JP7243013B2 - Surface-coated cutting tools with excellent fracture resistance - Google Patents

Description

TECHNICAL FIELD The present invention relates to a surface-coated cutting tool (hereinafter simply referred to as a "coated tool") that is particularly excellent in fracture resistance in the cutting of stainless steel, steel materials with fused surfaces, and the like.

In the cutting of stainless steel and steel materials with residual fused surfaces, in particular, cutting tools coated with AlTiN by the CVD method should exhibit high wear resistance in continuous high-speed cutting due to the hardness and oxidation resistance of the coating. However, on the other hand, in unstable machining such as stainless steel with high toughness of the work material and welding surface machining where the depth of cut fluctuates, the high hardness of the coating causes particles to fall off. There was a problem that the original performance could not be exhibited due to the progress of abnormal damage accompanied by chipping of the tool, which occurred remarkably.

On the other hand, a technique has been proposed in which a Ti-based adhesion layer having excellent adhesion is provided on the surface of the base material, and components of the base material or the surface of the base material are diffused into the adhesion layer to obtain high adhesion. .
For example, in Patent Document 1, by adjusting the diffusion amount of C and Co from the cemented carbide substrate side to the TiN layer side of the coating film and having a desired concentration gradient, it is possible to improve adhesion. Also, in Patent Document 2, the Co content in the titanium carbide coating, which is the first layer on the hard coating layer side from the WC-based cemented carbide substrate side, and the Cr content ratio to the Co content, It is described that the adhesion of the titanium carbide coating is improved by defining the thickness.
Further, in Patent Document 3, the adhesion between the WC cemented carbide substrate and the TiN layer coated on the surface thereof is improved by increasing the Cr concentration in the TiN layer coated on the surface of the WC cemented carbide substrate. is described.

Patent No. 6041160 Patent No. 5046196 Patent No. 6276288

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. Because of the accompanying abnormal damage, excellent chipping resistance is required.
Therefore, in Patent Documents 1 to 3, in coated tools, a Ti-based adhesion layer having excellent adhesion is formed on the tool substrate by diffusing the substrate component or the component of the substrate surface into the adhesion layer. , was proposed to avoid the occurrence of defects.
However, in these CVD-AlTiN films, although the effect of improving the adhesion by element diffusion is recognized, the diffusion of the elements excessively increases the hardness of the adhesion layer itself, resulting in a CVD-AlTiN film with high hardness during processing. There was a problem in that cracks generated from the surface propagated to the inside, causing chipping of the tool due to detachment of coating particles.

Accordingly, it is an object of the present invention to provide a surface-coated cutting tool that solves the above problems and prevents the development of abnormal damage accompanied by chipping of the tool even during long-term use, thereby exhibiting excellent chipping resistance. .

From the above-mentioned point of view, the present inventors have made extensive research to improve and improve the chipping resistance of coated tools formed by chemical vapor deposition with a hard coating layer composed of a composite nitride of Al and Ti. As a result, the following findings were obtained.

That is, the present inventors appropriately diffused the Cr component and the C component toward the surface side of the hard coating layer from the region in contact with the substrate in the lower layer of the hard coating layer made of CVD-AlTiN, so that the respective components , a concentration gradient distribution region, specifically, a region where the Cr component has a maximum concentration at different positions in order from the substrate surface of the lower layer of the hard coating layer toward the surface side of the hard coating layer, and , provide a region where the C component has the maximum concentration, obtain an adhesion layer composed of carbonitrides of Ti and Cr, control the crystal orientation and the residual stress of the film, and suppress an excessive increase in the hardness of the film. It was found that, as a result of preventing the internal propagation of cracks and reducing the shedding of particles, a film with excellent chipping resistance can be obtained.

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 containing Co and Cr as binder phase components,
(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 20.0 μm,
(b) the lower layer is made of Ti and Cr carbonitrides and has an average layer thickness of 0.2 to 1.6 μm;
(b-1) the lower layer, in a range from the outermost surface of the substrate to a layer thickness of 0.1 μm,
The Cr concentration value of the maximum Cr concentration region having the maximum Cr concentration value and having a Cr concentration of 90% or more of the maximum Cr concentration value is 1.2 times or more the total average Cr concentration of the lower layer and is 0.5 atomic % or more and 5.0 atomic % or less, and the region width of the maximum Cr concentration region is 0.02 μm or more, and
(b-2) The lower layer has a maximum C concentration value in a range from the outermost surface of the substrate to the boundary with the upper layer with a layer thickness exceeding 0.1 μm, and is 90% or more of the maximum C concentration value. The C concentration value of the maximum C concentration region having a C concentration of is 1.2 times or more the total average C concentration of the lower layer, and is 7.0 atomic % or more and 25.0 atomic % or less and the region width of the maximum C concentration region is 0.02 μm or more,
again,
(c) the upper layer is a layer containing a composite nitride or composite carbonitride of Al and Ti, and has an average layer thickness of 0.4 to 18.4 μm;
Composition formula: (Al _X Ti _1-X ) (C _Y N _1-Y ), the average content ratio of Al to the total amount of Ti and Al in the composite nitride or composite carbonitride layer X _avg and the average content ratio Y _avg of C to the total amount of C and N in the composite nitride or composite carbonitride layer (where X _avg and Y _avg are both atomic ratios) are respectively 0 .75 ≤ X _avg ≤ 0.90, 0 ≤ Y _avg < 0.05, and comprising a composite nitride or composite carbonitride layer having a NaCl-type face-centered cubic crystal structure. Cutting tools.
(2) When X-ray diffraction is performed on the lower layer composed of the carbonitrides of Ti and Cr, the orientation index TC (200 ) satisfies 0.5≦TC(200)≦4.5.
Formula (A) TC(200)=[I(200)/I ₀ (200)]
×[(1/n)×Σ(I(hkl)/I ₀ (hkl)] ⁻¹
however,
I (200); measured value of X-ray diffraction peak intensity in (200) plane I ₀ (200);
Average value of standard X-ray diffraction peak intensity Σ(I(hkl)/I ₀ (hkl)) on the (200) plane of the TiN crystal plane described in ICDD card 00-038-1420;
Each of the six planes (111), (200), (220), (311), (222), and (400) ([measured value of X-ray diffraction peak intensity] / [listed on ICDD card (3) In (1) or (2), the value of the film residual stress in the lower layer composed of the Ti and Cr carbonitrides is A surface-coated cutting tool characterized by satisfying -500 to 500 MPa.
(4) When X-ray diffraction is performed on the upper layer, the orientation index TC (111) in the cubic crystal (111) plane represented by the following formula (B) is 2.0 ≤ TC The surface-coated cutting tool according to any one of (1) to (3), wherein (111)≦4.0 is satisfied.
Formula (B) TC(111)=[I(111)/I ₀ (111)]
×[(1/6)×Σ(I(hkl)/I ₀ (hkl)] ⁻¹
however,
I (111); measured value of X-ray diffraction peak intensity in the (111) plane I ₀ (111);
Average value of standard X-ray diffraction peak intensity Σ(I(hkl)/I ₀ (hkl)) on the (111) plane of the AlN crystal plane described in ICDD card 00-046-1200;
Each of the six planes (111), (200), (220), (311), (222), and (400) ([measured value of X-ray diffraction peak intensity] / [listed on ICDD card (5) When X-ray diffraction is performed on the upper layer, the cubic crystal (200 ) of (1) to (4), wherein the value of diffraction line intensity on the plane, I (111) / I (200), satisfies the relationship of 0.9 ≤ I (111) / I (200) A surface-coated cutting tool according to any one of the preceding claims. ”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.

(a) Tool Substrate A tungsten carbide-based cemented carbide is used as the tool substrate. The present invention is characterized in that Cr and C each have a maximum content concentration in different regions of the hard coating layer. A hard coating layer having a desired concentration distribution can be formed by diffusing these components into the hard coating layer during film formation under specific conditions.

(b) Hard Coating Layer The hard coating layer comprises a lower layer and an upper layer, and as another layer, a top layer may be provided on the upper layer.
If the average layer thickness of the hard coating layer is less than 0.6 μm, sufficient adhesion and abrasion resistance cannot be ensured over a long period of use, so the average layer thickness is made 0.6 μm or more. On the other hand, if the average layer thickness exceeds 20.0 μm, peeling or defects are likely to occur.

(c) lower layer;
<Average layer thickness>
The lower layer is made of composite carbonitride of Ti and Cr, and is provided directly above and in direct contact with the tool substrate. If the average layer thickness of the lower layer is less than 0.2 μm, sufficient adhesion cannot be obtained, so the lower limit is made 0.2 μm or more. On the other hand, if the thickness exceeds 1.6 μm, deformation of the obtained film becomes remarkable, and peeling from the substrate tends to occur at an early stage of cutting, so the upper limit was made 1.6 μm or less.

<Component composition>
The lower layer has a Cr content relative to the total amount of all constituent elements of the lower layer in a range from the outermost surface of the substrate to a layer thickness of 0.1 μm (hereinafter also referred to as a “substrate-adjacent region” of the lower layer). The Cr concentration value of the maximum Cr concentration region having the maximum Cr concentration value and having a Cr concentration of 90% or more of the maximum Cr concentration value is 1.2 times or more the total average Cr concentration of the lower layer And, it is 0.5 atomic % or more and 5.0 atomic % or less, and the region width of the maximum Cr concentration region is defined as 0.02 μm or more.
Here, the reason why the Cr concentration value of the maximum Cr concentration region having a concentration of 90% or more of the maximum Cr concentration value is 1.2 times or more of the total average Cr concentration of the lower layer is that the Cr concentration value is , If it is less than 1.2 times, the Cr concentration gradient is insufficient and the effect of improving the grain boundary toughness at the interface of the lower layer with the substrate due to Cr diffusion is not sufficient, or the entire region close to the substrate of the lower layer This is because the decrease in hardness becomes significant, the difference in hardness from the upper layer increases, and separation between the layers tends to occur.
Further, the reason why the Cr concentration value of the maximum Cr concentration region is specified in the range of 0.5 atomic % or more and 5.0 atomic % or less is that when the Cr content is less than 0.5 atomic %, the lower layer due to Cr diffusion The effect of improving the grain boundary toughness at the interface with the substrate is not sufficient, and the film tends to peel off from the substrate. This is because the decrease in hardness at the interface with the substrate becomes significant, and the difference in hardness from the upper layer becomes large, making separation between the layers more likely to occur.
In addition, in the lower layer, in the range from the outermost surface of the substrate to the boundary with the upper layer beyond the layer thickness of 0.1 μm (hereinafter also referred to as the “upper region” of the lower layer), The maximum C concentration value of the C content with respect to the total amount of all constituent elements, and the concentration value of the maximum C concentration region having a C concentration of 90% or more of the maximum C concentration value is the total average C concentration of the lower layer 1.2 times or more and 7.0 atomic % or more and 25.0 atomic % or less, and the region width of the maximum C concentration region is defined as 0.02 μm or more.
Here, if the concentration value of the maximum C concentration region is less than 1.2 times the total average C concentration value of the lower layer, the C concentration gradient is insufficient and the diffusion of C from the substrate is insufficient. This is because sufficient and desired adhesion cannot be obtained, or the hardness of the entire lower layer increases significantly, and brittle fracture easily occurs in the layer.
The reason why the C content is specified in the range of 7.0 atomic % or more and 25.0 atomic % or less is that if C is less than 7.0 atomic %, diffusion of C from the base material is insufficient. The desired adhesion at the interface between the layer and the substrate is not obtained, and the film tends to peel off from the substrate. This is because the increase in hardness at the interface becomes excessive and brittle fracture easily occurs in the layer.
The reason why the width of each of the maximum concentration regions of Cr and C is specified to be 0.02 μm or more is that if the width is less than 0.02 μm, the width of the region is insufficient and the desired effect cannot be exhibited.

<Crystal structure>
The TiCr composite carbonitride constituting the lower layer can improve hardness by adopting a NaCl-type face-centered cubic structure (hereinafter also simply referred to as "cubic crystal structure").
By setting the orientation index TC (200) of the cubic crystal (200) plane of the lower layer to 0.5 or more, the diffusion of Cr is sufficiently promoted, resulting in a more uniform Cr diffusion state. The grain boundary toughness effect of the adhesion layer is improved, and on the other hand, by making it 4.5 or less, the segregation of Cr is suppressed and the internal fracture of the adhesion layer originating from the grain boundary is difficult to occur, so 0.5 ≤ It is desirable that TC(200)≦4.5.

<Film residual stress>
By setting the film residual stress value of the lower layer to -500 MPa or more, the peeling resistance effect during processing can be enhanced, and by setting it to 500 MPa or less, the growth of cracks generated from the outside of the film during processing can be suppressed. Since it has the effect of increasing the effect and improving the chipping resistance, it is preferably −500 to 500 MPa.

(d) 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 0.4 μm, the hard layer in the entire coating is insufficient and wear resistance is poor, so the average layer thickness is made 0.4 μm or more. On the other hand, if the average layer thickness exceeds 18.4 μm, the layer thickness of the hard layer becomes excessive, and sudden fracture tends 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). The high-temperature strength is improved by the component, and the high-temperature hardness and heat resistance are complemented by the Al component, so that even under high-temperature cutting conditions, a low wear coefficient can be 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 if the value of the average Al content X _avg (atomic ratio) is less than 0.75, 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 close to the maximum hardness and is specified in the range of 0.75 or more and 0.90 or less, where a particularly high effect can be obtained. bottom.
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 structure>
Al and Ti composite nitrides or composite carbonitrides (Al _X Ti _1-X ) (C _Y N _1-Y ) constituting the upper layer have a NaCl-type face-centered cubic structure (hereinafter simply referred to as “cubic crystal structure ) can be used to improve hardness.
That is, by forming a composite nitride or 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.
When the orientation index TC (111) in the (111) plane of the cubic crystal structure of the upper layer is 2.0 or more, it is possible to suppress the dropout of crystal grains during processing, so that the effect as a hard layer is further improved. TC(111) is desirably 2.0 or more and 4.0 or less, because if it is 4.0 or less, peeling between layers can be suppressed by increasing the adhesion to the lower layer. .
In addition, the value of the diffraction line intensity of the cubic (111) plane and the cubic (200) plane in the upper layer,
When I(111)/I(200) is 0.9 or more, crystal grains are less likely to fall off during processing, so it is desirable that I(111)/I(200)≧0.9. .

(e) top layer
In the present invention, an Al oxide such as α-Al ₂ O ₃ or κ-Al ₂ O ₃ is further formed on the composite nitride layer or the composite carbonitride layer, which is the upper layer, if necessary. A layer, a nitride layer or a carbonitride layer of Ti can be provided in a range of 0.5 to 15.0 μm from the viewpoint of improving wear resistance.

A method for forming a hard coating layer;
In the present invention, the Cr content and the C content each have a specific concentration distribution and a film thickness in a specific range. A surface comprising a hard coating layer made of a composite nitride or composite carbonitride of Ti and Ti, including an upper layer having a specific range of layer thickness and a specific crystal structure, and exhibiting excellent fracture resistance A coated cutting tool can be formed, for example, by forming a film under the following conditions using a CVD method (chemical vapor deposition method).
Furthermore, the same applies to a surface-coated cutting tool comprising a hard coating layer having a specific orientation index and a specific residual stress value in the lower layer and/or the upper layer, respectively.

<Film formation of lower layer>
In the method for forming the lower layer according to the present invention, the first step (Cr diffusion step) is performed on the tool substrate at a relatively high temperature (800 to 900 ° C.) using the CVD method (gas group A). When the TiCN film is formed, the diffusion of Cr from the tool substrate is promoted, and then, as the second step (C diffusion step), the CVD method (gas group B ), the diffusion of C is promoted, and as a result, in a region up to 0.1 μm from the tool substrate surface, there is a maximum Cr concentration region including the maximum Cr concentration value in the lower layer. Then, an excellent adhesion layer having a maximum C concentration region including the maximum C concentration value in the lower layer can be obtained in the region from the tool substrate surface to the boundary with the upper layer exceeding 0.1 μm.
[Deposition conditions]
1) First step (Cr diffusion step)
Processing method: Film formation using CVD method Reaction gas composition (% by volume):
Gas group A: TiCl ₄ : 0.01 to 0.04%, N ₂ : 1 to 10%, H ₂ : balance,
Reaction atmosphere pressure: 4.0 to 5.0 kPa,
Reaction atmosphere temperature: 800-900°C
2) Second step (C diffusion step)
Processing method: Film formation using CVD method Reaction gas composition (% by volume):
Gas group B: TiCl ₄ : 0.01 to 0.04%, N ₂ : 1 to 10%, H ₂ : residual Reaction atmosphere pressure: 4.0 to 5.0 kPa,
Reaction atmosphere temperature: 700-850°C

<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, in the method of forming an AlTiN layer and an AlTiCN layer according to the present invention, the third step (initial nucleation step) is to form AlTiN crystals and AlTiCN crystals that serve as initial nuclei for forming the AlTiN film and the AlTiCN film. and the fourth step (crystal growth step), that is, the step of growing the AlTiN crystal and the AlTiCN crystal, which are the initial nuclei, to form the AlTiN film and the AlTiCN film. membrane.
An outline of the film forming conditions in each film forming step is shown below. In particular, in the step of forming initial nuclei of fine AlTiN crystals and AlTiCN crystals in the third step, the following gas group C and gas group D 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 4 steps, the following gas group E and gas group F 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.). nucleation is suppressed and crystallization is promoted by changing to the ammonia gas that has been dehydrated, and furthermore, the third step and the fourth step are alternately repeated every 30 to 120 seconds to form crystals. A desired crystal can be obtained by the growth.
The number of repetitions of the third step and the fourth step is adjusted according to the target film thickness.

[Deposition conditions]
1) Third step (initial nucleation step)
Processing method: Film formation using CVD method Reaction gas composition (% by volume):
Gas group C: 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 D: NH ₃ : 0.1 to 0.8%, H ₂ : 25 to 35%,
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 C and supply of gas group D: 0.10 to 0.20 seconds
Preheating temperature for gas group D: 300 to 450°C

2) Fourth step (crystal growth step)
Processing method: Film formation using CVD method Reaction gas composition (% by volume):
Gas group E: 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 F: NH ₃ : 0.1 to 0.8%, H ₂ : 25 to 35%,
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 E and supply of gas group F: 0.10 to 0.20 seconds
Preheating temperature for gas group F: 50 to 250°C
The volume % of each gas component in the reaction gas composition (% by volume) in each of the third step and the fourth step is the total of gas group C and gas group D in the third step, which is 100% by volume. In the fourth step, the volume % of each component calculated assuming that the total of gas group E and gas group F is 100 volume % is shown.

In the surface-coated cutting tool according to the present invention, an adhesion layer made of Ti and Cr carbonitrides containing Cr components and C components diffused from the tool base is provided on the surface of the tool base, thereby greatly reducing the falling off of particles. In order to suppress it and exhibit excellent fracture resistance properties, it brings about an improvement in tool life.

1 is a cross-sectional schematic diagram showing the relationship between a tool substrate of a coated tool according to the present invention, a lower layer (TiCrCN layer including a Cr-rich region) and an upper layer (AlTiCN layer) constituting a hard coating layer. FIG.

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. bottom.

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.
That is, first, as a first step, any one of the tool substrates A to C is placed in a chemical vapor deposition apparatus, and the temperature conditions and pressure conditions described in the formation conditions (formation symbols) A to H shown in Table 2 Below, film formation is performed for a certain period of time using gas group A (TiCl ₄ , N ₂ and balance H ₂ ) having the composition shown in Table 2. By using the gas group A and setting the film formation temperature to a high temperature of 800° C. to 900° C., the film formation speed is high, and a deposited layer composed of coarse crystal grains with clear grain boundaries is formed. In this temperature range, diffusion of Cr is promoted, and as a result, the deposited film obtained exhibits the maximum Cr content.
Next, as the second step, gas group B (TiCl ₄ , Film formation is performed for a certain period of time using N ₂ and the remainder H ₂ ). By using gas group B and lowering the film formation temperature to 700° C. to 850° C., the partial pressure in the furnace is low and the film formation speed is very low, so that a deposited film made of fine crystal grains is formed. In this temperature range, the diffusion of C is promoted instead of Cr, resulting in the maximum C content.

Subsequently, as the third step (initial nucleation step), the supply conditions for gas group C and gas group D and the gas reaction conditions ( Film formation is performed for a certain period of time based on the pressure, temperature, and process time (seconds).
Subsequently, as the fourth step (crystal growth step), the supply conditions of gas group E and gas group F and the gas reaction conditions (pressure, Based on the temperature and process time (seconds), film formation was carried out for a certain period of time, and the coated tools 1 to 3, 6 and 7 of the present invention shown in Tables 6 and 7 were obtained.
In addition, for the coated tools 4, 5 and 8 of the present invention, after film formation under the formation conditions (formation symbols) D, E, and H shown in Table 4, κ-Al ₂ O was added as the uppermost layer, respectively. Inventive Tools 4, 5 and 8 shown in Tables 6 and 7 were obtained by forming _three layers, l-TiCN layer and α-Al ₂ O ₃ layer, under the formation conditions shown in Table 5.

For the purpose of comparison, films were formed under conditions a to c, f, and g shown in Tables 2, 3, and 4, and comparative coated tools 1 to 3, 6, and 7 were obtained.
Further, after film formation was performed under the formation conditions d, e, and h shown in Tables 2, 3, and 4, a κ-Al ₂ O ₃ layer, a l-TiCN layer, or an α- Comparative example tools 4, 5 and 8 shown in Table 9 were obtained by forming Al ₂ O ₃ layers under the formation conditions shown in Table 5.

Tables 6 and 7 show the target average total layer thickness of the hard coating layer of the coated tools 1 to 8 of the present invention, and
For the lower layer, target average layer thickness, type of formed film, total average Cr concentration, total average C concentration, 90% of the maximum Cr concentration value in the region adjacent to the substrate (region from the outermost surface of the substrate to 0.1 μm in the thickness direction) 90% of the maximum Cr concentration value in the maximum Cr concentration region having a concentration of ≥ 90%, the width of the maximum Cr concentration region, and the upper region (the region from the outermost surface of the substrate to the upper layer exceeding 0.1 μm in the thickness direction) the concentration value of the maximum C concentration region having a concentration equal to or higher than the above, the region width of the maximum C concentration region, the crystal characteristics of the formed film (crystal structure, orientation index (TC (200))),
For the upper layer (Al _X Ti _1-X ) (C _Y N _1-Y ), the target average layer thickness, average Al content ratio (X _avg ), average C content ratio (Y _avg ), crystal characteristics (crystal structure, orientation index (TC(111))),
For the top layer, the type of compound and the measurement result of the target average layer thickness are shown.
The same applies to the hard coating layers of the coated tools 1 to 8 of Comparative Examples.

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 a result, the coated tools 1 to 8 of the present invention are shown in Tables 6 and 7, and the coated tools 1 to 8 of the comparative examples are shown in Tables 8 and 9.
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 9 for comparative coated tools 1-8.
The maximum point and the maximum content of Cr and C contained in the lower layer were measured by the following method.
An EDS detector attached to the TEM performs a line scan at intervals of 4 nm in the surface direction of the hard coating layer from the outermost surface of the substrate to obtain the distribution of the contained elements, and the content of Cr and C in the entire lower layer. The maximum content of each element was defined with the point showing the average content in the lower layer and the maximum content of Cr and C in the lower layer as the center, and the distance from the substrate surface was defined as the maximum point. When the deviation amount is within -10% in the range of 2 points on the substrate side and 2 or more points on the surface side (that is, 20 nm area) centering on the maximum point, the maximum density is defined as the maximum density area.

In addition, for the crystal structure of the AlTiN layer and the AlTiCN layer, an X-ray diffractometer is used, the Cu-Kα ray is used as the radiation source, the measurement range (2θ): 20 to 120 degrees, the scan step: 0.013 degrees, around 1 step Under the condition of measurement time: 0.48 sec/step, for example, X-ray diffraction is performed on the surface of the hard coating layer parallel to the surface of the tool base, and JCPDS00-038-1420 cubic TiN and JCPDS00-046-1200 cubic Crystalline AlN, X-ray diffraction appearing between the diffraction angles of the same crystal plane shown in each (for example, 36.66-38.53°, 43.59-44.77°, 61.81-65.18°) It can be confirmed by the peak.
Then, the measured value I (hkl) of the X-ray diffraction peak intensity in each plane of (111), (200), (220), (311), (222), and (400) and the ICDD card 00- 046-1200, the average value I ₀ (hkl) of the standard X-ray diffraction peak intensity in each plane of the AlN crystal plane described in 046-1200, the orientation index TC (111), (200 It is possible to obtain I(111)/I(200), which is the ratio of the diffraction peak intensity I(111) of the (111) plane to the diffraction peak intensity I(200) of the ) plane.

Next, in a state in which each of the above-described coated tools was clamped to the tip of a cutter made of tool steel with a fixing jig, the coated tools 1 to 8 of the present invention and the coated tools 1 to 8 of comparative examples were coated with stainless A dry interrupted cutting test of steel was carried out to evaluate the maximum machining length up to tool breakage, and the results are shown in Table 10.

≪Cutting conditions≫
Cutting test: dry face milling, center cut machining,
Work material: JIS/SUS316L
100mm wide and 400mm long block with holes
(4 holes with a diameter of 50 mm at 50 mm intervals)
Cutting speed: 150 m/min.
Notch: 2.0 mm,
Single blade feed amount: 0.3 mm/blade,
Machining length: Machining until the cutting edge is chipped (Evaluation ends at the maximum machining length of 8.0m)

As is clear from the cutting test results shown in Table 10, the hard coating layer of the coated tool of the present invention has a maximum Cr content and a C content of A lower layer composed of a composite carbonitride of Ti and Cr having a maximum value is provided in direct contact with the lower layer, and has a specific chemical composition and a NaCl-type face-centered cubic crystal structure. By providing an upper layer made of AlTi composite nitride or AlTi composite carbonitride, chipping due to falling off of fine crystal grains is avoided, and excellent chipping resistance is exhibited over a long period of time. .

As described above, the surface-coated cutting tool of the present invention exhibits excellent chipping resistance even when used for cutting stainless steel and steel materials with a fused surface remaining. We are fully satisfied with the improvement in performance, labor saving and energy saving in cutting, and cost reduction.

Claims (5)

A surface-coated cutting tool comprising a hard coating layer on the surface of a tool substrate made of a tungsten carbide-based cemented carbide containing Co and Cr as binder phase components,
(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 20.0 μm,
(b) the lower layer is made of Ti and Cr carbonitrides and has an average layer thickness of 0.2 to 1.6 μm;
(b-1) the lower layer, in a range from the outermost surface of the substrate to a layer thickness of 0.1 μm,
The concentration value of the maximum Cr concentration region having the maximum Cr concentration value and having a concentration of 90% or more of the maximum Cr concentration value is 1.2 times or more the total average Cr concentration of the lower layer, and , 0.5 atomic % or more and 5.0 atomic % or less, the region width of the maximum Cr concentration region is 0.02 μm or more, and
(b-2) The lower layer has a maximum C concentration value in a range from the outermost surface of the substrate to the boundary with the upper layer with a layer thickness exceeding 0.1 μm, and is 90% or more of the maximum C concentration value. is 1.2 times or more the total average C concentration of the lower layer, and is 7.0 atomic % or more and 25.0 atomic % or less, The region width of the maximum C concentration region is 0.02 μm or more,
again,
(c) the upper layer is a layer containing a composite nitride or composite carbonitride of Al and Ti, and has an average layer thickness of 0.4 to 18.4 μm;
When represented by the composition formula: (Al _X Ti _1-X ) (C _Y N _1-Y ), the average content ratio X of Al with respect to the total amount of Ti and Al in the composite nitride or composite carbonitride layer _avg and the average content ratio Y _avg of C to the total amount of C and N in the composite nitride or composite carbonitride layer (where X _avg and Y _avg are both atomic ratios) are each 0.75 ≤ X _avg ≤ 0.90, 0 ≤ Y _avg < 0.05, and comprising a composite nitride or composite carbonitride layer having a NaCl-type face-centered cubic crystal structure. . When X-ray diffraction was performed on the lower layer composed of the carbonitrides of Ti and Cr, the orientation index TC (200) in the cubic (200) plane represented by the following formula (A) was 2. The surface-coated cutting tool according to claim 1, wherein 0.5≦TC(200)≦4.5 is satisfied.
Formula (A) TC(200)=[I(200)/I ₀ (200)]
×[(1/n)×Σ(I(hkl)/I ₀ (hkl)] ⁻¹
however,
I (200); measured value of X-ray diffraction peak intensity in (200) plane I ₀ (200);
Average value of standard X-ray diffraction peak intensity Σ(I(hkl)/I ₀ (hkl)) on the (200) plane of the TiN crystal plane described in ICDD card 00-038-1420;
Each of the six planes (111), (200), (220), (311), (222), and (400) ([measured value of X-ray diffraction peak intensity] / [listed on ICDD card Total value of the average value of the standard diffraction peak intensity of TiN]) 3. The surface-coated cutting tool according to claim 1, wherein the film residual stress value in the lower layer composed of the carbonitrides of Ti and Cr satisfies -500 to 500 MPa. When the upper layer was subjected to X-ray diffraction, the orientation index TC (111) in the cubic crystal (111) plane represented by the following formula (B) was 2.0 ≤ TC (111) ≤ 4. The surface-coated cutting tool according to any one of claims 1 to 3, which satisfies 4.0.
Equation (B) TC(111)=[I(111)/I ₀ (111)]
×[(1/6)×Σ(I(hkl)/I ₀ (hkl)] ⁻¹
however,
I (111); measured value of X-ray diffraction peak intensity in the (111) plane I ₀ (111);
Average value of standard X-ray diffraction peak intensity Σ(I(hkl)/I ₀ (hkl)) on the (111) plane of the AlN crystal plane described in ICDD card 00-046-1200;
Each of the six planes (111), (200), (220), (311), (222), and (400) ([measured value of X-ray diffraction peak intensity] / [listed on ICDD card the average value of standard diffraction peak intensities of AlN]) When X-ray diffraction was performed on the upper layer, the diffraction line intensity value of the cubic crystal (200) plane with respect to the diffraction line intensity value of the cubic crystal (111) plane, I(111)/I(200), was 0. 5. The surface-coated cutting tool according to any one of claims 1 to 4, which satisfies the relationship .9≤I(111)/I(200).

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