【０００１】
【発明が属する技術分野】
本発明は、切削加工に使用されるエンドミルの表面被覆材として有用な硬質皮膜を被覆することにより、優れた耐摩耗性を発揮する被覆エンドミルに関する。
【０００２】
【従来の技術】
ＡｌＣｒ系皮膜は、耐高温酸化特性に優れた硬質皮膜材として、下記に示す特許文献１から４が開示されている。
【特許文献１】特許第３０２７５０２号公報（第６頁、図１）
【特許文献２】特許第３０３９３８１号公報（第４頁、図１）
【特許文献３】特開平２００２−１６０１２９号公報（第３頁、図１）
【０００３】
特許文献１は金属成分としてＡｌＣｒとＣ、Ｎ、Ｏの１種より選択されるＡｌＣｒ系硬質膜において、高硬度を有する非晶質膜に関する事例が開示されている。しかしこの非晶質膜の硬度は最大でもヌープ硬さ２１ＧＰａ程度であり、耐摩耗効果は期待できず、密着性に関しても十分ではない。特許文献２及び特許文献３に開示されている硬質皮膜はＡｌＣｒの窒化物であり、約１０００℃の耐高温酸化特性を有しているが、１０００℃以上の耐酸化特性の検討は行われていない。硬度はＨＶ２１ＧＰａ程度で硬度の改善が不十分であり耐摩耗性に乏しい。
【０００４】
【発明が解決しようとする課題】
本願発明は、上記の問題点を改善し、Ｃｒ系皮膜の欠点である硬度を高めることにより耐摩耗性を改善し、その結果優れた寿命を発揮する被覆エンドミルを提供することを目的とする。
【０００５】
【課題を解決するために手段】
本発明は、被覆エンドミルにおいて、該被覆はアーク放電式イオンプレーティング法により被覆された硬質皮膜であり、該硬質皮膜は、（ＡｌｘＣｒ１−ｘ−ｙＳｉｙ）（Ｎ１−α−β−γＢαＣβＯγ）、但し、ｘ、ｙ、α、β、γは夫々原子比率を示し、０．４５＜ｘ＜０．７５、０≦ｙ＜０．２、０≦α＜０．１２、０≦β＜０．２、０．０１≦γ≦０．２５、からなり、Ｘ線回折における（１１１）面の回折強度をＩ（１１１）、（２００）面の回折強度をＩ（２００）とした時、Ｉ（２００）／Ｉ（１１１）の値が４以下からなり、Ｘ線光電子分光分析における５２５ｅＶから５３５ｅＶの範囲に、少なくともＣｒ、Ａｌ及び／又はＳｉと酸素との結合エネルギーを有し、該エンドミルの基体は高速度鋼からなり、ＶとＣｏの和が重量％で３≦（Ｖ＋Ｃｏ）≦１１、Ｃｒが重量％で３．８≦Ｃｒ≦４．５、としたことを特徴とする被覆エンドミルである。上記構成を採用することにより、基体と硬質皮膜との密着性に優れ、高硬度化することが可能となり、その結果、優れた耐摩耗性を発揮する本発明の被覆エンドミルを完成させた。
【０００６】
本発明硬質皮膜は、Ｘ線回折における（２００）面回折ピークの２θの半価幅が、０．５度以上、１度以下の広がりを有する場合、皮膜硬度並びに耐酸化性改善への寄与が大きい。また、ナノインデンテーションによる硬度測定法により接触深さと最大荷重時の最大変位量が求められる（Ｗ． Ｃ． Ｏｌｉｖｅｒ ａｎｄ Ｇ． Ｍ． Ｐｈａｒｒ： Ｊ． Ｍａｔｅｒ． Ｒｅｓ．， Ｖｏｌ．７， Ｎｏ．６， Ｊｕｎｅ、１９９２、１５６４−１５８３）。この数値を用いて、Ｅ＝１００−｛（接触深さ）／（最大荷重時の最大変位量）｝
の数式で、弾性回復率Ｅを定義し、３０％≦Ｅ＜４０％とすることにより、耐摩耗性と密着性のバランスが最適となる。更に、Ｘ線回折によるＣｒの立方晶系化合物とＡｌの六方晶系化合物のピークが検出され、該Ｃｒの立方晶系化合物の（２００）面ピーク強度をＱ１、Ａｌの六方晶系化合物の（００１）面ピーク強度をＱ２とした時、ピーク強度比Ｑ２／Ｑ１の値が、０≦Ｑ２／Ｑ１≦０．１とすることは、皮膜硬度を向上させることに有効である。また、本願発明の硬質皮膜は、硬質皮膜表面の凸部を機械的処理により平滑にすると、表面の摩擦係数が低減しこれによって切屑排出性が改善される。本発明に用いる高速度鋼は、硬さがＨＲＣ６４以上、ＨＲＣ６８未満であることが好ましい。
【０００７】
【発明の実施の形態】
本発明の硬質皮膜を構成する金属元素の組成は、（ＡｌｘＣｒ１−ｘ−ｙＳｉｙ）において、ｘが０．４５＜ｘ＜０．７５、ｙが０≦ｙ＜０．２を満足する必要がある。ｘの値が０．４５以下では皮膜硬度並びに耐高温酸化特性の改善効果が十分ではなく、ｘの値が０．７５以上、ｙの値が０．２以上では、残留圧縮応力が過大になり、被覆直後に自己破壊を誘発する場合がある。非金属元素の組成は、（Ｎ１−α−β−γＢαＣβＯγ）において、αは０．１２以上では皮膜が脆化し、好ましいαの上限値は０．０８である。硼素の添加は被加工物との耐溶着性と高温環境下での摩擦係数を低減し、潤滑性を向上させる効果がある。次に、βは、０．２以上で皮膜は脆化する。好ましいβの上限値は０．１６である。炭素の添加は硬質皮膜の硬度を高め、室温での摩擦係数の低減し、潤滑性を向上させる効果がある。γは０．０１以上、０．２５以下にすることが必要である。γが０．０１未満では、添加効果を得ることができず、０．２５を超えて大きくなると皮膜硬度は低下し、耐摩耗性に乏しくなる。好ましくは、γは、０．０５以上０．２以下である。γの添加は、基体と皮膜との密着性向上、皮膜が緻密化することによる高硬度化、酸化物形成により耐高温酸化性の改善に効果的である。更に、金属元素のＡｌ、Ｃｒ、Ｓｉに対する非金属元素のＮ、Ｂ、Ｃ、Ｏの比は、化学量論的に（Ｎ、Ｂ、Ｃ、Ｏ）／（Ａｌ、Ｃｒ、Ｓｉ）＞１．１がより好ましい。
【０００８】
本発明のＸ線回折における（１１１）面の回折強度をＩ（１１１）、（２００）面の回折強度をＩ（２００）とした時、Ｉ（２００）／Ｉ（１１１）の値が４以下としたのは、皮膜の密着性は残留圧縮応力に強く依存し、この残留圧縮応力は成膜条件であるイオンエネルギーに強く依存している。即ち、イオンエネルギーが低い条件下では皮膜の残留圧縮応力は低い結果となる。逆に、イオンエネルギーが高い条件下では皮膜の残留圧縮応力は高い結果となる。ここで、イオンエネルギーを決定する要素は、具体的には成膜条件であるバイアス電圧、反応ガス圧力であり、これによって制御することができる。本発明は、残留圧縮応力が高い場合、Ｘ線回折において皮膜は（１１１）面に強く配向し、皮膜の硬度も、この高い残留圧縮応力の影響を受けて高硬度とする事が可能となる。一方、皮膜の密着性に着目すると、硬質皮膜内の残留圧縮応力を高くすると、皮膜の高硬度化を達成できるが、基体と皮膜界面とのせん断応力が増大する方向に作用するため、密着性を損なうこととなり、好ましくない。従って、基体と皮膜との密着性及び皮膜硬度とのバランスを最適に制御することが重要となる。本発明では、Ｉ（２００）／Ｉ（１１１）の値を４以下とすることにより、両者のバランスを最適に制御することを可能にした。Ｉ（２００）／Ｉ（１１１）の値が４を超えて大きくなると、皮膜の硬度が急激に低下し、エンドミルに適用する硬質皮膜としては満足な性能を得ることが出来ないのである。そこで、４以下の値に限定した。
【０００９】
該硬質皮膜はＸ線光電子分光分析にて、５２５ｅＶから５３５ｅＶにＣｒ、Ａｌ及び／又はＳｉと酸素との結合エネルギーを有することが必要であり、皮膜が緻密化し、酸化雰囲気において酸素の拡散経路となる結晶粒界が不明瞭となり、内向拡散し難くする機能を有する。Ｃｒ、Ａｌ及び／又はＳｉが窒化物、酸化物もしくは酸窒化物の状態で存在しているため、硬質皮膜が緻密化し高硬度を有する。本発明皮膜の特徴である、Ｃｒ、Ａｌ及び／又はＳｉと酸素との結合状態を形成するには、一定以上の酸素を含有させることが必要である。基体にバイアス電圧を印加すると、密着性を一段と高めることができる。成膜条件は、ガス圧を１．５〜５．０Ｐａ、被覆基体温度を３５０〜７００℃、バイアス電圧を−１５〜−３００Ｖのバイアス電圧とすることが好ましく、この範囲において皮膜の密着性と皮膜硬度とのバランスが最適となり、耐高温酸化特性並びに耐摩耗性の優れた緻密な硬質皮膜が得られる。
【００１０】
本発明の被覆エンドミルに用いる高速度鋼は、ＶとＣｏの和が、重量％で３≦（Ｖ＋Ｃｏ）≦１１、Ｃｒが重量％で３．８≦Ｃｒ≦４．５の範囲とする。高速度鋼中のＶ及びＣｏは、硬度及び耐熱強度を決定する添加元素であると同時に靭性と耐摩耗性を決定する添加元素でもある。３重量％未満の場合は、高温環境下における基体強度が十分ではなく、工具寿命は不安定であった。これは、切削過程において切刃の塑性変形を生じるためである。一方、１１重量％を越える場合は、硬質皮膜内に発生する残留圧縮応力の緩和が不十分であり、密着性が十分ではなく、微細な皮膜剥離が発生する場合があり、切刃にチッピングや欠けが発生してしまい短寿命を招いた。Ｃｒは、高速度鋼の熱処理性を高め、硬さを充分に高めるため上記の範囲とした。基体中のＶ、Ｃｏ及びＣｒが上記範囲を満足する場合、高速度鋼中のマトリックスの耐熱強度も優れる。本発明の硬質皮膜の密着性に及ぼす影響を考慮した結果、基体中のＶ、ＣｏとＣｒの含有量を上記範囲内に決定した。この範囲内であれば、上記硬質皮膜内に発生する残留圧縮応力に対して、基体内部で緩和することが可能であり密着性に優れ、該硬質皮膜の優れた耐酸化性と高硬度である特性を充分に発揮することができる。これらの構成により、エンドミルによる切削加工の高速化並びに長寿命化を達成することが可能となる。
【００１１】
該硬質皮膜の結晶粒のアスペクト比について、本発明の柱状結晶構造をした皮膜破断面の膜厚Ｔについて、膜厚Ｔの２５％から５０％の厚みであるＴ１に相当する上下膜厚方向の上端位置と下端位置とを求める。この時、上端位置と下端位置は、Ｔ／２に相当する基準位置より上下膜厚方向に略均等となる様に割り振る。各上下端位置における水平方向の上端側粒径Ｋと下端側粒径Ｌを求める。そこで、アスペクト比をＴ１／（（Ｋ＋Ｌ）／２）とすると、柱状結晶構造からなる該硬質皮膜の結晶粒のアスペクト比が、１．２から５である。アスペクト比が５を超えて大きくなると、結晶粒が膜厚方向に細長くなり、皮膜の靭性が低下し好ましくない。１．２未満では粒状結晶が増加する傾向となり、皮膜硬度が低下し好ましくない。更に、該硬質皮膜の残留圧縮応力が、１ＧＰａ以上、５ＧＰａ以下であることが、硬質皮膜に靭性を持たせ、皮膜硬度と基体密着性とのバランスに適した範囲となり、性能の改善に効果的である。
【００１２】
ナノインデンテーションによる硬度測定法によるＥは、３０％≦Ｅ＜４０％であり、皮膜の成膜条件であるバイアス電圧、反応ガス圧やその分圧比、成膜時の基体温度を最適に制御することにより達成できる。Ｅが４０％以上の場合、硬質皮膜内に残留圧縮応力が高くなり過ぎて靭性に乏しくなり密着性を劣化させる。３０％未満の場合は強度不足による異常摩耗等により耐摩耗性が十分でない。好ましいＥの値は３２％〜３８％である。
【００１３】
該硬質皮膜のＣｒの立方晶系化合物ピーク強度をＱ１、Ａｌの六方晶系化合物のピーク強度をＱ２とした時、ピーク強度比Ｑ２／Ｑ１の値が０．１を超えて大きくなると、硬度が急激に低下する。そこで、Ｑ２／Ｑ１の値が０．１以下とすることは、必要な皮膜硬度を得ることに有効であり好ましい。
【００１４】
本発明の皮膜を被覆し被覆基体表面の研磨面や研削面に沿った硬質皮膜表面の凸部や、被覆中に発生したマクロ粒子等の付着により凸部が形成される場合があるため、その凸部を機械的処理により平滑にすることにより、切屑除去効果に更に優れ望ましい。更に、被覆後に切刃エッジに機械的処理を施すことにより、なじみ効果も確認され、耐欠損、耐チッピング特性を改善することができ、より好ましい硬質皮膜を得ることができる。
【００１５】
本発明のエンドミル基体の硬さは、ＨＲＣ６４以上、ＨＲＣ６８未満である。基体がＨＲＣ６４未満となる場合、過酷な切削環境下において切刃が塑性変形を伴った摩耗進行も確認され、刃先強度が十分ではなく好ましくない。また、ＨＲＣ６８以上となる場合は、硬質皮膜内に発生する残留圧縮応力の緩和が不十分であり、微細な皮膜剥離が発生する場合があり、好ましくない。更に、本発明の硬質皮膜において金属成分の４原子％未満を周期律表の４ａ、５ａ、６ａ族の金属成分の１種以上で置き換えた場合、また本発明に関わる硬質皮膜を１層以上含有する複層構造においても、同様な効果が確認され好ましく、本発明の技術的範囲に含まれるものである。以下、実施例に基づき、本発明を具体的に説明する。
【００１６】
【実施例】
（実施例１）
成膜には酸素含有の合金ターゲットを用い、反応ガスを真空装置内に導入し全圧を３．０Ｐａ、バイアス電圧を−１００Ｖ、被覆温度を４５０℃とし、膜厚を約５μｍとし、（Ａｌ０．６Ｃｒ０．４）（Ｎ０．８０Ｃ０．０８Ｏ０．１０Ｂ０．０２）を成膜し、本発明例１とした。皮膜組成は、電子プローブＸ線マイクロアナリシス及びオージェ電子分光法により決定した。Ｘ線光電子分光分析は、ＰＨＩ社製１６００Ｓ型Ｘ線光電子分光分析装置を用いて分析した。本発明例１のＸ線光電子分光分析結果を図１に示す。図１は結合エネルギーが５３０ｅＶ近傍のナロースペクトル示し、Ｃｒ−Ｏ及びＡｌ−Ｏの結合の存在を示す。図２はＣｒ−Ｎ及びＣｒ−Ｏの結合の存在を示す。図３はＡｌ−Ｎ及びＡｌ−Ｏの結合の存在を示す。図４のＸ線回折結果は、硬質皮膜のＸ線回折における（１１１）面の回折強度をＩ（１１１）、（２００）面の回折強度をＩ（２００）とした時に、Ｉ（２００）／Ｉ（１１１）の値が４以下であることを示す。
【００１７】
（実施例２）
実施例１と同様に、（ＡｌｘＣｒ１−ｘ−ｙＳｉｙ）（Ｎ０．９５Ｏ０．０５）を成膜し、比較例２、ｘ＝０．２０、ｙ＝０、比較例３、ｘ＝０．３０、ｙ＝０、本発明例４、ｘ＝０．５０、ｙ＝０、本発明例５、ｘ＝０．６０、ｙ＝０、本発明例６、ｘ＝０．７０、ｙ＝０、比較例７、ｘ＝０．８０、ｙ＝０及び（ＡｌｘＣｒ１−ｘ）Ｎ系の従来例９、ｘ＝０．２０、従来例１０、ｘ＝０．５０、従来例１１、ｘ＝０．７０、を製作し、押込硬さを測定した。試験機は微小押込み硬さ試験機を用い、圧子はダイヤモンド製の対稜角１１５度の三角錐圧子を用い、最大荷重を４９ｍＮ、荷重負荷ステップ４．９ｍＮ／ｓｅｃ、最大荷重時の保持時間は１秒とした。測定値は１０点測定の平均値を示した。図５より、本発明例４〜６、Ａｌ添加量、４５〜７５原子％の範囲で、酸素を含有しない系より高硬度を示した。本発明の硬質皮膜は、酸素を含有することにより高硬度となり、４０ＧＰａ以上を得ることが出来る。これによって密着性並びに耐摩耗性に優れた硬質皮膜が得られる。
【００１８】
（実施例３）
高速度鋼を基体に用い、表１に示す皮膜組成の、本発明例１２〜２２、比較例２３〜３０及び従来例１０を製作した。アークイオンプレーティング法による被覆条件は、被覆基体温度４５０℃、反応圧は３．５Ｐａでバイアス電圧を−１５０Ｖの条件で被覆処理を行なった。表１に皮膜の組成等を示す。
【００１９】
【表１】
【００２０】
表１の試料を用いて、大気中１１００℃の酸化条件で処理した皮膜の酸化層、実施例２同様に微小押込み硬さ、薄板の変形量より算出した残留圧縮応力、弾性回復率を測定した。表１より、酸化層厚さは、本発明例１２〜２２は、殆ど酸化進行が無く、耐高温酸化特性に優れていることが確認された。従来例１０は酸化進行が著しく硬質皮膜は殆ど酸化物となり、酸素の内向拡散が基体まで達していた。押込み硬さもＣ、Ｂを含有させることにより、更に高硬度となる。残留圧縮応力は、本発明例１２〜２２は低く、更に、図６に示す、本発明例１２及び従来例１０の荷重変位曲線より、本発明例１２は、最大荷重時における最大変位量が大きく、塑性変形量が小さく、同一応力が硬質皮膜に作用した際、弾性回復する割合が大きく塑性変形し難いことを示す。この荷重変位曲線よりＥを求めた。Ｅが大きい程弾性回復特性に優れる。表１より、本発明例１２〜２２は弾性回復特性に優れ、硬質皮膜の剥離やクラックの低減が可能となり、密着性に優れた硬質皮膜を得ることができる。これは、皮膜硬度差よりも大きな効果がある。
【００２１】
次に、表１の本発明例及び比較例を用いて圧痕試験による皮膜剥離状況を併記する。測定はロックウェル硬度計により１４７０Ｎの荷重で圧痕を形成し、光学顕微鏡により観察した。本発明例１２〜２２は剥離が無く、優れた密着性を示した。これは本発明例が適正なＥ値の範囲内にあるためである。比較例２３〜３０、従来例１０は被覆基体の塑性変形に追従することができず、圧痕周辺部に膜剥離が発生した。
【００２２】
（実施例４）
表１に示す本発明例１２から２２、比較例２３から３０及び従来例１０の硬質皮膜を、表１に示す（Ｖ＋Ｃｏ）の組成と硬度をもつ高速度鋼を基体として、外径１２ｍｍの４枚刃の切刃を有する高速度鋼製エンドミルに、各組成からなるターゲットを配置したアークイオンプレーティング装置内に工具をセットし、真空中４５０℃で１時間の脱ガス加熱工程を実施し、Ａｒイオンによる被覆基体のクリーニング処理を行なった。実施例３と同じ方法でエンドミル表面に、硬質皮膜を３μｍの厚さで被覆した。表１に示す本発明例１２から２２、比較例２３から３０及び従来例１０の被覆エンドミルを用いて、下記条件の切削試験を行い被覆エンドミルが切削不能に至るまでの時間を表１に併記する。
（切削諸元）
被削材：ＳＫＤ１１（硬さＨＢ２１９）
切り込み：Ｒｄ：６ｍｍ、Ａｄ：１２ｍｍ
切削速度：３０ｍ／ｍｉｎ
送り：０．０５ｍｍ／刃（１０７ｍｍ／ｍｉｎ）
切削油：エアーブロー
【００２３】
表１より、本発明例１２〜２２の高速度鋼を基体とした硬質皮膜被覆エンドミルは、従来例１０と比較して切削不能に至るまでの切削時間が長く、耐摩耗性に優れている。本発明例２０は本発明皮膜被覆後にダイヤモンド粒子を含有した粒子を工具すくい面に投射することにより、硬質皮膜表面を平滑にしたが、本発明例１２と比較しても、より切削寿命が延長している。比較例２３は被覆条件をバイアス電圧−５００Ｖで被覆した硬質皮膜のＸ線回折による最強強度面指数が（２２０）面を示し、Ｉ（２００）／Ｉ（１１１）の値が４．５となり、本発明例に比べて切削寿命が短い。比較例２６はターゲットに含有する酸素濃度が１８００ｐｐｍからなるターゲットを使用した場合を示すが、Ｘ線光電子分光分析により酸化物としての結合状態が確認されない場合を示し、本発明例に比べて切削寿命が短い。比較例２７はＡｌ含有量が２０原子％の場合であり、弾性回復率は３０％以下となり、切削寿命が短く、耐摩耗性が十分ではない。比較例２８はＡｌ含有量が８０原子％の場合であり、切削寿命が短く耐摩耗性に劣る。比較例２９は酸素含有量が５５原子％の場合であるが、耐摩耗性が十分ではない。比較例３０はＳｉ含有量が３４原子％の場合であるが耐摩耗性が十分ではない。
【００２４】
本発明例１２、１３、１４はそれぞれ基体の（Ｖ＋Ｃｏ）値が異なる場合の本発明例であるが従来例に比べ、切削寿命が長い。一方、比較例２４、２５に基体中の（Ｖ＋Ｃｏ）値が２．５重量％の場合と１２．１重量％の場合を示す。基体中の（Ｖ＋Ｃｏ）値が２．５重量％の場合、切刃の逃げ面側へ塑性変形を生じ、基体強度が十分ではなく、チッピングが多発した。基体中の（Ｖ＋Ｃｏ）値が１２．１重量％の場合は、微小な硬質皮膜剥離が観察され、高硬度を有する該硬質皮膜との密着性が悪く、不安定な摩耗状態であり、本発明である硬質皮膜の特性を十分に発揮できなかった。従って、被覆エンドミルによる切削加工においては硬質皮膜により、被覆基体の影響がかなり大きいことが明らかである。本発明例１５は基体の硬度がＨＲＣ６３．８であるが従来例に比べ切削寿命が長い。更に、比較例２８、３０は半価幅が１度以上となり、また、結晶粒径のアスペクト比についても５を超えて大きくなっていて、耐摩耗性が十分ではなく、工具寿命が短い。これらは、皮膜の（１１１）面配向が強い為、残留圧縮応力も高くなって皮膜の密着性が低下したことが短寿命となった原因と考えられる。更に比較例２８はピーク強度比Ｑ２／Ｑ１の値が、０．１を超えて大きい値を示した。このことは、膜組成におけるＡｌ含有量の多いため、Ａｌの六方晶系化合物の含有割合が増加したためである。これによって、皮膜の硬度が低下し、十分な耐摩耗性が得られなかった。
【００２５】
【発明の効果】
本願発明の被覆エンドミルを適用することにより、切削加工に用いても十分な耐摩耗性を有し、基体表面とその直上の硬質皮膜とが密着性の改善を図り、更に耐高温酸化特性に優れた被覆エンドミルを得ることが出来た。
【図面の簡単な説明】
【図１】図１は、本発明例のＣｒ−Ｏ及びＡｌ−Ｏの結合エネルギーを示す。
【図２】図２は、本発明例のＣｒ−Ｎ及びＣｒ−Ｏの結合エネルギーを示す。
【図３】図３は、本発明例のＡｌ−Ｎ及びＡｌ−Ｏの結合エネルギーを示す。
【図４】図４は、本発明例のＸ線回折結果を示す。
【図５】図５は、本発明例と従来例のＡｌ添加量と皮膜硬度の関係を示す。
【図６】図６は、本発明例１２及び従来例１０の荷重変位曲線を示す。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a coated end mill that exhibits excellent wear resistance by coating a hard coating useful as a surface coating material of an end mill used for cutting.
[0002]
[Prior art]
Patent Literatures 1 to 4 shown below disclose AlCr-based coatings as hard coating materials having excellent resistance to high-temperature oxidation.
[Patent Document 1] Japanese Patent No. 3027502 (page 6, FIG. 1)
[Patent Document 2] Japanese Patent No. 3039381 (page 4, FIG. 1)
[Patent Document 3] JP-A-2002-160129 (page 3, FIG. 1)
[0003]
Patent Literature 1 discloses an AlCr-based hard film selected from AlCr and one of C, N, and O as a metal component, and an example relating to an amorphous film having high hardness. However, the hardness of this amorphous film is at most about 21 GPa, the Knoop hardness, and abrasion resistance cannot be expected, and adhesion is not sufficient. The hard coatings disclosed in Patent Literature 2 and Patent Literature 3 are nitrides of AlCr and have a high-temperature oxidation resistance of about 1000 ° C, but the oxidation resistance at a temperature of 1000 ° C or higher has been studied. Absent. The hardness is about HV21 GPa and the improvement of the hardness is insufficient and the wear resistance is poor.
[0004]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a coated end mill which solves the above problems and improves wear resistance by increasing hardness, which is a drawback of a Cr-based coating, and as a result, exhibits an excellent life.
[0005]
[Means for solving the problem]
The present invention provides a coated end mill, the coating is a hard film coated by arc discharge type ion plating method, the rigid coating, (Al x Cr 1-x -y Si y) (N 1-α- β-γ B α C β O γ), where, x, y, α, β , γ represents a respective atomic ratio, 0.45 <x <0.75,0 ≦ y <0.2,0 ≦ α <0.12, 0 ≦ β <0.2, 0.01 ≦ γ ≦ 0.25, and the diffraction intensity of the (111) plane in X-ray diffraction is the diffraction intensity of the I (111), (200) plane. Is I (200), the value of I (200) / I (111) is 4 or less, and at least Cr, Al and / or Si, oxygen and oxygen fall within the range of 525 eV to 535 eV in X-ray photoelectron spectroscopy. And the base of the end mill is made of high-speed steel, and the sum of V and Co 3 ≦ (V + Co) ≦ 11, Cr by weight% are coated end mill being characterized in that a 3.8 ≦ Cr ≦ 4.5, in weight percent. By adopting the above configuration, the adhesion between the substrate and the hard coating is excellent and the hardness can be increased, and as a result, the coated end mill of the present invention which exhibits excellent wear resistance has been completed.
[0006]
When the half-value width at 2θ of the (200) plane diffraction peak in X-ray diffraction has a spread of 0.5 ° or more and 1 ° or less in the hard coating of the present invention, the hard coating and the oxidation resistance are improved. large. The contact depth and the maximum displacement at the time of the maximum load are determined by a hardness measurement method using nanoindentation (WC Oliver and GM Phar: J. Mater. Res., Vol. 7, No. 6). , June, 1992, 1564-1584). Using this numerical value, E = 100 − {(contact depth) / (maximum displacement at maximum load)}
By defining the elastic recovery rate E by the following formula, and setting 30% ≦ E <40%, the balance between the wear resistance and the adhesion is optimized. Further, the peaks of a cubic compound of Cr and a hexagonal compound of Al are detected by X-ray diffraction. The peak intensity of the (200) plane of the cubic compound of Cr is Q1, and the peak of the hexagonal compound of Al is ( When the (001) plane peak intensity is Q2, setting the peak intensity ratio Q2 / Q1 to 0 ≦ Q2 / Q1 ≦ 0.1 is effective in improving the film hardness. Further, in the hard coating of the present invention, when the projections on the surface of the hard coating are smoothed by mechanical treatment, the coefficient of friction of the surface is reduced, thereby improving the chip dischargeability. The high-speed steel used in the present invention preferably has a hardness of HRC64 or more and less than HRC68.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
The composition of the metal elements constituting the hard coating of the present invention, in the (Al x Cr 1-x- y Si y), x is 0.45 <x <0.75, y a is 0 ≦ y <0.2 Need to be satisfied. When the value of x is 0.45 or less, the effect of improving the film hardness and the high-temperature oxidation resistance is not sufficient. When the value of x is 0.75 or more and the value of y is 0.2 or more, the residual compressive stress becomes excessive. In some cases, self-destruction may be induced immediately after coating. The composition of non-metallic elements, in (N 1-α-β- γ B α C β O γ), α is coating embrittlement at least 0.12, the upper limit of the preferred alpha is 0.08. The addition of boron has the effect of reducing the welding resistance to the workpiece and the coefficient of friction in a high-temperature environment, and improving the lubricity. Next, when β is 0.2 or more, the film becomes brittle. The preferred upper limit of β is 0.16. The addition of carbon has the effect of increasing the hardness of the hard coating, reducing the coefficient of friction at room temperature, and improving lubricity. γ needs to be 0.01 or more and 0.25 or less. If γ is less than 0.01, the effect of addition cannot be obtained, and if γ exceeds 0.25, the film hardness decreases and the wear resistance becomes poor. Preferably, γ is 0.05 or more and 0.2 or less. The addition of γ is effective for improving the adhesion between the substrate and the film, increasing the hardness by densifying the film, and improving the high-temperature oxidation resistance by forming an oxide. Further, the ratio of N, B, C, O of the non-metallic element to Al, Cr, Si of the metal element is stoichiometrically ((N, B, C, O) / (Al, Cr, Si)> 1). .1 is more preferred.
[0008]
When the diffraction intensity of the (111) plane in the X-ray diffraction of the present invention is I (111) and the diffraction intensity of the (200) plane is I (200), the value of I (200) / I (111) is 4 or less. The reason is that the adhesion of the film strongly depends on the residual compressive stress, and this residual compressive stress strongly depends on the ion energy which is a film forming condition. That is, under the condition that the ion energy is low, the result is that the residual compressive stress of the film is low. Conversely, under conditions of high ion energy, the residual compressive stress of the coating is high. Here, the factors that determine the ion energy are, specifically, the bias voltage and the reaction gas pressure, which are the film forming conditions, and can be controlled by this. According to the present invention, when the residual compressive stress is high, the film is strongly oriented to the (111) plane in X-ray diffraction, and the hardness of the film can be made high due to the influence of the high residual compressive stress. . On the other hand, focusing on the adhesion of the coating, if the residual compressive stress in the hard coating is increased, the hardness of the coating can be increased. However, since the shear stress between the substrate and the interface of the coating increases, the adhesion is increased. Is impaired, which is not preferable. Therefore, it is important to optimally control the balance between the adhesion between the substrate and the coating and the hardness of the coating. In the present invention, by setting the value of I (200) / I (111) to 4 or less, it is possible to optimally control the balance between the two. If the value of I (200) / I (111) exceeds 4 and becomes large, the hardness of the film rapidly decreases, and satisfactory performance as a hard film applied to an end mill cannot be obtained. Therefore, the value is limited to 4 or less.
[0009]
The hard film needs to have a binding energy of Cr, Al and / or Si and oxygen between 525 eV and 535 eV by X-ray photoelectron spectroscopy analysis, and the film becomes dense, and a diffusion path of oxygen in an oxidizing atmosphere. The crystal grain boundary becomes indistinct and has a function of making inward diffusion difficult. Since Cr, Al and / or Si are present in the state of nitride, oxide or oxynitride, the hard film becomes dense and has high hardness. In order to form a bonding state between Cr, Al and / or Si and oxygen, which is a feature of the coating of the present invention, it is necessary to contain a certain amount or more of oxygen. When a bias voltage is applied to the substrate, the adhesion can be further improved. The film forming conditions are preferably such that the gas pressure is 1.5 to 5.0 Pa, the temperature of the coated substrate is 350 to 700 ° C., and the bias voltage is a bias voltage of −15 to −300 V. The balance with the film hardness is optimized, and a dense hard film excellent in high-temperature oxidation resistance and abrasion resistance can be obtained.
[0010]
In the high-speed steel used in the coated end mill of the present invention, the sum of V and Co is in a range of 3 ≦ (V + Co) ≦ 11 by weight% and in a range of 3.8 ≦ Cr ≦ 4.5 by weight% of Cr. V and Co in the high-speed steel are additive elements that determine hardness and heat resistance, and are also additive elements that determine toughness and wear resistance. If the amount is less than 3% by weight, the substrate strength in a high-temperature environment was not sufficient, and the tool life was unstable. This is because plastic deformation of the cutting edge occurs in the cutting process. On the other hand, if it exceeds 11% by weight, the residual compressive stress generated in the hard coating is insufficiently relaxed, the adhesiveness is not sufficient, fine peeling of the coating may occur, and chipping or chipping may occur on the cutting edge. Chipping occurred, resulting in a short life. Cr is in the above range in order to enhance the heat treatment property of the high-speed steel and sufficiently increase the hardness. When V, Co and Cr in the substrate satisfy the above range, the heat resistance of the matrix in the high speed steel is also excellent. As a result of considering the effect of the hard coating of the present invention on the adhesion, the contents of V, Co and Cr in the base were determined within the above ranges. Within this range, the residual compressive stress generated in the hard coating can be relieved inside the substrate and has excellent adhesion, and the hard coating has excellent oxidation resistance and high hardness. Characteristics can be fully exhibited. According to these configurations, it is possible to achieve high-speed cutting and long life of cutting by the end mill.
[0011]
Regarding the aspect ratio of the crystal grains of the hard coating, the thickness T of the fracture surface of the coating having the columnar crystal structure of the present invention in the upper and lower film thickness directions corresponding to T1 which is 25% to 50% of the film thickness T. Find the top and bottom positions. At this time, the upper end position and the lower end position are allocated so as to be substantially equal in the upper and lower film thickness directions from the reference position corresponding to T / 2. The upper-side particle diameter K and the lower-side particle diameter L in the horizontal direction at each upper and lower end position are obtained. Therefore, assuming that the aspect ratio is T1 / ((K + L) / 2), the aspect ratio of the crystal grains of the hard coating having a columnar crystal structure is 1.2 to 5. When the aspect ratio exceeds 5 and becomes large, the crystal grains become elongated in the film thickness direction, and the toughness of the film decreases, which is not preferable. If it is less than 1.2, the number of granular crystals tends to increase, and the film hardness decreases, which is not preferable. Further, when the residual compressive stress of the hard film is 1 GPa or more and 5 GPa or less, the hard film has toughness, and is in a range suitable for the balance between the film hardness and the substrate adhesion, and is effective in improving performance. It is.
[0012]
E by the hardness measurement method by nanoindentation is 30% ≦ E <40%, and the bias voltage, the reaction gas pressure, the partial pressure ratio thereof, and the substrate temperature at the time of film formation are optimally controlled. This can be achieved by: When E is 40% or more, the residual compressive stress in the hard coating becomes too high, resulting in poor toughness and poor adhesion. If it is less than 30%, the wear resistance is insufficient due to abnormal wear due to insufficient strength. Preferred values of E are between 32% and 38%.
[0013]
When the peak intensity of the cubic compound of Cr in the hard coating is Q1 and the peak intensity of the hexagonal compound of Al is Q2, if the peak intensity ratio Q2 / Q1 exceeds 0.1, the hardness is increased. It drops sharply. Therefore, setting the value of Q2 / Q1 to 0.1 or less is effective and preferable in obtaining the required film hardness, and is preferable.
[0014]
The convex portion of the hard coating surface along the polished surface or the ground surface of the coated substrate surface coated with the coating of the present invention, or a convex portion may be formed due to adhesion of macroparticles generated during coating. The smoothing of the projections by a mechanical treatment is more preferable for the effect of removing chips. Furthermore, by applying a mechanical treatment to the cutting edge after coating, a conforming effect is also confirmed, the chipping resistance and chipping resistance can be improved, and a more preferable hard coating can be obtained.
[0015]
The hardness of the end mill substrate of the present invention is not less than HRC64 and less than HRC68. When the substrate is less than HRC64, wear progress with plastic deformation of the cutting edge is also confirmed under severe cutting environment, and the cutting edge strength is not sufficient, which is not preferable. If the HRC is 68 or more, the residual compressive stress generated in the hard coating is not sufficiently relaxed, and fine coating peeling may occur, which is not preferable. Further, when less than 4 atomic% of the metal component in the hard coating of the present invention is replaced by one or more of the metal components belonging to groups 4a, 5a and 6a of the periodic table, and one or more hard coatings related to the present invention are contained. The same effect is also confirmed in the multilayer structure described above, which is preferable and is included in the technical scope of the present invention. Hereinafter, the present invention will be specifically described based on examples.
[0016]
【Example】
(Example 1)
An oxygen-containing alloy target was used for film formation, a reaction gas was introduced into a vacuum apparatus, the total pressure was 3.0 Pa, the bias voltage was -100 V, the coating temperature was 450 ° C., the film thickness was about 5 μm, and (Al 0.6 Cr 0.4 ) (N 0.80 C 0.08 O 0.10 B 0.02 ) was formed as Inventive Example 1. The coating composition was determined by electron probe X-ray microanalysis and Auger electron spectroscopy. The X-ray photoelectron spectroscopy was analyzed using a PHI 1600S X-ray photoelectron spectrometer. FIG. 1 shows the results of X-ray photoelectron spectroscopy analysis of Example 1 of the present invention. FIG. 1 shows a narrow spectrum in which the binding energy is around 530 eV, and shows the presence of Cr—O and Al—O bonds. FIG. 2 shows the presence of Cr-N and Cr-O bonds. FIG. 3 shows the presence of Al—N and Al—O bonds. The X-ray diffraction result of FIG. 4 shows that when the diffraction intensity of the (111) plane in the X-ray diffraction of the hard film is I (111) and the diffraction intensity of the (200) plane is I (200), I (200) / Indicates that the value of I (111) is 4 or less.
[0017]
(Example 2)
In the same manner as in Example 1, (Al x Cr 1-xy Si y ) (N 0.95 O 0.05 ) was formed, and Comparative Example 2, x = 0.20, y = 0, Comparative Example 3, x = 0.30, y = 0, present invention example 4, x = 0.50, y = 0, present invention example 5, x = 0.60, y = 0, present invention example 6, x = 0 .70, y = 0, Comparative example 7, x = 0.80, y = 0 and (Al x Cr 1-x) N system of a conventional example 9, x = 0.20, the conventional example 10, x = 0. 50, Conventional Example 11, x = 0.70, and the indentation hardness was measured. The tester used was a micro indentation hardness tester. The indenter used was a triangular pyramid indenter made of diamond with a diagonal angle of 115 degrees, the maximum load was 49 mN, the load step was 4.9 mN / sec, and the holding time at the maximum load was 1 Seconds. The measured value was an average of 10 measurements. From FIG. 5, in Examples 4 to 6 of the present invention and in the range of the added amount of Al of 45 to 75 atomic%, the hardness was higher than that of the system containing no oxygen. The hard coating of the present invention becomes high hardness by containing oxygen, and can obtain 40 GPa or more. As a result, a hard coating excellent in adhesion and abrasion resistance can be obtained.
[0018]
(Example 3)
Using high-speed steel as the substrate, Examples 12 to 22, Comparative Examples 23 to 30, and Conventional Example 10 having the coating compositions shown in Table 1 were produced. The coating was performed by arc ion plating under the conditions of a coating substrate temperature of 450 ° C., a reaction pressure of 3.5 Pa, and a bias voltage of −150 V. Table 1 shows the composition of the film and the like.
[0019]
[Table 1]
[0020]
Using the samples shown in Table 1, the oxide layer of the film treated under the oxidizing conditions of 1100 ° C. in the atmosphere, the microindentation hardness, the residual compressive stress calculated from the deformation of the thin plate, and the elastic recovery were measured in the same manner as in Example 2. . From Table 1, it was confirmed that the oxidation layer thicknesses of Examples 12 to 22 of the present invention hardly proceeded with oxidation and were excellent in high-temperature oxidation resistance. In the conventional example 10, the oxidation progressed remarkably, and the hard coating almost became an oxide, and the inward diffusion of oxygen reached the substrate. The indentation hardness is further increased by including C and B. The residual compressive stress is low in Examples 12 to 22 of the present invention. Further, from the load displacement curves of Example 12 of the present invention and Conventional Example 10 shown in FIG. It shows that the amount of plastic deformation is small, and when the same stress acts on the hard film, the elastic recovery is large and the plastic deformation is difficult. E was determined from this load displacement curve. The larger the E, the better the elastic recovery characteristics. From Table 1, it can be seen that Examples 12 to 22 of the present invention are excellent in elastic recovery characteristics, enable peeling of the hard film and reduce cracks, and can provide a hard film having excellent adhesion. This has a greater effect than the film hardness difference.
[0021]
Next, the peeling state of the film by the indentation test will be described together with the present invention examples and comparative examples in Table 1. For the measurement, an indentation was formed with a load of 1470 N using a Rockwell hardness tester, and observed with an optical microscope. Inventive Examples 12 to 22 showed no peeling and exhibited excellent adhesion. This is because the example of the present invention is within the range of an appropriate E value. Comparative Examples 23 to 30 and Conventional Example 10 could not follow the plastic deformation of the coated substrate, and film peeling occurred around the indentation.
[0022]
(Example 4)
The hard coatings of Examples 12 to 22 of the present invention, Comparative Examples 23 to 30 and Conventional Example 10 shown in Table 1 were prepared by using a high-speed steel having a composition and hardness of (V + Co) shown in Table 1 as a base and having a diameter of 12 mm. A high-speed steel end mill having a single cutting edge, a tool was set in an arc ion plating apparatus in which targets of each composition were arranged, and a degassing heating process was performed at 450 ° C. for 1 hour in a vacuum, The coated substrate was cleaned with Ar ions. A hard film was coated on the end mill surface in a thickness of 3 μm in the same manner as in Example 3. Using the coated end mills of Inventive Examples 12 to 22, Comparative Examples 23 to 30, and Conventional Example 10 shown in Table 1, a cutting test was performed under the following conditions, and the time until the coated end mill became uncuttable is also shown in Table 1. .
(Cutting specifications)
Work material: SKD11 (hardness HB219)
Cut: Rd: 6 mm, Ad: 12 mm
Cutting speed: 30m / min
Feed: 0.05mm / blade (107mm / min)
Cutting oil: air blow [0023]
As shown in Table 1, the hard film-coated end mills of the invention examples 12 to 22 using the high-speed steel as a base have a longer cutting time until cutting becomes impossible and are superior in wear resistance as compared with the conventional example 10. In the present invention example 20, the hard coating surface was smoothened by projecting particles containing diamond particles on the tool rake surface after coating the present invention film, but the cutting life was further extended as compared with the present invention example 12. are doing. In Comparative Example 23, the strongest surface index by X-ray diffraction of a hard film coated with a bias voltage of -500 V under coating conditions shows a (220) plane, and the value of I (200) / I (111) becomes 4.5, The cutting life is shorter than that of the present invention. Comparative Example 26 shows the case where a target having an oxygen concentration of 1800 ppm contained in the target was used, but the case where the bonding state as an oxide was not confirmed by X-ray photoelectron spectroscopy was shown. Is short. In Comparative Example 27, the Al content was 20 atomic%, the elastic recovery was 30% or less, the cutting life was short, and the wear resistance was not sufficient. Comparative Example 28 was a case where the Al content was 80 atomic%, and the cutting life was short and the wear resistance was poor. Comparative Example 29 is a case where the oxygen content is 55 atomic%, but the abrasion resistance is not sufficient. Comparative Example 30 is a case where the Si content is 34 atomic%, but the abrasion resistance is not sufficient.
[0024]
Inventive Examples 12, 13 and 14 are examples of the present invention in which the (V + Co) values of the substrates are different, but the cutting life is longer than that of the conventional example. On the other hand, Comparative Examples 24 and 25 show the cases where the (V + Co) value in the substrate is 2.5% by weight and 12.1% by weight. When the (V + Co) value in the substrate was 2.5% by weight, plastic deformation occurred on the flank side of the cutting edge, the substrate strength was not sufficient, and chipping occurred frequently. When the (V + Co) value in the substrate is 12.1% by weight, minute hard film peeling is observed, adhesion to the hard film having high hardness is poor, and the film is in an unstable wear state. , The characteristics of the hard film could not be sufficiently exhibited. Therefore, it is clear that the influence of the coated substrate is considerably large due to the hard coating in the cutting process using the coated end mill. In Example 15 of the present invention, the hardness of the substrate was 63.8, but the cutting life was longer than that of the conventional example. Further, in Comparative Examples 28 and 30, the half width was 1 degree or more, and the aspect ratio of the crystal grain size was also larger than 5, and the wear resistance was not sufficient and the tool life was short. These are considered to be due to the fact that the (111) plane orientation of the film was strong, the residual compressive stress was also increased, and the adhesion of the film was reduced, resulting in a shorter life. In Comparative Example 28, the value of the peak intensity ratio Q2 / Q1 was larger than 0.1. This is because the content of the Al hexagonal compound was increased due to the large Al content in the film composition. As a result, the hardness of the coating decreased, and sufficient wear resistance was not obtained.
[0025]
【The invention's effect】
By applying the coated end mill of the present invention, it has sufficient abrasion resistance even when used for cutting, improves the adhesion between the substrate surface and the hard coating immediately thereon, and has excellent high-temperature oxidation resistance. A coated end mill was obtained.
[Brief description of the drawings]
FIG. 1 shows the binding energies of Cr—O and Al—O according to the present invention.
FIG. 2 shows the binding energies of Cr—N and Cr—O of the present invention.
FIG. 3 shows binding energies of Al—N and Al—O of the present invention.
FIG. 4 shows an X-ray diffraction result of an example of the present invention.
FIG. 5 shows the relationship between the amount of Al added and the film hardness of the present invention and the conventional example.
FIG. 6 shows load displacement curves of Example 12 of the present invention and Conventional Example 10.
