22. These are not suitable for use in cutting tools because all of these materials have a low melting point and low oxidation resistance. In addition, a simple substance of Hf, a simple substance of Nb, a simple substance of Ta, and a simple substance of Mo have low adhesion to the base body 10. However, this does not apply to alloys containing Ti, Zr, V, Cr, Ta, Nb, Hf, and Al.

The metal layer 22 may be an Al—Cr alloy layer containing an Al—Cr alloy. Since the metal layer 22 has particularly high adhesion to the base body 10, the effect of improving the adhesion between the base body 10 and the coating film 20 is high.

When the metal layer 22 is an Al—Cr alloy layer, the Al content in the metal layer 22 may be greater than the content of Cr in the metal layer 22. For example, the composition ratio (atomic %) of Al and Cr in the metal layer 22 may be 70:30. With such a composition ratio, the adhesion between the base body 10 and the metal layer 22 is higher.

The metal layer 22 may contain components other than the metal elements (Zr, V, Cr, W, Al, Si, Y). However, from the perspective of adhesion to the base body 10, the metal layer 22 may contain at least 95 atomic % or more of the metal elements in a combined amount. More preferably, the metal layer 22 may contain 98 atomic % or more of the metal elements in a combined amount. For example, in a case where the metal layer 22 is an Al—Cr alloy layer, the metal layer 22 may contain at least 95 atomic % or more of Al and Cr in a combined amount. Furthermore, the metal layer 22 may contain at least 98 atomic % or more of Al and Cr in a combined amount. Note that the proportion of the metal components in the metal layer 22 can be identified by, for example, analysis using an energy dispersive X-ray spectrometer (EDS).

In addition, since Ti has poor wettability with the base body 10 according to the embodiment, it is preferable that the metal layer 22 does not contain Ti as much as possible from the viewpoint of improving adhesion with the base body 10. Specifically, the Ti content in the metal layer 22 may be 15 atomic % or less.

As described above, in the coated tool 1 according to the embodiment, by providing the metal layer 22 having higher wettability with the base body 10 than the hard layer 21 between the base body 10 and the hard layer 21, it is possible to improve the adhesion between the base body 10 and the coating film 20. Since the metal layer 22 has high adhesion to the hard layer 21, the hard layer 21 is less likely to peel off from the metal layer 22.

The cBN used as the base body 10 is an insulator. The cBN as an insulator has room for improvement in adhesion with a film formed by a physical vapor deposition method (PVD). In contrast, in the coated tool 1 according to the embodiment, the metal layer 22 having electrical conductivity is provided on the surface of the base body 10, and thus the adhesion between the hard layer 21 formed by PVD and the metal layer 22 is high.

Hard Layer 21

The configuration of the hard layer 21 will be described with reference to FIG. 5. FIG. 5 is a schematic enlarged view of a V portion illustrated in FIG. 4.

As illustrated in FIG. 5, the hard layer 21 has a laminate portion 23 located on the metal layer 22 and a third metal nitride layer 24 located on the laminate portion 23.

The laminate portion 23 includes a plurality of first metal nitride layers 23a and a plurality of second metal nitride layers 23b. The laminate portion 23 has a configuration in which the first metal nitride layers 23a and the second metal nitride layers 23b are alternately layered.

The thickness of each of the first metal nitride layer 23a and the second metal nitride layer 23b may be 50 nm or less. In this way, by forming the first metal nitride layer 23a and the second metal nitride layer 23b thin, the residual stress of the first metal nitride layer 23a and the second metal nitride layer 23b is small. As a result, for example, peeling and cracking of the first metal nitride layer 23a and the second metal nitride layer 23b are less likely to occur, so that the durability of the coating film 20 is high.

The first metal nitride layer 23a is a layer that contacts the metal layer 22, and the second metal nitride layer 23b is formed on the first metal nitride layer 23a.

The first metal nitride layer 23a and the second metal nitride layer 23b may contain a metal contained in the metal layer 22.

For example, it is assumed that two kinds of metals (here, “first metal” and “second metal”) are included in the metal layer 22. In this case, the first metal nitride layer 23a contains a nitride of the first metal and the third metal. The third metal is a metal not included in the metal layer 22. The second metal nitride layer 23b contains a nitride of the first metal and the second metal.

For example, in the embodiment, the metal layer 22 may contain Al and Cr. In this case, the first metal nitride layer 23a may contain Al. Specifically, the first metal nitride layer 23a may be an AlTiN layer containing AlTiN, which is a nitride of Al and Ti. The second metal nitride layer 23b may be an AlCrN layer containing AlCrN, which is a nitride of Al and Cr.

In this way, the first metal nitride layer 23a containing the metal contained in the metal layer 22 is located on the metal layer 22, and thus the adhesion between the metal layer 22 and the hard layer 21 is high. This makes it difficult for the hard layer 21 to peel off from the metal layer 22, so the durability of the coating film 20 is high.

The first metal nitride layer 23a, that is, the AlTiN layer is excellent in terms of, for example, wear resistance in addition to adhesion to the metal layer 22 described above. The second metal nitride layer 23b, that is, the AlCrN layer, has excellent heat resistance and oxidation resistance, for example. In this manner, the coating film 20 includes the first metal nitride layer 23a and the second metal nitride layer 23b having different compositions from each other, and thus properties such as wear resistance and heat resistance of the hard layer 21 can be controlled. Accordingly, the tool life of the coated tool 1 can be extended. For example, in the hard layer 21 according to the embodiment, mechanical properties such as adhesion with the metal layer 22 and wear resistance can be improved while maintaining excellent heat resistance of AlCrN.

Note that the laminate portion 23 may be formed by, for example, an arc ion plating method (AIP method). The AIP method is a method in which target metals (here, an AlTi target and an AlCr target) are evaporated by using an arc discharge in a vacuum atmosphere, and are combined with N₂gas to form metallic nitrides (here, AlTiN and AlCrN). Note that the metal layer 22 may also be formed by the AIP method.

The third metal nitride layer 24 may be located on the laminate portion 23. Specifically, the third metal nitride layer 24 is in contact with the second metal nitride layer 23b of the laminate portion 23. The third metal nitride layer 24 is, for example, a metal nitride layer (AlTiN layer) containing Ti and Al similar to the first metal nitride layer 23a.

The thickness of the third metal nitride layer 24 may be greater than each thickness of the first metal nitride layer 23a and the second metal nitride layer 23b. Specifically, as described above, when the thickness of the first metal nitride layer 23a and the second metal nitride layer 23b is 50 nm or less, the thickness of the third metal nitride layer 24 may be 1 μm or more. For example, the thickness of the third metal nitride layer 24 may be 1.2 μm.

As a result, for example, when the coefficient of friction of the third metal nitride layer 24 is low, the welding resistance of the coated tool 1 can be improved. In addition, for example, when the hardness of the third metal nitride layer 24 is high, the wear resistance of the coated tool 1 can be improved. In addition, for example, when the oxidation start temperature of the third metal nitride layer 24 is high, the oxidation resistance of the coated tool 1 can be improved.

The thickness of the third metal nitride layer 24 may be greater than the thickness of the laminate portion 23. Specifically, in the embodiment, when the thickness of the laminate portion 23 is 0.5 μm or less, the thickness of the third metal nitride layer 24 may be 1 μm or more. For example, when the thickness of the laminate portion 23 is 0.3 μm, the thickness of the third metal nitride layer 24 may be 1.2 μm. In this way, the third metal nitride layer 24 is thicker than the laminate portion 23, and thus the effect of improving the welding resistance, wear resistance, etc. described above is further enhanced.

The thickness of the metal layer 22 may be, for example, 0.1 μm or more and less than 0.6 μm. That is, the metal layer 22 may be thicker than each of the first metal nitride layer 23a and the second metal nitride layer 23b, and may be thinner than the laminate portion 23.

Cutting Tool

A configuration of a cutting tool including the coated tool 1 described above will be described with reference to FIG. 6. FIG. 6 is a front view illustrating an example of a cutting tool according to the embodiment.

As illustrated in FIG. 6, a cutting tool 100 according to the embodiment includes the coated tool 1 and a holder 70 for fixing the coated tool 1.

The holder 70 is a rod-shaped member that extends from a first end (upper end in FIG. 6) toward a second end (lower end in FIG. 6). The holder 70 is made of, for example, steel or cast iron. In particular, it is preferable to use steel having high toughness among these members.

The holder 70 has a pocket 73 at an end portion on the first end side. The pocket 73 is a portion in which the coated tool 1 is mounted, and has a seating surface intersecting with the rotation direction of the work material and a binding side surface inclined with respect to the seating surface. A screw hole into which a screw 75 described later is screwed is provided on the seating surface.

The coated tool 1 is located in the pocket 73 of the holder 70, and is mounted on the holder 70 by the screw 75. That is, the screw 75 is inserted into the through hole 5 of the coated tool 1, and the tip end of the screw 75 is inserted into the screw hole formed in the seating surface of the pocket 73, and the screw portions are screwed together. Thus, the coated tool 1 is mounted on the holder 70 such that the cutting edge 8 (see FIG. 1) protrudes outward from the holder 70.

In the embodiment, a cutting tool used for so-called turning processing is exemplified. Examples of the turning processing include boring, external turning, and groove-forming. Note that, a cutting tool is not limited to those used in the turning processing. For example, the coated tool 1 may be used as a cutting tool used for milling processing.

For example, the cutting processing of the work material includes the steps of (1) rotating a work material, (2) bringing the cutting edge 8 of the coated tool 1 into contact with the rotating work material to cut the work material, and (3) separating the coated tool 1 from the work material. Here, representative examples of the material of the work material include carbon steel, alloy steel, stainless steel, cast iron, non-ferrous metals, etc.

EXAMPLES

Examples of the present disclosure will be described below. The present disclosure is not limited to the following examples.

First, 72 to 82 vol % of TiN raw powder, 13 to 23 vol % of Al raw powder, and 1 to 11 vol % of Al₂O₃raw powder are prepared. Then, an organic solvent is added to each raw powder prepared. As the organic solvent, alcohols such as acetone and isopropyl alcohol (IPA) may be used. Then, the resultant mixture is milled and mixed for 20 to 24 hours with a ball mill. After the milling and mixing, the solvent is evaporated, whereby a first mixture powder is produced.

cBN powder having an average particle diameter of 2.5 to 4.5 μm and cBN powder having an average particle diameter of 0.5 to 1.5 μm are mixed in a volume ratio of 8:2 to 9:1. An organic solvent is further added. As the organic solvent, alcohols such as acetone and IPA may be used. Then, the resultant mixture is milled and mixed for 20 to 24 hours with a ball mill. After the milling and mixing, the solvent is evaporated, whereby a second mixture powder is produced.

The resulting first mixture powder and second mixture powder are mixed in a volume ratio of 68:32 to 78:22. An organic solvent and an organic binder are added to the mixture powder. As the organic solvent, alcohols such as acetone and IPA may be used. As the organic binder, paraffin, acrylic resin, or the like may be used. Thereafter, the mixture is milled and mixed for 20 to 24 hours with the ball mill, and then the organic solvent is additionally evaporated, whereby a third mixture powder is produced. Note that a dispersant can be added as necessary in the step using the ball mill.

The third mixture powder is molded into a molded object of a predetermined shape. A known method such as uniaxial pressing or cold isostatic pressing (CIP) may be used for the molding. The molded object is heated to a predetermined temperature within a range from 500° C. to 1000° C., whereby the organic binder is evaporated and removed.

The molded object is loaded into an ultra-high pressure heating device, and is heated at 1200° C. to 1500° C. for 15 to 30 minutes under a pressure of 4 to 6 GPa. As a result, the cubic boron nitride sintered compact according to the embodiment is obtained. The obtained cubic boron nitride sintered compact is attached to a seat of a tip body made of cemented carbide via a bonding material. As a result, the tip according to an Example is obtained.