JP2004322229A - Gear processing method and coated hob - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated hob having a blade part of high speed tool steel having a film structure as a base material, for sufficiently exhibiting oxidation resistance, and securing adhesion and hardness of the base material as a tool base body and a hard coating film, and also to provide a gear processing method. <P>SOLUTION: This hob is formed by alternately covering a surface with at least one layer or more of respective layers of a (a) layer of the hard coating film composed of the chemical composition indicated by (Ti<SB>x</SB>AL<SB>(1-x-y)</SB>Si<SB>y</SB>)(C<SB>z</SB>N<SB>1-z</SB>), and a (b) layer of the hard coating film composed of the chemical composition indicated by (Ti<SB>U</SB>Al<SB>(1-U-v)</SB>Cr<SB>v</SB>) (C<SB>w</SB>N<SB>1-w</SB>), and has the (b) layer of the hard coating film on a surface of the base material. A cutting speed is set in a range of 100 m/min to 300 m/min. A complete dry cutting or cutting with very small oil agent s cc/min (here, 0 < s ≤ 20) sprayed in a spray manner on a cutting part forms a tooth shape. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【表２】

【表３】

【００１８】
〔実施例２〕本発明品であるＴｉＡｌＳｉＮ膜を被膜した表１の本発明品４、７について、切削速度を５０ｍ／ｍｉｎ 、８０ｍ／ｍｉｎ 、１００ｍ／ｍｉｎ 、２００ｍ／ｍｉｎ 及び３００ｍ／ｍｉｎ で、本発明品４は微量油剤を噴霧状にして切削部に吹き付けて切削を行い、本発明品７は完全乾式で切削加工した。この結果を表２に示す。５０ｍ／ｍｉｎ から３００ｍ／ｍｉｎ まで、切削速度が上がるにつれて、クレータ摩耗は増加し、逃げ面摩耗幅についても同様な結果となったが、微量油剤を噴霧状にして切削部に吹き付けた方がよい成績を挙げた。図５は、表２の結果を示すグラフである。
【００１９】
〔実施例３〕本発明品であるＴｉＡｌＳｉＮ膜（本発明品１〜７）と従来例であるＴｉＡｌＮ膜の耐熱特性を比較するため、実施例１と同時に作成したコーティング被覆超硬チップを大気中で８００℃、１時間加熱保持し、鋼球による擦過痕を利用したカロテスト法により表面からの酸化物層の厚さを測定した結果を表３に示す。従来例のＴｉＡｌＮ膜は高温度の環境下でコーティング被覆膜の表面から酸化層が進行しているが、本発明品であるＴｉＡｌＳｉＮ膜は酸化層がほとんど観察されることが無く耐酸化性はＴｉＡｌＮ膜よりも格段に優れている。
【００２０】
〔実施例４〕実施例１と同じホブの高速歯切加工を、切削部に１０ｃｃ／ｍｉｎの微小油剤を霧状に吹き付けて行った結果を表１の本発明５に示す。完全乾式と比較してクレータ摩耗の進行は進行することなく寿命を向上させている。これは微小な油剤がホブとワークの間で潤滑剤として作用することで摩擦係数を低減し、加工による発熱を押さえる働きをするためであると考えられる。この方式は微小潤滑（ＭＱＬ：Ｍｉｎｉｍｕｍ Ｑｕａｎｔｉｔｙ Ｌｕｂｒｉｃａｔｉｏｎ）作用としてエンドミル加工などに使用されているが、ホブによる高速歯車加工においても効果を発揮し、本発明品であるＴｉＡｌＳｉＮ膜と併用することによりさらに効果的に作用する。
【００２１】
〔本発明の実施の形態の効果〕上記の実施例から、本発明品であるＴｉＡｌＳｉＮ膜からなる硬質被膜のａ層と、ＴｉＡｌＣｒＣＮからなる硬質被膜のｂ層と、を含むコーティング膜を被覆したホブによる歯車加工は、従来のＴｉＡｌＮ膜を被覆したものに較べてすくい面のクレータ摩耗とフランク面の逃げ面摩耗の進行を遅れさせることができ、完全乾式あるいはエアを吹き付けた時の寿命を大幅に向上させることができる。また微小な油剤の噴霧吹き付けによりさらに摩耗の進行を防ぎ、より効果的な歯車加工が実現できる。
【図面の簡単な説明】
【図１】本発明品のコーティング被覆のコーティング膜の構成を示すブロック図。
【図２】図１の構成の硬質被膜を被覆したコーティング被覆ホブを使用したホブ盤を用いた本発明の歯車加工法の実施形態を示す概略側面図。
【図３】本発明品のコーティング被覆ホブのコーティング膜を形成するイオンプレーティング装置の概略断面図。
【図４】コーティング被覆ホブ切削後の切刃の摩耗形態を表した概略斜視図。
【図５】表２の結果を示すグラフである。
【符号の説明】
２０・・工具母材 ２１・・硬質被膜ａ層 １２・・硬質被膜ｂ層[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear processing method and a coating-coated hob for forming a tooth profile by using a hob having a blade portion made of high-speed tool steel as a base material.
[0002]
2. Description of the Related Art In the past, in gear processing, a wet method using an oil agent during cutting has been the mainstream, but recently, a dry method using no oil agent at the time of cutting has appeared in consideration of environmental problems. . As for the hob of the tool body, it has become possible to dry-process high-speed cutting by coating the hob with a TiAlN film having improved heat resistance. For example, in Japanese Patent No. 3165658, using a hob provided with a blade portion made of high-speed tool steel,
(Ti _1-x Al _x ) (N _y C _1-y ) 0.2 ≦ x ≦ 0.85,
Using a hob coated with at least one layer of a film having a composition of 0.25 ≦ y ≦ 1.0, a cutting speed of not less than 120 m / min and not more than 400 m / min and dry cutting without using a cutting oil, or We propose a gear machining method characterized by creating a tooth profile by blowing air to the cutting part.
[0003]
However, when gear processing is performed using the invention of this cited example, dry cutting can be realized at a high speed, but the heat resistance of the TiAlN film applied to the hob is insufficient, so that craters are formed. There is a drawback that wear progresses quickly and reaches a practical wear limit width early.
The Patent Document 2 nitride forming elements and M in Giyashapa, substantially _{(Ti z Al x M 1-} z-x) (1-w) (N y C 1-y) w however 0.2 ≦ x ≦ 0.9, 0.2 ≦ y ≦ 1.0, 0.1 ≦ z ≦ 0.8,
0.7 ≦ (z + x) <1.0, 0.45 ≦ w ≦ 0.55
A gear shaper processing method and a gear shaper characterized by processing at least a cutting speed of 300 m / min or less without using a cutting oil, using a film having at least one layer coated on at least a flank of a film having the following composition: . Then, as one of the nitride forming elements M, various third elements such as V and B are added, and the third element is added as "the nitride forming element M can replace TiAl and form a good quality nitride". Examples described above do not suggest that the third element has a positive effect. In addition, the cutting process can be realized as "the same as when no nitride-forming element is added", and it is only demonstrated that there is no effect even in the case of adding a small amount of V and B in the examples. . Therefore, none of the above cited examples fall within the category of the effect of the TiAlN film, and the early wear of the hob under high-speed cutting conditions cannot be avoided. It cannot be said that the processing method used was proposed.
[0004]
[Patent Document 1] Japanese Patent No. 3165658 Claim 1
[Patent Document 2] Japanese Patent No. 2961106 Claims 3 and 7
[0005]
An object of the present invention is to solve the disadvantage of the prior art that the TiAlN film applied to the hob has an insufficient heat resistance, so that the crater wear progresses rapidly, and the problem that the TiAlN film reaches the practical wear limit early is solved. It is an object of the present invention to provide a coating-coated hob and a gear machining method, which can sufficiently exhibit chemical properties and have a film structure in which adhesion and hardness between a coating base material as a tool base and a hard coating are secured.
[0006]
SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems by using a hob having a blade portion made of high-speed tool steel as a base material.
On the surface of the hob _{(Ti x Al (1-x} -y) Si y) (C z N 1-z), however, in atomic percent of the metal element, 0.3 ≦ x ≦ 0.45,0.1 A layer of a hard coating having a chemical composition represented by <y ≦ 0.3, 0 ≦ z ≦ 0.4,
_{(Ti U Al (1-U} -v) Cr v) (C w N 1-w) , however 0.3 ≦ u ≦ 0.55 primitive fraction of metal elements, 0.01 ≦ v ≦ 0.2, 0 ≦ w ≦ 0.2
The b layer of the hard coating having the chemical composition represented by, and each layer is alternately coated at least one or more layers, and the b layer of the hard coating using a hob on the surface of the base material ,
When the cutting speed is in the range of 100m / min to 300m / min,
The present invention described above is provided by providing a gear processing method and a coating-coated hob, wherein a completely dry-type or a fine oil agent s cc / min, where 0 <s ≦ 20 is sprayed and cut to a cutting portion. Solved the problem.
[0007]
According to the structure of the present invention, the a layer capable of sufficiently exhibiting the oxidation resistance of the TiAlSiN-based film and the b layer of the TiAlCrCN layer in which the a layer is coated on the coating base material. This provides a coating-coated hob and a gear machining method having a film structure in which the adhesion and hardness between the coating base material as the tool base and the hard coating are ensured, and is compared with a conventional coating with a TiAlN film. The progress of crater wear on the rake face and flank wear on the flank face can be delayed, and as a result, the life of the hob in high-speed cutting can be extended significantly without significant progress of flank wear. .
[0008]
In particular, it has been found that, in the above-mentioned gear processing, a method of forming a tooth profile by spraying a minute oil agent of 20 cc / min or less into a cutting portion and spraying the same onto a cutting portion can further obtain an effect more than a completely dry type. This has the effect of suppressing the heat generated by cutting by the oil droplets of the minute oil entering between the work and the cutting edge of the hob, forming a lubricating film and reducing the friction coefficient, and as a result, the progress of wear due to heat abrasion is suppressed. It is thought to be due to
[0009]
Atomic ratio of Ti in the metal elements constituting the hard coating a layer of the present invention _{(Ti x Al (1-x} -y) Si y) (C z N 1-z) , from the measurement results of the film hardness, It is necessary to satisfy the atomic ratio of the metal element of 28% or more and 45% or less. More preferably, it is 31% or more and 44% or less. Similarly, from the viewpoint of oxidation resistance, the more the amount of Si added to the hard coating a layer is more than 10% in terms of the atomic ratio of the metal element, the higher the effect is. Since the chipping phenomenon (film jump) occurs in this range, the range is limited to this range. More preferably, it is 13% or more and 28% or less. The atomic ratio of C may be 0%, but if it exceeds 40%, the adhesion to the layer b is reduced, so that it is limited to this range. More preferably, it is 0% or more and 35% or less. To improve the adhesion of the hard coating layer a in the invention, the film of the hard coating b layer for suppressing underlayer hardness reduction in the coating equal crystal structure a layer _{(Ti U Al (1-U} -v) Cr _v ) It must be a ( _{CwN1 -w} ) type coating. Therefore, the atomic fraction of each metal element in the hard coating b layer needs to satisfy 30% or more and 55% or less in terms of the atomic fraction of the metal element based on the measurement result of the film hardness of Ti. More preferably, it is 32% or more and 54% or less. If the content of Cr is less than 1%, there is no effect, and if it exceeds 20%, the adhesiveness is reduced and the material cannot withstand cutting. More preferably, it is 1% or more and 19% or less. The atomic ratio of C may be 0%, but if it exceeds 40%, the toughness is insufficient, so it is 50% or less. More preferably, it is 0% or more and 17% or less.
[0010]
FIG. 1 is a block diagram showing the configuration of a coating film of a coating-coated hob according to an embodiment of the present invention. Coating Application hob of the present invention product is a high-speed steel as a base material, a tool 20 formed by coating the hard coating, components of the hard _{coating, (Ti U Al (1-} U-v) Cr v ) (C _w N _1-w ) where the _primary fraction of the metal element is 0.3 ≦ u ≦ 0.55, 0.01 ≦ v ≦ 0.2, 0 ≦ w ≦ 0.2
A hard coating b layer 21 having a chemical composition represented by
on the b layer 21, components of the hard coating _{(Ti x Al 1-x-} y Si y) (C z N 1-z), however, 0.30 ≦ x ≦ 0 in atomic percent of metallic elements .45,
One or more a layers 22 each having a chemical composition represented by 0.1 <y ≦ 0.3 and 0 ≦ z ≦ 0.4 are alternately coated. FIG. 1 shows only one layer.
[0011]
FIG. 2 is a schematic side view showing an embodiment of the gear machining method of the present invention using a hobbing machine using the coated hob hob coated with the hard coating of the present invention shown in FIG. The cutting speed is in the range of 100 m / min to 300 m / min, and the cutting is performed by spraying a completely dry or fine oil scc / min, where 0 <s ≦ 20, onto the cutting portion. This is a gear processing method that can greatly improve the life when completely dry or air is blown. In particular, in the above-mentioned gear processing, a fine oil agent of 20 cc / min or less is sprayed and sprayed on a cutting portion to form a tooth profile. It has also been found that the method of forming satisfactorily obtains an effect more than that of the completely dry method. This has the effect of suppressing the heat generated by cutting by the oil droplets of the minute oil entering between the work and the cutting edge of the hob, forming a lubricating film and reducing the friction coefficient, and as a result, the progress of wear due to heat abrasion is suppressed. It is thought to be due to The hob 23 is mounted on a hob shaft of a hob head 24 having a rotating mechanism, and the work 25 is fixed to a rotatable table fixture. While the hob head 24 is rotating at a high speed, the hob head 24 moves close to the synchronously rotating work 25 and is fed by cutting. The outer periphery of the work 25 is shaved by the blade portion 26 of the fed hob 23 to form a tooth pattern 27 of the work. During cutting, the cutting oil is not supplied, but air is supplied from a completely dry type or an air nozzle installed near the processing section. When spraying a mist of fine oil, it is supplied during cutting using the air nozzle 28.
[0012]
[Example 1] A coating-coated hob coated with a hard coating of the present invention is made of high-speed steel and has a laminated structure of a nitride or carbonitride of TiAlSi and a nitride or carbonitride of TiAlCr. The one with the film was used. Also, a product coated with a TiAlN film was used as a comparison of the present invention. The shape of the coating-coated hob has a module m of 2.87, a pressure angle of 15 °, and an outer diameter of 95 mm. The specifications of the work gear, which is a work, are: tooth size m 2.87, pressure angle 15 °, number of teeth 48, helix angle 31 °, outer diameter 166.6 mm, tooth height, 7.995, tooth thickness 3. 917. The work material was SCM420H and the hardness was 180HB. High-speed cutting was performed in a completely dry type or in a state where air was blown to the cutting portion at a cutting speed of gear processing in a range of 100 m / min to 300 m / min. Further, in order to confirm the lubricating effect of the micro oil agent, high speed cutting was performed by spraying an oil agent of 20 cc / min or less in a mist state on the cutting portion.
[0013]
Next, as shown in FIG. 3, which shows a schematic cross-sectional view of an ion plating apparatus for forming a coating film of the coating-coated hob of the present invention, an arc-type ion plating is performed. A hob (not shown) was attached to the tool mounting jig 3 of the apparatus 1, exhausted to 0.133 Pa or less by the vacuum apparatus 11, and heated to 400 to 500 ° C. by the heater 12. After reaching a predetermined temperature, ion bombardment is performed with arcon gas introduced from the gas inlet 6 and nitrogen gas of 0.666 to 0.4 Pa is introduced from the gas inlet 7 to allow the metal evaporation source 5 to generate Ti0. 0.5 Al0.4Cr0.1, Ti0.3Al0.5Cr0.2, Ti0.5Al0. By combining three targets having different compositions at element ratios of 5 and applying a substrate voltage of 10 to 100 V, a hard coating b layer was formed. Was evaporated to form a TiAlCrN film or a TiAlCrCN film as a hard coating b layer. Then, on the hard coating b layer, the element ratios of Ti0.4 Al0.4 Si0.2, Ti0.3 Al0.5 Si0.2, Ti0.35 Al0.35 Si0.3, and Ti0.5 Al0.5 were different. By combining four targets having the compositions and applying a substrate voltage of 10 to 100 V, hard coating layers a having various compositions indicated by the atomic percentages of the metal elements shown in the table were obtained. Then on the hard coating b _{layer, Ti 0.4 Al 0.4 Si 0.2,} Ti 0.3 Al 0.5 Si 0.2, Ti 0.35 Al 0.35 Si 0.3, Ti 0 _A combination of four targets having different compositions at an element fraction of _0.5 Al _0.5 and applying a substrate voltage of 10 to 100 V to obtain TiAlSi of various compositions indicated by the atomic fractions of the metal elements shown in the table. A nitride or carbonitride hard coating a layer was obtained. The composition of the atomic fraction was determined by electron probe analysis.
[0014]
Table 1 shows the results of cutting the coating-coated hob according to the above-mentioned method. FIG. 4 schematically shows the form of the wear measurement site of the hob. From the results of Example 1 in Table 1, a coating-coated hob provided with a hard coating b layer that is a TiAlCrN film or a TiAlCrCN film of the present invention and a hard coating a layer that is a nitride or carbonitride of TiAlSi. The crater wear of the present inventions 1 to 7 was smaller than that of TiAlN (conventional examples 1 to 3), and the same result was obtained for the flank wear width. As described above, the Si component in the metal element constituting the hard coating a layer of the present invention has a large effect on the heat resistance effect during cutting, but in TiAlSiCN, the Si content is less than 10% by the atomic fraction of the metal element. cases, _i.e., not _{(Ti x Al (1-x} -y) Si y) (C z N 1-z) with y <0.1 heat effect for a small content of Si when the can sufficiently exhibit . When the Si content exceeds 30% (y> 0.3) (Comparative Example 2), the coating film becomes brittle and chipping (film skipping) occurs during cutting. More preferably, it is 11% or more and 24% or less. From the measurement results of the film hardness, it is necessary that the atomic ratio of Ti in the metal element constituting the hard coating a layer of the present invention satisfies 30% or more and 45% or less in atomic fraction of the metal element. (Comparative Example 1) More preferably, it is 31% or more and 44% or less. Furthermore, the film hardness increases as the atomic ratio of carbon increases, but if it exceeds 40% (z> 0.4), the adhesion to the b-layer decreases (Comparative Example 4). More preferably, it is 13% or more and 28% or less.
[0015]
To improve the adhesion of the hard coating layer a in the invention, the film of the hard coating b layer for suppressing underlayer hardness reduction in the coating equal crystal structure a layer _{(Ti U Al (1-U} -v) Cr _v ) It must be a ( _{CwN1 -w} ) type coating. Therefore, the atomic fraction of each metal element in the hard coating b layer needs to satisfy the atomic percentage of the metal element of 30% or more and 55% or less from the measurement result of the film hardness of Ti (Comparative Example 1). ). More preferably, it is 32% or more and 54% or less. If the content of Cr is less than 1%, the film is insufficiently densified because it is small, and the adhesion to the base material becomes insufficient. If it exceeds 20% (v> 0.2), the film hardness decreases and the flank wear width increases (Comparative Example 1). . More preferably, it is 1% or more and 19% or less. The atomic ratio of C may be 0%, and as the ratio increases, the film hardness increases, but if it exceeds 20%, the toughness is insufficient, so that it is 20% or less (Comparative Example 3). More preferably, it is 0% or more and 17% or less.
[0016]
In Example 1 for a film thickness _{(Ti x Al 1-x-} y Si y) (C z N 1-z),
However, the a layer having a chemical composition represented by the following atomic ratio of the metal element: 0.30 ≦ x ≦ 0.45, 0.1 <y ≦ 0.3, 0 ≦ z ≦ 0.4 is 0.3 μm in the range of _{~5.0μm, (Ti U Al (1} -U-v) Cr v) (C w N 1-w) , however primitive fraction of the metal elements 0.3 ≦ u ≦ 0.55,0. The b layer of the hard coating having a chemical composition represented by 01 ≦ v ≦ 0.2 and 0 ≦ w ≦ 0.2 has a range of 0.3 μm to 5.0 μm. It is desirable to combine them into one or more layers, and the total film thickness is 2 μm to 10 μm or less. This is because the effect of the coating film cannot be expected if the total film thickness is less than 2 μm, and the probability of occurrence of chipping (film skipping) increases if the film thickness exceeds 10 μm.
[0017]
[Table 1]

[Table 2]

[Table 3]

[0018]
[Example 2] With respect to the present invention products 4 and 7 of Table 1 coated with the TiAlSiN film of the present invention, the cutting speed was 50 m / min, 80 m / min, 100 m / min, 200 m / min and 300 m / min. The product 4 of the present invention was cut by spraying a small amount of oil onto the cutting portion in a spray form, and the product 7 of the present invention was completely dry-cut. Table 2 shows the results. Crater wear increased as the cutting speed increased from 50 m / min to 300 m / min, and the same result was obtained for the flank wear width. However, it is better to spray a small amount of oil into the cutting part in a spray form. Scored. FIG. 5 is a graph showing the results of Table 2.
[0019]
Example 3 In order to compare the heat resistance of the TiAlSiN film of the present invention (products of the present invention 1 to 7) and the TiAlN film of the prior art, a coated coated carbide chip produced simultaneously with Example 1 was used in the atmosphere. At 800 ° C. for 1 hour, and the results of measuring the thickness of the oxide layer from the surface by a calotest method using a scratch mark with a steel ball are shown in Table 3. In the TiAlN film of the conventional example, an oxidized layer progresses from the surface of the coating film under a high-temperature environment. However, the TiAlSiN film of the present invention has almost no oxidized layer observed and has an oxidation resistance. It is much better than a TiAlN film.
[0020]
[Example 4] The results of the same high-speed gear cutting as in Example 1 performed by spraying a fine oil of 10 cc / min on the cut portion in a mist state are shown in Table 1 of the present invention 5. The life of the crater is improved without progress of the crater wear as compared with the completely dry type. This is considered to be because the minute oil acts as a lubricant between the hob and the work to reduce the friction coefficient and to suppress the heat generated by processing. This method is used for end milling and the like as a function of minimum quantum lubrication (MQL), but is also effective in high-speed gear machining with a hob, and is further effective when used in combination with the TiAlSiN film of the present invention. Acts in a way.
[0021]
[Effects of the embodiment of the present invention] From the above examples, the hob coated with the coating film including the layer a of the hard film made of the TiAlSiN film and the layer b of the hard film made of TiAlCrCN according to the present invention. Gear processing can delay the progress of crater wear on the rake face and flank wear on the flank face compared to the conventional TiAlN film coated, greatly extending the life when completely dry or air blown. Can be improved. Further, the spraying and spraying of a minute oil agent further prevents the progress of abrasion, thereby realizing more effective gear machining.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a coating film of a coating of the present invention.
FIG. 2 is a schematic side view showing an embodiment of the gear machining method of the present invention using a hobbing machine using a coating-coated hob coated with a hard coating having the configuration of FIG.
FIG. 3 is a schematic sectional view of an ion plating apparatus for forming a coating film of a coating-coated hob of the present invention.
FIG. 4 is a schematic perspective view showing a wear mode of a cutting blade after cutting a coating-coated hob.
FIG. 5 is a graph showing the results of Table 2.
[Explanation of symbols]
20 ・ ・ Tool base material 21 ・ ・ Hard coating a layer 12 ・ ・ Hard coating b layer

Claims (4)

Using a hob with a blade part whose base material is high-speed tool steel,
On the surface of the hob _{(Ti x Al (1-x} -y) Si y) (C z N 1-z), however, in atomic percent of the metal element, 0.3 ≦ x ≦ 0.45,0.1 A layer of a hard coating having a chemical composition represented by <y ≦ 0.3, 0 ≦ z ≦ 0.4,
_{(Ti U Al (1-U} -v) Cr v) (C w N 1-w) , however 0.3 ≦ u ≦ 0.55 primitive fraction of metal elements, 0.01 ≦ v ≦ 0.2, 0 ≦ w ≦ 0.2
The b layer of the hard coating having the chemical composition represented by, and each layer is alternately coated at least one or more layers, and the b layer of the hard coating using a hob on the surface of the base material ,
When the cutting speed is in the range of 100m / min to 300m / min,
A gear machining method wherein a completely dry type or a minute oil agent s cc / min where 0 <s ≦ 20 is sprayed to a cutting portion and cut. A layer of the hard coating,
_{(Ti x Al (1-x} -y) Si y) (C z N 1-z), however, in atomic percent of metallic elements, 0.28 ≦ x ≦ 0.33,0.13 <y ≦ 0 .28, having a chemical composition represented by 0 ≦ z ≦ 0.35,
The b layer of the hard coating,
_{(Ti U Al (1-U} -v) Cr v) (C w N 1-w) , however 0.3 ≦ u ≦ 0.55 primitive fraction of metal elements, 0.01 ≦ v ≦ 0.2, 0 ≦ w ≦ 0.2
2. The method according to claim 1, wherein the gear has a chemical composition represented by the following formula. A hob having a blade portion based on high-speed tool steel,
On the surface of the hob _{(Ti x Al (1-x} -y) Si y) (C z N 1-z), however, in atomic percent of the metal element, 0.3 ≦ x ≦ 0.45,0.1 A layer of a hard coating having a chemical composition represented by <y ≦ 0.3, 0 ≦ z ≦ 0.4,
_{(Ti U Al (1-U} -v) Cr v) (C w N 1-w) , however 0.3 ≦ u ≦ 0.55 primitive fraction of metal elements, 0.01 ≦ v ≦ 0.2, 0 ≦ w ≦ 0.28
A b layer of a hard coating having a chemical composition represented by: and a hob wherein at least one or more layers are alternately coated, and the b layer of the hard coating is on the surface of the base material. ,
When the cutting speed is in the range of 100m / min to 300m / min,
A coating-coated hob characterized in that a completely dry type or a fine oil agent s cc / min where 0 <s ≦ 20 is sprayed to form a tooth profile by spraying on a cutting portion. A layer of the hard coating,
_{(Ti x Al (1-x} -y) Si y) (C z N 1-z), however, in atomic percent of metallic elements, 0.28 ≦ x ≦ 0.33,0.13 <y ≦ 0 .28, having a chemical composition represented by 0 ≦ z ≦ 0.35,
The b layer of the hard coating,
_{(Ti U Al (1-U} -v) Cr v) (C w N 1-w) , however 0.3 ≦ u ≦ 0.55 primitive fraction of metal elements, 0.01 ≦ v ≦ 0.2, 0 ≦ w ≦ 0.28
4. The coating-coated hob according to claim 3, comprising a chemical composition represented by the following formula:

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