JP2004017164A

JP2004017164A - Hard film coated high speed steel broach

Info

Publication number: JP2004017164A
Application number: JP2002170899A
Authority: JP
Inventors: Takashi Ishikawa; 石川　剛史
Original assignee: Hitachi Tool Engineering Ltd
Current assignee: Moldino Tool Engineering Ltd
Priority date: 2002-06-12
Filing date: 2002-06-12
Publication date: 2004-01-22

Abstract

<P>PROBLEM TO BE SOLVED: To provide a broach tool wherein the hardness of a hard film covered on the surface of a broach cutting edge is maintained under high temperature environment, having excellent oxidation resistance and a low affinity to iron diffused from a workpiece to inside the hard film in a cutting process. <P>SOLUTION: This hard film coated high-speed steel broach is covered with at least one or more layers of a hard film containing one or more kinds of elements selected from elements of the groups IVa, Va, and VIa of the periodic table and Al and Si, element B, elements selected from one or more kinds of N, C, and O. At least one layer of the hard film is a hard film wherein either the binding energy of Ti and O or the binding energy of Cr to O including the binding energy of B to N is recognized by X-ray photo-electric spectrochemical analysis. The range of V and Co contained in the base material of the high-speed steel is 3 ≤(V+Co) ≤11 in weight %. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明が属する技術分野】
本発明は、機械構造部品に代表される金属材料等の切削加工に用いる、硬質皮膜被覆高速度鋼製ブローチに関する。
【０００２】
【従来の技術】
機械構造部品に代表される金属材料等の切削加工に、多数の切刃からなるブローチが用いられる。これらブローチの切削寿命の延長もしくは被加工物の高精度化を目的とし、ブローチ表面に硬質皮膜を被覆した硬質皮膜被覆ブローチが用いられている。また被覆される硬質皮膜としては、皮膜硬度がＨＶ２０００以上からなる例えばＴｉＮ皮膜もしくはＴｉ（ＣＮ）皮膜、更には特開平１１−３００５１８号公報に見られるＴｉＮ皮膜よりも耐酸化性に優れた（ＴｉＡｌ）Ｎ皮膜を被覆した被覆ブローチが提案されている。
【０００３】
しかしながら、近年のブローチ加工では、被加工物を更に高能率、且つ、高精度な加工物に仕上げる要求が高まっていることに加え、熱処理後の高硬度材を直接加工する要求も高まっている。また、その切削環境においても、人体及び地球環境への配慮により、油剤を用いた切削加工から、切削液中に塩素等の有害な物質を含有しないドライ切削もしくはセミドライ切削の加工要求も高まっている。このように、ブローチ加工における切削環境は、より過酷な状況を強いられており、さらなる高性能ブローチの開発が望まれている。被加工物の高硬度化、高速切削加工及び切削工具の長寿命化の要求に加え、切削環境としては、クーラントのドライ化及びセミドライ化により、工具切刃近傍では、切削温度が高くなる傾向にあり、硬質皮膜が酸化すると同時に工具刃先に凝着現象が発生し、ブローチ表面に被覆される耐摩耗皮膜と被加工物との間に化学反応が生じ、工具の短寿命や被加工物の精度を劣化させる。このような場合、従来までの前記ＴｉＮ皮膜、Ｔｉ（ＣＮ）皮膜、（ＴｉＡｌ）Ｎ皮膜では、凝着を抑制する効果と耐摩耗性のバランスが十分ではなく、摩擦抵抗の増加により、十分な切削寿命が得られてはいない。また、これら凝着物とともに硬質皮膜が剥離、脱落する現象も確認されており、このような場合は更に切削寿命は不安定で短くなる傾向にある。以上のように、これらの加工要求に対し、満足される切削特性は得られてはいない。
【０００４】
【発明が解決しようとする課題】
本発明者は、これら苛酷な切削環境下で使用したブローチの逃げ面及びすくい面の損傷状態を注意深く解析した結果、工具逃げ面側では硬質皮膜内に酸素が拡散しており、硬質皮膜最表面に強度の低い酸化物を形成し、この強度の低い酸化物を起点とした脱落が繰り返されている事実を突き止めた。また、切屑の排出部となる工具すくい面側では被加工物である鉄と酸素が皮膜内部に拡散しており、この鉄と酸素が硬質皮膜の酸化を助長し、摩耗が進行していた。以上のように、切刃先端近傍では著しく温度が上昇し、硬質皮膜の酸化による摩耗進行と同時に被覆母材の軟化を伴い、その結果として工具切刃の欠損もしくはチッピングが発生していることが明らかとなった。
【０００５】
本発明はこうした事情に鑑み、ブローチの切刃部表面に被覆する硬質皮膜の高温硬度、耐酸化性の改善並びに被加工物から切削過程で硬質皮膜内部に拡散する鉄に対して、低い親和性を有し、更に摩擦抵抗の低い硬質皮膜を被覆し、切削温度上昇を抑制させるとともに、また、工具母材としては、これら高硬度からなる硬質皮膜との密着性を維持するために靭性のある耐チッピング性に優れた母材とする。これらの改善により、切削加工の高能率化並びに長寿命化を達成することのできる硬質皮膜被覆高速度鋼製ブローチの構成を提供することを課題とする。
【０００６】
【課題を解決するための手段】
これら課題を達成するための本発明は、周期律表の４ａ、５ａ、６ａ族の元素、Ａｌ、Ｓｉから選ばれる１種以上から選択された元素と、Ｂ元素とＮ、Ｃ、Ｏのうち１種以上より選択された元素とを含む硬質皮膜を少なくとも１層以上被覆してなる硬質皮膜被覆高速度鋼製ブローチにおいて、該硬質皮膜の少なくとも１層は、Ｘ線光電子分光分析でＢとＮの結合エネルギーを含み、ＴｉとＯの結合エネルギーもしくはＣｒとＯの結合エネルギーのどちらかが認知される硬質皮膜であり、該高速度鋼の母材中に含まれるＶ及びＣｏが、重量％で３≦（Ｖ＋Ｃｏ）≦１１の範囲であることを特徴とする硬質皮膜被覆高速度鋼製ブローチである。
【０００７】
【発明の実施の形態】
加工の高能率化並びに長寿命化を達成する為には、被覆する硬質皮膜が高温環境下でより高い硬度を維持する、硬質皮膜の高温硬度、また高温環境下で優れた耐酸化性を有し、切削過程で被加工物から硬質皮膜内部へ拡散する鉄に対して、低い親和性を有し、更に摩擦抵抗の低い硬質皮膜を被覆することにより、切削温度上昇を抑制させる必要がある。また、工具母材としても高温環境下において母材の軟化を抑制する耐熱性と、これら硬質皮膜と高い密着性を有する母材強度を維持することが必要である。その手段として、硬質皮膜の少なくとも１層は、Ｘ線光電子分光分析でＢとＮの結合エネルギーを含み、更にＴｉとＯの結合エネルギーもしくはＣｒとＯの結合エネルギーのどちらかが認知される硬質皮膜であり、該硬質皮膜被覆高速度鋼製ブローチの母材中に含まれるＶ及びＣｏが、重量％で１０≦（Ｖ＋Ｃｏ）≦２０の範囲にすることが極めて有効である。上記該硬質皮膜は、高温環境下における皮膜硬度並びに耐酸化性に優れ、また被加工物中の鉄に対して、親和性が低く、潤滑作用を併せ持っているため、切削温度上昇を抑制する作用を有する。これは該硬質皮膜内のＢがＢＮとして存在することにより，高温環境下で該硬質皮膜最表面のＢＮ結合が、ＢとＯの結合に変わり、緻密で強度の高いＢ酸化物を硬質皮膜最表面に形成し、この緻密で強度の高いＢ酸化物がその後の酸化防止層として作用する。また同時に、緻密で強度の高いＢ酸化物は動的な酸化環境下においても、該硬質皮膜と剥離し難く耐酸化性に優れる。
【０００８】
更に、硬質皮膜の高温環境下における軟化は、酸素の拡散に起因するため、耐酸化性に著しく優れる本発明皮膜は高温硬度に関しても著しく改善された。更に、硬質皮膜内にＢＮとして存在する場合の利点として、鉄に対して極めて親和性が低いことである。このことにより、被加工物である鉄に対して優れた摩擦特性を示し、切削温度を抑制する作用も有する。更に、硬質皮膜の高硬度化に対しても、硬質皮膜内にＢＮとして存在する場合、硬質皮膜格子内の内部応力を高め、硬質皮膜を著しく高硬度化させる。しかしながら、高硬度化されると同時に、硬質皮膜内に残留する圧縮応力も高くなってしまうため、この残留圧縮応力に耐えうる強度を有する母材とすることが必要となる。そこで、母材中に含まれるＶ及びＣｏを、重量％で１０≦（Ｖ＋Ｃｏ）≦２０の範囲に限定する必要がある。この範囲であれば、上記硬質皮膜内に発生する残留圧縮応力に対しても、母材内部で緩和することが可能であり密着性に優れ、上記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。また、母材中のＶとＣｏ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。これらの構成により、ブローチによる切削加工の高能率化並びに長寿命化を達成することが可能となる。
【０００９】
より好ましい硬質皮膜としては、該硬質皮膜内に最小結晶粒径が０．５ｎｍ以上、５０ｎｍ以下である結晶質相と、アモルファス相を含み、更に、該硬質皮膜はＸ線回折における回折強度が（２００）面で最大ピークを示し、その（２００）面の回折線が２θの半価幅で１．５度以上であることとする。更に好ましくは、該硬質皮膜の少なくとも１層が、Ｂ元素と金属成分としてＴｉもしくはＣｒ、及びＴｉとＣｒを成分とする硬質皮膜であり、該硬質皮膜とは別の少なくとも１層は金属元素として少なくともＡｌとＴｉを含み、非金属元素として少なくともＮを含む硬質皮膜を用いることが、より好ましい。このような構成を採用することで、ブローチ切刃表面に被覆する硬質皮膜が高温環境下で、より高い硬度を維持することが可能となり、また優れた耐酸化性を有するとともに、切削過程で被加工物から硬質皮膜内部に拡散する鉄に対して、低い親和性を有し、更に摩擦抵抗の低い硬質皮膜を採用することにより、切削温度上昇を抑制し、更にブローチ母材の耐熱性と硬質皮膜との密着強度を改善することにより、ブローチによる切削加工の高速、高能率化並びに長寿命化が達成され、従来技術の課題を解決するに至った。
【００１０】
本発明である硬質皮膜を被覆したブローチ母材として用いる高速度鋼は、母材中に含まれるＶ及びＣｏが、重量％で３≦（Ｖ＋Ｃｏ）≦１１の範囲である必要がある。母材中のＶ及びＣｏは高速度鋼の硬度及び耐熱強度を決定する添加元素であるが、３重量％未満の場合は、高温環境下における母材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部が逃げ面側へ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、該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、切刃部にチッピングや欠けが発生し、短寿命を招いた。本発明である該硬質皮膜の該ブローチ母材への密着強度に及ぼす影響を考慮した結果、本発明者は高速度鋼中のＶとＣｏの含有量を上記範囲内に決定した。また、該硬質皮膜中にＢとＮの結合が確認されない場合、上述したように皮膜の高温硬度、耐酸化性並びに潤滑特性ともに十分ではなく、従来課題を解決するには至らなかった。また、ＢとＮの結合エネルギーは認められるが、ＴｉとＯの結合エネルギーとＣｒとＯの結合エネルギーの何れも認められない場合は、潤滑特性が十分ではなく、切削温度を抑制するには至らなかった。該高速度鋼は、母材硬さがＨＲＣ６４以上、ＨＲＣ６８未満であることが好ましい。母材硬度がＨＲＣ６４未満となる場合、過酷な切削環境下において切刃が逃げ面側へ、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い場合があり、好ましくない。また、ＨＲＣ６８を超える場合は、該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確認され、好ましくない。
【００１１】
硬質皮膜内に最小結晶粒径が０．５ｎｍ以上、５０ｎｍ以下である結晶質相と、アモルファス相としたのは、硬質皮膜内の最小結晶粒径が０．５ｎｍ以上、５０ｎｍ以下となる場合、皮膜硬度が高く、且つ、高温硬度も著しく改善され、更に耐摩耗性に優れ好ましい。また、同時にアモルファス相を含む場合は、結晶と結晶の界面である結晶粒界が著しく減少し、結晶粒界を介して進行する酸素の拡散抑制に効果的であり、より好ましい。更に、該硬質皮膜は、（２００）面に強く配向した場合が最も皮膜内の格子欠陥が少なく、高密度であり耐酸化性に優れることより（２００）面に最大のピーク強度をもつことが好ましい。更にその半価幅が１．５度以上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く好ましい。また、該硬質皮膜の少なくとも１層が、Ｂ元素と金属成分としてＴｉもしくはＣｒ、及びＴｉとＣｒを成分とする硬質皮膜であることが更に好ましい。Ｂ元素と、金属成分として、ＴｉもしくはＣｒ、及びＴｉとＣｒ、より構成される場合、皮膜硬度、耐酸化性並びに摺動特性のバランスが最も優れ、更に好ましい。該硬質皮膜は該被覆母材との優れた密着性、皮膜硬度及び耐酸化性を有すものの、母材との密着性を更に改善し、切削寿命を安定化させるために、該硬質皮膜とは別の少なくとも１層は金属元素として少なくともＡｌとＴｉを含み、非金属元素として少なくともＮを含む硬質皮膜と多層にすることも可能である。
【００１２】
更に硬質皮膜の母材への密着性を改善し、切削寿命を延ばすために、被覆前後に切刃近傍のバリやカエリ、及び被覆中に付着したドロップレット等の欠陥をショットブラスト等の機械的処理により除去することも好ましい。以下、本発明を実施例に基づいて説明するが、下記実施例は本発明を限定するものではなく、本発明主旨に基づき適宜変更を施すことは何れも本発明の技術的範囲に含まれるものである。
【００１３】
【実施例】
本発明の硬質皮膜被覆高速度鋼製ブローチは、その被覆方法については、特に限定されるものではないが、被覆母材への熱影響、工具の疲労強度、皮膜の密着性等を考慮した場合、比較的低温で被覆でき、被覆した皮膜に適度な圧縮応力が残留するアーク放電方式イオンプレーティング法による被覆処理を行なった。アークイオンプレーティング装置を用い、金属成分の蒸発源である各種合金製ターゲット、並びに反応ガスであるＮ_２ガス、ＣＨ_４ガス、Ａｒ＋Ｏ_２混合ガス、Ｂ_３Ｎ_３Ｈ_６から目的の皮膜が得られるものを選択し、被覆母材温度４００℃、反応ガス圧力３．０Ｐａの条件下にて、被覆母材である各種高速度工具鋼製のスプラインブローチにバイアス電圧−１５０Ｖを印加し、被覆処理を行った。この時の全硬質被複層の厚さはブローチ各部において０．２〜２．０μｍの範囲であった。硬質皮膜へのＢ添加に関しては、金属ターゲット内に予め所定量添加した合金ターゲットも用いる場合と、被覆中にＢ含有気体を真空容器内に導入する場合においても可能である。更に必要に応じ予め、アークイオンプレーティング法によりＴｉＡｌＮ系皮膜を被覆した後、該硬質皮膜を被覆した。
【００１４】
【表１】

【００１５】
表１において、組成の定量分析にはエネルギー分散型Ｘ線分光法、オージェ光電子分光法及び電子線エネルギーロス分光法により総合的に決定した。またＸ線光電子分光分析によるＢとＮの結合エネルギー、ＴｉとＯの結合エネルギー、ＣｒとＯの結合エネルギーの定性分析には、硬質皮膜表面を１０分間Ａｒイオンミーリング後（ＳｉＯ_２換算で表面から約２０ｎｍ除去）に行なった。分析結果を表１に併記する。該硬質皮膜内のアモルファス相の定性分析及び結晶質相からなる最小結晶粒径の測定は、硬質皮膜断面を透過型電子顕微鏡によりランダムに選択した視野の断面写真より実測した。表１に透過型電子顕微鏡による断面写真から実測した結晶質相からなる最小結晶粒径を併記する。結晶粒径の実測方法は、断面写真から断面の面積を円の面積として置き換えた場合の直径である等価円直径により求めた。得られた硬質皮膜被覆高速度鋼製ブローチを用い、以下の条件で切削試験を行った。切削諸元を次に示す。被削材に１個当たりの切削長が４０ｍｍからなる、調質後の硬度がＨＢ２２０のＳ５３Ｃ材を用い、切削速度６ｍ／ｍｉｎ、エアブローを用いた乾式切削で切削試験を行った。切削個数２０００個、即ち総切削長８０ｍ切削後のブローチ逃げ面摩耗量を比較した。同時に被加工物表面の面粗さを工具軸方向に測定した。その結果を表１に併記する。また、併せて同一切削条件で加工した比較例を表１、従来例を表２に示す。
【００１６】
【表２】

【００１７】
表１に示す本発明例は、従来例に比して安定した切削寿命が得られている。以下本発明例の詳細について述べる。表１に示す本発明例である各組成の透過型電子顕微鏡による格子像観察結果から、本発明例１６を除いた何れの該硬質皮膜内にもＢを含有したアモルファス相が確認された。図１に本発明例１の硬質皮膜のＸ線光電子分光分析によるＣｒの２ｐ軌道から得られた結合エネルギーを示し、少なくともＣｒとＮ、ＣｒとＯの結合エネルギーが確認された。図２に本発明例１の硬質皮膜のＸ線光電子分光分析によるＢの１ｓ軌道から得られた結合エネルギーをそれぞれ示し、少なくともＢとＮの結合エネルギーが確認された。本発明例１、２、３はそれぞれ母材の（Ｖ＋Ｃｏ）（重量％）の合計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１７、１８に母材中の（Ｖ＋Ｃｏ）（重量％）の合計が２．５重量％の場合と１２．３重量％の場合の比較例を示す。母材中の（Ｖ＋Ｃｏ）（重量％）の合計が２．５重量％の場合、逃げ面側へ塑性変形を生じ、母材強度が十分ではなく、チッピングが多発した。母材中の（Ｖ＋Ｃｏ）（重量％）の合計が１２．３重量％の場合は、微小な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、本発明である該硬質皮膜の特性を十分に発揮できなかった。したがって、前記過酷なブローチによる切削加工においては、硬質皮膜によって、被覆母材の影響がかなり大きいこと明らかである。本発明例４は母材の硬度がＨＲＣ６３．８であるが従来例に比べ、切削寿命が長い。本発明例５は本発明である該硬質皮膜の成分がＴｉであるＴｉ（ＮＯＢ）皮膜の場合であるが従来例に比べ切削寿命が長い。本発明例６は本発明である（ＴｉＳｉ）（ＮＯＢ）の場合であるが、従来例に比べ切削寿命が長い。本発明例７は本発明である該硬質皮膜の成分がＣｒである（ＣｒＳｉ）（ＣＮＯＢ）の場合であるが従来例に比べ切削寿命が長い。本発明例８は（ＣｒＴｉ）（ＮＯＢ）の場合であるが、従来例に比べ切削寿命が長い。本発明例９は本発明である該硬質皮膜と（ＴｉＡｌ）Ｎ皮膜と多層にした場合の事例であるが、従来例に比べ切削寿命が長く、更に（ＴｉＡｌ）Ｎ皮膜等と組み合わせた多層膜がより小さい摩耗量を示した。本発明例１０はＴｉ（ＣＮＯ）皮膜との多層膜であるが、従来例に比べ切削寿命が長い。本発明例１１は本発明である該硬質皮膜の最強強度を示す面指数が（１１１）面の場合であるが従来例に比べては切削寿命に優れるものの、（２００）面に最も強く配向する硬質皮膜がより好ましい。本発明例１２は（ＣｒＡｌＳｉ）（ＮＯＢ）皮膜との多層膜であるが従来例に比べ切削寿命が長い。本発明例１３は本発明である該硬質皮膜内の結晶質相の最小結晶粒径が５０ｎｍを越える場合であるが、従来例に比べては切削寿命に優れるものの、５０ｎｍ以下がより好ましいといえる。本発明例１４は該硬質皮膜のＸ線回折から得られる（２００）面の半価幅が１．５度未満の場合であるが従来例に比べて切削寿命が長いものの、１．５度以上がより好ましいといえる。本発明例１５は、被覆時にＢ気体を用いた場合の事例であり、Ｂ含有量が多い場合であるが従来例に比べ切削寿命が長い。本発明例１６は、該硬質皮膜内に透過型電子顕微鏡による観察結果からアモルファス相が確認されたかった場合の例を示すが、従来例に比べ切削寿命が長い。
【００１８】
【発明の効果】
以上の如く、本発明の硬質皮膜被覆高速度鋼製ブローチは、従来の硬質皮膜被覆ブローチに比べ、ブローチ切刃表面に被覆する硬質皮膜が高温環境下でより高い硬度を維持することができ、優れた耐酸化性を有し、切削過程で被加工物から硬質皮膜内部へ拡散する鉄に対して、低い親和性を有し、摩擦抵抗の低い硬質皮膜であるため切削温度上昇を抑制させる効果を有しており、また、工具母材としても最適な（Ｖ＋Ｃｏ）含有量に規定しているため、高靭性で耐チッピング性に優れた母材であり、高硬度硬質皮膜の残留圧縮応力を母材内部で緩和し、密着性に優れる。これらの改善により、切刃のコーナー部のチッピング、欠けもしくは皮膜剥離等に起因した異常摩耗を著しく抑制することが可能となり、ブローチによる切削加工の高能率化、高速化並びに長寿命化により、生産性向上並びにコスト低減に極めて有効である。
【図面の簡単な説明】
【図１】
図１は、本発明例１のＸ線光電子分光分析によるＣｒの結合エネルギーを示す。
【図２】
図２は、本発明例１のＸ線光電子分光分析によるＢの結合エネルギーを示す。[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a hard film-coated high-speed steel broach used for cutting a metal material or the like represented by a mechanical structural component.
[0002]
[Prior art]
A broach including a large number of cutting blades is used for cutting a metal material or the like represented by a mechanical structural component. For the purpose of extending the cutting life of these broaches or increasing the precision of a workpiece, a hard film-coated broach in which a hard film is coated on the surface of a broach is used. As the hard film to be coated, for example, a TiN film or a Ti (CN) film having a film hardness of HV2000 or more, and more excellent in oxidation resistance than the TiN film found in JP-A-11-300188 (TiAl ) A coating broach coated with an N film has been proposed.
[0003]
However, in broaching in recent years, there is an increasing demand for finishing a workpiece with higher efficiency and higher precision, and also an increasing demand for directly processing a hardened material after heat treatment. Also, in the cutting environment, due to consideration for the human body and the global environment, there has been an increasing demand for cutting from oil-based cutting to dry cutting or semi-dry cutting in which cutting fluid does not contain harmful substances such as chlorine. . As described above, the cutting environment in broaching has been forced to be more severe, and the development of further high-performance broaches has been desired. In addition to demands for higher hardness of workpieces, high-speed cutting, and longer tool life, cutting temperatures tend to increase near the tool cutting edge due to dry and semi-dry coolant. At the same time, the hard coating is oxidized and, at the same time as the hard coating is oxidized, an adhesive phenomenon occurs on the tool edge, causing a chemical reaction between the wear-resistant coating coated on the broach surface and the workpiece, resulting in a short tool life and precision of the workpiece. Deteriorates. In such a case, the conventional TiN film, Ti (CN) film and (TiAl) N film do not have a sufficient balance between the effect of suppressing adhesion and the abrasion resistance. Cutting life has not been obtained. In addition, it has been confirmed that the hard coating peels off and falls off together with these adhered substances. In such a case, the cutting life tends to be unstable and short. As described above, satisfactory cutting characteristics have not been obtained for these processing requirements.
[0004]
[Problems to be solved by the invention]
The present inventor has carefully analyzed the damage state of the flank and rake face of the broach used under these severe cutting environments, and as a result, oxygen diffuses into the hard coating on the tool flank side, and the hard coating outermost surface It was found that a low-strength oxide was formed and that the drop-off starting from the low-strength oxide was repeated. Also, on the tool rake face side, which is a chip discharge portion, iron and oxygen, which are workpieces, diffused into the film, and the iron and oxygen promoted oxidation of the hard film, and wear was progressing. As described above, the temperature rises remarkably near the tip of the cutting edge, causing the wear of the hard coating to progress due to the oxidation and the softening of the coating base material, resulting in the occurrence of chipping or chipping of the tool cutting edge. It became clear.
[0005]
In view of these circumstances, the present invention improves the high-temperature hardness and oxidation resistance of the hard coating that covers the cutting blade surface of the broach, and has a low affinity for iron that diffuses from the workpiece into the hard coating during the cutting process. With a hard coating having a low frictional resistance, the cutting temperature rise is suppressed, and as a tool base material, there is toughness in order to maintain adhesion with the hard coating having high hardness. A base material with excellent chipping resistance. An object of the present invention is to provide a configuration of a hard film-coated high-speed steel broach capable of achieving high efficiency of cutting work and long life by these improvements.
[0006]
[Means for Solving the Problems]
In order to achieve these objects, the present invention provides an element selected from at least one element selected from the group consisting of groups 4a, 5a, and 6a of the periodic table, Al and Si, and a B element and N, C, and O. In a hard film-coated high-speed steel broach comprising at least one hard film containing at least one element selected from one or more elements, at least one layer of the hard film is composed of B and N by X-ray photoelectron spectroscopy. Is a hard coating in which either the binding energy of Ti and O or the binding energy of Cr and O is recognized, and V and Co contained in the base material of the high-speed steel are A hard film-coated high-speed steel broach characterized by the range of 3 ≦ (V + Co) ≦ 11.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
In order to achieve higher processing efficiency and longer service life, the hard coating to be coated maintains high hardness under high temperature environment, has high temperature hardness of hard coating, and has excellent oxidation resistance under high temperature environment. However, it is necessary to suppress a rise in cutting temperature by coating a hard film having low affinity and low frictional resistance with respect to iron that diffuses from the workpiece into the hard film during the cutting process. Further, it is necessary for the tool base material to maintain heat resistance for suppressing softening of the base material in a high-temperature environment and strength of the base material having high adhesion to these hard films. As a means for this, at least one layer of the hard coating contains the binding energies of B and N by X-ray photoelectron spectroscopy, and furthermore, either the binding energy of Ti and O or the binding energy of Cr and O is recognized. It is extremely effective that V and Co contained in the base material of the hard film-coated high-speed steel broach satisfy 10 ≦ (V + Co) ≦ 20 by weight%. The hard coating is excellent in coating hardness and oxidation resistance in a high-temperature environment, and has a low affinity for iron in a workpiece and has a lubricating effect, thereby suppressing an increase in cutting temperature. Having. This is because the presence of B in the hard coating as BN changes the BN bond on the outermost surface of the hard coating into a bond between B and O in a high-temperature environment, and converts the dense and high-strength B oxide into the hard coating. The dense and high-strength B oxide formed on the surface functions as a subsequent antioxidant layer. At the same time, the dense and high-strength B oxide is hardly peeled off from the hard coating even in a dynamic oxidizing environment and has excellent oxidation resistance.
[0008]
Further, the softening of the hard coating in a high-temperature environment is caused by the diffusion of oxygen, and thus the coating of the present invention, which is remarkably excellent in oxidation resistance, also has a remarkably improved high-temperature hardness. Another advantage of the presence of BN in the hard coating is that it has a very low affinity for iron. Thereby, it shows an excellent friction characteristic with respect to iron, which is a workpiece, and also has an effect of suppressing a cutting temperature. Further, when BN is present in the hard coating, the internal stress in the hard coating lattice is increased, and the hardness of the hard coating is significantly increased. However, at the same time as the hardness is increased, the compressive stress remaining in the hard coating also increases. Therefore, it is necessary to use a base material having a strength that can withstand the residual compressive stress. Therefore, it is necessary to limit V and Co contained in the base material to a range of 10 ≦ (V + Co) ≦ 20 by weight%. Within this range, even the residual compressive stress generated in the hard coating can be relaxed inside the base material, and has excellent adhesion, and the hard coating has excellent oxidation resistance and high hardness. Can be sufficiently exhibited. When V and Co in the base material satisfy the above range, the heat resistance of the matrix in the high-speed steel is also excellent. With these configurations, it is possible to achieve high efficiency and long life of cutting by the broach.
[0009]
More preferred hard coatings include a crystalline phase having a minimum crystal grain size of 0.5 nm or more and 50 nm or less and an amorphous phase in the hard coating, and the hard coating has a diffraction intensity in X-ray diffraction of ( The maximum peak is shown on the (200) plane, and the diffraction line on the (200) plane has a half width of 2θ of 1.5 ° or more. More preferably, at least one layer of the hard coating is a hard coating containing a B element and Ti or Cr as a metal component, and Ti and Cr as components, and at least one layer different from the hard coating is a metal element. It is more preferable to use a hard coating containing at least Al and Ti and at least N as a nonmetallic element. By adopting such a configuration, the hard coating covering the surface of the broach cutting blade can maintain a higher hardness in a high-temperature environment, and has excellent oxidation resistance, and can be coated during the cutting process. By adopting a hard coating that has low affinity for the iron that diffuses into the hard coating from the workpiece and has a low frictional resistance, the cutting temperature rise is suppressed, and the heat resistance and hardness of the broach base material are further improved. By improving the adhesion strength with the film, high-speed, high-efficiency and long life of the cutting by the broach have been achieved, and the problem of the prior art has been solved.
[0010]
In the high-speed steel used as the broach base material coated with the hard coating according to the present invention, V and Co contained in the base material need to be in a range of 3 ≦ (V + Co) ≦ 11 by weight%. V and Co in the base metal are additive elements that determine the hardness and heat resistance of the high-speed steel. However, when the content is less than 3% by weight, the base material strength in a high-temperature environment is not sufficient, and the tool life is unstable. Met. This is because the cutting edge portion is plastically deformed toward the flank side 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 adhesion is not sufficient, and fine coating peeling may occur. Chipping and chipping occurred, resulting in a short life. As a result of considering the effect of the hard coating of the present invention on the adhesion strength to the broach base material, the present inventors determined the contents of V and Co in the high-speed steel within the above range. Further, when the bond between B and N is not confirmed in the hard coating, the high-temperature hardness, oxidation resistance and lubricating properties of the coating are not sufficient as described above, and the conventional problems have not been solved. In addition, when the binding energy between B and N is recognized, but neither the binding energy between Ti and O or the binding energy between Cr and O is recognized, the lubricating properties are not sufficient, and it is difficult to suppress the cutting temperature. Did not. The high-speed steel preferably has a base metal hardness of HRC64 or more and less than HRC68. When the base metal hardness is less than HRC64, the cutting edge is also observed to progress to the flank side with severe plastic deformation under severe cutting environment, and the cutting edge strength may not be sufficient, which is not preferable. On the other hand, if it exceeds HRC68, the residual compressive stress generated in the hard coating is insufficiently relaxed, and it is confirmed that fine coating peeling may occur, which is not preferable.
[0011]
The crystalline phase in which the minimum crystal grain size is 0.5 nm or more and 50 nm or less in the hard coating, and the amorphous phase are used when the minimum crystal grain size in the hard coating is 0.5 nm or more and 50 nm or less. The film hardness is high, the high-temperature hardness is remarkably improved, and the abrasion resistance is excellent. Further, when an amorphous phase is contained at the same time, the crystal grain boundaries at the interface between the crystals are remarkably reduced, which is effective for suppressing the diffusion of oxygen proceeding through the crystal grain boundaries, which is more preferable. Further, when the hard coating is strongly oriented to the (200) plane, it has the least lattice defects in the coating, has a high density and is excellent in oxidation resistance, and thus has the maximum peak strength on the (200) plane. preferable. Furthermore, when the half width has a spread of 1.5 degrees or more, the contribution to the improvement of the film hardness and the oxidation resistance is large, which is preferable. Further, it is more preferable that at least one layer of the hard coating is a hard coating containing a B element and Ti or Cr as a metal component, and Ti and Cr as components. When composed of the B element and Ti or Cr as the metal component, and Ti and Cr, the balance between the film hardness, the oxidation resistance and the sliding characteristics is most excellent, and is more preferable. Although the hard coating has excellent adhesion to the coated base material, coating hardness and oxidation resistance, the hard coating is used to further improve the adhesion to the base material and stabilize the cutting life. It is also possible that at least one other layer includes at least Al and Ti as metal elements and a hard coating containing at least N as a nonmetal element.
[0012]
Furthermore, in order to improve the adhesion of the hard coating to the base material and extend the cutting life, before and after coating, defects such as burrs and burrs near the cutting edge, and droplets and other defects adhering to the coating are mechanically shot, such as by shot blasting. It is also preferable to remove by processing. Hereinafter, the present invention will be described based on examples, but the following examples do not limit the present invention, and any appropriate modifications based on the gist of the present invention are included in the technical scope of the present invention. It is.
[0013]
【Example】
The hard film-coated high-speed steel broach of the present invention is not particularly limited in its coating method, but when considering the thermal effect on the coated base material, the fatigue strength of the tool, the adhesion of the film, and the like. A coating treatment was performed by an arc discharge ion plating method in which coating could be performed at a relatively low temperature and an appropriate compressive stress remained in the coated film. Using an arc ion plating apparatus, a target film can be obtained from various alloy targets that are evaporation sources of metal components, and N ₂ gas, CH ₄ gas, Ar + O ₂ mixed gas, and B ₃ N ₃ H ₆ that are reaction gases. Under the conditions of a coating base material temperature of 400 ° C. and a reaction gas pressure of 3.0 Pa, a bias voltage of −150 V is applied to a spline broach made of various high-speed tool steels as a coating base material to perform coating processing. Was done. At this time, the thickness of the entire hard multilayer was in the range of 0.2 to 2.0 μm at each part of the broach. Regarding the addition of B to the hard coating, it is possible to use either an alloy target to which a predetermined amount is added in advance in a metal target or to introduce a B-containing gas into a vacuum vessel during coating. Further, if necessary, a TiAlN-based film was previously coated by an arc ion plating method, and then the hard film was coated.
[0014]
[Table 1]

[0015]
In Table 1, the quantitative analysis of the composition was comprehensively determined by energy dispersive X-ray spectroscopy, Auger photoelectron spectroscopy, and electron beam energy loss spectroscopy. For the qualitative analysis of B and N bond energies, Ti and O bond energies, and Cr and O bond energies by X-ray photoelectron spectroscopy, the hard coating surface is subjected to Ar ion milling for 10 minutes (from the surface in terms of SiO _2). About 20 nm). The analysis results are also shown in Table 1. The qualitative analysis of the amorphous phase in the hard coating and the measurement of the minimum crystal grain size composed of the crystalline phase were actually measured from a cross-sectional photograph of a visual field in which the cross section of the hard coating was randomly selected with a transmission electron microscope. Table 1 also shows the minimum crystal grain size of the crystalline phase actually measured from a cross-sectional photograph taken by a transmission electron microscope. The actual measurement method of the crystal grain size was determined from the equivalent circular diameter which is the diameter when the area of the cross section was replaced by the area of the circle from the cross section photograph. A cutting test was performed using the obtained hard film-coated high-speed steel broach under the following conditions. The cutting specifications are shown below. A cutting test was performed by dry cutting using an air blow with a cutting speed of 6 m / min using a S53C material having a cutting length of 40 mm per piece and a hardness HB220 after tempering of 40 mm per piece. The number of cuts was 2,000, that is, the flank wear of the broach after cutting the total cutting length of 80 m was compared. At the same time, the surface roughness of the workpiece surface was measured in the tool axis direction. The results are also shown in Table 1. Table 1 shows a comparative example processed under the same cutting conditions, and Table 2 shows a conventional example.
[0016]
[Table 2]

[0017]
In the example of the present invention shown in Table 1, a stable cutting life was obtained as compared with the conventional example. Hereinafter, the details of the present invention will be described. From the results of observation of a lattice image of each composition as an example of the present invention shown in Table 1 with a transmission electron microscope, an amorphous phase containing B was confirmed in any of the hard films except for the example 16 of the present invention. FIG. 1 shows the binding energy obtained from the 2p orbital of Cr by X-ray photoelectron spectroscopy of the hard coating of Example 1 of the present invention, and at least the binding energy of Cr and N and Cr and O was confirmed. FIG. 2 shows the binding energies obtained from the 1s orbital of B by X-ray photoelectron spectroscopy of the hard coating of Example 1 of the present invention, and at least the binding energies of B and N were confirmed. Examples 1, 2, and 3 of the present invention are examples of the present invention in which the sum of (V + Co) (% by weight) of the base materials is different, but the cutting life is longer than that of the conventional example. On the other hand, Comparative Examples 17 and 18 show Comparative Examples in which the sum of (V + Co) (% by weight) in the base material is 2.5% by weight and 12.3% by weight. When the total of (V + Co) (% by weight) in the base material was 2.5% by weight, plastic deformation occurred on the flank side, the base material strength was not sufficient, and chipping occurred frequently. When the total of (V + Co) (% by weight) in the base material is 12.3% by weight, minute peeling of the film is observed, adhesion to the hard film having high hardness is poor, and an unstable wear state is caused. Thus, the characteristics of the hard coating of the present invention could not be sufficiently exhibited. Therefore, it is clear that in the cutting work using the severe broach, the influence of the coated base material is considerably large due to the hard coating. In Example 4 of the present invention, although the hardness of the base material was HRC 63.8, the cutting life was longer than that of the conventional example. Inventive Example 5 is a Ti (NOB) film in which the component of the hard film of the present invention is Ti, but has a longer cutting life than the conventional example. Inventive Example 6 is the case of (TiSi) (NOB) of the present invention, but has a longer cutting life than the conventional example. Example 7 of the present invention is a case where the component of the hard coating of the present invention is Cr (CrSi) (CNOB), but has a longer cutting life than the conventional example. Example 8 of the present invention is the case of (CrTi) (NOB), but has a longer cutting life than the conventional example. Inventive Example 9 is an example in which the hard coating and the (TiAl) N coating of the present invention are multi-layered. However, the cutting life is longer than that of the conventional example, and the multilayer coating in combination with the (TiAl) N coating is used. Showed a smaller amount of wear. Inventive Example 10 is a multilayer film with a Ti (CNO) film, but has a longer cutting life than the conventional example. Example 11 of the present invention is a case where the surface index indicating the strongest strength of the hard coating of the present invention is the (111) plane. Although the cutting index is superior to the conventional example, it is most strongly oriented to the (200) plane. Hard coatings are more preferred. Inventive Example 12 is a multilayer film with a (CrAlSi) (NOB) film, but has a longer cutting life than the conventional example. Inventive Example 13 is a case where the minimum crystal grain size of the crystalline phase in the hard coating of the present invention exceeds 50 nm. However, although the cutting life is superior to that of the conventional example, 50 nm or less is more preferable. . Invention Example 14 is a case where the half-value width of the (200) plane obtained from the X-ray diffraction of the hard coating is less than 1.5 degrees. However, although the cutting life is longer than that of the conventional example, it is 1.5 degrees or more. Is more preferable. Inventive Example 15 is a case in which B gas was used at the time of coating, in which the B content was large, but the cutting life was longer than that of the conventional example. Inventive Example 16 shows an example in which an amorphous phase was not confirmed in the hard coating from the result of observation with a transmission electron microscope, but the cutting life is longer than that of the conventional example.
[0018]
【The invention's effect】
As described above, the hard film-coated high-speed steel broach of the present invention can maintain a higher hardness in a high-temperature environment in which the hard film coated on the broach cutting blade surface is higher than the conventional hard film-coated broach, It has excellent oxidation resistance, has low affinity for iron that diffuses from the workpiece into the hard coating during the cutting process, and has the effect of suppressing the rise in cutting temperature due to the low frictional resistance of the hard coating. In addition, since it is specified as the optimal (V + Co) content also as a tool base material, it is a base material having high toughness and excellent chipping resistance, and has a residual compressive stress of a high hardness hard film. Relaxes inside the base material and has excellent adhesion. These improvements make it possible to significantly reduce abnormal wear caused by chipping, chipping, or peeling of the corners of the cutting edge, and by increasing the efficiency, speed, and service life of cutting with a broach, This is extremely effective for improving the performance and reducing the cost.
[Brief description of the drawings]
FIG.
FIG. 1 shows the binding energy of Cr by X-ray photoelectron spectroscopy of Example 1 of the present invention.
FIG. 2
FIG. 2 shows the binding energy of B by X-ray photoelectron spectroscopy of Example 1 of the present invention.

Claims

Includes elements selected from at least one element selected from the group consisting of elements of groups 4a, 5a and 6a of the periodic table, Al and Si, and element B and elements selected from at least one of N, C and O In a hard film-coated high-speed steel broach having at least one hard film coated thereon, at least one layer of the hard film contains a binding energy of B and N by X-ray photoelectron spectroscopy, and a bond of Ti and O Is a hard coating in which either the energy or the binding energy of Cr and O is recognized, and V and Co contained in the base material of the high-speed steel are in the range of 3 ≦ (V + Co) ≦ 11 by weight%. A high-speed steel broach coated with a hard coating.

The hard coating-coated high-speed steel broach according to claim 1, wherein the particle diameter of the crystal grains contained in the hard coating is an equivalent circular diameter that is the diameter when the area of the particle cross section is replaced by the area of a circle. A hard film-coated high-speed steel broach characterized by containing, when determined, a crystalline phase having a minimum crystal grain size of 0.5 nm or more and 50 nm or less, and an amorphous phase.

The hard film-coated high-speed steel broach according to claim 1 or 2, wherein the hard film has a diffraction peak in X-ray diffraction at a (200) plane, and a diffraction line of the (200) plane has a maximum intensity. A hard film-coated high-speed steel broach characterized by having a half-value width of 2θ of 1.5 ° or more.

The hard film-coated high-speed steel broach according to any one of claims 1 to 3, wherein at least one layer of the hard film is a hard film containing a B element and Ti or Cr as a metal component, and a Ti and Cr component. A high-speed steel broach coated with a hard coating, characterized in that:

The hard film-coated high-speed steel broach according to any one of claims 1 to 4, wherein at least one layer other than the hard film includes at least Al and Ti as metal elements and at least N as a nonmetal element. A high-speed steel broach coated with a hard coating.

The hard-coated high-speed steel broach according to claim 1, wherein a base metal hardness of the hard-coated high-speed steel roughing end mill is HRC64 or more and less than HRC68. brooch.