JP2020151794A - Surface-coated cutting tool - Google Patents

Abstract

To provide a surface-coated cutting tool exerting excellent chipping resistance and wear resistance for an extended period even in high-speed high-feed processing or the like of a ductile cast iron and the like.SOLUTION: In a surface-coated cutting tool, the hard coating layer of a tool substrate includes a composite nitride layer or composite carbonitride layer of Ti and Al having an average layer thickness of 1.0-20.0 μm and having crystal grains of the NaCl type face-centered cubic structure. In the analysis about a cut surface parallel to the tool substrate, the composition of a crystal grain A group is (Ti1-XAAlXA)(CYAN1-YA), and the average of XA, XAavg and average of YA, YAavg satisfy 0.75≤XAavg≤0.95 and 0.0000≤YAavg≤0.0150, respectively. The composition of a crystal grain B group is (Ti1-XBAlXB)(CYBN1-YB), and the average of XB, XBavg satisfies 0.70≤XBavg≤0.90, and 0.05≤XAavg-XBavg≤0.25. Besides, the average of YB, YBavg satisfies 0.0000≤YBavg≤0.0150, and the area ratio of the crystal grain A group is in the range of 20 to 80%.SELECTED DRAWING: Figure 1

Description

INDUSTRIAL APPLICABILITY The present invention provides a hard coating layer with excellent chipping resistance and abrasion resistance in high-speed, high-feed intermittent cutting, which is accompanied by high heat generation and exerts a strong impact load on the cutting edge, for a long period of time. It relates to a surface-coated cutting tool (hereinafter, may be referred to as a coated tool) that exhibits excellent cutting performance over its use.

Conventionally, Ti-Al-based composite nitride is used as a hard coating layer on the surface of a tool substrate (hereinafter, collectively referred to as a tool substrate) composed of a tungsten carbide (hereinafter referred to as WC) -based cemented carbide or the like. There are coating tools in which a material layer is coated and formed by a vapor deposition method, and these are known to exhibit excellent abrasion resistance.
However, although the conventional covering tool coated with the Ti-Al-based composite nitride layer has relatively excellent wear resistance, abnormal wear is likely to occur when used under high-speed, high-feed intermittent cutting conditions. , Various proposals have been made for improving the hard coating layer.

For example, in Patent Document 1, the (Ti _1-x Al _x ) (C _y N _1-y ) layer (provided that the average content of Al x _avg and the average content of C y _avg are described on the surface of the tool substrate. , 0.60 ≤ x _avg ≤ 0.95, 0 ≤ y _avg ≤ 0.005), and the crystal grains having a NaCl-type face-centered cubic structure of the layer are {111. } An individual crystal grain having an orientation and a face-centered cubic structure of NaCl type has a columnar structure having an average particle width W of 0.1 to 2.0 μm and an average aspect ratio A of 2 to 10. Further, in the individual crystal grains having the NaCl-type face-centered cubic structure, there is a periodic composition change of Ti and Al in the composition formula: (Ti _1-x Al _x ) ( _Cy N _1-y ). However, a covering tool is described in which the difference Δx between the average of the maximum values of x and the average of the minimum values, which changes periodically, is 0.03 to 0.25.

Further, for example, Patent Document 2 includes a tool substrate and a single-layer or multi-layer wear protection coating having a thickness in the range of 3 μm to 25 μm applied by a CVD process.
The wear protective coating, at least one of _{Ti 1-x Al} x thickness of _{1.5μm~17μm C y N z (0.70 ≦} x <1,0 ≦ y <0.25,0.75 ≦ z < 1.15) A layered structure in which the Ti _1-x Al _{x Cy} N _z layer has a plurality of layers of 150 nm or less, has the same crystal structure (crystal phase), and is composed of Ti and Al. Covering tools are described that are formed in regions where stoichiometric proportions alternate and alternate periodically and have a face-centered cubic crystal structure of at least 90 vol%.

Japanese Unexamined Patent Publication No. 2016-64485 Special Table 2017-508632

In recent years, there has been a strong demand for labor saving and energy saving in cutting, and along with this, cutting tends to be faster and more efficient, and covering tools have even more chipping resistance and chipping resistance. Abnormal damage resistance such as peeling resistance is required, and excellent wear resistance is required over a long period of use.

Therefore, the present invention has been made in view of such a situation, and even when it is subjected to high-speed high-feed cutting of ductile cast iron or the like, it has excellent chipping resistance and abrasion resistance over a long period of use. The purpose is to provide a covering tool that demonstrates its performance.

The present inventor has a chipping resistance and abrasion resistance of a covering tool including a composite nitride layer of Ti and Al or a composite carbonitride layer (hereinafter, these may be collectively referred to as "TiAlCN layer"). In order to improve it, we repeated diligent studies.

As a result, on the cut surface of the TiAlCN layer parallel to the tool substrate, when two groups of crystal grains having a NaCl-type face-centered cubic structure having a predetermined difference in the Al content ratio are present in a specific ratio, Al We have obtained a new finding that the difference in the coefficient of thermal expansion due to the difference in the content ratio causes local strain in the TiAlCN layer and improves the fracture resistance.

The present invention is based on this finding and is as follows.
"(1) A surface-coated cutting tool in which a hard coating layer is provided on the surface of a tool substrate.
(A) The hard coating layer contains at least a composite nitride or composite carbonitride layer of Ti and Al having an average layer thickness of 1.0 to 20.0 μm.
(B) The Ti and Al composite nitride layer or composite carbonitride layer contains at least crystal grains having a NaCl-type face-centered cubic structure.
(C) When the cut surface parallel to the tool substrate is analyzed from the direction perpendicular to the surface of the tool substrate, a plurality of crystal grains having the NaCl-type face-centered cubic structure having different Ti and Al compositions are present. When each is divided into crystal grain A group and crystal grain B group,
When the crystal grain A group is represented by the composition formula: (Ti _1-XA Al _XA ) (C _YA N _1-YA ), the average X _Aavg of the content ratio X _A of Al in the total amount of Ti and Al, and The average Y _Aavg of the content ratio Y _A in the total amount of C and N of C (however, X _Aavg and Y _Aavg are both atomic ratios) are 0.75 ≤ X _Aavg ≤ 0.95 and _0.0000 , respectively. _{Satisfying ≤Y Aavg} ≤ 0.0150,
When the crystal grain B group is represented by the composition formula: (Ti _1-XB Al _XB ) ( _CYB N _1-YB ), the average X _Bavg of the content ratio X _B of Al in the total amount of Ti and Al, and The average Y _Bavg of C and Y _B in the total amount of C and N (however, X _Bavg and Y _Bavg are both atomic ratios) is 0.70 ≤ X _Bavg ≤ 0.90, 0.05 ≤ X. _{Satisfying Aavg-} X _Bavg ≤ 0.25, 0.0000 ≤ Y _Bavg ≤ 0.0150,
(D) The area ratio of the crystal grain A group on the cut surface is 20 to 80%.
A surface coating cutting tool characterized by that.
(2) In the crystal grains of the crystal grain A group, a periodic composition change of Ti and Al exists along one of the equivalent crystal orientations represented by <001> of the crystal grains. , periodically varying difference [Delta] X _a between the average value of the average value and the minimum value of the maximum value of X _a to the surface-coated cutting according to (1), which is a 0.03 to 0.25 tool.
(3) In the crystal grains of the crystal grain B group, a periodic composition change of Ti and Al exists along one of the equivalent crystal orientations represented by <001> of the crystal grains. , according to the difference [Delta] X _B between the average value of the average value and the minimum value of the maximum value of _{X B} which changes periodically it is characterized in that it is a 0.03 to 0.25 (1) or (2) Surface coating cutting tool.
(4) Of the carbide layer, nitride layer, carbonitride layer, coal oxide layer and carbonitride oxide layer of Ti between the tool substrate and the composite nitride or composite carbonitride layer of Ti and Al. The surface coating cutting tool according to any one of (1) to (3) above, which comprises one layer or two or more layers of the above and has a lower layer having a total average layer thickness of 0.1 to 20 μm. ..
(5) The above (1) to (4), wherein an upper layer including at least an aluminum oxide layer is present above the composite nitride or composite carbonitride layer with a total average layer thickness of 1 to 25 μm. The surface coating cutting tool described in any of. "

The cutting tool of the present invention exhibits excellent chipping resistance and abrasion resistance over a long period of use even when it is used for high-speed high-feed cutting of ductile cast iron or the like.

It is a schematic diagram which shows the structure in the cut surface parallel to the tool substrate of the TiAlCN layer of this invention, and the shape and dimension of each structure are not copying the actual sintered structure. It is a schematic diagram which shows the cycle, the maximum value, and the local value of the periodic composition change of Ti and Al. It is a schematic diagram which shows the composition change in the crystal particle which has a NaCl type face-centered cubic structure in which the composition change of Ti and Al exists periodically.

Hereinafter, the covering tool of the present invention will be described in more detail. In the present specification and claims, when the numerical range is expressed by using "~", the range shall include the numerical values of the upper limit and the lower limit.

1. 1. Average thickness of hard coating layer:
The hard coating layer contains at least a TiAlCN layer. The hard coating layer including the TiAlCN layer has high hardness and excellent wear resistance, but the effect is remarkably exhibited particularly when the average layer thickness is 1.0 to 20.0 μm. The reason is that if the average layer thickness is less than 1.0 μm, sufficient wear resistance cannot be ensured over a long period of use because the average layer thickness is thin, while if the average layer thickness exceeds 20.0 μm, This is because the crystal grains of the TiAlCN layer are likely to be coarsened and chipping is likely to occur.

2. 2. Crystal grains of NaCl-type face-centered cubic structure in the TiAlCN layer It is difficult to achieve the object of the present invention unless the crystals of the NaCl-type face-centered cubic structure are contained in the TiAlCN layer. In order to achieve this purpose, in the cross section parallel to the surface of the tool substrate, the area ratio occupied by the crystal grains of the NaCl-type face-centered cubic structure is 60% or more, preferably 80% or more, more preferably 100% ( It is preferable that all the crystal grains have a NaCl-type face-centered cubic structure).

3. 3. Composition of TiAlCN layer constituting the hard coating layer:
The TiAlCN layer constituting the hard coating layer contains crystal grain A group and crystal grain B group having different Al content ratios.
The composition of the crystal grain A group is represented by the composition formula: (Ti _1-XA Al _XA ) (C _YA N _1-YA ), and the average X _Aavg of the content ratio X _A of Al in the total amount of Ti and Al and The average Y _Aavg of the content ratio Y _A in the total amount of C and N of C (however, X _Aavg and Y _Aavg are both atomic ratios) are 0.75 ≤ X _Aavg ≤ 0.95 and _0.0000 , respectively. _{Satisfying ≤Y Aavg} ≤ 0.0150,
The composition of the crystal grain B group is expressed by the composition formula: (Ti _1-XB Al _XB ) ( _CYB N _1-YB ), and the average X _Bav of the content ratio X _B of Al in the total amount of Ti and Al and The average Y _Bavg of C and Y _B in the total amount of C and N (however, X _Bavg and Y _Bavg are both atomic ratios) is 0.70 ≤ X _Bavg ≤ 0.90, 0.05 ≤ X. It is preferable to satisfy _Aavg −X _Bavg ≦ 0.25 and 0.0000 ≦ Y _Bavg ≦ 0.0150.

Next, the reason why the composition of the crystal grain A group and the crystal grain B group is preferably in the above range will be described.
(1) Average content ratio of Al The average content ratio of Al _satisfies 0.75 ≤ X _Aavg ≤ 0.95 in the crystal grain A group and 0.70 ≤ X _Bavg ≤ 0.90 in the crystal grain B group. As a result, the TiAlCN layer secures hardness, and when it is subjected to high-speed high-feed cutting of ductile cast iron or the like, its wear resistance is sufficient, and the Ti content ratio does not decrease relatively. This is because chipping resistance can be ensured without causing brittleness.
Then, by satisfying the Al content ratio of the crystal grain A group and the crystal grain B group of 0.05 ≤ X _Aavg- X _Bavg ≤ 0.25, thermal expansion occurs between the crystal grain A group and the crystal grain B group. The difference in the coefficients becomes appropriate, appropriate local strain is applied, and the fracture resistance is improved.

(2) Average content ratio of C The average content ratio of C in the crystal grain A group and the crystal grain B group When both Y _Aavg and Y _Bavg are in trace amounts in the range of 0.0000 or more and 0.0150 or less, the TiAlCN layer. The adhesion between the and the tool substrate or the lower layer described later is improved, and the impact during cutting is alleviated by improving the lubricity, and as a result, the chipping resistance and chipping resistance of the TiAlCN layer are improved. On the other hand, if the average content of C deviates from this range, the toughness of the TiAlCN layer is lowered, and the fracture resistance and chipping resistance are conversely impaired, which is not preferable.

Here, the average contents of Al in the TiAlCN layer, X _Aavg , X _Bavg , and the average contents of C, Y _Aavg and Y _Bavg , were determined as follows. From the direction perpendicular to the surface of the tool substrate, the surface polished surface parallel to the tool substrate is irradiated with an electron beam from the sample surface side using an electron probe microanalyzer (EPMA, Electron-Probe-Micro-Analyzer). Perform mapping analysis. From the mapping analysis result, the average composition was obtained for each crystal grain, and it was divided into a crystal grain group having a relatively high Al content and a crystal grain group having a relatively low Al content, and a crystal grain group having a relatively high Al content. Average Al Content of (Crystal A Group) X _Aavg , Average Content of C Y _Aavg , Average Al Content of Crystal Grain Group (Crystal B Group) with Relatively Low Al Content X _Bavg , C The average content ratio Y _{Bavg of} was determined.

4. Discrimination between Crystal Grain A Group and Crystal Grain B Group As described above, the crystal grain A group and the crystal grain B group are discriminated from each other. When it is difficult to distinguish a sample or the like in which a periodic composition change of Ti and Al exists in the crystal grains by the above method, the following method is additionally used to distinguish the sample. Mapping analysis by energy dispersive X-ray Spectrometry (EDS) using a transmission electron microscope on the surface polishing surface parallel to the tool substrate from the direction perpendicular to the surface of the tool substrate. I do. When the average composition was obtained for each crystal grain from the mapping analysis result, it was divided into a crystal grain group having a relatively high Al content and a crystal grain group having a relatively low Al content, and the crystal grains having a relatively high Al content. The group is referred to as a crystal grain A group, and the crystal grain group having a relatively low Al content is referred to as a crystal grain B group.

5. Area ratio occupied by the crystal grain A group The area ratio occupied by the crystal grain A group in the cross section parallel to the tool substrate is preferably 20 to 80 area%. The reason for setting this range is that if it is less than 20 area%, the area ratio of the crystal grain B group increases relatively, and local strain occurs due to the difference in the coefficient of thermal expansion from the crystal grain A group. On the other hand, when it exceeds 80 area%, the area ratio of the crystal grain A group becomes relatively dominant, and the occurrence of local strain caused by the difference in the coefficient of thermal expansion from the crystal grain B group is small. This is to become. A more preferable area ratio is 40 to 60 area%.

6. Compositional changes in crystal grain A group and crystal grain B group (1) Crystal grain A group In the crystal grain of crystal grain A group, a periodic composition change of Ti and Al occurs at <001> of the crystal grain. It preferably exists along one of the equivalent crystal orientations represented.
Here, the cyclic composition changes, along one of the orientation of the crystal orientation of the equivalent represented by the crystal grains <001>, performs line analysis graph the change in the proportion X _A of Al when ized refers to be repeated at intervals with the value of X _a. As shown in FIG. 2, to approximate the change in _{X A} with a straight line (Xm). This straight line is drawn so that the area of the area surrounded by the straight line and the curve showing the repetitive change is equal on the upper side and the lower side of the straight line. The repeated change for each area where the straight line crosses, calculated maximum value _{(P max)} and minimum value _{(P min),} the difference [Delta] X _A between the average value of the average value and the minimum value of the maximum value 0.03 It is preferably 0.25. When ΔX _A is in this range, sufficient hardness and fracture resistance are further improved.
Needless to say, a known measurement noise removing method (for example, a moving average method) is used for graphing.

(2) Crystal grain B group In the crystal grain of the crystal grain B group, the periodic composition change of Ti and Al becomes one of the equivalent crystal orientations represented by <001> of the crystal grain. It preferably exists along.
Here, the periodic change in composition, there is determined in the same way as the grain group A, the difference [Delta] X _B between the average value of the average value and the minimum value of the maximum value 0.03 to 0.25 Is preferable. When ΔX _B is in this range, sufficient hardness and fracture resistance are further improved.

(3) Measurement of periodic composition change of Ti and Al The existence of the periodic composition change of Ti and Al is observed by observing the TiAlCN layer using a transmission electron microscope (TEM: for example, magnification of 200,000 times). Confirm. Then, for example, using EDS, a surface analysis was performed on a region of 400 nm × 400 nm in a cross section parallel to the surface of the tool substrate, and a change in color shading in stripes in cubic crystal grains having a NaCl-type face-centered cubic structure. When is observed (see FIG. 3), it is determined that there is a periodic compositional change of Ti and Al in TiAlCN in the cubic crystal grains. Then, by performing electron beam analysis on the crystal grains, the periodic composition change is set to one of the equivalent crystal orientations represented by <001> of the crystal grains having a NaCl-type face-centered cubic structure. After confirming that it exists along the direction and setting the magnification so that the composition change for about 10 cycles from the shade is within the measurement range based on the result of the surface analysis along the direction, the surface of the tool substrate A line analysis by EDS was performed along the normal direction in the range of 5 cycles, the change was plotted on a graph, and the change in the Al content ratio was linearly approximated to each region defined by the direct line. Find the maximum and minimum values of the change in, and calculate the difference between the average values of the differences.

7. The hard coating layer including the lower TiAlCN layer exhibits sufficient chipping resistance and abrasion resistance by itself, but one of Ti's carbide layer, nitride layer, carbon oxide layer and carbon dioxide oxide layer or When a lower layer composed of two or more Ti compound layers and having a total average layer thickness of 0.1 to 20.0 μm is provided, in combination with the effect of this layer, even more excellent chipping resistance is achieved. Demonstrates resistance and wear resistance. However, when the lower layer composed of one or more Ti compound layers of the carbide layer, the nitride layer, the coal oxide layer and the carbon dioxide oxide layer of Ti is provided, the total average layer thickness of the lower layers is 0. If it is less than .1 μm, the effect of the lower layer is not sufficiently exhibited, while if it exceeds 20.0 μm, the crystal grains are likely to be coarsened and chipping is likely to occur.

8. Upper layer It is preferable that a layer containing aluminum oxide is provided on the upper part of the TiAlCN layer with a total average layer thickness of 1.0 to 25.0 μm because further excellent chipping resistance and abrasion resistance are exhibited. Here, if the total average layer thickness is less than 1.0 μm, the effect of providing the upper layer is not sufficiently exhibited, while if it exceeds 25 μm, chipping is likely to occur.

9. Tool Base As the tool base, any base material conventionally known as this type of tool base can be used as long as it does not hinder the achievement of the object of the present invention. For example, cemented carbide (WC-based cemented carbide, WC, as well as those containing Co or added with carbonitrides such as Ti, Ta, Nb, etc.), cermet (TiC, TiN, etc.) , TiCN or the like as a main component), ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cBN sintered body, or diamond sintered body is preferable.

10. Manufacturing Method The TiAlCN layer is, for example, on a tool substrate or the lower layer on the tool substrate.
It can be obtained by supplying a reaction gas having a specific composition to a CVD apparatus under predetermined conditions.
That is, the reaction gas is a separate CVD apparatus for the gas group A consisting of NH ₃ , N ₂ , and H ₂ and the gas group B consisting of AlCl ₃ , Al (CH ₃ ) ₃ , TiCl ₄ , N ₂ , and H _2. And mix just before the film-deposited body.

The composition of the reaction gas is, for example,
Gas group A: NH ₃ : 0.8 to 1.6%, N ₂ : 0.0 to 2.0%, H ₂ : 30.0 to 35.0%
Gas group B: AlCl ₃ : 0.5 to 0.7%, Al (CH ₃ ) ₃ : 0.00 to 0.08%,
TiCl ₄ : 0.1 to 0.3%, N ₂ : 0.0 to 6.0%, H ₂ : Remaining (% of gas group A and gas group B is the total of gas group A and gas group B gas) By volume% of
And
Reaction atmosphere pressure: 4.5-5.0 kPa
Reaction atmosphere temperature: 750-800 ° C
Is.

Specific supply of the gas group A and the gas group B is performed according to the description of JP-A-2016-117934 or JP-A-2017-201711, and the rotational speed of the gas supply pipe and the ejection hole angle of the gas supply pipe. Is a predetermined value.

Next, an embodiment will be described.
Here, as an example of the coated tool of the present invention, a tool applied to an insert cutting tool using a WC-based ultra-high pressure sintered body as a tool substrate will be described, but the above-mentioned tool substrate is used. The same applies when applied to drills and end mills.

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, a tool base A made of WC-based superhard alloy having an insert shape of JOMU140715ZZER-M manufactured by Mitsubishi Materials Co., Ltd. C was produced respectively.

Next, a TiAlCN layer is formed on the surfaces of these tool bases A to C by CVD using the CVD apparatus described in JP-A-2016-117934 under the conditions shown in Table 2, and is shown in Table 5. The covering tools 1 to 10 of the present invention were obtained.

The gas composition and the like for forming the TiAlCN layer are generally as follows.
Gas group A: NH ₃ : 0.8 to 1.6%, N ₂ : 0.0 to 2.0%, H ₂ : 30.0 to 35.0%
Gas group B: AlCl ₃ : 0.5 to 0.7%, Al (CH ₃ ) ₃ : 0.00 to 0.08%,
TiCl ₄ : 0.1 to 0.3%, N ₂ : 0.0 to 6.0%, H ₂ : Remaining (% of gas group A and gas group B is the total of gas group A and gas group B gas) By volume% of
Reaction atmosphere pressure: 4.5-5.0 kPa
Reaction atmosphere temperature: 750-800 ° C

Here, the gas group A and the gas group B are supplied as the raw material gas A and the raw material gas B of the CVD apparatus described in JP-A-2016-117934, respectively, and the rotational speed of the gas supply pipe and the gas supply are supplied. The ejection hole angle of the pipe is as follows.
Rotation speed of gas supply pipe: 10 to 30 rpm
Gas supply pipe outlet angle:
α: 60-90 °
β1 and β2: 90-120 °
γ1 and γ2: 180 °

In the covering tools of the present invention, 4 to 10 formed the lower layer and / or the upper layer shown in Table 4 under the film forming conditions shown in Table 3.

Further, for the purpose of comparison, a hard coating layer containing the TiAlCN layer shown in Table 5 is deposited and formed on the surfaces of the tool substrates A to C by performing CVD under the conditions shown in Table 2 to form a comparative coating tool 1. 10 was manufactured.
For the comparative covering tools 4 to 10, the lower layer and / or the upper layer shown in Table 4 were formed according to the formation conditions shown in Table 3.

Further, the cross section of the coating tools 1 to 10 of the present invention and the comparative coating tools 1 to 10 in the direction perpendicular to the tool substrate of the hard coating layer was measured using a scanning electron microscope (magnification of 5000 times) and within the observation field. When the layer thicknesses at 5 points were measured and averaged to obtain the average layer thickness, the average layer thicknesses shown in Tables 4 and 5 were shown in each case.
For the hard coating layers of the coating tools 1 to 10 of the present invention and the comparative coating tools 1 to 10, the average Al content ratios X _Aavg and X _Bavg and the average C content ratios Y _Aavg and Y _Bavg were calculated by using the above-mentioned method. .. In addition, the difference between the presence or absence of a period along the equivalent orientation represented by <001> of the composition change of Ti and Al and the average value of the maximum value and the average value of the minimum value of the Al content ratio, ΔX _A and ΔX _B, are obtained. It was.
These results are summarized in Table 5. Although not shown in Table 5, it has been confirmed that the area ratio of the NaCl-type face-centered cubic structure is 60% or more in both the invention covering tools 1 to 10 and the comparative covering tools 1 to 10. ..

Subsequently, with respect to the covering tools 1 to 10 and the comparative covering tools 1 to 10 of the present invention, wet face milling of ductile cast iron was performed in a state where they were clamped to the tip of a tool steel cutter having a cutter diameter of 63 mm with a fixing jig. A machining test was carried out and the flank wear width of the cutting edge was measured.

The cutting test is as follows.
Cutting test: Wet face milling work material: Ductile cast iron FCD450: Width 45 mm
Cutting speed: 200m / min
Notch: 1.0 mm
Single blade feed amount: 1.0 mm / blade cutting time: 7 minutes (normal cutting speed: 150 m / min)
Table 6 shows the results of the cutting test. Since the comparative covering tools 1 to 10 have reached the end of their life due to the occurrence of chipping, the time until the end of their life is shown.

From the results shown in Table 6, all of the coating tools 1 to 10 of the present invention are used for high-speed high-feed cutting of ductile cast iron and the like because the hard coating layer has excellent chipping resistance and peeling resistance. Even if it is present, chipping does not occur and excellent wear resistance is exhibited for a long period of time. On the other hand, the comparative covering tools 1 to 10 which do not satisfy the matters specified in the covering tool of the present invention cause chipping when used for high-speed high-feed cutting of ductile cast iron and the like, and are used in a short time. It has reached the end of its life.

As described above, the covering tool of the present invention can be used as a covering tool for high-speed high-feed cutting of ductile cast iron, and further exhibits excellent chipping resistance and peeling resistance for a long period of time. It is possible to fully satisfy the high performance of cutting equipment, labor saving and energy saving of cutting processing, and cost reduction.

Claims (5)

A surface-coated cutting tool in which a hard coating layer is provided on the surface of a tool substrate.
(A) The hard coating layer contains at least a composite nitride or composite carbonitride layer of Ti and Al having an average layer thickness of 1.0 to 20.0 μm.
(B) The Ti and Al composite nitride layer or composite carbonitride layer contains at least crystal grains having a NaCl-type face-centered cubic structure.
(C) When the cut surface parallel to the tool substrate is analyzed from the direction perpendicular to the surface of the tool substrate, a plurality of crystal grains having the NaCl-type face-centered cubic structure having different Ti and Al compositions are present. When each is divided into crystal grain A group and crystal grain B group,
When the crystal grain A group is represented by the composition formula: (Ti _1-XA Al _XA ) (C _YA N _1-YA ), the average X _Aavg of the content ratio X _A of Al in the total amount of Ti and Al, and The average Y _Aavg of the content ratio Y _A in the total amount of C and N of C (however, X _Aavg and Y _Aavg are both atomic ratios) are 0.75 ≤ X _Aavg ≤ 0.95 and _0.0000 , respectively. _{Satisfying ≤Y Aavg} ≤ 0.0150,
When the crystal grain B group is represented by the composition formula: (Ti _1-XB Al _XB ) ( _CYB N _1-YB ), the average X _Bavg of the content ratio X _B of Al in the total amount of Ti and Al, and The average Y _Bavg of C and Y _B in the total amount of C and N (however, X _Bavg and Y _Bavg are both atomic ratios) is 0.70 ≤ X _Bavg ≤ 0.90, 0.05 ≤ X. _{Satisfying Aavg-} X _Bavg ≤ 0.25, 0.0000 ≤ Y _Bavg ≤ 0.0150,
(D) The area ratio of the crystal grain A group on the cut surface is 20 to 80%.
A surface coating cutting tool characterized by that. In the crystal grains of the crystal grain A group, a periodic composition change of Ti and Al exists along one of the equivalent crystal orientations represented by <001> of the crystal grains, and is periodic. the surface-coated cutting tool according to claim 1, the difference [Delta] X _a between the average value of the average value and the minimum value of the maximum value of the varying X _a is characterized by a 0.03 to 0.25 in. In the crystal grains of the crystal grain B group, a periodic composition change of Ti and Al exists along one of the equivalent crystal orientations represented by <001> of the crystal grains, and is periodic. the surface-coated cutting tool according to claim 1 or 2 difference [Delta] X _B between the average value of the average value and the minimum value of the maximum value of the varying X _B is characterized by a 0.03 to 0.25 in. One of Ti carbide layer, nitride layer, carbonitride layer, coal oxide layer and carbonitride oxide layer between the tool substrate and the composite nitride or composite carbonitride layer of Ti and Al. The surface coating cutting tool according to any one of claims 1 to 3, further comprising two or more layers and having a lower layer having a total average layer thickness of 0.1 to 20 μm. The invention according to any one of claims 1 to 4, wherein an upper layer including at least an aluminum oxide layer is present above the composite nitride or composite carbonitride layer with a total average layer thickness of 1 to 25 μm. Surface coating cutting tool.

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