JP3700658B2

JP3700658B2 - Cutting tool made of surface-coated cubic boron nitride based sintered material that exhibits excellent chipping resistance with a hard coating layer in intermittent heavy cutting

Info

Publication number: JP3700658B2
Application number: JP2002048901A
Authority: JP
Inventors: 直方関; 新土屋; 智阿川
Original assignee: Mitsubishi Materials Corp
Current assignee: Mitsubishi Materials Corp
Priority date: 2002-02-26
Filing date: 2002-02-26
Publication date: 2005-09-28
Anticipated expiration: 2022-02-26
Also published as: JP2003245806A

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、かつ高温硬さと耐熱性にもすぐれ、したがって特に各種の鋼や鋳鉄などの断続切削加工を、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立方晶窒化硼素基焼結材料製切削工具（以下、被覆ＢＮ基工具という）に関するものである。
【０００２】
【従来の技術】
一般に、被覆ＢＮ基工具には、各種の鋼や鋳鉄などの被削材の旋削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や、前記スローアウエイチップを着脱自在に取り付けて、面削加工や溝加工、さらに肩加工などに用いられる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ＢＮ基工具として、例えば特開平８−１１９７７４号公報などに記載されるように、きわめて硬質であり、反面靭性に劣るために、切削速度は高いが、切り込みや送りが小さい条件で切削加工が行なわれる高速表面仕上げ加工にしか用いられていなかった立方晶窒化硼素基焼結材料製切削工具を基体（以下、ＢＮ基基体という）とし、このＢＮ基基体の表面に、切削工具自体に靭性を付与せしめて、通常の条件での切り込みや送りで各種の鋼や鋳鉄などの連続切削加工や断続切削加工を行なっても、切刃部に欠けやチッピング（微小欠け）などが発生しないようにする目的で、組成式：（Ａｌ_ZＴｉ_1-Z）Ｎ（ただし、原子比で、Ｚは０．６０〜０．８５を示す）を満足するＡｌとＴｉの複合窒化物［以下、（Ａｌ，Ｔｉ）Ｎで示す］層からなる硬質被覆層を０．５〜１０μｍの平均層厚で物理蒸着してなる被覆ＢＮ基工具が知られている。
【０００４】
さらに、上記の被覆ＢＮ基工具が、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ＢＮ基基体を装入し、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Ａｌ−Ｔｉ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：９０Ａ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ＢＮ基基体には、例えば−２５０Ｖのバイアス電圧を印加した条件で、前記ＢＮ基基体の表面に、上記（Ａｌ，Ｔｉ）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、断続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、特に断続重切削加工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ＢＮ基工具を開発すべく、上記の従来被覆ＢＮ基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ＢＮ基工具を構成する（Ａｌ，Ｔｉ）Ｎ層は、層厚全体に亘って実質的に均一な組成を有し、したがって均質な高温硬さと耐熱性を有するが、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ＢＮ基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Ａｌ含有量の高い（Ｔｉ含有量の低い）Ａｌ−Ｔｉ合金、他方側に相対的にＴｉ含有量の高い（Ａｌ含有量の低い）Ｔｉ−Ａｌ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ＢＮ基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ＢＮ基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ＢＮ基基体の表面に（Ａｌ，Ｔｉ）Ｎ層を形成すると、この結果の（Ａｌ，Ｔｉ）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ＢＮ基基体が上記の一方側の相対的にＡｌ含有量の高い（Ｔｉ含有量の低い）Ａｌ−Ｔｉ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Ａｌ最高含有点が形成され、また前記ＢＮ基基体が上記の他方側の相対的にＴｉ含有量の高い（Ａｌ含有量の低い）Ｔｉ−Ａｌ合金のカソード電極に最も接近した時点で層中にＡｌ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Ａｌ最高含有点とＡｌ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Ａｌ最高含有点から前記Ａｌ最低含有点、前記Ａｌ最低含有点から前記Ａｌ最高含有点へＡｌ（Ｔｉ）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（Ａｌ，Ｔｉ）Ｎ層において、例えば対向配置のカソード電極（蒸発源）のそれぞれの組成を調製すると共に、ＢＮ基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Ａｌ最高含有点が、組成式：（Ａｌ_XＴｉ_1-X）Ｎ（ただし、原子比で、Ｘは０．６０〜０．８５を示す）、
上記Ａｌ最低含有点が、組成式：（Ａｌ_YＴｉ_1-Y）Ｎ（ただし、原子比で、Ｙは０．２５〜０．５０を示す）、
をそれぞれ満足し、かつ隣り合う上記Ａｌ最高含有点とＡｌ最低含有点の厚さ方向の間隔を０．０１〜０．１μmとすると、
上記Ａｌ最高含有点部分では、上記の従来（Ａｌ，Ｔｉ）Ｎ層のもつ高温硬さと耐熱性に相当するすぐれた高温硬さと耐熱性（高温特性）を示し、一方上記Ａｌ最低含有点部分では、前記Ａｌ最高含有点部分に比してＡｌ含有量が低く、Ｔｉ含有量の高いものとなるので、高強度と高靭性が確保され、かつこれらＡｌ最高含有点とＡｌ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すぐれた高温特性を保持した状態で一段とすぐれた強度と靭性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，Ａｌ）Ｎ層からなる被覆ＢＮ基工具は、特に各種の鋼や鋳鉄などの断続切削加工を、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、ＢＮ基基体の表面に、（Ａｌ，Ｔｉ）Ｎからなる硬質被覆層を０．５〜１０μｍの全体平均層厚で物理蒸着してなる被覆ＢＮ基工具において、
上記硬質被覆層が、層厚方向にそって、Ａｌ最高含有点（Ｔｉ最低含有点）とＡｌ最低含有点（Ｔｉ最高含有点）とが所定間隔をおいて交互に繰り返し存在し、かつ前記Ａｌ最高含有点から前記Ａｌ最低含有点、前記Ａｌ最低含有点から前記Ａｌ最高含有点へＡｌ（Ｔｉ）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Ａｌ最高含有点が、組成式：（Ａｌ_XＴｉ_1-X）Ｎ（ただし、原子比で、Ｘは０．６０〜０．８５を示す）、
上記Ａｌ最低含有点が、組成式：（Ａｌ_YＴｉ_1-Y）Ｎ（ただし、原子比で、Ｙは０．２５〜０．５０を示す）、
をそれぞれ満足し、かつ隣り合う上記Ａｌ最高含有点とＡｌ最低含有点の間隔が、０．０１〜０．１μmである、
断続重切削加工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ＢＮ基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ＢＮ基工具において、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）Ａｌ最高含有点の組成
（Ａｌ，Ｔｉ）Ｎ層におけるＡｌは、高強度および高靭性を有するＴｉＮ層の高温硬さおよび耐熱性（高温特性）を向上させる目的で含有するものであり、したがってＡｌ成分の含有割合が高くなればなるほど高温特性は向上したものになるが、その割合（Ｘ値）がＴｉとの合量に占める割合（原子比）で０．６０未満では所望のすぐれた高温特性を確保することができず、一方その割合が同じく０．８５を越えて高くなると、高強度および高靭性を有する（Ａｌ，Ｔｉ）Ｎ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ることから、その割合を０．６〜０．８５と定めた。
【００１０】
（ｂ）Ａｌ最低含有点の組成
上記の通りＡｌ最高含有点は高温特性のすぐれたものであるが、反面強度および靭性の劣るものであるため、このＡｌ最高含有点の強度と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Ａｌ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Ａｌの割合（Ｙ）がＴｉとの合量に占める割合（原子比）で０．５０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、一方その割合が同じく０．２５未満になると、相対的にＴｉの割合が多くなり過ぎて、Ａｌ最低含有点に所望の高温特性を具備せしめることができなくなることから、その割合を０．２５〜０．６５と定めた。
【００１１】
（ｃ）Ａｌ最高含有点とＡｌ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温特性と、強度および靭性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Ａｌ最高含有点であれば強度および靭性不足、Ａｌ最低含有点であれば高温特性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０．５μｍ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１０μｍを越えると、切刃にチッピングが発生し易くなることから、その平均層厚を０．５〜１０μｍと定めた。
【００１３】
【発明の実施の形態】
つぎに、この発明の被覆ＢＮ基工具を実施例により具体的に説明する。
原料粉末として、いずれも０．５〜４μｍの範囲内の平均粒径を有する立方晶窒化硼素（以下、ｃ−ＢＮで示す）粉末、炭化チタン（以下、ＴｉＣで示す）粉末、窒化チタン（以下、ＴｉＮで示す）粉末、炭窒化チタン（以下、ＴｉＣＮで示す）粉末、炭化タングステン（以下、ＷＣで示す）粉末、Ａｌ粉末、ＴｉとＡｌの金属間化合物粉末であるＴｉ₃Ａｌ粉末、ＴｉＡｌ粉末、およびＴｉＡｌ₃粉末、さらに組成式：Ｔｉ₂ＡｌＮを有する複合金属窒化物粉末、硼化チタン（以下、ＴｉＢ₂で示す）粉末、窒化アルミニウム（以下、ＡｌＮで示す）粉末、硼化アルミニウム（以下、ＡｌＢ₂で示す）粉末、酸化アルミニウム（Ａｌ₂Ｏ₃で示す）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の圧力で直径：５０ｍｍ×厚さ：１．５ｍｍの寸法をもった圧粉体にプレス成形し、ついでこの圧粉体を、圧力：１Ｐａの真空雰囲気中、９００〜１３００℃の範囲内の所定温度に３０分間保持の条件で焼結して切刃片用予備焼結体とし、この予備焼結体を、別途用意した、Ｃｏ：８質量％、ＷＣ：残りの組成、並びに直径：５０ｍｍ×厚さ：２ｍｍの寸法をもったＷＣ基超硬合金製支持片と重ね合わせた状態で、通常の超高圧焼結装置に装入し、通常の条件である圧力：５ＧＰａ、温度：１２００〜１４００℃の範囲内の所定温度に保持時間：０．５時間の条件で超高圧焼結し、焼結後上下面をダイヤモンド砥石を用いて研摩し、ワイヤー放電加工装置にて一辺３ｍｍの正三角形状に分割し、さらにＣｏ：５質量％、ＴａＣ：５質量％、ＷＣ：残りの組成およびＣＩＳ規格ＴＮＧＡ１６０４０８の形状（厚さ：４．７６mm×一辺長さ：１６mmの正三角形）をもったＷＣ基超硬合金製チップ本体のろう付け部（コーナー部）に、質量％で、Ｃｕ：３０％、Ｚｎ：２８％、Ｎｉ：２％、Ａｇ：残りからなる組成を有するＡｇ合金のろう材を用いてろう付けし、これに仕上げ研摩を施すことによりＢＮ基チップ基体Ａ〜Ｒをそれぞれ製造した。
【００１４】
ついで、上記のＢＮ基チップ基体Ａ〜Ｒ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所定間隔をもって設けた多段回転支持板上に載置し、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Ａｌ最低含有点形成用Ｔｉ−Ａｌ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Ａｌ最高含有点形成用Ａｌ−Ｔｉ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ＢＮ基チップ基体に−１０００Ｖの直流バイアス電圧を印加して、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ＢＮ基チップ基体表面を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、前記回転テーブル上で自転しながら回転するＢＮ基基体に−１００Ｖの直流バイアス電圧を印加して、それぞれのカソード電極(前記Ａｌ最低含有点形成用Ｔｉ−Ａｌ合金およびＡｌ最高含有点形成用Ａｌ−Ｔｉ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ＢＮ基チップ基体の表面に、層厚方向に沿って表３，４に示される目標組成のＡｌ最低含有点とＡｌ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Ａｌ最高含有点から前記Ａｌ最低含有点、前記Ａｌ最低含有点から前記Ａｌ最高含有点へＡｌ（Ｔｉ）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形成することにより、本発明被覆ＢＮ基工具１〜１８をそれぞれ製造した。
【００１５】
また、比較の目的で、上記のＢＮ基チップ基体Ａ〜Ｒの表面への硬質被覆層の形成を、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を用い、カソード電極（蒸発源）として種々の成分組成をもったＡｌ−Ｔｉ合金を装着し、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、Ａｒガスを装置内に導入して１０ＰａのＡｒ雰囲気とし、この状態でＢＮ基チップ基体に−８００ｖのバイアス電圧を印加してＢＮ基チップ基体表面をＡｒガスボンバート洗浄し、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、前記ＢＮ基チップ基体に印加するバイアス電圧を−１００Ｖに下げて、前記カソード電極とアノード電極との間にアーク放電を発生させる条件にて行なって、前記ＢＮ基チップ基体Ａ〜Ｒ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、かつ層厚方向に沿って実質的に組成変化のない（Ｔｉ，Ａｌ）Ｎ層からなる硬質被覆層を蒸着形成する以外は、上記の本発明被覆ＢＮ基工具１〜１８の製造条件と同じ条件で従来被覆ＢＮ基工具１〜１８をそれぞれ製造した。
【００１６】
つぎに、上記本発明被覆ＢＮ基工具１〜１８および従来被覆ＢＮ基工具１〜１８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・ＳＣＭ４４０の長さ方向等間隔４本縦溝入り丸棒の浸炭焼入れ材（表面硬さ：ＨＲＣ６０）、
切削速度：１５０ｍ／ｍｉｎ．、
切り込み：０．３ｍｍ、
送り：０．０７ｍｍ／ｒｅｖ．、
切削時間：２０分、
の条件での合金鋼の乾式断続高切り込み切削加工試験、
被削材：ＪＩＳ・Ｓ４５Ｃの長さ方向等間隔４本縦溝入り丸棒の高周波焼入れ材（表面硬さ：ＨＲＣ５５）、
切削速度：１５０ｍ／ｍｉｎ．、
切り込み：０．１ｍｍ、
送り：０．３ｍｍ／ｒｅｖ．、
切削時間：３０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の長さ方向等間隔４本縦溝入り丸棒、
切削速度：６００ｍ／ｍｉｎ．、
切り込み：０．５ｍｍ、
送り：０．１ｍｍ／ｒｅｖ．、
切削時間：６０分、
の条件での鋳鉄の乾式断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。
【００１７】
【表１】

【００１８】
【表２】

【００１９】
【表３】

【００２０】
【表４】

【００２１】
【表５】

【００２２】
この結果得られた本発明被覆ＢＮ基工具１〜１８を構成する硬質被覆層におけるＡｌ成分最高含有点とＡｌ成分最低含有点の組成、並びに従来来被覆ＢＮ基工具１〜１８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ＢＮ基工具１〜１８の硬質被覆層におけるＡｌ成分最高含有点とＡｌ成分不含有点間の間隔、およびこれの全体層厚、並びに従来被覆ＢＮ基工具１〜１８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。
【００２３】
【発明の効果】
表２〜５に示される結果から、硬質被覆層が層厚方向にＡｌ最低含有点とＡｌ最高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Ａｌ最高含有点から前記Ａｌ最低含有点、前記Ａｌ最低含有点から前記Ａｌ最高含有点へＡｌ（Ｔｉ）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ＢＮ基工具は、いずれも各種の鋼や鋳鉄などの断続切削加工を、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、硬質被覆層が層厚方向に沿って実質的に組成変化のない（Ｔｉ，Ａｌ）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と耐熱性を有するものの、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断続切削加工を、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ＢＮ基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ＢＮ基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 this invention, the hard coating layer has high strength and high toughness, and is excellent in high-temperature hardness and heat resistance. Therefore, particularly in intermittent cutting of various steels and cast irons, A cutting tool made of a surface-coated cubic boron nitride-based sintered material (hereinafter referred to as a coated BN-based tool) that exhibits excellent chipping resistance when subjected to heavy cutting conditions such as high feed. is there.
[0002]
[Prior art]
In general, a coated BN base tool is provided with a throwaway tip that is detachably attached to the tip of a cutting tool when turning a work material such as various steels or cast iron, or the throwaway tip is detachably attached. In addition, a slow-away end mill tool that performs a cutting process in the same manner as a solid type end mill used for chamfering, grooving, and shoulder machining is known.
[0003]
Further, as a coated BN-based tool, for example, as described in JP-A-8-119774, etc., it is extremely hard and inferior to toughness. Therefore, cutting is performed under conditions where cutting speed is high but cutting and feeding are small. A cutting tool made of cubic boron nitride-based sintered material, which has been used only for high-speed surface finishing where machining is performed, is a base (hereinafter referred to as a BN-based base), and the cutting tool itself is attached to the surface of the BN-based base. Even if continuous cutting or intermittent cutting of various steels and cast iron is performed by cutting and feeding under normal conditions with toughness added, the cutting edge will not chip or chip (fine chipping). purposes, composition formula _{_{to: (Al Z Ti 1-Z}} ) N ( provided that an atomic ratio, Z is shows the 0.60 to 0.85) composite nitride of Al and Ti satisfying the following ( Al, Ti) N ] It is coated BN group tool formed by physical vapor deposition of hard coating layer with an average layer thickness of 0.5~10μm consisting layer are known.
[0004]
Further, the above-mentioned coated BN-based tool is, for example, the above-mentioned BN-based substrate is loaded into an arc ion plating apparatus which is one type of physical vapor deposition apparatus schematically shown in FIG. For example, in the state heated to a temperature of 500 ° C., an arc discharge is generated between the anode electrode and the cathode electrode (evaporation source) in which an Al—Ti alloy having a predetermined composition is set, for example, under a current of 90 A, At the same time, nitrogen gas is introduced into the apparatus as a reaction gas to form a reaction atmosphere of, for example, 2 Pa. On the other hand, the BN base substrate is subjected to, for example, a −250 V bias voltage on the surface thereof. It is also known that it is produced by vapor-depositing a hard coating layer composed of an (Al, Ti) 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. Although there is no problem when using the above conventional coated carbide tools under normal cutting conditions, the above-mentioned conventional coated cemented carbide tools have a high cutting depth and high feed with high mechanical impact. When heavy cutting conditions such as the above are used, chipping (microcracking) is likely to occur due to insufficient 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 BN-based tool in order to develop a coated BN-based tool that exhibits excellent chipping resistance with a hard coating layer particularly in intermittent heavy cutting. As a result of conducting research with a focus on the hard coating layer,
(A) The (Al, Ti) N layer constituting the conventional coated BN-based tool formed using the arc ion plating apparatus shown in FIG. 2 has a substantially uniform composition throughout the layer thickness. Therefore, for example, the arc ion plating apparatus having the structure shown in the schematic plan view of FIG. 1A and the schematic front view of FIG. A BN-based substrate mounting rotary table is provided in the part, and an Al—Ti alloy with a relatively high Al content (low Ti content) is placed on one side and Ti is contained on the other side across the turntable. Using an arc ion plating apparatus in which a high amount (low Al content) Ti—Al alloy is used as a cathode electrode (evaporation source) and facing each other, a plurality of BN bases are provided along the outer periphery of the rotary table of the apparatus The In this state, the atmosphere inside the apparatus is changed to a nitrogen atmosphere, the rotary table is rotated, and the BN base substrate itself is rotated for the purpose of uniforming the thickness of the hard coating layer formed by vapor deposition. When an arc discharge is generated between the cathode electrode (evaporation source) and the anode electrode on both sides of the substrate to form an (Al, Ti) N layer on the surface of the BN base, the resulting (Al, Ti) N In the layer, the BN-based substrate arranged in a ring shape on the rotary table is a cathode electrode (evaporation source) of the Al—Ti alloy having a relatively high Al content (low Ti content) on the one side. The point where the highest Al content point is formed in the layer at the time closest to the layer, and the BN-based substrate is a cathode electrode of Ti-Al alloy having a relatively high Ti content (low Al content) on the other side. Closest to At the time, the lowest Al content point is formed in the layer, and by rotating the rotary table, the highest Al content point and the lowest Al content point appear alternately in the layer thickness direction along the layer thickness direction, and It has a component concentration distribution structure in which the Al (Ti) content continuously changes from the Al highest content point to the Al lowest content point, and from the Al lowest content point to the Al highest content point.
[0007]
(B) In the (Al, Ti) N layer having the repeated continuous change component concentration distribution structure of (a) above, for example, the respective compositions of the cathode electrode (evaporation source) arranged opposite to each other are prepared, and a BN base is mounted. Control the rotation speed of the rotating table
The Al highest content point is the composition formula: (Al _x Ti _1-x ) N (wherein X is 0.60 to 0.85 in atomic ratio),
The Al minimum content point is a composition formula: (Al _Y Ti _1-Y ) N (however, Y is 0.25 to 0.50 in atomic ratio),
And the interval in the thickness direction between the adjacent Al highest content point and Al lowest content point adjacent to each other is 0.01 to 0.1 μm,
The Al highest content point part shows excellent high temperature hardness and heat resistance (high temperature characteristics) corresponding to the high temperature hardness and heat resistance of the conventional (Al, Ti) N layer, while the Al minimum content point part has In addition, since the Al content is low and the Ti content is high compared to the Al highest content point portion, high strength and high toughness are ensured, and the interval between the Al highest content point and the Al lowest content point is increased. Since it has been made extremely small, it has excellent strength and toughness while maintaining excellent high temperature characteristics as the characteristics of the entire layer. Therefore, from the (Ti, Al) N layer having such a structure, a hard coating layer is provided. The coated BN-based tool has an excellent hard coating layer even when intermittent cutting of various steels and cast iron is performed under heavy cutting conditions such as high cutting with high mechanical impact and high feed. Chippin To become able to exert sex.
The research results shown in (a) and (b) above were obtained.
[0008]
The present invention has been made on the basis of the above research results, and a physical coating of a hard coating layer made of (Al, Ti) N with a total average layer thickness of 0.5 to 10 μm on the surface of a BN-based substrate. In the coated BN base tool,
In the hard coating layer, the Al highest content point (Ti lowest content point) and the Al lowest content point (Ti highest content point) are alternately present at predetermined intervals along the layer thickness direction, and the Al A component concentration distribution structure in which the Al (Ti) content continuously changes from the highest content point to the Al lowest content point, from the lowest Al content point to the highest Al content point,
Furthermore, the Al highest content point is the composition formula: (Al _X Ti _1-X ) N (however, X is 0.60 to 0.85 in atomic ratio),
The Al minimum content point is a composition formula: (Al _Y Ti _1-Y ) N (however, Y is 0.25 to 0.50 in atomic ratio),
And the interval between the adjacent Al highest content point and Al lowest content point adjacent to each other is 0.01 to 0.1 μm.
This is characterized by a coated BN-based tool that exhibits excellent chipping resistance with a hard coating layer in intermittent heavy cutting.
[0009]
Next, the reason why the configuration of the hard coating layer constituting the coated BN-based tool of the present invention is limited as described above.
(A) Composition of Al highest content point (Al, Ti) Al in the N layer is contained for the purpose of improving the high temperature hardness and heat resistance (high temperature characteristics) of the TiN layer having high strength and high toughness. Therefore, the higher the content ratio of the Al component, the higher the high temperature characteristics. However, when the ratio (X value) is less than 0.60 in terms of the ratio (atomic ratio) to the total amount with Ti, the desired superiority is obtained. However, if the ratio is also higher than 0.85, even if (Al, Ti) N points having high strength and high toughness are present adjacent to each other, the layer itself Decrease in strength and toughness is unavoidable, and as a result, chipping and the like are likely to occur. Therefore, the ratio is set to 0.6 to 0.85.
[0010]
(B) Composition of the lowest Al content point As described above, the highest Al content point has excellent high-temperature characteristics, but on the other hand, it is inferior in strength and toughness. For this purpose, the Al content is high, and the Al minimum content points that have high strength and high toughness are alternately interposed in the thickness direction. Therefore, the Al content (Y) is the same as that of Ti. If the ratio (atomic ratio) in the amount exceeds 0.50, the desired excellent strength and toughness cannot be ensured. On the other hand, if the ratio is also less than 0.25, the ratio of Ti is relatively high. The ratio is set to 0.25 to 0.65 because it becomes too large to provide desired high temperature characteristics at the Al minimum content point.
[0011]
(C) Interval between the highest Al content point and the lowest Al content point If the distance is less than 0.01 μm, it is difficult to clearly form each point with the above composition. The strength and toughness cannot be ensured, and when the distance exceeds 0.1 μm, the disadvantages of the respective points, that is, when the Al maximum content point is insufficient, the strength and toughness are insufficient, and when the Al minimum content point is high, the temperature is high. Insufficient characteristics appear locally in the layer, which makes it easier for chipping to occur on the cutting edge and promotes the progress of wear, so the interval was set to 0.01 to 0.1 μm. .
[0012]
(D) Overall average layer thickness of hard coating layer If the layer thickness is less than 0.5 μm, the desired wear resistance cannot be ensured. On the other hand, if the average layer thickness exceeds 10 μm, chipping occurs on the cutting edge. Since it becomes easy to generate | occur | produce, the average layer thickness was determined to be 0.5-10 micrometers.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, the coated BN-based tool of the present invention will be specifically described with reference to examples.
As raw material powders, cubic boron nitride (hereinafter referred to as c-BN) powder, titanium carbide (hereinafter referred to as TiC) powder, titanium nitride (hereinafter referred to as “c-BN”) having an average particle diameter in the range of 0.5 to 4 μm. , TiN) powder, titanium carbonitride (hereinafter referred to as TiCN) powder, tungsten carbide (hereinafter referred to as WC) powder, Al powder, Ti ₃ Al intermetallic compound powder of Ti and Al, TiAl powder , And TiAl ₃ powder, further a composite metal nitride powder having a composition formula: Ti ₂ AlN, titanium boride (hereinafter referred to as TiB ₂ ) powder, aluminum nitride (hereinafter referred to as AlN) powder, aluminum boride (hereinafter referred to as “TiB _2” ) , AlB ₂ ) powder and aluminum oxide (Al ₂ O ₃ ) powder were prepared, and these raw material powders were blended into the blending composition shown in Table 1 and wetted in a ball mill for 72 hours After mixing and drying, the green compact was pressed into a green compact having a diameter of 50 mm × thickness: 1.5 mm at a pressure of 100 MPa, and then the green compact was 900 in a vacuum atmosphere at a pressure of 1 Pa. Sintered at a predetermined temperature within a range of ˜1300 ° C. for 30 minutes to obtain a pre-sintered body for a cutting edge piece. This pre-sintered body was prepared separately, Co: 8 mass%, WC: remaining And a pressure of the normal conditions under the condition of a super-high pressure sintering apparatus in a state of being superposed on a support piece made of a WC-based cemented carbide having a diameter of 50 mm × thickness: 2 mm. : 5 GPa, temperature: 1200 ° C. to 1400 ° C. Predetermined temperature: Holding time: 0.5 hours under high pressure sintering, after sintering, the upper and lower surfaces are polished with a diamond grindstone, wire electric discharge machine Is divided into equilateral triangles with a side of 3 mm, and Co: 5% by mass, TaC: 5% by mass, WC: remaining composition and WC-based cemented carbide chip body with the shape of CIS standard TNGA160408 (thickness: 4.76 mm × one side length: 16 mm regular triangle) The brazing part (corner part) is brazed using a brazing material of an Ag alloy having a composition of Cu: 30%, Zn: 28%, Ni: 2%, and Ag: the remainder in mass%. BN-based chip bases A to R were manufactured by finishing polishing.
[0014]
Next, each of the above BN-based chip bases A to R is ultrasonically cleaned in acetone and dried, and is then placed on the rotary table in the arc ion plating apparatus shown in FIG. Placed on a multi-stage rotating support plate provided at intervals, as a cathode electrode (evaporation source) on one side, Ti-Al alloy for forming the lowest Al content point with various component compositions, cathode electrode on the other side (evaporation) As a source), Al-Ti alloys for forming the highest Al content point with various component compositions are arranged opposite to each other across the rotary table, and a bombard cleaning metal Ti is also mounted. While maintaining a vacuum of 5 Pa or less, the inside of the apparatus is heated to 500 ° C. with a heater, and then the DC bias voltage of −1000 V is applied to the BN-based chip substrate that rotates while rotating on the rotary table. Is applied, and a current of 100 A is caused to flow between the metal Ti of the cathode electrode and the anode electrode to generate an arc discharge, thereby cleaning the surface of the BN-based chip substrate with Ti bombardment, and then nitrogen as a reactive gas in the apparatus. A gas is introduced to form a reaction atmosphere of 2 Pa, and a DC bias voltage of −100 V is applied to a BN base substrate that rotates while rotating on the rotary table, so that each cathode electrode (for forming the Al minimum content point) is applied. An arc discharge is generated by flowing a current of 100 A between the Ti-Al alloy and the Al-Ti alloy for forming the highest Al content point) and the anode electrode, and thus along the layer thickness direction on the surface of the BN-based chip substrate. The Al minimum content point and the Al maximum content point of the target composition shown in Tables 3 and 4 are alternately present at the target intervals shown in Tables 3 and 4 alternately, and It has a component concentration distribution structure in which the Al (Ti) content continuously changes from the Al highest content point to the Al lowest content point, from the Al lowest content point to the Al highest content point, and also Tables 3 and 4 The coated BN-based tools 1 to 18 of the present invention were manufactured by vapor-depositing a hard coating layer having a target overall layer thickness shown in FIG.
[0015]
For the purpose of comparison, the hard coating layer is formed on the surfaces of the BN-based chip substrates A to R in various ways as a cathode electrode (evaporation source) using a normal arc ion plating apparatus shown in FIG. The Al-Ti alloy having the composition of the above is mounted, the inside of the apparatus is evacuated and the inside of the apparatus is heated to 500 ° C. while maintaining a vacuum of 0.5 Pa or less, and then Ar gas is introduced into the apparatus In this state, a bias voltage of −800 V is applied to the BN-based chip substrate to clean the surface of the BN-based chip substrate with Ar gas bombardment, and nitrogen gas is introduced as a reaction gas into the apparatus. While the reaction atmosphere is 2 Pa, the bias voltage applied to the BN-based chip substrate is lowered to −100 V to generate an arc discharge between the cathode electrode and the anode electrode. The target compositions and target layer thicknesses shown in Tables 5 and 6 are provided on the respective surfaces of the BN-based chip bases A to R, and the composition changes substantially along the layer thickness direction. The conventional coated BN base tools 1 to 18 were manufactured under the same conditions as the manufacturing conditions of the above-described coated BN base tools 1 to 18 except that a hard coating layer composed of a non- (Ti, Al) N layer was formed by vapor deposition. .
[0016]
Next, for the above-described coated BN base tools 1 to 18 and the conventional coated BN base tools 1 to 18, in a state where this is screwed to the tip of the tool steel tool with a fixing jig,
Work material: Carburized and hardened material (surface hardness: HRC60) of four fluted round bars at equal intervals in the length direction of JIS / SCM440
Cutting speed: 150 m / min. ,
Cutting depth: 0.3 mm,
Feed: 0.07 mm / rev. ,
Cutting time: 20 minutes,
Dry interrupted high cut cutting test of alloy steel under the conditions of
Work material: Induction hardened material (surface hardness: HRC55) of round bars with four longitudinal grooves at equal intervals in the length direction of JIS / S45C,
Cutting speed: 150 m / min. ,
Incision: 0.1 mm,
Feed: 0.3 mm / rev. ,
Cutting time: 30 minutes,
Carbon steel dry and intermittent high feed cutting test under the conditions of
Work material: JIS / FC300 lengthwise equidistant 4 bars with vertical grooves,
Cutting speed: 600 m / min. ,
Cutting depth: 0.5mm,
Feed: 0.1 mm / rev. ,
Cutting time: 60 minutes,
The dry interrupted 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.
[0017]
[Table 1]

[0018]
[Table 2]

[0019]
[Table 3]

[0020]
[Table 4]

[0021]
[Table 5]

[0022]
The composition of the Al component highest content point and the Al component lowest content point in the hard coating layer constituting the coated BN base tool 1-18 of the present invention obtained as a result, and the conventional hard coating layer of the coated BN base tool 1-18 When the composition was measured using an Auger spectroscopic analyzer, each showed substantially the same composition as the target composition.
In addition, the distance between the Al component highest content point and the Al component non-contained point in the hard coating layer of these coated BN base tools 1 to 18 of the present invention, the overall layer thickness thereof, and the conventional coated BN base tools 1 to 18 When the cross section of the thickness of the hard coating layer was measured using a scanning electron microscope, all showed substantially the same value as the target value.
[0023]
【The invention's effect】
From the results shown in Tables 2 to 5, in the hard coating layer, the lowest Al content point and the highest Al content point are repeatedly present at predetermined intervals in the thickness direction, and the lowest Al content from the highest Al content point. The present invention-coated BN-based tool having a component concentration distribution structure in which the Al (Ti) content continuously changes from the content point, the Al minimum content point to the Al maximum content point, is a variety of steel, cast iron, etc. Even when interrupted cutting is performed under heavy cutting conditions such as high cutting with high mechanical impact and high feed, the hard coating layer exhibits excellent chipping resistance, whereas the hard coating layer is a layer. In a conventional coated carbide tool composed of a (Ti, Al) N layer that does not substantially change in composition along the thickness direction, the hard coating layer has excellent high-temperature hardness and heat resistance, but is inferior in strength and toughness. To be Mappings occurs, this is apparent that lead to a relatively short time service life due.
As described above, the coated cemented carbide tool of the present invention is not only for cutting under normal conditions, but also for intermittent cutting of various steels and cast iron, in particular, high cutting and high feed with high mechanical impact. Even when performed under heavy cutting conditions such as the above, it exhibits excellent chipping resistance and excellent wear resistance over a long period of time. It is possible to cope with the above sufficiently.
[Brief description of the drawings]
FIG. 1 shows an arc ion plating apparatus used for forming a hard coating layer constituting a coated BN-based 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 for forming a hard coating layer constituting a conventional coated BN-based tool.

Claims

Surface-coated cubic boron nitride- based sintered body obtained by physical vapor deposition of a hard coating layer made of a composite nitride of Al and Ti on the surface of a cubic boron nitride-based sintered material base with an overall average layer thickness of 0.5 to 10 μm. In the cutting tool made of binder material ,
In the hard coating layer, the Al highest content point (Ti lowest content point) and the Al lowest content point (Ti highest content point) are alternately present at predetermined intervals along the layer thickness direction, and the Al A component concentration distribution structure in which the Al (Ti) content continuously changes from the highest content point to the Al lowest content point, from the lowest Al content point to the highest Al content point,
Furthermore, the Al highest content point is the composition formula: (Al _X Ti _1-X ) N (however, X is 0.60 to 0.85 in atomic ratio),
The Al minimum content point is a composition formula: (Al _Y Ti _1-Y ) N (however, Y is 0.25 to 0.50 in atomic ratio),
And the interval between the Al highest content point and the Al lowest content point adjacent to each other is 0.01 to 0.1 μm,
A cutting tool made of a surface-coated cubic boron nitride-based sintered material that exhibits excellent chipping resistance with a hard coating layer in intermittent heavy cutting characterized by