JP2022138563A - Surface-coated machining tool - Google Patents

Abstract

To provide a surface-coated machining tool which is excellent in wear resistance, exerts high defect resistance and is suitable for milling in particular.SOLUTION: The surface-coated machining tool is provided which comprises, on a surface of a tool substrate made of tungsten carbide- based cemented carbide alloy, a lower layer having an average layer thickness of 0.6-21.0 μm and made of Ti nitride or carbonitride and an upper layer having an average layer thickness of 0.5-20.0 μm and including a complex nitride layer made of Ai and Ti having a Nacl type face-centered cubic crystal structure or a complex carbonitride layer, wherein when residual stress of the tungsten carbide-based cemented carbide alloy on a flank face of a cutting blade of the tool substrate is defined as S1 and residual stress of the tool substrate on a rake face of the cutting blade is defined as S2: α)S1<S2, β)S1≤-200 MPa, γ)an absolute value of a difference between S1 and S2 is larger than 250.SELECTED DRAWING: Figure 1

Description

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

In the cutting of stainless steel and steel materials with residual fused surfaces, in particular, cutting tools coated with AlTiN by the CVD method exhibit high wear resistance in continuous high-speed cutting due to the hardness and oxidation resistance of the coating. It is known.
On the other hand, in unstable machining such as stainless steel with high toughness of the work material, welding surface machining where the depth of cut fluctuates, or rough machining that requires a high depth of cut with an emphasis on machining efficiency, a high film thickness is required. Due to the hardness, there is a problem that the particles fall off remarkably, and abnormal damage accompanied by chipping of the tool progresses, so that the original performance cannot be exhibited.

On the other hand, for example, in Patent Document 1, the hard coating layer formed on the substrate surface by chemical vapor deposition is composed of a composite nitride (TiAlN) layer of Ti and Al or a composite carbonitride (TiAlCN). , has a face-centered cubic structure of at least 90% by volume, and when subjected to X-ray diffraction, the orientation index TC (111) in the (111) plane is the maximum, and the value is at least 1.5 or more There is, and when the residual stress value of the composite nitride layer or composite carbonitride layer is in a residual compression state of 0 MPa or less and -5000 MPa or more, improvement in crack resistance and wear resistance as a tool is observed. It is
In deriving the orientation index TC (111) of the (111) plane, X-ray Measurements of diffraction peak intensities are used.

Further, in Patent Document 2, in a surface-coated cutting tool having a rake face and a flank face, and a boundary portion thereof forming a cutting edge, a film of NaCl having a specific composition is formed on the surface of a base material using a CVD method. Excellent wear resistance when the orientation index TC (111) in the (111) plane of the TiAlN layer of the type crystal structure shows the maximum value and the value satisfies 1.0 < TC (111) ≤ 4.0 It is described that a surface-coated cutting tool exhibiting excellent toughness and chipping resistance is obtained.
In deriving the orientation index TC (111) of the (111) plane, (111), (200), (220), (311), which are the preferred crystal growth orientations of the composite carbonitride of Ti and Al, and (222) crystal planes are measured values of X-ray diffraction peak intensity.

Japanese Patent Publication No. 2018-522748 JP 2017-124463 A

In recent years, there has been a strong demand for labor saving and energy saving in cutting, and along with this, cutting has become even faster and more efficient. Due to the accompanying abnormal damage, excellent chipping resistance is required, and furthermore, excellent wear resistance is required for long-term use.
In Patent Document 1 and Patent Document 2, in the coated tool, the crystal plane of the crystal grain of the Al and Ti composite carbonitride having a cubic crystal structure formed as a hard coating layer using a chemical vapor deposition method is set to (111 ) surface, a coated tool has been proposed that has both excellent chipping resistance and wear resistance.
However, simply by orienting the crystal planes of the crystal grains of the Al, Ti composite carbonitride of the NaCl-type crystal structure of a specific composition to the (111) plane and defining the orientation index within a specific range, the fracture resistance Although the resistance is improved, the wear resistance is lowered, so it is impossible to achieve both fracture resistance and wear resistance, and as a result, there is a problem that long-term use cannot be realized.

Therefore, the present invention aims to solve the above problems and provide a surface-coated cutting tool that exhibits excellent wear resistance without causing early wear damage even during long-term use, and also exhibits high chipping resistance. aim.

From the above-mentioned viewpoint, the present inventors have achieved both improvement and enhancement of chipping resistance and wear resistance of a coated tool formed by chemical vapor deposition with a hard coating layer composed of a composite carbonitride of Al and Ti. As a result of earnest research in order to achieve this, the following findings were obtained.

That is, the present inventors have found that in forming a lower layer of a hard coating layer made of CVD-AlTiN on a tungsten carbide-based cemented carbide substrate, for example, wet blasting or driving is applied to the cutting edge flank of the substrate. By performing pretreatment such as blasting, or by performing wet blasting or dry blasting as a post-treatment after forming the hard coating layer, or by performing both of them, the cutting edge flank and rake face of the substrate It has been found that by intentionally imparting appropriate values of residual stress to each of the above, a surface-coated cutting tool with excellent chipping resistance can be obtained without lowering wear resistance.

Specifically, the residual stress S1 on the cutting edge flank surface of the tungsten carbide-based cemented carbide substrate of the surface-coated tool is set to a value smaller than the residual stress S2 on the cutting edge rake surface (S1<S2), and at least -200 MPa. A residual stress below (S1 ≤ -200 MPa), that is, a residual compressive stress of 200 MPa or more is applied, and the residual stress S2 on the cutting edge rake surface of the base is set to a value larger than the residual stress S1 on the cutting edge flank surface (S1 <S2), and the absolute value of the difference between S1 and S2 is set to a value greater than 250, more preferably, the residual stress S1 on the cutting edge flank is -850 MPa or less (S1 ≤ -850 MPa), That is, while applying a residual compressive stress of 850 MPa or more, the residual stress S2 on the rake face of the cutting edge of the base is set to a value larger than the residual stress S1 (S1 < S2), and the absolute value of the difference between S1 and S2 is 500 or more. It was made based on the knowledge that by increasing the value, it is possible to obtain a surface-coated cutting tool that is excellent in chipping resistance without lowering wear resistance and is particularly suitable for milling (milling). .
Here, the residual stress S1 on the flank of the cutting edge is, for example, "-200 MPa", which means that the residual stress S1 is a residual compressive stress and the residual compressive stress value is 200 MPa. , "S1 ≤ -200 MPa" means that "the residual stress S1 is -200 MPa or less", that is, "the residual compressive stress S1 is 200 MPa or more". The same applies to the residual stress S2 on the rake face of the cutting edge.

The present invention was made based on the above findings,
"(1) A surface-coated cutting tool having a hard coating layer on the surface of a tool substrate made of a tungsten carbide-based cemented carbide,
(a) The hard coating layer has at least two layers, a lower layer in direct contact with the outermost surface of the tool substrate and an upper layer in direct contact with the lower layer, and the total average layer of the hard coating layer The thickness is 0.6 to 21.0 μm,
(b) the lower layer is made of Ti nitride or carbonitride and has an average layer thickness of 0.05 to 2.0 μm;
(c) the upper layer is a composite nitride layer of Al and Ti or a layer containing a composite carbonitride, and has an average layer thickness of 0.5 to 20.0 μm;
When represented by the composition formula: (Al _X Ti _1-X ) (C _Y N _1-Y ), Al accounts for the total amount of Ti and Al in the composite nitride layer or the composite carbonitride layer The average content ratio X _avg and the average content ratio Y _avg of C with respect to the total amount of C and N in the composite nitride or the composite carbonitride layer (wherein both X _avg and Y _avg are atomic ratios) , respectively satisfying 0.70 ≤ X _avg ≤ 0.90 and 0 ≤ Y _avg < 0.05, composed of a composite nitride layer or a composite carbonitride layer having a NaCl-type face-centered cubic crystal structure,
(d) When the residual stress of the tungsten carbide-based cemented carbide on the cutting edge flank of the surface-coated tool is S1 and the residual stress on the rake face is S2,
α) S1<S2
β) S1≤-200MPa
γ) Surface-coated cutting tools each satisfying that the absolute value of the difference between S1 and S2 is greater than 250.
(2) When performing X-ray diffraction in the upper layer, the diffraction line intensity value in the cubic crystal (200) plane with respect to the diffraction line intensity value in the cubic crystal (111) plane, I(111)/I(200) but,
The surface-coated cutting tool according to (1), which satisfies the relationship 1.0≦I(111)/I(200).
(3) When the residual stress S1 of the tungsten carbide-based cemented carbide on the cutting edge flank of the surface-coated tool and the residual stress S2 on the rake face are
α) S1<S2
β) S1≤-850MPa
γ) The surface-coated cutting tool according to (1) or (2), wherein the absolute value of the difference between S1 and S2 is greater than 500. ”
It is characterized by
In this specification, when "-" or "-" is used when indicating a numerical range, it means including the lower limit and the upper limit of the numerical range.
Next, the tool substrate and the hard coating layer of the coated tool of the present invention will be specifically described.

1. tool substrate;
A tungsten carbide-based cemented carbide is used as the tool substrate. In the present invention, a residual stress of −200 MPa or less, more preferably −850 MPa or less is applied to the cutting edge flank of the cemented carbide substrate, thereby increasing the adhesion with the hard coating layer and enabling continuous high-speed cutting. It can be used as a cutting tool having cutting performance excellent in chipping resistance and wear resistance in the interrupted cutting area as well as in the cutting area.
In addition, by setting the residual stress value on the cutting edge flank of the alloy substrate to −200 MPa or less, more preferably −850 MPa or less, it is possible to suppress the development of cracks during processing and exhibit high fracture resistance. can.
On the other hand, as with the flank face, the compressive residual stress on the rake face increases, and when the absolute value of the difference between the residual stress value on the flank face and the residual stress value on the rake face becomes 250 MPa or less, the effect of suppressing the occurrence of thermal cracks can be seen. However, when plastic deformation occurs after the middle stage of processing, the stress state mismatch between the coating and the substrate makes it easier for the coating to peel off. The value should be greater than 250 MPa, preferably greater than 500 MPa.
The residual stress can be applied to the tool substrate by wet blasting or dry blasting as a pretreatment before forming the hard coating layer described later or as a post-treatment after forming the hard coating layer described later.
When performing wet blasting or dry blasting as a pretreatment before forming the hard coating layer, setting the film forming temperature to a lower temperature than usual can suppress the relaxation of residual stress. The service life of the battery can be extended.
For example, residual stress is applied to the substrate by blasting. Before or after forming the hard coating layer, dry or wet blasting is applied to the tool surface using media using abrasive grains of alumina, silicon nitride, or zirconia. It is carried out by projection.
blasting conditions;
Abrasive grains: ₂ grains of ZrO, ₃ grains of Al ₂ O Abrasive grain shape: spherical and/or polygonal Abrasive grain size (particle diameter): 125-425 μm (spherical) / <125 μm (polygonal)
Blast pressure: 0.1-0.4MPa
Blast projection at 70-90° from the flank, projection time: 4-16 seconds

2. hard coating layer;
The hard coat layer comprises a lower layer and an upper layer, and as other layers, a top layer can be provided on the upper layer.
If the average layer thickness of the hard coating layer is less than 0.6 μm, sufficient adhesion, wear resistance, and chipping resistance cannot be ensured over a long period of use, so it is made 0.6 μm or more. On the other hand, if the average layer thickness exceeds 21.0 μm, peeling or chipping is likely to occur.

(a) lower layer;
<Average layer thickness>
The lower layer is made of Ti nitride or carbonitride and is provided directly above and in direct contact with the tool base. If the average layer thickness of the lower layer is less than 0.05 μm, sufficient adhesion cannot be obtained, so it is made 0.05 μm or more. On the other hand, if the thickness exceeds 2.0 μm, deformation of the obtained hard coating layer becomes remarkable, and peeling from the tool substrate is likely to occur at an early stage of cutting.

<Component composition>
The composition of the lower layer is not particularly limited as long as it is a nitride or _carbonitride of _Ti , so that it does not hinder the object of the present invention. In this case, the range of 0≤Z≤0.05 is preferable.
That is, if the Z content is more than 0.05, the hardness of the lower layer excessively increases, and peeling from the interface between the lower layer and the substrate tends to occur.

(b) upper layer <average layer thickness>
The upper layer is made of composite nitride or composite carbonitride of Ti and Al, and is provided directly above and in direct contact with the lower layer. If the average layer thickness of the upper layer is less than 0.5 μm, the hard layer in the entire coating is insufficient and wear resistance is poor, so the average layer thickness is made 0.5 μm or more. On the other hand, if the average layer thickness exceeds 20.0 μm, the layer thickness of the hard layer becomes excessive, and peeling and chipping are likely to occur during processing.

<Component composition>
The upper layer is composed of a composite nitride layer (AlTiN layer) of Al and Ti or a composite carbonitride layer (AlTiCN layer), and exhibits uniform wear resistance and toughness throughout the layer. The high-temperature strength is improved by the Al component, and the high-temperature hardness and heat resistance are complemented by the Al component. Therefore, even under high-temperature cutting conditions, a low wear coefficient is maintained and excellent heat resistance can be exhibited.
Specifically, the composite nitride or composite carbonitride constituting the composite nitride layer or composite carbonitride layer of Al and Ti has a composition formula: (Al _X Ti _1-X ) (C _Y N _{1- Y} ), but when the value of the average Al content X _avg (atomic ratio) is less than 0.70, the high-temperature hardness becomes insufficient and wear resistance decreases. When the value of _avg (atomic ratio) exceeds 0.90, the high-temperature strength of the (Al _x Ti _1-x )(C _Y N _1-y ) layer itself decreases due to the decrease in the relative Ti content, Since chipping and chipping are likely to occur, the value of the average content of Al X _avg (atomic ratio) is defined in the range of 0.70 or more and 0.90 or less, which is close to the maximum hardness and obtains a particularly high effect. did.
In addition, although the C component has the effect of improving hardness, if the average content ratio Y _avg (atomic ratio) of the C component is 0.05 or more, the high-temperature strength decreases. _avg (atomic ratio) was defined as 0≦Y _avg <0.05.

<Crystal Orientation>
Al and Ti composite nitrides or composite carbonitrides (Al _X Ti _1-X ) (C YN _{1-Y )} constituting the upper layer have a NaCl-type face-centered cubic structure (hereinafter simply “cubic Hardness can be improved by adopting a "crystal structure".
That is, by forming a composite nitride layer or a composite carbonitride layer of Al and Ti having high orientation in the (111) plane of the cubic crystal structure, it is possible to increase the hardness.
Further, the ratio I(111)/I(200) of the diffraction line intensity value I(111) of the (111) plane to the diffraction line intensity value I(200) of the (200) plane in the upper layer is 1.0 or more. It is desirable that I(111)/I(200)≧1.0 because the crystal grains are less likely to come off during working.

(c) top layer
In the present invention, on the AlTi composite nitride layer or the AlTi composite carbonitride layer, which is the upper layer, from the viewpoint of improving wear resistance and responding to a wider range of processing applications, if necessary, A top layer may be provided.
Specifically, a layer made of Al oxide such as α-Al ₂ O ₃ and κ-Al ₂ O ₃ , a Ti nitride layer or a carbonitride layer, etc. are provided within a range of 4.5 μm or less. be able to.

3. A method for forming a hard coating layer;
(a) Method for imparting residual stress to tool substrate Residual stress can be imparted to the tool substrate by blasting (wet blasting or dry blasting) as a pretreatment before forming the hard coating layer described later, or for removing the hard coating layer. It can be performed as a post-treatment after film formation.
When the blasting treatment is performed as a pretreatment before forming the hard coating layer described later, the film formation temperature is set to be lower than the conventional treatment temperature, so that residual tensile stress in the hard coating layer can be suppressed. , the life of the cutting tool can be extended.

(b) Film formation method for lower layer
The lower layer of the hard coating layer is a compound layer composed of Ti and nitrogen, or a compound layer composed of Ti, nitrogen and carbon. By adjusting the reaction gas composition (gas group A) and the reaction atmosphere such as pressure and temperature within appropriate ranges, a TiN layer or a TiCN layer with excellent adhesion can be formed.
[Deposition conditions]
1) TiN layer;
Processing method: Film formation using CVD Reaction gas composition (% by volume)
TiCl ₄ : 3.0-6.0%, N ₂ : 25.0-35.0%, H ₂ : remainder,
Reaction atmosphere pressure: 4.0 to 12.0 kPa,
Reaction atmosphere temperature: 780-900°C
2) TiCN layer;
Processing method: Film formation using CVD Reaction gas composition (% by volume)
_TiCl4 : 3.0-6.0%, _N2 : 15.0-30.0%,
CH ₄ or CH ₃ CN: 0.6-2.0%, H ₂ : remainder,
Reaction atmosphere pressure: 7.0 to 12.0 kPa,
Reaction atmosphere temperature: 780-900°C

(c) Method of depositing upper layer <Deposition of upper layer>
Next, in the method for forming the upper layer according to the present invention, the conditions for forming the AlTi composite nitride layer or the AlTi composite carbonitride layer are set, for example, by using two types of NH ₃ gas with different heating temperatures, Coarse grains can be obtained by suppressing nucleation with gas and promoting crystallization.
That is, the method for forming an AlTiN layer or an AlTiCN layer according to the present invention includes the second step (initial nucleation step), that is, forming AlTiN crystals or AlTiCN crystals as initial nuclei for forming an AlTiN film or an AlTiCN film. and the third step (crystal growth step), that is, the step of growing the AlTiN crystal or AlTiCN crystal, which is the initial nucleus, to form an AlTiN film or AlTiCN film. membrane.
An outline of the film formation conditions in each film formation step is shown below. In particular, in the step of forming initial nuclei of fine AlTiN crystals or AlTiCN crystals in the second step, the following gas group B and gas group C are used. When forming a film by alternately supplying to the reactor with a phase difference, by using ammonia gas preheated at a high temperature (for example, 300 to 450 ° C.), nucleation is promoted and subsequently performed. In the 3 steps, the following gas group D and gas group E are alternately supplied to the reactor with a phase difference, and the ammonia gas used is preheated at a low temperature (for example, 50 to 250 ° C.). By changing to the ammonia gas that has been dehydrated, it is possible to suppress nucleation and promote crystallization, thereby obtaining desired crystals.
The number of repetitions of the second step and the third step is adjusted according to the target film thickness.

[Deposition conditions]
1) Second step (initial nucleation step)
Processing method: Film formation using CVD method Reaction gas composition (% by volume):
Gas group B: TiCl ₄ : 0.01 to 0.04%, AlCl ₃ : 0.01 to 0.05%,
N ₂ : 0 to 10%, C ₂ H ₄ : 0 to 0.5%, H ₂ : remaining gas group C: NH ₃ : 0.1 to 0.8%, H ₂ : 25.0 to 35.0 %,
Reaction atmosphere pressure: 4.0 to 5.0 kPa,
Reaction atmosphere temperature: 700-850°C
Supply cycle: 1 to 5 seconds,
Gas supply time per cycle: 0.15 to 0.25 seconds,
Phase difference between supply of gas group B and supply of gas group C: 0.10 to 0.20 seconds Preheating temperature of gas group C: 300 to 450°C

2) Third step (crystal growth step)
Processing method: Film formation using CVD method Reaction gas composition (% by volume):
Gas group D: TiCl ₄ : 0.01 to 0.04%, AlCl ₃ : 0.01 to 0.05%,
N ₂ : 0-10%, C ₂ H ₄ : 0-0.5%, H ₂ : balance,
Gas group E: NH ₃ : 0.1 to 0.8%, H ₂ : 25.0 to 35.0%,
Reaction atmosphere pressure: 4.0 to 5.0 kPa,
Reaction atmosphere temperature: 700-850°C
Supply cycle: 1 to 5 seconds,
Gas supply time per cycle: 0.15 to 0.25 seconds,
Phase difference between supply of gas group D and supply of gas group E: 0.10 to 0.20 seconds Preheating temperature of gas group E: 50 to 250°C
Note that the volume % of each gas component in the reaction gas composition (% by volume) in each of the second step and the third step is determined by taking the total of gas group B and gas group C as 100% by volume in the second step. The calculated volume % of each component is shown, and in the third step, the volume % of each component is shown assuming that the total of gas group D and gas group E is 100 volume %.

The surface-coated cutting tool according to the present invention maintains the wear resistance of the hard coating layer during cutting by applying a predetermined range of residual stress to each of the flank and rake face of the tool substrate, and has an anti-peeling effect. and suppress the progress of cracks, exhibit fracture resistance and chipping resistance, and improve the tool life.
In particular, in milling, thermal cracks generated from the rake face of the tool during processing propagate to the flank face side, causing chipping of the cutting edge, so the residual stress on the flank face is reduced to -200 MPa or less, that is, , a remarkable effect of suppressing crack growth is exhibited by placing it under high compressive residual stress.
On the other hand, as with the flank face, the compressive residual stress on the rake face increases, and when the absolute value of the difference between the residual stress value on the flank face and the residual stress value on the rake face becomes 250 MPa or less, the effect of suppressing the occurrence of thermal cracks can be seen. However, when plastic deformation occurs after the middle stage of processing, the stress state mismatch between the coating and the substrate makes it easier for the coating to peel off. The value should be greater than 250 MPa.

Cross section showing the relationship between the tool substrate of the coated tool according to the present invention, the lower layer (Ti(C)N layer), the upper layer (CVD-AlTiN(C) layer), and the uppermost layer constituting the hard coating layer It is a schematic diagram. FIG. 2 shows a cross-sectional view of an H-shaped can-making member, which is a work material for the coated tool according to the present invention.

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

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 sintered at a predetermined temperature within the range of ~1470°C for 1 hour. After sintering, tool substrates A to C made of WC-based cemented carbide with an insert shape of ISO standard SEEN1203AFTN were produced respectively. did.

Then, each of these tool substrates A to C was loaded into a chemical vapor deposition apparatus, and the coated tools 1 to 8 of the present invention were produced according to the following procedure.
As described above, in the present invention, the tool substrates A to C are subjected to pretreatment before the formation of the hard coating layer and/or as post-treatment after the formation of the hard coating layer. It is assumed that blasting is performed at 100° C. and residual stresses are imparted to the rake face and flank face of the substrate (see Table 2).
Next, as a first step, any one of the tool substrates A to C is placed in a chemical vapor deposition apparatus, and under the temperature and pressure conditions described in the formation conditions (formation symbols) A to H shown in Table 3. , a gas group A (TiCl ₄ , N ₂ , CH ₄ , CH ₃ CN and the balance H ₂ ) having the composition shown in Table 3 is used to form a film for a certain period of time.

Regarding the coated tools 1 to 5 of the present invention, following the first step, as the second step (upper layer initial nucleus formation step), the gas described in the formation conditions (formation symbols) A to E shown in Table 4 Based on the gas compositions of group B and gas group C, supply conditions, and gas reaction conditions (pressure, temperature, process time (seconds)), film formation is performed for a certain period of time, and the third step (crystal growth step of the upper layer). , the gas composition, supply conditions, and gas reaction conditions (pressure, temperature, process time (seconds) of gas group D and gas group E described in formation conditions (formation symbols) A to E shown in Table 5. ), film formation was carried out for a certain period of time, and the coated tools 1 to 5 of the present invention shown in Table 7 were obtained.
In addition, for the coated tools 6 to 8 of the present invention, following the first step, the second step (upper layer initial nucleus formation step) was performed under the formation conditions (formation symbols) F to H shown in Table 4 above. After film formation, in the third step (crystal growth step of the upper layer), after film formation under the formation conditions (formation symbols) F to H shown in Table 5, further, as the top layer, κ-Al ₂ O ₃ layers, l-TiCN layers or α-Al ₂ O ₃ layers were formed under the conditions shown in Table 6 to obtain coated tools 6 to 8 of the present invention shown in Table 7.

For the purpose of comparison, films were formed under conditions a to e shown in Tables 3, 4 and 5 to obtain comparative coated tools 1 to 5.
Further, after film formation was performed under formation conditions f to h shown in Tables 3, 4 and 5, κ-Al ₂ O ₃ layer, l-TiCN layer or α-Al ₂ layer was formed as the uppermost layer, respectively. Comparative tools 6 to 8 shown in Table 8 were obtained by forming an O ₃ layer under the conditions shown in Table 6.

Table 7 shows the residual stress on the flank and rake face of the tool substrate of the coated tools 1 to 8 of the present invention, the target average total layer thickness of the hard coating layer, the target average layer thickness of the lower layer, the type of film formed, and the upper layer. Target average layer thickness, average Al content ratio (Xavg), average C content ratio (Yavg), crystal structure and diffraction line intensity ratio (I (111) / I (200)), target average layer thickness and formation of the uppermost layer shows the membrane.
Table 8 shows the residual stress on the flank and rake face of the tool substrate, the target average total layer thickness of the hard coating layer, the target average layer thickness of the lower layer, the type of film formed, and the type of formed film, for the coated tools 1 to 8 of Comparative Examples. Target average layer thickness of the layer, average Al content (Xavg), average C content (Yavg), crystal structure and diffraction line intensity ratio (I (111) / I (200)), target average layer thickness of the top layer similarly shown.

Here, the measurement of the thickness of the hard coating layer of the coated tools 1 to 8 of the present invention and the coated tools 1 to 8 of the comparative examples was performed using a scanning electron microscope (magnification: 5000).
That is, the tool base is polished so that the cross section in the direction perpendicular to the tool substrate is exposed, each layer is observed in a field of view of 5000 to 20000 times, and the average value of the layer thickness measured at 5 points in the observation field is the average layer thickness. As such, the coated tools 1 to 8 of the present invention are shown in Table 7, and the coated tools 1 to 8 of the comparative examples are shown in Table 8.
Further, the average Al content X _avg (atomic ratio) of AlTiN or AlTiCN in the upper layer and the average content Y _avg (atomic ratio) of the C component were measured using an electron probe microanalyser (EPMA, Electron-Probe-Micro-Analyser). ) was used to irradiate an electron beam from the surface side of a sample whose surface was polished, and the characteristic X-ray analysis results obtained were averaged from 10 points.
The values of X _avg and Y _avg are shown in Table 7 for inventive coated tools 1-8 and in Table 8 for comparative coated tools 1-8.

Further, the crystal structures of the AlTiN layer and the AlTiCN layer in the upper hard coating layer of the coated tool of the present invention and the coated tool of the comparative example were measured using an X-ray diffractometer using a Cu-Kα ray as a radiation source, and the measurement range (2θ) : 20 to 120 degrees, scan step: 0.013 degrees, measurement time per step: 0.48 sec/step, for example, on the hard coating layer surface parallel to the tool substrate surface, X-ray diffraction between the diffraction angles of the same crystal planes shown in JCPDS00-038-1420 cubic TiN and JCPDS00-046-1200 cubic AlN, respectively (for example, 36.66-38.53°, 43.59-44. 77°, 61.81 to 65.18°).
In addition, from the measured value I (hkl) of the X-ray diffraction peak intensity in the (200) plane and the (111) plane, the diffraction peak intensity I (200) of the (111) plane for the (200) plane A ratio of diffraction peak intensities I(111), I(111)/I(200), can be obtained.
Moreover, the residual stress of the tool substrate is measured using an X-ray diffractometer using Cuκα using the sin ² ψ method. For the measurement, the diffraction peak of the WC (211) plane is used, and calculation is performed using a Young's modulus of 534 GPa and a Poisson's ratio of 0.22.

Next, with the various coated tools clamped on the tip of the tool steel cutter with a fixing jig, the coated tools 1 to 8 of the present invention and the coated tools 1 to 8 of the comparative examples were welded as follows. The members were face-milled, and the maximum machining length up to tool breakage was evaluated. Table 9 shows the results.

≪Cutting conditions≫
Cutting test: Continuous wet face milling Work material: SS400 welding member
T1 = 30 mm, width 100 mm, length 400 mm H-type can manufacturing member Fig. 2
Rotation speed: 637 min ^-1 ,
Cutting speed: 250m/min. ,
Notch: 3.0mm,
Single blade feed amount: 0.2 mm/tooth,
Cutting time: Stopped when the cutting edge breaks or when the cutting length reaches 8 m.

As is clear from the cutting test results shown in Table 9, the coated tool of the present invention controls the residual compressive stress on the flank and rake face of the tungsten carbide-based cemented carbide substrate to an arbitrary value. The hard coating layer in direct contact with the substrate surface includes a Ti nitride layer or carbonitride layer as a lower layer, and an Al and Ti composite nitride layer or composite carbonitride layer having an NaCl-type face-centered cubic crystal structure as an upper layer. By providing the material layer, it is possible to avoid the occurrence of chipping or the like caused by falling off of fine crystal grains, and to exhibit excellent chipping resistance and wear resistance over a long period of time.

As described above, the surface-coated cutting tool of the present invention can be used not only for continuous cutting and intermittent cutting of ordinary steel grades, but also for intermittent cutting of stainless steel and other difficult-to-cut materials with fused surfaces. In addition to excellent wear resistance, fracture resistance and chipping resistance are also demonstrated in rough machining, which requires a high depth of cut with an emphasis on machining efficiency. This fully satisfies labor saving, energy saving, and cost reduction.

Claims (3)

A surface-coated cutting tool having a hard coating layer on the surface of a tool substrate made of a tungsten carbide-based cemented carbide,
(a) The hard coating layer has at least two layers, a lower layer in direct contact with the outermost surface of the tool substrate and an upper layer in direct contact with the lower layer, and the total average layer of the hard coating layer The thickness is 0.6 to 21.0 μm,
(b) the lower layer is made of Ti nitride or carbonitride and has an average layer thickness of 0.05 to 2.0 μm;
(c) the upper layer is a composite nitride layer of Al and Ti or a layer containing a composite carbonitride, and has an average layer thickness of 0.5 to 20.0 μm;
When represented by the composition formula: (Al _X Ti _1-X ) (C _Y N _1-Y ), Al accounts for the total amount of Ti and Al in the composite nitride layer or the composite carbonitride layer The average content ratio X _avg and the average content ratio Y _avg of C with respect to the total amount of C and N in the composite nitride or the composite carbonitride layer (wherein both X _avg and Y _avg are atomic ratios) , respectively satisfying 0.70 ≤ X _avg ≤ 0.90 and 0 ≤ Y _avg < 0.05, composed of a composite nitride layer or a composite carbonitride layer having a NaCl-type face-centered cubic crystal structure,
(d) When the residual stress of the tungsten carbide-based cemented carbide on the cutting edge flank of the surface-coated tool is S1 and the residual stress on the rake face is S2,
α) S1<S2
β) S1≤-200MPa
γ) A surface-coated cutting tool, wherein the absolute value of the difference between S1 and S2 is greater than 250. When X-ray diffraction is performed on the upper layer, the diffraction line intensity value in the cubic crystal (200) plane with respect to the diffraction line intensity value in the cubic crystal (111) plane, I(111)/I(200), is
2. The surface-coated cutting tool according to claim 1, which satisfies the relationship 1.0≤I(111)/I(200). (3) When the residual stress S1 of the tungsten carbide-based cemented carbide on the cutting edge flank of the surface-coated tool and the residual stress S2 on the rake face are
α) S1<S2
β) S1≤-850MPa
γ) The surface-coated cutting tool according to claim 1 or claim 2, wherein the absolute value of the difference between S1 and S2 is greater than 500, respectively.

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