JP2004209608A

JP2004209608A - Gear cutting tool made of surface coated high speed tool steel having hard coated layer exhibiting excellent wear resistance in high speed gear cutting processing

Info

Publication number: JP2004209608A
Application number: JP2003000801A
Authority: JP
Inventors: Koichi Maeda; 浩一前田; Yusuke Tanaka; 裕介田中
Original assignee: Mitsubishi Materials Corp; Mitsubishi Materials Kobe Tools Corp
Current assignee: Mitsubishi Materials Corp; Mitsubishi Materials Kobe Tools Corp
Priority date: 2003-01-07
Filing date: 2003-01-07
Publication date: 2004-07-29
Anticipated expiration: 2023-01-07
Also published as: JP3956390B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gear cutting tool made of surface coated high speed tool steel having a hard coated layer exhibiting excellent wear resistance in high speed gear cutting processing. <P>SOLUTION: The tool is constituted by physical vapor-depositing the hard coating layer comprising composite nitride of Al and Ti on a surface of a base body comprising a gear cutting tool body made of high speed tool steel at the total average layer thickness of 1-10 μm. In the hard covering layer, the Al highest containing point and the Al lowest containing point alternately and repeatedly exist at a predetermined interval and the hard coating layer has a component concentration distribution structure that the Al content is continuously varied from the Al highest containing point to the Al lowest containing point, and from the Al lowest containing point to the Al highest containing point. In the hard coated layer, the Al highest containing point satisfies the composition formula: (Al<SB>1-X</SB>Ti<SB>X</SB>)N (provided that X represents 0.05-0.30 at an atomic ratio) and the Al lowest containing point satisfies the composition formula: (Al<SB>1-Y</SB>Ti<SB>Y</SB>)N (provided that Y represents 0.35-0.60 at an atomic ratio) respectively. The interval of the adjacent Al highest containing point and Al lowest containing point is made to 0.01-0.1 μm. <P>COPYRIGHT: (C)2004,JPO&NCIPI

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、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表面に、（Ａｌ，Ｔｉ）Ｎからなる硬質被覆層を１〜１０μｍの全体平均層厚で物理蒸着してなる被覆歯切工具において、
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]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a surface-coated high-speed tool steel that exhibits excellent wear resistance, especially in high-speed gear cutting with high heat generation, such as various types of steel and cast iron, in which the hard coating layer has excellent high-temperature properties. The present invention relates to a gear cutting tool (hereinafter referred to as a coated gear cutting tool).
[0002]
[Prior art]
2. Description of the Related Art Conventionally, various gears are generally used as structural members of automobiles, aircrafts, and various drive devices, and a solid hob (for example, see a schematic perspective view of FIG. 3) or a pinion cutter (for example, FIG. ), And a gear cutting tool such as a shaving cutter is used.
[0003]
As a coated hobbing tool, for example, a hobbing tool main body composed of a high-speed tool steel machined into a shape shown in FIGS. 3 and 4 is used as a base, and the surface of the base has a composition formula: (Al _{From a} layer of a composite nitride of Al and Ti [hereinafter, referred to as (Al, Ti) N] that satisfies _1-Y Ti _Y ) N (where Y represents 0.35 to 0.60 in atomic ratio). A coated tooth cutting tool is proposed in which a hard coating layer is physically vapor-deposited at an average layer thickness of 1 to 10 μm, and the (Al, Ti) N layer constituting the hard coating layer is made of Al having a high-temperature hardness and heat resistance. It is also known that a coated tooth cutting tool having such a hard coating layer exhibits excellent gear cutting performance because of its strength due to Ti and Ti (for example, see Patent Documents 1 and 2).
[0004]
Further, the above-mentioned coated tooth cutting tool is charged into the arc ion plating apparatus, which is a kind of a physical vapor deposition apparatus schematically shown in FIG. Is heated to a temperature of 400 ° C. in a vacuum atmosphere of 2 Pa, and between the anode electrode and the cathode electrode (evaporation source) on which an Al—Ti alloy having a predetermined composition is set, for example, voltage: 35 V, current: An arc discharge is generated under the condition of 90 A, and at the same time, a nitrogen gas is introduced as a reaction gas into the apparatus to make a reaction atmosphere of, for example, 2 Pa. It is also known that the substrate is manufactured by depositing a hard coating layer composed of the (Al, Ti) N layer on the surface of the base under the conditions applied.
[0005]
[Patent Document 1]
Patent No. 2793772 [Patent document 2]
Patent No. 3165658 [0006]
[Problems to be solved by the invention]
In recent years, the performance of gear cutting equipment has been remarkably improved, while 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 tends to be faster, In the conventional coated tooth cutting tool described above, there is no problem when this is used under normal gear cutting conditions, but when this is used under high-speed gear cutting conditions with high heat generation, a hard coating layer is formed. At present, the progress of abrasion is accelerated, and the service life is reached in a relatively short time.
[0007]
[Means for Solving the Problems]
In view of the above, the inventors of the present invention have developed a hard coated tool that constitutes the above-mentioned conventional coated tooth cutting tool, in order to develop a coated tooth cutting tool that exhibits excellent wear resistance particularly in high-speed tooth cutting. Focusing on the layers and conducting research,
(A) The (Al, Ti) N layer constituting the conventional coated tooth 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 layer 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. And 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 a cathode electrode (evaporation source) with the rotary table interposed therebetween. A plurality of substrates (gear cutting tool bodies) are formed in a ring shape along the outer periphery of the table at a position radially away from the center axis of the rotary table of the apparatus by a predetermined distance in the radial direction. In this state, the rotary table is rotated while the atmosphere in the apparatus is set to a nitrogen atmosphere, and the cathode electrodes on both sides are rotated while the base 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 (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 formed on a rotary table. When the substrate arranged in a ring shape approaches the cathode electrode (evaporation source) of the Al-Ti alloy having a relatively high Al content on one side, an Al maximum content point is formed in the layer. When the substrate comes closest to the cathode electrode of the Al-Ti alloy having a relatively low Al content on the other side, an Al lowest content point is formed in the layer, and the rotation of the rotary table causes the Al to be formed in the layer. The Al maximum content point and the Al minimum content point alternately and repeatedly appear at predetermined intervals along the layer thickness direction, the Al maximum content point from the Al maximum content point, and the Al maximum content point from the Al minimum content point. (1) 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 and continuously changing component concentration distribution structure of the above (a), for example, the respective compositions of the cathode electrodes (evaporation sources) arranged opposite to each other are prepared, and the base is mounted. By controlling the rotation speed of the turntable,
The highest Al content point is determined by the composition formula: (Al _1-X Ti _X ) N (where X is 0.05 to 0.30 in atomic ratio),
The above-mentioned Al minimum content point is represented by a composition formula: (Al _1-Y Ti _Y ) N (however, in the atomic ratio, Y represents 0.35 to 0.60),
Each satisfying the above, and the distance in the thickness direction between the adjacent Al maximum content point and Al minimum content point is 0.01 to 0.1 μm,
Since the Al content is relatively high in the Al highest content portion compared to the conventional (Al, Ti) N layer, the Al content exhibits higher hardness and heat resistance (high temperature characteristics), On the other hand, the Al lowest content portion has 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 highest content portion. Since it has a composition, it has relatively high strength, and since the interval between these Al maximum content points and Al minimum content points is extremely small, it is excellent in a state of maintaining high strength as a characteristic of the whole layer. Thus, a coated cutting tool composed of an (Al, Ti) N layer having such a structure with a hard coating layer exhibits excellent wear resistance in high-speed 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 based on the above research results, and has a hard coating layer made of (Al, Ti) N on the surface of a base made of a gear cutting tool body made of high-speed tool steel. In a coated tooth cutting tool obtained by physical vapor deposition with a total average layer thickness of 10 to 10 μm,
The hard coating layer has an Al maximum content point and an Al minimum content point alternately and repeatedly provided at predetermined intervals along the layer thickness direction, and the Al maximum content point and the Al minimum content point, the Al Having a component concentration distribution structure in which the Al content continuously changes from the lowest content point to the highest Al content point,
Furthermore, the above Al maximum content point is
Compositional formula: (Al _1-X Ti _X ) N (where X represents 0.05 to 0.30 in atomic ratio),
The above Al minimum content point is
Composition _{_{formula: (Al 1-Y Ti Y}} ) N ( provided that an atomic ratio, Y denotes the 0.35 to 0.60),
Respectively, and the interval between the adjacent Al maximum content point and Al minimum content point is 0.01 to 0.1 μm,
The present invention is characterized by a coated tooth cutting tool in which a hard coating layer exhibits excellent wear resistance in high-speed gear cutting.
[0010]
Next, the reason why the configuration of the hard coating layer constituting the coated tooth cutting tool of the present invention is limited as described above will be described.
(A) Al in the composition (Al, Ti) N layer having the highest content of Al improves high-temperature hardness and heat resistance (high-temperature characteristics), and Ti has an effect of improving strength. If the X value indicating the proportion of Ti at the highest content point is less than 0.05 in the proportion (atomic ratio) to the total amount with Al, the proportion of Ti becomes too low, and the strength rapidly decreases, and When the X value exceeds 0.30, the ratio of Al relatively decreases and the excellent high-temperature characteristics provided by Al tend to decrease. In particular, since high-speed gear cutting causes acceleration of wear, the ratio is 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 has poor strength, but in order to compensate for the insufficient strength of the highest Al content point, In this case, the lowest Al content point which has a high Ti content and thereby has a high strength is alternately interposed in the thickness direction, so that the Y value indicating the Ti content 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. Therefore, the desired high-temperature characteristics cannot be provided at the Al minimum content point, so the ratio is set to 0.35 to 0.60.
[0012]
(C) Interval between the highest Al content point and the lowest Al content point If the interval is less than 0.01 μm, it is difficult to clearly form each point with the above composition, and as a result, the desired high-temperature characteristics and When the distance exceeds 0.1 μm, the strength of each layer cannot be ensured, and the disadvantages of the respective points, that is, insufficient strength at the highest Al content point, and insufficient high-temperature characteristics at the lowest Al content point are in the layer. Locally, the chipping is likely to occur on the cutting edge and the abrasion progress is promoted. Therefore, the interval is set to 0.01 to 0.1 μm.
[0013]
(D) If the average 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 thickness exceeds 10 μm, chipping occurs on the cutting edge. The average layer thickness was determined to be 1 to 10 μm because it was easier.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the coated tooth cutting tool of the present invention will be specifically described with reference to examples.
(Example 1)
The gear cutting tool main body is made of high-speed tool steel of JIS SKH55 and SKH51 and has a diameter of 85 mm x length: 125 mm, and is machined to an outer diameter of 80 mm x length: 120 mm. A solid hob shown in the schematic perspective view of FIG. 3 and having the overall dimensions shown in FIG.
[0015]
Next, the above-described two types of gear cutting tool bodies (solid hobs) are used as bases, and each of these bases is ultrasonically cleaned in acetone and dried, and then the arc ion plating apparatus shown in FIG. Attached along the outer periphery of the rotary table at a predetermined distance in the radial direction from the center axis on the rotary table, and as the cathode electrode (evaporation source) on one side, the lowest Al content point having various component compositions An Al-Ti alloy for forming, and an Al-Ti alloy for forming the highest content point of Al having various component compositions as a cathode electrode (evaporation source) on the other side are arranged to face each other with the rotary table interposed therebetween, and for bombarding cleaning. Metal Ti was also installed, and while the inside of the apparatus was evacuated and kept at a vacuum of 0.5 Pa or less, the inside of the apparatus was heated to 400 ° C. with a heater, and then rotated on the rotary table while rotating. Applying a DC bias voltage of -1000 V to the substrate, causing a current of 100 A 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 substrate with Ti bombarding, Next, nitrogen gas was introduced into the apparatus as a reaction gas to make a reaction atmosphere of 10 Pa, and 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 is passed 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 arc discharge, thereby forming a layer on the surface of the base. Along the thickness direction, the Al minimum content point and the Al maximum content point of the target composition shown in Table 1 are alternately shown in the target interval also shown in Table 1. Having a component concentration distribution structure in which the Al content is repeatedly present and the Al content continuously changes from the Al highest content point to the Al lowest content point, and the Al lowest content point to the Al highest content point; The coated tooth cutting tools 1 to 6 of the present invention were produced by depositing a hard coating layer having a target overall layer thickness shown in Table 1.
[0016]
Further, for the purpose of comparison, the above two types of substrates (gear cutting tool bodies) were subjected to ultrasonic cleaning in acetone and dried, and then applied to a normal arc ion plating apparatus shown in FIG. Al-Ti alloys (Al-Ti alloys corresponding to the above-described Al-Ti alloy for forming the lowest Al content point of the present invention) having various component compositions were mounted as cathode electrodes (evaporation sources). In addition, the metal Ti for bombarding is also mounted, and the inside of the apparatus is first evacuated and heated to 400 ° C. with a heater while maintaining a vacuum of 0.5 Pa or less, and then rotated while rotating on the rotary table. A DC bias voltage of -1000 V is applied to the base, and a current of 100 A flows between the metal Ti of the cathode electrode and the anode electrode to generate an arc discharge. After bombarding, nitrogen gas is introduced into the apparatus as a reaction gas to obtain 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 A current of 100 A is caused to flow between the cathode electrode and the anode electrode to generate an arc discharge, so that the surface of the substrate has a target composition and a target layer thickness shown in Table 2, and extends along the layer thickness direction. Conventional coated tooth cutting tools 1 to 6 were manufactured by depositing a hard coating layer composed of an (Al, Ti) N layer having substantially no composition change.
[0017]
Next, using the coated tooth cutting tools 1 to 6 of the present invention and the conventional coated tooth cutting tools 1 to 6 as described above, the material is made of low alloy steel of JIS SCr420H, module: 1.75, pressure angle: 17. 5 degrees, number of teeth: 33, helix angle: 36 degrees left twist, tooth height: 5.36 mm, tooth width: 15.5 mm
Cutting speed (rotation speed): 250 m / min,
Feed: 2.5 mm / rev,
Processing form: Climb, no shift, dry (air blow),
High-speed gear cutting (the cutting speed is usually 150 m / min when processing low alloy steel gears whose material is JIS / SCr420H), and gear cutting until the flank wear width reaches 0.2 mm The number was measured. The measurement results are shown in Tables 1 and 2, respectively.
[0018]
(Example 2)
As the gear cutting tool body, a material having the dimensions of 150 mm × thickness: 25 mm, which is also made of high-speed tool steel of JIS SKH55 and SKH51, is machined into a pitch circle diameter: 100 mm. × A disk-type pinion cutter (100 type described in JIS B 4356) shown in a schematic perspective view in FIG. 4 having an overall dimension of 22 mm in thickness and having a number of cutter teeth of 40 was manufactured.
[0019]
Next, the above-mentioned gear cutting tool body (pinion cutter) was used as a base, and the surfaces of these bases were ultrasonically cleaned in acetone and dried, and then charged into an arc ion plating apparatus also shown in FIG. Under the same conditions as in Example 1, the Al minimum content points and the Al maximum content points of the target compositions shown in Table 1 alternately exist at the target intervals shown in Table 1 along the layer thickness direction. 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, and the Al lowest content point to the Al highest content point, and is also shown in Table 1. The coated tooth cutting tools 7 to 12 of the present invention were produced by depositing a hard coating layer having a target overall layer thickness.
[0020]
For the purpose of comparison, the base of the above-mentioned gear cutting tool body (pinion cutter) was ultrasonically cleaned in acetone, dried, and charged into a usual arc ion plating apparatus also shown in FIG. Then, under the same conditions as in Example 1, the (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 is formed. Conventional coated tooth cutting tools 7 to 12 were respectively manufactured by depositing a hard coating layer.
[0021]
Next, using the coated tooth cutting tools 7 to 12 of the present invention and the conventional coated tooth cutting tools 7 to 12 described above, the material was made into a low alloy steel of JIS SCr420H, module: 2.5, pressure angle: 20 degrees. , Number of teeth: 36, tooth width: 25mm
Number of strokes: 1000 strokes / min,
Circumferential feed: 0.5mm / stroke,
Radial feed: 0.02mm / stroke,
High-speed gear cutting (the number of strokes in the case of processing a low alloy steel gear of the above-mentioned material is JIS / SCr420H is usually 600 strokes / min) under the conditions described above, and the gear until the flank wear width reaches 0.2 mm. The number of processing was measured. The measurement results are shown in Tables 1 and 2, respectively.
[0022]
[Table 1]

[0023]
[Table 2]

[0024]
The resulting hard coating layers constituting the coated tooth cutting tools 1 to 12 of the present invention and the conventional coated tooth cutting tools 1 to 12 were subjected to the content of Al and Ti along the thickness direction using an Auger spectrometer. Was measured. From these measurement results, in the hard coating layers of the coated tooth cutting tools 1 to 12 of the present invention, the target interval between the highest Al content point and the lowest Al content point having substantially the same composition as the target composition along the thickness direction is determined. Are present alternately at substantially the same intervals as above, and the overall average layer thickness of the hard coating layer also shows substantially the same value as the target overall layer thickness, and further from the Al maximum content point to the Al minimum content point, the Al It was also confirmed that the composition had a component concentration distribution structure in which the Al content continuously changed from the lowest content point to the highest Al content point. On the other hand, in the hard coating layers of the conventional coated tooth cutting tools 1 to 12, there is no change in composition along the thickness direction, and the composition is substantially the same as the target composition and the overall average is substantially the same as the target total layer thickness. It was confirmed to show the layer thickness.
[0025]
【The invention's effect】
From the results shown in Tables 1 and 2, it can be seen from the results that the hard coating layer has the Al minimum content points and the Al maximum content points repeatedly and alternately at predetermined intervals in the layer thickness direction, and the Al minimum content points and the Al minimum content points Each of the coated tooth cutting tools 1 to 12 according to the present invention having a component concentration distribution structure in which the Al content continuously changes from the content point and the Al minimum content point to the Al maximum content point, the tooth cutting of a steel gear. In high-speed gear cutting with high heat generation, the hard coating layer exhibits excellent wear resistance, whereas the hard coating layer changes composition substantially along the thickness direction. In conventional coated tooth cutting tools 1 to 12 made of a (Al, Ti) N layer having no cutting, in a high-speed cutting operation involving high temperature, wear of a cutting edge progresses rapidly due to lack of high-temperature characteristics, and is used in a relatively short time. It is clear that it will last a lifetime.
As described above, the coated tooth cutting tool according to the present invention can be used not only for cutting under normal conditions, but also for cutting various steel gears and the like under high-speed conditions with high heat generation. In addition, since the hard coating layer exhibits excellent wear resistance and exhibits excellent performance over a long period of time, the performance of the gear cutting device has been improved, and the power saving and energy saving of the gear cutting have been achieved. Further, it is possible to sufficiently satisfy cost reduction.
[Brief description of the drawings]
1 shows an arc ion plating apparatus used for forming a hard coating layer constituting a coated tooth 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 conventional arc ion plating apparatus used for forming a hard coating layer constituting a conventional coated tooth 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

Surface-coated high-speed tool steel made by physical vapor deposition of a hard coating layer made of a composite nitride of Al and Ti with a total average layer thickness of 1 to 10 μm on the surface of a gear cutting tool body composed of high-speed tool steel In gear cutting tools,
The hard coating layer has an Al maximum content point and an Al minimum content point alternately and repeatedly provided at predetermined intervals along the layer thickness direction, and the Al maximum content point and the Al minimum content point, the Al Having a component concentration distribution structure in which the Al content continuously changes from the lowest content point to the highest Al content point,
Further, the above-mentioned Al maximum content point is determined by a composition formula: (Al _1-X Ti _X ) N (where X represents 0.05 to 0.30 in atomic ratio),
The above-mentioned Al minimum content point is represented by a composition formula: (Al _1-Y Ti _Y ) N (however, in the atomic ratio, Y represents 0.35 to 0.60),
Respectively, and the interval between the adjacent Al maximum content point and Al minimum content point is 0.01 to 0.1 μm,
A surface-coated high-speed tool steel gear-cutting tool with a hard coating layer that exhibits excellent wear resistance in high-speed gear cutting.