Ultrafine Tungsten Carbide Powder Manufacturing Improvement

Because of its excellent properties such as high hardness, high red hardness, high compressive strength, high wear resistance and good corrosion resistance, superfine tungsten carbide powder is known as "industrial teeth" and widely used in almost all sectors of the national economy and various fields of modern technology. As the main material of cemented carbide, tungsten carbide has been devoted to improving its contradictory properties of hardness and toughness.

Some studies have shown that for supersonic flame sprayed tungsten carbide-based cemented carbide coatings, refinement of tungsten carbide grain can significantly improve the hardness and toughness of materials, and the wear resistance of coatings also increases with the decrease of tungsten carbide grain size.

However, in the traditional process of preparing ultra-fine tungsten carbide powder, because of its small grain size, large specific surface area, high Gibbs free energy and long time high temperature treatment, it is difficult to effectively maintain the ultra-fine grain size of tungsten carbide. Therefore, the powder is easy to bond into clusters and must be crushed. The process prolongs the production process, consumes large energy and costs high. In order to overcome the shortcomings of traditional technology, some scholars have improved the traditional spray technology to prepare ultrafine tungsten carbide powder.

83wt% tungsten carbide powder (particle size 100-300nm) and 17wt% cobalt powder (particle size 1-2 micron m) were added into the ball mill and added with absolute alcohol. The grinding balls were selected from two kinds of scale YG6 cemented carbide grinding balls, namely, 16mm and 6mm 6mm, the ball material was 1 4:, the ball milling speed was 50r/min, the milling time was 12h. After wet grinding, the polyethylene glycol containing 2% of the mixed powder quality was added. The pelletizing powder is obtained by pelletizing, the inlet temperature is controlled at 240 C, the outlet temperature is controlled at 120 C, the speed of atomizer is 18 000 r/min, the drying and protective atmosphere is nitrogen, and the tower pressure is 2 KPa. The pelletizing powder is degreased in a tubular furnace at 800 C for 12 h. The degreased powder is sintered in a vertical sintering furnace in a transient state, and the powder is carried in nitrogen gas (carrier gas). Under the action of 150 ml/min flow rate, the sintered powder is obtained by accelerating and continuously uniform vertical direct current through the heating zone of the vertical sintering furnace, and sintering is completed in the heating zone. The sintered powder is cooled and graded, i.e. the ultra-fine tungsten carbide-based spherical thermal spraying powder.

Compared with the existing technology, the improved process has a shorter sintering time, which strongly inhibits the growth of ultrafine grains of tungsten carbide and chromium carbide, keeps their original grain size well, strongly restricts the oxidation decarbonization behavior of tungsten carbide, and obtains high-performance ultrafine grain tungsten carbide-based spherical thermal spraying powder, avoids agglomeration between sintered powders, and eliminates conventional workmanship. The follow-up process of mechanical crushing in the process shortens the production process, improves the production efficiency and product utilization ratio, and reduces the preparation cost.

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