JP2013176817A - Drill made of diamond-coated cemented carbide having excellent wear resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drill made of diamond-coated cemented carbide having not only excellent chipping resistance but also excellent wear resistance in a long-term use in the overlap drilling or the like of CFRP and Al.SOLUTION: A drill made of diamond-coated cemented carbide includes a base body of WC-based cemented carbide mainly made of WC and Co, and containing 3-15 mass% of Co while a diamond film of an average film thickness of 5-30 μm is coated on the base body. A ratio of h1/h2 is ≥1.2 and ≤2.0 where h1 denotes the film thickness of an outer circumferential part of a cutting edge of the drill, and h2 denotes the film thickness of a chisel edge. Preferably, a value of w2 is ≥15 cm, and ≤25 cm, and a ratio w1/w2 is ≥0.5 and ≤0.9 where w1, w2 denote the half peak width of the peak around 1,333 cmat the Raman spectrometry of the outer circumferential part of the cutting edge and the chisel edge, respectively. More preferably, the ratio σ2/σ1 is ≥0.6 and ≤0.9 where σ1, and σ2 denote values of the compressive residual stress in the outer circumferential part of the cutting edge and the chisel edge, respectively.

Description

  The present invention relates to a diamond-coated cemented carbide drill that not only has excellent chipping resistance, but also exhibits excellent wear resistance over a long period of use, such as in the overlap drilling of CFRP and Al.

Conventionally, a diamond-coated cemented carbide drill in which a diamond film is coated on a base made of a tungsten carbide group (WC-based) cemented carbide is known. Since the property and wear resistance are not sufficient, various proposals have been made to improve this.

  For example, as shown in Patent Document 1, in a diamond-coated cutting tool, by increasing the average layer thickness of the diamond layer on the flank face of the cutting edge portion than that of the diamond layer on the rake face, the tool life is extended. It has been proposed to improve the processing quality for difficult-to-cut materials.

  In addition, for example, as shown in Patent Document 2, in a throwaway cutting tip made of an artificial diamond-coated cemented carbide, the thickness of the diamond coating layer is the standard thickness at the corner of the rake face of the cutting blade, and at least the chip application It has been proposed to increase the life of the tool by suppressing the peeling of the artificial diamond coating layer by making the other parts including the contact part relatively thicker than the standard thickness.

JP 2011-101910 A Japanese Patent Laid-Open No. 5-162007

In recent years, there has been a strong demand for labor saving and energy saving in the technical field of cutting work, and further cost reduction, and the versatility of cutting drills has also been demanded. When a diamond-coated drill is used for drilling difficult-to-cut materials such as CFRP alone or a composite material of CFRP and Al alloy, the wear progresses quickly, and welding occurs at the chisel edge. There have been problems such as deterioration of hole accuracy and missing cutting edges.
Further, for example, in the diamond-coated drill shown in Patent Document 1, the diamond coating thickness on the flank side is increased and the coating thickness on the rake surface side is reduced, so that the sharpness of the edge is ensured. However, since the thickness of the chisel edge portion is thick, welding occurs at that portion, and the hole accuracy is not sufficiently secured, which is a problem.
Therefore, an object of the present invention is to provide a diamond-coated drill that maintains the sharpness of the edge portion, suppresses the occurrence of welding, and ensures excellent hole accuracy and chipping resistance of the cutting edge.

In the drilling of difficult-to-cut materials such as CFRP alone or a composite material of CFRP and Al alloy, the present inventors make it difficult to cause breakage of the cutting edge and breakage of the drill, and excellent for long-term use. As a result of intensive studies to provide a diamond-coated tool that exhibits excellent wear resistance, the following findings were obtained.

That is, when forming a diamond film in a hot filament CVD apparatus, the thermal filament is brought as close as possible to the outer peripheral edge of the drill, the drill body cools the shank portion, and the temperature difference between the drill base (WC cemented carbide) As a result, the difference in supply amount of active species (methyl radicals, atomic hydrogen) for diamond film formation can be increased.
Thereby, the difference in film thickness of the diamond film between the chisel edge part and the outer peripheral part of the cutting edge can be increased, and further, the difference in film quality of the diamond film to be formed can be increased.
The inventors reduced the film thickness of the diamond at the chisel edge by reducing the film thickness of the diamond by reducing the crystallinity of the diamond by depositing the diamond by the above method. In addition, it has been found that the sharpness of the chisel edge portion can be maintained, so that it can be processed with great bite even when cutting an aluminum alloy.
On the other hand, in the outer peripheral portion of the cutting edge, it has been found that the wear resistance can be improved because the film thickness of diamond can be increased and the crystallinity can be increased.
In other words, by changing the film thickness and crystallinity of the diamond film on the chisel edge and the outer periphery of the cutting edge, a diamond-coated drill that ensures excellent hole position accuracy and at the same time exhibits excellent wear resistance over a long period of use. I found out that I could get it.

The present invention has been made based on the above findings,
“(1) Tungsten carbide-based cemented carbide containing tungsten carbide and cobalt as main components and containing 3 to 15% by mass of cobalt is used as a drill base, and an average film thickness of 5 is formed on the outer periphery of the tip of the drill base. In a diamond-coated cemented carbide drill coated with a diamond film of ˜30 μm,
Diamond coated carbide characterized in that the value of h1 / h2 is 1.2 or more and 2.0 or less when the film thickness of the outer peripheral part of the cutting edge of the drill is h1 and the film thickness of the chisel edge part is h2. Alloy drill.
(2) In the case of Raman spectroscopic measurement of the outer peripheral part and chisel edge part of the above-mentioned drill, the value of w2 is 15 cm when the half-value width of the peak centered at 1333 cm ⁻¹ derived from diamond is w1 and w2, respectively. The diamond-coated cemented carbide drill according to (1), wherein the drill is made of ^{−1 to} 25 cm ⁻¹ and w1 / w2 is 0.5 or more and 0.9 or less.
(3) When the values of the compressive residual stress at the outer peripheral portion of the cutting edge and the chisel edge portion of the drill are σ1 and σ2, respectively, the value of σ2 is 1.8 GPa or less and the value of σ2 / σ1 is 0.6. The drill made of a diamond-coated cemented carbide according to the above (1) or (2), wherein the drill is 0.9 or less. "
It is characterized by.

  Hereinafter, the present invention will be described in detail.

As a drill base of the diamond-coated drill of the present invention, WC having at least tungsten carbide (indicated by WC) as a hard phase component and Co as a binder phase component, and having a Co content of 3 to 15% by mass. Use base cemented carbide.
The Co component has an effect of improving the strength and toughness of the substrate by forming a binder phase. However, when the Co content in the WC-based cemented carbide is less than 3% by mass, no improvement in toughness can be expected. When the Co content exceeds 15% by mass, plastic deformation easily occurs and the progress of uneven wear is promoted. Therefore, the Co content in the WC-based cemented carbide is 3 to 15% by mass. It is determined.

  Further, if the thickness of the diamond film coated on the substrate surface is less than 5 μm, sufficient wear resistance cannot be exhibited over a long period of use, whereas if the diamond film thickness exceeds 30 μm, chipping is performed. Therefore, the film thickness of the diamond film was determined to be 5 to 30 μm.

In the diamond-coated drill of the present invention, as shown in FIG. 1, when the thickness of the outer peripheral portion of the cutting edge of the drill is h1, and the thickness of the chisel edge portion is h2, the value of h1 / h2 is 1.2 or more and 2 The diamond coating thickness was determined to be less than or equal to 0.0. One reason for this is that the sharpness of the chisel edge is maintained by reducing the thickness of the chisel edge. The wear resistance is maintained by relatively increasing the film thickness of the blade outer peripheral portion.
In other words, the sharpness of the chisel edge portion can be maintained by forming a relatively thin diamond film at the chisel edge portion by the film forming method described later, so that the biting at the time of cutting the aluminum alloy can be ensured. it can.
However, when the value of h1 / h2 is less than 1.2, it may be possible to ensure the biting during the cutting of the aluminum alloy, but on the other hand, the effect of extending the tool life is reduced, and h1 / h2 If the value exceeds 2.0, the amount of wear of the cutting edge near the chisel edge increases and the life is reached early. Therefore, the value of h1 / h2 is determined to be 1.2 or more and 2.0 or less.
For the measurement of the diamond film thickness at the outer peripheral part of the cutting edge and the chisel edge part, the cutting edge part is cut and SEM observation is performed, the three-point measurement of the film thickness of the target part is performed, and the average value is taken as each film thickness.
In the present invention, the “chisel edge portion” refers to “within a range of 100 μm from the center tip portion of the drill”, and the “cutting blade outer peripheral portion” refers to “within a range of 100 μm from the shoulder portion of the outer peripheral portion of the drill. ".

In the diamond-coated drill of the present invention, when Raman spectroscopic measurement was performed on the outer peripheral portion and the chisel edge portion of the drill with an Ar laser, the half-value widths of the peaks centered at 1333 cm ⁻¹ derived from diamond were w1 and w2, respectively. Sometimes, it is desirable that the value of w2 is 15 cm ⁻¹ or more and 25 cm ⁻¹ or less and the value of w1 / w2 is 0.5 or more and 0.9 or less.
This is because the crystallinity of the diamond film at the chisel edge is reduced to some extent and is relatively lower than the crystallinity at the outer periphery of the cutting edge. This is because the occurrence of welding is suppressed and wear resistance is ensured at the outer peripheral portion of the cutting edge.
That is, when the value of w2 is less than 15 cm ⁻¹ , the effect of suppressing the occurrence of welding with the work material is reduced. On the other hand, when it exceeds 25 cm ⁻¹ , the wear resistance is significantly reduced. The value of is desirably 15 cm ⁻¹ or more and 25 cm ⁻¹ or less. In addition, when the value of w1 / w2 is less than 0.5, the wear resistance decrease in the vicinity of the chisel edge portion becomes significant, while when the value of w1 / w2 exceeds 0.9, the work material is Therefore, the value of w1 / w2 is preferably 0.5 or more and 0.9 or less.
Such a value of w2 and a value of w1 / w2 can be formed by a film forming method described later.

In the diamond-coated drill of the present invention, when the compressive residual stress values at the outer peripheral portion of the cutting edge and the chisel edge portion are σ1 and σ2, respectively, the value of σ2 is 1.8 GPa or less and the value of σ2 / σ1 is 0. It is preferable to set it to 6 or more and 0.9 or less.
This is because if the value of σ2 exceeds 1.8 GPa, film peeling or the like is likely to occur due to welding of the work material. The lower limit of σ2 is not particularly set from the technical point of view, but when the value of w2 is about 25 cm ⁻¹ , the lower limit is about 1.2 to 1.4 GPa in terms of manufacturing method. Further, when the value of σ2 / σ1 is less than 0.6, wear at the chisel edge portion is likely to proceed, whereas when this value exceeds 0.9, chipping due to welding of the work material is likely to occur. Because it becomes.
Incidentally, the cutting edge outer peripheral portion, the residual compressive stress in the diamond film in the chisel edge portion can be determined by the 2θ-sin ² φ method using X-ray diffraction that the Co and bulb.

The diamond-coated drill of the present invention can be manufactured, for example, by the following method.
First, a WC-based cemented carbide drill base composed of a cemented carbide sintered body containing WC and Co as main components and containing 3 to 15% by mass of Co is manufactured, and then Co in the vicinity of the surface of the cemented carbide drill base is prepared. Is removed by chemical etching (sulfuric acid + hydrogen peroxide + water), and then inserted into a hot filament CVD device, the shank part of the drill base is cooled and supported by a water cooling jig, and the filament is near the outer periphery of the drill. The film can be manufactured by forming a diamond film while adjusting the position of the filament according to the film thickness of the diamond film to be formed.
It is also necessary to adjust the position of the filament according to the drill diameter. For example, when the drill diameter is smaller than 6 mm, the filament position is moved downward, and when the drill diameter is larger than 10 mm, It is necessary to adjust the filament position by moving it upward so that the desired film thickness is obtained.
By such a diamond film formation method, the ratio h1 / h2 of the film thickness of the outer peripheral portion of the cutting edge of the drill to the thickness of the chisel edge portion is 1.2 or more and 2.0 or less, and 1333 cm in Raman spectroscopic measurement. The ratio value w1 / w2 of the half width of the peak centered at ⁻¹ is 0.5 or more and 0.9 or less, and the ratio value σ2 / σ1 of the compressive residual stress is 0.6 or more and 0.9 or less. Certain diamond coated drills of the present invention can be manufactured.

  The diamond-coated drill of the present invention has a relatively thin diamond film thickness at the chisel edge portion as compared with the outer peripheral portion of the cutting edge, lowers the crystallinity of the diamond, and further reduces the compressive residual stress to an appropriate range. By maintaining, the occurrence of welding with the work material can be suppressed, and the sharpness of the chisel edge can be maintained, so that the hole position accuracy can be ensured and excellent over a long period of use. It exhibits wear resistance.

It is a schematic explanatory drawing near the drill center front-end | tip of the diamond covering drill of this invention.

  Next, the diamond-coated drill of the present invention will be specifically described with reference to examples.

(A) WC powder, Co powder, Cr ₃ C ₂ powder, VC powder, TaC powder, NbC powder, TiC powder, and ZrC, all having a predetermined average particle size in the range of 0.5 to 3 μm as raw material powder The powder was blended in the proportions shown in Table 1, and after further adding a binder and a solvent, mixed in a ball mill for 24 hours in acetone, dried under reduced pressure, and then press-molded at a pressure of 100 MPa. WC-based cemented carbide is obtained by sintering in a 1 Pa vacuum atmosphere at a temperature of 1380 to 1450 ° C. for 1 to 2 hours and then sintering under furnace cooling conditions. Alloy sintered bodies 1 to 5 were produced.
Next, by grinding the WC-based cemented carbide sintered bodies 1 to 5 so that the outer diameter of the groove forming portion is 8 mm, a WC-based cemented carbide drill base (hereinafter simply referred to as “drill base”). 1) to 5).

(B) Next, the drill bases 1 to 5 are immersed in an etching solution in which sulfuric acid, hydrogen peroxide, and water are mixed at 1: 1: 100 (volume ratio) for 2 to 4 seconds. Co near the surface is removed by etching to a depth of several microns.

(C) Next, the drill bases 1 to 5 are inserted into a hot filament CVD apparatus, the drill base is cooled and supported by a water cooling jig at the shank, and the filament is set at a position 5 mm from the outer periphery of the drill. An electric current is passed through the filament to a temperature of 2200 ° C., hydrogen gas and methane gas are introduced into the apparatus, and a diamond film is formed on the drill bases 1 to 5 in the atmospheric gas, whereby the present invention shown in Table 2 is formed. Diamond-coated WC-based cemented carbide drills (hereinafter simply referred to as “the drills of the present invention”) 1 to 10 were produced.

For comparison, the diamond-coated WC-based cemented carbide drills of the comparative examples shown in Table 3 (hereinafter simply referred to as “comparative example drills”) according to the steps (a) to (c) in the above manufacturing steps of the present invention drills 1 to 10. 1) to 10).
In addition, in the manufacturing method of comparative example drills 1 to 10, there is no mechanism for cooling the drill base, and therefore the distance between the drill and the filament is in the range of 10 to 15 mm in order to keep the substrate temperature properly, This is different from the production method of the present invention.

Next, for the inventive drills 1 to 10 and comparative drills 1 to 10 manufactured above, the cutting edge of the drill is cut, and the chisel edge (within a range of 100 μm from the center tip of the drill) and the outer periphery of the cutting edge (Within a range of 100 μm from the shoulder of the outer periphery of the drill) is observed with an SEM, the film thickness is measured at three points of each part, and the measured values are averaged to obtain the film thickness h1 of the outer periphery of the cutting edge The thickness h2 of the chisel edge portion was determined.
Tables 2 and 3 show the values of h1, h2, and h1 / h2.

Moreover, about the chisel edge part and cutting-blade outer peripheral part of this invention drill 1-10 and comparative example drill 1-10, the Raman spectroscopic measurement by Ar laser is performed, and the half-value width w1 of the peak centering on 1333 cm < ^-1 > derived from a diamond. , W2 was obtained.
Tables 2 and 3 show the values of w1, w2, and w1 / w2.

Moreover, about the diamond film of the chisel edge part of this invention drill 1-10 and comparative example drill 1-10, and a cutting-blade outer peripheral part, the value of each compressive residual stress is measured with the following measuring methods (three-point measurement), From the average value, the value σ1 of the compressive residual stress at the outer peripheral portion of the cutting edge and the value σ2 of the compressive residual stress at the chisel edge portion were obtained.
That is, an X-ray diffractometer is used to generate X-rays using a Co tube at a current and voltage of 40 mA, 200 kV, and the (311) peak of diamond is ψ angle by the 2θ-sin ² ψ method. Was measured by changing the angle from 0 to 39 degrees.
Tables 2 and 3 show the values of σ1, σ2, and σ2 / σ1.

Next, using the above-described drills 1 to 10 and comparative drills 1 to 10, the composite material of CFRP and Al alloy A7075 (CFRP material on the inlet side: 15 mm, Al material on the outlet side: 5 mm) under the following conditions: A drilling test was conducted.
Cutting speed: 110 m / min,
Feed: 0.12 mm / rev. ,
Hole depth: 20 mm (through hole),
In the above cutting test, in the case of normal wear, the service life was determined when the maximum flank wear width of the cutting edge exceeded 0.3 mm, and the number of drilling operations was measured.
In addition, when the service life was reached due to chipping, drill breakage, etc., the number of drilling operations so far was measured.
Table 4 shows the measurement results.

As is clear from the results of Tables 2 to 4, the drills 1 to 10 of the present invention have a relatively thin film thickness of the diamond at the chisel edge portion as compared with the outer peripheral portion of the cutting edge, and the crystallinity of the diamond. In addition, by maintaining the compression residual stress within the proper range, the occurrence of welding with the work material can be suppressed and the sharpness of the chisel edge can be maintained, so the biting to the Al alloy is maintained. For this reason, the occurrence of damage such as abnormal chipping is relatively small, and further, since the excellent wear resistance is exhibited over a long period of use, the tool life is generally prolonged.
That is, for the drills 1, 3, 5, 6, and 9 of the present invention in which all of h1 / h2, w1 / w2, and σ2 / σ1 are within the predetermined numerical range according to claims 1 to 3, the wear form is normal wear. Moreover, the number of drilling operations is all 156 holes or more, and the tool life is very long.
In addition, if one or both of w1 / w2 and σ2 / σ1 are outside the predetermined numerical range according to claims 2 and 3, the tool life will be due to chipping, but the number of drilling operations will be around 100. Thus, it is understood that the wear resistance is excellent.
On the other hand, the comparative example drills 1 to 10 have not only a small number of drilling processes (31 at the maximum) as compared with the drill of the present invention, but also chipping at the cutting edge early due to welding or the like. It is clear that abnormal damage occurs and the tool life is very short.

The diamond-coated cemented carbide drill of the present invention not only excels in chipping resistance in the overlap drilling of CFRP and Al, but also exhibits excellent wear resistance over a long period of use. It can cope with energy saving and cost reduction sufficiently satisfactorily.

Claims (3)

A tungsten carbide-based cemented carbide containing tungsten carbide and cobalt as main components and containing 3 to 15% by mass of cobalt is used as a drill base, and diamond having an average film thickness of 5 to 30 μm on the outer periphery of the tip of the drill base In a diamond-coated cemented carbide drill with a film coating,
Diamond coated carbide characterized in that the value of h1 / h2 is 1.2 or more and 2.0 or less when the film thickness of the outer peripheral part of the cutting edge of the drill is h1 and the film thickness of the chisel edge part is h2. Alloy drill. In the case of Raman spectroscopic measurement of the outer peripheral part and chisel edge part of the drill, the value of w2 is 15 cm ⁻¹ or more when the half-value widths of the peaks centered at 1333 cm ⁻¹ derived from diamond are w1 and w2, respectively. 2. The diamond-coated cemented carbide drill according to claim 1, wherein the drill is made of a diamond-coated cemented carbide according to claim 1, which has a value of 25 cm ⁻¹ or less and a w1 / w2 value of 0.5 to 0.9. When the compressive residual stress values at the outer peripheral portion and the chisel edge portion of the drill are σ1 and σ2, respectively, the value of σ2 is 1.8 GPa or less and the value of σ2 / σ1 is 0.6 or more and 0.00. The diamond-coated cemented carbide drill according to claim 1 or 2, wherein the drill is made of 9 or less.