A kind of preparation method of nano-coated composite powder

Abstract

The invention discloses a method for preparing a nano-coated composite powder, which belongs to the technical field of material preparation. The method for preparing a nano-coated composite powder in the invention includes adding Precipitating agent, obtain the nano-precursor coated on the surface of the powder particle, reduce to obtain the nano-coated composite powder with "core-shell" structure, by using the solvation effect of the metal compound in the organic solution, and the precipitant in the organic solution The weak electrolyte properties in the medium avoid the shortcomings of high local concentration during the precipitation reaction, long reaction time, and coarse particle size of the reaction product. The average particle size of the prepared metal precursor is less than 200nm, and it is colloidally coated on the powder particles. On the surface, after low-temperature reduction, nano-metal or alloy particles are attached to the surface of powder particles, forming a nano-coating layer with a highly uniform phase distribution.

Description

technical field [0001] The invention belongs to the technical field of material preparation, and relates to a preparation method of nano-coated composite powder. Background technique [0002] Due to their excellent structure, physical and mechanical properties, nano-powders and coatings are the hotspots in current materials research. Usually, refractory metal alloys (such as alloys based on tungsten, molybdenum, tantalum, niobium, rhenium, etc.) and hard materials (such as WC, TiC, TiN, Ti(C, N), TaC, NbC, Mo 2 C. TiB 2 , B 4 C, etc. are cemented carbide or ceramic materials of the hard phase) produced or prepared by powder metallurgy. Its production process mainly includes: mixing the refractory metal matrix and additive elements (such as Co, Cu, Ti, etc.), hard phase and binder metal (such as Mn, Fe, Co, Ni, Cu, etc.) by ball milling to obtain a powder mixture ; After further pressing and sintering, refractory metal alloys (such as W-Cu, Mo-Ti-Zr alloys), hard material...

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Problems solved by technology

Usually, the ball milling time is more than 15 hours, which takes a long time and the production efficiency is low

Other defects are: (1) The wear of the tank body and the grinding balls may cause pollution; (2) When the ball milling time is insufficient or the process is not good, the WC and Co phases in the WC-Co mixture are not uniformly distributed, and after compression molding , the probability of direct contact between WC particles increases, resulting in the merging and growth of WC grains during the sintering process; (3) Due to the crushing effect of ball milling, the WC particle size distribution in the obtained WC-Co mixture is wide, which leads to the hardness after sintering. The WC grain size distribution of the cemented carbide is wide, that is, the cemented carbide is "thick and thin". According to the "Ostwald ripening" aging mechanism, during the sintering process, the fine WC particles are preferentially dissolved quickly, and at the same time they are precipitated on the original coarse WC surface. resulting in unusually large WC grains in the alloy

However, the metal salt precursor prepared by chemical precipitation in aqueous solution generally has a large particle size, and the shape is difficult to control. It is difficult to prepare a nano-coated composite powder with a uniform phase and a special shape.

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