JP3750153B2

JP3750153B2 - Ceramic sliding parts

Info

Publication number: JP3750153B2
Application number: JP13152495A
Authority: JP
Inventors: 剛久山本; 松夫樋口
Original assignee: Sumitomo Electric Industries Ltd
Current assignee: Sumitomo Electric Industries Ltd
Priority date: 1995-05-30
Filing date: 1995-05-30
Publication date: 2006-03-01
Anticipated expiration: 2021-03-01
Also published as: JPH08325079A

Description

【０００１】
【産業上の利用分野】
本発明は、金属との摺動において耐摩耗性と高強度を要求されるセラミックス摺動部品、特に金属の曲げや絞り加工あるいはスタンピング（打抜き成形）等に用いる塑性加工工具や打ち抜き型のようなセラミックス摺動工具に関する。
【０００２】
【従来の技術】
セラミックスは、軽量で優れた耐摩耗性を有するため、金属の絞り加工や曲げ加工等に用いる塑性加工工具、打抜き金型、圧延ロール、送りロール、軸受け等の金属との摺動部品として用いられている。
【０００３】
これらセラミックスからなる摺動部品の摺動特性を向上させるために、セラミックスの表層部に固体潤滑剤を充填したセラミックス複合体や、油溜めの機能を備えるために表層に多数の穴や溝を設けたセラミックスが用いられている。
【０００４】
例えば、固体潤滑剤を充填したセラミックス複合体として、特開昭５９−２３２９８１号公報には、極低温下や高温下で優れた潤滑性を維持するために、特にＳｉＣ焼結体の摺動表面に散在する空孔を利用し、空孔内に３０％以上のテフロンを含浸させる方法が記載されている。特開昭６１−２８１０８７号公報には、長期耐久性を発現させるために、高熱伝導セラミックスに例えば焼結前の成形段階で任意の形状の溝を設け、そこに樹脂を含浸させる方法が開示されている。
【０００５】
また、油溜の機能を持たせる方法としては、特開昭６２−４９２４号公報に記載されているように、マスキングした摺動部材の表面へ窒化ケイ素の被膜をコーティングし、未被膜部の金属部をエッチング除去して形成した凹部を油溜めとする方法や、特開平２−２３９１７１号公報に記載されているように、焼結前に異物、例えばタングステン粉を添加し、焼結後その添加粉末を溶解除去して油溜めとする方法、特開平６−３２６４６号公報に記載のごとく、焼結後の焼結肌の凹凸や焼結肌のバレル研削肌の凹凸を油溜めとして利用する方法等がある。
【０００６】
しかしながら、樹脂等の固体潤滑剤を含浸させるための空孔や溝、油溜めとして用いられる凹部や焼結肌の凹凸は、優れた潤滑性を示すが、その潤滑性を維持し且つ長期耐久性を発現するのに必要な量の固体潤滑剤や油を確保するため大きく且つ深い形状にする必要があり、従って一方でセラミックス部品の強度を低下させるという欠点がある。異物の添加と除去により油溜めを形成する方法も、除去後に異物の影響が残るため同様にセラミックス部品の強度を低下させる。
【０００７】
又、これらの大きな気孔、深い溝や凹部、凹凸の焼結肌を持つセラミックス部品では、摺動時に高い負荷が作用した場合、摺動する金属側の仕上がり面に引っかき傷等がついたり、セラミックス摺動部品自身が欠けたりする欠点がある。
【０００８】
一方、金属の基材にセラミックスをコーティングして摺動部品を形成する方法もあるが、金属へのセラミックスコーティングは使用環境温度が高くなると、金属とセラミックスの熱膨張差により界面での剥離が起こりやすくなるなど、使用に大きな制約が存在する。
【０００９】
【本発明が解決しようとする課題】
本発明は、かかる従来の事情に鑑み、金属と摺動するセラミックス部品の強度を低下させることなく摺動時の耐摩耗性の向上を図ることにより、寿命を大幅に延長し長期間の使用を可能とするセラミックス摺動部品を提供することを目的とする。
【００１０】
【課題を解決するための手段】
上記目的を達成するため、本発明が提供するセラミックス摺動部品は、金属と摺動するセラミックスの表面に、少なくとも主たる２方向に沿った多数の微細な条痕を設け、条痕の交点にそれぞれ凹部が形成されていることを特徴とするものである。
【００１１】
【作用】
本発明のセラミックス摺動部品では、金属との摺動面に少なくとも主たる２方向に沿って多数の微細な条痕を設けてある。条痕の主たる方向は２方向又は３方向以上であり、従って各主たる方向に沿う各条痕群は互いに交差している。かかる互いに交差する主たる２方向の条痕を設けることによって、セラミックスの強度を低下させることがなく、同時に摺動時の摩擦係数が小さくなり、耐摩耗性の向上を図ることができる。これは、摺動時に相手側の金属面が、セラミックスの摺動面全体に均等に又は交点の凹部形状に順応して塑性変形するため、セラミックスの特定箇所での応力集中が少なくなり、セラミックスが摩耗し難くなるためと考えられる。
【００１２】
セラミックスの摺動面に設ける条痕は、平均で幅０.５μｍ〜２０μｍ、及び深さ０.１μｍ〜３μｍの微細なものとし、できるだけ多くの条痕を摺動面の全体に可能な限り均等な密度で設けることが好ましく、これにより主たる２方向の条痕の交点に多数の凹部を摺動面全体に設けることができる。尚、条痕の平均幅は０.５μｍ〜１０μｍの範囲が更に好ましい。
【００１３】
この条痕の幅が０.５μｍ未満、又は深さが０.１μｍ未満の場合には、条痕の交差する凹部への相手側金属の塑性変形量が減少するうえに、金属がセラミックスと摺動を開始する部位で局所的に応力が集中し、セラミックスが摩耗し易くなる。逆に、条痕の幅が２０μｍを越え、又は深さが３μｍを越える大きな又は深い条痕の場合には、条痕の端部での摩耗が顕著となるため好ましくない。
【００１４】
かかる多数の条痕の形成によって、セラミックスの摺動表面の表面粗さを、ＪＩＳＢ０６０１に準拠する１０点平均最大高さ粗さ（Ｒｚ）で０.５〜３μｍの範囲とすることにより、一層摺動特性を向上させることができる。Ｒｚが３μｍより大きいと、表面の鋭利な突起部で局所的に摩擦抵抗が高くなるため摩耗し易くなるうえ、セラミックスの強度劣化を招く恐れがある。逆にＲｚが０.５μｍより小さいと、複数の微小な条痕及びこれを交差させて設けた凹部の効果が少なくなる。
【００１５】
尚、条痕の交点を摺動面に均等に配置するためには、可能な限り各主たる方向に属する条痕の方向と間隔を揃えることが好ましいが、若干の形成方法によっては、同じ主たる方向に属する条痕群の中で各条痕の方向及び間隔に若干のズレないしバラツキが生じても良い。従って、これらのズレないしバラツキを含める意味で条痕の方向を主たる方向と称するのであり、これらのズレないしバラツキによっては、同じ主たる方向の条痕同士が交差したり、他の主たる方向に属する条痕群との交点が増加することもあり得る。
【００１６】
本発明のセラミックス摺動部品を潤滑油の存在下で使用する場合、主たる２方向の条痕の交点に形成された多数の凹部が潤滑油の油溜めとして機能する。又、セラミックスの摺動面の表面粗さを上記のごとくＲｚで０.５〜３μｍとすることで摺動時の摩擦抵抗を低くでき、鉱物油等の潤滑油から潤滑付与機能の低いエマルジョン系の潤滑油への置き換えや、積極的に潤滑剤を供給しない無潤滑での使用が可能となる。
【００１７】
その結果、セラミックス摺動部品を例えば打抜き型等として用いる場合、加工された工作物の表面からの潤滑剤の除去が不要となるか、フロン等の脱脂力の高い洗浄用有機溶剤を用いなくても容易に工作物から潤滑油の除去が可能となり、製造設備の簡略化や作業環境の向上を図ることが可能となる。
【００１８】
主たる２方向の条痕が交点においてなす角度のうち小さい方の角度（以下、交差角度と称する）は６０°未満が好ましく、３０°未満が更に好ましい。又、金属との主たる摺動方向が、主たる２方向の条痕の交点におて、該交点で２本の条痕がなす小さい方の交差角度内を通る方向となるように、更に好ましくは交差角度を２等分する方向に平行となるように、条痕の主たる２方向を定めることが好ましい。従って、この摺動方向と各主たる２方向の条痕がなす角度（摺動方向により交差角度を２等分した各角度）は、好ましくは共に３０°未満、更に好ましくは１５°未満となる。このように条痕の交差角度及び／又は条痕と摺動方向とのなす角度を設定することにより、摺動時の局所的な摩擦抵抗が低下し、セラミックス摺動部品及び相手側の金属共に摩擦が更に減少する。
【００１９】
本発明の複数の微細な条痕をセラミックス表面に設ける方法としては、ダイヤモンド砥石による研削方法やレーザーによる加工法等がある。ダイヤモンド砥石での研削の場合、砥石の高周速と微小な切込みによって加工損傷を抑制することが望ましい。また、レーザー加工法の場合も、材質に応じて照射する熱量と、照射間隔を適宜設定し、熱による加工損傷を抑制することが望ましい。
【００２０】
摺動部品として用いるセラミックス材料に制限はないが、窒化ケイ素及び／又はサイアロン、ジルコニア、炭化ケイ素、又はアルミナ等の、理論密度に近い緻密な焼結体が得られ、高硬度で摺動性に優れた材料が好ましい。使用するセラミックス材料は、摺動する相手材の金属、使用する条件又は使用用途によって適宜選択できる。
【００２１】
セラミックス摺動部品が金属板の打抜きパンチ等の高負荷が作用する塑性加工工具である場合、セラミックス材料の曲げ強度がＪＩＳＲ１６０１に準拠する３点曲げ強度で１００ｋｇ／ｍｍ²以上、シャルピー衝撃値が０.１ｋｇ・ｍ／ｃｍ²以上であると、加工時における工具の破損、欠損、チッピングを防ぐのに有効である。
【００２２】
セラミックス材料が窒化ケイ素及び／又はサイアロンの場合、８８〜９８重量％の窒化ケイ素及び／又はサイアロンを含み、β型の窒化ケイ素及び／又はサイアロン（即ちβ−窒化ケイ素及び／又はβ’−サイアロン）の長軸方向の平均結晶粒径が５μｍ以下であることが望ましい。
【００２３】
窒化ケイ素及びサイアロン成分が９８重量％を越えると強度特性の劣化原因となり、８８重量％未満では耐摩耗性の点で好ましくない。又、この平均結晶粒径が５μｍを越えると、強度特性の劣化や硬度の低下による耐摩耗性の低下が起こるため好ましくない。更に好ましくは、β型の窒化ケイ素及び／又はサイアロンの長軸方向の平均結晶粒径を２.５μｍ以下とすれば、強度及び硬度等の機械的特性が一層向上する。
【００２４】
尚、強度特性の向上を図るためには、焼結体中の窒化ケイ素及び／又はサイアロンの結晶をα型とβ型との混合結晶相とすれば更に機械的特性面で好ましく、この際のα型とβ型の比率をα＜３０％とするのが靭性と硬度の関係からより一層好ましい。
【００２５】
セラミックス材料がジルコニアの場合、セラミックス材料に含まれるジルコニア量が９２〜９９重量％で、ジルコニアの平均結晶粒径が１.５μｍ以下であることが好ましい。この平均結晶粒径が１.５μｍを越えると、強度特性の劣化や耐摩耗性の低下が起こるため好ましくない。ジルコニア成分が９９重量％を越えると強度特性の劣化原因となり、９２重量％未満であると耐摩耗性の点で好ましくない。更には、部分安定化ジルコニアが機械的特性に優れるため好ましい。
【００２６】
【実施例】
実施例１
セラミックス材料のブロックと鋼製のリングとを用い、ブロックオンリング試験による摩擦摩耗試験を潤滑油の存在下で実施した。リングには表面粗さが、中心線平均粗さＲａで０.１μｍの軸受け鋼（ＳＵＪ−２）を用い、試験は摺動速度０.２ｍ／ｓｅｃ、荷重１００Ｎで行った。
【００２７】
一方、セラミックス材料のブロックは、平滑な市販の窒化ケイ素板の表面を平面研削盤で２方向に研削することにより交差する多数の条痕を設け、各交点に凹部形成した板を使用した。尚、条痕の幅は平均２０μｍ、深さは平均２μｍであり、主たる２方向の条痕の交差角度を２５°に設けた。比較のために、同じ窒化ケイ素板の表面に平面研削盤で１方向にのみ条痕を設けたセラミックス板も使用した。尚、この比較例の場合も、条痕の幅は平均２０μｍ、深さは平均２μｍとした。
【００２８】
各ブロックは、リングの回転方向（主たる摺動方向）に対して条痕が平行又は直角となるようにセットした。ここで、条痕が２方向の場合にブロックの条痕とリングの回転方向が平行とは、回転方向が２方向の条痕がなす交差角度を２等分する方向に向いていること（以下同様）をいい、従ってこの実施例では回転方向により２方向の条痕の交差角度を２等分した角度は１２.５°となる。
【００２９】
これらの摺動試験により、摺動時の摩擦係数と比摩耗量を測定し、その結果をブロックの条痕の交差の有無、即ち条痕が２方向か１方向か、リング回転方向に対して直角方向のブロックの表面粗さＲｚ、リングに対するブロックの向きと共に、表１に示す。
【００３０】
【表１】

【００３１】
以上の結果から、金属と摺動するセラミックスの表面に研削による複数の条痕を交差させて複数の凹部を設けることにより、摺動時の摩擦係数が低減され、耐摩耗性の向上することが確認された。また、複数の条痕を摺動方向と平行に設ければ、摺動時の摩擦係数を一層低減し、耐摩耗性の更なる向上が可能であることが判った。
【００３２】
実施例２
窒化ケイ素ブロックの表面に設ける複数の条痕の幅と深さ、２方向の条痕の交差角度を下記表２のように変化させ、実施例１と同じ試験を実施した結果を表２に示す。尚、ブロックの条痕とリングの回転方向は全て平行に設定したので、リングの回転方向により２方向の条痕の交差角度が２等分された角度（表２に示すリングの回転方向とブロックの条痕とがなす角度Ａ）は、表２に示すとおりである。
【００３３】
【表２】

【００３４】
以上の結果から、摺動面上での条痕は幅が平均０.５〜２０μｍ、好ましくは０.５〜１０μｍ、深さが平均０.１〜３μｍの大きさで摺動面全体に設けること、２方向の条痕の交差角度（角度Ｂ）を６０°未満、好ましくは３０°未満にすること、及び２方向の条痕と摺動方向とのなす角度（角度Ａ）を３０°未満、好ましくは１５°未満にすることによって、摺動時の摩擦係数がより一層低減され、耐摩耗性のより一層の向上が確認された。
【００３５】
実施例３
使用するブロックのセラミックス材料と、その表面に設けた２方向の条痕の幅と深さを変えることにより表面粗さＲｚを変化させ、実施例１と同じ試験を行った結果を表３に示す。尚、全てのブロックは、リングの回転方向に対して条痕が平行になるようにブロックをセットした。又、ブロックの表面粗さＲｚは、リングの回転方向に対して直角と平行の２方向について測定した。
【００３６】
【表３】

【００３７】
以上の結果から、金属と摺動するセラミックスの表面に２方向の複数の条痕を交差させて複数の凹部を設ける場合、摺動表面の表面粗さが摺動方向に対し平行及び直角方向ともに、ＪＩＳＢ０６０１に準拠する１０点平均最大高さ粗さＲｚで０.５〜３μｍの範囲内にあるとき、摺動時の摩擦係数が一層低減され、耐摩耗性の更なる向上効果が確認された。
【００３８】
実施例４
各種の市販セラミックス材料を用いて、幅１０ｍｍで厚み１.５ｍｍの打抜き型を作製し、厚み０.５ｍｍの銅板の打ち抜きを行った。２０万ショット及び１００万ショット後におけるパンチ先端の摩耗量を測定し、表４に示すごとく摩耗量により耐摩耗性を評価した。使用したパンチ先端部の表面粗さ（Ｒｚ）を摺動方向に対して垂直及び平行方向について測定した結果、それぞれ１.１μｍ及び０.８μｍであった。
【００３９】
尚、各セラミックス材料の銅板との摺動面には、平面研削盤で２方向の研削による条痕を交差させ複数の凹部を形成した。条痕の幅は平均３μｍ及び深さは平均１.５μｍとし、２方向の条痕の交差角度は約４０°に設け、条痕が摺動方向に対して平行（条痕と摺動方向のなす角度約２０°）にセットした。
【００４０】
【表４】

【００４１】
以上の結果から、金属と摺動する部品の表面に複数の条痕を交差させて複数の凹部を設ける場合、窒化ケイ素及び／又はサイアロン、ジルコニア、炭化ケイ素、あるいはアルミナからなるセラミックス材料を用いることで耐摩耗性が向上することが確認された。
【００４２】
又、これらのセラミックス材料の曲げ強度が、ＪＩＳＲ１６０１に準拠する３点曲げ強度で１００ｋｇ/ｍｍ²以上、及びシャルピー衝撃値が０.１ｋｇ・ｍ/ｃｍ²以上である場合、特に耐久性に優れることが確認された。
【００４３】
実施例５
下記表５に示す各セラミックス材料からなる打ち抜き型を用い、実施例４と同じ条件で銅版の打抜きを１００万ショット行った際のパンチの摩耗量を表５に示す。ただし、セラミックス材料の銅版との摺動面には、実施例４と同様に平面研削盤で２方向の研削による条痕を交差させ複数の凹部を作製した。パンチ先端部の表面粗さ（Ｒｚ）は、摺動方向に対して直角方向及び平行方向においてそれぞれ０.９μｍ及び０.５μｍであった。
【００４４】
表５に示すセラミックス材料の平均結晶粒径は、任意の２次元断面を鏡面ラッピング加工した後、化学エッチングした面をＳＥＭで観察し、任意の５０μｍ×５０μｍの視野から任意の５０個の結晶粒子について測定し、その平均値を算出して求めた。
【００４５】
尚、ジルコニアは、平均粒径０.６μｍ以下でＢＥＴ値１２〜１８ｍ²/ｇの原料粉末に助剤としてイットリア、マグネシア、カルシア及びアルミナの内の１種の粉末を添加して、大気中または真空中にて２〜１５℃/分で昇温し、１３５０〜１７００℃で１〜６時間焼結して製造した。尚、試料２８と２９については、前記焼結後１０００気圧のアルゴン中にて１３５０〜１７００℃で１時間のＨＩＰ処理を施した。
【００４６】
又、窒化ケイ素及びサイアロンは、平均粒径０.７μｍでＢＥＴ値１０〜１５ｍ²／ｇの原料粉末に助剤としてイットリア、アルミナ、マグネシア、チタニア及び窒化アルミニウムの内の１種以上の粉末を添加し、１〜９.８気圧の窒素中にて５〜１５℃／分で昇温し、１５００〜１８００℃で１〜６時間焼結して製造した。試料３２〜３４、３７、３８については、前記焼結後１０００気圧の窒素中にて１５００〜１７００℃で１時間のＨＩＰ処理を施した。
【００４７】
尚、試料３３、３５、３８はβ−窒化ケイ素又はβ’−サイアロンとα−窒化ケイ素又はα’−サイアロンとからなり、α又はα’型が３０％未満の比率で混在した結晶相を有する焼結体であった。又、試料３９と４０はβ−窒化ケイ素又はβ’−サイアロンとα−窒化ケイ素又はα’−サイアロンとからなり、α又はα’型が３０％を越える比率で混在した結晶相を有する焼結体であった。
【００４８】
【表５】

【００４９】
この結果、セラミックス材料がジルコニアの場合、９２〜９９重量％のジルコニアを含み、その平均結晶粒径が１.５μｍ以下のとき、特に耐摩耗性に優れることが確認された。又、窒化ケイ素及び／又はサイアロンの場合には、それらが８８〜９８重量％含まれ、β型の窒化ケイ素及び／又はβ’型のサイアロンの長軸方向の平均結晶粒径が５μｍ以下のとき、同様に耐摩耗性に優れることが確認された。
【００５０】
【発明の効果】
本発明によれば、セラミックス部品の強度を低下させることなく、摺動時の耐摩耗性の向上を図ることができ、金属の曲げ及び絞り加工工具、打ち抜き型、圧延ロール、軸受け等の金属と摺動する工具に適用したとき、その寿命を大幅に延長し長期間の使用が可能となる。[0001]
[Industrial application fields]
The present invention relates to ceramic sliding parts that require high wear resistance and high strength in sliding with metal, particularly plastic working tools and punching dies used for metal bending, drawing or stamping (punching). The present invention relates to a ceramic sliding tool.
[0002]
[Prior art]
Ceramics are lightweight and have excellent wear resistance, so they are used as sliding parts with metals such as plastic working tools, punching dies, rolling rolls, feed rolls, bearings, etc. used for metal drawing and bending. ing.
[0003]
In order to improve the sliding characteristics of sliding parts made of these ceramics, a ceramic composite in which the ceramic surface layer is filled with a solid lubricant, and a number of holes and grooves are provided in the surface layer to provide an oil sump function. Ceramics are used.
[0004]
For example, as a ceramic composite filled with a solid lubricant, Japanese Patent Application Laid-Open No. 59-232981 discloses a sliding surface of a SiC sintered body particularly in order to maintain excellent lubricity at extremely low temperatures or high temperatures. And a method of impregnating 30% or more of Teflon into the pores is described. JP-A-61-281087 discloses a method in which a groove having an arbitrary shape is formed in a high thermal conductive ceramic, for example, in a molding step before sintering, and a resin is impregnated therein in order to develop long-term durability. ing.
[0005]
Further, as a method for providing an oil reservoir function, as described in Japanese Patent Application Laid-Open No. 62-4924, the surface of the masked sliding member is coated with a silicon nitride film, and the metal in the uncoated part is formed. As described in JP-A-2-239171, a foreign substance, for example, tungsten powder is added before sintering, and the addition is performed after sintering. Method for dissolving and removing powder to make oil sump, as described in Japanese Patent Application Laid-Open No. 6-32646, and using the unevenness of sintered skin after sintering and the unevenness of barrel grinding skin of sintered skin as an oil sump Etc.
[0006]
However, pores and grooves for impregnating solid lubricants such as resin, recesses used as oil sumps and unevenness of sintered skin show excellent lubricity, but maintain the lubricity and long-term durability In order to secure a sufficient amount of solid lubricant and oil necessary to develop the material, it is necessary to make it large and deep, and there is a disadvantage that the strength of the ceramic component is reduced. The method of forming an oil sump by adding and removing foreign matter also reduces the strength of the ceramic component because the influence of the foreign matter remains after removal.
[0007]
Also, in ceramic parts with these large pores, deep grooves and recesses, and uneven sintered skin, when a high load is applied during sliding, the finished surface on the sliding metal side may be scratched, etc. There is a drawback that the sliding part itself is missing.
[0008]
On the other hand, there is also a method of forming a sliding part by coating ceramics on a metal substrate. However, when the environmental temperature of the ceramic coating on the metal increases, peeling at the interface occurs due to the difference in thermal expansion between the metal and ceramics. There are significant restrictions on use, such as ease of use.
[0009]
[Problems to be solved by the present invention]
In view of such conventional circumstances, the present invention significantly improves the wear resistance during sliding without lowering the strength of ceramic parts that slide with metal, thereby significantly extending the service life. An object of the present invention is to provide a ceramic sliding part that can be made.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the ceramic sliding component provided by the present invention is provided with a large number of fine striations along at least two main directions on the surface of the ceramic sliding with the metal, and at each intersection of the striations. A concave portion is formed.
[0011]
[Action]
In the ceramic sliding component of the present invention, a large number of fine streaks are provided along at least two main directions on the sliding surface with the metal. The main direction of the streak is two directions or three or more directions. Therefore, the streak groups along each main direction intersect each other. By providing the main two-direction streak intersecting each other, the strength of the ceramic is not lowered, and at the same time, the friction coefficient at the time of sliding is reduced, so that the wear resistance can be improved. This is because the metal surface of the other side during plastic sliding is plastically deformed evenly over the entire sliding surface of the ceramic or adapting to the concave shape of the intersection, reducing the stress concentration at a specific location of the ceramic. This is considered to be difficult to wear.
[0012]
The striations on the ceramic sliding surface should be as fine as possible with an average width of 0.5 μm to 20 μm and a depth of 0.1 μm to 3 μm, and as many streaks as possible on the entire sliding surface should be as uniform as possible. It is preferable to provide it with a high density, so that a large number of recesses can be provided on the entire sliding surface at the intersections of the main two-way streaks. The average width of the streaks is more preferably in the range of 0.5 μm to 10 μm.
[0013]
If the width of the streak is less than 0.5 μm or the depth is less than 0.1 μm, the amount of plastic deformation of the counterpart metal to the recess where the streak intersects is reduced, and the metal slides with the ceramic. Stress concentrates locally at the site where the movement starts, and the ceramic is likely to wear. On the contrary, when the width of the stripe exceeds 20 μm, or the depth of the stripe exceeds 3 μm, the wear at the end of the stripe is not preferable.
[0014]
By forming such a large number of striations, the surface roughness of the sliding surface of the ceramic is further reduced to a range of 0.5 to 3 μm in terms of 10-point average maximum height roughness (Rz) in accordance with JIS B0601. Sliding characteristics can be improved. When Rz is larger than 3 μm, the frictional resistance is locally increased at the sharp protrusions on the surface, so that it is likely to be worn and the strength of the ceramic may be deteriorated. On the other hand, when Rz is smaller than 0.5 μm, the effect of a plurality of minute streaks and concave portions provided by intersecting them is reduced.
[0015]
In order to evenly arrange the intersections of the striations on the sliding surface, it is preferable to align the direction and spacing of the streaks belonging to each main direction as much as possible, but depending on some forming methods, the same main direction There may be slight deviation or variation in the direction and interval of each striation in the streak group belonging to. Therefore, the direction of the streak is referred to as the main direction in the sense that these deviations or variations are included. Depending on these deviations or variations, the striations in the same main direction may cross each other or may belong to other main directions. There may be an increase in the number of intersections with the trace group.
[0016]
When the ceramic sliding component of the present invention is used in the presence of lubricating oil, a large number of recesses formed at the intersections of the main two-way streaks function as oil reservoirs for the lubricating oil. Moreover, the frictional resistance at the time of sliding can be lowered by setting the surface roughness of the sliding surface of the ceramic to 0.5 to 3 μm at Rz as described above, and an emulsion system having a low lubrication function from a lubricating oil such as mineral oil. It is possible to replace it with a lubricating oil or to use it without lubrication without actively supplying a lubricant.
[0017]
As a result, when ceramic sliding parts are used as, for example, punching dies, it is not necessary to remove the lubricant from the surface of the processed workpiece, or it is necessary to use a cleaning organic solvent having high degreasing power such as Freon. In addition, it is possible to easily remove the lubricating oil from the workpiece, thereby simplifying the manufacturing equipment and improving the working environment.
[0018]
Of the angles formed by the main two-direction streaks at the intersection, the smaller angle (hereinafter referred to as the intersection angle) is preferably less than 60 °, and more preferably less than 30 °. More preferably, the main sliding direction with the metal is at the intersection of the main two-direction striations, and the direction passing through the smaller crossing angle formed by the two striations at the intersection. It is preferable to define two main directions of the streak so as to be parallel to the direction in which the crossing angle is equally divided. Therefore, the angle formed by the sliding direction and the main two-direction streaks (each angle obtained by equally dividing the crossing angle by the sliding direction) is preferably less than 30 °, and more preferably less than 15 °. By setting the crossing angle of the striations and / or the angle between the striations and the sliding direction in this way, the local frictional resistance during sliding decreases, and both the ceramic sliding component and the counterpart metal Friction is further reduced.
[0019]
Examples of the method for providing a plurality of fine streaks on the ceramic surface of the present invention include a grinding method using a diamond grindstone and a processing method using a laser. In the case of grinding with a diamond grindstone, it is desirable to suppress processing damage by a high peripheral speed of the grindstone and a minute cut. Also in the case of laser processing, it is desirable to appropriately set the amount of heat to be irradiated and the irradiation interval in accordance with the material, thereby suppressing processing damage due to heat.
[0020]
There is no limitation on the ceramic material used as the sliding part, but a dense sintered body close to the theoretical density such as silicon nitride and / or sialon, zirconia, silicon carbide, or alumina can be obtained, and it has high hardness and slidability. Excellent materials are preferred. The ceramic material to be used can be appropriately selected depending on the metal of the mating material to be slid, the conditions to be used, or the intended use.
[0021]
When the ceramic sliding part is a plastic working tool with a high load such as a punching punch of a metal plate, the bending strength of the ceramic material is 100 kg / mm ² or more with a three-point bending strength in accordance with JIS R1601, and the Charpy impact value is When it is 0.1 kg · m / cm ² or more, it is effective to prevent tool breakage, chipping and chipping during processing.
[0022]
When the ceramic material is silicon nitride and / or sialon, it contains 88 to 98% by weight of silicon nitride and / or sialon, and β-type silicon nitride and / or sialon (ie β-silicon nitride and / or β′-sialon). The average crystal grain size in the major axis direction is desirably 5 μm or less.
[0023]
If the silicon nitride and sialon components exceed 98% by weight, the strength characteristics will be deteriorated, and if it is less than 88% by weight, it is not preferable in terms of wear resistance. On the other hand, if the average crystal grain size exceeds 5 μm, it is not preferable because wear characteristics are deteriorated due to deterioration of strength characteristics and hardness. More preferably, mechanical properties such as strength and hardness are further improved if the average crystal grain size in the major axis direction of β-type silicon nitride and / or sialon is 2.5 μm or less.
[0024]
In order to improve the strength characteristics, it is preferable in terms of mechanical characteristics if the silicon nitride and / or sialon crystal in the sintered body is a mixed crystal phase of α type and β type. The ratio of α type and β type is more preferably α <30% from the relationship between toughness and hardness.
[0025]
When the ceramic material is zirconia, the amount of zirconia contained in the ceramic material is preferably 92 to 99% by weight, and the average crystal grain size of zirconia is preferably 1.5 μm or less. If the average crystal grain size exceeds 1.5 μm, it is not preferable because strength characteristics are deteriorated and wear resistance is lowered. When the zirconia component exceeds 99% by weight, it causes deterioration of strength characteristics, and when it is less than 92% by weight, it is not preferable in terms of wear resistance. Furthermore, partially stabilized zirconia is preferable because of its excellent mechanical properties.
[0026]
【Example】
Example 1
Using a ceramic material block and a steel ring, a friction wear test by a block-on-ring test was conducted in the presence of lubricating oil. The ring was made of bearing steel (SUJ-2) having a surface roughness of 0.1 μm in centerline average roughness Ra, and the test was performed at a sliding speed of 0.2 m / sec and a load of 100N.
[0027]
On the other hand, the ceramic material block used was a plate in which a large number of striations intersecting each other were formed by grinding a surface of a smooth commercially available silicon nitride plate in two directions with a surface grinder, and a recess was formed at each intersection. In addition, the width of the streak averaged 20 μm, the depth averaged 2 μm, and the intersecting angle of the streak in the main two directions was set at 25 °. For comparison, a ceramic plate in which the surface of the same silicon nitride plate was provided with striations in only one direction with a surface grinder was also used. In this comparative example as well, the width of the streak was 20 μm on average and the depth was 2 μm on average.
[0028]
Each block was set so that the striations were parallel or perpendicular to the rotation direction of the ring (main sliding direction). Here, when the striations are in two directions, the block striations and the rotation direction of the ring are parallel to each other, and the rotation direction is in a direction that bisects the crossing angle formed by the striations in the two directions (hereinafter referred to as “the direction of rotation”). Therefore, in this embodiment, the angle obtained by dividing the crossing angle of the two directions of the striations into two equal parts according to the rotation direction is 12.5 °.
[0029]
By these sliding tests, the friction coefficient and the specific wear amount at the time of sliding are measured, and the result is obtained based on the presence or absence of crossing of the block striations, that is, whether the striations are in two directions or one direction, or in the ring rotation direction. Table 1 shows the surface roughness Rz of the block in the perpendicular direction and the orientation of the block with respect to the ring.
[0030]
[Table 1]

[0031]
From the above results, it is possible to reduce the friction coefficient during sliding and improve the wear resistance by providing a plurality of recesses by crossing a plurality of streaks by grinding on the surface of the ceramic sliding with the metal. confirmed. Further, it was found that if a plurality of striations are provided in parallel with the sliding direction, the friction coefficient during sliding can be further reduced, and the wear resistance can be further improved.
[0032]
Example 2
The width and depth of a plurality of striations provided on the surface of the silicon nitride block and the crossing angle of the striations in two directions are changed as shown in Table 2 below. . Since the block striations and the rotation direction of the ring are all set in parallel, the angle obtained by dividing the crossing angle of the striations in the two directions by the ring rotation direction is divided into two equal parts (the rotation direction of the ring shown in Table 2 and the block). Table 2 shows the angle A) formed by the striations.
[0033]
[Table 2]

[0034]
From the above results, the striations on the sliding surface have an average width of 0.5 to 20 μm, preferably 0.5 to 10 μm and a depth of 0.1 to 3 μm on the entire sliding surface. The crossing angle (angle B) between the two-direction streak is less than 60 °, preferably less than 30 °, and the angle (angle A) between the two-direction streak and the sliding direction is less than 30 °. The friction coefficient at the time of sliding was further reduced by making the angle less than 15 °, and it was confirmed that the wear resistance was further improved.
[0035]
Example 3
Table 3 shows the results of performing the same test as in Example 1 by changing the surface roughness Rz by changing the ceramic material of the block to be used and the width and depth of the two-direction streaks provided on the surface. . All the blocks were set so that the striations were parallel to the rotation direction of the ring. The surface roughness Rz of the block was measured in two directions perpendicular to and parallel to the ring rotation direction.
[0036]
[Table 3]

[0037]
From the above results, when a plurality of recesses are formed by intersecting a plurality of striations in two directions on the surface of the ceramic that slides with the metal, the surface roughness of the sliding surface is both parallel and perpendicular to the sliding direction. When the 10-point average maximum height roughness Rz in accordance with JIS B0601 is in the range of 0.5 to 3 μm, the friction coefficient during sliding is further reduced, and a further improvement effect of wear resistance is confirmed. It was.
[0038]
Example 4
Using various commercially available ceramic materials, a punching die having a width of 10 mm and a thickness of 1.5 mm was produced, and a copper plate having a thickness of 0.5 mm was punched. The wear amount of the punch tip after 200,000 shots and 1 million shots was measured, and the wear resistance was evaluated by the wear amount as shown in Table 4. The surface roughness (Rz) of the used punch tip was measured in the direction perpendicular to and parallel to the sliding direction, and found to be 1.1 μm and 0.8 μm, respectively.
[0039]
In addition, on the sliding surface of each ceramic material with the copper plate, a plurality of recesses were formed by crossing the striations by grinding in two directions with a surface grinder. The width of the streak is 3 μm on average and the depth is 1.5 μm on average. The crossing angle between the two directions is about 40 °, and the streak is parallel to the sliding direction. The angle formed is about 20 °.
[0040]
[Table 4]

[0041]
From the above results, when a plurality of recesses are provided by crossing a plurality of striations on the surface of a component that slides on a metal, a ceramic material made of silicon nitride and / or sialon, zirconia, silicon carbide, or alumina is used. It was confirmed that the wear resistance improved.
[0042]
Further, when the bending strength of these ceramic materials is 100 kg / mm ² or more in terms of the three-point bending strength according to JIS R1601, and the Charpy impact value is 0.1 kg · m / cm ² or more, the durability is particularly excellent. It was confirmed.
[0043]
Example 5
Table 5 shows the wear amount of the punch when one million shots of the copper plate were punched under the same conditions as in Example 4 using the punching die made of each ceramic material shown in Table 5 below. However, on the sliding surface of the ceramic material with the copper plate, as in Example 4, a plurality of recesses were produced by intersecting the striations by grinding in two directions with a surface grinder. The surface roughness (Rz) of the punch tip was 0.9 μm and 0.5 μm in the direction perpendicular to the sliding direction and in the parallel direction, respectively.
[0044]
The average crystal grain size of the ceramic material shown in Table 5 is that any two-dimensional cross section is mirror-wrapped, and then the chemically etched surface is observed with an SEM, and an arbitrary 50 crystal particles are observed from an arbitrary 50 μm × 50 μm field of view. Was measured and the average value was calculated.
[0045]
In addition, zirconia is obtained by adding one kind of powder of yttria, magnesia, calcia and alumina as an auxiliary agent to a raw material powder having an average particle size of 0.6 μm or less and a BET value of 12 to 18 m ² / g. The temperature was raised at 2 to 15 ° C./min in vacuum, and sintered at 1350 to 1700 ° C. for 1 to 6 hours for production. Samples 28 and 29 were subjected to HIP treatment for 1 hour at 1350 to 1700 ° C. in argon at 1000 atmospheres after the sintering.
[0046]
For silicon nitride and sialon, one or more powders of yttria, alumina, magnesia, titania and aluminum nitride are added as auxiliary materials to the raw material powder having an average particle size of 0.7 μm and a BET value of 10 to 15 m ² / g. Then, it was heated at 5 to 15 ° C./min in nitrogen at 1 to 9.8 atm, and sintered at 1500 to 1800 ° C. for 1 to 6 hours for production. Samples 32-34, 37, and 38 were subjected to HIP treatment for 1 hour at 1500 to 1700 ° C. in nitrogen at 1000 atmospheres after the sintering.
[0047]
Samples 33, 35 and 38 are composed of β-silicon nitride or β′-sialon and α-silicon nitride or α′-sialon, and have a crystal phase in which α or α ′ type is mixed at a ratio of less than 30%. It was a sintered body. Samples 39 and 40 consist of β-silicon nitride or β′-sialon and α-silicon nitride or α′-sialon, and have a crystalline phase in which α or α ′ type is mixed in a ratio exceeding 30%. It was a body.
[0048]
[Table 5]

[0049]
As a result, when the ceramic material was zirconia, it was confirmed that the ceramic material was particularly excellent in wear resistance when it contained 92 to 99% by weight of zirconia and the average crystal grain size was 1.5 μm or less. In the case of silicon nitride and / or sialon, they are contained in an amount of 88 to 98% by weight, and the average crystal grain size in the major axis direction of β-type silicon nitride and / or β′-type sialon is 5 μm or less. Similarly, it was confirmed that it was excellent in wear resistance.
[0050]
【The invention's effect】
According to the present invention, the wear resistance during sliding can be improved without reducing the strength of the ceramic component, and metal bending and drawing tools, punching dies, rolling rolls, bearings, etc. When applied to a sliding tool, its life is greatly extended and it can be used for a long time.

Claims

A ceramic sliding component in which a large number of fine striations along at least two main directions are provided on the surface of a ceramic that slides with a metal, and a recess is formed at each intersection of the striations.

2. The ceramic sliding part according to claim 1, wherein the width of the striations is 0.5 to 20 μm on average and the depth is 0.1 to 3 μm on average.

The surface roughness of the ceramic surface provided with a plurality of striations is in the range of 0.5 to 3 μm in terms of the 10-point average maximum height roughness in accordance with JIS B0601, both in parallel and perpendicular to the sliding direction. The ceramic sliding part according to claim 1 or 2, characterized by the above.

The ceramic sliding part according to any one of claims 1 to 3, wherein the smaller intersection angle at the intersection of the striations provided in the two main directions is less than 60 °.

The main two-direction striations are arranged so that the main sliding direction with the metal is the direction passing through the smaller intersection angle formed by the two striations at the intersection of the main two-direction striations. The ceramic sliding part according to claim 1, wherein the ceramic sliding part is provided.

The ceramic sliding component according to any one of claims 1 to 5, wherein the ceramic material constituting the sliding component is silicon nitride and / or sialon, zirconia, silicon carbide, or alumina.

7. The ceramic according to claim 6, wherein the ceramic material has a bending strength of 100 kg / mm ² or more and a Charpy impact value of 0.1 kg · m / cm ² or more as a three-point bending strength according to JIS R1601. Sliding parts.

The ceramic material contains silicon nitride and / or sialon in an amount of 88 to 98% by weight, and the average crystal grain size in the major axis direction of β-type silicon nitride and / or β′-type sialon is 5 μm or less, The ceramic sliding part according to claim 7.

The ceramic sliding part according to claim 7, wherein the ceramic material contains 92 to 99% by weight of zirconia, and the average crystal grain size of zirconia is 1.5 µm or less.