JP7231885B2 - A surface-coated cutting tool with a hard coating layer that exhibits excellent chipping resistance - Google Patents

Description

The present invention provides a surface-coated cutting tool (hereinafter referred to as , sometimes referred to as coated tools).

Conventionally, 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 a coated tool in which a Ti—Al-based composite carbonitride layer is formed as a hard coating layer by physical vapor deposition on the surface of a tool substrate (hereinafter collectively referred to as the tool substrate). It is known to exhibit excellent wear resistance.
However, although the conventional coated tool coated with the Ti—Al-based composite carbonitride layer has relatively excellent wear resistance, it is prone to abnormal wear such as chipping when used under high-speed intermittent cutting conditions. Therefore, various proposals have been made to improve the lubricity of the hard coating layer.

For example, in Patent Document 1, Ti _1-x Al _x C _y N, which is a hard coating having a thickness of 1 to 16 μm and 85% by volume or more of fcc structure crystal grains, is deposited on a substrate by CVD. It has a _z layer (0.40≤x≤0.95, 0≤y≤0.10, 0.85≤z≤1.15), and has AlN with a hexagonal crystal structure at the grain boundary of the layer Ti _1-o Al _o C _p N _q (0.95≦o≦1.00, 0≦p≦0.10, 0.85≦q≦1.15, ox≧0.05) was precipitated. A coated tool is described.

Further, for example, Patent Document 2 includes a plurality of crystal grains and an amorphous phase between the crystal grains,
Each of the crystal grains has a structure in which a Ti _1-x Al _x N layer having an fcc structure and a Ti _1-y Al _y N layer having an fcc structure are alternately laminated, and the Ti ₁ The Al composition ratio x of _{the -x} Al _x N layer satisfies the relationship of 0≦x<1, and the Al composition ratio y of the Ti _1-y Al _y N layer satisfies the relationship of 0<y≦1. The Al composition ratio x and the Al composition ratio y satisfy the relationship (y−x)≧0.2, and the amorphous phase is a carbide, nitride or carbonitride of at least one of Ti and Al. A coated tool having a hard coating comprising:

International Patent Publication No. 2017/016826 Japanese Patent Application Laid-Open No. 2016-3368

The hard coatings described in Patent Documents 1 and 2 have hexagonal and amorphous phases at grain boundaries that generally reduce strength, so they were subjected to high-speed interrupted cutting with a higher load. In such cases, chipping is likely to occur, making it difficult to achieve satisfactory cutting performance.

Therefore, the present invention provides a cutting tool that exhibits excellent cutting performance over a long period of use by providing a hard coating layer with excellent chipping resistance even when used for high-speed interrupted cutting of cast iron, alloy steel, etc. intended to

The present inventors have improved the chipping resistance of a composite nitride layer or composite carbonitride layer of Ti and Al as a hard coating layer (hereinafter, the composite nitride layer or composite carbonitride layer is also referred to as a TiAlCN layer). As a result of intensive investigation, when moderately small crystal grains (microcrystalline grains) exist between large grains, while maintaining the wear resistance provided by large grains, during cutting New knowledge was obtained that crack propagation is inhibited and chipping resistance is improved in high-speed interrupted cutting of cast iron and alloy steel.

The present invention is based on this finding,
"(1) In a surface-coated cutting tool having a hard coating layer on the surface of the tool substrate,
(a) the hard coating layer includes at least a composite nitride layer or composite carbonitride layer of Ti and Al with an average layer thickness of 2.0 to 20.0 μm,
(b) When the composite nitride layer or composite carbonitride layer is represented by the composition formula: (Ti _(1-x) Al _x ) (C _y N _(1-y) ), the combination of Ti and Al of Al The average content ratio x _avg in the amount and the average content ratio y _avg of C in the total amount of C and N (where x _avg and y _avg are both atomic ratios) are respectively 0.60≦x _avg ≦0. 95, satisfying 0.00≦y _avg ≦0.05,
(c) The composite nitride layer or composite carbonitride layer has an area occupied by crystal grains having a NaCl-type face-centered cubic structure of the composite nitride or composite carbonitride layer when the longitudinal section of the layer is observed. The ratio satisfies 90 area% or more,
(d) Further, in an upper layer side region obtained by bisected the composite nitride layer or composite carbonitride layer into an upper layer side and a lower layer side in the layer thickness direction, individual crystal grains having the NaCl type face-centered cubic structure When the crystal grain size d is obtained, the area of the crystal grains with the crystal grain size d of 0.01 μm < d ≤ 0.20 μm with respect to the total area of the composite nitride layer or composite carbonitride layer in the upper layer side region present in a proportion of 10 to 40 area %,
(e) In addition, in the bisected upper layer side, crystal grains having a crystal grain size d of 0.01 μm < d ≤ 0.20 μm of each crystal grain having a face-centered cubic structure of the NaCl type are separated from each other. The average value L (dsum) of the maximum length L in the direction parallel to the tool base surface of each adjacent and connected region is L (dsum) ≤ 5.0 µm,
A surface-coated cutting tool that satisfies
(2) The composite nitride layer or the composite carbonitride layer according to (1), wherein the area ratio of crystal grains having the NaCl-type face-centered cubic structure is 95 area% or more. Surface coated cutting tools.
(3) Crystal grains having a crystal grain size d of 0.20 μm<d of each crystal grain having the NaCl-type face-centered cubic structure among the crystal grains constituting the composite nitride layer or the composite carbonitride layer , wherein crystal grains having an aspect ratio A of 2 to 20 are present in an area ratio of 30 area% or more with respect to the total area of the composite nitride layer or composite carbonitride layer (1) or (2) A surface-coated cutting tool as described.
(4) The normal to the {111} plane of the crystal grains having the NaCl-type face-centered cubic structure among the crystal grains constituting the composite nitride layer or the composite carbonitride layer and perpendicular to the tool substrate surface When the inclination angle number distribution is obtained by measuring the inclination angle formed by the direction of The surface-coated cutting tool according to any one of (1) to (3), wherein the total frequency is 45% or more of the total frequency in the inclination angle frequency distribution. ”
is.

The coated tool of the present invention has a hard coating layer with excellent chipping resistance, and exhibits excellent cutting performance over long-term use.

It is a schematic diagram of a longitudinal section (a cross section perpendicular to the surface of the tool substrate) of the hard coating layer of the present invention, where the crystal grain size d corresponds to 0.01 μm < d ≤ 0.20 μm corresponds to the fine grain structure, and 0.20 μm ≤ d corresponds to it. is described as a coarse-grained structure. The shape and dimensions of each tissue are not a sketch of the actual tissue.

The cutting tool of the present invention will be described in more detail below. In addition, in the description of the present specification and the scope of claims, when a numerical range is expressed using "-", the range includes the numerical values of the upper limit and the lower limit. The unit of the numerical value of the lower limit is the same as that of the numerical value of the upper limit.

Average layer thickness of hard coating layer:
The hard coating layer of the present invention is a composite nitride layer or composite carbonitride layer of Ti and Al represented by the composition formula: (Ti _(1-x) Al _x ) (C _y N _(1-y) ) At least include. This TiAlCN layer has high hardness and excellent wear resistance, and its effect is conspicuous especially when the average layer thickness is 2.0 to 20.0 μm. The reason for this is that if the average layer thickness is less than 2.0 μm, the layer thickness is too thin to ensure sufficient wear resistance over long-term use. Crystal grains in the layer tend to coarsen, and chipping tends to occur. More preferably, the average layer thickness is 4.0 to 12.0 μm.

Composition of the TiAlCN layer:
The TiAlCN layer of the present invention is represented by the above composition formula: (Ti _(1-x) Al _x ) (C _y N _(1-y) ), the average content ratio of Al to the total amount of Ti and Al x _avg and the average content ratio y _avg of C in the total amount of C and N (where x _avg and y _avg are both atomic ratios) are 0.60 ≤ x _avg ≤ 0.95 and 0.00 ≤ The composition is controlled to satisfy y _avg ≦0.05.
The reason for this is that if the average Al content x _avg is less than 0.60, the TiAlCN layer is inferior in oxidation resistance, so when subjected to high-speed intermittent cutting of alloy steel, etc., the wear resistance is not sufficient. . On the other hand, if the average Al content x _avg exceeds 0.95, the amount of precipitated hexagonal crystals, which are inferior in hardness, increases and the hardness decreases, resulting in a decrease in wear resistance.
In addition, the reason why the average content ratio y _avg of the C component contained in the TiAlCN layer is set to 0.00 ≤ y _avg ≤ 0.05 is that even if C is contained, if it is a small amount, the hardness can be improved. This is because if the average content is in the range of 0.05 or less, the hardness can be improved while maintaining the chipping resistance. It should be noted that even if the composite nitride layer or composite carbonitride layer (TiAlCN layer) of Ti and Al referred to here contains a small amount of unavoidable impurities such as O and Cl, the effects of the invention described above are not impaired.

Here, the average content of Al in the TiAlCN layer x _avg is obtained by using Auger Electron Spectroscopy (AES), irradiating an electron beam from the longitudinal section side of a sample whose cross section is polished, and measuring the layer thickness direction. It is the average of the analysis results of Auger electrons obtained by five-line analysis. Further, the average content ratio y _avg of C can be obtained by secondary-ion-mass-spectroscopy (SIMS). That is, in a sample having a polished sample surface, an ion beam is irradiated in a range of 70 μm×70 μm from the surface side of the TiAlCN layer, and surface analysis by the ion beam and etching by the sputtered ion beam are alternately repeated, thereby increasing the depth direction. Concentration measurement is performed. First, the average of the data obtained by measuring a depth of at least 0.5 μm at a pitch of 0.1 μm or less from a portion intruded 0.5 μm or more in the depth direction of the TiAlCN layer is obtained. Furthermore, the results of repeated calculations at at least five points on the sample surface are averaged to determine the average C content _yavg .

Area ratio of crystal grains having a NaCl-type face-centered cubic structure in the TiAlCN layer:
It is necessary for the TiAlCN layer to have crystal grains (sometimes referred to as cubic crystal grains) having a NaCl-type face-centered cubic crystal structure. is preferably at least 90 area % or more. As a result, the area ratio of crystal grains having a high-hardness NaCl type face-centered cubic crystal structure is increased, and the hardness is improved. Furthermore, this area ratio is more preferably 95 area % or more, and may be 100 area %.

Grain size and area ratio of crystal grains having a NaCl-type face-centered cubic structure in the upper layer side region obtained by bisected the TiAlCN layer in the layer thickness direction into an upper layer side and a lower layer side:
The crystal grain size d of each crystal grain having a NaCl-type face-centered cubic structure in the upper layer side region obtained by bisected the TiAlCN layer in the layer thickness direction into an upper layer side and a lower layer side is 0.01 μm < d ≤ 0 It is preferred that crystallites of 0.20 μm are present. The reason for this is that microcrystals exist between large crystal grains of 0.20 μm<d, and if the crystal grain size of the microcrystals is 0.01 μm or less, the grain size is too small, and more than 0.20 μm. This is because the crystal grains become larger and the grain boundaries are reduced, so that the chipping resistance is not improved.
Further, the area ratio of the microcrystals is preferably 10 to 40 area % in the upper layer side region of the TiAlCN layer. The reason for this is that if it is less than 10 area%, the number of microcrystals decreases and crack propagation is not sufficiently inhibited. This is because there is no improvement in performance.

Crystal grains having a NaCl-type face-centered cubic structure in the upper layer side region obtained by bisected the TiAlCN layer in the layer thickness direction into an upper layer side and a lower layer side have a grain size d of 0.01 µm < d ≤ 0.20 µm. The average value L (dsum) of the maximum length L in the direction parallel to the tool base surface of each region where the crystal grains are adjacent and connected:
Crystal grains having a crystal grain size d of 0.01 µm < d ≤ 0.20 µm in the upper layer side region obtained by bisected the TiAlCN layer in the layer thickness direction into upper layer side and lower layer side are adjacent to each other and connected. The average value L (dsum) of the maximum length L in the direction parallel to the tool base surface of each region (region formed only by crystal grains with a grain size d of 0.01 μm < d ≤ 0.20 μm) is It is preferable to satisfy 0.2 μm≦L(dsum)≦5.0 μm. The reason for this is that when L (dsum) exceeds 5.0 μm, fine crystal grains exist in layers in a direction parallel to the surface of the tool substrate, and improvement in chipping resistance cannot be expected, and L (dsum) is less than 0.2 μm, the aggregation of fine crystal grains is small or few, and improvement in chipping resistance cannot be expected. The maximum length L in each region is the maximum length connecting two different points on the grain boundaries of the crystal grains defining the region.

Here, the crystal grain size, area ratio and maximum length L of crystal grains having a face-centered cubic crystal structure of NaCl type are measured as follows. In the vertical cross section of the upper layer side region that bisects the TiAlCN layer in the layer thickness direction into the upper layer side and the lower layer side, 100 μm in the direction parallel to the tool substrate surface and the length that bisects the average layer thickness in the layer thickness direction The range of height shall be the measurement range. This measurement range was polished, and an electron beam backscatter diffraction imaging apparatus was used to irradiate the polished surface with an electron beam at an incident angle of 70 degrees, an acceleration voltage of 15 kV, an irradiation current of 1 nA, and an electron beam at intervals of 0.01 μm. The crystal structure of each crystal grain having a NaCl-type face-centered cubic crystal structure is analyzed based on the electron beam backscatter diffraction image obtained by irradiation. That is, when there is an orientation difference of 5 degrees or more between adjacent measurement points (pixels), it is defined as a grain boundary, and 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 respect to all adjacent pixels is not treated as a crystal grain, but a crystal grain in which two or more pixels are connected is treated as a crystal grain. Grain size is defined as the diameter of a circle having the same area as the defined grain. The area ratio is defined as the ratio of the sum of the areas of the crystal grains to the area of the measurement range. Furthermore, in the measurement range, each region where crystal grains having a grain size d of 0.01 μm < d ≤ 0.20 μm are adjacent and connected is specified, and the maximum length L is obtained in each region. An average value L (dsum) is calculated.

Area ratio of crystal grains having an aspect ratio A of 2 to 20 for crystal grains having a NaCl-type face-centered cubic structure and a grain size d of 0.20 μm<d in the TiAlCN layer:
Regarding crystal grains having a NaCl-type face-centered cubic structure and having a crystal grain size of 0.20 μm<d, when the longitudinal section of the layer is observed, crystal grains having an aspect ratio A of 2 to 20 are found. It is preferably present in an area ratio of 30 to 90 area % with respect to the total area of the composite nitride layer or composite carbonitride layer. The reason why this numerical range is set is that the wear resistance and chipping resistance of the layer can be improved by the crystal grains having an appropriate aspect ratio A and area ratio. That is, when the area ratio of crystal grains having an aspect ratio A of less than 2 is large, or when the area ratio is lower than 30% even if the aspect ratio A is within the range, a sufficient columnar structure is not formed, Equiaxed crystals with a small aspect ratio fall off, and as a result, a sufficient wear resistance improvement effect cannot be exhibited. This is because the grains themselves cannot maintain their strength, and the chipping resistance cannot be sufficiently improved. Further, even if the aspect ratio A is within the above range, if the area ratio is too high, the toughness of the TiAlCN layer itself is improved, but the resistance to peeling from the substrate is reduced, resulting in the effect of improving chipping resistance. This is because

In addition, the aspect ratio A is obtained by observing a vertical cross section of the hard coating layer with a scanning electron microscope in a range where the width is 100 μm and the height includes the entire hard coating layer. , the particle width w in the direction parallel to the substrate surface and the particle length l in the direction perpendicular to the substrate surface are measured and calculated as A=l/w.

Frequency distribution of the inclination angle between the normal to the {111} plane, which is the crystal plane of the crystal grains having the NaCl-type face-centered cubic structure in the TiAlCN layer, and the direction perpendicular to the tool substrate surface:
The tilt angle formed by the normal to the {111} plane, which is the crystal plane of the crystal grains having the NaCl-type face-centered cubic structure in the TiAlCN layer, and the direction perpendicular to the tool substrate surface is measured, and the measured tilt angle is Among them, the measured tilt angles within the range of 0 to 45 degrees with respect to the normal direction are divided into every 0.25 degree pitch, and the frequencies existing in each division are aggregated to obtain the tilt angle number distribution. When there is a maximum peak in the tilt angle section within the range of 0 to 12 degrees, and the sum of the frequencies existing within the range of 0 to 12 degrees is 45 to 90 of the total frequencies in the tilt angle distribution. %. The reason for this is that within this range, the orientation of the crystal grains aligns in the same direction within a certain range, which improves the strength of the grain boundaries, resulting in improved wear resistance and chipping resistance. be. That is, if it is less than 45%, wear resistance is not improved, and if it exceeds 90%, improvement in chipping resistance cannot be expected, and as a result, the effect of improving cutting performance cannot be exhibited.

Here, the inclination angle distribution is obtained as follows.
First, with the longitudinal section (the section perpendicular to the surface of the tool substrate) of the hard coating layer containing the composite nitride layer or composite carbonitride layer of Ti and Al having a face-centered cubic structure of NaCl type as a polishing surface, Set in the lens barrel of a field emission scanning electron microscope. On the polished surface (cross-sectional polished surface), the measurement range is a length of 100 μm in the horizontal direction to the tool substrate surface and a length equivalent to the layer thickness in the direction perpendicular to the tool substrate surface. An electron beam having an incident angle of 70 degrees and an acceleration voltage of 15 kV was applied to the polished surface of the measurement range with an irradiation current of 1 nA, and each crystal grain having a NaCl-type face-centered cubic structure existing within the measurement range of the cross-sectional polished surface. Based on the electron beam backscatter diffraction image obtained by irradiating at an interval of 0.01 μm/step, the crystal plane of the crystal grain with respect to the normal line of the substrate surface (the direction perpendicular to the substrate surface in the cross-sectional polished surface) is measured at each measurement point (point irradiated with the electron beam).

Then, based on the measurement results, the tilt angles within the range of 0 to 45 degrees are classified into pitches of 0.25 degrees, and the frequencies present in each division are counted. Then, the inclination angle number distribution is obtained. From the obtained tilt angle frequency distribution, confirm the presence or absence of the highest peak of the frequency existing within the range of 0 to 12 degrees, and the frequency existing within the range of 0 to 45 degrees (entire frequency in the tilt angle frequency distribution) Find the ratio of frequencies that exist within the range of 0 to 12 degrees for . In addition, in the inclination angle distribution graph, it is more preferable that the total number of frequencies existing within the range of 0 to 12 degrees is 50% or more of all the frequencies in the inclination angle number distribution.
In determining the distribution of the number of tilt angles, in the case of ideal random orientation, the number of tilt angles should be a constant value regardless of the tilt angle formed by the normal direction of a certain crystal plane with respect to the normal direction of the tool substrate surface. is standardized to

Other layers:
As a hard coating layer, the TiAlCN layer of the present invention has sufficient chipping resistance and wear resistance. and/or at least an aluminum oxide layer when a lower layer comprising a Ti compound layer having a total average layer thickness of 0.1 to 20.5 μm is provided adjacent to the tool substrate is provided on the TiAlCN layer as an upper layer with a total average layer thickness of 1.0 to 25.5 μm, combined with the effects of these layers, further excellent wear resistance properties and thermal stability.
Here, if the total average layer thickness of the lower layer is less than 0.1 μm, the effect of the lower layer is not sufficiently exhibited, while if it exceeds 20.5 μm, the crystal grains of the lower layer tend to coarsen, causing chipping. easier to do. When the total average layer thickness of the upper layer including the aluminum oxide layer is less than 1.0 μm, the effect of the upper layer is not sufficiently exhibited, while when it exceeds 25.5 μm, the crystal grains of the upper layer tend to coarsen. , chipping is more likely to occur.

Tool substrate:
As the tool substrate, any conventionally known substrate for this type of tool substrate can be used as long as it does not interfere with the achievement of the object of the present invention. For example, cemented carbide (WC-based cemented carbide, containing Co in addition to WC, and further containing carbonitrides such as Ti, Ta, Nb, etc.), cermet (TiC, TiN, TiCN, etc. as a main component), ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), or cBN sintered body. Among these various base materials, it is particularly preferable to select WC-based cemented carbide, cermet (TiCN-based cermet), and cBN sintered body. The reason for this is that they have an excellent balance between hardness and strength at high temperatures and are excellent as tool substrates for cutting tools.

Deposition method (conditions):
The TiAlCN layer of the present invention is formed, for example, on a tool substrate or at least one layer of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer and carbonitride oxide layer on the tool substrate. , NH ₃ , N ₂ and H ₂ and a gas group B consisting of AlCl ₃ , TiCl ₄ , N ₂ , C ₂ H ₄ and H ₂ (reactive gas ( 1) and the reaction gas (2)) can be obtained by supplying each with a predetermined phase difference.
As an example of the gas composition of the reaction gas, the following reaction gas (1) and reaction gas (2) are used, where % is volume % (the sum of gas group A and gas group B is taken as a whole).

Reactive gas (1)
Gas group A: NH ₃ : 2.0 to 3.0%, N ₂ : 0.0 to 5.0%, H ₂ : 50 to 60%
Gas group B: AlCl ₃ : 0.60 to 1.00%, TiCl ₄ : 0.10 to 0.40%,
N ₂ : 2.0 to 10.0%, C ₂ H ₄ : 0.0 to 3.0%, H ₂ : residual Reaction atmosphere pressure: 4.5 to 5.0 kPa
Reaction atmosphere temperature: 650-850°C
Supply cycle: 4.00 to 30.00 seconds Gas supply time per cycle: 0.30 to 0.90 seconds Supply phase difference between gas group A and gas group B: 0.10 to 0.30 seconds

reaction gas (2)
Gas group A: NH ₃ : 0.2-0.6%, N ₂ : 0.0-5.0%, H ₂ : 50-60%
Gas group B: AlCl ₃ : 0.06 to 0.20%, TiCl ₄ : 0.01 to 0.06%,
N ₂ : 2.0 to 10.0%, C ₂ H ₄ : 0.0 to 0.5%, H ₂ : residual Reaction atmosphere pressure: 4.5 to 5.0 kPa
Reaction atmosphere temperature: 650-850°C
Supply cycle: 4.00 to 30.00 seconds Gas supply time per cycle: 0.30 to 0.90 seconds Supply phase difference between gas group A and gas group B: 0.10 to 0.30 seconds Reactant gas Phase difference between (1) and reaction gas (2): 2.00 to 15.00 seconds

Next, examples will be described.
Here, as a specific example of the coated tool of the present invention, an insert cutting tool using a WC-based cemented carbide as a tool substrate will be described. It is the same when it is used, and it is the same when it is applied to drills and end mills.

<Example 1>
As raw material powders, WC powder, TiC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, and Co powder, all having an average particle size of 1 to 3 μm, were prepared. After blending with the composition, wax is further added and mixed in a ball mill for 24 hours in acetone, dried under reduced pressure, and then pressed into a green compact of a predetermined shape at a pressure of 98 MPa. Vacuum sintering is performed at a predetermined temperature within the range of ~1470°C for 1 hour, and after sintering, WC-based cemented carbide tool substrates A to C having an insert shape of ISO standard SEEN1203AFSN are produced respectively. bottom.

Next, a TiAlCN layer was formed on the surfaces of these tool substrates A to C by CVD using a CVD apparatus to obtain coated tools 1 to 11 of the present invention shown in Table 6.
The film-forming conditions are as described in Tables 2 and 3, and are roughly as follows. % of the gas composition is volume % (the sum of gas group A and gas group B is taken as a whole).
Reactive gas (1)
Gas group A: NH ₃ : 2.0 to 3.0%, N ₂ : 0.0 to 5.0%, H ₂ : 50 to 60%
Gas group B: AlCl ₃ : 0.60 to 1.00%, TiCl ₄ : 0.10 to 0.40%,
N ₂ : 2.0 to 10.0%, C ₂ H ₄ : 0.0 to 3.0%, H ₂ : residual Reaction atmosphere pressure: 4.5 to 5.0 kPa
Reaction atmosphere temperature: 650-850°C
Supply cycle: 4.00 to 30.00 seconds Gas supply time per cycle: 0.30 to 0.90 seconds Supply phase difference between gas group A and gas group B: 0.10 to 0.30 seconds

reaction gas (2)
Gas group A: NH ₃ : 0.2-0.6%, N ₂ : 0.0-5.0%, H ₂ : 50-60%
Gas group B: AlCl ₃ : 0.06 to 0.20%, TiCl ₄ : 0.01 to 0.06%,
N ₂ : 2.0 to 10.0%, C ₂ H ₄ : 0.0 to 0.5%, H ₂ : residual Reaction atmosphere pressure: 4.5 to 5.0 kPa
Reaction atmosphere temperature: 650-850°C
Supply cycle: 4.00 to 30.00 seconds Gas supply time per cycle: 0.30 to 0.90 seconds Supply phase difference between gas group A and gas group B: 0.10 to 0.30 seconds Reactant gas Phase difference between (1) and reaction gas (2): 2.00 to 15.00 seconds. A layer and/or top layer was formed.

For the purpose of comparison, the surfaces of the tool substrates A to C were subjected to CVD under the conditions shown in Tables 2 and 3 to vapor-deposit a hard coating layer containing the TiAlCN layer shown in Table 6 to form a comparative coating. Tools 1-11 were produced.
For the comparative coated tools 4 to 11, the lower layer and/or the upper layer shown in Table 5 were formed under the forming conditions shown in Table 4.

Further, the average content of Al x _avg and the average content of N y _avg were obtained for the hard coating layers of the coated tools 1 to 11 of the present invention and the comparative coated tools 1 to 11 by the method described above. In the area ratio of crystal grains with a NaCl-type face-centered cubic structure, the area ratio of crystal grains with an aspect ratio A of 2 to 20, and the distribution of the number of inclination angles formed by the normal to the {111} plane, the inclination The ratio of the angles existing within the range of 0 to 12 degrees was obtained. In addition, in the upper layer side region of the TiAlCN layer, the average value of the area ratio occupied by crystal grains of the NaCl type face-centered cubic structure of 0.01 μm < d ≤ 0.20 μm, and the maximum length L in the direction parallel to the tool substrate surface L(dsum) was obtained. These results are summarized in Table 6.

The average layer thickness was obtained by examining the vertical cross section (the cross section in the direction perpendicular to the surface of the tool substrate) of each constituent layer of the coated tools 1 to 11 of the present invention and the comparative coated tools 1 to 11 using a scanning electron microscope. Select a magnification (for example, 5000 times magnification) and observe, measure and average the layer thickness at five points in the observation field, and determine the upper layer from the surface of the TiAlCN layer to half the length of the average layer thickness. side area.

Subsequently, each of the coated tools 1 to 11 of the present invention and the comparative coated tools 1 to 11 was clamped to the tip of a tool steel cutter having a cutter diameter of 100 mm with a fixing jig, and the alloy steel shown below was used. Dry high-speed face milling and center-cut machining tests were carried out, and the flank wear width of the cutting edge was measured. Table 7 shows the results of the cutting test. The comparison coated tools 1 to 11 reached the end of their lives due to the occurrence of chipping, so the time until the end of their lives is shown.

Cutting test 1: Dry high-speed face milling, center cut cutting test Cutter diameter: 100 mm
Work material: JIS/SCM440 block material with a width of 80 mm and a length of 400 mm Rotational speed: 1114 min ^-1
Cutting speed: 350m/min
Notch: 3.0mm
Feed: 0.3 mm/blade Cutting time: 8 minutes (normal cutting speed is 200 m/min)

<Example 2>
As raw material powders, WC powder, TiC powder, ZrC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder and Co powder, all having an average particle size of 1 to 3 μm, were prepared. The composition shown in Table 8 was blended, wax was further added, ball mill mixing was performed in acetone for 24 hours, and drying was performed under reduced pressure. After that, it was press-molded into a green compact of a predetermined shape at a pressure of 98 MPa, and the green compact was vacuum sintered under the condition of holding 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 edges were honed with a radius of curvature of 0.07 mm to produce WC-based cemented carbide tool substrates α to γ each having an insert shape conforming to ISO standard CNMG120412.

Next, on the surfaces of these tool substrates α to γ, a TiAlCN layer was formed using a CVD apparatus under the conditions shown in Tables 2 and 3 in the same manner as in Example 1. Invention coated tools 12-22 were obtained.
For the coated tools 15 to 20 and 22 of the present invention, the lower layer and/or the upper layer shown in Table 9 were formed under the film forming conditions shown in Table 4.

In the same manner as in Example 1, for the purpose of comparison, a hard coating containing a TiAlCN layer shown in Table 10 was applied to the surfaces of tool substrates α to γ by using the CVD method under the conditions shown in Tables 2 and 3. The layers were deposited to produce comparative coated tools 12-22.
For the comparative coated tools 15 to 20 and 22, the lower layer and/or the upper layer shown in Table 9 were formed under the forming conditions shown in Table 4.

Further, in the same manner as in Example 1, the average Al content x _avg and the average N content of the hard coating layers of the coated tools 12 to 22 of the present invention and the comparative coated tools 12 to 22 were evaluated using the methods described above. _yavg was determined. In the area ratio of crystal grains with a NaCl-type face-centered cubic structure, the area ratio of crystal grains with an aspect ratio A of 2 to 20, and the distribution of the number of inclination angles formed by the normal to the {111} plane, the inclination The ratio of the angles existing within the range of 0 to 12 degrees was obtained. In addition, in the upper layer side region of the TiAlCN layer, the area ratio occupied by the crystal grains of the NaCl type face-centered cubic structure of 0.01 μm < d ≤ 0.20 μm, the average of the maximum length L in the direction parallel to the tool substrate surface A value L(dsum) was determined. These results are summarized in Table 10.
Note that the average layer thickness and the region on the upper layer side were the same as in Example 1.

Next, the coated tools 12 to 22 of the present invention and the comparative coated tools 12 to 22 are shown below with each of the various coated tools screwed to the tip of the tool steel cutting tool with a fixing jig. A dry interrupted cutting test was performed to measure the flank wear width of the cutting edge. The results are shown in Table 11. The comparison coated tools 12 to 22 reached the end of their lives due to the occurrence of chipping, so the time until the end of their lives is shown.

Cutting test: Dry high-speed interrupted cutting Work material: JIS FCD600 Round bar with 8 equally spaced longitudinal grooves Cutting speed: 300m/min
Notch: 3.0mm
Feed: 0.3mm/rev
Cutting time: 5 minutes (normal cutting speed is 200m/min)

From the results shown in Tables 7 and 11, the coated tools 1 to 22 of the present invention are all suitable for high-speed interrupted cutting of cast iron, alloy steel, etc., because the hard coating layer has excellent chipping resistance. It exhibits excellent wear resistance over a long period of time without chipping even when worn. On the other hand, the comparative coated tools 1 to 22, which did not satisfy even one of the items specified for the coated tool of the present invention, caused chipping when used for high-speed interrupted cutting of cast iron, alloy steel, etc. , the service life is reached in a short time.

As described above, the coated tool of the present invention can be used as a coated tool for high-speed interrupted cutting of materials other than cast iron and alloy steel, and exhibits excellent wear resistance over a long period of time. It is possible to fully satisfy the improvement of the performance of the cutting process, the labor saving and energy saving of the cutting process, and the cost reduction.

Claims (4)

In a surface-coated cutting tool having a hard coating layer on the surface of the tool substrate,
(a) the hard coating layer includes at least a composite nitride layer or composite carbonitride layer of Ti and Al with an average layer thickness of 2.0 to 20.0 μm,
(b) When the composite nitride layer or composite carbonitride layer is represented by the composition formula: (Ti _(1-x) Al _x ) (C _y N _(1-y) ), the combination of Ti and Al of Al The average content ratio x _avg in the amount and the average content ratio y _avg of C in the total amount of C and N (where x _avg and y _avg are both atomic ratios) are respectively 0.60 ≤ x _avg ≤ 0 .95, satisfying 0.00≦y _avg ≦0.05,
(c) The composite nitride layer or composite carbonitride layer has an area occupied by crystal grains having a NaCl-type face-centered cubic structure of the composite nitride or composite carbonitride layer when the longitudinal section of the layer is observed. The ratio satisfies 90 area% or more,
(d) Further, in the upper layer side region obtained by bisected the composite nitride layer or the composite carbonitride layer into an upper layer side and a lower layer side in the layer thickness direction, crystal grains having the NaCl type face-centered cubic structure When the individual crystal grain size d is obtained, the crystal grains with the crystal grain size d of 0.01 μm<d≦0.20 μm are included in the total area of the composite nitride layer or composite carbonitride layer in the upper layer side region. Exists in an area ratio of 10 to 40 area%,
(e) In addition, in the bisected upper layer side, crystal grains having a crystal grain size d of 0.01 μm < d ≤ 0.20 μm of each crystal grain having a face-centered cubic structure of the NaCl type are separated from each other. The average value L (dsum) of the maximum length L in the direction parallel to the tool base surface of each adjacent and connected region is L (dsum) ≤ 5.0 µm,
A surface-coated cutting tool that satisfies The surface coating cutting according to claim 1, wherein the composite nitride layer or the composite carbonitride layer has an area ratio of 95 area% or more of the crystal grains having the NaCl type face-centered cubic structure. tool. Among the crystal grains constituting the composite nitride layer or the composite carbonitride layer, the aspect ratio of the crystal grains having a crystal grain size d of 0.20 μm<d of each crystal grain having the NaCl type face-centered cubic structure 3. The surface coating cutting according to claim 1 or 2, wherein crystal grains having A of 2 to 20 are present in an area ratio of 30 area % or more with respect to the total area of the composite nitride layer or composite carbonitride layer. tool. normal to the {111} plane of the crystal grains having the NaCl-type face-centered cubic structure among the crystal grains constituting the composite nitride layer or the composite carbonitride layer and the direction perpendicular to the tool substrate surface; When the inclination angle number distribution is obtained by measuring the inclination angle formed by the The surface-coated cutting tool according to any one of claims 1 to 3, wherein is 45% or more of all frequencies in the inclination angle frequency distribution.

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