JP6604136B2 - Surface-coated cutting tool having excellent chipping resistance and wear resistance with a hard coating layer and method for producing the same - Google Patents

Description

  The present invention achieves both high fracture resistance and wear resistance with a hard coating layer in high-speed intermittent cutting with high heat generation of alloy steel and the like, and an impact load acting on the cutting edge. The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits excellent cutting performance over a long period of use.

Conventionally, generally composed of tungsten carbide (hereinafter referred to as WC) based cemented carbide, titanium carbonitride (hereinafter referred to as TiCN) based cermet or cubic boron nitride (hereinafter referred to as cBN) based ultra high pressure sintered body There is known a coated tool in which a Cr—Al composite nitride layer is formed by physical vapor deposition on the surface of a tool base (hereinafter collectively referred to as a tool base) as a hard coating layer, These are known to exhibit excellent wear resistance.
However, the above-mentioned coated tool coated with the conventional Cr-Al composite nitride layer is relatively excellent in wear resistance, but generates abnormal wear such as chipping and chipping when used under high-speed intermittent cutting conditions. Therefore, various proposals have been made for improving the hard coating layer.

For example, Patent Document 1 discloses that a hard coating layer formed by physically vapor-depositing a hard coating layer made of a composite nitride layer of Cr and Al on the surface of a tool base with an overall average layer thickness of 1 to 15 μm. However, along the layer thickness direction, the Al highest content point and the Al lowest content point are alternately present at predetermined intervals, and from the Al highest content point, the Al lowest content point, from the Al lowest content point. It has a component concentration distribution structure in which the Al content continuously changes to the Al highest content point, and the Al highest content point has a composition formula: (Cr _1-X Al _X ) N (however, in atomic ratio) , X represents 0.40 to 0.60), and the Al minimum content point is the composition formula: (Cr _1-Y Al _Y ) N (wherein the atomic ratio, Y is 0.05 to 0.30. The above-mentioned Al highest content point and Al minimum content adjacent to each other. Spacing of, by a 0.01 to 0.1 m, it has been proposed to improve the chipping resistance of the hard coating layer in the heavy cutting conditions.

Further, for example, in Patent Document 2, in a coated tool formed by vapor-depositing a hard coating layer composed of a composite nitride layer of Al and Cr having an average layer thickness of 1 to 10 μm on the surface of a tool base,
The composite nitride layer of Al and Cr is
Composition formula: When expressed by (Al _1-X Cr _X ) N,
0.3 ≦ X ≦ 0.6 (where X represents an atomic ratio), and
Using a field emission scanning electron microscope, each crystal grain having a cubic crystal lattice existing within the measurement range of the surface polished surface is irradiated with an electron beam, and the crystal grain is normal to the surface polished surface. The tilt angle formed by the normal of the {100} plane, which is the crystal plane, is measured, and among the measured tilt angles, the measured tilt angles within the range of 0 to 45 degrees are classified for each pitch of 0.25 degrees. In addition, in the inclination angle number distribution graph obtained by counting the frequencies existing in each section, the highest peak exists in the inclination angle section within the range of 30 to 40 degrees, and exists within the range of 30 to 40 degrees. Steel with a large mechanical load applied to the cutting edge by making the coated tool such that the total frequency to be shown shows a slope angle distribution graph that accounts for 60% or more of the total power in the slope angle distribution graph And used for heavy cutting of cast iron Even if, coated tool which exhibits excellent chipping resistance have been proposed.

Japanese Patent No. 3969230 JP 2009-56539 A

In recent years, there has been a strong demand for energy saving and energy saving in cutting work, and along with this, cutting work tends to be faster and more efficient, and coated tools have even more chipping resistance, chipping resistance, Abnormal damage resistance such as peel resistance is required, and excellent wear resistance over long-term use is required.
However, although the conventional coated tools described in Patent Documents 1 and 2 have been proposed for improving chipping resistance and fracture resistance under heavy cutting conditions such as high cutting and high feed, the conventional coated tools described above are proposed. When used under high-speed intermittent cutting conditions that cause high heat generation and an impact load on the cutting edge, the chipping resistance and fracture resistance are satisfied to some extent, but wear resistance Is not enough.
Therefore, even when subjected to high-speed intermittent cutting of alloy steel, etc., it is possible to achieve both excellent fracture resistance and wear resistance, and also exhibits excellent cutting performance over a long period of use. There is a need for a coated tool.

In view of the above, the inventors of the present invention from the above-described composite nitride of Cr and Al (hereinafter, sometimes referred to as “(Cr, Al) N” or “(Cr _1−x Al _x ) N”). The following findings were obtained as a result of intensive research aimed at achieving both fracture resistance and wear resistance of the coated tool formed by physical vapor deposition of the hard coating layer.

  The present inventors have intensively studied the crystal structure of the (Cr, Al) N layer constituting the hard coating layer. As a result, the (Cr, Al) N layer has an NaCl type face-centered cubic structure (hereinafter simply referred to as “cubic”). A crystal structure having a crystal structure "or" cubic crystal "), and the crystal grains having the cubic structure have a cubic structure with a completely new idea that the average orientation difference in the crystal grains is 2 degrees or more. Succeeded to increase both hardness and toughness by causing distortion in crystal grains having a crystal structure, and as a result, it was found that the wear resistance could be improved while improving the fracture resistance of the hard coating layer. It was.

Specifically, the hard coating layer is composed of a (Cr, Al) N layer formed by physical vapor deposition, and the component composition of the (Cr, Al) N layer is expressed by a composition formula: (Cr _1-x Al _x ) When expressed by N, the average content ratio x _avg (where x _avg is an atomic ratio) of the total amount of Cr and Al in Al is 0.40 ≦ x _avg ≦ 0.95 (preferably, 0.1%). 40 ≦ x _avg ≦ 0.72), and the crystal grains constituting the (Cr, Al) N layer are those having a cubic structure, and the crystal orientation of the cubic structure crystal grains is When analyzing from the longitudinal cross-sectional direction using an electron beam backscattering diffractometer, and determining the average orientation difference within each crystal grain, the crystal grains having an average orientation difference within the crystal grain of 2 degrees or more (Cr, when present at the area ratio of 5 to 50% of the area of al) N layer, the strain in the crystal grains of the standing-cubic structure Hesitate to be able, as compared with the conventional hard coating layer, (Cr, Al) hardness and toughness of the N layer is increased, as a result, we have found that the wear resistance is improved at the same time as the chipping resistance.

  The (Cr, Al) N layer having the above-described configuration is, for example, a tool base mounted in a physical vapor deposition apparatus, a nitrogen atmosphere of 0.2 to 0.5 Pa inside the apparatus, and an absolute value in the tool base. In a state where a negative bias voltage of 900 V or more is applied, the Cr—Al alloy target disposed in the apparatus is discharged, and the tool substrate surface treatment is performed, and then arc discharge is performed between the Cr—Al alloy target and the anode electrode. The film can be formed by a physical vapor deposition method that generates

The present invention has been made based on the above findings,
“(1) Surface coating in which a hard coating layer is formed on the surface of a tool base made of any of tungsten carbide-based cemented carbide, titanium carbonitride-based cermet, or cubic boron nitride-based ultrahigh-pressure sintered body In cutting tools,
(A) The hard coating layer is a composite nitride of Cr and Al having an average layer thickness of 1 to 15 μm,
When expressed by the composition formula: (Cr _1-x Al _x ) N, the average content ratio x _avg (where x _avg is an atomic ratio) of the total amount of Cr and Al in the composite nitride layer is 0. 40 ≦ x _avg ≦ 0.95 is satisfied,
(B) The composite nitride layer includes a composite nitride phase of Cr and Al having a NaCl type face centered cubic structure,
(C) The compressive residual stress of the composite nitride layer satisfies 1.0 GPa to 8.0 GPa,
(D) The crystal orientation of the crystal grains of Cr and Al composite nitride having the NaCl-type face-centered cubic structure is analyzed from the longitudinal section direction using an electron beam backscattering diffractometer, and the individual crystal grains are analyzed. When determining the inner average orientation difference, the surface area of the crystal grains in which the average orientation difference within the crystal grains is 2 degrees or more occupies 5% or more and 50% or less of the area of the composite nitride layer. Coated cutting tool.
(2) The area ratio of the crystal grains having an average orientation difference in the crystal grains of 2 degrees or more per unit layer thickness in the layer thickness direction of the composite nitride layer is the interface side between the tool base and the hard coating layer. The surface-coated cutting tool according to (1), wherein the surface-coated cutting tool gradually increases from the surface toward the surface of the hard coating layer.
(3) The method for producing a surface-coated cutting tool according to (1) or (2),
A tool substrate is mounted in a physical vapor deposition device, the inside of the device is set to a nitrogen atmosphere of 0.2 to 0.5 Pa, and a negative bias voltage of 900 V or more in absolute value is applied to the tool substrate in the device. The hard coating is performed by a physical vapor deposition method in which the processed Cr—Al alloy target is discharged, the surface of the tool base is processed at a target surface maximum magnetic flux density of 5 mT or more, and then arc discharge is generated between the Cr—Al alloy target and the anode electrode. The method for producing a surface-coated cutting tool according to (1) or (2), wherein a layer is formed. "
It has the characteristics.
The “inside crystal grain average orientation difference” means a GOS (Grain Orientation Spread) value described later.

The present invention will be described in detail below.

Average layer thickness of the composite nitride layer constituting the hard coating layer:
The hard coating layer of the present invention includes a composite nitride layer of Cr and Al represented by a composition formula: (Cr _1-x Al _x ) N formed by physical vapor deposition. This composite nitride layer has excellent heat resistance and wear resistance, but the effect is particularly remarkable when the average layer thickness is 1 to 15 μm. The reason is that if the average layer thickness is less than 1 μm, the layer thickness is so thin that sufficient wear resistance over a long period of time cannot be secured, while if the average layer thickness exceeds 15 μm, (Cr , Al) N layer crystal grains are likely to be coarsened, and defects are likely to occur. Therefore, the average layer thickness was set to 1 to 15 μm.

Composition of the (Cr, Al) N layer constituting the hard coating layer:
In the hard coating layer composed of the (Cr, Al) N layer of the present invention, the average content ratio x _avg (where x _avg is an atomic ratio) of the total amount of Cr and Al in Al is 0.40 ≦ x _avg ≦ Satisfy 0.95.
The reason is that when the average content ratio x _{avg of} Al is less than 0.40, the (Cr, Al) N layer is reduced in hardness, so when it is subjected to high-speed intermittent cutting such as alloy steel, Abrasion is not enough. On the other hand, if the average content ratio x _{avg of} Al exceeds 0.95, the average content ratio of Cr is relatively decreased, so that heat resistance and fracture resistance are decreased. Therefore, the average Al content ratio x _avg was determined to be 0.40 ≦ x _avg ≦ 0.95. Preferably, 0.40 ≦ x _avg ≦ 0.72.

Compressive residual stress of the (Cr, Al) N layer constituting the hard coating layer:
When the compressive residual stress in the hard coating layer composed of the (Cr, Al) N layer of the present invention is less than 1.0 GPa, since the hardness of the hard coating layer is low, the wear resistance is not sufficient. When it exceeds 0 GPa, the wear resistance is improved, but the fracture resistance is lowered.
Therefore, in the present invention, the compressive residual stress of the hard coating layer made of the (Cr, Al) N layer is set to 1.0 GPa or more and 8.0 GPa or less.
The measurement of the compressive residual stress can be carried out by the 2θ-sin ² ψ method using an X-ray diffractometer. In this case, a Cr tube is used and measurement is performed at the (222) peak. The calculation is performed using a Young's modulus of 300 GPa and a Poisson's ratio of 0.2.

In-grain average orientation difference (GOS value) of crystal grains having a cubic structure constituting the (Cr, Al) N layer:
In the present invention, the average orientation difference (GOS value) within a crystal grain of a (Cr, Al) N crystal grain having a cubic structure is obtained using an electron beam backscatter diffraction apparatus.
Specifically, the longitudinally polished surface is analyzed at intervals of 0.01 μm from the direction perpendicular to the longitudinal section of the (Cr, Al) N layer, and as shown in FIG. , Also referred to as “pixel”), if there is an orientation difference of 5 degrees or more, it is defined as a grain boundary. A region surrounded by the grain boundary is defined as one crystal grain. However, a single pixel that has an orientation difference of 5 degrees or more with all adjacent pixels is not a crystal grain, and a pixel having two or more pixels connected is treated as a crystal grain.
Then, the orientation difference between a certain pixel in the cubic crystal grain and all the other pixels in the same crystal grain is calculated, and this is obtained as the orientation difference in the crystal grain. It is defined as a (Grain Orientation Spread) value.
The GOS value is described in, for example, the document “The Journal of the Japan Society of Mechanical Engineers (A) 71, 712 (2005-12), Paper No. 05-0367 1722-1728”.
The “inside crystal grain average orientation difference” in the present invention means this GOS value. When the GOS value is expressed by a mathematical expression, the number of pixels in the same crystal grain is n, the numbers assigned to different pixels in the same crystal grain are i and j (where 1 ≦ i, j ≦ n), pixel i And α _{ij (i ≠ j)} , the difference in crystal orientation obtained from the crystal orientation at and the crystal orientation at pixel j,


Can be expressed as
In addition, the average orientation difference and GOS value within a crystal grain is a numerical value obtained by calculating the orientation difference between a certain pixel in a crystal grain and all other pixels in the same crystal grain and averaging the values. However, a large numerical value is obtained when there are many continuous orientation changes in the crystal grains.

The average misorientation (GOS value) in crystal grains was analyzed at intervals of 0.01 μm from the direction perpendicular to the longitudinal section of the (Cr, Al) N layer. The width was 3 μm, and the vertical length was within the measurement range of the layer thickness. The measurement from the plane direction is performed at an interval of 0.01 μm / step, the total number of pixels belonging to the cubic crystal grains constituting the (Cr, Al) N layer is obtained, and the average orientation difference (GOS value) in the grains is calculated. By dividing by 1 degree interval, and summing up the number of pixels of the crystal grains whose average grain orientation difference (GOS value) is included in the range of the value and dividing by the total number of pixels, It can be obtained by creating a frequency distribution (histogram) indicating the area ratio of (GOS value).
In the case of the present invention according to claim 2, the longitudinal section of the (Cr, Al) N layer is divided into a predetermined unit layer thickness in the layer thickness direction, and each section is divided from the direction perpendicular to the layer thickness direction. By obtaining the area ratio of crystal grains having an average orientation difference (GOS value) in the crystal grains of 2 degrees or more, and comparing the area ratios in the respective unit layer thicknesses divided along the layer thickness direction, A change in the area ratio from the interface side between the base and the hard coating layer toward the surface side of the hard coating layer can be obtained.

For example, with respect to cubic crystal grains of the (Cr, Al) N layer of the present invention, the average orientation difference (GOS value) within the grains is obtained, and the frequency distribution (histogram) is created. As shown in FIG. It can be seen that the ratio of the area of the crystal grains having an average grain orientation difference (GOS value) of 2 degrees or more to the total area of the (Cr, Al) N layer is in the range of 5% to 50% .
FIG. 3 shows the (Cr, Al) N layer of the present invention having the frequency distribution (histogram) shown in FIG. 2, and the layer thickness is equally divided into three unit layer thicknesses in the layer thickness direction. FIG. 3 shows the area ratio in each section of each unit layer thickness. In the (Cr, Al) N layer shown in FIG. 3, the surface of the hard coating layer is formed from the interface side between the tool base and the hard coating layer. It can be seen that the area ratio increases toward the side.
As described above, the cubic crystal grains constituting the (Cr, Al) N layer of the present invention have a crystal orientation within the crystal grains as compared with the crystal grains constituting the conventional (Cr, Al) N layer. Therefore, the crack growth is suppressed, and as a result, the fracture resistance of the hard coating layer is improved.
And the coated tool in which the hard coating layer which consists of a (Cr, Al) N layer provided with the above-mentioned average orientation difference (GOS value) in a crystal grain was provided on the surface of a tool base accompanied with high heat generation, and with respect to a cutting edge In high-speed intermittent cutting of alloy steel and the like on which impact loads are applied, it exhibits excellent wear resistance as well as excellent fracture resistance.
However, in the case where the crystal grains having an average orientation difference (GOS value) in the crystal grains of 2 degrees or more account for less than 5% of the total area of the (Cr, Al) N layer, Since the crystal orientations of the crystal grains are too uniform, cracks are likely to progress and the defect resistance is not sufficient, so that the cubic crystal grains having an average orientation difference (GOS value) in the grains of 2 degrees or more are (Cr, Al ) The area ratio in the total area of the N layer is 5% or more and 50% or less . A preferred area ratio is 20% or more and 40% or less.
Further, a cubic crystal whose average orientation difference in crystal grains (GOS value) is 2 degrees or more from the interface side between the tool base and the (Cr, Al) N layer toward the surface side of the (Cr, Al) N layer. When the area ratio of the crystal grains increases, the fracture resistance can be further improved without reducing the adhesion strength between the tool base and the (Cr, Al) N layer.

The above-mentioned coated tool having the (Cr, Al) N layer of the present invention can be manufactured by, for example, the following method.
The (Cr, Al) N layer of the present invention is formed by, for example, an arc ion plating (hereinafter referred to as “AIP”) method which is a kind of physical vapor deposition.
(A) First, in a state where a tool base tool composed of any of tungsten carbide-based cemented carbide, titanium carbonitride-based cermet, or cubic boron nitride-based ultrahigh pressure sintered body is cleaned and dried, It is mounted along the outer periphery at a position that is a predetermined distance in the radial direction from the central axis on the rotary table. A Cr—Al alloy target having a predetermined composition is placed in the apparatus.
(B) The interior of the apparatus is evacuated and kept at a vacuum of 10-2 Pa or less, and the interior of the apparatus is heated to 500 ° C. with a heater, and then set to an Ar gas atmosphere of 0.5 to 2.0 Pa, and the rotary table A DC bias voltage of −200 to −1000 V is applied to the rotating tool base while rotating above, and the tool base surface is bombarded with argon ions for 5 to 30 minutes.
(C) Thereafter, the inside of the apparatus is maintained in a nitrogen gas atmosphere of 0.2 to 0.5 Pa, and a negative DC bias voltage of 900 V or more in absolute value is applied to the tool base that rotates while rotating on the rotary table. Then, the Cr—Al alloy target disposed in the apparatus is discharged at a target surface maximum magnetic flux density of 5 mT or more, and the tool substrate surface is treated.
(D) Next, a nitrogen gas pressure in the apparatus is set to a reaction atmosphere of 4 Pa, a DC bias voltage of −50 V is applied to a rotating tool base while rotating on the rotary table, and Cr— An arc discharge is generated by flowing a current of 100 A between the Al alloy target and the anode electrode, and a (Cr, Al) N layer having a target composition and a target average layer thickness is formed on the surface of the tool base.
The coated tool of the present invention can be produced by the above steps (a) to (d).
In the manufacturing method of the present invention, the tool substrate surface treatment in the step (c) is a characteristic step, and although the details are unknown by this step, it is assumed that the initial nucleus to be formed is distorted. is doing. Further, when the film formation is advanced in the step (d), the strained state is inherited from the initial nucleus, so that the crystal orientation difference caused by the strain accumulates, and as a result, a large orientation difference occurs in the crystal grain. It is estimated to be. In any case, due to the characteristic step of the tool substrate surface treatment in the step (c), the crystal grains whose average orientation difference (GOS value) in the grains is 2 degrees or more are all in the (Cr, Al) N layer. It is possible to form a (Cr, Al) N layer having an area ratio of 5% to 50% .

The present invention relates to a surface-coated cutting tool in which a hard coating layer is provided on the surface of a tool base. The hard coating layer is composed of a (Cr, Al) N layer having an average layer thickness of 1 to 15 μm, and a composition formula: (Cr _When expressed by _1- xAl _x ) N, the average content ratio x _avg (where x _avg is an atomic ratio) of the total amount of Cr and Al in Al is 0.40 ≦ x _avg ≦ 0.95 (preferably 0.40 ≦ x _avg ≦ 0.72), and the (Cr, Al) N layer has excellent wear resistance because it has a compressive residual stress of 1.0 GPa or more and 8.0 GPa. The crystal grains constituting the (Cr, Al) N layer exist with a cubic structure, and the crystal orientation of the crystal grains is analyzed from the longitudinal cross-sectional direction using an electron beam backscattering diffractometer. When the average misorientation within a grain is calculated for each grain, the mean misorientation within the grain is 2 degrees or more. When the crystal grains are present in an area ratio of 5% or more and 50% or less with respect to the total area of the (Cr, Al) N layer, distortion occurs in the crystal grains having a cubic structure, and the progress of cracks is suppressed. Therefore, the fracture resistance is improved. As a result, the hard coating layer made of the (Cr, Al) N layer of the coated tool of the present invention can achieve both excellent fracture resistance and wear resistance, and therefore has excellent cutting performance over a long period of use. This is achieved and the life of the coated tool is extended.

It is a schematic explanatory drawing of the measuring method which calculates | requires the average orientation difference within a crystal grain. 2 shows an example of a histogram of the average orientation difference in crystal grains of individual crystal grains having a cubic structure in the cross section of the (Cr, Al) N layer constituting the hard coating layer of the coated tool 2 of the present invention. In the cross section of the (Cr, Al) N layer constituting the hard coating layer of the coated tool 2 of the present invention, the area of cubic crystal grains in which the average orientation difference in the crystal grains at each unit layer thickness in the layer thickness direction is 2 degrees or more It is an example of the figure which shows the change of a ratio. It is the schematic of the arc ion plating (AIP) apparatus for vapor-depositing a hard coating layer, (a) is a front view, (b) shows a side view.

Next, the coated tool of the present invention will be specifically described with reference to examples.
As a concrete explanation, a cubic boron nitride (hereinafter referred to as “cBN”)-based sintered body and tungsten carbide (hereinafter referred to as “WC”)-based cemented carbide are used as a tool base. Although a tool is demonstrated, it is the same also about the coated tool which uses a titanium carbonitride based cermet as a tool base.

[Example 1]
Tool substrate production:
As the raw material powder, cBN powder, TiN powder, TiC powder, Al powder, AlN powder, and Al ₂ O ₃ powder each having an average particle diameter in the range of 0.5 to 4 μm are prepared. The mixture is blended in the composition shown in FIG. 1, wet mixed with a ball mill for 80 hours, dried, and then pressed into a green compact having a diameter of 50 mm × thickness: 1.5 mm under a pressure of 120 MPa. The green compact is sintered in a vacuum atmosphere at a pressure of 1 Pa at a predetermined temperature within a range of 900 to 1300 ° C. for 60 minutes to obtain a presintered body for a cutting edge piece. In addition, Co: 8% by mass, WC: remaining composition, and diameter: 50 mm × thickness: 2 mm, superposed on a WC-based cemented carbide support piece with a normal super-high pressure Insert into the sintering machine and under normal conditions Pressure: 4GPa, temperature: 1200 ° C to 1400 ° C, holding at a predetermined temperature: ultra high pressure sintering for 0.8 hours. After sintering, the upper and lower surfaces are polished using a diamond grindstone, and wire electric discharge machining. It is divided into predetermined dimensions by an apparatus, and further Co: 5 mass%, TaC: 5 mass%, WC: remaining composition and shape of JIS standard CNGA120408 (thickness: 4.76 mm × inscribed circle diameter: 12.7 mm) The brazing part (corner part) of the insert body made of a WC-based cemented carbide having a 80 ° rhombus) has a composition consisting of Zr: 37.5%, Cu: 25%, Ti: the remainder in mass%. After brazing using a brazing material of Ti-Zr-Cu alloy and processing the outer periphery to a predetermined dimension, subject the cutting edge to a honing process with a width of 0.13 mm and an angle of 25 °, and then finish polishing ISO standard C The tool substrate 1-3 having the insert shape of GA120408 were prepared, respectively.

Formation of hard coating layer:
A hard coating layer was formed on the tool bases 1 to 3 produced by the above-described process using an AIP apparatus as shown in FIG.
(A) The tool bases 1 to 3 are ultrasonically cleaned in acetone and dried. Then, the tool bases 1 to 3 are arranged along the outer periphery at a predetermined distance in the radial direction from the central axis on the rotary table in the arc ion plating apparatus. Install. In addition, a Cr—Al alloy target having a predetermined composition is disposed as a cathode electrode (evaporation source) for tool substrate surface treatment and film formation before film formation.
(B) First, the interior of the apparatus was evacuated and kept at a vacuum of 10 ⁻² Pa or less, and the interior of the apparatus was heated to 500 ° C. with a heater, and then set to an Ar gas atmosphere of 0.5 to 2.0 Pa. A DC bias voltage of −200 to −1000 V is applied to the tool base that rotates while rotating on the rotary table, and the tool base surface is bombarded with argon ions for 5 to 30 minutes.
(C) Thereafter, the inside of the apparatus is held at the atmospheric pressure shown in Table 2, and a DC bias voltage shown in Table 2 is applied to the tool base that rotates while rotating on the rotary table, and Cr- The Al alloy target is discharged under the conditions shown in Table 2, and the tool substrate surface is treated.
(D) Next, the nitrogen gas in the apparatus is set to the atmospheric pressure shown in Table 2, a DC bias voltage shown in Table 2 is applied to the tool base that rotates while rotating on the rotary table, and the predetermined composition is applied. An arc discharge is generated by passing the current shown in Table 2 between the Cr-Al alloy target and the anode electrode, and the target composition and target average layer thickness (Cr, Al) shown in Table 3 are formed on the surface of the tool base. N layer is formed.
In the steps (a) to (d), coated tools (referred to as “the present invention tool”) 1 to 8 of the present invention were produced.

  For comparison, the tool bases 1 to 3 were treated on the tool base surface under the conditions shown in Table 4, and then the (Cr, Al) N layer having the target composition and the target average layer thickness under the conditions shown in Table 4. The coated tools of comparative examples shown in Table 5 (referred to as “comparative tool”) 1 to 10 were produced.

  The cross sections in the direction perpendicular to the tool base of the inventive tools 1 to 8 and comparative coated tools 1 to 10 produced above were measured using a scanning electron microscope (magnification 5000 times). The layer thickness was measured and averaged to obtain the average layer thickness.

In addition, regarding the average content ratio x _avg of Al in the (Cr, Al) N layer, the electron beam was measured on the sample surface in a sample whose surface was polished using an electron-microbe-analyzer (EPMA). The average Al content ratio x _avg was determined from the 10-point average of the analysis results of the obtained characteristic X-rays.

  Further, the residual stress of the (Cr, Al) N layer was determined by the 2θ-sin2ψ method using an X-ray diffractometer. The X-ray diffraction was calculated using a Cr tube, measuring the (222) peak, using a Young's modulus of 300 GPa and a Poisson's ratio of 0.2.

Further, with respect to the longitudinal section of the (Cr, Al) N layer, the crystal orientation of each cubic crystal grain of the (Cr, Al) N layer is analyzed using an electron beam backscattering diffractometer, and 5 degrees between adjacent pixels. If there is a difference in orientation, the grain boundary is defined as a grain boundary, and the region surrounded by the grain boundary is defined as one crystal grain. A crystal grain between a pixel in the crystal grain and all other pixels in the same crystal grain. The internal orientation difference is obtained, and the crystal grain orientation difference is 0 degree or more and less than 1 degree, 1 degree or more and less than 2 degree, 2 degree or more and less than 3 degree, 3 degree or more and less than 4 degree,. Is divided every one degree to obtain the average orientation difference (GOS value) in the crystal grain, and the frequency distribution (histogram) is created. From the frequency distribution (histogram), the average orientation difference (GOS value) in the grain is The area ratio of the crystal grains showing 2 degrees or more to the total area of the (Cr, Al) N layer was determined.
Furthermore, the layer thickness of the (Cr, Al) N layer is changed to three unit layer thicknesses in the layer thickness direction (that is, “layer thickness region on the tool substrate side”, “intermediate region”, and “layer thickness on the hard coating layer surface side). It was equally divided into three unit layer thicknesses of “region”, and the area ratio in each unit layer thickness was measured.
FIG. 2 shows a histogram of the average orientation difference (GOS value) within a crystal grain of each crystal grain having a cubic structure, which was obtained for the longitudinal section of the (Cr, Al) N layer of the tool 2 of the present invention. FIG. 3 shows that the average orientation difference (GOS value) within the crystal grains at each unit layer thickness in the layer thickness direction obtained for the longitudinal section of the (Cr, Al) N layer of the tool 2 of the present invention is 2 degrees or more. The value of the area ratio of cubic crystal grains is shown.

  Tables 3 and 5 show the various values obtained above.

Then, about the said invention tools 1-8 and comparative example tools 1-10,
Cutting condition A:
Work material: JIS-SCr420 (60HRC) lengthwise equal 8 round grooved round bars,
Cutting speed: 150 m / min. ,
Cutting depth: 0.15mm,
Feed: 0.10 mm / rev. ,
Cutting time: 25 minutes,
The chrome steel was subjected to a dry strong interrupted cutting test under the above conditions, the flank wear width of the cutting edge was measured, and the presence or absence of chipping was observed.
Table 6 shows the results.

[Example 2]
Tool substrate production ::
As raw material powders, Co powder, VC powder, Cr ₃ C ₂ powder, TiC powder, TaC powder, NbC powder, WC powder, all having an average particle diameter of 0.5 to 5 μm, are prepared. Blended in the composition shown in Table 7, added with wax, wet-mixed with a ball mill for 72 hours, dried under reduced pressure, press-molded at a pressure of 100 MPa, sintered these compacts, predetermined dimensions WC-based cemented carbide tool bases 11 to 13 having an insert shape of ISO standard SEEN1203AFTN1 were manufactured.

Film formation process:
Using the AIP apparatus shown in FIG. 4 for the WC-base cemented carbide tool bases 11 to 13, the same steps as (a), (b), (c), and (d) of Example 1 were performed. Then, the surface of the tool substrate is treated under the conditions shown in Table 8, and then the (Cr, Al) N layer having the target layer thickness and target composition is formed by vapor deposition under the conditions shown in Table 8. Invention tools 11-18 were produced.

  For comparison, the tool base surface is treated on the tool bases 11 to 13 under the conditions shown in Table 10, and then the (Cr, Al) N layer having the target composition and the target average layer thickness under the conditions shown in Table 11. The coated tools (referred to as “comparative example tools”) 11 to 20 of the comparative example shown in Table 11 were produced.

The present invention tools 11-18 prepared above, Comparative Example tool 11-20, in the same manner as in Example 1, the average composition of each layer, the average layer thickness, residual stress, the crystal grains mean misorientation (GOS value) Cubic crystals in which the crystal grains showing 2 degrees or more occupy the area ratio of the total area of the (Cr, Al) N layer, and the average orientation difference (GOS value) in the crystal grains in each unit layer thickness in the layer thickness direction is 2 degrees or more The value of the area ratio of crystal grains was determined.
Tables 9 and 11 show the various values obtained above.

Next, for the inventive tools 11 to 18 and the comparative tools 11 to 20, a single-blade high-speed face milling test was performed under the following cutting conditions B using a SE445R0506E cutter.
Cutting condition B:
Work material: Block material of JIS / SCM440,
Cutting speed: 300 m / min. ,
Rotational speed: 770 rev / min,
Cutting depth: 2.5mm,
Feed: 0.2mm / tooth,
Cutting time: Performed under conditions of 10 minutes, and measured the flank wear width.
Table 12 shows the results.

According to the results of Table 6, the inventive tools 1 to 8 have a small flank wear width and no defect, whereas the comparative tools 1 to 10 have flank wear, or In some cases, the lifetime of the defect was short.
Further, according to the results shown in Table 12, the tools 11 to 18 of the present invention have a small flank wear width and no defect occurs, whereas the flank wear of the comparative tools 11 to 20 progresses. Or, a product having a short lifetime due to a defect occurred.
From this result, it can be seen that the tool of the present invention is excellent in both fracture resistance and wear resistance.

  The surface-coated cutting tool of the present invention is not only for cutting under normal cutting conditions such as various steels, but also alloy steel, stainless steel, etc. that are accompanied by high heat generation and a heavy load on the cutting edge part. Even in high-speed interrupted cutting, it exhibits excellent chipping resistance and wear resistance, and exhibits excellent cutting performance over a long period of time. And it can cope with energy saving and cost reduction sufficiently satisfactorily.

Claims (3)

In a surface-coated cutting tool in which a hard coating layer is formed on the surface of a tool base composed of any of tungsten carbide-based cemented carbide, titanium carbonitride-based cermet, or cubic boron nitride-based ultrahigh pressure sintered body,
(A) The hard coating layer is a composite nitride of Cr and Al having an average layer thickness of 1 to 15 μm,
When expressed by the composition formula: (Cr _1-x Al _x ) N, the average content ratio x _avg (where x _avg is an atomic ratio) of the total amount of Cr and Al in the composite nitride layer is 0. 40 ≦ x _avg ≦ 0.95 is satisfied,
(B) The composite nitride layer includes a composite nitride phase of Cr and Al having a NaCl type face centered cubic structure,
(C) The compressive residual stress of the composite nitride layer satisfies 1.0 GPa to 8.0 GPa,
(D) The crystal orientation of the crystal grains of Cr and Al composite nitride having the NaCl-type face-centered cubic structure is analyzed from the longitudinal section direction using an electron beam backscattering diffractometer, and the individual crystal grains are analyzed. When determining the inner average orientation difference, the surface area of the crystal grains in which the average orientation difference within the crystal grains is 2 degrees or more occupies 5% or more and 50% or less of the area of the composite nitride layer. Coated cutting tool.   The area ratio of the crystal grains having an average orientation difference in the crystal grains of 2 degrees or more per unit layer thickness in the layer thickness direction of the composite nitride layer is determined by the hard coating from the interface side between the tool base and the hard coating layer. The surface-coated cutting tool according to claim 1, which gradually increases toward the surface side of the layer.   It is a manufacturing method of the surface coating cutting tool of Claim 1 or 2, Comprising: A tool base | substrate is mounted in a physical vapor deposition apparatus, the inside of an apparatus is made into nitrogen atmosphere of 0.2-0.5Pa, and absolute value is set in a tool base | substrate. In the state where a negative bias voltage of 900 V or more is applied, the Cr—Al alloy target disposed in the apparatus is discharged, and the surface of the tool base is treated with a target surface maximum magnetic flux density of 5 mT or more. The method for producing a surface-coated cutting tool according to claim 1, wherein the hard coating layer is formed by physical vapor deposition that generates arc discharge between the alloy target and the anode electrode.