JP6364195B2 - Surface-coated cutting tool with excellent chipping resistance in high-speed intermittent cutting - Google Patents
Surface-coated cutting tool with excellent chipping resistance in high-speed intermittent cutting Download PDFInfo
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- 238000005520 cutting process Methods 0.000 title claims description 102
- 239000010410 layer Substances 0.000 claims description 199
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 145
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Landscapes
- Cutting Tools, Boring Holders, And Turrets (AREA)
- Chemically Coating (AREA)
- Chemical Vapour Deposition (AREA)
Description
本発明は、硬質被覆層がすぐれた潤滑性、耐チッピング性、耐摩耗性を備えることから、鋼や鋳鉄等の高速断続切削加工に用いた場合でも、長期の使用に亘ってすぐれた切削性能を発揮する表面被覆切削工具に関する。 Since the hard coating layer has excellent lubricity, chipping resistance, and wear resistance, the present invention has excellent cutting performance over a long period of use even when used for high-speed intermittent cutting of steel, cast iron, etc. The present invention relates to a surface-coated cutting tool that exhibits
従来から、超硬合金からなる工具基体表面に、硬質被覆層として、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、硬質皮膜の中でも、α型酸化アルミニウム層は、熱安定性にすぐれ、反応性が低く、かつ、高硬度であるという点から、前述したような周期律表の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被覆層の最表面層として被覆形成されることが多い。
Conventionally, the surface of a tool base made of cemented carbide is made of carbide, nitride, carbonitride or the like of at least one element selected from groups 4a, 5a, and 6a of the periodic table as a hard coating layer. It is known to improve the wear resistance of a cutting tool by forming a hard coating.
Among the hard coatings, the α-type aluminum oxide layer has excellent thermal stability, low reactivity, and high hardness, and from the groups 4a, 5a, and 6a of the periodic table as described above. The coating is often formed as the outermost surface layer of a hard coating layer made of carbide, nitride, carbonitride, or the like of at least one selected element.
前述したような最表面層としてα型酸化アルミニウム層を形成した硬質被覆層に関する先行技術としては、結晶粒形状に着目した技術として、例えば、工具基体の表面に、(a)下部層としてTi化合物層、(b)上部層として平板多角形(平坦六角形状を含む)状、かつ、たて長形状の結晶粒組織構造を有しZrを含有するα型酸化アルミニウム層を蒸着形成し、かつ、(c)上部層の結晶粒の内、面積比率で60%以上の結晶粒の内部は、少なくとも一つ以上のΣ3で表される構成原子共有格子点形態からなる結晶格子界面により分断されている表面被覆切削工具によって、硬質被覆層が高速重切削加工ですぐれた耐摩耗性を発揮することが知られている(例えば、特許文献1参照)。 As the prior art relating to the hard coating layer in which the α-type aluminum oxide layer is formed as the outermost surface layer as described above, as a technique focusing on the crystal grain shape, for example, on the surface of the tool base, (a) a Ti compound as the lower layer A layer, (b) a flat plate polygon (including a flat hexagonal shape) as an upper layer, and an α-type aluminum oxide layer containing Zr having a vertically long grain structure and vapor-deposited, and (C) Of the crystal grains in the upper layer, the interior of the crystal grains having an area ratio of 60% or more is divided by a crystal lattice interface composed of at least one constituent atom shared lattice point form represented by Σ3. It is known that a hard coating layer exhibits excellent wear resistance in high-speed heavy cutting with a surface-coated cutting tool (see, for example, Patent Document 1).
また、4a、5a、6a族元素の炭化物、窒化物および/またはこれらの固溶体を主体とする硬質相と鉄族金属を主体とする結合相、残りが炭化タングステンから(WC)なるWC基超硬合金において、硬質相の少なくとも一部の結晶粒内に4a、5a、6a族元素の炭化物、窒化物、酸化物およびまたはそれらの固溶体からなる少なくとも一種の化合物(結晶粒を構成する硬質相成分は除く)が存在する構造とすることにより得た硬度と靭性のバランスにすぐれたWC基超硬合金からなる工具基体に炭化チタンなどからなる硬質被覆層をCVD法で形成した表面被覆切削工具が非常にすぐれた耐欠損性と耐摩耗性を示すことが知られている(例えば、特許文献2参照)。 Further, a hard phase mainly composed of carbides, nitrides and / or solid solutions of group 4a, 5a, and 6a elements, a binder phase mainly composed of iron group metals, and a WC-based carbide composed of tungsten carbide (WC) as the remainder. In an alloy, at least one kind of compound consisting of carbides, nitrides, oxides and / or solid solutions of group 4a, 5a and 6a elements in at least some of the crystal grains of the hard phase (the hard phase component constituting the crystal grains is The surface-coated cutting tool in which a hard coating layer made of titanium carbide or the like is formed on a tool base made of a WC-based cemented carbide with a good balance between hardness and toughness obtained by adopting a CVD method is very useful. It is known that it exhibits excellent fracture resistance and wear resistance (see, for example, Patent Document 2).
また、WC基超硬合金製工具基体表面に0.2〜2.0μmの平均層厚のCrN層からなる硬質被覆層を物理蒸着で形成した表面被覆切削工具において、前記CrN層が、平均層厚と等しい高さを有し、工具基体表面に対して直立方向に成長した縦長平板状CrN結晶粒からなり、かつ、CrN層の表面から0.1μmの深さの水平断面における結晶粒組織を観察した場合、短辺が5〜100nm、アスペクト比が3以上である縦長平板状CrN結晶粒の占める面積割合が、全水平断面積の30%以上である構成とすることによって、断続重切削加工で硬質被覆層がすぐれた耐欠損性を発揮することが知られている(例えば、特許文献3参照)。 Further, in the surface-coated cutting tool in which a hard coating layer composed of a CrN layer having an average layer thickness of 0.2 to 2.0 μm is formed on the surface of a tool base made of a WC-based cemented carbide alloy by physical vapor deposition, the CrN layer is an average layer. A grain structure in a horizontal cross section having a height equal to the thickness and made of vertically long plate-like CrN crystal grains grown in an upright direction with respect to the tool base surface and having a depth of 0.1 μm from the surface of the CrN layer. When observed, the ratio of the area occupied by the vertically long plate-like CrN crystal grains having a short side of 5 to 100 nm and an aspect ratio of 3 or more is 30% or more of the total horizontal cross-sectional area. It is known that the hard coating layer exhibits excellent fracture resistance (see, for example, Patent Document 3).
さらに、Al2O3層中にチタン酸化物を含有させることに着目した技術として、超硬合金またはサーメットからなる工具基体上の単一層または多層の被覆の場合には0.5〜25μmの厚さを有する少なくとも1層は、Al2O3層およびZrO2および/またはHfO2層を有し該層中に、チタンの酸化物、炭酸化物、窒酸化物または炭酸窒化物からなる第3の微細分散性相が導入されていることにより、耐摩耗性が改善することが知られている(例えば、特許文献4参照)。 Furthermore, as a technique focused on including titanium oxide in the Al 2 O 3 layer, a thickness of 0.5 to 25 μm in the case of a single layer or multilayer coating on a tool substrate made of cemented carbide or cermet. At least one layer having an Al 2 O 3 layer and a ZrO 2 and / or HfO 2 layer, in which a third oxide comprising titanium oxide, carbonate, nitride oxide or carbonitride is formed. It is known that the wear resistance is improved by introducing a finely dispersible phase (see, for example, Patent Document 4).
前述したような従来の硬質被覆層としての酸化アルミニウム層の被覆形成方法としては、通常は、化学蒸着(CVD)法や物理蒸着(PVD)法が採用されているが、その他に、ゾル−ゲル法によって酸化アルミニウム層を形成することも知られている。ゾルーゲル法は溶液から出発して多孔質ゲル、有機無機ハイブリッド、ガラス、セラミックス、ナノコンポジットを作成できる材料合成法である。高温材料を従来の熔融法や焼結法に比べて低い温度で作成でき、また、種々の微細構造や、バルク体、ファイバー、コーティング、粒子など様々な形態の製品を作るのに応用できる比較的新しい被覆形成方法として期待されている。 As a conventional method for forming a coating of an aluminum oxide layer as a hard coating layer as described above, a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method is usually employed. It is also known to form an aluminum oxide layer by the method. The sol-gel method is a material synthesis method that can create a porous gel, organic-inorganic hybrid, glass, ceramics, and nanocomposite starting from a solution. High temperature materials can be produced at lower temperatures than conventional melting and sintering methods, and can be applied to produce various microstructures, products of various forms such as bulk bodies, fibers, coatings, and particles. It is expected as a new coating formation method.
硬質被覆層として酸化アルミニウム層をCVD法により被覆形成した表面被覆切削工具においては、鋼や鋳鉄等の高速断続切削加工に際し、被覆工具のすくい面での耐摩耗性向上が挙げられるが、これは、特に、形成されるα型酸化アルミニウムの熱安定性、非反応性が高いことによるものである。 In surface-coated cutting tools in which an aluminum oxide layer is formed by a CVD method as a hard coating layer, the wear resistance on the rake face of the coated tool can be improved during high-speed intermittent cutting of steel, cast iron, etc. In particular, this is due to the high thermal stability and non-reactivity of the α-type aluminum oxide formed.
前記特許文献1に開示されたα型酸化アルミニウム層においては、高温強度および表面性状が満足できるものでないため、より高速条件下での重切削加工を行った場合には、チッピングを発生しやすいばかりか、熱塑性変形、偏摩耗をも発生しやすく、これを原因とした耐摩耗性の低下により、比較的短時間で使用寿命に至るという課題があった。 The α-type aluminum oxide layer disclosed in Patent Document 1 is not satisfactory in high-temperature strength and surface properties. Therefore, when heavy cutting is performed under higher speed conditions, chipping is likely to occur. However, there is a problem that thermoplastic deformation and uneven wear are likely to occur, and due to this deterioration of wear resistance, the service life is reached in a relatively short time.
また、前記特許文献2に開示された炭化チタン層は、結晶性が低く機械的特性や界面強度が劣るため剥離を生じやすく、酸化アルミニウム層の被覆を行ったとしても結果的に急激に摩耗が進んでしまうという課題があった。 In addition, the titanium carbide layer disclosed in Patent Document 2 has low crystallinity and poor mechanical properties and interface strength, and thus easily peels off. Even when the aluminum oxide layer is coated, the titanium carbide layer is rapidly worn. There was a problem of progress.
また、前記特許文献3に開示されたCrN層は、断続重切削加工に用いた場合には、層内でのクラックの進展を避けられず、これを原因として層の剥離や欠損が生じるという課題があった。 In addition, when the CrN layer disclosed in Patent Document 3 is used for intermittent heavy cutting, it is unavoidable that cracks develop in the layer, and this causes peeling and chipping of the layer. was there.
また、前記特許文献4に開示されたAl2O3層およびZrO2および/またはHfO2層を有し該層中にチタンの酸化物、炭酸化物、窒酸化物または炭酸窒化物から成る第3の微細分散性相が導入した複合材料においては、切削時に生じる熱により、刃先の塑性変形が起きるという課題が生じていた。 Further, there is provided an Al 2 O 3 layer and a ZrO 2 and / or HfO 2 layer disclosed in Patent Document 4 and a third layer made of an oxide, carbonate, nitride oxide or carbonitride of titanium in the layer. In the composite material in which the finely dispersible phase is introduced, there has been a problem that the plastic deformation of the cutting edge occurs due to heat generated during cutting.
そこで、本発明が解決しようとする技術的課題、すなわち、本発明の目的は、硬質被覆層として酸化アルミニウム層を被覆形成した表面被覆切削工具において、鋳鉄や炭素鋼等の高速断続切削に用いた場合にあっても、チッピングや剥離が起こりにくく、長期間に亘ってすぐれた切削性能を発揮する表面被覆切削工具を提供することである。 Therefore, the technical problem to be solved by the present invention, that is, the object of the present invention, was used for high-speed intermittent cutting of cast iron, carbon steel, etc. in a surface-coated cutting tool in which an aluminum oxide layer was formed as a hard coating layer. Even in such a case, it is an object to provide a surface-coated cutting tool that hardly causes chipping and peeling and exhibits excellent cutting performance over a long period of time.
そこで、本発明者等は、工具基体表面に耐摩耗性にすぐれた酸化アルミニウム層を形成すべく、これまで切削工具用の硬質被覆層の形成法としては、十分な研究が行われていなかったゾル−ゲル法による酸化アルミニウム層の形成に注目して鋭意検討したところ、ゾルーゲル法で酸化アルミニウム層を形成した後の乾燥及び焼成処理を所定の方法にて行うか、ゾルーゲル法で酸化アルミニウム層を形成する際に、酸化アルミニウムの結晶化を促進する効果のあるTi酸化物を応用し、あらかじめCVD法やPVD法、ゾル-ゲル法等で形成されたTi酸化物層上にゾル−ゲル法での酸化アルミニウム層を形成することで、複雑な結晶粒形状を有する酸化アルミニウム層を所望のサイズとアスペクト比にて形成させることができ、切れ刃に断続的・衝撃的負荷が作用する高速断続切削加工に供した場合でも、隣接する結晶粒同士が凹凸に沿って互いに噛み合うことで、結晶粒同士の密着力が高まり、耐チッピング性、耐剥離性にすぐれ、長期間に亘ってすぐれた切削性能を維持できることを見出した。 Therefore, the present inventors have not been sufficiently studied as a method for forming a hard coating layer for a cutting tool so far to form an aluminum oxide layer having excellent wear resistance on the surface of the tool base. As a result of diligent investigation focusing on the formation of the aluminum oxide layer by the sol-gel method, the aluminum oxide layer is formed by the sol-gel method and then dried and fired by a predetermined method, or the aluminum oxide layer is formed by the sol-gel method. When forming, a Ti oxide having an effect of promoting crystallization of aluminum oxide is applied, and a sol-gel method is used on a Ti oxide layer formed in advance by a CVD method, a PVD method, a sol-gel method, or the like. By forming an aluminum oxide layer, an aluminum oxide layer having a complex crystal grain shape can be formed with a desired size and aspect ratio, and intermittently on the cutting edge・ Even when subjected to high-speed intermittent cutting where impact load is applied, the adjacent crystal grains mesh with each other along the unevenness to increase the adhesion between the crystal grains, providing excellent chipping resistance and peeling resistance. It was found that excellent cutting performance can be maintained over a long period of time.
即ち、酸化アルミニウム層をRTA(赤外線加熱)法などの基体のみを加熱できる熱処理方法で、あるいは、酸化アルミニウム層を形成する際にTi酸化物を応用したゾル-ゲル法により、酸化アルミニウム層下部に優先的に結晶化するような起点を意図して配置し熱処理することで、特定の結晶粒を選択的に結晶成長させることができ、結晶成長時に他の結晶粒に阻害されることなく、酸化アルミニウム層中のあらゆる方向に結晶成長した、凹凸性の高い結晶粒界からなる複雑形状の結晶粒が形成できる。さらに、焼成条件により結晶粒のサイズ及びアスペクト比、酸化アルミニウム層の結晶構造を制御することができ、結晶粒同士のアンカー効果により粒界における強度が大きく向上するとともに、優れた耐摩耗性や潤滑性を有するために、大きな衝撃や刃先近傍で発熱により、剥離や微小チッピングなどの異常損傷が起きやすい高速断続切削を行った場合においても長期間に亘ってすぐれた切削性能が発揮されることを見出した。 That is, the aluminum oxide layer is formed on the lower portion of the aluminum oxide layer by a heat treatment method such as an RTA (infrared heating) method, or by a sol-gel method using a Ti oxide when forming the aluminum oxide layer. By placing and heat-treating with the intention to preferentially crystallize, specific crystal grains can be selectively grown and oxidized without being obstructed by other crystal grains during crystal growth. Crystal grains having a complicated shape composed of crystal grain boundaries with high unevenness, which have grown in all directions in the aluminum layer, can be formed. Furthermore, the size and aspect ratio of the crystal grains and the crystal structure of the aluminum oxide layer can be controlled by the firing conditions, and the strength at the grain boundary is greatly improved by the anchor effect between the crystal grains, as well as excellent wear resistance and lubrication. Therefore, even when performing high-speed intermittent cutting that is prone to abnormal damage such as peeling or microchipping due to large impacts or heat generation near the cutting edge, excellent cutting performance is demonstrated over a long period of time. I found it.
本発明は、前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からなる工具基体の表面に、硬質被覆層を被覆形成してなる表面被覆切削工具において、
(a)前記硬質被覆層は、0.2〜5.0μmの平均層厚を有する酸化アルミニウム層を具備し、
(b)前記酸化アルミニウム層を構成する結晶粒は、α型またはα型とγ型の混相の結晶構造を有し、
(c)前記酸化アルミニウム層の縦断面における各々の結晶粒形状を電子線後方散乱回折法により定め、層厚垂直方向の粒径に対する層厚方向の粒径の比を各結晶粒のアスペクト比とした場合に、前記結晶粒の平均アスペクト比は、0.5〜5.0であり、
(d)前記酸化アルミニウム層の縦断面における各々の結晶粒形状を電子線後方散乱回折法により定め、各結晶粒の周長と結晶粒面積を求めた場合に、当該結晶粒面積と等しい面積を有する円の周長に対する当該結晶粒の周長の比の平均値が、1.8〜3.0であることを特徴とする表面被覆切削工具。
(2) 前記酸化アルミニウム層は、チタン酸化物の結晶粒を含有し、
(a)前記酸化アルミニウム層中の全金属元素に占めるTiの含有割合は、0.02at%を超え10at%以下であり、
(b)前記チタン酸化物の結晶粒は、平均粒径0.01〜0.10μmのチタン酸化物微粒子であり、該チタン酸化物微粒子は前記酸化アルミニウム層を構成する結晶粒を囲繞するように凝集形成されているとともに、前記酸化アルミニウム層を構成する結晶粒の周長上に存在するチタン酸化物微粒子の数の平均値が、5〜50個であることを特徴とする(1)に記載の表面被覆切削工具。
(3) 炭化タングステン基超硬合金からなる工具基体の表面に、硬質被覆層を被覆形成してなる表面被覆切削工具において、
上記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)まzたは(2)に記載の表面被覆切削工具。
(4) 炭窒化チタン基サーメットからなる工具基体の表面に、硬質被覆層を被覆形成してなる表面被覆切削工具において、
上記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)または(2)に記載の表面被覆切削工具。
(5) 前記酸化アルミニウム層は、ゾルーゲル法によりチタン酸化物層上に形成することを特徴とする前記(1)乃至(4)に記載の表面被覆切削工具の製造方法。」
を特徴とするものである。
The present 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 made of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet,
(A) The hard coating layer comprises an aluminum oxide layer having an average layer thickness of 0.2 to 5.0 μm,
(B) The crystal grains constituting the aluminum oxide layer have an α-type or α-type and γ-type mixed phase crystal structure,
(C) The shape of each crystal grain in the longitudinal section of the aluminum oxide layer is determined by an electron beam backscatter diffraction method , and the ratio of the grain size in the layer thickness direction to the grain size in the layer thickness vertical direction is defined as the aspect ratio of each crystal grain. when an average aspect ratio of the crystal grains, Ri 0.5-5.0 der,
(D) When each crystal grain shape in the longitudinal section of the aluminum oxide layer is determined by an electron beam backscatter diffraction method, and the perimeter of each crystal grain and the crystal grain area are obtained, an area equal to the crystal grain area is The surface-coated cutting tool, wherein the average value of the ratio of the circumference of the crystal grains to the circumference of the circle is 1.8 to 3.0.
(2) The aluminum oxide layer contains titanium oxide crystal grains,
(A) The content ratio of Ti in all the metal elements in the aluminum oxide layer is more than 0.02 at% and 10 at% or less,
(B) The titanium oxide crystal grains are titanium oxide fine particles having an average particle diameter of 0.01 to 0.10 μm, and the titanium oxide fine particles surround the crystal grains constituting the aluminum oxide layer. (1) The average number of titanium oxide fine particles that are aggregated and are present on the circumference of crystal grains constituting the aluminum oxide layer is 5 to 50. Surface coated cutting tool.
(3) In a surface-coated cutting tool formed by coating a hard coating layer on the surface of a tool base made of a tungsten carbide-based cemented carbide,
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 is formed, and an average content of Co as a binder phase metal contained in the base surface hardened layer is The surface-coated cutting tool according to (1) or z (2), wherein the surface-coated cutting tool is less than 2.0% by mass.
(4) In a surface-coated cutting tool formed by coating a hard coating layer on the surface of a tool base composed of a titanium carbonitride-based cermet,
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 is formed, and the total average of Co and Ni as binder phase metals contained in the base surface hardened layer Content is less than 2.0 mass%, The surface-coated cutting tool as described in (1) or (2) characterized by the above-mentioned.
(5) The method for manufacturing a surface-coated cutting tool according to (1) to (4), wherein the aluminum oxide layer is formed on the titanium oxide layer by a sol-gel method. "
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.
(a)硬質被覆層を構成する酸化アルミニウム層の平均層厚:
本発明の表面被覆切削工具は、硬質被覆層としてゾル−ゲル法により成膜した平均層厚0.2〜5.0μmの酸化アルミニウム層を備えているが、酸化アルミニウム層の平均層厚が0.2μm未満であると、前述したような凹凸性の高い結晶粒界によって奏される結晶粒同士のアンカー効果による粒界における強度の向上という本発明に特有な効果が十分に奏されず、一方、平均層厚が5.0μmを超えると、層の剥離が生じやすくなるため、好ましくない。そのため、酸化アルミニウム層の平均層厚は0.2〜5.0μmと定めた。
(A) Average layer thickness of the aluminum oxide layer constituting the hard coating layer:
The surface-coated cutting tool of the present invention includes an aluminum oxide layer having an average layer thickness of 0.2 to 5.0 μm formed as a hard coating layer by a sol-gel method, but the average layer thickness of the aluminum oxide layer is 0. When the thickness is less than 2 μm, the effect specific to the present invention, that is, the improvement in strength at the grain boundary due to the anchor effect between the crystal grains exhibited by the crystal grain boundary having high unevenness as described above, is not sufficiently achieved, When the average layer thickness exceeds 5.0 μm, the layer is likely to be peeled off, which is not preferable. Therefore, the average layer thickness of the aluminum oxide layer is set to 0.2 to 5.0 μm.
(b)酸化アルミニウム層を構成する結晶粒の結晶構造:
酸化アルミニウムの結晶形態にはα、κ、γ、δ、θがあるが、ゾルーゲル法を用いて酸化アルミニウム層を形成した場合、γ型の結晶構造を有する結晶粒から構成される酸化アルミニウム層が主に形成されるが、γ型酸化アルミニウムは高い潤滑性を有することから、耐溶着性や切削時の発熱抑制効果は高いものの、高温硬さが優れず、耐摩耗性が乏しいために、特に刃先付近での発熱が大きくなる高速切削においては比較的短時間で摩滅してしまうことから、単独では表面被覆切削工具の硬質被覆層として十分ではなかった。本発明においては、所定の乾燥及び焼成処理により酸化アルミニウム層を形成する、あるいは、TiO2やTi2O3、Ti3O5、Ti4O7などのチタン酸化物(以下、「Ti酸化物」とも記す。)を酸化アルミニウム層の下地に応用することによって、結晶化を促進させるため、焼成条件はもちろん、Ti酸化物下地層厚みによっても酸化アルミニウム層の結晶構造を制御できる。なお、刃先温度が高くなる高速切削においては、高温硬さや耐熱性に優れたα型の酸化アルミニウム層であることが望ましく、刃先での発熱抑制や耐溶着性が求められる切削形態においてはα型酸化アルミニウムとともにγ型酸化アルミニウムを含んでいる方が良い。したがって、酸化アルミニウム層を構成する結晶粒の結晶構造は、α型またはα型とγ型の混相と定めた。
(B) Crystal structure of crystal grains constituting the aluminum oxide layer:
There are α, κ, γ, δ, and θ in the crystal form of aluminum oxide, but when an aluminum oxide layer is formed using a sol-gel method, an aluminum oxide layer composed of crystal grains having a γ-type crystal structure is formed. Although mainly formed, γ-type aluminum oxide has high lubricity, so although it has high welding resistance and heat generation suppressing effect at the time of cutting, it is not excellent in high temperature hardness and poor in wear resistance. In high-speed cutting in which heat generation near the cutting edge increases, it wears out in a relatively short time, so that it is not sufficient as a hard coating layer for a surface-coated cutting tool alone. In the present invention, an aluminum oxide layer is formed by a predetermined drying and baking treatment, or a titanium oxide such as TiO 2 , Ti 2 O 3 , Ti 3 O 5 , Ti 4 O 7 (hereinafter referred to as “Ti oxide”). Is applied to the base of the aluminum oxide layer to promote crystallization, and the crystal structure of the aluminum oxide layer can be controlled not only by the firing conditions but also by the thickness of the Ti oxide base layer. In high-speed cutting where the cutting edge temperature is high, it is desirable that the α-type aluminum oxide layer is excellent in high-temperature hardness and heat resistance. In cutting forms that require suppression of heat generation at the cutting edge and welding resistance, the α-type It is better to contain γ-type aluminum oxide together with aluminum oxide. Therefore, the crystal structure of the crystal grains constituting the aluminum oxide layer was determined to be α-type or α-type and γ-type mixed phase.
(c)酸化アルミニウム層を構成する結晶粒のアスペクト比および結晶粒形状:
本発明においては、酸化アルミニウム層を構成する結晶粒のアスペクト比を所定の値に制御するとともに酸化アルミニウム結晶粒の周縁部、すなわち粒界の形状を凹凸の多い形状とすることによって、隣接する結晶粒同士が凹凸に沿って互いに噛み合うことで、いわゆるアンカー効果による高い密着力を付与でき、耐摩耗性および耐チッピング性を向上させることができることを見出した。また、前述の結晶粒の周縁部の形状については、結晶粒の結晶粒面積と等しい面積を有する円の周長に対する結晶粒の周長の比の値を用いることによって、定量的に評価できることを数多くの実験を行うことにより確認した。
すなわち、該酸化アルミニウム層の縦断面を、例えば縦横8μm×6μmの観察視野、測定ステップ50nmにて電子線後方散乱回折法を用いて、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場合に、前記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と定めた。
また、上記平均アスペクト比と同様に、横8μm×6μmの観察視野、測定ステップ50nmにて電子線後方散乱回折法により該酸化アルミニウム層を構成する結晶粒各々の形状を5視野に対して求め、各結晶粒の粒界の長さ、つまり各結晶粒形状の外周の長さを各結晶粒の周長とした場合に、結晶粒の結晶粒面積を電子線後方散乱回折法により求めた結晶粒面積と等しい面積を有する円の周長に対する当該結晶粒の周長の比の平均値が、1.8未満であると粒界形状は凹凸が少なく、比較的滑らかになってしまい、結晶粒同士の噛み合いが小さくなるために、アンカー効果が得られず、結晶粒同士の結合力の向上の効果が十分に奏されない。一方、3.0を超えると一つの結晶粒に着目した場合、凹凸の非常に大きい結晶粒形状となるため、例えば、細長い凸部などの形状的に脆弱な部分が形成されてしまうため、クラックが発生しやすく、性能が劣位となる。したがって、結晶粒の結晶粒面積を電子線後方散乱回折法により求めた結晶粒面積と等しい面積を有する円の周長に対する当該結晶粒の平均値は、1.8〜3.0と定めた。
(C) Aspect ratio and crystal grain shape of crystal grains constituting the aluminum oxide layer:
In the present invention, by controlling the aspect ratio of the crystal grains constituting the aluminum oxide layer to a predetermined value and making the peripheral portion of the aluminum oxide crystal grains, that is, the shape of the grain boundary, a shape with many irregularities, adjacent crystals It has been found that by allowing the grains to mesh with each other along the unevenness, a high adhesion force due to a so-called anchor effect can be imparted, and wear resistance and chipping resistance can be improved. The shape of the peripheral edge of the crystal grain can be quantitatively evaluated by using the value of the ratio of the circumference of the crystal grain to the circumference of a circle having an area equal to the crystal grain area of the crystal grain. This was confirmed by conducting numerous experiments.
That is, the vertical cross section of the aluminum oxide layer is divided into 5 visual fields, for example, using an electron beam backscatter diffraction method at an observation visual field of 8 μm × 6 μm in vertical and horizontal directions and a measurement step of 50 nm. In this case, the maximum diameter in the vertical direction of the layer thickness is defined as the grain size in the vertical direction of the layer thickness, and the maximum diameter in the layer thickness direction is defined as the grain size in the layer thickness direction. When the ratio of the grain sizes in the direction is calculated and the average value is defined as the average aspect ratio of the crystal grains in the aluminum oxide layer, the average aspect ratio of the crystal grains is less than 0.5 for wear resistance. On the other hand, if it exceeds 5.0, a coarse structure is formed, and drop-off chipping is easily performed. Therefore, the average aspect ratio of the crystal grains constituting the aluminum oxide layer was determined to be 0.5 to 5.0.
Further, similarly to the above average aspect ratio, the shape of each crystal grain constituting the aluminum oxide layer is obtained with respect to 5 fields of view by an electron beam backscatter diffraction method at an observation field of 8 μm × 6 μm in a lateral direction and a measurement step of 50 nm, When the length of the grain boundary of each crystal grain, that is, the length of the outer periphery of each crystal grain shape is the circumference of each crystal grain, the crystal grain area of the crystal grain obtained by electron beam backscatter diffraction method If the average value of the ratio of the circumference of the crystal grains to the circumference of a circle having an area equal to the area is less than 1.8, the grain boundary shape has few irregularities and becomes relatively smooth, Therefore, the anchor effect cannot be obtained, and the effect of improving the bonding force between the crystal grains is not sufficiently achieved. On the other hand, if one crystal grain exceeds 3.0, it becomes a crystal grain shape with very large irregularities, so that, for example, a shape-fragile part such as an elongated convex part is formed. Is likely to occur and the performance is inferior. Therefore, the average value of the crystal grains with respect to the circumference of a circle having an area equal to the crystal grain area obtained by the electron beam backscattering diffraction method was determined to be 1.8 to 3.0.
なお、前記酸化アルミニウム層は、工具基体に直接成膜することで、その性能を発揮することは可能であるが、炭窒化チタンを含む超硬合金を基体とする場合は窒素雰囲気中での焼成により、工具基体表面付近に、Ti、Ta、Nb、Zrのうち、少なくとも1種の耐摩耗性の高い炭窒化物を多く含有させ、基体表面硬化層を形成させるとともに、酸化アルミニウム層と工具基体と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、該基体表面硬化層形成後の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。その際、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)を用いて工具基体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1μm×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の平均含有量を検出した場合に、2.0質量%未満にすれば、工具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。 The aluminum oxide layer can exhibit its performance by forming a film directly on the tool base. However, when a cemented carbide containing titanium carbonitride is used as the base, firing is performed in a nitrogen atmosphere. Thus, in the vicinity of the surface of the tool base, a large amount of at least one kind of highly wear-resistant carbonitride of Ti, Ta, Nb, and Zr is contained to form a base surface hardened layer, and an aluminum oxide layer and a tool base It is possible to improve the adhesion strength and extend the tool life. In addition, it is preferable that the hardness of the cemented carbide base body after this base-surface hardened layer formation is 2200 or more and 2800 or less in terms of Vickers hardness (Hv). At that time, Co in the vicinity of the substrate surface is relatively reduced by containing a large amount of carbonitride, and for example, 0.5 to 3 in the depth direction from the tool substrate surface using a scanning electron microscope (SEM). 2.0 mass when the average content of Co as a binder phase metal is detected by observing a cross section of 0.0 μm and quantitative analysis by wavelength dispersive X-ray spectroscopy in an analysis visual field region of 1 μm × 1 μm. If it is less than%, carbonitrides that cause surface hardening of the tool substrate are sufficiently formed, and wear resistance is further improved.
また、炭窒化チタン基サーメットを基体とする場合には、焼結工程において昇温およ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圧力の窒素雰囲気中で実施すると、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、工具基体のごく表面のみ脱窒されることにより、NiやCo金属結合相へのTiやNbなどの溶解および内部から工具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、工具基体表面硬化層が形成されるためである。なお、工具基体表面硬化層形成後の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、その際は前述した超硬合金基体と同様に、工具基体表面付近におけるNiおよびCoは相対的に減ることとなり、結合相金属としてのNiおよびCoの合計平均含有量を2.0質量%未満にすれば、工具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。 When the titanium carbonitride-based cermet is used as a substrate, the atmosphere when holding at the highest temperature and the highest temperature in the sintering step 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 carried out in a nitrogen atmosphere at a constant pressure, a carbonitride having a high hardness is uniformly formed inside the substrate. Is treated under a relatively high nitrogen pressure, and when treated in a nitrogen atmosphere with a reduced pressure from the middle of holding or when the temperature is lowered, only the very surface of the tool base is denitrified, resulting in a Ni or Co metal bonded phase. This is because dissolution of Ti, Nb, etc. and diffusion from the inside to the tool base surface become active, and formation of carbonitrides such as Ti, Nb, etc. is promoted on the surface, and a tool base surface hardened layer is formed. In addition, it is preferable that the hardness of the cermet base | substrate after forming a tool base surface hardened layer is 2000-2600 in terms of Vickers hardness (Hv). In this case, similarly to the cemented carbide substrate described above, Ni and Co in the vicinity of the tool substrate surface are relatively reduced, and the total average content of Ni and Co as the binder phase metal is 2.0% by mass. If it is less than this, the carbonitride which causes the surface hardening of the tool base is sufficiently formed, and the wear resistance is further improved.
また、本発明の表面被覆切削工具は、工具基体の表面に直接酸化アルミニウム層を形成せずに、当業者において既に知られている硬質皮膜、即ち、周期律表の4a、5a、6a族およびSiから選ばれる少なくとも1種以上の元素を含有する窒化物、もしくは酸化物からなる少なくとも1層以上の硬質皮膜を物理蒸着(PVD)法、化学蒸着(CVD)法またはゾル−ゲル法により形成した後、該硬質皮膜の表面に前記酸化アルミニウム層を被覆形成してもよい。 Further, the surface-coated cutting tool of the present invention does not form an aluminum oxide layer directly on the surface of the tool base, but is already known to those skilled in the art, that is, a hard coating, that is, groups 4a, 5a, 6a in the periodic table and A hard film of at least one layer made of nitride or oxide containing at least one element selected from Si was formed by physical vapor deposition (PVD), chemical vapor deposition (CVD), or sol-gel method. Thereafter, the aluminum oxide layer may be formed on the surface of the hard coating.
本発明の表面被覆切削工具の硬質被覆層を構成する酸化アルミニウム層は、後述するようにゾル−ゲル法による酸化アルミニウム層の形成方法としてRTA法などによる熱処理を実施するか、あるいは、CVD法等で成膜されたTi酸化物の上にゾル−ゲル法により酸化アルミニウム層を成膜することで、特定の箇所で選択的に結晶化を促進でき、該酸化アルミニウム層中の結晶粒は比較的自由度高く結晶成長できるため、凹凸性の高い複雑形状の結晶粒界を有する酸化アルミニウム結晶粒が形成される。
なお、刃先に多く負荷のかかる切込の大きい断続切削では、結晶化促進効果を有するTi酸化物自体を該酸化アルミニウム層中に分散形成させ、性能向上に寄与させることができる。該酸化アルミニウム層中にTi酸化物微粒子を分散せしめるには、上記記載のTi酸化物下地上に酸化アルミニウムを成膜したのち、下地Ti酸化物が分解し、酸化アルミニウム層中に拡散混合する900℃以上の温度で焼成するのが望ましい。該方法によるとTi酸化物が微粒となり、酸化アルミニウム層中に侵入すると共に、該酸化アルミニウム結晶粒の周囲に形成されるため、断続切削時の衝撃を緩和することができ、優れた耐摩耗性を長時間にわたって発揮できる。
As described later, the aluminum oxide layer constituting the hard coating layer of the surface-coated cutting tool of the present invention is subjected to a heat treatment by an RTA method or the like as a method for forming an aluminum oxide layer by a sol-gel method, or a CVD method or the like. By forming an aluminum oxide layer on the Ti oxide formed by the sol-gel method, crystallization can be selectively promoted at a specific location, and the crystal grains in the aluminum oxide layer are relatively Since the crystal can be grown with a high degree of freedom, aluminum oxide crystal grains having complex grain boundaries with high unevenness are formed.
In interrupted cutting with a large depth of cut that requires a lot of load on the cutting edge, Ti oxide itself having a crystallization promoting effect can be dispersedly formed in the aluminum oxide layer to contribute to performance improvement. In order to disperse the Ti oxide fine particles in the aluminum oxide layer, after forming the aluminum oxide film on the Ti oxide base described above, the base Ti oxide is decomposed and diffused and mixed in the aluminum oxide layer 900 It is desirable to bake at a temperature of ℃ or higher. According to this method, the Ti oxide becomes fine particles and penetrates into the aluminum oxide layer and is formed around the aluminum oxide crystal grains, so that the impact during intermittent cutting can be reduced and excellent wear resistance. Can be demonstrated for a long time.
(d)酸化アルミニウム層中のTi酸化物の含有割合:
本発明の酸化アルミニウム層は、所定の焼成処理や酸化アルミニウム層のTi酸化物を下地として用いることで、結晶粒の周縁部の形状を凹凸が多い形状とすることを特徴としているが、Ti酸化物を下地として用いた場合に焼成条件によっては、該酸化アルミニウム層中にTi酸化物粒を導入することができ、特に断続切削において耐摩耗性を向上しうることを見出した。
その際、前記Ti酸化物結晶粒は、酸化アルミニウム層を透過型電子顕微鏡(TEM)で観察した場合に、図1、図2、図3に示すように、平均粒径0.01〜0.10μmの微細結晶粒として観察され、例えばTEMを用いたエネルギー分散形X線分析装置による元素マッピングを行うと、Ti酸化物結晶粒は酸化アルミニウム結晶粒の周囲に形成されていることがわかる。そして、その数の平均値は、結晶粒の一周長上に5〜50個であることが分かる。
さらに、Ti酸化物が分散された酸化アルミニウム層中の全金属元素中に占めるTiの含有割合を、例えば、縦断面視野領域0.2μm×0.3μmの範囲でTEMに付属されたエネルギー分散形X線分析装置による観察視野範囲内の定量分析を5視野実施し、その平均値を求めると、0.02at%を超え10at%以下であることが分かる。
なお、図1によれば、酸化アルミニウム結晶粒の結晶粒界には、該酸化アルミニウム結晶粒を取り囲むようにTi酸化物微粒子(図1中、矢印で示した部分)が形成されていることが観察される。
(D) Content ratio of Ti oxide in the aluminum oxide layer:
The aluminum oxide layer of the present invention is characterized in that the peripheral portion of the crystal grain has a shape with many irregularities by using a predetermined baking treatment or Ti oxide of the aluminum oxide layer as a base. It was found that Ti oxide particles can be introduced into the aluminum oxide layer depending on the firing conditions when an object is used as a base, and wear resistance can be improved particularly in intermittent cutting.
At that time, the Ti oxide crystal grains have an average particle diameter of 0.01 to 0.00 mm as shown in FIGS. 1, 2 and 3 when the aluminum oxide layer is observed with a transmission electron microscope (TEM). Observed as fine crystal grains of 10 μm, for example, when element mapping is performed by an energy dispersive X-ray analyzer using TEM, it can be seen that Ti oxide crystal grains are formed around aluminum oxide crystal grains. And it turns out that the average value of the number is 5-50 pieces on the circumference of a crystal grain.
Furthermore, the content ratio of Ti in the total metal elements in the aluminum oxide layer in which the Ti oxide is dispersed is, for example, the energy dispersion type attached to the TEM in the range of the longitudinal cross-sectional viewing area of 0.2 μm × 0.3 μm. When the quantitative analysis within the observation visual field range by the X-ray analyzer is carried out and the average value is obtained, it is found that it is more than 0.02 at% and not more than 10 at%.
According to FIG. 1, Ti oxide fine particles (portions indicated by arrows in FIG. 1) are formed at the crystal grain boundaries of the aluminum oxide crystal grains so as to surround the aluminum oxide crystal grains. Observed.
ここで、酸化アルミニウム結晶粒の周囲に形成されているTi酸化物微粒子の数の平均値が、一周長上に5個未満では、十分に切削時の衝撃を緩和することができず、一方、50個を超えると酸化アルミニウム素地より孤立してしまい切削時に脱落しやすく好ましくない。したがって、好ましい酸化アルミニウム結晶粒の周囲に形成されているTi酸化物微粒子の数は、5〜50個と定めた。 Here, if the average value of the number of Ti oxide fine particles formed around the aluminum oxide crystal grains is less than 5 on the circumference, the impact during cutting cannot be sufficiently mitigated, If the number exceeds 50, it is isolated from the aluminum oxide substrate and is likely to fall off during cutting. Therefore, the number of Ti oxide fine particles formed around the preferable aluminum oxide crystal grains is determined to be 5-50.
本発明の表面被覆切削工具の硬質被覆層を構成する酸化アルミニウム層は、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 aluminum oxide layer constituting the hard coating layer of the surface-coated cutting tool of the present invention can be formed 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(ASB)、アルミニウムプロポキシド)に溶媒としてアルコール(例えば、エタノール、1−ブタノール)や水を添加し、さらに、触媒として酸(例えば、塩酸、硝酸)、界面活性剤としてラウリン酸ナトリウム(C11H23COONa)、または、ドデシルベンゼンスルホン酸ナトリウム(DBSN)を添加した後、−10〜20℃以下の温度範囲にて、攪拌したのち、撹拌時の温度範囲と同様、−10〜20℃以下の温度範囲にて保持する熟成処理を、例えば、撹拌と熟成処理の合計時間が12時間以上という長時間かけて行うことによってアルミナゾルを形成する。なお、本発明で用いるアルミナゾルはジメチルホルムアミド(DMF)やアセチルアセトン(AcAc)をキレート化剤として用いることが望ましい。これは過度の結晶化促進を抑制するためであり、過度の結晶化促進を抑制させる効果のあるキレート化剤を使用しない場合には、結晶化が促進されやすく、酸化アルミニウムの結晶化が該層中のあらゆる場所で開始されてしまうことから、結晶の成長が別の結晶の成長に阻害されるために、微粒の組織となる傾向にあり、所望のサイズ、アスペクト比を有する複雑形状の結晶粒が形成されない。つまり、キレート化剤を使用することで結晶化開始温度が高くなるよう調製を行うと同時に、所定の焼成処理やTi酸化物を使用することで酸化アルミニウム層中の限定された特定の箇所で結晶化を開始させることで、結晶成長方向に関して比較的高い自由度をもちながら結晶成長できる結果、複雑形状の結晶粒界を有する酸化アルミニウム結晶粒を所望のサイズとアスペクト比で形成させることが出来る。
また、界面活性剤を使用するとゾルの濡れ性が向上し、膜の均一性が向上する。但し、ゾル中に添加した界面活性剤は乾燥工程において熱分解させて層中から取り除かないとクラックが形成しやすくなるため、十分取り除ける量としてAlのアルコキシドに対してモル比で0.1以下が望ましい。
Preparation of alumina sol:
First, an alcohol (eg, ethanol, 1-butanol) or water is added as a solvent to an aluminum alkoxide (eg, aluminum secondary butoxide (ASB) or aluminum propoxide), and an acid (eg, hydrochloric acid or nitric acid) is used as a catalyst. After adding sodium laurate (C 11 H 23 COONa) or sodium dodecylbenzenesulfonate (DBSN) as a surfactant, stirring was performed at a temperature range of −10 to 20 ° C. As in the temperature range, the aging treatment that is held in the temperature range of −10 to 20 ° C. or lower is performed, for example, by performing the stirring and the aging treatment for a long time of 12 hours or longer to form the alumina sol. The alumina sol used in the present invention desirably uses dimethylformamide (DMF) or acetylacetone (AcAc) as a chelating agent. This is to suppress excessive crystallization promotion. When a chelating agent having an effect of suppressing excessive crystallization promotion is not used, crystallization is easily promoted, and crystallization of aluminum oxide is performed in the layer. Since the growth of the crystal is inhibited by the growth of another crystal, it tends to become a fine-grained structure, and the crystal grain of a complicated shape having a desired size and aspect ratio Is not formed. In other words, preparation is performed so that the crystallization start temperature is increased by using a chelating agent, and at the same time, crystals are produced at a specific limited place in the aluminum oxide layer by using a predetermined baking treatment or Ti oxide. As a result, the crystal growth can be performed while having a relatively high degree of freedom in the crystal growth direction. As a result, aluminum oxide crystal grains having complex-shaped grain boundaries can be formed with a desired size and aspect ratio.
Further, when a surfactant is used, the wettability of the sol is improved and the uniformity of the film is improved. However, since the surfactant added in the sol is likely to crack if it is thermally decomposed in the drying process and not removed from the layer, the amount that can be sufficiently removed is 0.1 or less in terms of molar ratio to the alkoxide of Al. desirable.
なお、Ti酸化物による酸化アルミニウムの結晶化促進効果のメカニズムは明らかにされていないが、Ti酸化物が還元される際にAlを酸化するための酸素供給源となると考えられ、Ti酸化物の表面から酸化アルミニウム結晶粒が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。なお、酸化アルミニウム中のTi酸化物微粒子は焼成時に酸化アルミニウム結晶粒界を沿うように配置、形成されるが、該Ti酸化物微粒子の粒径は焼成時の雰囲気により粒径は変化し、雰囲気中の酸素量が多いと粒径は大きくなる傾向にあり、平均粒径が0.01μm未満であると、アルミニウムが酸化するのに必要な酸素の供給が十分ではないため結晶化しにくく、平均粒径が0.10μmを超えると、酸化アルミニウム層中に粗大なTi酸化物が含有していることとなり、焼成後はクラックや剥離の起点となりやすい。そのため、酸化アルミニウム層中のTi酸化物微粒子の平均粒径は0.01〜0.10μmとする。 Although the mechanism of the crystallization promotion effect of aluminum oxide by Ti oxide has not been clarified, it is considered that it becomes an oxygen supply source for oxidizing Al when Ti oxide is reduced. It becomes a starting point for growing aluminum oxide crystal grains from the surface, and crystallization is possible at a relatively low temperature in a limited portion near the Ti oxide. The Ti oxide fine particles in aluminum oxide are arranged and formed along the aluminum oxide crystal grain boundary at the time of firing. The particle diameter of the Ti oxide fine particles varies depending on the atmosphere at the time of firing, and the atmosphere When the amount of oxygen in the medium is large, the particle size tends to increase. When the average particle size is less than 0.01 μm, the supply of oxygen necessary for oxidation of aluminum is not sufficient, so that the crystallization is difficult. When the diameter exceeds 0.10 μm, a coarse Ti oxide is contained in the aluminum oxide layer, and after firing, it tends to be a starting point for cracks and peeling. Therefore, the average particle diameter of the Ti oxide fine particles in the aluminum oxide layer is set to 0.01 to 0.10 μm.
前述のような酸化アルミニウム層中にTi酸化物微粒子を分散含有させる構成とする場合、酸化アルミニウム層中の全金属元素に占めるTiの含有割合が、0.02at%以下であると、切削時の衝撃を緩和するのに必要なTi酸化物微粒子量が十分ではなく、一方、10at%を超えるとチタン酸化物の含有比率が高すぎるため酸化アルミニウムの有するすぐれた高温硬さと耐酸化性を発揮できない。したがって、酸化アルミニウム層中の全金属元素に占めるTiの含有割合は0.02at%を超え、10at%以下とすることが望ましい。 When the Ti oxide fine particles are dispersed and contained in the aluminum oxide layer as described above, the content ratio of Ti in the total metal elements in the aluminum oxide layer is 0.02 at% or less when cutting. The amount of Ti oxide fine particles necessary to alleviate the impact is not sufficient. On the other hand, if it exceeds 10 at%, the content of titanium oxide is too high, so that the excellent high temperature hardness and oxidation resistance of aluminum oxide cannot be exhibited. . Therefore, it is desirable that the content ratio of Ti in all the metal elements in the aluminum oxide layer is more than 0.02 at% and 10 at% or less.
通常行われるアルミナゾルの調製においては、40〜80℃での攪拌と、その攪拌温度で数時間程度の熟成処理が行われるが、本発明においては、−10〜20℃の低温度範囲における攪拌と熟成を、例えば、合計12時間以上行う長時間の低温処理を行うことが望ましい。
ここで、攪拌および熟成処理時の温度が20℃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20℃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、前記記載の所定の焼成方法やTi酸化物を用いた後工程の焼成処理において結晶化しにくくなってしまうため、−10〜20℃の低温温度範囲とした。
In the usual preparation of alumina sol, stirring at 40 to 80 ° C. and aging treatment for about several hours is performed at the stirring temperature. In the present invention, stirring in a low temperature range of −10 to 20 ° C. For example, it is desirable to perform long-term low-temperature treatment in which aging is performed for a total of 12 hours or more, for example.
Here, since the hydrolysis and polycondensation reaction proceed rapidly when the temperature during stirring and aging treatment exceeds 20 ° C., the aluminum oxide precursor is difficult to be formed densely, and in the subsequent baking treatment, α-type Since it becomes difficult to form aluminum oxide, the upper limit of the temperature during stirring and aging treatment is set to 20 ° C., whereas when the temperature during stirring and aging treatment is less than −10 ° C., hydrolysis and polycondensation reaction hardly proceed, Since it becomes difficult to crystallize in the subsequent baking process using the predetermined baking method and the Ti oxide described above, the low temperature range is set to −10 to 20 ° C.
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。 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.
乾燥処理および焼成処理:
RTA法にて熱処理する場合には前述のように調製したアルミナゾルを、工具基体の表面へ直接、あるいは、工具基体表面に化学蒸着(CVD)法や物理蒸着(PVD)法で形成した下地層としての硬質皮膜の表面へ塗布し、それに続き、アルミナゾル中の有機成分の熱分解速度がゆっくり進むよう5〜20℃/secというRTA法を使用した一般的なゾル-ゲル膜の形成にはあまり用いられない比較的遅い昇温速度で加熱し、100〜600℃、より好ましくは200〜500℃で5分以上保持して乾燥、冷却したのち、再度前記表面にアルミナゾルを塗布し、上記条件で乾燥処理を行う工程を所望の膜厚となるまで繰り返し実施し、アルミナの乾燥ゲルを形成後、600〜1100℃の温度範囲でRTA法による焼成処理を行って酸化アルミニウム層を被覆形成する。RTA法とは赤外線ランプから放射される電磁波により加熱する方法で、Siウェハー等の熱処理など、半導体産業で良く用いられている。非接触かつ急速な昇降温が可能であるとともに、近赤外線が用いられるため、被加熱物の透過率はもちろん、色などの表面状態によっても、吸収されやすさが異なるために、局所的な加熱が可能である。なお、本発明では昇温速度が速いと塗布膜中の有機成分が急激に燃焼、揮発するため、塗布膜中にポアができやすく緻密な膜となりにくい。また、1回の塗布による膜厚は、例えば焼成後における正味の膜厚として0.2μm以下がよく、薄く繰り返し形成することで、より緻密な膜が形成できる。
また、酸化アルミニウムの結晶化促進に効果のあるTi酸化物を応用する場合には、アルミナゾルを工具基体表面にCVD法などでTi酸化物層を形成した下地層の表面へ塗布するが、この場合も上記同様1回の塗布による膜厚は、0.2μm以下がよく、薄く繰り返し形成することで、より緻密な膜が形成できる。また、この場合乾燥や焼成などの熱処理はRTA法で行わなくてもよく、通常の電気炉で十分である。
電気炉を用いる場合には100〜600℃、より好ましくは200〜500℃での乾燥処理を1回以上繰り返し行い、次いで、600〜1100℃の温度範囲で焼成処理を行って酸化アルミニウム層を被覆形成する。
Drying and baking treatment:
When heat treatment is performed by the RTA method, the alumina sol prepared as described above is applied directly to the surface of the tool base or as a base layer formed on the surface of the tool base by chemical vapor deposition (CVD) or physical vapor deposition (PVD). Is applied to the surface of a hard film of the material, and is used less frequently for the formation of a general sol-gel film using the RTA method of 5 to 20 ° C./sec so that the thermal decomposition rate of the organic component in the alumina sol proceeds slowly. Heated at a relatively slow heating rate that is not possible, held at 100 to 600 ° C., more preferably 200 to 500 ° C. for 5 minutes or longer, dried and cooled, then coated with alumina sol on the surface again, and dried under the above conditions The treatment process is repeated until a desired film thickness is obtained, and after forming an alumina dry gel, firing is performed by the RTA method in a temperature range of 600 to 1100 ° C. A ruminium layer is coated. The RTA method is a method of heating by electromagnetic waves radiated from an infrared lamp, and is often used in the semiconductor industry such as heat treatment of Si wafers. Since non-contact and rapid temperature rise and fall are possible, and near infrared rays are used, the ease of absorption varies depending not only on the transmittance of the object to be heated but also on the surface condition such as color, so local heating Is possible. In the present invention, when the rate of temperature rise is high, the organic component in the coating film is rapidly burned and volatilized. Therefore, pores are easily formed in the coating film, and it is difficult to form a dense film. Moreover, the film thickness by one application | coating is 0.2 micrometers or less as a net film thickness after baking, for example, and a denser film | membrane can be formed by forming repeatedly thinly.
In addition, when applying Ti oxide that is effective in promoting crystallization of aluminum oxide, alumina sol is applied to the surface of the underlying layer formed with a Ti oxide layer on the surface of the tool base by CVD or the like. In the same manner as above, the film thickness by one application is preferably 0.2 μm or less, and a denser film can be formed by repeatedly forming thin films. Further, in this case, heat treatment such as drying and baking may not be performed by the RTA method, and a normal electric furnace is sufficient.
When an electric furnace is used, a drying treatment at 100 to 600 ° C., more preferably 200 to 500 ° C., is repeated once or more, and then a baking treatment is performed at a temperature range of 600 to 1100 ° C. to coat the aluminum oxide layer Form.
前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、硬質皮膜表面に、複雑形状を有する酸化アルミニウムの結晶粒からなるα型結晶構造またはα型とγ型結晶構造を有する酸化アルミニウム層が形成され、焼成条件によっては、Ti酸化物微粒子が分散含有した酸化アルミニウムが形成される。 Alumina oxide having an α-type crystal structure or an α-type and γ-type crystal structure composed of aluminum oxide crystal grains having a complex shape is formed on the surface of the hard film by a subsequent baking treatment after a dry gel is formed by the drying treatment. A layer is formed, and depending on the firing conditions, aluminum oxide in which Ti oxide fine particles are dispersed and formed is formed.
前記酸化アルミニウム層の膜厚は、アルミナゾルの塗布厚さおよび塗布回数に依存するが、前述したように、被覆形成された酸化アルミニウム層の膜厚が0.2μm未満では、長期の使用に亘って表面被覆切削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、膜厚が5.0μmを越えると酸化アルミニウム層が脱落チッピングを生じやすくなることから、酸化アルミニウム層の膜厚は0.2〜5.0μmとする。 Although the film thickness of the aluminum oxide layer depends on the coating thickness and the number of coatings of the alumina sol, as described above, when the film thickness of the coated aluminum oxide layer is less than 0.2 μm, it can be used for a long time. Excellent wear resistance cannot be exhibited as a surface-coated cutting tool. On the other hand, if the film thickness exceeds 5.0 μm, the aluminum oxide layer is liable to cause chipping, so the film thickness of the aluminum oxide layer is 0. 2 to 5.0 μm.
また、乾燥処理の温度範囲を100〜600℃、より好ましくは200〜500℃、焼成処理の温度範囲を600〜1100℃と定めたのは、それぞれ、乾燥温度については、100℃未満では有機溶媒や界面活性剤などの熱分解が起こらず、600℃を超えるとゲルの体積収縮が急激に進行してクラック等を発生し、皮膜が剥離等を生じやすくなるためであり、焼成温度については、600℃未満ではRTA法などの所定の焼成方法やTi酸化物を用いても結晶化が起こらないため耐摩耗性が十分でなく、一方、1100℃を越える温度で焼成した場合、工具基体の劣化や粒状組織の粗大化が進んでしまうために耐欠損性、耐チッピング性、平滑性が低下傾向を示すという理由による。 Further, the temperature range of the drying treatment is set to 100 to 600 ° C., more preferably 200 to 500 ° C., and the temperature range of the baking treatment is set to 600 to 1100 ° C. This is because thermal decomposition of the surface active agent or the like does not occur, and when the temperature exceeds 600 ° C., the volumetric shrinkage of the gel rapidly proceeds to generate cracks and the like, and the film is likely to peel off. If the temperature is lower than 600 ° C., crystallization does not occur even if a predetermined baking method such as RTA method or Ti oxide is used, so that the wear resistance is not sufficient. This is because the fracture resistance, chipping resistance, and smoothness tend to decrease due to the progress of coarsening of the granular structure.
本発明の表面被覆切削工具によれば、工具基体の表面に、ゾル−ゲル法によって成膜した酸化アルミニウムを被覆形成するものであり、それ自身が、すぐれた表面平滑性、潤滑性、耐溶着性、耐チッピング性を備えるとともに、酸化アルミニウム層を構成する結晶粒の周縁部の形状が凹凸の多い形状を有していることから、結晶粒同士の結合力が高まる。これらの効果が相俟って、これを、高熱発生を伴うとともに、切れ刃に断続的・衝撃的負荷が作用する鋼や鋳鉄などの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って、その効果は絶大である。 According to the surface-coated cutting tool of the present invention, the surface of the tool base is coated with the aluminum oxide film formed by the sol-gel method, and itself has excellent surface smoothness, lubricity, and welding resistance. Since the shape of the peripheral part of the crystal grain which comprises an aluminum oxide layer has many unevenness | corrugations, it has the property and chipping resistance, and the bond strength of crystal grains increases. Combined with these effects, this is accompanied by high heat generation, and even when used for high-speed intermittent cutting such as steel or cast iron where intermittent and impact loads are applied to the cutting edge, chipping, peeling, etc. It exhibits excellent cutting performance over a long period of time without causing abnormal damage, and its effect is enormous.
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.
(a1) 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、VC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:0.05mmのホーニング加工を施すことによりISO・CNMG120408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,E1,E2,E3,E4,E5(工具基体A,B,C,D,E,E1,E2,E3,E4,E5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E2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E3については、1kPaの窒素雰囲気中にて40分間、超硬基体E4については、2kPaの窒素雰囲気中にて10分間、超硬基体E5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。
(A1) As 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 having an average particle diameter of 1 to 3 μm, NbC powder, Cr 3 C 2 powder, VC powder and Co powder are prepared, and these raw material powders are blended into the prescribed blending composition shown in Table 1, and then added with wax and ball mill mixed in acetone for 24 hours. After drying, it is press-molded into a green compact of a predetermined shape at a pressure of 98 MPa, this green compact is vacuum-sintered under a condition of holding for 1 hour at a temperature of 1400 ° C. in a vacuum of 5 Pa, and after sintering, Tool base A, B, C, D, E, E1, E2, made of WC-base cemented carbide with insert shape specified in ISO / CNMG120408 by applying honing of R: 0.05mm to the cutting edge E3 E4, E5 were prepared (tool substrate A, B, C, D, E, E1, E2, E3, E4, E5 of) a.
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 E2, and in a nitrogen atmosphere of 1 kPa for the carbide substrate E3. The substrate surface is cured by cooling for 40 minutes in a nitrogen atmosphere of 2 kPa for the carbide substrate E4 and for 120 minutes in a nitrogen atmosphere of 3.3 kPa for the carbide substrate E5. did.
(b1) 次いで、上記工具基体A〜E5に対して、下地層を形成した。なお、下地層の形成にあたり、上記工具基体A及びB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、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C及び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。
また、上記工具基体Eについてはゾル-ゲル法により表5に示す膜厚のTiO2層からなる下地層を予め形成した。
一方、上記工具基体E1,E2,E3,E4,E5については、下地層の形成を特に行わなかった。
(B1) Next, a base layer was formed on the tool bases A to E5. In forming the base layer, the tool bases A and B are inserted into a chemical vapor deposition apparatus and are formed into TiN layers having a granular crystal structure and TiCN having a vertically long crystal structure using the film forming conditions shown in Table 2. An underlayer was formed in advance with a film composition shown in Table 5 as a Ti compound layer composed of a layer (hereinafter referred to as 1-TiCN), TiO 2 , and Ti 2 O 3 . On the other hand, the tool bases C and D are inserted into an arc ion plating apparatus which is a kind of physical vapor deposition apparatus, and an underlayer composed of a Ti 0.5 Al 0.5 N layer having a thickness shown in Table 5 is provided. Pre-formed.
For the tool base E, an underlayer composed of a TiO 2 layer having a thickness shown in Table 5 was formed in advance by a sol-gel method.
On the other hand, for the tool bases E1, E2, E3, E4, and E5, no base layer was particularly formed.
(c1) 次いで、下地層の上に、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(ASB)に、溶媒として、同じく表3に示す所定量のエタノールを添加して、恒温槽中5℃で攪拌を行い、さらに、触媒として表3に示す所定量の水を添加した塩酸を滴下により1時間かけて添加した。
(C1) Next, an alumina sol for coating an aluminum oxide layer on the underlayer by a sol-gel method was prepared as follows.
A predetermined amount of ethanol shown in Table 3 was added as a solvent to aluminum secondary butoxide (ASB), which is a predetermined amount of aluminum alkoxide shown in Table 3, and the mixture was stirred at 5 ° C. in a thermostatic bath. As shown in Table 3, hydrochloric acid added with a predetermined amount of water was added dropwise over 1 hour.
(d1) これを、恒温槽中5℃に保持したまま、12時間以上攪拌を継続し、さらに、5℃で24時間低温で熟成処理し、さらに、キレート化剤として表3に示す所定量のアセチルアセトンを添加したアルミナゾルを調製した。
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(ASB)):(水):(エタノール):(塩酸):(アセチルアセトン)
=1:(50〜100):20:(0.5〜0.8):(0.8〜1.2)
になるように調整を行った。
(D1) While maintaining this at 5 ° C. in a thermostatic bath, stirring was continued for 12 hours or more, and further aging treatment was carried out at 5 ° C. for 24 hours at a low temperature. An alumina sol to which acetylacetone was added was prepared.
The final solution composition is in molar ratio
(Aluminum secondary butoxide (ASB)): (water): (ethanol): (hydrochloric acid): (acetylacetone)
= 1: (50 to 100): 20: (0.5 to 0.8): (0.8 to 1.2)
Adjustments were made to
(e1) 次いで、前記超硬基体A〜E5に、化学蒸着法、物理蒸着法及びゾル-ゲル法により形成したTi化合物層上に、あるいは、特別な表面処理を施していない基体表面上に前記アルミナゾルを塗布した。 (E1) Next, the carbide substrates A to E5 are formed on a Ti compound layer formed by a chemical vapor deposition method, a physical vapor deposition method and a sol-gel method, or on a substrate surface which has not been subjected to a special surface treatment. Alumina sol was applied.
(f1) 次いで、前記塗布したアルミナゾルを、表4に示す所定条件の乾燥処理を行い、さらに塗布と乾燥を繰り返した後、600〜1100℃で表4に示す条件の焼成処理を行い、本発明酸化アルミニウム層を被覆形成することにより、表5、6に示す本発明の表面被覆切削工具1〜21(本発明工具1〜21という)を製造した。 (F1) Next, the coated alumina sol was subjected to a drying process under predetermined conditions shown in Table 4, and after repeated coating and drying, a baking process under conditions shown in Table 4 was performed at 600 to 1100 ° C. By coating the aluminum oxide layer, the surface-coated cutting tools 1 to 21 (referred to as the present invention tools 1 to 21) of the present invention shown in Tables 5 and 6 were produced.
本発明工具1〜21について、酸化アルミニウム層の縦断面を透過型電子顕微鏡(TEM)で観察したところ、酸化アルミニウム層には凹凸性の高い結晶粒界が形成されており、本発明工具の一部には、該結晶粒周囲に新たな微粒結晶粒が形成されていることが確認された。この凹凸性の高い結晶粒形状の確認には電子線後方散乱回折法を用い、酸化アルミニウム層中の各結晶粒のアスペクト比、各結晶粒の面積と等しい面積を有する円の周長に対する当該結晶粒の周長の比をそれぞれ求めた。また、結晶構造の確認には、X線回折装置と透過型電子顕微鏡(TEM)を用い、制限視野電子線回折法によりその各結晶粒を解析したところ、その結晶粒から明瞭な電子線回折パターンが得られ、そのパターンの解析及びX線回折パターンから、酸化アルミニウムはα型もしくはα型とγ型の混相を有していることが確認された。さらに、微粒結晶粒はチタン酸化物であることをTEMによるエネルギー分散形X線分析装置を用いて特定した。 With respect to the inventive tools 1 to 21, when the longitudinal section of the aluminum oxide layer was observed with a transmission electron microscope (TEM), a highly irregular crystal grain boundary was formed in the aluminum oxide layer. In the part, it was confirmed that new fine crystal grains were formed around the crystal grains. The confirmation of the crystal grain shape with high unevenness is performed by using an electron beam backscatter diffraction method, and the crystal with respect to the aspect ratio of each crystal grain in the aluminum oxide layer and the circumference of a circle having an area equal to the area of each crystal grain. The ratio of the circumference of each grain was determined. In addition, for confirmation of the crystal structure, each crystal grain was analyzed by a limited-field electron diffraction method using an X-ray diffractometer and a transmission electron microscope (TEM), and a clear electron beam diffraction pattern was obtained from the crystal grain. From the analysis of the pattern and the X-ray diffraction pattern, it was confirmed that the aluminum oxide has α-type or α-type and γ-type mixed phase. Furthermore, it was specified using a TEM energy dispersive X-ray analyzer that the fine crystal grains were titanium oxide.
図1に、一例として、本発明工具15の酸化アルミニウム層の縦断面TEM写真を、また、図2および図3に、同じく本発明工具15について、その酸化アルミニウム層の表面と断面TEM写真を示す。図2、図3によれば、酸化アルミニウム層中に分散する微細Ti酸化物粒が、酸化アルミニウム結晶粒を囲繞するように凝集形成されていることが確認できる。
(比較例1)
As an example, FIG. 1 shows a vertical cross-sectional TEM photograph of an aluminum oxide layer of the tool 15 of the present invention, and FIGS. 2 and 3 also show the surface of the aluminum oxide layer and a cross-sectional TEM photograph of the tool 15 of the present invention. . 2 and 3, it can be confirmed that the fine Ti oxide grains dispersed in the aluminum oxide layer are aggregated so as to surround the aluminum oxide crystal grains.
(Comparative Example 1)
比較のため、以下の製造方法で表面被覆切削工具を製造した。 For comparison, a surface-coated cutting tool was manufactured by the following manufacturing method.
即ち、前記(a1)の工具基体A〜E5に対して、前記(b1)の工程で、硬質皮膜を形成し、前記(d1)の工程(表3参照)で、アルミナゾルを調製した。 That is, a hard film was formed in the step (b1) on the tool bases A to E5 in (a1), and an alumina sol was prepared in the step (d1) (see Table 3).
次いで、前記(d1)の工程にかえて、恒温槽中40℃に保持したまま、12時間攪拌を継続し、さらに、40℃で24時間熟成するという処理を行い、キレート化剤としてアセチルアセトンを添加することによってアルミナゾルを調製した。 Next, in place of the step (d1), stirring is continued for 12 hours while maintaining at 40 ° C. in a thermostatic bath, and further aging is performed at 40 ° C. for 24 hours, and acetylacetone is added as a chelating agent. An alumina sol was prepared.
次いで、前記(e1)と同様にして、超硬基体A〜E5に、化学蒸着法により形成した前記Ti化合物層上に、あるいは、特別な表面処理を施していない基体表面上に前記アルミナゾルを塗布した。 Next, in the same manner as in the above (e1), the alumina sol is applied to the carbide substrates A to E5 on the Ti compound layer formed by chemical vapor deposition or on the substrate surface not subjected to special surface treatment. did.
次いで、前記塗布したアルミナゾルを、前記(f1)と同様にして、乾燥処理を行い、さらに塗布と乾燥処理を繰り返した後、焼成処理を行ったが、その際、乾燥条件と焼成条件は本発明工具とは異なる条件を用いて、酸化アルミニウム層を最表面に被覆形成することにより、表7、8に示す比較例の表面被覆切削工具1〜21(比較例工具1〜21という)を製造した。 Next, the coated alumina sol was subjected to a drying treatment in the same manner as in (f1) above, and further subjected to a firing treatment after repeating the coating and the drying treatment. At that time, the drying conditions and firing conditions were set according to the present invention. Surface-coated cutting tools 1 to 21 (referred to as Comparative Examples Tools 1 to 21) of Comparative Examples shown in Tables 7 and 8 were manufactured by coating an aluminum oxide layer on the outermost surface using conditions different from the tools. .
前記本発明工具1〜21および比較例工具1〜21について、エネルギー分散型X線分光法装置を付属した透過型電子顕微鏡を用い、酸化アルミニウム層の縦断面を10万倍の観察視野範囲0.2×0.3μmで5視野に対して元素マッピング分析し、Ti酸化物微粒子の数の平均値を求めると共に、その結果を平面と仮定して、酸化アルミニウム層に分散含有される該微細Ti酸化物粒の面積を円の面積として算出した場合の近似円の直径を5点測定し、その平均値を該微細Ti酸化物粒の平均粒径とした。
また、酸化アルミニウム層中の全金属元素に占めるTiの含有割合を縦断面視野領域0.2μm×0.3μmの範囲でTEMに付属されたエネルギー分散形X線分析装置による観察視野範囲内の定量面分析を5視野実施し、その平均値を求めることにより測定した。
また、超硬基体表面のCoの含有量は走査型電子顕微鏡(SEM)を用いた波長分散型X線分光法により、酸化アルミニウム層または超硬基体の縦断面観察視野内を定量分析し、その平均値を採用した。超硬基体表面のCo含有量は基板表面から深さ方向に0.5〜3.0μmの範囲内における分析視野領域1μm×1μmの面分析にて5視野測定した。
また、同時に酸化アルミニウム層の平均層厚を走査型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。
表6、8に、測定結果を示す。
For the inventive tools 1 to 21 and comparative tools 1 to 21, a transmission electron microscope equipped with an energy dispersive X-ray spectroscopy apparatus was used, and the longitudinal field of view of the aluminum oxide layer was 100,000 times the observation field range of 0.1. Elemental mapping analysis is performed for 5 fields of view at 2 × 0.3 μm to obtain the average value of the number of Ti oxide fine particles, and the fine Ti oxidation dispersed and contained in the aluminum oxide layer assuming that the result is a plane The diameter of the approximate circle when the area of the object grain was calculated as the area of the circle was measured at five points, and the average value was taken as the average particle diameter of the fine Ti oxide particles.
In addition, the content ratio of Ti in the total metal elements in the aluminum oxide layer is determined within the observation visual field range by the energy dispersive X-ray analyzer attached to the TEM in the range of the vertical sectional visual field area of 0.2 μm × 0.3 μm. The surface analysis was carried out by 5 fields of view and the average value was obtained.
The content of Co on the surface of the carbide substrate is quantitatively analyzed in the longitudinal section observation field of the aluminum oxide layer or the carbide substrate by wavelength dispersive X-ray spectroscopy using a scanning electron microscope (SEM). The average value was adopted. The Co content on the surface of the cemented carbide substrate was measured in five fields by area analysis of an analysis field area of 1 μm × 1 μm within a range of 0.5 to 3.0 μm in the depth direction from the substrate surface.
At the same time, when the average thickness of the aluminum oxide layer was measured by cross-section using a scanning electron microscope, all showed the same average value (average value of five locations) as the target layer thickness.
Tables 6 and 8 show the measurement results.
つぎに、本発明工具1〜21および比較例工具1〜21について、以下に示す、炭素鋼の乾式高速断続切削試験、鋳鉄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。
切削条件1:
被削材:JIS・SCM435の長さ方向等間隔4本縦溝入り丸棒、
切削速度:360m/min、
切り込み:1.2mm、
送り:0.2mm/rev、
切削時間:5分、
(通常の切削速度は、220m/min)、
切削条件2:
被削材:JIS・FCD450の長さ方向等間隔4本縦溝入り丸棒、
切削速度:320m/min、
切り込み:1.0mm、
送り:0.2mm/rev、
切削時間:5分、
(通常の切削速度は、200m/min)、
これらの結果を表6、8に示す。
Next, with respect to the inventive tools 1 to 21 and the comparative tools 1 to 21, the following carbon steel dry high-speed intermittent cutting test and cast iron wet high-speed intermittent cutting test were carried out. The width was measured.
Cutting condition 1:
Work material: JIS · SCM435 lengthwise equally spaced four round grooved round bars,
Cutting speed: 360 m / min,
Cutting depth: 1.2mm,
Feed: 0.2mm / rev,
Cutting time: 5 minutes
(Normal cutting speed is 220 m / min),
Cutting condition 2:
Work material: JIS / FCD450 lengthwise equidistant round bars with 4 vertical grooves,
Cutting speed: 320 m / min,
Cutting depth: 1.0 mm,
Feed: 0.2mm / rev,
Cutting time: 5 minutes
(Normal cutting speed is 200 m / min),
These results are shown in Tables 6 and 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・CNMG120412のチップ形状をもったTiCN基サーメット製の工具基体F,G,H,I,J,J1,J2,J3,J4、J5(工具基体F〜J5という)を製造した。但し、工具基体J1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J3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J4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J5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 / CNMG120212 chip shape. TiCN-based cermet tool bases F, G, H, I, J, J1, J2, J3, J4, and J5 (referred to as tool bases F to J5) were manufactured. However, for the tool base J1, in a nitrogen atmosphere of 1.3 kPa, the rate of temperature increase 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. The tool base J3 is always heated in a 13 Pa vacuum and held at 1540 ° C. for 60 minutes, and the tool base J4 is heated from room temperature to 1540 ° C. in a nitrogen atmosphere of 1.3 kPa and held for 30 minutes. , A vacuum of 13 Pa, further held at 1540 ° C. for 5 minutes, and the tool substrate J5 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F〜J5に対して、下地層を形成した。
なお、下地層の形成にあたり、上記工具基体F及びG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、表10のTi化合物からなる皮膜構成にて下地層を予め形成した。一方、上記工具基体H、I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10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J〜J5については、下地層の形成を特に行わなかった。
Next, a base layer was formed on the tool bases F to J5.
In forming the base layer, the tool bases F and G were inserted into a chemical vapor deposition apparatus, and the base layer was formed using the film formation conditions shown in Table 2 with the coating composition made of the Ti compound shown in Table 10. Pre-formed. On the other hand, the tool bases H and I are inserted into an arc ion plating apparatus which is a kind of physical vapor deposition apparatus, and an underlayer composed of a Ti 0.5 Al 0.5 N layer having a thickness shown in Table 10 is provided. Pre-formed.
On the other hand, for the tool bases J to J5, the base layer was not particularly formed.
ついで、下地層を形成した上記工具基体F,G,H,Iおよび、下地層を形成していない上記工具基体J〜J5のいずれに対しても、実施例1と同様に表3、4の調製条件及び乾燥条件、焼成条件を用い、酸化アルミニウム主体層を成膜し、表10、11に示す本発明の被覆工具22〜42(本発明工具22〜42という)を製造した。 Next, in the same manner as in Example 1, the tool bases F, G, H, and I on which the base layer is formed and the tool bases J to J5 on which the base layer is not formed are as shown in Tables 3 and 4. Using the preparation conditions, drying conditions, and firing conditions, an aluminum oxide main layer was formed to produce coated tools 22 to 42 of the present invention shown in Tables 10 and 11 (referred to as the present invention tools 22 to 42).
本発明工具22〜42について実施例1と同様に酸化アルミニウム層の結晶構造、結晶粒の平均アスペクト比、等面積円の周長に対する結晶粒の周長の比の平均値、酸化アルミニウム層中の全金属元素に占めるTiの含有割合(at%)、結晶粒界に存在するTi酸化物微粒子の平均数(個)、結晶粒界に存在するTi酸化物微粒子の平均粒径(μm)、TiCN基サーメット表面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(at%)を測定・算出した。
表11にその結果を示す。
As in Example 1, for the inventive tools 22 to 42, the crystal structure of the aluminum oxide layer, the average aspect ratio of the crystal grains, the average value of the ratio of the circumference of the crystal grains to the circumference of the equal area circle, Ti content in all metal elements (at%), average number of Ti oxide fine particles present at grain boundaries (average), average particle diameter of Ti oxide fine particles present at crystal grain boundaries (μm), TiCN The total average content (at%) of Co and Ni as binder phase metals contained on the surface of the base cermet was measured and calculated.
Table 11 shows the results.
[比較例2]
前記実施例2で用いたのと同じ工具基体F〜J5を用いて、実施例2と同様に、ゾル−ゲル法により、表3に示すゾル調製条件、表4に示す乾燥・焼成条件を用いて表13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12、13に示す比較例の被覆工具22〜42(比較例工具22〜42という)を製造した。
[Comparative Example 2]
Using the same tool bases F to J5 as used in Example 2, the sol preparation conditions shown in Table 3 and the drying and firing conditions shown in Table 4 were used by the sol-gel method in the same manner as in Example 2. Then, an aluminum oxide main layer was formed until the predetermined target layer thickness shown in Table 13 was obtained, and the coated tools 22 to 42 (referred to as comparative tools 22 to 42) of comparative examples shown in Tables 12 and 13 were manufactured.
酸化アルミニウム層の結晶構造、結晶粒の平均アスペクト比、等面積円の周長に対する結晶粒の周長の比の平均値、酸化アルミニウム層中の全金属元素に占めるTiの含有割合(at%)、結晶粒界に存在するTi酸化物微粒子の平均数(個)、結晶粒界に存在するTi酸化物微粒子の平均粒径(μm)、TiCN基サーメット表面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(at%)を表13に示す。 The crystal structure of the aluminum oxide layer, the average aspect ratio of the crystal grains, the average value of the ratio of the circumference of the crystal grains to the circumference of the equal area circle, the content ratio of Ti in all the metal elements in the aluminum oxide layer (at%) , The average number of Ti oxide fine particles present at the crystal grain boundary (pieces), the average particle size of the Ti oxide fine particles present at the crystal grain boundary (μm), Co as a binder phase metal contained on the TiCN-based cermet surface, and Table 13 shows the total average content (at%) of Ni.
上記本発明工具22〜42、比較例工具22〜42について、次の条件で乾式高速断続切削加工試験を行った。
切削条件1:
被削材:JIS・SCM435の長さ方向等間隔4本縦溝入り丸棒、
切削速度:280m/min、
切り込み:1.4mm、
送り:0.25mm/rev、
切削時間:5分、
(通常の切削速度は、220m/min)、
切削条件2:
被削材:JIS・FCD450の長さ方向等間隔4本縦溝入り丸棒、
切削速度:340m/min、
切り込み:0.8mm、
送り:0.4mm/rev、
切削時間:5分、
(通常の切削速度は、200m/min)、
これらの結果を表11、13に示す。
The above-described inventive tools 22 to 42 and comparative tools 22 to 42 were subjected to a dry high-speed intermittent cutting test under the following conditions.
Cutting condition 1:
Work material: JIS · SCM435 lengthwise equally spaced four round grooved round bars,
Cutting speed: 280 m / min,
Cutting depth: 1.4mm,
Feed: 0.25mm / rev,
Cutting time: 5 minutes
(Normal cutting speed is 220 m / min),
Cutting condition 2:
Work material: JIS / FCD450 lengthwise equidistant round bars with 4 vertical grooves,
Cutting speed: 340 m / min,
Cutting depth: 0.8mm,
Feed: 0.4mm / rev,
Cutting time: 5 minutes
(Normal cutting speed is 200 m / min),
These results are shown in Tables 11 and 13.
表6、11及び表8、13に示される結果から、本発明工具1〜42においては、工具基体の表面に、ゾル−ゲル法によって酸化アルミニウム層が被覆形成され該酸化アルミニウム層は、すぐれた表面平滑性、耐溶着性、結晶粒同士の密着力を備えることから、これを、鋼、鋳鉄等の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耐摩耗性、切屑排出性を発揮するのである。 From the results shown in Tables 6 and 11 and Tables 8 and 13, in the tools 1 to 42 of the present invention, the surface of the tool base was coated with an aluminum oxide layer by a sol-gel method, and the aluminum oxide layer was excellent. Since it has surface smoothness, adhesion resistance, and adhesion between crystal grains, even when this is used for high-speed intermittent cutting of steel, cast iron, etc., without causing abnormal damage such as chipping and peeling, It exhibits excellent wear resistance and chip discharge over a long period of use.
これに対して、表面の酸化アルミニウム層に複雑形状結晶粒が形成されていない比較例工具1〜42においては、表面平滑性、耐溶着性は優れるものの、結晶粒同士の密着力が不十分であり、断続切削の大きな衝撃に耐えきれず、特にホーニング部付近での微小チッピングが起こりやすくなるために、異常損傷が起きやすく、優れた耐摩耗性を維持できず、クレータ摩耗が進行するため、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, in Comparative Examples Tools 1 to 42 in which no complex-shaped crystal grains are formed on the surface aluminum oxide layer, the surface smoothness and welding resistance are excellent, but the adhesion between the crystal grains is insufficient. Yes, it can not withstand the large impact of intermittent cutting, especially because minute chipping near the honing part is likely to occur, abnormal damage is likely to occur, excellent wear resistance can not be maintained, crater wear proceeds, It is clear that the service life is reached in a short time.
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−ゲル法によって酸化アルミニウム層が被覆形成され該酸化アルミニウム層は、すぐれた表面平滑性、耐溶着性、結晶粒同士の密着力を備えることから、これを、鋼、鋳鉄等の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絶大である。 According to the surface-coated cutting tool of the present invention, an aluminum oxide layer is coated on the surface by a sol-gel method, and the aluminum oxide layer has excellent surface smoothness, welding resistance, and adhesion between crystal grains. Therefore, even when it is used for high-speed intermittent cutting of steel, cast iron, etc., it exhibits excellent cutting performance over a long period of use without causing abnormal damage such as chipping and peeling. The tool life can be extended, and its practical effect is enormous.
Claims (5)
(a)前記硬質被覆層は、0.2〜5.0μmの平均層厚を有する酸化アルミニウム層を具備し、
(b)前記酸化アルミニウム層を構成する結晶粒は、α型またはα型とγ型の混相の結晶構造を有し、
(c)前記酸化アルミニウム層の縦断面における各々の結晶粒形状を電子線後方散乱回折法により定め、層厚垂直方向の粒径に対する層厚方向の粒径の比を各結晶粒のアスペクト比とした場合に、前記結晶粒の平均アスペクト比は、0.5〜5.0であり、
(d)前記酸化アルミニウム層の縦断面における各々の結晶粒形状を電子線後方散乱回折法により定め、各結晶粒の周長と結晶粒面積を求めた場合に、当該結晶粒面積と等しい面積を有する円の周長に対する当該結晶粒の周長の比の平均値が、1.8〜3.0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 formed by coating a hard coating layer on the surface of a tool base made of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet,
(A) The hard coating layer comprises an aluminum oxide layer having an average layer thickness of 0.2 to 5.0 μm,
(B) The crystal grains constituting the aluminum oxide layer have an α-type or α-type and γ-type mixed phase crystal structure,
(C) The shape of each crystal grain in the longitudinal section of the aluminum oxide layer is determined by an electron beam backscatter diffraction method , and the ratio of the grain size in the layer thickness direction to the grain size in the layer thickness vertical direction is defined as the aspect ratio of each crystal grain. when an average aspect ratio of the crystal grains, Ri 0.5-5.0 der,
(D) When each crystal grain shape in the longitudinal section of the aluminum oxide layer is determined by an electron beam backscatter diffraction method, and the perimeter of each crystal grain and the crystal grain area are obtained, an area equal to the crystal grain area is The surface-coated cutting tool, wherein the average value of the ratio of the circumference of the crystal grains to the circumference of the circle is 1.8 to 3.0.
(a)前記酸化アルミニウム層中の全金属元素に占めるTiの含有割合は、0.02at%を超え10at%以下であり、
(b)前記チタン酸化物の結晶粒は、平均粒径0.01〜0.10μmのチタン酸化物微粒子であり該チタン酸化物微粒子は前記酸化アルミニウム層を構成する結晶粒を囲繞するように凝集形成されているとともに、前記酸化アルミニウム層を構成する結晶粒の周長上に存在するチタン酸化物微粒子の平均数は、5〜50個であることを特徴とする請求項1に記載の表面被覆切削工具。 The aluminum oxide layer contains titanium oxide crystal grains,
(A) The content ratio of Ti in all the metal elements in the aluminum oxide layer is more than 0.02 at% and 10 at% or less,
(B) The titanium oxide crystal grains are titanium oxide fine particles having an average particle diameter of 0.01 to 0.10 μm, and the titanium oxide fine particles are aggregated so as to surround the crystal grains constituting the aluminum oxide layer. 2. The surface coating according to claim 1, wherein an average number of titanium oxide fine particles formed and present on the circumference of crystal grains constituting the aluminum oxide layer is 5 to 50. 3. Cutting tools.
上記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請求項1または請求項2に記載の表面被覆切削工具。 In a surface-coated cutting tool formed by coating a hard coating layer on the surface of a tool substrate made of a tungsten carbide-based cemented carbide,
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 is formed, and an average content of Co as a binder phase metal contained in the base surface hardened layer is The surface-coated cutting tool according to claim 1, wherein the surface-coated cutting tool is less than 2.0% by mass.
上記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請求項1または請求項2に記載の表面被覆切削工具。 In a surface-coated cutting tool formed by coating a hard coating layer on the surface of a tool base made of titanium carbonitride-based cermet,
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 is formed, and the total average of Co and Ni as binder phase metals contained in the base surface hardened layer Content is less than 2.0 mass%, The surface-coated cutting tool of Claim 1 or Claim 2 characterized by the above-mentioned.
The method for producing a surface-coated cutting tool according to any one of claims 1 to 4, wherein the aluminum oxide layer is formed on the titanium oxide layer by a sol-gel method.
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