JP3543768B2 - Surface coated cemented carbide gear cutting tool with a hard coating layer that exhibits excellent heat-resistant plastic deformation properties - Google Patents

Description

【０００１】
【発明の属する技術分野】
この発明は、硬質被覆層がすぐれた耐熱塑性変形性を発揮し、したがって高熱発生を伴なう高速切削加工でも、特にすくい面と逃げ面の交わる先端切刃部に摩耗進行促進の原因となる偏摩耗の発生がなく、すぐれた耐摩耗性を長期に亘って発揮する表面被覆超硬合金製歯切工具（以下、被覆歯切工具という）に関するものである。
【０００２】
【従来の技術】
従来、一般に、自動車や航空機、さらに各種駆動装置などの構造部材として各種歯車が用いられており、これら歯車の歯形の歯切加工に、図１に概略斜視図で示されるソリッドホブ（むく歯切工具）や、ピニオンカッタ、さらにシェービングカッタなどの歯切工具が用いられている。
また、上記の歯切工具として、炭化タングステン基超硬合金の素材から例えば図１に示される形状に加工された基体（以下、超硬基体という）の表面に、ＴｉとＡｌの複合窒化物［以下、（Ｔｉ，Ａｌ）Ｎで示す］層からなる硬質被覆層を１〜１０μｍの平均層厚で物理蒸着してなる被覆歯切工具が広く知られている。
【０００３】
さらに、上記の従来被覆歯切工具が、例えば図２に概略説明図で示される物理蒸着装置の１種であるアークイオンプレーティング装置を用い、ヒータで装置内を、例えば雰囲気を１．３×１０^-3Ｐａの真空として、５００℃の温度に加熱した状態で、アノード電極と所定組成を有するＴｉ−Ａｌ合金がセットされたカソード電極（蒸発源）との間に、例えば電圧：３５Ｖ、電流：９０Ａの条件でアーク放電を発生させ、同時に装置内に反応ガスとして窒素ガスを導入し、一方超硬基体には、例えばー２００Ｖのバイアス電圧を印加した条件で、前記超硬基体の表面に、上記の（Ｔｉ，Ａｌ）Ｎからなる硬質被覆層を物理蒸着することにより製造されることも知られている。
【０００４】
【発明が解決しようとする課題】
一方、近年の歯切加工に対する省力化および省エネ化、さらに低コスト化の要求は強く、これに伴い、歯切加工は切削機械の高性能化とも相俟って高速化の傾向にあるが、上記の従来被覆歯切工具においては、これを鋼などの通常の条件での歯切加工に用いた場合には問題はないが、これを高速加工条件で用いると、歯切加工時に発生する高熱によって、特にすくい面と逃げ面の交わる先端切刃部に偏摩耗の原因となる熱塑性変形を起し易く、この結果切刃の摩耗進行が促進し、比較的短時間で使用寿命に至るのが現状である。
【０００５】
【課題を解決するための手段】
そこで、本発明者等は、上述のような観点から、鋼などの歯車の高速歯切加工に用いた場合にも、先端切刃部に熱塑性変形の発生のない被覆歯切工具を開発すべく、特にこれを構成する硬質被覆層について研究を行った結果、
（ａ）上記の従来被覆歯切工具の硬質被覆層を構成する（Ｔｉ，Ａｌ）Ｎ層におけるＡｌの割合を、金属成分全体に占める割合（原子比）で、かつ厚さ断面中央部をオージェ分光分析装置で測定（以下同じ）して、０．２５〜０．６５の割合に特定した上で、この（Ｔｉ，Ａｌ）Ｎ層に、同じく金属成分全体に占める割合（原子比）で、０．０１〜０．３０の割合のＴａを固溶含有させると、この結果のＴｉとＡｌとＴａの複合窒化物［以下、（Ｔｉ，Ａｌ，Ｔａ）Ｎで示す］層は，被覆歯切工具の硬質被覆層として適用した場合に、すぐれた耐熱塑性変形性を発揮するようになること。
【０００６】
（ｂ）上記の通り上記（Ｔｉ，Ａｌ，Ｔａ）Ｎ層は、被覆歯切工具の硬質被覆層としてすぐれた耐熱塑性変形性を発揮するが、十分な靭性（耐欠損性）を具備するものでないために、硬質被覆層を前記（Ｔｉ，Ａｌ，Ｔａ）Ｎ層単独で構成した被覆歯切工具には、特に高速歯切加工で先端切刃部に欠けやチッピングが発生し易いこと。
【０００７】
（ｃ）しかし、上記の従来被覆歯切工具の硬質被覆層を構成する（Ｔｉ，Ａｌ）Ｎ層におけるＡｌの割合を、金属成分全体に占める割合（原子比）で、０．２５〜０．７５に特定した（Ｔｉ，Ａｌ）Ｎ層を内側層とし、上記の（Ｔｉ，Ａｌ，Ｔａ）Ｎ層を外側層とした硬質被覆層を形成してなる被覆歯切工具は、前記（Ｔｉ，Ａｌ）Ｎ層によってすぐれた靭性が確保され、かつ前記（Ｔｉ，Ａｌ，Ｔａ）Ｎ層によってすぐれた耐熱塑性変形性が確保されることから、鋼などの高速歯切加工でも先端切刃部に偏摩耗の発生なく、かつ欠けやチッピングの発生もなく、すぐれた切削性能を長期に亘って発揮するようになること。
以上（ａ）〜（ｃ）に示される研究結果を得たのである。
【０００８】
この発明は、上記の研究結果に基づいてなされたものであって、 超硬基体の表面に、
内側層を、０．２〜５μｍの平均層厚を有し、かつ組成式：［Ｔｉ_1-XＡｌ_X］Ｎで表わした場合、厚さ断面中央部のオージェ分光分析装置による測定（原子比）で、Ｘ：０．２５〜０．７５を満足する（Ｔｉ，Ａｌ）Ｎ層で構成し、
外側層を、０．３〜７μｍの平均層厚を有し、かつ組成式：［Ｔｉ_1-(V+W)Ａｌ_VＴａ_W］Ｎで表わした場合、同じく厚さ断面中央部のオージェ分光分析装置による測定（原子比）で、Ｖ：０．２５〜０．６５、Ｗ：０．０１〜０．３０を満足する（Ｔｉ，Ａｌ，Ｔａ）Ｎ層で構成した硬質被覆層を１〜１０μｍの全体平均層厚で物理蒸着してなる、硬質被覆層がすぐれた耐熱塑性変形性を発揮する被覆歯切工具に特徴を有するものである。
【０００９】
つぎに、この発明の被覆歯切工具において、硬質被覆層を構成する内側層および外側層の組成式および平均層厚を上記の通りに特定した理由を説明する。
（Ａ）内側層
（ａ）組成式：［Ｔｉ_1-XＡｌ_X］Ｎ
（Ｔｉ，Ａｌ）Ｎ層におけるＡｌはＴｉＮに対して硬さを高め、かつ耐熱性を向上させるために固溶するものであり、したがってこのＡｌの含有によって耐摩耗性の向上が図られるようになるが、Ａｌの割合（Ｘ値）が０．２５未満では所望の耐摩耗性向上効果が得られず、一方Ａｌの割合（Ｘ値）が０．７５を超えると、ＴｉＮによってもたらされるすぐれた靭性が著しく損なわれ、先端切刃部に欠けやチッピングが発生し易くなることから、Ａｌの割合（Ｘ値）を０．２５〜０．７５、望ましくは０．４０〜０．６５と定めた。
（ｂ）平均層厚
その平均層厚が０．２μｍ未満では（Ｔｉ，Ａｌ）Ｎ層によってもたらされるすぐれた靭性を硬質被覆層に具備せしめることができず、一方その平均層厚が５μｍを超えると硬質被覆層に熱塑性変形が発生し易くなることから、その平均層厚を０．２〜５μｍ、望ましくは０．３〜４μｍと定めた。
【００１０】
（Ｂ）外側層
（ａ）組成式：［Ｔｉ_1-(V+W)Ａｌ_VＴａ_W］Ｎ
Ａｌの割合（Ｖ値）が０．２５未満では上記内側層におけると同様に所望の耐摩耗性向上効果が得られず、一方Ａｌの割合（Ｖ値）が外側層の場合、共存含有するＴａ成分との関係で、０．６５を超えると、ＴｉＮによってもたらされるすぐれた靭性が著しく損なわれ、先端切刃部に欠けやチッピングが発生し易くなることから、Ａｌの割合（Ｖ値）を０．２５〜０．６５、望ましくは０．３５〜０．６０と定めた。
また、Ｔａ成分には、上記の通り（Ｔｉ，Ａｌ，Ｔａ）Ｎ層の熱塑性変形を著しく抑制する作用があるが、Ｔａの割合（Ｗ値）が０．０１未満では所望のすぐれた耐熱塑性変形性を具備せしめることができず、この結果先端切刃部に摩耗進行促進の原因となる偏摩耗の発生が避けられず、一方Ｔａの割合（Ｗ値）が０．３を超えると、（Ｔｉ，Ａｌ，Ｔａ）Ｎ層の靭性が急激に低下するようになり、先端切刃部に欠けやチッピングが発生し易くなることから、Ｔａの割合（Ｗ値）を０．０１〜０．３０、望ましくは０．０２〜０．２５と定めた。
ｂ）平均層厚
その平均層厚が０．３μｍ未満では（Ｔｉ，Ａｌ，Ｔａ）Ｎ層によってもたらされるすぐれた耐熱塑性変形性を硬質被覆層に具備せしめることができず、一方その平均層厚が７μｍを超えると先端切刃部に欠けやチッピングが発生し易くなることから、その平均層厚を０．３〜７μｍ、望ましくは０．５〜５μｍと定めた。
【００１１】
また、硬質被覆層の全体平均層厚を１〜１０μｍとしたのは、その全体平均層厚が１μｍでは所望のすぐれた耐摩耗性を確保することができず、一方その全体平均層厚が１０μｍを越えると、先端切刃部に欠けやチッピングが発生し易くなるという理由によるものであり、望ましくは３〜７μｍとするのがよい。
【００１２】
【発明の実施の形態】
つぎに、この発明の被覆歯切工具を実施例により具体的に説明する。
まず、原料粉末として、いずれも１〜３μｍの平均粒径を有するＷＣ粉末、ＴｉＣ粉末、ＺｒＣ粉末、ＶＣ粉末、ＴａＣ粉末、ＮｂＣ粉末、Ｃｒ₃ Ｃ₂ 粉末、ＴｉＮ粉末、ＴａＮ粉末、およびＣｏ粉末を用意し、これら原料粉末を、表１に示される配合組成に配合し、ボールミルで７２時間湿式混合し、乾燥した後、１００ＭＰａ の圧力で圧粉体にプレス成形し、この圧粉体を６Ｐａの真空中、温度：１４００℃に１時間保持の条件で焼結して、直径：８５ｍｍ×長さ：１２５ｍｍの超硬合金製丸棒素材を形成し、この素材から機械加工にて、外径：８０ｍｍ×長さ：１２０ｍｍの寸法、３条右捩れ×２０溝の形状をもった図１に示されるソリッドホブ形式の超硬基体Ａ〜Ｊを形成した。
【００１３】
ついで、これら超硬基体Ａ〜Ｊを、アセトン中で超音波洗浄し、乾燥した状態で、それぞれ図２に例示される通常のアークイオンプレーティング装置に装入し、一方カソード電極（蒸発源）として、それぞれ種々の成分組成をもった内側層形成用Ｔｉ−Ａｌ合金および外側層形成用Ｔｉ−Ａｌ―Ｔａ合金を装着し、装置内を排気して０．５Ｐａの真空に保持しながら、ヒーターで装置内を５００℃に加熱した後、Ａｒガスを装置内に導入して１０ＰａのＡｒ雰囲気とし、この状態で超硬基体に−８００ｖのバイアス電圧を印加して超硬基体表面をＡｒガスボンバート洗浄し、ついで装置内に反応ガスとして、窒素ガスを導入して６Ｐａの反応雰囲気とすると共に、前記超硬基体に印加するバイアス電圧を−２００ｖに下げて、前記カソード電極とアノード電極との間にアーク放電を発生させ、もって前記超硬基体Ａ〜Ｊのそれぞれの表面に、表２に示される目標組成および目標層厚の（Ｔｉ，Ａｌ）Ｎ層からなる内側層と（Ｔｉ，Ａｌ，Ｔａ）Ｎ層からなる外側層で構成された硬質被覆層を蒸着することにより、本発明被覆歯切工具１〜１０を製造し、また表３に示される通り前記外側層の形成を行なわない以外は同一の条件で従来被覆歯切工具１〜１０をそれぞれ製造した。
【００１４】
なお、この結果得られた本発明被覆歯切工具１〜１０および従来被覆歯切工具１〜１０を構成するそれぞれの硬質被覆層について、これの構成層個々の厚さ断面中央部の組成をオージェ分光分析装置を用いて測定し、さらにその層厚を走査型電子顕微鏡を用いて測定したところ、いずれの場合も目標組成および目標層厚と実質的に同じ組成および層厚を示した。
【００１５】
つぎに、上記の本発明被覆歯切工具１〜１０および従来被覆歯切工具１〜１０を用いて、材質がＪＩＳ・ＳＣｒ４２０Ｈの高硬度鋼にして、モジュール：１．７５、圧力角：１７．５度、歯数：３３、ねじれ角：３６度左捩れ、歯丈：５．８６ｍｍ、歯幅：１５．５ｍｍの寸法および形状をもった歯車の加工を、
切削速度（回転速度）：４００ｍ／ｍｉｎ、
送り：２．５ｍｍ／ｒｅｖ、
加工形態：クライム、シフトなし、ドライ（エラーブロー）、
の高速歯切加工条件で行い、逃げ面摩耗幅が０．１０ｍｍに至る（使用寿命）までの歯車加工数を測定した。この測定結果をそれぞれ表２、３に示した。
【００１６】
【表１】

【００１７】
【表２】

【００１８】
【表３】

【００１９】
【発明の効果】
表２、３に示される結果から、本発明被覆歯切工具１〜１０は、いずれも内側層の（Ｔｉ，Ａｌ）Ｎ層と共存した外側層の（Ｔｉ，Ａｌ，Ｔａ）Ｎ層の作用によって硬質被覆層がすぐれた耐熱塑性変形性を具備するようになることから、高硬度鋼の歯切加工を高い発熱を伴う高速で行っても、先端切刃部に熱塑性変形の発生がなくなり、すぐれた耐摩耗性を発揮するのに対して、実質的に硬質被覆層が前記内側層に相当する（Ｔｉ，Ａｌ）Ｎ層だけからなる従来被覆歯切工具１〜１０においては、先端切刃部に熱塑性変形を起し、偏摩耗が発生し、これが原因で摩耗進行が著しく促進されるようになり、この結果比較的短時間で使用寿命に至ることが明らかである。
上述のように、この発明の被覆歯切工具は、低合金鋼などの歯車の通常の条件での歯切加工は勿論のこと、特に高硬度鋼などの歯車の高速歯切加工でもすぐれた耐熱塑性変形性を示し、すぐれた耐摩耗性を長期に亘って発揮するものであるから、歯車加工装置のＦＡ化並びに歯切加工の省力化および省エネ化、さらに低コスト化に十分満足に対応できるものである。
【図面の簡単な説明】
【図１】ソリッドホブの概略斜視図である。
【図２】アークイオンプレーティング装置の概略説明図である。[0001]
TECHNICAL FIELD OF THE INVENTION
According to the present invention, the hard coating layer exhibits excellent heat-resistant plastic deformability, and therefore, even in high-speed cutting with high heat generation, it causes wear progression particularly at the tip cutting edge where the rake face and the flank intersect. The present invention relates to a surface-coated cemented carbide tooth cutting tool (hereinafter referred to as a coated tooth cutting tool) which does not generate uneven wear and exhibits excellent wear resistance over a long period of time.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, various gears are generally used as structural members of automobiles, aircrafts, and various driving devices. A solid hob (a solid gear cutting tool) shown in a schematic perspective view in FIG. ), A pinion cutter, and a shaving cutter.
Further, as the above-mentioned gear cutting tool, a composite nitride of Ti and Al [hereinafter referred to as a cemented carbide substrate] formed from a tungsten carbide-based cemented carbide material into, for example, the shape shown in FIG. A coated tooth cutting tool obtained by physically depositing a hard coating layer having a thickness of (Ti, Al) N] with an average layer thickness of 1 to 10 μm is widely known.
[0003]
Further, the above-mentioned conventional coated tooth cutting tool uses an arc ion plating apparatus, which is a kind of physical vapor deposition apparatus schematically shown in FIG. 2, for example. When heated to a temperature of 500 ° C. under a vacuum of 10 ⁻³ Pa, for example, a voltage: 35 V, a current is applied between the anode electrode and a cathode electrode (evaporation source) on which a Ti—Al alloy having a predetermined composition is set. : An arc discharge was generated under the conditions of 90 A, and at the same time, nitrogen gas was introduced as a reaction gas into the apparatus, while a bias voltage of, for example, -200 V was applied to the surface of the cemented carbide substrate. It is also known that the hard coating layer made of (Ti, Al) N is manufactured by physical vapor deposition.
[0004]
[Problems to be solved by the invention]
On the other hand, in recent years, there is a strong demand for labor saving and energy saving, and further cost reduction for gear cutting, and with this, gear cutting tends to be speeded up in conjunction with high performance of cutting machines, In the above-mentioned conventional coated tooth cutting tool, there is no problem if this is used for the tooth cutting under normal conditions such as steel. In particular, the tip cutting edge where the rake face and flank intersect tends to cause thermoplastic deformation that causes uneven wear, and as a result, the progress of wear of the cutting edge is promoted, and the service life is shortened in a relatively short time. It is the current situation.
[0005]
[Means for Solving the Problems]
In view of the above, the present inventors have developed a coated gear cutting tool that does not generate thermoplastic deformation at the tip cutting edge even when used for high-speed gear cutting of gears such as steel. In particular, as a result of research on the hard coating layer that constitutes this,
(A) The ratio of Al in the (Ti, Al) N layer constituting the hard coating layer of the conventional coated tooth cutting tool is a ratio (atomic ratio) to the entire metal component, and the center of the thickness section is Auger. After measuring with a spectrophotometer (the same applies hereinafter) and specifying a ratio of 0.25 to 0.65, this (Ti, Al) N layer has the same ratio (atomic ratio) to the total metal component, When a solid solution containing 0.01 to 0.30 of Ta is contained, the resulting composite nitride layer of Ti, Al, and Ta (hereinafter, referred to as (Ti, Al, Ta) N) becomes a coated gear. When applied as a hard coating layer on tools, it exhibits excellent heat-resistant plastic deformation properties.
[0006]
(B) As described above, the (Ti, Al, Ta) N layer exhibits excellent heat-resistant plastic deformation properties as a hard coating layer of a coated tooth cutting tool, but has sufficient toughness (breakage resistance). Therefore, in the coated tooth cutting tool in which the hard coating layer is composed of the (Ti, Al, Ta) N layer alone, chipping and chipping are apt to occur particularly in the high-speed tooth cutting at the tip cutting edge.
[0007]
(C) However, the ratio of Al in the (Ti, Al) N layer constituting the hard coating layer of the above-mentioned conventional coated tooth cutting tool is 0.25 to 0. The coated tooth cutting tool comprising a hard coating layer formed by using the (Ti, Al) N layer specified as No. 75 as an inner layer and the (Ti, Al, Ta) N layer as an outer layer, The excellent toughness is ensured by the Al) N layer, and the excellent heat-resistant plastic deformability is ensured by the (Ti, Al, Ta) N layer. To exhibit excellent cutting performance for a long time without uneven wear and without chipping or chipping.
The research results shown in (a) to (c) above were obtained.
[0008]
The present invention has been made based on the results of the above-mentioned research, and comprises the steps of:
When the inner layer has an average layer thickness of 0.2 to 5 μm and is represented by a composition formula: [Ti _1-x Al _x ] N, the thickness is measured by an Auger spectrometer at the center of the cross section (atomic ratio). ), A (Ti, Al) N layer satisfying X: 0.25 to 0.75,
The outer layer has a mean layer thickness of 0.3～7Myuemu, and composition formula: when represented by _{[Ti 1- (V + W)} Al V Ta W] N, also the thickness of the center of the section of the Auger spectroscopy A hard coating layer composed of a (Ti, Al, Ta) N layer satisfying V: 0.25 to 0.65 and W: 0.01 to 0.30 as measured by an analyzer (atomic ratio) is 1 to The present invention is characterized by a coated tooth cutting tool in which a hard coating layer is formed by physical vapor deposition with an overall average layer thickness of 10 μm and exhibits excellent heat-resistant plastic deformation properties.
[0009]
Next, the reason why the composition formula and the average layer thickness of the inner layer and the outer layer constituting the hard coating layer are specified as described above in the coated tooth cutting tool of the present invention will be described.
(A) Inner layer (a) Composition formula: [Ti _1-x Al _x ] N
Al in the (Ti, Al) N layer increases the hardness with respect to TiN and forms a solid solution in order to improve heat resistance. Therefore, the inclusion of Al improves wear resistance. However, if the Al content (X value) is less than 0.25, the desired effect of improving wear resistance cannot be obtained. On the other hand, if the Al content (X value) exceeds 0.75, the excellent effect provided by TiN is obtained. Since the toughness is significantly impaired and chipping or chipping is likely to occur at the tip cutting edge, the ratio of Al (X value) is set to 0.25 to 0.75, preferably 0.40 to 0.65. .
(B) Average layer thickness If the average layer thickness is less than 0.2 μm, the excellent toughness provided by the (Ti, Al) N layer cannot be provided to the hard coating layer, while the average layer thickness exceeds 5 μm. Therefore, the average thickness of the hard coating layer is set to 0.2 to 5 μm, preferably 0.3 to 4 μm.
[0010]
(B) an outer layer (a) a composition _{formula: [Ti 1- (V + W} ) Al V Ta W] N
When the proportion (V value) of Al is less than 0.25, the desired effect of improving the wear resistance cannot be obtained as in the case of the inner layer, whereas when the proportion (V value) of Al is the outer layer, the coexisting Ta is contained. If the ratio exceeds 0.65 in relation to the components, the excellent toughness provided by TiN will be significantly impaired, and chipping and chipping will easily occur at the tip cutting edge. .25 to 0.65, preferably 0.35 to 0.60.
As described above, the Ta component has an effect of remarkably suppressing the thermoplastic deformation of the (Ti, Al, Ta) N layer. However, if the Ta ratio (W value) is less than 0.01, a desired excellent heat-resistant plasticity is obtained. Deformability cannot be provided, and as a result, uneven wear, which promotes the progress of wear at the tip cutting edge, is inevitable. On the other hand, when the ratio of Ta (W value) exceeds 0.3, ( Since the toughness of the Ti, Al, Ta) N layer suddenly decreases and chipping or chipping easily occurs at the tip cutting edge, the ratio of Ta (W value) is set to 0.01 to 0.30. , Desirably 0.02 to 0.25.
b) Average layer thickness If the average layer thickness is less than 0.3 μm, the hard coating layer cannot have the excellent heat-resistant plastic deformation provided by the (Ti, Al, Ta) N layer, while the average layer thickness If it exceeds 7 μm, chipping and chipping are likely to occur in the tip cutting edge portion, so the average layer thickness is set to 0.3 to 7 μm, preferably 0.5 to 5 μm.
[0011]
Further, the reason why the overall average layer thickness of the hard coating layer is 1 to 10 μm is that if the overall average layer thickness is 1 μm, a desired excellent wear resistance cannot be secured, while the overall average layer thickness is 10 μm. Is exceeded, chipping or chipping is likely to occur in the tip cutting edge portion, and the thickness is desirably 3 to 7 μm.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the coated tooth cutting tool of the present invention will be specifically described with reference to examples.
First, WC powder, TiC powder, ZrC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder, TaN powder, and Co powder each having an average particle diameter of 1 to 3 μm are used as raw material powders. These raw material powders were blended in the composition shown in Table 1, wet-mixed in a ball mill for 72 hours, dried, and then pressed into a green compact at a pressure of 100 MPa. In a vacuum at a temperature of 1400 ° C. for 1 hour to form a cemented carbide round bar material having a diameter of 85 mm and a length of 125 mm. : 80 mm x length: 120 mm, solid hob type carbide substrates A to J shown in FIG.
[0013]
Next, these super-hard substrates A to J were ultrasonically cleaned in acetone and dried, and then loaded into a usual arc ion plating apparatus illustrated in FIG. 2, respectively, while one cathode electrode (evaporation source) was used. A heater was mounted while mounting a Ti-Al alloy for forming an inner layer and a Ti-Al-Ta alloy for forming an outer layer, each having various component compositions, and evacuating the apparatus to maintain a vacuum of 0.5 Pa. After heating the inside of the apparatus to 500 ° C., an Ar gas was introduced into the apparatus to form an Ar atmosphere of 10 Pa. In this state, a bias voltage of −800 V was applied to the ultra-hard substrate to cause the surface of the ultra-hard substrate to undergo Ar gas bombardment. After cleaning, nitrogen gas was introduced into the apparatus as a reaction gas to make a reaction atmosphere of 6 Pa, and the bias voltage applied to the superhard substrate was reduced to -200 V, and the cathode voltage was lowered. Arc discharge is generated between the substrate and the anode electrode, and an inner layer composed of a (Ti, Al) N layer having a target composition and a target layer thickness shown in Table 2 is formed on each surface of the superhard substrates A to J. And a hard coating layer composed of an outer layer composed of a (Ti, Al, Ta) N layer, thereby producing coated tooth cutting tools 1 to 10 of the present invention. The conventional coated tooth cutting tools 1 to 10 were respectively manufactured under the same conditions except that the formation of No. 1 was not performed.
[0014]
For each of the hard coating layers constituting the coated tooth cutting tools 1 to 10 of the present invention and the conventional coated tooth cutting tools 1 to 10 obtained as a result, the composition at the center of the thickness section of each of the constituent layers is Auger. The thickness was measured using a spectroscopic analyzer, and the layer thickness was measured using a scanning electron microscope. In each case, the target composition and the target layer thickness were substantially the same.
[0015]
Next, using the coated tooth cutting tools 1 to 10 of the present invention and the conventional coated tooth cutting tools 1 to 10 described above, the material is made of high hardness steel of JIS SCr420H, module: 1.75, pressure angle: 17. 5 degrees, number of teeth: 33, helix angle: 36 degrees left twist, tooth length: 5.86 mm, tooth width: processing of gears with dimensions and shapes of 15.5 mm,
Cutting speed (rotation speed): 400 m / min,
Feed: 2.5 mm / rev,
Processing form: climb, no shift, dry (error blow),
, And the number of gears processed until the flank wear width reached 0.10 mm (service life) was measured. The measurement results are shown in Tables 2 and 3, respectively.
[0016]
[Table 1]

[0017]
[Table 2]

[0018]
[Table 3]

[0019]
【The invention's effect】
From the results shown in Tables 2 and 3, the coated tooth cutting tools 1 to 10 of the present invention all have the function of the outer layer (Ti, Al, Ta) N layer coexisting with the inner layer (Ti, Al) N layer. Since the hard coating layer has excellent heat-resistant plastic deformability due to, even if high-speed cutting with high heat is performed at high speed with high heat generation, there is no occurrence of thermoplastic deformation at the tip cutting edge portion, In the conventional coated tooth cutting tools 1 to 10 which exhibit excellent wear resistance and have a hard coating layer consisting essentially of only the (Ti, Al) N layer corresponding to the inner layer, the tip cutting edge is used. It is evident that thermoplastic deformation occurs in the part and uneven wear occurs, which causes the progress of wear to be remarkably accelerated, resulting in a relatively short service life.
As described above, the coated gear cutting tool of the present invention has excellent heat resistance, not only in gear cutting of low-alloy steel and the like under normal conditions, but also particularly in high-speed gear cutting of gears of high hardness steel and the like. Since it exhibits plastic deformability and exhibits excellent wear resistance over a long period of time, it can sufficiently respond to the use of FA in gear processing equipment, labor saving and energy saving of gear cutting, and further cost reduction. Things.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view of a solid hob.
FIG. 2 is a schematic explanatory view of an arc ion plating apparatus.

Claims (1)

炭化タングステン基超硬合金基体の表面に、
内側層を、０．２〜５μｍの平均層厚を有し、かつ組成式：［Ｔｉ_1-XＡｌ_X］Ｎで表わした場合、厚さ断面中央部のオージェ分光分析装置による測定（原子比）で、Ｘ：０．２５〜０．７５を満足するＴｉとＡｌの複合窒化物層で構成し、外側層を、０．３〜７μｍの平均層厚を有し、かつ組成式：［Ｔｉ_1-(V+W)Ａｌ_VＴａ_W］Ｎで表わした場合、同じく厚さ断面中央部のオージェ分光分析装置による測定（原子比）で、Ｖ：０．２５〜０．６５、Ｗ：０．０１〜０．３０を満足するＴｉとＡｌとＴａの複合窒化物層で構成した硬質被覆層を１〜１０μｍの全体平均層厚で物理蒸着してなる、硬質被覆層がすぐれた耐熱塑性変形性を発揮する表面被覆超硬合金製歯切工具。On the surface of the tungsten carbide-based cemented carbide substrate,
When the inner layer has an average layer thickness of 0.2 to 5 μm and is represented by a composition formula: [Ti _1-x Al _x ] N, the thickness is measured by an Auger spectrometer at the center of the cross section (atomic ratio). ), A composite nitride layer of Ti and Al satisfying X: 0.25 to 0.75, the outer layer has an average layer thickness of 0.3 to 7 μm, and the composition formula: [Ti in _{1- (V + W) Al V} Ta W] when expressed in N, likewise determined by Auger spectrometer thickness center of the section (atomic ratio), V: 0.25~0.65, W: 0 Excellent heat resistant plastic deformation in which the hard coating layer is formed by physical vapor deposition of a hard coating layer composed of a composite nitride layer of Ti, Al, and Ta satisfying 0.11 to 0.30 with an overall average thickness of 1 to 10 μm. Surface-coated cemented carbide gear cutting tool that exhibits excellent properties.

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