JP4716095B2 - Surface-coated high-speed tool steel gear cutting tool that exhibits excellent chipping resistance due to high-speed gear cutting of alloy steel - Google Patents

Description

  The present invention has excellent wear resistance and fracture resistance even when the hard coating layer has excellent wear resistance as well as wear resistance, and therefore, particularly when used for high-speed gear cutting with high heat generation such as alloy steel. The present invention relates to a surface-coated high-speed tool steel gear cutting tool (hereinafter referred to as a coated gear cutting tool) that exhibits the properties.

Conventionally, various gears are generally used as structural members for automobiles, aircrafts, and various drive devices. For gear cutting of these gear teeth, a solid hob (for example, see the schematic perspective view of FIG. 3) or a pinion cutter (for example, FIG. 4). In addition, a cutting tool such as a shaving cutter is used.

Further, as a coated gear cutting tool, for example, a gear cutting tool body made of high-speed tool steel machined to the shape shown in FIG. 3 or FIG. 4 is used as a base, and a composition formula: (Al _{1- (X + Y) Cr X} Si Y) N ( provided that an atomic ratio, X is .20 to .75, Y is Cr satisfying a shows the 0.01 to 0.30), mainly Al and Si A coated cutting tool formed by physically vapor-depositing a hard coating layer composed of a composite nitride layer as a component has been proposed, and the composite nitride layer constituting the hard coating layer is known to have excellent wear resistance. ing.

Further, the above-described coated cutting tool is loaded with the above-mentioned substrate in an arc ion plating apparatus, which is one of physical vapor deposition apparatuses schematically shown in FIG. Is heated to a temperature of 400 ° C. under a vacuum atmosphere of 2 Pa, and the voltage between the anode electrode and the cathode electrode (evaporation source) in which a Cr—Al—Si alloy having a predetermined composition is set is, for example, 35 V Arc discharge was generated under the condition of current: 90 A, and simultaneously nitrogen gas was introduced into the apparatus as a reaction gas to obtain a reaction atmosphere of, for example, 2 Pa. On the other hand, a bias of −200 V, for example, was applied to the base body (gear cutting tool body). It is also known that it is produced by vapor-depositing a hard coating layer composed of the (CrAl, Si) N layer on the surface of the substrate under the condition of applying a voltage.
Japanese Patent Laid-Open No. 2003-321764

In recent years, the performance of gear cutting machines has been remarkably improved. On the other hand, there is a strong demand for labor saving and energy saving and further cost reduction for gear cutting, and with this, gear cutting has a tendency to increase in speed. In the above conventional coated gear cutting tool, there is no major problem when this is used under normal gear cutting conditions, but when this is used under high speed gear cutting conditions such as alloy steel with high heat generation. However, the chipping resistance and wear resistance are not sufficient yet, and the service life is reached in a relatively short time due to the occurrence of chipping (chips and chipping) or the progress of wear of the hard coating layer. is there.

In view of the above, the inventors of the present invention have developed the above-described conventional coating tool in order to develop a coated gear cutting tool that exhibits excellent fracture resistance and wear resistance, particularly in high-speed gear cutting. As a result of conducting research, focusing on the hard coating layer that constitutes the gear cutting tool,

(A) Heat-resistant plastic deformation of a layer by increasing the content ratio of Si as a component of a composite nitride of Cr, Al, and Si [hereinafter referred to as (Cr, Al, Si) N] constituting the hard coating layer The content ratio is at most about 1 to 10 atomic%, and when it is further contained, the content ratio of the Al component is 45 to 65 atomic%, Cr Since the content ratio of the component is reduced, among the characteristics of the conventional (Cr, Al, Si) N layer, particularly the high temperature strength is reduced, and as a result, the fracture resistance is inferior. Become. On the other hand, if a sufficient amount of Cr component is included to ensure a predetermined high-temperature strength, in this case, it is inevitable that the content ratio of the Al component is extremely low. The high temperature hardness of the material should be low.


(B) Compared with the (Cr, Al, Si) N layer of (a) above, the Si content ratio is extremely high, while the content ratio of the Si component is increased, the Al content ratio is decreased,
Composition _{formula: [Cr 1- (A + B} ) Al A Si B] N ( provided that an atomic ratio, A is 0.01 to 0.10, B represents a from 0.35 to 0.50) shall satisfy Therefore, although the high-temperature hardness and high-temperature oxidation resistance become insufficient due to the low content of the Al component, the (Cr, Al, Si) N layer (hereinafter referred to as the thin layer) has further improved the heat-resistant plastic deformation property due to the high Si content. A)
Compared to the thin layer A, the Al content rate is relatively high, while the Si content rate is relatively low,
Composition _{formula: [Cr 1- (C + D} ) Al C Si D] N ( provided that an atomic ratio, C is 0.20 to 0.35, D denotes the 0.15 to 0.30) shall satisfy Therefore, compared to the thin layer A, it has a low Si content and a relatively low heat-resistant plastic deformability, but has a high high-temperature hardness and high-temperature oxidation resistance due to a relatively high Al content. (Cr, Al, Si) N layer (hereinafter referred to as thin layer B),
Are alternately laminated in a state where each layer has an average layer thickness of 5 to 20 nm (nanometer), and (Cr, Al, Si) of the alternately laminated structure of thin layer A and thin layer B as a result. In the N layer (in this case, both the thin layer A and the thin layer B contain a Cr component of 35 atomic% or more, thus maintaining high high-temperature strength), the excellent heat resistance by the high Si-containing thin layer A described above It should have plastic deformability and high temperature hardness and high temperature oxidation resistance due to the relatively high Al-containing thin layer B.


(C) The (Cr, Al, Si) N layer having the alternate layered structure of the thin layer A and the thin layer B of (b) is excellent in heat plastic deformation required for high speed gear cutting of alloy steel. However, since both the thin layer A and the thin layer B have a relatively low content of the Al component, they do not have sufficiently satisfactory high temperature hardness and high temperature oxidation resistance. ) (Cr, Al, Si) N layer, ie,
Composition formula: [Cr _{1− (E + F)} Al _E Si _F ] N (wherein E is 0.45 to 0.65 and F is 0.01 to 0.10 in atomic ratio) The (Cr, Al, Si) N layer of phase structure does not have sufficient heat-resistant plastic deformation required for high-speed gear cutting of alloy steel, but it has excellent high-temperature hardness due to the high content of Al component. When the hard coating layer is formed as the lower layer of the (Cr, Al, Si) N layer having the alternate layered structure of the thin layer A and the thin layer B, the high-temperature oxidation resistance is obtained. Since the hard coating layer has excellent heat plastic deformation and high temperature strength, and excellent high temperature hardness and high temperature oxidation resistance, the coated cutting tool formed by vapor deposition of this hard coating layer is: Even in the above high-speed gear cutting of alloy steel with high heat generation, Thermal plastic deformation without generation of exert over the superior wear resistance to long term that that.
The research results shown in (a) to (c) above were obtained.


This invention was made based on the above research results, and on the surface of the carbide substrate,
(A) Both are composed of an upper layer and a lower layer made of (Cr, Al, Si) N, the upper layer has an average layer thickness of 0.5 to 1.5 μm, and the lower layer has an average layer thickness of 2 to 6 μm. And
(B) Each of the upper layers has an alternate layered structure of thin layers A and thin layers B each having an average layer thickness of 5 to 20 nm (nanometer),
The thin layer A is
Composition formula: [Cr _{1− (A + B)} Al _A Si _B ] N (wherein A is 0.01 to 0.10 and B is 0.35 to 0.50 in terms of atomic ratio) (Cr , Al, Si) N layer,
The thin layer B is
Composition formula: [Cr _{1− (C + D)} Al _C Si _D ] N (wherein C is 0.20 to 0.35 and D is 0.15 to 0.30 in atomic ratio) (Cr , Al, Si) N layer,
(C) the lower layer has a single phase structure;
Composition formula: [Cr _{1− (E + F)} Al _E Si _F ] N (wherein E is 0.45 to 0.65 and F is 0.01 to 0.10 in atomic ratio) (Cr , Al, Si) N layer,

The present invention is characterized by a coated gear cutting tool which has a hard coating layer exhibiting excellent fracture resistance by high-speed gear cutting of alloy steel formed by vapor-depositing a hard coating layer made of

Next, regarding the hard coating layer of the coated cutting tool of the present invention, the reason why the numerical values are limited as described above will be described.

(A) Composition formula and average layer thickness of lower layer As described above, the Al component in the (Cr, Al, Si) N layer constituting the hard coating layer is improved in high-temperature hardness, and the Cr component is improved in high-temperature strength. At the same time, the high-temperature oxidation resistance is improved in the state where Al and Cr coexist, and the Si component also has the effect of improving the heat-resistant plastic deformation property. In the lower layer, the content ratio of the Al component is relatively increased. Thus, while maintaining high high-temperature hardness and high-temperature oxidation resistance, if the E value indicating the Al content is less than 0.45 in terms of the total amount of Cr and Si (atomic ratio, the same shall apply hereinafter), it is desirable. High temperature hardness and high temperature oxidation resistance cannot be ensured, and wear progresses rapidly. On the other hand, if the E value indicating the proportion of Al exceeds 0.65, high temperature strength As a result, chipping, slight missing Since defects such as cracks are likely to occur, the E value was set to 0.45 to 0.65.

  Further, if the F value indicating the proportion of Si is a proportion of the total amount of Cr and Al, and less than 0.01, it is not possible to ensure a predetermined heat resistant plastic deformation improvement effect, while the F value is 0. When it exceeds 10, since a clear decreasing tendency appears in the high-temperature strength, the F value is set to 0.01 to 0.10.

  Furthermore, if the average layer thickness is less than 2 μm, the excellent high-temperature hardness and heat-resistant plastic deformability cannot be imparted to the hard coating layer over a long period of time, resulting in a short tool life, while the average layer thickness is When the thickness exceeds 6 μm, defects are likely to occur. Therefore, the average layer thickness is set to 2 to 6 μm.

(B) Composition formula of the upper layer thin layer A The Si component in (Cr, Al, Si) N of the upper layer thin layer A is relatively increased in content as described above, so that the heat-resistant plastic deformation is achieved. Has the effect of preventing the occurrence of thermoplastic deformation, which causes uneven wear in high-speed cutting of high hardness steel with high heat generation, but the B value indicating the content ratio is the total amount of Cr and Al. If the ratio is less than 0.35, the desired excellent effect cannot be ensured for the above action. On the other hand, if the B value exceeds 0.50, relatively high temperature hardness and acid resistance Even if there is a thin layer B having excellent chemical properties, the high temperature hardness and high temperature oxidation resistance of the upper layer are inevitably lowered, and wear is promoted. Therefore, the B value is set to 0.35 to 0. .50.

  Moreover, if the A value indicating the proportion of Al is the proportion of the total amount of Cr and Si, and less than 0.01, the minimum high-temperature hardness and high-temperature oxidation resistance cannot be ensured, and the cause of accelerated wear On the other hand, if the A value exceeds 0.10, the high-temperature strength decreases, causing the occurrence of defects, so the A value was determined to be 0.01 to 0.10.

(C) Composition formula of the upper layer thin layer B In the upper layer thin layer B, the Si component content ratio is relatively low, and the Al component content ratio is kept high, so that the relatively high temperature is high. It is provided with hardness and high-temperature oxidation resistance to reinforce the lack of high-temperature hardness and high-temperature oxidation resistance of the adjacent thin layer A, so that the excellent heat-resistant plastic deformation property of the thin layer A and the thin layer The upper layer having high-temperature hardness and high-temperature oxidation resistance of B is formed. If the C value indicating the Al content in the composition formula is less than 0.20, the desired high-temperature hardness and high-temperature acid resistance It is not possible to ensure the chemical conversion, and the progress of wear is promoted. On the other hand, if the C value exceeds 0.35, the high temperature strength of the entire upper layer is lowered, which causes the occurrence of defects. Therefore, the C value was set to 0.20 to 0.35.

  Further, if the D value indicating the proportion of Si is a proportion of the total amount of Cr and Al, and less than 0.15, the heat resistance plastic deformation of the entire upper layer is inevitably lowered, while the D value is 0.30. Since the high-temperature strength suddenly drops when the value exceeds D, the D value is set to 0.15 to 0.30.

(D) Single layer average layer thickness of thin layer A and thin layer B of the upper layer If each layer average layer thickness is less than 5 nm, it is difficult to clearly form each thin layer with the above composition. The desired excellent heat-resistant plastic deformation property and the predetermined high temperature hardness and high temperature oxidation resistance cannot be ensured for the layer, and the disadvantage that each thin layer has when the average layer thickness of each layer exceeds 20 nm, that is, In the case of the thin layer A, insufficient high-temperature hardness and high-temperature oxidation resistance, and in the case of the thin layer B, insufficient heat-resistant plastic deformability appears locally in the layer, and this is likely to cause defects or progress of wear. Each layer has an average layer thickness of 5 to 20 nm because it is promoted.

(E) Average layer thickness of the upper layer If the average layer thickness is less than 0.5 μm, the excellent heat-resistant plastic deformation and high temperature hardness cannot be imparted to the hard coating layer over a long period of time, resulting in a short tool life. On the other hand, if the average layer thickness exceeds 1.5 μm, defects are likely to occur. Therefore, the average layer thickness was set to 0.5 to 1.5 μm.

In the coated cutting tool of the present invention, the hard coating layer is composed of a (Cr, Al, Si) N layer, and the surface layer of the hard coating layer is excellent by adopting an alternate laminated structure of the thin layer A and the thin layer B. It has particularly high heat generation because it has heat plastic deformation, predetermined high temperature hardness and high temperature oxidation resistance, and the lower layer of the single phase structure has excellent high temperature hardness and high temperature oxidation resistance. Even in high-speed gear cutting of alloy steel, the hard coating layer exhibits excellent fracture resistance and heat-resistant plastic deformation, and as a result, there is no occurrence of thermoplastic deformation that causes uneven wear in the cutting edge, and the cutting edge is normal. It takes a wear form and exhibits excellent wear resistance over a long period of time without the occurrence of defects.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, the coated gear cutting tool of the present invention will be specifically described with reference to examples.

Example 1
As the gear cutting tool body, the outer diameter: 108mm x length: 160mm from the material with the dimensions of diameter: 110mm x length: 170mm made of high speed tool steel of JIS / SKH55 and SKH51 The solid hob shown in the schematic perspective view of FIG. 3 having the overall dimensions of 3 and having the shape of three right-handed twists × 12 grooves was manufactured.

(A) Next, the above two kinds of gear cutting tool bodies (solid hobs) are used as substrates, and each of these substrates is subjected to ultrasonic cleaning in acetone and dried, and then the arc ions shown in FIG. Attached along the outer periphery at a predetermined distance in the radial direction from the central axis on the rotary table in the plating apparatus, and corresponds to the target composition shown in Table 1 as the cathode electrode (evaporation source) on one side. As the upper layer of the thin layer A forming Cr-Al-Si alloy having the above component composition, the surface having the component composition corresponding to the target composition shown in Table 1, respectively, as the other cathode electrode (evaporation source) A Cr-Al-Si alloy for forming a thin layer B is disposed opposite to each other with the rotary table in between, and a cathode electrode along the rotary table at a position shifted by 90 degrees from both the Cr-Al-Si alloys. Fitted with a Cr-Al-Si alloy for the lower layer formed as (evaporation source),
(B) First, after the inside of the apparatus is evacuated and kept at a vacuum of 0.1 Pa or less, the inside of the apparatus is heated to 400 ° C. with a heater, and then rotates on the rotary table while rotating on the rotary tool main body base. A DC bias voltage of −1000 V is applied, and a current of 100 A is passed between the Cr—Al—Si alloy for forming the lower layer and the anode electrode to generate an arc discharge. Bombard cleaning with Cr-Al-Si alloy,
(C) Introducing nitrogen gas as a reaction gas into the apparatus to make a reaction atmosphere of 3 Pa, applying a DC bias voltage of −100 V to the gear cutting tool main body rotating while rotating on the rotary table, and An arc discharge is generated by passing a current of 100 A between the lower layer forming Cr—Al—Si alloy and the anode electrode, so that the target composition and target shown in Table 1 are formed on the surface of the gear cutting tool main body. (Cr, Al, Si) N layer having a single-phase structure of layer thickness is deposited as a lower layer of the hard coating layer,
(D) Next, nitrogen gas was introduced into the apparatus as a reaction gas to make a reaction atmosphere of 2 Pa, and a DC bias voltage of −100 V was applied to the gear cutting tool main body rotating while rotating on the rotary table. In this state, a predetermined current in a range of 50 to 200 A is passed between the cathode electrode and the anode electrode of the Cr-Al-Si alloy for forming the thin layer A to generate arc discharge, and the gear cutting tool body A thin layer A having a predetermined layer thickness is formed on the surface of the substrate, and after the thin layer A is formed, the arc discharge is stopped, and instead, between the cathode electrode and the anode electrode of the Cr-Al-Si alloy for forming the thin layer B Similarly, a predetermined current in the range of 50 to 200 A is supplied to generate arc discharge to form a thin layer B having a predetermined thickness, and then the arc discharge is stopped (in this case, starting from the formation of the thin layer B). You may) Formation of thin layer A by arc discharge between the cathode electrode and anode electrode of Cr-Al-Si alloy for forming layer A, and arc discharge between cathode electrode and anode electrode of Cr-Al-Si alloy for forming thin layer B The formation of the thin layer B is alternately repeated, so that the target composition and the target layer thickness of the thin layer A and the thin layer B shown in Table 1 along the layer thickness direction are formed on the surface of the gear cutting tool main body. The coated layers for cutting tools 1 to 6 of the present invention were manufactured by vapor-depositing the upper layers composed of alternating layers with the same overall target layer thickness shown in Table 1.


For comparison purposes, the above two types of base materials (gear cutting tool main body) were ultrasonically cleaned in acetone and dried, and then loaded into the arc ion plating apparatus shown in FIG. Then, as a cathode electrode (evaporation source), Cr—Al—Si alloys each having a component composition corresponding to the target composition shown in Table 2 were mounted, and the inside of the apparatus was first evacuated to a vacuum of 0.1 Pa or less. The heater is heated to 400 ° C. with a heater, and then a DC bias voltage of −1000 V is applied to the gear cutting tool body base, and the cathode electrode is composed of the Cr—Al—Si alloy and the anode electrode. A current of 100 A is passed between them to generate an arc discharge, so that the surface of the main body of the gear cutting tool is bombarded with the Cr—Al—Si alloy, and then nitrogen gas is introduced into the apparatus as a reaction gas. And 3 Pa of reaction atmosphere, the bias voltage applied to the gear cutting tool body substrate is lowered to -100 V, and arc discharge is generated between the cathode electrode and the anode electrode of the Cr-Al-Si alloy, Therefore, by vapor-depositing a hard coating layer composed of a (Cr, Al, Si) N layer having a single-phase structure having a target composition and a target layer thickness shown in Table 2 on the surface of the gear cutting tool main body base, Coated gear cutting tools 1 to 6 (hereinafter referred to as comparative coated gear cutting tools 1 to 6) were produced.

Next, using the above-described coated gear cutting tools 1 to 6 and comparative coated gear cutting tools 1 to 6 described above, the material is made of a low alloy steel of JIS / SCr420H, module: 2.5, pressure angle: 20 degrees. , The processing of gears with the dimensions and shape of the number of teeth: 28, twist angle: 25 degrees left twist, tooth width: 50 mm,
Cutting speed (rotational speed): 220 m / min,
Feed: 2.0mm / rev,
Processing form: climb, no shift, dry (air blow),
Under the conditions of high-speed dry gear cutting (the cutting speed in the case of processing a low alloy steel gear of which the material is JIS / SCr420H is usually 120 m / min),
The number of gears processed until the flank wear width reached 0.2 mm was measured. The measurement results are shown in Tables 1 and 2, respectively.

(Example 2)
In addition, as a gear cutting tool body, a material having a size of outer diameter: 110 mm × thickness: 20 mm made of high-speed tool steel of the same material as JIS / SKH55 and SKH51 is used to machine a pitch circle diameter: 105 mm. X Thickness: A disk type pinion cutter (100 type described in JIS B 4356) shown in a schematic perspective view in FIG. 4 having an overall dimension of 18 mm and a shape of cutter teeth: 44 was manufactured.

  Next, the above-described gear cutting tool body (pinion cutter) is used as a base, and the surfaces of these bases are ultrasonically cleaned in acetone and dried, and then loaded into the arc ion plating apparatus shown in FIG. A lower layer composed of a (Cr, Al, Si) N layer having a single-phase structure with the target composition and target layer thickness shown in Table 1 under the same conditions as in Example 1, and along the layer thickness direction. The coated layer of the present invention is formed by vapor-depositing a surface layer composed of alternately laminated thin layers A and B having a target composition and a single target layer thickness shown in Table 1 with an overall target layer thickness also shown in Table 1. Cutting tools 7 to 12 were produced.

For comparison purposes, the surface of the base of the above-described gear cutting tool body (pinion cutter) is ultrasonically cleaned in acetone and dried, and is then loaded into the arc ion plating apparatus shown in FIG. By vapor-depositing a hard coating layer composed of a (Cr, Al, Si) N layer having a single-phase structure with the target composition and target layer thickness shown in Table 2 under the same conditions as in Example 1 above, Coated gear cutting tools 7 to 12 (hereinafter referred to as comparative coated gear cutting tools 7 to 12) were produced.


Next, using the above-described coated cutting tool 7-12 and comparative coated cutting tool 7-12 of the present invention, the material is made of low alloy steel of JIS / SCr420H, module: 2.25, pressure angle: 20 degrees. , Processing of gears having the size and shape of the number of teeth: 44, tooth width: 20 mm,
Number of strokes: 900 stroke / min,
Circumferential feed: 0.5mm / stroke,
Radius feed: 0.015mm / stroke,
Gears with high-speed gear cutting under the above conditions (the number of strokes is usually 600 strokes / min when processing low-alloy steel gears with the above material is JIS / SCr420H), and the flank wear width reaches 0.2 mm. The number of processes was measured. The measurement results are shown in Tables 1 and 2, respectively.

The thin layer A and thin layer B of the hard coating layer made of (Cr, Al, Si) N of the coated cutting tools 1 to 12 of the present invention obtained as a result, and the composition of the lower layer, and The composition of the hard coating layer made of (Cr, Al, Si) N of the comparative coated gear cutting tools 1 to 12 was measured by an energy dispersive X-ray analysis method using a transmission electron microscope. It showed substantially the same composition.

Further, when the average layer thickness of the constituent layers of the hard coating layer was subjected to cross-sectional measurement using a transmission electron microscope, all showed the same average value (average value of five locations) as the target layer thickness.


From the results shown in Tables 1 and 2, the coated cutting tool of the present invention has a single-phase structure lower layer composed of (Cr, Al, Si) N, each of which has a hard coating layer having a different composition, and a layer thickness. Are made of an upper layer having an alternately laminated structure of thin layers A and B each having a thickness of 5 to 20 nm, thereby providing excellent heat plastic deformation and predetermined high temperature hardness, high temperature strength and high temperature oxidation resistance, Since the lower layer of the single-phase structure has excellent high-temperature hardness and high-temperature oxidation resistance, even with high-speed gear cutting of alloy steel with high heat generation, the hard coating layer has excellent fracture resistance, Demonstrates heat-resistant plastic deformation. As a result, there is no chipping at the cutting edge, there is no occurrence of thermoplastic deformation that causes uneven wear, and the cutting edge is in a normal wear form with no chipping. It exhibits excellent wear resistance over a long period of time.

As described above, the coated gear cutting tool of the present invention can be used not only for gear cutting under normal conditions, but also for gear cutting such as various alloy steel gears, especially for high-speed gear cutting with high heat generation. In this case, the hard coating layer exhibits excellent wear resistance and fracture resistance, and exhibits excellent performance over a long period of time. It can cope with labor saving, energy saving and cost reduction of processing sufficiently satisfactorily.

The arc ion plating apparatus used for forming the hard coating layer which comprises the covering gear cutting tool of this invention is shown, (a) is a schematic plan view, (b) is a schematic front view. It is a schematic explanatory drawing of a normal arc ion plating apparatus. It is a schematic perspective view of a solid hob. It is a schematic perspective view of a disk-type pinion cutter.

Claims (1)

On the surface of the gear cutting tool body made of high-speed tool steel,
(A) Both are composed of an upper layer and a lower layer made of a composite nitride of Cr, Al and Si, the upper layer having a layer thickness of 0.5 to 1.5 μm, and the lower layer having a layer thickness of 2 to 6 μm. And
(B) Each of the upper layers has an alternate laminated structure of thin layers A and B having a layer thickness of 5 to 20 nm (nanometer),
The thin layer A is
A composition formula: (Cr _{1− (A + B)} Al _A Si _B ) N (wherein, A represents 0.01 to 0.10 and B represents 0.35 to 0.50 in atomic ratio) and Cr A composite nitride layer of Al and Si;
The thin layer B is
Cr satisfying the composition formula: (Cr _{1− (C + D)} Al _C Si _D ) N (wherein C is 0.20 to 0.35 and D is 0.15 to 0.30 in atomic ratio) A composite nitride layer of Al and Si,
(C) the lower layer has a single phase structure;
Composition formula: (Cr _{1− (E + F)} Al _E Si _F ) N (wherein, in terms of atomic ratio, E represents 0.45 to 0.65, F represents 0.01 to 0.10) and Cr A composite nitride layer of Al and Si;
Vapor-depositing a hard coating layer consisting of
A surface-coated high-speed tool steel gear cutting tool that exhibits high chipping resistance with a hard coating layer by high-speed gear cutting of alloy steel.

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