JP2020157457A - Surface-coated cutting tool excellent in defect resistance - Google Patents

Abstract

To provide a surface-coated cutting tool exerting excellent defect resistance in cutting of a stainless steel, a fusion surface-remaining steel material and the like.SOLUTION: There is provided a surface-coated cutting tool having a hard coating layer of 0.6-20.0 μm in overall average layer thickness including the upper and lower layers on the surface of a Co, Cr-containing tungsten carbide-based hard metal substrate. The lower layer consists of a TiCr composite carbonitride, has a maximum Cr concentration area of 0.5 atom% or more but 5.0 atom% or less of Cr in an area from the outermost surface of the substrate to a layer thickness of 0.1 μm and has a maximum C concentration area of 7.0 atom% or more but 25.0 atom% or less of C in an area over the above area to 1.6 μm. The upper layer consists of an AlTi composite (carbo)nitride (composition formula: (AlXTi1-X)(CYN1-Y) and satisfies 0.75≤Xavg≤0.90 and 0≤Yavg<0.05, has an NaCl type face-centered cubic crystal structure and has the film thickness of 0.4 to 18.4 μm.SELECTED DRAWING: Figure 1

Description

The present invention relates to a surface-coated cutting tool having excellent fracture resistance (hereinafter, simply referred to as "coated tool") in cutting of stainless steel, steel materials having a fusing surface remaining, and the like.

In cutting of stainless steel and steel materials with a fusing surface remaining, especially in cutting tools coated with AlTiN by the CVD method, high wear resistance is exhibited in the continuous high-speed cutting region due to the film hardness and oxidation resistance characteristics. However, on the other hand, in unstable machining such as stainless steel with high toughness of the work material and machining of melted cross section where the depth of cut fluctuates, the high film hardness causes particles to fall off. There was a problem that the original performance could not be exhibited due to the remarkable occurrence and the progress of abnormal damage accompanied by the chipping of the tool.

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 the 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, it is possible to improve the adhesion by adjusting the diffusion amount of C and Co from the cemented carbide base material side to the TiN layer side of the coating film and having a desired concentration gradient. In addition, Patent Document 2 describes the Co content in the titanium carbide film, which is the first layer on the hard coating layer side from the WC-based cemented carbide base material side, and the Cr content ratio to the Co content. It is described that the adhesion of the titanium carbide film is improved by specifying it.
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 have been strong demands for labor saving and energy saving in cutting, and along with this, cutting tends to be faster and more efficient. In coated tools, the occurrence of particles falling off causes tool loss. Excellent fracture resistance is required because it causes abnormal damage.
Therefore, in Patent Documents 1 to 3, in the coating tool, the substrate component or the component on the surface of the substrate is diffused into the adhesion layer to form a Ti-based adhesion layer having excellent adhesion on the tool substrate. , It was proposed to avoid the occurrence of defects.
However, in these CVD-AlTiN films, although the effect of improving adhesion is recognized by element diffusion, the hardness of the adhesion layer itself is excessively increased due to element diffusion, and the CVD-AlTiN film having high hardness during processing. There was a problem that cracks generated from the surface propagated to the inside and the tool was damaged due to the film particles falling off.

Therefore, an object of the present invention is to provide a surface-coated cutting tool that solves such a problem, prevents the progress of abnormal damage accompanied by a tool defect even during long-term use, and exhibits excellent chipping resistance. ..

From the above viewpoint, the present inventors have conducted extensive research in order to improve and improve the fracture resistance of a coating tool in which a hard coating layer made of a composite nitride of Al and Ti is coated and formed by chemical vapor deposition. As a result, the following findings were obtained.

That is, in the lower layer of the hard coating layer made of CVD-AlTiN, the present inventors appropriately diffuse the Cr component and the C component from the region in contact with the substrate toward the surface side of the hard coating layer, and each component is formed. , A region having a concentration gradient distribution region, specifically, a region in which the Cr component has the 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 , A region where the C component has the maximum concentration is provided, an adhesion layer made of carbon nitride of Ti and Cr is obtained, the crystal orientation and the residual stress of the film are controlled, and the excessive increase in the film hardness is suppressed. As a result, it was found that as a result of preventing internal growth due to cracks and reducing particle shedding, a film having excellent fracture resistance can be obtained.

The present invention has been made based on the above findings.
"(1) In 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 a bonding phase component.
(A) The hard coating layer has at least two layers, a lower layer directly in contact with the outermost surface of the tool substrate and an upper layer directly in contact with the lower layer, and is an overall average layer of the hard coating layer. The thickness is 0.6-20.0 μm and
(B) The lower layer is made of Ti and Cr carbonitride, and the average layer thickness thereof is 0.2 to 1.6 μm.
(B-1) The lower layer has a layer thickness of 0.1 μm from the outermost surface of the substrate.
The Cr concentration value in 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 in the lower layer. Moreover, it 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 also.
(B-2) The lower layer has a maximum C concentration value in the range from the outermost surface of the substrate to the boundary with the upper layer in a layer thickness of more than 0.1 μm, and is 90% or more of the maximum C concentration value. The C concentration value in the maximum C concentration region having the 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. Yes, the maximum C concentration region is 0.02 μm or more.
Also,
(C) The upper layer is a layer containing a composite nitride or a composite carbonitride of Al and Ti, and the average layer thickness thereof is 0.4 to 18.4 μm.
Composition formula: When represented by (Al _X Ti _1-X ) ( _CY 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 of C with respect to the total amount of C and N in the composite nitride or composite carbonitride layer occupied _{Y avg (however,} X _{avg, Y avg} any atomic ratio), respectively, 0 A surface coating comprising a composite nitride or composite carbonitride layer satisfying .75 ≦ X _avg ≦ 0.90 and 0 ≦ Y _avg <0.05 and having a NaCl-type surface-centered cubic structure. Cutting tools.

(2) When the lower layer made of the carbonitride of Ti and Cr is subjected to X-ray diffraction, the orientation index TC (200) on the cubic (200) plane represented by the following formula (A). ) Satisfies 0.5 ≦ TC (200) ≦ 4.5. The surface coating cutting tool according to (1).
Equation (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 on plane (200) I ₀ (200);
Average value of standard X-ray diffraction peak intensity on the (200) plane of the TiN crystal plane described on the ICDD card 00-038-1420 Σ (I (hkl) / I ₀ (hkl));
([Measured value of X-ray diffraction peak intensity] / [Posted on ICDD card] on each of the six surfaces (111), (200), (220), (311), (222), and (400). [3] In (1) or (2), the value of the film residual stress in the lower layer made of the carbonitride of Ti and Cr is the total value of the values of the standard diffraction peak intensities of TiN. A surface coating cutting tool characterized by satisfying −500 to 500 MPa.
(4) When the upper layer is subjected to X-ray diffraction, the orientation index TC (111) on the cubic (111) plane, which is represented by the following formula (B), is 2.0 ≦ TC. (111) The surface coating cutting tool according to any one of (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 on plane (111) I ₀ (111);
Average value of standard X-ray diffraction peak intensity on the (111) plane of the AlN crystal plane described on the ICDD card 00-046-1200 Σ (I (hkl) / I ₀ (hkl));
([Measurement value of X-ray diffraction peak intensity] / [Posted on ICDD card] of each of the six surfaces (111), (200), (220), (311), (222), and (400). The total value of the values of the standard diffraction peak intensities of AlN]) (5) When X-ray diffraction was performed on the upper layer, the cubic crystal (200) with respect to the diffraction line intensity of the cubic (111) plane. ), The value of the diffraction line intensity in the plane, I (111) / I (200), satisfies the relationship of 0.9 ≦ I (111) / I (200), according to (1) to (4). The surface coating cutting tool described in any one. It is characterized by.
In the present specification, when "~" or "-" is used to indicate a numerical range, it means that the lower limit and the upper limit of the numerical range are included.

Next, the tool base and the hard coating layer of the covering tool of the present invention will be specifically described.

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

(B) Hard coating layer The hard coating layer includes a lower layer and an upper layer, and an uppermost layer may be provided on the upper layer as another layer.
If the average thickness of the hard coating layer is less than 0.6 μm, the adhesion and abrasion resistance cannot be sufficiently ensured over a long period of use, so the average thickness is set to 0.6 μm or more. On the other hand, if the average layer thickness exceeds 20.0 μm, peeling or chipping is likely to occur, so it is desirable to set the average layer thickness to 20.0 μm or less.

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

<Ingredient composition>
The lower layer has a Cr content with respect to the total amount of all the 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 “base proximity region” of the lower layer). The Cr concentration value in 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 in the lower layer. Moreover, it is defined as 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.
Here, the reason why the Cr concentration value in the maximum Cr concentration region having a concentration of 90% or more of the maximum Cr concentration value is 1.2 times or more the total average Cr concentration in 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 grain boundary toughness at the interface of the lower layer with the substrate by Cr diffusion is not sufficient, or in the entire region near the substrate of the lower layer. This is because the decrease in hardness becomes remarkable, the difference in hardness from the upper layer becomes large, and peeling between layers is likely to occur.
Further, the reason why the Cr concentration value in the maximum Cr concentration region is defined 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 grain boundary toughness at the interface with the substrate is not sufficient, and film peeling from the substrate is likely to occur. On the other hand, when the Cr content exceeds 5.0 atomic%, the lower layer due to Cr diffusion into the lower layer This is because the decrease in hardness at the interface with the substrate becomes remarkable, the difference in hardness with the upper layer becomes large, and peeling between layers is likely to occur.
Further, in the lower layer, in the range from the outermost surface of the substrate to the boundary with the upper layer beyond the region where the layer thickness is up to 0.1 μm (hereinafter, also referred to as “upper region” of the lower layer), the lower layer The concentration value in the maximum C concentration region having the maximum C concentration value of the C content with respect to the total amount of all the constituent elements and having a C concentration of 90% or more of the maximum C concentration value becomes the total average C concentration of the lower layer. It is defined as 1.2 times or more, 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.
Here, when the concentration value in the maximum C concentration region is less than 1.2 times the total average C concentration value in the lower layer, the C concentration gradient is insufficient and the diffusion of C from the base material is inadequate. This is because sufficient and desired adhesion cannot be obtained, or the hardness of the entire lower layer increases remarkably, and brittle fracture in the layer is likely to occur.
The reason why the C content is defined 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%, the diffusion of C from the substrate is insufficient, so the lower part The desired adhesion at the interface of the layer with the substrate cannot be obtained, and the film is easily peeled off from the substrate. On the other hand, if it exceeds 25.0 atomic%, the diffusion of C becomes excessive and the layer is with the substrate of the lower layer. This is because the increase in hardness at the interface becomes excessive and brittle fracture in the layer is likely to occur.
Further, the reason why the region width of the maximum concentration region of each of Cr and C is defined as 0.02 μm or more is that the region width is insufficient if it is less than 0.02 μm, and the desired effect cannot be exhibited.

<Crystal structure>
The hardness of the TiCr composite carbonitride constituting the lower layer can be improved by adopting a NaCl-type face-centered cubic structure (hereinafter, also simply referred to as “cubic structure”).
By setting the orientation index TC (200) on the cubic (200) plane of the lower layer to 0.5 or more, the diffusion of Cr is sufficiently promoted, and as a result, a more uniform diffusion state of Cr is obtained. The grain boundary toughness effect of the adhesion layer is improved, while when it is 4.5 or less, segregation of Cr is suppressed and internal destruction of the adhesion layer starting from the grain boundary is less likely to occur. It is desirable that TC (200) ≤ 4.5.

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

(D) Upper layer <average layer thickness>
The upper layer is made of a composite nitride or a composite carbonitride of Ti and Al, and is provided 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 film is insufficient and the abrasion resistance is inferior, so the average layer thickness is set to 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 defects are likely to occur during processing, so the average layer thickness is set to 18.4 μm or less.

<Ingredient composition>
The upper layer is composed of an Al and Ti composite nitride layer (AlTiN layer) or a composite carbonitride layer (AlTiCN layer), and exhibits uniform wear resistance, heat resistance and toughness throughout the layer, and Ti. Since the high-temperature strength is improved by the component and the high-temperature hardness and heat resistance are complemented by the Al component, a low wear coefficient is maintained even under high-temperature cutting conditions, 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 ) ( _CY N _1- ). It can be represented by _Y ), but when the value of the average content ratio X _avg (atomic ratio) of Al is less than 0.75, the high temperature hardness becomes insufficient and the wear resistance deteriorates, while X _When the value of _avg (atomic ratio) exceeds 0.90, the high temperature strength of the (Al _X Ti _1-X ) ( _CY N _1-Y ) layer itself decreases due to the relative decrease in the Ti content ratio. Since chipping and chipping are likely to occur, the value of the average Al content ratio X _avg (atomic ratio) is specified in the range of 0.75 or more and 0.90 or less, which is close to the maximum hardness and a particularly high effect can be obtained. did.
Further, the C component has an effect of improving the hardness, but when the average content ratio _Avg (atomic ratio) of the C component is 0.05 or more, the high temperature strength decreases, so that the average content ratio Y of the C component _{The avg} (atomic ratio) was defined as 0 ≦ Y _avg <0.05.

<Crystal structure>
The Al, Ti composite nitride or composite carbonitride (Al _X Ti _1-X ) ( _CY N _1-Y ) constituting the upper layer is a NaCl-type face-centered cubic structure (hereinafter, simply "cubic structure"). In some cases, the hardness can be improved by taking.).
That is, the hardness can be increased by forming an Al, Ti composite nitride or composite carbonitride layer having high orientation on the (111) plane of the cubic structure.
When the orientation index TC (111) on the (111) plane of the cubic structure of the upper layer is 2.0 or more, it is possible to suppress the dropping of crystal grains during processing, so that the effect as a hard layer is further enhanced. It is desirable that the TC (111) is 2.0 or more and 4.0 or less because it can be exhibited and peeling between layers can be suppressed by further enhancing the adhesion with the lower layer at 4.0 or less. ..
Further, 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, it is difficult for crystal grains to fall off during processing, so it is desirable that I (111) / I (200) ≥ 0.9. ..

(E) Top layer
In the present invention, it is further composed of Al oxides such as α-Al ₂ O ₃ and κ-Al ₂ O ₃ on the composite nitride layer or the composite carbonitride layer, which is an upper layer, if necessary. The layer and the Ti nitride layer or the carbonitride layer can be provided in the range of 0.5 to 15.0 μm from the viewpoint of improving wear resistance and the like.

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

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

<Formation of upper layer>
Then, in the method of forming the upper layer according to the present invention, the film formation conditions of AlTi composite nitride layer or AlTi composite carbonitride layer, for example, using two different types of NH ₃ gas with the heating temperature, a high temperature ammonia Coarse grains can be obtained by suppressing nucleation with gas and promoting crystallization.
That is, the method for forming an AlTiN layer and an AlTiCN layer according to the present invention forms a third step (initial nucleation step), that is, an AlTiN crystal and an AlTiCN crystal which are 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 and forming the AlTiN film and the AlTiCN film are alternately repeated. It is a film.
The outline of the film forming conditions in each film forming step is shown below. In particular, in the step of forming the initial nuclei of the fine AlTiN crystal and the AlTiCN crystal in the third step, the following gas group C and gas group D are used. Nuclear formation is promoted by using ammonia gas preheated at a high temperature (for example, 300 to 450 ° C.) when the phase difference is provided and the gas is alternately supplied to the reactor to form a film. In the four steps, the following gas group E and gas group F are alternately supplied to the reactor with a phase difference to perform film formation, and the ammonia gas used is preheated at a low temperature (for example, 50 to 250 ° C.). By changing to the produced ammonia gas, nucleation is suppressed and crystallization is promoted, and further, the first step and the second step are alternately repeatedly formed every 30 to 120 seconds to form crystals. It is possible to grow and obtain a desired crystal.
The number of repetitions of the third step and the fourth step is adjusted according to the target film thickness.

[Film formation conditions]
1) Third step (initial nucleation step)
Treatment method: Film formation using CVD method Reaction gas composition (volume%):
Gas group C: 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 D: NH ₃ : 0.1 to 0.8%, H ₂ : 25 to 35%,
Reaction atmosphere pressure: 4.0-5.0 kPa,
Reaction atmosphere temperature: 700-850 ° C
Supply cycle: 1 to 5 seconds,
Gas supply time per cycle: 0.15-0.25 seconds,
Phase difference between the supply of gas group C and the supply of gas group D: 0.10 to 0.20 seconds
Preheating temperature of gas group D: 300-450 ° C

2) Fourth step (crystal growth step)
Treatment method: Film formation using CVD method Reaction gas composition (volume%):
Gas group E: 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 F: NH ₃ : 0.1 to 0.8%, H ₂ : 25 to 35%,
Reaction atmosphere pressure: 4.0-5.0 kPa,
Reaction atmosphere temperature: 700-850 ° C
Supply cycle: 1 to 5 seconds,
Gas supply time per cycle: 0.15-0.25 seconds,
Phase difference between supply of gas group E and supply of gas group F: 0.10 to 0.20 seconds
Preheating temperature of gas group F: 50-250 ° C
The volume% of each gas component in each reaction gas composition (volume%) of the third step and the fourth step is 100% by volume of the total of the gas group C and the gas group D in the third step. In the fourth step, the volume% of each component calculated as 100% by volume of the total of the gas group E and the gas group F is shown.

The surface-coated cutting tool according to the present invention is provided with a close contact layer made of carbides of Ti and Cr containing Cr component and C component diffused from the tool base on the surface portion of the tool base, thereby significantly suppressing the dropping of particles. However, since it exhibits excellent fracture resistance, it improves the tool life.

It is sectional drawing which shows the relationship between the tool base of the covering tool which concerns on this invention, the lower layer (TiCrCN layer including Cr rich region) which constitutes a hard coating layer, and the upper layer (AlTiCN layer).

Next, the covering 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 having an average particle size of 1 to 3 μm are prepared, and these raw material powders are blended as shown in Table 1. It was blended into the composition, further added with wax, mixed in a ball mill in acetone for 24 hours, dried under reduced pressure, press-molded into a green compact of a predetermined shape at a pressure of 98 MPa, and this green compact was pressed in a vacuum of 5 Pa at 1370. Vacuum sintered at a predetermined temperature within the range of ~ 1470 ° C. under the condition of holding for 1 hour, and after sintering, prepare tool bases A to C made of WC-based superhard alloy having an insert shape of ISO standard SEEN1203AFTN. did.

Then, each of these tool bases A to C was charged into a chemical vapor deposition apparatus, and the coated tools 1 to 8 of the present invention were manufactured by the following procedure.
That is, first, as the first step, any of the tool substrates A to C is placed in the 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 are shown. Underneath, a film is formed for a certain period of time by the gas group A (TiCl ₄ , N ₂ and the balance H ₂ ) having the component 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., a thin-film deposition layer composed of crystal grains having a high film formation rate, coarse particles, and clear grain boundaries is formed. In this temperature range, the resulting vapor deposition film exhibits the maximum Cr content as a result of the accelerated diffusion of Cr.
Then, as a second step, the gas group B (TiCl ₄ , TiCl ₄ ,) having the component composition shown in Table 2 under the temperature and pressure conditions described in the formation conditions (formation symbols) A to H shown in Table 2. A film is formed with N ₂ and the balance H ₂ ) for a certain period of time. By using the 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 rate is very slow, so that a vapor deposition film made of fine crystals is formed. In this temperature range, the maximum value of C content is shown as a result of promoting the diffusion of C instead of Cr.

Subsequently, as the third step (initial nucleation step), the supply conditions of the gas group C and the gas group D and the gas reaction conditions described in the formation conditions (formation symbols) A to H shown in Table 3 ( Film formation is performed for a certain period of time based on pressure, temperature, and process time (seconds).
Subsequently, as the fourth step (crystal growth step), the supply conditions of the gas group E and the gas group F and the gas reaction conditions (pressure,) described in the formation conditions (formation symbols) A to H shown in Table 4 are continued. Film formation was carried out for a certain period of time based on the temperature and the process time (seconds)) to obtain the coating tools 1 to 3, 6 and 7 of the present invention shown in Tables 6 and 7.
Further, with respect to the covering 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, the top layer is κ-Al ₂ O, respectively. _{The three} layers, the l-TiCN layer, or the α-Al ₂ O ₃ layer were formed under the formation conditions shown in Table 5 to obtain the tools 4, 5 and 8 of the present invention shown in Tables 6 and 7.

Further, for the purpose of comparison, film formation was carried out under the formation conditions a to c, f and g shown in Tables 2, 3 and 4, to obtain Comparative Examples Covering Tools 1-3, 6 and 7.
Further, after the film formation was performed under the formation conditions d, e, and h shown in Tables 2, 3 and 4, the top layer was κ-Al ₂ O ₃ layer, l-TiCN layer or α-, respectively. By forming the Al ₂ O ₃ layer under the formation conditions shown in Table 5, Comparative Examples Tools 4, 5 and 8 shown in Table 9 were obtained.

Tables 6 and 7 show the target average total thickness of the hard coating layers of the coating tools 1 to 8 of the present invention, and
For the lower layer, the target average layer thickness, the type of film formed, the total average Cr concentration, the total average C concentration, and 90% of the maximum Cr concentration value in the substrate proximity region (the region from the outermost surface of the substrate to 0.1 μm in the thickness direction). 90% of the maximum C concentration value in the maximum Cr concentration region having the above concentration, the region 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 Cr concentration region having the above concentration, the region width of the maximum Cr concentration region, the crystal characteristics of the formed film (crystal structure, orientation index (TC (200))),
For the upper layer (Al _X Ti _1-X ) ( _CY 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 measurement results of the type of compound and the target average layer thickness are shown.
Comparative Example The same applies to the hard coating layers of the coating tools 1 to 8.

Here, the film thicknesses of the hard coating layers of the coating tools 1 to 8 of the present invention and the coating tools 1 to 8 of the comparative example were measured using a scanning electron microscope (magnification: 5000 times).
That is, polishing is performed 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 obtained by measuring the layer thickness of 5 points in the observation field of view is the average layer thickness. As shown in Tables 6 and 7, the covering tools 1 to 8 of the present invention are shown in Tables 8 and 9, and the covering tools 1 to 8 of Comparative Examples are shown in Tables 8 and 9.
Regarding the average content of AlTiN or AlTiCN in the upper layer, X- _avg (atomic ratio) and the average content of C component, Y- _avg (atomic ratio), the electron probe microanalyzer (EPMA, Electron-Probe-Micro-Analyzer) ) Was used to irradiate the sample whose surface was polished with an electron beam from the sample surface side, and the obtained characteristic X-ray was obtained from the 10-point average of the analysis results. Table 7 shows the covering tools 1 to 8 of the present invention, and Table 9 shows the values of X _avg and Y _{avg for} the covering tools 1 to 8 of Comparative Examples.
The measurement for the maximum point and the maximum value of the contents of Cr and C contained in the lower layer was carried out by the following method.
A line scan was performed at intervals of 4 nm from the outermost surface of the substrate toward the surface of the hard coating layer using an EDS detector installed in the TEM to obtain the distribution of contained elements and determine the Cr and C contents in the entire lower layer. The points showing the average contents in the lower layer and the maximum values of Cr and C in the lower layer were taken as the center, the maximum contents of each element were taken, and the distance from the substrate surface was taken as the maximum point. The maximum concentration is defined as the maximum concentration when the deviation amount is within -10% in the range of two points on the substrate side and two points or more on the surface side (that is, a 20 nm region) with the maximum point as the center.

Regarding the crystal structure of the AlTiN layer and AlTiCN layer, an X-ray diffractometer is used, and the measurement range (2θ): 20 to 120 degrees, the scan step: 0.013 degrees, and one step around using Cu-Kα rays as the radiation source. Measurement time: Under the condition of 0.48 sec / step, for example, X-ray diffraction was performed on the surface of the hard coating layer parallel to the surface of the tool substrate, and JCPDS00-038-1420 cubic TiN and JCPDS00-046-1200 cubic were performed. Crystal AlN, X-ray diffraction appearing between the diffraction angles of the same crystal plane shown in each (eg, 36.66 to 38.53 °, 43.59 to 44.77 °, 61.81 to 65.18 °) It can be confirmed by the peak.
Then, the measured values I (hkl) of the X-ray diffraction peak intensities in each of the acquired surfaces (111), (200), (220), (311), (222), and (400) and the ICDD card 00- From the average value I ₀ (hkl) of the standard X-ray diffraction peak intensities on each of the AlN crystal planes described in 046-1200, the orientation indices TC (111), (200) on the (111) plane of the cubic crystal. 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), can be obtained.

Next, with the various covering tools clamped to the tip of the tool steel cutter with a fixing jig, the covering tools 1 to 8 of the present invention and the covering tools 1 to 8 of the comparative example are shown below in stainless steel. A dry intermittent cutting test of steel was carried out, an evaluation was carried out regarding the maximum machining length up to a tool breakage, and the results are shown in Table 10.

≪Cutting conditions≫
Cutting test: Dry face milling cutter, center cut cutting process,
Work material: JIS / SUS316L
Block material with holes 100 mm wide and 400 mm long
(4 holes with a diameter of 50 mm at intervals of 50 mm)
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 damaged (evaluation is completed at the maximum machining length of 8.0 m)

As is clear from the cutting test results shown in Table 10, the coated tool of the present invention has, as its hard coating layer, sequentially the maximum value of Cr content and the C content with respect to the outermost surface of the tool substrate. A lower layer made of a composite carbonitride of Ti and Cr having a maximum value is provided in direct contact with the lower layer, and further has a specific component composition with respect to the lower layer and has a NaCl-type surface-centered cubic structure. By providing an upper layer made of AlTi composite nitride or AlTi composite carbonitride, it is possible to avoid the occurrence of chipping and the like due to the shedding of fine crystal grains, and to exhibit excellent fracture resistance over a long period of time. ..

As described above, the surface-coated cutting tool of the present invention exhibits excellent fracture resistance, especially when used for cutting stainless steel or steel materials having a fusing surface remaining. It is fully satisfactory in terms of high performance, labor saving and energy saving in cutting, and cost reduction.

Claims (5)

In 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 a bonding phase component.
(A) The hard coating layer has at least two layers, a lower layer directly in contact with the outermost surface of the tool substrate and an upper layer directly in contact with the lower layer, and is an overall average layer of the hard coating layer. The thickness is 0.6-20.0 μm and
(B) The lower layer is made of Ti and Cr carbonitride, and the average layer thickness thereof is 0.2 to 1.6 μm.
(B-1) The lower layer has a layer thickness of 0.1 μm from the outermost surface of the substrate.
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, 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 the range from the outermost surface of the substrate to the boundary with the upper layer in a layer thickness of more than 0.1 μm, and is 90% or more of the maximum C concentration value. The concentration value of the maximum C concentration region having the concentration of is 1.2 times or more and 7.0 atomic% or more and 25.0 atomic% or less with respect to the total average C concentration of the lower layer. The maximum C concentration region is 0.02 μm or more, and is
Also,
(C) The upper layer is a layer containing a composite nitride or a composite carbonitride of Al and Ti, and the average layer thickness thereof is 0.4 to 18.4 μm.
Composition formula: When represented by (Al _X Ti _1-X ) ( _CY N _1-Y ), the average content ratio X of Al to the total amount of Ti and Al in the composite nitride or composite carbonitride layer X. _The average content ratio of C to the total amount of C and N in the _avg and the composite nitride or composite carbonitride layer Y _avg (however, both X _avg and Y _avg are atomic ratios) is 0.75, respectively. A surface-coated cutting tool that satisfies ≤X _avg ≤0.90, 0≤Y _avg <0.05, and is composed of a composite nitride or composite carbonitride layer having a NaCl-type surface-centered cubic structure. .. When X-ray diffraction was performed on the lower layer made of the carbonitrides of Ti and Cr, the orientation index TC (200) on the cubic (200) plane, which is represented by the following formula (A), was determined. The surface coating cutting tool according to claim 1, wherein 0.5 ≤ TC (200) ≤ 4.5 is satisfied.
Equation (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 on plane (200) I ₀ (200);
Average value of standard X-ray diffraction peak intensity on the (200) plane of the TiN crystal plane described on the ICDD card 00-038-1420 Σ (I (hkl) / I ₀ (hkl));
([Measurement value of X-ray diffraction peak intensity] / [Posted on ICDD card] of each of the six surfaces (111), (200), (220), (311), (222), and (400). The average value of the standard diffraction peak intensity of TiN]) The surface coating cutting tool according to claim 1 or 2, wherein the value of the film residual stress in the lower layer made of the carbonitride of Ti and Cr satisfies −500 to 500 MPa. When X-ray diffraction is performed on the upper layer, the orientation index TC (111) on the cubic (111) plane, which is represented by the following formula (B), is 2.0 ≦ TC (111) ≦. The surface coating cutting tool according to any one of claims 1 to 3, wherein the surface coating cutting tool 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 on plane (111) I ₀ (111);
Average value of standard X-ray diffraction peak intensity on the (111) plane of the AlN crystal plane described on the ICDD card 00-046-1200 Σ (I (hkl) / I ₀ (hkl));
([Measurement value of X-ray diffraction peak intensity] / [Posted on ICDD card] of each of the six surfaces (111), (200), (220), (311), (222), and (400). The average value of the standard diffraction peak intensities of AlN]) When X-ray diffraction was performed on the upper layer, the diffraction line intensity value on the cubic (200) plane, I (111) / I (200), was 0 with respect to the diffraction line strength value on the cubic (111) plane. The surface-coated cutting tool according to any one of claims 1 to 4, wherein the relationship of .9 ≦ I (111) / I (200) is satisfied.