JP7568566B2 - Inserts and Cutting Tools - Google Patents

Description

The present disclosure relates to an insert and a cutting tool.

Inserts having a base material such as cemented carbide, cermet, or ceramics are known as tools used in cutting processes such as turning and milling (see Patent Document 1).

JP 2002-3284 A

The above-mentioned conventional techniques leave room for further improvement in terms of improving the finished surface quality of the workpiece without compromising durability.

The present disclosure has been made in consideration of the above, and aims to provide an insert and cutting tool that can improve the quality of the finished surface of the workpiece without compromising durability.

The insert according to one aspect of the present disclosure has a first surface having a rake face, a second surface having a clearance face, and a ridge portion located between the first surface and the second surface, and a cutting edge is located on at least a portion of the ridge portion. The cutting edge has at least a third surface, and when the average arithmetic surface roughness Ra of the third surface in a direction parallel to the ridge portion is Ra1, Ra1 is 0.20 μm or less.

A cutting tool according to one aspect of the present disclosure has a rod-shaped holder having a pocket at an end and the above-mentioned insert positioned within the pocket.

This disclosure makes it possible to improve the quality of the finished surface of the workpiece without compromising durability.

FIG. 1 is a perspective view showing an example of an insert according to an embodiment. FIG. 2 is a side cross-sectional view showing an example of an insert according to an embodiment. FIG. 3 is a schematic side view showing the configuration of the coating layer according to the embodiment. FIG. 4 is a schematic plan view of the third coating layer as viewed in a direction perpendicular to the third surface. FIG. 5 is a schematic enlarged view of the V portion shown in FIG. FIG. 6 is a schematic enlarged view of portion VI shown in FIG. FIG. 7 is a front view illustrating an example of a cutting tool according to an embodiment. FIG. 8 is a diagram showing the measurement results of the average arithmetic surface roughness Ra of the third surface. FIG. 9 is a diagram showing the results of measuring the ten-point average surface roughness Rz of the third surface. FIG. 10 is a graph showing the results of a wear resistance test on the inserts according to Example 1 and Comparative Examples 1, 3, and 4. FIG. 11 is a graph showing the results of a chipping resistance test for the inserts according to Example 1 and Comparative Examples 1, 3, and 4. FIG. 12 is a table showing the results of residual stress measurement for the second coating layer of the inserts according to Example 1 and Comparative Example 1.

Below, a detailed description will be given of a form for implementing the insert and cutting tool according to the present disclosure (hereinafter, referred to as an "embodiment") with reference to the drawings. Note that the insert and cutting tool according to the present disclosure are not limited to this embodiment. Furthermore, each embodiment can be appropriately combined as long as the processing content is not contradictory. Furthermore, the same parts in each of the following embodiments are given the same reference numerals, and duplicated explanations will be omitted.

In addition, in the embodiments described below, expressions such as "constant," "orthogonal," "vertical," and "parallel" may be used, but these expressions do not necessarily mean "constant," "orthogonal," "vertical," or "parallel" in the strict sense. In other words, each of the above expressions allows for deviations due to, for example, manufacturing precision, installation precision, and the like.

<Insert>
Fig. 1 is a perspective view showing an example of an insert according to an embodiment. As shown in Fig. 1, the insert 1 according to the embodiment may have a tip body 2 and a cutting edge portion 3. The insert 1 according to the embodiment has, for example, a hexahedral shape in which the upper and lower surfaces (surfaces intersecting with the Z-axis shown in Fig. 1) are parallelograms.

The insert 1 has a first surface 6 (here, the top surface), a second surface 7 (here, the side surface) connected to the first surface 6, and a ridge portion 8 located between the first surface 6 and the second surface 7. The first surface 6 has a scooping surface that scoops up chips generated by cutting. In addition, the second surface 7 has a clearance surface.

When viewed in a plan view, the first surface 6 has multiple (four here) corners 61. The corners 61 are areas that include the corners of the first surface 6. A cutting edge 11 is located on the ridge portion 8 of at least one of the multiple corners 61. The insert 1 cuts the workpiece by bringing the cutting edge 11 into contact with the workpiece.

(Chip body 2)
The tip body 2 is formed of, for example, a cemented carbide. The cemented carbide contains W (tungsten), specifically WC (tungsten carbide). The cemented carbide may also contain at least one of Ni (nickel) and Co (cobalt). The tip body 2 may also be formed of a cermet. The cermet contains, for example, Ti (titanium), specifically TiC (titanium carbide) or TiN (titanium nitride). The cermet may also contain Ni or Co.

A seat surface 4 for attaching the cutting edge portion 3 may be located on one of the locations of the tip body 2 that corresponds to the corner portion 61 of the insert 1. A through hole 5 that passes through the tip body 2 from top to bottom may be located in the center of the tip body 2. A screw 75 for attaching the insert 1 to the holder 70 described below is inserted into the through hole 5 (see FIG. 7).

(Cutting edge portion 3)
The cutting edge portion 3 is attached to the seat surface 4 of the tip body 2, thereby being integrated with the tip body 2. The cutting edge portion 3 constitutes one of a plurality of corner portions 61 of the insert 1. The cutting edge portion 3 also constitutes the first surface 6, the second surface 7, and a part of the ridge portion 8 described above. The cutting edge 11 is located on at least a part of the ridge portion 8 of the cutting edge portion 3.

The configuration of the cutting edge portion 3 will be described with reference to FIG. 2. FIG. 2 is a side cross-sectional view showing an example of an insert 1 according to an embodiment. As shown in FIG. 2, the cutting edge portion 3 has a base body 10. The cutting edge portion 3 may also have a coating layer 20.

(Base 10)
The substrate 10 may be a cemented carbide, a cermet, or a ceramic. It may also be a boron nitride sintered body containing a plurality of boron nitride particles. In the embodiment, the substrate 10 may be a cubic boron nitride (cBN) sintered body and may contain a plurality of cubic boron nitride particles. The substrate 10 may have a bonding phase containing TiN, Al, Al ₂ O ₃ , or the like between the plurality of boron nitride particles. The plurality of boron nitride particles are firmly bonded by such a bonding phase. The substrate 10 does not necessarily have to have a bonding phase. In addition, although the substrate 10 is located at the cutting edge portion 3 in FIG. 1 and FIG. 2, the substrate 10 may be the tip body 2 and the cutting edge portion 3. In other words, for example, a rectangular substrate 10 may be used.

At least a portion of the cutting edge 11 is provided with a third surface 9 that is continuous with the first surface 6 and the second surface 7. The third surface 9 is, for example, a C surface (chamfered surface) that is formed by cutting the corner between the first surface 6 and the second surface 7 obliquely and linearly. The third surface 9 may also be an R surface (rounded surface) that is formed by rounding the corner between the first surface 6 and the second surface 7.

A substrate 30 made of, for example, cemented carbide or cermet may be located on the underside of the base 10. In this case, the base 10 is joined to the seating surface 4 of the chip body 2 via the substrate 30 and a joining material 40. The joining material 40 is, for example, a brazing material. In the portion of the chip body 2 other than the seating surface 4, the base 10 may be joined to the chip body 2 via the joining material 40.

(Covering layer 20)
The coating layer 20 is applied to the base 10 for the purpose of improving the wear resistance, heat resistance, etc. of the cutting edge portion 3. In the example of Fig. 2, the coating layer 20 is located on both the tip body 2 and the base 10, but it is sufficient that the coating layer 20 is located at least on the base 10. When the coating layer 20 is located on the side surface of the base 10 corresponding to the second surface 7 of the cutting edge portion 3, the second surface 7 has high wear resistance and heat resistance.

Figure 3 is a schematic side view showing the configuration of the coating layer according to the embodiment. Also, Figure 4 is a schematic plan view of the third coating layer 203 viewed from a direction perpendicular to the third surface 9.

As shown in FIG. 3, the coating layer 20 has a first coating layer 201 located on the first surface 6, a second coating layer 202 located on the second surface 7, and a third coating layer 203 located on the third surface 9.

Here, if the average arithmetic surface roughness Ra in the direction D1 (see FIG. 4) parallel to the ridge line portion 8 on the third surface 9 is Ra1, Ra1 may be 0.20 μm or less. The insert 1 having such a configuration can improve the finished surface quality of the workpiece without compromising durability.

In addition, when the average arithmetic surface roughness Ra in the direction D2 (see FIG. 4) perpendicular to the ridge line portion 8 on the third surface 9 is Ra2, the difference between Ra1 and Ra2 may be 0.1 μm or less. With the insert 1 having such a configuration, the finished surface roughness of the workpiece can be reduced.

In addition, when the ten-point average surface roughness Rz in the direction D1 parallel to the ridge line portion 8 on the third surface 9 is Rz1, Rz1 may be 1.5 μm or less. With the insert 1 having such a configuration, the finished surface roughness of the workpiece can be reduced.

In addition, when the ten-point average surface roughness Rz in the direction D2 perpendicular to the ridge line portion 8 on the third surface 9 is Rz2, the difference between Rz1 and Rz2 may be 0.2 μm or less. With the insert 1 having such a configuration, the finished surface roughness of the workpiece can be reduced.

In addition, the second coating layer 202 located on the second surface 7 of the coating layer 20 may contain cubic crystal grains. For example, the cubic crystal grains contained in the second coating layer 202 may be AlTiN.

Of the residual stresses measured for the first coating layer 201 and the second coating layer 202 by the 2D method (a stress measurement method using an X-ray two-dimensional detector), the residual stress in the vicinity of the cutting edge 11 of the first coating layer 201 is designated as σ1, and the residual stress in the vicinity of the cutting edge 11 of the second coating layer 202 is designated as σ2.

For example, as shown in Fig. 3, for the second coating layer 202, the residual stress σ2 ₁₁ in the direction perpendicular to the first surface 6 and the residual stress σ2 ₂₂ in the direction parallel to the first surface 6 are measured using the 2D method. The average value of the obtained σ2 ₁₁ and σ2 ₂₂ may be calculated as σ2. Similarly, for the first coating layer 201, the residual stress in the direction parallel to the first surface 6 and perpendicular to the ridge between the first surface 6 and the second surface 7 may be measured as σ1 ₂₂ , and the residual stress in the direction perpendicular to σ1 ₂₂ may be measured as σ1 ₁₁ using the 2D method, and the average value of these may be calculated as σ1.

σ1 and σ2 may both be compressive stresses. In general, coated tools that have tensile stresses as residual stresses in the coating layer are prone to cracking. In contrast, inserts 1 in which σ1 and σ2 are both compressive stresses are less likely to crack. Therefore, inserts 1 having such a configuration are highly durable.

The residual stress value of σ1 may be -1050 MPa or more and -750 MPa or less. The residual stress value of σ2 may be -1400 MPa or more and -1100 MPa or less. The insert 1 having such a configuration has even higher durability.

The thickness of the second coating layer 202 may be 0.5 μm or more and 5.0 μm or less. The insert 1 having the above configuration has high peel resistance and high impact resistance of the coating layer 20, so that the durability of the coating layer 20 is further increased.

(Specific configuration of coating layer 20)
Next, a specific configuration of the coating layer 20 will be described with reference to Fig. 5. Fig. 5 is a schematic enlarged view of the V portion shown in Fig. 2.

As shown in FIG. 5, the coating layer 20 has at least a hard layer 21. The hard layer 21 may have one or more metal nitride layers. The hard layer 21 is a layer that has superior wear resistance compared to the metal layer 22. The hard layer 21 may be a single layer. Alternatively, multiple metal nitride layers may be overlapped. Alternatively, the hard layer 21 may have a laminated portion 23 in which multiple metal nitride layers are laminated, and a third metal nitride layer 24 located on the laminated portion 23. The configuration of the hard layer 21 will be described later.

(Metal layer 22)
The coating layer 20 may also have a metal layer 22. The metal layer 22 may be located between the substrate 10 and the hard layer 21. Specifically, the metal layer 22 may be in contact with the substrate 10 on one surface and in contact with the hard layer 21 on the other surface.

The metal layer 22 has higher adhesion to the substrate 10 than the hard layer 21. Examples of metal elements having such properties include Zr, V, Cr, W, Al, Si, and Y. The metal layer 22 contains at least one of the above metal elements.

Note that elemental Ti, elemental Zr, elemental V, elemental Cr, and elemental Al are not used as the metal layer 22. These elements all have low melting points and low oxidation resistance, making them unsuitable for use in cutting tools. Also, elemental Hf, elemental Nb, elemental Ta, and elemental Mo have low adhesion to the substrate 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. Such a metal layer 22 has particularly high adhesion to the substrate 10, and is therefore highly effective in improving adhesion between the substrate 10 and the coating layer 20.

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

The metal layer 22 may contain components other than the above metal elements (Zr, V, Cr, W, Al, Si, Y). However, from the viewpoint of adhesion to the substrate 10, the metal layer 22 may contain at least 95 atomic % or more of the above metal elements in total. More preferably, the metal layer 22 may contain at least 98 atomic % or more of the above metal elements in total. For example, when the metal layer 22 is an Al-Cr alloy layer, the metal layer 22 may contain at least Al and Cr in total at 95 atomic % or more. Furthermore, the metal layer 22 may contain at least Al and Cr in total at 98 atomic % or more. The proportion of the metal components in the metal layer 22 can be determined, for example, by analysis using EDS (energy dispersive X-ray spectrometry).

In addition, since Ti has poor wettability with the substrate 10 according to the embodiment, it is preferable that the metal layer 22 contains as little Ti as possible from the viewpoint of improving adhesion with the substrate 10. Specifically, the Ti content in the metal layer 22 may be 15 atomic % or less.

In this way, in the insert 1 according to the embodiment, the metal layer 22, which has higher wettability with the base 10 than the hard layer 21, is provided between the base 10 and the hard layer 21, thereby improving the adhesion between the base 10 and the coating layer 20. In addition, since the metal layer 22 also has high adhesion with the hard layer 21, the hard layer 21 is unlikely to peel off from the metal layer 22.

The cBN used as the base 10 is an insulator. As an insulator, there is room for improvement in the adhesion of cBN to films formed by physical vapor deposition (PVD). In contrast, in the insert 1 according to the embodiment, a conductive metal layer 22 is provided on the surface of the base 10, so that the adhesion between the hard layer 21 formed by PVD and the metal layer 22 is high.

(Hard layer 21)
Next, the configuration of the hard layer 21 will be described with reference to Fig. 6. Fig. 6 is a schematic enlarged view of part VI shown in Fig. 5.

As shown in FIG. 6, 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 laminated portion 23 has a plurality of first metal nitride layers 23a and a plurality of second metal nitride layers 23b. The laminated portion 23 has a configuration in which the first metal nitride layers 23a and the second metal nitride layers 23b are alternately laminated.

The thickness of the first metal nitride layer 23a and the second metal nitride layer 23b may each 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 or cracking of the first metal nitride layer 23a and the second metal nitride layer 23b is less likely to occur, and the durability of the coating layer 20 is high.

The first metal nitride layer 23a is a layer in contact with 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 the metal contained in the metal layer 22.

For example, suppose that metal layer 22 contains two types of metals (here, "first metal" and "second metal"). In this case, first metal nitride layer 23a contains nitrides of the first metal and a third metal. The third metal is a metal that is not contained in metal layer 22. In addition, second metal nitride layer 23b contains nitrides of the first metal and a second metal.

For example, in an 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. Also, the second metal nitride layer 23b may be an AlCrN layer containing AlCrN, which is a nitride of Al and Cr.

In this way, by positioning the first metal nitride layer 23a containing the metal contained in the metal layer 22 on the metal layer 22, 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, and therefore the durability of the coating layer 20 is high.

The first metal nitride layer 23a, i.e., the AlTiN layer, has excellent adhesion to the metal layer 22, as described above, and also has excellent wear resistance. The second metal nitride layer 23b, i.e., the AlCrN layer, has excellent heat resistance and oxidation resistance, for example. In this way, the coating layer 20 includes the first metal nitride layer 23a and the second metal nitride layer 23b, which have different compositions, and thus the properties of the hard layer 21, such as wear resistance and heat resistance, can be controlled. This can extend the tool life of the insert 1. For example, in the hard layer 21 according to the embodiment, mechanical properties such as adhesion to the metal layer 22 and wear resistance can be improved while maintaining the excellent heat resistance of AlCrN.

The laminated portion 23 may be formed by, for example, an arc ion plating method (AIP method). The AIP method is a method in which a target metal (here, an AlTi target and an AlCr target) is evaporated by using an arc discharge in a vacuum atmosphere, and then combined with _N2 gas to form a metal nitride (here, AlTiN and AlCrN). The metal layer 22 may also be formed by the AIP method.

The third metal nitride layer 24 may be located on the laminated portion 23. Specifically, the third metal nitride layer 24 contacts the second metal nitride layer 23b of the laminated 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 thicker than the thicknesses of the first metal nitride layer 23a and the second metal nitride layer 23b. Specifically, when the thicknesses of the first metal nitride layer 23a and the second metal nitride layer 23b are 50 nm or less as described above, 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 friction coefficient of the third metal nitride layer 24 is low, the adhesion resistance of the insert 1 can be improved. Also, for example, when the hardness of the third metal nitride layer 24 is high, the wear resistance of the insert 1 can be improved. Also, for example, when the oxidation onset temperature of the third metal nitride layer 24 is high, the oxidation resistance of the insert 1 can be improved.

The thickness of the third metal nitride layer 24 may be thicker than the thickness of the laminated portion 23. Specifically, in the embodiment, when the thickness of the laminated 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 laminated portion 23 is 0.3 μm, the thickness of the third metal nitride layer 24 may be 1.2 μm. In this way, by making the third metal nitride layer 24 thicker than the laminated portion 23, the effect of improving the above-mentioned adhesion resistance, wear resistance, etc. 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 thinner than the laminate portion 23.

<Cutting tools>
Next, a configuration of a cutting tool including the above-mentioned insert 1 will be described with reference to Fig. 7. Fig. 7 is a front view showing an example of a cutting tool according to an embodiment.

As shown in FIG. 7, the cutting tool 100 according to the embodiment has an insert 1 and a holder 70 for fixing the insert 1.

The holder 70 is a rod-shaped member that extends from a first end (the upper end in FIG. 7) to a second end (the lower end in FIG. 7). The holder 70 is made of, for example, steel or cast iron. Of these materials, it is particularly preferable to use steel, which has high toughness.

The holder 70 has a pocket 73 at the end on the first end side. The pocket 73 is the portion where the insert 1 is attached, and has a seating surface that intersects with the rotation direction of the workpiece and a restraining side surface that is inclined relative to the seating surface. The seating surface has a screw hole into which a screw 75, which will be described later, is screwed.

The insert 1 is located in the pocket 73 of the holder 70 and is attached to the holder 70 by a screw 75. That is, the screw 75 is inserted into the through hole 5 of the insert 1, and the tip of the screw 75 is inserted into a screw hole formed in the seating surface of the pocket 73 to screw the threaded portions together. As a result, the insert 1 is attached to the holder 70 so that the cutting edge portion 3 protrudes outward from the holder 70.

In the embodiment, a cutting tool used for so-called turning is exemplified. Examples of turning include internal diameter machining, external diameter machining, and grooving. Note that cutting tools are not limited to those used for turning. For example, the insert 1 may be used in a cutting tool used for milling.

For example, cutting of a workpiece includes (1) a step of rotating the workpiece, (2) a step of bringing the cutting edge 11 of the insert 1 into contact with the rotating workpiece to cut the workpiece, and (3) a step of removing the insert 1 from the workpiece. Representative examples of the material of the workpiece include carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metals.

(Example)
Next, an example of a manufacturing method of the insert 1 will be described. Here, an example of a manufacturing method in the case where the base body 10 is made of cBN will be described. First, TiN raw material powder of 72 vol% to 82 vol%, Al raw material powder of 13 vol% to 23 vol%, _{and Al2O3} raw material powder of 1 vol% to 11 vol% are prepared. Then, an organic solvent is added to each of the prepared raw material powders. As the organic solvent, alcohols such as acetone and isopropyl alcohol (IPA) can be used. Then, the materials are crushed and mixed in a ball mill for 20 hours to 24 hours. After crushing and mixing, the solvent is evaporated to obtain a first mixed powder.

Next, cBN powder with an average particle size of 2.5 μm to 4.5 μm and cBN powder with an average particle size of 0.5 μm to 1.5 μm are mixed in a volume ratio of 8 to 9:1 to 2.0. An organic solvent is then added. As the organic solvent, alcohols such as acetone and IPA can be used. The mixture is then pulverized and mixed in a ball mill for 20 to 24 hours. After pulverization and mixing, the solvent is evaporated to obtain a second mixed powder.

Next, the first mixed powder and the second mixed powder are mixed in a volume ratio of 68 to 78:22 to 32. An organic solvent and an organic binder are added to the mixed powder. As the organic solvent, alcohols such as acetone and IPA can be used. As the organic binder, paraffin, acrylic resin, etc. can be used. After that, the mixture is pulverized and mixed in a ball mill for 20 to 24 hours, and then the organic solvent is evaporated to obtain a third mixed powder. In addition, a dispersant may be added as necessary in the process using the ball mill.

Then, this third mixed powder is molded into a predetermined shape to obtain a molded body. For molding, known methods such as uniaxial pressing and cold isostatic pressing (CIP) can be used. This molded body is heated to a predetermined temperature in the range of 300°C to 600°C to evaporate and remove the organic binder.

Next, the compact is placed in an ultra-high pressure heating device and heated at 1200°C to 1500°C for 15 minutes to 30 minutes under a pressure of 4 GPa to 6 GPa. This produces a cubic boron nitride sintered body according to the embodiment. The resulting cubic boron nitride sintered body is then attached to the seat of a tip body made of cemented carbide via a bonding material.

Next, a coating layer 20 is formed on the surface of the chip by physical vapor deposition (PVD). The coating layer 20 is then treated with AeroWrap (registered trademark) under the conditions shown below to produce inserts according to Example 1 and Comparative Examples 3 to 5. Comparative Example 1 is an insert in which the coating layer 20 was not treated with AeroWrap (registered trademark), and Comparative Example 2 is a commercially available insert.

<AeroWrap (registered trademark) treatment conditions>
Equipment: AeroWrap (registered trademark) manufactured by Yamashita Works
Media: Multi-cone Media diameter: 0.1-0.5mm
Wing inverter frequency: 40Hz
Spray time: 0 seconds (no treatment, Comparative Example 1), 5 seconds (Comparative Example 2), 10 seconds (Example 1), 15 seconds (Comparative Example 3)
Wet/Dry: Wet

The media is sprayed by the rotation of the blades. The rotation speed of the blades is controlled by an inverter to 40 Hz (40 rotations per second).

The surface roughness of the third surface 9 was measured for the inserts according to Example 1 and Comparative Examples 1 to 5. For example, a shape analysis laser microscope VK-X1000 manufactured by KEYENCE was used for the surface roughness measurement. As specific measurement conditions, when the third surface 9 was observed from a direction perpendicular to the third surface 9, an area surrounded by 750 μm in a direction parallel to the first surface 6 and 300 μm in a direction perpendicular to the first surface 6 was scanned with a red semiconductor laser having a wavelength of 661 nm. After that, five roughness curves were extracted in the direction parallel to the first surface 6 at a measurement distance of 0.4 mm in the center of the third surface 9 within the measurement area, and the roughness curves of the five measured points were combined to obtain one roughness curve. The arithmetic surface roughness (Ra) and ten-point surface roughness (Rz) were measured from the obtained roughness curve.

Figure 8 shows the measurement results of the average arithmetic surface roughness Ra of the third surface 9. Figure 8 shows the average arithmetic surface roughness Ra1 in the direction D1 parallel to the ridge line 8 on the third surface 9 and the average arithmetic surface roughness Ra2 in the direction D2 perpendicular to the ridge line 8 on the third surface 9 for Example 1 and Comparative Examples 1 to 5.

As shown in Figure 8, the average arithmetic surface roughness Ra1 of the inserts according to Comparative Examples 1 to 4 was greater than 0.20 μm, whereas the average arithmetic surface roughness Ra1 of the inserts according to Example 1 and Comparative Example 5 was less than 0.20 μm.

In addition, for the insert of Example 1, the difference between the average arithmetic surface roughness Ra1 and the average arithmetic surface roughness Ra2 was 0.1 μm or less. Specifically, Ra1 was greater than Ra2, and the difference (Ra1-Ra2) was 0.01 μm or more and 0.025 μm or less.

Figure 9 shows the results of measuring the ten-point average surface roughness Rz of the third surface 9. Figure 9 shows the ten-point average surface roughness Rz1 in the direction D1 parallel to the ridgeline 8 on the third surface 9 and the ten-point average surface roughness Rz2 in the direction D2 perpendicular to the ridgeline 8 on the third surface 9 for Example 1 and Comparative Examples 1 to 5.

As shown in Figure 9, the ten-point average surface roughness Rz1 of the inserts according to Comparative Examples 1 to 5 was greater than 1.5 μm, whereas the ten-point average surface roughness Rz1 of the insert according to Example 1 was 1.5 μm or less.

In addition, for the insert of Example 1, the difference between the ten-point average surface roughness Rz1 and the ten-point average surface roughness Rz2 was 0.2 μm or less. Specifically, Rz1 was larger than Rz2, and the difference (Rz1-Rz2) was 0.1 μm or more and 0.20 μm or less.

In addition, wear resistance tests and chipping resistance tests were conducted on the inserts of Example 1 and Comparative Examples 1, 3, and 4 under the following conditions.

<Fracture resistance test>
Work material: SCr420
Cutting speed: 160 m/min Feed: 0.2 mm/rev
Cutting depth: 0.2 mm
Cutting condition: Dry Evaluation method: Number of impacts until chipping

Figure 10 is a graph showing the results of a wear resistance test for the inserts according to Example 1 and Comparative Examples 1, 3, and 4. Also, Figure 11 is a graph showing the results of a chipping resistance test for the inserts according to Example 1 and Comparative Examples 1, 3, and 4.

As shown in Figures 10 and 11, the insert according to Example 1 has the same wear resistance and chipping resistance as the insert according to Comparative Example 1, i.e., the insert not subjected to AeroWrap (registered trademark) treatment. It is also found that the inserts according to Comparative Examples 3 and 4 have the same wear resistance and chipping resistance as the insert not subjected to AeroWrap (registered trademark) treatment. Note that the insert according to Comparative Example 5, i.e., the insert exposed to the media for 30 seconds in the AeroWrap (registered trademark) treatment, had the same chipping resistance as the insert according to Comparative Example 1, but its wear resistance was worse.

The reason for the deterioration of the wear resistance of the insert in Comparative Example 5 is believed to be that the thickness of the coating layer located at the corner of the boundary between the second and third surfaces became too thin due to the media exposure time being set to 30 seconds. In contrast, the insert in Example 1 had good wear resistance because the media exposure time was limited to 10 seconds, which prevented the thickness of the coating layer located at the corner of the boundary between the second and third surfaces from becoming too thin.

Further, the surface roughness of the finished surface of the workpiece used in the above-mentioned wear resistance test was measured.
<Measurement conditions>
Measuring device: Olympus LEXT OLS4000
Measurement length: 4.0 mm
Cutoff value: 0.8 mm
Scanning speed: 0.6 mm/sec

The workpiece cut using the insert according to Example 1 had a smaller finished surface roughness than the workpiece cut using the insert according to Comparative Example 1. In addition, the workpiece cut using the insert according to Example 1 had a smaller finished surface roughness than the workpiece cut using the insert according to Comparative Example 3 and the workpiece cut using the insert according to Comparative Example 4.

For the inserts of Example 1 and Comparative Example 1, the residual stress of the second coating layer was measured under the following conditions. Residual stress measurements were performed for the first coating layer at a position 0.8 mm away from the cutting edge of the cutting edge toward the center of the insert. For the second coating layer, measurements were performed at a position 1.3 mm away from the cutting edge of the cutting edge in a direction parallel to the first surface and 0.5 mm away from the cutting edge in a direction perpendicular to the first surface. The residual stress value was determined by averaging the residual stress values of the first coating layer in two mutually perpendicular directions, and the residual stress values of the second coating layer in directions parallel and perpendicular to the first surface, which were determined as σ1 and σ2, respectively.

<Conditions for residual stress measurement>
Equipment: Bruker Japan D8 Discover Plus IμS
Radiation source: CuKα
Collimator diameter: 0.3 mm
Measured diffraction line: TiAlN (311) plane, 2θ = 75.5°
Measurement method: 2D method

Figure 12 is a table showing the results of residual stress measurements on the second coating layer of the inserts according to Example 1 and Comparative Example 1. Note that Figure 12 also shows the results of measuring the surface roughness of the third surface of the inserts according to Example 1 and Comparative Examples 1 to 3, along with the results of measuring the residual stress on the second coating layer of the inserts according to Example 1 and Comparative Example 1. The results of the surface roughness measurements are similar to those shown in Figures 8 and 9.

As shown in Figure 12, in the insert of Example 1, σ1 was a compressive stress of -1050 MPa or more and -750 MPa or less, and σ2 was a compressive stress of -1400 MPa or more and -1100 MPa or less. In contrast, σ2 of the insert of Comparative Example 1 was outside the range of -1400 MPa or more and -1100 MPa or less.

<Other embodiments>
In the above-described embodiment, the insert 1 has been described in which the base 10 made of boron nitride particles or the like is attached to the tip body 2 made of cemented carbide or the like, and these are coated with the coating layer 20. However, the insert according to the present disclosure may be, for example, a hexahedral base whose upper and lower surfaces are parallelogram-shaped, and the entire base is made of a cubic boron nitride sintered body, with a coating layer formed on top of the base.

In the above embodiment, an example was shown in which the shape of the upper and lower surfaces of the insert 1 is a parallelogram, but the shape of the upper and lower surfaces of the insert 1 may be a rhombus, a square, or the like. In addition, the shape of the upper and lower surfaces of the insert 1 may be a triangle, a pentagon, a hexagon, or the like.

The shape of the insert 1 may be either positive or negative. The positive type is a type in which the side surface is inclined relative to a central axis passing through the center of the upper surface and the center of the lower surface of the insert 1, and the negative type is a type in which the side surface is parallel to the central axis.

In the above embodiment, an example in which the substrate 10 contains particles of cubic boron nitride (cBN) has been described. The substrate disclosed in the present application may contain particles of hexagonal boron nitride (hBN), rhombohedral boron nitride (rBN), wurtzite boron nitride (wBN), or the like. The substrate 10 is not limited to boron nitride, and may be, for example, a cemented carbide or a cermet. The cemented carbide contains W (tungsten), specifically WC (tungsten carbide). The cemented carbide may contain Ni (nickel) or Co (cobalt). The cermet contains, for example, Ti (titanium), specifically TiC (titanium carbide) or TiN (titanium nitride). The cermet may contain Ni or Co.

In the above embodiment, the insert 1 is described as being used for cutting processing, but the insert according to the present application can also be used in tools other than cutting tools, such as drilling tools and blades.

Further advantages and modifications may readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and equivalents thereof.

REFERENCE SIGNS LIST 1 Insert 2 Tip body 3 Cutting edge portion 4 Seat surface 5 Through hole 6 First surface 7 Second surface 8 Ridge line portion 9 Third surface 10 Base body 11 Cutting edge 20 Coating layer 21 Hard layer 22 Metal layer 23 Laminated portion 23a First metal nitride layer 23b Second metal nitride layer 24 Third metal nitride layer 100 Cutting tool 201 First coating layer 202 Second coating layer 203 Third coating layer

Claims (6)

A substrate made of any one of a cemented carbide, a cermet, a boron nitride sintered body, and a ceramic;
a coating layer overlying the substrate;
having
The substrate is
a first surface having a rake surface;
a second surface having a flank surface;
a ridge portion located between the first surface and the second surface ;
A cutting edge located at least part of the ridge line portion;
having
The cutting edge has at least a portion having a third surface,
When the average arithmetic surface roughness Ra of the third surface in a direction parallel to the ridge line portion is Ra1, the Ra1 is 0.20 μm or less,
When the average arithmetic surface roughness Ra of the third surface in a direction perpendicular to the ridge line portion is Ra2, the difference between Ra1 and Ra2 is 0.1 μm or less ,
the coating layer has a first coating layer located on the first surface and a second coating layer located on the second surface,
The residual stress measured by the 2D method in the vicinity of the cutting edge of the first coating layer is σ1,
In the vicinity of the cutting edge of the second coating layer, the residual stress measured by the 2D method is σ2,
The σ1 is an average value of the residual stress σ1 ₂₂ in the direction parallel to the first surface and perpendicular to the ridge line portion and the residual stress σ1 ₁₁ in the direction perpendicular to the direction of the σ1 ₂₂ for the first coating layer,
The σ2 is an average value of the residual stress σ2 ₁₁ in a direction perpendicular to the first surface and the residual stress σ2 ₂₂ in a direction parallel to the first surface for the second coating layer,
The σ1 is −1050 MPa or more and −750 MPa or less,
The insert, wherein the σ2 is −1400 MPa or more and −1100 MPa or less. 2. The insert according to claim 1 , wherein, when a ten-point average surface roughness Rz of the third surface in a direction parallel to the ridge line portion is defined as Rz1, the Rz1 is 1.5 μm or less. 3. The insert according to claim 2 , wherein, when a ten-point average surface roughness Rz of the third surface in a direction perpendicular to the ridge line portion is Rz2, a difference between Rz1 and Rz2 is 0.2 μm or less. The coating layer is
A hard layer;
The insert according to any one of claims 1 to 3 , further comprising a metal layer other than a simple substance selected from Ti, Zr, V, Cr, Ta, Nb, Hf and Al, located between said base body and said hard layer. 5. The insert according to claim 4 , wherein the metal layer contains at least one of the following elements: Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, Y. a rod-shaped holder having a pocket at one end;
and an insert according to any one of claims 1 to 5 located in the pocket.

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