JP3679076B2

JP3679076B2 - Hard coating tool

Info

Publication number: JP3679076B2
Application number: JP2002270940A
Authority: JP
Inventors: 和幸久保田
Original assignee: Hitachi Tool Engineering Ltd
Current assignee: Moldino Tool Engineering Ltd
Priority date: 2002-09-18
Filing date: 2002-09-18
Publication date: 2005-08-03
Anticipated expiration: 2022-09-18
Also published as: JP2004106102A

Description

【０００１】
【発明が属する技術分野】
本発明は、金属材料等の切削加工に使用される硬質皮膜被覆工具に関するものである。
【０００２】
【従来の技術】
従来はＴｉＮ、Ｔｉ（ＣＮ）等を被覆した切削工具が汎用的かつ一般的であった。ＴｉＮは比較的耐酸化性に優れるため、切削時の発熱によって生じる工具のすくい面摩耗に対して、優れた耐摩耗性を示すだけでなく、基体との密着性も良好であることが特長である。また、Ｔｉ（ＣＮ）は、ＴｉＮに比べ高硬度かつ被加工物から排出される切り粉との接触抵抗が低いため工具表面の発熱が抑制される。このことから、被削材との機械的な擦り摩耗によって工具逃げ面に生じるフランク摩耗を抑制することができる。しかしながら、金属加工の高能率化を目的とした切削速度の高速化傾向に対し、上記硬質皮膜では、十分な耐酸化性、耐摩耗性を示さなくなった。この様な背景から、皮膜の耐酸化性、耐摩耗性をより向上させる研究がなされ、その結果、特許第３２４８８９７号公報には（ＴｉＳｉ）Ｎ皮膜をａ層とし、（ＴｉＡｌ）Ｎ皮膜をｂ層として、ａ層とｂ層とを１層以上交互に被覆することによって得られた皮膜が耐酸化性、耐摩耗性を有するという技術が開示されている。一方、特開２００１−２９３６０１号公報では、耐摩耗性皮膜中に、ＢＮ、ＴｉＢ_２、ＴｉＢ等の超微粒化合物を含む皮膜についての開示があり、この超微粒化合物が非晶質構造を有し、皮膜の硬度を向上させる働きがあると記載されている。これにより耐摩耗性、高滑り性、高焼き付き性、被削材の加工精度向上が図れるとのことであるが、超微粒化合物の特性や存在状態についての詳細な記述はなされていない。
【０００３】
（ＴｉＡｌ）Ｎ皮膜は、その皮膜中に含有するＴｉとＡｌの成分比率又はＳｉやＣの皮膜中の含有量により異なるが、概略２３００〜２８００のビッカース硬さを有する。また、耐酸化性が前記ＴｉＮ、Ｔｉ（ＣＮ）に比べ著しく優れるため、刃先が高温に達する切削条件下においては、切削工具の性能をめざましく向上させる。また、（ＴｉＡｌＳｉ）（ＣＮ）皮膜は、（ＴｉＡｌ）Ｎ皮膜よりも耐酸化性を向上させようとＳｉを含有させたものである。更に、同じ効果を目論み、（ＴｉＡｌ）系に第３元素としてＺｒやＨｆ、Ｂの含有が試みられている。近年では、こうした硬質皮膜被覆切削工具が使用される環境は益々過酷になり、例えば、切削速度の高速化傾向、また従来使用されていた湿式での切削加工が環境問題上重要視されるなかで、乾式での切削加工が注目されている。また、金型用鋼材の多種含有元素の影響による鋼材の難削化、高能率加工を重視した高送り加工の傾向にあり、硬質皮膜被覆切削工具の使用環境は益々過酷なものとなってきている。
【０００４】
本発明者の研究によれば、大気中における（ＴｉＡｌ）Ｎ皮膜の酸化開始温度は、ＴｉＮの４５０℃に対し、Ａｌの含有量に依存して７５０〜９００℃に向上する。しかしながら、前述の乾式高速切削加工においては、使用する工具の刃先温度が９００℃以上の高温に達する。このような過酷の条件下で行われている切削加工では、硬質皮膜の耐酸化性が重要であることは言うまでもないが、それよりも先に硬質皮膜被覆切削工具の刃先部と被加工物が化学反応を起こすことで発生する、溶着現象を防ぐことが不可欠である。近年の金型用鋼材には金型の性能を著しく向上させるために様々な元素の含有が行われるようになり、切削工具への溶着現象は益々発生しやすくり、硬質皮膜の酸化による摩耗よりも先に硬質皮膜中への被加工物元素の拡散が発生しやすい状況になってきている。このため、従来のＴｉとＡｌの窒化物などは、大気中における酸化抵抗は著しく優れるものの、高温状態での切削においては、前記化学反応の１種である溶着や被加工物の拡散を防ぐことが困難であり、十分な工具寿命が得られないのが現状である。
【０００５】
【発明が解決しようとする課題】
本発明はこうした事情に鑑みなされたものであって、従来の耐酸化性の優れる（ＴｉＡｌ）Ｎ皮膜など、耐酸化性の優れる硬質皮膜の耐摩耗性並びに密着性を犠牲にすること無く、更に高温状態での耐溶着性並びに硬質皮膜中への被加工物元素の拡散を改善し、切削加工の乾式化、高速化、高送り化に対応する硬質皮膜被覆工具を提供することが目的である。
【０００６】
【課題を解決するための手段】
本発明者は、硬質皮膜の耐溶着性、耐摩耗性、母材との密着性に及ぼす、様々な元素との影響および皮膜の最適な層構造について鋭意研究を重ねた結果、金属成分が、ＴｉとＢで構成される窒化物、炭窒化物、酸窒化物、酸炭窒化物のいずれかであるａ層と、金属成分がＡｌとＴｉで構成される窒化物、炭窒化物、酸窒化物、酸炭窒化物のいずれかであるｂ層とが、それぞれ一層以上交互に被覆され、該ａ層のＸ線回折における（２００）面の格子定数Ａが、０．４２００≦Ａ≦０．４２７０ｎｍの範囲にあり、かつ該ａ層のラマン分光分析において、ｃ−ＢＮ並びにｈ−ＢＮのピークが検出され、そのときのｃ−ＢＮのピーク強度をＱ１、またｈ−ＢＮのピーク強度をＱ２としたときに、ピーク強度比Ｑ１／Ｑ２≧１．０であることを特徴とする硬質皮膜被覆工具とすることで、乾式の高速切削加工、高送り加工において、切削工具の性能が極めて良好となることをつきとめ本発明に到達した。ここでの高送り加工とは、切削条件中の１刃当たりの送り量が０．３ｍｍ／刃を越えるような切削と定義する。また、本発明は、該ａ層がＴｉとＢの合金ターゲットを用いて被覆され、皮膜の組成が、該ａ層に含まれるＢの含有量Ｍを金属成分のみの原子％で示すと、０．１≦Ｍ≦４０であり、該ａ層の膜厚Ｄが、Ｄ≧０．１μｍであることが好ましい。
【０００７】
【発明の実施の形態】
ａ層の構成について詳細を述べる。一般に（ＴｉＡｌ）Ｎ皮膜は、大気中で酸化テストを行うと、皮膜表面近傍のＡｌが最表面に向かって外向拡散し、Ａｌ_２Ｏ_３層を形成する。この現象により、その後の皮膜内への酸素の進入が抑制される。本発明者の研究によれば、このことが耐酸化性向上の理由と考えられるが、この時、最表層に形成されるＡｌ_２Ｏ_３層直下には、Ａｌを含有しない非常にポーラスなＴｉ酸化物が形成する。静的な酸化テストにおいては、酸化の進行である酸素の内向拡散に対し、最表面に形成されたＡｌ_２Ｏ_３層が、酸化保護膜として機能するものの、動的な切削においては、最表面のＡｌ_２Ｏ_３層は、その直下のポーラスなＴｉ酸化物層より容易に剥離してしまい、酸化の進行に対し十分な効果を発揮しない。また、この最表面に形成されたＡｌ_２Ｏ_３層が動的な切削に対し、剥離しなければ、Ａｌ_２Ｏ_３の化学的安定性から被加工物との溶着現象を防ぐことができるのだが、現状この化学的に安定なＡｌ_２Ｏ_３の剥離を防ぐことは困難である。つまり、高温下で発生する溶着現象は最表層に形成されるＡｌ_２Ｏ_３が剥離してしまうために発生することが明らかとなった。また、（ＴｉＡｌＳｉ）（ＣＮ）膜や（ＴｉＡｌＺｒＢ）Ｎ、（ＴｉＡｌＢ）Ｎ、（ＴｉＡｌＳｉＢ）Ｎについても、従来の（ＴｉＡｌ）Ｎ膜にＳｉ、Ｚｒ、Ｂなどを含有させることで硬質皮膜そのものの高硬度化や耐酸化性を若干良好にさせるが、前述同様、酸化物に対する生成自由エネルギーの差から表面の酸化保護膜のＡｌ_２Ｏ_３層が直ちに形成され、更にその直下にポーラスなＴｉの酸化物を形成してしまい、その結果切削中の皮膜剥離をもたらす。よって、動的な切削における溶着現象を防ぐには至らないのである。
【０００８】
しかしながら、溶着現象の原因となるＡｌを除く、ＴｉとＢで構成される窒化物、炭窒化物、酸窒化物、酸炭窒化物等は、皮膜自体の耐酸化性は、従来のＴｉとＡｌの窒化物と同程度であり、高温下における溶着現象に対しては、ＴｉとＡｌの窒化物などよりも優れている。本発明者は、各種元素の溶着発生現象への抵抗性、つまり鋼に含まれる元素と、硬質皮膜中に含まれる元素との濡れ性という観点から鋭意研究を重ねた結果、本発明硬質皮膜は高温下における被加工物の溶着を防ぐのに効果があることをつきとめた。本発明者は、硬質皮膜中に含有させるＢについて、切削工具に適用した際に生じる現象を詳細に調査した結果、Ｂの有効性は、硬質皮膜の高硬度化や耐酸化性向上ではなく、切削時におけるＦｅとの親和性が低いことや被加工物の膜中への拡散現象がほとんど発生しないことである。図１に本発明のａ層を用いた硬質皮膜被覆切削工具の切削加工後の切刃近傍を、基体方向に元素分析を行った結果を示す。また、図２に従来の（ＴｉＡｌ）Ｎを同様に分析した結果を示す。図１、２の比較により、図１には皮膜内部に被加工物であるＦｅ元素は見られないが、図２の従来膜である（ＴｉＡｌ）Ｎでは膜の最表層にＡｌの酸化物が形成されており、被加工物であるＦｅが膜中に拡散していることがわかる。図２に示した傾向は従来の（ＴｉＡｌＳｉ）（ＣＮ）や（ＴｉＡｌＺｒＢ）Ｎ、（ＴｉＡｌＢ）Ｎなどにも見られることを確認した。つまり、本発明のａ層を使用することで、被加工物との高温下における化学反応が発生しにくい特性を持っているのである。また、同時に、耐酸化性も従来のＴｉとＡｌの窒化物とほぼ同程度であることを見出したのである。本発明者等は更に、鋭意研究を重ね、（ＴｉＡｌＢ）Ｎといった耐酸化性の優れる従来の（ＴｉＡｌ）ＮにＢを含有させる実験を試み、その硬質皮膜の耐溶着性に着目し、評価を行った結果、前述Ａｌを含有させている従来の皮膜は、そのなかに含まれるＡｌはＴｉやＢよりも高温下におけるＦｅとの親和性が高いため、最表層に酸素の内部拡散を防ぐＡｌ_２Ｏ_３層を形成させる前に、被加工物中の含有物と化学反応が発生していることを得た。切削工具にこのようなＡｌを含有させている硬質皮膜を適用した場合、この溶着現象により、工具すくい面に異常なクレーター摩耗の進行促進、更に境界部には溶着物が多量に貯め込まれ、チッピングをもたらすのである。このような実験結果からも硬質皮膜被覆工具の最表面には耐酸化性を十分にもった皮膜を被覆するよりも、従来使用してきたＴｉとＡｌの窒化物などの特異的な酸化機構を発生させるまでに硬質皮膜被覆工具表面に溶着を防ぐための、いわば自己潤滑皮膜が必要になるのである。つまり、本発明の硬質皮膜を切削工具最表層に被覆させることで、被加工物との溶着を防ぎ、その結果異常摩耗を防ぐことで、従来使用してきたＴｉとＡｌの窒化物などを被覆した硬質皮膜被覆工具の寿命よりも著しく伸びることを確認した。
【０００９】
ａ層は、静的及び動的条件下において優れた耐溶着性を有すものの、皮膜自身がもつ残留圧縮応力が大きいため基体との密着性においては十分でない。そのため、基体表面直上には、密着性、耐摩耗性、耐酸化性等をバランス良く適度に付与するため、ＡｌとＴｉで構成される窒化物、炭窒化物、酸窒化物、酸炭窒化物等のｂ層を被覆することが好ましい。また、基体表面直上には、上記記載の硬質皮膜の他に元素周期表に記載される４ａ、５ａ、６ａ族の金属を１種以上含んだ合金膜をもちいてもよい。（ＴｉＡｌ）系窒化物等の皮膜であるｂ層におけるＡｌの役割は、皮膜の耐摩耗性及び耐酸化性を向上させることである。そのため、密着性、耐摩耗性、耐酸化性をバランス良く得るためには、好ましくはｂ層のＡｌ含有量Ｆを、皮膜の金属成分のみの原子％で、３０≦Ｆ≦７５に調整することが好ましい。ｂ層における好ましいＡｌの含有量Ｆを設定した理由については、Ｆが３０原子％以上のときに耐酸化性が著しく向上し始めるためである。また、７５原子％以下に調整する理由は、耐酸化性が向上しても、皮膜硬度が著しく低下し耐摩耗性が劣化してしまうためである。
【００１０】
以上のように本発明においては、基体との密着性、皮膜自体の耐摩耗性および耐酸化性をバランス良く有するｂ層を基体表面直上に被覆し、その上に著しく耐溶着性や被加工物元素拡散性に優れるａ層を被覆することが極めて重要であり、その結果、乾式の高速切削並びに高送り切削に対応する切削工具を得ることが可能となる。また、ａ層の結晶格子の大きさを限定した理由について述べる。本発明の硬質皮膜を硬質皮膜被覆切削工具として成り立たせるためには硬質皮膜物性中の結晶格子の大きさ、つまり格子定数は重要である。高い密着性を保つためには、第１として、物理蒸着法特有に発生する残留圧縮応力を低減させなければならない。本発明に至るまでの鋭意研究の結果、本発明の硬質皮膜の格子定数と残留圧縮応力の相関性を導き出すに至った。第２として、硬質皮膜同士の密着性を確保するために本発明に使用される異種硬質皮膜をヘテロエピタキシャルの関係に保たなければならない。この両者の条件を満足させるために、本発明者は、ａ層のＸ線回折における（２００）面の格子定数Ａが０．４２００≦Ａ≦０．４２７０の範囲になるよう制御することで成し得たのである。つまり硬質皮膜の特長を最大限に導き出すためには、Ａの数値が０．４２７０を越えてしまうと硬質皮膜の残留圧縮応力が顕著に増大し、切削加工中の剥離が発生し満足な切削性能が得られないのである。また、基体表面直上にｂ層を被覆した後、ａ層並びにｂ層をそれぞれ交互に積層した多層皮膜によっても同様の効果が得られた。ａ層はラマン分光分析において、ｃ−ＢＮとｈ−ＢＮのピークを検出することができ、そのときのｃ−ＢＮのピーク強度をＱ１、ｈ−ＢＮのピーク強度をＱ２としたときに、ピーク強度比がＱ１／Ｑ２≧１．０の関係でなければならない。これは、硬質皮膜の潤滑性を維持したまま硬度を向上させるためである。本発明の硬質皮膜におけるａ層内部には、図３に示すようにｃ−ＢＮとｈ−ＢＮのピークが検出される。ｃ−ＢＮとｈ−ＢＮの硬度を比較すると、ｃ−ＢＮの方が高い硬度を示す。従って、硬質皮膜中にｃ−ＢＮが多く含まれるようにコーティング条件を制御することによって皮膜硬度が高くなり、耐摩耗性を向上させることができるのである。また、各層は必要に応じて窒化物、炭窒化物、酸窒化物、酸炭窒化物のいずれかに調整でき、それらを被覆した工具についても同様の切削性能が得られる。
【００１１】
金属成分がＴｉとＢで構成される窒化物、炭窒化物、酸窒化物、酸炭窒化物ある硬質皮膜のＢの含有量Ｍについて限定した理由を述べる。Ｔｉに対してＢの含有量が０．１原子％未満の場合、本発明の目的とする溶着や元素拡散を防ぐ効果が得られない。従って、目標とする近年の過酷な切削加工に対応できないため、著しく効果の出はじめる０．１原子％以上としたのである。また、ＴｉとＢで構成される本発明の硬質皮膜は、ＴｉＮなどで良く見られるような柱状晶を呈するが、Ｂの含有量が４０原子％を越えると柱状晶から微細粒状結晶構造に変化することが認められた。このようにＢの含有量が多い硬質皮膜は、内部の欠陥が多く、密度も低くなることが認められた。また、皮膜密着性を阻害する内部応力が非常に大きくなり容易に剥離現象が発生することを確認した。更には、硬質皮膜の結晶が微細であるために切削加工中に発生する粒界破壊の頻度が高く、それに起因する異常摩耗が認められた。本発明者等は、以上の様な知見を得るに至り、本発明の硬質皮膜中のＢ含有量Ｍを、原子％で、０．１≦Ｍ≦４０に限定したのである。本発明の硬質皮膜を作成するにあたっては、物理蒸着法が好ましい。従って成膜のもととなるターゲットが必要になる。そのターゲットはＴｉとＢからなる２種を用いても良いが、組成のばらつきや、放電の安定性を考慮するとＴｉとＢの合金ターゲットがより好ましい。
【００１２】
硬質皮膜中に含有させるＢ含有量によって、ＴｉとＢで構成される硬質皮膜中の金属元素の存在形態に特徴があることを確認した。従来の硬質皮膜であるＴｉとＡｌの窒化物などは、その組成によって異なるが、実用化されている皮膜を取り上げると、一般にＴｉＮと同じ結晶格子形態であるＮａＣｌ型Ｂ１構造をとることがわかっており、ＴｉＮ格子中のＴｉがＡｌに置き換わっている形態をとり、いわば、Ａｌが固溶された状態にある。しかしながら、本発明のＴｉとＢで構成される硬質皮膜は、Ｂの含有量に左右されるものの、その含有量が０．１原子％以上になると、前記ＴｉとＡｌの窒化物などとは異なった形態を示す。Ｂの含有量が０．１原子％以上になるとＢはＴｉＮ格子中のＴｉに置き換わる形態の他に、Ｂの化合物が単独で存在するような形態になる。つまり、Ｂの含有量が０．１原子％以上になると、例えば、本発明の硬質皮膜であるＴｉとＢの窒化物の場合、硬質皮膜中にはＴｉＮの結晶とＢＮの結晶が混在する形態をとるのである。Ｂの含有量が０．１原子％未満ではＢがＴｉＮ結晶格子の中に完全に取り込まれ、固溶体の形態を呈する。この結晶形態の変化が切削性能に多大な影響を及ぼす。本発明の組成範囲にある窒化物の場合、ＴｉＮ類似の結晶のほかにＢＮの結晶が存在する。このＢＮは自己潤滑が優れるという事やＦｅとの濡れ性が低いという事が知られており、このＢＮ結晶の存在が、主として化学反応が起因のクレーター摩耗を著しく抑制させる効果があるものと考えられる。また、ＢＮは酸化に対する自由生成エネルギーの面からも酸化に対する抵抗力があるため、高温下における硬質皮膜の特性が劣化しない。これらの驚くべき事実は、本発明者が鋭意研究を重ねることで得られた結果である。しかしながら、Ｂの含有量が４０原子％を越えると、上記ＢＮの結晶は存在するが、内部応力が非常に大きくなるために、良好な密着性を維持することが困難となる。つまり、切削加工の様に硬質皮膜に外部からの衝撃を与えると硬質皮膜が自身の内部応力に耐えられず、容易に剥離が発生してしまい、硬質皮膜被覆工具としての役割を果たさなくなることが認められた。従って、本発明者等の目標である切削工具を提供するためには、硬質皮膜中に含有されるＢの量は４０原子％を越えてはいけないことになり、かつ、硬質皮膜中にＢＮの結晶を存在させるような、新しい技術を創生しなければならないのである。
【００１３】
本発明の硬質皮膜について、その膜厚Ｄを規定した理由について述べる。本硬質皮膜の特性が近年の過酷な切削加工に対応するためには、Ｄ≧０．１μｍを被覆しなければならない。つまり、それよりも薄い場合は、硬質皮膜の特性が発揮されないのである。また、本発明に記載の硬質皮膜を工具すくい面に厚く被覆し、すくい面摩耗が著しく発生するような切削加工に適用した場合、従来の硬質皮膜である（ＴｉＡｌ）Ｎや（ＴｉＡｌＳｉ）（ＣＮ）、（ＴｉＡｌＺｒＢ）Ｎ、（ＴｉＡｌＢ）Ｎでは、すでに説明したようにクレーター摩耗が容易に発生し、高能率加工を満足させるにいたらない。本発明者は、適用する金属成分がＴｉとＢで構成される硬質皮膜の効果を十分に発揮させるための最適膜厚を詳細に調査した結果、その膜厚ＤがＤ≧０．１μｍであることを明らかにした。この調査に基づき、被覆される工具すくい面の膜厚ＤがＤ≧０．１μｍであることがより好ましい。
【００１４】
本発明の硬質皮膜被覆工具は、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、被覆基体への熱影響、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、もしくはスパッタリング等の被覆基体側にバイアス電圧を印加する物理蒸着法であることが望ましい。以下、本発明を実施例に基づいて説明する。
【００１５】
【実施例】
小型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とＯ_２混合ガスから目的の皮膜が得られるものを選択し、被覆基体温度４００℃にて、被覆基体である外径８ｍｍφの超硬合金製インサートに−１５０Ｖの電位を印加させて被覆を行った。
【００１６】
得られた硬質皮膜被覆インサートを用い、次に示す乾式の高能率切削条件にて、刃先の欠けないしは摩耗等により工具が切削不能となるまで加工を行い、その時の切削長を工具寿命とした。表１に本発明例、比較例及び従来例に関する硬質皮膜の詳細及びその切削結果を示す。
【００１７】
【表１】

【００１８】
インサート切削条件は、切削工具は正面フライス（インサート形状：ＳＥＥ４２ＴＮ特殊形）を使用し、切削方法はセンターカット方式、被削材形状は巾１００ｍｍ、長さ２５０ｍｍ、被削材はＳ５０Ｃ（ＨＲＣ３０）、切り込みは２．０ｍｍ、切削速度は１５０ｍ／ｍｉｎ、１刃送り量は０．３０ｍｍ／刃、切削油は無しである。
【００１９】
表１に示したように、本発明の硬質皮膜は、その格子定数の大きさとラマン分光分析におけるｈ−ＢＮとｃ−ＢＮのピーク強度比が切削性能に大きく影響を及ぼすことは明らかである。つまり、本発明例１〜２０に示す様に、ａ層のＸ線回折における（２００）面の格子定数Ａが、０．４２００≦Ａ≦０．４２７０ｎｍの範囲を満たし、更にラマン分光分析によるｃ−ＢＮ、ｈ−ＢＮが検出され、そのときのｃ−ＢＮのピーク強度Ｑ１並びにｈ−ＢＮのピーク強度Ｑ２の比、Ｑ１／Ｑ２≧１．０の時は、材料の特性を如何なく発揮し、大幅な切削寿命の向上をもたらし、十分満足できる結果が得られている。しかし例えば、比較例２１、２２、２５は、ａ層のＸ線回折における（２００）面の格子定数Ａが、０．４２００≦Ａ≦０．４２７０ｎｍの範囲を満足していないのに加え、ラマン分光分析においてｈ−ＢＮのピーク強度が強いため、ピーク強度比も満足されていないことから、従来例２８から３４と比較しても効果が認められなかった。更に、比較例２３、２４、２６、２７は、ａ層のＸ線回折における（２００）面の格子定数Ａが、０．４２００≦Ａ≦０．４２７０ｎｍの範囲を満足しない状態で、しかもラマン分光分析におけるｃ−ＢＮのピーク強度が強くなると硬質皮膜の内部応力が著しく増大し、早期剥離発生後、欠損に至ってしまった。表１に示したように、本発明の硬質皮膜は、ＢＮの結晶の存在と、その化学構造の制御によって、耐溶着性はもとより、耐熱性も優れるため、著しい工具性能向上をもたらすことは明らかである。しかし例えば、比較例２１、２４は硬質皮膜中に添加されるＢ量が微量のため、ＴｉＮ結晶格子の中に取り込まれ、固溶体の形態をとっており、その結果、膜としてはＴｉとＢで構成される硬質皮膜であるが、本発明の目的である工具性能の改善には遠く至らないのである。また、比較例２２、２３、２５、２６、２７では、ＴｉとＢで構成される硬質皮膜中にＢＮの結晶が存在することが認められても、添加されるＢ添加量がＴｉに対して５０原子％を越えてしまっている。このような場合、切削加工においては、硬質皮膜が自身の内部応力に負けて、容易に剥離が発生する。特に、比較例２６は、硬質皮膜全体の内部応力が最も高くなり、約−６ＧＰａにも到達してしまうことが認められ、切削試験では、インサートの切削初期に工具逃げ面、すくい面に大きな剥離が発生し、切削続行が不可能となった。従って、本発明の硬質皮膜は、膜中のＢＮ結晶を存在させることも非常に重要な技術であるが、単に存在させるのではなく、添加するＢの量も含め、硬質皮膜被覆工具の設計を行わない限り、著しく優れた性能を発揮する工具の提供は不可能であることは明らかである。一方、従来例２８の（ＴｉＳｉ）Ｎ皮膜と（ＴｉＡｌ）Ｎ皮膜との２層膜とした試料、また従来例２９から３４の（ＴｉＡｌ）系の窒化物層に第３元素としてＺｒ、Ｂ、Ｓｉを添加した試料に対し、本発明例は、いずれの場合も工具寿命で優っていることが確認された。本発明皮膜の成膜実施にあたっては、使用する導入ガスの検討も同時に行った。その結果、著しく優れた耐溶着性を保つためには、金属成分がＴｉとＢで構成される窒化物、炭窒化物、酸窒化物、酸炭窒化物いずれかで、Ｂの含有量Ｍが金属成分のみの原子％で、０．１≦Ｍ≦４０．０であることが望ましいが、工具の発熱並びに被加工物との摩擦を考慮した場合、成膜時に上記記載の皮膜を製膜する上で必要となる窒素、酸素を含むガスの他に、炭素を含むガスを導入し、炭窒化物、酸炭窒化物を被覆することにより更に優れた工具性能を発揮する。本発明硬質皮膜の適用は、実施例で示したインサートだけでなく、旋削用途など他の高能率切削加工にも十分対応できうるものである。
【００２０】
【発明の効果】
本発明の硬質皮膜被覆工具は、ＴｉとＢで構成される窒化物、炭窒化物、酸窒化物、酸炭窒化物のいずれかである層にラマン分光分析においてｃ−ＢＮとｈ−ＢＮのピークが検出される皮膜が被覆され、この皮膜が優れた耐溶着、耐拡散性、耐酸化性、耐摩耗性を達成することにより、乾式高能率切削加工において著しく長い工具寿命が得られ、切削加工における生産性の向上に極めて有効である。
【図面の簡単な説明】
【図１】図１は、本発明例の皮膜を被覆した工具の切削後の刃先近傍における元素分析結果を示す。
【図２】図２は、従来例の皮膜を被覆した工具の切削後の刃先近傍における元素分析結果を示す。
【図３】図３は、本発明例の皮膜のラマン分光解析結果で、ｃ―ＢＮとｈ―ＢＮとの回折ピークを示す。[0001]
[Technical field to which the invention belongs]
The present invention relates to a hard film-coated tool used for cutting a metal material or the like.
[0002]
[Prior art]
Conventionally, a cutting tool coated with TiN, Ti (CN) or the like has been widely used. TiN is relatively excellent in oxidation resistance, so it not only exhibits excellent wear resistance against tool rake face wear caused by heat generated during cutting, but also has good adhesion to the substrate. is there. Moreover, since Ti (CN) has a higher hardness than TiN and a low contact resistance with the chips discharged from the workpiece, heat generation on the tool surface is suppressed. From this, it is possible to suppress flank wear that occurs on the tool flank due to mechanical rubbing wear with the work material. However, the hard coating does not exhibit sufficient oxidation resistance and wear resistance against the tendency to increase the cutting speed for the purpose of improving the efficiency of metal working. From such a background, studies have been made to further improve the oxidation resistance and wear resistance of the coating. As a result, Japanese Patent No. 3248897 discloses a (TiSi) N coating as a layer and a (TiAl) N coating as b. As a layer, a technique is disclosed in which a film obtained by alternately covering one or more a layers and b layers has oxidation resistance and wear resistance. On the other hand, in Japanese Patent Application Laid-Open No. 2001-293601, BN, TiB ₂ There is a disclosure about a film containing an ultrafine compound such as TiB, and it is described that this ultrafine compound has an amorphous structure and has a function of improving the hardness of the film. This is intended to improve wear resistance, high slipperiness, high seizure property, and machining accuracy of the work material, but there is no detailed description of the characteristics and existence state of the ultrafine compound.
[0003]
The (TiAl) N coating has a Vickers hardness of approximately 2300 to 2800, although it varies depending on the component ratio of Ti and Al contained in the coating or the content of Si or C in the coating. In addition, since the oxidation resistance is remarkably superior to those of TiN and Ti (CN), the performance of the cutting tool is remarkably improved under cutting conditions where the cutting edge reaches a high temperature. The (TiAlSi) (CN) film contains Si so as to improve the oxidation resistance as compared with the (TiAl) N film. Furthermore, aiming at the same effect, attempts have been made to contain Zr, Hf, and B as the third element in the (TiAl) system. In recent years, the environment in which these hard coating coated cutting tools are used has become increasingly severe. For example, the trend toward higher cutting speeds and the fact that conventional wet cutting has become an important environmental issue. Attention has been focused on dry cutting. In addition, there is a tendency for high-feed machining with emphasis on high-efficiency machining, making the steel difficult to machine due to the effects of various elements in the steel for molds, and the usage environment of hard coating coated cutting tools has become increasingly severe. Yes.
[0004]
According to the study of the present inventor, the oxidation start temperature of the (TiAl) N film in the atmosphere is improved to 750 to 900 ° C. depending on the Al content with respect to 450 ° C. of TiN. However, in the dry high-speed cutting described above, the cutting edge temperature of the tool used reaches a high temperature of 900 ° C. or higher. It goes without saying that the oxidation resistance of the hard coating is important in the cutting performed under such severe conditions, but the cutting edge portion of the hard coating coated cutting tool and the work piece are before that. It is essential to prevent the welding phenomenon that occurs when a chemical reaction occurs. In recent years, steel materials for metal molds contain various elements in order to significantly improve the performance of the metal mold, and the phenomenon of welding to cutting tools is more likely to occur, rather than wear due to oxidation of hard coatings. However, it is becoming easier for the workpiece elements to easily diffuse into the hard coating. For this reason, although conventional Ti and Al nitrides, etc., have extremely good oxidation resistance in the atmosphere, they prevent welding and diffusion of the workpiece, which are one of the chemical reactions, in cutting at high temperatures. However, it is difficult to obtain a sufficient tool life.
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of such circumstances, and without sacrificing the wear resistance and adhesion of a hard coating having excellent oxidation resistance, such as a conventional (TiAl) N coating having excellent oxidation resistance, The objective is to provide a hard coating tool that improves welding resistance at high temperatures and diffusion of workpiece elements into the hard coating, and is suitable for dry machining, high speed, and high feed cutting. .
[0006]
[Means for Solving the Problems]
The inventor has conducted extensive research on the influence of various elements on the adhesion resistance, wear resistance, and adhesion to a base material and the optimum layer structure of the film. A layer which is one of nitride, carbonitride, oxynitride and oxycarbonitride composed of Ti and B, and nitride, carbonitride and oxynitride whose metal components are composed of Al and Ti And b layers that are either oxycarbonitrides are alternately coated one or more layers, and the lattice constant A of the (200) plane in the X-ray diffraction of the a layer is 0.4200 ≦ A ≦ 0. C-BN and h-BN peaks were detected in the Raman spectroscopic analysis of the a layer in the range of 4270 nm. At that time, the peak intensity of c-BN was Q1, and the peak intensity of h-BN was Q2. The peak intensity ratio is Q1 / Q2 ≧ 1.0. It is to be hard-coated tool of high-speed cutting of dry, at high feed machining, we have reached the present invention found that the performance of the cutting tool becomes extremely good. The high feed processing here is defined as cutting in which the feed amount per blade in the cutting condition exceeds 0.3 mm / tooth. Further, according to the present invention, when the a layer is coated using an alloy target of Ti and B, and the composition of the film indicates the content M of B contained in the a layer in atomic percent of only the metal component, 0 0.1 ≦ M ≦ 40, and the film thickness D of the a layer is preferably D ≧ 0.1 μm.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The configuration of the a layer will be described in detail. In general, when an oxidation test is performed in the atmosphere for a (TiAl) N film, Al in the vicinity of the film surface diffuses outward toward the outermost surface, and Al ₂ O ₃ Form a layer. This phenomenon suppresses the subsequent entry of oxygen into the film. According to the inventor's research, this is considered to be the reason for improving the oxidation resistance. At this time, Al formed on the outermost layer ₂ O ₃ A very porous Ti oxide containing no Al is formed immediately below the layer. In the static oxidation test, Al formed on the outermost surface against the inward diffusion of oxygen, which is the progress of oxidation. ₂ O ₃ Although the layer functions as an oxidation protective film, in dynamic cutting, the outermost Al ₂ O ₃ The layer is easily peeled off from the porous Ti oxide layer immediately below, and does not exhibit a sufficient effect on the progress of oxidation. In addition, Al formed on this outermost surface ₂ O ₃ If the layer does not peel off for dynamic cutting, Al ₂ O ₃ Although it is possible to prevent the phenomenon of welding with the workpiece due to the chemical stability of ₂ O ₃ It is difficult to prevent peeling. In other words, the phenomenon of welding that occurs at high temperatures is caused by Al formed on the outermost layer. ₂ O ₃ It has become clear that this occurs because of peeling. In addition, (TiAlSi) (CN) film, (TiAlZrB) N, (TiAlB) N, and (TiAlSiB) N also have a hard film itself by adding Si, Zr, B, etc. to the conventional (TiAl) N film. Although the hardness and oxidation resistance are slightly improved, as described above, the surface oxidation protective film Al is different from the difference in free energy of formation relative to the oxide. ₂ O ₃ A layer is immediately formed, and a porous Ti oxide is formed immediately below the layer, resulting in film peeling during cutting. Therefore, the welding phenomenon in dynamic cutting cannot be prevented.
[0008]
However, nitrides composed of Ti and B, carbonitrides, oxynitrides, oxycarbonitrides, etc., excluding Al, which causes the welding phenomenon, have the same oxidation resistance as that of the conventional Ti and Al. It is similar to the nitride of Nd, and is superior to the nitride of Ti and Al for the welding phenomenon at high temperature. The inventor has conducted extensive research from the viewpoint of resistance to the phenomenon of welding of various elements, that is, wettability between elements contained in steel and elements contained in the hard film. It has been found that it is effective in preventing the welding of workpieces at high temperatures. As a result of investigating in detail the phenomenon that occurs when applied to a cutting tool for B to be contained in the hard film, the effectiveness of B is not an increase in the hardness or oxidation resistance of the hard film, That is, the affinity with Fe during cutting is low and the diffusion phenomenon of the workpiece into the film hardly occurs. FIG. 1 shows the result of elemental analysis in the substrate direction of the vicinity of the cutting edge of the hard film coated cutting tool using the a layer of the present invention after cutting. Further, FIG. 2 shows the result of the same analysis of conventional (TiAl) N. From the comparison of FIGS. 1 and 2, there is no Fe element as a work piece in FIG. 1, but in the conventional film of FIG. 2 (TiAl) N, an oxide of Al is present on the outermost layer of the film. It can be seen that Fe, which is a workpiece, is diffused in the film. It was confirmed that the tendency shown in FIG. 2 was also observed in conventional (TiAlSi) (CN), (TiAlZrB) N, (TiAlB) N, and the like. In other words, by using the a layer of the present invention, it has a characteristic that a chemical reaction with a workpiece is difficult to occur at a high temperature. At the same time, the inventors have found that the oxidation resistance is almost the same as that of conventional nitrides of Ti and Al. The present inventors have further conducted intensive research and tried an experiment in which B is contained in conventional (TiAl) N having excellent oxidation resistance such as (TiAlB) N, focusing on the welding resistance of the hard coating, and evaluating it. As a result, the conventional film containing Al described above has a higher affinity with Fe at a higher temperature than Ti and B, so that Al contained therein contains Al to prevent internal diffusion of oxygen in the outermost layer. ₂ O ₃ Before forming the layer, it was found that a chemical reaction had occurred with the inclusions in the workpiece. When such a hard film containing Al is applied to the cutting tool, this welding phenomenon promotes the progress of abnormal crater wear on the rake face of the tool, and a large amount of deposits are stored in the boundary part. It brings about chipping. From these experimental results, rather than coating the outermost surface of the hard coating tool with a coating with sufficient oxidation resistance, a specific oxidation mechanism such as nitrides of Ti and Al that have been used in the past has been generated. In other words, a self-lubricating film is required to prevent welding on the surface of the hard film-coated tool. In other words, the outermost layer of the cutting tool is coated with the hard coating of the present invention, thereby preventing welding with the workpiece, and as a result, preventing abnormal wear, thereby covering conventionally used nitrides of Ti and Al, etc. It was confirmed that the life of the hard-coated tool was significantly increased.
[0009]
The layer a has excellent welding resistance under static and dynamic conditions, but the residual compressive stress of the coating itself is large, so that the adhesion with the substrate is not sufficient. Therefore, nitrides, carbonitrides, oxynitrides, oxycarbonitrides composed of Al and Ti are provided just above the substrate surface in order to appropriately provide adhesion, wear resistance, oxidation resistance, etc. in a balanced manner. It is preferable to coat the b layer such as. In addition to the hard film described above, an alloy film containing one or more metals of groups 4a, 5a, and 6a described in the periodic table of elements may be used immediately above the substrate surface. The role of Al in the b layer, which is a (TiAl) -based nitride film, is to improve the wear resistance and oxidation resistance of the film. Therefore, in order to obtain a good balance of adhesion, wear resistance, and oxidation resistance, preferably the Al content F of the b layer is adjusted to 30 ≦ F ≦ 75 with only the atomic% of the metal component of the film. Is preferred. The reason why the preferable Al content F is set in the b layer is that the oxidation resistance starts to be remarkably improved when F is 30 atomic% or more. Moreover, the reason for adjusting to 75 atomic% or less is that even if the oxidation resistance is improved, the film hardness is remarkably lowered and the wear resistance is deteriorated.
[0010]
As described above, in the present invention, the b layer having a good balance between adhesion to the substrate, wear resistance and oxidation resistance of the coating itself is coated directly on the surface of the substrate, and remarkably welding resistance and workpiece are further formed thereon. It is extremely important to coat the a layer having excellent element diffusibility, and as a result, it is possible to obtain a cutting tool that supports dry high-speed cutting and high-feed cutting. The reason for limiting the size of the crystal lattice of the a layer will be described. In order to make the hard coating of the present invention effective as a hard coating-coated cutting tool, the size of the crystal lattice in the physical properties of the hard coating, that is, the lattice constant is important. In order to maintain high adhesion, first, it is necessary to reduce the residual compressive stress generated peculiar to physical vapor deposition. As a result of diligent research up to the present invention, the correlation between the lattice constant of the hard film of the present invention and the residual compressive stress has been derived. Secondly, in order to ensure adhesion between the hard coatings, the different hard coatings used in the present invention must be maintained in a heteroepitaxial relationship. In order to satisfy both of these conditions, the present inventor has made control by controlling the lattice constant A of the (200) plane in the X-ray diffraction of the a layer to be in the range of 0.4200 ≦ A ≦ 0.4270. It was possible. In other words, in order to derive the features of the hard coating to the maximum, if the value of A exceeds 0.4270, the residual compressive stress of the hard coating will increase significantly, causing peeling during cutting and satisfying cutting performance. Cannot be obtained. The same effect was obtained by a multilayer coating in which the a layer and the b layer were alternately laminated after the b layer was coated directly on the substrate surface. The layer a can detect c-BN and h-BN peaks in Raman spectroscopic analysis. When the peak intensity of c-BN is Q1 and the peak intensity of h-BN is Q2, The intensity ratio must be in the relationship of Q1 / Q2 ≧ 1.0. This is to improve the hardness while maintaining the lubricity of the hard coating. As shown in FIG. 3, c-BN and h-BN peaks are detected in the a layer of the hard coating of the present invention. Comparing the hardness of c-BN and h-BN, c-BN shows higher hardness. Therefore, by controlling the coating conditions so that a large amount of c-BN is contained in the hard film, the film hardness is increased and the wear resistance can be improved. Each layer can be adjusted to any one of nitride, carbonitride, oxynitride, and oxycarbonitride as required, and the same cutting performance can be obtained for a tool coated with these layers.
[0011]
The reason why the content M of B in the hard film having nitride, carbonitride, oxynitride and oxycarbonitride in which the metal component is composed of Ti and B is limited will be described. When the B content is less than 0.1 atomic% with respect to Ti, the effect of preventing the intended welding and element diffusion of the present invention cannot be obtained. Therefore, since it cannot cope with the target of severe cutting work in recent years, it is set to 0.1 atomic% or more where the effect starts to be remarkable. In addition, the hard coating of the present invention composed of Ti and B exhibits columnar crystals that are often seen in TiN, etc., but when the B content exceeds 40 atomic%, it changes from columnar crystals to a fine granular crystal structure. Admitted to do. Thus, it was recognized that the hard film having a large B content has many internal defects and a low density. In addition, it was confirmed that the internal stress that hinders the adhesion of the film becomes very large and the peeling phenomenon easily occurs. Furthermore, since the crystal of the hard coating is fine, the frequency of grain boundary fracture occurring during the cutting process is high, and abnormal wear due to this was observed. The present inventors have obtained the above knowledge and limited the B content M in the hard film of the present invention to 0.1 ≦ M ≦ 40 in atomic%. In producing the hard coating of the present invention, physical vapor deposition is preferred. Therefore, a target for film formation is required. Two targets composed of Ti and B may be used as the target, but an alloy target of Ti and B is more preferable in consideration of variation in composition and stability of discharge.
[0012]
It was confirmed that the presence form of the metal element in the hard film composed of Ti and B is characterized by the B content contained in the hard film. The conventional hard coatings such as nitrides of Ti and Al vary depending on their compositions, but it is understood that when a practically used coating is taken up, it generally takes the NaCl type B1 structure which is the same crystal lattice form as TiN. In other words, the Ti in the TiN lattice is replaced by Al, so to speak, Al is in a solid solution state. However, although the hard film composed of Ti and B of the present invention depends on the B content, when the content is 0.1 atomic% or more, it is different from the Ti and Al nitrides. The form is shown. When the content of B is 0.1 atomic% or more, B becomes a form in which the compound of B exists alone in addition to the form in which Ti in the TiN lattice is replaced. That is, when the B content is 0.1 atomic% or more, for example, in the case of a Ti and B nitride that is the hard coating of the present invention, a form in which TiN crystals and BN crystals are mixed in the hard coating. Is taken. When the B content is less than 0.1 atomic%, B is completely taken into the TiN crystal lattice and takes the form of a solid solution. This change in crystal form greatly affects the cutting performance. In the case of the nitride in the composition range of the present invention, BN crystals exist in addition to TiN-like crystals. This BN is known to have excellent self-lubrication and low wettability with Fe, and the presence of this BN crystal is considered to have the effect of significantly suppressing crater wear mainly due to chemical reaction. It is done. In addition, since BN is resistant to oxidation from the viewpoint of free generation energy against oxidation, the characteristics of the hard coating at high temperatures do not deteriorate. These surprising facts are the results obtained by the inventor's extensive research. However, if the B content exceeds 40 atomic%, the BN crystals exist, but the internal stress becomes very large, and it becomes difficult to maintain good adhesion. In other words, when an external impact is applied to the hard coating as in cutting, the hard coating cannot withstand its own internal stress, and peeling may occur easily, making it difficult to serve as a hard coating tool. Admitted. Therefore, in order to provide the cutting tool which is the target of the present inventors, the amount of B contained in the hard film must not exceed 40 atomic%, and BN is contained in the hard film. We must create new technologies that make crystals exist.
[0013]
The reason why the thickness D of the hard coating of the present invention is specified will be described. In order for the characteristics of the hard coating to cope with the severe cutting work in recent years, D ≧ 0.1 μm must be coated. That is, when it is thinner than that, the characteristics of the hard coating are not exhibited. In addition, when the hard coating described in the present invention is thickly coated on the rake face of the tool and applied to a cutting process in which rake face wear is remarkably generated, the conventional hard coating (TiAl) N or (TiAlSi) (CN ), (TiAlZrB) N, and (TiAlB) N, crater wear easily occurs as described above, and high-efficiency machining is not satisfied. As a result of investigating in detail the optimum film thickness for sufficiently exerting the effect of the hard film in which the metal component to be applied is composed of Ti and B, the film thickness D is D ≧ 0.1 μm. It revealed that. Based on this investigation, the thickness D of the tool rake face to be coated is more preferably D ≧ 0.1 μm.
[0014]
The coating method of the hard film-coated tool of the present invention is not particularly limited. However, when considering the thermal effect on the coated substrate, the fatigue strength of the tool, the adhesion of the film, etc., at a relatively low temperature. It is desirable to be a physical vapor deposition method in which a bias voltage is applied to the coated substrate side, such as arc discharge ion plating in which the coating film can be coated and compressive stress remains in the coated film, or sputtering. Hereinafter, the present invention will be described based on examples.
[0015]
【Example】
Using a small arc ion plating apparatus, various alloy targets that are evaporation sources of metal components, and N that is a reaction gas ₂ Gas, CH ₄ Gas, Ar and O ₂ A gas mixture from which a desired film was obtained was selected, and coating was performed by applying a potential of −150 V to a cemented carbide insert having an outer diameter of 8 mmφ as a coated substrate at a coated substrate temperature of 400 ° C.
[0016]
Using the obtained hard coating-coated insert, machining was performed under the following dry-type high-efficiency cutting conditions until the tool became uncut due to chipping or abrasion of the blade edge, and the cutting length at that time was defined as the tool life. Table 1 shows the details of the hard coating and the cutting results for the inventive examples, comparative examples, and conventional examples.
[0017]
[Table 1]

[0018]
The insert cutting conditions are as follows. The cutting tool uses a face mill (insert shape: SEE42TN special type), the cutting method is the center cut method, the work material shape is 100 mm wide, the length is 250 mm, the work material is S50C (HRC30), Cutting is 2.0 mm, cutting speed is 150 m / min, blade feed is 0.30 mm / blade, and no cutting oil is used.
[0019]
As shown in Table 1, in the hard coating of the present invention, it is clear that the magnitude of the lattice constant and the peak intensity ratio of h-BN and c-BN in Raman spectroscopic analysis greatly affect the cutting performance. That is, as shown in Examples 1 to 20 of the present invention, the lattice constant A of the (200) plane in the X-ray diffraction of the a layer satisfies the range of 0.4200 ≦ A ≦ 0.4270 nm, and c by Raman spectroscopic analysis. -BN and h-BN are detected, and the ratio of the peak intensity Q1 of c-BN and the peak intensity Q2 of h-BN at that time, when Q1 / Q2 ≧ 1.0, the characteristics of the material are exhibited. As a result, the cutting life is greatly improved and satisfactory results are obtained. However, for example, in Comparative Examples 21, 22, and 25, the lattice constant A of the (200) plane in the X-ray diffraction of the a layer does not satisfy the range of 0.4200 ≦ A ≦ 0.4270 nm. Since the peak intensity of h-BN was strong in the spectroscopic analysis, the peak intensity ratio was not satisfied. Therefore, no effect was recognized even when compared with Conventional Examples 28 to 34. Furthermore, in Comparative Examples 23, 24, 26, and 27, the (200) plane lattice constant A in the X-ray diffraction of the a layer does not satisfy the range of 0.4200 ≦ A ≦ 0.4270 nm, and Raman spectroscopy is performed. When the peak intensity of c-BN in the analysis was increased, the internal stress of the hard coating was remarkably increased, leading to defects after early peeling. As shown in Table 1, it is clear that the hard coating of the present invention has a remarkable improvement in tool performance because of its excellent heat resistance as well as welding resistance by the presence of BN crystals and control of its chemical structure. It is. However, for example, in Comparative Examples 21 and 24, since the amount of B added to the hard film is very small, it is taken into the TiN crystal lattice and takes the form of a solid solution. As a result, the film is composed of Ti and B. Although it is a hard film comprised, it does not go far to the improvement of the tool performance which is the objective of this invention. Further, in Comparative Examples 22, 23, 25, 26, and 27, even though it is recognized that BN crystals are present in the hard film composed of Ti and B, the amount of added B is relative to Ti. It has exceeded 50 atomic%. In such a case, in the cutting process, the hard coating loses its own internal stress, and peeling easily occurs. In particular, in Comparative Example 26, it was recognized that the internal stress of the entire hard coating became the highest and reached about −6 GPa, and in the cutting test, a large peeling occurred on the tool flank and rake face at the initial stage of cutting of the insert. Occurred, making it impossible to continue cutting. Therefore, in the hard coating of the present invention, the presence of BN crystals in the film is also a very important technique. However, the hard coating coating tool including the amount of B to be added is not simply present. Clearly, it would be impossible to provide a tool that would perform significantly better if not done. On the other hand, a sample formed as a two-layer film of (TiSi) N film and (TiAl) N film of Conventional Example 28, and (TiAl) -based nitride layers of Conventional Examples 29 to 34 as Zr, B, It was confirmed that the example of the present invention was superior in tool life in any case to the sample to which Si was added. In carrying out the film formation of the present invention, the introduction gas to be used was also examined. As a result, in order to maintain remarkably excellent welding resistance, the metal component is any of nitride, carbonitride, oxynitride, and oxycarbonitride composed of Ti and B, and the content M of B is Although it is desirable that 0.1 ≦ M ≦ 40.0 by atomic% of only the metal component, the film described above is formed at the time of film formation in consideration of heat generation of the tool and friction with the workpiece. In addition to the gas containing nitrogen and oxygen required above, a gas containing carbon is introduced to coat carbonitride and oxycarbonitride, thereby further improving tool performance. The application of the hard coating of the present invention can sufficiently cope with not only the inserts shown in the embodiments but also other high-efficiency cutting such as turning applications.
[0020]
【The invention's effect】
The hard film-coated tool of the present invention is a layer of any one of nitride, carbonitride, oxynitride, and oxycarbonitride composed of Ti and B. In Raman spectroscopy, c-BN and h-BN are used. A film with a peak detected is coated, and this film achieves excellent welding resistance, diffusion resistance, oxidation resistance, and wear resistance, resulting in extremely long tool life in dry high-efficiency cutting. It is extremely effective for improving productivity in processing.
[Brief description of the drawings]
FIG. 1 shows the results of elemental analysis in the vicinity of a cutting edge of a tool coated with a film of an example of the present invention after cutting.
FIG. 2 shows the results of elemental analysis in the vicinity of the cutting edge of a tool coated with a conventional film after cutting.
FIG. 3 is a result of Raman spectroscopic analysis of the film of the present invention and shows diffraction peaks of c-BN and h-BN.

Claims

A layer in which the metal component is any one of nitride, carbonitride, oxynitride, and oxycarbonitride composed of Ti and B; and nitride, carbonitride composed of metal components composed of Al and Ti And b layers that are any one of oxynitride and oxycarbonitride are alternately coated one or more layers, and the lattice constant A of the (200) plane in the X-ray diffraction of the a layer is 0.4200 ≦ In the range of A ≦ 0.4270 nm, and in the Raman spectroscopic analysis of the layer a, c-BN and h-BN peaks are detected, and the peak intensity of c-BN at that time is defined as Q1 and h-BN peaks. A hard coating tool characterized by a peak strength ratio Q1 / Q2 ≧ 1.0 when the strength is Q2.

The hard film-coated tool according to claim 1, wherein the a layer is coated using an alloy target of Ti and B, and the composition of the a layer indicates that the content M of B is expressed in atomic% of only the metal component. A hard coating tool characterized by 0.1 ≦ M ≦ 40.

The hard film-coated tool according to claim 1 or 2, wherein the thickness a of the a layer is D ≧ 0.1 µm.