JP2006315148A - Gear cutting tool made of surface coated high speed steel with hard coating layer exhibiting excellent lubricity in high speed dry gear cutting of alloy steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gear cutting tool made of surface coated high speed steel with hard coating layer exhibiting excellent lubricity in high speed dry gear cutting. <P>SOLUTION: A gear cutting tool is constituted of an upper layer and a lower layer composed of (a) (Ti, Al, V)N on the surface of a base body of a high speed tool steel, the upper layer has a film thickness of 0.5 to 1.5 μm and the lower layer has a film thickness of 2 to 6 μm, respectively. (b) The upper layer has an alternate structure of a thin layer A and a thin layer B having a layer thickness of 5 to 20 nm laminated alternately, and the thin layer A is composed of a (Ti, Al, V)N layer satisfying a composition formula, (Ti<SB>1-(A+B)</SB>Al<SB>A</SB>V<SB>B</SB>)N (wherein A shows a range of 0.01 to 0.10, and B shows a range of 0.50 to 0.70 by atomic ratio), and the thin layer B is composed of a (Ti, Al, V)N layer satisfying a composition formula, (Ti<SB>1-(C+D)</SB>Al<SB>C</SB>V<SB>D</SB>)N. (c) The upper lower layer has a single-phase structure, and is formed by depositing and forming a hard coated layer composed of a (Ti, Al, V)N layer satisfying a composition formula, (Ti<SB>1-(E+F)</SB>Al<SB>E</SB>V<SB>F</SB>)N. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention has excellent wear resistance and lubricity even when the hard coating layer has excellent lubricity as well as wear resistance, and therefore is used for high speed dry 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).

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-Y Ti _Y ) From an Al / Ti composite nitride [hereinafter referred to as (Al, Ti) N] layer satisfying N (wherein Y represents 0.35 to 0.60 in atomic ratio) A coated cutting tool formed by physically vapor-depositing a hard coating layer having an average layer thickness of 1 to 10 μm is proposed, and the (Al, Ti) N layer constituting the hard coating layer has high-temperature hardness and heat resistance due to Al, It is also known that a coated cutting tool formed with such a hard coating layer exhibits excellent gear cutting performance because it has strength due to Ti and Ti (see, for example, Patent Document 1 and Patent Document 2). Further, a coated gear cutting tool in which V (vanadium) is further added as a nitride forming element of the (Al, Ti) N layer constituting the hard coating layer is also known (see, for example, Patent Document 3).

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 at a temperature of 400 ° C. under a vacuum atmosphere of 2 Pa, for example, voltage: 35 V, current: between the anode electrode and the cathode electrode (evaporation source) on which an Al—Ti alloy having a predetermined composition is set. An arc discharge is generated under the condition of 90 A, and simultaneously, nitrogen gas is introduced into the apparatus as a reaction gas to create a reaction atmosphere of 2 Pa, for example. It is also known that it is produced by vapor-depositing a hard coating layer composed of the (Al, Ti) N layer on the surface of the substrate under the applied conditions.
Japanese Patent No. 2793772 Japanese Patent No. 3165658 JP 2000-24836 A

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 problem when it is used under normal gear cutting conditions, but when this is used under high speed dry gear cutting conditions such as alloy steel with high heat generation. The present situation is that the flank wear due to welding is increased, the progress of wear of the hard coating layer is promoted, and the service life is reached in a relatively short time.

In view of the above, the present inventors have developed the above-described conventional coating tool in order to develop a coated cutting tool that exhibits excellent lubricity and wear resistance with a hard coating layer particularly in high-speed dry gear cutting. As a result of conducting research, focusing on the hard coating layer that constitutes the gear cutting tool,
(A) V is contained as a component of the (Ti, Al) N layer constituting the hard coating layer to form a composite nitride layer of Ti, Al, and V, or the hard coating layer is constituted (Ti, Al). The lubricity is improved if the content ratio of V, which is a component of the Al, V) N layer, is increased. However, when the V content ratio is about 1 to 9 atomic%, it is required for high speed dry gear cutting of alloy steel. Lubricity and the effect of preventing welding cannot be ensured, and in order to satisfy these requirements satisfactorily, it is necessary to contain 50 to 70 atomic% of V far exceeding the above 1 to 9 atomic%. On the other hand, in order to practically use a (Ti, Al, V) N layer containing 50 to 70 atomic% V component as a hard coating layer, it is necessary to contain a predetermined amount of Ti to ensure a predetermined high temperature strength. In this case, however, it is inevitable that the content ratio of the Al component becomes extremely low, and as a result, the high temperature hardness and heat resistance are extremely low.

(B) the composition _{formula: (Ti 1- (A + B} ) Al A V B) N ( provided that an atomic ratio, A is 0.01 to 0.10, B represents a 0.50 to 0.70) satisfies A (Ti, Al, V) N layer having a V content ratio of 50 to 70 atomic%;
Composition formula: (Ti _{1− (C + D)} Al _C V _D ) N (wherein, C is 0.25 to 0.40 and D is 0.20 to 0.35 in an atomic ratio), relative (Ti, Al, V) N layer with an increased Al component content,
Are alternately laminated in a state where each layer thickness is 5 to 20 nm (nanometer), the (Ti, Al, V) N layer is formed by the above-described high V due to the alternately laminated structure of thin layers. The excellent lubricity of the contained (Ti, Al, V) N layer (hereinafter referred to as the thin layer A), the V content ratio is relatively low compared to the thin layer A, and the relatively Al content A predetermined relatively high high-temperature hardness and heat resistance of the (Ti, Al, V) N layer (hereinafter referred to as the thin layer B) having a high ratio.

(C) The (Ti, Al, V) N layer having the alternately laminated structure of the thin layer A and the thin layer B in (b) above has high lubricity and prevention of welding required for high-speed dry gear cutting of alloy steel. Although it has an effect, it does not have a sufficiently satisfactory high temperature hardness and heat resistance, so it is provided as an upper layer of the hard coating layer, while the lower layer, although it can not be said that the lubricity is sufficient, The (Ti, Al, V) N layer, which is a hard coating layer having a relatively high Al component content, excellent high-temperature hardness and heat resistance,
Compositional formula: (Ti _{1− (E + F)} Al _E V _F ) N (wherein E is 0.50 to 0.65 and F is 0.01 to 0.09 in terms of atomic ratio) (Ti, Al, V) N layer of single phase structure,
With this structure, the hard coating layer has high temperature hardness, heat resistance, and high temperature strength in addition to excellent lubricity. The gear cutting tool has the high lubricity and anti-welding effect required for high-speed dry gear cutting of alloy steel with high heat generation, and also exhibits excellent wear resistance over a long period of time. .
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 a high-speed tool steel substrate,
(A) Both are composed of an upper layer and a lower layer made of (Ti, Al, V) N, the upper layer has a thickness of 0.5 to 1.5 μm, and the lower layer has a thickness of 2 to 6 μm. ,
(B) Each of the upper layers has an alternately laminated structure of thin layers A and B having a layer thickness of 5 to 20 nm (nanometer),
The thin layer A is
Composition formula: (Ti _{1− (A + B)} Al _A V _B ) N (wherein A is 0.01 to 0.10 and B is 0.50 to 0.70 in terms of atomic ratio) (Ti , Al, V) N layer,
The thin layer B is
Composition formula: (Ti _{1− (C + D)} Al _C V _D ) N (wherein C is 0.25 to 0.40 and D is 0.20 to 0.35 in terms of atomic ratio) (Ti , Al, V) N layer,
(C) the lower layer has a single phase structure;
Composition formula: (Ti _{1− (E + F)} Al _E V _F ) N (wherein E is 0.50 to 0.65 and F is 0.01 to 0.09 in atomic ratio) (Ti , Al, V) N layer,
It is characterized by a surface-coated high-speed tool steel gear cutting tool that exhibits excellent lubricity in high-speed dry gear cutting of alloy steel formed by vapor-depositing a hard coating layer made of

Next, the reason why the structure of the hard coating layer constituting the coated cutting tool of the present invention is limited as described above will be described.

(A) Composition formula and layer thickness of the lower layer As described above, the Al component in the (Ti, Al, V) N layer constituting the hard coating layer improves high-temperature hardness and heat resistance, while the Ti component Has the effect of improving the high temperature strength and the lubricity of the V component, and the lower layer has a relatively high Al component content to provide high high temperature hardness and heat resistance. When the E value indicating the ratio is less than 0.50 in the ratio of the total amount of Ti and V (atomic ratio, the same applies hereinafter), the ratio of Ti is relatively increased, and high-speed dry gear cutting of alloy steel is performed. The required high temperature hardness and heat resistance cannot be ensured, and the progress of wear is rapidly promoted. On the other hand, if the E value indicating the proportion of Al exceeds 0.65, the relative In addition, the ratio of Ti becomes too small, and the high-temperature strength rapidly decreases, As a result, chipping (slight chipping) and the like are likely to occur, so the E value was set to 0.50 to 0.65.

Further, the F value indicating the proportion of V is the proportion of the total amount of Ti and Al. If the F value is less than 0.01, the predetermined lubricity cannot be ensured, while the F value exceeds 0.09. Since the high temperature hardness and the heat resistance are drastically reduced, the F value is determined to be 0.01 to 0.09.

Furthermore, if the layer thickness is less than 2 μm, the excellent high-temperature hardness and heat resistance cannot be imparted to the hard coating layer over a long period of time, resulting in a shortened tool life, while the layer thickness exceeds 6 μm. Then, since the chipping is likely to occur, the layer thickness is set to 2 to 6 μm.

(B) Composition formula of thin layer A of the upper layer V component in (Ti, Al, V) N of thin layer A of the surface layer has a relatively high content ratio as described above to improve lubricity. Therefore, it is contained for the purpose of adapting to high-speed dry gear cutting of alloy steel with high heat generation. Therefore, if the B value is less than 0.50, the desired excellent lubricity cannot be ensured. If the B value exceeds 0.70, the high temperature strength that the layer itself should have cannot be secured, and chipping is likely to occur. Therefore, the B value was set to 0.50 to 0.70.

Further, the A value indicating the proportion of Al is the proportion of the total amount of Ti and V. If it is less than 0.01, the minimum high-temperature hardness and heat resistance cannot be ensured, which causes accelerated wear. On the other hand, when the A value exceeds 0.10, a tendency to decrease in high-temperature strength appears, which causes chipping. Therefore, the A value was determined to be 0.01 to 0.10.
(C) Composition formula of thin layer B of the upper layer In the thin layer B of the upper layer, the content ratio of the V component is relatively lower than that of the thin layer A, and the content ratio of the Al component is relatively By keeping the thin layer A high, the thin layer A has insufficient high-temperature hardness and heat resistance, reinforces the high-temperature hardness and heat resistance shortage of the adjacent thin layer A, and thus has the excellent thin layer A. The upper layer having a relatively high high-temperature hardness and heat resistance of the thin layer B is formed, but the C value indicating the Al content in the composition formula is less than 0.25. , The predetermined high temperature hardness and heat resistance cannot be ensured, which causes wear promotion. On the other hand, when the C value exceeds 0.40, the high temperature strength rapidly decreases, Since chipping is likely to occur in the layer, the C value is set to 0.25 to 0. .40.

Further, the D value indicating the ratio of V is the ratio of the total amount of Ti and Al. If the value is less than 0.20, the lubricity of the entire upper layer is inevitably deteriorated, while the D value exceeds 0.35. Then, since the high temperature strength of the entire upper layer is drastically reduced, the D value was set to 0.20 to 0.35.

(D) Layer thicknesses of upper layer thin layer A and layer B If each layer thickness is less than 5 nm, it is difficult to form each thin layer clearly with the above composition. Excellent lubricity, further high temperature hardness and heat resistance cannot be ensured, and if the thickness of each layer exceeds 20 nm, each thin layer has defects, ie, if it is thin layer A, high temperature hardness and heat resistance Insufficient lubricity, if thin layer B, insufficient lubricity will appear locally in the layer, which may cause chipping and promote the progress of wear. It was set to ˜20 nm.

(E) Layer thickness of the upper layer

If the layer thickness is less than 0.5 μm, the excellent lubricity and the predetermined high temperature hardness and heat resistance cannot be imparted to the hard coating layer over a long period of time, resulting in a shortened tool life, while the layer thickness When the thickness exceeds 1.5 μm, chipping is likely to occur. Therefore, the layer thickness is set to 0.5 to 1.5 μm.

In the coated cutting tool according to the present invention, the hard coating layer is composed of (Ti, Al, V) N layers. The upper layer of the hard coating layer has an alternate laminated structure of thin layers A and thin layers B. The high-temperature hardness and heat resistance of the single-phase structure is maintained while maintaining high-temperature hardness and heat resistance, and the lower layer of the same phase structure has excellent high-temperature hardness and heat resistance. Even in high-speed dry gear cutting of alloy steel with high heat generation, excellent wear resistance is exhibited over a long period of time without occurrence of chipping in the hard coating layer.

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: 75 mm x length: 110 mm by machining from a material with a diameter: 80 mm x length: 130 mm 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-hand twists × 18 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. The upper layer with the component composition corresponding to the target composition shown in Table 1 as the Ti-Al-V alloy for forming the thin layer A of the upper layer having the component composition and the cathode electrode (evaporation source) on the other side A Ti-Al-V alloy for forming a thin layer B is disposed opposite to the rotary table, and a cathode electrode (steamed along the rotary table at a position shifted by 90 degrees from both the Ti-Al-V alloys. Source) The Ti-Al-V alloy for the lower layer formed is attached as,
(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 lower layer forming Ti—Al—V alloy and the anode electrode to generate an arc discharge. Bombarded with Ti-Al-V 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 A current of 100 A is passed between the Ti-Al-V alloy for forming the lower layer and the anode electrode to generate an arc discharge, so that the target composition and target shown in Table 1 are formed on the surface of the gear cutting tool main body. (Ti, Al, V) 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 the range of 50 to 200 A is passed between the cathode electrode and the anode electrode of the Ti-Al-V alloy for forming the thin layer A to generate arc discharge, and the gear cutting tool body A thin layer A having a predetermined 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 Ti-Al-V 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)) again said thin layer The thin layer A is formed by arc discharge between the cathode electrode and the anode electrode of the Ti-Al-V alloy for forming, and the thin layer is formed by arc discharge between the cathode electrode and the anode electrode of the Ti-Al-V alloy for forming the thin layer B. The formation of the layer B is alternately repeated, so that the thin layer A and the thin layer B having the target composition and the target layer thickness shown in Table 1 along the layer thickness direction are alternately laminated on the surface of the gear cutting tool main body. The present invention coated gear cutting tools 1 to 6 were respectively produced by vapor-depositing and forming an upper layer consisting of the above with the 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. As the cathode electrode (evaporation source), a Ti—Al—V alloy having a component composition corresponding to the target composition shown in Table 2 is mounted, and the apparatus is first evacuated to a vacuum of 0.1 Pa or less. The heater is heated to 400 ° C. with a heater, a DC bias voltage of −1000 V is applied to the gear cutting tool main body, and the Ti—Al—V alloy of the cathode electrode 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 Ti-Al-V alloy, and then nitrogen gas is introduced into the apparatus as a reactive gas. and a bias voltage applied to the gear cutting tool body base is lowered to -100V to generate an arc discharge between the cathode electrode and the anode electrode of the Ti-Al-V alloy, Coating is performed by vapor-depositing a hard coating layer composed of a (Ti, Al, V) 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 base of the gear cutting tool main body. The 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 cutting tool 1-6 of the present invention and the comparative coated cutting tool 1-6, the material is made of low alloy steel of JIS / SCr420H, module: 1.5, pressure angle: 14. Machining of gears with dimensions and shapes of 5 degrees, number of teeth: 70, twist angle: 30 degrees right twist, tooth width: 22.5 mm,
Cutting speed (rotational speed): 230 m / min,
Feed: 3mm / 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 the low alloy steel gear whose material is JIS / SCr420H is usually 150 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: 105 mm × thickness: 22 mm made of high-speed tool steel of the same material as JIS / SKH55 and SKH51 is used to machine a pitch circle diameter: 100 mm. × 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 50 cutter teeth 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 (Ti, Al, V) 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 an upper layer composed of alternating layers of a thin layer A and a thin layer B having a target composition and a single target layer thickness shown in Table 1 with the overall target layer thickness shown in Table 1 as well. 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 (Ti, Al, V) 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, pressure angle: 20 degrees, tooth Machining of gears with dimensions and shape of number: 15 and tooth width: 22.5 mm,

Number of strokes: 1150 stroke / min,
Circumferential feed: 0.3 mm / stroke,
Radius feed: 0.03mm / stroke,
Gears with high-speed gear cutting under the above conditions (the number of strokes is usually 750 strokes / min when the above material is made of a low alloy steel gear of 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 composed of (Ti, Al, V) N of the coated cutting tools 1 to 12 of the present invention obtained as a result of this, and the composition of the lower layer, and The composition of the hard coating layer made of (Ti, Al, V) N of the comparative coated gear cutting tools 1 to 12 was measured by energy dispersive X-ray analysis 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 according to the present invention has a single-phase structure lower layer composed of (Ti, Al, V) N, each of which has a hard coating layer having a different composition, and a layer thickness. Is composed of an upper layer having an alternating laminated structure of thin layers A and B each having a thickness of 5 to 20 nm, the lower layer has excellent high temperature hardness and heat resistance, and the upper layer has excellent lubricity. Because the hard coating layer has these excellent characteristics, the hard coating layer is excellent even when gear cutting of alloy steel gears is performed under high-speed dry gear cutting conditions with high heat generation. Compared with the high-speed dry gear cutting conditions, the comparative coated gear cutting tool in which the hard coating layer is composed of a (Ti, Al, V) N layer having a single-phase structure, while exhibiting excellent lubricity and wear resistance. Due to lack of wear resistance and lubricity, the service life can be shortened in a relatively short time. Rukoto is clear.
As described above, the coated gear cutting tool of the present invention is not only gear cutting under normal conditions, but also gear cutting of various alloy steel gears, etc., especially high speed dry gear cutting with high heat generation. Even when performed under the conditions, the hard coating layer exhibits excellent wear resistance and lubricity, 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 cutting tool base made of high-speed tool steel,
(A) All are composed of an upper layer and a lower layer made of a composite nitride of Ti, Al, and V (vanadium), the upper layer being 0.5 to 1.5 μm and the lower layer being 2 to 6 μm in thickness. Each with
(B) Each of the upper layers has an alternately laminated structure of thin layers A and B having a layer thickness of 5 to 20 nm (nanometer),
The thin layer A is
Ti satisfying the composition formula: (Ti _{1− (A + B)} Al _A V _B ) N (wherein A is 0.01 to 0.10 and B is 0.50 to 0.70 in atomic ratio) A composite nitride layer of Al and V;
The thin layer B is
Ti satisfying the composition formula: (Ti _{1- (C + D)} Al _C V _D ) N (wherein C represents 0.25 to 0.40 and D represents 0.20 to 0.35 in atomic ratio) A composite nitride layer of Al and V,
(C) the lower layer has a single phase structure;
Ti satisfying the composition formula: (Ti _{1− (E + F)} Al _E V _F ) N (wherein E represents 0.50 to 0.65 and F represents 0.01 to 0.09 in atomic ratio) A composite nitride layer of Al and V;
Vapor-depositing a hard coating layer consisting of
A surface-coated high-speed tool steel cutting tool that exhibits excellent lubricity with a hard coating layer in high-speed dry gear cutting of alloy steel.

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