Cutting tool

Abstract

A cutting tool, comprising a substrate and a coating disposed on the substrate, wherein the coating comprises a first layer, the first layer is composed of Al.sub.aTi.sub.bCr.sub.(1abcd)Si.sub.cCu.sub.dN, and the a, the b, the c, and the d satisfy 0.50a0.75, 0.10b0.25, 0.005c0.20, 0.005d<0.10, and a+b+c+d<1.

Claims

1. A cutting tool, comprising a substrate and a coating disposed on the substrate, wherein the coating comprises a first layer, the first layer is composed of Al.sub.aTi.sub.bCr.sub.(1abcd)Si.sub.cCu.sub.dN, and the a, the b, the c, and the d satisfy 0.50a0.75, 0.10b0.25, 0.005c0.20, 0.005d<0.10, and a+b+c+d<1.

2. The cutting tool according to claim 1, the c and the d satisfy a relationship: c/d1.

3. The cutting tool according to claim 1, wherein the first layer has a thickness of 0.5 m or more and 10 m or less.

4. The cutting tool according to claim 1, wherein the coating further comprises a second layer disposed between the substrate and the first layer, and the second layer is composed of a first compound consisting of at least one element selected from a first group consisting of Group 4, 5, and 6 elements in the periodic table, aluminum, and silicon or consisting of at least one element selected from the first group and at least one element selected from a second group consisting of carbon, nitrogen, oxygen, and boron.

5. The cutting tool according to claim 1, wherein the coating further comprises a third layer disposed on the opposite side of the first layer to the substrate, and the third layer is composed of a second compound consisting of at least one element selected from the first group consisting of Group 4, 5, and 6 elements in the periodic table, aluminum, and silicon or consisting of at least one element selected from the first group and at least one element selected from the second group consisting of carbon, nitrogen, oxygen, and boron.

6. The cutting tool according to claim 1, wherein the coating has a thickness of 0.5 m or more and 12 m or less.

7. The cutting tool according to claim 1, wherein the substrate comprises a cemented carbide, a cermet, cubic boron nitride sintered material, diamond sintered material, high-speed steel, or a ceramic.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is an enlarged schematic sectional view of an examples of a cutting tool according to Embodiment 1.

(2) FIG. 2 is an enlarged schematic sectional view of an examples of the cutting tool according to Embodiment 1.

(3) FIG. 3 is an enlarged schematic sectional view of an examples of the cutting tool according to Embodiment 1.

(4) FIG. 4 is an enlarged schematic sectional view of an examples of the cutting tool according to Embodiment 1.

(5) FIG. 5 is a perspective view for illustrating an embodiment of the cutting tool.

(6) FIG. 6 is a schematic sectional view of a cathode arc ion plating apparatus used in Examples.

(7) FIG. 7 is a schematic top view of the cathode arc ion plating apparatus shown in FIG. 6.

DETAILED DESCRIPTION

Problem to be Solved by the Present Disclosure

(8) Materials to be cut have been diversified in recent years, and nickel-based alloys referred to as difficult-to-cut materials have been increasingly cut especially in the aircraft and medical fields. Continuous machining of nickel-based alloys with cutting tools increases the cutting edge temperature to high temperature, and reduces the life of the cutting tools. Accordingly, cutting tools have been desired that can have a long tool life especially even in continuous machining of nickel-based alloy.

(9) Thereupon, an object of the present disclosure is to provide a cutting tool that can have a long tool life especially even in continuous machining of nickel-based alloy.

Advantageous Effect of the Present Disclosure

(10) The present disclosure enables providing a cutting tool that can have a long tool life especially even in continuous machining of nickel-based alloy.

Description of Embodiments

(11) Embodiments of the present disclosure are first enumerated for description. (1) A cutting tool of the present disclosure is a cutting tool, comprising a substrate and a coating disposed on the substrate, wherein the coating comprises a first layer, the first layer is composed of Al.sub.aTi.sub.bCr.sub.(1abcd)Si.sub.cCu.sub.dN, and the a, the b, the c, and the d satisfy 0.50a0.75, 0.10b0.25, 0.005c0.20, 0.005d<0.10, and a+b+c+d<1.

(12) The present disclosure enables providing a cutting tool that can have a long tool life especially even in continuous machining of nickel-based alloy. (2) In the above-mentioned (1), the c and the d may satisfy the relationship: c/d1. This further improves the tool life. (3) In the above-mentioned (1) and (2), the first layer may have a thickness of 0.5 m or more and 10 m or less. This further improves the tool life. (4) In any of the above-mentioned (1) to (3), the coating may further comprise a second layer disposed between the substrate and the first layer, and the second layer is composed of a first compound consisting of at least one element selected from a first group consisting of Group 4, 5, and 6 elements in the periodic table, aluminum, and silicon or consisting of at least one element selected from the first group and at least one element selected from a second group consisting of carbon, nitrogen, oxygen, and boron.

(13) This further improves the tool life. (5) In any of the above-mentioned (1) to (4), the coating may further comprise a third layer disposed on the opposite side of the first layer to the substrate, and the third layer is composed of a second compound consisting of at least one element selected from the first group consisting of Group 4, 5, and 6 elements in the periodic table, aluminum, and silicon or consisting of at least one element selected from the first group and at least one element selected from the second group consisting of carbon, nitrogen, oxygen, and boron.

(14) This further improves the tool life. (6) In any of the above-mentioned (1) to (5), the coating may have a thickness of 0.5 m or more and 12 m or less. This further improves the tool life. (7) In any of the above-mentioned (1) to (6), the substrate may comprise a cemented carbide, a cermet, cubic boron nitride sintered material, diamond sintered material, high-speed steel, or a ceramic. This further improves the tool life.

Details on Embodiments of the Present Disclosure

(15) With reference to drawings, specific examples of the cutting tool of the present disclosure will be described below. In the drawing of the present disclosure, the same reference signs indicate the same parts or equivalent parts. The dimensional relationships among the length, the width, the thickness, the depth, and the like, are appropriately modified for clarifying and simplifying the drawings, and do not necessarily show the actual dimensional relationships.

(16) In the present disclosure, an expression in the form A to B means that A or more and B or less. If no unit is added to A, and a unit is added to only B, the unit of A is the same as the unit of B.

(17) If, in the present disclosure, the atomic ratio of a compound and the like expressed in a chemical formula is not particularly limited, shall include all the conventionally known atomic ratios, and should not be necessarily limited to only the ratio(s) in the stoichiometric range.

(18) In the present disclosure, one or more numerical values are described as each of the lower limit and the upper limit of the numerical range, the combination of any one numerical value described as the lower limit and any one numerical value described as the upper limit shall also be disclosed.

Embodiment 1: Cutting Tool

(19) As shown in FIGS. 1 to 4, a cutting tool 1 according to an embodiment of the present disclosure (hereinafter also described as Embodiment 1) is a cutting tool 1, comprising a substrate 2 and a coating 3 disposed on substrate 2, wherein coating 3 comprises a first layer 13, first layer 13 is composed of Al.sub.aTi.sub.bCr.sub.(1abcd)Si.sub.cCu.sub.dN, and the a, the b, the c, and the d satisfy 0.50a0.75, 0.10b0.25, 0.005c0.20, 0.005d<0.10, and a+b+c+d<1.

(20) The cutting tool of Embodiment 1 can have a long tool life especially even in continuous machining of nickel-based alloy. It is conjectured that the reason therefor is as follows.

(21) Aluminum (Al) contained in the first layer improves the hardness at high temperature of the first layer. If the above-mentioned a is 0.50 or more, the hardness at high temperature and the heat resistance of the first layer are improved. If the above-mentioned a is 0.75 or less, the production of hexagonal crystals is suppressed, and a deterioration in the hardness at high temperature of the first layer is suppressed.

(22) Titanium (Ti) contained in the first layer improves the strength at high temperature of the first layer. If the above-mentioned b is 0.10 or more, the effect of improving the strength at high temperature is sufficiently obtained. If the above-mentioned b is 0.25 or less, the content of aluminum in the first layer can be sufficiently secured, and the hardness at high temperature of the first layer is therefore improved.

(23) If chromium (Cr) and aluminum are contained in the first layer, the heat resistance and the oxidation resistance at high temperature of the first layer are improved.

(24) Silicon (Si) contained in the first layer improves the oxidation resistance and the heat resistance of the first layer. If the above-mentioned c is 0.005 or more, the oxidation resistance of the first layer is improved. Crystal grains in the first layer are micronized to improve the hardness of the first layer. If the above-mentioned c is 0.20 or less, a deterioration in the toughness of the first layer is suppressed, and occurrence of chipping is suppressed.

(25) Copper (Cu) contained in the first layer is low soluble in nickel and chromium that are components of nickel-based alloy (in the case where nickel-based alloy is nickel-chromium alloy). Therefore, the first layer containing copper scarcely adheres to material to be cut comprising nickel-based alloy during cutting.

(26) Since copper does not form a nitride, copper meanwhile tends to break the crystal lattice of the coating comprising a nitride to reduce the hardness of the coating. Copper and silicon can be added to the first layer to improve the hardness of the first layer. This is knowledge that, as a result of intensive research, the present inventors have found.

(27) As mentioned above, the first layer of Embodiment 1 can have high hardness at high temperature and heat resistance due to aluminum, high strength at high temperature due to titanium, high oxidation resistance and heat resistance due to chromium and silicon, high adhesion resistance due to copper, and high hardness due to the addition of copper and silicon. The cutting tool can have a long tool life even in continuous machining of nickel-based alloy, in which the cutting edge is likely to be at high temperature during cutting.

(28) <Cutting Tool>

(29) As shown in FIGS. 1 to 4, cutting tool 1 according to Embodiment 1 comprises substrate 2 and coating 3 disposed on substrate 2. Coating 3 may cover the entire surface of substrate 2. Even though coating 3 does not cover part of substrate 2 or even though coating 3 has portions with different structures, the cutting tool does not depart from the scope of the present embodiment. Coating 3 may cover at least the portion of substrate 2 participating in cutting. In the present disclosure, the portion of substrate 2 participating in cutting depends on the size or the shape of substrate 2, and means a region surrounded by the cutting edge ridgeline thereof and a virtual plane wherein the distance from the cutting edge ridgeline to substrate 2 along a perpendicular line of a tangent line of the cutting edge ridgeline is, for example, any of 5 mm, 3 mm, 2 mm, 1 mm, and 0.5 mm in substrate 2.

(30) The cutting tool 1 of the present embodiment can be suitably used as cutting tool 1 such as a drill, an end mill, an indexable cutting insert for drills, an indexable cutting insert for end mills, an indexable cutting insert for milling, an indexable cutting insert for lathe-turning, a metal saw, a gear-cutting tool, a reamer, or a tap.

(31) FIG. 5 is a perspective view for illustrating an embodiment of the cutting tool. A cutting tool 1 is used as an indexable cutting insert. Cutting tool 1 has a rake face 21, a flank face 22, and a cutting edge ridgeline 23 on which rake face 21 intersects with flank face 22.

(32) <Substrate>

(33) Any conventionally known substrate is usable. For example, the substrate may comprise any of cemented carbides (such as WC-based cemented carbide, cemented carbide containing WC and Co, cemented carbide in which a carbonitride of Ti, Ta, Nb, or the like is added to WC and Co), cermets (containing TIC, TIN, TiCN, and the like as the main ingredients), high-speed steel, ceramics (such as titanium carbide, silicon carbide, silicon nitride, aluminum nitride, and aluminum oxide), cubic boron nitride sintered material, or diamond sintered material.

(34) Especially, the substrate may be WC-based cemented carbide or a cermet (especially TiCN-based cermet). WC-based cemented carbide or the cermet have hardness and strength, especially at high temperature, in an excellently balanced manner. If WC-based cemented carbide or the cermet is used as the substrate of the cutting tool, the material can contribute to the expansion of the life of the cutting tool.

(35) <Coating>

(36) <<Structure of Coating>>

(37) The coating of Embodiment 1 comprises the first layer. The coating covers the substrate, and therefore has the action of improving various characteristics of the cutting tool such as abrasion resistance and chipping resistance, resulting in extending the life of the cutting tool. The coating can comprise other layers besides the first layer. As shown in FIGS. 2 to 4, examples of the other layers include a second layer 14 disposed between substrate 2 and first layer 13, and a third layer 16 disposed on the opposite side of first layer 13 to substrate 2.

(38) <<Thickness of Coating>>

(39) The thickness of the coating may be 0.4 m or more and 20 m or less, 0.5 m or more and 12 m or less, 1 m or more and 10 m or less, or 2 m or more and 8 m or less. If the thickness of the coating is 0.5 m or more, the life of the cutting tool can be further extended. Meanwhile, if the entire thickness of the coating is 12 m or less, the coating is less likely to chip during the early stage of cutting, the life of the cutting tool can be further extended.

(40) The thickness of the coating is measured by observing the cross section of the coating through a scanning electron microscope (SEM). A specific measuring method is as follows. A cutting tool is cut in the direction along the normal line of the principal surface of the coating to provide a sectional sample. The sectional sample is observed through an SEM. The observation magnification is set at 5000 to 10000, and the measurement visual field is set at 100 to 500 m.sup.2. The thicknesses at three points of the coating are measured in one visual field, and the average value of the thicknesses at the three points is calculated. The average value corresponds to the thickness of the coating. The thicknesses of the layers described below are measured in the same method unless otherwise specified.

(41) <<Crystal Structure of Coating>>

(42) The coating may have a cubic crystal structure. If the coating may have a cubic crystal structure, the hardness of the coating is improved. The layers (for example, the first layer, the third layer, and the second layer) in the coating have cubic crystal structures. The crystal structures of the coating and the layers in the coating can be analyzed with an X-ray diffractometer, which is known in the art.

(43) <<Hardness of Coating>>

(44) The coating may have a hardness of 30 GPa or more and 50 GPa or less, or 35 GPa or more and 45 GPa or less. In this case, the coating has a sufficient hardness. The hardness of the coating is measured by the nanoindenter method (measuring apparatus: ENT-1100a, which is available from ELIONIX INC.). The hardnesses at ten points on the surface of the coating are specifically measured at a measurement load of 10 mN (1 gf) by the method in accordance with ISO 14577 to calculate the average value of the hardnesses at the ten points. The average value corresponds to the hardness of the coating.

(45) <First Layer>

(46) <<Composition of First Layer>>

(47) The first layer is composed of Al.sub.aTi.sub.bCr.sub.(1abcd)Si.sub.cCu.sub.dN, and the a, the b, the c, and the d satisfy 0.50a0.75, 0.10b0.25, 0.005c0.20, 0.005d<0.10, and a+b+c+d<1. a may be 0.500 or more and 0.750 or less, 0.550 or more and 0.700 or less, or 0.600 or more and 0.650 or less. b may be 0.100 or more and 0.250 or less, 0.100 or more and 0.200 or less, or 0.120 or more and 0.180 or less. c may be 0.005 or more and 0.200 or less, 0.010 or more and 0.150 or less, or 0.050 or more and 0.100 or less. d may be 0.005 or more and 0.100 or less, 0.010 or more and 0.090 or less, or 0.030 or more and 0.080 or less. a+b+c+d is less than 1, and may be 0.950 or less, 0.910 or less, or 0.890 or less. c/d may be 1 or more, more than 1, 1 or more and 20 or less, 1.2 or more and 10 or less, 1.25 or more and 5 or less, or 2 or more and 4 or less. If c/d is 1 or more, the film hardness is improved, and the tool life is improved.

(48) In the present disclosure, the expression the first layer is composed of Al.sub.aTi.sub.bCr.sub.(1abcd)Si.sub.cCu.sub.dN. means that as long as the effect of the present disclosure is not deteriorated, the first layer can contain inevitable impurities besides Al.sub.aTi.sub.bCr.sub.(1abcd)Si.sub.cCu.sub.dN. Examples of the inevitable impurities include oxygen and carbon. The total content of the inevitable impurities in the first layer may be more than 0% by atom and less than 1% by atom. In the present disclosure, the term % by atom means the ratio of the number of atoms to the total number of atoms constituting the layer (%).

(49) a, b, c, d, and the content of the inevitable impurities in the first layer are measured by the elemental analysis of the cross section of the coating through a transmission electron microscope (TEM). The specific measuring method is as follows. A cutting tool is cut in the direction along the normal line of the principal surface of the coating to provide a thin section sample including the cross section of the coating. The thin section sample is irradiated with an electron beam using an EDS (Energy-Dispersive X-ray Spectroscopy) attached to the TEM. The energy of the characteristic X-rays generated at that time and the numbers of the characteristic X-rays generated are measured to subject the first layer to elemental analysis. Five measurement regions not overlapping each other are randomly set in the first layer and subjected to elemental analysis. The average composition of the five regions is determined. The average composition corresponds to the composition of the first layer. The compositions of the second layer and the third layer described below are also measured by the same method. It has been confirmed that the results of measurement do not vary even at randomly selected measurement points.

(50) In the composition of the first layer Al.sub.aTi.sub.bCr.sub.(1abcd)Si.sub.cCu.sub.dN, in the present disclosure, the ratio A.sub.N1/A.sub.M1 of the number of N atoms Ani to the total number of Al, Ti, Cr, Si, and Cu atoms Ami is 0.8 or more and 1.2 or less. The ratio A.sub.N1/A.sub.M1 can be measured by Rutherford backscattering spectroscopy (RBS). It has been confirmed that if the above-mentioned ratio A.sub.N1/A.sub.M1 is in the ranges, the effect of the present disclosure is not deteriorated.

(51) <Thickness of First Layer>

(52) The first layer may have a thickness of 0.4 m or more and 12 m or less, 0.5 m or more and 10 m or less, 1 m or more and 8 m or less, or 2 m or more and 5 m or less. If the first layer has a thickness of 0.5 m or more, the first layer is high in abrasion resistance, and the life of the cutting tool can be further extended. Meanwhile, if the first layer has a thickness of 10 m or less, the coating is less likely to chip in the early stage of cutting, and the life of the cutting tool can be further extended.

(53) <Second Layer>

(54) As shown in FIGS. 2 and 4, coating 3 can further comprise second layer 14 disposed between substrate 2 and first layer 13. Second layer 14 may be disposed directly on the substrate.

(55) The second layer can be composed of the first compound consisting of at least one element selected from the first group consisting of Group 4, 5, and 6 elements in the periodic table, aluminum (Al), and silicon (Si) or consisting of at least one element selected from the first group and at least one element selected from the second group consisting of carbon (C), nitrogen (N), oxygen (O), and boron (B). Examples of the Group 4 elements in the periodic table include titanium (Ti), zirconium (Zr), and hafnium (Hf). Examples of the Group 5 elements in the periodic table include vanadium (V), niobium (Nb), and tantalum (Ta). Examples of the Group 6 elements in the periodic table include chromium (Cr), molybdenum (Mo), and tungsten (W). The second layer enables enhancing the adhesion between the substrate and the coating, and improves the tool life. As long as the effect of the present disclosure is not deteriorated, the second layer can contain inevitable impurities besides at least one element selected from the first group or the first compound.

(56) The second layer can be composed of the first compound consisting of at least one element selected from a first group consisting of Cr, Al, Ti, and Si or consisting of at least one element selected from the first group and at least one element selected from the second group consisting of carbon, nitrogen, oxygen, and boron.

(57) Examples of the first compound include TiWCN, TiN, TiAlN, TiAlON, Al.sub.2O.sub.3, TiAlSiN, TiCrSiN, TiAlCISiN, AlClN, AlCrO, AlCrON, AlCrSiN, AlCrBN, TiZrN, TiAlMoN, TiAlNbN, TiSiN, AlCrTaN, AlVN, AlTiVN, TiB.sub.2, TiCrHfN, CrSiWN, TiAlCN, TiSiCN, AlZrON, AlClCN, AlHfN, CrSiBON, TiAlWN, AlCrMoCN, TiCN, TiCON, ZrN, and ZrCN.

(58) As long as the effect of the present embodiment is not deteriorated, the thickness of the second layer is not particularly limited, and can be, for example, 0.1 m or more and 2 m or less.

(59) <Third Layer>

(60) As shown in FIGS. 3 and 4, coating 3 can further comprise third layer 16 disposed on the opposite side of first layer 13 to substrate 2. Third layer 16 may be disposed directly on first layer 13. Other layers may be disposed between first layer 13 and third layer 16. Third layer 16 may be the outermost layer.

(61) The third layer can be composed of a second compound consisting of at least one element selected from the first group consisting of Group 4, 5, and 6 elements in the periodic table, aluminum (Al), and silicon (Si) or consisting of at least one element selected from the first group and at least one element selected from the second group consisting of carbon (C), nitrogen (N), oxygen (O), and boron (B). The third layer enables reducing the coefficient of friction of the coating to extend the life of the cutting tool. As long as the effect of the present disclosure is not deteriorated, the third layer can contain impurities besides at least one element selected from the first group or the above-mentioned second compound.

(62) The third layer can be composed of the second compound consisting of at least one element selected from a first group consisting of Cr, Al, Ti, and Si or consisting of at least one element selected from the first group and at least one element selected from the second group consisting of carbon, nitrogen, oxygen, and boron.

(63) Examples of the second compound include AlTiBN, TiAlN, TiAlON, Al.sub.2O.sub.3, TiAlSiN, TiCrSiN, TiAlCrSiN, AlClN, AlCrO, AlCrON, AlCrSiN, AlClBN, TiZrN, TiAlMoN, TiAlNbN, TiSiN, AlCrTaN, AlVN, AlTiVN, TiB.sub.2, TiCrHfN, CrSiWN, TiAlCN, TiSiCN, AlZrON, AlClCN, AlHfN, CrSiBON, TiAlWN, AlCrMoCN, TICN, TiCON, ZrN, and ZrCN.

(64) The third layer may have a thickness of 0.1 m or more and 2 m or less. If the third layer has a thickness of 0.1 m or more, the effect of imparting lubricity due to the third layer is easily obtained. Although the upper limit of a thickness of the third layer is not particularly limited, in the case of more than 2 m, the above-mentioned effect of imparting lubricity tends not to be able to be further improved. The third layer may have a thickness of 2 m or less in view of cost.

(65) <Intermediate Layer>

(66) The coating can comprise an intermediate layer disposed between the third layer and the first layer or between the first layer and the second layer. Examples of the intermediate layer include TiAlCeN, AlTiN, AlTiBN, AlTiSiN, AlTiYN, and AlTiLaN. The intermediate layer may have a thickness of 0.1 m or more and 2 m or less, 0.3 m or more and 1.5 m or less, or 0.4 m or more and 1.0 m or less.

Embodiment 2: Method for Manufacturing Cutting Tool

(67) In Embodiment 2, the method for manufacturing the cutting tool of Embodiment 1 will be described. The manufacturing method comprises the first step of providing a substrate and the second step of forming a coating on the substrate. The second step comprises a step of forming a first layer. Details of the steps will be described below.

(68) <First Step>

(69) In the first step, the substrate is provided. The substrate described in Embodiment 1 can be used as the substrate. Any conventionally known substrate can be provided.

(70) <Second Step>

(71) In the second step, the coating is formed on the substrate. The second step comprises the step of forming the first layer.

(72) In the step of forming the first layer, the first layer is formed by physical vapor deposition (PVD). It is highly effective to form a layer comprising a highly crystalline compound for improving the abrasion resistance of the coating comprising the first layer. The present inventors have examined various methods as the method for forming the first layer and consequently found that it is highly effective to use physical vapor deposition.

(73) As the PVD, at least one selected from the group consisting of cathode arc ion plating, balanced magnetron sputtering, unbalanced magnetron sputtering, and HiPIMS is usable. Especially cathode arc ion plating, which ionizes raw material elements at a high ionization rate, may be used. Since the use of cathode arc ion plating enables the metal ion bombardment treatment of the surface of the substrate before the formation of the first layer, the adhesion between the substrate and the coating comprising the first layer is remarkably improved.

(74) Cathode arc ion plating can be performed, for example, in a procedure involving disposing a substrate and a target as the cathode in an apparatus, then impressing high voltage on the target for arcing to ionize atoms constituting the target, resulting in vaporization, and depositing the substance on the substrate.

(75) <Other Steps>

(76) The second step can comprise steps of surface processing such as surface grinding and shot blasting besides the step of forming the first layer. The second step can comprise steps of forming other layers such as the second layer, the third layer, and the intermediate layer. The other layers can be formed by conventionally known chemical vapor deposition or physical vapor deposition. The other layers may be formed by physical vapor deposition from the viewpoint that the first layer and the other layers can be successively formed in a physical vapor deposition apparatus.

EXAMPLES

(77) The present embodiment will be further specifically described by Examples. The present embodiment is not, however, limited by these Examples.

(78) <<Manufacturing of Cutting Tool>>

(79) FIG. 6 is a schematic sectional view of a cathode arc ion plating apparatus used in the present Examples. FIG. 7 is a schematic top view of the apparatus in FIG. 6.

(80) The apparatus in FIGS. 6 and 7 includes a chamber 101 provided with cathodes 106 and 107 for first layers as alloy targets to be used as metal raw materials for a coating 3, and a rotational substrate holder 104 for disposing a substrate thereon. The compositions of cathodes 106 and 107 are adjusted so that the compositions described in the following Table 1 are obtained.

(81) In an apparatus for a sample on which a second layer or a third layer is formed, a cathode for the second layer or a cathode for the third layer (not shown) are also further installed in a chamber 101. The cathode for the second layer and the cathode for the third layer have compositions adjusted so that the compositions described in the following Table 2 are obtained.

(82) An arc power source 108 is attached to cathode 106, and an arc power source 109 is attached to cathode 107. A bias power source 110 is attached to substrate holder 104. Chamber 101 is provided with a gas inlet for introducing gas 105 and a gas outlet 103 for adjusting the pressure in chamber 101. The apparatus has a structure in which the gas in chamber 101 can be aspirated from gas outlet 103 with a vacuum pump.

(83) A chip with a shape of CNMG120416 in accordance with JIS made of a K20-grade cemented carbide in accordance with JIS was attached to substrate holder 104 as the substrate.

(84) While the pressure was reduced with a vacuum pump in chamber 101, the substrate being rotated was then heated to a temperature of 500 C. with a heater installed in the apparatus. The chamber 101 was evacuated to a pressure of 1.010.sup.4 Pa. Argon gas was then introduced from the gas inlet to maintain the pressure in the chamber 101 at 2.0 Pa. While the voltage from the bias power source 110 was gradually increased to 1000 V, the surface of the substrate was cleaned for 15 minutes. The argon gas was then exhausted from the chamber 101 to clean the substrate (argon bombardment treatment). A substrate for cutting tools as samples was provided by the above procedure.

(85) Then, while nitrogen was introduced as reactive gas with the substrate being rotated at the center, cathode 106 and cathode 107 were each supplied with an arc current of 150 A under the following conditions to generate metal ions from cathode 106 and cathode 107, resulting in the formation of a first layer having the compositions shown in the following Table 1 on the substrate with the substrate maintained at a temperature of 550 C., the reactive gas maintained at a pressure of 2.0 Pa, and the voltage from bias power source 110 maintained at a certain constant value in the range of 50 V to 300 V.

(86) If the second layer was formed, the second layer was formed on the substrate, and the first layer was then formed on the second layer. The second layer was formed in the following procedure. The substrate temperature was set at 550 C., and the gas pressure in the apparatus was set at 4.0 Pa. A mixed gas of nitrogen gas and argon gas was introduced as the reactive gas. The cathode electrode was then supplied with an arc current of 150 A. The supply of the arc current generated metal ions and the like from the arc evaporation source to form the second layer.

(87) If the third layer was formed, the third layer was formed on the first layer. The third layer was formed in the following procedure. The substrate temperature was set at 550 C., and the gas pressure in the apparatus was set at 4.0 Pa. A mixed gas of nitrogen gas and argon gas was introduced as the reactive gas. The cathode electrode was then supplied with an arc current of 150 A. The supply of the are current generated metal ions and the like from the arc evaporation source to form the third layer.

(88) Cutting tools as samples were manufactured by the above-mentioned method.

(89) TABLE-US-00001 TABLE 1 First layer Sample Al.sub.aTi.sub.bCr.sub.(1abcd)Si.sub.cCu.sub.dN No. a b c d a + b + c + d c/d Thickness[m] 1 0.500 0.150 0.050 0.040 0.740 1.25 1.5 2 0.600 0.220 0.010 0.008 0.838 1.25 6.0 3 0.750 0.120 0.050 0.040 0.960 1.25 6.0 4 0.700 0.100 0.030 0.010 0.840 3 4.0 5 0.580 0.200 0.120 0.030 0.930 4 6.0 6 0.520 0.250 0.150 0.030 0.950 5 4.0 7 0.560 0.100 0.005 0.005 0.670 1 3.0 8 0.650 0.190 0.010 0.005 0.855 2 7.0 9 0.540 0.250 0.100 0.010 0.900 10 1.5 10 0.600 0.120 0.200 0.010 0.930 20 5.5 11 0.700 0.140 0.010 0.005 0.855 2 9.0 12 0.530 0.130 0.020 0.010 0.690 2 3.0 13 0.550 0.200 0.100 0.100 0.950 1 7.0 14 0.560 0.200 0.070 0.070 0.900 1 10.0 15 0.500 0.160 0.150 0.080 0.890 0.8 2.0 16 0.680 0.120 0.009 0.005 0.814 1.8 0.5 17 0.630 0.210 0.010 0.005 0.855 2 10 18 0.500 0.110 0.017 0.010 0.637 1.7 0.4 19 0.710 0.110 0.040 0.010 0.870 4 12 20 0.560 0.230 0.030 0.010 0.830 3 7.0 21 0.630 0.100 0.150 0.030 0.910 5 8.0 1-1 0.400 0.210 0.100 0.010 0.720 10 6.0 1-2 0.800 0.100 0.030 0.010 0.940 3 3.0 1-3 0.560 0.050 0.017 0.010 0.637 1.7 5.5 1-4 0.590 0.300 0.030 0.020 0.940 1.5 1.5 1-5 0.740 0.140 0.004 0.040 0.924 0.1 4.0 1-6 0.600 0.100 0.220 0.030 0.950 7.3 8.0 1-7 0.570 0.120 0.050 0.004 0.744 12.5 7.0 1-8 0.630 0.180 0.050 0.120 0.980 0.42 6.0 1-9 0.600 0.150 0.000 0.000 0.750 5.0 1-10 0.550 0.100 0.020 0.000 0.670 6.0 1-11 0.680 0.250 0.000 0.03 0.960 0 3.0

(90) TABLE-US-00002 TABLE 2 Cutting test Second layer Third layer Thickness Cutting Sample Thickness Thickness of coating distance No. Composition [m] Composition [m] [m] [m] 1 1.5 18 2 6.0 19 3 6.0 21 4 4.0 22 5 6.0 18 6 AlTiN 1 5.0 20 7 TiCN 0.5 3.5 19 8 7.0 18 9 1.5 15 10 5.5 16 11 9.0 17 12 3.0 16 13 7.0 17 14 10.0 18 15 2.0 16 16 0.5 15 17 10 17 18 0.4 16 19 12 16 20 AlTiBN 8 15 14 21 TiSiN 12 20 13 1-1 6.0 5 1-2 3.0 4 1-3 5.5 5 1-4 1.5 4 1-5 4.0 8 1-6 8.0 5 1-7 7.0 8 1-8 6.0 3 1-9 5.0 7 1-10 6.0 9 1-11 3.0 7
<<Evaluation>>
<Measurement of Composition of First Layer>

(91) The cutting tools as the samples were measured for the composition of the first layer by the method described in Embodiment 1. Table 1 shows the values of a, b, c, and d in Al.sub.aTi.sub.bCr.sub.(1abcd)Si.sub.cCu.sub.dN of the first layer. Table 1 further shows a+b+c+d and c/d.

(92) <Measurement of Compositions of Second Layer and Third Layer>

(93) The cutting tools as the samples were measured for the compositions of the second layers and the third layers by the method described in Embodiment 1. Table 2 shows the results. The described signs - in Table 2 mean that the corresponding layers were absent.

(94) <Measurement of Thicknesses of First Layer, Second Layer, and Third Layer>

(95) The cutting tools as the samples were measured for the thicknesses of the first layer, the second layer, and the third layer by the method described in Embodiment 1. Tables 1 and 2 show the results.

(96) <Crystal Structure of Coating>

(97) The crystal structures of the coatings were analyzed by the method described in Embodiment 1 in the cutting tool as the samples. The Samples 1 to 21 had cubic crystal structures.

(98) <Hardness of Coating>

(99) The hardnesses of the coatings were analyzed by the method described in Embodiment 1 in the cutting tools as the samples. In the Samples 1 to 21, the hardnesses of the coatings were 30 GPa or more and 50 GPa or less.

(100) <Cutting Test>

(101) The samples were subjected to continuous lathe-turning tests under the following cutting conditions. The cutting distances were measured until the abrasion widths or the breakage widths of the cutting edges reached 100 m. Table 2 shows the results. A long cutting distance means a long tool life.

(102) <<Cutting Conditions>>

(103) Material to be cut: Inconel 718 Cutting speed Vc: 50 m/min Feed speed f: 0.25 mm/rev Cut ap: 1.5 mm Cutting oil: present

(104) The above-mentioned cutting conditions correspond to conditions for the continuous machining of nickel-based alloy.

(105) The cutting tools as Samples 1 to 21 corresponds to Examples, and the cutting tools as Samples 1-1 to 1-11 corresponds to Comparative Examples. It was confirmed that the cutting tools as Samples 1 to 21 had a long tool life as compared with the cutting tools as Samples 1-1 to 1-11 in the continuous machining of nickel-based alloy.

(106) As mentioned above, the embodiments and Examples of the present disclosure were described, but the above-mentioned configurations of the embodiments and Examples have been expected to be appropriately combined or variously modified since the beginning.

(107) The embodiments and Examples disclosed herein are illustrations in all respects, and should be considered to be unlimited. The scope of the present invention is indicated by Claims rather than the above-mentioned embodiments and Examples, and is intended to include any modifications within the scope and meaning equivalent to Claims.

REFERENCE SIGNS LIST

(108) 1 Cutting tool; 2 Substrate; 3 Coating; 13 First layer; 14 Second layer; 16 Third layer; 21 Rake face; 22 Flank face; 23 Cutting edge ridgeline; 101 Chamber; 103 Gas outlet; 104 Substrate holder, 105 Gas, 106, 107 Cathode; 108, 109 Arc power source; 110 Bias power source.