Titanium Tungsten Alloy by Molten Salt Electrolysis

At present, the main methods for preparing Ti-W alloys are high temperature vacuum melting, powder metallurgy and mechanical alloying. However, these methods have some disadvantages, such as high production cost, complex process or low purity of products, which reduce the properties of Ti-W alloys and greatly limit their application.

Fused salt electrolysis (FFC) can prepare many kinds of high melting point or refractory metals and their alloys which are difficult to produce by conventional methods. There are no liquid metals in the whole process. It is a new method to prepare Ti-W alloys with short process flow, less equipment investment, low reaction temperature and low energy consumption. The process includes:

(1)Titanium dioxide and WO₃ powders with average particle size less than 2 micron and purity greater than 98% were mixed in the proportion of 9:1-3:7, and a mixture of carbon powder or carbon powder equivalent to 5-10% of the total weight of the two powders and titanium hydride powder in the proportion of 10:(1-10) was added as pore-forming agent, followed by 6-12% polyvinyl alcohol (PVA) solution or distilled water as binder, which was evenly mixed by mechanical method. Mixed powders were obtained.

(2)The prepared mixed powders were moulded and pressed at a pressure of 3-15 MPa for 1-3 min to form a plain blank, or 60-80% slurry was prepared by adding distilled water into the prepared mixed powders and then grouted in the mould to form a green body; the prepared electrode green body was a cylindrical shape with a diameter of not less than 60 mm and a height of 3-10 mm. Or a thin plate with a side length of 50-150 mm and a height of 3-10 mm;

(3)The green body is dried naturally at room temperature or below 150 ℃ until the water content is not more than 5%. The titanium dioxide-WO₃ mixture electrode is sintered at 900-1200 ℃ for 3-10 H. The cathode is made of high purity graphite and electrolysed with CaCl₂ as molten salt under argon atmosphere. The electrolysis temperature is 800-1100 ℃ and the electrolytic voltage is 2.8-3.2V. The vacuum is first pumped to the best before electrolysis. After the electrolysis, the solid electrolyte products on the cathode are put forward to molten salt and cooled to room temperature. After the cooling, the electrolyte products are cleaned and desalted to prepare titanium tungsten alloy.

The preparation temperature of Ti-W alloy can be obviously reduced by molten salt electrolysis. Ti-W alloy with high purity, controllable composition and fine grain can be obtained at lower temperature. The manufacturing process is simple and the cost is relatively low.

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