JP5861982B2 - Surface coated cutting tool whose hard coating layer exhibits excellent peeling resistance in high-speed intermittent cutting - Google Patents
Surface coated cutting tool whose hard coating layer exhibits excellent peeling resistance in high-speed intermittent cutting Download PDFInfo
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この発明は、軸受鋼や合金工具鋼等の高硬度材の切削加工を、高速で、かつ、切刃に断続的・衝撃的負荷が作用する高速断続切削条件で行った場合でも、硬質被覆層がすぐれた耐剥離性を発揮し、長期に亘ってすぐれた耐摩耗性を示す表面被覆切削工具（以下、被覆工具という）に関するものである。 The present invention provides a hard coating layer even when high-hardness materials such as bearing steel and alloy tool steel are machined at high speed and under high-speed intermittent cutting conditions in which intermittent and impact loads are applied to the cutting edge. The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits excellent peeling resistance and exhibits excellent wear resistance over a long period of time.
従来、一般に、炭化タングステン（以下、ＷＣで示す）基超硬合金または炭窒化チタン（以下、ＴｉＣＮで示す）基サーメットで構成された基体（以下、これらを総称して工具基体という）の表面に、
（ａ）下部層が、Ｔｉの炭化物（以下、ＴｉＣで示す）層、窒化物（以下、同じくＴｉＮで示す）層、炭窒化物（以下、ＴｉＣＮで示す）層、炭酸化物（以下、ＴｉＣＯで示す）層、および炭窒酸化物（以下、ＴｉＣＮＯで示す）層のうちの１層または２層以上からなるＴｉ化合物層、
（ｂ）上部層が、化学蒸着した状態でα型の結晶構造を有する酸化アルミニウム層（以下、Ａｌ２Ｏ３層で示す）、
以上（ａ）および（ｂ）で構成された硬質被覆層を蒸着形成してなる被覆工具が知られている。
Conventionally, generally on the surface of a substrate (hereinafter collectively referred to as a tool substrate) composed of a tungsten carbide (hereinafter referred to as WC) -based cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) -based cermet. ,
(A) The lower layer is a Ti carbide (hereinafter referred to as TiC) layer, a nitride (hereinafter also referred to as TiN) layer, a carbonitride (hereinafter referred to as TiCN) layer, a carbon oxide (hereinafter referred to as TiCO). And a Ti compound layer composed of one or more of a carbonitride oxide (hereinafter referred to as TiCNO) layer,
(B) an aluminum oxide layer (hereinafter referred to as an Al 2 O 3 layer) having an α-type crystal structure in a state where the upper layer is chemically vapor-deposited
A coated tool formed by vapor-depositing the hard coating layer constituted by (a) and (b) is known.
しかし、上記従来の被覆工具は、例えば各種の鋼や鋳鉄などの通常の連続切削や断続切削では優れた耐摩耗性を発揮するが、これを、高速断続切削に用いた場合には、被覆層のチッピングが発生しやすく、工具寿命が短命になるという問題点があった。
そこで、被覆層の耐チッピング性を改善するために、上部層に改良を加えた被覆工具が提案されている。
例えば、特許文献１に示すように、工具基体表面に、下部層として、ＴｉＣ、ＴｉＮ、ＴｉＣＮ、ＴｉＣＯおよびＴｉＣＮＯのうちの１種または２種以上からなるＴｉ化合物層、上部層としてＡｌ２Ｏ３層を蒸着形成してなる被覆工具において、硬質被覆層の上部層を構成するＡｌ２Ｏ３層について、上部層の上側部では、柱状結晶粒が縦方向に並列配置した柱状結晶組織、また、上部層の下側部では粒状結晶組織とし、上部層厚さ方向に異なる結晶組織構造を有せしめることにより、
耐チッピング性を改善した被覆工具が提案されている。
However, the above-mentioned conventional coated tools exhibit excellent wear resistance in normal continuous cutting and interrupted cutting such as various steels and cast irons, but when this is used for high-speed interrupted cutting, the coating layer There is a problem in that chipping is likely to occur and the tool life is shortened.
Therefore, in order to improve the chipping resistance of the coating layer, a coating tool in which the upper layer is improved has been proposed.
For example, as shown in Patent Document 1, a Ti compound layer made of one or more of TiC, TiN, TiCN, TiCO, and TiCNO is used as the lower layer on the tool base surface, and Al 2 O 3 is used as the upper layer. In the coated tool formed by vapor-depositing a layer, for the Al 2 O 3 layer constituting the upper layer of the hard coating layer, in the upper part of the upper layer, a columnar crystal structure in which columnar crystal grains are arranged in parallel in the vertical direction, By having a granular crystal structure in the lower part of the upper layer and having a different crystal structure in the upper layer thickness direction,
Coated tools with improved chipping resistance have been proposed.
近年の切削装置の高性能化はめざましく、一方で切削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、切削加工は一段と高速化すると共に、切刃にはますます高負荷が作用する傾向にあるが、上記の従来被覆工具においては、これを鋼や鋳鉄などの通常の条件での連続切削や断続切削に用いた場合には問題はないが、特にこれを高硬度材の高速断続切削条件で用いた場合には、切刃に断続的・衝撃的負荷が作用することによって、上部層のＡｌ２Ｏ３層にクラックが発生し、これが層中を伝播・進展することによって、ついには層の剥離に生じ、これが原因で、比較的短時間で使用寿命に至るのが現状である。 The performance of cutting equipment has been remarkable in recent years, while the demands for labor saving and energy saving and further cost reduction for cutting are strong. With this, cutting is further speeded up, and the cutting blade is increasingly used. Although there is a tendency for high loads to work, the above-mentioned conventional coated tools have no problem when used for continuous cutting or intermittent cutting under normal conditions such as steel or cast iron. When used in high-speed intermittent cutting conditions for hardened materials, intermittent and impact loads are applied to the cutting edge, causing cracks in the upper Al 2 O 3 layer, which propagate and propagate through the layer. By doing so, it finally occurs in the peeling of the layer, and due to this, the service life is reached in a relatively short time.
そこで、本発明者等は、上述のような観点から、Ｔｉ化合物層からなる下部層とＡｌ２Ｏ３層からなる上部層の密着性を改善するとともに、上部層のＡｌ２Ｏ３層に発生したクラックの伝播・進展を抑制し、もって、剥離、チッピング等の異常損傷の発生を防止するとともに、工具寿命の長寿命化を図るべく鋭意研究を行った結果、次のような知見を得たのである。 Accordingly, the present inventors have generated in terms as described above, as well as improve the adhesion of the upper layer including the lower layer and the Al 2 O 3 layer consisting of Ti compound layer, in the Al 2 O 3 layer of the upper layer As a result of diligent research to prevent the occurrence of abnormal damage such as peeling and chipping, and to extend the tool life, the following knowledge was obtained. It is.
即ち、Ｔｉ化合物層からなる下部層とＡｌ２Ｏ３層からなる上部層とを被覆形成した被覆工具において、上部層を、層厚方向に縦長に成長した柱状結晶粒と、平均粒径５０〜５００ｎｍの粒状結晶粒とから構成するとともに、さらに、上部層表層側は、柱状結晶粒同士が相互に隙間なく隣接して成長している実質的な柱状組織とし、かつ、下部層近傍の上部層は、隣接していない柱状結晶粒相互の間隙を埋めるように粒状結晶粒を形成した柱状−粒状混合組織として構成した場合には、切刃に断続的・衝撃的負荷が作用する高速断続切削に用いた場合でも、上部層と下部層の密着性が向上するとともに、上部層に発生したクラックの伝播・進展が、上部層の下部層近傍の柱状−粒状混合組織で抑制されることによって、剥離、チッピング等の異常損傷の発生を防止し得ることを見出したのである。 That is, in a coated tool in which a lower layer made of a Ti compound layer and an upper layer made of an Al 2 O 3 layer are coated, the upper layer is made of columnar crystal grains grown vertically in the layer thickness direction, and an average particle size of 50 to Further, the upper layer surface side has a substantially columnar structure in which the columnar crystal grains are grown adjacent to each other without any gap, and the upper layer in the vicinity of the lower layer. Is a high-speed intermittent cutting in which intermittent and impact loads are applied to the cutting edge when it is configured as a columnar-grain mixed structure in which granular grains are formed so as to fill gaps between columnar grains that are not adjacent to each other. Even when it is used, the adhesion between the upper layer and the lower layer is improved, and the propagation / propagation of cracks generated in the upper layer is suppressed by the columnar-granular mixed structure in the vicinity of the lower layer of the upper layer. , Chipping, etc. It was found that it is possible to prevent the occurrence of abnormal damage.
この発明は、上記知見に基づいてなされたものであって、
「（１） 炭化タングステン基超硬合金または炭窒化チタン基サーメットで構成された工具基体の表面に、
（ａ）下部層が、Ｔｉの炭化物層、窒化物層、炭窒化物層、炭酸化物層および炭窒酸化物層のうちの１層または２層以上からなり、かつ、３〜２０μｍの合計平均層厚を有するＴｉ化合物層、
（ｂ）上部層が、３〜１５μｍの平均層厚を有し、かつ、α型の結晶構造を有するＡｌ２Ｏ３層、
上記（ａ）および（ｂ）の蒸着層からなる硬質被覆層が形成された表面被覆切削工具において、
（ｃ）上記上部層は、層厚方向に縦長に成長した柱状結晶粒と、平均粒径５０〜５００ｎｍの粒状結晶粒とから構成され、
（ｄ）下部層直上及び下部層側の上部層においては、隣接していない柱状結晶粒相互の間隙に粒状結晶粒が存在する柱状−粒状混合組織が形成され、
（ｅ）上部層表層側においては、柱状結晶粒同士が相互に隙間なく隣接して成長している実質的な柱状組織が形成されている、
ことを特徴とする表面被覆切削工具。
（２） 下部層と上部層の界面から、上部層側に１μｍまでの深さ領域においては、該深さ領域の縦断面面積の３０〜７０面積％を粒状結晶粒が占める柱状−粒状混合組織が形成されていることを特徴とする前記（１）に記載の表面被覆切削工具。
（３） 上部層において、上部層の平均層厚の６０％以上の平均結晶粒長さと、アスペクト比（平均結晶粒長さ／平均結晶粒幅）２．５〜７．０を有する柱状結晶粒が、上部層表層側の縦断面面積の６０面積％以上を占める実質的な柱状組織が形成されていることを特徴とする前記（１）または（２）に記載の表面被覆切削工具。」
に特徴を有するものである。
This invention has been made based on the above findings,
“(1) On the surface of a tool base made of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet,
(A) The lower layer is composed of one or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer and carbonitride oxide layer, and a total average of 3 to 20 μm A Ti compound layer having a layer thickness,
(B) an Al 2 O 3 layer in which the upper layer has an average layer thickness of 3 to 15 μm and has an α-type crystal structure;
In the surface-coated cutting tool in which the hard coating layer formed of the vapor deposition layer of (a) and (b) is formed ,
(C) The upper layer is composed of columnar crystal grains grown vertically in the layer thickness direction and granular crystal grains having an average grain size of 50 to 500 nm,
(D) In the upper layer immediately above the lower layer and the upper layer on the lower layer side, a columnar-grain mixed structure in which granular crystal grains exist in the gaps between columnar crystal grains that are not adjacent to each other is formed,
(E) On the upper layer surface side, a substantial columnar structure is formed in which columnar crystal grains are grown adjacent to each other without a gap,
A surface-coated cutting tool characterized by that.
(2) In a depth region of 1 μm from the interface between the lower layer and the upper layer to the upper layer side, a columnar-grain mixed structure in which the granular crystal grains occupy 30 to 70% by area of the longitudinal sectional area of the depth region Is formed. The surface-coated cutting tool according to (1), wherein
(3) In the upper layer, columnar crystal grains having an average crystal grain length of 60% or more of the average layer thickness of the upper layer and an aspect ratio (average crystal grain length / average crystal grain width) of 2.5 to 7.0 However, the surface-coated cutting tool according to (1) or (2), wherein a substantially columnar structure occupying 60% by area or more of the longitudinal sectional area on the upper surface side is formed. "
It has the characteristics.
以下に、この発明の被覆工具の硬質被覆層の構成層について詳細に説明する。 Hereinafter, the constituent layers of the hard coating layer of the coated tool of the present invention will be described in detail.
下部層（Ｔｉ化合物層）：
Ｔｉ化合物層（例えば、ＴｉＣ層、ＴｉＮ層、ＴｉＣＮ層、ＴｉＣＯ層およびＴｉＣＮＯ層）は、基本的にはＡｌ２Ｏ３層の下部層として存在し、自身の具備するすぐれた高温強度によって硬質被覆層が高温強度を具備するようになるほか、工具基体、Ａｌ２Ｏ３層のいずれにも密着し、硬質被覆層の工具基体に対する密着性を維持する作用を有するが、その合計平均層厚が３μｍ未満では、前記作用を十分に発揮させることができず、一方その合計平均層厚が２０μｍを越えると、特に高熱発生を伴う高速重切削・高速断続切削では熱塑性変形を起し易くなり、これが偏摩耗の原因となることから、その合計平均層厚を３〜２０μｍと定めた。
Lower layer (Ti compound layer):
Ti compound layers (eg, TiC layer, TiN layer, TiCN layer, TiCO layer and TiCNO layer) basically exist as the lower layer of Al 2 O 3 layer, and are hard-coated by their excellent high-temperature strength. In addition to the high temperature strength of the layer, the layer adheres to both the tool substrate and the Al 2 O 3 layer, and maintains the adhesion of the hard coating layer to the tool substrate, but the total average layer thickness is If the thickness is less than 3 μm, the above-mentioned effect cannot be sufficiently exerted. On the other hand, if the total average layer thickness exceeds 20 μm, it becomes easy to cause thermoplastic deformation particularly in high-speed heavy cutting and high-speed intermittent cutting with high heat generation. Since it causes uneven wear, the total average layer thickness was determined to be 3 to 20 μm.
上部層（Ａｌ２Ｏ３層）：
上部層は、３〜１５μｍの平均層厚を有し、かつ、α型の結晶構造を有するＡｌ２Ｏ３層で構成するが、この発明では、上部層表層側と、下部層近傍の上部層（即ち、下部層直上と下部層側の上部層）とを、それぞれ異なる結晶粒組織構造として構成することによって、上部層と下部層の密着性の向上を図るとともに、上部層に発生したクラックの伝播・進展を抑える。
ただ、上部層の平均層厚が３μｍ未満であると、長期の使用にわたってすぐれた高温強度および高温硬さを発揮することができず、一方、１５μｍを越えると、チッピングが発生し易くなることから、上部層の平均層厚は３〜１５μｍと定めた。
Upper layer (Al 2 O 3 layer):
The upper layer has an average layer thickness of 3 to 15 μm and is composed of an Al 2 O 3 layer having an α-type crystal structure. In the present invention, the upper layer surface side and the upper layer near the lower layer (I.e., the upper layer immediately above the lower layer and the upper layer on the lower layer side) are configured as different crystal grain structures, respectively, thereby improving the adhesion between the upper layer and the lower layer, and the cracks generated in the upper layer. Suppress propagation and progress.
However, if the average layer thickness of the upper layer is less than 3 μm, excellent high-temperature strength and high-temperature hardness cannot be exhibited over a long period of use, while if it exceeds 15 μm, chipping tends to occur. The average thickness of the upper layer was determined to be 3 to 15 μm.
（ａ）下部層直上及び下部層側の上部層（下部層近傍の上部層）における柱状−粒状混合組織
図１の模式図に示すように、Ｔｉ化合物層からなる下部層の直上の上部層及び下部層側の上部層には、隣接していない柱状結晶粒相互の間隙を恰も埋めるように粒状結晶粒を形成することにより、柱状−粒状混合組織からなる組織構造とする。
粒状結晶粒の平均粒径は、５０〜５００ｎｍとするが、粒状結晶粒の平均粒径が５０ｎｍ未満では、５０ｎｍの粒状結晶粒が相互に隣接する箇所が多く存在し、その界面にクラックが進展し、上部層のＡｌ２Ｏ３が剥離しやすくなり、一方、粒状結晶粒の平均粒径が５００ｎｍを超えると、柱状結晶粒間の界面にポアが形成され、そのポアが存在することで上部層のＡｌ２Ｏ３の耐チッピング性が低下するため、粒状結晶粒の平均粒径は１００〜５００ｎｍと定めた。
上記の柱状−粒状混合組織からなる組織構造とすることにより、特に、下部層のＴｉ化合物層と上部層の粒状結晶粒との間での密着性向上が図られ、さらに、上部層に発生したクラックの伝播・進展が、下部層近傍の上記粒状結晶粒によって抑えられ、その結果、硬質被覆層の耐剥離性が向上する。
下部層近傍の上記柱状−粒状混合組織は、下部層と上部層の界面から、上部層側に１μｍまでの深さ領域の縦断面を、例えば、走査型電子顕微鏡で観察・測定した場合、該深さ領域の縦断面面積の３０〜７０面積％を粒状結晶粒が占める柱状−粒状混合組織が形成されていることが好ましい。該深さ領域における粒状結晶粒の占有面積割合が３０面積％未満の場合には下部層と上部層の界面における隣接していない柱状結晶粒相互の間隙を埋めるように粒状結晶粒が形成されず、上部層で発生したクラックの伝播・進展が抑制されず、上部層のＡｌ２Ｏ３の耐剥離性が低下し、一方、７０面積％を超える場合には、相対的に上部層のＡｌ２Ｏ３の柱状組織が低下し、Ａｌ２Ｏ３の耐摩耗性が低下するため、
下部層近傍の上部層における柱状−粒状混合組織に占める粒状結晶粒の占有面積割合は、測定した縦断面面積の３０〜７０面積％であることが好ましい。
(A) Columnar-granular mixed structure in the upper layer immediately above the lower layer and the upper layer on the lower layer side (upper layer in the vicinity of the lower layer) As shown in the schematic diagram of FIG. 1, the upper layer immediately above the lower layer made of the Ti compound layer, In the upper layer on the lower layer side, granular crystal grains are formed so as to fill gaps between columnar crystal grains that are not adjacent to each other, thereby forming a structure structure composed of a columnar-grain mixed structure.
The average grain size of the granular crystal grains is 50 to 500 nm. If the average grain size of the granular crystal grains is less than 50 nm, there are many places where the 50 nm granular crystal grains are adjacent to each other, and cracks develop at the interface. and becomes Al 2 O 3 top layer is easily peeled off, while when the average particle diameter of the granular crystal grains exceeds 500 nm, pores formed at the interface between the columnar crystal grains, the upper by its pores are present Since the chipping resistance of Al 2 O 3 in the layer is lowered, the average grain size of the granular crystal grains is determined to be 100 to 500 nm.
By adopting a structure composed of the above-mentioned columnar-granular mixed structure, the adhesion between the Ti compound layer of the lower layer and the granular crystal grains of the upper layer is improved, and further, it occurs in the upper layer. Propagation / propagation of cracks is suppressed by the granular crystal grains in the vicinity of the lower layer, and as a result, the peel resistance of the hard coating layer is improved.
When the columnar-granular mixed structure in the vicinity of the lower layer is observed and measured with a scanning electron microscope, for example, in a longitudinal section of a depth region from the interface between the lower layer and the upper layer to the upper layer side up to 1 μm, It is preferable that a columnar-granular mixed structure in which the granular crystal grains occupy 30 to 70% by area of the longitudinal sectional area of the depth region is formed. When the occupied area ratio of the granular crystal grains in the depth region is less than 30 area%, the granular crystal grains are not formed so as to fill the gaps between the non-adjacent columnar grains at the interface between the lower layer and the upper layer. , propagation and progress of cracks generated in the upper layer is not inhibited, and decrease peeling resistance Al 2 O 3 top layer, whereas, if it exceeds 70% by area, the relatively upper layer Al 2 Since the columnar structure of O 3 is lowered and the wear resistance of Al 2 O 3 is lowered,
The occupied area ratio of the granular crystal grains in the columnar-granular mixed structure in the upper layer in the vicinity of the lower layer is preferably 30 to 70 area% of the measured longitudinal sectional area.
（ｂ）上部層表層側における実質的に単一の柱状組織
図１の模式図に示すように、上部層表層側においては、柱状結晶粒同士が相互に隙間なく隣接して成長している実質的な柱状組織を形成するが、このような柱状組織構造によって、上部層のＡｌ２Ｏ３層は、すぐれた耐熱性と高温硬さを維持することができ、その結果、長期の使用に亘ってすぐれた耐摩耗性を発揮することができる。
上部層について、電界放出型走査電子顕微鏡と電子後方散乱回折像装置を用い、断面研磨面の測定範囲内に存在する上部層酸化アルミニウム層の六方晶結晶格子を有する結晶粒個々に電子線を照射して、工具基体表面の法線に対して、前記結晶粒の結晶面である（０００１）面および（１０−１０）面の法線がなす傾斜角を測定し、この結果得られた測定傾斜角から、それぞれ隣接する結晶粒相互間の界面における（０００１）面の法線同士、および（１０−１０）面の法線同士の交わる角度を求め、さらに、前記（０００１）面の法線同士、および（１０−１０）面の法線同士の交わる角度が２度以上の場合を結晶粒として定義することで識別し、その結果得られた結晶粒で測定した場合、柱状結晶粒の平均長さは、上部層の平均層厚の６０％以上であり、かつ、そのアスペクト比（平均結晶粒長さ／平均結晶粒幅）２．５〜７．０である柱状結晶粒が、相互に隙間なく隣接して成長している実質的な柱状組織であることが好ましい。
ここで、柱状結晶粒の平均長さが、上部層の平均層厚の６０％未満である場合には実験結果より上部層Ａｌ２Ｏ３の特定面、例えば(０００１)面の配向性が低下し、それに伴い耐摩耗性および耐チッピング性が低下するため、柱状結晶粒の平均長さは、上部層の平均層厚の６０％以上であることが望ましい。また、柱状結晶粒のアスペクト比（平均結晶粒長さ／平均結晶粒幅）が２．５未満であると、Ａｌ２Ｏ３の柱状結晶粒間の粒界強度が低下することによって上部層Ａｌ２Ｏ３の高温強度が低下し、一方、そのアスペクト比（平均結晶粒長さ／平均結晶粒幅）が７．０を超えると、柱状結晶粒間の界面が増え、クラックの伝播・進展を抑制できないため、柱状結晶粒のアスペクト比（平均結晶粒長さ／平均結晶粒幅）は、２．５〜７．０であることが望ましい。
また、実質的な柱状組織とは、上部層の縦断研磨面を前記記載の手法にてＡｌ２Ｏ３結晶粒を識別し、上部層Ａｌ２Ｏ３全体の面積に対する柱状結晶粒の面積を求めた場合、６０面積％以上を柱状結晶粒が占めている組織状態をいう。
(B) A substantially single columnar structure on the upper layer surface side As shown in the schematic diagram of FIG. 1, on the upper layer surface layer side, the columnar crystal grains are grown adjacent to each other without a gap. This columnar structure allows the upper Al 2 O 3 layer to maintain excellent heat resistance and high temperature hardness, and as a result, over a long period of use. Excellent wear resistance can be demonstrated.
For the upper layer, use a field emission scanning electron microscope and an electron backscatter diffraction imaging device to irradiate individual crystal grains having a hexagonal crystal lattice of the upper aluminum oxide layer existing within the measurement range of the cross-section polished surface. Then, the inclination angle formed by the normal lines of the (0001) plane and the (10-10) plane, which are crystal planes of the crystal grains, is measured with respect to the normal line of the tool base surface, and the measurement tilt obtained as a result From the angles, the angles at which the normal lines of the (0001) planes and the normal lines of the (10-10) planes intersect each other at the interface between adjacent crystal grains are obtained, and further, the normal lines of the (0001) planes And the angle at which the normals of the (10-10) planes intersect each other are defined as crystal grains, and the average length of the columnar crystal grains when measured with the resulting crystal grains of the average thickness of the upper layer 6 %, And columnar crystal grains having an aspect ratio (average crystal grain length / average crystal grain width) of 2.5 to 7.0 are substantially grown adjacent to each other without a gap. A columnar structure is preferable.
Here, when the average length of the columnar crystal grains is less than 60% of the average layer thickness of the upper layer, the orientation of the specific surface of the upper layer Al 2 O 3 , for example, the (0001) plane is reduced from the experimental results. In addition, the wear resistance and chipping resistance are lowered accordingly, so that the average length of the columnar crystal grains is preferably 60% or more of the average layer thickness of the upper layer. Further, when the aspect ratio (average crystal grain length / average crystal grain width) of the columnar crystal grains is less than 2.5, the grain boundary strength between the Al 2 O 3 columnar crystal grains decreases, so that the upper layer Al On the other hand, when the high-temperature strength of 2 O 3 decreases, and the aspect ratio (average crystal grain length / average crystal grain width) exceeds 7.0, the interface between columnar crystal grains increases, and the propagation and progress of cracks increases. Since it cannot be suppressed, the aspect ratio of the columnar crystal grains (average crystal grain length / average crystal grain width) is desirably 2.5 to 7.0.
In addition, the substantial columnar structure means that the vertical polishing surface of the upper layer is identified by Al 2 O 3 crystal grains by the above-described method, and the area of the columnar crystal grains with respect to the entire area of the upper layer Al 2 O 3 is obtained. In this case, it means a structure state in which columnar crystal grains occupy 60 area% or more.
（ｃ）上部層（Ａｌ２Ｏ３層）の形成
下部層近傍では柱状−粒状混合組織であり、一方、上部層表層側では実質的な柱状組織である上部層（Ａｌ２Ｏ３層）は、例えば、以下に示す化学蒸着によって形成することができる。
まず、第１段階として、
反応ガス組成（容量％）：ＡｌＣｌ３ １〜５％、ＣＯ２ ０．１〜０．５％、残部Ｈ２、
反応雰囲気温度：９００〜９５０℃、
反応雰囲気圧力：６〜１０ｋＰａ、
時間：１０〜６０ｍｉｎ、
という蒸着条件で、しかも、同時に、反応ガス中に、Ｈ２Ｓ ０．０５−０．１ｖｏｌ％とＢＣｌ３ ０．０１−０．０５ｖｏｌ％を２ｍｉｎ間毎に交互に添加して成膜することにより、柱状結晶粒の成長と粒状結晶粒の形成を同時に行うことができ、その結果、下部層の直上の上部層及び下部層側の上部層に、隣接していない柱状結晶粒相互の間隙を恰も埋めるように粒状結晶粒が存在する柱状−粒状混合組織からなる組織構造を形成することができる。
次いで、第２段階として、
反応ガス組成（容量％）：ＡｌＣｌ３ １〜５％、ＣＯ２ ５〜１５％、ＨＣｌ １〜５％、Ｈ２Ｓ ０．５〜１％、残部Ｈ２、
反応雰囲気温度：９６０〜１０４０℃、
反応雰囲気圧力：６〜１０ｋＰａ、
の条件で目標とする上部層層厚になるまで蒸着することにより、少なくとも上部層表層側には、柱状結晶粒同士が相互に隙間なく隣接して成長している実質的な柱状組織を形成することができる。
(C) columnar in form lower layer near the upper layer (Al 2 O 3 layer) - a particulate mixed structure, while the upper layer is the upper layer surface side is substantially columnar texture (Al 2 O 3 layer) is For example, it can be formed by chemical vapor deposition shown below.
First, as the first stage,
Reaction gas composition (volume%): AlCl 3 1-5%, CO 2 0.1-0.5%, balance H 2 ,
Reaction atmosphere temperature: 900-950 ° C.
Reaction atmosphere pressure: 6 to 10 kPa,
Time: 10-60 min
At the same time, H 2 S 0.05-0.1 vol% and BCl 3 0.01-0.05 vol% are alternately added to the reaction gas every 2 min to form a film. Thus, the growth of the columnar crystal grains and the formation of the granular crystal grains can be performed simultaneously. As a result, the gap between the columnar crystal grains that are not adjacent to each other in the upper layer immediately above the lower layer and the upper layer on the lower layer side is formed. It is possible to form a structure composed of a columnar-grain mixed structure in which granular crystal grains exist so as to fill the ridges.
Then, as the second stage,
Reaction gas composition (volume%): AlCl 3 1-5%, CO 2 5-15%, HCl 1-5%, H 2 S 0.5-1%, balance H 2 ,
Reaction atmosphere temperature: 960-1040 ° C.
Reaction atmosphere pressure: 6 to 10 kPa,
By vapor deposition until the target upper layer thickness is reached under the above conditions, at least the upper layer surface layer side forms a substantial columnar structure in which columnar crystal grains are grown adjacent to each other without a gap. be able to.
この発明の被覆工具は、Ａｌ２Ｏ３層からなる上部層を、層厚方向に縦長に成長した柱状結晶粒と、平均粒径５０〜５００ｎｍの粒状結晶粒とから構成するとともに、さらに、上部層表層側は、柱状結晶粒同士が相互に隙間なく隣接して成長している実質的な柱状組織とし、かつ、下部層近傍の上部層は、隣接していない柱状結晶粒相互の間隙を埋めるように粒状結晶粒を形成した柱状−粒状混合組織として構成したことにより、軸受鋼や合金工具鋼等の高硬度材の切削加工を高速で、かつ切れ刃に対して断続的・衝撃的負荷が作用する高速断続切削条件で行っても、すぐれた高温強度と高温硬さを示し、硬質被覆層の剥離等の異常損傷の発生もなく、長期の使用にわたってすぐれた切削性能を発揮するものである。 The coated tool of the present invention comprises an upper layer composed of an Al 2 O 3 layer composed of columnar crystal grains grown vertically in the layer thickness direction and granular crystal grains having an average grain size of 50 to 500 nm, The surface layer side has a substantially columnar structure in which the columnar crystal grains are grown adjacent to each other without any gap, and the upper layer near the lower layer fills the gap between the columnar crystal grains that are not adjacent to each other. In this way, it is configured as a columnar-granular mixed structure in which granular crystal grains are formed, so that high-hardness materials such as bearing steel and alloy tool steel can be cut at high speed, and intermittent and impact loads are applied to the cutting edge. Even under high-speed interrupted cutting conditions, it exhibits excellent high-temperature strength and high-temperature hardness, and exhibits excellent cutting performance over a long period of use without occurrence of abnormal damage such as peeling of the hard coating layer. .
つぎに、この発明の被覆工具を実施例により具体的に説明する。 Next, the coated tool of the present invention will be specifically described with reference to examples.
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、Ｃｒ3Ｃ2粉末、ＴｉＮ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、さらにワックスを加えてアセトン中で２４時間ボールミル混合し、減圧乾燥した後、９８ＭＰａの圧力で所定形状の圧粉体にプレス成形し、この圧粉体を５Ｐａの真空中、１３７０〜１４７０℃の範囲内の所定の温度に１時間保持の条件で真空焼結し、焼結後、切刃部にＲ：０．０７ｍｍのホーニング加工を施すことによりＩＳＯ・ＣＮＭＧ１２０４０８に規定するスローアウエイチップ形状をもったＷＣ基超硬合金製の工具基体Ａ〜Ｅをそれぞれ製造した。 As raw material powders, WC powder, TiC powder, ZrC powder, VC powder, TaC powder, NbC powder, Cr 3 C 2 powder, TiN powder, and Co powder each having an average particle diameter of 1 to 3 μm are prepared. The raw material powder is blended in the blending composition shown in Table 1, added with wax, ball mill mixed in acetone for 24 hours, dried under reduced pressure, and press-molded into a green compact of a predetermined shape at a pressure of 98 MPa. The green compact is vacuum-sintered in a vacuum of 5 Pa at a predetermined temperature within a range of 1370 to 1470 ° C. for 1 hour. After sintering, the cutting edge is subjected to a honing process of R: 0.07 mm. Thus, tool bases A to E made of a WC-based cemented carbide having a throwaway tip shape specified in ISO · CNMG120408 were manufactured.
また、原料粉末として、いずれも０．５〜２μｍの平均粒径を有するＴｉＣＮ（質量比でＴｉＣ／ＴｉＮ＝５０／５０）粉末、Ｍｏ2 Ｃ粉末、ＺｒＣ粉末、ＮｂＣ粉末、ＴａＣ粉末、ＷＣ粉末、Ｃｏ粉末、およびＮｉ粉末を用意し、これら原料粉末を、表２に示される配合組成に配合し、ボールミルで２４時間湿式混合し、乾燥した後、９８ＭＰａの圧力で圧粉体にプレス成形し、この圧粉体を１．３ｋＰａの窒素雰囲気中、温度：１５４０℃に１時間保持の条件で焼結し、焼結後、切刃部分にＲ:０．０７ｍｍのホーニング加工を施すことによりＩＳＯ規格・ＣＮＭＧ１２０４０８のチップ形状をもったＴｉＣＮ基サーメット製の工具基体ａ〜ｅを形成した。 In addition, as raw material powders, TiCN (mass ratio TiC / TiN = 50/50) powder, Mo 2 C powder, ZrC powder, NbC powder, TaC powder, WC powder, all having an average particle diameter of 0.5 to 2 μm. Co powder and Ni powder are prepared, and these raw material powders are blended in the blending composition shown in Table 2, wet mixed by a ball mill for 24 hours, dried, and pressed into a compact at a pressure of 98 MPa. The green compact was sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour, and after sintering, the cutting edge portion was subjected to a honing process of R: 0.07 mm. Tool bases a to e made of TiCN base cermet having a standard / CNMG120408 chip shape were formed.
ついで、これらの工具基体Ａ〜Ｅおよび工具基体ａ〜ｅのそれぞれを、通常の化学蒸着装置に装入し、
（ａ）まず、表３（表３中のｌ−ＴｉＣＮは特開平６−８０１０号公報に記載される縦長成長結晶組織をもつＴｉＣＮ層の形成条件を示すものであり、これ以外は通常の粒状結晶組織の形成条件を示すものである）に示される条件にて、表４に示される目標層厚のＴｉ化合物層を蒸着形成し、
（ｂ）ついで、表５に示されるＡ〜Ｃの二段階の条件にて、上部層のＡｌ２Ｏ３層を表６に示される目標層厚で形成し、本発明被覆工具１〜１０をそれぞれ製造した。
Then, each of these tool bases A to E and tool bases a to e is charged into a normal chemical vapor deposition apparatus,
(A) First, Table 3 (l-TiCN in Table 3 indicates the conditions for forming a TiCN layer having a vertically elongated crystal structure described in JP-A-6-8010, and the other conditions are ordinary granularity. The Ti compound layer having the target layer thickness shown in Table 4 is formed by vapor deposition under the conditions shown in Table 4).
(B) Next, under the two-stage conditions A to C shown in Table 5, the upper Al 2 O 3 layer is formed with the target layer thickness shown in Table 6, and the coated tools 1 to 10 of the present invention are formed. Each was manufactured.
また、比較の目的で、上記工具基体Ａ〜Ｃ、ａ〜ｃに、上記（ａ）と同様にして表４に示される目標層厚のＴｉ化合物層を蒸着形成した後、表５に示されるＡ〜Ｃの条件（但し、第一段階は行わずに、第二段階の条件のみにて成膜する）にて、上部層のＡｌ２Ｏ３層を表７に示される目標層厚で形成し、比較被覆工具１〜６を製造した。
さらに、参考のため、上記工具基体Ｄ，ｄに対して、先行技術文献（特開平１０−７６４０６号公報）に示されるのとほぼ同等の条件（表５のａ参照）で、上部層の下側部（基体側）に粒状結晶組織を、また、上部層の上側部に柱状結晶組織を形成した比較被覆工具７，８を製造した。
なお、比較被覆工具７，８における柱状結晶組織の形成は、所定層厚の粒状Ａｌ２Ｏ３層を形成した後に、該粒状Ａｌ２Ｏ３層の表面を、ＨＣｌ：３容量％、Ｈ２：残り、からなる組成を有する反応ガスを用い、雰囲気温度：１０５０℃、雰囲気圧力：１０ｋＰａ、保持時間：１５分の条件で処理し、その表面にＣｌを吸着させた状態でＡｌ２Ｏ３層を成膜することにより行った。
また、さらに、参考のため、上記工具基体Ｅ，ｅに対して、先行技術文献（特開平１０−７６４０６号公報）に示されるのとほぼ同等のＡｌ２Ｏ３層形成条件（表５のｂ参照）で、上部層全体を粒状結晶組織とした比較被覆工具９，１０を製造した。
For comparison purposes, a Ti compound layer having a target layer thickness shown in Table 4 is formed on the tool bases A to C and a to c in the same manner as (a) above, and then shown in Table 5. The upper Al 2 O 3 layer is formed with the target layer thickness shown in Table 7 under the conditions of A to C (however, the first stage is not performed and the film is formed only under the second stage conditions). Comparative coated tools 1 to 6 were manufactured.
Further, for reference, the tool bases D and d are below the upper layer under the same conditions (see a in Table 5) as shown in the prior art document (Japanese Patent Laid-Open No. 10-76406). Comparative coated tools 7 and 8 having a granular crystal structure formed on the side (base side) and a columnar crystal structure formed on the upper side of the upper layer were manufactured.
The formation of the columnar crystal structure in comparison coated tool 7 and 8, after forming the particulate the Al 2 O 3 layer having a predetermined layer thickness, the surface of the particulate the Al 2 O 3 layer, HCl: 3 volume%, H 2 : Al 2 O 3 layer in a state in which Cl is adsorbed on the surface by using a reactive gas having a composition consisting of: remaining, treated under conditions of atmospheric temperature: 1050 ° C., atmospheric pressure: 10 kPa, holding time: 15 minutes Was performed by forming a film.
Furthermore, for reference, Al 2 O 3 layer formation conditions (b in Table 5) that are substantially equivalent to those shown in the prior art document (Japanese Patent Laid-Open No. 10-76406) are provided for the tool bases E and e. In comparison, comparative coated tools 9, 10 having the entire upper layer as a granular crystal structure were manufactured.
ついで、上記の本発明被覆工具１〜１０と比較被覆工具１〜１０について、下部層近傍の上部層（下部層と上部層の界面から、上部層側に１μｍまでの深さ領域）に形成された粒状結晶粒について、電界放出型走査電子顕微鏡と電子後方散乱回折像装置を用い、断面研磨面の測定範囲内に存在する上部層酸化アルミニウム層の六方晶結晶格子を有する結晶粒個々に電子線を照射して、工具基体表面の法線に対して、前記結晶粒の結晶面である（０００１）面および（１０−１０）面の法線がなす傾斜角を測定し、この結果得られた測定傾斜角から、それぞれ隣接する結晶粒相互間の界面における（０００１）面の法線同士、および（１０−１０）面の法線同士の交わる角度を求め、さらに、前記（０００１）面の法線同士、および（１０−１０）面の法線同士の交わる角度が２度以上の場合を結晶粒として定義することで識別し、得られた個々の粒状結晶粒の最大径として、粒状結晶粒の平均粒径を求めるとともに、該深さ領域の縦断面総面積に占める粒状結晶粒の占有面積割合を求めた。ここでの粒状結晶粒とは結晶粒の最大径とその最大径に垂直な線を引いた場合に作成される結晶粒との交線において、その最大値をとる線分と前記最大径の比０．６〜１．０であることと定義した。
ついで、同じく本発明被覆工具１〜１０と比較被覆工具１〜１０について、上部層の縦断面に観察される柱状結晶粒について、その平均結晶粒長さとアスペクト比（平均結晶粒長さ／平均結晶粒幅）を前記記載の手法にてＡｌ２Ｏ３結晶粒を識別し、上部層Ａｌ２Ｏ３の最表面から膜の深さ方向に線を引き、その直線とＡｌ２Ｏ３結晶粒との交線が最大となる値を平均結晶粒長さとし、また、平均結晶粒長さ(線分)の中点に垂直な線を引き、その直線とＡｌ２Ｏ３結晶粒との交線の長さを平均結晶粒幅として求め、さらに、該上部層の縦断面総面積に占める柱状結晶粒の占有面積割合を求めた。
表６、７に、これらの値を示す。
Next, the above-described inventive coated tools 1 to 10 and comparative coated tools 1 to 10 are formed in the upper layer in the vicinity of the lower layer (from the interface between the lower layer and the upper layer to a depth region of 1 μm on the upper layer side). Using a field emission scanning electron microscope and an electron backscatter diffraction image apparatus, the individual crystal grains having a hexagonal crystal lattice of the upper aluminum oxide layer existing within the measurement range of the cross-section polished surface Was measured, and the inclination angle formed by the normal lines of the (0001) plane and the (10-10) plane, which are crystal planes of the crystal grains, was measured with respect to the normal line of the tool base surface. From the measured inclination angle, the angles at which the normal lines of the (0001) planes and the normal lines of the (10-10) planes intersect each other at the interface between the adjacent crystal grains are obtained. Lines, and (10-1 ) By identifying the case where the angle between the normals of the surface is 2 degrees or more is defined as a crystal grain, as the maximum diameter of the individual granular crystal grains obtained, the average grain size of the granular crystal grains, The ratio of the occupied area of the granular crystal grains to the total area of the longitudinal section of the depth region was determined. The granular crystal grains here are the ratio between the maximum diameter of the crystal grains and the maximum diameter in the line of intersection with the crystal grains created when a line perpendicular to the maximum diameter is drawn. It was defined as 0.6 to 1.0.
Next, for the present invention coated tools 1 to 10 and comparative coated tools 1 to 10, the average crystal grain length and aspect ratio (average crystal grain length / average crystal) of the columnar crystal grains observed in the longitudinal section of the upper layer Grain width) is identified by the method described above, Al 2 O 3 crystal grains are identified, a line is drawn from the outermost surface of the upper layer Al 2 O 3 in the depth direction of the film, and the straight line and the Al 2 O 3 crystal grains Is the average grain length, and a line perpendicular to the midpoint of the average grain length (line segment) is drawn, and the line of intersection between the straight line and the Al 2 O 3 grain The length was determined as the average crystal grain width, and the ratio of the area occupied by the columnar crystal grains to the total vertical sectional area of the upper layer was determined.
Tables 6 and 7 show these values.
また、本発明被覆工具１〜１０及び比較被覆工具１〜１０の硬質被覆層の各構成層の厚さを、走査型電子顕微鏡を用いて測定（縦断面測定）したところ、いずれも目標層厚と実質的に同じ平均層厚（５点測定の平均値）を示した。 Moreover, when the thickness of each structural layer of the hard coating layer of this invention coated tool 1-10 and comparative coated tool 1-10 was measured using the scanning electron microscope (longitudinal section measurement), all were target layer thickness. The average layer thickness (average value of 5-point measurement) was substantially the same.
つぎに、上記の本発明被覆工具１〜１０及び比較被覆工具１〜１０の各種の被覆工具について、いずれも工具鋼製バイトの先端部に固定治具にてネジ止めした状態で、
被削材：ＪＩＳ・ＳＵＪ２（ＨＲＣ６２）の長さ方向等間隔４本縦溝入り丸棒、
切削速度： ３１５ ｍ／ｍｉｎ．、
切り込み： １．５ ｍｍ、
送り： ０．１７ ｍｍ／ｒｅｖ．、
切削時間： ５ 分、
の条件（切削条件Ａという）での軸受鋼の乾式高速断続切削試験（通常の切削速度は、２００ｍ／ｍｉｎ．）、
被削材：ＪＩＳ・ＳＫＤ１１（ＨＲＣ５８）の長さ方向等間隔４本縦溝入り丸棒、
切削速度： ３２５ ｍ／ｍｉｎ．、
切り込み： ２．２ ｍｍ、
送り： ０．２ ｍｍ／ｒｅｖ．、
切削時間： ５ 分、
の条件（切削条件Ｂという）での合金工具鋼の乾式高速断続切削試験（通常の切削速度は、２５０ｍ／ｍｉｎ．）、
被削材：ＪＩＳ・ＳＫ３（ＨＲＣ６１）の長さ方向等間隔４本縦溝入り丸棒、
切削速度： ２８５ ｍ／ｍｉｎ．、
切り込み： ２．０ ｍｍ、
送り： ０．１７ ｍｍ／ｒｅｖ．、
切削時間： ５ 分、
の条件（切削条件Ｃという）での炭素工具鋼の乾式高速断続切削試験（通常の切削速度は２００ｍ／ｍｉｎ．）、
を行い、いずれの切削試験でも切刃の逃げ面摩耗幅を測定した。
表７にこの測定結果を示した。
Next, for the various coated tools of the present invention coated tools 1 to 10 and the comparative coated tools 1 to 10, all are screwed with a fixing jig to the tip of the tool steel tool,
Work material: JIS / SUJ2 (HRC62) lengthwise equidistant four round grooved round bars,
Cutting speed: 315 m / min. ,
Cutting depth: 1.5 mm,
Feed: 0.17 mm / rev. ,
Cutting time: 5 minutes,
Dry high-speed intermittent cutting test of bearing steel under the conditions (cutting condition A) (normal cutting speed is 200 m / min.),
Work material: JIS · SKD11 (HRC58) lengthwise equidistant four round grooved round bars,
Cutting speed: 325 m / min. ,
Cutting depth: 2.2 mm,
Feed: 0.2 mm / rev. ,
Cutting time: 5 minutes,
Dry high-speed intermittent cutting test (normal cutting speed is 250 m / min.) Of the alloy tool steel under the conditions (referred to as cutting conditions B),
Work material: JIS · SK3 (HRC61) lengthwise equidistant four round grooved round bars,
Cutting speed: 285 m / min. ,
Cutting depth: 2.0 mm,
Feed: 0.17 mm / rev. ,
Cutting time: 5 minutes,
A dry high-speed intermittent cutting test (normal cutting speed is 200 m / min.) Of carbon tool steel under the following conditions (referred to as cutting conditions C),
In each cutting test, the flank wear width of the cutting edge was measured.
Table 7 shows the measurement results.
表６〜８に示される結果から、本発明被覆工具１〜１０は、いずれも、上部層が、層厚方向に縦長に成長した柱状結晶粒と、平均粒径１００〜５００ｎｍの粒状結晶粒とから構成され、さらに、上部層表層側は、柱状結晶粒同士が相互に隙間なく隣接して成長している実質的な柱状組織であり、かつ、下部層近傍の上部層は、隣接していない柱状結晶粒相互の間隙を埋めるように粒状結晶粒が形成された柱状−粒状混合組織であることから、切刃に断続的・衝撃的負荷が作用する高速断続切削条件下でも、上部層と下部層の密着性が向上し、上部層に発生したクラックの伝播・進展が、下部層近傍の上部層に形成された柱状−粒状混合組織で抑制されることによって、剥離、チッピング等の異常損傷の発生が防止され、すぐれた耐摩耗性を発揮する。
これに対して、上部層が柱状組織のみで形成された比較被覆工具１〜６においては、剥離の発生によって短時間で寿命となった。また、上部層の下側部（基体側）に粒状結晶組織が、また、上部層の上側部に柱状結晶組織が形成された比較被覆工具７，８では、剥離の発生により寿命となるか、或いは、剥離が発生しない場合であっても耐摩耗性は不十分であった。さらに、上部層全体を粒状組織で構成した比較被覆工具９，１０では、剥離の発生は見られなかったものの耐摩耗性が劣り、短時間で使用寿命となった。
From the results shown in Tables 6 to 8, all of the coated tools 1 to 10 of the present invention have columnar crystal grains in which the upper layer grows vertically in the layer thickness direction, and granular crystal grains having an average grain diameter of 100 to 500 nm. Furthermore, the upper layer surface layer side is a substantially columnar structure in which columnar crystal grains are grown adjacent to each other without a gap, and the upper layer in the vicinity of the lower layer is not adjacent. Because it is a columnar-granular mixed structure in which granular grains are formed so as to fill the gaps between the columnar grains, the upper layer and the lower layer even under high-speed intermittent cutting conditions in which intermittent and impact loads are applied to the cutting edge The adhesion of the layer is improved, and the propagation / propagation of cracks generated in the upper layer is suppressed by the columnar-granular mixed structure formed in the upper layer near the lower layer, thereby preventing abnormal damage such as peeling and chipping. Occurrence is prevented and excellent wear resistance is achieved. To.
On the other hand, in the comparative coated tools 1-6 in which the upper layer was formed only of the columnar structure, the life was shortened in a short time due to the occurrence of peeling. Further, in the comparative coated tools 7 and 8 in which the granular crystal structure is formed in the lower part (base side) of the upper layer and the columnar crystal structure is formed in the upper part of the upper layer, the life is caused by the occurrence of peeling, Or even if it is a case where peeling does not generate | occur | produce, abrasion resistance was inadequate. Further, in the comparative coated tools 9 and 10 in which the entire upper layer was composed of a granular structure, although no peeling was observed, the wear resistance was inferior and the service life was shortened in a short time.
上述のように、この発明の被覆工具は、軸受鋼や合金工具鋼等の高硬度材の高速断続切削加工ですぐれた切削性能を示すが、通常の鋼や鋳鉄の連続切削、断続切削等において使用することも勿論可能であることから、切削装置の高性能化並びに切削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。
As described above, the coated tool of the present invention exhibits excellent cutting performance in high-speed intermittent cutting of high-hardness materials such as bearing steel and alloy tool steel, but in continuous cutting and intermittent cutting of normal steel and cast iron. Of course, since it can be used, it is possible to satisfactorily meet the demands for higher performance of the cutting device, labor saving and energy saving of the cutting work, and cost reduction.
Claims (3)
（ａ）下部層が、Ｔｉの炭化物層、窒化物層、炭窒化物層、炭酸化物層および炭窒酸化物層のうちの１層または２層以上からなり、かつ、３〜２０μｍの合計平均層厚を有するＴｉ化合物層、
（ｂ）上部層が、３〜１５μｍの平均層厚を有し、かつ、α型の結晶構造を有するＡｌ２Ｏ３層、
上記（ａ）および（ｂ）の蒸着層からなる硬質被覆層が形成された表面被覆切削工具において、
（ｃ）上記上部層は、層厚方向に縦長に成長した柱状結晶粒と、平均粒径５０〜５００ｎｍの粒状結晶粒とから構成され、
（ｄ）下部層直上及び下部層側の上部層においては、隣接していない柱状結晶粒相互の間隙に粒状結晶粒が存在する柱状−粒状混合組織が形成され、
（ｅ）上部層表層側においては、柱状結晶粒同士が相互に隙間なく隣接して成長している実質的な柱状組織が形成されている、
ことを特徴とする表面被覆切削工具。 On the surface of the tool base composed of tungsten carbide based cemented carbide or titanium carbonitride based cermet,
(A) The lower layer is composed of one or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer and carbonitride oxide layer, and a total average of 3 to 20 μm A Ti compound layer having a layer thickness,
(B) an Al 2 O 3 layer in which the upper layer has an average layer thickness of 3 to 15 μm and has an α-type crystal structure;
In the surface-coated cutting tool in which the hard coating layer formed of the vapor deposition layer of (a) and (b) is formed ,
(C) The upper layer is composed of columnar crystal grains grown vertically in the layer thickness direction and granular crystal grains having an average grain size of 50 to 500 nm,
(D) In the upper layer immediately above the lower layer and the upper layer on the lower layer side, a columnar-grain mixed structure in which granular crystal grains exist in the gaps between columnar crystal grains that are not adjacent to each other is formed,
(E) On the upper layer surface side, a substantial columnar structure is formed in which columnar crystal grains are grown adjacent to each other without a gap,
A surface-coated cutting tool characterized by that.
In the upper layer, columnar crystal grains having an average crystal grain length of 60% or more of the average layer thickness of the upper layer and an aspect ratio (average crystal grain length / average crystal grain width) of 2.5 to 7.0 are The surface-coated cutting tool according to claim 1 or 2, wherein a substantially columnar structure occupying 60% by area or more of the longitudinal sectional area of the layer is formed.
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