JPH07100858B2 - Diamond coated tungsten carbide based cemented carbide cutting tool chip - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is made of a diamond-coated tungsten carbide-based cemented carbide that has a diamond coating layer with extremely high adhesive strength and therefore exhibits excellent cutting performance for an extremely long period of time. It relates to cutting tool tips.

[Prior Art] In recent years, much research has been done on forming a diamond coating layer on the surface of various types of substrates, and as a method therefor, a CVD method (chemical vapor deposition method) by thermal decomposition of a gas such as CH ₄ or a carbon ion substrate is used. Low-pressure vapor phase synthesis methods such as PVD method (physical vapor deposition method) for colliding with hydrogen have been proposed.

[Problems to be solved by the invention]

However, since the diamond coating layer formed by the above low-pressure vapor phase synthesis method has low adhesion strength to the substrate, it is currently impossible to put it into practical use as a cutting tool tip under high load. Is.

[Means for solving problems]

Therefore, from the viewpoints described above, the present inventors have formed a diamond coating layer having high adhesion strength on a substrate, and in order to enable its use as a cutting tool, tungsten carbide (hereinafter referred to as WC) is particularly used as a substrate. ) As a result of conducting research focusing on the base cemented carbide, (a) diamond nuclei are generated on the surface of the WC base cemented carbide substrate in the low pressure vapor phase synthesis method on WC, and on the Co, diamond nuclei are formed. Part of it turns into graphite.

(B) Therefore, it is preferable that the Co content as a binder phase in the WC-based cemented carbide substrate is as small as possible. However, considering that it will lead to a decrease in alloy strength if the Co content is 1 to 4 weight%. When it is set to%, the adhesion strength of the diamond coating layer is high and the strength as a cutting tool can be secured.

(C) The grain size of WC in the WC-based cemented carbide is defined as coarse grains, and 2
If the average particle size is up to 10 μm, the diamond coating layer will be formed faster and its adhesion strength will be higher.

(D) A small amount of free carbon, preferably ISO (International Standardization Organizatio), in a WC-based cemented carbide substrate.
n) If free carbon equivalent to the standard CO1 to CO8, and more desirably the same CO1 to CO4, is dispersed evenly and finely, the diamond becomes difficult to graphitize and the formed diamond coating layer becomes difficult to peel off. thing.

The findings shown in the above (a) to (d) have been obtained.

The present invention has been made based on the above findings, and has a composition containing Co: 1 to 4% by weight, the balance being substantially WC and a trace amount of free carbon, and the free carbon being finely and uniformly. Diamond-coated WC-based cemented carbide cutting formed by forming a low-pressure vapor-phase synthetic diamond coating layer on the surface of a WC-based cemented carbide substrate that has a coarse-grained structure in which WC has an average grain size of 2-10 μm It is characterized by a tool tip.

In the diamond-coated WC-based cemented carbide cutting tool tip of the present invention (hereinafter abbreviated as coated cutting tip), the Co content is limited to 1 to 4% by weight as described above. If the content is less than 1% by weight, the substrate strength required for the cutting tool tip cannot be secured. On the other hand, if the content exceeds 4% by weight, not only the formation rate of the diamond coating layer becomes slow, but also the diamond This is because some of them are graphitized, and it becomes impossible to secure the desired excellent wear resistance and adhesive strength, and the reason why the average particle size of WC is coarse particles of 2 to 10 μm is If the average particle size is less than 2 μm, not only the formation rate of the diamond coating layer becomes extremely slow as described above, but also the adhesion strength becomes low, while the WC having an average particle size exceeding 10 μm. Since the production of the cemented carbide is difficult, it is to the average particle diameter was defined as 2 to 10 [mu] m.

〔Example〕

Next, the coated cutting tip of the present invention will be specifically described by way of examples.

First, as the raw material powder, various WC powders having a predetermined average particle size within the range of 2 to 10 μm, Co powder of the same 1.2 μm, and fine carbon black are used, and these raw material powders are blended to a predetermined blending composition. Then, after mixing under normal conditions,
It is press-molded, sintered (sintering temperature: a predetermined temperature within the range of 1430 to 1500 ° C), then polished, and has the shape of CIS (Cemented Carbide Tool Association) standard SPP422, and each is shown in Table 1. Indicated composition (in this case, free carbon content according to CIS standard), average particle size of WC, and Rockwell hardness (A
A throw-away tip as a WC-based cemented carbide substrate having a scale) was formed.

Then, as described in, for example, Japanese Patent Application Laid-Open No. 58-91100 and shown schematically in FIG. 1, chemical vapor deposition using a hot filament as a thermoelectron emitting material, which is one of the low-pressure vapor phase synthesis methods. Using the apparatus, the substrate 5 after the above-mentioned etching treatment is placed on the support base 4 located below the metallic tungsten hot filament 3 provided in the reaction vessel (diameter: 120 mm quartz tube) 1 of the apparatus. Then, CH ₄ and H are passed through the reaction mixture gas introducing pipe 2 opened above the hot filament 3.
₂ and the reaction mixture gas of CH ₄ / H ₂ : volume ratio 0.005 was introduced, substrate temperature: 700 ° C., hot filament temperature: 200
Diamond coating was performed under the conditions of 0 ° C., atmospheric pressure in the reaction vessel: 10 torr, and reaction time: 3 to 6 hours for a predetermined time, and the surface of the substrate was coated with a diamond having an average layer thickness shown in Table 1. Inventive coated cutting chips 1-7 and comparative coated cutting chips 1-3 were each produced by forming layers.

In each of the comparative coated cutting chips 1 to 3, any one of the component composition of the substrate and the average particle size of WC is out of the range of the present invention.

Next, the coated cutting chips 1 to 7 of the present invention obtained as a result of the above
And for the comparative coated cutting tips 1 to 3, Work material: Al-18 wt% Si alloy, Cutter diameter: Double positive type with diameter 160 mm, Cutting speed: 530 m / min, Feed: 0.15 mm / Flute, Depth of cut: 1 mm The cutting time: 100 minutes, the milling cutting test is performed, and after the test, observe the peeling state of the diamond coating layer on the cutting edge, the welding state of the work material, the state of the cutting edge itself, and further measure the wear amount. did. The results are shown in Table 1.

〔The invention's effect〕

From the results shown in Table 1, the coated chips 1 to 1 of the present invention
In No. 7, since the diamond coating layer was formed quickly and the adhesion strength to the substrate was extremely high, there was almost no peeling of the coating layer or welding of the work material to the cutting edge, and the cutting edge also showed normal wear, While exhibiting further excellent wear resistance, as seen in the comparative coated cutting tips 1 to 3, if any of the component composition of the substrate and the average particle size of WC deviates from the scope of the present invention, It is clear that the formation speed of the diamond coating layer becomes slow or the adhesive strength becomes low, so that a phenomenon not desirable as a cutting tool appears on the cutting edge and the desired wear resistance is not exhibited. .

As described above, in the diamond-coated WC-based cemented carbide cutting tool tip of the present invention, the diamond coating layer
Since the adhesion strength to the surface of the WC-based cemented carbide substrate is extremely high, it exhibits excellent cutting performance for an extremely long period of time.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of a chemical vapor deposition apparatus using a hot filament as a thermoelectron emitting material. 1: reaction vessel, 2: reaction mixture gas introduction tube 3: hot filament, 4: support 5: substrate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroaki Yamashita 1-297 Kitabukuro-cho, Omiya City, Saitama Prefecture Central Research Laboratory, Mitsubishi Metals Co., Ltd. (72) Inventor Hironori Yoshimura 1-27-20 Nishishinagawa, Shinagawa-ku, Tokyo Mitsubishi Metals Co., Ltd. Tokyo Works (56) References JP-A-58-91100 (JP, A)

Claims (1)

[Claims] 1. A composition containing 1 to 4% by weight of Co, the remainder being substantially composed of tungsten carbide and a trace amount of free carbon, and the free carbon being finely and uniformly dispersed, and having an average particle diameter of tungsten carbide. A diamond-coated tungsten carbide-based cemented carbide cutting tool tip having a low-pressure vapor-phase synthetic diamond coating layer formed on the surface of a tungsten carbide-based cemented carbide substrate having a coarse grain structure of 2 to 10 μm.