CN-122013180-A - Method for realizing submicron diamond homogenization cobalt plating in high-temperature molten salt environment

Abstract

The invention provides a method for realizing uniform cobalt plating of submicron diamond in a high-temperature molten salt environment, belonging to the technical field of diamond surface metallization treatment. Based on the redox reaction principle, through controlling parameters such as the type of molten salt, the content of reducing agent, the content of cobalt salt, the experimental temperature and the like, vacuumizing in a tube furnace and performing reaction diffusion under the protection of argon atmosphere, the uniform cobalt coating is formed on the surface of the diamond. The reaction temperature is controlled at 800-1000 ℃, the heat preservation time is 1-2 h, a high-purity cobalt coating can be obtained on the surface of the diamond, the deposition mass ratio of local cobalt plating can reach 20.17%, the total deposition mass ratio can reach 1.78%, and the coating mainly contains carbon and cobalt elements and has low impurity content. Compared with the traditional methods such as electroless cobalt plating, the method has the advantages of high safety, good deposition efficiency, simple and convenient operation and the like, and is suitable for surface metallization treatment of submicron-scale diamond powder.

Inventors

• TAN XIAOYUE
• DAI ZHENYU
• WU YUCHENG
• PAN YAFEI
• LUO LAIMA
• Xie Siyao

Assignees

• 合肥工业大学

Dates

Publication Date

20260512

Application Date

20260214

Claims (8)

1. 1. A method for realizing uniform cobalt plating of submicron diamond in a high-temperature molten salt environment is characterized in that submicron diamond powder, cobalt salt, zinc powder and molten salt medium are mixed in a protective atmosphere, and uniform deposition of a cobalt metal layer on the surface of the submicron diamond is realized through oxidation-reduction reaction in the high-temperature molten salt environment.
2. 2. The method of claim 1, comprising the steps of: (1) Mixing submicron diamond powder with dilute hydrochloric acid, stirring to make the diamond powder fully contact with acid liquor, removing surface impurities and greasy dirt, and roughening the diamond surface to provide more active sites for subsequent cobalt plating treatment; (2) Removing crystal water, namely heat-treating CoCl 2 ·6H 2 O for a period of time in an argon protective atmosphere to completely remove the crystal water and obtain anhydrous CoCl 2 powder; (3) Salt bath mixing, namely, firstly mixing the pretreated diamond powder with a molten salt medium to uniformly disperse the diamond powder in the molten salt, mixing the CoCl 2 with the crystal water removed and zinc powder serving as a reducing agent in proportion, and grinding to ensure that all the components are fully and uniformly mixed; (4) The molten salt reaction is carried out, namely, the uniformly mixed materials are filled into a graphite crucible, then the crucible is placed into a vacuum tube furnace, the vacuum is pumped and high-purity argon is filled into the vacuum tube furnace as a protective atmosphere after the crucible is sealed, the temperature is raised to the reaction temperature, zinc powder and cobalt ions are subjected to oxidation-reduction reaction, and generated cobalt atoms are diffused in a molten salt medium and deposited on the surface of diamond, so that a uniform cobalt coating is formed; (5) And (3) after the reaction is finished, cooling to room temperature along with a furnace, taking out a reaction product, washing and drying the product to obtain diamond powder with cobalt plated on the surface.
3. 3. The method of claim 2, wherein in the step (1), submicron diamond powder and dilute hydrochloric acid are mixed according to a volume ratio of 1:1-3, then stirred at room temperature for 15-30 min, repeatedly washed with deionized water until the pH value is neutral after the treatment is completed, and finally dried at 80-100 ℃.
4. 4. The method according to claim 2, wherein in step (2), the temperature for removing the crystal water is 200 to 400 ℃, more preferably 300 to 400 ℃, and the holding time is 1 to 2 hours, more preferably 1.5 to 2 hours.
5. 5. The method of claim 2, wherein in the step (3), the mass ratio of diamond, coCl 2 , zinc powder, molten salt medium is 3-6:1-1.5:0.1-1:20.
6. 6. The method according to claim 5, wherein in step (3), the molten salt medium consists of CaCl 2 and KCl in a mass ratio of 1:1-2, more preferably 1:1.
7. 7. The method according to claim 2, wherein in step (4), the reaction temperature is 800 to 1000 ℃, more preferably 900 to 950 ℃, and the incubation time is 1 to 2 hours, more preferably 1.5 to 2 hours.
8. 8. The submicron cobalt-plated diamond powder prepared by the method according to any one of claims 1 to 7.

Description

Method for realizing submicron diamond homogenization cobalt plating in high-temperature molten salt environment Technical Field The invention belongs to the technical field of diamond surface metallization treatment, and particularly relates to a method for realizing submicron diamond homogenization cobalt plating in a high-temperature molten salt environment. Background Diamond, which is a natural material with the highest hardness in nature, is widely used in various cutting and grinding tools such as diamond drills, saw blades, thin-wall drills, grinding tools, and the like due to its excellent wear resistance and superhard properties. Among them, polycrystalline diamond compacts (PDC compacts) have become key materials for cutting teeth of drill bits in the fields of petroleum drilling, geological exploration, etc., and are bearing important tasks of cutting rock strata at high speed, by virtue of high hardness, excellent wear resistance and good impact toughness. The performance advantages of the PDC composite sheet mainly come from the two aspects that firstly, the D-D bonds formed among particles in the polycrystalline diamond structure are highly densely combined, so that the hardness of materials is guaranteed, the wear resistance is obviously improved, and secondly, the effective combination of the diamond layer and the hard alloy substrate further enhances the weldability and the impact toughness of the whole structure. In order to promote the formation of D-D bonds between diamond grains and improve poor wettability and high interfacial energy between diamond and cemented carbide substrates, the addition of metallic cobalt (Co) as a binder is currently commonly employed. Cobalt has good wettability and proper diffusion performance, can effectively promote the combination among diamond particles, plays a role in bridging an interface, and enhances the stability of a combined interface. However, cobalt catalyzes the graphitization of diamond at high temperature, so that the hardness and wear resistance of the PDC are reduced, and the comprehensive performance of the composite sheet is affected. Therefore, the addition mode and content control of cobalt become key factors for determining the material performance. At present, the common external cobalt powder adding mode can realize fixed-point and quantitative adding, but has the problems of uneven mixing, easy oxidation of cobalt powder, poor dispersibility and the like. In contrast, the cobalt layer is plated on the surface of the diamond by utilizing the surface treatment technology, so that diamond metallization is realized, a continuous and uniform cobalt coating layer can be formed on the surface of the diamond, good interface metallurgical bonding is realized, and the bonding strength, sintering compactness and high-temperature stability between the diamond and a metal matrix are remarkably improved, thereby effectively improving the mechanical property and service life of the tool. Among various surface cobalt plating methods, the redox reaction method based on molten salt environment has significant advantages. The reaction principle is Zn+Co 2+→Co+Zn2+. Since the standard reduction potential of zinc (E ° (Zn 2+/Zn) = -0.76V) is significantly lower than that of cobalt (E ° (Co 2+/Co) = -0.28V), i.e. zinc is more reducing, the reaction free energy change Δg <0 is thermodynamically spontaneously occurring. The currently commonly used diamond surface metallization methods also include electroless plating, electroplating, vacuum physical/chemical vapor deposition, vacuum plating, and the like. The chemical plating needs to go through multiple processes such as surface activation and sensitization, chemical reagent preparation is complex and has potential safety hazards, particularly, the deposition rate on submicron diamond powder is slow, the plating effect is poor, the cobalt coating prepared by an electroplating method mainly depends on physical adsorption and combination, the interface diffusion effect is weak, the bonding strength is limited, the cost is high, the common vacuum plating is carried out under the condition of being lower than 400 ℃, the metal powder deposition layer is thinner, the bonding strength is low, and in the chemical/physical vapor deposition method, most of the plating layers are physically attached to the diamond, chemical reaction does not occur generally, and the plating layers are easy to fall off. Based on the method, the invention provides a molten salt cobalt plating process, the molten salt provides a good fluid contact environment for diamond and metallic cobalt, and the diamond and the metallic cobalt continuously exchange in the molten salt to promote cobalt particles to be uniformly deposited on the surface of the diamond. The high-temperature ion environment is favorable for realizing the strong metallurgical bonding of the coating and the diamond substrate. Through interdiffusion and interfacial chem