Method for eliminating color difference of a polycrystalline diamond compact polishing surface

Abstract

This invention belongs to the field of polishing polycrystalline diamond composite sheets, specifically relating to a method for eliminating color difference on the polished surface of polycrystalline diamond composite sheets. The method includes the following steps: holding the polycrystalline diamond composite sheet at 450–550°C, then naturally cooling it in air, and finally grinding to remove oxide impurities from the polished surface. This invention's method for eliminating color difference on the polished surface of polycrystalline diamond composite sheets forms oxide impurities on the polished surface through high-temperature treatment, followed by grinding to remove these impurities, thus eliminating color difference and making the PCD surface color more uniform. Electron microscopy examination has shown that the polycrystalline diamond structure and composition of the polycrystalline diamond sheet obtained by this color difference elimination method are essentially the same as before the high-temperature treatment, proving the effectiveness of the method.

Description

Technical Field

[0001] This invention belongs to the field of polishing polycrystalline diamond composite sheets, and specifically relates to a method for eliminating color difference on the polished surface of polycrystalline diamond composite sheets. Background Technology

[0002] Polycrystalline diamond (PCD) composite sheets combine the high wear resistance of PCD with the high impact resistance of cemented carbide, resulting in exceptionally superior cutting performance. They are manufactured into various cutting tools for precision machining of non-ferrous metals and their alloys, high-hardness materials, non-metallic materials, and reinforced composite materials. Tools made with PCD composite sheets not only significantly improve tool durability and machining efficiency but also ensure machining accuracy and greatly improve the surface quality of the workpiece. In particular, they solve many machining problems involving difficult-to-machine materials, greatly expanding the application range of cutting processes.

[0003] To avoid scratching the surface of the workpiece and ensure rapid chip removal during cutting, the PCD surface of most composite sheets needs to be polished to achieve a mirror finish. Current polishing processes typically utilize the high-speed rotation of a diamond wheel to polish the PCD. However, the high temperatures generated during polishing cause thermal deformation of the polycrystalline diamond composite sheet. As polishing time increases, the contact area between the polycrystalline diamond and the wheel surface continuously changes, ultimately leading to uneven color on the polished polycrystalline diamond surface, i.e., color difference.

[0004] To eliminate color differences on polished surfaces, it is generally necessary to further increase the polishing time. However, eliminating color differences by increasing the polishing time will bring the following problems: First, if the polishing time is too long, local areas of the polycrystalline diamond composite sheet will be burned; second, the polycrystalline diamond composite sheet is composed of cobalt-tungsten alloy and polycrystalline diamond, and the two have different coefficients of thermal expansion, which will cause cracking if polished for a long time; third, solving color differences through polishing is inefficient and greatly increases polishing energy consumption and cost. Summary of the Invention

[0005] The purpose of this invention is to provide a method for eliminating color difference on the polished surface of polycrystalline diamond composite sheets, so as to overcome the above-mentioned shortcomings of existing methods that eliminate color difference by increasing polishing time.

[0006] To achieve the above objectives, the technical solution adopted by this invention is as follows:

[0007] A method for eliminating color difference on the polished surface of a polycrystalline diamond composite sheet includes the following steps: keeping the polycrystalline diamond composite sheet at 450-550℃, then naturally cooling it in air, and then polishing it to remove oxidized impurities from the polished surface after cooling.

[0008] The method for eliminating color difference on the polished surface of polycrystalline diamond composite sheets (PCD) of this invention involves high-temperature treatment to achieve a uniform oxidation degree of the Co metal on the PCD polished surface (mainly transforming it into cobalt tetroxide, black), followed by polishing to remove surface oxide impurities, thereby eliminating color difference and making the PCD surface color more uniform. Electron microscopy examination has proven that the microstructure and composition of the polycrystalline diamond obtained by the color difference elimination method of this invention are essentially the same as before the high-temperature treatment, demonstrating the effectiveness of the method.

[0009] Preferably, the heat preservation time is 50–90 minutes. At this heat preservation temperature, the oxidation degree of the PCD polished surface can be further optimized, thereby better eliminating color difference on the polished surface.

[0010] Preferably, before the heat preservation, the polycrystalline diamond composite sheet is cleaned with alcohol, dried, and its surface is wiped clean. This pretreatment of the polycrystalline diamond composite sheet provides clean and tidy conditions for the subsequent heat preservation at 450–550°C, thereby reducing the impact on the formation of oxide impurities.

[0011] Preferably, sandpaper is used for polishing. Sandpaper polishing is a low-cost and easy-to-operate method.

[0012] More preferably, the sandpaper grit is between 240# and 480#. Using sandpaper of this grit can further avoid affecting the surface of the composite sheet. Attached Figure Description

[0013] Figure 1 This is an electron microscope image of polycrystalline diamond before heat treatment in an embodiment of the present invention;

[0014] Figure 2 This is an electron microscope image of the heat-treated polycrystalline diamond in an embodiment of the present invention.

[0015] Figure 3 This is a comparison diagram of the composition of polycrystalline diamond before and after heat treatment in an embodiment of the present invention. Detailed Implementation

[0016] To address the shortcomings of eliminating color difference by increasing polishing time, such as excessive polishing time, easy burning, easy cracking, and low efficiency, this invention keeps the polycrystalline diamond composite sheet at 450-550℃, then cools it naturally in the air, and then polishes it to remove the oxidized impurities on the polished surface after cooling.

[0017] Before using the color difference elimination method of this invention, polycrystalline diamond composite sheets are rubbed on a grinding wheel until they reach the polished surface standard (roughness Ra below 0.05μm). At this time, due to the inherent characteristics of the grinding wheel processing method, color difference still exists on the polished surface.

[0018] The principle of eliminating color difference in this invention is that the Co metal on the polished surface of the PCD is oxidized to a uniform degree through high-temperature treatment (mainly converted into cobalt tetroxide, black), thereby making the PCD surface color uniform.

[0019] The implementation process of the present invention will be described in detail below with reference to specific embodiments.

[0020] I. Specific embodiments of the method for eliminating color difference on the polished surface of the polycrystalline diamond composite sheet of the present invention are as follows:

[0021] Example 1

[0022] The method for eliminating color difference on the polished surface of polycrystalline diamond composite sheets in this embodiment includes the following steps:

[0023] (1) Clean the surface of the polycrystalline diamond composite sheet (PCD) with alcohol, then dry it with a hair dryer, and finally wipe the PCD surface with a lint-free cloth.

[0024] (2) Heat the muffle furnace to 500℃ and keep it at that temperature. Place the cleaned PCD in a stainless steel tray and then put it back into the muffle furnace to keep it at that temperature for 1 hour. After 1 hour of high-temperature treatment, remove the blade from the muffle furnace and let it cool naturally in the air. After cooling, use 300# sandpaper to remove the oxidation impurities on the PCD surface. The color difference of the PCD can then be removed, and the color of the PCD surface will become more uniform.

[0025] In other embodiments of this example, using 240# or 480# sandpaper to remove oxidation impurities from the PCD surface can achieve essentially the same effect.

[0026] Example 2

[0027] The method for eliminating color difference on the polished surface of polycrystalline diamond composite sheets in this embodiment includes the following steps:

[0028] (1) Clean the surface of the polycrystalline diamond composite sheet (PCD) with alcohol, then dry it with a hair dryer, and finally wipe the PCD surface with a lint-free cloth.

[0029] (2) Heat the muffle furnace to 450℃ and keep it at that temperature. Place the cleaned PCD in a stainless steel tray and then put it back into the muffle furnace for 90 minutes. After the high-temperature treatment, remove the blade from the muffle furnace and let it cool naturally in the air. After cooling, use 300# sandpaper to remove the oxidation impurities on the PCD surface. The color difference of the PCD can be removed and the color of the PCD surface will become more uniform.

[0030] Example 3

[0031] The method for eliminating color difference on the polished surface of polycrystalline diamond composite sheets in this embodiment includes the following steps:

[0032] (1) Clean the surface of the polycrystalline diamond compact (PCD) with alcohol, then dry it with a hair dryer, and finally wipe the PCD surface with a lint-free cloth.

[0033] (2) Heat the muffle furnace to 550 °C and keep it warm. Place the cleaned PCD in a stainless steel tray, and then put it into the muffle furnace for 50 minutes of heat preservation. After the high-temperature treatment, take out the blade from the muffle furnace and let it cool naturally in the air. After cooling, remove the oxidized impurities on the PCD surface with 300# sandpaper, and the color difference of the PCD can be removed, and the color of the PCD surface tends to be consistent.

[0034] II. Experimental Example

[0035] In this experimental example, the PCD before and after heat treatment in Example 1 was detected by electron microscopy to observe the changes in the structure and composition of the polycrystalline diamond. The changes in its structure are as Figure 1 and Figure 2 shown, and the comparison of the composition before and after heat treatment is as Figure 3 shown.

[0036] Figure 1 and Figure 2 In, the left figure is the secondary electron mode, and the right figure is the backscattered mode. Figure 3 In, CK, CoK, and WL are the respective proportions of carbon element (mainly in diamond form), cobalt element, and tungsten element; the suffixes K and L respectively represent the line series of the element. When the atomic number Z of the analyzed element is less than 32, the K line series is used; when 32 < Z < 72 for the analyzed element, the L line series is used.

[0037] It can be seen from Figures 1-3 that the structure and composition of the polycrystalline diamond after heat treatment are basically the same as those before heat treatment, indicating that the treatment method of the present invention has basically no influence on the microstructure and composition of the polycrystalline diamond, which proves the effectiveness of the present method.

[0038] In summary, compared with the method of eliminating color difference by increasing the polishing time, the method of eliminating color difference using the present invention has the following advantages:

[0039] 1) High efficiency. One muffle furnace can process 80 polycrystalline diamond compacts per hour as required.

[0040] 2) Low energy consumption. Only the furnace needs to be kept warm during the heat treatment process, without other energy consumption.

[0041] 3) Low cost and simple operation.

Claims

1. A method for eliminating color difference of a polished surface of a polycrystalline diamond compact, characterized in that, Includes the following steps: Polycrystalline diamond composite sheets are rubbed on a grinding wheel until the polished surface meets the standard. The polycrystalline diamond composite sheets are then kept at 450~550℃ for 50~90 minutes to ensure that the Co metal on the PCD polished surface reaches a uniform degree of oxidation. After that, they are naturally cooled in the air. After cooling, the surface is polished to remove the oxidation impurities.

2. The method of claim 1, wherein the method further comprises: The standard for the polished surface is a roughness Ra of less than 0.05 μm.

3. The method of claim 1 or 2, wherein the color difference of the PCD polishing surface is eliminated by the following steps: Before the heat preservation process, clean the polycrystalline diamond composite sheet with alcohol, dry it, and wipe the surface clean. ​ 4. The method of claim 1, wherein the method further comprises: The polishing is done using sandpaper.

5. The method of claim 4, wherein the color difference of the PCD polished surface is eliminated by, Sandpaper sizes range from 240# to 480#.

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