JP3872244B2

JP3872244B2 - Hard film and hard film coated member with excellent wear resistance

Info

Publication number: JP3872244B2
Application number: JP37117199A
Authority: JP
Inventors: 夏樹一宮; 保之山田; 龍哉安永; 俊樹佐藤
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 1999-12-27
Filing date: 1999-12-27
Publication date: 2007-01-24
Anticipated expiration: 2019-12-27
Also published as: JP2001181826A

Description

【０００１】
【発明の属する技術分野】
本発明は、フライス加工，切削加工，穿孔加工等の加工に使用される切削工具の表面被覆材、或は金型，軸受け，ダイス，ロールなど高硬度が要求される耐摩耗部材の表面被覆材、もしくは成形機用スクリューやシリンダ等の耐熱・耐食部材の表面被覆材として有用な硬質皮膜に関し、更には該硬質皮膜を被覆することによって優れた耐摩耗性を発揮する硬質皮膜被覆部材に関するものである。
【０００２】
【従来の技術】
高速度工具や超硬合金工具など高い耐摩耗性が要求される切削工具は、工具の基材表面にＴｉＮやＴｉＣＮ等の硬質皮膜を形成することにより耐摩耗性の向上が図られている。
【０００３】
またこれらの皮膜より一層優れた特性を示す皮膜材料として、Ｔｉと、Ｔｉ以外の４ａ，５ａ，６ａ族金属元素の複合（炭）窒化物が提案されている（例えば、特開昭６０−２４８８７９号公報，特開平４−２２１０５７号公報，特開平７−１７３６０８号公報）。具体的には、（Ｔｉ，Ｍ）（Ｎ，Ｃ）［但し、ＭはＺｒ，Ｈｆ，Ｖ，Ｎｂ，Ｔａ，Ｃｒ，Ｍｏ，Ｗ］で示される硬質皮膜であり、これらの皮膜は耐摩耗性の上では非常に優れた特性を発揮するが、ＴｉＮやＴｉＣＮに比べると密着性が不十分であり、使用中に皮膜が剥離するという問題があった。
【０００４】
そこで、例えば特開平１０−１５８８６１号公報に示されている様に、ＴｉＮを中間層に用いることにより密着性の改善が試みられているが、十分な密着性は得られていなかった。特に、切削工具に使用した場合には、密着性が不十分であることに加えて、折角、高硬度の（Ｔｉ，Ｍ）（Ｎ，Ｃ）膜をコーティングしているにもかかわらず、中間層のＴｉＮの硬度が高くないために耐摩耗性が劣化するという問題があった。即ち、上記（Ｔｉ，Ｍ）（Ｎ，Ｃ）を切削工具用の耐摩耗コーティング材料に用いた場合は、耐摩耗特性で優れた性能を発揮することで最近注目されている（Ｔｉ，Ａｌ）Ｎ膜と比較すると、Ｓ５０Ｃ等の炭素鋼に代表される低硬度材の切削においては同程度の耐摩耗特性を示すものの、ＳＫＤ６１焼入れ鋼等に代表される高硬度材の切削に至っては、上記（Ｔｉ，Ａｌ）Ｎ膜に比べ耐摩耗特性が劣ることが指摘されていた。
【０００５】
また皮膜の密着性を向上させる手段として、界面での結晶組織を連続的に成長させる方法が検討されている。例えば、特開平９−１７００６７号公報では（Ｔｉ，Ａｌ）ＣＮ系硬質膜を基材に密着性良く積層させるために、被覆する硬質層と基材の結晶組織が界面で不連続にならないよう連続的にエピタキシャル成長させることが検討されており、六方晶である炭化タングステンを主体とした超硬基材の結晶面と立方晶である（Ｔｉ，Ａｌ）ＣＮ系硬質層の結晶面が特定の方向関係を維持してエピタキシャル成長させれば高い密着性が得られることが示されている。
【０００６】
さらに特開平７−１３３１１１号公報には、２層以上の異なる硬質層を積層させる多層硬質皮膜においても、結晶構造が六方晶であるＡｌＮと立方晶であるＴｉＮの各層の厚さを２０ｎｍ以下とすることにより、両者の結晶構造が同一の立方晶構造になるようにエピタキシャル成長させることができ、層間界面の密着性が高くなると共に、格子歪に誘起された高硬度が発現することが開示されている。
【０００７】
しかしながら、特開平７−１３３１１１号公報のように六方晶のＡｌＮと立方晶のＴｉＮを同じ立方晶構造としてエピタキシャル成長させるには各層の厚さを２０ｎｍ以下にする必要があり、厚さ数μｍの硬質膜を得る為には数百層もの積層を繰り返す必要がある。このため、エピタキシャル成長により界面密着性はある程度良いものの、生産工程が非常に煩雑になるという問題があった。
【０００８】
【発明が解決しようとする課題】
本発明は上記事情に着目してなされたものであって、２層以上の異なる硬質層が積層された硬質皮膜であって、厚さ数μｍ以上であっても、優れた耐摩耗性及び密着性を発揮する硬質皮膜と、上記硬質皮膜が形成された硬質皮膜被覆部材を提供しようとするものである。
【０００９】
【課題を解決するための手段】
上記課題を達成した本発明に係る耐摩耗性に優れた硬質皮膜とは、１種以上の金属元素を含む窒化物，炭化物，炭窒化物からなり、これらの中から選ばれた化学組成の異なる２種以上が積層されて基板上に形成される硬質皮膜であって、各層の厚さが０．４μｍ以上で、皮膜全体の厚さが０．８〜５０μｍであると共に、いずれの層も実質的に岩塩型結晶構造からなり、且つ各層の結晶組織が界面で実質的にエピタキシャル成長しており、
および、表面側最外層の組成が
（Ｖ_uＴｉ_1-u）（Ｎ_vＣ_1-v）
但し０．２５≦ｕ≦０．７５，０．６≦ｖ≦１
であると共に、
表面から２番目に層の組成が、
（Ａｌ_ｘＴｉ_1- _ｘ）（Ｎ_ｙＣ_1- _ｙ）
但し０．５６≦ｘ≦０．６５，０．６≦ｙ≦１
であることを要旨とするものである。
【００１１】
本発明に係る上記硬質皮膜を形成すれば、優れた耐摩耗性を発揮する硬質皮膜被覆部材を得ることができる。尚、切削工具の表面に本発明に係る硬質皮膜を形成する場合には、上記硬質皮膜の厚さを２０μｍ以下とすることが推奨される。
【００１２】
【発明の実施の形態】
本発明において採用する硬質層は、１種以上の金属元素を含む窒化物，炭化物，炭窒化物からなり、且つ岩塩型（ＮａＣｌ型）構造を有するものであり、その例としては、従来より単層として使用実績があるＴｉＮ，ＴｉＣＮ，ＡｌＴｉＮなどがあり、これらを下地とし、その上に更に岩塩型（ＮａＣｌ型）結晶からなる硬質層を積層するものであり、特開平７−１３３１１１号公報に記載の技術のように硬質層の厚さが２０ｎｍ以上になるとエピタキシャル成長界面を形成できないという制約は受けず、層間界面は実質的にエピタキシャル成長構造であるにもかかわらず、一層の厚さをμｍオーダーまで厚くすることが可能である。従って、膜全体の強度と信頼性を向上させることができる。
【００１３】
こうして、耐摩耗性，耐酸化性，耐反応性などの目的とする表面特性を獲得しつつ、基材との密着性、硬質層相互の密着性を維持することができ、しかも多層膜全体としての強度も維持することができ、これまでの多層膜で生じていた種々の問題をすべて解決することができる。
【００１４】
また、本発明に係る硬質皮膜を高速度鋼基材や超硬合金基材の上に形成する場合には、これらの基材との密着性を優先して基材側の硬質膜を選定すればよい。
【００１５】
本発明に採用できる硬質層の組成としては、ＴｉＮ，ＴｉＣＮ，ＡｌＴｉＮ，ＴｉＶＮ，ＡｌＴｉＶＮ等が挙げられるが、高速度鋼や超硬基材との密着性を確保する下地層としてはＴｉＮ，ＴｉＣＮ，ＡｌＴｉＮ等を用い、その上に積層して耐摩耗性，耐酸化性，耐反応性などの表面機能を発現する層としては、ＴｉＶＮ，ＡｌＴｉＶＮ等を用いることが推奨される。
【００１６】
中でも、表面側に積層された最外層の組成は
（Ｖ_uＴｉ_1-u）（Ｎ_vＣ_1-v）
但し０．２５≦ｕ≦０．７５，０．６≦ｖ≦１
とすることが望ましい。
【００１７】
その理由は、ｕの値が、０．２５以上０．７５以下の範囲において、（Ｖ，Ｔｉ）（Ｎ，Ｃ）膜の硬度が高くなり、（Ｖ，Ｔｉ）（Ｎ，Ｃ）膜を表面側に形成することによる優れた特性が発揮できるからであり、またＶを添加することによる潤滑性と耐溶着性の向上効果が十分に得られるからである。なお、ｕの値は、高い硬度を得る上で０．３０≦ｕ≦０．７０が望ましく、０．４０≦ｕ≦０．６０がより望ましい。またｖの値が０．６未満では、（Ｖ，Ｔｉ）（Ｎ，Ｃ）膜の靭性が低下し、十分な密着力が得られなくなるので、０．６≦ｖ≦１であることが必要である。
【００１８】
更に、表面から第２番目の層の組成は、
（Ａｌ_xＴｉ_1-x）（Ｎ_yＣ_1-y）
但し０．２５≦ｘ≦０．７５，０．６≦ｙ≦１
とすることが望ましい。ｘの範囲が０．２５以上０．７５以下であることが望ましい理由は、以下の通りである。ＴｉＣＮの結晶構造は、金属元素であるＴｉ原子と、非金属元素であるＣ原子またはＮ原子とが３次元的に交互に並んだ岩塩（ＮａＣｌ）型構造をとっている。このＴｉＣＮにＶを添加していくと、Ｖは岩塩型構造を組んでいるＴｉＣＮのＴｉのサイトに置換型で入ると考えられるが、ＶはＴｉよりも原子半径が小さいために、Ｖの添加量が増加すると共に（Ｖ，Ｔｉ）（Ｎ，Ｃ）の格子定数は小さくなる。一方、（Ａｌ，Ｔｉ）（Ｎ，Ｃ）も岩塩型構造をとっており、Ａｌの添加量が増えると、（Ａｌ，Ｔｉ）（Ｎ，Ｃ）の格子定数は小さくなる。耐摩耗性で優れた性能を示す上記（Ｖ_uＴｉ_1-u）（Ｎ，Ｃ）の組成範囲（０．２５≦ｕ≦０．７５）における（Ｖ，Ｔｉ）（Ｎ，Ｃ）の格子定数と、ｘの範囲が０．２５以上０．７５以下の（Ａｌ_xＴｉ_1-x）（Ｎ，Ｃ）の格子定数とが近い値を示すため、同じ岩塩型構造をとる（Ｖ，Ｔｉ）（Ｎ，Ｃ）と（Ａｌ，Ｔｉ）（Ｎ，Ｃ）の格子のミスマッチが小さくなり、（Ｖ，Ｔｉ）（Ｎ，Ｃ）と（Ａｌ，Ｔｉ）（Ｎ，Ｃ）が実質的にエピタキシャル成長して優れた密着性を示すと考えられる。更にｘの範囲が０．２５以上０．７５以下では、（Ａｌ，Ｔｉ）（Ｎ，Ｃ）の硬度も最も高くなり、優れた耐摩耗性を示す。また、ｘの値が０．７５を超えると、（Ａｌ_xＴｉ_1-x）（Ｎ_yＣ_1-y）の結晶構造が立方晶（岩塩型結晶構造）から第２層の（Ｖ，Ｔｉ）（Ｎ，Ｃ）と異なる六方晶に変化して、十分な密着力が得られなくなると共に、硬度も大幅に低下してしまう。なお、より高い密着性及び硬度を得る上で、ｘの範囲は０．４０≦ｘ≦０．７０が望ましく、０．５６≦ｘ≦０．６５であればより望ましい。
【００１９】
またｙの値は、０．６未満では、（Ａｌ_xＴｉ_1-x）（Ｎ_yＣ_1-y）膜の靭性が低下し、十分な密着力が得られないので０．６≦ｙ≦１とすることが望ましい。
【００２０】
本発明に係る硬質皮膜の厚さは、薄過ぎると耐摩耗性が不十分となるので０．８μｍ以上とすることが必要であり、１．５μｍ以上であれば望ましい。一方厚過ぎると膜自体にクラックが入り易くなって強度が不十分となるので５０μｍ以下の厚さとすることが必要であり、３０μｍ以下であれば望ましい。尚、本発明の硬質皮膜は切削工具の表面に形成することにより非常に優れた効果を発揮するが、皮膜が厚過ぎると切れ味が低下しチッピング等が発生するので、特に高い密着性が要求される切削工具に適用する場合には、皮膜の厚さを２０μｍ以下とすることが望ましい。
【００２１】
また本発明に係る硬質皮膜の各層の厚みは、十分な耐摩耗性を発揮させる上で０．４μｍ以上であることが必要である。硬質皮膜の積層数は、２層以上であれば特に制限はないが、積層数が多くなるにしたがって生産工程数が増えコスト上昇につながるので８層以下とすることが推奨される。
【００２２】
本発明に係る硬質皮膜を形成する方法としては、アークイオンプレーティング法を採用することが推奨される。その理由は、イオン化効率を高くすることや反応性を高めること、又は基板にバイアス電圧を印加することなどによって一層密着性の優れた皮膜を得ることができるからである。またカソードとして目的とする組成比の合金ターゲットを用いれば、皮膜組成のコントロールが容易であり推奨される。
【００２３】
本発明は硬質皮膜を被覆する基材の材質を限定するものではないが、基材表面に密着性よく被覆して優れた耐摩耗性を発揮させるためには、超硬合金，高速度工具鋼，ダイス鋼，サーメットまたはセラミック等の硬質物質が適している。
【００２４】
特に切削工具に使用する場合には、本発明皮膜の優れた密着性により、低硬度材の切削においては従来例よりも優れた耐摩耗性が得られると共に、高硬度材の切削においても十分な耐摩耗性が得られ、低硬度材から高硬度材まで切削が可能な切削工具とすることができる。
【００２５】
以下、実施例について説明するが、本発明は下記の実施例に限定されるものではなく、前・後記の趣旨に基づいて適宜変更することは本発明の技術的範囲に含まれるものである。
【００２６】
【実施例】
実施例１
超硬チップをアークイオンプレーティング装置内に置き、真空排気を行い、ヒータによって炉内雰囲気温度を約４００℃で６０分間保持した。その後、ワークに−１５０Ｖのバイアス電圧を印加すると共に、炉内に高純度Ｎ₂ガスを０．９３Ｐａとなるまで導入し、種々の組成を有するＴｉＡｌカソードを用いてアーク放電を行い、表１に示す組成の第１層を成膜した。その後、種々の組成を有するＴｉＶカソード及びＡｌカソードを用いてアーク放電を行い、表１に示す組成の第２層を成膜した。尚、（Ａｌ，Ｔｉ）Ｎ系膜と（Ｖ，Ｔｉ）Ｎ系膜はいずれも岩塩型（ＮａＣｌ型）の結晶構造であり、Ａｌ，Ｔｉ，Ｖの組成を変化させることにより格子定数を制御することができる。第１層と第２層の格子定数が近くなると両層の界面がエピタキシャル成長するが、両層の格子定数の差が大きくなると第１層と第２層の界面が不連続になる。このことを利用として、各種組成の第１層と第２層を積層させることにより岩塩型結晶構造であり異なる界面構造を有する２層系硬質層を作製した。また、比較のため、Ａｌカソードにより六方晶構造であるＡｌＮを第２層として積層したサンプルも作製した。これらの皮膜の組成は、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確認した。
【００２７】
得られた試験片の第１層と第２層の界面を透過電子顕微鏡（ＴＥＭ）により断面観察を行い、界面の結晶構造が連続（エピタキシャル成長）であるか、不連続であるかを調べた。またスクラッチ試験器を用いて、膜損傷時の発生音波（ＡＥ信号）の変化とテスト後の光学顕微鏡観察によって皮膜が剥離したときの荷重を調べ、第１層と第２層の界面構造と密着性の関係を調べた。結果は表１に併記する。尚、表１において「第１層と第２層の結晶の連続性」の欄の○×の評価は、界面の結晶構造においてエピタキシャル成長している部分が８０％以上の場合を○、エピタキシャル成長している部分が８０％未満の場合を×とした。
【００２８】
【表１】

【００２９】
Ｎｏ．１〜４は、硬質膜と基材間の剥離密着性を調べた試験結果である。Ｎｏ．１〜３に示すように、超硬基材と（Ａｌ，Ｔｉ）Ｎ系膜の界面の剥離臨界荷重は、膜組成に係らず全て９０Ｎ以上となっており、十分良い密着性を示している。しかし、Ｎｏ．４に示すように、超硬基材と（Ｖ，Ｔｉ）Ｎ系膜の界面の剥離荷重は２２Ｎと低く、（Ｖ，Ｔｉ）Ｎ単層では実用に耐える密着性が得られず、（Ａｌ，Ｔｉ）Ｎ系膜を下地（第１層）とするなどの工夫が必要であることが分かる。
【００３０】
Ｎｏ．５〜２５は第１層と第２層の間の密着性を調べた試験結果である。まずＮｏ．５〜１７では、第１層と第２層の厚さを各々２μｍとし、膜組成を変化させて密着性を調べた。（Ａｌ，Ｔｉ）Ｎ系膜と（Ｖ，Ｔｉ）Ｎ系膜の結晶構造は共に岩塩型構造であり、格子定数も近いので、ほとんどの組成において第１層と第２層の界面が実質的にエピタキシャル成長構造になっている。但し、（Ａｌ，Ｔｉ）Ｎ系膜のＡｌ量と、（Ｖ，Ｔｉ）Ｎ系膜のＶ量が多すぎるか、少なすぎる場合には、実質的にエピタキシャル成長構造となっていない。本発明例としてＮｏ．８のサンプルの第１層と第２層の界面の写真を図１に、比較例としてＮｏ．１１のサンプルの第１層と第２層の界面の写真を図２に示す。図１では、界面のほとんどの結晶が連続的につながっているが、図２では、界面の結晶構造が不連続になっている部分が多く確認できる。
【００３１】
界面構造がエピタキシャル成長の場合は剥離臨界荷重が９０Ｎ前後となっており、（Ａｌ，Ｔｉ）Ｎ系膜と超硬基材の界面の密着性に近い実用に耐えうる値となっている。しかし、Ｎｏ．５，１１，１２，１７の様に（Ａｌ，Ｔｉ）Ｎ系膜のＡｌ量と、（Ｖ，Ｔｉ）Ｎ系膜のＶ量が多すぎるか、少なすぎる場合には、第１層と第２層の界面が不連続となっており、界面の剥離臨界荷重は３０Ｎ前後まで低くなってしまった。また、Ｎｏ．１８は第２層を岩塩型構造ではないＡｌＮ（六方晶）とした例である。この場合も第１層と第２層の界面が不連続となる為、剥離臨界荷重は３２Ｎと低くなっている。
【００３２】
以上の様に、（Ｖ，Ｔｉ）Ｎ系膜の下地として（Ａｌ，Ｔｉ）Ｎ系膜を用いると超硬基材との密着性を確保することができ、しかも第１層と第２層の界面を実質的にエピタキシャル成長させることにより、硬質層間界面も優れた密着性を得ることができ、全体として実用に耐え得る密着性が得られることが分かる。
【００３３】
Ｎｏ．１９〜２５は第１層と第２層の厚さを変えた場合の試験結果である。いずれの界面も実質的にエピタキシャル成長している。しかし、膜厚の合計が２０μｍを超える付近から両層の剥離臨界荷重が低下し始め、膜厚の合計が５０μｍを超えると両層の剥離臨界荷重が極端に低下することが分かる。
【００３４】
実施例２
実施例１に示した各硬質膜の耐摩耗性の評価を目的として、ボールオンディスク試験を実施した。ボールとしては、鏡面仕上げをした直径１０ｍｍの超硬球の表面に実施例１と同様の方法により表２に示す組成及び層を有する皮膜を形成した超硬球を用い、Ｓ５５Ｃ製のディスクに対し、荷重１０Ｎ、摺動速度１ｍ／sec、温度５００℃、摺動距離５００ｍの条件で摺動試験を行い、摩耗量と摩擦係数を測定した。なお摩耗量は超硬球に生じた摺動痕の幅をとった。結果は表２に示す。
【００３５】
【表２】

【００３６】
Ｎｏ．１〜４は、単層の硬質膜の耐摩耗性を調べた試験結果である。Ｎｏ．１〜３に示すように、（Ａｌ，Ｔｉ）Ｎ系膜が単層の場合は、ボールの摩耗量が０．６ｍｍ前後で、摩擦係数が０．５前後となっている。また（Ｖ，Ｔｉ）Ｎ系膜が単層であるＮｏ．４の場合には、実施例１でも示したように超硬基材との密着性が不足しており、摩耗試験においても膜が剥離してしまい、摩耗量及び摩擦係数の測定はできなかった。
【００３７】
Ｎｏ．５〜１７は第１層と第２層の膜厚を各々２μｍずつとし、両層の組成を変化させたときの影響を調べた試験結果である。Ｎｏ．５，１１，１２，１７の様に、ＡｌとＴｉの組成比及びＶとＴｉの組成比が本発明に係る範囲から外れている場合は、第１層と第２層の界面が不連続なので、摩耗試験時に両層の界面が剥離して膜損傷が発生し、表面凹凸により摩擦係数が０．８前後まで上昇する。これに対して、ＡｌとＴｉの組成比及びＶとＴｉの組成比が本発明に係る範囲の場合（Ｎｏ．６〜１０、Ｎｏ．１３〜１６）は両層の界面が実質的にエピタキシャル構造となって密着性が向上するため、摩耗試験時に両層の界面が剥離することなく、実用的な耐久性が得られた。また、摩耗量は０．２ｍｍ前後で、摩擦係数は０．２〜０．３程度であって、（Ａｌ，Ｔｉ）Ｎ単層よりも小さな値となっており、最表面が（Ｖ，Ｔｉ）Ｎ系になることにより優れた耐摩耗特性が得られることが分かる。
【００３８】
Ｎｏ．１８の様に、第２層が六方晶のＡｌＮである場合も、摩耗試験時に両層の界面剥離により膜損傷が発生し、摩擦係数が０．８程度まで高くなった。
【００３９】
Ｎｏ．１９〜２５は、第１層と第２層のＡｌとＴｉの組成比、ＶとＴｉの組成比を各々５０原子％とし、各層の膜厚を変化させたときの影響を調べたものである。Ｎｏ．１９のように全体の膜厚が０．４μｍと薄い場合は、摩耗量が０．８ｍｍ程度まで大きくなっているが、Ｎｏ．２０の様に全体の膜厚が０．８μｍになると摩耗量が０．２５ｍｍと小さくなっており、Ｎｏ．６〜１０及びＮｏ．２１〜２３などの様に、全体の膜厚が４μｍ以上になると摩耗量が０．２０前後まで小さくなる。このことから、本発明においては皮膜全体の膜厚を０．８μｍ以上に設定した。但し、Ｎｏ．２５のように全体の膜厚が５０μｍを超えると膜中の残留応力が増大して膜が剥離するため、摩耗量及び摩擦係数の測定は不可能であった。従って、皮膜全体厚さの上限は５０μｍに設定した。
【００４０】
実施例３
超硬合金製ボールエンドミル（径５Ｒ）に対し、実施例１と同様の方法により表３に組成及び膜厚を示す硬質皮膜を形成し、切削試験を行った。切削試験に用いた被削材はＳ５５Ｃであり、切削速度は９８ｍ／ｍｉｎ、送りは１刃あたり０．０５ｍｍ、切り込み量はピックフィード０．５ｍｍ、軸方向切り込みは４．０ｍｍで、エアブローしながらダウンカットにて切削を行い、切削長５０ｍを加工した後の先端部と境界部の摩耗量を測定した。結果は表３に示す。
【００４１】
【表３】

【００４２】
Ｎｏ．１〜４とＮｏ．１８は従来例であり、Ｎｏ．５，１１，１２，１７，１９，２５は比較例、Ｎｏ．６〜１０，Ｎｏ．１３〜１６，Ｎｏ．２０〜２４は本発明例である。本発明例は、先端部と境界部のいずれにおいても比較例及び従来例と比べて摩耗量が非常に小さく、優れた耐摩耗性を発揮することが分かる。
【００４３】
【発明の効果】
本発明は以上の様に構成されているので、２層以上の異なる硬質層が積層された硬質皮膜であって、厚さ数μｍ以上であっても、優れた耐摩耗性及び密着性を発揮する硬質皮膜と、上記硬質皮膜が形成された硬質皮膜被覆部材が提供できることとなった。
【図面の簡単な説明】
【図１】本発明例（実施例１のＮｏ．８）の層界面を透過型電子顕微鏡で撮像した写真の複写である。
【図２】比較例（実施例１のＮｏ．１１）の層界面を透過型電子顕微鏡で撮像した写真の複写である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface covering material for a cutting tool used for milling, cutting, drilling, or the like, or a surface covering material for a wear-resistant member requiring high hardness such as a die, a bearing, a die, or a roll. Or, it relates to a hard coating useful as a surface coating material for heat and corrosion resistant members such as screws and cylinders for molding machines, and further relates to a hard coating coated member that exhibits excellent wear resistance by coating the hard coating. is there.
[0002]
[Prior art]
Cutting tools that require high wear resistance, such as high-speed tools and cemented carbide tools, have improved wear resistance by forming a hard film such as TiN or TiCN on the surface of the tool substrate.
[0003]
Further, as a film material exhibiting properties superior to those of these films, composite (carbon) nitrides of Ti and Group 4a, 5a, and 6a metal elements other than Ti have been proposed (for example, JP-A-60-248879). No. 4, JP-A-4-221557, JP-A-7-173608). Specifically, it is a hard film represented by (Ti, M) (N, C) [where M is Zr, Hf, V, Nb, Ta, Cr, Mo, W]. However, the adhesion is insufficient compared with TiN and TiCN, and there is a problem that the film peels off during use.
[0004]
Thus, for example, as shown in JP-A-10-158861, attempts have been made to improve adhesion by using TiN as an intermediate layer, but sufficient adhesion has not been obtained. In particular, when used for cutting tools, in addition to insufficient adhesion, it is in the middle even though it is coated with a (Ti, M) (N, C) film with high bending angle and high hardness. There was a problem that the wear resistance deteriorated because the TiN hardness of the layer was not high. That is, when (Ti, M) (N, C) is used as a wear-resistant coating material for a cutting tool, it has recently attracted attention because of its excellent performance in wear resistance (Ti, Al). Compared to the N film, although it shows the same level of wear resistance in the cutting of a low-hardness material typified by carbon steel such as S50C, the cutting of a high-hardness material typified by SKD61 hardened steel etc. It has been pointed out that the wear resistance is inferior to that of the (Ti, Al) N film.
[0005]
As a means for improving the adhesion of the film, a method of continuously growing a crystal structure at the interface has been studied. For example, in Japanese Patent Laid-Open No. 9-170067, in order to laminate a (Ti, Al) CN hard film on a substrate with good adhesion, the hard layer to be coated and the crystal structure of the substrate are not continuous at the interface. The epitaxial growth is considered, and the crystal plane of the cemented carbide base mainly composed of hexagonal tungsten carbide and the crystal plane of the cubic (Ti, Al) CN hard layer have a specific directional relationship. It is shown that high adhesion can be obtained if epitaxial growth is performed while maintaining the above.
[0006]
Furthermore, in JP-A-7-133111, even in a multilayer hard film in which two or more different hard layers are laminated, the thickness of each layer of AlN that is hexagonal and TiN that is cubic is 20 nm or less. By doing so, it is disclosed that both crystal structures can be epitaxially grown so as to have the same cubic structure, adhesion at the interlayer interface is enhanced, and high hardness induced by lattice strain is expressed. Yes.
[0007]
However, as described in JP-A-7-133111, in order to epitaxially grow hexagonal AlN and cubic TiN as the same cubic crystal structure, the thickness of each layer must be 20 nm or less, and the thickness is several μm. In order to obtain a film, it is necessary to repeat several hundred layers. For this reason, although the interfacial adhesion is good to some extent by epitaxial growth, there is a problem that the production process becomes very complicated.
[0008]
[Problems to be solved by the invention]
The present invention has been made paying attention to the above circumstances, and is a hard film in which two or more different hard layers are laminated, and has excellent wear resistance and adhesion even when the thickness is several μm or more. The present invention is intended to provide a hard coating that exhibits the properties and a hard coating-coated member on which the hard coating is formed.
[0009]
[Means for Solving the Problems]
The hard film with excellent wear resistance according to the present invention that has achieved the above-mentioned problems is composed of nitride, carbide, carbonitride containing one or more metal elements, and the chemical composition selected from these is different. It is a hard film formed by laminating two or more kinds on a substrate, each layer has a thickness of 0.4 μm or more, and the entire film has a thickness of 0.8 to 50 μm. In the form of a rock salt type crystal structure, and the crystal structure of each layer is substantially epitaxially grown at the interface,
And the composition of the outermost layer on the surface side is (V _u Ti _1-u ) (N _v C _1-v )
However, 0.25 ≦ u ≦ 0.75, 0.6 ≦ v ≦ 1
And
The composition of the layer second from the surface
(Al _x Ti _1- _x ) (N _y C _1- _y )
However, 0.56 ≦ x ≦ 0.65, 0.6 ≦ y ≦ 1
This is the gist.
[0011]
If the said hard film which concerns on this invention is formed, the hard film coating | coated member which exhibits the outstanding abrasion resistance can be obtained. In addition, when forming the hard film which concerns on this invention on the surface of a cutting tool, it is recommended that the thickness of the said hard film shall be 20 micrometers or less.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The hard layer employed in the present invention is made of a nitride, carbide or carbonitride containing one or more metal elements and has a rock salt type (NaCl type) structure. There are TiN, TiCN, AlTiN, etc. that have been used as layers, and these are used as a base, and a hard layer made of a rock salt type (NaCl type) crystal is further laminated thereon, as disclosed in JP-A-7-133111. When the thickness of the hard layer is 20 nm or more as in the described technique, there is no restriction that an epitaxial growth interface cannot be formed, and even though the interlayer interface is substantially an epitaxial growth structure, the thickness of one layer is reduced to the μm order. It can be thickened. Therefore, the strength and reliability of the entire film can be improved.
[0013]
In this way, the desired surface properties such as wear resistance, oxidation resistance, and reaction resistance can be obtained, while maintaining the adhesion to the base material and the adhesion between the hard layers. The strength of the film can be maintained, and all the various problems that have occurred in the conventional multilayer films can be solved.
[0014]
In addition, when the hard film according to the present invention is formed on a high-speed steel base material or a cemented carbide base material, the hard film on the base material side should be selected giving priority to adhesion to these base materials. That's fine.
[0015]
Examples of the composition of the hard layer that can be employed in the present invention include TiN, TiCN, AlTiN, TiVN, AlTiVN, etc. As the underlayer for ensuring adhesion with high-speed steel or carbide substrate, TiN, TiCN, It is recommended to use TiVN, AlTiVN, or the like as a layer that uses AlTiN or the like and is laminated thereon to exhibit surface functions such as wear resistance, oxidation resistance, and reaction resistance.
[0016]
Among these, the composition of the outermost layer laminated on the surface side is (V _u Ti _1-u ) (N _v C _1-v )
However, 0.25 ≦ u ≦ 0.75, 0.6 ≦ v ≦ 1
Is desirable.
[0017]
The reason for this is that the hardness of the (V, Ti) (N, C) film increases in the range of u value from 0.25 to 0.75, and the (V, Ti) (N, C) film becomes This is because excellent characteristics can be exhibited by forming on the surface side, and the effect of improving lubricity and welding resistance by adding V can be sufficiently obtained. The value of u is preferably 0.30 ≦ u ≦ 0.70 and more preferably 0.40 ≦ u ≦ 0.60 in order to obtain high hardness. Further, if the value of v is less than 0.6, the toughness of the (V, Ti) (N, C) film decreases and sufficient adhesion cannot be obtained, so 0.6 ≦ v ≦ 1 is required. It is.
[0018]
Furthermore, the composition of the second layer from the surface is
(Al _x Ti _1-x ) (N _y C _1-y )
However, 0.25 ≦ x ≦ 0.75, 0.6 ≦ y ≦ 1
Is desirable. The reason why the range of x is preferably 0.25 or more and 0.75 or less is as follows. The crystal structure of TiCN has a rock salt (NaCl) type structure in which Ti atoms that are metal elements and C atoms or N atoms that are nonmetal elements are alternately arranged three-dimensionally. When V is added to TiCN, it is thought that V enters the TiCN Ti site of the rock salt structure in a substitutional form, but V has an atomic radius smaller than that of Ti. As the amount increases, the lattice constant of (V, Ti) (N, C) decreases. On the other hand, (Al, Ti) (N, C) also has a rock salt structure, and the lattice constant of (Al, Ti) (N, C) decreases as the amount of Al added increases. (V, Ti) (N, C) lattice in the composition range (0.25 ≦ u ≦ 0.75) of the above (V _u Ti _1-u ) (N, C) showing excellent performance in wear resistance Since the constants and the lattice constants of (Al _x Ti _1-x ) (N, C) in the range of x from 0.25 to 0.75 are close to each other, they have the same rock salt structure (V, Ti ) (N, C) and (Al, Ti) (N, C) lattice mismatch is reduced, and (V, Ti) (N, C) and (Al, Ti) (N, C) are substantially reduced. It is considered that the epitaxial growth shows excellent adhesion. Further, when the range of x is 0.25 or more and 0.75 or less, the hardness of (Al, Ti) (N, C) is the highest and shows excellent wear resistance. When the value of x exceeds 0.75, the crystal structure of (Al _x Ti _1-x ) (N _y C _1-y ) changes from cubic (rock salt type crystal structure) to (V, Ti ) It changes to a hexagonal crystal different from (N, C), and sufficient adhesion cannot be obtained, and the hardness is also greatly reduced. In order to obtain higher adhesion and hardness, the range of x is preferably 0.40 ≦ x ≦ 0.70, and more preferably 0.56 ≦ x ≦ 0.65.
[0019]
On the other hand, if the value of y is less than 0.6, the toughness of the (Al _x Ti _1-x ) (N _y C _1-y ) film decreases and sufficient adhesion cannot be obtained, so 0.6 ≦ y ≦ 1 is desirable.
[0020]
If the thickness of the hard coating according to the present invention is too thin, the wear resistance becomes insufficient, so it is necessary to set it to 0.8 μm or more, and it is desirable if it is 1.5 μm or more. On the other hand, if it is too thick, cracks are likely to occur in the film itself and the strength becomes insufficient. Therefore, it is necessary to set the thickness to 50 μm or less, and 30 μm or less is desirable. The hard coating of the present invention exhibits a very excellent effect when formed on the surface of a cutting tool. However, if the coating is too thick, sharpness is reduced and chipping occurs, so that particularly high adhesion is required. When applied to a cutting tool, the thickness of the coating is desirably 20 μm or less.
[0021]
Further, the thickness of each layer of the hard coating according to the present invention needs to be 0.4 μm or more in order to exhibit sufficient wear resistance. The number of laminated hard coatings is not particularly limited as long as it is two or more, but it is recommended that the number of production layers be eight or less because the number of production steps increases and the cost increases as the number of lamination increases.
[0022]
As a method for forming the hard coating according to the present invention, it is recommended to employ an arc ion plating method. The reason is that it is possible to obtain a film having further excellent adhesion by increasing ionization efficiency, increasing reactivity, or applying a bias voltage to the substrate. If an alloy target having a desired composition ratio is used as the cathode, it is easy to control the coating composition and it is recommended.
[0023]
Although the present invention does not limit the material of the base material on which the hard film is coated, in order to exhibit excellent wear resistance by coating the base material surface with good adhesion, cemented carbide, high speed tool steel Hard materials such as die steel, cermet or ceramic are suitable.
[0024]
Especially when used in cutting tools, the excellent adhesion of the coating of the present invention provides superior wear resistance in cutting low hardness materials than in conventional examples, and is sufficient in cutting high hardness materials. Abrasion resistance is obtained, and a cutting tool capable of cutting from a low hardness material to a high hardness material can be obtained.
[0025]
Hereinafter, although an Example is described, this invention is not limited to the following Example, It is contained in the technical scope of this invention changing suitably based on the meaning of the above-mentioned and postscript.
[0026]
【Example】
Example 1
The carbide tip was placed in an arc ion plating apparatus, evacuated, and the furnace atmosphere temperature was maintained at about 400 ° C. for 60 minutes by a heater. Thereafter, a bias voltage of −150 V was applied to the workpiece, high purity N ₂ gas was introduced into the furnace until 0.93 Pa, and arc discharge was performed using TiAl cathodes having various compositions. A first layer having the composition shown was formed. Thereafter, arc discharge was performed using a TiV cathode and an Al cathode having various compositions, and a second layer having the composition shown in Table 1 was formed. The (Al, Ti) N-based film and the (V, Ti) N-based film have a rock salt type (NaCl type) crystal structure, and the lattice constant is controlled by changing the composition of Al, Ti, V. can do. When the lattice constants of the first layer and the second layer are close to each other, the interface between the two layers is epitaxially grown. However, when the difference between the lattice constants of the two layers is increased, the interface between the first layer and the second layer becomes discontinuous. Utilizing this fact, a two-layer hard layer having a rock salt type crystal structure and a different interface structure was produced by laminating a first layer and a second layer having various compositions. For comparison, a sample was also prepared in which AlN having a hexagonal crystal structure was laminated as a second layer with an Al cathode. The composition of these films was confirmed by electron probe X-ray microanalysis and Auger electron spectroscopy.
[0027]
The cross section of the interface between the first layer and the second layer of the obtained test piece was observed with a transmission electron microscope (TEM) to examine whether the crystal structure of the interface was continuous (epitaxial growth) or discontinuous. Also, using a scratch tester, the change in the sound wave (AE signal) generated when the film was damaged and the load when the film was peeled off by optical microscope observation after the test were examined, and the interface structure between the first and second layers was in close contact I examined the relationship of sex. The results are also shown in Table 1. In Table 1, the evaluation of ○ × in the column of “continuity of the crystal of the first layer and the second layer” is ○ when the portion where the epitaxial growth is 80% or more in the crystal structure of the interface, The case where the part which exists is less than 80% was set as x.
[0028]
[Table 1]

[0029]
No. 1-4 are the test results which investigated peeling adhesiveness between a hard film and a base material. No. 1-3, the critical peeling load at the interface between the cemented carbide substrate and the (Al, Ti) N-based film is all 90 N or more regardless of the film composition, indicating sufficiently good adhesion. . However, no. As shown in FIG. 4, the peeling load at the interface between the carbide substrate and the (V, Ti) N-based film is as low as 22N, and the (V, Ti) N single layer does not provide the adhesion that can withstand practical use. , Ti) N-based film is used as a base (first layer).
[0030]
No. 5 to 25 are test results obtained by examining the adhesion between the first layer and the second layer. First, no. In Nos. 5 to 17, the thicknesses of the first layer and the second layer were each 2 μm, and the film composition was changed to examine the adhesion. Since the crystal structures of the (Al, Ti) N-based film and the (V, Ti) N-based film are both rock-salt structures and have close lattice constants, the interface between the first layer and the second layer is substantially the same in most compositions. It has an epitaxial growth structure. However, when the amount of Al in the (Al, Ti) N-based film and the amount of V in the (V, Ti) N-based film are too large or too small, the epitaxial growth structure is not substantially formed. As an example of the present invention, No. A photograph of the interface between the first layer and the second layer of the sample No. 8 is shown in FIG. A photograph of the interface between the first layer and the second layer of 11 samples is shown in FIG. In FIG. 1, most of the crystals at the interface are connected continuously, but in FIG. 2, there are many portions where the crystal structure of the interface is discontinuous.
[0031]
When the interface structure is epitaxial growth, the critical separation load is about 90 N, which is a value that can withstand practical use close to the adhesion between the (Al, Ti) N-based film and the cemented carbide substrate. However, no. When the amount of Al in the (Al, Ti) N-based film and the amount of V in the (V, Ti) N-based film are too large or too small as in 5, 11, 12, 17, the first layer and the first layer The interface between the two layers is discontinuous, and the critical peeling load at the interface has been lowered to around 30N. No. 18 is an example in which the second layer is AlN (hexagonal crystal) which is not a rock salt type structure. Also in this case, since the interface between the first layer and the second layer is discontinuous, the critical separation load is as low as 32N.
[0032]
As described above, when an (Al, Ti) N-based film is used as a base for a (V, Ti) N-based film, adhesion with a carbide substrate can be ensured, and the first layer and the second layer can be secured. It can be seen that by substantially epitaxially growing the interface, excellent adhesion can also be obtained at the hard interlayer interface, and as a whole, adhesion that can withstand practical use can be obtained.
[0033]
No. 19 to 25 are test results when the thicknesses of the first layer and the second layer are changed. Both interfaces are substantially epitaxially grown. However, it can be seen that the critical separation load of both layers begins to decrease from the vicinity of the total thickness exceeding 20 μm, and the critical separation load of both layers is extremely decreased when the total thickness exceeds 50 μm.
[0034]
Example 2
For the purpose of evaluating the wear resistance of each hard film shown in Example 1, a ball-on-disk test was conducted. As the balls, super hard balls formed with a film having a composition and layer shown in Table 2 on the surface of a hard ball having a mirror finish of 10 mm in diameter by the same method as in Example 1 were used. A sliding test was conducted under the conditions of 10 N, sliding speed 1 m / sec, temperature 500 ° C., sliding distance 500 m, and the wear amount and the friction coefficient were measured. The amount of wear was the width of a sliding mark generated on the hard ball. The results are shown in Table 2.
[0035]
[Table 2]

[0036]
No. 1-4 are the test results which investigated the abrasion resistance of the hard film of a single layer. No. 1 to 3, when the (Al, Ti) N-based film is a single layer, the wear amount of the ball is around 0.6 mm and the friction coefficient is around 0.5. No. 1 in which the (V, Ti) N-based film is a single layer. In the case of 4, the adhesion with the cemented carbide substrate was insufficient as shown in Example 1, the film was peeled even in the wear test, and the amount of wear and the coefficient of friction could not be measured. .
[0037]
No. 5 to 17 are test results obtained by examining the influence when the film thicknesses of the first layer and the second layer are 2 μm each and the composition of both layers is changed. No. When the composition ratio of Al and Ti and the composition ratio of V and Ti are outside the range according to the present invention as in 5, 11, 12, and 17, the interface between the first layer and the second layer is discontinuous. During the wear test, the interface between the two layers peels off and film damage occurs, and the friction coefficient rises to around 0.8 due to surface irregularities. On the other hand, when the composition ratio of Al and Ti and the composition ratio of V and Ti are within the ranges according to the present invention (No. 6 to 10, No. 13 to 16), the interface between both layers is substantially an epitaxial structure. As a result, adhesion was improved and practical durability was obtained without the interface between the two layers being peeled off during the wear test. Further, the wear amount is around 0.2 mm, the friction coefficient is about 0.2 to 0.3, which is smaller than the (Al, Ti) N single layer, and the outermost surface is (V, Ti It can be seen that excellent wear resistance characteristics can be obtained by using N).
[0038]
No. As shown in FIG. 18, even when the second layer was hexagonal AlN, film damage occurred due to interfacial peeling between the two layers during the wear test, and the friction coefficient increased to about 0.8.
[0039]
No. Nos. 19 to 25 are the results of investigating the influence of changing the film thickness of each layer by setting the composition ratio of Al and Ti of the first layer and the second layer and the composition ratio of V and Ti to 50 atomic%, respectively. . No. When the entire film thickness is as thin as 0.4 μm as in No. 19, the wear amount is increased to about 0.8 mm. As shown in No. 20, when the total film thickness is 0.8 μm, the wear amount is as small as 0.25 mm. 6-10 and no. As in the case of 21 to 23, etc., when the total film thickness is 4 μm or more, the wear amount is reduced to around 0.20. Therefore, in the present invention, the film thickness of the entire film was set to 0.8 μm or more. However, no. When the total film thickness exceeds 50 μm as in 25, the residual stress in the film increases and the film peels off, so that it is impossible to measure the wear amount and the friction coefficient. Therefore, the upper limit of the total film thickness was set to 50 μm.
[0040]
Example 3
A hard film having the composition and film thickness shown in Table 3 was formed on a cemented carbide ball end mill (diameter 5R) in the same manner as in Example 1, and a cutting test was performed. The work material used for the cutting test was S55C, the cutting speed was 98 m / min, the feed was 0.05 mm per blade, the cutting amount was 0.5 mm pick feed, the axial cutting was 4.0 mm, while air blowing Cutting was performed by down-cutting, and the amount of wear at the tip and boundary after machining a cutting length of 50 m was measured. The results are shown in Table 3.
[0041]
[Table 3]

[0042]
No. 1-4 and No.1. No. 18 is a conventional example. Nos. 5, 11, 12, 17, 19, and 25 are comparative examples. 6-10, no. 13-16, no. 20-24 are examples of the present invention. It can be seen that the example of the present invention has an extremely small amount of wear at both the tip and the boundary, as compared with the comparative example and the conventional example, and exhibits excellent wear resistance.
[0043]
【The invention's effect】
Since the present invention is configured as described above, it is a hard film in which two or more different hard layers are laminated, and exhibits excellent wear resistance and adhesion even when the thickness is several μm or more. And a hard film covering member on which the hard film is formed can be provided.
[Brief description of the drawings]
FIG. 1 is a copy of a photograph taken with a transmission electron microscope of a layer interface of an example of the present invention (No. 8 in Example 1).
FIG. 2 is a copy of a photograph obtained by imaging the layer interface of a comparative example (No. 11 in Example 1) with a transmission electron microscope.

Claims

A hard film made of nitride, carbide, carbonitride containing one or more metal elements, and formed on a substrate by laminating two or more different chemical compositions selected from these,
The thickness of each layer is 0.4 μm or more, and the total thickness of the film is 0.8 to 50 μm. Each layer is substantially composed of a rock salt type crystal structure, and the crystal structure of each layer is substantially at the interface. Epitaxially grown,
And the composition of the outermost layer on the surface side is (V _u Ti _1-u ) (N _v C _1-v )
However, 0.25 ≦ u ≦ 0.75, 0.6 ≦ v ≦ 1
And
The composition of the layer second from the surface
(Al _x Ti _1- _x ) (N _y C _1- _y )
However, 0.56 ≦ x ≦ 0.65 , 0.6 ≦ y ≦ 1
Hard film with excellent wear resistance characterized by

A hard film-coated member formed with the hard film according to claim 1.

A cutting tool in which the hard coating according to claim 1 is formed with a thickness of 20 μm or less.