JP2005219156A - Cutting tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress abrasive wear caused by local high load by accelerating the discharge of chip in cutting to effectively prevent chip clogging. <P>SOLUTION: This cutting tool formed of cemented carbide such as a carbide solid cutting drill equivalent to a material type K10, particularly a small diameter drill with a diameter of 0.03-16 mm originally liable to cause chip clogging, is a cutting tool with a WC/C protective film provided on the surface of a diamond film coating a part including at least a cutting edge of a cutting drill or the like, by a CVD method. The WC/C protective film is preferably a film in which a carbon layer with WC in the state of being embedded in the grating of noncrystalline carbon forms a stratified film structure. The required necessary film thickness of the WC/C protective film of such a stratified film structure is 1-20 μm, and Vickers hardness is preferably less than 1000. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an improvement in a cutting tool made of a cemented carbide with a diamond coating, such as a drill.

  In the field of cutting tools such as cutting drills made of cemented carbide, high wear resistance and high durability tool performance has been obtained using a diamond film synthesized by CVD. However, the diamond film obtained by the CVD method is a film made of a polycrystalline body, and the surface thereof has a large number of irregularities of about 2 to 5 μm. There was a problem that the cutting edge was lost due to welding or clogging of chips. Such a problem was particularly remarkable in dry or semi-dry cutting.

In order to solve such problems, there has been proposed a cutting tool in which a diamond film obtained by the CVD method is further coated with a DLC film (carbon film similar to diamond) on the surface (see Patent Document 1). about). Since this is an added DLC film, the cutting edge is rounded and the sharpness is lowered, and the hardness of the DLC film itself is as high as 4000 to 5000 (Vickers hardness) equivalent to crystalline diamond. There was a phenomenon that so-called abrasive wear, in which the film was broken by a high load, caused the tool life to not extend as expected.
JP 2003-25117 A: Description of claims

  The present invention has been made to solve the above-described problems, and promotes the discharge of chips during cutting to effectively prevent clogging of chips, and suppresses abrasive wear due to local high loads. Provide cutting tools that can.

  The above problem is that a protective film made of WC and C is applied to the surface of a diamond film coated by a CVD method on at least a portion including a cutting blade of a cutting tool made of cemented carbide. This can be solved by a cutting tool.

  The protective film preferably has a layered film structure in which a carbon layer in which WC is embedded in a lattice of amorphous carbon, has a thickness of 1 to 20 μm, and has a Vickers hardness of 1000. More preferably, it is less than. Further, it is more preferable that this protective film is lapped. The present invention is preferably applied to a cutting tool which is a cutting drill having a diameter of 0.03 mm to 16 mm.

  In the cutting tool of the present invention, the protective film made of WC and C is applied to the surface of the diamond film coated with the CVD method on the portion including the cutting blade, so the low friction property (friction coefficient: 0) of this protective film. 0.1 to 0.2) can effectively promote the discharge of cutting chips and prevent clogging. Furthermore, this protective film has a hardness of about 1/4 compared with the DLC film, and it is difficult to cause defects such as cracking of the film due to a local high load, so that the abrasive wear caused by the local high load is effectively prevented. The advantage that can be suppressed was obtained. Thus, in the present invention, there is an excellent effect that the tool life can be improved by about 150% by taking advantage of the low friction and load resistance of the protective film made of WC and C. Therefore, the present invention has a very large practical value as a cutting tool that has solved the conventional problems.

Next, an embodiment according to the cutting tool of the present invention will be described.
First, the cutting tool of the present invention is intended for a cutting tool made of cemented carbide, and includes, for example, a solid carbide cutting drill equivalent to grade K10, etc., but the drill size is originally clogged with chips. Can be preferably applied by a small diameter drill having a diameter of 0.03 mm to 16 mm.

  And the most characteristic feature is that the coating structure adopts the following special double structure, and the surface of the diamond film coated by the CVD method on the part including at least the cutting blade such as a cutting drill And a protective film made of WC and C (hereinafter referred to as a WC / C protective film). In this case, the diamond film coated by the CVD method may be coated by a known ordinary method. The film thickness is preferably 6 to 20 μm.

  The WC / C protective film coated on the CVD diamond film produces a favorable result because of its low friction. In the present invention, the protective film is embedded in the lattice of amorphous carbon. It is preferable that the carbon layer in this state is a film having a layered film structure. The necessary and sufficient film thickness of the WC / C protective film having such a layered film structure is 1 to 20 μm, and the Vickers hardness is preferably less than 1000.

  In the present invention, a special effect is obtained that a defect such as cracking of the film hardly occurs at a place where a local high load is applied. This is because the WC / C protective film is the DLC film described above. Unlike a film having a Vickers hardness of 4000 to 5000, the Vickers hardness is considered to have a low hardness of less than 1000. Since it is difficult for defects due to local high loads to occur in this way, it is thought that abrasive wear due to local high loads that are likely to occur when cutting green compacts and brittle bodies can be suppressed, and tool life can be improved. is there.

  Next, a method for producing a WC / C protective film having a Vickers hardness of less than 1000 will be briefly described. A plasma accelerated PVD method using sputtering (magnetron sputtering) is suitable for the WC / C protective film. In the vacuum furnace, after etching the workpiece with argon gas, the metal which is the coating material is ionized by sputtering, released into the plasma atmosphere, reacted with the hydrocarbon gas, and deposited as a protective film on the workpiece. This processing temperature is 250 ° C. or lower.

  In this way, the WC / C protective film of the present invention can be coated on the CVD diamond film, but the obtained film surface may be left as it is. It is preferable to perform lapping with a lapping material to form a smoother surface because the friction coefficient is further reduced.

Next, the friction coefficient was measured about the Example and comparative example of this invention. The results are shown in Table 1. As compared with Comparative Example (21) CVD diamond film, Examples (1) and (2) show excellent low friction properties. Comparative Example (22) CVD diamond film + DLC film It was equivalent.
The measurement was performed by a pin-on-disk method using a 200 g vertical constant load, a pin: SUJ, and a base material: SNGN160404 carbide tip.

実施例試料１：ＣＶＤ法ダイヤモンド膜＋ＰＶＤ法ＷＣ／Ｃ膜
同じく試料２：ＣＶＤ法ダイヤモンド膜＋ＰＶＤ法ＷＣ／Ｃ膜＋ラップ加工
比較例試料２１：ＣＶＤ法ダイヤモンド膜
同じく試料２２：ＣＶＤ法ダイヤモンド膜＋ＤＬＣ膜

Example Sample 1: CVD method diamond film + PVD method WC / C film Same sample 2: CVD method diamond film + PVD method WC / C film + lapping comparative example Sample 21: Same as CVD method diamond film Sample 22: CVD method diamond film + DLC film

  A drilling life test was conducted under the following conditions for Examples and Comparative Examples of the present invention for carbide cutting drills. The results are shown in Table 2. According to this, all of the examples of the present invention could be used without any defects at 270 holes. Further, during that time, the discharge of the chips was good, and the abrasion of the blade edge and the peeling of the WC / C coating on the flute were not observed.

  Moreover, it was found that the working life of the example was 1.5 times longer than that of Comparative Example 21 (CVD diamond film). Further, Comparative Example 22 (CVD diamond film + DLC film) had a lifetime of 210 holes, but the DLC film on the blade flank, which is often seen in abrasive wear, is largely missing. Exfoliation was observed in a wide range. Chipping occurs in the peeled portion, and a phenomenon that the drill is lost therefrom is observed. It was found that the present invention is superior in these respects.

比較例試料２０：被覆膜なし。試料２１、２２は前記に同じ。
寿命比較：前記試験条件における欠損が生じた穴あけ回数で示す。

Comparative sample 20: No coating film. Samples 21 and 22 are the same as described above.
Lifespan comparison: Shown by the number of drilling in which defects occurred in the test conditions.

The test conditions were as follows.
Drill dimensions: 0.5φ × 8 × 40mm
Workpiece: Compact powder before firing with cemented carbide Workpiece dimensions: 50 x 8 x 80 mm
Machining content: 0.5φ × 5.0mm blind hole drilling machine: FANAUC α-T14iD
Rotation speed: 1500 RPM
Feeding speed: 100m / min
Feed amount: 0.3mm / rev

Claims (5)

  A cutting tool characterized in that a protective film made of WC and C is applied to the surface of a diamond film coated with a CVD method on at least a portion including a cutting blade of a cutting tool made of cemented carbide.   The cutting tool according to claim 1, wherein the protective film has a layered film structure in which a carbon layer in which WC is buried in a lattice of amorphous carbon.   The cutting tool according to claim 2, wherein the protective film has a thickness of 1 to 20 µm and a Vickers hardness of less than 1000.   The cutting tool according to claim 2 or 3, wherein the protective film is lapped. The cutting tool according to claim 4, wherein the cutting tool is a cutting drill having a diameter of 0.03 mm to 16 mm.