性を有する結晶から構成される高破壊靱性層との少なくとも２層構造を有する耐摩耗層／高破壊靱性層の複層酸化アルミニウム焼結体を製造する。焼結は、使用する原料粉末により適正な温度は異なるが、好適には、１４００℃から１７００℃の範囲である。また、上記のマグネシウムを表面に塗布などした成形体などを用いず、マグネシウムを含有しない酸化アルミニウム成形体、又は仮焼結体をマグネシウム化合物を含む粉末に埋没させ、あるいは、マグネシウムを含む雰囲気中で本焼結を行うことにより、同様の複層酸化アルミニウム焼結体を製造することも可能である。これらの方法により作製される複層焼結体の層境界は、明確な境界を有する必要はなく、連続的に変化するものでも同じ特性が得られる。
本発明の方法により、乾式のピン・オン・ディスク法で測定される比摩耗量が１×１０-9ｍｍ2 ／Ｎまでの高い耐摩耗性を有する表面層と、破壊靱性が少なくとも５ＭＰａ・ｍ1/2 の内部層との少なくとも２層からなる耐摩耗層／高破壊靱性層の複層酸化アルミニウム焼結体、また、切断面の組織観察において、結晶粒のアスペクト比が１．５までで粒径が３μｍまでの結晶粒が少なくとも８０面積％を占める表面層と、アスペクト比が少なくとも１．５で粒径が少なくとも３μｍの粒子が少なくとも３０面積％含まれる内部層とを有する請求項６記載の複層酸化アルミニウム焼結体、及びこれらの複層酸化アルミニウム焼結体を構成要素として含む耐摩擦性構造部材を作製し、提供することができる。
【００１５】
【実施例】
次に、実施例に基づいて本発明を具体的に説明するが、本発明は、以下の実施例によって何ら限定されるものではない。
実施例
高靱性層の素材として、市販の高純度酸化アルミニウム粉末に粒成長促進剤を０．０１重量％添加（実施例１、比較例１）した粉末と、市販の酸化マグネシウム無添加の低ソーダ酸化アルミニウム粉末（実施例２−１〜２−３、比較例２）を用いた。湿式で解砕、混合した粉末３０ｇを５２ｍｍ×４４ｍｍの超硬合金製の金型を使用し、４０ＭＰａの圧力で一軸成形した。その後、ゴム袋に封入し、冷間静水圧成形を行った。成形体の気孔率は、実施例１が４６％、実施例２−１が４３％であった。一部の成形体は、大気中、１０００℃（実施例１、実施例２−２）、及び１５００℃（実施例２−３）で仮焼結した。仮焼結体の気孔率は、実施例１、実施例２−２、実施例２−３がそれぞれ、２９％、３９％、３％であった。
【００１６】
成形体、仮焼結体に硝酸マグネシウムの水溶液をハンドスプレーを用いて試料から３０ｃｍの距離から２回噴霧した（実施例１、２−１〜３）。なお、実施例２−３は、開気孔がほとんど存在しないため、噴霧した溶液は、仮焼結体に浸透せず、表面に堆積した。他の試料は、噴霧後、直ちに内部に浸透した。マグネシウム溶液を噴霧した成形体、仮焼結体を十分に乾燥の後、マグネシウム溶液を噴霧していない成形体（比較例１、２）とともに、大気中、１５００〜１６００℃で２時間、本焼結を行った。
【００１７】
続いて、板状の焼結体から２７×３０ｍｍの板状の試験片を機械加工により作製し、回転半径１０ｍｍ、回転数１７２ｒｐｍ、加重２４．５Ｎ、試験時間１０ｍｉｎの乾式ピン・オン・ディスク摩耗試験を行った。ボールには、市販の酸化アルミニウム焼結体ボールを使用した。また、焼結体から４×３×２０ｍｍの試験片を切り出し、ＪＩＳ−Ｒ１６０７で制定される破壊靱性試験を行った。微細組織は、鏡面研磨、熱腐食した試験片を走査電子顕微鏡で観察し、０．４ｍｍ2の面積の酸化アルミニウム粒子の形態を写真に撮影した。そして、粒子径、アスペクト比、アスペクト比が１．５以上の粒子の面積割合を計測した。また、比較例として、市販の純度９９％（比較例３）、９９．９％（比較例４）の耐摩耗用酸化アルミニウム焼結体を同様に試験した。
【００１８】
図１に、実施例２−１〜３の破面の走査電子顕微鏡写真を示す。写真左側が表面である。成形体、仮焼温度の上下に関係なく、ほぼ同一厚さの表面層が形成されていることが観察される。また、内部層との境界近傍を除き、表面層内は、表面からの距離によらず、均一な組織である。実施例２−３は、噴霧した溶液が内部に浸透せず、表面のみにマグネシウムが存在してたため、スピネルなどの化合物の生成や、表面から内部に向かって組織が連続的に変化することが予想されるが、実施例では、浸透させた試料と同等の組織を示しており、表面層の形成、厚さが仮焼結体の気孔率に依存しないことを示している。図２に、実施例２−２の表面層と内部層の境界部の破面の電子顕微鏡写真を示す。両層の境界には、反応層の形成も見られず、表面層が微細な結晶粒で構成され、内部層は、アスペクト比の大きな粗粒で構成される健全な複層焼結体であることが分かる。
表１に、作製した部材の破壊靱性、ボール・オン・ディスクによる摩耗率と組織観察による粒子の割合を示す。
【００１９】
【表１】
上記実施例に示されるように、本発明によって、単一層の焼結体に比べ、破壊靱性と耐摩耗性が高度に両立した焼結体を容易に得ることが可能である。
【００２１】
【発明の効果】
以上詳述したように、本発明は、結晶粒成長抑制剤を含有しない純度９０％以上の酸化アルミニウム成形体又は仮焼結体に、マグネシウムを含む溶液などを塗布した後、通常の焼結で製造される酸化アルミニウムを主成分とする耐摩耗性部材の製造方法に係るものであり、本発明によれば、（１）簡便、かつ安価な方法により、耐摩耗性と高い破壊靱性を同時に満たす酸化アルミニウム耐摩耗性構造部材を作製できる、（２）通常の焼結で耐摩耗性と破壊靱性が高度に両立した酸化アルミニウム耐摩耗性部材を製造することができる、（３）本発明の酸化アルミニウム耐摩耗性部材は、耐摩耗性と高い破壊靱性が要求される機械の摺動部品、半導体製造装置の部品等として有用である、という効果が得られる。
【図面の簡単な説明】
【図１】実施例２−１〜３の破面の走査電子顕微鏡写真を示す。
【図２】実施例２−２の表面層と内部層の境界部の破面の電子顕微鏡を示す。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a wear-resistant aluminum oxide member having a layered structure, and more specifically, a wear-resistant layer made of equiaxed crystals having a small particle size, and a surface layer of the member, , A method for producing a wear resistant / high fracture toughness multi-layer aluminum oxide member having at least a two-layer structure with a high fracture toughness layer composed of anisotropic crystals, and a wear resistant layer / high produced by the method The present invention relates to a multilayer aluminum oxide sintered body of a fracture toughness layer. The aluminum oxide wear-resistant member produced according to the present invention is, for example, a sliding part of a machine that requires wear resistance and high fracture toughness, ore or powder, or a transfer pipe lining such as slurry, a blast nozzle, Not only structural materials such as mechanical seals, cutting tools, molds, and crusher parts, but also artificial joints and dental materials that require high mechanical reliability and wear resistance, as well as biological and chemical inertness. It is useful as a structural member for living body substitute parts and semiconductor manufacturing equipment.
[0002]
[Prior art]
In general, aluminum oxide is chemically stable, has excellent hardness and moderate mechanical strength, is abundant in resources, is inexpensive, and is more resistant to wear than other structural ceramics. Are better. Aluminum oxide has no biotoxicity, and there is no problem as a biomaterial such as a machine member for food industry and an artificial joint. In addition, since aluminum oxide is a very stable compound, it can be used for applications that extremely dislike active impurities such as machine parts for semiconductor manufacturing. Furthermore, aluminum oxide can be used as a manufacturing machine part such as a ceramic product because it does not cause defects such as coloring even if aluminum oxide is mixed slightly. Also in the metal industry, aluminum oxide is contained in a large amount as an impurity in the ore and can be easily removed even if it is mixed in the ore.
[0003]
For the above reasons, aluminum oxide is widely used as a variety of wear-resistant materials. However, since the aluminum oxide sintered body is inferior in fracture toughness, which is an index of material reliability, wear resistance is inferior to aluminum oxide in members that are subjected to large impacts or members that require high reliability. However, structural ceramics such as silicon nitride and zirconium oxide have been used.
[0004]
As means for further improving the wear resistance of the aluminum oxide sintered body, for example, materials in which additives are added to the entire sintered body have been reported (for example, see Patent Documents 1 to 3). It focuses on wearability and does not consider fracture toughness, which is an indicator of material reliability.
[0005]
On the other hand, for the purpose of improving fracture toughness, for example, materials in which the microstructure of a sintered body is controlled have been reported (see, for example, Patent Documents 4 to 9). In addition, magnesium oxide is added to many commercially available aluminum oxide sintered bodies for the purpose of suppressing abnormal grain growth, but on the contrary, sintered bodies in which abnormal grains are uniformly formed without adding magnesium have a high strength. However, it is known that fracture toughness is greatly improved and not only defect tolerance is improved but also chipping and chipping during processing are reduced (see Non-Patent Document 1). However, these materials are characterized by a structure composed of crystal grains having a large aspect ratio and a relatively large grain size, so that sintering at a relatively high temperature is required and wear resistance is deteriorated. .
[0006]
Examples of materials aiming to achieve both wear resistance and fracture toughness include, for example, elements such as 3a, 4a, 5a, and 6a elements of the periodic table, Fe, Ni, Co, and Si from the surface of the aluminum oxide sintered body. A material in which a surface modified layer is formed by adding iron or the like to the entire sintered body and heat-treating under atmosphere control (see Patent Documents 11 and 12), etc. It has been. Further, there is known a method (Japanese Patent Application No. 2002-173188) in which powders to which different oxides are added in the surface layer and the inner layer are laminated and sintered at the same time. However, these require an increase in the number of steps of the surface modification treatment and expensive atmosphere control. Since the aluminum oxide sintered body is a relatively inexpensive material for structural ceramics, it can be produced by a simple and inexpensive method in the technical field, and it is a structural member that simultaneously satisfies wear resistance and high fracture toughness. There was a strong demand for development.
[0007]
[Patent Document 1]
JP-A-7-206514 [Patent Document 2]
JP-A-7-237961 [Patent Document 3]
JP 2001-302336 A [Patent Document 4]
JP-A-7-257963 [Patent Document 5]
Japanese Patent Laid-Open No. 7-277814 [Patent Document 6]
Japanese Patent Laid-Open No. 10-158055 [Patent Document 7]
JP 11-071168 A [Patent Document 8]
JP-A-11-1365 [Patent Document 9]
JP 2001-322865 A [Patent Document 10]
JP-A-6-16468 [Patent Document 11]
JP-A-9-328447 [Patent Document 12]
JP 2001-316171 A [Non-Patent Document 1]
Y. Yoshizawa et. Al., J. Ceram. Soc. Jpn., 108 (2000) 558
[0008]
[Problems to be solved by the invention]
Under such circumstances, the present inventors have developed a new method for manufacturing an aluminum oxide member that makes it possible to drastically solve the problems of the prior art in view of the prior art. As a result of intensive research as a goal, we focused on the difference in the required characteristics of the surface layer and internal layer of the member, and in the surface layer where wear resistance and strength are required, a microstructure composed of fine crystal grains As a result of developing various wear-resistant members that have a microstructure that is composed of crystal grains with a large aspect ratio and a relatively large grain size that can provide high fracture toughness in the inner layer. In addition, it is extremely easy to perform normal sintering after applying inexpensive magnesium ions to the aluminum oxide molded body that contains almost no crystal grain growth inhibitor, or to the portion of the temporary sintered body to which wear resistance is desired. Only Do operation, found that it is possible to achieve both a high level fracture toughness and high wear resistance, and have completed the present invention.
[0009]
That is, an object of the present invention is to provide a method for producing an aluminum oxide wear-resistant member that is inexpensive and has both high wear resistance and high fracture toughness. Further, the present invention is a wear-resistant member mainly composed of aluminum oxide composed of at least two layers of a surface layer having excellent wear resistance and an inner layer having a fracture toughness of 5 MPa · m 1/2 or more, An object of the present invention is to provide a wear-resistant member mainly composed of aluminum oxide, which is produced by applying main sintering to an aluminum oxide molded body containing almost no magnesium or a pre-sintered body. To do.
[0010]
[Means for Solving the Problems]
The present invention for solving the above-described problems comprises the following technical means.
(1) A wear-resistant layer / high fracture having at least a two-layer structure in which a wear-resistant layer composed of equiaxed crystals having a small grain size is arranged on the surface of a high fracture tough material composed of crystals having anisotropy. A method for producing a multilayer aluminum oxide sintered body of a toughness layer, wherein (a) aluminum oxide powder containing at least 90% aluminum oxide not containing magnesium oxide exceeding the impurity level is molded or after molding , To form a molded body by pre-sintering, (b) attach a component containing at least one kind of magnesium ion or magnesium compound to the wear-resistant layer forming part, (c) subject this to main sintering, A method for producing a multilayer aluminum oxide sintered body characterized by the above.
(2) The multilayer aluminum oxide sintered body according to (1) above, wherein the sintered body of aluminum oxide powder or the pre-sintered body is embedded in a powder containing a magnesium compound and main sintering is performed. Production method.
(3) The said (1) description characterized by apply | coating or impregnating the molded object of aluminum oxide powder, or a temporary sintered compact with the solution or slurry containing at least 1 type of a magnesium ion or a magnesium compound. Of producing a multilayer aluminum oxide sintered body.
(4) The method for producing a multilayer aluminum oxide sintered body according to (1) above, wherein magnesium ions are implanted into an aluminum oxide powder molded body or a temporary sintered body using an accelerator.
(5) The molded body to which the magnesium ion or the magnesium compound is adhered, or the temporary sintered body is subjected to at least one method selected from normal pressure sintering, hot pressing, and hot isostatic pressing. The method for producing a multilayer aluminum oxide sintered body according to (1), wherein sintering is performed.
(6) The specific wear amount measured by the dry pin-on-disk method, produced by the method according to any one of (1) to (5) above, is up to 1 × 10 −9 mm 2 / N. A multilayer aluminum oxide sintered body of a wear resistant layer / high fracture toughness layer composed of at least two layers of a surface layer having high wear resistance and an inner layer having a fracture toughness of at least 5 MPa · m 1/2 Including wear-resistant structural members .
(7) In the observation of the structure of the cut surface, the surface layer in which the crystal grains having an aspect ratio of up to 1.5 and the grain size of up to 3 μm occupy at least 80 area%, and the aspect ratio of at least 1.5 and the grain size There wear resistant structural member including as a component a multilayer aluminum oxide sintered product of the (6) further comprising an inner layer of at least 3μm particles contained at least 30% by area.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in more detail.
In consideration of the characteristics required for the surface and the inside of the material, the material surface has excellent wear resistance, a small aspect ratio and a fine grain structure, and the inside has excellent fracture toughness and an aspect ratio. The present invention relates to a method for producing a multilayer aluminum oxide sintered body characterized by having a fine structure composed of large and large crystal grains. Usually, in a sintered body having a single composition, a sintering temperature at which a structure composed of fine crystal grains is obtained, and a sintering at which a structure composed of crystal grains having a large aspect ratio and a large grain size are obtained. The temperatures are very different and it is difficult to sinter them simultaneously at the same sintering temperature.
For this reason, in this invention, the powder whose aluminum oxide content does not contain the crystal grain growth inhibitor added in the case of preparation of a high intensity | strength aluminum oxide sintered compact is 90% or more normally is used. In the present invention, high-purity aluminum oxide powder, low-soda aluminum oxide powder, ordinary-purity aluminum oxide powder, etc. are used as the raw material aluminum oxide material. Preferably, particles having a large aspect ratio are formed in the sintered body. Therefore, a high-purity aluminum oxide powder to which an oxide is added or a low-soda aluminum oxide powder not containing magnesium is used.
[0012]
The above powder is molded by die molding, cold isostatic pressing, casting molding, waste mud molding, doctor blade, extrusion, or the like, or after molding, a compact is produced. Forming a surface wear-resistant layer on the molded body thus produced, green molded body, degreased molded body, or pre-sintered molded body below the temperature at which particles with large aspect ratio are generated A compound that becomes magnesium oxide in a sintering process at a high temperature or a component containing ions is attached to a desired portion or the whole by an appropriate means, and preferably, these solutions, ions, gases, slurries, or powders Is applied, driven or impregnated. The porosity of the formed body and the pre-sintered body is not particularly limited as long as it is pre-sintering below the temperature at which particles having a large aspect ratio are generated in the inner layer. Examples of the solution and slurry include a magnesium chloride aqueous solution, a magnesium nitrate aqueous solution, a magnesium ethoxide alcohol solution, and a slurry of fine magnesium oxide powder. However, the present invention is not limited to these materials and can be used in the same manner as long as they have the same effect.
[0013]
Examples of the solution and slurry application and impregnation methods include spraying, brushing, dipping, screen printing, ink jet printing, and dropping. However, the present invention is not limited to these methods, and can be used in the same manner as long as they have the same effect. In addition to the method of applying or impregnating a magnesium compound or a solution containing ions or slurry, the molded body or the pre-sintered body is implanted with magnesium ions using an accelerator, or treated in a gas containing magnesium. In addition, it is also possible to similarly use a molded body or a surface layer of a pre-sintered body in which a compound that becomes magnesium oxide by precipitation at a high temperature is deposited. It is also possible to apply aluminum oxide powder and a magnesium compound or a slurry containing ions to build up on the surface of the molded body. If the amount of magnesium contained in the sintered wear-resistant surface layer is too small, a sufficient grain growth inhibitory effect will not appear, so the amount of magnesium contained in the sintered wear-resistant surface layer will be magnesium oxide. The concentration is adjusted to 0.005% by weight or more in terms of solution, viscosity, particle diameter, coating amount, amount of impregnation, number of times of application, number of times of impregnation, main sintering conditions, and the like. The thickness of the surface layer can be adjusted similarly.
[0014]
Magnesium is applied to the surface by the above method, or the molded body and the pre-sintered body impregnated in the surface layer are subjected to atmospheric pressure sintering, hot pressing at a temperature at which particles having a large aspect ratio are sufficiently generated in the inner layer, Or, by sintering by one or more methods selected from hot isostatic pressing, the wear layer of the surface layer made of equiaxed crystals with a small grain size and the internal anisotropy A multi-layer aluminum oxide sintered body having a wear-resistant layer / high fracture toughness layer having at least a two-layer structure with a high fracture toughness layer composed of crystals having a structure is produced. The proper temperature for sintering varies depending on the raw material powder used, but is preferably in the range of 1400 ° C to 1700 ° C. Also, without using a molded body coated with magnesium on the surface, an aluminum oxide molded body that does not contain magnesium, or a temporary sintered body is buried in a powder containing a magnesium compound, or in an atmosphere containing magnesium By performing the main sintering, a similar multilayer aluminum oxide sintered body can be produced. The layer boundary of the multilayered sintered body produced by these methods does not need to have a clear boundary, and the same characteristics can be obtained even if it continuously changes.
According to the method of the present invention, a surface layer having a high wear resistance up to 1 × 10 −9 mm 2 / N as measured by a dry pin-on-disk method, and a fracture toughness of at least 5 MPa · m In the multilayer aluminum oxide sintered body of wear-resistant layer / high fracture toughness layer consisting of at least two layers with the inner layer of 1/2 , and in the observation of the structure of the cut surface, the aspect ratio of the crystal grains is up to 1.5 7. A surface layer occupying at least 80 area% of crystal grains having a particle size of up to 3 [mu] m, and an inner layer containing at least 30 area% of particles having an aspect ratio of at least 1.5 and a particle diameter of at least 3 [mu] m. It is possible to produce and provide a multilayer aluminum oxide sintered body, and a friction-resistant structural member containing these multilayer aluminum oxide sintered bodies as constituent elements.
[0015]
【Example】
EXAMPLES Next, although this invention is demonstrated concretely based on an Example, this invention is not limited at all by the following Examples.
EXAMPLE As a raw material of the high toughness layer, a powder obtained by adding 0.01% by weight of a grain growth accelerator to a commercially available high-purity aluminum oxide powder (Example 1 and Comparative Example 1), and a commercially available low soda not containing magnesium oxide Aluminum oxide powder (Examples 2-1 to 2-3, Comparative Example 2) was used. 30 g of powder pulverized and mixed by wet was uniaxially molded at a pressure of 40 MPa using a cemented carbide mold of 52 mm × 44 mm. Then, it enclosed with the rubber bag and cold isostatic pressing was performed. The porosity of the molded body was 46% in Example 1 and 43% in Example 2-1. Some molded bodies were pre-sintered at 1000 ° C. (Example 1, Example 2-2) and 1500 ° C. (Example 2-3) in the atmosphere. The porosity of the temporary sintered body was 29%, 39%, and 3% in Example 1, Example 2-2, and Example 2-3, respectively.
[0016]
An aqueous solution of magnesium nitrate was sprayed twice from a distance of 30 cm from the sample to the molded body and the temporary sintered body using a hand spray (Examples 1, 2 to 1-3). In Example 2-3, since there were almost no open pores, the sprayed solution did not penetrate into the temporary sintered body and was deposited on the surface. Other samples penetrated the interior immediately after spraying. After sufficiently drying the molded body sprayed with the magnesium solution and the pre-sintered body, and the molded body not sprayed with the magnesium solution (Comparative Examples 1 and 2), the main firing was performed at 1500 to 1600 ° C. for 2 hours in the air. Yui was done.
[0017]
Subsequently, a 27 × 30 mm plate-shaped test piece was produced from the plate-shaped sintered body by machining, and dry pin-on-disk wear with a rotation radius of 10 mm, a rotation speed of 172 rpm, a load of 24.5 N, and a test time of 10 min. A test was conducted. A commercially available aluminum oxide sintered ball was used as the ball. Further, a 4 × 3 × 20 mm test piece was cut out from the sintered body, and a fracture toughness test established by JIS-R1607 was performed. The microstructure was mirror-polished and thermally corroded specimens were observed with a scanning electron microscope, and the form of aluminum oxide particles having an area of 0.4 mm 2 was photographed. Then, the particle diameter, aspect ratio, and area ratio of particles having an aspect ratio of 1.5 or more were measured. As comparative examples, commercially available aluminum oxide sintered bodies for wear resistance having a purity of 99% (Comparative Example 3) and 99.9% (Comparative Example 4) were similarly tested.
[0018]
In FIG. 1, the scanning electron micrograph of the fracture surface of Examples 2-1 to 3 is shown. The left side of the photo is the surface. It is observed that a surface layer having almost the same thickness is formed regardless of the shape of the compact and the calcining temperature. Further, except for the vicinity of the boundary with the inner layer, the inside of the surface layer has a uniform structure regardless of the distance from the surface. In Example 2-3, since the sprayed solution did not penetrate into the interior and magnesium was present only on the surface, the formation of compounds such as spinel and the structure continuously changed from the surface toward the interior. As expected, the examples show the same structure as the infiltrated sample, indicating that the formation and thickness of the surface layer does not depend on the porosity of the temporary sintered body. In FIG. 2, the electron micrograph of the fracture surface of the boundary part of the surface layer of Example 2-2 and an internal layer is shown. There is no reaction layer formed at the boundary between the two layers, the surface layer is composed of fine crystal grains, and the inner layer is a sound multilayer sintered body composed of coarse grains having a large aspect ratio. I understand that.
Table 1 shows the fracture toughness of the manufactured member, the wear rate by ball-on-disk, and the proportion of particles by structure observation.
[0019]
[Table 1]
As shown in the above examples, according to the present invention, it is possible to easily obtain a sintered body having a high degree of fracture toughness and wear resistance compared to a single layer sintered body.
[0021]
【The invention's effect】
As described above in detail, the present invention can be applied to normal sintering after applying a solution containing magnesium to an aluminum oxide molded body or a pre-sintered body having a purity of 90% or more that does not contain a crystal grain growth inhibitor. The present invention relates to a method for producing a wear-resistant member mainly composed of aluminum oxide. According to the present invention, (1) a simple and inexpensive method satisfies both wear resistance and high fracture toughness at the same time. An aluminum oxide wear-resistant structural member can be produced. (2) An aluminum oxide wear-resistant member having both high wear resistance and fracture toughness can be produced by ordinary sintering. (3) Oxidation of the present invention The aluminum wear-resistant member is useful as a sliding part of a machine that requires high wear resistance and high fracture toughness, a part of a semiconductor manufacturing apparatus, and the like.
[Brief description of the drawings]
FIG. 1 shows scanning electron micrographs of fracture surfaces of Examples 2-1 to 2-3.
FIG. 2 shows an electron microscope of a fracture surface at the boundary between the surface layer and the inner layer of Example 2-2.
Claims (7)
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| JP6725115B2 (en) | 2017-12-25 | 2020-07-15 | 昭和電工株式会社 | Alumina sintered body, abrasive grains, and grindstone |
| JP6604687B2 (en) | 2017-12-25 | 2019-11-13 | 昭和電工株式会社 | Method for producing alumina sintered body |
| WO2023127564A1 (en) * | 2021-12-27 | 2023-07-06 | クラレノリタケデンタル株式会社 | Alumina workable body for dental use |
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2003
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07108433A (en) * | 1993-07-09 | 1995-04-25 | O M Ltd | Automatic drill changer at drilling machine |
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