JP2007030130A - Gear cutting tool made of surface coated cemented carbide having hard coated layer exhibiting excellent wear resistance in high-speed cutting gear cutting of alloy steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gear cutting tool made of surface coated cemented carbide having hard coated layer exhibiting excellent wear resistance in high-speed gear cutting of alloy steel. <P>SOLUTION: In the gear cutting tool made of surface coated cemented carbide, a hard coated layer including an upper layer and a lower layer is formed on the surface of a tungsten carbide-base cemented carbide-made gear cutting tool base body by deposition, wherein (a) the upper layer and the lower layer are both formed of (Ti, Al, B)N, the upper layer has an average layer thickness ranging from 0.5 to 1.5 μm and the lower layer has an average layer thickness ranging from 2 to 6 μm, (b) the upper layer has an alternately stacking layer structure of a thin layer A and a thin layer B respectively having an average layer thickness of 5 to 20 nm per layer, the thin layer A is formed of (Ti, Al, B)N layer satisfying a composition formula [Ti<SB>1-(E+F</SB>)Al<SB>E</SB>B<SB>F</SB>]N, the thin layer B is formed of (Ti, Al, B)N layer satisfying a composition formula: [Ti<SB>1-(M+N)</SB>Al<SB>M</SB>B<SB>N</SB>]N, and (c) the lower layer is formed of (Ti, Al, B) N layer having a single phase structure and satisfying a composition formula [Ti<SB>1-(X+Y)</SB>Al<SB>X</SB>B<SB>Y</SB>]N. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  This invention also has a high thermal conductivity as well as high-temperature hardness and high-temperature strength, so that the hard coating layer is particularly suitable for high-speed gear cutting with high heat generation such as alloy steel. The present invention relates to a surface-coated cemented carbide gear cutting tool (hereinafter referred to as a coated carbide gear cutting tool) that exhibits excellent wear resistance over a long period of time.

Conventionally, various gears are generally used as structural members for automobiles, aircrafts, and various drive devices, and coated carbide gear cutting tools (solid hobs) are used for gear cutting of gear teeth.

Further, as the coated carbide gear cutting tool, for example, as shown in a schematic perspective view in FIG. 3, a plurality of tooth grooves are formed radially with respect to the rotation axis and along the length direction. Between the front and rear surfaces that face the tooth gap and the front surface is a rake face with respect to the rotation direction, and the tooth is composed of a top surface (tooth tip tooth surface) and both side surfaces (left and right tooth surfaces) that are flank surfaces Various hard parts are formed on the surface of a tungsten carbide based cemented carbide cutting tool body (hereinafter referred to as a carbide cutting base) machined into a shape in which a plurality of parts are continuously formed along the length direction. A coated carbide gear cutting tool formed by physical vapor deposition of a coating layer is known.

On the other hand, as a hard coating layer of a cutting tool made of a surface-coated cemented carbide such as a normal throwaway tip, end mill, and drill, for example,

_{Formula: [Ti 1- (X + Y} ) Al X B Y] N ( provided that an atomic ratio, X is .50 to 0.60, Y represents a 0.01-0.10)

It is known that a hard coating layer composed of a composite nitride of Ti, Al, and B (boron) satisfying the following conditions (hereinafter referred to as (Ti, Al, B) N) is deposited with a layer thickness of 2 to 8 μm. Further, the (Ti, Al, B) N layer constituting the hard coating layer has high temperature hardness by Al as a constituent component, high temperature strength by Ti, and thermal conductivity by B, Since the heat removal effect is exhibited by the B component, it is also known to exhibit excellent wear resistance even when used for cutting alloy steel that generates heat during cutting.

Furthermore, the above-mentioned coated carbide cutting tool provided with the above-mentioned hard coating layer is obtained by, for example, applying the above-mentioned carbide cutting base to an arc ion plating apparatus which is a kind of physical vapor deposition apparatus schematically shown in FIG. For example, between the anode electrode and the cathode electrode (evaporation source) in which a Ti—Al—B alloy having a predetermined composition is set in a state where the inside of the apparatus is heated to a temperature of, for example, 500 ° C. with a heater. 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 form a reaction atmosphere of, for example, 2 Pa. On the other hand, a bias voltage of, for example, −100 V was applied to the substrate. It is also known that it is produced by vapor-depositing a hard coating layer comprising the (Ti, Al, B) N layer on the surface of the substrate.
Japanese Patent No. 2793696

  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. In the coated carbide gear cutting tool, there is no 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, In particular, since the thermal conductivity (heat extraction effect) of the hard coating layer is not sufficient, the cutting edge is subject to thermoplastic deformation that causes uneven wear, and the wear progress is promoted. The current situation is that it reaches the end of its life.

In view of the above, the present inventors have developed the above-described conventional cemented carbide cutting tool that exhibits 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, B) N layer that constitutes the hard coating layer of the coated carbide gear cutting tool,
(A) In the (Ti, Al, B) N layer constituting the hard coating layer, the thermal conductivity is improved by increasing the content ratio of the B component, but in the conventional (Ti, Al, B) N layer described above. When the B content is about 1 to 10 atomic%, the high thermal conductivity required for high-speed gear cutting of alloy steel cannot be ensured. In order to satisfy these requirements satisfactorily, It is necessary to contain 15 to 35 atomic% of B, far exceeding atomic%, while a (Ti, Al, B) N layer containing 15 to 35 atomic% of B component is put to practical use as a hard coating layer. It is necessary to ensure a predetermined high-temperature strength by containing a predetermined amount of Ti. In this case, however, it is inevitable that the content ratio of the Al component is extremely low, and as a result, the high-temperature hardness is extremely low. To be.

(B) the composition _{formula: [Ti 1- (E + F} ) Al E B F] N ( provided that an atomic ratio, E is 0.01 to 0.10, F denotes the 0.15-0.35) satisfies A (Ti, Al, B) N layer having a B content of 15 to 35 atomic%;
_{Formula: [Ti 1- (M + N} ) Al M B N] N ( provided that an atomic ratio, M is 0.25 to 0.40, N denotes the 0.01-0.10) satisfies, relative (Ti, Al, B) N layer with an increased content of Al component,
Are alternately laminated in a state where each layer has an average layer thickness of 5 to 20 nm (nanometers), and the resulting (Ti, Al, B) N layer is formed by the laminated structure of the thin layers. The excellent thermal conductivity of the (Ti, Al, B) N layer (hereinafter referred to as the thin layer A) having a high B content, the B content ratio being lower than that of the thin layer A, and relative And (Ti, Al, B) N layer (hereinafter referred to as thin layer B) having a high Al content ratio has a predetermined relatively high high temperature hardness.

(C) The (Ti, Al, B) N layer having the alternately laminated structure of the thin layer A and the thin layer B of (b) above has excellent thermal conductivity required for high-speed gear cutting of alloy steel and a predetermined value. However, since it does not have a sufficiently satisfactory high temperature hardness, it is provided as the upper layer of the hard coating layer, while the lower layer has insufficient thermal conductivity, but relative (Ti, Al, B) N layer having a composition corresponding to the above conventional hard coating layer having a high Al component content and excellent high-temperature hardness,
_{Formula: [Ti 1- (X + Y} ) Al X B Y] N ( provided that an atomic ratio, X is .50 to 0.60, Y represents a 0.01-0.10) satisfies the single (Ti, Al, B) N layer of single phase structure,
With this structure, the resulting hard coating layer has high-temperature hardness and high-temperature strength in addition to excellent thermal conductivity. The gear cutting tool should exhibit excellent wear resistance over a long period of time without chipping even in high-speed gear cutting of alloy steel with high heat generation.
The research results shown in (a) to (c) above were obtained.

The present invention has been made on the basis of the above research results, and a plurality of tooth spaces are formed radially and along the length direction with respect to the rotation axis. The tooth part that consists of the front and rear faces that face the groove and the front face is a rake face with respect to the rotation direction, and the top face (tooth tip tooth face) and both side faces (left and right tooth faces) that are flank faces On the surface of the tungsten carbide based cemented carbide cutting tool base having a shape formed continuously along the direction,
(A) Both are composed of an upper layer and a lower layer made of (Ti, Al, B) 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: [Ti _{1− (E + F)} Al _E B _F ] N (wherein A represents 0.01 to 0.10 and F represents 0.15 to 0.35 in terms of atomic ratio) (Ti , Al, B) N layer,
The thin layer B is
Composition formula: [Ti _{1− (M + N)} Al _M B _N ] N (wherein M is 0.25 to 0.40 and N is 0.01 to 0.10 in atomic ratio) (Ti , Al, B) N layer,
(C) the lower layer has a single phase structure;
_{Formula: [Ti 1- (X + Y} ) Al X B Y] N ( provided that an atomic ratio, X is .50 to 0.60, Y represents a 0.01-0.10) satisfying (Ti , Al, B) N layer,
For the coated carbide cutting tool (surface coated cemented carbide cutting tool) that exhibits excellent wear resistance in high-speed gear cutting of alloy steel, formed by vapor-depositing a hard coating layer consisting of It has characteristics.

Next, regarding the hard coating layer of the coated carbide gear cutting tool of the present invention, the reason why the numerical values 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, B) N layer constituting the hard coating layer improves the high temperature hardness, while the Ti component has a high temperature strength. Furthermore, the B component has the effect of improving the thermal conductivity, and the lower layer has a relatively high Al component content to provide a high high temperature hardness, but the X value indicating the Al content rate. Is less than 0.50 in the total amount of Ti and B (atomic ratio, the same shall apply hereinafter), the ratio of Ti is relatively high, and the excellent high temperature required for high-speed gear cutting of alloy steel Hardness cannot be secured, and the progress of wear is accelerated rapidly. On the other hand, when the X value indicating the Al ratio exceeds 0.60, the Ti ratio is relatively decreased, High-temperature strength drops rapidly, resulting in chipping (slight chipping). Since it becomes easy, X value was defined as 0.50-0.60.
Further, the Y value indicating the ratio of B is the ratio of the total amount of Ti and Al, and if it is less than 0.01, the predetermined thermal conductivity cannot be ensured, while the Y value exceeds 0.10. Then, since it becomes difficult to ensure the predetermined high-temperature strength, the Y value is set to 0.01 to 0.10.
Furthermore, if the layer thickness is less than 2 μm, the excellent 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 layer thickness exceeds 6 μm, chipping occurs. The layer thickness was determined to be 2 to 6 μm because it easily occurs.

(B) Composition formula of upper layer thin layer A The B component in (Ti, Al, B) N of the upper layer thin layer A is relatively increased in content as described above to improve thermal conductivity. Therefore, it has the effect of preventing the occurrence of thermoplastic deformation by exhibiting excellent heat removal effect in high-speed gear cutting of alloy steel with high heat generation, but the F value indicating the content ratio is the total amount of Ti and Al. If the ratio is less than 0.15, a desired excellent effect cannot be ensured for the above action. On the other hand, if the F value exceeds 0.35, a thin layer B having an excellent high-temperature strength is formed adjacently. Even if it exists, the high temperature strength of the upper layer is inevitably lowered, and this causes chipping. Therefore, the F value is set to 0.15 to 0.35.
Further, the E value indicating the proportion of Al is the proportion of the total amount of Ti and B, and if it is less than 0.01, the minimum high-temperature hardness cannot be ensured, causing wear promotion, while the E If the value exceeds 0.10, the high-temperature strength decreases and causes chipping, so the E value was determined to be 0.01 to 0.10.

(C) Composition formula of upper layer thin layer B In the upper layer thin layer B, the content ratio of the B component is relatively low, while the content ratio of the Al component is maintained relatively high, The high-temperature hardness of the thin layer A is strengthened, and the lack of high-temperature hardness of the adjacent thin layer A is reinforced, so that the excellent thermal conductivity of the thin layer A and the predetermined high-temperature hardness of the thin layer B are obtained. However, when the M value indicating the Al content ratio in the composition formula of the thin layer B is less than 0.25, the Al content ratio is too low, and a predetermined high temperature is obtained. Hardness cannot be ensured, and as a result, the progress of wear is promoted. On the other hand, when the M value exceeds 0.40, the content ratio of the Ti component is relatively lowered, and the high temperature of the upper layer is increased. A decrease in strength is unavoidable and causes chipping. It was set to 0.40.
Further, the N value indicating the ratio of B is the ratio of the total amount of Ti and Al. If the N value is less than 0.01, a decrease in the thermal conductivity of the entire upper layer is unavoidable, while the N value exceeds 0.10. Then, the N value was determined to be 0.01 to 0.10 because the high temperature strength decreased and chipping was likely to occur.

(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 thermal conductivity and predetermined high-temperature hardness cannot be ensured, and when the thickness of each layer exceeds 20 nm, each thin layer has defects, that is, if it is thin layer A, the high-temperature hardness is insufficient. In the case of the thin layer B, a thermal conductivity deficiency appears locally in the layer, and this makes it easy to generate chipping and promotes the progress of wear. It was determined.

(E) Layer thickness of the upper layer If the layer thickness is less than 0.5 μm, the excellent thermal conductivity of itself and the predetermined 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 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 carbide gear cutting tool of the present invention, the hard coating layer is composed of a (Ti, Al, B) N layer, and the upper layer of the hard coating layer has an alternately laminated structure of the thin layer A and the thin layer B. It has excellent thermal conductivity and predetermined high-temperature hardness, and the lower layer of the single-phase structure has excellent high-temperature hardness. Therefore, even in high-speed gear cutting of alloy steel with high heat generation, The coating layer exhibits an excellent heat removal effect, and as a result, excellent wear resistance is exhibited over a long period without occurrence of thermoplastic deformation that causes uneven wear in the cutting edge portion.

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

WC powder, TiC powder, ZrC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder, TaN powder and Co powder all having an average particle diameter of 1 to 3 μm are prepared as raw material powders. These raw material powders are blended in the composition shown in Table 1, wet mixed by a ball mill for 72 hours, dried, and then pressed into a green compact at a pressure of 100 MPa. Medium, sintered at 1400 ° C. for 1 hour to form a cemented carbide round bar material of diameter: 85 mm × length: 125 mm, and machined from this material, outer diameter: 80 mm × Length: Solid hob type carbide gear cutting bases A to J shown in FIG. 3 each having the overall dimensions of 120 mm and the shape of three right-handed twists × 19 grooves were manufactured.

(A) Next, each of the above-mentioned superhard gear cutting bases A to J is ultrasonically cleaned in acetone and dried, and the central axis on the rotary table in the arc ion plating apparatus shown in FIG. A thin layer of an upper layer having a component composition corresponding to the target composition shown in Table 2 as a cathode electrode (evaporation source) on one side, mounted along a peripheral portion at a predetermined distance in the radial direction from Ti-Al-B alloy for forming A and Ti-Al- for forming thin layer B of the upper layer having the component composition corresponding to the target composition shown in Table 2 as the cathode electrode (evaporation source) on the other side B alloy is placed opposite to the rotary table, and Ti-Al- for forming a lower layer as a cathode electrode (evaporation source) along the rotary table at a position shifted by 90 degrees from both Ti-Al-B alloys. Wearing B alloy And,

(B) First, the inside of the apparatus is evacuated and kept at a vacuum of 0.1 Pa or less, the interior of the apparatus is heated to 500 ° C. with a heater, and then rotated onto the rotating table while rotating on the rotating table. A DC bias voltage of −1000 V is applied, and a current of 100 A is passed between the Ti—Al—B alloy for forming the lower layer and the anode electrode to generate an arc discharge. Bombarded with Ti-Al-B 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 carbide cutting base rotating while rotating on the rotary table, and An arc discharge is generated by flowing a current of 100 A between the Ti—Al—B alloy for forming the lower layer and the anode electrode, so that the target composition and target shown in Table 2 are formed on the surface of the cemented carbide cutting base. (Ti, Al, B) 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 as a reaction gas into the apparatus to make a reaction atmosphere of 2 Pa, and a DC bias voltage of −100 V was applied to the carbide cutting base 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 Ti-Al-B alloy for forming the thin layer A to generate arc discharge, and the cemented carbide cutting A thin layer A having a predetermined thickness is formed on the surface of the substrate. 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-B 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). May be used again to form the thin layer A. Formation of thin layer A by arc discharge between the cathode electrode and anode electrode of the i-Al-B alloy, and thin layer B by arc discharge between the cathode electrode and anode electrode of the Ti-Al-B alloy for forming the thin layer B Are alternately and repeatedly formed on the surface of the cemented carbide substrate by alternating lamination of thin layers A and B having a target composition and a single target layer thickness shown in Table 2 along the layer thickness direction. Similarly, the coated carbide carbide cutting tools 1 to 10 of the present invention were manufactured by vapor-depositing the upper layer with the entire target layer thickness shown in Table 2.

Further, for the purpose of comparison, the above-described superhard gear cutting bases A to J are ultrasonically cleaned in acetone and dried, and then loaded into the arc ion plating apparatus shown in FIG. As the (evaporation source), a Ti—Al—B alloy having a component composition corresponding to the target composition shown in Table 3 is mounted, and the apparatus is first evacuated and kept at a vacuum of 0.1 Pa or less. Then, after heating the inside of the apparatus to 500 ° C. with a heater, a DC bias voltage of −1000 V is applied to the cemented carbide cutting base, and 100 A is applied between the Ti—Al—B alloy of the cathode electrode and the anode electrode. When an electric current is applied to generate an arc discharge, the surface of the cemented carbide cutting substrate is bombarded with the Ti—Al—B alloy, and then nitrogen gas is introduced into the apparatus as a reaction gas to obtain a reaction atmosphere of 3 Pa. In addition, the bias voltage applied to the cemented carbide cutting base is lowered to −100 V, and arc discharge is generated between the cathode electrode and the anode electrode of the Ti—Al—B alloy, thereby the carbide cutting base. A comparative coated carbide gear cutting tool is formed by vapor-depositing a hard coating layer composed of a (Ti, Al, B) N layer having a single phase structure with the target composition and target layer thickness shown in Table 3 on the surface of 1 to 10 were produced.

Next, using the above-described coated carbide cutting tool 1-10 of the present invention and the comparative coated carbide cutting tool 1-10, the material is alloy steel of JIS / SCr420H,

Module: 1.5, Pressure angle: 14.5 degrees, Number of teeth: 70, Twist angle: 30 degrees Right twist, Teeth width: Processing of gears with dimensions and shapes of 22.5 mm,

Cutting speed (rotational speed): 500 m / min,
Feed: 1.5mm / rev,
Processing form: climb, no shift, dry (air blow),
The high-speed gear cutting conditions (the cutting speed in the case of machining the above-mentioned JIS / SCr420H alloy steel gear is usually 350 m / min),
The number of gear machining until the flank wear width reached 0.1 mm was measured.
The measurement results are shown in Tables 2 and 3, respectively.

The thin layer A and the thin layer B constituting the hard coating layer made of (Ti, Al, B) N of the coated carbide cutting tool 1 to 10 of the present invention obtained as a result of this, and the composition of the lower layer In addition, the composition of the hard coating layer made of (Ti, Al, B) N of the comparative coated carbide gear cutting tools 1 to 10 was measured by an energy dispersive X-ray analysis method using a transmission electron microscope. Each showed substantially the same composition as the target 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 2 and 3, the coated carbide cutting tool of the present invention has a single-phase structure lower layer made of (Ti, Al, B) N, each of which has a hard coating layer having a different composition, It consists of an upper layer having an alternating layer 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 the upper layer has excellent thermal conductivity. In addition, since the hard coating layer combines these excellent characteristics, even when gear cutting of alloy steel gears is performed under high-speed gear cutting conditions with high heat generation, the hard coating layer is Excellent heat removal effect is achieved by the upper layer, and excellent wear resistance is exhibited without the occurrence of thermoplastic deformation that causes uneven wear at the cutting edge, whereas the hard coating layer has a single-phase structure. The comparative coated carbide gear cutting tool composed of (Ti, Al, B) N layer is Under gear cutting conditions, especially the thermal deformation of the cutting edge occurs due to insufficient thermal conductivity, and this causes the wear form to become an uneven wear form. It is clear that the service life is reached.
As described above, the surface-coated cemented carbide gear cutting tool of the present invention (the coated carbide gear cutting tool of the present invention) is not only gear cutting under normal conditions, but also 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 coated carbide 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 cemented carbide cutting tool (solid hob).

Claims (1)

On the surface of the tungsten carbide base cemented carbide cutting tool base,
(A) Both are composed of an upper layer and a lower layer made of a composite nitride of Ti, Al, and B (boron), the upper layer being an average layer of 0.5 to 1.5 μm, and the lower layer being an average layer of 2 to 6 μm Each has a thickness,
(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− (E + F)} Al _E B _F ] N (wherein E is 0.01 to 0.10 and F is 0.15 to 0.35 in atomic ratio) A composite nitride layer of Al and B;
The thin layer B is
Ti satisfying the composition formula: [Ti _{1− (M + N)} Al _M B _N ] N (wherein M is 0.25 to 0.40 and N is 0.01 to 0.10 in atomic ratio) A composite nitride layer of Al and B,
(C) the lower layer has a single phase structure;
Ti satisfying the composition formula: [Ti _{1− (X + Y)} Al _X B _Y ] N (wherein X is 0.50 to 0.60 and Y is 0.01 to 0.10 in atomic ratio) A composite nitride layer of Al and B;
A surface-coated cemented carbide cutting tool that exhibits excellent wear resistance in high-speed gear cutting of alloy steel, characterized by being formed by vapor-depositing a hard coating layer comprising:

Images