JP2007331033A - Surface-coated cermet cutting tool with hard coating layer exerting excellent chipping and abrasion resistance in high-speed intermittent cutting processing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-coated cermet cutting tool with a hard coating layer exerting excellent chipping and abrasion resistance in high-speed intermittent cutting processing. <P>SOLUTION: In the surface-coated cermet cutting tool with the hard coating layer in which a lower layer is a Ti compound layer, and an upper layer is an α type Al<SB>2</SB>O<SB>3</SB>layer, a modified WC layer is provided in the lower layer as an intervention layer between layers, and the upper layer is composed of a modified α type Al<SB>2</SB>O<SB>3</SB>layer showing a constituent atom sharing lattice point distribution graph, which has the highest peak in Σ3 and a distribution ratio of the Σ3 to the entire ΣN+1 ranges 60% or more, when projecting electron beams to individual crystal particles with a cubic crystal lattice existing in a measurement range of a polished plane utilizing a field-emission scanning electron microscope, measuring inclination angles formed by normal lines of (0001) faces and (10-10) faces being crystal faces of the crystal particles with respect to the normal lines of the polished plane, and preparing the constituent atom sharing lattice point distribution graph, based on this measured values. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

In the present invention, the aluminum oxide (hereinafter referred to as Al ₂ O ₃ ) layer constituting the upper layer of the hard coating layer has excellent high-temperature strength, and tungsten carbide (hereinafter referred to as WC) constituting the hard coating layer. In particular, the cutting of various work materials such as steel and cast iron, because the layer exhibits excellent thermal conductivity, suppresses overheating of the hard coating layer during cutting, and suppresses the reduction in high-temperature hardness. Is a cutting tool made of surface-coated cermet (hereinafter referred to as coating) that exhibits excellent chipping resistance and wear resistance even when subjected to high-speed intermittent cutting conditions with high mechanical thermal shock and heat generation. Cermet tool).

Conventionally, in general, on the surface of a substrate (hereinafter collectively referred to as a tool substrate) composed of a 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) an Al ₂ O ₃ layer (hereinafter referred to as an α-type Al ₂ O ₃ layer) having an average layer thickness of 1 to 15 μm and having an α-type crystal structure in a state where chemical vapor deposition is performed,
A coated cermet tool formed by chemical vapor deposition of the hard coating layer composed of (a) and (b) above is known, and this coated cermet tool is used for continuous cutting and intermittent cutting of various steels and cast irons, for example. It is well known to be used in

  In the above-mentioned coated cermet tool, the constituent layer of the hard coating layer generally has a granular crystal structure, and the TiCN layer constituting the Ti compound layer as the lower layer is intended to improve the strength of the layer itself. In a normal chemical vapor deposition apparatus, a mixed gas containing organic carbonitride is used as a reaction gas, and it is formed by chemical vapor deposition at a medium temperature range of 700 to 950 ° C. so that it has a vertically grown crystal structure. It is also known to do.

Furthermore, the above coated cermet tool hard layer α type the Al ₂ O ₃ layer constituting the of the crystal structure of corundum type hexagonal close packed crystal constituent atoms consisting of Al and oxygen in the lattice points exist respectively, i.e. 1 The atomic arrangement of the α-type Al ₂ O ₃ unit cell is composed of crystal grains having a crystal structure represented by a schematic diagram [(a) is a perspective view, (b) is a plan view of cross sections 1 to 9]. It is also known.
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. On the other hand, there is a strong demand for labor saving and energy saving and further cost reduction for cutting, and along with this, cutting tends to be faster. In cermet tools, there is no problem when this is used for continuous cutting and intermittent cutting under normal conditions such as steel and cast iron, but this is especially high-speed intermittent cutting with high mechanical thermal shock and heat generation. When used for processing, since the α-type Al ₂ O ₃ layer constituting the hard coating layer does not have sufficient high-temperature strength, chipping (slight chipping) easily occurs in the hard coating layer. A remarkable temperature rise of the hard coating layer due to the generation of high heat is inevitable, and due to these, 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 α type the Al ₂ O ₃ layer described above constituting the upper layer of the hard coating layer, in particular the α-type the Al ₂ O ₃ layer As a result of research to improve chipping resistance of
(A) The α-type Al ₂ O ₃ layer (hereinafter referred to as “conventional α-type Al ₂ O ₃ layer”) constituting the upper layer of the hard coating layer of the conventional coated cermet tool is, for example, an ordinary chemical vapor deposition apparatus. At
Reaction gas composition: volume%, AlCl ₃ : 2 to 4%, CO ₂ : 6 to 8%, HCl: 1.5 to 3%, H ₂ S: 0.05 to 0.2%, H ₂ : remaining ,
Reaction atmosphere temperature: 1020 to 1050 ° C.
Reaction atmosphere pressure: 6 to 10 kPa,
It is formed by vapor deposition under the conditions (called normal conditions).
Reaction gas composition: by _{volume%, AlCl 3: 6~10%,} CO 2: 10~15%, HCl: 3~5%, H 2 S: 0.05~0.2%, H 2: remainder,
Reaction atmosphere temperature: 1020 to 1050 ° C.
Reaction atmosphere pressure: 3 to 5 kPa,
In other words, in the reaction gas composition, the content ratio of AlCl ₃ , CO ₂ , and HCl is relatively high and the atmospheric pressure is relatively low (reaction gas component high). When the vapor deposition is performed under the content-adjusted low-pressure conditions), the α-type Al ₂ O ₃ layer (hereinafter referred to as “modified α-type Al ₂ O ₃ layer”) formed under the high-reacted gas content adjusted low-pressure conditions is α In addition to the excellent high-temperature hardness and heat resistance of the Al ₂ O ₃ layer itself, it has superior high-temperature strength and improved chipping resistance compared to the conventional α-type Al ₂ O ₃ layer. To come to do.

(B) About the conventional α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer of the conventional coated cermet tool and the modified α-type Al ₂ O ₃ layer of (a) above,
Using a field emission scanning electron microscope, as illustrated in the schematic explanatory diagrams in FIGS. 2A and 2B, each crystal grain existing within the measurement range of the surface polished surface is irradiated with an electron beam, The tilt angle formed by the normal lines of the (0001) plane and the (10-10) plane, which are the crystal planes of the crystal grains, with respect to the normal line of the polished surface [FIG. 2 (a) shows the tilt angle of the crystal plane. (B) shows the case where the inclination angle is 45 degrees, all the inclination angles of the individual crystal grains including these angles are measured. In this case, the crystal grains Has a crystal structure of a corundum type hexagonal close-packed crystal in which constituent atoms composed of Al and oxygen are present at lattice points as described above, and based on the measured tilt angle, crystal grains adjacent to each other are obtained. Each of the constituent atoms shares one constituent atom between the crystal grains at the interface The distribution of child points (constituent atom shared lattice points) is calculated, and N lattice points that do not share constituent atoms between the constituent atom shared lattice points (where N is two or more on the crystal structure of the corundum hexagonal close-packed crystal) Even if the upper limit of N is 28 from the point of distribution frequency, the even number of 4, 8, 14, 24, and 26 does not exist), and the existing constituent atomic shared lattice point form is expressed as ΣN + 1, When a constituent atom shared lattice point distribution graph showing the distribution ratio of each ΣN + 1 to the entire ΣN + 1 is created (in this case, there are constituent atomic shared lattice point forms of Σ5, Σ9, Σ15, Σ25, and Σ27) In contrast to the conventional α-type Al ₂ O ₃ layer, as shown in FIG. 5, the distribution ratio of Σ3 shows a relatively low constituent atom shared lattice point distribution graph of 30% or less. The modified α-type Al ₂ O ₃ As shown in FIG. 4, the layer shows a very high constituent atom shared lattice point distribution graph in which the distribution ratio of Σ3 is 60% or more, and this high distribution ratio of Σ3 indicates AlCl ₃ , CO ₂ constituting the reaction gas. , And the content of HCl, and also the atmospheric reaction pressure.
In the modified α-type Al ₂ O ₃ layer and the conventional α-type Al ₂ O ₃ layer, units of Σ3, Σ7, and Σ11 among constituent atomic shared lattice point forms at the interface between crystal grains adjacent to each other When the form is illustrated by a schematic diagram, it is as shown in FIGS.

(C) Generally, the WC layer as a constituent layer of the hard coating layer of the coated cermet tool is a normal chemical vapor deposition apparatus.
Reaction gas composition: volume%, WF ₆ : 0.5 to 5%, C ₆ H ₆ : 0.5 to 10%, H ₂ : 10 to 35%, Ar: remaining,
Reaction atmosphere temperature: 500 to 900 ° C.
Reaction atmosphere pressure: 5 to 30 kPa,
The WC layer is formed by the same chemical vapor deposition apparatus, for example,
Reaction gas composition: by _{volume%, WF 6: 0.04~0.4%,} CH 3 CN: 0.06~0.6%, NH 3: 0.1~1%, H 2: 40~80% , Ar: rest,
Reaction atmosphere temperature: 980-1100 ° C.,
Reaction atmosphere pressure: 5 to 15 kPa,
As a result, the resulting WC layer (hereinafter referred to as a modified WC layer) has excellent adhesion and thermal conductivity. Therefore, the WC layer is formed as a lower layer of the hard coating layer. When present as an interlayer intervening layer in a Ti compound layer composed of two or more constituent layers, the modified WC layer is firmly bonded and joined to any of the constituent layers of the Ti compound layer, and high-speed intermittent cutting is performed. The temperature rise of the hard coating layer due to the high heat sometimes generated is remarkably suppressed by the excellent heat removal effect (thermal conductivity) of the modified WC layer as the interlayer intervening layer. As a result, the overheating of the hard coating layer is prevented. It is avoided and sudden wear resistance deterioration caused by overheating can be avoided.

(D) Therefore, as an interlayer intervening layer in the Ti compound layer composed of two or more constituent layers which are the lower layers of the hard coating layer, it has high thermal conductivity and excellent adhesion, and as a result, excellent heat removal. The modified WC layer that exhibits the effect is provided, and in addition to the excellent high temperature hardness and heat resistance, the modified α-type Al ₂ O ₃ layer having a further excellent high temperature strength is used as the upper layer of the hard coating layer. In addition, the coated cermet tool formed by vapor deposition on the surface of the tool base together with the Ti compound layer having excellent high-temperature strength of the lower layer is particularly suitable for high-speed intermittent cutting with intense mechanical thermal shock and high heat generation. The modified WC layer significantly suppresses the temperature rise of the hard coating layer without causing chipping in the hard coating layer, and exhibits excellent wear resistance over a long period of time. To become a.
The research results shown in (a) to (d) 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) a Ti compound layer having a total average layer thickness of 3 to 20 μm, wherein the lower layer is composed of two or more constituent layers of a TiC layer, a TiN layer, a TiCN layer, a TiCO layer, and a TiCNO layer;
(B) an α-type Al ₂ O ₃ layer whose upper layer has an average layer thickness of 1 to 15 μm;
In the coated cermet tool formed by chemical vapor deposition of the hard coating layer constituted by (a) and (b) above,
(1) A modified WC layer having an average layer thickness of 0.1 to 2 μm as an interlayer intervening layer in the Ti compound layer composed of two or more constituent layers,
With chemical vapor deposition,
(2) The α-type Al ₂ O ₃ layer as the upper layer has an α-type crystal structure in the same chemical vapor deposition state, and exists within the measurement range of the surface polished surface using a field emission scanning electron microscope. The crystal grains having a hexagonal crystal lattice are irradiated with electron beams, and the (0001) plane and the (10-10) plane are the crystal planes of the crystal grains with respect to the normal line of the surface polished surface. The inclination angle formed by the line is measured. In this case, the crystal grains have a crystal structure of a corundum type hexagonal close-packed crystal in which constituent atoms composed of Al and oxygen are present at lattice points. Based on the angle, the distribution of lattice points (constituent atom shared lattice points) in which each of the constituent atoms shares one constituent atom between the crystal grains at the interface between adjacent crystal grains is calculated, Share constituent atoms between constituent atomic lattice points There are N lattice points (where N is an even number of 2 or more on the crystal structure of the corundum hexagonal close-packed crystal, but when the upper limit of N is 28 in terms of distribution frequency, 4, 8, 14, 24 In the constituent atomic shared lattice distribution graph showing the distribution ratio of each ΣN + 1 in the entire ΣN + 1 when the existing constituent atomic shared lattice point form is expressed by ΣN + 1, the highest peak is at Σ3. And a modified α-type Al ₂ O ₃ layer showing a constituent atom shared lattice point distribution graph in which the distribution ratio of the Σ3 to the entire ΣN + 1 of the Σ3 is 60% or more,
The hard coating layer is characterized by a coated cermet tool that exhibits excellent chipping resistance and wear resistance in high-speed intermittent cutting.

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) Modified WC layer (interlayer intervening layer)
As described above, the modified WC layer is firmly adhered and bonded to any of the constituent layers of the Ti compound layer, and is sufficiently removed even in high-speed intermittent cutting with significant heat generation due to its excellent thermal conductivity. It has a function of exerting a thermal effect and suppressing the temperature rise of the hard coating layer so as to satisfactorily exhibit the excellent wear resistance inherent in the hard coating layer. If the thickness is less than 1 μm, the above-mentioned effect cannot be exhibited sufficiently. On the other hand, an average layer thickness of up to 2 μm is sufficient for the above-mentioned action, so the average layer thickness is determined to be 0.1 to 2 μm.

(B) Ti compound layer (lower layer)
The Ti compound layer basically exists as a lower layer of the modified α-type Al ₂ O ₃ layer, which is the upper layer, and contributes to improving the high temperature strength of the hard coating layer by its excellent high temperature strength. The tool substrate and the modified WC layer and the modified α-type Al ₂ O ₃ layer are firmly adhered to each other, and thus contribute to improving the adhesion of the hard coating layer to the tool substrate. If the layer thickness is less than 3 μm, the above-mentioned effect cannot be sufficiently exerted. On the other hand, if the total average layer thickness exceeds 20 μm, thermoplastic deformation is caused particularly in high-speed cutting of difficult-to-cut materials with high heat generation. Since it becomes easy to cause uneven wear, the total average layer thickness is determined to be 3 to 20 μm.

(B) modified α type the Al ₂ O ₃ layer (upper layer)
Distribution ratio of Σ3 in the atom sharing lattice point distribution graph of the reformed α-type Al ₂ O ₃ layer is the content of AlCl 3, _{CO 2,} and HCl composing the street reactive gas, further atmospheric reaction pressure However, in this case, if the distribution ratio of Σ3 is less than 60%, high-temperature intermittent cutting will ensure no excellent chipping in the hard coating layer, ensuring an excellent high-temperature strength improvement effect. Therefore, the distribution ratio of Σ3 is determined to be 60% or more. As described above, the modified α-type Al ₂ O ₃ layer has a further excellent high-temperature strength in addition to the excellent high-temperature hardness and heat resistance of the α-type Al ₂ O ₃ layer itself as described above. However, if the average layer thickness is less than 1 μm, the above-mentioned properties of the modified α-type Al ₂ O ₃ layer cannot be sufficiently provided to the hard coating layer, while if the average layer thickness exceeds 15 μm, The average layer thickness was determined to be 1 to 15 μm because thermoplastic deformation that causes uneven wear tends to occur and wear accelerates.

  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.

In this invention-coated cermet tool, the modified α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer has an excellent high temperature hardness and heat resistance in addition to the excellent high-temperature hardness and heat resistance of the α-type Al ₂ O ₃ itself. The hard WC coating has excellent heat removal effect due to the excellent thermal conductivity of the modified WC layer provided as an interlayer intervening layer on the Ti compound layer consisting of two or more constituent layers. Since the temperature rise of the layer is remarkably suppressed, cutting of various steels and cast irons, especially with strong mechanical thermal shock, is combined with the excellent high-temperature strength of the lower Ti compound layer. Even when used in high-speed cutting conditions where high heat generation is unavoidable, the hard coating layer does not generate chipping and exhibits excellent wear resistance over a long period of time. This makes it possible to prolong the 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 were blended into the composition shown in Table 1, added with wax, ball milled in acetone for 24 hours, dried under reduced pressure, and pressed into a green compact with 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 24 hours, dried, and pressed into a compact at a pressure of 98 MPa. The green compact was sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour, and after 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.

Then, each of these tool bases A to F and tool bases a to f is charged into a normal chemical vapor deposition apparatus,
First, Table 3 (l-TiCN in Table 3 indicates the conditions for forming a TiCN layer having a vertically grown crystal structure described in JP-A No. 6-8010, and other than that, a normal granular crystal structure is shown. Under the conditions shown in Table 4), the Ti compound layer and the modified WC layer are vapor-deposited as the lower layer of the hard coating layer and the interlayer intervening layer with the combinations and target layer thicknesses shown in Table 4.
Then, similarly modified α type the Al ₂ O ₃ layer under the conditions shown in Table 3 (a) ~ the upper layer of the hard coating layer or the same in combination and the target layer thickness shown in Table 4 of the (f) The coated cermet tools 1 to 13 of the present invention were produced by vapor deposition as follows.

For the purpose of comparison, as shown in Table 5, as the upper layer of the hard coating layer, conventional α type the Al ₂ O ₃ layer under the conditions shown in Table 3 to any one of (a) ~ (f) Similarly, the conventional coated cermet tools 1 to 13 were produced under the same conditions except that the vapor deposition was performed with the combinations and target layer thicknesses shown in Table 4 and the modified WC layer as an interlayer intervening layer was not formed.

Subsequently, each of the modified α-type Al ₂ O ₃ layer and the conventional α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer of the above-described coated cermet tool 1-13 of the present invention and the conventional coated cermet tool 1-13, respectively. Constituent atom shared lattice point distribution graphs were respectively prepared using a field emission scanning electron microscope.
That is, the constituent atomic shared lattice point distribution graph shows a mirror of a field emission scanning electron microscope in a state where the surfaces of the modified α-type Al ₂ O ₃ layer and the conventional α-type Al ₂ O ₃ layer are polished surfaces. An electron beam with an acceleration voltage of 15 kV at an incident angle of 70 degrees is applied to the polished surface with an irradiation current of 1 nA to each crystal grain 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 with respect to the normal line of the surface polished surface (0001) plane and (10 − 10) Measure the tilt angle formed by the normals of the surface, and based on the measured tilt angle obtained as a result, at the interface between adjacent crystal grains, each of the constituent atoms is one between the crystal grains. The number of lattice points that share constituent atoms (constituent atom shared lattice points) N is the number of lattice points that do not share constituent atoms between the constituent atomic shared lattice points (where N is an even number of 2 or more on the crystal structure of the corundum hexagonal close-packed crystal, but in terms of distribution frequency) When the upper limit of N is 28, the even number of 4, 8, 14, 24, and 26 does not exist.) When the existing constituent atomic shared lattice point form is expressed as ΣN + 1, each ΣN + 1 occupies the entire ΣN + 1 Created by determining the percentage.

As a result, in the constituent atomic share lattice point distribution graphs of various modified α-type Al ₂ O ₃ layers and conventional α-type Al ₂ O ₃ layers obtained as a result, the entire ΣN + 1 (from the above results, Σ3, Σ7, Σ11, Σ13, The distribution ratios of Σ3 in the total distribution ratios of Σ17, Σ19, Σ21, Σ23, and Σ29) are shown in Tables 4 and 5, respectively.

In the above-mentioned various atom sharing lattice point distribution graphs of, as shown in Tables 4 and 5, the reformed α-type the Al ₂ O ₃ layer of the present invention coated cermet tool are both distribution ratio of Σ3 is 60% In contrast to the above constituent atomic shared lattice point distribution graph, the conventional α-type Al ₂ O ₃ layer of the conventional coated cermet tool has a constituent atomic shared lattice point distribution graph in which the distribution ratio of Σ3 is 30% or less. Was shown.
FIG. 4 is a graph showing the distribution of constituent atomic shared lattice points of the modified α-type Al ₂ O ₃ layer of the coated cermet tool 3 of the present invention, and FIG. 5 is a graph of the conventional α-type Al ₂ O ₃ layer of the conventional coated cermet tool 5. The constituent atom shared lattice point distribution graphs are respectively shown.

  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 / S48C lengthwise equidistant four round grooved round bars,
Cutting speed: 350 m / min,
Incision: 1.5mm,
Feed: 0.4mm / rev,
Cutting time: 10 minutes,
A dry high-speed intermittent cutting test of carbon steel under the conditions (referred to as cutting condition A) (normal cutting speed is 200 m / min),
Work material: JIS / SNCM439 round direction bar with four equal intervals in the length direction,
Cutting speed: 300 m / min,
Cutting depth: 2mm,
Feed: 0.3mm / rev,
Cutting time: 10 minutes,
Dry high-speed intermittent cutting test (normal cutting speed is 150 m / min) of alloy steel under the conditions (referred to as cutting conditions B),
Work material: JIS / FCD600 lengthwise equal 4 round bars with longitudinal grooves,
Cutting speed: 350 m / min,
Cutting depth: 2mm,
Feed: 0.4mm / rev,
Cutting time: 10 minutes,
A dry high-speed intermittent cutting test (normal cutting speed is 180 m / min) of ductile cast iron under the above conditions (referred to as cutting condition C), and the flank wear width of the cutting edge was measured in any cutting test. The measurement results are shown in Table 6.

From the results shown in Tables 4 to 6, the coated cermet tools 1 to 13 of the present invention have a modified α-type Al ₂ O ₃ layer that is the upper layer of the hard coating layer, and the distribution ratio of Σ3 is 60% or more. FIG. 5 shows a graph of constituent atom sharing lattice distributions. As a result, the modified α-type Al ₂ O ₃ layer has excellent high-temperature strength in addition to excellent high-temperature hardness and heat resistance. Since the modified WC layer provided as an intervening layer in the compound layer exhibits an excellent heat removal effect and remarkably suppresses the temperature rise of the hard coating layer, the excellent high temperature strength and phase of the lower Ti compound layer can be obtained. On the other hand, in particular, the mechanical thermal shock is extremely high, and even in high-speed intermittent cutting of steel and cast iron with high heat generation, it exhibits excellent wear resistance over a long period without chipping. The upper layer of the hard coating layer has a distribution ratio of Σ3 It consists of a conventional α-type the Al ₂ O ₃ layer indicating 0% or less of the atom sharing lattice point distribution graphs, as a result the conventional α type the Al ₂ O ₃ layer becomes as having no high-temperature strength sufficiently satisfied, further wherein In the conventional coated cermet tools 1 to 13 where there is no formation of the modified WC layer and overheating of the hard coating layer is unavoidable, the mechanical thermal shock resistance of the hard coating layer is insufficient with high-speed intermittent cutting. Therefore, chipping occurs in the hard coating layer and the wear progress is relatively fast, so that 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 is required not only for continuous cutting and intermittent cutting under normal conditions such as various types of steel and cast iron, but particularly for a hard coating layer with high high-temperature strength and heat removal. The hard coating layer exhibits excellent chipping resistance and wear resistance even during high-speed intermittent cutting, and exhibits excellent cutting performance over a long period of time. It is possible to cope with the reduction of cost and cost.

FIG. 4 is a schematic diagram showing an atomic arrangement of a unit cell of a corundum type hexagonal close-packed crystal constituting an α-type Al ₂ O ₃ layer, where (a) is a perspective view and (b) is a plan view of cross sections 1 to 9. . It is a schematic diagram showing the measurement mode of the inclination angle of the crystal grains (0001) plane and (10-10) plane in the α-type the Al ₂ O ₃ layer. FIG. 3 is a schematic diagram showing unit forms of constituent atomic shared lattice points at the interface between adjacent crystal grains, where (a) shows Σ3, (b) shows Σ7 (c) and Σ11 unit forms. . 4 is a constituent atomic shared lattice point distribution graph of a modified α-type Al ₂ O ₃ layer of the coated cermet tool 3 of the present invention. 4 is a constituent atomic shared lattice point distribution graph of a conventional α-type Al ₂ O ₃ layer of a conventional coated cermet tool 5.

Claims (1)

On the surface of the tool base composed of tungsten carbide based cemented carbide or titanium carbonitride based cermet,
(A) The lower layer is composed of two or more of the constituent layers consisting of a Ti carbide layer, a nitride layer, a carbonitride layer, a carbonate layer, and a carbonitride oxide layer, and a total of 3 to 20 μm A Ti compound layer having an average layer thickness;
(B) an aluminum oxide layer whose upper layer has an α-type crystal structure in the state of chemical vapor deposition and has an average layer thickness of 1 to 15 μm;
In the surface-coated cermet cutting tool formed by chemical vapor deposition of the hard coating layer composed of (a) and (b) above,
(1) A modified tungsten carbide layer having an average layer thickness of 0.1 to 2 μm as an interlayer intervening layer in the Ti compound layer composed of two or more constituent layers,
With chemical vapor deposition,
(2) A hexagonal crystal having an α-type crystal structure in the same chemical vapor deposition state as the upper layer and having a field-emission scanning electron microscope in the measurement range of the surface polished surface. The crystal grains having a lattice are irradiated with an electron beam, and the normals of the (0001) plane and (10-10) plane, which are crystal planes of the crystal grains, are inclined with respect to the normal line of the polished surface In this case, the crystal grains have a crystal structure of a corundum type hexagonal close-packed crystal in which constituent atoms composed of Al and oxygen are present at lattice points, respectively. Based on the measured tilt angle obtained as a result Calculating a distribution of lattice points (constituent atom shared lattice points) in which each of the constituent atoms shares one constituent atom between the crystal grains at an interface between adjacent crystal grains; Shared constituent atoms between points There are N lattice points (N is an even number of 2 or more on the crystal structure of the corundum hexagonal close-packed crystal, but when the upper limit of N is 28 from the point of distribution frequency, 4, 8, 14, 24 In the constituent atomic shared lattice distribution graph showing the distribution ratio of each ΣN + 1 in the entire ΣN + 1 when the existing constituent atomic shared lattice point form is expressed by ΣN + 1, the highest peak is at Σ3. And a modified aluminum oxide layer showing a constituent atom shared lattice point distribution graph in which the distribution ratio of the Σ3 to the entire ΣN + 1 of the Σ3 is 60% or more,
A surface-coated cermet cutting tool with a hard coating layer that exhibits excellent chipping resistance and wear resistance in high-speed intermittent cutting.

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