JP2016175141A - Cutting tool with hard carbon coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress both of decrease of sharpness and decrease in strength of a blade edge due to abrasion by making a tool angle of a cutting edge by the hard carbon coating small even while increasing a curvature radius of the tip of a base material.SOLUTION: A twist drill 1 (cutting tool with hard carbon coating) is formed with a cutting edge 10 by a rake face 21 and a flank face 22 in which the rake face 21 and the flank face 22 are formed by polishing the hard carbon coating 12. A curvature radius R1 of the tip of a base material 11 is formed in 10 μm or more and 20 μm or less. The rake face 21 is formed by polishing a portion of the base material 11 along with the hard carbon coating 12. The flank face 22 is formed by polishing only the hard carbon coating 12 without exposing the base material 11. A blade angle α of the cutting edge 10 formed by the rake face 21 and the flank face 22 is formed in 50° or more and 90° or less. A distance v from the tip working point (a) of the cutting edge 10 to the exposed part 23 of the base material 11 is formed in 12 μm or more and 35 μm or less.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a cutting tool such as a drill or an end mill used for material processing, and relates to a cutting tool with a hard carbon coating in which a hard carbon coating is coated on the surface of a substrate.

Cutting tools with a hard carbon coating in which a hard carbon coating such as CVD diamond is coated on the surface of a cemented carbide base material are widely used in industrial applications. In such a cutting tool with a hard carbon coating, when the thickness of the hard carbon coating is increased, the tool life due to wear of the blade is extended, but the curvature radius of the cutting edge is increased by the hard carbon coating. For this reason, it becomes easy to peel a coating film by the fall of processing quality, or the raise of cutting resistance. In particular, in the drilling of carbon fiber reinforced plastic (CFRP), the amount of burrs increases.
Therefore, as a countermeasure, there has been proposed a method of sharply forming the cutting edge by polishing the hard carbon coating on the tool cutting edge.

For example, Patent Document 1 describes that after a super-hard film made of diamond and / or diamond-like carbon is formed on a substrate, the diamond film on the rake face side is removed by polishing to finish it smoothly. Has been. Patent Document 2 describes that at least the edge of the cutting edge and the surface of the diamond coating layer on the flank near the edge are polished and smoothed without being exposed. In Patent Document 3, a diamond film is coated on the blade part of a base material (a cemented carbide base material), the rake face side of the blade part is polished, and the diamond film on the flank side is removed by polishing. Is described.
Patent Document 4 describes that at least the flank side of the cutting edge of the cutting edge is ground so that the surface roughness is superior to that of diamond coating. Furthermore, Patent Document 5 describes that a tip polishing portion refracted in two steps is provided by polishing the surface of a diamond coating provided on the blade portion, and the tip portion of the blade portion is sharpened.

Japanese Patent Laid-Open No. 7-60509 Japanese Patent Laid-Open No. 3-190605 Japanese Patent Laid-Open No. 3-67602 Japanese Patent No. 3477182 Japanese Patent No. 5597327

However, in the methods described in Patent Documents 1 to 3, since the entire diamond film on the flank face and the rake face is uniformly and thinly polished, the processing volume of the diamond film becomes large and the processing time is long. . In addition, when the diamond film is thin, it is not possible to secure a polishing allowance for sufficiently sharpening the cutting edge, so it is necessary to form a thick film in the state before polishing, which may reduce the production efficiency. It becomes a problem.
On the other hand, in the method of Patent Document 4 or 5, since only the cutting edge is locally sharpened, the processing time and production efficiency are not a problem, but the angle of the cutting edge becomes obtuse. For this reason, although the curvature radius of the cutting edge is small and sharpness is good at the initial stage of cutting, there is a problem that the sharpened effect is lost immediately because the amount of increase in the curvature radius of the cutting edge due to the wear of the cutting edge is large.
Therefore, it is conceivable to try to solve these problems by reducing the radius of curvature of the cutting edge of the base material so that a sharp cutting edge angle can be obtained even if the hard carbon coating is sharpened. When the curvature radius of the cutting edge of the base material is reduced, the toughness of the cutting edge is lowered, so that the cutting edge is easily damaged.

  The present invention has been made in view of such circumstances, and while the radius of curvature of the tip of the base material is increased, the blade angle of the cutting edge portion by the hard carbon coating can be reduced, and the sharpness is reduced due to wear. An object of the present invention is to provide a cutting tool with a hard carbon coating that can suppress both the reduction of the cutting edge strength and the cutting edge strength.

  The present invention is a cutting tool with a hard carbon film, wherein the surface of the substrate is coated with a hard carbon film, the rake face and the flank are formed by polishing the hard carbon film, the rake surface A cutting edge is formed by the flank and the curvature radius of the tip of the substrate is 10 μm or more and 20 μm or less, and the rake surface polishes part of the substrate together with the hard carbon coating The flank is formed by polishing only the hard carbon film without exposing the base material, and the blade angle of the cutting edge portion formed by the rake face and the flank is It is formed at 50 ° or more and 90 ° or less, and the distance from the tip action point of the cutting blade portion to the exposed portion of the base material is formed at 12 μm or more and 35 μm or less.

Even if the curvature radius of the tip of the substrate is increased by polishing the hard carbon film uniformly coated on the surface of the substrate until the part of the substrate is exposed to form a rake face. The blade angle of the cutting edge can be made small, and the tip (cutting edge) of the cutting edge can be sharpened. Thereby, since cutting resistance at the time of processing of a work material can be made small, sharpness improves and processing quality can be improved. Furthermore, by exposing a part of the substrate near the cutting edge, the residual stress of the hard carbon coating is relieved, and as a result, the occurrence of peeling of the hard carbon coating during cutting is reduced, thereby improving the tool life. Is obtained.
In addition, when the work material is processed, wear of the cutting edge gradually progresses, so that the tip of the cutting edge becomes round and the radius of curvature gradually increases. Since the blade angle is formed small by the flank and the rake face, the rate of increase in the radius of curvature at the tip of the cutting edge due to wear of the hard carbon coating at the tip of the cutting edge can be kept small. Furthermore, about the base material, the curvature radius is formed large and the rigidity is improved. For this reason, it is possible to prevent the cutting edge part from being lost and the cutting edge part from being damaged together with the base material.
In addition, the flank compared to the rake face is in contact with the work material even at a position away from the tip action point of the cutting edge during machining of the work material. For this reason, the flank is easily worn by sliding with the work material. Therefore, in the cutting tool with a hard carbon coating of the present invention, the rake face is processed until the base material is exposed, but the flank face is ensured to be covered with the hard carbon coating.
Thus, in the cutting tool with a hard carbon coating of the present invention, the hard carbon coating is polished until a part of the substrate is exposed to form a rake face, thereby increasing the curvature radius of the tip of the substrate. While forming, since the blade angle of the cutting edge portion by the hard carbon coating can be formed small, it is possible to suppress both the reduction of the sharpness due to wear and the reduction of the strength of the blade edge, it is possible to maintain a good sharpness, Long tool life can be achieved.

In the cutting tool with a hard carbon coating according to the present invention, the tip of the cutting edge part may form an arcuate corner part that connects between the rake face and the flank face.
By cutting the tip of the cutting edge part into a circular arc shape, chipping and chipping of the cutting edge can be prevented.

In the cutting tool with a hard carbon coating according to the present invention, a chamfered portion may be provided at the tip of the cutting edge portion.
By providing a chamfered portion (chamfer), chipping and chipping of the blade edge can be prevented.

In the cutting tool with a hard carbon coating of the present invention, the thickness of the hard carbon coating is 10 μm or more and 25 μm or less.
If the hard carbon film is less than 10 μm, there is little polishing allowance, it is difficult to achieve both the exposure of the flank face and the reduction of the blade angle, and the tool life is small due to the small volume of the film near the corner after polishing. There are problems such as shortening. On the other hand, when the hard carbon film exceeds 25 μm, there is a problem that the hard carbon film is likely to be peeled off because the crystal grains become coarse, and a film formation time is required.

  According to the present invention, the hard carbon coating is polished until a part of the base material is exposed to form a rake face, thereby forming a cutting radius by the hard carbon coating while forming a large radius of curvature at the tip of the base material. Therefore, it is possible to suppress both a reduction in sharpness and a reduction in blade edge strength due to wear.

It is the schematic of the tool front-end | tip part of the twist drill which concerns on this invention. It is principal part sectional drawing of the front-end | tip of the cutting blade part of the twist drill enclosed with the dashed-two dotted line shown in FIG. FIG. 2 is a cross-sectional view of a main portion of a tip of a twist drill surrounded by an alternate long and two short dashes line shown in FIG. 1, (a) before machining the workpiece and (b) cutting the workpiece by machining the workpiece. The worn state, (c) shows a state in which the wear of the cutting edge has progressed further than the state of (b). It is a figure explaining other embodiment of this invention, (a)-(b) are all principal part sectional drawings of the front-end | tip of the cutting blade part of a twist drill.

Hereinafter, embodiments of a cutting tool with a hard carbon coating according to the present invention will be described with reference to the drawings.
As shown in FIG. 1, the cutting tool with a hard carbon coating according to the present embodiment has a tool tip 2 that is rotated around an axis, and a pair of cutting edges 10 are provided around the tool tip 2. This is a two-blade twist drill 1 that is disposed at a position that is 180 ° apart in the direction and that has two twisted grooves 20 inside the cutting edge portion 10.

  The tool tip 2 of the twist drill 1 is coated with a hard carbon film 12 on the surface of the base material 11 as shown in FIG. A hard material such as cemented carbide, cermet, and high speed steel can be suitably used for the base material 11. The hard carbon film 12 may be a high-hardness carbon film such as a polycrystalline diamond film, an amorphous carbon film (diamond-like carbon (DLC)), or tetrahedral amorphous carbon (TAC). And the preferable film thickness of the hard carbon film 12 shall be 10 micrometers or more and 25 micrometers from a viewpoint of prevention of film | membrane peeling and abrasion resistance.

  The twist drill 1 of the present embodiment is obtained by coating the surface of a base material 11 made of a cemented carbide with a hard carbon coating 12 made of a polycrystalline diamond film, and the hard carbon coating 12 is formed on the surface of the base material 11. The film is coated with a substantially constant film thickness of about 15 μm, that is, uniformly.

  In addition, for the coating of the hard carbon film 12 on the base material 11, for example, a known method such as a microwave plasma CVD method, a hot filament CVD method, a high frequency plasma CVD method, or the like can be suitably used. Other coating methods can also be applied.

  As described above, in the cutting edge portion 10 of the twist drill 1 coated with the hard carbon coating 12, the hard carbon coating 12 is coated around the base material 11 with a constant film thickness as shown by a broken line in FIG. . For this reason, the curvature radius R2 of the tip of the cutting edge portion 10 coated with the hard carbon coating 12 is larger than the curvature radius R1 of the tip of the substrate 11 by the film thickness of the hard carbon coating 12. Then, by polishing the hard carbon film 12 coated on the surface of the base material 11 in this way, the rake face 21 and the flank face 22 are formed, and the rake face 21 and the flank face 22 form the cutting edge portion 10. Is formed.

The curvature radius R1 of the tip of the substrate 11 is formed to be 10 μm or more and 20 μm or less, the rake surface 21 is formed by polishing a part of the substrate 11 together with the hard carbon coating 12, and the flank 22 is It is formed by polishing only the hard carbon film 12 without exposing the substrate 11. In addition, the blade angle α of the cutting edge portion 10 formed by the rake face 21 and the flank face 22 is formed to be 50 ° or more and 90 ° or less (in the case of a twist drill, a value near the shoulder portion). The distance v from the tip action point a to the exposed portion 23 of the substrate 11 is formed to be 12 μm or more and 35 μm or less.
The rake face 21 and the flank face 22 can be polished by mechanical polishing such as an elastic grindstone, brush, sand blast, or other means such as laser processing or ion beam processing.

  In this way, a part of the base material 11 is polished together with the hard carbon coating 12 on the rake face 21 of the twist drill 1, and only the hard carbon coating 12 is polished on the flank 22, thereby cutting the cutting edge. The blade angle α of the portion 10 is provided in a sharp cross-sectional shape as shown by a solid line in FIG.

  In the twist drill 1 configured as described above, a rake face 21 is formed by polishing the hard carbon film 12 uniformly coated on the surface of the base material 11 until a part of the base material 11 is exposed. Thereby, even if the curvature radius R1 of the front-end | tip of the base material 11 is enlarged, the cutter angle (alpha) of the cutting-blade part 10 can be formed small, and the front-end | tip (cutting-blade) of the cutting-blade part 10 can be sharpened. Thereby, since cutting resistance at the time of work material processing can be made small, sharpness can improve and processing quality can be improved. Furthermore, by reducing the cutting resistance during machining of the work material, it is possible to prevent the hard carbon coating 12 from being peeled off, so that the tool life can be improved.

  Further, at the time of processing the work material, the wear of the cutting edge portion gradually proceeds, so that the tip of the cutting edge portion 10 before cutting shown in FIG. ) And (c), the tip of the cutting edge 10 is worn and rounded, and its radius of curvature R3 gradually increases. However, the tip of the cutting edge portion 10 is formed with the rake face 21 and the flank face 22 formed by polishing so that the blade angle α is previously reduced. The increase rate of the radius of curvature R3 at the tip of the cutting edge portion 10 can be kept small. Furthermore, about the base material 11, the curvature radius R1 is formed large, and rigidity is improved. For this reason, it is possible to prevent the cutting edge portion 10 from being lost and the cutting edge portion 10 from being lost together with the base material 11.

  Further, the flank 22 is in contact with the work material even at a position away from the tip action point of the cutting edge portion 10 when the work material is processed, compared to the rake face 21. For this reason, the flank 22 is easily worn by sliding with the work material. In this respect, in the twist drill 1, the rake face 21 is processed until the base material 11 is exposed, but the flank face 22 is ensured to be covered with the hard carbon film 12.

As described above, in the twist drill 1, the hard carbon coating 12 is polished until a part of the base material 11 is exposed to form the rake face 21, thereby forming a large curvature radius R <b> 1 at the tip of the base material 11. However, since the blade angle α of the cutting edge portion 10 by the hard carbon coating 12 can be formed small, it is possible to suppress both the reduction in sharpness and the reduction in cutting edge strength due to wear. Therefore, a good sharpness can be maintained in the machining of the work material, and the tool life can be increased.
In addition, the drill which coated the polycrystalline diamond film | membrane by CVD method and applied this invention like this embodiment can be used suitably for the drilling process of carbon fiber reinforced plastics (CFRP).

In the twist drill 1 of the above embodiment, as shown in FIG. 2, when the rake face 21 and the flank face 22 are polished, the hard carbon coating 12 at the tip of the cutting edge portion 10 is removed to remove the tip. Although it has a sharp shape, an arc shape connecting the rake face 21 and the flank face 22 to the tip of the cutting edge part 10A like a cutting edge part 10A of a twist drill shown in FIG. The corner portion 24 may be formed. Further, when the rake face 21 and the flank face 22 are polished like the cutting edge part 10B of the twist drill shown in FIG. 4B, the hard carbon film 12 at the tip of the cutting edge part 10B is not coated. The corner portion 25 may be formed by polishing while leaving the surface shape. As shown in FIGS. 4 (a) and 4 (b), when the tips of the cutting edge portions 10A and 10B are formed by rounding in an arc shape, the effect of preventing chipping and chipping of the cutting edge can be enhanced. .
Further, in order to obtain an effect of preventing chipping or chipping of the blade edge, a configuration in which a chamfered portion 26 (chamfer) is provided at the tip of the cutting blade portion 10C as in the cutting blade portion 10C of a twist drill shown in FIG. 4B. Is also effective.

An experiment was performed to confirm the effect of the twist drill according to the present invention described above.
For each twist drill sample, a hard carbon film made of a polycrystalline silicon diamond film is coated on the surface of a base material made of cemented carbide by a microwave plasma CVD method to a thickness of 15 μm, and then a femtosecond laser is used. The rake face and flank face were formed by laser processing. The shape of the cutting edge portion of each sample is as shown in Table 1. In addition, the curvature radius R1, the blade angle α, and the distance v in Table 1 are the dimension values of the portion related to the cutting edge as shown in FIG. The distance v was measured along the direction perpendicular to the cutting edge. Each sample has a diameter of 10 mm, a clearance angle of 10 °, and a twist angle of 15 °. Ten samples (N = 10) were prepared for each sample, and Table 1 lists the average values of the ten dimensional values.

  In Examples 1 and 2, the rake face is formed by polishing a part of the substrate together with the hard carbon film, and the flank is formed by polishing only the hard carbon film without exposing the substrate. Formed. In Comparative Examples 1 and 2, both the rake face and the flank face are formed by polishing only the hard carbon film without exposing the base material. For this reason, in Comparative Examples 1 and 2, the distance v is described as “−” in Table 1.

Then, using each of the manufactured samples, drilling (through hole) processing is performed on the surface of a work piece made of carbon fiber reinforced plastic (CFRP) having a plate thickness of 10 mm. This state was observed with a microscope, and the time when burrs were generated on the cut surface, or the time when shoulder breakage or peeling of the diamond film shown in FIG. 1 occurred was evaluated as the tool life. Note that the test was completed after processing a maximum of 200 holes. Moreover, the state of the cutting edge part at the time of this tool life was observed with the microscope.
In addition, as described above, “the number of processed holes” in Table 1 describes the result of the sample that has been drilled the most out of 10 samples each, that is, the maximum number of processed holes. did.
Cutting speed: 100 m / min
Tool feed amount per tooth: 0.07mm / tooth

As is clear from the results of Table 1, in Examples 1 and 2, 200 holes could be processed in all 10 samples, but in Comparative Examples 1 and 2, 200 holes were processed. The result reached the end of life. In other words, the number of processed holes until the end of the service life was higher in the first and second embodiments to which the present invention was applied than in the first and second comparative examples.
In Examples 1 and 2, stable drilling was possible, and the hole quality was good with almost no burrs. On the other hand, in comparison with Examples 1 and 2, Comparative Example 1 resulted in a situation in which the shoulder portion of the drill was broken about 1 mm in width and the base was broken. Further, in Comparative Example 2, the amount of burrs generated was relatively large, and burrs were generated in all drills, resulting in a lifetime without reaching 200 holes. Further, in Comparative Example 2, in the observation of the blade edge after the test, local peeling of the diamond film with a width of about several tens to several hundreds of μm was observed.

In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
For example, in the above embodiment, the twist drill has been described. However, the cutting tool with a hard carbon coating of the present invention is not limited to this, and can be applied to a rotary tool such as an end mill or a reamer.

1 Twist drill (cutting tool with hard carbon coating)
2 Tool tip 10, 10A, 10B, 10C Cutting edge 11 Base 12 Hard carbon coating 20 Torsion groove 21 Rake face 22 Relief face 23 Exposed parts 24, 25 Corner part 26 Chamfering part 30 Shoulder α Blade angle

Claims (4)

A cutting tool with a hard carbon coating in which a hard carbon coating is coated on the surface of a substrate,
By polishing the hard carbon film, a rake face and a flank face are formed, and a cutting edge part is formed by the rake face and the flank face,
The radius of curvature of the tip of the substrate is formed to be 10 μm or more and 20 μm or less,
The rake face is formed by polishing a part of the substrate together with the hard carbon film,
The flank is formed by polishing only the hard carbon film without exposing the substrate,
The blade angle of the cutting edge portion formed by the rake face and the flank face is formed to be 50 ° or more and 90 ° or less,
A cutting tool with a hard carbon coating, wherein the distance from the tip action point of the cutting edge part to the exposed part of the substrate is 12 μm or more and 35 μm or less.   2. The cutting tool with a hard carbon coating according to claim 1, wherein a tip end of the cutting edge portion is formed by an arc-shaped corner portion that connects between the rake face and the flank face.   The cutting tool with a hard carbon coating according to claim 1, wherein a chamfered portion is provided at a tip of the cutting edge portion.   4. The cutting tool with a hard carbon coating according to claim 1, wherein the hard carbon coating has a thickness of 10 μm or more and 25 μm or less. 5.

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