A preparation method of rare earth oxide dispersion strengthened fine grain tungsten materials

Abstract

This invention relates to a preparation method of rare earth oxide dispersion strengthened fee grain tungsten materials, the mass percent of the rare earth oxide is of 0.1-2%, and the rest ingredient is W. Weigh soluble rare earth salt and tungstate, dissolve into water to made into 50-100 g / L of rare earth salt solution and 150-300 g / L of tungstate solution, respectively. Firstly, add trace alkali in rare earth salt solution to control pH in 7-8, then add organic dispersant and stir to form evenly suspended R(OH)3 particle colloid (R refers to rare earth element). Secondly pour the tungstate solution into the R(OH)3colloid, add trace acid to control pH in 6-7, then add organic dispersant and stir to form tungstic acid micro particles, which wrap around the colloidal particles, forming coprecipitation coating particle colloid. Thirdly, the coprecipitation coating particle colloidal is spray-dried, forming tungsten and rare earth oxide compound precursor powder. Alter that, ultrafine or nanoscale tungsten powder with particle size of 50˜500 nm is obtained through a process of calcination subsequent with hydrogen thermal reduction. Finally, the tungsten powder is subjected to ordinary compression molding and then conventional high temperature sintering. The trace rare earth oxide dispersion strengthened high performance fine grain tungsten materials prepared by this invention, its density is close to full density (98.5% or higher), its grain size is uniform and very fine (average in 5˜10 microns), and the rare earth oxides particles evenly distribute in tungsten intracrystalline or grain, boundary with particle size of 100˜500 nm.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application claims priority to the PCT application Ser. No. PCT / CN2014 / 088882, filed on Oct. 20, 2014, the disclosure of which is expressly incorporated by reference herein in its entirety.TECHNICAL FIELD[0002]The invention relates to field of nanomaterials and powder metallurgy field, especially a preparation method of rare earth oxide dispersion strengthened fine grain tungsten materials by nano-composite technology.TECHNICAL BACKGROUND[0003]Tungsten has characteristics such as high melting point, high hardness, good high temperature strength, thermal conductivity, electrical conductivity, low thermal expansion coefficient low sputtering and plasma effect, does not react with H, low H+ retention, is a very important high temperature structural materials and functional materials and is widely used as a plasma facing material and divertor component material in the nuclear fusion field.[0004]Among the tungsten materials which h...

AI Technical Summary

Benefits of technology

[0006]In order to solve the problems in the above method in the preparing high performance rare-earth oxide dispersion strengthened fine grain tungsten materials, the present invention adopts the heterogeneous precipitation—spray drying—calcining—thermal reduction—conventional sintering technology to prepare high performance rare-earth oxide dispersion strengthened fine grain tungsten materials, its density is close to full density (98.5% or higher), and the rare earth oxides particles evenly distribute in tungsten intracrystalline or grain boundary, its grain size is uniform and very fine (average in about 10 microns or less), with good room temperature and high temperature performance as well as high thermal loading shock resistance.

[0019]1. Compared with the conventional high energy ball mill and mechanical alloying, adopt “heterogeneous precipitation—spray drying” adding rare earth oxide in tungsten matrix, heterogeneous precipitation improves the compatibility of tungsten and rare earth oxides particles surface, spray drying achieves the uniformity of composition, microstructure in powder and alloy, so rare earth elements in tungsten matrix distribute more uniform, and do not introduce impurities.

[0020]2. Compared with high energy ball mill and mechanical alloying, ultrafine tungsten composite powder containing trace rare earth oxides prepared by “heterogeneous precipitation—spray drying—calcining—hydrogen reduction” method has much higher sintering activity; The powder of this invention can reach more than 98.5% density sintered at 1800˜2000□ by conventional sintering, grain size for sintered body is about 5˜10 microns, and microstructure more evenly, excellent toughness at room temperature and high temperature.

Problems solved by technology

However, this material exists defects such as coarse grain, fiber microstructure, high DBTT, low recrystallization temperature, high brittleness.

But there exist some problems in the preparation of above: using high-energy ball milling or mechanical alloying preparation powder is easy to produce heterogeneous component distribution and impurities, and SPS, hot-pressing sintering method is not suitable for the engineering of large scale preparation.

And although Guo's method improve the oxide dispersion distribution uniformity in tungsten matrix, but Ni must be added as sinter activator, and Ni element in many fields, such as nuclear fusion, nuclear fission is forbidden to use, this will be greatly limit the application scope.

But due to poor compatibility of tungsten and rare earth oxide on the surface of the particles, if sol spray drying method is directly used to prepare tungsten materials containing trace rare earth oxide, rare earth oxide particle dispersion strengthening effect for tungsten is very limited, leading to poor performance, so it is difficult to meet the application requirement of nuclear fusion.