JP2717594B2 - Diamond coated cutting tool and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cutting tool characterized by coating a polycrystalline diamond film on a cemented carbide substrate, and more particularly, to a cutting edge of the cutting tool. By coating the diamond film only on the working portion of the cutting tool centered on the vicinity of the cutting portion and the cutting edge portion, the processing performance of the chip is improved, and furthermore, the deformation of the cutting tool base is eliminated, and the cutting edge portion is removed. The present invention relates to a diamond-coated cutting tool having improved sharpness by reducing the center line average roughness of a diamond film to 0.5 μm or less.

(Prior Art) A hot filament CVD method disclosed in JP-A-58-91100, a microwave plasma CVD method disclosed in JP-A-58-110494, and a JP-A-63-85094 are disclosed. Since the gas-phase synthesis method of diamond such as the direct-current discharge plasma CVD method shown in JP-A-64-33096 and the thermal plasma CVD method shown in JP-A-64-33096 was invented, for example, JP-A-60-208473 or New Diamond Magazine ; Vol3, No.3, p26−
As shown in 31 (1987), development of application of this method to cutting tools has been actively conducted. The diamond film obtained by the vapor phase synthesis method includes a polycrystalline diamond film having an automorphic surface obtained by the CVD method and a diamond-like film obtained by other methods and containing amorphous carbon as a main component. is there. Generally, the former diamond film has a higher hardness than the latter, and is used as a film of a cutting tool that requires high wear resistance. The present invention relates to a cutting tool in which the former diamond film is coated on a cutting tool base.

However, in general, when a diamond film is coated on a cutting tool, there is a disadvantage in that the flow of chips becomes worse and the sharpness becomes worse as compared with an uncoated cutting tool. Also,
There is also a problem that the cutting tool deviates from a predetermined size by being coated on a portion other than a necessary portion.

(Problems to be Solved by the Invention) The cause of the above-mentioned poor chip flow is that the diamond film coated by the CVD method is polycrystalline having an automorphic surface, so that the surface unevenness is large, and This is because the coefficient of friction between the chips and the diamond film increases. This effect increases as the film thickness increases, and becomes significant when the surface roughness is 1 μm or more. The cause of the decrease in sharpness due to the diamond film coating is that the cutting edge is rounded by the coating. The roundness of the cutting edge increases with the film thickness, and as a result, the sharpness worsens with the film thickness.
Also, factors that cause the cutting tool to deviate from the specified dimensions include:
In addition to the coated diamond film being too thick, the cutting tool may be curved due to internal stresses generated in the diamond film.

At present, when a diamond film having a high hardness is coated by the CVD method, it is an unavoidable phenomenon that the surface of the diamond film becomes rough and the flow of chips is deteriorated. Further, a phenomenon in which the cutting edge becomes rounder as the film thickness increases and a phenomenon in which a thin cutting tool curves due to internal stress generated in the coated diamond film are unavoidable phenomena caused by coating the diamond.

(Means for Solving the Problems) In order to minimize such inconvenience of diamond coating, in the present invention, a method is employed in which diamond is not coated except for necessary parts, or even if coated, diamond can be easily removed in a later processing step. And tried to implement it.

Attempts to coat a diamond film on a substrate with high adhesive strength have been made in the past, but it has been found that relatively few of these materials can provide high adhesive strength with diamond. Materials that can provide high adhesion strength include:
For example, there are elements such as Ta, W, Mo, and Si, and ceramics such as tungsten carbide and silicon nitride.
Therefore, a material other than these, that is, a material (mask material) having low adhesion strength to diamond is coated on the cutting tool base before the diamond coating treatment, and then a portion where the diamond film is to be coated with high adhesion strength, that is, a cutting edge Then, the mask material in the vicinity of the cutting edge portion is removed by polishing or dissolving by a chemical method, and the material of the cutting tool base is obtained. Alternatively, a mask material coating prevention material is previously coated on the vicinity of the cutting edge portion, and after the mask material coating, the mask material coating prevention material is removed, so that only the cutting edge portion and the vicinity of the cutting edge portion remain as cloth. After that, the diamond coating process is performed to coat the diamond with good adhesion to the vicinity of the cutting edge, and the other portion, that is, the remaining portion of the mask material, has low adhesion strength. It can be spontaneously peeled off due to a stress due to a difference in thermal expansion coefficient from the tool base, or can be easily removed by applying a small force.

At least the surface layer of the cutting tool base must be made of a material that can provide high adhesion strength with the diamond film. In the present invention, a tungsten carbide-based cemented carbide is used as a base material, which is widely used as a cutting tool material and has a high adhesion strength with a diamond film.

As the mask material, any material may be used as long as it is a material that does not have a high adhesion strength with the diamond film and that remains stably on the substrate surface up to the diamond film synthesis temperature (600 to 1000 ° C.). Table 1 shows the materials used as the mask material and the materials that are not used as the mask material and their properties. In addition, the mask material is coated by various physical vapor deposition methods such as a vacuum vapor deposition method, an ion plating method, a sputter vapor deposition method, a thermal CVD method, and a plasma CVD method.
It can be performed by various known methods such as a spraying method, a thermal spraying method, a printing method, and a plating method.

By coating the mask material to prevent the diamond film from covering the cutting edge portion and the portion where the chip flows except the vicinity of the cutting edge, the flow of the chip is greatly improved. But,
When the diamond film thickness is, for example, about 5 μm, there is no problem because the center line average roughness of the film surface can be covered to 0.5 μm or less. Due to the roughness, the flow of the swarf becomes worse, and the roundness of the cutting edge increases with the film thickness, resulting in poor sharpness.

In order to solve this problem, in the present invention, after coating the diamond film, the diamond film of the portion corresponding to the rake face and / or the flank face of the cutting edge is polished to reduce the surface roughness to 1 μm or less. As a result, it was possible to produce a diamond-coated cutting tool with good chip flow and sharpness. Also, the deformation of the cutting tool could be minimized by limiting the coating of the diamond film on portions other than the cutting edge. The details will be shown below with examples.

Example 1 Using a cemented carbide drill having a diameter of 6 mm, a titanium carbide film as a mask material was first coated on the surface of the drill to a thickness of 3 μm by an ion plating method. Next, the flank of the main cutting edge of the drill and the titanium carbide film in the margin portion from the tip to 12 mm were removed by grinding, and then the diamond was coated with the diamond by a microwave plasma CVD method. During the diamond coating process, diamond was adhered to both the part where the mask material was coated and the part where it was removed, but after the coating process was completed and the drill was cooled to room temperature, all the diamond film on the mask material surface was peeled off and the mask material was removed. Only the diamond film of the portion from which was removed remained. The film thickness of the diamond coated on the portion where the drill mask material was removed by this treatment was 5 μm.

For comparison, the same size drill is coated with diamond without coating the mask material, 12 mm from the tip of the drill
The entire surface was coated with a diamond film at a thickness of 5 μm.

Drilling of an aluminum alloy plate was performed using both the drill of the present invention and a drill manufactured for comparison. The processing conditions are as follows.

Work material Aluminum alloy (ADC12) Plate thickness 12mm Rotation speed 8000rpm Feed speed 4000mm / min Cutting oil Water-soluble emulsion As a result of the processing test, the drill of the present invention showed good chip flow and stable hole accuracy. On the other hand, in the comparative drill, the chips were bent thickly, tended to be clogged, and the cutting resistance increased.

Example 2 F was used as a mask material on the surface of a drill made of cemented carbide having a diameter of 3 mm.
The e-Cr alloy was coated with a thickness of 3 μm by a sputter deposition method. Then, the first flank of the main cutting edge of the drill and the mask material in the margin portion from the tip to 6 mm were removed by grinding, and then the diamond was coated with a thickness of 15 μm by microwave CVD. The diamond film on the mask material after the coating process was lifted from the base material and could be easily removed by applying a light force. After completion of the diamond coating, the surface of the diamond film coated with the drill was polished to smooth the surface of the film, and the rounded cutting edge was sharpened by the diamond coating.

For comparison, a drill having a thickness of 15 μm was coated on a portion 6 mm from the tip without coating the mask material on a drill having the same dimensions.

A drilling test was performed on glass fiber reinforced plastic using the drill of the present invention and a comparative drill according to a conventional method.
The processing conditions are as follows.

Work material Glass fiber reinforced plastic plate Thickness 3mm Rotation speed 40000rpm Feed rate 500mm / min Cutting oil None As a result of the test, the drill of the present invention has good glass fiber cutting performance and good chip evacuation, and as a result, hole dimensional accuracy it was high. On the other hand, in the comparative drill, since the cutting edge was rounded, the cutting performance of the fiber was poor and burrs were generated on the outlet side of the hole. In addition, the discharge of chips was poor. The life of the drill was about 20,000 for both the present invention and the conventional drill.

Example 3 A cemented carbide cutter blade 1 whose schematic diagram and cross-sectional view are shown in FIG. 1 was prepared, and a diamond-coated cutter blade was prepared according to the procedure shown in FIG. That is, first, a range of 1 mm on both sides from the tip of the cutting edge 2 shown in FIG. 2A is coated with the thermoplastic resin 3 as shown in FIG. 2B, and then the entire cutter blade is formed to a thickness of 2 μm as shown in FIG. Ni plating 4 was applied. Thereafter, the resin covering the cutting edge portion of the cutter blade was peeled off as shown in FIG.
A diamond coating process was performed as follows. A diamond film 5 of about 15 μm was synthesized on the cutting edge portion 2 of the cutter blade 1, and the diamond film of the plated portion was all peeled off after the coating treatment. Further, the surface of the diamond film was polished as shown in FIG.

As a comparative example, a non-plated cutter blade was coated with a diamond film having a thickness of 15 μm. This is because the diamond film is not coated on both sides of the cutter blade with the same thickness, and the thermal stress due to the difference in thermal expansion coefficient between the diamond film and the cemented carbide is greatly different on both sides of the blade. According to the method of the present invention in which diamond is coated only in the vicinity of the cutting edge, the effect of this thermal stress is small, so that the method does not bend, and the surface of the diamond film in the subsequent step can be easily polished to provide excellent cutting performance. Could be obtained.

(Effect) According to the method of the present invention, the diamond film can be coated only in the vicinity of the cutting edge of the cutting tool. Therefore, a factor that hinders the flow of chips and deformation of the cutting tool due to the coating of the diamond film. Was minimized. Furthermore, the flank side or rake face side or both sides of the diamond film coated on the cutting edge of these cutting tools is smoothed by polishing the surface to provide cutting tools with good chip flow and excellent sharpness. Can be industrially very beneficial.

[Brief description of the drawings]

FIG. 1A is a perspective view of a cutter blade according to an embodiment of the present invention,
FIG. 2B is a cross-sectional view taken along the line AA of FIG. 1A, and FIGS. DESCRIPTION OF SYMBOLS 1 ... Cutter blade base 2 ... Cutter blade cutting edge 3 ... Thermoplastic resin 4 ... Ni plating layer 5 ... Diamond film 6 ... Diamond film after surface polishing

Continuation of front page (72) Inventor Kenichiro Yamagishi 20 Ishigane, Toyama City, Toyama Prefecture Fuji Koshiuchi Co., Ltd. (56) References JP-A-3-215669 (JP, A)

Claims (4)

(57) [Claims] 1. A diamond coating film is formed only on a cutting edge portion and a vicinity of a cutting edge portion of a cutting tool substrate made of a cemented carbide, and the film surface of the diamond coating film is polished. The diamond-coated cutting tool is characterized by having a diameter of 0.5 μm or less. 2. A cutting tool portion made of a cemented carbide alloy and a cutting edge portion on the surface of the cutting tool substrate and a vicinity of the cutting edge portion coated with a mask material adhesion preventing material, and then the substrate surface is coated with a mask material having low adhesion strength to diamond. Next, the mask material adhesion preventing material is removed,
A method of manufacturing a diamond-coated cutting tool, wherein a diamond coating process is performed thereafter by a CVD method so that diamond is coated only on the cutting edge portion and near the cutting edge portion. 3. The mask material is a single or double element of Group 4A, Group 5A excluding Ta, Group 6A, Group 8 and Group 1B excluding Mo and W, and each element of B, Al and Si in the periodic table of elements. Alloys of at least one kind, or a single layer of one or more of carbides, oxides, nitrides, carbonitrides, oxynitrides, and graphite of the above elements, or a single layer or a multilayer of two or more kinds The method for producing a diamond-coated cutting tool according to claim 2, wherein the method comprises: 4. A mask material having the structure described in claim 3 is coated on the surface of a cemented carbide cutting tool substrate, and then the mask material coated on the cutting edge portion and the vicinity of the cutting edge portion of the substrate is removed. A method for producing a diamond-coated cutting tool, characterized in that the diamond-coated cutting tool is removed and then coated with diamond by a CVD method so that only the portion from which the mask material has been removed is coated with diamond.