JP6423286B2 - Surface coated cutting tool with excellent chipping and wear resistance with excellent hard coating layer - Google Patents
Surface coated cutting tool with excellent chipping and wear resistance with excellent hard coating layer Download PDFInfo
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- 238000005520 cutting process Methods 0.000 title claims description 73
- 239000011247 coating layer Substances 0.000 title claims description 19
- 239000010410 layer Substances 0.000 claims description 258
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 133
- 239000010936 titanium Substances 0.000 claims description 91
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- 229910052782 aluminium Inorganic materials 0.000 claims description 14
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 13
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- 239000000758 substrate Substances 0.000 description 26
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- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 17
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- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 9
- 229910017604 nitric acid Inorganic materials 0.000 description 9
- 238000000576 coating method Methods 0.000 description 8
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- FIPWRIJSWJWJAI-UHFFFAOYSA-N Butyl carbitol 6-propylpiperonyl ether Chemical group C1=C(CCC)C(COCCOCCOCCCC)=CC2=C1OCO2 FIPWRIJSWJWJAI-UHFFFAOYSA-N 0.000 description 4
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- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- -1 aluminum alkoxide Chemical class 0.000 description 3
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- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
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- OQCFWECOQNPQCG-UHFFFAOYSA-N 1,3,4,8-tetrahydropyrimido[4,5-c]oxazin-7-one Chemical compound C1CONC2=C1C=NC(=O)N2 OQCFWECOQNPQCG-UHFFFAOYSA-N 0.000 description 1
- LTMRRSWNXVJMBA-UHFFFAOYSA-L 2,2-diethylpropanedioate Chemical compound CCC(CC)(C([O-])=O)C([O-])=O LTMRRSWNXVJMBA-UHFFFAOYSA-L 0.000 description 1
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- WRQNANDWMGAFTP-UHFFFAOYSA-N Methylacetoacetic acid Chemical compound COC(=O)CC(C)=O WRQNANDWMGAFTP-UHFFFAOYSA-N 0.000 description 1
- 229910010413 TiO 2 Inorganic materials 0.000 description 1
- NRTOMJZYCJJWKI-UHFFFAOYSA-N Titanium nitride Chemical compound [Ti]#N NRTOMJZYCJJWKI-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 150000004703 alkoxides Chemical class 0.000 description 1
- SMZOGRDCAXLAAR-UHFFFAOYSA-N aluminium isopropoxide Chemical group [Al+3].CC(C)[O-].CC(C)[O-].CC(C)[O-] SMZOGRDCAXLAAR-UHFFFAOYSA-N 0.000 description 1
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- BEPAFCGSDWSTEL-UHFFFAOYSA-N dimethyl malonate Chemical compound COC(=O)CC(=O)OC BEPAFCGSDWSTEL-UHFFFAOYSA-N 0.000 description 1
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- 238000010894 electron beam technology Methods 0.000 description 1
- XYIBRDXRRQCHLP-UHFFFAOYSA-N ethyl acetoacetate Chemical compound CCOC(=O)CC(C)=O XYIBRDXRRQCHLP-UHFFFAOYSA-N 0.000 description 1
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Landscapes
- Cutting Tools, Boring Holders, And Turrets (AREA)
Description
この発明は、ステンレス鋼等の熱伝導性に乏しい被削材の湿式高速断続切削加工において、硬質被覆層がすぐれた耐チッピング性と耐摩耗性を発揮するゾル−ゲル法で硬質被覆層を形成した表面被覆切削工具（以下、「被覆工具」という）に関する。 In this invention, a hard coating layer is formed by a sol-gel method that exhibits excellent chipping resistance and wear resistance in wet high-speed intermittent cutting of a work material with poor thermal conductivity such as stainless steel. The present invention relates to a surface-coated cutting tool (hereinafter referred to as “coated tool”).
従来から、工具基体表面に、周期律表の４ａ、５ａ、６ａ族から選ばれた少なくとも１種以上の元素の炭化物、窒化物、炭窒化物等からなる硬質皮膜を被覆形成することにより、切削工具の耐摩耗性向上を図ることが知られている。
そして、硬質皮膜のうちでも、α型酸化アルミニウム層は、熱安定性に優れ、反応性が低く、かつ、高硬度であるという点から、上記周期律表の４ａ、５ａ、６ａ族から選ばれた少なくとも１種以上の元素の炭化物、窒化物、炭窒化物等からなる硬質皮膜の最表面層として、α型酸化アルミニウム層を被覆形成した被覆工具が知られているが、切削条件が厳しくなるにしたがって、それに耐え得る切削性能を備えた被覆工具が求められており、そのため、硬質皮膜の最表面層を構成するα型酸化アルミニウム層についても種々の改良・提案がなされている。
その一つとして、高熱発生を伴うとともに、切れ刃に断続的・衝撃的な高負荷が作用する断続切削条件で使用される被覆工具おいて、硬質被覆層中に空孔を導入することによって、硬質被覆層の耐チッピング性を改善することが提案されている。
Conventionally, cutting is performed by coating a hard film made of carbide, nitride, carbonitride, or the like of at least one element selected from groups 4a, 5a, and 6a of the periodic table on the tool base surface. It is known to improve the wear resistance of tools.
Among the hard coatings, the α-type aluminum oxide layer is selected from groups 4a, 5a, and 6a in the periodic table from the viewpoints of excellent thermal stability, low reactivity, and high hardness. Further, a coated tool having an α-type aluminum oxide layer formed thereon is known as the outermost surface layer of a hard coating made of carbide, nitride, carbonitride, or the like of at least one element, but cutting conditions are severe. Accordingly, there is a need for a coated tool having cutting performance that can withstand it, and various improvements and proposals have been made for the α-type aluminum oxide layer that constitutes the outermost surface layer of the hard coating.
As one of them, by introducing voids in the hard coating layer in the coated tool used in intermittent cutting conditions that are accompanied by high heat generation and intermittent and impact high load acts on the cutting edge, It has been proposed to improve the chipping resistance of the hard coating layer.
例えば、特許文献１では、ＷＣ基超硬合金、ＴｉＣＮ基サーメットで構成された工具基体の表面に、（ａ）Ｔｉの炭化物層、窒化物層、炭窒化物層、炭酸化物層、窒酸化物層、および炭窒酸化物層からなるＴｉ化合物層のうちの１層または２層以上からなり、かつ３〜２０μｍの平均層厚を有する下部強靭層、（ｂ）走査型電子顕微鏡により観察された縦断面組織にもとづく測定で、５〜３０％の空孔率を有する多孔質酸化アルミニウム蒸着層からなり、かつ０．５〜１５μｍの平均層厚を有する上部硬質層、（ｃ）窒化チタンからなり、かつ０．５〜５μｍの平均層厚を有する表面補強層からなる硬質被覆層を化学蒸着により形成した被覆工具が提案されており、この被覆工具による合金鋼、鋳鉄の乾式切削加工において、耐チッピング性が改善されることが明らかにされている。 For example, in Patent Document 1, (a) a Ti carbide layer, a nitride layer, a carbonitride layer, a carbonate layer, a nitride oxide is formed on the surface of a tool base composed of a WC-based cemented carbide and a TiCN-based cermet. And a lower tough layer having an average layer thickness of 3 to 20 μm, and observed by a scanning electron microscope It consists of a porous aluminum oxide vapor-deposited layer having a porosity of 5 to 30% as measured based on the longitudinal cross-sectional structure, and an upper hard layer having an average layer thickness of 0.5 to 15 μm, (c) consisting of titanium nitride In addition, there has been proposed a coated tool in which a hard coating layer composed of a surface reinforcing layer having an average layer thickness of 0.5 to 5 μm is formed by chemical vapor deposition. In dry cutting of alloy steel and cast iron using this coated tool, Chipping ability It has been shown to be good.
また、特許文献２では、ＷＣ基超硬合金、ＴｉＣＮ基サーメットからなる工具基体の表面に、硬質被覆層として、Ｔｉ化合物層からなる下部層と酸化アルミニウム層からなる上部層を化学蒸着法で被覆形成した被覆工具において、上部層の層厚方向に０．１μｍの厚み幅間隔で、各厚み幅領域に存在する孔径２〜３０ｎｍの空孔の空孔密度を測定した場合に、空孔密度が２００〜５００個／μｍ２の厚み幅領域と空孔密度が０〜２０個／μｍ２の厚み幅領域とが、上部層の層厚方向に沿って、交互に少なくとも複数領域形成されているような空孔分布形態を形成することが提案されており、この被覆工具を用いた炭素鋼、合金鋼、鋳鉄の乾式高速断続切削加工において、耐チッピング性、耐欠損性が改善されることが明らかにされている。 Further, in Patent Document 2, a lower layer made of a Ti compound layer and an upper layer made of an aluminum oxide layer are coated by chemical vapor deposition on the surface of a tool base made of a WC-based cemented carbide or TiCN-based cermet as a hard coating layer. In the formed coated tool, when the hole density of holes having a diameter of 2 to 30 nm existing in each thickness width region is measured at a thickness width interval of 0.1 μm in the layer thickness direction of the upper layer, the hole density is 200-500 pieces / [mu] m pore density and thickness width region of 2 and a 0-20 pieces / [mu] m 2 thickness width region, along the thickness direction of the upper layer, as is at least a plurality of regions formed alternately It has been proposed to form a uniform pore distribution pattern, and it is clear that chipping resistance and fracture resistance are improved in dry high-speed intermittent cutting of carbon steel, alloy steel, and cast iron using this coated tool Has been.
特許文献３では、ＷＣ基超硬合金、ＴｉＣＮ基サーメットからなる工具基体の表面に、硬質被覆層として、Ｔｉ化合物層からなる下部層と酸化アルミニウム層からなる上部層を化学蒸着法で被覆形成した被覆工具において、上部層中に孔径分布がバイモーダルな分布をとる孔径２〜５０ｎｍの微小空孔を導入すること、好ましくは、該微小空孔の孔径分布の第１ピークが２〜１０ｎｍに存在し、孔径２ｎｍごとにポアを数えたときの第１ピークにおけるポア数密度が２００〜５００個／μｍ２であって、該微小空孔の孔径分布の第２ピークが、２０〜５０ｎｍに存在し、孔径２ｎｍごとにポアを数えたときの第２ピークにおけるポア数密度が１０〜５０個／μｍ２である微小空孔を導入することが提案されており、この被覆工具を用いた炭素鋼、合金鋼、鋳鉄の乾式高速断続切削加工において、耐チッピング性、耐欠損性が改善されることが明らかにされている。 In Patent Document 3, a lower layer made of a Ti compound layer and an upper layer made of an aluminum oxide layer are coated and formed as a hard coating layer on the surface of a tool base made of a WC-based cemented carbide or TiCN-based cermet. In the coated tool, it is preferable to introduce a fine pore having a pore diameter distribution of 2 to 50 nm in the upper layer, and preferably the first peak of the fine pore diameter distribution is present at 2 to 10 nm. The pore number density at the first peak when the pores are counted every 2 nm is 200 to 500 / μm 2 , and the second peak of the pore size distribution of the micropores exists at 20 to 50 nm. , it has been proposed to pore number density in the second peak when the counted pores per pore size 2nm introduces microvoided is 10-50 / [mu] m 2, using the coated tool carbon , Alloy steel, in a dry high speed interrupted cutting of cast iron, chipping resistance, that chipping resistance is improved are clarified.
上記特許文献１〜３で提案されている被覆工具は、いずれも硬質被覆層を構成する酸化アルミニウム層は化学蒸着で形成されており、酸化アルミニウムの熱安定性、非反応性によって、ある程度の耐チッピング性、耐摩耗性を発揮する。
しかし、例えば、ステンレス鋼等の熱伝導性に乏しい被削材の湿式高速断続切削加工においては、大きな衝撃が加わるとともに切れ刃近傍での発熱も大きく、高温硬さの低下や酸化アルミニウム層中の空孔もしくは比較的脆弱である結晶粒界などからクラックが発生し、結晶粒ごと脱落するため、結果として、チッピング等の異常損傷を発生しやすく短寿命となることが多く、長期の使用にわたって十分な耐摩耗性を発揮し得ないという問題があった。
In all of the coated tools proposed in Patent Documents 1 to 3, the aluminum oxide layer constituting the hard coating layer is formed by chemical vapor deposition. Due to the thermal stability and non-reactivity of aluminum oxide, a certain degree of resistance is achieved. Demonstrates chipping and wear resistance.
However, for example, in wet high-speed intermittent cutting of a work material with poor thermal conductivity such as stainless steel, a large impact is applied and heat generation near the cutting edge is large, resulting in a decrease in high-temperature hardness and in the aluminum oxide layer. Cracks are generated from vacancies or relatively weak crystal grain boundaries, and the crystal grains fall off. As a result, abnormal damage such as chipping is likely to occur, often resulting in a short life and sufficient for long-term use. There was a problem that it was not possible to exhibit excellent wear resistance.
そこで、本発明者等は、ステンレス鋼等の熱伝導性に乏しい被削材の湿式高速断続切削加工等のチッピングを発生し易い切削条件においても、耐チッピング性に優れたα型酸化アルミニウム層をゾル−ゲル法により形成すべく鋭意検討したところ、α型酸化アルミニウム層の結晶粒界及び結晶粒内に微細空孔を均一に分散分布することにより、ステンレス鋼等の湿式高速断続切削加工において、α型酸化アルミニウム層表面から工具基体への熱伝導経路が減少するとともに、α型酸化アルミニウム層の摩耗が進行した場合にも、微細空孔に切削液が入り込むため、切れ刃部分の表面積が大きくなることによる放熱効果が高まり、α型酸化アルミニウム層及び工具基体の温度上昇を抑制し得ることから、高温硬さの低下を防止することができ長期の使用にわたって耐摩耗性を維持し得ること得ること、さらに、均一に分散分布する微細空孔によって、α型酸化アルミニウム層の耐熱的衝撃性及び耐機械的衝撃性が向上することを見出した。 Therefore, the present inventors have formed an α-type aluminum oxide layer excellent in chipping resistance even under cutting conditions that are likely to generate chipping such as wet high-speed intermittent cutting of a work material having poor thermal conductivity such as stainless steel. As a result of diligent study to form by the sol-gel method, by uniformly dispersing and distributing fine pores in the crystal grain boundaries and crystal grains of the α-type aluminum oxide layer, in wet high-speed intermittent cutting such as stainless steel, The heat conduction path from the surface of the α-type aluminum oxide layer to the tool base decreases, and even when the wear of the α-type aluminum oxide layer progresses, the cutting fluid enters the fine holes, so the surface area of the cutting edge is large. The heat dissipation effect is increased and the temperature rise of the α-type aluminum oxide layer and the tool base can be suppressed. It has been found that the wear resistance can be maintained over use, and further, the thermal shock resistance and mechanical shock resistance of the α-type aluminum oxide layer are improved by the finely dispersed pores.
また、α型酸化アルミニウム層中に均一に分散分布する微細空孔を形成するにあたり、微細空孔の周囲あるいは微細空孔の周囲の一部分に、微細空孔に隣接してＴｉ酸化物を形成することによって、微細空孔の存在によりもたらされるα型酸化アルミニウム層の強度低下が防止されることを見出した。 Further, when forming fine vacancies that are uniformly distributed in the α-type aluminum oxide layer, a Ti oxide is formed adjacent to the fine vacancies around the fine vacancies or a part of the circumference of the fine vacancies. As a result, it was found that the strength reduction of the α-type aluminum oxide layer caused by the presence of fine pores is prevented.
さらに、ゾル−ゲル法で形成したα型酸化アルミニウム層は、その表面粗さが非常に小さいため、切屑流れが良く、化学蒸着法等で成膜したα型酸化アルミニウム層に比して切削加工時の発熱が抑制されるため、溶着等に起因するチッピングの発生を抑制し得ることを見出した。 Furthermore, the α-type aluminum oxide layer formed by the sol-gel method has a very small surface roughness, so the chip flow is good, and the cutting process is better than the α-type aluminum oxide layer formed by chemical vapor deposition. It was found that the generation of chipping due to welding or the like can be suppressed because heat generation at the time is suppressed.
そして、このようなα型酸化アルミニウム層を被覆形成した被覆工具を、切れ刃に断続的・衝撃的負荷が作用するステンレス鋼等の熱伝導性に乏しい被削材の湿式高速断続切削加工に供した場合、チッピングを発生することがなく、長期の使用に亘ってすぐれた耐摩耗性を発揮することを見出したのである。 Then, such a coated tool coated with an α-type aluminum oxide layer is subjected to wet high-speed intermittent cutting of a work material with poor thermal conductivity such as stainless steel in which intermittent and impact loads are applied to the cutting edge. In this case, it was found that chipping does not occur and excellent wear resistance is exhibited over a long period of use.
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） Ｔｉ成分を含有する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からなる工具基体の表面に、硬質被覆層が被覆形成された表面被覆切削工具において、
（ａ）前記硬質被覆層は、ゾル−ゲル法により形成された０．５〜４．０μｍの平均層厚を有するα型酸化アルミニウム層であり、
（ｂ）前記α型酸化アルミニウム層中には、平均孔径が１０〜１００ｎｍである微細空孔が分散して形成され、かつ、α型酸化アルミニウム層の縦断面で測定した前記微細空孔の平均密度は３０〜７０個／μｍ２であり、
（ｃ）前記微細空孔は、α型酸化アルミニウム結晶粒の結晶粒界及び結晶粒内に均一に分散分布し、所定の観察視野範囲における前記空孔密度を所定視野数にわたって求めた場合の標準偏差が１５個／μｍ２以下であり、
（ｄ）前記微細空孔のうち、微細空孔の周囲の少なくとも一部分に、微細空孔に隣接してＴｉ酸化物が形成されている微細空孔の個数割合は、全微細空孔数の５０％以上であることを特徴とする表面被覆切削工具。
（２） 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からなる工具基体の表面に、下部層と上部層からなる硬質被覆層が被覆形成された表面被覆切削工具において、
（ａ）前記下部層は、化学蒸着法、物理蒸着法またはゾル−ゲル法により成膜されたＴｉの窒化物層、炭窒化物層、酸化物層、炭酸化物層、炭窒酸化物層、ＴｉとＡｌの窒化物層の何れか１層または２層以上からなるＴｉ化合物層であり、
（ｂ）前記上部層は、ゾル−ゲル法により形成された０．５〜４．０μｍの平均層厚を有するα型酸化アルミニウム層であり、
（ｃ）前記α型酸化アルミニウム層中には、平均孔径が１０〜１００ｎｍである微細空孔が分散して形成され、かつ、α型酸化アルミニウム層の縦断面で測定した前記微細空孔の平均密度は３０〜７０個／μｍ２であり、
（ｄ）前記微細空孔は、α型酸化アルミニウム結晶粒の結晶粒界及び結晶粒内に均一に分散分布し、所定の観察視野範囲における前記空孔密度を所定視野数にわたって求めた場合の標準偏差が１５個／μｍ２以下であり、
（ｅ）前記微細空孔のうち、微細空孔の周囲の少なくとも一部分に、微細空孔に隣接してＴｉ酸化物が形成されている微細空孔の個数割合は、全微細空孔数の５０％以上であることを特徴とする表面被覆切削工具。
（３） 前記α型酸化アルミニウム層におけるα型酸化アルミニウム結晶粒のアスペクト比を層厚垂直方向の粒径に対する層厚方向の粒径の比とした場合に前記結晶粒の平均アスペクト比は、０．５〜５．０であることを特徴とする（１）または（２）に記載の表面被覆切削工具。
（４） 前記α型酸化アルミニウム層の表面粗さＲａは０．０３μｍ以下であることを特徴とする（１）乃至（３）のいずれかに記載の表面被覆切削工具。
（５） 炭化タングステン基超硬合金からなる工具基体の表面から深さ方向に０．５〜３．０μｍの平均層厚を有する基体表面硬化層が形成され、該基体表面硬化層に含まれる結合相金属としてのＣｏの平均含有量が、２．０質量％未満であることを特徴とする（１）乃至（４）のいずれかに記載の表面被覆切削工具。
（６） 炭窒化チタン基サーメットからなる工具基体の表面から深さ方向に０．５〜３．０μｍの平均層厚を有する基体表面硬化層が形成され、該基体表面硬化層に含まれる結合相金属としてのＣｏ及びＮｉの合計平均含有量が、２．０質量％未満であることを特徴とする（１）乃至（４）のいずれかに記載の表面被覆切削工具。」
を特徴とするものである。
This invention has been made based on the above findings,
“(1) In a surface-coated cutting tool in which a hard coating layer is formed on the surface of a tool base composed of a tungsten carbide-based cemented carbide containing a Ti component or a titanium carbonitride-based cermet,
(A) The hard coating layer is an α-type aluminum oxide layer formed by a sol-gel method and having an average layer thickness of 0.5 to 4.0 μm,
(B) In the α-type aluminum oxide layer, fine pores having an average pore diameter of 10 to 100 nm are dispersed and formed, and the average of the fine pores measured in the longitudinal section of the α-type aluminum oxide layer The density is 30-70 / μm 2 ,
(C) The standard in the case where the fine vacancies are uniformly distributed in the crystal grain boundaries and crystal grains of the α-type aluminum oxide crystal grains, and the vacancy density in a predetermined observation visual field range is obtained over a predetermined visual field number. The deviation is 15 pieces / μm 2 or less,
(D) Among the fine vacancies, the number ratio of the fine vacancies in which Ti oxide is formed adjacent to the fine vacancies in at least a part around the fine vacancies is 50 of the total fine vacancies. A surface-coated cutting tool characterized by being at least%.
(2) In a surface-coated cutting tool in which a hard coating layer composed of a lower layer and an upper layer is coated on the surface of a tool base composed of a tungsten carbide-based cemented carbide or a titanium carbonitride-based cermet,
(A) The lower layer is a Ti nitride layer, carbonitride layer, oxide layer, carbonate layer, carbonitride oxide layer formed by chemical vapor deposition, physical vapor deposition, or sol-gel method, Ti compound layer composed of one or more of Ti and Al nitride layers,
(B) The upper layer is an α-type aluminum oxide layer formed by a sol-gel method and having an average layer thickness of 0.5 to 4.0 μm,
(C) In the α-type aluminum oxide layer, fine pores having an average pore diameter of 10 to 100 nm are dispersed and formed, and the average of the fine pores measured in the longitudinal section of the α-type aluminum oxide layer The density is 30-70 / μm 2 ,
(D) The standard in the case where the fine vacancies are uniformly distributed in the crystal grain boundaries and crystal grains of the α-type aluminum oxide crystal grains, and the vacancy density in a predetermined observation visual field range is obtained over a predetermined visual field number. The deviation is 15 pieces / μm 2 or less,
(E) Among the fine vacancies, the number ratio of the fine vacancies in which Ti oxide is formed adjacent to the fine vacancies in at least a part around the fine vacancies is 50 of the total fine vacancies. A surface-coated cutting tool characterized by being at least%.
(3) When the aspect ratio of the α-type aluminum oxide crystal grains in the α-type aluminum oxide layer is the ratio of the grain size in the layer thickness direction to the grain size in the layer thickness vertical direction, the average aspect ratio of the crystal grains is 0 The surface-coated cutting tool according to (1) or (2), wherein the surface-coated cutting tool is .5 to 5.0.
(4) The surface-coated cutting tool according to any one of (1) to (3), wherein the α-type aluminum oxide layer has a surface roughness Ra of 0.03 μm or less.
(5) Bonding included in the base surface hardened layer in which a base surface hardened layer having an average layer thickness of 0.5 to 3.0 μm is formed in the depth direction from the surface of the tool base made of tungsten carbide base cemented carbide. The surface-coated cutting tool according to any one of (1) to (4), wherein an average content of Co as a phase metal is less than 2.0% by mass.
(6) A base surface hardened layer having an average layer thickness of 0.5 to 3.0 μm in the depth direction from the surface of the tool base made of a titanium carbonitride-based cermet is formed, and the binder phase contained in the base surface hardened layer The surface-coated cutting tool according to any one of (1) to (4), wherein the total average content of Co and Ni as a metal is less than 2.0% by mass. "
It is characterized by.
以下、本発明について、詳細に説明する。 Hereinafter, the present invention will be described in detail.
この発明の被覆工具は、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からなる工具基体の表面に、硬質被覆層として、少なくともゾル−ゲル法により形成されたα型酸化アルミニウム層を被覆形成する。
そして、前記ゾル−ゲル法により形成されたα型酸化アルミニウム層においては、該層中に微細空孔が形成されるとともに、α型酸化アルミニウム層を形成するゾル−ゲルの工程において、工具基体あるいは下部層の成分であるＴｉがα型酸化アルミニウム層へ拡散し、しかも、前記微細空孔の周囲の少なくとも一部分に、微細空孔に隣接してＴｉ酸化物を形成することが必要である。
そこで、本発明の被覆工具では、使用する工具基体によって、硬質被覆層の構造（下部層の形成の要否）が異なる。
なお、本発明では、上部層は、下部層からのＴｉ成分の拡散によってＴｉ酸化物を必ず含有するから、上部層を厳密に表現すれば「Ｔｉ酸化物を含有するα型酸化アルミニウム層」ということになるが、便宜上、単に、「α型酸化アルミニウム層」と表現することとする。
The coated tool of the present invention is formed by coating at least an α-type aluminum oxide layer formed by a sol-gel method as a hard coating layer on the surface of a tool base made of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet. To do.
In the α-type aluminum oxide layer formed by the sol-gel method, fine vacancies are formed in the layer, and in the sol-gel step of forming the α-type aluminum oxide layer, the tool base or It is necessary that Ti, which is a component of the lower layer, diffuses into the α-type aluminum oxide layer, and that Ti oxide is formed adjacent to the fine vacancies in at least a part of the periphery of the fine vacancies.
Therefore, in the coated tool of the present invention, the structure of the hard coating layer (necessity of forming the lower layer) differs depending on the tool base used.
In the present invention, the upper layer necessarily contains Ti oxide due to the diffusion of the Ti component from the lower layer. Therefore, if the upper layer is expressed strictly, it is called “α-type aluminum oxide layer containing Ti oxide”. However, for convenience, it is simply expressed as “α-type aluminum oxide layer”.
まず、工具基体である炭化タングステン基超硬合金がその成分としてＴｉを含有する場合には、その表面へ、直接、ゾル−ゲル法によりα型酸化アルミニウム層を形成することができ、また、これによって、α型酸化アルミニウム層中へのＴｉ成分の拡散が生じる。
ただし、工具基体である炭化タングステン基超硬合金がその成分としてＴｉを含有する場合に、炭化タングステン基超硬合金の表面に下部層を形成し、その上に、ゾル−ゲル法により上部層を形成しても良く、この場合には、炭化タングステン基超硬合金−下部層−上部層の密着強度の向上が図られる。
しかし、工具基体である炭化タングステン基超硬合金がその成分としてＴｉを含有していない場合には、化学蒸着法、物理蒸着法またはゾル−ゲル法により成膜されたＴｉの窒化物層、炭窒化物層、酸化物層、炭酸化物層、炭窒酸化物層、ＴｉとＡｌの窒化物層の何れか１層または２層以上からなるＴｉ化合物層を下部層として形成し、この上に、上部層としての前記ゾル−ゲル法によりα型酸化アルミニウム層を形成することにより、下部層成分であるＴｉをα型酸化アルミニウム層中へ拡散させることが必要である。
上記の如く、工具基体である炭化タングステン基超硬合金からのＴｉの拡散、あるいは、下部層であるＴｉ化合物層からのＴｉの拡散によって、α型酸化アルミニウム層中の微細空孔の周囲の少なくとも一部分に、微細空孔に隣接してＴｉ酸化物が形成される。
なお、ここで、炭化タングステン基超硬合金がその成分としてＴｉを含有するとは、炭化タングステン基超硬合金に含有される金属成分全体の中で、２．０質量％以上のＴｉが含有される場合をいう。
First, when the tungsten carbide base cemented carbide which is a tool substrate contains Ti as its component, an α-type aluminum oxide layer can be directly formed on the surface by a sol-gel method. As a result, the Ti component diffuses into the α-type aluminum oxide layer.
However, when the tungsten carbide base cemented carbide, which is the tool base, contains Ti as its component, a lower layer is formed on the surface of the tungsten carbide base cemented carbide, and an upper layer is formed thereon by a sol-gel method. In this case, the adhesion strength of the tungsten carbide-based cemented carbide-lower layer-upper layer can be improved.
However, when the tungsten carbide base cemented carbide which is the tool base does not contain Ti as its component, a Ti nitride layer formed by chemical vapor deposition, physical vapor deposition or sol-gel method, carbon Form a nitride layer, oxide layer, carbonate layer, carbonitride oxide layer, Ti compound layer composed of one or more of Ti and Al nitride layers as a lower layer, It is necessary to diffuse Ti as a lower layer component into the α-type aluminum oxide layer by forming the α-type aluminum oxide layer by the sol-gel method as the upper layer.
As described above, at least around the micropores in the α-type aluminum oxide layer by diffusion of Ti from the tungsten carbide base cemented carbide as the tool base or diffusion of Ti from the Ti compound layer as the lower layer. In part, Ti oxide is formed adjacent to the microvoids.
Here, the tungsten carbide-based cemented carbide containing Ti as its component means that 2.0% by mass or more of Ti is contained in the entire metal component contained in the tungsten carbide-based cemented carbide. Refers to cases.
一方、工具基体として炭窒化チタン基サーメットを用いる場合には、工具基体の成分として必ずＴｉが含有されており、このＴｉの拡散が生じることから、炭窒化チタン基サーメット表面に、直接、ゾル−ゲル法によりα型酸化アルミニウム層を形成することができる。また、炭窒化チタン基サーメット表面に、前記下部層を介して、ゾル−ゲル法によりα型酸化アルミニウム層を形成することも勿論可能であり、この場合には、炭窒化チタン基サーメット−下部層−上部層の密着強度が向上する。 On the other hand, when a titanium carbonitride-based cermet is used as the tool base, Ti is always contained as a component of the tool base, and this Ti diffusion occurs, so that the sol- An α-type aluminum oxide layer can be formed by a gel method. Further, it is of course possible to form an α-type aluminum oxide layer on the surface of the titanium carbonitride-based cermet by the sol-gel method via the lower layer. In this case, the titanium carbonitride-based cermet-lower layer -The adhesion strength of the upper layer is improved.
下部層は、化学蒸着法、物理蒸着法またはゾル−ゲル法により成膜されたＴｉの窒化物層、炭窒化物層、酸化物層、炭酸化物層、炭窒酸化物層、ＴｉとＡｌの窒化物層の何れか１層または２層以上からなるＴｉ化合物層として形成される。
下部層は、前記のとおり、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からなる工具基体と上部層との密着強度を高めるとともに、後記するように、下部層の成分であるＴｉを上部層のα型酸化アルミニウム層中へ拡散させ、酸化アルミニウム層中に形成される微細空孔の周囲の一部分にＴｉ酸化物を形成し、微細空孔の存在によりもたらされるα型酸化アルミニウム層の強度低下を防止する。
上部層は、ゾル−ゲル法により成膜した平均層厚０．５〜４．０μｍのα型酸化アルミニウム層を備えるが、上部層の平均層厚が０．５μｍ未満であると、長期の使用に亘って十分な耐摩耗性を発揮することができず、一方、平均層厚が４．０μｍを超えると、チッピングが発生しやすくなるため、ゾル−ゲル法により形成するα型酸化アルミニウム層の層厚は０．５〜４．０μｍと定めた。
また、ゾル−ゲル法によりα型酸化アルミニウム層を形成することにより、従来の成膜法（例えば、化学蒸着法、物理蒸着法等）により成膜したα型酸化アルミニウム層に比して、その表面粗さＲａが小さく０．０３μｍ以下であるため、熱伝導性に乏しいステンレス鋼等の被削材の湿式高速断続切削加工において、摩擦により発生する高熱による工具基体の強度低下を防止し得るとともに、溶着に起因するチッピングの発生を抑制することができる。
The lower layer is a Ti nitride layer, carbonitride layer, oxide layer, carbonate layer, carbonitride oxide layer, Ti and Al layer formed by chemical vapor deposition, physical vapor deposition or sol-gel method. It is formed as a Ti compound layer composed of one or more of the nitride layers.
As described above, the lower layer increases the adhesion strength between the upper layer and the tool base made of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet. The α-type aluminum oxide layer is diffused into the α-type aluminum oxide layer, and Ti oxide is formed in a part of the periphery of the fine vacancies formed in the aluminum oxide layer. Prevent decline.
The upper layer includes an α-type aluminum oxide layer having an average layer thickness of 0.5 to 4.0 μm formed by a sol-gel method. If the average layer thickness of the upper layer is less than 0.5 μm, long-term use On the other hand, when the average layer thickness exceeds 4.0 μm, chipping is likely to occur. Therefore, the α-type aluminum oxide layer formed by the sol-gel method is not easily exhibited. The layer thickness was set to 0.5 to 4.0 μm.
In addition, by forming an α-type aluminum oxide layer by a sol-gel method, compared to an α-type aluminum oxide layer formed by a conventional film formation method (for example, chemical vapor deposition method, physical vapor deposition method, etc.) Since the surface roughness Ra is small and 0.03 μm or less, it is possible to prevent the strength reduction of the tool base due to high heat generated by friction in wet high-speed intermittent cutting of a work material such as stainless steel with poor thermal conductivity. The occurrence of chipping due to welding can be suppressed.
図１（ａ）に、本発明のゾル−ゲル法により形成したα型酸化アルミニウム層についての、ＣＰ加工した断面ＳＥＭ像を示し、図１（ｂ）に、その模式図を示す。
本発明のα型酸化アルミニウム層は、後記するゾル−ゲル法により成膜されることにより、図１（ｂ）にも示されるように、層中に微細な空孔が結晶粒界ばかりでなく結晶粒内にも均一に分散して形成され、この微細空孔の存在によって、ステンレス鋼等の湿式高速断続切削において、α型酸化アルミニウム層表面から工具基体への熱伝導経路が減少し、さらに、切れ刃部分の表面積が大きいことにより放熱効果が高まり、α型酸化アルミニウム層及び工具基体の温度上昇を抑制し得る。
その結果として、切れ刃部分の高温硬さの低下を防止することができるため、すぐれた耐摩耗性が発揮される。
さらに、層中に均一に分散分布する微細空孔によって、高速断続切削における耐熱的衝撃性及び耐基体的衝撃性が向上する。
なお、前掲特許文献１〜３でも層中に空孔を形成することは知られているが、前記従来技術では、結晶粒界に空孔が形成されやすく、本発明でいうように、微細な空孔が結晶粒界ばかりでなく結晶粒内にも均一に分散して形成されるものではなかった。
FIG. 1A shows a cross-sectional SEM image obtained by CP processing of an α-type aluminum oxide layer formed by the sol-gel method of the present invention, and FIG. 1B shows a schematic diagram thereof.
The α-type aluminum oxide layer of the present invention is formed by a sol-gel method to be described later, so that as shown in FIG. It is formed evenly distributed in the crystal grains, and the presence of these fine pores reduces the heat conduction path from the α-type aluminum oxide layer surface to the tool base in wet high-speed intermittent cutting of stainless steel and the like, and Since the surface area of the cutting edge portion is large, the heat dissipation effect is enhanced, and the temperature rise of the α-type aluminum oxide layer and the tool base can be suppressed.
As a result, it is possible to prevent the high-temperature hardness of the cutting edge portion from being lowered, and thus excellent wear resistance is exhibited.
Further, the fine pores uniformly distributed in the layer improve the thermal shock resistance and the substrate impact resistance in high-speed intermittent cutting.
In the above-mentioned Patent Documents 1 to 3, it is known that vacancies are formed in the layer. However, in the conventional technique, vacancies are easily formed in the crystal grain boundaries, and as described in the present invention, fine pores are formed. The vacancies were not uniformly dispersed not only in the crystal grain boundaries but also in the crystal grains.
ここで、α型酸化アルミニウム層中に形成される微細空孔の平均孔径が１０ｎｍ未満であると、切削加工時の熱伝導経路の遮断効果が小さく、一方、平均孔径が１００ｎｍを超えると層中に脆弱部が形成されることになり破壊を起こしやすくなる。
したがって、α型酸化アルミニウム層中に形成される微細空孔の平均孔径は１０〜１００ｎｍとする。
Here, if the average pore diameter of the fine pores formed in the α-type aluminum oxide layer is less than 10 nm, the effect of blocking the heat conduction path during cutting is small, while if the average pore diameter exceeds 100 nm, A weak part is formed on the surface, and it is easy to cause destruction.
Therefore, the average pore diameter of fine pores formed in the α-type aluminum oxide layer is 10 to 100 nm.
また、α型酸化アルミニウム層の縦断面について測定した微細空孔の平均密度が、３０個／μｍ２未満であると、切削加工時の熱伝導経路の減少に寄与せず、一方、７０個／μｍ２を超えるとα型酸化アルミニウム層の強度が低下することから、微細空孔の平均密度は、３０〜７０個／μｍ２とする。 Further, if the average density of fine pores measured for the longitudinal section of the α-type aluminum oxide layer is less than 30 / μm 2, it does not contribute to the reduction of the heat conduction path during the cutting process, while 70 / If it exceeds μm 2 , the strength of the α-type aluminum oxide layer decreases, so the average density of fine pores is 30 to 70 / μm 2 .
また、α型酸化アルミニウム層中に形成される微細空孔について、前記空孔密度を所定の観察視野範囲及び視野数、例えば０．３×０．３μｍの視野範囲における観察を１０視野ずつ求め、全視野にわたって標準偏差（即ち、微細空孔の分散分布の度合い）を求めたとき、その値が１５個／μｍ２より大きいと、局所的に微細空孔が集中して形成されることとなり、高速断続切削時の衝撃によって、異常損傷を発生することになるから、微細空孔の標準偏差を１５個／μｍ２以下として、微細空孔を均一に分散分布させる。 Further, for the fine vacancies formed in the α-type aluminum oxide layer, the vacancy density is determined for each 10 visual fields in a predetermined observation visual field range and the number of visual fields, for example, a visual field range of 0.3 × 0.3 μm, When the standard deviation (that is, the degree of dispersion distribution of fine vacancies) is obtained over the entire visual field, if the value is larger than 15 / μm 2 , fine vacancies are locally concentrated and formed. Since abnormal damage occurs due to impact during high-speed intermittent cutting, the standard deviation of the fine holes is set to 15 pieces / μm 2 or less, and the fine holes are uniformly distributed.
本発明のα型酸化アルミニウム層における微細空孔の平均孔径、平均密度、分布の標準偏差（即ち、微細空孔の分散分布の度合い）は前記のとおりであるが、本発明のα型酸化アルミニウム層には、微細空孔の周囲の少なくとも一部分にＴｉ酸化物が形成されている微細空孔が存在する。このようなＴｉ酸化物は、下部層からのＴｉ成分の拡散によって形成され、微細空孔の周囲の少なくとも一部分にＴｉ酸化物が形成されていることによって、微細空孔が存在することによるα型酸化アルミニウム層の脆弱化が防止され、特に、耐チッピング性の向上に寄与する。そして、耐チッピング性向上効果を得るためには、α型酸化アルミニウム層中に存在する微細空孔の全個数のうち、５０％以上の微細空孔について、微細空孔の周囲の少なくとも一部分にＴｉ酸化物が形成されていることが必要であり、５０％未満の場合には、α型酸化アルミニウム層の強度低下を補うことは難しいため、耐チッピング性向上効果を期待することはできない。なお、微細空孔の全個数のうち、５０％以上の微細空孔の周囲の少なくとも一部分にＴｉ酸化物が形成されていることが必要である。また、耐チッピング性に寄与するために、Ｔｉ酸化物の粒径は０．０３〜０．１μｍとなることが望ましい。これは０．０３μｍ未満であると、切削加工時の負荷を吸収することができず、一方、０．１μｍを超えると比較的粗大な粒子が形成され、Ｔｉ酸化物粒子自体が脆弱部となりうるためである。 In the α-type aluminum oxide layer of the present invention, the average pore diameter, average density, and standard deviation of distribution (that is, the degree of dispersion of fine pores) are as described above. The layer has fine vacancies in which Ti oxide is formed in at least a part of the periphery of the fine vacancies. Such a Ti oxide is formed by diffusion of a Ti component from the lower layer, and the Ti oxide is formed in at least a part of the periphery of the fine vacancies, so that the α-type due to the presence of the fine vacancies is formed. Brittleness of the aluminum oxide layer is prevented, and particularly contributes to improvement of chipping resistance. In order to obtain an effect of improving chipping resistance, 50% or more of the fine vacancies in the total number of fine vacancies existing in the α-type aluminum oxide layer are formed on at least a part of the circumference of the fine vacancies. It is necessary that an oxide is formed, and when it is less than 50%, it is difficult to compensate for the decrease in strength of the α-type aluminum oxide layer, and therefore an effect of improving chipping resistance cannot be expected. In addition, it is necessary that Ti oxide is formed in at least a part of the periphery of the fine holes of 50% or more out of the total number of fine holes. Moreover, in order to contribute to chipping resistance, the particle size of the Ti oxide is desirably 0.03 to 0.1 μm. If this is less than 0.03 μm, the load during cutting cannot be absorbed. On the other hand, if it exceeds 0.1 μm, relatively coarse particles are formed, and the Ti oxide particles themselves can be fragile parts. Because.
α型酸化アルミニウム層中の微細空孔の周囲の少なくとも一部分に、Ｔｉ酸化物が隣接して形成されているか否かは、例えば、走査型電子顕微鏡（ＳＥＭ）とオージェ電子分光装置（ＡＥＳ）を用いて確認することができる。まず、０．７×０．７μｍの観察視野範囲に観察される微細空孔の位置をＳＥＭにて特定し、続いて、該観察範囲をオージェ電子分光装置を用いて、前記ＳＥＭにて特定した微細空孔の周囲の元素マッピングを行うと微細空孔の周囲の少なくとも一部分に、Ｔｉ酸化物が隣接して形成されているか否かを判別することができる。 Whether or not the Ti oxide is formed adjacent to at least a part of the fine pores in the α-type aluminum oxide layer is determined by, for example, using a scanning electron microscope (SEM) and an Auger electron spectrometer (AES). Can be confirmed. First, the position of the microscopic void observed in the observation field range of 0.7 × 0.7 μm was specified by SEM, and then the observation range was specified by the SEM using an Auger electron spectrometer. When element mapping around the fine vacancies is performed, it can be determined whether or not Ti oxide is formed adjacent to at least a part of the circumference of the fine vacancies.
本発明のα型酸化アルミニウム層におけるα型酸化アルミニウム結晶粒の平均アスペクト比は、０．５未満では耐摩耗性に乏しく、一方、５．０を超えると粗大組織となるため脱落チッピングがしやすくなる。したがって、酸化アルミニウム層を構成する結晶粒の平均アスペクト比は０．５〜５．０とすることが好ましい。 When the average aspect ratio of the α-type aluminum oxide crystal grains in the α-type aluminum oxide layer of the present invention is less than 0.5, the wear resistance is poor. Become. Therefore, the average aspect ratio of the crystal grains constituting the aluminum oxide layer is preferably 0.5 to 5.0.
本発明のゾル−ゲル法によるα型酸化アルミニウム層は、工具基体表面に直接あるいは下部層を介して形成するが、工具基体自体に特定の処理を施しておくことで、工具基体と硬質被覆層の密着強度を更に高めることができる。
例えば、炭化タングステン基超硬合金を工具基体とする場合、窒素雰囲気中での焼成により、工具基体表面付近に、耐摩耗性の高いＴｉ炭窒化物等を多く含有させ、基体表面硬化層を形成させることによって、工具基体と硬質被覆層の密着強度を向上させ、工具寿命を延長することが可能となる。
なお、Ｔｉばかりでなく、さらに、Ｔａ、Ｎｂ、Ｚｒの１種または２種以上を含有させておくことにより、基体表面硬化層を形成させてもよい。
そして、炭窒化物を多く含有させることで基体表面付近におけるＣｏは相対的に減ることとなり、例えば、走査型電子顕微鏡（ＳＥＭ）を用いた表面から深さ方向に０．５〜３．０μｍの断面観察を行い、分析視野領域１×１μｍの範囲にて波長分散型Ｘ線分光法による定量分析により、結合相金属としてのＣｏの含有量を検出した場合に、Ｃｏの含有量を２．０質量％未満にすれば、基体の表面硬化の要因となる炭窒化物が十分に形成され、耐摩耗性がより向上する。
なお、基体表面硬化層を形成した後の炭化タングステン基超硬合金基体の硬さはビッカース硬さ（Ｈｖ）で２２００以上、２８００以下であることが好ましい。
また、基体表面硬化層の平均層厚は０．５μｍ以下であると耐摩耗性が十分発揮できないまま比較的すぐに磨滅してしまい、３．０μｍ以上であるとチッピングしやすくなるので、基体表面硬化層の平均層厚は０．５〜３．０μｍであることが好ましい。
The α-type aluminum oxide layer by the sol-gel method of the present invention is formed directly on the tool base surface or via a lower layer, but the tool base and the hard coating layer are formed by subjecting the tool base itself to a specific treatment. The adhesion strength can be further increased.
For example, when a tungsten carbide base cemented carbide is used as a tool base, a hardened surface of the base is formed by containing a large amount of highly wear-resistant Ti carbonitride near the tool base surface by firing in a nitrogen atmosphere. By doing so, the adhesion strength between the tool base and the hard coating layer can be improved, and the tool life can be extended.
In addition to Ti, the substrate surface hardened layer may be formed by further containing one or more of Ta, Nb, and Zr.
And by containing a large amount of carbonitrides, Co in the vicinity of the substrate surface is relatively reduced. For example, 0.5 to 3.0 μm in the depth direction from the surface using a scanning electron microscope (SEM). When the content of Co as a binder phase metal is detected by cross-sectional observation and quantitative analysis by wavelength dispersive X-ray spectroscopy in an analysis visual field region of 1 × 1 μm, the Co content is set to 2.0. When the amount is less than mass%, carbonitrides that cause surface hardening of the substrate are sufficiently formed, and wear resistance is further improved.
In addition, it is preferable that the hardness of the tungsten carbide based cemented carbide substrate after forming the substrate surface hardened layer is 2200 or more and 2800 or less in terms of Vickers hardness (Hv).
Further, if the average thickness of the substrate surface hardened layer is 0.5 μm or less, it will be worn away relatively quickly without sufficiently exhibiting the wear resistance, and if it is 3.0 μm or more, chipping is likely to occur. It is preferable that the average layer thickness of a hardened layer is 0.5-3.0 micrometers.
また、炭窒化チタン基サーメットを工具基体とする場合には、焼結工程において昇温及び最高温度で保持する際の雰囲気を所定の窒素雰囲気とし、保持の途中もしくは降温する際に減圧することにより、全焼結工程を一定圧力の窒素雰囲気中で実施した場合よりも表面を硬化させることができる。これは、最高温度で保持するまでの工程を一定の窒素圧力下で実施すると、基体内部に均一に硬さの高い炭窒化物が分散形成されるが、これを昇温、または保持の途中までは比較的高い窒素圧力下で処理し、保持の途中もしくは降温時から、より減圧された窒素雰囲気にして処理すると、基体のごく表面のみ脱窒されることにより、ＮｉやＣｏなどの結合相へのＴｉやＮｂなどの溶解及び内部から基体表面への拡散が活発となり、ＴｉやＮｂなどの炭窒化物の形成が表面にて促進され、基体表面硬化層が形成されるためである。
そして、上記炭化タングステン基超硬合金からなる工具基体と同様に、基体表面付近におけるＮｉ及びＣｏは相対的に減ることとなり、例えば、走査型電子顕微鏡（ＳＥＭ）を用いた表面から深さ方向に０．５〜３．０μｍの断面観察を行い、分析視野領域１×１μｍの範囲にて波長分散型Ｘ線分光法による定量分析した場合に、結合相金属としてのＮｉ及びＣｏの合計含有量を２．０質量％未満にすれば、基体の表面硬化の要因となる炭窒化物が十分に形成され、耐摩耗性がより向上する。
なお、基体表面硬化層を形成した後の炭窒化チタン基サーメット基体の硬さはビッカース硬さ（Ｈｖ）で２０００以上、２６００以下であることが好ましい。
また、基体表面硬化層の平均層厚は０．５μｍ以下であると耐摩耗性が十分発揮できないまま比較的すぐに磨滅してしまい、３．０μｍ以上であるとチッピングしやすくなるので、基体表面硬化層の平均層厚は０．５〜３．０μｍであることが好ましい。
In addition, when using a titanium carbonitride-based cermet as a tool base, the atmosphere during holding at the highest temperature and the highest temperature in the sintering process is a predetermined nitrogen atmosphere, and the pressure is reduced during holding or when the temperature is lowered. The surface can be cured more than when the entire sintering process is performed in a nitrogen atmosphere at a constant pressure. This is because when the process up to holding at the maximum temperature is performed under a constant nitrogen pressure, carbonitrides with high hardness are uniformly dispersed inside the substrate. Is treated under a relatively high nitrogen pressure, and during the holding or when the temperature is lowered, when the atmosphere is further reduced to a nitrogen atmosphere, only the very surface of the substrate is denitrified, resulting in a binder phase such as Ni or Co. This is because dissolution of Ti, Nb, etc. and diffusion from the inside to the substrate surface become active, and formation of carbonitrides such as Ti, Nb, etc. is promoted on the surface, and a cured substrate surface layer is formed.
Then, similarly to the tool base made of the above-mentioned tungsten carbide base cemented carbide, Ni and Co in the vicinity of the base surface are relatively reduced. For example, in the depth direction from the surface using a scanning electron microscope (SEM). When the cross-sectional observation of 0.5 to 3.0 μm is performed and quantitative analysis is performed by wavelength dispersion X-ray spectroscopy in the analysis visual field region of 1 × 1 μm, the total content of Ni and Co as the binder phase metal is When the amount is less than 2.0% by mass, carbonitrides that cause surface hardening of the substrate are sufficiently formed, and wear resistance is further improved.
In addition, it is preferable that the hardness of the titanium carbonitride-based cermet substrate after forming the substrate surface hardened layer is 2000 to 2600 in terms of Vickers hardness (Hv).
Further, if the average thickness of the substrate surface hardened layer is 0.5 μm or less, it will be worn away relatively quickly without sufficiently exhibiting the wear resistance, and if it is 3.0 μm or more, chipping is likely to occur. It is preferable that the average layer thickness of a hardened layer is 0.5-3.0 micrometers.
本発明のα型酸化アルミニウム層は、例えば、以下に示すゾル−ゲル法によって形成することができる。 The α-type aluminum oxide layer of the present invention can be formed, for example, by the sol-gel method shown below.
アルミナゾルの調製：
まず、アルミニウムのアルコキシド（例えば、アルミニウムセカンダリブトキシド、アルミニウムイソプロポキシド）にアルコール（例えば、メタノール、エタノール）を添加し、次いで、微量の硝酸を添加した後、加水分解反応を徐々に進めて、前駆体を密に形成させるために１０℃以下の温度範囲にて１２時間以上攪拌することによってアルミナゾルを調製する。本発明においては、−１０〜１０℃の低温度範囲における攪拌と熟成を、例えば、合計１２時間以上という長時間をかけての低温処理を行うことが望ましい。
これは、攪拌および熟成処理時の温度が１０℃を超えると加水分解および重縮合反応が急速に進んでしまうため、酸化アルミニウム前駆体が密に形成されにくく、後工程の焼成処理で、α型酸化アルミニウムが形成されにくくなることから、攪拌および熟成処理時の温度の上限を１０℃とし、一方、攪拌および熟成処理時の温度が−１０℃未満では、加水分解および重縮合反応が進みにくく、結晶化しにくくなってしまうという理由からである。
なお、撹拌及び熟成時間を合計１２時間以上としたのは、前記撹拌及び熟成時の温度範囲で起こる化学反応を十分に平衡状態までもっていき、加水分解縮重合したＡｌとＯのネットワークが密に形成された安定な酸化アルミニウム前駆体ゾルを得るために必要な時間である。
Preparation of alumina sol:
First, an alcohol (eg, methanol, ethanol) is added to an aluminum alkoxide (eg, aluminum secondary butoxide, aluminum isopropoxide), and then a small amount of nitric acid is added. In order to form a dense body, an alumina sol is prepared by stirring for 12 hours or more in a temperature range of 10 ° C. or less. In the present invention, it is desirable to perform the low temperature treatment over a long period of time, for example, 12 hours or more in total, for stirring and aging in a low temperature range of −10 to 10 ° C.
This is because when the temperature during stirring and aging treatment exceeds 10 ° C., the hydrolysis and polycondensation reaction proceed rapidly, so that the aluminum oxide precursor is difficult to be formed densely, and the α-type is formed in the subsequent baking treatment. Since it is difficult to form aluminum oxide, the upper limit of the temperature at the time of stirring and aging treatment is 10 ° C. On the other hand, when the temperature at the time of stirring and aging treatment is less than -10 ° C, hydrolysis and polycondensation reaction hardly proceed, This is because it becomes difficult to crystallize.
In addition, the stirring and aging time was set to 12 hours or more in total so that the chemical reaction occurring in the temperature range during the stirring and aging was sufficiently brought to an equilibrium state, and the network of hydrolytic polycondensation Al and O was dense. This is the time required to obtain the formed stable aluminum oxide precursor sol.
また、微量添加する硝酸の濃度は、０．５〜４．０Ｎが望ましく、アルミニウムのアルコキシドに対する硝酸の添加量は、０．１〜０．６倍（モル比）が望ましい。また、その際には、水の添加量が少ないとゾル中のコロイド粒子が十分に分散しなくなるため、不十分な解膠状態やゲル化により、膜付き不良の発生や成膜自体ができなくなる。 The concentration of nitric acid to be added in a small amount is desirably 0.5 to 4.0 N, and the amount of nitric acid added to the aluminum alkoxide is desirably 0.1 to 0.6 times (molar ratio). Also, in that case, if the amount of water added is small, the colloidal particles in the sol will not be sufficiently dispersed, so that insufficient peptization or gelation will not cause film formation or film formation itself. .
なお、一般的に酸化アルミニウムの結晶化、特にα化には１０００℃以上の高温が必要とされるが、Ｔｉ化合物は酸化アルミニウムの結晶化促進に寄与し、特に、Ｔｉ酸化物を用いると比較的低温で結晶化が可能になる。Ｔｉ酸化物による酸化アルミニウムの低温結晶化促進効果のメカニズムは明確に解明されているわけではないが、各種金属酸化物の標準生成自由エネルギーを考慮すると熱力学的にＴｉ酸化物はＡｌ酸化物よりも不安定であり、Ｔｉ酸化物はＡｌ元素を酸化しうる、つまり、Ｔｉ酸化物が還元することにより、Ａｌを酸化するための酸素供給源となると考えられること、さらに、複数の金属酸化物のうち、Ａｌの標準生成自由エネルギーに最も近い金属元素がＴｉであるため、特にＴｉ酸化物は酸化アルミニウムの結晶化促進に効果が大きいのではないかと考えられること、ゾル-ゲル法は例えば石英の製造方法で知られるように金属元素とＯのネットワーク形成によるゾル状態、ゲル状態を経ることで通常では得ることのできない比較的低温で結晶化を達成出来る手法であることを考えると、Ｔｉ酸化物の酸素供給によりＡｌとＯのネットワーク形成を比較低温の段階で形成助長させている可能性も考えられ、Ｔｉ酸化物の表面が酸化アルミニウム結晶粒の成長する起点となり、Ｔｉ酸化物近傍の限定した箇所においては比較的低温で結晶化が可能になる。 In general, high temperature of 1000 ° C. or higher is required for crystallization of aluminum oxide, particularly α-crystallization, but the Ti compound contributes to the crystallization promotion of aluminum oxide, especially when using Ti oxide. Crystallization becomes possible at low temperatures. The mechanism of the low-temperature crystallization accelerating effect of aluminum oxide by Ti oxide is not clearly elucidated, but considering the standard free energy of formation of various metal oxides, Ti oxide is thermodynamically more than Al oxide. Ti oxides can oxidize Al elements, that is, Ti oxides are considered to be an oxygen supply source for oxidizing Al by reduction, and more than one metal oxide Of these, Ti is the metal element closest to the standard free energy of formation of Al, and therefore Ti oxide is considered to be particularly effective in promoting crystallization of aluminum oxide. As is known in the manufacturing method, it is relatively low temperature that cannot normally be obtained through the sol state and gel state due to the network formation of metal element and O Considering that this is a technique that can achieve crystallization with the oxygen supply of Ti oxide, the formation of Al and O networks may be promoted at a relatively low temperature stage. It becomes a starting point for growth of aluminum oxide crystal grains, and crystallization is possible at a relatively low temperature in a limited portion near the Ti oxide.
本発明のα型酸化アルミニウム膜は、上記Ｔｉ化合物やＴｉ酸化物が基体もしくは下部層にあるとともにアルミナゾルの各成分、特に水や硝酸の濃度が重要である。アルミナゾルの成分である原料の有機基はもちろん、一部の水やアルコール、硝酸などは、焼成時に酸化アルミニウムを形成する際の不純物成分になると考えられる。多くの検証試験を行った結果、焼成前の酸化アルミニウムの膜中に存在する硝酸は他成分と比較し、均一に分布しており、それらを適切な濃度範囲に設定した場合には、膜中に均一に微細空孔を適切な形成数だけ分布させることができることが分かった。加えて、乾燥条件や焼成条件を調整することで、膜中に均一形成される微細空孔の存在は維持しつつ、乾燥や焼成の際に高温の雰囲気と接することとなる酸化アルミニウム層のごく表面のみを緻密にすることができ、表面粗さは小さくなり、切削時の酸化雰囲気からの保護や切削抵抗低減の効果により、耐酸化性や耐溶着性が向上する。 In the α-type aluminum oxide film of the present invention, the Ti compound and Ti oxide are present in the substrate or the lower layer, and the concentration of each component of the alumina sol, particularly water and nitric acid is important. In addition to the organic group of the raw material that is a component of the alumina sol, a part of water, alcohol, nitric acid, and the like are considered to be impurity components when forming aluminum oxide during firing. As a result of many verification tests, nitric acid present in the aluminum oxide film before firing is distributed more uniformly than other components, and when they are set to an appropriate concentration range, As a result, it was found that the fine pores can be uniformly distributed in an appropriate number. In addition, by adjusting the drying and firing conditions, the presence of fine pores that are uniformly formed in the film is maintained, while the aluminum oxide layer that comes into contact with a high-temperature atmosphere during drying and firing is extremely small. Only the surface can be made dense, the surface roughness is reduced, and the oxidation resistance and welding resistance are improved by the protection from the oxidizing atmosphere at the time of cutting and the effect of reducing the cutting resistance.
また、成膜の際には、成膜基体の材料や成膜基体形状によっては、膜付き不良やクラックが生じる場合があるが、界面活性剤やキレート化剤を添加することでそれらを効果的に抑制することが可能である。特に添加種を限定するわけではないが、界面活性剤としては例えばドデシルベンゼンスルホン酸ナトリウム（Ｃ１２Ｈ２５Ｃ６Ｈ４ＳＯ３Ｎａ）、ラウリン酸ナトリウム（Ｃ１１Ｈ２３ＣＯＯＮａ）などが挙げられ、キレート化剤としては例えばβ−ケトエステル類としてのキレート剤であるアセト酢酸メチル、アセト酢酸エチル、マロン酸ジメチル、マロン酸ジエチルなどが挙げられる。 Also, during film formation, depending on the material of the film formation substrate and the shape of the film formation substrate, defective film attachment and cracks may occur. However, adding a surfactant or chelating agent effectively It is possible to suppress it. Although not particularly limiting the type additives, for example sodium dodecylbenzene sulfonate as a surfactant (C 12 H 25 C 6 H 4 SO 3 Na), sodium laurate (C 11 H 23 COONa) are like Examples of the chelating agent include methyl acetoacetate, ethyl acetoacetate, dimethyl malonate, and diethyl malonate which are chelating agents as β-ketoesters.
アルミナゾルの加熱処理：
次いで、上記アルミナゾルについて、ゾル中で起きている加水分解・縮合反応が平衡状態に至るまで進める目的で６時間以上加熱撹拌する。なお、加熱処理は一般的な有機合成で使用されるようなオイルバス等による還流加熱処理を用いることが望ましく、ゾルの成分にもよるが８０〜１８０℃の温度で加熱処理を行うことが望ましい。
Heat treatment of alumina sol:
Next, the alumina sol is heated and stirred for 6 hours or more for the purpose of proceeding until the hydrolysis / condensation reaction occurring in the sol reaches an equilibrium state. In addition, it is desirable to use a reflux heat treatment such as an oil bath used in general organic synthesis as the heat treatment, and it is desirable to perform the heat treatment at a temperature of 80 to 180 ° C. depending on the components of the sol. .
乾燥・焼成：
工具基体あるいは下部層（例えば、Ｔｉ化合物層）を被覆した工具基体を、上記で調製したアルミナゾル中へ浸漬処理し、その後、０．５ｍｍ／ｓｅｃの速度でアルミナゾル中からこれを引き上げ、それに続き１００〜６００℃で１０分乾燥処理を施し、この浸漬処理と乾燥処理を所要の層厚になるまで繰り返し行い、次いで、窒素雰囲気中、８００〜１１００℃の温度範囲で焼成処理を行う。
Drying and firing:
A tool base or a tool base coated with a lower layer (for example, a Ti compound layer) is dipped in the alumina sol prepared above, and then pulled up from the alumina sol at a rate of 0.5 mm / sec. A drying treatment is performed at ˜600 ° C. for 10 minutes, this immersion treatment and drying treatment are repeated until the required layer thickness is obtained, and then a firing treatment is carried out in a temperature range of 800 to 1100 ° C. in a nitrogen atmosphere.
上記乾燥処理によって、アルミナの乾燥ゲルが形成され、次いで行う焼成処理によって、酸化アルミニウム層中に、所定の平均孔径、平均密度、標準偏差の微細空孔が形成されるとともに、該微細空孔の周囲の少なくとも一部分にＴｉ酸化物が形成されたゾル−ゲル法によるα型酸化アルミニウム層が形成される。 A dry gel of alumina is formed by the above drying treatment, and fine pores having a predetermined average pore diameter, average density, and standard deviation are formed in the aluminum oxide layer by the subsequent baking treatment. An α-type aluminum oxide layer is formed by a sol-gel method in which Ti oxide is formed on at least a part of the periphery.
上記α型酸化アルミニウム層の膜厚は、アルミナゾルへの浸漬回数に依存するが、被覆形成された上記α型酸化アルミニウム層の平均層厚が０．５μｍ未満では、長期の使用にわたって被覆工具としてすぐれた耐摩耗性を発揮することができず、一方、平均層厚が４．０μｍを越えるとα型酸化アルミニウム層が剥離を生じやすくなることから、上記α型酸化アルミニウム層の膜厚は０．５〜４．０μｍとする。 The film thickness of the α-type aluminum oxide layer depends on the number of times of immersion in the alumina sol, but if the average thickness of the coated α-type aluminum oxide layer is less than 0.5 μm, it is excellent as a coated tool over a long period of use. On the other hand, when the average layer thickness exceeds 4.0 μm, the α-type aluminum oxide layer is liable to be peeled off. The thickness is 5 to 4.0 μm.
本発明の表面被覆切削工具によれば、工具基体の表面に、直接あるいは下部層を介してゾル−ゲル法によって成膜したα型酸化アルミニウム層が被覆形成され、該α型酸化アルミニウム層中には、所定の平均孔径、平均密度、標準偏差の微細空孔が形成されるとともに、該微細空孔の周囲の少なくとも一部分にＴｉ酸化物が形成された微細空孔が、全微細空孔数の５０％以上形成されていることによって、ステンレス鋼等の熱伝導性に乏しい被削材の切れ刃に高負荷が作用する湿式高速断続切削加工に供した場合、α型酸化アルミニウム層は、すぐれた耐熱的衝撃性、耐機械的衝撃性、耐摩耗性を示し、また、強度の低下もなくすぐれた耐チッピング性を示すことから、長期の使用にわたってすぐれた切削性能を発揮するのである。 According to the surface-coated cutting tool of the present invention, the α-type aluminum oxide layer formed by the sol-gel method is coated on the surface of the tool base directly or via the lower layer, and the α-type aluminum oxide layer is covered with the α-type aluminum oxide layer. Are formed with fine pores having a predetermined average pore diameter, average density, and standard deviation, and fine pores in which Ti oxide is formed at least at a part of the periphery of the fine pores, having a total number of fine pores. The α-type aluminum oxide layer is excellent when it is subjected to wet high-speed intermittent cutting in which a high load acts on the cutting edge of a work material with poor thermal conductivity such as stainless steel by being formed at 50% or more. It exhibits thermal shock resistance, mechanical impact resistance, wear resistance, and excellent chipping resistance without a decrease in strength. Therefore, it exhibits excellent cutting performance over a long period of use.
つぎに、本発明を実施例により具体的に説明する。 Next, the present invention will be specifically described with reference to examples.
（ａ） 原料粉末として、平均粒径０．８μｍの微粒ＷＣ粉末、平均粒径２〜３μｍの中粒ＷＣ粉末といずれも１〜３μｍの平均粒径を有するＴｉＣＮ粉末、ＺｒＣ粉末、ＴａＣ粉末、ＮｂＣ粉末、Ｃｒ3Ｃ2粉末およびＣｏ粉末を用意し、これら原料粉末を、表１に示す所定の配合組成に配合し、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、１４００℃の温度にて１時間保持の条件で真空焼結し、焼結後、切刃部にＲ：０．０６ｍｍのホーニング加工を施すことによりＩＳＯ・ＳＮＧＡ１２０４０８に規定するインサート形状をもったＷＣ基超硬合金製の工具基体Ａ，Ｂ，Ｃ，Ｄ，Ｅ，Ｆ，Ｇ，Ｈ，Ｉ（工具基体Ａ，Ｂ，Ｃ，Ｄ，Ｅ，Ｆ，Ｇ，Ｈ，Ｉという）を製造した。
但し、１４００℃にて１時間保持後１３２０℃までの冷却を、超硬基体Ｆについては、３．３ｋＰａの窒素雰囲気中にて４０分間行い、超硬基体Ｇについては、１ｋＰａの窒素雰囲気中にて４０分間、超硬基体Ｈについては、２ｋＰａの窒素雰囲気中にて１０分間、超硬基体Ｉについては、３．３ｋＰａの窒素雰囲気中にて１２０分間かけて冷却することで基体表面を硬化処理した。
(A) As a raw material powder, fine WC powder having an average particle diameter of 0.8 μm, medium WC powder having an average particle diameter of 2 to 3 μm, and TiCN powder, ZrC powder, TaC powder each having an average particle diameter of 1 to 3 μm, After preparing NbC powder, Cr 3 C 2 powder and Co powder, these raw material powders were blended in the prescribed blending composition shown in Table 1, added with wax, ball mill mixed in acetone for 24 hours, and dried under reduced pressure , Pressed into a green compact of a predetermined shape at a pressure of 98 MPa, this green compact was vacuum-sintered at a temperature of 1400 ° C. for 1 hour in a vacuum of 5 Pa, and after sintering, the cutting edge portion R: 0.06mm honing process is applied to the tool base A, B, C, D, E, F, G, H, I made of WC-base cemented carbide with the insert shape specified in ISO / SNGA120408. (Tool substrate A, It was prepared C, D, E, F, G, H, a) that I.
However, after holding at 1400 ° C. for 1 hour, cooling to 1320 ° C. is performed for 40 minutes in a nitrogen atmosphere of 3.3 kPa for the carbide substrate F, and in a nitrogen atmosphere of 1 kPa for the carbide substrate G. The substrate surface is cured by cooling for 40 minutes in a nitrogen atmosphere of 2 kPa for carbide substrate H and for 120 minutes in a nitrogen atmosphere of 3.3 kPa for carbide substrate I. did.
（ｂ） ついで、上記工具基体Ａ〜Ｉに対して、下層を形成した。
なお、下層の形成にあたり、上記工具基体Ａ〜Ｃについては、化学蒸着装置に装入し、表２に示す成膜条件を用いて、粒状結晶組織を有するＴｉＮ層、ＴｉＣＮ層、ＴｉＣＯ層、ＴｉＣＮＯ層、縦長成長結晶組織のＴｉＣＮ層（以下、ｌ−ＴｉＣＮで示す）、ＴｉＯ２、Ｔi２Ｏ３からなるＴｉ化合物層を表５に示す皮膜構成にて下地層を予め形成した。一方、上記工具基体Ｄについては、物理蒸着装置の一種であるアークイオンプレーティング装置に装入し、表５に示す膜厚のＴｉ０．５Ａｌ０．５Ｎ層からなる下地層を予め形成した。
一方、上記工具基体Ｅ，Ｆ，Ｇ，Ｈ，Ｉについては、下地層の形成を特に行わなかった。
(B) Next, a lower layer was formed on the tool bases A to I.
In forming the lower layer, the tool bases A to C are inserted into a chemical vapor deposition apparatus, and the TiN layer, TiCN layer, TiCO layer, TiCNO having a granular crystal structure are formed using the film formation conditions shown in Table 2. An underlayer was formed in advance with a layer structure, a TiCN layer (hereinafter referred to as 1-TiCN) having a vertically-grown crystal structure, and a Ti compound layer composed of TiO 2 and Ti 2 O 3 in the film configuration shown in Table 5. On the other hand, the tool base D is inserted into an arc ion plating apparatus which is a kind of physical vapor deposition apparatus, and an underlayer composed of Ti 0.5 Al 0.5 N layers having thicknesses shown in Table 5 is formed in advance. did.
On the other hand, for the tool bases E, F, G, H, and I, the base layer was not particularly formed.
（ｃ） 一方、α型酸化アルミニウム層をゾル−ゲル法で被覆形成するためのアルミナゾルの調製を、次のように行った。
表３に示す所定量のアルミニウムのアルコキシドであるアルミニウムセカンダリブトキシドに、同じく表３に示す所定量のエタノールを添加した後、恒温槽中１０℃以下で攪拌を行い、さらに、所定量の水を添加した硝酸を滴下により１〜３時間かけて添加した。
(C) On the other hand, an alumina sol for coating the α-type aluminum oxide layer by a sol-gel method was prepared as follows.
After adding the predetermined amount of ethanol shown in Table 3 to the aluminum secondary butoxide, which is an alkoxide of the predetermined amount of aluminum shown in Table 3, the mixture is stirred at 10 ° C. or less in a thermostatic bath, and further, a predetermined amount of water is added. The nitric acid was added dropwise over 1 to 3 hours.
（ｄ） さらに、アルミナゾルにおけるアルミニウムと水のモル比を１：４０〜１：１５０の範囲になるように、表３に示す所定量の水を添加し、これをオイルバスによる還流装置を用いて表３に示す温度でゾル中の加水分解・縮重合反応を安定させることを目的として所定時間撹拌した。
最終的な溶液組成は、モル比で、
（アルミニウムセカンダリブトキシド）：（水）：（エタノール）：（硝酸）
＝１：（４０〜１５０）：（１５〜３０）：（０．１〜０．６）
になるように調整を行った。
(D) Further, a predetermined amount of water shown in Table 3 was added so that the molar ratio of aluminum to water in the alumina sol was in the range of 1:40 to 1: 150, and this was added using a reflux apparatus using an oil bath. The mixture was stirred for a predetermined time at the temperature shown in Table 3 for the purpose of stabilizing the hydrolysis / condensation polymerization reaction in the sol.
The final solution composition is in molar ratio
(Aluminum secondary butoxide): (water): (ethanol): (nitric acid)
= 1: (40-150): (15-30): (0.1-0.6)
Adjustments were made to
（ｅ） ついで、上記工具基体Ａ〜Ｉを、上記アルミナゾル中に浸漬し、その後、上記工具基体Ａ〜Ｉをアルミナゾル中から引き上げ速度０．５ｍｍ／ｓｅｃで引き上げ、５００℃で１０分間の乾燥処理を行い、さらに、浸漬、引き上げ、乾燥処理を繰り返した後、表３に示す条件で焼成処理を行い、α型酸化アルミニウム層中に微細空孔が形成され、該微細空孔の周囲の少なくとも一部に隣接してＴｉ酸化物が形成されている微細空孔が存在する本発明のα型酸化アルミニウム層を被覆形成することにより、表５、６に示す本発明の被覆工具１〜１５（本発明工具１〜１５という）を製造した。なお、下地層の形成を特に行わなかった工具基体Ｅ，Ｆ，Ｇ，Ｈ，Ｉについては、走査型電子顕微鏡（ＳＥＭ）を用いた表面から深さ方向に０．５〜３．０μｍの断面観察を行い、分析視野領域１×１μｍの範囲にて波長分散型Ｘ線分光法による結合相金属の定量分析と表面硬化層厚の測定を実施した。その結果を表５に示す。 (E) Next, the tool bases A to I are immersed in the alumina sol, and then the tool bases A to I are pulled up from the alumina sol at a lifting speed of 0.5 mm / sec and dried at 500 ° C. for 10 minutes. Further, after repeating the dipping, pulling up and drying processes, a baking treatment is performed under the conditions shown in Table 3 to form fine vacancies in the α-type aluminum oxide layer, and at least one around the fine vacancies. By coating and forming the α-type aluminum oxide layer of the present invention in which fine pores in which Ti oxide is formed adjacent to the part are present, the coated tools 1 to 15 of the present invention shown in Tables 5 and 6 Invention tools 1 to 15) were produced. In addition, about the tool bases E, F, G, H, and I in which the formation of the underlayer was not particularly performed, a cross section of 0.5 to 3.0 μm in the depth direction from the surface using a scanning electron microscope (SEM). Observation was performed, and the quantitative analysis of the binder phase metal and the measurement of the thickness of the hardened surface layer were performed by wavelength dispersion X-ray spectroscopy in the analysis visual field region of 1 × 1 μm. The results are shown in Table 5.
前記本発明工具１〜１５について、α型酸化アルミニウム層の平均層厚を透過電子顕微鏡を用いて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値（５ヶ所の平均値）を示した。 When the average layer thickness of the α-type aluminum oxide layer was measured for a cross section of the inventive tools 1 to 15 using a transmission electron microscope, the average values (average values at five locations) were substantially the same as the target layer thickness. Indicated.
また、Ｘ線回折装置と走査型電子顕微鏡（ＳＥＭ）及びオージェ電子分光分析装置（ＡＥＳ）を用い、酸化アルミニウム層の結晶構造とα型酸化アルミニウム層中の微細空孔の平均孔径、平均密度、分布の標準偏差、微細空孔に隣接してＴｉ酸化物が形成されている微細空孔の個数割合を求めた。
α型酸化アルミニウム層中の微細空孔の平均孔径に関しては走査型電子顕微鏡により０．７×０．７μｍの視野範囲における観察を行い、微細空孔の面積を円の面積として置き換えた場合の直径を５視野１０点ずつ測定し、その平均値とした。
また、平均密度に関しては、０．３×０．３μｍの視野範囲における観察を１０視野ずつ行い、各視野の単位面積当たりの空孔数を測定し、平均して算出した。また、微細空孔の分布の標準偏差に関しては、上記にて測定した各視野毎の単位面積当たりの空孔数を全視野にわたり標準偏差をとることで求めた。
Ｔｉ酸化物が形成されている微細空孔は、上記走査型電子顕微鏡による観察とオージェ電子分光法による該観察視野範囲の元素マッピングの結果を照らし合わせることにより特定し、観察視野範囲内において該当する微細空孔の数を求めた。
また、α型酸化アルミニウム結晶粒の平均アスペクト比は電子線後方散乱回折装置（ＥＢＳＤ）を用いて該酸化アルミニウム層の縦断面を、例えば層厚×１０μｍの観察視野、測定ステップ５０ｎｍにて観察を行い、上記観察視野範囲内における各々の結晶粒形状を５視野に対して求めた場合に、層厚垂直方向の最大径を層厚垂直方向の粒径、層厚方向の最大径を層厚方向の粒径と定義し、層厚垂直方向の粒径に対する層厚方向の粒径の比を各々算出し、その平均値を該酸化アルミニウム層中の結晶粒の平均アスペクト比とした。
α型酸化アルミニウム結晶粒の表面粗さＲａはレーザー顕微鏡を用い、ＪＩＳ規格Ｂ−０６０１（２００１）に基づき、１０μｍ×１０μｍの測定視野において５視野測定し、平均値を算出した。
なお、図２（ａ）に、本発明工具２のα型酸化アルミニウム層についてのＣＰ加工した断面ＳＥＭ像を示し、図２（ｂ）に、その部分拡大図を示す。
In addition, using an X-ray diffractometer, a scanning electron microscope (SEM), and an Auger electron spectrometer (AES), the crystal structure of the aluminum oxide layer and the average pore diameter, average density of fine pores in the α-type aluminum oxide layer, The standard deviation of the distribution and the ratio of the number of fine holes in which Ti oxide is formed adjacent to the fine holes were determined.
The average pore diameter in the α-type aluminum oxide layer was observed in a field of view of 0.7 × 0.7 μm with a scanning electron microscope, and the diameter when the area of the fine holes was replaced with the area of a circle Were measured at 10 points in 5 fields, and the average value was obtained.
Further, regarding the average density, 10 observations were made in the visual field range of 0.3 × 0.3 μm, and the number of holes per unit area of each visual field was measured and averaged. Further, regarding the standard deviation of the distribution of fine pores, the number of pores per unit area for each visual field measured as described above was obtained by taking the standard deviation over the entire visual field.
The fine vacancies in which the Ti oxide is formed are identified by comparing the observation with the scanning electron microscope and the result of element mapping in the observation visual field range by Auger electron spectroscopy, and fall within the observation visual field range. The number of fine holes was determined.
The average aspect ratio of the α-type aluminum oxide crystal grains is determined by observing the longitudinal section of the aluminum oxide layer using an electron beam backscattering diffractometer (EBSD), for example, with an observation field of thickness of 10 μm and a measurement step of 50 nm. When the respective crystal grain shapes in the observation visual field range are obtained with respect to five visual fields, the maximum diameter in the vertical direction of the layer thickness is the grain size in the vertical direction of the layer thickness, and the maximum diameter in the layer thickness direction is the layer thickness direction The ratio of the grain size in the layer thickness direction to the grain size in the layer thickness vertical direction was calculated, and the average value was defined as the average aspect ratio of the crystal grains in the aluminum oxide layer.
The surface roughness Ra of the α-type aluminum oxide crystal grains was measured using a laser microscope, based on JIS standard B-0601 (2001), in five measurement fields of 10 μm × 10 μm, and an average value was calculated.
FIG. 2A shows a cross-sectional SEM image obtained by CP processing of the α-type aluminum oxide layer of the tool 2 of the present invention, and FIG. 2B shows a partially enlarged view thereof.
[比較例１]
比較のため、以下の製造方法で比較例の被覆工具を製造した。
[Comparative Example 1]
For comparison, a coated tool of a comparative example was manufactured by the following manufacturing method.
（イ）まず、反応原料における各成分の溶液組成はモル比で、
（アルミニウムセカンダリブトキシド）：（水）：（エタノール）：（硝酸）
＝１：（３０〜８０）：（１５〜４０）：（０．５〜１．２）
になるように調整し、表４に示す条件でアルミナゾルを調製した。
（ロ）次いで、上記工具基体Ａ〜Ｉの表面に、上記アルミナゾルを塗布した。
（ハ）ついで、上記塗布したアルミナゾルを、表４に示す条件で乾燥処理を行い、さらに塗布と乾燥を所定層厚になるまで繰り返した後、焼成処理を行うことにより、表５、７に示す比較例の被覆工具１〜１５（比較例工具１〜１５という）を製造した。
(A) First, the solution composition of each component in the reaction raw material is a molar ratio,
(Aluminum secondary butoxide): (water): (ethanol): (nitric acid)
= 1: (30 to 80): (15 to 40): (0.5 to 1.2)
The alumina sol was prepared under the conditions shown in Table 4.
(B) Next, the alumina sol was applied to the surfaces of the tool bases A to I.
(C) Next, the coated alumina sol is dried under the conditions shown in Table 4, and after repeating the coating and drying until a predetermined layer thickness is obtained, the firing treatment is performed, and the results are shown in Tables 5 and 7. Comparative tools 1 to 15 (referred to as comparative tools 1 to 15) were produced.
比較例工具１〜１５について、α型酸化アルミニウム層の平均層厚を透過電子顕微鏡を用いて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値（５ヶ所の平均値）を示した。 About Comparative example tools 1-15, when the cross-sectional measurement was carried out using the transmission electron microscope about the average layer thickness of alpha type aluminum oxide layer, all showed the average value (average value of five places) substantially the same as target layer thickness. It was.
また、比較例工具１〜１５について、実施例１と同様にして、α型酸化アルミニウム層中の微細空孔の平均孔径、平均密度、分布の標準偏差、微細空孔に隣接してＴｉ酸化物が形成されている微細空孔の個数割合、α型酸化アルミニウム結晶粒の平均アスペクト比、表面粗さＲａを求めた。
なお、図３（ａ）に、比較例工具３のα型酸化アルミニウム層についてのＣＰ加工した断面ＳＥＭ像を、また、図４（ａ）に、比較例工具１８のα型酸化アルミニウム層についてのＣＰ加工した断面ＳＥＭ像を示し、それぞれの部分拡大図を、図３（ｂ）、図４（ｂ）に示す。
For Comparative Tools 1 to 15, as in Example 1, the average pore diameter, average density, standard deviation of the distribution of fine pores in the α-type aluminum oxide layer, and the Ti oxide adjacent to the fine pores The ratio of the number of fine vacancies in which the .alpha. Was formed, the average aspect ratio of the α-type aluminum oxide crystal grains, and the surface roughness Ra were determined.
3A shows a cross-sectional SEM image obtained by CP processing of the α-type aluminum oxide layer of the comparative tool 3 and FIG. 4A shows the α-type aluminum oxide layer of the comparative tool 18. FIG. 3 (b) and FIG. 4 (b) show cross-sectional SEM images obtained by CP processing, and partial enlarged views of the respective images.
つぎに、本発明工具１〜１５および比較例工具１〜１５について、以下に示す、ステンレス鋼の湿式高速断続切削試験を実施し、いずれも切刃の逃げ面摩耗幅を測定した。
被削材：ＪＩＳ・ＳＵＳ３１６の長さ方向等間隔４本縦溝入り丸棒、
切削速度：１５０ｍ／ｍｉｎ、
切り込み：１．４ｍｍ、
送り：０．１８ｍｍ／ｒｅｖ、
切削時間：５分、
（通常の切削速度は、１２０ｍ／ｍｉｎ）。
これらの結果を表８に示す。
Next, the present invention tools 1 to 15 and comparative tools 1 to 15 were subjected to the following wet high-speed intermittent cutting test of stainless steel, and all measured the flank wear width of the cutting edge.
Work material: JIS / SUS316 lengthwise equidistant 4 round grooved round bars,
Cutting speed: 150 m / min,
Cutting depth: 1.4mm,
Feed: 0.18mm / rev,
Cutting time: 5 minutes
(Normal cutting speed is 120 m / min).
These results are shown in Table 8.
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、Ｍｏ2Ｃ粉末、ＮｂＣ粉末、ＴａＣ粉末、ＷＣ粉末、Ｃｏ粉末、およびＮｉ粉末を用意し、これらを表９に示す所定の配合組成に配合し、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Ｊ，Ｋ，Ｌ，Ｍ，Ｎ，Ｏ，Ｐ，Ｑ，Ｒ（工具基体Ｊ〜Ｒという）を製造した。但し、工具基体Ｏについては１．３ｋＰａの窒素雰囲気中、昇温速度を２℃／ｍｉｎとし、室温より１５４０℃まで昇温させ３０分保持した後、１３Ｐａの真空とし、さらに、１５４０℃にて３０分保持後降温させて表面硬化させた。工具基体Ｐについては、常に１３Ｐａの真空中にて昇温および１５４０℃にて６０分保持、工具基体Ｑについては１．３ｋＰａの窒素雰囲気中で室温より１５４０℃まで昇温させ３０分保持した後、１３Ｐａの真空とし、さらに、１５４０℃にて５分保持、工具基体Ｒについては１．３ｋＰａの窒素雰囲気中で室温より１５４０℃まで昇温させ３０分保持した後、１３Ｐａの真空とし、さらに、１５４０℃にて９０分保持後降温させて表面硬化させた。 TiCN (mass ratio TiC / TiN = 50/50) powder, Mo 2 C powder, NbC powder, TaC powder, WC powder, Co powder, and raw material powder, all having an average particle diameter of 0.5 to 2 μm, and Ni powders were prepared, blended into the prescribed composition shown in Table 9, wet mixed for 24 hours with a ball mill, dried, and then pressed into a green compact at a pressure of 98 MPa. Sintered in a nitrogen atmosphere of 3 kPa at a temperature of 1540 ° C. for 1 hour, and after sintering, the cutting edge part is subjected to a honing process of R: 0.07 mm to form an ISO standard / CNMG120408 chip shape. TiCN based cermet tool bases J, K, L, M, N, O, P, Q, and R (referred to as tool bases J to R) were manufactured. However, for the tool base O, in a nitrogen atmosphere of 1.3 kPa, the rate of temperature rise was 2 ° C./min, the temperature was raised from room temperature to 1540 ° C. and held for 30 minutes, then a vacuum of 13 Pa was applied, and further at 1540 ° C. After holding for 30 minutes, the temperature was lowered to cure the surface. For the tool base P, the temperature was always increased and held at 1540 ° C. for 60 minutes in a vacuum of 13 Pa. For the tool base Q, the temperature was raised from room temperature to 1540 ° C. in a nitrogen atmosphere of 1.3 kPa for 30 minutes. , A vacuum of 13 Pa, and further held at 1540 ° C. for 5 minutes, and the tool substrate R was heated from room temperature to 1540 ° C. in a nitrogen atmosphere of 1.3 kPa and held for 30 minutes, and then a vacuum of 13 Pa was further obtained. After holding at 1540 ° C. for 90 minutes, the temperature was lowered to cure the surface.
ついで、上記工具基体Ｊ〜Ｒに対して、実施例１と同様に表２に示す下地層の成膜条件、表３の調製条件及び焼成条件を用い、α型酸化アルミニウム層を成膜し、表１０、１１に示す本発明の被覆工具１６〜３０（本発明工具１６〜３０という）を製造した。なお、実施例１と同様に下地層の形成を特に行わなかった工具基体Ｎ，Ｏ，Ｐ，Ｑ，Ｒについては、走査型電子顕微鏡（ＳＥＭ）を用いた表面から深さ方向に０．５〜３．０μｍの断面観察を行い、分析視野領域１×１μｍの範囲にて波長分散型Ｘ線分光法による結合相金属の定量分析と表面硬化層厚の測定を実施した。その結果を表１０に示す。 Next, an α-type aluminum oxide layer was formed on the tool bases J to R using the underlayer film formation conditions shown in Table 2 and the preparation conditions and firing conditions shown in Table 3 in the same manner as in Example 1. The coated tools 16-30 of the present invention shown in Tables 10 and 11 (referred to as the present invention tools 16-30) were produced. In addition, about the tool bases N, O, P, Q, and R in which the formation of the base layer was not particularly performed in the same manner as in Example 1, 0.5 in the depth direction from the surface using a scanning electron microscope (SEM). A cross-sectional observation of ˜3.0 μm was performed, and quantitative analysis of the binder phase metal and measurement of the surface hardened layer thickness were performed by wavelength dispersive X-ray spectroscopy in an analysis visual field region of 1 × 1 μm. The results are shown in Table 10.
［比較例２］
前記実施例２で用いたのと同じ工具基体Ｊ〜Ｒを用いて、実施例２と同様に、ゾル−ゲル法により、表２に示す下地層の成膜条件、表３に示すゾル調製条件、焼成条件を用いて表１２に示す所定目標層厚になるまで酸化アルミニウム主体層を成膜し、表１０，１２に示す比較例の被覆工具１６〜３０（比較例工具１６〜３０という）を製造した。
[Comparative Example 2]
Using the same tool bases J to R used in Example 2, the sol-gel method was used to form the underlayer shown in Table 2 and the sol preparation conditions shown in Table 3 as in Example 2. Then, the aluminum oxide main layer was formed using firing conditions until the predetermined target layer thickness shown in Table 12 was reached, and the coated tools 16 to 30 (referred to as Comparative Tools 16 to 30) of Comparative Examples shown in Tables 10 and 12 were used. Manufactured.
上記本発明工具１６〜３０、比較例工具１６〜３０のα型酸化アルミニウム層について、実施例１の場合と同様にして、α型酸化アルミニウム層中の微細空孔の平均孔径、平均密度、分布の標準偏差、微細空孔に隣接してＴｉ酸化物が形成されている微細空孔の個数割合、α型酸化アルミニウム結晶粒の平均アスペクト比、表面粗さＲａを求めた。
表１１、表１２に、その結果を示す。
About the alpha type aluminum oxide layer of the said invention tool 16-30 of the said invention tools 16-30, it carries out similarly to the case of Example 1, and the average hole diameter of the micro void | hole in an alpha type aluminum oxide layer, average density, distribution Standard deviation, the number ratio of fine vacancies in which Ti oxide is formed adjacent to the fine vacancies, the average aspect ratio of α-type aluminum oxide crystal grains, and the surface roughness Ra.
Tables 11 and 12 show the results.
上記本発明工具１６〜３０、比較例工具１６〜３０について、次の条件で湿式高速断続切削加工試験を行った。
被削材：ＪＩＳ・ＳＵＳ４３０の長さ方向等間隔４本縦溝入り丸棒、
切削速度：１８０ｍ／ｍｉｎ、
切り込み：２．２ｍｍ、
送り：０．２４ｍｍ／ｒｅｖ、
切削時間：５分、
（通常の切削速度は、１４０ｍ／ｍｉｎ）。
これらの結果を表１３に示す。
About the said this invention tools 16-30 and comparative example tools 16-30, the wet high-speed intermittent cutting test was done on the following conditions.
Work material: JIS / SUS430 lengthwise equal 4 round bars with flutes,
Cutting speed: 180 m / min,
Cutting depth: 2.2mm,
Feed: 0.24mm / rev,
Cutting time: 5 minutes
(Normal cutting speed is 140 m / min).
These results are shown in Table 13.
表８、１３に示される結果から、本発明工具１〜３０においては、工具基体の表面に、直接あるいは下部層を介してゾル−ゲル法によって成膜したα型酸化アルミニウム層が被覆形成され、該α型酸化アルミニウム層中には、所定の平均孔径、平均密度、標準偏差の微細空孔が形成されるとともに、該微細空孔の周囲の少なくとも一部分にＴｉ酸化物が形成された微細空孔が、全微細空孔数の５０％以上形成されていることによって、熱伝導性に乏しいステンレス鋼の切れ刃に高負荷が作用する湿式高速断続切削加工に供した場合、α型酸化アルミニウム層は、すぐれた耐熱的衝撃性、耐機械的衝撃性、耐摩耗性を示し、また、強度の低下もなくすぐれた耐チッピング性を示すことから、長期の使用にわたってすぐれた切削性能を発揮する。 From the results shown in Tables 8 and 13, in the tools 1 to 30 of the present invention, the surface of the tool base is coated with an α-type aluminum oxide layer formed by a sol-gel method directly or via a lower layer, In the α-type aluminum oxide layer, fine pores having a predetermined average pore diameter, average density, and standard deviation are formed, and at least a part of the periphery of the fine pores is formed with Ti oxide. However, when it is subjected to a wet high-speed intermittent cutting process in which a high load acts on a cutting edge made of stainless steel with poor thermal conductivity due to the formation of 50% or more of the total number of fine pores, the α-type aluminum oxide layer is It exhibits excellent thermal shock resistance, mechanical shock resistance, and wear resistance, and also exhibits excellent chipping resistance without a decrease in strength, and thus exhibits excellent cutting performance over a long period of use.
これに対して、比較例工具１〜３０は、ステンレス鋼の湿式高速断続切削加工においてチッピング、剥離等の異常損傷の発生、あるいは、耐摩耗性が不足により、短時間で使用寿命に至ることは明らかである。
なお、前述の実施例では、インサート形状の工具を用いて硬質被覆層の性能を評価したが、ドリル、エンドミルなどでも同様の結果が得られることはいうまでもない。
On the other hand, the comparative tools 1 to 30 can reach the service life in a short time due to the occurrence of abnormal damage such as chipping and peeling in the wet high-speed intermittent cutting of stainless steel, or due to insufficient wear resistance. it is obvious.
In the above-described embodiment, the performance of the hard coating layer was evaluated using an insert-shaped tool, but it goes without saying that the same result can be obtained with a drill, an end mill, or the like.
本発明の表面被覆切削工具によれば、表面に、ゾル−ゲル法によってα型酸化アルミニウム層が被覆形成され、該α型酸化アルミニウム層は、すぐれた耐熱的衝撃性、耐機械的衝撃性、耐摩耗性、耐チッピング性を備えることから、これを、ステンレス鋼等の熱伝導性に乏しい被削材の湿式高速断続切削加工に用いた場合でも、チッピング、剥離等の異常損傷を発生することなく、長期の使用に亘ってすぐれた切削性能を発揮するものであり、工具寿命の長寿命化を図ることができ、その実用上の効果は大きい。 According to the surface-coated cutting tool of the present invention, the surface is coated with an α-type aluminum oxide layer by a sol-gel method, and the α-type aluminum oxide layer has excellent thermal shock resistance, mechanical shock resistance, Since it has wear resistance and chipping resistance, it may cause abnormal damage such as chipping and peeling even when it is used for wet high-speed intermittent cutting of work materials with poor thermal conductivity such as stainless steel. In other words, it exhibits excellent cutting performance over a long period of use, and can prolong the tool life, and its practical effect is great.
Claims (6)
（ａ）前記硬質被覆層は、ゾル−ゲル法により形成された０．５〜４．０μｍの平均層厚を有するα型酸化アルミニウム層であり、
（ｂ）前記α型酸化アルミニウム層中には、平均孔径が１０〜１００ｎｍである微細空孔が分散して形成され、かつ、α型酸化アルミニウム層の縦断面で測定した前記微細空孔の平均密度は３０〜７０個／μｍ２であり、
（ｃ）前記微細空孔は、α型酸化アルミニウム結晶粒の結晶粒界及び結晶粒内に均一に分散分布し、所定の観察視野範囲における前記空孔密度を所定視野数にわたって求めた場合の標準偏差が１５個／μｍ２以下であり、
（ｄ）前記微細空孔のうち、微細空孔の周囲の少なくとも一部分に、微細空孔に隣接してＴｉ酸化物が形成されている微細空孔の個数割合は、全微細空孔数の５０％以上であることを特徴とする表面被覆切削工具。 In a surface-coated cutting tool in which a hard coating layer is formed on the surface of a tool base made of a tungsten carbide-based cemented carbide containing a Ti component or a titanium carbonitride-based cermet,
(A) The hard coating layer is an α-type aluminum oxide layer formed by a sol-gel method and having an average layer thickness of 0.5 to 4.0 μm,
(B) In the α-type aluminum oxide layer, fine pores having an average pore diameter of 10 to 100 nm are dispersed and formed, and the average of the fine pores measured in the longitudinal section of the α-type aluminum oxide layer The density is 30-70 / μm 2 ,
(C) The standard in the case where the fine vacancies are uniformly distributed in the crystal grain boundaries and crystal grains of the α-type aluminum oxide crystal grains, and the vacancy density in a predetermined observation visual field range is obtained over a predetermined visual field number. The deviation is 15 pieces / μm 2 or less,
(D) Among the fine vacancies, the number ratio of the fine vacancies in which Ti oxide is formed adjacent to the fine vacancies in at least a part around the fine vacancies is 50 of the total fine vacancies. A surface-coated cutting tool characterized by being at least%.
（ａ）前記下部層は、化学蒸着法、物理蒸着法またはゾル−ゲル法により成膜されたＴｉの窒化物層、炭窒化物層、酸化物層、炭酸化物層、炭窒酸化物層、ＴｉとＡｌの窒化物層の何れか１層または２層以上からなるＴｉ化合物層であり、
（ｂ）前記上部層は、ゾル−ゲル法により形成された０．５〜４．０μｍの平均層厚を有するα型酸化アルミニウム層であり、
（ｃ）前記α型酸化アルミニウム層中には、平均孔径が１０〜１００ｎｍである微細空孔が分散して形成され、かつ、α型酸化アルミニウム層の縦断面で測定した前記微細空孔の平均密度は３０〜７０個／μｍ２であり、
（ｄ）前記微細空孔は、α型酸化アルミニウム結晶粒の結晶粒界及び結晶粒内に均一に分散分布し、所定の観察視野範囲における前記空孔密度を所定視野数にわたって求めた場合の標準偏差が１５個／μｍ２以下であり、
（ｅ）前記微細空孔のうち、微細空孔の周囲の少なくとも一部分に、微細空孔に隣接してＴｉ酸化物が形成されている微細空孔の個数割合は、全微細空孔数の５０％以上であることを特徴とする表面被覆切削工具。 In a surface-coated cutting tool in which a hard coating layer composed of a lower layer and an upper layer is coated on the surface of a tool base composed of a tungsten carbide-based cemented carbide or a titanium carbonitride-based cermet,
(A) The lower layer is a Ti nitride layer, carbonitride layer, oxide layer, carbonate layer, carbonitride oxide layer formed by chemical vapor deposition, physical vapor deposition, or sol-gel method, Ti compound layer composed of one or more of Ti and Al nitride layers,
(B) The upper layer is an α-type aluminum oxide layer formed by a sol-gel method and having an average layer thickness of 0.5 to 4.0 μm,
(C) In the α-type aluminum oxide layer, fine pores having an average pore diameter of 10 to 100 nm are dispersed and formed, and the average of the fine pores measured in the longitudinal section of the α-type aluminum oxide layer The density is 30-70 / μm 2 ,
(D) The standard in the case where the fine vacancies are uniformly distributed in the crystal grain boundaries and crystal grains of the α-type aluminum oxide crystal grains, and the vacancy density in a predetermined observation visual field range is obtained over a predetermined visual field number. The deviation is 15 pieces / μm 2 or less,
(E) Among the fine vacancies, the number ratio of the fine vacancies in which Ti oxide is formed adjacent to the fine vacancies in at least a part around the fine vacancies is 50 of the total fine vacancies. A surface-coated cutting tool characterized by being at least%.
A base surface hardened layer having an average layer thickness of 0.5 to 3.0 μm in the depth direction from the surface of the tool base made of a titanium carbonitride-based cermet is formed, and as a binder phase metal contained in the base surface hardened layer The surface-coated cutting tool according to any one of claims 1 to 4, wherein a total average content of Co and Ni is less than 2.0 mass%.
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