JP3962911B2

JP3962911B2 - Surface coated cemented carbide cutting tool with excellent chipping resistance with hard coating layer under heavy cutting conditions

Info

Publication number: JP3962911B2
Application number: JP2002157305A
Authority: JP
Inventors: 秀充高岡; 恵滋中村
Original assignee: Mitsubishi Materials Corp
Current assignee: Mitsubishi Materials Corp
Priority date: 2002-05-30
Filing date: 2002-05-30
Publication date: 2007-08-22
Anticipated expiration: 2022-05-30
Also published as: JP2003340609A

Description

【０００１】
【発明の属する技術分野】
この発明は、硬質被覆層が高強度と高靭性を有し、さらに高温硬さも具備し、したがって特に各種の鋼や鋳鉄などの切削加工を、高い機械的衝撃を伴う高切り込みや高送りなどの重切削条件で行なった場合に、硬質被覆層がすぐれた耐チッピング性を発揮する表面被覆超硬合金製切削工具（以下、被覆超硬工具という）に関するものである。
【０００２】
【従来の技術】
一般に、被覆超硬工具には、各種の鋼や鋳鉄などの被削材の旋削加工や平削り加工にバイトの先端部に着脱自在に取り付けて用いられるスローアウエイチップ、穴あけ切削加工などに用いられるドリルやミニチュアドリル、さらに面削加工や溝加工、肩加工などに用いられるソリッドタイプのエンドミルなどがあり、また前記スローアウエイチップを着脱自在に取り付けて前記ソリッドタイプのエンドミルと同様に切削加工を行うスローアウエイエンドミル工具などが知られている。
【０００３】
また、被覆超硬工具として、炭化タングステン（以下、ＷＣで示す）基超硬合金または炭窒化チタン（以下、ＴｉＣＮで示す）基サーメットからなる基体（以下、これらを総称して超硬基体と云う）の表面に、組成式：（Ｔｉ_1-XＮｂ_X）Ｎ（ただし、原子比で、Ｘは０．３０〜０．５０を示す）を満足するＴｉとＮｂの複合窒化物［以下、（Ｔｉ，Ｎｂ）Ｎで示す］層からなる硬質被覆層を１〜１５μｍの平均層厚で物理蒸着してなる被覆超硬工具が提案され、各種の鋼や鋳鉄などの連続切削や断続切削加工に用いられている。
【０００４】
さらに、上記の被覆超硬工具が、例えば図２に概略説明図で示される物理蒸着装置の１種であるアークイオンプレーティング装置に上記の超硬基体を装入し、ヒータで装置内を、例えば５００℃の温度に加熱した状態で、アノード電極と所定組成を有するＴｉ−Ｎｂ合金がセットされたカソード電極（蒸発源）との間に、例えば電流：１４０Ａの条件でアーク放電を発生させ、同時に装置内に反応ガスとして窒素ガスを導入して、例えば２Ｐａの反応雰囲気とし、一方上記超硬基体には、例えば−１００Ｖのバイアス電圧を印加した条件で、前記超硬合金基体の表面に、上記（Ｔｉ，Ｎｂ）Ｎ層からなる硬質被覆層を蒸着することにより製造されることも知られている。
【０００５】
【発明が解決しようとする課題】
近年の切削加工装置の高性能化はめざましく、一方で切削加工に対する省力化および省エネ化、さらに低コスト化の要求は強く、これに伴い、切削加工は高切り込みや高送りなどの重切削条件で行なわれる傾向にあるが、上記の従来被覆超硬工具においては、これを通常の切削加工条件で用いた場合には問題はないが、切削加工を高い機械的衝撃を伴う高切り込みや高送りなどの重切削条件で行なった場合には、特に硬質被覆層の強度および靭性不足が原因でチッピング（微小割れ）が発生し易くなり、比較的短時間で使用寿命に至るのが現状である。
【０００６】
【課題を解決するための手段】
そこで、本発明者等は、上述のような観点から、特に重切削加工条件で硬質被覆層がすぐれた耐チッピング性を発揮する被覆超硬工具を開発すべく、上記の従来被覆超硬工具を構成する硬質被覆層に着目し、研究を行った結果、
（ａ）上記の図２に示されるアークイオンプレーティング装置を用いて形成された従来被覆超硬工具を構成する（Ｔｉ，Ｎｂ）Ｎ層は、層厚全体に亘って実質的に均一な組成を有し、したがって均質な強度および靭性、さらに高温硬さを有するが、例えば図１（ａ）に概略平面図で、同（ｂ）に概略正面図で示される構造のアークイオンプレーティング装置、すなわち装置中央部に超硬基体装着用回転テーブルを設け、前記回転テーブルを挟んで、一方側に相対的にＮｂ含有量の高いＴｉ−Ｎｂ合金、他方側に相対的にＮｂ含有量の低いＴｉ−Ｎｂ合金をカソード電極（蒸発源）として対向配置したアークイオンプレーティング装置を用い、この装置の前記回転テーブルの外周部に沿って複数の超硬基体をリング状に装着し、この状態で装置内雰囲気を窒素雰囲気として前記回転テーブルを回転させると共に、蒸着形成される硬質被覆層の層厚均一化を図る目的で超硬基体自体も自転させながら、前記の両側のカソード電極（蒸発源）とアノード電極との間にアーク放電を発生させて、前記超硬基体の表面に（Ｔｉ，Ｎｂ）Ｎ層を形成すると、この結果の（Ｔｉ，Ｎｂ）Ｎ層においては、回転テーブル上にリング状に配置された前記超硬基体が上記の一方側の相対的にＮｂ含有量の高いＴｉ−Ｎｂ合金のカソード電極（蒸発源）に最も接近した時点で層中にＮｂ最高含有点が形成され、また前記超硬基体が上記の他方側の相対的にＮｂ含有量の低いＴｉ−Ｎｂ合金のカソード電極に最も接近した時点で層中にＮｂ最低含有点が形成され、上記回転テーブルの回転によって層中には層厚方向にそって前記Ｎｂ最高含有点とＮｂ最低含有点が所定間隔をもって交互に繰り返し現れると共に、前記Ｎｂ最高含有点から前記Ｎｂ最低含有点、前記Ｎｂ最低含有点から前記Ｎｂ最高含有点へＮｂ含有量が連続的に変化する成分濃度分布構造をもつようになること。
【０００７】
（ｂ）上記（ａ）の繰り返し連続変化成分濃度分布構造の（Ｔｉ，Ｎｂ）Ｎ層において、対向配置の一方側のカソード電極（蒸発源）であるＴｉ−Ｎｂ合金におけるＮｂ含有量を上記の従来（Ｔｉ，Ｎｂ）Ｎ層の形成に用いたＴｉ−Ｎｂ合金のＮｂ含有量に相当するものとし、かつ同他方側のカソード電極（蒸発源）であるＴｉ−Ｎｂ合金におけるＮｂ含有量を上記の従来（Ｔｉ，Ｎｂ）Ｎ層の形成に用いたＴｉ−Ｎｂ合金のＮｂ含有量に比して相対的に低いものとする共に、超硬基体が装着されている回転テーブルの回転速度を制御して、
上記Ｎｂ最高含有点が、組成式：（Ｔｉ_1-XＮｂ_X）Ｎ（ただし、原子比で、Ｘは０．３０〜０．５０を示す）、
上記Ｎｂ最低含有点が、組成式：（Ｔｉ_1-YＮｂ_Y）Ｎ（ただし、原子比で、Ｙは０．０５〜０．２５を示す）、
をそれぞれ満足し、かつ隣り合う上記Ｎｂ最高含有点とＮｂ最低含有点の厚さ方向の間隔を０．０１〜０．１μmとすると、
上記Ｎｂ最高含有点部分では、上記の従来（Ｔｉ，Ｎｂ）Ｎ層と同等のＮｂ含有量となることから、前記従来（Ｔｉ，Ｎｂ）Ｎ層と同等のすぐれた高温硬さを示し、一方上記Ｎｂ最低含有点部分では、前記Ｎｂ最高含有点部分に比してＮｂ含有量が低く、Ｔｉ含有量の高いものとなるので、一段と高い強度と靭性が確保され、かつこれらＮｂ最高含有点とＮｂ最低含有点の間隔をきわめて小さくしたことから、層全体の特性として高強度と高靭性を保持した状態ですぐれた高温硬さを具備するようになり、したがって、硬質被覆層がかかる構成の（Ｔｉ，Ｎｂ）Ｎ層からなる被覆超硬工具は、各種の鋼や鋳鉄などの切削加工を、特に高い機械的衝撃を伴うので高強度と高靭性が要求される、高切り込みや高送りなどの重切削条件で行なった場合にも、硬質被覆層がすぐれた耐チッピング性を発揮するようになること。
以上（ａ）および（ｂ）に示される研究結果を得たのである。
【０００８】
この発明は、上記の研究結果に基づいてなされたものであって、超硬基体の表面に、（Ｔｉ，Ｎｂ）Ｎ層からなる硬質被覆層を１〜１５μｍの全体平均層厚で物理蒸着してなる被覆超硬工具において、
上記硬質被覆層が、厚さ方向にそって、Ｎｂ最高含有点とＮｂ最低含有点とが所定間隔をおいて交互に繰り返し存在し、かつ前記Ｎｂ最高含有点から前記Ｎｂ最低含有点、前記Ｎｂ最低含有点から前記Ｎｂ最高含有点へＮｂ含有量が連続的に変化する成分濃度分布構造を有し、
さらに、上記Ｎｂ最高含有点が、組成式：（Ｔｉ_1-XＮｂ_X）Ｎ（ただし、原子比で、Ｘは０．３０〜０．５０を示す）、
上記Ｎｂ最低含有点が、組成式：（Ｔｉ_1-YＮｂ_Y）Ｎ（ただし、原子比で、Ｙは０．０５〜０．２５を示す）、
を満足し、かつ隣り合う上記Ｎｂ最高含有点とＮｂ最低含有点の間隔が、０．０１〜０．１μmである、
重切削加工条件で硬質被覆層がすぐれた耐チッピング性を発揮する被覆超硬工具に特徴を有するものである。
【０００９】
つぎに、この発明の被覆超硬工具において、これを構成する硬質被覆層の構成を上記の通りに限定した理由を説明する。
（ａ）Ｎｂ最高含有点の組成
Ｎｂ最高含有点の（Ｔｉ，Ｎｂ）ＮにおけるＮｂ成分は、高強度および高靭性を有するＴｉＮの高温硬さを向上させる目的で含有するものであり、したがってＮｂ成分の含有割合が高くなればなるほど高温硬さは高く、強度および靭性は低下したものになるが、Ｎｂの割合を示すＸ値がＴｉとの合量に占める割合（原子比）で０．５０を越えて高くなると、高強度および高靭性を有するＮｂ最低含有点が隣接して存在しても層自体の強度および靭性の低下は避けられず、この結果チッピングなどが発生し易くなり、一方同Ｘ値が同０．３０未満では所望のすぐれた高温硬さを確保することができなくなることから、Ｎｂ最高含有点でのＮｂの割合を示すＸ値を０．３０〜０．５０と定めた。
【００１０】
（ｂ）Ｎｂ最低含有点の組成
上記の通りＮｂ最高含有点は高い高温硬さをもつものであるが、反面強度および靭性の劣るものであるため、このＮｂ最高含有点の強度および靭性不足を補う目的で、Ｔｉ含有割合が高く、これによって高強度および高靭性を有するようになるＮｂ最低含有点を厚さ方向に交互に介在させるものであり、したがってＮｂの割合を示すＹ値がＴｉとの合量に占める割合（原子比）で０．２５を越えると、所望のすぐれた強度および靭性を確保することができず、一方同Ｙ値が０．０５未満になると、相対的にＴｉの割合が多くなり過ぎて、Ｎｂ最低含有点に所定の高温硬さを具備せしめることができなくなることから、Ｎｂ最低含有点でのＮｂの割合を示すＹ値を０．０５〜０．２５と定めた。
【００１１】
（ｃ）Ｎｂ最高含有点とＮｂ最低含有点間の間隔
その間隔が０．０１μm未満ではそれぞれの点を上記の組成で明確に形成することが困難であり、この結果層に所望の高強度および高靭性、さらに高温硬さを確保することができなくなり、またその間隔が０．１μmを越えるとそれぞれの点がもつ欠点、すなわちＮｂ最高含有点であれば強度および靭性不足、Ｎｂ最低含有点であれば高温硬さ不足が層内に局部的に現れ、これが原因で切刃にチッピングが発生し易くなったり、摩耗進行が促進されるようになることから、その間隔を０．０１〜０．１μmと定めた。
【００１２】
（ｄ）硬質被覆層の全体平均層厚
その層厚が１μｍ未満では、所望の耐摩耗性を確保することができず、一方その平均層厚が１５μｍを越えると、チッピングが発生し易くなることから、その平均層厚を１〜１５μｍと定めた。
【００１３】
【発明の実施の形態】
つぎに、この発明の被覆超硬工具を実施例により具体的に説明する。
（実施例１）
原料粉末として、いずれも１〜３μｍの平均粒径を有するＷＣ粉末、ＴｉＣ粉末、ＶＣ粉末、ＴａＣ粉末、ＮｂＣ粉末、Ｃｒ₃Ｃ₂粉末、およびＣｏ粉末を用意し、これら原料粉末を、表１に示される配合組成に配合し、ボールミルで７２時間湿式混合し、乾燥した後、１００ＭＰａの圧力で圧粉体にプレス成形し、この圧粉体を６Ｐａの真空中、温度：１４００℃に１時間保持の条件で焼結し、焼結後、切刃部分にＲ：０．０３のホーニング加工を施してＩＳＯ規格・ＳＮＭＧ１２０４１２のチップ形状をもったＷＣ基超硬合金製の超硬基体Ａ１〜Ａ１０を形成した。
【００１４】
また、原料粉末として、いずれも０．５〜２μｍの平均粒径を有するＴｉＣＮ（重量比でＴｉＣ／ＴｉＮ＝５０／５０）粉末、Ｍｏ₂Ｃ粉末、ＮｂＣ粉末、ＮｂＣ粉末、ＴａＣ粉末、ＷＣ粉末、Ｃｏ粉末、およびＮｉ粉末を用意し、これら原料粉末を、表２に示される配合組成に配合し、ボールミルで２４時間湿式混合し、乾燥した後、１００ＭＰａの圧力で圧粉体にプレス成形し、この圧粉体を２ｋＰａの窒素雰囲気中、温度：１５００℃に１時間保持の条件で焼結し、焼結後、切刃部分にＲ：０．０３のホーニング加工を施してＩＳＯ規格・ＣＮＭＧ１２０４０８のチップ形状をもったＴｉＣＮ系サーメット製の超硬基体Ｂ１〜Ｂ６を形成した。
【００１５】
ついで、上記の超硬基体Ａ１〜Ａ１０およびＢ１〜Ｂ６のそれぞれを、アセトン中で超音波洗浄し、乾燥した状態で、図１に示されるアークイオンプレーティング装置内の回転テーブル上に外周部にそって装着し、一方側のカソード電極（蒸発源）として、種々の成分組成をもったＮｂ最低含有点形成用Ｔｉ−Ｎｂ合金、他方側のカソード電極（蒸発源）として、種々の成分組成をもったＮｂ最高含有点形成用Ｔｉ−Ｎｂ合金を前記回転テーブルを挟んで対向配置し、またボンバート洗浄用金属Ｔｉも装着し、まず、装置内を排気して０．５Ｐａ以下の真空に保持しながら、ヒーターで装置内を５００℃に加熱した後、前記回転テーブル上で自転しながら回転する超硬基体に−８５０Ｖの直流バイアス電圧を印加し、カソード電極の前記金属Ｔｉとアノード電極との間に８５Ａの電流を流してアーク放電を発生させ、もって超硬基体表面をＴｉボンバート洗浄し、ついで装置内に反応ガスとして窒素ガスを導入して３Ｐａの反応雰囲気とすると共に、前記回転テーブル上で自転しながら回転する超硬基体に−１００Ｖの直流バイアス電圧を印加し、それぞれのカソード電極(前記Ｎｂ最低含有点形成用Ｔｉ−Ｎｂ合金およびＮｂ最高含有点形成用Ｔｉ−Ｎｂ合金)とアノード電極との間に１００Ａの電流を流してアーク放電を発生させ、もって前記超硬基体の表面に、厚さ方向に沿って表３，４に示される目標組成のＮｂ最低含有点とＮｂ最高含有点とが交互に同じく表３，４に示される目標間隔で繰り返し存在し、かつ前記Ｎｂ最高含有点から前記Ｎｂ最低含有点、前記Ｎｂ最低含有点から前記Ｎｂ最高含有点へＮｂ含有量が連続的に変化する成分濃度分布構造を有し、かつ同じく表３，４に示される目標全体層厚の硬質被覆層を蒸着することにより、本発明被覆超硬工具としての本発明表面被覆超硬合金製スローアウエイチップ（以下、本発明被覆超硬チップと云う）１〜１６をそれぞれ製造した。
【００１６】
また、比較の目的で、これら超硬基体Ａ１〜Ａ１０およびＢ１〜Ｂ６を、アセトン中で超音波洗浄し、乾燥した状態で、それぞれ図２に示される通常のアークイオンプレーティング装置に装入し、カソード電極（蒸発源）として種々の成分組成をもったＴｉ−Ｎｂ合金を装着し、さらにボンバート洗浄用金属Ｔｉも装着し、まず、装置内を排気して０．５Ｐａ以下の真空に保持しながら、ヒーターで装置内を５００℃に加熱した後、前記超硬基体に−１０００Ｖの直流バイアス電圧を印加し、カソード電極の前記金属Ｔｉとアノード電極との間に１００Ａの電流を流してアーク放電を発生させ、もって超硬基体表面をＴｉボンバート洗浄し、ついで装置内に反応ガスとして窒素ガスを導入して２Ｐａの反応雰囲気とすると共に、超硬基体に−１００Ｖの直流バイアス電圧を印加し、前記カソード電極のＴｉ−Ｎｂ合金とアノード電極との間に１００Ａの電流を流してアーク放電を発生させ、もって前記超硬基体Ａ１〜Ａ１０およびＢ１〜Ｂ６のそれぞれの表面に、表５，６に示される目標組成および目標層厚を有し、かつ厚さ方向に沿って実質的に組成変化のない（Ｔｉ，Ｎｂ）Ｎ層からなる硬質被覆層を蒸着することにより、従来被覆超硬工具としての従来表面被覆超硬合金製スローアウエイチップ（以下、従来被覆超硬チップと云う）１〜１６をそれぞれ製造した。
【００１７】
つぎに、上記本発明被覆超硬チップ１〜１６および従来被覆超硬チップ１〜１６について、これを工具鋼製バイトの先端部に固定治具にてネジ止めした状態で、
被削材：ＪＩＳ・ＳＮＣＭ４３９の丸棒、
切削速度：１２０ｍ／ｍｉｎ．、
切り込み：６．５ｍｍ、
送り：０．１６ｍｍ／ｒｅｖ．、
切削時間：５分、
の条件での合金鋼の乾式連続高切り込み切削加工試験、
被削材：ＪＩＳ・Ｓ２０Ｃの長さ方向等間隔４本縦溝入り丸棒、
切削速度：１３５ｍ／ｍｉｎ．、
切り込み：１．５ｍｍ、
送り：０．６ｍｍ／ｒｅｖ．、
切削時間：７分、
の条件での炭素鋼の乾式断続高送り切削加工試験、さらに、
被削材：ＪＩＳ・ＦＣ３００の丸棒、
切削速度：２００ｍ／ｍｉｎ．、
切り込み：６．６ｍｍ、
送り：０．２ｍｍ／ｒｅｖ．、
切削時間：１０分、
の条件での鋳鉄の乾式連続高切り込み切削加工試験を行い、いずれの切削加工試験でも切刃の逃げ面摩耗幅を測定した。この測定結果を表３〜６に示した。
【００１８】
【表１】

【００１９】
【表２】

【００２０】
【表３】

【００２１】
【表４】

【００２２】
【表５】

【００２３】
【表６】

【００２４】
（実施例２）
原料粉末として、平均粒径：５．５μｍを有する中粗粒ＷＣ粉末、同０．８μｍの微粒ＷＣ粉末、同１．３μｍのＴａＣ粉末、同１．２μｍのＮｂＣ粉末、同１．２μｍのＮｂＣ粉末、同２．３μｍのＣｒ₃Ｃ₂粉末、同１．５μｍのＶＣ粉末、同１．１μｍのＺｒＣ粉末、同１．０μｍの（Ｔｉ，Ｗ）Ｃ粉末、および同１．８μｍのＣｏ粉末を用意し、これら原料粉末をそれぞれ表７に示される配合組成に配合し、さらにワックスを加えてアセトン中で２４時間ボールミル混合し、減圧乾燥した後、１００ＭＰａの圧力で所定形状の各種の圧粉体にプレス成形し、これらの圧粉体を、６Ｐａの真空雰囲気中、７℃／分の昇温速度で１３７０〜１４７０℃の範囲内の所定の温度に昇温し、この温度に１時間保持後、炉冷の条件で焼結して、直径が８ｍｍ、１３ｍｍ、および２６ｍｍの３種の超硬基体形成用丸棒焼結体を形成し、さらに前記の３種の丸棒焼結体から、研削加工にて、表７に示される組合せで、切刃部の直径×長さがそれぞれ６ｍｍ×１３ｍｍ、１０ｍｍ×２２ｍｍ、および２０ｍｍ×４５ｍｍの寸法、並びにいずれもねじれ角が３０度の４枚刃スクエア形状をもった超硬基体（エンドミル）Ｃ−１〜Ｃ−８をそれぞれ製造した。
【００２５】
ついで、これらの超硬基体（エンドミル）Ｃ−１〜Ｃ−８を、アセトン中で超音波洗浄し、乾燥した状態で、同じく図１に示されるアークイオンプレーティング装置に装入し、上記実施例１と同一の条件で、層厚方向に沿って表８に示される目標組成のＮｂ最高含有点とＮｂ最低含有点とが交互に同じく表８に示される目標間隔で繰り返し存在し、かつ前記Ｎｂ最高含有点から前記Ｎｂ最低含有点、前記Ｎｂ最低含有点から前記Ｎｂ最高含有点へＮｂ含有量が連続的に変化する成分濃度分布構造を有し、かつ同じく表８に示される目標全体層厚の硬質被覆層を蒸着することにより、本発明被覆超硬工具としての本発明表面被覆超硬合金製エンドミル（以下、本発明被覆超硬エンドミルと云う）１〜８をそれぞれ製造した。
【００２６】
また、比較の目的で、上記の超硬基体（エンドミル）Ｃ−１〜Ｃ−８を、アセトン中で超音波洗浄し、乾燥した状態で、同じく図２に示される通常のアークイオンプレーティング装置に装入し、上記実施例１と同一の条件で、表９に示される目標組成および目標層厚を有し、かつ厚さ方向に沿って実質的に組成変化のない（Ｔｉ，Ｎｂ）Ｎ層からなる硬質被覆層を蒸着することにより、従来被覆超硬工具としての従来表面被覆超硬合金製エンドミル（以下、従来被覆超硬エンドミルと云う）１〜８をそれぞれ製造した。
【００２７】
つぎに、上記本発明被覆超硬エンドミル１〜８および従来被覆超硬エンドミル１〜８のうち、本発明被覆超硬エンドミル１〜３および従来被覆超硬エンドミル１〜３については、
被削材：平面寸法：１００ｍｍ×２５０ｍｍ、厚さ：５０ｍｍのＪＩＳ・ＳＫＤ６１の板材、
切削速度：２２ｍ／ｍｉｎ．、
溝深さ（切り込み）：３ｍｍ、
テーブル送り：１２０ｍｍ／分、
の条件での工具鋼の乾式高切り込み溝切削加工試験、本発明被覆超硬エンドミル４〜６および従来被覆超硬エンドミル４〜６については、
被削材：平面寸法：１００ｍｍ×２５０ｍｍ、厚さ：５０ｍｍのＪＩＳ・ＳＵＳ３１６の板材、
切削速度：２０ｍ／ｍｉｎ．、
溝深さ（切り込み）：２ｍｍ、
テーブル送り：３００ｍｍ／分、
の条件でのステンレス鋼の湿式高送り溝切削加工試験、本発明被覆超硬エンドミル７，８および従来被覆超硬エンドミル７，８については、
被削材：平面寸法：１００ｍｍ×２５０ｍｍ、厚さ：５０ｍｍのＪＩＳ・ＳＣＭ４４０の板材、
切削速度：５２ｍ／ｍｉｎ．、
溝深さ（切り込み）：７ｍｍ、
テーブル送り：１７０ｍｍ／分、
の条件での合金鋼の乾式高送り溝切削加工試験をそれぞれ行い、いずれの溝切削加工試験でも切刃部の外周刃の逃げ面摩耗幅が使用寿命の目安とされる０．１ｍｍに至るまでの切削溝長を測定した。この測定結果を表８、９にそれぞれ示した。
【００２８】
【表７】

【００２９】
【表８】

【００３０】
【表９】

【００３１】
（実施例３）
上記の実施例２で製造した直径が８ｍｍ（超硬基体Ｃ−１〜Ｃ−３形成用）、１３ｍｍ（超硬基体Ｃ−４〜Ｃ−６形成用）、および２６ｍｍ（超硬基体Ｃ−７、Ｃ−８形成用）の３種の丸棒焼結体を用い、この３種の丸棒焼結体から、研削加工にて、溝形成部の直径×長さがそれぞれ４ｍｍ×１３ｍｍ（超硬基体Ｄ−１〜Ｄ−３）、８ｍｍ×２２ｍｍ（超硬基体Ｄ−４〜Ｄ−６）、および１６ｍｍ×４５ｍｍ（超硬基体Ｄ−７、Ｄ−８）の寸法、並びにいずれもねじれ角が３０度の２枚刃形状をもった超硬基体（ドリル）Ｄ−１〜Ｄ−８をそれぞれ製造した。
【００３２】
ついで、これらの超硬基体（ドリル）Ｄ−１〜Ｄ−８の切刃に、ホーニングを施し、アセトン中で超音波洗浄し、乾燥した状態で、同じく図１に示されるアークイオンプレーティング装置に装入し、上記実施例１と同一の条件で、厚さ方向に沿って表１０に示される目標組成のＮｂ最高含有点とＮｂ最低含有点とが交互に同じく表１０に示される目標間隔で繰り返し存在し、かつ前記Ｎｂ最高含有点から前記Ｎｂ最低含有点、前記Ｎｂ最低含有点から前記Ｎｂ最高含有点へＮｂ含有量が連続的に変化する成分濃度分布構造を有し、かつ同じく表１０に示される目標全体層厚の硬質被覆層を蒸着することにより、本発明被覆超硬工具としての本発明表面被覆超硬合金製ドリル（以下、本発明被覆超硬ドリルと云う）１〜８をそれぞれ製造した。
【００３３】
また、比較の目的で、上記の超硬基体（ドリル）Ｄ−１〜Ｄ−８の切刃に、ホーニングを施し、アセトン中で超音波洗浄し、乾燥した状態で、同じく図２に示される通常のアークイオンプレーティング装置に装入し、上記実施例１と同一の条件で、表１１に示される目標組成および目標層厚を有し、かつ厚さ方向に沿って実質的に組成変化のない（Ｔｉ，Ｎｂ）Ｎ層からなる硬質被覆層を蒸着することにより、従来被覆超硬工具としての従来表面被覆超硬合金製ドリル（以下、従来被覆超硬ドリルと云う）１〜８をそれぞれ製造した。
【００３４】
つぎに、上記本発明被覆超硬ドリル１〜８および従来被覆超硬ドリル１〜８のうち、本発明被覆超硬ドリル１〜３および従来被覆超硬ドリル１〜３については、
被削材：平面寸法：１００ｍｍ×２５０ｍｍ、厚さ：５０ｍｍのＪＩＳ・Ｓ４０Ｃの板材、
切削速度：３５ｍ／ｍｉｎ．、
送り：０．３１ｍｍ／ｒｅｖ、
穴深さ：８ｍｍ
の条件での炭素鋼の湿式高送り穴あけ切削加工試験、本発明被覆超硬ドリル４〜６および従来被覆超硬ドリル４〜６については、
被削材：平面寸法：１００ｍｍ×２５０ｍｍ、厚さ：５０ｍｍのＪＩＳ・ＳＮＣＭ４３９の板材、
切削速度：４０ｍ／ｍｉｎ．、
送り：０．５ｍｍ／ｒｅｖ、
穴深さ：１５ｍｍ
の条件での合金鋼の湿式高送り穴あけ切削加工試験、本発明被覆超硬ドリル７，８および従来被覆超硬ドリル７，８については、
被削材：平面寸法：１００ｍｍ×２５０ｍｍ、厚さ：５０ｍｍのＪＩＳ・ＦＣ２５０の板材、
切削速度：７０ｍ／ｍｉｎ．、
送り：０．７５ｍｍ／ｒｅｖ、
穴深さ：３０ｍｍ
の条件での鋳鉄の湿式高送り穴あけ切削加工試験、をそれぞれ行い、いずれの湿式穴あけ切削加工試験（水溶性切削油使用）でも先端切刃面の逃げ面摩耗幅が０．３ｍｍに至るまでの穴あけ加工数を測定した。この測定結果を表１０、１１にそれぞれ示した。
【００３５】
【表１０】

【００３６】
【表１１】

【００３７】
この結果得られた本発明被覆超硬工具としての本発明被覆超硬チップ１〜１６、本発明被覆超硬エンドミル１〜８、および本発明被覆超硬ドリル１〜８を構成する硬質被覆層におけるＮｂ最高含有点とＮｂ最低含有点の組成、並びに従来被覆超硬工具としての従来被覆超硬チップ１〜１６、従来被覆超硬エンドミル１〜８、および従来被覆超硬ドリル１〜８の硬質被覆層の組成をオージェ分光分析装置を用いて測定したところ、それぞれ目標組成と実質的に同じ組成を示した。
また、これらの本発明被覆超硬工具の硬質被覆層におけるＮｂ最高含有点とＮｂ最低含有点間の間隔、およびこれの全体層厚、並びに従来被覆超硬工具の硬質被覆層の厚さを、走査型電子顕微鏡を用いて断面測定したところ、いずれも目標値と実質的に同じ値を示した。
【００３８】
【発明の効果】
表３〜１１に示される結果から、硬質被覆層が厚さ方向に、すぐれた高温硬さを有するＮｂ最高含有点と、高強度と高靭性を有するＮｂ最低含有点とが交互に所定間隔をおいて繰り返し存在し、かつ前記Ｎｂ最高含有点から前記Ｎｂ最低含有点、前記Ｎｂ最低含有点から前記Ｎｂ最高含有点へＮｂ含有量が連続的に変化する成分濃度分布構造を有する本発明被覆超硬工具は、いずれも各種の鋼や鋳鉄などの切削加工を、高い機械的衝撃を伴う高切り込みや高送りなどの重切削条件で行なった場合にも、硬質被覆層が特に厚さ方向に繰り返し存在する前記Ｎｂ最低含有点の存在によってすぐれた耐チッピング性を発揮するのに対して、硬質被覆層が厚さ方向に沿って実質的に組成変化のない（Ｔｉ，Ｎｂ）Ｎ層からなる従来被覆超硬工具においては、前記硬質被覆層がすぐれた高温硬さを有するものの、強度および靭性に劣るものであるために、チッピングが発生し、これが原因で比較的短時間で使用寿命に至ることが明らかである。
上述のように、この発明の被覆超硬工具は、通常の条件での切削加工は勿論のこと、特に各種の鋼や鋳鉄などの切削加工を、高い機械的衝撃を伴う高切り込みや高送りなどの重切削条件で行なった場合にも、すぐれた耐チッピング性を発揮し、長期に亘ってすぐれた耐摩耗性を示すものであるから、切削加工の省力化および省エネ化、さらに低コスト化に十分満足に対応できるものである。
【図面の簡単な説明】
【図１】この発明の被覆超硬工具を構成する硬質被覆層を形成するのに用いたアークイオンプレーティング装置を示し、（ａ）は概略平面図、（ｂ）は概略正面図である。
【図２】従来被覆超硬工具を構成する硬質被覆層を形成するのに用いた通常のアークイオンプレーティング装置の概略説明図である。[0001]
BACKGROUND OF THE INVENTION
In the present invention, the hard coating layer has high strength and high toughness, and also has high-temperature hardness. Therefore, cutting of various types of steel and cast iron, particularly high cutting with high mechanical impact, high feed, etc. The present invention relates to a surface-coated cemented carbide cutting tool (hereinafter referred to as a coated cemented carbide tool) that exhibits excellent chipping resistance when subjected to heavy cutting conditions.
[0002]
[Prior art]
In general, coated carbide tools are used for throwaway inserts that are detachably attached to the tip of a cutting tool for drilling and cutting of various materials such as steel and cast iron, and for flat cutting. There are drills, miniature drills, solid type end mills used for chamfering, grooving, shoulder processing, etc. Also, the throwaway tip is detachably attached and cutting is performed in the same way as the solid type end mill Throwaway end mill tools are known.
[0003]
Further, as a coated carbide tool, a substrate made of tungsten carbide (hereinafter referred to as WC) -based cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) -based cermet (hereinafter collectively referred to as a carbide substrate). ), A composite nitride of Ti and Nb satisfying the composition formula: (Ti _1-X Nb _X ) N (wherein X is 0.30 to 0.50 in atomic ratio) [hereinafter, ( Coated carbide tools formed by physical vapor deposition of a hard coating layer composed of a layer of Ti, Nb) N] with an average layer thickness of 1 to 15 μm have been proposed for continuous cutting and intermittent cutting of various steels and cast irons. It is used.
[0004]
Furthermore, the above-mentioned coated carbide tool is, for example, the above-mentioned carbide substrate is inserted into an arc ion plating apparatus which is one type of physical vapor deposition apparatus schematically shown in FIG. For example, in a state heated to a temperature of 500 ° C., an arc discharge is generated between the anode electrode and a cathode electrode (evaporation source) in which a Ti—Nb alloy having a predetermined composition is set, for example, at a current of 140 A, At the same time, nitrogen gas is introduced into the apparatus as a reaction gas to give a reaction atmosphere of, for example, 2 Pa, while the cemented carbide substrate is applied to the surface of the cemented carbide substrate with a bias voltage of, for example, −100 V applied. It is also known that it is produced by vapor-depositing a hard coating layer composed of the (Ti, Nb) N layer.
[0005]
[Problems to be solved by the invention]
In recent years, the performance of cutting machines has been dramatically improved, while on the other hand, there is a strong demand for labor saving and energy saving and further cost reduction for cutting, and as a result, cutting is performed under heavy cutting conditions such as high cutting and high feed. In the above conventional coated carbide tools, there is no problem when used under normal cutting conditions, but the cutting is performed with high mechanical impact, high cutting depth, high feed, etc. Under the heavy cutting conditions, chipping (microcracking) is likely to occur due to the lack of strength and toughness of the hard coating layer, and the service life is reached in a relatively short time.
[0006]
[Means for Solving the Problems]
In view of the above, the present inventors have developed the above-mentioned conventional coated carbide tool in order to develop a coated carbide tool that exhibits excellent chipping resistance with a hard coating layer particularly under heavy cutting conditions. As a result of conducting research with a focus on the hard coating layer,
(A) The (Ti, Nb) N layer constituting the conventional coated carbide tool formed using the arc ion plating apparatus shown in FIG. 2 has a substantially uniform composition throughout the layer thickness. Arc ion plating apparatus having a structure shown in FIG. 1 (a) in a schematic plan view and in FIG. 1 (b) in a schematic front view. That is, a carbide base mounting rotary table is provided in the center of the apparatus, and the Ti—Nb alloy with a relatively high Nb content is placed on one side and Ti with a relatively low Nb content is placed on the other side across the rotary table. Using an arc ion plating apparatus in which an Nb alloy is used as a cathode electrode (evaporation source) and facing each other, a plurality of carbide substrates are mounted in a ring shape along the outer periphery of the rotary table of the apparatus, and in this state, the apparatus While rotating the rotary table under an atmosphere of nitrogen and rotating the hard substrate itself for the purpose of uniforming the thickness of the hard coating layer to be deposited, the cathode electrode (evaporation source) and the anode on both sides are rotated. When an arc discharge is generated between the electrodes and a (Ti, Nb) N layer is formed on the surface of the carbide substrate, the resulting (Ti, Nb) N layer is ring-shaped on the rotary table. When the disposed carbide substrate is closest to the cathode electrode (evaporation source) of the Ti—Nb alloy having a relatively high Nb content on one side, the highest Nb content point is formed in the layer. When the cemented carbide substrate comes closest to the cathode electrode of the Ti—Nb alloy having a relatively low Nb content on the other side, the lowest Nb content point is formed in the layer, and the rotation of the rotary table causes No layer The Nb highest content point and the Nb lowest content point appear alternately with a predetermined interval along the direction, and the Nb content from the Nb highest content point to the Nb lowest content point and from the Nb lowest content point to the Nb highest content point To have a component concentration distribution structure whose amount changes continuously.
[0007]
(B) In the (Ti, Nb) N layer of the repeated continuous change component concentration distribution structure of (a) above, the Nb content in the Ti—Nb alloy which is the cathode electrode (evaporation source) on one side of the opposing arrangement is The Nb content in the Ti—Nb alloy, which is the cathode electrode (evaporation source) on the other side, corresponds to the Nb content of the Ti—Nb alloy conventionally used for forming the (Ti, Nb) N layer. The Ti-Nb alloy used for forming the conventional (Ti, Nb) N layer should have a relatively low Nb content and control the rotation speed of the turntable on which the carbide substrate is mounted. do it,
The Nb highest content point is the composition formula: (Ti _1-X Nb _X ) N (wherein X is 0.30 to 0.50 in atomic ratio),
The Nb minimum content point is a composition formula: (Ti _1-Y Nb _Y ) N (wherein Y represents 0.05 to 0.25 in atomic ratio),
And the distance in the thickness direction between the adjacent highest Nb content point and the lowest Nb content point is 0.01 to 0.1 μm,
The Nb highest content point portion has an Nb content equivalent to that of the conventional (Ti, Nb) N layer, and thus exhibits an excellent high-temperature hardness equivalent to that of the conventional (Ti, Nb) N layer. In the Nb minimum content point portion, the Nb content is lower than that of the Nb maximum content point portion, and the Ti content is high. Therefore, higher strength and toughness are secured, and these Nb maximum content points Since the interval between the minimum Nb content points is extremely small, the entire layer has excellent high-temperature hardness while maintaining high strength and high toughness, and therefore, the hard coating layer is applied in this configuration ( Coated carbide tools made of Ti, Nb) N layers require cutting and cutting of various steels and cast irons, especially with high mechanical impact, so high strength and high toughness are required. When performed under heavy cutting conditions Also, it becomes to exhibit chipping resistance of the hard coating layer has excellent.
The research results shown in (a) and (b) above were obtained.
[0008]
The present invention has been made based on the above research results. A hard coating layer composed of a (Ti, Nb) N layer is physically vapor-deposited on the surface of a carbide substrate with an overall average layer thickness of 1 to 15 μm. In the coated carbide tool
In the hard coating layer, the Nb highest content point and the Nb lowest content point are alternately present at predetermined intervals along the thickness direction, and the Nb lowest content point, the Nb A component concentration distribution structure in which the Nb content continuously changes from the lowest content point to the Nb highest content point,
Further, the highest Nb content point is the composition formula: (Ti _1-X Nb _X ) N (wherein X is 0.30 to 0.50 in atomic ratio),
The Nb minimum content point is a composition formula: (Ti _1-Y Nb _Y ) N (wherein Y represents 0.05 to 0.25 in atomic ratio),
And the interval between the Nb highest content point and the Nb lowest content point adjacent to each other is 0.01 to 0.1 μm.
It is characterized by a coated cemented carbide tool that exhibits excellent chipping resistance under heavy cutting conditions.
[0009]
Next, in the coated carbide tool of the present invention, the reason why the structure of the hard coating layer constituting the tool is limited as described above will be described.
(A) Composition of Nb highest content point The Nb component in (Ti, Nb) N having the highest Nb content point is contained for the purpose of improving the high-temperature hardness of TiN having high strength and high toughness. The higher the content of the component, the higher the high temperature hardness and the lower the strength and toughness. However, the ratio (atomic ratio) of the X value indicating the ratio of Nb to the total amount of Ti is 0.50. When the value exceeds N, the lowering of the strength and toughness of the layer itself is unavoidable even when the Nb minimum content point having high strength and toughness is adjacent to each other, and as a result, chipping and the like are liable to occur. If the X value is less than 0.30, the desired excellent high-temperature hardness cannot be secured. Therefore, the X value indicating the ratio of Nb at the highest Nb content point is set to 0.30 to 0.50. .
[0010]
(B) Composition of the lowest Nb content point As described above, the highest Nb content point has high high-temperature hardness, but on the other hand, the strength and toughness are inferior. For the purpose of supplementing, the Ti content is high, whereby the Nb minimum content points that have high strength and high toughness are alternately interposed in the thickness direction. Therefore, the Y value indicating the Nb content is Ti and If the ratio (atomic ratio) in the total amount exceeds 0.25, the desired excellent strength and toughness cannot be ensured, while if the Y value is less than 0.05, relatively Ti Since the ratio increases so much that the Nb minimum content point cannot be provided with a predetermined high-temperature hardness, the Y value indicating the ratio of Nb at the Nb minimum content point is set to 0.05 to 0.25. It was.
[0011]
(C) Interval between the highest Nb content point and the lowest Nb content point If the distance is less than 0.01 μm, it is difficult to clearly form each point with the above composition. High toughness and high-temperature hardness cannot be secured, and when the distance exceeds 0.1 μm, the disadvantages of each point, that is, if Nb is the highest content point, insufficient strength and toughness, Nb minimum content point If there is, a lack of high-temperature hardness appears locally in the layer, which makes it easy for chipping to occur on the cutting edge and promotes the progress of wear. It was set to 1 μm.
[0012]
(D) Overall average layer thickness of hard coating layer If the layer thickness is less than 1 μm, desired wear resistance cannot be ensured. On the other hand, if the average layer thickness exceeds 15 μm, chipping tends to occur. Therefore, the average layer thickness was determined to be 1 to 15 μm.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, the coated carbide tool of the present invention will be specifically described with reference to examples.
Example 1
As raw material powders, WC powder, TiC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, and Co powder, all having an average particle diameter of 1 to 3 μm, were prepared. And then wet-mixed with a ball mill for 72 hours, dried, and press-molded into a green compact at a pressure of 100 MPa. The green compact was vacuumed at 6 Pa at a temperature of 1400 ° C. for 1 hour. Sintered under the holding conditions, and after sintering, the cutting edge portion was subjected to a honing process of R: 0.03, and the carbide bases A1 to A10 made of WC-base cemented carbide having the ISO standard / SNMG120212 chip shape. Formed.
[0014]
In addition, as raw material powders, TiCN (weight ratio TiC / TiN = 50/50) powder, Mo ₂ C powder, NbC powder, NbC powder, TaC powder, WC powder all having an average particle diameter of 0.5 to 2 μm. Co powder and Ni powder are prepared, and these raw material powders are blended in the blending composition shown in Table 2, wet mixed by a ball mill for 24 hours, dried, and then pressed into a compact at a pressure of 100 MPa. The green compact was sintered in a nitrogen atmosphere of 2 kPa at a temperature of 1500 ° C. for 1 hour, and after sintering, the cutting edge portion was subjected to a honing process of R: 0.03 to obtain ISO standard / CNMG120408. TiCN-based cermet carbide substrates B1 to B6 having the following chip shape were formed.
[0015]
Next, each of the above-mentioned carbide substrates A1 to A10 and B1 to B6 is ultrasonically cleaned in acetone and dried, on the rotary table in the arc ion plating apparatus shown in FIG. Therefore, as one cathode electrode (evaporation source), Ti-Nb alloy for forming Nb minimum content point with various component compositions, and as another cathode electrode (evaporation source), various component compositions are used. The Ti-Nb alloy for forming the highest Nb content point is placed opposite to the rotary table, and the bombard cleaning metal Ti is also mounted. First, the inside of the apparatus is evacuated and kept at a vacuum of 0.5 Pa or less. However, after heating the inside of the apparatus to 500 ° C. with a heater, a DC bias voltage of −850 V was applied to the carbide substrate rotating while rotating on the rotary table, and the metal of the cathode electrode was applied. An arc discharge is generated by passing an electric current of 85 A between i and the anode electrode, thereby cleaning the surface of the carbide substrate with Ti bombardment, and then introducing nitrogen gas as a reaction gas into the apparatus to form a reaction atmosphere of 3 Pa. In addition, a DC bias voltage of −100 V is applied to the carbide substrate that rotates while rotating on the rotary table, and the respective cathode electrodes (Ti-Nb alloy for forming the lowest Nb content point and Ti for forming the highest Nb content point) -Nb alloy) and the anode electrode to cause an arc discharge by causing a current of 100 A to flow, so that the Nb minimum of the target composition shown in Tables 3 and 4 along the thickness direction is formed on the surface of the cemented carbide substrate. The containing point and the Nb highest containing point are alternately repeatedly present at the target intervals shown in Tables 3 and 4, and the Nb lowest containing point and the Nb lowest containing point from the Nb highest containing point. By depositing a hard coating layer having a component concentration distribution structure in which the Nb content continuously changes from the point to the Nb highest content point and having the target total layer thickness also shown in Tables 3 and 4, the present invention The surface-coated cemented carbide throwaway tips (hereinafter referred to as the present coated carbide tips) 1 to 16 as coated carbide tools were produced, respectively.
[0016]
Further, for the purpose of comparison, these carbide substrates A1 to A10 and B1 to B6 are ultrasonically cleaned in acetone and dried, and then loaded into a normal arc ion plating apparatus shown in FIG. In addition, Ti—Nb alloys with various component compositions are mounted as cathode electrodes (evaporation sources), and metal bombard cleaning Ti is also mounted. First, the inside of the apparatus is evacuated and kept at a vacuum of 0.5 Pa or less. However, after heating the inside of the apparatus to 500 ° C. with a heater, a DC bias voltage of −1000 V was applied to the cemented carbide substrate, and a current of 100 A was passed between the metal Ti and the anode electrode of the cathode electrode to cause arc discharge. Thus, the surface of the carbide substrate is cleaned by Ti bombardment, and then nitrogen gas is introduced as a reaction gas into the apparatus to form a reaction atmosphere of 2 Pa. A DC bias voltage of 00 V was applied, and a current of 100 A was passed between the Ti—Nb alloy of the cathode electrode and the anode electrode to generate an arc discharge, whereby each of the carbide substrates A1 to A10 and B1 to B6. A hard coating layer composed of a (Ti, Nb) N layer having the target composition and target layer thickness shown in Tables 5 and 6 and substantially no composition change along the thickness direction is deposited on the surface of Thus, conventional surface-coated cemented carbide throwaway tips (hereinafter referred to as conventional coated carbide tips) 1 to 16 as conventional coated carbide tools were produced, respectively.
[0017]
Next, with the present invention coated carbide tips 1-16 and conventional coated carbide tips 1-16, in a state where this is screwed to the tip of the tool steel tool with a fixing jig,
Work material: JIS / SNCM439 round bar,
Cutting speed: 120 m / min. ,
Incision: 6.5 mm,
Feed: 0.16 mm / rev. ,
Cutting time: 5 minutes
Dry continuous high-cut cutting test of alloy steel under the conditions of
Work material: JIS / S20C lengthwise equidistant round bars with 4 vertical grooves,
Cutting speed: 135 m / min. ,
Incision: 1.5mm,
Feed: 0.6 mm / rev. ,
Cutting time: 7 minutes
Carbon steel dry intermittent high feed cutting test under the conditions of
Work material: JIS / FC300 round bar,
Cutting speed: 200 m / min. ,
Cutting depth: 6.6 mm,
Feed: 0.2 mm / rev. ,
Cutting time: 10 minutes,
The dry continuous high-cut cutting test of cast iron was performed under the conditions described above, and the flank wear width of the cutting edge was measured in any cutting test. The measurement results are shown in Tables 3-6.
[0018]
[Table 1]

[0019]
[Table 2]

[0020]
[Table 3]

[0021]
[Table 4]

[0022]
[Table 5]

[0023]
[Table 6]

[0024]
(Example 2)
As raw material powder, medium coarse WC powder having an average particle diameter of 5.5 μm, fine WC powder of 0.8 μm, TaC powder of 1.3 μm, NbC powder of 1.2 μm, NbC of 1.2 μm Powder, 2.3 μm Cr ₃ C ₂ powder, 1.5 μm VC powder, 1.1 μm ZrC powder, 1.0 μm (Ti, W) C powder, and 1.8 μm Co powder Each of these raw material powders was blended in the blending composition shown in Table 7, and then added with wax, ball milled in acetone for 24 hours, dried under reduced pressure, and then various types of compacted powders having a predetermined shape at a pressure of 100 MPa. The compact is pressed into a body, and these green compacts are heated to a predetermined temperature within a range of 1370 to 1470 ° C. at a heating rate of 7 ° C./min in a 6 Pa vacuum atmosphere, and kept at this temperature for 1 hour. After sintering under furnace cooling conditions, the diameter is 8m m, 13 mm, and 26 mm round bar sintered bodies for forming a carbide substrate were formed, and further, from the above three kinds of round bar sintered bodies, by grinding, in combinations shown in Table 7, Carbide substrate (end mill) C- having a four-blade square shape with a diameter x length of the cutting edge of 6 mm x 13 mm, 10 mm x 22 mm, and 20 mm x 45 mm, respectively, and a twist angle of 30 degrees. 1 to C-8 were produced.
[0025]
Then, these carbide substrates (end mills) C-1 to C-8 were ultrasonically washed in acetone and dried, and then charged into the arc ion plating apparatus shown in FIG. Under the same conditions as in Example 1, the Nb highest content point and the Nb lowest content point of the target composition shown in Table 8 along the layer thickness direction alternately and repeatedly exist at the target interval shown in Table 8, and The target total layer having a component concentration distribution structure in which the Nb content continuously changes from the Nb highest content point to the Nb lowest content point, from the Nb lowest content point to the Nb highest content point, and also shown in Table 8 By vapor-depositing a hard coating layer having a thickness, end mills made of the surface coated cemented carbide of the present invention (hereinafter referred to as the present coated carbide end mill) 1 to 8 as the coated carbide tool of the present invention were produced.
[0026]
For the purpose of comparison, the above-mentioned carbide substrates (end mills) C-1 to C-8 are ultrasonically cleaned in acetone and dried, and the ordinary arc ion plating apparatus shown in FIG. 2 is also used. (Ti, Nb) N having the target composition and target layer thickness shown in Table 9 and substantially no composition change along the thickness direction under the same conditions as in Example 1 above. By vapor-depositing a hard coating layer consisting of layers, conventional surface-coated cemented carbide end mills (hereinafter referred to as conventional coated carbide end mills) 1 to 8 as conventional coated carbide tools were produced, respectively.
[0027]
Next, of the present invention coated carbide end mills 1-8 and conventional coated carbide end mills 1-8, the present invention coated carbide end mills 1-3 and conventional coated carbide end mills 1-3 are as follows:
Work material: Plane dimensions: 100 mm × 250 mm, thickness: 50 mm JIS / SKD61 plate material,
Cutting speed: 22 m / min. ,
Groove depth (cut): 3 mm,
Table feed: 120 mm / min,
With respect to the tool steel dry type high cutting groove cutting test under the conditions of the present invention, the coated carbide end mills 4-6 of the present invention and the conventional coated carbide end mills 4-6,
Work material: Plane size: 100 mm × 250 mm, thickness: 50 mm JIS / SUS316 plate material,
Cutting speed: 20 m / min. ,
Groove depth (cut): 2 mm,
Table feed: 300mm / min,
For the wet high feed grooving cutting test of stainless steel under the following conditions, the coated carbide end mills 7 and 8 of the present invention and the conventional coated carbide end mills 7 and 8:
Work material: Plane dimension: 100 mm × 250 mm, thickness: 50 mm JIS / SCM440 plate material,
Cutting speed: 52 m / min. ,
Groove depth (cut): 7 mm,
Table feed: 170 mm / min,
In each of the groove cutting tests, the flank wear width of the outer peripheral edge of the cutting edge reaches 0.1 mm, which is a guide for the service life. The cutting groove length of was measured. The measurement results are shown in Tables 8 and 9, respectively.
[0028]
[Table 7]

[0029]
[Table 8]

[0030]
[Table 9]

[0031]
(Example 3)
The diameters produced in Example 2 above were 8 mm (for forming carbide substrates C-1 to C-3), 13 mm (for forming carbide substrates C-4 to C-6), and 26 mm (for carbide substrates C-). 7, for C-8 formation), from these three types of round bar sintered bodies, the diameter x length of the groove forming portion is 4 mm x 13 mm (by grinding), respectively. Carbide substrates D-1 to D-3), 8 mm × 22 mm (Carbide substrates D-4 to D-6), and 16 mm × 45 mm (Carbide substrates D-7 and D-8), and all Carbide substrates (drills) D-1 to D-8 having a two-blade shape with a twist angle of 30 degrees were manufactured.
[0032]
Next, the cutting edges of these carbide substrates (drills) D-1 to D-8 are subjected to honing, ultrasonically cleaned in acetone and dried, and the arc ion plating apparatus shown in FIG. 1 is also used. In the same conditions as in Example 1 above, the target interval shown in Table 10 in which the highest Nb content point and the lowest Nb content point of the target composition shown in Table 10 along the thickness direction are also shown in Table 10 alternately. And a component concentration distribution structure in which the Nb content continuously changes from the Nb highest content point to the Nb lowest content point, and from the Nb lowest content point to the Nb highest content point, and By depositing a hard coating layer having a target overall layer thickness shown in FIG. 10, drills made of the surface coated cemented carbide of the present invention (hereinafter referred to as the present coated carbide drill) 1-8 as the coated carbide tool of the present invention. Were manufactured respectively.
[0033]
For comparison purposes, the cutting edges of the above-mentioned carbide substrates (drills) D-1 to D-8 are honed, ultrasonically cleaned in acetone, and dried, as shown in FIG. The sample was charged into a normal arc ion plating apparatus, had the target composition and target layer thickness shown in Table 11 under the same conditions as in Example 1, and substantially changed in composition along the thickness direction. By vapor-depositing a hard coating layer comprising no (Ti, Nb) N layer, conventional surface-coated cemented carbide drills (hereinafter referred to as conventional coated carbide drills) 1 to 8 as conventional coated carbide tools are respectively provided. Manufactured.
[0034]
Next, of the present invention coated carbide drills 1-8 and conventional coated carbide drills 1-8, the present invention coated carbide drills 1-3 and conventional coated carbide drills 1-3,
Work material: Plane dimension: 100 mm × 250 mm, thickness: 50 mm JIS / S40C plate material,
Cutting speed: 35 m / min. ,
Feed: 0.31mm / rev,
Hole depth: 8mm
For the wet high feed drilling test of carbon steel under the conditions of the present invention, the coated carbide drills 4-6 of the present invention and the conventional coated carbide drills 4-6,
Work material: Plane dimension: 100 mm × 250 mm, thickness: 50 mm JIS / SNCM439 plate material,
Cutting speed: 40 m / min. ,
Feed: 0.5mm / rev,
Hole depth: 15mm
With respect to the wet high feed drilling test of alloy steel under the conditions of the present invention, the coated carbide drills 7 and 8 of the present invention and the conventional coated carbide drills 7 and 8,
Work material: Plane dimension: 100 mm × 250 mm, thickness: 50 mm JIS / FC250 plate material,
Cutting speed: 70 m / min. ,
Feed: 0.75mm / rev,
Hole depth: 30mm
Each of the wet high-feed drilling tests of cast iron under the conditions of The number of drilling operations was measured. The measurement results are shown in Tables 10 and 11, respectively.
[0035]
[Table 10]

[0036]
[Table 11]

[0037]
In the hard coating layer which comprises this invention coated carbide tip 1-16 as this invention coated carbide tool obtained as a result, this invention coated carbide end mill 1-8, and this invention coated carbide drill 1-8. Composition of Nb highest content point and Nb lowest content point, and conventionally coated carbide tips 1 to 16 as conventional coated carbide tools, conventionally coated carbide end mills 1 to 8, and hard coating of conventionally coated carbide drills 1 to 8 The composition of the layers was measured using an Auger spectroscopic analyzer, and each showed substantially the same composition as the target composition.
Further, the distance between the Nb highest content point and the Nb lowest content point in the hard coating layer of these coated carbide tools of the present invention, and the overall layer thickness thereof, and the thickness of the hard coating layer of the conventional coated carbide tool, When the cross section was measured using a scanning electron microscope, all showed substantially the same value as the target value.
[0038]
【The invention's effect】
From the results shown in Tables 3 to 11, the Nb highest content point where the hard coating layer has excellent high temperature hardness and the Nb lowest content point having high strength and high toughness alternately in the thickness direction at predetermined intervals. And the present invention has a component concentration distribution structure in which the Nb content continuously changes from the highest Nb content point to the lowest Nb content point, and from the lowest Nb content point to the highest Nb content point. For hard tools, the hard coating layer is repeated especially in the thickness direction even when cutting various steels and cast irons under heavy cutting conditions such as high cutting and high feed with high mechanical impact. Conventionally, the hard coating layer is composed of a (Ti, Nb) N layer having substantially no composition change along the thickness direction while exhibiting excellent chipping resistance due to the presence of the Nb minimum content point. Coated carbide tool smell Although having a high-temperature hardness of the hard coating layer is excellent, because it is inferior in strength and toughness, chipping occurs and this is apparent that lead to a relatively short time service life due.
As described above, the coated carbide tool of the present invention can be used not only for cutting under normal conditions, but also for cutting various steels and cast irons. Even under heavy cutting conditions, it exhibits excellent chipping resistance and excellent wear resistance over a long period of time. It can respond satisfactorily.
[Brief description of the drawings]
FIG. 1 shows an arc ion plating apparatus used for forming a hard coating layer constituting a coated carbide tool of the present invention, wherein (a) is a schematic plan view and (b) is a schematic front view.
FIG. 2 is a schematic explanatory view of a normal arc ion plating apparatus used to form a hard coating layer constituting a conventional coated carbide tool.

Claims

Surface-coated carbide formed by physical vapor deposition of a hard coating layer composed of a composite nitride layer of Ti and Nb with a total average layer thickness of 1 to 15 μm on the surface of a tungsten carbide-based cemented carbide substrate or a titanium carbonitride cermet substrate In the alloy cutting tool, in the hard coating layer, the Nb highest content point and the Nb lowest content point are alternately present at predetermined intervals along the thickness direction, and from the Nb highest content point, the Nb Having a component concentration distribution structure in which the Nb content continuously changes from the lowest content point, the Nb lowest content point to the Nb highest content point,
Further, the highest Nb content point is the composition formula: (Ti _1-X Nb _X ) N (wherein X is 0.30 to 0.50 in atomic ratio),
The Nb minimum content point is a composition formula: (Ti _1-Y Nb _Y ) N (wherein Y represents 0.05 to 0.25 in atomic ratio),
And the distance between the Nb highest content point and the Nb lowest content point adjacent to each other is 0.01 to 0.1 μm,
A surface-coated cemented carbide cutting tool that exhibits excellent chipping resistance under hard cutting conditions characterized by