JP2008093770A - Surface coated cutting tool with hard coated layer exhibiting excellent chipping resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface coated cutting tool with a hard coated layer exhibiting excellent chipping resistance in high speed heavy cutting machining. <P>SOLUTION: The hard coated layer constituted by alternately laminating a Ti-Cr composite carbonitride layer a Cr inclusion rate of which is 0.01-0.1 (atomic ratio) and an Al<SB>2</SB>O<SB>3</SB>layer is provided on a surface of a tool base body, or this alternately laminated layer is made an upper part layer, a TiN layer, a TiC layer, TiCN layer or one layer or more than one layers of a (Ti, Zr)N layer, a (Ti, Zr)C layer and a (Ti, Zr)CN layer at least a Ti component of one layer of a lower part layer of which is substituted with Zr is or are provided as the lower part layer between the upper part layer and the tool base body surface, and the Ti-Cr composite carbonitride layer which is a constitutive layer of the upper part layer is constituted of the Ti-Cr composite carbonitride layer which is a constitutive atom covalent lattice point distribution graph formed in accordance with a measuring result of an inclination made by a normal of a (001) face and a (011) face of a crystal grain existing in a measuring area of a surface polishing surface and a normal of the surface polishing surface. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  This invention exhibits excellent chipping resistance with a hard coating layer, especially when milling processing of steel, tool steel, cast iron, etc. is performed at high speed and under high-speed heavy cutting conditions such as high feed and high cutting. The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool).

Conventionally, a substrate composed of a tungsten carbide group (hereinafter referred to as WC group) cemented carbide or a titanium carbonitride group (hereinafter referred to as TiCN group) cermet (hereinafter collectively referred to as a tool substrate). ), As a lower layer of the hard coating layer, a Ti compound layer such as a Ti carbonitride layer (hereinafter referred to as “conventional TiCN layer”), or a composite carbonitride layer of titanium and chromium (hereinafter referred to as “ Coating tools are known in which a Ti—Cr composite carbonitride layer ”is formed by vapor deposition, and an Al ₂ O ₃ layer is vapor-deposited as an upper layer of the hard coating layer. It is also well known that it is used for continuous cutting and intermittent cutting of steel and cast iron.

And the said conventional TiCN layer is in a normal chemical vapor deposition apparatus, for example,
(B) Reaction gas composition (volume%):
TiCl _4: 2~10%,
CH ₃ CN: 1~5%,
N _2: 10~30%,
H ₂ : Remaining
(B) Reaction atmosphere temperature: 800-930 ° C.
(C) Reaction atmosphere pressure: 6 to 15 kPa,
It is known that it is vapor-deposited under the conditions of
It is known that the Ti—Cr composite carbonitride layer is formed, for example, by performing chemical vapor deposition by adding a small amount of CrCl ₃ to the reaction gas for forming the conventional TiCN layer.

In the above-mentioned coated tool, the constituent layer of the hard coating layer generally has a granular crystal structure. For the purpose of improving the strength of the conventional TiCN layer, an organic carbonitride is used as a reaction gas in a normal chemical vapor deposition apparatus. It is also known to form a TiCN layer (hereinafter, referred to as an l-TiCN layer) having a vertically elongated crystal structure by chemical vapor deposition at a medium temperature range of 700 to 950 ° C. using a mixed gas containing.
JP-A-10-244405 JP 2001-11632 A Japanese Patent Laid-Open No. 6-8010

In recent years, the performance of cutting machines has been remarkable. On the other hand, there are strong demands for labor saving and energy saving of cutting work.Accordingly, cutting has been further increased in speed and high feed and high cutting depth. In the above conventional coated tool, there is no problem when this is used for milling cutting under normal processing conditions such as steel, tool steel and cast iron, but when this is used for high-speed high-feed high-cutting, Since the high temperature strength of the Al ₂ O ₃ layer of the hard coating layer is not sufficient, it cannot withstand the mechanical and thermal loads under high-speed, high-feed, high-cut milling, and chipping (small chipping) occurs early. However, at present, the service life is reached in a relatively short time.

Therefore, the present inventors aim to improve the chipping resistance of the hard coating layer of the coated tool provided with the Ti—Cr composite carbonitride layer as the lower layer of the Al ₂ O ₃ layer from the above viewpoint. , As a result of research,
(A) In a conventional coated tool having an Al ₂ O ₃ layer as an upper layer and a Ti—Cr composite carbonitride layer as a lower layer, the Al ₂ O ₃ layer has excellent high-temperature hardness and heat resistance, Under high-speed heavy cutting conditions such as high feed and high cutting, it does not have satisfactory high-temperature strength, but the average layer thickness of the Al ₂ O ₃ layer is 0.2 to ₂ μm, and further 0.2 to 2 μm. By forming the hard coating layer as an alternate laminated structure with the Ti—Cr composite carbonitride layer having an average layer thickness, the excellent high-temperature strength of the Ti—Cr composite carbonitride layer makes it possible to form the Al ₂ O ₃ layer. Strength is complemented, and the hard coating layer as a whole has excellent high temperature hardness, heat resistance and excellent high temperature strength, and as a result, the occurrence of chipping under high speed heavy cutting conditions is suppressed. thing.
That is, the Ti—Cr composite carbonitride layer, which is a constituent layer of the above-described alternately laminated structure,
(B) Reaction gas composition (volume%):
TiCl _4: 2~10%,
CrCl ₃ : 0.02 to 1%,
CH ₃ CN: 1~5%,
N _2: 10~30%,
H ₂ : Remaining
(B) Reaction atmosphere temperature: 800-930 ° C.
(C) Reaction atmosphere pressure: 15 to 25 kPa,
The Ti—Cr composite carbonitride layer formed as a result of vapor deposition under the following conditions contains Cr at a ratio of 1 to 10 atomic% in the ratio to the total amount with Ti, and the above conventional The same crystal structure of the NaCl type face centered cubic crystal as that of the TiCN layer (see FIG. 1 above), that is, a crystal structure of NaCl type face centered cubic crystal in which a part of Ti atoms are replaced by Cr atoms, The high temperature strength is further improved by the action of Cr contained in the substitution, so the chipping resistance of the hard coating layer in high-speed, high-feed, high-cut milling cutting that requires extremely high mechanical and thermal loads on the cutting edge. To improve.

(B) For the conventional TiCN layer and the Ti—Cr composite carbonitride layer,
Using a field emission scanning electron microscope, as illustrated in the schematic explanatory diagrams in FIGS. 2A and 2B, each crystal grain existing within the measurement range of the surface polished surface is irradiated with an electron beam, The inclination angle formed by the normal lines of the (001) plane and the (011) plane, which are the crystal planes of the crystal grains, with respect to the normal line of the surface polished surface (FIG. 2A shows (001) of the crystal planes. When the tilt angle of the surface is 0 degree and the tilt angle of the (011) plane is 45 degrees, the tilt angle of the (001) plane is 45 degrees and the tilt angle of the (011) plane is 0 degree. Are measured at the interface between crystal grains adjacent to each other, based on the measured tilt angles obtained as a result of the measurement. Calculate the distribution of lattice points (constituent atom shared lattice points) in which each atom shares one constituent atom between the crystals, The constituent atomic shared lattice point form in which there are N lattice points that do not share constituent atoms between the constituent atomic shared lattice points (N is an even number of 2 or more in the crystal structure of the NaCl type face centered cubic crystal) is represented by ΣN + 1. When the constituent atomic shared lattice point distribution graph showing the distribution ratio of each ΣN + 1 to the entire ΣN + 1 (however, the upper limit value of N is 28 in relation to the frequency) is created, the conventional TiCN layer is shown in FIG. As illustrated, the Ti—Cr composite carbonitride layer has a relatively low constituent atom shared lattice point distribution graph in which the distribution ratio of Σ3 is 30% or less, as shown in FIG. , Σ3 has the highest peak, and the distribution ratio of Σ3 shows an extremely high constituent atom shared lattice point distribution graph of 60% or more, and the distribution ratio of Σ3 in the Ti—Cr composite carbonitride layer is Depending on the Cr content in the layer Changes Te, further, Cr content in the layer, can be adjusted by the mixing ratio of CrCl ₃ in the reaction gas.

(C) In other words, when the Ti—Cr composite carbonitride layer is formed by vapor deposition, the content of CrCl _{3 in} the reaction gas at the time of vapor deposition is 0.02 to 1% by volume, and the formed Ti—Cr composite nitride layer By making the Cr content ratio of 1 to 10 atomic% in the ratio to the total amount of Ti, the distribution ratio of Σ3 in the constituent atomic shared lattice point distribution graph becomes extremely high of 60% or more. As a result, the Ti-Cr composite carbonitride layer has a further improved high-temperature strength as compared with the conventional TiCN layer. Therefore, even if the Cr content ratio in the layer deviates from the above range, Alternatively, even if the value is higher, the distribution ratio of Σ3 in the constituent atom shared lattice distribution graph becomes less than 60%, and the desired high temperature strength improvement effect cannot be obtained.

(D) Since the Ti—Cr composite carbonitride layer has a higher high-temperature strength than the conventional TiCN layer in addition to the hardness and strength of the conventional TiCN layer, the Ti—Cr composite Coated tools with a hard coating layer with a laminated structure in which carbonitride layers and Al ₂ O ₃ layers are alternately laminated by chemical vapor deposition are used in high-speed, high-feed, high-cut milling processes that require extremely high mechanical and thermal loads. However, the hard coating layer exhibits excellent chipping resistance and exhibits excellent performance over a long period of time.

(E) In a coated tool provided with a hard coating layer composed of an alternately laminated structure of the Ti—Cr composite carbonitride layer and the Al ₂ O ₃ layer, the total average layer thickness is set as a lower layer of the hard coating layer. One or more of a 2 to 10 μm titanium nitride (TiN) layer, a titanium carbide (TiC) layer, a titanium carbonitride (TiCN) layer, or at least one titanium component of these layers A composite nitride layer of titanium and zirconium partially substituted with zirconium (hereinafter referred to as (Ti, Zr) N), a composite carbide layer of titanium and zirconium (hereinafter referred to as (Ti, Zr) C) layer or titanium; By forming a composite carbonitride (hereinafter referred to as (Ti, Zr) CN) layer of zirconium by chemical vapor deposition, the strength of the hard coating layer is secured, and chipping occurs under high speed heavy cutting conditions. Control is the thing.

(F) Regarding the formation of the lower layer, the TiN layer, TiC layer, and TiCN layer can be formed by vapor deposition under the same formation conditions as in the conventional method, and a part of the titanium component of these layers is replaced with zirconium. The (Ti, Zr) N layer, the (Ti, Zr) C layer, or the (Ti, Zr) CN layer are formed by adding a small amount of ZrCl ₄ to the reaction gas forming the TiN layer, TiC layer, and TiCN layer, respectively. It can be formed by chemical vapor deposition.
The research results shown in (a) to (f) above were obtained.

This invention was made based on the above research results,
“(1) At least on the surface of a tool base made of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet,
(A) It has an average layer thickness of 0.2 to 2 μm, and the content ratio of chromium to the total amount of titanium and chromium (Cr / (Ti + Cr)) is 0.01 to 0.1 in atomic ratio. A composite carbonitride layer of titanium and chromium,
(B) an aluminum oxide layer having an average layer thickness of 0.2-2 μm,
A hard coating layer comprising a hard coating layer formed by chemical vapor deposition, wherein at least three layers (a) and (b) are alternately laminated, and the total average layer thickness is 1 to 6 μm. A surface-coated cutting tool with excellent chipping resistance.
(2) In a surface-coated cutting tool in which a hard coating layer composed of at least an upper layer and a lower layer is vapor-deposited on the surface of a tool base composed of a tungsten carbide-based cemented carbide or a titanium carbonitride-based cermet,
The upper layer is
(A) It has an average layer thickness of 0.2 to 2 μm, and the content ratio of chromium to the total amount of titanium and chromium (Cr / (Ti + Cr)) is 0.01 to 0.1 in atomic ratio. A composite carbonitride layer of titanium and chromium,
(B) an aluminum oxide layer having an average layer thickness of 0.2-2 μm,
The above (a) and (b) are alternately laminated at least three layers, and consists of alternate lamination formed by chemical vapor deposition so that the total average layer thickness is 1 to 6 μm,
The lower layer is
(C) consisting of one or more of a titanium nitride layer, a titanium carbide layer, and a titanium carbonitride layer formed by chemical vapor deposition with a total average layer thickness of 2 to 10 μm.
A surface-coated cutting tool that exhibits excellent chipping resistance due to its hard coating layer.
(3) In the surface-coated cutting tool according to (2),
At least one of the lower layers (c) includes a titanium-zirconium composite nitride layer in which a part of titanium is replaced with zirconium, a titanium-zirconium composite carbide layer, or a titanium-zirconium composite carbonitride layer,
The surface-coated cutting tool according to (2) above, wherein
(4) In the surface-coated cutting tool according to (2) or (3),
Between the upper layer and the lower layer, an intermediate layer having a total average layer thickness of 0.2 to 1 μm composed of one or more of a titanium carbonate layer, a titanium nitride oxide layer, and a titanium carbonitride oxide layer is interposed. The surface-coated cutting tool according to (2) or (3) above, wherein
(5) In the surface-coated cutting tool according to (1) to (4),
The composite carbonitride layer of titanium and chromium in the above (a) uses a field emission scanning electron microscope to irradiate each crystal grain existing within the measurement range of the surface polished surface with an electron beam, and The tilt angle formed by the normal lines of the (001) plane and (011) plane, which are crystal planes of the crystal grains, is measured. In this case, the crystal grains have titanium, chromium, and carbon at lattice points. Each of the constituent atoms has a crystal structure of NaCl type face centered cubic crystal in which constituent atoms composed of nitrogen and nitrogen are present, respectively, at the interface between adjacent crystal grains based on the measured tilt angle. Calculates the distribution of lattice points that share one constituent atom between the crystal grains (constituent atom shared lattice points), and N lattice points that do not share constituent atoms between the constituent atom shared lattice points (N is N An even number of 2 or more in the crystal structure of the NaCl type face centered cubic crystal When the configuration of existing constituent atomic shared lattice points is represented by ΣN + 1, the constituent atomic shared lattice point distribution graph showing the distribution ratio of each ΣN + 1 in the entire ΣN + 1 (however, the upper limit is 28 in terms of frequency) In any of the above, it is a composite carbonitride layer of titanium and chromium that shows a constituent atomic shared lattice point distribution graph in which the highest peak exists in Σ3 and the distribution ratio of the Σ3 in the entire ΣN + 1 is 60% or more. The surface-coated cutting tool according to any one of (1) to (4), which is characterized in that "
It has the characteristics.

Next, the reason why the constituent layers of the hard coating layer of the coated tool of the present invention are limited as described above will be described.
(A) Titanium-chromium composite carbonitride layer (Ti-Cr composite carbonitride layer) which is a constituent layer of an alternately laminated structure
The Ti—Cr composite carbonitride layer has excellent high-temperature hardness and excellent high-temperature strength, but this characteristic is obtained by chemical vapor deposition by adding CrCl ₃ to the reaction gas at a ratio of 0.02 to 1% by volume. As a result of setting the Cr content ratio in the deposited layer to 1 to 10 atomic% in the ratio to the total amount with Ti, the distribution ratio of Σ3 in the constituent atomic shared lattice point distribution graph is 60% or more. On the other hand, if the distribution ratio of Σ3 is less than 60%, the effect of improving the high temperature strength is small, and it is inevitable that chipping occurs in the hard coating layer in the high-speed, high-feed, high-cut milling process. Since the excellent wear resistance cannot be exhibited, the Cr content ratio (Cr / (Ti + Cr)) with respect to the total amount of Ti and Cr is set to 0.01 to 0.1 (however, the atomic ratio). , And it was defined as 60% or more a distribution ratio of [sum] 3.
In addition, when the average layer thickness of the Ti—Cr composite carbonitride layer is less than 0.2 μm, the shortage of high-temperature strength of the Al ₂ O ₃ layer that is a constituent layer of the alternately laminated structure is supplemented, On the other hand, when the average layer thickness exceeds 2 μm, sufficient adhesion strength with the adjacent Al ₂ O ₃ layer cannot be secured, and the hard coating layer is likely to chip. Therefore, the average layer thickness was set to 0.2 to 2 μm.

(B) Aluminum oxide layer (Al ₂ O ₃ layer) which is a constituent layer of an alternately laminated structure
The Al ₂ O ₃ layer has excellent high-temperature hardness and heat resistance, and exhibits wear resistance against wear during cutting, but exhibits sufficient wear resistance when the average layer thickness is less than 0.2 μm. In addition, when the average layer thickness is 2 μm or more, it is not only possible to secure sufficient adhesion strength with the adjacent Ti—Cr composite carbonitride layer, but under high speed heavy cutting conditions. Since chipping is likely to occur due to insufficient high-temperature strength, the average layer thickness was set to 0.2 to 2 μm.

(C) Alternating stack (upper layer) composed of an aluminum oxide layer (Al ₂ O ₃ layer) and a composite carbonitride layer of titanium and chromium (Ti—Cr composite carbonitride layer)
The Al ₂ O ₃ layer and the Ti—Cr composite carbonitride layer are alternately laminated at least 3 layers, and a hard coating layer (upper layer) having an alternately laminated structure so that the total average layer thickness is 1 to 6 μm. Is formed by chemical vapor deposition, and the lack of high-temperature strength of the Al ₂ O ₃ layer is supplemented by alternately laminating Ti—Cr composite carbonitride layers having excellent high-temperature strength, and the hard coating layer (upper layer) as a whole However, if the total average layer thickness of the hard coating layer (upper layer) composed of alternating layers is less than 1 μm, sufficient wear resistance can be demonstrated in high-speed, high-feed, high-cut milling processing. On the other hand, if the total average layer thickness exceeds 6 μm, chipping and abnormal wear are likely to occur. Therefore, the total average layer thickness of the hard coating layer (upper layer) was set to 1 to 6 μm.

(D) a titanium nitride (TiN) layer, a titanium carbide (TiC) layer, a titanium carbonitride (TiCN) layer, or a lower layer composed of two or more layers, or at least one of these layers is Titanium and zirconium composite nitride ((Ti, Zr) N) layer, titanium and zirconium composite carbide ((Ti, Zr) C) layer or titanium and zirconium composite carbonitride Lower layer formed of a material ((Ti, Zr) CN) layer TiN layer, TiC layer, TiCN layer constituting the lower layer of the hard coating layer, and at least one of these layers is (Ti, Zr) The N layer, the (Ti, Zr) C layer, or the (Ti, Zr) CN lower layer are all provided with excellent strength, and the Al ₂ O ₃ layer constituting the upper layer of the hard coating layer, Ti -Excellent adhesion and bonding strength with Cr composite carbonitride layer, contributing to improved chipping resistance under high speed heavy cutting conditions.
Among the above lower layers, the formation conditions of the TiN layer, TiC layer, and TiCN layer are the same as those in the conventional method, and (Ti, Zr) N layer in which a part of Ti is replaced with Zr, (Ti, Zr) The C layer and the (Ti, Zr) CN layer contain 0.1 to 1% of ZrCl ₄ in each reaction gas forming the TiN layer, TiC layer, and TiCN layer. It can be formed by vapor deposition. And about the Zr content ratio (Zr / (Ti + Zr)) with respect to the total amount of Ti and Zr in the (Ti, Zr) N layer, (Ti, Zr) C layer, (Ti, Zr) CN layer, the Zr content ratio Is less than 0.02, the effect of improving the strength cannot be expected. On the other hand, when the content ratio of Zr exceeds 0.15, the hardness decreases, so (Ti, Zr) The content ratio of Zr in the N layer, the (Ti, Zr) C layer, and the (Ti, Zr) CN layer is preferably 0.02 to 0.15 in atomic ratio.

(E) Total average layer thickness of 0.2 to 1 μm consisting of one layer or two or more of a titanium carbonate layer (TiCO layer), a titanium nitride oxide layer (TiNO layer) and a titanium carbonitride oxide layer (TiCNO layer) Intermediate layer of Titanium carbonate (TiCO) layer, Titanium oxynitride (TiNO) layer and Titanium carbonitride oxide (TiCNO) layer Intermediate layer having a total average layer thickness of 0.2 to 1 μm consisting of one or more layers If the intermediate layer is interposed between the upper layer and the lower layer, the intermediate layer has excellent adhesion to both the upper layer and the lower layer, and also has high adhesion strength. It has the effect of increasing the bonding strength between the layers and, as a result, further increasing the high temperature strength of the entire hard coating layer and further improving the chipping resistance, but if the total average layer thickness is less than 0.2 μm, the bonding strength is improved. Less effective If the total average layer thickness exceeds 1 μm, abnormal damage such as chipping is likely to occur. Therefore, the total average layer thickness of the intermediate layer is set to 0.2 to 1 μm.

It is generally known that a TiN layer having a gold color is coated on the hard coating layer for the purpose of facilitating identification of a use corner after cutting of the coated tool. Alternatively, for the purpose of identifying the use corner, a TiN layer may be coated on the outermost layer of the upper layer composed of an alternately laminated structure of Al ₂ O ₃ layers and Ti—Cr composite carbonitride layers. In this case, the thickness of the coating layer of the TiN layer is sufficient to be 0.2 to 1 μm.

Also, in recent years, after forming a hard coating layer, a physical method, specifically, a dry or wet blasting process using a grinding wheel, a brush made of nylon, etc., SiC, Al ₂ O ₃ and ZrO ₂ particles as a medium, etc. Thus, it is known that the surface of the hard coating layer is smoothed and the welding resistance is improved, but it is of course possible to apply this to the coated tool of the present invention.

The coated tool of the present invention includes a hard coating layer having an alternately laminated structure of a Ti—Cr composite carbonitride layer and an Al ₂ O ₃ layer on the surface thereof (Claim 1), or this as an upper layer, Between the upper layer and the tool substrate, a TiN layer, a TiC layer, a lower layer composed of two or more of the TiCN layers, or at least one of these layers is a (Ti, Zr) N layer, ( A lower layer made of a Ti, Zr) C layer or a (Ti, Zr) CN layer is provided (Claims 2 and 3), or further, one of a TiCO layer, a TiNO layer and a TiCNO layer is provided between the upper layer and the lower layer. An intermediate layer comprising two or more layers is provided (Claim 4), and further, the Ti-Cr composite carbonitride layer contains 1 to 10 atomic% Cr in a proportion of the total amount with Ti, Distribution ratio of Σ3 in constituent atomic grid distribution graph Since it is configured as an extremely high material of 60% or more (Claim 5), not only milling processing under normal conditions such as various steels, tool steels, and cast irons, especially mechanical and thermal loads are large. In addition, it exhibits excellent chipping resistance and wear resistance even at high speed, high feed and high depth of cut with high heat generation, and exhibits excellent cutting performance over a long period of time.

  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, TiN powder, TaN powder, and Co powder all having an average particle diameter of 1 to 3 μm are prepared. Then, blended into the composition shown in Table 1, added with wax, ball mill mixed in alcohol for 10 hours, dried under reduced pressure, and then press molded into a compact of a predetermined shape at a pressure of 98 MPa. Is vacuum-sintered at a predetermined temperature in the range of 1370 to 1470 ° C. for 1 hour in a vacuum of 5 Pa, and after sintering, the cutting edge portion has a width of 0.15 mm and an angle of 20 degrees Chamfor Honing As a result, tool bases A to F made of a WC-based cemented carbide having a throwaway tip shape specified in ISO · SEEN1203AFTN1 were produced.

Next, a lower layer is formed by vapor deposition on the surface of these tool bases A to F with the conditions shown in Table 5 and the target average layer thickness shown in Table 7, or further, the conditions shown in Table 6 and Table 7 below. After the intermediate layer is formed by vapor deposition with the target average layer thickness shown, a Ti—Cr composite carbonitride layer is formed with the conditions shown in Table 2 and the target average layer thickness shown in Table 8 using a normal chemical vapor deposition apparatus. Then, an Al ₂ O ₃ layer having a crystal form of κ type or α type was formed by vapor deposition under the conditions shown in Table 4 and the target average layer thickness shown in Table 8, and Ti—Cr composite carbonitride the present invention coated tool 18 having a hard coating layer consisting of alternating stacked layers and the Al ₂ O ₃ layer was produced. (The “target content ratio” in Tables 2 and 5 is the value of Cr / (Ti + Cr) or Zr / (Ti + Zr) expressed in atomic ratio.)

For the purpose of comparison, a TiCN layer is formed in place of the Ti—Cr composite carbonitride layer under the conditions shown in Table 3 and the target average layer thickness shown in Table 10, and other conditions (for example, lower layer, intermediate layer) Comparative forming tools 1 to 18 were manufactured by setting the same conditions as the above-described coated tools 1 to 18 of the present invention as to the conditions for forming the Al ₂ O ₃ layer. (The lower layer, the intermediate layer, and the layer thickness of the comparative coated tools 1 to 18 are shown in Table 9.)
For example, a TiCN layer having a vertically long crystal structure formed for the purpose of improving the strength of the layer as disclosed in JP-A-6-8010 is shown as “l-TiCN” in Table 5.

Next, the field emission of the Ti—Cr composite carbonitride layer constituting the alternate laminated structure of the hard coating layer of the above-described coated tool of the present invention and the TiCN layer constituting the alternate laminated structure of the hard coated layer of the comparative coated tool is described. Using a scanning electron microscope, a constituent atom shared lattice distribution graph was created.
In other words, the constituent atomic shared lattice point distribution graph is shown in the column of the field emission scanning electron microscope in a state where the surfaces of the Ti-Cr composite carbonitride layer of the present invention and the conventional TiCN layer are respectively polished surfaces. Electron backscattering is performed by irradiating the polishing surface with an electron beam having an acceleration voltage of 15 kV at an incident angle of 70 degrees with an irradiation current of 1 nA on each crystal grain within the measurement range of the surface polishing surface. Using a diffraction image apparatus, a region of 30 × 50 μm is spaced at a spacing of 0.1 μm / step and the (001) plane and (011) plane, which are crystal planes of the crystal grains, with respect to the normal line of the surface polishing plane Measure the tilt angle formed by the normal, and based on the measured tilt angle, each of the constituent atoms shares one constituent atom between the crystal grains at the interface between the adjacent crystal grains. Lattice points (constituent atom sharing (Distribution point) distribution, and there are N lattice points that do not share constituent atoms between the constituent atomic shared lattice points (N is an even number of 2 or more in the crystal structure of the NaCl-type face-centered cubic crystal) When the atomic shared lattice point form is represented by ΣN + 1, it was created by determining the distribution ratio of each ΣN + 1 to the entire ΣN + 1 (however, the upper limit value is 28 due to frequency).

In the atomic distribution lattice point distribution graph of the Ti—Cr composite carbonitride layer constituting the alternately laminated structure of the hard coating layers of the coated tool of the present invention obtained as a result, the entire ΣN + 1 (N is in the range of 2 to 28) Table 8 shows the distribution ratio of Σ3 in all the even numbers).
For comparison, in the constituent atomic shared lattice point distribution graph of the TiCN layer of the comparative coated tool, the distribution ratio of Σ3 in the entire ΣN + 1 (N is all even numbers in the range of 2 to 28) is shown in Table 10, respectively. Indicated.

In each of the above-mentioned various constituent atomic share lattice point distribution graphs, as shown in Tables 8 and 10, respectively, Ti—Cr composite carbonitride layers constituting the alternately laminated structure of the present coated tools 1 to 18 are all Σ3. In contrast to the constituent atom sharing lattice distribution graph in which the distribution ratio occupied by 60% or more is shown, the conventional TiCN layers of the comparative coated tools 1 to 18 all share constituent atoms with a Σ3 distribution ratio of less than 30%. A grid point distribution graph was shown.
3 is a constituent atomic shared lattice distribution graph of the Ti—Cr composite carbonitride layer formed under the condition A-7 in the present coated tool 5, and FIG. 4 is a comparison coated tool 5. FIG. 6 shows a constituent atom shared lattice point distribution graph of a conventional TiCN layer formed under the conditions of a-7. FIG.

  Further, for the above-described inventive coated tools 1-18 and comparative coated tools 1-18, the constituent layers of these hard coating layers were observed using an Auger spectroscopic analyzer (observation of the longitudinal section of the layers). And the thickness of the constituent layer of the hard coating layer of these coated tools was measured using a scanning electron microscope (same longitudinal section measurement). The average layer thickness (average value of 5-point measurement) substantially the same as the target layer thickness was shown.

First, front milling with a single blade was performed on the above-described inventive coated tools 1 to 18 and comparative coated tools 1 to 18 under the following cutting conditions A to C.
[Cutting conditions A]
Work material: JIS / SCr420H block material,
Cutting speed: 380 m / min,
Cutting depth: 4 mm,
Single blade feed rate: 0.4 mm / tooth,
Cutting time: 5 minutes,
Wet high speed high cutting high feed cutting test of alloy steel under the conditions of (normal cutting speed, cutting, feed are 200 m / min, 1.5 mm, 0.2 mm / blade, respectively),
[Cutting conditions B]
Work material: Block material of JIS / SKD11,
Cutting speed: 320 m / min,
Cutting depth: 3.5 mm,
Single blade feed rate: 0.4 mm / tooth,
Cutting time: 5 minutes,
Tool steel wet high-speed high-cut high-feed cutting test (normal cutting speed, cutting and feed are 150 m / min, 1.5 mm, and 0.15 mm / tooth, respectively),
[Cutting conditions C]
Work material: JIS / FC350 block,
Cutting speed: 420 m / min,
Cutting depth: 4.3 mm,
Feed: 0.45 mm / tooth,
Cutting time: 5 minutes,
Cast iron wet high speed high cutting high feed cutting test (normal cutting speed, cutting, feed are 250 m / min, 1.5 mm, 0.2 mm / blade, respectively),
The flank wear width of the cutting edge in each of the above cutting tests was measured, and the measurement results are shown in Table 11.

From the results shown in Tables 8, 10, and 11, the present invention coated tools 1 to 18 are configured such that the upper layer of the hard coating layer has an alternately laminated structure of Ti—Cr composite carbonitride layers and Al ₂ O ₃ layers. And, the Ti—Cr composite carbonitride layer, which is a constituent layer of the alternately laminated structure, contains 1 to 10 atomic% of Cr in the proportion of the total amount with Ti, and is a constituent atomic shared lattice point distribution graph. The distribution ratio of Σ3 is extremely high with 60% or more, so it has high mechanical and thermal load, and high-speed, high-feed, high-speed feeds for various steels, tool steels and cast irons with high heat generation. In incision milling, the hard coating layer exhibits excellent chipping resistance and excellent wear resistance, whereas the alternating laminated structure of the hard coating layer is conventionally formed of a TiCN layer and an Al ₂ O ₃ layer For coated tools 1-18 Therefore, it cannot withstand the severe mechanical and thermal loads of high-speed, high-feed, high-cut milling, and chipping occurs in the hard coating layer, and wear is also accelerated. It is clear that

  As described above, the coated tool of the present invention is not only milled under normal conditions such as various types of steel, tool steel, and cast iron, and particularly has a large mechanical and thermal load and is accompanied by high heat generation. Even under high-speed, high-feed, high-cut high-speed heavy cutting conditions, it exhibits excellent chipping resistance and wear resistance, and exhibits excellent cutting performance over a long period of time. It can be used satisfactorily for labor saving, energy saving, and cost reduction.

It is a schematic diagram which shows the crystal structure of the NaCl type face centered cubic crystal which the conventional TiCN layer of a hard coating layer has. It is a schematic explanatory drawing which shows the measurement aspect of the inclination angle of the (001) plane and the (011) plane of the crystal grain which has a crystal structure of a NaCl type face centered cubic crystal. It is a constituent atom shared lattice point distribution graph of the Ti-Cr compound carbonitride layer formed on formation condition A-7 of the present invention covering tool 5. It is a constituent atom shared lattice point distribution graph of the conventional TiCN layer formed on the formation condition a-7 of the comparative coating tool 5.

Claims (5)

At least on the surface of the tool base composed of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet,
(A) It has an average layer thickness of 0.2 to 2 μm, and the content ratio of chromium to the total amount of titanium and chromium (Cr / (Ti + Cr)) is 0.01 to 0.1 in atomic ratio. A composite carbonitride layer of titanium and chromium,
(B) an aluminum oxide layer having an average layer thickness of 0.2-2 μm,
A hard coating layer comprising a hard coating layer formed by chemical vapor deposition, wherein at least three layers (a) and (b) are alternately laminated, and the total average layer thickness is 1 to 6 μm. A surface-coated cutting tool with excellent chipping resistance. In a surface-coated cutting tool in which a hard coating layer composed of at least an upper layer and a lower layer is vapor-deposited on the surface of a tool base composed of a tungsten carbide-based cemented carbide or a titanium carbonitride-based cermet,
The upper layer is
(A) It has an average layer thickness of 0.2 to 2 μm, and the content ratio of chromium to the total amount of titanium and chromium (Cr / (Ti + Cr)) is 0.01 to 0.1 in atomic ratio. A composite carbonitride layer of titanium and chromium,
(B) an aluminum oxide layer having an average layer thickness of 0.2-2 μm,
The above (a) and (b) are alternately laminated at least three layers, and consists of alternate lamination formed by chemical vapor deposition so that the total average layer thickness is 1 to 6 μm,
The lower layer is
(C) consisting of one or more of a titanium nitride layer, a titanium carbide layer, and a titanium carbonitride layer formed by chemical vapor deposition with a total average layer thickness of 2 to 10 μm.
A surface-coated cutting tool that exhibits excellent chipping resistance due to its hard coating layer. The surface-coated cutting tool according to claim 2,
At least one of the lower layers (c) includes a titanium-zirconium composite nitride layer in which a part of titanium is replaced with zirconium, a titanium-zirconium composite carbide layer, or a titanium-zirconium composite carbonitride layer,
The surface-coated cutting tool according to claim 2, wherein The surface-coated cutting tool according to claim 2 or 3,
Between the upper layer and the lower layer, an intermediate layer having a total average layer thickness of 0.2 to 1 μm composed of one or more of a titanium carbonate layer, a titanium nitride oxide layer, and a titanium carbonitride oxide layer is interposed. The surface-coated cutting tool according to claim 2 or 3, wherein The surface-coated cutting tool according to claim 1,
The composite carbonitride layer of titanium and chromium in the above (a) uses a field emission scanning electron microscope to irradiate each crystal grain existing within the measurement range of the surface polished surface with an electron beam, and The tilt angle formed by the normal lines of the (001) plane and (011) plane, which are crystal planes of the crystal grains, is measured. In this case, the crystal grains have titanium, chromium, and carbon at lattice points. Each of the constituent atoms has a crystal structure of NaCl type face centered cubic crystal in which constituent atoms composed of nitrogen and nitrogen are present, respectively, at the interface between adjacent crystal grains based on the measured tilt angle. Calculates the distribution of lattice points that share one constituent atom between the crystal grains (constituent atom shared lattice points), and N lattice points that do not share constituent atoms between the constituent atom shared lattice points (N is N An even number of 2 or more in the crystal structure of the NaCl type face centered cubic crystal When the configuration of existing constituent atomic shared lattice points is represented by ΣN + 1, the constituent atomic shared lattice point distribution graph showing the distribution ratio of each ΣN + 1 in the entire ΣN + 1 (however, the upper limit is 28 in terms of frequency) In any of the above, it is a composite carbonitride layer of titanium and chromium that shows a constituent atomic shared lattice point distribution graph in which the highest peak exists in Σ3 and the distribution ratio of the Σ3 in the entire ΣN + 1 is 60% or more. The surface-coated cutting tool according to any one of claims 1 to 4, wherein the surface-coated cutting tool is characterized in that:

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