JP3956390B2

JP3956390B2 - Surface coated high speed tool steel gear cutting tool with excellent wear resistance with hard coating layer in high speed gear cutting

Info

Publication number: JP3956390B2
Application number: JP2003000801A
Authority: JP
Inventors: 浩一前田; 裕介田中
Original assignee: Mitsubishi Materials Corp
Current assignee: Mitsubishi Materials Corp
Priority date: 2003-01-07
Filing date: 2003-01-07
Publication date: 2007-08-08
Anticipated expiration: 2023-01-07
Also published as: JP2004209608A

Description

【０００１】
【発明の属する技術分野】
この発明は、硬質被覆層がすぐれた高温特性を有し、したがって特に各種の鋼や鋳鉄などの高熱発生を伴う高速歯切加工で、すぐれた耐摩耗性を発揮する表面被覆高速度工具鋼製歯切工具（以下、被覆歯切工具という）に関するものである。
【０００２】
【従来の技術】
従来、一般に自動車や航空機、さらに各種駆動装置などの構造部材として各種歯車が用いられ、これら歯車の歯形の歯切加工に、ソリッドホブ（例えば図３の概略斜視図参照）やピニオンカッタ（例えば図４の概略斜視図参照）、さらにシェービングカッタなどの歯切工具が用いられている。
【０００３】
また、被覆歯切工具として、例えば図３や図４に示される形状に機械加工された高速度工具鋼で構成された歯切工具本体を基体とし、この基体の表面に、組成式：（Ａｌ_1-YＴｉ_Y）Ｎ（ただし、原子比で、Ｙは０．３５〜０．６０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１〜１０μｍの平均層厚で物理蒸着してなる被覆歯切工具が提案され、前記硬質被覆層を構成する（Ａｌ，Ｔｉ）Ｎ層が、Ａｌによる高温硬さと耐熱性、およびＴｉによる強度を有することから、かかる硬質被覆層を形成してなる被覆歯切工具はすぐれた歯切性能を発揮することも知られている（例えば特許文献１および特許文献２参照）。
【０００４】
さらに、上記の被覆歯切工具が、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基体を装入し、ヒータで装置内を、例えば雰囲気を２Ｐａの真空雰囲気として、４００℃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、例えば電圧：３５Ｖ、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、一方上記基体（歯切工具本体）には、例えば−２００Ｖのバイアス電圧を印加した条件で、前記基体の表面に、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】
【特許文献１】
特許第２７９３７７２号
【特許文献２】
特許第３１６５６５８号
【０００６】
【発明が解決しようとする課題】
近年の歯切加工装置の高性能化はめざましく、一方で歯切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、歯切加工は高速化の傾向にあるが、上記の従来被覆歯切工具においては、これを通常の歯切加工条件で用いた場合には問題はないが、これを高い発熱を伴う高速歯切加工条件で用いた場合には、硬質被覆層の摩耗進行が促進され、比較的短時間で使用寿命に至るのが現状である。
【０００７】
【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、特に高速歯切加工ですぐれた耐摩耗性を発揮する被覆歯切工具を開発すべく、上記の従来被覆歯切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歯切工具を構成する（Ａｌ，Ｔｉ）Ｎ層は、層厚全体に亘って均質な高温硬さと耐熱性、および強度を有するが、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Ａｌ−Ｔｉ合金、他方側に相対的にＡｌ含有量の低いＡｌ−Ｔｉ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上の中心軸から半径方向に所定距離離れた位置にテーブルの外周部に沿って複数の基体（歯切工具本体）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基体が上記の一方側の相対的にＡｌ含有量の高い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、また前記基体が上記の他方側の相対的にＡｌ含有量の低いＡｌ−Ｔｉ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。
【０００８】
（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、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_1-XＴｉ_X）Ｎ（ただし、原子比で、Ｘは０．０５〜０．３０を示す）、
上記Ａｌ最低含有点が、組成式：（Ａｌ_1-YＴｉ_Y）Ｎ（ただし、原子比で、Ｙは０．３５〜０．６０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層に比してＡｌ含有量が相対的に高くなることから、より一段とすぐれた高温硬さと耐熱性（高温特性）を示し、一方上記Ａｌ最低含有点部分は、上記の従来（Ａｌ，Ｔｉ）Ｎ層ののもつ組成に相当する組成、すなわち前記Ａｌ最高含有点部分に比してＡｌ含有量が低く、Ｔｉ含有量の高い組成をもつので、相対的に高強度を具備するようになり、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高強度を保持した状態ですぐれた高温特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（Ａｌ，Ｔｉ）Ｎ層からなる被覆歯切工具は、高い発熱を伴う高速歯切加工ですぐれた耐摩耗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。
【０００９】
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、装置中央部に高速度工具鋼で構成された歯切工具本体からなる基体の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Ａｌ最高含有点形成用Ａｌ−Ｔｉ合金、他方側にＡｌ最低含有点形成用Ａｌ−Ｔｉ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、前記回転テーブルの外周部に沿って複数の前記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、前記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、前記基体の表面に、（Ａｌ，Ｔｉ）Ｎ層からなる硬質被覆層を１〜１０μｍの全体平均層厚で蒸着してなる被覆歯切工具にして、
上記硬質被覆層が、層厚方向にそって、Ａｌ最高含有点とＡｌ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_1-XＴｉ_X）Ｎ（ただし、原子比で、Ｘは０．０５〜０．３０を示す）、
上記Ａｌ最低含有点が、
組成式：（Ａｌ_1-YＴｉ_Y）Ｎ（ただし、原子比で、Ｙは０．３５〜０．６０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、
高速歯切加工で硬質被覆層がすぐれた耐摩耗性を発揮する被覆歯切工具に特徴を有するものである。
【００１０】
つぎに、この発明の被覆歯切工具において、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、高温硬さおよび耐熱性（高温特性）を向上させ、かつＴｉは強度を向上させる作用を有するものであり、したがってＡｌ最高含有点でのＴｉの割合を示すＸ値がＡｌとの合量に占める割合（原子比）で０．０５未満になると、Ｔｉの割合が低くなり過ぎて、急激に強度が低下し、切刃にチッピング（微小欠け）などが発生し易くなり、一方同Ｘ値が０．３０を越えると、相対的にＡｌの割合が低下し、Ａｌによってもたらされるすぐれた高温特性に低下傾向が現れるようになり、特に高速歯切加工では摩耗促進の原因となることから、その割合を０．０５〜０．３０と定めた。
【００１１】
（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、反面強度の劣るものであるため、このＡｌ最高含有点の強度不足を補う目的で、相対的にＴｉ含有割合が高く、これによって高強度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Ｔｉの割合を示すＹ値がＡｌとの合量に占める割合（原子比）で０．３５未満では、所望のすぐれた強度を確保することができず、一方その割合を示すＹ値が０．６０を越えると、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０．３５〜０．６０と定めた。
【００１２】
（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。
【００１３】
（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１〜１０μｍと定めた。
【００１４】
【発明の実施の形態】
つぎに、この発明の被覆歯切工具を実施例により具体的に説明する。
（実施例１）
歯切工具本体として、材質がＪＩＳ・ＳＫＨ５５および同ＳＫＨ５１の高速度工具鋼からなる直径：８５ｍｍ×長さ：１２５ｍｍの寸法をもった素材から、機械加工にて外径：８０ｍｍ×長さ：１２０ｍｍの全体寸法をもち、かつ４条右捩れ×２０溝の形状をもった図３に概略斜視図で示されるソリッドホブを製造した。
【００１５】
ついで、上記の２種の材質の歯切工具本体（ソリッドホブ）を基体とし、これらの基体のそれぞれを、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の中心軸から半径方向に所定距離離れた位置にテーブルの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Ａｌ最低含有点形成用Ａｌ−Ｔｉ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４００℃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前記基体に−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、もって前記基体表面を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１０Ｐａ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前記基体に−１００Ｖの直流バイアス電圧を印加し、かつそれぞれのカソード電極(前記Ａｌ最低含有点形成用Ａｌ−Ｔｉ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、もって前記基体の表面に、層厚方向に沿って表１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１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１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、本発明被覆歯切工具１〜６をそれぞれ製造した。
【００１６】
また、比較の目的で、上記の２種類の材質の基体（歯切工具本体）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Ａｌ−Ｔｉ合金（本願発明の上記のＡｌ最低含有点形成用Ａｌ−Ｔｉ合金に相当するＡｌ−Ｔｉ合金）を装着し、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４００℃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前記基体に−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、もって前記基体表面を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１０Ｐａ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前記基体に−１００Ｖの直流バイアス電圧を印加し、かつそれぞれのカソード電極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、もって前記基体の表面に、表２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（Ａｌ，Ｔｉ）Ｎ層からなる硬質被覆層を蒸着することにより、従来被覆歯切工具１〜６をそれぞれ製造した。
【００１７】
つぎに、上記の本発明被覆歯切工具１〜６および従来被覆歯切工具１〜６を用いて、材質がＪＩＳ・ＳＣｒ４２０Ｈの低合金鋼にして、モジュール：１．７５、圧力角：１７．５度、歯数：３３、ねじれ角：３６度左捩れ、歯丈：５．３６ｍｍ、歯幅：１５．５ｍｍの寸法および形状をもった歯車の加工を、
切削速度（回転速度）：２５０ｍ／ｍｉｎ、
送り：２．５ｍｍ／ｒｅｖ、
加工形態：クライム、シフトなし、ドライ（エアーブロー）、
の条件で高速歯切加工（上記の材質がＪＩＳ・ＳＣｒ４２０Ｈの低合金鋼歯車の加工の場合の切削速度は通常１５０ｍ／ｍｉｎ）で行い、逃げ面摩耗幅が０．２ｍｍに至るまでの歯車加工数を測定した。この測定結果を表１，２それぞれに示した。
【００１８】
（実施例２）
また、歯切工具本体として、同じく材質がＪＩＳ・ＳＫＨ５５および同ＳＫＨ５１の高速度工具鋼からなる外径：１５０ｍｍ×厚さ：２５ｍｍの寸法をもった素材から、機械加工にてピッチ円直径：１００ｍｍ×厚さ：２２ｍｍの全体寸法をもち、かつカッタ歯数：４０の形状をもった図４に概略斜視図で示されるディスク型ピニオンカッタ（ＪＩＳ・Ｂ・４３５６記載の１００形）を製造した。
【００１９】
ついで、上記の歯切工具本体（ピニオンカッタ）を基体とし、これらの基体の表面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１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１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１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、本発明被覆歯切工具７〜１２をそれぞれ製造した。
【００２０】
また、比較の目的で、上記の歯切工具本体（ピニオンカッタ）の基体を、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２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（Ａｌ，Ｔｉ）Ｎ層からなる硬質被覆層を蒸着することにより、従来被覆歯切工具７〜１２をそれぞれ製造した。
【００２１】
つぎに、上記の本発明被覆歯切工具７〜１２および従来被覆歯切工具７〜１２を用いて、材質がＪＩＳ・ＳＣｒ４２０Ｈの低合金鋼にして、モジュール：２．５、圧力角：２０度、歯数：３６、歯幅：２５ｍｍの寸法および形状をもった歯車の加工を、
ストローク数：１０００ストローク／ｍｉｎ、
円周送り：０．５ｍｍ／ストローク、
半径送り：０．０２ｍｍ／ストローク、
の条件で高速歯切加工（上記の材質がＪＩＳ・ＳＣｒ４２０Ｈの低合金鋼歯車の加工の場合のストローク数は通常６００ストローク／ｍｉｎ）で行い、逃げ面摩耗幅が０．２ｍｍに至るまでの歯車加工数を測定した。この測定結果を表１，２にそれぞれ示した。
【００２２】
【表１】

【００２３】
【表２】

【００２４】
この結果得られた本発明被覆歯切工具１〜１２および従来被覆歯切工具１〜１２を構成する硬質被覆層について、厚さ方向に沿ってオージェ分光分析装置を用いてＡｌおよびＴｉの含有量を測定した。これらの測定結果から、本発明被覆歯切工具１〜１２の硬質被覆層では、厚さ方向に沿って目標組成と実質的に同じ組成を有するＡｌ最高含有点とＡｌ最低含有点とが目標間隔と実質的に同じ間隔で交互に存在し、かつ硬質被覆層の全体平均層厚も目標全体層厚と実質的に同じ値を示し、さらに前記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含有量が連続的に変化する成分濃度分布構造をもつことも確認された。一方従来被覆歯切工具１〜１２の硬質被覆層においては、厚さ方向に沿って組成変化が見られず、かつ目標組成と実質的に同じ組成および目標全体層厚と実質的に同じ全体平均層厚を示すことが確認された。
【００２５】
【発明の効果】
表１，２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歯切工具１〜１２は、いずれも鋼製歯車の歯切加工を、高い発熱を伴う高速歯切加工条件で行なった場合にも、硬質被覆層がすぐれた耐摩耗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（Ａｌ，Ｔｉ）Ｎ層からなる従来被覆歯切工具１〜１２においては、高温を伴う高速歯切加工では高温特性不足が原因で切刃の摩耗進行が速く、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、この発明の被覆歯切工具は、通常の条件での歯切加工は勿論のこと、特に各種の鋼製歯車などの歯切加工を、高い発熱を伴う高速条件で行なった場合にも、硬質被覆層がすぐれた耐摩耗性を発揮し、長期に亘ってすぐれた性能を示すものであるから、歯切加工装置の高性能化、並びに歯切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】この発明の被覆歯切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】従来被覆歯切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。
【図３】ソリッドホブの概略斜視図である。
【図４】ディスク型ピニオンカッタの概略斜視図である。[0001]
BACKGROUND OF THE INVENTION
This invention is made of a surface-coated high-speed tool steel that has excellent high-temperature characteristics, and therefore exhibits excellent wear resistance especially in high-speed gear cutting with high heat generation such as various steels and cast iron. The present invention relates to a gear cutting tool (hereinafter referred to as a coated gear cutting tool).
[0002]
[Prior art]
Conventionally, various gears are generally used as structural members for automobiles, aircrafts, and various drive devices. For gear cutting of these gear teeth, a solid hob (for example, see the schematic perspective view of FIG. 3) or a pinion cutter (for example, FIG. 4). In addition, a cutting tool such as a shaving cutter is used.
[0003]
Further, as a coated gear cutting tool, for example, a gear cutting tool body made of high-speed tool steel machined to the shape shown in FIG. 3 or FIG. 4 is used as a base, and a composition formula: (Al _1-Y Ti _Y ) From an Al / Ti composite nitride [hereinafter referred to as (Al, Ti) N] layer satisfying N (wherein Y represents 0.35 to 0.60 in atomic ratio) A coated cutting tool formed by physically vapor-depositing a hard coating layer having an average layer thickness of 1 to 10 μm is proposed, and the (Al, Ti) N layer constituting the hard coating layer has high-temperature hardness and heat resistance due to Al, It is also known that a coated cutting tool formed with such a hard coating layer exhibits excellent gear cutting performance because it has strength due to Ti and Ti (see, for example, Patent Document 1 and Patent Document 2).
[0004]
Further, the above-described coated cutting tool is loaded with the above-mentioned substrate in an arc ion plating apparatus, which is one of physical vapor deposition apparatuses schematically shown in FIG. Is heated at a temperature of 400 ° C. under a vacuum atmosphere of 2 Pa, for example, voltage: 35 V, current: between the anode electrode and the cathode electrode (evaporation source) on which an Al—Ti alloy having a predetermined composition is set. An arc discharge is generated under the condition of 90 A, and simultaneously, nitrogen gas is introduced into the apparatus as a reaction gas to create a reaction atmosphere of 2 Pa, for example. It is also known that it is produced by vapor-depositing a hard coating layer composed of the (Al, Ti) N layer on the surface of the substrate under the applied conditions.
[0005]
[Patent Document 1]
Patent No. 2793772 [Patent Document 2]
Japanese Patent No. 3165658 [0006]
[Problems to be solved by the invention]
In recent years, the performance of gear cutting machines has been remarkably improved. On the other hand, there is a strong demand for labor saving and energy saving and further cost reduction for gear cutting, and with this, gear cutting has a tendency to increase in speed. In the above conventional coated gear cutting tool, there is no problem when it is used under normal gear cutting conditions, but when it is used under high speed gear cutting conditions with high heat generation, a hard coating layer is used. The progress of wear is promoted and the service life is reached in a relatively short time.
[0007]
[Means for Solving the Problems]
In view of the above, the present inventors have developed a hard coating that constitutes the above-described conventional coated gear cutting tool in order to develop a coated gear cutting tool that exhibits excellent wear resistance particularly in high-speed gear cutting. As a result of conducting research focusing on the layer,
(A) The (Al, Ti) N layer constituting the conventional coated cutting tool formed by using the arc ion plating apparatus shown in FIG. 2 has a uniform high-temperature hardness and heat resistance throughout the entire thickness. For example, an arc ion plating apparatus having a structure shown in a schematic plan view in FIG. 1A and a schematic front view in FIG. An Al-Ti alloy having a relatively high Al content on one side and an Al-Ti alloy having a relatively low Al content on the other side as cathode electrodes (evaporation sources) across the rotary table The arc ion plating apparatus is used, and a plurality of base bodies (gear cutting tool main bodies) are formed in a ring shape along the outer periphery of the table at a predetermined distance in the radial direction from the central axis on the rotary table of the apparatus. In this state, the cathode inside the apparatus is rotated while the rotary table is rotated with the atmosphere inside the apparatus as a nitrogen atmosphere, and the substrate itself is rotated for the purpose of uniformizing the thickness of the hard coating layer formed by vapor deposition. When an arc discharge is generated between the (evaporation source) and the anode electrode to form an (Al, Ti) N layer on the surface of the substrate, the resulting (Al, Ti) N layer is on the turntable. When the substrate arranged in a ring shape is closest to the cathode electrode (evaporation source) of the Al-Ti alloy having a relatively high Al content on one side, the highest Al content point is formed in the layer. In addition, when the substrate is closest to the cathode electrode of the Al—Ti alloy having a relatively low Al content on the other side, an Al minimum content point is formed in the layer, and the rotation of the rotary table causes the layer to be contained in the layer. And the Al highest content point and the Al lowest content point alternately appear at predetermined intervals along the layer thickness direction, the Al highest content point to the Al lowest content point, the Al lowest content point to the Al highest content point To have a component concentration distribution structure in which the Al content changes continuously.
[0008]
(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 electrodes (evaporation sources) arranged opposite to each other are prepared, and the substrate is mounted. Control the rotation speed of the rotary table,
The Al highest content point is the composition formula: (Al _1-X Ti _X ) N (wherein X is 0.05 to 0.30 in atomic ratio),
The Al minimum content point is a composition formula: (Al _1-Y Ti _Y ) N (where Y represents 0.35 to 0.60 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,
In the Al highest content point portion, the Al content is relatively higher than that of the conventional (Al, Ti) N layer, and thus exhibits a higher temperature hardness and heat resistance (high temperature characteristics). On the other hand, the Al minimum content point portion is a composition corresponding to the composition of the conventional (Al, Ti) N layer, that is, the Al content is lower and the Ti content is higher than the Al maximum content point portion. Since it has a composition, it has relatively high strength, and the distance between these Al highest content point and Al minimum content point has been made extremely small. Therefore, a coated gear cutting tool consisting of an (Al, Ti) N layer with a hard coating layer exhibits excellent wear resistance in high-speed gear cutting with high heat generation. To become
The research results shown in (a) and (b) above were obtained.
[0009]
The present invention has been made on the basis of the above research results, and is provided with a rotary table for mounting a base made of a gear cutting tool body made of high-speed tool steel at the center of the apparatus, and sandwiching the rotary table The arc ion plating apparatus in which the Al—Ti alloy for forming the highest Al content point on one side and the Al—Ti alloy for forming the lowest Al content point on the other side as a cathode electrode (evaporation source) is used to rotate the rotation. A plurality of the bases are mounted in a ring shape along the outer periphery of the table, and in this state, the rotary table is rotated with the atmosphere inside the apparatus as a nitrogen atmosphere, and the bases themselves are rotated while the cathode electrodes on both sides are rotated. by generating arc discharge between the (evaporation source) and the anode electrode, the surface of the substrate, (Al, Ti) a hard coating layer consisting of N layers overall 1~10μm Rights In the coated gear cutting tool comprising depositing a layer thickness,
In the hard coating layer, the highest Al content point and the lowest Al content point are present alternately at predetermined intervals along the thickness direction, and the lowest Al content point, the Al content point, from the highest Al content point. A component concentration distribution structure in which the Al content continuously changes from the lowest content point to the Al highest content point,
Furthermore, the above Al highest content point,
Composition formula: (Al _1-X Ti _X ) N (however, in atomic ratio, X represents 0.05 to 0.30),
The minimum Al content point is
Composition formula: (Al _{1 -Y} Ti _Y ) N (wherein Y represents 0.35 to 0.60 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.
It is characterized by a coated gear cutting tool that exhibits excellent wear resistance with a hard coating layer in high-speed gear cutting.
[0010]
Next, the reason why the structure of the hard coating layer constituting the coated cutting tool of the present invention is limited as described above will be described.
(A) Composition of Al highest content point (Al, Ti) Al in the N layer improves the high temperature hardness and heat resistance (high temperature characteristics), and Ti has the effect of improving the strength. When the X value indicating the ratio of Ti at the highest content point is less than 0.05 as a ratio (atomic ratio) to the total amount with Al, the ratio of Ti becomes too low, and the strength rapidly decreases. Chipping (small chipping) is likely to occur on the blade. On the other hand, if the X value exceeds 0.30, the proportion of Al is relatively lowered, and the excellent high temperature characteristics brought about by Al are likely to decrease. In particular, since high speed gear cutting causes wear acceleration, the ratio was set to 0.05 to 0.30.
[0011]
(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. In particular, the Ti content ratio is high, and the Al minimum content points that have high strength thereby intervene alternately in the thickness direction, and therefore the Y value indicating the Ti ratio occupies the total amount with Al If the ratio (atomic ratio) is less than 0.35, the desired excellent strength cannot be ensured. On the other hand, if the Y value indicating the ratio exceeds 0.60, the ratio of Ti becomes relatively large. In addition, since it becomes impossible to provide desired high-temperature characteristics at the Al minimum content point, the ratio was determined to be 0.35 to 0.60.
[0012]
(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. Strength cannot be ensured, and if the distance exceeds 0.1 μm, each point has a defect, that is, if Al is the highest content point, the strength is insufficient, and if it is the lowest Al content point, the high temperature characteristics are insufficient. Therefore, the chipping is likely to occur on the cutting edge, and the progress of wear is promoted. Therefore, the interval is set to 0.01 to 0.1 μm.
[0013]
(D) If the overall average layer thickness of the hard coating layer is less than 1 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, the average layer thickness was determined to be 1 to 10 μm.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Next, the coated gear cutting tool of the present invention will be specifically described with reference to examples.
Example 1
As the gear cutting tool body, the outer diameter: 80mm x length: 120mm by machining from a material with the dimensions of diameter: 85mm x length: 125mm made of high speed tool steel of JIS / SKH55 and SKH51 The solid hob shown in the schematic perspective view of FIG. 3 having the overall dimensions of 4 and having the shape of four right-handed twists × 20 grooves was manufactured.
[0015]
Next, the main body of the above two types of materials (solid hob) is used as a base, and each of these bases is ultrasonically cleaned in acetone and dried, and then the arc ion plating apparatus shown in FIG. Mounted along the outer periphery of the table at a predetermined distance in the radial direction from the center axis on the inner rotary table, and the lowest Al content point with various component compositions as the cathode electrode (evaporation source) on one side Al-Ti alloy for forming, Al-Ti alloy for forming the highest Al content point with various composition as opposed cathode electrode (evaporation source), facing each other across the rotary table, and for bombard cleaning The metal Ti is also mounted, and the inside of the apparatus is first evacuated and kept at a vacuum of 0.5 Pa or less, and the inside of the apparatus is heated to 400 ° C. with a heater and then rotated while rotating on the rotary table. A DC bias voltage of −1000 V is applied to the substrate, and a current of 100 A is caused to flow between the metal Ti and the anode electrode of the cathode electrode to generate an arc discharge. Next, nitrogen gas was introduced into the apparatus as a reaction gas to make a reaction atmosphere of 10 Pa, a DC bias voltage of −100 V was applied to the substrate rotating while rotating on the rotary table, and each cathode electrode ( A current of 100 A flows between the Al-Ti alloy for forming the lowest Al content point and the Al-Ti alloy for forming the highest Al content point) and the anode electrode to generate an arc discharge, and a layer is formed on the surface of the substrate. Along the thickness direction, the lowest Al content point and the highest Al content point of the target composition shown in Table 1 are alternately repeated at the target interval shown in Table 1. It has a component concentration distribution structure that exists repeatedly, and the Al 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 The present invention coated gear cutting tools 1 to 6 were produced by vapor-depositing a hard coating layer having a target overall layer thickness shown in FIG.
[0016]
For comparison purposes, the above two types of base materials (gear cutting tool main body) are ultrasonically cleaned in acetone and dried, respectively, in a normal arc ion plating apparatus shown in FIG. The Al-Ti alloy having various component compositions as the cathode electrode (evaporation source) (Al-Ti alloy corresponding to the Al-Ti alloy for forming the Al minimum content point of the present invention) was mounted, Also, a bombard cleaning metal Ti is mounted, and the inside of the apparatus is first evacuated and kept at a vacuum of 0.5 Pa or less, and the inside of the apparatus is heated to 400 ° C. with a heater and then rotated while rotating on the rotary table. A DC bias voltage of −1000 V is applied to the substrate, 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. After bombard cleaning, nitrogen gas is introduced into the apparatus as a reaction gas to make a reaction atmosphere of 10 Pa, and a DC bias voltage of −100 V is applied to the substrate rotating while rotating on the rotary table, and An arc discharge is generated by flowing a current of 100 A between the cathode electrode and the anode electrode, and thus the surface of the substrate has the target composition and target layer thickness shown in Table 2 and along the layer thickness direction. Conventionally, the coated gear cutting tools 1 to 6 were manufactured by vapor-depositing a hard coating layer composed of an (Al, Ti) N layer having substantially no composition change.
[0017]
Next, using the above-described coated cutting tool 1-6 of the present invention and the conventional coated cutting tool 1-6, the material is made of a low alloy steel of JIS / SCr420H, module: 1.75, pressure angle: 17. Machining of gears with dimensions and shapes of 5 degrees, number of teeth: 33, twist angle: 36 degrees left-handed, tooth height: 5.36 mm, tooth width: 15.5 mm,
Cutting speed (rotational speed): 250 m / min,
Feed: 2.5mm / rev,
Processing form: climb, no shift, dry (air blow),
Gear cutting until the flank wear width reaches 0.2 mm with high speed gear cutting (cutting speed is usually 150 m / min when processing low-alloy steel gears with the above material is JIS / SCr420H) Number was measured. The measurement results are shown in Tables 1 and 2, respectively.
[0018]
(Example 2)
In addition, as a gear cutting tool body, a material having a size of outer diameter: 150 mm × thickness: 25 mm made of high-speed tool steel of the same material as JIS / SKH55 and SKH51 is used to machine a pitch circle diameter: 100 mm. X Thickness: A disk-type pinion cutter (100 type described in JIS B / 4356) shown in a schematic perspective view in FIG. 4 having an overall size of 22 mm and a shape of the number of cutter teeth: 40 was manufactured.
[0019]
Next, the above-described gear cutting tool body (pinion cutter) is used as a base, and the surfaces of these bases are ultrasonically cleaned in acetone and dried, and then loaded into the arc ion plating apparatus shown in FIG. Under the same conditions as in Example 1, the lowest Al content point and the highest Al content point of the target composition shown in Table 1 along the layer thickness direction are repeatedly present at the target interval shown in Table 1 alternately. And a component concentration distribution structure in which the Al 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 is also shown in Table 1. By coating a hard coating layer having a target overall layer thickness, the present invention coated gear cutting tools 7 to 12 were produced.
[0020]
For comparison purposes, the base of the above-mentioned gear cutting tool body (pinion cutter) is ultrasonically cleaned in acetone and dried, and then loaded into the ordinary arc ion plating apparatus shown in FIG. Then, under the same conditions as in Example 1 above, it is composed of an (Al, Ti) N layer having the target composition and target layer thickness shown in Table 2 and having substantially no composition change along the layer thickness direction. Conventionally, the coated gear cutting tools 7 to 12 were manufactured by depositing a hard coating layer, respectively.
[0021]
Next, using the above-described coated gear cutting tools 7 to 12 and the conventional coated gear cutting tools 7 to 12, the material is made of a low alloy steel of JIS / SCr420H, module: 2.5, pressure angle: 20 degrees. , Processing of gears having the size and shape of the number of teeth: 36, tooth width: 25 mm,
Number of strokes: 1000 strokes / min,
Circumferential feed: 0.5mm / stroke,
Radius feed: 0.02mm / stroke,
Gears with high speed gear cutting under the above conditions (the number of strokes is usually 600 strokes / min when machining the above alloy JIS / SCr420H low alloy steel gears), and the flank wear width reaches 0.2 mm. The number of processes was measured. The measurement results are shown in Tables 1 and 2, respectively.
[0022]
[Table 1]

[0023]
[Table 2]

[0024]
About the hard coating layer which comprises this invention coated gear cutting tool 1-12 obtained as a result of this, and the conventional coated gear cutting tool 1-12, content of Al and Ti using an Auger spectrometer along a thickness direction Was measured. From these measurement results, in the hard coating layers of the coated cutting tools 1 to 12 of the present invention, the Al maximum content point and the Al minimum content point having substantially the same composition as the target composition along the thickness direction are the target intervals. And the average average layer thickness of the hard coating layer also shows substantially the same value as the target total layer thickness, and further, from the Al maximum content point to the Al minimum content point, the Al It was also confirmed that it has a component concentration distribution structure in which the Al content continuously changes from the lowest content point to the Al highest content point. On the other hand, in the hard coating layers of the conventional coated gear cutting tools 1 to 12, no composition change is observed along the thickness direction, and the composition is substantially the same as the target composition and the target overall layer thickness. It was confirmed that the layer thickness was shown.
[0025]
【The invention's effect】
From the results shown in Tables 1 and 2, in the hard coating layer, the lowest Al content point and the highest Al content point are repeatedly present at predetermined intervals in the layer thickness direction, and the lowest Al content from the highest Al content point. The present invention coated gear cutting tools 1 to 12 having a component concentration distribution structure in which the Al content continuously changes from the content point, the Al minimum content point to the Al maximum content point are all gear cutting of a steel gear. Even when performed under high-speed gear cutting conditions with high heat generation, the hard coating layer exhibits excellent wear resistance, whereas the hard coating layer substantially changes in composition along the layer thickness direction. With conventional coated gear cutting tools 1-12 consisting of (Al, Ti) N layers without cracks, high-speed gear cutting with high temperature causes rapid wear of the cutting blade due to insufficient high-temperature characteristics and can be used in a relatively short time It is clear that it reaches the end of its life.
As described above, the coated cutting tool of the present invention is not only gear cutting under normal conditions, but particularly when gear cutting of various steel gears is performed under high speed conditions with high heat generation. In addition, the hard coating layer exhibits excellent wear resistance and exhibits excellent performance over a long period of time. Furthermore, it can cope with cost reduction sufficiently satisfactorily.
[Brief description of the drawings]
FIG. 1 shows an arc ion plating apparatus used to form a hard coating layer constituting a coated gear cutting 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 gear cutting tool.
FIG. 3 is a schematic perspective view of a solid hob.
FIG. 4 is a schematic perspective view of a disk-type pinion cutter.

Claims

A rotating table for mounting a base body composed of a gear cutting tool body made of high-speed tool steel is provided in the central part of the apparatus, and the Al-Ti alloy for forming the Al highest content point is formed on one side with the rotating table in between. Using an arc ion plating apparatus in which an Al-Ti alloy for forming the lowest Al content point is disposed as a cathode electrode (evaporation source), and mounting the plurality of substrates in a ring shape along the outer periphery of the rotary table, In this state, while rotating the turntable with the atmosphere inside the apparatus as a nitrogen atmosphere and rotating the substrate itself, an arc discharge is generated between the cathode electrode (evaporation source) and the anode electrode on both sides , on the surface of the substrate, the Al and Ti overall average layer surface-coated high speed tool steel gear cutting tool made by depositing a thickness of hard layer of 1~10μm made of a composite nitride layer of Te,
In the hard coating layer, the Al highest content point and the Al lowest content point are present alternately at predetermined intervals along the layer thickness direction, and the Al lowest content point, the Al A component concentration distribution structure in which the Al content continuously changes from the lowest content point to the Al highest content point,
Furthermore, the Al highest content point, the composition _{_{formula: (Al 1-X Ti X}} ) N ( provided that an atomic ratio, X is shows the 0.05 to 0.30),
The Al minimum content point is the composition formula: (Al _{1 -Y} Ti _Y ) N (wherein Y represents 0.35 to 0.60 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 surface-coated high-speed tool steel gear cutting tool that exhibits excellent wear resistance with a hard coating layer in high-speed gear cutting.