JP2007210066A - SURFACE COATED CERMET CUTTING TOOL INCLUDING REFORMED k-TYPE ALUMINUM OXIDE LAYER OF HARD COATING LAYER HAVING EXCELLENT GRAIN BOUNDARY SURFACE STRENGTH - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface coated cermet-made cutting tool including a reformed κ(Kappa)-type aluminum oxide layer of a hard coating layer having excellent grain boundary surface strength. <P>SOLUTION: The hard coating layer is formed on the surface of a tool base formed of WC-base cemented carbide or TiCN-base cermet by vapor deposition. The hard coating layer includes a lower layer, which is a Ti compound layer having the total average layer thickness ranging from 3 to 20 μm; and an upper layer. The upper layer is a reformed κ(Kappa)-type Al<SB>2</SB>O<SB>3</SB>layer having the average layer thickness ranging from 1 to 15 μm, having κ(Kappa)-type crystal structure in the chemically deposited state, and showing a crystal grain boundary surface array in which the crystal grain boundary surface unit having the angle made by crossing normals of the (001) faces in the boundary surface (crystal grain boundary surface unit) of the adjacent crystal grains of 1° or less, having the angle made by crossing normals of the (010) faces ranging from 55 to 65° occupies 40% or more of the total crystal grain surface units. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  This invention is a modified κ (kappa) type of hard coating layer even when intermittent cutting of various materials such as steel and cast iron is performed under heavy cutting conditions such as high cutting and high feed. The present invention relates to a surface-coated cermet cutting tool (hereinafter referred to as a coated cermet tool) in which the aluminum oxide layer has excellent grain interface strength.

Conventionally, generally on the surface of a substrate (hereinafter collectively referred to as a tool substrate) composed of a tungsten carbide (hereinafter referred to as WC) -based cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) -based cermet. ,
(A) The lower layer is a Ti carbide (hereinafter referred to as TiC) layer, a nitride (hereinafter also referred to as TiN) layer, a carbonitride (hereinafter referred to as TiCN) layer, a carbon oxide (hereinafter referred to as TiCO). A Ti compound layer consisting of one or two or more layers of carbonitride oxide (hereinafter referred to as TiCNO) layers and having an overall average layer thickness of 3 to 20 μm,
(B) Aluminum oxide having an upper layer having an average layer thickness of 1 to 15 μm and having a κ (kappa) type crystal structure in a state of chemical vapor deposition (hereinafter referred to as κ type Al ₂ O ₃ layer) layer,
There is known a coated cermet tool formed by vapor-depositing a hard coating layer composed of the above (a) and (b), and this coated cermet tool is an upper layer κ-type Al ₂ O constituting the hard coating layer. _{Since the three} layers have excellent high-temperature strength, it is also known to exhibit excellent chipping resistance particularly when used for intermittent cutting, as well as continuous cutting of various steels and cast iron, for example.

  Moreover, in the above-mentioned coated cermet tool, the constituent layer of the hard coating layer generally has a granular crystal structure, and further, the TiCN layer constituting the Ti compound layer as the lower layer is improved in strength of the layer itself. The purpose is to use a gas mixture containing organic carbonitrides as a reaction gas in a normal chemical vapor deposition apparatus, and to form a vertically grown crystal structure formed by chemical vapor deposition at a medium temperature range of 700 to 950 ° C. It is also known to do.

Furthermore, the Al ₂ O ₃ layer has an α type, θ type, etc. in addition to the κ type crystal structure described above, and the κ type Al ₂ O ₃ layer is different from the α type Al ₂ O ₃ layer. It is also known that the high temperature hardness is relatively low but the high temperature strength is high.
Japanese Unexamined Patent Publication No. 6-31503 Japanese Patent Laid-Open No. 6-8010

In recent years, the performance of cutting equipment has been remarkable, while on the other hand, there has been a strong demand for labor saving and energy saving and further cost reduction for cutting, and with this, cutting has increased cutting and feeding among cutting conditions. Although there is a tendency to be performed under heavy cutting conditions, the above conventional coated cermet tool has no problem when used for continuous cutting or intermittent cutting under normal conditions such as steel or cast iron. Is used for interrupted cutting under the above-mentioned heavy cutting conditions to which a strong mechanical impact is repeatedly applied, the κ-type Al ₂ O ₃ layer constituting the hard coating layer is sufficient for the intermittent heavy cutting conditions. Therefore, the hard coating layer is likely to be chipped (small chipping), and as a result, the service life is reached in a relatively short time.

The present inventors have, from the viewpoint as described above, focuses on coated cermet tool κ type the Al ₂ O ₃ layer described above constituting the upper layer of the hard coating layer, particularly the κ type the Al ₂ O ₃ layer As a result of research to improve the high-temperature strength of
(A) The κ-type Al ₂ O ₃ layer as the upper layer constituting the hard coating layer of the conventional coated cermet tool is, for example, in a normal chemical vapor deposition apparatus,
Reaction gas composition: volume%, AlCl ₃ 3-10%, CO ₂ 3-6%, HCl 1-4%, H ₂ S 0.1-0.5%, H ₂ remaining,
Reaction atmosphere temperature: 920-1020 ° C.
Reaction atmosphere pressure: 5 to 10 kPa,
It is formed by vapor deposition under the conditions (called normal conditions).
Reaction gas composition: volume%, AlCl ₃ 3-6%, CO ₂ 0.5-3%, HCl 1-3%, CH ₃ CN 0.1-0.3%, H ₂ S 0.1-0. 5%, H ₂ remaining,
Reaction atmosphere temperature: 780-880 ° C.
Reaction atmosphere pressure: 5 to 10 kPa,
Compared with the above conditions, that is, the above normal conditions, in the reaction gas composition, CO ₂ is relatively low, and an organic compound such as CH ₃ CN is newly added, and the ambient temperature is further lowered. When vapor deposition is performed under the conditions (reactive gas composition adjustment low temperature conditions), the resulting κ-type Al ₂ O ₃ layer formed under the reaction gas composition adjustment low temperature conditions
Using a field emission scanning electron microscope, each crystal grain having an orthorhombic crystal structure existing within the measurement range of the surface polished surface parallel to the surface of the tool substrate is irradiated with an electron beam to form a constituent crystal of the crystal grain. When the angles at which the normal lines of the (001) plane and the (010) plane, which are the planes, intersect with the normal line of the surface polished surface are measured, according to the measurement results, the interface between adjacent crystal grains (crystal grains The crystal grain interface unit in which the (001) plane normal intersects with each other in (interface unit) is 10 ° or less and the (010) plane normal intersects between 55 ° and 65 ° The crystal grain interface arrangement occupying a ratio of 40% or more of the grain interface units (see FIG. 3).

Incidentally, the “crystal grain interface unit” as used herein means that the crystal grains having an orthorhombic crystal structure existing within the measurement range of the surface polished surface parallel to the tool substrate surface are irradiated with an electron beam, Measure the angle at which the normal lines of the (001) plane and (010) plane that are the constituent crystal planes of the crystal grains intersect with the normal line of the surface-polished surface, and based on the measured values obtained as a result, With respect to a unit measurement region where measurement is performed, the measurement value obtained from the unit measurement region and the measurement value in the unit measurement region adjacent to the unit measurement region are represented by the normals of (001) planes. The absolute value of the difference between the measured values is calculated for each of the intersecting angle and the angle at which the normal lines of the (010) plane intersect, and the absolute value of the difference between at least one angle is equal to or greater than a certain value (for example, “2 Unit measurement area When the boundary between each other is defined as a crystal grain boundary, it means the length of a unit line segment constituting the boundary between the unit measurement regions (that is, the crystal grain boundary).
The angle at which the normal lines of the (001) plane intersect or the angle at which the normal lines of the (010) plane intersect is hereinafter referred to as “intersection angle”.
(B) On the other hand, in the above conventional κ-type Al ₂ O ₃ layer, the crossing angle between the normal lines of the (001) plane at the interface between adjacent crystal grains (crystal grain interface unit) is 10 ° or less. In addition, the crystal grain interface unit whose crossing angle between the normal lines of the (010) plane is 55 ° or more and 65 ° or less only shows a crystal grain interface arrangement with a ratio of 15% or less of the total crystal grain interface unit. (See FIG. 4).
(C) The κ-type Al ₂ O ₃ layer formed by adjusting the reaction gas composition at a low temperature condition has excellent grains based on stable grain boundary formation in addition to the high temperature hardness and heat resistance of the Al ₂ O ₃ itself. Because it has interfacial strength, it has a higher high-temperature strength than the conventional κ-type Al ₂ O ₃ layer, and the coated cermet tool formed by vapor deposition as the upper layer of the hard coating layer has the same lower layer. Combined with the excellent high-temperature strength of a certain Ti compound layer, the conventional κ-type Al ₂ O is also used in the case where the intermittent cutting is performed under heavy cutting conditions such as high cutting and high feed. Compared to the conventional coated cermet tool formed by vapor deposition of ₃ layers, the hard coating layer will exhibit even better chipping resistance.
The research results shown in (a) to (c) above were obtained.

The present invention has been made based on the above research results, and on the surface of a tool base composed of a WC-based cemented carbide or TiCN-based cermet,
(A) Ti carbide layer (TiC layer), nitride layer (TiN layer), carbonitride layer (TiCN layer), carbonate layer (TiCO layer) and carbonitride, all chemically vapor-deposited as lower layers As an upper layer of the Ti compound layer (b) composed of one or two or more oxide layers (TiCNO layers) and having a total average layer thickness of 3 to 20 μm, κ (kappa) Using a field emission scanning electron microscope, irradiate each crystal grain with an orthorhombic crystal structure within the measurement range of the surface polished surface parallel to the tool substrate surface with an electron beam. Then, the angles at which the normal lines of the (001) plane and (010) plane, which are the constituent crystal planes of the crystal grains, intersect with the normal line of the surface polished surface are measured, and from the measured values obtained as a result, The interface between adjacent grains (grain interface unit ) The angle at which the (001) plane normals intersect (intersection angle) is 10 ° or less and the angle at which the (010) plane normals intersect (intersection angle) is 55 ° or more and 65 ° or less. An aluminum oxide layer having an average unit thickness of 1 to 15 μm, wherein the interface unit exhibits a crystal grain interface arrangement that accounts for 40% or more of the total crystal grain interface unit;
Features of the surface-coated cermet cutting tool (coated cermet tool) in which the modified κ (copper) type Al ₂ O ₃ layer of the hard coating layer composed of (a) and (b) has excellent grain interface strength It is what you have.

Hereinafter, the reason why the constituent layers of the hard coating layer of the coated cermet tool of the present invention are numerically limited as described above will be described.
(A) Lower Ti compound layer The Ti compound layer exists as a lower layer of the κ-type Al ₂ O ₃ layer, and contributes to improving the high temperature strength of the hard coating layer by its excellent high temperature strength. The substrate and the κ-type Al ₂ O ₃ layer are firmly adhered to each other, thereby improving the adhesion of the hard coating layer to the tool substrate. However, when the average layer thickness is less than 3 μm, the above-described operation is sufficiently achieved. On the other hand, if the average layer thickness exceeds 20 μm, it becomes easy to cause thermoplastic deformation especially in high-speed cutting with high heat generation, which causes uneven wear. Was determined to be 3 to 20 μm.
(B) Upper layer modified κ (copper) type Al ₂ O ₃ layer Using a field emission scanning electron microscope, an orthorhombic crystal structure existing within the measurement range of the surface polished surface parallel to the tool substrate surface Irradiate each individual crystal grain with an electron beam, and measure the angle at which the normal lines of the (001) plane and (010) plane, which are constituent crystal planes of the crystal grain, intersect with the normal line of the polished surface From the measured values obtained as a result, the intersection angle between the normal lines of the (001) planes at the interface between adjacent crystal grains (grain interface unit) is 10 ° or less, and the method of the (010) plane. The modified κ-type Al ₂ O ₃ layer showing a crystal grain interface arrangement in which a crystal grain interface unit having an angle of intersection between lines of 55 ° or more and 65 ° or less accounts for 40% or more of the total crystal grain interface unit, in addition to the high-temperature hardness and heat resistance possessed by the Al ₂ O ₃ itself, the crystal pair of κ type Al ₂ O ₃ In order to form a very stable grain boundary, it has excellent grain interface strength, not only cracking, but also crack propagation is suppressed, and it has a much higher high-temperature strength, so it has strong mechanical strength Intermittent heavy cutting with repeated impact exerts excellent chipping resistance compared to the conventional κ-type Al ₂ O ₃ layer that constitutes the hard coating layer of the above conventional coated cermet tool. If the average layer thickness is less than 1 μm, the desired excellent wear resistance cannot be sufficiently exhibited. On the other hand, if the average layer thickness exceeds 15 μm, chipping tends to occur. The average layer thickness was determined to be 1-15 μm.
The actual analysis procedure using the field emission scanning electron microscope will be described as follows.

  The surface polished surface is irradiated with an electron beam, and the normal of the crystal plane at each measurement point intersects the normal of the surface polished surface (in the present invention, each normal of the (001) plane and the (010) plane) Is measured with respect to the normal of the surface polished surface), crystal orientation data at each measurement point is obtained, and crystal orientation data at each measurement point is obtained from crystal orientation data at a measurement point adjacent thereto. Comparison is made to determine whether or not there is an angle difference of a certain level or more (for example, in the present invention, an angle difference of “2 ° or more”), and an angle difference of a certain value or more (angle difference of 2 ° or more) If there is, it is determined as a “grain boundary”, and the length of the boundary between the measurement points in that case is counted as the minimum unit of the grain boundary. In other words, when the deviation of 2 ° or more is in either one of the normals on the (001) plane or the normal lines on the (010) plane, the boundary of the measurement point is determined as a “grain boundary” On the contrary, there is no “grain boundary” between the measurement points where the deviation between the normals is less than 2 °, and it is handled as the same crystal grain.

For example, among the measurement values obtained from a certain unit measurement area i (that is, the minimum unit of analysis), the angle between the normal of the (001) plane and the normal of the surface polished surface is defined as θ _i (001), (011) When the angle between the normal of the surface and the normal of the surface-polished surface is expressed as θ _i (010), considering the adjacent unit measurement regions A and B, the crystal orientation data obtained from the region A is ((Θ _A (001), θ _A (010)), and the crystal orientation data obtained from the region B is expressed as (θ _B (001), θ _B (010)), and using this, For adjacent areas A and B,

(001) intersection angle of normal to each other face phi _{(001) A-B} is
φ (001) _A−B = θ _A (001) −θ _B (001)
(010) intersection angle of normal to each other face phi _{(010) A-B} is
φ (010) _A−B = θ _A (010) −θ _B (010)

Next, and this _{φ (001) A-B,} φ (010) when the absolute value of at least one value of _A-B is 2 ° or more, the boundary between the regions A and B is "crystalline The boundary length between the region A and the region B is a crystal grain interface unit. Since both the region A and the region B are the minimum unit of analysis, the specific unit length of the crystal grain interface unit is the unit step length at the time of performing the analysis. In the following description, since the unit step of analysis is 0.1 μm / step, the unit length of the crystal grain interface unit is 0.1 μm.
By such a procedure, acquisition of crystal orientation data, determination of crystal grain boundaries, counting of crystal grain interface units, and the like are performed.
In addition, for the purpose of identification before and after the use of the cutting tool, a TiN layer having a golden color tone may be vapor-deposited as the outermost surface layer of the hard coating layer as necessary, but the average layer thickness in this case is It may be 0.1 to 1 μm, and if the thickness is less than 0.1 μm, a sufficient discrimination effect cannot be obtained, while the discrimination effect by the TiN layer is sufficient for an average layer thickness of up to 1 μm.

The coated cermet tool of the present invention constitutes the upper layer of the hard coating layer even when it is used for cutting various steels and cast irons, etc. to perform intermittent cutting with strong mechanical impact under heavy cutting conditions. The improved κ-type Al ₂ O ₃ layer has excellent high temperature strength in addition to the excellent high temperature hardness and heat resistance of Al ₂ O ₃ itself, so it has excellent chipping resistance It is possible to further extend the service life.

  Next, the coated cermet tool of the present invention will be specifically described with reference to examples.

WC powder, TiC powder, ZrC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder, TaN powder, and Co powder all having an average particle diameter of 1 to 3 μm are prepared as raw material powders. These raw material powders are blended in the blending composition shown in Table 1, added with wax, ball milled in acetone for 40 hours, dried under reduced pressure, and pressed into a compact of a predetermined shape at a pressure of 98 MPa. The green compact was vacuum sintered at a predetermined temperature in the range of 1370 to 1470 ° C. for 1 hour in a vacuum of 5 Pa. After sintering, the cutting edge portion was R: 0.07 mm honing By processing, tool bases A to F made of a WC-based cemented carbide having a throwaway tip shape defined in ISO · CNMG 160412 were produced.

In addition, as raw material powders, TiCN (mass ratio TiC / TiN = 50/50) powder, Mo ₂ C powder, ZrC powder, NbC powder, TaC powder, WC powder, all having an average particle diameter of 0.5 to 2 μm. Co powder and Ni powder are prepared, and these raw material powders are blended in the blending composition shown in Table 2, wet mixed by a ball mill for 40 hours, dried, and pressed into a compact at a pressure of 98 MPa. The green compact was sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour, and after the sintering, the cutting edge portion was subjected to a honing process of R: 0.07 mm. Tool bases a to f made of TiCN-based cermet having standard / CNMG 160412 chip shapes were formed.

Next, each of the tool bases A to F and the tool bases a to f was charged into a normal chemical vapor deposition apparatus. First, Table 3 (l-TiCN in Table 3 is disclosed in JP-A-6-8010). The conditions shown in Table 4 are the conditions shown in Table 4 below, which show the conditions for forming a TiCN layer having a vertically grown crystal structure, and the conditions for forming a normal granular crystal structure. A Ti compound layer having a layer thickness is deposited and formed as a lower layer of the hard coating layer, and then the modified κ-type Al ₂ O ₃ layer having the target layer thickness shown in Table 4 is formed on the hard coating layer under the conditions shown in Table 5. The coated cermet tools 1 to 13 according to the present invention were produced by vapor deposition as the upper layer of each.

For comparison purposes, the conventional κ-type Al ₂ O ₃ layer having the target layer thickness shown in Table 7 was vapor-deposited as the upper layer of the hard coating layer under the conditions shown in Table 6. Coated cermet tools 1 to 13 were produced.

Next, an electric field is applied to each of the modified κ-type Al ₂ O ₃ layer constituting the hard coating layer of the above-described coated cermet tool and the conventional κ-type Al ₂ O ₃ layer constituting the hard coating layer of the conventional coated cermet tool. Using an emission scanning electron microscope, crossing angle distribution graphs were created as illustrated in FIGS. 3 and 4. Incidentally, FIG. 3, the crossing angle distribution graph of the present invention coated cermet tool 2 of the kappa type the Al ₂ O ₃ layer, 4, of the conventional coated cermet tool 2 kappa type the Al ₂ O ₃ layer of the crossing angle distribution graphs respectively Show.

The crossing angle distribution graph is obtained by setting the surface of the κ-type Al ₂ O ₃ layer in a lens barrel of a field emission scanning electron microscope in a state where the surface of the κ-type Al ₂ O ₃ layer is a polishing surface parallel to the surface of the tool base. An electron beam with an acceleration voltage of 15 kV at an incident angle of 70 degrees on the surface is irradiated with an irradiation current of 1 nA on each crystal grain having an orthorhombic crystal structure existing within the measurement range of the surface-polished surface. Using a backscatter diffraction image apparatus, a region of 30 × 50 μm is spaced at a spacing of 0.1 μm / step, and the (001) plane and (010) are the crystal planes of the crystal grains with respect to the normal line of the polished surface. The angle at which each normal of the surface intersects with the normal of the surface polished surface is measured, and from the measured value obtained as a result, the (001) plane at the interface between adjacent crystal grains (grain interface unit) When the crossing angle between the normals is 2 ° or more and 10 ° or less In consideration of the symmetry of the orthorhombic crystal structure, the crossing angle between the (010) plane normals is set to 0 within the range of the crossing angle between the (010) plane normals of 0 to 120 °. It was created by dividing each pitch of 25 ° and counting the frequency of crystal grain interface units existing in each division.

From the crossing angle distribution graph created for various κ-type Al ₂ O ₃ layers, the crossing angle between the normals of the (001) planes at the interface between adjacent crystal grains (grain interface unit) is 2 ° or more and 10 ° or less. And the ratio of the crystal grain interface unit whose crossing angle between the normal lines of the (010) plane is 55 ° or more and 65 ° or less to the total crystal grain interface unit is shown in Tables 4 and 7. Indicated.

As can be seen from the crossing angle distribution graph illustrated as FIGS. 3 and 4 and the numerical ratios shown in Tables 4 and 7, the hard coating layers of the present coated cermet tools 1 to 13 and the conventional coated cermet tools 1 to 13 are configured. In any of the κ-type Al ₂ O ₃ layers, the crossing angle between the normal lines of the (001) plane of the adjacent region is 2 ° or more and 10 ° or less, and the normal line of the (010) plane of the adjacent region Although there is a distribution peak in the range where the crossing angle is 55 ° or more and 65 ° or less, in the coated cermet tools 1 to 13 of the present invention, the peak value is a value of 40% or more, whereas the conventional coating is used. In the cermet tools 1-13, the peak value was only 15% or less.

  Moreover, when the thickness of the constituent layer of the hard coating layer of the present coated cermet tools 1 to 13 and the conventional coated cermet tools 1 to 13 obtained as a result was measured using a scanning electron microscope (longitudinal section measurement). , Each showed an average layer thickness (average value of 5-point measurement) substantially the same as the target layer thickness.

Next, for the various coated cermet tools of the present invention coated cermet tool 1-13 and the conventional coated cermet tool 1-13, all of them are screwed with a fixing jig to the tip of the tool steel tool,
Work material: JIS / SNCM431 lengthwise equal 4 round bars with vertical grooves,
Cutting speed: 270 m / min,
Incision: 6mm,
Feed: 0.25mm / rev,
Cutting time: 8 minutes
Dry interrupted high cutting test of alloy steel under the conditions (cutting condition A) (normal cutting is 2 mm),
Work material: JIS-S25C round bar with four equal grooves in the longitudinal direction,
Cutting speed: 300 m / min,
Cutting depth: 2mm,
Feed: 0.65mm / rev,
Cutting time: 8 minutes
Of carbon steel under the following conditions (referred to as cutting condition B) (normal feed is 0.3 mm / rev),
Work material: JIS / FCD400 in the longitudinal direction, 4 equally spaced round bars,
Cutting speed: 240 m / min,
Cutting depth: 5.5 mm,
Feed: 0.35mm / rev,
Cutting time: 8 minutes
The dry interrupted high cut cutting test (normal cutting is 2 mm) of ductile cast iron under the above conditions (referred to as cutting condition C) was carried out, and the flank wear width of the cutting blade was measured in any cutting test. The measurement results are shown in Table 8.

表４、７、８に示される結果から、本発明被覆サーメット工具１〜１３は、いずれも硬質被覆層の上部層は、それぞれ隣接する結晶粒相互の界面（結晶粒界面単位）における（００１）面の法線同士の交差角が１０°以下で、かつ（０１０）面の法線同士の交差角が５５〜６５°である結晶粒界面単位が全結晶粒界面単位の４０％以上を占める結晶粒界面配列示すκ（カッパー）型Ａｌ₂Ｏ₃層で構成されているので、Ａｌ₂Ｏ₃自体のもつ高温硬さと耐熱性に加えて、その結晶対称性から非常に安定な粒界を形成し、粒界面強度を高め、クラックの発生ばかりか、クラックの伝播も抑え、その結果、一段とすぐれた高温強度を有するものであることから、鋼および鋳鉄の強い機械的衝撃を伴う断続重切削加工で、すぐれた耐チッピング性を示し、長期に亘ってすぐれた切削性能を発揮するのに対して、硬質被覆層の上部層が、それぞれ隣接する結晶粒相互の界面（結晶粒界面単位）における（００１）面の法線同士の交差角が１０°以下で、かつ（０１０）面の法線同士の交差角が５５〜６５°である結晶粒界面単位が全結晶粒界面単位の１５％以下を占めるにすぎないκ型Ａｌ₂Ｏ₃層で構成された従来被覆サーメット工具１〜１３においては、いずれも上記の断続重切削加工では、前記κ型Ａｌ₂Ｏ₃層の高温強度不足が原因で硬質被覆層にチッピングが発生し、比較的短時間で使用寿命に至ることが明らかである。

From the results shown in Tables 4, 7, and 8, in the coated cermet tools 1 to 13 of the present invention, the upper layer of the hard coating layer is (001) at the interface (crystal grain interface unit) between adjacent crystal grains. A crystal in which the crossing angle between the normals of the planes is 10 ° or less and the crossing angle between the normals of the (010) planes is 55 to 65 ° occupies 40% or more of the total grain interface units Since it is composed of κ (copper) type Al ₂ O ₃ layer showing the grain boundary arrangement, in addition to the high temperature hardness and heat resistance of Al ₂ O ₃ itself, it forms a very stable grain boundary due to its crystal symmetry In addition, the grain interface strength is increased, and not only cracks are generated, but also crack propagation is suppressed. As a result, it has excellent high-temperature strength, which makes it possible to perform intermittent heavy cutting with strong mechanical impact on steel and cast iron. With excellent chipping resistance The upper layer of the hard coating layer intersects the normal lines of the (001) plane at the interface between adjacent crystal grains (crystal grain interface unit), while exhibiting excellent cutting performance over a long period of time. Κ-type Al ₂ O in which the crystal grain interface unit having an angle of 10 ° or less and the (010) plane normal crossing angle of 55 to 65 ° occupies 15% or less of the total crystal grain interface unit _In the conventional coated cermet tools 1 to 13 composed of _three layers, any of the intermittent heavy cutting described above causes chipping in the hard coating layer due to insufficient high-temperature strength of the κ-type Al ₂ O ₃ layer. It is clear that the service life is reached in a relatively short time.

  As described above, the coated cermet tool of the present invention has excellent resistance not only to continuous cutting and interrupted cutting under normal conditions such as various steels and cast iron, but also particularly when interrupted cutting is performed under heavy cutting conditions. Since it exhibits chipping performance and exhibits excellent cutting performance over a long period of time, it can sufficiently satisfy the high performance of cutting equipment, labor saving and energy saving of cutting processing, and further cost reduction. .

It is a schematic explanatory drawing which shows the direction of the normal line of the (001) plane of the crystal grain (crystal lattice) and the direction of the normal line of the (010) plane in the κ-type Al ₂ O ₃ layer constituting the hard coating layer. In the κ-type Al ₂ O ₃ layer constituting the hard coating layer, (a) shows the state where the normal line of the (001) plane intersects the normal line of the surface polished surface at the crystal grain interface, and (b) shows (010) It is a schematic explanatory drawing which shows the state where the normals of a surface cross. It is a crossing angle distribution graph of the normal lines of the (010) plane of the κ-type Al ₂ O ₃ layer constituting the hard coating layer of the coated cermet tool 2 of the present invention. It is a crossing angle distribution graph of the normal lines of the (010) plane of the κ-type Al ₂ O ₃ layer constituting the hard coating layer of the conventional coated cermet tool 2.

Claims (1)

On the surface of the tool base composed of tungsten carbide based cemented carbide or titanium carbonitride based cermet,
(A) As a lower layer, all consisted of one or two or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride layer, which are chemically vapor-deposited, And a Ti compound layer having a total average layer thickness of 3 to 20 μm,
(B) The upper layer has a κ (kappa) type crystal structure in the state of chemical vapor deposition, and exists within the measurement range of the surface polished surface parallel to the tool substrate surface using a field emission scanning electron microscope. Each crystal grain having an orthorhombic crystal structure is irradiated with an electron beam, and the normal lines of the (001) plane and the (010) plane, which are constituent crystal planes of the crystal grains, are normal lines of the polished surface. The angle at which the normals of the (001) planes intersect each other at the interface between adjacent crystal grains (crystal grain interface unit) is 10 ° or less, and ( 010) The crystal grain interface unit in which the angle between the normals of the planes is 55 ° or more and 65 ° or less indicates a crystal grain interface arrangement that occupies a ratio of 40% or more of the total crystal grain interface units, and is 1 to 15 μm An aluminum oxide layer having an average layer thickness,
Surface-coated cermet cutting in which the modified κ (kappa) type aluminum oxide layer of the hard coating layer formed by vapor-depositing the hard coating layer composed of (a) and (b) has excellent grain interface strength tool.

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