JP2004243494A

JP2004243494A - Surface coated cutting tool

Info

Publication number: JP2004243494A
Application number: JP2003037557A
Authority: JP
Inventors: Hiroshi Ohata; 浩志大畑
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 2003-02-17
Filing date: 2003-02-17
Publication date: 2004-09-02
Anticipated expiration: 2023-02-17
Also published as: JP4099081B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface coated tool exhibiting excellent fracture resistance and wear resistance of a hard film in a surface coated tool excellent in chipping resistance and having the hard film including at least Ti and Al. <P>SOLUTION: In this surface coated cutting tool 1, at least one layer of the hard film 3 comprising at least one of nitride, nitroxide, carbonitride, and carbonitroxide including at least Ti and Al, and having a thickness of 0.1 to 10μm is coated on a surface of a substrate 2 comprising cemented carbide, cermet, or ceramic. A crystal particle 4 (a minimum unit particle) constituting the hard film 3 is a longitudinally long growth particle extending to the thickness direction of the hard film 3, an end part of 40% or more of a total number of the crystal particles 4 is formed in a shape of V, and the crystal particles 4 are engaged to each other. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、表面を高硬度で高靭性の被覆膜で被覆した表面被覆切削工具に関する。
【０００２】
【従来の技術】
従来より、表面被覆工具の耐摩耗性、耐欠損性を改善するために物理蒸着（ＰＶＤ）法や化学蒸着（ＣＶＤ）法によりＴｉＣ、ＴｉＮ、ＴｉＣＮ等の硬質膜を被覆した工具が一般的に広く用いられている。
【０００３】
また、最近では加工速度の高速化やステンレス鋼等の難削材への対応が要求され、特に耐熱性、耐酸化性および硬度に優れた（Ｔｉ，Ａｌ）Ｎ膜が多用されている。
【０００４】
かかる（Ｔｉ，Ａｌ）Ｎ膜に関して、特許文献１では、前記硬質膜の結晶粒径のアスペクト（縦／横）比を制御して縦長に成長した組織とすることによって、バラつきがなく安定した寿命の硬質膜が得られることが記載されている。
【０００５】
【特許文献１】
特開平１０−３１５０１１号公報
【０００６】
【発明が解決しようとする課題】
しかしながら、上記特許文献１に記載された硬質膜についても、過酷な切削条件によっては切刃部分に微小なマイクロクラックが生じたり、マイクロクラックが要因で早期に大きな欠損が発生したり、摩耗が進行しやすく、更なる膜質の改善が求められていた。
【０００７】
したがって、本発明の課題は、少なくともＴｉとＡｌを含む硬質膜を被覆した表面被覆工具において、硬質膜の耐チッピング性を改善して耐欠損性や耐摩耗性に優れた長寿命の表面被覆工具を提供することである。
【０００８】
【課題を解決するための手段】
本発明においては、前記硬質膜を構成する結晶粒子（最小単位の粒子）が前記硬質膜の厚み方向に向かって伸びる縦長成長をしており、かつ該結晶粒子同士が複雑に成長し合い、結合し合った構成とすることによって、硬質膜の耐チッピング性が向上し、切削工具としての耐欠損性および耐摩耗性が向上することを知見した。
【０００９】
すなわち、本発明の表面被覆切削工具は、超硬合金、サーメットおよびセラミックのいずれかからなる基体の表面に、少なくともＴｉとＡｌを含む窒化物、窒酸化物、炭窒化物、炭窒酸化物の１種以上で構成される厚みが０．１〜１０μｍの硬質膜を少なくとも１層被覆したものであって、前記硬質膜を構成する結晶粒子が前記硬質膜の厚み方向に向かって伸びる縦長成長をしており、かつ該結晶粒子総数に対して４０％以上の結晶粒子の端部がＶ字状をなして結晶粒子同士が互いに噛合されていることを特徴とする。
【００１０】
ここで、前記硬質膜を形成する結晶粒の最大幅（ｗ_１）の平均値が０．１〜１．５μｍであることによって、結晶粒子同士の噛合による粒子間の固定力を高めることができるとともに、硬質膜の耐摩耗性を高めることができる。
【００１１】
また、前記結晶粒子の組成を（Ｔｉ_ａＡｌ_ｂ）Ｃ_ｘＮ_ｙＯ_ｚ（ただし、ａ＋ｂ＝１、ｘ＋ｙ＋ｚ＝１）とした場合、少なくとも一方の端部がＶ字状をなす結晶粒子の平均組成が０．３≦ａ≦０．６を満足し、かつどちらの端部もＶ字状をなさない結晶粒子の平均組成が０．６＜ａ≦０．９であることによって、結晶粒子の耐摩耗性、及び耐酸化性が高く維持され、高温・高荷重の過酷な切削条件下においても、高い耐摩耗性をもつ。
【００１２】
さらに、前記結晶粒子のうち、端部がＶ字状をなす結晶粒子の割合が、前記硬質膜を構成する結晶粒子の総数に対して４０〜８０％であることによって、結晶粒子同士の結合力が強く硬質膜の靭性を高めて工具の対チッピング性を高めることができる。
【００１３】
さらにまた、前記Ｖ字状に噛合されるＶ字の平均角度が、前記硬質膜の成長方向に対して１０〜８０°であること、特に１０〜４５°であることによって、隣接する結晶粒子の側面およびまたはＶ字状成長部との接触面が強固に付着できる結果、硬質膜の耐摩耗性および耐欠損性を高めることができる。
【００１４】
【発明の実施の形態】
本発明の表面被覆切削工具について、その一例についての模式断面図である図１、硬質膜断面の透過型電子顕微鏡写真である図２および図２の写真における各粒子の形状を特定した図３を基に説明する。
【００１５】
図１によれば、表面被覆切削工具（以下、単に工具と略す。）１は、超硬合金、サーメットおよびセラミックのいずれかからなる基体２の表面に、少なくともＴｉとＡｌを含む窒化物、窒酸化物、炭窒化物、炭窒酸化物の１種以上で構成される厚みが０．１〜１０μｍの硬質膜３を少なくとも１層被覆したものである。
【００１６】
本発明によれば、硬質膜３の断面における１００００倍の透過型電子顕微鏡写真（ＴＥＭ）である図２、および図２の写真における各粒子の形状を特定した図３に示すように、硬質膜３を構成する結晶粒子（最小単位の粒子）４が硬質膜３の厚み方向に向かって伸びる縦長成長をしており、かつ結晶粒子４総数に対して４０％以上の結晶粒子４のどちらかの端部がＶ字状をなして結晶粒子４同士が互いに噛合されていることが大きな特徴であり、これによって、硬質膜３の耐衝撃性が向上してマイクロチッピング等の発生を防止し、その結果、マイクロチッピングに伴う大きな欠損や早期摩耗を防止することができる。
【００１７】
すなわち、結晶粒子（最小単位の粒子）４が硬質膜３の厚み方向に向かって伸びる縦長成長組織ではなく粒状結晶の集合体からなると、硬質膜３の耐チッピング性、耐摩耗性が低下する。また、硬質膜３の結晶粒子４が単純な柱状をなして厚み方向に整列した組織からなる場合、または結晶粒子４のうち、端部がＶ字状をなす粒子の数が結晶粒子総数に対して４０％より少ない場合でも、硬質膜３の耐チッピング性が低下してマイクロチッピングが発生しやすくなる。
【００１８】
なお、本発明において、結晶粒子４の厚み方向とは硬質膜３が成膜されている基体２表面に対して実質的に垂直な方向であり、結晶粒子４の幅方向とは基体２表面に対して実質的な接線の平行方向をいう。また、本発明において、端部がＶ字状をなす粒子とは、上記１００００倍の透過型電子顕微鏡写真で観察される結晶粒子４の中で、厚み方向に端部を有するとともに、この端部から０．２μｍの厚み方向の長さ位置における結晶粒子４の幅が０．３５μｍ以下のシャープな端部をなす形状の結晶粒子４を指す。
【００１９】
ここで、硬質膜３を形成する結晶粒子４の最大幅（ｗ_１）の平均値が０．１〜１．５μｍであることが結晶粒子同士の噛合による粒子間の固定力を強くするとともに硬質膜の耐摩耗性を高める点で望ましい。なお、本発明における結晶粒子４の最大幅ｗ_１とは、図３に示すように各結晶粒子４の幅が最大となる部分の長さを指す。また、本発明において結晶粒の平均長さ（ｗ_２）は硬質膜の膜厚（ｔ）によって異なるが、結晶粒の平均長さ（ｗ_２）＝硬質膜の膜厚（ｔ）ではなく、ｗ_２＝０．２ｔ〜０．５ｔとなる。すなわち、硬質膜の粒子成長の途中で核形成が生じて別の粒子がＶ字状に割り込んで成長し、先に成長していた粒子は先細りして（逆）Ｖ字状の終端形状となる。さらに、本発明の表面被覆工具においては、硬質膜３の結晶粒径の縦／横（ｗ_２／ｗ_１）比は平均で１．１〜５、特に２〜３．５の範囲にあることによって、結晶粒子同士を複雑に成長し合い、結合し合った構成とすることになり、結果的に硬質膜の耐チッピング性が向上し、切削工具としての耐欠損性および耐摩耗性が向上する点で望ましい。
【００２０】
また、硬質膜の結晶粒の組成を（Ｔｉ_ａＡｌ_ｂ）Ｃ_ｘＮ_ｙＯ_ｚ（ただし、ａ＋ｂ＝１、ｘ＋ｙ＋ｚ＝１）とした場合、端部がＶ字状に噛合している結晶粒子の平均組成が０．３≦ａ≦０．６を満足し、かつ、どちらの端部もＶ字状に噛合していない粒子の平均組成が０．６≦ａ≦０．９であることが結晶粒子の耐摩耗性、及び耐酸化性が高く維持され、高温・高荷重下の過酷な切削条件下においても、高い耐摩耗性をもつ点で望ましい。なお、この場合、結晶粒の組成は透過型電子顕微鏡、および透過型電子顕微鏡測定装置に付随するＥＤＳ（エネルギー分散型分光分析）装置にて分析することができる。
【００２１】
さらに、硬質膜３の結晶粒のうち、端部がＶ字状をなす結晶粒子の割合が、前記硬質膜を構成する結晶粒子の総数に対して４０〜８０％であることが、、結晶粒子同士の結合力を高めて硬質膜の靭性を向上させ、工具の耐チッピング性を高める点で望ましい。
【００２２】
さらにまた、硬質膜３の耐チッピング性を高めるためには、前記Ｖ字状をなす結晶粒子のＶ字の平均角度θが、前記硬質膜の厚み方向（成長方向）に対して１０〜８０°、特に１０〜４５°、さらに２０〜４０°であることが、隣接する結晶粒子の側面およびまたはＶ字状成長部との接触面が強固に付着できて硬質膜３の耐摩耗性および耐欠損性を高める点で望ましい。
【００２３】
また、本発明によれば、硬質膜３は、ＴｉとＡｌを主とする複合窒化物、複合炭化物、複合炭窒化物のいずれか一種の単層硬質膜または二種以上からなる多層硬質膜で構成されるものであり、具体的には、例えば（Ｔｉ，Ａｌ）Ｎ、（Ｔｉ，Ａｌ）Ｃ、（Ｔｉ，Ａｌ）ＣＮ等の単層であっても良いが、基体２と硬質膜３との密着性を高めるために例えば基体２上にＴｉＮやＴｉＣの下地膜（図示せず）をまず成膜し、その上に上記硬質膜３を形成してもよい。また、図１に示すように、硬質膜３の表面にＴｉＮ膜等の表面膜５を積層するものであってもよい。
【００２４】
さらに、本発明によれば、硬質膜３の構成としては、主含有元素であるＴｉとＡｌの他に、他の金属元素Ｍ（例えばＹ，Ｚｒ，Ｍｇ，Ｃｒ，Ｓｉ，Ｔａ，Ｂ，Ｖ，Ｎｂのうちのいずれか一種の元素）を加えた複合窒化物、複合炭化物、複合炭窒化物、複合窒酸化物、複合炭酸化物または複合炭窒酸化物のいずれか（ＴｉａＡｌｂＭｃ）ＣｘＮｙＯｚ（ただし、ａ＋ｂ＋ｃ＝１、ｘ＋ｙ＋ｚ＝１）であっても良い。この場合、ｃ≦０．３であることが耐酸化性、耐摩耗性の点で望ましい。
【００２５】
（製造方法）
本発明の表面被覆切削工具を製造するには、まず、超硬合金、サーメットまたはセラミックスのいずれかからなる工具形状の基体を作製する。
【００２６】
本発明における硬質膜３の被覆方法としては、基本的にカソードアーク方式のイオンプレーティング方法を用いる。本発明によれば、硬質膜３の成膜条件として、アーク電流を０〜３００Ａの範囲で断続的に変化させることによって、硬質膜中に新たな核形成をうながして上述した組織に制御することができる。
【００２７】
また、バイアス定常電圧２０〜２００Ｖ、成膜圧力０．５〜３Ｐａ、成膜温度５００〜６００℃に制御することが望ましい。
【００２８】
【実施例】
（実施例１）
ＷＣにＣｏ１０質量％とＴｉＣ２質量％とＮｂＣ１質量％とを添加したＳＤＫＮ１２０３形状の超硬合金製基体を、カソードアーク方式のイオンプレーティング装置に入れて、バイアス電圧２０〜２００Ｖ、成膜圧力０．５〜３Ｐａ、基体（基板）温度５２５℃の成膜条件で、アーク定常電流を１５０Ａとして表１に示す条件で断続的にアーク電流を変化させて表１に示す組成および膜厚の硬質膜を成膜し、さらに試料によっては表１に示す表面膜を成膜してスローアウェイチップを作製した。
【００２９】
得られたチップについて、下記条件で切削テストを行った。結果は表１に示した。
＜切削条件＞
被削材：ＳＫＤ１１材
切削速度：１５０ｍ／分
１刃あたりの送り：０．３ｍｍ
切り込み深さ：２ｍｍ
その他：乾式切削
評価方法：平均逃げ面摩耗幅が０．２ｍｍになるまでの可能切削距離
また、上記切削テストを行ったチップの硬質膜について透過型電子顕微鏡にて断面観察を行い、倍率１００００倍で硬質膜の任意５箇所について観察し、膜断面の像を２３ｃｍ×１６ｃｍの写真に撮り、写真内にある結晶粒子の形状を模式化して確認しながら、いずれかの端部がＶ字状をなす結晶粒の数を数えるとともに、一視野にて観察されるＶ字状をなす結晶粒子の先端角度（Ｖ字の平均角度）をそれぞれ測定して平均値を算出した。また、結晶粒の長さ（ｗ_２）、結晶粒の最大幅（ｗ_１）、長さ／幅比（ｗ_２／ｗ_１）を個別に測定した後、それらの平均値を求めた。さらに、透過型電子顕微鏡および付随するＥＤＳ（エネルギー分散型分光分析）装置を用いて各結晶粒子の組成を測定し、端部がＶ字状をなす粒子、および端部がＶ字状をなさない粒子について、それぞれ平均組成をそれぞれ求めた。結果は表１に示した。
【００３０】
【表１】

【００３１】
表１から明らかなように、本発明に従い、断続的にアーク電流を変化させた試料Ｎｏ．１〜５は、結晶粒の端部がＶ字状をなし、すなわち結晶粒がＶ字状に噛合されており、硬質膜が剥離しにくく良好な切削性能を示すものであるのに対して、一定のアーク電流で成膜し、結晶粒端部がＶ字状をなさず単純な縦長成長をした結晶となった試料Ｎｏ．６、および縦長成長をせず粒状晶となった試料Ｎｏ．７ではマイクロチッピングに起因する硬質膜の剥離が発生して切削性能も低いものであった。
【００３２】
【発明の効果】
以上詳述した通り、本発明によれば、硬質膜を構成する結晶粒子が硬質膜の厚み方向に向かって伸びる縦長成長をしており、かつ該結晶粒子総数に対して４０％以上の結晶粒子の端部がＶ字状をなして結晶粒子同士が互いに噛合されている構成とすることによって、硬質膜の耐チッピング性が向上し、工具としての耐欠損性および耐摩耗性が向上する。
【図面の簡単な説明】
【図１】本発明の表面被覆切削工具の断面構成を説明するための概念図である。
【図２】本発明の表面被覆切削工具の断面の透過型電子顕微鏡写真である。
【図３】図２の透過型電子顕微鏡写真中の各粒子を模式化した模式図である。
【符号の説明】
１表面被覆切削工具（工具）
２基体
３硬質膜
４結晶粒
５表面膜[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface-coated cutting tool whose surface is coated with a coating film having high hardness and high toughness.
[0002]
[Prior art]
Conventionally, in order to improve the wear resistance and fracture resistance of surface-coated tools, a tool in which a hard film such as TiC, TiN, or TiCN is coated by a physical vapor deposition (PVD) method or a chemical vapor deposition (CVD) method is generally used. Widely used.
[0003]
Recently, it has been required to increase the processing speed and cope with difficult-to-cut materials such as stainless steel, and in particular, (Ti, Al) N films having excellent heat resistance, oxidation resistance and hardness are frequently used.
[0004]
With regard to such a (Ti, Al) N film, Patent Document 1 discloses a stable life without variation by controlling the aspect ratio (vertical / horizontal) ratio of the crystal grain size of the hard film to form a vertically elongated structure. It is described that a hard film can be obtained.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-315011
[Problems to be solved by the invention]
However, even with the hard film described in Patent Document 1, depending on the severe cutting conditions, a minute microcrack is generated in the cutting edge portion, a large defect is generated early due to the microcrack, or wear progresses. Therefore, further improvement in film quality has been demanded.
[0007]
Therefore, an object of the present invention is to provide a long-life surface-coated tool that improves chipping resistance of a hard film and has excellent fracture resistance and wear resistance in a surface-coated tool coated with a hard film containing at least Ti and Al. Is to provide.
[0008]
[Means for Solving the Problems]
In the present invention, the crystal particles (smallest unit particles) constituting the hard film are grown in a longitudinal direction extending in the thickness direction of the hard film, and the crystal particles grow in a complicated manner and are bonded. It has been found that the chipping resistance of the hard film is improved and the chipping resistance and the wear resistance as a cutting tool are improved by adopting the combined structure.
[0009]
That is, the surface-coated cutting tool of the present invention comprises a nitride, nitride oxide, carbonitride, carbonitride oxide containing at least Ti and Al on the surface of a substrate made of any one of cemented carbide, cermet and ceramic. At least one layer of a hard film composed of one or more kinds and having a thickness of 0.1 to 10 μm is coated, and crystal grains constituting the hard film are elongated in the thickness direction of the hard film. And 40% or more of the crystal grains with respect to the total number of crystal grains are V-shaped, and the crystal grains are meshed with each other.
[0010]
Here, when the average value of the maximum width (w ₁ ) of the crystal grains forming the hard film is 0.1 to 1.5 μm, it is possible to increase the fixing force between the particles due to the engagement of the crystal particles. At the same time, the wear resistance of the hard film can be increased.
[0011]
In addition, when the composition of the crystal grains is (Ti _a Al _b ) C _x N _y O _z (where a + b = 1, x + y + z = 1), the average of crystal grains in which at least one end is V-shaped. The average composition of the crystal grains satisfying 0.3 ≦ a ≦ 0.6 and neither end portion being V-shaped is 0.6 <a ≦ 0.9. High wear resistance and oxidation resistance are maintained, and it has high wear resistance even under severe cutting conditions of high temperature and high load.
[0012]
Further, among the crystal particles, the ratio of the crystal particles whose end portions are V-shaped is 40 to 80% with respect to the total number of crystal particles constituting the hard film, whereby the bonding force between the crystal particles is However, it is possible to increase the toughness of the hard film and the chipping property of the tool.
[0013]
Furthermore, the average angle of the V-shaped meshed with the V-shape is 10 to 80 °, particularly 10 to 45 ° with respect to the growth direction of the hard film. As a result that the side surface and / or the contact surface with the V-shaped growth portion can be firmly attached, the wear resistance and fracture resistance of the hard film can be improved.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 which is a schematic cross-sectional view of an example of the surface-coated cutting tool of the present invention, FIG. 2 which is a transmission electron micrograph of a hard film cross-section, and FIG. 3 which specifies the shape of each particle in the photograph of FIG. Based on the explanation.
[0015]
According to FIG. 1, a surface-coated cutting tool (hereinafter simply referred to as a tool) 1 includes a nitride, a nitrogen containing at least Ti and Al on the surface of a substrate 2 made of cemented carbide, cermet, or ceramic. At least one layer of the hard film 3 having a thickness of 0.1 to 10 μm composed of one or more of oxide, carbonitride, and carbonitride is coated.
[0016]
According to the present invention, as shown in FIG. 2 which is a 10000 times transmission electron micrograph (TEM) in the cross section of the hard film 3 and the shape of each particle in the photograph of FIG. The crystal grains (minimum unit grains) 4 constituting the crystal grains 4 are elongated in the longitudinal direction extending in the thickness direction of the hard film 3 and any one of the crystal grains 4 of 40% or more with respect to the total number of crystal grains 4 The main feature is that the ends are V-shaped and the crystal grains 4 are meshed with each other, thereby improving the impact resistance of the hard film 3 and preventing the occurrence of microchipping, etc. As a result, it is possible to prevent large defects and early wear associated with microchipping.
[0017]
That is, if the crystal particles (minimum unit particles) 4 are not a vertically elongated structure extending in the thickness direction of the hard film 3 but an aggregate of granular crystals, the chipping resistance and wear resistance of the hard film 3 are lowered. In addition, when the crystal particles 4 of the hard film 3 have a simple columnar structure and are aligned in the thickness direction, or the number of particles having an end V-shaped among the crystal particles 4 with respect to the total number of crystal particles. Even if it is less than 40%, the chipping resistance of the hard film 3 is lowered, and microchipping is likely to occur.
[0018]
In the present invention, the thickness direction of the crystal particles 4 is a direction substantially perpendicular to the surface of the substrate 2 on which the hard film 3 is formed, and the width direction of the crystal particles 4 is the surface of the substrate 2. In contrast, it refers to the parallel direction of a substantial tangent. Further, in the present invention, the particle having an end of a V shape has an end in the thickness direction in the crystal particle 4 observed in the transmission electron micrograph of 10,000 times, and this end To 0.2 μm in the length direction in the thickness direction, the crystal particle 4 having a sharp end with a width of 0.35 μm or less.
[0019]
Here, the average value of the maximum width (w ₁ ) of the crystal particles 4 forming the hard film 3 is 0.1 to 1.5 μm, and the fixing force between the particles due to the engagement of the crystal particles is strengthened and hard This is desirable in terms of increasing the wear resistance of the film. In the present invention, the maximum width w ₁ of the crystal particles 4 indicates the length of the portion where the width of each crystal particle 4 is maximum as shown in FIG. In the present invention, the average length (w ₂ ) of crystal grains varies depending on the film thickness (t) of the hard film, but the average length of crystal grains (w ₂ ) = not the film thickness (t) of the hard film, the w ₂ = 0.2t~0.5t. That is, nucleation occurs in the middle of particle growth of the hard film, and another particle cuts into a V shape and grows, and the previously grown particle tapers (reversely) into a V-shaped terminal shape. . Further, in the surface-coated tool of the present invention, the vertical / horizontal (w ₂ / w ₁ ) ratio of the crystal grain size of the hard film 3 is in the range of 1.1 to 5, particularly 2 to 3.5 on average. As a result, the crystal grains grow and bond together in a complicated manner, resulting in improved chipping resistance of the hard film and improved chipping resistance and wear resistance as a cutting tool. Desirable in terms.
[0020]
Further, when the composition of the crystal grains of the hard film is (Ti _a Al _b ) C _x N _y O _z (where a + b = 1, x + y + z = 1), the crystal grains whose ends are meshed in a V shape The average composition of the particles satisfying 0.3 ≦ a ≦ 0.6, and the average composition of the particles in which neither end meshes in a V shape is 0.6 ≦ a ≦ 0.9. It is desirable in terms of maintaining high wear resistance and oxidation resistance of crystal grains and having high wear resistance even under severe cutting conditions under high temperature and high load. In this case, the composition of the crystal grains can be analyzed by a transmission electron microscope and an EDS (energy dispersive spectroscopic analysis) apparatus attached to the transmission electron microscope measurement apparatus.
[0021]
Furthermore, the ratio of the crystal grains whose ends are V-shaped among the crystal grains of the hard film 3 is 40 to 80% with respect to the total number of crystal grains constituting the hard film. It is desirable in that the bonding strength between the two is increased to improve the toughness of the hard film and to increase the chipping resistance of the tool.
[0022]
Furthermore, in order to improve the chipping resistance of the hard film 3, the V-shaped average angle θ of the V-shaped crystal grains is 10 to 80 ° with respect to the thickness direction (growth direction) of the hard film. In particular, the angle of 10 to 45 °, and further 20 to 40 °, allows the side surfaces of adjacent crystal particles and / or the contact surface with the V-shaped growth portion to adhere firmly, so that the hard film 3 has wear resistance and chipping resistance. It is desirable in terms of enhancing the performance.
[0023]
Further, according to the present invention, the hard film 3 is a single layer hard film of a composite nitride mainly composed of Ti and Al, a composite carbide, or a composite carbonitride, or a multilayer hard film composed of two or more types. Specifically, it may be a single layer such as (Ti, Al) N, (Ti, Al) C, (Ti, Al) CN, etc. For example, a base film (not shown) of TiN or TiC may be first formed on the substrate 2 and the hard film 3 may be formed thereon. Further, as shown in FIG. 1, a surface film 5 such as a TiN film may be laminated on the surface of the hard film 3.
[0024]
Furthermore, according to the present invention, the hard film 3 is composed of, in addition to the main elements Ti and Al, other metal elements M (for example, Y, Zr, Mg, Cr, Si, Ta, B, V, V). , Nb), a composite nitride, a composite carbide, a composite carbonitride, a composite nitrided oxide, a composite carbonate, or a composite carbonitride (TiaAlbMc) CxNyOz (however, a + b + c = 1, x + y + z = 1). In this case, c ≦ 0.3 is desirable from the viewpoint of oxidation resistance and wear resistance.
[0025]
(Production method)
In order to manufacture the surface-coated cutting tool of the present invention, first, a tool-shaped substrate made of cemented carbide, cermet, or ceramic is prepared.
[0026]
As a coating method of the hard film 3 in the present invention, a cathode arc type ion plating method is basically used. According to the present invention, as the film forming conditions of the hard film 3, the arc current is intermittently changed in the range of 0 to 300 A, and thereby the new nucleation is promoted in the hard film and controlled to the above-described structure. Can do.
[0027]
Further, it is desirable to control the bias steady voltage 20 to 200 V, the film forming pressure 0.5 to 3 Pa, and the film forming temperature 500 to 600 ° C.
[0028]
【Example】
(Example 1)
A base made of cemented carbide in the form of SDKN1203 in which 10 mass% of Co, 2 mass% of TiC and 1 mass% of NbC are added to WC is placed in a cathode arc type ion plating apparatus, a bias voltage of 20 to 200 V, a deposition pressure of 0. A hard film having a composition and film thickness shown in Table 1 is obtained by intermittently changing the arc current under the conditions shown in Table 1 with a steady arc current of 150 A under film forming conditions of 5 to 3 Pa and a substrate (substrate) temperature of 525 ° C. A throw-away tip was manufactured by forming a film and further forming a surface film shown in Table 1 depending on the sample.
[0029]
About the obtained chip | tip, the cutting test was done on the following conditions. The results are shown in Table 1.
<Cutting conditions>
Work material: SKD11 material Cutting speed: 150 m / min Feed per tooth: 0.3 mm
Cutting depth: 2mm
Other: Dry cutting evaluation method: Possible cutting distance until the average flank wear width reaches 0.2 mm Further, the hard film of the chip subjected to the above cutting test is observed with a transmission electron microscope, and the magnification is 10,000 times 5) Observe any part of the hard film, take an image of the cross section of the film on a photo of 23cm x 16cm, and check the shape of the crystal particles in the photo, while confirming that either end is V-shaped. The number of crystal grains formed was counted, and the average value was calculated by measuring the tip angle (V-shaped average angle) of the V-shaped crystal grains observed in one field of view. The length of the crystal grains _(w 2), the maximum width of the crystal grains _(w 1), was separately measured the length / width ratio _{_(w} 2 / w _1), was determined and the average value. Furthermore, the composition of each crystal particle is measured using a transmission electron microscope and an accompanying EDS (energy dispersive spectroscopic analysis) device, and the end portion is V-shaped and the end portion is not V-shaped. The average composition was determined for each particle. The results are shown in Table 1.
[0030]
[Table 1]

[0031]
As is apparent from Table 1, in accordance with the present invention, the sample No. 1-5, while the ends of the crystal grains are V-shaped, that is, the crystal grains are meshed in a V-shape, the hard film is difficult to peel, and exhibits good cutting performance, Sample No. 1 was formed with a constant arc current and became a crystal in which the crystal grain ends were not V-shaped and were simply grown vertically. 6 and Sample No. which became granular crystals without vertical growth. In No. 7, the hard film was peeled off due to microchipping and the cutting performance was low.
[0032]
【The invention's effect】
As described above in detail, according to the present invention, the crystal grains constituting the hard film are grown in the longitudinal direction extending in the thickness direction of the hard film, and 40% or more of the crystal grains with respect to the total number of crystal grains By adopting a configuration in which the ends of the V-shaped and the crystal grains are engaged with each other, the chipping resistance of the hard film is improved, and the fracture resistance and wear resistance as a tool are improved.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram for explaining a cross-sectional configuration of a surface-coated cutting tool according to the present invention.
FIG. 2 is a transmission electron micrograph of a cross section of the surface-coated cutting tool of the present invention.
FIG. 3 is a schematic diagram schematically showing each particle in the transmission electron micrograph of FIG.
[Explanation of symbols]
1 Surface coated cutting tool (tool)
2 Substrate 3 Hard film 4 Crystal grain 5 Surface film

Claims

A thickness of 0.1 or more of nitrides, nitrides, carbonitrides, and carbonitrides containing at least Ti and Al is formed on the surface of a substrate made of cemented carbide, cermet, or ceramic. In a coated cutting tool in which at least one layer of a hard film of 1 to 10 μm is coated, the crystal particles constituting the hard film are growing vertically in the thickness direction of the hard film, and the total number of the crystal particles A surface-coated cutting tool characterized in that the ends of 40% or more of crystal grains are V-shaped and the crystal grains are meshed with each other.

2. The surface-coated cutting tool according to claim 1, wherein an average value of maximum widths (w ₁ ) of crystal grains forming the hard film is 0.1 to 1.5 μm.

When the composition of the crystal grains is (Ti _a Al _b ) C _x N _y O _z (where a + b = 1, x + y + z = 1), the average composition of crystal grains in which at least one end is V-shaped is 2. The average composition of crystal grains satisfying 0.3 ≦ a ≦ 0.6 and having neither V-shape at either end is 0.6 <a ≦ 0.9. Or the surface covering cutting tool of 2.

The ratio of the crystal particles whose end portions are V-shaped among the crystal particles is 40 to 80% with respect to the total number of crystal particles constituting the hard film. The surface-coated cutting tool according to any one of the above.

5. The surface-coated cutting tool according to claim 1, wherein an average angle of the V-shaped meshed with the V-shaped is 10 to 80 ° with respect to a growth direction of the hard film.