KR102454037B1 - A Diamond Composite Polycrystalline - Google Patents

Abstract

The present invention relates to a diamond composite polycrystal used by being attached to a substrate made of an integral cemented carbide and ceramic as a technology for a cemented carbide cutting tool.
The diamond composite polycrystalline body according to the present invention is used fixed on a hard base material, and includes diamond particles and a binder. In the diamond composite polycrystal, the upper diamond particles on the surface side have a columnar crystal structure in which the aspect ratio (Y/X, vertical Y with respect to the hard base material, horizontal direction X) is 1.2 or more, and the binder is Al, Co, Ti , Ta, Mo, Nb, and at least one selected from W, the amount of the binder included in the diamond composite polycrystal decreases from the bottom to the top, and there is no binder on the surface of the diamond composite polycrystal, or 1 weight % or less.

Description

A Diamond Composite Polycrystalline

The present invention relates to a diamond composite polycrystal used by being attached to a substrate made of an integral cemented carbide and ceramic as a technology for a cemented carbide cutting tool.

Diamond is one of the hardest materials on Earth. Today, diamond-coated cutting tools artificially made through chemical vapor synthesis (CVD) are used as tools suitable for machining difficult-to-machine materials, aluminum-silicon alloys, magnesium alloys or graphite materials.

A tool to which diamond is applied is a PCD tool that forms a diamond layer by mixing diamond particles and a binder (binder) on the surface of the tool base material and then sintering, and a diamond film is formed by synthesizing diamond on the surface of the tool base material by CVD. There are CVD diamond forming tools.

Among them, in the case of PCD, a raw material powder obtained by mixing a binder powder consisting of particles of a metal component such as diamond powder and cobalt on a hard base material such as WC-Co cemented carbide is placed on it, and sintered. However, since PCD has a metal binder, the lifespan is shorter than that of a CVD diamond tool made of only diamond, and the surface roughness of the workpiece is poor.

In addition, CVD diamond tools have excellent wear resistance, which guarantees a long service life and excellent surface roughness of the workpiece. have

Unexamined Patent Publication No. 2020-0057422 Unexamined Patent Publication No. 2019-0131488

An object of the present invention is to improve the short-lived shortcomings of PCD tools and the shortcomings that can only be used in continuous machining of CVD diamond tools, and provide a cutting tool that has a longer lifespan compared to PCD tools and can be used for high-speed and interrupted machining. To provide a diamond composite polycrystal that can be applied.

In order to achieve the above object, the present invention provides a diamond composite polycrystal used fixed on a hard base material, comprising diamond particles and a binder, and the lower diamond particles, which are the side fixed to the hard base material, among the diamond composite polycrystals. Having an equiaxed crystal structure, the upper diamond particles on the surface side of the diamond composite polycrystal have a columnar crystal structure in which the aspect ratio (Y/X, vertical Y with respect to the hard base material, horizontal direction X) is 1.2 or more, and the binder is Al , Co, Ti, Ta, Mo, Nb, and at least one selected from W, the amount of the binder contained in the diamond composite polycrystal decreases from the bottom to the top, and the binder is on the surface of the diamond composite polycrystal. It provides a diamond composite polycrystal, characterized in that absent, or less than 1% by weight.

The diamond composite polycrystal according to the present invention consists of a lower portion containing diamond particles having excellent toughness and a significant amount of binder, and an upper portion having a larger aspect ratio than the lower portion and containing almost no binder. It is possible to realize a diamond cutting tool that has a remarkably improved long life and can be used for high-speed and intermittent machining, which could not be applied with conventional CVD diamond film.

The diamond composite polycrystal according to the present invention forms a sloping functional layer in which the binder content decreases toward the upper part compared to the lower part, thereby obtaining sufficient bonding strength between the upper and lower parts.

1 is a schematic diagram of a cross-section of a diamond composite polycrystal according to an embodiment of the present invention.
2 shows the X-ray-diffraction analysis results of the upper layer of the diamond composite polycrystal according to an embodiment of the present invention.

Hereinafter, the configuration and operation of the embodiment of the present invention will be described with reference to the accompanying drawings. In describing the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, when a part 'includes' a certain component, this means that other components may be further included, rather than excluding other components, unless otherwise stated.

The diamond composite polycrystal according to the present invention is used to be fixed on a hard base material, and includes diamond particles and a binder, and among the diamond composite polycrystals, the lower diamond particle, which is the side fixed to the hard base material, has an equiaxed crystal structure. In the diamond composite polycrystal, the upper diamond particles on the surface side have a columnar crystal structure in which the aspect ratio (Y/X, vertical Y with respect to the hard base material, horizontal direction X) is 1.2 or more, and the binder is Al, Co, Ti , Ta, Mo, Nb, and at least one selected from W, the amount of the binder contained in the diamond composite polycrystal decreases from the bottom to the top, and the surface of the diamond composite polycrystal has no binder or 1 wt% It is characterized by the following.

In the case of a composite of general diamond particles and a binder, the toughness is excellent due to the presence of the metal binder, but there is a problem in that the lifespan is short and the surface roughness characteristics of the workpiece are deteriorated. In the diamond composite polycrystal according to the present invention, a composite of diamond particles and a binder is located on the side adjacent to the base material, and a layer made of only diamond or a binder content of 1 wt% or less is formed on the surface to extend the lifespan, It is possible to improve the surface roughness characteristics of the workpiece (that is, to make it a lower surface roughness state).

In addition, when the amount of the binder included in the diamond composite polycrystal decreases from the bottom to the top, it means that it includes both continuously decreasing, discontinuously decreasing, or intermittently decreasing.

In addition, in the diamond composite polycrystal, 'the diamond grains in the lower part have an equiaxed crystal structure' means that the aspect ratio (the longest part and the shortest part) is less than 1.2, 80% or more of the total area of the lower part, preferably It means more than 90%.

In addition, in the diamond composite polycrystal, 'surface' means a depth of 50 µm from the surface of the diamond complex polycrystal, preferably up to a depth of 5 µm from the surface.

The hard base material (ie, the base of the tool) to which the diamond composite polycrystal according to the present invention is bonded is a main component of at least one selected from WC-Co cemented carbide, cermet, cBN, Si, SiC, Si ₃ N ₄ , AlN Any material that can be used by being joined to the tip of the tool, such as a ceramic sintered body, can be used without particular limitation. The diamond composite polycrystal according to the present invention may be bonded (fixed) to the tip of various types of tools by bonding (fixing) to the tip of various types of tools, for example, by sintering directly on the surface of the base material or by bonding using a brazing material.

In addition, when the average size of the diamond particles is less than 0.1㎛, the workpiece surface roughness is excellent but the wear resistance is poor. Therefore, it is preferable to use a 0.1 ~ 100㎛ range.

In addition, in the X-ray diffraction analysis of the diamond composite polycrystal, the peak intensity I ₀ of the (111) plane, the peak intensity I ₁ of the (200) plane, the peak intensity I ₂ of the (220) plane, and the peak of the (311) plane When referring to the strength I ₃ , it is preferable that 1≤I ₀ /I _x ≤25 (x=1 to 3). That is, it is preferable that crystal growth is made mainly on the (111) plane in a state where the peak intensity of the (111) plane is equal to or higher than that of the (200) plane, the (220) plane, and the (311) plane.

In addition, it is preferable that the surface of the diamond composite polycrystal is mirror-finished through polishing to implement an appropriate surface roughness of the workpiece.

The diamond composite polycrystal according to the present invention can be manufactured by various methods, such as a method of heat-treating a mixture of diamond particles and a binder after sintering, a method of heat-treating diamond after manufacturing it by high-temperature, high-pressure molding, or PVD or CVD method.

[Example]

As shown in FIG. 1, the diamond composite polycrystal according to the present invention is fixed to a hard base material and used, and is formed through the following process.

The surface of the WC-10wt% Co carbide substrate (base material) was treated with a Murakami solution for 10 minutes and then etched for additional 3 minutes using Caro's acid.

Then, on the lower layer, the filament temperature was 2400 ° C, the deposition pressure was changed to 20 ~ 80 torr in stages, and a mixture gas of hydrogen (H ₂ ) and methane (CH ₄ ) was used as a precursor gas, and the composition ratio of methane (CH ₄ ) was adjusted to 0.5 to 3 vol%. After the flow rate of the mixed gas was 1.5slm to form polycrystalline diamond, the temperature of the heat treatment furnace was changed to 500~1000℃ step by step, and a diamond composite polycrystal was formed through heat treatment under vacuum process conditions of 10 ^-2 Torr. did.

<Ingredient Analysis>

The results of analyzing the Co content (ie, binder content) from the surface of the composite polycrystal prepared through the above process to the interface with the base material are shown in Table 1 below.

measurement position Co (at.%) surface 0.39 1/3 depth point from the surface 5.77 2/3 deep from the surface 7.27 3/3 deep from the surface
(near the base material interface) 7.35

As can be seen in Table 1 above, the diamond composite polycrystal according to the present invention has a sloped structure in which the content of Co decreases as it goes up from the bottom to the top.

<X-ray diffraction analysis>

2 is an X-ray-diffraction analysis result of a diamond composite polycrystal according to an embodiment of the present invention. As can be seen in FIG. 2 , the diamond composite polycrystal according to the embodiment of the present invention has the strongest peak intensity at the (111) plane during X-ray diffraction analysis, and the second strongest peak is at the (110) plane. appear. That is, growth is mainly made on the (111) plane, and growth is made next to the (110) plane.

<Evaluation of cutting performance>

In order to evaluate the cutting performance of the diamond composite polycrystal according to an embodiment of the present invention, high-speed (wear resistance) and interrupted (chipping resistance) machining tests were performed under the following conditions. In addition, in order to compare two types of general diamond polycrystalline (PCD) tools with the Example of the present invention, the same cutting performance evaluation was performed.

High-speed machining test (comparison of wear)

The high-speed abrasion resistance test conditions were performed as follows, and the results are shown in Table 2 below.

vc = 800m/min

fn = 0.1mm/rev

ap = 0.2mm

Dry, Si 25% aluminum alloy

cutting length Example Comparative Example 1
(Korloy PCD #1) Comparative Example 2
(Korloy PCD #2) 10km 9㎛ 21㎛ 30㎛ 20km 12㎛ 25㎛ 55㎛ 30km 14㎛ 28㎛ 60㎛ 40km 18㎛ 32㎛ 70㎛

As can be seen in Table 2 above, it can be seen that the diamond composite polycrystal according to the present invention has excellent (low) initial tool wear and wear increase rate compared to the conventional PCD tool under high-speed machining conditions.

Interrupted machining test (comparison of wear)

Interrupted machining test conditions were performed as follows, and the results are shown in Table 3 below.

vc = 15m/min

fn = 0.37mm/rev

ap = 0.5mm

dry, carbide

number of machining Example Comparative Example 1
(Korloy PCD #1) Comparative Example 2
(Korloy PCD #2) 1 time processing 50㎛ 90㎛ 110㎛ 2 times processing 80㎛ 150㎛ damage 3 times processing 120㎛ edge chipping -

As can be seen in Table 3 above, it can be seen that the diamond composite polycrystal of the embodiment of the present invention can be processed more stably compared to the existing PCD tool under the condition of interrupted processing (chipping resistance, breakage resistance).

Claims (4)

A diamond composite polycrystal used fixed on a hard base material,
comprising diamond particles and a binder;
Among the diamond composite polycrystals, the lower diamond particles that are fixed to the hard base material have an equiaxed crystal structure,
Among the diamond composite polycrystals, the upper diamond particles on the surface side have a columnar crystal structure in which the aspect ratio (Y/X, vertical Y with respect to the hard base material, horizontal direction X) is 1.2 or more,
The binder includes at least one selected from Al, Co, Ti, Ta, Mo, Nb, and W,
The amount of the binder contained in the diamond composite polycrystal decreases from the bottom toward the top,
There is no binder on the surface of the diamond composite polycrystal, or less than 1% by weight,
In the diamond composite polycrystal, in X-ray diffraction analysis, the peak intensity I ₀ of the (111) plane, the peak intensity I ₁ of the (200) plane, the peak intensity I ₂ of the (220) plane, and the peak of the (311) plane When the strength I ₃ , 1≤I ₀ /I _x ≤25 (x=1~3), diamond composite polycrystal.
The method of claim 1,
The average size of the diamond particles is 0.1 ~ 100㎛, diamond composite polycrystals. delete The method of claim 1,
The surface of the diamond composite polycrystal is mirror-finished through polishing, diamond composite polycrystal.

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