CN115125537B - Method for removing cobalt in polycrystalline diamond compact - Google Patents

Abstract

The invention discloses a method for removing cobalt in a polycrystalline diamond compact, which comprises the following steps: after an alloy substrate of the polycrystalline diamond compact is additionally provided with a protection tool, the alloy substrate is immersed in a cobalt-removing solution for soaking, and then is washed and dried to complete removal of cobalt in the polycrystalline diamond compact; wherein the cobalt-removing solution is prepared by the following method: adding Lewis acid and phosphate into sulfuric acid solution to prepare the cobalt-removing solvent. Compared with the prior art, the method for removing cobalt in the polycrystalline diamond compact shortens the cobalt removing period by half under the condition of reaching the same cobalt removing depth and cobalt removing content, greatly improves the cobalt removing efficiency, reduces the production cost, improves the processing capacity, improves the field working environment, reduces the safety risk of field workers, and has less environmental pollution.

Description

A method for removing cobalt in polycrystalline diamond compact

technical field

The invention relates to the technical field of preparing nanocomposite materials, in particular to a method for removing cobalt from polycrystalline diamond composite sheets.

Background technique

Polycrystalline diamond compact (PDC) is a kind of superhard composite material which is sintered with cemented carbide substrate under high temperature and ultra-high pressure after mixing diamond micropowder and a small amount of binder cobalt powder. It has both polycrystalline diamond Its ultra-high hardness and wear resistance, as well as the weldability and toughness of cemented carbide, are widely used in oil and gas drilling, geological exploration, mineral mining, hard material processing, metal material processing and other fields.

Binder cobalt plays an important role in the synthesis, processing and use of PDC. During the synthesis of PDC, cobalt promotes the formation of D-D bonds between diamond grains through the dissolution-recrystallization process, but it also causes PDC to grind The reason for the failure is that cobalt has a strong affinity with carbon at high temperature and low pressure, which will convert diamond into graphite, and correspondingly reduce the wear resistance of PDC samples; at the same time, the thermal expansion coefficients of cobalt and diamond differ greatly. The high temperature process of grinding, welding, and drilling will easily lead to increased stress, which will cause cracks inside the PDC, resulting in failure forms such as wear, chipping, and broken teeth. Therefore, after the PDC is synthesized, the cobalt in the diamond layer can be removed, which can greatly improve the performance of the PDC. The PDC decobaltization technology generally uses corrosive strong acid or a mixed solution of several strong acids as the decobalt reagent, and uses the strong corrosiveness of the strong acid reagent to achieve the decobalt effect. However, the decobalt removal efficiency is low and the cobalt removal period is long. At the same time, the use of some strong acid reagents nitric acid, hydrofluoric acid, and hydrochloric acid has a high risk and causes pollution to the environment.

Contents of the invention

In order to solve the above-mentioned technical problems, the purpose of the present invention is to provide a method for removing cobalt in polycrystalline diamond compacts to solve the problem of low cobalt removal efficiency, long cycle and dangerous use of strong acids in polycrystalline diamond compacts in the prior art. sex issue.

The technical solution of the present invention to solve the above technical problems is as follows: a method for removing cobalt in a polycrystalline diamond compact is provided, comprising:

After installing protective tooling on the alloy base of the polycrystalline diamond composite sheet, immerse it in a cobalt removal solution, then rinse and dry to complete the removal of cobalt from the polycrystalline diamond composite sheet;

Wherein, the cobalt removal solution is prepared by adding Lewis acid and phosphate into the sulfuric acid solution to obtain the cobalt removal solution.

The beneficial effect of the present invention is: the present invention uses Lewis acid, sulfuric acid and phosphate to soak polycrystalline diamond composite sheet, removes composite sheet cobalt, and Lewis acid and sulfuric acid react with metal cobalt in composite sheet to generate divalent cobalt ion, divalent cobalt ion, two Cobalt ions and phosphate ions in phosphate regenerate coordination ion precipitation, accelerate the reaction process, and accelerate the reaction process. Compared with the prior art, the method of the present invention is used to remove cobalt in the polycrystalline diamond composite sheet, achieving the same Under the requirements of cobalt removal depth and cobalt content, the cobalt removal cycle is shortened by half, which greatly improves the cobalt removal efficiency, reduces production costs, improves processing capacity, improves the on-site working environment, and reduces the safety risks of on-site staff. Environmental pollution is less.

On the basis of above-mentioned technical scheme, the present invention can also be improved as follows:

Further, the concentration of sulfuric acid solution is 6-9mol/L, the concentration of Lewis acid in sulfuric acid solution is 150-180g/L, and the concentration of phosphate is 5-15g/L.

Further, the Lewis acid is aluminum trichloride or ferric chloride.

Further, the phosphate is sodium dihydrogen phosphate or potassium dihydrogen phosphate.

Further, the soaking temperature is 120-160°C.

Further, the immersion pressure is 0.8-1Mpa.

Further, the soaking time is 5-15d.

Further, the thickness of the composite layer of the polycrystalline diamond composite sheet is 1.2-3mm.

The present invention has the following beneficial effects:

1. Adopt the method of the present invention to remove cobalt in the polycrystalline diamond composite sheet. When the thickness of the composite layer is 1.2mm, the decobalt period to reach the standard decobalt depth of 0.6mm is 5-7d; when the thickness of the composite layer is 3mm, it reaches The decobaltization period of the standard decobaltization depth of 1.2mm is 12-15d. Compared with the existing technology, the decobaltization period is shortened by half.

2. By adopting the method of the present invention to remove cobalt in the polycrystalline diamond composite sheet, the cobalt content in the composite layer can be reduced from 4-7wt% to below 0.5wt%.

3. The cobalt removal solution of the present invention does not contain highly volatile and corrosive strong acids such as nitric acid and hydrofluoric acid, which can improve the on-site working environment, reduce the safety risks of on-site workers, and cause less environmental pollution.

Description of drawings

Fig. 1 is the XRF figure after the cobalt removal of the polycrystalline diamond compact of embodiment 1;

Fig. 2 is the XRF figure after the cobalt removal of the polycrystalline diamond compact of embodiment 2;

Fig. 3 is the XRF figure after the cobalt removal of the polycrystalline diamond compact of embodiment 3;

Fig. 4 is the XRF figure after the cobalt removal 15d of the polycrystalline diamond composite sheet of comparative example 1;

Fig. 5 is the XRF pattern after 40 days of cobalt removal of the polycrystalline diamond compact of Comparative Example 1.

Detailed ways

The principles and features of the present invention are described below in conjunction with the accompanying drawings, and the examples given are only used to explain the present invention, and are not intended to limit the scope of the present invention. Those who do not indicate the specific conditions in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used were not indicated by the manufacturer, and they were all conventional products that could be purchased from the market.

Example 1:

A method for removing cobalt in a polycrystalline diamond compact, comprising the following steps:

(1) prepare the sulfuric acid solution of 9mol/L, then add 180g aluminum trichloride and 15g sodium dihydrogen phosphate in every 1L sulfuric acid solution, make decobalt solution;

(2) After the alloy base of the polycrystalline diamond composite sheet (cobalt content is 4.8wt%) that the composite layer thickness is 1.2mm is installed anti-corrosion protection frock, be placed in the pressure reactor, add step (1) prepared Cobalt solution, ensure that the liquid level of the decobalt solution is immersed in the polycrystalline diamond composite sheet, seal the reaction kettle, quickly heat up to 120°C, after constant temperature, self-boost to 0.8Mpa constant pressure, soak for 5d;

(3) Depressurize the reaction kettle after soaking in step (2), lower the temperature to room temperature, take out the polycrystalline diamond composite sheet, rinse and dry, and complete the removal of cobalt in the polycrystalline diamond composite sheet.

Example 2:

A method for removing cobalt in a polycrystalline diamond compact, comprising the following steps:

(1) prepare the sulfuric acid solution of 6mol/L, then add 150g aluminum trichloride and 5g sodium dihydrogen phosphate in every 1L sulfuric acid solution, make decobalt solution;

(2) After the alloy substrate of the polycrystalline diamond composite sheet (with a cobalt content of 6wt%) with a composite layer thickness of 3mm is equipped with anti-corrosion protection frocks, it is placed in a pressure reactor, and the cobalt removal solution prepared in step (1) is added , to ensure that the liquid level of the decobalt solution soaks the polycrystalline diamond composite sheet, seal the reaction kettle, rapidly raise the temperature to 160°C, after constant temperature, self-boost to 1Mpa constant pressure, and soak for 15d;

(3) Depressurize the reaction kettle after soaking in step (2), lower the temperature to room temperature, take out the polycrystalline diamond composite sheet, rinse and dry, and complete the removal of cobalt in the polycrystalline diamond composite sheet.

Example 3:

A method for removing cobalt in a polycrystalline diamond compact, comprising the following steps:

(1) prepare the sulfuric acid solution of 8mol/L, then add 165g aluminum trichloride and 10g sodium dihydrogen phosphate in every 1L sulfuric acid solution, make decobalt solution;

(2) After the alloy substrate of the polycrystalline diamond composite sheet (with a cobalt content of 6wt%) with a composite layer thickness of 3mm is equipped with anti-corrosion protection frocks, it is placed in a pressure reactor, and the cobalt removal solution prepared in step (1) is added , to ensure that the liquid level of the decobalt solution soaks the polycrystalline diamond composite sheet, seal the reaction kettle, rapidly raise the temperature to 150°C, after constant temperature, self-boost to 0.9Mpa constant pressure, and soak for 12 days;

(3) Depressurize the reaction kettle after soaking in step (2), lower the temperature to room temperature, take out the polycrystalline diamond composite sheet, rinse and dry, and complete the removal of cobalt in the polycrystalline diamond composite sheet.

Comparative example 1:

A method for removing cobalt in a polycrystalline diamond compact, comprising the following steps:

(1) adding a concentration of 4mol/L nitric acid solution to pure hydrofluoric acid to obtain a decobalt solution; wherein, the volume ratio of pure hydrofluoric acid and nitric acid solution is 4:6;

(2) After the alloy substrate of the polycrystalline diamond composite sheet (with a cobalt content of 6wt%) with a composite layer thickness of 3mm is equipped with anti-corrosion protection frocks, it is placed in a pressure reactor, and the cobalt removal solution prepared in step (1) is added , to ensure that the liquid level of the decobalt solution soaks the polycrystalline diamond composite sheet, seal the reaction kettle, and soak for 15 days at 50°C;

(3) After the soaking in step (2), take out the polycrystalline diamond composite sheet, rinse and dry, and complete the removal of cobalt in the polycrystalline diamond composite sheet;

(4) Repeat step (2) for the polycrystalline diamond composite sheet obtained in step (3), and continue to soak for 25 days at 50°C. After soaking, take out the polycrystalline diamond composite sheet, rinse and dry, and complete the final polycrystalline diamond composite. Cobalt removal from flakes.

Test case

The cobalt-removed polycrystalline diamond compacts in Examples 1-3 and Comparative Example 1 were analyzed by X-ray fluorescence spectroscopy for the depth of cobalt removal. The test voltage was 40V. The results are shown in Figures 1-5. The metal cobalt content in the sheet, the results are shown in Table 1.

As can be seen from Figures 1-5, the light-colored area is the decobalted area, and the black area is due to the presence of metal cobalt, and X-rays cannot completely penetrate the sample, which is the non-decobalted area. The decobalt depth is shown in Table 1. It can be seen that using the method, for a polycrystalline diamond composite sheet with a composite layer thickness of 1.2 mm, it only takes 7 days to reach the standard decobalt depth of 0.6 mm, and for a polycrystalline diamond composite sheet with a composite layer thickness of 3 mm, it only takes Need 12-15d; And adopt the method of comparative example 1, for the polycrystalline diamond composite sheet that composite layer thickness is 3mm, decobalt 15d can only reach the unqualified decobalt depth of 0.886mm, even if continue to decobalt 25d, eventually also It can only reach the decobalt depth of 1.16mm, and fails to reach the standard decobalt depth of 1.2mm. It can be seen that the method of the present invention can shorten the cobalt removal cycle by half and greatly improve the The efficiency of cobalt removal reduces the production cost, improves the processing capacity, improves the on-site working environment, reduces the safety risk of the on-site staff, and has less environmental pollution.

Table 1 Cobalt removal depth and cobalt content of polycrystalline diamond compact

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (5)

1. A method for removing cobalt from a polycrystalline diamond compact is characterized by comprising the following steps: after an alloy substrate of the polycrystalline diamond compact is additionally provided with a protection tool, the alloy substrate is immersed in a cobalt-removing solution for soaking, and then is washed and dried to complete removal of cobalt in the polycrystalline diamond compact;

wherein the cobalt-removing solution is prepared by the following method: adding Lewis acid and phosphate into a sulfuric acid solution to prepare a cobalt-removed solution;

the concentration of the sulfuric acid solution is 6-9mol/L, the concentration of Lewis acid in the sulfuric acid solution is 150-180g/L, and the concentration of phosphate is 5-15g/L;

the soaking temperature is 120-160 ℃;

the soaking pressure is 0.8-1MPa.

2. The method of removing cobalt from a polycrystalline diamond compact of claim 1, wherein the lewis acid is aluminum trichloride or ferric trichloride.

3. The method of removing cobalt from a polycrystalline diamond compact of claim 1, wherein the phosphate is sodium dihydrogen phosphate or potassium dihydrogen phosphate.

4. The method of removing cobalt from a polycrystalline diamond compact of claim 1, wherein the soaking time is between 5 days and 15 days.

5. The method of removing cobalt from a polycrystalline diamond compact of claim 1, wherein the thickness of the composite layer of the polycrystalline diamond compact is 1.2mm to 3mm.

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