JP2013146843A - Surface-coated cutting tool in which hard coating layer demonstrates excellent chipping resistance and excellent wear resistance in high-speed and heavy cutting work - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface-coated cutting tool in which a hard coating layer demonstrates excellent chipping resistance and excellent wear resistance in the high-speed and heavy cutting work of a large black thickness-deviated component or the like.SOLUTION: In a surface-coated cutting tool, a lower layer composed of a Ti compound layer (here, a modified TiCN layer is essential), and an upper layer composed of a modified AlOlayer are coated on a surface of a tool base body. A ratio GBLa/Ta of a grain boundary length GBLa (μm) measured on the TiCN layer having a longitudinally-grown crystalline structure to the measured layer thickness Ta (μm) of the modified TiCN layer is 275-520. Furthermore, a ratio GBLb/Tb of a grain boundary length GBLb (μm) measured on the modified AlOlayer having a columnar structure to the measured layer thickness Tb (μm) of the modified AlOlayer is 40-165. Still furthermore, a value (GBLb/Tb)/(GBLa/Ta) is in a range of 0.1 to 0.6.

Description

  This invention is accompanied by high heat generation and high-speed heavy cutting with a particularly high thermal and mechanical load acting on the cutting edge, particularly high-speed heavy cutting in which the cutting stress varies greatly during processing. The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) in which a coating layer exhibits excellent wear resistance.

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) Ti carbide (hereinafter referred to as TiC) layer, nitride (hereinafter also referred to as TiN) layer, carbonitride (hereinafter referred to as TiCN) layer formed by chemical vapor deposition of the lower layers. A Ti compound layer consisting of two or more of a carbon oxide (hereinafter referred to as TiCO) layer and a carbonitride oxide (hereinafter referred to as TiCNO) layer and having a total average layer thickness of 3 to 20 μm,
(B) an α-type aluminum oxide (hereinafter referred to as Al ₂ O ₃ ) layer having an average layer thickness of 1 to 15 μm, in which the upper layer is formed by chemical vapor deposition;
A coated tool formed by forming a hard coating layer composed of the above (a) and (b) is known, and this coated tool is also used for cutting various steels and cast irons, for example. Are known.

For example, as shown in Patent Document 1, in a coated tool in which a Ti compound layer and an Al ₂ O ₃ layer are formed on the surface of a tool base, TC (006) is 2 for the orientation index TC of the Al ₂ O ₃ layer. A coated tool having a larger orientation index TC (104) of 2> TC (104)> 0.5 has been proposed.
However, in this coated tool, although the wear resistance of the coating is increased, there is a problem that chipping resistance and fracture resistance are inferior.

JP 2009-28894 A

In recent years, the performance of cutting machines has been remarkable. On the other hand, there is a strong demand for labor saving and energy saving and further cost reduction for cutting work.Accordingly, cutting speed has been further increased, and cutting tools have been improved. Thermal and mechanical loads are also increasing.
In the above-mentioned conventional coated tool, there is no problem when it is used for continuous cutting and intermittent cutting under normal conditions such as steel and cast iron. When used for high-speed heavy cutting of large black skin uneven parts, chipping, chipping, etc. are likely to occur because the cutting edge is subject to large thermal and mechanical loads. Since the cutting stress at the time of cutting greatly varies depending on the cutting location of the metal, the Al ₂ O ₃ layer, which is a hard coating layer, undergoes plastic deformation when the cutting stress suddenly increases. At present, wear progresses and the service life is reached in a relatively short time.

Therefore, the present inventors, from the above viewpoint, in order to improve the chipping resistance and wear resistance of the hard coating layer of the above-mentioned coated tool, the Ti compound layer as the lower layer of the hard coating layer, and As a result of earnest research on the layer structure of the Al ₂ O ₃ layer, which is the upper layer of the hard coating layer, a large thermal and mechanical load is applied to the cutting edge and high speed heavy cutting with large fluctuations in cutting stress For example, even when used for high-speed heavy cutting of the above-mentioned large black skinned parts, there is no risk of chipping, chipping, etc., and excellent wear resistance is demonstrated over a long period of use. The knowledge about the layer structure of the hard coating layer was obtained.

  In other words, as a coated tool used for high-speed heavy cutting with a large change in cutting stress, a large thermal and mechanical load is applied to the cutting edge as in high-speed heavy cutting of large black skinned parts. In the lower layer, in particular, the modified TiCN layer of the vertically grown crystal structure, chipping by dispersing cracks along the grain boundaries generated during cutting with a large thermal and mechanical load, and suppressing the propagation and progress thereof, On the other hand, it is important to suppress the occurrence of defects. On the other hand, in the upper layer, the occurrence of uneven wear is suppressed by suppressing grain boundary sliding that occurs due to a large change in cutting stress during cutting, which in turn prevents deterioration of wear resistance. It was found that it is important to plan.

First, the knowledge about the lower layer is as follows.
In FIG. 1 (a), a crystal structure of NaCl face-centered cubic crystal in which constituent atoms consisting of Ti, carbon, and nitrogen are present at lattice points (FIG. 1 (b) is cut along the (011) plane. A TiCN layer having a vertically long crystal structure (hereinafter referred to as an l-TiCN layer) having a state) is shown as a schematic diagram.
The l-TiCN layer as the lower layer constituting the hard coating layer of the conventional coated tool is, for example, a normal chemical vapor deposition apparatus.
Reaction gas composition: by _{volume%, TiCl 4: 2~10%,} CH 3 CN: 0.5~3%, N 2: 10~30%, H 2: remainder,
Reaction atmosphere temperature: 800 to 900 ° C.
Reaction atmosphere pressure: 6-20 kPa,
It is formed by vapor deposition under the conditions (referred to as normal conditions).
By the way, the inventors changed this deposition condition,
First, as the first stage,
Reaction gas composition: by _{volume%, TiCl 4: 5~20%,} C 3 H 3 N: 0.5~3.0%, N 2: 7~20%, H 2: remainder,
Reaction atmosphere temperature: 700-850 ° C.
Reaction atmosphere pressure: 6-20 kPa,
Under the conditions, vapor deposition is performed until the layer thickness of the vapor deposition layer is about 20% of the target layer thickness,
Then, as the second stage,
Reaction gas composition: by _{volume%, TiCl 4: 3~12%,} CH 3 CN: 0.2~2%, C 3 H 3 N: 0.1~0.5%, Ar: 10~30%, H ₂ : The rest,
Reaction atmosphere temperature: 700-850 ° C.
Reaction atmosphere pressure: 6-20 kPa,
In this condition, vapor deposition was performed until the target layer thickness was reached. As a result, an l-TiCN layer (hereinafter referred to as a “modified TiCN layer”) formed sequentially under the conditions of the first and second stages. ”) Has the function of relaxing and absorbing the stress generated in the layer during the cutting process, and the high temperature strength is further improved. Therefore, the upper layer of the hard coating layer is composed of the Al ₂ O ₃ layer, and The coating tool in which the lower layer is composed of one or more of the TiC layer, the TiN layer, the TiCN layer, the TiCO layer, and the TiCNO layer, and the modified TiCN layer, is particularly large. It has been found that the modified TiCN layer exhibits excellent chipping resistance and fracture resistance even in high-speed heavy cutting where thermal and mechanical loads are applied and the cutting stress varies greatly.

Next, although it is knowledge about the upper layer, the Al ₂ O ₃ layer of the columnar structure constituting the upper layer of the hard coating layer of the conventional coated tool is, for example, in a normal chemical vapor deposition apparatus,
Reaction gas composition: by _{volume%, AlCl 3: 1~5%,} CO 2: 3~7%, HCl: 0.3~3%, H 2 S: 0.02~0.4%, H 2: remainder ,
Reaction atmosphere temperature: 950-1100 ° C.
Reaction atmosphere pressure: 6-13 kPa,
(Hereinafter referred to as normal conditions).
However, the inventors changed this deposition condition,
First, as the first stage,
Reaction gas composition: by _{volume%, AlCl 3: 1~5%,} CO 2: 10~15%, HCl: 0.3~3%, SF 6: 0.1~1%, H 2: remainder,
Reaction atmosphere temperature: 950-1100 ° C.
Reaction atmosphere pressure: 20-40 kPa,
(The CO ₂ gas content ratio is relatively high compared to normal conditions, the reaction atmosphere pressure is relatively high, and SF ₆ is added as a reaction gas component instead of H ₂ S) Vapor deposition until the layer thickness of the deposited layer is about 5-20% of the target layer thickness,
Then, as the second stage,
Reaction gas composition:% by volume, AlCl ₃ : 6 to 10%, CO ₂ : 3 to 7%, HCl: 0.3 to 3%, H ₂ S: 0.5 to 1%, H ₂ : remaining,
Reaction atmosphere temperature: 950-1100 ° C.
Reaction atmosphere pressure: 10-20 kPa,
Under the above conditions (the content ratio of AlCl ₃ and H ₂ S gas is relatively high compared to the normal conditions, and the reaction atmosphere is also a relatively high pressure). The Al ₂ O ₃ layer having a columnar structure sequentially formed under the conditions of the first stage and the second stage (hereinafter, this Al ₂ O ₃ layer is referred to as “modified Al ₂ O ₃ layer”) has a grain boundary. It has been found that since it is excellent in plastic deformation resistance due to slipping, it exhibits excellent wear resistance without occurrence of uneven wear or the like even in high-speed heavy cutting where large fluctuations in cutting stress occur.

The coated tool of the present invention includes at least the modified TiCN layer as a lower layer, and the modified Al ₂ O ₃ layer as an upper layer, thereby providing wear resistance as well as chipping resistance and fracture resistance. In addition to this, the grain boundary length per unit layer thickness in each of the lower layer and the upper layer is maintained within a predetermined appropriate range, and the grain boundary length per unit layer thickness is further improved. By making the ratio value within a predetermined appropriate range, a large thermal and mechanical load is applied to the cutting edge, and high-speed heavy cutting with large fluctuations in cutting stress, for example, the large black skinned parts The present inventors have found that even when used in high-speed heavy cutting, there is no risk of chipping, chipping, etc., and excellent wear resistance is exhibited over a long period of use.

This invention has been made based on the above findings,
`` On the surface of the tool base made of tungsten carbide base cemented carbide,
(A) Ti compound comprising one or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride oxide layer having a total average layer thickness of 3 to 15 μm In the layer, at least one of the Ti compound layers is a modified Ti carbonitride layer (hereinafter referred to as “modified TiCN layer”) having a vertically grown crystal structure having an average layer thickness of 2.5 to 14 μm. Lower layer composed,
(B) an upper layer composed of an Al ₂ O ₃ layer of a columnar structure having an average layer thickness of 5 to 20 μm with an orientation index TC (006) value of (006) of 1.5 or more,
In the surface-coated cutting tool in which the hard coating layer composed of the above (a) and (b) is coated with an overall average layer thickness of 8 to 30 μm,
(C) For the modified TiCN layer of (a) above, a cubic crystal existing in a measurement range of 30 μm in width of the polished surface of the longitudinal section of the layer using a field emission scanning electron microscope and an electron backscatter diffraction image apparatus Inclination formed by normalizing (001) plane and (011) plane, which are crystal planes of the crystal grains, with respect to the normal lines of the vertical cross-section polished surface by irradiating each crystal grain having a crystal lattice with an electron beam The angle is measured, and the angle at which the normal lines of the (001) plane and the normal lines of the (011) plane intersect each other at the interface between adjacent crystal grains is obtained from the measured inclination angle. The vertical cross-section polishing of the layer using a field emission scanning electron microscope after identifying the case where the angle between the normals of the surface) and the normals of the (011) surface is 5 degrees or more as a grain boundary The part of the measurement area on the surface that is identified as the grain boundary When the grain boundary length GBLa (μm) at which the angle between the normal lines of the (001) plane and the normal lines of the (011) plane intersects is 15 degrees or more, the grain boundary length GBLa (μm) ) And the measured thickness Ti (μm) of the modified Ti compound layer, the value GBLa / Ta is a modified TiCN layer having a vertically grown crystal structure in the range of 275 to 520,
(D) The Al ₂ O ₃ layer having an orientation index TC (006) value of (006) in (b) of 1.5 or more is obtained by using a field emission scanning electron microscope and an electron backscatter diffraction image device. The crystal grains having a hexagonal crystal lattice existing within a measurement range of 30 μm in width of the longitudinally polished surface are irradiated with an electron beam, and the (0001) plane and (10-10) which are crystal planes of the crystal grains are used. ) Surface normals are measured, and from these measured angles, the (0001) plane normals and the (10-10) normals at the interface between adjacent crystal grains are measured. The intersecting angle is obtained, and the interface between adjacent crystal lattices in which the normals of the (0001) planes and the (10-10) planes intersect is 5 degrees or more is a grain boundary. Identify and use a field emission scanning electron microscope to study the longitudinal section of the layer. The measurement area in the plane, if the calculated length of the grain boundaries of the portion identified as intergranular GBLB ([mu] m), the ratio of the layer thickness Tb of the measured above _{the Al} 2 _{O 3} layer ([mu] m) values GBLB / Tb is a columnar Al ₂ O ₃ layer in the range of 40 to 165,
(E) Furthermore, the ratio (GBLb / Tb) / (GBLa / Ta) of the value of GBLa / Ta obtained in (c) and the value of GBLb / Tb obtained in (d) is 0.1 to A surface-coated cutting tool characterized by being in the range of 0.6. "
It has the characteristics.

Next, the constituent layers of the hard coating layer of the coated tool of the present invention will be described in detail.
(A) Lower layer A Ti compound layer composed of one or more of a TiC layer, a TiN layer, a TiCN layer (including a modified TiCN layer), a TiCO layer, and a TiCNO layer itself has high-temperature strength. In addition to the fact that the hard coating layer has high-temperature strength due to the presence of this, the tool base and the Al ₂ O ₃ layer, which is the upper layer, are firmly adhered to each other, so that the hard coating layer adheres to the tool base. Although it has the effect of contributing to the improvement, if the total average layer thickness is less than 3 μm, the above-mentioned effect cannot be exhibited sufficiently. On the other hand, if the total average layer thickness exceeds 15 μm, the heat generation is particularly accompanied by high heat generation. The total average layer thickness is determined to be 3 to 15 μm because the mechanical and mechanical load is large and the chipping is easily caused by high-speed heavy cutting accompanied by a sudden change in cutting stress.

(B) Modified TiCN Layer of Lower Layer As described above, the modified TiCN layer of the lower layer can be formed by the following method, for example.
First, with a normal chemical vapor deposition system,
≪First stage≫
Reaction gas composition: by _{volume%, TiCl 4: 5~20%,} C 3 H 3 N: 0.5~3.0%, N 2: 7~20%, H 2: remainder,
Reaction atmosphere temperature: 700-850 ° C.
Reaction atmosphere pressure: 6-20 kPa,
Under the conditions, vapor deposition is performed until the thickness of the vapor deposition layer reaches about 20% of the target layer thickness.
after that,
≪Second stage≫
Reaction gas composition: by _{volume%, TiCl 4: 3~12%,} CH 3 CN: 0.2~2%, C 3 H 3 N: 0.1~0.5%, Ar: 10~30%, H ₂ : The rest,
Reaction atmosphere temperature: 700-850 ° C.
Reaction atmosphere pressure: 6-20 kPa,
In this condition, vapor deposition is performed until the target layer thickness is reached.
By sequentially forming the film under the conditions of the first stage and the second stage, the modified TiCN layer can be formed.

The crystal grains constituting the modified TiCN layer have a NaCl-type face-centered cubic crystal structure in which constituent atoms composed of Ti, carbon, and nitrogen are present at lattice points (see FIG. 1). For the modified TiCN layer, using a field emission scanning electron microscope and an electron backscatter diffraction image apparatus, the crystal grains of the modified TiCN layer existing within the measurement range of the vertical cross-section polished surface were irradiated with an electron beam, The inclination angle formed by the normal lines of the (001) plane and the (011) plane, which are crystal planes of the crystal grains, with respect to the normal line of the longitudinally polished surface (FIG. 2A shows (001 among the crystal planes). ) When the tilt angle of the 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. Shows the case, but measure the inclination angle of each crystal grain including these angles) In this case, the crystal grains have a NaCl-type face-centered cubic crystal structure in which constituent atoms composed of Ti, carbon, and nitrogen are present at lattice points as described above. Based on the angle between the normal lines of the (001) plane and the normal lines of the (011) plane at the interface between adjacent crystal grains, and the normal lines of the (001) plane, and The case where the angle at which the normals of the (011) plane intersect is 5 degrees or more is identified as a grain boundary, and then the vertical cross-section polished surface of the modified TiCN layer is modified with the modified TiCN by a field emission scanning electron microscope. Measured in the range of layer thickness (μm) × width 30 (μm), and the angle between the normal lines of the (001) plane and the normal lines of the (011) plane among the parts identified as grain boundaries The grain boundary length for grain boundaries of 15 degrees or more When GBLa (μm) is obtained and the ratio of GBLa (μm) to the layer thickness Ta (μm) of the modified TiCN layer is obtained, the value of GBLa / Ta shows a value of 275 to 520.
Note that the value of GBLa / Ta varies depending on the combination of the reaction gas composition, the reaction atmosphere temperature, and the reaction atmosphere pressure during film formation.

The modified TiCN layer, which has a large value of GBLa / Ta of 275 to 520, has a large fluctuation in cutting stress even when a large thermal and mechanical load is applied to the cutting edge in high speed heavy cutting. Even so, it has the action of relaxing and absorbing the stress generated at that time, and it has a higher temperature strength, and even if cracks occur in the layer, it is distributed along the grain boundaries. Therefore, the occurrence of chipping can be greatly reduced because of the effect of suppressing the propagation / progress of cracks.
However, when the GBLa / Ta value is less than 275, the stress relaxation / absorption action cannot be expected and the chipping resistance is insufficient. On the other hand, the GBLa / Ta value exceeds 520. Since the modified TiCN layer itself tends to become brittle, the GBLa / Ta value was set to 275 to 520.
In addition, the value of GBLa / Ta in the conventional TiCN layer is a small value of about 100 to 200 (see Table 8) and is a TiCN layer having no stress relaxation / absorption action. Generation of chipping was observed in the hard coating layer.
In addition to the high temperature hardness and high temperature strength of the normal TiCN layer itself, the modified TiCN layer has a further excellent high temperature strength. However, if the average layer thickness is less than 2.5 μm, it is desirable. Since the hard coating layer cannot be sufficiently provided with excellent stress relaxation / absorption action and high-temperature strength improvement effect, on the other hand, if the average layer thickness exceeds 14 μm, chipping tends to occur. The thickness was determined to be 2.5-14 μm.
Note that the modified TiCN layer does not have to be a single layer, and a plurality of layers can be provided.

(C) Upper layer (modified Al ₂ O ₃ layer)
The upper layer composed of the modified Al ₂ O ₃ layer has excellent high-temperature hardness and heat resistance, and further has excellent plastic deformation resistance, thereby contributing to improvement in wear resistance of the hard coating layer.
As described above, the modified Al ₂ O ₃ layer can be formed by the following method, for example.
For example, in a normal chemical vapor deposition system,
≪First stage≫
Reaction gas composition: by _{volume%, AlCl 3: 1~5%,} CO 2: 10~15%, HCl: 0.3~3%, SF 6: 0.1~1%, H 2: remainder,
Reaction atmosphere temperature: 950-1100 ° C.
Reaction atmosphere pressure: 20-40 kPa,
(The CO ₂ gas content ratio is relatively high compared to the normal conditions, the reaction atmosphere pressure is relatively high, SF ₆ is added instead of H ₂ S as a reaction gas component, Vapor deposition until the layer thickness is about 5-20% of the target layer thickness,
≪Second stage≫
Reaction gas composition:% by volume, AlCl ₃ : 6 to 10%, CO ₂ : 3 to 7%, HCl: 0.3 to 3%, H ₂ S: 0.5 to 1%, H ₂ : remaining,
Reaction atmosphere temperature: 950-1100 ° C.
Reaction atmosphere pressure: 10-20 kPa,
Under the above conditions (the content ratio of AlCl ₃ and H ₂ S gas is relatively high compared to the normal conditions, and the reaction atmosphere is also a relatively high pressure). The modified Al ₂ O ₃ layer having a columnar structure sequentially formed under the conditions of the first stage and the second stage not only exhibits excellent high-temperature hardness and heat resistance, but also exhibits plastic resistance due to grain boundary sliding. Because of its excellent deformability, it exhibits excellent wear resistance without the occurrence of uneven wear even in high-speed heavy cutting where large fluctuations in cutting stress occur.

Further, the modified Al ₂ O ₃ layer was subjected to (012) plane, (104) plane, (110) plane, (006) plane, (113) plane, (202) plane, (024) by X-ray diffraction. The reflection intensity of the surface and the (116) surface was obtained, and from these values, the value of the orientation index TC (006) of the (006) surface was obtained. In the modified Al ₂ O ₃ layer, TC (006) was 1 .5 or more.
In the conventional Al ₂ O ₃ layer, TC (006) was 1.0 or more (see Table 9).
The (006) plane orientation index TC (006) in the present invention is the peak intensity of X-ray diffraction obtained from the (hkl) plane when X-ray diffraction is performed on the Al ₂ O ₃ layer constituting the upper layer. The value is I (hkl), JCPDS card No. When the standard diffraction intensity of the (hkl) plane described in 46-1212 is I ₀ (hkl),


Is defined as Here, (hkl) is the eight faces (012), (104), (110), (006), (113), (202), (024), and (116).

Next, with respect to the modified Al ₂ O ₃ layer, by using a field emission scanning electron microscope and an electron backscatter diffraction image apparatus, each crystal grain having a hexagonal crystal lattice existing within the measurement range of the vertical cross-section polished surface is used. Inclination angles (c, c ′, a, a ′ in FIG. 4) formed by normal lines of the (0001) plane and the (10-10) plane, which are crystal planes of the crystal grains shown in FIG. And the angle at which the normal lines of the (0001) plane and the normal lines of the (10-10) plane intersect each other at the interface between the adjacent crystal grains is obtained from the measured inclination angle. The angle between the normals of the (0001) planes and the normals of the (10-10) planes is 5 degrees or more (that is, aa ′ ≧ 0 ° and cc ′ ≧ 5 °, or a−a ′ ≧ 5 ° and cc ′ ≧ 0 °) is an interface between adjacent crystal lattices. Identified by field emission scanning electron microscope, a longitudinal section polished surface reforming _{the Al} 2 _{O 3} layer, a range of modified _Al 2 _{O 3} layer thickness ([mu] m) × width 30 ([mu] m), in measured particle When the grain boundary length GBLb (μm) of the portion identified as the boundary is obtained and the ratio with the measured layer thickness Tb (μm) of the modified Al ₂ O ₃ layer is obtained, the value of GBLb / Tb is It was within the range of 40-165.
The value of GBLb / Tb varies depending on the combination of the reaction gas composition, the reaction atmosphere temperature, and the reaction atmosphere pressure during film formation.

The modified Al ₂ O ₃ layer having a GBLb / Tb value of 40 to 165 has a large fluctuation in cutting stress even when a large thermal / mechanical load is applied to the cutting edge in high speed heavy cutting. Even with high-temperature hardness and heat resistance, in addition to excellent plastic deformation resistance due to intergranular sliding, even in high-speed heavy cutting that causes large fluctuations in cutting stress, uneven wear, etc. occurs. Excellent wear resistance.
However, when the GBLb / Tb value is less than 40, the chipping resistance is insufficient. On the other hand, when the GBLb / Tb value exceeds 165, the plastic deformation resistance of the modified Al ₂ O ₃ layer itself is low. Since sufficient wear resistance cannot be exhibited due to the decrease, the value of GBLb / Tb was determined to be 40 to 165.
In addition, since the value of GBLb / Tb in the conventional Al ₂ O ₃ layer is about 200 to 300 (see Table 7) and is a layer that does not exhibit sufficient plastic deformation resistance, In high-speed heavy cutting with large fluctuations in cutting stress, the occurrence of uneven wear was observed and the wear resistance was poor.
Note that if the thickness of the modified Al ₂ O ₃ layer as the upper layer is less than 5 μm, sufficient wear resistance cannot be exhibited over a long period of use, while if it exceeds 20 μm, chipping resistance is not obtained. In order to decrease, the thickness of the modified Al ₂ O ₃ layer was determined to be 5 to 20 μm.

In the present invention, there is a relationship of 0.6 ≧ (GBLb / Tb) / (GBLa / Ta) ≧ 0.1 between the value of GBLa / Ta in the lower layer and the value of GBLb / Tb in the upper layer. It is necessary to maintain.
This is because when the value of the ratio (GBLb / Tb) / (GBLa / Ta) is less than 0.1, sufficient wear resistance cannot be exhibited over a long period of use. If the value of exceeds 0.6, the chipping resistance is lowered.
In the present invention, the overall average layer thickness of the lower layer and the upper layer is set to 8 to 30 μm. However, when the thickness is less than 8 μm, sufficient wear resistance cannot be exhibited over a long period of use. On the other hand, if it exceeds 30 μm, the chipping resistance is lowered.

Further, in the present invention, 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 is 0.1 to 1 μm may be sufficient, 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.
Furthermore, the present invention is not limited to subjecting the surface of the modified Al ₂ O ₃ layer to mechanical treatment (for example, wet blast treatment, brush treatment, elastic grindstone treatment) or the like for the purpose of smoothing the surface. Not what you want.

The coated tool of the present invention is accompanied by a large heat generation, a large thermal and mechanical load on the cutting edge, and a large variation in cutting stress. Even when subjected to high-speed heavy cutting of black skin uneven thickness parts, the modified TiCN layer of the lower layer of the hard coating layer has a stress relaxation / absorption action, a crack propagation / propagation suppression action, Excellent resistance to chipping with high-temperature strength, and the modified Al ₂ O ₃ layer as the upper layer of the hard coating layer exhibits excellent plastic deformation resistance in addition to excellent hardness and heat resistance. There is no occurrence of uneven wear and the like, and excellent chipping resistance and wear resistance are exhibited over a long period of use.

It is a schematic diagram which shows the crystal structure of the NaCl type face centered cubic crystal which the TiCN 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 normal line of the (001) plane of a crystal grain and the (011) plane in the modified TiCN layer which comprises the lower layer of a hard coating layer. The normal of the longitudinal section polishing surface, crystal grains of the (0001) plane in the upper layer (reforming _{the Al} 2 _{O 3} layer), is a schematic diagram showing the relationship between the {10-10} plane and their normal . It is a schematic diagram showing the measurement mode of the crystal grains (0001) plane and (10-10) plane normal to the tilt angle of the upper layer (reforming _{the Al} 2 _{O 3} layer).

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

As raw material powders, WC powder, TiC powder, ZrC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder, TaN powder, and Co powder each having an average particle diameter of 2 to 5 μm are prepared. The raw material powder is blended in the blending composition shown in Table 1, added with wax, ball mill mixed in acetone for 24 hours, dried under reduced pressure, and press-molded into a green compact of a predetermined shape at a pressure of 98 MPa. The green compact is vacuum-sintered in a vacuum of 5 Pa at a predetermined temperature within a range of 1370 to 1470 ° C. for 1 hour, and after sintering, the cutting edge portion has a width of 0.2 mm and an angle of 20 degrees. By processing, tool bases A to F made of WC-based cemented carbide having an insert shape specified in ISO · SNMM250924 were manufactured.

(A) Next, on the surface of these tool bases A to F, a Ti chemical layer excluding the modified TiCN layer is used as a lower layer of the hard coating layer under the conditions shown in Table 2 using a normal chemical vapor deposition apparatus. Vapor deposition,
(B) Next, the modified TiCN layer is subjected to the conditions shown in Table 3, that is,
First, as the first stage,
Reaction gas composition:% by volume, TiCl ₄ : predetermined amount in the range of 5-20%, C ₃ H ₃ N: predetermined amount in the range of 0.5-3.0%, N ₂ : 7-20% A predetermined amount within the range, H ₂ : remaining,
Reaction atmosphere temperature: a predetermined temperature within a range of 700 to 850 ° C.,
Reaction atmosphere pressure: a predetermined pressure in the range of 6 to 20 kPa,
Under the conditions, vapor deposition is performed until the layer thickness reaches about 20% of the target layer thickness,
Then, as the second stage,
Reaction gas composition:% by volume, TiCl ₄ : predetermined amount in the range of 3-12%, CH ₃ CN: predetermined amount in the range of 0.2-2%, C ₃ H ₃ N: 0.1-0 A predetermined amount within a range of 5%, Ar: a predetermined amount within a range of 10 to 30%, H ₂ : remaining,
Reaction atmosphere temperature: a predetermined temperature within a range of 700 to 850 ° C.,
Reaction atmosphere pressure: a predetermined pressure in the range of 6 to 20 kPa,
Under the conditions, the vapor deposition is performed with the combination shown in Table 6 and the target layer thickness also shown in Table 6,
(C) Next, the modified Al ₂ O ₃ layer was subjected to the conditions shown in Table 4, that is,
First, as the first stage,
By _volume%, AlCl 3:: Reaction gas composition predetermined amount within a range of _1~5%, CO 2: the predetermined amount in the range 10-15%, HCl: a predetermined amount in the 0.3 to 3% range , SF ₆ : a predetermined amount within a range of 0.1 to 1%, H ₂ : remaining,
Reaction atmosphere temperature: a predetermined temperature within a range of 950 to 1100 ° C.,
Reaction atmosphere pressure: a predetermined pressure within a range of 20 to 40 kPa,
Under the conditions, vapor deposition until reaching a layer thickness of about 5-20% of the target layer thickness,
Then, as the second stage,
Reaction gas composition: volume%, AlCl ₃ : predetermined amount in the range of 6-10%, CO ₂ : predetermined amount in the range of 3-7%, HCl: predetermined amount in the range of 0.3-3% , H ₂ S: a predetermined amount within the range of 0.5 to 1%, H ₂ : remaining,
Reaction atmosphere temperature: a predetermined temperature within a range of 950 to 1100 ° C.,
Reaction atmosphere pressure: a predetermined pressure within a range of 10 to 20 kPa,
Under the conditions, the present coated tools 1 to 10 were produced by vapor deposition with the target layer thicknesses shown in Table 7, respectively.

For the purpose of comparison, as a lower layer of the hard coating layer, a Ti compound layer is formed by vapor deposition in the combination shown in Table 8 and with the target layer thickness shown in Table 8 under the conditions shown in Table 2. Further, Al ₂ O ₃ layers as upper layers were formed by vapor deposition under the conditions shown in Table 5 and with the target layer thicknesses shown in Table 9, thereby producing conventional coated tools 1 to 10 respectively.

X-ray diffraction was performed on the Al ₂ O ₃ layer of the present invention coated tool and the conventional coated tool, and (012), (104), (110), (006), (113), (202), (024), TC (006) was determined by measuring the X-ray diffraction intensity from each surface of (116). Tables 7 and 9 show these values.

Next, with respect to the modified TiCN layer and the conventional TiCN layer constituting the hard coating layer of the present invention coated tool and the conventional coated tool, a longitudinal section of each of the above layers is obtained using a field emission scanning electron microscope and an electron backscatter diffraction image apparatus. GBLa (μm) of the polished surface was measured, and the ratio of GBLa (μm) to the layer thickness Ta (μm) of the modified TiCN layer and the conventional TiCN layer was determined.
That is, the modified TiCN layer and the conventional TiCN layer are set in a lens barrel of a field emission scanning electron microscope in a state where the vertical cross section of the TiCN layer is a polished surface, and accelerated to 15 kV at an incident angle of 70 degrees on the polished surface. 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 normals The case where the intersecting angle is 5 degrees or more is set as a grain boundary, and the measurement area (TiCN layer thickness (μm)) of the polished surface of the modified TiCN layer and the conventional TiCN layer is measured by a field emission scanning electron microscope. X region having a width of 30 (μm)), and the (001) plane normals and the (011) plane normals among the parts identified as grain boundaries in the measurement region The grain boundary length GBLa (μm) was determined for a grain boundary having an angle of 15 ° or more. Then, the value of the ratio of GBLa (μm) to the layer thickness Ta (μm) of the modified TiCN layer and the conventional TiCN layer (corresponding to the length of the grain boundary per unit layer thickness of the TiCN layer) was obtained.

  The values of GBLa and GBLa / Ta for the various modified TiCN layers and conventional TiCN layers obtained as a result are shown in Tables 6 and 8, respectively.

  As shown in Tables 6 and 8, respectively, the modified TiCN layer of the coated tool of the present invention has a GBLa / Ta value in the range of 275 to 520, whereas the conventional TiCN of the conventional coated tool. All the layers had a GBLa / Ta value of less than 275.

Next, a field emission scanning electron microscope and an electron backscatter diffraction image apparatus were used for the modified Al ₂ O ₃ layer and the conventional Al ₂ O ₃ layer constituting the hard coating layer of the present invention coated tool and the conventional coated tool. Then, GBLb (μm) of the vertical cross-section polished surface of each layer is measured, and the ratio of GBLb (μm) to the layer thickness Tb (μm) of the modified Al ₂ O ₃ layer and the conventional Al ₂ O ₃ layer is determined. Asked.
That is, in a state where the vertical cross section of the modified Al ₂ O ₃ layer and the conventional Al ₂ O ₃ layer is a polished surface, it is set in a lens barrel of a field emission scanning electron microscope, and the polished surface is set to 70 degrees. An electron beam with an acceleration voltage of 15 kV at an incident angle is irradiated at an irradiation current of 1 nA to each crystal grain existing within the measurement range of the vertical cross-section polished surface, and a predetermined measurement region is formed using an electron backscatter diffraction image apparatus. At an interval of 0.1 μm / step, the inclination angle formed by the normal lines of the (0001) plane and the (10-10) plane, which are crystal planes of the crystal grains, is measured with respect to the normal line of the vertical cross-section polished surface. Then, based on the measured tilt angle obtained as a result, the angles at which the (0001) plane normal lines and the (10-10) plane normal lines cross each other at the interface between adjacent crystal grains are obtained, and , Normals of the (0001) plane, and On the angle of intersection of the normal line between the 10-10) plane was set not less than 5 degrees a grain boundary, by field emission scanning electron microscope, reforming _{the Al} 2 _{O 3} layer, a conventional _Al 2 _{O 3} The measurement area (Al ₂ O ₃ layer thickness (μm) × width of 30 μm range) of the polished surface of the longitudinal section of the layer is scanned, and the length of the grain boundary of the portion identified as the grain boundary in the measurement area GBLb (μm) was determined. Then, the value of the ratio of GBLb (μm) to the layer thickness Tb (μm) of the modified Al ₂ O ₃ layer and the conventional Al ₂ O ₃ layer (the length of the grain boundary per unit layer thickness of the Al ₂ O ₃ layer) Equivalent).

Tables 7 and 9 show the values of GBLb and GBLb / Tb for the various modified Al ₂ O ₃ layers and the conventional Al ₂ O ₃ layers obtained as a result.

As shown in Tables 7 and 9, respectively, the modified Al ₂ O ₃ layer of the coated tool of the present invention has a GBLb / Tb value in the range of 40 to 165, whereas the conventional coated tool All of the conventional Al ₂ O ₃ layers had a GBLb / Tb value exceeding 200.

Further, for the above-described coated tools 1 to 10 of the present invention and the conventional coated tools 1 to 10, 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 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 all the above-mentioned various coated tools are screwed to the tip of the tool steel tool with a fixing jig, the present coated tools 1 to 10 and the conventional coated tools 1 to 10,
Work material and processing part: low charcoal with outer diameter 4,300mm, inner diameter 3,900mm, thickness 110mm
110mm thick surface of large black skin uneven parts made of steel,
Cutting speed: 220 m / min,
Cutting depth: 10mm,
Feed: 1mm / rev,
Outer diameter wet high speed heavy cutting test under the above conditions (cutting condition A) (normal cutting speed is 120 m / min)
Work material and processing part: Low charcoal with outer diameter 3,800mm, inner diameter 3,500mm, thickness 300mm
The surface of the outer diameter-inner diameter width of 300 mm of a large black skin uneven part made of steel,
Cutting speed: 150 m / min,
Incision: 13mm,
Feed: 1mm / rev,
End face wet high speed heavy cutting test under the above conditions (cutting condition B) (normal cutting speed is 80 m / min)
In each cutting test, the number of machining passes was counted. (Cutting the surface to be processed once is one pass)
The number of machining passes is based on the number of machining passes when the wear amount on the cutting edge flank reaches the standard wear amount of 1 mm. When a chip disposal failure state in which the chips cannot be divided is reached, the number of finished machining passes is counted at that time. Note that the number of machining passes is not counted during machining.
The results are shown in Table 10.

From the results shown in Tables 6 to 10, the coated tools 1 to 10 of the present invention are composed of a modified TiCN layer having GBLa / Ta = 275 to 520 as at least one of the lower layers of the hard coating layer, and hard. Since the upper layer of the coating layer is composed of a modified Al ₂ O ₃ layer with GBLb / Tb = 40 to 165, the thermal and mechanical load is extremely high, and the high-speed heavy cutting in which the cutting stress varies greatly. Also in the processing, the modified TiCN layer disperses cracks along grain boundaries generated during cutting, suppresses propagation / progress, and has a stress relaxation / absorption function. The modified Al ₂ O ₃ layer Suppresses the occurrence of uneven wear due to plastic deformation due to the occurrence of intergranular slip, thus providing excellent chipping resistance and fracture resistance, and excellent wear resistance over a long period of use. .
On the other hand, the TiCN layer of the lower layer of the hard coating layer has a conventional BLCN layer with a GBLa / Ta value of less than 275, or the GBLb / Tb value of the upper Al ₂ O ₃ layer exceeds 200. Conventional Al ₂ O ₃ layer, which is a value, or, further, a conventional coated tool 1 composed of a hard coating layer whose (GBLb / Tb) / (GBLa / Ta) value is outside the range of 0.1 to 0.6. No. 10 to 10 are insufficient in resistance to thermal and mechanical loads of the hard coating layer and resistance to large fluctuations in cutting stress. It is clear that chipping occurs in the coating layer, and the wear resistance is inferior, and the service life is reached in a relatively short time.

As described above, the coated tool of the present invention is suitably used for high-speed heavy cutting such as large black skin uneven parts represented by rough flange processing of wind power generation parts. Of course, it can be applied to continuous cutting, interrupted cutting, and heavy cutting under normal conditions such as using various types of steel and cast iron, as well as excellent cutting performance over a long period of time. Therefore, it is possible to satisfactorily meet the demands for higher performance of the cutting device, labor saving and energy saving of cutting, and cost reduction.

Claims (1)

On the surface of the tool base made of tungsten carbide base cemented carbide,
(A) Ti compound comprising one or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride oxide layer having a total average layer thickness of 3 to 15 μm In the layer, at least one of the Ti compound layers is a modified Ti carbonitride layer (hereinafter referred to as “modified TiCN layer”) having a vertically grown crystal structure having an average layer thickness of 2.5 to 14 μm. Lower layer composed,
(B) an upper layer composed of a columnar textured modified Al ₂ O ₃ layer having an average layer thickness of 5 to 20 μm with a value of (006) plane orientation index TC (006) of 1.5 or more;
In the surface-coated cutting tool in which the hard coating layer composed of the above (a) and (b) is coated with an overall average layer thickness of 8 to 30 μm,
(C) For the modified TiCN layer of (a) above, a cubic crystal existing in a measurement range of 30 μm in width of the polished surface of the longitudinal section of the layer using a field emission scanning electron microscope and an electron backscatter diffraction image apparatus Inclination formed by normalizing (001) plane and (011) plane, which are crystal planes of the crystal grains, with respect to the normal lines of the vertical cross-section polished surface by irradiating each crystal grain having a crystal lattice with an electron beam The angle is measured, and the angle at which the normal lines of the (001) plane and the normal lines of the (011) plane intersect each other at the interface between adjacent crystal grains is obtained from the measured inclination angle. The vertical cross-section polishing of the layer using a field emission scanning electron microscope after identifying the case where the angle between the normals of the surface) and the normals of the (011) surface is 5 degrees or more as a grain boundary The part of the measurement area on the surface that is identified as the grain boundary When the grain boundary length GBLa (μm) at which the angle between the normal lines of the (001) plane and the normal lines of the (011) plane intersects is 15 degrees or more, the grain boundary length GBLa (μm) ) And the measured thickness Ti (μm) of the modified TiCN layer, GBLa / Ta is a modified TiCN layer having a vertically grown crystal structure in the range of 275 to 520,
(D) The modified Al ₂ O ₃ layer having the (006) plane orientation index TC (006) of (b) above is 1.5 or more, using a field emission scanning electron microscope and an electron backscatter diffraction image. Using an apparatus, each crystal grain having a hexagonal crystal lattice existing in a measurement range with a width of 30 μm on the polished surface of the longitudinal cross section is irradiated with an electron beam, and the (0001) plane and (10 −10) The inclination angle formed by the normals of the planes is measured, and the normals of the (0001) planes and the normal lines of the (10-10) planes at the interfaces between adjacent crystal grains are measured from the measured inclination angles. The angle at which the two intersect each other is obtained, and the interface between adjacent crystal lattices at which the normal between the (0001) planes and the (10-10) planes intersect each other is 5 degrees or more Identify the layer and use a field emission scanning electron microscope to The ratio of the measurement area in the polished surface, if determined the length of the crystal grain boundary of the portion identified as intergranular GBLB ([mu] m), the measured the modified the Al ₂ O ₃ layer thickness Tb ([mu] m) The value GBLb / Tb is a columnar textured modified Al ₂ O ₃ layer in the range of 40-165,
(E) Furthermore, the ratio (GBLb / Tb) / (GBLa / Ta) of the value of GBLa / Ta obtained in (c) and the value of GBLb / Tb obtained in (d) is 0.1 to A surface-coated cutting tool characterized by being in the range of 0.6.