JP2009101462A - Surface-coated cutting tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-coated cutting tool having a rigid coat layer exhibiting excellent chipping resistance in high-speed and high-feed intermittent cutting. <P>SOLUTION: The surface-coated cutting tool has a lower layer made of a Ti-based compound layer and an upper layer made of an Al<SB>2</SB>O<SB>3</SB>layer vapor-deposited on the surface of a tool base. At least one of Ti-based compound layers is a TiCrCN layer satisfying the relation: (Ti<SB>1-X</SB>Cr<SB>X</SB>)C<SB>1-Y</SB>N<SB>Y</SB>(where 0.005≤X≤0.05 and 0.45≤Y≤0.55). On the assumption that gradient angles of normal lines of a (001) plane and a (011) plane with respect to a normal line of a polished surface on a vertical section of the layer are measured by means of a field mission scanning electron microscope, and a grain boundary is specified when the angle of normal lines of the (001) plane intersecting with each other or normal lines of the (011) plane intersecting with each other is 2 degrees or larger, GBL is defined as a length of a grain boundary where the normal lines of the (001) plane intersect with each other and the normal lines of the (011) plane intersect with each other with an angle of 15 degrees or larger among crystal grain interfaces identified as the grain boundary in a measurement region. T is defined as a thickness of the measured TiCNO layer. At least one of other layers includes a modified TiCNO layer having a ratio of GBL/T ranging from 320 to 600. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  This invention exhibits high chipping resistance with a hard coating layer in high-speed, high-feed intermittent cutting such as steel and cast iron, which is accompanied by large heat generation and repeatedly and intermittently imposes a heavy load on the cutting edge. The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool).

As a conventional coated tool, a base made of tungsten carbide group (hereinafter referred to as WC group) cemented carbide or titanium carbonitride group (hereinafter referred to as TiCN group) cermet (hereinafter collectively referred to as a tool base) On the surface)
A TiCN (hereinafter referred to as 1-TiCN) layer having a vertically grown crystal structure, a Ti-based compound layer composed of a TiC layer, a TiN layer, a TiCN layer, and a TiCNO layer having a granular crystal structure, and an Al ₂ O ₃ layer, In a coated tool deposited with an average layer thickness of 30 μm,
Adjacent to the l-TiCN layer,
Compositional formula; (Ti _1-X Cr _X ) CN (wherein the atomic ratio is X: 0.005 to 0.05) Ti and Cr composite carbonitride (hereinafter referred to as TiCrCN) having a vertically grown crystal structure. It is also known that a coated tool having an average layer thickness of 1 to 10 μm is used, and this coated tool is used for continuous cutting and intermittent cutting of various steels and cast iron, for example. ing.
JP-A-10-244405

  In recent years, the performance of cutting machines has been remarkable, while demands for labor saving, energy saving, high efficiency, and low cost for cutting are strong, and accordingly, cutting tends to be performed under more severe conditions. However, in the above-mentioned conventional coated tool, there is no problem when it is used for continuous cutting or intermittent cutting under normal conditions such as steel or cast iron, but this particularly involves high heat generation, and When used under high-speed, high-feed, intermittent cutting conditions in which a large impact load is repeatedly and intermittently applied to the cutting edge, the high temperature strength and heat resistance of the Ti-based compound layer constituting the hard coating layer are insufficient. In the present situation, chipping (small chipping) and thermoplastic deformation are likely to occur in the hard coating layer, and as a result, the service life is reached in a relatively short time.

In view of the above, the inventors of the present invention focused on the TiCNO layer, particularly the TiCNO layer, in order to improve the chipping resistance of the hard coating layer of the above-mentioned coated tool. As a result,
(A) The TiCNO (hereinafter referred to as conventional TiCNO) layer constituting the Ti-based compound layer of the hard coating layer of the conventional coated tool is, for example, an ordinary chemical vapor deposition apparatus.
Reaction gas composition: by _{volume%, TiCl 4: 2~10%,} CO: 1~5%, CH 4: 0.1~5%, N 2: 5~30%, H 2: remainder,
Reaction atmosphere temperature: 950 to 1050 ° C.
Reaction atmosphere pressure: 6-25 kPa,
It is formed by vapor deposition under the conditions (called normal conditions)
Change this deposition condition,
Reaction gas composition: volume%, TiCl ₄ : 2 to 10%, CO: 1 to 5%, N ₂ : 50 to 60%, H ₂ : remaining,
Reaction atmosphere temperature: 850 to 900 ° C.
Reaction atmosphere pressure: 10-22 kPa,
In other words, compared to the normal conditions, when the vapor deposition was performed until the target layer thickness (1 to 8 μm) was reached under the high nitrogen gas composition without addition of methane and the low temperature vapor deposition conditions, the vapor deposition was performed under such conditions. The TiCNO (hereinafter referred to as “modified TiCNO”) layer has further improved high-temperature strength, can prevent the occurrence of chipping due to intermittent and repeated mechanical impacts during cutting, and also has heat resistance. Improved, even if the cutting edge is overheated by the high heat generated during cutting, it is excellent in heat-resistant plastic deformation and the occurrence of uneven wear is suppressed, so the coated tool with the modified TiCNO layer as a constituent layer of the hard coating layer is It exhibits excellent chipping resistance in high-speed, high-feed intermittent cutting, and exhibits excellent wear resistance over a long period of time.

(B) And about said modified TiCNO layer,
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 vertical cross-section polished surface is irradiated with an electron beam, The inclination angle formed by the normal lines of the (001) plane and the (011) plane, which are the crystal planes of the crystal grains, with respect to the normal line of the vertical cross-section polished surface (FIG. When the tilt angle of the (001) plane is 0 degree and the tilt angle of the (011) plane is 45 degrees, the tilt angle of the (001) plane is 45 degrees and the tilt angle of the (011) plane is 0 degree. In this case, all inclination angles of the individual crystal grains including these angles are measured, and in this case, the crystal grains have constituent atoms composed of Ti, carbon, nitrogen and oxygen at lattice points. Each has a NaCl-type face-centered cubic crystal structure, and based on the resulting measured tilt angle, When the angles at which the (001) plane normals and the (011) plane normals intersect at the interface between adjacent crystal grains are obtained, the (001) plane normals and (011) The case where the angle between the normals of the planes is 2 degrees or more is set as a grain boundary, and a field emission electron microscope is used thereon, and the vertical cross-section polished surface of the modified TiCNO layer is, for example, a layer The length of the grain boundary where the angle between the normal lines of the (001) planes and the normal lines of the (011) planes of the portion measured as thickness x width 30 μm and identified as grain boundaries is 15 degrees or more. When the thickness (μm, hereinafter referred to as GBL) is obtained and the ratio of the thickness of the GBL to the modified TiCNO layer (μm, hereinafter denoted by T) (ie, GBL / T) is obtained, the modified TiCNO is obtained. As shown in Tables 5 and 6, the layer has a GBL / T of 320 to The high GBL / T value varies depending on the combination of the reaction gas composition, the reaction atmosphere temperature, and the reaction atmosphere pressure during the film formation (in addition, the conventional TiCNO deposited by vapor deposition under the above normal conditions). As for the layer, GBL / T is a small value as shown in Tables 7 and 8.)

(C) The above-mentioned modified TiCNO layer has a higher high-temperature strength and heat resistance than the conventional TiCNO layer, and a coated tool formed by vapor deposition as a constituent layer of a hard coating layer, The TiCrCN layer has excellent high-temperature strength and high-temperature hardness, and in combination with the excellent high-temperature hardness and heat resistance of the Al ₂ O ₃ layer, which is the upper layer, a large heat especially for the cutting edge portion. Even when used under high feed interrupted cutting conditions that are subject to mechanical and impact loads, chipping resistance and wear resistance have a hard coating layer superior to conventional coated tools with a conventional TiCNO layer deposited. To come out.
The research results shown in (a) to (c) above were obtained.

This invention was made based on the above research results,
“(1) On the surface of a tool base made of tungsten carbide group (WC group) cemented carbide or titanium carbonitride group (TiCN group) cermet,
(A) A Ti carbide (TiC) layer, a nitride (TiN) layer, a carbonitride (TiCN) layer, a carbonate (TiCO) layer, a carbonitride oxide (which is formed by chemical vapor deposition in all cases) A Ti-based compound layer composed of at least two of a TiCNO) layer and a composite carbonitride (TiCrCN) layer of Ti and Cr and having a total average layer thickness of 2 to 15 μm,
(B) an aluminum oxide (Al ₂ O ₃ ) layer having an average layer thickness of 1 to 15 μm, wherein the upper layer is formed by chemical vapor deposition;
In the surface-coated cutting tool formed by forming the hard coating layer composed of (a) and (b) above,
(C) At least one of the Ti-based compound layers constituting the lower layer is
_{Formula: (Ti 1-X Cr X} ) C 1-Y N Y
In this case, Ti and Cr composite charcoal having a vertically grown crystal structure satisfying 0.005 ≦ X ≦ 0.05 and 0.45 ≦ Y ≦ 0.55 (where X and Y are atomic ratios). A nitride (TiCrCN) layer;
(D) At least one of the Ti-based compound layers constituting the lower layer is a titanium carbonitride oxide layer having an average layer thickness of 1 to 8 μm, and an electric field is applied to the titanium carbonitride oxide layer. Using an emission scanning electron microscope, each crystal grain existing within the measurement range of 30 μm in width of the vertical cross section polished surface of the above layer is irradiated with an electron beam, and the crystal is compared with the normal line of the vertical cross section polished surface. The inclination angles formed by the normal lines of the (001) plane and the (011) plane, which are crystal planes of the grains, are measured, and the normal lines of the (001) planes at the interfaces between adjacent crystal grains are determined from the measured tilt angles. And the angle at which the normal lines of the (011) plane intersect, and the angle at which the normal lines of the (001) plane and the normal lines of the (011) plane intersect each other is 2 degrees or more. Use field emission electron microscope after setting In the measurement region on the vertical cross-section polished surface of the layer, grains whose normals of the (001) plane and normals of the (011) plane intersect with each other among the parts identified as grain boundaries are 15 degrees or more. The length of the boundary (μm) is obtained, and the ratio of the grain boundary length (μm) to the measured thickness of the titanium carbonitride oxide layer (μm) is titanium carbonitride oxide (modified) Quality TiCNO) layer,
A surface-coated cutting tool (coated tool). "
It has the characteristics.

Next, the reason why the constituent layers of the hard coating layer of the coated tool of the present invention are numerically limited as described above will be described below.
(A) Lower layer (Ti compound layer)
At least a Ti-based compound layer composed of a TiC layer, a TiN layer, a TiCN layer (including a 1-TiCN layer), a TiCO layer, a TiCrCN layer, and a modified TiCNO layer has a predetermined high-temperature strength. In addition to the high temperature strength of the hard coating layer due to its presence, it firmly adheres to both the tool base and the upper Al ₂ O ₃ layer, contributing to improved adhesion of the hard coating layer to the tool base. However, if the total average layer thickness is less than 2 μm, the above-described effect cannot be sufficiently exerted. On the other hand, if the total average layer thickness exceeds 15 μm, the cutting edge is repeatedly intermittent. Therefore, the total average layer thickness was determined to be 2 to 15 μm.

(B) Lower modified TiCNO layer High nitrogen gas composition without addition of methane and low temperature deposition conditions compared to normal conditions,
That is,
Reaction gas composition: volume%, TiCl ₄ : 2 to 10%, CO: 1 to 5%, N ₂ : 50 to 60%, H ₂ : remaining,
Reaction atmosphere temperature: 850 to 900 ° C.
Reaction atmosphere pressure: 10-22 kPa,
The modified TiCNO layer having a vertically grown crystal structure formed by chemical vapor deposition under the above conditions is a crystal structure of NaCl type face centered cubic crystal in which constituent atoms composed of Ti, carbon, nitrogen and oxygen are present at lattice points, respectively. Furthermore, the modified TiCNO layer was irradiated with an electron beam on each crystal grain of the modified TiCNO layer existing within the measurement range of the vertical cross-section polished surface, using a field emission scanning electron microscope. The inclination angle formed by the normal lines of the (001) plane and the (011) plane, which are the crystal planes of the crystal grains, is measured with respect to the normal line of the vertical cross-section polished surface. The angles of the (001) plane normal lines and the (011) plane normal lines at the interface between adjacent crystal grains are obtained, and the (001) plane normal lines and (011) ) Surface law After setting the case where the angle of crossing is 2 degrees or more as a grain boundary, the vertical cross-section polished surface of the modified TiCNO layer was measured with a field emission electron microscope, in a measurement region, for example, layer thickness × width 30 μm. Among the parts identified as grain boundaries, the angle between the normals of the (001) planes and the normal lines of the (011) planes is 15 ° or more. When the grain boundary length GBL (μm) is determined for the tilted grain boundary) and the ratio of GBL (μm) to the layer thickness T (μm) of the modified TiCNO layer is determined, GBL / T is 320 Since the modified TiCNO layer having a value of ~ 600 and GBL / T having such a large value comes to have a higher temperature strength, the cutting edge portion is formed by high-speed high-feed intermittent cutting. In contrast, a large thermal and shock load is applied. Even, it is possible to greatly reduce the risk of chipping in the hard coating layer.
However, when the GBL / T value exceeds 600, the modified TiCNO layer itself tends to become brittle, while the GBL / T value is less than 320 (conventional deposition formed under normal conditions). When the GBL / T value of the TiCNO layer is less than 320), the high temperature strength is insufficient, and improvement in chipping resistance cannot be expected. Therefore, the value of GBL / T is set to 320 to 600.
Note that the value of GBL / T is influenced by the reaction gas composition and the reaction atmosphere temperature. For example, the GBL / T in a conventional TiCNO layer formed by vapor deposition under a low nitrogen gas composition and a high temperature condition rather than the deposition condition of the modified TiCNO layer. Is a small value of less than about 200 (see Tables 7 and 8), and high-temperature strength has not been improved. Therefore, chipping occurs in the hard coating layer under severe cutting conditions such as high-speed and high-feed intermittent cutting. It was seen (see Table 9).
In addition, the modified TiCNO layer has a higher temperature strength than that of the conventional TiCNO layer, but if the average layer thickness is less than 1 μm, a sufficient high temperature strength improvement effect cannot be expected. If the average layer thickness is up to 8 μm, sufficient chipping resistance can be exhibited, so the average layer thickness was set to 1 to 8 μm.

(C) TiCrCN layer of lower layer Composition formula: (Ti _1-X Cr _X ) C _1-Y N _Y
In the TiCrCN layer having a vertically grown crystal structure represented by the following formula, the Cr content (X value) in the total amount with Ti in the layer is 0.005 ≦ X ≦ 0.05 (however, atomic ratio), When the content ratio (Y value) of the N component in the total amount with the C component is within the range of 0.45 ≦ Y ≦ 0.55 (however, the atomic ratio), it has excellent high temperature strength and excellent high temperature hardness. . In other words, whether the Cr content (X value) is less than 0.005 or more than 0.05, it is possible to provide excellent high-temperature strength sufficient to suppress chipping in high-speed, high-feed intermittent cutting. In addition, when the content ratio (Y value) of the N component is less than 0.45, a desired strength cannot be ensured. On the other hand, when the Y value exceeds 0.55, a desired high hardness is obtained. It can no longer be obtained.
In addition, when the average thickness of the TiCrCN layer is less than 1 μm, the effect of improving the high temperature strength and the effect of improving the high temperature hardness cannot be expected. On the other hand, when the average layer thickness exceeds 14 μm, the thermoplasticity causes uneven wear. Since deformation tends to occur and wear is accelerated, the average layer thickness is preferably 1 to 14 μm.

(D) an upper layer of Al ₂ O ₃ layer the Al ₂ O ₃ layer of the upper layer has excellent high-temperature hardness and heat resistance and contributes to improvement in wear resistance of the hard coating layer, the average layer thickness thereof If the thickness is less than 1 μm, sufficient wear resistance cannot be imparted to the hard coating layer, while if the average layer thickness exceeds 15 μm, chipping is likely to occur. Was set to 1 to 15 μm.

  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 necessary, but the average layer thickness in this case may be 0.1 to 1 μm, This is because 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 with an average layer thickness of up to 1 μm.

  Even when the coated tool of the present invention is used for high-speed high-feed intermittent cutting such as steel and cast iron, which is accompanied by large heat generation and repeatedly receives a large impact load on the cutting edge, Since at least one layer of the lower layer is composed of the modified TiCNO layer, it has excellent high-temperature strength and high-temperature hardness, so there is no chipping in the hard coating layer, and it can be used over a long period of use. It exhibits excellent wear resistance.

  Next, the coated 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 performing the processing, tool bases A to F made of WC-based cemented carbide having an insert shape specified in ISO · CNMG120408 were manufactured.

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 an insert shape of standard / CNMG12041 were formed.

Next, on the surface of these tool bases A to F and tool bases a to f, a Ti-based compound layer (except for the modified TiCNO layer) is used as a lower layer of the hard coating layer using a normal chemical vapor deposition apparatus. Vapor deposition was performed under the conditions shown in Table 3.
The modified TiCNO layer is then
Reaction gas composition: volume%, TiCl ₄ : predetermined amount in the range of 2 to 10%, CO: predetermined amount in the range of 1 to 5%, N ₂ : predetermined amount in the range of 50 to 60%, H ₂ : the rest,
Reaction atmosphere temperature: a predetermined temperature within a range of 850 to 900 ° C,
Reaction atmosphere pressure: a predetermined pressure in the range of 10-22 kPa,
In the conditions shown in Table 4, vapor deposition is performed with the combinations shown in Tables 5 and 6 and with the target layer thicknesses shown in Tables 5 and 6 as well. The present invention coated tools 1 to 20 were respectively produced by vapor-depositing Al ₂ O ₃ layers with the target layer thicknesses shown in Tables 5 and 6 respectively.

For the purpose of comparison, as a lower layer of the hard coating layer, a Ti-based compound layer (conventional TiCNO layer) is vapor-deposited with the combinations and target layer thicknesses shown in Tables 7 and 8 under the conditions shown in Table 3. further the Al ₂ O ₃ layer as an upper layer, under the conditions shown in Table 3, and were respectively manufactured conventional coated tool 20 by vapor deposited at the target layer thickness shown in tables 7 and 8.

Next, with respect to the modified TiCNO layer and the conventional TiCNO layer constituting the hard coating layer of the present invention-coated tool and the conventional coated tool, using a field emission scanning electron microscope, the GBL (μm ) And the ratio of GBL (μm) to the thickness of the TiCNO layer (μm) was determined.
That is, the modified TiCNO layer and the conventional TiCNO layer are set in a lens barrel of a field emission scanning electron microscope in a state where the longitudinal cross-sections of the TiCNO layer and the conventional TiCNO layer are used as a polished surface, and the surface is accelerated by 15 kV at an incident angle of 70 degrees A voltage electron beam is irradiated at an irradiation current of 1 nA to individual crystal grains existing within the measurement range of the vertical cross-section polished surface, and a predetermined measurement region is set to 0.1 μm / step using an electron backscatter diffraction image apparatus. At an interval, the inclination angle formed by the normal lines of the (001) plane and (011) plane, which are crystal planes of the crystal grains, is measured with respect to the normal line of the vertical cross-section polished surface, and the measured inclination obtained as a result Based on the angles, the angles at which the (001) plane normal lines and the (011) plane normal lines intersect each other at the interface between adjacent crystal grains are obtained. , And (011) plane normal After setting the case where the angle at which the crossing angle is 2 degrees or more as the grain boundary, the field emission scanning electron microscope was used to measure the vertical cross-section polished surface of the modified TiCNO layer (layer thickness × width 30 μm range). The region where the normals of the (001) planes and the normals of the (011) planes intersect with each other among the parts identified as grain boundaries in the measurement region is 15 degrees or more. The grain boundary length GBL (μm) was determined for the boundary. Then, the value of the ratio between GBL (μm) and the layer thickness T (μm) of the modified TiCNO layer (corresponding to the length of the grain boundary per unit layer thickness of the modified TiCNO layer) was determined.

  The values of GBL, T, and GBL / T for various modified TiCNO layers and conventional TiCNO layers obtained as a result are shown in Tables 5 to 8, respectively.

  As shown in Tables 5 to 8 respectively, the modified TiCNO layer of the coated tool of the present invention has a GBL / T value in the range of 320 to 600, whereas the conventional TiCNO of the conventional coated tool. All the layers had a GBL / T value of less than 320.

Further, regarding the above-described coated tools 1 to 20 of the present invention and the conventional coated tools 1 to 20, the constituent layers of the hard coating layer were observed using an electron beam microanalyzer (EPMA) and an Auger spectroscopic analyzer (longitudinal section of the layer). As a result, it was confirmed that both the former and the latter were composed of a Ti-based compound layer and an Al ₂ O ₃ layer having substantially the same composition as the target composition.
Moreover, when the thickness of the constituent layer of the hard coating layer of these coated tools was measured using a scanning electron microscope (similarly longitudinal section measurement), the average layer thickness (5 The average value of point measurement) was shown.

Next, in the state where each of the above various coated tools is screwed to the tip of the tool steel tool with a fixing jig, the present coated tools 1-20 and the conventional coated tools 1-20,
Work material: JIS / FCD700 lengthwise equal length 4 round bar with round groove,
Cutting speed: 450 m / min,
Cutting depth: 1.5 mm,
Feed: 0.6 mm / rev,
Cutting time: 8 minutes,
Dry high-speed high-feed intermittent cutting test under normal conditions (cutting conditions A) (normal cutting speed and feed are 200 m / min and 0.3 mm / rev, respectively)
Work material: JIS / SNCM439 round direction bar with 4 equal intervals in the length direction,
Cutting speed: 450 m / min,
Incision: 2 mm,
Feed: 0.55 mm / rev,
Cutting time: 8 minutes,
Dry high-speed high-feed intermittent cutting test of alloy steel under the following conditions (cutting condition B) (normal cutting speed and feed are 250 m / min and 0.25 mm / rev, respectively)
Work material: JIS · S45C lengthwise equal 4 round grooved round bars,
Cutting speed: 500 m / min,
Cutting depth: 2.0 mm,
Feed: 0.6 mm / rev,
Cutting time: 7 minutes,
Wet high-speed high-feed intermittent cutting test under normal conditions (cutting condition C) (normal cutting speed and feed are 250 m / min and 0.3 mm / rev, respectively)
In each cutting test, the flank wear width of the cutting edge was measured. The measurement results are shown in Table 9.

  From the results shown in Tables 5 to 9, all of the coated tools 1 to 20 of the present invention are modified TiCNO layers in which at least one of the lower layers of the hard coating layer is GBL / T = 320 to 600. As a result, the modified TiCNO layer has superior high-temperature strength and excellent chipping resistance even in high-speed, high-feed, intermittent cutting, where a large impact load is repeatedly and intermittently applied to the cutting edge. The TiCNO layer of the lower layer of the hard coating layer has a GBL / T value of less than 320, while exhibiting excellent chipping of the hard coating layer and excellent wear resistance at the same time. In the conventional coated tools 1 to 20 composed of more than 600 conventional TiCNO layers, the high temperature strength and heat resistance of the hard coating layer is insufficient. Chipping occurs, or, abrasion resistance was apparently too low can lead to a relatively short time service life.

  As described above, the coated tool of the present invention is not only continuous cutting and intermittent cutting under normal conditions such as various steels and cast irons, but also a high speed that repeatedly and intermittently applies a large impact load to the cutting edge portion. The hard coating layer shows excellent chipping resistance even during high-feed interrupted cutting, and exhibits excellent cutting performance over a long period of time. Furthermore, it can cope with cost reduction sufficiently satisfactorily.

It is a schematic diagram which shows the crystal structure of the NaCl type face centered cubic crystal which the TiCNO layer which comprises the lower layer of a hard coating layer has. It is a schematic explanatory drawing which shows the measurement aspect of the inclination angle of the (001) plane of a crystal grain and the (011) plane in the TiCNO layer which comprises the lower layer of a hard coating layer.

Claims (1)

On the surface of the tool base composed of tungsten carbide based cemented carbide or titanium carbonitride based cermet,
(A) Of the Ti carbide layer, nitride layer, carbonitride layer, carbonitride layer, carbonitride oxide layer, and Ti and Cr composite carbonitride layer, all of which the lower layer is formed by chemical vapor deposition And a Ti-based compound layer having a total average layer thickness of 2 to 15 μm,
(B) an aluminum oxide layer having an average layer thickness of 1 to 15 μm, wherein the upper layer is formed by chemical vapor deposition;
In the surface-coated cutting tool formed by forming the hard coating layer composed of (a) and (b) above,
(C) At least one of the Ti-based compound layers constituting the lower layer is
_{Formula: (Ti 1-X Cr X} ) C 1-Y N Y
In this case, Ti and Cr composite charcoal having a vertically grown crystal structure satisfying 0.005 ≦ X ≦ 0.05 and 0.45 ≦ Y ≦ 0.55 (where X and Y are atomic ratios). A nitride layer,
(D) At least one of the Ti-based compound layers constituting the lower layer is a titanium carbonitride oxide layer having an average layer thickness of 1 to 8 μm, and an electric field is applied to the titanium carbonitride oxide layer. Using an emission scanning electron microscope, each crystal grain existing within the measurement range of 30 μm in width of the vertical cross section polished surface of the above layer is irradiated with an electron beam, and the crystal is compared with the normal line of the vertical cross section polished surface. The inclination angles formed by the normal lines of the (001) plane and the (011) plane, which are crystal planes of the grains, are measured, and the normal lines of the (001) planes at the interfaces between adjacent crystal grains are determined from the measured tilt angles. And the angle at which the normal lines of the (011) plane intersect, and the angle at which the normal lines of the (001) plane and the normal lines of the (011) plane intersect each other is 2 degrees or more. Use field emission electron microscope after setting In the measurement region on the vertical cross-section polished surface of the layer, grains whose normals of the (001) plane and normals of the (011) plane intersect with each other among the parts identified as grain boundaries are 15 degrees or more. The length of the boundary (μm) is obtained, and the ratio of the grain boundary length (μm) to the measured thickness of the titanium carbonitride oxide layer (μm) is a titanium carbonitride oxide layer having a value of 320 to 600. is there,
A surface-coated cutting tool characterized by that.

Images