Niobium Tungsten Dualistic Ultrafine Tungsten Carbide

Ultrafine tungsten carbide having high strength, hardness and wear resistance to meet the development of modern industrial and specialty materials, widely used in making integrated circuit boards micro drill, drill a dot matrix printer, hard processing tool material, medical tooth drill and so on.

Aiming at the defects of the existing technology, a method of preparation of niobium tungsten dualistic composite carbides nano powder was proposed. The ultrafine / nano niobium tungsten compound carbide powder was prepared by the chemical coprecipitation nano in situ composite technology. The following process was as follows:

(1) Weigh 2332g of ammonium paratungstate with 5 crystal water (5(NH₄)₂O-12WO₃-5H₂O), and dissolve it in 30L fluoro citric acid solution, add 300ml surfactant PEG-600, stir to obtain a sol solution. The concentration of fluonilic acid was 80 g/L as yttrium oxide and 1.0 mol/L as HF acid concentration.

(2) The concentrated ammonia water with a concentration of 9.6N was slowly added to the sol solution until the pH value of the solution = 9 to 10, the addition of ammonia water was stopped, and the aging was allowed to stand for 30 minutes, the stirring of the solution was maintained during the addition of ammonia water.

(3) The ammonia-neutralized precipitate was filtered with a suction filter, and the precipitate was thoroughly washed with warm ammonia water until the fluorine content in the precipitate was less than 0.3%.

(4) The washed precipitate was placed in a hot air circulation oven and dried at 120° C for 5 hours, and then taken out and sieved through a 100 mesh sieve to obtain cerium-tungsten consisting of Nb(OH)₅, (NH₄)(10H₂W₁₂O₄₂)•4H₂O precursor composite powder.

(5) The niobium tungsten precursor composite powder was reduced in the fourteen tube hydrogen reduction furnace. The reduction temperature was 780°C, and the heat preservation time was 1 hours, and the niobium tungsten composite powder was obtained.

(6) The carbon black 900g with a fixed carbon content of more than 95% and mixed with 4078g niobium tungsten composite powder, loaded into graphite vessel, carbonized in the vacuum carbon tube, carbonization temperature 1320°C, and after the heat preservation 1h cooling to the room temperature, after the furnace was cooled to the room temperature, and the niobium tungsten compound carbide powder was obtained.

(7) The dualistic composite carbide powder after 100 mesh sieves was used to detect the powder properties. The powder grain size was 50 to 200nm, the Fisher particle size 1.07μm, the total carbon content 8.76%, the free carbon content 0.07%, the oxygen content < 0.1%, the nitrogen content < 0.01%, the tungsten content 45.6%, and the allowance for niobium.

The molecular scale of niobium and tungsten is mixed by chemical coprecipitation method, and the purity of nano niobium tungsten carbide powder is high, the size of grain is fine and the size of grain is from 10 to 200nm.

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