JP4888771B2 - Surface coated cutting tool with excellent chipping resistance due to hard coating layer - Google Patents

Description

  The present invention provides a hard coating even when cutting various materials such as steel and cast iron under high-speed intermittent cutting conditions that cause high heat generation and intermittent and impactful loads on the cutting edge. The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits excellent chipping 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. As a hard coating layer,
(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). And a Ti compound layer composed of one or more of a carbonitride oxide (hereinafter referred to as TiCNO) layer,
(B) Two-phase mixed oxide of aluminum oxide (hereinafter referred to as Al ₂ O ₃ ) and zirconium oxide (hereinafter referred to as ZrO ₂ ) having an α-type or κ-type crystal structure in a state where the upper layer is chemically vapor-deposited A two-phase mixed oxide layer having a structure and 0.1 to 10% by weight of ZrO ₂ dispersed in an Al ₂ O ₃ substrate (hereinafter simply referred to as “conventional two-phase mixed oxide layer”),
It is well known that a coated tool formed by vapor-depositing is used for cutting various steels and cast irons, for example.

Further, in the conventional coated tool, the TiCN layer of the Ti compound layer constituting the lower layer of the hard coating layer is formed as an organic carbonitride as a reaction gas in a normal chemical vapor deposition apparatus for the purpose of improving the strength of the layer itself. It is also known to form a vertically elongated crystal structure by chemical vapor deposition at a medium temperature range of 700 to 950 ° C. using a mixed gas containing benzene.
JP 2001-38504 A Japanese Patent Laid-Open No. 6-8010

  In recent years, the performance of cutting machines has been remarkable. On the other hand, there has been a strong demand for labor saving and energy saving and further cost reduction for cutting work. In the case of tools, there is no problem when this is used for continuous or intermittent cutting under normal conditions such as steel or cast iron. However, this is accompanied by high heat generation and intermittent and impact on the cutting edge. When used for high-speed intermittent cutting that requires a heavy load, the grain boundary strength in the conventional two-phase mixed oxide layer that constitutes the upper layer of the hard coating layer is not sufficient, so chipping is caused by cracks generated from the grain boundary strength. Is likely to occur, and due to this, the service life is reached in a relatively short time.

In view of the above, the present inventors have focused on the coated tool in which the above-described conventional two-phase mixed oxide layer constitutes the upper layer of the hard coating layer, and in particular, the hard coating layer in high-speed intermittent cutting. As a result of research to improve chipping resistance,
(A) The conventional two-phase mixed oxide layer as the upper layer constituting the hard coating layer of the conventional coated tool has excellent high-temperature hardness and a predetermined high-temperature strength. In the device
Reaction gas composition (volume%)
AlCl ₃ : 1 to 10%,
ZrCl _4: 0.01~10%,
CO _2: 1~30%,
HCl: 1-30%,
H ₂ S: 0.01~1%,
H ₂ : Remaining
(B) Reaction atmosphere temperature: 900 to 1050 ° C.
(C) Reaction atmosphere pressure: 4 to 70 kPa
Under the above conditions (referred to as normal conditions), it is formed by vapor deposition on the Ti compound layer which is the lower layer of the conventional coated tool. However, in the upper layer composed of such a conventional two-phase mixed oxide layer, as already described, Since the grain boundary strength between the Al ₂ O ₃ phase and the ZrO ₂ phase is not sufficient, it does not exhibit satisfactory chipping resistance in high-speed intermittent cutting.

(B) Therefore, on the Ti compound layer, which is the lower layer of the hard coating layer formed by vapor deposition, with a normal chemical vapor deposition apparatus,
(A) First, as the first stage,
Reaction gas composition (volume%); AlCl ₃ : 0.1 to 0.9%, ZrCl ₄ : 0.1 to 0.3%, HCl: 0.1 to 1.9%, CO ₂ : 0.4 to 1.2%, H ₂ : remaining,
Reaction atmosphere temperature: 950-960 ° C.
Reaction atmosphere pressure; 5-7 kPa,
Under these conditions, coating for 5 to 30 minutes to form a two-phase mixed oxide layer,
(B) Next, as the second stage,
Reaction gas composition _{(volume%); AlCl 3: 1~1.8%} , ZrCl 4: 0.4~0.6%, HCl: 2~4%, CO 2: 1.4~2%, H 2 S : 0.05~0.1%, H _2: remainder,
Reaction atmosphere temperature; 960-980 ° C.,
Reaction atmosphere pressure; 8-10 kPa,
Under these conditions, coating for 5 to 30 minutes to form a two-phase mixed oxide layer,
(C) Finally, as the third stage,
Reaction gas composition (volume%): AlCl ₃ : 1.8 to ₄ %, ZrCl ₄ : 0.6 to 1.2%, HCl: 2 to 4%, CO ₂ : 2 to 6%, H ₂ S: 0 .1 to 0.6%, H ₂ : remaining,
Reaction atmosphere temperature; 980-1100 ° C.
Reaction atmosphere pressure; 10-50 kPa,
Under the conditions, a two-phase mixed oxide layer is formed,
Two-phase mixed oxidation with an average layer thickness of 2 to 15 μm is performed by changing the reaction gas composition, the reaction atmosphere temperature and the reaction atmosphere pressure during vapor deposition stepwise according to the above conditions (a) to (c). object layer (hereinafter, referred to as "modified two-phase mixed oxide layer") to form a top layer consisting of an upper layer formed in this condition, ZrO ₂ is _Al 2 _{O 3} matrix (alpha-type _Al 2 _{O 3} Is a main component of the substrate, but a small amount of κ-type Al ₂ O ₃ is also present.) Has a uniformly dispersed two-phase mixed oxide structure, and Zr accounts for the total amount of Al in the layer When the content ratio is X (however, the atomic ratio), X = 0.003 to 0.2 is satisfied, and ZrO ₂ which is a dispersed phase in the modified two-phase mixed oxide layer is (−111). ) Shows monoclinic crystals oriented in the plane, and further the substrate in the modified two-phase mixed oxide layer If the _Al 2 _{O 3} phase constituting X-ray diffraction was performed, the value of the diffraction intensity from the (01-12) plane of the α-type _Al 2 _{O 3} phase which is mainly the matrix I (01-12) and ( The value of the diffraction intensity I (11-20) from the (11-20) plane shows the first and second largest values, and the value I (01-12) / I (11) of the ratio of the diffraction intensity values. −20) indicates a value of 1 to 3.
The (01-12) plane and the (11-20) plane include planes equivalent to each other, and the diffraction intensity value I (01-12) is equivalent to the (01-12) plane and the same. The diffraction intensity value I (11-20) is the total value of diffraction intensities from the (11-20) plane and its equivalent surface.

(C) The upper layer composed of the modified two-phase mixed oxide layer formed by vapor deposition under the chemical vapor deposition conditions of (b) above is particularly between the ZrO ₂ phase as a dispersed phase and the Al ₂ O ₃ phase as a base phase. Since the grain boundary strength is increased and the lubricity and heat resistance are also improved, the excellent high-temperature hardness of the conventional two-phase mixed oxide layer of the conventional coated tool formed under the normal conditions of (a) above. In addition, since it has excellent high-temperature strength, lubricity, and heat resistance, the hard coating layer provided with this as the upper layer of the hard coating layer is intermittent and shocking with high heat generation. Even when used for cutting under severe conditions such as high-speed interrupted cutting with a heavy load, the hard coating layer exhibits superior chipping resistance compared to conventional coated tools, and it is superior over a long period of time. Demonstrate wear resistance.
The research results shown in (a) to (c) above were obtained.

This invention was made based on the above research results,
“On the surface of the tool base made of tungsten carbide base cemented carbide or titanium carbonitride base cermet,
(A) The lower layer is one or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride oxide layer having an overall average layer thickness of 3 to 20 μm. A Ti compound layer comprising:
(B) The upper layer is a two-phase mixed oxide layer of an aluminum oxide phase and a zirconium oxide phase mainly composed of α-type aluminum oxide having an average layer thickness of 2 to 15 μm and a chemical vapor deposited state and having a hexagonal crystal structure The content ratio of zirconium in the mixed oxide is 0.003 to 0.2 (however, atomic ratio) with respect to the total amount with aluminum. In the mixed oxide layer, (−111 ) The monoclinic zirconium oxide phase oriented in the plane is uniformly dispersed in the aluminum oxide phase. Further, the X-ray diffraction of the aluminum oxide phase from the (01-12) plane of the α-type aluminum oxide The value of the diffraction intensity I (01-12) and the value of the diffraction intensity I (11-20) from the (11-20) plane indicate the first and second largest diffraction intensity values, and ratio The value I (01-12) / I (11-20) is a two-phase mixed oxide layer of aluminum oxide phase and the zirconium oxide phase which satisfies a value of 1 to 3,
A surface-coated cutting tool (coated tool) which is formed by vapor-depositing the hard coating layer composed of (a) and (b) and exhibits excellent chipping resistance. "
It has the characteristics.

Below, the constituent layer of the hard coating layer of the coated tool of this invention is demonstrated in detail.
(A) Lower layer (Ti compound layer)
Ti compound layer composed of one or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride layer exists as a lower layer of the hard coating layer, In addition to contributing to improving the high temperature strength of the hard coating layer due to its excellent high temperature strength, it adheres firmly to both the tool base and the modified two-phase mixed oxide layer, so that the hard coating layer is bonded to the tool base. Although it has an effect of improving the strength, if the average layer thickness is less than 3 μm, the above-mentioned effect cannot be sufficiently exhibited. On the other hand, if the average layer thickness exceeds 20 μm, particularly in high-speed intermittent cutting with high heat generation. Since it becomes easy to cause thermoplastic deformation, which causes uneven wear, the average layer thickness was determined to be 3 to 20 μm.

(B) Upper layer (modified two-phase mixed oxide layer)
The Al component, which is a component of the modified two-phase mixed oxide layer of the aluminum oxide phase and the zirconium oxide phase mainly composed of α-type aluminum oxide having a hexagonal crystal structure in the state of chemical vapor deposition, The Zr component is contained in the layer in a trace amount (percentage of the total amount of Al, Zr / (Al + Zr) is 0.003 to 0.2 (atomic ratio)). This contributes to the improvement of the high temperature strength, lubricity and heat resistance of the upper layer (modified two-phase mixed oxide layer), but the above effect is expected when the Zr component content is less than 0.003. On the other hand, when the content ratio of the Zr component exceeds 0.2, the zirconium oxide phase becomes coarse and defects are likely to occur. Therefore, the content ratio of the Zr component in the total amount with the Al component ( Zr / (Al + Zr) ratio value) is 0 003 to 0.2 (provided that an atomic ratio) was defined as).

In order to form a two-phase mixed oxide layer having a structure in which the ZrO ₂ phase is uniformly dispersed in the Al ₂ O ₃ phase substrate by chemical vapor deposition, each of the reaction gas composition, reaction atmosphere temperature and reaction atmosphere pressure at the time of vapor deposition is used. It can be formed by performing chemical vapor deposition while changing the conditions stepwise according to the following conditions (a) to (c).
That is,
(A) First, as the first stage,
Reaction gas composition (volume%); AlCl ₃ : 0.1 to 0.9%, ZrCl ₄ : 0.1 to 0.3%, HCl: 0.1 to 1.9%, CO ₂ : 0.4 to 1.2%, H ₂ : remaining,
Reaction atmosphere temperature: 950-960 ° C.
Reaction atmosphere pressure; 5-7 kPa,
Under these conditions, coating for 5 to 30 minutes to form a two-phase mixed oxide layer,
(B) Next, as the second stage,
Reaction gas composition _{(volume%); AlCl 3: 1~1.8%} , ZrCl 4: 0.4~0.6%, HCl: 2~4%, CO 2: 1.4~2%, H 2 S : 0.05~0.1%, H _2: remainder,
Reaction atmosphere temperature; 960-980 ° C.,
Reaction atmosphere pressure; 8-10 kPa,
Under these conditions, coating for 5 to 30 minutes to form a two-phase mixed oxide layer,
(C) Finally, as the third stage,
Reaction gas composition (volume%): AlCl ₃ : 1.8 to ₄ %, ZrCl ₄ : 0.6 to 1.2%, HCl: 2 to 4%, CO ₂ : 2 to 6%, H ₂ S: 0 .1 to 0.6%, H ₂ : remaining,
Reaction atmosphere temperature; 980-1100 ° C.
Reaction atmosphere pressure; 10-50 kPa,
Under these conditions, a two-phase mixed oxide layer having an average layer thickness of 2 to 15 μm is formed.
According to the above conditions (a) to (c), by performing chemical vapor deposition while changing the vapor deposition conditions stepwise, finally, the Al ₂ O ₃ phase (mainly α-type Al ₂ O ₃ , Forming a modified two-phase mixed oxide layer having an average layer thickness of 2 to 15 μm in a two-phase mixed oxide structure in which the ZrO ₂ phase is uniformly dispersed in the substrate (a small amount of κ-type Al ₂ O ₃ is also present) Can do.

In the modified two-phase mixed oxide layer formed by vapor deposition under the above vapor deposition conditions (a) to (c), the ZrO ₂ phase as the dispersed phase has a monoclinic crystal structure oriented in the (−111) plane. Since the ZrO ₂ phase is uniformly dispersed in the substrate, the lubricity of the modified two-phase mixed oxide layer is improved, and the friction coefficient is low and the thermal conductivity is low. Heat resistance is also improved.
Further, the Al ₂ O ₃ phase constituting the substrate of the modified two-phase mixed oxide layer (mainly α-type Al ₂ O ₃ but a trace amount of κ-type Al ₂ O ₃ also exists) is α. The value of the diffraction intensity I (01-12) from the (01-12) plane of the type Al ₂ O ₃ and the value of the diffraction intensity I (11-20) from the (11-20) plane are the first to second largest. And the ratio of the diffraction intensity values I (01-12) / I (11-20) is 1 to 3, so that the grain boundary strength between the Al ₂ O ₃ phase and the ZrO ₂ phase is increased. Because it is strengthened, it is possible to suppress the occurrence of cracks in the modified two-phase mixed oxide layer that constitutes the upper layer of the hard coating layer under severe cutting conditions such as high-speed intermittent cutting. However, it prevents crack growth / propagation and, as a result, contributes to improving the chipping resistance of the hard coating layer. To become.
However, when the thickness of the upper layer is less than 2 μm, the ratio I (01-12) / I (11-20) of the diffraction intensity value does not become 1 to 3, so that the Al ₂ O ₃ phase and the ZrO ₂ Since the strengthening action of the crystal grain boundary between phases cannot be expected, on the other hand, chipping tends to occur when the layer thickness of the upper layer exceeds 15 μm. Therefore, the average layer thickness of the upper layer is set to 2 to 15 μm.

In the conventional coated tool in which the upper layer of the hard coating layer is a conventional two-phase mixed oxide layer, the dispersed phase ZrO ₂ phase is composed of monoclinic (110) plane, (−111) plane and tetragonal crystal. Although the X-ray diffraction peak appears on the (111) plane, and the Al ₂ O ₃ phase of the substrate has peaks on the (01-12) plane and the (11-20) plane, the diffraction intensity value The ratio value I (01-12) / I (11-20) is much smaller than 1 (see FIG. 2), and such mixed oxidation of the ZrO ₂ phase and the Al ₂ O ₃ phase is performed. In the physical layer, the grain boundary strength between the Al ₂ O ₃ phase and the ZrO ₂ phase is not sufficient, and the high temperature strength of the upper layer is not sufficient, so that under the severe cutting condition of high-speed intermittent cutting, the upper layer Cracks are likely to occur in the (conventional two-phase mixed oxide layer), and the growth and propagation of the generated cracks Can not be suppressed, chipping resistance of the hard coating layer of the conventional coated tool is consequently deteriorating.

The measurement conditions by X-ray diffraction for the modified two-phase mixed oxide layer or the conventional two-phase mixed oxide layer are as follows.
That is, using a normal X-ray diffractometer, the Cu anode (target) installed in the X-ray tube is acceleratedly irradiated with thermoelectrons generated from the metal W filament under conditions of a voltage of 40 kV and a current of 350 mA. To generate Cu-Kα rays, which are characteristic X-rays having a wavelength of 0.154 nm, from the surface of the Cu anode, and irradiate the surface of the two-phase mixed oxide layer with the characteristic X-rays. Of these, the X-ray intensity diffracted at an angle equal to the X-ray incident angle θ with respect to the surface of the layer was measured by an X-ray detector. The measurement range at this time is θ = 7.5 to 65 °. As a result of the above measurement, the diffraction intensity from the (01-12) and (11-20) planes of the α-type aluminum oxide of the aluminum oxide phase constituting the base of the modified two-phase mixed oxide layer is first and The diffraction peak of (−111) plane was obtained from the zirconium oxide phase which showed the second largest peak value and was uniformly dispersed in the substrate.
In the present invention, the plane index, for example, the plane represented by (αβγδ) includes not only the (αβγδ) plane but also a plane equivalent thereto, and the diffraction intensity value I (αβγδ) is ( The total value of diffraction intensities from the (αβγδ) plane and its equivalent plane.

As described above, the coated tool of the present invention is a ZrO ₂ phase having a monoclinic crystal structure oriented in the (−111) plane of the modified two-phase mixed oxide layer of aluminum oxide and zirconium oxide constituting the upper layer. Is dispersed and distributed in a substrate made of Al ₂ O ₃ phase (mainly α-type Al ₂ O ₃ , but a small amount of κ-type Al ₂ O ₃ is present), and the Al ₂ O ₃ phase is X-ray diffracted In addition, the diffraction intensity from the (01-12) plane and the (11-20) plane of α-type Al ₂ O _{3 is} the 1-2th largest value, and the value I (01 -12) / I (11-20) satisfies the value of 1 to 3, in addition to the excellent high temperature hardness of the conventional two-phase mixed oxide layer of the conventional coated tool, It has lubricity and heat resistance, and it has high heat generation and intermittent and shock loads on various steels and cast irons. That even when used in high-speed intermittent cutting conditions, exhibits chipping resistance of the hard coating layer is superior, and makes it possible to further life extension of service life.

  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 2 to 4 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.

Next, each of the tool bases A to F and the tool bases a to f was charged into a normal chemical vapor deposition apparatus. First, Table 3 (l-TiCN in Table 3 is disclosed in JP-A-6-8010). The combinations shown in Table 5 under the conditions shown in Table 5 are the conditions for forming the TiCN layer having the vertically grown crystal structure described, and the other conditions for forming the normal granular crystal structure. And Ti compound layer was vapor-deposited as a lower layer of a hard coating layer with target layer thickness.
Next, the modified two-phase mixed oxide layer having the target layer thickness shown in Table 5 is used as the upper layer of the hard coating layer by combining the first, second, and third stage deposition conditions as shown in Table 4. The coated tools 1 to 13 of the present invention were manufactured by vapor deposition.

  For comparison purposes, comparative coating tools 1 to 13 are formed by forming a conventional two-phase mixed oxide layer with the target layer thickness shown in Table 6 under the conditions shown in Table 4 as the upper layer of the hard coating layer. Were manufactured respectively.

Subsequently, the modified two-phase mixed oxide layer constituting the upper layer of the hard coating layer of the present invention-coated tools 1 to 13 and the conventional two-phase mixing constituting the upper layer of the hard coating layer of the comparative coating tools 1 to 13 For each Al ₂ O ₃ phase of the oxide layer, the diffraction intensity of each crystal plane was measured by X-ray diffraction, and the crystal planes from which the first and second diffraction intensities were obtained are shown in Tables 5 and 6, and , The value I (01-12) / I (11) of the ratio of the diffraction intensity value I (01-12) from the (01-12) plane and the diffraction intensity value I (11-20) from the (11-20) plane −20) is also shown in Tables 5 and 6.
Tables 5 and 6 also show the surfaces on which the ZrO ₂ phase was subjected to X-ray diffraction and the strongest X-ray diffraction intensity values were obtained.
The modified two-phase mixed oxide layer constituting the upper layer of the hard coating layer of the coated tools 1 to 13 of the present invention was examined by a transmission electron microscope. As a result, ZrO ₂ was found in the Al ₂ O ₃ phase substrate. It has been confirmed that the phases are uniformly dispersed.
An X-ray diffraction chart for the Al ₂ O ₃ phase and the ZrO ₂ phase of the coated tool 4 of the present invention is shown in FIG. 1, and an X-ray diffraction chart for the Al ₂ O ₃ phase and the ZrO ₂ phase of the comparative coated tool 5 is shown. As shown in FIG.

As shown in Tables 5 and 6, respectively, the modified two-phase mixed oxide layer of the coated tool according to the present invention has (01-12) plane and (11-20) plane of Al ₂ O ₃ phase in X-ray diffraction. The diffraction intensity from 1 shows the second highest peak value, and the ratio I (01-12) / I (11-20) of the diffraction intensity value satisfies the value of 1 to 3, and ZrO _{The two} phases exist as monoclinic structures oriented in the (−111) plane, whereas in the Al ₂ O ₃ phase of the comparative coated tool, I (01-12), I (11-20) Does not show the 1st to 2nd largest peak value, and the value of I (01-12) / I (11-20) also deviates from 1 to 3, and also for the ZrO ₂ phase, ZrO ₂ phase peaks other than monoclinic (tetragonal) are detected, and diffraction intensity other than the (−111) plane is strong. Thus, the orientation of the (−111) plane was low.

  Further, when the thicknesses of the constituent layers of the hard coating layers of the present coated tools 1 to 13 and the comparative coated tools 1 to 13 were measured using a scanning electron microscope (longitudinal cross section measurement), both of them were the target layer thickness. The substantially same average layer thickness (average value of 5-point measurement) was shown.

Next, for the various coated tools of the present invention coated tools 1-13 and comparative coated tools 1-13, all are screwed to the tip of the tool steel tool with a fixing jig,
[Cutting conditions A]
Work material: JIS / SNCM439 round bars with four equal grooves in the longitudinal direction,
Cutting speed: 360 m / min,
Cutting depth: 1.5 mm,
Feed: 0.3 mm / rev,
Cutting time: 5 minutes,
Dry high-speed intermittent cutting test of nickel chrome molybdenum steel under normal conditions (normal cutting speed is 200 m / min),
[Cutting conditions B]
Work material: JIS / FCD500 lengthwise equidistant 4 round bars with vertical grooves,
Cutting speed: 380 m / min,
Cutting depth: 1.7 mm,
Feed: 0.3 mm / rev,
Cutting time: 5 minutes,
Cast iron dry high-speed intermittent cutting test under the conditions (normal cutting speed is 180 m / min),
[Cutting conditions C]
Work material: JIS-S25C round bars with four equal grooves in the longitudinal direction,
Cutting speed: 370 m / min,
Cutting depth: 2.0 mm,
Feed: 0.45 mm / rev,
Cutting time: 5 minutes,
Carbon steel dry high-speed intermittent cutting test under normal conditions (normal cutting speed is 250 m / min)
In each cutting test, the flank wear width of the cutting edge was measured. The measurement results are shown in Table 7.

From the results shown in Tables 5 to 7, according to the present invention coated tools 1 to 13, the upper layer of the hard coating layer is an Al ₂ O ₃ phase mainly composed of α-type Al ₂ O ₃ having a hexagonal crystal structure. A monoclinic crystal formed by vapor deposition as a modified two-phase mixed oxide layer composed of a two-phase mixed oxide structure of ZrO ₂ phase, and oriented in the (−111) plane in the modified two-phase mixed oxide layer When the ZrO ₂ phase of ZrO ₂ is uniformly dispersed in the Al ₂ O ₃ phase substrate and X-ray diffraction is performed on the Al ₂ O ₃ phase, the (01-12) plane of the α-type Al ₂ O ₃ and (11 −20) The value of the diffraction intensity from the surface is the first to second largest value, and the ratio I (01-12) / I (11-20) of the diffraction intensity values is a value of 1 to 3. Therefore, it has excellent high temperature hardness, grain boundary strength, lubricity, heat resistance, high heat generation, and against cutting edges. The modified two-phase mixed oxide layer in addition to the high-temperature strength and high joint strength of the Ti compound layer that forms the lower layer of the hard coating layer even in high-speed intermittent cutting of steel and cast iron that are subjected to continuous and shock loads The superior high-temperature hardness, high-temperature strength, lubricity, and heat resistance of the material significantly improves the chipping resistance of the hard coating layer, and exhibits excellent tool properties over a long period of time. In the comparative coated tools 1 to 13 in which the conventional two-phase mixed oxide layer is formed by vapor deposition, the hard coating layer has a particularly high temperature strength under severe cutting conditions such as high-speed intermittent cutting. It is clear that chipping occurs and the service life is reached in a relatively short time.

  As described above, the coated tool of the present invention can be used not only for cutting under normal conditions such as various types of steel and cast iron, but also for high-speed intermittent cutting with high heat generation and intermittent and impact load. Since the hard coating layer exhibits excellent chipping resistance and exhibits excellent cutting performance over a long period of time, it is sufficient for improving the performance of cutting equipment, saving labor and energy, and reducing costs It can respond to satisfaction.

4 is an X-ray diffraction chart of the Al ₂ O ₃ phase and the ZrO ₂ phase of the modified two-phase mixed oxide layer constituting the upper layer of the hard coating layer of the present coated tool 4. 4 is an X-ray diffraction chart of an Al ₂ O ₃ phase and a ZrO ₂ phase of a conventional two-phase mixed oxide layer constituting an upper layer of a hard coating layer of a comparative coating 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 one or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride oxide layer having an overall average layer thickness of 3 to 20 μm. A Ti compound layer comprising:
(B) The upper layer is a two-phase mixed oxide layer of an aluminum oxide phase and a zirconium oxide phase mainly composed of α-type aluminum oxide having an average layer thickness of 2 to 15 μm and a chemical vapor deposited state and having a hexagonal crystal structure The content ratio of zirconium in the mixed oxide is 0.003 to 0.2 (however, atomic ratio) with respect to the total amount with aluminum. In the mixed oxide layer, (−111 ) The monoclinic zirconium oxide phase oriented in the plane is uniformly dispersed in the aluminum oxide phase. Further, the X-ray diffraction of the aluminum oxide phase from the (01-12) plane of the α-type aluminum oxide The value of the diffraction intensity I (01-12) and the value of the diffraction intensity I (11-20) from the (11-20) plane indicate the first and second largest diffraction intensity values, and ratio The value I (01-12) / I (11-20) is a two-phase mixed oxide layer of aluminum oxide phase and the zirconium oxide phase which satisfies a value of 1 to 3,
A surface-coated cutting tool that exhibits excellent chipping resistance with a hard coating layer formed by vapor-depositing the hard coating layer constituted by (a) and (b).

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