JP4706909B2 - Surface coated high speed tool steel gear cutting tool with excellent wear resistance with hard coating layer in high speed gear cutting of alloy steel - Google Patents

Description

  The present invention is characterized in that the hard coating layer has excellent heat resistance, and also has high-temperature hardness and high-temperature strength, and therefore, even when used for high-speed gear cutting with high heat generation such as alloy steel, Surface-coated high-speed tool steel gear cutting tool (hereinafter referred to as coated high-speed gear cutting tool) that exhibits excellent wear resistance without the occurrence of thermoplastic deformation that causes uneven wear that accelerates the progress of wear in the layer It is about.

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

In order to improve the wear resistance of the tool, a hard coating layer is usually provided on the surface of the tool. However, for a gear cutting tool, for example, a high machined shape shown in FIGS. 3 and 4 is used. A coated high-speed gear cutting tool is known in which a gear cutting tool body made of high-speed tool steel is used as a base and a hard coating layer having excellent wear resistance is provided on the surface of the base. As the hard coating layer, for example, the composition formula: [Ti _{1− (X + Y)} Al _X Cr _Y ] N (wherein the atomic ratio, X is 0.45 to 0.65, and Y is 0.01 to 0.15). ),

It is known that a hard coating layer composed of a composite nitride of Ti, Al, and Cr [hereinafter referred to as (Ti, Al, Cr) N] satisfying the following conditions is formed by vapor deposition with a layer thickness of 2 to 8 μm. Further, the (Ti, Al, Cr) N layer constituting the hard coating layer has improved high-temperature hardness and high-temperature oxidation resistance by Al as a constituent component, high-temperature strength by the same Ti, and further improved heat resistance by the same Cr. It is also known to have characteristics.

Furthermore, the coated high-speed gear cutting tool provided with the hard coating layer is applied to the above-mentioned base (high-speed gear cutting tool main body), for example, an arc ion plating apparatus which is a kind of physical vapor deposition apparatus schematically shown in FIG. ) Between the anode electrode and the cathode electrode (evaporation source) in which a Ti—Al—Cr alloy having a predetermined composition is set, with the heater heated to a temperature of, for example, 400 ° C. For example, arc discharge was generated under the condition of current: 90 A, and nitrogen gas was introduced into the apparatus at the same time as a reaction gas to obtain a reaction atmosphere of, for example, 2 Pa, while a bias voltage of, for example, −100 V was applied to the substrate. It is also known that it is manufactured by vapor-depositing a hard coating layer composed of the (Ti, Al, Cr) N layer on the surface of the substrate under conditions.
JP-A-7-237010

  In recent years, the performance of cutting devices has been dramatically improved. On the other hand, there is a strong demand for labor saving and energy saving and further cost reduction for cutting, and with this, cutting tends to be faster. For coated gear cutting tools, there is no problem when 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, it is particularly hard. Thermoplastic deformation occurs due to the lack of heat resistance of the coating layer, and the uneven wear form is promoted, so that the progress of wear is promoted, so that 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 to develop a coated high-speed gear cutting tool exhibiting excellent wear resistance with a hard coating layer particularly in high-speed gear cutting of alloy steel. As a result of conducting research by focusing on the (Ti, Al, Cr) N layer that constitutes the hard coating layer of the high-speed gear cutting tool,
(A) In the (Ti, Al, Cr) N layer constituting the hard coating layer, the heat resistance is improved if the content ratio of the Cr component is increased, but 1 in the conventional (Ti, Al, Cr) N layer described above. When the Cr content is about 15 atomic%, high-speed gear cutting of alloy steel with high heat generation cannot provide high heat resistance sufficient to prevent the occurrence of thermoplastic deformation of the hard coating layer. In order to satisfy the requirements satisfactorily, 40-60 atomic% Cr content far exceeding 1-15 atomic% is required, while 40-60 atomic% Cr component was contained (Ti, Al, In order to use the Cr) N layer 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, the content ratio of the Al component is extremely low. Inevitable, this results in high temperature hardness And those become very low high-temperature oxidation resistance.

(B) the composition _{formula: [Ti 1- (A + B} ) Al A Cr B] N ( provided that an atomic ratio, A is 0.01 to 0.10, B represents a 0.40 to 0.60) satisfies A (Ti, Al, Cr) N layer having a Cr content of 40 to 60 atomic%;
_{Formula: [Ti 1- (C + D} ) Al C Cr D] N ( provided that an atomic ratio, C is 0.20 to 0.35, D represents a 0.15 to 0.30) satisfies, relative (Ti, Al, Cr) N layer with a large content ratio of Al component,
Are alternately laminated in a state where each layer has an average layer thickness of 5 to 20 nm (nanometers), and this (Ti, Al, Cr) N layer is formed by the above-described alternate lamination structure of thin layers. Excellent heat resistance of (Ti, Al, Cr) N layer (hereinafter referred to as thin layer A) having a high Cr content, a lower Cr content ratio than the thin layer A, and a relatively high Al content (Ti, Al, Cr) N layer (hereinafter referred to as the thin layer B) has relatively high high temperature hardness and high temperature oxidation resistance.

(C) The (Ti, Al, Cr) N layer having the alternately laminated structure of the thin layer A and the thin layer B of (b) above has excellent heat resistance required for high-speed gear cutting of alloy steel and a predetermined value. Although it has a high temperature hardness, it does not have a sufficiently satisfactory high temperature hardness and high temperature oxidation resistance, so it is provided as the upper layer of the hard coating layer, while the lower layer has insufficient heat resistance, (Ti, Al, Cr) N layer having a composition corresponding to the above conventional hard coating layer having a relatively high content of Al component and having excellent high temperature hardness and high temperature oxidation resistance,
_{Formula: [Ti 1- (E + F} ) Al E Cr F] N ( provided that an atomic ratio, E is 0.45 to 0.65, F represents a 0.01 to 0.15) satisfies the single (Ti, Al, Cr) N layer of single phase structure,
The resulting hard coating layer has a combination of high-temperature hardness, high-temperature oxidation resistance, and high-temperature strength in addition to excellent heat resistance. The coated high-speed gear cutting tool formed by vapor deposition of the above-mentioned high-speed gear cutting of alloy steel accompanied by high heat generation eliminates the occurrence of thermoplastic deformation that causes uneven wear in the hard coating layer, and has a normal wear form. Since it comes to take, it will show excellent wear resistance for a long 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, Cr) N, the upper layer has a layer thickness of 0.5 to 1.5 μm, and the lower layer has a layer thickness of 2 to 6 μm. ,
(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
Composition formula: [Ti _{1 − (A + B)} Al _A Cr _B ] N (wherein A represents 0.01 to 0.10 and B represents 0.40 to 0.60 in terms of atomic ratio) (Ti , Al, Cr) N layer,
The thin layer B is
Composition formula: [Ti _{1− (C + D)} Al _C Cr _D ] N (wherein C is 0.20 to 0.35 and D is 0.15 to 0.30 in atomic ratio) (Ti , Al, Cr) N layer,
(C) the lower layer has a single phase structure;
Composition formula: [Ti _{1− (E + F)} Al _E Cr _F ] N (wherein E is 0.45 to 0.65 and F is 0.01 to 0.15 in atomic ratio) (Ti , Al, Cr) N layer,
For coated high-speed gear cutting tools (surface-coated high-speed tool steel gear cutting tools) that exhibit excellent wear resistance in high-speed gear cutting of alloy steel, which is formed by vapor-depositing a hard coating layer consisting of It has characteristics.

Next, the reason why the numerical values of the hard coating layer of the coated high-speed gear cutting tool of the present invention are limited as described above will be described.
(A) Composition formula and layer thickness of lower layer As described above, the Al component in the (Ti, Al, Cr) N layer constituting the hard coating layer improves the high temperature hardness and high temperature oxidation resistance, while the same Ti The component has the effect of improving the high-temperature strength and further the heat resistance of the Cr component, and the lower layer has a relatively high content ratio of the Al component to provide high high-temperature hardness and high-temperature oxidation resistance. When the E value indicating the Al content ratio is less than 0.45 in the total amount of Ti and Cr (atomic ratio, the same shall apply hereinafter), the Ti ratio is relatively high, and the high speed gear cutting of the alloy steel. The excellent high-temperature hardness and high-temperature oxidation resistance required for processing cannot be secured, and the progress of wear is rapidly accelerated. On the other hand, when the E value indicating the Al ratio exceeds 0.65 , The ratio of Ti becomes relatively small and the high temperature strength suddenly The E value was determined to be 0.45 to 0.65, since it dropped drastically and as a result, chipping (small chipping) was likely to occur.
Further, the F value indicating the proportion of Cr is the proportion of the total amount of Ti and Al. If the F value is less than 0.01, the predetermined heat resistance cannot be ensured, while the F value exceeds 0.15. The above-mentioned excellent characteristics of the lower layer, that is, high temperature hardness, high temperature oxidation resistance, and high temperature strength, suddenly decrease, so the F value was set to 0.01 to 0.15.
Furthermore, if the layer thickness is less than 2 μm, the excellent high-temperature hardness and high-temperature oxidation resistance cannot be imparted to the hard coating layer over a long period of time, resulting in short tool life, while the layer thickness is 6 μm. If it exceeds, chipping is likely to occur, so the layer thickness was determined to be 2 to 6 μm.

(B) Composition formula of upper layer thin layer A The Cr component in (Ti, Al, Cr) N of the upper layer thin layer A is relatively increased in content as described above to improve heat resistance. Therefore, it is included for the purpose of improving the heat-resistant plastic deformability in high-speed gear cutting of alloy steel with high heat generation, and therefore, if the B value is less than 0.40, the desired excellent heat resistance is ensured. On the other hand, if the B value exceeds 0.60, the content ratio of the Ti component is relatively reduced, and the high-temperature strength that the layer itself should have can be ensured, causing chipping. Therefore, the B value was set to 0.40 to 0.60.
Further, the A value indicating the proportion of Al is the proportion of the total amount of Ti and Cr, and if it is 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 0.06, a tendency to decrease in the high temperature strength appears, which causes chipping. Therefore, the A value is set to 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 Cr 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 high-temperature oxidation resistance, reinforces high-temperature hardness and high-temperature oxidation resistance of the adjacent thin layer A, The upper layer having the excellent heat resistance of the layer A and the relatively high high temperature hardness and high temperature oxidation resistance of the thin layer B is formed, and the Al content in the composition formula is shown. When the C value is less than 0.20, the predetermined relatively high high temperature hardness and high temperature oxidation resistance cannot be ensured, and the progress of wear is promoted, while the C value is 0.35. If this is exceeded, a drop in the high-temperature strength of the entire upper layer is inevitable, and chipping occurs. For this reason, the C value was set to 0.20 to 0.35.
Further, the D value indicating the ratio of Cr is the ratio of the total amount of Ti and Al, and if it is less than 0.15, the heat resistance of the entire upper layer is inevitably lowered, while the D value exceeds 0.30. Then, since the high-temperature strength of the entire upper layer suddenly decreases, the D value was set to 0.15 to 0.30.

(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. It is impossible to ensure excellent heat resistance, and a predetermined relatively high high-temperature hardness and high-temperature oxidation resistance. Further, when the thickness of each layer exceeds 20 nm, the disadvantage of each thin layer, that is, the thin layer A If there is insufficient high-temperature hardness and high-temperature oxidation resistance, and if it is thin layer B, insufficient heat resistance will appear locally in the layer, which may cause chipping or promote wear progress. Each layer thickness was determined to be 5 to 20 nm.

(E) Layer thickness of the upper layer If the layer thickness is less than 0.5 μm, it is impossible to provide the hard coating layer with its excellent heat resistance and predetermined high temperature hardness and high temperature oxidation resistance over a long period of time. On the other hand, if the layer thickness exceeds 1.5 μm, chipping tends to occur. Therefore, the layer thickness is set to 0.5 to 1.5 μm.

  In the coated high-speed gear cutting tool according to the present invention, the hard coating layer is composed of a (Ti, Al, Cr) N layer, and the upper layer of the hard coating layer is formed by alternately laminating a thin layer A and a thin layer B. It has excellent heat resistance while maintaining a predetermined high temperature hardness and high temperature oxidation resistance, and the lower layer of the single phase structure has relatively high high temperature hardness and high temperature oxidation resistance. Even in high-speed gear cutting of alloy steel with high heat generation, thermoplastic deformation of the hard coating layer is remarkably suppressed, and excellent wear resistance is exhibited over a long period of time.

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

The material is made of a high-speed tool steel of JIS / SKH51 and SKH55, with a diameter of 110 mm x length of 200 mm, and machined to have an overall diameter of 108 mm x length of 180 mm, In addition, a high-speed gear cutting tool body (solid hob) shown in a schematic perspective view in FIG. 3 having a shape of three right-handed twists × 12 grooves was manufactured.

(A) Next, a high speed gear cutting tool body (solid hob) made of the above two materials is used as a base, and each of these bases is ultrasonically cleaned in acetone and dried, and the arc shown in FIG. Attached along the outer peripheral portion at a predetermined distance in the radial direction from the central axis on the rotary table in the ion plating apparatus, each having a target composition shown in Table 1 as a cathode electrode (evaporation source) on one side. The Ti-Al-Cr alloy for forming the upper layer A having the corresponding component composition and the cathode electrode (evaporation source) on the other side also had component compositions corresponding to the target compositions shown in Table 1, respectively. Ti-Al-Cr alloy for forming thin layer B of the upper layer is disposed opposite to the rotary table, and the cathode is formed along the rotary table at a position shifted by 90 degrees from both Ti-Al-Cr alloys. The Ti-Al-Cr alloy for the lower layer formed by mounting a cathode electrode (vapor 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 an electric current of 100 A is passed between the Ti—Al—Cr alloy for forming the lower layer and the anode electrode to generate an arc discharge. Bombard cleaning with Ti-Al-Cr 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 flowing a current of 100 A between the Ti—Al—Cr alloy for forming the lower layer and the anode electrode, so that the target composition shown in Table 1 and (Ti, Al, Cr) N layer having a single phase structure with a target 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-Cr 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-Cr 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 Ti-Al-Cr alloy for forming layer A, and arc discharge between cathode electrode and anode electrode of Ti-Al-Cr alloy for forming thin layer B The thin layer B is repeatedly formed alternately, 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 formed on the surface of the high-speed cutting tool main body. The coated high-speed gear cutting tools 1 to 6 of the present invention were manufactured by vapor-depositing the upper layers composed of the alternating layers with the overall target layer thicknesses shown in Table 1, respectively.

For comparison purposes, the high-speed gear cutting tool main body made of the above two types of materials is 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—Cr alloy having a component composition corresponding to the target composition shown in Table 2 is attached, and the apparatus is first evacuated to a vacuum of 0.1 Pa or less. While being held, the inside of the apparatus is heated to 400 ° C. with a heater, and then a DC bias voltage of −1000 V is applied to the base of the gear cutting tool body, and between the Ti—Al—Cr alloy of the cathode electrode and the anode electrode A current of 100 A is applied to the electrode to generate an arc discharge, so that the surface of the main body of the gear cutting tool is bombarded with the Ti—Al—Cr alloy, and then nitrogen gas is introduced into the apparatus as a reaction gas. Then, the reaction atmosphere is 3 Pa, and the bias voltage applied to the gear cutting tool main body is lowered to −100 V to generate an arc discharge between the cathode electrode and the anode electrode of the Ti—Al—Cr alloy. Thus, a hard coating layer composed of a (Ti, Al, Cr) N layer having a single phase structure having the target composition and target layer thickness shown in Table 2 is formed on the surface of the high-speed gear cutting tool main body by vapor deposition. Thus, coated high-speed gear cutting tools 1 to 6 (hereinafter referred to as comparative coated high-speed gear cutting tools 1 to 6) were produced, respectively.

Next, using the above-described coated high-speed gear cutting tools 1 to 6 and the comparative coated high-speed gear cutting tools 1 to 6, the material is alloy steel of JIS / SCr420H,
Module: 2.5, pressure angle: 20 degrees, number of teeth: 28, twist angle: 25 degrees right-hand twist, tooth width: processing of gears with dimensions and shapes of 50 mm,
Cutting speed (rotational speed): 240 m / min,
Feed: 2.2 mm / rev,
Processing form: climb, no shift, dry (air blow),
Under the conditions of high speed gear cutting (the cutting speed in the case of the above JIS / SCr420H alloy steel gear 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.

Moreover, as a high-speed gear cutting tool body, a material having a dimension of an outer diameter: 110 mm × thickness: 25 mm made of high-speed tool steel made of JIS / SKH51 and SKH55 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 size of 20 mm and a number of cutter teeth: 44 was manufactured.

  Next, the above-described high-speed 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. Under the same conditions as in Example 1, the lower layer composed of a (Ti, Al, Cr) N layer having a single-phase structure with the target composition and target layer thickness shown in Table 1, and also in the layer thickness direction Along with the target composition shown in Table 1 and the upper layer consisting of alternating layers of thin layers A and B having a single target layer thickness, the present invention is coated by vapor deposition with the overall target layer thickness also shown in Table 1. High-speed gear cutting tools 7 to 12 were produced, respectively.

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

Next, using the above-described coated high-speed gear cutting tool 7 to 12 and comparative coated high-speed gear cutting tool 7 to 12, the material is made of alloy steel of JIS / SCr420H,
Module: 2.25, pressure angle: 20 degrees, number of teeth: 44, tooth width: processing of gears with dimensions and shapes of 20 mm,
Number of strokes: 1200 stroke / min,
Circumferential feed: 0.5 mm / stroke,
Radius feed: 0.015 mm / stroke,
Measures the number of gears processed until the flank wear width reaches 0.2 mm under high speed gear cutting conditions (the number of strokes is usually 600 strokes / min when machining JIS / SCr420H alloy steel gears). did. The measurement results are shown in Tables 1 and 2, respectively.

The thin layer A and the thin layer B of the upper layer constituting the hard coating layer made of (Ti, Al, Cr) N of the coated high-speed gear cutting tools 1 to 12 of the present invention obtained as a result, and the composition of the lower layer, In addition, the composition of the hard coating layer made of (Ti, Al, Cr) N of the comparative coated high-speed gear cutting tools 1 to 12 was measured by energy dispersive X-ray analysis using a transmission electron microscope. The composition was substantially the same as the 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 high-speed gear cutting tool of the present invention has a single-phase lower layer composed of (Ti, Al, Cr) N, and a hard coating layer each having a different composition, Consists 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 high temperature oxidation resistance, and the upper layer has excellent heat resistance. Since the hard coating layer has these excellent characteristics, the hard coating layer can be used even when gear cutting of alloy steel gears is performed under high-speed gear cutting conditions with high heat generation. Since it exhibits excellent heat-resistant plastic deformation, gear cutting is performed while maintaining a normal wear form. As a result, the hard coating layer has a single phase while exhibiting excellent wear resistance. Comparison consisting of (Ti, Al, Cr) N layers of structure Under high-speed gear cutting tools, under the above high-speed gear cutting conditions, thermoplastic deformation occurs due to lack of heat resistance, and gear cutting in an uneven wear mode is inevitable. As a result, it is clear that the service life is reached in a relatively short time.
As described above, the surface-coated high-speed tool steel gear cutting tool of the present invention (the present invention coated high-speed gear cutting tool) is not limited to gear cutting under normal conditions, particularly various alloy steel gears, etc. Even when the gear cutting is performed under high-speed gear cutting conditions with high heat generation, the hard coating layer exhibits excellent wear resistance and exhibits excellent performance over a long period of time. It is possible to satisfactorily cope with the high performance of the cutting device, the labor saving and energy saving of gear cutting, and the cost reduction.

The arc ion plating apparatus used for forming the hard coating layer which comprises the covering high-speed 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 Ti, Al, and Cr, 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. Have
(B) Each of the upper layers has an alternately laminated structure of thin layers A and B each having an average layer thickness of 5 to 20 nm (nanometer),
The thin layer A is
Ti satisfying the composition formula: [Ti _{1− (A + B)} Al _A Cr _B ] N (wherein A represents 0.01 to 0.10 and B represents 0.40 to 0.60) A composite nitride layer of Al and Cr;
The thin layer B is
_{Formula: [Ti 1- (C + D} ) Al C Cr D] N ( provided that an atomic ratio, C is 0.20 to 0.35, D denotes the 0.15 to 0.30) and Ti which satisfies A composite nitride layer of Al and Cr,
(C) the lower layer has a single phase structure;
Ti satisfying the composition formula: [Ti _{1− (E + F)} Al _E Cr _F ] N (wherein E is 0.45 to 0.65 and F is 0.01 to 0.15 in atomic ratio) A composite nitride layer of Al and Cr;
A surface-coated high-speed tool steel cutting tool that exhibits excellent wear resistance in high-speed gear cutting of alloy steel, characterized in that the hard coating layer is formed by vapor deposition.

Images