Nano Tungsten Powder Forming by Powder Injection

Powder injection moulding (PIM) is a new near net-size forming technology developed by combining traditional powder metallurgy with modern plastic injection moulding technology. The most important feature of PIM is that it can directly produce parts with the final shape, minimize the amount of machining and save raw materials, and has wide material adaptability. It has been widely used in the preparation of ceramics and refractory metals.

Recently, some researchers have made new breakthroughs in the field of nano-tungsten powder injection molding. The method includes:

1.Slurry preparation: first, the size of 200nm nano tungsten powder 3000g, polyethylene glycol 90g in deionized water ball milling mixing, and then spray drying, spray granulation machine inlet temperature of 240 degrees, the outlet temperature of 130 degrees, the speed of 8700rpm, collected granulating material.

2.Feed preparation. The pelletizer 3000g and the binder 142g of the above components were mixed in the roller. The mixing temperature was 170 ℃ and the rotating speed was 30r/min. After the mixture formed a melting state, the mixture continued to mix for 40 minutes, and then the mixture was taken out for cooling.

3.Injection moulding: The raw tungsten billet is produced by crushing the feed and putting it into the injection mould in the injection moulding machine at 160 ℃.

4.Degreasing: tungsten green billet is placed in trichloroethylene solution for 5 hours, trichloroethylene is heated by water bath at 45 ℃, and then dried. At this time, most of the paraffin components have been removed. After removal, most of the paraffin components have been put in high purity hydrogen atmosphere. The temperature rises to 420 ℃ in 1 ℃/min for 30 min, then to 600 ℃ in 2 ℃/min for 10 ℃/min. The degreasing billet was obtained by heating to 900 ℃ and holding for 30 minutes after cooling in the furnace.

5.Sintering: Degreasing green body is put into crucible, high purity hydrogen is injected into high temperature sintering furnace, and the temperature rises to 1550 ℃ at the rate of 5 ℃/min, holding for 2 hours. Tungsten products of injection moulding are obtained by cooling the furnace to room temperature.

After spray granulation, the loading capacity of tungsten powder is 50%, and the density and density of the tungsten powder are higher. The density of tungsten products sintered by 2H at 1550 degrees is higher than 95%. The shrinkage deformation is small, the surface quality is good, and the dimension accuracy is high.

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