KR100821535B1 - Hard multilayer coatings and hard multilayer coating tools comprising the same - Google Patents

Abstract

The hard multilayer coating comprises (a) a backing layer comprising a TiAlN + CrN mixture layer and a TiAlN layer disposed on the body and alternately stacked with each other, and (b) the surface of the hard multilayer coating disposed on the backing layer. It provides a CrN layer. The hard multilayer coating may also include (c) an interlayer disposed between the back layer and the CrN layer. Also disclosed is a hard multilayer coating tool comprising a tool base as a body coated with a hard multilayer coating.

Description

HARD MULTILAYER COATING, AND HARD MULTILAYER COATED TOOL INCLUDING THE HARD MULTILAYER COATING}

The present invention relates generally to hard multilayer coatings, and more particularly to hard multilayer coatings having high lubricity (welding resistance) in addition to good wear resistance and toughness.

A hard multi-layer coating tool is introduced, comprising (i) a tool base made of high speed tool steel or cemented carbide and (ii) a hard multilayer coating disposed on the surface of the tool base. The hard multilayer coating comprises a TiAlN layer and a TiAlN + CrN mixture layer alternately stacked on each other. As an example of a hard multilayer coating tool, Patent Document 1 (JP-2002-275618A) discloses a rotary cutting tool comprising a TiAlN layer and a mixture layer alternately stacked on one another, where the TiAlN layer has high hardness, The mixture layer comprises a relatively low hardness CrN layer. In the rotary cutting tool disclosed above, excellent wear resistance is obtained due to the presence of a high hardness TiAlN layer, and toughness is increased due to the presence of a mixture layer containing relatively low hardness CrN, thereby suppressing chipping and peeling of the coating. This significantly improves the durability of the tool.

However, due to the relatively large coefficient of friction of the TiAlN layer, when a cutting tool is used to cut a workpiece made of easily weldable material such as copper or a copper alloy, deposition between the cutting tool and the workpiece is caused by the deposition of the TiAlN layer. It can be easily caused due to the large coefficient of friction. Welding deteriorates cutting performance, such as machining accuracy, and causes wear of the cutting tool at an early stage, and the durability of the desired cutting tool cannot be obtained. For example, in cutting operations using rotary cutting tools, such as ball end mills and drills, welding is easily caused, particularly in frictional contact with the workpiece, such as around the axis of rotation and the parts that make up each slope. This is easily caused in part of the rotary cutting tool.

The present invention has been made in view of the problems of the background art discussed above. It is therefore an object of the present invention to improve the weldability of hard multilayer coatings composed predominantly of TiAlN.

In order to achieve the above object, the first invention comprises: (a) a back layer comprising a TiAlN layer and a TiAlN + CrN mixture layer disposed on a predetermined body and alternately stacked on each other; (b) an intermediate layer disposed on said back layer and composed of a TiAlN + CrN mixture layer; (c) forming a hard multilayer coating, characterized in that it consists of a CrN layer disposed on the intermediate layer and providing a surface of the hard multilayer coating.

In the hard multilayer coating of the first invention, the second invention has a thickness of the back layer of 2 µm to 8 µm, an intermediate layer of 0.1 µm to 5 µm, and a CrN layer of 0.1 µm to 5 µm, and a hard multilayer The total thickness of the coating is not greater than 10 μm.

The third invention provides a backing layer comprising (a) a TiAlN layer and a TiAlN + CrN mixture layer disposed on a predetermined body and alternately stacked with each other, and (b) a rear layer disposed on the backing layer and further comprising A hard multi-layer coating is formed, which is composed of a CrN layer providing a surface.

 In the hard multilayer coating of the third invention, in the fourth invention, the thickness of the back layer is 2 μm to 8 μm, the thickness of the CrN layer is 0.1 μm to 8 μm, and the total thickness of the hard multilayer coating is not greater than 10 μm. It is characterized by.

In the hard multilayer coating of any one of the first to fourth inventions, the fifth invention is characterized in that the bottom and top layers of the rear layer are formed of the TiAlN layer.

In any one of the first to fifth inventions, the sixth invention is characterized in that the hard multilayer coating is disposed on the surface of the cutting tool.

The seventh invention forms a hard multilayer coating tool, wherein the hard multilayer coating tool is coated with the hard multilayer coating of one of the first to fifth inventions.

In the hard multilayer coatings of the first to sixth inventions, it is possible to obtain excellent wear resistance and toughness due to the presence of a backing layer comprising a TiAlN layer and a TiAlN + CrN mixture layer laminated alternately with each other. In addition, since the CrN layer constitutes the top of the hard multilayer coating and the friction coefficient of the hard multilayer coating surface is small, the lubricity and the welding resistance can be improved. In addition, since the oxidation start temperature of the CrN layer is high at about 700 ° C., excellent characteristics of the coating are stably maintained even in a high temperature environment.

Thus, when such a hard multilayer coating is applied to a rotary cutting tool such as a ball end mill, the hardness can be achieved, for example, when cutting a workpiece made of ferrous or nonferrous material (e.g., a copper alloy) of low hardness and easy to weld. It is possible to obtain excellent cutting performance and durability over a wide range of uses up to cutting workpieces made of hard materials such as heat-treated steel of about 50 HRC. Specifically, due to the presence of the CrN layer, In the later stages of the cutting operation, it is possible to suppress wear on each inclined surface and to suppress the change of the inclined angle to the negative side, so that the cutting capacity is maintained satisfactorily for a long time, thereby improving the durability of the tool and improving the finished surface of the workpiece. The quality is stable. Rotary cutting tools such as ball end mills The workpiece is easily welded to the distal end because of the distal end located around the axis of rotation and the cutting capacity of the distal end is small. However, due to the presence of the CrN layer, welding is suppressed so that cutting performance and durability are satisfactorily maintained. In addition, since the excellent characteristics of the coating can be stably obtained even in a high temperature environment, the cutting tool can perform the cutting operation with high efficiency even under the severe cutting conditions of high temperature caused by, for example, frictional heat or the like.

Further, in the first invention, since the intermediate layer composed of the TiAlN + CrN mixture layer (including CrN) is disposed between the back layer and the CrN layer, the CrN layer is laminated with the intermediate layer having high adhesion, thereby chipping the CrN layer and Peeling can also be advantageously suppressed.

In the fifth invention in which the top layer and the bottom layer of the back layer are each formed by a TiAlN layer, the back layer is formed on a predetermined body (for example, a tool base material) with excellent adhesion due to the TiAlN layer forming the bottom layer. The backing layer, on the other hand, can have good wear resistance due to the TiAlN layer forming the top layer. Since the CrN layer is disposed on the TiAlN layer directly or through the intermediate layer as the top layer, the high hardness TiAlN layer is not in direct contact with the workpiece. However, the TiAlN layer functions to suppress the deformation of the CrN layer, thereby improving the wear resistance of the CrN layer.

In the hard multilayer coating tool of the seventh invention, it is possible to obtain essentially the same effects as in the first to fifth inventions.

The present invention can be advantageously applied to hard multilayer coatings for coating the base material of rotary cutting tools (eg end mills, drills and tabs) with cutting edges. However, the present invention is directed to any other machining tool, such as a non-rotating cutting tool (e.g. a replaceable insert secured to a tool holder for lathe work) and a cold forming tool for plasticizing the workpiece to form the workpiece in the desired shape. Applicable to In addition, the present invention may also be applied to hard multilayer coatings provided as surface protective coatings for coating bodies and members (eg electronic components) other than machining tools. The base material of the machining tool covered with the hard multilayer coating is preferably made of cemented carbide or high speed tool steel. However, the tool base may be made of any other metallic material.

As the method for forming the hard multilayer coating according to the present invention, the arc ion plating method is advantageously used. However, a physical vapor deposition (PVD) method such as a sputtering method, or alternatively, a chemical vapor deposition (CVD) method such as a plasma CVD method and a thermal CVD method may be used.

The total thickness of the hard multilayer coating of the present invention is preferably 10 μm or less, because if the total thickness exceeds 10 μm, the coating can be easily peeled from the body. In addition, when the main body has a cutting edge, when the total thickness exceeds 10 m, the cutting edge may be rounded, thereby degrading cutting performance. The thickness of the back layer is preferably 2 μm or more because if the thickness of the back layer is less than 2 μm, satisfactory coating performance and strength such as sufficient wear resistance, heat resistance and toughness cannot be obtained. In addition, in order that the total thickness of a hard multilayer coating may be 10 micrometers or less, it is preferable that the thickness of a back layer is 8 micrometers or less.

The thickness of the TiAlN layer included in the back layer is 160 nm to 2000 nm, and the thickness of the TiAlN + CrN mixture layer included in the back layer is suitably 10 nm to 1000 nm, thus chipping and peeling off by the TiAlN + CrN mixture layer. Is effectively prevented and wear resistance can be maintained by the TiAlN layer. When the back layer includes a plurality of TiAlN layers and a plurality of TiAlN + CrN mixture layers, the TiAlN + CrN mixture layers may have respective thicknesses equal to each other, and the TiAlN layers may also have respective thicknesses equal to each other. However, the TiAlN layer and the TiAlN + CrN mixture layer may take any one of various arrangements, such as an arrangement in which the thicknesses of the TiAlN layer or the TiAlN + CrN mixture layer are different from each other so that the thickness of the layer is continuously changed. The mixing crystal ratio between Ti and Al of the TiAlN layer included in the back layer is preferably about 2: 8 (= Ti: Al) to 6: 4 (= Ti: Al). The mixed crystal ratio between Ti and Al of the TiAlN layer of the TiAlN + CrN mixture layer included in the back layer or forming the intermediate layer may be substantially the same as the mixed crystal ratio of the TiAlN layer, It does not have to be the same.

The total number of TiAlN + CrN mixture layers and TiAlN layers stacked on each other to form the back layer is preferably three or more such that each of the bottom layer and the top layer of the back layer is formed of the TiAlN layer. However, the top layer of the back layer may be formed of, for example, a TiAlN + CrN mixture layer, in which case the thickness of the TiAlN + CrN mixture layer is as small as several tens of nm. In this case, although the intermediate layer consisting of other TiAlN + CrN mixture layers other than the TiAlN + CrN mixture layer forming the top layer can be formed, the TiAlN + CrN mixture layer forming the top layer can be used as the intermediate layer. The third invention includes not only a configuration in which the top layer of the back layer on which the CrN layer is directly disposed is formed of a TiAlN layer, but also a configuration in which the top layer of the back layer on which the CrN layer is directly disposed is formed of a TiAlN + CrN mixture layer.

It is appropriate that the thickness of the intermediate layer is at least 0.1 μm, since sufficient adhesion between layers cannot be obtained if the thickness of the intermediate layer is less than 0.1 μm. It is appropriate that the thickness of the CrN layer constituting the top of the hard multilayer coating is 0.1 μm or more, because if the thickness of the CrN layer is less than 0.1, sufficient lubricity cannot be obtained. It is preferable that the thickness of a CrN layer is 0.5 micrometer or more. When the hard multilayer coating has an intermediate layer, in order to make the total thickness of the hard multilayer coating 10 μm or less, each of the thickness of the CrN layer and the thickness of the intermediate layer is not larger than 5 μm, and the hard multilayer coating does not have an intermediate layer. It is appropriate that the thickness of CrN is not larger than 8 mu m. If the hard multilayer coating does not have an intermediate layer, in order for the hard multilayer coating to have the desired coating strength and performance, the total thickness of the hard multilayer coating is not less than 2.1 μm, wherein the thickness of the backing layer is not less than 2 μm and also the hard multilayer If the coating has an interlayer, it is appropriate that the total thickness of the hard multilayer coating is not less than 2.2 μm. If the hard multilayer coating has an intermediate layer, the total thickness of the hard multilayer coating is preferably not less than 2.5 μm.

Each of the mixture layer of the intermediate layer and the back layer is formed of a TiAlN + CrN mixture layer. Although the mixture layer of the intermediate layer and the back layer may be composed of exactly the same composition, for example, the mixing ratio between TiAlN and CrN, the mixing crystal ratio between Ti and Al, and the arc current and bias used for forming the layer By changing the layer forming conditions such as the voltage, the composition and the characteristics can be surely different from each other. In the present invention, the CrN layer is provided to constitute the top of the hard multilayer coating. However, in the first invention in which an intermediate layer containing CrN is formed, even if the intermediate layer is arranged to constitute the top of the hard multilayer coating without providing the CrN layer, the effect of improving the lubricity to some extent can be expected.

As long as the other elements contained do not interfere with the desired effect favorable to the properties required for hard multilayer coatings, such as wear resistance, toughness, adhesion, heat resistance and weldability, that is, other elements contained do not seriously deteriorate these properties. In addition, each of the TiAlN layer, the TiAlN + CrN mixture layer (including the intermediate layer), and the CrN layer may contain carbon or other elements in addition to the unavoidable impurity elements. For example, CrCN, a carbonitride containing C (carbon) as well as pure nitride of chromium, can be used as CrN. In addition, TiAlCN, which is a carbonitride containing C (carbon) as well as pure nitride of TiAl, can be used as TiAlN.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a group diagram showing an end mill as one embodiment of the present invention, in which Fig. (A) is a front view viewed from a direction perpendicular to the axis of the end mill, and Fig. (B) is an enlarged bottom view, and Fig. ( c) is a cross-sectional view of the layered portion of the cutting tooth with a hard multilayer coating.

FIG. 2 is a cross-sectional view showing another embodiment of the hard multilayer coating different from the hard multilayer coating shown in FIG. 1C.

3 is a diagram schematically showing an example of an arc type ion plating apparatus capable of advantageously forming the hard multilayer coating of FIGS. 1 and 2.

Fig. 4 is a group showing the measurement results of the friction coefficients of CrN and TiAlN in comparison with each other, wherein the measurement was made by the ball-on-disk method.

FIG. 5 is a group of drawings for explaining the measurement results of the widths of the side wear of each of the coating cutting tools (including the invention product and the comparative product) different in coating composition, wherein each coating cutting tool is defined in cutting conditions. FIG. Measurements were made after being used to cut C1100 (copper) at.

FIG. 6 is a group of drawings for explaining the results of the measurement of the width of the side wear of each of the coating cutting tools (including the invention product and the comparative product) different in the composition of the coating, wherein each coating cutting tool is defined cutting The measurements were made after being used to cut S50C (mechanical structural carbon steel) under the conditions.

* Description of the symbols for the main parts of the drawings *

10: ball end mill (hard multilayer coating tool)

12: tool base material (body)

20, 28: hard multilayer coating

22: back layer

22a: TiAlN layer

22b: mixture layer

24: middle layer

26: CrN layer

Detailed embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a group of views showing a ball end mill 10 which is an example of a hard multilayer coated rotary cutting tool to which the present invention is applied, and FIG. (A) is viewed in a direction perpendicular to the axis of the ball end mill 10. FIG. It is a front view, and FIG. (B) is an expanded bottom view seen from the far-end side of the ball end mill 10 (as seen from the right side of the ball end mill 10 of FIG. (A)). The ball end mill 10 includes a tool base material 12 made of cemented carbide. The tool base material 12 includes a cutting tooth 14 and a shank portion formed integrally with each other. The cutting tooth 14 is formed with cutting edges in the form of a pair of peripheral cutting edges 16 and a pair of ball nose-type end cutting edges 18, which are arranged so as to be symmetrical with respect to the axis. Thus, while the ball end mill 10 rotates about an axis, a cutting operation can be performed by the ball nose type end cutting edge 18 and the peripheral cutting edge 16. The surface of the cutting tooth 14 is coated with a hard multilayer coating 20, indicated by the diagonal lines in Figs. (A) and (b) of Fig. 1. FIG. 1C is a cross-sectional view of the layered portion of the cutting tooth 14 coated with the hard multilayer coating 20. The ball end mill 10 corresponds to a hard multilayer coating tool, while the tool base 12 corresponds to a predetermined body on which the hard multilayer coating 20 is disposed.

As is apparent from FIG. 1C, the hard multilayer coating 20 is composed of a back layer 22, an intermediate layer 24, and a CrN layer 26 constituting the top outer side of the hard multilayer coating 20. . The overall thickness of the hard multilayer coating 20 is 2.2 μm to 10 μm. The back layer 22 is composed of three or more layers including the TiAlN layer 22a and the TiAlN + CrN mixture layer 22b, which layers are alternately stacked on each other. The thickness of the back layer 22 is 2 micrometers-8 micrometers. The average thickness of each TiAlN layer 22a is 160 nm to 2000 nm, while the average thickness of each mixture layer 22b is 10 nm to 1000 nm. In this embodiment, the TiAlN layer 22a having the same thickness and the mixture layer 22b having the same thickness are alternately stacked with each other. Each mixture layer 22b is a layer in which TiAlN and CrN are mixed at a prescribed ratio. The mixed crystal ratio between Ti and Al in TiAlN layer 22a and TiAlN in mixture layer 22b is in the range of 2: 8 (= Ti: Al) to 6: 4 (= Ti: Al). In this embodiment, the mixed crystal ratio between Ti and Al is 4: 6 (= Ti: Al). Each top layer and bottom layer of the back portion are formed of a TiAlN layer 22a. The total number of TiAlN layers 22a and mixture layer 22b is an odd number of 3 or more.

The hardness (Hv) of TiAlN is about 23000-3000, while the hardness (Hv) of CrN is about 1800-2300. The hardness of each mixture layer 22b containing TiAlN and CrN is lower than the hardness of each TiAlN layer 22a containing only TiAlN. Accordingly, in the back layer 22 in which the TiAlN layer 22a having a large hardness and the mixture layer 22b having a relatively low hardness are alternately laminated with each other, due to the presence of the TiAlN layer 22a having a large hardness Excellent wear resistance can be obtained and improved toughness can be obtained due to the presence of the mixture layer 22b having a low hardness, so that the risk of chipping and peeling of the coating 20 can be reduced. As described above, the average thickness of each TiAlN layer 22a is 160 nm to 2000 nm, the average thickness of each mixture layer 22b is 10 nm to 1000 nm, and the total thickness of the back layer 22 is 2 μm to 8 μm Then, wear resistance can be maintained due to the presence of the TiAlN layer 22a and chipping and peeling can be effectively prevented due to the presence of the mixture layer 22b.

The intermediate layer 24 is a mixture layer in which TiAlN and CrN are mixed with each other. In this embodiment, the intermediate layer 24 is identical in composition to the mixture layer 22b. The intermediate layer 24 is disposed on the rear layer 22, and more specifically, is disposed in contact with the TiAlN layer 22a, which is the uppermost layer of the rear layer 22. The thickness of the intermediate layer 24 is 0.1 micrometer-5 micrometers. Thus, the intermediate layer 24 of TiAlN + CrN is disposed on the back layer 24, ie, the top TiAlN layer 22a, before the arrangement of the CrN layer 26, and thus the CrN layer 26 to the back layer 24. Adhesion is improved. The mixed crystal ratio of Ti and Al of TiAlN in the intermediate layer 24 is in the range of 2: 8 (= Ti: Al) to 6: 4 (= Ti: Al). In this embodiment, the mixed crystal ratio between Ti and Al is 4: 6 (= Ti: Al).

The CrN layer 26 is disposed in contact with the intermediate layer 24 and has a thickness of 0.1 μm to 5 μm. CrN constituting the CrN layer 26 has a friction coefficient smaller than that of TiAlN. Thus, due to the CrN layer 26 provided to constitute the top outer surface of the hard multilayer coating 20, to improve the lubricity between the workpiece and the coating 20, that is, between the workpiece and the coating 20. It is possible to improve the weldability.

4 is a group of diagrams showing the results of measurement of coefficients of friction of CrN and TiAlN made according to the ball-on-disk method substantially the same as the test method specified in JIS R1613. In Fig. 4, Fig. (A) shows the conditions of the test and Fig. (B) shows the test results. The friction coefficient curve in FIG. (B) shows the change of each friction coefficient in the starting period. The coefficient of friction of TiAlN is concentrated in the range of about 0.5 to 0.7, while the coefficient of friction of CrN is about 0.3. In addition, FIG. 4C shows the friction coefficient measured at high temperature (400 ° C.). The finish coefficient of TiAlN measured at high temperature is about 0.7, while the coefficient of friction of CrN measured at high temperature is about 0.25. Therefore, the friction coefficient measured at high temperature is substantially the same as the value measured at room temperature (25 ° C.) (FIG. 4B). The friction coefficient shown in FIG. 4C was measured under the same test conditions as in FIG. 4A except that the temperature was 400 ° C.

Although the hard multilayer coating 20 described above comprises an intermediate layer 24, as in the hard multilayer coating 28 of FIG. 2, the CrN layer 26 is back with the intermediate layer 24 omitted. May be disposed directly on layer 22. In this case, the back layer 22 can have substantially the same structure as the hard multilayer coating 20, and the thickness of the CrN layer 26 can be increased due to the absence of the intermediate layer 24. Thus, the thickness of the CrN layer 26 may be 0.1 μm to 8 μm.

TiAlN contained in the TiAlN layer 22a and the mixture layer 22a and the intermediate layer 24 of the back layer 22 is a pure nitride of TiAl containing no carbon. However, the pure nitride of TiAl is replaced with TiAlCN, a carbonitride containing carbon whose amount is determined so that hardness, adhesion and other properties are not degraded. CrN contained in the mixture layer 22b, the intermediate layer 24 and the CrN layer 26 of the back layer 22 is a pure nitride of chromium not containing carbon. However, pure nitride of chromium is replaced by CrCN, a carbonitride containing carbon whose amount is determined so that lubricity, heat resistance and other properties are not degraded.

On the other hand, FIG. 3 is a schematic diagram (schematic diagram) showing an arc type ion plating apparatus 30 that can be advantageously used to form the hard multilayer coating 20 or 28. The arc type ion plating apparatus 30 includes: a support member 32 for supporting a large number of intermediate products in the form of a base material 12 in which the hard multilayer coating 20 has not yet been formed and the cutting edges 16 and 18 are already formed; A rotating device 34 for rotating the support member 32 about an axis of rotation substantially oriented in the vertical direction; A bias voltage power supply 36 for applying a negative bias voltage to the base material 12; A processing container in the form of a chamber 38 which houses the base material 12 therein; First and second arc discharge power supplies 44 and 46; A reaction gas supply device 40 for supplying a reaction gas into the chamber 38; And components such as, for example, a vacuum device 42 that draws gas inside the reactor 22 with a vacuum pump to reduce the internal pressure of the chamber 38. The support member 32 is a cylindrical or triangular cylindrical member centered on the rotation axis. The plurality of base materials 12 are supported by the support members 32 such that each base material 12 is substantially horizontal and the cutting edges 14 protrude radially outward of the support member 32. The reaction gas supply device 40 is equipped with a tank in which nitrogen gas N ₂ is stored, and nitride of TiAl and nitride of Cr can be formed by supplying nitrogen gas into the chamber 38. It should be noted that when carbonitrides of TiAl and carbonitrides of Cr are formed, a tank for storing hydrocarbon gas (CH ₄ , C ₂ H _2, etc.) is provided to supply hydrocarbon gas in addition to nitrogen gas.

The first arc discharge power source 44 is connected to the first evaporation source (target) 48 as a cathode, which is in the form of a TiAl alloy constituting TiAlN contained in the mixture layer 22b and the TiAlN layer 22a, and It is also connected to the anode 50. The first arc discharge power source 44 functions to supply a predetermined arc current between these evaporation sources and the anode to cause an arc discharge between the first evaporation source 48 and the anode 50, so that TiAl is the first evaporation source ( 48) from evaporation. The evaporated TiAl becomes metal ions (cations) and is attached to the tool base material 12 to which a negative bias voltage is applied by the bias voltage power supply 36. Similarly, the second arc discharge power source 46 is a second evaporation source (target) 52 as a cathode formed of Cr constituting CrN contained in the mixture layer 22b, the intermediate layer 24, and the CrN layer 26. Is also connected to the anode 54. The second arc discharge power supply 46 functions to supply a predetermined arc current between these evaporation sources and the anode to cause an arc discharge between the second evaporation source 52 and the anode 54, so that Cr is the second evaporation source ( 52). The evaporated Cr becomes metal ions (positive ions) and is attached to the tool base material 12 supplied with the negative bias voltage by the bias voltage power supply 36.

When the hard multilayer coating 20, 28 is formed on the surface of the cutting portion 14 of the tool base material 12 using the arc type ion plating apparatus 30, the internal pressure of the chamber 38 is supplied with the reactive gas supply. The device 40 and the vacuum device 42 maintain a predetermined value (eg, 1.33 × 5 × 10 ⁻¹ Pa to 1.33 × 40 × 10 ⁻¹ Pa), and a predetermined value of the negative bias voltage (eg, − 50V to -150V) is applied to the tool base material 12 by the bias voltage power supply 36. In this case, the vacuum device 42 evacuates the chamber 30, and at the same time, the reaction gas supply device 40 draws the reaction gas into the chamber 30 so that the internal pressure of the chamber 30 is maintained at the predetermined value. Supply. Thereafter, the rotary device 34 is operated so that the support member 32 is rotated at a predetermined rotational speed (for example, 3 min ⁻¹ ), and the first arc discharge power supply 44 and the second arc discharge power supply ( By selectively energizing (ON) or turning off the voltage (46), a hard multilayer coating (20, 28) is formed on the tool base (12).

Specifically, when the first arc discharge power supply 44 maintains ON (energy supply) and the second arc discharge power supply 46 maintains OFF (energy disconnected), an arc current is generated between the first evaporation source 48 and the anode ( 50) to release metal ions of TiAl from the first evaporation source 48. The released metal ions of TiAl react with nitrogen gas, whereby TiAlN is formed and adheres to the surface of the tool base material 12, thereby forming the TiAlN layer 22a. The value of the arc current supplied by the first arc discharge power supply 44 and the power-on time for which the first arc discharge power supply 44 is kept ON are determined according to the desired thickness of the TiAlN layer 22a.

In addition, when the second arc discharge power supply 46 maintains ON (energy supply) and the first arc discharge power supply 44 maintains OFF (energy disconnected), an arc current is generated between the second evaporation source 52 and the anode 54. ) And metal ions of Cr are released from the first evaporation source 48. The released metal ions of Cr may react with nitrogen gas to form CrN and adhere to the surface of the tool base material 12, thereby forming the CrN layer 26. The value of the arc current supplied by the second arc discharge power supply 46 and the power-on time while the second arc discharge power supply 46 is kept ON are determined according to the desired thickness of the CrN layer 26.

In addition, when both the first arc discharge power source 44 and the second arc discharge power source 46 are kept ON (energy supply), the arc current is supplied between the first evaporation source 48 and the anode 50 while the second arc discharge power source 44 is turned on. An arc current is also supplied between the evaporation source 52 and the anode 54. In this case, metal ions of TiAl are released from the first evaporation source 48 and metal ions of Cr are released from the second evaporation source 52. The released metal ions of TiAl and metal ions of Cr react with nitrogen gas, whereby TiAlN and CrN are formed to adhere to the surface of the tool base material 12. Since the first evaporation source 48 and the second evaporation source 52 are mounted on opposite sides of the support member 32, TiAlN and CrN are alternately attached to the tool base material 12 as the support member 32 is rotated. It is possible to form a mixture layer 22b and an intermediate layer 24 in which TiAlN and CrN are mixed with each other. The power-on time for which the first arc discharge power supply 44 and the second arc discharge power supply 46 keep ON is determined according to the desired thicknesses of the mixture layer 22b and the intermediate layer 24. The value of the arc current supplied by the first arc discharge power supply 44 and the second arc discharge power supply 46 is determined according to the desired thickness of the mixture layer 22b and the intermediate layer 24 and the mixing ratio between TiAlN and CrN. .

Thus, as each of the first arc discharge power source 44 and the second arc discharge power source 46 is switched between the power supply state and the power disconnected state (ON and OFF states), the back layers 22 (alternatively alternately stacked) It is possible to continuously form a TiAlN + CrN mixture layer 22b and a TiAlN layer 22a), an intermediate layer 24 composed of a TiAlN + CrN mixture layer, and a CrN layer 26, thereby providing a hard multilayer coating. 20 and 28 may be disposed on the surface of the tool base material 12. Operations for the formation of the hard multilayer coatings 20 and 28, such as switching each of the first arc discharge power supply 44 and the second arc discharge power supply 46, can be automatically executed by a control device including a computer. .

In the hard multilayer coatings 20 and 28 of the present embodiment, due to the presence of the backing layer 22 including the TiAlN + CrN mixture layer 22b and the TiAlN layer 22a alternately laminated with each other, excellent wear resistance and It is possible to obtain toughness. In addition, since the CrN layer 26 constitutes the top of the hard multilayer coatings 20 and 28 and the surface of the hard multilayer coatings 20 and 28 has a low coefficient of friction, it is possible to improve lubricity and weldability. . In addition, since the oxidation start temperature of the CrN layer 26 is as high as about 700 ° C., excellent characteristics of the coating are stably maintained even in a high temperature environment.

Therefore, in the ball end mill 10 coated with the hard multilayer coatings 20 and 28, for example, from the case of cutting a workpiece made of ferrous or nonferrous material having a low hardness and being easy to be welded, the hardness is about 50 degrees. It is possible to obtain excellent cutting performance and durability over a wide range of uses up to the cutting of workpieces made of hard materials such as HRC heat treated steel. Specifically, due to the presence of the CrN layer 26, it is possible to suppress wear on each inclined surface and to prevent the inclination angle from changing to the negative side in the later stage of the cutting operation, so that the cutting capacity is maintained satisfactorily for a long time. This improves the durability of the tool and stabilizes the quality of the finished surface of the workpiece. The ball end mill 10 has a distal end located around the rotation axis, and the workpiece is easily welded to the distal end because the cutting capacity of the distal end is small. However, due to the presence of the CrN layer 26, welding is suppressed so that cutting performance and durability are satisfactorily maintained. In addition, since the excellent characteristics of the coating can be stably obtained even in a high temperature environment, the cutting tool can perform the cutting operation with high efficiency even in the harsh cutting conditions of high temperature caused by, for example, frictional heat and the like.

In the present embodiment in which each of the uppermost layer and the lowermost layer of the back layer 22 is provided as the TiAlN layer 22a, the back layer 22 is tooled with excellent adhesion by the TiAlN layer 22a constituting the bottom layer. It may be attached to the base material 12, and the back layer 22 may have excellent wear resistance by the TiAlN layer 22a constituting the uppermost layer. Since the CrN layer 26 is disposed directly on the TiAlN layer 22a forming the uppermost layer or through the intermediate layer 24, the TiAlN layer 22a having high hardness does not come into direct contact with the workpiece. However, the TiAlN layer 22a functions to suppress the deformation of the CrN layer 26, so that the wear resistance of the CrN layer 26 is improved.

Further, in the hard multilayer coating 20 of FIG. 1, since the intermediate layer 24 composed of the TiAlN + CrN mixture layer (containing CrN) is disposed between the back layer 22 and the CrN layer 26, the CrN layer (26) is laminated with high adhesion to the back layer 22 having the top layer formed of the TiAlN layer 22a, so that the chipping and peeling of the CrN layer 26 can also be more advantageously suppressed.

In addition, in the hard multilayer coatings 20 and 28 of this embodiment, since the total thickness of the coatings 20 and 28 is not larger than 10 micrometers, peeling of the coatings 20 and 28 from the tool base material 12 is suppressed. It is possible to obtain excellent adhesion between the coatings 20 and 28 and the tool base material 12. In addition, since the total thickness is not larger than 10 µm, the peripheral cutting edge 16 and the ball nose type end cutting edge 18 can be avoided from being rounded, whereby a decrease in cutting performance can be prevented. On the other hand, since the total thickness of the coatings 20 and 28 is not smaller than 2.2 mu m, the desired coating strength and coating performance can be obtained. That is, since the thickness of the back layer 22 is not smaller than 2 m, coating performance and strength such as sufficient wear resistance, heat resistance and toughness required for the back layer 22 can be obtained. In addition, since each thickness of the intermediate | middle layer 24 and the CrN layer 26 is not less than 0.1 micrometer, coating performance, such as sufficient adhesiveness and lubricity, can be obtained.

FIG. 5 is a group of drawings showing measurement results of VB wear width (side wear width) for each ball end mill 10 having a ball nose end cutting edge 18 each having a radius R of 1.5 mm, Measurements were made after each ball end mill 10 was used to cut C1100 (JIS: copper) 400 mm under the cutting conditions specified in FIG. 5 (a). The ball end mill 10 had various coatings, respectively, as indicated in FIG. 5 (b). As shown in Fig. 5 (b), the VB wear width of the product of the present invention ranges from 0.035 μm to 0.049 μm, so that the product of the present invention has improved wear resistance than the comparative product and is easy to weld like copper or the like. It can be seen that even one workpiece has excellent durability. For example, the durability of each of the articles of the invention is more than twice the durability of a comparative article having a coating consisting only of the backing layer 22 of a multi-layered structure, since the VB wear width of the comparative article is 0.093 μm. In the product as well as the comparative product, the uppermost layer and the lowermost layer of the back layer 22 each having a multilayer structure (TiAlN layer 22a and TiAlN + CrN mixture layer 22b are alternately laminated). It should be noted that is made of TiAlN layer 22a.

FIG. 6 is a group of drawings showing the measurement results of the respective VB wear widths (lateral wear widths) of the ball end mills 10 having the respective ball nose end cutting edges 18 having a radius R of 3 mm, Measurements were then made after each ball end mill 10 was used to cut S50C (JIS: mechanical structural carbon steel) over a 56 mm distance under the cutting conditions specified in FIG. 6 (a). The ball end mill 10 had each of the various coatings specified in FIG. 6 (b). As shown in Fig. 6 (b), the wear width of the VB in the present invention is in the range of 0.063 μm to 0.078 μm, so that the product of the present invention has improved wear resistance than the comparative product and also has a high hardness material such as carbon steel. It can be seen that it also has excellent durability even for workpieces made of steel. For example, the durability of each of the articles of the invention is 10% better than a comparative article having a coating consisting solely of a backing layer 22 having a multi-layered structure, since the VB wear width of the comparative article is 0.091 μm. In the product of the present invention as well as in the comparative product, the uppermost layer and the lowermost layer of the back layer 22 having a multilayer structure (TiAlN layer 22a and TiAlN + CrN mixture layer 22b are alternately laminated with each other), respectively. It should be noted that is made of TiAlN layer 22a.

While the preferred embodiments of the present invention have been described as described above, the present invention is not limited to the details of the above embodiments, and various other changes, changes, and improvements may be made to those skilled in the art without departing from the scope and spirit of the invention as defined in the following claims. It can be seen that it can be carried out by.

A hard multilayer coating is placed on the surface of a tool base material such as a rotary cutting tool, and since the hard multilayer coating of the present invention has sufficient wear resistance and welding resistance, for example, it is made of copper alloy or other material having low hardness and easy to weld. It is possible to obtain excellent cutting performance and durability in a wide range from cutting a workpiece to cutting a workpiece made of a hard material such as heat-treated steel. Thus, the hard multilayer coating of the present invention is advantageously used as a hard coating to be placed on the surface of a cutting tool such as a ball end mill. In addition, it can also be applied to coatings provided as surface protective coatings of bodies, such as electronic components, for example, in addition to machining tools.

Claims (7)

A rear layer comprising a TiAlN layer and a TiAlN + CrN mixture layer disposed on the body and alternately stacked with each other; An intermediate layer disposed on said back layer and composed of a TiAlN + CrN mixture layer, and And a CrN layer disposed over said intermediate layer to provide an outer surface of the hard multilayer coating. The method of claim 1, The rear layer has a thickness of 2 ㎛ ~ 8 ㎛, The intermediate layer has a thickness of 0.1 ㎛ ~ 5 ㎛, The CrN layer has a thickness of 0.1 μm to 5 μm, and also Hard multilayer coating, characterized in that the total thickness of the hard multilayer coating is not greater than 10 μm. A back layer comprising a TiAlN layer and a TiAlN + CrN mixture layer disposed on the body and alternately stacked with each other, and also And a CrN layer disposed on said back layer to provide a surface of the hard multilayer coating. The method of claim 3, wherein The back layer has a thickness of 2 ㎛ ~ 8 ㎛, The CrN layer has a thickness of 0.1 μm to 8 μm, and also Hard multilayer coating, characterized in that the total thickness of the hard multilayer coating is not greater than 10 μm. The hard multilayer coating according to any one of claims 1 to 4, wherein the top and bottom layers of the back layer are made of the TiAlN layer. 5. The hard multilayer coating of claim 1, wherein the hard multilayer coating is disposed on a surface of the cutting tool. 6. A hard multilayer coating according to any one of claims 1 to 4, and A hard multilayer coating tool comprising a tool base material coated with said hard multilayer coating.

Images