JP2020146777A - Surface-coated cutting tool exerting excellent chipping resistance and wear resistance in heavy-load cutting process - Google Patents

Abstract

To provide a surface-coated cutting tool having a hard coating layer exerting excellent chipping resistance and wear resistance in a heavy-load cutting process.SOLUTION: In a surface-coated cutting tool, a hard coating layer comprising the alternate lamination structure by the layers A and B is provided on the surface of a tool substrate. The layer A has an average component composition of (Al1-xCrx)N (here, 0.20≤x≤0.60 in atomic ratio) and the layer B has that composition of (Al1-a-bCraSib)N (here, 0.20≤a≤0.60 and 0.01≤b≤0.20 in the atomic ratio. The absolute value of difference in grating constants of crystal grains composing the layers A and B is 0.05(Å) or less. Besides, the full width at half maximum of I(200) is 0.3 to 1.0 (degree), and I(200) and I(111) satisfy 1<I(200)/I(111)<10 when defining the X-ray diffraction peak intensities from (200) and (111) planes obtained by X-ray diffraction about whole alternate lamination structure as I(200) and I(111), respectively.SELECTED DRAWING: Figure 1

Description

According to the present invention, the hard coating layer exhibits excellent chipping resistance and abrasion resistance in high-load cutting (for example, high-speed high-feed deep hole drilling) in which a high load acts on the cutting edge, and is excellent over a long period of use. It relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits excellent cutting performance.

In general, surface-coated cutting tools include slow-away chips that are detachably attached to the tip of a cutting tool for turning and planing of various types of work materials such as steel and cast iron, and drilling and cutting of the work materials. There are drills and miniature drills used for machining, solid type end mills used for surface cutting, grooving, shoulder machining, etc. of the work material, and the solid with the throwaway tip detachably attached. Slow-away end mill tools that perform cutting in the same way as type end mills are known.

Further, as a coating tool, a hard coating layer made of a composite nitride layer of Al and Cr or a composite nitride layer of Ti and Al is used as a tungsten carbide (hereinafter referred to as WC) -based cemented carbide or titanium carbonitride (titanium carbon nitride). The surface of a substrate made of a base cermet (hereinafter referred to as TiCN) or a cubic boron nitride sintered body (hereinafter referred to as cBN) (hereinafter collectively referred to as a tool substrate) is coated by an arc ion plating method. The formed covering tool is known.
Many proposals have been made to improve the cutting performance of the covering tool.

For example, Patent Document 1 describes a hard layer composed of a metal component containing Cr and Al as main components and at least one element selected from C, N, O, and B on the surface of a tool substrate. In a hard film coating tool coated with one or more layers, the hard layer contains Si, and the hard layer is relatively rich in Si and amorphous, and a crystalline compound phase relatively poor in Si. It has been proposed that this hard film coating tool has absorptive wear resistance and oxidation wear resistance that can cope with dry cutting and high speed of cutting of high hardness steel. There is.

Patent Document 2 describes a hard film coated by an arc discharge type ion plating method, wherein the hard film is (Al _x Cr _{1-xy S y} ) (N _1-α-β-γ B _α). C _β O _γ ) However, x, y, α, β, and γ each indicate an atomic ratio, and 0.45 <x <0.85, 0 ≦ y <0.35, 0.50 ≦ x + y <1.0. , 0 ≦ α <0.15, 0 ≦ β <0.65, 0.003 <γ <0.2, 0 <α + β + γ <1.0, and consists of at least one layer, which is a rock salt in X-ray diffraction measurement. It has a structural type crystal structure, and the half-value width of 2θ of the diffraction peak on either the (111) plane or the (200) plane is 0.5 degrees or more and 2.0 degrees or less, and is contained in the hard film. A hard film has been proposed in which more oxygen is present at the crystal particle interface than inside the crystal particles, and this hard film has excellent adhesion to the cutting tool substrate, excellent high temperature oxidation resistance, and high hardness. It is said to have.

In Patent Document 3, in a coated cutting tool in which a hard film is coated on the surface of a base material for the purpose of improving the durability of the coated cutting tool, the hard film is arranged on the base material and a nanobeam diffraction pattern is provided. Indexed to the crystal structure of WC, a layer consisting of carbides consisting of C, W, Ti and unavoidable components, and an A content ratio of Al among metal (including semi-metal) elements arranged on the a layer. (Atomic%) is the largest, Al content ratio (atomic%) is 50% or more, Cr content ratio (atomic%) is 20% or more, and total content ratio (atomic%) of Al and Cr is 85% or more. , A layer b made of a nitride or a carbide having a Si content ratio (atomic%) of 5% to 15%, and the layer b has a NaCl-type crystal structure, and the film thickness of the layer a Has proposed a coated cutting tool having a diameter of 1 nm to 30 nm.

According to Patent Document 4, in a hard film coating tool in which a cemented carbide substrate is coated with a hard film having compressive stress, the first hard film and the second hard film are coated, and the first hard film is (Al _a Cr _{1). -A-b} Si _b ) _c N _d , a and b represent atomic%, c and d represent atomic ratios, 50 ≦ a ≦ 70, 0 ≦ b <15 and 0.85 ≦ c / d ≦ 1.25 In the second hard film, (Ti _{1-e S e} ) _f N _g , e represents atomic%, f and g represent atomic ratios, and 1 ≦ e ≦ 20 and 0.85 ≦ f / g ≦ 1. It is .25, and 0.965 ≦ d1 / d2 ≦ 0. When the surface spacing (nm) of the (200) planes in the X-ray diffraction of the first hard film and the second hard film is d1 and d2, respectively. A hard film coating tool of 990 has been proposed, and according to this hard film coating tool, it is possible to improve wear resistance while reducing compressive stress and ensuring adhesion in a thickened hard film. It is said that.

JP-A-2002-337007 Japanese Unexamined Patent Publication No. 2005-126736 International Publication No. 2014/156699 Japanese Unexamined Patent Publication No. 2011-93085

In recent years, the performance of cutting equipment has been remarkably improved, while there are strong demands for labor saving, energy saving, and cost reduction for cutting, and the cutting conditions have become stricter accordingly.
In the conventional covering tools proposed in Patent Documents 1 to 4, there is no particular problem when this is used for cutting steel or cast iron under normal conditions, but a high load acts on the cutting edge in particular. When used under harsh cutting conditions, chipping and the like are likely to occur, and the wear resistance is not satisfactory. Therefore, the service life is currently reached in a relatively short time.

For example, the composite nitride of Al, Cr, and Si (hereinafter referred to as "(Al, Cr, Si) N") layer in the coating tool proposed in Patent Documents 1 and 2 has high hardness and oxidation resistance. Although it is a film with excellent wear resistance, there is a problem that chipping resistance is reduced when it is used for cutting such as high-speed high-feed deep-hole drilling in which a continuous high load acts on the cutting edge. was there.
Further, in Patent Document 3, the adhesion is improved by providing a carbide layer containing W and Ti under the (Al, Cr, Si) N layer, and in Patent Document 4, (Al, Cr). , Si) Abrasion resistance is improved by laminating the N layer with the composite nitride of Ti and Si (hereinafter referred to as "(Ti, Si) N"), but all coating tools are cut. When used under harsh cutting conditions in which a high load acts on the blade, it is unavoidable that chipping of the hard coating layer occurs, which causes a problem that the tool life is shortened.

Therefore, from the above viewpoint, the present inventors have performed high-load cutting in which a high load acts on the cutting edge, for example, a high-speed high-feed deep hole drill for a work material such as carbon steel, alloy steel, or stainless steel. As a result of intensive research, the following findings were obtained in order to develop a coating tool that exhibits excellent chipping resistance for the hard coating layer during processing and at the same time exhibits excellent wear resistance over a long period of use. Obtained.

In the (Al, Cr, Si) N layer proposed in Patent Documents 1 to 4, Al, which is a component constituting the layer, improves high-temperature hardness and heat resistance, and Cr improves high-temperature strength and Cr. In the state where Cr and Al coexist and are contained, there is an action of improving high temperature oxidation resistance, and Si has an action of improving heat resistance. However, due to the inclusion of the Si component, (Al, Cr, Si) ) Due to the large lattice strain of the N layer, when a high load is applied, the (Al, Cr, Si) N layer does not have sufficient toughness to withstand this, and therefore chipping is likely to occur. I found.
In particular, when the hard coating layer to be coated on the surface of the tool substrate is formed as a laminated structure of the (Al, Cr, Si) N layer and another hard film, the (Al, Cr, Si) N layer itself. In addition to the low toughness of the hard coating layer, large strain occurs due to lattice mismatch at the laminated interface with other hard layers, so that the toughness of the hard coating layer as a whole is further lowered, and the occurrence of chipping cannot be avoided.

Therefore, the present inventors set the lattice constant of the (Al, Cr, Si) N layer so that lattice distortion is unlikely to occur by adjusting the amount of the component added, and when laminated with another hard layer, the present inventors set the lattice constant. Hard by minimizing the lattice mismatch at the laminated interface and adopting a laminated structure with other hard layers that have good adhesion to both the tool substrate and the (Al, Cr, Si) N layers. While improving the adhesion strength of the coating layer, the toughness of the hard coating layer as a whole is improved, and a coating tool with excellent chipping resistance and abrasion resistance can be obtained even under cutting conditions where a high load acts. I found that.

That is, specifically, in the coating tool of the present invention, at least one layer A and one layer B are alternately laminated on the surface of the tool substrate to form a hard coating layer, and a composite nitride of Al and Cr having a predetermined composition. The layer (hereinafter referred to as "(Al, Cr) N") is the A layer, and the (Al, Cr, Si) N layer having a predetermined composition is the B layer, and the lattice constant (aA) of the crystal grains constituting the A layer is used. ) And the absolute value (| aA-aB |) of the difference between the lattice constants (aB) of the crystal grains constituting the B layer are set to a small value to suppress the decrease in toughness due to the lattice mismatch.
Further, when the entire hard coating layer composed of the A layer and the B layer is subjected to X-ray diffraction, the diffraction peak intensity I (200) summarizing the diffraction peaks from the (200) plane of the crystal grains of the rock salt type cubic structure constituting each layer. ) Is set within a predetermined numerical range to enhance the crystallinity of the hard coating layer as a whole.
Further, the value (I) of the ratio (I) of the diffraction peak intensity I (111) summarizing the diffraction peaks from the (111) plane of the crystal grains of the rock salt type cubic structure constituting the A layer and the B layer and the above I (200). By keeping (200) / I (111)) within a predetermined numerical range, the hardness and toughness of the hard coating layer are balanced.
Then, by forming the hard coating layer of the coating tool of the present invention as the alternating laminated structure of the A layer and the B layer, a high load cutting process in which a high load acts on the cutting edge, for example, carbon steel or alloy steel In high-speed, high-feed deep-hole drilling of work materials such as stainless steel, it exhibits excellent chipping resistance and wear resistance.

Further, the covering tool of the present invention is a composite nitride of Ti, Si and W (hereinafter, "(Ti, Si)" on the outermost surface of the alternating lamination of the A layer and the B layer and directly above the B layer. , W) N ”) is formed, and the value of I (200) / I (111) of the hard coating layer composed of the C layer is set within a predetermined range to further improve the resistance. It can exhibit chipping resistance and abrasion resistance.

Further, the covering tool of the present invention has further excellent resistance by forming a D layer having a composition modulation structure of Si component at the interface between the B layer and the C layer forming the outermost surface of the alternating lamination. It can exhibit chipping resistance and abrasion resistance.

The present invention has been made based on the above research results and has the following features.
"(1) A hard coating layer having a total layer thickness of 0.5 to 8.0 μm on the surface of a tool substrate made of either a tungsten carbide-based cemented carbide, a titanium nitride-based cermet, or a cubic boron nitride sintered body. In the surface coating cutting tool provided with
(A) In the hard coating layer, at least one layer A having an average layer thickness of 0.005 to 4.0 μm and a layer B having an average layer thickness of 0.005 to 4.0 μm are alternately arranged. Including alternating laminated structure laminated in
(B) The A layer is
Composition formula: (Al _1-x Cr _x ) N
A composite nitride layer of Al and Cr having an average composition satisfying 0.20 ≦ x ≦ 0.60 (where x indicates the content ratio of Cr according to the atomic ratio) when represented by.
(C) The B layer is
Composition formula: (Al _1-ab Cr _a Si _b ) N
When represented by, 0.20 ≦ a ≦ 0.60, 0.01 ≦ b ≦ 0.20 (where a indicates the Cr content ratio according to the atomic ratio, and b indicates the Si content ratio according to the atomic ratio). It is a composite nitride layer of Al, Cr and Si having an average composition satisfying the above.
(D) The layers A and B constituting the alternating laminated structure contain crystal grains having a rock salt-type cubic structure.
(E) When the lattice constants of the crystal grains of the rock salt type cubic structure of the A layer and the crystal grains of the rock salt type cubic structure of the B layer are aA (Å) and aB (Å), respectively. , The absolute value of the difference between aA (Å) and aB (Å) | aA-aB | satisfies | aA-aB | ≤0.05 (Å).
(F) The X-ray diffraction peak intensity from the summarized (200) plane obtained by X-ray diffraction for the entire alternating laminated structure composed of the A layer and the B layer is the summarized (200) plane and the summarized (111) plane. When the X-ray diffraction peak intensity from I (111) is I (111), the half-value total width of I (200) is 0.3 to 1.0 (degrees), and the ratio of the ratio of I (200) to I (111). A surface-coated cutting tool, characterized in that the value satisfies 1 <I (200) / I (111) <10.
(2) A layer C having a layer thickness of 0.1 to 4.0 μm is provided on the outermost surfaces of the layers A and B constituting the alternating laminated structure and directly above the layer B, and the layer C is provided. Is
Composition formula: (Ti _1-α-β Si _α W _β ) N
When represented by, 0.01 ≤ α ≤ 0.20, 0.01 ≤ β ≤ 0.10. (However, α indicates the Si content ratio according to the atomic ratio, and β indicates the W content ratio according to the atomic ratio). The surface coating cutting tool according to (1) above, which is a composite nitride layer of Ti, Si and W having an average composition satisfying the above.
(3) For the hard coating layer composed of the C layer, the X-ray diffraction peak intensity from the (200) plane obtained by X-ray diffraction is Ic (200), and the X-ray diffraction peak intensity from the (111) plane is determined. In the case of Ic (111), the value of the ratio of the Ic (200) to the Ic (111) is the above (2), which satisfies 1 <Ic (200) / Ic (111) <50. The surface coating cutting tool described.
(4) A layer thickness of 0.1 to 2.0 μm is provided at the interface between the B layer, which is the outermost surface of the alternating stack consisting of the A layer and the B layer, and the C layer provided directly above the B layer. D layer is provided, D layer composition _{formula: (Al 1-k-lmn} Ti k Cr l Si m W n) n
When represented by, 0.20 ≦ k ≦ 0.65, 0.10 ≦ l ≦ 0.35, 0 <m ≦ 0.15, 0 <n ≦ 0.05 (where k, l, m, n) Satisfies the average composition of 0 <(1-k-l-mn)) in terms of atomic ratio, and the composition modulation structure in which the content ratio of the Si component changes along the layer thickness direction is formed. The surface coating cutting tool according to (2) or (3) above. "

The X-ray diffraction peak intensity from the summarized (200) plane is I (200), and the X-ray diffraction peak intensity from the summarized (111) plane is I (111). Measures the alternating lamination of the A layer and the B layer for the entire alternating lamination structure obtained by X-ray diffraction in a state where the A layer and the B layer are overlapped, not the A layer alone or the B layer alone. It refers to the X-ray diffraction peak intensity from the (200) plane or the (111) plane.

In the coating tool of the present invention, the hard coating layer is at least one layer each of the A layer composed of (Al _1-x Cr _x ) N and the B layer composed of (Al _1-ab Cr _a Si _b ) N. The lattice constant aA (Å) calculated from the diffraction peak angle of the (200) plane of the crystal grains of the A layer and the diffraction peak of the (200) plane of the crystal grains of the B layer are included, including alternating stacking in which they are laminated alternately. The difference from the lattice constant aB (Å) calculated from the angle is reduced to suppress the decrease in toughness due to the lattice mismatch between the A layer and the B layer, and the overall (200) plane diffraction of the hard coating layer as a whole. The half-value full width of the peak intensity is set within the range of 0.3 to 1.0 (degrees) to enhance the crystallinity of the hard coating layer as a whole, and the crystal grains of the rock salt type cubic structure of the A layer and the B layer are summarized. The value of the ratio of the X-ray diffraction peak intensity I (111) from the (111) plane to the X-ray diffraction peak intensity I (200) from the (200) plane is 1 <I (200) / I (111). ) <10, the hardness and toughness of the hard coating layer are balanced.
As a result, excellent chipping resistance and wear resistance are exhibited in high-load cutting of carbon steel, alloy steel, stainless steel, etc., in which a high load acts on the cutting edge, and the life of the tool can be extended.

Further, the covering tool of the present invention is preferably the outermost surface of the A layer and the B layer constituting the alternating laminated structure, and directly above the B layer (Ti _1-α-β Si _α W _β ). The C layer having an average composition of N is formed, and the X-ray diffraction peak intensity from the (200) plane obtained by X-ray diffraction of the crystal grains of the rock salt type cubic structure of the hard coating layer composed of the C layer is Ic (200). ), And the value of the ratio of Ic (111) to Ic (200) when the X-ray diffraction peak intensity from the (111) plane is Ic (111) is 1 <Ic (200) / Ic (111) < By setting it to 50, better chipping resistance and abrasion resistance are exhibited.
More preferably, by forming the D layer having a Si composition modulation structure at the interface between the B layer and the C layer, further excellent chipping resistance and abrasion resistance are exhibited, and the life of the tool is further extended. Is planned.

A schematic vertical cross-sectional view of one aspect of the hard coating layer of the coating tool of the present invention is shown. (A) and (b) show schematic longitudinal sectional views of another aspect of the hard coating layer of the coating tool of the present invention. The arc ion plating apparatus used for forming the hard coating layer is shown, (a) is a schematic plan view, and (b) is a schematic front view. An example of the X-ray diffraction chart measured about the covering tool of this invention is shown. A schematic vertical cross-sectional view of one aspect of the composition modulation structure in the D layer of the covering tool of the present invention is shown.

Next, the covering tool of the present invention will be described in more detail.

Layer A:
FIG. 1 shows a schematic schematic vertical cross-sectional view of the hard coating layer of the coating tool of the present invention. Al is high temperature hardness in the (Al, Cr) N layer constituting the A layer of the hard coating layer having an alternating laminated structure. It has the effect of improving heat resistance, improving high temperature strength, and improving high temperature oxidation resistance in a state where Cr and Al coexist and contain.
The average composition of the A layer composed of (Al, Cr) N is
Composition formula: (Al _1-x Cr _x ) N
When the x value (atomic ratio) indicating the Cr content ratio is less than 0.20, the high temperature strength decreases, which causes deterioration of chipping resistance, and the relative increase in Al content ratio causes the deterioration of chipping resistance. The appearance of crystal grains having a hexagonal structure reduces the hardness and wear resistance.
On the other hand, when the x value (atomic ratio) exceeds 0.60, sufficient high-temperature hardness and heat resistance cannot be ensured due to the relative decrease in the Al content ratio, and the wear resistance is lowered.
Therefore, the Cr content ratio x value (atomic ratio) in the A layer was set to 0.20 ≦ z ≦ 0.60.

Layer B:
Cr in the B layer composed of the N layers (Al, Cr, Si) constituting the alternating lamination with the A layer improves the high temperature strength and the chipping resistance of the hard coating layer as in the case of the A layer. At the same time, the coexistence and content with the Al component contributes to the improvement of high temperature oxidation resistance and improves the wear resistance.
Further, Si, which is a constituent component of the B layer, has an action of improving heat resistance and heat-resistant plastic deformation, but at the same time, increases the lattice strain of the B layer, and as a result, lowers the chipping resistance of the B layer. It will be.
The average composition of the B layer composed of (Al, Cr, Si) N is
Composition formula: (Al _1-ab Cr _a Si _b ) N
When represented by, if the a value (atomic ratio) indicating the Cr content ratio is less than 0.20, the high temperature strength decreases, which causes deterioration of chipping resistance, and the relative increase in the Al content ratio causes the deterioration of the chipping resistance. The appearance of crystal grains having a hexagonal structure reduces the hardness and wear resistance.
On the other hand, when the a value (atomic ratio) exceeds 0.60, sufficient high-temperature hardness and heat resistance cannot be ensured due to the relative decrease in the Al content ratio, and the wear resistance is lowered.
Further, when the b value (atomic ratio) indicating the Si content ratio is less than 0.01, the effect of improving the heat resistance and heat-resistant plastic deformation in the B layer is small, while the b value (atomic ratio) is 0.20. If it exceeds the limit, the effect of improving the wear resistance tends to decrease, and at the same time, the lattice strain of the B layer increases, so that the lattice mismatch between the A layer and the B layer increases, and as a result, high load cutting Chipping resistance under processing conditions decreases.
Therefore, the Cr content ratio a value (atomic ratio) in the B layer is set to 0.40 ≦ a ≦ 0.80, and the Si content ratio b value (atomic ratio) is set to 0.01 ≦ b ≦ 0. It was set to .20.

Alternating lamination consisting of A layer and B layer:
The average layer thickness of the A layer and the B layer constituting the alternating stack is 0.005 to 4.0 μm, which alleviates the lattice mismatch between the A layer and the B layer and at the same time reduces the lattice mismatch of the A layer and the B layer. This is to fully exert the provided action and to exhibit the chipping resistance and abrasion resistance of the hard coating layer as a whole.
Further, at least one layer A and one layer B are alternately laminated to form a hard coating layer having a total layer thickness of 0.5 to 8.0 μm, which is a total layer of hard coating layers. If the thickness is less than 0.5 μm, sufficient wear resistance for a long period of time cannot be exhibited, while if the total layer thickness exceeds 8.0 μm, abnormal damage such as chipping, chipping, and peeling is likely to occur. Therefore, the total thickness of the hard coating layer is 0.5 to 8.0 μm.
As will be described later, a hard coating layer is provided with a C layer having a layer thickness of 0.1 to 4.0 μm, which is the outermost surface of the alternate lamination composed of the A layer and the B layer and directly above the B layer. In this case, the total layer thickness of the A layer and the B layer constituting the alternating laminated structure plus the layer thickness of the C layer is hard-coated. The total layer thickness.

In forming the alternating laminate consisting of the A layer and the B layer, the adhesion strength between the tool substrate and the hard coating layer can be ensured by forming the A layer directly on the surface of the tool substrate, and the hard coating layer By forming the B layer on the outermost surface, chipping resistance in high-load cutting can be ensured.
Therefore, it is desirable to form the A layer directly above the surface of the tool substrate and the B layer on the outermost surface of the hard coating layer in constructing the alternating lamination.
As will be described later, from a composite nitride of Ti, Si, and W having an average composition represented by the composition formula: (Ti _1-α-β Si _α W _β ) N directly above the B layer on the outermost surface. C layer (however, 0.01 ≦ α ≦ 0.20 and 0.01 ≦ β ≦ 0.10, where α and β indicate the Si content ratio and the W content ratio according to the atomic ratio, respectively). It is preferably formed (see FIG. 2A).
Further, it is more preferable that a D layer having a composition modulation structure in which the content ratio of the Si component changes along the layer thickness direction is formed at the interface between the B layer and the C layer (FIG. 2B). , See FIG. 5).

The composition of the A layer and the B layer, the average layer thickness of the layer, the total thickness of the hard coating layer, the layer thickness and composition of the C layer described later, and the D of the composition-modulated structure formed at the interface between the B layer and the C layer. The change in the content ratio of the Si component in the layer in the layer thickness direction is determined by scanning electron microscope (SEM) and transmission electron microscope (TEM) for the longitudinal cross section of the hard coating layer perpendicular to the surface of the tool substrate. , It can be measured by cross-sectional measurement using an energy dispersive X-ray spectrum (EDS).

Lattice constant of crystal grains of rock salt type cubic structure of A layer and B layer constituting the alternating laminated structure:
In the present invention, in the alternating laminated structure consisting of A layer and B layer, when the lattice constants of the crystal grains of the rock salt type cubic structure in each layer are aA and aB, respectively, the A layer and the B layer are formed. By controlling the vapor deposition conditions at the time, the difference (absolute value) | aA-aB | of the lattice constants of the A layer and the B layer is set to 0.05 (Å) or less.
As a result, the lattice mismatch between the A layer and the B layer can be minimized, and the decrease in toughness due to the lattice mismatch can be suppressed.
In the present invention, the alternating lamination consisting of the A layer and the B layer is formed, for example, by using the arc ion plating apparatus shown in FIG. 3, but when the A layer and the B layer are formed, for example, the target The lattice constant of the crystal grains of the rock salt type cubic structure can be controlled by the composition and the bias voltage.
Then, electron beam diffraction by TEM is performed on the crystal grains of the rock salt type cubic structure of the A layer and the B layer, and the lattice constant aA (Å) in the A layer and the lattice constant aB (Å) in the B layer can be calculated. However, if the absolute value | aA-aB | of the difference between the calculated lattice constants aA (Å) and aB (Å) exceeds 0.05 (Å), the lattice mismatch between the A layer and the B layer becomes large. Therefore, the hard coating layer is liable to break during high-load cutting, so the absolute value of the difference in the lattice constants of the crystal grains of the rock salt-type cubic structure of the A layer and the B layer is | aA-aB | ≤0. Let it be 05 (Å). More preferably, | aA-aB | <0.03 (Å).

Further, X-ray diffraction was performed on the entire hard coating layer composed of alternating layers of A layer and B layer for the crystal grains of the rock salt type cubic structure constituting each layer, and the X-ray diffraction from the summarized (200) plane was performed. When the peak intensity is determined as I (200) and the X-ray diffraction peak intensity from the summarized (111) plane is determined as I (111), the half-value total width of the X-ray diffraction peak intensity I (200) is 0.3 ( If it is less than the degree), the crystal grains are coarse-grained, so that cracks are easily propagated through the grain boundaries and the chipping resistance is lowered.
On the other hand, when the full width at half maximum of I (200) exceeds 1.0 (degrees), the crystal grains are amorphized and sufficient crystallinity cannot be maintained, so that the wear resistance is lowered.
Therefore, the full width at half maximum of I (200) is set to 0.3 to 1.0 (degrees).
Then, among the arc ion plating conditions for forming the A layer and the B layer, the full width at half maximum of I (200) is set to 0.3 by controlling the arc current, the bias voltage, the reaction gas pressure and the film forming temperature. It can be maintained in the range of ~ 1.0 (degrees).

Further, the I (200) and I (111) obtained by performing X-ray diffraction on the crystal grains of the rock salt type cubic structure constituting each layer with respect to the entire hard coating layer composed of alternating layers of A layer and B layer. ), When the value I (200) / I (111) of these ratios is 1 or less, the chipping resistance is lowered because the (111) plane orientation, which is the closest surface, is strong, while I (200). ) / I (111) is 10 or more, the orientation of (200) becomes extremely strong, and the wear resistance is lowered.
Therefore, in order to have both excellent chipping resistance and abrasion resistance, the value of I (200) / I (111) needs to be 1 <I (200) / I (111) <10. is there.
Then, among the arc ion plating conditions for forming the A layer and the B layer, for example, by controlling the arc current, the bias voltage, the reaction gas pressure, and the film forming temperature, I (200) / I (111) The value of can be maintained in the above range.

FIG. 4 shows an example of an X-ray diffraction chart measured for the coating tool of the present invention. From the chart, I obtained from the entire crystal grains of the rock salt type cubic structure of the A layer and the B layer constituting the alternating laminated structure. It can be seen that the value of (200) / I (111) is more than 1 and less than 10, and the full width at half maximum of I (200) is in the range of 0.3 to 1.0 (degrees).

Layer C:
The coating tool of the present invention exhibits excellent chipping resistance and abrasion resistance by forming the hard coating layer as an alternating stack of the A layer and the B layer, but FIGS. 2 (a) and 2 (b) show. As shown in the above, a C layer made of a composite nitride of Ti, Si, and W is 0.1 to 4 on the outermost surfaces of the A layer and the B layer constituting the alternating lamination and directly above the B layer. By forming the layer with a layer thickness of 0.0 μm, wear resistance can be further improved especially in high-speed cutting.
The C layer is
Composition formula: (Ti _1-α-β Si _α W _β ) N
When represented by, 0.01 ≤ α ≤ 0.20 and 0.01 ≤ β ≤ 0.10. (However, α indicates the Si content ratio according to the atomic ratio, and β indicates the W content ratio according to the atomic ratio). It is an N layer having a satisfactory average composition (Ti, Si, W).
In the C layer containing Ti as a main component, the inclusion of the Si component improves the oxidation resistance and heat-resistant plastic deformation, and the inclusion of the W component further improves the high-temperature strength and resistance. Abrasion is improved.
However, when the Si content ratio α is less than 0.01, the effect of improving the oxidation resistance and the heat-resistant plastic deformation is small, while when α exceeds 0.20, the lattice strain increases, and it is self-contained under high load cutting conditions. It becomes easy to break.
Further, when the W content ratio β is less than 0.01, the effect of improving the strength at high temperature is small, while when β exceeds 0.10, the lattice strain increases and the chipping resistance in high load cutting decreases. ..
Therefore, α and β are in the range of 0.01 ≦ α ≦ 0.20 and 0.01 ≦ β ≦ 0.10 (where α and β are atomic ratios), respectively.
The layer thickness of the C layer is 0.1 to 4 from the viewpoint of exhibiting chipping resistance and abrasion resistance of the hard coating layer as a whole while preventing abnormal damage such as peeling due to excessive intra-layer strain. It is preferably 0 μm.

Further, for Ic (200) and Ic (111) obtained by X-ray diffraction on the crystal grains of the rock salt type cubic structure of the hard coating layer composed of the C layer, the values of these ratios Ic (200) / Ic (111) is preferably more than 1 and less than 50.
This is because when the value of Ic (200) / Ic (111) is 1 or less, the (111) plane orientation, which is the densest surface, is strong and the chipping resistance is lowered, while Ic (200) / Ic (111). ) Is 50 or more, the reason is that (200) orientation becomes extremely strong and wear resistance is lowered. Further, a more preferable range is more than 1 and less than 30.

Further, as shown in FIG. 2B, for example, the value b of the Si content ratio of the alternately laminated B layer and the value α of the Si content ratio of the C layer are not equivalent values, and Si between the B layer and the C layer. When there is a gap in the content ratio of, in order to improve the adhesion between the B layer and the C layer, a D layer having a composition-modulating structure at the interface between the B layer and the C layer is added to 0.1 to 2. It is preferably formed with a layer thickness of 0 μm.
The D layer is
Composition _{formula: (Al 1-k-lmn} Ti k Cr l Si m W n) N
When represented by, 0.20 ≦ k ≦ 0.65, 0.10 ≦ l ≦ 0.35, 0 <m ≦ 0.15, 0 <n ≦ 0.05 (where k, l, m, n) Is a layer having an average composition of 0 <(1-kl-mn)) in terms of atomic ratio and having a composition-modulating structure in which the content ratio of the Si component changes along the layer thickness direction.
In the composition modulation structure, at the interface between the B layer and the C layer, the Si content ratio is continuous from the B layer to the C layer or from the C layer to the B layer along the layer thickness direction. A layered structure that changes to.
By forming the composition modulation structure at the interface between the B layer and the C layer, a sudden change in the Si content between the B layer and the C layer is suppressed, and as a result, the adhesion between the B layer and the C layer is enhanced. , Peeling is prevented and chipping resistance is improved.
In the composition modulation structure, for example, as shown in FIG. 3A, an Al—Cr—Si alloy target for forming the B layer and a Ti—Si—W alloy target for forming the C layer are used. It is formed by simultaneously vapor-depositing layers B and C on a tool substrate that is placed facing the arc ion plating device and mounted on a rotary table that rotates in the arc ion plating device so as to rotate. Can be done. If the above composition formula is satisfied, the D layer forms an Al—Cr alloy target for forming the A layer and a C layer instead of the Al—Cr—Si alloy target for forming the B layer. The same effect can be exhibited even if it is formed by simultaneous vapor deposition using a Ti—Si—W alloy target for the purpose.
As shown in FIG. 5, the Si content ratio in the composition modulation structure of the D layer formed by the above method is the content ratio of the Si component of the C layer and the B layer or the A layer along the layer thickness direction in the D layer. It changes continuously between.
Further, to confirm the existence of the composition modulation structure, the Si content ratio is measured in the vertical direction (layer thickness direction) to the tool substrate surface in the vertical cross section perpendicular to the tool substrate surface of the B layer and the C layer, and the Si content ratio is measured in the B layer. The position of the B layer deviating from the average composition b of Si and the position of the C layer deviating from the average composition α of Si in the C layer are specified, and the position between these two positions is the region where the composition modulation structure is formed. Can be identified as being.

Next, the covering tool of the present invention will be specifically described with reference to Examples.
As a specific description, a surface-coated drill using a tungsten carbide (WC) -based cemented carbide as a tool (drill) base will be described, but a titanium carbonitride-based cermet or a cubic boron nitride (cBN) sintered body will be described. The same applies to a covering tool (insert, end mill, etc.) using the above as a tool base.

[Example 1]
<< Coating tool with a hard coating layer consisting of alternating layers A and B >>
Preparation of drill substrate ::
As raw material powders, Co powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, and WC powder having an average particle size of 0.5 to 5 μm are prepared, and these raw material powders are shown in Table 1. It was blended to the blending composition shown, further waxed, wet-mixed in a ball mill for 72 hours, dried under reduced pressure, press-molded at a pressure of 100 MPa, and these powder compacts were sintered and then having a diameter of 3 mm. A WC group that forms a round bar sintered body for forming a tool substrate, and is further ground by grinding to have dimensions of 2 mm x 45 mm for each of the diameter and length of the groove forming portion, and a two-flute shape with a twist angle of 30 degrees. Drill substrates 1 to 3 made of super hard alloy were manufactured.

Film formation process:
Using the arc ion plating apparatus shown in FIG. 3, the drill bases 1 to 3 were used.
(A) The drill bases 1 to 3 are ultrasonically cleaned in acetone, dried, and then gently placed on the outer peripheral portion at a position radially separated from the central axis on the rotary table in the arc ion plating apparatus by a predetermined distance. And attach it.
(B) First, while holding by evacuating the system to ¹⁰ -2 Pa or less of vacuum, after heating the inside of the apparatus to 500 ° C. by the heater, set to Ar gas atmosphere 0.5～2.0Pa, A DC bias voltage of −200 to −1000 V is applied to the tool substrate that rotates while rotating on the rotary table, and the surface of the drill substrate is bombarded with argon ions for 5 to 30 minutes.
(C) Next, a hard coating layer having an alternating laminated structure of A layer and B layer was formed as follows.
First, nitrogen gas is introduced into the apparatus as a reaction gas to create a predetermined reaction atmosphere within the range of 2 to 10 Pa shown in Table 2, and the temperature inside the apparatus also shown in Table 2 is maintained. A predetermined DC bias voltage within the range of 25 to -75 V shown in Table 2 is applied to the drill substrate that rotates while rotating on the rotary table under the control of the rotation speed of the rotary table shown in Table 2, and the A layer is formed. A predetermined current in the range of 90 to 180A shown in Table 2 is passed between the cathode electrode (evaporation source) and the anode electrode to generate an arc discharge, and an A layer having a predetermined layer thickness is formed.
After that, a predetermined current in the range of 90 to 180A also shown in Table 2 is passed between the cathode electrode (evaporation source) for forming the B layer and the anode electrode to generate an arc discharge, and the A layer formed above is formed. A layer B having a predetermined layer thickness is formed on the surface of the above.
The formation of the A layer and the B layer are alternately repeated to form a hard coating layer having an alternating laminated structure of A layer and B layer having the average composition, the average layer thickness, and the total layer thickness shown in Table 4. By doing so, the coated tools of the present invention (referred to as “tools of the present invention”) 1 to 6 shown in Table 4 were produced.
In the vapor deposition deposition steps of (a) to (c) above, among the vapor deposition conditions of the A layer and the B layer, the lattice of crystal grains having a rock salt type cubic structure of the A layer and the B layer by adjusting the bias voltage. By controlling the constants aA and aB and adjusting the arc current value, the partial pressure of nitrogen gas as the reaction gas, the bias voltage, the film formation temperature, etc., the rock salt type of the entire hard coating layer composed of the A layer and the B layer. The half-value full width of I (200) and the value of I (200) / I (111) of the crystal grains having a cubic structure were controlled.
In the steps (a) to (c) of Example 1, the Ti—Si—W alloy target for forming the C layer shown in FIG. 3 is not used.

For comparison, Table 5 shows that the drill substrates 1 to 3 were deposited with a hard coating layer having an alternating laminated structure consisting of layers A and B under the conditions shown in Table 3 in the same manner as in Example 1. The shown comparative example covering tools (referred to as "comparative example tools") 1 to 6 were produced.

For the tools 1 to 6 of the present invention and the tools 1 to 6 of the comparative examples produced above, the vertical cross section perpendicular to the surface of the tool substrate of the hard coating layer is obtained by scanning electron microscope (SEM), transmission electron microscope (TEM), and energy. Using dispersed X-ray spectroscopy (EDS), the composition of the A layer and the B layer and the layer thickness were measured at a plurality of points, and the average composition and the average layer thickness were calculated by averaging them.
In addition, thin film X-ray diffraction from a direction perpendicular to the surface of the tool substrate, or electron diffraction by TEM is performed on the vertical cross sections of the A layer and the B layer perpendicular to the surface of the tool substrate from a direction parallel to the surface of the tool substrate. The lattice constants aA and aB of the crystal grains of the rock salt type cubic structure of each layer were obtained, and the values of | aA-aB | were calculated.
Further, X-ray diffraction is performed on the entire hard coating layer composed of the A layer and the B layer from the direction perpendicular to the surface of the tool substrate, and the X-ray diffraction peak (X in which the A layer and the B layer overlap) is summarized from the (200) plane. The half-value full width of the line diffraction peak) was measured, and the X-ray diffraction peaks (X-ray diffraction peaks in which the A layer and the B layer overlapped) intensities I (200) and I (111) were evaluated as I (200). The value of / I (111) was calculated (see FIG. 4).
An X-ray diffractometer using a Cu tube was used for X-ray diffraction.

Tables 4 and 5 show the absolute values of the differences in the lattice constants of the tools 1 to 6 of the present invention and the tools 1 to 6 of the comparative examples | aA-aB |, the full width at half maximum of I (200), and I (200) / I (111). ) Indicates the value.

Next, regarding the tools 1 to 6 of the present invention and the tools 1 to 6 of the comparative example,
Work Material-Plane Dimensions: Plate Material of Alloy Steel SCM440,
Cutting speed: 80 m / min. ,
Feed: 0.08 mm / rev,
Hole depth: 40 mm,
SCM440 wet high-speed high-feed drilling cutting test (normal cutting speed and feed are 50 m / min. And 0.06 mm / rev, respectively) under the conditions of (using water-soluble cutting oil), tip cutting edge The number of drilling operations until the flank wear width of the surface reached 0.3 mm or the life was reached due to the occurrence of chipping of the cutting edge was measured, and the worn state of the cutting edge was observed. The machining was performed up to 1000 holes, and the flank wear width at the time of 1000 holes was measured for those that did not reach the end of their life.
Table 6 shows the measurement results.

According to the results in Table 6, in the tools 1 to 6 of the present invention, the average flank wear width is about 0.16 mm, and no chipping is observed, whereas the tools 1 to 6 in Comparative Example have flakes. Surface wear progressed, and in some cases, chipping occurred in a short time and the life was reached.

[Example 2]
<< Coating tool with alternating lamination of A layer and B layer and hard coating layer consisting of C layer >>
The WC-based cemented carbide drill bases 1 to 3 produced in Example 1 were charged into the arc ion plating apparatus shown in FIG. 3, and the conditions shown in Table 2 were the same as in the case of Example 1. A layer and a B layer were alternately laminated. However, the outermost surface of the alternating lamination was the B layer.
Then, under the conditions shown in Table 7, a C layer composed of (Ti, Si, W) N layers having a predetermined average composition and a predetermined layer thickness is formed on the surface of the B layer, and the A layer and the B layer are alternately laminated. The tools 11 to 16 of the present invention shown in Table 8 in which a hard coating layer composed of the C layer and the C layer were vapor-deposited were produced (see FIG. 2A).

For the tools 11 to 16 of the present invention produced above, the average composition of each layer and the average layer thickness of each layer were calculated in the same manner as in Example 1.
In addition, thin film X-ray diffraction from a direction perpendicular to the surface of the tool substrate, or electron diffraction by TEM for each of the vertical cross sections of the A layer and the B layer perpendicular to the surface of the tool substrate from a direction parallel to the surface of the tool substrate. The lattice constants aA and aB of the crystal grains having the rock salt type cubic structure of each layer were obtained, and the values of | aA-aB | were calculated.
In addition, the overall X-ray diffraction peak (X-ray diffraction peak where the A layer and the B layer overlap) from the (200) plane of the A layer and the B layer is measured from the direction perpendicular to the surface of the tool substrate, and the full width at half maximum thereof. Was calculated.
Further, from the direction perpendicular to the surface of the tool substrate, the X-ray diffraction peaks (X-ray diffraction peaks in which the A layer and the B layer overlap) and the (200) of the C layer are summarized from the (200) plane of the A layer and the B layer. The X-ray diffraction peak from the plane is measured as Ic (200), and the summarized X-ray diffraction peak from the (111) plane of the A layer and the B layer (the overlapping X-ray diffraction peak of the A layer and the B layer) and C The X-ray diffraction peak from the layer (111) plane is measured as Ic (111), and I (200) / I for each of the X-ray diffraction peak in which the A layer and the B layer overlap and the X-ray diffraction peak in the C layer. The values of (111) and Ic (200) / Ic (111) were calculated.
Table 8 shows various values obtained above.
FIG. 4 shows an example of the X-ray diffraction results measured for the tool of the present invention. The full width at half maximum of I (200), which is the sum of the entire hard coating layer composed of the A layer and the B layer, is 0.5 (degrees). It can be seen that the value I (200) / I (111) of the ratio of I (200) to I (111) is 3.0. Further, it can be seen that the Ic (200) / Ic (111) of the hard coating layer composed of the C layer is 2.0.

Next, regarding the tools 11 to 16 of the present invention,
Work Material-Plane Dimensions: Plate Material of Alloy Steel SCM440,
Cutting speed: 100 m / min. ,
Feed: 0.08 mm / rev,
Hole depth: 40 mm,
Wet high-speed high-feed drilling cutting test of SCM440 under the conditions of (normal cutting speed and feed are 50 m / min. And 0.06 mm / rev, respectively),
(Using water-soluble cutting oil), measure the number of drilling operations until the flank wear width of the cutting edge surface reaches 0.3 mm or the life of the cutting edge due to chipping of the cutting edge, and observe the worn state of the cutting edge. did. The machining was performed up to 1000 holes, and the flank wear width at the time of 1000 holes was measured for those that did not reach the end of their life.
Table 9 shows the test results.

[Example 3]
<< A coating tool provided with alternating layers A and B and a C layer, and a hard coating layer having a D layer with a composition modulation structure at the interface between the B layer and the C layer >>
The WC-based cemented carbide drill bases 1 to 3 produced in Example 1 were charged into the arc ion plating apparatus shown in FIG. 3, and are shown in Table 2 in the same manner as in Examples 1 and 2. Layers A and B were alternately formed under the conditions shown.
However, after the simultaneous vapor deposition of the C layer is started under the conditions shown in Table 7 from the middle of forming the B layer on the outermost surface of the alternating lamination, and the simultaneous vapor deposition of the B layer and the C layer is continued for a while. , The vapor deposition of the B layer was stopped, and the vapor deposition of only the C layer was continued.
When the predetermined layer thickness was reached, the vapor deposition of the C layer was also stopped.
A table having a hard coating layer composed of alternating layers A and B and a C layer by the above steps, and a D layer having a composition-modulating structure of Si component formed at the interface between the B layer and the C layer. The tools 21 to 26 of the present invention shown in FIG. 10 were produced (see FIGS. 2 (b) and 5).
The content ratio of Si in the D layer of the composition modulation structure is continuously changed within the range of the maximum Si content ratio of the B layer or the C layer and the minimum Si content ratio of the B layer or the C layer. Become.

For the tools 21 to 26 of the present invention produced above, the average composition of each layer and the average layer thickness of each layer were calculated in the same manner as in Example 2.
In addition, the full width at half maximum of the summarized X-ray diffraction peaks (X-ray diffraction peaks in which the A layer and the B layer overlap) from the (200) plane of the A layer and the B layer was measured.
The summarized X-ray diffraction peaks from the (200) planes of the A and B layers (X-ray diffraction peaks in which the A and B layers overlap) and the X-ray diffraction peaks from the (200) plane of the C layer are Ic (200). ), And the summarized X-ray diffraction peaks from the (111) planes of the A and B layers (X-ray diffraction peaks in which the A and B layers overlap) and the X-ray diffraction peaks from the C layer (111) plane are obtained. Obtained as Ic (111), I (200) / I (111), Ic (200) / Ic (111) for the X-ray diffraction peak where the A layer and the B layer overlap and the X-ray diffraction peak of the C layer, respectively. The value of was calculated.
Further, the layer thickness of the D layer on which the composition modulation structure was formed was measured by the following method.
For the B and C layers on the outermost surface of the alternating lamination, the Si content ratio was measured in the vertical direction (layer thickness direction) to the tool substrate surface in the vertical cross section perpendicular to the tool substrate surface, and the composition of Si in the B layer was determined. The position in the B layer deviating from the average composition b and the position in the C layer in which the composition of Si deviated from the average composition α in the C layer were specified.
Such measurements were performed at a plurality of locations, the distance between these two positions was measured, and the average value of the measured values was determined as the layer thickness of the D layer on which the composition modulation structure was formed.
Table 10 shows various values.

Next, the tools 21 to 26 of the present invention are subjected to a wet high-speed high-feed hole drilling cutting test under the same cutting conditions as in Example 2, and the flank wear width of the tip cutting edge surface reaches 0.3 mm or chipping of the cutting edge. The number of drilling processes from the occurrence to the end of the life was measured, and the state of wear of the cutting edge was observed. The machining was performed up to 1000 holes, and the flank wear width at the time of 1000 holes was measured for those that did not reach the end of their life.
Table 11 shows the test results.

According to the results of Tables 9 and 11, in the tools 11 to 16 and 21 to 26 of the present invention, the average flank wear width is as small as about 0.13 mm and about 0.11 mm, respectively, and has excellent wear resistance. The occurrence of chipping is suppressed.
In particular, it can be seen that the tools 21 to 26 of the present invention are further excellent in wear resistance as compared with the tools 11 to 16 of the present invention.
From these results, it can be seen that the tool of the present invention exhibits excellent chipping resistance and wear resistance in high-load cutting of work materials such as carbon steel, alloy steel, and stainless steel.

The surface-coated cutting tool of the present invention has excellent chipping resistance and abrasion resistance not only in high-load cutting of work materials such as carbon steel, alloy steel, and stainless steel, but also in cutting of various work materials. Since it exhibits excellent cutting performance over a long period of time, it can fully respond to high performance of cutting equipment, labor saving and energy saving of cutting processing, and cost reduction. is there.

Claims (4)

A hard coating layer having a total layer thickness of 0.5 to 8.0 μm was provided on the surface of a tool substrate made of either a tungsten carbide-based cemented carbide, a titanium nitride-based cermet, or a cubic boron nitride sintered body. In surface coating cutting tools
(A) In the hard coating layer, at least one layer A having an average layer thickness of 0.005 to 4.0 μm and a layer B having an average layer thickness of 0.005 to 4.0 μm are alternately arranged. Including alternating laminated structure laminated in
(B) The A layer is
Composition formula: (Al _1-x Cr _x ) N
A composite nitride layer of Al and Cr having an average composition satisfying 0.20 ≦ x ≦ 0.60 (where x indicates the content ratio of Cr according to the atomic ratio) when represented by.
(C) The B layer is
Composition formula: (Al _1-ab Cr _a Si _b ) N
When represented by, 0.20 ≦ a ≦ 0.60, 0.01 ≦ b ≦ 0.20 (where a indicates the Cr content ratio according to the atomic ratio, and b indicates the Si content ratio according to the atomic ratio). It is a composite nitride layer of Al, Cr and Si having an average composition satisfying the above.
(D) The layers A and B constituting the alternating laminated structure contain crystal grains having a rock salt-type cubic structure.
(E) When the lattice constants of the crystal grains of the rock salt type cubic structure of the A layer and the crystal grains of the rock salt type cubic structure of the B layer are aA (Å) and aB (Å), respectively. , The absolute value of the difference between aA (Å) and aB (Å) | aA-aB | satisfies | aA-aB | ≤0.05 (Å).
(F) The X-ray diffraction peak intensity from the summarized (200) plane obtained by X-ray diffraction for the entire alternating laminated structure composed of the A layer and the B layer is the summarized (200) plane and the summarized (111) plane. When the X-ray diffraction peak intensity from I (111) is I (111), the half-value total width of I (200) is 0.3 to 1.0 (degrees), and the ratio of the ratio of I (200) to I (111). A surface coating cutting tool characterized in that the value satisfies 1 <I (200) / I (111) <10. A C layer having a layer thickness of 0.1 to 4.0 μm is provided on the outermost surfaces of the A layer and the B layer constituting the alternating laminated structure and directly above the B layer, and the C layer is
Composition formula: (Ti _1-α-β Si _α W _β ) N
When represented by, 0.01 ≤ α ≤ 0.20, 0.01 ≤ β ≤ 0.10. (However, α indicates the Si content ratio according to the atomic ratio, and β indicates the W content ratio according to the atomic ratio). The surface coating cutting tool according to claim 1, wherein the composite nitride layer of Ti, Si and W has an average composition satisfying the above. For the entire hard coating layer composed of the C layer, the X-ray diffraction peak intensity from the (200) plane obtained by X-ray diffraction is Ic (200), and the X-ray diffraction peak intensity from the (111) plane is Ic ( 111) The surface according to claim 2, wherein the value of the ratio of Ic (200) to Ic (111) satisfies 1 <Ic (200) / Ic (111) <50. Cover cutting tool. At the interface between the B layer, which is the outermost surface of the alternating stack consisting of the A layer and the B layer, and the C layer provided directly above the B layer, a D layer having a layer thickness of 0.1 to 2.0 μm is formed. provided, D layer composition _{formula: (Al 1-k-lmn} Ti k Cr l Si m W n) n
When represented by, 0.20 ≦ k ≦ 0.65, 0.10 ≦ l ≦ 0.35, 0 <m ≦ 0.15, 0 <n ≦ 0.05 (where k, l, m, n) A composition-modulated structure is formed in which the average composition of 0 <(1-k-l-mn)) is satisfied in terms of atomic ratio, and the content ratio of the Si component changes along the layer thickness direction. The surface coating cutting tool according to claim 2 or 3.